Photocrosslinkable copolyesters and method for obtaining same by post-functionalisation

Abstract

The present invention relates to a method for functionalising a copolyester of glycerol and of a dicarboxylic acid monomer, the method comprising the following steps: a) bringing the copolyester of glycerol and a dicarboxylic acid monomer into contact with an itaconic crosslinking agent selected from itaconic acid, itaconic anhydride and mixtures thereof; b) heating the mixture from step a) in the presence of a stabilising agent for enough time to form a photocrosslinkable functionalised copolyester; c) cooling and recovering the photocrosslinkable functionalised copolyester. The present invention also relates to a photocrosslinkable copolyester, in particular which can be obtained by this method, to the photocrosslinkable compositions comprising same, to the crosslinked copolyesters obtained by crosslinking (advantageously photocrosslinking), and to the uses thereof.

Description

[0001]DESCRIPTION TITLE: PHOTOCROSSLINKABLE COPOLYESTERS AND METHOD FOR OBTAINING THE SAME BY POST-FUNCTIONALIZATION FIELD OF THE INVENTIONThe present invention relates to photocrosslinkable copolyesters, comprising in particular unsaturated bonds. The present invention also relates to their preparation method and their use, in particular in crosslinking methods such as 3D printing methods, and the corresponding crosslinked copolyesters. STATE OF THE ARTBiodegradable polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA) and their copolymers, such as poly(glycerol sebacate) (PGS), are now ubiquitous in the preparation of biomaterials useful both as medical biomaterials and as surface coatings.Conventionally, these polyesters are prepared by melt polycondensation of glycerol and a diacid, at high temperature and reduced pressure, with fairly long reaction times. However, with the development of 3D printing application techniques, which require working at near-ambient temperature, under atmospheric pressure, and preferably with short reaction times, new materials have been sought whose preparation processes would be compatible with the requirements of 3D printing application, while retaining satisfactory thermomechanical properties. Similarly, conventional processes are also not compatible with the integration of temperature-sensitive organic molecules into the biomaterial.Thus, photocrosslinkable materials have been developed, obtained by copolymerization of glycerol with sebacic acid and unsaturated acids, the unsaturations being able to be subsequently subjected to a photocrosslinking reaction, for example under UV irradiation (see in particular WO2019 / 215441 and WO2021 / 078962). However, the unsaturated acids used are often derivatives of (meth)acrylic acid, which are toxic, which is problematic both for their handling and for the final products, which generally contain at least trace amounts of them. Other authors have therefore turned to the use of itaconic acid (unsaturated acid) as a comonomer.This comonomer is particularly interesting because, unlike (meth)acrylic acid derivatives, it is not toxic and is easily biosourced, which allows the production of photocrosslinkable polymers that can be used for a wide range of applications, including biomedical applications, with a relatively low carbon footprint. Thus, Rueben et al. (MRS Advances (2018), 3(27), 1551-1556) describe the synthesis of copolymers of glycerol, sebacic acid and itaconic acid, but with particularly long preparation times (24 hours). Patent application CN114456335 also describes copolymers of polyols, aliphatic diacids and itaconic acid, and in particular copolymers of glycerol, sebacic acid and itaconic acid. However, the inventors demonstrated that the preparation process by polycondensation of CN114456335 was not reproducible.Indeed, under the conditions described, uncontrolled parasitic reactions (in particular crosslinking reactions) are observed, linked to the reactivity of the α,β-unsaturated double bonds of itaconic acid, reactions which induce heterogeneity of the functional copolymer, and which increase the viscosity of the product obtained until it sets in mass, which makes it impossible to use in applications as a coating or in a 3D printing process for example. There is therefore a need for photocrosslinkable copolyesters whose preparation process is simple, reliable and reproducible to implement, and in particular suitable for industrial scale, avoiding the occurrence of uncontrolled parasitic reactions. Preferably, the crosslinking time will be reduced and suitable for 3D printing processes, in particular at room temperature and atmospheric pressure.The monomers used will preferably be non-toxic and bio-sourced, in order to limit the carbon footprint of the copolyesters obtained. In addition, the processing temperatures are generally lower than in conventional processes, and advantageously compatible with organic molecules sensitive to high temperatures. BRIEF DESCRIPTION OF THE INVENTION To this end, according to a first aspect of the invention, a process for preparing a photocrosslinkable copolyester is proposed, comprising the polycondensation of a glycerol copolyester with a dicarboxylic acid monomer, with at least one anti-itaconic crosslinking agent, in the presence of a stabilizing agent. The stabilizing agent has the effect of limiting, or even eliminating, the occurrence of parasitic reactions. The polycondensation yields are therefore improved, and the photocrosslinkable copolyester has a viscosity suitable for the intended applications (in particular in 3D printing), as well as improved purity.Thus, according to a first aspect, the invention relates to a process for functionalizing a copolyester of glycerol and a dicarboxylic acid monomer, comprising the following steps: a) Contacting the copolyester of glycerol and a dicarboxylic acid monomer with an itaconic crosslinking agent chosen from itaconic acid, itaconic anhydride and mixtures thereof, b) Heating the mixture from step a) in the presence of a stabilizing agent for a time sufficient to form a photocrosslinkable functionalized copolyester, c) Cooling and recovering the photocrosslinkable functionalized copolyester. According to another aspect, the invention relates to a photocrosslinkable copolyester of glycerol and a dicarboxylic acid monomer, with an itaconic functionalization rate greater than or equal to 0.004 mmol / g, preferably greater than or equal to 0.04 mmol / g, more preferably greater than or equal to 1 mmol / g.According to another aspect, the invention relates to a photocrosslinkable composition comprising a photocrosslinkable copolyester according to the invention, and optionally, a photoinitiator. According to another aspect, the invention relates to a method for preparing a crosslinked copolyester by photocrosslinking, comprising a step of UV irradiation of the photocrosslinkable composition or the photocrosslinkable copolyester of the invention. According to another aspect, the invention relates to a crosslinked copolyester obtained by crosslinking the photocrosslinkable copolyester according to the invention or a photocrosslinkable composition according to the invention. According to another aspect, the invention relates to the use of a photocrosslinkable composition or a photocrosslinkable copolyester according to the invention for preparing a product by 3D printing. DETAILED DESCRIPTION OF THE INVENTION For the purposes of the present invention, the term “a” or “an” means “one or more” or “at least one”.For the purposes of the present invention, a range of values ​​designated by the expression "between a and b" represents the range of values ​​from strictly greater than a to strictly less than b (i.e. excluding the limits a and b), while any range of values ​​designated by the expression "from a to b" represents the range of values ​​from a to b, i.e. including the strict limits a and b. By "approximately" is meant in the present description that the value concerned may be less than or greater than 10%, in particular 5%, in particular 1%, than the indicated value. Glycerol is a triol of the following formula:. .The compounds mentioned in the description may be of fossil or bio-sourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. In the same way, the compounds mentioned may also come from the recycling of materials already used, that is to say they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This concerns in particular the monomers, that is to say in particular glycerol, the dicarboxylic acid monomer and the itaconic crosslinking agent. By "photocrosslinkable" polymer (including a copolyester) is meant, within the meaning of the present invention, a polymer which, under the influence of light irradiation, and more particularly UV irradiation, undergoes crosslinking reactions, thus modifying its chemical structure.In general, these are radical reactions in the presence of a photoinitiator. For the purposes of the present invention, "room temperature" means a temperature generally between 15°C and 40°C, preferably between 20°C and 30°C, in particular around 25°C. "Atmospheric pressure" means here a pressure of around 1 bar. 1.Process for functionalizing a photocrosslinkable copolyester The invention relates to a process for functionalizing a copolyester of glycerol and a dicarboxylic acid monomer, comprising the following steps: a) Contacting the copolyester of glycerol and a dicarboxylic acid monomer with an itaconic crosslinking agent chosen from itaconic acid, itaconic anhydride and mixtures thereof, b) Heating the mixture from step a) in the presence of a stabilizing agent for a time sufficient to form a photocrosslinkable functionalized copolyester, c) Cooling and recovering the photocrosslinkable functionalized copolyester. According to any one of the variants of the invention, step (a) of contacting is carried out in a reactor. The following steps can take place in the same reactor or in another reactor.Given the heating and pressure conditions, a person skilled in the art will be able to adapt the type and number of reactor(s) required for the process. Preferably, steps (a) and (b) are carried out under an inert atmosphere, in particular under a nitrogen (N2) atmosphere. Advantageously, steps (a) and / or (b) are carried out in the absence of inorganic acid, such as phosphoric acid. Itaconic crosslinking agent The itaconic crosslinking agent is chosen from itaconic acid and / or itaconic anhydride. The use of itaconic anhydride makes it possible to limit the production of water molecules (H2O) during the polycondensation reaction, and thus to improve the overall yield of the functionalization, and / or the reaction rate, in particular under temperature conditions which may be milder (in particular at a temperature less than or equal to 100°C), which makes it possible to reduce the reaction times.Copolyester of glycerol and a dicarboxylic acid monomer The dicarboxylic acid monomer may be aliphatic, aromatic or aliphatic / aromatic. The dicarboxylic acid monomer may not be itaconic acid. An aliphatic / aromatic dicarboxylic acid monomer comprises an aliphatic part and an aromatic part. The dicarboxylic acid monomer preferably comprises from 4 to 36 carbon atoms. By "aliphatic" is meant a linear, branched and / or cyclic hydrocarbon group, whether saturated or unsaturated but not aromatic. According to preferred variants of the invention, the dicarboxylic acid monomer is aliphatic, in particular saturated, in particular linear or branched, preferably it is a (C3-C20)alkanediyldicarboxylic acid, more preferably a (C8-C15)alkanediyldicarboxylic acid. A (Cx-Cy)alkanediyl group is a divalent, saturated, linear or branched hydrocarbon group comprising from x to y carbon atoms.Advantageously, the dicarboxylic acid monomer comprises or consists of a diacid of general formula [HOOC-(CH2)n-COOH] in which n is a number ranging from 1 to 30, preferably a number ranging from 5 to 10. In particular, the dicarboxylic acid monomer may be chosen from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, hexadecanedioic acid, octadecanedioic acid and a mixture of two or more of these dicarboxylic acids. Preferably, the dicarboxylic acid monomer may be chosen from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and a mixture of two or more of these dicarboxylic acids. According to variants of the invention, the dicarboxylic acid monomer may be a mixture of at least two dicarboxylic acids.Preferably then, the dicarboxylic acid monomer comprises sebacic acid.Preferably, the dicarboxylic acid monomer comprises or consists of sebacic acid.According to preferred variants of the invention, the dicarboxylic acid monomer, glycerol and the itaconic crosslinking agent are the only monomers during the polycondensation. Very preferably, the sebacic acid monomer and glycerol are the only monomers constituting the copolyester of glycerol and a dicarboxylic acid monomer.Advantageously, the glycerol / dicarboxylic acid monomer molar ratio varies from 1 / 2 to 10 / 1, in particular from 1 / 1 to 5 / 1, preferably from 1 / 1 to 2 / 1.The copolyester of glycerol and a dicarboxylic acid monomer (hereinafter referred to as the non-functionalized copolyester) advantageously has one or more of the following characteristics: - a number-average molar mass (Mn) of the non-functionalized copolyester greater than or equal to 500 g / mol, preferably greater than or equal to 1000 g / mol, more preferably greater than or equal to 1500 g / mol, advantageously greater than or equal to 2000. g / mol ;- a number-average molar mass (Mn) of the non-functionalized copolyester less than or equal to 10,000 g / mol, preferably less than or equal to 3,500 g / mol, preferably less than or equal to 3,000 g / mol; - a dispersity Đ (Mw / Mn) of the non-functionalized copolyester less than 10, preferably less than or equal to 8; - a residual monomer content less than or equal to 5% by weight of the weight of the non-functionalized copolyester; - a content of (1,2,3-triacylglyceride) units less than or equal to 20 mol% relative to all the units of the non-functionalized copolyester; - a molar ratio of the (1,3-diacylglyceride) unit to the (1,2-diacylglyceride) unit greater than 1 of the non-functionalized copolyester. The copolyester of glycerol and a dicarboxylic acid monomer can be obtained in particular by implementing the processes described in EP3149067 and EP1448656.The number-average molar mass (Mn), the mass-average molar mass (Mw), and the dispersity (also called polydispersity and noted Đ, which is the Mw / Mn ratio), can be measured in a known manner by size exclusion chromatography (SEC) analysis, in particular as described below. The rate of residual monomers as well as the rate of units (1,2,3-triacylglyceride) is measured in a known manner by NMR. 13 C, where appropriate combined with 2D HSQC / HMBC and NMR experiments 13C, as described below. The copolyester of glycerol and a dicarboxylic acid monomer can also be characterized by a free hydroxyl content, or number of free hydroxyl functions per gram of copolyester. The free hydroxyl content is determined by NMR, typically 13C NMR, and is expressed in mol / g of copolyester. For example, the hydroxyl number, expressed in mg KOH / g of copolyester, can be measured, for example using the method of the ASTM E222-23 standard. The method of the ASTM E222-23 standard consists of acetylating the hydroxyls present with acetic anhydride followed by KOH determination. The hydroxyl number is then easily converted by a person skilled in the art into mmol of free OH / g of copolyester. The number of free hydroxyls of the non-functionalized copolyester, denoted N OH and expressed in mol ,is then obtained simply by multiplying the free hydroxyl content by the mass of non-functionalized copolyester. Advantageously, the molar ratio of itaconic crosslinking agent / NOH varies from 1:100 to 2:1, in particular from 1:1 to 2:1. Stabilizing agentAs used herein, a “stabilizing agent” means a compound that makes it possible to limit (or even eliminate) side reactions of the double bond of the itaconate function, such as, for example, radical reactions leading to uncontrolled crosslinking of the polymer, or Michael reactions. Preferably, the stabilizing agent does not react with the double bond with significant yields, or reacts reversibly. For example, the stabilizing agent may carry out a Michael addition reaction in a reversible manner. It is therefore a nucleophilic compound that is not very reactive towards the crosslinking agent such as a phenol or an aniline. A phenol is understood to be an organic compound comprising a phenol function: , substituted or unsubstituted, in particular by one or more substituents chosen from a halogen atom, -NO2, or a C1-C6 alkyl, C1-C6 alkoxy, NH-C1-C alkyl group 6. An aniline is an organic compound comprising a function aniline : with Rn representing H or a C1-C6 alkyl group, substituted or unsubstituted, in particular by one or more substituents chosen from a halogen atom, -NO2, or a C1-C6 alkyl group, C1-C6 alkoxy, NH-C1-C alkyl 6. According to a first variant, the stabilizing agent comprises or consists of a compound of general formula wherein X is O or NRn, with Rn being H or C1-C6 alkyl, R1 is H, -CO-aryl or -CO-heteroaryl, R is independently H, halogen, -NO2, -OH, C1-C6 alkoxy, -COOH, -COO-C1-C6 alkyl, NH-C1-C6 alkyl, -SR2, or C1-C6 alkyl optionally substituted with OR2 or SR2, R2 is independently C1-C8 alkyl and p is a number from 1 to 4, preferably 1 or 2. Preferably, p is 1 or 2, and R is independently H, -OH, -COOH, C1-C6 alkyl optionally substituted with SR2 wherein R2 is C1-C8 alkyl, or a C1-C6 alkoxy group. Advantageously, R1 represents H or -CO-phenyl. For the purposes of the present invention, the term "halogen atom" or "halogen" means fluorine, chlorine, bromine and iodine atoms.For the purposes of the present invention, the term "(C1-C6) alkyl" group means a saturated, linear or branched monovalent hydrocarbon chain comprising 1 to 6, preferably 1 to 4, carbon atoms. For example, methyl, ethyl, propyl, isopropyl, butyl, pentyl or hexyl groups may be mentioned. For the purposes of the present invention, the term "(C1-C6) alkoxy" group means a (C1-C6) alkyl group, as defined above, linked to the rest of the molecule via an oxygen atom. For example, methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, t-butoxy, n-pentoxy or n-hexoxy groups may be mentioned. By "aryl" is meant here an aromatic hydrocarbon group, preferably comprising from 6 to 10 carbon atoms, and comprising one or more fused rings, such as for example a phenyl or naphthyl group. Advantageously, this is phenyl.By "heteroaryl" is meant here an aromatic group comprising 5 to 10 cyclic atoms including one or more heteroatoms, advantageously 1 to 4 and even more advantageously 1 or 2, such as for example sulfur, nitrogen or oxygen atoms, the other cyclic atoms being carbon atoms. Examples of heteroaryl groups are furyl, thienyl, pyrrolyl, pyridinyl, imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, quinolyl, isoquinolyl, quinoxalyl or indyl. The stabilizing agent can therefore be used alone or in a mixture. Typically, these are aniline, phenol, methoxyphenol (especially 4-methoxyphenol or guaiacol), syringol, 4,6-bis(octylthiomethyl)-o-cresol and / or 2-hydroxy-4-methoxybenzophenone.The amount of stabilizing agent introduced is advantageously between 0.01% and 5% by mass relative to the total mass of the monomers, preferably ranging from 0.1% to 2%, preferably from 0.5% to 1.6%. Step (a) of bringing the non-functionalized copolyester into contact with an itaconic crosslinking agent is typically carried out at a temperature ranging from 20°C to 200°C. When the itaconic crosslinking agent is itaconic acid, then step (a) is preferably carried out at a temperature ranging from 100°C to 180°C, in particular from 110°C to 160°C. When the itaconic crosslinking agent is itaconic anhydride, then step (a) is preferably carried out at a temperature ranging from 30°C to 110°C, preferably from 40°C to 90°C. According to one embodiment, the contacting is carried out in the absence of solvent or diluent.In step (a), the non-functionalized copolyester and the itaconic crosslinking agent may be brought into contact in a solvent, in particular a polar aprotic solvent (such as for example CyreneTM (dihydrolevoglucosenone), 1,2,3-trimethoxypropane), preferably bio-sourced, or water. Preferably, the solvent is water. Thus, according to variants of the invention, the contacting of step (a) is carried out by adding water to a mixture of non-functionalized copolyester and itaconic crosslinking agent. The addition of water to the mixture allows homogenization of the mixture and thus reduces its overall viscosity. In order to promote this homogenization, stirring may be implemented in a known manner.According to these variants, the water is added in an amount by mass of between 0% and 100% by mass, preferably ranging from 5% to 50% by mass, more preferably ranging from 10% to 40% by mass relative to the mass of non-functionalized copolyester and itaconic crosslinking agent used. According to other particular variants of the invention, the contacting is carried out by introducing the itaconic crosslinking agent into a mixture comprising the non-functionalized copolyester and water. The mixing of the non-functionalized copolyester and water may take place at room temperature (approximately 23°C at atmospheric pressure) in a reactor, which may be the same as that of step (a). This preliminary mixing step may optionally comprise heating the non-functionalized copolyester and water, for example at a temperature varying from approximately 50°C to 100°C.The medium is then heated for a sufficient time to homogeneously dissolve or disperse the non-functionalized copolyester in the water. In order to promote homogenization of the medium, stirring may be carried out in a known manner, whether or not there is heating. According to any one of these variants, the itaconic crosslinking agent may be introduced into the mixture comprising the non-functionalized copolyester and water, in solid form or as a solution in water, preferably in solid form. According to one variant, the itaconic crosslinking agent is introduced into a mixture comprising the non-functionalized copolyester and water, in solid form, and the contacting is followed by a step of melting and / or dissolving the itaconic crosslinking agent in the aqueous medium.According to other variants, in particular when the itaconic crosslinking agent is introduced in the form of a solution in water, for example at room temperature, the reflux heating step is optional. The stabilizing agent can also be added during step a). Step b) In step (b), the functionalization reaction comprises an esterification of a free alcohol function of the glycerol copolyester and a dicarboxylic acid monomer, by the itaconic crosslinking agent. Depending on the reaction conditions, transesterification reactions may also be observed, but they generally remain in the minority. When the itaconic crosslinking agent is itaconic acid, a water molecule is formed for each ester bond formed. Thus, in this embodiment, a by-product of the functionalization reaction is water.According to a particular variant of the invention, the functionalization step will be carried out under conditions that make it possible to remove water from the reaction medium (or from the reactor). Removing water as it is formed during functionalization has several advantages: it makes it possible to improve the yield of the reaction and to accelerate its kinetics. Preferably, the water thus recovered will be recycled as a solvent for the contacting step (a). Furthermore, when the itaconic crosslinking agent is itaconic acid, measuring the quantity of water removed also makes it possible to monitor the progress of the functionalization reaction. To remove water during the functionalization step, a reactor and suitable temperature and pressure conditions may be used to distill the water. Regardless of the embodiment, the pressure in the reactor during step (b) may be constant or variable.The functionalization step (b) is typically carried out at a pressure of between 0.0001 and 2 bars. Preferably, the functionalization reaction will be carried out under reduced pressure, the pressure typically being less than or equal to 30 mbar, in particular less than or equal to 20 mbar, preferably less than or equal to 10 mbar. According to a variant of the invention, at the end of step (a), prior to applying reduced pressure, the pressure is preferably reduced to an intermediate pressure between atmospheric pressure and the target reduced pressure, possibly in stages. Any method known to those skilled in the art can be used to lower the pressure, in particular using a pump (in particular a vane pump), a membrane pump, a rotary pump, etc. Such an intermediate pressure is less than 1 bar and varies, for example, from 800 mbar to 50 mbar. The reaction medium is then placed under reduced pressure, and preferably under vacuum.Here, the term "vacuum" means that the pressure is lowered until a value of around 1 mbar is reached. The heating step b) is preferably carried out at a temperature of between 20°C and 250°C. The temperature of the functionalization step b) may be variable or stable. When the itaconic crosslinking agent is itaconic acid, then the functionalization step b) is preferably carried out at a temperature ranging from 50°C to 250°C, preferably from 100°C to 200°C, in particular from 120°C to 190°C. In a particular embodiment, the heating of step b) comprises a step of maintaining the reaction at a temperature ranging from 110°C to 200°C, preferably from 120°C to 180°C, in particular at approximately 130°C. When the itaconic crosslinking agent is itaconic anhydride, then functionalization step b) is preferably carried out at a temperature ranging from 30°C to 130°C, in particular from 40 to 100°C.The temperature is preferably reached by applying an isotherm or a heating ramp. The heating ramp may comprise one or more stages, also called temperature maintenance periods, and the ramp typically has a slope of between +0.1°C / min and +1°C / min. According to one embodiment, step b) of functionalization is carried out in the presence of a catalyst, in particular at a content of 5000 ppm or less, preferably 3000 ppm or less, advantageously 2000 ppm or less, relative to the total mass of non-functionalized copolyester and itaconic crosslinking agent used.The catalyst may in particular comprise or consist of a Brønstedt acid (such as, for example, sulfuric acid, para-toluene sulfonic acid) or a Lewis acid (such as, for example, AlCl3, TiCl4, TiOBu4, butylstannoic acid, metal salts of trifluoromethanesulfonate or triflate, such as, for example, bismuth triflate), or a mixture thereof. Particularly advantageous catalysts are metal triflates (or trifluoromethylsulfonate), the metal being of oxidation state (III) chosen from Lanthanide triflates (Ln(TfO)3), yttrium triflate, scandium triflate, bismuth triflate and iron triflate. Preferably, the catalyst comprises or consists of a food grade catalyst.By "food grade catalyst" is meant a catalyst suitable for food contact (for animals and humans) which meets requirements ensuring that there is no risk of toxicity induced by this catalyst for the polyester manufactured. Such a catalyst meets in particular the requirements of American standards 21 CFR 175.300, 21 CFR 177.2420 and / or 21 CFR 175.105 in force on the filing date. The food grade catalyst is advantageously tin-based, and preferably chosen from organotin compounds comprising a carboxyl function (-C(O)OH) or a function (-Sn(O)OH). According to particular variants of the invention, the catalyst is chosen from alkyltins comprising a carboxyl function (-C(O)OH) or a function (- Sn(O)OH), the alkyl group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms.Among these particular compounds, mention may be made of food grade monobutyltin oxide (or stannoic acid) and food grade monobutyltin tris(2-ethylhexanoate). According to preferred variants of the invention, the catalyst is food grade monobutyltin oxide (or stannoic acid). Examples of catalysts useful for the purposes of the invention include monobutyltin oxide marketed under the name FASCAT 9100 and monobutyltin tris(2-ethylhexanoate) marketed under the name FASCAT 9102 by the company PMC Organometallix. In particular, the catalyst monobutyltin oxide marketed under the name FASCAT 9100 by the company PMC Organometallix will be preferred.Thus, a catalyst will advantageously be introduced into the reaction medium, at the end of step (a) or step b), in an amount less than or equal to 5000 ppm relative to the total mass of the monomers, preferably an amount greater than or equal to 2500 ppm. Advantageously, in particular when the molar ratio of itaconic crosslinking agent / NOH is 1:1 to 2:1, this step will be considered to be complete when a molar conversion rate of the number of free hydroxyl functions of 70%, preferably 80% or in particular 90% or more is observed. The molar conversion rate can be determined by measuring the mass of distillate (water) removed, or by monitoring the disappearance of the free itaconic crosslinking agent or of the free hydroxyl functions by NMR or size exclusion chromatography (SEC) on samples taken from the reaction medium. Generally, the molar conversion rate is determined and / or monitored by 13C NMR.For example, the disappearance of the signal of the carbons carrying a free hydroxyl function or the -COOH functions carried by the free diacids of the dicarboxylic acid monomer or of the itaconic crosslinking agent may be monitored. Alternatively, when the second functionalization step (b) is carried out with stirring, the step may be considered to be complete when the torque of the stirring motor reaches a predetermined target value, preferably chosen to guarantee a molar mass and a viscosity of the functionalized copolyester suitable for the applications targeted in the invention. Advantageously, the heating of step b) is carried out for 30 minutes to 12 hours, preferably for 1 hour to 5 hours. Subsequent steps The method may also comprise a subsequent step of post-treatment of the functionalized copolyester obtained, in particular to reduce the level of itaconic crosslinking agent and / or residual stabilizing agent.This may be a washing step and / or a liquid-liquid extraction step, with a water-immiscible organic solvent, preferably dichloromethane, preferably followed by washing with an aqueous phase, in particular a neutral aqueous phase, and / or one loaded with salts (for example NaCl) and / or acid (for example a hydrochloric acid solution, in particular 1N or 2N). The liquid-liquid extraction and / or washing are carried out in a known manner. 2. Photocrosslinkable copolyester and compositionThe photocrosslinkable copolyester according to the invention has an itaconic functionalization rate greater than or equal to 0.004 mmol / g, preferably greater than or equal to 0.04 mmol / g, more preferably greater than or equal to 1 mmol / g. Preferably, it is capable of being obtained by the functionalization process according to the invention.As used herein, the "itaconic functionalization rate" means the rate of C=C double bonds provided by the itaconic crosslinking agent in the photocrosslinkable copolyester, expressed in mmol of double bonds / g of photocrosslinkable copolyester obtained. The itaconic functionalization rate is typically measured by carbon 13 nuclear magnetic resonance (NMR). 13C). The itaconic functionalization rate can also be obtained indirectly by measuring the free itaconic acid by size exclusion chromatography (SEC). The rate of free (or residual) itaconic acid is then measured. Assuming that the rest of the itaconic acid involved has completely reacted, the itaconic functionalization rate corresponds to the difference between the amount of itaconic acid involved in the reaction (or initial), and the amount of free itaconic acid, these quantities being expressed in mmol / g of polymer obtained. The itaconic functionalization rate is typically measured by carbon 13 nuclear magnetic resonance (NMR 13C). For a copolymer of glycerol and itaconic crosslinking agent without any other monomer, and in particular without any other dicarboxylic acid monomer, with a glycerol: itaconic crosslinking agent molar ratio of 1:1 and a sequence of 100 glycerol / diacid monomers, the theoretical itaconic functionalization rate is 5.23 mmol / g, confirmed experimentally as being between 5 and 6 mmol / g. Thus, the photocrosslinkable copolyester has an itaconic functionalization rate generally less than or equal to 10 mmol / g, in particular less than or equal to 8 mmol / g, preferably less than or equal to 6 mmol / g. Advantageously, the itaconic functionalization rate is typically greater than or equal to 0.1 mmol / g, in particular greater than or equal to 0.5 mmol / g,in particular greater than or equal to 1 mmol / g. The photocrosslinkable copolyester may also have at least one of the following characteristics: - a number-average molar mass (Mn) of the photocrosslinkable copolyester greater than or equal to 500 g / mol, in particular greater than or equal to 1000 g / mol, preferably greater than or equal to 1500 g / mol, preferably greater than or equal to 1700 g / mol; - a number-average molar mass (Mn) of the photocrosslinkable copolyester less than or equal to 10000 g / mol, preferably less than or equal to 3500 g / mol, preferably less than or equal to 3000 g / mol; - a dispersity Đ of the photocrosslinkable copolyester less than 12, preferably less than or equal to 8, in particular less than or equal to 6; - a residual monomer content less than 25% by weight, preferably less than or equal to 20% by weight, relative to the weight of the photocrosslinkable copolyester; and / or- a rate of (1,2,3-triacylglyceride) units of less than 25 mol%,preferably less than or equal to 20 mol%, in particular 15 mol% or less, relative to all the units of the photocrosslinkable copolyester. The photocrosslinkable copolyester may also have at least one of the following characteristics: - a molar ratio of the unit (1,3-diacylglyceride) to the unit (1,2-diacylglyceride) greater than 1 of the non-functionalized copolyester; - a glass transition temperature (Tg) of –100°C to +30°C, preferably of –80°C to +10°C, preferably of –60°C to 0°C, in particular of -50°C to -25°C., The invention also relates to a photocrosslinkable composition comprising:^ a photocrosslinkable copolyester as described herein, and^ optionally, a photoinitiator. As used herein, a "photoinitiator" means a compound which, when exposed to light, and in particular to UV light, produces a radical which will make it possible to initiate the photocrosslinking reaction, which is generally radical. The use of excessively large quantities of photoinitiator can generate undesirable reactions during the photocrosslinking step. Thus, advantageously, the photoinitiator is present at a content of less than or equal to 5% by mass, more preferably less than or equal to 1% by mass relative to the total weight of the photocrosslinkable composition. Photoinitiators suitable for photocrosslinking are well known to those skilled in the art. The photoinitiators will in particular be chosen from the family of type I photoinitiators.Type I photoinitiators are monomolecular systems that proceed by homolytic cleavage of a CC bond, in particular by Norrish I cleavage. The molecules involved are generally aromatic ketones which undergo, after absorption of light, a homolytic cleavage of the bond in the α position relative to the carbonyl group (Norrish I cleavage) from their triplet excited state, which leads to the formation of two free radicals capable of initiating a radical polymerization reaction (see in particular Ley et al. 14th International Francophone Colloquium on Optical Methods and Techniques for Industry / 16th French Congress of the FLUVISU / SFO Club (CMOI-FLUVISU 2015), CMOI Club - Société Française d'Optique, Nov 2015, Pleumeur-Bodou, France. pp.124-129. hal-01583762). Type I photoinitiators are in particular any precursor of benzoyl radical:. Type II photoinitiators are in particular any precursor of a ketyl radical (inert) and with a radical precursor (an amine). Examples include 2,4,6-Trimethylbenzoyldi-Phenylphosphinate (TPO L), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), or 1-Hydroxycyclohexyl phenyl ketone (HCHPK). The photocrosslinkable composition may further comprise one or more additives conventional in the art, such as fillers. The fillers may be organic or inorganic. The additive may also be chosen from the group consisting of stabilizers, compatibilizing agents, shaping agents, regulators of release of an active ingredient, antioxidants. The composition may further comprise an active ingredient, more particularly with respect to plants, for example a phytosanitary active ingredient and / or a biostimulant. Such compositions may be used to coat plants or parts of plants.According to this embodiment, the invention also relates to a method for treating plants comprising the application to at least part of the plants or to the soil of the photocrosslinkable composition. As active ingredients with respect to plants, mention may also be made in particular of plant stimulation agents for agricultural application, in particular rubber trees, such as Hevea brasiliensi. A plant protection product, plant protection product or plant protection product, is a substance or a mixture of substances of a chemical or biological nature (of natural or synthetic origin) used in agriculture, horticulture or forestry to protect cultivated plants against bioaggressors (animal pests, phytopathogenic agents, parasitic plants, weeds) or to optimize crops by promoting the growth of cultivated plants and treating their environment (in particular the soils).A "biostimulant" is a substance that stimulates plant nutrition processes independently of the nutrients it contains with the aim of improving one or more of the following characteristics of plants or their rhizosphere: nutrient use efficiency, tolerance to abiotic stress, quality characteristics, availability of nutrients confined in the soil or rhizosphere (in accordance with EU Regulation 2019 / 1009). Biostimulants can be natural preparations of low concern (NPPCs). NPPCs are:- Either natural substances for biostimulant use (SNUBs).- Or basic substances. Basic substances are defined by Article 23 of Regulation (EC) 1107 / 2009. They are substances of phytosanitary interest but whose main use is other than plant protection (e.g. foodstuffs).Preferably, the formulation according to the invention comprises a phytosanitary active ingredient and / or a biostimulant chosen from the group consisting of stimulants, fertilizers, pesticides, fungicides, nutrients, bactericides, insecticides, growth regulators. Preferably, the formulation according to the invention comprises a phytosanitary active ingredient and / or a biostimulant which is a precursor of ethylene, preferably ethephon. The composition according to the invention may be in the form of a paste, patch, granules or solution to be propellant, preferably in the form of a paste. 4. Photocrosslinking method The invention also relates to a method for photocrosslinking the photocrosslinkable composition or a photocrosslinkable copolyester described herein, comprising a step of UV irradiation of the photocrosslinkable composition or the photocrosslinkable copolyester, preferably in the presence of a photoinitiator.Advantageously, the irradiation is carried out at a temperature ranging from 15°C to 30°C. The irradiation is typically carried out at atmospheric pressure. Preferably, the irradiation is carried out at a wavelength of between 250 nm and 500 nm, preferably ranging from 300 to 450 nm, more preferably from 350 to 400 nm, in particular around 365 nm. Advantageously, the irradiation is carried out at a power of 5 to 25 mW / cm2, in particular from 8 to 20 mW / cm. 2. Advantageously, the photoinitiator is present at a content of less than or equal to 5% by mass, more preferably less than or equal to 1% by mass relative to the total weight of the photocrosslinkable composition. The photoinitiators are as defined above. The photocrosslinkable composition or the photocrosslinkable copolyester is generally irradiated for a period of between 1s and 5h. Preferably, the photoinitiator is added to the composition or to the crosslinkable copolyester at room temperature. This avoids any undesirable crosslinking reaction. More particularly, the invention relates to the use of the photocrosslinkable composition for the preparation of products by 3D printing, preferably by 3D printing by photocrosslinking.Examples of such technologies are stereolithography (SLA), printing processes known as "Digital Light Processing" (DLP), "Continuous Liquid Interface Production" (CLIP), "Daylight Polymer Printing" (DPP), or "Film Transfer Imaging" (FTI).5. Crosslinked copolyester and uses The invention also relates to a crosslinked copolyester obtained by crosslinking, in particular thermal crosslinking and / or photocrosslinking, of the photocrosslinkable copolyester of the invention or of a photocrosslinkable composition according to the invention. According to a variant, the crosslinked copolyester is therefore capable of being obtained by the photocrosslinking process described above.According to another variant, the crosslinked copolyester is capable of being obtained by thermal crosslinking, in particular with thermal initiation optionally in the presence of initiators chosen in particular from producers of radicals by thermal decomposition, such as for example peroxides, such as cumene hydroperoxide, or azos, such as for example azobiisobutyronitrile (AIBN), in a dispersed or non-dispersed medium. The crosslinked copolyester advantageously has:^ a glass transition temperature Tg of between -100°C and +30°C, preferably from -80°C to +10°C, in particular from -60°C to 0°C, and / or^ a storage modulus G' at 37°C and at 10 Hz greater than or equal to 0.02 MPa. Thus, the photocrosslinkable composition according to the invention or the photocrosslinkable copolyester according to the invention is useful for the preparation of products by 3D printing.The products are, for example, implants, patches diffusing active ingredients, particles (in particular micro- and macroparticles), coatings, fibers and threads, etc. DESCRIPTION OF THE FIGURES Other characteristics, aims and advantages of the invention will emerge from the description which follows, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings. [Fig. 1] represents a simplified reaction scheme of the reactions involved in the synthesis of poly(glycerol-co-sebacate-co-itaconate) according to Example 1. [Fig. 2] represents the storage moduli G* measured on the copolyesters of Examples 2 and 3, after photocrosslinking in the presence or absence of a photoinitiator. EXAMPLES The examples which follow are given for illustrative purposes, but must in no case be considered as limiting the present invention.Materials and methodsStructural analysis: NMRThe structural analysis as well as the determination of the itaconic functionalization rate and the proportion of unreacted (residual) itaconic anhydride or acid present in the polymer are carried out by NMR analysis. The spectra are acquired on a BRUKER Avance III 600 MHz spectrometer equipped with a BBFO-zgrad 5mm "broadband" probe. The NMR experiment. 1 Quantitative H, uses a single 30° pulse sequence and a 3-second repetition delay between each of the 64 acquisitions. The samples are solubilized in a deuterated solvent, deuterated acetone (acetone d 6) unless otherwise indicated. The 1H NMR spectrum coupled with 2D HSQC / HMBC and 13C NMR experiments allow the quantification of the microstructure of the different functional PGS (see attribution tables). The itaconic conversion rate corresponds to the molar percentage of grafted itaconic crosslinker / (grafted + free itaconic crosslinker). Macrostructure analysis: SEC RIThe SEC technique ("Size Exclusion Chromatography") allows the separation of macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the largest being eluted first. Without being an absolute method, SEC allows the understanding of the molar mass distribution of a polymer.From commercial standard products, the different number-average (Mn) and weight-average (Mw) molar masses can be determined and the polydispersity index (Đ = Mw / Mn), also called "dispersity", calculated. The "macrostructure" of the copolyesters is analyzed by size exclusion chromatography with differential refractometer detection (SEC RI), in low-weight polystyrene (PS) calibration extended with medium-weight standards. The samples are dissolved at a concentration of approximately 1g / L in THF without butylated hydroxytoluene (BHT), then stirred for two hours before being injected. The analysis temperature is 35°C, with a mobile phase flow rate of 1mL / minute on 2 Mixed E + 2 Mixed 2 columns marketed by Agilent.Thermal analysis: DSCThe thermal analysis of copolyesters is carried out by differential scanning calorimetry on a DSC 3+ calorimeter marketed by Mettler Toledo, in standard aluminum crucibles with sealed lids and pierced with two diametrically opposed holes, under a Helium flow rate of 40mL / minute using the following temperature ramp:1. isothermal 25°C for 2 minutes,2. ramp from 25°C to -100°C at 10°C / minute,3. isothermal at -100°C for 2 minutes,4. ramp from -100°C to 100°C at 10°C / minute,5. ramp from 100°C to -100°C at -30°C / minute,6. isothermal at -100°C for 2 minutes,7. from -100°C to 200°C at 10°C / minute. The measurement carried out at ramp 7 corresponds to the Tg of the crosslinked copolyester. Structural analysis: MIR The kinetic monitoring of photocrosslinking was carried out with a mid-infrared spectrometer (MIR) with wavelengths between 4000 and 650cm. -1, (Vertex 70'' model marketed by Brucker) equipped with a germanium crystal on a Vertex 70-3 spectrometer with MCT detector. An accumulation of number of scans (Ns) of 32 is used. The spectrometer was equipped with a 365nm UV LED lamp with a power of 9mW / cm 2 irradiating at a distance of 5cm from the sample. Crosslinking is monitored by following the disappearance of the C=C band of itaconate at 1638cm -1 as a function of UV irradiation time (measurement of peak area of ​​the band at 1638cm -1). Measurement of mechanical properties: storage modulus G'The mechanical properties are measured on an Anton Paar rheometer model MCR302, equipped with a 20mm diameter plane-plane geometry. The measurements are carried out on a cylindrical sample 2mm thick and 2cm in diameter, obtained by molding in a metal mold then crosslinking for 1 hour under a UV LED lamp (LED 365nm, 9Mw / cm2) at room temperature. This sample is subjected to a frequency sweep from 0.1 to 100 Hertz in sinusoidal shear stress at 0.1% strain, at a temperature of 37°C. The resulting stress is measured. The results used are the storage modulus (G') at 37°C and 10Hz, they are expressed in megapascal (MPa). The moduli G*, G' and G'' are calculated according to the equations below: avec :^ σ the measured stress and ε the strain imposed on the sample.^ G', the real part of G*, called the storage modulus, which characterizes the rigidity of the viscoelastic material. G' characterizes the elastic behavior (the energy conserved and totally restored by the material);^ i, the "imaginary" unit (i2 = –1);^ G'', the imaginary part of G*, called the loss modulus or dissipation modulus, which characterizes the viscous behavior (the energy dissipated in the form of heat).Example 1: Synthesis of non-functionalized glycerol-co-sebacate copolyester, noted PGS In a 500mL jacketed reactor topped with a distillation column, a condenser and a distillate recovery trap, under nitrogen flow, glycerol (1 molar equivalent) and sebacic acid (1 molar equivalent) are added. The reactor is then gradually heated to 130°C with stirring and under nitrogen.Once the temperature of 130°C is reached in the medium, the reaction is left for 24 hours under atmospheric pressure and nitrogen flow, at 130°C, the water is continuously removed. When the conversion exceeds 80% by measuring the quantity of water produced, the reaction is stopped. The PGS thus obtained is recovered in the form of a white paste after cooling to room temperature. It has a number-average molar mass of approximately 1852 g / mol, a mass-average molar mass Mw of approximately 5067 g / mol, a dispersity of approximately Đ = 2.7, and a free hydroxyl content of 5 mmol / g. Example 2: Synthesis of photocrosslinkable copolyesters according to the invention: itaconate-grafted glycerol-co-sebacate copolyester. In the following, PGS-IA will be referred to as a copolyester: itaconate-grafted glycerol-co-sebacate obtained with an itaconic acid as crosslinking agent, and PGS-ANHYTA as a copolyester: itaconate-grafted glycerol-co-sebacate obtained with an itaconic anhydride as crosslinking agent.Comparative process without stabilizer: In a 500mL double jacketed reactor topped with a distillation column, a condenser and a distillate recovery trap, under nitrogen flow, the PGS of example 1 and the itaconic crosslinking agent are added. The reactor is then gradually heated to 130°C under stirring and nitrogen. Once the temperature of 130°C is reached in the medium, the reaction is left under atmospheric pressure and nitrogen flow, at 130°C with the water continuously removed for 3 hours. A light yellow viscous liquid is obtained, corresponding to PGS-IA or PGS-ANHYTA, then cooled to room temperature.Process of the invention with stabilizer:In a 500mL jacketed reactor topped with a distillation column, a condenser and a distillate recovery trap, under nitrogen flow, the PGS of example 1, the itaconic crosslinking agent (0.4 molar equivalents relative to the 1,3-diacylglyceride units of the PGS of Example 1 (majority unit)) and 4-methoxyphenol as a stabilizing agent (1.56% by mass relative to the total mass of the mixture including the stabilizing agent), are added. The reactor is then heated to 130 °C (or 80 °C or 140 °C) gradually with stirring and under nitrogen. Once the temperature of 130 °C (or 80 °C or 140 °C) is reached in the medium, the reaction is left under atmospheric pressure and nitrogen flow, at 130 °C (or 140 °C) with the water continuously removed for the reaction time indicated in Table 1. A light yellow viscous liquid is obtained, corresponding to PGS-IA or PGS-ANHYTA, then is cooled to room temperature. The processes of tests 1 to 6 are carried out without solvents. The reaction conditions of the different examples carried out are summarized in Tables 1 and 2.[TABLE 1] Test 1 Test 2 Test 3 Test 4 Test 5Agent Anhydride Anhydride Anhydride Crosslinking acid itaconic itaconic itaconic itaconic itaconic itaconic itaconic ee Nature of 4- 4- 4-. / / stabilizer methoxyphen methoxyphen methoxyphen ol ol ol Duration of3h30 3h30 20h30 3h 3hheating step Temperature80 °C 130°C 130°C 130°C 130°Ctarget Pressure Atm. Atm Atm. Atm. Atm. Appearance of liquid liquid gel orange liquid liquid PGS-IA or viscous viscous insoluble in viscous viscous PGS-ANHYTA yellow orange yellow orange acetone and yellow yellow obtained after THF orange orange cooling [TABLE 2] Test 6 Test 7 Test 8 Test 9 Test 10 Crosslinking agent Acid Acid Acid Acid Acid itaconic itaconic itaconic itaconic itaconic Nature of 4- 4- Guaicol Irganox® MEHQ + stabilizer methoxyp methoxyp 1520L oxybenzone henol henol Duration of the heating step 3h45 3h20 3h30 3h30 3h30 Target temperature 130°C 140°C 130°C 130°C 130°C Pressure Atm. Under Atm. Atm. Atm. reduced pressure (less than 10 mbar) Appearance of PGS-IA liquid liquid liquid liquid liquid or PGS-ANHYTA viscous viscous viscous viscous viscous obtained after yellow yellow yellow yellow yelloworange cooling orange orange orange orange Results of NMR analyses (acetone d6) of PGS-IA or PGS-ANHYTA obtained in tests 1 and 3 to 6 (no analysis carried out for the photocrosslinkable copolyester of test 2 because it is not soluble in acetone) [TABLE 3] Test 1 Test 2 Test 4 Test 5 Test 6 Test 7 Structural characterization of the photocrosslinkable copolyester %molar of 1-acylglyceride / polymer ≈ 3.4 ≈ 2 ≈ 3.5 ≈ 2.8 ≈ 4.5 ≈ 12.0 %molar of 2-acylglyceride / polymer ≈ 0.3 0 ≈ 0.3 ≈ 0.5 ≈ 0.5 ≈ 1.2 %molar of 1,2-diacylglyceride / polymer ≈ 1.4 ≈ 2.4 ≈ 3.5 ≈ 3.7 ≈ 3.9 ≈ 4.0 mol% of 1,3-diacylglyceride / polymer ≈ 7.5 ≈ 4.3 ≈ 6.7 ≈ 6.8 ≈ 7.1 ≈ 9.0 mol% of 1,2,3-triacylglyceride / polymer ≈ 3.9 ≈ 4.5 ≈ 5.1 ≈ 5.5 ≈ 3.9 ≈ 2.2 mol% of itaconic crosslinking agent ≈11 ≈ 17 ≈ 12 ≈ 10 ≈ 9 ≈ 9grafted / polymer Presence of free monomers or reagents%molar of free glycerol ≈ 0.1 ≈ 1.1 ≈ 0.4 ≈ 0.4 ≈ 0.6 ≈ 7.1%molar of free itaconic crosslinking agent ≈ 27 ≈ 22 ≈ 21 ≈ 20 ≈ 24 ≈ 6Quantity ofOH in the product (mmol / g) 2.3 2 2.5 3.3 3.2 7.7 Quantity of unsaturations in the product* 1.2 1.2 2.3 2.2 2.4 1.2(mmol / g) *Takes into account the unsaturations of the free and grafted itaconic acid or anhydride Calculation of the number-average (Mn) and mass-average (Mw) molar masses and dispersity 5 by SEC analysis (dissolution in THF, poly(styrene) standard) of PGS-IA or PGS-ANHYTA obtained in tests 1 and 3 to 6 (no analysis carried out for the photocrosslinkable copolyester of test 2 because it is not soluble in THF) [TABLE 4] Mn (g / mol) Mw (g / mol) Dispersity, ĐTest 1 2127 6235 2.9Test 2 2017 7664 3.8Test 4 2318 17791 7.4Test 5 2271 29113 12.8Test 6 1507 4713 3.1Test 7 1084 2522 2.3Test 8 2141 6054 2.8Mn (g / mol) Mw (g / mol) Dispersity, ĐTest 9 2183 6509 3.0Test 10 2213 6660 3.0Example 3 (reference): Synthesis of a reference photocrosslinkable copolyester: the copolyester: glycerol-co-sebacate grafted methacrylate, noted PGS-MA according to the Journal of Biomaterials Applications, 4, 1114–1130, 2020and Macromol. Rapid Commun, 41, 1900484, 2020. In a 500mL jacketed reactor topped with a condenser and a stirring blade with motor, under nitrogen flow, the PGS of Example 1 and 4-methoxyphenol as stabilizing agent (2.7% by mass relative to the mass of PGS, methacrylic anhydride and 4-methoxyphenol), are dissolved in dichloromethane (15.6% massique), at room temperature, with stirring and under nitrogen. After dissolution, the compounds, methacrylic anhydride (50% by mass relative to the PGS) is added at 0°C by controlled addition. The reaction medium is allowed to return to room temperature and maintained under stirring and under nitrogen for 24 hours. At the end of the reaction, liquid / liquid extractions are carried out with an acid solution, then water (with or without salt such as sodium chloride) until the aqueous phases return to pH 5-7. The organic phases are combined and allowed to evaporate. A white viscous liquid is obtained, corresponding to the PGS-MA, then cooled to room temperature. Example 4: Photocrosslinking The photocrosslinkable copolyesters of examples 2 and 3 are allowed to crosslink under a UV lamp (LED 365nm, 9Mw / cm 2) during an exposure time of 1 hour (distance between the lamp and the surface of the sample: 5 cm), at room temperature and atmospheric pressure, in the presence or absence of photoinitiator 2,4,6-Trimethylbenzoyldi-Phenylphosphinate (TPO L), or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), or 1-Hydroxycyclohexyl phenyl ketone (HCHPK). The photoinitiator is previously introduced in a mass percentage of 1% by mass relative to the total mixture. A molar compensation of the stabilizing agent present in the functional PGS is carried out with the photoinitiator. Infrared analysis validates the almost total disappearance of the C=C band of itaconate at 1638cm-1, which confirms the efficiency of the photocrosslinking reaction. Table 5 reports the measurements of the glass transition temperatures Tg of the copolyesters with and without photoinitiator.Tg measurement by differential scanning calorimetry analysis of PGS-IA or PGS-ANHYTA obtained in tests 1 to 6 [TABLE 5] Tg – midpoint after one hour of irradiation under UV (°C) Without photoinitiator -29Test 2. HCHPK -16 TPO L -12 Without photoinitiator -31Test 5 HCHPK -21TPO L -22 The rheology measurements carried out on the crosslinked copolyesters thus obtained are reported in Figure 2. It can be seen from these measurements that the crosslinked copolyester is much more rigid than the photocrosslinkable copolyester, further confirming the effectiveness of the photocrosslinking reaction. Conclusion The process of the invention is simple, fast, reliable and reproducible to implement. It also makes it possible to avoid the occurrence of uncontrolled parasitic reactions, thanks to the use of a stabilizing agent. The photocrosslinkable copolyesters of Example 2 are obtained from nontoxic and biosourced monomers, and are suitable for the manufacture of products in 3D printing processes.They have mechanical and physicochemical properties of the same order of magnitude as the photocrosslinkable polymers of the prior art (see comparative example 3), but using an itaconate crosslinking agent, i.e. non-toxic and 100% biosourced / biosourceable. Bibliographic references:^ CN114456335^ EP3149067^ WO2019 / 215441^ WO2021 / 078962^ Rueben et al. MRS Advances (2018), 3(27), 1551-1556.

Claims

CLAIMS 1. Procédé de fonctionnalisation d’un copolyester du glycérol et d’un monomère diacide carboxylique, comprenant les étapes suivantes : a) Mise en contact du copolyester du glycérol et d’un monomère diacide carboxylique avec un agent réticulant itaconique choisi parmi l’acide itaconique, l’anhydride itaconique et leurs mélanges, le monomère diacide carboxylique étant de aliphatic preference, b ) Chauffage du mélange de l’étape a) en présence d’un agent stabilisant pendant un sufficient time to form a photocrosslinkable functionalized copolyester, c ) Refroidissement et récupération du copolyester fonctionnalisé photoréticulable.

2. Procédé selon la revendication 1, dans lequel le monomère diacide carboxylique a pour formula [HOOC-(CH2)n-COOH], in which n is a number ranging from 1 to 30, preferably a number ranging from 5 to 10, advantageously sebacic acid (n=8).

3. Procédé selon la revendication 1 ou 2, dans lequel le chauffage de l’étape b) comprend a step of maintaining the reaction at a temperature between 20°C and 250°C.

4. Procédé selon l’une quelconque des revendications 1 à 3, dans lequel l’agent stabilisant est un phénol ou une aniline, notamment l’aniline, du phénol, du méthoxyphénol (en particulier 4-méthoxyphénol ou le guaïacol), le syringol, le 4,6- Bis(octylthiomethyl)-o-cresol et / ou la 2-hydroxy-4-methoxybenzophenone.

5. Procédé selon l’une quelconque des revendications 1 à 4, dans lequel l’étape b) de heating is conducted at a pressure between 0.0001 and 2 bar.

6. Procédé selon l’une quelconque des revendications 1 à 5, dans lequel le chauffage de l’étape b) est réalisé pendant 30 minutes à 12h.

7. Copolyester photoréticulable du glycérol et d’un monomère diacide carboxylique avec an itaconic functionalization rate greater than or equal to 0.004 mmol / g, preferably greater than or equal to 0.04 mmol / g, more preferably greater than or equal to 1 mmol / g.

8. Copolyester photoréticulable selon la revendication 7, susceptible d’être obtenu par le method according to any one of claims 1 to 6.

9. Copolyester photoréticulable selon l’une quelconque des revendications 7 à 8, présentant en outre au moins une des caractéristiques suivantes : - sa masse molaire moyenne en nombre (Mn) est supérieure ou égale à 500 g / mol, de préférence supérieure ou égale à 1500 g / mol ; - sa masse molaire moyenne en nombre (Mn) est inférieure ou égale à 10000 g / mol, de préférence inférieure ou égale à 3500 g / mol ; - sa dispersité Đ (Mw / Mn) est inférieure ou égale à 12, de préférence inférieure ouequal to 8; - un taux de monomères résiduels inférieur ou égal à 25% en poids, de préférence inférieur ou égal 20% en poids par rapport poids du copolyester photoréticulable; and / or - un taux d'unités (1,2,3-triacylglycéride) inférieur ou égal à 25 mol%, de préférence inférieur ou égal à 20% par rapport à l'ensemble des unités du copolyester photocrosslinkable.

10. Composition photoréticulable comprenant ^ Un copolyester photoréticulable selon l’une quelconque des revendications 7 à 9, and ^ optionnellement, un photoamorceur, avantageusement à une teneur inférieure ou equal to 5% by mass relative to the total mass of the composition.

11. Procédé de préparation d’un copolyester réticulé par photoréticulation, comprenant a step of UV irradiation of the photocrosslinkable composition of claim 10 or ’un copolyester photoréticulable selon l’une quelconque des revendications 7 à 9.

12. Copolyester réticulé obtenu par réticulation, notamment réticulation thermique et / ou photocrosslinking, of the photocrosslinkable copolyester of any of the r evendications 7 à 9 ou d’une composition photoréticulable selon la revendication 10.

13. Copolyester réticulé selon la revendication 12, susceptible d’être obtenu par le procédé of claim 11.

14. Copolyester réticulé selon la revendication 12 ou 13, caractérisé en ce qu’il possède : - une température de transition vitreuse Tg comprise entre -100°C et +30°C, de préférence de -80°C à +10°C, notamment de -60°C à 0°C, et / ou - un module de stockage G’ à 37°C et à 10 Hz supérieur ou égal à 0,02 MPa.

15. Utilisation de la composition photoréticulable de la revendication 10 ou du copolyester photoréticulable de l’une quelconque des revendications 7 à 9 pour la préparation d’un produced by 3D printing.

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