US-12617926-B2 - Recycling of pre-impregnated fiber materials

US12617926B2US 12617926 B2US12617926 B2US 12617926B2US-12617926-B2

Abstract

A method for recycling prepreg materials including the steps of: a) providing at least one prepreg material including a first thermosetting polymer resin, partially crosslinked, and a weave including fibers, b) applying a vitrimerization reaction mixture to the at least one prepreg material, c) placing the at least one prepreg material coated with the vitrimerization reaction mixture on a mold of a predefined shape, d) applying a thermocompression to the at least one prepreg material at a temperature (T1) greater than or equal to the glass transition temperature (Tg) of the first resin, so as to activate the reaction between the vitrimerization reaction mixture and the thermosetting polymer leading to the formation of a vitrimer polymer and the transformation of the at least one prepreg material into a vitrimer composite material of the predefined shape.

Inventors

Pierre PILUSO
Pascal Tiquet

Assignees

COMMISSARIAT A L'ENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

Dates

Publication Date: 20260505
Application Date: 20240315
Priority Date: 20230315

Claims (9)

1 . A method for recycling prepreg materials comprising the steps of: a) providing at least one prepreg material comprising a first thermosetting polymer resin, partially crosslinked, and a weave comprising fibers, b) applying a vitrimerization reaction mixture to the at least one prepreg material, c) placing the at least one prepreg material coated with the vitrimerization reaction mixture on a mold of a predefined shape, d) applying a thermocompression to the at least one prepreg material at a temperature (T1) greater than or equal to a glass transition temperature (Tg) of the first resin, so as to activate a reaction between the vitrimerization reaction mixture and the thermosetting polymer leading to formation of a vitrimer polymer and a transformation of the at least one prepreg material into a vitrimer composite material of the predefined shape.
2 . The recycling method according to claim 1 further comprising the steps of: e) arranging the vitrimer composite material shaped according to step d) on a second mold of a determined conformation, f) applying a thermocompression to the vitrimer composite material at the temperature (T1) so as to reshape the vitrimer composite material.
3 . The recycling method according to claim 1 , wherein the vitrimerization reaction mixture comprises precursor reagents so as to form a second resin comprising accessible hydroxyl groups so as to allow function exchange reactions with the first thermosetting polymer resin.
4 . The recycling method according to claim 1 , wherein the vitrimerization reaction mixture comprises precursor reagents of a second resin, and a catalyst for transformation into vitrimer resin, selected from the group consisting of an organometallic or organic compound.
5 . The recycling method according to claim 4 , wherein a proportion of the catalyst is between 2 to 15% by weight of the vitrimerization reaction mixture.
6 . The recycling method according to claim 1 , wherein the application of the vitrimerization reaction mixture is carried out by spraying onto the at least one prepreg material.
7 . The recycling method according to claim 1 , wherein the application of the vitrimerization reaction mixture is carried out by: i) soaking the at least one prepreg material in a bath of the vitrimerization reaction mixture for coating the at least one prepreg material, ii) filtering the vitrimerization reaction mixture, and recovering the at least one coated prepreg material.
8 . The recycling method according to claim 1 , wherein the first resin of the at least one prepreg material is made of epoxy-amine polymer and the vitrimerization reaction mixture consists of DGEBA, phthalic anhydride, zinc acetate, and an acetone solvent.
9 . The recycling method according to claim 1 , which further comprising total recycling steps of: g) arranging the vitrimer composite material in a composition comprising at least one monofunctional alcohol, h) applying a thermal treatment at a temperature (T2) greater than or equal to the glass transition temperature (Tg) so as to allow the dissolution of the vitrimer resin and recovery of the fibers of the weave so as to recycle compounds of the vitrimer composite material.

Description

The present invention relates to the field of prepreg composite materials intended to form fiber-reinforced composite materials with reinforcement. In particular, the invention concerns a method for recycling prepreg composite materials out of use so as to allow them to be reshaped and/or repaired. According to a second aspect, the invention concerns an intermediate material comprising a prepreg composite material coated with a vitrimerization reaction mixture, in particular obtained at the end of an intermediate step of the recycling method. The composite materials reinforced with fibers are mainly used to replace metals to lighten structures, in a wide range of application: sport (cycles, board sports), transport (structure of cars, trains), aerospace (structure of planes, space shuttles). These systems consist of a thermosetting polymer resin, crosslinked during the shaping of the material, and of a reinforcement, in particular a fiber weave, which can be of variable nature (mainly carbon fibers, glass fibers, fibers of polymers . . . ) and organization (woven according to different models, non-woven). One of the ways of shaping these composites is to carry out a prepreg of the fiber weave with the non-crosslinked resin, so as to obtain a prepreg composite material. This prepreg composite is then covered with a protective film known under the name “backing”, allowing the prepreg to be rolled and transported in a reel to the place of use. Indeed, the resin not being crosslinked at this stage, it has a sticky nature which prevents the prepregs from being stacked and stored thus before use. At the time of use, the rolls of prepregs are cut with their backing to the right size from the reels, then the prepreg sheets without their backing are stacked so as to obtain the desired composite thickness and are hot pressed to the desired shape. During heating, the resin crosslinks irreversibly, and the composite thus formed is then demolded. If the use of prepreg composites allows for great simplicity of implementation such as the absence of resin handling by the user and the possible custom cutting, it nevertheless includes defects. First, the crosslinking reaction of resins of the prepreg composites occurs at any temperature, although the lower the temperature, the slower the reaction progresses. This involves either storing rolls of prepreg materials under specific conditions, typically via refrigeration, or using them quickly once received. Thus, in practice, significant lengths and masses of prepreg materials may be lost because having exceeded their lifetime recommended by the supplier at a given storage temperature, the crosslinking reaction has progressed too far to allow their shaping. The result is that a large quantity of these prepregs becomes waste, causing a significant environmental issue. In addition, the method for cutting prepreg materials involves the existence of cutting scraps. These scraps currently find it difficult to find applications, even if some are starting to emerge at industrial levels, but which systematically lead to a strong devaluation of the material and are typically used for consumer goods. One of the objects of the present invention aims to overcome at least one of the aforementioned drawbacks. To this end, the present invention proposes a method for recycling prepreg materials comprising the steps of: a) providing at least one prepreg material comprising a first thermosetting polymer resin, partially crosslinked, and a weave comprising fibers,b) applying a vitrimerization reaction mixture to the at least one prepreg material,c) placing the at least one prepreg material coated with the vitrimerization reaction mixture on a mold of a predefined shape,d) applying a thermocompression to the at least one prepreg material at a temperature T1 greater than or equal to the glass transition temperature Tg of the first resin, so as to activate the reaction between the vitrimerization reaction mixture and the thermosetting polymer leading to the formation of a vitrimer polymer and the transformation of the at least one prepreg material into a vitrimer composite material of the predefined shape. Thanks to the method of the invention, it is possible to recycle prepreg materials, the first resin of which is partly crosslinked and which is out of use for reasons of aging (storage conditions under conditions not making it possible to avoid partial crosslinking of the first resin and/or the storage period given by the supplier has been exceeded) or which comes from scraps from the cuts of a prepreg. It is in fact possible to carry out hot reshaping or to locally repair the first resin using a vitrimerization reaction mixture which uses a dynamic covalent chemistry leading to vitrimers whose viscoelastic properties are similar to those of glass. Thus, the application of a mechanical force at a temperature T1 above or equal to the glass transition temperature Tg of the vitrimer polymer makes it