Aliphatic-aromatic polyesters with controlled residual mixed cyclic oligomer content

Abstract

An aliphatic-aromatic polyester in which the amount of residual mixed cyclic oligomers is controlled and which has a specific ratio of a cyclic oligomer containing at least two types of dicarboxylic acid aliphatic units having a molecular weight of 1000 or less and a cyclic oligomer containing only one type of dicarboxylic acid aliphatic unit having a molecular weight of 1000 or less, and a method for producing the same.

Description

[Technical field]

[0001] The present invention relates to aliphatic-aromatic polyesters with suitable thermal stability and terminal acidity, and a controlled content of mixed residual cyclic oligomers as by-products of the polymerization process, and a method for obtaining the same, which can be more stably processed into films and therefore more productive. [Background technology]

[0002] The content of mixed residual cyclic oligomers in aliphatic-aromatic polyesters is known to be undesirable since it has a detrimental effect on the properties of the polyesters, in particular on the mechanical performance and transparency of the films obtained therefrom. Patent application WO2016 / 050963 describes a combined process for the preparation of polyesters comprising an esterification or transesterification step followed by a polycondensation step, characterized in that the polycondensation step is carried out in the presence of a catalyst comprising a mixture of at least one titanium compound and at least one zirconium compound, the Ti / (Ti+Zr) weight ratio being ≧0.01 and ≦0.70. WO2016 / 050963 teaches that this process makes it possible to obtain polyesters with reduced production of mixed cyclic residues that are removed by distillation during the polycondensation step.

[0003] Nonetheless, some of these mixed residual cyclic oligomers remain trapped within the forming polyester. It has been found that by appropriately selecting the conditions of the process described in WO2016 / 050963, in particular by adding a suitable amount of phosphorus-containing compound relative to the catalyst used in combination with specific temperature and pressure conditions, it is possible to obtain aliphatic-aromatic polyesters with a controlled amount of mixed residual cyclic oligomers, characterized in that the ratio of cyclic oligomers containing at least two aliphatic dicarboxylic acid units and having a molecular weight (MM) of less than 1000 to cyclic oligomers containing only one aliphatic dicarboxylic acid unit and having a MM of less than 1000 is between 0.30 and 1.40, more preferably between 0.40 and 1.20, even more preferably between 0.45 and 0.80, and further characterized in that the predominant saturated aliphatic dicarboxylic acid in the mixture of dicarboxylic acids is less than 95 mol % relative to the sum of all other saturated aliphatic dicarboxylic acids and, in the case of the presence of two or more saturated aliphatic dicarboxylic acids, is 45 mol % or more relative to the sum of all saturated aliphatic dicarboxylic acids. Summary of the Invention [Means for solving the problem]

[0004] Surprisingly, the polyester obtained by this improved process allows for more stable film making conditions, in particular better bubble stability, which makes it possible to carry out the filming process at higher flow rates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] In the present invention, the term "mixed residual cyclic oligomers" refers to residual cyclic oligomers having a molecular weight (MM) of 1000 or less that remain in the polymer mass after the polycondensation step. Thus, one aspect of the present invention is a method for producing a pharmaceutical composition comprising the steps of: 1. subjecting a mixture comprising an aliphatic diol, at least one aromatic dicarboxylic acid, and at least two aliphatic dicarboxylic acids, esters, salts or derivatives thereof, to esterification and / or transesterification to produce oligomers; 2. Polycondensation of the oligomers obtained from step 1 in the presence of a catalyst comprising titanium, optionally zirconium or a mixture thereof, and a phosphorus-containing compound belonging to the family of organic phosphates or phosphites, at a temperature between 220° C. and 260° C. and a pressure between 0.5 mbar and 350 mbar. The method for producing an aliphatic-aromatic polyester includes the steps of: The term "derivative" of a dicarboxylic acid refers to a compound in which the hydroxyl of the acid is replaced with a group containing a halogen, nitrogen, or sulfur atom bonded to the carbon of the carbonyl group.

[0006] Advantageously, the phosphorus-containing compound is chosen from compounds of general formula (1) or (2): [ka] (wherein R1, R2 and R3 may be selected from either H, C1-C20 alkyl or cycloalkyl, C6-C20 aryl, alkylaryl, or a polyalkylene oxide or polyalkylalkylene oxide chain.

[0007] In a preferred embodiment of the process according to the invention, the catalyst comprises a mixture of at least one titanium compound, the titanium to phosphorus ratio being between 2 and 20, preferably between 3 and 15. Further aspects of the present invention include: (a) a dicarboxylic acid component, (a1) 40 to 80 mol % of units derived from at least one aromatic dicarboxylic acid; (a2) 20 to 60 mol % of units derived from at least two kinds of saturated aliphatic C4 to C24 dicarboxylic acids A dicarboxylic acid component comprising (b) Aliphatic diol component a content of mixed residual cyclic oligomers between 1.0% and 4.0%, said mixed residual cyclic oligomers being characterized in that the ratio of cyclic oligomers comprising at least two aliphatic dicarboxylic acid units having a MM less than 1000 to cyclic oligomers comprising only one aliphatic dicarboxylic acid unit having a MM less than 1000 is between 0.30 and 1.40, more preferably between 0.40 and 1.20, even more preferably between 0.45 and 0.80, and further characterized in that when component a2) is composed of more than two saturated aliphatic dicarboxylic acids, the predominant saturated aliphatic dicarboxylic acid in component a2) is between 45 and 95 mol % relative to the sum of all other saturated aliphatic dicarboxylic acids.

[0008] The term "predominant saturated aliphatic dicarboxylic acid" in the present invention is meant to apply when the ratio of acids is not equimolar and thus refers to a saturated aliphatic dicarboxylic acid that is present in a molar percentage greater than the respective percentages of the other saturated aliphatic dicarboxylic acids. In a preferred embodiment of the present invention, the content of mixed residual cyclic oligomers is 2% to 3.5%.

[0009] As regards the aliphatic-aromatic polyesters produced by the process according to the invention, these comprise a diol component (component b) derived from at least one aliphatic diol selected 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-enediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, 2-methyl-1,3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, glycols with molecular weights of 100 to 4000, such as polyethylene glycol, polypropylene glycol, and mixtures thereof. Preferably, the diol component comprises at least 50 mole % of one or more diols selected from 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol. More preferably, the diol component comprises or consists of 1,2-ethanediol, 1,4-butanediol, or a mixture thereof. Even more preferably, the diol component comprises or consists of 1,4-butanediol.

[0010] The dicarboxylic acid component of the polyester produced by the method according to the present invention comprises 40 to 80 mol %, preferably 40 to 75 mol %, more preferably 42 to 60 mol %, and even more preferably 45 to 49.5 mol % of units derived from at least one aromatic dicarboxylic acid (component a1) relative to the entire dicarboxylic acid component, and 20 to 60 mol %, preferably 25 to 60 mol %, more preferably 40 to 58 mol %, and even more preferably 50.5 to 55 mol % of units derived from at least two saturated aliphatic dicarboxylic acids (component a2) relative to the entire dicarboxylic acid component. The dicarboxylic acid component is further characterized in that the predominant saturated aliphatic dicarboxylic acid in component a2) is less than 95 mol % relative to the sum of all other saturated aliphatic dicarboxylic acids, and in the case where component a2) is composed of more than two saturated aliphatic dicarboxylic acids, it is more than 45 mol % by mole relative to the sum of all saturated aliphatic dicarboxylic acids.

[0011] The aromatic dicarboxylic acid is advantageously chosen from terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid, their esters, salts and mixtures. In a preferred embodiment, the aromatic dicarboxylic acid is - 1 to 99 mol %, preferably 5 to 95 mol %, more preferably 10 to 80 mol % of terephthalic acid, its ester or its salt; 99 to 1 mol %, preferably 95 to 5 mol %, more preferably 90 to 20 mol % of 2,5-furandicarboxylic acid, its ester or salt Includes. In a particularly preferred embodiment of the invention, the aromatic dicarboxylic acid is terephthalic acid, its esters and salts. The aliphatic dicarboxylic acids are advantageously chosen from saturated C4-C24, preferably C5-C24, more preferably C5-C13, more preferably C5-C11 dicarboxylic acids, their C1-C2, more preferably C1-C4 alkyl esters, their salts, and mixtures thereof. In a preferred embodiment of the invention, the aliphatic dicarboxylic acid is selected from glutaric acid, 2-methylglutaric acid, adipic acid, succinic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, and their C1-24 alkyl esters.

[0012] In a preferred embodiment of the present invention, the predominant saturated aliphatic dicarboxylic acid is at least 45 mol %, preferably 60 mol % or more, more preferably 65 mol % or more, even more preferably 85 mol % or more, based on the sum of all saturated aliphatic dicarboxylic acids, when component a2) comprises more than two saturated aliphatic dicarboxylic acids. Such predominant saturated aliphatic dicarboxylic acids are preferably selected from adipic acid, azelaic acid, sebacic acid, brassylic acid, their C1-C24, preferably C1-C4 esters, salts and mixtures thereof. In a particularly preferred form of the invention, one of the aliphatic dicarboxylic acids is azelaic acid.

[0013] In a preferred embodiment of the process according to the invention, the aliphatic-aromatic polyesters produced are advantageously chosen from: (A) A polyester comprising repeating units derived from a phthalic acid-type aromatic dicarboxylic acid, preferably terephthalic acid, an aromatic dicarboxylic acid and an aliphatic diol (AAPE-A), characterized by an aromatic unit content between 42 and 60 mol %, preferably between 45 and 49.5 mol %, relative to the total number of moles of the dicarboxylic acid component. The AAPE-A polyesters are preferably selected from the group consisting of poly(1,4-butylene adipate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene brassylate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene sebacate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene Poly(1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4-butylene brassylate-co-1,4-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 adipate-co-1,4-butylene poly(1,4-butylene brassylate-co-1,4-butylene terephthalate), poly(1,4-butylene brassylate-co-1,4-butylene azelate-co-1,4-butylene terephthalate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene sebacate-co-1,4-butylene terephthalate), poly(1,4 -butylene azelate-co-1,4-butylene sebacate-co-1,4-butylene brassylate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene brassylate-co-1,4-butylene terephthalate), poly(1,4-butylene adipate-co-1,4-butylene sebacate-co-1,4-butylene brassylate-co-1,4-butylene terephthalate).

[0014] (B) A polyester (AAPE-B) comprising repeating units derived from an aromatic heterocyclic dicarboxylic acid compound, preferably 2,5-furandicarboxylic acid, an aromatic dicarboxylic acid and an aliphatic diol, characterized by a content of aromatic units between 40 mol % and 80 mol %, preferably between 40 mol % and 75 mol %, relative to the total number of moles of the dicarboxylic acid component. The AAPE-B polyester is preferably selected from the following: poly(1,4-butylene adipate-co-1,4-butylene succinate-co-2,5-furandicarboxylate), poly(1,4-butylene sebacate-co-1,4-butylene succinate-co-2,5-furandicarboxylate), poly(1,4-butylene brassylate-co-1,4-butylene succinate-co-2,5-furandicarboxylate), poly(1,4-butylene adipate-co- 1,4-butylene sebacate-co-2,5-furandicarboxylate), poly(1,4-butylene azelate-co-1,4-butylene sebacate-co-2,5-furandicarboxylate), poly(1,4-butylene brassylate-co-1,4-butylene sebacate-co-2,5-furandicarboxylate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-2,5-furandicarboxylate), poly(1,4-butylene adipate-co -1,4-butylene brassylate-co-2,5-furandicarboxylate), poly(1,4-butylene brassylate-co-1,4-butylene azelate-co-2,5-furandicarboxylate), poly(1,4-butylene azelate-co-1,4-butylene succinate-co-2,5-furandicarboxylate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene sebacate-co-2,5-furandicarboxylate) , poly(1,4-butylene azelate-co-1,4-butylene sebacate-co-1,4-butylene brassylate-co-2,5-furandicarboxylate), poly(1,4-butylene adipate-co-1,4-butylene azelate-co-1,4-butylene brassylate-co-2,5-furandicarboxylate), poly(1,4-butylene adipate-co-1,4-butylene sebacate-co-1,4-butylene brassylate-co-2,5-furandicarboxylate).

[0015] The polyesters produced by the process according to the invention are characterized by a content of mixed residual cyclic oligomers between 1.0% and 4.0%, said oligomers being characterized by a ratio between cyclic oligomers comprising at least two aliphatic dicarboxylic acid units with a MM of less than 1000 and cyclic oligomers comprising only one aliphatic dicarboxylic acid unit with a MM of less than 1000 of between 0.30 and 1.40, more preferably between 0.40 and 1.20, even more preferably between 0.45 and 0.80, and further characterized in that the predominant saturated aliphatic dicarboxylic acid in component a2) is less than 95 mol % relative to the sum of all other saturated aliphatic dicarboxylic acids and more than 45 mol % relative to the sum of all other saturated aliphatic dicarboxylic acids when component a2) is composed of more than two saturated aliphatic dicarboxylic acids. In preferred embodiments of the invention, the cyclic oligomers containing only one type of aliphatic dicarboxylic acid unit are (ADA-BDO)2, (AZA-BDO)2, (SEBA-BDO)2, (BRA-BDO)2, (ADA-BDO)3, (AZA-BDO)3, (SEBA-BDO)3, (BRA-BDO)3, (ADA-BDO)4, (AZA-BDO)4.

[0016] In a preferred embodiment of the present invention, the cyclic oligomer containing at least two kinds of aliphatic dicarboxylic acid units is (ADA-BDO-SUC-BDO), (SEBA-BDO-SUC-BDO), (BRA-BDO-SUC-BDO), (ADA-BDO-AZA-BDO), (ADA-BDO-SEBA-BDO), (ADA-BDO-BRA-BDO), (AZA-BDO-SEBA-BDO), (AZA-BDO-BRA-BDO), (SEBA-BDO-BRA-BDO), (SUC-BDO)2-(SEBA-BDO), (SUC-BDO)-(SE BA-BDO)2, (SUC-BDO)-(ADA-BDO)2, (SUC-BDO)2-(ADA-BDO), (SUC-BDO)-(BRA-BDO)2, (SUC-BDO)2-(BRA-BDO), (ADA-BDO)2-(AZA-BDO), (ADA-BDO)- (AZA-BDO)2, (ADA-BDO)2-(SEBA-BDO), (ADA-BDO)-(SEBA-BDO)2, (ADA-BDO)2-(BRA-BDO), (ADA-BDO)-(BRA-BDO)2, (AZA-BDO)2-(SEBA-BDO), (AZA- BDO)-(SEBA-BDO)2, (AZA-BDO)2-(BRA-BDO), (AZA-BDO)-(BRA-BDO)2, (SEBA-BDO)2-(BRA-BDO), (SEBA-BDO)-(BRA-BDO)2, (SUC-BDO)-(PTA-BDO)-( SEBA-BDO), (SUC-BDO)-(PTA-BDO)-(BRA-BDO), (SUC-BDO)-(PTA-BDO)-(ADA-BDO), (ADA-BDO)-(PTA-BDO)-(AZ-BDO), (ADA-BDO)-(PTA-BDO)-(SEBA -BDO), (ADA-BDO)-(PTA-BDO)-(BRA-BDO), (SEBA-BDO)-(PTA-BDO)-(AZ-BDO), (BRA-BDO)-(PTA-BDO)-(AZ-BDO), (BRA-BDO)-(PTA-BDO)-(SEBA-BDO ), (ADA-BDO)-(AZA-BDO)-(SEBA-BDO), (ADA-BDO)-(AZA-BDO)-(BRA-BDO), (ADA-BDO)-(BRA-BDO)-(SEBA-BDO), (BRA-BDO)-(AZA-BDO)-(SEBA-BDO),(SUC-BDO)2-(ADA-BDO)2, (SUC-BDO)2-(BRA-BDO)2, (SUC-BDO)2-(SEBA-BDO)2, (ADA-BDO)2-(AZA-BDO)2, (ADA-BDO)2-(SEBA-BDO)2, (ADA-BDO)2-(BRA-BDO)2, where ADA corresponds to an ester of adipic acid and a diol component, AZA corresponds to an ester of azelaic acid and a diol component, SEBA corresponds to an ester of sebacic acid and a diol component, BRA corresponds to an ester of brassylic acid and a diol component, SUC corresponds to an ester of succinic acid and a diol component, PTA corresponds to an ester of terephthalic acid, and BDO corresponds to the diol component 1,4-butanediol. For example, the cyclic oligomer (ADA-BDO-AZA-BDO) consists of one butylene adipate unit and one butylene azelate unit.

[0017] In addition to the dicarboxylic acid and diol components, the aliphatic-aromatic polyesters produced by the process according to the invention preferably contain repeat units derived from at least one hydroxy acid or the corresponding lactone in an amount of 0 to 49 mol %, preferably 0 to 30 mol %, based on the total number of moles of the dicarboxylic acid components. Examples of advantageous hydroxy acids are glycolic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyheptanoic acid, 9-hydroxynonanoic acid, lactic acid or lactide. The hydroxy acids may be incorporated into the chain as is or may be pre-reacted with a diacid or diol. In the process according to the invention, the hydroxy acid is advantageously added during the esterification step. Longer molecules having two functional groups, including a non-terminal functional group, may also be present in an amount not exceeding 10 mole percent based on the total number of moles of dicarboxylic acid components. Examples are dimer acid, ricinoleic acid, acids incorporating epoxy functional groups, and polyoxyethylenes with molecular weights between 200 and 10,000. In the process according to the invention, these long molecules carrying two functional groups are advantageously added during the esterification step.

[0018] Diamines, amino acids and amino alcohols may also be present in amounts up to 30 mole percent based on the total moles of the dicarboxylic acid component. In the process according to the invention, such diamines, amino acids and amino alcohols are advantageously added during the esterification step. During the esterification step of the process for producing polyesters according to the invention, one or more molecules characterized by having three or more reactive functional groups may be added in an amount of 0.02 to 3 mole % based on the total number of moles of dicarboxylic acid component (and any hydroxy acid) to obtain branched products. Examples of these molecules are glycerol, pentaerythritol, trimethylolpropane, citric acid, dipentaerythritol, monoanhydrosorbitol, monoanhydromannitol, acid triglycerides or polyglycerols.

[0019] The molecular weight Mn of the polyester obtained by the method according to the present invention is preferably 20,000 or more, more preferably 30,000 or more, and even more preferably 50,000 or more. When the polydispersity index Mw / Mn of the molecular weight is taken into consideration, it is preferably 1.5 to 10, more preferably 1.6 to 5, and further preferably 1.8 to 2.5. The molecular weights Mn and Mw may be measured by gel permeation chromatography (GPC). Measurements can be performed on a chromatographic system maintained at 40°C using a set of two columns in series (mixed porosity of 5 μm and 3 μm particle sizes), a refractive index detector, chloroform as eluent (flow 0.5 ml / min) and polystyrene as the reference standard.

[0020] In the method described in patent application WO2016 / 050963, the use of a catalyst comprising a mixture of at least one titanium-containing compound and at least one zirconium-containing compound, in which the weight ratio Ti / (Ti+Zr) in the polycondensation step is ≧0.01 and ≦0.70, preferably ≧0.02 and ≦0.60, allows to obtain lower amounts of residual cyclic oligomers after extraction of the polycondensation distillate. In particular, the content of these cyclic oligomers is determined gravimetrically after separation from the polycondensation distillate. In the present invention, it is instead possible to control the amount of mixed residual cyclic oligomers remaining in the formed polyester by using a phosphorus-containing compound in a mixture with at least one titanium-containing compound having a titanium to phosphorus ratio between 2 and 20, preferably between 3 and 15, where the ratio of cyclic oligomers containing at least two dicarboxylic aliphatic units having a MM of less than 1000 to cyclic oligomers containing only one dicarboxylic aliphatic unit having a MM of less than 1000 is between 0.30 and 1.40. The residual mixed cyclic oligomers extracted are weighed.

[0021] An accurately weighed polymer sample of approximately 30 g was extracted with 150 ml of acetonitrile at 40° C. for 96 h. The liquid phase was collected by filtration and the granules on the filter were washed with 25 ml of acetonitrile. The two liquid aliquots were combined in a 250 ml volumetric flask and the solvent was evaporated to constant weight on a rotary evaporator at 45° C. The composition of the residual mixed cyclic oligomers was analyzed by dissolving the oligomers in 1 ml of THF and diluting them with acetonitrile to a concentration of approximately 1000 ppm. 100 μl of the acetonitrile / THF solution was diluted with 800 μl of methanol and 100 μl of 0.1% N aqueous ammonium acetate. Analyses were performed by HPLC-MS using a Thermo Accela 1250 HPLC system coupled to a Thermo LCQ Fleet mass spectrometer in ESI+ mode. The species were separated using a Phenomenex Luna Omega C18 PS 100 × 2.1 mm 1.6 μm column, eluting according to the profile in Table 1.

[0022] [Table 1]

[0023] Oligomers were recognized based on the molecular weight (MM) of the protonated and ammonia adducts. The percentage of residual mixed cyclic oligomers was determined by processing the chromatograms in base peak mode and integrating the species recognized as cyclic oligomers based on their molecular weight. The ratio of the total area of ​​the peaks assigned to oligomers containing at least two aliphatic acids with MM less than 1000 to the total area of ​​the peaks assigned to cyclic oligomers containing only one aliphatic dicarboxylic acid unit with MM less than 1000 represents the percentage of mixed cyclic oligomers. The terminal acid group content of the aromatic aliphatic polyester is preferably 100 meq / kg or less, more preferably 60 meq / kg or less, and further preferably 40 meq / kg or less.

[0024] The acid end group content can be measured as follows: 1.5-3 g of polyester is placed in a 100 ml flask with 60 ml of chloroform. After the polyester is completely dissolved, 25 ml of 2-propanol is added, followed by 1 ml of deionized water immediately prior to analysis. The resulting solution is titrated against a KOH solution previously standardized with ethanol. The titration end point is determined using a suitable indicator (eg a glass electrode for acid-base titrations in non-aqueous media). The content of terminal acid groups is calculated from the consumption of KOH solution in ethanol according to the following formula:

number

[0025] For use in typical applications of plastic materials (e.g., cellular film formation, injection molding, foamed products, etc.), the polyesters obtained by the process according to the invention preferably have a melt mass flow rate (MFR) between 500 and 1 g / 10 min, more preferably between 100 and 2 g / 10 min, and even more preferably between 80 and 3 g / 10 min. Advantageously, MFRs between 25 and 3.5 g / 10 min (measured at 190 ° C / 2.16 kg according to ISO 1133-1) may be used. Preferably, the aliphatic-aromatic polyesters obtainable by the process according to the invention have an intrinsic viscosity (measured with an Ubbelohde viscometer on a solution in CHCl3 at a concentration of 0.2 g / dl at 25°C) of 0.4 or more, preferably between 0.4 and 2, more preferably between 0.7 and 1.5 dl / g. Preferably, the polyesters obtainable by the process according to the invention are biodegradable. In the sense of the present invention, biodegradable polymer is understood to mean a biodegradable polymer which has a relative biodegradability of 90% or more after 180 days, in comparison with microcrystalline cellulose, according to ISO 14855-1 (2013).

[0026] The polyesters obtainable by the process according to the invention may be used in blends with one or more polymers of synthetic or natural origin, whether biodegradable or not, and may also be obtained by reactive extrusion processes. In particular, the polyesters obtainable by the process according to the invention may be used in mixtures with biodegradable polyesters of the hydroxyacid or polyester-ether type. Of these biodegradable hydroxy acid polyesters, preferred are poly-L-lactic acid, poly-D-lactic acid and stereocomplex poly-DL-lactic acid, polycaprolactone, polyhydroxybutyrate, polyhydroxybutyrate valerate, polyhydroxybutyrate propanoate, polyhydroxybutyrate hexanoate, polyhydroxybutyrate decanoate, polyhydroxybutyrate dodecanoate, polyhydroxybutyrate hexadecanoate, polyhydroxybutyrate octadecanoate, and poly-3-hydroxybutyrate-4-hydroxybutyrate. Preferably, the mixture of polyesters obtainable by the process according to the invention and the above-mentioned biodegradable hydroxy acid polyesters is characterized by a content of said biodegradable polyesters ranging from 1 to 99% by weight, preferably from 5 to 95% by weight, relative to the total weight of the polyesters obtainable by the process according to the invention.

[0027] The polyesters obtainable by the process according to the invention may also be used in mixtures with polymers of natural origin, such as, for example, starch, cellulose, chitin, chitosan, alginates, proteins, such as gluten, zein, casein, collagen, gelatin, natural gums, rosin acids and their derivatives, lignin itself or purified, hydrolyzed, basified etc. lignin or its derivatives. The starches and celluloses may be modified, such as esters of starch or cellulose with a degree of substitution of 0.2 to 2.5, hydroxypropylated starches, starches modified with fatty chains, and cellophane. Mixtures of polyester and starch are particularly preferred. Starch may be used in both unstructured and gelled forms or as a filler. By destructured starch is meant starches as described in patents EP 0 118 240 and EP 0 327 505, in particular starches which have been modified in such a way that they do not show the so-called "Maltese cross" under polarized optical microscopy and do not show the so-called "ghosts" under phase-contrast optical microscopy.

[0028] The starch may be the continuous, dispersed or co-continuous phase. Starch particle dimensions are measured cross-sectionally relative to the flow direction during extrusion, or in any case the direction in which the material is produced. Starch particle size is measured from the two-dimensional profile obtained from a cross section. The average starch particle size is calculated as the arithmetic mean of the particle sizes. If the particle has a circular cross section, the particle size corresponds to the diameter of that circle. For particles having an elliptical cross section or other cross section similar to an ellipse, the particle size (d) is calculated by the following formula:

number

[0029] Preferably, the polyester mixtures obtainable by the process according to the invention with the abovementioned polymers of natural origin are characterized by a content of said polymers of natural origin ranging from 1 to 99% by weight, more preferably from 5 to 95% by weight, even more preferably from 10 to 40% by weight, relative to the total weight of the polyesters obtainable by the process according to the invention. The polyesters obtainable by the process according to the invention can also be used in mixtures with polyolefins, aromatic polyesters, polyesters and polyether-urethanes, polyurethanes, polyamides, polyamino acids, polyethers, polyureas, polycarbonates and mixtures thereof.

[0030] Of the vinyl polymers, preferred are polyethylene, polypropylene, their copolymers, polyvinyl alcohol, polyvinyl acetate, polyethylvinyl acetate and polyethylenevinyl alcohol. Among the aromatic polyesters, preferred are PET, PBT, PTT, especially those with a renewable content of more than 30%, and furandicarboxylated polyalkylenes. Among the latter, preferred are poly(1,2-ethylene-2,5-furandicarboxylate), poly(1,3-propylene-2,5-furandicarboxylate), poly(1,4-butylene-2,5-furandicarboxylate) and mixtures thereof.

[0031] Examples of polyamides include 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 combinations of these types 6 / 9, 6 / 10, 6 / 11, 6 / 12. The polycarbonate may be polyethylene carbonate, polypropylene carbonate, polybutylene carbonate, mixtures and copolymers thereof. The polyether may be polyethylene glycol, polypropylene glycol, polybutylene glycol, copolymers and mixtures thereof having a molecular weight of 70,000 to 500,000.

[0032] Preferably, the polyester blends obtained by the process according to the invention using the abovementioned polymers (polyolefins, aromatic polyesters, polyesters and polyetherurethanes, polyurethanes, polyamides, polyamino acids, polyethers, polyureas, polycarbonates and mixtures thereof) are characterized by a content of said polymers varying in the range from 0.5 to 99% by weight, more preferably from 5 to 50% by weight, with respect to the total weight of the polyesters obtained by the process according to the invention.

[0033] The polyesters obtainable by the process according to the invention are highly suitable for use, alone or in blends with other polymers, in many practical applications for the production of articles such as films, fibers, nonwovens, foils, and molded, thermoformed, blow molded, foam molded and laminated articles, including those produced using extrusion coating techniques. Examples of polyester-containing products obtainable by the process according to the invention are: -films (uniaxially and biaxially oriented films) and multilayer films with other polymeric materials; - Films for use as mulch films in agricultural fields; -Stretch films including food thin films, agricultural packaging and waste packaging; -Bags and liners for organic matter collection, such as food waste and grass clippings; -Single and multi-layer thermoformed food packaging, such as containers for milk, yogurt, meat, beverages, etc.; - Coatings obtained using extrusion coating technology; - multi-layer laminates having layers of cardboard, plastic, aluminum and metallized film; - Foam or expandable beads for the production of special sintered forms; -Foamed and semi-foamed products, including foam blocks formed from pre-expanded particles; - Expanded foams, thermoformed foam sheets and containers made from them for food packaging; -General fruit and vegetable containers; - compositions containing gelatinized, destructured and / or complex starches, native starches, flours, other fillers of natural, vegetable or inorganic origin as fillers; - Fibres, microfibers, bicomponent fibres with a core made of a hard polymer such as PLA, PET, PTT and an outer shell of the material according to the invention, double-blend bicomponent fibres, fibres with various cross sections from round to multilobal fibres, flocked, woven, nonwoven or spunbonded or thermobonded fabrics for the health, hygiene, agriculture and clothing sectors.

[0034] They can be used as a substitute for plasticized PVC. In a particularly preferred embodiment, the polyesters according to the invention are used to manufacture films. The processing of the aliphatic-aromatic polyester granules according to the invention by bubble film technology surprisingly makes it possible to optimize the process flow rates due to the high stability of the process itself (stability of the tube width, uniformity of the thickness along the circumference of the bubble, absence of adhesion phenomena of the film on the rollers). The process according to the invention is characterized in that it comprises an esterification or transesterification step and a polycondensation step, said polycondensation step being carried out in the presence of a catalyst comprising at least one titanium-containing compound and optionally at least one zirconium-containing compound, the weight ratio Ti / (Ti+Zr) being 0.01 to 0.7, preferably 0.02 to 0.60, if a zirconium compound is present.

[0035] Furthermore, the catalyst is used in a mixture with phosphorus compounds belonging to the family of organic phosphates or phosphites. Advantageously, the phosphorus-containing compound is chosen from compounds of general formula (1) or (2): [ka] (wherein R1, R2 and R3 may be selected from either H, C1-C20 alkyl or cycloalkyl, C6-C20 aryl, alkylaryl, or a polyalkylene oxide or polyalkylalkylene oxide chain.

[0036] In a particularly preferred embodiment, the phosphorus-containing compound is trioctyl phosphate. In a preferred embodiment of the process according to the invention, the catalyst comprises a mixture with at least one titanium-containing compound, the weight ratio of titanium to phosphorus being between 2 and 20, preferably between 3 and 15. In the esterification / transesterification step, preferably a molar ratio between the aliphatic diol and the dicarboxylic acid, esters and salts thereof is provided between 1 and 2.5, preferably between 1.05 and 1.9. The dicarboxylic acids, their esters or salts, the aliphatic diols and other comonomers which make up the polyester may be fed separately to this stage and mixed in the reactor or may be premixed, preferably at T<70° C., before being fed to the reactor.

[0037] It is also possible to premix some of the components and then modify the composition, for example during the esterification / transesterification reaction. In the case of polyesters in which the dicarboxylic acid component contains repeat units derived from multiple dicarboxylic acids, whether aliphatic or aromatic, it is also possible to premix some of these with the aliphatic diol, preferably at T<70° C., and add the remaining dicarboxylic acids, diols and other comonomers to the esterification / transesterification reactor. The esterification / transesterification step of the process according to the invention is advantageously carried out at a temperature between 200 and 250° C. and a pressure between 0.7 and 1.5 bar, preferably in the presence of an esterification / transesterification catalyst. The esterification / transesterification catalyst, which can advantageously also be used as a component of the catalyst for the polycondensation step, may be fed directly to the esterification / transesterification reactor or may first be dissolved in one or more aliquots of the dicarboxylic acid, ester or salt thereof, and / or aliphatic diol to facilitate distribution and make it more uniform in the reaction mixture.

[0038] In a preferred embodiment, the esterification / transesterification catalyst is selected from organometallic tin compounds, e.g. stannic acid derivatives, titanium compounds, e.g. titanates such as tetrabutylorthotitanate or tetra(isopropyl)orthotitanate, zirconium compounds, e.g. zirconates such as tetrabutylorthotitanate and tetra(isopropyl)orthotitanate, antimony compounds, aluminum, e.g. Al-triisopropyl, zinc compounds and mixtures thereof. With regard to the organometallic esterification / transesterification catalysts of the above mentioned type, during the esterification / transesterification step of the process according to the invention they are preferably present in a concentration of between 12 and 120 ppm of metal, relative to the amount of polyester that can theoretically be obtained by converting all the dicarboxylic acids fed to the reactor. In a preferred embodiment, the catalyst for the esterification / transesterification step is a titanate, more preferably diisopropyl, triethanolamino titanate, preferably used at a metal concentration of 12 to 120 ppm relative to the amount of polyester theoretically obtainable by converting all of the dicarboxylic acid fed to the reactor.

[0039] Preferably, the reaction time of the esterification / transesterification step in the process according to the invention is between 4 and 8 hours. At the end of the esterification / transesterification process, an oligomeric product is obtained with Mn<5000, intrinsic viscosity of 0.05-0.15 dl / g, and acid value<150 meq / kg. In a preferred embodiment of the process according to the invention, the catalyst is fed to the polycondensation step together with the oligomeric products at the end of the esterification / transesterification step. The polycondensation step in the process according to the invention is carried out in the presence of a catalyst comprising titanium, optionally zirconium or a mixture thereof, and a phosphorus-containing compound belonging to the family of organic phosphates or phosphites, the total amount of titanium being between 80 and 500 ppm relative to the amount of polyester that can theoretically be obtained by catalytically converting all the dicarboxylic acids fed to the reactor. The titanium to phosphorus ratio should be between 2 and 20, preferably between 3 and 15. If present, the total amount of zirconium should be such that the Ti / (Ti+Zr) ratio is kept in the range of 0.01 to 0.70.

[0040] In a preferred embodiment, the titanium-containing polycondensation catalyst is a titanate advantageously chosen from compounds having the general formula Ti(OR)4, where R is a ligand comprising one or more atoms of carbon, oxygen, phosphorus and / or hydrogen. Several ligand groups R may be present on the same titanium atom, but these groups are preferably identical in order to facilitate the preparation of the titanate. Additionally, two or more R ligands may be derived from a single compound and may be chemically bonded together in addition to being bound by titanium (so-called multidentate ligands such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethanediamine, etc.). R is advantageously selected from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3-oxobutanoic acid, ethanediamine, and linear or branched C1-C12 alkyl residues, such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl, ethylhexyl. In a preferred embodiment, R is selected from C1-C12 alkyl residues, preferably C1-C8, more preferably n-butyl.

[0041] The preparation of titanates is well known in the literature, and is typically prepared by reacting titanium tetrachloride with a precursor alcohol of formula ROH in the presence of a base such as ammonia, or by transesterification from other titanates. Commercially available examples of titanates which can be used in the process according to the invention include Tyzor® TPT (tetraisopropyl titanate), Tyzor® TnBT (tetra n-butyl titanate) and Tyzor® TE (diisopropyl triethanolamino titanate). The zirconium-containing polycondensation catalyst, when used in combination with a titanium-containing polycondensation catalyst, is a zirconate advantageously chosen from compounds having the general formula Zr(OR)4, where R is a ligand group containing one or more atoms of carbon, oxygen, phosphorus and / or hydrogen. As in the case of the titanates, several different (preferably identical) ligand groups R may be present on the same zirconium atom in order to favour the preparation of the zirconates.

[0042] In addition, two or more R ligands may be derived from a single compound and may be chemically bonded together in addition to being bonded to zirconium (so-called polydentate ligands such as triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, ethanediamine, etc.). R is advantageously selected from H, triethanolamine, citric acid, glycolic acid, malic acid, succinic acid, 3-oxobutanoic acid, ethanediamine, and linear or branched C1-C12 alkyl residues, such as ethyl, propyl, n-butyl, pentyl, isopropyl, isobutyl, isopentyl, hexyl, or ethylhexyl. In a preferred embodiment, R is selected from C1-C12 alkyl residues, preferably C1-C8, more preferably n-butyl. Methods for the preparation of zirconates are known in the literature and are similar to those described above for the titanates. Commercially available examples of zirconates which can be used in the process according to the invention include 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).

[0043] The polycondensation catalyst and phosphorus-containing compound are fed to the polycondensation step by feeding the various components separately to the reactor. It is also possible to premix some of the components and then adjust the composition of the catalyst, for example, when the catalyst is contacted with the oligomer product. If in the esterification / transesterification step of the process according to the invention a catalyst comprising a titanium and / or zirconium compound is used, in a preferred embodiment of the process according to the invention this catalyst is not separated from the oligomer product but is fed together with said oligomer product to the polycondensation step, advantageously used as polycondensation catalyst or as a component of a polycondensation catalyst, the molar ratio between titanium and zirconium being able to be adjusted by adding appropriate amounts of titanium and zirconium compounds to said polycondensation step. The catalyst for the polycondensation step may be the same as the catalyst for the esterification / transesterification step.

[0044] The polycondensation step is advantageously carried out by feeding the oligomer product to a polycondensation reactor and reacting it in the presence of a catalyst at a temperature of 220-260° C. and a pressure of 0.5 mbar-350 mbar. Preferably, the reaction time of the polycondensation step in the method according to the present invention is 4 to 8 hours. Depending on the particular molecular weight characteristics of the polyester and the desired viscosity, the process according to the invention may provide, after the polycondensation step, one or more steps of chain extension, reactive processing or reactive extrusion with other polymers by using peroxides, divinyl ethers, bisoxazolines, polyepoxides, di- and polyisocyanates, carbodiimides or dianhydrides. The invention will be described with the aid of several embodiments, which should be understood as illustrative and not limiting the scope of protection of the present patent application. EXAMPLES

[0045] Working Example Example 1 (Comparative) - Preparation of Poly(1,4-butylene adipate-co-1,4-butylene azelaic acid-co-1,4-butylene terephthalate) [PBATAz] with no added phosphorus-containing compound and a molar ratio of azelaic acid to the sum of aliphatic carboxylic acids of 0.15

[0046] Esterification process 8068 g of terephthalic acid, 6802 g of adipic acid, 1546 g of azelaic acid, 13961 g of 1,4-butanediol, 4.76 g of glycerol, and 5.50 g of an 80% w / w solution of diisopropyl triethanolamino titanate in ethanol (Tyzor TE, corresponding to 21 ppm with respect to the amount of PBATAz theoretically obtained by converting all the adipic acid, all the azelaic acid, and all the terephthalic acid fed to the reactor) at a diol to dicarboxylic acid molar ratio (MGR) of 1.50 were fed to a steel reactor of geometric volume 60 liters, equipped with a mechanical stirring system, a nitrogen inlet, a distillation column, a high boiling point distillate knockdown system, and a connection to a high vacuum system. The temperature of the mass was gradually increased to 230° C. over a period of 120 minutes.

[0047] Polycondensation Phase When 95% of the theoretical water was distilled off, 20.20 g of tetra n-butyl titanate (corresponding to 129 ppm metal with respect to the amount of PBATAz theoretically obtained by converting all the adipic, azelaic and terephthalic acids fed to the reactor) was added. The reactor temperature was then increased to 242° C. and the pressure was gradually reduced to below 1.2 mbar over 60 minutes. The reaction was allowed to proceed for about 4.30 hours, the time required to obtain PBATAz with a MFR of 4.3 g / 10 min (190° C., 2.16 kg), after which the material was discharged in the form of strings into a water bath and granulated.

[0048] Example 2 - Preparation of poly(1,4-butylene adipate-co-1,4-butylene azelaic acid-co-1,4-butylene terephthalate) [PBATAz] having a molar ratio of azelaic acid to the sum of aliphatic carboxylic acids of 0.15 and doped with a phosphorus-containing compound having a Ti / P weight ratio of 10. Example 1 was repeated with the addition of 4.63 g of trioctyl phosphate to the polycondensation step (corresponding to 15 ppm of phosphorus relative to the amount of PBATAz theoretically obtained by converting all the adipic acid, all the azelaic acid, all the azelaic acid and all the terephthalic acid fed to the reactor, thus corresponding to a Ti / P weight ratio of 10).

[0049] Example 3 - Preparation of poly(1,4-butylene adipate-co-1,4-butylene azelaic acid-co-1,4-butylene terephthalate) [PBATAz] having a molar ratio of azelaic acid to the sum of aliphatic carboxylic acids of 0.4 and doped with a phosphorus-containing compound having a Ti / P weight ratio of 10. Example 2 was repeated by feeding the monomers in the esterification step with a molar ratio of azelaic acid to total aliphatic dicarboxylic acids of 0.4 instead of 0.15. 7863 g terephthalic acid, 4679 g adipic acid, 4017 g azelaic acid, 13605 g 1,4-butanediol, 4.64 g glycerol, and 5.50 g of an 80% w / w solution of diisopropyl triethanolamino titanate in ethanol (Tyzor TE, equivalent to 21 ppm metal relative to the amount of PBATAz theoretically obtained by converting all the adipic acid, all the azelaic acid, and all the terephthalic acid fed to the reactor) were added.

[0050] Example 4 (Comparative) - Preparation of poly(1,4-butylene adipate-co-1,4-butylene azelaic acid-co-1,4-butylene terephthalate) [PBATAz] with a molar ratio of azelaic acid to the total aliphatic carboxylic acids of 0.4 and a phosphorus-containing compound added with a Ti / P weight ratio of 10. Example 3 was repeated, but the polycondensation phase was carried out under temperature and pressure conditions outside the scope of the present invention: instead of increasing the reactor temperature to 242° C. and gradually decreasing the pressure to less than 1.2 mbar over 60 minutes, the reactor temperature was increased to 267° C. and the pressure was gradually decreased to less than 3 mbar over 60 minutes. Samples of polyesters according to Examples 1-4 were taken at the beginning (IS) of the reactor unloading stage (stage of removing the product from the reactor) and at the end (FS) of the reactor unloading stage, and their MFR, terminal acid group content (CEG), mixed residual cyclic oligomer content, and ratio between cyclic oligomers containing at least two kinds of dicarboxylic aliphatic units with MM less than 1000 and cyclic oligomers containing only one kind of dicarboxylic aliphatic unit with MM less than 1000 were measured according to the method described in the present application. The values ​​shown in Table 1 are the average values ​​of the measured values.

[0051] [Table 2]

[0052] The granules of Example 1 (comparative) and Example 2 were fed into a Ghioldi model blown film machine with a screw diameter of 40 mm and L / D of 30. The film-forming head was characterized by an air gap of 0.9 mm and L / D of 12. The film-forming temperature was set at 145° C. and the blow ratio (BUR) was set at 3.2 with the aim of obtaining a film with a thickness of 20 microns (10+10). The blow ratio (BUR) is defined as the ratio of the bubble diameter to the die diameter. For processing the granules of Example 1 (comparative), the maximum flow rate at which a film thickness of 20 microns could be obtained due to a stable process (stable tube width, uniform thickness along the circumference of the bubble, no film adhesion phenomenon at the rollers) was 15 m / min; whereas for processing the granules of Example 2, it was possible to operate at 19 m / min.

Claims

1. a. A dicarboxylic acid component, a1) 40 to 80 mol % of units derived from at least one aromatic dicarboxylic acid, a2) 20 to 60 mol% of units derived from at least two saturated C4 to C24 dicarboxylic acids, preferably C5 to C24, preferably C5 to C13, more preferably C5 to C11, their C1 to C24 alkyl esters, preferably C1 to C4 alkyl esters, salts thereof and mixtures thereof a dicarboxylic acid component comprising: b. Diol aliphatic component 1. An aliphatic-aromatic polyester comprising: a) a residual cyclic mixed oligomer content of 1.0% to 4.0%, measured by the gravimetric method described herein, wherein the residual cyclic mixed oligomers have a ratio between cyclic oligomers comprising at least two dicarboxylic acid aliphatic units with a MM lower than 1000 and cyclic oligomers comprising only one dicarboxylic acid aliphatic unit with a MM lower than 1000 of 0.30 to 1.40, preferably 0.40 to 1.20, and even more preferably 0.45 to 0.80, determined by a method described herein involving HPLC-MS analysis; and b) an aliphatic-aromatic polyester comprising at least saturated aliphatic dicarboxylic acids of component a2 of 45 to 95 mol % relative to the sum of all other saturated aliphatic dicarboxylic acids.

2. The diol aliphatic component may be 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, neopentyl glycol, 2 2. The aliphatic-aromatic polyester according to claim 1, wherein the aromatic hydrocarbon group is selected from the group consisting of 1,3-dimethyl-1,3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, cyclohexanemethanediol, pentaerythritol, glycerol, polyglycerol, trimethylolpropane, polyalkylene glycols having a molecular weight of 100 to 4000, such as polyethylene glycol and polypropylene glycol, and mixtures thereof.

3. 3. The aliphatic-aromatic polyester of claim 2, wherein the diol aliphatic component is selected from 1,2-ethanediol and 1,4-butanediol.

4. 2. The aliphatic-aromatic polyester of claim 1, wherein the aromatic dicarboxylic acid is selected from terephthalic acid, isophthalic acid, 2,5-furandicarboxylic acid, esters thereof, salts thereof, and mixtures thereof.

5. 5. The aliphatic-aromatic polyester of claim 4, wherein the aromatic dicarboxylic acid is terephthalic acid.

6. 2. The aliphatic-aromatic polyester of claim 1, wherein the aliphatic dicarboxylic acid is selected from the group consisting of succinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, brassylic acid, and C1 to C24 alkyl esters thereof.

7. 7. The aliphatic-aromatic polyester of claim 6, wherein one of the aliphatic dicarboxylic acids is azelaic acid.

8. The following steps:

1. subjecting a mixture comprising an aliphatic diol and at least a dicarboxylic acid, ester, salt thereof or derivative thereof to an esterification and / or transesterification step to produce an oligomer; 2. subjecting the oligomer obtained in step 1 to polycondensation in the presence of a catalyst comprising a titanium-containing catalyst, a titanium-containing catalyst and a zirconium-containing catalyst, or a mixture thereof, and a phosphorus-containing compound belonging to the organic phosphate or phosphite family, at a temperature between 220°C and 260°C and a pressure between 0.5 mbar and 350 mbar; 2. A method for producing the aliphatic-aromatic polyester of claim 1, comprising:

9. The phosphorus-containing compound 【Chemistry 1】 wherein R1, R2, and R3 can be independently selected from H, C1-C20 alkyl or C1-C20 cycloalkyl, aryl or C6-C20 alkylaryl, or polyalkylene oxide or alkyl-polyalkylene oxide chains.

10. 10. The method of claim 8 or 9, wherein the catalyst comprises a mixture of compounds containing at least titanium.

11. 10. The method according to claim 8 or 9, wherein the molar ratio of titanium to phosphorus is between 2 and 20, preferably between 3 and 15.

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