Weatherable heat-resistant copolyester and method of making and using same

Abstract

The application provides a weather-resistant and heat-resistant copolyester, a preparation method and application thereof, and the preparation method comprises the following steps: (1) reacting a dibasic acid or an anhydride or a dibasic carboxylic acid ester with HBPA under the action of a catalyst to obtain component 1; (2) reacting the dibasic acid or the anhydride or the dibasic carboxylic acid ester with a dibasic alcohol under the action of a catalyst to obtain component 2; and (3) mixing the component 1 and the component 2 and reacting to obtain the copolyester. The copolyester prepared by the application has high Tg, high HBPA retention rate, good color, can improve the hardness of the copolyester, and has good heat resistance, weather resistance, scratch resistance and chemical stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, and relates to a weather-resistant and heat-resistant copolyester, its preparation method and application. Background Technology

[0002] Polyesters are high-molecular-weight resins formed by the condensation polymerization of diols and diacids. The most representative example is polyethylene terephthalate (PET), which is prepared from terephthalic acid (TPA) and ethylene glycol (EG). Copolyesters, on the other hand, refer to polyesters modified with alcohols or acids, including PETG, PCTG, PCTA, and biodegradable copolyesters. PCTG polymer materials, as a special type of copolyester distinct from traditional PET, are typically produced by introducing a third or even fourth component into the poly(1,4-cyclohexanedimethyl terephthalate) (PCT) formulation. The PCT copolymer obtained by introducing diols during copolymerization is called PCTG. Diols include propylene glycol, neopentyl glycol, and diethylene glycol.

[0003] Hydrogenated bisphenol A (HBPA), containing two cyclohexyl groups and two hydroxyl groups, exhibits high structural rigidity due to steric hindrance during rotation and configurational changes. Its two six-membered alicyclic structures are also highly stable, resulting in excellent chemical stability, UV resistance, thermal stability, and weather resistance. However, while this unique structure contributes to HBPA's superior performance, it also leads to its low reactivity. The two hydroxyl groups in HBPA are secondary hydroxyl groups, exhibiting lower reactivity than primary alcohols such as ethylene glycol (EG), butanediol (BD), and 1,4-cyclohexanediethanol (CHDM). This, coupled with significant steric hindrance, further reduces its reactivity. When introduced into polyester systems, the polycondensation stage must be conducted under high temperature and low vacuum conditions to increase molecular weight, leading to a series of side reactions such as dehydration, oxidation, and thermal decomposition of HBPA. This makes it difficult to obtain products with good color, high molecular weight, and high HBPA retention. Therefore, HBPA is typically used with epoxy resins as precursors, indirectly enhancing its reactivity, and is commonly applied in powder coatings where high resin molecular weight is not critical.

[0004] CN113993836A discloses a class of copolyesters with three characteristics: (1) the ability to be synthesized in a directed manner, (2) the need for fewer diol residues to prepare the copolyester, and (3) repeating units of completely alternating diol residues. In Example 4, a method for introducing HBPA into a copolyester system to obtain compound S8 is described: terephthaloyl chloride is used as the starting material, first esterified with tert-butanol in dichloromethane, then reduced to a mono-acid tert-butyl ester structure, and then reacted with HBPA in dichloromethane. The entire synthetic procedure is complex, requiring the use of acyl chloride as the starting monomer and synthesis in a solvent.

[0005] CN113896870A and CN115109240A both disclose methods for introducing HBPA into copolyester systems, utilizing the low loss factor of HBPA to synthesize copolyesters with low dielectric constants. However, the above synthesis methods all use environmentally unfriendly, halogen-containing terephthaloyl chloride as the starting monomer, and prepare the copolyester in the organic solvent tetrahydrofuran.

[0006] The literature RG Gaughan, HW Hill Jr., JE Inda, Preparation and Properties of the Polyester Made from 2,2-Bis(4-Hydroxycyclohexyl)propane and Adipic Acid, J. Polym. Sci. A Polym. Chem., 24:419-426, reports a method for preparing polyesters from HBPA with adipic acid, sebacic acid, and terephthalic acid. Through a series of experiments with different reaction conditions and catalytic systems, a sample with an intrinsic viscosity of 0.36 dL / g was finally synthesized. Although this synthetic route does not require the use of acyl chlorides as starting monomers, the low molecular weight limits its application.

[0007] Therefore, it is of great significance to introduce HBPA into the copolyester system using non-acyl chloride starting monomers and non-solvent methods to prepare copolyesters with high molecular weight, high Tg, high HBPA retention rate and good color. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a weather-resistant and heat-resistant copolyester, its preparation method, and its applications. The present invention employs a non-acyl chloride starting monomer and a non-solvent-based process to introduce HBPA into the copolyester system, thereby preparing a copolyester with high molecular weight, high Tg, high HBPA retention rate, and good color. The hardness of the copolyester is significantly improved, and its heat resistance, weather resistance, scratch resistance, and chemical stability are enhanced, thus optimizing the application scenarios of the copolyester and improving its application potential.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] On one hand, the present invention provides a method for preparing a copolyester, the method comprising the following steps:

[0011] (1) A dicarboxylic acid or anhydride or dicarboxylic acid ester reacts with HBPA under the action of a catalyst to obtain component 1;

[0012] (2) A dicarboxylic acid or anhydride or dicarboxylic acid ester reacts with a diol under the action of a catalyst to obtain component 2;

[0013] (3) Mix component 1 and component 2 and react to obtain the copolyester.

[0014] In this invention, component 1 is obtained by reacting a diacid, anhydride, or dicarboxylic acid ester with HBPA, and component 2 is obtained by reacting a diacid, anhydride, or dicarboxylic acid ester with a diol. Then, components 1 and 2 are reacted to obtain a copolyester. This method results in a copolyester with high Tg, high HBPA retention rate, good color, improved hardness, and good heat resistance, weather resistance, scratch resistance, and chemical stability.

[0015] Preferably, the dicarboxylic acid or anhydride or dicarboxylic acid ester described in steps (1) and (2) is independently selected from, but not limited to, any one or a combination of at least two of the following compounds:

[0016]

[0017] Preferably, the molar ratio of the dicarboxylic acid or anhydride or dicarboxylic acid ester to HBPA in step (1) is 1:1.1 to 1:1.4, for example 1:1.1, 1:1.2, 1:1.3 or 1:1.4, preferably 1:1.2.

[0018] Preferably, the catalyst in step (1) is a silicon-aluminum composite catalyst.

[0019] Preferably, the silicon-aluminum composite catalyst is prepared by a hydrolysis-combination-calcination method using a silicon source and an aluminum source. The specific preparation method is disclosed in paragraph 0012 of CN114605622A, which includes the following steps:

[0020] (A) Prepare an alcoholic solution by mixing aluminum source and silicon source with ethanol in a molar ratio, and prepare a hydrolysis solution by mixing anhydrous ethanol and water;

[0021] (B) Place the prepared alcohol solution in a constant temperature water bath and stir, while adding the hydrolysis solution dropwise at a rate of 0.2 mL / min to 0.8 mL / min;

[0022] (C) After the addition is complete, continue stirring for 20 to 50 minutes, centrifuge, wash with deionized water, vacuum dry, and after returning to room temperature, place in a muffle furnace for calcination. After returning to room temperature again, grind to obtain the required silicon-aluminum composite catalyst powder.

[0023] Preferably, the silicon source includes, but is not limited to, any one or a combination of at least two of sodium silicate, tetraethyl orthosilicate, or sodium metasilicate.

[0024] Preferably, the aluminum source includes, but is not limited to, any one or a combination of at least two of aluminum oxide, sodium aluminate, aluminum isopropoxide, aluminum sulfate, aluminum stearate, or aluminum acetate.

[0025] Preferably, the amount of catalyst used in step (1) is 0.02% to 0.08% of the mass of the dicarboxylic acid, anhydride, or dicarboxylic acid ester in step (1), for example, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, or 0.08%, preferably 0.04%.

[0026] Preferably, the reaction in step (1) is carried out under the protection of a protective gas, preferably nitrogen.

[0027] Preferably, the reaction temperature in step (1) is 235-255°C (e.g., 235°C, 238°C, 240°C, 245°C, 248°C, 250°C or 255°C), and the reaction time is 3-6 hours (e.g., 3 hours, 4 hours, 5 hours or 6 hours).

[0028] In this invention, if the temperature of the reaction in step (1) is too low, the esterification will not be complete, resulting in a low HBPA conversion rate. If the temperature is too high, it will lead to more side reactions and severe yellowing.

[0029] Preferably, in step (1), a dicarboxylic acid or anhydride or dicarboxylic acid ester, HBPA and catalyst are added to the reactor, and the air in the reactor is replaced with nitrogen (e.g., replaced 3 times). After replacement, the pressure is increased to 0.2-0.4 MPa (e.g. 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa or 0.4 MPa) with nitrogen. Then, the temperature is gradually increased until all raw materials melt. The temperature is increased to the reaction temperature of 235-255°C with stirring (e.g. 100 rpm) and the reaction is carried out for 3-6 hours (e.g. 3 hours, 4 hours, 5 hours or 6 hours). The mass of the by-product is collected to calculate the conversion rate (the by-product is water, and the conversion rate is calculated by weighing the water). The reaction is terminated when the conversion rate is >95%.

[0030] Preferably, the diol in step (2) comprises, but is not limited to, any one or a combination of at least two of the following diols:

[0031]

[0032] Preferably, the molar ratio of the dicarboxylic acid or anhydride or dicarboxylic acid ester to the diol in step (2) is 1:1.3 to 1:1.8, for example 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7 or 1:1.8, preferably 1:1.6.

[0033] Preferably, the diol in step (2) comprises at least one diol A selected from the group consisting of:

[0034]

[0035] and at least one diol B selected from the following:

[0036]

[0037] Preferably, the molar ratio of diol A to diol B is 1:0.6 to 1:8, for example, 1:0.6, 1:0.8, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8.

[0038] Preferably, the catalyst in step (2) is selected from any one or a combination of at least two of the following: sodium acetate, zinc acetate, manganese acetate, antimony acetate, aluminum acetate, cobalt acetate, magnesium acetate, tetrabutyl titanate, isopropyl titanate, dibutyltin oxide, dibutyltin dilaurate, antimony glycolate, antimony trioxide, germanium oxide, cerium hydroxide, lanthanum chloride, or lanthanum hydroxide.

[0039] Preferably, the amount of catalyst used in step (2) is 0.01% to 0.08% of the mass of the dicarboxylic acid, anhydride, or dicarboxylic acid ester in step (2), for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, or 0.08%.

[0040] Preferably, the reaction in step (2) is carried out under the protection of a protective gas, preferably nitrogen.

[0041] Preferably, the reaction temperature in step (2) is 225-250℃ (e.g., 225℃, 230℃, 235℃, 238℃, 240℃, 245℃, 248℃ or 250℃), and the reaction time is 3-6 hours (e.g., 3 hours, 4 hours, 5 hours or 6 hours).

[0042] Preferably, in step (2), a dicarboxylic acid or anhydride or dicarboxylic acid ester, a diol, and a catalyst are added to the reactor. The air inside the reactor is replaced with nitrogen (e.g., replaced 3 times). After replacement, the pressure is increased to 0.1 MPa with nitrogen, and then the temperature is gradually increased until all raw materials melt. The temperature is increased to the reaction temperature of 225-250°C with stirring (e.g., 100 rpm). The reaction is carried out for 3-6 hours. The mass of the by-product is collected to calculate the conversion rate (the by-product is water, and the conversion rate is calculated by weighing the water). The reaction is terminated when the conversion rate is >95%.

[0043] Preferably, the reaction in step (3) is carried out under the protection of a protective gas, preferably nitrogen.

[0044] Preferably, after mixing component 1 and component 2 in step (3), a stabilizer is added.

[0045] Preferably, the stabilizer is selected from any one or a combination of at least two of phosphoric acid, phosphorous acid, hypophosphite, pyrophosphate, ammonium phosphate, trimethyl phosphate, dimethyl phosphate, triphenyl phosphate, triethyl phosphoroacetate, diphenyl phosphate, triphenyl phosphite, and diphenyl phosphite.

[0046] Preferably, the amount of stabilizer used in step (3) is 0.01% to 0.08% of the mass of the dicarboxylic acid, anhydride, or dicarboxylic acid ester used in step (2), for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, or 0.08%.

[0047] Preferably, in step (3), components 1 and 2 are added to the reactor, and the air inside the reactor is replaced with nitrogen. The mixture is stirred at atmospheric pressure at 40–100 rpm (e.g., 40 rpm, 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm, or 100 rpm) for 10–40 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, or 40 min) for 10–40 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, or 40 min). The temperature is then raised to 260–265 °C, the pressure reduced to 1 kPa, and the reaction is continued for 2–5 hours. The temperature is then raised further to 270–275 °C, the rotation speed is adjusted to 120 rpm, and the pressure is gradually reduced to below 30 Pa for 2–7 hours (e.g., 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or 7 hours). Sampling and analysis are performed. Within the reaction time, the polymer viscosity reaches 0.5–0.85 dl / g. Stirring is then stopped, the vacuum is removed, and the material is discharged under pressure to obtain a weather-resistant and heat-resistant copolyester sample.

[0048] On the other hand, the present invention provides a copolyester prepared by the preparation method described above.

[0049] The copolyester obtained by the preparation method described in this invention has an intrinsic viscosity of 0.5–0.85 dl / g, a number-average molecular weight Mn of 8000–26000 (e.g., 8000, 9000, 10000, 12000, 15000, 18000, 20000, 23000 or 26000), and a molecular weight distribution index of 1.0–1.9 (e.g., 1.0, 1.1, 1.2, 1.3, 1.5, 1.7 or 1.9).

[0050] Preferably, the copolyester has a Tg of 70-125°C (e.g., 70°C, 90°C, 100°C, 110°C, 120°C or 125°C) and an HDT > 110°C (e.g., 115°C, 120°C, 130°C, 140°C, 150°C, etc.).

[0051] Preferably, the HBPA retention rate in the copolyester is ≥82%, for example, 82%, 83%, 85%, 88%, 90%, 92%, 95%, 97%, 98%, etc.

[0052] The copolyester of the present invention has high Tg, high HBPA retention rate, and good color, which can improve the hardness of the copolyester and has good heat resistance, weather resistance, scratch resistance and chemical stability.

[0053] On the other hand, the present invention provides the application of the copolyester described above in outdoor use scenarios such as photovoltaic materials, new energy materials or building materials.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] This invention relates to a method that reacts a diacid, anhydride, or dicarboxylic acid ester with HBPA to obtain component 1, and reacts the diacid, anhydride, or dicarboxylic acid ester with a diol to obtain component 2. Then, components 1 and 2 are reacted to obtain a copolyester. This method results in a copolyester with high Tg, high HBPA retention, and good color. It also improves the hardness of the copolyester and provides good heat resistance, weather resistance, scratch resistance, and chemical stability. This optimizes the application scenarios of the copolyester and enhances its application potential. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] The silicon-aluminum composite catalyst used in the following examples is the same silicon-aluminum composite catalyst used in Example 2 of CN114605622A.

[0058] Example 1

[0059] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0060] (1) 249.2 g (1.5 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA, and 0.10 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.3 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature of the reactor was gradually increased to 240 °C. The reaction was carried out for 5 hours. The mass of the by-product was collected and the conversion rate was calculated. The reaction was terminated when the conversion rate was >95%. The product was used as component 1.

[0061] (2) 249.2 g (1.5 mol) of terephthalic acid, 207.7 g (1.44 mol) of 1,4-cyclohexanediethanol, 59.6 g (0.96 mol) of ethylene glycol, 0.05 g of tetrabutyl titanate, and 0.10 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 250 °C for 5 hours. The mass of the by-products was collected and the conversion rate was calculated. The reaction was stopped when the conversion rate was >95%. The product was used as component 2.

[0062] (3) Combine component 1 and component 2, add 0.10 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, raise the temperature to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 3 hours; continue to raise the temperature to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 7 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0063] Example 2

[0064] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0065] (1) 249.2 g (1.5 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA and 0.10 g of self-made silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.4 MPa with nitrogen. Then the temperature was gradually increased until all raw materials melted. The mixture was stirred at 100 rpm. At the same time, the temperature of the reactor was gradually increased to 255 °C. The reaction was carried out for 3 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was used as component 1.

[0066] (2) 249.2 g (1.5 mol) of terephthalic acid, 173.1 g (1.2 mol) of 1,2-cyclohexanediol, 125.0 g (1.2 mol) of neopentyl glycol, 0.05 g of tetrabutyl titanate, and 0.10 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 230 °C for 4 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was taken as component 2.

[0067] (3) Combine component 1 and component 2, add 0.10 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 5 hours; then, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 7 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0068] Example 3

[0069] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0070] (1) 249.2 g (1.5 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA, and 0.10 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.2 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm, and the temperature of the reactor was gradually increased to 235 °C. The reaction was carried out for 6 hours. The mass of the by-product was collected and the conversion rate was calculated. The reaction was terminated when the conversion rate was >95%. The product was used as component 1.

[0071] (2) 249.2 g (1.5 mol) of terephthalic acid, 139.4 g (1.2 mol) of 1,4-cyclohexanediol, 125.0 g (1.2 mol) of neopentyl glycol, 0.05 g of tetrabutyl titanate, and 0.10 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 250 °C for 3 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was taken as component 2.

[0072] (3) Combine component 1 and component 2, add 0.10 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 2 hours; then, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 5 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0073] Example 4

[0074] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0075] (1) 249.2 g (1.5 mol) of isophthalic acid, 432.7 g (1.8 mol) of HBPA and 0.10 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.4 MPa with nitrogen. Then the temperature was gradually increased until all raw materials melted. The mixture was stirred at 100 rpm. At the same time, the temperature of the reactor was gradually increased to 255 °C. The reaction was carried out for 3 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was used as component 1.

[0076] (2) 249.2 g (1.5 mol) of isophthalic acid, 173.1 g (1.2 mol) of 1,4-cyclohexanediol, 108.1 g (1.2 mol) of 1,4-butanediol, 0.05 g of tetrabutyl titanate, and 0.10 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 225 °C for 6 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was taken as component 2.

[0077] (3) Combine component 1 and component 2, add 0.10 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 5 hours; then, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 6 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0078] Example 5

[0079] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0080] (1) 324.4 g (1.5 mol) of 2,6-naphthalenedicarboxylic acid, 432.7 g (1.8 mol) of HBPA and 0.13 g of self-made silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.2-0.4 MPa with nitrogen. Then the temperature was gradually increased until all raw materials melted. The reactor was stirred at 100 rpm and the temperature was gradually increased to 240 °C. The reaction was carried out for 4 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was used as component 1.

[0081] (2) 324.4 g (1.5 mol) of 2,6-naphthalenedicarboxylic acid, 173.1 g (1.2 mol) of 1,4-cyclohexanediol, 141.8 g (1.2 mol) of 1,6-hexanediol, 0.06 g of tetrabutyl titanate, and 0.13 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 240 °C for 5 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was taken as component 2.

[0082] (3) Combine component 1 and component 2, add 0.13g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa, and react for 2 to 5 hours; then, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa, react for 7 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0083] Example 6

[0084] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0085] (1) 218.0 g (0.9 mol) of 4,4'-biphenyl dicarboxylic acid, 259.6 g (1.08 mol) of HBPA and 0.09 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.3 MPa with nitrogen. Then the temperature was gradually increased until all raw materials melted. The mixture was stirred at 100 rpm. At the same time, the temperature of the reactor was gradually increased to 250 °C. The reaction was carried out for 5 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was used as component 1.

[0086] (2) 508.7 g (2.1 mol) of 4,4'-biphenyl dicarboxylic acid, 94.2 g (0.48 mol) of 4,8-tricyclo[5.2.1.O2,7]decanediethanol, 461.5 g (2.88 mol) of 2-butyl-2-ethyl-1,3-propanediol, 0.10 g of tetrabutyl titanate, and 0.20 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 240 °C for 4 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was used as component 2.

[0087] (3) Combine component 1 and component 2, add 0.20g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60rpm and stir at normal pressure for 30min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1KPa and react for 3 hours; again, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120rpm, gradually reduce the pressure to below 30Pa and react for 3 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0088] Example 7

[0089] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0090] (1) 58.3 g (0.3 mol) of dimethyl terephthalate, 86.5 g (0.36 mol) of HBPA and 0.02 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.4 MPa with nitrogen. Then the temperature was gradually increased until all raw materials melted. The mixture was stirred at 100 rpm. At the same time, the temperature of the reactor was gradually increased to 240 °C. The reaction was carried out for 5 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was used as component 1.

[0091] (2) 524.3 g (2.7 mol) of dimethyl terephthalate, 94.2 g (0.48 mol) of 4,8-tricyclo[5.2.1.O2,7]decanediethanol, 238.3 g (3.84 mol) of ethylene glycol, 0.10 g of tetrabutyl titanate, and 0.21 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 225 °C for 6 hours. The mass of the by-product was collected and the conversion rate was calculated. If the conversion rate was >95%, the reaction was stopped and the product was used as component 2.

[0092] (3) Combine component 1 and component 2, add 0.21g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 5 hours; then, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 2 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0093] Comparative Example 1

[0094] In this comparative example, a method for preparing a copolyester is provided (this comparative example is based on Example 1 without HBPA), specifically including the following steps:

[0095] 498.4 g (3.0 mol) of terephthalic acid, 415.3 g (2.88 mol) of 1,4-cyclohexanediethanol, 119.2 g (1.92 mol) of ethylene glycol, 0.10 g of tetrabutyl titanate, and 0.20 g of zinc acetate were added to a 2 L reactor. After the raw materials and catalyst were added, the air inside the reactor was purged with nitrogen three times. After purging, the pressure was increased to 0.1 MPa with nitrogen. The temperature was then gradually increased until all raw materials melted, and the reactor was stirred at 100 rpm while gradually increasing the temperature to 250 °C for 6 hours. The mass of by-products was collected to calculate the conversion rate. If the conversion rate was >95%, the reaction was terminated. Subsequently, 0.20 g of triethyl phosphoroacetate was added as a stabilizer, and the air inside the reactor was purged with nitrogen three times. The stirring speed was adjusted to 60 rpm and the reactor was stirred at atmospheric pressure for 30 minutes. Subsequently, the temperature was raised to 260℃ and the reactor temperature was controlled below 265℃. The pressure was slowly reduced to 1 kPa, and the reaction was carried out for 3 hours. Then, the temperature was raised to 270℃ and the reactor temperature was controlled between 265 and 275℃. The rotation speed was adjusted to 120 rpm, and the pressure was gradually reduced to below 30 Pa. The reaction was carried out for 7 hours. The stirring was stopped, the vacuum was removed, and the product was discharged under pressure to obtain the copolyester sample.

[0096] Comparative Example 2

[0097] In this comparative example, a method for preparing a copolyester is provided (this comparative example is based on Example 1 without 1,4-cyclohexanediethanol), specifically including the following steps:

[0098] (1) 249.2 g (1.5 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA and 0.10 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.3 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature of the reactor was gradually increased to 240 °C. The reaction was carried out for 5 hours, and the product was taken as component 1.

[0099] (2) 99.7 g (0.6 mol) of terephthalic acid, 59.6 g (0.96 mol) of ethylene glycol, 0.02 g of tetrabutyl titanate, and 0.04 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 250°C for 5 hours. The product was taken as component 2.

[0100] (3) Combine component 1 and component 2, add 0.04 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 3 hours; then, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 7 hours, stop stirring, remove the vacuum, and pressurize to discharge the copolyester sample.

[0101] Comparative Example 3

[0102] In this comparative example, a method for preparing a copolyester is provided (this comparative example is based on Example 1, but with HBPA and 1,4-cyclohexanediethanol removed), specifically including the following steps:

[0103] 498.4 g (3.0 mol) of terephthalic acid, 297.9 g (4.8 mol) of ethylene glycol, 0.10 g of tetrabutyl titanate, and 0.20 g of zinc acetate were added to a 2 L reactor. After the raw materials and catalyst were added, the air inside the reactor was purged with nitrogen three times. After purging, the pressure was increased to 0.1 MPa with nitrogen. The temperature was then gradually increased until all raw materials melted, and the reactor was stirred at 100 rpm while gradually increasing the temperature to 250 °C for 6 hours. The mass of by-products was collected to calculate the conversion rate. If the conversion rate was >95%, the reaction was terminated. Subsequently, 0.20 g of triethyl phosphoroacetate was added as a stabilizer, and the air inside the reactor was purged with nitrogen three times. The stirring speed was adjusted to 60 rpm and stirred at atmospheric pressure for 30 minutes. Subsequently, the temperature was raised to 260℃ and the reactor temperature was controlled below 265℃. The pressure was slowly reduced to 1 kPa, and the reaction was carried out for 3 hours. Then, the temperature was raised to 270℃ and the reactor temperature was controlled between 265 and 275℃. The rotation speed was adjusted to 120 rpm, and the pressure was gradually reduced to below 30 Pa. The reaction was carried out for 7 hours. The stirring was stopped, the vacuum was removed, and the product was discharged under pressure to obtain the copolyester sample.

[0104] Comparative Example 4

[0105] This comparative example provides a method for preparing a copolyester (this comparative example is based on Example 1, where all raw materials are reacted together to prepare the copolyester), specifically including the following steps:

[0106] 498.4 g (3.0 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA, 207.7 g (1.44 mol) of 1,4-cyclohexanediol, 59.6 g (0.96 mol) of ethylene glycol, 0.05 g of tetrabutyl titanate, 0.10 g of silicon-aluminum composite catalyst, and 0.10 g of zinc acetate were added to a 2 L reactor. After the raw materials and catalyst were added, the air inside the reactor was purged with nitrogen three times. After purging, the pressure was increased to 0.1 MPa with nitrogen. The temperature was then gradually increased until all raw materials melted, and the reactor was stirred at 100 rpm while gradually increasing the temperature to 250 °C for 5 hours. The mass of by-products was collected to calculate the conversion rate. If the conversion rate was >95%, the reaction was terminated. Subsequently, 0.10 g of triethyl phosphoroacetate was added as a stabilizer, and the air inside the reactor was purged with nitrogen three times. The stirring speed was adjusted to 60 rpm and stirred at atmospheric pressure for 30 minutes. Subsequently, the temperature was raised to 260℃ and the reactor temperature was controlled below 265℃. The pressure was slowly reduced to 1 kPa, and the reaction was carried out for 3 hours. Then, the temperature was raised to 270℃ and the reactor temperature was controlled between 265 and 275℃. The rotation speed was adjusted to 120 rpm, and the pressure was gradually reduced to below 30 Pa. The reaction was carried out for 7 hours. The stirring was stopped, the vacuum was removed, and the product was discharged under pressure to obtain the copolyester sample.

[0107] Comparative Example 5

[0108] The only difference between this comparative example and Example 1 is that the raw materials used in step (2) do not include 1,4-cyclohexanediethanol, and the amount of ethylene glycol used is 2.4 mol. All other steps are the same as in Example 1. The specific steps are as follows:

[0109] (1) 249.2 g (1.5 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA and 0.10 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.3 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature of the reactor was gradually increased to 240 °C. The reaction was carried out for 5 hours, and the product was taken as component 1.

[0110] (2) 249.2 g (1.5 mol) of terephthalic acid, 149.0 g (2.4 mol) of ethylene glycol, 0.05 g of tetrabutyl titanate, and 0.10 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 250 °C for 5 hours. The product was taken as component 2.

[0111] (3) Combine component 1 and component 2, add 0.10 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, continue to heat to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 3 hours; then, continue to heat to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 7 hours, stop stirring, remove the vacuum, and pressurize to discharge the copolyester sample.

[0112] Comparative Example 6

[0113] The only difference between this comparative example and Example 1 is that the raw materials used in step (2) do not include ethylene glycol, and the amount of 1,4-cyclohexanediethanol used is 2.4 mol. All other steps are the same as in Example 1. The specific steps are as follows:

[0114] (1) 249.2 g (1.5 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA, and 0.10 g of silicon-aluminum composite catalyst were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.3 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature of the reactor was gradually increased to 240 °C. The reaction was carried out for 5 hours. The mass of the by-product was collected and the conversion rate was calculated. The reaction was terminated when the conversion rate was >95%. The product was used as component 1.

[0115] (2) 249.2 g (1.5 mol) of terephthalic acid, 346.1 g (2.4 mol) of 1,4-cyclohexanediethanol, 0.05 g of tetrabutyl titanate, and 0.10 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 250 °C for 5 hours. The mass of the by-products was collected and the conversion rate was calculated. The reaction was stopped when the conversion rate was >95%. The product was used as component 2.

[0116] (3) Combine component 1 and component 2, add 0.10 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, raise the temperature to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 3 hours; continue to raise the temperature to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 7 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0117] Comparative Example 7

[0118] The only difference between this comparative example and Example 1 is that the silicon-aluminum composite catalyst used in step (1) is replaced with an equal mass of tetrabutyl titanate catalyst. The specific steps are as follows:

[0119] In this embodiment, a method for preparing a weather-resistant and heat-resistant copolyester is provided, specifically including the following steps:

[0120] (1) 249.2 g (1.5 mol) of terephthalic acid, 432.7 g (1.8 mol) of HBPA and 0.10 g of tetrabutyl titanate were added to the reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.3 MPa with nitrogen. Then the temperature was gradually increased until all raw materials melted. The mixture was stirred at 100 rpm and the temperature of the reactor was gradually increased to 240 °C. The reaction was carried out for 5 hours. The mass of the by-product was collected and the conversion rate was calculated. The reaction was terminated when the conversion rate was >95%. The product was used as component 1.

[0121] (2) 249.2 g (1.5 mol) of terephthalic acid, 207.7 g (1.44 mol) of 1,4-cyclohexanediethanol, 59.6 g (0.96 mol) of ethylene glycol, 0.05 g of tetrabutyl titanate, and 0.10 g of zinc acetate were added to another reactor. After the raw materials and catalyst were added, the air in the reactor was replaced with nitrogen three times. After the replacement was completed, the pressure was increased to 0.1 MPa with nitrogen. Then the temperature was gradually increased until all the raw materials melted. The mixture was stirred at 100 rpm and the temperature was gradually increased to 250 °C for 5 hours. The mass of the by-products was collected and the conversion rate was calculated. The reaction was stopped when the conversion rate was >95%. The product was used as component 2.

[0122] (3) Combine component 1 and component 2, add 0.10 g of triethyl phosphoroacetate as a stabilizer, replace the air in the reactor with nitrogen three times, adjust the speed to 60 rpm and stir at normal pressure for 30 min. Then, raise the temperature to 260℃ and control the reactor temperature below 265℃, slowly reduce the pressure to 1 kPa and react for 3 hours; continue to raise the temperature to 270℃ and control the reactor temperature between 265 and 275℃, adjust the speed to 120 rpm, gradually reduce the pressure to below 30 Pa and react for 7 hours, stop stirring, remove the vacuum, and pressurize to discharge the material to obtain the weather-resistant and heat-resistant copolyester sample.

[0123] The copolyesters obtained in the examples and comparative examples were subjected to performance tests according to relevant standards:

[0124] 1.IV (Intrinsic Viscosity): GB / T 14190-2008 Test Method for Fiber Grade Polyester Chips (PET).

[0125] 2. Mn (number average molecular weight): Detected by Waters e2695 gel chromatography with a 2414RI detector, a Styragel HR3 5μm 7.8*300mm (THF) column, and chloroform as the mobile phase.

[0126] 3. Tg (glass transition temperature): GB / T 19466.2-2004 Plastics. Differential scanning calorimetry (DSC).

[0127] 4. Molecular weight distribution index: Same as the reference standard for number-average molecular weight test.

[0128] 5. HDT: GB / T 1634-2019 Determination of the temperature of plastic under load.

[0129] 6. HBPA Retention Rate: In the 1H NMR spectrum, the integral at the HBPA characteristic peak (δ0.8ppm) is the percentage of the theoretical integral, with the integral of the characteristic peaks of terephthalic acid or dimethyl terephthalate (δ8.1ppm), 2,6-naphthalenedicarboxylic acid (δ8.08, 8.19, 8.75ppm), and 4,4'-biphenyldicarboxylic acid (δ7.75, 8.03ppm) being 1.

[0130] 7. Color value: GB / T 39822-2021 Determination of the yellow index and its variation value of plastics. Measured using a Hunter colorimeter. The higher the L value, the whiter the color and the better the transparency; the lower the b value, the bluer the color, and the higher the b value, the yellower the color.

[0131] 8. Gloss: Tested according to GB 8807—1988 Test Method for Mirror Gloss of Plastics, with an incident angle of 60°.

[0132] The test results are shown in Table 1.

[0133] Table 1

[0134]

[0135]

[0136] QUV accelerated aging test:

[0137] Tested according to IEC 61646:2008, the UVB (280–320 nm) energy in the metal halide lamp accounts for 3%–10% of the total energy, and the lamp irradiance is 180 W / m. 2 The samples to be tested were prepared to a specific size and placed in a QUV aging test chamber for ultraviolet irradiation. The total irradiation energy was 180 kWh / m². 2 The resin surface was tested under the following conditions: QUV-B, light exposure at 60℃, condensate at 10℃, light exposure every 8 hours, condensation every 4 hours, for a total of 1600 hours. After the sample aging was completed, relevant performance tests were performed.

[0138] The test results are shown in Table 2.

[0139] Table 2

[0140]

[0141] Comparative Example 1 is based on Example 1 without HBPA; Comparative Example 2 is based on Example 1 without CHDM; and Comparative Example 3 is based on Example 1 without both HBPA and CHDM. The changes in color value and gloss before and after aging indicate that both HBPA and cyclic diols must be present to achieve good weather resistance. Comparative Example 4 is based on Example 1 with a single-stage synthesis; and Comparative Example 7 is based on Example 1 without the silicon-aluminum composite catalyst. The changes in color value and gloss before and after aging indicate that the synthesis method for this product must involve stepwise esterification of components 1 and 2, followed by condensation polymerization, and component 1 must use a silicon-aluminum composite catalyst. Only in this way can the product achieve good weather resistance.

[0142] The applicant declares that this invention illustrates the weather-resistant and heat-resistant copolyester, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A method for preparing a copolyester, characterized in that, The preparation method includes the following steps: (1) A dicarboxylic acid or anhydride or dicarboxylic acid ester reacts with HBPA under the action of a catalyst to obtain component 1; (2) A dicarboxylic acid or anhydride or dicarboxylic acid ester reacts with a diol under the action of a catalyst to obtain component 2; (3) Mix component 1 and component 2 and react to obtain the copolyester; The catalyst mentioned in step (1) is a silicon-aluminum composite catalyst; The diol in step (2) comprises at least one diol A selected from the following: ； and at least one diol B selected from the following: ； The molar ratio of diol A to diol B is 1:0.6 to 1:8; The catalyst in step (2) is selected from zinc acetate and / or tetrabutyl titanate; The dicarboxylic acid or anhydride or dicarboxylic acid ester mentioned in steps (1) and (2) is selected from any one or a combination of at least two of the following compounds: ； The silicon-aluminum composite catalyst is prepared by a hydrolysis-combination-calcination method using silicon and aluminum sources.

2. The preparation method according to claim 1, characterized in that, The molar ratio of the dicarboxylic acid or anhydride or dicarboxylic acid ester to HBPA in step (1) is 1:1.1 to 1:1.

4.

3. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of the dicarboxylic acid or anhydride or dicarboxylic acid ester to HBPA is 1:1.

2.

4. The preparation method according to claim 1, characterized in that, The silicon source includes any one or a combination of at least two of sodium silicate, tetraethyl orthosilicate, or sodium metasilicate.

5. The preparation method according to claim 1, characterized in that, The aluminum source includes any one or a combination of at least two of aluminum oxide, sodium aluminate, aluminum isopropoxide, aluminum sulfate, aluminum stearate, or aluminum acetate.

6. The preparation method according to claim 1, characterized in that, The amount of catalyst used in step (1) is 0.02% to 0.08% of the mass of the dicarboxylic acid, anhydride, or dicarboxylic acid ester in step (1).

7. The preparation method according to claim 1, characterized in that, The amount of catalyst used in step (1) is 0.04% of the mass of the dicarboxylic acid, acid anhydride, or dicarboxylic acid ester in step (1).

8. The preparation method according to claim 1, characterized in that, The reaction in step (1) is carried out under the protection of a protective gas.

9. The preparation method according to claim 8, characterized in that, The protective gas is nitrogen.

10. The preparation method according to claim 1, characterized in that, The reaction temperature in step (1) is 235~255℃, and the reaction time is 3~6 hours.

11. The preparation method according to claim 1, characterized in that, Step (1) Add the dicarboxylic acid or anhydride or dicarboxylic acid ester, HBPA and catalyst into the reactor. Replace the air in the reactor with nitrogen. After replacement, pressurize with nitrogen to 0.2~0.4 MPa. Then gradually heat up until all raw materials melt. Stir and heat up to the reaction temperature of 235~255℃. React for 3~6 hours.

12. The preparation method according to claim 1, characterized in that, The molar ratio of the dicarboxylic acid or anhydride or dicarboxylic acid ester to the diol in step (2) is 1:1.3 to 1:1.

8.

13. The preparation method according to claim 1, characterized in that, In step (2), the molar ratio of the dicarboxylic acid or anhydride or dicarboxylic acid ester to the diol is 1:1.

6.

14. The preparation method according to claim 1, characterized in that, The amount of catalyst used in step (2) is 0.01%-0.08% of the mass of the dicarboxylic acid in step (2).

15. The preparation method according to claim 1, characterized in that, The reaction in step (2) is carried out under the protection of a protective gas.

16. The preparation method according to claim 15, characterized in that, The protective gas is nitrogen.

17. The preparation method according to claim 1, characterized in that, The reaction temperature in step (2) is 225-250℃, and the reaction time is 3-6 hours.

18. The preparation method according to claim 1, characterized in that, Step (2) Add the dicarboxylic acid or anhydride or dicarboxylic acid ester, diol and catalyst into the reactor. Replace the air in the reactor with nitrogen. After replacement, pressurize with nitrogen to 0.1 MPa. Then gradually heat up until all raw materials melt. Stir and heat up to the reaction temperature of 225~250℃. React for 3~6 hours.

19. The preparation method according to claim 1, characterized in that, The reaction described in step (3) is carried out under the protection of a protective gas.

20. The preparation method according to claim 19, characterized in that, The protective gas is nitrogen.

21. The preparation method according to claim 1, characterized in that, After mixing components 1 and 2 in step (3), a stabilizer is added.

22. The preparation method according to claim 21, characterized in that, The stabilizer is selected from any one or a combination of at least two of phosphoric acid, phosphorous acid, hypophosphite, pyrophosphate, ammonium phosphate, trimethyl phosphate, dimethyl phosphate, triphenyl phosphate, triethyl phosphoroacetate, diphenyl phosphate, triphenyl phosphite, and diphenyl phosphite.

23. The preparation method according to claim 21, characterized in that, The amount of stabilizer used in step (3) is 0.01% to 0.08% of the mass of the dicarboxylic acid, acid anhydride, or dicarboxylic acid ester in step (2).

24. The preparation method according to claim 1, characterized in that, Step (3) Add component 1 and component 2 into the reactor, replace the air in the reactor with nitrogen, mix for 10 to 40 minutes under normal pressure and stirring at 40 to 100 rpm, then raise the temperature to 260 to 265°C, reduce the pressure to 1 kPa, and react for 2 to 5 hours; continue to raise the temperature to 270°C to 275°C, adjust the speed to 100 to 150 rpm, gradually reduce the pressure to below 30 Pa, and react for 2 to 7 hours.

25. The copolyester prepared by the method according to any one of claims 1-24.

26. The copolyester according to claim 25, characterized in that, The intrinsic viscosity of the copolyester is 0.5~0.85 dl / g.

27. The copolyester according to claim 25, characterized in that, The copolyester has a number-average molecular weight Mn of 8000~26000 and a molecular weight distribution index of 1.0~1.

9.

28. The copolyester according to claim 25, characterized in that, The copolyester has a Tg of 70~125℃ and an HDT of >110℃.

29. The copolyester according to claim 25, characterized in that, The copolyester has an HBPA retention rate of ≥82%.

30. The application of the copolyester according to any one of claims 25-29 in photovoltaic materials, new energy materials or building materials.

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