A method for preparing a modified polybutylene succinate copolyester

Abstract

The application discloses a preparation method of modified polybutylene succinate copolyester. The preparation method uses a hydroxyl fatty acid or a dibasic acid as a modifier, and sequentially performs 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 first esterification reaction is performed at a lower temperature, so that the raw material 1,4-butanediol is prevented from being cyclized to generate a cyclic by-product at high temperature, and the consumption of the raw material 1,4-butanediol is effectively reduced. By using an organic ring-opening catalyst in the polymerization process, the use of a toxic metal compound is avoided, so that the problems existing in the prior art are solved. The method disclosed by the application is simple in operation, wide in application range, easy to implement in industrialization, and stable in product quality, and the obtained product is high in intrinsic viscosity and good in quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material synthesis, and particularly relates to a preparation method of modified polybutylene succinate copolyester. BACKGROUND

[0002] Polybutylene succinate is a typical biodegradable plastic, which is milky white in appearance, colorless and odorless, and can be gradually decomposed into nontoxic and harmless products such as water and carbon dioxide in the environment such as compost and soil by microorganisms and enzymes in the bodies of plants and animals, so that it becomes a polyester material with great development and application prospect. Compared with other common biodegradable plastics (such as polylactic acid, polyhydroxyalkanoic acid, etc.), polybutylene succinate has excellent processing performance, wide temperature resistance range, strong controllability of degradation period and other advantages, and can be widely applied to the fields of packaging, tableware, agricultural film, medical supplies and the like to replace traditional non-degradable plastics.

[0003] However, polybutylene succinate material also has some defects, such as low melting point, high crystallinity, low degradation rate, high brittleness, poor ductility and the like. With the continuous expansion of the application field of polybutylene succinate products, single polybutylene succinate has been unable to meet people's needs.

[0004] Copolymerization can be started from molecular structure design, which is one of the effective means to adjust and improve the chemical and physical properties of polymers. Therefore, polybutylene succinate materials can be modified by copolymerization with other monomers to meet people's needs. For example, patent CN103497316A successfully prepared low-end carboxyl content polybutylene succinate copolyester by adding co-monomers such as adipic acid during polymerization; patent CN103788348A improved the low strength problem of polybutylene succinate product 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 polybutylene succinate by adding lactic acid during polymerization; the literature “Novel random PBS-based copolymers containing aliphatic side chains for sustainable flexible food packaging” significantly improved the gas barrier property of polybutylene succinate material by adding ethylene glycol and neopentyl glycol during polymerization; the master's thesis “Synthesis and degradation performance of biodegradable polybutylene succinate copolymer” prepared a series of polybutylene succinate copolyesters by adding terminal hydroxyl diols and branched diols during polymerization, and studied their various properties.

[0005] However, in the preparation methods of the above disclosed polybutylene succinate copolyesters, in order to improve the esterification efficiency, the esterification step is usually carried out at high temperature (> 150℃). Since 1,4-butanediol is easy to dehydrate to form cyclic by-products at high temperature, high temperature esterification conditions will cause a large amount of 1,4-butanediol to dehydrate to form cyclic by-products, increasing material consumption; at the same time, tetrahydrofuran in the cyclic by-product will also corrode the metal equipment, shorten its service life and increase the production cost.

[0006] In addition, the polyester will inevitably produce cyclic by-products during the preparation process. These cyclic by-products have a great influence on the processing forming process and product quality of the polyester product. At present, there are few reports on the cyclic by-products of degradable copolyesters. Patent CN114507338A and the literature "Purification, characterization and ring-opening polymerization of poly(butylene succinate) cyclic dimers" report a method of re-opening the ring polymerization of cyclic by-products in poly(butylene succinate) by using ring-opening catalysts. However, the catalysts used in the above method are tin compounds, and the toxicity of tin compounds will have adverse effects on the environment in the process of catalyst preparation and treatment, product processing and use, and waste disposal. SUMMARY

[0007] To solve the above problems, the present application provides a method for preparing a modified poly(butylene succinate) copolyester, which has low content of cyclic by-products, low content of terminal carboxyl groups, low color value b value and high product quality.

[0008] The technical scheme adopted to achieve the purpose of the present application is:

[0009] A method for preparing a modified poly(butylene succinate) copolyester, the preparation method comprising the following steps:

[0010] a) The slurry of succinic acid, 1,4-butanediol, modifier and esterification catalyst is transported to the first esterification kettle, and the first esterification reaction is carried out at a reaction temperature of 80-130℃ to obtain the first esterification reaction liquid;

[0011] b) The first esterification reaction liquid in step a) is transported to the second esterification kettle, and the second esterification reaction is carried out at a reaction temperature of 140-190℃ to obtain the second esterification reaction liquid;

[0012] c) The second esterification reaction liquid in step b) is transported to the pre-polycondensation kettle, and the pre-polycondensation reaction is carried out by adding polymerization catalyst and ring-opening catalyst to obtain the pre-polycondensation reaction liquid;

[0013] d) The pre-polycondensation reaction liquid in step c) is transported to the final polycondensation kettle, and the final polycondensation reaction is carried out by adding a stabilizer to obtain the final polycondensation reaction liquid.

[0014] The application adopts two-stage esterification, through reducing the reaction temperature of the first esterification, the first esterification is carried out under the condition of less than 150 DEG C, more than 80% of 1, 4-butanediol completes the esterification reaction, the problem that 1, 4-butanediol is easy to dehydrate to form a cyclic by-product under high temperature is effectively avoided, in the second esterification, the reaction temperature is increased, the material after the first esterification is quickly completed the second esterification, the smooth progress of the pre-polycondensation reaction is ensured, through using the organic ring-opening catalyst in the polymerization process, the content of the cyclic by-product in the polyester is effectively reduced, meanwhile, the use of the toxic metal compound catalyst is avoided, the quality of the product is significantly improved.

[0015] In some embodiments of the application, the ring-opening catalyst 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-butylammonium tetraphenylborate.

[0016] Further, the ring-opening catalyst is added in an amount of 0.01wt% to 0.1wt% of the total mass of the reaction raw materials, which are succinic acid, 1,4-butanediol, and the modifier.

[0017] In some embodiments of the application, the esterification catalyst is one or more of benzene sulfonic acid, 4-methylbenzene sulfonic acid, p-dodecylbenzene sulfonic acid, 2,4-dimethylbenzene sulfonic acid, 2,5-dimethylbenzene sulfonic acid, zinc acetate, germanium acetate, cobalt acetate, titanium dioxide, and tetra-n-butyl titanate.

[0018] In some embodiments of the application, when the modifier is a hydroxy fatty acid, the molar ratio of succinic acid, 1,4-butanediol, and the hydroxy fatty acid in the slurry is 1:1.05-1.55:0.1-0.7.

[0019] Further, the slurry is prepared at a temperature of 30-60 DEG C.

[0020] Further, the hydroxy fatty acid is one or more of glycolic acid, lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 3-hydroxyhexanoic acid, and 6-hydroxyhexanoic acid.

[0021] In some embodiments of the application, when the modifier is a dibasic acid, the acid-alcohol molar ratio of succinic acid, the dibasic acid, and 1,4-butanediol in the slurry is 1:1.05-1.55, and the molar ratio of succinic acid to the dibasic acid modifier is 5:5-9:1.

[0022] Further, the slurry is prepared at a temperature of 30-60 DEG C.

[0023] Further, when the modifier is a dibasic acid, the dibasic acid is one or more of furandicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, dimer acid, terephthalic acid, adipic acid, 2,6-naphthalenedicarboxylic acid.

[0024] In some embodiments of the present application, the reaction pressure of the first esterification reaction in step a) is 50-100 KPaA.

[0025] The pressure values used in the present application are all absolute pressures.

[0026] Further, the residence time of the first esterification reaction in step a) is 0.5-4.5 h.

[0027] Further, the pressure of the second esterification reaction in step b) is normal pressure, and the residence time is 0.5-3.5 h.

[0028] Further, the reaction temperature of the pre-polycondensation reaction in step c) is 200-250℃, and the reaction pressure is 1-10 KPaA.

[0029] Further, the residence time of the pre-polycondensation reaction in step c) is 0.5-1.5 h.

[0030] In some embodiments of the present application, the polymerization catalyst is one or more of organic titanium or metal oxide, wherein the organic titanium includes titanium ethylene glycol, titanium propylene glycol, titanium butylene glycol, tetraethyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, and the metal oxide includes magnesium oxide, aluminum oxide, calcium oxide, titanium dioxide, zinc oxide, germanium dioxide.

[0031] Further, the reaction temperature of the final polycondensation reaction in step d) is 220-280℃, and the reaction pressure is 20-200 PaA.

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

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

[0034] In a further preferred scheme of the present application, the second esterification reaction liquid obtained in step b) is transported to a stirred bubble column, auxiliary gas is introduced, and then input into the pre-polycondensation kettle in step c).

[0035] By transporting the second esterification reaction liquid obtained in step b) to a stirred bubble column and introducing auxiliary gas, residual water in the esterification reaction can be 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.

[0036] Further, the auxiliary gas is at least one of nitrogen, helium and argon, the empty tower gas speed is 0.01-0.2 m / s; the removal temperature is 150-200 DEG 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.

[0037] The preparation method of the copolyester is a continuous production process, the continuous preparation process is simple in operation and strong in controllability, and the quality of the esterification product is significantly improved, the product has a large intrinsic viscosity, and the product quality is good.

[0038] In some embodiments of the present application, the esterification rate of the primary esterification reaction is 80-90%, and the esterification rate of the secondary esterification reaction is ≥98%.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] (1) Two-stage esterification process is used, the primary esterification reaction is carried out at a lower temperature, the raw material 1,4-butanediol is prevented from being cyclized to form a cyclic by-product at a high temperature, and the consumption of the raw material 1,4-butanediol is effectively reduced; then the secondary esterification reaction is carried out at a higher temperature, the esterification rate of the reaction system is further improved, and the smooth progress of the pre-polycondensation reaction is ensured. Through the two-stage esterification, the raw material consumption is effectively reduced, and the modified polybutylene succinate copolyester with high intrinsic viscosity and high quality is obtained.

[0041] (2) By introducing an organic ring-opening catalyst, the content of the cyclic by-product in the product is reduced, and the introduction of a toxic metal compound catalyst is avoided, and the product quality is significantly improved.

[0042] (3) In the preferred scheme of the present application, by transporting the second esterification reaction liquid to a stirred bubble column and introducing auxiliary gas, 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. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a preparation method flowchart of the modified polybutylene succinate copolyester of the present application;

[0044] Figure 2Another preparation method of the modified polybutylene succinate copolyester is shown in the flowchart. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0046] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. All the numerical identifiers, such as pH, temperature, length, flow rate, and ranges, are approximate values. It should be understood that although the term "about" is not always explicitly stated before all the numerical identifiers. It should also be understood that although the reagents described in the present application are only examples, their equivalents are known in the art.

[0047] The present application provides a preparation method of a modified polybutylene succinate copolyester, Figure 1 The flowchart of the preparation method is shown in the figure. Figure 1 The preparation method comprises the following steps:

[0048] a) preparing a slurry at 30-60°C, the slurry comprising succinic acid, 1,4-butanediol, a modifier and an esterification catalyst, conveying the slurry to a first esterification kettle, and performing a first esterification reaction at a reaction temperature of 80-130°C to obtain a first esterification reaction liquid;

[0049] b) conveying the first esterification reaction liquid in step a) to a second esterification kettle, performing a second esterification reaction at a reaction temperature of 140-190°C to obtain a second esterification reaction liquid;

[0050] c) conveying the second esterification reaction liquid in step b) to a pre-polycondensation kettle, adding a polymerization catalyst and a ring-opening catalyst to perform a pre-polycondensation reaction to obtain a pre-polycondensation reaction liquid;

[0051] d) conveying the pre-polycondensation reaction liquid in step c) to a final polycondensation kettle, adding a stabilizer to perform a final polycondensation reaction to obtain a final polycondensation reaction liquid.

[0052] The final polycondensation reaction liquid is transferred to a discharge port by a gear pump, cooled by a water bath, drawn and granulated to obtain the target product.

[0053] Optionally, the ring-opening catalyst 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-butylammonium tetraphenylborate.

[0054] Optionally, when the modifying agent is a hydroxy fatty acid, the molar ratio of succinic acid, 1,4-butanediol, and hydroxy fatty acid in the reaction slurry is 1:1.05-1.55:0.1-0.7.

[0055] Optionally, when the modifying agent is a dibasic acid, the acid-alcohol molar ratio of succinic acid, dibasic acid, and 1,4-butanediol in the slurry is 1:1.05-1.55, and the molar ratio of succinic acid to dibasic acid modifying agent is 5:5-9:1.

[0056] Optionally, the reaction pressure of the first esterification reaction in step a) is 50-100 KPaA.

[0057] Optionally, the residence time of the first esterification reaction in step a) is 0.5-4.5 h.

[0058] Optionally, the pressure of the second esterification reaction in step b) is atmospheric pressure, and the residence time is 0.5-3.5 h.

[0059] Optionally, the reaction temperature of the pre-polycondensation reaction in step c) is 200-250℃, and the reaction pressure is 1-10 KPaA.

[0060] Optionally, the residence time of the pre-polycondensation reaction in step c) is 0.5-1.5 h.

[0061] Optionally, the reaction temperature of the final polycondensation reaction is 220-280℃, and the reaction pressure is 20-200 PaA.

[0062] Optionally, the residence time of the final polycondensation reaction in step d) is 0.1-1.5 h.

[0063] In some embodiments of the present application, the second esterification reaction liquid in step b) can also be fed to a stirred bubble column, and an auxiliary gas is introduced; and then fed to the pre-polycondensation kettle in step c), as shown in Figure 2

[0064] 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℃, the removal pressure is 10-50 KPaA, the stirring rate is 60-150 rpm, and the residence time is 0.5-4.5 h.

[0065] ​In some embodiments of the present application, the reaction raw materials are collectively referred to as succinic acid, 1,4-butanediol, and a modifier.

[0066] The viscosity of the copolyester is tested according to the method described in GB-T 30294-2013 Polybutylene succinate, the solvent is phenol / 1,1,2,2-tetrachloroethane (mass ratio 50:50), and the Ubbelohde capillary viscometer is numbered 4-0.8. The carboxyl content of the copolyester is tested according to the method described in GB-T 30294-2013 Polybutylene succinate, the mixed solvent is phenol-chloroform, the volume ratio is 2:3, the standard titration solution is potassium hydroxide-benzyl alcohol, the concentration is 0.01 mol / L, the bromophenol blue indicator concentration is 0.2%, and the sample is prepared by dissolving 0.5 g of the sample in 25.00 mL of the phenol-chloroform mixed solvent. The color value of the copolyester is evaluated using the L, a, b color system, in which L is the lightness factor, a and b are color measurement numbers. Among them, b represents the yellow-blue balance, which is very important for the color of the polyester, and the lower the b value, the better the color. The cyclic by-products are characterized by gas chromatography-mass spectrometry (GC-MS).

[0067] Example 1

[0068] The raw materials succinic acid, 1,4-butanediol, and 3-hydroxyvaleric acid are configured into a slurry at a molar ratio of 1:1.05:0.1 and a benzene sulfonic acid esterification catalyst (0.03wt% of the total mass of the reaction raw materials) at 30°C, then sent to the first esterification kettle at a flow rate of 20 Kg / h for primary esterification reaction, and stayed for 1 h at a temperature of 130°C and a pressure of 100 KPaA to obtain the first esterification reaction liquid. Then the first esterification reaction liquid is transported to the second esterification kettle for secondary esterification reaction, and stayed for 2.5 h at normal pressure and 160°C to obtain the second esterification reaction liquid. Then the second esterification reaction liquid is transported to the pre-polycondensation kettle for pre-polycondensation reaction, while 0.004 Kg / h of magnesium oxide (0.02wt% of the total mass of the reaction raw materials) and 0.002 Kg / h of tetra-n-butylammonium tetraphenylborate (0.01wt% of the total mass of the reaction raw materials) are added, and stayed for 1.5 h at 200°C and 1 KPaA to obtain the pre-polycondensation reaction liquid. The pre-polycondensation reaction liquid is transported to the final polycondensation reactor for final polycondensation reaction, while 0.01 Kg / h of stabilizer trimethyl phosphite (0.05wt% of the total mass of the reaction raw materials) is added, and stayed for 1 h at 220°C and 20 PaA to obtain the final polycondensation reaction liquid. The final polycondensation reaction liquid is transferred to the discharge port by a gear pump, cooled by a water bath, drawn, and granulated to obtain the target product polybutylene succinate-3-hydroxyvalerate copolymer.

[0069] Example 2

[0070] The raw materials succinic acid, 1,4-butanediol and 4-hydroxybutyric acid were configured into a slurry in a molar ratio of 1:1.5:0.7 with an esterification catalyst titanium dioxide (0.04wt% of the total mass of the reaction raw materials) at 60°C, and then sent to the first esterification reactor at a flow rate of 25 Kg / h for a first esterification reaction, under the conditions of a temperature of 110°C and a pressure of 80 KPaA for 1.5 h to obtain a first esterification reaction liquid. Then the first esterification reaction liquid was transported to the second esterification reactor for a second esterification reaction under the conditions of normal pressure and 150°C for 2.5 h to obtain a second esterification reaction liquid. Next, the second esterification reaction liquid was transported to the pre-polycondensation reactor for a pre-polycondensation reaction, while adding 0.01 Kg / h of zinc oxide (0.04wt% of the total mass of the reaction raw materials) and 0.02 Kg / h of 1,8-diazabicycloundec-7-ene (0.08wt% of the total mass of the reaction raw materials) under the conditions of 220°C and 5 KPaA for 1.5 h to obtain a pre-polycondensation reaction liquid. Finally, the pre-polycondensation reaction liquid was transported to the final polycondensation reactor for a final polycondensation reaction, while adding 0.02 Kg / h of a stabilizer triethyl phosphate (0.08wt% of the total mass of the reaction raw materials) under the conditions of 250°C and 100 PaA for 0.7 h to obtain a final polycondensation reaction liquid. The final polycondensation reaction liquid was transferred to the discharge port by a gear pump, cooled by a water bath, drawn and cut into particles to obtain the target product poly(butyric acid succinate-4-hydroxybutyric acid butanediol ester) copolymer.

[0071] Example 3

[0072] The raw materials succinic acid, 1,4-butanediol, glycolic acid were configured into a slurry in a molar ratio of 1:1.45:0.3 with an esterification catalyst p-dodecylbenzenesulfonic acid (0.05wt% of the total mass of the reaction raw materials) at 40℃, then transported to the first esterification kettle at a flow rate of 20Kg / h for the first esterification reaction, and stayed for 2h at a temperature of 100℃ and a pressure of 60KPaA to obtain the first esterification reaction liquid. Then the first esterification reaction liquid was transported to the second esterification kettle for the second esterification reaction, and stayed for 2h at 180℃ under normal pressure to obtain the second esterification reaction liquid. Then the second esterification reaction liquid was transported to the pre-polycondensation kettle for pre-polycondensation reaction, while 0.006Kg / h of tetra-n-butyl titanate (0.03wt% of the total mass of the reaction raw materials) and 0.02Kg / h of 7-methyl-1,5,7-triazabicyclodec-5-ene (0.1wt% of the total mass of the reaction raw materials) were added, and stayed for 1.5h at 240℃ and 8KPaA to obtain the pre-polycondensation reaction liquid. Finally, the pre-polycondensation reaction liquid was transported to the final polycondensation reactor for final polycondensation reaction, while 0.008Kg / h of stabilizer tri-m-tolyl phosphite (0.04wt% of the total mass of the reaction raw materials) was added, and stayed for 1.5h at 230℃ and 50PaA to obtain the final polycondensation reaction liquid. The final polycondensation reaction liquid was transferred to the discharge port through a gear pump, discharged by water bath cooling, drawn and cut into particles to obtain the target product poly(butylenesuccinate-co-glycolate).

[0073] Example 4

[0074] The raw materials succinic acid, furandicarboxylic acid, 1,4-butanediol were configured into a slurry in a molar ratio of 0.6:0.4:1.3 with an esterification catalyst zinc acetate (0.04wt% of the total mass of the reaction raw materials) at 45℃, then transported to the first esterification kettle at a flow rate of 25Kg / h for the first esterification reaction, and stayed for 2.5h at a temperature of 110℃ and a pressure of 80KPaA to obtain the first esterification reaction liquid. Then the first esterification reaction liquid was transported to the second esterification kettle for the second esterification reaction, and stayed for 2h at 180℃ under normal pressure to obtain the second esterification reaction liquid. Then the second esterification reaction liquid was transported to the pre-polycondensation kettle for pre-polycondensation reaction, while 0.01Kg / h of titanium glycolate (0.04wt% of the total mass of the reaction raw materials) and 0.01Kg / h of tetra-n-butyl ammonium tetraphenylborate (0.04wt% of the total mass of the reaction raw materials) were added, and stayed for 1h at 250℃ and 10KPaA to obtain the pre-polycondensation reaction liquid. Finally, the pre-polycondensation reaction liquid was transported to the final polycondensation reactor for final polycondensation reaction, while 0.01Kg / h of stabilizer trimethyl phosphate (0.04wt% of the total mass of the reaction raw materials) was added, and stayed for 1h at 260℃ and 60PaA to obtain the final polycondensation reaction liquid. The final polycondensation reaction liquid was transferred to the discharge port through a gear pump, discharged by water bath cooling, drawn and cut into particles to obtain the target product poly(butylenesuccinate-co-furandicarboxylate).

[0075] Example 5

[0076] The raw materials succinic acid, terephthalic acid and 1,4-butanediol were configured into a slurry at a molar ratio of 0.7:0.3:1.4 and 55°C with an esterification catalyst 2,5-dimethylbenzenesulfonic acid (0.05wt% of the total mass of the reaction raw materials), and then transported to the first esterification kettle at a flow rate of 25Kg / h for a first esterification reaction, which was carried out at a temperature of 130°C and a pressure of 90KPaA for 2.5h, to obtain a first esterification reaction liquid. The first esterification reaction liquid was then transported to the second esterification kettle for a second esterification reaction, which was carried out at 190°C under normal pressure for 2h, to obtain a second esterification reaction liquid. The second esterification reaction liquid was then transported to the pre-polycondensation kettle for a pre-polycondensation reaction, while 0.01Kg / h of germanium dioxide (0.04wt% of the total mass of the reaction raw materials) and 0.015Kg / h of 1,5,7-triazabicyclodec-5-ene (0.06wt% of the total mass of the reaction raw materials) were added, which was carried out at 250°C and 5KPaA for 1.5h, to obtain a pre-polycondensation reaction liquid. Finally, the pre-polycondensation reaction liquid was transported to the final polycondensation reactor for a final polycondensation reaction, while 0.01Kg / h of stabilizer triisopropyl phosphite (0.04wt% of the total mass of the reaction raw materials) was added, which was carried out at 280°C and 100PaA for 1h, to obtain a final polycondensation reaction liquid. The final polycondensation reaction liquid was transferred to the discharge port by a gear pump, cooled by water bath, drawn and cut into particles, to obtain the target product poly(butylene succinate-co-terephthalate).

[0077] Example 6

[0078] The raw materials succinic acid, 1,4-butanediol and lactic acid were configured into a slurry in a molar ratio of 1:1.1:0.6 at 55°C with an esterification catalyst 4-methylbenzenesulfonic acid (0.04wt% of the total mass of the reaction raw materials), then transported to the first esterification kettle at a flow rate of 20Kg / h for a first esterification reaction, and stayed for 3.5h at a temperature of 85°C and a pressure of 70KPaA, to obtain a first esterification reaction liquid. Then the first esterification reaction liquid was transported to the second esterification kettle for a second esterification reaction, and stayed for 2.5h at normal pressure and 160°C, to obtain a second esterification reaction liquid. Subsequently, the second esterification liquid was transported to a stirred bubble column, and the column temperature was controlled at 170°C, the pressure was 40-45KPaA, the auxiliary gas was nitrogen, the empty column gas velocity was 0.05m / s, the stirring rate was 100rpm, and the residence time was 3h. Then the mixed liquid in the stirred bubble column was transported to the pre-polycondensation kettle for pre-polycondensation reaction, and 0.01Kg / h germanium dioxide (0.05wt% of the total mass of the reaction raw materials) and 0.004Kg / h 1,8-diazabicycloundec-7-ene (0.02wt% of the total mass of the reaction raw materials) were added at the same time, and stayed for 0.5h at 210°C and 5KPaA, to obtain a pre-polycondensation reaction liquid. Finally, the pre-polycondensation reaction liquid was transported to the final polycondensation reactor for final polycondensation reaction, and 0.012Kg / h stabilizer tri-m-tolyl phosphite (0.06wt% of the total mass of the reaction raw materials) was added at the same time, and stayed for 1h at 240°C and 100PaA, to obtain a final polycondensation reaction liquid. The final polycondensation reaction liquid was transferred to the discharge port by a gear pump, cooled by water bath, drawn and pelletized, to obtain the target product poly(butylenesuccinate-co-lactate-co-butanediol).

[0079] Example 7

[0080] The raw materials succinic acid, 1,4-butanediol and 6-hydroxyhexanoic acid were configured into a slurry in a molar ratio of 1:1.3:0.6 with zinc acetate as the esterification catalyst (0.04wt% of the total mass of the reaction raw materials) at 45°C, and then transported to the first esterification kettle at a flow rate of 25Kg / h for a first esterification reaction, with a temperature of 115°C and a pressure of 90KPaA for 2.5h, to obtain the first esterification reaction liquid. The first esterification reaction liquid was then transported to the second esterification kettle for a second esterification reaction, under normal pressure at 170°C for 2h, to obtain the second esterification reaction liquid. The second esterification liquid was then transported to the stirring bubble column, with a column temperature of 180°C, a pressure of 35-40KPaA, helium as the auxiliary gas, an empty column gas velocity of 0.15m / s, a stirring rate of 80rpm, and a residence time of 1h. The mixed liquid in the stirring bubble column was then transported to the pre-polycondensation kettle for pre-polycondensation reaction, while adding 0.015Kg / h of tetra-n-butyl titanate (0.06wt% of the total mass of the reaction raw materials) and 0.0075Kg / h of 1,5,7-triazabicyclodec-5-ene (0.03wt% of the total mass of the reaction raw materials), under the conditions of 200°C and 1KPaA for 1.5h, to obtain the pre-polycondensation reaction liquid. Finally, the pre-polycondensation reaction liquid was transported to the final polycondensation reactor for final polycondensation reaction, while adding 0.015Kg / h of the stabilizer triethyl phosphite (0.06wt% of the total mass of the reaction raw materials), under the conditions of 220°C and 20PaA for 1h, to obtain the final polycondensation reaction liquid. The final polycondensation reaction liquid was transferred to the discharge port by a gear pump, cooled by water bath, drawn and pelletized, to obtain the target product poly(butylenesuccinate-co-3-hydroxyvalerate).

[0081] Example 8

[0082] The raw materials succinic acid, adipic acid, 1,4-butanediol were configured into a slurry in a molar ratio of 0.85:0.15:1.5 with an esterification catalyst cobalt acetate (0.06wt% of the total mass of the reaction raw materials) at 50℃, then transported to the first esterification kettle at a flow rate of 20Kg / h for the first esterification reaction, and stayed for 3h at a temperature of 130℃ and a pressure of 60KPaA, to obtain the first esterification reaction liquid. Then the first esterification reaction liquid was transported to the second esterification kettle for the second esterification reaction, and stayed for 2h at 180℃ under normal pressure, to obtain the second esterification reaction liquid. Subsequently, the second esterification liquid was transported to the stirring bubble column, and the column temperature was controlled at 190℃, the pressure was 25-30KPaA, the auxiliary gas was helium, the empty column gas velocity was 0.02m / s, the stirring rate was 140rpm, and the residence time was 3.5h. Then the mixed liquid in the stirring bubble column was transported to the pre-polycondensation kettle for pre-polycondensation reaction, while 0.012Kg / h of titanium glycol (0.06wt% of the total mass of the reaction raw materials) and 0.016Kg / h of 7-methyl-1,5,7-triazabicyclodec-5-ene (0.08wt% of the total mass of the reaction raw materials) were added, and stayed for 1.5h at 240℃ and 2.5KPaA, to obtain the pre-polycondensation reaction liquid. Finally, the pre-polycondensation reaction liquid was transported to the final polycondensation reactor for final polycondensation reaction, while 0.01Kg / h of stabilizer triphenyl phosphate (0.05wt% of the total mass of the reaction raw materials) was added, and stayed for 0.7h at 260℃ and 80PaA, to obtain the final polycondensation reaction liquid. The final polycondensation reaction liquid was transferred to the discharge port by a gear pump, cooled by water bath, drawn and pelletized, to obtain the target product poly(butylenesuccinate-co-adipate-co-butanediol ester).

[0083] Comparative Example 1

[0084] Compared with Example 1, the first esterification stage used the same high temperature (160℃) and normal pressure reaction conditions as the second esterification stage, and the rest of the conditions were consistent with Example 1.

[0085] Comparative Example 2

[0086] Compared with Example 6, the first esterification stage used the same high temperature (160℃) and normal pressure reaction conditions as the second esterification stage, and the rest of the conditions were consistent with Example 6.

[0087] Comparative Example 3

[0088] Compared with Example 3, no ring-opening catalyst was added in the pre-polycondensation stage.

[0089] Comparative Example 4

[0090] Compared with Example 7, no ring-opening catalyst was added in the pre-polycondensation stage.

[0091] Comparative Example 5

[0092] Compared with Example 7, the first esterification stage uses high temperature (170℃) and normal pressure reaction conditions consistent with the second esterification stage, the esterification liquid is not subjected to the stirring bubble column, and the pre-polycondensation stage does not add a ring-opening catalyst.

[0093] Comparative Example 6

[0094] Compared with Example 6, the pre-polycondensation stage uses a conventional antimony compound as a ring-opening catalyst, and the rest of the conditions are consistent with Example 6.

[0095]

[0096] As can be seen from the comparison of Example 1 and Comparative Example 1 and the comparison of Example 6 and Comparative Example 2, the first esterification stage uses a low-temperature and low-pressure process, which can effectively avoid the ring-closure side reaction of the raw material 1,4-butanediol, reduce the content of the cyclic byproduct and the content of the terminal carboxyl group, improve 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 a lower alcohol acid ratio condition.

[0097] As can be seen from the comparison of Example 3 and Comparative Example 3 and the comparison of Example 7 and Comparative Example 4, the pre-polycondensation stage adds a ring-opening catalyst, which can effectively reduce the content of the cyclic byproduct in the product.

[0098] As can be seen from the comparison of Example 3, Example 4 and Example 7, Example 8, when a titanium-based catalyst is used as a polymerization catalyst, the esterification reaction liquid is subjected to the stirring bubble column and then subjected to the polycondensation reaction, which can effectively improve the color value of the copolyester and improve the product quality. This is because the titanium-based catalyst is prone to hydrolysis and other side reactions during the catalysis of the polyester polymerization, causing the product to turn yellow. After being subjected to the stirring bubble column treatment, the residual water and unreacted dihydric alcohol in the esterification reaction liquid are effectively removed, avoiding the problem of the product turning yellow and the b value increasing due to the side reactions of the titanium-based catalyst.

[0099] As can be seen from the comparison of Example 7 and Comparative Example 5, without low-temperature esterification, without the stirring bubble column for the esterification liquid, and without adding a ring-opening catalyst in the pre-polycondensation stage, the copolyester obtained not only has weaker performance indicators such as viscosity, carboxyl content, and color value than the method provided by the present application, but also has a cyclic byproduct content that is much higher than the product prepared by the method provided by the present application. Therefore, the present method can significantly improve the quality of the product.

[0100] As can be seen from the comparison of Example 6 and Comparative Example 6, when an organic compound is used as a ring-opening catalyst, the same effect as the traditional tin compound ring-opening catalyst can be achieved, thereby avoiding the introduction of a toxic metal compound catalyst and significantly improving the product quality.

[0101] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a modified polybutylene succinate copolyester, characterized by, The preparation method comprises the following steps: a) conveying the mixed slurry of succinic acid, 1,4-butanediol, modifier and esterification catalyst to a first esterification kettle, performing a first esterification reaction at a reaction temperature of 80-130℃ to obtain a first esterification reaction liquid; b) conveying the first esterification reaction liquid in step a) to a second esterification kettle, performing a second esterification reaction at a reaction temperature of 140-190℃ to obtain a second esterification reaction liquid; c) conveying the second esterification reaction liquid in step b) to a pre-polycondensation kettle, adding a polymerization catalyst and a ring-opening catalyst to perform a pre-polycondensation reaction to obtain a pre-polycondensation reaction liquid; d) conveying the pre-polycondensation reaction liquid in step c) to a final polycondensation kettle, adding a stabilizer to perform a final polycondensation reaction to obtain a final polycondensation reaction liquid; The ring-opening catalyst 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-butylammonium tetraphenylborate. The modifier in step a) is a hydroxy fatty acid or a dibasic acid.

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

3. The method of preparing a modified polybutylene succinate copolyester according to claim 1, characterized in that, The esterification catalyst is one or more of benzene sulfonic acid, 4-methylbenzene sulfonic acid, p-dodecylbenzene sulfonic acid, 2,4-dimethylbenzene sulfonic acid, 2,5-dimethylbenzene sulfonic acid, zinc acetate, germanium acetate, cobalt acetate, titanium dioxide, tetra-n-butyl titanate.

4. The method of preparing a modified polybutylene succinate copolyester according to claim 1, characterized in that, When the modifier is a hydroxy fatty acid, the molar ratio of succinic acid, 1,4-butanediol and the hydroxy fatty acid in the slurry is 1:1.05-1.55:0.1-0.

7.

5. The method of preparing a modified polybutylene succinate copolyester according to claim 4, characterized in that, The hydroxy fatty acid is one or more of glycolic acid, lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 3-hydroxyhexanoic acid and 6-hydroxyhexanoic acid.

6. The method of making a modified polybutylene succinate copolyester according to claim 1, wherein, When the modifier is a dibasic acid, the acid-alcohol molar ratio of succinic acid, the dibasic acid and 1,4-butanediol in the slurry is 1:1.05-1.55, wherein the molar ratio of succinic acid to the dibasic acid modifier is 5:5-9:

1.

7. The method of making a modified polybutylene succinate copolyester according to claim 6, wherein, The dibasic acid is one or more of furandicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, dimer acid, terephthalic acid, adipic acid and 2,6-naphthalene dicarboxylic acid.

8. The method of making a modified polybutylene succinate copolyester according to claim 1, wherein, The reaction pressure of the first esterification reaction in step a) is 50-100KPaA.

9. The method of making a modified polybutylene succinate copolyester according to claim 1, wherein, The reaction temperature of the pre-polycondensation reaction in step c) is 200-250℃, and the reaction pressure is 1-10KPaA.

10. The method of making a modified polybutylene succinate copolyester according to claim 1, wherein, The polymerization catalyst in step c) is one or more of organic titanium or metal oxide, wherein the organic titanium includes titanium glycolate, titanium propylene glycolate, titanium butylene glycolate, tetraethyl titanate, tetraisopropyl titanate and tetra-n-butyl titanate, and the metal oxide includes magnesium oxide, aluminum oxide, calcium oxide, titanium dioxide, zinc oxide and germanium dioxide.

11. The method of making a modified polybutylene succinate copolyester according to claim 1, wherein, The reaction temperature of the final polycondensation reaction in step d) is 220-280℃, and the reaction pressure is 20-200PaA.

12. The method of making a modified polybutylene succinate copolyester according to claim 1, wherein, The second esterification reaction liquid obtained in step b) is transported to a stirring bubble column, auxiliary gas is introduced, the residual water in the esterification reaction is removed, and then the pre-polycondensation kettle in step c) is input.

13. The method of making a modified polybutylene succinate copolyester according to claim 12, wherein, The removal pressure of the stirring bubble column is 10-50 KPaA.

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