An aliphatic-aromatic polyester composition, polyester fiber, and methods for preparing and using the same

Abstract

The present invention discloses an aliphatic-aromatic polyester composition, a polyester fiber, and a preparation method and application thereof. The aliphatic-aromatic polyester composition of the present invention comprises the following components: i) an aliphatic-aromatic polyester based on aliphatic and aromatic dicarboxylic acids and aliphatic dihydroxy compounds; ii) titanium element, based on the weight of the aliphatic-aromatic polyester composition, the content of the titanium element is 55-88 ppm, and the acid value of the aliphatic-aromatic polyester composition is ≤ 0.84 mg KOH / g according to the standard DIN EN 12634-1998. The aliphatic-aromatic polyester composition of the present invention not only has a low yellowness index and good coloring performance, but also effectively improves the hydrolysis resistance, and can be widely applied to the field of polyester fibers.

Description

Technical Field

[0001] The present invention relates to the technical field of polyester compositions, and more specifically, to an aliphatic-aromatic polyester composition, polyester fiber, and their preparation methods and applications. Background Art

[0002] With the rapid development of polymer materials, while their importance has become increasingly prominent, people have also discovered their deficiencies, that is, most synthetic polymer materials are difficult to degrade in nature, causing "white pollution". As an essential fiber material for human production and life, its waste has also attracted much attention. In particular, traditional synthetic chemical fibers, such as PET fibers and PBT fibers, are difficult to degrade and have become new pollution sources. Fiber products made of biodegradable materials can be decomposed into carbon dioxide and water under the action of microorganisms, which is harmless to the environment and has become the best choice to replace traditional chemical fiber materials.

[0003] During the process of processing polyester materials into fibers, it is usually necessary to color them. To facilitate coloring, it is generally required that the polyester material has a low yellowness index. Aliphatic-aromatic polyesters obtained from aliphatic dicarboxylic acids such as adipic acid, aromatic dicarboxylic acids such as terephthalic acid, and aliphatic dihydroxy compounds such as 1,4-butanediol are known in the prior art. When synthesizing aliphatic-aromatic polyesters, common catalysts include tin compounds, antimony compounds, cobalt compounds, lead compounds, zinc compounds, aluminum compounds, or titanium compounds, and titanium compounds are most preferred. Titanium compounds, such as tetrabutyl titanate or tetraisopropyl titanate, have the advantage that the residual toxicity in the product or downstream products is small compared to other compounds. This property is particularly important in biodegradable polyesters because products containing them will directly enter the environment after being discarded. However, it has been found that when using adipic acid and simultaneously using titanium compounds as catalysts, the resulting aliphatic-aromatic polyesters usually exhibit colors from yellow to red, making it difficult to meet the color requirements of fiber products.

[0004] In order to improve the color of aliphatic-aromatic polyesters, the prior art discloses a method for preparing aliphatic-aromatic polyesters. By adding 0.03 wt% to 0.04 wt% of a phosphorus compound during the polymerization process (between step ii and step iii), an aliphatic-aromatic polyester with a whiteness index of at least 25 is obtained. The phosphorus compound, as a passivator for the titanium catalyst, weakens the activity of the titanium catalyst to a certain extent, resulting in a relatively high acid value (1.1 to 1.4 mg KOH / g) of the resulting aliphatic-aromatic polyester, and further reducing the hydrolysis resistance of the aliphatic-aromatic polyester. Therefore, it is necessary to develop a biodegradable polyester that simultaneously has a low yellowness index and good hydrolysis resistance. Summary of the Invention

[0005] The object of the present invention is to overcome the defects and deficiencies that existing biodegradable polyesters cannot simultaneously have a low yellowness index and good hydrolysis resistance, and to provide an aliphatic-aromatic polyester composition which not only has a low yellowness index YI value but also has good hydrolysis resistance.

[0006] Another object of the present invention is to provide a method for preparing an aliphatic-aromatic polyester composition.

[0007] Another object of the present invention is to provide a polyester fiber based on the aliphatic-aromatic polyester composition described in the present invention as the base resin.

[0008] Another object of the present invention is to provide a method for preparing a polyester fiber.

[0009] Another object of the present invention is to provide an application of the polyester fiber in masks and clothing.

[0010] The above objects of the present invention are achieved by the following technical solutions:

[0011] An aliphatic-aromatic polyester composition, characterized in that the composition comprises the following components:

[0012] i) An aliphatic-aromatic polyester based on aliphatic and aromatic dicarboxylic acids and aliphatic dihydroxy compounds, and the aliphatic-aromatic polyester contains at least the following components:

[0013] A) Dicarboxylic acid component:

[0014] a1) 46.2-49.5 mol% of an aromatic dicarboxylic acid or its ester derivative, or a mixture thereof, based on the total molar amount of a1) and a2);

[0015] a2) 50.5-53.8 mol% of an aliphatic dicarboxylic acid or its ester derivative, or a mixture thereof, based on the total molar amount of a1) and a2);

[0016] wherein the sum of the molar percentages of components a1) and a2) is 100%;

[0017] And B) Dihydroxy compound component:

[0018] b1) At least an equimolar amount of a C2-C6 aliphatic alkanediol as that of component A, or a mixture thereof;

[0019] b2) 0-3 wt% of a compound containing at least three functional groups based on the total weight of component A and b1;

[0020] ii) Titanium element, based on the weight of the aliphatic-aromatic polyester composition, the content of the titanium element is 55-88 ppm,

[0021] The aliphatic-aromatic polyester composition has an acid value ≤ 0.84 mg KOH / g according to the standard DIN EN 12634-1998.

[0022] According to the standard ASTM E313-73, the yellow index YI value of the aliphatic-aromatic polyester composition is ≤ 23.

[0023] The aliphatic-aromatic polyester composition is boiled in water at 60 °C for 48 h, and the viscosity number retention rate η of the aliphatic-aromatic polyester composition after boiling is ≥ 65%, indicating its good hydrolysis resistance.

[0024] η = η1 / η0

[0025] Wherein,

[0026] η1 represents the viscosity number of the aliphatic-aromatic polyester composition after boiling in water at 60 °C for 48 h.

[0027] η0 represents the viscosity number of the aliphatic-aromatic polyester composition before boiling.

[0028] Specifically, the hydrolysis resistance of the aliphatic-aromatic polyester composition is evaluated as follows:

[0029] 1) The sample of the aliphatic-aromatic polyester composition is dehumidified and dried at 80 °C for 4 h, and its initial viscosity number η0 before boiling is tested according to the standard GB / T17931-1999.

[0030] 2) The sample of the aliphatic-aromatic polyester composition is placed in a water bath at 60 °C and boiled for 48 h.

[0031] 3) After 48 h, the sample of the aliphatic-aromatic polyester composition is taken out, transferred to a desiccator, and stored at ambient temperature for 24 h to achieve the equilibrium condition inside the sample.

[0032] 4) After reaching equilibrium, the sample is dehumidified and dried at 80 °C for 4 h, and its viscosity number η1 after boiling for 48 h is tested according to the standard GB / T17931-1999.

[0033] When adipic acid is used as a raw material and a titanium compound is simultaneously used as a catalyst, the resulting aliphatic-aromatic polyester usually exhibits a color ranging from yellow to red. If the titanium element content in the aliphatic-aromatic polyester composition is too high, it will affect the color of the aliphatic-aromatic polyester composition, with the yellow index (YI) value being too high. Moreover, the excessive titanium element content will also weaken the hydrolysis resistance of the aliphatic-aromatic polyester composition. In addition, during the synthesis of the aliphatic-aromatic polyester, if the addition amount of the titanium element exceeds a certain range, the thermal decomposition reaction (reverse reaction) of the aliphatic-aromatic polyester will also intensify due to the increase in the addition amount of the titanium element, resulting in the yellowing of the product color. When the titanium element content is too low, the residence time of the polymerization reaction is too long, which is not conducive to reducing the acid value of the aliphatic-aromatic polyester, and a low-acid-value aliphatic-aromatic polyester composition cannot be obtained. The high acid value will further weaken the hydrolysis resistance of the aliphatic-aromatic polyester composition. At the same time, the high acid value will also cause the thermal decomposition reaction during the polymerization of the aliphatic-aromatic polyester to deteriorate further, resulting in the yellowing of the product color.

[0034] It should be noted here that the titanium element in the present invention can come from a titanium compound, such as tetrabutyl titanate or tetraisopropyl titanate, or can also come from other titanium-containing compounds additionally added during the polymerization process.

[0035] In a specific embodiment, preferably, the component A) dicarboxylic acid component comprises the following components:

[0036] a1) 47.3 to 48.8 mol% of an aromatic dicarboxylic acid or its ester derivative, or a mixture thereof, based on the total molar amount of a1) and a2);

[0037] a2) 51.2 to 52.7 mol% of adipic acid or its ester derivative, or a mixture thereof, based on the total molar amount of a1) and a2);

[0038] wherein the total molar percentage of components a1) and a2) is 100%.

[0039] In a specific embodiment, the aromatic dicarboxylic acid in a1) can be an aromatic dicarboxylic acid having 8 to 20 carbon atoms, preferably 8 to 12 carbon atoms, such as, for example, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid, and their ester-forming derivatives. Specifically mentioned here are di-C1-C6 alkyl esters, such as dimethyl, diethyl, di-n-propyl, di-isopropyl, di-n-butyl, di-isobutyl, di-tert-butyl, di-n-pentyl, di-isopentyl, or di-n-hexyl esters. The acid anhydrides of these dicarboxylic acids a1 are also suitable ester-forming derivatives.

[0040] The aromatic dicarboxylic acid or its ester-forming derivative a1 can be used alone or as a mixture of two or more. Terephthalic acid or its ester-forming derivative, such as dimethyl terephthalate, is particularly preferably used.

[0041] In a specific embodiment, the above a2) is adipic acid or its ester derivative, or a mixture thereof.

[0042] Examples of the ester derivatives that can be mentioned are, in particular, di-C1-C6 alkyl esters, such as dimethyl, diethyl, di-n-propyl, di-isopropyl, di-n-butyl, di-isobutyl, di-tert-butyl, di-n-pentyl, di-isopentyl or di-n-hexyl esters. The acid anhydride of the dicarboxylic acid can also be used.

[0043] The dicarboxylic acid or its ester-forming derivative in the present invention can be used alone or in the form of a mixture of two or more.

[0044] The dihydroxy compound component b1 is generally selected from branched or straight-chain aliphatic alkanediols having 2 to 6 carbon atoms. Examples of suitable aliphatic alkanediols are: 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, 2-ethyl-2-butyl-1,3-propanediol, in particular ethylene glycol, 1,3-propanediol, 1,4-butanediol. Particularly preferably 1,4-butanediol, especially in combination with adipic acid as component a2). A mixture of different aliphatic alkanediols can also be used.

[0045] Component b2) preferably includes compounds having at least three functional groups. Particularly preferred compounds have 3 to 6 hydroxyl groups. Examples that can be mentioned are: tartaric acid, citric acid, malic acid, trimethylolpropane, trimethylolethane, pentaerythritol, polyether triol, glycerol, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic anhydride, 1,2,4,5-benzenetetracarboxylic acid and pyromellitic dianhydride. Polyhydric alcohols, such as trimethylolpropane, pentaerythritol and glycerol, are preferred, and glycerol is particularly preferred.

[0046] The amount of component b2), based on the total weight of components A) and b1), is more preferably 0.02 to 1 wt%, and particularly preferably 0.08 to 0.60 wt%.

[0047] The aliphatic-polyester composition described in the present invention may further include component C) used as a chain extender, and component C) is selected from

[0048] c1) isocyanate

[0049] c2) peroxide

[0050] c3) Epoxides,

[0051] c4) Oxazolines, oxazines, caprolactams and / or carbodiimides

[0052] In the component c1) of the present invention, aromatic diisocyanates or aliphatic diisocyanates can be used as the isocyanate. For example, the aromatic diisocyanate can be 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.

[0053] Among them, diphenylmethane 2,2'-, 2,4'- or 4,4'-diisocyanate is particularly preferably used as component c1).

[0054] The isocyanates that can also be used include tris(4-isocyanatophenyl)methane with three rings. This polynuclear aromatic diisocyanate can be formed, for example, during the production of diisocyanates with one or two rings.

[0055] For the present invention, the aliphatic diisocyanate can be any straight-chain or branched-chain alkylene diisocyanate or cycloalkylene diisocyanate containing 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms. For example, it can be: hexamethylene-1,6-diisocyanate, isophorone diisocyanate or methylene bis(4-isocyanatocyclohexane).

[0056] Particularly preferred aliphatic diisocyanate is hexamethylene-1,6-diisocyanate.

[0057] The dosage of component c1), based on the total weight of the aliphatic-aromatic polyester composition, can be 0.05 to 2 wt%, particularly preferably 0.1 to 1.5 wt%.

[0058] The peroxide (component c2) of the present invention can be a mixture of one or more of the following compounds:

[0059] Benzoyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)methylcyclododecane, n-butyl 4,4-bis(butylperoxy)valerate, dicumyl peroxide, tert-butyl peroxybenzoate, dibutyl peroxide, α,α-bis(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hex-3-yne and cumene hydroperoxide.

[0060] The dosage of component c2) can be 0.1 - 2 wt% based on the total weight of the aliphatic-aromatic polyester composition, and is particularly preferably 0.2 - 1 wt%.

[0061] The epoxide (component c3) of the present invention can be: 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, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and polybutylene glycol diglycidyl ether, one or several of the copolymers containing epoxy groups based on styrene, acrylate and / or methacrylate.

[0062] The dosage of component c3) can be 0.1 - 2 wt% based on the total weight of the aliphatic-aromatic polyester composition, and is preferably 0.2 - 1 wt%.

[0063] Component c4) of the present invention can be dioxazolines and dioxazines with a bridging part being a single bond (CH2)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.

[0064] The dioxazoline in component c4) can preferably be 2,2'-bis(2-oxazoline), bis(2-oxazolinyl)methane, 1,2-bis(2-oxazolinyl)ethane, 1,3-bis(2-oxazolinyl)propane or 1,4-bis(2-oxazolinyl)butane, especially 1,4-bis(2-oxazolinyl)benzene, 1,2-bis(2-oxazolinyl)benzene or 1,3-bis(2-oxazolinyl)benzene.

[0065] The dioxazine is preferably 2,2'-bis(2-dioxazine), bis(2-dioxazinyl)methane, 1,2-bis(2-dioxazinyl)ethane, 1,3-bis(2-dioxazinyl)propane or 1,4-bis(2-dioxazinyl)butane, especially 1,4-bis(2-dioxazinyl)benzene, 1,2-bis(2-dioxazinyl)benzene or 1,3-bis(2-dioxazinyl)benzene.

[0066] The carbodiimide may be: 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.

[0067] The dosage of component c4), based on the total weight of the aliphatic-aromatic polyester composition, may be 0.1 to 2 wt%, preferably 0.2 to 1 wt%.

[0068] In the aliphatic-aromatic polyester composition, component i), particularly preferably the aliphatic-aromatic polyester, includes: as the aromatic dicarboxylic acid (component a1): terephthalic acid or its ester derivatives, or a mixture thereof; as the aliphatic dicarboxylic acid (component a2): adipic acid or its ester derivatives, or a mixture thereof; as the dihydroxy compound component (component b1): 1,4-butanediol; as component b2): glycerol, pentaerythritol, trimethylolpropane, and as component c1): hexamethylene-1,6-diisocyanate.

[0069] In a specific embodiment, preferably, based on the weight of the aliphatic-aromatic polyester composition, the content of the titanium element is 63 to 81 ppm.

[0070] Preferably, the acid value of the aliphatic-aromatic polyester composition is ≤0.78 mg KOH / g according to the standard DIN EN 12634-1998.

[0071] Preferably, the yellow index YI value of the aliphatic-aromatic polyester composition is ≤19 according to the standard ASTM E313-73.

[0072] Preferably, the aliphatic-aromatic polyester composition is boiled in water at 60°C for 48 hours, and the viscosity number retention rate η of the aliphatic-aromatic polyester composition after boiling is ≥72%.

[0073] Preferably, according to the standard ISO 1133-2-2011, the melt index of the aliphatic-aromatic polyester composition measured at 190°C and 2.16 kg is 1.0 to 22.0 g / 10 min, more preferably 2.0 to 10.0 g / 10 min.

[0074] Meanwhile, the aliphatic-aromatic polyester composition of the present invention also has biodegradability.

[0075] For the present invention, a substance or a mixture of substances has the characteristic of "biodegradable" if it shows a degree of biodegradation percentage of at least 90% as defined in DIN EN 13432.

[0076] Biodegradation generally results in the decomposition of a polyester or a polyester mixture over a reasonable period of investigation. Degradation can occur through enzymatic, hydrolysis or oxidation pathways, and / or by exposure to electromagnetic radiation such as ultraviolet radiation, most often caused by exposure to microorganisms such as bacteria, yeast, fungi and algae. The biodegradability can be quantified by mixing the polyester with compost and storing it for a specific period of time. For example, according to DIN EN 13432, during the composting process, air without CO2 is introduced into the matured compost, and the compost is subjected to a specific temperature process. Here, the biodegradability is defined as the percentage degree of biodegradation expressed as the ratio of the net amount of CO2 released by the sample (after subtracting the amount of CO2 released by the compost without the sample) to the maximum amount of CO2 that the sample can release (calculated from the carbon content in the sample).

[0077] Other methods for determining biodegradability are described in ASTM D5338 and ASTM D6400.

[0078] The present invention also specifically protects a method for preparing the aliphatic-aromatic polyester composition, comprising the following steps:

[0079] Mix component A with component B, with or without a titanium catalyst, to form a paste, and then perform the following operations.

[0080] Step i), subject the paste to an esterification or transesterification reaction with all or part of the titanium catalyst until the viscosity number of the esterification or transesterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 12 - 21 ml / g.

[0081] Step ii), subject the esterification or transesterification product obtained in step i) to a pre-polycondensation reaction until the viscosity number of its prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 36 - 52 ml / g.

[0082] Step iii), subject the prepolymer obtained in step ii) to a polycondensation reaction until the viscosity number of its final polymerization product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T17931-1999 is 145 - 203 ml / g.

[0083] Step iv), slicing the final polymerization product obtained in step iii) to obtain polyester particles, and then contacting the polyester particles with an aqueous tetrahydrofuran solution to obtain the aliphatic-aromatic polyester composition.

[0084] It should be noted that:

[0085] In the preparation method of the aliphatic-aromatic polyester composition of the present invention, the specific operation for measuring the viscosity number according to GB / T 17931-1999 is as follows:

[0086] The viscosity number of the product is measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 at a constant temperature water bath of 25 ± 0.05 °C according to the provisions of GB / T 17931-1999.

[0087] Preferably, in step i), the component A dicarboxylic acid component and the component B dihydroxy compound component are mixed in a preliminary step. The substances usually mixed are:

[0088] 1.0 mol equivalent of a mixture composed of aliphatic and aromatic dicarboxylic acids or their esters (component A), 1.2 to 2.4 mol equivalents, preferably 1.3 to 1.8 mol equivalents of C2-C6 aliphatic alkanediols (component b1), and based on the total weight of components A) and b1), preferably 0 to 3 wt%, more preferably 0.02 to 1 wt%, and particularly preferably 0.08 to 0.60 wt% of a compound b2 containing at least three functional groups.

[0089] The catalyst can be a tin compound, an antimony compound, a cobalt compound, a lead compound, a zinc compound, an aluminum compound or a titanium compound, more preferably a zinc compound, an aluminum compound or a titanium compound, and most preferably a titanium compound.

[0090] Furthermore, in the preparation method of the present invention, the dosage of the titanium catalyst is 0.001 to 1 wt% of the mass of the final polymerization product in step iii), preferably 0.03 to 0.2 wt%, and preferably the addition amount of the catalyst in step i) is 50 to 80% of the total catalyst dosage. Controlling the addition amount of the catalyst can make the subsequent processing process more stable.

[0091] The titanium catalyst can be tetrabutyl titanate or tetraisopropyl titanate, and its toxicity with respect to the residual amounts remaining in the product or downstream products is small. This property is particularly important in biodegradable polyesters because they will directly enter the environment in the form of compost bags or covering films.

[0092] Meanwhile, in step i), the temperature of the esterification reaction can be 180 to 260 °C, preferably 220 to 250 °C, and the reaction pressure is 40 to 120 KPa, preferably 60 to 90 KPa.

[0093] Step i) can be carried out in a mixing device such as a vertical reactor with stirring, and the residence time is 2 to 6 h, preferably 3 to 5 h.

[0094] In step ii), the liquid obtained from the esterification reaction in step i) together with the remaining catalyst is added to the reactor for the pre-condensation reaction. The reaction temperature is 235 to 260 °C, preferably 240 to 250 °C, and the pressure is 600 to 3000 Pa, preferably 800 to 2100 Pa. The typical residence time is 2 to 6 h, preferably 3 to 4 h.

[0095] Steps i), ii), and iii) can be carried out under the same titanium catalyst.

[0096] In step iii), if necessary, an additional titanium-containing compound can be added to the reaction system. The available additional titanium-containing compounds are one or a mixture of titanium tetrachloride, ferrous titanate, and barium metatitanate. The addition amount of the titanium-containing compound can be 0 to 0.06 wt%, preferably 0.001 to 0.04 wt%, based on the amount of the final polymerization product after step iii).

[0097] The polycondensation process in step iii) occurs in a reactor such as a rotary disk reactor or a cage reactor. The reaction temperature for the polycondensation is preferably 235 to 260 °C, preferably 240 to 250 °C, the pressure is 50 to 600 Pa, preferably 100 to 300 Pa, and the typical residence time is preferably 2 to 6 h, preferably 3 to 5 h.

[0098] Preferably, after step iii) and before step iv), the final polymerization product is subjected to the chain extension reaction as described in step iii-1) using a chain extender.

[0099] The specific operation of the chain extension reaction is as follows:

[0100] In step iii-1), after the completion of step iii), the final polymerization product obtained in step iii) is added to a twin-screw extruder or a static mixer, and a chain extender in an amount of 0.05 to 2 wt%, particularly preferably 0.1 to 1.5 wt% based on the mass of the final polymerization product, is added and reacted at 195 to 225 °C for 5 to 12 min to obtain a chain extension product. The viscosity number of the chain extension product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 163 to 232 mL / g.

[0101] In a specific embodiment, the chain extender is one or several of isocyanate, peroxide, epoxide, oxazoline, oxazine, caprolactam, and / or carbodiimide.

[0102] The chain extender can be, for example, one or more of toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, and isophorone diisocyanate.

[0103] Further preferably, the chain extender is hexamethylene-1,6-diisocyanate, and its dosage is 0.1-1.5 wt% of the weight of the chain growth product.

[0104] In order to further improve the yellowness index and hydrolysis resistance of the aliphatic-aromatic polyester composition, step iv) can be carried out. In step iv), the weight content of tetrahydrofuran in the tetrahydrofuran aqueous solution is 10-65 wt%, preferably 25-45 wt%. When the content of tetrahydrofuran in the tetrahydrofuran aqueous solution is relatively high, the content of tetrahydrofuran remaining in the polyester particles is relatively high. When the content of tetrahydrofuran in the tetrahydrofuran aqueous solution is relatively low, the elution effect cannot be effectively achieved, and the improvement of the yellowness index and hydrolysis resistance of the polyester composition is not obvious.

[0105] Further preferably, the contact treatment temperature in step iv) is 20-65 °C, more preferably 35-55 °C.

[0106] Further preferably, the contact treatment time in step iv) is 2-20 h, more preferably 5-16 h, and further preferably 8-12 h.

[0107] Preferably, the mass ratio of the polyester particles to the tetrahydrofuran aqueous solution in step iv) is 1:1-1:10.

[0108] Even more preferably, the mass ratio of the polyester particles to the tetrahydrofuran aqueous solution in step iv) is 1:2-1:5.

[0109] The contact treatment temperature, time of the polyester particles with the tetrahydrofuran aqueous solution, and the mass ratio of the polyester particles to the tetrahydrofuran aqueous solution will all affect the final elution effect and the yellowness index and hydrolysis resistance of the prepared aliphatic-aromatic polyester composition.

[0110] If the contact temperature is too high, the tetrahydrofuran volatilizes quickly and is lost more. If the contact temperature is too low, the elution effect cannot be effectively achieved, and the improvement of the yellowness index and hydrolysis resistance of the polyester composition is not obvious.

[0111] If the contact time is too long, the content of tetrahydrofuran remaining in the polyester composition is too much. If the contact time is too short, the elution effect cannot be effectively achieved, and the improvement of the yellowness index and hydrolysis resistance of the polyester composition is not obvious.

[0112] If the mass ratio of the polyester particles to the aqueous tetrahydrofuran solution is too high, although the elution effect can be effectively improved, more solvents are consumed, more waste liquid is generated, the economic efficiency is low, and the content of tetrahydrofuran remaining in the polyester composition is too high; if the mass ratio of the polyester particles to the aqueous tetrahydrofuran solution is too low, the uniform dispersion of the polyester particles in the solution cannot be achieved, the elution effect is uneven, and the elution effect is poor, and the improvement of the yellow index and hydrolysis resistance of the polyester composition is not obvious.

[0113] The aliphatic-aromatic polyester composition of the present invention further contains a small amount of tetrahydrofuran. The tetrahydrofuran mainly comes from three parts. One part is derived from the decomposition of 1,4-butanediol to generate tetrahydrofuran during the polyester synthesis process; one part is derived from the "biting" of the polyester terminal groups due to thermal decomposition during the polymerization process. The third part is derived from the residue of the aqueous tetrahydrofuran solution in the contact treatment process described in step iv). The tetrahydrofuran remaining in the polyester particles is not desired in the present invention. In principle, the lower the content of tetrahydrofuran remaining in the polyester particles, the better.

[0114] The reduction of the tetrahydrofuran content can be achieved by controlling the reaction temperature, reaction pressure, etc. of steps i), ii), and iii), or by optimizing and controlling the contact treatment conditions in step iv), such as optimizing the concentration of the aqueous tetrahydrofuran solution, the temperature and time of the contact treatment, and the solid-liquid ratio of the contact treatment. If the reaction temperature of steps i), ii), and iii) is too low, the polymerization time is often too long, and it is difficult to obtain a polyester with a low acid value. If the reaction pressure is too low, the equipment requirements are higher, and a large amount of capital investment is required. The contact treatment conditions in step iv) also need to consider the elution effect and the improvement effect on the color and hydrolysis resistance of the polyester product.

[0115] The aliphatic-aromatic polyester composition prepared by the preparation method of the present invention contains the following components:

[0116] i) An aliphatic-aromatic polyester based on aliphatic and aromatic dicarboxylic acids and aliphatic dihydroxy compounds, and the aliphatic-aromatic polyester contains at least the following components:

[0117] A) Dicarboxylic acid component:

[0118] a1) 46.2-49.5 mol% of an aromatic dicarboxylic acid or its ester derivative, or a mixture thereof, based on the total molar amount of a1) and a2);

[0119] a2) 50.5-53.8 mol% of an aliphatic dicarboxylic acid or its ester derivative, or a mixture thereof, based on the total molar amount of a1) and a2);

[0120] wherein the sum of the molar percentages of components a1) and a2) is 100%;

[0121] and B) a dihydroxy compound component:

[0122] b1) at least an equimolar amount of a C2-C6 aliphatic alkanediol with respect to component A, or a mixture thereof;

[0123] b2) a compound containing at least three functional groups in an amount of 0 to 3 wt% based on the total weight of components A and b1;

[0124] ii) titanium element, the content of titanium element is 55 to 88 ppm based on the weight of the aliphatic-aromatic polyester composition,

[0125] iii) tetrahydrofuran, the content of tetrahydrofuran is 40 to 170 ppm based on the weight of the aliphatic-aromatic polyester composition,

[0126] The aliphatic-aromatic polyester composition has an acid value ≤ 0.84 mg KOH / g according to the standard DIN EN 12634-1998.

[0127] Preferably, the content of the tetrahydrofuran is 86 to 136 ppm based on the weight of the aliphatic-aromatic polyester composition.

[0128] The aliphatic-aromatic polyester composition prepared by the preparation method of the present invention has an odor grade less than or equal to 4.5 according to the standard FLTM BO131-03.

[0129] The present invention also specifically protects the use of the aliphatic-aromatic polyester composition in the preparation of polyester fibers.

[0130] The polyester composition of the present invention has a low yellowness index and good hydrolysis resistance. Based on the polyester composition of the present invention as the base resin, it is also suitable for producing a biodegradable polymer mixture containing one or more components selected from the following:

[0131] aliphatic polyesters, polycaprolactone, starch (thermoplastic or non-plasticized), cellulose, polyhydroxyalkanoates, and polylactic acid.

[0132] The biodegradable polymer mixture can be used to prepare polyester fibers.

[0133] The present invention also specifically protects a polyester fiber, comprising the following components:

[0134] i) 5 to 15 wt% of the above-mentioned aliphatic-aromatic polyester composition based on the total weight of components i) to iv);

[0135] ii) 35 to 70 wt% of an aliphatic polyester based on the total weight of components i) to iv);

[0136] iii) based on the total weight of components i) to iv), 10 to 40 wt% of one or more components selected from starch, wood flour, cellulose, polyhydroxyalkanoate, polyglycolic acid and polylactic acid;

[0137] iv) 10 to 35 wt% of one or more components selected from talc, calcium carbonate, barium sulfate, montmorillonite and kaolin, based on the total weight of components i) to iv).

[0138] The present invention also specifically protects an application of the polyester fiber in masks and clothing.

[0139] Compared with the prior art, the present invention has the following beneficial effects:

[0140] The aliphatic-aromatic polyester composition of the present invention contains 55 to 88 ppm of titanium, based on the mass of the aliphatic-aromatic polyester composition. According to standard DIN EN 12634-1998, the acid value of the aliphatic-aromatic polyester composition is ≤0.84 mg KOH / g. Through comprehensive regulation of the titanium content and the acid value, the aliphatic-aromatic polyester composition not only has a low yellowness index and good coloring performance, but also effectively improves the hydrolysis resistance, and can be widely used in the field of polyester fibers.

[0141] Furthermore, the tetrahydrofuran content of the aliphatic-aromatic polyester composition of the present invention is 20-170 ppm, and according to the FLTM BO131-03 standard, the odor level thereof is less than or equal to 4.5. DETAILED DESCRIPTION

[0142] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0143] The raw material information of the embodiments and comparative examples of the present invention are described as follows:

[0144] 1,4-Butanediol was purchased from Xinjiang Meike Chemical Co., Ltd.;

[0145] Terephthalic acid was purchased from Zhuhai INEOS Chemical Co., Ltd.;

[0146] Adipic acid was purchased from Chongqing Huafeng Chemical Group Co., Ltd.;

[0147] Sebacic acid was purchased from Hengshui Jinghua Chemical Co., Ltd.;

[0148] Glycerin was sourced from Aladdin;

[0149] Tetrabutyl titanate was purchased from Jianyi Chemical Import & Export Co., Ltd.;

[0150] Titanium tetrachloride was purchased from Aladdin.

[0151] Hexamethylene diisocyanate was purchased from Aladdin.

[0152] The performance test method involved in the present invention is specifically described as follows:

[0153] Test for the molar content of aromatic dicarboxylic acid (a1) and adipic acid (a2) in the aliphatic-aromatic polyester:

[0154] Take 20 mg of the aliphatic-aromatic polyester composition sample and dissolve it in 0.6 mL of deuterated chloroform, and then measure it at room temperature using a Bruker AV 500 nuclear magnetic resonance spectrometer. 1 HNMR, calibrate the chloroform solvent peak near 7.26 ppm.

[0155] Reference: Chen, X.; Chen, W.; Zhu, G.; Huang, F.; Zhang, J., Synthesis, 1H-NMR characterization, and biodegradation behavior of aliphatic-aromatic random copolyester. J. Appl. Polym. Sci. 2007, 104(4): 2643-2649. It can be known that for aromatic dicarboxylic acids, such as terephthalic acid, the 4 hydrogen atoms on the benzene ring in the repeating unit appear near 8.10 ppm; for aliphatic dicarboxylic acids, such as adipic acid, the 4 hydrogen atoms of the two CH2 units adjacent to the carbonyl group in the repeating unit appear near 2.33 ppm. Thus, the molar content of the diacid component can be represented by the integral areas (I T and I A ) of these two peaks:

[0156] Molar content of aromatic dicarboxylic acid in the aliphatic-aromatic polyester = I T / (I T +I A )×100%;

[0157] Molar content of adipic acid in the aliphatic-aromatic polyester = I A / (I T +I A )×100%.

[0158] Viscosity number test:

[0159] According to the provisions of GB / T 17931-1999, it is measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C, and the sample concentration is 5 mg / ml.

[0160] Acid value:

[0161] Determine the acid value AN (mg KOH / g) of the sample according to DIN EN 12634 in October 1998.

[0162] The solvent mixture used includes: 1 volume part of dimethyl sulfoxide, 8 volume parts of isopropyl alcohol, and 7 volume parts of toluene, and the volume of the solvent mixture is 150 ml.

[0163] According to the provisions of the DIN EN 12634 standard, pre-titrate the sample to determine the appropriate sample mass to ensure that the volume of the titrant consumed is 2 - 3 ml. Add the sample to the solvent mixture and heat it to 70 - 85 °C to dissolve all the samples into a clear solution. Keep the solution temperature at 65 - 75 °C during the titration process to avoid precipitation of the sample. If appropriate, use tetrabutylammonium hydroxide as the titrant and avoid using highly toxic tetramethylammonium hydroxide. At the same time, to avoid the solvent mixture absorbing CO2 in the air and thus affecting the volume of the titrant consumed by the blank solvent, when testing the volume of the titrant consumed by the blank solvent, the blank solvent should be pretreated in the same process as the sample test operation, such as heating the blank solvent for the same time and temperature, and then titrating the blank solvent.

[0164] Test method for yellow index YI:

[0165] According to ASTM E313 - 73, use a Minolta CM - 5 spectrophotometer to measure the yellow index of the aliphatic - aromatic polyester composition particles. The particle size of the particles is 1.2 to 5.4 g / 100 particles, and parallel tests are carried out three times to determine the average value. Use a glass cuvette (from Minolta) to fill the particulate material to be analyzed (the filling height is at least 3 cm). The particulate material is compacted by the pressure of the measuring head of the Minolta instrument.

[0166] Evaluation of hydrolysis resistance:

[0167] The evaluation of the hydrolysis resistance of the aliphatic - aromatic polyester composition is carried out as follows:

[0168] 1) Dehumidify and dry the aliphatic - aromatic polyester composition sample at 80 °C for 4 hours, and test its initial viscosity number η0 before boiling water according to the standard GB / T17931 - 1999;

[0169] 2) Place the aliphatic - aromatic polyester composition sample in a 60 °C water bath and boil it for 48 hours;

[0170] 3) After 48 hours, take out the aliphatic - aromatic polyester composition sample, transfer it to a desiccator, and store it at ambient temperature for 24 hours to achieve the equilibrium conditions inside the sample.

[0171] 4) After reaching equilibrium, the sample is dehumidified and dried at 80 °C for 4 hours, and its viscosity number η1 after boiling in water for 48 hours is tested according to Standard GB / T 17931-1999.

[0172] Viscosity number retention rate of the aliphatic-aromatic polyester composition after boiling in water

[0173] η = η1 / η0

[0174] Wherein,

[0175] η1 represents the viscosity number of the aliphatic-aromatic polyester composition after boiling in water at 60 °C for 48 hours,

[0176] η0 represents the viscosity number of the aliphatic-aromatic polyester composition before boiling in water.

[0177] The larger the viscosity number retention rate η of the aliphatic-aromatic polyester composition after boiling in water, the stronger the hydrolysis resistance of the sample; the smaller the viscosity number retention rate η, the weaker the hydrolysis resistance of the sample.

[0178] Titanium element content:

[0179] The titanium element content in the aliphatic-aromatic polyester composition is analyzed by ICP-OES with reference to US EPA Method 3052:1996 and measured according to the following procedure:

[0180] Weigh about 0.1 g of the aliphatic-aromatic polyester composition, add 5 ml of nitric acid after crushing to completely immerse the aliphatic-aromatic polyester composition, then drop 1.0 ml of hydrogen peroxide and react for 2 min, seal it in a microwave digestion tank and digest at 210 °C for 3 hours, then cool to room temperature, filter with a 0.45 μm filter membrane and dilute to 50 ml with distilled water, and test by ICP-OES.

[0181] Test method for the content of tetrahydrofuran THF:

[0182] Weigh about 1.2 g of the sample, with a headspace temperature of 105 °C and a headspace time of 2 hours. Test using an Agilent 7697A-7890A device.

[0183] The test parameters and test methods of Agilent 7697A-7890A are shown in Table 1 and Table 2:

[0184] Table 1 Test parameters of Aglient 7697A

[0185]

[0186] Table 2 Test parameters of Aglient 7890A

[0187]

[0188]

[0189] GC temperature programming:

[0190] Initial value: 50 °C, holding time: 3 minutes;

[0191] Heat up to 200 °C at a heating rate of 12 °C / min, holding time: 4 minutes.

[0192] Comparative Examples 1 - 7

[0193] Comparative Example 1:

[0194] Step i): Physically mix 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.30 kg of glycerol and 0.560 kg of tetrabutyl titanate at room temperature in an esterification reactor, and then carry out an esterification reaction on this mixture at 235 °C and a pressure of 90 KPa for 4 - 5 h to obtain an esterification product. The viscosity number of the esterification product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 23 ml / g.

[0195] Step ii): Transfer the esterification product into a vertical stirred full-mixing reactor, add 0.400 kg of tetrabutyl titanate into this reactor, heat it to 242 °C, and react at a pressure of 1800 Pa for 2 - 3 h. Most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 65 ml / g;

[0196] Step iii): Transfer the reaction mixture into a final polymerization reactor, carry out polycondensation at a temperature of 248 °C and a pressure of 115 Pa for 2 - 3 h. The remaining excessive 1,4-butanediol and other by-products are distilled off. Then, granulate and dry to obtain a final polymerization product. The viscosity number of the final polymerization product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 181 ml / g.

[0197] Step iv), Put polyester particles into a reactor according to the mass ratio of polyester particles to an aqueous tetrahydrofuran solution of 1:5 for contact treatment. The mass concentration of the aqueous tetrahydrofuran solution is 45%, the contact treatment temperature is 35 °C, and the contact treatment time is 8 h.

[0198] After the contact treatment process, a drying process may also be included, and the drying can be carried out in a blast drying tower.

[0199] According to the test method of the present invention, in step iv), the viscosity number, acid value, melt index, titanium element content, THF content, and yellowness index of the obtained biodegradable composition after drying are measured, and the hydrolysis resistance and odor are evaluated. The specific data are shown in Table 1.

[0200] Comparative Example 2:

[0201] Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.30 kg of glycerol and 0.235 kg of tetrabutyl titanate are physically mixed at room temperature in an esterification reactor, and then the mixture is subjected to an esterification reaction at 240 °C and 85 KPa for 5 - 6 h to obtain an esterification product. The viscosity number of the esterification product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T17931-1999 is 8 ml / g.

[0202] Step ii): The esterification product is introduced into a vertical stirred full-mixing reactor, 0.125 kg of tetrabutyl titanate is added thereto, and the temperature is raised to 245 °C and the reaction is carried out at a pressure of 1600 Pa for 3 - 4 h. Most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 28 ml / g;

[0203] Step iii): The reaction mixture is transferred to a final polymerization reactor, and polycondensation is carried out at a temperature of 252 °C and a pressure of 145 Pa for 4 - 5 h. The remaining excessive 1,4-butanediol and other by-products are distilled off, and then pelletized and dried to obtain a final polymerization product. The viscosity number of the final polymerization product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 169 ml / g.

[0204] Step iv): The polyester particles are put into a reactor according to the mass ratio of polyester particles to an aqueous tetrahydrofuran solution of 1:5 for contact treatment. The mass concentration of the aqueous tetrahydrofuran solution is 45%, the contact treatment temperature is 35 °C, and the contact treatment time is 8 h.

[0205] After the contact treatment process, a drying process may also be included, and the drying can be carried out in a blast drying tower.

[0206] According to the testing method of the present invention, in step iv), the viscosity number, acid value, melt index, titanium element content, THF content, and yellowness index of the obtained biodegradable polyester composition after drying are tested, and the hydrolysis resistance and odor are evaluated. The specific data are shown in Table 1.

[0207] Comparative Example 3:

[0208] Step i): 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.30 kg of glycerol and 0.350 kg of tetrabutyl titanate are physically mixed at room temperature in an esterification reactor. Then, the mixture is subjected to an esterification reaction at 238 °C and a pressure of 90 KPa for 4 - 5 h to obtain an esterification product. The viscosity number of the esterification product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 17 ml / g.

[0209] Step ii): The esterification product is introduced into a vertical stirred tank reactor. 0.220 kg of tetrabutyl titanate is added to the reactor, and it is heated to 245 °C and reacted at a pressure of 2100 Pa for 3 - 4 h. Most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 48 ml / g;

[0210] Step iii): The reaction mixture is transferred to a final polymerization reactor and subjected to polycondensation at a temperature of 251 °C and a pressure of 100 Pa for 3 - 4 h. The remaining excessive 1,4-butanediol and other by-products are distilled off. Then, pelletizing and drying are carried out to obtain a final polymerization product. The viscosity number of the final polymerization product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to GB / T 17931-1999 is 180 ml / g.

[0211] According to the testing method of the present invention, in step iii), the viscosity number, acid value, melt index, titanium element content, THF content of the obtained biodegradable polyester composition after drying are tested, and the hydrolysis resistance and odor are evaluated. The specific data are shown in Table 1.

[0212] Comparative Example 4:

[0213] For Comparative Example 4, steps i) to iii) are the same as those of Comparative Example 3.

[0214] Step iv): The polyester particles are put into a reactor for contact treatment at a mass ratio of polyester particles to the aqueous tetrahydrofuran solution of 1:15. The mass concentration of the aqueous tetrahydrofuran solution is 5%, the contact treatment temperature is 20 °C, and the contact treatment time is 24 h.

[0215] After the contact treatment process, a drying process may also be included, and the drying can be carried out in a blast drying tower.

[0216] According to the test method of the present invention, the viscosity number, acid value, melt index, titanium element content, THF content, and yellow index of the obtained biodegradable polyester composition after drying in step iv) are tested, and the hydrolysis resistance and odor are evaluated. The specific data are shown in Table 1.

[0217] Comparative Example 5:

[0218] Comparative Example 5: Steps i) to iii) are the same as those in Comparative Example 3.

[0219] Step iv): The polyester particles are put into a reactor for contact treatment at a mass ratio of polyester particles to the aqueous tetrahydrofuran solution of 1:0.5. The mass concentration of the aqueous tetrahydrofuran solution is 75%, the contact treatment temperature is 40 °C, and the contact treatment time is 3 h.

[0220] After the contact treatment process, a drying process may also be included, and the drying can be carried out in a blast drying tower.

[0221] According to the test method of the present invention, the viscosity number, acid value, melt index, titanium element content, THF content, and yellow index of the obtained biodegradable polyester composition after drying in step iv) are tested, and the hydrolysis resistance and odor are evaluated. The specific data are shown in Table 1.

[0222] Comparative Example 6:

[0223] Step i): 420 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.30 kg of glycerol and 0.385 kg of tetrabutyl titanate are physically mixed at room temperature in an esterification reactor, and then the mixture is subjected to an esterification reaction at 238 °C and a pressure of 90 KPa for 4 - 5 h to obtain an esterification product. The viscosity number of the esterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T17931-1999 is 11 ml / g.

[0224] Step ii): Introduce the esterification product into a vertical stirred full-mixing reactor, add 0.200 kg of tetrabutyl titanate into the reactor, heat it to 245 °C, and react under a pressure of 2100 Pa for 3 - 4 h. Most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained, and the viscosity number of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 33 ml / g;

[0225] Step iii): Transfer the reaction mixture to a final polymerization reactor, and carry out polycondensation at a temperature of 251 °C and a pressure of 100 Pa for 3 - 4 h. The remaining excessive 1,4-butanediol and other by-products are distilled off. Then, granulate and dry to obtain the final polymerization product. The viscosity number of the final polymerization product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 173 ml / g.

[0226] Step iv): Put polyester particles into a reactor for contact treatment according to the mass ratio of polyester particles to the aqueous solution of tetrahydrofuran of 1:5. The mass concentration of the aqueous solution of tetrahydrofuran is 45%, the contact treatment temperature is 35 °C, and the contact treatment time is 8 h.

[0227] After the contact treatment process, a drying process may also be included, and drying can be carried out in a blast drying tower.

[0228] According to the test method of the present invention, test the viscosity number, acid value, melt index, titanium element content, THF content, yellow index of the biodegradable composition obtained after drying in step iv), and evaluate the hydrolysis resistance performance. The specific data are shown in Table 1.

[0229] Comparative Example 7:

[0230] Step i): Physically mix 585 kg of terephthalic acid, 437 kg of adipic acid, 760 kg of 1,4-butanediol, 2.60 kg of glycerol and 0.520 kg of tetrabutyl titanate at room temperature in an esterification reactor, and then carry out an esterification reaction on this mixture at 238 °C and a pressure of 90 KPa for 4 - 5 h to obtain an esterification product. The viscosity number of the esterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 24 ml / g.

[0231] Step ii): Introduce the esterification product into a vertical stirred tank full mixer reactor. Add 0.225 kg of tetrabutyl titanate to this reactor, heat to 245 °C, and react for 3 - 4 h under a pressure of 2100 Pa. Most of the excessive 1,4 - butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o - dichlorobenzene solution with a weight ratio of 1:1 is 55 ml / g according to the provisions of GB / T 17931 - 1999;

[0232] Step iii): Transfer the reaction mixture to a final polymerization reactor, and carry out polycondensation at a temperature of 251 °C and a pressure of 100 Pa for 3 - 4 h. The remaining excessive 1,4 - butanediol and other by - products are distilled off. Then, granulate and dry to obtain the final polymerization product. The viscosity number of the final polymerization product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o - dichlorobenzene solution with a weight ratio of 1:1 is 188 ml / g according to the provisions of GB / T 17931 - 1999.

[0233] Step iv): Put polyester particles into a reactor for contact treatment according to the mass ratio of polyester particles to the aqueous solution of tetrahydrofuran of 1:5. The mass concentration of the aqueous solution of tetrahydrofuran is 45%, the contact treatment temperature is 35 °C, and the contact treatment time is 8 h.

[0234] After the contact treatment process, a drying process may also be included. Drying can be carried out in a forced - air drying tower.

[0235] According to the test method described in the present invention, test the viscosity number, acid value, melt index, titanium element content, THF content, yellow index of the biodegradable composition obtained after drying in step iv), and evaluate the hydrolysis resistance performance. The specific data are shown in Table 1.

[0236] Table 1. Performance test results of Comparative Examples 1 - 7

[0237]

[0238]

[0239] Example 1

[0240] Step i): Physically mix 452 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4 - butanediol, 2.30 kg of glycerol and 0.400 kg of tetrabutyl titanate at room temperature in an esterification reactor. Then carry out an esterification reaction on this mixture at 240 °C and a pressure of 100 KPa for 4 - 5 h to obtain an esterification product. The viscosity number of the esterification product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o - dichlorobenzene solution with a weight ratio of 1:1 is 18 ml / g according to the provisions of GB / T17931 - 1999.

[0241] Step ii): Introduce the esterification product into a vertical stirred tank full mixer reactor. Add 0.200 kg of tetrabutyl titanate to this reactor, heat to 247 °C, and react for 3 - 4 h under a pressure of 1900 Pa. Most of the excessive 1,4 - butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer, measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o - dichlorobenzene solution with a weight ratio of 1:1, is 50 ml / g as specified in GB / T 17931 - 1999;

[0242] Step iii): Add 0.050 kg of titanium tetrachloride, transfer the reaction mixture to a final polymerization reactor, and carry out polycondensation at a temperature of 250 °C and a pressure of 120 Pa for 3 - 4 h. The remaining excessive 1,4 - butanediol and other by - products are distilled off. Then, granulate and dry to obtain the final polymerization product. The viscosity number of the final polymerization product, measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o - dichlorobenzene solution with a weight ratio of 1:1, is 181 ml / g as specified in GB / T17931 - 1999.

[0243] Step iv): Put the polyester particles into the reactor for contact treatment according to the mass ratio of polyester particles to the aqueous solution of tetrahydrofuran of 1:2. The mass concentration of the aqueous solution of tetrahydrofuran is 25%, the contact treatment temperature is 55 °C, and the contact treatment time is 12 h.

[0244] After the contact treatment process, a drying process may also be included. Drying can be carried out in a blast drying tower. According to the test method of the present invention, the viscosity number, acid value, melt index, titanium element content, THF content, yellow index of the biodegradable polyester composition obtained after drying in step iv) are tested, and the hydrolysis resistance and odor are evaluated. The specific data are shown in Table 2.

[0245] Examples 2 - 7:

[0246] Examples 2 - 7, steps i) to iii) are the same as those of Comparative Example 3. Step iv): Carry out the contact treatment process on the biodegradable polyester composition according to the process conditions shown in Table 2.

[0247] Table 2 Performance test results of Examples 1 - 7

[0248]

[0249]

[0250] Example 8:

[0251] Step i): Physically mix 425 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.30 kg of glycerol and 0.310 kg of tetrabutyl titanate at room temperature in an esterification reactor. Then, carry out an esterification reaction on this mixture at 233 °C and a pressure of 70 KPa for 3 - 4 h to obtain an esterification product. The viscosity number of the esterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T17931 - 1999 is 12 ml / g.

[0252] Step ii): Introduce the esterification product into a vertical stirred full-mixing reactor. Add 0.240 kg of tetrabutyl titanate to this reactor, heat it to 243 °C, and react at a pressure of 1200 Pa for 3 - 4 h. Most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931 - 1999 is 36 ml / g;

[0253] Step iii): Transfer the reaction mixture to a final polymerization kettle, carry out polycondensation at a temperature of 252 °C and a pressure of 110 Pa for 3 - 4 h. The remaining excessive 1,4-butanediol and other by-products are distilled off. Then, granulate and dry to obtain a final polymerization product. The viscosity number of the final polymerization product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931 - 1999 is 177 ml / g.

[0254] Step iv): Put polyester particles into a reactor for contact treatment according to the mass ratio of polyester particles to an aqueous tetrahydrofuran solution of 1:3. The mass concentration of the aqueous tetrahydrofuran solution is 65%, the contact treatment temperature is 30 °C, and the contact treatment time is 2 h.

[0255] There may also be a drying process after the contact treatment process, and the drying can be carried out in a blast drying tower.

[0256] According to the test method described in the present invention, test the viscosity number, acid value, melt index, titanium element content, THF content, yellow index of the biodegradable polyester composition obtained after drying in step iv), and carry out hydrolysis resistance and odor evaluations. The specific data are shown in Table 3.

[0257] Example 9:

[0258] Step i): 570 kg of dimethyl terephthalate, 437 kg of adipic acid, 730 kg of 1,4-butanediol, 2.60 kg of glycerol and 0.340 kg of tetrabutyl titanate are physically mixed at room temperature in an esterification reactor. Then, the mixture is subjected to an esterification reaction at 240 °C and a pressure of 65 KPa for 3 - 4 h to obtain an esterification product. The viscosity number of the esterification product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 is 21 ml / g according to the provisions of GB / T 17931-1999.

[0259] Step ii): The esterification product is introduced into a vertical stirred full-mixing reactor, and 0.250 kg of tetrabutyl titanate is added thereto. It is heated to 245 °C and reacted at a pressure of 900 Pa for 3 - 4 h. Most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 is 52 ml / g according to the provisions of GB / T 17931-1999;

[0260] Step iii): The reaction mixture is transferred to a final polymerization reactor and subjected to polycondensation at a temperature of 250 °C and a pressure of 118 Pa for 4 - 5 h. The remaining excessive 1,4-butanediol and other by-products are distilled off. Then, it is pelletized and dried to obtain a final polymerization product. The viscosity number of the final polymerization product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 is 186 ml / g according to the provisions of GB / T 17931-1999.

[0261] Step iv): Polyester particles are put into a reactor according to the mass ratio of polyester particles to an aqueous tetrahydrofuran solution of 1:8 for contact treatment. The mass concentration of the aqueous tetrahydrofuran solution is 40%, the contact treatment temperature is 65 °C, and the contact treatment time is 5 h.

[0262] There may also be a drying process after the contact treatment process, and the drying can be carried out in a blast drying tower.

[0263] According to the test method described in the present invention, the viscosity number, acid value, melt index, titanium element content, THF content, yellow index of the obtained biodegradable polyester composition after drying in step iv) are tested, and the hydrolysis resistance and odor are evaluated. The specific data are shown in Table 3.

[0264] Example 10:

[0265] Step i): 445 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.30 kg of glycerol and 0.285 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. Then, the mixture was subjected to an esterification reaction at 240 °C and a pressure of 75 KPa for 4 - 5 h to obtain an esterification product. The viscosity number of the esterification product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 was 14 ml / g according to the provisions of GB / T17931-1999.

[0266] Step ii): The esterification product was introduced into a vertical stirred full-mixing reactor. 0.185 kg of tetrabutyl titanate was added to the reactor, and the temperature was raised to 250 °C. The reaction was carried out at a pressure of 1400 Pa for 3 - 4 h, and most of the excess 1,4-butanediol was distilled off. A prepolymer was obtained. The viscosity number of the prepolymer measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 was 39 ml / g according to the provisions of GB / T 17931-1999;

[0267] Step iii): The reaction mixture was transferred to a final polymerization reactor and polycondensed at a temperature of 250 °C and a pressure of 130 Pa for 3 - 4 h. The remaining excess 1,4-butanediol and other by-products were distilled off. Then, pelletizing and drying were carried out to obtain a final polymerization product. The viscosity number of the final polymerization product measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 was 179 ml / g according to the provisions of GB / T 17931-1999.

[0268] Step iv), the polyester particles were put into a reactor for contact treatment according to the mass ratio of polyester particles to the aqueous solution of tetrahydrofuran of 1:5. The mass concentration of the aqueous solution of tetrahydrofuran was 45%, the contact treatment temperature was 35 °C, and the contact treatment time was 8 h.

[0269] After the contact treatment process, a drying process may also be provided, and the drying can be carried out in a blast drying tower.

[0270] According to the test method of the present invention, the viscosity number, acid value, melt index, titanium element content, THF content, yellow index of the biodegradable polyester composition obtained after drying in step iv) were tested, and the hydrolysis resistance performance was evaluated. The specific data are shown in Table 3.

[0271] Example 11:

[0272] Step i): Physically mix 475 kg of terephthalic acid, 437 kg of adipic acid, 690 kg of 1,4-butanediol, 2.40 kg of glycerol and 0.460 kg of tetrabutyl titanate at room temperature in an esterification reactor. Then, carry out an esterification reaction on this mixture at 230 °C and a pressure of 60 KPa for 3 - 4 h to obtain an esterification product. The viscosity number of the esterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T17931 - 1999 is 13 ml / g.

[0273] Step ii): Introduce the esterification product into a vertical stirred full-mixing reactor. Add 0.234 kg of tetrabutyl titanate to this reactor, heat to 240 °C, and react at a pressure of 630 Pa for 2 - 3 h. Most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931 - 1999 is 37 ml / g;

[0274] Step iii): Add 0.042 kg of titanium tetrachloride, transfer the reaction mixture to a final polymerization reactor, and carry out polycondensation at a temperature of 248 °C and a pressure of 110 Pa for 2 - 3 h. The remaining excessive 1,4-butanediol and other by-products are distilled off to obtain a final polymerization product. The viscosity number of the final polymerization product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931 - 1999 is 147 ml / g.

[0275] Step iii-1): Pass the final polymerization product from Step iii) through a static mixer, add 1.1 kg of hexamethylene diisocyanate, and carry out a blending reaction at 200 °C for 6 min. Then, granulate and dry to obtain a chain growth product. The viscosity number of the chain growth product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T17931 - 1999 is 192 ml / g.

[0276] Step iv): Charge polyester particles into a reactor for contact treatment at a mass ratio of polyester particles to an aqueous tetrahydrofuran solution of 1:2. The mass concentration of the aqueous tetrahydrofuran solution is 25%, the contact treatment temperature is 55 °C, and the contact treatment time is 12 h.

[0277] After the contact treatment process, there may also be a drying process, and drying can be carried out in a blast drying tower.

[0278] According to the testing method of the present invention, in step iv), the viscosity number, acid value, melt index, titanium element content, THF content, and yellowness index of the obtained biodegradable polyester composition after drying are measured, and the hydrolysis resistance performance is evaluated. The specific data are shown in Table 3.

[0279] Example 12:

[0280] Step i-1): 437 kg of adipic acid, 350 kg of 1,4-butanediol, and 2.60 kg of glycerol are physically mixed at room temperature in esterification reactor A. Then, the mixture is subjected to an esterification reaction at 192 °C and a pressure of 110 KPa for 2 - 3 h to obtain an esterification product P-1. The viscosity number of the esterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 7 ml / g.

[0281] Step i-2): 452 kg of terephthalic acid, 480 kg of 1,4-butanediol, and 0.440 kg of tetrabutyl titanate are physically mixed at room temperature in esterification reactor B. Then, the mixture is subjected to an esterification reaction at 240 °C and a pressure of 85 KPa for 3 - 4 h to obtain an esterification product P-2. The viscosity number of the esterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 16 ml / g.

[0282] Step ii): The esterification product P-1 from step i-1) is preheated to 230 °C and introduced into a vertical stirred full-mixing reactor together with the esterification product P-2 from step i-2). 0.100 kg of tetrabutyl titanate is added to the reactor, and the temperature is raised to 243 °C. The reaction is carried out at a pressure of 2200 Pa for 3 - 4 h, and most of the excessive 1,4-butanediol is distilled off. A prepolymer is obtained. The viscosity number of the prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 43 ml / g;

[0283] Step iii): The reaction mixture is transferred to a final polymerization reactor and subjected to polycondensation at a temperature of 248 °C and a pressure of 110 Pa for 2 - 3 h. The remaining excessive 1,4-butanediol and other by-products are distilled off. The viscosity number of the final polymerization product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 145 ml / g.

[0284] Step iii-1): Pass the end product of step iii) through a static mixer, add 1.1 kg of hexamethylene diisocyanate, and carry out a blending reaction at 220 °C for 7 min. Then, granulate using an underwater granulator and then dry to obtain a chain growth product. The chain growth product has an intrinsic viscosity of 195 ml / g as measured in a constant temperature water bath at 25 ± 0.05 °C in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 according to the provisions of GB / T 17931-1999.

[0285] According to the test method described in the present invention, test the intrinsic viscosity, acid value, melt index, titanium element content, THF content, and yellowness index of the biodegradable polyester composition obtained in step iii-1), and conduct hydrolysis resistance and odor evaluations. The specific data are shown in Table 3.

[0286] Table 3. Performance test results of Examples 8-12

[0287] Example 8 Example 9 Example 10 Example 11 Example 12 Terephthalic acid / mol% 46.2 49.5 47.3 48.8 47.5 Adipic acid / mol% 53.8 50.5 52.7 51.2 52.5 Titanium element content [ppm] 66 65 55 88 63 THF content [ppm] 142 116 89 40 243 Acid value [mg KOH / g] 0.81 0.77 0.84 0.58 0.84 Viscosity number [ml / g] 173 182 174 189 195 Melt index [g / 10min] 5.0 4.0 4.7 2.7 2.0 Yellow index YI 23.00 22.38 20.41 22.76 19.32 Viscosity number retention rate η 65.0 67.0 66.8 72.3 67.9 Odor grade 4.5 3.5 3.0 2.0 6.0

[0288] The data in Table 1, Table 2, and Table 3 show that when the titanium element content of the aliphatic-aromatic polyester composition is 55-88 ppm, preferably 63-81 ppm; and the acid value does not exceed 0.84 mg KOH / g, preferably does not exceed 0.78 mg KOH / g, the intrinsic viscosity retention rate η of the aliphatic-aromatic polyester composition after boiling in water at 60 °C for 48 h is higher, and the yellowness index YI value of the biodegradable polyester composition does not exceed 23, preferably does not exceed 19.

[0289] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. An aliphatic-aromatic polyester composition, characterized in that, The composition comprises the following components: i) An aliphatic-aromatic polyester based on aliphatic and aromatic dicarboxylic acids and aliphatic dihydroxy compounds, said aliphatic-aromatic polyester containing at least the following components: A) Dicarboxylic acid component: a1) 46.2 to 49.5 mol% of terephthalic acid or its ester derivatives, or a mixture thereof, based on the total molar amount of a1) and a2); a2) 50.5 - 53.8 mol% of adipic acid or its ester derivatives, or a mixture thereof, based on the total molar amount of a1) and a2); wherein the sum of the molar percentages of components a1) and a2) is 100%; and B) Dihydroxy compound component: b1) At least an equimolar amount of C2-C6 aliphatic alkanediols, or a mixture thereof, relative to component A; b2) 0 to 3 wt% of a compound containing at least three functional groups, based on the total weight of components A and b1; ii) Titanium element, the content of the titanium element being 55 to 88 ppm based on the weight of the aliphatic-aromatic polyester composition; The aliphatic-aromatic polyester composition has an acid value ≤ 0.84 mg KOH / g according to standard DIN EN 12634-1998; The yellow index YI value of the aliphatic-aromatic polyester composition is ≤ 23 as measured according to standard ASTM E313-73; The aliphatic-aromatic polyester composition is boiled in water at 60 °C for 48 hours, and the viscosity number retention rate η of the aliphatic-aromatic polyester composition after boiling is ≥ 65%, η = η1 / η0 wherein, η1 represents the viscosity number of the aliphatic-aromatic polyester composition after boiling in water at 60 °C for 48 hours, η0 represents the viscosity number of the aliphatic-aromatic polyester composition before boiling.

2. The aliphatic-aromatic polyester composition according to claim 1, characterized in that, The A) dicarboxylic acid component comprises the following components: a1) 47.3 to 48.8 mol% of terephthalic acid or its ester derivatives, or a mixture thereof, based on the total molar amount of a1) and a2); a2) 51.2 to 52.7 mol% of adipic acid or its ester derivatives, or a mixture thereof, based on the total molar amount of a1) and a2); wherein the sum of the molar percentages of components a1) and a2) is 100%.

3. The aliphatic-aromatic polyester composition according to claim 1, characterized in that, Based on the weight of the aliphatic-aromatic polyester composition, the content of the titanium element is 63 to 81 ppm.

4. The aliphatic-aromatic polyester composition according to claim 1, characterized in that, The aliphatic-aromatic polyester composition has an acid value ≤ 0.78 mg KOH / g according to standard DIN EN 12634-1998.

5. The aliphatic-aromatic polyester composition according to claim 1, characterized in that, The yellow index YI value of the aliphatic-aromatic polyester composition is ≤ 19 as measured according to standard ASTM E313-73.

6. The aliphatic-aromatic polyester composition according to claim 1, characterized in that, The aliphatic-aromatic polyester composition is boiled in water at 60 °C for 48 hours, and the viscosity number retention rate η of the aliphatic-aromatic polyester composition after boiling is ≥ 72%.

7. The aliphatic-aromatic polyester composition according to claim 1, characterized in that, The aliphatic-aromatic polyester composition further comprises component iii), tetrahydrofuran, the content of tetrahydrofuran being 40 to 170 ppm based on the weight of the aliphatic-aromatic polyester composition.

8. The aliphatic-aromatic polyester composition according to claim 7, characterized in that, Based on the weight of the aliphatic-aromatic polyester composition, the content of tetrahydrofuran in the aliphatic-aromatic polyester composition is 86 to 136 ppm.

9. The aliphatic-aromatic polyester composition according to claim 7 or 8, characterized in that, According to the FLTM BO131-03 standard, its odor level is less than or equal to 4.

5.

10. A method for preparing the aliphatic-aromatic polyester composition according to any one of claims 1 to 9, characterized in that, It includes the following steps: Mix the component A and component B, with or without a titanium catalyst, to form a paste, and then perform the following operations. Step i), subject the paste to an esterification or transesterification reaction with all or part of the titanium catalyst until the viscosity number of the esterification or transesterification product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 12 - 21 ml / g. Step ii), subject the esterification or transesterification product obtained in step i) to a pre-polycondensation reaction until the viscosity number of its prepolymer measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T17931-1999 is 36 - 52 ml / g. Step iii), subject the prepolymer obtained in step ii) to a polycondensation reaction until the viscosity number of its final polymer product measured in a phenol / o-dichlorobenzene solution with a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05 °C according to GB / T 17931-1999 is 145 - 203 ml / g. Step iv), contact the polyester particles obtained in step iii) with an aqueous tetrahydrofuran solution to obtain the aliphatic-aromatic polyester composition. In the aqueous tetrahydrofuran solution in step iv), the weight content of tetrahydrofuran is 10 - 65 wt%. In step iv), the contact treatment temperature is 20 - 65 °C. In step iv), the contact treatment time is 2 - 20 h. In step iv), the mass ratio of the polyester particles to the aqueous tetrahydrofuran solution is 1:1 - 1:

10.

11. The preparation method according to claim 10, characterized in that, After step iii) and before step iv), perform step iii-1), subject the final polymer product to a chain extension reaction with a chain extender until the viscosity number of its chain extension product measured according to GB / T 17931-1999 is 163 - 232 mL / g.

12. The preparation method according to claim 11, characterized in that, The chain extender is one or more of isocyanate, peroxide, epoxide, oxazoline, oxazine, caprolactam, and / or carbodiimide.

13. The preparation method according to claim 12, wherein The chain extender is hexamethylene-1,6-diisocyanate, and its dosage is 0.1 - 1.5 wt% of the weight of the chain extension product.

14. Use of the aliphatic-aromatic polyester composition according to any one of claims 1 - 9 in the preparation of polyester fibers.

15. A polyester fiber, characterized in that, It includes the following components: i) Based on the total weight of components i) - iv), 5 - 15 wt% of the aliphatic-aromatic polyester composition according to any one of claims 1 - 9; ii) Based on the total weight of components i) - iv), 35 - 70 wt% of an aliphatic polyester; iii) Based on the total weight of components i) - iv), 10 - 40 wt% of one or more components selected from starch, wood powder, cellulose, polyhydroxyalkanoate, polyglycolic acid, and polylactic acid; iv) Based on the total weight of components i) - iv), 10 - 35 wt% of one or more components selected from talc, calcium carbonate, barium sulfate, montmorillonite, and kaolin.

16. Use of the polyester fiber according to claim 15 in masks and clothing.

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