Synthesis process for a polyol polyester

Abstract

The present invention relates to a process for synthesizing a polyol polymer, preferably glycerol, and polycarboxylate units, preferably dicarboxylic acid diesters, particularly sebacate units, especially PGS, comprising the introduction of a basic organocatalyst. The invention also relates to a polymer obtainable by this process. A third object of the invention is a polyol polyester exhibiting high average molar masses with a controlled water content, the absence of trace metals, and a limited acid value.

Description

Title of the invention: Process for synthesizing a polyol polyester FIELD OF INVENTION

[0001] The field of the present invention is that of the synthesis of aliphatic polyesters, in particular glycerol polyester, obtained by transesterification of hydroxyl groups of a polyol and carboxyl groups of a diester by a polycondensation reaction. STATE OF THE ART

[0002] Polyesters are widely used to prepare biomaterials used particularly in biomedical applications as materials for polymeric frameworks, for the encapsulation of biomolecules, or for surface coatings. In particular, among biocompatible aliphatic polyesters, glycerol and diacid polymers are used in the medical field for their biodegradability properties, such as for tissue engineering, drug delivery, implants, controlled release of substances, etc.

[0003] A conventional method for synthesizing a glycerol polymer and a diacid is carried out in a molten medium at high temperature with long reaction times and consists of an esterification step followed by polycondensation conducted at very low pressure. Such a process is described, for example, in patent application EP1448656A1 or US9359472B2 in the presence of water. A notable problem with these processes is the long reaction time. They require 24 to 48 hours, particularly to eliminate the water formed during the reaction, and lead to polymers with structural and physicochemical properties that do not always meet application requirements. The low miscibility of glycerol and sebacic acid necessitates a high reaction temperature to exceed the melting point of sebacic acid, allowing for progressive homogenization of the reaction medium.The main consequences are the obtaining of polymers with a wide molecular weight distribution (D) and incomplete conversion of monomers after long reaction times, because water, a co-product of the reaction, is difficult to eliminate completely, even after long heating at very low pressure.

[0004] Other processes for the synthesis of glycerol polyesters have been described implementing the use of metal catalysts to accelerate the synthesis of polyesters from the condensation of glycerol and dicarboxylic acids, in particular polyglycerol sebacate (PGS), for example in US20200247945A1 which describes the use for this purpose of sulfated titanium dioxide.

[0005] In WO2021252554A1, a process for obtaining polymers by transesterification of polyols and alkyl esters of polycarboxylic acids is described, leading to polymers with a reduced acid functional group and a low water content. The use of a catalyst, such as dibutyltin or potassium hydroxide, is recommended. However, the reaction time remains long to achieve a macrostructure of the same order as conventional synthesis processes. Performing the transesterification at temperatures of around 180°C during the long reaction time can result in a risk of glycerol degradation (glycerol degradation temperature = 176°C). Furthermore, this document does not explain how to eliminate traces of residual metal catalyst present in the polymer (i.e., traces of Sn or K), which can be prohibitive for certain applications of the polymer.

[0006] Some of the metallic catalysts used in these processes have a toxicological profile that is not always acceptable with the use of polyesters to prepare biomaterials, which requires syntheses in a highly controlled toxicity environment. Furthermore, metallic residues from the catalysts used may be incompatible with subsequent modifications of the polymer or undesirable for the application, such as titanium or tin residues.

[0007] Thus, the presence of water, residual dicarboxylic acid monomers in significant quantities, the presence of carboxylic acid chain ends on the polymer or even acidic or metallic catalytic residues, have a significant impact on the application, in particular when the polymer is used as a raw material for the preparation of crosslinked compositions possibly including active ingredients.

[0008] Four problems can thus be highlighted: - acidic functions, particularly those linked to free diacid monomers, can lead to premature acidification of the surrounding environment when the polymer is placed in aqueous solution, which can lead to a decrease in biocompatibility resulting in cytotoxicity; - Acidic functionalities may be incompatible with subsequent chemical modifications of the polymer, particularly the crosslinking chemistry used to obtain polyurethanes. Poly(glycerol sebacate urethane) (PGSU), for example, is obtained by adding a diisocyanate, such as rhexamethylene diisocyanate (HDI), which reacts primarily with the hydroxyl (OH) groups present on the polymer to form a polyurethane network. However, it is known to those skilled in the art that these acidic functionalities can also react with isocyanate (NCO) groups to form an amide group with the release of carbon dioxide. (CO2) gas. During the crosslinking reaction to obtain, for example, a molded part, the released CO2 often remains trapped in the matrix, resulting in the formation of bubbles that frequently become trapped. The presence of bubbles is undesirable for the application (degraded mechanical properties). - The residual free water present in acid-formed PGS, typically measured between 0.10% and 1% by mass, is incompatible with subsequent chemical modifications of the polymer, particularly the crosslinking chemistry used to obtain polyurethanes. PGSU, for example, is obtained by adding a diisocyanate, such as hexamethylene diisocyanate (HDI), which reacts primarily with the hydroxyl (OH) groups present on the polymer to form a polyurethane network.However, it is known to those skilled in the art that free water reacts very rapidly with isocyanate (NCO) functions to form an amine function with the release of gaseous carbon dioxide (CO2), and the same result is obtained as before with bubbles trapped in the crosslinked composition on the one hand, and on the other hand a decrease in the selectivity of the reaction forming a polyurethane network, with the obtaining of a less dense network than intended, the presence of unwanted amine functions, resulting in losses of performance of the thermomechanical properties, not to mention a loss of reproducibility of the crosslinking process. - Metallic residues from catalysts can interfere with subsequent modifications of the synthesized polyester or may be undesirable for an application, particularly in the field of biomaterials. TECHNICAL PROBLEM

[0009] The technical problem that the present invention aims to solve is to provide an efficient and less energy-intensive synthetic process for a polyol polymer, preferably glycerol, and polycarboxylate units, preferably dicarboxylic acid diesters, particularly sebacate units, especially PGS, which meets all the constraints defined above and overcomes the problems encountered with prior processes. In particular, the objective of the invention is to provide an efficient and less energy-intensive synthetic process for a polyol polymer, preferably glycerol, and polycarboxylate units, preferably dicarboxylic acid diesters, particularly sebacate units, especially PGS, with reduced reaction times, compatible with industrial application and in a non-toxic environment. Description of the invention

[0010] Continuing its efforts, the Applicant has developed a process for the synthesis of a polyol polymer, preferably glycerol and polycarboxylate units, preferably dicarboxylic acid diester, in particular sebacate units, especially PGS, which is efficient, less energy-intensive and significantly faster, which overcomes the synthesis difficulties described above and which offers a non-toxic environment.

[0011] In particular, the Applicant has developed a synthesis process which makes it possible to obtain a polyol polymer, preferably glycerol and polycarboxylate units, preferably dicarboxylic acid diester, in particular sebacate units, in particular PGS, having an amount of water equal to zero or very close to zero (less than or equal to 0.3% mass relative to the polymer) at the polymerization output, an acid number, expressed in a known manner in mg of KOH / g of polymer, equal to zero or very close to zero (less than 2 mg of KOH / g of polymer) and containing neither residual dicarboxylic acid monomers, nor residual carboxylic acid chain ends, nor acidic catalytic residues. The polymer also does not contain any residual traces of metallic catalysts, such as transition metal, poor metal or rare earth, in particular tin (Sn), and / or enzymatic residues.Thus, the polymer obtained is compatible with a biological environment and compatible with different crosslinking chemistries. The process of the invention uses a basic organocatalyst that is non-toxic, non-carcinogenic, non-mutagenic, non-reprotoxic, and separable from the medium by a liquid-liquid extraction or distillation process.

[0012] The reaction to obtain the polymer is a transesterification reaction, which releases an alcohol, preferably methanol, which is easier to remove from the medium than water.

[0013] Thus, a first object of the invention is a process for synthesizing a polyester from a polyol and a dicarboxylic acid diester comprising the following steps:

[0014] (a) of bringing the polyol monomers, preferably glycerol, into contact with dicarboxylic acid diester, with a polyol:dicarboxylic acid diester molar ratio ranging from 0.5:1 to 10:1;

[0015] (b) transesterification under an inert atmosphere at a temperature above 25 °C;

[0016] (c) of placing the reaction medium obtained at the end of step (b) under vacuum, of preferably at a pressure less than or equal to 100 mbara (10000 Pa);

[0017] (d) of polycondensation under vacuum, preferably at the same pressure or lower than that of step (c), at a temperature above 25 °C;

[0018] said process comprising the introduction of a basic organocatalyst selected from the Brpnstedt base family, more preferably from guanidine derivatives and amidine derivatives, and more preferably still from guanidine derivatives.

[0019] A second object of the invention is a polyester that can be obtained by the process according to the invention.

[0020] A third object of the invention is such a polyol and dicarboxylic acid diester polyester having a number-average molar mass (Mn) greater than or equal to 1000 g / mol, preferably greater than or equal to 2000 g / mol, preferably greater than or equal to 2500 g / mol, a water content less than or equal to 0.3% by mass relative to the polymer, a metallic element content less than or equal to 0.1% by weight of the polymer, and an acid number less than 2 mg KOH / g of polymer. Summary of the invention

[0021] The invention, described in more detail below, relates to at least one of the implementations listed in the following points.

[0022] 1. Process for synthesizing a polyester from a polyol and a diacid diester carboxylic acid comprising the following steps: (a) of contacting polyol monomers, preferably glycerol, and dicarboxylic acid diester, with a polyol:dicarboxylic acid diester molar ratio ranging from 0.5:1 to 10:1; (b) transesterification under an inert atmosphere at a temperature above 25 °C; (c) vacuuming the reaction medium obtained following step (b), preferably at a pressure less than or equal to 100 mbara (10000 Pa); (d) of vacuum polycondensation, preferably at the same or lower pressure as in step (c), at a temperature above 25 °C; said process comprising the introduction of a homogeneous basic organocatalyst selected from the Brønstedt base family, more preferably from guanidine derivatives, with the exception of guanidine, and from amidine derivatives and mixtures thereof.

[0023] 2. Method according to embodiment 1, characterized in that the molar ratio dicarboxylic acid polyokdiester varies from 0.9:1 to 3:1.

[0024] 3. A process according to embodiment 1 or 2, characterized in that the diacid diester carboxylic is a compound of the following formula (I): ROOC-(CH2)n-COOR' (I) in which R and R' independently represent a linear or branched alkyl chain, or a vinyl function, and n represents an integer from 1 to 30, preferably from 1 to 10, preferably the dicarboxylic acid diester is chosen from the group consisting of malonic acid diesters, succinic acid diesters, glutaric acid diesters, adipic acid diesters, pimelic acid diesters, suberic acid diesters, azelaic acid diesters, sebacic acid diesters and mixtures thereof, more preferably dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate, dimethyl azelate, dimethyl sebacate, and their mixtures, even more preferentially the dicarboxylic acid diester is dimethyl sebacate.

[0025] 4. A method according to any one of embodiments 1 to 3, characterized in that the step (b) is carried out at a temperature less than or equal to 200 °C, preferably at a temperature ranging from 65 °C to 200 °C, preferably from 120 °C to 180 °C.

[0026] 5. A method according to any one of embodiments 1 to 4, characterized in that the step (b) is carried out over a period of time ranging from 0.25 h to 10 h, preferably from 1 h to 5 h.

[0027] 6. A method according to any one of embodiments 1 to 5, characterized in that the step (d) is carried out at a temperature less than or equal to 250 °C, preferably at a temperature ranging from 65 °C to 250 °C, preferably from 80 °C to 200 °C, more preferably from 100 °C to 180 °C.

[0028] 7. A method according to any one of embodiments 1 to 6, characterized in that the step (d) is carried out over a period of time ranging from 0.1 h to 12 h, preferably from 0.5 h to 4 h.

[0029] 8. A method according to any one of embodiments 1 to 7, characterized in that The basic organocatalyst is chosen from compounds corresponding to the following general formula (II): i

[0030] II

[0031] in which X represents the group -CRaRbRc (amidine derivatives) or -NR4R5 (guanidine derivatives), preferably -NR4R5; Each RI, R2, R3, R4 and R5 represents, independently of each other, a hydrogen atom or an alkyl radical in C1-C10, preferably in C1-C4, aryl in C6- CIO, an alkenyl radical in C2-C10, preferably in C2-C4, or forms a heterocycle with a substituent of another nitrogen atom; Ra, Rb and Rc independently represent a hydrogen atom or an alkyl radical in Cl-CIO, preferably in C1-C4, an aryl radical in C6-C10, an alkenyl radical in C2-C10, preferably in C2-C4, or form a heterocycle with a nitrogen atom substituent; provided that when X represents - NR4R5, the set of Ri cannot each represent a hydrogen atom (guanidine).

[0032] 9. A method according to any one of embodiments 1 to 8, characterized in that The basic organocatalyst is monocyclic or bicyclic, preferably bicyclic.

[0033] 10. A method according to any one of embodiments 1 to 9, characterized in that The basic organocatalyst is chosen from among the guanidine or amidine derivatives corresponding to one of the following formulas (III) to (V): or LrTR2 or li ru 1. -[H MYY R3 IV V

[0034] in which Y represents N(Rj)p, j being 4 or 5, or C(Rk)p, k being a, b or c, p being the remaining valence, RB R2 and R3, as well as the Rj and the Rk not forming a cycle, are such as described in embodiment 8, n and m being integers from 1 to 5.

[0035] 11. A process according to embodiment 10, characterized in that the basic organocatalyst is chosen from among the bicyclic derivatives of guanidine of formula III (Y represents N(Rj)p), preferably from the bicycles [4.4.0] and the bicycles [3.3.0], the Ri (i= 1 to 5) not forming a ring each represent, independently of each other, a hydrogen atom or an alkyl radical in C1-C10, preferably in C1-C4.

[0036] 12. A process according to embodiment 10, characterized in that the basic organocatalyst is chosen from among the bicyclic derivatives of amidine of formula III (Y represents C(Rk)p), preferably from the bicycles [5.4.0], the R; (i= 1 to 5) not forming a ring each represent, independently of each other, a hydrogen atom or an alkyl radical in Cl-CIO, preferably in C1-C4.

[0037] 13. A method according to any one of embodiments 1 to 12, characterized in that The basic organocatalyst is introduced at a stage chosen from: during step (b), after the transesterification of step (b), or before vacuum sealing. of step (c) or after vacuuming in step (c), preferably during step (b) while heating to the reaction temperature.

[0038] 14. A method according to any one of embodiments 1 to 13, characterized in that the organocatalyst is introduced in an amount ranging from 0.01% to 5% by weight, relative to the total weight of polyol monomers and dicarboxylic acid diester, preferably from 0.02% to 3% by weight, more preferably from 0.05% to 1% by weight.

[0039] 15. A method according to any one of embodiments 1 to 14, characterized in that Step (d) of polycondensation further includes removal of the alcohol produced by the polycondensation reaction, preferably by distillation.

[0040] 16. A method according to any one of embodiments 1 to 15, characterized in that the process further includes a step of recovering the organocatalyst, preferably by distillation or liquid-liquid extraction.

[0041] 17. Polyester that can be obtained by the process according to any one of the achievements 1 to 16.

[0042] 18. Polyol polyester, preferably glycerol, preferably still of poly(glycerol sebacate), according to embodiment 17, presenting - an average number-average molar mass (Mn) greater than or equal to 1000 g / mol, preferably greater than or equal to 2000 g / mol, preferably greater than or equal to 2500 g / mol, - a water content of less than 0.3% by weight relative to the total weight of the polymer, less than or equal to 0.2% by weight, preferably even less than or equal to 0.1% by weight of the weight of the polymer, - a metallic residue content of less than or equal to 0.1% by weight of the polymer, preferably less than or equal to 0.05% by weight, and - an acid value of less than 2 mg KOH / g of polymer, preferably less than or equal to 0.4 mg KOH / g of polymer. DEFINITIONS

[0043] In the present, unless expressly stated otherwise, all percentages (%) indicated are percentages (%) in moles.

[0044] In the present, unless otherwise indicated, pressure is expressed as absolute pressure indicated by the unit "bara" which corresponds to "absolute bar".

[0045] On the other hand, any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​from greater than a to less than b (i.e., excluding bounds a and b), while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​from a to b (i.e., including the strict bounds a and b). In the present case, when an interval of values ​​is designated The expression "from a to b" also and preferentially refers to the interval represented by the expression "between a and b".

[0046] When referring to a "major" compound, for the purposes of this invention, it is understood that this compound is the majority among the compounds of the same type in the composition; that is, it is the one that represents the largest quantity by mass among the compounds of the same type. Conversely, a "minor" compound is a compound that does not represent the largest mass fraction among the compounds of the same type. Preferably, "major" means a mass proportion of more than 50%; when the compound represents 100% by mass, it is also described as "major."

[0047] The compounds mentioned in the description may be of fossil origin or bio-based. 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 used, that is to say, they may be partially or totally derived from a recycling process, or obtained from raw materials themselves derived from a recycling process. Monomers are particularly relevant.

[0048] For the purposes of the present invention, an alkyl diester of a dicarboxylic acid will be called a "dicarboxylic acid diester".

[0049] For the purposes of this invention, the term "metallic elements" will conventionally refer to alkali metals, alkaline earth metals, transition metals, weak metals, lanthanides, and actinides. By definition, these elements do not include C, H, N, O, P, S, and Se. DETAILED DESCRIPTION OF THE INVENTION

[0050] The process according to the invention for preparing a polyester from a polyol, preferably glycerol, and a dicarboxylic acid diester comprises steps (a), (b), (c), and (d) as shown above in embodiment 1. Steps (a) and (b) / monomers

[0051] According to step (a) of the process of the invention, the polyol monomers, preferably glycerol and dicarboxylic acid diester are brought into contact.

[0052] The polyol monomer preferentially has two or three -OH functions, preferably three. The polyol monomer is very preferentially glycerol.

[0053] The dicarboxylic acid diester monomer according to the invention can be aliphatic, aromatic, or aliphatic / aromatic. In the latter case, the dicarboxylic acid diester comprises an aliphatic part and an aromatic part. It comprises Preference for 3 to 36 carbon atoms. By aliphatic, we mean linear, cyclic or branched aliphatic, whether saturated or unsaturated.

[0054] According to preferred embodiments of the invention, the dicarboxylic acid diester monomer is aliphatic and comprises 3 to 36 carbon atoms.

[0055] According to these variants, the dicarboxylic acid diester monomer may preferentially correspond to the following formula (I) ROOC-(CH2)n-COOR', in which n represents an integer from 1 to 30, preferably a number from 1 to 10, and R and R' represent, independently of each other, a linear or branched alkyl chain, in C1-C1, preferably in C1-C4, preferably also methyl or ethyl.

[0056] Preferably, according to these variants of the invention, the dicarboxylic acid diester monomer can be chosen from the diesters corresponding to malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid or a mixture of two or more of these dicarboxylic acid diesters, more preferably the dicarboxylic acid diester is chosen from the group consisting of dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl pimelate, dimethyl suberate, dimethyl azelate, dimethyl sebacate, and mixtures thereof. According to variations of the invention, the dicarboxylic acid diester monomer may be a mixture of at least two different dicarboxylic acid diesters. Preferably, the dicarboxylic acid diester monomer comprises dimethyl sebacate.

[0057] According to preferred embodiments of the invention, the dicarboxylic acid diester monomer is dimethyl sebacate.

[0058] According to preferred embodiments of the invention, the dicarboxylic acid diester monomer and glycerol are the only monomers. Most preferably, the dimethyl sebacate monomer and glycerol are the only monomers.

[0059] According to any one of the embodiments of the invention, the monomers are brought into contact in a container or reactor. The subsequent reactions can take place in the same reactor. Given the heating and pressure conditions, those skilled in the art will be able to adapt the type of container or reactor required for the process.

[0060] The dicarboxylic acid diester monomer can be used in liquid or solid form, preferably in liquid form at room temperature or slightly above room temperature.

[0061] According to the invention, the contacting of the monomers is advantageously carried out at a temperature below 100°C, preferably below 50°C. Advantageously, the diester monomers of dicarboxylic acids have a significantly lower melting point than their corresponding dicarboxylic acids, This facilitates the contact of the monomers. When the dicarboxylic acid diester monomer is introduced in solid form, the contact of the monomers is followed by a melting step of the diester monomer, in order to homogenize the medium.

[0062] Alternatively, adding an organic solvent to the monomer mixture allows for homogenization of the mixture and thus reduces its overall viscosity. To promote this homogenization, agitation is carried out in a known manner.

[0063] Thus, according to variants of the invention, the contacting of the monomers in step (a) is carried out in the presence of an organic solvent, preferably in the presence of a polar organic solvent.

[0064] According to these variants, an organic solvent, more preferably polar and aprotic, is optionally added to the monomers in a mass quantity of between 0% and 1000% of the mass of the monomers involved, preferably from 5% to 500% of the mass of the monomers involved, more preferably from 10% to 50% of the mass of the monomers involved.

[0065] In the case where the solvent is a polar organic solvent, it is preferably aprotic, chosen by those skilled in the art as enabling the solubilization of the monomers and the polymer produced and with a boiling point high enough to carry out the reaction under the required conditions, such as tetrahydrofuran, dichloromethane, acetone, acetonitrile, trifluorotoluene, diphenyl ether.

[0066] However, according to particularly preferred variants of the invention, step (a) is carried out in the absence of solvent.

[0067] According to step (a) of the process of the invention, the polyol monomers, preferably glycerol and dicarboxylic acid diester are brought into contact with a polyol dicarboxylic acid diester molar ratio ranging from 0.5 / 1 to 10 / 1, preferably ranging from 0.9 / 1 to 3 / 1, preferably still ranging from 1 / 1 to 2 / 1.

[0068] According to an advantageous embodiment of the invention, after the monomers in step (a) have been brought into contact, the reaction medium is brought to reflux by heating. Refluxing the medium allows, for example, the melting of the dicarboxylic acid diester monomer when it is introduced in solid form, by heating it to a temperature ranging from 25 °C to 200 °C. During this heating step, which ensures a homogeneous medium, care is taken to ensure that the vapors are properly condensed in the reactor, for example by setting the column to total reflux, according to methods well known to those skilled in the art. This step is optional if the dicarboxylic acid diester monomer is introduced in liquid form.

[0069] The polyol monomers and dicarboxylic acid diester react with each other according to transesterification step (b) of the process of the invention, under an inert atmosphere at a temperature above 25 °C, advantageously less than or equal to 200 °C, preferably ranging from 65 °C to 200 °C, preferably from 120 °C to 180 °C, by applying an isotherm or by applying a temperature ramp from +0.1 °C / min to +1 °C / min, either in one step or in several ramps interspersed with holding periods until the target temperature is reached. The transesterification reaction time is defined until the conversion to monomers is greater than 70%, preferably greater than 80%, preferably greater than 90%, typically ranging from 0.25 h to 10 h depending on the conditions applied, preferably between 1 h and 5 h. The conversion is determined by measuring the mass of distillate produced (alcohol, preferably methanol), or by 13C NMR by quantifying free glycerol, or by SEC by quantifying free dimethyl sebacate or free glycerol. These different measurement methods are explained in the section reserved for examples. Catalyst

[0070] An essential element of the invention consists of the use of a basic organocatalyst as a catalyst.

[0071] An organocatalyst is a small organic molecule consisting of the elements C, H, N, O, P, S and Se, preferably C, H and N. The organocatalyst according to the invention is not an enzyme.

[0072] According to the invention, the basic organocatalyst is chosen from among Brpnstedt's organic bases, preferably from guanidine derivatives, amidine derivatives and mixtures thereof, more preferably from guanidine derivatives and mixtures thereof.

[0073] According to a preferred embodiment of the invention, the organocatalyst is chosen from compounds corresponding to the following general formula (II): bU X I r3 II in which X represents the group - CRaRbRc (amidine derivatives) or - NR4R5 (guanidine derivatives), preferably - NR4R5; Each RI, R2, R3, R4 and R5 represents, independently of each other, a hydrogen atom or an alkyl radical in C1-C10, preferably in C1-C4, aryl in C6-C10, an alkenyl radical in C2-C10, preferably in C2-C4, or forms a heterocycle with a substituent of another nitrogen atom; Ra, Rb, and Rc independently represent a hydrogen atom or an alkyl radical in Cl-ClO, preferably in C1-C4, an aryl radical in C6-C10, a radical alkenyl in C2-C10, preferably in C2-C4, or forms a heterocycle with a nitrogen atom substituent; provided that when X represents - NR4R5, the set of Ri cannot each represent a hydrogen atom (guanidine).

[0074] For the purposes of this invention, the term "C1-C10 alkyl radical" refers to a monovalent, saturated, linear or branched hydrocarbon chain comprising 1 to 10, preferably 1 to 4, carbon atoms. Examples include methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, sec-butyl, pentyl, and hexyl groups.

[0075] For the purposes of this invention, the term "C2-C10 alkenyl radical" refers to a monovalent hydrocarbon chain having a carbon-carbon double bond, linear or branched, comprising 2 to 10, preferably 2 to 4, carbon atoms. Examples include the ethenyl, propenyl, etc. groups.

[0076] By "C6-C10 aryl radical" is meant here an aromatic hydrocarbon group, preferably comprising 6 to 10 carbon atoms, and including one or more fused rings, such as for example a phenyl or naphthyl group. Advantageously, this is phenyl.

[0077] By "heterocycle", we mean here an aliphatic (non-aromatic) group comprising 5 to 10 cyclic atoms of which one or two nitrogen atoms, the other cyclic atoms being carbon atoms.

[0078] Guanidine is by definition excluded from the family of compounds with general formula (II).

[0079] According to a preferred embodiment of the invention, the basic organocatalyst is monocyclic or bicyclic, preferably bicyclic.

[0080] According to this embodiment, the organocatalyst is preferably chosen from compounds derived from guanidine or amidine of general formula (III), (IV) and (V): u 7 or U 7 or 7 h y1 jY NY j" "3

[0081] in which Y represents N(Rj)p, j being 4 or 5, or C(Rk)p, k being a, b or c, p being the remaining valence, RB R2 and R3, as well as the Rj and the Rk not forming a cycle are as described above, n and m being integers from 1 to 5.

[0082] According to some implementations, the basic organocatalyst is chosen from among the guanidine derivatives of general formula (III), (IV) or (V), that is to say from among the compounds for which Y represents N(Rj)p.

[0083] According to these implementations of the invention, the organocatalyst is chosen from among the guanidine derivatives corresponding to the following formulas (VI) to (XII): NH N"' '■ I .... xx ... N" N " TL 'hT Formula VI Formula VII Formula HIV Formula IX Formula X Formula XI Formula XII

[0084] among which we can mention 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD) of formula VI; 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) of formula VII; or 1,1,3,3-tetramethylguanidine of formula XII.

[0085] According to preferred embodiments of the invention, the basic organocatalyst is bicyclic.

[0086] According to some of these embodiments, the basic organocatalyst is chosen from among the bicyclic guanidine derivatives of formula III. The organocatalyst is then preferably chosen from the [4,4,0] and [3,3,0] bicycles, each of the Ri (i = 1 to 5) not forming a ring representing, independently of each other, a hydrogen atom or an alkyl radical in C1-C10, preferably in C1-C4. Examples include 7-methyl-1,5,7-triazabicyclo[4,4,0]dec-5-ene (mTBD) of formula VI, and 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) of formula VII.

[0087] According to other embodiments of this embodiment, the basic organocatalyst is chosen from among the bicyclic amidine derivatives of formula III. The organocatalyst is then preferably chosen from the [5.4.0] bicyclics, each of the Rb R2, R3 and the non-ring-forming Rk atoms representing, independently of each other, a hydrogen atom or an alkyl radical in the C1-C10 position, preferably in the C1-C4 position. For example, 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) has the following formula XIII: ............... XIII

[0088] Such compounds and others suitable for the present invention are described in particular in Superbases for Organic Synthesis: Guanidines, Amidines, Phosphazenes and Related Organocatalysts Edited by Tsutomu Ishikawa © 2009 John Wiley & Sons, Ltd. ISBN: 978-0-470-51800-7.

[0089] The organocatalyst is preferentially soluble in the reaction medium, so that the organocatalysis process is homogeneous. It is optionally separable from the medium by a separation process such as distillation under reduced pressure or liquid-liquid extraction.

[0090] The organocatalyst can be used in the process of the invention in an amount from 0.01% to 5% by weight, relative to the total weight of polyol monomers and dicarboxylic acid diester, preferably from 0.02% to 3% by weight, more preferably from 0.05% to 1% by weight.

[0091] The introduction of the organocatalyst into the process can be carried out at any stage of the process up to the beginning of step (d).

[0092] Thus, it can be introduced at the beginning of step (b), preferably during the temperature rise to the reaction temperature or when the reaction medium has reached a reaction temperature of 25 °C or higher and is homogeneous. Indeed, the organocatalyst is preferentially introduced once the medium is homogeneous.

[0093] The introduction of the organocatalyst can also be done directly during step (b) or at the end of step (b) before reducing the pressure to an intermediate pressure, or during the reduction, for example when reaching a plateau, or just before the vacuuming of step (c), or even after the vacuuming of step (c).

[0094] According to a preferred embodiment, the introduction of the organocatalyst is carried out at a step chosen from: during step (b), at the end of the transesterification of step (b), before the vacuuming of step (c) or after the vacuuming of step (c), preferably during step (b) during the temperature rise towards the reaction temperature.

[0095] These basic catalysts have several advantages over the state of the art: These basic catalysts are selective for the desired reaction (transesterification), generating weakly branched chains with a significantly higher molar mass compared to those obtained without a catalyst. This is achieved by limiting parasitic chemistry (etherification and glycerol degradation) in prior art processes where the reaction media contain acidic species (acidic PGS synthesis: presence of carboxylic acids and / or acid catalyst chemistry (in transesterification or esterification)). This improved selectivity allows the reaction according to the invention to be carried out in steps b) and c) at higher temperatures than in prior art processes. - These catalysts are made up of organic elements (C, H, N, O, P, S and Se, preferably C, H and N), and therefore do not introduce metallic elements into the reaction medium. - These catalysts can easily be removed from the medium by a distillation step under reduced pressure due to their low molar mass, advantageously where appropriate during step (c) or (d), or by liquid-liquid extraction, known to those skilled in the art.

[0096] According to one embodiment of the invention, at the end of these steps of the process, the polyester produced can be recovered in a known manner, stored where appropriate, and possibly processed for its subsequent uses. Step (c)

[0097] According to a preferred embodiment of the invention, at the end of step (b), the process can continue with a step (c) by which the reaction medium is placed under vacuum.

[0098] Here, "vacuum" means reducing the pressure to a value less than or equal to 100 mbar, preferably less than 50 mbar, and even more preferably less than 10 mbar. In one embodiment, the pressure is within a range from 5 mbar to 50 mbar, preferably from 5 mbar to 10 mbar.

[0099] Following step (b), prior to the evacuation in step (c), the pressure can be gradually reduced, possibly in steps, to an intermediate pressure between atmospheric pressure and a vacuum. Any method known to those skilled in the art can be used to lower the pressure via a ramp or manually, in particular using a diaphragm pump, a rotary pump, etc. Such an intermediate pressure is less than 1 bar and varies, for example, from 700 mbar to 200 mbar. Step (d)

[0100] Following step (c), the process of the invention continues with a polycondensation step (d) at a temperature above 25 °C, preferably at a temperature less than or equal to 250 °C, preferably ranging from 65 °C to 250 °C, preferably further from 80 °C to 200 °C, preferably further from 100 °C to 180 °C, possibly following a ramp of between +0.1 °C / min and 1 °C / min. Once the target temperature is reached, the pressure is gradually reduced as close to a vacuum as possible. The pressure in step (d) is preferably the same as, or less than, that of step (c). In one embodiment, the pressure in step (d) is less than 50 mbar, preferably even less than 10 mbar. According to one embodiment, the pressure is within a range of 5 mbara to 50 mbara, preferably from 5 mbara to 10 mbara.

[0101] Polycondensation can take place instantaneously in the time required to establish the vacuum at the end of step (b), or over a period of up to 12 hours, preferably up to 6 hours, preferably up to 4 hours.

[0102] According to any one of the embodiments of the invention, the end of polycondensation is determined by means of the stirring motor torque reaching a target value guaranteeing a target molar mass via a target viscosity index and / or by SEC (Size Exclusion Chromatography) measurement of a sample taken from the container. The polycondensation time is, for example, from 0.1 h to 12 h, or even from 0.5 h to 4 h.

[0103] According to advantageous embodiments of the invention, concurrently with step (d), the alcohol, preferably methanol, produced by the polycondensation reaction is removed, for example, by distillation or any other known method for alcohol removal. According to advantageous embodiments of the invention, concurrently with steps (b) and (d), the alcohol produced by the transesterification and polycondensation reactions is removed, for example, by distillation or any other known method for alcohol removal. When alcohol removal is carried out by distillation, this may occur in conjunction with stirring and / or purging of the contents of the container by reaction under an inert gas.

[0104] Similarly, the organocatalyst can be partially or totally removed by distillation in step (c) or (d). It can be recovered for recycling. End of process

[0105] Steps (a) to (d) of the process according to the invention make it possible to obtain the polyester after a cumulative reaction time of less than 12 h, preferably less than 10 h, preferably less than 8 h.

[0106] Following these steps of the process according to the invention, the manufactured polyester can be recovered in a known manner, stored if necessary, and possibly processed for subsequent uses using techniques known to those skilled in the art. Measuring the nitrogen content of the polyester, by analysis using methods known to those skilled in the art (elemental analysis, total nitrogen Kjeldahl), allows the residual catalyst content in the polymer to be measured.

[0107] An optional treatment step may be applied to remove the last traces of catalyst, such as liquid-liquid extraction by dissolving the polyester in an organic solvent (e.g., dichloromethane) and aqueous washes before final drying of the polyester in batch or continuous processes (oven, scraped film evaporator). Depending on the process operation, this treatment may be applied either at the end of step (b), when the process stops at that stage, or at the end of step (d).

[0108] A measurement of the nitrogen content on polyester after treatment and drying, by analysis according to methods known to those skilled in the art (elemental analysis by fluorescence X (C, H, N and P), total nitrogen Kjeldahl (organic N)), allows us to measure the residual catalyst level in the polymer. Polyol polyester

[0109] A second object of the invention relates to a polyester that can be obtained by the process according to the invention described above.

[0110] A third object of the invention is a polyol polyester, preferably of glycerol, having an average number molar mass Mn greater than or equal to 1000g / mol, preferably greater than or equal to 2000 g / mol, preferably even greater than or equal to 2500 g / mol, an amount of water less than or equal to 0.3% by weight of the polymer, a rate of metallic elements less than or equal to 0.1% by weight of the polymer and an acid number less than 2 mg KOH / g of polymer.

[0111] According to certain embodiments, it is possible to obtain a polyol and dicarboxylic acid diester polyester which further exhibits one or more of the following characteristics, preferably all of the following characteristics: - a residual monomer content of less than 10% by weight relative to the total weight of the polymer, - a proportion of (1,2,3-triacylglyceride) units less than 20 mol% relative to the total acylglyceride units of the polymer, - a dispersion D less than 18.

[0112] The residual monomer content may be less than 5% by weight relative to the total weight of the polymer when the number-average molar mass Mn is greater than or equal to 1000 g / mol.

[0113] The water content may be less than 0.2% by weight relative to the total weight of the polymer, preferably 0.1% by weight, and more preferably 0.05% by weight. The water content corresponds to the amount of water present in the polymer at the end of its synthesis. Indeed, the polymer obtained can reabsorb water during storage in an uncontrolled atmosphere.

[0114] The acid number may be less than 1 mg KOH / g of polymer, preferably less than 0.5 mg KOH / g of polymer, more preferably less than 0.4 mg KOH / g of polymer, even more preferably less than 0.1 mg KOH / g of polymer.

[0115] The rate of metallic residues may be less than or equal to 0.08% by weight of the polymer, preferably less than or equal to 0.05% by weight of the polymer, preferably even less than or equal to 0.005% by weight of the polymer.

[0116] The proportion of (1,2,3-triacylglyceride) units may be less than 20 mol% relative to the total acylglyceride units of the polymer when the number-average molar mass Mn is greater than or equal to 1000 g / mol. By "total acylglyceride units", we mean the total of mono-, di- and tri-substituted glycerol monomeric units.

[0117] The dispersion D may be less than 18, preferably less than 15.

[0118] According to a particularly preferred embodiment, the polyol and dicarboxylic acid diester polyester is poly(glycerol sebacate).

[0119] One of the advantages of the process according to the invention is to allow obtaining polymers with Mn chains greater than 1000 g / mol after a reduced synthesis time, while controlling the characteristics mentioned above.

[0120] The residual monomer rate is determined according to the method described in the examples.

[0121] The macro structure (Mn, Mw) of the glycerol polyester and a dicarboxylic acid diester is determined by SEC according to the method described in the examples.

[0122] The microstructure of the glycerol polyester and a dicarboxylic acid diester is determined by 13C NMR according to the method described in the examples.

[0123] The acid value is determined according to the method described in the examples.

[0124] The water content is determined according to the method described in the examples.

[0125] The elemental dosage of metallic elements is determined according to the method described in the examples.

[0126] The rate of (1,2,3-triacylglyceride) units is determined according to the method described in the examples.

[0127] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration and not limitation. EXAMPLES OF THE INVENTION'S IMPLEMENTATION

[0128] 1. Measurement methods used to characterize the polymer

[0129] L1 Determination of the microstructure of PGS polymers

[0130] The microstructure of the polymers is determined by ¹H NMR analysis, supplemented by ¹³C NMR analysis when the resolution of the ¹H NMR spectra does not allow for the identification and quantification of all species. The measurements are performed using a BRUKER 500 MHz NMR spectrometer at frequencies of 500.43 MHz for proton observation and 125.83 MHz for carbon observation.

[0131] The following unit percentages of the polymer are taken into account for the determination of the unit percentage (1,2,3-triacylglyceride) (in mol%, determined by 13C NMR): • a: 1-acylglyceride motif, • b: 2-acylglyceride unit, • c: 1,3-diacylglyceride unit, • d: 1,2-diacylglyceride motif, and • [1,2,3] ■ 1,2,3-triacylglyceride motif.

[0132] The ratio of (1,2,3-triacylglyceride) units to the total acylglyceride units of the polymer therefore corresponds to the value 100 from which a, b, c and d are subtracted.

[0133] 1,2 Determination of the macrostructure of PGS polymers and the rates of residual monomers

[0134] The SEC (Size Exclusion Chromatography) technique allows the separation of macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, with the largest being eluted first.

[0135] While not an absolute method, SEC allows for the determination of the molar mass distribution of a polymer. Using commercial standard products, the various number-average (Mn) and weight-average (Mw) molar masses can be determined.

[0136] Size exclusion chromatography analyses were performed using a Viscotek instrument (Malvem Instruments) equipped with 4 columns, a guard column, and 3 detectors (differential refractometer and viscometer, and light scattering). The samples were dissolved at a concentration of 1 mg / mL in unstabilized THF, then stirred for 2 hours before injection.

[0137] 1 mL of a solution of the sample was filtered through a 0.45 qm PTFE membrane. 100 qL of this solution were eluted in THF using a flow rate of 1 mL.min⁻¹ at a temperature of 35 °C. OmniSEC software was used for data acquisition and analysis.

[0138] The technique used is size exclusion chromatography (SEC) with a column set optimized for the separation of low-mass species.

[0139] The analytical conditions used in the study are described in the following table: THF eluent without antioxidant. Injection volume 100 qL. Temperature 35 °C. Detector RI Waters. Mobile phase flow rate 1 mL / min. Columns: 2 Mixed D + 2 Mixed E

[0140] The calibration used for the Moore calculation is a PS calibration, covering a range from 2,520,000 to 162 g.mol'.

[0141] The calibration used is a mixed low and medium weight PS calibration of PSS Standards. The mass range extends from 162 to 66,000 g.mol1. The calibration allows the determination of the Mn (g.mol1), Mw (g.mol1), and D (Mw / Mn) values ​​in PS equivalent:

[0142] The calculation of the macrostructure does not take into account residual monomers because they are not considered to be part of the polymer.

[0143] The determination of the level of dimethyl sebacate, sebacic acid and glycerol is carried out by external calibration.

[0144] A standard curve using samples of dimethyl sebacate, sebacic acid and glycerol at different concentrations was prepared.

[0145] L3 Determination of the acid number of PGS polymers

[0146] The acid value is determined by acid-base titration. Weigh 0.1 g of the sample (polymer) into a beaker. Add the solvent mixture (25 mL of propan-2-ol and 25 mL of diethyl ether (previously neutralized)). Add 2–3 drops of phenolphthalein. Titrate with 0.1 N KOH (the concentration of which has been measured) until a pink color appears. The acid value is determined according to the formula:

[0147] With:

[0148] N = normality of the potassium hydroxide solution 0.1N,

[0149] V = volume, in mL, of the potassium hydroxide solution,

[0150] m = mass, in g, of the test piece.

[0151] The limit of quantification of the method was defined at 0.4 mg KOH / g. The limit of detection of the method was defined at 0.1 mg KOH / g. 1.4 Determination of the water content of PGS polymers

[0152] The water content is determined by titration with a Karl Fischer titrator according to the ISO 14897:2023 method.

[0153] The limit of quantification of the method was defined at 0.01% by weight relative to the total weight of the polymer. 1.5 Elemental assay of PGS polymers

[0154] The metal content is determined by ICP-AES atomic emission spectrometry. Approximately 100 mg of sample are weighed, the exact amount of sample is measured, and it is introduced into a microwave reactor. Then, 5 mL of concentrated nitric acid is added. The sample is mineralized according to the "all matrices" program. The medium is quantitatively transferred into a 50 mL volumetric flask with ultrapure water. Ultrapure water is added to fill to the calibration mark. The solution is filtered through a 0.45 µm GHP filter, and then the residue is analyzed by ICP-AES (Arcos instrument from Spectro & PQ 9000 Analytik Jena). The elements Li, Na K, Be, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, P, S, As, Se, are retained and quantified.

[0155] 1.6 Determination of total nitrogen in PGS polymers by the Kjedhal method

[0156] The nitrogen content is determined by applying the Kjedhal method. One gram of PGS is weighed into a digestion tube in the presence of 11 g of catalyst (a mixture of potassium sulfate and copper sulfate). 25 mL of sulfuric acid is added. The mixture is incubated for 30 min at 150 °C and then for 2 h at 400 °C. The mixture is then distilled. An Erlenmeyer flask containing 15 mL of 0.1 N sulfuric acid is placed at the distillate outlet, and the mineralized mixture is distilled for 6 min in the presence of 50 mL of water and excess sodium hydroxide. The distillate is then titrated with a 0.1 N sodium hydroxide solution. 2. Examples of implementation of the invention 2.1. Synthesis of poly(glycerol sebacate)

[0157] The reactions are conducted in a 100 mL glass reactor stirred by a magnetic stir bar, surmounted by a glass distillation column and a condenser connected to a distillate recovery vessel. The reactor is connected to a manifold allowing nitrogen purging or vacuuming of the reactor.

[0158] A quantity of glycerol and a quantity of dicarboxylic acid diester—here, dimethyl sebacate—are introduced at room temperature under a nitrogen flow (0.1 L / min) in step (a). The products are used as is, without further purification, except for inerting under nitrogen for 15 min before introduction into the reactor. The molar ratios between the monomers are specified in Table 1.

[0159] The nitrogen flow is maintained throughout step (b), under atmospheric pressure, with an agitation speed increased to 400 rpm and a heating setpoint fixed at a target temperature and for a defined time specified in Table 1.

[0160] If necessary, the catalyst is introduced into the reaction medium in a concentration defined at 0.5% w / w in Table 1a at this stage of the process and expressed in relation to the total mass of monomers involved.

[0161] The methanol distilled during this step is recovered in the distillate recovery pot.

[0162] Next, a gradual vacuum is applied to the reactor contents in step (c). The pressure is slowly reduced over approximately 15 minutes to a target value of less than 10 mbar. Once the pressure in the reaction vessel has stabilized, the medium is allowed to react at a target temperature and for a number of hours as defined in Table 1 during step (d).

[0163] The PGS produced is transferred from the reactor vessel to a container after the installation has been returned to atmospheric pressure and allowed to cool to ambient temperature. The product is finally transferred to a freezer for storage, where it is frozen for at least about 24 hours before analysis. 2.2. Results

[0164] Table 1a below gives the operating conditions of the synthesis process, Table 1b gives the results of the measurements carried out on the PGS obtained at the end of these syntheses.

[0165] Syntheses of PGS carried out without a catalyst via the acid route and the ester route (not according to the invention)

[0166] [Tables la] Glycerol / Monomer 2 Molar Ratio Test (mol / mol) Monomer 2 Nature of Catalyst dl (h) Tl (°C) d2 (h) T2 (°C) 1 1.0 Sebacacic acid Without catalyst eur 22 130 2 140 2 1.1 Sebacacic acid Without catalyst eur 4 130 0 - 3 1.1 Sebacacic acid Without catalyst eur 4 130 2 140 4 1.1 Dimethyl sebacate Without catalyst eur 4 160 2 160 5 1.1 Dimethyl sebacate SnOct2 4 160 2 160 6 1.1 Dimethyl sebacate Zn(OAc)2 4 160 2 160 7 1.1 Sebacate Dimethyl MgO 4 160 2 160 8 1.1 Dimethyl sebacate La2O3 4 160 2 160 9 1.1 Dimethyl sebacate Triethylamine 5 160 3 160 10 1.1 Dimethyl sebacate DABCO* 5 160 2.5 160

[0167] dl = Esterification or transesterification time, Tl = Esterification or transesterification temperature, d2 = Polycondensation time, T2 = Polycondensation temperature * DABCO = 1,4-Diazabicyclo[2.2.2]octane

[0168] [Tables 1b] Test Mn (g / mol) Mw (g / mol) D asl (% w / w) sdl (% w / w) gl (% P / P) Acid index (mg KOH / g polymer) Water content (% P / P) [1.2.3] (%mol) 1* 2640 9020 3.4 2.1 0 0.8 49 0.6 16.9 2 640 790 1.2 4 0 2.3 91 1.8 1 3 770 1040 1.4 3.7 0 1.9 90 1.8 2.4 4 675 792 1.2 0 >5 2.9 <LQ <LQ 1 5 ND ND ND 0 >5 >3 Not measured Not sure ND 6 ND ND ND 0 >5 >3 Not measured Not sure ND 7 ND ND ND 0 >5 >3 <LQ <LQ ND 8 726 879 1,2 0 >5 >3 <LQ <LQ < 1 9 460 480 1,0 0 74 >3 Not measured Not sure < 1 10 880 1390 1.6 0 12 >3 Not measured Not sure 1

[0169] LOQ: Limit of quantification, set at 0.4 mg KOH / g for acid value and 0.01% for water content; * carried out in the presence of 15% w / w water. ND: not determined due to insufficient conversion of monomers, ASL = free sebacic acid content, SDL = free dimethyl sebacate content, GL = free glycerol content, [1,2,3] = 1,2,3-triacylglyceride motif content.

[0170] According to the processes of Examples 2 and 3, carried out from sebacic acid, without a catalyst for total durations of 4h and 6h respectively, and without solvent – ​​in accordance with the prior art – a PGS is obtained with a Mn value of less than 1000 g / mol. According to the process described in Example 1, 24h of synthesis without a catalyst, in the presence of water, is required to obtain an Mn greater than 1000 g / mol with a residual monomer content of less than 5% by weight of the polymer obtained. According to Example 4, carried out from dimethyl sebacate, without a catalyst for a total duration of 6h and without solvent, a PGS is obtained which does indeed have a free sebacic acid content of 0%, an acid value < 0.5 mg KOH / g, and a non-significant water content, but the PGS has an Mn value that reaches a value of less than 1000 g / mol. Example 5 is carried out with dimethyl sebacate and with a catalyst Tin-based catalysts, which are not among the catalysts of the invention, and zinc octoate (SnOct2), which is toxic (reprotoxic according to ECHA), are also not used. Compared to Example 5, monomer conversion is low, and very few PGS oligomers were detected. The same observation can be made with the zinc acetate catalyst in Example 6, which is also not among the catalysts of the invention. Finally, when the MgO and La2O3 catalysts are used alone in Examples 7 and 8, monomer conversion is low, and the synthesis yields only very low molecular weight polymers with a very low yield. When the triethylamine and DABCO catalysts are used alone in Examples 9 and 10, the synthesis yields only very low molecular weight polymers (less than 1000 g / mol) with a significantly high residual monomer content.

[0171] Syntheses of PGS carried out in the presence of an organocatalyst (according to the invention)

[0172] Table 2a below gives the operating conditions of the synthesis process according to the invention, starting from glycerol and dimethyl sebacate. Table 2b gives the results of the measurements carried out on the PGS obtained at the end of these syntheses.

[0173] The catalysts used are therefore from the guanidine family, such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,1,3,3-tetramethylguanidine (TMG), 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD), or from the amidines, such as 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU), with a catalyst concentration expressed as a mass percentage relative to the total mass of monomers and indicated in Table 2a.

[0174] [Tables2a] Test Molar Ratio G lycerol / dimethyl sebacate (mol / mol) Catalyst Type Catalyst Quantity (% mass) dl (h) Tl (°C) d2 (h) T2 (°C) 11 1.1 TBD 0.5 4 160 0.5 160 12 1.1 TBD 0.5 4 150 2 150 13 1.1 TBD 0.25 4 160 2 160 14 1.1 TMG 3 4 160 2 160 15 1.1 mTBD 0.5 4 160 2 160 16 1.1 DBU 0.5 4 160 2 160

[0175] dl = Transesterification time, Tl = Transesterification temperature, d2 = Polycondensation time, T2 = Polycondensation temperature, TBD = 1,5,7-triazabicyclo [4.4.0] dec-5-ene, TMG = 1,1,3,3 tetramethylguanidine, mTBD = 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, DBU = 1,8-Diazabicyclo[5.4.0]undec-7-ene.

[0176] [Tables2b] Test Mn (g / mol) Mw (g / mol) D sdl (%w / w) gl (%w / w) Acid number (mg KOH / g of polymer) Water content (%w / w) [1.2.3] (%mol) 11 2790 12615 4.5 1.0 2.0 <lq <lq 17 12 2840 16615 5,8 1,2 1,7 16 13 2500 10555 4,2 1,6 2,2 14 1750 4260 2,4 3,0 2,3 15 3155 39765 12,6 0,9 2515 10855 4,3 1,3 1,9

[0177] LQ: Limit of quantification, set at 0.4 mg KOH / g for acid number and 0.01% for water content, SDL = Free dimethyl sebacate content, GL = Free glycerol content, [1,2,3] = 1,2,3-triacylglyceride motif content.

[0178] Elemental dosage of PGS prepared according to the invention

[0179] [Tables3] Test Catalyst used Results Kjedhal nitrogen in ppm (mass %) 14 TMG 3000 ppm (0.3) 15 mTBD 900 ppm (0.09) 16 DBU 600 ppm (0.06)

[0180] During the analysis of metallic elements, quantities of residual Ca, Mg, Ag, and Zn less than 90 ppm (0.009% by mass of the polymer) were detected. Thus, none of the target elements from the list of selected metals were detected in significant quantities.

[0181] Comparison of example 1 (non-conforming) with examples 11, 12, 13, 14, 15 and 16 (conforming to the invention):

[0182] According to the processes carried out with the preferred catalysts derived from guanidine (TBD, TMG, mTBD) and amidine (DBU), in accordance with the invention, PGS are obtained with Mn values ​​exceeding 2500 g / mol (tests 11 to 13), 1750 g / mol (test 14), 3155 g / mol (test 15) and 2515 g / mol (test 16), respectively, with a residual monomer content for the bicyclic catalysts (tests 11 to 13 and 15 to 16) of less than 5% by weight of the weight of the polymer obtained, with a total duration of 4.5 h to 6 h and reaction temperatures between 150 °C and 160 °C. The acid number and the water content is also negligible: the acceleration of the reaction kinetics compared to that of example 1 is therefore very significant, as is the obtaining of a polymer without acid functions or water and a level of 1,2,3-triacylglycerides motifs which remains controlled and without metallic residues, with the detection of only nitrogen in small quantities (<0.3 wt%) in examples 14, 15 and 16.

[0183] Comparison of examples 2 and 3 (non-conforming) with examples 11, 12, 13, 14, 15 and 16 (conforming to the invention):

[0184] It is observed that the process carried out by acidic route and with reaction times of the same order of magnitude as the examples carried out with the process according to the invention (i.e. around 6h), the molar masses are very significantly lower with high residual monomer levels, high acid indices and high free water levels.

[0185] Comparison of examples 4 to 8 (non-conforming) with examples 11, 12, 13, 14, 15 and 16 (conforming to the invention):

[0186] It is observed in the same way as before that despite the use of dimethyl sebacate in examples 4 to 8, without a catalyst or with catalysts that are not part of the invention, i.e. non-organic and not belonging to the families of guanidine and amidine derivatives in syntheses with reaction times of the same order of magnitude (i.e. about 6h), the molar masses are very significantly lower with high residual monomer levels, synonymous with a low conversion.

[0187] Comparison of examples 9 and 10 (non-conforming) with examples 11, 12, 13, 14, 15 and 16 (conforming to the invention):

[0188] It is observed in the same way as before that despite the use of dimethyl sebacate in examples 9 and 10, with organic catalysts but which are not part of the invention (here triethylamine and DABCO) in syntheses with reaction times of the same order of magnitude (i.e. about 6h), the molar masses are very significantly lower with high residual monomer levels, synonymous with a low conversion.

[0189] Finally, it is observed that no element from the metal families was detected in significant quantity. The residual nitrogen concentration in the samples of the examples according to the invention is low, with values ​​below 0.3% by mass, as shown in Table 3. This demonstrates that a significant portion of the catalyst was removed by evaporation.< / lq>

Claims

Demands

1. A process for the synthesis of a polyester from a polyol and a dicarboxylic acid diester comprising the following steps: (a) contacting the polyol monomers, preferably glycerol, and the dicarboxylic acid diester, with a polyol-dicarboxylic acid diester molar ratio from 0.5:1 to 10:1; (b) transesterification under an inert atmosphere at a temperature above 25 °C; (c) evacuating the reaction medium obtained from step (b), preferably at a pressure less than or equal to 100 mbar (10000 Pa); (d) polycondensation under vacuum, preferably at a pressure equal to or lower than that of step (c), at a temperature above 25 °C; said process comprising the introduction of a basic organocatalyst selected from the Brønsted bases, preferably from the group consisting of guanidine derivatives, excluding guanidine, and amidine derivatives and their mixtures.

2. A process according to claim 1, characterized in that the polyokdiester molar ratio of dicarboxylic acid varies from 0.9:1 to 3:1, preferably from 1:1 to 2:

1.

3. A process according to claim 1 or 2, characterized in that the dicarboxylic acid diester is a compound of the following formula (I): ROOC-(CH2)n-COOR' (I) in which R and R' independently represent a linear or branched alkyl chain, or a vinyl function, and n represents an integer from 1 to 30, preferably from 1 to 10, preferably the dicarboxylic acid diester is selected from the group consisting of malonic acid diesters, succinic acid diesters, glutaric acid diesters, adipic acid diesters, pimelic acid diesters, suberic acid diesters, azelaic acid diesters, sebacic acid diesters and mixtures thereof, more preferably dimethyl malonate, dimethyl succinate, glutarate of dimethyl, dimethyl adipate, dimethyl pimelate, dimethyl suberate, dimethyl azelate, dimethyl sebacate, and their mixtures, even more preferentially the dicarboxylic acid diester is dimethyl sebacate.

4. A method according to any one of claims 1 to 3, characterized in that step (b) is carried out at a temperature less than or equal to 200 °C, preferably at a temperature ranging from 65 °C to 200 °C, preferably from 120 °C to 180 °C.

5. A method according to any one of claims 1 to 4, characterized in that step (b) is carried out for a duration ranging from 0.25 h to 10 h, preferably from 1 h to 5 h.

6. A method according to any one of claims 1 to 5, characterized in that step (d) is carried out at a temperature less than or equal to 250 °C, preferably at a temperature ranging from 65 °C to 250 °C, preferably from 80 °C to 200 °C, more preferably from 100 °C to 180 °C.

7. A method according to any one of claims 1 to 6, characterized in that step (d) is carried out for a duration ranging from 0.1 h to 12 h, preferably from 0.5 h to 4 h.

8. A process according to any one of claims 1 to 7, characterized in that the basic organocatalyst is selected from compounds corresponding to the following formula (II): N^'XH in which X represents the group -CRaRbRc (amidine derivatives) or -NR4R5 (guanidine derivatives), preferably -NR4R5; each RI, R2, R3, R4 and R5 represents, independently of each other, a hydrogen atom or an alkyl radical in Cl-ClO, preferably in C1-C4, aryl in C6-C10, an alkenyl radical in C2-C10, preferably in C2-C4, or alternatively forms with a substituent of another nitrogen atom a heterocycle; Ra, Rb and Rc independently represent a hydrogen atom or an alkyl radical in Cl-CIO, preferably in Cl-C4, an aryl radical in C6-C10, an alkenyl radical in C2-C10, preferably in C2-C4 or form a heterocycle with a nitrogen atom substituent; provided that when X represents - NR4R5, the set of Ri cannot represent a hydrogen atom.

9. - A method according to any one of claims 1 to 8, characterized in that the basic organocatalyst is monocyclic or bicyclic, preferably corresponding to one of the following formulas (III) to (V): m tv y in which Y represents N(Rj)p, j being 4 or 5, or C(Rk)p, k being a, b or c, p being the remaining valence, Rb R2 and R3, as well as the Rj and Rk not forming a ring are as described above, n and m being integers from 1 to 5.

10. A process according to any one of claims 1 to 9, characterized in that the introduction of the basic organocatalyst is carried out at a step chosen from: during step (b), at the end of the transesterification of step (b), before the vacuuming of step (c) or after the vacuuming of step (c), preferably during step (b) during the temperature rise to the reaction temperature.

11. A process according to any one of claims 1 to 10, characterized in that the organocatalyst is introduced in an amount from 0.01% to 5% by weight, relative to the total weight of polyol monomers and dicarboxylic acid diester, preferably from 0.02% to 3% by weight, more preferably from 0.05% to 1% by weight.

12. A process according to any one of claims 1 to 11, characterized in that the polycondensation step (d) further comprises an removal of the alcohol produced by the polycondensation reaction, preferably by distillation.

13. A method according to any one of claims 1 to 12, characterized in that the method further comprises a recovery step

14.

15. of the organocatalyst, preferably by distillation or liquid-liquid extraction. Polyester that can be obtained by the process according to any one of claims 1 to 13. Polyester according to claim 14, having - an average number-average molar mass (Mn) greater than or equal to 1000 g / mol, preferably greater than or equal to 2000 g / mol, preferably greater than or equal to 2500 g / mol, - a water content of less than 0.3% by weight relative to the total weight of the polymer, less than or equal to 0.2% by weight, preferably even less than or equal to 0.1% by weight of the weight of the polymer, - a metallic residue content of less than or equal to 0.1% by weight of the polymer, preferably less than or equal to 0.05% by weight, and - an acid value of less than 2 mg KOH / g of polymer, preferably less than or equal to 0.4 mg KOH / g of polymer.