Halogen-free environment-friendly end-capping reagent and method for carrying out end capping on sulfone polymer by using halogen-free environment-friendly end-capping reagent

Abstract

The invention relates to the technical field of synthesis of high molecular material sulfone polymers, in particular to a halogen-free environment-friendly end-capping reagent and a method for carrying out end capping on sulfone polymers by using the halogen-free environment-friendly end-capping reagent. At least one halogen-free environment-friendly end-capping reagent selected from methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, trimethyl carbonate, propylene carbonate and ethylene carbonate is introduced; and at least one ionic liquid selected from the group consisting of 1-ethyl-3-methylimidazole acetate, 1-ethyl-3-methylimidazole methane sulfonate, tetrabutylammonium p-toluenesulfonate and choline acetate is used as a catalyst. According to the method, the problems of environmental pollution and toxic residues caused by a traditional halogen end-capping reagent are effectively avoided. The invention also keeps the bisphenol monomer slightly excessive. And the prepared polysulfone resin has the advantages of obviously enhanced terminal group stability, pure color, high transparency and low chlorine content, and is suitable for the high value-added application fields of medical instruments, food contact materials, electronic devices and the like.

Description

Technical Field

[0001] This invention relates to the field of sulfone polymer synthesis technology, specifically a halogen-free environmentally friendly end-capping agent and a method for end-capping sulfone polymers. Background Technology

[0002] Polysulfone resin is a class of high-performance specialty engineering plastics. Its main chain contains sulfone groups (-SO2-), aromatic ether bonds, and isopropylidene structures, exhibiting excellent high-temperature resistance, high mechanical strength, and chemical stability (resistance to acids, alkalis, and organic solvents). These superior properties make it one of the core materials in fields such as water treatment, aerospace, electronic equipment, and medical devices. Notably, the global market size for medical-grade polysulfone resin is projected to exceed US$1.4 billion in 2024, with future growth primarily dependent on innovative iterations in blood purification technology and high-end medical devices. Polysulfone resin is typically synthesized through the condensation reaction of bisphenol monomers with 4,4'-dihalodiphenyl sulfone. The resulting product usually contains phenolic hydroxyl / phenolic hydroxyl salts or chloride end groups. Therefore, end-capping agents need to be introduced during the reaction to control molecular chain growth, regulate end group activity, and thus improve the product's appearance properties (such as yellowness, light transmittance, and haze). A conventional strategy is to design polysulfone to contain some chloride end groups while simultaneously modifying the easily oxidized phenolic hydroxyl / phenolic hydroxyl salts to improve its thermal stability. However, in the field of medical materials, about 30% of the world's leading medical device companies have explicitly required the use of "halogen-free / low-halogen" materials, which indicates that low-halogen or halogen-free materials will become the future trend. Halogen residues (such as chloride ions and fluoride ions) and their leaching pose multiple risks: (1) Biocompatibility risk: may lead to cytotoxicity and sensitization, which does not meet the biocompatibility standards of medical devices such as ISO 10993. Residual halogen small molecules have the risk of migration, especially during high-temperature sterilization or long-term immersion in body fluids. (2) Material performance risk: adversely affects the thermal stability and chemical resistance of polysulfone resin itself. For example, uncapped chlorine end groups may cause main chain breakage at high temperatures (>200 ℃), resulting in a decrease in mechanical properties; high chlorine content polysulfone may adsorb more ethylene oxide (EO) gas, increasing the risk of excessive residues; it is easy to dissolve and aggravate yellowing under high temperature and high pressure. In addition, if the end capping group is not active enough, it will lead to poor stability of polymer end groups, affecting the long-term performance of the material. The aforementioned problems have all limited the practical application of polysulfone resin in the medical industry.

[0003] End capping is an essential step in the preparation of polysulfone resin, which effectively improves the quality of the final polysulfone resin product. However, the mainstream end capping agent for industrial production of polysulfone is still chloromethane, which has significant problems in its application: (1) Safety and environmental risks: Chloromethane has neurotoxicity and long-term exposure can damage the central nervous system; at the same time, it is a volatile organic compound (VOC), which participates in photochemical reactions after emission to generate pollutants such as ozone, seriously polluting the environment. (2) Operation and process difficulties: It has a low boiling point and requires high pressure or low temperature storage, making operation complicated. Its gaseous characteristics make accurate measurement difficult, which can easily lead to improper dosage (excess or deficiency). It can easily escape to the upper space in the polymerization reactor, resulting in low end capping efficiency and prolonged reaction time. In heterogeneous systems, diffusion is limited, and the end capping rate is usually only 70-80%. There is a risk of leakage. (2) Cost and compliance pressure: Special recycling equipment is required after end capping, which is difficult and costly to recycle. Polysulfone medical devices with residual chloromethane require additional compliance certification, which limits their application in the medical field. In addition, the end-capping methods involved in existing patents also have their own limitations: Chinese patent CN 104530419 A uses 3,4'-difluorobenzophenone, 3-chloro-4-fluorobenzophenone, and 3,4'-dichlorobenzophenone for end-capping. The main drawback is that the end-capping agents are poorly soluble in water and have high boiling points, making post-processing removal difficult. Furthermore, controlling the end-capping conditions is challenging, potentially leading to only monohalogen substitution and the introduction of halogen atoms into the polysulfone chain. Chinese patent CN 115010926 A uses water-soluble sodium 2-bromoethylsulfonate, 1,3-propanesulfonate lactone, and 1,4-propanesulfonate lactone to achieve end-capping of polysulfone terminal hydroxyl groups / terminal hydroxyl salts. Although its hydrophilicity facilitates removal, sodium 2-bromoethylsulfonate poses a risk of residual bromine, limiting its medical applications. Sulfonate lactones (such as 1,3-propanesulfonate lactone) are listed as potential carcinogens and easily decompose and release acidic substances during high-temperature processing (such as injection molding), accelerating material aging, thus also limiting their potential in the biomedical field. Most of the second end-capping agents described in Chinese Patent CN 119842078 A are toxic and have safety concerns. For example, dimethyl sulfate and diethyl sulfate are highly toxic substances with carcinogenic and corrosive properties; while chloromethane, bromomethane, and iodomethane are all medium to high levels of toxicity and are unfriendly to the environment and human health. The p-aminophenol and p-methylaminophenol mentioned in Patent CN113388112 A are sensitive to light and oxygen, easily oxidized and discolored, and slightly soluble in water. In the post-processing stage of polysulfone, incomplete removal of the end-capping agent may affect the appearance and properties of the polysulfone. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems in the prior art, the present invention provides a method for preparing halogen-free environmentally friendly end-capping agent-terminated polysulfone.

[0005] A method for preparing a halogen-free, environmentally friendly end-capping agent, polysulfone, includes the following steps: (1) The bisphenol monomer, 4,4'-dihalodiphenyl sulfone, basic salt-forming agent, dehydrating agent and high-boiling-point aprotic solvent are mixed in the order of addition under stirring, and then nitrogen is purged. (2) Raise the temperature to the temperature required for salt formation, carry out the salt formation reaction under the condition of nitrogen purging, and reflux to remove the water produced by salt formation; (3) When the water is collected to the theoretical yield, stop the reflux, raise the temperature to carry out the polymerization reaction, and when the target viscosity is reached, the desired sulfone polymer solution is obtained; (4) Add the halogen-free end-capping agent and ionic liquid catalyst to an appropriate amount of solvent used for polymerization, then add it to a flask to dilute the polymerization solution and cool it down. At the same time, heat the temperature down to 90~150 ℃ to carry out the end-capping reaction and obtain a sulfone resin with the target molecular weight.

[0006] Furthermore, the halogen-free capping agent is any one or more of ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, trimethyl carbonate, propylene carbonate, and ethylene carbonate, mixed in any proportion.

[0007] Furthermore, the ionic liquid catalyst is any one or more of the following: imidazole ionic liquids: 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) and 1-ethyl-3-methylimidazolium methane sulfonate ([EMIM][MeSO3]); quaternary ammonium salt ionic liquids: tetrabutylammonium p-toluenesulfonate ([N(Bu)4][TsO]); and bio-based ionic liquids: choline acetate ([Ch][Ac]), mixed in any proportion.

[0008] Furthermore, the weight-average molecular weight of the sulfone resin is between 50,000 and 100,000 Daltons. Furthermore, in step (1), the preparation method satisfies at least one of the following conditions: the molar ratio of the bisphenol monomer to 4,4'-dihalodiphenyl sulfone is 1.0001~1.01:1, preferably 1.005:1.

[0009] Furthermore, the bisphenol monomer is any one or more of bisphenol A, bisphenol S, and biphenyl hydroquinone mixed in any proportion; the 4,4'-dihalodiphenyl sulfone includes any one or more of 4,4'-difluorodiphenyl sulfone and 4,4'-dichlorodiphenyl sulfone mixed in any proportion.

[0010] Furthermore, the molar ratio of the alkaline salt-forming agent to 4,4'-dihalodiphenyl sulfone is 1.1 to 1.8:1; preferably 1.5:1.

[0011] Furthermore, the alkaline salt-forming reagent is mainly an inorganic compound, including at least one of sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, and potassium hydroxide; preferably sodium carbonate or potassium carbonate.

[0012] Furthermore, the dehydrating agent is characterized by having a boiling point lower than that of the solvent to avoid high-temperature decomposition and solvent evaporation during azeotropic water removal. The dehydrating agent is any one or more of toluene, chlorobenzene, o-xylene, p-xylene, and m-xylene mixed in any proportion, preferably toluene; the mass ratio of the dehydrating agent to the solvent is 0.05~0.4:1.

[0013] Furthermore, the high-boiling-point aprotic solvent is any one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane, mixed in any proportion, preferably N,N-dimethylacetamide or sulfolane.

[0014] Furthermore, in step (1), the order of adding materials is as follows: first, add all the water-removing agent and high-boiling-point aprotic solvent by weight, and then add all the bisphenol monomer, all the 4,4-dihalodiphenyl sulfone and basic salt-forming reagent.

[0015] Furthermore, in step (2), the preparation method satisfies at least one of the following conditions: The salt formation temperature is 170~220 ℃; preferably 180 ℃.

[0016] The nitrogen purging time is until the reflux begins, at which point the nitrogen purging can be turned off.

[0017] The salt formation time is 4 to 10 hours, preferably 5 hours.

[0018] Furthermore, the molar amount of the theoretical water production in step (3) is 3 times the molar amount of 4,4'-dihalodiphenyl sulfone in step (1).

[0019] Furthermore, the polymerization reaction temperature is 190~240 ℃, preferably 210 ℃.

[0020] Furthermore, the target viscosity of the sulfone polymer solution is 5000~50000 mPa·s.

[0021] Furthermore, the polymerization time is 3 to 25 hours.

[0022] Furthermore, in step (4), the preparation method satisfies at least one of the following conditions: The molar ratio of the end-capping agent to the 4'-dihalodiphenyl sulfone monomer is 5~1000:1; the mass amount of the ionic liquid catalyst is 1~2% of the mass of the polymer solution after polymerization.

[0023] The sealing temperature is 85~160 ℃, and the sealing time is 0.5~6 h.

[0024] Furthermore, the above preparation method also includes post-treatment of polysulfone. Specifically, the polysulfone solution is poured into water to precipitate and pulverized into powder. After washing with deionized water, the solvent and by-product salts are removed by boiling multiple times. Then, the product is dried and granulated to obtain end-capped polysulfone resin.

[0025] Applications of methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, trimethyl carbonate, propylene carbonate, and ethylene carbonate as halogen-free, environmentally friendly end-capping agents for sulfone polymers.

[0026] A sulfone polymer halogen-free environmentally friendly end-capping agent, comprising any one or more of ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, trimethyl carbonate, propylene carbonate, and ethylene carbonate in any proportion.

[0027] Applications of 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium methane sulfonate, tetrabutylammonium p-toluenesulfonate, and choline acetate as end-capping catalysts for sulfone polymers.

[0028] A sulfone polymer-terminated catalyst comprising any one or more of 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium methane sulfonate, tetrabutylammonium p-toluenesulfonate, and choline acetate in any proportion.

[0029] Compared with the prior art, the technical effects of this invention are reflected in: (1) This invention uses a halogen-free, environmentally friendly end-capping agent and a slight excess of bisphenol monomer to minimize the end-chlorine content in the sulfone polymer. Subsequently, a final end-capping reaction is performed on the hydroxyl groups / salts to ensure that the sulfone polymer resin contains almost no halogen atoms. This effectively ensures that no or very low amounts of halogen atoms are released when it is used in the medical and electronic industries, thereby reducing the potential impact on the human body and ultimately obtaining a sulfone polymer resin that meets the requirements of high-quality applications; (2) The end-capping agent selected in this invention remains liquid under end-capping conditions, which can effectively improve end-capping efficiency. This end-capping agent has a good end-capping effect on phenolic hydroxyl groups or phenolic hydroxyl salts, and the resulting sulfone polymer is end-capped with methyl or ethyl groups. Its structure and properties are relatively stable and comparable to those of traditional chloromethane end-capping agents. More importantly, this end-capping agent is safe and environmentally friendly, and will not cause toxicity to the environment or human body. Moreover, the operation can be carried out under normal pressure conditions. (3) The present invention also provides a halogen-free ionic liquid as a catalyst for the end-capping reaction. This catalyst can effectively improve the reaction efficiency, enhance the end-capping activity of the phenolic hydroxyl / salt, thereby increasing the end-capping rate, shortening the end-capping time, significantly reducing the content of phenolic hydroxyl / salt in the product, and finally obtaining a sulfone polymer resin with higher stability and better resistance to yellowing; (4) This invention also provides a post-treatment method for the end-capped sulfone polymer solution: the polysulfone solution is poured into water to precipitate and pulverized into powder, washed with deionized water, and then boiled multiple times to remove solvent and by-product salts, further removing salts remaining on the surface of the powder and embedded inside the particles. Through this two-step process, a pure sulfone polymer resin with high purity, high transparency, and low impurity content can be obtained, meeting the application requirements of high-end polysulfone products in the medical industry. Detailed Implementation

[0030] To enable researchers in the art to better understand the technical solutions of this invention, the following detailed description of the technical solutions of this invention is provided in conjunction with specific embodiments. This invention can be implemented in different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to make the content disclosed in this invention clearer, more accurate, and more thorough.

[0031] Example 1 In a 1000 mL four-necked flask equipped with nitrogen protection, condenser, stirrer, temperature sensor, and water separator, the stirring speed was set to 200 rpm / min. Then, at room temperature, 235.4 g of solvent N,N-dimethylformamide, 23.5 g of dehydrating agent m-xylene, 76 g of bisphenol A monomer, 95 g of 4,4'-dichlorodiphenyl sulfone, and 64.6 g of anhydrous potassium carbonate were added sequentially to the flask. Nitrogen protection was then applied. The temperature was set to 180 °C, and salt formation and reflux dehydration were continued at this temperature for 4 h after droplets began to fall from the water separator. Once the theoretical product water volume was collected in the water separator, reflux was stopped, and the temperature was gradually increased to 210 °C to distill off the dehydrating agent and begin polymerization for 8 h. After polymerization, 5.6 g of dimethyl carbonate and 3.8 g of the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) were added to 200 g of N,N-dimethylformamide. After nitrogen purging and deoxygenation, the mixture was added to the polymerization solution, and the polymerization temperature was lowered to 90 °C for 3 h to end-cap. The end-capped polysulfone solution was poured into water to precipitate and pulverized into powder. The powder was washed with deionized water and then boiled multiple times to remove solvent and byproduct salts. Subsequently, the powder was dried and granulated to obtain the end-capped polysulfone resin.

[0032] Example 2 In a 1000 mL four-necked flask equipped with nitrogen protection, condenser, stirrer, temperature sensor, and water separator, the stirring speed was set to 250 rpm / min. Then, at room temperature, 253.6 g of solvent N,N-dimethylformamide, 25.4 g of dehydrating agent m-xylene, 80.2 g of bisphenol A monomer, 100.7 g of 4,4'-dichlorodiphenyl sulfone, and 70.9 g of anhydrous sodium carbonate were added sequentially to the flask. Nitrogen protection was then applied. The temperature was set to 185 °C, and salt formation and reflux dehydration were continued at this temperature for 5 h after droplets began to fall from the water separator. Once the theoretical product water volume was collected in the water separator, reflux was stopped, and the temperature was gradually increased to 220 °C to distill off the dehydrating agent and begin polymerization for 8 h. After polymerization, 11 g of ethyl methyl carbonate and 4 g of the ionic liquid tetrabutylammonium p-toluenesulfonate ([N(Bu)4][TsO]) were added to 250 g of N,N-dimethylformamide. After nitrogen purging and deoxygenation, the mixture was added to the polymerization solution, and the polymerization temperature was lowered to 100 °C for end-capping for 2.5 h. The end-capped polysulfone solution was poured into water to precipitate and pulverized into powder. The powder was washed with deionized water and then boiled multiple times to remove the solvent and by-product salts. Subsequently, the powder was dried and granulated to obtain the end-capped polysulfone resin.

[0033] Example 3 In a 1000 mL four-necked flask equipped with nitrogen protection, condenser, stirrer, temperature sensor, and water separator, the stirring speed was set to 200 rpm / min. Then, at room temperature, 287.9 ​​g of solvent sulfolane, 30 g of dehydrating agent toluene, 98.2 g of bisphenol S monomer, 109.1 g of 4,4'-dichlorodiphenyl sulfone, and 83.6 g of anhydrous sodium carbonate were added sequentially to the flask. Nitrogen protection was then applied. The temperature was set to 185 °C, and salt formation and reflux dehydration were continued at this temperature for 7 h after droplets began to fall from the water separator. Once the theoretical product water volume was collected in the water separator, reflux was stopped, and the temperature was gradually increased to 208 °C to distill off the dehydrating agent and begin polymerization for 6 h. After polymerization, 10.5 g of diethyl carbonate and 3.5 g of the ionic liquid 1-ethyl-3-methylimidazolium methane sulfonate ([EMIM][MeSO3]) were added to 240 g of sulfolane. After nitrogen purging and deoxygenation, the mixture was added to the polymerization solution, and the polymerization temperature was lowered to 120 °C for 2 h to end-cap. The end-capped polysulfone solution was poured into water to precipitate and pulverized into powder. The powder was washed with deionized water and then boiled multiple times to remove solvent and byproduct salts. The resulting product was then dried and granulated to obtain the end-capped polyethersulfone resin.

[0034] Example 4 In a 1000 mL four-necked flask equipped with nitrogen protection, condenser, stirrer, temperature sensor, and water separator, the stirring speed was set to 300 rpm / min. Then, at room temperature, 227.2 g of solvent N-methylpyrrolidone, 30 g of dehydrating agent p-xylene, 73.4 g of bisphenol A monomer, 91.9 g of 4,4'-dichlorodiphenyl sulfone, and 61.9 g of anhydrous potassium carbonate were added to the flask sequentially. Nitrogen protection was then applied. The temperature was set to 170 °C, and salt formation and reflux dehydration were continued at this temperature for 4 h after droplets began to fall from the water separator. Once the theoretical product water volume was collected in the water separator, reflux was stopped, and the temperature was gradually increased to 195 °C to distill off the dehydrating agent and begin polymerization for 10 h. After polymerization, 8.2 g of diethyl carbonate and 3.0 g of the ionic liquid 1-ethyl-3-methylimidazolium methane sulfonate ([EMIM][MeSO3]) were added to 200 g of N-methylpyrrolidone. After nitrogen purging and deoxygenation, the mixture was added to the polymerization solution, and the polymerization temperature was lowered to 120 °C for end-capping for 2 h. The end-capped polysulfone solution was poured into water to precipitate and pulverized into powder. The powder was washed with deionized water and then boiled multiple times to remove the solvent and byproduct salts. Subsequently, the powder was dried and granulated to obtain the end-capped polyethersulfone resin.

[0035] Comparative Example 1 The difference from Example 1 is that the mass of bisphenol A monomer is 75.0 g; the mass of 4,4-dichlorodiphenyl sulfone is 95.3 g, and all other experimental conditions are the same.

[0036] Comparative Example 2 The difference from Example 1 is that dimethyl carbonate is not used for end capping, but the same amount of ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) is added as a catalyst, and chloromethane, a conventional end capping agent, is used for end capping. All other conditions are the same.

[0037] Comparative Example 3 The difference from Example 1 is that dimethyl carbonate is not used for end capping and 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) is not added as a catalyst. Only the conventional end capping agent chloromethane is used for end capping, and all other conditions are the same.

[0038] Comparative Example 4 The difference from Example 1 lies in the post-treatment stage. After end-capping, the resin was directly precipitated at the same temperature, pulverized, and then washed in cold deionized water without boiling to obtain polysulfone resin. All other experimental conditions were the same.

[0039] Comparative Example 5 The difference from Example 3 is that diethyl carbonate is not used for end capping and 1-ethyl-3-methylimidazolium methane sulfonate ([EMIM][MeSO3]) is not added as a catalyst. Only the conventional end capping agent chloromethane is used for end capping, and all other conditions are the same.

[0040] After injection molding, the products obtained in Examples 1-4 and Comparative Examples 1-5 were tested for color swatches and the ion content of the granules was measured using existing methods. The product test data are shown in the table below: Table 1. Performance Test Statistics for Each Product

[0041] The color sample size is 40 mm × 40 mm × 2 mm. The testing instruments are a yellowness index meter and a haze meter. The yellowness index test standard is ASTM S313-10; the haze and transmittance test standards are ASTM D1003. The stability of polysulfone products can be evaluated through the yellowness results. After injection molding, the lower the yellowness index, the better its thermal stability. The lower the color, the better its end-sealing effect. In addition, the higher the transmittance and the lower the haze, the purer and higher the quality.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or alterations made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a halogen-free, environmentally friendly end-capping agent for polysulfone, characterized in that, Includes the following steps: (1) The bisphenol monomer, 4,4'-dihalodiphenyl sulfone, basic salt-forming agent, dehydrating agent and high-boiling-point aprotic solvent are mixed in the order of addition under stirring, and then nitrogen is purged. (2) Raise the temperature to the temperature required for salt formation, carry out the salt formation reaction under the condition of nitrogen purging, and reflux to remove the water produced by salt formation; (3) When the water is collected to the theoretical yield, stop the reflux, raise the temperature to carry out the polymerization reaction, and when the target viscosity is reached, the desired sulfone polymer solution is obtained; (4) Add the halogen-free end-capping agent and ionic liquid catalyst to an appropriate amount of solvent used for polymerization, then add it to a flask to dilute the polymerization solution and cool it down. At the same time, heat the temperature down to 90~150 ℃ to carry out the end-capping reaction and obtain a sulfone resin with the target molecular weight.

2. The preparation method according to claim 1, characterized in that, The halogen-free capping agent is any one or more of ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, trimethyl carbonate, propylene carbonate, and ethylene carbonate, mixed in any proportion.

3. The preparation method according to claim 1, characterized in that, The ionic liquid catalyst is any one or more of 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) and 1-ethyl-3-methylimidazolium methane sulfonate ([EMIM][MeSO3]), tetrabutylammonium p-toluenesulfonate ([N(Bu)4][TsO]), and choline acetate ([Ch][Ac]) in any proportion.

4. The preparation method according to claim 1, characterized in that, The bisphenol monomer is any one or more of bisphenol A, bisphenol S, and biphenyl hydroquinone mixed in any proportion; the 4,4'-dihalodiphenyl sulfone includes any one or more of 4,4'-difluorodiphenyl sulfone and 4,4'-dichlorodiphenyl sulfone mixed in any proportion.

5. The preparation method according to claim 1, characterized in that, The dehydrating agent is any one or more of toluene, chlorobenzene, o-xylene, p-xylene, and m-xylene, mixed in any proportion; the mass ratio of the dehydrating agent to the solvent is 0.05~0.4:

1.

6. The preparation method according to claim 1, characterized in that, The high-boiling-point aprotic solvent is any one or more of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane, mixed in any proportion.

7. Applications of methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, trimethyl carbonate, propylene carbonate, and ethylene carbonate as halogen-free and environmentally friendly end-capping agents for sulfone polymers.

8. A halogen-free, environmentally friendly end-capping agent for sulfone polymers, characterized in that, It contains any one or more of methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, trimethyl carbonate, propylene carbonate, and ethylene carbonate, mixed in any proportion.

9. Applications of 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium methane sulfonate, tetrabutylammonium p-toluenesulfonate, and choline acetate as end-capping catalysts for sulfone polymers.

10. A sulfone polymer-terminated catalyst, characterized in that, It contains any one or more of 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium methane sulfonate, tetrabutylammonium p-toluenesulfonate, and choline acetate, mixed in any proportion.

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