METHOD FOR A COMPOSITE MATERIAL IMPREGNATED WITH THERMOPLASTIC POLYMER, OBTAINED FROM A PREPOLYMER AND A CHAIN EXTENDER

Abstract

A process for a composite material, including an assembly of one or more reinforcing fibers, impregnated with at least one thermoplastic polymer with a glass transition temperature Tg of less than or equal to 75 C. and a melting point of from 150 C. to less than 250 C. or a Tg of greater than 75 C., the process including: i) a step of impregnating said assembly in bulk melt form with at least one thermoplastic polymer, which is the product of polymerization by polyaddition reaction of a reactive precursor composition including: a) at least one prepolymer P(X)n of said thermoplastic polymer, and b) at least one chain extender, represented by Y-A-Y, ii) a step of cooling and obtaining a fibrous preimpregnate, and iii) a step of processing and final forming of said composite material.

Claims

1. A process for manufacturing a composite material comprising an assembly of one or more synthetic or natural reinforcing fibers, melt-impregnated with at least one thermoplastic polymer as matrix, having a glass transition temperature Tg of less than or equal to 75 C. and a melting point (Tm) ranging from 150 C. to less than 250 C. or a Tg of greater than 75 C., said process comprising: i) a step of impregnating said assembly in bulk melt form with at least one thermoplastic polymer, having a viscosity at the impregnation temperature in bulk melt form not exceeding 200 Pa.Math.s, with said at least one polymer being the product of polymerization by polyaddition reaction of a reactive precursor composition comprising: a) at least one prepolymer P(X)n of said thermoplastic polymer, comprising a hydrocarbon-based molecular chain P and bearing at its ends n identical reactive functions X, with X being a reactive function from among: OH, NH.sub.2 or COOH, with n ranging from 1 to 3, and a number-average molecular mass Mn ranging from 500 to 10 000 g.Math.mol-1, b) at least one chain extender, represented by Y-A-Y, comprising two identical functions Y that are reactive with at least one of said functions X of said prepolymer a), with A being a covalent single bond bonding the two functions Y or a non-polymeric hydrocarbon-based diradical, ii) a step of cooling and obtaining a fibrous preimpregnate iii) a step of processing and final forming of said composite material.

2. The process as claimed in claim 1, wherein the thermoplastic polymer is obtained by polymerization of a precursor reactive composition comprising a prepolymer of said impregnation polymer, chosen from: a polyamide, a polyester, copolymers thereof including polyamide-polyethers or mixtures thereof.

3. The process as claimed in claim 1, wherein: the prepolymer P(X)n corresponds to n=1 or 2, X is a reactive function chosen from: OH, NH.sub.2, COOH, said hydrocarbon-based molecular chain P has a semi-cycloaliphatic or semi-aromatic structure and said polymer has a Tg of greater than 75 C.

4. The process as claimed in claim 1, wherein the thermoplastic polymer is obtained from a precursor composition comprising an extender b) with said function Y being chosen from the following relative to the function X of said prepolymer: for X being NH.sub.2 or OH: Y chosen from the following groups: maleimide, optionally blocked isocyanate, oxazinone and oxazolinone, cyclic anhydride, epoxide, and when X is COOH: Y chosen from the following groups: oxazoline, oxazine, imidazoline or aziridine, such as 1,1-iso- or terephthaloyl-bis(2-methylaziridine).

5. The process as claimed in claim 1, wherein when Y is chosen from oxazinone, oxazolinone, oxazine, oxazoline and imidazoline, and A represents a covalent single bond between the two functions Y or an alkylene (CH.sub.2)m- with m ranging from 1 to 14 and or A represents a cycloalkylene or an alkyl-substituted or unsubstituted arylene, from among o-, m- or p-phenylenes or naphthalenic arylenes.

6. The process as claimed in claim 1, wherein the weight content of said extender in said thermoplastic polymer ranges from 1% to 20%.

7. The process as claimed in claim 1, wherein a chain of said polymer comprises at least two chains of said prepolymer a) linked together via an extender molecule b), the number of prepolymer chains a) per chain of said polymer ranging from 2 to 80.

8. The process as claimed in claim 1, wherein the polymer is semi-crystalline with a Tg of less than 75 C. and a melting point Tm ranging from 150 C. to less than 250 C.

9. The process as claimed in claim 1, wherein the prepolymer a) bears a function X=carboxyl with n=2 (0.1) and in that said extender bears a function Y=oxazoline.

10. The process as claimed in claim 9, wherein the thermoplastic polymer has a repeating unit structure according to formula (I) below: (I) ##STR00002## with R=A with A being as defined above and chosen from a covalent single bond or a diradical of an optionally substituted aliphatic or cycloaliphatic or aromatic hydrocarbon-based chain, R being an optionally substituted aliphatic or cycloaliphatic or aromatic hydrocarbon-based chain in which the shortest chain linking the neighboring O and NH units comprises 2 or 3 carbon atoms, P being the chain of said prepolymer a) bearing functions X=carboxyl.

11. The process as claimed in claim 9, wherein the extender is chosen from: phenylene-bis-oxazolines.

12. The process as claimed in claim 1, wherein the prepolymer a) is a polyamide prepolymer obtained from: the polycondensation of at least one linear or branched aliphatic diamine and of at least one aromatic and/or cycloaliphatic dicarboxylic acid comprising at least one optionally substituted ring of 4, 5 or 6 carbon atoms and/or the polycondensation of at least one cycloaliphatic diamine with at least one linear or branched aliphatic, cycloaliphatic or aromatic dicarboxylic acid and optionally with the presence of at least one compound chosen from: a lactam, an aminocarboxylic acid or the stoichiometric combination of an aliphatic dicarboxylic acid and an aliphatic diamine.

13. The process as claimed in claim 1, wherein the thermoplastic polymer is a semi-aromatic and/or semi-cycloaliphatic homopolyamide or copolyamide polyamide, corresponding to one of the following formulae: polyamides from among: 8.T, 9.T, 10.T, 11.T, 12.T, 6.T/9.T, 9.T/10.T, 9.T/11.T, 9.T/12.T, 9/6.T, 10/6.T, 11/6.T, 12/6.T, 10/9.T, 10/10.T, 10/11.T, 10/12.T, 11/9.T, 11/10.T, 11/11.T, 11/12.T, 12/9.T, 12/10.T, 12/11.T, 12/12.T, 6.10/6.T, 6.12/6.T, 9.10/6.T, 9.12/6.T, 10.10/6.T, 10.12/6.T, 6.10/9.T, 6.12/9.T, 9.10/9.T, 9.12/9.T, 10.10/9.T, 10.12/9.T, 6.10/10.T, 6.12/10.T, 9.10/10.T, 9.12/10.T, 10.10/10.T, 10.12/10.T, 6.10/12.T, 6.12/12.T, 9.10/12.T, 9.12/12.T, 10.10/12.T, 11/6.T/9.T, 11/6.T/10.T, 11/6.T/11.T, 11/6.T/12.T, 11/9.T/10.T, 11/9.T/11.T, 11/9.T/12.T, 11/10.T/11.T, 11/10.T/12.T, 11/11.T/12.T, 6.T/10.T, 6.T/11.T, 6.T/12.T, 10.T/11.T, 10.T/12.T, 11.T/12.T, 12/6.T/10.T, 12/6.T/11.T, 12/6.T/12.T, 12/9.T/10.T, 12/9.T/11.T, 12/9.T/12.T, 12/10.T/11.T, 12/10.T/12.T, 12/11.T/12.T or preceding terpolymer polyamides with 12/ replaced with 9/, 10/, 6.10/, 6.12/, 10.10/, 10.12/, 9.10/ and 9.12/ or all the polyamides mentioned above in which terephthalic (T) is partially or totally replaced with isophthalic (I), naphthalene-2,6-dicarboxylic and/or with 1,3- or 1,4-CHDA (cyclohexanedicarboxylic acid), with all or some of the aliphatic diamines possibly being replaced with cycloaliphatic diamines or all the polyamides mentioned above, with replacement of the C.sub.6 to C.sub.12 aliphatic diamine with a cycloaliphatic diamine from among BMACM, BACM and/or IPDA and with replacement of all or some of the aromatic diacid T with a linear or branched C.sub.6 to C.sub.18 aliphatic diacid.

14. The process as claimed in claim 1, wherein the thermoplastic polymer is a semi-crystalline polyamide.

15. The process as claimed in claim 1, comprising a step i) prior to the impregnation step i), of preparation of said polymer by polyaddition reaction of said precursor reactive composition comprising said prepolymer a) and said extender b), said reaction being performed in bulk in melt form in an extruder transferring on-line said molten polymer onto said assembly of fibers for said impregnation step i).

16. The process as claimed in claim 1, wherein the impregnation step i) is performed in a mold for the final processing of said composite material.

17. The process as claimed in claim 1, wherein the impregnation step i) is performed outside the mold for the final processing of said composite material.

18. The process as claimed in claim 1, wherein the melt impregnation step i) comprises a prior step of sprinkling said assembly of fibers with said polymer in powder form, followed by a step of heating and melting of said powder and optionally a step of calendering, thus making it possible to obtain a preimpregnated fibrous material as intermediate product in step ii), before said final processing step iii).

19. The process as claimed in claim 16, wherein the processing step iii) is performed in a closed mold with molding by resin transfer (RTM), structured reaction injection molding (S-RIM) or infusion molding or compression injection molding.

20. The process as claimed in claim 1, wherein the processing step iii) is performed by thermocompression of preimpregnates under reduced pressure.

21. The process as claimed in claim 16, wherein the processing step iii) is performed in an open mold by pultrusion through a heating die, with optional additional transformation of the semi-finished products obtained.

22. The process as claimed in claim 16, wherein the assembly of fibers is in the form of a preform placed in said mold.

23. The process as claimed in claim 1, wherein the fibers are long fibers chosen from carbon, glass, ceramic and aramid fibers.

24. The process as claimed in claim 1, wherein the polymer matrix comprises carbon-based fillers in dispersed form.

25. The process as claimed in claim 1, wherein the composite material is in the form of a composite part or article, for applications in the aeronautics, motor vehicle, railway, road transport, wind power, photovoltaic, nautical, sports and leisure, building, civil engineering, electrical or electronics field.

26. The use of a polymer as defined in claim 1, as polymer for the bulk melt impregnation of an assembly of one or more synthetic or natural reinforcing fibers, for the manufacture of a preimpregnated fibrous material or of a final part made of composite material.

27. The use as claimed in claim 26, comprising the manufacture of a composite part.

Description

EXAMPLES

A Preparation of a Polyamide Polymer by Chain Extension of a Reactive Prepolymer (or Oliciomer)

A-1 Preparation of the Reactive Prepolymer P(X)n

[0078] This procedure is representative of all the types of polyamide prepolymers according to the invention. [0079] 5 kg of the following starting materials are placed in a 14-liter autoclave reactor: [0080] 500 g of water, [0081] the diamines, [0082] the amino acids or lactams, [0083] the diacids, [0084] 35 g of sodium hypophosphite in solution, [0085] 0.1 g of a Wacker AK1000 antifoam (the company Wacker Silicones).

[0086] The nature and molar ratios of the molecular units and structures of the reactive prepolymer polyamides (by reference test) are given in table 1 below.

[0087] The closed reactor is purged of its residual oxygen and then heated to a temperature of 230 C. of the material. After stirring for 30 minutes under these conditions, the pressurized vapor that has formed in the reactor is gradually pressure-reduced over the course of 60 minutes, while at the same time gradually increasing the temperature of the material such that it becomes established at a minimum of Tm+10 C. at atmospheric pressure for the semi-crystalline polymers of Tm>230 C., or 250 C. for the other polymers.

[0088] The oligomer (prepolymer) is then emptied out by the bottom valve and then cooled in a water bath and then ground.

[0089] The characteristics are presented in Table 1 below.

TABLE-US-00001 TABLE 1 Characteristics of the prepolymers prepared Molecular structure and Acid molar number Mn composition Tm Tg Tc H meq/kg potentiometry Ref (%) Monomers used X ( C.) ( C.) ( C.) (J/g) (*) g/mol Prep. 1 11 Aminoundecanoic acid COOH 178.8 43.2 155 75 809 2473 Adipic acid (1 molecule per chain) Prep. 2 6I/10I hexamethylenediamine COOH (**) 94.5 (**) (**) 900 2222 (30/70) decanediamine isophthalic acid Prep. 3 MXDT/10T m-xylylenediamine COOH 270.3 119.4 240.8 50.1 621 3221 (41.2/58.8) decanediamine terephthalic acid (*): Milliequivalents per kilogram (**): Amorphous polymer

A-2 Preparation of the Polyamide Polymer E by Chain Extension with an Extender of Y-A-Y Type

[0090] 10 g of the dried and ground above prepolymer are mixed with a stoichiometric amount of 1,3-phenylenebis(2-oxazoline) (PBO).

[0091] The mixture is introduced under nitrogen flushing into a DSM brand co-rotating conical screw microextruder (15 ml volume) preheated to a temperature T1 equal to 200 C. for prep. 1 and 2 and T1: 280 C. for prep. 3, with rotation of the screws at 100 rpm. The mixture is left to recirculate in the microextruder and the increase in viscosity is monitored by measuring the normal force. After approximately 2 minutes, a plateau is reached and the contents of the microextruder are emptied out in the form of a rod. The air-cooled product is formed into granules.

TABLE-US-00002 TABLE 2 Analytical characteristics of the polyamides E obtained with chain extension Mn 1 (determined by size exclusion chromatography in T.sub.1 Tm Tg Tc H PMMA equivalent) Ref Prepolymer ( C.) ( C.) ( C.) ( C.) (J/g) (g/mol) E1 According to Prep. 1 200 174.7 34 142.8 57 28100 the invention E2 According to Prep. 2 200 (*) 110 (*) (*) 28500 the invention E3 According to Prep. 3 280 273 135 230.5 36 9900 the invention (*) Amorphous polymer

A-3 Preparation of the Comparative Polyamides PA without Chain Extender

[0092] The comparative polyamides free of chain extenders are synthesized according to a procedure identical to that for the reactive prepolymers P(X)n with this procedure being representative of all the comparative polyamides prepared, except that the molar mass Mn of the comparative polymer is adjusted with a smaller excess of diacid than that with the corresponding prepolymer, according to the method that is well known to those skilled in the art.

[0093] The characteristics of these comparative polyamides CE are presented in Table 3 below.

TABLE-US-00003 TABLE 3 Analytical characteristics of the comparative polyamides CE free of chain extenders Mn 1 (determined Molecular by size exclusion structure chromatography in and molar Tm Tg Tc H PMMA equivalent) Ref composition Monomers used ( C.) ( C.) ( C.) (J/g) (g/mol) CE1 11 Aminoundecanoic acid 188.5 47.3 158.4 72.4 28250 (100) Adipic acid (1 molecule per chain) CE2 6I/10I hexamethylenediamine (*) 108.3 (*) (*) 28540 (30/70) decanediamine isophthalic acid CE3 MXDT/10T m-xylylenediamine 279.2 130.7 241.4 43.6 10000 (41.2/58.8) decanediamine terephthalic acid (*) Amorphous polymer

A-4 Comparison of the Melt Viscosities of the PAs According to the Invention E and the Comparative PAs CE

[0094] The viscosities of the polymers according to the invention CE and of the comparative polyamides free of chain extenders CE are reported in Tables 4 to 6 below:

TABLE-US-00004 TABLE 4 Viscosities of the polyamides E1 of the invention and comparative CE1 (PA 11 base) Viscosity E1 Viscosity CE1 T ( C.) (Pa .Math. s) (Pa .Math. s) 200 756.4 751.2 225 128.2 340.6 250 22.51 166.5 275 5.72 86.9 300 1.75 48

[0095] These results are represented in FIG. 1.

TABLE-US-00005 TABLE 5 Viscosities of tests E3 and CE3 (amorphous PA 6I/10I base) Viscosity E2 Viscosity CE2 T ( C.) (Pa .Math. s) (Pa .Math. s) 200 42080 42150 250 423 12600

TABLE-US-00006 TABLE 6 Viscosities of tests E4 and CE4 (PA MXDT/10T base) Viscosity E4 Viscosity CE4 T ( C.) (Pa .Math. s) (Pa .Math. s) 280 187 189 300 46.2 126

[0096] The results clearly show that the melt viscosities of the PAs according to the invention are lower than those of the comparative PAs for temperatures T>T.sub.1 with a difference that increases as the temperature increases.