Composition, its use in recycling an epoxy resin-based material, and associated recycling process

Abstract

The invention relates to a composition comprising: an aqueous solution of hydrogen peroxide; one or more organic carbonates selected from dialkyl carbonates and alkylene carbonates or one or more lactones; and one or more organic acids selected from monocarboxylic acids comprising at least 10 carbon atoms and polycarboxylic acids. The invention also relates to the use of this composition for recycling a material comprising a polyepoxy matrix, as well as to a recycling process for such a material using this composition.

Description

Title of the invention: Composition, its use for recycling an epoxy resin-based material and associated recycling process. Technical field

[0001] The present invention relates to the field of recycling materials comprising a polymer matrix obtained from an epoxy resin, these materials being able to further comprise reinforcements.

[0002] It relates more particularly to a particular composition enabling the degradation of these materials and the recovery of reinforcements when they are present in these materials.

[0003] The invention also relates to the use of such a particular composition for the recycling of the materials mentioned above, whether or not they include reinforcements, as well as to a recycling process for such materials which implements this particular composition. Prior art

[0004] Composite materials are classically obtained from formulations formed by incorporating fillers and / or reinforcements into a polymer matrix, in particular formed from a thermosetting resin such as epoxy resin, also known as epoxy resin.

[0005] Composite materials formed from epoxy resin and reinforced with carbon fibers are, due to their lightness, high strength and high rigidity, used in a wide variety of fields ranging from sports and leisure to the automotive and aeronautical sectors.

[0006] In the constant concern to optimize the management of waste and used or end-of-life materials, the question arises in particular of the recycling of reinforced composite materials in order to separate and recover recyclable materials which include carbon fibers.

[0007] This is all the more true given that carbon fibers are high value-added reinforcements, particularly considering their manufacturing process, which is lengthy, consumes a great deal of energy, and releases carbon dioxide. Indeed, carbon fibers are typically obtained from polyacrylonitrile, a petroleum-derived polymer, which is first subjected to controlled oxidation at temperatures between 200 °C and 300 °C, then to carbonization under an inert atmosphere at temperatures between 1000 °C and 1500 °C.

[0008] Several processes for recycling carbon fibers contained in composite materials obtained from epoxy resin are known to date, including mechanical (grinding) and thermal (pyrolysis) processes are used. However, such processes lead to at least partial degradation of the carbon fibers.

[0009] Chemical recycling processes are also described, in particular in documents JP 2002-121322 A, CN 105906836 A, CN 112552473 A, US 8,920,932 B2 and JP 5880960 B2.

[0010] However, these involve reactions which must be carried out at high temperatures or pressures (JP 2002-121322 A, CN 105906836 A), under aggressive pH conditions (CN 112552473) or in the presence of reagents or solvents which may be toxic, polluting or non-recyclable, or even covered by the REACH regulation of the European Chemicals Agency ECHA such as, for example, A,A-dimethylformamide and A-methyl-2-pyrrolidone (CN 105906836 A, CN 112552473 A, US 8,920,932 B2).

[0011] In view of the constraints just mentioned, it is observed that no chemical recycling process for such composite materials is currently implemented on an industrial scale.

[0012] The object of the present invention is, therefore, to overcome the disadvantages of the mechanical, thermal and chemical processes of the prior art and to propose a process for recycling, by chemical means, a reinforced composite material obtained from epoxy resin allowing the polyepoxy matrix to be degraded in order to release, without degrading them, the carbon fibers contained in this reinforced composite material so that they can be recycled.

[0013] This recycling process must also be scalable to industrial production and characterized by the lowest possible environmental and energy impact. In particular, the process must be able to be implemented under mild operating conditions, especially in terms of temperature and pressure, using environmentally friendly, non-toxic, non-polluting, recyclable solvents and reagents that comply with REACH regulations.

[0014] Another object of the invention is to propose a process which is not limited solely to the recycling of carbon fibers contained in the composite material, but which is also suitable for recycling any type of reinforcement, whether these reinforcements are in the form of fibers, sheets, fabrics or in the form of particulate fillers, whether these reinforcements are made of carbon or any other material such as, for example, glass or plant matter.

[0015] Finally, and more generally, another object of the present invention is to provide a composition that allows the degradation, under mild conditions, of a material obtained from an epoxy resin, whether this material is a composite material and includes reinforcements or whether this material does not include reinforcements, or whether the composite material is a prepreg, that is to say, a composite material in in which the epoxy resin has not been fully crosslinked, or that it has been (thermo)cured and therefore corresponds to a composite material comprising a polyepoxy matrix in which the epoxy resin has been fully crosslinked. Description of the invention

[0016] The goals stated above, as well as others, are achieved, in the first place, by a composition of the type mentioned above, which includes at least one reagent and at least one solvent.

[0017] According to the invention, the composition comprises: (a) an aqueous solution of hydrogen peroxide H₂O₂, (b) one or more organic carbonates selected from dialkyl carbonates (b1) and alkylene carbonates (b2), or one or more lactones (b1), and (c) one or more organic acids selected from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2).

[0018] The composition according to the invention comprises hydrogen peroxide, which is a reagent whose only by-products likely to be formed are water and oxygen and one or more organic carbonates (b), or one or more lactones (b1), which are high boiling point, non-flammable and non-corrosive solvents.

[0019] This composition, which therefore includes compounds that are non-toxic and environmentally friendly, allows for the efficient and gentle degradation of a material obtained from epoxy resin, whether or not this material includes reinforcements and / or whether this epoxy resin is wholly or partly cross-linked.

[0020] The composition according to the invention makes it particularly possible to degrade the material obtained from epoxy resin by depolymerization of its polyepoxy matrix, this depolymerization resulting from the oxidation of the matrix by hydrogen peroxide as a reagent acting as an oxidizing agent.

[0021] As previously stated, the composition according to the invention also comprises one or more organic carbonates (b), or one or more lactones (b').

[0022] In the case where the composition includes one or more organic carbonates (b), this or these organic carbonates (b) are chosen from dialkyl carbonates (bl) and alkylene carbonates (b2).

[0023] Thus, the composition may comprise only one organic carbonate, either a dialkyl carbonate (bl) or an alkylene carbonate (b2).

[0024] The composition may also include a mixture of two, three, or even more organic carbonates (b), in particular a mixture of several dialkyl carbonates (bl), a mixture of several alkylene carbonates (b2), or a mixture of one or several dialkyl carbonates (bl) with one or more alkylene carbonates (b2).

[0025] In one embodiment of the invention, the dialkyl carbonate(bl), which are also known as acyclic alkyl carbonates, are selected from dimethyl carbonate and diethyl carbonate.

[0026] In one embodiment of the invention, the alkylene carbonate(b2), which are also known as cyclic alkyl carbonates, are selected from ethylene carbonate and propylene carbonate.

[0027] In an advantageous embodiment, alkylene carbonate (b2) is propylene carbonate.

[0028] Propylene carbonate offers numerous advantages. It is a biodegradable, non-flammable, non-corrosive, non-toxic, aprotic polar solvent with a boiling point of 242 °C. Obtained by the reaction of propylene epoxide and carbon dioxide (CCl), it also allows for the valorization of this CO₂. Furthermore, propylene carbonate is miscible with hydrogen peroxide for maximum reactivity. Propylene carbonate is therefore a so-called "green solvent" that can be used on a large scale and at a controlled cost.

[0029] The composition may include one or more lactones (b1) instead of one or more organic carbonates (b).

[0030] Thus, the composition may comprise only one lactone or comprise a mixture of two, three, or even more lactones (b1).

[0031] In a variant of the invention, the lactone(s) (b1) are chosen from α-acetolactone, β-propiolactone, γ-butyrolactone, β-valerolactone and γ-valerolactone.

[0032] In an advantageous embodiment, the lactone(s) (b1) are chosen from β-valerolactone and γ-valerolactone.

[0033] According to one embodiment, the molar proportion of the organic carbonate(s) (b) or the lactone(s) (b1) in the composition is between 15 mol% and 40 mol%. Advantageously, this molar proportion of the organic carbonate(s) (b) or the lactone(s) (b1) in the composition is between 20 mol% and 35 mol% and, preferably, between 25 mol% and 30 mol%.

[0034] According to one embodiment, the molar proportion of aqueous hydrogen peroxide solution H2O2(a) in the composition is between 30 mol% and 85 mol%. Advantageously, this molar proportion of aqueous H2O2(a) solution in the composition is between 60 mol% and 80 mol%, and preferably between 68 mol% and 74 mol%. Regardless of the molar proportion of aqueous H2O2(a) solution in the composition, the molar proportion of pure hydrogen peroxide in the composition is between 5 mol% and 20 mol%.

[0035] As also indicated previously, the composition according to the invention further comprises one or more organic acids (c).

[0036] The presence of at least one organic acid (c) allows the oxidation reaction of the polyepoxy matrix of the material to be catalyzed and, consequently, the degradation by depolymerization of the crosslinked epoxy resin in whole or in part.

[0037] This or these organic acids (c) are chosen from monocarboxylic acids (cl) comprising at least 10 carbon atoms and polycarboxylic acids (c2).

[0038] If from a reaction point of view any monocarboxylic acid can catalyze the oxidation reaction of the polyepoxy matrix of the material, the choice is made for monocarboxylic acids (cl) comprising at least 10 carbon atoms for industrial safety reasons.

[0039] The composition according to the invention may comprise only one organic acid (c) or, on the contrary, a mixture of two, three, or even more organic acids (c), in particular a mixture of several monocarboxylic acids (cl), a mixture of several polycarboxylic acids (c2) or a mixture of one or more monocarboxylic acids (cl) with one or more polycarboxylic acids (c2).

[0040] In one embodiment of the invention, the monocarboxylic acid (cl) is lauric acid.

[0041] In one embodiment of the invention, the polycarboxylic acid(s) (c2) are chosen among the dicarboxylic acids, for example tartaric acid, and the tricarboxylic acids, for example citric acid.

[0042] The dicarboxylic acid(s) (c2) are advantageously chosen from tartaric acid and citric acid.

[0043] In an advantageous embodiment allowing the number of compounds present in the composition according to the invention to be limited, the latter comprises only one organic acid (c). Preferably, this organic acid (c) is tartaric acid or citric acid.

[0044] According to one embodiment, the molar proportion of the organic acid(s) (c) in the composition is between 0.1 mol% and 5 mol%. Advantageously, this molar proportion of the organic acid(s) (c) in the composition is between 0.1 mol% and 1.1 mol%, preferably between 0.4 mol% and 0.6 mol% and, more preferably, between 0.48 mol% and 0.55 mol%.

[0045] According to an alternative embodiment of the invention, the organic acid(s) (c) can be replaced either by one or more mineral acids (dl), or by one or more hydroxides (d2).

[0046] In the case where the catalyst is not formed by an organic acid (d) but by a mineral acid (dl), this mineral acid (dl) is chosen from sulfuric acid h2SO4 and phosphoric acid H3PO4.

[0047] In the case where the catalyst is not formed by an organic acid (d) but by a hydroxide (d2), this hydroxide (d2) is a hydroxide of an alkali metal or a hydroxide of an alkaline earth metal.

[0048] In an advantageous embodiment, the hydroxide (d2) is a hydroxide of an alkali metal, preferably chosen from sodium hydroxide NaOH and potassium hydroxide KOH.

[0049] According to one embodiment, the molar proportion of the mineral acid(s) (dl) or of the hydroxide(s) (d2) in the composition is between 0.01 mol% and 0.2 mol%. Advantageously, this molar proportion of the mineral acid(s) (dl) or of the hydroxide(s) (d2) in the composition is between 0.05 mol% and 0.15 mol% and, preferably, between 0.08 mol% and 0.12 mol%.

[0050] The present invention relates, secondly, to the use of a particular composition for the recycling of a material, denoted M, this material M being obtained from an epoxy resin.

[0051] According to the invention, this particular composition is a composition as defined above, that is to say, a composition which comprises: (a) an aqueous solution of hydrogen peroxide H2O2, (b) one or more organic carbonates selected from dialkyl carbonates (b1) and alkylene carbonates (b2), or one or more lactones (b1), and (c) one or more organic acids selected from monocarboxylic acids (c1) comprising at least 10 carbon atoms and polycarboxylic acids (c2), or alternatively, - either one or more mineral acids (dl) chosen from sulfuric acid H2SO4 and phosphoric acid H3PO4- - either one or more hydroxides (d2) of an alkali metal or an alkaline earth metal.

[0052] The characteristics described above in connection with the composition and, in particular, the characteristics relating to the compounds (a), (b), (bl), (b2), (b1), (c), (cl), (c2), (dl) and (d2) forming this composition and to their respective molar proportions, are of course applicable to the present use for the recycling of material M.

[0053] As previously stated, this material M is a material obtained from an epoxy resin, that is to say a material which comprises a polyepoxy matrix resulting from the total crosslinking of the epoxy resin.

[0054] The use according to the invention makes it possible to degrade, under mild and environmentally friendly conditions, the polyepoxy matrix of the material M by depolymerization by oxidation of the latter.

[0055] In one variant of the use according to the invention, the material M is a composite material C comprising reinforcements R.

[0056] Such R reinforcements can in particular be chosen from fibre, webs, fabrics and particulate fillers.

[0057] In the case where the R reinforcements are formed by fibers, these fibers can be continuous, long or short, unidirectional or multidirectional.

[0058] In the case where the reinforcements R are formed by particulate charges, these charges can be in the form of particles or balls.

[0059] The R reinforcements can be formed from plant materials, mineral materials, glass or even carbon.

[0060] In an advantageous embodiment, the R reinforcements are formed by glass fibers or by carbon fibers.

[0061] In a first variant, the material M, whether it is a composite material C including reinforcements R or not, is a hardened material, that is to say a material in which the epoxy resin is totally crosslinked to form a polyepoxy matrix.

[0062] In a second embodiment, the composite material C comprising reinforcements R is a material in which the epoxy resin is not or is only partially crosslinked. Such a material is commonly referred to as "prepreg".

[0063] Whether in the first or second variant, it is possible to efficiently degrade the polyepoxy matrix or the non-crosslinked or partially crosslinked epoxy resin and recover the R reinforcements as well as the epoxy resin resulting from the oxidation degradation. It should be noted that these R reinforcements are recovered without any deterioration of their structure or constituent material.

[0064] The present invention relates, thirdly, to a method for recycling a material M obtained from an epoxy resin.

[0065] According to the invention, this method comprises the following successive steps (1), (3) and, where applicable, (4): (1) contacting the material M with a composition as defined above, it being specified that the characteristics relating to the compounds (a), (b), (bl), (b2), (b1), (c), (cl), (c2), (dl) and (d2) forming this composition as well as to their respective molar proportions may be taken alone or in combination, (3) a collection of the liquid phase from step (1), and (4) optionally, recovery of depolymerized resin from the liquid phase collected in step (3).

[0066] The recycling process according to the invention is characterized by easy implementation, which is industrially transferable and without risk in terms of industrial and environmental safety.

[0067] During step (1) of bringing the material M into contact with the composition defined above- above, the polyepoxy matrix or the partially crosslinked epoxy resin forming material M undergoes degradation by oxidation, thereby obtaining a liquid phase which includes epoxy resin resulting from this degradation.

[0068] This contacting step (1) may or may not be carried out under agitation.

[0069] Following step (1), a step (3) of collecting the phase is implemented liquid, this liquid phase comprising epoxy resin resulting from the degradation of the polymer matrix of material M.

[0070] According to a particularly advantageous embodiment, the recycling process according to the invention may, in addition, include an additional step (4) which is implemented after the step (3) of collecting the liquid phase and which consists of recovering the epoxy resin contained in this liquid phase.

[0071] The process according to the invention therefore makes it possible to recover, for possible subsequent reuse, the epoxy resin from the depolymerized polyepoxy matrix, thus promoting the recycling of all the constituent elements of this material M.

[0072] This recovery step (4) can be carried out by precipitation or distillation of this epoxy resin.

[0073] In an advantageous embodiment of the process according to the invention, at least the step (1) of bringing the material M into contact with the composition is carried out at atmospheric pressure.

[0074] In an advantageous embodiment of the process according to the invention, at least step (1) of bringing the material M into contact with the composition is carried out at a temperature between 5 °C and 90 °C, advantageously between 15 °C and 80 °C and, preferably, between 20 °C and 75 °C.

[0075] Shaking and / or heating the composition with which the material M is brought into contact increases the degradation kinetics of the material M.

[0076] The duration of step (1) of contacting the material M with the composition can, of course, be adapted to the configuration of this material M to be recycled.

[0077] In a variant of the process according to the invention, the step (1) of bringing the material M into contact with the composition is carried out for a period of at least 12 h, this period advantageously being between 18 h and 36 h.

[0078] As previously stated in the context of using the composition according to the invention, the material M can be a composite material C comprising reinforcements R, it being specified that these reinforcements R can be formed by fibers, webs, fabrics, or even by particulate fillers, and be made of plant material, mineral material, glass, or even carbon. Furthermore, the composite material C can be either a hardened material or a prepreg.

[0079] Thus, in the case where the material M is a composite material C comprising reinforcements R, the recycling process according to the invention may, in addition, comprise, among steps (1) and (3), then step (2): (2) a separation of the solid phase including the reinforcements R from the liquid phase from step (1).

[0080] Indeed, in the case where the material M is a composite material C comprising reinforcements R, at the end of step (1) of bringing it into contact with the composition, a liquid phase is obtained comprising the epoxy resin resulting from the degradation by oxidation of the polymer matrix of the composite material C and a solid phase comprising the reinforcements R released from this polymer matrix, it being specified that this polymer matrix corresponds to the polyepoxy matrix of the hardened composite material C or to the non- or partially crosslinked epoxy resin of the composite material C formed by a prepreg.

[0081] This separation step (2) can be carried out by any known solid / liquid separation technique, for example by filtration or centrifugation.

[0082] In an advantageous embodiment, the recycling process according to the invention may, furthermore, comprise at least one of the following steps (0) and (2'): (0) a mechanical or chemical treatment of the composite material C, and (2') a rinsing of the reinforcements R separated in step (2), it being specified that step (0) is carried out before step (1) and that step (2') is carried out after step (2).

[0083] Step (0) is a pre-treatment step of the composite material C which is carried out before step (1) of bringing this composite material C into contact with the composition in such a way as to promote the degradation of the polyepoxy matrix or the non-crosslinked or partially crosslinked epoxy resin which this composite material C contains.

[0084] This pretreatment can be a mechanical treatment, for example carried out by means of a light abrasion of the composite material C, or a treatment using a solvent aimed at bringing the composite material C into contact with a chemical compound having, for example, an action on the three-dimensional structure of the material, by making it swell.

[0085] Step (2') is an additional treatment step performed on the reinforcements R that were separated and recovered at the end of step (2) of the process according to the invention. This step (2') consists of rinsing these reinforcements R, as recovered at the end of step (2), so as to remove any residual trace of degraded epoxy resin that might remain on their surface.

[0086] This rinsing can in particular be carried out by means of the composition according to the invention or of a solution comprising a chemical compound known for its dissolving properties, for example by means of a solution comprising dimethyl sulfoxide (DMSO).

[0087] In a particular embodiment, the recycling process according to the invention includes, furthermore, after step (3) and, where appropriate, before step (4), at least one additional cycle comprising the following successive substeps (i), (ii) and (iii): (i) contacting the composite material C with the liquid phase collected in step (3), (ii) a separation of the solid phase comprising the reinforcements R from the liquid phase resulting from step (i), and (iii) a collection of the liquid phase from step (i).

[0088] In this particular embodiment, it is equally possible to carry out the implementation of a single complementary cycle or of several complementary cycles.

[0089] The implementation conditions described above in connection with steps (1) to (3) are transposable to these steps (i) to (iii).

[0090] As will be seen in the examples below, the liquid phase collected in step (3) can be used to recycle a composite material C with good performance.

[0091] Other features and advantages of the invention will become apparent from the following examples, which relate to the preparation of different recycling compositions and their implementation for recycling a composite material C comprising reinforcements R.

[0092] It is specified that these examples are given only as an illustration of the objects of the invention and do not in any way constitute a limitation of these objects.

[0093] Detailed description of particular embodiments

[0094] The tests were conducted on samples cut from the same composite material C, in this case a hardened composite material comprising a polyepoxy matrix and carbon fibers as reinforcements R.

[0095] The samples are in the form of rectangles of approximately 40 mg and with dimensions of 35 mm x 15 mm x 0.125 mm.

[0096] Different recycling compositions were prepared from the following compounds: - as a reactant: H2O2 (H2O2 being used at 30% vol in water) - as a solvent: propylene carbonate (denoted CP), γ-valerolactone (denoted γ-Val) - as a catalyst: NaOH, H2SO4, citric acid (AcC), tartaric acid (noted as AcT) Example 1

[0097] The operating protocol implemented for conducting tests 1 to 12 was as follows: different compositions were prepared by introducing and mixing the different compounds, in their respective molar proportions, as mentioned in Table 1 below.

[0098] A sample of composite material C was placed without stirring, for a period of between 15 h and 65 h, in each of the compositions previously heated to a temperature between 70 °C and 90 °C, the conditions of duration and temperature being specified in Table 1.

[0099] At the end of the considered time of contact of the sample with the composition considered, the carbon fibers were recovered by filtration using a polyamide cloth having a pore size of 5 pm.

[0100] It is specified that for test 8, eight samples, marked (8*), were placed in the composition under consideration, and not just one as for tests 1 to 6 and 8 to 12.

[0101] The carbon fibers thus recovered were first washed twice with water and then twice with ethanol before being placed for 1 h in an oven at 70 °C.

[0102] After this drying process, the quantity of residual epoxy resin, which corresponds to the epoxy resin still present on the surface of the carbon fibers after contact with the composition, was determined by thermal gravity analysis (TGA). The corresponding results are indicated as a percentage of epoxy resin still present on the surface of the carbon fibers, denoted % resin in Table 1. It is specified that recycling is considered: - as "excellent", if the percentage of residual polyepoxy matrix is ​​strictly less than 1% (noted <1), - considered "good" if the percentage of residual polyepoxy matrix is ​​between 1% and 10%, and - as "bad", if the percentage of residual polyepoxy matrix is ​​strictly greater than 10%, it being specified that a percentage of 34% means that the polyepoxy matrix has not been degraded. [Table 1] Test Composition Molar proportions Time (h) Temperature (T) % resin (%) 1 H2O2 100 24 70 11.2 2 CP / H2O2 30 / 70 24 70 15.6 3 CP / H2O2 30 / 70 65 90 <1 4 CP / H2O2 / ACT 29.9 / 67.3 / 2.8 24 70 2.3 5 CP / H2O2 / ACT 30.6 / 69 / 0.4 24 70 4.5 6 CP / H2O2 / ACC 30 / 67.6 / 2.4 24 70 <1 7 CP / H2O2 / AcC 30.6 / 68.9 / 0.5 24 70 <1 8 CP / H2O2 / ACC(8*) 30.6 / 68.9 / 0.5 24 70 1 9 CP / H2O2 / AcC 30.6 / 68.9 / 0.5 15 90 3.6 10 CP / H2O2 / H2SO4 30.7 / 69.2 / 0.1 24 70 7.5 11 CP / H2O2 / NaOH 30.7 / 69.2 / 0.1 24 70 6.4 12 y-Val / H2O2 / ACC 28.2 / 71.2 / 0.6 24 70 <1

[0103] Table 1 shows that the recycling from tests 4 to 12, which use compositions all conforming to the invention, is good (tests 4, 5 and 8 to 12), or even excellent for tests 6, 7 and 12. These results are to be compared with the poor results from tests 1 and 2 which use reference compositions, under identical conditions of duration and temperature (with the exception of test 9).

[0104] The results of tests 7 and 8 show that these good recycling performances are achieved whether 1 or 8 samples are recycled in the same composition.

[0105] It should be noted that excellent recycling was achieved with test 3, which also uses a reference composition. However, it was observed that achieving this result required significantly increasing the duration and temperature conditions. Example 2

[0106] Table 2 below shows the quantity of residual epoxy resin as determined by TGA, firstly, on carbon fibers recovered from the recycling of samples subjected to tests 10 and 11 of Example 1 and, secondly, on these same carbon fibers recovered from the recycling of tests 10 and 11 subjected, in a second step, to an additional rinsing step. The corresponding tests are numbered 13 and 14 respectively.

[0107] After 24 hours, the samples from tests 13 and 14 were rinsed in a dimethyl sulfoxide solution and then dried, and the amount of residual epoxy resin was determined by TGA. The corresponding results are shown as the percentage of residual epoxy resin on the surface of the carbon fibers, denoted % resin in Table 2. [Table 2] Test Compounds Molar Proportions Rinse % of resin (%) 10 CP / H2O2 / H2SO4 30.7 / 69.2 / 0.1 no 9.70 13 CP / H2O2 / H2SO4 30.7 / 69.2 / 0.1 yes 4.30 11 CP / H2O2 / NaOH 30.7 / 69.2 / 0.1 no 8.20 14 CP / H2O2 / NaOH 30.7 / 69.2 / 0.1 yes <1

[0108] Table 2 shows that rinsing the carbon fibers obtained after the step of contacting the composite material C with the compositions according to the invention further improves fiber recycling and, consequently, fiber quality, particularly for subsequent reuse. Example 3

[0109] This example 3 aims to evaluate the performance of the recycling process according to the invention, by reusing the liquid phase resulting from this recycling.

[0110] The operating protocol implemented for conducting this test consisted of carrying out a first recycling cycle by placing a sample of the composite material C for a period of 24 h without agitation in the test composition 6 previously heated to a temperature of 70 °C.

[0111] At the end of the 24 hours, the carbon fibers were recovered by filtration using a polyamide cloth having a pore size of 5 pm, the liquid phase from the filtration having been collected.

[0112] The carbon fibres thus recovered at the end of this first recycling cycle were first washed twice with water and then twice with ethanol before being placed for 1 h in an oven at 70 °C.

[0113] At the end of this drying, the residual quantity of resin on the carbon fibers was determined by TGA and reported in Table 3 below (test 6i).

[0114] A second recycling cycle was implemented by placing a new sample of composite material C, for the same 24-hour period, in the liquid phase collected at the end of the first recycling cycle and previously heated to a temperature of 70 °C. It is specified that the depolymerized resin present in the liquid phase at the end of the first recycling cycle was not extracted from this liquid phase.

[0115] At the end of the 24 hours, the carbon fibers were recovered by filtration using a polyamide cloth having a pore size of 5 pm, the liquid phase resulting from this filtration having been collected.

[0116] The carbon fibres thus recovered at the end of this second recycling cycle were then washed and dried, according to the same methods as those implemented during the first recycling cycle.

[0117] At the end of this drying, the residual quantity of resin on the carbon fibers was determined by TGA and reported in Table 3 below (test 62).

[0118] A third recycling cycle (test 63) and then a fourth recycling cycle (test 64) were subsequently implemented in succession according to the same operating protocol as that described above for the second recycling cycle, by successively submitting two new samples of the composite material C to each of the liquid phases resulting from the previous carbon fiber filtration step.

[0119] The amount of residual epoxy resin on the carbon fibers was determined by TGA at the end of each successive recycling cycle. The corresponding results are shown in Table 3 below. [Table 3] Test Composition Molar proportions Time (h) Temperature rc> % of resin (%) 6i CP / H2O2 / AcC 30.6 / 68.9 / 0.5 24 70 <1 62 Liquid phase from 61 24 70 6.30 63 Liquid phase from 62 24 70 5.50 64 Liquid phase from 63 24 70 10.18

[0120] It is observed that the liquid phases collected at the end of the filtration steps of the second, third and fourth cycles allow the composite material samples C to be degraded, admittedly in a slightly less efficient way than during the first recycling cycle, but still satisfactorily.

[0121] These tests show that the liquid phase obtained at the end of the step of contacting the composition according to the invention with the sample can be reused several times, on the one hand, without the resin depolymerized during each of the contacting steps having been extracted and, on the other hand, without the addition of any compound, whether it be hydrogen peroxide, solvent or catalyst. Bibliography

[0122] CN 112552473 A

[0123] JP 2002-121322 A

[0124] CN 105906836 A

[0125] US 8,920,932 B2

[0126] JP ​​5880960 B2

Claims

Demands

1. Use of a composition comprising: - an aqueous solution of hydrogen peroxide H2Q2(a), - one or more organic carbonates (b) selected from dialkyl carbonates (bl) and alkylene carbonates (b2), or one or more lactones (b1), and - either one or more organic acids (c) selected from monocarboxylic acids (cl) comprising at least 10 carbon atoms and polycarboxylic acids (c2), or one or more mineral acids (dl) selected from sulfuric acid H2SO4 and phosphoric acid H3PO4, or one or more hydroxides of an alkali or alkaline earth metal (d2) such as sodium hydroxide NaOH or potassium hydroxide KOH, for the recycling of a material M obtained from an epoxy resin, the material M being advantageously a hardened material.

2. Use according to claim 1, wherein the dialkyl carbonate(bl) is / are selected from dimethyl carbonate and diethyl carbonate.

3. Use according to claim 1 or 2, wherein the alkylene carbonate(b2) is selected from ethylene carbonate and propylene carbonate, the alkylene carbonate(b2) advantageously being propylene carbonate.

4. Use according to claim 1, wherein the lactone(s) (b1) are selected from α-acetolactone, β-propiolactone, γ-butyrolactone, β-valerolactone and γ-valerolactone and, advantageously, from β-valerolactone and γ-valerolactone.

5. Use according to any one of claims 1 to 4, wherein the molar proportion of aqueous H2O2 solution (a) in the composition is between 30% mol and 85% mol, advantageously between 60% mol and 80% mol and preferably between 68% mol and 74% mol, the molar proportion of Pure H2O2 in the composition being between 5% mol and 20% mol.

6. Use according to any one of claims 1 to 5, wherein the molar proportion of the organic carbonate(s) (b) or lactone(s) (b1) in the composition is between 15% mol and 40% mol, advantageously between 20% mol and 35% mol and, preferably, between 25% mol and 30% mol.

7. Use according to any one of claims 1 to 6, wherein the molar proportion of the organic acid(s) (c) in the composition is between 0.1% mol and 5% mol, advantageously between 0.1% mol and 1.1% mol, preferably between 0.4% mol and 0.6% mol and, more preferably, between 0.48% mol and 0.55% mol.

8. Use according to any one of claims 1 to 7, wherein the polycarboxylic acid(s) (c2) are selected from dicarboxylic acids such as tartaric acid, and tricarboxylic acids such as citric acid.

9. Use according to any one of claims 1 to 6, wherein the molar proportion of the mineral acid(s) (dl) or hydroxide(s) (d2) in the composition is between 0.01% mol and 0.2% mol, advantageously between 0.05% mol and 0.15% mol and preferably between 0.08% mol and 0.12% mol.

10. A process for recycling a material M obtained from an epoxy resin, said process comprising the following successive steps (1), (3) and, where applicable, (4): (1) contacting the material M with a composition as defined in any one of claims 1 to 9, (3) collecting the liquid phase from step (1), and (4) optionally, recovering epoxy resin from the liquid phase collected in step (3).

11. A method according to claim 10, wherein the material M is a composite material C comprising reinforcements R, this method further comprising, between steps (1) and (3), the following step (2): (2) a separation of the solid phase comprising the reinforcements R from the liquid phase obtained from step (1).

12. A method according to claim 11, further comprising at least one of the following steps (0) and (2'): (0) a mechanical or solvent treatment of the composite material C, and (2') a rinsing of the reinforcements R separated in step (2), step (0) being carried out before step (1) and step (2') being carried out after step (2).

13. A method according to claim 11 or 12, further comprising, after step (3) and, where appropriate, before step (4), at least one additional cycle comprising successive substeps (i), (ii) and (iii) following: (i) contacting the composite material C with the liquid phase collected in step (3), (ii) separating the solid phase including the reinforcements R from the liquid phase from step (i), and (iii) collecting the liquid phase from step (i).

14. A method according to any one of claims 11 to 13, wherein at least step (1) is carried out at atmospheric pressure and at a temperature between 5 °C and 90 °C, advantageously between 15 °C and 80 °C and preferably between 20 °C and 75 °C.

15. Use according to any one of claims 1 to 9 or method according to any one of claims 10 to 14, wherein the material M is a composite material C comprising reinforcements R, these reinforcements R being able to be selected in particular from particulate fillers, webs, fabrics and fibers, these fibers being able to be continuous, long or short, unidirectional or multidirectional.

16. Composition comprising: - an aqueous solution of hydrogen peroxide |-|QQ2(a), - one or more organic carbonates (b) selected from dialkyl carbonates (bl) and alkylene carbonates (b2), or one or more lactones (b1), and - one or more hydroxides of an alkali or alkaline earth metal (d2) such as sodium hydroxide NaOH or potassium hydroxide KOH.

17. Composition according to claim 16, wherein the molar proportion of the hydroxide(s) (d2) in the composition is between 0.01% mol and 0.2% mol, advantageously between 0.05% mol and 0.15% mol and preferably between 0.08% mol and 0.12% mol.