Title of Invention	"SPIN PACK ASSEMBLY"
Abstract	A spin pack assembly for use in melt spinning elastic fibers. The spin pack assembly includes a circular breaker plate having a center aperture and several circular patterns of apertures with each circular pattern having a plurality of apertures. Each circular pattern is located concentrically about an axis of the center aperture. The apertures in the outer circular patterns have a greater diameter than the apertures in the inner circular patterns. The spin pack assembly also has a spinneret plate where the exit aperture of the spinneret plate is recessed in the body of the spin pack assembly.

Title of Invention

"SPIN PACK ASSEMBLY"

Abstract

A spin pack assembly for use in melt spinning elastic fibers. The spin pack assembly includes a circular breaker plate having a center aperture and several circular patterns of apertures with each circular pattern having a plurality of apertures. Each circular pattern is located concentrically about an axis of the center aperture. The apertures in the outer circular patterns have a greater diameter than the apertures in the inner circular patterns. The spin pack assembly also has a spinneret plate where the exit aperture of the spinneret plate is recessed in the body of the spin pack assembly.

Full Text	SPIN PACK ASSEMBLY FIELD OF THE INVENTION [0001] The present invention relates to devices and methods for use in melt spinning of elastomeric fibers, such as polyurethane fibers. Exemplary embodiments relate to a spin pack assembly used to produce such fibers. BACKGROUND OF THE INVENTION [0002] The vast majority of thermoplastic polyurethane (TPU) fibers are made by a dry spinning process involving dissolving the TPU in a solvent. Melt spinning TPU fibers has been gaining in use in recent years. Melt spinning does not involve the use of a solvent, and therefore is more environmentally friendly. [0003] Melt spinning TPU fibers involves feeding TPU polymer into an extruder and from the extruder to a spinneret where the fiber exits the spinneret. Polymers, such as TPU, tend to crystallize or crosslink so as to form lumps if they remain in melt processing equipment for too long. This is especially the case where crosslinking agents are added to the TPU prior to being fed to the spinneret. These early formed crystallized polymer and/or crosslinked polymer lumps may find their way through the spinneret and cause defects or undesirable properties in the fiber. Fiber breakage can also result. Lumps of crystallized and/or crosslinked material may also accumulate in the cavities upstream of the fiber opening. This can result in excessive back pressure and reduced material flow. Back pressure can build up to the point where fiber can no longer be produced. This requires shutting down the process of manufacturing the fiber and cleaning the equipment to remove the blocking material. [0004] Another problem that can occur with melt spinning TPU fibers is that the modulus of the fibers can be too high for circular knitting applications. [0005] Thus, there exists a need for improvements in melt spinning of elastomeric fibers. SUMMARY OF THE INVENTION [0006] It is an object of an exemplary embodiment to melt spin elastic fibers, such as TPU, in a process that gives long run times. [0007] It is another object of an exemplary embodiment to make a melt spun TPU fiber with lower modulus, as measured at 100% elongation. [0008] It is another object of an exemplary embodiment to provide a spin pack assembly that produces a fiber with more desirable properties, provides faster running rates, and achieves longer run times. [0009] Further objects of exemplary embodiments will be made apparent in the detailed description herein and the appended claims. [0010] These objects are accomplished in an exemplary embodiment by using a spin pack assembly to produce a fiber. The spin pack assembly includes a breaker plate comprising a circular metal plate with a plurality of apertures of different size diameters. The aperture in the center of the breaker plate is the smallest hole and the apertures are progressively larger the farther they are from the center of the breaker plate. The apertures the greatest distance from the center have the largest diameter. This configuration of the holes in the breaker plate provides for first-in/first-out flow of material throughout generally the entire cavity within the spin pack assembly. The flow in the exemplary embodiment provides for increased flow in areas radially disposed from a central axis of the spin pack assembly. In the exemplary embodiment this approach generally avoids material being resident within the spin pack assembly for a time that is less than a reaction time after which numerous lumps of cross linked and/or crystallized material form within the assembly. The approach of the exemplary embodiment provides desirable flow properties that produce fewer defects in the fiber. In addition, the exemplary structure of the spin pack assembly provides lower back pressure buildup through longer running times which reduces process downtime and increases productivity. [0011] In the exemplary embodiment of the spin pack assembly, the spin pack assembly has a generally cylindrical body with a body opening. The fiber is produced by passing the material through a fiber opening in a spinneret plate. The fiber is produced at an exit. The exit is disposed axially inward relative to the body opening. This structure in the exemplary embodiment allows the fibers to cool more slowly relative to prior designs. This results in lower modulus fiber and enables faster running rates. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a cross-sectional view of an exemplary spin pack assembly including a breaker plate and a recessed spinneret plate fiber exit opening. [0013] FIG. 2 is a top view of an exemplary breaker plate used in the assembly of FIG1. [0014] FIG. 3 is a top view of an exemplary prior art breaker plate. [0015] FIG. 4 is an isometric view of an exemplary transport channel piece of the exemplary assembly of FIG. 1. [0016] FIG. 5 is an isometric view of an exemplary prior art transport channel piece. [0017] FIG. 6 is an isometric view of a spacer and spinneret plate of an exemplary embodiment. [0018] FIG. 7 is an isometric view of a prior art spinneret plate. [0019] FIG. 8 is an exploded view of the components in the exemplary spin pack assembly within the body. [0020] FIG. 9 is an isometric view of the components shown in FIG. 8 in an assembled condition. [0021] FIG. 10 is an isometric view of the cylindrical body of the exemplary spin pack assembly showing the recessed fiber exit of an exemplary embodiment. [0022] FIG. 11 is an isometric view showing a prior art spin pack assembly including the fiber exit opening closer to the body exit. DETAILED DESCRIPTION OF THE INVENTION [0023] Referring now to the drawings and particularly to FIG. 1 there is shown therein a spin pack assembly (10) of an exemplary embodiment. The spin pack assembly 10 includes a generally cylindrical body 12. Body 12 extends along a central axis 14. [0024] In the exemplary embodiment the body includes the body opening 16 at an axial end thereof. Body opening 16 is of a smaller diameter than a bore 18 which extends within the body. In the assembled position of the spin pack assembly the bore includes a number of stacked components. These components in the exemplary embodiment include an annular spacer 20. In the exemplary embodiment spacer 20 is supported on an inward extending annular step 22 that bounds the bore. [0025] A spinneret plate 24 is positioned adjacent to spacer 20. Spinneret plate 24 includes an axially positioned fiber opening 26 therein. Opening 26 produces a single fiber from the exemplary spin pack assembly in a manner later discussed. The single fiber is produced at an exit 28 from the fiber opening. The exit is disposed axially inward of the body opening in the exemplary embodiment. The exemplary spinneret plate 24 further includes a recess area therein which is bounded by a generally planar annular surface 30. Planar annular surface 30 generally extends in surrounding relation of the fiber opening 26. [0026] An annular washer 32 is positioned in the assembly adjacent to the spinneret plate 24. The annular washer 32 of the exemplary embodiment includes a central opening that corresponds in diameter to the recess in the spinneret plate. [0027] The exemplary assembly further includes a breaker plate 34. The breaker plate 34 of the exemplary embodiment includes a plurality of apertures 36 therethrough. As later discussed in detail the arrangement of apertures of the exemplary embodiment provides material flow properties through the spin pack assembly that provides desirable properties in producing the fiber. [0028] Adjacent to the breaker plate 34 of the exemplary embodiment is a screen 38. As best shown in FIG. 8 the screen of the exemplary embodiment includes a central porous area and a peripheral annular solid area. Of course it should be understood that this structure is exemplary and in other embodiments other approaches may be used. [0029] The exemplary assembly further includes a transport channel piece 40. The transport channel piece of the exemplary embodiment includes an annular portion 42 and a cylindrical projection portion 44. An inlet 46 operative to receive fluid material extends axially through the transport channel piece. In the exemplary embodiment the transport channel piece includes a generally planar annular surface 48. In the exemplary embodiment the generally planar annular surface extends in surrounding relation of the inlet 46. The exemplary transport channel piece 40 also includes on the cylindrical projection portion, a recess in which a compression washer 50 is positioned. Compression washer 50 facilitates fluid tight connection with a conduit that supplies the fluid material which forms the fiber. [0030] The exemplary spin pack assembly further includes a compression nut 52. Compression nut 52 of the exemplary embodiment includes an external annular threaded portion 54. Threaded portion 54 is configured to engage mating threads positioned in a corresponding portion of the bore 18. Compression nut 52 further includes an access opening 56 which is axially centered therein. The cylindrical projecting portion of the transport channel piece of the exemplary embodiment extends through the access opening in the assembled condition of the spin pack assembly. It should be further understood that the compression nut 52 may include apertures or other suitable structures that facilitate rotation of the compression nut so as to hold the components of the spin pack assembly in assembled stacked relation in the bore during use and for also enabling the disassembly of the components as may be desirable for replacement, cleaning or other purposes. Of course it should be understood* that these structures are exemplary and in other embodiments other approaches may be used. [0031] As is apparent from FIGS. 8 and 9, in the exemplary embodiment of the assembly, the spacer, spinneret plate, washer, breaker plate, screen and transport channel piece may be assembled in the bore 18. The assembled components are held in place therein by tightening the compression nut 52. Further, when the components are assembled the spin pack assembly includes a cavity area generally indicated 58, through which the material flows between the inlet 46 and the exit 28. In addition as can be appreciated, the components of the spin pack assembly may be removed for repair, replacement or cleaning by loosening the compression nut 52 and removing the various components from the bore. It should be further understood that these components are exemplary and the principles described herein may be used with other components in spin pack assemblies or other assemblies which are adapted for producing fibers of thermoplastic materials. [0032] FIG. 2 shows a top view of the exemplary breaker plate 34. As discussed, the exemplary breaker plate 34 includes a plurality of apertures 36. In the exemplary embodiment the apertures include an axially aligned central aperture 60. Central aperture 60 in the assembled position of the spin pack assembly is aligned with the axis 14. The exemplary breaker plate 34 further includes apertures arranged in three concentric circular patterns about the central aperture 60. Apertures 62 are included in the first concentric circular pattern. Apertures 64 are included in the second concentric circular pattern and are disposed radially outward relative to the apertures 62 in the first concentric circular pattern. Apertures 66 in the third concentric circular pattern are disposed radially outward of the apertures 64 in the second concentric circular pattern. Of course it should be understood while in the exemplary embodiment three concentric circular patterns are used, in other embodiments other approaches may be used. [0033] In exemplary embodiments the apertures 62 in the first concentric circular pattern are of a smaller effective diameter for purposes of material flow and have a smaller cross-sectional area than the apertures 64 in the second concentric circular pattern. Likewise, in the exemplary embodiment the apertures 66 in the third concentric circular pattern have a greater diameter and cross-sectional area than the apertures 64 in the second concentric circular pattern. [0034] Further, in the exemplary embodiment the. radial distance from the central aperture 60 to the apertures 62 in the first concentric circular pattern, is a greater radial distance than the radial distance between the apertures 62 and the apertures 64, and is also a greater radial distance than between the apertures 64 and the apertures 66. This configuration in the exemplary embodiment provides flow properties which have proven desirable for purposes of producing fibers of the exemplary embodiment. [0035] During operation of the exemplary embodiment the plurality of apertures provide a greater material flow with increasing radial distance from the axis 14. This approach provides for a desirable flow pattern within the cavity area 58. The aperture arrangement provides a first-in/first-out flow generally throughout the entire cavity area. This flow which can alternatively be referred to as plug flow, assures that generally the polymer melt in the cavity area is not resident during operation for the reaction time that would otherwise result in the production of crosslinked and/or crystalline material which forms semi-solid lumps in the polymer melt. For purposes of this disclosure the term "lumps" should be understood to include solid and semi-solid bodies which have a consistency less fluid than the other material flowing through the cavity area. As previously discussed, such lumps are undesirable, and may cause defects and undesirable properties in the fiber which is produced. Such lumps within the cavity area can also produce increased back pressure which impedes the flow of material through the spin pack assembly to produce the fiber. Such reduced flow results in slower running speeds and eventually stoppage of the production process so that the spin pack assembly can be cleaned. [0036] The principles employed in connection with the exemplary breaker plate 34 can be further appreciated from the pattern of apertures shown in the prior art breaker plate 68 shown in FIG. 3. The prior art breaker plate 68 includes a uniform pattern of apertures. This uniform pattern generally results in most material passing through the central apertures and through the opening the spinneret plate to produce the fiber. Material passing through other apertures moves more slowly and thus more material remains within the spin pack assembly for a period of time that reaches the reaction time. As a result, lumps form within the cavity area. These lumps operate to restrict flow which results in increased back pressure and slower operating speeds. The formation of such lumps also impacts the quality of the fiber material produced at the spinneret opening. These undesirable aspects are reduced by applying the principles described herein. [0037] Although in an exemplary embodiment the arrangement of concentric circular patterns of apertures is used to achieve desirable flow properties, in other embodiments other approaches may be used. These may include for example, breaker plates which include arcuate patterns of apertures to achieve desirable characteristics. These arcuate patterns may include elongated slots or spirals that achieve flow characteristics that produce the desirable results as described. In other embodiments spiral arrangements of apertures including apertures of various shapes may be used. In still other embodiments structures other than breaker plates may be employed so as to achieve the desired flow properties. These flow properties can be achieved through the use of apertures, vanes, weirs or other structures. Of course these approaches are exemplary and in other embodiments other approaches may be used. [0038] A further useful aspect of the exemplary spin pack assembly is the shape associated with the cavity area 58. In the exemplary embodiment the cavity area is axially bounded by the generally annular surfaces 48 and 30. These generally annular surfaces provide advantages in the nature of maximizing flow rates and minimizing surface area. [0039] FIG. 4 shows the transport channel piece 40 of the exemplary embodiment. The planar surface 48 surrounds the material inlet and during operation forces material to flow radially outwardly as the material enters the recessed area therein at elevated pressure. This structure helps to move the material through the transport channel piece generally more quickly compared to the prior art structure 70 which is shown in FIG. 5. As can be appreciated the prior transport channel piece 70 includes a more conical chamber. The conical chamber increases the area and potential material residence time within the cavity. The structure of the exemplary piece 40 is intended to minimize those conditions which may result in undesirable lumps within the material. Similar principles apply to the configuration of the planar annular surface 30 which surrounds the fiber opening in the spinneret plate 34. Of course these approaches are exemplary and in other embodiments other approaches may be used. [0040] A further useful aspect of the exemplary embodiment of the spin pack assembly is the configuration of the fiber exit from the spinneret plate relative to the . body opening. In the exemplary embodiment the exit 28 of the axially positioned fiber opening 26 is axially disposed inwardly relative to the flat annular surface 72 in which . the body opening 16 extends. In the exemplary embodiment the fiber exit 28 is disposed axially inwardly more than 5 millimeters (mm) in the body annular surface. Further in the exemplary embodiment used in the production of TPU fiber, the exit is recessed 15.5 mm relative to the body annular surface. In alternative embodiments greater recesses may be used. This recessed configuration allows the fiber to cool more slowly. This results because during the critical period after the fiber first exits the opening in the spinneret plate, the fiber remains surrounded by the hot body of the spin pack assembly. Further, as the fiber passes out the exit it is surrounded within the recess by relatively stagnant hot air that further facilitates slower cooling. This slowness to cool in the exemplary embodiment results in a fiber having a lower modulus at 100% elongation. This lower modulus is especially desirable when the fiber is to be used in circular knitting processes such as to make fabric. [0041] FIG. 10 shows the axial end of the spin pack assembly of an exemplary embodiment with the exit 28 of the spinneret plate axially recessed inwardly relative to the opening in the body. FIG. 11 contrasts the prior art approach in which the exit from the spinneret plate was generally at the same level or only recessed slightly such as in the range of 2 mm from the body annular surface. Similarly FIG. 6 shows an isometric view of the spacer 20 which serves to recess the opening in the spinneret plate and the exit therein, from the body opening. This is in contrast to the prior art spinneret plate 74 shown in FIG. 7. [0042] As can be appreciated from a comparison to the exemplary embodiment to the prior art, the exemplary embodiment slows the cooling of the fiber through the use of recessed fiber exit and the surround body recess. This approach substantially improves the properties of the fiber which is produced using the spin pack assembly of the exemplary embodiment. Of course these structures are exemplary and in other embodiments other approaches may be used. [0043] In an exemplary embodiment the polymer material to be melt spun into elastic fibers is fed to an extruder to melt the polymer. The melted polymer can optionally be fed from the extruder and'mixed with a crosslinking agent and fed to a manifold. If no crosslinking agent is used, the polymer melt is fed directly to a manifold. The polymer flows from the manifold to a melt pump. The melt pump feds the polymer to the spin pack assembly. The polymer melt enters the spin pack assembly through the inlet 46. The polymer melt proceeds from the entrance 46 through the screen 38. The screen 38 removes any foreign matter and unmelted polymer. The polymer melt material proceeds through the screen 38 to the breaker plate 34. The polymer passes through the apertures in the breaker plate to the spinneret plate 24. From the spinneret plate 24 a fiber is formed at the exit 28 as the polymer melt is passed through the fiber opening 26 in the spinneret plate 24. The fiber is cooled and coated with finishing oil and wound into bobbins. [0044] The most desirable elastic fiber to use in this exemplary embodiment is a lightly crosslinked thermoplastic polyurethane (TPU). The preferred TPU polymer will be described below. [0045] The preferred TPU embodiment is a polyether TPU. The TPU is made from a blend of hydroxyl terminated intermediates reacted with a polyisocyanate and a hydroxyl terminated chain extender. [0046] It has been found that when using a polyether TPU polymer to make melt spun fiber, a blend of hydroxyl terminated intermediates having different number average molecular weights gives superior processing features for melt spinning fibers. It has been found that if the blend of hydroxyl terminated intermediates is such that the higher molecular weight intermediate blended with the lower molecular weight intermediate gives a weighted average molecular weight of at least 1200 Daltons. Preferably, from 1200 to 4000 Daltons, and more preferably from 1500 to 2500 Daltons, the TPU can be melt spun for extended periods of time without excessive pressure building up in the exemplary spin pack assembly. This avoids excessive pressure which results in fiber breakage, thus requiring the melt spinning operation to be halted until the spin pack can be cleaned. [0047] To produce the melt-spun fibers according to an exemplary embodiment, it is required to have a TPU made from a blend of at least two hydroxyl terminated intermediates and a crosslinking agent. The blend of intermediates has a first polyether intermediate as the major component and with a higher Mn than the second intermediate. The second intermediate is selected from the group consisting of polyether, polyester,' polycarbonate, polycaprolactone, and mixtures thereof; and the second intermediate has a lower Mn than the first intermediate. Preferably, the second intermediate is also a polyether. For simplicity, the embodiment will be described herein in terms of polyether TPU having a blend of polyether intermediates. It should be recognized that the second intermediate can be other than polyether intermediates, but must be present in lower amounts and have a lower Mn than the first polyether intermediate. [0048] The polyether TPU used can be made by reacting a blend of at least two polyether hydroxyl terminated intermediates with a polyisocyanate and a chain extender. [0049] Hydroxyl terminated polyether intermediates are polyether polyols derived from a diol or polyol having a total of from 2 to 15 carbon atoms, preferably an alkyl diol or glycol which is reacted with an ether comprising an alkylene oxide having from 2 to 6 carbon atoms, typically ethylene oxide or propylene oxide or mixtures thereof. For example, hydroxyl functional polyether can be produced by first reacting propylene glycol with propylene oxide followed by subsequent reaction with ethylene oxide. Primary hydroxyl groups resulting from ethylene oxide are more reactive than secondary hydroxyl groups and thus are preferred. Useful commercial polyether polyols include poly(ethylene glycol) comprising ethylene oxide reacted with ethylene glycol, poly(propylene glycol) comprising propylene oxide reacted with propylene glycol, poly(tetramethyl glycol) comprising water reacted with tetrahydrofuran (PTMEG). Polytetramethylene ether glycol (PTMEG) is the preferred polyether intermediate. Polyether polyols further include polyamide adducts of an alkylene oxide and can include, for example, ethylenediamine adduct comprising the reaction product of ethylenediamine and propylene oxide, diethylenetriamine adduct comprising the reaction product of diethylenetriamine with propylene oxide, and similar polyamide type polyether polyols. Copolyethers can also be utilized in exemplary embodiments. Typical copolyethers include the reaction product of THF and ethylene oxide or THF and propylene oxide. These are available from BASF as Poly THF B, a block copolymer, and poly THF R, a random copolymer. The various polyether intermediates generally have a number average molecular weight (Mn), as determined by assay of the terminal functional groups which is an average molecular weight greater than 700, such as from about 700 to about 10,000, desirably from about 1000 to about 5,000, and preferably from about 1000 to about 2500 Daltons. [0050] Exemplary embodiments use a blend of two or more polyether intermediates, with one polyether being a higher molecular weight than the other polyether. The lower molecular weight polyether will have a molecular weight Mn of from 700 to 1500 Daltons while the higher molecular weight polyether will have a Mn from about 1500 to about 4000 Daltons, preferably from about 1800 to about 2500 Daltons. The blend should have a weighted average molecular weight of greater than 1200 Daltons, preferably greater than 1500 Daltons. For example, a 1000 gram sample of a blend of 70% by weight of a 2000 Mn polyether and 30% by weight of a 1000 Mn polyether would have a weighted average Mn of 1538 Daltons of the two components in the 1000 grams mixture. The 2000 Mn polyether component would have 0.35 moles (1000 x 0.7/2000). The 1000 Mn polyether component would have 0.3 moles (1000 x 0.3/1000). The total moles would be 0.65 (0.35 + 0.3) moles in the 1000 gram sample and have a weighted average Mn of (1000/0.65) or 1538 M„. [0051] The weight ratio in the blend of the first polyether hydroxyl terminated intermediate to the second hydroxyl terminated intermediate is from about 60:40 to about 90:10, and preferably from about 70:30 to 90:10. The amount of the first polyether intermediate is greater than the amount of the second intermediate. [0052] The second necessary ingredient to make the TPU polymer of this embodiment is a polyisocyanate. [0053] The polyisocyanates generally have the formula R(NCO)n where n is generally from 2 to 4 with 2 being highly preferred inasmuch as the composition is a thermoplastic. Thus, polyisocyanates having a functionality of 3 or 4 are utilized in very small amounts, for example less than 5% and desirably less than 2% by weight based upon the total weight of all polyisocyanates, inasmuch as they cause crosslinking. R can be aromatic, cycloaliphatic, and aliphatic, or combinations thereof generally having a total of from 2 to about 20 carbon atoms. Examples of suitable aromatic diisocyanates include diphenyl methane-4, 4'-diisocyanate (MDI), Hi2 MDI, m-xylylene diisocyanate (XDI), m-tetramethyl xylylene diisocyanate (TMXDI), phenylene-1, 4-diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI), and diphenylmethane-3, 3'-dimethoxy-4, 4'- diisocyanate (TODI). Examples of suitable aliphatic diisocyanates include isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CHDI), hexamethylene diisocyanate (HDI), l,6-diisocyanato-2,2,4,4-tetramethyl hexane (TMDI), 1,10-decane diisocyanate, and trans-dicyclohexylmethane diisocyanate (HMDI). A highly preferred diisocyanate is MDI containing less than about 3% by weight of ortho-para (2,4) isomer. A blend of two or more polyisocyanates may be used. [0054] The third necessary ingredient to make the TPU polymer is the chain extender. Suitable chain extenders are lower aliphatic or short chain glycols having from about 2 to about 10 carbon atoms and include for instance ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, triethylene glycol, Cis- trans-isomers of cyclohexyl dimethylol, neopentyl glycol, 1,4-butanediol, 1,6-hexandiol, 1,3-butanediol, and 1,5-pentanediol. Aromatic glycols can also be used as the chain extender and are the preferred choice for high heat applications. Benzene glycol (HQEE) and xylenene glycols are suitable chain extenders for use in making the TPU of this invention. Xylenene glycol is a mixture of 1,4-di(hydroxymethyl) benzene and 1,2- di(hydroxymethyl) benzene. Benzene glycol is the preferred aromatic chain extender and specifically includes hydroquinone, i.e., bis(beta-hydroxyethyl) ether also known as l,4-di(2-hydroxyethoxy) benzene; resorcinol, i.e., bis(beta-hydroxyethyl) ether also known as l,3-di(2-hydroxyethyl) benzene; catechol, i.e., bis(beta-hydroxyethyl) ether also known as 1,2-di(2-hydroxyethoxy) benzene; and combinations thereof. For high heat resistant fibers, benzene glycol (HQEE) is the desired chain extender. Excellent results are obtained by using HQEE together with an isomer of HQEE. [0055] It is preferred to use a co-chain extender together with the chain extender described above. The co-chain extender can be one of the materials described above as a chain extender. The co-chain extender is preferably selected from a material capable of reducing the crystallization rate of the TPU and eliminating high temperature melting peaks of the TPU. Branched compounds, such as dipropylene glycol and neopentyl glycol are excellent co-chain extenders. Also, for high heat applications, an isomer of HQEE, such as hydroxyl ethyl resorcinol (HER), is a very effective co-chain extender. When a co-chain extender is used, the level used is from about 2 to about 50 mole percent, preferably 10 to 30 mole percent, of the total moles of the chain extender and the co-chain extender. [0056] A blend of two or more chain extenders can be used with a blend of two or more co-chain extenders, if desired. However, for simplicity, usually one chain extender is used with one co-chain extender. [0057] The above three necessary ingredients (blend of different Mn polyether intermediates, polyisocyanate, and chain extender) are preferably reacted in the presence of a catalyst. [0058] Generally, any conventional catalyst can be utilized to react the diisocyanate with the polyether intermediates or the chain extender and the same is well known in the art and in the literature. Examples of suitable catalysts include the various alkyl ethers or alkyl thiol ethers of bismuth or tin wherein the alkyl portion has from 1 to about 20 carbon atoms with specific examples including bismuth octoate, bismuth laurate, and the like. Preferred catalysts include the various tin catalysts such as stannous octoate, dibutyltin dioctoate, dibutyltin dilaurate, and the like. The amount of such catalyst is generally small such as from about 20 to about 200 parts per million based upon the total weight of the polyurethane forming monomers. [0059] The polyether TPU polymers of this invention can be made by any of the conventional polymerization methods well known in the art and literature. [0060] Thermoplastic polyurethanes of exemplary embodiments are preferably made via a "one shot" process wherein all the components are added together simultaneously or substantially simultaneously to a heated extruder and reacted to form the polyurethane. The equivalent ratio of the diisocyanate to the total equivalents of the hydroxyl terminated polyether intermediates and the diol chain extender is generally from about 0.95 to about 1.10, desirably from about 0.97 to about 1.03, and preferably from about 0.97 to about 1.00. It is preferred that the equivalent ratio is less than 1.0 such that the TPU has terminal hydroxyl groups to enhance the reaction with the crosslinking agent during the fiber spinning process. The Shore A hardness of the TPU formed should be from 65A to 95A, and preferably from about 75A to about 85A, to achieve the most desirable melt spun fibers. Reaction temperatures utilizing urethane catalyst are generally from about 175°C to about 245°C and preferably from about 180°C to about 220°C. The molecular weight (Mw) of the thermoplastic polyurethane is generally from about 25,000 to about 300,000 and desirably from about 50,000 to about 200,000 and preferably about 75,000 to about 150,000 as measured by GPC relative to polystyrene standards. The preferred Mw is lower than the prior art recommends for the TPU fiber, but the lower Mw allows for better mixing of the TPU with the crosslinking agent to give excellent fiber spinning. • [0061] The thermoplastic polyurethanes can also be prepared utilizing a pre-polymer process. In the pre-polymer route, the hydroxyl terminated polyether intermediates are reacted with generally an equivalent excess of one or more polyisocyanates to form a pre-polymer solution having free or unreacted polyisocyanate therein. Reaction is generally carried out at temperatures of from about 80°C to about 220°C and preferably from about 150°C to about 200°C in the presence of a suitable urethane catalyst. Subsequently, a selective type of chain extender as noted above is added in an equivalent amount generally equal to the isocyanate end groups as well as to any free or unreacted diisocyanate compounds. The overall equivalent ratio of the total diisocyanate to the total equivalent of the hydroxyl terminated polyethers and the chain extender is thus from about 0.95 to about 1.10, desirably from about 0.98 to about 1.05 and preferably from about 0.99 to about 1.03. The equivalent ratio of the hydroxyl terminated polyethers to the chain extender is adjusted to give 65A to 95A, preferably 75A to 85A Shore hardness. The chain extension reaction temperature is generally from about 180°C to about 250°C with from about 200°C to about 240°C being preferred. Typically, the pre-polymer route can be carried out in any conventional device with an extruder being preferred. Thus, the polyether intermediates are reacted with an equivalent excess of a diisocyanate in a first portion of the extruder to form a pre-polymer solution and subsequently the chain extender is added at a downstream portion and reacted with the pre-polymer solution. Any conventional extruder can be utilized, with extruders equipped with barrier screws having a length to diameter ratio of at least 20 and preferably at least 25. The prepolymer method can reduce high temperature melting peaks of the TPU and eliminate the need for a co-chain extender as described in the one- shot process above. [0062] Useful additives can be utilized in suitable amounts and include opacifying pigments, colorants, mineral fillers, stabilizers, lubricants, UV absorbers, processing aids, and other additives as desired. Useful opacifying pigments include titanium dioxide, zinc oxide, and titanate yellow, while useful tinting pigments include carbon black, yellow oxides, brown oxides, raw and burnt sienna or umber, chromium oxide green, cadmium pigments, chromium pigments, and other mixed metal oxide and organic pigments. Useful fillers include diatomaceous earth (superfloss) clay, silica, talc, mica, wallostonite, barium sulfate,, and calcium carbonate. If desired, useful stabilizers such as antioxidants can be used and include phenolic antioxidants, while useful photostabilizers include organic phosphates, and organotin thiolates (mercaptides). Useful lubricants include metal stearates, paraffin oils and amide waxes. Useful UV absorbers include 2- (2'-hydroxyphenol) benzotriazoles and 2-hydroxybenzophenones. [0063] Plasticizer additives can also be utilized advantageously to reduce hardness without affecting properties. [0064] During the melt spinning process, the TPU polymer described above is lightly crosslinked with a crosslinking agent. The crosslinking agent is a pre-polymer of a hydroxyl terminated intermediate that is a polyether, polyester, polycarbonate, polycaprolactone, or mixture thereof reacted with a polyisocyanate. A polyester or polyether is the preferred hydroxyl terminated intermediate to make the crosslinking agent. The crosslinking agent, pre-polymer, will have an isocyanate functionality of greater than about 1.0, preferably from about 1.0 to about 3.0, and more preferably from about 1.8 to about 2.2. It is particularly preferred if both ends of hydroxyl terminated intermediate is capped with an isocyanate, thus having an isocyanate functionality of 2.0. [0065] The polyisocyanate used to make the crosslinking agent are the same as described above in making the TPU polymer. A diisocyanate, such as MDI, is the preferred diisocyanate. [0066] The hydroxyl terminated polyester intermediate used to make the crosslinking agent is generally a linear or branched polyester having a number average molecular weight (Mn) of from about 500 to about 10,000, desirably from about 700 to about 5,000, and preferably from about 700 to about 4,000, an acid number generally less than 1.3 and preferably less than 0.8. The molecular weight is determined by assay of the terminal functional groups and is related to the number average molecular weight. The polymers are produced by (1) an esterification reaction of one or more glycols with one or more dicarboxylic acids or anhydrides or (2) by transesterification reaction, i.e., the reaction of one or more glycols with esters of dicarboxylic acids. Mole ratios generally in excess of more than one mole of glycol to acid are preferred so as to obtain linear chains having a preponderance of terminal hydroxyl groups. Suitable polyester intermediates also include various lactones such as polycaprolactone typically made from e-caprolactone and a bifunctional initiator such as diethylene glycol. The dicarboxylic acids of the desired polyester can be aliphatic, cycloaliphatic, aromatic, or combinations thereof. Suitable dicarboxylic acids which may be used alone or in mixtures generally have a total of from 4 to 15 carbon atoms and include: succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, dodecanedioic, isophthalic, terephthalic, cyclohexane dicarboxylic, and the like. Anhydrides of the above dicarboxylic acids such as phthalic anhydride, tetrahydrophthalic anhydride, or the like, can also be used. Adipic acid is the preferred acid. The glycols which are reacted to form a desirable polyester intermediate can be aliphatic, aromatic, or combinations thereof, and have a total of from 2 to 12 carbon atoms, and include ethylene glycol, neopentyl glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-l,3-propanediol, 1,4- cyclohexanedimethanol, decamethylene glycol, dodecamethylene glycol, and the like. 1,4-butanediol and mixtures with neopentyl glycol are the preferred glycol. [0067] U.S. Patent No. 4,131,731 is hereby incorporated by reference for its disclosure of hydroxyl terminated polycarbonates and their preparation. Such polycarbonates are linear and have terminal hydroxyl groups with essential exclusion of other terminal groups. The essential reactants are glycols and carbonates. Suitable glycols are selected from cycloaliphatic and aliphatic diols containing 4 to 40, and preferably 4 to 12 carbon atoms, and from polyoxyalkylene glycols containing 2 to 20 alkoxy groups per molecular with each alkoxy group containing 2 to 4 carbon atoms. Diols suitable for use in exemplary embodiments include aliphatic diols containing 4 to 12 carbon atoms such as butanediol-1,4, pentanediol-1,4, neopentyl glycol, hexanediol- 1,6, 2,2,4-trimethylhexanediol-l,6, decanediol-1,10, hydrogenated dilinoleylglycol, hydrogenated dioleylglycol; and cycloaHphatic diols such as cyclohexanediol-1,3, dimethylolcyclohexane-1,4, cyclohexanediol-1,4, dimethylolcyclohexane-1,3, 1,4- endomethylene-2-hydroxy-5-hydroxymethyl cyclohexane, and polyalkylene glycols. The diols used in the reaction may be a single diol or a mixture of diols depending on the properties desired in the finished product. [0068] Polycarbonate intermediates which are hydroxyl terminated are generally those known in the art and in the literature. Suitable carbonates are selected from alkylene carbonates composed of a 5 to 7 membered ring having the following general formula (Formula Removed) where R is a saturated divalent radical containing 2 to 6 linear carbon atoms. Suitable carbonates for use herein include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-ethylene carbonate, 1,3-pentylene carbonate, 1,4-pentylene carbonate, 2,3- pentylene carbonate, and 2,4-pentylene carbonate. [0069] Also, suitable herein are dialkylcarbonates, cycloaHphatic carbonates, and diarylcarbonates. The dialkylcarbonates can contain 2 to 5 carbon atoms in each alkyl group and specific examples thereof are diethylcarbonate and dipropylcarbonate. CycloaHphatic carbonates, especially dicycloaliphatic carbonates, can contain 4 to 7 carbon atoms in each cyclic structure, and there can be one or two of such structures. When one group is cycloaHphatic, the other can be either alkyl or aryl. On the other hand, if one group is aryl, the other can be alkyl or cycloaHphatic. Preferred examples of diarylcarbonates, which can contain 6 to 20 carbon atoms in each aryl group, are diphenylcarbonate, ditolylcarbonate, and dinaphthylcarbonate. [0070] The reaction is carried out by reacting a glycol with a carbonate, preferably an alkylene carbonate in the molar range of 10:1 to 1:10, but preferably 3:1 to 1:3 at a temperature of 100°C to 300°C and at a pressure in the range of 0.1 to 300 mm of mercury in the presence or absence of an ester interchange catalyst, while removing low boiling glycols by distillation. [0071] More specifically, the hydroxyl terminated polycarbonates are prepared in two stages. In the first stage, a glycol is reacted with an alkylene carbonate to form a low molecular weight hydroxyl terminated polycarbonate. The lower boiling point glycol is removed by distillation at 100°C to 300°C, preferably at 150°C to 250°C, under a reduced pressure of 10 to 30 mm Hg, preferably 50 to 200 mm Hg. A fractionating column is used to separate the by-product glycol from the reaction mixture. The by- product glycol is taken off the top of the column and the unreacted alkylene carbonate and glycol reactant are returned to the reaction vessel as reflux. A current of inert gas or an inert solvent can be used to facilitate removal of by-product glycol as it is formed. When amount of by-product glycol obtained indicates that degree of polymerization of the hydroxyl terminated polycarbonate is in the range of 2 to 10, the pressure is gradually reduced to 0.1 to 10 mm Hg and the unreacted glycol and alkylene carbonate are removed. This marks the beginning of the second stage of reaction during which the low molecular weight hydroxyl terminated polycarbonate is condensed by distilling off glycol as it is formed at 100°C to 300°C, preferably 150°C to 250°C and at a pressure of 0.1 to 10 mm Hg until the desired molecular weight of the hydroxyl terminated polycarbonate is attained. Molecular weight (Mn) of the hydroxyl terminated polycarbonates can vary from about 500 to about 10,000 but in a preferred embodiment, it will be in the range of 500 to 2500. [0072] If a polyether crosslinking agent is desired, it is made from a hydroxyl terminated polyether intermediate as described above for making the TPU polymer and is reacted with a polyisocyanate to form a pre-polymer. [0073] The crosslinking agents have a number average molecular weight (Mn) of from about 1,000 to about 10,000, preferably from about 1,200 to about 4,000 and more preferably from about 1,500 to about 2,800. Crosslinking agents with a Mn above about 1500 give better set properties. [0074] The weight percent of crosslinking agent used with the TPU polymer is from about 5.0% to about 20%, preferably about 8.0% to about 15%,and more preferably from about 10% to about 13% The percentage of crosslinking agent used is weight percent based upon the total weight of TPU polymer and crosslinking agent. [0075] The exemplary melt spinning process to make TPU fibers involves feeding a preformed TPU polymer, usually which is melted in the extruder and the crosslinking agent is added continuously downstream near the point where the TPU melt exits the extruder or after the TPU melt exits the extruder. The crosslinking agent can be added to the extruder before the melt exits the extruder or after the melt exits the extruder. If added after the melt exits the extruder, the crosslinking agent needs to be mixed with the TPU melt using static or dynamic mixers to assure proper mixing of the crosslinking agent into the TPU polymer melt. After, exiting the extruder and mixer, the melted TPU polymer with crosslinking agent flows into a manifold. The manifold divides the melt stream into different streams, where each stream is fed to a plurality of spin pack assemblies. Usually, there is a melt pump for each different stream flowing from the manifold, with each melt pump feeding several spin pack assemblies. Each spin pack assembly may be of the type previously described or may have alternative structure. [0076] The TPU melt material is forced by elevated pressure through the spin pack assembly and exits the spinneret plate in the form of a fiber. The size of the hole in the spinneret plate is based on the desired size (denier) of the fiber. The fiber is drawn or stretched as it leaves the spin pack assembly and is cooled before winding onto bobbins. The fibers are stretched by winding the bobbins at a higher speed than that of fiber exiting the spin pack assembly. For the melt spun TPU fibers, the bobbins are usually wound at a rate of 4 to 6 times the speed of the fiber exiting the spin pack assembly, but can be wound slower or faster depending on the particular equipment. Typical bobbin winding speeds can vary from 100 to 3000 meters per minute, but more typical speeds are 300 to 1200 meters per minute for TPU melt spun fibers. Finish oils, such as silicone oils, are usually added to the surface of the fibers after cooling and just prior to being wound into bobbins. [0077] An important aspect of the exemplary melt spinning process is the mixing of the TPU polymer melt with the crosslinking agent. Proper uniform mixing is important to achieve uniform fiber properties and to achieve long run times without experiencing fiber breakage. The mixing of the TPU melt and crosslinking agent should be a method which achieves plug-flow, i.e., first in first out. The proper mixing can be achieved with a dynamic mixer or a static mixer. Static mixers are more difficult to clean; therefore, a dynamic mixer is preferred. A dynamic mixer which has a feed screw and mixing pins is the preferred mixer. U.S. Patent 6,709,147, which is incorporated herein by reference, describes such a mixer and has mixing pins which can rotate. The mixing pins can also be in a fixed position, such as attached to the barrel of the mixer and extending toward the centerline of the feed screw. The mixing feed screw can be attached by threads to the end of the extruder screw and the housing of the mixer can be bolted to the extruder machine. The feed screw of the dynamic mixer should be a design which moves the polymer melt in a progressive manner with very little back mixing to achieve plug-flow of the melt. The L/D of the mixing screw should be from over 3 to less than 30, preferably from about 7 to about 20, and more preferably from about 10 to about 12. [0078] The temperature in the mixing zone where the TPU polymer melt is mixed with the crosslinking agent is from about 200°C to about 240°C, preferably from about 210°C to about 225°C. These temperatures are necessary to get the reaction while not degrading the polymer. [0079] The TPU formed is reacted with the crosslinking agent during the fiber spinning process to give a molecular weight (Mw) of the TPU in fiber form of from about 200,000 to about 800,000, preferably from about 2.50,000 to about 500,000, more preferably from about 300,000 to about 450,000. The reaction in the fiber spinning process between the TPU and the crosslinking agent at the point where the TPU exits the spin pack assembly should be above 20%, preferably from about 30% to about 60%, and more preferably from about 40% to about 50%. Typical prior art TPU melt spinning reaction between the TPU polymer and the crosslinking agent is less than 20%> and usually about 10-15% reaction. The reaction is determined by the disappearance of the NCO groups. The higher % reaction of the exemplary embodiment improves melt strength thus allowing a higher spinning temperature which improves the spinnability of the TPU. The fibers are normally aged in an oven on the bobbins to fully complete the reaction and thus all of the NCO groups disappear in the fiber as used in garments. [0080] The spinning temperature (the temperature of the polymer melt in the spin pack assembly) should be higher than the melting point of the polymer, and preferably from about 10°C to about 20°C above the melting point of the polymer. The higher the spinning temperature one can use, generally the better the spinning. However, if the spinning temperature is too high, the polymer can degrade. Therefore, from about 10°C to about 20°C above the melting point of the TPU polymer, is the optimum for the exemplary embodiment for achieving a balance of good spinning without degradation of the polymer. If the spinning temperature is too low, polymer can solidify in the spinneret and cause fiber breakage. The spinning temperature for the fibers produced in exemplary embodiments is greater than 200°C and preferably from about 205°C to about 220°C. [0081] An important aspect of making melt spun TPU fibers is the time one can run the process continuously without stopping. The necessity to stop the process is usually a result of fiber breaking. Fiber breaking occurs when the pressure at the inlet of the spin pack assembly increases to an unacceptable level. When the pressure reaches about 140 to 200 Kg force per square cm., fiber breakage will usually occur. Pressure buildup can occur for several reasons such as improper mixing leading to formation of products due to self reaction of the crosslinking agent causing partial blockage of the small exit hole in the spinneret for the fiber. The exemplary embodiment allows for much longer run times before exceeding harmful pressure build-up resulting in fiber breakage. [0082] The following examples show advantages of the exemplary spin pack assembly relative to a conventional spin pack assembly. The spin pack assembly of the exemplary embodiment was evaluated against the prior art spin pack assembly. The evaluation was conducted by melt spinning a thermoplastic polyurethane (TPU) polymer. The TPU polymer used was made by reacting a polyether hydroxyl terminated intermediate (a blend of 2000 Mn PTMEG and 1000 Mn PTMEG), a glycol aromatic chain extender [a blend of benzene glycol (HQEE) and hydroxyl ethyl resorcinol (HER)], and a diisocyanate (MDI). The three components (polyether intermediate, glycol chain extender, and diisocyanate) were reacted in a twin screw extruder using the one-shot process at 200°C. The TPU polymer was palletized and used in Examples 1 and 2 below to spin fibers. The exit at which the fiber was produced by the spin pack assembly was axially recessed about 15.5 mm from the opening of the body of the spin pack assembly. Example 1 (Comparative) [0083] The TPU polymer described above was used to melt spin 40 denier fibers. The TPU polymer pellets were melted in an extruder and the polymer melt was mixed with a polyester prepolymer crosslinking agent (Hyperlast® 5255) in a dynamic mixer. The TPU melt containing the crosslinking agent was then fed to the prior art spin pack assembly and 40 denier melt spun fibers were produced. A silicon finish oil was applied to the fibers and they were wound onto bobbins at a speed of 600 meters per minute. After continuous running for 60 hours, the pressure in the spin pack showed an increase over the beginning pressure of 81.2% and fibers started to break. The run was terminated because of fiber breakage. Example 2 [0084] In this Example, the spin pack assembly of the described exemplary embodiment was used to make 40 denier fibers. The same TPU polymer and the same crosslinking agent were used and the same melt spinning process was used as in Example 1. The only difference was that the spin pack assembly of the exemplary embodiment was used in place of the prior art spin pack assembly. After continuous running for 120 hours, the pressure in the spin pack showed an increase of only 9.5% over the initial pressure. The run was terminated after 120 hours because all material was consumed. [0085] Physical property tests on the fibers made by Comparative Example 1 and Example 2 showed that the fibers made by Example 2 had a lower 100% modulus indicating that the recessed exit of the fibers from the spin pack assembly allowed the fibers to cool slower, thus improving their properties for kitting and weaving. [0086] The Examples show that the spin pack assembly of the exemplary embodiment has major advantages in making elastic fibers, such as TPU. By dramatically increasing the run time before experiencing fiber breakage because of excess pressure build-up, the melt spinning process is more economical and there is less waste from scrap material generated as a result of fiber breakage. The properties of the TPU fibers are also improved resulting in better knitting and weaving the fibers into garments. [0087] Melt spun TPU fibers can be made in a variety of denier. Denier is a term in the art designating the fiber size. Denier is the weight in grams of 9000 meters of fiber length. Typical melt spun TPU fibers are made in a denier size less than 240, more typical from 10 to less than 240 denier size, with 20 and 40 denier being a popular size. [0088] The elastic TPU fibers are used to combine by knitting or weaving with other fibers such as natural and synthetic fibers to make various articles of clothing. The TPU fibers can be dyed various colors. [0089] The melt spun elastic TPU fibers of exemplary embodiments are normally combined by knitting or weaving with other fibers, such as cotton, nylon or polyester to make various end use articles, including clothing garments. The weight % of the melt spun elastic fibers in the end use application can vary depending on the desired elasticity. For example, woven fabrics have from 1-8 wt.%, underwear from 2-5 wt.%, bathing suits and sportswear from 8-30 wt.%, foundation garments from 10-45 wt.%, and medical hose from 35-60 wt.% of the elastic melt spun fibers with the remaining amount being another type of non-elastic fiber. [0090] The exemplary configuration of the exemplary spin pack assembly provides for the fiber produced to cool more slowly which has been found to decrease the 100% modulus. This decrease in modulus allows the fiber to perform better in knitting operations, such as circular knitting. [0091] The exemplary spin pack assembly produces improved material flow properties for the polymer, which allows for greater run time before experiencing problems, such as fiber breakage. [0092] While in accordance with the Patent Statutes, the best mode and preferred embodiment has been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims. CLAIMS What is claimed is: 1. Apparatus comprising: a spin pack assembly operative to receive a fluid thermoplastic material generally free of lumps therein, and to output a single fiber of the material, wherein the material reacts to form lumps therein generally within a reaction time after the material is received within the spin pack assembly, the assembly including: ' . . a cylindrical body, the cylindrical body extending along a central axis, and wherein the body includes a first axial end and a second axial portion axially disposed from the first axial end; an inlet adjacent the second axial portion, wherein the inlet is operative to receive the material at elevated pressure; a spinneret plate adjacent the first axial end, wherein the spinneret plate includes one axially positioned fiber opening, wherein the opening is operative to output the single fiber; a cavity area within the body, wherein the cavity area is fluidly intermediate of the inlet and the fiber opening; a breaker plate, wherein the breaker plate extends in the cavity area, and wherein the breaker plate includes a plurality of apertures therethrough, wherein each of the apertures is operative to provide material flow therethrough, and wherein the apertures are positioned to provide material flow through the cavity area such that a residence time that material is within the cavity area is less than the reaction time generally throughout the entire cavity area. 2. The apparatus according to claim 1 wherein the apertures are positioned to provide a first-in/first-out flow generally throughout the entire cavity area. 3. The apparatus according to claim 2 wherein the plurality of apertures are positioned to provide greater material flow with increasing radial distance from the axis in the cavity area. 4. The apparatus according to claim 3 wherein the plurality of apertures each have greater cross-sectional area with increasing radial distance from the axis. 5. The apparatus according to claim 4 wherein the plurality of apertures are arranged iri a plurality of concentric circular patterns about the axis. 6. The apparatus according to claim 5 wherein all the apertures included in each concentric circular pattern have generally the same cross-sectional area. 7. The apparatus according to claim 6 wherein the breaker plate includes one axially aligned central aperture. 8. The apparatus according to claim 7 wherein each of plurality of apertures in a first concentric circular pattern closest to the axis, is disposed radially from the central aperture a first radial distance, and wherein the plurality of apertures in a second concentric circular pattern disposed radially outward and immediately adjacent the apertures in the first concentric circular pattern, are disposed radially outward from the apertures in the first concentric circular pattern a second radial distance, wherein the first radial distance is greater than the second radial distance. 9. The apparatus according to claim 8 wherein the breaker plate includes a third concentric circular pattern of apertures disposed radially outward from and immediately adjacent to the second concentric circular pattern of apertures, and wherein the plurality of apertures in the third concentric circular pattern of apertures are disposed radially outward from the apertures in the second concentric circular pattern a third radial distance, wherein the first radial distance is greater than the third radial distance. 10. The apparatus according to claim 9 wherein the cavity area is bounded adjacent the first axial end by a generally planar first annular surface. 11. The apparatus according to claim 10 wherein the cavity area is bounded adjacent the second axial portion by a generally planar second annular surface. 12. The apparatus according to claim 11 wherein the body includes an annular body opening adjacent the first axial end, wherein the body opening is generally aligned with the axis, and wherein the fiber opening in the spinneret plate includes an exit at which the fiber is output, and wherein the.exit is disposed axially inward within the body relative to the body opening at least 5 mm. 13. The apparatus according to claim 12 and further comprising a screen, wherein the screen extends in the cavity area, and wherein the screen is positioned intermediate of the inlet and the breaker plate. 14. The apparatus according to claim 13 wherein the spin pack assembly further includes: a transport channel piece, and a compression nut, wherein the transport channel piece includes a annular portion and an axially centered cylindrical projection portion, wherein the inlet extends through the annular portion and the cylindrical projection portion, and wherein the compression nut includes an external annular threaded portion and an axially centered access opening, wherein the annular threaded portion is operatively releasibly engaged with the body, and wherein the cylindrical projection portion extends in the access opening. 15.. The apparatus according to claim 14 wherein the material comprises thermoplastic polyurethane (TPU) polymer. 16. The apparatus according to claim 15 wherein the exit is disposed axially inward within the body relative to the body opening about 15.5 mms. 17. The apparatus according to claim 16 wherein the TPU within the cavity area is at least 200°C. 18. The apparatus according to claim 1 wherein the breaker plate includes a plurality of apertures, wherein the apertures are arranged in a plurality of concentric circular patterns about the axis, wherein the apertures in each concentric circular pattern have greater cross-sectional area with increasing radial distance from the axis. 19. The apparatus according to claim 18 wherein the breaker plate includes a central aperture aligned with the axis. 20. The apparatus according to claim 19 wherein the central aperture has a smaller cross-sectional area than apertures in at least one of the plurality of concentric circular patterns. 21. The apparatus according to claim 19 wherein the plurality of concentric circular patterns include a first concentric circular pattern and a second concentric circular pattern, wherein the plurality of apertures in the first concentric circular pattern are radially disposed a first distance from the central aperture, and wherein the apertures in the second concentric circular pattern are disposed radially outward a second distance from the apertures in the first concentric circular pattern, and wherein the first radial distance is greater than the second radial distance. 22. The apparatus according to claim 18 wherein the plurality of apertures include apertures in at least three concentric circular patterns. 23. The apparatus according to claim 1 wherein the body includes a body opening extending about the axis adjacent the first axial end, and wherein the fiber opening includes an exit, wherein the fiber is output at the exit, and wherein the exit is disposed axially inward relative to the body opening at least 5 mm. 24. The apparatus according to claim 23 wherein the material comprises thermoplastic polyurethane (TPU) polymer, and wherein the exit is disposed axially inward relative to the body opening about 15.5 mm. 25. The apparatus comprising: an assembly operative to receive'a fluid thermoplastic polyurethane (TPU) polymer material generally free of lumps-, and to output a single fiber of the material, wherein the material reacts to form lumps therein generally within a reaction time after the material is received within the assembly, the assembly including: a body, wherein the body includes a cavity area, wherein the cavity area has a cavity cross-sectional area; an inlet in fluid communication with the cavity area wherein the inlet is operative to receive the material at elevated pressure, and wherein the inlet has an inlet cross-sectional area, wherein the inlet cross-sectional area is less than the cavity cross-sectional area; a fiber outlet in fluid connection with the cavity area, wherein the fiber outlet is operative to output the single fiber; at least one member extending in the cavity area, wherein the at least one member is operative to direct material flow in the cavity area, wherein the at least one member is operative to maintain first-in/first-out flow generally throughout the entire cavity area. 26. The apparatus according to claim 25 wherein the body includes an annular body opening disposed away from the inlet, and wherein the fiber outlet includes an exit, wherein the single fiber passes from the fiber outlet at the exit, and wherein the exit is recessed inwardly relative to the body opening at least 5 mm. 27. The apparatus according to claim 25 wherein the body includes an annular body opening disposed away from the inlet, and wherein the fiber outlet includes an exit, and wherein the single fiber passes from the fiber outlet at the exit, and wherein exit is recessed inwardly relative to the body opening about 15.5 mm. 28. The apparatus according to claim 26 wherein the at least one member comprises a plate including a plurality of apertures therethrough. 29. The apparatus according to claim 28, wherein the assembly includes: a generally cylindrical body, wherein the body extends along a central axis, and wherein the body has first axial end and a second portion axially disposed from the first axial end; wherein the inlet is axially centered adjacent the second portion, and the body opening is axially centered adjacent the first axial end; and wherein the cavity area comprises a generally cylindrical area within the body, and wherein the plate including the plurality of apertures extends in the cavity area; and further including a spinneret plate, wherein the spinneret plate includes the fiber outlet. 30. The apparatus according to claim 29 wherein the plurality of apertures in the plate are arranged to provide greater material flow with increasing radial distance from the axis. 31. The apparatus according to claim 30 wherein the plate includes a plurality of apertures arranged in at least one arcuate pattern. 32. The apparatus according to claim 31 wherein the at least one arcuate pattern includes apertures having increased cross-sectional area with increased radial distance from the axis. 33. The apparatus according to claim 32 wherein the at least one arcuate pattern includes a plurality of concentric circular patterns of apertures, wherein the apertures in each concentric circular pattern are generally the same size. 34. The apparatus according to claim 33 wherein the plate includes a central aperture aligned with the axis. 35. The apparatus according to claim 34 wherein the plurality of concentric circular patterns includes a first concentric circular pattern, wherein apertures in the first concentric circular pattern are disposed radially closest to the central aperture, and wherein the plurality of concentric circular patterns includes a second concentric circular pattern, wherein the apertures in the second concentric circular pattern are disposed radially outward relative to the apertures in the first concentric circular pattern, and wherein no apertures in other concentric circular patterns extend radially intermediate of the apertures in the first concentric circular pattern and the apertures in the second concentric circular pattern, and wherein apertures in the first concentric circular pattern are disposed from the central aperture a first radial distance, and wherein apertures in the second concentric circular pattern are disposed from apertures in the first concentric circular pattern a second radial distance, and wherein the first radial distance is greater than the second radial distance. 36. The apparatus according to claim 35 wherein the plate includes at least three concentric circular patterns of apertures. 37. The apparatus according to claim 36 wherein the assembly comprises a spin pack assembly, and wherein the spin pack assembly includes a transport channel piece, wherein the transport channel piece includes the inlet, and further including a compression nut, wherein the compression nut includes an external annular threaded portion and an axially centered access opening, and wherein the annual threaded portion engages the body, and wherein the transport channel piece extends in the access opening.

Full Text

SPIN PACK ASSEMBLY
FIELD OF THE INVENTION
[0001] The present invention relates to devices and methods for use in melt spinning
of elastomeric fibers, such as polyurethane fibers. Exemplary embodiments relate to a
spin pack assembly used to produce such fibers.
BACKGROUND OF THE INVENTION
[0002] The vast majority of thermoplastic polyurethane (TPU) fibers are made by a
dry spinning process involving dissolving the TPU in a solvent. Melt spinning TPU
fibers has been gaining in use in recent years. Melt spinning does not involve the use of
a solvent, and therefore is more environmentally friendly.
[0003] Melt spinning TPU fibers involves feeding TPU polymer into an extruder and
from the extruder to a spinneret where the fiber exits the spinneret. Polymers, such as
TPU, tend to crystallize or crosslink so as to form lumps if they remain in melt
processing equipment for too long. This is especially the case where crosslinking agents
are added to the TPU prior to being fed to the spinneret. These early formed crystallized
polymer and/or crosslinked polymer lumps may find their way through the spinneret and
cause defects or undesirable properties in the fiber. Fiber breakage can also result.
Lumps of crystallized and/or crosslinked material may also accumulate in the cavities
upstream of the fiber opening. This can result in excessive back pressure and reduced
material flow. Back pressure can build up to the point where fiber can no longer be
produced. This requires shutting down the process of manufacturing the fiber and
cleaning the equipment to remove the blocking material.
[0004] Another problem that can occur with melt spinning TPU fibers is that the
modulus of the fibers can be too high for circular knitting applications.
[0005] Thus, there exists a need for improvements in melt spinning of elastomeric
fibers.
SUMMARY OF THE INVENTION
[0006] It is an object of an exemplary embodiment to melt spin elastic fibers, such as
TPU, in a process that gives long run times.

[0007] It is another object of an exemplary embodiment to make a melt spun TPU
fiber with lower modulus, as measured at 100% elongation.
[0008] It is another object of an exemplary embodiment to provide a spin pack
assembly that produces a fiber with more desirable properties, provides faster running
rates, and achieves longer run times.
[0009] Further objects of exemplary embodiments will be made apparent in the
detailed description herein and the appended claims.
[0010] These objects are accomplished in an exemplary embodiment by using a spin
pack assembly to produce a fiber. The spin pack assembly includes a breaker plate
comprising a circular metal plate with a plurality of apertures of different size diameters.
The aperture in the center of the breaker plate is the smallest hole and the apertures are
progressively larger the farther they are from the center of the breaker plate. The
apertures the greatest distance from the center have the largest diameter. This
configuration of the holes in the breaker plate provides for first-in/first-out flow of
material throughout generally the entire cavity within the spin pack assembly. The flow
in the exemplary embodiment provides for increased flow in areas radially disposed from
a central axis of the spin pack assembly. In the exemplary embodiment this approach
generally avoids material being resident within the spin pack assembly for a time that is
less than a reaction time after which numerous lumps of cross linked and/or crystallized
material form within the assembly. The approach of the exemplary embodiment
provides desirable flow properties that produce fewer defects in the fiber. In addition,
the exemplary structure of the spin pack assembly provides lower back pressure buildup
through longer running times which reduces process downtime and increases
productivity.
[0011] In the exemplary embodiment of the spin pack assembly, the spin pack
assembly has a generally cylindrical body with a body opening. The fiber is produced by
passing the material through a fiber opening in a spinneret plate. The fiber is produced at
an exit. The exit is disposed axially inward relative to the body opening. This structure
in the exemplary embodiment allows the fibers to cool more slowly relative to prior
designs. This results in lower modulus fiber and enables faster running rates.

BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional view of an exemplary spin pack assembly
including a breaker plate and a recessed spinneret plate fiber exit opening.
[0013] FIG. 2 is a top view of an exemplary breaker plate used in the assembly of
FIG1.
[0014] FIG. 3 is a top view of an exemplary prior art breaker plate.
[0015] FIG. 4 is an isometric view of an exemplary transport channel piece of the
exemplary assembly of FIG. 1.
[0016] FIG. 5 is an isometric view of an exemplary prior art transport channel piece.
[0017] FIG. 6 is an isometric view of a spacer and spinneret plate of an exemplary
embodiment.
[0018] FIG. 7 is an isometric view of a prior art spinneret plate.
[0019] FIG. 8 is an exploded view of the components in the exemplary spin pack
assembly within the body.
[0020] FIG. 9 is an isometric view of the components shown in FIG. 8 in an
assembled condition.
[0021] FIG. 10 is an isometric view of the cylindrical body of the exemplary spin
pack assembly showing the recessed fiber exit of an exemplary embodiment.
[0022] FIG. 11 is an isometric view showing a prior art spin pack assembly including
the fiber exit opening closer to the body exit.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Referring now to the drawings and particularly to FIG. 1 there is shown
therein a spin pack assembly (10) of an exemplary embodiment. The spin pack assembly
10 includes a generally cylindrical body 12. Body 12 extends along a central axis 14.
[0024] In the exemplary embodiment the body includes the body opening 16 at an
axial end thereof. Body opening 16 is of a smaller diameter than a bore 18 which
extends within the body. In the assembled position of the spin pack assembly the bore
includes a number of stacked components. These components in the exemplary
embodiment include an annular spacer 20. In the exemplary embodiment spacer 20 is
supported on an inward extending annular step 22 that bounds the bore.

[0025] A spinneret plate 24 is positioned adjacent to spacer 20. Spinneret plate 24
includes an axially positioned fiber opening 26 therein. Opening 26 produces a single
fiber from the exemplary spin pack assembly in a manner later discussed. The single
fiber is produced at an exit 28 from the fiber opening. The exit is disposed axially
inward of the body opening in the exemplary embodiment. The exemplary spinneret
plate 24 further includes a recess area therein which is bounded by a generally planar
annular surface 30. Planar annular surface 30 generally extends in surrounding relation
of the fiber opening 26.
[0026] An annular washer 32 is positioned in the assembly adjacent to the spinneret
plate 24. The annular washer 32 of the exemplary embodiment includes a central
opening that corresponds in diameter to the recess in the spinneret plate.
[0027] The exemplary assembly further includes a breaker plate 34. The breaker
plate 34 of the exemplary embodiment includes a plurality of apertures 36 therethrough.
As later discussed in detail the arrangement of apertures of the exemplary embodiment
provides material flow properties through the spin pack assembly that provides desirable
properties in producing the fiber.
[0028] Adjacent to the breaker plate 34 of the exemplary embodiment is a screen 38.
As best shown in FIG. 8 the screen of the exemplary embodiment includes a central
porous area and a peripheral annular solid area. Of course it should be understood that
this structure is exemplary and in other embodiments other approaches may be used.
[0029] The exemplary assembly further includes a transport channel piece 40. The
transport channel piece of the exemplary embodiment includes an annular portion 42 and
a cylindrical projection portion 44. An inlet 46 operative to receive fluid material
extends axially through the transport channel piece. In the exemplary embodiment the
transport channel piece includes a generally planar annular surface 48. In the exemplary
embodiment the generally planar annular surface extends in surrounding relation of the
inlet 46. The exemplary transport channel piece 40 also includes on the cylindrical
projection portion, a recess in which a compression washer 50 is positioned.
Compression washer 50 facilitates fluid tight connection with a conduit that supplies the
fluid material which forms the fiber.
[0030] The exemplary spin pack assembly further includes a compression nut 52.
Compression nut 52 of the exemplary embodiment includes an external annular threaded

portion 54. Threaded portion 54 is configured to engage mating threads positioned in a
corresponding portion of the bore 18. Compression nut 52 further includes an access
opening 56 which is axially centered therein. The cylindrical projecting portion of the
transport channel piece of the exemplary embodiment extends through the access
opening in the assembled condition of the spin pack assembly. It should be further
understood that the compression nut 52 may include apertures or other suitable structures
that facilitate rotation of the compression nut so as to hold the components of the spin
pack assembly in assembled stacked relation in the bore during use and for also enabling
the disassembly of the components as may be desirable for replacement, cleaning or
other purposes. Of course it should be understood* that these structures are exemplary
and in other embodiments other approaches may be used.
[0031] As is apparent from FIGS. 8 and 9, in the exemplary embodiment of the
assembly, the spacer, spinneret plate, washer, breaker plate, screen and transport channel
piece may be assembled in the bore 18. The assembled components are held in place
therein by tightening the compression nut 52. Further, when the components are
assembled the spin pack assembly includes a cavity area generally indicated 58, through
which the material flows between the inlet 46 and the exit 28. In addition as can be
appreciated, the components of the spin pack assembly may be removed for repair,
replacement or cleaning by loosening the compression nut 52 and removing the various
components from the bore. It should be further understood that these components are
exemplary and the principles described herein may be used with other components in
spin pack assemblies or other assemblies which are adapted for producing fibers of
thermoplastic materials.
[0032] FIG. 2 shows a top view of the exemplary breaker plate 34. As discussed, the
exemplary breaker plate 34 includes a plurality of apertures 36. In the exemplary
embodiment the apertures include an axially aligned central aperture 60. Central
aperture 60 in the assembled position of the spin pack assembly is aligned with the axis
14. The exemplary breaker plate 34 further includes apertures arranged in three
concentric circular patterns about the central aperture 60. Apertures 62 are included in
the first concentric circular pattern. Apertures 64 are included in the second concentric
circular pattern and are disposed radially outward relative to the apertures 62 in the first
concentric circular pattern. Apertures 66 in the third concentric circular pattern are

disposed radially outward of the apertures 64 in the second concentric circular pattern.
Of course it should be understood while in the exemplary embodiment three concentric
circular patterns are used, in other embodiments other approaches may be used.
[0033] In exemplary embodiments the apertures 62 in the first concentric circular
pattern are of a smaller effective diameter for purposes of material flow and have a
smaller cross-sectional area than the apertures 64 in the second concentric circular
pattern. Likewise, in the exemplary embodiment the apertures 66 in the third concentric
circular pattern have a greater diameter and cross-sectional area than the apertures 64 in
the second concentric circular pattern.
[0034] Further, in the exemplary embodiment the. radial distance from the central
aperture 60 to the apertures 62 in the first concentric circular pattern, is a greater radial
distance than the radial distance between the apertures 62 and the apertures 64, and is
also a greater radial distance than between the apertures 64 and the apertures 66. This
configuration in the exemplary embodiment provides flow properties which have proven
desirable for purposes of producing fibers of the exemplary embodiment.
[0035] During operation of the exemplary embodiment the plurality of apertures
provide a greater material flow with increasing radial distance from the axis 14. This
approach provides for a desirable flow pattern within the cavity area 58. The aperture
arrangement provides a first-in/first-out flow generally throughout the entire cavity area.
This flow which can alternatively be referred to as plug flow, assures that generally the
polymer melt in the cavity area is not resident during operation for the reaction time that
would otherwise result in the production of crosslinked and/or crystalline material which
forms semi-solid lumps in the polymer melt. For purposes of this disclosure the term
"lumps" should be understood to include solid and semi-solid bodies which have a
consistency less fluid than the other material flowing through the cavity area. As
previously discussed, such lumps are undesirable, and may cause defects and undesirable
properties in the fiber which is produced. Such lumps within the cavity area can also
produce increased back pressure which impedes the flow of material through the spin
pack assembly to produce the fiber. Such reduced flow results in slower running speeds
and eventually stoppage of the production process so that the spin pack assembly can be
cleaned.

[0036] The principles employed in connection with the exemplary breaker plate 34
can be further appreciated from the pattern of apertures shown in the prior art breaker
plate 68 shown in FIG. 3. The prior art breaker plate 68 includes a uniform pattern of
apertures. This uniform pattern generally results in most material passing through the
central apertures and through the opening the spinneret plate to produce the fiber.
Material passing through other apertures moves more slowly and thus more material
remains within the spin pack assembly for a period of time that reaches the reaction time.
As a result, lumps form within the cavity area. These lumps operate to restrict flow
which results in increased back pressure and slower operating speeds. The formation of
such lumps also impacts the quality of the fiber material produced at the spinneret
opening. These undesirable aspects are reduced by applying the principles described
herein.
[0037] Although in an exemplary embodiment the arrangement of concentric circular
patterns of apertures is used to achieve desirable flow properties, in other embodiments
other approaches may be used. These may include for example, breaker plates which
include arcuate patterns of apertures to achieve desirable characteristics. These arcuate
patterns may include elongated slots or spirals that achieve flow characteristics that
produce the desirable results as described. In other embodiments spiral arrangements of
apertures including apertures of various shapes may be used. In still other embodiments
structures other than breaker plates may be employed so as to achieve the desired flow
properties. These flow properties can be achieved through the use of apertures, vanes,
weirs or other structures. Of course these approaches are exemplary and in other
embodiments other approaches may be used.
[0038] A further useful aspect of the exemplary spin pack assembly is the shape
associated with the cavity area 58. In the exemplary embodiment the cavity area is
axially bounded by the generally annular surfaces 48 and 30. These generally annular
surfaces provide advantages in the nature of maximizing flow rates and minimizing
surface area.
[0039] FIG. 4 shows the transport channel piece 40 of the exemplary embodiment.
The planar surface 48 surrounds the material inlet and during operation forces material to
flow radially outwardly as the material enters the recessed area therein at elevated
pressure. This structure helps to move the material through the transport channel piece

generally more quickly compared to the prior art structure 70 which is shown in FIG. 5.
As can be appreciated the prior transport channel piece 70 includes a more conical
chamber. The conical chamber increases the area and potential material residence time
within the cavity. The structure of the exemplary piece 40 is intended to minimize those
conditions which may result in undesirable lumps within the material. Similar principles
apply to the configuration of the planar annular surface 30 which surrounds the fiber
opening in the spinneret plate 34. Of course these approaches are exemplary and in other
embodiments other approaches may be used.
[0040] A further useful aspect of the exemplary embodiment of the spin pack
assembly is the configuration of the fiber exit from the spinneret plate relative to the .
body opening. In the exemplary embodiment the exit 28 of the axially positioned fiber
opening 26 is axially disposed inwardly relative to the flat annular surface 72 in which
. the body opening 16 extends. In the exemplary embodiment the fiber exit 28 is disposed
axially inwardly more than 5 millimeters (mm) in the body annular surface. Further in
the exemplary embodiment used in the production of TPU fiber, the exit is recessed 15.5
mm relative to the body annular surface. In alternative embodiments greater recesses
may be used. This recessed configuration allows the fiber to cool more slowly. This
results because during the critical period after the fiber first exits the opening in the
spinneret plate, the fiber remains surrounded by the hot body of the spin pack assembly.
Further, as the fiber passes out the exit it is surrounded within the recess by relatively
stagnant hot air that further facilitates slower cooling. This slowness to cool in the
exemplary embodiment results in a fiber having a lower modulus at 100% elongation.
This lower modulus is especially desirable when the fiber is to be used in circular
knitting processes such as to make fabric.
[0041] FIG. 10 shows the axial end of the spin pack assembly of an exemplary
embodiment with the exit 28 of the spinneret plate axially recessed inwardly relative to
the opening in the body. FIG. 11 contrasts the prior art approach in which the exit from
the spinneret plate was generally at the same level or only recessed slightly such as in the
range of 2 mm from the body annular surface. Similarly FIG. 6 shows an isometric view
of the spacer 20 which serves to recess the opening in the spinneret plate and the exit
therein, from the body opening. This is in contrast to the prior art spinneret plate 74
shown in FIG. 7.

[0042] As can be appreciated from a comparison to the exemplary embodiment to
the prior art, the exemplary embodiment slows the cooling of the fiber through the use of
recessed fiber exit and the surround body recess. This approach substantially improves
the properties of the fiber which is produced using the spin pack assembly of the
exemplary embodiment. Of course these structures are exemplary and in other
embodiments other approaches may be used.
[0043] In an exemplary embodiment the polymer material to be melt spun into
elastic fibers is fed to an extruder to melt the polymer. The melted polymer can
optionally be fed from the extruder and'mixed with a crosslinking agent and fed to a
manifold. If no crosslinking agent is used, the polymer melt is fed directly to a manifold.
The polymer flows from the manifold to a melt pump. The melt pump feds the polymer
to the spin pack assembly. The polymer melt enters the spin pack assembly through the
inlet 46. The polymer melt proceeds from the entrance 46 through the screen 38. The
screen 38 removes any foreign matter and unmelted polymer. The polymer melt material
proceeds through the screen 38 to the breaker plate 34. The polymer passes through the
apertures in the breaker plate to the spinneret plate 24. From the spinneret plate 24 a
fiber is formed at the exit 28 as the polymer melt is passed through the fiber opening 26
in the spinneret plate 24. The fiber is cooled and coated with finishing oil and wound
into bobbins.
[0044] The most desirable elastic fiber to use in this exemplary embodiment is a
lightly crosslinked thermoplastic polyurethane (TPU). The preferred TPU polymer will
be described below.
[0045] The preferred TPU embodiment is a polyether TPU. The TPU is made from a
blend of hydroxyl terminated intermediates reacted with a polyisocyanate and a hydroxyl
terminated chain extender.
[0046] It has been found that when using a polyether TPU polymer to make melt
spun fiber, a blend of hydroxyl terminated intermediates having different number
average molecular weights gives superior processing features for melt spinning fibers. It
has been found that if the blend of hydroxyl terminated intermediates is such that the
higher molecular weight intermediate blended with the lower molecular weight
intermediate gives a weighted average molecular weight of at least 1200 Daltons.
Preferably, from 1200 to 4000 Daltons, and more preferably from 1500 to 2500 Daltons,

the TPU can be melt spun for extended periods of time without excessive pressure
building up in the exemplary spin pack assembly. This avoids excessive pressure which
results in fiber breakage, thus requiring the melt spinning operation to be halted until the
spin pack can be cleaned.
[0047] To produce the melt-spun fibers according to an exemplary embodiment, it is
required to have a TPU made from a blend of at least two hydroxyl terminated
intermediates and a crosslinking agent. The blend of intermediates has a first polyether
intermediate as the major component and with a higher Mn than the second intermediate.
The second intermediate is selected from the group consisting of polyether, polyester,'
polycarbonate, polycaprolactone, and mixtures thereof; and the second intermediate has a
lower Mn than the first intermediate. Preferably, the second intermediate is also a
polyether. For simplicity, the embodiment will be described herein in terms of polyether
TPU having a blend of polyether intermediates. It should be recognized that the second
intermediate can be other than polyether intermediates, but must be present in lower
amounts and have a lower Mn than the first polyether intermediate.
[0048] The polyether TPU used can be made by reacting a blend of at least two
polyether hydroxyl terminated intermediates with a polyisocyanate and a chain extender.
[0049] Hydroxyl terminated polyether intermediates are polyether polyols derived
from a diol or polyol having a total of from 2 to 15 carbon atoms, preferably an alkyl diol
or glycol which is reacted with an ether comprising an alkylene oxide having from 2 to 6
carbon atoms, typically ethylene oxide or propylene oxide or mixtures thereof. For
example, hydroxyl functional polyether can be produced by first reacting propylene
glycol with propylene oxide followed by subsequent reaction with ethylene oxide.
Primary hydroxyl groups resulting from ethylene oxide are more reactive than secondary
hydroxyl groups and thus are preferred. Useful commercial polyether polyols include
poly(ethylene glycol) comprising ethylene oxide reacted with ethylene glycol,
poly(propylene glycol) comprising propylene oxide reacted with propylene glycol,
poly(tetramethyl glycol) comprising water reacted with tetrahydrofuran (PTMEG).
Polytetramethylene ether glycol (PTMEG) is the preferred polyether intermediate.
Polyether polyols further include polyamide adducts of an alkylene oxide and can
include, for example, ethylenediamine adduct comprising the reaction product of
ethylenediamine and propylene oxide, diethylenetriamine adduct comprising the reaction

product of diethylenetriamine with propylene oxide, and similar polyamide type
polyether polyols. Copolyethers can also be utilized in exemplary embodiments.
Typical copolyethers include the reaction product of THF and ethylene oxide or THF and
propylene oxide. These are available from BASF as Poly THF B, a block copolymer,
and poly THF R, a random copolymer. The various polyether intermediates generally
have a number average molecular weight (Mn), as determined by assay of the terminal
functional groups which is an average molecular weight greater than 700, such as from
about 700 to about 10,000, desirably from about 1000 to about 5,000, and preferably
from about 1000 to about 2500 Daltons.
[0050] Exemplary embodiments use a blend of two or more polyether intermediates,
with one polyether being a higher molecular weight than the other polyether. The lower
molecular weight polyether will have a molecular weight Mn of from 700 to 1500
Daltons while the higher molecular weight polyether will have a Mn from about 1500 to
about 4000 Daltons, preferably from about 1800 to about 2500 Daltons. The blend
should have a weighted average molecular weight of greater than 1200 Daltons,
preferably greater than 1500 Daltons. For example, a 1000 gram sample of a blend of
70% by weight of a 2000 Mn polyether and 30% by weight of a 1000 Mn polyether
would have a weighted average Mn of 1538 Daltons of the two components in the 1000
grams mixture. The 2000 Mn polyether component would have 0.35 moles (1000 x
0.7/2000). The 1000 Mn polyether component would have 0.3 moles (1000 x 0.3/1000).
The total moles would be 0.65 (0.35 + 0.3) moles in the 1000 gram sample and have a
weighted average Mn of (1000/0.65) or 1538 M„.
[0051] The weight ratio in the blend of the first polyether hydroxyl terminated
intermediate to the second hydroxyl terminated intermediate is from about 60:40 to about
90:10, and preferably from about 70:30 to 90:10. The amount of the first polyether
intermediate is greater than the amount of the second intermediate.
[0052] The second necessary ingredient to make the TPU polymer of this
embodiment is a polyisocyanate.
[0053] The polyisocyanates generally have the formula R(NCO)n where n is
generally from 2 to 4 with 2 being highly preferred inasmuch as the composition is a
thermoplastic. Thus, polyisocyanates having a functionality of 3 or 4 are utilized in very
small amounts, for example less than 5% and desirably less than 2% by weight based

upon the total weight of all polyisocyanates, inasmuch as they cause crosslinking. R can
be aromatic, cycloaliphatic, and aliphatic, or combinations thereof generally having a
total of from 2 to about 20 carbon atoms. Examples of suitable aromatic diisocyanates
include diphenyl methane-4, 4'-diisocyanate (MDI), Hi2 MDI, m-xylylene diisocyanate
(XDI), m-tetramethyl xylylene diisocyanate (TMXDI), phenylene-1, 4-diisocyanate
(PPDI), 1,5-naphthalene diisocyanate (NDI), and diphenylmethane-3, 3'-dimethoxy-4, 4'-
diisocyanate (TODI). Examples of suitable aliphatic diisocyanates include isophorone
diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CHDI), hexamethylene diisocyanate
(HDI), l,6-diisocyanato-2,2,4,4-tetramethyl hexane (TMDI), 1,10-decane diisocyanate,
and trans-dicyclohexylmethane diisocyanate (HMDI). A highly preferred diisocyanate is
MDI containing less than about 3% by weight of ortho-para (2,4) isomer. A blend of
two or more polyisocyanates may be used.
[0054] The third necessary ingredient to make the TPU polymer is the chain
extender. Suitable chain extenders are lower aliphatic or short chain glycols having from
about 2 to about 10 carbon atoms and include for instance ethylene glycol, diethylene
glycol, propylene glycol, dipropylene glycol, tripropylene glycol, triethylene glycol, Cis-
trans-isomers of cyclohexyl dimethylol, neopentyl glycol, 1,4-butanediol, 1,6-hexandiol,
1,3-butanediol, and 1,5-pentanediol. Aromatic glycols can also be used as the chain
extender and are the preferred choice for high heat applications. Benzene glycol (HQEE)
and xylenene glycols are suitable chain extenders for use in making the TPU of this
invention. Xylenene glycol is a mixture of 1,4-di(hydroxymethyl) benzene and 1,2-
di(hydroxymethyl) benzene. Benzene glycol is the preferred aromatic chain extender
and specifically includes hydroquinone, i.e., bis(beta-hydroxyethyl) ether also known as
l,4-di(2-hydroxyethoxy) benzene; resorcinol, i.e., bis(beta-hydroxyethyl) ether also
known as l,3-di(2-hydroxyethyl) benzene; catechol, i.e., bis(beta-hydroxyethyl) ether
also known as 1,2-di(2-hydroxyethoxy) benzene; and combinations thereof. For high
heat resistant fibers, benzene glycol (HQEE) is the desired chain extender. Excellent
results are obtained by using HQEE together with an isomer of HQEE.
[0055] It is preferred to use a co-chain extender together with the chain extender
described above. The co-chain extender can be one of the materials described above as a
chain extender. The co-chain extender is preferably selected from a material capable of
reducing the crystallization rate of the TPU and eliminating high temperature melting

peaks of the TPU. Branched compounds, such as dipropylene glycol and neopentyl
glycol are excellent co-chain extenders. Also, for high heat applications, an isomer of
HQEE, such as hydroxyl ethyl resorcinol (HER), is a very effective co-chain extender.
When a co-chain extender is used, the level used is from about 2 to about 50 mole
percent, preferably 10 to 30 mole percent, of the total moles of the chain extender and the
co-chain extender.
[0056] A blend of two or more chain extenders can be used with a blend of two or
more co-chain extenders, if desired. However, for simplicity, usually one chain extender
is used with one co-chain extender.
[0057] The above three necessary ingredients (blend of different Mn polyether
intermediates, polyisocyanate, and chain extender) are preferably reacted in the presence
of a catalyst.
[0058] Generally, any conventional catalyst can be utilized to react the diisocyanate
with the polyether intermediates or the chain extender and the same is well known in the
art and in the literature. Examples of suitable catalysts include the various alkyl ethers or
alkyl thiol ethers of bismuth or tin wherein the alkyl portion has from 1 to about 20
carbon atoms with specific examples including bismuth octoate, bismuth laurate, and the
like. Preferred catalysts include the various tin catalysts such as stannous octoate,
dibutyltin dioctoate, dibutyltin dilaurate, and the like. The amount of such catalyst is
generally small such as from about 20 to about 200 parts per million based upon the total
weight of the polyurethane forming monomers.
[0059] The polyether TPU polymers of this invention can be made by any of the
conventional polymerization methods well known in the art and literature.
[0060] Thermoplastic polyurethanes of exemplary embodiments are preferably made
via a "one shot" process wherein all the components are added together simultaneously
or substantially simultaneously to a heated extruder and reacted to form the
polyurethane. The equivalent ratio of the diisocyanate to the total equivalents of the
hydroxyl terminated polyether intermediates and the diol chain extender is generally
from about 0.95 to about 1.10, desirably from about 0.97 to about 1.03, and preferably
from about 0.97 to about 1.00. It is preferred that the equivalent ratio is less than 1.0
such that the TPU has terminal hydroxyl groups to enhance the reaction with the
crosslinking agent during the fiber spinning process. The Shore A hardness of the TPU

formed should be from 65A to 95A, and preferably from about 75A to about 85A, to
achieve the most desirable melt spun fibers. Reaction temperatures utilizing urethane
catalyst are generally from about 175°C to about 245°C and preferably from about 180°C
to about 220°C. The molecular weight (Mw) of the thermoplastic polyurethane is
generally from about 25,000 to about 300,000 and desirably from about 50,000 to about
200,000 and preferably about 75,000 to about 150,000 as measured by GPC relative to
polystyrene standards. The preferred Mw is lower than the prior art recommends for the
TPU fiber, but the lower Mw allows for better mixing of the TPU with the crosslinking
agent to give excellent fiber spinning.
• [0061] The thermoplastic polyurethanes can also be prepared utilizing a pre-polymer
process. In the pre-polymer route, the hydroxyl terminated polyether intermediates are
reacted with generally an equivalent excess of one or more polyisocyanates to form a
pre-polymer solution having free or unreacted polyisocyanate therein. Reaction is
generally carried out at temperatures of from about 80°C to about 220°C and preferably
from about 150°C to about 200°C in the presence of a suitable urethane catalyst.
Subsequently, a selective type of chain extender as noted above is added in an equivalent
amount generally equal to the isocyanate end groups as well as to any free or unreacted
diisocyanate compounds. The overall equivalent ratio of the total diisocyanate to the
total equivalent of the hydroxyl terminated polyethers and the chain extender is thus
from about 0.95 to about 1.10, desirably from about 0.98 to about 1.05 and preferably
from about 0.99 to about 1.03. The equivalent ratio of the hydroxyl terminated
polyethers to the chain extender is adjusted to give 65A to 95A, preferably 75A to 85A
Shore hardness. The chain extension reaction temperature is generally from about 180°C
to about 250°C with from about 200°C to about 240°C being preferred. Typically, the
pre-polymer route can be carried out in any conventional device with an extruder being
preferred. Thus, the polyether intermediates are reacted with an equivalent excess of a
diisocyanate in a first portion of the extruder to form a pre-polymer solution and
subsequently the chain extender is added at a downstream portion and reacted with the
pre-polymer solution. Any conventional extruder can be utilized, with extruders
equipped with barrier screws having a length to diameter ratio of at least 20 and
preferably at least 25. The prepolymer method can reduce high temperature melting

peaks of the TPU and eliminate the need for a co-chain extender as described in the one-
shot process above.
[0062] Useful additives can be utilized in suitable amounts and include opacifying
pigments, colorants, mineral fillers, stabilizers, lubricants, UV absorbers, processing
aids, and other additives as desired. Useful opacifying pigments include titanium
dioxide, zinc oxide, and titanate yellow, while useful tinting pigments include carbon
black, yellow oxides, brown oxides, raw and burnt sienna or umber, chromium oxide
green, cadmium pigments, chromium pigments, and other mixed metal oxide and organic
pigments. Useful fillers include diatomaceous earth (superfloss) clay, silica, talc, mica,
wallostonite, barium sulfate,, and calcium carbonate. If desired, useful stabilizers such as
antioxidants can be used and include phenolic antioxidants, while useful photostabilizers
include organic phosphates, and organotin thiolates (mercaptides). Useful lubricants
include metal stearates, paraffin oils and amide waxes. Useful UV absorbers include 2-
(2'-hydroxyphenol) benzotriazoles and 2-hydroxybenzophenones.
[0063] Plasticizer additives can also be utilized advantageously to reduce hardness
without affecting properties.
[0064] During the melt spinning process, the TPU polymer described above is lightly
crosslinked with a crosslinking agent. The crosslinking agent is a pre-polymer of a
hydroxyl terminated intermediate that is a polyether, polyester, polycarbonate,
polycaprolactone, or mixture thereof reacted with a polyisocyanate. A polyester or
polyether is the preferred hydroxyl terminated intermediate to make the crosslinking
agent. The crosslinking agent, pre-polymer, will have an isocyanate functionality of
greater than about 1.0, preferably from about 1.0 to about 3.0, and more preferably from
about 1.8 to about 2.2. It is particularly preferred if both ends of hydroxyl terminated
intermediate is capped with an isocyanate, thus having an isocyanate functionality of 2.0.
[0065] The polyisocyanate used to make the crosslinking agent are the same as
described above in making the TPU polymer. A diisocyanate, such as MDI, is the
preferred diisocyanate.
[0066] The hydroxyl terminated polyester intermediate used to make the crosslinking
agent is generally a linear or branched polyester having a number average molecular
weight (Mn) of from about 500 to about 10,000, desirably from about 700 to about
5,000, and preferably from about 700 to about 4,000, an acid number generally less than

1.3 and preferably less than 0.8. The molecular weight is determined by assay of the
terminal functional groups and is related to the number average molecular weight. The
polymers are produced by (1) an esterification reaction of one or more glycols with one
or more dicarboxylic acids or anhydrides or (2) by transesterification reaction, i.e., the
reaction of one or more glycols with esters of dicarboxylic acids. Mole ratios generally
in excess of more than one mole of glycol to acid are preferred so as to obtain linear
chains having a preponderance of terminal hydroxyl groups. Suitable polyester
intermediates also include various lactones such as polycaprolactone typically made
from e-caprolactone and a bifunctional initiator such as diethylene glycol. The
dicarboxylic acids of the desired polyester can be aliphatic, cycloaliphatic, aromatic, or
combinations thereof. Suitable dicarboxylic acids which may be used alone or in
mixtures generally have a total of from 4 to 15 carbon atoms and include: succinic,
glutaric, adipic, pimelic, suberic, azelaic, sebacic, dodecanedioic, isophthalic,
terephthalic, cyclohexane dicarboxylic, and the like. Anhydrides of the above
dicarboxylic acids such as phthalic anhydride, tetrahydrophthalic anhydride, or the like,
can also be used. Adipic acid is the preferred acid. The glycols which are reacted to
form a desirable polyester intermediate can be aliphatic, aromatic, or combinations
thereof, and have a total of from 2 to 12 carbon atoms, and include ethylene glycol,
neopentyl glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol,
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-l,3-propanediol, 1,4-
cyclohexanedimethanol, decamethylene glycol, dodecamethylene glycol, and the like.
1,4-butanediol and mixtures with neopentyl glycol are the preferred glycol.
[0067] U.S. Patent No. 4,131,731 is hereby incorporated by reference for its
disclosure of hydroxyl terminated polycarbonates and their preparation. Such
polycarbonates are linear and have terminal hydroxyl groups with essential exclusion of
other terminal groups. The essential reactants are glycols and carbonates. Suitable
glycols are selected from cycloaliphatic and aliphatic diols containing 4 to 40, and
preferably 4 to 12 carbon atoms, and from polyoxyalkylene glycols containing 2 to 20
alkoxy groups per molecular with each alkoxy group containing 2 to 4 carbon atoms.
Diols suitable for use in exemplary embodiments include aliphatic diols containing 4 to
12 carbon atoms such as butanediol-1,4, pentanediol-1,4, neopentyl glycol, hexanediol-
1,6, 2,2,4-trimethylhexanediol-l,6, decanediol-1,10, hydrogenated dilinoleylglycol,

hydrogenated dioleylglycol; and cycloaHphatic diols such as cyclohexanediol-1,3,
dimethylolcyclohexane-1,4, cyclohexanediol-1,4, dimethylolcyclohexane-1,3, 1,4-
endomethylene-2-hydroxy-5-hydroxymethyl cyclohexane, and polyalkylene glycols.
The diols used in the reaction may be a single diol or a mixture of diols depending on the
properties desired in the finished product.
[0068] Polycarbonate intermediates which are hydroxyl terminated are generally
those known in the art and in the literature. Suitable carbonates are selected from
alkylene carbonates composed of a 5 to 7 membered ring having the following general
formula
(Formula Removed)
where R is a saturated divalent radical containing 2 to 6 linear carbon atoms. Suitable
carbonates for use herein include ethylene carbonate, trimethylene carbonate,
tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,3-butylene
carbonate, 1,2-ethylene carbonate, 1,3-pentylene carbonate, 1,4-pentylene carbonate, 2,3-
pentylene carbonate, and 2,4-pentylene carbonate.
[0069] Also, suitable herein are dialkylcarbonates, cycloaHphatic carbonates, and
diarylcarbonates. The dialkylcarbonates can contain 2 to 5 carbon atoms in each alkyl
group and specific examples thereof are diethylcarbonate and dipropylcarbonate.
CycloaHphatic carbonates, especially dicycloaliphatic carbonates, can contain 4 to 7
carbon atoms in each cyclic structure, and there can be one or two of such structures.
When one group is cycloaHphatic, the other can be either alkyl or aryl. On the other
hand, if one group is aryl, the other can be alkyl or cycloaHphatic. Preferred examples of
diarylcarbonates, which can contain 6 to 20 carbon atoms in each aryl group, are
diphenylcarbonate, ditolylcarbonate, and dinaphthylcarbonate.
[0070] The reaction is carried out by reacting a glycol with a carbonate, preferably an
alkylene carbonate in the molar range of 10:1 to 1:10, but preferably 3:1 to 1:3 at a
temperature of 100°C to 300°C and at a pressure in the range of 0.1 to 300 mm of
mercury in the presence or absence of an ester interchange catalyst, while removing low
boiling glycols by distillation.
[0071] More specifically, the hydroxyl terminated polycarbonates are prepared in
two stages. In the first stage, a glycol is reacted with an alkylene carbonate to form a
low molecular weight hydroxyl terminated polycarbonate. The lower boiling point
glycol is removed by distillation at 100°C to 300°C, preferably at 150°C to 250°C, under
a reduced pressure of 10 to 30 mm Hg, preferably 50 to 200 mm Hg. A fractionating
column is used to separate the by-product glycol from the reaction mixture. The by-
product glycol is taken off the top of the column and the unreacted alkylene carbonate
and glycol reactant are returned to the reaction vessel as reflux. A current of inert gas or
an inert solvent can be used to facilitate removal of by-product glycol as it is formed.
When amount of by-product glycol obtained indicates that degree of polymerization of
the hydroxyl terminated polycarbonate is in the range of 2 to 10, the pressure is gradually
reduced to 0.1 to 10 mm Hg and the unreacted glycol and alkylene carbonate are
removed. This marks the beginning of the second stage of reaction during which the low
molecular weight hydroxyl terminated polycarbonate is condensed by distilling off
glycol as it is formed at 100°C to 300°C, preferably 150°C to 250°C and at a pressure of
0.1 to 10 mm Hg until the desired molecular weight of the hydroxyl terminated
polycarbonate is attained. Molecular weight (Mn) of the hydroxyl terminated
polycarbonates can vary from about 500 to about 10,000 but in a preferred embodiment,
it will be in the range of 500 to 2500.
[0072] If a polyether crosslinking agent is desired, it is made from a hydroxyl
terminated polyether intermediate as described above for making the TPU polymer and
is reacted with a polyisocyanate to form a pre-polymer.
[0073] The crosslinking agents have a number average molecular weight (Mn) of
from about 1,000 to about 10,000, preferably from about 1,200 to about 4,000 and more
preferably from about 1,500 to about 2,800. Crosslinking agents with a Mn above about
1500 give better set properties.
[0074] The weight percent of crosslinking agent used with the TPU polymer is from
about 5.0% to about 20%, preferably about 8.0% to about 15%,and more preferably from
about 10% to about 13% The percentage of crosslinking agent used is weight percent
based upon the total weight of TPU polymer and crosslinking agent.
[0075] The exemplary melt spinning process to make TPU fibers involves feeding a
preformed TPU polymer, usually which is melted in the extruder and the crosslinking
agent is added continuously downstream near the point where the TPU melt exits the
extruder or after the TPU melt exits the extruder. The crosslinking agent can be added to
the extruder before the melt exits the extruder or after the melt exits the extruder. If
added after the melt exits the extruder, the crosslinking agent needs to be mixed with the
TPU melt using static or dynamic mixers to assure proper mixing of the crosslinking
agent into the TPU polymer melt. After, exiting the extruder and mixer, the melted TPU
polymer with crosslinking agent flows into a manifold. The manifold divides the melt
stream into different streams, where each stream is fed to a plurality of spin pack
assemblies. Usually, there is a melt pump for each different stream flowing from the
manifold, with each melt pump feeding several spin pack assemblies. Each spin pack
assembly may be of the type previously described or may have alternative structure.
[0076] The TPU melt material is forced by elevated pressure through the spin pack
assembly and exits the spinneret plate in the form of a fiber. The size of the hole in the
spinneret plate is based on the desired size (denier) of the fiber. The fiber is drawn or
stretched as it leaves the spin pack assembly and is cooled before winding onto bobbins.
The fibers are stretched by winding the bobbins at a higher speed than that of fiber
exiting the spin pack assembly. For the melt spun TPU fibers, the bobbins are usually
wound at a rate of 4 to 6 times the speed of the fiber exiting the spin pack assembly, but
can be wound slower or faster depending on the particular equipment. Typical bobbin
winding speeds can vary from 100 to 3000 meters per minute, but more typical speeds
are 300 to 1200 meters per minute for TPU melt spun fibers. Finish oils, such as silicone
oils, are usually added to the surface of the fibers after cooling and just prior to being
wound into bobbins.
[0077] An important aspect of the exemplary melt spinning process is the mixing of
the TPU polymer melt with the crosslinking agent. Proper uniform mixing is important
to achieve uniform fiber properties and to achieve long run times without experiencing
fiber breakage. The mixing of the TPU melt and crosslinking agent should be a method
which achieves plug-flow, i.e., first in first out. The proper mixing can be achieved with
a dynamic mixer or a static mixer. Static mixers are more difficult to clean; therefore, a
dynamic mixer is preferred. A dynamic mixer which has a feed screw and mixing pins is
the preferred mixer. U.S. Patent 6,709,147, which is incorporated herein by reference,
describes such a mixer and has mixing pins which can rotate. The mixing pins can also
be in a fixed position, such as attached to the barrel of the mixer and extending toward
the centerline of the feed screw. The mixing feed screw can be attached by threads to the
end of the extruder screw and the housing of the mixer can be bolted to the extruder
machine. The feed screw of the dynamic mixer should be a design which moves the
polymer melt in a progressive manner with very little back mixing to achieve plug-flow
of the melt. The L/D of the mixing screw should be from over 3 to less than 30,
preferably from about 7 to about 20, and more preferably from about 10 to about 12.
[0078] The temperature in the mixing zone where the TPU polymer melt is mixed
with the crosslinking agent is from about 200°C to about 240°C, preferably from about
210°C to about 225°C. These temperatures are necessary to get the reaction while not
degrading the polymer.
[0079] The TPU formed is reacted with the crosslinking agent during the fiber
spinning process to give a molecular weight (Mw) of the TPU in fiber form of from
about 200,000 to about 800,000, preferably from about 2.50,000 to about 500,000, more
preferably from about 300,000 to about 450,000. The reaction in the fiber spinning
process between the TPU and the crosslinking agent at the point where the TPU exits the
spin pack assembly should be above 20%, preferably from about 30% to about 60%, and
more preferably from about 40% to about 50%. Typical prior art TPU melt spinning
reaction between the TPU polymer and the crosslinking agent is less than 20%> and
usually about 10-15% reaction. The reaction is determined by the disappearance of the
NCO groups. The higher % reaction of the exemplary embodiment improves melt
strength thus allowing a higher spinning temperature which improves the spinnability of
the TPU. The fibers are normally aged in an oven on the bobbins to fully complete the
reaction and thus all of the NCO groups disappear in the fiber as used in garments.
[0080] The spinning temperature (the temperature of the polymer melt in the spin
pack assembly) should be higher than the melting point of the polymer, and preferably
from about 10°C to about 20°C above the melting point of the polymer. The higher the
spinning temperature one can use, generally the better the spinning. However, if the
spinning temperature is too high, the polymer can degrade. Therefore, from about 10°C
to about 20°C above the melting point of the TPU polymer, is the optimum for the
exemplary embodiment for achieving a balance of good spinning without degradation of
the polymer. If the spinning temperature is too low, polymer can solidify in the spinneret
and cause fiber breakage. The spinning temperature for the fibers produced in exemplary
embodiments is greater than 200°C and preferably from about 205°C to about 220°C.
[0081] An important aspect of making melt spun TPU fibers is the time one can run
the process continuously without stopping. The necessity to stop the process is usually a
result of fiber breaking. Fiber breaking occurs when the pressure at the inlet of the spin
pack assembly increases to an unacceptable level. When the pressure reaches about 140
to 200 Kg force per square cm., fiber breakage will usually occur. Pressure buildup can
occur for several reasons such as improper mixing leading to formation of products due
to self reaction of the crosslinking agent causing partial blockage of the small exit hole in
the spinneret for the fiber. The exemplary embodiment allows for much longer run times
before exceeding harmful pressure build-up resulting in fiber breakage.
[0082] The following examples show advantages of the exemplary spin pack
assembly relative to a conventional spin pack assembly. The spin pack assembly of the
exemplary embodiment was evaluated against the prior art spin pack assembly. The
evaluation was conducted by melt spinning a thermoplastic polyurethane (TPU) polymer.
The TPU polymer used was made by reacting a polyether hydroxyl terminated
intermediate (a blend of 2000 Mn PTMEG and 1000 Mn PTMEG), a glycol aromatic
chain extender [a blend of benzene glycol (HQEE) and hydroxyl ethyl resorcinol
(HER)], and a diisocyanate (MDI). The three components (polyether intermediate,
glycol chain extender, and diisocyanate) were reacted in a twin screw extruder using the
one-shot process at 200°C. The TPU polymer was palletized and used in Examples 1
and 2 below to spin fibers. The exit at which the fiber was produced by the spin pack
assembly was axially recessed about 15.5 mm from the opening of the body of the spin
pack assembly.
Example 1 (Comparative)
[0083] The TPU polymer described above was used to melt spin 40 denier fibers.
The TPU polymer pellets were melted in an extruder and the polymer melt was mixed
with a polyester prepolymer crosslinking agent (Hyperlast® 5255) in a dynamic mixer.
The TPU melt containing the crosslinking agent was then fed to the prior art spin pack
assembly and 40 denier melt spun fibers were produced. A silicon finish oil was applied
to the fibers and they were wound onto bobbins at a speed of 600 meters per minute.
After continuous running for 60 hours, the pressure in the spin pack showed an increase
over the beginning pressure of 81.2% and fibers started to break. The run was
terminated because of fiber breakage.
Example 2
[0084] In this Example, the spin pack assembly of the described exemplary
embodiment was used to make 40 denier fibers. The same TPU polymer and the same
crosslinking agent were used and the same melt spinning process was used as in
Example 1. The only difference was that the spin pack assembly of the exemplary
embodiment was used in place of the prior art spin pack assembly. After continuous
running for 120 hours, the pressure in the spin pack showed an increase of only 9.5%
over the initial pressure. The run was terminated after 120 hours because all material
was consumed.
[0085] Physical property tests on the fibers made by Comparative Example 1 and
Example 2 showed that the fibers made by Example 2 had a lower 100% modulus
indicating that the recessed exit of the fibers from the spin pack assembly allowed the
fibers to cool slower, thus improving their properties for kitting and weaving.
[0086] The Examples show that the spin pack assembly of the exemplary
embodiment has major advantages in making elastic fibers, such as TPU. By
dramatically increasing the run time before experiencing fiber breakage because of
excess pressure build-up, the melt spinning process is more economical and there is less
waste from scrap material generated as a result of fiber breakage. The properties of the
TPU fibers are also improved resulting in better knitting and weaving the fibers into
garments.
[0087] Melt spun TPU fibers can be made in a variety of denier. Denier is a term in
the art designating the fiber size. Denier is the weight in grams of 9000 meters of fiber
length. Typical melt spun TPU fibers are made in a denier size less than 240, more
typical from 10 to less than 240 denier size, with 20 and 40 denier being a popular size.
[0088] The elastic TPU fibers are used to combine by knitting or weaving with other
fibers such as natural and synthetic fibers to make various articles of clothing. The TPU
fibers can be dyed various colors.
[0089] The melt spun elastic TPU fibers of exemplary embodiments are normally
combined by knitting or weaving with other fibers, such as cotton, nylon or polyester to
make various end use articles, including clothing garments. The weight % of the melt
spun elastic fibers in the end use application can vary depending on the desired elasticity.
For example, woven fabrics have from 1-8 wt.%, underwear from 2-5 wt.%, bathing
suits and sportswear from 8-30 wt.%, foundation garments from 10-45 wt.%, and
medical hose from 35-60 wt.% of the elastic melt spun fibers with the remaining amount
being another type of non-elastic fiber.
[0090] The exemplary configuration of the exemplary spin pack assembly provides
for the fiber produced to cool more slowly which has been found to decrease the 100%
modulus. This decrease in modulus allows the fiber to perform better in knitting
operations, such as circular knitting.
[0091] The exemplary spin pack assembly produces improved material flow
properties for the polymer, which allows for greater run time before experiencing
problems, such as fiber breakage.
[0092] While in accordance with the Patent Statutes, the best mode and preferred
embodiment has been set forth, the scope of the invention is not limited thereto, but
rather by the scope of the attached claims.

CLAIMS
What is claimed is:
1. Apparatus comprising:
a spin pack assembly operative to receive a fluid thermoplastic material generally
free of lumps therein, and to output a single fiber of the material, wherein the material
reacts to form lumps therein generally within a reaction time after the material is
received within the spin pack assembly,
the assembly including: ' . .
a cylindrical body, the cylindrical body extending along a central axis,
and wherein the body includes a first axial end and a second axial portion axially
disposed from the first axial end;
an inlet adjacent the second axial portion, wherein the inlet is operative to
receive the material at elevated pressure;
a spinneret plate adjacent the first axial end, wherein the spinneret plate
includes one axially positioned fiber opening, wherein the opening is operative to
output the single fiber;
a cavity area within the body, wherein the cavity area is fluidly
intermediate of the inlet and the fiber opening;
a breaker plate, wherein the breaker plate extends in the cavity area, and
wherein the breaker plate includes a plurality of apertures therethrough, wherein
each of the apertures is operative to provide material flow therethrough, and
wherein the apertures are positioned to provide material flow through the cavity
area such that a residence time that material is within the cavity area is less than
the reaction time generally throughout the entire cavity area.
2. The apparatus according to claim 1 wherein the apertures are positioned to
provide a first-in/first-out flow generally throughout the entire cavity area.
3. The apparatus according to claim 2 wherein the plurality of apertures are
positioned to provide greater material flow with increasing radial distance from the axis
in the cavity area.
4. The apparatus according to claim 3 wherein the plurality of apertures each have
greater cross-sectional area with increasing radial distance from the axis.
5. The apparatus according to claim 4 wherein the plurality of apertures are
arranged iri a plurality of concentric circular patterns about the axis.
6. The apparatus according to claim 5 wherein all the apertures included in each
concentric circular pattern have generally the same cross-sectional area.
7. The apparatus according to claim 6 wherein the breaker plate includes one axially
aligned central aperture.
8. The apparatus according to claim 7 wherein each of plurality of apertures in a
first concentric circular pattern closest to the axis, is disposed radially from the central
aperture a first radial distance, and wherein the plurality of apertures in a second
concentric circular pattern disposed radially outward and immediately adjacent the
apertures in the first concentric circular pattern, are disposed radially outward from the
apertures in the first concentric circular pattern a second radial distance, wherein the first
radial distance is greater than the second radial distance.
9. The apparatus according to claim 8 wherein the breaker plate includes a third
concentric circular pattern of apertures disposed radially outward from and immediately
adjacent to the second concentric circular pattern of apertures, and wherein the plurality
of apertures in the third concentric circular pattern of apertures are disposed radially
outward from the apertures in the second concentric circular pattern a third radial
distance, wherein the first radial distance is greater than the third radial distance.
10. The apparatus according to claim 9 wherein the cavity area is bounded adjacent
the first axial end by a generally planar first annular surface.
11. The apparatus according to claim 10 wherein the cavity area is bounded adjacent
the second axial portion by a generally planar second annular surface.
12. The apparatus according to claim 11 wherein the body includes an annular body
opening adjacent the first axial end, wherein the body opening is generally aligned with
the axis, and wherein the fiber opening in the spinneret plate includes an exit at which
the fiber is output, and wherein the.exit is disposed axially inward within the body
relative to the body opening at least 5 mm.
13. The apparatus according to claim 12 and further comprising a screen, wherein the
screen extends in the cavity area, and wherein the screen is positioned intermediate of the
inlet and the breaker plate.
14. The apparatus according to claim 13 wherein the spin pack assembly further
includes:
a transport channel piece, and
a compression nut,
wherein the transport channel piece includes a annular portion and an axially
centered cylindrical projection portion, wherein the inlet extends through the annular
portion and the cylindrical projection portion, and
wherein the compression nut includes an external annular threaded portion and an
axially centered access opening, wherein the annular threaded portion is operatively
releasibly engaged with the body, and wherein the cylindrical projection portion extends
in the access opening.
15.. The apparatus according to claim 14 wherein the material comprises
thermoplastic polyurethane (TPU) polymer.
16. The apparatus according to claim 15 wherein the exit is disposed axially inward
within the body relative to the body opening about 15.5 mms.
17. The apparatus according to claim 16 wherein the TPU within the cavity area is at
least 200°C.
18. The apparatus according to claim 1 wherein the breaker plate includes a plurality
of apertures, wherein the apertures are arranged in a plurality of concentric circular
patterns about the axis, wherein the apertures in each concentric circular pattern have
greater cross-sectional area with increasing radial distance from the axis.
19. The apparatus according to claim 18 wherein the breaker plate includes a central
aperture aligned with the axis.
20. The apparatus according to claim 19 wherein the central aperture has a smaller
cross-sectional area than apertures in at least one of the plurality of concentric circular
patterns.
21. The apparatus according to claim 19 wherein the plurality of concentric circular
patterns include a first concentric circular pattern and a second concentric circular
pattern, wherein the plurality of apertures in the first concentric circular pattern are
radially disposed a first distance from the central aperture, and wherein the apertures in
the second concentric circular pattern are disposed radially outward a second distance
from the apertures in the first concentric circular pattern, and wherein the first radial
distance is greater than the second radial distance.
22. The apparatus according to claim 18 wherein the plurality of apertures include
apertures in at least three concentric circular patterns.
23. The apparatus according to claim 1 wherein the body includes a body opening
extending about the axis adjacent the first axial end, and wherein the fiber opening
includes an exit, wherein the fiber is output at the exit, and wherein the exit is disposed
axially inward relative to the body opening at least 5 mm.
24. The apparatus according to claim 23 wherein the material comprises
thermoplastic polyurethane (TPU) polymer, and wherein the exit is disposed axially
inward relative to the body opening about 15.5 mm.
25. The apparatus comprising:
an assembly operative to receive'a fluid thermoplastic polyurethane (TPU)
polymer material generally free of lumps-, and to output a single fiber of the material,
wherein the material reacts to form lumps therein generally within a reaction time after
the material is received within the assembly,
the assembly including:
a body, wherein the body includes a cavity area, wherein the cavity area
has a cavity cross-sectional area;
an inlet in fluid communication with the cavity area wherein the inlet is
operative to receive the material at elevated pressure, and wherein the inlet has an
inlet cross-sectional area, wherein the inlet cross-sectional area is less than the
cavity cross-sectional area;
a fiber outlet in fluid connection with the cavity area, wherein the fiber
outlet is operative to output the single fiber;
at least one member extending in the cavity area, wherein the at least one
member is operative to direct material flow in the cavity area, wherein the at least
one member is operative to maintain first-in/first-out flow generally throughout
the entire cavity area.
26. The apparatus according to claim 25 wherein the body includes an annular body
opening disposed away from the inlet, and wherein the fiber outlet includes an exit,
wherein the single fiber passes from the fiber outlet at the exit, and wherein the exit is
recessed inwardly relative to the body opening at least 5 mm.
27. The apparatus according to claim 25 wherein the body includes an annular body
opening disposed away from the inlet, and wherein the fiber outlet includes an exit, and
wherein the single fiber passes from the fiber outlet at the exit, and wherein exit is
recessed inwardly relative to the body opening about 15.5 mm.
28. The apparatus according to claim 26 wherein the at least one member comprises a
plate including a plurality of apertures therethrough.
29. The apparatus according to claim 28, wherein the assembly includes:
a generally cylindrical body, wherein the body extends along a central axis, and
wherein the body has first axial end and a second portion axially disposed from the first
axial end;
wherein the inlet is axially centered adjacent the second portion, and the body
opening is axially centered adjacent the first axial end;
and wherein the cavity area comprises a generally cylindrical area within the
body, and wherein the plate including the plurality of apertures extends in the cavity
area;
and further including a spinneret plate, wherein the spinneret plate includes the
fiber outlet.
30. The apparatus according to claim 29 wherein the plurality of apertures in the
plate are arranged to provide greater material flow with increasing radial distance from
the axis.
31. The apparatus according to claim 30 wherein the plate includes a plurality of
apertures arranged in at least one arcuate pattern.
32. The apparatus according to claim 31 wherein the at least one arcuate pattern
includes apertures having increased cross-sectional area with increased radial distance
from the axis.
33. The apparatus according to claim 32 wherein the at least one arcuate pattern
includes a plurality of concentric circular patterns of apertures, wherein the apertures in
each concentric circular pattern are generally the same size.
34. The apparatus according to claim 33 wherein the plate includes a central aperture
aligned with the axis.
35. The apparatus according to claim 34 wherein the plurality of concentric circular
patterns includes a first concentric circular pattern, wherein apertures in the first
concentric circular pattern are disposed radially closest to the central aperture, and
wherein the plurality of concentric circular patterns includes a second concentric circular
pattern, wherein the apertures in the second concentric circular pattern are disposed
radially outward relative to the apertures in the first concentric circular pattern, and
wherein no apertures in other concentric circular patterns extend radially intermediate of
the apertures in the first concentric circular pattern and the apertures in the second
concentric circular pattern, and wherein apertures in the first concentric circular pattern
are disposed from the central aperture a first radial distance, and wherein apertures in the
second concentric circular pattern are disposed from apertures in the first concentric
circular pattern a second radial distance, and wherein the first radial distance is greater
than the second radial distance.
36. The apparatus according to claim 35 wherein the plate includes at least three
concentric circular patterns of apertures.
37. The apparatus according to claim 36 wherein the assembly comprises a spin pack
assembly, and wherein the spin pack assembly includes a transport channel piece,
wherein the transport channel piece includes the inlet, and further including a
compression nut, wherein the compression nut includes an external annular threaded
portion and an axially centered access opening, and wherein the annual threaded portion
engages the body, and wherein the transport channel piece extends in the access opening.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=3Zxd9w3ENpxvcxQevsLAmg==&loc=+mN2fYxnTC4l0fUd8W4CAA==

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Patent Number

279341

Indian Patent Application Number

5261/DELNP/2008

PG Journal Number

03/2017

Publication Date

20-Jan-2017

Grant Date

18-Jan-2017

Date of Filing

18-Jun-2008

Name of Patentee

LUBRIZOL ADVANCED MATERIALS, INC.

Applicant Address

9911 BRECKSVILLE ROAD, CLEVELAND, OHIO 44141-3247, U.S.A.

Inventors:

#	Inventor's Name	Inventor's Address
1	RAVI R. VEDULA	34936 CLEAR CREEK DRIVE, NORTH RIDGEVILLE, OHIO 44039, USA.
2	JAMES E. BRYSON, JR.,	2415 WYANDOTTE AVENUE, CUYAHOGA FALLS, OHIO 44223, USA.

PCT International Classification Number

D01D 1/00

PCT International Application Number

PCT/US2006/062348

PCT International Filing date

2006-12-20

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/753,139	2005-12-22	U.S.A.