Biodegradable aliphatic polyesters, as well as methods for preparing and using the same.

Abstract

The present invention discloses a biodegradable aliphatic polyester, as well as a preparation method and use thereof. The preparation method for the biodegradable aliphatic polyester of the present invention includes the steps of dispersing a polyester product obtained by an esterification reaction and a polycondensation reaction in an aqueous tetrahydrofuran solution, conducting a contact treatment, and then post-treatment to obtain the biodegradable aliphatic polyester. The contact treatment time is 2 to 20 hours and the temperature is 20 to 65°C. The biodegradable aliphatic polyester of the present invention has a whiteness index of 20 or more and an acid value of 1.45 mg KOH / g or less. The contact treatment step with an aqueous tetrahydrofuran solution improves the color of the aliphatic polyester while maintaining a low acid value and avoiding performance degradation of the aliphatic polyester.

Description

[Technical Field]

[0001] The present invention relates to the technical field of biodegradable materials, and more specifically to a biodegradable aliphatic polyester, and a preparation method and use thereof. [Background Art]

[0002] Biodegradable aliphatic polyesters such as polybutylene succinate (PBS) and polybutylene adipate have good processability, can be processed with conventional molding equipment via methods including extrusion molding, injection molding, blow molding, spinning, blister molding, lamination and foaming, and have a wide range of product applications. Main application fields include packaging fields such as beverage bottles and food packaging bags, daily necessities fields such as disposable tableware, and agricultural fields such as biodegradable mulch films.

[0003] Aliphatic diacids used for preparing biodegradable aliphatic polyesters often contain impurities at the level of hundreds to thousands of ppm due to differences in raw material sources and production processes. For example, succinic acid usually contains trace amounts of formic acid, acetic acid, lactic acid, pyruvic acid, fumaric acid, sodium sulfate and the like. The presence of trace impurities not only affects polymerization efficiency, but also affects the appearance of polyester products, causing the products to turn yellowish or reddish, making it difficult to achieve high whiteness. Zhu Guixiang et al. (Effects of impurity content in bio-based succinic acid on properties of biodegradable copolyester [J]. Petrochemical Technology, 2012, 41(11): 1302-1306) reported that nitrogen-containing impurities and trace formic acid in bio-based succinic acid may cause the polyester to turn yellow.

[0004] To meet the end-use requirements of polyester products, for example, due to appearance and color requirements for products such as straws, coffee capsules and other products, the materials used are often required to have good whiteness. In the prior art, to improve the color of degradable polyester products, phosphorus-containing passivating agents or color stabilizers are usually added during polymerization.

[0005] WO2018219708 A1 discloses a method for preparing aliphatic-aromatic polyesters in which an aliphatic-aromatic polyester with a whiteness index of 25 or higher can be obtained by adding 0.03-0.04 wt.% of a phosphorus compound during polymerization. However, the phosphorus compound may weaken the activity of the titanium catalyst to some extent as a passivator, which may lead to an increase in the acid value of the resulting aliphatic-aromatic polyester and weaken its hydrolysis resistance.

[0006] CN103649167A discloses a color-stable, biodegradable aliphatic-aromatic copolyester, a method for producing the same, and a product thereof, wherein the whiteness of the aliphatic-aromatic copolyester is improved by adding a color-reducing compound. However, the resulting polyester still has a yellowish tint and cannot meet the practical requirements for high whiteness.

[0007] Therefore, there is a need for the development of biodegradable aliphatic polyesters with improved whiteness. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2018 / 219708 [Patent Document 2] Chinese Patent Application Publication No. 103649167 Specification [Overview of the project] [Problems that the invention aims to solve]

[0009] This invention overcomes the drawback of the conventional technology described above, namely low whiteness, and provides a method for preparing biodegradable aliphatic polyester that improves the color of the aliphatic polyester while maintaining a low acid value and avoiding performance degradation of the aliphatic polyester through a contact treatment step with an aqueous tetrahydrofuran solution.

[0010] Another object of the present invention is to provide a biodegradable aliphatic polyester prepared by the above preparation method.

[0011] The technical solutions employed by the present invention to solve the above technical problems are as follows. A method for preparing biodegradable aliphatic polyesters, Mix component A and component B, and then carry out the esterification reaction and polycondensation reaction in order. Polyester products are obtained , obtained The aforementioned The process includes the steps of dispersing a polyester product in an aqueous tetrahydrofuran solution, performing a contact treatment, and undergoing post-treatment to obtain the biodegradable aliphatic polyester, wherein the contact treatment time is 2 to 20 hours, the temperature is 20 to 65°C, the concentration of the aqueous tetrahydrofuran solution is 10 to 65 wt.%, and the mass ratio of the polyester product to the aqueous tetrahydrofuran solution is 1:(1 to 10). The aforementioned component A is an aliphatic dicarboxylic acid compound or a derivative thereof. Component B contains an equimolar amount of an aliphatic dihydroxy compound with respect to component A. [Means for solving the problem]

[0012] The technical solutions employed by the present invention to solve the above technical problems are as follows. A method for preparing biodegradable aliphatic polyesters, The process includes the steps of mixing component A and component B, sequentially carrying out esterification and polycondensation reactions, dispersing the resulting polyester product in an aqueous tetrahydrofuran solution, performing a contact treatment, and undergoing post-treatment to obtain the biodegradable aliphatic polyester, wherein the contact treatment time is 2 to 20 hours, the temperature is 20 to 65°C, the concentration of the aqueous tetrahydrofuran solution is 10 to 65 wt.%, and the mass ratio of the polyester product to the aqueous tetrahydrofuran solution is 1:(1 to 10). The aforementioned component A is an aliphatic dicarboxylic acid compound or a derivative thereof. Component B contains an equimolar amount of an aliphatic dihydroxy compound with respect to component A.

[0013] The inventors have discovered that the whiteness index of biodegradable aliphatic polyesters can be significantly improved by performing a contact treatment after synthesizing the polyester product. The color substances contained in polyester are generally small molecule substances or oligomers containing chromophores, and during contact between the polyester product and the tetrahydrofuran aqueous solution, these substances that affect the color migrate from the polyester to the tetrahydrofuran aqueous solution, thereby achieving the technical effect of increased whiteness.

[0014] The contact treatment time and temperature must be controlled within an appropriate range. If the temperature is too low or the time is too short, small molecular substances or oligomers that affect the whiteness index cannot be effectively extracted, resulting in poor color effect in the resulting biodegradable aliphatic polyester. Since the boiling point of tetrahydrofuran is 66°C, if the contact treatment temperature is too high, the tetrahydrofuran will boil easily, and the amount of tetrahydrofuran that volatilizes will be large, resulting in excessive loss.

[0015] Preferably, the contact treatment time is 5 to 16 hours.

[0016] More preferably, the contact treatment time is 10 to 12 hours.

[0017] Preferably, the contact treatment temperature is 35 to 55°C.

[0018] Preferably, the concentration of the tetrahydrofuran aqueous solution is 25-45 wt.%, and the mass ratio of the polyester product to the tetrahydrofuran aqueous solution is 1:(2-5).

[0019] When the tetrahydrofuran content is within the above range, the effective content of tetrahydrofuran becomes appropriate, and impurities can be effectively removed while ensuring that the residual content of tetrahydrofuran in the biodegradable aliphatic polyester as the final product is reduced. When the mass ratio of the polyester product to the aqueous tetrahydrofuran solution is greater than 1, that is, when the solid-liquid ratio is large, the efficiency of the contact treatment becomes low. If the concentration of the aqueous tetrahydrofuran solution is too high, the residual amount of tetrahydrofuran in the biodegradable aliphatic polyester becomes excessively high, which makes the product unable to meet the requirements of food contact regulations and affects the subsequent use of the product. In the present invention, the residual amount of tetrahydrofuran in the biodegradable aliphatic polyester is 110 ppm or less.

[0020] In some embodiments, the residual amount of tetrahydrofuran in the biodegradable aliphatic polyester is 60 ppm or less.

[0021] Furthermore, in some embodiments, the residual amount of tetrahydrofuran in the biodegradable aliphatic polyester is 30 ppm or less.

[0022] By controlling the above time, temperature, tetrahydrofuran concentration and mass ratio, the viscosity number retention rate η of the polyester product before and after the contact treatment is 96% or more, η=VN1 / VN0 wherein VN0 refers to the viscosity number of the polyester product before the contact treatment step, VN1 refers to the viscosity number of the biodegradable aliphatic polyester obtained by the contact treatment step.

[0023] The viscosity number is detected in accordance with the method of GB / T 17931-1999.

[0024] A viscosity number retention rate η of 96% or more means that the contact treatment hardly leads to performance degradation of the polyester.

[0025] The inventors of the present invention have found that other organic solvents (e.g., alcohols, acetone) can also extract small molecules other than white substances to some extent, but the viscosity value of the polyester product decreases significantly, and aliphatic polyesters have a low viscosity number retention rate after contact with other organic solvents.

[0026] Preferably, the preparation method is The process includes the steps of mixing component A and component B, and mixing with or without a catalyst to produce a paste-like substance. In step i), the paste is subjected to an esterification or transesterification reaction with all or part of the catalyst until the viscosity of the esterification or transesterification product reaches 5 to 60 ml / g, as measured in a phenol / o-dichlorobenzene solution in a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05°C according to GB / T 17931-1999. In step ii), the esterification or transesterification product obtained in step i) is mixed with the remaining catalyst, and a preliminary polycondensation reaction is carried out in a 1:1 by weight phenol / o-dichlorobenzene solution according to GB / T 17931-1999, in a constant temperature water bath at 25±0.05℃, until the viscosity number of the prepolymer reaches 20-110 ml / g. In step iii), the polycondensation reaction of the prepolymer obtained in ii) is carried out so that the viscosity of the polycondensed polyester is 130-240 ml / g when measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05℃, according to GB / T 17931-1999.

[0027] If necessary, after step iii), component C, which is a chain extender, may be added and step iv) may be carried out. The polycondensed polyester obtained in step iii) is mixed with the chain extender and the polyaddition reaction is carried out until the viscosity number of the chain extension product is 150-260 ml / g when measured in a 1:1 by weight phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05℃ according to GB / T 17931-1999.

[0028] Excess diol components are usually removed by distillation and returned to the circuit after, for example, distillation purification.

[0029] Preferably, the catalyst is a titanium catalyst.

[0030] The titanium catalyst may optionally be tetrabutyl titanate or tetraisopropyl titanate.

[0031] The amount of titanium catalyst used in the preparation method of the present invention is 0.001 to 1 wt.%, preferably 0.03 to 0.2 wt.%, of the mass of the polycondensed polyester in step iii), and the amount of catalyst added in step i) is 50 to 80% of the total catalyst amount. By controlling the amount of catalyst added, subsequent processing can be made more stable.

[0032] In step i), the temperature is set to 140-220°C, preferably 155-205°C, and the pressure is set to 0.6-1.2 bar, preferably 0.8-1.0 bar. Step i) can be carried out in a mixing apparatus such as a vertical reaction vessel with a stirring function. A typical holding time is 2-6 hours.

[0033] In step ii), the liquid obtained in step i) (esterification or transesterification), along with the remaining catalyst if appropriate, is added to a reactor suitable for the pre-condensation reaction. In step ii), the temperature is set to 220-270°C, preferably 230-250°C, and the pressure is set to 0.2-0.8 bar, preferably 0.35-0.55 bar. A typical holding time is 75-180 minutes.

[0034] Step iii) can be performed in a finishing machine such as a rotary disk reactor or a squirrel-cage reactor. In step iii), the temperature is set to 230-270°C, preferably 230-250°C, and the pressure is set to 0.2-5 mbar, preferably 0.5-3 mbar. A typical holding time is 60-150 minutes, preferably 75-120 minutes.

[0035] Step iv) can be carried out in an extruder, continuous kneader, or static mixer, and the polycondensed polyester obtained in step iii) is added to a twin-screw extruder or static mixer with a chain extender (component C) in an amount of 0-3 wt.%, preferably 0.05-2 wt.%, particularly preferably 0.1-1.5 wt.%, based on the weight of the biodegradable polyester composition, and the reaction is carried out at a temperature of 180-235°C for a holding time of 3-15 minutes to obtain a chain extension product. In a static mixer, SMR, SMX, or SMXL components, or a combination thereof, can be used. Examples of List reactors include a single-screw DISCOTHERM B or a twin-screw CRP or ORP reactor. The extruders that can be used are single-screw or twin-screw extruders.

[0036] Preferably, the post-processing includes separation and drying.

[0037] Preferably, the drying is carried out in a forced-air drying tower, at a temperature of 55-80°C, for a duration of 10-75 hours, and with a dry air dew point of less than -30°C.

[0038] More preferably, the drying is performed at a temperature of 60-70°C, for a duration of 15-45 hours, and with a dry air dew point of less than -35°C.

[0039] Optionally, the aliphatic dicarboxylic acid compound or its derivative is an aliphatic diacid or its derivative containing 2 to 40 carbon atoms.

[0040] Preferably, the aliphatic dicarboxylic acid compound or its derivative is an aliphatic diacid or its derivative containing 4 to 14 carbon atoms.

[0041] Preferably, the aliphatic diacid is one or more of succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, or brassic acid.

[0042] More preferably, the aliphatic dicarboxylic acid compound is succinic acid and / or adipic acid.

[0043] The derivatives of the aliphatic dicarboxylic acid compound include dimethyl, diethyl, di-n-propyl, diisopropyl, di-n-butyl, diisobutyl, di-tert-butyl, di-n-pentyl, diisopentyl, di-n-hexyl ester, or anhydrides of dicarboxylic acids.

[0044] Preferably, the aliphatic dicarboxylic acid compound consists of 60 to 100 mol% succinic acid or a derivative thereof and 0 to 40 mol% adipic acid or a derivative thereof.

[0045] More preferably, the aliphatic dicarboxylic acid compound comprises 70 to 95 mol% of a derivative of succinic acid or its ester and 5 to 30 mol% of a derivative of adipic acid or its ester.

[0046] Preferably, the aliphatic dihydroxy compound is an aliphatic alkanediol containing 2 to 6 carbon atoms.

[0047] More preferably, the aliphatic dihydroxy compound is 1,3-propanediol and / or 1,4-butanediol.

[0048] Preferably, the molar ratio of component B to component A is (1-2):1. More preferably, the molar ratio of component B to component A is (1.05-1.7):1. Even more preferably, the molar ratio of component B to component A is (1.15-1.6):1.

[0049] Preferably, it contains at least three of the functional groups. Crosslinking agent This is one or more of the following: malic acid, citric acid, glycerol, pentaerythritol, or trimethylolpropane.

[0050] More preferably, containing at least three of the functional groups Crosslinking agent These are malic acid and / or glycerol.

[0051] More preferably, the compound containing the at least three functional groups is malic acid and / or glycerol.

[0052] If the content of trifunctional crosslinking agents is too high, excessive crosslinking of polyester is likely to occur, affecting the plasticity of the material.

[0053] Preferably, the chain extender (component C) accounts for 0.01 to 4 wt% based on the total amount of biodegradable aliphatic polyester.

[0054] Preferably, The component c1 used includes an isocyanate having two or more functional groups or a mixture of different isocyanates. Aromatic or aliphatic diisocyanates can be used, but more functional isocyanates can also be used.

[0055] The component c1 used includes an isocyanate having two or more functional groups or a mixture of different isocyanates. Aromatic or aliphatic diisocyanates can be used, but more functional isocyanates can also be used.

[0056] In the present invention, aromatic diisocyanate c1 is particularly 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.

[0057] Of these, diphenylmethane-2,2'-, 2,4'-, or 4,4'-diisocyanates are particularly preferred to be used as component c1, while the other diisocyanates are usually used in the form of a mixture.

[0058] Another isocyanate c1 that can be used is tris(4-isocyanatophenyl)methane, which has three rings. This polynuclear aromatic diisocyanate may be formed, for example, during the production of diisocyanates with one or two rings.

[0059] In the present invention, aliphatic diisocyanate c1 is 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). A particularly preferred aliphatic diisocyanate c1 is hexamethylene diisocyanate.

[0060] Preferred isocyanurates are aliphatic isocyanurates derived from alkylene diisocyanates or cycloalkylene diisocyanates having 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms, such as isophorone diisocyanate or methylenebis(4-isocyanatocyclohexane). The alkylene diisocyanate may be a linear or branched compound. Particularly preferred are n-hexamethylene diisocyanates, such as cyclic trimers, pentamers or more oligomeric isocyanurates based on hexamethylene diisocyanate.

[0061] The amount of component c1 used is typically 0-3 wt.%, preferably 0.05-2 wt.%, and particularly preferably 0.1-1.5 wt.%, based on the total amount of the biodegradable aliphatic polyester composition.

[0062] Suitable examples of peroxides (component c2) having two or more functional groups include compounds selected from benzoyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)methylcyclododecane, 4,4-di(butylperoxy)butyl pentanoate, dicumyl peroxide, tert-butylperbenzoate, dibutylperoxide, α,α-di(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-bis(tert-butylperoxy)-2,5-dimethyl-3-hexine, and tert-butylperoxycumene.

[0063] Examples of epoxides (component c3) having two or more functional groups used include hydroquinone, diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Other examples of epoxides include diglycidyl terephthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, dimethyl diglycidyl phthalate, phenylenediglycidyl 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, and trimethylolpropane polyglycidyl ether. , Ne This includes opentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol glycidyl ether, dipropylene glycol diglycidyl ether, polypropylene diol diglycidyl ether, and polybutylene glycol diglycidyl ether.

[0064] Examples of epoxides (component c3) having two or more functional groups that can be used include hydroquinone, diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Other examples of epoxides include diglycidyl terephthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, dimethyl diglycidyl phthalate, phenylenediglycidyl 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.

[0065] Particularly suitable epoxides having two or more functional groups are copolymers based on styrene, acrylate, and / or methacrylate, and containing epoxy. The epoxy-containing units are preferably glycidyl methacrylate or glycidyl acrylate.

[0066] The amount of component c3 used is typically 0-3 wt.%, preferably 0.1-2 wt.%, and particularly preferably 0.2-1 wt.%, based on the total amount of the biodegradable aliphatic polyester composition. Component c3 can also function as an acid remover.

[0067] The component c4 used is an oxazoline, oxazine, caprolactam, and / or carbodiimide having two or more functional groups.

[0068] Particularly preferred dioxazolines and dioxazines are those in which the bridge portion is a single bond, (CH2)z-alkylene, where z=2,3 or 4, for example, methylene, ethane-1,2-diyl, propane-1,3-diyl, propane-1,2-diyl, or phenylene. Particularly preferred dioxazolines that can be considered 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. Preferred dioxazines are 2,2'-di(2-dioxazine), di(2-dioxazinyl)methane, 1,2-di(2-dioxazinyl)ethane, 1,3-di(2-dioxazinyl)propane, or 1,4-di(2-dioxazinyl)butane, particularly 1,4-di(2-dioxazinyl)benzene, 1,2-di(2-dioxazinyl)benzene, or 1,3-di(2-dioxazinyl)benzene.

[0069] Carbodiimide may specifically 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, or di-tert-butylcarbodiimide.

[0070] The amount of component c4 used is typically 0-3 wt.%, preferably 0.1-2 wt.%, and particularly preferably 0.2-1 wt.%, based on the total amount of the biodegradable aliphatic polyester composition. Component c4 can also function as an acid remover.

[0071] The present invention further protects the high-whiteness biodegradable aliphatic polyester prepared by the above preparation method.

[0072] The whiteness index of the aforementioned biodegradable aliphatic polyester is 20 or higher.

[0073] In some embodiments, the whiteness index of the biodegradable aliphatic polyester is 26 or higher. Furthermore, in some embodiments, the whiteness index of the biodegradable aliphatic polyester is 30 or higher.

[0074] The whiteness index is measured according to the ASTM E313-73 method.

[0075] The acid value of the biodegradable aliphatic polyester is 1.45 mg KOH / g or less.

[0076] In some embodiments, the acid value of the biodegradable aliphatic polyester is 1.2 mg KOH / g or less. Furthermore, in some embodiments, the acid value of the biodegradable aliphatic polyester is 1.0 mg KOH / g or less.

[0077] The acid value is measured according to DIN EN12634.

[0078] In this invention, the biodegradable aliphatic polyester has a melt mass flow rate of 22 g / 10 min or less when measured under conditions of 190°C and 2.16 kg.

[0079] In certain embodiments, the biodegradable aliphatic polyester has a melt mass flow rate of 15 g / 10 min or less when measured under conditions of 190°C and 2.16 kg.

[0080] In this invention, a substance or mixture of substances is considered to have the characteristic of "biodegradability" if it exhibits a biodegradability rate of at least 90% as defined in DIN EN 13432. In other words, it is biodegradable. .

[0081] In this invention, a substance or mixture of substances is characterized as "biodegradable" if it exhibits a biodegradability of at least 90% as defined in DIN EN 13432.

[0082] The present invention, as an ingredient, The biodegradable aliphatic polyester is 35 to 70 parts by weight, 5 to 15 parts by weight of aliphatic-aromatic copolyester, 10 to 40 parts by weight of one or more of starch, wood flour, cellulose, polyhydroxyalkanoate, polyglycolic acid, or polylactic acid, Further protect the polyester mixture containing 10 to 35 parts by weight of inorganic filler.

[0083] Preferably, the inorganic filler is one or more of talc, calcium carbonate, barium sulfate, montmorillonite, or kaolin.

[0084] Preferably, the polyester mixture has a melt mass flow rate of 8 g / 10 min or less and a tetrahydrofuran content of 60 ppm or less when measured under the conditions of EN ISO 1133-2-2011, 190°C, and 2.16 kg, and more preferably, the polyester mixture has a melt mass flow rate of 5 g / 10 min or less and a tetrahydrofuran content of 25 ppm or less. [Effects of the Invention]

[0085] The present invention further protects the use of the polyester mixture in the manufacture of biodegradable straws and coffee capsule shells.

[0086] Compared to the conventional technology, the beneficial effects of the present invention are as follows:

[0087] This invention develops a biodegradable aliphatic polyester with high whiteness and low acid value. Through a contact treatment process with an aqueous tetrahydrofuran solution, the color of the aliphatic polyester is improved while maintaining a low acid value and avoiding performance degradation of the aliphatic polyester. [Modes for carrying out the invention]

[0088] The present invention will be further described below with reference to specific embodiments.

[0089] All raw materials used in this embodiment are commercially available.

[0090] Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in the art. [Examples]

[0091] Biodegradable aliphatic polyester P1 was prepared by the following preparation method.

[0092] Step i): 800 kg of succinic acid, 880 kg of 1,4-butanediol, 2.02 kg of glycerol, and 0.441 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The mixture was then subjected to an esterification reaction for 3 to 4 hours at a temperature of 175 to 190°C and a pressure of 0.95 to 1.1 bar to obtain the esterification product. The viscosity of the esterification product was measured in a phenol / o-dichlorobenzene solution in a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05°C according to GB / T 17931-1999, and the viscosity was found to be 27 ml / g.

[0093] Step ii): The esterification product was introduced into a static mixer and then placed into a vertically stirred complete mixing reactor. 0.249 kg of tetrabutyl titanate was added to this reactor and reacted for 95 to 125 minutes under conditions of 230 to 250°C and 0.2 to 0.7 bar pressure. Most of the excess 1,4-butanediol was removed by distillation to obtain the prepolyester. The viscosity of the prepolyester was measured in a 1:1 phenol / o-dichlorobenzene solution in a constant temperature water bath at 25 ± 0.05°C according to GB / T 17931-1999, and the viscosity was 65 ml / g.

[0094] The prepolyester was added to a cage reactor, and a polycondensation reaction was carried out at a reaction temperature of 240-250°C and a reaction pressure of 0.20-0.35 mbar for 120-150 minutes. Polycondensed polyester P1 was prepared with a viscosity of 192 ml / g, as measured in a 1:1 weight ratio phenol / o-cresol solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999.

[0095] Biodegradable aliphatic polyester P2 was prepared by the following preparation method.

[0096] Step i): 800 kg of succinic acid, 310 kg of adipic acid, 980 kg of 1,4-butanediol, 2.71 kg of malic acid, and 0.526 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The mixture was then subjected to an esterification reaction for 3 to 4 hours at a temperature of 186 to 195°C and a pressure of 0.95 to 1.1 bar to obtain the esterification product. The viscosity of the esterification product was measured in a phenol / o-dichlorobenzene solution in a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05°C according to GB / T 17931-1999, and the viscosity was found to be 24 ml / g.

[0097] Step ii): The esterification product was introduced into a static mixer and then placed into a vertically stirred complete mixing reactor. 0.283 kg of tetrabutyl titanate was added to this reactor and reacted for 85 to 135 minutes under conditions of 235 to 245°C and 0.36 to 0.48 bar pressure. Most of the excess 1,4-butanediol was removed by distillation to obtain the prepolyester. The viscosity of the prepolyester was measured in a 1:1 phenol / o-dichlorobenzene solution in a constant temperature water bath at 25 ± 0.05°C according to GB / T 17931-1999, and the viscosity was 58 ml / g.

[0098] The prepolyester was added to a cage reactor, and a polycondensation reaction was carried out at a reaction temperature of 242-248°C and a reaction pressure of 0.22-0.30 mbar for 110-140 minutes. Polycondensed polyester P2 was prepared with a viscosity of 196 ml / g, as measured in a 1:1 phenol / o-cresol solution by weight in a constant temperature water bath at 25±0.05°C, according to GB / T 17931-1999.

[0099] Biodegradable aliphatic polyester P3 was prepared by the following preparation method.

[0100] Step i): 800 kg of succinic acid, 880 kg of 1,4-butanediol, 1.85 kg of glycerol, 0.85 kg of malic acid, and 0.482 kg of tetrabutyl titanate were physically mixed at room temperature in an esterification reactor. The mixture was then subjected to an esterification reaction for 3.5 to 4.5 hours at a temperature of 180 to 195°C and a pressure of 0.90 to 1.0 bar to obtain the esterification product. The viscosity of the esterification product was measured in a phenol / o-dichlorobenzene solution in a weight ratio of 1:1 in a constant temperature water bath at 25 ± 0.05°C according to GB / T 17931-1999, and the viscosity was found to be 29 ml / g.

[0101] Step ii): The esterification product was introduced into a static mixer and then placed into a vertically stirred complete mixing reactor. 0.256 kg of tetrabutyl titanate was added to this reactor and reacted for 95 to 145 minutes under conditions of 230 to 250°C and 0.3 to 0.45 bar pressure. Most of the excess 1,4-butanediol was removed by distillation to obtain the prepolyester. The viscosity of the prepolyester was measured in a 1:1 phenol / o-dichlorobenzene solution in a constant temperature water bath at 25 ± 0.05°C according to GB / T 17931-1999, and the viscosity was 71 ml / g.

[0102] The prepolyester was added to a cage reactor, and a polycondensation reaction was carried out at a reaction temperature of 235-248°C and a reaction pressure of 0.23-0.38 mbar for 125-160 minutes. Polycondensed polyester P3 was prepared with a viscosity of 199 ml / g, as measured in a 1:1 phenol / o-cresol solution by weight in a constant temperature water bath at 25±0.05°C, according to GB / T 17931-1999.

[0103] Examples 1-12 Biodegradable aliphatic polyester P1 was dispersed in an aqueous tetrahydrofuran solution of concentration A according to the contact treatment process described in Table 1. The contact treatment was performed with a mass ratio of polyester product to aqueous tetrahydrofuran solution of B, and the contact treatment time was set to C and the temperature to D. Next, the biodegradable aliphatic polyester was obtained by separation and drying.

[0104] Example 13 Biodegradable aliphatic polyester P2 was dispersed in an aqueous tetrahydrofuran solution of concentration A according to the contact treatment process described in Table 1. The contact treatment was performed with a mass ratio of polyester product to aqueous tetrahydrofuran solution of B, and the contact treatment time was set to C and the temperature to D. Next, the biodegradable aliphatic polyester was obtained by separation and drying.

[0105] Example 14 Biodegradable aliphatic polyester P3 was dispersed in an aqueous tetrahydrofuran solution of concentration A according to the contact treatment process described in Table 1. The contact treatment was carried out with a mass ratio of polyester product to aqueous tetrahydrofuran solution of B, and the contact treatment time was set to C and the temperature to D. Next, the biodegradable aliphatic polyester was obtained by separation and drying.

[0106] [Table 1-1] [Table 1-2]

[0107] Comparative Examples 1-10 Biodegradable aliphatic polyester P1 was dispersed in an aqueous tetrahydrofuran solution of concentration A according to the contact treatment process described in Table 2. The contact treatment was performed with a mass ratio of polyester product to aqueous tetrahydrofuran solution of B, and the contact treatment time was set to C and the temperature to D. Next, the biodegradable aliphatic polyester was obtained by separation and drying.

[0108] Here, In Comparative Example 1, a biodegradable aliphatic polyester was obtained by separating and drying the material without any contact treatment.

[0109] Contact treatment in Comparative Example 2: The polyester product was dispersed in an ethanol aqueous solution of concentration A, and a contact treatment was performed with a mass ratio of polyester product to ethanol aqueous solution of B, with the contact treatment time set to C and the temperature to D.

[0110] Contact treatment in Comparative Example 3: The polyester product was dispersed in an aqueous acetone solution of concentration A, and a contact treatment was performed with a mass ratio of polyester product to aqueous acetone solution of B, with the contact treatment time set to C and the temperature to D.

[0111] Contact treatment for Comparative Examples 4-10: The polyester product was dispersed in an aqueous tetrahydrofuran solution of concentration A, and a contact treatment was performed with a mass ratio of polyester product to aqueous tetrahydrofuran solution of B. The contact treatment time was C and the temperature was D.

[0112] [Table 2]

[0113] Performance testing The biodegradable polyesters prepared in the above examples and comparative examples were used as test samples, and performance tests were conducted on each. The specific methods are as follows.

[0114] (1) Tetrahydrofuran residue (THF content) Approximately 1.2 g of the test sample was weighed, and the headspace temperature was set to 105°C and the headspace time to 2 hours. An Agilent 7697A-7890A instrument was used for the gas chromatography test. The gas chromatography heating program was as follows: initial temperature 50°C, holding time: 3 minutes; heating to 200°C, heating rate 12°C / min, holding time: 4 minutes.

[0115] (2) Whiteness index The whiteness index of the test samples was measured using a Minolta CM-5 spectrophotometer according to ASTM E313-73. Test sample particles with particle sizes ranging from 1.2 to 5.4 g / 100 were selected, and the average value was obtained from three parallel tests. The test samples to be analyzed were packed into glass cuvettes (Minolta) (with a packing height of at least 3 cm). The test samples were compressed using the pressure from the measuring head of the Minolta instrument.

[0116] (3) Viscosity number retention rate The viscosity number (VN0) of the polyester product before contact treatment (excluding Comparative Example 1) and the viscosity number (VN1) of the biodegradable polyester after contact treatment were detected, and the viscosity number retention rate (η)η = VN1 / VN0 was calculated. The viscosity number was measured in a constant temperature water bath at 25±0.05℃ in a phenol / o-dichlorobenzene solution in a weight ratio of 1:1 according to GB / T 17931-1999, with a sample concentration of 5 mg / ml.

[0117] (4) Acid value The acid value AN (mg KOH / g) of the test sample was measured in reference to DIN EN 12634, October 1998. The solvent mixture used contained 1 part by volume of dimethyl sulfoxide, 8 parts by volume of isopropanol, and 7 parts by volume of toluene, with a volume of 150 ml. The sample was pre-titrated according to the DIN EN 12634-1998 standard to determine the appropriate sample mass and to confirm 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 obtain a clear solution. During titration, the solution temperature was maintained at 65-75°C to avoid sample precipitation. Tetrabutylammonium hydroxide was used as the titrant; highly toxic tetramethylammonium hydroxide should be avoided. Furthermore, to prevent the solvent mixture from absorbing CO2 from 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 must be pretreated according to the same process as the sample testing procedure. For example, the blank solvent was heated for the same time and temperature, and then the blank solvent was titrated.

[0118] (5) MFR The meltmass flow rate was detected at 190°C and 2.16 kg according to the ISO 1133-2-2011 standard method. The test results for the examples are shown in Table 3, and the test results for the comparative examples are shown in Table 4.

[0119] [Table 3]

[0120] According to the test results in Table 3, the biodegradable aliphatic polyesters prepared in each example of the present invention had a whiteness index of 20 or higher, reaching 30 or higher in some examples, an acid value of 1.45 mg KOH / g or less in all examples, reaching 1.0 mg KOH / g or less in some examples, and a tetrahydrofuran content of 110 ppm or less, reaching 30 ppm or less in some examples. After contact treatment with an aqueous tetrahydrofuran solution, the biodegradable aliphatic polyesters had a viscosity number retention rate of 96% or higher, indicating that the contact treatment by the preparation method of the present invention does not adversely affect the performance of the biodegradable aliphatic polyester itself.

[0121] According to Examples 1-6, when the contact treatment time was 5-16 hours and the temperature was 35-55°C, the biodegradable aliphatic polyesters exhibited a higher whiteness index and a lower tetrahydrofuran content. In Examples 6-12, when the concentration of the tetrahydrofuran aqueous solution was 25-45 wt.% and the mass ratio of the polyester product to the tetrahydrofuran aqueous solution was 1:(2-5), the biodegradable aliphatic polyesters exhibited an even higher whiteness index and an even lower tetrahydrofuran content.

[0122] [Table 4]

[0123] According to the test results in Table 4, in Comparative Example 1, the biodegradable aliphatic polyester prepared by a preparation method involving direct separation and drying without contact treatment had a whiteness index of only 15, indicating low whiteness. In Comparative Example 2, the tetrahydrofuran aqueous solution was replaced with an ethanol aqueous solution of equal concentration and weight, and in Comparative Example 3, the tetrahydrofuran aqueous solution was replaced with an acetone aqueous solution of equal concentration and weight. It was difficult to achieve both whiteness and viscosity number retention with biodegradable aliphatic polyesters.

[0124] Comparative Examples 4 to 10 showed that if the contact treatment time, temperature, or concentration of the tetrahydrofuran aqueous solution, and the mass ratio of the polyester product to the tetrahydrofuran aqueous solution are not within the range specified by the preparation method of the present invention, it is not possible to obtain a biodegradable aliphatic polyester with high whiteness, low tetrahydrofuran content, and low acid value.

[0125] It is clear that the above embodiments of the present invention are merely examples to clearly illustrate the present invention and do not limit its embodiments. Those skilled in the art can make other different forms of variations or modifications based on the above description. It is not necessary to list, nor can it be described, all embodiments here. Any modifications, equivalent substitutions, or improvements made without departing from the spirit and principles of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing biodegradable aliphatic polyesters, The process includes the steps of mixing component A and component B, sequentially carrying out esterification and polycondensation reactions to obtain a polyester product, dispersing the obtained polyester product in an aqueous tetrahydrofuran solution, performing a contact treatment, and undergoing post-treatment to obtain the biodegradable aliphatic polyester, The contact treatment time is 2 to 20 hours, the temperature is 20 to 65°C, the concentration of the tetrahydrofuran aqueous solution is 10 to 65 wt.%, and the mass ratio of the polyester product to the tetrahydrofuran aqueous solution is 1:(1 to 10). The aforementioned component A is an aliphatic dicarboxylic acid compound or a derivative thereof. The aforementioned component B includes an aliphatic dihydroxy compound, A method for preparing a biodegradable aliphatic polyester, characterized in that the biodegradable aliphatic polyester contains a component derived from component A and a component derived from the aliphatic dihydroxy compound in a 1:1 molar ratio.

2. The preparation method according to claim 1, characterized in that the contact treatment time is 5 to 16 hours and the temperature is 35 to 55°C.

3. The preparation method according to claim 1, characterized in that the concentration of the aqueous tetrahydrofuran solution is 25 to 45 wt.%, and the mass ratio of the polyester product to the aqueous tetrahydrofuran solution is 1:(2 to 5).

4. The viscosity number retention rate η of the polyester product before and after the contact treatment is 96% or higher. η=VN １ / VN ０ Here, VN ０ This refers to the viscosity number of the polyester product before the contact treatment step, VN １ The preparation method according to claim 1, characterized in that "viscosity number" refers to the viscosity number of the biodegradable aliphatic polyester obtained by the contact treatment step.

5. The preparation method according to claim 1, characterized in that the aliphatic dicarboxylic acid compound is an aliphatic diacid or a derivative thereof containing 2 to 40 carbon atoms.

6. The preparation method according to claim 1, characterized in that the aliphatic dihydroxy compound is an aliphatic alkanediol containing 2 to 6 carbon atoms.

7. The preparation method according to claim 1, characterized in that the biodegradable aliphatic polyester has a whiteness index of 20 or more, an acid value of 1.45 mg KOH / g or less, and a tetrahydrofuran residue of 110 ppm or less, and the whiteness index is measured according to the ASTM E313-73 method.

8. The preparation method according to claim 7, characterized in that the biodegradable aliphatic polyester has a whiteness index of 26 or higher.

9. The preparation method according to claim 7, characterized in that the amount of tetrahydrofuran residue of the biodegradable aliphatic polyester is 60 ppm or less.

10. The preparation method according to claim 7, characterized in that the acid value of the biodegradable aliphatic polyester is 1.2 mg KOH / g or less.

11. The preparation method according to claim 7, characterized in that the biodegradable aliphatic polyester has a melt mass flow rate of 22 g / 10 min or less when measured at 190°C and 2.16 kg in accordance with the EN ISO 1133-2-2011 standard.

12. A method for preparing a polyester mixture, comprising the step of preparing a biodegradable aliphatic polyester by the method described in any one of claims 1 to 11, The aforementioned polyester mixture has the following components: The biodegradable aliphatic polyester is 35 to 70 parts by weight, 5 to 15 parts by weight of aliphatic-aromatic copolyester, 10 to 40 parts by weight of one or more of starch, wood flour, cellulose, polyhydroxyalkanoate, polyglycolic acid, or polylactic acid, A method for preparing a polyester mixture, characterized by comprising 10 to 35 parts by weight of an inorganic filler.

13. The method for preparing a polyester mixture according to claim 12, characterized in that the polyester mixture, when measured in accordance with EN ISO 1133-2-2011 under conditions of 190°C and 2.16 kg, has a melt mass flow rate of 8 g / 10 min or less and a tetrahydrofuran content of 60 ppm or less.

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