A structure control agent, its preparation method and use

Abstract

The application provides a structure control agent and a preparation method and application thereof. The preparation method of the structure control agent comprises the following steps: mixing cyclosiloxane, a solvent and water, and reacting at 55-60 DEG C for 14-20 h under the catalysis of acid clay and hydrochloric acid. The preparation method provided by the application does not use controlled chemical raw materials, has mild reaction conditions, simple preparation process, and the obtained structure control agent is applied to a heat-vulcanized silicone rubber system, so that the prepared silicone rubber mixing rubber has good processing performance, excellent anti-structuring property, lower volatile content after vulcanization, hygiene and environmental protection, higher tear strength on the basis of excellent physical and mechanical properties, and can meet the requirements of some special products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of synthesis of heat vulcanized silicone rubber, and more particularly to a structure control agent, a preparation method and application thereof. BACKGROUND

[0002] Heat vulcanized silicone rubber is one of the important products of silicone materials. It is an elastomer formed by mixing high molecular weight linear polysiloxane, reinforcing fillers, various additives and vulcanizing agents, and then vulcanizing under heating and pressure. Generally speaking, the silicone rubber compound reinforced with white carbon black will become hard during storage, the plasticity decreases, and gradually loses the processability of remilling and molding. This phenomenon is called "structuralization" effect. The structure control agent is a mixing agent added to prevent and delay or reduce the structuralization tendency of silicone rubber. During the mixing of silicone rubber, the white carbon black is compressed and dispersed in the raw rubber, and the structure control agent added does not react with the raw rubber, but preferentially condenses with the active hydroxyl groups on the surface of the white carbon black, thereby inhibiting the structuralization between the white carbon black and the raw rubber molecules, and improving the remilling and processing performance of the silicone rubber.

[0003] In the field of heat vulcanized silicone rubber, the most widely used structure control agent is low viscosity hydroxyl silicone oil. In addition, silazane, diphenylsilanediol, and alkoxysilane hydrolysate are also used as structure control agents, but they all have the problems of single function and insufficient performance. Low viscosity hydroxyl terminated methyl vinyl silicone oil has a network structure formed by the active vinyl groups in the middle of the molecular chain, which not only has good anti-structuralization property, but also can effectively reduce the volatile matter of vulcanized silicone rubber, and can improve the tear resistance of heat vulcanized silicone rubber to some extent. It is a silicone rubber structuralization control agent with multiple functions.

[0004] At present, the preparation of low viscosity hydroxyl terminated methyl vinyl silicone oil has been reported. CN114316272A discloses a preparation method in which dimethyldichlorosilane and methyl vinyl dichlorosilane are used as raw materials, and a hydrolysis reaction is carried out in a hydrolysis medium to obtain a hydrolysate. After adjusting the hydrolysate to be neutral, dehydration treatment is carried out to obtain hydroxyl terminated methyl vinyl silicone oil. However, due to the large amount of hydrogen chloride generated during hydrolysis, the hydrolysis and condensation reactions are not easy to control, and a part of the linear polysiloxane will be self-polymerized into cyclosiloxane, and a mixture of hydroxyl terminated siloxane oligomers and cyclosiloxane is often obtained.

[0005] CN116376026A also discloses a preparation method using dimethyldichlorosilane and methylvinyl dichlorosilane as raw materials, which uses ammonia hydrolysis method to prepare low viscosity hydroxy vinyl silicone oil, which is essentially to replace pure water with NH4Cl-NH3 buffer solution to inhibit the formation of cyclosiloxane in the hydrolysis process. However, this method needs to strictly control the amount and flow rate of the raw materials to maintain a certain pH value and temperature, and the process is not easy to control in the production process, and the operation is relatively complex; and the ammonia water is very volatile due to the volatility of ammonia gas, and a large amount of smoke will be generated in the reaction container after contacting with chlorosilane in gaseous state, increasing the risk.

[0006] CN111690138A provides a low viscosity vinyl hydroxy silicone oil and a preparation method thereof, which uses methylcyclosiloxane, methylvinyl tetra ring body, acetic anhydride and catalyst concentrated sulfuric acid as raw materials, reacts at 130-165℃ to obtain acetoxy terminated intermediate product, then is added dropwise to aqueous alkali solution at 50-80℃ to carry out neutralization and hydrolysis reaction to obtain crude product, and finally the finished product is obtained after decolorization, filtration and devolatilization. This method is complex, a large amount of acetic anhydride, an easily controlled product, is needed, and a large amount of aqueous alkali solution is needed for neutralization and hydrolysis, which produces a large amount of waste water and waste gas, has high environmental protection treatment cost, and the catalyst concentrated sulfuric acid is easy to carbonize at high temperature, which affects the product quality. SUMMARY

[0007] The first object of the present application is to provide a preparation method of a structure control agent, which does not use controlled chemical raw materials, has mild reaction conditions, simple preparation process, and good processing performance of the prepared silicone rubber compound, excellent anti-structuring property, lower volatile content after vulcanization, good health and environmental protection, and further preferred higher tear strength to meet the requirements of some special products.

[0008] The preparation method of the structure control agent provided by the present application comprises the following steps:

[0009] The cyclosiloxane, solvent and water are mixed, and the reaction is carried out at 55-60℃ for 14-20h under the catalysis of acid clay and hydrochloric acid.

[0010] The applicant of the present application found that by using cationic ring-opening equilibrium method, using acid clay and hydrochloric acid as double catalysts, the cyclosiloxane, solvent and water were subjected to ring-opening equilibrium reaction at a certain temperature, low viscosity hydroxy terminated methyl vinyl silicone oil with high hydroxyl content and easy to control vinyl content could be successfully prepared, and the yield of the preparation method was high, and the low viscosity hydroxy terminated methyl vinyl silicone oil could be used as a structure control agent.

[0011] In one specific embodiment of the present invention, the cyclosiloxane can be a methylcyclosiloxane or a vinylcyclosiloxane known in the art. To further improve the performance of the obtained heat-cured silicone rubber, in a preferred embodiment of the present invention, the cyclosiloxane is hexamethylcyclotrisiloxane (D3) and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (D3). vi The mass ratio of hexamethylcyclotrisiloxane to 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane is further (80-96):(20-4).

[0012] In a specific embodiment of the present invention, commercially available hydrochloric acid can be used, and the concentration of hydrochloric acid can be 12 mol / L.

[0013] In a preferred embodiment of the present invention, in order to improve the performance of the obtained structure control agent, the mass ratio of cyclosiloxane, water, acid clay and hydrochloric acid is 100:(7-15):(8-20):(0.02-0.08), preferably 100:(9-12):(10-15):(0.04-0.06).

[0014] In specific embodiments of the present invention, the solvent can be a solvent that does not react with the raw materials. In a preferred embodiment of the present invention, the solvent is preferably tetrahydrofuran (THF). In a preferred embodiment of the present invention, the mass ratio of the solvent to the cyclosiloxane is (80-150):100, more preferably (100-130):100.

[0015] In a preferred embodiment of the present invention, the method for preparing the structure control agent provided by the present invention includes the following steps:

[0016] Hexamethylcyclotrisiloxane (D3) and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (D3) vi A mixture of tetrahydrofuran and water was reacted at 55–60 °C for 14–20 h under the catalysis of acidic clay and hydrochloric acid.

[0017] In a preferred embodiment of the present invention, in order to further improve tear resistance and reduce the volatile content of the vulcanized rubber, based on the good processing performance and excellent physical and mechanical properties of the silicone rubber compound, the reaction system contains, by weight, 100 parts of cyclosiloxane (of which, hexamethylcyclotrisiloxane (D3) 80-96 parts and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (D3)). vi) 20-4 parts, tetrahydrofuran 80-150 parts, water 7-15 parts, acid clay 8-20 parts and hydrochloric acid 0.02-0.08 parts. Further preferably, the cyclosiloxane 100 parts (wherein hexamethylcyclotrisiloxane (D3) 80-96 parts, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (D3 vi ) 20-4 parts, tetrahydrofuran 80-150 parts, water 7-15 parts, acid clay 8-20 parts and hydrochloric acid 0.02-0.08 parts. Further preferably, the cyclosiloxane 100 parts (wherein hexamethylcyclotrisiloxane (D3) 80-96 parts, 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (D3

[0018] In a preferred embodiment of the present application, the raw material of the structure control agent provided by the present application is composed of hexamethylcyclotrisiloxane (D3), 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (D3 vi ), tetrahydrofuran, water, acid clay and hydrochloric acid. That is, the structure control agent provided by the present application is prepared by the reaction of hexamethylcyclotrisiloxane (D3), 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (D3 vi ), tetrahydrofuran, water, acid clay and hydrochloric acid.

[0019] In a specific embodiment of the present application, after the reaction is completed, the solid is filtered off, the filtrate is subjected to distillation to recover the solvent, and the remaining oil phase is washed with water to neutral; the oil layer after water washing is subjected to low-boiling removal under reduced pressure at 85°C, and finally subjected to activated carbon adsorption treatment to obtain colorless transparent low-viscosity hydroxyl-terminated methylvinyl silicone oil, i.e. the structure control agent.

[0020] The structure control agent obtained by the present application has a viscosity of 20-40 mm 2 / s at 25°C, a hydroxyl content of 6-10 wt%, and a vinyl content of 1-6 wt%.

[0021] Another object of the present application is to provide the structure control agent obtained by the above preparation method.

[0022] The structure control agent obtained by the present application has obvious advantages when applied to a heat vulcanized silicone rubber system.

[0023] The structure control agent obtained by the present application is preferably a silicone rubber structure control agent.

[0024] That is, a further object of the present application is the use of the above preparation method or the structure control agent obtained by the above preparation method in the preparation of heat vulcanized silicone rubber.

[0025] In the specific embodiments of the present application, the formula of the heat-vulcanized silicone rubber can be the formula of the heat-vulcanized silicone rubber commonly used in the art, and in the specific embodiments of the present application, the heat-vulcanized silicone rubber prepared by using methyl vinyl silicone rubber gum can be selected. The heat-vulcanized silicone rubber can further include white carbon black, zinc stearate, and the above-mentioned structure control agent. The amount of the structure control agent added can be 3% to 5% of the methyl vinyl silicone rubber gum. In the preferred embodiments of the present application, the structure control agent provided by the present application and the low-viscosity hydroxyl silicone oil can be used in combination, i.e., the structure control agent provided by the present application and the low-viscosity hydroxyl silicone oil are compounded and used as a silicone rubber structure control agent in the preparation of the heat-vulcanized silicone rubber. In the alternative embodiments, the mass ratio of the structure control agent provided by the present application and the low-viscosity hydroxyl silicone oil can be the ratio commonly used in the art, such as 5:1 to 1:5, etc. The low-viscosity hydroxyl silicone oil can be the commercially available hydroxyl silicone oil with low viscosity and high hydroxyl content in the art, such as the hydroxyl silicone oil with viscosity (25°C) ≤40 mm 2 / s and hydroxyl content ≥6%.

[0026] The present application has the following advantages:

[0027] 1) The preparation method of the structure control agent provided by the present application does not use controlled chemical raw materials, the reaction conditions are mild, the preparation process is simple, the solvent can be recycled, the operation is easy to control, the equipment investment is small, and it is conducive to large-scale production.

[0028] 2) The structure control agent prepared by the present application has obvious advantages when applied to the heat-vulcanized silicone rubber system. The silicone rubber compound prepared therefrom has good processing performance and excellent anti-structuralization property. At the same time, the volatile content of the obtained compound after vulcanization is lower, which is hygienic and environmentally friendly. In the more preferred scheme, the compound has higher tear strength while meeting the excellent physical and mechanical properties. The structure control agent provided by the present application can be used alone or in combination with the low-viscosity hydroxyl silicone oil. DETAILED DESCRIPTION

[0029] The specific embodiments of the present application will be further described in detail below in conjunction with the examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0030] The specific conditions not specified in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained by purchase. Hydrochloric acid is commercially available hydrochloric acid with a concentration of 12 mol / L.

[0031] In the present application, the weight parts can be μg, mg, g, kg and other weight units known in the art, and can also be multiples thereof, such as 1 / 10, 1 / 100, 10 times, 100 times, etc. In the present application, the amount of each substance is determined according to the above-mentioned proportions, and the total mass of the substances can be less than 100 mass parts, can be greater than 100 mass parts, as long as it is within the above-mentioned proportion value.

[0032] Example 1

[0033] A 5L three-necked flask equipped with a reflux condenser was charged with 915g D3, 85g D3 Vi , 1100g THF, 120g acid clay, 0.5g hydrochloric acid and 100g water, and stirred at 55-60°C for 16h; after cooling, the filtrate was distilled under reduced pressure to recover THF at 45°C, and then the oil phase was transferred to a separatory funnel and washed with water until neutral; the oil layer after water washing was dehydrated at 85°C / -0.092MPa to remove low boiling point substances, and finally treated with activated carbon to obtain a colorless transparent oil product.

[0034] The oil product obtained was characterized by 1 H-NMR, and the results were as follows:

[0035] 1 H-NMR (DMSO-d6, 500MHz), δ (ppm): -0.06-0.17 (m, 3H, ≡Si-CH3), 5.75-6.03 (m, 3H, ≡Si-CH=CH2), 6.18 (s, 1H, ≡Si-OH).

[0036] Thus, the target product, hydroxyl-terminated methyl vinyl silicone oil, was obtained in Example 1, and its performance was tested, and the results are shown in Table 1.

[0037] Example 2

[0038] A 5L three-necked flask equipped with a reflux condenser was charged with 930g D3, 70g D3 Vi , 1300g THF, 140g acid clay, 0.4g hydrochloric acid and 110g water, and stirred at 55-60°C for 16h; the remaining steps were the same as in Example 1.

[0039] The oil product obtained was characterized by 1 H-NMR, and the results were as follows:

[0040] Example 3

[0041] A 5L three-necked flask equipped with a reflux condenser was charged with 900g D3, 100g D3, 1200g THF, 130g acid clay, 0.6g hydrochloric acid and 90g water, and stirred at 55-60°C for 14h; the remaining steps were the same as in Example 1. Vi A 5L three-necked flask equipped with a reflux condenser was charged with 900g D3, 100g D3, 1200g THF, 130g acid clay, 0.6g hydrochloric acid and 90g water, and stirred at 55-60°C for 14h; the remaining steps were the same as in Example 1.

[0042] The product was characterized by H-NMR, and the hydrogen spectrum was substantially the same as in Example 1, indicating that the product obtained was a hydroxyl-terminated methyl vinyl silicone oil. The product was tested for related properties, and the results are shown in Table 1. 1 The product was characterized by H-NMR, and the hydrogen spectrum was substantially the same as in Example 1, indicating that the product obtained was a hydroxyl-terminated methyl vinyl silicone oil. The product was tested for related properties, and the results are shown in Table 1.

[0043] Example 4

[0044] A 5L three-necked flask equipped with a reflux condenser was charged with 960g D3, 40g D3, 1000g THF, 100g acid clay, 0.4g hydrochloric acid and 90g water, and stirred at 55-60°C for 16h; the remaining steps were the same as in Example 1. Vi A 5L three-necked flask equipped with a reflux condenser was charged with 960g D3, 40g D3, 1000g THF, 100g acid clay, 0.4g hydrochloric acid and 90g water, and stirred at 55-60°C for 16h; the remaining steps were the same as in Example 1.

[0045] The product was characterized by H-NMR, and the hydrogen spectrum was substantially the same as in Example 1, indicating that the product obtained was a hydroxyl-terminated methyl vinyl silicone oil. The product was tested for related properties, and the results are shown in Table 1. 1 The product was characterized by H-NMR, and the hydrogen spectrum was substantially the same as in Example 1, indicating that the product obtained was a hydroxyl-terminated methyl vinyl silicone oil. The product was tested for related properties, and the results are shown in Table 1.

[0046] Example 5

[0047] A 5L three-necked flask equipped with a reflux condenser was charged with 960g D3, 40g D3, 1000g THF, 100g acid clay, 0.4g hydrochloric acid and 90g water, and stirred at 55-60°C for 16h; the remaining steps were the same as in Example 1. Vi A 5L three-necked flask equipped with a reflux condenser was charged with 960g D3, 40g D3, 1000g THF, 100g acid clay, 0.4g hydrochloric acid and 90g water, and stirred at 55-60°C for 16h; the remaining steps were the same as in Example 1.

[0048] The product was characterized by H-NMR, and the hydrogen spectrum was substantially the same as in Example 1, indicating that the product obtained was a hydroxyl-terminated methyl vinyl silicone oil. The product was tested for related properties, and the results are shown in Table 1. 1 The product was characterized by H-NMR, and the hydrogen spectrum was substantially the same as in Example 1, indicating that the product obtained was a hydroxyl-terminated methyl vinyl silicone oil. The product was tested for related properties, and the results are shown in Table 1.

[0049] Example 6

[0050] A 5L three-necked flask equipped with a reflux condenser was charged with 960g D3, 40g D3, 1000g THF, 100g acid clay, 0.4g hydrochloric acid and 90g water, and stirred at 55-60°C for 16h; the remaining steps were the same as in Example 1. Vi A 5L three-necked flask equipped with a reflux condenser was charged with 960g D3, 40g D3, 1000g THF, 100g acid clay, 0.4g hydrochloric acid and 90g water, and stirred at 55-60°C for 16h; the remaining steps were the same as in Example 1.

[0051] The product was characterized by H-NMR, and the hydrogen spectrum was substantially the same as in Example 1, indicating that the product obtained was a hydroxyl-terminated methyl vinyl silicone oil. The product was tested for related properties, and the results are shown in Table 1. 1The product was characterized by 1H-NMR, and the 1H NMR results were basically the same as those in Example 1, indicating that the product was hydroxyl-terminated methyl vinyl silicone oil. Related tests were performed, and the results are shown in Table 1.

[0052] Example 7

[0053] Add 800g D3 and 200g D3 to a 5L three-necked flask equipped with a reflux condenser. Vi 1500g THF, 200g acidic clay, 0.8g hydrochloric acid and 150g water were stirred and reacted at 55-60℃ for 20h; the remaining steps were the same as in Example 1.

[0054] use 1 The product was characterized by 1H-NMR, and the 1H NMR results were basically the same as those in Example 1, indicating that the product was hydroxyl-terminated methyl vinyl silicone oil. Related tests were performed, and the results are shown in Table 1.

[0055] Table 1. Performance of hydroxyl-terminated methyl vinyl silicone oils obtained in the examples.

[0056]

[0057] The viscosity of the silicone oil was tested according to GB / T 10247-2008 at a test temperature of 25℃. The hydroxyl content was determined using the lithium aluminum hydride method. The vinyl content was determined using a modified iodometric method, employing a trifluorotrichloroethane-butyl acetate solvent system, with the reaction mechanism being the same as the iodometric method. Yield = (Product mass / Cyclosiloxane mass) × 100%.

[0058] Experimental Example

[0059] The silicone oils prepared in Examples 1-7 were used to verify the silicone rubber compound, and the resulting rubber compounds were tested. A commercially available low-viscosity hydroxyl silicone oil (viscosity 28 mmHg at 25°C) was selected (purchased from Wuxi Quanli Technology Co., Ltd.). 2 The rubber compound was prepared using a rubber compound with a hydroxyl content of 8.5% ( / s) as a comparative example. The specific steps are as follows:

[0060] By weight, 75 parts of vinyl with a molar content of 0.12% and a molecular weight of 60 × 10⁻⁶ were used. 4 A g / mol methyl vinyl silicone rubber raw material, with a vinyl molar content of 0.23% and a molecular weight of 72 × 10⁻⁶ g / mol, is obtained from 25 parts of the raw material. 4 45 parts of methyl vinyl silicone rubber raw material with a specific surface area of ​​130 m² / mol g / mol 2 / g of precipitated silica, 0.1 parts of zinc stearate and 3.4 parts of structure control agent are added to a kneader and mixed in an intensive kneader. The silica is added in batches and multiple times. After kneading into a ball and vacuum heat treatment at 150℃, the compound is obtained.

[0061] After standing overnight, 100 parts of the mixed rubber was wrapped on the roll of an open mill, 1 part of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane was added, and after 3-5 times of thin passing, it was vulcanized and formed on a flat vulcanizing machine, the first stage vulcanization condition was 170℃×10min, the second stage vulcanization condition was 200℃×4h, and then the performance after vulcanization was determined according to GB / T 528-2009, GB / T 529-2008, GB / T 531.1-2008 and other national standards. For the anti-structuring effect test, 200g of the prepared mixed rubber was placed in a constant temperature drying oven at 200℃ for 2.5h, and after cooling, it was re-mixed in an open mill with a roll spacing of 3mm, and the number of rolls required for the rubber to reach a smooth and hair-free state was recorded, that is, the re-mixing number of the mixed rubber. The lower the re-mixing number, the better the anti-structuring effect of the silicone rubber. For the test of volatile matter of the mixed rubber, the test was carried out according to the 2022 version of “Determination of volatile organic compounds in silicone products” (Bestimmung von flüchtigen Verbindungen in Silikon) prepared by the Federal Institute for Risk Evaluation of Germany.

[0062] The performance results of the obtained mixed rubber are shown in Table 2. Among them, application examples 1-7 correspond to using the product provided in examples 1-7 as a structure control agent. The structure control agent used in application example 8 is a mixture, that is, a low viscosity hydroxyl silicone oil (viscosity at 25℃ is 28mm 2 / s, hydroxyl content is 8.5%) commercially available (purchased from Wuxi Quanli Technology Co., Ltd.): product provided in example 1 = 1:1 (mass ratio) to be compounded, and the structure control agent used in comparative example 1 is a low viscosity hydroxyl silicone oil (viscosity at 25℃ is 28mm 2 / s, hydroxyl content is 8.5%) commercially available (purchased from Wuxi Quanli Technology Co., Ltd.).

[0063] Table 2 Test results of silicone rubber performance

[0064]

[0065] The structure control agent provided by the application is very effective when applied to a heat vulcanized silicone rubber system. As can be seen from Table 2, compared with the comparative example, the mixed rubber prepared in application examples 1-8 not only has good anti-structuring effect, but also has higher tear resistance on the basis of meeting excellent physical and mechanical properties, and has lower volatile matter, is sanitary and environmentally friendly, and can meet the needs of some special products, such as silicone rubber products such as pipes, sheets and rings used for contact with food, thereby widening the application range of silicone rubber. In addition, the structure control agent provided by the application can be used alone or in combination with a low viscosity hydroxyl silicone oil.

[0066] ​Finally, the method of the present application is only a preferred embodiment, and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a structure control agent, characterized by, It comprises the following steps: mixing cyclosiloxane, solvent and water, reacting at 55-60℃ for 14-20h under the catalysis of acid clay and hydrochloric acid; the cyclosiloxane is hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane; the mass ratio of the hexamethylcyclotrisiloxane and 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane is (80-96):(20-4); the mass ratio of the cyclosiloxane, water, acid clay and hydrochloric acid is 100:(7-15); (8～20)：(0.02～0.08)。 2. The production method according to claim 1, characterized by, the mass ratio of the cyclosiloxane, water, acid clay and hydrochloric acid is 100:(9-12):(10-15):(0.04-0.06).

3. The preparation method according to claim 1, characterized in that, the solvent is tetrahydrofuran.

4. The production method according to claim 3, characterized by, the mass ratio of the solvent and the cyclosiloxane is (80-150):

100.

5. The production method according to claim 4, characterized by, the mass ratio of the solvent and the cyclosiloxane is (100-130):

100.

6. The production method according to any one of claims 1 to 5, characterized by, It further comprises: after the reaction, filtering off the solid, distilling the filtrate to recover the solvent, and washing the remaining oil phase with water to neutral; washing the oil layer with water at 85℃ under reduced pressure to remove low-boiling substances, and finally treating with activated carbon adsorption to obtain colorless transparent low-viscosity hydroxyl-terminated methyl vinyl silicone oil, i.e. the structure control agent.

7. The structure control agent obtained by the preparation method in any one of claims 1 to 6.

8. The use of the structure control agent in claim 7 in the preparation of heat vulcanized silicone rubber.

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