Biodegradable aliphatic polyesters and methods for preparing and using 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, more particularly to biodegradable aliphatic polyesters, and methods for their preparation and use. [Background technology]

[0002] Biodegradable aliphatic polyesters such as polybutylene succinate (PBS) and polybutylene adipate are easy to process and can be processed using standard molding equipment using methods such as extrusion molding, injection molding, blow molding, spinning, blister molding, lamination, and foaming. These products have a wide range of uses, with major applications including packaging such as beverage bottles and food packaging bags, daily necessities such as disposable tableware, and agricultural applications such as biodegradable mulch films.

[0003] Aliphatic diacids used in the preparation of biodegradable aliphatic polyesters often contain impurities at levels ranging from hundreds to thousands of ppm due to differences in raw material origin and production processes. For example, succinic acid typically contains trace amounts of formic acid, acetic acid, lactic acid, pyruvic acid, fumaric acid, and sodium sulfate. The presence of trace impurities not only affects polymerization efficiency but also the appearance of polyester products, causing them to appear yellow or reddish, making it difficult to achieve high whiteness. Zhu Guixiang et al. (Effect of Impurity Content in Biobased Succinic Acid on the Properties of Biodegradable Copolyesters [J]. Petrochemical Engineering, 2012, 41(11):1302-1306) reported that nitrogen-containing impurities and trace amounts of formic acid in biobased succinic acid can cause the polyester to appear yellowish.

[0004] To meet the needs of end-stage applications of polyester products, the materials used often require good whiteness due to the appearance and color requirements of products such as straws, coffee capsules, and other products. In the prior art, phosphorus-containing passivators or color stabilizers are usually added during polymerization to improve the color of degradable polyester products.

[0005] WO2018219708 A1 discloses a method for preparing an aliphatic-aromatic polyester, in which an aliphatic-aromatic polyester having a whiteness index of 25 or more is obtained by adding 0.03 to 0.04 wt.% of a phosphorus compound during polymerization. However, the phosphorus compound acts as a passivator for the titanium catalyst and may weaken the activity of the titanium catalyst to some extent, leading to an increase in the acid value of the resulting aliphatic-aromatic polyester and potentially weakening the hydrolysis resistance of the aliphatic-aromatic polyester.

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

[0007] Therefore, there is a demand 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 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention overcomes the drawback of the prior art, namely low whiteness, and provides a method for preparing biodegradable aliphatic polyesters by improving the color of the aliphatic polyester while maintaining a low acid value through a contact treatment step with an aqueous tetrahydrofuran solution, and also by avoiding deterioration of the performance of the aliphatic polyester.

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

[0011] Another object of the present invention is to provide uses of the above biodegradable aliphatic polyesters. [Means for solving the problem]

[0012] The technical solutions adopted by the present invention to solve the above technical problems are as follows: 1. A method for preparing a biodegradable aliphatic polyester, comprising: The method includes the steps of mixing component A and component B, sequentially carrying out an esterification reaction and a polycondensation reaction, dispersing the resulting polyester product in an aqueous tetrahydrofuran solution, carrying out a contact treatment, and then carrying out a post-treatment to obtain the biodegradable aliphatic polyester, wherein the contact treatment is carried out for 2 to 20 hours at a temperature of 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), Component A is an aliphatic dicarboxylic acid compound or a derivative thereof, The component B contains an aliphatic dihydroxy compound in an amount equimolar to that of the component A.

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

[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 results for the resulting biodegradable aliphatic polyester. Because the boiling point of tetrahydrofuran is 66°C, if the contact treatment temperature is too high, tetrahydrofuran will easily boil, and the amount of tetrahydrofuran that volatilizes will be too high, resulting in excessive losses.

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

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

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

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

[0019] When the tetrahydrofuran content is within the above range, the effective tetrahydrofuran content is appropriate, ensuring low residual tetrahydrofuran content in the final biodegradable aliphatic polyester while effectively removing impurities. If the mass ratio of the polyester product to the aqueous tetrahydrofuran solution is greater than 1, i.e., if the solid-liquid ratio is high, the efficiency of the contact treatment will be low. If the concentration of the aqueous tetrahydrofuran solution is too high, the residual tetrahydrofuran content in the biodegradable aliphatic polyester will be too high, making it unable to meet food contact regulations and affecting the product's subsequent use. 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 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 where 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 determined according to the GB / T 17931-1999 method.

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

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

[0026] Preferably, the preparation method comprises: mixing component A with component B, with or without the addition of a catalyst, to form a paste; In step i), the paste is esterified or transesterified with all or part of a catalyst until the viscosity number of the esterified or transesterified product reaches 5-60 ml / g when measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999 standard; In step ii), the esterification or transesterification product obtained in step i) is mixed with the remaining catalyst, and the mixture is subjected to a preliminary polycondensation reaction until the viscosity number of the prepolymer reaches 20-110 ml / g when measured in a constant temperature water bath at 25±0.05°C in a phenol / o-dichlorobenzene solution of 1:1 by weight in accordance with GB / T 17931-1999; In step iii), the prepolymer obtained in step ii) is subjected to polycondensation reaction so that the viscosity number 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°C according to GB / T 17931-1999 standard.

[0027] If necessary, after step iii), step iv) may be carried out by adding a chain extender, component C. 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-extended product reaches 150 to 260 ml / g when measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C according to GB / T 17931-1999.

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

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

[0030] Optionally, the titanium catalyst is 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, the 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 device such as a vertical reactor with stirring. The typical holding time is 2-6 hours.

[0033] In step ii), the liquid obtained in step i) (esterification or transesterification) is added, if appropriate, together with the remaining catalyst, 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. Typical retention times are 75-180 minutes.

[0034] Step iii) can be carried out in a finishing machine such as a rotating disk reactor or a 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. Typical holding times are 60-150 minutes, preferably 75-120 minutes.

[0035] Step iv) can be carried out in an extruder, continuous kneader, or static mixer. The polycondensed polyester obtained in step iii) is added to a twin-screw extruder or static mixer together with a chain extender (component C) in an amount of 0 to 3 wt.%, preferably 0.05 to 2 wt.%, and particularly preferably 0.1 to 1.5 wt.%, based on the weight of the biodegradable polyester composition. The chain-extended product is obtained at a reaction temperature of 180 to 235°C and a holding time of 3 to 15 minutes. 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 twin-screw CRP or ORP reactor. The extruder that can be used is either a single-screw or twin-screw extruder.

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

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

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

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

[0040] Preferably, the aliphatic dicarboxylic acid compound or derivative thereof is an aliphatic diacid or derivative thereof 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 brassylic acid.

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

[0043] Derivatives of the aliphatic dicarboxylic acid compounds include dimethyl, diethyl, di-n-propyl, diisopropyl, di-n-butyl, diisobutyl, di-tert-butyl, di-n-pentyl, diisopentyl, di-n-hexyl esters, or anhydrides of dicarboxylic acids.

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

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

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

[0049] The biodegradable aliphatic polyester contains 0 to 3 wt %, preferably 0.01 to 2 wt %, more preferably 0.05 to 1.2 wt %, and particularly preferably 0.08 to 0.2 wt %, of a crosslinking agent containing at least three functional groups, based on the total weight of the biodegradable aliphatic polyester.

[0050] Preferably, the compound containing at least three functional groups is one or more of malic acid, citric acid, glycerol, pentaerythritol or trimethylolpropane.

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

[0052] If the content of the trifunctional crosslinking agent is too high, the polyester is likely to be over-crosslinked, which affects 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 the biodegradable aliphatic polyester.

[0054] The component C includes one or more of the following components: c1: isocyanates and / or isocyanurates having two or more functional groups c2: Peroxides with two or more functional groups c3: Epoxide with two or more functional groups c4: Oxazolines, oxazines, caprolactams and / or carbodiimides having two or more functional groups.

[0055] The component c1 used comprises an isocyanate with a functionality of two or more or a mixture of different isocyanates. Aromatic or aliphatic diisocyanates can be used, but higher functionality isocyanates can also be used.

[0056] According to the invention, the aromatic diisocyanate c1 is in particular toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, naphthalene-1,5-diisocyanate or xylene diisocyanate.

[0057] Of these, diphenylmethane-2,2'-, 2,4'- or 4,4'-diisocyanate is particularly preferably used as component c1, the other diisocyanates usually being used in the form of mixtures.

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

[0059] In the present invention, the aliphatic diisocyanate C1 is in particular any linear or branched alkylene diisocyanate or cycloalkylene diisocyanate containing 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms, such as hexamethylene diisocyanate, isophorone diisocyanate or methylenebis(4-isocyanatocyclohexane). 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 diisocyanates may be linear or branched. Particularly preferred are cyclic trimer, pentamer, or higher oligomeric isocyanurates based on n-hexamethylene diisocyanate, for example, hexamethylene diisocyanate.

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

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

[0063] The amount of component c2 used is usually 0 to 3 wt.%, preferably 0.1 to 2 wt.%, and particularly preferably 0.2 to 1 wt.%, based on the total amount of the biodegradable aliphatic polyester composition.

[0064] The epoxides having two or more functional groups (component c3) used are, for example, hydroquinone diglycidyl ether, resorcinol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Examples of other epoxides include diglycidyl terephthalate, diglycidyl tetrahydrophthalate, diglycidyl hexahydrophthalate, dimethyl diglycidyl phthalate, phenylene diglycidyl ether, ethylene diglycidyl ether, trimethylene diglycidyl ether, tetramethylene diglycidyl ether, hexamethylene diglycidyl ether, sorbitol diglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, diglycol diglycidyl ether, polyethylene glycol diglycidyl ether, propanediol diglycidyl ether, dipropylene glycol diglycidyl ether, polypropanediol diglycidyl ether, and polybutanediol diglycidyl ether.

[0065] Particularly suitable components of epoxides with two or more functional groups are copolymers based on styrene, acrylate and / or methacrylate and containing an epoxy group, the epoxy-bearing unit being preferably glycidyl methacrylate or glycidyl acrylate.

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

[0067] The components c4 used are oxazolines, oxazines, caprolactams and / or carbodiimides having two or more functional groups.

[0068] Particularly preferred dioxazolines and dioxazines are those in which the bridging moiety is 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; particularly preferred dioxazolines that may 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, in particular 1,4-di(2-dioxazinyl)benzene, 1,2-di(2-dioxazinyl)benzene or 1,3-di(2-dioxazinyl)benzene.

[0069] The carbodiimide may be specifically 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 usually 0 to 3 wt.%, preferably 0.1 to 2 wt.%, and particularly preferably 0.2 to 1 wt.%, based on the total amount of the biodegradable aliphatic polyester composition. Component c4 can also function as an acid scavenger.

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

[0072] The biodegradable aliphatic polyester has a whiteness index of 20 or more.

[0073] In some embodiments, the biodegradable aliphatic polyester has a whiteness index of 26 or greater. Additionally, in some embodiments, the biodegradable aliphatic polyester has a whiteness index of 30 or greater.

[0074] 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 number of the biodegradable aliphatic polyester is 1.2 mg KOH / g or less. In some embodiments, the acid number of the biodegradable aliphatic polyester is 1.0 mg KOH / g or less.

[0077] The acid number is determined in accordance with DIN EN12634.

[0078] In the present 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 a specific embodiment, 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] Furthermore, in a specific embodiment, the biodegradable aliphatic polyester has a melt mass flow rate of 6 g / 10 min or less when measured under conditions of 190° C. and 2.16 kg.

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

[0082] The present invention includes, as a component: 35 to 70 parts by weight of the biodegradable aliphatic polyester; 5 to 15 parts by weight of an aliphatic-aromatic copolyester; 10 to 40 parts by weight of one or more of starch, wood flour, cellulose, polyhydroxyalkanoate, polyglycolic acid, and polylactic acid; The polyester mixture containing 10 to 35 parts by weight of an inorganic filler provides further protection.

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

[0084] Preferably, the polyester blend has a melt mass-flow rate of 8 g / 10 min or less and a tetrahydrofuran content of 60 ppm or less, as measured according to EN ISO 1133-2-2011, at 190°C and 2.16 kg, and more preferably 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 covers the use of said polyester blends in the manufacture of biodegradable straws, coffee capsule shells.

[0086] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0087] The present invention develops a biodegradable aliphatic polyester with high whiteness and a low acid value. By contacting the aliphatic polyester with an aqueous tetrahydrofuran solution, the color of the aliphatic polyester is improved while maintaining a low acid value and preventing performance degradation of the aliphatic polyester. DETAILED DESCRIPTION OF THE INVENTION

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

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

[0090] Unless otherwise specified, the reagents, methods and equipment utilized in the present invention are conventional reagents, methods and equipment within the skill of the art. [Example]

[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 in an esterification reactor at room temperature, and then the mixture was esterified at a temperature of 175-190°C and a pressure of 0.95-1.1 bar for 3-4 hours to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 27 ml / g.

[0093] Step ii): The esterified product was introduced into a static mixer and then into a vertically stirred, thoroughly mixed reactor. 0.249 kg of tetrabutyl titanate was added to the reactor and the reaction was carried out at a temperature of 230-250°C and a pressure of 0.2-0.7 bar for 95-125 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolyester. The viscosity number of the prepolyester was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was 65 ml / g.

[0094] The prepolyester was added to a cage reactor and polycondensation reaction was carried out for 120-150 minutes at a reaction temperature of 240-250°C and a reaction pressure of 0.20-0.35 mbar, to prepare polycondensation polyester P1 having a viscosity of 192 ml / g when measured in a constant temperature water bath at 25±0.05°C in a 1:1 weight ratio phenol / o-cresol solution in accordance with 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 in an esterification reactor at room temperature, and the mixture was then esterified at a temperature of 186-195°C and a pressure of 0.95-1.1 bar for 3-4 hours to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 24 ml / g.

[0097] Step ii): The esterified product was introduced into a static mixer and then into a vertically stirred, thoroughly mixed reactor. 0.283 kg of tetrabutyl titanate was added to the reactor and the reaction was carried out for 85 to 135 minutes at a temperature of 235 to 245°C and a pressure of 0.36 to 0.48 bar. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolyester. The viscosity number of the prepolyester was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was 58 ml / g.

[0098] The prepolyester was added to a cage reactor and polycondensation reaction was carried out for 110-140 minutes at a reaction temperature of 242-248°C and a reaction pressure of 0.22-0.30 mbar, to prepare polycondensed polyester P2 having a viscosity of 196 ml / g when measured in a constant temperature water bath at 25±0.05°C in a 1:1 weight ratio phenol / o-cresol solution in accordance with 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 in an esterification reactor at room temperature, and the mixture was then esterified at a temperature of 180-195°C and a pressure of 0.90-1.0 bar for 3.5-4.5 hours to obtain an esterified product. The viscosity number of the esterified product was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was found to be 29 ml / g.

[0101] Step ii): The esterified product was introduced into a static mixer and then into a vertically stirred, thoroughly mixed reactor. 0.256 kg of tetrabutyl titanate was added to the reactor and the reaction was carried out at a temperature of 230-250°C and a pressure of 0.3-0.45 bar for 95-145 minutes. Most of the excess 1,4-butanediol was removed by distillation to obtain a prepolyester. The viscosity number of the prepolyester was measured in a 1:1 weight ratio phenol / o-dichlorobenzene solution in a constant temperature water bath at 25±0.05°C in accordance with GB / T 17931-1999, and was 71 ml / g.

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

[0103] Examples 1 to 12 Biodegradable aliphatic polyester P1 was dispersed in a tetrahydrofuran aqueous solution at a concentration of A according to the contact treatment steps shown in Table 1, and contact treatment was carried out with the mass ratio of the polyester product to the tetrahydrofuran aqueous solution set to B, the contact treatment time set to C, and the temperature set to D. Next, after separation and drying, a biodegradable aliphatic polyester was obtained.

[0104] Example 13 Biodegradable aliphatic polyester P2 was dispersed in a tetrahydrofuran aqueous solution at a concentration of A according to the contact treatment steps shown in Table 1, and contact treatment was carried out with the mass ratio of the polyester product to the tetrahydrofuran aqueous solution set to B, the contact treatment time set to C, and the temperature set to D. Next, after separation and drying, a biodegradable aliphatic polyester was obtained.

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

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

[0107] Comparative Examples 1 to 10 Biodegradable aliphatic polyester P1 was dispersed in a tetrahydrofuran aqueous solution at a concentration of A according to the contact treatment steps shown in Table 2, and contact treatment was carried out with the mass ratio of the polyester product to the tetrahydrofuran aqueous solution set to B, the contact treatment time set to C, and the temperature set to D. Next, after separation and drying, a biodegradable aliphatic polyester was obtained.

[0108] where: In Comparative Example 1, the contact treatment was not carried out, and the biodegradable aliphatic polyester was obtained by separation and drying.

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

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

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

[0112] [Table 2]

[0113] Performance Test The biodegradable polyesters prepared in the above examples and comparative examples were used as test samples and performance tests were carried out on each of them. The specific methods are as follows.

[0114] (1) Residual tetrahydrofuran content (THF content) Approximately 1.2 g of test sample was weighed, and the headspace temperature was set to 105°C and the headspace time to 2 hours. The gas chromatography test was performed using an Agilent 7697A-7890A instrument. The gas chromatography heating program was: initial temperature 50°C, hold time: 3 minutes; temperature increase to 200°C, heating rate 12°C / min, hold 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 between 1.2 and 5.4 g / 100 were selected, and the average value was obtained from three parallel tests. A glass cuvette (Minolta) was filled with the test sample to be analyzed (fill height at least 3 cm). The test sample was compressed using pressure from the measurement head of the Minolta instrument.

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

[0117] (4) Acid value The acid value (AN) of the test sample (mg KOH / g) was determined according to DIN EN 12634, October 1998. The solvent mixture used contained 1 part dimethyl sulfoxide, 8 parts isopropanol, and 7 parts toluene by volume, with a total volume of 150 ml. According to the DIN EN 12634-1998 standard, the sample was pre-titrated to determine the appropriate sample mass and ensure that the volume of titrant consumed was 2-3 ml. The sample was added to the solvent mixture and heated to 70-85°C to dissolve the entire sample and form a clear solution. The solution temperature was maintained between 65-75°C during the titration to avoid sample precipitation. Tetrabutylammonium hydroxide was used as the titrant; tetramethylammonium hydroxide, which is highly toxic, should be avoided. In addition, to prevent the solvent mixture from absorbing CO2 in the air and affecting the volume of titrant consumed by the blank solvent, when testing the volume of titrant consumed by the blank solvent, the blank solvent should be pretreated according to the same process as the sample test operation, for example, the blank solvent should be heated for the same time and temperature, and then the blank solvent should be titrated.

[0118] (5) MFR The melt mass flow rate was determined according to the ISO 1133-2-2011 standard method at 190°C and 2.16 kg. The test results of the examples are shown in Table 3, and the test results of 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 more, and in some examples, even 30 or more, an acid value of 1.45 mg KOH / g or less, and in some examples, even 1.0 mg KOH / g or less, and a tetrahydrofuran content of 110 ppm or less, and in some examples, even 30 ppm or less. After contact treatment with an aqueous tetrahydrofuran solution, the biodegradable aliphatic polyesters had a viscosity number retention rate of 96% or more, indicating that the contact treatment using the preparation method of the present invention did not adversely affect the performance of the biodegradable aliphatic polyester itself.

[0121] According to Examples 1 to 6, when the contact treatment time was 5 to 16 hours and the temperature was 35 to 55° C., the biodegradable aliphatic polyester had a higher whiteness index and a lower tetrahydrofuran content. In Examples 6 to 12, when the concentration of the tetrahydrofuran aqueous solution was 25 to 45 wt. % and the mass ratio of the polyester product to the tetrahydrofuran aqueous solution was 1:(2 to 5), the biodegradable aliphatic polyester had an even higher whiteness index and a 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 in which direct separation and drying were carried out without performing a 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 high whiteness and high viscosity number retention with the biodegradable aliphatic polyester.

[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 ranges specified in 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 examples of the present invention are merely examples for clearly explaining the present invention and do not limit the embodiments of the present invention. Those skilled in the art can make other different changes or modifications based on the above description. It is not necessary to comprehensively list and describe all embodiments here. Any modifications, equivalent replacements, improvements, etc. 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. 1. A method for preparing a biodegradable aliphatic polyester, comprising: The method includes the steps of mixing component A and component B, sequentially carrying out an esterification reaction and a polycondensation reaction, dispersing the resulting polyester product in an aqueous tetrahydrofuran solution, carrying out a contact treatment, and then carrying out a 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); Component A is an aliphatic dicarboxylic acid compound or a derivative thereof, A method for preparing a biodegradable aliphatic polyester, wherein the component B contains an aliphatic dihydroxy compound in an amount equimolar to that of the component A.

2. 2. The method according to claim 1, wherein the contact treatment is carried out for 5 to 16 hours at a temperature of 35 to 55°C.

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

4. the viscosity number retention η of the polyester product before and after the contact treatment is 96% or more; η=VN １ / VN ０ Here, VN ０ refers to the viscosity number of the polyester product before the contacting 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. 2. The method according to claim 1, wherein the aliphatic dicarboxylic acid compound is an aliphatic diacid containing 2 to 40 carbon atoms or a derivative thereof.

6. 2. The method of claim 1, wherein the aliphatic dihydroxy compound is an aliphatic alkanediol containing 2 to 6 carbon atoms.

7. A high-whiteness biodegradable aliphatic polyester, characterized by being prepared by the preparation method according to any one of claims 1 to 6.

8. The high-whiteness biodegradable aliphatic polyester according to claim 7, wherein 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 residual amount of tetrahydrofuran of 110 ppm or less.

9. 9. The high-whiteness biodegradable aliphatic polyester according to claim 8, wherein the biodegradable aliphatic polyester has a whiteness index of 26 or more, preferably a whiteness index of 30 or more.

10. 9. The high-whiteness biodegradable aliphatic polyester according to claim 8, wherein the residual amount of tetrahydrofuran in the biodegradable aliphatic polyester is 60 ppm or less.

11. 9. The high-whiteness biodegradable aliphatic polyester according to claim 8, wherein the acid value of the biodegradable aliphatic polyester is 1.2 mg KOH / g or less.

12. The high-whiteness biodegradable aliphatic polyester according to claim 8, wherein 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.

13. As ingredients, 35 to 70 parts by weight of the biodegradable aliphatic polyester according to any one of claims 7 to 12; 5 to 15 parts by weight of an aliphatic-aromatic copolyester; 10 to 40 parts by weight of one or more of starch, wood flour, cellulose, polyhydroxyalkanoate, polyglycolic acid, and polylactic acid; and 10 to 35 parts by weight of an inorganic filler.

14. The polyester blend according to claim 13, wherein the polyester blend has a melt mass flow rate of 8 g / 10 min or less and a tetrahydrofuran content of 60 ppm or less, when measured in accordance with EN ISO 1133-2-2011 at 190°C and 2.16 kg.

15. Use of the polyester mixture according to any one of claims 13 to 14 in the manufacture of biodegradable straws, coffee capsule shells.

Images