PHOTOCROSSLINKABLE COPOLYESTERS AND PROCESS FOR OBTAINING THEM BY POST-FUNCTIONALIZATION

Abstract

The present invention relates to a process for functionalizing a copolyester of glycerol and a dicarboxylic acid monomer, comprising the following steps: Contacting the copolyester of glycerol and a dicarboxylic acid monomer with an itaconic crosslinking agent chosen from itaconic acid, itaconic anhydride and mixtures thereof, Heating the mixture from step a) in the presence of a stabilizing agent for a time sufficient to form a photocrosslinkable functionalized copolyester, Cooling and recovering the photocrosslinkable functionalized copolyester. The present invention also relates to a photocrosslinkable copolyester in particular capable of being obtained by this process, the photocrosslinkable compositions comprising them, the crosslinked copolyesters obtained by crosslinking (advantageously photocrosslinking) and their uses.

Description

Title of the invention: PHOTOCROSSLINKABLE COPOLYESTERS AND PROCESS FOR OBTAINING SAME BY POST- FUNCTIONALIZATION FIELD OF THE INVENTION

[0001] The present invention relates to photoreticlable copolyesters, comprising in particular unsaturated bonds. The present invention also relates to their preparation process and their use, in particular in crosslinking processes such as 3D printing processes, and to the corresponding crosslinked copolyesters. STATE OF THE ART

[0002] Biodegradable 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.

[0003] Conventionally, these polyesters are prepared by melt polycondensation of glycerol and a diacid, at high temperature and under reduced pressure, with fairly long reaction times.

[0004] 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 thermo-mechanical properties.

[0005] 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.

[0006] 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 fa bio-sourced, which allows the production of photo-crosslinkable polymers that can be used for a wide range of applications, including biomedical ones, with a relatively low carbon footprint.

[0007] 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 (24h).

[0008] Patent application CN1144563 also describes copolymers of polyols, aliphatic diacids and itaconic acid, and in particular copolymers of glycerol, sebacic acid and itaconic acid. However, the inventors have demonstrated that the process for preparing CN1144563 by polycondensation was not reproducible. Indeed, under the conditions described, uncontrolled parasitic reactions (in particular crosslinking reactions) linked to the reactivity of the α,[3-unsaturated double bonds of itaconic acid are observed, reactions which induce heterogeneity of the functional copolymer, and which increase the viscosity of the product obtained until it solidifies, which makes it impossible to use in applications as a coating or in a 3D printing process for example.

[0009] 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 STATEMENT OF THE INVENTION

[0010] 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 itaconic crosslinking agent, in the presence of a stabilizing agent.

[0011] 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.

[0012] 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:

[0013] 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,

[0014] b) Heating the mixture from step a) in the presence of a stabilizing agent for a time sufficient to form a photocrosslinkable functionalized copolyester,

[0015] c) Cooling and recovery of the photocrosslinkable functionalized copolyester.

[0016] According to another aspect, the invention relates to a photocrosslinkable copolyester of glycerol and of 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.

[0017] According to another aspect, the invention relates to a photocrosslinkable composition comprising a photocrosslinkable copolyester according to the invention, and optionally, a photoinitiator.

[0018] According to another aspect, the invention relates to a process for preparing a crosslinked copolyester by photocrosslinking, comprising a step of UV irradiation of the photocrosslinkable composition or the photocrosslinkable copolyester of the invention.

[0019] 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.

[0020] According to another aspect, the invention relates to the use of a photocrosslinkable composition or a photocrosslinkable copolyester according to the invention for the preparation of a product by 3D printing. DETAILED DESCRIPTION OF THE INVENTION

[0021] For the purposes of the present invention, the term “a” or “an” means “one or more” or “at least one”.

[0022] 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.

[0023] By "approximately" is meant in the present description that the value concerned may be 10% lower or higher, in particular 5%, in particular 1%, than the indicated value.

[0024] Glycerol is a triol with the following formula: OH

[0025] The compounds mentioned in the description may be of fossil or biosourced origin. In the latter case, they may be, partially or totally, derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of materials already in use, i.e. they may be, partially or totally, derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. This includes monomers, i.e. in particular glycerol, the dicarboxylic acid monomer and the itaconic crosslinking agent.

[0026] For the purposes of the present invention, the term “photocrosslinkable” polymer (including a copolyester) means 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.

[0027] For the purposes of the present invention, the term "ambient temperature" means a temperature generally between 15°C and 40°C, preferably between 20°C and 30°C, in particular approximately 25°C.

[0028] By "atmospheric pressure" is meant here a pressure of approximately 1 bar.

[0029] 1. Process for functionalizing a photocrosslinkable copolyester

[0030] The invention relates to a process for functionalizing a copolyester of glycerol and a dicarboxylic acid monomer, comprising the following steps:

[0031] 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,

[0032] b) Heating the mixture from step a) in the presence of a stabilizing agent for a time sufficient to form a photocrosslinkable functionalized copolyester,

[0033] c) Cooling and recovery of the photocrosslinkable functionalized copolyester.

[0034] 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 know how to adapt the type and number of reactor(s) necessary for the process.

[0035] Preferably, steps (a) and (b) are carried out under an inert atmosphere, in particular under a nitrogen (N2) atmosphere. Itaconic crosslinking agent

[0036] 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 temperature less than or equal to 100°C), which makes it possible to reduce reaction times.

[0037] Covolyester of slycerol and a dicarboxylic acid monomer

[0038] 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 portion and an aromatic portion. 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.

[0039] 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-C2o)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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] Preferably, the dicarboxylic acid monomer comprises or consists of sebacic acid.

[0045] According to preferred variants of the invention, the dicarboxylic acid monomer, the glycerol and the itaconic crosslinking agent are the only monomers during the polycondensation. Very preferably, the sebacic acid monomer and the glycerol are the only monomers constituting the copolyester of glycerol and a dicarboxylic acid monomer.

[0046] Advantageously, the glycerol / dicarboxylic acid monomer molar ratio varies from Vis at 10 / 1, especially from 1 / 1 to 5 / 1, preferably from 1 / 1 to 2 / 1.

[0047] The copolyester of glycerol and a dicarboxylic acid monomer (hereinafter called non-functionalized copolyester) advantageously has one or more of the following characteristics:

[0048] - a number-average molar mass (Mn) of the non-functionalized copolyester su less 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;

[0049] - a number-average molar mass (Mn) of the non-functionalized copolyester in less than or equal to 10,000 g / mol, preferably less than or equal to 3500 g / mol, preferably less than or equal to 3000 g / mol;

[0050] - a dispersity D (Mw / Mn) of the non-functionalized copolyester less than 10, of preference less than or equal to 8;

[0051] - a residual monomer level less than or equal to 5% by weight of the weight of the co non-functionalized polyester;

[0052] - a rate of units (1,2,3-triacylglyceride) less than or equal to 20 mol% relative to all the units of the non-functionalized copolyester;

[0053] - a molar ratio of the (1,3-diacylglyceride) unit to the (1,2-diacylglyceride) unit greater than 1 of the non-functionalized copolyester.

[0054] The copolyester of glycerol and a dicarboxylic acid monomer can be obtained in particular by implementing the processes described in EP3149067 and EP1448656.

[0055] The number-average molar mass (Mn), the mass-average molar mass (Mw), and the dispersity (also called polydispersity and noted D, which is the Mw / Mn ratio), can be measured in a known manner by size exclusion chromatography (SEC) analysis, in particular as described below.

[0056] The level of residual monomers as well as the level of units (1,2,3-triacylglyceride) is measured in a known manner by 13C NMR, where appropriate combined with 2D HSQC / HMBC and 13C NMR experiments, as described below.

[0057] 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 index, 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 and then KOH determination. The hydroxyl index is then easily converted by a person skilled in the art into mmol of free OH / g of copolyester.

[0058] The number of free hydroxyls of the non-functionalized copolyester, noted N0H and expressed in mol is then obtained simply by multiplying the free hydroxyl content by the mass of non-functionalized copolyester.

[0059] 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 agent

[0060] As used herein, a “stabilizing agent” means a compound that limits (or even eliminates) side reactions of the double bond of the function itaconate, such as radical reactions leading to crosslinking in controlled polymer reaction, or Michael reactions. Preferably, the stabilizing agent does not react with the double bond with significant yields, or reacts with reversible manner. For example, the stabilizing agent may carry out a reaction Michael addition reaction in a reversible manner. It is therefore a nucleophilic compound little reactive towards the crosslinking agent such as a phenol or aniline.

[0061] A phenol is an organic compound containing a phenol function: ,.OH, 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-C6 alkyl group.

[0062] An aniline is understood to be an organic compound comprising an aniline function: , , NHRn with Rn representing H or a C1-C6 alkyl group, substituted or not ' I substituted, in particular by one or more substituents chosen from a halogen atom, -NO2, or a C1-C6 alkyl, C1-C6 alkoxy, NH-C1-C6 alkyl group.

[0063] According to a first variant, the stabilizing agent comprises or consists of a compound of general formula R^ (rX—J • pk* XH

[0064] in which

[0065] X represents O or NRn, with Rn representing H or a C1-C6 alkyl group,

[0066] Ri represents H, -CO-aryl or -CO-heteroaryl,

[0067] R independently represents H, a halogen atom, -NO2, -OH, a C1-C6 alkoxy group, -COOH, -COO-C1-C6 alkyl, NH-C1-C6 alkyl, -SR2, or a C1-C6 alkyl group optionally substituted with an OR2 or SR2 group,

[0068] R2 independently represents a C1-C8 alkyl group and

[0069] p is a number ranging from 1 to 4, preferably 1 or 2.

[0070] Preferably, p is 1 or 2, and R independently represents H, -OH, -COOH, a C1-C6 alkyl group optionally substituted by an SR2 group in which R2 re has a C1-C8 alkyl group, or a C1-C6 alkoxy group. Advantageously, R1 represents H or -CO-phenyl.

[0071] For the purposes of the present invention, the term “halogen atom” or “halogen” means fluorine, chlorine, bromine and iodine atoms.

[0072] By “(Ch-CL) alkyl” group is meant, within the meaning of the present invention, a saturated, linear or branched monovalent hydrocarbon chain, comprising 1 to 6, preferably 1 to 4, carbon atoms. By way of example, mention may be made of methyl, ethyl, propyl, isopropyl, butyl, pentyl or hexyl groups.

[0073] By “(GQ) alkoxy” group is meant, for the purposes of the present invention, a (Ci-C6)alkyl group, as defined above, linked to the rest of the molecule via an oxygen atom. By way of example, mention may be made of the methoxy, ethoxy, n-propoxy, iso-propoxy, n-butoxy, t-butoxy, n-pentoxy, or n-hexoxy groups.

[0074] 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.

[0075] 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, oxa-diazolyl, thiadiazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, quinolyl, isoquinolyl, quinoxalyl or indyl.

[0076] The stabilizing agent can therefore be used alone or in a mixture.

[0077] Typically, these are aniline, phenol, methoxyphenol (especially 4-methoxyphenol or guaiacol), syringol, 4,6-bis(octylthiomethyl)-o-cresol and / or 2-hydroxy-4-methoxybenzophenone.

[0078] The quantity of stabilizing agent introduced is advantageously between 0.01% and 5% by mass relative to the total mass of the monomers, preferably between 0.1% and 2%, preferably between 0.5% and 1.6%. Step a)

[0079] Step (a) of bringing the non-functionalized copolyester into contact with an itaconic crosslinking agent is typically carried out at a temperature of between 20°C and 200°C. When the itaconic crosslinking agent is itaconic acid, then step (a) is preferably carried out between 100°C and 180°C, in particular between 110°C and 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.

[0080] According to one embodiment, the contacting is carried out in the absence of solvent or diluent.

[0081] During 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 Cyrene™ (dihydrolevoglucosenone), 1,2,3-trimethoxypropane), preferably bio-sourced, or water. Preferably, the solvent is water.

[0082] 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 can be implemented in a known manner.

[0083] 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.

[0084] According to other particular variants of the invention, the contacting is carried out by the introduction of the itaconic crosslinking agent into a mixture comprising the non-functionalized copolyester and water.

[0085] The mixing of the non-functionalized copolyester and the water may take place at room temperature (about 23°C at atmospheric pressure) in a reactor, which may be the same as that of step (a). This pre-mixing step may optionally comprise heating the non-functionalized copolyester and the water, for example at a temperature ranging from about 50°C to 100°C. The medium is then heated for a time sufficient to dissolve or disperse the non-functionalized copolyester homogeneously 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.

[0086] According to any one of these variants, the itaconic crosslinking agent can 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.

[0087] 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.

[0088] 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.

[0089] The stabilizing agent can also be added during step a). Step b)

[0090] In step (b), the functionalization reaction comprises an esterification of a free alcohol function of the glycerol copolyester and of 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.

[0091] When the itaconic crosslinking agent is itaconic acid, one water molecule is formed for each ester bond formed.

[0092] Thus, in this embodiment, a by-product of the functionalization reaction is water.

[0093] According to a particular variant of the invention, the functionalization step will be carried out under conditions allowing the water to be removed from the reaction medium (or from the reactor). Removing the water as it is formed during the 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).

[0094] Furthermore, when the itaconic crosslinking agent is itaconic acid, measuring the quantity of water eliminated also makes it possible to monitor the progress of the functionalization reaction.

[0095] To remove water during the functionalization step, a reactor and temperature and pressure conditions suitable for distilling the water can be used.

[0096] 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.

[0097] 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.

[0098] 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 diaphragm pump, a rotary pump, etc. Such an intermediate pressure is less than 1 bar and varies, for example, from 800 mbar to 50 mbar.

[0099] The reaction medium is then placed under reduced pressure, and preferably under vacuum. Here, "vacuum" means that the pressure is lowered until a value around Imbar is reached.

[0100] The heating step b) is preferably carried out at a temperature 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 at a reaction temperature between 110°C and 200°C, preferably between 120°C and 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.

[0101] 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.

[0102] 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.

[0103] The catalyst may in particular comprise or consist of a Brpnstedt acid (such as, for example, sulfuric acid, para-toluene sulfonic acid) or a Lewis acid (such as, for example, A1C13, TiCl4, TiOBu4, butylstannoic acid, metal salts of trifluoromethanesulfonates 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.

[0104] Preferably, the catalyst comprises or consists of a food grade catalyst.

[0105] By "food grade catalyst" is meant a catalyst suitable for food contact (for animals and humans) which meets requirements guaranteeing 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.

[0106] The food grade catalyst is advantageously based on tin, 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 function carboxyl (-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).

[0107] According to preferred variants of the invention, the catalyst is food grade monobutyltin oxide (or stannoic acid).

[0108] 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. Particularly preferred is the catalyst monobutyltin oxide marketed under the name FASCAT 9100 by the company PMC Organometallix.

[0109] 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.

[0110] 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.

[0111] 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 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 from carbons carrying a free hydroxyl function or the -COOH functions carried by the free diacids of the carboxylic diacid monomer or of the itaconic crosslinking agent can be monitored.

[0112] Alternatively, when the second functionalization step (b) is carried out with stirring, it may be considered that the step is 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.

[0113] Advantageously, the heating of step b) is carried out for 30 minutes to 12 hours, preferably for 1 hour to 5 hours. Subsequent steps

[0114] The process may also comprise a subsequent step of post-treatment of the functionalized copolyester obtained, in particular to reduce the level of re- itaconic crosslinker 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 composition

[0115] The 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.

[0116] 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 (13C NMR).

[0117] 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 remainder of the itaconic acid used has completely reacted, the itaconic functionalization rate corresponds to the difference between the amount of itaconic acid used in the reaction (or initial), and the amount of free itaconic acid, these amounts being expressed in mmol / g of polymer obtained.

[0118] The itaconic functionalization rate is typically measured by carbon 13 nuclear magnetic resonance (13C NMR). 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.

[0119] 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.

[0120] 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.

[0121] The photocrosslinkable copolyester may also have at least one of the characteristics- following characteristics:

[0122] - a number-average molar mass (Mn) of the photocrosslinkable copolyester su less 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;

[0123] - a number-average molar mass (Mn) of the photocrosslinkable copolyester in less than or equal to 10,000 g / mol, preferably less than or equal to 3500 g / mol, preferably less than or equal to 3000 g / mol;

[0124] - a dispersity D of the photocrosslinkable copolyester less than 12, preferably in less than or equal to 8, in particular less than or equal to 6;

[0125] - a residual monomer level of less than 25% by weight, preferably less or equal to 20% by weight, relative to the weight of the photocrosslinkable copolyester; and / or

[0126] - a rate of units (1,2,3-triacylglyceride) less than 25 mol%, preferably less or equal to 20 mol%, in particular 15 mol% or less, relative to all the units of the photocrosslinkable copolyester.

[0127] The photocrosslinkable copolyester may also have at least one of the following characteristics:

[0128] - a molar ratio of the (1,3-diacylglyceride) unit to the (1,2-diacylglyceride) unit greater than 1 of the non-functionalized copolyester;

[0129] - a glass transition temperature (Tg) of -100°C to +30°C, preferably of -80°C to +10°C, preferably -60°C to 0°C, especially -50°C to -25°C. 3. Photocrosslinkable composition

[0130] The invention also relates to a photocrosslinkable composition comprising: • a photocrosslinkable copolyester as described herein, and • optionally, a photoinitiator.

[0131] As used herein, a “photoinitiator” means a compound which, when exposed to light, and in particular to UV light, produces a radical which will allow the initiation of the photocrosslinking reaction, which is generally radical.

[0132] 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.

[0133] 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 which proceed by homolytic cleavage of a CC bond, in particular by Norrish I type cleavage. The molecules involved are generally ketones. aromatics which undergo, after absorption of light, a homolytic cleavage of the bond in position a relative to the carbonyl group (Norrish I type 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 French-speaking Colloquium on Optical Methods and Techniques for Industry / 16th French congress of the FLUVISU / SFO club (CMOI-FLUVISU 2015), Club CMOI - Société Française d'Optique, Nov 2015, Pleumeur-Bodou, France, pp. 124-129. hal-01583762).

[0134] Type I photoinitiators are in particular any benzoyl radical precursor: Type ] R 4—................................> «ARyfe-R \--? Q X--ÿ 0 two Radkâl bsnzyte,

[0135] Type II photoinitiators are in particular any precursor of a ketyl radical (inert) and with a radical precursor (an amine). Type h 0 - y V....: /

[0136] Mention may in particular be made of 2,4,6-Trimethylbenzoyldi-Phenylphosphinate (TPO L), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), or 1-Hydroxycyclohexyl phenyl ketone (HCHPK).

[0137] 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.

[0138] 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.

[0139] 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.

[0140] A phytosanitary product, plant protection product or phytopharmaceutical product is a substance or 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 (particularly soils).

[0141] A "biostimulant" means 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, abiotic stress tolerance, quality characteristics, availability of nutrients confined in the soil or rhizosphere (in accordance with EU Regulation 2019 / 1009). Biostimulants may be natural preparations of low concern (NPPCs). NPPCs are:

[0142] - Either natural substances for biostimulant use (SNUB).

[0143] - Either basic substances.

[0144] Basic substances are defined by Article 23 of Regulation (EC) No 1107 / 2009. These are substances of phytosanitary interest but whose main use is other than plant protection (e.g. foodstuffs).

[0145] 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.

[0146] Preferably, the formulation according to the invention comprises a phytosanitary active ingredient and / or a biostimulant which is a precursor of ethylene, preferably ethephon.

[0147] 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 process

[0148] 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.

[0149] Advantageously, the irradiation is carried out at a temperature between 15°C and 30°C.

[0150] Irradiation is typically conducted at atmospheric pressure.

[0151] Preferably, the irradiation is carried out at a wavelength between 250 nm and 500 nm, preferably between 300 and 450 nm, preferably between 350 and 400 nm, especially around 365 nm.

[0152] Advantageously, the irradiation is carried out at a power of 5 to 25 mW / cm2, in particular 8 to 20 mW / cm2.

[0153] Advantageously, the photoinitiator is present at a content 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.

[0154] The photoinitiators are as defined above.

[0155] The photocrosslinkable composition or the photocrosslinkable copolyester is generally irradiated for a period of between 1s and 5h.

[0156] Preferably, the photoinitiator is added to the composition or crosslinkable copolyester at room temperature. This avoids any undesirable crosslinking reaction.

[0157] 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

[0158] 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.

[0159] According to a variant, the crosslinked copolyester is therefore capable of being obtained by the photocrosslinking process described above.

[0160] 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 even azos, such as for example razobiisobutyronitrile (AIBN), in a dispersed medium or not.

[0161] The crosslinked copolyester advantageously has: • a glass transition temperature Tg between -100°C and +30°C, preferably between -80°C and +10°C, in particular between -60°C and 0°C, and / or • a storage modulus G' at 37°C and at 10 Hz greater than or equal to 0.02 MPa.

[0162] 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.

[0163] The products are for example implants, patches diffusing active ingredients, particles (including micro- and macroparticles), coatings, fibers and threads, ... DESCRIPTION OF FIGURES

[0164] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the attached drawings.

[0165] [Fig.l] represents a simplified reaction scheme of the reactions involved in the synthesis of poly(glycerol-co-sebacate-co-itaconate) according to Example 1.

[0166] [Fig.2] represents the storage modules G* measured on the copolyesters of the examples 2 and 3, after photocrosslinking in the presence or absence of photoinitiator. EXAMPLES

[0167] The following examples are given for illustrative purposes, but should in no way be considered as limiting the present invention. Materials and methods Structural analysis: NMR

[0168] The 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 quantitative 'H NMR experiment uses a single 30° pulse sequence and a repetition delay of 3 seconds between each of the 64 acquisitions. The samples are solubilized in a deuterated solvent, deuterated acetone (acetone d6) unless otherwise indicated. The 'H NMR spectrum coupled with the 2D HSQC / HMBC and 13C NMR experiments allow the quantification of the microstructure of the different functional PGS (see attribution tables).

[0169] The itaconic conversion rate corresponds to the molar percentage of grafted itaconic crosslinking agent / (grafted + free itaconic crosslinking agent). Macrostructure analysis: SEC RI

[0170] The SEC (Size Exclusion Chromatography) technique allows macromolecules in solution to be separated 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.

[0171] Without being an absolute method, SEC makes it possible to understand the distribution of molar masses 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 (D = Mw / Mn), also called "dispersity", calculated.

[0172] 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: DSC

[0173] The thermal analysis of the 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 to -30°C / minute, 6. isothermal at -100°C for 2 minutes, 7. from -100°C to 200°C at 10°C / minute.

[0174] The measurement carried out at ramp 7 corresponds to the Tg of the crosslinked copolyester. Structural analysis: MIR

[0175] The kinetic monitoring of photocrosslinking was carried out with a mid-infrared spectrometer (MIR) with wavelengths between 4000 and 650cm *, (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 / cm2 irradiating at a distance of 5cm from the sample. The monitoring of the crosslinking is carried out by following the disappearance of the C=C band of itaconate at 1638cm 1 as a function of the irradiation time under UV (measurement of the area of ​​the peak of the band at 1638cm').

[0176] Measurement of mechanical properties: storage modulus G'

[0177] The mechanical properties are measured on an Anton Paar rheometer model MCR302, equipped with a 20mm diameter plane-plane geometry.

[0178] 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 tem- room temperature.

[0179] This sample is subjected to a frequency sweep from 0.1 to 100 Hertz in sinusoidal shear stress at 0.1% deformation, 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).

[0180] The moduli G*, G' and G” are calculated according to the equations below: a G * - G' -L rGt!

[0181] with: • o the measured stress and e the deformation imposed on the sample. • G', the real part of G*, called the conservation module, which characterizes the stiffness 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 loss modulus or loss modulus sipation, which characterizes viscous behavior (energy dissipated in the form of heat).

[0182] Example 1: Synthesis of non-functionalized glycerol-co-sebacate copolyester, noted PGS

[0183] 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.

[0184] 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 D = 2.7, and a free hydroxyl content of 5 mmol / g.

[0185] Example 2: Synthesis of photocrosslinkable copolyesters according to the invention: itaconate-grafted glycerol-co-sebacate copolyester

[0186] In the following we will note PGS-IA a copolyester: glycerol-co-sebacate grafted itaconate obtained with an itaconic acid as crosslinking agent, and PGS-ANHYTA a copolyester: glycerol-co-sebacate grafted itaconate obtained with an itaconic anhydride as a crosslinking agent. Comparative process without stabilizer:

[0187] 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 heated to 130°C gradually with stirring and under 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 is cooled to room temperature. Process of the invention with stabilizer:

[0188] 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 equivalent relative to the 1,3-diacylglyceride units of the PGS of Example 1 (majority unit)) and the 4-methoxyphenol as 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 cooled to room temperature.

[0189] The methods of tests 1 to 6 are carried out without solvents.

[0190] The reaction conditions of the different examples carried out are summarized in Tables 1 and 2. Test 1 Test 2 Test 3 Test 4 Test 5 Itaconic crosslinking agent Itaconic anhydride Itaconic anhydride Itaconic anhydride Itaconic acid Itaconic acid Nature of stabilizer 4-methoxyph enol 4-methoxyph enol 4-methoxyph enol 4-methoxyph enol 4-methoxyph enol Duration of heating step 3h30 3h30 20h30 3h 3h Target temperature 80°C 130°C 130°C 130°C 130°C Pressure Atm. Atm Atm. Atm. Atm. Appearance of PGS-IA or PGS-ANHY TA obtained after cooling orange-yellow viscous liquid orange-yellow viscous liquid orange gel insoluble in acetone and THF orange-yellow viscous liquid orange-yellow viscous liquid Test 6 Test 7 Test 8 Test 9 Test 10 Itaconic crosslinking agent Itaconic acid Itaconic acid Itaconic acid Itaconic acid Itaconic acid Nature of stabilizer 4-methoxy phenol 4-methoxy phenol Guaicol Irganox® 1520L MEHQ + oxybenzone Duration of heating step 3h45 3h20 3h30 3h30 3h30 Target temperature 130°C 140°C 130°C 130°C 130°C Pressure Atm. Under reduced pressure (less than 10 mbar) Atm. Atm. Atm. Appearance of PGS-IA or PGS-ANHYTA obtained after cooling orange-yellow viscous liquid orange-yellow viscous liquid orange-yellow viscous liquid orange-yellow viscous liquid orange-yellow viscous liquid

[0193] 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) 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 mol% of 2-acylglyceride / polymer «0.3 0 «0.3 «0.5 «0.5 « 1.2 mol% 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 grafted itaconic crosslinking agent / polymer « 11 « 17 « 12 « 10 «9 «9 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 « 6 Quantity of OH in the product (mmol / g) 2.3 2 2.5 3.3 3.2 7.7 Quantity of unsaturations in the product* (mmol / g) 1.2 1.2 2.3 2.2 2.4 1.2

[0195] *Takes into account the unsaturations of the free and grafted itaconic acid or anhydride

[0196] Calculation of the number-average (Mn) and mass-average (Mw) molar masses and of the dispersity by SEC analysis (dissolution in THF, poly(styrene) standard) of the 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) Mn (g / mol) Mw (g / mol) Dispersity, D Test 1 2127 6235 2.9 Test 2 2017 7664 3.8 Test 4 2318 17791 7.4 Test 5 2271 29113 12.8 Test 6 1507 4713 3.1 Test 7 1084 2522 2.3 Test 8 2141 6054 2.8 Test 9 2183 6509 3.0 Test 10 2213 6660 3.0

[0198] Example 3 (reference): Synthesis of a reference photocrosslinkable copolyester: the copolyester:glycerol-co-sebacate grafted methacrylate, noted PGS-MA according to Journal of Biomaterials Applications, 4,1114-1130, 2020 and Macromol. Rapid Commun, 41,1900484, 2020.

[0199] 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% by mass), at room temperature, with stirring and under nitrogen. After dissolution, compounds, methacrylic anhydride (50% by mass relative to PGS) is added at 0°C by controlled addition. The reaction medium is allowed to return to room temperature and maintained under stirring and 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 evaporated. A white viscous liquid is obtained, corresponding to PGS-MA, then cooled to room temperature.Example 4: Photocrosslinking.

[0200] The photocrosslinkable copolyesters of Examples 2 and 3 are crosslinked under a UV lamp (LED 365nm, 9Mw / cm2) for an exposure time of 1 hour (distance between the lamp and the surface of the sample: 5cm), 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 into 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.

[0201] Infrared analysis validates the almost total disappearance of the C=C band of itaconate at 1638cm *, which confirms the effectiveness of the photocrosslinking reaction.

[0202] Table 5 reports the measurements of the glass transition temperatures Tg of the copolyesters with and without photoprotector.

[0203] Measurement of Tg by differential scanning calorimetry analysis of PGS-IA or PGS-ANHYTA obtained in tests 1 to 6

[0204] [Tables5] Oligomer Photoinitiator Tg - midpoint after one hour of UV irradiation (°C) Test 2 Without photoinitiator -29 HCHPK -16 TPOL -12 Test 5 Without photoinitiator -31 HCHPK -21 TPOL -22

[0205] The rheology measurements carried out on the crosslinked copolyesters thus obtained are reported in [Fig.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

[0206] The method of the invention is simple, rapid, 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.

[0207] The photocrosslinkable copolyesters of Example 2 are obtained from non-toxic and bio-sourced 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% bio-sourced / bio-sourced. Bibliographic references:

[0208] CN1144563 EP3149067 WO2019 / 215441 WO2021 / 078962 Rueben et al. MRS Advances (2018), 3(27), 1551-1556

Claims

Claims

1. 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 selected from itaconic acid, itaconic anhydride and mixtures thereof, b. Heating the mixture of 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.

2. A method according to claim 1, wherein the dicarboxylic acid monomer has the formula [HOOC-(CH2)n-COOH], wherein n is a number ranging from 1 to 30, preferably a number ranging from 5 to 10, advantageously sebacic acid (n=8).

3. A method according to claim 1 or 2, wherein the heating of step b) comprises a step of maintaining at a reaction temperature of between 20°C and 250°C.

4. A method according to any one of claims 1 to 3, wherein the stabilizing agent is a phenol or an aniline, especially aniline, phenol, methoxyphenol (especially 4-methoxyphenol or guaiacol), syringol, 4,6-Bis(octylthiomethyl)-o-cresol and / or 2-hydroxy-4-methoxybenzophenone.

5. A method according to any one of claims 1 to 4, wherein step b) of heating is carried out at a pressure of between 0.0001 and 2 bar.

6. A method according to any one of claims 1 to 5, wherein the heating of step b) is carried out for 30 minutes to 12 hours.

7. 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.

8. Photocrosslinkable copolyester according to claim 7, obtainable by the process according to any one of claims 1 to 6.

9. Photocrosslinkable copolyester according to any one of claims 7 to 8, further having at least one of the following characteristics: - its number-average molar mass (Mn) is greater than or equal to 500 g / mol, preferably greater than or equal to 1500 g / mol; - its number-average molar mass (Mn) is less than or equal to 10000 g / mol, preferably less than or equal to 3500 g / mol; - its dispersity D (Mw / Mn) is less than or equal to 12, preferably less than or equal to 8; - a residual monomer content less than or equal to 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 less than or equal to 25 mol%, preferably less than or equal to 20% relative to all the units of the photocrosslinkable copolyester.

10. Photocrosslinkable composition comprising • A photocrosslinkable copolyester according to any one of claims 7 to 9, and • optionally, a photoinitiator, advantageously at a content less than or equal to 5% by mass relative to the total mass of the composition.

11. A process for preparing a crosslinked copolyester by photocrosslinking, comprising a step of UV irradiation of the photocrosslinkable composition of claim 10 or a photocrosslinkable copolyester according to any one of claims 7 to 9.

12. Crosslinked copolyester obtained by crosslinking, in particular thermal crosslinking and / or photocrosslinking, of the photocrosslinkable copolyester of any one of claims 7 to 9 or of a photocrosslinkable composition according to claim 10.

13. Crosslinked copolyester according to claim 12, obtainable by the process of claim 11.

14. Crosslinked copolyester according to claim 12 or 13, characterized in that it has: - a glass transition temperature Tg between - 100°C and +30°C, preferably between -80°C and +10°C, in particular between -60°C and 0°C, and / or - a storage modulus G' at 37°C and 10 Hz greater than or equal to 0.02 MPa.

15. Use of the photocrosslinkable composition of claim 10 or the photocrosslinkable copolyester of any one of claims 7 to 9 for the preparation of a product by 3D printing.

Images