Title of Invention	METHOD AND APPARATUS FOR THE MANUFACTURE OF COMPOSITE SHEETS.
Abstract	Method for the manufacture of composite sheets, in which: a bundle of parallel threads is driven in a given direction, a lap of thread or threads oriented transversely relative to this given direction is combined with this bundle, the bundle of threads and/or the lap of thread or threads comprisi9ng at least one organic material and at least one reinforcing material, and the combination comprising at least 10% by weight of organic material, the combination is heated, being displaced in the given direction, and is fixed by the action of heat and/or of pressure, then by cooling, so as to form a composite band, the band is collected in the form of one or more composite sheets.

Title of Invention

METHOD AND APPARATUS FOR THE MANUFACTURE OF COMPOSITE SHEETS.

Abstract

Method for the manufacture of composite sheets, in which: a bundle of parallel threads is driven in a given direction, a lap of thread or threads oriented transversely relative to this given direction is combined with this bundle, the bundle of threads and/or the lap of thread or threads comprisi9ng at least one organic material and at least one reinforcing material, and the combination comprising at least 10% by weight of organic material, the combination is heated, being displaced in the given direction, and is fixed by the action of heat and/or of pressure, then by cooling, so as to form a composite band, the band is collected in the form of one or more composite sheets.

Full Text	The present invention relates to a direct method, and an apparatus for carrying out the said method, for the manufacture of composite sheets. It also relates to the composite products obtained. Composite sheets are usually formed from at least two materials which have different melting points and which generally comprise an organic material and a reinforcing material, the reinforcing material being, for example, in the form of threads embedded in the organic matrix. The manufacture of composite sheets generally takes a long time between the preparation of the reinforcing threads and the moment when the sheets are finally obtained, the structures used for producing the sheets usually not being the threads, as such, but complex structures incorporating the threads and requiring prior processing steps. In particular, it is already known to manufacture composite sheets in the form of panels or of curved pieces from fabrics formed both from reinforcing threads and from thermoplastic threads, in that the fabrics are stacked and the stack thus produced is then hot-pressed, as described in the utility model FR 2,500,360. Such a method has, in particular, the disadvantage of being a discontinuous method. It is also known (patent FR 2,743,822) to manufacture composite sheets from glass/organic material fabrics which are deposited continuously onto a conveyor and are then preheated in a hot-air oven, before being introduced into a "band press" (of the type described in the patent US-A-4,277,539), where they are successfully heated and cooled, whilst at the same time being compressed. Although this method is quicker than the method described above, it is desirable to improve the manufacture of composite sheets even further by providing quicker and more economical methods, whilst at the same time ensuring that products preserving good properties, in particular mechanical properties, are obtained. The object of the present invention is to provide a method which is improved, as compared with existing methods, for the manufacture of composite sheets, in particular a quicker and more economical method than the existing methods. This object is achieved by means of the method according to the invention, comprising at least the following steps: • a bundle of parallel threads is driven in a given direction, • a lap of thread or threads oriented transversely relative to this given direction is combined with this bundle, the bundle of threads and/or the lap of thread or threads comprising at least one organic material and at least one reinforcing material, • the combination is heated, being displaced in the given direction, and is fixed (or set) by the action of heat and/or of pressure, then by cooling, so as to form a composite band, • the band is collected in the form of one or more composite sheets. The various steps, such as the driving of the bundle, the combining of the lap, etc., advantageously take place continuously, this term also embracing intermittent drive and combination, as in the case of combination with a carriage (this embodiment being explained later). By "sheet" (and likewise by "band") is meant, according to the present invention, an element of small thickness in relation to its surface, generally plane (but, where appropriate, possibly being curved) and rigid, although having, as required, sufficient flexibility to be capable of being collected and stored in wound-up form. In general, it is a solid element, but, in some cases, it may be perforated (the term "sheet" and the term "band" thus also, by extension, designate structures of the netting or fabric type, according to the invention). By "composite" is meant, according to the present invention, the combination of at least two materials of different melting points, including in general an organic material and a reinforcing material, the content of the lower melting point material (the organic material) being at least 10% by weight of the said combination. The method according to the invention makes it possible to obtain composite sheets in a single operation from simple starting structures; in fact, the method according to the invention essentially employs unidirectional structures or threads; in particular, the reinforcing material used in the method according to the invention is provided solely in the form of threads, separate from one another and unconnected within "complex" structures (in particular, "multi- dimensional" structures of the fabric or netting type). The use of the simplest reinforcing structures in the manufacture of the sheets according to the invention has advantages particularly in terms of cost and of ease of use. From these simple structures, the method according to the invention makes it possible to obtain the desired sheets directly, with little labour being required and with the transfers from one installation to another and the intermediate storages being dispensed with. It combines, in particular, a step of assembly in a plane transverse to the given direction and a step of melting and solidifying the organic material in order to culminate in the finished product. Such a method is particularly quick and economical. Reference will simply be made, hereafter, to the "bundle of threads" in order to designate the bundle of parallel threads which is driven continuously in a given direction, the said bundle being mentioned in the definition of the invention, and "the lap of thread or threads" will designate the lap of transversely oriented thread or threads, the said lap being mentioned in the definition of the invention, that is to say, more specifically, one or more threads distributed transversely on the surface defined by the bundle of parallel threads. According to the invention, at least the bundle of threads or at least the lap of threads is formed from threads of at least two materials which comprise at least one organic material and at least one reinforcing material, this "reinforcing material" generally being a material selected from the materials commonly used for the reinforcement of organic materials (such as glass, carbon, aramid, etc.) or being capable, where appropriate, of being understood in a broad sense as a material having a melting point higher than that of the abovementioned organic material; in other words, at least the bundle of threads or at least the lap of threads is formed from threads of at least two materials having different melting points, the material with the lower melting point being an organic material. The organic material is, for example, polypropylene, polyethylene, polybutylene terephthalate, polyethylene terephthalate, phenylene polysulphide or any other thermoplastic or polymeric organic material selected from thermoplastic polyesters, polyamides, etc., the reinforcing material or the material with the higher melting point preferably being glass. Preferably, the bundle and the lap are selected in such a way that the combination of the bundle and of the lap comprises at least 10% by weight of organic material and between 20 and 90% by weight of reinforcing material (preferably glass), preferably between 30 and 85% by weight of reinforcing material, and, in a particularly preferred way, between 40 and 80% by weight of reinforcing material. Particularly advantageously, the combination of the bundle and of the lap consists of the reinforcing material, in the proportions mentioned, and of the organic material in a proportion representing the complement to 100% by weight of the said combination. The bundle and/or the lap may comprise partially threads consisting of one of the materials and partially threads consisting of the other material, these threads being arranged alternately in the bundle and/or the lap and being preferably intimately mixed. The bundle and/or the lap may also comprise mixed threads obtained by the joining and simultaneous winding of the threads of one of the materials and of the threads of the other material, these mixed threads likewise being capable of being blended with threads of one of the materials and/or with threads of the other material. Preferably, the combination of the bundle and of the lap and/or the bundle and/or the lap comprises at least 50% (advantageously at least 80% and, in a particularly preferred way, 100%) by weight of co- blended threads, that is to say of threads composed of filaments of one of the materials and the filaments of the other material, the filaments being blended within the threads (advantageously in an approximately homogeneous way), these threads generally being obtained by assembling the filaments directly at the time of the manufacture of the said filaments (according to the methods described, for example, in the patents EP 0,599,695 and EP 0,616,055). The use of these structures having at least 50% and preferably at least 80% by weight of co-blended threads makes it possible, in particular, to obtain more homogeneous composite products having good mechanical properties, the production of the composite sheets taking place, furthermore, within a reduced time and advantageously at lower pressure. Preferably, these co-blended threads consist of glass filaments and of filaments of thermoplastic organic material, the said filaments being intimately mixed. Preferably, the bundle of threads consists essentially of co-blended threads and the lap of threads consists of continuous (generally parallel) or cut co-blended threads and/or of continuous (generally parallel) or cut reinforcing threads and/or of continuous (generally parallel) or cut threads of organic material. In the method according to the invention, the threads of the bundle and the threads of the lap most often emanate from one or more supports (or packages) on which they are wound, the threads of the lap being cut, as required, before being combined with the threads of the bundle. The bundle and the lap can be combined in various ways, for example by means of one or more depositing arms or by means of a carriage carrying the threads of the lap which are arranged in parallel or by depositing the threads pneumatically (if appropriate, with the formation of loops or of a mat) or by depositing the cut threads, etc. According to a first embodiment, combination takes place by the lap of threads (in this case, they are preferably continuous threads) being incorporated transversely into the bundle of parallel threads, the bundle being, in this particular case, separated into two parts (one part being vertically in line with the other, for example one thread out of two being temporarily raised relative to the initial plane of the bundle and, if appropriate, the other threads being temporarily lowered relative to the initial plane) delimiting a space, within which the threads are projected with the aid of a rapier loom. This loom comprises, for example, two rapiers equipped with grippers, one rapier introducing, for example, the threads of the lap into the middle of the bundle and the second rapier extracting the threads from the other side of the bundle, the threads then being cut. The loom may also comprise a single rapier. According to a second embodiment, a carriage carrying the lap of threads in the form of parallel continuous threads delivers the lap into the bundle of parallel threads, the lap and the bundle subsequently being, if appropriate, sewn to one another by means of binding threads delivered continuously (for example, fine threads of polyester or of polypropylene or of glass) . These binding threads are put to use, for example, by means of the periodic movement of a transverse needle bar. Contrary to the previous embodiment, the threads of the lap and of the bundle are not intermingled, but are simply bound to one another. The products obtained in this case have good alignment (and therefore little shrinkage) and a high degree of deformability. According to a third embodiment, combination takes place by the lap of threads (in this case, these are likewise preferably continuous threads) being incorporated transversely into the bundle of parallel threads with the aid of a netting loom with weft insertion by a rotary arm or rotary arms. This loom may comprise one or more rotary arms, the threads of the lap coming either from a bobbin or bobbins arranged on the wheel carrying the depositing arms, this wheel being driven in rotation, or from a bobbin or bobbins arranged on another support in movement (synchronous with the movement of the depositing arms) or from a stationary bobbin or stationary bobbins, in this case the arm or arms being generally hollow arms with an axial passage. The products obtained in this embodiment have very little shrinkage and very good mechanical properties. According to a fourth embodiment, combination takes place by the threads being cut above the bundle of parallel threads, the cut threads being oriented in various directions, particularly in directions transverse to that of the bundle of threads, the cut threads forming a lap which is superposed on the bundle of threads. Preferably, in this embodiment, the threads fall onto one or more deflectors (as a rule, a metal plate, or, if appropriate, a plurality of metal plates, inclined at an angle of the order of 45 to 80° relative to the bundle of threads), making it possible to orient them more accurately in directions transverse relative to the given direction, before they are distributed on the bundle of parallel threads. According to a fifth embodiment, combination takes place by one or more threads being projected transversely in the form of a mat onto the bundle of parallel threads, the lap of threads in the form of the mat being, if appropriate, covered by a second bundle of parallel threads which is displaced in the same direction as the first bundle of parallel threads. The combination of the bundle and lap of threads (displaced at a speed of, for example, between 0.5 and 10 m/min) passes into at least one zone, where it is heated to a temperature between the melting points of the materials forming the combination, this temperature also being below the degradation temperature of the material having the lowest melting point. In the present invention, the "degradation temperature" designates, by extension, the minimum temperature at which decomposition of the molecules making up the material is observed (as traditionally defined and understood by the average person skilled in the art) or an undesirable change in the material, such as an inflammation of the material, a loss of intactness of the material (resulting in the material flowing out of the lap) or an undesirable colouring of the material (for example, yellowing), is observed. This degradation temperature can be evaluated in the traditional way by thermogravimetry and/or by noting the minimum temperature at which one of the abovementioned effects occurs. In the present invention, the combination is heated sufficiently to make it possible for at least some of the threads to be bound to one another by means of the material with the lowest melting point, after heating and/or compression, and, in most cases (except when a structure of a netting type is desired instead), to make it possible to obtain a solid or approximately solid structure. As examples, the heating temperature may be of the order of 190 to 230°C when the lap of threads consists of glass and of polypropylene, it may be of the order of 280 to 310°C when the lap consists of glass and of polyethylene terephthalate (PET) , and it may be of the order of 270 to 280-290°C when the lap consists of glass and of polybutylene terephthalate (PBT). The combination may be heated in several ways, for example with the aid of a double-band laminating machine, or with the aid of heated cylinders or of an irradiation device, such as an infrared radiation device (for example, in the form of an infrared oven or lamp or lamps or panel or panels), and/or at least one hot-air blowing device (for example, a forced- convection hot-air oven). Heating may be sufficient to make it possible to fix the combination by means of the melted organic material (thermofixing). In many cases, however, the heated combination also undergoes compression with the aid of a compression device, for example with the aid of at least one two-roll calender. The force exerted on the combination during its passage through the compression device, for example during its simultaneous passage between two rolls of a calender, is generally several kgf/cm, even several tens of kgf/cm. The pressure exerted in the compression device compacts the lap of threads, the structure obtained being set by cooling, this cooling being capable of being carried out, at least partially, simultaneously with the compression or also being capable of being carried out after a hot-compression step. The compression device may comprise at least one calender, in particular a calender maintained at a temperature below the solidification point of the material with the lowest melting point (the calender is, for example, at a temperature of between 20 and 150°C), in order to solidify the said material. The compression device may also comprise a plurality of calenders, particularly where large thicknesses are concerned and if it is desirable to have very good planeness and/or high production speeds. Moreover, particularly when use is made of materials with high melting points or having a high crystallization rate (for example, polyesters), and when the aim is to obtain solid or approximately solid sheets, it may be desirable to heat the calender (or at least the first calender) of the compression device to a temperature higher than 75°C, preferably higher than 100°C, even higher than 150°C. In this case, the rolls of the heated calender are preferably covered with an anti-adhesive covering based, for example, on PTFE and/or a mould release film (made of silicone-coated paper or of glass cloth coated, for example, with PTFE) is unwound between each roll and the lap of threads (this film may, if appropriate, be in the form of an endless band). According to one embodiment of the invention, the compression device may also comprise or consist of a band press (equipped, for example, with bands of steel or of glass cloth or of aramid cloth, the cloth preferably being coated with PTFE) comprising a hot zone (in particular, with one or more calenders) followed by a cold zone (with cooling elements in the form of bars, plates, etc. and, if appropriate, one or more calenders). Cooling may take place in the compression device (for example, in a cold calender or in the cold zone of a double-band flat laminating machine) or may take place outside the compression device, for example by natural or forced convection. In order to accelerate its cooling, the composite band obtained at the exit of the abovementioned compression device can pass onto a cooling table, in which cold water circulates, this table, if appropriate, being slightly curved convexly, in order to improve contact with the band. In order to improve cooling and/or contact even further, the table may be combined with press rollers, preferably cooled (for example, by water circulation), and/or with one or more freely bearing or pressed cooled plates and/or with one or more air-blowing nozzles, and/or the band may be drawn by take-up rollers located, for example, at the exit of the table. The composite band, after being compressed and cooled, can be wound onto a mandrel, the diameter of which is a function of the thickness of the band (the sheet formed then corresponds to the wound band), or can be cut by a cutting device (for example, a guillotine or circular-saw device) , so as to form a plurality of sheets. Although the present method is essentially described in terms of the combination of one lap of threads and of one bundle of parallel threads, it is quite clear that a plurality of laps may be combined with one or more bundles of threads in the same way as described above. It is possible, in particular, to combine a plurality of laps of threads in order to form sheets of greater thickness. Thus, according to one embodiment of the invention: • a first bundle of parallel threads is driven in a given direction, • a lap of threads oriented transversely relative to this given direction is combined with this first bundle, • at least one second bundle of parallel threads is combined with the bundle and with the lap in the given direction, the first bundle of threads and/or the lap of threads and/or the second bundle of threads comprising at least two materials having different melting points, • the combination is heated, being displaced in the given direction, and is fixed by the action of heat and/or of pressure, then by cooling, so as to form a composite band, • the band is collected in the form of one or more composite sheets. It is also possible, before compression of the assembly, to unwind one or more surface films onto one or two faces of the combination, these films adhering under hot conditions to the combination of the bundle(s) and lap(s). These films may be of a material or materials identical to or different from those (or one of those) of the threads of the combination (they may be metallic, organic, etc.), these films preferably being of a nature or having a covering of a nature close to the nature of the material of lowest melting point present in the combination. In more general terms, it is possible to apply to the surface of the combination and/or introduce into the combination other structures in the form of threads or an assembly of threads, cellular structures, or structures containing elements in the form of powder, of granules or of liquid, leaves or panels or films, of an essentially metallic or polymeric or mineral or vegetable nature, which are continuous or discontinuous, and imparting particular properties to the composite sheets obtained (additional reinforcement by means of threads of different nature, improvement in the mechanical properties, protection against electromagnetic radiation, improvement in thermal or acoustic insulation, lightened composite structures, improved moulding capacity, surface appearance, etc.). The band obtained in the method according to the invention may be collected in the form of packages (that is to say, as it were, in the form of a single wound composite sheet) or of a plurality of sheets cut to the dimensions required by the users. The present invention also relates to an apparatus for carrying out the method. This apparatus comprises: a) one or more devices (or members) for feeding at least one bundle of parallel threads, b) one or more devices (or members) for feeding at least one lap of threads, c) one or more devices for orienting the threads of the lap transversely to the direction of the parallel threads of the bundle (for example, according to the embodiment, a rapier loom, a carriage loom, a netting loom with weft insertion by rotary arms, or a deflector, as described in the various embodiments explained above), d) at least one device (or member) for heating the combination of the bundle and of the lap, e) and at least one device for cooling the combination. The apparatus according to the invention may also comprise at least one compression device and/or at least one cutting device and/or at least one device for collecting the composite sheets. The cooling device may also be a compression device, or the apparatus according to the invention may comprise at least one device for compressing the combination of the bundle and of the lap separate from the cooling device. The composite sheets obtained as a result of the combination of steps of the method according to the invention are particularly economical and comprise filaments of a material having a higher melting point (generally reinforcing filaments) which are embedded in the sheet and are arranged, generally with regard to at least part of them, in the direction of travel of the sheet during its manufacture and, preferably likewise with regard to the other part (or at least another part of these filaments) in a direction transverse to the direction of travel. The sheet thus comprises at least one assembly of filaments of a material having a higher melting point, which are arranged approximately parallel in a first direction, and, if appropriate, at least one second assembly of filaments of a material having a higher melting point, which are arranged approximately parallel in a second direction preferably transverse to the first, all these filaments being embedded in the material having a lower melting point. The sheets obtained generally have a thickness of between a few tenths of a millimetre and approximately 2 mm, are rigid and easy to cut and have good mechanical properties. They may be used as such in moulding methods or in combination with other products. They may be used, for example, for the thermoforming and the moulding of pieces made of composite products. As a general rule, the sheets obtained have little shrinkage (the ratio between the length of the thread in one direction and the length of the sheet in this direction, this ratio being evaluated with regard to threads passing through the sheet in this direction and not with regard to cut threads) in each of the preferred directions of orientation of the threads, the shrinkage generally being below 6%, or even 2% or 1%, in at least one direction. With regard to sheets obtained, using a netting loom with weft insertion by rotary arms, even the complete or virtually complete absence of shrinkage can be seen. Other advantages and characteristics of the invention may be gathered from the following accompanying drawings which illustrate the invention, but without limiting it, and in which: • Figure 1 shows a diagrammatic view of an apparatus allowing a first implementation of the invention, • Figure 2 shows a diagrammatic view of an apparatus allowing a second implementation of the invention, • Figure 3 shows a diagrammatic view of an apparatus allowing a third implementation of the invention, • Figure 4 shows a diagrammatic view of an apparatus allowing a fourth implementation of the invention, • Figure 5 shows a diagrammatic view of part of an apparatus for implementing the invention, • Figure 6 shows a diagrammatic view of part of an apparatus for implementing the invention. In the method illustrated in Figure 1, a double-rapier weaving loom 1 is fed with a bundle of threads 2 (having, for example, 4 threads per cm) which come from rovings 3, the threads passing through a comb and arriving in parallel in the weaving loom (a part which is not visible and is not shown in the figure) , these threads being, for example, composite threads composed of glass filaments and of polypropylene filaments blended with one another. A fabric 4 is manufactured by the insertion, for example at 120 strokes/mn, of a thread 5 (coming from a roving 6 and likewise composed of glass filaments and of polypropylene filaments) per cm, in the form of a cloth-like assembly. The fabric passes under a first cylinder 7 heated, for example, to 200°C and having, for example, a diameter of the order of 300 mm, and then passes over a second heated cylinder 8. The polypropylene filaments melt in contact with the hot surfaces. The product then passes into the nip of a calender 9, thermostatically controlled at, for example, 40°C, where it is cooled and converted into a sheet 10, for example with a thickness of about 0.7 mm, composed, for example, of 40% by weight of polypropylene and of 60% by weight of glass filaments oriented in two perpendicular directions. It is subsequently, for example, wound onto a tube 11 having a diameter of 100 mm. In Figure 2, a bundle 20 of parallel composite threads composed, for example, of glass filaments and of polypropylene filaments is unwound from one or more beams 21 and is introduced into a knitting machine 22 equipped with a weft insertion carriage 23 capable of taking up a plurality of threads 24 simultaneously (these threads having come from rovings 25 and likewise being composite threads) and of depositing them transversely to the direction of displacement of the bundle of threads, for example at the rate of 2 threads per cm. These threads 24 may be bound to the threads of the bundle by means of a simultaneous knitting operation, the binding threads being products having a linear density, or mass per unit length, of less than 50 tex (g/km). The sewn product subsequently passes into a consolidation device similar to that of Figure 1. In an economical variant which does not employ- binding threads, a second bundle of threads is brought onto the lap of threads deposited by means of a carriage, in order to block them. The non-sewn assembly is subsequently conveyed directly onto the consolidation and winding system. In another more elaborate variant, use is made of a plurality of weft insertion carriages which are movable in the plane along two axes and which make it possible to produce multi-layer surfaces having a plurality of directions, for example 0o/-45°/+45o/90°. These thicker products may or may not be bound by knitting and may be directly consolidated in line by melting and cooling under pressure or simply thermofixed by melting/cooling, without pressure being applied. Figure 3 describes a method for the manufacture of a plane product in the form of a consolidated glass/ thermoplastic composite product, in which use is made of two bundles of composite parallel threads 30 and 31 and a lap of composite threads 32 which come from rovings 33 deposited transversely in the form of a mat having continuous threads. The bundles of parallel threads may come from creels, not shown in Figure 3, or be wound on beams 34 and 35, these threads passing through combs 36, 37 keeping them parallel, then through take-up cylinders 38, 39 making it possible to reduce the tensions of the threads, before these enter the consolidation device. A plurality of threads 32 are deposited between these bundles by means of a carriage 40 which is displaced transversely to the direction of displacement of the bundles in an alternating movement, in order to form a mat (or a lap of looped threads) . This carriage is, for example, equipped with a cylinder-type take-up system coupled to a compressed-air ejector having a Venturi effect. The combination of the bundles and of the lap subsequently passes between the continuous bands 41 (made of glass fabrics impregnated with polytetra- fluoroethylene - PTFE -) of a flat laminating press 42. This laminating press comprises a heating zone 43 and a zone 44 cooled by water circulation and, between these two zones, pressing cylinders 45 which compress the melteed thermoplastic material under a pressure in the vicinity of, for example, 10 to 20 N/cm2. At the exit of this double-band press, the product has a homogeneous appearance, this appearance being capable of being improved, for example, by two polypropylene films 46 and 47 deposited on either side of the combination between the bands of the press. The rigid sheet obtained is subsequently either wound onto a tube 48 having a diameter of, for example, 100 mm or is cut continuously into a plurality of rectangles by means of blades and an automatic shearing machine which are not shown. In one variant, the double-band press is replaced by a device comprising two heated rollers covered with PTFE, followed by a calender having two cooled cylinders. The two polypropylene surface films 46 and 47 are, in this case, preferably introduced into the nip of the cold calender. The method shown in Figure 4 closely resembles that shown in Figure 3 (the same references being adopted again for the same elements). The difference is in the type of mat which is sandwiched between the two warps of parallel threads. Here, this mat is, for example, formed by threads 50 of pure glass which are cut to a length of 50 or 100 mm and are oriented in the transverse direction by means of a deflecting plate 51. Two polypropylene films 52 and 53 having a thickness of, for example, 50 µm may, if appropriate, be introduced on either side of this mat. Two other polypropylene films, not shown, may also be added on each side of the product, in order to improve its surface appearance. The product obtained may be wound or cut into sheets. The cut-thread mat may also consist of the thread of the same nature as that of the threads of the bundle (for example: 60% glass and 40% polypropylene). In this case, there is no need to introduce films 52 and 53 into the core of the product. • That part of the apparatus which is shown in Figure 5 is a variant of the "consolidation" part of the methods shown in Figures 1 and 2. It follows, for example, a weaving or knitting loom with weft insertion 60. The organic part is melted contactlessly by means of two infrared radiation panels 61 which are retractable in order to avoid the risks of the combination being damaged (or burnt) during stoppages of the loom. After the partially melted product has been deflected on a thermostatically controlled bar 62, the said product is compacted and cooled in the nip of a calender 63, for example at 40°C, and then passes, if appropriate, over a convexly-curved cooling table 64. The product, driven by rollers 65, 66, is subsequently cut into sheets 67 with the aid of one or more cutting devices 68. Where a shutdown of the weaving (or knitting) loom is concerned, an accumulator 69 draws to the rear that part of the product which is located between the end of the infrared panels and the entrance of the calender, so as not to have zones of non-compacting product corresponding to each stoppage. Moreover, in order to avoid the product being damaged on the deflecting bar, thermostatically controlled at, for example, 220°C, a move-away bar 7 0 moves the product away. The method in Figure 6 is a variant of the method described in Figure 5 and leads to products which are simply thermofixed, without consolidation. The previous system of compacting/cooling by calender and convexly-curved cooling table is replaced, here, by air-blowing boxes 71. The sheets produced according to the present invention are particularly suitable for the production of composite articles by moulding. CLAIMS 1. Method for the manufacture of composite sheets, in which: • a bundle of parallel threads is driven in a given direction, a lap of thread or threads oriented transversely relative to this given direction is combined with this bundle, the bundle of threads and/or the lap of thread or threads comprising at least one organic material and at least one reinforcing material, and the combination comprising at least 10% by weight of organic material, • the combination is heated, being displaced in the given direction, and is fixed by the action of heat and/or of pressure, then by cooling, so as to form a composite band, • the band is collected in the form of one or more composite sheets. 2. Method according to Claim 1, characterized in that the reinforcing material is provided solely in the form of threads, separate from one another and unconnected. 3. Method according to one of Claims 1 and 2, characterized in that the combination comprises at least 50% by weight of co-blended threads. 4. Method according to Claim 3, characterized in that the co-blended threads consist mainly of glass filaments and of filaments of thermoplastic organic material which are intimately mixed. 5. Method according to one of Claims 1 to 4, characterized in that the lap of threads is a lap of continuous thread or continuous threads and is combined with the bundle of threads, using a rapier loom. 6. Method according to one of Claims 1 to 4, characterized in that the lap of thread or threads is a lap of continuous thread or continuous threads and is combined with the bundle of threads, using a weft insertion carriage, the threads of the bundle and of the lap being, if appropriate, sewn to one another by means of binding threads. 7. Method according to one of Claims 1 to 4, characterized in that the lap of thread or threads is a lap of continuous thread or continuous threads, and in that combination takes place by the lap of threads being incorporated transversely into the bundle of parallel threads with the aid of a netting loom with weft insertion by rotary arms. 8. Method according to one of Claims 1 to 4, characterized in that the lap of thread or threads is a lap of cut thread or cut threads, and in that combination takes place by the threads being cut above the bundle of parallel threads, the threads falling, preferably beforehand, onto one or more deflectors. 9. Method according to one of Claims 1 to 4, characterized in that combination takes place by one or more threads being projected transversely in the form of a mat onto the bundle of parallel threads, the lap of threads in the form of the mat being, if appropriate, covered by a second bundle of parallel threads which is displaced in the same direction as the first bundle of parallel threads. 10. Method according to one of Claims 1 to 9, characterized in that: • a first bundle of parallel threads is driven in a given direction, • a lap of threads oriented transversely relative to this given direction is combined with this first bundle, • at least one second bundle of parallel threads is combined with the bundle and with the lap in the given direction, the first bundle of threads and/or the lap of threads and/or the second bundle of threads comprising at least two materials having different melting points, • the combination is heated, being displaced in the given direction, and/or is fixed by the action of heat and/or of pressure, then by cooling, so as to form a composite band, • the band is collected in the form of one or more composite sheets. 11. Method according to one of Claims 1 to 10, characterized in that other elements imparting particular properties to the composite sheets obtained are applied to the surface of the combination and/or introduced into the combination. 12. Apparatus for the manufacture of at least one composite sheet as claimed in claim 1 this apparatus comprising: a) one or more devices (or members) for feeding at least one bundle of parallel threads, b) one or more devices (or members) for feeding at least one lap of threads, c) one or more devices for orienting the threads of the lap transversely to the direction of the parallel threads of the bundle, d) at least one device (or member) for heating the combination of the bundle and of the lap, e) and at least one device for cooling the combination. 13. Apparatus according to Claim 12, characterized in that it comprises, furthermore, at least one compression device and/or at least one cutting device and/or at least one device for collecting the composite sheets. 14. Apparatus according to one of Claims 12 and 13, characterized in that the device for orienting the threads of the lap is a a rapier loom, a carriage loom, a netting loom with weft insertion by rotary arms, or a deflector. 15. Apparatus according to one of Claims 12 to 14, characterized in that it comprises, furthermore, an accumulator and/or a move-away bar drawing the product to the rear and/or moving the product away from the heating zones and/or for compression in the event of a stoppage of an upstream device. 16. Composite sheet based on at least one thermoplastic organic material and on at least reinforcing threads, which is obtained by means of the method according to one of Claims 1 to 11 and which is characterized in that the shrinkage is below 6%. Method for the manufacture of composite sheets, in which: a bundle of parallel threads is driven in a given direction, a lap of thread or threads oriented transversely relative to this given direction is combined with this bundle, the bundle of threads and/or the lap of thread or threads comprising at least one organic material and at least one reinforcing material, and the combination comprising at least 10% by weight of organic material, the combination is heated, being displaced in the given direction, and is fixed by the action of heat and/or of pressure, then by cooling, so as to form a composite band, the band is collected in the form of one or more composite sheets.

Full Text

The present invention relates to a direct
method, and an apparatus for carrying out the said
method, for the manufacture of composite sheets. It
also relates to the composite products obtained.
Composite sheets are usually formed from at
least two materials which have different melting points
and which generally comprise an organic material and a
reinforcing material, the reinforcing material being,
for example, in the form of threads embedded in the
organic matrix. The manufacture of composite sheets
generally takes a long time between the preparation of
the reinforcing threads and the moment when the sheets
are finally obtained, the structures used for producing
the sheets usually not being the threads, as such, but
complex structures incorporating the threads and
requiring prior processing steps.
In particular, it is already known to
manufacture composite sheets in the form of panels or
of curved pieces from fabrics formed both from
reinforcing threads and from thermoplastic threads, in
that the fabrics are stacked and the stack thus
produced is then hot-pressed, as described in the
utility model FR 2,500,360. Such a method has, in
particular, the disadvantage of being a discontinuous
method.
It is also known (patent FR 2,743,822) to
manufacture composite sheets from glass/organic
material fabrics which are deposited continuously onto
a conveyor and are then preheated in a hot-air oven,
before being introduced into a "band press" (of the
type described in the patent US-A-4,277,539), where
they are successfully heated and cooled, whilst at the
same time being compressed. Although this method is
quicker than the method described above, it is
desirable to improve the manufacture of composite
sheets even further by providing quicker and more
economical methods, whilst at the same time ensuring
that products preserving good properties, in particular
mechanical properties, are obtained.
The object of the present invention is to
provide a method which is improved, as compared with
existing methods, for the manufacture of composite
sheets, in particular a quicker and more economical
method than the existing methods.
This object is achieved by means of the method
according to the invention, comprising at least the
following steps:
• a bundle of parallel threads is driven in a given
direction,
• a lap of thread or threads oriented transversely
relative to this given direction is combined with
this bundle, the bundle of threads and/or the lap of
thread or threads comprising at least one organic
material and at least one reinforcing material,
• the combination is heated, being displaced in the
given direction, and is fixed (or set) by the action
of heat and/or of pressure, then by cooling, so as to
form a composite band,
• the band is collected in the form of one or more
composite sheets.
The various steps, such as the driving of the
bundle, the combining of the lap, etc., advantageously
take place continuously, this term also embracing
intermittent drive and combination, as in the case of
combination with a carriage (this embodiment being
explained later).
By "sheet" (and likewise by "band") is meant,
according to the present invention, an element of small
thickness in relation to its surface, generally plane
(but, where appropriate, possibly being curved) and
rigid, although having, as required, sufficient
flexibility to be capable of being collected and stored
in wound-up form. In general, it is a solid element,
but, in some cases, it may be perforated (the term
"sheet" and the term "band" thus also, by extension,
designate structures of the netting or fabric type,
according to the invention).
By "composite" is meant, according to the
present invention, the combination of at least two
materials of different melting points, including in
general an organic material and a reinforcing material,
the content of the lower melting point material (the
organic material) being at least 10% by weight of the
said combination.
The method according to the invention makes it
possible to obtain composite sheets in a single
operation from simple starting structures; in fact, the
method according to the invention essentially employs
unidirectional structures or threads; in particular,
the reinforcing material used in the method according
to the invention is provided solely in the form of
threads, separate from one another and unconnected
within "complex" structures (in particular, "multi-
dimensional" structures of the fabric or netting type).
The use of the simplest reinforcing structures in the
manufacture of the sheets according to the invention
has advantages particularly in terms of cost and of
ease of use. From these simple structures, the method
according to the invention makes it possible to obtain
the desired sheets directly, with little labour being
required and with the transfers from one installation
to another and the intermediate storages being
dispensed with. It combines, in particular, a step of
assembly in a plane transverse to the given direction
and a step of melting and solidifying the organic
material in order to culminate in the finished product.
Such a method is particularly quick and economical.
Reference will simply be made, hereafter, to
the "bundle of threads" in order to designate the
bundle of parallel threads which is driven continuously
in a given direction, the said bundle being mentioned
in the definition of the invention, and "the lap of
thread or threads" will designate the lap of
transversely oriented thread or threads, the said lap
being mentioned in the definition of the invention,
that is to say, more specifically, one or more threads
distributed transversely on the surface defined by the
bundle of parallel threads.
According to the invention, at least the bundle
of threads or at least the lap of threads is formed
from threads of at least two materials which comprise
at least one organic material and at least one
reinforcing material, this "reinforcing material"
generally being a material selected from the materials
commonly used for the reinforcement of organic
materials (such as glass, carbon, aramid, etc.) or
being capable, where appropriate, of being understood
in a broad sense as a material having a melting point
higher than that of the abovementioned organic
material; in other words, at least the bundle of
threads or at least the lap of threads is formed from
threads of at least two materials having different
melting points, the material with the lower melting
point being an organic material. The organic material
is, for example, polypropylene, polyethylene,
polybutylene terephthalate, polyethylene terephthalate,
phenylene polysulphide or any other thermoplastic or
polymeric organic material selected from thermoplastic
polyesters, polyamides, etc., the reinforcing material
or the material with the higher melting point
preferably being glass.
Preferably, the bundle and the lap are selected
in such a way that the combination of the bundle and of
the lap comprises at least 10% by weight of organic
material and between 20 and 90% by weight of
reinforcing material (preferably glass), preferably
between 30 and 85% by weight of reinforcing material,
and, in a particularly preferred way, between 40 and
80% by weight of reinforcing material. Particularly
advantageously, the combination of the bundle and of
the lap consists of the reinforcing material, in the
proportions mentioned, and of the organic material in a
proportion representing the complement to 100% by
weight of the said combination. The bundle and/or the
lap may comprise partially threads consisting of one of
the materials and partially threads consisting of the
other material, these threads being arranged
alternately in the bundle and/or the lap and being
preferably intimately mixed. The bundle and/or the lap
may also comprise mixed threads obtained by the joining
and simultaneous winding of the threads of one of the
materials and of the threads of the other material,
these mixed threads likewise being capable of being
blended with threads of one of the materials and/or
with threads of the other material.
Preferably, the combination of the bundle and
of the lap and/or the bundle and/or the lap comprises
at least 50% (advantageously at least 80% and, in a
particularly preferred way, 100%) by weight of co-
blended threads, that is to say of threads composed of
filaments of one of the materials and the filaments of
the other material, the filaments being blended within
the threads (advantageously in an approximately
homogeneous way), these threads generally being
obtained by assembling the filaments directly at the
time of the manufacture of the said filaments
(according to the methods described, for example, in
the patents EP 0,599,695 and EP 0,616,055). The use of
these structures having at least 50% and preferably at
least 80% by weight of co-blended threads makes it
possible, in particular, to obtain more homogeneous
composite products having good mechanical properties,
the production of the composite sheets taking place,
furthermore, within a reduced time and advantageously
at lower pressure. Preferably, these co-blended threads
consist of glass filaments and of filaments of
thermoplastic organic material, the said filaments
being intimately mixed.
Preferably, the bundle of threads consists
essentially of co-blended threads and the lap of
threads consists of continuous (generally parallel) or
cut co-blended threads and/or of continuous (generally
parallel) or cut reinforcing threads and/or of
continuous (generally parallel) or cut threads of
organic material.
In the method according to the invention, the
threads of the bundle and the threads of the lap most
often emanate from one or more supports (or packages)
on which they are wound, the threads of the lap being
cut, as required, before being combined with the
threads of the bundle.
The bundle and the lap can be combined in
various ways, for example by means of one or more
depositing arms or by means of a carriage carrying the
threads of the lap which are arranged in parallel or by
depositing the threads pneumatically (if appropriate,
with the formation of loops or of a mat) or by
depositing the cut threads, etc.
According to a first embodiment, combination
takes place by the lap of threads (in this case, they
are preferably continuous threads) being incorporated
transversely into the bundle of parallel threads, the
bundle being, in this particular case, separated into
two parts (one part being vertically in line with the
other, for example one thread out of two being
temporarily raised relative to the initial plane of the
bundle and, if appropriate, the other threads being
temporarily lowered relative to the initial plane)
delimiting a space, within which the threads are
projected with the aid of a rapier loom. This loom
comprises, for example, two rapiers equipped with
grippers, one rapier introducing, for example, the
threads of the lap into the middle of the bundle and
the second rapier extracting the threads from the other
side of the bundle, the threads then being cut. The
loom may also comprise a single rapier.
According to a second embodiment, a carriage
carrying the lap of threads in the form of parallel
continuous threads delivers the lap into the bundle of
parallel threads, the lap and the bundle subsequently
being, if appropriate, sewn to one another by means of
binding threads delivered continuously (for example,
fine threads of polyester or of polypropylene or of
glass) . These binding threads are put to use, for
example, by means of the periodic movement of a
transverse needle bar. Contrary to the previous
embodiment, the threads of the lap and of the bundle
are not intermingled, but are simply bound to one
another. The products obtained in this case have good
alignment (and therefore little shrinkage) and a high
degree of deformability.
According to a third embodiment, combination
takes place by the lap of threads (in this case, these
are likewise preferably continuous threads) being
incorporated transversely into the bundle of parallel
threads with the aid of a netting loom with weft
insertion by a rotary arm or rotary arms. This loom may
comprise one or more rotary arms, the threads of the
lap coming either from a bobbin or bobbins arranged on
the wheel carrying the depositing arms, this wheel
being driven in rotation, or from a bobbin or bobbins
arranged on another support in movement (synchronous
with the movement of the depositing arms) or from a
stationary bobbin or stationary bobbins, in this case
the arm or arms being generally hollow arms with an
axial passage. The products obtained in this embodiment
have very little shrinkage and very good mechanical
properties.
According to a fourth embodiment, combination
takes place by the threads being cut above the bundle
of parallel threads, the cut threads being oriented in
various directions, particularly in directions
transverse to that of the bundle of threads, the cut
threads forming a lap which is superposed on the bundle
of threads. Preferably, in this embodiment, the threads
fall onto one or more deflectors (as a rule, a metal
plate, or, if appropriate, a plurality of metal plates,
inclined at an angle of the order of 45 to 80° relative
to the bundle of threads), making it possible to orient
them more accurately in directions transverse relative
to the given direction, before they are distributed on
the bundle of parallel threads.
According to a fifth embodiment, combination
takes place by one or more threads being projected
transversely in the form of a mat onto the bundle of
parallel threads, the lap of threads in the form of the
mat being, if appropriate, covered by a second bundle
of parallel threads which is displaced in the same
direction as the first bundle of parallel threads.
The combination of the bundle and lap of
threads (displaced at a speed of, for example, between
0.5 and 10 m/min) passes into at least one zone, where
it is heated to a temperature between the melting
points of the materials forming the combination, this
temperature also being below the degradation
temperature of the material having the lowest melting
point. In the present invention, the "degradation
temperature" designates, by extension, the minimum
temperature at which decomposition of the molecules
making up the material is observed (as traditionally
defined and understood by the average person skilled in
the art) or an undesirable change in the material, such
as an inflammation of the material, a loss of
intactness of the material (resulting in the material
flowing out of the lap) or an undesirable colouring of
the material (for example, yellowing), is observed.
This degradation temperature can be evaluated in the
traditional way by thermogravimetry and/or by noting
the minimum temperature at which one of the
abovementioned effects occurs.
In the present invention, the combination is
heated sufficiently to make it possible for at least
some of the threads to be bound to one another by means
of the material with the lowest melting point, after
heating and/or compression, and, in most cases (except
when a structure of a netting type is desired instead),
to make it possible to obtain a solid or approximately
solid structure.
As examples, the heating temperature may be of
the order of 190 to 230°C when the lap of threads
consists of glass and of polypropylene, it may be of
the order of 280 to 310°C when the lap consists of
glass and of polyethylene terephthalate (PET) , and it
may be of the order of 270 to 280-290°C when the lap
consists of glass and of polybutylene terephthalate
(PBT).
The combination may be heated in several ways,
for example with the aid of a double-band laminating
machine, or with the aid of heated cylinders or of an
irradiation device, such as an infrared radiation
device (for example, in the form of an infrared oven or
lamp or lamps or panel or panels), and/or at least one
hot-air blowing device (for example, a forced-
convection hot-air oven).
Heating may be sufficient to make it possible
to fix the combination by means of the melted organic
material (thermofixing). In many cases, however, the
heated combination also undergoes compression with the
aid of a compression device, for example with the aid
of at least one two-roll calender. The force exerted on
the combination during its passage through the
compression device, for example during its simultaneous
passage between two rolls of a calender, is generally
several kgf/cm, even several tens of kgf/cm. The
pressure exerted in the compression device compacts the
lap of threads, the structure obtained being set by
cooling, this cooling being capable of being carried
out, at least partially, simultaneously with the
compression or also being capable of being carried out
after a hot-compression step.
The compression device may comprise at least
one calender, in particular a calender maintained at a
temperature below the solidification point of the
material with the lowest melting point (the calender
is, for example, at a temperature of between 20 and
150°C), in order to solidify the said material.
The compression device may also comprise a
plurality of calenders, particularly where large
thicknesses are concerned and if it is desirable to
have very good planeness and/or high production speeds.
Moreover, particularly when use is made of materials
with high melting points or having a high
crystallization rate (for example, polyesters), and
when the aim is to obtain solid or approximately solid
sheets, it may be desirable to heat the calender (or at
least the first calender) of the compression device to
a temperature higher than 75°C, preferably higher than
100°C, even higher than 150°C. In this case, the rolls
of the heated calender are preferably covered with an
anti-adhesive covering based, for example, on PTFE
and/or a mould release film (made of silicone-coated
paper or of glass cloth coated, for example, with PTFE)
is unwound between each roll and the lap of threads
(this film may, if appropriate, be in the form of an
endless band).
According to one embodiment of the invention,
the compression device may also comprise or consist of
a band press (equipped, for example, with bands of
steel or of glass cloth or of aramid cloth, the cloth
preferably being coated with PTFE) comprising a hot
zone (in particular, with one or more calenders)
followed by a cold zone (with cooling elements in the
form of bars, plates, etc. and, if appropriate, one or
more calenders).
Cooling may take place in the compression
device (for example, in a cold calender or in the cold
zone of a double-band flat laminating machine) or may
take place outside the compression device, for example
by natural or forced convection. In order to accelerate
its cooling, the composite band obtained at the exit of
the abovementioned compression device can pass onto a
cooling table, in which cold water circulates, this
table, if appropriate, being slightly curved convexly,
in order to improve contact with the band. In order to
improve cooling and/or contact even further, the table
may be combined with press rollers, preferably cooled
(for example, by water circulation), and/or with one or
more freely bearing or pressed cooled plates and/or
with one or more air-blowing nozzles, and/or the band
may be drawn by take-up rollers located, for example,
at the exit of the table.
The composite band, after being compressed and
cooled, can be wound onto a mandrel, the diameter of
which is a function of the thickness of the band (the
sheet formed then corresponds to the wound band), or
can be cut by a cutting device (for example, a
guillotine or circular-saw device) , so as to form a
plurality of sheets.
Although the present method is essentially
described in terms of the combination of one lap of
threads and of one bundle of parallel threads, it is
quite clear that a plurality of laps may be combined
with one or more bundles of threads in the same way as
described above. It is possible, in particular, to
combine a plurality of laps of threads in order to form
sheets of greater thickness. Thus, according to one
embodiment of the invention:
• a first bundle of parallel threads is driven in a
given direction,
• a lap of threads oriented transversely relative to
this given direction is combined with this first
bundle,
• at least one second bundle of parallel threads is
combined with the bundle and with the lap in the
given direction, the first bundle of threads and/or
the lap of threads and/or the second bundle of
threads comprising at least two materials having
different melting points,
• the combination is heated, being displaced in the
given direction, and is fixed by the action of heat
and/or of pressure, then by cooling, so as to form a
composite band,
• the band is collected in the form of one or more
composite sheets.
It is also possible, before compression of the
assembly, to unwind one or more surface films onto one
or two faces of the combination, these films adhering
under hot conditions to the combination of the
bundle(s) and lap(s). These films may be of a material
or materials identical to or different from those (or
one of those) of the threads of the combination (they
may be metallic, organic, etc.), these films preferably
being of a nature or having a covering of a nature
close to the nature of the material of lowest melting
point present in the combination.
In more general terms, it is possible to apply
to the surface of the combination and/or introduce into
the combination other structures in the form of threads
or an assembly of threads, cellular structures, or
structures containing elements in the form of powder,
of granules or of liquid, leaves or panels or films, of
an essentially metallic or polymeric or mineral or
vegetable nature, which are continuous or
discontinuous, and imparting particular properties to
the composite sheets obtained (additional reinforcement
by means of threads of different nature, improvement in
the mechanical properties, protection against
electromagnetic radiation, improvement in thermal or
acoustic insulation, lightened composite structures,
improved moulding capacity, surface appearance, etc.).
The band obtained in the method according to
the invention may be collected in the form of packages
(that is to say, as it were, in the form of a single
wound composite sheet) or of a plurality of sheets cut
to the dimensions required by the users.
The present invention also relates to an
apparatus for carrying out the method. This apparatus
comprises:
a) one or more devices (or members) for feeding at
least one bundle of parallel threads,
b) one or more devices (or members) for feeding at
least one lap of threads,
c) one or more devices for orienting the threads of
the lap transversely to the direction of the
parallel threads of the bundle (for example,
according to the embodiment, a rapier loom, a
carriage loom, a netting loom with weft insertion
by rotary arms, or a deflector, as described in
the various embodiments explained above),
d) at least one device (or member) for heating the
combination of the bundle and of the lap,
e) and at least one device for cooling the combination.
The apparatus according to the invention may
also comprise at least one compression device and/or at
least one cutting device and/or at least one device for
collecting the composite sheets. The cooling device may
also be a compression device, or the apparatus
according to the invention may comprise at least one
device for compressing the combination of the bundle
and of the lap separate from the cooling device.
The composite sheets obtained as a result of
the combination of steps of the method according to the
invention are particularly economical and comprise
filaments of a material having a higher melting point
(generally reinforcing filaments) which are embedded in
the sheet and are arranged, generally with regard to at
least part of them, in the direction of travel of the
sheet during its manufacture and, preferably likewise
with regard to the other part (or at least another part
of these filaments) in a direction transverse to the
direction of travel. The sheet thus comprises at least
one assembly of filaments of a material having a higher
melting point, which are arranged approximately
parallel in a first direction, and, if appropriate, at
least one second assembly of filaments of a material
having a higher melting point, which are arranged
approximately parallel in a second direction preferably
transverse to the first, all these filaments being
embedded in the material having a lower melting point.
The sheets obtained generally have a thickness of
between a few tenths of a millimetre and approximately
2 mm, are rigid and easy to cut and have good
mechanical properties. They may be used as such in
moulding methods or in combination with other products.
They may be used, for example, for the thermoforming
and the moulding of pieces made of composite products.
As a general rule, the sheets obtained have
little shrinkage (the ratio between the length of the
thread in one direction and the length of the sheet in
this direction, this ratio being evaluated with regard
to threads passing through the sheet in this direction
and not with regard to cut threads) in each of the
preferred directions of orientation of the threads, the
shrinkage generally being below 6%, or even 2% or 1%,
in at least one direction. With regard to sheets
obtained, using a netting loom with weft insertion by
rotary arms, even the complete or virtually complete
absence of shrinkage can be seen.
Other advantages and characteristics of the
invention may be gathered from the following accompanying drawings
which illustrate the invention, but without limiting
it, and in which:
• Figure 1 shows a diagrammatic view of an apparatus
allowing a first implementation of the invention,
• Figure 2 shows a diagrammatic view of an apparatus
allowing a second implementation of the invention,
• Figure 3 shows a diagrammatic view of an apparatus
allowing a third implementation of the invention,
• Figure 4 shows a diagrammatic view of an apparatus
allowing a fourth implementation of the invention,
• Figure 5 shows a diagrammatic view of part of an
apparatus for implementing the invention,
• Figure 6 shows a diagrammatic view of part of an
apparatus for implementing the invention.
In the method illustrated in Figure 1, a
double-rapier weaving loom 1 is fed with a bundle of
threads 2 (having, for example, 4 threads per cm) which
come from rovings 3, the threads passing through a comb
and arriving in parallel in the weaving loom (a part
which is not visible and is not shown in the figure) ,
these threads being, for example, composite threads
composed of glass filaments and of polypropylene
filaments blended with one another.
A fabric 4 is manufactured by the insertion,
for example at 120 strokes/mn, of a thread 5 (coming
from a roving 6 and likewise composed of glass
filaments and of polypropylene filaments) per cm, in
the form of a cloth-like assembly.
The fabric passes under a first cylinder 7
heated, for example, to 200°C and having, for example,
a diameter of the order of 300 mm, and then passes over
a second heated cylinder 8. The polypropylene filaments
melt in contact with the hot surfaces. The product then
passes into the nip of a calender 9, thermostatically
controlled at, for example, 40°C, where it is cooled
and converted into a sheet 10, for example with a
thickness of about 0.7 mm, composed, for example, of
40% by weight of polypropylene and of 60% by weight of
glass filaments oriented in two perpendicular
directions. It is subsequently, for example, wound onto
a tube 11 having a diameter of 100 mm.
In Figure 2, a bundle 20 of parallel composite
threads composed, for example, of glass filaments and
of polypropylene filaments is unwound from one or more
beams 21 and is introduced into a knitting machine 22
equipped with a weft insertion carriage 23 capable of
taking up a plurality of threads 24 simultaneously
(these threads having come from rovings 25 and likewise
being composite threads) and of depositing them
transversely to the direction of displacement of the
bundle of threads, for example at the rate of 2 threads
per cm.
These threads 24 may be bound to the threads of
the bundle by means of a simultaneous knitting
operation, the binding threads being products having a
linear density, or mass per unit length, of less than
50 tex (g/km). The sewn product subsequently passes
into a consolidation device similar to that of Figure
1.
In an economical variant which does not employ-
binding threads, a second bundle of threads is brought
onto the lap of threads deposited by means of a
carriage, in order to block them. The non-sewn assembly
is subsequently conveyed directly onto the
consolidation and winding system.
In another more elaborate variant, use is made
of a plurality of weft insertion carriages which are
movable in the plane along two axes and which make it
possible to produce multi-layer surfaces having a
plurality of directions, for example 0o/-45°/+45o/90°.
These thicker products may or may not be bound by
knitting and may be directly consolidated in line by
melting and cooling under pressure or simply
thermofixed by melting/cooling, without pressure being
applied.
Figure 3 describes a method for the manufacture
of a plane product in the form of a consolidated glass/
thermoplastic composite product, in which use is made
of two bundles of composite parallel threads 30 and 31
and a lap of composite threads 32 which come from
rovings 33 deposited transversely in the form of a mat
having continuous threads.
The bundles of parallel threads may come from
creels, not shown in Figure 3, or be wound on beams 34
and 35, these threads passing through combs 36, 37
keeping them parallel, then through take-up cylinders
38, 39 making it possible to reduce the tensions of the
threads, before these enter the consolidation device.
A plurality of threads 32 are deposited between
these bundles by means of a carriage 40 which is
displaced transversely to the direction of displacement
of the bundles in an alternating movement, in order to
form a mat (or a lap of looped threads) . This carriage
is, for example, equipped with a cylinder-type take-up
system coupled to a compressed-air ejector having a
Venturi effect.
The combination of the bundles and of the lap
subsequently passes between the continuous bands 41
(made of glass fabrics impregnated with polytetra-
fluoroethylene - PTFE -) of a flat laminating press 42.
This laminating press comprises a heating zone 43 and a
zone 44 cooled by water circulation and, between these
two zones, pressing cylinders 45 which compress the
melteed thermoplastic material under a pressure in the
vicinity of, for example, 10 to 20 N/cm2.
At the exit of this double-band press, the
product has a homogeneous appearance, this appearance
being capable of being improved, for example, by two
polypropylene films 46 and 47 deposited on either side
of the combination between the bands of the press. The
rigid sheet obtained is subsequently either wound onto
a tube 48 having a diameter of, for example, 100 mm or
is cut continuously into a plurality of rectangles by
means of blades and an automatic shearing machine which
are not shown.
In one variant, the double-band press is
replaced by a device comprising two heated rollers
covered with PTFE, followed by a calender having two
cooled cylinders. The two polypropylene surface films
46 and 47 are, in this case, preferably introduced into
the nip of the cold calender.
The method shown in Figure 4 closely resembles
that shown in Figure 3 (the same references being
adopted again for the same elements). The difference is
in the type of mat which is sandwiched between the two
warps of parallel threads. Here, this mat is, for
example, formed by threads 50 of pure glass which are
cut to a length of 50 or 100 mm and are oriented in the
transverse direction by means of a deflecting plate 51.
Two polypropylene films 52 and 53 having a thickness
of, for example, 50 µm may, if appropriate, be
introduced on either side of this mat. Two other
polypropylene films, not shown, may also be added on
each side of the product, in order to improve its
surface appearance. The product obtained may be wound
or cut into sheets.
The cut-thread mat may also consist of the
thread of the same nature as that of the threads of the
bundle (for example: 60% glass and 40% polypropylene).
In this case, there is no need to introduce films 52
and 53 into the core of the product.
• That part of the apparatus which is shown in
Figure 5 is a variant of the "consolidation" part of
the methods shown in Figures 1 and 2. It follows, for
example, a weaving or knitting loom with weft insertion
60. The organic part is melted contactlessly by means
of two infrared radiation panels 61 which are
retractable in order to avoid the risks of the
combination being damaged (or burnt) during stoppages
of the loom. After the partially melted product has
been deflected on a thermostatically controlled bar 62,
the said product is compacted and cooled in the nip of
a calender 63, for example at 40°C, and then passes, if
appropriate, over a convexly-curved cooling table 64.
The product, driven by rollers 65, 66, is subsequently
cut into sheets 67 with the aid of one or more cutting
devices 68.
Where a shutdown of the weaving (or knitting)
loom is concerned, an accumulator 69 draws to the rear
that part of the product which is located between the
end of the infrared panels and the entrance of the
calender, so as not to have zones of non-compacting
product corresponding to each stoppage. Moreover, in
order to avoid the product being damaged on the
deflecting bar, thermostatically controlled at, for
example, 220°C, a move-away bar 7 0 moves the product
away.
The method in Figure 6 is a variant of the
method described in Figure 5 and leads to products
which are simply thermofixed, without consolidation.
The previous system of compacting/cooling by calender
and convexly-curved cooling table is replaced, here, by
air-blowing boxes 71.
The sheets produced according to the present
invention are particularly suitable for the production
of composite articles by moulding.
CLAIMS
1. Method for the manufacture of composite sheets,
in which:
• a bundle of parallel threads is driven in a given
direction,
a lap of thread or threads oriented transversely
relative to this given direction is combined with
this bundle, the bundle of threads and/or the lap of
thread or threads comprising at least one organic
material and at least one reinforcing material, and
the combination comprising at least 10% by weight of
organic material,
• the combination is heated, being displaced in the
given direction, and is fixed by the action of heat
and/or of pressure, then by cooling, so as to form a
composite band,
• the band is collected in the form of one or more
composite sheets.
2. Method according to Claim 1, characterized in
that the reinforcing material is provided solely in the
form of threads, separate from one another and
unconnected.
3. Method according to one of Claims 1 and 2,
characterized in that the combination comprises at
least 50% by weight of co-blended threads.
4. Method according to Claim 3, characterized in
that the co-blended threads consist mainly of glass
filaments and of filaments of thermoplastic organic
material which are intimately mixed.
5. Method according to one of Claims 1 to 4,
characterized in that the lap of threads is a lap of
continuous thread or continuous threads and is combined
with the bundle of threads, using a rapier loom.
6. Method according to one of Claims 1 to 4,
characterized in that the lap of thread or threads is a
lap of continuous thread or continuous threads and is
combined with the bundle of threads, using a weft
insertion carriage, the threads of the bundle and of
the lap being, if appropriate, sewn to one another by
means of binding threads.
7. Method according to one of Claims 1 to 4,
characterized in that the lap of thread or threads is a
lap of continuous thread or continuous threads, and in
that combination takes place by the lap of threads
being incorporated transversely into the bundle of
parallel threads with the aid of a netting loom with
weft insertion by rotary arms.
8. Method according to one of Claims 1 to 4,
characterized in that the lap of thread or threads is a
lap of cut thread or cut threads, and in that
combination takes place by the threads being cut above
the bundle of parallel threads, the threads falling,
preferably beforehand, onto one or more deflectors.
9. Method according to one of Claims 1 to 4,
characterized in that combination takes place by one or
more threads being projected transversely in the form
of a mat onto the bundle of parallel threads, the lap
of threads in the form of the mat being, if
appropriate, covered by a second bundle of parallel
threads which is displaced in the same direction as the
first bundle of parallel threads.
10. Method according to one of Claims 1 to 9,
characterized in that:
• a first bundle of parallel threads is driven in a
given direction,
• a lap of threads oriented transversely relative to
this given direction is combined with this first
bundle,
• at least one second bundle of parallel threads is
combined with the bundle and with the lap in the
given direction, the first bundle of threads and/or
the lap of threads and/or the second bundle of
threads comprising at least two materials having
different melting points,
• the combination is heated, being displaced in the
given direction, and/or is fixed by the action of
heat and/or of pressure, then by cooling, so as to
form a composite band,
• the band is collected in the form of one or more
composite sheets.
11. Method according to one of Claims 1 to 10,
characterized in that other elements imparting
particular properties to the composite sheets obtained
are applied to the surface of the combination and/or
introduced into the combination.
12. Apparatus for the manufacture of at least one
composite sheet as claimed in claim 1 this apparatus comprising:
a) one or more devices (or members) for feeding at
least one bundle of parallel threads,
b) one or more devices (or members) for feeding at
least one lap of threads,
c) one or more devices for orienting the threads of
the lap transversely to the direction of the
parallel threads of the bundle,
d) at least one device (or member) for heating the
combination of the bundle and of the lap,
e) and at least one device for cooling the
combination.
13. Apparatus according to Claim 12, characterized
in that it comprises, furthermore, at least one
compression device and/or at least one cutting device
and/or at least one device for collecting the composite
sheets.
14. Apparatus according to one of Claims 12 and 13,
characterized in that the device for orienting the
threads of the lap is a a rapier loom, a carriage loom,
a netting loom with weft insertion by rotary arms, or a
deflector.
15. Apparatus according to one of Claims 12 to 14,
characterized in that it comprises, furthermore, an
accumulator and/or a move-away bar drawing the product
to the rear and/or moving the product away from the
heating zones and/or for compression in the event of a
stoppage of an upstream device.
16. Composite sheet based on at least one
thermoplastic organic material and on at least
reinforcing threads, which is obtained by means of the
method according to one of Claims 1 to 11 and which is
characterized in that the shrinkage is below 6%.
Method for the manufacture of composite sheets, in which: a bundle of
parallel threads is driven in a given direction, a lap of thread or threads
oriented transversely relative to this given direction is combined with this
bundle, the bundle of threads and/or the lap of thread or threads comprising
at least one organic material and at least one reinforcing material, and the
combination comprising at least 10% by weight of organic material, the
combination is heated, being displaced in the given direction, and is fixed by
the action of heat and/or of pressure, then by cooling, so as to form a
composite band, the band is collected in the form of one or more composite
sheets.

Documents:

in-pct-2002-201-kol-granted-abstract.pdf

in-pct-2002-201-kol-granted-claims.pdf

in-pct-2002-201-kol-granted-correspondence.pdf

in-pct-2002-201-kol-granted-description (complete).pdf

in-pct-2002-201-kol-granted-drawings.pdf

in-pct-2002-201-kol-granted-form 1.pdf

in-pct-2002-201-kol-granted-form 18.pdf

in-pct-2002-201-kol-granted-form 2.pdf

in-pct-2002-201-kol-granted-form 26.pdf

in-pct-2002-201-kol-granted-form 3.pdf

in-pct-2002-201-kol-granted-form 5.pdf

in-pct-2002-201-kol-granted-letter patent.pdf

in-pct-2002-201-kol-granted-priority document.pdf

in-pct-2002-201-kol-granted-reply to examination report.pdf

in-pct-2002-201-kol-granted-specification.pdf

in-pct-2002-201-kol-granted-translated copy of priority document.pdf

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Patent Number

219005

Indian Patent Application Number

IN/PCT/2002/201/KOL

PG Journal Number

16/2008

Publication Date

18-Apr-2008

Grant Date

16-Apr-2008

Date of Filing

07-Feb-2002

Name of Patentee

SAINT-GOBAIN VETROTEX FRANCE S.A

Applicant Address

130 AVENUE DES FOLLAZ F-73000 CHAMBERY

Inventors:

#	Inventor's Name	Inventor's Address
1	LOUBINOUX DOMINIQUE	LES CLOS DES MOULINS, 137 RUE DE FONTVIEILLE, 73290 LA MOTTE SERVOLEX

PCT International Classification Number

D04H 3/04

PCT International Application Number

PCT/FR00/02354

PCT International Filing date

2000-08-22

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	99/10,842	1999-08-27	France