COMPOSITION AND METHOD FOR COMPOSITE MATERIAL IMPREGNATED WITH SEMI-CRYSTALLINE POLYAMIDE, OBTAINED FROM A PREPOLYMER AND A CHAIN EXTENDER

Abstract

A molding composition including at least one semi-crystalline polyamide derived from the polyaddition of a) at least one polyamide prepolymer bearing n identical functions X chosen from carboxyl, amine and hydroxyl, and of b) at least one non-polymeric reactive extender bearing two identical functions Y that are reactive with said functions X with n ranging from 1 to 3, the polyamide and prepolymer a) including 55 mol % to 95 mol % of amide units A, 5 mol %-45 mol % of amide units B with A corresponding to x.T in which x is a linear aliphatic C9-C18 diamine and B corresponding to x.T in which x may be B1): specific branched aliphatic diamine dependent on x or B2): MXD or B3): linear aliphatic diamine which depends on x, the polyamide having a Tg of at least 90 C. and a Tm of less than or equal to 280 C.

Claims

1. A non-reactive molding composition comprising at least one thermoplastic polymer and optionally reinforcing fibers or fibrous reinforcement, and, in this case, said at least one polymer being able to impregnate said fibers (or said fibrous reinforcement) and to form the thermoplastic matrix of the composite material: wherein at least one thermoplastic polymer is a semi-crystalline polyamide polymer with a glass transition temperature Tg of at least 80 C., and a melting point Tm of less than or equal to 280 C. and in that it is a polyaddition polymer between a) at least one thermoplastic polyamide prepolymer, bearing n identical reactive end functions X, chosen from: NH.sub.2, CO.sub.2H and OH, with n being from 1 to 3, and b) at least one chain extender Y-A-Y, with A being a single bond linking the two functions Y or a hydrocarbon-based diradical, of non-polymeric structure and bearing two identical reactive end functions Y, which are reactive by polyaddition with at least one function X of said prepolymer a), and said extender b) having a molecular mass of less than 500, and wherein the thermoplastic polyamide polymer and its prepolymer a) comprise in their respective structures different amide units A and B and optionally amide units C and D, selected as follows: A: is a major amide unit present in a molar content ranging from 55% to 95%, chosen from units x.T, where x is a linear aliphatic C.sub.9 to C.sub.18 diamine, and in which T is terephthalic acid, B: is an amide unit different from A, said unit B being present in a molar content ranging from 5% to 45%, depending on the Tm of the polyamide based on unit A and said amide unit B is chosen from x.T units where x is chosen from: B1) a branched aliphatic diamine bearing a single methyl or ethyl branch (or branching) and having a main chain length different by at least two carbon atoms relative to the main chain length of the diamine x of said associated unit A, or B2) m-xylylenediamine (MXD) or B3) a linear aliphatic C4 to C18 diamine when, in the unit A, said diamine x is a linear aliphatic C.sub.11 to C.sub.18 diamine and x is a C.sub.9 to C.sub.18 diamine when, in the unit A, said diamine x is a C.sub.9 or C.sub.10 diamine, C: optional amide unit different from A and from B, chosen from amide units based on a cycloaliphatic and/or aromatic structure or based on xT as defined above for B but with x different from x for the unit B, D: optional amide unit different from A, B and C when C is present and chosen from aliphatic amide units derived from: C.sub.6 to C.sub.12 amino acids or lactams or mixtures thereof the reaction of a linear aliphatic C.sub.6 to C.sub.18, and of a linear aliphatic C.sub.6 to C.sub.18, and under the condition that the sum of the molar contents of A+B+C+D is equal to 100%.

2. The composition as claimed in claim 1, wherein amide unit C is present and in partial replacement for B in a molar content ranging up to 25% relative to said unit B.

3. The composition as claimed in claim 1, wherein unit D is present and in partial replacement for B in a molar content ranging up to 70% relative to said unit B.

4. The composition as claimed in claim 1, wherein the difference Tm-Tc, between the melting point Tm and the crystallization temperature Tc of said matrix polymer, does not exceed 50 C.

5. The composition as claimed in claim 1, wherein the heat of crystallization, measured by differential scanning calorimetry (DSC) according to standard ISO 11357-3, is greater than 40 J/g.

6. The composition as claimed in claim 1, wherein amide unit A is present with a molar content ranging from 55% to 80%, relative to all of the units of said polymer.

7. The composition as claimed in claim 1, wherein unit B corresponds to x T with x chosen according to option B1).

8. The composition as claimed in claim 1, wherein unit B corresponds to x T with x chosen according to option B2), x being MXD.

9. The composition as claimed in claim 1, wherein unit B corresponds to a linear aliphatic diamine according to option B3).

10. The composition as claimed in claim 1, wherein the units A and B are selected as follows: for the unit A which is 9T, said unit B is selected from: 10T, 11T, 12T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 30% to 45%, for the unit A which is 10T, said unit B is selected from: 9T, 11T, 12T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 25% to 45%, for the unit A which is 11T, said unit B is selected from: 9T, 10T, 12T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 20% to 45%, for the unit A which is 12T, said unit B is selected from: 9T, 10T, 11T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 20% to 45%.

11. The composition as claimed in claim 10, wherein the unit A is a unit 9T and the unit B is selected from: 10T, 11T, 12T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 30% to 45%.

12. The composition as claimed in claim 10, wherein the unit A is a unit 10T and the unit B is selected from: 9T, 11T, 12T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 25% to 45%.

13. The composition as claimed in claim 10, wherein the unit A is a unit 11T and the unit B is selected from: 9T, 10T, 12T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 20% to 45%.

14. The composition as claimed in claim 10, wherein the unit A is a unit 12T and the unit B is selected from: 10T, 11T, 13T, 14T, 15T, 16T, 17T and 18T, MPMD.T and MXD.T, with a molar content of B ranging from 20% to 45%.

15. The composition as claimed in claim 7, wherein part of the unit B which is up to 70%, is replaced with a unit C and/or D as defined according to one of claims 1 to 3.

16. The composition as claimed in claim 1, wherein reactive prepolymers a) have a number-average molecular mass Mn ranging from 500 to 10,000.

17. The composition as claimed in claim 1, wherein the weight content of said extender in said semi-crystalline polyamide thermoplastic polymer ranges from 1% to 20% by weight.

18. The composition as claimed in claim 1, wherein a chain of the 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 preferably ranging from 2 to 80.

19. The composition as claimed in claim 1, wherein prepolymer a) bears X=carboxyl and n=2 (0.1) and in that said extender bears Y=oxazoline.

20. The composition as claimed in claim 19, wherein semi-crystalline thermoplastic polyamide polymer has a repeating unit structure according to formula (I) below: ##STR00002## with R being identical to A as defined above and chosen from a single bond or 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 polyamide prepolymer a) bearing said functions X=carboxyl.

21. The composition as claimed in claim 19, wherein extender is chosen from phenylene-bisoxazolines.

22. The composition as claimed in claim 1, wherein it comprises a fibrous reinforcement with long fibers.

23. A process for manufacturing a thermoplastic composite material based on at least one composition as defined according to claim 1, wherein the process comprises a step i) of melt impregnation of a fibrous reinforcement with a molding composition, as defined above, but without said fibrous reinforcement or with at least one polymer as defined above, in an open mold or in a closed mold or not in a mold, and optionally followed by a step ii) of final processing consecutive to or separate from said step i).

24. The process as claimed in claim 23, wherein it comprises, simultaneously or after an interval, a processing step ii) comprising molding and final forming of said preimpregnated fibrous reinforcement from step i) to form the final composite part in a mold or not in a mold.

25. The process as claimed in claim 24, wherein processing in step ii) is performed according to an RTM, compression injection molding or pultrusion technique or by infusion or thermocompression of a preimpregnate under reduced pressure.

26. The use of a composition as defined according to claim 1, without said fibrous reinforcement or the use of a polymer as contained in said composition for the bulk melt impregnation of a fibrous reinforcement as thermoplastic matrix of a composite material, for the manufacture of mechanical parts or of structural parts of said composite material.

27. The use as claimed in claim 26 wherein the mechanical parts or structural parts of said composite material concern applications in the motor vehicle, railway, marine or maritime, wind power or photovoltaic field, the solar energy field, including solar panels and components of solar power stations, the sports, aeronautical and aerospace fields, the road transport field regarding trucks, and the construction, civil engineering, protective panel, leisure, electrical and electronic fields.

28. The use as claimed in claim 27, wherein it concerns applications in the wind power field and in that the Tg of said polyamide is at least 80 C.

29. The use as claimed in claim 27, wherein it concerns applications in the motor vehicle field and in that the Tg of said polyamide is at least 100 C.

30. The use as claimed in claim 27, wherein it concerns applications in the aeronautical field and in that the Tg of said polyamide is at least 120 C.

Description

[0079] The examples that follow are presented to illustrate the invention and its performance qualities and do not in any way limit its scope.

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

[0080] 5 kg of the following starting materials are placed in a 14-liter autoclave reactor:

[0081] 500 g of water,

[0082] Amines: MXD (m-xylylenediamine) and decanediamine (proportion: see below)

[0083] Diacid: T (terephthalic)

[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 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 reduced in pressure 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 Tm +10 C. at atmospheric pressure.

[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 of the prepolymer obtained are presented below:

[0090] Structure (mol % of the units): MXD.T/10.T (41.2/58.8)

[0091] function X: carboxyl

[0092] meq./kg of X: 621

[0093] Mn (potentiometry): 3221

[0094] Tg: 119.4 C.

[0095] Tm/Tc: 270.3 C./240.8 C.

[0096] delta H (H): 50.1 J/g

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

[0097] 10 g of the dried and ground prepolymer presented above are mixed with a stoichiometric amount of 1,3-phenylenebis(2-oxazoline) (PBO).

[0098] The mixture is introduced under nitrogen flushing into a DSM co-rotating conical screw microextruder (15 ml volume) preheated to 280 C., 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.

[0099] The characteristics of said polymer are as follows:

[0100] Tg: 135 C.

[0101] Tm/Tc: 273 C./230.5 C.

[0102] delta H (H): 36 J/g

[0103] Mn (SEC): 9900 g/mol in PMMA equivalent

A-3 Preparation of Comparative PA Without Extender

[0104] The comparative polyamides free of PA chain extenders are synthesized according to a protocol similar to that for the reactive prepolymers P(X)n. The Mn is adjusted according to a controlled excess of diacid, according to the method that is well known to those skilled in the art. The amine and diacid components are the same with the same proportions of the components except for the adjustment of the ratio of acid/amine functions to have the targeted Mn comparable to that of the polymer obtained with the extender described above.

[0105] The characteristics obtained are presented below:

[0106] Structure (mol % of the units): MXD.T/10.T (41.2/58.8)

[0107] Tg: 130.7 C.

[0108] Tm/Tc: 279.2 C./241.4 C.

[0109] delta H (H): 43.6 J/g

[0110] Mn (SEC): 10 000 g/mol in PMMA equivalent

A-4 Comparison of the Melt Viscosities Between PA with Extender According to the Invention and the Comparative PA Without Extender

[0111] This viscosity was measured at two reference temperatures: 280 C. and 300 C. for the two compared polyamides, with the results presented in the table below, which show that as the temperature increases above the melting point, the viscosity of the polyamide according to the invention decreases much more substantially than that of the comparative polyamide without said chain extender.

TABLE-US-00001 Melt viscosity polyamide Melt viscosity comparative according to the invention polyamide without extender Temperature (Pa .Math. s) (Pa .Math. s) 280 187 189 300 46.2 126

[0112] This greater fluidity of the polyamide according to the invention is an advantage of the invention relative to the prior art in the context of more efficient impregnation of a fibrous reinforcement for the preparation of thermoplastic composite materials with a fibrous reinforcement having said polymer as thermoplastic matrix, with increased mechanical performance of said materials.