A method for continuous preparation of aliphatic aromatic copolyesters

Abstract

This invention relates to the field of polymer material preparation and discloses a method for the continuous preparation of aliphatic aromatic copolyesters. The method includes: (1) esterifying components a and b in a stirred vertical esterification reactor; (2) esterifying components b and c in a stirred vertical esterification reactor; (3) introducing the products of steps (1) and (2) into a stirred vertical esterification reactor for further esterification; (4) introducing the product of step (3) into a pre-polymerization reactor for pre-polymerization; (5) introducing the product from the pre-polymerization reactor into a final polymerization reactor for final polymerization; and (6) introducing the product from the final polymerization reactor into a thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20. The method for the continuous preparation of aliphatic aromatic copolyesters according to this invention not only enables the continuous preparation of aliphatic aromatic copolyesters but also produces aliphatic aromatic copolyesters with high molecular weight and significantly better tensile mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polymer material preparation, and specifically to a method for the continuous preparation of aliphatic aromatic copolyesters. Background Technology

[0002] Polymer materials have been widely used in our daily lives, becoming indispensable. However, with the widespread use of single-use plastic products, large quantities of difficult-to-recycle plastics are directly discarded into the environment, creating alarming phenomena such as white pollution and microplastics. This harms the living environment for both humans and the natural world, drawing widespread attention from countries around the world. There are two main approaches to solving this problem: one is to recycle and reuse these polymer materials, and the other is to use biodegradable materials to replace non-degradable single-use plastic products.

[0003] Currently, the main commercially available biodegradable material used as packaging film and bag material is fatty aromatic copolyester (butylene terephthalate-adipate-co-butylene glycol) (PBAT), with BASF as an example. The main production process of this product is "esterification-polymerization-chain extension". Because the organic titanium catalyst used in the PBAT preparation process is difficult to produce high molecular weight products, if it is used as a membrane bag material, isocyanate chain extension is required to achieve the effect of melt thickening and increase the molecular weight to a certain extent to meet the processing performance requirements. However, isocyanate molecules used as chain extenders have a certain degree of toxicity, which limits the application of PBAT.

[0004] CN102558515A discloses a method for the continuous preparation of biodegradable plastics, which mainly includes the following steps: a slurry prepared from one or more diacids and one or more diols is continuously added to a first esterification reactor for esterification reaction to obtain homopolymer or copolyester oligomers. The obtained esterified product is then further esterified in a second esterification reactor to obtain another esterified product. The obtained esterified product is continuously fed into a first polycondensation reactor for polycondensation reaction, where small molecules are removed under low vacuum conditions to obtain a prepolymer. This prepolymer is continuously fed into a second polycondensation reactor under high vacuum for condensation polymerization to remove small molecules. The obtained polymer is then continuously polymerized in a final polycondensation reactor with a thickening effect to obtain high molecular weight biodegradable plastic chips with a melt index of less than 5. However, the technical solution of this patent application has a drawback: the reaction process is difficult to effectively suppress the side reaction of butanediol cyclization to form tetrahydrofuran during the esterification stage, resulting in insufficient esterification and a low esterification rate. Increasing the esterification rate requires consuming a large amount of butanediol, and the low vacuum esterification process is prone to mist entrainment and pipe blockage. In addition, the polycondensation stage of this process has poor thermal stability, a narrow reaction window, and the product is prone to yellowing, making it difficult to stably and continuously prepare polymer products with low melt index.

[0005] CN102453237A discloses a method for preparing a biodegradable polyester, comprising the following steps: (1) under first esterification reaction conditions, reacting component a and component b in a first reactor in the presence of a first catalyst and a second catalyst to obtain a first reaction mixture, wherein the molar ratio of component a to component b is 1:0.8-3; (2) under second esterification reaction conditions, reacting component b and component c in a second reactor in the presence of a first catalyst and a second catalyst to obtain a second reaction mixture, wherein the molar ratio of component c to component b is 1:0.8-3; (3) under polycondensation reaction conditions, reacting the first reaction mixture and the second reaction mixture in the presence of a third catalyst; wherein component a is an aromatic diacid and / or an anhydride of an aromatic diacid, component b is an aliphatic diol, and component c is at least one selected from aliphatic diacid, an anhydride of an aliphatic diacid, alicyclic diacid, and an anhydride of an alicyclic diacid; the first catalyst is an oxide selected from M, M(OR1). n and M(-OOCR2) n At least one compound or a mixture thereof, wherein M is titanium, antimony or zinc, n is the valence state of M, and R1 is C1-C2. 10 Alkyl group, R2 is C1-C 30 The first catalyst is an alkyl group; the second catalyst is at least one organotin compound; the third catalyst is at least one compound with the chemical formula RE(R3)3, wherein RE is a rare earth metal element, R3 is at least one selected from halogen, alkoxy, aryloxy, acetylacetonyl and R4COO- group, and R4 is a C1-C2 group. 30 The alkyl group. However, the patent application provides a method for the intermittent preparation of biodegradable polyester, which is a process for small-scale laboratory testing. In the industrial continuous polymerization process, necessary adjustments are required for specific equipment and process conditions. Summary of the Invention

[0006] This invention provides a method for the continuous preparation of aliphatic aromatic copolyesters, which adopts a process route of "diesterization at atmospheric pressure esterification - pre-condensation - final condensation - liquid phase thickening" to prepare high molecular weight aliphatic aromatic copolyesters.

[0007] The technical solution of this invention is a further optimization based on the prior patent application CN102453237A. The technical solution in patent application CN102453237A is a laboratory-scale pilot-scale process. Intermittent preparation of aliphatic aromatic copolyesters can produce high-molecular-weight biodegradable polyesters. However, in the pilot-scale continuous preparation of aliphatic aromatic copolyesters, product instability and difficulty in achieving the required melt flow index were observed. Through further research, the inventors of this invention, by selecting the type of reactor for each different reaction stage and precisely controlling the timing of reaction termination in each reactor, achieved better stability in the product obtained from the continuous preparation process, thus completing this invention.

[0008] Specifically, the present invention provides a method for the continuous preparation of aliphatic aromatic copolyesters, the method comprising the following steps:

[0009] (1) In the presence of a first catalyst and / or a second catalyst, component a and component b are subjected to an esterification reaction in a first esterification vessel, which is a vertical esterification reactor with stirring. When the esterification rate in the first esterification vessel reaches 90-95%, the next reaction step is introduced.

[0010] (2) In the presence of a first catalyst and / or a second catalyst, component b and component c are subjected to an esterification reaction in a second esterification reactor, which is a vertical esterification reactor with stirring. When the esterification rate in the second esterification reactor reaches 90-95%, the next reaction step is introduced.

[0011] (3) In the presence of a third catalyst, the products of the first esterification vessel and the second esterification vessel are introduced into the third esterification vessel for esterification reaction. The third esterification vessel is a vertical esterification reactor with stirring. When the esterification rate in the third esterification vessel reaches more than 98%, the next reaction step is introduced.

[0012] (4) The product of the third esterification reactor is introduced into the prepolymerization reactor for prepolymerization. The prepolymerization reactor is a vertical stirred tank. When the degree of polymerization reaches 20-30, the product is introduced into the next reaction step.

[0013] (5) The product of the prepolymerization reactor is introduced into the final polymerization reactor for final polymerization. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. When the degree of polymerization reaches 100-150, the product is introduced into the next reaction step.

[0014] (6) The product from the final polycondensation reactor is introduced into a thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20. The thickening reactor is a biaxial horizontal liquid phase thickening reactor.

[0015] Wherein, component a is an aromatic dicarboxylic acid, component b is an aliphatic diol, and component c is one or more of an aliphatic dicarboxylic acid and / or its anhydride;

[0016] The first catalyst is an oxide selected from M, M(OR1). n and M(-OOCR2) n At least one compound or a mixture thereof, wherein M is titanium, antimony or zinc, n is the valence state of M, and R1 is C1-C2. 10 Alkyl group, R2 is C1-C 30 Alkyl groups;

[0017] The second catalyst is at least one organotin compound;

[0018] The third catalyst is at least one compound with the chemical formula RE(R3)3, wherein RE is a rare earth metal element, R3 is at least one selected from halogen, alkoxy, aryloxy, acetylacetonyl, and R4COO- group, and R4 is a C1-C2 group. 30 Alkyl groups.

[0019] In the continuous preparation method of aliphatic aromatic copolyesters described in this invention, the esterification reactions in steps (1) to (3) are carried out in a vertical esterification reactor with stirring, and the pre-condensation in step (4) is carried out in a vertical stirred tank to facilitate better and more uniform mixing of materials, more thorough esterification, and reduced mist entrainment. The final condensation in step (5) is carried out in a horizontal cage-type film-forming final condensation reactor, and the melt thickening in step (6) is carried out in a biaxial horizontal liquid-phase thickening reactor to facilitate the full devolatilization of high-viscosity materials and prepare a high-viscosity, low-melt-index resin product. Therefore, the continuous preparation method of aliphatic aromatic copolyesters described in this invention can achieve continuous preparation of high-molecular-weight aliphatic aromatic copolyesters with good product stability. In particular, when the first catalyst is zinc acetate, the second catalyst is tin laurate, and the third catalyst is yttrium stearate, the performance of the prepared aliphatic aromatic copolyester is even better. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] 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.

[0022] The method for continuous preparation of aliphatic aromatic copolyesters according to the present invention includes the following steps:

[0023] (1) In the presence of a first catalyst and / or a second catalyst, component a and component b are subjected to an esterification reaction in a first esterification vessel, which is a vertical esterification reactor with stirring. When the esterification rate in the first esterification vessel reaches 90-95%, the next reaction step is introduced.

[0024] (2) In the presence of a first catalyst and / or a second catalyst, component b and component c are subjected to an esterification reaction in a second esterification reactor, which is a vertical esterification reactor with stirring. When the esterification rate in the second esterification reactor reaches 90-95%, the next reaction step is introduced.

[0025] (3) In the presence of a third catalyst, the products of the first esterification vessel and the second esterification vessel are introduced into the third esterification vessel for esterification reaction. The third esterification vessel is a vertical esterification reactor with stirring. When the esterification rate in the third esterification vessel reaches more than 98%, the next reaction step is introduced.

[0026] (4) The product of the third esterification reactor is introduced into the prepolymerization reactor for prepolymerization. The prepolymerization reactor is a vertical stirred tank. When the degree of polymerization reaches 20-30, the product is introduced into the next reaction step.

[0027] (5) The product of the prepolymerization reactor is introduced into the final polymerization reactor for final polymerization. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. When the degree of polymerization reaches 100-150, the product is introduced into the next reaction step.

[0028] (6) The product from the final polycondensation reactor is introduced into a thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20. The thickening reactor is a biaxial horizontal liquid phase thickening reactor.

[0029] In this invention, the first esterification vessel, the second esterification vessel, and the third esterification vessel are all vertical esterification reactors equipped with stirring. Their structural feature is that the reactor is divided into inner and outer chambers, allowing for thorough mixing of reactants, resulting in more complete esterification and preventing mist entrainment. The vertical esterification reactor with stirring can be a commercially available product, such as the patented product ZL201920053188.4 manufactured by Yangzhou Huitong Chemical Technology Co., Ltd., or the patented product ZL201420697931.7 manufactured by Wuxi Xingsheng New Material Technology Co., Ltd.

[0030] In this invention, the prepolymerization reactor is a vertical stirred tank, characterized by a multi-zone structure. The vertical stirred tank can be a commercially available product, such as the reaction apparatus of the patented product ZL201220466771.1 manufactured by China Kunlun Engineering Corporation.

[0031] In this invention, the final polycondensation reactor is a horizontal cage-type film-forming final polycondensation reactor, characterized by a disc agitator that increases the devolatilization area. The horizontal cage-type film-forming final polycondensation reactor can be a commercially available product, such as the reaction apparatus of the patented product ZL202021066179.8 from China Petroleum & Chemical Corporation.

[0032] In this invention, the thickening reactor is a biaxial horizontal liquid-phase thickening reactor, characterized by its shaftless design, self-cleaning function, larger reaction area, and smoother melt flow. The biaxial horizontal liquid-phase thickening reactor can be a commercially available product, such as the LSPLINETM reactor manufactured by Yangzhou Huite Technology Co., Ltd.

[0033] In step (1), when the esterification rate in the first esterification vessel reaches 90-95%, the next reaction step is introduced. In this invention, the "esterification rate" is detected by acid-base titration. Here, "next reaction step" refers to the esterification reaction in step (3).

[0034] In step (2), when the esterification rate in the second esterification vessel reaches 90-95%, the next reaction step is introduced. Here, "next reaction step" refers to the esterification reaction in step (3).

[0035] In step (3), when the esterification rate in the third esterification reactor reaches 98% or more, the next reaction step is introduced. Here, "next reaction step" refers to the pre-condensation reaction in step (4).

[0036] In step (4), when the degree of polymerization reaches 20-30, the next reaction step is initiated. In this invention, the method for detecting the "degree of polymerization" is nuclear magnetic resonance hydrogen spectroscopy (NMR spectroscopy). 1 (HNMR). Here, "next reaction step" refers to the final condensation reaction in step (5).

[0037] In step (5), when the degree of polymerization reaches 100-150, the next reaction step is introduced. Here, "next reaction step" refers to the melt thickening reaction in step (6).

[0038] In step (6), the melt thickening process causes the melt index of the reaction product to reach 1-20. Here, "melt index" refers to the melt mass flow rate per 10 minutes at 190°C and 2.16 kg load pressure.

[0039] In this invention, component a is an aromatic dicarboxylic acid with the general chemical formula HOOC-Ar-COOH, wherein Ar can be a group having at least one benzene ring, a naphthalene ring, and an anthracene ring, and preferably, Ar is an aryl group as follows:

[0040]

[0041] Among them, R5, R6, R7, R8, R9 and R 10 Each of the following can be independently hydrogen, C1-C4 alkyl, F, Cl, -NO2, -CN, or -OR 11 , where R 11 It is a C1-C4 alkyl group.

[0042] In the most preferred embodiment, component a is terephthalic acid.

[0043] In this invention, component b is an aliphatic diol. The general chemical formula of the aliphatic diol can be HO-R. 12 -OH, where R 12 It can be C 2-10 alkyl groups, and R 12 It can be a straight-chain alkyl group or a branched alkyl group. Preferably, component b is at least one selected from ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptahydrate, and octanediol.

[0044] In the most preferred embodiment, component b is butanediol, which may be, for example, 1,4-butanediol.

[0045] In this invention, component c is at least one of aliphatic dicarboxylic acid, an anhydride of aliphatic dicarboxylic acid, alicyclic dicarboxylic acid, and an anhydride of alicyclic dicarboxylic acid.

[0046] The general chemical formula of the aliphatic dicarboxylic acid can be HOOC-R. 13 -COOH, where R 13 It can be a chemical bond or C 1-12 alkyl groups, and the C 1-12 The alkyl group can be a straight-chain alkyl group or a branched alkyl group. Preferably, R 13 It is a C1-C8 alkyl group, that is, the aliphatic dicarboxylic acid is C3-C6. 10 Aliphatic dicarboxylic acids.

[0047] The alicyclic dicarboxylic acid can have the general chemical formula of a dicarboxylic acid having at least one alicyclic ring. Preferably, the alicyclic dicarboxylic acid is C5-C6. 10 Alicyclic dicarboxylic acids.

[0048] In the most preferred embodiment, component c is succinic acid.

[0049] According to a preferred embodiment of the present invention, component a is terephthalic acid, component b is 1,4-butanediol, and component c is succinic acid. The fatty aromatic copolyester prepared according to this preferred embodiment has a high molecular weight and good tensile mechanical properties.

[0050] In this invention, the first catalyst is an oxide selected from M, M(OR1). n and M(-OOCR2) n At least one compound or a mixture thereof, wherein M is titanium, antimony or zinc, n is the valence state of M, and R1 is C1-C2. 10 Alkyl group, R2 is C1-C 30 The alkyl group. To achieve a high molecular weight and improve the tensile mechanical properties of the final prepared aliphatic aromatic copolyester, the first catalyst is preferably at least one selected from alkoxytitanium, antimony acetate, zinc acetate, zinc oxide, antimony oxide, and titanium oxide. Most preferably, the first catalyst is zinc acetate.

[0051] In this invention, the second catalyst is at least one organotin compound. To ensure that the final prepared aliphatic aromatic copolyester has a high molecular weight and improves its tensile mechanical properties, the second catalyst is preferably selected from at least one of tin laurylate, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethyltin oxide, hexacyclohexylditin oxide, di(dodecyl)tin oxide, triethylhydroxytin, triphenylhydroxytin, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin chloride, dibutyltin sulfide, butyltin hydroxyoxide, methylstannic acid, ethylstannic acid, and butylstannic acid. Most preferably, the second catalyst is selected from tin laurylate.

[0052] In this invention, the third catalyst is at least one compound with the chemical formula RE(R3)3, wherein RE is a rare earth metal element, R3 is at least one selected from halogen, alkoxy, aryloxy, acetylacetonyl, and R4COO- group, and R4 is a C1-C2 group. 30 Alkyl groups. To achieve a high molecular weight in the final prepared aliphatic aromatic copolyester and improve its tensile mechanical properties, preferably, in the third catalyst, RE is selected from yttrium, lanthanum, cerium, praseodymium, neodymium, terbium, ytterbium, dysprosium, samarium, or scandium; the halogen is chlorine or bromine; the alkoxy group is a C3-C6 alkoxy group; the aryloxy group is an aryloxy group comprising at least one benzene ring and / or a naphthalene ring; and R4 in the R4COO- group is a C1-C6 alkoxy group. 20 Alkyl groups. In the most preferred embodiment, the third catalyst is yttrium stearate.

[0053] According to a preferred embodiment of the present invention, the first catalyst is zinc acetate, the second catalyst is selected from tin laurylate, and the third catalyst is yttrium stearate. The fatty aromatic copolyester prepared according to this preferred embodiment has a high molecular weight and good tensile mechanical properties.

[0054] According to the method provided by the present invention, in step (1), preferably, the esterification reaction in the first esterification vessel is carried out under normal pressure or slightly negative pressure, and the reaction temperature is 180-250°C.

[0055] According to the method provided by the present invention, in step (1), preferably, the molar ratio of the added amount of component a to component b is 1:0.8-3, more preferably 1:1-2.5, and even more preferably 1:1.2-2.5.

[0056] According to the method provided by the present invention, in step (2), preferably, the esterification reaction in the second esterification vessel is carried out under normal pressure or slightly negative pressure, and the reaction temperature is 150-250°C.

[0057] According to the method provided by the present invention, in step (2), preferably, the molar ratio of the amount of component c to component b added is 1:0.8-3, more preferably 1:1-2.5, and even more preferably 1:1.2-2.5.

[0058] According to the method provided by the present invention, preferably, the molar ratio of the added component a in step (1) and the added component c in step (2) is 1:0.01-100, more preferably 1:0.3-3, and even more preferably 1:0.5-2.

[0059] According to the method provided by the present invention, in step (3), preferably, the esterification reaction in the third esterification vessel is carried out under normal pressure and the reaction temperature is 230-235°C.

[0060] According to the method provided by the present invention, in step (4), preferably, the pre-polymerization is carried out under an absolute pressure of 600-1000 Pa and the reaction temperature is 190-250 °C.

[0061] According to the method provided by the present invention, in step (5), preferably, the final polycondensation is carried out at 200-300°C and a vacuum degree ≤300Pa (e.g., 50-300Pa). In the present invention, the vacuum degree refers to absolute pressure.

[0062] According to the method provided by the present invention, in step (6), preferably, the melt thickening is carried out at 200-250°C and a vacuum degree of 50-200Pa.

[0063] In this invention, the method for continuous preparation of fatty aromatic copolyesters may further include: sequentially underwater pelletizing, drying, and packaging the product from the thickening reactor.

[0064] The present invention will be further described below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0065] The reaction apparatus in the following embodiments includes a first esterification reactor, a second esterification reactor, a third esterification reactor, a prepolymerization reactor, a final polymerization reactor, and a thickening reactor. The first esterification reactor, the second esterification reactor, and the third esterification reactor are all vertical esterification reactors with stirring. The prepolymerization reactor is a vertical stirred reactor. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. The thickening reactor is a biaxial horizontal liquid-phase thickening reactor.

[0066] Example 1

[0067] This embodiment is used in the method for continuous preparation of aliphatic aromatic copolyesters described in this invention.

[0068] (1) Prepare a PTA slurry by mixing 350 kg / h terephthalic acid with 285 kg / h 1,4-butanediol and continuously feed it into the first esterification reactor. Add 0.2 kg / h zinc acetate and 0.1 kg / h tin laurylate and carry out the esterification reaction at atmospheric pressure and temperature of 220°C until the esterification rate reaches 95%.

[0069] (2) Prepare an SA slurry by mixing 300 kg / h succinic acid with 350 kg / h 1,4-butanediol and continuously feed it into the second esterification reactor. Add 0.2 kg / h zinc acetate and 0.1 kg / h tin laurylate and carry out the esterification reaction at atmospheric pressure and 200°C until the esterification rate reaches 95%.

[0070] (3) The products from the first and second esterification reactors are simultaneously introduced into the third esterification reactor, and 0.5 g / h of yttrium stearate is injected at the same time. The esterification reaction is carried out at atmospheric pressure and temperature of 230°C until the esterification rate reaches 98%.

[0071] (4) The product from the third esterification reactor is introduced into the prepolymerization reactor and prepolymerized for 2 hours at an absolute pressure of 1 kPa and a temperature of 235°C. The degree of polymerization of the product reaches 25.

[0072] (5) The product from the prepolymerization reactor is introduced into the final polymerization reactor and subjected to final polymerization for 5 hours at an absolute pressure of 150 Pa and a temperature of 235 °C. The degree of polymerization of the product reaches 120.

[0073] (6) The product from the final polycondensation reactor was introduced into the thickening reactor and the melt thickening reaction was carried out at an absolute pressure of 100 Pa and a temperature of 225 °C for 1.5 h. The resulting poly(butylene terephthalate) ester (PBST) was subjected to melt cooling and granulation. The melt index of the polymer product (190 °C, 2.16 kg) was 2.5 g / 10 min.

[0074] Example 2

[0075] This embodiment is used in the method for continuous preparation of aliphatic aromatic copolyesters described in this invention.

[0076] (1) Prepare a PTA slurry by mixing 350 kg / h terephthalic acid with 285 kg / h 1,4-butanediol and continuously feed it into the first esterification reactor. Add 0.2 kg / h zinc acetate and 0.1 kg / h tin laurylate and carry out the esterification reaction at atmospheric pressure and temperature of 220°C until the esterification rate reaches 95%.

[0077] (2) Prepare an SA slurry by mixing 269 kg / h succinic acid with 350 kg / h 1,4-butanediol and continuously feed it into the second esterification reactor. Add 0.22 kg / h zinc acetate and 0.12 kg / h tin laurylate and carry out the esterification reaction at atmospheric pressure and 200°C until the esterification rate reaches 95%.

[0078] (3) The products from the first and second esterification reactors are simultaneously introduced into the third esterification reactor, and 0.5 g / h of yttrium stearate is injected at the same time. The esterification reaction is carried out at atmospheric pressure and temperature of 230°C until the esterification rate reaches 98%.

[0079] (4) The product from the third esterification reactor was introduced into the prepolymerization reactor and prepolymerized for 2 hours at an absolute pressure of 1 kPa and a temperature of 235 °C. The degree of polymerization of the product reached 22.

[0080] (5) The prepolymerization product was introduced into the final polymerization kettle and subjected to final polymerization for 5 hours at an absolute pressure of 150 Pa and a temperature of 235 °C. The degree of polymerization of the product reached 110.

[0081] (6) The product from the final polycondensation reactor was introduced into the thickening reactor and the melt thickening reaction was carried out at an absolute pressure of 100 Pa and a temperature of 225 °C for 1.5 h. The resulting poly(butylene terephthalate) ester (PBST) was subjected to melt cooling and granulation. The melt index of the polymer product (190 °C, 2.16 kg) was 2.8 g / 10 min.

[0082] Example 3

[0083] This embodiment is used in the method for continuous preparation of aliphatic aromatic copolyesters described in this invention.

[0084] (1) Prepare a PTA slurry by mixing 350 kg / h terephthalic acid with 285 kg / h 1,4-butanediol and continuously feed it into the first esterification reactor. Add 0.2 kg / h zinc acetate and 0.1 kg / h tin laurylate and carry out the esterification reaction at atmospheric pressure and temperature of 220°C until the esterification rate reaches 95%.

[0085] (2) Prepare an SA slurry by mixing 269 kg / h succinic acid with 350 kg / h 1,4-butanediol and continuously feed it into the second esterification reactor. Add 0.22 kg / h zinc acetate and 0.12 kg / h tin laurylate and carry out the esterification reaction at atmospheric pressure and 200°C until the esterification rate reaches 95%.

[0086] (3) The products from the first and second esterification reactors are simultaneously introduced into the third esterification reactor, and 0.5 g / h of yttrium stearate is injected at the same time. The esterification reaction is carried out at atmospheric pressure and temperature of 230°C until the esterification rate reaches 98%.

[0087] (4) The product from the third esterification reactor was introduced into the prepolymerization reactor and prepolymerized for 2 hours at an absolute pressure of 1 kPa and a temperature of 235 °C. The degree of polymerization of the product reached 28.

[0088] (5) The prepolymerization product was introduced into the final polymerization kettle and subjected to final polymerization for 5 hours at an absolute pressure of 150 Pa and a temperature of 235 °C. The degree of polymerization of the product reached 140.

[0089] (6) The product from the final polycondensation reactor was introduced into the thickening reactor and the melt thickening reaction was carried out at an absolute pressure of 100 Pa and a temperature of 225 °C for 1.5 h. The resulting poly(butylene terephthalate) ester (PBST) was subjected to melt cooling and granulation. The melt index of the polymer product (190 °C, 2.16 kg) was 2.7 g / 10 min.

[0090] Example 4

[0091] PBST was prepared according to the method of Example 1, except that in steps (1) and (2), the same amount of tetrabutyl titanate was used instead of zinc acetate, and the melt index of the polymer product (190°C, 2.16 kg) was 3.8 g / 10 min.

[0092] Example 5

[0093] PBST was prepared according to the method of Example 1, except that in steps (1) and (2), the same amount of dibutyltin oxide was used instead of tin laurate, and the melt index (190°C, 2.16 kg) of the polymer product was 3.7 g / 10 min.

[0094] Example 6

[0095] PBST was prepared according to the method of Example 1, except that in step (3), lanthanum stearate was used instead of yttrium stearate in the same molar amount, and the melt index of the polymer product (190°C, 2.16 kg) was 3.6 g / 10 min.

[0096] Comparative Example 1

[0097] PBST was prepared according to the method in Example 1, except that both the final polycondensation reactor and the thickening reactor were vertical stirred tanks, and the melt index of the obtained polymer product (190°C, 2.16 kg) was 15.0 g / 10 min.

[0098] Test case

[0099] The weight-average molecular weight of the polymers prepared in Examples 1-6 and Comparative Example 1 was determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as solvent on a Waters-208 instrument (with a Waters 2410RI detector, flow rate of 1.5 ml / min, 30 °C). The weight-average molecular weight was calibrated with styrene standard.

[0100] The tensile mechanical properties, such as elongation at break and tensile strength at break, of the polymers prepared in Examples 1-6 and Comparative Example 1 were tested according to the method of ASTM D638-03.

[0101] Table 1

[0102]

[0103] As can be seen from the results in Table 1, the method for continuous preparation of aliphatic aromatic copolyesters according to the present invention can not only achieve continuous preparation of aliphatic aromatic copolyesters, but also produce aliphatic aromatic copolyesters with high molecular weight and significantly better tensile mechanical properties.

[0104] 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 the continuous preparation of aliphatic aromatic copolyesters, characterized in that, The method includes the following steps: (1) In the presence of the first catalyst and the second catalyst, component a and component b are subjected to esterification reaction in the first esterification vessel, which is a vertical esterification reactor with stirring. When the esterification rate in the first esterification vessel reaches 90-95%, the next reaction step is introduced. (2) In the presence of the first catalyst and the second catalyst, component b and component c are subjected to esterification reaction in the second esterification vessel, which is a vertical esterification reactor with stirring. When the esterification rate in the second esterification vessel reaches 90-95%, the next reaction step is introduced. (3) In the presence of a third catalyst, the products of the first esterification vessel and the second esterification vessel are introduced into the third esterification vessel for esterification reaction. The third esterification vessel is a vertical esterification reactor with stirring. When the esterification rate in the third esterification vessel reaches more than 98%, the next reaction step is introduced. (4) The product of the third esterification reactor is introduced into the prepolymerization reactor for prepolymerization. The prepolymerization reactor is a vertical stirred tank. When the degree of polymerization reaches 20-30, the product is introduced into the next reaction step. (5) The product of the prepolymerization reactor is introduced into the final polymerization reactor for final polymerization. The final polymerization reactor is a horizontal cage-type film-forming final polymerization reactor. When the degree of polymerization reaches 100-150, the product is introduced into the next reaction step. (6) The product from the final polycondensation reactor is introduced into the thickening reactor for melt thickening, so that the melt index of the reaction product reaches 1-20 g / 10 min. The test conditions are 190 °C and 2.16 kg. The thickening reactor is a reaction device of model LSPLINE™. Wherein, component a is terephthalic acid, component b is 1,4-butanediol, and component c is succinic acid; The first catalyst is zinc acetate; The second catalyst is tin lauryl sulfate; The third catalyst is yttrium stearate.

2. The method according to claim 1, characterized in that, In step (1), the esterification reaction in the first esterification vessel is carried out under normal pressure and the reaction temperature is 180-250℃.

3. The method according to claim 1, characterized in that, In step (1), the molar ratio of the amount of component a to the amount of component b added is 1:0.8-3.

4. The method according to claim 1 or 2, characterized in that, In step (2), the esterification reaction in the second esterification vessel is carried out under normal pressure and the reaction temperature is 150-250℃.

5. The method according to claim 1 or 2, characterized in that, In step (2), the molar ratio of the amount of component c to the amount of component b added is 1:0.8-3.

6. The method according to claim 1 or 2, characterized in that, The molar ratio of the amount of component a in step (1) to the amount of component c in step (2) is 1:0.01-100.

7. The method according to claim 1 or 2, characterized in that, In step (3), the esterification reaction in the third esterification vessel is carried out under normal pressure and the reaction temperature is 230-235℃.

8. The method according to claim 1 or 2, characterized in that, In step (4), the prepolymerization is carried out under an absolute pressure of 600-1000 Pa and a reaction temperature of 190-250 °C.

9. The method according to claim 1 or 2, characterized in that, In step (5), the final polycondensation is carried out at 200-300°C and a vacuum degree ≤300Pa.

10. The method according to claim 1 or 2, characterized in that, In step (6), the melt thickening is carried out at 200-250°C and a vacuum of 50-200Pa.

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