Process for manufacturing thermoplastic polymer composite parts, and object obtained by said process

1. A process for manufacturing an object made of a thermoplastic polymer composite from at least two parts made of (meth)acrylic thermoplastic polymer composite, said (meth)acrylic thermoplastic polymer composite comprising a fibrous reinforcement of long fibers having an aspect ratio of at least 7500 or continuous fibers and a thermoplastic polymer matrix, said process comprising the steps of:

impregnation of a fibrous reinforcement with a liquid (meth)acrylic composition,

polymerization of the liquid (meth)acrylic composition to manufacture the at least two parts made of (meth)acrylic thermoplastic polymer composite comprising the fibrous reinforcement and a (meth)acrylic thermoplastic polymer matrix,

deposition of a layer of (meth)acrylic thermoplastic polymer at least at an assembly interface zone,

arranging the two parts made of thermoplastic polymer composite adjacent or overlapping at said assembly interface zone, and

heating to melt the thermoplastic polymer matrix at said assembly interface zone, so as to form an object made of thermoplastic polymer composite comprising a welded interface,

wherein the thermoplastic polymer matrix is melted by a technique selected from the group consisting of: ultrasonic welding, induction welding, resistance wire welding, friction stir welding, laser welding, and heating by infrared or ultraviolet radiation, wherein at least one of the two parts made of thermoplastic polymer composite comprises the layer of (meth)acrylic thermoplastic polymer at least 0.5 mm thick on a surface intended to be welded, and wherein the (meth)acrylic thermoplastic polymer of the (meth)acrylic thermoplastic polymer composite and the layer of (meth)acrylic thermoplastic polymer has a glass transition temperature between 50° C. and 140° C. and the (meth)acrylic thermoplastic polymer or a portion of the (meth)acrylic thermoplastic polymer of the (meth)acrylic thermoplastic polymer composite and the layer of (meth)acrylic thermoplastic polymer has a melt flow index less than 20 g/10 min according to the standard ISO 1133.

2. The manufacturing process as claimed in claim 1 , wherein the fibrous reinforcement comprises fibers selected from the group consisting of carbon fibers, glass fibers, basalt fibers, polymer-based fibers, plant fibers, and mixtures thereof.

3. The manufacturing process as claimed in claim 1 , wherein the fibrous reinforcement is based on fibers having an aspect ratio of at least 10,000.

4. The manufacturing process as claimed in claim 1 , wherein said process further comprises, after the heating step, a step of applying pressure at the interface in order to weld the at least two parts made of thermoplastic polymer composite together.

5. The manufacturing process as claimed in claim 1 , wherein the (meth)acrylic thermoplastic polymer of the (meth)acrylic thermoplastic polymer composite and the (meth)acrylic thermoplastic polymer matrix is chosen from poly(methyl methacrylate) (PMMA), copolymers of methyl methacrylate (MMA), or mixtures thereof.

6. The manufacturing process as claimed in claim 1 , wherein the (meth)acrylic thermoplastic polymer of the (meth)acrylic thermoplastic polymer composite and the (meth)acrylic thermoplastic polymer matrix has a glass transition temperature (Tg) of between 70° C. and 140° C.

7. The manufacturing process as claimed in claim 1 , wherein the (meth)acrylic thermoplastic polymer matrix further comprises one or more additives or fillers.

8. The manufacturing process as claimed in claim 1 , wherein the liquid (meth)acrylic composition comprises a (meth)acrylic monomer, a precursor (meth)acrylic polymer and a radical initiator.

9. The manufacturing process as claimed in claim 1 , wherein the liquid (meth)acrylic composition comprises a (meth)acrylic monomer or a mixture of (meth)acrylic monomers, and a precursor (meth)acrylic polymer.

10. The manufacturing process as claimed in claim 9 , wherein the (meth)acrylic monomer or the mixture of (meth)acrylic monomers in the liquid (meth)acrylic composition are present at an amount of at least 40% by weight in the liquid (meth)acrylic composition.

11. The manufacturing process as claimed in claim 8 , wherein the precursor (meth)acrylic polymer in the liquid (meth)acrylic composition is present at an amount of at least 10% by weight in the liquid (meth)acrylic composition.

12. The manufacturing process as claimed in claim 8 , wherein the precursor (meth)acrylic polymer in the liquid (meth)acrylic composition is present at an amount of at most 60% by weight in the liquid (meth)acrylic composition.

13. The manufacturing process as claimed in claim 8 , wherein the liquid (meth)acrylic composition, comprises:

a) the (meth)acrylic monomer in proportions of between 40% and 90% based on the weight of the (meth)acrylic monomer and the (meth)acrylic polymer

b) the (meth)acrylic polymer in proportions of between 10% and 60% based on the weight of the (meth)acrylic monomer and the (meth)acrylic polymer.

14. The manufacturing process as claimed in claim 1 , wherein the parts made of thermoplastic polymer composite are manufactured at a temperature of less than 150° C.

15. The manufacturing process as claimed in claim 1 , wherein the parts made of thermoplastic polymer composite are manufactured by injection molding, infusion molding, or by molding pre-impregnated strips.

16. The manufacturing process as claimed in claim 1 , the layer of (meth)acrylic thermoplastic polymer is at least 1.0 mm thick on the surface intended to be welded.

17. The manufacturing process as claimed in claim 1 , wherein during the heating step, the temperature at the welded interface is between 160° C. and 300° C.

18. The manufacturing process as claimed in claim 1 , wherein the thermoplastic polymer matrix is melted by resistance wire welding.

19. The manufacturing process as claimed in claim 1 , wherein at least one of the two parts made of thermoplastic polymer composite comprises at least one resistive filament located at the assembly interface zone.