Silicon-based emulsifier, preparation method thereof and application of silicon-based emulsifier in fluorine-containing polymer emulsion polymerization

Abstract

The invention discloses a silicon-based emulsifier, a preparation method thereof and application of the silicon-based emulsifier in fluorine-containing polymer emulsion polymerization, and belongs to the technical field of high polymer material synthesis. The structure of the compound is shown as a general formula I or II. The silicon-based emulsifier has low surface tension, can effectively disperse polymer monomers, control the polymerization degree and regulate and control the performance of polymerized products when being applied to emulsion polymerization reaction of rubber production, is an excellent emulsifier for emulsion polymerization reaction, and has a plurality of advantages when being used as an effective substitute of an existing non-degradable fluorine-containing emulsifier.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer material synthesis, and particularly relates to a silicon-based emulsifier, a preparation method thereof and application of the silicon-based emulsifier in fluorine-containing polymer emulsion polymerization. BACKGROUND

[0002] Fluoropolymers (such as PVDF and its copolymers) are widely used in lithium battery separators, capacitor coatings, corrosion-resistant coatings and other fields due to their excellent chemical stability, thermal stability and electrochemical performance. The industrial production of fluoropolymers mainly relies on emulsion polymerization process, and surfactants are the key components for maintaining the stability of the emulsion and controlling the morphology of the polymer particles.

[0003] In traditional fluoropolymer emulsion polymerization, fluorine-containing surfactants (such as ammonium perfluorooctanoate) were the mainstream choice, which could efficiently and stably emulsify fluoromonomers. However, such surfactants have significant defects. Fluorine-containing surfactants have extremely strong chemical stability and are easily accumulated in the environment and living organisms, which have persistence and biological toxicity, posing a serious threat to the environment and human health. They have been listed as substances restricted or prohibited for use by many countries and international organizations. In addition, the synthesis process of fluorine-containing surfactants is complex and expensive, increasing the cost of industrial production. Moreover, some fluorine-containing surfactants may inhibit the polymerization of fluoromonomers, reducing the yield or causing the molecular weight distribution of the polymer to become wide.

[0004] To solve the above problems, the industry has gradually shifted to non-fluorine surfactants. There are many types of non-fluorine surfactants tried by the industry, each with different advantages and limitations. For example, alkyl sulfate salts (such as sodium lauryl sulfate) can achieve PVDF polymerization in a fluorine-free system, but the dosage needs to be strictly controlled, otherwise it may lead to polymerization inhibition or latex coagulation. Polyolefin block copolymers (such as polyethylene glycol-polypropylene glycol block copolymer) can stabilize the PVDF emulsion, but they have insufficient stability for high solid content systems and are prone to particle agglomeration. Polyvinyl alcohol (PVOH) as the only stabilizer needs a specific degree of hydrolysis (70-90 mol%) to achieve stable polymerization, and has limited compatibility with copolymerization monomers (such as hexafluoropropylene). Polyacrylic acid and its salts can assist in stabilizing the emulsion, but when used alone, they may lead to a wide distribution of polymer particle sizes, affecting the subsequent processing performance.

[0005] Silicon-based surfactants such as polysiloxane derivatives have low surface tension, good environmental compatibility and excellent stability due to their unique molecular structure containing siloxane segments and polar groups. The low polarity of siloxane segments enables them to efficiently reduce the surface tension of the aqueous phase, which is superior to traditional non-fluorinated surfactants, and is conducive to the dispersion of hydrophobic fluoromonomers in the aqueous phase, making them well suited for emulsion polymerization of fluoromonomers. Silicon-based surfactants have excellent biodegradability and low toxicity, which meets the environmental protection trend. The chemical inertness of siloxane segments is strong, and they can maintain surface activity at high temperatures above 100°C and in a wide pH range, which is suitable for the harsh conditions of fluoropolymer polymerization, such as VDF polymerization pressure usually 2-10 MPa, temperature 60-120°C.

[0006] However, there are significant gaps in the application of silicon-based surfactants in fluoropolymer polymerization in the prior art. The prior art is mostly limited to using silicon-based surfactants as "co-surfactants" in combination with other non-fluorinated surfactants such as polyacrylic acid, and there is no systematic study of their feasibility as primary surfactants. There is a lack of research on the correlation between the molecular structure of silicon-based surfactants and the stability of fluoromonomer polymerization, as well as the particle size of the polymer. For example, how does the length of the siloxane chain and the type of polar group affect the polymerization of different structures of fluoromonomers. There is also a lack of understanding of the influence of silicon-based surfactants on the final performance of fluoropolymers, such as the heat resistance of the membrane coating and the interfacial impedance of the electrochemical device. SUMMARY

[0007] To address the above problems in the prior art, the present application provides a silicon-based emulsifier, its preparation method and its application in fluoropolymer emulsion polymerization. By optimizing the structure and dosage of silicon-based surfactants, efficient and stable polymerization of fluoropolymer emulsion is achieved, and the application performance of the product in the field of electrochemical devices and coatings is improved, filling the gap in the prior art.

[0008] The silicon-based emulsifier has a structure as shown in general formula I or II: 、 ; wherein R 1 , R 2 , R 3 , R 4 are the same or different, n is an integer between 0 and 5, R 1 , R 2 , R 3 are at least one of C1-C4 straight-chain or branched alkyl, R 4 is at least one of hydrogen, alkyl, aryl, heteroatom group, and M is Li + , Na + , K+ or NH4 + or NH4

[0009] The silane-based emulsifier is characterized in that R 1 , R 2 , R 3 is methyl, R 4 is hydrogen, and M is NH4 + .

[0010] The preparation method of the silane-based emulsifier is characterized by comprising the following steps: 1) A reaction kettle is added with vinyltrichlorosilane and trimethylchlorosilane in a molar ratio of 1:3-5, a temperature control system is used to control the system temperature at 0-10℃, 0.35-0.5 mol of isopropanol is slowly added under stirring within 30-60 minutes, 0.5-1 mol of deionized water is slowly added under stirring within 30-60 minutes, after the dropwise addition is completed, the layers are separated, the aqueous phase is separated, the pH is measured, 50-200 mL of deionized water is added to the organic phase and stirred for 4-7 minutes, the layers are separated after standing, the pH is measured, and the method is repeated 5-10 times until the pH of the aqueous phase is 5-8. The organic phase is dried to obtain a siloxane intermediate: 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane; 2) The reaction kettle is added with the siloxane intermediate prepared in step 1), and then added with a mercapto carboxylic acid compound, a photoinitiator and a reaction solvent. The molar ratio of the siloxane intermediate, the mercapto carboxylic acid compound and the photoinitiator is 1:1-2:0.01-0.03. The reaction solvent is added in a proportion of 0.4-2 M of the siloxane intermediate. The thiol-ene click chemistry reaction is initiated by ultraviolet light. The wavelength of the ultraviolet light is 350-370 nm. The stirring reaction is carried out at 0-30℃ for 30-120 minutes. After confirming that the reaction is complete, the next step is directly carried out; 3) Sodium carbonate or ammonia water is added to the reaction kettle under stirring within 5-10 minutes. The molar ratio of the siloxane intermediate to sodium carbonate is 1:0.5-1.5. The molar ratio of the siloxane intermediate to sodium carbonate is 1:0.5-3. The stirring reaction is continued for 1-3 hours. The organic solvent is removed by reduced pressure distillation. 1-2 L of deionized water is added for dissolution, and then 50-100 mL of dichloromethane is added for washing. The organic phase is separated and removed. The aqueous phase is dried to remove water to obtain a silane-based emulsifier product.

[0011] The preparation method of the silane-based emulsifier is characterized in that in step 2), the mercapto carboxylic acid compound is one of 4-mercapto butyric acid, 2-mercapto acetic acid, 3-mercapto propionic acid, 3-mercapto butyric acid and 3-methyl-3-mercapto butyric acid.

[0012] The preparation method of the silicone-based emulsifier is characterized in that, in step 2), the photoinitiator is 2,2-dimethoxy-2-phenylacetophenone.

[0013] The preparation method of the silicone-based emulsifier is characterized in that, in step 2), the reaction solvent is tetrahydrofuran.

[0014] The preparation method of the silicone-based emulsifier is characterized in that the synthesis reaction equation comprises: Or .

[0015] The silicone-based emulsifier is used as an emulsifier in fluoropolymer emulsion polymerization.

[0016] The silicone-based emulsifier is used in fluoropolymer emulsion polymerization, and the amount of the silicone-based emulsifier is 0.01-1 wt%, preferably 0.05-0.5 wt%, and more preferably 0.1-0.25 wt% of the total amount of fluoromonomers.

[0017] The silicone-based emulsifier is used in fluoropolymer emulsion polymerization, and the fluoromonomer is at least one of vinylidene fluoride (VDF or VF2), tetrafluoroethylene (TFE), trifluoroethylene, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), fluoroethylene, hexafluoroisobutene, perfluorobutyl ethylene (PFBE), pentafluoropropylene, 3,3,3-trifluoro-1-propene, 2-trifluoromethyl-3,3,3-trifluoropropene, fluorinated vinyl ethers, fluorinated allyl ethers, non-fluorinated allyl ethers, and fluorinated dioxoles.

[0018] The silicone-based emulsifier has low surface tension, good environmental compatibility, excellent stability, and other characteristics, and its hydrophilic or hydrophobic ability can be easily adjusted by changing the synthesis conditions. The silicone-based emulsifier is used in emulsion polymerization reactions in rubber production, can effectively disperse polymer monomers, control the degree of polymerization, and regulate the performance of the polymerization product, is an excellent emulsifier for emulsion polymerization reactions, and has many advantages as an effective substitute for existing non-degradable fluorinated emulsifiers. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The nuclear magnetic resonance spectrum of the siloxane intermediate prepared in Example 1 is shown in the figure; Figure 2 The high-resolution mass spectrum characterization diagram of the emulsifier prepared in Example 1 is shown in the figure; Figure 3 The high-resolution mass spectrum characterization diagram of the emulsifier prepared in Example 2 is shown in the figure; Figure 4 The high-resolution mass spectrum characterization diagram of the emulsifier prepared in Example 3 is shown in the figure; Figure 5 High resolution mass spectrometry characterization of the emulsifier prepared for example 4; Figure 6 High resolution mass spectrometry characterization of the emulsifier prepared for example 5. DETAILED DESCRIPTION

[0020] The application will be described in greater detail with reference to the accompanying drawings and specific embodiments, it is obvious that the described embodiments are only a part of the embodiments of the application, and are not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0021] Example 1 1) Add 16.1 g of vinyltrichlorosilane and 38 g of trimethylchlorosilane to a reaction kettle, control the system temperature at 0°C, slowly add 21 g of isopropyl alcohol under stirring within 30 minutes, after the addition is completed, control the system temperature at 0°C and stir for 30 minutes, maintain the system temperature at 0°C, slowly add 9 g of deionized water under stirring within 30 minutes, after the dropwise addition is completed, stand and separate the layers, separate the aqueous phase, add 50 mL of deionized water to the organic phase and stir for five minutes, stand and separate the layers, separate the aqueous phase, measure the pH, repeat this method five times until the aqueous phase is washed to a pH of 7, dry the organic phase and sample test to determine the structure, which is the target product 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane, determine its structure by nuclear magnetic resonance, nuclear magnetic resonance data 1 H NMR (400 MHz, Chloroform-d) δ 5.95-5.89 (m, 1H), 5.89-5.79 (m, 2H), 0.11 (s, 27H). Use it for the next step reaction; 2) Add 32 g of freshly prepared 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane, 10.6 g of 3-mercaptopropionic acid, and 256 mg of 2,2-dimethoxy-2-phenylacetophenone to a reaction kettle, add 50 mL of tetrahydrofuran as a reaction solvent, irradiate the reaction system with ultraviolet light of 365 nm wavelength, stir at 0°C for 30 minutes, sample monitoring to determine that the reaction is complete, without post-treatment, directly proceed to the next step reaction; 3) 5.3 g of sodium carbonate was added into the reactor under stirring within 5 minutes. A large amount of carbon dioxide gas was released when the sodium carbonate was added. The reactor was opened. After the addition was completed, the reaction was continued for 1 hour. The solvent was concentrated. The surfactant prepared was dissolved in 1 L of deionized water. 50 mL of dichloromethane was added for washing. The organic phase was separated and removed. The water phase was dried to remove water to obtain the clean emulsifier product No. 1, sodium 3-((2-(1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)trisiloxan-3-yl)ethyl)thio)propanoate. High resolution mass spectrometry characterization was performed. HRMS (ESI) m / z. [M+H] + calcd for C 14 H 37 O5SSi4429.1439; Found 429.1436.

[0022] Example 2 1) 16.1 g of vinyltrichlorosilane and 50 g of trimethylchlorosilane were added into the reactor. The temperature of the system was controlled at 5°C. 25 g of isopropyl alcohol was slowly added under stirring within 40 minutes. After the addition was completed, the temperature of the system was controlled at 6°C. The reaction was stirred for 45 minutes. The temperature of the system was maintained at 4°C. 12 g of deionized water was slowly added under stirring within 45 minutes. After the dropwise addition was completed, the layers were separated by standing. The water phase was separated. The pH was measured. 100 mL of deionized water was added to the organic phase for stirring for 5 minutes. The layers were separated by standing. The water phase was separated. The pH was measured. This method was repeated for 6 times until the pH of the water phase was 5. After the organic phase was dried, the sample was tested to determine the structure. It was the target product, 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane. 2) 32 g (0.1 mol) of 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane, 10.5 g of 2-mercaptoacetic acid, and 320 mg of 2,2-dimethoxy-2-phenylacetophenone were added into the reactor. 100 mL of tetrahydrofuran was used as the reaction solvent. The reaction system was irradiated with ultraviolet light of 350 nm wavelength. The reaction was stirred at 15°C for 50 minutes. The sample was monitored to determine that the reaction was complete. No post-treatment was performed. The next step reaction was directly performed. 3) 9 mL of ammonia water was added into the reactor under stirring within 8 minutes. After the addition was completed, the reaction was continued for 1.5 hours. The solvent was concentrated. The surfactant prepared was dissolved in 1.3 L of deionized water. 65 mL of dichloromethane was added for washing. The organic phase was separated and removed. The water phase was dried to remove water to obtain the clean emulsifier product No. 2, ammonium 2-((2-(1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)trisiloxan-3-yl)ethyl)thio)acetate. High resolution mass spectrometry characterization was performed. HRMS (ESI) m / z. [M+Na] +C 13 H 34 C

[0023] Example 3 1) In a reaction kettle, add 16.1 g of vinyltrichlorosilane, 54 g of trimethylchlorosilane, control the system temperature at 10°C, slowly add 30 g of isopropyl alcohol under stirring within 60 minutes, after the addition is completed, control the system temperature at 10°C and stir for 60 minutes, maintain the system temperature at 10°C, slowly add 18 g of deionized water under stirring within 60 minutes, after the dropwise addition is completed, stand and separate the layers, separate the aqueous phase, measure the pH, add 200 mL of deionized water to the organic phase and stir for five minutes, stand and separate the layers, separate the aqueous phase, measure the pH, repeat this method for 10 times until the aqueous phase pH is washed to 8, after the organic phase is dried, sample test to determine the structure, which is the target product 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane; 2) In a reaction kettle, add freshly prepared 32 g of 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane, 14 g of 4-mercaptobutyric acid, and 485 mg of 2,2-dimethoxy-2-phenylacetophenone, add 150 mL of tetrahydrofuran as a reaction solvent, irradiate the reaction system with ultraviolet light of 370 nm wavelength, stir at 25°C for 70 minutes, sample test to determine that the reaction is complete, without post-treatment, directly proceed to the next step reaction; 3) Under stirring, add 14 mL of ammonia water to the reaction kettle within 8 minutes, after the addition is completed, continue to stir for 2.5 hours, concentrate the solvent, add 1.8 L of deionized water to dissolve the prepared surfactant, add 70 mL of dichloromethane to wash, separate and remove the organic phase, dry the aqueous phase to remove water to obtain a clean emulsifier product No. 3, 4-((2-(1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)trisiloxane-3-yl)ethyl)thio)butyric acid ammonium, perform high resolution mass spectrometry characterization, HRMS (ESI) m / z. [M+Na] + C 15 H 38 C

[0024] Example 4 1) The same as Example 1; 2) Add 32 g of freshly prepared 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3- vinyltrisiloxane, 20 g of 3-mercaptobutyric acid, and 650 mg of 2,2-dimethoxy-2- phenylacetophenone to a reaction kettle, add 200 mL of tetrahydrofuran as a reaction solvent, irradiate the reaction system with ultraviolet light of 365 nm wavelength, stir the reaction at 25°C for 100 minutes, take samples to monitor and determine that the reaction is complete, do not perform post-treatment, and directly perform the next step reaction; 3) Add 15 mL of ammonia water to the reaction kettle under stirring within 8 minutes, continue to stir the reaction for 2 hours after the addition is completed, concentrate the solvent, add 1.5 L of deionized water to dissolve the prepared surfactant, add 80 mL of dichloromethane for washing, separate and remove the organic phase, dry the water phase, remove the water to obtain clean emulsifier product No. 4, ammonium 3-((2-(1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)trisiloxan-3-yl)ethyl)thio)butyrate, perform high-resolution mass spectrometry characterization, HRMS (ESI) m / z. [M+H] + calcd for C 15 H 39 O5SSi4 443.1595; Found 443.1595.

[0025] Example 5 1) The step is the same as that in Example 1; 2) Add 32 g of freshly prepared 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3- vinyltrisiloxane, 26.8 g of 3-methyl-3-mercaptobutyric acid, and 768 mg of 2,2- dimethoxy-2-phenylacetophenone to a reaction kettle, add 250 mL of tetrahydrofuran as a reaction solvent, irradiate the reaction system with ultraviolet light of 370 nm wavelength, stir the reaction at 30°C for 30 minutes, take samples to monitor and determine that the reaction is complete, do not perform post-treatment, and directly perform the next step reaction; 3) Add 17 mL of ammonia water to the reaction kettle under stirring within 10 minutes, continue to stir the reaction for 3 hours after the addition is completed, concentrate the solvent, add 2 L of deionized water to dissolve the prepared surfactant, add 100 mL of dichloromethane for washing, separate and remove the organic phase, dry the water phase, remove the water to obtain clean emulsifier product No. 5, ammonium 3-((2-(1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)trisiloxan-3-yl)ethyl)thio)-3- methylbutyrate, perform high-resolution mass spectrometry characterization, HRMS (ESI) m / z. [M+Na] + calcd for C 16 H 40 O5SSi4Na 479.1571; Found 479.1569.

[0026] The excellent performance of the silicon-based emulsifier prepared by the present application is further proved by the corresponding experimental data in Table 1.

[0027] Table 1 Surface tension test table of the emulsifier aqueous solution prepared in Examples 1-5

[0028] Table 1 shows that the silicon-based emulsifier prepared by the present application has low surface tension, and can effectively disperse polymer monomers, control the degree of polymerization and regulate the performance of the polymerization product when applied in the emulsion polymerization reaction of rubber production, and is an excellent emulsifier for emulsion polymerization reaction.

[0029] The silicon-based emulsifier prepared by the present application is applied as an emulsifier in the emulsion polymerization of fluorine-containing polymers, and the amount of the silicon-based emulsifier is 0.01-1 wt% of the total amount of the fluorine-containing monomers, preferably 0.05-0.5 wt%, and more preferably 0.1-0.25 wt%; and the proportion of the silicon-based emulsifier in the total amount of the emulsifier is ≥90 wt%. The fluorine-containing monomers are at least one of vinylidene fluoride (VDF or VF2), tetrafluoroethylene (TFE), trifluoroethylene, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), fluoroethylene, hexafluoroisobutene, perfluorobutyl ethylene (PFBE), pentafluoropropylene, 3,3,3-trifluoro-1-propene, 2-trifluoromethyl-3,3,3-trifluoropropene, fluorinated vinyl ethers, fluorinated allyl ethers, non-fluorinated allyl ethers, and fluorinated dioxoles.

[0030] The use of the silicon-based emulsifier prepared by the present application in the polymerization reaction is further proved by the rubber polymerization experiment, and the performance test results are shown in Table 2.

[0031] Application Test 1: The reactor volume is 350L, water 230kg, emulsifier product (prepared in Example 1) 20g is added in the initial stage, after displacement and vacuum, fluorine-containing monomers are introduced and pressurized to 2.2MPa, the temperature reaches 90℃, the stirring speed is 300r / min, 275g of initiator is added, after 65kg of fluorine-containing monomers are consumed, 55g of chain transfer agent is added, the reaction is carried out to the end, and 98kg of fluorine-containing monomers are consumed in total, to prepare fluorine-containing polymers.

[0032] Application Test 2: The reactor volume is 350L, water 230kg, emulsifier product (prepared in Example 1) 10g is added in the initial stage, after displacement and vacuum, fluorine-containing monomers are introduced and pressurized to 2.2MPa, the temperature reaches 90℃, the stirring speed is 300r / min, 200g of initiator is added, after 65kg of fluorine-containing monomers are consumed, 55g of chain transfer agent is added, the reaction is carried out to the end, and 98kg of fluorine-containing monomers are consumed in total, to prepare fluorine-containing polymers.

[0033] Comparative Example: Reactor volume 350L, initial stage add water 230kg, fluorine-containing surfactant 200g (20% aqueous solution), after displacement vacuum, monomer is introduced to pressurize to 2.0MPa, temperature reaches 90℃, stirring speed 300r / min, add initiator 160g, after cumulative consumption of 65kg monomer, add 1.5kg chain transfer agent, reaction to end, total consumption of 100kg monomers, fluorine-containing polymer is prepared.

[0034] Table 2 Performance test table of fluorine-containing polymer prepared in application test 1-2 and comparative example

[0035] Table 2 shows that the silicon-based emulsifier prepared in Example 1 of the application is used as a main emulsifier in fluorine-containing polymer emulsion polymerization, the polymerization production is stable in actual process operation, the production process risk is controllable, meets the actual production demand, and is reliable; the raw material use meets the process requirements, the raw material itself is stable in physical properties, and the cost is replaceable; the final product is close to or better than the existing product in various aspects of performance, and is well applied in the market. The silicon-based emulsifier prepared in Examples 2-5 of the application can also achieve the beneficial effects described in the application when used in fluorine-containing polymer emulsion polymerization.

[0036] Although the embodiments of the application have been shown and described, it is to be understood that for the purpose of the present application, the embodiments can be substantially changed without departing from the spirit and the scope of the present application, the scope of the present application being defined by the appended claims and their equivalents.

Claims

1. A silicon-based emulsifier, characterized in that The structure is shown in general formula I or II: 、 ； wherein R 1 , R 2 , R 3 , R 4 are the same or different, n is an integer between 0 and 5, R 1 , R 2 , R 3 are at least one of C1-C4 linear, branched alkyl, R 4 is at least one of hydrogen, alkyl, aryl, heteroatom group, and M is at least one of Li + , Na + , K + , or NH4 + .

2. A silicon-based emulsifier as claimed in claim 1, characterized in that R 1 , R 2 , R 3 is methyl, R 4 is hydrogen, M is NH4 + .

3. A process for the preparation of a silicon-based emulsifier according to claim 1 or 2, characterized in that Comprising the following steps: 1) A reaction vessel is charged with vinyltrichlorosilane:trimethylchlorosilane in a molar ratio of 1:3-5, a temperature control system is used to control the system temperature at 0-10 。 C, 0.35-0.5 mol of isopropyl alcohol is slowly added under stirring for 30-60 minutes, 0.5-1 mol of deionized water is slowly added under continuous stirring for 30-60 minutes, after the dropwise addition is completed, it is allowed to stand and separate into layers, the aqueous phase is separated, the pH is measured, 50-200 mL of deionized water is added to the organic phase and stirred for 4-7 minutes, it is allowed to stand and separate into layers, the aqueous phase is separated, the pH is measured, this method is repeated 5-10 times, the washing is continued until the pH of the aqueous phase is 5-8, the organic phase is dried to obtain a siloxane intermediate: 1,1,1,5,5,5-hexamethyl-3-((trimethylsilyl)oxy)-3-vinyltrisiloxane; 2) The reaction kettle is added with the siloxane intermediate prepared in step 1), and then added with a mercapto carboxylic compound, a photoinitiator, and a reaction solvent, the molar ratio of the siloxane intermediate: the mercapto carboxylic compound: the photoinitiator is 1:1-2:0.01-0.03, the reaction solvent is added in a proportion of 0.4-2M of the concentration of the siloxane intermediate, the thiol-ene click chemistry reaction is initiated by ultraviolet light, the wavelength of the ultraviolet light is 350-370nm, the reaction is stirred at 0-30℃ for 30-120 minutes, and after confirming that the reaction is complete, the next step is directly performed; 3) Sodium carbonate or ammonia water is added to the reaction kettle under stirring for 5-10 minutes, the molar ratio of the siloxane intermediate: sodium carbonate is 1:0.5-1.5, the molar ratio of the siloxane intermediate: sodium carbonate is 1:0.5-3, the stirring reaction is continued for 1-3 hours, the organic solvent is removed by distillation under reduced pressure, 1-2L of deionized water is added for dissolution, then 50-100mL of dichloromethane is added for washing, the organic phase is separated and removed, the water phase is dried, and the water is removed to obtain a silane-based emulsifier product.

4. A process for the preparation of a silicon-based emulsifier as claimed in claim 3, characterized in that In step 2), the mercapto carboxylic compound is one of 4-mercapto butyric acid, 2-mercapto acetic acid, 3-mercapto propionic acid, 3-mercapto butyric acid, and 3-methyl-3-mercapto butyric acid.

5. A process for the preparation of a silicon-based emulsifier as claimed in claim 3, characterized in that In step 2), the photoinitiator is 2,2-dimethoxy-2-phenylacetophenone.

6. A process for the preparation of a silicon-based emulsifier as claimed in claim 3, characterized in that In step 2), the reaction solvent is tetrahydrofuran.

7. A process for the preparation of a silicon-based emulsifier as claimed in claim 3, characterized in that The synthesis reaction equation includes: or .

8. Use of a silane-based emulsifier as claimed in claim 1 as an emulsifier in fluoropolymer emulsion polymerization.

9. Use of a silicon-based emulsifier according to claim 8 in the emulsion polymerization of fluoropolymers, characterized in that The amount of the silane-based emulsifier is 0.01-1wt%, preferably 0.05-0.5wt%, and more preferably 0.1-0.25wt% of the total amount of the fluoromonomer.

10. Use of a silicon-based emulsifier according to claim 8 in the emulsion polymerization of fluoropolymers, characterized in that The fluoromonomer is at least one of vinylidene fluoride (VDF or VF2), tetrafluoroethylene (TFE), trifluoroethylene, chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), fluoroethylene, hexafluoroisobutene, perfluorobutyl ethylene (PFBE), pentafluoropropylene, 3,3,3-trifluoro-1-propene, 2-trifluoromethyl-3,3,3-trifluoropropene, fluorinated vinyl ethers, fluorinated allyl ethers, non-fluorinated allyl ethers, and fluorinated dioxoles.

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