Title of Invention

"LOW VOLATILE ORGANIC SOLVENT BASED ADHESIVE"

Abstract

A solvent based adhesive, comprising: a) from 38 to 75 weight percent of a first solvent being at least one alkyl substituted naphthalene having 1 or more alkyl groups and from 11 to 14 carbon atoms, or at least one alkyl substituted benzene having 1 or more alkyl groups and from 10 to 14 carbon atoms, or combinations thereof, wherein said at least one alkyl substituted naphthalene and/or said at least one alkyl substituted benzene is present in an amount of at least 5 weight percent; b) from 5 to 20 weight percent of a thermoplastic resin; and c) from 5 to 47 weight percent of an additional one or more solvents, as herein described wherein the weight percent values are based upon the weight of said solvent based adhesive.

Full Text

This invention relates to a solvent based adhesive that is capable of joining two thermoplastic materials together. Furthermore, the invention relates to a solvent based adhesive preferably having a low volatile organic content (VOC) and a solvent that volatilizes at a substantially reduced rate as compared to those solvents of conventional solvent based adhesives for thermoplastic materials. Additionally, the invention relates to a solvent based adhesive having a flash point substantially above 1000F as determined by the test method set forth in the ASTM D 3828-87. Preferably, the invention comprises a solvent based adhesive used to join two objects or articles made from chlorinated polyvinyl chloride (CPVC). A preferred solvent useful in a solvent based adhesive of the invention is naphthalene having one or more alkyl groups thereon and a total of 11 to 14 carbon atoms and/or benzene having 1 or more alkyl groups thereon and a total of 10 to 14 carbon atoms. BACKGROUND OF THE INVENTION Solvent based adhesives are used to join thermoplastic pipe and fittings. Often, thermoplastic pipe and fittings joined using solvent based adhesives can be tested the same day. Generally, solvent based adhesives comprise a mixture of solvents as well as resin and other additives such as thixotropic agents. The solvent based adhesive, typically, dissolves the surface layer of the thermoplastic material to which it is applied, causing it to swell. The resin in the adhesive accelerates the setting of the two materials to be joined, fills any voids and reduces internal stresses. The adhesive cures by evaporation The primary solvents used in conventional solvent based adhesives include tetrahydrofuran, methyl ethyl ketone and cyclohexanone. These solvents, when used in relatively large amounts, tend to be volatile and consequently adhesives made therefrom tend to have VOC levels in the range of 750 to BSO g/1 as measured by the South Coast Air Quality Management District (SCAQMD)316A. Furthermore, prior to the application of these conventional solvent based adhesives, the thermoplastic material desirably is prepared with either a primer, such as tetrahydrofuran, or a cleaner such as acetone, in order to minimize adhesive failure. In this cleaning process even more volatile organic compounds can be released into the atmosphere. Since these conventional solvent based adhesives are largely formed from relatively volatile solvents, the adhesive tends to spread to a large area and drip during application to the thermoplastic materials, causing additional volatization. Conventional solvent based adhesives and/or primers for adhesives also generally have low flash points. The low flash point requires special precautions in the handling and packaging to avoid combustion of these adhesives and/or primers. Evaporation of solvents from solvent based adhesives can contribute to air pollution. Several adhesives have been formulated which contain lower VOC levels than the conventional solvent based systems. The VOC levels of conventional solvent based adhesive systems was generally about 650 grams/liter as measured by the South Coast Air Quality Management District Test Method 316A prior to 1994. For example, Australian Patent Application 86750/91 discloses an adhesive comprising more than 80 weight percent of N-methyl-2-pyrrolidone, more than 0.25 weight percent of a viscosity modifier and more than 10 weight percent of a vinyl based polymer. Similarly, U.S. Patent No. 4,675,354 discloses a glue solution which comprises a solution of a water insoluble synthetic organic polymer in a solvent such as N-methyl-2-pyrrolidonc. Also, U.S. Patent No. 4,687,798 discloses a solvent cement used for joining water insoluble polymers The solvent cement comprises about 10-15 weight percent of a water insoluble polymer and a solvent The solvent comprises ethyl acetate and N-methyl-2-pyrrolidone. The ethyl acetate ranges from about 3 percent to about 50 percent by weight of the solvent with the balance being N-methyl-2-pyrrolidone. In addition, European Patent Application 0 547 593 Al discloses a low VOC adhesive composition. The composition disclosed in this European Patent Application comprises a mixture of from 5 weight percent to about 60 weight percent of at least one water insoluble polymer, from about 1 weight percent to about 30 weight percent of inorganic or synthetic resinous hollow microspheres and from about 20 weight percent to about 70 weight percent of at least one volatile organic liquid which is a solvent for the water insoluble polymer. U.S. Patent No. 5,470,894 to Patel et.al., provides for an additional example of a low VOC solvent based adhesive. The low VOC solvent based adhesive in this patent can be used to join CPVC pipes. The adhesive comprises a high vapor pressure solvent comprising from about 15 to about 35 weight percent of tetrahydrofuran and 0 to about 30 weight percent of methyl ethyl ketone; and a low vapor pressure solvent comprising about 20 to about 45 weight percent cyclohexanone, 0 to about 30 weight percent of N-methyl pyrrolidone and from 0 to 10 weight percent of dibasic esters. Patel, et. al. state that the VOC level of their adhesive is at or below 450 grams/liter, while the adhesive meets or exceeds the required performance standards such as hydrostatic burst strength and hydrostatic sustained pressure tests. There are alternatives to solvent based adhesives. These alternatives include mechanical, reactive, and/or thermal systems. Mechanical joining systems are generally expensive to use. Examples of mechanical joining systems include Acom Fittings from Hepworth Building Products; PolyGrip Fittings from Philmac Corporation and Uncopper Finings from Gcnova. 'Thermal systems can be unpredictable due to the difficulty in consistently producing adequate pipe/fitting unions. Examples of thermal systems include hot melt glues available from the Minnesota, Mining and Manufacturing Company. These thermal systems can be difficult to apply and can perform less consistently than solvent based adhesives. An example of a reactive system includes an epoxy. Epoxy is available from the Noble Corporation under the tradenamc Copper Bond. Other examples of an epoxy include General Purpose Urethane, High Shear Strength Urethane and All Purpose Epoxy, all available from the Hardman Corporation. These reactive systems can be problematic because they have long cure times and poor green strength. Their efficacy can also be temperature dependent. At low temperatures epoxy materials can have very long cure times. Furthermore, there may be by products of the chemical reactions which may be detrimental to the strength of the thermoplastic materials. There arc benefits to continuing to use solvent based adhesives to join thermoplastic materials. First, solvent based adhesives are easy to use, and many workers have years of experience using these types of adhesives. Second, there are typically low production costs in making the solvent based adhesives and generally long term durability once the adhesives are used to join the two thermoplastic materials. Further, the solvent based adhesives can be used on location to join the two thermoplastic materials together without any additional equipment. Fourth, the solvent based adhesive system usually cures rapidly, allowing for immediate testing. One technique can be used to apply the solvent system for all sizes of pipe. Generally, the solvent based adhesive system can be applied to the joint at any temperature in the range of 0" to 120°F. Also, the solvent based adhesive usually does not rely upon a chemical reaction for its efficacy. Therefore, overall the solvent based adhesives are generally practical and economical. SUMMARY OF THE INVENTION Accordingly, there is provided a solvent based adhesive, comprising: a) from 38 to 75 weight percent of a first solvent being at least one alkyl substituted naphthalene having 1 or more alkyl groups and from 11 to 14 carbon atoms, or at least one alkyl substituted benzene having 1 or more alkyl groups and from 10 to 14 carbon atoms, or combinations thereof, wherein said at least one alkyl substituted naphthalene and/or said at least one alkyl substituted benzene is present in an amount of at least 5 weight percent; b) from 5 to 20 weight percent of a thermoplastic resin; and c) from 5 to 47 weight percent of an additional one or more solvents, as herein described. wherein the weight percent values are based upon the weight of said solvent based adhesive. The present invention comprises a novel solvent based adhesive comprising a mixture of wo or more solvents and a resin. Optionally, the novel solvent based adhesive may contain a thixotropic agent such as silica. Preferably, the novel solvent based adhesive comprises 5-15 weight percent thermoplastic resin; 38-75 weight percent of substituted naphthalene and/or substituted benzenes with 1 or more alkyl groups; about 20-45 weight percent dimethyl adipate and optionally 1.5-2% by weight of silica based upon the weight of said solvent based adhesive. Optionally, the solvent based adhesive can contain N-methyl-2-pyrrolidone. All weight percentages are based upon the weight of the solvent based adhesive, unless otherwise stated. Most preferably, this novel solvent based adhesive has a flash point above 100'F as measured in accordance with ASTM D 3828-87. Preferably, the solvent based adhesive has a low VOC (i.e., not greater than 450 g/1 when tested according to the SCAQMD Test Method 316A). More preferably, a novel solvent comprises 5-15 weight percent thermoplastic resin, 38-75 weight percent of n-methyl-2-pyrrolidone and/or an alkyl substituted naphthalene and/or substituted benzene with 10-14 carbon atoms, 15 -45% by weight dimethyl adipate; optionally about 1.5-2% by weight of silica and optionally about 5-10% by weight of a ketone having a flash point greater than 70"F and more desirably above 1000F. Preferably, the ketone is either 5-methyl-2-hexanone (methyl-iso-amyl ketone) or 4-methyl-2-pentanone (methyl isobutyl ketone), or combinations thereof. The solvent based adhesive of the instant invention preferably has a VOC level of less than 450 grams/liter as measured by SCAQMD 316A. More preferably, the novel solvent based adhesive has a VOC level of less than 350 grams/liter and preferably less than 250 grams/liter as measured by SCAQMD 316A DETAILED DESCRIPTION OF THE INVENTION The solvent based adhesive of the instant invention comprises a mixture of two or more volatile organic liquid solvents that arc capable of vaporizing at ambient temperatures and a thermoplastic resin. Other ingredients, including other solvents, fillers, thixotropic agents or stabilizers may be added to the solvent adhesive as desired. The solvent based adhesives as described herein in further detail generally have the following characteristics: viscosity from 500-3000 centipoise; a green strength in about 1-3 minutes; less than 20% by weight solids in the adhesive, an indefinite shelf life in nonreactive containers and a relatively quick (i.e., less than a day) cure time. The cure time can be varied for different end-use needs by minor adjustments of the solvent ratios used. Preferably, the first, second, and optional additional solvents are mixed in proportions (as taught later in the specification) such that the total volatile organic content as measured by SCAQMD Test Method 316A is below 450 grams/liter (g/1), more desirably less than 400 g/1, still more desirably less than 350 g/1, and most preferably less than 250 g/1. Alkyl substituted naphthalenes and/or substituted benzenes with 1 or more alkyl groups, as disclosed below, were found to be an effective substitute for N-methyl-2-pyrrolidone (NMP) in these adhesives. The flash point of a material is used as one of the properties thai is considered when assessing the overall fiammability of a material. One method to determine a flash point of a material is ASTM D 3828-87, which is incorporated herein in its entirety. If a material has a higher flash point, the packaging and its shipping requirements may not be as stringent as those generally required for solvent cements and/or primers. The thermoplastic resins that can be used in the formulation of the solvent based adhesive of the instant invention include polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC). poly(acrylonitrile-butadiene-styrene) (ABS), polystyrene, and any other amorphous thermoplastic resins which are soluble in the mixture of the two or more volatile organic solvents. Generally, the resin used in the solvent based adhesive of the instant invention is the same as the resin used to form the thermoplastic materials to be joined. Preferably, the resin is either CPVC, PVC or ABS. Examples of possible ABS resins to be used include the Cycolac ABS resins from GE Plastics and the Lustran ABS resins from Monsanto. Most preferably, the resin is CPVC. The amount of thermoplastic resin added to the solvent based adhesive desirably ranges from 5 to 20 weight percent and more preferably from 10 to 15 weight percent. If CPVC and/or PVC resin is used, it should have an inherent viscosity in the range of 0.6 to 0.96. Preferably, the chlorination levels for the CPVC resins range from 58 to 72 weight percent. Preferably, the chlorination level for the PVC resin should be less than 57% by weight of the resin. Generally, the CPVC resin used is CPVC resin as defined in Class 23477 of the ASTM D1784. Examples of suitable CPVC to be used in the instant invention include TempRite 674x571 CPVC, a preferred compound and TempRite 677 x 670 CPVC, all available from The R.F. Goodrich Company. (TcmpRite is a registered trademark of The I3.F.Goodrich Company). In addition to the thermoplastic resin, the solvent based adhesive of the instant invention includes a mixture of two or more volatile organic liquid solvents that are capable of vapon/ing at ambient temperatures. The first organic solvent(s) that is used in the mixture is a low vapor pressure solvent. Alkyl substituted naphthalenes having one or more alkyl groups and a total of 11 to 14 carbon atoms and/or one or more alkyl substituted benzenes with 1 or more alkyl groups and a total of 10 to 14 carbon atoms are the most preferred low vapor pressure solvents. The preferred ben/enes have 2 or more, 3 or more and 4 or more alkyl groups. NMP can also be included in the solvent. NM? is commercially available from Aldrich Chemical, Ashland, BASF, Chemoxy International and Janssen Chemical. The alkyl substituted naphthalenes and substituted benzenes having 1 or more alkyl groups are available from petroleum distillation as isolatable fractions. They are available from Koch Specialty Chemical Group, Corpus Chrisli, Texas either under a chemical name e.g. methyl naphthalene or as a specific Sure Sol® product (used primarily for alkyl substituted benzenes). They are generally classified as specialty chemicals while benzene, xylcnc, toluene, cumene, and ethylbenzene are generally classified as commodity chemicals. The first organic liquid solvent is generally found in the novel adhesive in the range of from about 38 to 75 weight percent, and more desirably from 38 to 65 weight percent. Additional other solvents other than said NMP, alkyl substituted naphthalene and alkyl substituted benzene may be present in amounts from 5 to 47 weight percent, more desirably from 15 to 47 weight percent based upon said solvent based adhesive. Said additional solvents can include a second and optionally a third or more solvent. The second organic liquid solvent in the solvent based adhesive is chosen from the group comprising polycarboxylic acids desirably having from 4 to 15 carbon atoms; their mono, di alkyl esters desirably having from 4 to 19 carbon atoms such as pimelic acid, monomethyl glutarate, monomethyl pimelate, monomethyl azelate, monomethyl sebacate, monoethyl adipate, dimethyl succinate, dimethyl glutaraie, dimethyl adipate, dimethyl pimelate, dimethyl subrate, and dimethyl azelate; or chlorides of polycarboxylic acids desirably having from 4 to 15 carbon atoms such as glutaryl chloride, adipoyl chloride, and pimeloyl chloride; and alky] chlorides of said polycarboxylic acids having from 4 to 17 carbon atoms such as methyl adipoyl chloride and methyl primeloyl chloride etc.; or mixtures thereof. For example, mixtures of dimethyl glutaraie, dimethyl adipate and dimethyl succinate can be used. A commercially available example of such a mixture is DBE-9, available from DuPont Chemical Company. The most preferred second organic solvent is dimethyl adipate ("DMA"). DMA is available from the DuPont Chemical Company under the tradcnamc DBE-6. The DBE-6 is believed to be a mixture comprising 98.7% DMA, The solvent based adhesive of the invention also may include other ingredients such as minor amounts of other solvents which, preferably, do not raise the VOC level of the adhesive above 450 grams/liter and which arc miscible with the mixture of the two or more volatile liquid organic solvents. Examples of optional solvents which can be used include cyclic or linear ketones, esters of monocarboxylic acids and alkyl alcohols, halogenated solvents, ethers, and other liquids such as dimethylformanide (DMF) and dimethyl sulfoxide (DMSO). Ketones which can be used in the instant invention as additional solvents include acetone, methyl ethyl keione (MEK), methyl-iso-amyl ketone, methyl-iso-butyl ketone, isophorone, cyclohexanone and other ketones having 3 to 15 carbon atoms. Desirably these ketones are present in amounts of 15 weight percent or less more desirably from 5 to 10 weight percent based on the solvent based adhesive. Desirably the additional one or more solvents and especially the ketones all have a flash point of above 70°F, and more preferably above 100T as measured by ASTM D 3828-87. In one embodiment desirably all the additional one or more solvents and especially the kctoncs consist essentially of solvents having a flash point above 70*F and preferably 100°F. All the ketones when mixed as a ketone blend will desirably have a flash point above 700F. Desirably the amount of solvents, having a flash point below 50°F, is limited to less than 5 weight percent. Examples of esters ofmonocarboxylic acids having from 2 to 15 carbon atoms and alkyl alcohols having from 1 to 15 carbon atoms which can be used in the instant invention include methyl acetate, ethyl acetate (EA), ethyl formate, ethyl propionatc, and butyl acetate. Halogenated solvents which can be used include methylene chloride, ethylene dichloride and trichloroethylene. An ether derived from methyl cellulose is an example of an ether having from 3 to 15 carbon atoms that can be used as an additional solvent. Fillers which are known in the art and any other materials which can function as inert fillers can be used in the instant invention. Examples of fillers which can optionally be used in the instant invention include hollow spheres (glass or ceramic), polymers, glass spheres, magnesium silicate, magnesium oxide, shell flour, alumina, talc, barium sulfate, calcium carbonate, and other fine powder. These fillers are generally added to the composition in the amount of 0.05 to 20 weight percent. Preferred fillers include polymers and calcium carbonate. The solvent based adhesive also may include optionally thixotropic agents. Examples of possible thixotropic agents useful in the invention include fumed silica, precipitated silica, bentonite clay, ground quartz, mica, ethyl cellulose, hydrogenated castor oil, organic modified clay, other thickeners or viscosity adjusters. Preferred thixotropic agents include filmed silica. Generally, the amount of thixotropic agent used, if used at all, is in the range of 1 to 3% by weight, more desirably from 1.5 to 2% by weight based on the weight of the solvent based adhesive. Further, pigments, dyes, dispersions or colorants may he added to the solvent based adhesive. Examples of possible pigments which can be used include titanium dioxide, calcium carbonate or carbon black. The amount of pigment used is generally in the range of 0.05% by weight to 5.0% by weight based upon the weight of the solvent based adhesive. The low VOC solvent based adhesive may include other additives. This includes any additives known to those in the art. Suitable additives include, for example, but are not limited to, various stabilizers, antioxidants, electrostatic dissipativc agents, smoke retardants, moisture scavengers, and acid scavengers. Since several additives can be combined in countless variations, the total amount of additive can vary from application to application. Optimization of the particular additive composition can be determined easily by one of ordinary skill in the art. Optionally, from 0.5 % to 1.0% by weight of additives are added based upon the weight of the solvent based adhesive. The ingredients for the solvent based adhesive can be combined in any convenient manner. For example, all the ingredients can be mixed together uniformly by a mixing means such as a mixer. Preferably, the two solvents are first mixed together. No special sequence or order is necessary. The thermoplastic resin and the thixotropic agent are then added to the solvent mixture. No special order is required. A stir mixer such as a Grenier Mixer, Model 3002 with fast agitation can be used to dissolve the solids in the solvent quickly. The mixer can be set at 400-500 rpm for 10-15 minutes. The mixture may then be placed on a slower moving roller mixer to evenly blend the composition. An example of a possible roller mixer which can be used is the Paul 0. Abbe Ball Mill. The mixture can be placed in this Ball Mill for one hour at 160 rpm. There arc many uses of the solvent based adhesives of the instant invention. For example, the solvent based adhesive can be used to join thermoplastic pipe and fittings in various applications such as plumbing systems, cold and hot water distribution systems, sprinkler systems, spas, fire sprinkler systems, drain, waste and vent systems. The following non-limiting examples serve to further illustrate the present invention. EXAMPLES In the following examples as represented in Tables 1-5, an NMP based solvent adhesive was formulated. The desired VOC level was determined by the selection of the two solvents. Using SCAQMD 316A, the VOC constant for each of the solvents used in the solvent based adhesive was determined experimentally. The estimated VOC for the solvent based adhesive was then determined using the following equation: (VOC constant of solvent 1 x % of solvent 1 based upon total amount of solvents in the adhesive) + (VOC constant of solvent 2 x % of solvent 2 in adhesive based upon total amount of solvents) + similar calculations for additional solvents = estimated VOC level of the adhesive, Once this desired VOC constant was determined, the low VOC solvent based adhesive was formulated and the VOC level verified using SCAQMD 316A. The viscosity of the solvent cement was optimized by adding thixotropic agents. The green strength and the cure time were varied by adjustments of the solvent ratios while still maintaining a desired VOC level and viscosity. In the first examples (Examples 1-4), the amount of the NMP and dimethyl adipate (DMA) used varied. The formulation in the first examples were all tested for the VOC level, the cure time, the green strength and quick burst. The VOC level was measured using the test in SCAQMD 316A. The quick burst was measured using ASTM 1599 and the cure time is measured using Underwriters Laboratories UL 1821 The green strength was tested by a procedure whereby the tester tried to pull or twist apart the bonded pipe and fitting. In carrying out the procedure, the inner part of the thermoplastic fining and the outer part of the thermoplastic pipe (which fits in the fitting) were each coated with the same adhesive. At the end of one minute, the tester tried to pull or twist apart the two pieces Generally, the bonded pipe and fitting were subjected to 6 foot-Ibs. of torque during the test. If the two pieces did not come apart, then a "yes" was recorded and the experiment was repeated until a "no" was obtained. Each time the experiment was redone, one additional minute was added to the previous time. The first time that a "no" was reached, indicated the green strength. The formulations as well as the results are set forth in Table 1. The pipe used to generate the data in the tables, unless otherwise specified was SDR-11 also known as 3/4 inch CPVC tubing having an outside diameter of 0.875-0.878 and a wall thickness of 0 080-0.100 inch. Examples of commercial solvent cements with which the instant invention was compared and contrasted with include Orange Lo V.O.C. Medium Booked CPVC Cement (one step); two step cements available from Oatey; and the Weld-On CPVC 2714™ Orange Heavy Booked Cement (one step) and two step cements from IPS. Generally, the one step commercial solvent cements have a VOC level of about 450 grams/liter, whereas the two step cements have a VOC level greater than 650 grams/liter. (Table Removed) Examples 1 through 4 in Table 1 illustrate that solvent based adhesive formulations having DMA/NMP ratio of from 0.31 to 1.125 have a lower VOC level than standard solvent cement formulations. Examples 3 and 4 would be unacceptable for commercial use due to the high viscosity although still effective as an adhesive. (Table Removed) PF means the pipe failed before the adhesive failed. Examples 5 through 24 in Table 2 illustrate that solvent based adhesives having a DMA/NMP radio of from 0.3 to 1.3 and having either a third minor solvent or combination of solvents which provide a minor portion ( In these examples, the VOC levels are all below 300 g/1 and the bond strength passes all enumerated criteria. Formulations 15, 16, 17, and 18 would be commercially unacceptable due to the high viscosity, although still effective as adhesives. (Table Removed) Examples 25 through 32 in Table 3 illustrate that solvent based adhesives having a DMA/NMP ratio of 0.3 and having a third minor solvent comprising (Table Removed) Examples 33 through 43 illustrate that solvent based adhesives having a DMA/NMP ratio from 0.54 to 0.97 and having MEK (2-butanone) as a minor component at a level less than 10% by weight of the overall formulation will have a lower VOC level than commercial solvent based adhesives (with a VOC level of 450 grams/liter or greater) and will perform as well as these commercial solvent based adhesives. Furthermore. Example 38 illustrates that a solvent based adhesive having a DMA/NMP ratio less than 0.55 and having MEK. (2-butanone) as a minor component at a level less than 8% by weight of the overall formulation will have a VOC level of 201 grams/liter and will perform as well as conventional solvent based adhesives. The following examples in Table 5 illustrate how substituted naphthalenes with 11 to 14 carbon atoms and/or substituted benzenes with from 10 to 14 carbon atoms can be used in place of NMP in the solvent based adhesive and result in low VOC values according to SCAQMD 316A (e.g. as low as 73 g/l) and meet the physical properly tests of a solvent based adhesive. The examples with 8 weight percent MEK have less desirable flash points than the other examples using ketones with higher flash points. The addition of ketones tends to lower the time required for green strength but increase the VOC level. The particular ester of a dicarboxylic acid and methyl alcohol (DBE-6) could be substituted with other such esters. The methyl naphthalene used in the experiment was >95 weight percent purity. The SS-150 was a Sure Sol® which is 98 weight percent C,0 isomcrs of benzene and the SS-ISO ND was similar to SS-ISO but naphthalene depleted. Both the SS-ISO and 150 NU arc available as petroleum distillate fractions from Koch Specialty Chemical Group in Corpus Christi, Texas. (Table Removed) 1. Chlorinated polyvinyl chloride having 67.3 weight percent Cl and an inherent viscosity of 0.92. 2. Chlorinated polyvinyl chloride having 67.0 weight percent Cl and an inherent viscosity of 0.68. 3. Fumed Silica available from Aldrich. 4. Dimethyl adipale available from DuPonl under the tradename DBE-6 NMP is N-methyl-2-pyrrolidone, MEK is methyl ethyl kelone, MIAK is methyl-iso-amyl ketooe, MIBK is methy-isobutyl kelone. m-Naph is methyl naphthalene. The flash point of the ketones are 24, 10, and 73°F according to the Merck Index, 10th Ed. 5. VOC is volatile organic compounds as determined by SCAQMD 316A. 6. As determined by ASTM D3828-87 7. ASTM 493. See also ASTM DI598-86 and D1599-88. While all of the above examples of the invention did not individually pass all of the tests, the examples as a whole teach and suggest how to modify the deficient performance to achieve the desired properties. Example 49 teaches that MIAK instead of M1BK in example 50 would achieve the desired property. Example 52 when compared to 53 teaches a similar change. Other slight changes in the solvent blend (MlAK and MIBK vary only by one carbon atom per molecule) are anticipated to also compensate for deficient performance and thus total performance can be optimized by routine experimentation. In summary, a novel and unobvious solvent based adhesive has been described. Said adhesive desirably has a flash point over 100"F as measured by ASTM D3828-87. Although specific embodiments and examples have been disclosed herein, it should be borne in mind that these have been provided by way of explanation and illustration and the present invention is not limited thereby. Certainly modifications which are within the ordinary skill in the art are considered to lie within the scope of this invention as defined by the following claims. WE CLAIM : 1. A solvent based adhesive, comprising: a) from 38 to 75 weight percent of a first solvent being at least one alkyl substituted naphthalene having 1 or more alkyl groups and from 11 to 14 carbon atoms, or at least one alkyl substituted benzene having 1 or more alkyl groups and from 10 to 14 carbon atoms, or combinations thereof, wherein said at least one alkyl substituted naphthalene and/or said at least one alkyl substituted benzene is present in an amount of at least 5 weight percent; b) from 5 to 20 weight percent of a thermoplastic resin; and c) from 5 to 47 weight percent of an additional one or more solvents, as herein described wherein the weight percent values are based upon the weight of said solvent based adhesive. 2. A solvent based adhesive as claimed in claim 1, wherein said adhesive comprises a ketone. 3. A solvent based adhesive as claimed in claim 1 or 2, wherein said adhesive comprises acetone, cyclohexanone, methyl ethyl ketone, metho-iso-amyl ketone or combinations thereof. 4. A solvent based adhesive as claimed in claim 1, wherein said adhesive comprises N-methyl-2-pyrrolidone. 5. A solvent based adhesive as claimed in claim 1, wherein said additional one or more solvents has from 10 to 35 weight percent of one or more aliphatic polycarboxylic acids having a total of 4 to 15 carbon atoms, mono or dialkyl esters thereof having a total of 4 to 19 carbon atoms, alkyl chlorides of said polycarboxylic acids having a total of 4 to 17 carbon atoms chlorides of said polycarboxylic acids having a total of 4 to 15 carbon atoms or combinations thereof. 6. A solvent based adhesive as claimed in claim 1, comprising: a) from 38 to 70 weight percent of at least one alkyl substituted naphthalene having from 11 to 15 carbon atoms and/or alkyl substituted benzene having at least I alkyl group and from 10 to 14 carbon atoms, b) from 5 to 20 weight percent of a chlorinated polyvinyl chloride, and c) from 10 to 35 weight percent of one or more aliphatic polycarboxylic acids having a total of 4 to 5 carbon atoms, mono or dialkyl esters thereof, having a total of 4 to 19 carbon atoms alkyl chlorides of said polycarboxylic acids having a total of 4 to 17 carbon atoms, chlorides of said polycarboxylic acids having a total of 4 to 15 carbon atoms or combinations thereof, wherein the weight percent values are based upon the weight of said solvent based adhesive. 7. A solvent based adhesive as claimed in claim 1, comprising: a) a first solvent being at least one alkyl substituted benzene having one or more alkyl groups and from 10 to 14 carbon atoms in an amount of at least five percent by weight; b) chlorinated polyvinyl chloride in an amount of at least five percent by weight and not greater than 20 percent by weight; and c) an additional one or more solvents in an amount of at least five percent by weight and not greater than 47 percent by weight, wherein the weight percent values are based upon the weight of said solvent based adhesive. 8. A solvent based adhesive as claimed in claim 7 wherein the additional one or more solvents are selected from the group consisting of methyl- iso-amyl ketone, dimethyl adipate, and mixtures thereof. 9. A solvent based adhesive as claimed in claim 1, wherein said thermoplastic resin comprises polyvinyl chloride, chlorinated polyvinyl chloride, ABS. or polystyrene, and wherein said first solvent is present in an amount from 38 to 65 weight percent. 10. A solvent based adhesive substantially as herein described with reference to the foregoing examples.

Documents:

2977-del-1998-abstract.pdf

2977-del-1998-assignment.pdf

2977-del-1998-claims.pdf

2977-del-1998-correspondence-others.pdf

2977-del-1998-correspondence-po.pdf

2977-del-1998-description (complete).pdf

2977-del-1998-form-1.pdf

2977-del-1998-form-13.pdf

2977-del-1998-form-19.pdf

2977-del-1998-form-2.pdf

2977-del-1998-form-3.pdf

2977-del-1998-form-4.pdf

2977-del-1998-form-6.pdf

2977-del-1998-gpa.pdf

2977-del-1998-petition-138.pdf