A high emissivity copolyester resin, film and method of making same

Abstract

This invention relates to the field of organic polymer compound preparation technology. The invention discloses a high-emissivity copolyester resin, a film, and a method for preparing the same, made from the following raw materials in the indicated mass ratios: 1000 parts terephthalic acid, 300-372 parts ethylene glycol, 30-450 parts fluorinated functional monomers, 0.25-0.35 parts catalyst, and 0.05-0.1 parts heat stabilizer. The fluorinated functional monomers are directly reacted and linked to the polyester molecular backbone without precipitation, thus ensuring the infrared emissivity of the polyester resin. The resulting fluorinated copolyester resin has an infrared emissivity as high as 95.2%, which is significantly higher than that of traditional copolyester resins such as COC and COP; furthermore, it can be recycled multiple times, exhibiting good recyclability.

Description

Technical Field

[0001] This invention relates to the field of organic polymer compound preparation technology, specifically to a high emissivity copolyester resin, a film, and a method for preparing the same. Background Technology

[0002] The statements in this section provide only background information relevant to the disclosure of this application and may not constitute prior art.

[0003] Radiative cooling, as a passive cooling technology, enables spontaneous cooling with zero energy consumption and zero pollution, providing an innovative energy solution for addressing climate change and regulating human thermal comfort. The core principle of this technology is to radiate excess heat from an object into outer space at 3K as electromagnetic waves through an atmospheric window of 8-13 μm. Leveraging its passive and renewable characteristics, radiative cooling has achieved breakthroughs in many fields, including building cooling, solar cell heat dissipation, personal thermal management, and wearable device temperature control.

[0004] Currently, the research and development of traditional radiative cooling materials mainly focuses on systems containing CF, Si-O, CO, and Si-H bonds. Among them, the CF bond has become a research hotspot in this field due to its dual advantages of a wide emission wavelength range and high emission efficiency. For example, Wu Xueke et al. pointed out in their research published in *Nature Communications* (2024, 15:815) that the CF bond in the polytetrafluoroethylene (PTFE) molecular structure exhibits high selective emissivity in the 8–13 μm wavelength range; Zhu Hai et al.'s research in *Journal of Ceramics* (2025, Vol. 46, No. 1: 106-114) showed that the emissivity of the prepared PVDF-HFP film reached as high as 97% in the infrared band. However, while these fluorinated materials achieve excellent radiative cooling performance through CF bonds, they pose significant environmental risks: these materials are difficult to degrade, and if incinerated, they will release highly toxic hydrogen fluoride gas, which is harmful to human health; at the same time, hydrogen fluoride released into the atmosphere will combine with water vapor to form hydrofluoric acid mist, which, after settling, will cause soil and water acidification, thereby damaging the plant growth environment and threatening the survival of aquatic organisms.

[0005] Therefore, there is an urgent need to develop more environmentally friendly high-emissivity radiative cooling materials. Copolyester materials have better recyclability than PVDF-HFP films prepared by existing technologies. After use, they can be efficiently decomposed into original monomers or high-value chemical raw materials, enabling repeated recycling and reuse, thereby improving the environmental performance of the materials. However, copolyester films have limited infrared emissivity during daytime cooling, resulting in a generally small temperature difference with the ambient temperature, making it difficult to meet extreme cooling requirements, and improvements are urgently needed. Summary of the Invention

[0006] The purpose of this invention is to address the problem that traditional radiative cooling materials containing CF bonds cannot simultaneously achieve both radiative cooling performance and environmental performance. This invention provides a high emissivity copolyester resin, a film, and a method for preparing the same. The copolyester resin is used as the matrix to ensure environmental performance, while the addition of a specially structured fluorinated functional monomer significantly improves its infrared emissivity.

[0007] The technical solution of the present invention is as follows: One aspect of this invention provides a high emissivity copolyester resin, made from the following raw materials in the indicated mass ratios: 1000 parts by mass of terephthalic acid, 300-372 parts by mass of ethylene glycol, 30-450 parts by mass of fluorinated functional monomers, 0.25-0.35 parts by mass of catalyst, and 0.05-0.1 parts by mass of heat stabilizer.

[0008] According to a preferred embodiment, the catalyst is antimony trioxide or antimony glycol.

[0009] According to a preferred embodiment, the heat stabilizer is triphenyl phosphate or trimethyl phosphate.

[0010] According to a preferred embodiment, the structural formula of the fluorinated functional monomer is: .

[0011] According to a preferred embodiment, the copolyester resin has the following structural formula: ; Where: m: n = 50~99: 1~50.

[0012] According to a preferred embodiment, the viscosity of the copolyester resin is 0.60 dL / g to 0.80 dL / g.

[0013] According to a preferred embodiment, the viscosity of the copolyester resin is 0.60 dL / g, 0.65 dL / g, 0.70 dL / g, 0.75 dL / g, or 0.80 dL / g.

[0014] Another aspect of the present invention provides a method for preparing a high emissivity copolyester resin as described above, comprising the following steps: Step S1: Preparation of fluorine-containing functional monomers S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 50-80mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 8-10g of 25% NaOH aqueous solution, and stir at room temperature for 20-30min until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate). S1.2: Add 0.25~0.30g of tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 8.0~12mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30℃. Raise the temperature to 60~70℃, turn on the reflux condenser, and maintain the temperature with stirring for 2.5~3.5h. S1.3: After the reaction is complete, cool the system to room temperature and pour it into 100-120 mL of saturated NaCl solution. Stir for 10-15 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase 2-4 times (30 mL each time) with saturated NaCl solution to remove residual salts and unreacted 2-chloroethanol. Finally, add 5-8 g of anhydrous MgSO4 to dry the organic phase, let it stand for 30-40 min, and then filter. S1.4: Dimethyl sulfoxide was removed by vacuum distillation, and the product was obtained by rotary evaporation and drying. Step S2: Preparation of high emissivity copolyester resin S2.1: 1000 parts by mass of terephthalic acid, 300-372 parts by mass of ethylene glycol, 30-450 parts by mass of the fluorine-containing functional monomer obtained in step S1, 0.25-0.35 parts by mass of catalyst, and 0.05-0.1 parts by mass of heat stabilizer are added to the reactor to carry out the reaction; S2.2: When the temperature inside the reactor rises to 235-252℃ and the water output is 205-215 parts by mass, the temperature is raised to 276-283℃ for polycondensation, and a vacuum is slowly evacuated for 2.5-3.5 hours. When the residual pressure inside the reactor is 20-40 Pa and the resin viscosity is 0.60-0.80 dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

[0015] The fluorinated functional monomers prepared by the method of this application have superior yield and higher purity compared with commercially available monomers, which is more conducive to the preparation of copolyester resin materials.

[0016] The application of a high emissivity copolyester resin material as described above in the preparation of radiation cooling materials or coatings.

[0017] In another aspect, the present invention provides a high-emissivity copolyester resin film prepared using a high-emissivity copolyester resin material as described above.

[0018] Compared with existing technologies, the advantages of this invention are: 1. A high-emissivity copolyester resin and film, wherein the infrared emissivity of the prepared fluorinated copolyester resin is as high as 95.2%, which is significantly improved compared with traditional copolyester resins such as COC and COP; 2. A high emissivity copolyester resin and film, based on the material properties of copolyester resin, and the fluorinated functional monomer of this application is directly connected to the main chain of copolyester resin, which can be recycled multiple times and has good recyclability, thereby reducing environmental pollution, reducing resource consumption, and having green and environmentally friendly performance. 3. A method for preparing a high emissivity copolyester resin, which has a simple preparation process, convenient procedures, is easy to operate, and has strong practicality. Detailed Implementation

[0019] The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.

[0021] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0022] Example 1: Preparation of a high emissivity copolyester resin Step S1: Preparation of fluorine-containing functional monomers S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 50mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 8g of 25% NaOH aqueous solution, stir at room temperature for 20min, until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate); S1.2: Add 0.25 g tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 8.0 mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30 °C. Raise the temperature to 60 °C, turn on the reflux condenser, and maintain the temperature with stirring for 2.5 h. S1.3: After the reaction is complete, cool the system to room temperature and pour it into 100 mL of saturated NaCl solution. Stir for 10 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase twice with saturated NaCl solution (30 mL each time) to remove residual salts and unreacted 2-chloroethanol. Finally, add 5 g of anhydrous MgSO4 to dry the organic phase, let it stand for 30 min, and then filter. S1.4: Remove dimethyl sulfoxide organic solvent by vacuum distillation (temperature ≤80℃, pressure 5~10mmHg), and obtain the target product, fluorine-containing functional monomer, after evaporation.

[0023] Step S2: Preparation of high emissivity copolyester resin S2.1: 1000 parts by mass of terephthalic acid, 310 parts by mass of ethylene glycol, 440 parts by mass of the fluorine-containing target functional product obtained in step S1, 0.25 parts by mass of catalyst, and 0.05 parts by mass of heat stabilizer are added to the reactor and the pressure is increased to 0.2 MPa to carry out the reaction. S2.2: When the temperature inside the reactor rises to 235℃ and the output water volume is 205 parts by mass, the temperature is raised to 276℃ for polycondensation, and a vacuum is slowly evacuated for 2.5 hours. When the residual pressure inside the reactor is 20Pa and the resin viscosity is 0.60dL / g, nitrogen is introduced to discharge the material, and high emissivity polyester resin is obtained.

[0024] Example 2: Preparation of a high emissivity copolyester resin Step S1: Preparation of fluorine-containing functional monomers S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 55mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 8.5g of 25% NaOH aqueous solution, stir at room temperature for 22min, until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate); S1.2: Add 0.26 g of tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 8.5 mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30 °C. Raise the temperature to 63 °C, turn on the reflux condenser, and maintain the temperature with stirring for 2.8 h. S1.3: After the reaction is complete, cool the system to room temperature and pour it into 105 mL of saturated NaCl solution. Stir for 12 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase twice with saturated NaCl solution (30 mL each time) to remove residual salts and unreacted 2-chloroethanol. Finally, add 6 g of anhydrous MgSO4 to dry the organic phase, let it stand for 33 min, and then filter.

[0025] S1.4: Remove dimethyl sulfoxide organic solvent by vacuum distillation (temperature ≤80℃, pressure 5~10mmHg), and obtain the target product, fluorine-containing functional monomer, after evaporation.

[0026] Step S2: Preparation of high emissivity copolyester resin S2.1: 1000 parts by mass of terephthalic acid, 320 parts by mass of ethylene glycol, 377 parts by mass of the fluorine-containing target functional product obtained in step S1, 0.28 parts by mass of catalyst, and 0.07 parts by mass of heat stabilizer are added to the reactor and the pressure is increased to 0.2 MPa to carry out the reaction. S2.2: When the temperature inside the reactor rises to 238℃ and the output water volume is 208 parts by mass, the temperature is raised to 278℃ for polycondensation, and a vacuum is slowly evacuated for 2.9 hours. When the residual pressure inside the reactor is 25Pa and the resin viscosity is 0.65dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

[0027] Example 3: Preparation of a high emissivity copolyester resin Step S1: Preparation of fluorine-containing functional monomers S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 60mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 9g of 25% NaOH aqueous solution, stir at room temperature for 25min, until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate); S1.2: Add 0.28 g tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 9 mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30 °C. Raise the temperature to 65 °C, turn on the reflux condenser, and maintain the temperature with stirring for 3 hours. S1.3: After the reaction is complete, cool the system to room temperature and pour it into 110 mL of saturated NaCl solution. Stir for 13 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase three times with saturated NaCl solution (30 mL each time) to remove residual salt and unreacted 2-chloroethanol. Finally, add 6.5 g of anhydrous MgSO4 to dry the organic phase, let it stand for 35 min, and then filter. S1.4: Remove dimethyl sulfoxide organic solvent by vacuum distillation (temperature ≤80℃, pressure 5~10mmHg), and obtain the target product, fluorine-containing functional monomer, after evaporation.

[0028] Step S2: Preparation of high emissivity copolyester resin S2.1: 1000 parts by mass of terephthalic acid, 330 parts by mass of ethylene glycol, 310 parts by mass of the fluorine-containing target functional product obtained in step S1, 0.29 parts by mass of catalyst, and 0.08 parts by mass of heat stabilizer are added to the reactor and the pressure is increased to 0.2 MPa to carry out the reaction. S2.2: When the temperature inside the reactor rises to 240℃ and the output water volume is 210 parts by mass, the temperature is raised to 280℃ for polycondensation, and a vacuum is slowly evacuated for 3.1 hours. When the residual pressure inside the reactor is 30Pa and the resin viscosity is 0.70dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

[0029] Example 4: Preparation of a high emissivity copolyester resin Step S1: Preparation of fluorine-containing functional monomers S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 65mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 9.5g of 25% NaOH aqueous solution, stir at room temperature for 26min, until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate); S1.2: Add 0.27 g tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 9.5 mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30 °C. Raise the temperature to 66 °C, turn on the reflux condenser, and maintain the temperature with stirring for 3.2 h. S1.3: After the reaction is complete, cool the system to room temperature and pour it into 115 mL of saturated NaCl solution. Stir for 13 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase four times with saturated NaCl solution (30 mL each time) to remove residual salts and unreacted 2-chloroethanol. Finally, add 6.5 g of anhydrous MgSO4 to dry the organic phase, let it stand for 40 min, and then filter. S1.4: Remove dimethyl sulfoxide organic solvent by vacuum distillation (temperature ≤80℃, pressure 5~10mmHg), and obtain the target product, fluorine-containing functional monomer, after evaporation.

[0030] Step S2: Preparation of high emissivity copolyester resin Step S2.1: Add 1000 parts by mass of terephthalic acid, 340 parts by mass of ethylene glycol, 240 parts by mass of the fluorine-containing target functional product obtained in step S1, 0.33 parts by mass of catalyst, and 0.1 parts by mass of heat stabilizer into the reactor, and pressurize to 0.2 MPa to carry out the reaction; Step S2.2: When the temperature inside the reactor rises to 250℃ and the output water volume is 212 parts by mass, the temperature is raised to 280℃ for polycondensation, and a vacuum is slowly evacuated for 3.5 hours. When the residual pressure inside the reactor is 38Pa and the resin viscosity is 0.75dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

[0031] Example 5: Preparation of a high emissivity copolyester resin Step S1: Preparation of fluorine-containing functional monomers Step S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 70mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 10g of 25% NaOH aqueous solution, stir at room temperature for 30min, until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate). Step S1.2: Add 0.30 g of tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 11 mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30°C. Raise the temperature to 70°C, turn on the reflux condenser, and maintain the temperature with stirring for 3.5 h. Step S1.3: After the reaction is complete, cool the system to room temperature and pour it into 115 mL of saturated NaCl solution. Stir for 13 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase three times with saturated NaCl solution (30 mL each time) to remove residual salts and unreacted 2-chloroethanol. Finally, add 7 g of anhydrous MgSO4 to dry the organic phase, let it stand for 35 min, and then filter. Step S1.4: Remove dimethyl sulfoxide organic solvent by vacuum distillation (temperature ≤80℃, pressure 5~10mmHg), and obtain the target product, fluorine-containing functional monomer, after evaporation.

[0032] Step S2: Preparation of high emissivity copolyester resin S2.1: Add 1000 parts by mass of terephthalic acid, 350 parts by mass of ethylene glycol, 185 parts by mass of the fluorine-containing target functional product obtained in step S1, 0.35 parts by mass of catalyst, and 0.1 parts by mass of heat stabilizer into the reactor, and pressurize to 0.2 MPa to carry out the reaction; S2.2: When the temperature inside the reactor rises to 252℃ and the output water volume is 215 parts by mass, the temperature is raised to 282℃ for polycondensation, and a vacuum is slowly evacuated for 3.3 hours. When the residual pressure inside the reactor is 40Pa and the resin viscosity is 0.78dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

[0033] Example 6: Preparation of a high emissivity copolyester resin Step S1: Preparation of fluorine-containing functional monomers S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 80mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 9.5g of 25% NaOH aqueous solution, stir at room temperature for 28min, until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate); S1.2: Add 0.29 g of tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 12 mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30 °C. Raise the temperature to 68 °C, turn on the reflux condenser, and maintain the temperature with stirring for 3.1 h. S1.3: After the reaction is complete, cool the system to room temperature and pour it into 112 mL of saturated NaCl solution. Stir for 15 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase four times with saturated NaCl solution (30 mL each time) to remove residual salts and unreacted 2-chloroethanol. Finally, add 7.8 g of anhydrous MgSO4 to dry the organic phase, let it stand for 35 min, and then filter. S1.4: Remove dimethyl sulfoxide organic solvent by vacuum distillation (temperature ≤80℃, pressure 5~10mmHg), and obtain the target product, fluorine-containing functional monomer, after evaporation.

[0034] Step S2: Preparation of high emissivity copolyester resin S2.1: 1000 parts by mass of terephthalic acid, 360 parts by mass of ethylene glycol, 90 parts by mass of the fluorine-containing target functional product obtained in step S1, 0.33 parts by mass of catalyst, and 0.09 parts by mass of heat stabilizer are added to the reactor and the pressure is increased to 0.2 MPa to carry out the reaction. S2.2: When the temperature inside the reactor rises to 250℃ and the output water volume is 213 parts by mass, the temperature is raised to 281℃ for polycondensation, and a vacuum is slowly evacuated for 2.8 hours. When the residual pressure inside the reactor is 40Pa and the resin viscosity is 0.80dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

[0035] Example 7: Preparation of a high emissivity copolyester resin Step S1: Preparation of fluorine-containing functional monomers S1.1: Add 18g of 2,2-bis-(4-hydroxyphenyl)hexafluoropropane (CAS No.: 1478-61-1) to a 250mL three-necked flask, add 68mL of dimethyl sulfoxide organic solvent, and start stirring to disperse the 2,2-bis-(4-hydroxyphenyl)fluoropropane. Slowly add 8.8g of 25% NaOH aqueous solution, stir at room temperature for 22min, until the solution is homogeneous and transparent (the phenolic hydroxyl groups are completely converted to sodium phenolate). S1.2: Add 0.27 g tetrabutylammonium bromide (phase transfer catalyst) to the flask and stir until homogeneous. Slowly add 10 mL of 2-chloroethanol dropwise, controlling the dropping rate to keep the system temperature below 30 °C. Raise the temperature to 66 °C, turn on the reflux condenser, and maintain the temperature with stirring for 3.2 h. S1.3: After the reaction is complete, cool the system to room temperature and pour it into 108 mL of saturated NaCl solution. Stir for 15 min (salting out the organic product). Transfer to a separatory funnel and allow to separate into layers: take the upper organic phase; wash the organic phase three times with saturated NaCl solution (30 mL each time) to remove residual salts and unreacted 2-chloroethanol. Finally, add 8 g of anhydrous MgSO4 to dry the organic phase, let it stand for 32 min, and then filter. S1.4: Remove dimethyl sulfoxide organic solvent by vacuum distillation (temperature ≤80℃, pressure 5~10mmHg), and obtain the target product, fluorine-containing functional monomer, after evaporation.

[0036] Step S2: Preparation of high emissivity copolyester resin S2.1: 1000 parts by mass of terephthalic acid, 365 parts by mass of ethylene glycol, 50 parts by mass of the fluorine-containing target functional product obtained in step S1, 0.29 parts by mass of catalyst, and 0.07 parts by mass of heat stabilizer are added to the reactor and the pressure is increased to 0.2 MPa to carry out the reaction. S2.2: When the temperature inside the reactor rises to 250℃ and the output water volume is 210 parts by mass, the temperature is raised to 279℃ for polycondensation, and a vacuum is slowly evacuated for 2.6 hours. When the residual pressure inside the reactor is 30Pa and the resin viscosity is 0.76dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

[0037] Comparative Example 1 This comparative example provides a common polyester resin, the preparation process of which is the same as that of Example 1. The difference is that the preparation of the common polyester resin starts directly from step S2 of Example 1, and the reactants do not contain the fluorine-containing target functional product obtained in step S1. The rest is the same as the second step of Example 1.

[0038] Effect test The polyester resins prepared in Examples 1-7 and the comparative examples were extruded and cast in an extruder using a biaxial stretching process to obtain films with a thickness of 188 μm, and their properties were tested. The infrared emissivity (8~13 μm) of the films was tested according to the method in T / ZZB 2304-2021 "Radiation Cooling Films".

[0039] The emissivity (8~13μm) of ordinary polyester films prepared in Examples 1 to 7 and comparative examples was tested, and the test results are shown in Table 1.

[0040] Table 1 Test Results

[0041] As shown in Table 1, the emissivity (8~13μm) of the film made of high emissivity copolyester resin prepared in this application increases with the increase of the proportion of fluorinated functional monomers, with the lowest emissivity being 89.2% and the highest being 95.2%. In contrast, the emissivity of the film made of ordinary polyester resin is only 84.6%, which is much lower than that of the film made of fluorinated copolyester resin.

[0042] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A high emissivity copolyester resin, characterized in that, It is made from the following raw materials in the indicated weight ratios: 1000 parts terephthalic acid, 300 to 372 parts ethylene glycol, 30 to 450 parts fluorinated functional monomers, 0.25 to 0.35 parts catalyst and 0.05 to 0.1 parts heat stabilizer.

2. The high emissivity copolyester resin according to claim 1, characterized in that, The catalyst is antimony trioxide or antimony glycol.

3. The high emissivity copolyester resin according to claim 1, characterized in that, The heat stabilizer is triphenyl phosphate or trimethyl phosphate.

4. The high emissivity copolyester resin according to claim 1, characterized in that, The structural formula of the fluorine-containing functional monomer is: 。 5. The high emissivity copolyester resin according to claim 1, characterized in that, The structural formula of the copolyester resin is as follows: ； Where: m: n = 50~99: 1~50.

6. The high emissivity copolyester resin according to claim 1, characterized in that, The viscosity of the copolyester resin is 0.60 dL / g to 0.80 dL / g.

7. The high emissivity copolyester resin according to claim 6, characterized in that, The viscosity of the copolyester resin is 0.60 dL / g, 0.65 dL / g, 0.70 dL / g, 0.75 dL / g, or 0.80 dL / g.

8. A method for preparing a high emissivity copolyester resin according to any one of claims 1-7, characterized in that, Includes the following steps: Step S1: Preparation of fluorine-containing functional monomers S1.1: Mix 2,2-bis-(4-hydroxyphenyl)hexafluoropropane and dimethyl sulfoxide evenly, then slowly add 25% NaOH aqueous solution, and stir at room temperature for 20-30 minutes until the solution is homogeneous and transparent; S1.2: Add phase transfer catalyst to the product of step S1.1, stir evenly, slowly add 2-chloroethanol dropwise, control the dropping rate so that the system temperature does not exceed 30℃; after the dropping is completed, raise the temperature to 60~70℃, turn on the reflux condenser, and keep it at the temperature and stir for 2.5~3.5h. S1.3: After the reaction is complete, cool the system to room temperature, add saturated sodium chloride to salt out the organic product, then let it stand to separate the layers, and separate the upper organic phase; wash the organic phase 2-4 times with saturated NaCl solution to remove residual salt and unreacted 2-chloroethanol; finally dry the organic phase and filter to obtain the organic phase; S1.4: Dimethyl sulfoxide was removed by vacuum distillation, and the product was obtained by rotary evaporation and drying. Step S2: Preparation of high emissivity copolyester resin S2.1: Add 1000 parts of terephthalic acid, 300-372 parts of ethylene glycol, 30-450 parts of the fluorine-containing functional monomer obtained in step S1, 0.25-0.35 parts of catalyst, and 0.05-0.1 parts of heat stabilizer to the reactor and carry out the reaction; S2.2: When the temperature inside the reactor rises to 235-252℃ and the water output is 205-215 parts, the temperature is raised to 276-283℃ for polycondensation, and a vacuum is slowly evacuated for 2.5-3.5 hours. When the residual pressure inside the reactor is 20-40 Pa and the resin viscosity is 0.60-0.80 dL / g, nitrogen is introduced to discharge the material, and a high emissivity copolyester resin is obtained.

9. The use of a high emissivity copolyester resin material as described in any one of claims 1-7 in the preparation of radiation cooling materials or coatings.

10. A high-emissivity copolyester resin film prepared using a high-emissivity copolyester resin material as described in any one of claims 1-7.

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