Biodegradable polyester compositions, and methods for preparing and using same

Abstract

The present invention discloses a biodegradable polyester composition, as well as its preparation and use. The biodegradable polyester composition of the present invention comprises a biodegradable polyester and elemental titanium. The polymerizable monomers of the biodegradable polyester include an aromatic dicarboxylic acid or its ester, or a mixture thereof, an aliphatic dicarboxylic acid or its ester, or a mixture thereof, a dihydroxy compound, and a chain extender. The titanium content in the biodegradable polyester composition is 55-86 ppm, and the acid value of the biodegradable polyester composition is 1.10-1.96 mg KOH / g. By controlling the titanium content and acid value in the biodegradable polyester composition and combining it with specific types and amounts of polymerizable monomers, products made from the biodegradable polyester composition possess both excellent anti-aging properties and excellent disintegration properties, and can be used to manufacture biodegradable fruit and vegetable bags and garbage bags.

Description

[Technical Field]

[0001] The present invention relates to the technical field of biodegradable materials, and more particularly to a biodegradable polyester composition, as well as methods for preparing and using the same. [Background technology]

[0002] Polyester blends based on aliphatic-aromatic polyesters have excellent processability and mechanical properties and can be processed using various molding methods, including film blow molding and blow molding. They are widely used in applications such as fruit and vegetable bags and garbage bags. In this field, products such as fruit and vegetable bags and garbage bags must possess excellent mechanical properties before and during use, and be able to decompose along with food waste during composting after disposal, eliminating the need to separate garbage bags containing food waste for incineration. To meet these demands, biodegradable polyester products such as fruit and vegetable bags and garbage bags must have excellent resistance to aging during their shelf life and rapid disintegration after disposal.

[0003] CN110678502 A discloses a polymer composition for highly disintegrable films, which uses a composition prepared from specific proportions of an aliphatic polyester, an aliphatic-aromatic polyester, and a polyhydroxyalkanoate to improve the film's low-temperature disintegration rate, and is used in the field of cover films. However, the document does not consider the anti-aging properties of products made with the polymer composition during their shelf life. Because the film disintegrates quickly, its properties are easily deteriorated during storage, making it impossible to use normally. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Chinese Patent Application Publication No. 110678502 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a need to develop biodegradable polyester compositions that have excellent anti-aging properties during shelf life, degrade quickly after disposal, and produce products with excellent disintegration properties.

[0006] In order to overcome the above-mentioned drawback of the prior art that a long shelf life and high disintegration performance cannot be achieved at the same time, the present invention provides a biodegradable polyester composition by controlling the titanium element content in the biodegradable polyester composition to 55 to 86 ppm and the acid value to 1.10 to 1.96 mg KOH / g, and combining it with a specific type and content of polymerizable monomers, so that products made from the biodegradable polyester composition have both excellent anti-aging properties during the shelf life and excellent disintegration properties after disposal.

[0007] Another object of the present invention is to provide a method for preparing the above biodegradable polyester composition.

[0008] Another object of the present invention is to provide uses of the above biodegradable polyester composition. [Means for solving the problem]

[0009] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0010] A biodegradable polyester composition, comprising a biodegradable polyester and elemental titanium; The monomers for preparing the biodegradable polyester include component A, which is a dicarboxylic acid compound, component B, which is a dihydroxy compound, and component C, which is a chain extender; The component A is, based on the total molar amount of the component A, a1: 40 to 52 mol% of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof; a2: 48 to 60 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof; Component B contains a C2-C6 aliphatic alkanediol or a mixture thereof in an amount at least equimolar to that of component A, based on the total molar amount of component A; The component C accounts for 0 to 3 wt. % based on the weight of the biodegradable polyester composition, the content of titanium element in the biodegradable polyester composition is 55 to 86 ppm; the acid value of the biodegradable polyester composition is 1.10 to 1.96 mg KOH / g; The acid number of the biodegradable polyester composition is tested according to the DIN EN 12634-1998 standard method.

[0011] The content of titanium element in the biodegradable polyester composition is analyzed and tested using ICP-OES according to US EPA Method 3052:1996.

[0012] The synthesis of biodegradable polyesters is a reversible reaction. While high-molecular-weight biodegradable polyesters are synthesized using monomers under the influence of a catalyst, the high-molecular-weight biodegradable polyesters also undergo thermal decomposition under the influence of the catalyst. The amount of catalyst added has a significant impact on reaction efficiency. A low catalyst content can slow or limit the polymerization reaction, requiring more stringent reaction conditions such as high temperature, low vacuum, and long residence time. A high catalyst content can improve polymerization efficiency but also accelerate the thermal decomposition of biodegradable polyesters. Therefore, in addition to selecting the appropriate monomer type, monomer amount, reaction temperature, reaction pressure, and residence time, the synthesis of biodegradable polyesters requires the selection of an appropriate catalyst and catalyst amount. Titanium catalysts such as tetrabutyl titanate and tetraisopropyl titanate have been found to be common catalysts suitable for polyester systems.

[0013] Acid number is a fundamental parameter commonly used in literature and practice to characterize biodegradable polyesters. The acid number of a biodegradable polyester is a measure of the number of unreacted carboxylic acid groups at the end of the polyester chain. It is therefore similar to acidity and indicates the acidic content of the polymer. Biodegradable polyesters with a lower acid number typically result in better hydrolytic stability and improved anti-aging properties of the polyester, but also require longer for the polyester to fully decompose after disposal.

[0014] The present inventors have unexpectedly discovered that when the content of titanium element in the biodegradable polyester composition is 55 to 86 ppm and the acid value is 1.10 to 1.96 mg KOH / g, products made from the biodegradable polyester composition of the present invention have excellent anti-aging properties, are rapidly decomposed after disposal, and have excellent disintegration properties.

[0015] The biodegradable polyester composition of the present invention was stored at 60°C and 95% humidity for 72 hours, and the melt flow rate change rate η before and after storage was 3.90 (η = MFR1 / MFR0, Here, MFR1 represents the melt flow rate of the biodegradable polyester polymer after storage for 72 hours under conditions of 60°C and 95% humidity, and MFR0 represents the initial melt flow rate of the biodegradable polyester polymer before storage.

[0016] In a preferred embodiment, when the biodegradable polyester composition is stored under conditions of 60° C. and 95% humidity for 72 hours, the rate of change η in melt flow rate before and after storage is 2.95 or less.

[0017] The biodegradable polyester composition of the present invention has a weight retention rate of 30% or less after being left for 42 days, according to the ISO 14855-1-2012 standard method.

[0018] In a preferred embodiment, the biodegradable polyester composition has a weight retention rate of 18% or less after being left for 42 days, according to the ISO 14855-1-2012 standard method.

[0019] Generally, in aliphatic-aromatic polyesters, the higher the content of aromatic dicarboxylic acids, the better the mechanical properties and processability of the polyester. If other characteristic parameters remain the same, a too high content of aromatic dicarboxylic acids will result in a decrease in the decomposition properties of the polyester. In a particularly preferred embodiment, the acid component A of the aliphatic-aromatic polyester contains more than 50 mol% of aliphatic dicarboxylic acids a2. These polyesters are characterized by their excellent biodegradability.

[0020] Preferably, the content of titanium element in the biodegradable polyester composition is 63 to 79 ppm.

[0021] Preferably, the acid value of the biodegradable polyester composition is 1.18 to 1.45 mg KOH / g.

[0022] The present inventors have found that when the content of titanium element and the acid value in the biodegradable polyester composition satisfy the above ranges, the anti-aging properties and disintegration properties of the material are better overall.

[0023] Biodegradable polyester compositions are often processed by extrusion, which typically requires a lower melt flow rate due to the higher melt strength required, although a melt flow rate that is too low often leads to excessive melt pressure and excessive energy consumption during processing.

[0024] Typically, the higher the molecular weight of a biodegradable polyester composition, the lower its melt flow rate. The molecular weight of a biodegradable polyester composition can also have a limiting effect on the aging and degradation characteristics of products made therefrom. Typically, the higher the molecular weight, the longer a product can be preserved during storage and the longer it will take to completely decompose after disposal.

[0025] Preferably, the biodegradable polyester composition has a melt flow rate of 10 g / 10 min or less at 190° C. and 2.16 kg according to standard EN ISO 1133-2-2011.

[0026] More preferably, the biodegradable polyester composition has a melt flow rate of 1 to 8.5 g / 10 min at 190° C. and 2.16 kg according to standard EN ISO 1133-2-2011.

[0027] More preferably, the biodegradable polyester composition has a melt flow rate of 2.1 to 5.4 g / 10 min at 190° C. and 2.16 kg according to standard EN ISO 1133-2-2011.

[0028] Preferably, component A is a1: 44 to 51 mol% of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof; a2: 49 to 56 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof.

[0029] More preferably, said component A is a1: 47.3 to 50.6 mol% of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof; a2: 49.4 to 52.7 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof.

[0030] The aromatic dicarboxylic acid may be selected from aromatic dicarboxylic acids having from 8 to 20 carbon atoms. Preferably, the aromatic dicarboxylic acid has from 8 to 12 carbon atoms.

[0031] Optionally, the aromatic dicarboxylic acid is one or more of terephthalic acid, isophthalic acid, 2,6-naphthoic acid, and / or 1,5-naphthoic acid.

[0032] Furthermore, the esterification products of the aromatic dicarboxylic acids include di-C1-C6 alkyl esters, such as dimethyl ester, diethyl ester, di-n-propyl ester, diisopropyl ester, di-n-butyl ester, diisobutyl ester, di-tert-butyl ester, di-n-pentyl ester, diisopentyl ester, or di-n-hexyl ester. Acid anhydrides of aromatic dicarboxylic acids are also suitable derivatives for forming esters.

[0033] Preferably, the aromatic dicarboxylic acid is terephthalic acid.

[0034] The aliphatic dicarboxylic acid may be selected from aliphatic dicarboxylic acids having 2 to 40 carbon atoms. Preferably, the aliphatic dicarboxylic acid has 4 to 14 carbon atoms.

[0035] Optionally, the aliphatic dicarboxylic acid is one or more of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, or brassylic acid.

[0036] Preferably, the aliphatic dicarboxylic acid is adipic acid and / or sebacic acid.

[0037] The dihydroxy compound may be selected from branched or straight chain alkanediols having 2 to 6 carbon atoms.

[0038] Optionally, the dihydroxy compound is one or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,4-dimethyl-2-ethyl-1,3-hexanediol, 2,2-dimethyl-1,3-propanediol, and 2-ethyl-2-butyl-1,3-propanediol.

[0039] Preferably, the dihydroxy compound is 1,4-butanediol.

[0040] Preferably, the molar ratio between the component B and the component A is 1.2 to 2.4, and more preferably, the molar ratio between the component b1 and the component A is 1.3 to 1.8.

[0041] The biodegradable polyester composition contains 0 to 3 wt %, preferably 0.01 to 2 wt %, more preferably 0.05 to 1.5 wt %, and particularly preferably 0.01 to 0.45 wt %, of a crosslinking agent having at least three functional groups, based on the total weight of the biodegradable polyester composition.

[0042] Preferably, in the compound containing at least three functional groups, the functional groups are 3 to 6 hydroxy.

[0043] Preferably, the compound containing at least three functional groups is one or more of tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyethertriol, glycerol, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid anhydride, and 1,2,4,5-benzenetetracarboxylic acid.

[0044] More preferably, the compound containing at least three functional groups is one or more of trimethylolpropane, pentaerythritol or glycerol.

[0045] Preferably, the chain extender (component C) comprises one or more of the following components: c1: Difunctional or low-functional isocyanates and / or isocyanurates c2: Bifunctional or low-functional peroxides c3: Difunctional or low-functional epoxide c4: difunctional or low-functional oxazoline, oxazine, caprolactam and / or carbodiimide

[0046] The component c1 used comprises an isocyanate with a functionality of two or more or a mixture of different isocyanates. Aromatic or aliphatic diisocyanates can be used, but higher functionality isocyanates can also be used.

[0047] According to the invention, the aromatic diisocyanate c1 is in particular toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, naphthalene-1,5-diisocyanate or xylene diisocyanate.

[0048] In the present invention, the aliphatic diisocyanate C1 is in particular any linear or branched alkylene diisocyanate or cycloalkylene diisocyanate containing 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms, such as hexamethylene diisocyanate, isophorone diisocyanate or methylenebis(4-isocyanatocyclohexane). Particularly preferred aliphatic diisocyanates C1 are hexamethylene diisocyanate or isophorone diisocyanate, in particular hexamethylene diisocyanate.

[0049] Preferred isocyanurates are aliphatic isocyanurates derived from alkylene diisocyanurates or cycloalkylene diisocyanurates having 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms.

[0050] The amount of component c1 used is usually 0 to 3 wt.%, preferably 0.05 to 2 wt.%, and particularly preferably 0.1 to 1.5 wt.%, based on the total weight of the biodegradable polyester composition.

[0051] Suitable examples of peroxides having two or more functional groups (component c2) that can be used include compounds selected from benzoyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)methylcyclododecane, butyl 4,4-di(butylperoxy)pentanoate, dicumyl peroxide, tert-butyl perbenzoate, dibutyl peroxide, α,α-di(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexyne, and tert-butylperoxycumene.

[0052] The amount of component c2 used is usually 0 to 3 wt.%, preferably 0.1 to 2 wt.%, and particularly preferably 0.2 to 1 wt.%, based on the total weight of the biodegradable polyester composition.

[0053] The epoxides having two or more functional groups (component c3) used are, for example, hydroquinone diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Examples of other epoxides include diglycidyl terephthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, dimethyl diglycidyl phthalate, phenylene diglycidyl ether, ethylene diglycidyl ether, trimethylene diglycidyl ether, tetramethylene diglycidyl ether, hexamethylene diglycidyl ether, sorbitol diglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, diglycol diglycidyl ether, polyethylene glycol diglycidyl ether, propanediol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropanediol diglycidyl ether, and polybutanediol diglycidyl ether.

[0054] Particularly suitable components of epoxides with two or more functional groups are copolymers based on styrene, acrylate and / or methacrylate and containing an epoxy group, the epoxy-bearing unit being preferably glycidyl (meth)acrylate.

[0055] The amount of component c3 used is usually 0 to 3 wt.%, preferably 0.1 to 2 wt.%, and particularly preferably 0.2 to 1 wt.%, based on the total weight of the biodegradable polyester composition.

[0056] The components c4 used are oxazolines, oxazines, caprolactams and / or carbodiimides having two or more functional groups.

[0057] Particularly preferred dioxazolines and dioxazines are those in which the bridging moiety is a single bond, (CH)z-alkylene, where z=2, 3, or 4, such as methylene, ethane-1,2-diyl, propane-1,3-diyl, propane-1,2-diyl, or phenylene. Particularly preferred dioxazolines that come into consideration are 2,2'-di(2-oxazoline), di(2-oxazolinyl)methane, 1,2-di(2-oxazolinyl)ethane, 1,3-di(2-oxazolinyl)propane, or 1,4-di(2-oxazolinyl)butane, 1,4-di(2-oxazolinyl)benzene, 1,2-di(2-oxazolinyl)benzene, or 1,3-di(2-oxazolinyl)benzene.

[0058] Examples of carbodiimides include N,N'-di-2,6-diisopropylphenylcarbodiimide, N,N'-di-o-tolylcarbodiimide, N,N'-diphenylcarbodiimide, N,N'-dioctyldecylcarbodiimide, N,N'-di-2,6-dimethylphenylcarbodiimide, N-tolyl-N'-cyclohexylcarbodiimide, N,N'-di-2,6-di-tert-butylphenylcarbodiimide, N,N'-di-2,4,6-triisobutylphenylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, tert-butylisopropylcarbodiimide, di-β-naphthylcarbodiimide, and di-tert-butylcarbodiimide.

[0059] The amount of component c4 used is usually 0 to 3 wt.%, preferably 0.1 to 2 wt.%, and particularly preferably 0.2 to 1 wt.%, based on the total weight of the biodegradable polyester composition. Component c4 can also function as an acid scavenger.

[0060] Preferably, the monomers from which the biodegradable polyester is prepared are: a1: terephthalic acid or its ester, a2: Component A containing adipic acid or sebacic acid, its esters, or a mixture thereof; b1: 1,4-butanediol, b2: Component B containing one or more of glycerol, pentaerythritol, or trimethylolpropane; and component C, which is hexamethylene diisocyanate.

[0061] The present invention provides The method includes the steps of mixing the component A and the component B, with or without adding a titanium catalyst, to form a paste, and then performing the following operations: Step i): subjecting the paste to esterification or transesterification with all or part of a titanium catalyst until the viscosity of the esterified or transesterified product reaches 14-19 ml / g in a phenol / o-dichlorobenzene solution at a weight ratio of 1:1 in accordance with GB / T 17931-1999, as measured in a constant temperature water bath at 25±0.05°C; Step ii): subjecting the esterification or transesterification product obtained in step i) to a preliminary polycondensation reaction until the viscosity of the prepolymer measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999 is 62-78 ml / g; Step iii): The prepolymer obtained in step ii) is subjected to polycondensation reaction until the viscosity of the final polymerization product reaches 140-210 ml / g as measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, thereby obtaining a biodegradable polyester composition. This further protects the above method for preparing a biodegradable polyester composition.

[0062] If necessary, when component C is contained, step iii) may be followed by step iv) in which the final polymerization product obtained in step iii) is subjected to a chain extension reaction with a chain extender to obtain a biodegradable polyester composition, until the viscosity of the chain-extended product reaches 160 to 240 ml / g as measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999.

[0063] Excess diol components are usually removed by distillation and returned to the circuit after, for example, distillative purification.

[0064] Preferably, the titanium catalyst is tetrabutyl titanate and / or tetraisopropyl titanate.

[0065] In step i), the catalyst is added in an amount of 50-80 wt.% of the total amount or the total amount used. By reducing the amount of catalyst added, the subsequent processing process becomes more stable.

[0066] In step i), the temperature is set to 228-235°C and the pressure to 85-105 kPa. Step i) may be carried out in a mixing device, such as a vertical reactor equipped with a stirring function. The typical retention time is 120-190 minutes. After this reaction time, a prepolyester having a viscosity of 14-19 ml / g can usually be produced, as measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999.

[0067] In step ii), the liquid obtained in step i) (esterification or transesterification) is added, if necessary, together with the remaining catalyst, to a reactor suitable for pre-condensation reaction, at a temperature of 242-248°C and a pressure of 800-1800 Pa.

[0068] Step ii) may be carried out in a mixing device, such as a vertical reactor equipped with a stirring mechanism. A typical retention time is 170 to 240 minutes. After this reaction time, a prepolyester having a viscosity of 62 to 78 ml / g, as measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C, according to GB / T 17931-1999, is usually produced.

[0069] If necessary, a passivator may be added to the reaction system between step ii) and step iii). Usable passivators are typically phosphorus compounds, including phosphoric acid, phosphorous acid, and their esters. When a highly active titanium catalyst is used in the system, a passivator is typically added in step iii). The amount of passivator added may be 0.01 to 0.08 wt.%, preferably 0.02 to 0.05 wt.%, based on the amount of the final polymerization product obtained in step iii).

[0070] If appropriate, a color stabilizer for the condensation is mixed with the pre-condensed polyester between step ii) and step iii). Usable color stabilizers are, in particular, one or more of phosphorus compounds, such as phosphoric acid, phosphorous acid, triphenyl phosphite, triphenyl phosphate, IrgafosPEPQ, sodium hypophosphite, or sodium phosphite. The use of a color stabilizer usually slows down the condensation rate. Triphenyl phosphate is a particularly suitable color stabilizer, as it does not adversely affect the condensation rate. The amount of color stabilizer added may be 0.01 to 0.08 wt.%, preferably 0.02 to 0.05 wt.%, based on the amount of the final polymerization product from step iii).

[0071] Between step ii) and step iii), if necessary, a titanium compound other than the titanium catalyst may be added to the reaction system. Usable titanium-containing compounds include one or more of titanium dioxide, titanium tetrachloride, ferrous titanate, and barium metatitanate. The amount of the titanium-containing compound added may be 0 to 0.06 wt.%, preferably 0.001 to 0.04 wt.%, based on the weight of the final polymerization product obtained in step iii).

[0072] In the present invention, the content of titanium element can be controlled by adjusting the content of the titanium catalyst, and may also be adjusted by external addition of a titanium-containing compound.

[0073] The polycondensation process in step iii) occurs in a rotating disk reactor or a cage reactor, and the polycondensation reaction temperature is preferably 252-256°C. The pressure is set to 100-320 Pa, and the polycondensation reaction time is preferably 150-210 minutes. The reaction in step iii) can produce a reaction product with a viscosity number of 140-210 ml / g, as measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C, in accordance with GB / T 17931-1999.

[0074] If necessary, after step iii) is completed, the final polymerization product obtained in step iii) may be added to a twin-screw extruder or static mixer, and step iv) may be carried out with 0 to 3 wt. %, preferably 0.05 to 2 wt. %, and particularly preferably 0.1 to 1.5 wt. % of a chain extender (component C) based on the weight of the biodegradable polyester composition. The chain extender may be reacted at a temperature of 195 to 210°C for a residence time of 5 to 12 minutes to obtain a chain-extended product. The viscosity number of the chain-extended product measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 is 160 to 240 ml / g.

[0075] The present invention includes, as a component: 5 to 95 parts by weight of the biodegradable polyester composition; and 5 to 95 parts by weight of one or more of aliphatic polyester, starch, cellulose, polyhydroxyalkanoate, polyglycolic acid, or polylactic acid, to provide further protection.

[0076] The present invention further covers the use of the above biodegradable mixture in the manufacture of fruit and vegetable bags, garbage bags. [Effects of the Invention]

[0077] The present invention has the following advantageous effects compared to the prior art.

[0078] This invention develops a biodegradable polyester composition, in which the titanium content is controlled to 55-86 ppm and the acid value is controlled to 1.10-1.96 mg KOH / g. By combining it with a specific type and content of polymerization monomer, products made from the biodegradable polyester composition have excellent anti-aging properties, are quickly decomposed after disposal, and have excellent disintegration performance, and can be used to make fruit and vegetable bags and garbage bags. DETAILED DESCRIPTION OF THE INVENTION

[0079] The present invention will now be further described with reference to specific embodiments.

[0080] All raw materials used in the examples and comparative examples are commercially available.

[0081] In each of the Examples and Comparative Examples, the molar contents of aromatic dicarboxylic acid and aliphatic dicarboxylic acid, the titanium element content and the acid value in the biodegradable polyester composition were determined by the following methods.

[0082] Titanium element content: The titanium element content in the biodegradable polyester composition was measured by the following procedure using ICP-OES analysis, with reference to US EPA Method 3052:1996.

[0083] Approximately 0.1 g of biodegradable polyester composition was weighed and crushed, and 5 ml of nitric acid was added to completely immerse the biodegradable polyester composition. 1.0 ml of hydrogen peroxide was then added dropwise over 2 minutes. The mixture was sealed in a microwave digestion tank and decomposed at 210°C for 3-4 hours. After cooling to room temperature, the mixture was filtered through a 0.45 μm filter membrane, diluted to 50 ml with distilled water, and tested by ICP-OES.

[0084] Acid Value: The acid value of the sample was determined according to DIN EN 12634-1998, October 1998. The solvent mixture used contained 1 part dimethyl sulfoxide, 8 parts isopropanol, and 7 parts toluene by volume, with a total volume of 150 ml. According to the DIN EN 12634-1998 standard, the sample was pre-titrated to determine the appropriate sample mass and ensure that the volume of titrant consumed was 2-3 ml. The sample was added to the solvent mixture and heated to 70-85°C to dissolve the entire sample and form a clear solution. The solution temperature was maintained between 65-75°C during the titration to avoid sample precipitation. Tetrabutylammonium hydroxide was used as the titrant; tetramethylammonium hydroxide, which is highly toxic, should be avoided. In addition, to prevent the solvent mixture from absorbing CO2 in the air and affecting the volume of titrant consumed by the blank solvent, when testing the volume of titrant consumed by the blank solvent, the blank solvent should be pretreated according to the same process as the sample test operation, for example, the blank solvent should be heated for the same time and temperature, and then the blank solvent should be titrated.

[0085] Molar content of aromatic dicarboxylic acid and aliphatic dicarboxylic acid: 20 mg of a biodegradable polyester composition sample was dissolved in 0.6 mL of deuterated chloroform and measured at room temperature using a Bruker AV 500 nuclear magnetic resonance spectrometer. 1 H NMR was measured and calibrated to the chloroform solvent peak at approximately 7.26 ppm. For aromatic dicarboxylic acids such as terephthalic acid, the four hydrogen atoms on the benzene ring of the repeating unit appear at approximately 8.10 ppm, while for aliphatic dicarboxylic acids such as adipic acid, the four hydrogen atoms of the two CH2 units adjacent to the carbonyl of the repeating unit appear at approximately 2.33 ppm. Therefore, the molar content of the diacid component is determined by the integrated area (I) of the two peaks at 8.10 ppm and 2.33 ppm. T and I A ) can be expressed as

[0086] Molar content of aromatic dicarboxylic acid in aliphatic-aromatic polyester = I T / (IT +I A )×100% Molar content of aliphatic dicarboxylic acids in aliphatic-aromatic polyester = I A / (I T +I A )×100% Unless otherwise specified, the reagents, methods and equipment utilized in the present invention are conventional in the art.

[0087] Examples 1 to 14 Example 1 provides a biodegradable polyester composition, the preparation method of which follows the steps below: Step i): 445 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.350 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 230°C and 95 kPa pressure for 165 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 16 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.265 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 245°C and reacted at a pressure of 1300 Pa for 212 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was 65 ml / g. Step iii): While adding 0.17 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at 252°C and 145 Pa for 150 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 142 ml / g. Step iv): The final polymerization product of step iii) was placed in a static mixer, and 2.1 kg of hexamethylene diisocyanate was added. The mixture was blended at 200°C for 8 minutes, granulated, and dried to obtain a chain-extended product. The viscosity number of the chain-extended product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was found to be 173 ml / g.

[0088] Example 2 provides a biodegradable polyester composition, the preparation method of which follows the steps below: Step i): 508 kg of terephthalic acid, 437 kg of adipic acid, 730 kg of 1,4-butanediol, 3.65 kg of glycerol, and 0.325 kg of tetraisopropyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 235°C and 85 kPa pressure for 180 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 17 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.220 kg of tetraisopropyl titanate was added to the reactor. The reactor was heated to 242°C and reacted at a pressure of 1100 Pa for 228 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was 74 ml / g. Step iii): While adding 0.19 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at 254°C and 130 Pa for 186 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 174 ml / g.

[0089] Example 3 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 390 kg of terephthalic acid, 437 kg of adipic acid, 645 kg of 1,4-butanediol, 4.66 kg of trimethylolpropane, and 0.345 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 228°C and 105 kPa pressure for 170 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 15 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.230 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 246°C and reacted at a pressure of 1800 Pa for 170 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 62 ml / g. Step iii): While adding 0.15 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 252°C and a pressure of 124 Pa for 167 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 specifications, and was 140 ml / g. Step iv): The final polymerization product of step iii) was placed in a static mixer, and 1.6 kg of hexamethylene diisocyanate was added. The mixture was blended at 200°C for 10 minutes, granulated, and dried to obtain a chain-extended product. The viscosity number of the chain-extended product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 173 ml / g.

[0090] Example 4 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 386 kg of dimethyl terephthalate, 437 kg of adipic acid, 600 kg of 1,4-butanediol, 3.00 kg of glycerol, and 0.325 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 233°C and 100 kPa pressure for 190 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 14 ml / g. Step ii): The esterified product was placed in a vertically stirred reactor with complete mixing, and 0.205 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 248°C and reacted at a pressure of 800 Pa for 210 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 72 ml / g. Step iii): While adding 0.15 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 253°C and a pressure of 118 Pa for 194 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was 175 ml / g.

[0091] Example 5 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 540 kg of terephthalic acid, 437 kg of adipic acid, 755 kg of 1,4-butanediol, 3.75 kg of glycerol, and 0.425 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 235°C and 85 kPa pressure for 185 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 18 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.250 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 244°C and reacted at a pressure of 1460 Pa for 217 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 73 ml / g. Step iii): While adding 0.19 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 252°C and a pressure of 121 Pa for 177 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 specifications, and was 172 ml / g.

[0092] Example 6 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 515 kg of terephthalic acid, 437 kg of adipic acid, 740 kg of 1,4-butanediol, 3.75 kg of glycerol, and 0.356 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 235°C and 100 kPa pressure for 173 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 14 ml / g. Step ii): The esterified product was placed in a vertically stirred reactor with complete mixing, and 0.250 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 248°C and reacted at a pressure of 800 Pa for 240 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 58 ml / g. Step iii): 0.19 kg of phosphorous acid and 0.012 kg of titanium dioxide were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor for polycondensation at 255°C and 105 Pa for 180 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 173 ml / g.

[0093] Example 7 provides a biodegradable polyester composition, the preparation method follows the steps below: Step i): 535 kg of terephthalic acid, 651 kg of sebacic acid, 760 kg of 1,4-butanediol, 4.55 kg of glycerol, and 0.450 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 232°C and 90 kPa pressure for 175 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 19 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.260 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 247°C and reacted at a pressure of 960 Pa for 208 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 78 ml / g. Step iii): 0.230 kg of phosphorous acid and 0.045 kg of titanium tetrachloride were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor and polycondensed at 256°C and 100 Pa for 210 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 182 ml / g. Step iv): The final polymerization product of step iii) was placed in a static mixer, and 3.2 kg of hexamethylene diisocyanate was added. The mixture was blended at 200°C for 7 minutes, granulated, and dried to obtain a chain-extended product. The viscosity number of the chain-extended product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was found to be 209 ml / g.

[0094] Example 8 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.415 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 234°C and 85 kPa pressure for 182 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 18 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.260 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 245°C and reacted at a pressure of 1210 Pa for 230 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 69 ml / g. Step iii): While adding 0.170 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 254°C and a pressure of 125 Pa for 162 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 specifications, and was 145 ml / g. Step iv): The final polymerization product of step iii) was placed in a static mixer, and 2.4 kg of hexamethylene diisocyanate was added. The mixture was blended at 210°C for 9 minutes, granulated, and dried to obtain a chain-extended product. The viscosity number of the chain-extended product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was found to be 186 ml / g.

[0095] Example 9 provides a biodegradable polyester composition, the preparation method follows the steps below: Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.310 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 232°C and 98 KPa pressure for 150 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 14 ml / g. Step ii): The esterified product was placed in a vertically stirred reactor, 0.230 kg of tetrabutyl titanate was added to the reactor, and the reaction was carried out for 214 minutes at 243°C and a pressure of 1000 Pa. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 63 ml / g. Step iii): While adding 0.16 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 252°C and a pressure of 150 Pa for 164 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 specifications, and was 141 ml / g. Step iv): The final polymerization product of step iii) was placed in a static mixer, and 3.0 kg of hexamethylene diisocyanate was added. The mixture was blended at 195°C for 6 minutes, granulated, and dried to obtain a chain-extended product. The viscosity number of the chain-extended product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was found to be 188 ml / g.

[0096] Example 10 provides a biodegradable polyester composition, the preparation method of which follows the steps below: Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.395 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 235°C and 87 KPa pressure for 190 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 17 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.275 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 246°C and reacted at a pressure of 1100 Pa for 220 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 70 ml / g. Step iii): 0.16 kg of phosphorous acid and 0.035 kg of titanium tetrachloride were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor for polycondensation at 253°C and 132 Pa for 170 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 148 ml / g. Step iv): The final polymerization product of step iii) was placed in a static mixer, and 3.2 kg of hexamethylene diisocyanate was added. The mixture was blended at 200°C for 5 minutes, granulated, and dried to obtain a chain-extended product. The viscosity number of the chain-extended product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 185 ml / g.

[0097] Example 11 provides a biodegradable polyester composition, the preparation method of which follows the steps below: Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.280 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 234°C and 90 kPa pressure for 180 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 18 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.195 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 245°C and reacted at a pressure of 1080 Pa for 235 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 70 ml / g. Step iii): While adding 0.17 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at 255°C and 116 Pa for 210 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 186 ml / g.

[0098] Example 12 provides a biodegradable polyester composition, the preparation method of which follows the steps below: Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 5.85 kg of glycerol, and 0.390 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 235°C and 85 kPa pressure for 188 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 18 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.270 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 248°C and reacted at a pressure of 820 Pa for 205 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 77 ml / g. Step iii): 0.18 kg of phosphorous acid and 0.032 kg of titanium tetrachloride were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor and polycondensed at 255°C and 126 Pa for 196 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 178 ml / g. Step iv): The final polymerization product of step iii) was placed in a static mixer, and 3.8 kg of hexamethylene diisocyanate was added. The mixture was blended at 198°C for 7 minutes, granulated, and dried to obtain a chain-extended product. The viscosity number of the chain-extended product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was found to be 218 ml / g.

[0099] Example 13 provides a biodegradable polyester composition, the preparation method follows the steps below: Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 1.85 kg of glycerol, and 0.385 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 228°C and 105 kPa pressure for 176 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 15 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.283 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 247°C and reacted at a pressure of 1400 Pa for 186 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 64 ml / g. Step iii): 0.17 kg of phosphorous acid and 0.025 kg of titanium tetrachloride were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor for polycondensation at 254°C and 110 Pa for 170 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 160 ml / g.

[0100] Example 14 provides a biodegradable polyester composition, the preparation method follows the steps below: Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, and 0.355 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 228°C and 105 kPa pressure for 170 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 14 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.270 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 243°C and reacted at a pressure of 1670 Pa for 176 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 62 ml / g. Step iii): 0.17 kg of phosphorous acid and 0.038 kg of titanium tetrachloride were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor and polycondensed at 252°C and 180 Pa for 184 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 152 ml / g. The molar contents of aromatic dicarboxylic acid and aliphatic dicarboxylic acid, titanium element content, and acid value of the biodegradable polyester compositions of Examples 1 to 14 are shown in Table 1 below.

[0101] [Table 1]

[0102] Comparative Examples 1 to 7 Comparative Example 1 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 305 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.90 kg of glycerol, and 0.325 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 220°C and 110 kPa pressure for 124 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 9 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.190 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 250°C and reacted at a pressure of 2300 Pa for 230 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 57 ml / g. Step iii): While adding 0.14 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at 252°C and 100 Pa for 177 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 173 ml / g.

[0103] Comparative Example 2 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 585 kg of terephthalic acid, 437 kg of adipic acid, 760 kg of 1,4-butanediol, 3.90 kg of glycerol, and 0.465 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 238°C and 65 kPa pressure for 160 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 26 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.245 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 250°C and reacted at a pressure of 1900 Pa for 225 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 81 ml / g. Step iii): While adding 0.19 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at 250°C and 110 Pa for 165 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 171 ml / g.

[0104] Comparative Example 3 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.383 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 240°C and 60 kPa pressure for 210 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 33 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.260 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 245°C and reacted at a pressure of 800 Pa for 240 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 87 ml / g. Step iii): 0.10 kg of phosphorous acid and 0.012 kg of titanium tetrachloride were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor and polycondensed at 252°C and 105 Pa for 180 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 183 ml / g.

[0105] Comparative Example 4 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.330 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 230°C and 100 kPa pressure for 120 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 10 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.230 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 240°C and reacted at a pressure of 2200 Pa for 198 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was 48 ml / g. Step iii): While adding 0.21 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 248°C and a pressure of 170 Pa for 288 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 specifications, and was 185 ml / g.

[0106] Comparative Example 5 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.225 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 220°C and 100 kPa pressure for 130 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 8 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.155 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 245°C and reacted at a pressure of 1600 Pa for 210 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 53 ml / g. Step iii): While adding 0.12 kg of phosphorous acid to the prepolymer of step ii), the reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 258°C and a pressure of 110 Pa for 260 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 specifications, and was 186 ml / g.

[0107] Comparative Example 6 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.425 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 230°C and 85 kPa pressure for 160 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 22 ml / g. Step ii): The esterified product was placed in a vertically stirred, thoroughly mixed reactor, and 0.295 kg of tetrabutyl titanate was added to the reactor. The reactor was heated to 240°C and reacted at a pressure of 1300 Pa for 180 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 61 ml / g. Step iii): 0.23 kg of phosphorous acid and 0.038 kg of titanium tetrachloride were added to the prepolymer of step ii), and the reaction mixture was transferred to a final polymerization reactor and polycondensed at 250°C and 135 Pa for 240 minutes. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999, and was 183 ml / g.

[0108] Comparative Example 7 provides a biodegradable polyester composition, and the preparation method follows the steps below. Step i): 800 kg of succinic acid, 1,038 kg of 1,4-butanediol, 3.45 kg of glycerol, and 0.449 kg of tetrabutyl titanate were physically mixed in an esterification reactor at room temperature, and then the mixture was esterified at 200°C and 90 kPa pressure for 190 minutes to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 21 ml / g. Step ii): The esterified product was introduced into a static mixer and then into a vertically stirred, thoroughly mixed reactor. 0.241 kg of tetrabutyl titanate was added to the reactor, which was then heated to 240°C and reacted at a pressure of 2000 Pa for 250 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolymer. The viscosity number of the prepolymer was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 62 ml / g. Step iii): 0.18 kg of phosphorous acid was added to the prepolymer from step ii), and the reaction mixture was transferred to a final polymerization reactor. Polycondensation was carried out for 190 minutes at 245°C and 140 Pa pressure. Excess 1,4-butanediol and other by-products were removed by distillation to obtain the final polymerization product. The viscosity number of the final polymerization product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 214 ml / g. The molar contents of aromatic dicarboxylic acid and aliphatic dicarboxylic acid, titanium element content, and acid value of the biodegradable polyester compositions of Comparative Examples 1 to 7 are shown in Table 2 below.

[0109] [Table 2]

[0110] Characteristics Test The performance of the biodegradable polyester compositions prepared in the above examples and comparative examples was tested, and the specific method is as follows.

[0111] (1) Initial melt flow rate: Tested in accordance with EN ISO 1133-2-2011 under conditions of 190°C and 2.16 kg.

[0112] (2) Melt flow rate change rate: 1) The biodegradable polyester composition sample was dehumidified and dried at 80°C for 4 hours, and the initial melt index MFR0 was tested before storing in a constant temperature and humidity chamber according to the standard EN ISO 1133-2-2011 (190°C, 2.16 kg). 2) A 10-15 g sample of the biodegradable polyester composition was wrapped in gauze and placed in a constant temperature and humidity chamber at 60°C and 95% humidity for 72 hours. After 72 hours, the biodegradable polyester composition sample was removed from the chamber and placed in a dryer. It was then stored at ambient temperature for 24 hours to allow the sample to reach internal equilibrium. Once equilibrium was reached, the sample was dehumidified and dried at 80°C for 4 hours. After 72 hours, the melt index (MFR1) was tested according to the standard EN ISO 1133-2-2011 (190°C, 2.16 kg). Melt flow rate change rate before and after storage η = MFR1 / MFR0 MFR1 represents the melt flow rate of the biodegradable polyester polymer after storage for 72 hours under conditions of 60°C and 95% humidity, and MFR0 represents the initial melt flow rate of the biodegradable polyester polymer before storage. The larger the melt index change rate η before and after storage, the faster the property deterioration rate of the sample during storage and the worse the anti-aging properties. Conversely, the smaller the melt index change rate η before and after storage, the more stable the material properties, the slower the property deterioration rate during storage and the better the anti-aging properties.

[0113] (III) Weight retention rate The test was conducted in accordance with the standard method of ISO 14855-1 (2012). First, a biodegradable polyester composition sample was pressed into a film 35±3 μm thick and cut into a 10 cm × 10 cm test piece. The sample weight at this time was recorded as M0. The sample was then buried in compost soil and placed in a constant temperature and humidity box, where the experimental temperature was fixed at (28±2)°C and the humidity at 60±5%. After 42 days, the composted test piece was removed, washed, dried, and weighed. The sample weight at this time was recorded as M1. Sample weight retention = M1 / M0 × 100% The lower the sample weight retention, the better the disintegration properties of the biodegradable polyester composition. The film was produced as follows. The obtained biodegradable polyester composition was dehumidified and dried at 80°C for 4 hours, and then placed in a film blowing machine to perform film blowing. The screw diameter was 55 mm, the aspect ratio was 30:1, the screw rotation speed during extrusion was 30 r / min, the melt temperature was 145°C, the blow ratio was 3.5, and the film specifications were 550 mm wide and 35±3 μm thick.

[0114] The test results of the examples are shown in Table 3, and the test results of the comparative examples are shown in Table 4.

[0115] [Table 3]

[0116] [Table 4]

[0117] According to the test results in Table 3, the melt flow rate change rate η of the biodegradable polyester compositions prepared in the examples of the present invention was all 3.90 or less, and the melt flow rate change rate η of some preferred examples was 2.95 or less, indicating that the biodegradable polyester compositions have excellent anti-aging properties and good property retention during shelf life. The weight retention rate of the biodegradable polyester compositions prepared in the examples of the present invention was all 30.00% or less, and the weight retention rate of some preferred examples was 18% or less, indicating that the biodegradable polyester compositions have excellent disintegration properties.

[0118] In Examples 1 to 6, when the titanium element content remains unchanged and the acid value is also basically the same, the carboxylic acid monomer content is adjusted within the scope of the technical solution of the present invention, and as a result, the melt flow rate change rate η and weight retention rate of Examples 1 and 2 are relatively low, followed by Examples 3 and 6. Therefore, the preferred content of component a1 is 47.3 to 50.6 mol%, and the preferred content of component a2 is 49.4 to 52.7 mol%.

[0119] Comparative Examples 3 to 6 show that if the acid value of the biodegradable polyester composition is too low or too high, or if the titanium element content is too low or too high, it is not possible to obtain a biodegradable polyester composition that has both good anti-aging properties and excellent disintegration properties.

[0120] Examples 8 to 11 show that when the molar content of carboxylic acid monomer is constant, changes in the titanium element content and acid value both affect the anti-aging properties and disintegration properties of the biodegradable polyester composition, and among them, the melt flow rate change rate η and weight retention rate are relatively low in Examples 8 and 9. Therefore, it is preferable that the titanium element content in the biodegradable polyester composition is 63 to 79 ppm and the acid value is 1.18 to 1.45 mg KOH / g.

[0121] According to Comparative Examples 1 and 2, when the molar contents of aromatic dicarboxylic acid and aliphatic dicarboxylic acid exceed the technical range of the present invention, it is not possible to obtain a biodegradable polyester composition that combines excellent anti-aging properties and excellent disintegration properties.

[0122] In Comparative Example 7, in which 100 mol% succinic acid (aliphatic dicarboxylic acid) was used as the carboxylic acid monomer, the melt index change rate η of the biodegradable polyester composition was a very high 4.7 even after 72 hours of storage at 60°C and 95% humidity. Under composting conditions, the sample weight retention rate reached 45.31% after 42 days, indicating that the biodegradable polyester composition did not have excellent anti-aging properties and very poor disintegration properties.

[0123] Of course, it is clear that the above examples of the present invention are merely examples for clearly explaining the present invention, and do not limit the embodiments of the present invention. Those skilled in the art can make other different changes or modifications based on the above description. It is not necessary and cannot be possible to list all embodiments comprehensively here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A biodegradable polyester composition comprising: The biodegradable polyester composition comprises a biodegradable polyester and elemental titanium, The polymerizable monomers of the biodegradable polyester include component A, which is a dicarboxylic acid compound, component B, which is a dihydroxy compound, and component C, which is a chain extender; The component A is, based on the total molar amount of the component A, a1: 40 to 52 mol% of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof; a2: 48 to 60 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof; Component B comprises a C2 to C6 aliphatic alkanediol or a mixture thereof in an amount at least equimolar to that of component A, based on the total molar amount of component A; Component C accounts for 0 to 3 wt. % based on the weight of the biodegradable polyester composition; the content of titanium element in the biodegradable polyester composition is 55 to 86 ppm; The biodegradable polyester composition has an acid value of 1.10 to 1.96 mg KOH / g.

2. 2. The biodegradable polyester composition according to claim 1, wherein the content of the titanium element in the biodegradable polyester composition is 63 to 79 ppm.

3. The biodegradable polyester composition according to claim 1, wherein the acid value of the biodegradable polyester composition is 1.18 to 1.45 mg KOH / g.

4. The component A is a1: 44 to 51 mol% of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof; a2: 49 to 56 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof. The biodegradable polyester composition according to claim 1,

5. The component A is a1: 47.3 to 50.6 mol% of an aromatic dicarboxylic acid or an ester thereof, or a mixture thereof; a2: 49.4 to 52.7 mol % of an aliphatic dicarboxylic acid or an ester thereof, or a mixture thereof. The biodegradable polyester composition according to claim 4,

6. The monomers for preparing the biodegradable polyester are: a1: terephthalic acid or its ester, a2: Component A containing adipic acid or sebacic acid, an ester thereof, or a mixture thereof; b1: 1,4-butanediol, b2: Component B containing one or more of glycerol, pentaerythritol, or trimethylolpropane; The biodegradable polyester composition according to claim 1, characterized in that it comprises component C, which is hexamethylene diisocyanate.

7. The biodegradable polyester composition according to claim 1, wherein the biodegradable polyester composition has a melt flow rate of 10 g / 10 min or less under conditions of 190° C. and 2.16 kg.

8. The biodegradable polyester composition according to claim 7, wherein the biodegradable polyester composition has a melt flow rate of 1 to 8.5 g / 10 min under conditions of 190°C and 2.16 kg.

9. The biodegradable polyester composition was stored at 60°C and 95% humidity for 72 hours, and the melt flow rate change η before and after storage was 3.90 (η = MFR １ / MFR ０ , where MFR １ represents the melt flow rate of the biodegradable polyester polymer after storage for 72 hours under conditions of 60°C and 95% humidity, and MFR ０ The biodegradable polyester composition according to claim 1, wherein the initial melt flow rate of the biodegradable polyester polymer before storage is equal to or less than 1 / 2.

10. The biodegradable polyester composition according to claim 9, characterized in that when the biodegradable polyester composition is stored under conditions of 60°C and 95% humidity for 72 hours, the melt flow rate change rate η before and after storage is 2.95 or less.

11. The biodegradable polyester composition according to claim 1, wherein the weight retention rate after being left for 42 days is 30% or less, according to the ISO 14855-1-2012 standard method.

12. The biodegradable polyester composition according to claim 1, wherein the weight retention rate after being left for 42 days is 18% or less, according to the ISO 14855-1-2012 standard method.

13. A method for preparing the biodegradable polyester composition according to any one of claims 1 to 12, comprising: The method includes the steps of mixing the component A and the component B, with or without the addition of a titanium catalyst, to form a paste, and then performing the following operations: Step i): subjecting the paste to esterification or transesterification with all or a part of the titanium catalyst until the esterification or transesterification product reaches a viscosity number of 14-19 ml / g in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a thermostatic water bath at 25±0.05°C according to GB / T 17931-1999; Step ii): carrying out a preliminary polycondensation reaction of the esterification or transesterification product obtained in step i) until the viscosity number of the prepolymer measured in a phenol / o-dichlorobenzene solution in a weight ratio of 1:1 in accordance with GB / T 17931-1999 in a constant temperature water bath at 25±0.05°C is 62-78 ml / g; Step iii): The prepolymer obtained in step ii) is subjected to a polycondensation reaction until the final polymerization product has a viscosity number of 140 to 210 ml / g as measured in a phenol / o-dichlorobenzene solution at a weight ratio of 1:1 in accordance with GB / T 17931-1999 in a constant temperature water bath at 25±0.05°C, thereby obtaining the biodegradable polyester composition; If necessary, when component C is contained, after step iii), a preparation method is carried out in which the final polymerization product obtained in step iii) is subjected to a chain extension reaction with a chain extender to obtain the biodegradable polyester composition, until the chain extension product reaches a viscosity number of 160 to 240 ml / g as measured in a phenol / o-dichlorobenzene solution in a weight ratio of 1:1 in accordance with GB / T 17931-1999 in a constant temperature water bath at 25±0.05°C.

14. 14. The preparation method according to claim 13, characterized in that the titanium catalyst is tetrabutyl titanate and / or tetraisopropyl titanate.

15. 14. The preparation method according to claim 13, characterized in that between step ii) and step iii), a titanium-containing compound other than the titanium catalyst is added to the reaction system.

16. 16. The preparation method according to claim 15, wherein the amount of the titanium-containing compound added is 0-0.06 wt.%, based on the weight of the final polymerization product from step iii).

17. 16. The method of claim 15, wherein the titanium-containing compound is one or more of titanium dioxide, titanium tetrachloride, ferrous titanate, or barium metatitanate.

18. 14. The preparation method according to claim 13, characterized in that a passivating agent is added to the reaction system between step ii) and step iii).

19. The preparation method according to claim 18, characterized in that the amount of the passivating agent added is 0.01-0.08 wt.%, based on the weight of the final polymerization product from step iii).

20. 19. The preparation method according to claim 18, characterized in that the passivating agent is a phosphorus compound.

21. A biodegradable mixture comprising: As ingredients, 5 to 95 parts by weight of the biodegradable polyester composition according to any one of claims 1 to 12; and 5 to 95 parts by weight of one or more of aliphatic polyester, starch, cellulose, polyhydroxyalkanoate, polyglycolic acid, or polylactic acid.

22. 22. Use of the biodegradable mixture according to claim 21 in the manufacture of fruit and vegetable bags, garbage bags.

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