Fatty-aromatic copolyesters, processes for their preparation and their use

Abstract

The application relates to the technical field of PET depolymerization and biodegradable polyesters, and discloses a polyester and a preparation method thereof. The method comprises the following steps: (1) contacting bis(2-hydroxyethyl) terephthalate with 1,4-butanediol in the presence of an ester exchange catalyst and performing an ester exchange reaction; (2) contacting HOOC-R-COOH with 1,4-butanediol in the presence of an esterification catalyst and performing an esterification reaction; (3) contacting the product obtained in the ester exchange reaction in the step (1) and the product obtained in the esterification reaction in the step (2) in the presence of a polycondensation catalyst and performing a polycondensation reaction; wherein the purity of the bis(2-hydroxyethyl) terephthalate is not less than 97 wt%, and the metal ion content is not more than 50 ppm; and R is selected from C3-C16 alkylene. The method can directly prepare a regenerated aliphatic-aromatic copolyester product without converting BHET into terephthalic acid (PTA) monomers, and the product has a high molecular weight and a good color phase.

Description

Technical Field

[0001] This invention relates to the fields of PET depolymerization and biodegradable polyester technology, specifically to an aliphatic aromatic copolyester, its preparation method, and its applications. Background Technology

[0002] Polyethylene terephthalate (PET) is widely used in food and beverage packaging, clothing and textiles, engineering plastics and other fields due to its excellent performance and low production cost. Due to its huge application scenarios, 70 million tons of waste PET are generated globally every year. Waste PET that is not properly disposed of will have a bad impact on the ecological environment and is also a waste of resources. The proper treatment, recycling and reuse of waste PET has received widespread attention around the world.

[0003] Currently, the main methods for recycling waste PET include incineration, physical recycling, and chemical recycling. Incineration has low utilization value, and PET obtained through physical recycling cannot be reused multiple times. Chemical recycling depolymerizes polymers into smaller molecules, which are then repolymerized into usable materials, achieving closed-loop utilization and high-value recycling. In recent years, many methods for chemically depolymerizing waste plastics have emerged. Alcohololysis has become the main method due to its mild reaction conditions and ability to process complex waste polyesters. Alcohololysis is mainly divided into methanol alcoholysis and ethylene glycol alcoholysis. Methanol alcoholysis yields dimethyl terephthalate, which can be used as a raw material for the preparation of aromatic polyesters. However, the reaction produces a large amount of methanol, posing a high risk, and it is no longer used in industry. Ethylene glycol alcoholysis to obtain diethylene glycol terephthalate (BHET) is also a relatively mature technology, but the purity of the obtained BHET is low, and the BHET obtained by alcoholysis is not effectively utilized.

[0004] Therefore, in order to solve the above-mentioned problems, there is a need for a fatty aromatic copolyester, its preparation method and its application. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of unreasonable recycling methods for waste polyester, difficulty in efficiently converting diethylene terephthalate into fatty aromatic copolyesters, low molecular weight and color difference of fatty aromatic copolyesters in the existing technology, and to provide fatty aromatic copolyesters, their preparation methods and applications.

[0006] To achieve the above objectives, the present invention provides a method for preparing a fatty aromatic copolyester, characterized in that the method comprises: (1) contacting bis(2-hydroxyethyl) terephthalate with 1,4-butanediol in the presence of an ester exchange catalyst and performing an ester exchange reaction; (2) contacting HOOC-R-COOH with 1,4-butanediol in the presence of an esterification catalyst and performing an esterification reaction; (3) contacting the product obtained from the ester exchange reaction in step (1) and the product obtained from the esterification reaction in step (2) in the presence of a polycondensation catalyst and performing a polycondensation reaction; wherein, the purity of bis(2-hydroxyethyl) terephthalate is not less than 97 wt%, and the metal ion weight content is not greater than 50 ppm; R is selected from C3-C16 alkylene groups.

[0007] The second aspect of the present invention provides a fatty aromatic copolyester product prepared by the method described in one aspect of the present invention.

[0008] A third aspect of the present invention provides a fatty aromatic copolyester, characterized in that the Mn of the fatty aromatic copolyester is not less than 2 × 10⁻⁶. 4 g / mol, Mw not less than 5 × 10 4 g / mol, b value not greater than 5.

[0009] The fourth aspect of the present invention provides the application of the method described in one aspect of the present invention in improving at least one of the number-average molecular weight, weight-average molecular weight, and hue of aliphatic aromatic copolyesters.

[0010] Through the above technical solution, this invention utilizes high-purity BHET monomers obtained through chemical regeneration of polyester-containing raw materials. This eliminates the need to convert BHET into terephthalic acid (PTA) monomers, allowing for the direct preparation of recycled fatty aromatic copolyesters with Mn ≥ 2 × 10⁻⁶. 4 Mw≥5×10 4 With a b-value ≤ 5, it possesses high molecular weight, good mechanical properties, and excellent color, enabling the chemical recycling and reuse of high-performance fatty aromatic copolyesters from waste PET polyester, resulting in significant economic benefits. Detailed Implementation

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0012] As mentioned above, the present invention provides a method for preparing a fatty aromatic copolyester, characterized in that the method includes: (1) contacting bis(2-hydroxyethyl) terephthalate with 1,4-butanediol in the presence of an ester exchange catalyst and carrying out an ester exchange reaction; (2) contacting HOOC-R-COOH with 1,4-butanediol in the presence of an esterification catalyst and carrying out an esterification reaction; (3) contacting the product obtained from the ester exchange reaction in step (1) and the product obtained from the esterification reaction in step (2) in the presence of a polycondensation catalyst and carrying out a polycondensation reaction; wherein, the purity of bis(2-hydroxyethyl) terephthalate is not less than 97 wt%, and the metal ion weight content is not greater than 50 ppm; R is selected from C3-C16 alkylene groups.

[0013] In this invention, the purity of the bis(2-hydroxyethyl) terephthalate can be determined by testing with 1H NMR spectroscopy and high performance liquid chromatography.

[0014] In this invention, the metal ions mainly refer to Zn, Sb, and Ti, and the metal ions can be obtained by inductively coupled plasma mass spectrometry.

[0015] In some embodiments of the present invention, preferably, the transesterification catalyst is selected from metal salts, more preferably from at least one of sodium acetate, magnesium acetate, zinc acetate and zinc acetate dihydrate, and more preferably zinc acetate.

[0016] In some embodiments of the present invention, preferably, the esterification catalyst is selected from organotitanium compounds, more preferably from at least one of tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, titanium glycolate, and titanium acetylacetone oxide, and more preferably tetrabutyl titanate.

[0017] In some embodiments of the present invention, preferably, the polycondensation catalyst is selected from compounds containing rare earth elements, more preferably from at least one of lanthanum chloride, lanthanum acetylacetonate, neodymium isopropoxy, dysprosium acetylacetonate, and lanthanum stearate, and more preferably lanthanum acetylacetonate.

[0018] In some embodiments of the present invention, preferably, the esterification reaction and transesterification reaction are carried out in the presence of a protective gas.

[0019] In some embodiments of the present invention, preferably, the esterification reaction is stopped when the transesterification rate is greater than 90%.

[0020] In this invention, the transesterification rate refers to the conversion rate of the reaction between bis(2-hydroxyethyl) terephthalate (BHET) and 1,4-butanediol (BDO). The transesterification rate can be tested by taking a fraction and performing nuclear magnetic resonance hydrogen spectroscopy. The mass of EG obtained from the test / the theoretical mass of EG produced is the transesterification rate.

[0021] In this invention, the method for stopping the transesterification reaction includes stopping stirring and cooling the reaction system.

[0022] In this invention, the protective gas can be a common gas that provides an inert atmosphere. In some embodiments of this invention, preferably, the protective gas is selected from nitrogen and / or argon.

[0023] In some embodiments of the present invention, preferably, the polycondensation reaction is carried out in the presence of a stabilizer.

[0024] In some embodiments of the present invention, preferably, the polyester containing polyethylene terephthalate is pulverized into particles with a diameter of 0.1-3 cm.

[0025] In some embodiments of the present invention, preferably, the particles are dried until their moisture content is no more than 1 wt%.

[0026] In this invention, the moisture content is calculated by drying the PET in an oven, weighing it, and then drying until the PET weight is no longer lost.

[0027] In some embodiments of the present invention, preferably, the esterification reaction is stopped when the esterification rate is greater than 90%.

[0028] In this invention, the esterification rate refers to the conversion rate of the reaction between diacid and diol. The esterification rate can be tested by performing nuclear magnetic resonance hydrogen spectroscopy on the fraction, and the mass of water obtained from the test / the theoretical mass of water produced is the esterification rate.

[0029] In this invention, the method for stopping the esterification reaction includes stopping stirring and cooling the reaction system.

[0030] In some embodiments of the present invention, preferably, the amount of the transesterification catalyst is 0.005-0.5 wt%, more preferably 0.05-0.4 wt%, based on the total weight of the bis(2-hydroxyethyl) terephthalate.

[0031] In some embodiments of the present invention, preferably, the amount of the esterification catalyst is 0.001-0.7 wt%, more preferably 0.04-0.6 wt%, based on the total weight of the HOOC-R-COOH.

[0032] In some embodiments of the present invention, preferably, the amount of the polycondensation catalyst is 0.001-0.2 wt%, preferably 0.005-0.1 wt%, based on the total weight of the product obtained from the transesterification reaction in step (1) and the product obtained from the esterification reaction in step (2).

[0033] In some embodiments of the present invention, preferably, in step (1), the molar ratio of bis(2-hydroxyethyl) terephthalate and 1,4-butanediol is 1:1-5, more preferably 1:1-3.

[0034] In some embodiments of the present invention, preferably, in step (2), the molar ratio of HOOC-R-COOH to the 1,4-butanediol is 1:1.1-2, more preferably 1:1.1-1.5.

[0035] In some embodiments of the present invention, preferably, in step (3), the molar ratio of the product obtained by the transesterification reaction in step (1) to the product obtained by the esterification reaction in step (2) is 1:0.1-3, more preferably 1:0.3-2.5.

[0036] In some embodiments of the present invention, preferably, the temperature of the transesterification reaction is 120-180℃, more preferably 140-180℃; the pressure is 1000-20000Pa, more preferably 1000-10000Pa; and the time is 2-8h, more preferably 4-6h.

[0037] In some embodiments of the present invention, preferably, the temperature of the esterification reaction is 140-240°C, more preferably 160-230°C; and the time is 2-8 hours, more preferably 4-8 hours.

[0038] In some embodiments of the present invention, preferably, the temperature of the polycondensation reaction is 190-280℃, more preferably 200-260℃; the pressure is 20-20000Pa, more preferably 50-20000Pa; and the time is 2-10h, more preferably 2-8h.

[0039] In some embodiments of the present invention, preferably, the method for preparing bis(2-hydroxyethyl) terephthalate includes: in the presence of a depolymerization catalyst, mixing a polyester containing polyethylene terephthalate with an alcohol to carry out a depolymerization reaction, and then sequentially performing solid-liquid separation, decolorization and crystallization on the reaction system obtained from the reaction.

[0040] According to a preferred embodiment of the present invention, the depolymerization catalyst and the components and their mass ratios described herein correspond to the definitions in patent applications 202310836415.1 and / or 202310841232.9, which are hereby incorporated in their entirety by reference.

[0041] In some embodiments of the present invention, preferably, the depolymerization catalyst is selected from titanium-containing compounds and / or titanium-containing compositions, more preferably from at least one of organotitanium compounds, inorganic titanium compounds, titanium-silicon composite catalysts and titanium-rare earth composite catalysts, and more preferably from at least one of tetraethyl titanate, tetrabutyl titanate, tetraisopropyl titanate, tetraisobutyl titanate, titanium acetylacetone oxide, di(acetylacetone)diisopropyl titanate, titanium glycol, titanium phosphate, silicate-modified alkyl titanate and diol-modified alkyl titanate titanium.

[0042] In some embodiments of the present invention, preferably, the silicate-modified alkyl titanate is selected from at least one of n-butyl silicate-modified alkyl titanate, n-ethyl silicate-modified alkyl titanate, and n-propyl silicate-modified alkyl titanate.

[0043] In some embodiments of the present invention, preferably, the polyester is selected from polyesters with a polyethylene terephthalate (PET) content of greater than 70 wt% (more preferably 80-100 wt% PET content).

[0044] In some embodiments of the present invention, preferably, the depolymerization reaction is carried out in the presence of a protective gas.

[0045] In some embodiments of the present invention, preferably, the protective gas is selected from nitrogen and / or argon.

[0046] In some embodiments of the present invention, preferably, the amount of the depolymerization catalyst is 0.01-0.5 wt%, more preferably 0.02-0.3 wt%, and more preferably 0.05-0.2 wt%, based on the total weight of the polyester.

[0047] In some embodiments of the present invention, preferably, the mass ratio of the polyester to the alcohol is 1:2-10, more preferably 1:2-6.

[0048] In some embodiments of the present invention, preferably, the temperature of the depolymerization reaction is 200-240°C, more preferably 200-220°C.

[0049] In some embodiments of the present invention, preferably, the pressure of the depolymerization reaction is 0.2-0.6 MPa, more preferably 0.25-0.4 MPa.

[0050] In some embodiments of the present invention, preferably, the depolymerization reaction takes 2-5 hours, more preferably 2.5-4 hours.

[0051] In some embodiments of the present invention, preferably, the method of mixing the polyester containing polyethylene terephthalate with the alcohol includes stirring.

[0052] In some embodiments of the present invention, preferably, the stirring speed is 50-400 rpm, more preferably 100-300 rpm.

[0053] In some embodiments of the present invention, preferably, the temperature for solid-liquid separation is 60-80℃, more preferably 68-80℃; and the time is 3-15 min, more preferably 5-10 min.

[0054] In some embodiments of the present invention, preferably, the decolorization method includes mixing the filtrate obtained after solid-liquid separation with activated carbon.

[0055] In some embodiments of the present invention, preferably, the mixing temperature is 60-80°C, more preferably 68-75°C; the mixing time is 0.5-4h, more preferably 0.5-2h; and the amount of activated carbon used is 2-40g relative to 1L of filtrate.

[0056] In this invention, the crystallization method can be cooling crystallization, and the crystallization conditions can include: a temperature of 0-4℃ and a time of 1-8h.

[0057] The second aspect of the present invention provides a fatty aromatic copolyester product prepared by the method described in one aspect of the present invention.

[0058] A third aspect of the present invention provides a fatty aromatic copolyester, characterized in that the Mn of the fatty aromatic copolyester is not less than 2 × 10⁻⁶. 4 g / mol, Mw not less than 5 × 10 4 g / mol, b value not greater than 5.

[0059] In some embodiments of the present invention, preferably, the Mn of the fatty aromatic copolyester is 2 × 10⁻⁶. 4 g / mol⁻¹×10⁻¹ 5 g / mol, Mw not less than 5 × 10 4 g / mol⁻¹×10⁻¹ 5 g / mol, b value is 2-4.

[0060] In this invention, Mn and Mw can be determined by gel permeation chromatography.

[0061] In this invention, the b value can be obtained by spectrophotometer method.

[0062] In some embodiments of the present invention, preferably, the content of the ethylene glycol segment in the fatty aromatic copolyester is less than 0.7 mol%.

[0063] The fourth aspect of the present invention provides the application of the method described in one aspect of the present invention in improving at least one of the number-average molecular weight, weight-average molecular weight, and hue of aliphatic aromatic copolyesters.

[0064] The present invention will be described in detail below through examples. Unless otherwise specified, all raw materials used in the following examples are commercially available products. The depolymerization rate is >99%, determined by weighing the undepolymerized PET particles; the content or purity of BHET is determined by 1H NMR spectroscopy and high-performance liquid chromatography; the content of ethylene terephthalate structural units is determined by 1H NMR spectroscopy. "Butanediol" refers to 1,4-butanediol.

[0065] Example 1

[0066] After washing and drying PET polyester bottle material (0.6 cm in diameter), it was added to a reactor at a mass ratio of 1:4 with ethylene glycol, along with 0.1 wt% (based on the mass of PET) of titanium glycolate. The air inside the reactor was replaced with nitrogen to ensure airtightness. Nitrogen gas was then introduced to bring the pressure inside the reactor to 0.35 MPa. Stirring was started (83 rpm), and the reactor temperature was set to 210°C. The reaction time was 3 hours after the reactor temperature reached the set temperature to obtain the depolymerization product. The depolymerization rate of waste polyester was 100%. The mass of the oligomer with a degree of polymerization of 1-3 accounted for 99.5% of the total mass of the product, and BHET accounted for 89.3% of the depolymerization product.

[0067] The alcoholysis reaction solution was cooled to 100℃, and then the insoluble matter was filtered off while hot to obtain a filtrate. Deionized water was then added to the filtrate, with the filtrate and deionized water mixed at a volume ratio of 1:3. The mixture was then mixed with 5g of activated carbon (1L of depolymerization solution) at 71℃ for 1.2 hours and stirred for 2 hours before being filtered to obtain a filtrate. The filtrate was placed in an environment of 0-4℃ for 8 hours to precipitate crystals. After filtration and drying, bis(dihydroxyethyl) terephthalate (BHET) was obtained with a purity of 98.0%, a melting point of 109℃, a color value b = 0.9, and a metal ion content of 17ppm.

[0068] Under a nitrogen atmosphere, BHET (0.394 mol), butanediol (2.22 mol), and zinc acetate (0.0029 mol) were added to a three-necked flask equipped with a mechanical stirrer. The temperature was raised to 160 °C, and the system pressure was reduced from atmospheric pressure to 1000 Pa. The reaction was carried out for 6 hours. When the transesterification rate reached 90.5%, the stirring and heating were stopped, ending the transesterification reaction and yielding BHBT. The mass ratio of zinc acetate to BHET was 0.003:1, and the mass ratio of butanediol to BHET was 2:1.

[0069] Succinic acid (0.7 mol), butanediol (0.91 mol), and tetrabutyl titanate (0.250 g) were added to a three-necked flask equipped with a mechanical stirrer. The temperature was raised to 140 °C and maintained for 2 hours. Then the temperature was raised to 190 °C and the reaction time was 4 hours. The esterification rate was 95.6%. The heating was turned off to end the esterification reaction and obtain PBS oligomers.

[0070] The products of the transesterification reaction and the esterification reaction were mixed in a molar ratio of 50:50, with a total amount of 120g. Lanthanum acetylacetone (0.0826g) was added, and the temperature was raised to 190℃ and the reaction was carried out under low vacuum (1000Pa) for 2 hours. The temperature was then raised to 230℃ and the reaction time was 1 hour. Then, the reaction was carried out under high vacuum (<150Pa) for 2 hours, the reaction temperature was 245℃, and the reaction time was 4 hours to obtain the regenerated fatty aromatic copolyester PBST-1.

[0071] Example 2

[0072] The BHET preparation method is as described in Example 1.

[0073] Under a nitrogen atmosphere, BHET (0.394 mol), butanediol (2.22 mol), and zinc acetate (0.3 g) were added to a three-necked flask equipped with a mechanical stirrer. The mixture was heated to 160 °C, and then the system pressure was reduced to 1000 Pa. The reaction was allowed to proceed for 6 hours. When the transesterification rate reached 91.2%, the heating was stopped, and the transesterification reaction was terminated to obtain BHBT. The mass ratio of zinc acetate to BHET was 0.003:1, and the mass ratio of butanediol to BHET was 2:1.

[0074] Add succinic acid (1 mol), butanediol (1.4 mol), and tetrabutyl titanate (0.472 g) to a three-necked flask equipped with a mechanical stirrer. Heat to 160 °C and maintain for 2 hours. Then heat to 200 °C and react for 4.5 hours. The esterification rate is 96.2%. Turn off the heating to end the esterification reaction and obtain PBS oligomer.

[0075] The products of the transesterification reaction and the esterification reaction were mixed in a molar ratio of 30:70, with a total amount of 160g. Lanthanum chloride (0.118g) was added. Under pre-condensation conditions, the temperature was raised to 200℃ and the reaction was carried out under low vacuum (1000Pa) for 1.5 hours. The temperature was then raised to 220℃ and the reaction time was 1 hour. The final condensation was carried out under high vacuum conditions (<150Pa) at a reaction temperature of 230℃ for 5 hours to obtain the regenerated fatty aromatic copolyester PBST-2.

[0076] Example 3

[0077] The BHET preparation method is as described in Example 1.

[0078] Under a nitrogen atmosphere, BHET (0.394 mol), butanediol (2.22 mol), and zinc acetate (0.3 g) were added to a three-necked flask equipped with a mechanical stirrer. The mixture was heated to 160 °C, and the system pressure was gradually reduced to 1000 Pa. The reaction was allowed to proceed for 6.5 hours. When the transesterification rate reached 90.9%, the heating was stopped, and the transesterification reaction was terminated to obtain BHBT. The mass ratio of zinc acetate to BHET was 0.003:1, and the mass ratio of butanediol to BHET was 2:1.

[0079] Under esterification reaction conditions, succinic acid (0.5 mol), butanediol (0.75 mol), and tetrabutyl titanate (0.295 g) were added to a three-necked flask equipped with a mechanical stirrer. The temperature was raised to 160 °C and maintained for 2 hours. Then the temperature was raised to 220 °C and the reaction time was 3.5 hours. The esterification rate was 95%. The heating was turned off to end the esterification reaction and obtain PBS oligomers.

[0080] The products of the transesterification reaction and the esterification reaction were mixed at a molar ratio of 70:30, with a total amount of 80g. Isopropoxyneodymium (0.059g) was added. Under pre-condensation conditions, the temperature was raised to 220°C and the reaction was carried out under low vacuum (1000Pa) for 1 hour. The temperature was gradually raised to 230°C and the reaction was carried out for 1 hour. Finally, the condensation was carried out under high vacuum conditions (<150Pa) at a reaction temperature of 250°C for 4 hours to obtain the regenerated fatty aromatic copolyester PBST-3.

[0081] Example 4

[0082] The procedure was carried out according to Example 1, except that 0.4 g of zinc acetate was added to obtain the regenerated fatty aromatic copolyester PBST-4, in which the transesterification rate of BHET was increased to 95.6%.

[0083] Example 5

[0084] The procedure was carried out according to Example 1, except that the mass ratio of butanediol to BHET was increased to 5:1 to obtain the regenerated fatty aromatic copolyester PBST-5, in which the transesterification rate of BHET was increased to 97.5%.

[0085] Example 6

[0086] The BHET preparation method is as described in Example 1.

[0087] Under a nitrogen atmosphere, BHET (0.394 mol), butanediol (2.22 mol), and zinc acetate (0.3 g) were added to a three-necked flask equipped with a mechanical stirrer. The mixture was heated to 160 °C, and the system pressure was gradually reduced to 1000 Pa. The reaction time was 6 hours, and the transesterification rate reached 91.8%, yielding BHBT. The mass ratio of zinc acetate to BHET was 0.003:1, and the mass ratio of butanediol to BHET was 2:1.

[0088] Adipic acid (0.7 mol), butanediol (0.91 mol), and tetrabutyl titanate (0.25 g) were added to a three-necked flask equipped with a mechanical stirrer. The temperature was raised to 160 °C and maintained for 2.5 hours. Then the temperature was raised to 190 °C and the reaction time was 3.5 hours. The esterification rate was 95%. The esterification reaction was then terminated to obtain PBS oligomers.

[0089] The products of the transesterification reaction and the esterification reaction were mixed in a molar ratio of 50:50, with a total amount of 150g. Dysprosium acetylacetone (0.1g) was added, and the temperature was gradually increased to 190℃. The reaction was carried out under low vacuum (1000Pa) for 2 hours, and then gradually increased to 220℃ for 1.5 hours. Under high vacuum (150Pa), the reaction temperature was 230-260℃ and the reaction time was 3 hours to obtain the regenerated fatty aromatic copolyester PBAT-1.

[0090] Example 7

[0091] The BHET preparation method is as described in Example 1.

[0092] Under a nitrogen atmosphere, BHET (0.394 mol), butanediol (2.22 mol), and zinc acetate (0.3 g) were added to a three-necked flask equipped with a mechanical stirrer. The mixture was heated to 160 °C, and then the system pressure was reduced to 1000 Pa. The reaction time was 6 hours, and the transesterification rate reached 92.5%, yielding BHBT. The mass ratio of zinc acetate to BHET was 0.003:1, and the mass ratio of butanediol to BHET was 2:1.

[0093] Sebacic acid (0.7 mol), butanediol (0.91 mol), and tetrabutyl titanate (0.25 g) were added to a three-necked flask equipped with a mechanical stirrer. The temperature was raised to 160 °C and maintained for 2 hours. Then the temperature was raised to 190 °C and the reaction time was 2 hours. The esterification rate was 95%. The esterification reaction was then stopped to obtain PBS oligomers.

[0094] The products of the transesterification reaction and the esterification reaction were mixed in a molar ratio of 50:50, with a total amount of 200g. A rare earth catalyst (0.14g) was added, and the temperature was raised to 190℃. The reaction was carried out under low vacuum (1000Pa) for 2 hours. The temperature was then raised to 230℃ and the reaction time was 2 hours. Under high vacuum (150Pa), the reaction temperature was 260℃ and the reaction time was 3 hours to obtain the regenerated fatty aromatic copolyester PBSeT-1.

[0095] Example 8

[0096] The BHET preparation method is as described in Example 1.

[0097] Under a nitrogen atmosphere, BHET (0.394 mol), butanediol (2.22 mol), and zinc acetate (0.3 g) were added to a three-necked flask equipped with a mechanical stirrer. The mixture was heated to 160 °C, and then the system pressure was reduced to 1000 Pa. The reaction time was 6 hours, and the transesterification rate reached 92.0%, yielding BHBT. The mass ratio of zinc acetate to BHET was 0.003:1, and the mass ratio of butanediol to BHET was 2:1.

[0098] Add 0.7 mol of dodecanoic acid, 0.91 mol of butanediol, and 0.25 g of tetrabutyl titanate to a three-necked flask equipped with a mechanical stirrer. Heat to 160 °C and maintain for 2 hours. Then heat to 190 °C and react for 2.5 hours. The esterification rate is 95%. Stop the esterification reaction to obtain PBS oligomers.

[0099] The products of the transesterification reaction and the esterification reaction were mixed in a molar ratio of 50:50, with a total amount of 250g. A rare earth catalyst (0.16g) was added, and the temperature was raised to 190℃ and the reaction was carried out under low vacuum (1000Pa) for 2 hours. The temperature was then raised to 230℃ and the reaction was carried out for 2 hours. Finally, under high vacuum (150Pa), the reaction temperature was 255℃ and the reaction time was 6 hours to obtain the regenerated fatty aromatic copolyester PBDoT-1.

[0100] Example 9

[0101] The method of Example 1 was followed, except that the transesterification reaction was carried out for 1 hour, and the transesterification reaction was stopped after the transesterification rate reached 60.5% to obtain regenerated fatty aromatic copolyester PBST-6.

[0102] Example 10

[0103] The method of Example 1 was followed, except that the esterification reaction was carried out for 1.5 hours, and the esterification reaction was stopped after the esterification rate reached 80.2% to obtain regenerated fatty aromatic copolyester PBST-7.

[0104] Example 11

[0105] The method of Example 1 was followed, except that the transesterification reaction was carried out for 1.5 hours and stopped after the transesterification rate reached 78.9%, and the esterification reaction was carried out for 1 hour and stopped after the esterification rate reached 75.8%, to obtain regenerated fatty aromatic copolyester PBST-8.

[0106] Example 12

[0107] The method was carried out according to Example 1, except that the temperature of the depolymerization reaction was 196°C, and the resulting bis(dihydroxyethyl) terephthalate (BHET) had a purity of 97.0%, a melting point of 109°C, a color value b = 2.1, and a metal ion content of 37 ppm, ultimately yielding a recycled fatty aromatic copolyester.

[0108] Comparative Example 1

[0109] The method of Example 1 was followed, except that BHET (purity 93wt%, metal ion content 45ppm, catalog number: A57540) purchased from Innochem Reagents was used to conduct the experiment, and the regenerated fatty aromatic copolyester DPBST-1 was obtained.

[0110] Comparative Example 2

[0111] The procedure was carried out according to Example 1, except that no catalyst was added during the transesterification stage and no vacuum was applied, resulting in the regenerated fatty aromatic copolyester DPBST-2.

[0112] Comparative Example 3

[0113] The procedure was carried out according to Example 1, except that it was not mixed with activated carbon and was directly refrigerated. The obtained bis(dihydroxyethyl) terephthalate (BHET) had a purity of 94.3%, a melting point of 109°C, a color value b = 4.5, and a metal ion content of 86 ppm; the obtained recycled fatty aromatic copolyester had a b value of 4.6.

[0114] Test Example 1

[0115] The contents of terephthalic acid segment, fatty acid segment, ethylene glycol segment, and butanediol segment in the biodegradable polyester products (fatty aromatic copolyester PBST) obtained in the above examples and comparative examples are shown in Table 1. The ethylene glycol segment content reflects the degree of reaction in the transesterification stage; the lower the proportion of ethylene glycol segment, the more complete the transesterification stage and the better the effect.

[0116] The test method for the content of each unit in biodegradable polyester products is as follows: dissolve the biodegradable polyester sample in deuterated chloroform and perform nuclear magnetic resonance hydrogen spectrum testing. The molar content of each unit can be obtained by comparing the characteristic peak area integral of each unit.

[0117] Table 1

[0118]

[0119]

[0120] Test Example 2

[0121] The purity of BHBT in the examples and comparative examples was tested, and the test results are shown in Table 2.

[0122] The purity test method for BHBT is as follows: the BHBT oligomers prepared in the above examples and comparative examples are dissolved in methanol, and the molar content of each component is tested by ultra-high performance liquid chromatography to determine the purity of BHBT.

[0123] Table 2

[0124]

[0125]

[0126] Test Example 3

[0127] The fatty aromatic copolyester products obtained in the examples and comparative examples were subjected to performance tests.

[0128] (1) Mechanical property test method of the fatty aromatic copolyester: The fatty aromatic copolyesters prepared in the above examples and comparative examples were respectively made into melt-pressed tablets, and the prepared tablet samples were subjected to mechanical property test. The tensile mechanical properties of these tablet samples, such as tensile strength and elongation at break, were tested according to the method of GB / T1040.2-2006. The test results are shown in Table 3.

[0129] (2) Test method for thermal properties of the fatty aromatic copolyester: The fatty aromatic copolyesters prepared in the above examples and comparative examples were subjected to thermal property tests respectively. The glass transition temperature Tg and melting point Tm of the polymer were tested using a differential scanning calorimeter. The test results are shown in Table 4.

[0130] (3) Method for testing the molecular weight of the fatty aromatic copolyester: The fatty aromatic copolyesters prepared in the above examples and comparative examples were dissolved in tetrahydrofuran, and the number-average and weight-average molecular weights of the polymers were tested by gel permeation chromatography. The test results are shown in Table 4.

[0131] (4) Color test method for the aliphatic aromatic copolyester: According to the test method for polyester color in GB / T 14189-2015, the polyester sample is dried and pulverized, and the color of the sample is tested by an automatic colorimeter. The result is expressed as hunterlab color system b. The higher the b value, the worse the polymer hue.

[0132] Table 3

[0133]

[0134]

[0135] Table 4

[0136] <![CDATA[Mn,10 4 ]]> <![CDATA[Mw,10 4 ]]> Tg (°C) Tm (°C) b value Example 1 2.2 6.3 -12.4 130.7 2.3 Example 2 2.5 7.1 -21.8 —— 2.7 Example 3 3.2 6.9 3.9 179.7 2.9 Example 4 2.8 6.1 -11.2 129.4 2.7 Example 5 2.9 6.8 -12.9 131.3 2.8 Example 6 2.4 6.7 -30.8 125.8 2.9 Example 7 3.0 7.4 -43.8 122.3 2.6 Example 8 2.4 6.9 -50.2 113.5 2.7 Example 9 2.2 6.2 -16.5 121.5 3.2 Example 12 2.0 6.0 -12.2 129.8 3.2 Comparative Example 3 1.8 5.6 -12.0 128.3 4.6

[0137] As can be seen from the results in the tables above, compared with the comparative examples, the embodiments using the technical solution of the present invention have significantly better effects, such as higher molecular weight and better color of the prepared aliphatic aromatic copolyester products.

[0138] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a fatty aromatic copolyester, characterized in that, The method includes: (1) In the presence of an ester exchange catalyst, bis(2-hydroxyethyl) terephthalate was contacted with 1,4-butanediol and subjected to an ester exchange reaction. (2) In the presence of an esterification catalyst, HOOC-R-COOH is contacted with 1,4-butanediol and esterification reaction is carried out. (3) In the presence of a polycondensation catalyst, the product obtained from the transesterification reaction in step (1) and the product obtained from the esterification reaction in step (2) are brought into contact and polycondensation reaction is carried out. The purity of the bis(2-hydroxyethyl) terephthalate is greater than 97 wt%, and the metal ion weight content is not greater than 50 ppm. R is selected from C3-C16 alkylene groups.

2. The method according to claim 1, wherein, The transesterification catalyst is selected from metal salts, preferably from at least one of sodium acetate, magnesium acetate, zinc acetate and zinc acetate dihydrate, and more preferably zinc acetate.

3. The method according to claim 1 or 2, wherein, The esterification catalyst is selected from organotitanium compounds, preferably from at least one of tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, titanium glycolate, and titanium acetylacetone oxide, and more preferably tetrabutyl titanate.

4. The method according to any one of claims 1-3, wherein, The polycondensation catalyst is selected from compounds containing rare earth elements, preferably from at least one of lanthanum chloride, lanthanum acetylacetonate, neodymium isopropoxy, dysprosium acetylacetonate, and lanthanum stearate, and more preferably lanthanum acetylacetonate. Preferably, the esterification and transesterification reactions are carried out in the presence of a protective gas; Preferably, the protective gas is selected from nitrogen and / or argon; Preferably, the polycondensation reaction is carried out in the presence of a stabilizer; Preferably, the esterification reaction is stopped when the esterification rate is greater than 90%.

5. The method according to any one of claims 1-4, wherein, Based on the total weight of the bis(2-hydroxyethyl) terephthalate, the amount of the transesterification catalyst is 0.005-0.5 wt%, preferably 0.05-0.4 wt%. Preferably, based on the total weight of the HOOC-R-COOH, the amount of the esterification catalyst is 0.001-0.7 wt%, more preferably 0.04-0.6 wt%. Preferably, based on the total weight of the product obtained from the transesterification reaction in step (1) and the product obtained from the esterification reaction in step (2), the amount of the polycondensation catalyst is 0.001-0.2 wt%, preferably 0.005-0.1 wt%.

6. The method according to any one of claims 1-5, wherein, In step (1), the molar ratio of bis(2-hydroxyethyl) terephthalate and 1,4-butanediol is 1:1-5, preferably 1:1-3; Preferably, in step (2), the molar ratio of HOOC-R-COOH to 1,4-butanediol is 1:1.1-2, more preferably 1:1.1-1.5; Preferably, in step (3), the molar ratio of the product obtained from the transesterification reaction in step (1) to the product obtained from the esterification reaction in step (2) is 1:0.1-3, and more preferably 1:0.3-2.

5.

7. The method according to any one of claims 1-6, wherein, The temperature of the transesterification reaction is 120-180℃, preferably 140-180℃; the time is 2-8h, preferably 4-6h.

8. The method according to any one of claims 1-7, wherein, The esterification reaction is carried out at a temperature of 140-240℃, preferably 160-230℃, and for a time of 2-8 hours, preferably 4-8 hours. Preferably, the temperature of the polycondensation reaction is 190-280℃, more preferably 200-260℃; and the time is 2-10h, more preferably 2-8h.

9. The fatty aromatic copolyester product prepared by the method according to any one of claims 1-8.

10. A fatty aromatic copolyester, characterized in that, The Mn content of this fatty aromatic copolyester is not less than 2×10⁻⁶. 4 g / mol, Mw not less than 5 × 10 4 g / mol, b value not greater than 5.

11. The application of the method according to any one of claims 1-8 in improving at least one of the number-average molecular weight, weight-average molecular weight, and hue of a fatty aromatic copolyester.

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