Preparation method of alkoxy-terminated polydimethylsiloxane

Abstract

The invention relates to a preparation method of alkoxy modified polydimethylsiloxane, which comprises the following steps: (S1) in the presence of a cellulose immobilized Pt catalyst, carrying out hydrosilylation reaction on end hydrogen-containing silicone oil and vinyl alkoxy silane, or end vinyl silicone oil and hydrogen-containing alkoxy silane to prepare an end-capping reagent with double end alkoxy; and (S2) carrying out polycondensation on the double-end alkoxy end-capping reagent and linear hydroxyl end-capped polydimethylsiloxane in the presence of a phosphazene catalyst to prepare an alkoxy modified polydimethylsiloxane product with low ring body and low ion content. The alkoxy modified polydimethylsiloxane product prepared by the invention has the following advantages: the content of ions is low, and the color cannot be caused by Pt residue; the prepared alkoxy modified polydimethylsiloxane product is low in ring content, has no residue of micromolecular siloxane silane, and meets the application requirements of high-end fields such as bonding of optical glass parts, electronic packaging and the like.

Description

Technical Field

[0001] The invention belongs to the field of organic silicon, and specifically relates to a method for preparing alkoxy-terminated polydimethylsiloxane. Background Art

[0002] Since 2018, EU regulations have promulgated restrictions on low-ring bodies produced in the production of silicone, such as D3, D4, D5, and D6 substances. Traditional production processes such as ammonia glue and alkali glue can no longer meet the requirements for low-ring bodies in the preparation of alkoxy-modified polydimethylsiloxane from the perspective of polymerization technology. The presence of such low-boiling substances has an adverse effect on the application performance and safety of the product. In addition, the activity and residue of hydroxyl groups in the traditional 107 glue in the preparation of alcohol-type sealants will not only cause a viscosity peak in the preparation process, but also bring hidden dangers and troubles to equipment and production. Moreover, due to the activity of hydroxyl groups in 107 glue, it will cause problems with mixing and dispersion during the preparation process. And due to the problem of residual silicone hydroxyl groups in the preparation of alcohol-type glue, the shelf life of alcohol-type glue will be shortened. Therefore, alkoxy-modified polydimethylsiloxane was invented to solve such problems.

[0003] Currently, alkoxy-modified 107 glue is mainly achieved through two types of technical means. The first is to use the hydrosilylation reaction. This technology will bring about the problem of Pt-ene catalyst residues, and there will be residues of small molecular silanes such as small molecular vinylmethoxysilane, which will limit its application in some optical bonding fields. At the same time, there may be bubbles during the bonding process, and the residue of small molecular alkoxysilane will also affect the curing. Another technical approach is to use 107 glue and alkoxysilane condensation for modification. This method also has the problem of small molecular residues and metal ion residues, which affects the quality of the product and limits the application field of the product.

[0004] CN115926173A discloses a method for preparing a low-cyclic silicone oil, comprising the following steps: (1) reacting octamethyltetrasiloxane and a hydrogen-containing double end cap at 30-45°C in the presence of concentrated sulfuric acid as a catalyst to obtain an intermediate; (2) neutralizing the intermediate with sodium carbonate, filtering, and then evacuating at high temperature; (3) reacting the intermediate treated in step (2) with allyl epoxy polyether in the presence of chloroplatinic acid as a catalyst to obtain diepoxy-terminated polyether silicone oil; and (4) reacting the diepoxy-terminated polyether silicone oil with tertiary aminated polyether amine under weakly acidic conditions to obtain a low-cyclic silicone oil.

[0005] CN115612104A discloses a production process of electronic grade 107 with low ring body content, comprising the following steps: (1) adding dimethyldichlorosilane to a weak alkaline solution at a temperature of 20-50°C and under sufficient stirring, continuing to stir and react after the addition is completed, then standing to separate the upper organic phase 1; (2) adding the organic phase 1 separated in step (1) to a mixed solution of xylene and dimethyl sulfoxide, heating the temperature to 70-90°C, adding the weak alkaline solution while stirring, and reacting by stirring at the temperature, cooling the temperature to room temperature after the reaction is completed, separating the upper organic phase 2 after centrifugation, and washing the organic phase 2 with deionized water until the pH value is 7; (3) stirring the organic phase 2 washed in step (2), heating it to 130-140°C and keeping it warm for 20-40 minutes, then heating it to 180-190°C and keeping it warm for 30-50 minutes, and finally deionizing it under a vacuum of -0.1Mpa for 1-3 hours to obtain electronic grade 107 glue with low ring body content.

[0006] CN111378135A discloses a method for preparing a low-viscosity alkoxy-terminated polydimethylsiloxane, comprising the following steps: (1) mixing DMC and hexamethyldisiloxane, heating, adding phosphoric acid dropwise, stirring and refluxing to remove water to obtain a silicophosphate terminator; (2) heating the linear body, adding potassium hydroxide aqueous solution, stirring for polycondensation reaction, adding the silicophosphate terminator, and continuing the reaction to obtain hydroxy silicone oil; (3) adding the hydrogen-containing double head to the hydroxy silicone oil, stirring until the mixture is uniform, heating and adding the phosphazene catalyst, stirring the reaction, adding the ammonia terminator, and continuing the reaction to obtain a low-viscosity hydrogen-containing silicone oil; (4) mixing the low-viscosity hydrogen-containing silicone oil, vinyl trimethoxysilane, and platinum catalyst, stirring the reaction to obtain a low-viscosity alkoxy-terminated polydimethylsiloxane. The first step of the patent is to prepare a neutralizer, and the second step is to add potassium hydroxide aqueous solution at 130-150°C to introduce K + ions, and a large number of rings are produced. It is necessary to remove the low-boiling point substances by vacuum distillation. It is difficult to remove high-boiling point substances such as D5-D10 from the system, and the temperature needs to be raised to achieve removal. The hydroxy silicone oil obtained in the third step is added to the hydrogen-containing double head. The boiling point and flash point of the hydrogen-containing double head are very low, and water will be produced during the polycondensation and telomerization process, which is not conducive to the forward reaction, and a second degassing is required to obtain the hydrogen-containing silicone oil.

[0007] The preparation process of the above patent reduces the content of low-boiling-point small molecules, but still cannot meet actual needs, and has defects such as the inability to balance low ring body content and yield. Summary of the invention

[0008] In order to solve the problem of small molecule residues and metal ion residues in alkoxy-modified polydimethylsiloxane, and solve the problem of ring body content in synthesis technology, the present invention first prepares a cellulose-modified supported Pt-based catalyst, and uses the catalyst to prepare a low-viscosity capping agent with double-terminal alkoxy groups. Then, the prepared capping agent is used to undergo an efficient polycondensation and telomerization reaction with a linear body in the presence of a phosphazene catalyst to achieve the purpose of low ring body and low ion content residues. To achieve its purpose, the present invention adopts the following technical solutions:

[0009] A method for preparing an alkoxy-modified polydimethylsiloxane comprises the following steps:

[0010] (S1) in the presence of a cellulose-supported Pt-based catalyst, a hydrogen-terminated silicone oil and a vinyl alkoxysilane, or a vinyl-terminated silicone oil and a hydrogen-containing alkoxysilane, undergo a hydrosilylation reaction to prepare a double-terminal alkoxy end-capping agent;

[0011] (S2) A double-terminal alkoxy-capping agent is polycondensed with a linear hydroxyl-terminated polydimethylsiloxane in the presence of a phosphazene catalyst to prepare an alkoxy-modified polydimethylsiloxane product.

[0012] The present invention uses a cellulose-modified supported Pt-based catalyst to first prepare a double-terminal alkoxyl capping agent, which can be purified to remove small molecular substances in a low-viscosity state without introducing easily colored groups such as Pt-based catalysts.

[0013] Furthermore, in step (S1), the cellulose-immobilized Pt-based catalyst has a Pt loading rate of 1-5%, and is preferably prepared by a preparation method comprising the following steps: cellulose particles are sequentially treated with a weak alkaline solution, treated with siloxane, immersed in a platinum source solution, taken out, washed, and dried to obtain a cellulose-immobilized Pt-based catalyst.

[0014] Furthermore, the cellulose-immobilized Pt catalyst is prepared by a preparation method comprising the following steps: adding cellulose particles to a weak alkaline solution, pre-treating at 30-50°C for 0.5-2h, taking out, washing, drying, adding to siloxane, the siloxane is selected from at least one of vinyl siloxane or phenyl siloxane, treating at 50-90°C for 5-10h, filtering after the treatment, washing the filter cake, and drying to obtain modified cellulose; then adding the obtained modified cellulose to a platinum source solution, stirring and reacting at 40-80°C for 10-20h under inert atmosphere protection, filtering, washing the filter cake, and drying to obtain a cellulose-immobilized Pt catalyst. The particle size of the cellulose particles is 50-120μm, preferably 60-90μm.

[0015] Furthermore, the weak base solution is a 1-5wt% aqueous solution of sodium bicarbonate and / or potassium bicarbonate; the platinum source is selected from at least one of chloroplatinic acid and platinum tetrachloride; the concentration of the platinum source solution is 1-5wt%, preferably 2-3wt%, and the solvent is at least one of ethanol, methanol, and isopropanol.

[0016] Furthermore, the mass ratio of cellulose particles, weak alkaline solution and siloxane is 5-10:20-30:3-5; the mass ratio of modified cellulose and platinum source solution is 1:5-10.

[0017] Filtration, washing and drying are not particularly limited and are well known in the art; the inert atmosphere is at least one of nitrogen and argon.

[0018] Further, in step (S1), the amount of the modified cellulose supported catalyst added is 50-100 ppm based on the total mass of the reaction raw materials, calculated as platinum. The reaction raw materials are the sum of terminal hydrogen silicone oil and vinyl alkoxy silane, or the reaction raw materials are the sum of terminal vinyl silicone oil and hydrogen alkoxy silane.

[0019] Further, in step (S1), the molar ratio of terminal hydrogen silicone oil to vinyl siloxane is 1:1.05-1.2, and the molar ratio of terminal vinyl silicone oil to hydrogen siloxane is 1:1.05-1.2; preferably, in step (S1), the viscosity of terminal hydrogen silicone oil and terminal vinyl silicone oil is independently 1-100mm 2 / s, preferably 5-50mm 2 / s, more preferably 10-20 mm 2 / s.

[0020] Furthermore, in step (S1), the vinyl alkoxysilane is selected from at least one of vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl dimethoxyethoxysilane, and vinyl methoxydiethoxysilane; the hydrogen-containing alkoxysilane is selected from at least one of trimethoxysilane, triethoxysilane, dimethoxyethoxysilane, methoxydiethoxysilane, methyldimethoxysilane, methyldiethoxysilane, dimethylmethoxysilane, dimethylethoxysilane, and triisopropylsilane.

[0021] Furthermore, in step (S2), the phosphazene catalyst is selected from at least one of phosphazene chloride and phosphazene base, and the polymerization degree of the phosphazene catalyst is 2-5; the amount of the phosphazene catalyst used is 1-20 ppm of the entire system.

[0022] Furthermore, in step (S2), the linear hydroxyl-terminated polydimethylsiloxane has a viscosity of 50 to 110 mm 2 / s, hydroxyl content of 1.2-3.8%; volatile matter ≤0.1%; the mass ratio of the double-ended alkoxy capping agent to the linear hydroxyl-terminated polydimethylsiloxane is 0.006-0.02:1. Those skilled in the art know that the lower the viscosity of the linear hydroxyl-terminated polydimethylsiloxane, the smaller the molecular weight and the higher the hydroxyl content. Those skilled in the art can flexibly adjust the dosage ratio according to the viscosity of the linear hydroxyl-terminated polydimethylsiloxane.

[0023] Further, in step (S2), the linear hydroxyl-terminated polydimethylsiloxane is first dehydrated at 50-100° C., preferably 65-85° C., under vacuum conditions of -900 to -1000 mbar for 1-5 h; then, the nitrogen pressure is released at a pressure of -700 to -800 mbar, a double-ended alkoxy end-capping agent is added, stirred, a phosphazene catalyst is added, and the pressure is evacuated to -100 to -1000 mbar, and the polymerization reaction is carried out at 50-120° C., preferably 65-85° C., for 2-4 h, and then the nitrogen pressure is released and a neutralizing agent of 1.5 to 2 times the amount of the catalyst is added, and the reaction is neutralized for 2-5 h. After the neutralization is completed, the reaction is dehydrated at -100 to -1000 mbar and 120-160° C. for 1-5 h, and the temperature is reduced and packaged to obtain a product non-condensed alkoxy-modified polydimethylsiloxane.

[0024] Furthermore, if the phosphazene catalyst is phosphazene chloride, the neutralizing agent is selected from at least one of silazane, triethylamine, propylamine, isooctylamine, and tetramethyldivinyldisilazane; if the phosphazene catalyst is a phosphazene base, the neutralizing agent is selected from at least one of phosphoric acid and silicon alkoxide of phosphoric acid.

[0025] The present invention uses cellulose, a renewable support material, which is cheap and easy to obtain. In addition, cellulose particles have a high specific surface area and porosity, providing multiple active sites for the loading of the catalyst. At the same time, cellulose particles have good mechanical strength, and their physical and chemical properties have good stability. Using terminal hydrogen silicone oil and vinyl alkoxy silane, or terminal vinyl silicone oil and hydrogen alkoxy silane, a double-terminal alkoxy end-capping agent is prepared by a silylation reaction; this step is very critical, and the prepared end-capping agent avoids the introduction of low-molecular substances. In this step, the end-capping agent can be de-purified, and at the same time, due to the use of cellulose-loaded catalysts, the introduction of colored impurities such as Pt into the end-capping agent is avoided. The third is the use of phosphazene catalysts, which have the remarkable feature of having few by-products, and the prepared alkoxy-modified polydimethylsiloxane can meet the requirements of SVHC (D4 / D5 / D6 each ≤1000ppm) without relying on expensive de-low equipment. The alkoxy-terminated polydimethylsiloxane products prepared by this process can be applied to some high-end application scenarios. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further explained and illustrated by specific embodiments below.

[0027] Linear hydroxyl-terminated polydimethylsiloxane comes from Jiangxi Bluestar Xinghuo Silicone Co., Ltd., volatile matter ≤ 0.1%, linear hydroxyl-terminated polydimethylsiloxane 1 viscosity 50mm 2 / s, hydroxyl content is 3.8%; linear hydroxyl-terminated polydimethylsiloxane 2 has a viscosity of 110 mm 2 / s, and the hydroxyl content is 1.2%.

[0028] The organosilicon ring content was measured using GC-FID chromatography based on the internal standard method.

[0029] Metal ions: ICP-MS analysis: Use ICP-MS quantitative analysis method to digest the sample, and then use standard solution to make a standard curve for quantitative detection.

[0030] The chromaticity is tested according to GB / T 605-2006.

[0031] The Pt loading of the catalyst was tested according to GB / T19720-2005.

[0032] Preparation Example 1

[0033] Weigh 3g of sodium carbonate, add 100g of water to dissolve in a beaker, then add 50g of cellulose particles with an average particle size of 60μm, heat to 45℃, stir magnetically for about 1h, then add 15g of vinyltrimethoxysilane, heat to 75℃ for 6h, filter, then wash the filter cake 3 times with deionized water, place the filter cake in a vacuum drying oven at 50℃, dry for 8h, and set aside. Weigh 30g of the above-treated cellulose particles in a three-necked flask, add 150g of 2wt% chloroplatinic acid ethanol solution, under 50℃, nitrogen protection, stir for 16h, complete the loading of Pt on the fiber, filter, take the filter cake, wash, place the filter cake in a vacuum drying oven at 50℃ and dry for 18h, and prepare a loaded Pt catalyst. Referring to the test method of GB / T19720-2005, the Pt loading amount in the loaded catalyst prepared in the test preparation example 1 is 2.6wt%.

[0034] Example 1

[0035] (S1) Add 84.5 g of vinyltrimethoxysilane to a 500 ml four-necked flask equipped with a thermometer, a condenser, and a stirrer, then add the supported Pt catalyst prepared in Preparation Example 1, and heat to 70° C. Then dropwise add a 10 mm thick 2 / s of terminal hydrogen-containing silicone oil, the amount of terminal hydrogen-containing silicone oil added is such that the molar ratio of active H (Si-H) and vinyl of the terminal hydrogen-containing silicone oil is 1:1.05, the dripping rate is controlled at 4-7g / min, and the amount of supported Pt catalyst added (in terms of Pt) is 50ppm of the total mass of vinyl trimethoxysilane and terminal hydrogen-containing silicone oil. After the dropwise addition is completed, react for 2h, filter to remove the supported Pt catalyst, and then heat the filtrate to 150℃, -99mbar, remove low molecular weight substances, and obtain a double-terminal alkoxy end-capping agent.

[0036] (S2) Add 500g of linear hydroxyl-terminated polydimethylsiloxane 1 to a 500ml four-necked flask equipped with a thermometer, a condenser and a stirrer, heat to 70°C, dehydrate at -999mbar for 1h, release the pressure to 700mbar with nitrogen, then add 10g of the double-terminal alkoxy-capping agent obtained in step (S1), mix and stir for 20min. After mixing, release the pressure to 700mbar with nitrogen, add 2ppm of phosphazene base, control the vacuum at 950-999mbar, react for 2h, and then cool to obtain alkoxy-terminated polydimethylsiloxane.

[0037] Example 2

[0038] (S1) 107 g of trimethoxysilane was added to a 500 ml four-necked flask equipped with a thermometer, a condenser, and a stirrer, and then the supported Pt catalyst of Preparation Example 1 was added and the temperature was raised to 70° C. Then, a 20 mm thick 2 / s of vinyl-terminated silicone oil, the amount of vinyl-terminated silicone oil added is such that the molar ratio of the active hydrogen of the alkenyl group and trimethoxysilane in the vinyl-terminated silicone oil is 1:1.05, the dripping rate is controlled at 4-7g / min, and the amount of the supported Pt catalyst added (in terms of Pt) is 100ppm of the total mass of trimethoxysilane and vinyl-terminated silicone oil. After the dropwise addition is completed, react for 2h, and then filter to remove the supported Pt catalyst. Then, the filtrate is heated to 150°C and -99mbar to remove low molecular weight substances to obtain a double-terminal alkoxy end-capping agent.

[0039] (S2) Add 500g of linear hydroxyl-terminated polydimethylsiloxane 1 to a 500ml four-necked flask equipped with a thermometer, a condenser and a stirrer, heat to 70°C, dehydrate at -999mbar for 1h, release the pressure to 700mbar with nitrogen, then add 10g of the double-terminated alkoxy-terminated agent prepared above, mix and stir for 20min. After mixing, release the pressure to 700mbar with nitrogen, add 5ppm of phosphazene acid, control the vacuum at 950-999mbar, react for 2h, and then cool to obtain alkoxy-terminated polydimethylsiloxane.

[0040] Example 3

[0041] The other conditions are the same as those in Example 1, except that in step (S2), the linear hydroxyl-terminated polydimethylsiloxane 1 is replaced by an equal mass of linear hydroxyl-terminated polydimethylsiloxane 2, and the amount of the double-terminated alkoxy capping agent is changed to 3 g.

[0042] Comparative Example 1

[0043] Add 280g of vinyl silicone oil with a viscosity of 20000mPa.s to a 500ml four-necked flask equipped with a thermometer, condenser and stirrer, then heat to 90°C and dehydrate for 1h at -99KPa. After dehydration, cool to 70°C. Then add 1.84g of trimethoxysilane and mix for 20min. Add 3ppm of Custer catalyst, react for 4h and then cool to obtain alkoxy-terminated polydimethylsiloxane product.

[0044] Comparative Example 2

[0045] In a 500ml four-necked flask equipped with a thermometer, condenser, and stirrer, add 280g of a 500mm 2 / s of vinyl silicone oil, then heated to 90°C, dehydrated at -999 mbar for 1 hour, and cooled to 70°C after dehydration. Then 11g of trimethoxysilane was added and mixed for 20 minutes. 3ppm of Custer catalyst was added, reacted for 4 hours, and then cooled to obtain alkoxy-terminated polydimethylsiloxane product.

[0046] Comparative Example 3

[0047] 280g of hydrogenated silicone oil with a viscosity of 20000mPa.s was added to a 500ml four-necked flask equipped with a thermometer, a condenser and a stirrer, and then the temperature was raised to 90°C and dehydrated for 1h at -999mbar. After the dehydration was completed, the temperature was lowered to 70°C. Then 2.23g of vinyltrimethoxysilane was added and mixed for 20min. 2ppm of Custer catalyst was added, and the reaction was continued for 4h before cooling to obtain an alkoxy-terminated polydimethylsiloxane product.

[0048] Comparative Example 4

[0049] Add 280g of 107 glue with a viscosity of 20000mPa.s to a 500ml four-necked flask equipped with a thermometer, condenser and stirrer, then heat to 105℃, dehydrate at -999mbar for 1h, add 2.29g of tetramethoxysilane and mix for 20min after dehydration. Add 30ppm of tetramethylammonium hydroxide silicon alkoxide, react for 4h, heat to 150℃ to break the solvent for 1h, then dehydrate at 150℃, -99mbar for 2h, and cool to obtain alkoxy-terminated polydimethylsiloxane product.

[0050] Comparative Example 5

[0051] Other conditions are the same as those in Example 1, except that the supported Pt-based catalyst is replaced by a commercial Pt / C catalyst with a Pt loading rate of 3%. The amount of Pt / C catalyst used, calculated as Pt, is 50 ppm of the total mass of vinyltrimethoxysilane and terminal hydrogenated silicone oil.

[0052] The preparation method of the alkoxy-modified polydimethylsiloxane with low ring body and low ion content provided by the present invention is shown in Table 1 below:

[0053] Table 1 Product index test

[0054]

[0055]

[0056] The comparison results of the residual ring bodies of the alkoxy-modified polydimethylsiloxane provided by the present invention are shown in Table 2 below:

[0057] Table 2 Low ring content of products

[0058]

Claims

1. A method for preparing an alkoxy-modified polydimethylsiloxane, characterized in that: The following steps are involved: (S1) in the presence of a cellulose-supported Pt-based catalyst, a hydrogen-terminated silicone oil and a vinyl alkoxysilane, or a vinyl-terminated silicone oil and a hydrogen-containing alkoxysilane, undergo a hydrosilylation reaction to prepare a double-terminal alkoxy end-capping agent; (S2) polycondensing the double-terminal alkoxy end-capping agent with a linear hydroxyl-terminated polydimethylsiloxane in the presence of a phosphazene catalyst to prepare an alkoxy-modified polydimethylsiloxane product.

2. The preparation method according to claim 1, characterized in that: In step (S1), the cellulose-immobilized Pt-based catalyst is prepared by a preparation method comprising the following steps: cellulose particles are sequentially treated with a weak alkaline solution, treated with siloxane, immersed in a platinum source solution, taken out, washed, and dried to obtain a cellulose-immobilized Pt-based catalyst.

3. The preparation method according to claim 2, characterized in that: The cellulose-immobilized Pt-based catalyst is prepared by a preparation method comprising the following steps: adding cellulose particles to a weak alkaline solution, pre-treating at 30-50° C. for 0.5-2 h, taking out, washing, drying, adding to siloxane, wherein the siloxane is selected from at least one of vinyl siloxane and phenyl siloxane, treating at 50-90° C. for 5-10 h, filtering after the treatment, washing the filter cake, and drying to obtain modified cellulose; The obtained modified cellulose is then added to a platinum source solution, and the reaction is stirred at 40-80°C for 10-20 hours under an inert atmosphere, filtered, the filter cake is washed, and dried to obtain a cellulose-immobilized Pt catalyst; the particle size of the cellulose particles is 50-120 μm, preferably 60-90 μm.

4. The preparation method according to claim 3, characterized in that: The weak base solution is a 1-5wt% aqueous solution of sodium bicarbonate and / or potassium bicarbonate; the platinum source is selected from at least one of chloroplatinic acid and platinum tetrachloride; the concentration of the platinum source solution is 1-5wt%, preferably 2-3wt%, and the solvent is at least one of ethanol, methanol, and isopropanol.

5. The preparation method according to claim 3, characterized in that: The mass ratio of cellulose particles, weak alkaline solution and siloxane is 5-10:20-30:3-5; the mass ratio of modified cellulose and platinum source solution is 1:5-10.

6. The preparation method according to claim 1, characterized in that: In step (S1), the amount of the cellulose-immobilized Pt-based catalyst added is 50-100 ppm of the total mass of the reaction raw materials, calculated as platinum; the reaction raw materials are the sum of terminal hydrogen-containing silicone oil and vinyl alkoxysilane, or the reaction raw materials are the sum of terminal vinyl silicone oil and hydrogen-containing alkoxysilane.

7. The preparation method according to claim 1, characterized in that: In step (S1), the molar ratio of terminal hydrogen silicone oil to vinyl siloxane is 1:1.05-1.2, and the molar ratio of terminal vinyl silicone oil to hydrogen siloxane is 1:1.05-1.2; preferably, in step (S1), the viscosity of terminal hydrogen silicone oil and terminal vinyl silicone oil is independently 1-100mm 2 / s, preferably 5-50mm 2 / s, more preferably 10-20 mm 2 / s; Furthermore, in step (S1), the vinyl alkoxysilane is selected from at least one of vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tripropoxysilane, vinyl dimethoxyethoxysilane, and vinyl methoxydiethoxysilane; the hydrogen-containing alkoxysilane is selected from at least one of trimethoxysilane, triethoxysilane, dimethoxyethoxysilane, methoxydiethoxysilane, methyldimethoxysilane, methyldiethoxysilane, dimethylmethoxysilane, dimethylethoxysilane, and triisopropylsilane.

8. The preparation method according to claim 1, characterized in that: In step (S2), the phosphazene catalyst is selected from at least one of phosphazene chloride and phosphazene base; the amount of the phosphazene catalyst used is 1-20 ppm of the entire system.

9. The preparation method according to claim 1, characterized in that: In step (S2), the linear hydroxyl-terminated polydimethylsiloxane has a viscosity of 50 to 110 mm 2 / s, hydroxyl content of 1.2-3.8%; volatile matter ≤0.1%; the mass ratio of double-terminated alkoxy blocking agent and linear hydroxyl-terminated polydimethylsiloxane is 0.006-0.02:

1.

10. The preparation method according to claim 1, characterized in that: In step (S2), the linear hydroxyl-terminated polydimethylsiloxane is first dehydrated at 50-100° C., preferably 65-85° C., under vacuum conditions of -900 to -1000 mbar for 1-5 h; then, the nitrogen pressure is released at a pressure of -700 to -800 mbar, a double-terminal alkoxy end-capping agent is added, stirred, a phosphazene catalyst is added, and the pressure is evacuated to -100 to -1000 mbar, and the polymerization reaction is carried out at 50-120° C., preferably 65-85° C. for 2-4 h, and then a neutralizing agent of 1.5 to 2 times the amount of the catalyst is added under nitrogen pressure release, and the reaction is neutralized for 2-5 h. After the neutralization is completed, the reaction is dehydrated at -100 to -1000 mbar and 120-160° C. for 1-5 h; Furthermore, if the phosphazene catalyst is phosphazene chloride, the neutralizing agent is selected from at least one of silazane, triethylamine, propylamine, isooctylamine, and tetramethyldivinyldisilazane; if the phosphazene catalyst is phosphazene base, the neutralizing agent is selected from at least one of phosphoric acid and silicon alkoxide of phosphoric acid.

Images