Process for the preparation of polybutylene-co-cohexanoate terephthalate

Abstract

The application discloses a preparation method of polybutylene terephthalate-co-adipate, which comprises the following steps: (1) fully mixing adipic acid and part of 1,4-butanediol to obtain slurry a; (2) fully mixing the slurry a, terephthalic acid and another part of 1,4-butanediol to obtain slurry b; (3) performing esterification reaction on the slurry b to obtain an esterification product, and adding a catalyst and a chain extender in the esterification reaction process; (4) performing pre-polycondensation reaction on the esterification product to obtain a pre-condensation product; and (5) performing final polycondensation reaction on the pre-condensation product together with a stabilizer to obtain the polybutylene terephthalate-co-adipate. The application adds a pre-ingredient process on the basis of the existing preparation method, so that the acting force between raw materials is small, the prepared slurry is not prone to sedimentation, the technical problem that the slurry conveying pipeline is frequently blocked due to the easy sedimentation of the slurry in the existing preparation process is solved, production fluctuation and non-planned shutdown of the device are avoided, and continuous production is ensured.

Description

Technical Field

[0001] This invention relates to a method for preparing polyester, specifically to a method for preparing polybutylene terephthalate-Co-adipate. Background Technology

[0002] Polybutylene terephthalate (PBAT), as an aliphatic aromatic copolyester, has good ductility and elongation at break, as well as excellent heat resistance and impact resistance. It can be widely used in soft and hard packaging materials, textiles, daily consumer goods, agriculture, and automobile manufacturing. Its final degradation products are carbon dioxide and water that can be absorbed and utilized by plants, which will not cause environmental pollution. It is in line with the green concept of sustainable development in today's society, and therefore it is highly favored by the market, with market demand increasing year by year.

[0003] In the production of polybutylene terephthalate (PBAT), the raw materials terephthalic acid, adipic acid, 1,4-butanediol, catalysts, and additives are processed through slurry preparation, esterification, pre-condensation, and final condensation to form PBAT particles via underwater pelletizing. In actual production, during the mixing and pulping process of terephthalic acid, adipic acid, and 1,4-butanediol, adipic acid has a certain solubility in 1,4-butanediol. Due to the interaction between the dicarboxylic acids adipic acid and terephthalic acid, and uneven dispersion, the slurry easily settles and clogs the slurry delivery pipeline, potentially causing plant shutdowns in severe cases. Summary of the Invention

[0004] Purpose of the invention: In order to solve the technical problems existing in the prior art, the present invention aims to provide a method for preparing polybutylene terephthalate-Co-adipate that can avoid pipeline blockage and achieve continuous production.

[0005] Technical solution: The preparation method of polybutylene terephthalate-Co-adipate of the present invention comprises the following steps:

[0006] (1) First, thoroughly mix adipic acid and a portion of 1,4-butanediol to obtain slurry a;

[0007] (2) Mix slurry a, terephthalic acid and another part of 1,4-butanediol thoroughly to obtain slurry b;

[0008] (3) Slurry b undergoes esterification to obtain esterified products. A catalyst and chain extender are added during the esterification process.

[0009] (4) The esterified product undergoes a pre-condensation reaction to obtain the pre-condensed product;

[0010] (5) The pre-condensed product and the stabilizer are subjected to a final polycondensation reaction to obtain polybutylene terephthalate-Co-adipate.

[0011] Further, in step (1), the particle size of adipic acid is 30-300 μm, the mixing temperature is 40-60℃, the mixing time is 3-5 h, the amount of adipic acid added accounts for 45-70% of the total acid molar content, and a portion of 1,4-butanediol accounts for 30-40% of the total 1,4-butanediol usage. The particle size and particle size distribution of adipic acid have a significant impact on the performance of the slurry. If the particle size is too small, the slurry formed by adipic acid and 1,4-butanediol will become viscous, and the adipic acid powder will easily float on the surface of the slurry. Conversely, if the particle size is too large, the adipic acid will easily settle.

[0012] Furthermore, in step (2), the mixing temperature is 40-50℃ and the time is 2-3h.

[0013] Furthermore, in steps (1) and (2), the molar ratio of total acid to total alcohol ranges from 1:1 to 1:2.

[0014] Further, in step (3), the esterification reaction conditions are: reaction temperature 230-245℃, reaction pressure 40-50kPa, esterification rate of esterified product 98%, catalyst is titanium catalyst, preferably titanate, more specifically tetrabutyl titanate, isopropyl titanate, etc., the amount of catalyst added is 100-200ppm based on the theoretical yield of copolyester, and the chain extender is polyol, the amount of chain extender added is 300-600ppm based on the theoretical yield of copolyester.

[0015] Furthermore, in step (4), the conditions for the pre-condensation reaction are: reaction temperature 250-260℃, reaction pressure 1.0-1.5kPa, and intrinsic viscosity of the pre-condensed material 0.35-0.40dL / g.

[0016] Further, in step (5), the conditions for the final polycondensation reaction are: reaction temperature 250-260℃, reaction pressure 50-200Pa, stabilizer is one or more of phosphoric acid, phosphorous acid, phosphate ester, and phosphite ester, more specifically one or more of phosphoric acid, trimethyl phosphate, phosphorous acid, triphenyl phosphate, and triphenyl phosphite, with an addition amount of 400-600μg / g, and the melt index of poly(butylene terephthalate-Co-adipate) is 3-10g / 10min, the melting point is 110-120℃, and the intrinsic viscosity is 1.3-1.4dL / g.

[0017] Invention Principle: This invention uses terephthalic acid, adipic acid, and 1,4-butanediol as raw materials, adds a pre-mixing step of adipic acid and 1,4-butanediol, and adopts a co-esterification method. Through a three-reactor production process, esterification and polycondensation reactions are carried out under the action of catalysts, stabilizers, chain extenders, etc., to produce poly(butylene terephthalate-Co-adipate). This solves the problem of slurry sedimentation causing blockage of slurry conveying pipelines, avoids production fluctuations and unplanned plant shutdowns, and ensures continuous production of poly(butylene terephthalate-Co-adipate).

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0019] (1) The present invention adds a pre-mixing process to the existing preparation of poly(butylene terephthalate-Co-adipate). Adipic acid is fully dispersed in 1,4-butanediol before mixing with terephthalic acid. The interaction force is greatly reduced, which can solve the technical problem in the prior art that the interaction force between adipic acid and terephthalic acid and the uneven dispersion cause the slurry to settle and block the slurry conveying pipeline, which can cause the plant to shut down in severe cases. This invention ensures the continuous production of poly(butylene terephthalate-Co-adipate).

[0020] (2) The preparation method adopted in this invention has the advantages of continuous production, no risk of shutdown, high production efficiency, low production cost and high safety. Detailed Implementation

[0021] The present invention will now be further described with reference to specific embodiments.

[0022] Example 1: The preparation method of polybutylene terephthalate-Co-adipate of the present invention is carried out according to the following steps:

[0023] (1) Add adipic acid and a portion of 1,4-butanediol together into a mixing tank and mix at 50°C. The adipic acid particle size is 110-130μm, the feed rate is 1660kg / h, and the 1,4-butanediol feed rate is 1228kg / h. After mixing for 4h, slurry a is obtained.

[0024] (2) Add slurry a, terephthalic acid and another part of 1,4-butanediol to another preparation tank and mix at 70°C. The feed rate of terephthalic acid is 1742 kg / h and the feed rate of 1,4-butanediol is 2709 kg / h. After mixing for 2 hours, slurry b is obtained.

[0025] (3) Slurry b enters the esterification kettle for esterification reaction, and catalyst and chain extender are added at the same time. The esterification temperature is 231℃ and the esterification pressure is 40kPaA. After the reaction is completed, the esterified product is obtained. The esterification rate of the esterified product is 98%.

[0026] (4) The esterified product enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization temperature is 245℃ and the prepolymerization pressure is 1.5kPaA. After the reaction is completed, the prepolymer is obtained. The intrinsic viscosity of the prepolymer is 0.35dL / g.

[0027] (5) The pre-shrinked material and stabilizer were added together to the final shrinkage reactor for final shrinkage polymerization. The final shrinkage temperature was 245℃, the final shrinkage pressure was 120Pa, and the stirring speed was moderate. The resulting polybutylene terephthalate (PET) had an intrinsic viscosity of 1.40 dL / g, a melting point of 118℃, and a melt index of 5 g / 10 min. The entire production process was normal, and all quality indicators of the product met the standards.

[0028] Example 2: The preparation method of polybutylene terephthalate-Co-adipate of the present invention is carried out according to the following steps:

[0029] (1) Add adipic acid and a portion of 1,4-butanediol together into a mixing tank and mix at 60°C. The adipic acid particle size is 110-130μm, the feed rate is 1570kg / h, and the 1,4-butanediol feed rate is 1160kg / h. After mixing for 5h, slurry a is obtained.

[0030] (2) Add slurry a, terephthalic acid and another part of 1,4-butanediol to another preparation tank and mix at 60°C. The feed rate of terephthalic acid is 1520 kg / h and the feed rate of 1,4-butanediol is 2420 kg / h. After mixing for 3 hours, slurry b is obtained.

[0031] (3) Slurry b enters the esterification kettle for esterification reaction, and catalyst and chain extender are added at the same time. The esterification temperature is 242℃ and the esterification pressure is 40kPaA. After the reaction is completed, the esterified product is obtained. The esterification rate of the esterified product is 98.5%.

[0032] (4) The esterified product enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization temperature is 255℃ and the prepolymerization pressure is 1.2kPaA. After the reaction is completed, the prepolymer is obtained. The intrinsic viscosity of the prepolymer is 0.39dL / g.

[0033] (5) The pre-shrinked material and stabilizer were added together to the final shrinkage reactor for final shrinkage polymerization. The final shrinkage temperature was 253℃, the final shrinkage pressure was 100Pa, and the stirring speed was moderate. The resulting polybutylene terephthalate (PET) had an intrinsic viscosity of 1.48 dL / g, a melting point of 115℃, and a melt index of 4.0 g / 10 min. The entire production process was normal, and all quality indicators of the product met the standards.

[0034] Example 3: The preparation method of polybutylene terephthalate-Co-adipate of the present invention is carried out according to the following steps:

[0035] (1) Add adipic acid and a portion of 1,4-butanediol together into a mixing tank and mix at 60°C. The adipic acid particle size is 110-130μm, the feed rate is 1520kg / h, and the 1,4-butanediol feed rate is 1125kg / h. After mixing for 5h, slurry a is obtained.

[0036] (2) Add slurry a, terephthalic acid and 1,4-butanediol together to another preparation tank and mix at 60°C. The feed rate of terephthalic acid is 1730 kg / h and the feed rate of 1,4-butanediol is 1126 kg / h. After mixing for 3 hours, slurry b is obtained.

[0037] (3) Slurry b enters the esterification kettle for esterification reaction, and catalyst and chain extender are added at the same time. The esterification temperature is 242℃ and the esterification pressure is 40kPaA. After the reaction is completed, the esterified product is obtained. The esterification rate of the esterified product is 98%.

[0038] (4) The esterified product enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization temperature is 255℃ and the prepolymerization pressure is 1.5kPaA. After the reaction is completed, the prepolymer is obtained. The intrinsic viscosity of the prepolymer is 0.37dL / g.

[0039] (5) The pre-shrinking material and stabilizer were added together to the final shrinkage reactor for final shrinkage reaction. The final shrinkage temperature was 253℃, the final shrinkage pressure was 100Pa, and the stirring speed was medium. The intrinsic viscosity of poly(butylene terephthalate-Co-adipate) was 1.45dL / g, the melting point was 120℃, and the melt index was 4.5g / 10min.

[0040] Comparative Example 1: The difference from Example 1 is that adipic acid and 1,4-butanediol are not pre-prepared. Instead, adipic acid, terephthalic acid, and 1,4-butanediol are directly prepared and pulped in a mixing tank. The prepared pulp is then subjected to esterification, pre-condensation, and final condensation polymerization to prepare terephthalic acid-Co-butylene adipate, according to the following steps:

[0041] (1) Adipic acid, terephthalic acid and 1,4-butanediol are added to a mixing tank and mixed at 60°C. The particle size of adipic acid is 110-130μm, the feed rate of adipic acid is 480kg / h, the feed rate of 1,4-butanediol is 708kg / h, and the feed rate of terephthalic acid is 545kg / h. After mixing for 3h, a slurry is obtained.

[0042] (2) The slurry enters the esterification kettle for esterification reaction, and a catalyst and chain extender are added at the same time. The esterification temperature is 242℃ and the esterification pressure is 40kPaA. After the reaction is completed, the esterified product is obtained. The esterification rate of the esterified product is 98%.

[0043] (3) The esterified product enters the prepolymerization reactor for prepolymerization reaction. The prepolymerization temperature is 255℃ and the prepolymerization pressure is 1.5kPaA. After the reaction is completed, the prepolymer is obtained. The intrinsic viscosity of the prepolymer is 0.31dL / g.

[0044] (4) The pre-shrinking material and stabilizer were added together to the final shrinkage reactor for final shrinkage reaction. The final shrinkage temperature was 253℃, the final shrinkage pressure was 100Pa, and the stirring speed was medium. The intrinsic viscosity of poly(butylene terephthalate-Co-adipate) was 1.36dL / g, the melting point was 118℃, and the melt index was 7.5g / 10min.

[0045] In actual production, it was found that when the slurry was prepared according to the above procedure, starting from the second day of production, the slurry began to settle, the slurry pump pressure was high and the interlock tripped, the slurry delivery pipeline was severely blocked, and production could not be carried out and was forced to stop.

Claims

1. A method for preparing polybutylene terephthalate-Co-adipate, characterized in that, Follow these steps: (1) Adipic acid and a portion of 1,4-butanediol are thoroughly mixed to obtain slurry a; the particle size of the adipic acid is 30-300 μm; the portion of 1,4-butanediol accounts for 30-40% of the total amount of 1,4-butanediol. (2) Mix slurry a, terephthalic acid and another part of 1,4-butanediol thoroughly to obtain slurry b; (3) Slurry b undergoes esterification to obtain esterified products. A catalyst and chain extender are added during the esterification process. (4) The esterified product undergoes a pre-condensation reaction to obtain a pre-condensed product; (5) The pre-condensed product and the stabilizer are subjected to a final polycondensation reaction to obtain polybutylene terephthalate-Co-adipate.

2. The preparation method according to claim 1, characterized in that, In step (1), the mixing temperature is 40-60℃.

3. The preparation method according to claim 1, characterized in that, In step (1), the amount of adipic acid added accounts for 45-70% of the total acid molar content.

4. The preparation method according to claim 1, characterized in that, In steps (1) and (2), the molar ratio of total acid to total alcohol is 1:1 to 1:

2.

5. The preparation method according to claim 1, characterized in that, In step (2), the mixing temperature is 40-50℃.

6. The preparation method according to claim 1, characterized in that, In step (3), the esterification reaction conditions are: reaction temperature 230-245℃ and reaction pressure 40-50kPa.

7. The preparation method according to claim 1, characterized in that, In step (4), the conditions for the pre-condensation reaction are: reaction temperature 250-260℃ and reaction pressure 1.0-1.5kPa.

8. The preparation method according to claim 1, characterized in that, In step (5), the reaction conditions for the final polycondensation reaction are: reaction temperature 250-260℃ and reaction pressure 50-200Pa.