A method for preparing a dibasic acid and dihydric alcohol modified polybutylene succinate copolyester

Abstract

The application discloses a preparation method of a binary acid and alcohol modified polybutylene succinate copolyester. The preparation method uses binary acid and binary alcohol as modifiers, sequentially passes through a first esterification reaction, a second esterification reaction, a pre-polycondensation reaction and a final polycondensation reaction to obtain the modified polybutylene succinate copolyester. The initial esterification temperature is reduced through a two-stage esterification mode, the problem that 1,4-butanediol is easy to dehydrate to form a cyclic byproduct under high temperature is overcome, the consumption of the raw material 1,4-butanediol is effectively reduced, and the use of a toxic metal compound is avoided through the use of an organic ring-opening catalyst in the polymerization process, so that the problems existing in the prior art are solved. The method is simple in operation, wide in application range, provides a flexible modifier adding mode for the production of modified copolyesters, enriches the product types of the degradable polyester family, and the obtained product is stable in quality, high in intrinsic viscosity and good in quality.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, specifically to a method for preparing polybutylene succinate copolyester modified with diacid and diol. Background Technology

[0002] Polybutylene succinate (PBS) is a typical biodegradable plastic. It is milky white, colorless, and odorless. In composting, soil, and other environments, it is easily decomposed by microorganisms and enzymes in plants and animals into non-toxic and harmless products such as water and carbon dioxide, making it a promising polyester material with significant development and application potential. Compared to other common biodegradable plastics (such as polylactic acid and polyhydroxyalkanoates), PBS has advantages such as excellent processing performance, a wide temperature tolerance range, and highly controllable degradation cycles. It can be widely used in packaging, tableware, agricultural films, medical supplies, and other fields, replacing traditional non-degradable plastics.

[0003] However, polybutylene succinate (PBS) materials also have some drawbacks, such as a low melting point, high crystallinity, low degradation rate, high brittleness, and poor ductility. As the application fields of PBS products continue to expand, PBS alone can no longer meet people's needs.

[0004] Copolymerization, starting from molecular structure design, is one of the effective means to regulate and improve the chemical and physical properties of polymers. Therefore, polybutylene succinate (PBS) materials can be modified by copolymerizing with other monomers to meet various needs. For example, patent CN103497316A successfully prepared a PBS copolyester with low carboxyl content by adding comonomers such as adipic acid during polymerization; patent CN103788348A improved the low strength of PBS products by adding polyols during polymerization; the literature "Biobased Seawater-Degradable Poly(butylene succinate-L-lactide) Copolyesters: Exploration of Degradation Performance and Degradation Mechanism in Natural Seawater" improved the seawater degradation performance of PBS by adding lactic acid during polymerization; and the literature "Novel random PBS-based copolymers containing aliphatic side chains for sustainable flexible food" further demonstrates this approach. The paper "Packaging" significantly improved the gas barrier properties of polybutylene succinate materials by adding ethylene glycol and neopentyl glycol during the polymerization process; the master's thesis "Synthesis and Degradation Performance Study of Biodegradable Polybutylene Succinate Copolymers" prepared a series of polybutylene succinate copolyesters by adding terminal hydroxyl diols and branched diols during the polymerization process, and studied their various properties.

[0005] However, in the above-disclosed methods for preparing polybutylene succinate copolyester, the esterification step is usually carried out at high temperatures (>150°C) to improve esterification efficiency. Since 1,4-butanediol readily dehydrates to form tetrahydrofuran at high temperatures, high-temperature esterification conditions lead to a large amount of 1,4-butanediol dehydrating to form tetrahydrofuran, increasing material consumption. Simultaneously, tetrahydrofuran can corrode metal equipment, shortening its service life and increasing production costs.

[0006] Furthermore, cyclic byproducts are inevitably generated during the preparation of polyester. These cyclic byproducts have a significant impact on the processing and molding technology and product quality of polyester products. Currently, there are few reports on the cyclic byproducts of biodegradable copolyesters. Patent CN114507338A and the literature "Purification, Characterization and Ring-Opening Polymerization of Cyclic Dimers of Polybutylene Succinate" report a method for re-ring-opening polymerization of cyclic byproducts in polybutylene succinate using a ring-opening catalyst. However, the catalysts used in the above methods are all tin compounds, and the toxicity of tin compounds will have adverse environmental impacts in the preparation and treatment of catalysts, the processing and use of products, and the disposal of waste. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a method for preparing polybutylene succinate copolyester modified with diacid and diol. The modified polyester prepared by this method has low content of cyclic byproducts, low content of terminal carboxyl groups, low color value (b value), and high product quality.

[0008] The technical solution adopted to achieve the purpose of this invention is:

[0009] A method for preparing a dicarboxylic acid and diol-modified polybutylene succinate copolyester, the method comprising the following steps:

[0010] a) Prepare a first slurry by mixing succinic acid, 1,4-butanediol and esterification catalyst A, and prepare a second slurry by mixing modifier diacid, diol and esterification catalyst B. Send the first slurry to the first esterification reactor, or send the first slurry and the second slurry to the first esterification reactor at the same time, and carry out an esterification reaction at a reaction temperature of 80-130°C to obtain the first esterification reaction solution.

[0011] b) The first esterification reaction solution described in step a) is transported to the second esterification reactor. When only the first slurry is added to the first esterification reactor in step a), the second slurry is also transported to the second esterification reactor. A second esterification reaction is carried out at a reaction temperature of 140-190°C to obtain the second esterification reaction solution.

[0012] c) The second esterification reaction solution described in step b) is transported to the prepolymerization reactor, and a polymerization catalyst and a ring-opening catalyst are added to carry out the prepolymerization reaction to obtain the prepolymerization reaction solution.

[0013] d) The pre-condensation reaction liquid described in step c) is transported to the final condensation reactor, a stabilizer is added to carry out the final condensation reaction, and the final condensation reaction liquid is obtained.

[0014] This invention employs a two-stage esterification process. By lowering the reaction temperature of the first esterification, the reaction is carried out at a temperature below 150°C, allowing 80-90% of 1,4-butanediol to complete the esterification reaction. This effectively avoids the problem of 1,4-butanediol easily dehydrating at high temperatures to form cyclic byproducts. In the second esterification, the reaction temperature is increased, allowing the material from the first esterification to quickly complete the second esterification, ensuring the smooth progress of the pre-condensation reaction. By using an organic ring-opening catalyst during the polymerization process, the content of cyclic byproducts in the polyester is effectively reduced, while avoiding the use of toxic metal compound catalysts, significantly improving product quality.

[0015] In this invention, the modifiers diacid and diol can be added to the first esterification vessel to undergo a first esterification reaction with succinic acid and 1,4-butanediol, followed by a second esterification reaction. Alternatively, the modifiers diacid and diol can be added to the second esterification vessel to undergo a second esterification reaction with the first esterification solution after esterification with succinic acid and 1,4-butanediol. Therefore, the preparation method described in this invention provides a flexible modifier addition method for the production of modified copolyesters, enriching the product range of the biodegradable polyester family.

[0016] In some embodiments of the present invention, the ring-opening catalyst is one or more selected from 1,8-diazabicycloundec-7-ene, 1,5,7-triazabicyclodec-5-ene, 7-methyl-1,5,7-triazabicyclodec-5-ene, and tetra-n-butyltetraphenylborate ammonium.

[0017] Furthermore, the amount of the ring-opening catalyst added is 0.01wt% to 0.1wt% of the total mass of the reaction raw materials, which are succinic acid, 1,4-butanediol and a modifier.

[0018] In some embodiments of the present invention, the esterification catalyst A or esterification catalyst B is independently selected from one or more of benzenesulfonic acid, 4-methylbenzenesulfonic acid, p-dodecylbenzenesulfonic acid, 2,4-dimethylbenzenesulfonic acid, 2,5-dimethylbenzenesulfonic acid, zinc acetate, germanium acetate, cobalt acetate, titanium dioxide, and tetrabutyl titanate. Esterification catalyst A and esterification catalyst B can be the same catalyst or different catalysts.

[0019] Furthermore, the molar ratio of succinic acid to 1,4-butanediol in the first slurry is 1:1.05 to 1.55, and the molar ratio of dicarboxylic acid to diol in the second slurry is 1:1.05 to 1.55; the molar ratio of succinic acid to dicarboxylic acid in the modifier is 5:5 to 9:1; the acid-alcohol molar ratio in the first slurry and the acid-alcohol molar ratio in the second slurry can be the same or different.

[0020] Furthermore, the dicarboxylic acid is one of succinic acid, furanyl dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, dimer acid, terephthalic acid, adipic acid, and 2,6-naphthalenedicarboxylic acid.

[0021] Furthermore, the diol is one of ethylene glycol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,10-decanediol, and dodecanediol.

[0022] In some embodiments of the present invention, the dicarboxylic acid may also be succinic acid, but the diol is any diol other than 1,4-butanediol.

[0023] Furthermore, the preparation temperature of the first slurry is 30–60°C, and the preparation temperature of the second slurry is 30–90°C.

[0024] In some embodiments of the present invention, the reaction pressure of the primary esterification reaction in step a) is 50-100 kPaA.

[0025] All pressure values ​​used in this invention refer to absolute pressure.

[0026] Furthermore, the residence time of the esterification reaction described in step a) is 0.5 to 4.5 h.

[0027] Furthermore, the pressure of the secondary esterification reaction described in step b) is atmospheric pressure, and the residence time is 0.5 to 3.5 h.

[0028] Furthermore, the reaction temperature of the pre-condensation reaction described in step c) is 200–250°C, and the reaction pressure is 1–10 kPaA.

[0029] Furthermore, the residence time of the pre-condensation reaction described in step c) is 0.5 to 1.5 hours.

[0030] In some embodiments of the present invention, the polymerization catalyst is one or more of organotitanium compounds or metal oxides, wherein the organotitanium compounds include titanium glycol, titanium propylene glycol, titanium butanediol, tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and the metal oxides include magnesium oxide, aluminum oxide, calcium oxide, titanium dioxide, zinc oxide, and germanium dioxide.

[0031] In some embodiments of the present invention, the reaction temperature of the final polycondensation reaction in step d) is 220–280°C, and the reaction pressure is 20–200 PaA.

[0032] Furthermore, the residence time of the final polycondensation reaction described in step d) is 0.1 to 1.5 h.

[0033] In some embodiments of the present invention, the stabilizer is one or more of trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, triphenyl phosphite, tri-m-toluene phosphite, dimethyl phosphate, trimethyl phosphate, triethyl phosphate, diphenyl phosphate, and triphenyl phosphate.

[0034] In some embodiments of the present invention, the second esterification reaction liquid obtained in step b) is transported to a stirred bubble column, an auxiliary gas is introduced, and then it is transported to the pre-condensation reactor in step c).

[0035] Furthermore, the auxiliary gas is at least one of nitrogen, helium, and argon; the empty tower gas velocity is 0.01–0.2 m / s; the removal temperature is 150–200 °C; the removal pressure is 10–50 kPaA; the stirring rate is 60–150 rpm; and the residence time is 0.5–4.5 h.

[0036] The copolyester preparation method described in this invention is a continuous production process. The continuous preparation process is simple to operate and highly controllable. Separate esterification not only improves the quality of the esterified product, but also provides a flexible way to add modifiers for the production of modified copolyesters, enriching the product types of the biodegradable polyester family. The resulting product has high intrinsic viscosity and good quality. Compared with the traditional intermittent production process, the batch variation of the product is smaller and the quality is more stable.

[0037] In some embodiments of the present invention, the esterification rate of the primary esterification reaction is 80-90%, and the esterification rate of the secondary esterification reaction is ≥98%.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] (1) A two-stage esterification process was used. The first esterification reaction was carried out at a lower temperature to avoid the cyclization of the raw material 1,4-butanediol at high temperatures, thus effectively reducing the consumption of the raw material 1,4-butanediol. Subsequently, a second esterification reaction was carried out at a higher temperature to further improve the esterification rate of the reaction system and ensure the smooth progress of the pre-condensation reaction. This invention effectively reduces raw material consumption while obtaining a modified polybutylene succinate copolyester with high intrinsic viscosity and high quality through a two-stage esterification process.

[0040] (2) By introducing an organic ring-opening catalyst, the content of cyclic byproducts in the product is reduced, while the use of toxic metal compound catalysts is avoided, which significantly improves the product quality.

[0041] (3) The preparation method described in this invention provides a flexible way of adding modifiers for the production of modified copolyesters, enriching the product range of the biodegradable polyester family.

[0042] (4) In a preferred embodiment of the present invention, by conveying the second esterification reaction liquid to a stirred bubble tower and introducing auxiliary gas, the residual water in the esterification reaction is removed, the influence of residual water on the titanium catalyst in the polymerization reaction is reduced, the color value b of the product is effectively reduced, and the quality of the product is significantly improved. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the preparation method of polybutylene succinate copolyester modified with dicarboxylic acid and diol as shown in Example 1 of the present invention.

[0044] Figure 2 This is a schematic diagram of the preparation method of polybutylene succinate copolyester modified with dicarboxylic acid and diol as shown in Example 2 of the present invention.

[0045] Figure 3 This is a schematic diagram of the preparation method of polybutylene succinate copolyester modified with dicarboxylic acid and diol as shown in Example 4 of the present invention.

[0046] Figure 4 This is a schematic diagram of the preparation method of polybutylene succinate copolyester modified with dicarboxylic acid and diol, as shown in Example 5 of the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. All numerical designations, such as pH, temperature, length, flow rate, and range, are approximate values. It should be understood that, although not always explicitly stated, all numerical designations are preceded by the term "approximately." It should also be understood that, although not always explicitly stated, the reagents described herein are merely examples, and their equivalents are known in the art.

[0049] This invention provides a method for preparing polybutylene succinate copolyester modified with diacid and diol. Figure 1-4 A schematic flowchart of the preparation method is provided. As shown in the figure, the preparation method includes the following steps:

[0050] a) Succinic acid, 1,4-butanediol and esterification catalyst A are prepared into a first slurry at 30-60°C, and modifier diacid, diol and esterification catalyst B are prepared into a second slurry at 30-90°C. The first slurry is then fed into a first esterification reactor, or the first and second slurries are fed into the first esterification reactor simultaneously. An esterification reaction is carried out at a reaction temperature of 80-130°C to obtain a first esterification reaction solution.

[0051] b) The first esterification reaction solution described in step a) is transported to the second esterification reactor. When only the first slurry is added to the first esterification reactor in step a), the second slurry is also transported to the second esterification reactor. A second esterification reaction is carried out at a reaction temperature of 140-190°C to obtain the second esterification reaction solution.

[0052] c) The second esterification reaction solution described in step b) is transported to the prepolymerization reactor, and a polymerization catalyst and a ring-opening catalyst are added to carry out the prepolymerization reaction to obtain the prepolymerization reaction solution.

[0053] d) The polycondensation reaction solution described in step c) is transported to the final polycondensation reactor, a stabilizer is added to carry out the final polycondensation reaction, and the final polycondensation reaction solution is obtained.

[0054] The final polycondensation reaction liquid is transferred to the discharge port by a gear pump, cooled in a water bath, and then drawn into strips and granulated to obtain the target product.

[0055] Optionally, the ring-opening catalyst is one or more selected from 1,8-diazabicycloundec-7-ene, 1,5,7-triazabicyclodec-5-ene, 7-methyl-1,5,7-triazabicyclodec-5-ene, and tetra-n-butyltetraphenylborate ammonium.

[0056] Optionally, the molar ratio of succinic acid to 1,4-butanediol in the first slurry is 1:1.05 to 1.55, and the molar ratio of dicarboxylic acid to diol in the second slurry is 1:1.05 to 1.55; the molar ratio of succinic acid to dicarboxylic acid in the modifier is 5:5 to 9:1.

[0057] Optionally, the reaction pressure of the primary esterification reaction described in step a) is 50–100 kPaA;

[0058] Optionally, the residence time of the esterification reaction described in step a) is 0.5 to 4.5 h.

[0059] Optionally, the pressure of the secondary esterification reaction described in step b) is atmospheric pressure, and the residence time is 0.5 to 3.5 h.

[0060] Optionally, the reaction temperature of the pre-condensation reaction described in step c) is 200–250°C, and the reaction pressure is 1–10 kPaA.

[0061] Optionally, the residence time of the pre-condensation reaction described in step c) is 0.5 to 1.5 hours.

[0062] Optionally, the final polycondensation reaction temperature is 220-280℃, and the reaction pressure is 20-200 PaA.

[0063] Optionally, the residence time of the final polycondensation reaction described in step d) is 0.1 to 1.5 h.

[0064] In some embodiments of the present invention, the second esterification reaction liquid described in step b) can also be conveyed to a stirred bubble column and an auxiliary gas is introduced; then it can be conveyed to the prepolymerization reactor described in step c), such as... Figure 3 Or as shown in Figure 4.

[0065] The auxiliary gas is at least one of nitrogen, helium and argon; the empty tower gas velocity is 0.01 to 0.2 m / s; the removal temperature is 150 to 200℃; the removal pressure is 10 to 50 kPaA; the stirring rate is 60 to 150 rpm; and the residence time is 0.5 to 4.5 h.

[0066] In some embodiments of the present invention, the reaction raw materials refer to the collective term for succinic acid, 1,4-butanediol, and modifiers dicarboxylic acid and diol.

[0067] The viscosity of the copolyester was tested according to the method described in GB-T30294-2013 Polybutylene succinate, using phenol / 1,1,2,2-tetrachloroethane (mass ratio 50:50) as the solvent, and an Ubbelohde capillary viscometer (number 4-0.8) as the instrument. The carboxyl content of the copolyester was tested according to the method described in GB-T30294-2013 Polybutylene succinate, using phenol-chloroform as the mixed solvent (volume ratio 2:3), potassium hydroxide-benzyl alcohol as the standard titration solution (concentration 0.01 mol / L), and bromophenol blue indicator concentration 0.2%. The sample was prepared by dissolving 0.5 g of sample in 25.00 mL of the phenol-chloroform mixed solvent. The color value of the copolyester was evaluated using the L, a, b color system, where L is the brightness factor, and a and b are the color measurements. b represents the yellow-blue balance, which is very important for the color of the polyester; the lower the b value, the better the color. The cyclic byproducts were characterized by gas chromatography-mass spectrometry (GC-MS).

[0068] Example 1

[0069] A first slurry was prepared by mixing succinic acid and 1,4-butanediol at a molar ratio of 1:1.05 with titanium dioxide as the esterification catalyst at 45°C. The amount of esterification catalyst added was 0.05 wt% of the total mass of succinic acid and 1,4-butanediol. A second slurry was prepared by mixing adipic acid as a modifier and 1,4-cyclohexanediethanol at a molar ratio of 1:1.05 with titanium dioxide as the esterification catalyst at 90°C. The amount of esterification catalyst added was 0.05 wt% of the total mass of the modifier, and the molar ratio of succinic acid to adipic acid was 5:5. The first slurry was fed to the first esterification reactor at a flow rate of 10.6 kg / h for a single esterification reaction, which was held at 100°C and 60 kPaA for 2.5 h to obtain the first esterification reaction solution. The first esterification reaction solution and the second slurry (the flow rate of the second slurry was 14.9 kg / h) were then fed to the second esterification reactor for a second esterification reaction. The reaction was carried out at 160°C and atmospheric pressure for 2 hours to obtain the second esterification reaction solution. Subsequently, the second esterification solution was fed to a pre-polymerization reactor for a pre-polymerization reaction. Simultaneously, 0.015 kg / h of germanium dioxide (0.06 wt% of total reactant mass) and 0.025 kg / h of 1,5,7-triazabicyclodec-5-ene (0.1 wt% of total reactant mass) were added. The reaction was carried out at 200°C and 1 kPaA for 2.5 hours to obtain the pre-polymerization reaction solution. Finally, the pre-polymerization reaction solution was fed to a final polymerization reactor. Simultaneously, 0.011 kg / h of triphenyl phosphite (0.05 wt% of total reactant mass) was added. The reaction was carried out at 220°C and 20 kPaA for 1.5 hours to obtain the final polymerization reaction solution. The final polycondensation reaction liquid is transferred to the discharge port via a gear pump, cooled in a water bath, and then drawn into strips and granulated to obtain the target product, poly(succinic acid-adipic acid-butanediol-1,4-cyclohexanediethanol ester copolymer).

[0070] Example 2

[0071] A first slurry was prepared by mixing succinic acid and 1,4-butanediol at a molar ratio of 1:1.1 with the esterification catalyst 4-methylbenzenesulfonic acid at 30°C. The amount of esterification catalyst added was 0.04 wt% of the total mass of succinic acid and 1,4-butanediol. A second slurry was prepared by mixing furanyl dicarboxylic acid and ethylene glycol at a molar ratio of 1:1.55 with the esterification catalyst 4-methylbenzenesulfonic acid at 30°C. The amount of esterification catalyst added was 0.04 wt% of the total mass of the modifiers. The molar ratio of succinic acid to furanyl dicarboxylic acid was 9:1. The first slurry was simultaneously fed into the first esterification reactor at a flow rate of 19.5 kg / h and the second slurry at a flow rate of 2.5 kg / h for a single esterification reaction. The reaction was carried out at 80°C and 50 kPaA for 3 h to obtain the first esterification reaction solution. The first esterification reaction solution was then transferred to a diester for a second esterification reaction, held at 140°C and atmospheric pressure for 2.5 h to obtain the second esterification reaction solution. The second esterification solution was then transferred to a prepolymerization reactor for prepolymerization, with 0.011 kg / h of alumina (0.05 wt% of total reactants) and 0.002 kg / h of 1,8-diazabicycloundec-7-ene (0.01 wt% of total reactants) added. The reaction was held at 220°C and 2.5 kPaA for 2 h to obtain the prepolymerization reaction solution. Finally, the prepolymerization reaction solution was transferred to a final polymerization reactor, with 0.011 kg / h of trimethyl phosphite (0.05 wt% of total reactants) added. The reaction was held at 240°C and 50 PaA for 1 h to obtain the final polymerization reaction solution. The final polycondensation reaction liquid is transferred to the discharge port via a gear pump, cooled in a water bath, and then drawn into strips and granulated to obtain the target product, poly(butanediol-furandicarboxylic acid-butanediol-ethylene glycol copolymer).

[0072] Example 3

[0073] A first slurry was prepared by mixing succinic acid and 1,4-butanediol at a molar ratio of 1:1.55 with cobalt acetate as an esterification catalyst at 60°C. The amount of esterification catalyst added was 0.05 wt% of the total mass of succinic acid and 1,4-butanediol. A second slurry was prepared by mixing 1,4-cyclohexanedicarboxylic acid and 1,6-hexanediol at a molar ratio of 1:1.25 with cobalt acetate as an esterification catalyst at 60°C. The amount of esterification catalyst added was 0.05 wt% of the total mass of the modifier, wherein the molar ratio of succinic acid to 1,4-cyclohexanedicarboxylic acid was 8:2. The first slurry was fed to the first esterification reactor at a flow rate of 20.6 kg / h for a single esterification reaction, and held at 130°C and 100 kPaA for 2.5 h to obtain the first esterification reaction solution. The first esterification reaction solution and the second slurry (the flow rate of the second slurry was 6.4 kg / h) were then fed to the second esterification reactor for a second esterification reaction. The reaction was carried out at 190°C and atmospheric pressure for 1.5 h to obtain the second esterification reaction solution. Subsequently, the second esterification solution was fed to a pre-polymerization reactor for a pre-polymerization reaction. Simultaneously, 0.016 kg / h of tetraethyl titanate (0.06 wt% of total reactants) and 0.019 kg / h of 7-methyl-1,5,7-triazabicyclodec-5-ene (0.07 wt% of total reactants) were added. The reaction was carried out at 250°C and 10 kPaA for 1.5 h to obtain the pre-polymerization reaction solution. Finally, the pre-polymerization reaction solution was fed to a final polymerization reactor. Simultaneously, 0.027 kg / h of triphenyl phosphate (0.1 wt% of total reactants) was added. The reaction was carried out at 280°C and 200 PaA for 1 h to obtain the final polymerization reaction solution. The final polycondensation reaction liquid is transferred to the discharge port via a gear pump, cooled in a water bath, and then drawn into strips and granulated to obtain the target product, poly(butanediol-cyclohexanedicarboxylic acid-butanediol-hexanediol copolymer).

[0074] Example 4

[0075] A first slurry was prepared by mixing succinic acid and 1,4-butanediol at a molar ratio of 1:1.2 with the esterification catalyst benzenesulfonic acid at 40℃. The amount of esterification catalyst added was 0.05 wt% of the total mass of succinic acid and 1,4-butanediol. A second slurry was prepared by mixing terephthalic acid and 1,3-propanediol at a molar ratio of 1:1.4 with the esterification catalyst benzenesulfonic acid at 60℃. The amount of esterification catalyst added was 0.05 wt% of the total mass of the modifier, wherein the molar ratio of succinic acid to terephthalic acid was 7:3. The first slurry was fed to the first esterification reactor at a flow rate of 15.8 kg / h for a single esterification reaction, and held at 130℃ and 90 kPaA for 2.5 h to obtain the first esterification reaction solution. The first esterification reaction solution and the second slurry (the flow rate of the second slurry was 8.2 kg / h) were then fed to the second esterification reactor for a second esterification reaction, held at 190°C and atmospheric pressure for 1.5 h to obtain the second esterification reaction solution. The second esterification solution was then fed to a stirred bubble column, with the column temperature controlled at 150°C, the pressure at 10–20 kPaA, the auxiliary gas being helium, the empty column gas velocity at 0.01 m / s, the stirring speed at 150 rpm, and the residence time at 4.5 h. The mixture in the stirred bubble column was then fed to a prepolymerization reactor for a prepolymerization reaction, with 0.019 kg / h of tetraisopropyl titanate (0.08 wt% of total reactants) and 0.024 kg / h of tetrabutyltetraphenylborate (0.08 wt% of total reactants) added. The mixture was held at 240°C and 5 kPaA for 1.5 h to obtain the prepolymerization reaction solution. Finally, the prepolymerization reaction solution was transferred to the final polymerization reactor, and 0.01 kg / h of the stabilizer triethyl phosphate (total reactant mass 0.04 wt%) was added. The mixture was held at 270℃ and 120 PaA for 0.8 h to obtain the final polymerization reaction solution. The final polymerization reaction solution was transferred to the discharge port via a gear pump, cooled in a water bath, discharged, drawn into strips, and pelletized to obtain the target product, poly(butanediol-terephthalic acid-butylene glycol) copolymer.

[0076] Example 5

[0077] A first slurry was prepared by mixing succinic acid and 1,4-butanediol with titanium dioxide as an esterification catalyst at a molar ratio of 1:1.3 at 40°C. The amount of esterification catalyst added was 0.05 wt% of the total mass of succinic acid and 1,4-butanediol. A second slurry was prepared by mixing terephthalic acid modifier and ethylene glycol with titanium dioxide as an esterification catalyst at a molar ratio of 1:1.35 at 60°C. The amount of esterification catalyst added was 0.05 wt% of the total mass of the modifier; wherein the molar ratio of succinic acid to terephthalic acid was 6:4. The first slurry was fed to the first esterification reactor at a flow rate of 18.5 kg / h and the second slurry was fed at a flow rate of 10 kg / h for a single esterification reaction. The reaction was carried out at 110°C and 80 kPaA for 3 h to obtain the first esterification reaction solution. The first esterification reaction solution was then transferred to a second esterification reactor for a second esterification reaction, held at 180°C and atmospheric pressure for 2.5 hours to obtain the second esterification reaction solution. The second esterification solution was then transferred to a stirred bubble column, with the column temperature controlled at 200°C, pressure at 40–50 kPaA, argon as the auxiliary gas, an empty column gas velocity of 0.20 m / s, a stirring speed of 60 rpm, and a residence time of 0.5 hours. The mixture in the stirred bubble column was then transferred to a prepolymerization reactor for a prepolymerization reaction, with 0.011 kg / h of germanium dioxide (0.04 wt% of total reactants) and 0.017 kg / h of tetrabutyltetraphenylborate (0.06 wt% of total reactants) added simultaneously. The mixture was held at 240°C and 5 kPaA for 1.5 hours to obtain the prepolymerization reaction solution. Finally, the prepolymerization reaction solution was transferred to the final polymerization reactor, and 0.014 kg / h of the stabilizer triethyl phosphate (0.05 wt% of the total mass of the reactants) was added. The mixture was held at 250°C and 80 PaA for 1 hour to obtain the final polymerization reaction solution. The final polymerization reaction solution was then transferred to the discharge port via a gear pump, cooled in a water bath, discharged, drawn into strips, and pelletized to obtain the target product, poly(butanediol-terephthalic acid-butylene glycol) copolymer.

[0078] Example 6

[0079] At 40°C, succinic acid and 1,4-butanediol were mixed with zinc acetate esterification catalyst at a molar ratio of 1:1.4 to prepare a first slurry. The catalyst addition amount was 0.05 wt% of the total mass of succinic acid and 1,4-butanediol. At 60°C, furanyl dicarboxylic acid modifier and 1,3-propanediol were mixed with zinc acetate esterification catalyst at a molar ratio of 1:1.2 to prepare a second slurry. The esterification catalyst addition amount was 0.05 wt% of the total mass of the modifier. The molar ratio of succinic acid to terephthalic acid was 6:4. The first slurry was fed to the first esterification reactor at a flow rate of 14.6 kg / h for a single esterification reaction, which was held at 90°C and 60 kPaA for 3.5 h to obtain the first esterification reaction solution. The first esterification reaction solution and the second slurry (flow rate of the second slurry was 9.9 kg / h) were then fed to the second esterification reactor for a second esterification reaction, held at 170°C and atmospheric pressure for 2.5 h to obtain the second esterification reaction solution. The second esterification solution was then fed to a stirred bubble column, with the column temperature controlled at 180°C, pressure at 25–35 kPaA, nitrogen as the auxiliary gas, an empty column gas velocity of 0.10 m / s, a stirring speed of 100 rpm, and a residence time of 2.5 h. The mixture in the stirred bubble column was then fed to a prepolymerization reactor for a prepolymerization reaction, with 0.015 kg / h of tetrabutyl titanate (total mass of reactants 0.06 wt%) as a polymerization catalyst and 0.017 kg / h of tetrabutyltetraphenylborate (total mass of reactants 0.07 wt%) as a ring-opening catalyst added. The mixture was held at 250°C and 7 kPaA for 1.5 h to obtain the prepolymerization reaction solution. Finally, the prepolymerization reaction solution was transferred to the final polymerization reactor, and 0.022 kg / h of the stabilizer triethyl phosphate (0.09 wt% of the total reactant mass) was added. The mixture was held at 260°C and 80 PaA for 1.5 h to obtain the final polymerization reaction solution. The final polymerization reaction solution was then transferred to the discharge port via a gear pump, cooled in a water bath, discharged, drawn into strips, and pelletized to obtain the target product, poly(butanediol-furandicarboxylic acid-butanediol-propylene glycol copolymer).

[0080] Comparative Example 1

[0081] Compared with Example 1, the first esterification stage adopted the same high temperature (160°C) and normal pressure reaction conditions as the second esterification stage, while the other conditions were the same as in Example 1.

[0082] Comparative Example 2

[0083] Compared with Example 4, the first esterification stage adopted the same high temperature (190°C) and normal pressure reaction conditions as the second esterification stage, while the other conditions were the same as in Example 4.

[0084] Comparative Example 3

[0085] Compared to Example 3, no ring-opening catalyst was added during the pre-polymerization stage.

[0086] Comparative Example 4

[0087] Compared to Example 4, no ring-opening catalyst was added during the pre-polymerization stage.

[0088] Comparative Example 5

[0089] Compared with Example 4, the first esterification stage adopted the same high temperature (190°C) and normal pressure reaction conditions as the second esterification stage, the esterification liquid was not stirred and bubbled in a tower, and no ring-opening catalyst was added in the pre-condensation stage.

[0090] Comparative Example 6

[0091] Compared to Example 6, the pre-condensation stage used a conventional tin compound as a ring-opening catalyst, while the other conditions were the same as in Example 6.

[0092]

[0093] As can be seen from the comparison between Example 1 and Comparative Example 1 and between Example 4 and Comparative Example 2, the use of low temperature and low pressure process in the first esterification stage can effectively avoid the cyclization side reaction of the raw material 1,4-butanediol, reduce the content of cyclic by-products and terminal carboxyl group, increase the color value L of the product, reduce the color value b of the product, and significantly improve the intrinsic viscosity of the product, thereby ensuring that a high-quality product is obtained under the condition of lower alcohol-acid ratio.

[0094] As can be seen from the comparison between Example 3 and Comparative Example 3 and between Example 4 and Comparative Example 4, the addition of a ring-opening catalyst in the pre-condensation stage can effectively reduce the content of cyclic by-products in the product.

[0095] A comparison of Examples 3 and 4 shows that when using a titanium-based catalyst as the polymerization catalyst, subjecting the esterification reaction solution to a stirred bubble column before polycondensation effectively improves the color value of the copolyester and enhances product quality. This is because titanium-based catalysts are prone to hydrolysis and other side reactions during polyester polymerization, leading to product yellowing. After treatment in the stirred bubble column, residual water and unreacted diols in the esterification reaction solution are effectively removed, avoiding the problem of product yellowing and increased b-value caused by side reactions of the titanium-based catalyst.

[0096] As can be seen from the comparison between Example 4 and Comparative Example 5, the copolyester obtained without low-temperature esterification, without stirring and bubbling in the esterification liquid, and without adding a ring-opening catalyst in the pre-condensation stage is not only weaker than the method provided by the present invention in terms of performance indicators such as viscosity, carboxyl content, and color value, but also has a much higher content of cyclic by-products in the final product than the product prepared by the method provided by the present invention. Therefore, this method can significantly improve the quality of the product.

[0097] As can be seen from the comparison between Example 6 and Comparative Example 6, when the organic compound used in this invention is used as a ring-opening catalyst, it can achieve the same effect as the traditional tin compound ring-opening catalyst, avoid the use of toxic metal compound catalysts, and significantly improve the quality of the product.

[0098] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a dicarboxylic acid and diol-modified polybutylene succinate copolyester, characterized in that, The preparation method includes the following steps: a) Succinic acid, 1,4-butanediol and esterification catalyst A are prepared into a first slurry, and diacid, diol and esterification catalyst B are prepared into a second slurry. The first slurry is fed into the first esterification reactor, or the first slurry and the second slurry are fed into the first esterification reactor at the same time. An esterification reaction is carried out once at a reaction temperature of 80~130℃ to obtain the first esterification reaction solution. b) The first esterification reaction solution described in step a) is transported to the second esterification reactor. When only the first slurry is added to the first esterification reactor in step a), the second slurry is also transported to the second esterification reactor. A second esterification reaction is carried out at a reaction temperature of 140~190℃ to obtain the second esterification reaction solution. c) The second esterification reaction solution described in step b) is transported to the prepolymerization reactor, and a polymerization catalyst and a ring-opening catalyst are added to carry out the prepolymerization reaction to obtain the prepolymerization reaction solution. d) The pre-condensation reaction liquid described in step c) is transported to the final condensation reactor, a stabilizer is added to carry out the final condensation reaction, and the final condensation reaction liquid is obtained. The ring-opening catalyst mentioned in step c) is one or more of 1,8-diazabicycloundec-7-ene, 1,5,7-triazabicyclodec-5-ene, 7-methyl-1,5,7-triazabicyclodec-5-ene, and tetra-n-butyltetraphenylborate ammonium.

2. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The amount of the ring-opening catalyst added is 0.01wt% to 0.1wt% of the total mass of the reaction raw materials, which are succinic acid, 1,4-butanediol and modifier.

3. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The esterification catalyst A or esterification catalyst B is independently selected from one or more of benzenesulfonic acid, 4-methylbenzenesulfonic acid, p-dodecylbenzenesulfonic acid, 2,4-dimethylbenzenesulfonic acid, 2,5-dimethylbenzenesulfonic acid, zinc acetate, germanium acetate, cobalt acetate, titanium dioxide, and tetrabutyl titanate.

4. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The molar ratio of succinic acid to 1,4-butanediol in the first slurry is 1:1.05 to 1.55, and the molar ratio of dicarboxylic acid to diol in the second slurry is 1:1.05 to 1.55; the molar ratio of succinic acid to dicarboxylic acid in the modifier is 5:5 to 9:

1.

5. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The dicarboxylic acid is one of succinic acid, furanyl dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, dimer acid, terephthalic acid, adipic acid, and 2,6-naphthalenedicarboxylic acid.

6. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The diol is one of ethylene glycol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,10-decanediol, and dodecanediol.

7. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The reaction pressure of the esterification reaction described in step a) is 50~100 kPaA.

8. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The reaction temperature of the pre-condensation reaction described in step c) is 200~250℃, and the reaction pressure is 1~10KPaA.

9. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The polymerization catalyst mentioned in step c) is one or more of organotitanium compounds or metal oxides, wherein the organotitanium compounds include titanium glycol, titanium propylene glycol, titanium butanediol, tetraethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, and the metal oxides include magnesium oxide, aluminum oxide, calcium oxide, titanium dioxide, zinc oxide, and germanium dioxide.

10. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The reaction temperature of the final polycondensation reaction described in step d) is 220~280℃, and the reaction pressure is 20~200PaA.

11. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 1, characterized in that, The second esterification reaction liquid obtained in step b) is transported to a stirred bubble column, an auxiliary gas is introduced, and then it is transported to the prepolymerization reactor in step c).

12. The method for preparing polybutylene succinate copolyester modified with diacid and diol according to claim 11, characterized in that, The removal pressure of the stirred bubbling tower is 10~50 kPaA.

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