A hydroxyl-terminated vinyl fluorosilicone oil and a method of making the same

Abstract

The present application relates to a kind of terminal hydroxyl vinyl fluorosilicone oil and its preparation method, the fluorosilicone oil contains two active groups of vinyl and hydroxyl in molecular structure, can simultaneously exert the reaction effect of both, its molecular weight is small, degree of polymerization is low, vinyl content and hydroxyl content are fixed, as reaction raw material or formula additive use effect constant, will not cause adverse effects to synthesis reaction or material performance by purity, component, group content variation etc.It is simple and easy to the preparation method of the present application, reaction efficiency is high, target product is clear, avoids many defects of chlorosilane hydrolysis method and cyclosiloxane ring-opening polymerization method.

Description

Technical Field

[0001] This invention relates to the field of fluorosilicone materials technology, specifically to a hydroxyl-terminated vinyl fluorosilicone oil and its preparation method. Background Technology

[0002] Fluorosilicone oil is a polysiloxane with a silicon-oxygen main chain and trifluoropropyl and methyl side chains. It mainly includes three types: methyl fluorosilicone oil, hydroxyl fluorosilicone oil, and vinyl fluorosilicone oil. Due to its molecular structure, it retains the excellent heat resistance, cold resistance, electrical insulation, and aging resistance of organosilicon materials, while also possessing the excellent properties of fluorine materials such as resistance to hydrocarbon solvents, oil resistance, friction resistance, and low surface energy. It can be widely used in aerospace, automotive, shipbuilding, petrochemical, and textile finishing industries, and has a very broad market prospect.

[0003] Hydroxyl fluorosilicone oils have different applications depending on their viscosity. The most widely used are low molecular weight hydroxyl fluorosilicone oils, which can be used as intermediates in the synthesis of high molecular weight polymers, as additives in the preparation of room temperature vulcanizing fluorosilicone rubber and liquid fluorosilicone rubber, as textile finishing agents, emulsion defoamers, and especially as structure control agents for hot vulcanizing fluorosilicone rubber. During storage, the silanol groups on the surface of silica interact with the silicon-oxygen bonds or terminal hydroxyl groups in the fluorosilicone raw rubber molecules to form hydrogen bonds or even chemical bonds. This causes the linear polysiloxane to gradually transform into a pseudo-crosslinked or micro-crosslinked semi-elastic solid structure, resulting in reduced plasticity, loss of remelting and processing properties, and the formation of a structured phenomenon. To control the interaction between raw rubber molecules and fillers and extend the shelf life of the rubber compound, structure control agents are usually added. Among all structure control agents, low molecular weight hydroxyl fluorosilicone oils are the most satisfactory.

[0004] Currently, the main methods for preparing low molecular weight hydroxyl fluorosilicone oil in the industry include chlorosilane hydrolysis and cyclosiloxane ring-opening polymerization. The chlorosilane hydrolysis method involves directly adding trifluoropropylmethyldichlorosilane to the aqueous phase for hydrolysis. While the process is simple, the hydrolysis products often contain 30%–40% cyclosiloxanes, with the remaining components mainly consisting of polymers of various chain lengths, resulting in a wide molecular weight distribution and unstable terminal hydroxyl groups that readily condense, leading to very low yields. Furthermore, the chlorosilane hydrolysis method inevitably generates large amounts of waste hydrochloric acid, causing significant environmental pressure. The cyclosiloxane ring-opening polymerization method primarily uses (3,3,3-trifluoropropyl)methylcyclotrisiloxane and water as reactants, undergoing ring-opening polymerization under the action of an acidic catalyst. To improve the polymerization effect, polar solvents are often added during the reaction. However, due to the equilibrium effect of the ring-opening polymerization reaction, the hydroxyl fluorosilicone oil prepared by this method usually contains a large number of unreacted rings, resulting in low product purity and numerous impurities, affecting further use.

[0005] Patent document CN201210077938.4 discloses a method for preparing low-polymerization-degree hydroxyl-terminated fluorosilicone oil. Trifluoropropylmethyldichlorosilane is added dropwise to a mixed system of cationic polyelectrolyte, organic solvent, and water for hydrolysis. The weakly basic groups in the cationic polyelectrolyte rapidly neutralize the HCl produced by the hydrolysis of chlorosilane, thereby obtaining hydroxyl-terminated fluorosilicone oil. Patent document CN201210470755.9 uses acidic clay and hydrochloric acid as dual catalysts to make (3, A hydroxyl fluorosilicone oil was prepared by ring-opening polymerization of (3,3,3-trifluoropropyl)methylcyclotrisiloxane, water, and tetrahydrofuran under stirring. Patent document CN201010299701.1 discloses a method for synthesizing low molecular weight hydroxyl-terminated fluorosilicone oil, using (3,3,3-trifluoropropyl)methylcyclotrisiloxane as the monomer and water as the end-capping agent, and carrying out ring-opening polymerization in a polar solvent with a heteropolyacid as a catalyst, to prepare low molecular weight hydroxyl fluorosilicone oils with an average degree of polymerization of 3-10. While these methods can all prepare hydroxyl fluorosilicone oils, they inevitably bring the aforementioned problems. Furthermore, the products prepared are all terminal hydroxyl structures, lacking vinyl groups in the molecular chain, which cannot meet the application requirements of fields requiring synergistic effects of hydroxyl and vinyl groups.

[0006] Furthermore, patent document CN201310524205.5 discloses a method for preparing vinyl-terminated fluorosilicone oil. The method involves mixing hydroxyl-terminated fluorosilicone oil or an acetone solution of hydroxyl-terminated fluorosilicone oil with (N,N-dialkylamino)dimethylvinylsilane, stirring the mixture at 20–120°C for 2–24 hours, followed by vacuum distillation and cooling to room temperature to obtain the vinyl-terminated fluorosilicone oil. In this document, the molar ratio of methylvinylsiloxane to methyltrifluoropropylsiloxane in the hydroxyl-terminated fluorosilicone oil is only m:n = 0–0.02, indicating a very low vinyl content. This limits the effectiveness of the vinyl group. If the hydroxyl groups of the fluorosilicone oil are reacted to generate vinyl groups to increase the vinyl content, the hydroxyl group's effect is lost. Additionally, the raw materials have high viscosity, resulting in poor reaction efficiency. The byproducts, dimethylamine or diethylamine, have low boiling points, are flammable and explosive, and are also toxic and corrosive, posing health hazards.

[0007] Therefore, it is of great significance to develop a vinyl-containing hydroxyl-terminated fluorosilicone oil. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a hydroxyl-terminated vinyl fluorosilicone oil and its preparation method. The hydroxyl-terminated vinyl fluorosilicone oil prepared by this invention contains both vinyl and hydroxyl active groups in its molecular structure, allowing for the simultaneous interaction of hydroxyl and vinyl groups. The product has a small molecular weight, low degree of polymerization, and a fixed vinyl and hydroxyl content. When used as a reaction raw material or formulation additive, its effect is consistent, and changes in purity, composition, or group content will not adversely affect the synthesis reaction or material properties. Furthermore, the preparation method of this invention is simple and highly efficient, avoiding many drawbacks of chlorosilane hydrolysis and cyclosiloxane ring-opening polymerization methods.

[0009] To achieve the above objectives, the present invention employs the following technical solution:

[0010] A hydroxyl-terminated vinyl fluorosilicone oil having the structure shown in formula (I):

[0011]

[0012] According to the present invention, the preparation method of the hydroxyl-terminated vinyl fluorosilicone oil includes the following steps:

[0013] (1) Vinylsilane acylation reaction:

[0014] Anhydrous sodium acetate and n-hexane were stirred and mixed, and the mixture was heated to reflux to remove water. Then, vinylmethyl dichlorosilane was added dropwise to the system to carry out an acylation reaction. After the addition was complete, the mixture was heated to reflux. After the reaction was complete, the mixture was cooled, filtered, and the solvent was recovered to obtain vinylmethyl diacetoxysilane.

[0015] (2) Ring-opening and end-capping reaction:

[0016] (3,3,3-trifluoropropyl)methylcyclotrisiloxane and vinylmethyldiacetoxysilane were mixed evenly, and the system temperature was lowered to 0-5°C using an ice-water bath. Then, a catalyst was added to the system to carry out the ring-opening and end-capping reaction. After maintaining the reaction for 0.5-1 h, the reaction was immediately quenched, filtered, and low-boiling substances were removed under negative pressure to obtain vinyl acetoxy fluorosilicone oligomers.

[0017] (3) Neutralization and hydrolysis treatment:

[0018] Dilute 25 wt% concentrated ammonia to 8-10 wt% and cool to 0-10°C using an ice-water bath. Then, add acetoxy fluorosilicone oligomer dropwise for neutralization and hydrolysis. After the addition is complete, continue stirring for 2-5 hours. Allow the mixture to stand and separate into layers. Add acetic acid dropwise to the organic phase until the system becomes neutral. Then wash with water and distill to remove moisture and impurities to obtain hydroxyl-terminated vinyl fluorosilicone oil.

[0019] According to the present invention, preferably, the molar ratio of vinylmethyl dichlorosilane to anhydrous sodium acetate in step (1) is 1:(2.1 to 2.3).

[0020] According to the present invention, preferably, the mass ratio of anhydrous sodium acetate to n-hexane in step (1) is 1:(1.2 to 2.0).

[0021] According to the present invention, preferably, the time for reflux water separation in step (1) is 2 to 4 hours.

[0022] According to the present invention, preferably, the temperature of the acylation reaction in step (1) is 45-60°C and the time of the acylation reaction is 3-6h.

[0023] According to the present invention, preferably, the temperature of the reflux reaction in step (1) is 69-70°C and the reflux reaction time is 2-4 hours.

[0024] According to the present invention, preferably, the conditions for recovering the solvent in step (1) are a temperature of 40 to 50°C and a pressure of -0.04 MPa to -0.08 MPa.

[0025] According to the present invention, preferably, the molar ratio of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and vinylmethyldiacetoxysilane in step (2) is 1:(3-6).

[0026] According to the present invention, preferably, the catalyst in step (2) is trifluoromethanesulfonic acid, and its amount is 0.5 to 1% of the total mass of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and vinylmethyldiacetoxysilane.

[0027] According to the present invention, preferably, the quencher in step (2) is anhydrous sodium acetate, and its amount is 1 to 5 times the mass of trifluoromethanesulfonic acid.

[0028] According to the present invention, preferably, the conditions for removing low-boiling substances in step (2) are a temperature of 50 to 70°C and a pressure of -0.092 MPa to -0.099 MPa.

[0029] According to the present invention, preferably, the mass ratio of acetoxyfluorosilicone oligomer to concentrated ammonia (25 wt%) in step (3) is 1:(0.25-0.40).

[0030] According to the present invention, preferably, the temperature of the neutralization and hydrolysis treatment and stirring reaction in step (3) is 0 to 10°C.

[0031] According to the present invention, preferably, the water washing temperature in step (3) is 20-30°C and the water washing time is 0.5-1h.

[0032] According to the present invention, preferably, the conditions for removing moisture and impurities in step (3) are a temperature of 40 to 60°C and a pressure of -0.05 MPa to -0.09 MPa.

[0033] The reaction route of this invention is as follows:

[0034]

[0035] Unless otherwise described in this invention, all aspects are based on conventional techniques in the field.

[0036] Compared with the prior art, the technical features and beneficial effects of the present invention are as follows:

[0037] 1. The hydroxyl-terminated vinyl fluorosilicone oil prepared by this invention contains both vinyl and hydroxyl reactive groups in its molecular structure. When used as a modifier for fluorosilicone rubber, the terminal hydroxyl groups significantly treat the silanol groups on the surface of hydrophilic silica, improving the affinity between silica and fluorosilicone raw rubber molecules, allowing for uniform dispersion in the rubber system. The vinyl groups participate in subsequent vulcanization reactions, enhancing the entanglement and bridging effect of raw rubber molecules and improving the mechanical properties of the rubber. This product functions as both a structural control agent and a system crosslinking agent.

[0038] 2. The short-chain fluorosilicone oil of the present invention has a small molecular weight, low degree of polymerization, fixed vinyl and hydroxyl content, and high product purity. When used as a reaction raw material or formulation additive, its effect is constant, avoiding adverse effects on the synthesis reaction or material performance caused by changes in purity, composition, and group content.

[0039] 3. Compared with the co-hydrolysis reaction of various chlorosilanes, the present invention avoids the defects of complex products and poor selectivity of target products caused by the differences in hydrolysis activity of different chlorosilanes. It has the advantages of fewer impurities, higher purity and clear target, and will not cause environmental pollution problems caused by the hydrolysis of chlorosilanes producing a large amount of hydrochloric acid.

[0040] 4. The preparation method of the present invention is simple, has high reaction efficiency, and the solvent and recycled raw materials can be recycled. It has low production cost, good safety, and is easy to realize industrial production. Attached Figure Description

[0041] Figure 1 The image shows the 1H NMR spectrum of the hydroxyl-terminated vinyl fluorosilicone oil prepared in Example 1 of this invention.

[0042] Figure 2 This is the gas chromatogram of the hydroxyl-terminated vinyl fluorosilicone oil prepared in Example 1 of the present invention. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments, but this description is not intended to limit the scope of the invention.

[0044] The raw materials described in the examples are all conventional raw materials that can be purchased on the market or prepared according to existing technologies.

[0045] Example 1

[0046] A hydroxyl-terminated vinyl fluorosilicone oil has the following structure:

[0047]

[0048] The preparation steps are as follows:

[0049] (1) Vinylsilane acylation reaction:

[0050] 1007 g of anhydrous sodium acetate and 1611 g of n-hexane were added to a reactor equipped with a mechanical stirrer, thermometer, water separator, reflux pipe, and dropping funnel. The mixture was stirred to form a suspension. The temperature was raised to 69 °C and maintained under reflux for 3 hours to separate residual water from the material. The reactor temperature was then lowered to 48 °C, and 770 g of vinylmethyl dichlorosilane was added dropwise to initiate an acylation reaction. The reaction was exothermic during the dropwise addition. The reactor temperature was lowered by a jacket to keep it below 60 °C for a total of 3 hours. After the dropwise addition was complete, the temperature was raised to 69–70 °C and refluxed for 4 hours. After the reaction was complete, the system was cooled to room temperature, and the sodium chloride and excess sodium acetate produced in the reaction were removed by filtration. The filtrate was collected, and the solvent was evaporated and recovered under conditions of 40–50 °C and -0.04 MPa to -0.08 MPa to obtain 977.4 g of vinylmethyl diacetoxysilane, with a yield of 95.2%.

[0051] (2) Ring-opening and end-capping reaction:

[0052] 468 g of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and 600 g of vinylmethyldiacetoxysilane were added to a reaction vessel and stirred until homogeneous. The system temperature was lowered to 0–5 °C using an ice-water bath. Then, 6.41 g of trifluoromethanesulfonic acid was rapidly added to the vessel to initiate a ring-opening and end-capping reaction. During the reaction, the vessel temperature was maintained at 0–5 °C using an ice-water bath. After stirring for 50 min, 10.5 g of anhydrous sodium acetate was immediately added to quench the reaction. Stirring was maintained for 3 h. The system was then brought back to room temperature, filtered under negative pressure, and the filtrate was collected. The remaining vinylmethyldiacetoxysilane and other low-boiling substances were removed under conditions of 60–70 °C and -0.099 MPa, yielding 606.8 g of vinyl-containing acetoxyfluorosilicone oligomers, with a yield of 92.5%.

[0053] (3) Neutralization and hydrolysis treatment:

[0054] Add 91.8 g of concentrated ammonia (25 wt%) and 195 g of water to another reactor equipped with a mechanical stirrer, thermometer, vent pipe, and dropping funnel. Stir and dilute, and lower the reactor temperature to 0–10 °C using an external ice-water bath. Then, slowly add 328 g of acetoxyfluorosilicone oligomer to the reactor for neutralization and hydrolysis. During this process, adjust the dropping rate to keep the reactor temperature below 10 °C until the addition is complete. Continue stirring at 0–10 °C for 4 hours. Then, allow the hydrolyzed reaction solution to stand and separate into layers. Take the lower organic phase and add acetic acid dropwise to it until the system becomes neutral. Add a total of 1.2 g of acetic acid. Then, wash the hydrolysate twice with 500 g of water at 20–30 °C for 0.5–1 hour each time. Finally, dehydrate the solution at 50–60 °C and -0.09 MPa until the liquid surface is bright and free of bubbles, yielding 261.7 g of the terminal hydroxyl vinyl fluorosilicone oil, with a yield of 91.6%.

[0055] The 1H NMR spectrum of the hydroxyl-terminated vinyl fluorosilicone oil prepared above is shown below. Figure 1 As shown, the chemical shift signal peaks are as follows: 0.16-0.28 ppm for H in Si-CH3, 0.77-0.86 ppm for the methylene H in Si-CH2CH2CF3 bonded to Si, 2.02-2.15 ppm for the methylene H in Si-CH2CH2CF3 bonded to -CF3, 5.82-6.09 ppm for the H in Si-CH=CH2, and 7.28 ppm for the solvent deuterated chloroform. The H in Si-OH is an active hydrogen, and due to the influence of the solvent deuterated chloroform, it is not shown. The integral area ratio of various H groups in the product is 1.5:3:3:6. The data characterized by this spectrum can indicate the molecular structure of the fluorosilicone oil.

[0056] In addition, the gas chromatogram of the product is as follows: Figure 2 As shown, the component at retention time 7.170 min is hydroxyl-terminated vinyl fluorosilicone oil with a content of 97.04%. The spectrum contains almost no unreacted raw materials and impurities, indicating that the product has a high purity.

[0057] Example 2

[0058] A method for preparing a hydroxyl-terminated vinyl fluorosilicone oil includes the following steps:

[0059] (1) Vinylsilane acylation reaction:

[0060] 985 g of anhydrous sodium acetate and 1500 g of n-hexane were added to a reactor equipped with a mechanical stirrer, thermometer, water separator, reflux pipe, and dropping funnel. The mixture was stirred to form a suspension. The temperature was raised to 69°C and maintained under reflux for 2 hours to separate residual moisture from the material. The reactor temperature was then lowered to 45°C, and 770 g of vinylmethyldichlorosilane was added dropwise for acylation. The reaction was exothermic during the addition. The reactor temperature was lowered by a jacket to keep it below 50°C for a total of 5 hours. After the addition was complete, the temperature was further raised to 69–70°C and refluxed for 2 hours. Once the reaction was complete, the system was cooled to room temperature. The generated sodium chloride and excess sodium acetate were removed by filtration. The filtrate was collected, and the solvent was evaporated and recovered under conditions of 40–50°C and -0.04 MPa to -0.08 MPa to obtain 970.1 g of vinylmethyldiacetoxysilane, with a yield of 94.5%.

[0061] (2) Ring-opening and end-capping reaction:

[0062] 468 g of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and 658 g of vinylmethyldiacetoxysilane were added to a reaction vessel and stirred until homogeneous. The system temperature was lowered to 0–5 °C using an ice-water bath. Then, 6.98 g of trifluoromethanesulfonic acid was rapidly added to the vessel to initiate a ring-opening and end-capping reaction. During the reaction, the vessel temperature was maintained at 0–5 °C using an ice-water bath. After stirring for 30 min, 11.4 g of anhydrous sodium acetate was immediately added to quench the reaction. Stirring was maintained for 4 h. The system was then restored to room temperature, filtered under negative pressure, and the filtrate was collected. The remaining vinylmethyldiacetoxysilane and other low-boiling substances were removed under conditions of 60–70 °C and -0.099 MPa, yielding 595.2 g of vinyl-containing acetoxyfluorosilicone oligomers, with a yield of 90.7%.

[0063] (3) Neutralization and hydrolysis treatment:

[0064] 100g of concentrated ammonia (25wt%) and 212.5g of water were added to another reactor equipped with a mechanical stirrer, thermometer, vent pipe, and dropping funnel. The mixture was stirred and diluted, and the reactor temperature was lowered to 0-10℃ using an ice-water bath outside the reactor. Then, 328g of acetoxyfluorosilicone oligomer was slowly added dropwise to the reactor for neutralization and hydrolysis. During this process, the dropping rate was adjusted to keep the reactor temperature below 10℃ until the addition was complete. The reaction was then continued at 0-10℃ with stirring for 3 hours. The hydrolyzed reaction solution was then allowed to stand and separate into layers. Acetic acid was added dropwise to the lower organic phase until the system became neutral. A total of 0.8g of acetic acid was added. The hydrolysate was then washed twice with 600g of water at 20-30℃ for 0.5-1 hours each time. Finally, the solution was dehydrated at 50-60℃ and -0.09MPa until the liquid surface was bright and free of bubbles, yielding 259.6g of the terminal hydroxyl vinyl fluorosilicone oil, with a yield of 90.8%.

[0065] Example 3

[0066] A method for preparing a hydroxyl-terminated vinyl fluorosilicone oil includes the following steps:

[0067] (1) Vinylsilane acylation reaction:

[0068] 940 g of anhydrous sodium acetate and 1410 g of n-hexane were added to a reactor equipped with a mechanical stirrer, thermometer, water separator, reflux pipe, and dropping funnel. The mixture was stirred to form a suspension. The temperature was raised to 69 °C and maintained under reflux for 3 hours to separate residual water from the material. The reactor temperature was then lowered to 47 °C, and 770 g of vinylmethyl dichlorosilane was added dropwise to initiate an acylation reaction. The reaction was exothermic during the addition. The reactor temperature was lowered by a jacket to keep it below 55 °C for a total of 4 hours. After the addition was complete, the temperature was raised to 69–70 °C and refluxed for 3 hours. After the reaction was complete, the system was cooled to room temperature. The sodium chloride and excess sodium acetate produced in the reaction were removed by filtration. The filtrate was collected, and the solvent was evaporated and recovered under conditions of 40–50 °C and -0.04 MPa to -0.08 MPa to obtain 958.9 g of vinylmethyl diacetoxysilane, with a yield of 93.4%.

[0069] (2) Ring-opening and end-capping reaction:

[0070] 468 g of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and 940 g of vinylmethyldiacetoxysilane were added to a reaction vessel and stirred until homogeneous. The system temperature was lowered to 0–5 °C using an ice-water bath. Then, 8.45 g of trifluoromethanesulfonic acid was rapidly added to the vessel to initiate a ring-opening and end-capping reaction. During the reaction, the vessel temperature was maintained at 0–5 °C using an ice-water bath. After stirring for 60 min, 13.9 g of anhydrous sodium acetate was immediately added to quench the reaction. Stirring was maintained for 3 h. The system was then restored to room temperature, filtered under negative pressure, and the filtrate was collected. The remaining vinylmethyldiacetoxysilane and other low-boiling substances were removed under conditions of 60–70 °C and -0.099 MPa, yielding 591.8 g of vinyl-containing acetoxyfluorosilicone oligomers, with a yield of 90.2%.

[0071] (3) Neutralization and hydrolysis treatment:

[0072] 120g of concentrated ammonia (25wt%) and 275g of water were added to another reactor equipped with a mechanical stirrer, thermometer, vent pipe, and dropping funnel. The mixture was stirred and diluted, and the reactor temperature was lowered to 0-10℃ using an ice-water bath outside the reactor. Then, 328g of acetoxyfluorosilicone oligomer was slowly added dropwise to the reactor for neutralization and hydrolysis. During this process, the dropping rate was adjusted to keep the reactor temperature below 10℃ until the addition was complete. The reaction was then maintained at 0-10℃ and stirred for another 3 hours. The hydrolyzed reaction solution was then allowed to stand and separate into layers. Acetic acid was added dropwise to the lower organic phase until the system became neutral. A total of 1.6g of acetic acid was added. The hydrolysate was then washed twice with 640g of water at 20-30℃ for 0.5-1 hour each time. Finally, the solution was dehydrated at 50-60℃ and -0.09MPa until the liquid surface was bright and free of bubbles, yielding 261.1g of the terminal hydroxyl vinyl fluorosilicone oil, with a yield of 91.3%.

[0073] Example 4

[0074] A method for preparing a hydroxyl-terminated vinyl fluorosilicone oil includes the following steps:

[0075] (1) Vinylsilane acylation reaction:

[0076] 1029 g of anhydrous sodium acetate and 1650 g of n-hexane were added to a reactor equipped with a mechanical stirrer, thermometer, water separator, reflux pipe, and dropping funnel. The mixture was stirred to form a suspension. The temperature was raised to 69 °C and maintained under reflux for 4 hours to separate residual water from the material. The reactor temperature was then lowered to 50 °C, and 770 g of vinylmethyl dichlorosilane was added dropwise to initiate an acylation reaction. The reaction was exothermic during the addition. The reactor temperature was lowered by a jacket to keep it below 60 °C for a total of 3 hours. After the addition was complete, the temperature was raised to 69–70 °C and refluxed for another 3 hours. Once the reaction was complete, the system was cooled to room temperature. The sodium chloride and excess sodium acetate produced in the reaction were removed by filtration. The filtrate was collected, and the solvent was evaporated and recovered under conditions of 40–50 °C and -0.04 MPa to -0.08 MPa to obtain 980.5 g of vinylmethyl diacetoxysilane, with a yield of 95.5%.

[0077] (2) Ring-opening and end-capping reaction:

[0078] 468 g of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and 752 g of vinylmethyldiacetoxysilane were added to a reaction vessel and stirred until homogeneous. The system temperature was lowered to 0–5 °C using an ice-water bath. Then, 7.32 g of trifluoromethanesulfonic acid was rapidly added to the vessel to initiate a ring-opening and end-capping reaction. During the reaction, the vessel temperature was maintained at 0–5 °C using an ice-water bath. After stirring for 45 min, 12.5 g of anhydrous sodium acetate was immediately added to quench the reaction. Stirring was maintained for 4 h. The system was then restored to room temperature, filtered under negative pressure, and the filtrate was collected. The remaining vinylmethyldiacetoxysilane and other low-boiling substances were removed under conditions of 60–70 °C and -0.099 MPa, yielding 602.2 g of vinyl-containing acetoxyfluorosilicone oligomers, with a yield of 91.8%.

[0079] (3) Neutralization and hydrolysis treatment:

[0080] 105g of concentrated ammonia (25wt%) and 220g of water were added to another reactor equipped with a mechanical stirrer, thermometer, vent pipe, and dropping funnel. The mixture was stirred and diluted, and the reactor temperature was lowered to 0-10℃ using an ice-water bath outside the reactor. Then, 328g of acetoxyfluorosilicone oligomer was slowly added dropwise to the reactor for neutralization and hydrolysis. During this process, the dropping rate was adjusted to keep the reactor temperature below 10℃ until the addition was complete. The reaction was then maintained at 0-10℃ and stirred for another 4 hours. The hydrolyzed reaction solution was then allowed to stand and separate into layers. Acetic acid was added dropwise to the lower organic phase until the system became neutral. A total of 1.5g of acetic acid was added. The hydrolysate was then washed twice with 550g of water at 20-30℃ for 0.5-1 hour each time. Finally, the solution was dehydrated at 50-60℃ and -0.09MPa until the liquid surface was bright and free of bubbles, yielding 263.7g of the terminal hydroxyl vinyl fluorosilicone oil, with a yield of 92.2%.

[0081] Comparative Example 1

[0082] 735 g of concentrated ammonia (25 wt%) and 1560 g of water were added to a reaction vessel equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel. The mixture was stirred and diluted. The temperature of the vessel was lowered to 0–10 °C using an ice-water bath outside the vessel. Then, 633 g of a pre-mixed mixture of trifluoropropylmethyldichlorosilane and 141 g of vinylmethyldichlorosilane were added dropwise through a constant-pressure dropping funnel to carry out a co-hydrolysis reaction. The temperature of the vessel was maintained below 10 °C during the addition until the addition was completed. The reaction was then stirred at 0–10 °C for another 4 hours. The hydrolyzed reaction solution was then allowed to stand and separate into layers. Acetic acid was added dropwise to the lower organic phase until the system became neutral. A total of 7.3 g of acetic acid was added. The hydrolysate was then washed twice with 2000 g of water at 20–30 °C for 0.5–1 hour each time. Finally, the hydrolysate was dehydrated at 50–60 °C and -0.09 MPa to obtain 538 g of co-hydrolysate.

[0083] Gas chromatography analysis of the co-hydrolysate revealed a diverse and highly disordered composition, containing various cyclosiloxanes and polysiloxanes with varying degrees of polymerization. This indicates that the chlorosilane hydrolysis method is unsuitable for obtaining high-purity hydroxyl-terminated vinyl fluorosilicone oil. Due to the different reactivity of trifluoropropylmethyldichlorosilane and vinylmethyldichlorosilane, they cannot form chains according to the designed route during co-hydrolysis. Instead, their individual hydrolysis reactions occur more frequently, resulting in ineffective co-hydrolysis, a high impurity content in the prepared system, and failure to obtain the target product.

[0084] Comparative Example 2

[0085] 468g of (3,3,3-trifluoropropyl)methylcyclotrisiloxane, 86g of tetramethyltetravinylcyclotetrasiloxane, 50g of water, 550g of acetone, and 10g of acid clay were added to a reactor equipped with a mechanical stirrer, thermometer, condenser, and reflux tube. The mixture was stirred to form a suspension, and the temperature was raised to 65°C for reflux reaction. After maintaining the reaction for 12 hours, the system was cooled to room temperature. Then, 10g of magnesium oxide was added to the reactor and stirred for 1 hour. The mixture was then filtered under negative pressure, and the filtrate was collected. The solvent acetone was removed under the conditions of 40–50°C and -0.04 MPa to -0.08 MPa to obtain 514g of copolymer.

[0086] Gas chromatography analysis of the copolymer revealed numerous and complex products with highly disordered components and poor selectivity. Significant amounts of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and tetramethyltetravinylcyclotetrasiloxane remained unreacted. This indicates that the ring-opening polymerization route using cyclosiloxanes is also unsuitable for obtaining high-purity hydroxyl-terminated vinyl fluorosilicone oil. Different ring structures exhibit varying ring-opening activities, resulting in poor copolymerization. Furthermore, even under the equilibrium effect of an acidic catalyst, a definite siloxane linkage structure cannot be obtained, leading to low purity and numerous impurities in the reaction product.

[0087] The technical content and features of the present invention are as described above, but the scope of protection of the present invention should not be limited to the content described in the embodiments, but should include various substitutions and modifications that do not depart from the present invention, and are covered by the claims of the present invention.

Claims

1. A method for preparing a hydroxyl-terminated vinyl fluorosilicone oil, wherein the hydroxyl-terminated vinyl fluorosilicone oil has the structure shown in formula (I): ； Includes the following steps: (1) Vinylsilane acylation reaction: Anhydrous sodium acetate and n-hexane were stirred and mixed, and the mixture was heated to reflux for water separation. Then, vinylmethyldichlorosilane was added dropwise to the system to carry out an acylation reaction at a temperature of 45-60°C for 3-6 hours. After the addition was complete, the mixture was heated to reflux at a temperature of 69-70°C for 2-4 hours. After the reaction was complete, the mixture was cooled, filtered, and the solvent was recovered to obtain vinylmethyldiacetoxysilane. (2) Ring-opening and end-capping reaction: (3,3,3-trifluoropropyl)methylcyclotrisiloxane and vinylmethyldiacetoxysilane were mixed evenly, and the system temperature was lowered to 0-5℃ using an ice-water bath. Then, trifluoromethanesulfonic acid was added as a catalyst to the system to carry out the ring-opening and end-capping reaction. After maintaining the reaction for 0.5-1h, the reaction was immediately quenched, filtered, and low-boiling substances were removed under negative pressure to obtain vinyl acetoxy fluorosilicone oligomers. (3) Neutralization and hydrolysis treatment: Dilute 25 wt% concentrated ammonia to 8-10 wt% and cool to 0-10℃ using an ice-water bath. Then, add vinyl-containing acetoxy fluorosilicone oligomer dropwise for neutralization and hydrolysis. After the addition is complete, continue stirring for 2-5 hours. Allow the mixture to stand and separate into layers. Add acetic acid dropwise to the organic phase until the system becomes neutral. Then wash with water and distill to remove water and impurities to obtain hydroxyl-terminated vinyl fluorosilicone oil.

2. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, In step (1), the molar ratio of vinylmethyl dichlorosilane to anhydrous sodium acetate is 1:(2.1~2.3); the mass ratio of anhydrous sodium acetate to n-hexane is 1:(1.2~2.0).

3. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, In step (1), the reflux water separation time is 2~4h; the conditions for solvent recovery are temperature 40~50℃ and pressure -0.04MPa to -0.08MPa.

4. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, In step (2), the molar ratio of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and vinylmethyldiacetoxysilane is 1:(3~6); the amount of catalyst used is 0.5~1% of the total mass of (3,3,3-trifluoropropyl)methylcyclotrisiloxane and vinylmethyldiacetoxysilane fed.

5. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, Step (2) uses anhydrous sodium acetate quencher, the amount of which is 1 to 5 times the mass of trifluoromethanesulfonic acid.

6. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, The conditions for removing low-boiling substances in step (2) are a temperature of 50~70℃ and a pressure of -0.092MPa to -0.099MPa.

7. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, In step (3), the mass ratio of acetoxyfluorosilicone oligomer to 25wt% concentrated ammonia is 1:(0.25~0.40).

8. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, The temperature for the neutralization and hydrolysis treatment and stirring reaction in step (3) is 0~10℃.

9. The method for preparing hydroxyl-terminated vinyl fluorosilicone oil according to claim 1, characterized in that, The water washing temperature in step (3) is 20~30℃ and the water washing time is 0.5~1h; the conditions for removing moisture and impurities are a temperature of 40~60℃ and a pressure of -0.05MPa to -0.09MPa.

Images