EP3784724A1

EP3784724A1 - Recovery of (meth)acrylic resin by depolymerization and hydrolysis

Info

Publication number: EP3784724A1
Application number: EP19729579.3A
Authority: EP
Inventors: Jean-Luc Dubois
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2018-04-27
Filing date: 2019-04-26
Publication date: 2021-03-03
Also published as: KR20210005113A; US11739192B2; WO2019207264A1; US20210040288A1; FR3080623B1; CA3097475A1; FR3080623A1; BR112020021672A2

Abstract

The invention relates to a process for recycling (100) an item based on thermoplastic (meth)acrylic polymer resin, characterized in that it comprises the following steps: - introduction (110) of the item into a system suitable for thermoplastic polymer recycling, - at least partial depolymerization (130) of the thermoplastic (meth)acrylic polymer resin so as to form (meth)acrylate monomers, - introduction (140) of a hydrolysis catalyst into a hydrolysis reactor, - introduction (150) of water into said hydrolysis reactor, and - conversion (160), in the hydrolysis reactor, of at least some of the (meth)acrylate monomers into (meth)acrylic acid. The invention also relates to a system for recycling an item based on thermoplastic (meth)acrylic polymer resin.

Description

VALORIZATION OF (METH) ACRYLIC RESIN BY DEPOLYMERIZATION AND

HYDROLYSIS

[Technical area]

The present invention relates generally to the recycling of articles based on polymeric resin (meth) acrylic and / or composite material based on (meth) acrylic polymer resin, in particular based on poly (methyl methacrylate) ).

[002] The invention finds applications in various industrial sectors such as the environment or plastics, and in particular in sectors facing post-consumer waste recycling issues such as end-of-life products, or industrial waste such as defective products or falls from plastics operations.

[Prior Art]

[003] In 2017, thousands of tons of thermoplastics were produced worldwide. The production and recycling of thermoplastics therefore appear to be major issues from an environmental and economic point of view, particularly the recycling of articles containing methacrylic polymers. Given the low cost of methacrylic thermoplastic polymers, their low weight and durability, these polymers are produced in very large quantities and are widely used. The accumulation of end-of-life products and products from processing or production processes gives rise to the problem of recycling these products. The products in question may comprise a methacrylic thermoplastic polymer resin and in some cases take the form of a composite article based on methacrylic thermoplastic polymer resin.

[004] In order to recycle products or articles made of methacrylic thermoplastic polymer, recycling methods have been developed. These methods make it possible to obtain, in general, the basic monomers of the thermoplastic polymer in for reuse in the manufacture of thermoplastic polymer article.

[005] Among the conventional methods of recycling articles comprising a methacrylic thermoplastic polymer resin, the depolymerization is known in bed of lead or molten tin. In this method, the articles are crushed and then decomposed in a molten lead / tin bed heated to a temperature generally above 400 ° C. Such a method, however, has several disadvantages. In depolymerization, a disadvantage is the accumulation of solid residues on the surface of the molten metal. In the case of composites, solid residues and / or fibers accumulate continuously. This process is therefore accompanied by fouling problems of the lead / tin bed and the reactor in which it is disposed. These problems are accentuated in the case of composites because the molten metal bed requires regular removal of the residues on its surface in order to continue to extract the gaseous monomer from the reactor. The cleaning of the reactor, and the various elements constituting the depolymerization device on a bed of molten metal, is an additional step in the treatment of articles which increases the environmental, energy and economic balance. In addition, toxic by-products, especially from the cleaning stages, containing lead or tin, are generated. This polluted waste should be treated appropriately, which implies significant associated costs. These various processes are energy intensive and expensive. In addition, the gases resulting from the depolymerization must be condensed and purified. Generally, the purification step for the isolation of the monomer is complex, is accompanied by losses and the yield in terms of monomer recovery is low. This recycling process is therefore generally unsatisfactory and is unsuited to the treatment of composites. Moreover, during the depolymerization of articles comprising methacrylic thermoplastic polymers, in particular composite articles, a certain number of impurities which are difficult to separate from the methyl methacrylate monomer are generated, which jeopardizes the reuse of methyl methacrylate in an identical application.

Also known is the fluidized bed depolymerization process in which the fluidized bed may be a bed of sand or silica placed in a fluidized bed reactor. In this process, an article for example based on polymethyl methacrylate resin, hereinafter referred to as PMMA, is premixed and then the ground material obtained is introduced into the reactor containing the fluidized bed under a flow of hot gas with a temperature generally greater than 400 ° C. In this fluidized bed, the resin is rapidly heated, depolymerized and it leads to the methyl methacrylate monomer, hereinafter referred to as MMA. Nevertheless, here again a certain number of impurities that are difficult to separate from the methyl methacrylate monomer can be generated, which compromises the reuse of methyl methacrylate in an identical application.

[007] DE19729065 discloses a thermal depolymerization process of polymethyl methacrylate to form the monomer. The process described does not include a hydrolysis step of the monomer.

[008] CN103588636 discloses a process for catalyzing the hydrolysis reaction of methyl methacrylate (MMA) to obtain a (meth) acrylic acid. The catalyst consists of a strongly acidic macroporous cation exchange resin which allows hydrolysis of MMA with water at a temperature between 50 and 75 ° C at atmospheric pressure and for a period of between 30 and 60 hours.

[009] US2004 / 0051886 discloses a process for preparing methacrylic acid from hydrolysis of purified methyl methacrylate from a process known as acetone cyanohydrin. The process described does not include a depolymerization step of a polymer.

[010] Thus, the conventional methods for recycling thermoplastic (meth) acrylic polymer resin, in particular based on poly (methyl methacrylate) PMMA, conventionally consist in the depolymerization of the polymer, and generally lead to obtaining monomers, such as MMA, contaminated with impurities, such as methyl isobutyrate, and / or methyl propionate, and / or methyl acrylate, and / or acrylate; ethyl.

[Technical problem]

The object of the invention is therefore to remedy at least one of the aforementioned drawbacks of the prior art.

[012] The invention aims in particular to provide a simple and effective solution for recycling articles based on (meth) acrylic polymers. The invention is further directed to a specific polymer depolymerization process, while allowing energy savings. The invention thus integrates in a context of sustainable development and in the recovery of waste thermoplastic resin (meth) acrylic.

[Brief description of the invention]

[013] For this purpose, according to a first aspect, the invention provides a method for recycling an article based on thermoplastic (meth) acrylic resin, characterized in that it comprises the following steps:

introduction of the article into a system adapted for the recycling of thermoplastic polymer,

at least partial depolymerization of the (meth) acrylic thermoplastic polymer resin so as to form (meth) acrylate monomers,

introduction of a hydrolysis catalyst into a hydrolysis reactor,

- introducing water into said hydrolysis reactor, and - converting, in the hydrolysis reactor, at least a portion of the (meth) acrylate monomers to (meth) acrylic acid.

[014] In the context of the process according to the invention, the thermoplastic polymer resin is at least partially converted into (meth) acrylic acid following hydrolysis of monomers of (meth) acrylates from the resin. It is then possible to obtain a mixture comprising monomers of (meth) acrylic esters and the corresponding (meth) acrylic acids but also impurities such as: isobutyrate, isobutyric acid and butanol esters and acids. The compounds of the mixture resulting from the hydrolysis according to the invention can be separated, taking into account the differences in the physicochemical properties of the compounds in the presence such as boiling temperatures, melting temperatures and / or solubilities in water. Purification processes can then be performed to obtain a relatively pure solution of the compound to be upgraded, such as, for example, methacrylic acid, which is a compound of interest. In addition, the use of a catalyst makes it possible to reduce the hydrolysis temperature or generally results in an acceleration of the hydrolysis reaction.

[015] According to other optional features of the recycling process:

the hydrolysis catalyst is selected from: Alumina, MgO, CaO, Mg (OH) ₂ , Ca (OH) ₂ , Al (OH) ₃ , a zeolite, an acid, a base, an amphoteric compound or a mixture of two or more of these compounds; and preferably Alumina, MgO, CaO, Mg (OH) ₂ , Ca (OH) ₂ , Al (OH) ₃ , a zeolite, a base, an amphoteric compound or a mixture of two or more of these compounds

the recycling process according to the invention may further comprise a step of regenerating the catalyst and more particularly the hydrolysis catalyst. This is particularly suitable when the hydrolysis catalyst is a heterogeneous catalyst. Indeed, the process may then comprise a step of contacting said heterogeneous hydrolysis catalyst with a regenerating substance in order to reactivate said heterogeneous hydrolysis catalyst;

the method further comprises a step of introducing a depolymerization initiation catalyst into said system adapted for the recycling of thermoplastic polymer. Such a depolymerization initiation catalyst makes it possible to induce a split within the polymer chain and thus accelerate the depolymerization. The initiation catalyst is preferably introduced into a depolymerization reactor, advantageously separate from the hydrolysis reactor;

the depolymerization initiation catalyst is chosen from: an organic peroxide, an inorganic peroxide or superoxide such as barium peroxide (BaCt), potassium superoxide (KO ₂ ), cesium superoxide (CsCt), a percarbonate , a peroxyhydrate compound, their salts and their mixture. Hydrogen peroxide (H ₂ O ₂ ) can be mentioned as an initiation catalyst for depolymerization.

Azobisisobutyronitrile (AIBN), sodium carbonate peroxyhydrate (2Na ₂ CC> ₃ .3H ₂ O ₂ ), or potassium or magnesium or calcium, ammonium carbonate peroxyhydrate ((NH ₄ ) ₂ CO ₃ 2H ₂ O ₂ ), urea peroxide (CO (NH ₂ ) _2, H ₂ O ₂ ), sodium sulfate peroxohydrate (2Na ₂ SO ₄ .H ₂ O ₂ .2H ₂ O), H ₂ O ₂ and inorganic salts, poly (vinyl pyrrolidone) polymer peroxide (PVP.H ₂ O ₂ ), persulfates, permanganates, perborates, phosphate salt peroxyhydrates. Preferably, the depolymerization initiation catalyst is sodium percarbonate;

the concentration of depolymerization initiation catalyst is such that the molar ratio between the concentration of depolymerization initiation catalyst and the concentration of (meth) acrylic thermoplastic polymer present in the introduced article is between 0.001 and 10;

the depolymerization is carried out in the hydrolysis reactor. In this case, the depolymerization can advantageously be carried out before the hydrolysis. It is then done in the absence of water. Alternatively, the depolymerization and hydrolysis steps are consecutive and in two separate reactors;

- The method further comprises a distillation step capable of generating a mixture enriched with (meth) acrylic acid. This separation step is possible in particular because of the differences in boiling temperature of the various compounds present; - The method further comprises a crystallization step capable of generating a mixture enriched with (meth) acrylic acid. A mixture enriched with (meth) acrylic acids is more particularly a composition comprising a majority of (meth) acrylic acids. Indeed, the process according to the invention makes it possible to obtain a mixture comprising one or more (meth) acrylic acids and impurities and because of the differences in melting temperature between the (meth) acrylic acids and the impurities, it is possible by crystallization to isolate one or more (meth) acrylic acids. In addition, the crystallization purification method is simple and inexpensive to implement;

the article to be recycled is made of composite material based on (meth) acrylic thermoplastic polymer resin and a reinforcement;

the method further comprises a step of recovering heat, preferably heat stored by the reinforcement. This heat recovery can be advantageously used in the recycling process to produce water vapor, to heat the reactor of the recycling system and / or to maintain ducts at a given temperature.

[016] The invention also relates to an article recycling system based on (meth) acrylic thermoplastic polymer resin. This system is mainly characterized in that it comprises:

means for introducing the article into said system, a hydrolysis reactor,

means for introducing water into said hydrolysis reactor, means for introducing a hydrolysis catalyst into said hydrolysis reactor, and

heating means, preferably capable of inducing depolymerization and hydrolysis of at least a portion of the article to be recycled.

[017] According to other characteristics of the system:

the system comprises one of the following devices: a reactive extruder, a fluidized bed device, a circulating fluidized bed device, a mixer-conveyor; a rotary stirring device, a stirred rotary kiln or a plate reactor.

- It further comprises a hydrolysis catalyst regeneration device. The hydrolysis catalyst regeneration device is preferably connected to the reactor or an integral part of said hydrolysis reactor.

It comprises one or more purification devices. Purification devices such as distillation and / or crystallization devices will, in combination with the hydrolysis reactor, form a relatively pure fraction of (meth) acrylic acid which can then be recovered.

- It includes a device adapted to heat recovery. The presence of a heat recovery device is particularly advantageous in the context of a recycling system comprising a hydrolysis reactor since it can be configured to recover the heat accumulated by the remaining solid fraction (non-depolymerized fraction or non depolymerizable such as glass fibers) in a depolymerization step so as to allow a hydrolysis step.

- The device adapted to the heat recovery is adapted to use the recovered heat to heat water and / or maintain at least a portion of the system according to the invention at a temperature above 100 ° C.

[018] Other features and advantages of the invention will appear on reading the following description, given by way of illustration and not limitation with reference to the appended figures which represent:

1, a diagram showing steps of the recycling method according to one embodiment, the dashed steps are optional,

Figure 2, a diagram of a recycling system according to the invention 3, a diagram of a twin-screw extruder for implementing the method according to one embodiment,

FIG. 4, a diagram of a fluidized bed device for implementing the method according to another embodiment, and

FIG. 5, a diagram of a recycling system, according to one embodiment, incorporating a heat recovery device,

FIG. 6, a schematic representation of a device for regenerating a hydrolysis catalyst,

FIG. 7a is a diagram of a device for regenerating the hydrolysis catalyst inside the recycling device according to one embodiment and FIG. 7b is a diagram of a device for regenerating the hydrolysis catalyst at a temperature of outside the recycling device according to one embodiment,

8, a diagram of a regeneration device of the hydrolysis catalyst coupled to a combined hydrolysis and depolymerization reactor according to one embodiment.

[Description of the invention]

[019] In the following description, the term "polymeric resin" means a binder material. The "resin" comprises polymers and / or oligomers. Thus, a "(meth) acrylic polymer resin" refers to any type of acrylic and methacrylic compounds, polymers, oligomers, or copolymers. However, it would not be outside the scope of the invention if the (meth) acrylic polymer resin comprised up to 10% by weight, preferably less than 5% by weight, of other non-acrylic monomers, chosen for example from the following group: butadiene, isoprene, styrene, substituted styrene such as α-methylstyrene or tert-butylstyrene, cyclosiloxanes, vinylnaphthalenes and vinylpyridines.

[020] The term "monomer", a molecule that can undergo polymerization. The term "polymerization" as used refers to the process of converting a monomer or mixture of monomers into a polymer.

[022] "Polymer" means either a copolymer or a homopolymer. A "copolymer" is a polymer comprising several different monomer units and a "homopolymer" is a polymer comprising identical monomeric units.

[023] "Thermoplastic (meth) acrylic polymer" means a polymer comprising essentially (meth) acrylic monomers which represent at least 50% by weight or more of the (meth) acrylic polymer. The (meth) acrylic monomers are, for example, chosen from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, acrylic acid, methacrylic acid, acrylate and the like. butyl, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, and mixtures thereof. Poly (methyl methacrylate) (PMMA) is a particular example of a (methacrylic) polymer obtained by polymerization of a methyl methacrylate monomer. The term "PMMA", within the meaning of the invention, denotes homopolymers and copolymers of methyl methacrylate (MMA), the weight ratio of MMA in PMMA being preferably at least 70% by weight for the copolymer of MMA.

[024] The term "(meth) acrylic acid" means methacrylic acid or acrylic acid.

[025] The term "copolymer based on methyl methacrylate" a copolymer having at least one methyl methacrylate monomer. For example, a methyl methacrylate copolymer may be a copolymer comprising at least 70%, preferably 80%, preferably 90% by weight of MMA in PMMA.

[026] The term "base monomer", the most important monomeric unit constitutive of a polymer. Thus, in PMMA, the base monomer is MMA.

[027] By "reduced molecular weight polymer" is meant a polymer, derived from an initial polymer or starting polymer, and whose molecular weight is lower than the molecular weight of the starting polymer. The weight average molecular weight can be measured by size exclusion chromatography.

For the purposes of the invention, the term "composite" is intended to mean a multi-component material comprising at least two immiscible components in which at least one component is a polymer and the other component may for example be a reinforcement.

By "reinforcement" is meant a non-depolymerizable or gasifiable solid material such as a "fibrous reinforcement" or a "mineral filler" which remain at the end of treatment.

By "fibrous reinforcement" is meant a set of fibers, unidirectional rovings or a continuous filament mat, fabrics, felts or nonwovens which may be in the form of strips, tablecloths, braids or wicks. or parts.

By "mineral fillers" is meant any powdery fillers for example quartz, marble, silica, aluminum hydroxide, TiCt.

[032] By "depolymerization" is meant unlike the polymerization process which is a process for converting monomer (s) into a polymer, the depolymerization here denotes a process in which an initial polymer P1 is converted into a polymer P2 of molecular weight reduced, or even its or its monomer (s) base.

By "partial depolymerization" is meant here a depolymerization in which the polymer is partially converted into monomer for example without the action of water (e.g. water vapor). This generally results in a mixture of polymer and monomer, the polymers having a lower average molecular weight than before the partial depolymerization. In contrast, complete depolymerization corresponds to the depolymerization of substantially all of the (meth) acrylic thermoplastic polymer resin.

By "hydrolysis catalyst" is meant an entity that catalyzes the hydrolysis reaction of the (meth) acrylic monomer. By "depolymerization initiation catalyst" is meant a compound capable of inducing radical scission of the polymer chain.

By "reactive extruder" is meant a reactor comprising one or more worm allowing in particular the stirring of the polymers introduced into said reactor.

[037] By "regenerator" or "regeneration" is meant a device in which the reactivation of a hydrolysis catalyst can be carried out through the introduction of a regenerating substance. Such a hydrolysis catalyst, for example alumina, can be reactivated under an oxidizing atmosphere in order to remove the carbonaceous residues which are deposited on its surface.

By "crystallization" is meant separation by selective solidification of a compound.

[039] In the description below of the various embodiments and in the accompanying figures, the same references are used to designate the same elements or similar elements.

The invention relates to a method for recycling a resin-based article made of (meth) acrylic thermoplastic polymer.

[041] The thermoplastic polymer (meth) acrylic resin may be a resin based on homo- and acrylic copolymers, polyalkyl acrylate or alkyl poly (meth) acrylates, such as for example the poly (methyl methacrylate), and mixtures thereof.

[042] In particular, the thermoplastic (meth) acrylic polymer resin may be a poly (methyl methacrylate) resin, also known as PMMA. In particular, such a PMMA may be the product marketed by ARKEMA under the name Altuglas®.

[043] The assembly of (meth) acrylic monomers, during a polymerization process, leads to the formation of a polymer having a linear or crosslinked chain of higher molecular weight than that of the base monomer.

[044] The article may for example be of composite material, that is to say based on the thermoplastic polymer resin (meth) acrylic intimately related to a reinforcement. A reinforcement may for example be a mineral filler such as quartz, marble, calcium phosphate, chalk or carbon black.

[045] A reinforcement may also be a fibrous reinforcement comprising an assembly of one or more fibers, generally several fibers, said assembly being able to have different shapes and dimensions, one-dimensional, two-dimensional or three-dimensional. The one-dimensional shape corresponds to long linear fibers. The two-dimensional form is fibrous mats or non-woven reinforcements or woven rovings or bundles of fibers, which may also be braided. The three-dimensional shape corresponds, for example, to non-woven fibrous mats or reinforcements or stacked or folded bundles of fibers or mixtures thereof, an assembly of the two-dimensional form in the third dimension. The fibers may be discontinuous or continuous. When the fibers are continuous, their assembly forms tissues.

[046] The origins of the fibers constituting the fibrous reinforcement may be natural or synthetic. As a natural material, mention may be made of vegetable fibers, wood fibers, animal fibers or mineral fibers. Vegetable fibers are, for example, sisal fibers, jute, hemp, linen, cotton, coconut, and banana fibers. Animal fibers are, for example, wool or hair. The mineral fibers may also be chosen from glass fibers, in particular of the E, R or S2 type, basalt fibers, carbon fibers, boron fibers or silica fibers. As the synthetic material, there may be mentioned polymeric fibers selected from thermosetting polymer fibers, thermoplastic polymers or mixtures thereof. The polymeric fibers may consist of polyamide (aliphatic or aromatic), polyester, polyvinyl alcohol, polyolefins, polyurethanes, polyvinyl chloride, polyethylene, unsaturated polyesters, epoxy resins and vinyl esters. [047] Referring to Figure 1, the recycling process 100 comprises a step 110 of introducing the article to be recycled in a system adapted for recycling. More particularly, in a reactor of said system. Depending on the system used, this reactor may be a portion of a twin screw extruder 300 as illustrated in FIG. 3, or the reactor 402 of a fluidized bed device 400 as illustrated in FIG. 4, or still a mixer-conveyor not shown in the figures.

[048] In one embodiment, the recycling process further comprises the introduction 120 of a depolymerization initiation catalyst into the system according to the invention for recycling thermoplastic polymer. The depolymerization initiation catalyst may more particularly be introduced into a depolymerization reactor or into the hydrolysis reactor, if depolymerization and hydrolysis are conducted in the same reactor. In other words, the depolymerization is carried out in the hydrolysis reactor.

[049] In a first preferred embodiment of the invention, the depolymerization step (130) and the hydrolysis take place in the same reactor.

[050] In a variant of the first preferred embodiment of the invention there is a depolymerization step alone before the depolymerization step (130) and the hydrolysis which take place in the same reactor.

[051] For example, the depolymerization initiation catalyst may be an organic peroxide, an inorganic peroxide or superoxide such as barium peroxide (BaCt), potassium superoxide (KO2), cesium superoxide (CsCb), a percarbonate, a peroxyhydrate compound, their salts and their mixture. Hydrogen peroxide (H2O2) may be mentioned as an initiation catalyst for depolymerization,

1 azobisisobutyronitrile (AIBN), sodium carbonate peroxyhydrate (2Na ₂ Cu ₃ .3H2O2), or potassium or magnesium or calcium, ammonium carbonate peroxyhydrate ((NH ₄₎ ₂ CO ₃ .H ₂ O ₂ ); urea peroxide (CO (NH ₂ ) ₂ .H ₂ O ₂ ); sodium sulphate peroxyhydrate (2Na 2 SO 4 .H 2 O 2 .2H 2 O); complexes of H ₂ O ₂ and inorganic salts, poly (vinyl pyrrolidone) polymeric peroxyhydrate (PVP H 2 O 2), persulfates, permanganates, perborates, phosphate salt peroxyhydrates. Preferably, the depolymerization initiation catalyst is chosen from perborates or percarbonates. More preferably, the depolymerization initiation catalyst is sodium percarbonate.

[052] The depolymerization initiation catalyst in a preferred mode is not liquid at 25 ° C. The depolymerization initiation catalyst, in a first preferred mode, is solid at 25 ° C. The depolymerization initiator if liquid in pure form at 25 ° C is, in a second preferred embodiment, supported by a solid or impregnated in a solid to form a solid powder or granules at 25 ° C.

[053] The amount of depolymerization initiation catalyst in the reactor may be such that the molar ratio between the molar amount of depolymerization initiation catalyst and the molar amount of (meth) acrylic thermoplastic polymer present in the reactor. introduced article is between 0.001 and 10, preferably between 0.005 and 5, more preferably between 0.01 and 1, and even more preferably between 0.01 and 0.5.

[054] The recycling process according to the invention comprises a step 130 of partial or complete depolymerization of the thermoplastic (meth) acrylic polymer resin. This depolymerization may be a conventional depolymerization step and preferably leads to the formation of (meth) acrylate monomers.

Nevertheless, as has been mentioned, depolymerization can also lead to the formation of impurities (e.g. methyl isobutyrate). As will be detailed later, preferably the depolymerization and hydrolysis reactions are carried out successively and can take place in the same reactor or in two different reactors.

[055] The recycling process may therefore comprise a depolymerization step in which the thermoplastic polymer resin (Meth) acrylic (eg PMMA resin) is depolymerized by conventional methods leading predominantly to the formation of (meth) acrylate monomer (eg methyl methacrylate). Typical depolymerization methods may be thermal pyrolysis, microwave induced pyrolysis or fluidized bed depolymerization, for example. Such depolymerization can be initiated within the polymer chain, that is to say anywhere in the polymer chain and, in this case, leads to the formation of two polymers of reduced molecular weight. The depolymerization can also be initiated at one end of the polymer chain and then extend along the chain to lead to the formation of basic monomer or comonomer base, and a reduced chain polymer.

[056] The at least partial depolymerization can be a partial depolymerization or a complete depolymerization.

[057] During the depolymerization, the temperature in the reactor may be between 300 ° C and 400 ° C, or for example less than or equal to 350 ° C in the presence of a depolymerization catalyst.

[058] Advantageously, the depolymerization can be followed by a purification step in which the (meth) acrylate monomer (eg methyl methacrylate) thus obtained can be collected by fractional distillation, for example, to yield fractions F1. and fractions F2. The fractions F1 and F2 are distinct and F1 can correspond to a pure fraction comprising at least 90% of methyl methacrylate, and the fraction F2 can correspond to a less pure fraction in which impurities, such as methyl isobutyrate, are majority. The fraction F1 can be valorized as methyl methacrylate whereas the fraction F2 will undergo a hydrolysis step according to the invention by means of the system according to the invention adapted for the recycling of thermoplastic. Thus, the process according to the invention may advantageously comprise a distillation step prior to the hydrolysis step. [059] As previously mentioned, the depolymerization can be separated in time or space from the hydrolysis.

[060] The recycling process according to the invention also comprises a step 140 for introducing a hydrolysis catalyst into a reactor (i.e. a hydrolysis reactor). This hydrolysis catalyst may have acidic, basic or acid-base properties. The acid hydrolysis catalyst may be an inorganic acid or an organic acid such as acetic, formic, nitric, benzoic, hydrochloric, sulfuric, orthophosphoric, phosphoric or boric acid, this list being nonlimiting.

[061] The basic hydrolysis catalyst may be, for example, sodium hydroxide NaOH, potassium hydroxide KOH, sodium carbonate Na ₂ CC> ₃ , Mg (OH) ₂ , MgCCb, CaCCb, a basic zeolite, a hydrotalcite, or else ammonia, this list being non-limiting.

[062] The hydrolysis catalyst may be a solid heterogeneous catalyst (non-liquid under the hydrolysis conditions), for example a metal oxide such as alumina Al2O3, magnesium oxide MgO, calcium oxide CaO, magnesium hydroxide Mg (OH) 2 or calcium hydroxide Ca (OH) 2, aluminum hydroxide Al (OH) 3, a zeolite, a silicoaluminate, a silica or a mixture thereof. In a preferred embodiment, the catalyst is an alumina catalyst. The hydrolysis catalyst is not a resin with acidic groups.

[063] The hydrolysis catalyst is selected from: Alumina, MgO, CaO, Mg (OH) ₂ , Ca (OH) ₂ , Al (OH) 3, a zeolite, an acid, a base, an amphoteric compound or a mixture of two or more of these compounds.

[064] The hydrolysis catalyst may be mixed, by dissolution or dilution, with water to form an aqueous solution. The aqueous solution containing the dissolved or diluted catalyst can then be introduced (and optionally beforehand vaporized) into the reactor of a system suitable for recycling thermoplastic polymer such as those previously described. The hydrolysis catalyst may also be suspended in water.

[065] The amount of hydrolysis catalyst in the reactor may be between 0.1 and 20% by weight of the thermoplastic polymer (meth) acrylic (eg PMMA) present in the article introduced, preferably between 0.5 and 10% by weight and even more preferably between 1 and 5% by weight.

[066] The temperature of the catalyst, when it is an inorganic solid, entering the reactor during step 140 the introduction of a hydrolysis catalyst in a reactor is at least 300 ° C, preferably at least 350 ° C, more preferably at least 400 ° C and preferably at least 450 ° C.

[067] The recycling process according to the invention comprises especially a step 150 in which water, for example in gaseous or liquid form, is introduced into the hydrolysis reactor of the system according to the invention adapted to the recycling of polymer. thermoplastic.

[068] Preferably, in a step 150, a gas comprising water vapor is introduced into the reactor.

[069] In a variant, step 150 may correspond to the introduction of an aqueous solution into the reactor of the system. Thanks to the heat generated by a heating means and / or generated by a device adapted to heat recovery, the aqueous solution is converted into a gas comprising steam so as to simultaneously perform the depolymerization and hydrolysis. Preferably, the hydrolysis is carried out after the depolymerization.

[070] Preferably, the amount of water is at least stoichiometric with respect to the amount of (meth) acrylate monomers to be hydrolysed. This means that the molar amount of water is at least 1 mol / 1 mol relative to the molar amount of (meth) acrylate monomers to be hydrolysed. More preferably, the amount of water added in step 150 is greater than the amount of (meth) acrylate monomers to be hydrolyzed. For example, in the context of the hydrolysis of a PMMA composed on average of 1000 units of methyl methacrylate, the The process according to the invention will comprise a step of introducing 150 water at a quantity corresponding to at least 1000 units of water so as to hydrolyze everything.

[071] Advantageously, the amount of water added by weight is greater than or equal to 15% of the mass of the (meth) acrylic thermoplastic polymer (eg PMMA) present in the introduced article, preferably greater than or equal to 20% and more preferably greater than or equal to 40%.

[072] It may also be noted that the amount of water should preferably not be too high so as to limit the energy consumed. Thus, preferably, the amount of water added by weight is less than or equal to 100% of the mass of the (meth) acrylic thermoplastic polymer (e.g. PMMA) present in the article introduced.

[073] In a step 160, the (meth) acrylic thermoplastic polymer resin of the article is converted into a mixture comprising (meth) acrylic acid. More particularly, at least a portion of the (meth) acrylate monomers are converted into (meth) acrylic acid in the hydrolysis reactor. This mixture may also comprise, depending on the conditions, a reduced molecular weight polymer and a monomer in the form of (meth) acrylic ester.

[074] The hydrolysis reactor is heated to a temperature between 100 ° C and 250 ° C, preferably between 125 ° C and 250 ° C and more preferably between 150 ° C and 250 ° C.

[075] During the hydrolysis, the temperature in the reactor can be between 100 ° C and 250 ° C, preferably between 125 ° C and 250 ° C and more preferably between 150 ° C and 250 ° C , and for example 200 ° C. Preferably, the temperature in the reactor is between 150 ° C. and 200 ° C.

[076] The method according to the invention, via step 160, provides a composition comprising in particular a mixture of (meth) acrylic acids. Depending on the composition of the thermoplastic (meth) acrylic polymer resin of the article, this mixture may contain, in addition to methacrylic acid and the acid acrylic, a wide variety of compounds. Indeed, the (meth) acrylic thermoplastic polymers can be depolymerized into monomers and then the monomers are optionally partially hydrolyzed to give the corresponding acids. For example, the mixture may comprise butyl and ethyl esters, such as n-butyl methacrylate, methyl methacrylate, methacrylic acid, isobutyric acid, butyl acrylate, acrylate and the like. ethyl, methyl acrylate and acrylic acid.

[077] Based on the physicochemical properties of the components of this mixture, it is possible to isolate the compounds of interest such as unhydrolyzed (meth) acrylic monomers or (meth) acrylic acids of other undesired compounds . For example, methyl methacrylate and methyl isobutyrate will separate well from the acids by distillation. Then a crystallization may allow the butyl esters to be separated from the acids, and in particular methacrylic acid and acrylic acid from the rest of the compounds.

[078] Table 1 shows the properties of some of the compounds that can be found in the context of the process according to the invention.

[079] Table 1

[080] In this context, the recycling process according to the invention can have a high efficiency when it is coupled to distillation and / or crystallization steps because of the differences in boiling and / or melting temperature. crystallization between the compounds of interest and the impurities, it is possible to obtain relatively pure compositions of valuable compounds.

[081] The purification can lead to the formation of several fractions more or less pure. For example, methyl methacrylate can be recovered for recovery as such or is reintroduced into the hydrolysis reactor to be hydrolysed. It is then possible to carry out an almost complete depolymerization of the (meth) acrylic polymer and to improve the yields of methacrylic acid, for example, by virtue of this system for reacting the reactor while reducing the energy cost of the system.

[082] Thus, the process according to the invention advantageously comprises one or more purification steps 170.

[083] The process may comprise a step 171 of distillation of (meth) acrylic acids and (meth) acrylic esters present following the introduction of steam. This distillation step allows separation due to differences in boiling temperature of the various compounds in the presence. Advantageously, this step can make it possible to generate a mixture predominantly comprising methyl methacrylate and / or methyl isobutyrate. In a preferred manner, this step can make it possible to generate a mixture comprising predominantly methyl methacrylate.

[084] The (meth) acrylic esters recovered after distillation can be reinjected into the hydrolysis reactor in order to be brought into contact with the steam. This allows hydrolysis of monomers to lead to the corresponding acids. For example, the monomer produced during the implementation of the recycling process can be condensed and collected by distillation in a container provided for this purpose, and the collected monomer can be reinjected into the reactor by means of return means bound to the reactor and the collector. It is then possible to carry out an almost complete depolymerization of the (meth) acrylic polymer and to improve the yields of methacrylic acid, thanks to this reactor feed system. Thus, advantageously, the process according to the invention comprises a step of reinjection, in the hydrolysis reactor, of a fraction formed during the distillation step. This fraction preferably comprises a majority of compounds bearing an ester function.

[085] Thus, in a variant, the recycling process comprises a step in which an ester (eg a monomer (meth) acrylate) produced in the system is separated by distillation 171, and then the ester is reintroduced into the reactor of hydrolysis of the system adapted for the recycling of thermoplastic, in order to be hydrolysed.

[086] The process according to the invention, and more particularly after a distillation step, makes it possible to obtain a mixture mainly comprising n-butyl methacrylate, methacrylic acid, isobutyric acid and acrylate. butyl and / or acrylic acid. Preferably, this step can make it possible to generate a mixture comprising predominantly methacrylic acid and / or acrylic acid. The mixture comprising predominantly methacrylic acid may in particular be contaminated with isobutyric acid. Because of the differences in melting temperature between these compounds, it is possible to separate methacrylic acid and isobutyric acid by crystallization in a melt. Thus, advantageously, the process may comprise a crystallization step 175. Advantageously, this step may make it possible to generate a mixture enriched in methacrylic acid and more particularly a composition comprising predominantly methacrylic acid. [087] More preferably, this step can be used to generate a mixture comprising predominantly methacrylic acid. For example, the hydrolysis of PMMA (following a depolymerization step) can lead to methacrylic acid and contaminants such as isobutyric acid. Due to the melting / crystallization temperature difference (see Table 1) between methacrylic acid and isobutyric acid, it is possible to carry out a melt crystallization purification of methacrylic acid. This purification method is simple and inexpensive to implement. Indeed, at 25 ° C all acids are liquid, decreasing the temperature to 0 ° C for example, acrylic and methacrylic acids solidify unlike isobutyric acid. The purge of the reactor makes it possible to eliminate isobutyric acid. Several crystallizations can be carried out in cascade so as to improve the purity.

[088] Advantageously, the recycling process according to the invention may further comprise a step 180 for regenerating the catalyst and more particularly the hydrolysis catalyst.

[089] For example, when the hydrolysis catalyst is a heterogeneous catalyst, the process may further comprise a step of contacting said hydrolysis catalyst with a regenerating substance to reactivate said hydrolysis catalyst. In the case where the catalyst is contaminated, its regeneration can be carried out with a flow of air at least 400 ° C or alternatively with depleted air for better temperature control or under hydrogen flow . According to another variant, the regeneration is carried out using a flow of ozone in the case of carbon deposition. Finally, in the case where the catalyst is deactivated by metallic pollutants, a simple washing or lastly its replacement can be operated.

[090] In addition, when the article to be recycled is a composite article based on a (meth) acrylic thermoplastic polymer resin, the recycling process according to the invention may advantageously furthermore comprise a step 190 of heat recovery.

[091] In this case, the article to be recycled into a composite polymer material comprising a reinforcement is introduced into a reactor of the recycling system 200 (e.g., a depolymerization reactor). The introduction of the article may be accompanied by a step of introducing a depolymerization initiation catalyst as described above and optionally by the addition of water. Preferably, the depolymerization reactor of the recycling system does not comprise water.

[092] The temperature in the reactor allows energy input in the form of heat promoting the depolymerization of the thermoplastic polymer resin into a mixture of products such as reduced molecular weight polymers and one or more ester monomers. (meth) acrylic. In addition, during the depolymerization, the reinforcement stores heat and this heat can be advantageously used in the recycling system. Indeed, the heat contained in the reinforcement can be transferred through a heat exchanger. The energy stored by the heat exchanger can for example be used to heat the water used in the context of the conversion step 160. The heat contained in the reinforcement can be transferred to the water which is transformed into water vapor which can then be transferred to a hydrolysis reactor. The use of heat recovered through the heat exchanger eliminates the additional step of heating the water. The reuse of heat reduces the energy cost of such a recycling system.

[093] After the energy transfer of the reinforcement to the water, the reinforcement can be recovered using recovery means at the outlet of the heat exchanger and can be reused.

[094] In one embodiment, the method further comprises a step of grinding the article to be recycled, the article being milled before its introduction into the system adapted for recycling the polymer. The grinding step makes it possible to reduce the dimensions of the article to be recycled and can be carried out using a grinder and / or crusher. The article is reduced to dimensions allowing the introduction of the ground material obtained in a system adapted for recycling according to the invention. Thus, the article can take the form of chips, granules or powder. The article can be introduced into the system adapted for recycling in one form or in several forms. Advantageously, the grinding step makes it easier to feed the reactor of the system adapted for recycling thermoplastics.

[095] In an optional step, the recycling process may include an in-line filtration step using a worm. During this in-line filtration step, the article is driven by an endless screw within a reactor allowing a rise in temperature sufficient to fluidify and / or melt at least a portion of the thermoplastic resin (meth) acrylic. This step then also involves the collection of the liquid and viscous resin. Thus, the article, preferably a polymeric composite article, is freed of a part of the thermoplastic resin (meth) acrylic or freed of fibers in the case of a fiber reinforcement for example, before depolymerization. One goal is to send less fiber to the reactor.

[096] In another aspect, the invention relates to a system 200 adapted for recycling (meth) acrylic thermoplastic polymer. In addition to the recycling of thermoplastic (meth) acrylic polymer resin articles. As shown in FIG. 2, the system can advantageously comprise:

means 211 for introducing the article into said system

200

a hydrolysis reactor 210,

means for introducing a hydrolysis catalyst 240 into said hydrolysis reactor,

means for introducing water 250, in liquid or gaseous form, into said hydrolysis reactor, and a heating means 260, preferably able to induce the depolymerization and hydrolysis of at least a portion of the article to be recycled.

[097] A suitable system for recycling a thermoplastic (meth) acrylic polymer resin-based article may, for example, be a so-called reactive extruder / conveyor (with external heating). A reactive extruder operates both a mechanical treatment of the article and a treatment inducing chemical modifications of the constituent polymer. The use of an extruder for the implementation of the recycling process is advantageous from an environmental point of view, safety and security of the process. Indeed, an extruder can process molten polymers of high viscosity without resorting to the addition of solvent to reduce the viscosity of molten polymers. The extruder has the advantage of allowing efficient heat transfer from the sleeve to the polymer. It also allows temperature control by zone and allows an output of solid (depolymerization residue) and gas (monomer).

[098] The means 211 for introducing the article into the reactor

210 may for example be selected from: a worm, a doser, a pneumatic transfer equipment, a gravity feeder, a conveyor belt or a conveyor belt, a system of hydraulic pushers, Preferably, the reactor 210 adapted to receive the article to be recycled is selected from: a worm, a conveyor belt and a pneumatic transfer. For example, the introduction is via a feed hopper and a worm.

[099] The means for introducing a hydrolysis catalyst 240 into the hydrolysis reactor may for example be selected from: a pump, a worm, a pneumatic transport, a conveyor belt. Preferably, the means for introducing a hydrolysis catalyst 240 into the hydrolysis reactor is selected from: a worm and pneumatic conveying. The water introduction means 250 in the hydrolysis reactor may for example be selected from: a pump, an evaporator, an injection of superheated steam. Preferably, the water introduction means 250 in the hydrolysis reactor in said reactor is selected from: a steam injection and a liquid water pump.

The heating means 260 may, for example, be selected from: a tubular or plate heat exchanger, a microwave oven, an extruder / screw conveyor. Preferably, the heating means 260 is selected from: heat exchangers hot tubular or plate.

The heating means may advantageously correspond to a pipe capable of introducing into the hydrolysis reactor water vapor at a temperature of at least 150 ° C.

The heating means is preferably capable of inducing the hydrolysis of at least a portion of the article to be recycled. That is, it is capable of heating at a temperature between 150 ° C and 250 ° C for a period of at least twenty minutes. Preferably, the heating means is adapted to heat at a temperature between 175 ° C and 250 ° C for a period of at least 30 minutes.

In order to allow the recovery of gases resulting from the implementation of the recycling process, the system 200 adapted for recycling may comprise one or more purification devices 270. For example, the system may comprise a cooling device that can correspond to a distillation separation system, for example a distillation column. The distillation column allows the separation of compounds according to their boiling point. Thanks to the distillation system of the recycling system 200, it is in particular possible to separate the (meth) acrylic monomer from its hydrolysis product. It is also possible to recover and recycle the hydrolysis catalyst, in the case where the catalyst is in liquid form.

As shown in FIG. 2, in an alternative embodiment, the recycling system 200 further comprises a device 280 adapted for heat recovery. Such a heat recovery device 280 may be any device known to those skilled in the art. Such a device makes it possible to recover the heat energy produced during gas condensation processes, to cool the reactor of the recycling system, or to recover the heat stored by the reinforcement of a composite material article to be recycled. Advantageously, this recovered energy can then be used to produce steam, to heat the reactor or to maintain ducts at a given temperature. Thus the device adapted to the heat recovery is adapted to use the recovered heat to heat water and / or maintain at least part of the system according to the invention at a temperature above 100 ° C.

Such a heat recovery device may for example be a heat exchanger. Conventionally, a heat exchanger allows the transfer of heat between two fluids. In the recycling process, the heat transfer is carried out between a solid and a coolant. The solid and the fluid can be fixed, or they can both be in motion, or the solid is fixed while the fluid is in motion. The solid and the fluid can flow parallel to each other and in the same direction. However, the solid and the fluid can flow parallel to each other but in opposite directions. They can also circulate perpendicularly.

The heat transfer can be achieved by a direct contact heat exchanger. Thus, during a heat transfer performed by a direct contact heat exchanger, the hot reinforcement is in intimate contact with the coolant. The fluid may be a liquid, for example water, a solvent or a mixture thereof. In other examples, the fluid may be a gaseous fluid such as a stream of air or gas for example. The contacting with the fluid can be carried out using an immersion or spraying device. The contacting can also be carried out by means of a nozzle or a nozzle series having holes through which the fluid can exit, the nozzles being directed towards the solid element. Other heat transfer fluids may be used, preferably the fluids available on site are used. For example, water, air, gas, but also the co-products of the depolymerization, in particular hydrocarbons that can be used as fuel and / or as a secondary heat transfer fluid. In fact, the hydrocarbons vaporize, in a manner similar to water, in contact with the hot residue. The hot gas is directed to a boiler where the hydrocarbons are condensed while boiling water. This water will be used in the process or to heat a primary heat transfer fluid.

Alternatively, the heat transfer can be achieved by an indirect contact heat exchanger. Such a heat exchanger may be, for example, a tubular heat exchanger, a plate heat exchanger, horizontal tubular bundle, vertical tubular bundle, a spiral heat exchanger, a fin exchanger, or a rotary exchanger or block. These examples are not limiting, and one skilled in the art will appreciate that other types of indirect contact heat exchangers can be used. An indirect contact heat exchanger can also implement a heat transfer fluid. The coolant may be a liquid, for example water, a solvent or a mixture thereof, molten salts or synthetic oil, for example such a synthetic oil may be the product marketed by the company ARKEMA under the name Jarytherm®.

The advantage of an indirect contact heat exchanger is that it can recover heat at different thermal levels. In other words, it is possible to achieve heat recovery at several thermal levels, each thermal level being associated with a different temperature. It is possible to have heat exchangers in cascade (or in stages) to allow a heat exchange with the reinforcement which is less and less hot from one exchanger to another. The presence of the hydrolysis catalyst makes it possible to improve the yields of (meth) acrylic acid but also makes it possible to lower the temperature of the reaction. Nevertheless, the hydrolysis catalyst may be contaminated by the products resulting from the depolymerization and / or hydrolysis reaction. Thus, the recycling system may comprise a device 290 for regenerating the hydrolysis catalyst. Such a device reduces the cost of recycling implemented by the system but also to reduce the production of waste.

In addition, the system according to the invention may comprise: a system allowing the exit of solid to evacuate solid elements from the reactor (s),

sensors for measuring the temperature in the reactor (s),

sensors for measuring the pressure in the reactor (s),

systems allowing the entry or the exit of fluid in the reactor (s), the fluid being able to be in the liquid or gaseous state, and / or

ducts to allow the circulation of fluids between the various elements of the system.

Figures 3 to 5 illustrate different embodiments of the system 200 according to the invention.

Referring to Figure 3, the recycling system according to the invention comprises an extruder, more particularly a twin-screw extruder 300 comprising an orifice 301 through which an article 302 comprising a PMMA resin, is inserted for example at The article to be recycled can be in the form of a powder or granule. Alternatively, the article may be introduced into the extruder after undergoing a first depolymerization step.

A twin-screw extruder may be, for example, a Clextral® type extruder. The twin-screw extruder comprises two screws 304, usually parallel, rotating inside a advantageously, the extruder has a modular character that is to say that the screw and the sleeve are modules assembled in series, and whose assembly can be modified. In the extruder, the PMMA resin-based article is heated and the resin is brought to the molten state by means of an external heating means 306 that regulates the temperature of the sleeve 305. The temperature in the reactor can be between 50.degree. ° C and 550 ° C and it can be controlled by means of temperature sensors not shown in Figure. Gas 307 comprising steam or an aqueous solution 307 is introduced into the extruder 300 to allow hydrolysis. The depolymerization can lead to products in the form of gases that are extracted out of the extruder for processing. The gases produced can be directed via a conduit 308 to a cooling system 309 to be condensed. The condensate obtained can then be collected in a chamber 310 provided for this purpose.

In a second embodiment, the system adapted for recycling a thermoplastic (meth) acrylic polymer resin article may comprise a fluidized bed device, as illustrated in FIG. a circulating fluidized bed makes it possible to obtain a homogeneous temperature within the bed thanks to a larger exchange surface between the fluid, the particles and the water vapor, allowing a very high heat transfer.

Referring to Figure 4, the article 401 comprising a PMMA resin composite is introduced into a reactor 402 of a device 400 fluidized bed. In this reactor, a mixture of solid particles 403 is suspended in a hot ascending gas stream 404, above a support 405, for example a grid. The grid is such that it does not allow the passage of particles but allows the passage of gas. The solid particle mixture comprises an inert fluidizing medium, for example sand, and comprises the pre-milled article 401 to be recycled. The ascending gas stream is a stream of fluidizing gas, for example air and / or steam an aqueous solution. Preferably, the gas contains less than 10% by weight of oxygen. The fluidization gas is injected into the lower part 406 of the reactor and its flow rate is such that it must allow fluidization of the mixture of particles. The gas flow causes a movement of the mixture of particles and a stirring favoring the heat transfer. The reactor may also comprise water supply means 407 to allow the introduction of either water vapor or an aqueous solution. In the case where the water is in the form of an aqueous solution, the latter is vaporized in situ in the reactor. In addition, these feed means 407 may comprise means for introducing the hydrolysis catalyst. In the reactor, the PMMA resin is depolymerized under the action of heat to in particular lead to the monomer methyl methacrylate. Said monomer is hydrolyzed to methacrylic acid in the reactor by means of steam. The methyl methacrylate monomer and the methacrylic acid are in the form of gas 408 and are removed from the reactor to a gas / solid separator 409 such as a cyclone. With the aid of a cooling system 410, the gases can be condensed in a chamber provided for this purpose. The gas / solid separator makes it possible to recover solids, for example reinforcement 411 resulting from a composite. Such reinforcement generally relates to mineral or multi-fiber fillers, unidirectional rovings or continuous filament mat, fabrics, felts or nonwovens which may be in the form of strips, tablecloths, braids, locks or rooms.

According to one variant, the fluidized bed device for recycling an article based on a (meth) acrylic thermoplastic polymer resin may be a circulating fluidized bed device. Such a circulating fluidized bed device has a greater fluidization velocity than in a conventional fluidized bed device. This speed is of the order of 4 to 8 m / s. In this type of fluidized bed the upper limit of the bed is not clear and entrainment of particles above the bed is greater. This device has the advantage of to allow a better heat exchange between the solid particles.

In a third embodiment, the system adapted for recycling a thermoplastic (meth) acrylic polymer resin-based article comprises a mixer-conveyor type device, for example a Paddle Dryer-type conveyor-mixer. . This device comprises a reactor in which a helix is disposed. The propeller thus makes it possible to mix and homogenize a mixture comprising the article to be recycled and steam. The mixer-conveyor has the advantage of allowing the treatment of large quantities of waste / solid residues. It also allows a good heat transfer between the wall and the waste. Such a device can be used at low temperature to dry a solid, but in the context of the invention, by increasing the temperature, it is possible to induce hydrolysis and optionally prior depolymerization.

Another type of system suitable for recycling an article based on (meth) acrylic thermoplastic polymer resin, comprises a device consisting of hollow plates, heated by a coolant circuit (pressurized steam, oil, salts, etc.). melted ..). During its treatment the article advances on the plates of increasing temperatures at first. The solid residue finishes its passage in the reactor by passing on plates which are at a lower temperature and where the heat exchange is from the residue to the coolant. The heat transfer fluid thus heated can then be used to preheat the article to the inlet of the reactor.

FIG. 5 illustrates, according to one embodiment of the invention, a recycling system coupled to a device 530 adapted for heat recovery.

The depolymerization reactor 520 of the recycling system is adapted to receive an article 510 to be recycled into a polymer composite material comprising a reinforcement and an initiation catalyst 511. Advantageously, the reactor of depolymerization 520 of the recycling system does not include water.

In addition, the depolymerization reactor comprises a duct 512 capable of transferring at least a portion of the mixture formed during the depolymerization and a heat recovery device 530 able to receive the reinforcement 510 having stored heat during heating. depolymerization step.

As shown in FIG. 5, the device 530 adapted for heat recovery can be coupled to a water reservoir 513 and to a conduit 514 and is configured to transfer the heat contained in the reinforcement to the water that turns into water vapor and is transferred to the hydrolysis reactor 540 via the conduit 514. Thus, the heat recovery device 530 reduces the energy cost of such a recycling system.

In addition, the device 530 adapted for heat recovery may include means for recovering the reinforcement that can be upgraded.

As mentioned above, the system 200 according to the invention comprises a hydrolysis reactor 540 capable of hydrolyzing the esters. For example, the methyl methacrylate will be hydrolysed to methacrylic acid and the methyl isobutyrate will be hydrolysed to isobutyric acid.

The system also includes a fractional distillation device 550 for acid separation from other impurities (e.g., esters). In addition, the fractional distillation device 550 makes it possible to reinject the esters into the hydrolysis reactor 540 via a conduit 560 and to transfer the acids into a crystallization device 570.

The crystallization device 570 is capable of separating impurities such as isobutyric acid 517 from methacrylic acid 516.

Figures 6 to 8 illustrate different embodiments of a regeneration device 290 of the hydrolysis catalyst. Referring to Figure 6, the regeneration device 290 may be disposed within the reactor 402 of a system 400 fluidized bed recycling. The regeneration device may comprise an enclosure 601 having a main axis X, a distal end 602 and a proximal end 603. The enclosure is connected to a supply conduit 604 located at the proximal end 603 for feeding the enclosure of the regeneration regeneration device 605.

In the case where the catalyst is contaminated, its regeneration can be carried out with a flow of air at least 400 ° C or alternatively with depleted air for better temperature control or under flow hydrogen. According to another variant, the regeneration is carried out using a flow of ozone in the case of carbon deposition. Finally, in the case where the catalyst is deactivated by metallic pollutants, a simple washing or lastly its replacement can be operated.

The chamber 601 of the regeneration device is also equipped with a conduit 606 for the output of fluid or particles from the enclosure. An element 607 is disposed around the enclosure 601. The element 607 is open at these two ends 608 and 609, and has a wall 610 radially surrounding the enclosure 601 with respect to the axis X. The element 607 is arranged so as to create a zone 611 in which the speed of the hydrolysis catalyst particles is reduced compared with that of the same fluidized particles in the reactor 402. Backpressure injection means 612 are provided at the level of the proximal end 603 to allow introduction of the hydrolysis catalyst into the regeneration device. Once regenerated using the regenerator 603, the hydrolysis catalyst is transported to the conduit 606 by pneumatic transport for example, to be reinjected into the reactor 402.

A regeneration device 290 of the hydrolysis catalyst according to another embodiment is illustrated in Figure 7A. In this embodiment, the device 290 for regenerating the The hydrolysis catalyst is located inside the hydrolysis reactor 700. The regeneration device 290 of the hydrolysis catalyst can comprise:

An enclosure 710 adapted to receive the hydrolysis catalyst particles and a regenerating substance to reactivate the hydrolysis catalyst,

Means 720 for supplying the enclosure with the regenerating substance,

Means for allowing the introduction of the hydrolysis catalyst into the regeneration chamber, and

Means 752 for allowing the introduction of the reactivated hydrolysis catalyst into the reactor of the recycling device.

According to this embodiment, the recycling system preferably operates in a fluid bed as described above and comprises a regeneration zone 1 and a reaction zone 2. The regeneration zone and the reaction zone are separated by separation means 711 of separation wall type being tubular or circular section. Preferably, the reaction zone 2 is located outside the separation means and the regeneration zone 1 inside the separation means. In addition, the regeneration zone and the reaction zone communicate through the separation means for the circulation of the catalyst from the reaction zone to the regeneration zone. The catalyst may be present in the reaction zone in the form of a fluidized bed 3 or integrated in the fluidized bed 3.

The recycling system is supplied with fluidization gas via injection means 721. The fluidization gas is a gas whose flow rate is adapted to allow the fluidized bed to be in fluidized form. Advantageously, the fluidization gas comprises water vapor. Preferably, these injection means are located under the hydrolysis reactor to promote a uniform supply of fluidization gas. Furthermore, the reaction zone is fed with a reaction fluid comprising the monomer (meth) acrylate, for example derived from the depolymerization by feed means 760. The internal regenerator 710 for regenerating the catalyst comprises means 720 for supplying the internal regenerator 710 with a regenerating substance 730. The internal regenerator makes it possible to bring the regenerating substance 730 into contact with the hydrolysis catalyst. The regeneration can be carried out with an air flow of at least 400 ° C or alternatively with depleted air for better temperature control or under hydrogen flow or ozone flow. The flow rate of the regeneration flow is adapted so that the fluidized bed in the regeneration zone is a fast fluidized bed, the linear velocity of the gas is preferably higher than in the reaction zone. The regeneration of the catalyst takes place mainly in the regeneration zone, nevertheless the regeneration is not total and the catalyst is transported by pneumatic transport via a pipe 740 located at the top of the internal regenerator to a first separator 750, cyclone type for example. The separator comprises a first evacuation pipe 751 for the elimination of the gases generated during the reactivation of the hydrolysis catalyst such as O2, CO2, N ₂ , CO and a second conduit 752 for reinjecting the catalyst into the reaction zone. .

The reactivated catalyst is then inside the reaction zone and in the presence of (meth) acrylate monomer resulting from the depolymerization 760 which leads to the (meth) acrylic acid.

A second separator 770, cyclone type for example, is located in the upper part of the reactor. The second separator comprises an opening 771, an exhaust duct 772 making it possible to recover the products of the reaction, in particular the (meth) acrylic acid leaving the recycling device. The second separator comprises a reinjection duct 773 for reinjecting the catalyst back into the reaction zone. Thus, thanks to such a device for regenerating the hydrolysis catalyst inside the recycling system, the yields of (meth) acrylic acid are improved, the hydrolysis of the (meth) acrylate monomer is almost complete and the regeneration of the Hydrolysis catalyst reduces the costs of such a system and improves the environmental impact.

In an alternative embodiment, the regeneration device 290 may be disposed outside the hydrolysis reactor. In particular, another embodiment of recycling of the hydrolysis catalyst is illustrated in FIG. 7B. In this embodiment, the regeneration device of the hydrolysis catalyst 780 is located outside the hydrolysis reactor 790.

The regenerator 780 of the hydrolysis catalyst comprises means 781 for supplying the regenerating substance regenerator 782. The regenerator makes it possible to bring the regenerating substance 782 into contact with the hydrolysis catalyst. The regeneration can be carried out with an air flow of at least 400 ° C or alternatively with depleted air for better temperature control or under hydrogen flow or ozone flow. Once reactivated, the catalyst is transported via line 783 to the hydrolysis reactor. The gases generated during the reactivation of the hydrolysis catalyst such as O ₂ , CO ₂ , N ₂ , CO are evacuated via a discharge pipe 784 of a separator 785. A hydrolysis device may correspond to a hydrolysis reactor in a fluidized bed as described above.

The reactivated catalyst is then in the presence, inside the hydrolysis reactor, of the (meth) acrylate monomer resulting from the depolymerization 791 and makes it possible to form (meth) acrylic acid. With a second separator 792, cyclone type for example, comprising a discharge conduit 793 for recovering the (meth) acrylic acid output of the hydrolysis reactor and a reinjection duct 794 for reinjecting the catalyst again in the hydrolysis reactor to obtain a better acid yield. When the hydrolysis catalyst is contaminated, it is transported to the catalyst regeneration device via a line 795. Thus, thanks to such a catalyst regeneration device hydrolysis outside the hydrolysis reactor, the (meth) acrylic acid yields are improved, the hydrolysis of the (meth) acrylate monomer is almost complete and the regeneration of the hydrolysis catalyst makes it possible to reduce the costs of such a system and improves the environmental impact.

Another embodiment of the recycling system 200 is illustrated in FIG. 8. In this embodiment, the regeneration device of the hydrolysis catalyst can be coupled to a reactor combining hydrolysis and depolymerization. Such a reactor 810 combining hydrolysis and depolymerization is suitable for the composite article recycling system. It may for example comprise a conduit 821 capable of introducing water into hydrolysis reactor 810. Advantageously, the hydrolysis catalyst may be introduced into the reactor in parallel with the steam or the aqueous solution. The reactor comprises means for introducing the article to be recycled 830 (eg PMMA) which is depolymerized at high temperature into reduced molecular chain monomer leading essentially to the formation of (meth) acrylate monomer (eg MMA). The monomers are then hydrolysed by virtue of the presence of steam and, advantageously, thanks to the presence of the hydrolysis catalyst in methacrylic acid. The methacrylic acid can then be removed from the reactor by means of evacuation 840, or led to a purification step as previously described. During the depolymerization and / or hydrolysis reactions, the hydrolysis catalyst may be contaminated. Thus the contaminated catalyst is transported in a catalyst regeneration device 850 by a transport means 860 such as a conduit for example. In order to reactivate the hydrolysis catalyst, a regenerating substance 870 is introduced by introduction means 880 into the regenerator, such as an air flow for example to reactivate the hydrolysis catalyst. The regenerator comprises means 890 for evacuating the gases generated during the decontamination of the hydrolysis catalyst, and means for reinjecting the catalyst 861 into the reactor. depolymerization and hydrolysis. Thus the catalyst can be reused for several cycles of hydrolysis.

Thus, the invention provides a simple and effective solution for recycling articles based on (meth) acrylic polymers. In addition, the process according to the invention allows the specific polymer depolymerization, while allowing an energy saving. The invention thus integrates in a context of sustainable development and in the recovery of waste thermoplastic resin (meth) acrylic.

[Examples]

Example: Simultaneous depolymerization and hydrolysis of PMMA to methacrylic acid

A rotating fluidized bed reactor is designed to perform the depolymerization-hydrolysis reaction of PMMA. This experimental reactor has an internal diameter of 30 cm. At its base it consists of a system of burners and steam injection, surmounted by a distribution grid, and the reaction zone. This reaction zone contains a central cone and at the top a lateral (tangential) outlet which makes it possible to eliminate the solid. At the top of the reactor, a cyclone separates the solids fines that are returned to the reactor and the gas that is withdrawn from the reactor.

In the lower part of the reactor, a toroidal distributor makes it possible to bring steam under the distribution grid. In the central part of this lower zone (under the distribution grid), a gas burner makes it possible to raise the temperature of the gas of the injected vapor.

The distribution grid consists of fins inclined at an angle of 23 ° relative to the horizontal. This inclination makes it possible to impart a rotational movement to the gaseous flow which itself rotates the solid which is in the reaction zone. The central cone has an outside diameter of 24 cm at its base, and a height of 24 cm. The distribution grid is therefore in the peripheral part of the reaction zone and the fins have a width of 3 cm. The fins overlap partially to print a rotational movement. The fins may be hinged, i.e. the angle may be adjusted. Among other advantages, this makes it easier to empty the experimental reactor by gravity. This also makes it possible to adjust the operation of the reactor.

The solid supply of the reactor is in its central part. The solid is fed from the top of the reactor and it falls on the tip of the cone which is at the base of the reaction zone. The solid is well distributed on the fluidized bed. Two solid inputs are provided, one for the PMMA granules (or crushed PMMA) and the other for feeding the solid catalyst.

The fluidization gas, consisting of water vapor and hot air from the gas burner, is introduced into the reaction zone by the fins of the distribution grid. The rotational movement of the gas generates a centrifugal force in the solid bed which keeps the solid in the reaction zone. Going up in the reaction zone the passage section increases due to the presence of the central cone. The heavier solids thus descend into the bed. The fines, or the lighter particles continue their gradual ascent. Between 0 and 15 cm above the tip of the central cone, a tangential outlet of the solid is provided. This evacuation of the solid can be partly obscured, which allows to select how high the solid will be withdrawn. The extraction zone is a rectangle 5 cm high and 1 cm wide (and adjustable in width between 1 mm and 10 mm) and is movable.

The solid that is withdrawn is essentially a catalyst, but also contains non-depolymerized PMMA as well as inorganic and organic fillers that were initially present in the PMMA granules / crushes. In the experimental reactor this solid is recovered and analyzed. In industrial operation, the solid would be directed to a reactor where carbon residues would be burned to warm up the catalyst and mineral fillers would be separated from the catalyst before it was returned to the reactor.

In the upper part of the reactor, a cyclone makes it possible to return the solids to the center of the reactor. The reaction gases are then directed to a condenser. In the laboratory installation, the condenser is of the tube-shell type and is cooled with cold water (25 ° C) against the current. Immediately after the condensation, the products of the reaction are brought into contact with an aqueous solution containing a polymerization inhibitor. At the end of the test, the aqueous solution is decanted, and the two fractions are analyzed.

In the upper part of the reactor, the two solids (catalyst and PMMA granules / ground materials) are injected separately. PMMA is injected at room temperature. The catalyst is preheated to simulate the return of solid after combustion of the residual organic fractions. The temperature of the catalyst can be adjusted. The typical temperature of the catalyst entering the reactor is 550 ° C when it is an inorganic solid. When it is an organic solid such as an acidic resin, its temperature is lowered to at most 100 ° C.

Example 1 according to the invention:

The PMMA used in the test consists of colored granules of PMMA type V826 pink Altuglas, and about 3 mm. The selected catalyst is a CONDEA alumina of the PURALOX SCCA 5/200 type of 193 m ² / g, and having an average particle diameter of 100 microns. It is mixed with sand (previously washed and dried) at a rate of 50 g of catalyst per 450 g of sand.

The reactor is fed with the catalyst preheated to 550 ° C, with a catalyst mix rate and sand of 0.5 kg / h. The PMMA granules are also supplied at room temperature with a flow rate of 17 g / min. The steam flow rate is set at 0.9 kg / h and the flue gas flow rate is 150 mol / h. (about 4.2 kg / h). The temperature of the flue gas and steam entering the reaction zone is adjusted to 575 ° C.

The PMMA conversion rate is 90%. The exit gas temperature is 400 ° C. The yield of methacrylic acid calculated on the amount of PMMA introduced is 62% by weight.

Comparative Example 2:

Example 1 is repeated but in the absence of catalyst. The yield of methacrylic acid is 2% by weight.

Comparative Example 3:

Example 1 is repeated but using an acidic resin Amberlyst 15 as a catalyst fed into the reactor at 65 ° C. In this configuration the reactor is unstable. The exit gas temperature is 350 ° C. The yield of methacrylic acid is 3% by weight.

Comparative Example 4:

Example 1 is reproduced using NAFION SAC from N.E. Chemcat type SAC-13 milled to a particle size of about 200 microns.

The reactor was fed with the catalyst preheated to 80 ° C, with a catalyst and sand flow of 1.0 kg / h. The operation of the reactor is very unstable.

The PMMA conversion rate is 70%. The exit gas temperature is 330 ° C. The yield of methacrylic acid calculated on the amount of PMMA introduced is 3% by weight.

Comparative Example 5:

The PMMA used in the test consists of colored granules of PMMA type V826 pink Altuglas, and about 3 mm. The selected catalyst is a CONDEA alumina of the PURALOX SCCA 5/200 type of 193 m ² / g, and having an average particle diameter of 100 microns. It is mixed with sand (previously washed and dried) at a rate of 50g of catalyst for 450g of sand.

The reactor is fed with the catalyst preheated to 300 ° C, with a catalyst and sand flow rate of 0.5 kg / h. The PMMA granules are also supplied at room temperature with a flow rate of 17 g / min. The steam flow rate is set at 0.36 kg / h and the flue gas flow rate is 270 mol / h or about 7.7 kg / h. The temperature of the flue gas and steam entering the reaction zone is adjusted to 300 ° C.

The PMMA conversion rate is 20%. The exit gas temperature is 190 ° C. In this configuration, the temperature of the gases also represents the temperature conditions present in the reactor. The yield of methacrylic acid calculated on the amount of PMMA introduced is 15% by weight.

[0167] Example 6 according to the invention:

Example 1 is repeated by adding with the PMMA sodium perborate at a rate of 3 g / h.

Example 7 according to the invention:

Example 6 is reproduced by replacing the perborate with Luperox 101PP10 which is a solid form of 2,5-dimethyl-2,5-di (tert-butylperoxy) -hexane at 3 g / h.

[0171] Other reaction configuration according to the invention.

It is used to make a twin screw extruder powered by PMMA granules. The temperature of the extruder can be adjusted by electric heating. The screw system is designed to have a first melting zone, then a plug area that prevents a rise of gases to the feed. A port allows the injection of liquid or gas after the melting zone. At the end of the extruder, the gas produced by the reaction is directed to a tube-calender condenser. The solid which has not depolymerized is directed to a storage capacity maintained at more than 100 ° C. The gases produced pass through a dust collection cyclone kept hot before the condensation zone. Example 8 according to the invention:

The extruder is fed with a flow rate of 5 kg / h of PMMA granules, and 1 kg / h of CONDEA alumina of the PURALOX SCCA 5/200 type, as well as a slight flow of inert gas (nitrogen ). After the plug zone, the extruder is fed with an aqueous solution of hydrogen peroxide at 10% by weight of H 2 O 2, and with a flow rate of 2 kg / h. The temperature of the extruder is maintained at 350 ° C. The yield of methacrylic acid is 73% by weight.

[0175] Example 9 according to the invention:

The previous example is reproduced with just a flow of water instead of hydrogen peroxide. With the PMMA granules, a solid flow rate of sodium percarbonate (Na ₂ CO ₃ · 1.5H ₂ O ₂₎ of 0.004 kg / h is added. The yield of methacrylic acid is 65% wt.

Claims

1. Method for recycling (100) an article based on a (meth) acrylic thermoplastic polymer resin, characterized in that it comprises the following steps:

introducing (110) the article into a system adapted for recycling thermoplastic polymer,

at least partial depolymerization (130) of the (meth) acrylic thermoplastic polymer resin so as to form (meth) acrylate monomers,

introducing (140) a hydrolysis catalyst into a hydrolysis reactor,

introducing (150) water into said hydrolysis reactor, and

converting (160) in the hydrolysis reactor at least a portion of the (meth) acrylate monomers to (meth) acrylic acid.

2. Recycling process according to claim 1, characterized in that the hydrolysis catalyst is selected from: Alumina, MgO, CaO, Mg (OH) ₂ , Ca (OH) ₂ , Al (OH) ₃ , a zeolite, an acid, a base, an amphoteric compound or a mixture of two or more of these compounds.

3. recycling process according to claim 1 or 2, characterized in that the method may further comprise a step (180) for regenerating the catalyst and more particularly the hydrolysis catalyst.

4. Recycling process according to any one of claims 1 to 3, characterized in that the method further comprises a step (120) for introducing a depolymerization initiation catalyst.

5. Recycling process according to claim 4, characterized in that the depolymerization initiation catalyst is chosen from: an organic peroxide, a peroxide or inorganic superoxide such as barium peroxide (BaCq), potassium superoxide (KO2), cesium superoxide (CsCt), a percarbonate, a peroxyhydrate compound, their salts and their mixture.

6. Recycling process according to claim 4, characterized in that the depolymerization initiation catalyst is solid at 25 ° C.

7. Recycling process according to claim 4, characterized in that the depolymerization initiation catalyst is chosen from perborates or percarbonates.

8. Recycling process according to claim 4, characterized in that the depolymerization initiation catalyst is sodium percarbonate.

9. Recycling process according to any one of claims 4 to 8, characterized in that the concentration of depolymerization initiation catalyst is such that the molar ratio between the concentration of depolymerization initiation catalyst and the polymer concentration. (Meth) acrylic thermoplastic present in the introduced article is between 0.001 and 10.

10. Recycling process according to any one of claims 1 to 9, characterized in that the depolymerization initiation catalyst is introduced into the hydrolysis reactor.

11. Recycling method according to any one of the claims

1 to 10, characterized in that the hydrolysis catalyst is selected from: Alumina, MgO, CaO, Mg (OH) 2, Ca (OH) 2, Al (OH) 3, a zeolite, an acid, a base, a amphoteric compound or a mixture of two or more of these compounds.

12. recycling process according to any one of claims 1 to 11, characterized in that the catalyst temperature, when it is an inorganic solid, entering the reactor during step 140 the introduction of a catalyst The hydrolysis rate in a reactor is at least 300 ° C, preferably at least 350 ° C, more preferably at least 400 ° C and preferably at least 450 ° C.

13. Recycling process according to any one of claims 1 to 12, characterized in that the depolymerization is carried out in the hydrolysis reactor.

14. Recycling process according to any one of claims 1 to 13, characterized in that the method further comprises a distillation step (171) capable of generating a mixture enriched with (meth) acrylic acid.

15. recycling process according to any one of claims 1 to 14, characterized in that the method further comprises a step (175) of crystallization capable of generating a mixture enriched with (meth) acrylic acid.

16. Recycling process according to any one of the claims

1 to 15, characterized in that the article to be recycled is made of composite material based on (meth) acrylic thermoplastic polymer resin and a reinforcement.

17. The recycling method according to any one of claims 1 to 16, characterized in that the method further comprises a step (190) of heat recovery.

18. Recycling process according to any one of the claims

1 to 17, characterized in that in step (150) a gas comprising water vapor is introduced into the reactor.

19. Recycling process according to any one of the claims

1 to 17, characterized in that step (150) corresponds to the introduction of an aqueous solution into the reactor.

20. recycling process according to any one of claims 1 to 17, characterized in that the amount of water in step (150) is at least stoichiometric with respect to the amount of monomers (meth) acrylates to be hydrolysed.

21. Recycling process according to any one of claims 1 to 17, characterized in that the amount of water added by weight in step (150) is greater than or equal to 15% of the mass of the thermoplastic polymer (meth ) acrylic present in the article introduced in step (110).

22. Recycling process according to any one of claims 1 to 21, characterized in that the temperature in the hydrolysis reactor is between 150 ° C and 250 ° C.

23. Recycling system (200) of an article based on thermoplastic (meth) acrylic polymer resin, characterized in that it comprises:

means (211) for introducing the article into said system,

a reactor (210) for hydrolysis,

means (250) for introducing water into said hydrolysis reactor,

means (240) for introducing a hydrolysis catalyst into said hydrolysis reactor, and

- Heating means (260), preferably capable of inducing the depolymerization and hydrolysis of at least a portion of the article to be recycled.

24. Recycling system according to claim 23, characterized in that the system comprises one of the following devices: a reactive extruder, a fluidized bed device, a circulating fluidized bed device, a mixer-conveyor; a rotary stirring device, a stirred rotary kiln or a plate reactor.

25. Recycling system according to claim 23 or 24, characterized in that the system further comprises a device (290) for regenerating hydrolysis catalyst.

26. Recycling system according to one of claims 23 to 25, characterized in that the system comprises one or more devices (270) purification.

27. Recycling system according to one of claims 23 to 26, characterized in that the system comprises a device (280) adapted to heat recovery.

28. Recycling system according to claim 27, characterized in that the device adapted to heat recovery is adapted to use the recovered heat to heat water and / or maintain at least a portion of the system at a temperature greater than 100 ° C.

29. Recycling system according to one of claims 23 to 28, characterized in that the system comprises a means (260) for heating capable of successively inducing a thermal depolymerization of at least a portion of the article to be recycled, in the presence of a depolymerization initiation catalyst chosen from an organic peroxide, a peroxide, an inorganic superoxide, a percarbonate or a peroxyhydrated compound, and then a hydrolysis of the (meth) acrylate monomers resulting from the depolymerization.