Hydrolysis-resistant catalyst for polyester and method for producing low-melting-point TPEE (Thermoplastic Polyether Ether) by adopting hydrolysis-resistant catalyst

Abstract

The invention discloses a hydrolysis-resistant catalyst for polyester and a method for producing low-melting-point TPEE by adopting the hydrolysis-resistant catalyst, and the hydrolysis-resistant catalyst is prepared by the following steps in sequence: firstly, weighing 0.5-1.5 kg of chitosan, adding the chitosan into 1kg of organic alcohol BDO, fully stirring until the chitosan is completely dispersed in the BDO, then dropwise adding 100-300g of surfactant monopotassium phosphate, stirring for 30-60 minutes, and then adding 0.5-1.5 kg of organic alcohol BDO, fully stirring until the chitosan is completely dispersed in the BDO to obtain the hydrolysis-resistant catalyst. Dissolving the chitosan solid in the dispersion liquid completely, then adding acetic acid into the solution, and adjusting the pH value to be 5-6 to obtain hydrolysis-resistant liquid; 1.25-2.5 kg of tetrabutyl titanate is weighed and dropwise added into the hydrolysis-resistant solution, full stirring is conducted till no floccules exist in the solution, meanwhile, the temperature of the solution is increased to 60-100 DEG C, negative pressure distillation is conducted under the condition of 10-40 kPa, low-boiling-point substances are removed, the clear and transparent hydrolysis-resistant titanium catalyst is obtained finally, and the titanium content ranges from 6.14% to 6.67%. The method can improve the catalytic efficiency, and effectively solves the problems that the catalyst is easy to hydrolyze to influence the chromaticity of the product and the catalytic activity is uncontrollable.

Description

Technical Field

[0001] The invention relates to a hydrolysis-resistant catalyst for polyester and a method for producing low-melting-point TPEE by using the hydrolysis-resistant catalyst, belonging to the technical field of polyester production methods. Background Art

[0002] Thermoplastic polyester elastomer (TPEE) is a block copolymer containing aromatic polyester hard segment (crystalline phase) and aliphatic polyester or polyester soft segment (continuous phase), also known as polyester rubber. TPEE is a high-performance engineering-grade elastomer that combines the softness and elasticity of rubber with the rigidity and easy processing of thermoplastics. TPEE has high mechanical strength, good elasticity, excellent impact resistance, creep resistance, cold resistance, bending fatigue resistance, oil resistance, chemical and solvent corrosion resistance, wide operating temperature range (-70~+200℃), wide hardness range (32D-80D), etc. Compared with other thermoplastic elastomers, TPEE has the highest heat resistance.

[0003] Low melting point polyester elastomer is based on TPEE, with modifier added to improve its low temperature processing performance, while retaining its high mechanical strength, good elasticity, impact resistance, creep resistance, cold resistance, bending fatigue resistance, oil resistance, chemical resistance and solvent corrosion resistance, etc. It has unique application advantages in the development of TPEE products for film, wire drawing and rubber coating. Due to these excellent comprehensive properties, it has been widely used in automotive parts, hydraulic hoses, cables and wires, electronic appliances, sports goods and construction.

[0004] In the production process of conventional TPEE and low-melting-point TPEE, titanium catalysts are often added, such as tetrabutyl titanate, to catalyze esterification and polycondensation reactions. Titanium catalysts are green, non-toxic, non-toxic, highly catalytic, and produce polyester with good color and low grayscale. However, the problem of easy hydrolysis in water is still a problem that has not been fundamentally solved in polyester production. After hydrolysis, titanium catalysts are easily accumulated on the wall of the reactor, resulting in poor heat exchange effect, thus affecting the color of the product and its final quality. Therefore, it is urgent to develop a titanium catalyst for polyester with high catalytic activity, stable catalytic performance and resistance to hydrolysis.

[0005] The Chinese invention patent with publication number CN113429551B discloses a method for synthesizing a low-melting-point thermoplastic polyester elastomer. The method uses dimethyl phthalate, diol, polyether polyol and polyester polyol as main raw materials and uses a titanate catalyst to synthesize the thermoplastic polyester elastomer.

[0006] The Chinese invention patent application with publication number CN113461921A discloses a method for preparing a low-melting-point thermoplastic polyester elastomer, wherein an aromatic dibasic acid, 1,4-butanediol, polytetramethylene glycol ether and a fourth component are mixed and a low-melting-point thermoplastic polyester elastomer is prepared under the action of a titanium catalyst.

[0007] The titanate catalysts used in the above two methods are easily hydrolyzed, resulting in poor product quality, and no method for continuously producing low-melting-point thermoplastic polyester elastomers has been found in the relevant public patent documents. Summary of the invention

[0008] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract of the specification of this application and the title of the invention, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0009] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0010] The primary purpose of the present invention is to provide a hydrolysis-resistant catalyst for polyester, which can improve the catalytic efficiency and effectively solve the problem that the catalyst is easy to hydrolyze and affects the product color and the catalytic activity is uncontrollable.

[0011] In order to solve the above technical problems, a hydrolysis-resistant catalyst for polyester of the present invention is prepared, which comprises the following steps in sequence: firstly, weighing 0.5-1.5 kg of chitosan, adding it to 1 kg of organic alcohol BDO, stirring it fully until the chitosan is completely dispersed in the BDO, then dropping 100 g-300 g of surfactant potassium dihydrogen phosphate to dissolve all the chitosan solids in the dispersion, then adding acetic acid to the solution through online pH meter monitoring to adjust the pH value between 5 and 6, and the above solution is a hydrolysis-resistant solution; weighing 1.25-2.5 kg of tetrabutyl titanate, dropping it into the above hydrolysis-resistant solution, stirring it fully until no flocs are present in the solution, and at the same time heating the solution to 60-100° C., performing negative pressure distillation under 10-40 kPa to remove low-boiling substances, and finally obtaining a clear and transparent hydrolysis-resistant titanium catalyst, wherein the titanium content is 6.14% to 6.67%.

[0012] Furthermore, the chitosan is 0.5 kg, the surfactant potassium dihydrogen phosphate is 100 g, 1.25 kg of tetrabutyl titanate is weighed and added dropwise to the hydrolysis-resistant liquid, and the solution is heated to 60° C. and subjected to negative pressure distillation at 10 kPa to obtain a hydrolysis-resistant titanium catalyst with a titanium content of 6.14%.

[0013] Furthermore, the chitosan is 1.0 kg, the surfactant potassium dihydrogen phosphate is 200 g, 2 kg of tetrabutyl titanate is weighed and added dropwise to the hydrolysis-resistant liquid, and the solution is heated to 80° C. and subjected to negative pressure distillation at 25 kPa to obtain a hydrolysis-resistant titanium catalyst with a titanium content of 6.67%.

[0014] Furthermore, the chitosan is 1.5 kg, the surfactant potassium dihydrogen phosphate is 300 g, 2.5 kg of tetrabutyl titanate is weighed and added dropwise to the hydrolysis-resistant liquid, and the solution is heated to 100° C. and subjected to negative pressure distillation at 40 kPa to obtain a hydrolysis-resistant titanium catalyst with a titanium content of 6.6%.

[0015] Another object of the present invention is to overcome the problems existing in the prior art and provide a method for producing low melting point TPEE using a hydrolysis-resistant catalyst, which can improve production efficiency and product quality.

[0016] In order to solve the above technical problems, the method of producing low melting point TPEE using a hydrolysis-resistant catalyst of the present invention comprises the following steps in sequence: the molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2: (0.5-1.5): (3-5), PTMEG accounts for 30-50% of the total acid mass ratio, all the above raw materials are continuously fed into a slurry preparation tank for premixing and preheating to 50°C, and then continuously output to a slurry preparation tank 1, and then continuously enter the first ester at a flow rate of 400-600kg / h. The first esterification kettle is used for esterification reaction at normal pressure and temperature of 200-210°C. The prepared hydrolysis-resistant catalyst is continuously added to the first esterification kettle at a flow rate of 0.4-0.6 kg / h, and the reaction is continued for 100-200 minutes. The by-products produced by the reaction are removed, and the primary esterification product discharged from the first esterification kettle is continuously transported to the second esterification kettle for further esterification. The reaction is continued for 100-140 minutes under vacuum conditions of an absolute pressure of 70-90 kPa and a temperature of 200-235°C to obtain a product with an esterification rate of more than 9 6% esterification product; it is pumped out by the esterification material pump, filtered by the first filter, and continuously sent to the pre-condensation kettle for pre-condensation reaction, and the temperature is raised to 235-240°C, and the residence time is 40-60min under the vacuum condition of absolute pressure 10-20kPa, and the unreacted 1,4-butanediol is removed. The pre-condensation product is pumped out by the first condensation material pump and filtered by the second filter, and then transferred to the second condensation kettle, and the residence time is 90-120m under the vacuum degree of 0.6-1.2kPa and the temperature of 240-245°C. in, the obtained polycondensation product is pumped out by the second polycondensation material pump, filtered by the filter three, and continuously enters the final polycondensation reactor. After staying for 120-180 minutes at 50-300Pa vacuum and 245-248°C, it is pumped out by the melt delivery pump, filtered by the filter four, metered by the melt metering pump, cooled by the melt heat exchanger, and finally conveyed to the pelletizer one through the filter five under the pressurization effect of the melt booster pump. After pelletizing, the slices are dried and conveyed to the slice silo for storage.

[0017] Furthermore, the by-products removed by the first esterification kettle enter the process tower, and after passing through the reflux tank at the top of the tower, a part is taken out for subsequent purification treatment, and a part is refluxed to the top of the first esterification kettle through the process tower.

[0018] Furthermore, part of the PTMEG enters the second slurry preparation tank for mixing, and then enters the precondensation kettle together with part of the hydrolysis-resistant catalyst.

[0019] Furthermore, the molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2:0.5:3, and PTMEG accounts for 30% of the total acid by mass.

[0020] Furthermore, the molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2:1:4, and PTMEG accounts for 40% of the total acid by mass.

[0021] Furthermore, the molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2:1.5:5, and PTMEG accounts for 50% of the total acid by mass.

[0022] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The hydrolysis-resistant catalyst for polyester can effectively solve the problem that the catalyst is easy to hydrolyze and affects the product color and the catalytic activity is uncontrollable, and avoids the problem that the hydrolysis product adheres to the reactor, which easily leads to the problem of poor product color. At the same time, it also solves the production problems such as poor heat exchange effect of the reactor caused by the easy hydrolysis of the catalyst and the need for frequent shutdown and cleaning.

[0023] 2. The low-melting-point TPEE polyester produced has good low-temperature processing performance, while retaining its high mechanical strength, good elasticity, excellent impact resistance, creep resistance, cold resistance, bending fatigue resistance, oil resistance, chemical resistance and solvent corrosion resistance, etc., and can obtain high-viscosity and high-elasticity low-melting-point thermoplastic polyester elastomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor. The accompanying drawings are only provided for reference and explanation, and are not used to limit the present invention.

[0025] in:

[0026] Figure 1 It is a flow chart of the flexible production system of low melting point TPEE in the present invention;

[0027] In the figure: 1. Slurry preparation tank; 1a. Top feeding port; 2a. Slurry preparation tank 1; 2b. Slurry preparation tank 2; 3. First esterification kettle; 4. Second esterification kettle; 5. Pre-polycondensation kettle; 6. Second polycondensation kettle; 7. Final polycondensation reactor; 8. Pelletizer 1; 9. Slice silo; 10. Additive addition system; 11. Vacuum catcher; 12. Vacuum collection tank; 13. Scraper condenser; 14. Hot well; 15. Process tower; 16. Tower top reflux tank; 17. Cold trap; 18. Vacuum pump; 19. Jet vacuum pump unit;

[0028] B1. Esterification material pump; B2. First polycondensation material pump; B3. Second polycondensation material pump; B4. Melt delivery pump; B5. Melt metering pump; B6. Melt booster pump; B7. Spray circulation pump;

[0029] H1. Melt heat exchanger, H2. Spray liquid heat exchanger;

[0030] F1. Filter 1; F2. Filter 2; F3. Filter 3; F4. Filter 4; F5. Filter 5;

[0031] G0. BDO feed pipe; G1. PTMEG feed pipe; G2. PTA feed pipe; G3. Isophthalic acid feed pipe. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below in conjunction with specific diagrams. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. All unspecified pressures herein refer to absolute pressures.

[0034] like Figure 1 As shown, in the flexible production system of low-melting-point TPEE of the present invention, the outlets of the BDO feed pipe G0 and the PTMEG feed pipe G1 are connected to the top inlet of the slurry preparation tank 1, the outlets of the PTA feed pipe G2 and the isophthalic acid feed pipe G3 are connected to the top feeding port 1a of the slurry preparation tank 1, the bottom outlet of the slurry preparation tank 1 is connected to the inlet of the slurry preparation tank 2a, the outlet of the slurry preparation tank 2a is connected to the slurry inlet of the first esterification kettle 3 through a screw pump, and the hydrolysis-resistant catalyst and other additives are injected into the first esterification kettle 3 through the additive addition system 10. The gas phase outlet of the first esterification kettle 3 is connected to the air inlet of the process tower 15, and the top of the process tower 15 is provided with a tower top reflux tank 16, and the gas phase outlet of the tower top reflux tank 16 is drawn out by a vacuum pump 18 through a cold trap 17.

[0035] The bottom outlet of the first esterification kettle 3 is connected to the inlet of the second esterification kettle 4. The second esterification kettle 4 and the first esterification kettle 3 share a process tower 15. The outlet of the second esterification kettle 4 is connected to the inlet of the esterification material pump B1. The outlet of the esterification material pump B1 is connected to the inlet of the filter-F1. The outlet of the filter-F1 is connected to the bottom inlet of the pre-condensation kettle 5. The gas phase outlet of the pre-condensation kettle 5 is connected to the middle inlet of the vacuum trap 11. The bottom outlet of the vacuum trap 11 is connected to the vacuum collection tank 12. The top outlet of the vacuum trap 11 is connected to the inlet of the scraper condenser 13. The gas phase of the scraper condenser 13 is pumped out by the vacuum pump 18 through the cold trap 17. The circulating liquid of the scraper condenser 13 is pumped out by the spray circulation pump B7 through the hot well 14, flows through the hot side of the spray liquid heat exchanger H2 for cooling, and then enters the upper part of the scraper condenser 13 for circulation spraying.

[0036] The discharge port of the pre-condensation kettle 5 is connected to the inlet of the first condensation material pump B2, the outlet of the first condensation material pump B2 is connected to the inlet of the second filter F2, the outlet of the second filter F2 is connected to the feed port of the second condensation kettle 6, and the discharge port of the second condensation kettle 6 is connected to the inlet of the second condensation material pump B3.

[0037] The outlet of the second polycondensation material pump B3 is connected to the inlet of filter three F3, the outlet of filter three F3 is connected to the feed port of the final polycondensation reactor 7, the melt outlet of the final polycondensation reactor 7 is connected to the inlet of the melt delivery pump B4, the outlet of the melt delivery pump B4 is connected to the inlet of filter four F4, the outlet of filter four F4 is connected to the inlet of the melt metering pump B5, the outlet of the melt metering pump B5 is connected to the inlet of the melt booster pump B6 via the melt heat exchanger H1, the outlet of the melt booster pump B6 is connected to the inlet of the pelletizer 8 via the filter five F5, and the discharge of the pelletizer 8 enters the slicing silo 9.

[0038] The gas phase of the second polycondensation reactor 6 and the final polycondensation reactor 7 is then extracted by a jet vacuum pump unit 19 , and the exhaust port of the jet vacuum pump unit 19 is extracted by a vacuum pump 18 through a cold trap 17 .

[0039] In addition, the PTMEG feed pipe G1 is also connected to the inlet of the slurry preparation tank 2b, the outlet of the slurry preparation tank 2b is connected to the top inlet of the precondensation kettle 5, and the inlet of the precondensation kettle 5 is also provided with an additive adding system 10, so that the system has flexible production characteristics, not only can it produce low-melting point TPEE, but also can be compatible with the production of conventional TPEE, low-melting point PBT, conventional PBT and other products. It has the characteristics of a wide range of applications. When the production capacity of a single variety is in excess, it can be transferred to other varieties, which can effectively improve equipment utilization and reduce the waste of equipment and labor resources.

[0040] Example 1

[0041] The preparation steps of hydrolysis-resistant catalyst for polyester are as follows:

[0042] First, weigh 0.5 chitosan, add it to 1kg of organic alcohol BDO, stir thoroughly until chitosan is completely dispersed in BDO, then drop 100g of surfactant potassium dihydrogen phosphate to dissolve all chitosan solids in the dispersion, then monitor through an online pH meter, add acetic acid to the solution, adjust the pH value to 5, and the above solution is a hydrolysis-resistant solution. Weigh 1.25kg of tetrabutyl titanate and drop it into the above hydrolysis-resistant solution, stir thoroughly until there is no floc in the solution, and at the same time heat the solution to 60°C, perform negative pressure distillation under 10kPa conditions, remove low-boiling substances, and finally obtain a clear and transparent hydrolysis-resistant titanium catalyst, wherein the titanium content in the hydrolysis-resistant catalyst is 6.14%.

[0043] Example 2

[0044] The preparation steps of hydrolysis-resistant catalyst for polyester are as follows:

[0045] First, 1.0 kg of chitosan was weighed and added to 1 kg of organic alcohol BDO, and the mixture was stirred until the chitosan was completely dispersed in the BDO. Then, 200 g of surfactant potassium dihydrogen phosphate was added dropwise to dissolve all the chitosan solids in the dispersion. Then, acetic acid was added to the solution through online pH meter monitoring to adjust the pH value to 5.5. The above solution was a hydrolysis-resistant solution. 2 kg of tetrabutyl titanate was weighed and added dropwise to the above hydrolysis-resistant solution, and the mixture was stirred until no flocs were present in the solution. At the same time, the solution was heated to 80°C and subjected to negative pressure distillation at 25 kPa to remove low-boiling substances. Finally, a clear and transparent hydrolysis-resistant titanium catalyst was obtained, wherein the titanium content in the hydrolysis-resistant catalyst was 6.67%.

[0046] Example 3

[0047] The preparation steps of hydrolysis-resistant catalyst for polyester are as follows:

[0048] First, 1.5 kg of chitosan was weighed and added to 1 kg of organic alcohol BDO, and the mixture was stirred until the chitosan was completely dispersed in the BDO. Then, 300 g of potassium dihydrogen phosphate, a surfactant, was added dropwise to dissolve all the chitosan solids in the dispersion. Then, acetic acid was added to the solution through an online pH meter to adjust the pH value to 6. The above solution was a hydrolysis-resistant solution. 2.5 kg of tetrabutyl titanate was weighed and added dropwise to the above hydrolysis-resistant solution, and the mixture was stirred until no flocs were present in the solution. At the same time, the solution was heated to 100° C. and subjected to negative pressure distillation at 40 kPa to remove low-boiling substances. Finally, a clear and transparent hydrolysis-resistant titanium catalyst was obtained, wherein the titanium content in the hydrolysis-resistant catalyst was 6.6%.

[0049] In order to characterize the hydrolysis resistance of the hydrolysis-resistant catalyst, 50% desalted water was added to the hydrolysis-resistant titanium-based catalyst obtained in Example 2 and boiled for 30 minutes. After completely removing the water under negative pressure, a catalytic synthesis PBT experiment was carried out on a homemade 5L test device. The test results and data of the intrinsic viscosity, melting point, terminal carboxyl group, chromaticity, ash content, etc. of the obtained PBT are shown in Table 1.

[0050] Table 1 Test results data table

[0051]

[0052] Based on the above test product analysis, it can be concluded that the hydrolysis-resistant catalyst after boiling in water still maintains the same catalytic performance as the original formulated catalyst, and its catalytic activity is not affected by water, which effectively solves the problem of easy hydrolysis of titanium-based catalysts and provides an effective hydrolysis-resistant catalyst.

[0053] Example 4

[0054] The production method of low melting point TPEE, the specific steps are as follows:

[0055] Terephthalic acid: isophthalic acid: 1,4-butanediol are mixed at a molar ratio of 2:0.5:3, and polytetramethylene glycol ether (PTMEG) is added at the same time, and transported into the slurry preparation tank 1 respectively, and the temperature is preheated to 50°C, wherein the mass ratio of PTMEG to total acid is 30%. All the above raw materials are continuously fed into the slurry preparation tank 1 for premixing, and then continuously output to the slurry preparation tank 2a, and then continuously enter the first esterification kettle 3 at a flow rate of 400kg / h, under normal pressure, The temperature is 200° C., and the esterification reaction is carried out. The hydrolysis-resistant catalyst prepared in Example 1 is continuously added to the first esterification kettle 3 through the auxiliary agent adding system 10 at a flow rate of 0.4 kg / h. The residence time is 100 min. The by-products including tetrahydrofuran and water produced by the reaction are removed. The removed by-products pass through the process tower 15 and the top reflux tank 16. A part of them is extracted for subsequent purification treatment, and a part of them is refluxed to the first esterification kettle 3 through the process tower to obtain the initial esterification product. The initial esterification product is continuously transported to the second esterification kettle 4 for further esterification. Under the vacuum conditions provided by the vacuum pump 18, the absolute pressure is 70 kPa and the temperature is 200° C., and the reaction is continued for 100 minutes to obtain an esterification product with an esterification rate of more than 96%. The esterification product is sent out by the esterification material pump B1, filtered by the filter F1, and continuously sent to the pre-condensation kettle 5 for pre-condensation reaction. The temperature is raised to 235° C., and the vacuum pump 18 provides a vacuum condition of an absolute pressure of 10 kPa. The residence time is 40 minutes to remove unreacted 1,4-butanediol and other by-products. The pre-condensation product is sent out by the first condensation material pump B2 and filtered by the filter F2, and then transferred to the second condensation kettle 6. The pre-condensation product is sent out by the first condensation material pump B2 and filtered by the filter F2. The second condensation product is transferred to the second condensation kettle 6 and the pre-condensation product is sent out by the first condensation material pump B2. The pre-condensation product is sent ... to the second condensation kettle 6. Under the high vacuum state provided by group 19, the vacuum degree is 0.6kPa, the temperature is 240℃, and the residence time is 90min, and the condensation product is obtained. It is continuously fed into the final condensation reaction kettle 7 by the second condensation material pump B3 through the filter three F3, and at 245℃, also under the high vacuum condition of 50Pa provided by the jet vacuum pump unit 19, after a residence time of 120min, it is sent out by the melt delivery pump B4, filtered by the filter four F4, metered by the melt metering pump B5, and then cooled by the melt heat exchanger H1. Under the pressurization action of the melt booster pump B6, it is finally conveyed to the pelletizer 8 through the filter five F5. After pelletizing, the slices are dried and conveyed to the slice silo 9 for storage.

[0056] Example 5

[0057] The production method of low melting point TPEE, the specific steps are as follows:

[0058] Terephthalic acid: isophthalic acid: 1,4-butanediol are added at a molar ratio of 2: 1: 4, and PTMEG is added at the same time, and transported into the slurry preparation tank 1 respectively, and the temperature is pre-heated to 50° C., wherein the mass ratio of PTMEG to total acid is 40%. All the above raw materials are continuously fed into the slurry preparation tank 1 for premixing, and then continuously output to the slurry preparation tank 2a, and then continuously enter the first esterification kettle 3 at a flow rate of 500 kg / h, and the esterification reaction is carried out at a temperature of 205° C. under normal pressure. The hydrolysis-resistant catalyst prepared in Example 2 is continuously added to the first esterification kettle 3 through the auxiliary agent addition system 10 at a flow rate of 0.5 kg / h, and the residence time is 150 min. The by-products including tetrahydrofuran and water produced by the reaction are removed. The removed by-products pass through the process tower 15, and after passing through the tower top reflux tank 16, a part of them is extracted for subsequent purification treatment, and a part of them is refluxed to the first esterification kettle 3 through the process tower to obtain the initial esterification product. The initial esterification product is continuously transported to the second esterification kettle 4 for further esterification. Under the vacuum conditions provided by the vacuum pump 18, the absolute pressure is 80 kPa and the temperature is 210°C. The reaction is continued for 120 minutes to obtain an esterification product with an esterification rate of more than 96%. The esterification product is sent out by the esterification material pump B1, filtered by the filter F1, and continuously sent to the pre-polycondensation kettle 5 for pre-polycondensation reaction. The temperature is raised to 238°C. Under the vacuum conditions of the absolute pressure of 12 kPa provided by the vacuum pump 18, the residence time is 50 minutes, and the unreacted 1,4-butanediol and other by-products are removed. The pre-polycondensation product is sent out by the first polycondensation material pump B2 and filtered by the filter F2, and then transferred to the second polycondensation kettle 6. Under the jet vacuum pump Under the high vacuum state provided by group 19, the vacuum degree is 1kPa, the temperature is 242°C, and the residence time is 105min, and the condensation product is obtained. It is continuously fed into the final condensation reaction kettle 7 by the second condensation material pump B3 through the filter three F3, and at 246°C, also under the high vacuum condition of 150Pa provided by the jet vacuum pump unit 19, after a residence time of 150min, it is sent out by the melt delivery pump B4, filtered by the filter four F4, metered by the melt metering pump B5, and then cooled by the melt heat exchanger H1. Under the pressurization action of the melt booster pump B6, it is finally conveyed to the pelletizer 8 through the filter five F5. After pelletizing, the slices are dried and conveyed to the slice silo 9 for storage.

[0059] Example 6

[0060] The production method of low melting point TPEE, the specific steps are as follows:

[0061] Terephthalic acid: isophthalic acid: 1,4-butanediol are added at a molar ratio of 2: 1.5: 5, and PTMEG is added at the same time, and transported into the slurry preparation tank 1 respectively, and the temperature is pre-heated to 50° C., wherein the mass ratio of PTMEG to total acid is 50%. All the above raw materials are continuously fed into the slurry preparation tank 1 for premixing, and then continuously output to the slurry preparation tank 2a, and then continuously enter the first esterification kettle 3 at a flow rate of 600 kg / h, and the esterification reaction is carried out at a temperature of 210° C. under normal pressure. The hydrolysis-resistant catalyst prepared in Example 3 is continuously added to the first esterification kettle 3 through the auxiliary agent addition system 10 at a flow rate of 0.6 kg / h, and the residence time is 200 min. The by-products including tetrahydrofuran and water produced by the reaction are removed. The removed by-products pass through the process tower 15, and after passing through the tower top reflux tank 16, a part of them is extracted for subsequent purification treatment, and a part of them is refluxed to the first esterification kettle 3 through the process tower to obtain the initial esterification product. The initial esterification product is continuously transported to the second esterification kettle 4 for further esterification. Under the vacuum conditions provided by the vacuum pump 18, the absolute pressure is 90 kPa and the temperature is 235° C. The reaction is continued for 140 minutes to obtain an esterification product with an esterification rate of more than 96%. The esterification product is sent out by the esterification material pump B1, filtered by the filter F1, and continuously sent to the pre-polycondensation kettle 5 for pre-polycondensation reaction. The temperature is raised to 240° C., and the vacuum pump 18 provides a vacuum condition of an absolute pressure of 20 kPa. The residence time is 60 minutes to remove unreacted 1,4-butanediol and other by-products. The pre-polycondensation product is sent out by the first polycondensation material pump B2 and filtered by the filter F2, and then transferred to the second polycondensation kettle 6. The pre-polycondensation product is sent out by the first polycondensation material pump B2 and filtered by the filter F2. The second polycondensation product is transferred to the second polycondensation kettle 6 and the jet vacuum pump unit is used to inject the pre-polycondensation product into the pre-polycondensation kettle 5. Under the high vacuum state provided by 19, the vacuum degree is 1.2KPa, the temperature is 245℃, and the residence time is 120min, and the condensation product is obtained. It is continuously fed into the final condensation reaction kettle 7 by the second condensation material pump B3 through the filter three F3, and at 248℃, also under the high vacuum condition of 300Pa provided by the jet vacuum pump unit 19, after a residence time of 180min, it is sent out by the melt delivery pump B4, filtered by the filter four F4, metered by the melt metering pump B5, and then cooled by the melt heat exchanger H1. Under the pressurization action of the melt booster pump B6, it is finally conveyed to the pelletizer 8 through the filter five F5. After pelletizing, the slices are dried and conveyed to the slice silo 9 for storage.

[0062] Comparative Example 1

[0063] The catalyst is different from that in Example 5: tetrabutyl titanate catalyst is used, and the rest is the same.

[0064] Comparative Example 2

[0065] Compared with Example 6, except that PTMEG is not added and tetrabutyl titanate catalyst is used, the rest is the same.

[0066] The products obtained in Examples 4-6, Comparative Example 1 and Comparative Example 2 were subjected to comparative tests, and the test data are shown in Table 2.

[0067] Table 2 Test results data table

[0068]

[0069] As can be seen from Table 2, in the preparation process, the addition of hydrolysis-resistant catalysts and the introduction of isophthalic acid can significantly improve the various properties of TPEE. Under the same residence time conditions, the intrinsic viscosity of the product is significantly higher than that of conventional tetrabutyl titanate, which shows that the catalyst prepared by this method has better hydrolysis resistance and higher catalytic activity; the obtained product is not much different from conventional TPEE in hardness, but the elongation at break is increased by 37% compared with conventional TPEE. This performance improvement will open up new uses for TPEE in special industry robots, spinning, etc.; the introduction of isophthalic acid effectively reduces the melting point of the product, with a maximum drop of 30°C, which brings better processing performance to TPEE and has a wider application in medical adhesives, polyester hot melt adhesives, etc.; at the same time, the use of hydrolysis-resistant catalysts in production can partially inhibit the generation of THF side reactions while retaining the high catalytic efficiency of the catalyst. According to the output calculation, compared with the conventional TPEE production method, the BDO unit consumption can be reduced by about 80kg per ton, which effectively reduces the side reactions of BDO and improves production efficiency.

[0070] The above is only a preferred embodiment of the present invention, which shows and describes the basic principles, main features and advantages of the present invention, but does not limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. In addition to the above embodiments, the present invention may have other implementation modes without departing from the spirit and scope of the present invention. The present invention may also have various changes and improvements, and all technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents. The technical features not described in the present invention can be realized by or using existing technologies, which will not be repeated here.

Claims

1. A hydrolysis-resistant catalyst for polyester, characterized in that: The preparation comprises the following steps in sequence: firstly, weighing 0.5-1.5 kg of chitosan, adding it to 1 kg of organic alcohol BDO, stirring fully until the chitosan is completely dispersed in the BDO, then dropping 100 g-300 g of surfactant potassium dihydrogen phosphate to dissolve all the chitosan solids in the dispersion, then adding acetic acid to the solution through online pH meter monitoring, adjusting the pH value between 5 and 6, and the above solution is a hydrolysis-resistant solution; weighing 1.25-2.5 kg of tetrabutyl titanate, dropping it into the above hydrolysis-resistant solution, stirring fully until no flocs exist in the solution, and at the same time heating the solution to 60-100° C., performing negative pressure distillation under 10-40 kPa conditions to remove low-boiling substances, and finally obtaining a clear and transparent hydrolysis-resistant titanium catalyst, wherein the titanium content is 6.14% to 6.67%.

2. The hydrolysis-resistant catalyst for polyester according to claim 1, characterized in that: The chitosan is 0.5 kg, the surfactant potassium dihydrogen phosphate is 100 g, and 1.25 kg of tetrabutyl titanate is weighed and added dropwise to the hydrolysis-resistant solution. At the same time, the solution is heated to 60° C. and subjected to negative pressure distillation at 10 kPa to obtain a hydrolysis-resistant titanium catalyst with a titanium content of 6.14%.

3. The hydrolysis-resistant catalyst for polyester according to claim 1, characterized in that: The chitosan is 1.0 kg, the surfactant potassium dihydrogen phosphate is 200 g, 2 kg of tetrabutyl titanate is weighed and added dropwise to the hydrolysis-resistant solution, and the solution is heated to 80° C. and subjected to negative pressure distillation at 25 kPa to obtain a hydrolysis-resistant titanium catalyst with a titanium content of 6.67%.

4. The hydrolysis-resistant catalyst for polyester according to claim 1, characterized in that: The chitosan is 1.5 kg, the surfactant potassium dihydrogen phosphate is 300 g, 2.5 kg of tetrabutyl titanate is weighed and added dropwise to the hydrolysis-resistant liquid, and the solution is heated to 100° C. and subjected to negative pressure distillation at 40 kPa to obtain a hydrolysis-resistant titanium catalyst with a titanium content of 6.6%.

5. A method for producing low melting point TPEE using a hydrolysis-resistant catalyst, characterized in that: The method comprises the following steps in sequence: the molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2: (0.5-1.5): (3-5), PTMEG accounts for 30-50% of the total acid mass ratio, all the above raw materials are continuously fed into the slurry preparation tank for premixing and preheating to 50°C, and then continuously output to the slurry preparation tank 1, and then continuously enter the first esterification kettle at a flow rate of 400-600kg / h, and the esterification reaction is carried out at normal pressure and a temperature of 200-210°C. , the prepared hydrolysis-resistant catalyst is continuously added to the first esterification kettle at a flow rate of 0.4-0.6 kg / h, and the reaction is continued for 100-200 minutes to remove the by-products produced by the reaction. The primary esterification product discharged from the first esterification kettle is continuously transported to the second esterification kettle for further esterification, and the reaction is continued for 100-140 minutes under the vacuum condition of 70-90 kPa absolute pressure and the temperature of 200-235°C to obtain an esterification product with an esterification rate of more than 96%; the esterification material is pumped out and After being filtered by the first filter, the mixture is continuously fed into a pre-condensation kettle for pre-condensation reaction, and the temperature is raised to 235-240°C. Under vacuum conditions of an absolute pressure of 10-20 kPa, the residence time is 40-60 min, and unreacted 1,4-butanediol is removed. The pre-condensation product is pumped out by the first polycondensation material pump and filtered by the second filter, and then transferred to the second polycondensation kettle. Under vacuum conditions of 0.6-1.2 kPa and a temperature of 240-245°C, the residence time is 90-120 min, and the polycondensation product is obtained. The polycondensation product is pumped out by the second polycondensation material pump, filtered by the filter three, and continuously enters the final polycondensation reactor. After staying for 120-180 minutes at 50-300Pa vacuum and 245-248℃, it is pumped out by the melt delivery pump, filtered by the filter four, metered by the melt metering pump, cooled by the melt heat exchanger, and finally conveyed to the pelletizer one through the filter five under the pressure of the melt booster pump. After pelletizing, the slices are dried and conveyed to the slice silo for storage.

6. The method for producing low melting point TPEE using a hydrolysis-resistant catalyst according to claim 5, characterized in that: The by-products removed by the first esterification kettle enter the process tower, and after passing through the reflux tank at the top of the tower, a part is taken out for subsequent purification treatment, and a part is refluxed to the top of the first esterification kettle through the process tower.

7. The method for producing low melting point TPEE using a hydrolysis resistant catalyst according to claim 5, characterized in that: Part of the PTMEG enters the second slurry preparation tank for mixing, and then enters the pre-condensation kettle together with part of the hydrolysis-resistant catalyst.

8. The method for producing low melting point TPEE using a hydrolysis resistant catalyst according to claim 5, characterized in that: The molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2:0.5:3, and PTMEG accounts for 30% of the total acid mass ratio.

9. The method for producing low melting point TPEE using a hydrolysis resistant catalyst according to claim 5, characterized in that: The molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2:1:4, and PTMEG accounts for 40% of the total acid mass ratio.

10. The method for producing low melting point TPEE using a hydrolysis resistant catalyst according to claim 5, characterized in that: The molar ratio of terephthalic acid, isophthalic acid and 1,4-butanediol is 2:1.5:5, and PTMEG accounts for 50% of the total acid mass ratio.

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