Process for obtaining a biodegradable branched aliphatic or aromatic-aliphatic polyester

Abstract

This invention relates to a process for obtaining a biodegradable aliphatic or aromatic-aliphatic branched polyester which comprises an esterification or transesterification step and a subsequent polycondensation step, characterised by the fact that said polycondensation step is carried out in the presence of a catalyst comprising titanium, or titanium / zirconium or mixtures thereof and phosphorus in the form of a mono- or di-ester of phosphoric acid and the branched polyester thus obtained.

Description

[0001] PROCESS FOR OBTAINING A BIODEGRADABLE BRANCHED ALIPHATIC OR AROMATIC-ALIPHATIC POLYESTER

[0002] DESCRIPTION

[0003] This invention relates to a process for obtaining a biodegradable aliphatic or aromatic-aliphatic branched polyester which comprises an esterification or transesterification step and a subsequent polycondensation step, characterised by the fact that said polycondensation step is carried out in the presence of a catalyst comprising titanium, or titanium / zirconium or mixtures thereof and phosphorus in the form of a mono- or di-ester of phosphoric acid and the branched polyester thus obtained.

[0004] The use of catalysts comprising titanium, or titanium / zirconium or mixtures thereof and phosphorus in the polycondensation step in the processes for preparing biodegradable aliphatic or aromatic-aliphatic polyesters is well known in the art.

[0005] For example, patent application WO2016 / 050963 describes a combined process for the production of polyesters that comprises an esterification or transesterification step and a subsequent polycondensation step, characterised by the fact that said polycondensation step is carried out in the presence of a catalyst comprising a mixture of at least one titanium -based compound and at least one zirconium-based compound in which the weight ratio Ti / (Ti+Zr) is equal to or greater than 0.01 and equal to or less than 0.70.

[0006] WO20 16 / 050963 teaches that, with this process, it is possible to obtain polyesters with a lower formation of mixed cyclical residues that are eliminated by distillation during the polycondensation step.

[0007] WO2023 / 104757 specifically mentions catalysts for the polycondensation of titanium and zirconium mixtures in the presence of phosphorus to produce aromatic-aliphatic polyesters.

[0008] This patent teaches that, with the said polycondensation catalysts, it is possible to obtain a controlled quantity of mixed residual cyclic oligomers.

[0009] In the cited patent applications, phosphorus belongs to the family of organic phosphates or phosphites.

[0010] WO2022 / 167410 provides examples of branched polyesters for extrusion coating produced by a process involving a catalytic polycondensation system not containing phosphorus.

[0011] In the preparation of biodegradable aliphatic and aromatic-aliphatic polyesters, there is a particular need for improved rheological properties that allow better processing of these polymers. It has been found that the combined use of catalysts based on titanium or titaniumzirconium mixtures and a phosphorus-containing additive belonging to the family of monoesters or organic esters of phosphoric acid allows a general improvement of the properties of the polyester. In particular, the rheological properties are improved by lowering the activation energy which corresponds to a lower susceptibility of the polyester to modify its rheological behaviour in function of temperature variations. This property allows for greater stability in processing operations by making a wider working temperature range accessible, resulting in greater processing ease. The possibility of transforming the material at lower temperatures without excessively increasing its viscosity allows thermal and hydrolytic degradation to be reduced during the transformation process, while accessing higher transformation temperatures without losing bubble stability and process regularity allows the specific absorption levels to be reduced, with the consequent possibility of increasing plant throughput and therefore productivity.

[0012] A first object of this invention is therefore a process for obtaining a biodegradable branched aliphatic or aromatic-aliphatic polyester comprising:

[0013] (i) an esterification / transesterification step in the presence of the diol and dicarboxylic components, and of at least one polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups, and of an esterification / transesterification catalyst; and

[0014] (ii) of a polycondensation step in the presence of a catalytic system characterised by the fact that it comprises titanium, or titanium / zirconium or mixtures thereof and phosphorus in the form of a mono- or di-ester of phosphoric acid in which the concentration of titanium, or titanium / zirconium is 0.5-5 mmol per kg of polymer, and the ratio of titanium / phosphorus or titanium+zirconium / phosphorus, by weight, is between 2 and 15, more preferably between 3 and 12.

[0015] The biodegradable branched polyesters obtained by the process according to this invention constitute a further object of the invention, such polyesters being characterised by branches obtained by means of a polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups and by a Z factor calculated according to the following formula:

[0016] Z = (E_act-20)3 / (RPxBD)

[0017] Where:

[0018] Eact is the activation energy measured by capillary rheometry at 150-170-190°C, y=103.68 s-1, expressed in KJ / gmol;

[0019] RP is the polymer branching %

[0020] PD is the polymer branching density; in which the said Z factor is between 1 and 8000. The process according to this invention comprises an esterification or transesterification step (i) in the presence of the diol and dicarboxylic components, and of at least one polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups, and of an esterification / transesterification catalyst; and a polycondensation step (ii), in the presence of a catalytic system characterised by the fact that it comprises titanium, or titanium / zirconium or mixtures thereof and phosphorus in the form of a mono- or di-ester of phosphoric acid in which the concentration of titanium, or titanium / zirconium is 0.5-5 mmol per kg of polymer, and the titanium / phosphorus or titanium+zirconium / phosphorus ratio, by weight, is between 2 and 15, more preferably between 3 and 12.

[0021] Advantageously, the phosphorus-containing compound is chosen from the compounds of general formula (1): where R1 is H or a cation of an alkaline or alkaline-earthy element or ammonium, R2 is indifferently chosen from C1-C20 alkyl or cycloalkyl, C6-C20 aryl or arylalkyl, or a polyalkylene oxide or alkyl-polyalkylene oxide chain and R3 can be indifferently chosen from H, or a cation of an alkaline or alkaline-earthy element or ammonium or C1-C20 alkyl or cycloalkyl, C6-C20 aryl or arylalkyl, or a polyalkyleneoxide or alkyl-polyalkyleneoxide chain. In a particularly preferred embodiment, the phosphorus-containing compound is polyethylene glycol tridecyl ether phosphate ammonium salt.

[0022] The esterification / transesterification step is preferably fed with a molar ratio of aliphatic diols to dicarboxylic acids, their esters and their salts, that is preferably between 1 and 2.5, preferably between 1.05 and 1.9.

[0023] The dicarboxylic acids, their esters or their salts, the aliphatic diols and any other comonomers that constitute the polyester can be fed to this stage separately, thus mixing in the reactor, or alternatively they may be premixed, preferably at T < 70°C, before being sent to the reactor.

[0024] It is also possible to premix part of the components and subsequently modify their composition, for example during the esterification / transesterification reaction.

[0025] In the case of polyesters in which the dicarboxylic component comprises repeating units derived from multiple dicarboxylic acids, whether aliphatic or aromatic, it is also possible to premix some of these with aliphatic diols, preferably at T < 70°C, adding the remaining portion of the dicarboxylic acids, diols and any other comonomers to the esterification / transesterification reactor.

[0026] The esterification / transesterification step of the process according to this invention is advantageously carried out at a temperature of 200-250°C and a pressure of 0.7-1.5 bar, preferably in the presence of an esterification / transesterification catalyst.

[0027] The esterification / transesterification catalyst, which can also be advantageously used as a component of the catalyst of the polycondensation stage, can in turn be fed directly to the esterification / transesterification reactor or can also be first dissolved in an aliquot of one or more of the dicarboxylic acids, their esters or their salts, and / or aliphatic diols, in such a way as to facilitate dispersion in the reaction mixture and make it more uniform.

[0028] In a preferred embodiment, the esterification / transesterification catalyst is chosen from organometallic tin compounds, for example stannoic acid derivatives, titanium compounds, for example titanates such as tetrabutyl orthotitanate or tetra(isopropyl) orthotitanate, zirconium compounds, for example zirconates such as tetrabutyl orthozirconate or tetra(isopropyl) orthozirconate, antimony compounds, aluminium compounds, for example Al-triisopropyl, and zinc compounds and mixtures thereof.

[0029] Regarding the organometallic esterification / transesterification catalysts of the type mentioned above, during the esterification / transesterification step of the process according to this invention, they are present in concentrations preferably between 0.13 and 2.5 mmol of metal per kg of polyester which can theoretically be obtained by converting all the dicarboxylic acid fed to the reactor.

[0030] In a preferred embodiment, the catalyst for the esterification / transesterification step is a titanate, more preferably diisopropyl, triethanolamine titanate, preferably used in a concentration of 0.13-2.5 mmol of metal per kg of polyester which can theoretically be obtained by converting all of the dicarboxylic acid fed to the reactor.

[0031] Preferably, the reaction time for the esterification / transesterification step in the process according to this invention is between 4 and 8 hours.

[0032] In an another preferred embodiment catalysts based on Ti chelated with citric acid (or hydroxy acids) and its (their) esters can also be used (Ti / C).

[0033] The use of these catalysts is preferable due to their greater stability to hydrolysis and greater control over the active Titanium concentration and, consequently, the Ti / P ratio.

[0034] The polycondensation step in the process according to this invention is carried out in the presence of a catalyst comprising titanium, optionally with zirconium or mixtures thereof, and a phosphorus-containing compound in the form of a mono- or di-ester of phosphoric acid, with a total amount of titanium of 0.5-5 mmol per kg of polyester which could theoretically be obtained by converting all the dicarboxylic acid fed to the reactor in the catalyst. The ratio of titanium to phosphorus is between 2 and 15, preferably between 3 and 12. If present, the total amount of zirconium must be such as to maintain the Ti / (Ti+Zr) ratio in the range 0.01-0.70.

[0035] In a preferred embodiment, the polycondensation catalyst comprising titanium is a titanate advantageously chosen from compounds having the general formula Ti(OR)4 where R is a ligand group comprising one or more carbon, oxygen, phosphorus and / or hydrogen atoms.

[0036] On the same titanium atom, different R ligand groups can be present, but preferably these groups are identical in order to facilitate the preparation of the titanate.

[0037] Also, two or more R ligands can be derived from a single compound and can be chemically linked to each other in addition to being linked by the titanium (so-called multidentate ligands such as, for instance, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethanediamine).

[0038] R is advantageously chosen from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3 -oxobutanoic acid, ethanediamine and linear or branched Cl -Cl 2 alkyl residues such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl, ethylhexyl. In a preferred embodiment, R is chosen from C1-C12 alkyl residues, preferably C1-C8, more preferably n-butyl.

[0039] Preparation of the titanates is known in the literature. Typically these are prepared by reacting titanium tetrachloride and the precursor alcohol with formula ROH in the presence of a base such as ammonia, or through the transesterification of other titanates.

[0040] Commercial examples of titanates that may be used in the process of this invention include the products Tyzor® TPT (tetra isopropyl titanate), Tyzor® TnBT (tetra n-butyl titanate), and Tyzor® TE (diisopropyl triethanolamine titanate).

[0041] When the polycondensation catalyst comprising zirconium is used together with the one comprising titanium, this is a zirconate advantageously chosen from compounds having general formula Zr(OR)4 in which R is a ligand group comprising one or more atoms of carbon, oxygen, phosphorus and / or hydrogen.

[0042] As in the case of titanates, on the same zirconium atom there can be multiple, different but preferably identical, ligand groups R, in order to facilitate preparation of the zirconate.

[0043] In addition, two or more R ligands can be derived from a single compound or can be chemically linked to each other in addition to being linked by the zirconium (so-called multidentate ligands such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethanediamine). R is advantageously chosen from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3 -oxobutanoic acid, ethanediamine, and linear or branched Cl-C12alkyl residues such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl, or ethylhexyl. In a preferred embodiment, R is chosen from C1-C12 alkyl residues, preferably C1-C8, more preferably n-butyl.

[0044] Preparation of the zirconates is known in the literature, and is similar to that described above for titanates.

[0045] Commercial examples of zirconates usable in the process according to this invention include the products Tyzor® NBZ (tetra n-butyl zirconate), Tyzor NPZ (tetra n-propyl zirconate), IG- NBZ (tetra n-butyl zirconate), Tytan TNBZ (tetra n-butyl zirconate), Tytan TNPZ (tetra n- propyl zirconate).

[0046] The polycondensation catalyst and the phosphorus-containing compounds are fed to the polycondensation stage by feeding the various components separately to the reactor.

[0047] It is also possible to premix some of the components and subsequently adjust the composition of the catalyst, for example when it comes into contact with the oligomer product.

[0048] When a catalyst containing titanium and / or zirconium compounds is used in the esterification / transesterification step of the process according to this invention, in a preferred embodiment of the process according to the invention, this catalyst is not separated from the oligomeric product and is fed together with it to the polycondensation stage and advantageously used as polycondensation catalyst or as a component thereof, possibly adjusting the molar ratio between titanium and zirconium by adding appropriate quantities of titanium and zirconium compounds to said polycondensation stage.

[0049] It is possible that the catalyst of the polycondensation stage is the same as that for the esterification / transesterification stage.

[0050] The polycondensation stage is advantageously carried out by feeding the oligomeric product to the polycondensation reactor and causing all the materials to react in the presence of the catalyst at a temperature of 220-260°C and at a pressure between 0.5 mbar and 350 mbar.

[0051] Preferably, the reaction time for the polycondensation step in the process according to this invention is between 4 and 8 hours.

[0052] The biodegradable branched aliphatic or aromatic-aliphatic polyester obtained by the process described above constitutes a further object of this invention, said polyester being characterised by branches obtained by means of a polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups, and by a Z factor calculated according to the following formula: Z = (E_act-20)3 / (RPxBD) where:

[0053] Eact is the activation energy measured by capillary rheometry at 150-170-190°C, y=103.68 s-1, expressed in KJ / gmol;

[0054] RP is the polymer branching %

[0055] PD is the polymer branching density; in which the said Z factor is between 1 and 8000.

[0056] The activation energy (Eact) expresses the influence of temperature on the shear viscosity of the polymer. The Eact of this invention is measured by capillary rheometry at 150-170-190°C, 7=103.68 s-1 following the method used in the article “Determination of polymer melts flowactivation energy a function of wide range shear rate - G. Toth et al. 2018 JPhis.:Conf.Ser. 1045012040”.

[0057] RP is the branching % of the polymer and represents the percentage in moles of the polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups with respect to the total moles of the dicarboxylic component. Said polyfunctional compound is added during the esterification / transesterification step . In this invention it is between 0.15 and 0.45, preferably 0.20 and 0.45, more preferably between 0.30 and 0.40.

[0058] PD is the branching density of the polymer, which is a function of the type of polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups used, it was calculated as defined in the article “Branching Features of a Polymer- Nguyen T. Hieu Ha &Grainne M. Moran 2012, Journal of Macromolecular Science, Part B, 51:10,1942- 1975, DOI: 10.1080 00222348.2012 663698”. In this invention, the branching density PD of the polymer is between 0.45 and 0.80, preferably between 0.50 and 0.67.

[0059] Said polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups is chosen from the group of poly functional molecules such as polyacids, polyols and their mixtures.

[0060] Examples of such polyacids are: pyromellitic acid, pyromellitic anhydride, ethylenediamine tetraacetic acid, furan-2,3,4,5-tetracarboxylic acid, naphthalene-l,4,5,8-tetracarboxylic acid, naphthal ene- 1 , 4, 5 , 8 -tetracarb oxy li c anhydride .

[0061] Examples of such polyols are: sorbitol, pentaerythritol, dipentaerythritol, di trimethylolpropane, trimethylolpropane, glycerol, diglycerol, triglycerol, tetraglycerol and mixtures thereof.

[0062] Preferably the polyfunctional compound is chosen from sorbitol, ditrimethylolpropane, glycerol, pentaerythritol. The biodegradable polyester obtained with the process of the invention and characterised by branches obtained by means of a polyfunctional compound containing at least three functional groups between acidic (COOH) and / or hydroxyl (OH), and by a Z factor between 0 and 8000, can be aromatic-aliphatic or aliphatic.

[0063] The biodegradable polyester obtained with the process of the following invention presents undoubted advantages thanks to the typicality of the process described.

[0064] The biodegradable branched polyester according to this invention is advantageously chosen from aliphatic and aromatic-aliphatic biodegradable polyesters. In a preferred embodiment, the polyester according to this invention is an aromatic-aliphatic polyester.

[0065] As regards aromatic-aliphatic polyesters, they have an aromatic part consisting mainly of polyfunctional aromatic acids, an aliphatic part consisting of aliphatic diacids and aliphatic diols and their mixtures.

[0066] As for aliphatic polyesters, they are obtained from aliphatic diacids and aliphatic diols and their mixtures.

[0067] By polyfunctional aromatic acids are meant aromatic dicarboxylic compounds of the phthalic acid type, preferably terephthalic acid or isophthalic acid, more preferably terephthalic acid, and heterocyclic aromatic dicarboxylic compounds, preferably 2,5-furandicarboxylic acid, 2,4- furandicarboxylic acid, 2,3-furandicarboxylic acid, 3,4-furandicarboxylic acid, their esters, their salts and mixtures thereof.

[0068] Aliphatic diacids are aliphatic dicarboxylic acids with carbon numbers from C2 to C24, preferably C4-C13, more preferably C4-C11, their alkyl esters C1-C24, preferably C1-C4, their salts and mixtures thereof. Preferably, the aliphatic dicarboxylic acids are chosen from: succinic acid, 2-methylsuccinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid and their C1-C24 alkyl esters. Preferably said aliphatic dicarboxylic acids are chosen from the group consisting of succinic acid, adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid and mixtures thereof.

[0069] The dicarboxylic component of the aliphatic or aromatic-aliphatic polyesters according to this invention may comprise up to 5% of unsaturated aliphatic dicarboxylic acids, preferably chosen from itaconic acid, fumaric acid, 4-methylene-pimelic acid, 3,4-bis(methylene)nonanedioic acid, 5-methylene-nonanedioic acid, their C1-C24, preferably C1-C4, alkyl esters, their salts and mixtures thereof. In a preferred embodiment of this invention, the unsaturated aliphatic dicarboxylic acids comprise mixtures comprising at least 50 mol%, preferably more than 60 mol%, more preferably more than 65 mol% of itaconic acid and / or its C1-C24, preferably Cl- C4, esters. More preferably, the unsaturated aliphatic dicarboxylic acids consist of itaconic acid. In the aliphatic or aromatic-aliphatic polyesters according to this invention, diols are understood to be compounds bearing two hydroxyl groups, preferably chosen from 1,2 -ethanediol, 1,2- propanediol, 1,3 -propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -hexanediol, 1,7- heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11 -undecanediol, 1,12- dodecanediol, 1,13 -tridecanediol, 1,4-cyclohexanedimethanol, neopentylglycol, 2-methyl-l,3- propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, 1,4- bis(hydroxymethyl)cyclohexane, dialkylene glycols and polyalkylene glycols with molecular weight 100-4000, such as, for example, polyethylene glycol, polypropylene glycol and mixtures thereof. Preferably, the diol component comprises at least 50 mol% of one or more diols chosen from 1,2-ethanediol, 1,3 -propanediol, 1,4-butanediol. In a preferred embodiment of this invention, the saturated aliphatic diol is 1,4-butanediol.

[0070] Advantageously, the diol can be obtained from renewable sources, starting from first or second generation sugars.

[0071] The diol component of the aliphatic or aromatic-aliphatic polyesters according to this invention can comprise up to 5% of unsaturated aliphatic diols, preferably chosen from cis 2-buten 1,4 diol, trans 2-buten 1,4 diol, 2-butyn 1,4 diol, cis 2-penten 1,5 diol, trans 2-penten 1,5 diol, 2- pentyn 1,5 diol, cis 2-hexen 1,6 diol, trans 2-hexen 1,6 diol, 2-hexyn 1,6 diol, cis 3hexen 1,6 diol, trans 3-hexen 1,6 diol, 3-hexyn 1,6 diol.

[0072] The polyesters of this invention can also advantageously comprise repeating units deriving from at least one hydroxyacid in an amount between 0 - 49%, preferably between 0 - 30%, by moles with respect to the total moles of the dicarboxylic component.

[0073] Examples of suitable hydroxy acids are glycolic acid, glycolide, hydroxybutyric, hydroxycaproic, hydroxyvaleric, 7-hydroxyheptanoic, 8-hydroxycaproic, 9-hydroxynonanoic, lactic acid, or lactide. Hydroxy acids can be inserted into the chain as such or as prepolymers / oligomers, or they can also be previously reacted with diacid diols.

[0074] The aromatic-aliphatic polyesters according to this invention are characterised by a content of aromatic acids between 30 and 70 mol%, preferably between 40 and 60 mol%, with respect to the total dicarboxylic component.

[0075] In a preferred embodiment, the aromatic-aliphatic polyesters are preferably chosen from: poly(l,4-butylene adipate-co-l,4-butylene terephthalate), poly(l,4-butylene sebacate-co-1,4- butylene terephthalate), poly(l,4-butylene azelate-co-l,4-butylene terephthalate), poly(l,4- butylene brassylate-co-l,4-butylene terephthalate), poly(l,4-butylene succinate-co-1,4- butylene terephthalate), poly(l,4-butylene adipate-co- 1,4-butylene sebacate-co-l,4-butylene terephthalate), poly(l,4-butylene azelate-co-l,4-butylene sebacate-co- 1 ,4-butylene terephthalate), poly( 1,4-butylene adipate-co- 1 ,4-butylene azelate-co- 1 ,4-butylene terephthalate), poly( 1,4-butylene succinate-co-l,4-butylene sebacate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene adipate-co- 1,4-butylene succinate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene azelate-co- 1,4-butylene succinate-co- 1 ,4-butylene terephthalate). In a particularly preferred embodiment, the aromatic-aliphatic polyester is poly(l,4-butylene adipate-co- 1,4-butylene terephthalate) and poly(l,4-butylene adipate-co- 1,4- butylene azelate-co-butylene terephthalate).

[0076] In a preferred embodiment, the aliphatic polyesters are preferably chosen from: poly(l,4- butylene succinate), poly(l,4-butylene adipate), poly( 1,4-butylene azelate), poly( 1,4-butylene sebacate), poly( 1,4-butylene succinate-co- 1,4-butylene adipate), poly( 1,4-butylene succinate- co- 1,4-butylene sebacate), poly(l,4-butylene succinate-co- 1,4-butylene azelate), poly(l,4- butylene succinate-co- 1,4-butylene adipate-co- 1,4-butylene azelate), poly(l,2-ethylene succinate), poly(l,2-ethylene sebacate), poly(l,2-ethylene azelate). In a particularly preferred embodiment, the aliphatic polyester is chosen from poly( 1,4-butylene succinate), poly(l,4- butylene succinate-co- 1,4-butylene azelate), poly( 1,4-butylene succinate-co- 1,4-butylene adipate) and poly(l,4-butylene succinate-co- 1,4-butylene sebacate).

[0077] The invention also includes mixtures of the various polyesters of the invention.

[0078] The biodegradable polyesters according to the invention are biodegradable according to the UNI EN13432 standard.

[0079] The polyester according to this invention may also optionally comprise 0 - 5% by weight, more preferably 0.05 - 4% by weight, even more preferably 0.05 - 3% by weight based on the total mixture, of at least one cross-linking and / or chain-extending agent.

[0080] This cross-linking and / or chain-extending agent improves hydrolysis stability and is chosen from di- and / or polyfunctional compounds bearing isocyanate, peroxide, carbodiimide, isocyanurate, oxazoline, epoxide, anhydride, divinylether groups and mixtures thereof. Preferably the cross-linking and / or chain-extending agent comprises at least one di- and / or polyfunctional compound bearing epoxide or carbodiimide groups.

[0081] Preferably the cross-linking and / or chain-extending agent comprises at least one di- and / or polyfunctional compound bearing isocyanate groups. More preferably, the cross-linking and / or chain-extending agent comprises at least 25% by weight of one or more di- and / or polyfunctional compounds bearing isocyanate groups. Particularly preferred are mixtures of di- and / or polyfunctional compounds bearing isocyanate groups with di- and / or polyfunctional compounds bearing epoxide groups, even more preferably comprising at least 75% by weight of di- and / or polyfunctional compounds bearing isocyanate groups.

[0082] The di- and poly-functional compounds bearing isocyanate groups are preferably chosen from p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4- diphenylmethanediisocyanate, l,3-phenylene-4-chloro diisocyanate, 1,5 -naphthalene diisocyanate, 4,4-diphenylene diisocyanate, 3,3'-dimethyl-4,4-diphenylmethane diisocyanate, 3-methyl-4,4'-diphenylmethane diisocyanate, diphenyl ester diisocyanate, 2,4-cyclohexane diisocyanate, 2,3-cyclohexane diisocyanate, 1-methyl 2,4-cyclohexyl diisocyanate, 1-methyl 2,6-cyclohexyl diisocyanate, bis(cyclohexyl isocyanate) methane, 2,4,6-toluene triisocyanate, 2,4,4-diphenyl ether triisocyanate, polymethylene-polyphenyl-polyisocyanates, methylene diphenyl diisocyanate, triphenylmethane triisocyanate, 3,3'ditolylene-4,4-diisocyanate, 4,4'- methylenebis(2-methyl-phenyl isocyanate), hexamethylene diisocyanate, 1,3 -cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate and mixtures thereof. In a preferred embodiment, the compound bearing isocyanate groups is 4,4-diphenylmethane-diisocyanate.

[0083] As for the di- and poly-functional compounds bearing peroxide groups, these are preferably chosen from benzoyl peroxide, lauroyl peroxide, isononanoyl peroxide, di-(t- butylperoxyisopropyl)benzene, t-butyl peroxide, dicumyl peroxide, alpha, alpha'di(t- butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hex-3-yne, di(4-t- butylcyclohexyl)peroxy dicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, 3,6,9-triethyl-3,6,9-trimethyl-l,4,7-triperoxonane, di(2-ethylhexyl) peroxydicarbonate and their mixtures. The di- and poly -functional compounds bearing carbodiimide groups which are preferably used in the mixture according to this invention are chosen from poly(cyclooctylene carbodiimide), poly(l,4-dimethylenecy cl oh exylene carbodiimide), poly(cyclohexylene carbodiimide), poly(ethylene carbodiimide), poly(butylene carbodiimide), poly(isobutylene carbodiimide), poly(nonylene carbodiimide), poly(dodecylene carbodiimide), poly(neopentylene carbodiimide), poly(l,4-dimethylene phenylene carbodiimide), poly(2, 2', 6, 6', tetraisopropyldiphenylene carbodiimide) (Stabaxol ® D), poly(2,4,6- triisolpropyl-l,3-phenylene carbodiimide) (Stabaxol ® P-100), poly(2,6 (Stabaxol ® P), poly(tolyl carbodiimide), poly (4, 4' -diphenylmethane carbodiimide), poly(3,3'-dimethyl- 4,4'biphenylene carbodiimide), poly(p-phenylene carbodiimide), poly(m-phenylene carbodiimide), poly(3,3'-dimethyl-4,4'-diphenylmethane carbodiimide), poly(naphthylene carbodiimide), poly(isophorone carbodiimide), poly(cumene carbodiimide), p-phenylene bis(ethylcarbodiimide), 1,6-hexamethylene bis(ethylcarbodiimide), 1,8-octam ethylene bis(ethyl carbodiimide), 1,10-decam ethylene bis(ethylcarbodiimide), 1,12-dodecam ethylene bis(ethylcarbodiimide) and mixtures thereof.

[0084] Examples of di- and poly-functional compounds bearing epoxide groups that can be advantageously used in the mixture according to this invention are all polyepoxides from epoxidized oils and / or from styrene - glycidyl ether-methyl methacrylate, glycidyl ether methyl methacrylate, in a molecular weight range from 1000 to 10000 and with a number of epoxides per molecule in the range from 1 to 30 and preferably from 5 to 25, and epoxides chosen from the group comprising: diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol poly glycidyl ether, di glycerol polyglycidyl ether, 1,2-epoxybutane, polyglycerol polyglycidyl ether, isoprene di epoxide, and cycloaliphatic di epoxides, 1,4- cyclohexanedimethanol diglycidyl ether, glycidyl 2-methylphenyl ether, glycerol propoxylated tri glycidyl ether, 1,4-butanediol diglycidyl ether, sorbitol polyglycidyl ether, glycerol diglycidyl ether, meta-xylenediamine tetraglycidyl ether and bisphenol A diglycidyl ether and mixtures thereof.

[0085] In a particularly preferred embodiment of the invention, the cross-linking and / or chainextending agent comprises compounds bearing isocyanate groups, preferably 4,4- diphenylmethanediisocyanate, and / or bearing carbodiimide groups, and / or bearing epoxide groups, preferably of the styrene-glycidyl ether-methyl methacrylate type. In a particularly preferred embodiment of the invention, the cross-linking and / or chain-extending agent comprises compounds bearing epoxide groups of the styreneglycidyl ether-methyl methacrylate type.

[0086] In addition to di- and poly-functional compounds bearing isocyanate, peroxide, carbodiimide, isocyanurate, oxazoline, epoxide, anhydride, divinylether groups, catalysts can also be used to increase the reactivity of the reactive groups. In the case of polyepoxides, fatty acid salts are preferably used, even more preferably calcium and zinc stearates.

[0087] The biodegradable polyester according to the invention can be mixed with other polymers of synthetic or natural origin, whether biodegradable or not. Another object of this invention are compositions comprising polyester according to this invention.

[0088] As regards the polymers of synthetic or natural origin, whether biodegradable or not, these are advantageously chosen from the group consisting of polyhydroxyalkanoates, vinyl polymers, diacid diol polyesters, polyamides, polyurethanes, polyethers, polyureas, polycarbonates and their mixtures. In a particularly preferred form, said polymers can be mixed in quantities of up to 80% by weight with the biodegradable polyester according to the invention. As for the polyhydroxyalkanoates, these can be present in quantities between 30 and 80% by weight, preferably between 40 and 75% by weight, even more preferably between 45 and 70% by weight, with respect to the total composition.

[0089] Said polyhydroxyalkanoates are preferably chosen from the group consisting of polyesters of lactic acid, poly-s-caprolactone, polyhydroxybutyrate, polyhydroxybutyrate-val erate, polyhydroxybutyrate propanoate, polyhydroxybutyrate-hexanoate, polyhydroxybutyratedecanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyrate-hexadecanoate, polyhydroxybutyrate-octadecanoate, poly 3 -hydroxybutyrate 4-hydroxybutyrate. Preferably, the polyhydroxyalkanoate of the composition comprises at least 80% by weight of one or more polyesters of lactic acid.

[0090] In a preferred embodiment, the lactic acid polyesters are chosen from the group consisting of poly-L-lactic acid, poly-D-lactic acid, poly-DL-lactic stereocomplex, copolymers comprising more than 50 mol% of said lactic acid polyesters or mixtures thereof.

[0091] Particularly preferred are lactic acid polyesters containing at least 95% by weight of repeating units derived from L-lactic or D-lactic acid or combinations thereof, with a molecular weight Mw greater than 50000 and with a melt viscosity between 50^-700 Pa*s preferably between 80^-500 Pa*s (measured according to the ASTM D3835 standard at T=190 °C, shear rate=1000s-l, D=lmm, L / D=10).

[0092] In a particularly preferred embodiment of this invention, the lactic acid polyester comprises at least 95% by weight of L-lactic acid derived units, < 5% by weight of D-lactic acid derived repeating units, exhibits a melting temperature in the range 135-175°C, a glass transition temperature (Tg) in the range 55-65°C, and an MFR (measured according to the ASTM-D1238 standard at 190°C and 2.16kg) in the range 1-50 g / 10 min.

[0093] Commercial examples of lactic acid polyesters having these properties are, for example, the products branded Ingeo™ Biopolymer 4043D, 325 ID, 6202D, the product branded Luminy® L105.

[0094] In a preferred embodiment of this invention, the composition comprises the biodegradable branched polyester of this invention and at least one polyhydroxy alkanoate.

[0095] Among the vinyl polymers, those preferred are: polyethylene, polypropylene, their copolymers, polyvinyl alcohol, polyvinyl acetate, polyethylene vinyl acetate and polyethylene vinyl alcohol, polystyrene, chlorinated vinyl polymers, polyacrylates.

[0096] Chlorinated vinyl polymers include, in addition to polyvinyl chloride, polyvinylidene chloride, polyethylene chloride, poly(vinyl chloride-vinyl acetate), poly(vinyl chloride-ethylene), poly(vinyl chloride-propylene), poly(vinyl chloride-styrene), poly(vinyl chloride-isobutylene) as well as copolymers in which polyvinyl chloride represents more than 50% in moles. These copolymers can be random, block or alternating.

[0097] As regards the polyamides of the composition according to this invention, these are preferably chosen from the group consisting of polyamide 6 and 6,6, polyamide 9 and 9,9, polyamide 10 and 10,10, polyamide 11 and 11,11, polyamide 12 and 12,12 and their combinations of the type 6 / 9, 6 / 10, 6 / 11, 6 / 12, their mixtures and copolymers, both random and block.

[0098] Preferably, the polycarbonates of the composition according to this invention are chosen from the group consisting of polyalkylene carbonates, more preferably polyethylene carbonates, polypropylene carbonates, polybutylene carbonates, mixtures thereof and both random and block copolymers.

[0099] The preferred polyethers are those chosen from the group consisting of polyethylene glycols, polypropylene glycols, polybutylene glycols, their copolymers and mixtures thereof with molecular weights from 70,000 to 500,000.

[0100] As regards diacid diol polyesters, these preferably include: a) a dicarboxylic component comprising, in relation to the total dicarboxylic component: al) 20 -100 mol% of units derived from at least one aromatic dicarboxylic acid, a2) 0-80 mol% of units derived from at least one saturated aliphatic di carboxylic acid, a3) 0-5 mol% of units derived from at least one unsaturated aliphatic dicarboxylic acid; b) a diol component comprising, in relation to the total diol component: bl) 95-100 mol% of units derived from at least one saturated aliphatic diol; b2) 0-5 mol% of units derived from at least one unsaturated aliphatic diol.

[0101] Preferably, aromatic dicarboxylic acids al, saturated aliphatic dicarboxylic acids a2, unsaturated aliphatic dicarboxylic acids a3, saturated aliphatic diols bl and unsaturated aliphatic diols b2 for said polyesters are chosen from those described above for the polyester according to this invention.

[0102] As for polymers of natural origin, these are advantageously chosen from starch, chitin, chitosan, alginates, proteins such as gluten, zein, casein, collagen, gelatin, natural gums, cellulose (including nanofibrils) and pectin.

[0103] The term starch here refers to all types of starch, namely: flour, native starch, hydrolyzed starch, destructured starch, gelatinized starch, plasticized starch, thermoplastic starch, biofillers comprising complexed starch or mixtures thereof. Particularly suitable according to the invention are starches such as potato, com, tapioca and pea starches. Starches that can be easily destructured and have high initial molecular weights, such as potato or corn starch, have proven to be particularly advantageous. Starch can be present either as such or in a chemically modified form, such as in the form of starch esters with a degree of substitution between 0.2 and 2.5, hydroxypropylated starch, or starch modified with fatty chains.

[0104] By destructured starch we refer here to the teachings of Patents EP-0 118240 and EP-0327 505, meaning starch processed in such a way as not to substantially present the so-called "Maltese crosses" under the optical microscope in polarized light and the so-called "ghosts" under the optical microscope in phase contrast. Advantageously, the destructuring of starch is carried out by an extrusion process at temperatures between 110-250 °C, preferably 130-180 °C, pressures between 0.1-7 MPa, preferably 0.3-6 MPa, preferably providing, during said extrusion, a specific energy greater than 0.1 kWh / kg.

[0105] The destructuring of starch preferably occurs in the presence of 1-40% by weight, with respect to the weight of the starch, of one or more plasticizers chosen from water and polyols having from 2 to 22 carbon atoms. As for the water, this can also be that naturally present in starch. Of the polyols, those preferred are polyols having 1 to 20 hydroxyl groups containing 2 to 6 carbon atoms, their organic and inorganic ethers, thioethers and esters.

[0106] Examples of such polyols are glycerin, diglycerol, polyglycerol, pentaritritol, ethoxylated polyglycerol, ethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3 -propanediol, 1,4- butanediol, neopentylglycol, sorbitol, sorbitol monoacetate, sorbitol diacetate, sorbitol monoethoxylate, sorbitol diethoxylate, and mixtures thereof.

[0107] In a preferred embodiment, the starch is destructured in the presence of glycerol or a mixture of plasticizers comprising glycerol, more preferably comprising between 2 and 90% by weight of glycerol. Preferably, the destructured and cross-linked starch according to this invention comprises between 1-40% by weight, with respect to the weight of the starch, of plasticizers. When present, the starch in the composition according to this invention is preferably in the form of particles having a cross-section that is circular, elliptical or in any case similar to an ellipse with an arithmetic mean diameter, measured taking into consideration the major axis of the particle, of less than 1 micron and more preferably less than 0.5 pm in mean diameter.

[0108] The biodegradable branched polyester according to the invention may optionally be further mixed with one or more additives chosen from the group consisting of plasticizers, UV stabilizers, lubricants, nucleating agents, surfactants, antistatic agents, pigments, compatibilising agents, lignin, silymarin, organic acids, antioxidants, anti-mould agents, waxes, processing aids and polymeric components preferably chosen from the group consisting of vinyl polymers and diacid-diol polyesters different from or the same as the aliphatic and / or aromatic-aliphatic polyesters described above. Each additive is present in a quantity preferably less than 10% by weight, more preferably less than 5% by weight, even more preferably less than 1% by weight with respect to the total weight of the mixture.

[0109] As for the plasticizers, in addition to the plasticizers preferably used for the preparation of destructured starch described above, they are chosen from the group consisting of trimellitates, such as esters of trimellitic acid with C4-C20 monoalcohols preferably chosen from the group consisting of n-octanol and n-decanol, and aliphatic esters having the following structure: Rl-O- C(O)-R4-C(O)-[-O-R2-OC(O)-R5-C(O)-]mO-R3 in which:

[0110] R1 is chosen from one or more of the groups formed by H, linear and branched alkyl residues, saturated and unsaturated of the C1-C24 type, residues of polyols esterified with monocarboxylic acids of C1-C24 type;

[0111] R2 comprises -CH2-C(CH3)2-CH2- and C2-C8 alkylene groups, and is constituted by at least 50 mol% of said -CH2-C(CH3)2-CH2- groups;

[0112] R3 is chosen from one or more of the groups formed by H, linear and branched alkyl residues, saturated and unsaturated of the C1-C24 type, residues of polyols esterified with C1-C24 monocarboxylic acids;

[0113] R4 and R5 are the same or different, comprise one or more C2-C22 alkylenes, preferably C2- C11, more preferably C4-C9, and consist of at least 50 mol% of C7 alkylenes; m is a number between 1-20, preferably 2-10, more preferably 3-7.

[0114] Preferably, in said esters at least one of the groups R1 and / or R3 comprises, preferably in an amount > 10 mol%, more preferably > 20 mol%, even more preferably > 25 mol%, with respect to the total amount of groups R1 and / or R3, polyol residues esterified with at least one C1-C24 monocarboxylic acid chosen from the group consisting of stearic acid, palmitic acid, 9- ketostearic acid, 10-ketostearic acid and mixtures thereof. Examples of aliphatic esters of this type are described in Italian patent application MI2014A000030 and in international patent applications WO 2015 / 104375 and WO 2015 / 104377.

[0115] Lubricants are preferably chosen from esters and metallic salts of fatty acids such as zinc stearate, calcium stearate, aluminium stearate and acetyl stearate. Preferably, the composition according to this invention comprises up to 1% by weight of lubricants, more preferably up to 0.5% by weight, with respect to the total weight of the composition.

[0116] Examples of nucleating agents include saccharin sodium salt, calcium silicate, sodium benzoate, calcium titanate, boron nitride, isotactic polypropylene, low molecular weight PLA. Pigments may also be added if required, such as titanium dioxide, clays, copper phthalocyanine, titanium dioxide, silicates, iron oxides and hydroxides, carbon black, and magnesium oxide. Processing aids such as slip and / or separating agents include, for example, biodegradable fatty acid amides such as oleamamide, erucamide, ethylene-bis-stearylamide, fatty acid esters such as glycerol oleates or glycerol stearates, saponified fatty acids such as stearates, and inorganic agents such as silicas or talc. Processing aids are present in quantities preferably less than 10% by weight, more preferably less than 5% by weight, even more preferably less than 1% by weight with respect to the total weight of the mixture.

[0117] An object of this invention is the use of the polyester according to this invention in a blown extrusion, cast film extrusion, extrusion coating, extrusion lamination, injection moulding process or in a foaming process (such as extrusion foaming, injection foaming, autoclave foaming, supercritical foaming) with or without crosslinking by chemical additives and with or without chemical blowing agents.

[0118] When used in extrusion coating it is preferable to add to the polyester inorganic filler for example selected from Talc, Mica, Kaolin, Montmorillonite, Sepiolite, Vermiculite, Calcium carbonate, Magnesium carbonate, Titanium dioxide, Zinc oxide, Alumina Magnesium oxide, Silica, Calcium silicates, Aluminum silicates and Wollastonite, thereby obtaining a composition. In this case the amount of inorganic filler may be from 1% to 35% by weight with respect the weight of said composition comprising the polyester and filler, preferably from 5 to 30%, more preferably from 10 to 27%.

[0119] In a particularly preferred embodiment of the invention Talc is used as inorganic filler.

[0120] According to a preferred embodiment the polyester according to this invention is used in extrusion-coating processes with 20-27% by weight of filler, preferably talc, preferably in the presence of a separating (or chill-roll release) agent, such as a fatty amide.

[0121] The invention is now illustrated with some embodiments to be understood as exemplifying and not in any way limiting the scope of protection of this patent application.

[0122] Preparation of polvCL4-butylene adipate-co- L4-butylene terephthalate) (PBAT)

[0123] Esterification step

[0124] The following were loaded into a steel reactor with a geometric volume of 24 litres and equipped with a mechanical stirring system, a nitrogen inlet, a distillation column and a system for removing high-boiling volatile compounds connected to a vacuum system: 2422g (14.6 mol) of terephthalic acid, 2402g (16.5 mol) of adipic acid, 4191g (46.6mol, MGR=1.50) of 1,4- butanediol, the polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups and the esterification catalyst. The system was gradually brought to 230°C over a time of 120 minutes under mechanical stirring. Conversion of the esterification reaction was followed by measuring the amount of water evolved from the process and distilled.

[0125] Once at least 95% of the water theoretically obtainable from the stoichiometry of the reaction had been collected and the melt was clear, a gradual vacuum ramp was applied from atmospheric pressure up to 100 mbar in approximately 30 minutes. The esterification step was then considered complete, the pressure was brought back to 1 atmosphere using nitrogen and the temperature was raised to 240°C.

[0126] Polycondensation step

[0127] The polymerisation catalyst was added and the system was kept stirred under a gentle flow of nitrogen for 5 minutes, then the phosphorus additive, if used, was also added. The system was kept stirred under a gentle flow of nitrogen for 5 minutes, then the pressure was gradually reduced to values below 3mbar over a time of 30 minutes and maintained so for the entire polymerisation step. After a reaction time of between 2.5 to 5 hours until the desired MFR was reached, the material was discharged by extruding it in spaghetti form into a water bath, dried with a flow of air and granulated.

[0128] EXAMPLE 1 (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 4.88 g (equivalent to 750 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) as polycondensation catalyst and 0.77 g of dibutyl phosphate as phosphorus additive.

[0129] EXAMPLE 2 (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 4.88 g (equivalent to 750 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) as polycondensation catalyst and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0130] EXAMPLE 3 (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 1.47 g (equivalent to 226 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) and 4.41 g (equivalent to 679 ppm by weight of the theoretical polymer) of tetrabutyl zirconate (Tyzor NBZ®) as polycondensation catalysts and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0131] EXAMPLE 4 (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 4.88 g (equivalent to 750 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) as polycondensation catalyst.

[0132] EXAMPLE 5 (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 4.88 g (equivalent to 750 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) as polycondensation catalyst and 1.27 g of a mixture of polyethylene glycol phosphate (1) dioctylester and polyethylene glycol phosphate (2: 1) octyl ester as phosphorus additive.

[0133] EXAMPLE 5 (bis) (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 4.88 g (equivalent to 750 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) as polycondensation catalyst and 1.58g of tri octyl phosphate as phosphorus additive.

[0134] EXAMPLE 6 (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 4.88 g (equivalent to 750 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) as polycondensation catalyst and 0.36 g of phosphoric acid as phosphorus additive.

[0135] EXAMPLE 7 (PBAT): Esterification step: 12.7 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 1.47 g (equal to 226 ppm by weight with respect to the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) and 4.41 g (equal to 679 ppm by weight with respect to the theoretical polymer) of tetrabutyl zirconate (Tyzor NBZ®) as polycondensation catalysts.

[0136] Preparation of poly(L4-butylene succinate) (PBS)

[0137] Esterification Step

[0138] The following were loaded into a steel reactor with a geometric volume of 24 litres and equipped with a mechanical stirring system, a nitrogen inlet, a distillation column and a system for removing high-boiling volatile compounds connected to a vacuum system: 4459g (37.8 mol) of succinic acid, 5102g (56.7 mol, MGR=1.50) of 1,4-butanediol. The polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups and the esterification catalyst were added. The system was gradually brought to 230°Cover a time of 120 minutes under mechanical stirring. Conversion of the esterification reaction was followed by measuring the amount of water evolved from the process and distilled.

[0139] Once at least 95% of the water theoretically obtainable from the stoichiometry of the reaction had been collected, a gradual vacuum ramp was applied from atmospheric pressure up to 100 mbar in approximately 30 minutes. The esterification step was then considered complete, the pressure was brought back to 1 atmosphere using nitrogen and the temperature was raised to 240°C.

[0140] Polycondensation step

[0141] The polycondensation catalyst was added and the system was stirred under a gentle flow of nitrogen for 5 minutes, then the phosphorus additive, if used, was added. The system was kept stirred under a gentle flow of nitrogen for 5 minutes, then the pressure was gradually reduced to values below 3mbar over a time of 30 minutes and maintained so for the entire polymerisation step. After a reaction time of between 2.5 to 5 hours until the desired MFR was reached, the material was discharged by extruding it in spaghetti form into a water bath, dried with a flow of air and granulated.

[0142] EXAMPLE 8 (PBS): Esterification step: 15,4 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 1.47 g (equivalent to 226 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) and 4.41 g (equivalent to 679 ppm by weight of the theoretical polymer) of tetrabutyl zirconate (Tyzor NBZ®) as polycondensation catalysts and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive. EXAMPLE 9 (PBAT): Esterification step: 5.71 g of glycerol (0.2% of the total dicarboxylic acid content of glycerol) as polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2-propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 1.47 g (equivalent to 226 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) and 4.41 g (equivalent to 679 ppm by weight of the theoretical polymer) of tetrabutyl zirconate (Tyzor NBZ®) as polycondensation catalysts and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0143] EXAMPLE 10 (PBAT): Esterification step: 8.57 g of glycerol (0.3% of the total dicarboxylic acid content of glycerol) as polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2-propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 1.47 g (equivalent to 226 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) and 4.41 g (equivalent to 679 ppm by weight of the theoretical polymer) of tetrabutyl zirconate (Tyzor NBZ®) as polycondensation catalysts and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0144] EXAMPLE 11 (PBAT): Esterification step: 11.42 g of glycerol (0.4% of the total dicarboxylic acid content of glycerol) as polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2-propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 1.47 g (equivalent to 226 ppm by weight of the theoretical polymer) of tetrabutyl titanate (Tyzor TnBT®) and 4.41 g (equivalent to 679 ppm by weight of the theoretical polymer) of tetrabutyl zirconate (Tyzor NBZ®) as polycondensation catalysts and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0145] EXAMPLE 12 (PBAT): Esterification step: 6,77 g of pentaerythritol (0.16% of the total dicarboxylic acid) as polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2-propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 9,76 g (equivalent to 1500 ppm by weight of the theoretical polymer) of citrate catalyst as polycondensation catalysts and 3,4 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0146] EXAMPLE 13 (PBAT): Esterification step: 8,5 g of pentaerythritol (0.2% of the total dicarboxylic acid) as polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2-propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 9,76 g (equivalent to 1500 ppm by weight of the theoretical polymer) of citrate catalyst as polycondensation catalysts and 3,4 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0147] EXAMPLE 14(PBS): Esterification step: 15,4 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2- propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 9,76 g (equivalent to 1500 ppm by weight of the theoretical polymer) of citrate catalyst as polycondensation catalysts and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0148] EXAMPLE 15(PBS):

[0149] Esterification step: 15,4 g of pentaerythritol (0.3% of the total pentaerythritol dicarboxylic acid) as a polyfunctional compound and 1.30 g (equal to 200 ppm by weight of the theoretical polymer) of solution of diisopropyl triethanolamine titanate in 2-propanol (Tyzor TE®) as esterification catalyst. Polycondensation step: 9,76 g (equivalent to 1500 ppm by weight of the theoretical polymer) of citrate catalyst as polycondensation catalysts and 2.20 g of polyethylene glycol tridecyl ether phosphate ammonium salt as phosphorus additive.

[0150] Tables from 1 to 6 show the products obtained in examples 1 to 15 as a function of the type of branching agent used (with the % used and the number of functional groups), the type of catalyst (titanium or titanium / zirconium in the presence or absence of different types of phosphorus P, with the Ti / P ratio when the phosphorus is present) and the activation energy measured by capillary rheometry at 150-170-190°C, y=103.68 s-1.

[0151] Table 1 :

[0152] As can be seen from Table 1, when a catalyst containing phosphorus in the form of a mono- or di-ester of phosphoric acid is used in the process of the invention, the activation energy measured is lower than when using a catalyst without phosphorus or with a tri substituted phosphorus. Table 2:

[0153] The data are confirmed in Table 2 where the type and quantity of branching agent have changed compared to Table 1.

[0154] Table 3 shows the values of the Z factor obtained for the polyesters of examples 1 to 11 using the formula Z = (E_act-20)3 / (RPxBD), therefore as a function of the polymer’s branching density PD.

[0155] Table 3: From Table 3 it can be seen that all the branched polymers obtained with the process of the invention have a Z factor value between 1 and 8000.

[0156] Table 4 shows the data relating to the mechanical performance of the film obtained with the polymer of example 3 at two different filming temperatures.

[0157] Table 4

[0158] As can be seen from Table 4, the possibility of transforming the polymer at lower temperatures does not affect the mechanical performance of the film.

[0159] Table 5 Table 6

Claims

1. CLAIMS1 Process for obtaining a biodegradable branched aliphatic or aromatic-aliphatic polyester comprising (i) an esterification / transesterification step in the presence of the diol and dicarboxylic components, and of at least one polyfunctional compound containing at least three acidic (COOH) and / or hydroxyl (OH) functional groups, and of an esterification / transesterification catalyst; and (ii) a polycondensation step in the presence of a catalyst characterised by the fact that it comprises titanium, or titanium / zirconium or mixtures thereof and phosphorus in the form of a mono- or di-ester of phosphoric acid in which the concentration of titanium, or titanium / zirconium is 0.5-5 mmol per kg of polymer, and the titanium / phosphorus or titanium+zirconium / phosphorus ratio, by weight, is between 2 and 15, more preferably between 3 and 12.

2. Process according to claim 1 wherein the phosphorus is in the form of an ester represented by the following formula:wherein R1 is H or a cation of an alkaline or alkaline-earthy element or ammonium, R2 is indifferently chosen from C1-C20 alkyl or cycloalkyl, C6-C20 aryl or alkyl aryl, or a polyalkylene oxide or alkyl-polyalkylene oxide chain and R3 can be indifferently chosen from H, or a cation of an alkaline or alkaline-earthy element or ammonium or C1-C20 alkyl or cycloalkyl, C6-C20 aryl or alkyl aryl, or a polyalkyleneoxide or alkylpolyalkyleneoxide chain.

3. Process according to claims 1 and 2 wherein the polyfunctional compound is chosen from sorbitol, xylitol, trimethylpropane, glycerol, pentaerythritol.

4. Biodegradable branched aliphatic or aromatic-aliphatic polyester obtained by the preparation process of claims 1 to 3 characterised by a Z factor calculated according to the following formula:Z = (E_act-20)3 / (RPxBD) in which:- Eact = the activation energy measured by capillary rheometry at 150-170-190°C, 7=103.68 s-1, expressed in KJ / gmol;- RP = is the polymer branching %- BD = is the polymer branching density in which the said Z factor is between 1 and 8000.

5. Biodegradable branched aliphatic or aromatic-aliphatic polyester according to claim 4 wherein the polymer branching % (RP) is between 0.15 and 0.45, preferably between 0.20 and 0.40 and the branching density (BD) of the polymer is between 0.45 and 0.80, preferably between 0.50 and 0.67.

6. Biodegradable branched polyester according to claim 5 wherein said polyester is chosen from biodegrabable aliphatic and aromatic-aliphatic polyesters.

7. Biodegradable branched polyester according to claim 6 wherein said polyester is an aromatic-aliphatic polyester.

8. Biodegradable branched polyester according to claim 7 wherein said aromatic-aliphatic polyester is characterised by a content of aromatic acids between 30 and 70% by moles, with respect to the total of the dicarboxylic component.

9. Biodegradable branched polyester according to claims 7 and 8 wherein said aromaticaliphatic polyester is chosen from poly(l,4-butylene adipate-co-l,4-butylene terephthalate), poly(l,4-butylene sebacate-co-l,4-butylene terephthalate), poly(l,4- butylene azelate-co-l,4-butylene terephthalate), poly(l,4-butylene brassylate-co-1,4- butylene terephthalate), poly(l,4-butylene succinate-co-l,4-butylene terephthalate), poly(l,4-butylene adipate-co-l,4-butylene sebacate-co-l,4-butylene terephthalate), poly(l,4-butylene azelate-co-l,4-butylene sebacate-co-l,4-butylene terephthalate), poly(l,4-butylene adipate-co-l,4-butylene azelate-co-l,4-butylene terephthalate), poly(l,4-butylene succinate-co-l,4-butylene sebacate-co-l,4-butylene terephthalate), poly(l,4-butylene adipate-co-l,4-butylene succinate-co-l,4-butylene terephthalate), poly(l,4-butylene azelate-co-l,4-butylene succinate-co-l,4-butylene terephthalate).

10. Film comprising the biodegradable branched polyester according to claim 4.

11. Use of the biodegradable branched aliphatic or aromatic-aliphatic polyester according to any of claims 4-9 in a blown extrusion, extrusion coating, extrusion lamination, injection moulding process, or in a foaming process.

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