High-thermal-stability double-ligand chelating type polyester titanium catalyst as well as preparation method and application thereof

Abstract

The invention relates to the field of polyester catalysts, and discloses a high-thermal-stability double-ligand chelating type polyester titanium catalyst as well as a preparation method and application thereof. The catalyst comprises the following raw materials: ethylene glycol titanium ester, a ligand I and a ligand II, the ligand I is one of an amino carboxylic acid ligand and an alcohol amine ligand, and the ligand II is a hydroxy carboxylic acid ligand; the catalyst is prepared by carrying out coordination reaction on ethylene glycol titanium ester by adopting a ligand I and a ligand II, according to the present invention, the hydrolysis resistance of the catalyst is significantly improved, the viscosity of the polyester product prepared from the catalyst is only reduced to 0.04-0.05 dL / g after the polyester product is treated at the temperature of 200 DEG C for 12 h, the thermal stability is significantly improved, the b value of the polyester product prepared from the catalyst is 5.12-5.5, and the yellowing effect of the polyester product is significantly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of polyester catalysts, in particular to a high-thermal-stability double-ligand chelating polyester titanium catalyst, a preparation method and applications thereof. BACKGROUND

[0002] PET polyester, full name polyethylene terephthalate, is widely used in chemical fibers, films, bottle pieces, engineering plastics, non-woven fabrics and other fields due to its good heat resistance, insulation, high resilience and excellent acid and solvent resistance. A catalyst needs to be used in the production process of PET polyester. The commonly used polyester catalyst is antimony catalyst. Antimony catalyst has excellent performance as a polyester catalyst, but antimony is a heavy metal element, which will be precipitated during the dyeing process of downstream polyester fabric, causing pollution to water environment and poor green environmental performance. Therefore, it is necessary to develop a green and environmentally friendly polyester catalyst to replace antimony catalyst.

[0003] Currently, new environmentally friendly catalysts mainly contain titanium and germanium elements, among which titanium has the characteristics of low cost and high catalytic activity, which attracts the attention of people in the field. The existing problems of titanium-based polyester catalysts are easy hydrolysis, poor hydrolysis resistance, yellowing of the prepared polyester product, and poor thermal stability. Therefore, the optimization of titanium-based catalysts in the prior art is mainly aimed at solving the above problems. For example, the patent with publication number CN111087595A discloses a method for preparing polyester using a high-activity polyester catalyst. In this technical solution, titanium ester and ethylene glycol are used to generate titanium glycol, and then titanium glycol is mixed with metal salts such as citric acid, acetate, and phosphate to form a homogeneous titanium catalyst. By using appropriate proportions of additives, the activity of the titanium-based catalyst and the color of the polyester are improved. In another example, the patent with publication number CN113881027B discloses a titanium-based polyester catalyst, a preparation method and applications thereof. In this patent, a titanium-based polyester catalyst is prepared by reacting hydroxyl carboxylic acid, titanium ester and water. The hydrolysis resistance of the titanium-based polyester catalyst is improved by partially hydrolyzing and mixing hydroxyl carboxylic acid. At the same time, the catalyst can be well dissolved in water or ethylene glycol and other solvents, and the color and thermal stability of the polyester are also improved. In the prior art, single ligand is mainly used to modify titanium-based catalysts. After research, it is found that the viscosity of the polyester prepared by using a titanium-based catalyst prepared by using a single ligand decreases to 0.078-0.095 under high temperature conditions of 200℃, and the thermal stability of the polyester is still low. SUMMARY

[0004] The present application provides a high-thermal-stability double-ligand chelating polyester titanium catalyst, a preparation method and applications thereof. The catalyst is prepared by using ligand one and ligand two to coordinate with titanium glycol ester. The hydrolysis resistance of the catalyst is significantly improved, the thermal stability of the polyester prepared by using the catalyst is significantly improved, and the color difference is significantly reduced.

[0005] The specific technical scheme of the present application is: A high-thermal-stability double-ligand chelating polyester titanium catalyst, raw materials including titanium glycolate, ligand one and ligand two, ligand one being one of amino carboxylic acid ligand and alcohol amine ligand, and ligand two being hydroxyl carboxylic acid ligand.

[0006] As preferred, the amino carboxylic acid ligand includes one or more of EDTA, EDTA-4Na, EDTA-2Na, glycine, dihydroxyethyl glycine and hydroxyethyl glycine; the alcohol amine ligand includes one or more of diethanolamine and triethanolamine; and the hydroxyl carboxylic acid ligand includes one or more of citric acid and lactic acid.

[0007] As preferred, the titanium glycolate is prepared by reacting titanium ester and ethylene glycol.

[0008] As preferred, the titanium ester includes one or more of titanium isopropylate, titanium tetrabutylate, titanium tetraethylate, titanium tetraisobutylate and titanium tetraisooctylate.

[0009] As preferred, the mass ratio of the titanium ester and ethylene glycol is 4-10:1.

[0010] As preferred, the molar ratio of titanium in the titanium glycolate to ligand one is 0.1-1.5, and the molar ratio of titanium in the titanium glycolate to ligand two is 0.1-2.0.

[0011] As preferred, the molar ratio of titanium in the titanium glycolate to ligand one is 0.2-1:1, and the molar ratio of titanium in the titanium glycolate to ligand two is 0.5-1.0:1.

[0012] A preparation method of the above high-thermal-stability double-ligand chelating polyester titanium catalyst, including the following steps: reacting ethylene glycol and titanium ester to generate titanium glycolate; then reacting the titanium glycolate with ligand one to generate a single-ligand chelating intermediate; and then reacting the single-ligand chelating intermediate with ligand two to generate the double-ligand chelating polyester titanium catalyst.

[0013] As preferred, the reaction temperature is 20-100 ℃.

[0014] As preferred, the reaction temperature is 30-80 ℃.

[0015] An application of the above high-thermal-stability double-ligand chelating polyester titanium catalyst in preparing polyester, including the following steps: performing esterification and polymerization reactions on the high-thermal-stability double-ligand chelating polyester titanium catalyst, a dibasic carboxylic acid and a dibasic alcohol to generate polyester.

[0016] The application provides a high-thermal-stability double-ligand chelating polyester titanium catalyst, which is prepared by subjecting titanium glycol ester to coordination reaction with ligand one and then to coordination reaction with ligand two. The ligand one adopts an amino carboxylic acid ligand and an alcohol amine ligand. The ethylenediaminetetraacetic acid ligand in the amino carboxylic acid ligand can form a five-membered ring structure after coordination with titanium. The triethanolamine ligand in the alcohol amine ligand can form a six-membered ring structure after coordination with titanium. These multi-membered ring structures can effectively prevent water molecules and enhance hydrolysis resistance. The ligand two adopts a hydroxyl carboxylic acid to further chelate titanium which is not completely chelated, so as to form a more stable chelate. The synergistic effect of the ligand one and the ligand two can significantly improve the activity of the catalyst, reduce the catalyst consumption, improve the color value of the polyester product prepared from the catalyst, and also significantly improve the thermal stability of the polyester product prepared from the catalyst.

[0017] Compared with the prior art, the application has the following technical effects: The high-thermal-stability double-ligand chelating polyester titanium catalyst is prepared by subjecting titanium glycol ester to coordination reaction with ligand one and ligand two. The hydrolysis resistance of the catalyst is significantly improved. The viscosity of the polyester product prepared from the catalyst decreases by only 0.04-0.05 dL / g after 12 h of treatment at 200 DEG C, and the thermal stability is significantly improved. The b value of the polyester product prepared from the catalyst is 5.12-5.5, and the yellowing effect of the polyester product is significantly reduced. DETAILED DESCRIPTION

[0018] The application will be further described below in combination with examples.

[0019] In order to better understand the content of the application, the application will be further described below in combination with specific examples. It should be understood that the following examples are only used to illustrate the application and are not used to limit the scope of the application.

[0020] Example 1 A preparation method of a high-thermal-stability double-ligand chelating polyester titanium catalyst, comprising the following steps: 70 g of ethylene glycol is added to a reaction bottle under room temperature, and then stirred and 20.4 g of tetrabutyl titanate is added. After the addition is completed, the reaction is continued to stir for 1.5 h to prepare titanium glycol ester. The titanium glycol ester is warmed to 80 DEG C, 13.15 g of ligand one (EDTA-4Na salt solution with a mass fraction of 33.3 wt%) is added, and the reaction is continued for 2.5 h to prepare a single-ligand chelating intermediate. Then, 5.8 g of ligand two (solid citric acid) is added to the single-ligand chelating intermediate, and the reaction is continued for 2.5 h. Small molecule compounds are removed under reduced pressure to prepare the high-thermal-stability double-ligand chelating polyester titanium catalyst.

[0021] The application of a high-thermal-stability double-ligand chelating polyester titanium catalyst in the preparation of polyester, comprising the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a high thermal stability dual-ligand chelating polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the mixture. After water cooling, the mixture was granulated to obtain polyester chips.

[0022] Example 2: A method for preparing a high thermal stability dual-ligand chelate polyester titanium catalyst includes the following steps: 70 g of ethylene glycol was added to a reaction flask at room temperature, followed by stirring and the addition of 20.4 g of tetrabutyl titanate. After the addition was complete, the reaction was continued for 1.5 h to prepare titanium glycolate. The titanium glycolate was heated to 80 °C, and 4.97 g of ligand one (triethanolamine solution, mass fraction 60 wt%) was added and reacted for 2.5 h to prepare a monoligand chelate intermediate. Then, 5.8 g of ligand two (citric acid solid) was added to the monoligand chelate intermediate and the reaction was continued for 2.5 h. Small molecule compounds were removed under reduced pressure to prepare a high thermal stability dual-ligand chelate polyester titanium catalyst.

[0023] The application of a highly thermally stable dual-ligand chelating titanium catalyst for polyester preparation includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a high thermal stability dual-ligand chelating polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the mixture. After water cooling, the mixture was granulated to obtain polyester chips.

[0024] Example 3: A method for preparing a high thermal stability dual-ligand chelate polyester titanium catalyst includes the following steps: 70 g of ethylene glycol was added to a reaction flask at room temperature, followed by stirring and the addition of 20.4 g of tetrabutyl titanate. After the addition was complete, the reaction was continued for 1.5 h to prepare titanium glycolate. The titanium glycolate was heated to 80 °C, and 13.15 g of ligand one (EDTA-4Na salt solution, mass fraction 33.3 wt%) was added and reacted for 2.5 h to prepare a monoligand chelate intermediate. Then, 3.0 g of ligand two (lactic acid solution, mass fraction 90 wt%) was added to the monoligand chelate intermediate and the reaction was continued for 2.5 h. Small molecule compounds were removed under reduced pressure to prepare a high thermal stability dual-ligand chelate polyester titanium catalyst.

[0025] The application of a highly thermally stable dual-ligand chelating titanium catalyst for polyester preparation includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a high thermal stability dual-ligand chelating polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the mixture. After water cooling, the mixture was granulated to obtain polyester chips.

[0026] Example 4: A method for preparing a high thermal stability dual-ligand chelate polyester titanium catalyst includes the following steps: 70 g of ethylene glycol was added to a reaction flask at room temperature, followed by stirring and the addition of 17.04 g of tetraisopropyl titanate. After the addition was complete, the reaction was continued for 1.5 h to prepare titanium glycolate. The titanium glycolate was heated to 80 °C, and 4.97 g of ligand one (triethanolamine solution, mass fraction 60 wt%) was added and reacted for 2.5 h to prepare a monoligand chelate intermediate. Then, 5.8 g of ligand two (citric acid solid) was added to the monoligand chelate intermediate and the reaction was continued for 2.5 h. Small molecule compounds were removed under reduced pressure to prepare a high thermal stability dual-ligand chelate polyester titanium catalyst.

[0027] The application of a highly thermally stable dual-ligand chelating titanium catalyst for polyester preparation includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a high thermal stability dual-ligand chelating polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the mixture. After water cooling, the mixture was granulated to obtain polyester chips.

[0028] Example 5: A method for preparing a high thermal stability dual-ligand chelate polyester titanium catalyst includes the following steps: 70 g of ethylene glycol was added to a reaction flask at room temperature, followed by stirring and the addition of 20.4 g of tetrabutyl titanate. After the addition was complete, the reaction was continued for 1.5 h to prepare titanium glycolate. The titanium glycolate was heated to 80 °C, and 4.97 g of ligand one (triethanolamine solution, mass fraction 60 wt%) was added and reacted for 2.5 h to prepare a monoligand chelate intermediate. Then, 3.0 g of ligand two (lactic acid solution, mass fraction 90 wt%) was added to the monoligand chelate intermediate and the reaction was continued for 2.5 h. Small molecule compounds were removed under reduced pressure to prepare a highly thermally stable dual-ligand chelate polyester titanium catalyst.

[0029] The application of a highly thermally stable dual-ligand chelating titanium catalyst for polyester preparation includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a high thermal stability dual-ligand chelating polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the mixture. After water cooling, the mixture was granulated to obtain polyester chips.

[0030] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that ligand 2 was not used, and the following steps were included: 70 g of ethylene glycol was added to a reaction flask at room temperature, then stirred and 20.4 g of tetrabutyl titanate was added. After the addition was completed, the reaction was stirred for 1.5 h to prepare titanium glycolate. The titanium glycolate was heated to 80 °C, and 13.15 g of ligand 1 (EDTA-4Na salt solution, mass fraction 33.3 wt%) was added and reacted for 2.5 h. Small molecule compounds were removed under reduced pressure to prepare a polyester titanium catalyst.

[0031] The application of a titanium-based catalyst in the preparation of polyester includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the reactor. After water cooling, the reactor was granulated to obtain polyester chips.

[0032] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that ligand 2 was not used, and the following steps were included: 70 g of ethylene glycol was added to a reaction flask at room temperature, then stirred and 20.4 g of tetrabutyl titanate was added. After the addition was completed, the reaction was stirred for 1.5 h to prepare titanium glycolate. The titanium glycolate was heated to 80 °C, and 4.97 g of ligand 1 (triethanolamine solution, mass fraction of 60 wt%) was added and reacted for 2.5 h. Small molecule compounds were removed under reduced pressure to prepare a polyester titanium catalyst.

[0033] The application of a titanium-based catalyst in the preparation of polyester includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the reactor. After water cooling, the reactor was granulated to obtain polyester chips.

[0034] Comparative Example 3: The difference between Comparative Example 3 and Examples 1 and 2 is that ligand one was not used, and the following steps were included: 70 g of ethylene glycol was added to a reaction flask at room temperature, then stirred and 20.4 g of tetrabutyl titanate was added. After the addition was completed, the reaction was stirred for 1.5 h to prepare ethylene glycol titanium ester. The ethylene glycol titanium ester was heated to 80 °C, and 5.8 g of ligand II (solid citric acid) was added to the monoligand chelation intermediate and the reaction was continued for 2.5 h. The small molecule compound was removed under reduced pressure to prepare a polyester titanium catalyst.

[0035] The application of a titanium-based catalyst in the preparation of polyester includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and a polyester titanium catalyst (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the reactor. After water cooling, the reactor was granulated to obtain polyester chips.

[0036] Comparative Example 4: The difference between Comparative Example 4 and the Examples is that the catalyst is titanium glycolate, and the process includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and titanium glycol (6 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the reactor. After water cooling, the reactor was granulated to obtain polyester chips.

[0037] Comparative Example 5: The difference between Comparative Example 5 and the Examples is that the catalyst is antimony glycolate, and the process includes the following steps: 830.0 g of terephthalic acid, 387.62 g of ethylene glycol, and antimony glycol (200 ppm) were added to a 2.5 L polymerization reactor and mixed thoroughly. Esterification was carried out at 260 °C and a pressure not exceeding 0.35 MPa. After the esterification reaction was completed, the pressure inside the reactor was evacuated to 40 Pa, and polycondensation was carried out at 278 °C. When the desired viscosity was reached, a small amount of nitrogen was used to pressurize the reactor. After water cooling, the reactor was granulated to obtain polyester chips.

[0038] Example of detection: The polyester chips obtained in Examples 1-5 and Comparative Examples 1-5 were tested; The test items include: polycondensation time, viscosity, color, melting point, and thermal stability; Viscosity was tested using the Ubbelohde viscometer method. Polyester chips were vacuum dried at 150 °C for 4 h to remove moisture. Approximately 0.5 g of the dried sample was accurately weighed and dissolved in a phenol-tetrachloroethane mixed solvent (mass ratio 1:1) at 100 °C to prepare a solution with a concentration of 0.005 g / mL. The Ubbelohde viscometer was cleaned and dried, and then vertically fixed in a constant temperature water bath at 30 ± 0.1 °C, ensuring the bulb of the viscometer was completely submerged. 10 mL of phenol-tetrachloroethane was pipetted into the viscometer, and after holding at this temperature for 15 min, the outflow time t0 of the solvent in the capillary was measured. This was repeated three times in parallel, and the average value was taken. The solvent was then poured out, and 10 mL of the prepared polyester solution was injected. After holding at this temperature for 15 min, the outflow time t of the solution was measured again. This was repeated three times in parallel, and the average value was taken. The relative viscosity η was then calculated. r =t / t0, then calculate the specific viscosity ηsp=η r -1, and finally calculate the intrinsic viscosity [η]; Lab values ​​were tested using a colorimeter. The instrument was warmed up for 30 minutes and calibrated using the standard white board provided with it. The error between the Lab value displayed on the white board and the standard value after calibration was ensured to be ≤0.1. The ambient temperature was controlled at 23±2 ℃ and the humidity at 50±10% to avoid temperature changes affecting the instrument's accuracy. The sample was placed flat on the test stage, and the "diffuse reflection + specular reflection" mode was selected. Each sample was measured three times at different locations, and the L, a, and b values ​​for each group were recorded. The melting point was tested according to the method disclosed in GB / T 19466.3-2004: Differential Scanning Calorimetry (DSC) for Plastics - Part 3: Determination of Melting and Crystallization Temperature and Enthalpy. Test method for thermal stability: After placing polyester chips in a 200 ℃ forced-air drying oven for 12 h, test the polyester viscosity and calculate the difference in polyester viscosity before and after heat treatment. The test results are shown in Table 1; Table 1. Polyester Test Results

[0039] As shown in Table 1, the polycondensation time for PET polyester prepared using the high thermal stability dual-ligand chelate titanium-based polyester catalysts obtained in Examples 1 to 5 was 95–100 min, while the polycondensation time for PET polyester prepared using the single-ligand titanium-based polyester catalysts obtained in Comparative Examples 1 to 3 was 115–120 min. This indicates that the high thermal stability dual-ligand chelate titanium-based polyester catalysts exhibit higher catalytic activity and shorter polycondensation reaction time compared to the single-ligand titanium-based polyester catalysts. Furthermore, the results from Examples 1–5 and Comparative Example 5 show that the high thermal stability dual-ligand chelate titanium-based polyester catalysts prepared in this invention have higher catalytic activity than antimony glycolate, and the amount of high thermal stability dual-ligand chelate titanium-based polyester catalysts used in this invention is significantly lower than that of antimony glycolate. These results indicate that the high thermal stability dual-ligand chelate titanium-based polyester catalysts prepared in this invention have higher catalytic activity than antimony glycolate polyester catalysts, require less dosage, and are free of heavy metals and are environmentally safe.

[0040] Analysis of the polyester viscosity and melting point results showed no significant differences in viscosity and melting point between the polyesters obtained in Examples 1 to 5 and Comparative Examples 1 to 5. This indicates that the polyester products prepared using the high thermal stability dual-ligand chelate titanium-based polyester catalyst of this invention have performance similar to those prepared using antimony glycolate and titanium glycolate. The use of the high thermal stability dual-ligand chelate titanium-based polyester catalyst in the preparation of PET polyester products does not significantly alter the performance of the polyester products. Furthermore, the Lab values ​​of the polyesters obtained in Examples 1 to 5 and Comparative Examples 1 to 6 show that the L values ​​are between 84.3 and 88.3, ​​indicating that the polyesters are all bright in color with high luminance. The a values ​​of the polyesters obtained in Examples 1 to 5 and Comparative Examples 1 to 6 are all negative and have small absolute values, indicating that the polyester colors are slightly greenish, but the degree of green is very slight. The b-values ​​of Examples 1 to 5 were 5.12–5.5, while those of Comparative Examples 1 to 5 were 5.9–6.17, indicating a yellowish tint to the polyester color. However, the yellow tint of the polyesters obtained in Examples 1 to 5 was significantly reduced compared to that obtained in Comparative Examples 1 to 5. The results from Examples 1 to 5 and Comparative Examples 1 to 4 show that the yellowing effect of the monoligand titanium polyester catalyst is reduced compared to titanium glycolate. The diligand polyester catalyst further reduces the yellowing effect on top of the monoligand titanium polyester catalyst. This indicates that coordination modification of the titanium polyester catalyst with ligands can reduce side reactions in the preparation of PET polyester using the titanium polyester catalyst. Compared to monoligand coordination, diligand coordination can more significantly reduce side reactions in the preparation of PET polyester using the titanium polyester catalyst, thereby significantly reducing the yellowing problem of the titanium catalyst-based polyester product.

[0041] The polyesters obtained in Examples 1 to 5 showed a viscosity decrease of 0.04–0.05 dL / g after heat treatment at 200 °C for 12 h. The polyesters obtained in Comparative Examples 1 to 3 showed a viscosity decrease of 0.09–0.11 dL / g after heat treatment at 200 °C for 12 h, and the polyester obtained in Comparative Example 4 showed a viscosity decrease of 0.105 dL / g after heat treatment at 200 °C for 12 h. Analysis of the above polyester thermal stability results shows that the thermal stability of polyester products prepared by the single-ligand titanium-based catalyst did not change significantly, while the thermal stability of polyester products prepared by the dual-ligand titanium-based catalyst was significantly improved. This result indicates that single-ligand coordination does not significantly enhance the thermal stability of titanium-based catalyst polyester products, while the dual-ligand coordination provided by this invention significantly enhances the thermal stability of titanium-based catalyst polyester products. Furthermore, further analysis of the results of Examples 1 to 4 revealed that the use of aminocarboxylic acid ligands and alkanolamine ligands alone can enhance the thermal stability of titanium-based catalyst polyester products to a certain extent. Using aminocarboxylic acid ligands alone is more effective than using alcoholamine ligands alone in enhancing the thermal stability of titanium-based catalyst polyester products, while using hydroxycarboxylic acid ligands alone reduces the thermal stability of titanium-based catalyst polyester products. These results indicate that the high thermal stability dual-ligand chelated titanium-based polyester catalyst provided by this invention significantly improves the thermal stability of titanium-based catalyst polyester products through the synergistic effect of ligand one and ligand two.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high thermal stability dual-ligand chelate polyester-titanium catalyst, characterized in that, The raw materials include ethylene glycol titanium ester, ligand one and ligand two. Ligand one is one of an aminocarboxylic acid ligand and an alkanolamine ligand, and ligand two is a hydroxycarboxylic acid ligand.

2. The high thermal stability dual-ligand chelated polyester titanium catalyst according to claim 1, characterized in that, The aminocarboxylic acid ligands include one or more of EDTA, EDTA-4Na, EDTA-2Na, glycine, dihydroxyethylglycine, and hydroxyethylglycine; the alcoholamine ligands include one or more of diethanolamine and triethanolamine; and the hydroxycarboxylic acid ligands include one or more of citric acid and lactic acid.

3. The high thermal stability dual-ligand chelated polyester titanium catalyst according to claim 1, characterized in that, Ethylene glycol titanium esters are produced by reacting titanate esters with ethylene glycol. The titanate esters include one or more of tetraisopropyl titanate, tetrabutyl titanate, tetraethyl titanate, and tetraisobutyl titanate.

4. The high thermal stability dual-ligand chelated polyester titanium catalyst according to claim 3, characterized in that, The mass ratio of titanate to ethylene glycol is 4~10:

1.

5. The high thermal stability dual-ligand chelated polyester titanium catalyst according to claim 1, characterized in that, The molar ratio of titanium to ligand one in ethylene glycol titanium ester is 0.1~1.5:1, and the molar ratio of titanium to ligand two in ethylene glycol titanium ester is 0.1~2.0:

1.

6. The high thermal stability dual-ligand chelated polyester titanium catalyst according to claim 5, characterized in that, The molar ratio of titanium to ligand one in ethylene glycol titanium ester is 0.2~1:1, and the molar ratio of titanium to ligand two in ethylene glycol titanium ester is 0.5~1.0:

1.

7. A method for preparing a high thermal stability dual-ligand chelated polyester titanium catalyst according to any one of claims 1 to 6, characterized in that, Includes the following steps: Ethylene glycol and titanate are reacted to generate ethylene glycol titanium ester, which is then reacted with ligand one to generate a monoligand chelate intermediate. The monoligand chelate intermediate is then reacted with ligand two to generate a diligand chelate polyester titanium catalyst.

8. The preparation method according to claim 7, characterized in that, The reaction temperature is 20~100 ℃.

9. The preparation method according to claim 7 or 8, characterized in that, The reaction temperature is 30~80℃.

10. The application of a high thermal stability dual-ligand chelating polyester titanium catalyst according to any one of claims 1 to 6 in the preparation of polyester, characterized in that, Includes the following steps: Polyesters are produced by esterification and polymerization of a high thermal stability dual-ligand chelating polyester titanium catalyst, a dicarboxylic acid, and a diol.

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