Photocrosslinkable copolyesters and methods for obtaining the same by post-functionalization

Abstract

The present invention relates to a process for functionalizing a copolyester of glycerol and dicarboxylic acid monomers, said process comprising the following steps: a) contacting a copolyester of glycerol and dicarboxylic acid monomers and an itaconic crosslinking agent selected from itaconic acid, itaconic anhydride and mixtures thereof, b) heating the mixture obtained from step a) in the presence of a stabilizer for a time sufficient to form a photo-crosslinkable functionalized copolyester, c) cooling and recovering the photo-crosslinkable functionalized copolyester. The present invention also relates to a photo-crosslinkable copolyester, in particular a photo-crosslinkable copolyester obtainable by the process, to a photo-crosslinkable composition comprising said photo-crosslinkable copolyester, to a crosslinked copolyester obtained by crosslinking, advantageously photo-crosslinking, and to the use thereof.

Description

Technical Field

[0001] This invention relates to photocrosslinkable copolyesters, particularly photocrosslinkable copolyesters containing unsaturated bonds. The invention also relates to methods for their preparation and their uses, particularly in crosslinking methods (e.g., 3D printing methods), and the corresponding crosslinked copolyesters. Background Technology

[0002] Biodegradable polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), and their copolymers (e.g., poly(glycerol sebacate) (PGS)), are now widely used in the preparation of biomaterials, which can be used as medical biomaterials or as surface coatings.

[0003] These polyesters are typically produced by melt polycondensation of glycerol and diacid under high temperature and reduced pressure for a considerable reaction time.

[0004] However, with the development of 3D printing applications, it is necessary to operate at temperatures close to ambient temperature and atmospheric pressure, and preferably with shorter reaction times. Therefore, new materials and their preparation methods are being sought that can meet the requirements of 3D printing applications while maintaining satisfactory thermomechanical properties.

[0005] Similarly, traditional methods are not suitable for integrating temperature-sensitive organic molecules into biomaterials. Therefore, photocrosslinking materials have been developed through the copolymerization of glycerol with sebacic acid and unsaturated acids, where the unsaturated groups can subsequently undergo photocrosslinking reactions, for example, under ultraviolet light irradiation (see WO2019 / 215441 and WO2021 / 078962 for details). However, the unsaturated acids used are often derivatives of (meth)acrylic acid, which are toxic, posing problems for their handling and the final products, which typically contain at least trace amounts of these substances.

[0006] Therefore, other authors have turned to itaconic acid (an unsaturated acid) as a comonomer. This comonomer is particularly noteworthy because, unlike derivatives of (meth)acrylic acid, it is non-toxic and readily available from biological sources, enabling the production of photocrosslinkable polymers that can be used in a wide range of applications, including biomedical applications, with a relatively low carbon footprint.

[0007] Rueben et al. (MRS Advances (2018), 3(27), 1551-1556) correspondingly described the synthesis of copolymers of glycerol, sebacic acid and itaconic acid, but the preparation time was particularly long (24 hours).

[0008] Patent application CN114456335 also describes copolymers of polyols, aliphatic diacids, and itaconic acid, particularly copolymers of glycerol, sebacic acid, and itaconic acid. However, the inventors have demonstrated that the polycondensation preparation method in CN114456335 cannot be reproduced. Specifically, under the stated conditions, uncontrolled side reactions (particularly crosslinking reactions) related to the reactivity of the α,β-unsaturated double bonds of itaconic acid are observed. These reactions lead to heterogeneity of the functionalized copolymer and increase the viscosity of the resulting product until it solidifies, making the copolymer unusable in applications such as coatings or 3D printing.

[0009] Therefore, there is a need for photocrosslinkable copolyesters whose preparation methods are simple, reliable, and repeatable, and particularly suitable for industrial-scale production, while avoiding uncontrolled side reactions. The crosslinking time should preferably be short and suitable for 3D printing methods, especially at ambient temperature and atmospheric pressure. The monomers used are preferably non-toxic and bioavailable to limit the carbon footprint of the resulting copolyester. Furthermore, the processing temperature is typically lower than conventional methods and is advantageously compatible with heat-sensitive organic molecules. Summary of the Invention

[0010] Therefore, in a first aspect of the present invention, a method for preparing a photocrosslinkable copolyester is provided, the method comprising polycondensation of a copolyester of glycerol and a dicarboxylic acid monomer and at least one itaconic acid crosslinking agent in the presence of a stabilizer.

[0011] The stabilizer has the effect of limiting or even eliminating side reactions. The polycondensation yield is correspondingly improved, and the photocrosslinkable copolyester has a viscosity suitable for the intended application (especially 3D printing) and improved purity.

[0012] Therefore, in a first aspect, the present invention relates to a method for copolyesterifying glycerol with a dicarboxylic acid monomer, the method comprising the following steps: a) Contact glycerol with a copolyester of dicarboxylic acid monomers and an itaconic acid crosslinking agent selected from itaconic acid, itaconic anhydride, and mixtures thereof. b) In the presence of a stabilizer, the mixture obtained from step a) is heated for a time sufficient to form a photocrosslinkable functionalized copolyester. c) Cooling and recycling of photocrosslinkable functionalized copolyesters.

[0013] On the other hand, the present invention relates to a photocrosslinkable copolyester of glycerol and dicarboxylic acid monomers, wherein the degree of itaconic acid functionalization is greater than or equal to 0.004 mmol / g, preferably greater than or equal to 0.04 mmol / g, and more preferably greater than or equal to 1 mmol / g.

[0014] On the other hand, the present invention relates to a photocrosslinkable composition comprising the photocrosslinkable copolyester of the present invention and an optional photoinitiator.

[0015] On the other hand, the present invention relates to a method for preparing crosslinked copolyesters by photocrosslinking, the method comprising the step of irradiating the photocrosslinkable composition or photocrosslinkable copolyester of the present invention with ultraviolet light.

[0016] On the other hand, the present invention relates to a crosslinked copolyester obtained by crosslinking the photocrosslinkable copolyester of the present invention or the photocrosslinkable composition of the present invention.

[0017] On the other hand, the present invention relates to the use of the photocrosslinkable composition or photocrosslinkable copolyester of the present invention for the preparation of products by 3D printing. Invention Details For the purposes of this invention, the term "a" or "an" means "one or more" or "at least one".

[0019] For the purposes of this invention, a numerical range expressed as "between a and b" represents a numerical range within the range strictly greater than a to strictly less than b (i.e., excluding the endpoints a and b), while any numerical range expressed as "a to b" represents a numerical range from a to b (i.e., including the strict endpoints a and b).

[0020] In this specification, the term “about” should be understood to mean that the value may be 10% lower or higher than the indicated value, especially 5%, and particularly 1%.

[0021] Glycerol is a triol with the following formula: .

[0022] The compounds mentioned in this specification may be fossil-derived or bio-based. In the latter case, they may be obtained, in whole or in part, from biomass or from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also be derived from the recycling of used materials, i.e., they may be derived, in whole or in part, from recycling processes or from raw materials that themselves originate from recycling processes. This particularly relates to monomers, i.e., especially glycerol, dicarboxylic acid monomers, and itaconic acid crosslinking agents.

[0023] For the purposes of this invention, "photocrosslinkable" polymers (including copolyesters) should be understood as polymers that undergo a crosslinking reaction under the influence of light, more specifically, ultraviolet light, thereby altering their chemical structure. Generally, these are free radical reactions in the presence of a photoinitiator.

[0024] For the purposes of this invention, "ambient temperature" should be understood to generally refer to a temperature between 15°C and 40°C, preferably between 20°C and 30°C, and especially about 25°C.

[0025] In this article, "atmospheric pressure" should be understood as a pressure of approximately 1 bar.

[0026] 1. A method for functionalizing photocrosslinkable copolyesters This invention relates to a method for copolyesterifying glycerol with a dicarboxylic acid monomer, the method comprising the following steps: a) Contact glycerol with a copolyester of dicarboxylic acid monomers and an itaconic acid crosslinking agent selected from itaconic acid, itaconic anhydride, and mixtures thereof. b) In the presence of a stabilizer, the mixture obtained from step a) is heated for a time sufficient to form a photocrosslinkable functionalized copolyester. c) Cooling and recycling of photocrosslinkable functionalized copolyesters.

[0027] According to any variant of the invention, contact step a) is carried out in a reactor. Subsequent steps may be carried out in the same reactor or in different reactors. Those skilled in the art will be able to adjust the type and number of reactors required for the method, taking into account heating and pressure conditions.

[0028] Steps a) and b) are preferably carried out in an inert atmosphere, especially in a nitrogen (N2) atmosphere.

[0029] Step a) and / or step b) are advantageously carried out in the absence of inorganic acids (e.g., phosphoric acid).

[0030] Itaconic acid crosslinking agents The itaconic acid crosslinking agent is selected from itaconic acid and / or itaconic anhydride. The use of itaconic anhydride allows for the restriction of water molecule (H2O) generation during the polycondensation reaction, thereby increasing the overall yield of functionalization and / or the reaction rate, especially under potentially milder temperature conditions (especially at temperatures below or equal to 100°C), which can shorten the reaction time.

[0031] Copolyester of glycerol and dicarboxylic acid monomer The dicarboxylic acid monomer can be aliphatic, aromatic, or aliphatic / aromatic. The dicarboxylic acid monomer cannot be itaconic acid. Aliphatic / aromatic dicarboxylic acid monomers comprise both an aliphatic and an aromatic moiety. The dicarboxylic acid monomer preferably contains 4 to 36 carbon atoms. "Aliphatic" should be understood to refer to straight-chain, branched, and / or cyclic hydrocarbon groups, which can be saturated or unsaturated, but are not aromatic.

[0032] According to a preferred variant of the invention, the dicarboxylic acid monomer is aliphatic, especially saturated, and can be linear or branched, preferably (C3-C4)-3-4-5-6-6-7-8-9 ... 20 Alkyl dicarboxylic acid, more preferably (C8-C 15 )Alkyldicarboxylic acid. (Cx -C y Alkyl groups are saturated, straight-chain or branched divalent hydrocarbon groups containing x to y carbon atoms.

[0033] Dicarboxylic acid monomers advantageously include or consist of the general formula [HOOC-(CH2]). n The diacid composition of [-COOH], wherein n is a number in the range of 1 to 30, preferably a number in the range of 5 to 10.

[0034] The dicarboxylic acid monomer may be specifically selected from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, and mixtures of two or more of these dicarboxylic acids.

[0035] Preferably, the dicarboxylic acid monomer may be selected from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, and mixtures of two or more of these dicarboxylic acids.

[0036] According to a variant of the invention, the dicarboxylic acid monomer can be a mixture of at least two dicarboxylic acids. In this case, the dicarboxylic acid monomer preferably includes sebacic acid.

[0037] The dicarboxylic acid monomer preferably includes or is composed of sebacic acid.

[0038] According to a preferred variant of the invention, during the polycondensation process, the dicarboxylic acid monomer, glycerol, and itaconic acid crosslinking agent are the only monomers. Most preferably, the sebacic acid monomer and glycerol are the only constituent monomers of the copolyester of glycerol and the dicarboxylic acid monomer.

[0039] The molar ratio of glycerol to dicarboxylic acid monomers is advantageously in the range of 1 / 2 to 10 / 1, especially 1 / 1 to 5 / 1, and preferably 1 / 1 to 2 / 1.

[0040] Copolyesters of glycerol and dicarboxylic acid monomers (hereinafter referred to as nonfunctionalized copolyesters) advantageously possess one or more of the following characteristics: - The number-average molar mass (Mn) of the nonfunctionalized copolyester is 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, and advantageously greater than or equal to 2000 g / mol. - The number-average molar mass (Mn) of the nonfunctionalized copolyester is less than or equal to 10,000 g / mol, preferably less than or equal to 3,500 g / mol, and more preferably less than or equal to 3,000 g / mol. - Dispersion of nonfunctionalized copolyesters (Mw / Mn) is less than 10, preferably less than or equal to 8; - The residual monomer content is less than or equal to 5% by weight of the nonfunctionalized copolyester; - The content of 1,2,3-triacylglycerol units is less than or equal to 20 mol% relative to the total number of units in the nonfunctionalized copolyester. - The molar ratio of 1,3-diacylglycerol units to 1,2-diacylglycerol units in the nonfunctionalized copolyester is greater than 1.

[0041] Copolyesters of glycerol and dicarboxylic acid monomers can be obtained, in particular, by the methods described in EP3149067 and EP1448656.

[0042] Number-average molar mass (Mn), weight-average molar mass (Mw), and dispersion (also known as polydispersity, denoted by Mn) The ratio of Mw to Mn can be determined in a known manner by size exclusion chromatography (SEC) analysis, particularly as described below.

[0043] The content of residual monomers and the content of 1,2,3-triacylglycerol units are determined in a known manner by... 13 C NMR, combined with 2D HSQC / HMBC and, when appropriate 13 The C NMR experiment was performed as follows.

[0044] Copolyesters of glycerol and dicarboxylic acid monomers can also be characterized by the content of free hydroxyl groups or the number of free hydroxyl functional groups per gram of copolyester. The content of free hydroxyl groups is determined by NMR (typically 1000 NMR spectroscopy). 13 The hydroxyl value is determined by CNMR and expressed as moles per gram of copolyester. For example, the hydroxyl value can be measured using, for instance, the method of ASTM standard E222-23, expressed as milligrams of KOH per gram of copolyester. The method of ASTM standard E222-23 involves acetylation of the present hydroxyl groups with acetic anhydride, followed by titration with KOH. Those skilled in the art can then readily convert the hydroxyl value into millimoles of free hydroxyl groups per gram of copolyester.

[0045] The number of free hydroxyl groups in a nonfunctionalized copolyester (denoted as N) OH (and expressed in moles), which is simply obtained by multiplying the content of free hydroxyl groups by the mass of the nonfunctionalized copolyester.

[0046] Itaconic acid crosslinking agent / N OH The molar ratio is advantageously in the range of 1:100 to 2:1, especially 1:1 to 2:1.

[0047] stabilizer As used herein, "stabilizer" should be understood to mean a compound that can limit (or even eliminate) secondary reactions of the double bonds of the itaconic acid ester functional group (e.g., radical reactions or Michael reactions leading to uncontrolled crosslinking of the polymer). Preferably, the stabilizer does not react with the double bonds in significant yield, or the reaction is reversible. For example, the stabilizer can undergo a Michael addition reaction in a reversible manner. Therefore, it is a nucleophilic compound with low reactivity to crosslinking agents, such as phenol or aniline.

[0048] Phenol should be understood as referring to organic compounds containing the phenol functional group: The phenolic functional group may be substituted or unsubstituted, especially substituted by one or more substituents selected from halogen atoms, -NO2 or C1-C6 alkyl, C1-C6 alkoxy or NH-(C1-C6 alkyl) groups.

[0049] Aniline should be understood as referring to organic compounds containing the aniline functional group. , where R n Represents H or C1-C6 alkyl, which may or may not be substituted, especially by one or more substituents selected from halogen atoms, -NO2 or C1-C6 alkyl, C1-C6 alkoxy or NH-(C1-C6 alkyl) groups.

[0050] According to the first variant, the stabilizer comprises or is composed of the general formula: Compound composition in X represents O or NR n , where R n Represents H or C1-C6 alkyl, R1 represents H, -CO-aryl, or -CO-heteroaryl. R independently represents H, a halogen atom, -NO2, -OH, C1-C6 alkoxy, -COOH, -COO-(C1-C6 alkyl), NH-(C1-C6 alkyl), -SR2, or C1-C6 alkyl (optionally substituted with an OR2 or SR2 group). R2 independently represents C1-C8 alkyl, and p is a number in the range of 1 to 4, preferably 1 or 2.

[0051] Preferably, p is 1 or 2, and R independently represents H, -OH, -COOH, C1-C6 alkyl (optionally substituted with an SR2 group, wherein R2 represents C1-C8 alkyl) or C1-C6 alkoxy. R1 advantageously represents H or -CO-phenyl.

[0052] For the purposes of this invention, "halogen atom" or "halogen" should be understood to mean fluorine, chlorine, bromine or iodine atom.

[0053] For the purposes of this invention, "C1-C6 alkyl" groups should be understood to refer to monovalent saturated straight-chain or branched hydrocarbon chains having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Examples include methyl, ethyl, propyl, isopropyl, butyl, pentyl, or hexyl.

[0054] For the purposes of this invention, the term "C1-C6 alkoxy" should be understood to refer to a C1-C6 alkyl group as defined above, which is attached to the remainder of the molecule by an oxygen atom. Examples include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, n-pentoxy, or n-hexoxy.

[0055] In this document, "aryl" should be understood to refer to an aromatic hydrocarbon group, preferably containing 6 to 10 carbon atoms and comprising one or more fused rings, such as phenyl or naphthyl. Advantageously, the aryl group is phenyl.

[0056] In this article, "heteroaryl" should be understood as an aromatic group containing 5 to 10 ring atoms, one or more (preferably 1 to 4, or even more preferably 1 or 2) of which are heteroatoms, such as sulfur, nitrogen, or oxygen atoms, and the remaining ring atoms are carbon atoms. Examples of heteroaryl groups are: furanyl, thiophene, pyrrole, pyridinyl, imidazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, oxadiazolyl, thiadiazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, quinolinyl, isoquinolinyl, quinoxalinyl, or indoleyl.

[0057] Therefore, stabilizers can be used alone or in mixtures.

[0058] Typically, stabilizers are aniline, phenol, methoxyphenol (especially 4-methoxyphenol or guaiacol), 2,6-dimethoxyphenol, 4,6-bis(octylthiomethyl)-o-cresol and / or 2-hydroxy-4-methoxybenzophenone.

[0059] The amount of stabilizer introduced relative to the total mass of the monomer is advantageously between 0.01% by mass and 5% by mass, preferably between 0.1% and 2%, and more preferably between 0.5% and 1.6%.

[0060] Step a) Step a) of contacting the nonfunctionalized copolyester with an itaconic acid crosslinking agent is typically carried out at a temperature ranging from 20°C to 200°C. When the itaconic acid crosslinking agent is itaconic acid, step a) is preferably carried out at a temperature ranging from 100°C to 180°C, particularly from 110°C to 160°C. When the itaconic acid crosslinking agent is itaconic anhydride, step a) is preferably carried out at a temperature ranging from 30°C to 110°C, more preferably from 40°C to 90°C.

[0061] According to one implementation, the contact is carried out without solvents or diluents.

[0062] In step a), the nonfunctionalized copolyester and itaconic acid crosslinking agent can be contacted in a solvent, particularly in a polar aprotic solvent (e.g., Cyrene™ or 1,2,3-trimethoxypropane), preferably a bio-based solvent, or in water. Water is the preferred solvent.

[0063] Therefore, according to a variant of the invention, the contact in step a) is achieved by adding water to the mixture of the nonfunctionalized copolyester and the itaconic acid crosslinking agent. Adding water to the mixture homogenizes it, thereby reducing its overall viscosity. To promote this homogenization, stirring can be performed using known methods.

[0064] According to these variants, the amount of water added, relative to the mass of the nonfunctionalized copolyester and itaconic acid crosslinking agent used, is between 0% and 100% by mass, preferably in the range of 5% to 50% by mass, and more preferably in the range of 10% to 40% by mass.

[0065] According to other specific variations of the invention, contact is achieved by introducing an itaconic acid crosslinking agent into a mixture comprising a nonfunctionalized copolyester and water.

[0066] The mixing of the nonfunctionalized copolyester and water can be carried out in a reactor at ambient temperature (approximately 23°C at atmospheric pressure), which can be the same reactor as in step a). This pre-mixing step may optionally include heating the nonfunctionalized copolyester and water, for example, to a temperature in the range of approximately 50°C to 100°C. The medium is then heated for a time sufficient to dissolve or homogenize the nonfunctionalized copolyester in the water. To promote homogenization of the medium, it can be stirred in a known manner, regardless of heating.

[0067] According to any of these variants, itaconic acid crosslinking agents can be introduced into a mixture comprising a nonfunctionalized copolyester and water in solid or aqueous form (preferably solid).

[0068] According to one variant, an itaconic acid crosslinking agent is introduced in solid form into a mixture comprising a nonfunctionalized copolyester and water, followed by a step of melting and / or dissolving the itaconic acid crosslinking agent in an aqueous medium.

[0069] Depending on other variants, especially when itaconic acid crosslinking agents are introduced in aqueous solution form (e.g., at ambient temperature), the step of heating to reflux is optional.

[0070] Stabilizers can also be added during step a).

[0071] Step b) In step b), the functionalization reaction involves esterification of the free alcohol functional groups of the copolyester of glycerol and dicarboxylic acid monomers using itaconic acid crosslinking agents. Depending on the reaction conditions, transesterification may also be observed, but these reactions are usually less common.

[0072] When the crosslinking agent of itaconic acid is itaconic acid, one water molecule is generated for each ester bond formed.

[0073] Therefore, in this embodiment, the byproduct of the functionalization reaction is water.

[0074] According to a specific variant of the invention, the functionalization step should be carried out under conditions where water can be removed from the reaction medium (or from the reactor). Removing the generated water during the functionalization process has several advantages: it can increase the reaction yield and accelerate its reaction kinetics. The water thus recovered is preferably recycled as a solvent for contact step a).

[0075] Furthermore, when the itaconic acid crosslinking agent is itaconic acid, measuring the amount of water removed can also monitor the progress of the functionalization reaction.

[0076] To remove water during the functionalization process, a reactor and appropriate temperature and pressure conditions can be used to distill the water.

[0077] Regardless of the implementation, the pressure within the reactor during step b) can be constant or variable. Functionalization step b) is typically carried out at pressures between 0.0001 bar and 2 bar.

[0078] The functionalization reaction is preferably carried out under reduced pressure, typically less than or equal to 30 mbar, especially less than or equal to 20 mbar, and preferably less than or equal to 10 mbar.

[0079] According to a variation of the invention, at the end of step a), before being placed under depressurization, the pressure is preferably reduced to an intermediate pressure between atmospheric pressure and the target depressurization value, optionally achieved through a constant pressure stage. Any method known to those skilled in the art can be used to reduce the pressure, particularly using pumps (especially impeller pumps), diaphragm pumps, rotary pumps, etc. This intermediate pressure is less than 1 bar, for example in the range of 50 to 800 mbar.

[0080] The reaction medium is then placed under reduced pressure, preferably under vacuum. In this document, "vacuum" should be understood as a pressure reduced to approximately 1 millibar.

[0081] Heating step b) is preferably carried out at a temperature between 20°C and 250°C. The temperature of functionalization step b) can be variable or stable. When the itaconic acid crosslinking agent is itaconic acid, functionalization step b) is preferably carried out at a temperature in the range of 50°C to 250°C, preferably 100°C to 200°C, and especially 120°C to 190°C. In a particular embodiment, heating in step b) includes maintaining the reaction temperature in the range of 110°C to 200°C, preferably 120°C to 180°C, and especially about 130°C. When the itaconic acid crosslinking agent is itaconic anhydride, functionalization step b) is preferably carried out at a temperature in the range of 30°C to 130°C, and especially 40°C to 100°C.

[0082] Preferably, isothermal conditions or a heating ramp are used to achieve this temperature. The heating ramp may include one or more isothermal stages (also known as heat preservation stages), and the gradient of the ramp is typically between +0.1°C / min and +1°C / min.

[0083] According to one embodiment, the functionalization step b) is carried out in the presence of a catalyst, the catalyst content of which is particularly 5000 ppm or less, preferably 3000 ppm or less, and advantageously 2000 ppm or less, relative to the total mass of the nonfunctionalized copolyester and itaconic acid crosslinking agent used.

[0084] The catalyst may specifically comprise or consist of Brønsted acids (e.g., sulfuric acid, p-toluenesulfonic acid) or Lewis acids (e.g., AlCl3, TiCl4, TiOBu4, butylstannic acid, metal trifluoromethanesulfonates or trifluoromethanesulfonates, such as bismuth trifluoromethanesulfonate) or mixtures thereof. Particularly advantageous catalysts are metal trifluoromethanesulfonates (or trifluoromethanesulfonates) in which the metal is in oxidation state (III), selected from lanthanum trifluoromethanesulfonate (Ln(TfO)3), yttrium trifluoromethanesulfonate, scandium trifluoromethanesulfonate, bismuth trifluoromethanesulfonate, and iron trifluoromethanesulfonate.

[0085] The catalyst preferably contains or consists of a food-grade catalyst.

[0086] "Food-grade catalyst" should be understood as a catalyst suitable for food contact (for animals and humans) that meets the requirements to ensure that the catalyst does not pose a toxic risk to the polyester produced. Such catalysts particularly comply with the requirements of U.S. Standards 21 CFR 175.300, 21 CFR 177.2420, and / or 21 CFR 175.105, which are in force as of the application date.

[0087] Food-grade catalysts are advantageously tin-based catalysts, preferably selected from organotin compounds containing a carboxyl group (-C(O)OH) or a functional group (-Sn(O)OH). According to specific variants of the invention, the catalyst is selected from alkyltin compounds containing a carboxyl functional group (-C(O)OH) or a functional group (-Sn(O)OH), wherein the alkyl group has 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms. These specific compounds include food-grade monobutyltin oxide (or stannic acid) and food-grade tris(2-ethylhexanoic acid) monobutyltin.

[0088] According to a preferred variant of the invention, the catalyst is food-grade monobutyltin oxide (or stannic acid).

[0089] Examples of catalysts that can be used for the purposes of this invention include monobutyltin oxide sold by PMC Organometallix under the name FASCAT 9100 and tris(2-ethylhexanoic acid) monobutyltin sold under the name FASCAT 9102. Particularly preferred is the monobutyltin oxide catalyst sold by PMC Organometallix under the name FASCAT 9100.

[0090] Therefore, at the end of step a) or in step b), the catalyst is advantageously introduced into the reaction medium in an amount less than or equal to 5000 ppm relative to the total mass of the monomers, preferably greater than or equal to 2500 ppm.

[0091] In particular, when the molar ratio of itaconic acid crosslinker to NOH is 1:1 to 2:1, this step will be advantageously considered complete when the molar conversion of the observed number of free hydroxyl functional groups reaches 70%, preferably 80%, or especially 90% or higher.

[0092] Molar conversion can be determined by measuring the mass of the removed distillate (water), or by sampling the reaction medium and monitoring the disappearance of free itaconic acid crosslinking agents or free hydroxyl functional groups using NMR or size exclusion chromatography (SEC). Molar conversion is typically determined by... 13 C NMR can be used to determine and / or monitor the signal. For example, the disappearance of the signal from carbons with free hydroxyl functional groups can be monitored, or the disappearance of the signal from -COOH functional groups in free diacids of dicarboxylic acid monomers or in itaconic acid crosslinking agents can be monitored.

[0093] Alternatively, when the second step (b) of functionalization is carried out under stirring, the step can be considered complete when the torque of the stirring motor reaches a predetermined target value, which is preferably selected to ensure that the molar mass and viscosity of the functionalized copolyester are suitable for the application targeted by the present invention.

[0094] The heating in step (b) is advantageously carried out for 30 minutes to 12 hours, preferably 1 hour to 5 hours.

[0095] Next steps The method may further include a post-treatment step of the resulting functionalized copolyester, particularly to reduce the content of residual itaconic acid crosslinking agents and / or stabilizers. This post-treatment step may be a washing step and / or a liquid-liquid extraction step using a water-immiscible organic solvent (preferably dichloromethane), preferably followed by washing with an aqueous phase (especially a neutral aqueous phase) and / or a saline phase (e.g., NaCl) and / or an acidic aqueous phase (e.g., hydrochloric acid solution, especially 1 N or 2 N). The liquid-liquid extraction and / or washing are performed in a known manner.

[0096] 2. Photocrosslinkable copolyester and its composition The itaconic acid functionalization degree of the photocrosslinkable copolyester of the present invention is greater than or equal to 0.004 mmol / g, preferably greater than or equal to 0.04 mmol / g, and more preferably greater than or equal to 1 mmol / g. It is preferably obtained by the functionalization method of the present invention.

[0097] As used in this article, "itaconic acid functionalization degree" should be understood as referring to the content of C=C double bonds provided by itaconic acid crosslinking agents in photocrosslinkable copolyesters, expressed in millimoles of double bonds per gram of photocrosslinkable copolyester. The itaconic acid functionalization degree is usually determined by carbon-13 nuclear magnetic resonance (NMR). 13 Measured by C NMR.

[0098] The degree of itaconic acid functionalization can also be indirectly obtained by determining free itaconic acid using size exclusion chromatography (SEC). The content of free (or residual) itaconic acid is then determined. Assuming that the remaining portion of the itaconic acid used has completely reacted, the degree of itaconic acid functionalization corresponds to the difference between the amount of itaconic acid used in the reaction (or the initial amount) and the amount of free itaconic acid, expressed in millimoles per gram of the resulting polymer.

[0099] The functionalization degree of itaconic acids is usually determined by carbon-13 nuclear magnetic resonance (NMR). 13 C NMR determination. For copolymers of glycerol and itaconic acid crosslinking agents, especially those free of other monomers and other dicarboxylic acid monomers, with a molar ratio of glycerol to itaconic acid crosslinking agent of 1:1 and a chain length of 100 glycerol / dicarboxylic acid monomers, the theoretical value of the degree of itaconic acid functionalization is 5.23 mmol / g, and experiments have confirmed that it is between 5 and 6 mmol / g.

[0100] Therefore, the degree of itaconic acid functionalization of photocrosslinkable copolyesters is usually less than or equal to 10 mmol / g, especially less than or equal to 8 mmol / g, and preferably less than or equal to 6 mmol / g.

[0101] The functionalization degree of itaconic acid is advantageously generally greater than or equal to 0.1 mmol / g, especially greater than or equal to 0.5 mmol / g, and especially greater than or equal to 1 mmol / g.

[0102] Photocrosslinkable copolyesters may also have at least one of the following characteristics: - The number-average molar mass (Mn) of the photocrosslinkable copolyester is greater than or equal to 500 g / mol, especially greater than or equal to 1000 g / mol, preferably greater than or equal to 1500 g / mol, and more preferably greater than or equal to 1700 g / mol. - The number-average molar mass (Mn) of the photocrosslinkable copolyester is less than or equal to 10,000 g / mol, preferably less than or equal to 3,500 g / mol, and more preferably less than or equal to 3,000 g / mol; - Dispersion of photocrosslinkable copolyester Less than 12, preferably less than or equal to 8, especially less than or equal to 6; - The residual monomer content is less than 25% by weight relative to the weight of the photocrosslinkable copolyester, preferably less than or equal to 20% by weight; and / or - The content of 1,2,3-triacylglycerol units is less than 25 mol% relative to the total number of units in the photocrosslinkable copolyester, preferably less than or equal to 20 mol%, especially 15 mol% or less.

[0103] Photocrosslinkable copolyesters may also have at least one of the following characteristics: - In nonfunctionalized copolyesters, the molar ratio of 1,3-diacylglycerol units to 1,2-diacylglycerol units is greater than 1; - The glass transition temperature (Tg) is -100°C to +30°C, preferably -80°C to +10°C, more preferably -60°C to 0°C, especially -50°C to -25°C.

[0104] 3. Photocrosslinkable composition The present invention also relates to a photocrosslinkable composition comprising: As described in this article, photocrosslinkable copolyesters, and Optional photoinitiator.

[0105] As used in this article, “photoinitiator” should be understood as a compound that, when exposed to light, especially ultraviolet light, generates free radicals, thereby initiating a photocrosslinking reaction (usually a free radical reaction).

[0106] Using an excessive amount of photoinitiator can produce undesirable reactions during the photocrosslinking step. Therefore, it is advantageous that the content of photoinitiator is less than or equal to 5% by mass relative to the total weight of the photocrosslinkable composition, more preferably less than or equal to 1% by mass.

[0107] Photoinitiators suitable for photocrosslinking are well known to those skilled in the art. Photoinitiators are particularly selected from the type I photoinitiator family. Type I photoinitiators are unimolecular systems whose reactions proceed via homolytic cleavage of C-C bonds (especially via Norrish type I cleavage). The molecules involved are typically aromatic ketones, which, upon absorbing light, undergo homolytic cleavage (Norrish I-type cleavage) of the bond at the α-position relative to the carbonyl group from the triplet excited state, resulting in the formation of two free radicals capable of initiating free radical polymerization (see, in particular, Ley et al., 14th International French Optical Symposium on Optical Methods and Techniques for Industry [14th International French Optical Symposium on Optical Methods and Techniques for Industry] / 16th French Congress of the Club FLUVISU / SFO (CMOI-FLUVISU 2015), Club CMOI – French Optical Society, Nov. 2015, Pleumeur-Bodou, France. pp.124-129. hal-01583762).

[0108] Type I photoinitiators are specifically precursors of any benzoyl radical. Type II photoinitiators are specifically designed to add a radical precursor (amine) to any hexadecyl radical precursor (inert). These specifically include 2,4,6-trimethylbenzoyl diphenylphosphine ester (TPO-L), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), or 1-hydroxycyclohexylphenyl ketone (HCHPK).

[0109] The photocrosslinkable composition may also contain one or more standard additives in the prior art, such as fillers. Fillers may be organic or inorganic. Additives may also be selected from stabilizers, compatibilizers, molding agents, active ingredient release modifiers, and antioxidants.

[0110] The composition may also contain active ingredients, more particularly plant-targeting active ingredients, such as phytosanitary active ingredients and / or biostimulants. Such compositions can be used to coat plants or parts of plants. According to this embodiment, the invention also relates to a plant treatment method comprising applying a photocrosslinkable composition to at least a portion of a plant or to soil.

[0111] Plant-targeted active ingredients specifically include phytostimulants used for agricultural purposes, particularly for stimulating plants of the genus Rubber Tree (such as the Brazilian rubber tree).

[0112] Phytosanitary products, plant protection products, or herbal medicines refer to one or more substances (of natural or synthetic origin) with chemical or biological properties that are used in agriculture, horticulture, or forestry to protect cultivated plants from pests (animal pests, plant pathogens, parasitic plants, weeds) or to optimize crop yields by promoting the growth of cultivated plants and by treating their growing environment (especially the soil).

[0113] "Biostimulant" should be understood as a substance that can stimulate plant nutrient processes independently of any nutrients it contains, with the aim of improving one or more of the following characteristics of the plant or its rhizosphere: nutrient use efficiency, tolerance to abiotic stress, quality characteristics, and availability of nutrients locked in the soil or rhizosphere (according to EU Regulation 2019 / 1009). Biostimulants can be low-risk natural preparations (NPLCs). NPLCs are: - Natural substances (NSBU) used for biostimulant purposes, or - Basic substances.

[0114] The definition of basic substances is found in Article 23 of Regulation (EC) 1107 / 2009. These substances are those with phytosanitary value, but whose primary use is not plant protection (e.g., food).

[0115] The formulations of the present invention preferably contain phytosanitary active ingredients and / or biostimulants, which are selected from stimulants, fertilizers, insecticides, fungicides, nutrients, fungicides, insecticides and growth regulators.

[0116] The formulations of the present invention preferably contain phytosanitary active ingredients and / or biostimulants, which are ethylene precursors, preferably ethephon.

[0117] The compositions of the present invention may be in the form of pastes, patches, granules or spray solutions, preferably in the form of pastes.

[0118] 4. Photocrosslinking methods The present invention also relates to a method for photocrosslinking the photocrosslinkable composition or photocrosslinkable copolyester described herein, the method comprising the step of irradiating the photocrosslinkable composition or photocrosslinkable copolyester with ultraviolet light, preferably in the presence of a photoinitiator.

[0119] The irradiation is advantageously carried out at a temperature in the range of 15°C to 30°C.

[0120] The irradiation is usually carried out at atmospheric pressure.

[0121] Preferably, the wavelength of irradiation is between 250 nm and 500 nm, more preferably in the range of 300 nm to 450 nm, more preferably in the range of 350 nm to 400 nm, and especially about 365 nm.

[0122] Irradiation is advantageous at 5 to 25 mW / cm 2 Especially 8 to 20 mW / cm 2 It is performed at a power level.

[0123] Advantageously, the content of photoinitiator is less than or equal to 5% by mass relative to the total weight of the photocrosslinkable composition, more preferably less than or equal to 1% by mass.

[0124] The photoinitiator is as described above.

[0125] The typical irradiation time for photocrosslinkable compositions or photocrosslinkable copolyesters is between 1 second and 5 hours.

[0126] It is preferable to add the photoinitiator to the crosslinkable composition or copolyester at ambient temperature. This avoids any unwanted crosslinking reactions.

[0127] More specifically, the present invention relates to the use of photocrosslinkable compositions for the preparation of products by 3D printing (preferably photocrosslinked 3D printing). Examples of such techniques are stereolithography (SLA) and methods known as digital light processing (DLP), continuous liquid interface fabrication (CLIP), solar polymer printing (DPP), and thin film transfer imaging (FTI).

[0128] 5. Cross-linked copolyesters and their applications The present invention also relates to crosslinked copolyesters obtained by crosslinking (especially thermal crosslinking and / or photocrosslinking) the photocrosslinkable copolyester of the present invention or the photocrosslinkable composition of the present invention.

[0129] According to one variant, the crosslinked copolyester can therefore be obtained by the photocrosslinking method described above.

[0130] According to another variant, crosslinked copolyesters can be obtained by thermal crosslinking, especially by thermal initiation, optionally in the presence of an initiator, particularly selected from substances that generate free radicals by thermal decomposition, such as peroxides (e.g., cumene hydroperoxide) or azo compounds (e.g., azobisisobutyronitrile (AIBN)), in a dispersed or non-dispersed medium.

[0131] Cross-linked copolyesters advantageously possess the following characteristics: The glass transition temperature Tg is preferably between -100°C and +30°C, between -80°C and +10°C, and especially between -60°C and 0°C, and / or Storage modulus G' greater than or equal to 0.02 MPa at 37°C and 10 Hz.

[0132] Therefore, the photocrosslinkable composition of the present invention or the photocrosslinkable copolyester of the present invention can be used to prepare products by 3D printing.

[0133] Examples of the products include implants, patches that diffuse active ingredients, particles (especially microparticles and large particles), coatings, fibers and threads, etc. Attached Figure Description

[0134] Further features, objects and advantages of the present invention will become apparent from the following description, which is purely illustrative and non-limiting, and should be read in conjunction with the accompanying drawings.

[0135] [ Figure 1 [ ] is a schematic diagram of a simplified reaction scheme involved in the synthesis of poly(glycerol-co-sebate-co-itaconate) according to Example 1.

[0136] [ Figure 2 [This is a schematic diagram of the storage modulus G* measured after photocrosslinking of the copolyesters of Examples 2 and 3 with or without a photoinitiator.] Detailed Implementation

[0137] Example The following examples are given by way of illustration, but should not be construed as limiting the invention in any way.

[0138] Materials and methods Structural analysis: NMR Structural analysis was performed using NMR to determine the degree of itaconic acid functionalization and the proportion of unreacted (residual) itaconic anhydride or itaconic acid in the polymer. Spectra were acquired using a Bruker Avance III 600 MHz spectrometer equipped with a 5 mm BBFO Z-class "broadband" probe. Quantitative analysis was then conducted. 1The 1H NMR experiments used a simple 30° pulse sequence with 64 acquisitions and a 3-second repetition delay between each acquisition. Unless otherwise specified, the sample was dissolved in a deuterated solvent, i.e., deuterated acetone (acetone-d). 6 (in) . Combined 1 H NMR spectra and 2D HSQC / HMBC and 13 C10 NMR experiments can be used to quantitatively analyze the microstructure of different functionalized PGS (see the attribution table).

[0139] The itaconic acid conversion rate corresponds to the molar percentage of grafted itaconic acid crosslinking agent / (grafted + free itaconic acid crosslinking agent).

[0140] Macroeconomic structural analysis: SEC-RI Size exclusion chromatography (SEC) technology allows for the separation of macromolecules in solution based on their size by passing them through a column packed with porous gel. Macromolecules are separated according to their hydrodynamic volume, with the largest molecules eluting first.

[0141] While the SEC method is not absolute, it provides information on the molar mass distribution in a polymer. Different number-average molar masses (Mn) and weight-average molar masses (Mw) can be determined based on commercially available standards, and the polydispersity index (PDI) can be calculated. = Mw / Mn), also known as "dispersion".

[0142] The "macrostructure" of the copolyester was analyzed by size exclusion chromatography (SEC-RI) with a differential refractometer and calibrated using low molecular weight polystyrene (PS) supplemented with a medium molecular weight standard. The sample was dissolved in butylated hydroxytoluene (BHT)-free THF at a concentration of approximately 1 g / L, stirred for two hours, and then injected. The analysis was conducted at 35 °C, with a mobile phase flow rate of 1 mL / min, using an Agilent 2 Mixed E + 2 Mixed 2 column.

[0143] Thermal Analysis: DSC Thermal analysis of the copolyester was performed using differential scanning calorimetry on a DSC3+ calorimeter sold by Mettler Toledo, using a sealed standard aluminum crucible with two opposing holes in the crucible lid, a helium flow rate of 40 mL / min, and the following temperature ramp: 1. Maintain the temperature at 25℃ for 2 minutes. 2. Cool down from 25℃ to -100℃ at a rate of 10℃ / minute. 3. Maintain the temperature at -100℃ for 2 minutes. 4. Increase the temperature from -100℃ to 100℃ at a rate of 10℃ / minute. 5. Cool down from 100℃ to -100℃ at a rate of -30℃ / minute on a ramp. 6. Maintain the temperature at -100℃ for 2 minutes. 7. Increase the temperature from -100℃ to 200℃ at a rate of 10℃ / minute.

[0144] The measurements taken at slope 7 correspond to the Tg of the cross-linked copolyester.

[0145] Structural Analysis: MIR Using wavelengths of 4000 and 650 cm -1 The photocrosslinking kinetics were monitored using a mid-infrared spectrometer (MIR) (a Vertex 70” model sold by Bruker), equipped with a germanium crystal and MCT detector on a Vertex 70-3 spectrometer. The cumulative scan count (Ns) used was 32. The spectrometer was equipped with a power of 9 mW / cm². 2 A 365 nm ultraviolet LED lamp was used to irradiate the sample at a distance of 5 cm. The intensity of the irradiation was tracked at 1638 cm⁻¹ as the duration of ultraviolet irradiation varied. -1 The disappearance of the C=C band of itaconic acid at 1638 cm⁻¹ (measured at 1638 cm⁻¹) -1 The peak area of ​​the spectral band is used to monitor the crosslinking process.

[0146] Measurement of mechanical properties: Storage modulus G' Mechanical properties were measured on an Anton Paar MCR302 rheometer, which is equipped with a 20 mm diameter planar geometry.

[0147] Measurements were performed on cylindrical samples with a thickness of 2 mm and a diameter of 2 cm, which were molded in a metal mold and then subjected to UV light under an LED lamp (LED 365 nm, 9 Mw / cm²) at ambient temperature. 2 Crosslinking was performed for 1 hour to obtain the product.

[0148] The sample was subjected to a frequency sweep from 0.1 to 100 Hz at 37 °C under a sinusoidal shear load with a strain of 0.1%. The stresses obtained were measured. The results are expressed as the storage modulus (G') at 37 °C and 10 Hz, in megapascals (MPa).

[0149] The moduli G*, G', and G'' are calculated according to the following formula: in: σ is the measured stress, and ε is the strain applied to the sample; G' is the real part of G*, called the storage modulus, which characterizes the stiffness of a viscoelastic material. G' characterizes the elastic behavior (the energy stored and fully recovered by the material). i is the "imaginary" unit (i 2 =-1); G'' is the imaginary part of G*, called the loss modulus or dissipation modulus, which characterizes viscous behavior (energy dissipated in the form of heat).

[0150] Example 1: Synthesis of nonfunctionalized glycerol-co-sebate copolyester (denoted as PGS) Glycerol (1 molar equivalent) and sebacic acid (1 molar equivalent) were added to a 500 mL jacketed reactor under a nitrogen flow. The reactor was topped with a distillation column, a condenser, and a collector for recovering the distillate. The reactor was then gradually heated to 130 °C under nitrogen with stirring. Once the temperature in the medium reached 130 °C, the reaction was carried out at 130 °C for 24 hours under atmospheric pressure and a nitrogen flow, with continuous removal of moisture. The reaction was stopped when the conversion exceeded 80% (measured by the amount of water produced).

[0151] After cooling to ambient temperature, the obtained PGS was recovered as a white paste. Its number-average molar mass was approximately 1852 g / mol, its weight-average molar mass (Mw) was approximately 5067 g / mol, and its dispersibility was approximately... =2.7, with a free hydroxyl content of 5 mmol / g.

[0152] Example 2: Synthesis of the photocrosslinkable copolyester of the present invention: itaconic acid ester-grafted glycerol-co-sebate copolyester In the following text, PGS-IA refers to an itaconic acid ester-grafted glycerol-co-sebate copolyester obtained by using itaconic acid as a crosslinking agent, and PGS-ANHYTA refers to an itaconic acid ester-grafted glycerol-co-sebate copolyester obtained by using itaconic anhydride as a crosslinking agent.

[0153] Comparison methods without stabilizers: The PGS and itaconic acid crosslinking agent from Example 1 were added to a 500 mL jacketed reactor under a nitrogen flow. The reactor was topped with a distillation column, a condenser, and a collector for recovering the distillate. The reactor was gradually heated to 130°C under stirring and nitrogen. Once the temperature in the medium reached 130°C, the reaction was continued at 130°C under atmospheric pressure and a nitrogen flow for 3 hours to remove moisture. A pale yellow viscous liquid, corresponding to PGS-IA or PGS-ANHYTA, was obtained and then cooled to ambient temperature.

[0154] The method of the present invention, including a stabilizer: The PGS from Example 1, itaconic acid crosslinking agent (0.4 molar equivalents, relative to the 1,3-diacylglycerol ester unit (major unit) of the PGS from Example 1), and 4-methoxyphenol as a stabilizer (1.56% by mass, relative to the total mass of the mixture containing the stabilizer) were added to a 500 mL jacketed reactor under a nitrogen flow. The reactor was topped with a distillation column, a condenser, and a collector for recovering the distillate. The reactor was then gradually heated to 130°C (or 80°C or 140°C) under nitrogen with stirring. Once the temperature in the medium reached 130°C (or 80°C or 140°C), the reaction was continued at 130°C (or 140°C) under atmospheric pressure and a nitrogen flow to remove moisture, for the reaction times shown in Table 1. A pale yellow viscous liquid was obtained, corresponding to PGS-IA or PGS-ANHYTA, and then cooled to ambient temperature.

[0155] Tests 1 through 6 were performed without solvent.

[0156] The reaction conditions for each of the various embodiments are summarized in Tables 1 and 2.

[0157] [Table 1] [Table 2] NMR analysis results of PGS-IA or PGS-ANHYTA obtained in Test 1 and Tests 3 to 6 (acetone d 6 (The photocrosslinkable copolyester of test 2 was not analyzed because it is insoluble in acetone.) [Table 3] *Consider the unsaturated groups of free and grafted itaconic acid or anhydrides. The number-average molar mass (Mn) and weight-average molar mass (Mw) of PGS-IA or PGS-ANHYTA obtained in Tests 1 and 3 through 6 were calculated by SEC analysis (polystyrene standard dissolved in THF). (The photocrosslinkable copolyester of Test 2 was not analyzed because it is insoluble in THF.) [Table 4] Example 3 (Reference): Synthesis of a reference photocrosslinkable copolyester: A methacrylate-grafted glycerol-co-sebate copolyester, denoted as PGS-MA, according to the Journal of Biomaterials Applications, 4, 1114-1130, 2020 and Macromol. Rapid Commun, 41, 1900484, 2020.

[0158] PGS from Example 1 and 4-methoxyphenol (2.7% by mass, relative to the mass of PGS, methacrylic anhydride, and 4-methoxyphenol) as a stabilizer were dissolved in dichloromethane (15.6% by mass) and placed in a 500 mL jacketed reactor equipped with a condenser and an electric paddle stirrer. The mixture was stirred under nitrogen at ambient temperature. Once the compounds were dissolved, methacrylic anhydride (50% by mass, relative to PGS) was added in a controlled manner at 0°C. The reaction medium was allowed to return to ambient temperature and maintained under stirring and nitrogen for 24 hours. At the end of the reaction, liquid / liquid extraction was performed first with an acid solution and then with water (with or without the addition of a sodium chloride-type salt) until the aqueous phase returned to pH 5-7. The organic phases were combined and evaporated. A white viscous liquid, PGS-MA, was obtained and then cooled to ambient temperature.

[0159] Example 4: Photocrosslinking In the presence or absence of photoinitiators 2,4,6-trimethylbenzoyl diphenylphosphine ester (TPO-L), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), or 1-hydroxycyclohexylphenyl ketone (HCHPK), under ambient temperature and atmospheric pressure, under ultraviolet light (LED 365 nm, 9 mW / cm²), 2 The photocrosslinkable copolyesters in Examples 2 and 3 were crosslinked by irradiation for 1 hour (distance between lamp and sample surface: 5 cm). A photoinitiator was pre-introduced at a mass percentage of 1% of the total mixture. The photoinitiator was used to compensate for the molar amount of stabilizer present in the functionalized PGS.

[0160] Infrared analysis allows for verification at 1638 cm⁻¹ -1 The C=C band of itaconic acid ester at the location almost completely disappeared, which confirms the effectiveness of the photocrosslinking reaction.

[0161] Table 5 lists the measured glass transition temperature (Tg) of copolyesters with and without photoinitiators.

[0162] The Tg of PGS-IA or PGS-ANHYTA obtained in tests 1 to 6 was measured by differential scanning calorimetry.

[0163] [Table 5] Figure 2 The rheological measurements of the resulting crosslinked copolyester are shown in the figure. These measurements indicate that the stiffness of the crosslinked copolyester is much higher than that of the photocrosslinkable copolyester, further confirming the effectiveness of the photocrosslinking reaction.

[0164] in conclusion The method of this invention is simple, rapid, reliable, and repeatable. Due to the use of a stabilizer, the method also avoids uncontrolled side reactions.

[0165] The photocrosslinkable copolyesters of Example 2 were derived from non-toxic and bio-based monomers and are suitable for product manufacturing in 3D printing methods. Their mechanical and physicochemical properties are on the same order of magnitude as those of prior art photocrosslinkable polymers (see Comparative Example 3), but they use itaconic acid ester crosslinking agents, which are non-toxic and 100% bio-based / bio-based reagents.

[0166] References: CN114456335 EP3149067 WO2019 / 215441 WO2021 / 078962 Rueben et al., MRS Advances (2018), 3(27), 1551-1556.

Claims

1. A method for copolyesterifying glycerol with a dicarboxylic acid monomer, the method comprising the following steps: a) Contacting glycerol with a copolyester of a dicarboxylic acid monomer and an itaconic acid crosslinking agent selected from itaconic acid, itaconic anhydride, and mixtures thereof, wherein the dicarboxylic acid monomer is preferably aliphatic. b) In the presence of a stabilizer, the mixture obtained from step a) is heated for a time sufficient to form a photocrosslinkable functionalized copolyester. c) Cooling and recycling of photocrosslinkable functionalized copolyesters.

2. The method according to claim 1, wherein, The dicarboxylic acid monomer has the formula [HOOC-(CH2)]. n -COOH], where n is a number in the range of 1 to 30, preferably in the range of 5 to 10, and advantageously sebacic acid (n=8).

3. The method according to claim 1 or 2, wherein, The heating in step b) includes maintaining the reaction temperature between 20°C and 250°C.

4. The method according to any one of claims 1 to 3, wherein, The stabilizer is phenol or aniline, especially aniline, phenol, methoxyphenol (particularly 4-methoxyphenol or guaiacol), 2,6-dimethoxyphenol, 4,6-bis(octylthiomethyl)-o-cresol and / or 2-hydroxy-4-methoxybenzophenone.

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

6. The method according to any one of claims 1 to 5, wherein, The heating in step b) continues for 30 minutes to 12 hours.

7. A photocrosslinkable copolyester of glycerol and dicarboxylic acid monomers, wherein the degree of itaconic acid functionalization is greater than or equal to 0.004 mmol / g, preferably greater than or equal to 0.04 mmol / g, and more preferably greater than or equal to 1 mmol / g.

8. The photocrosslinkable copolyester according to claim 7, which can be obtained by the method according to any one of claims 1 to 6.

9. The photocrosslinkable copolyester according to any one of claims 7 and 8, further comprising 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 10,000 g / mol, preferably less than or equal to 3,500 g / mol; - Its dispersion (Mw / Mn) is less than or equal to 12, preferably less than or equal to 8; - The residual monomer content is less than or equal to 25% by weight relative to the weight of the photocrosslinkable copolyester, preferably less than or equal to 20% by weight; and / or - The content of 1,2,3-triacylglycerol units is less than or equal to 25 mol% relative to the total number of units in the photocrosslinkable copolyester, preferably less than or equal to 20%.

10. A photocrosslinkable composition comprising The photocrosslinkable copolyester according to any one of claims 7 to 9, and Optional photoinitiator, advantageously, the content of the photoinitiator is less than or equal to 5% by mass relative to the total mass of the composition.

11. A method for preparing a crosslinkable copolyester by photocrosslinking, the method comprising the step of irradiating the photocrosslinkable composition according to claim 10 or the photocrosslinkable copolyester according to any one of claims 7 to 9 with ultraviolet light.

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

13. The crosslinked copolyester according to claim 12, which can be obtained by the method according to claim 11.

14. The crosslinked copolyester according to claim 12 or 13, characterized in that, The crosslinked copolyester has the following characteristics: - A glass transition temperature Tg between -100°C and +30°C, preferably between -80°C and +10°C, especially between -60°C and 0°C, and / or - Storage modulus G' greater than or equal to 0.02 MPa at 37°C and 10 Hz.

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

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