FR2949791A1 - PROCESS FOR PRODUCING PRE-IMPREGNATED FIBROUS MATERIAL OF THERMOPLASTIC POLYMER - Google Patents

Abstract

The invention relates to a method of manufacturing a fibrous material such as a nonwoven fabric, felt, which may be in the form of strips, webs, braids, locks or pieces, based on reinforcing fibers and thermoplastic polymer. According to the invention at least two sets of different fibers are used, a first series of fibers comprising mineral fibers and a second series of fibers comprising thermoplastic polymer fibers having a melting temperature Tf, the two sets of fibers are available at contact one of the other then heated all of the two sets of fibers to a temperature at least equal to the melting temperature Tf of the thermoplastic fibers and then allowed to cool to room temperature. The invention applies to the manufacture of 3D parts.

Description

FIELD OF THE INVENTION The present invention relates to a method of manufacturing a fibrous material, such as a fabric, felt, non-woven material which may be in the form of strips, tablecloths or , braids, locks or pieces, based on reinforcing fibers and thermoplastic polymer. The fibers that can be used in the composition of the material are more particularly carbon fibers, glass fibers, polymer-based fibers, vegetable fibers, used alone or as a mixture. Of interest in the present invention are lightweight composite materials for the manufacture of mechanical parts having a 3-dimensional structure and having properties of good mechanical strength, thermal and able to evacuate electrostatic charges, that is to say to say properties compatible with the manufacture of parts in the field of mechanics, aeronautics and nautical. STATE OF THE ART It is known to use refractory fabrics pre-impregnated with a resin in order to produce a thermally insulating matrix so as to provide thermal protection for mechanical devices subjected to high temperatures, as may be the case in the field. aeronautics or the automobile. Reference can be made to European Patent No. 0 398 787, which describes a thermal protection layer comprising a refractory fabric intended to protect the ferrule of a ramjet engine chamber. In addition to the complexity of producing this thermal protection layer, the refractory fabric embedded in this layer only fulfills the function of heat shield. In recent years, composite fibers have also been used to manufacture, in particular, various aeronautical or automobile parts. These composite fibers, which are characterized by good thermomechanical and chemical resistance, consist of a reinforcing filament reinforcement intended to distribute the tensile, flexural or compressive tensile forces, in some cases to provide protection chemical material and give it its shape. Ref: 0276-ARK11 One can for example refer to the patent application FR 2 918 081 which describes a process for impregnating continuous fibers with a composite polymer matrix containing a thermoplastic polymer. Methods for manufacturing composite parts from these coated fibers include various techniques such as, for example, contact molding, spray molding, autoclaved draping or low pressure molding. A technique for making hollow parts is that called filament winding, which consists in impregnating dry fibers with a resin and then winding them on a mandrel formed of reinforcements and of a shape adapted to the part to be manufactured. The piece obtained by winding is then cured by heating. Another technique for making plates or shells consists in impregnating fiber fabrics and then pressing them into a mold in order to consolidate the laminated composite obtained.

For the manufacture of polymeric material with fiber reinforcement, a sizing step is generally used, which consists in depositing a thermoplastic polymer film on fibers. Thus, the process for manufacturing preimpregnated material from Cyntex comprises, as a fiber coating step, the continuous passage of fibers in a molten bath of thermoplastic polymer containing an organic solvent such as benzophenone; this solvent makes it possible to adapt the viscosity of the melted mixture and to ensure a good coating of the fibers. The pre-impregnated fibers of polymers are then shaped (for example cut into strips and then placed under a press, for producing the structural parts, and then heated to a temperature above the melting temperature of the polymer to ensure the cohesion of the polymer. material and in particular the adhesion of the polymer to the fibers.

The technical problem Depending on the chemical nature of the polymer, the heating temperatures can rise to temperatures above 250 ° C, and even higher than 320 ° C, temperatures much higher than the boiling temperature of the solvent, resulting in a sudden departure of solvent, causing defects in the room and therefore a lack of reproducibility of the process as well as the risk of explosion endangering the operators. Ref: 0276-ARK11 Another known method of fiber sizing is the continuous passage of the fibers in an aqueous dispersion of polymeric powder and then drying the fibers to evaporate the water in an oven, followed by a heat treatment for the fusion of the polymer. This heat treatment can be done in a shaping die, especially to make strips of pre-impregnated material. These strips are then used for the manufacture of structural parts, by arrangement in a mold, a press, etc. This process requires two separate heating zones or the use of two separate furnaces is complex and difficult to implement.

As another state of the art relating to the manufacture of a fibrous material, reference may be made to document US Pat. No. 4 541884 from Imperial Chemical Industries or to document EP 0406 067 filed in the joint names of Atochem and the State. French. As prior art relating to the introduction of fibers for the formation of fibrous material and the constitution of structures based on this fibrous material, reference may be made to US Pat. No. 6,607,626; US Pat. No. 6,939,424 and US Pat. No. 7,235,149. SUMMARY OF THE INVENTION The subject of the invention is a new process for the on-line and continuous manufacture of fibrous material, making it possible to overcome the above disadvantages. The proposed method also makes it possible to obtain a homogeneous fibrous material. There can be no irregularities in the structure or node susceptible to embrittle the material with risks of rupture as is the case with the methods of the prior art. More specifically, the subject of the invention is a process for manufacturing a fibrous material pre-impregnated with a thermoplastic polymer, consisting of i) using at least two sets of different fibers, a first series of fibers comprising mineral fibers and a second series of fibers comprising thermoplastic polymer fibers having a melting temperature Tf, ii) arranging the two series of fibers in contact with each other and then iii) heating all of the two series of fibers to one another. temperature at least equal to the melting temperature Tf of the thermoplastic fibers and to allow the whole to cool to room temperature. Ref: 0276-ARK11 A device for setting up the two series of fibers advantageously makes it possible to shape the two series, for example, in the form of a strip or a sheet, or a strip that is cut to the desired length. This device can also provide calendering.

The mineral fibers may be arranged side by side or may be woven in two directions. These fibers may be of the same chemical nature or be of a different nature, for example carbon fibers woven with glass fibers. In order to improve the mechanical strength of the structure made from the appropriate arrangement of several materials (stack of several strips for example), it is expected to have on the assembly of the two sets of fibers, just before step iii ) inorganic fillers in powder form, conductive or not, such as silica, metal powder, powdery carbon black, carbon fibrils, carbon nanotubes, but also silicon carbide, carbonitride nanotubes boron, boron nitride or silicon. Preferably, the charges used are conducting electricity and / or heat, such as carbon nanotubes, carbon fibrils or even carbon black.

Preferably, carbon nanotubes are used. It is recalled that carbon nanotubes NTC means one or more hollow tubes with one or more graphitic plane walls or graphene sheets, coaxial, or graphene sheet wound on itself. This or these tubes, most often opening (ie open at one end) resemble several coaxially arranged mesh tubes; in cross section the CNTs are in the form of concentric rings. The external diameter of the CNT is from 2 to 50 nm. We speak of single-walled carbon nanotubes (SWNTs) or multi-walled carbon nanotubes (MWNTs).

The dusting of the loads can be ensured by means of a vibrating support, in order to ensure a homogeneous distribution on the fibers. For example, the CNT powder is deposited directly on the fibrous material, placed flat on a vibrating support, in order to allow the distribution of the powder on the fibers. Ref: 0276-ARK11 Before the dispersion of the charges on the two series of fibers, these charges can be subjected to a chemical treatment in order to bring them functions for example polar in order to improve their adhesion on the polymeric fibers or subjected to a heat treatment, for example greater than 900 ° C and better at 1000 ° C to remove metal impurities due to their synthesis process. Advantageously, the charges are neither chemically nor thermally treated. The thermoplastic fibers may consist of a single type of polymer or of several polymers; in the case of several polymers, the melting temperature Tf above is that of the highest melting temperature polymer. The polymers used in the constitution of the fibers of the second series of fibers can be chosen, without limitation, from: polyethylenimines (PEI), polyamides (PI), polyolefins such as polyethylene, especially high density polypropylene and copolymers of ethylene and / or polypropylene; thermoplastic polyurethanes (TPU); polyesters such as polyhydroxyalkanoates; polyethylene terephthalates (PET) or butylene (PBT); polyphenylsulfides (PPS) - polyvinyl chlorides - silicone or fluorosilicone polymers; polyvinyl alcohol) - polyarylether ketones (PAEK: PolyArylEtherKetone) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK); polyamides such as polyamide such as polyamide 6 (PA-6), polyamide 11 (PA-11), polyamide 12 (PA-12), polyamide 6.6 (PA-6.6), polyamide 4.6 (PA-6), 4.6), polyamide 6.10 (PA-6.10), polyamide 6.12 (PA-6.12), aromatic polyamides, in particular polyphthalamides and aramid, and block copolymers, in particular polyamide / polyether, at least one monomer of formula (I):

Ref: 0276-ARK11 CFX = CHX '(I) where X and X' independently denote a hydrogen or halogen atom (in particular fluorine or chlorine) or a perhalogenated (in particular perfluorinated) alkyl radical, and preferably X = F and X '= H, such as polyvinylidene fluoride (PVDF), preferably in a form, copolymers of vinylidene fluoride with for example hexafluoropropylene (HFP), fluoroethylene / propylene copolymers (FEP), copolymers of ethylene with either fluoroethylene / propylene (FEP), or tetrafluoroethylene (TFE), or perfluoromethylvinyl ether (PMVE), or chlorotrifluoroethylene (CTFE), some of these polymers being marketed especially by the ARKEMA company under the name Kynar; and - their mixture.

For the fluoropolymers, it is preferred to use a homopolymer of vinylidene fluoride (VDF of formula CH2 = CF2) or copolymer of VDF comprising by weight at least 50% by weight of VDF and at least one other monomer copolymerizable with VDF. The VDF content must be greater than 80% by weight, or even better 90% by weight, to ensure good mechanical strength to the structural part, especially when subjected to thermal stresses. The comonomer may be a fluorinated monomer chosen, for example, from vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); ethylene tetrafluoroethylene (ETFE), hexafluoropropylene (HFP); perfluoro (alkyl vinyl) ethers such as perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE) and perfluoro (propyl vinyl) ether (PPVE); perfluoro (1,3-dioxole); perfluoro (2,2-dimethyl-1,3-dioxole) (PDD). Preferably, the optional comonomer is chosen from chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE). The comonomer may also be an olefin such as ethylene or propylene. The preferred comonomer is HFP. For structural parts that must withstand high temperatures, in addition to the fluorinated polymers, it is advantageous to use

Ref: 0276-ARK11 the invention the PAEK (PolyArylEtherKetone) such as PEK, PEEK, PEKK, PEKEKK etc. Compared to the processes of the prior art, the process according to the present invention is perfectly well suited to polymers having high melting temperatures, for example greater than 130 ° C, such as fluoropolymers, PAEKs, high density polyethylenes. , or else PET or PBT or PBT. It is also possible to use Kevlar fibers or aramid fibers. The mineral fibers to which the invention applies are in particular the fibers of carbon, glass, boron, silica, natural fibers such as flax, silk including spider, hemp, sisal. Organic fibers may be mixed with the mineral fibers to form the first series of fibers which is to be impregnated with polymer after the melting of the thermoplastic polymer fibers. In this case we will choose of course organic fibers that is to say polymer fibers whose melting temperature is higher than the melting temperature Tf fibers of the second series that one melts. Thus, there is no risk of fusion for the organic fibers present in the first series of fibers. The fibrous material made with the process is obtained with 50% mineral fibers and 50% thermoplastic polymer fibers, preferably with 30% mineral fibers and 70% thermoplastic polymer fibers. The invention also relates to the use of fibrous material as described for the manufacture of mechanical parts in 3D, in particular the wings of an airplane, the fuselage of an airplane, the hull of a boat, the spars or spoilers of an automobile, or brake discs, or the cylinder body or steering wheels. The invention also relates to a system for implementing the method, this system comprising a device for placing fibers in such a way as to arrange the two series of fibers in contact with each other, and a device for heating the fibers. two sets of fibers. According to the invention, the heating of the two sets of mineral fibers and of polymer is carried out by a laser heating or a plasma torch or an infrared oven.

Ref: 0276-ARK11 The system may include a calendering device. It can also be provided that the heating is carried out by the calendering device.

Other features and advantages of the invention will become clear from reading the description which is given below and which is given by way of illustrative and non-limiting example and with reference to the figures in which: FIG. diagram of a first implementation system of the method according to the invention, - Figure 2 shows the diagram of a second implementation system of the method according to the invention, - Figure 3 shows the cross-sectional diagram. AA of a fiber-coated support 50 according to the method, - Figure 4 shows the cross-sectional diagram BB of the support 50 after melting of the thermoplastic polymer fibers according to the method, - Figure 5 shows the diagram of a third system of implementation of the method.

The systems shown in Figures 1, 2 and 5 allow implementation of the proposed in-line and continuous manufacturing process according to the invention for the manufacture of fibrous material pre-impregnated with thermoplastic polymer. Each system comprises a device 100 for setting up the two series of fibers, namely the first series of fibers 1 which comprises mineral fibers and the second series of fibers 2 which comprises thermoplastic polymer fibers having their melting temperature equal to Tf . These devices have the same reference 100 in Figures 1, 2 and 5 and provide the same function namely to have the two sets of fibers in contact with one another.

Each system also comprises a heating device 110 and possibly a calendering device 115 as is the case for the systems of FIGS. 1 and 5. It may be provided that the calendering device performs the heating function of two sets of fibers. .

Ref: 0276-ARK11 In the example of the system shown in Figure 1, the device 100 for placing fibers has two superimposed paths. The two series of fibers are brought by the two superimposed paths towards the same direction, these two paths approaching until the two sets of fibers are intercalated to form a homogeneous plane imposed by the size of the fibers, the fibers having constant dimensions. The homogeneous plane is in the form of a strip conveyed so as to pass in front of the heating device 110. This heating device makes it possible, in a few seconds, to reach the desired melting temperature Tf so that the thermoplastic polymer fibers having a melting temperature less than or equal to Tf, melt. The molten polymer adheres to the fibers of the first series (having mineral fibers). After passage to ambient temperature, the strip of fibrous material 10 thus produced can be used as required, for example, be cut by a cutting device 200 to enter the manufacture of mechanical parts. Figure 2 shows a device adapted to the establishment of two sets of fibers on a support 50 serving as a mold to form the structure of a 3D piece of fibrous material.

In this example, the fiber placement device consists of two arms 102 and 103 disposed above a horizontal plane driven by a mechanical system not shown treadmill type 101. Several supports 50 are arranged on this mat the one behind the others following the without advancement. The arm 102 makes it possible to place the fibers of the first series 1 on a support 50 while the arm 103 makes it possible to place the fibers of the second series on a support 50 on which the fibers of the first series have been put in place. Of course, the arms 102 and 103 are motorized so that they can be moved closer to the surface of the supports 50 in order to have a good accuracy in setting up the fibers. For the net stop of the fibers at the edges of the supports 50, the system may comprise cutting arms. When the supports 50 comprise the two sets of fibers, they are conveyed into the heating zone. Each support 50 is placed facing the

Ref: 0276-ARK11 heater 110 to allow the melting of the thermoplastic polymer fibers of the second series. The diagram of FIG. 3 illustrates a support 50 covered with two sets of fibers 1 and 2, seen in cross section.

The diagram of FIG. 4 makes it possible to illustrate this support 50 after melting the fibers of the second series. Only the fibers of the first series 1 can be seen on the section. In the example of the system shown in FIG. 5, the positioning device 100 comprises two channels whose exits are opposite each other. The two series of fibers 1 and 2 are brought by the two paths on the same plane so as to come into contact and to be intercalated in a zone of vis-à-vis and form a homogeneous plane imposed by the size of the fibers. The plane formed by the two sets of fibers in contact, passes for a few seconds in the heating zone provided to obtain the fusion of the thermoplastic polymer fibers. In this example, the calendering device 115 can additionally provide the heating function and substitute for the device 110. At the outlet of the calendering device, the fibrous material is obtained in the form of a strip 10 which can then be used as required. .

In this example, the two series of fibers are each driven by a treadmill type device 111 and 112. It may advantageously be provided rules 113 and 114 for maintaining the spacing of fibers on each of the mats. It is understood that when talking about contacting the fibers by interposing them, this is not limited to placing a fiber of a series between two fibers of the other series. Indeed, the positioning devices 100 allow to place two fibers side by side of the same series between two fibers of the other series. Preferably, such an arrangement will be used to have for example a mineral fiber for two thermoplastic polymer fibers.

This is not limited to placing the fibers side by side. It may also be provided, in the case where the mineral fibers already constitute a weave of two-way weaving type, to put the thermoplastic polymer fibers in contact with this weaving, for example in

Ref: 0276-ARK11 placing on one side of the weaving, this face being then placed facing the heating device. Other systems, for example the mechanical systems described in US Pat. No. 6,607,626; US 6,939,424 and US 7,235,149 could also be suitable for fiber placement. Ref: 0276-ARK11

Claims (12)

REVENDICATIONS1. A process for producing a thermoplastic polymer prepreg fiber material comprising i) using at least two sets of different fibers, a first series of fibers comprising mineral fibers and a second series of fibers comprising thermoplastic polymer fibers having a melting temperature Tf, ii) arranging the two sets of fibers in contact with each other and then iii) heating all of the two series of fibers to a temperature at least equal to the melting temperature Tf of the thermoplastic fibers and allow all to cool to room temperature. 2. A method of manufacturing a fibrous material pre-impregnated with thermoplastic polymer according to claim 1, characterized in that the two series of fibers are placed so as to be in the form of strip or sheet, or ribbon. 3. The manufacturing method according to claim 1 or 2, characterized in that the mineral fibers are arranged side by side or woven in two directions. 4. The manufacturing method according to claim 3, characterized in that the mineral fibers are of the same chemical nature or of different nature. 5. Manufacturing process according to any one of the preceding claims, characterized in that the mineral fibers are selected from carbon fibers, glass, boron, silica, natural fibers such as flax, especially silk. spider, hemp, sisal. 6. Manufacturing process according to any one of the preceding claims, characterized in that the first series of fibers comprises organic fibers whose melting temperature is higher than the melting temperature Tf of the fibers of the second series. Ref: 0276-ARK11 30 7. Manufacturing process according to any one of the preceding claims, characterized in that there is arranged on the assembly of the two sets of fibers, just before step iii) inorganic fillers in powder form, conductive or not such as silica, metal powder, powdery carbon black, carbon fibrils, carbon nanotubes, or as nanotubes of silicon carbide, boron carbonitride, boron nitride or silicon. 8. Manufacturing process according to claim 7, characterized in that the charges used are electrically conductive and / or heat such as carbon nanotubes (CNTs), fibrils (NFC) carbon or the black of carbon. 9. The manufacturing method according to claim 7, characterized in that the CNT powder is deposited and in that this powder is deposited directly distributed on the fibrous material. 10. The manufacturing method according to claim 7 characterized in that, before the dispersion of the charges on the two sets of fibers, these fillers are subjected to a chemical treatment to improve their adhesion to the polymeric fibers or subjected to a heat treatment, greater than 900 ° C and better than 1000 ° C to remove metal impurities due to their synthesis process. 11. Manufacturing process according to claim 7, characterized in that the charges are neither chemically nor thermally treated. 12. Manufacturing method according to any one of the preceding claims, characterized in that the thermoplastic polymer fibers forming part of the fibers of the second series of fibers consist of a single type of polymer or of several polymers; in the case of several polymers, the melting temperature Tf is that of the highest melting temperature polymer. Ref: 0276-ARK1113. Manufacturing process according to claim 12, characterized in that the polymers forming part of the fibers of the second series of are chosen from: polyethylenimines (PEI), polyimides (PI), polyolefins such as polyethylene especially high density polypropylene and copolymers of ethylene and / or polypropylene; thermoplastic polyurethanes (TPU); polyesters such as polyhydroxyalkanoates; polyethylene terephthalate or butylene; polyvinyl chlorides - silicone or fluorosilicone polymers; poly (vinyl alcohol) - polyaryletherketones (PAEK) such as polyetheretherketone (PEEK) and polyetherketoneketone (PEKK); polyamides such as polyamide such as polyamide 6 (PA-6), polyamide 11 (PA-11), polyamide 12 (PA-12), polyamide 6.6 (PA-6.6), polyamide 4.6 (PA-6), 4.6), polyamide 6.10 (PA-6.10), polyamide 6.12 (PA-6.12), aromatic polyamides, in particular polyphthalamides and aramid, and block copolymers, in particular polyamide / polyether, - fluorinated polymers comprising to the month a monomer of formula (I): CFX = CHX '(I) where X and X' independently denote a hydrogen or halogen atom (in particular fluorine or chlorine) or a perhalogenated alkyl radical (in perfluorinated compound), and preferably X = F and X '= H, such as polyvinylidene fluoride (PVDF), preferably in a form, the copolymers of vinylidene fluoride with for example hexafluoropropylene (HFP) , fluoroethylene / propylene copolymers (FEP), copolymers of ethylene with either fluoroethylene / propylene (FEP) or tetrafluoroethyl lene (TFE), either perfluoromethylvinyl ether (PMVE) or chlorotrifluoroethylene (CTFE), some of these polymers being for example marketed under the name Kynar; and their mixture. Ref. 0276-ARK1114. Production method according to Claim 13, characterized in that, for the fluoropolymers, a homopolymer of vinylidene fluoride (VDF of formula CH2 = CF2) or VDF copolymer comprising at least 50% by weight of VDF and at least 50% by weight of VDF is chosen. minus another monomer copolymerizable with VDF. 15. The manufacturing method according to claim 14, characterized in that the VDF content is greater than 80% by weight, and preferably 90% by weight, to ensure good mechanical strength to the structure of parts made of fibrous material. 16. The manufacturing method according to claim 14, characterized in that the comonomer is a fluorinated monomer chosen for example from vinyl fluoride; trifluoroethylene (VF3); chlorotrifluoroethylene (CTFE); 1,2-difluoroethylene; tetrafluoroethylene (TFE); hexafluoropropylene (HFP); perfluoro (alkyl vinyl) ethers such as perfluoro (methyl vinyl) ether (PMVE), perfluoro (ethyl vinyl) ether (PEVE) and perfluoro (propyl vinyl) ether (PPVE); perfluoro (1,3-dioxole); perfluoro (2,2-dimethyl-1,3-dioxole) (PDD) or an olefin such as ethylene or propylene. 17. The manufacturing method according to claim 14, characterized in that the comonomer is chosen from chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), trifluoroethylene (VF3) and tetrafluoroethylene (TFE), preferably the comonomer is HFP. 18. Manufacturing process according to claim 13, characterized in that for structures of parts made of fibrous material to withstand high temperatures, in addition to the fluorinated polymers, PAEK such as PEK, PEEK, PEKK, PEKEKK are used. 19. Use of the fibrous material prepreg of thermoplastic polymer obtained by the process according to claim 1, for the manufacture of 3D mechanical component structures, such as airplane wings, the fuselage of an aircraft, the hull of a boat, the spars or spoilers of a car, or brake discs, or the body of the cylinder or steering wheels. 20. System for implementing the method according to claim 1 characterized in that it comprises a device (100) for placing the fibers so as to arrange the two sets of fibers in contact with each other and a heater (110) of the two series of fibers such as a laser heater or a plasma torch or an infrared furnace. 21. System for carrying out the method according to claim 1, characterized in that it comprises a calendering device (115) of the two series of fibers. Ref: 0276-ARK11