Preparation method of vinyl silicone oil with medium and low viscosity and low hydroxyl content

Abstract

The invention belongs to the field of organic silicon silicone oil, and particularly relates to a preparation method of vinyl silicone oil with medium and low viscosity and low hydroxyl content. According to the specific technical scheme, the method comprises the following steps: (1) dehydrating a raw material linear body and a viscosity control agent; (2) preparing an acidic resin loaded linear phosphazene catalyst; (3) adding the acidic resin loaded linear phosphazene catalyst, and reacting under vacuum and nitrogen bubbling conditions; (4) then adding an end-capping reagent for continuous reaction; and (5) after the reaction is finished, filtering the catalyst, and removing low molecules to finally obtain the vinyl silicone oil with medium and low viscosity and low hydroxyl content. The method is simple in process, does not need neutralization operation, does not introduce other impurities into the silicone oil, and the prepared silicone oil is excellent in quality; the catalyst can be repeatedly used, so that the production cost is reduced. The product obtained by the method disclosed by the invention is high in yield and low in volatile component, has higher vinyl retention rate and lower silicon hydroxyl content, and is suitable for being applied to downstream high-end products.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of silicone oils, and particularly relates to a preparation method of a low-hydroxyl-content vinyl silicone oil with medium or low viscosity. BACKGROUND

[0002] Vinyl silicone oil generally refers to a compound with vinyl (-CH=CH2) at the end or side chain of polydimethylsiloxane, which can form a three-dimensional network structure through silicane hydrogen addition or peroxide initiation crosslinking polymerization, and thus plays a particularly key role in the continuous demand for high-performance polymer materials. Vinyl silicone oil is used as a main raw material in downstream fields such as addition type liquid silicone rubber, high temperature vulcanized silicone rubber, silicone release agent, and daily chemical emulsion. For example, addition type liquid silicone rubber (LSR) can be applied to electronic potting adhesive, medical devices and other scenarios, and has excellent weather resistance and precise molding property.

[0003] At present, the method for producing vinyl silicone oil in the industry is generally to use cyclosiloxane as a raw material, tetramethyldivinyl disiloxane as an end-capping agent, and to carry out ring-opening polymerization and equilibrium reaction under the action of a catalyst to obtain a polymerization intermediate with a specific viscosity. The polymerization intermediate is a mixture composed of a siloxane ring body (content 12-15%) and a vinyl end-capped polydimethylsiloxane (content 85-88%), and after the activity of the catalyst is terminated, low molecules are removed by a thin film evaporator, so that the vinyl silicone oil with the target viscosity can be obtained. This method has problems of low production efficiency, low yield and high energy consumption, and most of the catalysts need to be neutralized or treated at high temperature to break the medium, which on the one hand introduces other element impurities into the silicone oil, and on the other hand may cause residual odor of the silicone oil, affecting the product quality.

[0004] CN103333338A discloses a synthesis method of vinyl silicone oil, which uses methylcyclosiloxane, methylvinylcyclosiloxane and a vinyl end-capping agent as raw materials, and carries out polymerization catalyzed by an alkali metal hydroxide. After the polymerization reaction is completed, cooling, dilute acid neutralization, water washing, separation and rectification to remove low-boiling substances are carried out to obtain the vinyl silicone oil. This method has complicated steps and low production efficiency; in addition, water washing also increases the content of silicon hydroxyl groups in the vinyl silicone oil, affecting the product quality and downstream application. For example, when high-silicon hydroxyl content vinyl silicone oil is mixed with silica to prepare addition type liquid silicone rubber, the stability of the base glue decreases, the viscosity increases at room temperature, and the plasticity decreases, which affects subsequent processing and product performance.

[0005] CN113698606A discloses a synthesis method of a low-ring-body-content vinyl silicone oil, which uses dimethylsiloxane ring body and tetramethyldivinyl disiloxane as raw materials to synthesize the vinyl silicone oil, and adds a polymerization inhibitor before low-molecular removal, and obtains the vinyl silicone oil with a ring body content of 0.15% or less after high-temperature low-molecular removal.

[0006] CN118994583A discloses a preparation method of vinyl silicone oil, which prepares an alkaline catalyst under vacuum conditions, mixes dimethylsiloxane ring body, alkaline catalyst and vinyl end-capping agent for reaction, then adds silicon hydroxyl control agent for continuous reaction, removes catalyst, and then removes low molecular under dry dehydrated gas and vacuum conditions to obtain vinyl silicone oil with low silicon hydroxyl content.

[0007] Another common process is to use linear body siloxane as raw material to obtain target product through condensation-rearrangement equilibrium reaction. This process needs to first carry out condensation reaction of silicon hydroxyl, and then carry out secondary depolymerization rearrangement equilibrium reaction in the presence of vinyl end-capping agent, to finally obtain vinyl polysiloxane intermediate, and obtain target viscosity vinyl silicone oil after removing a small amount of low molecular. However, this process has high requirements for process conditions. A large amount of water is generated in the condensation reaction of silicon hydroxyl. On the one hand, the presence of water will affect the rightward progress of polymerization reaction, and dehydrating treatment needs to be added in the process. On the other hand, the water in the reaction system will affect the quality of the final product, so it is necessary to completely remove the water as much as possible. In addition, the condensation of silicon hydroxyl cannot proceed to the right indefinitely. If the dehydration condensation degree of linear body is too high, hydroxyl gum will be formed, which not only easily damages the stirring motor, but also adversely affects the subsequent rearrangement reaction.

[0008] CN117777452A discloses a method for preparing medium and low viscosity vinyl silicone oil from linear body siloxane. First, the linear body is dehydrated, then the end-capping agent and linear phosphazene catalyst are added and reacted for several hours under nitrogen atmosphere, and finally the terminating agent is added to terminate the reaction, and then the low molecular removal treatment is carried out to obtain medium and low viscosity vinyl silicone oil. This method does not vacuum during the condensation reaction, rearrangement reaction and termination reaction, and only dehydrates by passing nitrogen. This method cannot completely remove the water in the system, which not only affects the catalytic activity, but also causes the prepared vinyl silicone oil to have high silicon hydroxyl content and low vinyl content, affecting the use of downstream products.

[0009] CN118955911A discloses a method for preparing medium and high viscosity vinyl silicone oil from linear body siloxane. Linear body, end-capping agent and linear phosphazene catalyst are added to the dehydrated linear body, and reacted under vacuum conditions. After the reaction is completed, potassium hydroxide is added for gum reduction and neutralization. This method uses low viscosity vinyl silicone oil as end-capping agent, which can reduce the loss of end-capping agent during vacuuming, but increases the production cost. In addition, the one-step method has strict requirements for catalytic activity, and it is difficult to remove hydroxyl in the system with high viscosity. The final medium and high viscosity silicone oil product may contain high silicon hydroxyl.

[0010] In view of the shortcomings of the above methods, a method for preparing vinyl silicone oil with simple process and higher efficiency is needed, which can not only improve the product yield and vinyl retention rate, but also greatly reduce the production cost and improve the production efficiency. Summary of the Invention

[0011] To address the above technical problems, the present invention aims to provide a method for preparing a medium-to-low viscosity vinyl silicone oil with low hydroxyl content. The vinyl silicone oil prepared by this method has low silanol content, high vinyl retention rate, high yield, and low cyclic content. It requires no neutralization operation, does not introduce other impurities into the silicone oil, produces high-quality silicone oil, and the catalyst can be reused, resulting in low cost and a simple process.

[0012] According to one aspect of the present invention, a method for preparing a medium-to-low viscosity vinyl silicone oil with low hydroxyl content is provided, the specific technical solution including the following steps: Step 1: Dehydrate the linear body and viscosity control agent under vacuum at 50~70℃ for 0.5~2 h, and set aside after dehydration; Step 2: Linear phosphazene, acidic resin, and organic solvent are placed in a three-necked flask and refluxed with stirring. After the reaction is complete, the mixture is filtered to obtain modified acidic resin. The modified acidic resin is then placed in a vacuum drying oven and heat-treated under vacuum conditions to finally obtain an acidic resin-supported linear phosphazene catalyst.

[0013] Step 3: Add the acidic resin-supported linear phosphazene catalyst described in Step 2 to the raw materials described in Step 1, and polymerize for 1-4 hours under vacuum and nitrogen bubbling conditions to obtain vinyl polydimethylsiloxane intermediate. Step 4: Add the end-capping agent to the vinyl polydimethylsiloxane intermediate described in Step 3 in a certain proportion, react at normal pressure for 0.5-2 h, and then react under vacuum and nitrogen bubbling conditions for 1-4 h. After the reaction is completed, filter to remove the catalyst and remove low molecular weight molecules to obtain a medium-low viscosity vinyl silicone oil with low hydroxyl content.

[0014] As a preferred embodiment of the above technical solution, the linear body described in step one is hydroxyl-terminated polydimethylsiloxane with a viscosity of 50~200 cP, preferably 70~130 cP.

[0015] Preferably, the viscosity control agent is a vinyl silicone oil with a viscosity of 10-200 cP, more preferably 20-100 cP.

[0016] Preferably, the raw materials for preparation are, by weight, 100 parts of the linear body, 0.2-3 parts of the viscosity control agent, 0.1-5 parts of the end-capping agent, and 0.1-1 parts of the acidic resin-supported linear phosphazene catalyst.

[0017] Preferably, in step two, the organic solvent includes at least one of n-heptane, cyclohexane, toluene, xylene, tetrachloroethane, N,N-dimethylformamide, tetrahydrofuran, and chloroform.

[0018] Preferably, in step two, the acidic resin is a cation exchange resin, such as any one of Amberlite IRC120, Amberlite SR1L, Dowex 50WX8-200, Diaion PK212, Lewatit S-100, NKC-9, and SXC-9.

[0019] Preferably, in step two, the reflux reaction temperature is 60~140℃ and the reaction time is 5~8 h.

[0020] Preferably, in step two, the vacuum heat treatment temperature is 80~150℃ and the vacuum heat treatment time is 1~3h.

[0021] Preferably, in steps three and four, the reaction temperature is 60~120℃, more preferably 70-100℃, and the vacuum degree is maintained at -85~-95 KPa under vacuum and nitrogen bubbling conditions.

[0022] Preferably, in steps three and four, the specific operation method for vacuuming and nitrogen bubbling is to fully open the vacuum valve at the top of the reactor and introduce a small amount of nitrogen gas for bubbling at the bottom. The nitrogen flow rate for nitrogen bubbling at the bottom of the reactor is 0.5~4 m³ / s. 3 / h / m 3 The reactor is preferably 0.8~2 m. 3 / h / m 3 The reactor is preferably 1 to 1.5 m in size. 3 / h / m 3 Reactor.

[0023] Preferably, after the reaction is completed, the medium-low viscosity, low hydroxyl content vinyl silicone oil does not require the addition of a neutralizing agent. Instead, it can be obtained by simply filtering to recover the catalyst and remove low molecular weight molecules to obtain vinyl silicone oil with qualified volatile content.

[0024] Preferably, the volatile matter content of the medium-low viscosity, low hydroxyl content vinyl silicone oil is 0.1-2%, more preferably 0.1-1%, and even more preferably 0.1-0.5%.

[0025] Preferably, the relative value of the silanol content of the medium-low viscosity, low-hydroxyl content vinyl silicone oil is 1.000~1.100, more preferably 1.000~1.030.

[0026] The viscosity range of the low hydroxyl content vinyl silicone oil described above is 10~5000 cP, preferably 20~1000 cP, and more preferably 50-400 cP.

[0027] The technical method of the present invention has the following beneficial effects: 1. The process technology of this invention is simple and efficient. In traditional ring-opening polymerization processes using siloxane cyclic compounds as raw materials, the conversion rate of polymerization intermediates is <88%, a large number of cyclic compounds are present, the yield is low, and catalyst residues or other elemental impurities are easily introduced after neutralization. This invention uses linear compounds as raw materials and linear phosphazenes supported on acidic resins as catalysts. After condensation-rearrangement reactions, the conversion rate of the obtained polymerization intermediates is >99%. Only simple removal of low molecular weight molecules is needed to obtain vinyl silicone oil with low volatile content.

[0028] 2. The method of this invention has low energy consumption and is more economical and environmentally friendly. The polymerization process of this invention has a lower temperature, a milder reaction, and a shorter reaction time, effectively reducing energy consumption. At the same time, the catalyst can be reused, further reducing production costs and meeting environmental and economic requirements.

[0029] 3. The vinyl silicone oil prepared by the process technology of this invention has excellent quality. Using linear polymers as raw materials and combining them with an acidic resin-supported linear phosphazene catalyst, the reaction is carried out using a combination of vacuuming and nitrogen bubbling techniques. The final silicone oil product has low volatile content, high vinyl retention rate, and significantly reduced relative silanol content, making it suitable for the production of downstream products such as liquid adhesives and release agents that require high-quality vinyl silicone oil. Detailed Implementation

[0030] The present invention will be further explained below with reference to the embodiments, but the embodiments should not be construed as limiting the present invention in any way.

[0031] Relative value test method of silanol group Add 50 g of vinyl silicone oil to a container, accurately weigh and add 3 g of tetraethyl orthosilicate and 1.5 g of dibutyltin dilaurate. Stir the mixture rapidly for 2 min. After stirring, cover and let stand for 2 min, then test its viscosity. Continue to let it stand for 4 h, then test its viscosity again. Divide the two viscosity values ​​to obtain the relative value of silanol groups in the vinyl silicone oil. The smaller the relative value of silanol groups, the lower the silanol content of the silicone oil.

[0032] Example 1 Preparation of linear phosphazene catalyst supported on acidic resin: 97.2 g of acidic resin AmberliteIRC120, 97 g of linear phosphazene, and 248.5 g of n-heptane were added to a 1 L three-necked flask and refluxed at 100 °C for 6 h. After the reaction was completed, the mixture was cooled and filtered to obtain modified acidic resin. Subsequently, it was placed in a vacuum drying oven and heat-treated at 120 °C under vacuum for 3 h to finally obtain the linear phosphazene catalyst supported on acidic resin.

[0033] 1000 g of a linear polymer with a viscosity of 112 cP and 4.5 g of viscosity control agent (51 cP vinyl silicone oil) were heated to 55°C and dehydrated under vacuum stirring for 1 h. After dehydration, 5 g of the above-mentioned acidic resin-supported linear phosphazene catalyst was added, and the mixture was stirred and heated to 80°C under vacuum and nitrogen bubbling conditions (nitrogen flow rate 0.8 m). 3 / h / m 3 (Reactor). After 2 hours, the vacuum was removed and nitrogen bubbling was stopped. 19 g of the end-capping agent, divinyldisiloxane, was added. The reaction was carried out at atmospheric pressure for 1 hour, followed by heating to 100°C and reacting under vacuum and nitrogen bubbling conditions for 3 hours. After the reaction, the conversion rate was measured to be 99.28%. The catalyst was removed by filtration, and the low molecular weight molecules were removed to obtain the final product. Its volatile matter content was 0.14%, viscosity was 332 cP, vinyl content was 0.558%, and relative silanol content was 1.010.

[0034] Example 2 The preparation of the acid resin-supported linear phosphazene catalyst was the same as in Example 1, except that AmberliteIRC120 was replaced with Dowex50WX8-200.

[0035] 1000 g of a linear polymer with a viscosity of 112 cP and 3 g of viscosity control agent (49 cP vinyl silicone oil) were heated to 55°C, and then vacuum stirred for dehydration for 1 h. After dehydration, 4.3 g of acidic resin-supported linear phosphazene catalyst was added, and the mixture was stirred and heated to 80°C under vacuum and nitrogen bubbling conditions (nitrogen flow rate 1.0 m). 3 / h / m 3 (Reactor). After 2 hours, the vacuum was removed and nitrogen bubbling was stopped. 17.9 g of the end-capping agent, divinyldisiloxane, was added and reacted at atmospheric pressure for 1 hour. Then, the temperature was raised to 100°C and reacted for 4 hours under vacuum and nitrogen bubbling conditions. After the reaction, the conversion rate was measured to be 99.31%. The catalyst was removed by filtration, and the low molecular weight molecules were removed to obtain the final product. Its volatile matter content was 0.16%, viscosity was 306 cP, vinyl content was 0.487%, and relative silanol content was 1.015.

[0036] Example 3 The preparation of the acidic resin-supported linear phosphazene catalyst was the same as in Example 1, except that AmberliteIRC120 was replaced with DiaionPK212.

[0037] 1000 g of a linear polymer with a viscosity of 112 cP and 10 g of viscosity control agent (51 cP vinyl silicone oil) were heated to 55°C, and then vacuum stirred and dehydrated for 1 h. After dehydration, 6.1 g of acidic resin-supported linear phosphazene catalyst was added, and the mixture was stirred and heated to 70°C under vacuum and nitrogen bubbling conditions (nitrogen flow rate 0.8 m). 3 / h / m 3 (Reactor). After 2 hours, the vacuum was removed and nitrogen bubbling was stopped. 27 g of the end-capping agent, divinyldisiloxane, was added and reacted at atmospheric pressure for 1 hour. Then, the temperature was raised to 90°C and reacted for 3 hours under vacuum and nitrogen bubbling conditions. After the reaction, the conversion rate was measured to be 99.31%. The catalyst was removed by filtration, and the low molecular weight molecules were removed to obtain the final product. Its volatile matter content was 0.12%, the viscosity was 110 cP, the vinyl content was 1.051%, and the relative value of silanol was 1.012.

[0038] Example 4 The preparation of the acid resin-supported linear phosphazene catalyst was the same as in Example 1, except that AmberliteIRC120 was replaced with LewatitS-100.

[0039] 1500 g of a linear polymer with a viscosity of 112 cP and 15 g of viscosity control agent (98 cP vinyl silicone oil) were heated to 55°C, and then vacuum stirred and dehydrated for 1 h. After dehydration, 7 g of acidic resin-supported linear phosphazene catalyst was added, and the mixture was stirred and heated to 80°C under vacuum and nitrogen bubbling conditions (nitrogen flow rate 1.2 m). 3 / h / m 3 (Reactor). After 2 hours, the vacuum was removed and nitrogen bubbling was stopped. 43.5 g of the end-capping agent, divinyldisiloxane, was added and reacted at atmospheric pressure for 1 hour. Subsequently, the temperature was raised to 90°C, and the reaction was carried out under vacuum and nitrogen bubbling for 4 hours. After the reaction, the conversion rate was measured to be 98.91%. The catalyst was removed by filtration, and after the removal of low molecular weight molecules, the final product was obtained. Its volatile matter content was 0.13%, viscosity was 73 cP, vinyl content was 1.153%, and relative silanol content was 1.007.

[0040] Example 5 The preparation of the linear phosphazene catalyst supported on the acidic resin is the same as in Example 1.

[0041] 1500 g of a linear polymer with a viscosity of 112 cP and 15 g of viscosity control agent (98 cP vinyl silicone oil) were heated to 55 °C, and then vacuum stirred for dehydration for 1 h. After dehydration, 7.9 g of acidic resin-supported linear phosphazene catalyst was added, and the mixture was stirred and heated to 70 °C under vacuum and nitrogen bubbling conditions (nitrogen flow rate 1.2 m). 3 / h / m 3(Reactor). After 2 hours, the vacuum was removed and nitrogen bubbling was stopped. 26.5 g of the end-capping agent, divinyldisiloxane, was added and reacted at atmospheric pressure for 1 hour. Subsequently, the temperature was raised to 90°C, and the reaction was carried out under vacuum and nitrogen bubbling for 4 hours. After the reaction, the conversion rate was measured to be 99.37%. The catalyst was removed by filtration, and after the removal of low molecular weight molecules, the final product was obtained. Its volatile matter content was 0.19%, viscosity was 351 cP, vinyl content was 0.545%, and relative silanol content was 1.015.

[0042] Example 6 The preparation of the linear phosphazene catalyst supported on the acidic resin is the same as in Example 1.

[0043] 2000 g of a linear polymer with a viscosity of 155 cP and 5 g of viscosity control agent (22 cP vinyl silicone oil) were heated to 55°C, and then vacuum stirred and dehydrated for 1 h. After dehydration, 5.6 g of acidic resin-supported linear phosphazene catalyst was added, and the mixture was stirred and heated to 80°C under vacuum and nitrogen bubbling conditions (nitrogen flow rate 1.5 m). 3 / h / m 3 (Reactor). After 2 hours, the vacuum was removed and nitrogen bubbling was stopped. 7.7 g of the end-capping agent, divinyldisiloxane, was added, and the reaction was carried out at atmospheric pressure for 0.5 hours. Subsequently, the temperature was raised to 100℃, and the reaction was carried out under vacuum and nitrogen bubbling conditions for 4 hours. After the reaction, the conversion rate was measured to be 99.40%. The catalyst was removed by filtration, and after the removal of low molecular weight molecules, the final product was obtained. Its volatile matter content was 0.17%, viscosity was 381 cP, vinyl content was 0.181%, and relative silanol content was 1.044.

[0044] Comparative Example 1 The reaction was carried out according to Example 1, except that only a vacuum was drawn during the reaction and nitrogen bubbling was not performed. After the reaction, a polymerization intermediate was obtained, and its conversion rate was tested to be 97.84% and its viscosity was 275 cP. After desaturation, the product was obtained, and its volatile matter content was tested to be 0.44%, its viscosity was 297 cp, its vinyl content was 0.550%, and its relative silanol content was 1.129.

[0045] Comparative Example 2 The reaction was carried out according to Example 1, except that no vacuum was applied during the reaction, and only nitrogen bubbling was performed (nitrogen flow rate was 1.8 m³ / s). 3 / h / m 3 (Reactor). After the reaction, a polymerization intermediate was obtained, with a conversion rate of 96.83% and a viscosity of 264 cP. After desaturation, the product was obtained, with a volatile content of 0.53%, a viscosity of 304 cP, a vinyl content of 0.548%, and a relative silanol value of 1.122.

[0046] Comparative Example 3 The reaction was carried out according to Example 1, with the only difference being that 1000 g of linear polymer was dehydrated and then 5 g of acidic resin-supported linear phosphazene catalyst was directly added. The reaction was carried out under vacuum and heated to 80°C. The viscosity of the reaction system was monitored, and stirring was stopped when the viscosity reached 12000 cP. After the negative pressure was removed, 19 g of end-capping agent was added, and the reaction was carried out at atmospheric pressure for 1 h. Then, the temperature was raised to 100°C and the reaction was carried out under vacuum for 3 h. After the reaction, a polymerization intermediate was obtained, with a conversion rate of 97.75%, a viscosity of 349 cP, a volatile content of 0.29% after dehydration, a viscosity of 379 cP, a vinyl content of 0.524%, and a relative silanol value of 1.151.

[0047] Comparative Example 4 The reaction was carried out according to Example 1, with the only difference being that the catalyst was 0.012 g of linear phosphazene, and 0.0168 g of potassium hydroxide was added and stirred for 3 h to terminate the reaction after the polymerization reaction was completed. A polymerization intermediate was obtained after the reaction, with a conversion rate of 97.33%, a viscosity of 331 cP, a volatile content of 0.79% after de-oxidation, a viscosity of 360 cP, a vinyl content of 0.531%, and a relative silanol value of 1.133.

[0048] Comparative Example 5 Using 2000 g of siloxane cyclic compounds (DMC) as raw material, the mixture was vacuum dehydrated at 80℃ for 1.5 h, then heated to 105℃ and 40 g of tetramethyldivinyldisiloxane was added as a capping agent. The catalyst was 0.1 g of tetramethylammonium hydroxide. The mixture was reacted at this temperature for 8 h. After the reaction was completed, the temperature was raised to 160℃ to break the catalyst. After 3 h, a polymerization intermediate was obtained, with a conversion rate of 87.65% and a viscosity of 217 cP. After dehydration, the final product was obtained, with a volatile content of 0.49%, a viscosity of 303 cP, a vinyl content of 0.527%, and a relative silanol value of 1.130.

[0049] As can be seen from the results of the above examples and comparative examples, the traditional method of preparing vinyl silicone oil by ring-opening polymerization using siloxane cyclic polymers (DMC) as raw materials has a low conversion rate and requires high-temperature catalyst destruction after the reaction, resulting in a long reaction time. In contrast, the technical solution of the present invention has a simple process, high yield, high production efficiency, and does not require the addition of a neutralizing agent. The catalyst can be reused, significantly reducing energy consumption and production costs.

[0050] This invention uses linear polymers as raw materials to prepare vinyl silicone oil through a condensation-rearrangement equilibrium reaction. A combined vacuum and nitrogen bubbling method is employed instead of simple vacuuming or nitrogen purging for dehydration. Furthermore, linear phosphazene is loaded onto an acidic resin as a catalyst, which not only improves the polymerization conversion rate and the end-capping efficiency of the capping agent but also effectively reduces the relative silanol content of the vinyl silicone oil. Only simple removal of low-molecular-weight molecules is required to obtain a finished product with low volatile matter, high vinyl retention, and very low silanol content.

[0051] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a medium-to-low viscosity vinyl silicone oil with low hydroxyl content, characterized in that, Includes the following steps: Step 1: Dehydrate the linearizing agent and viscosity control agent under vacuum at 50~70℃ for 0.5~2 h; Step 2: The linear phosphazene, acidic resin and organic solvent are mixed, refluxed and filtered, and then subjected to vacuum heat treatment to obtain the acidic resin supported linear phosphazene catalyst. Step 3: Add the catalyst obtained in Step 2 to the raw material after Step 1 treatment, and polymerize under vacuum and nitrogen bubbling conditions for 1-4 h to obtain vinyl polydimethylsiloxane intermediate; Step 4: Add a capping agent to the intermediate obtained in Step 3, react at atmospheric pressure for 0.5-2 h, and then react under vacuum and nitrogen bubbling conditions for 1-4 h. After the reaction is completed, filter the catalyst and remove low molecular weight molecules to obtain the vinyl silicone oil.

2. The method according to claim 1, characterized in that, The linear agent is hydroxyl-terminated polydimethylsiloxane with a viscosity of 50-200 cP, preferably 70-130 cP, and the viscosity control agent is vinyl silicone oil with a viscosity of 10-200 cP, preferably 20-100 cP.

3. The method according to claim 1, characterized in that, The raw materials, by weight, include: 100 parts of the linear body, 0.2-3 parts of the viscosity control agent, 0.1-5 parts of the end-capping agent, and 0.1-1 parts of the acidic resin-supported linear phosphazene catalyst.

4. The method according to claim 1, characterized in that, The acidic resin mentioned in step two is a macroporous cation exchange resin.

5. The method according to claim 1, characterized in that, The organic solvent mentioned in step two includes at least one of n-heptane, cyclohexane, toluene, xylene, tetrachloroethane, N,N-dimethylformamide, tetrahydrofuran, and chloroform.

6. The method according to claim 1, characterized in that, The reflux reaction temperature in step two is 60~140℃, and the reaction time is 5~8 h; the vacuum heat treatment temperature is 80~150℃, and the vacuum heat treatment time is 1~3 h.

7. The method according to claim 1, characterized in that, In steps three and four, the reaction temperature is 60~120℃, preferably 70~100℃, and the vacuum degree is maintained at -85~-95 KPa under vacuum and nitrogen bubbling conditions.

8. The method according to claim 1, characterized in that, The nitrogen flow rate for nitrogen bubbling at the bottom of the reactor is 0.5~4m³. 3 / h / m 3 The reactor is preferably 0.8~2 m. 3 / h / m 3 The reactor is preferably 1 to 1.5 m in size. 3 / h / m 3 Reactor.

9. The method according to any one of claims 1-8, characterized in that, The viscosity range of the medium-low viscosity, low hydroxyl content vinyl silicone oil is 10~5000 cP, preferably 20~1000 cP; The volatile matter content of the medium-to-low viscosity, low hydroxyl content vinyl silicone oil is 0.1-2%, preferably 0.1-1%, and more preferably 0.1-0.5%.

10. The method according to claim 9, characterized in that, The relative value of the silanol content of the medium-low viscosity, low-hydroxyl content vinyl silicone oil is 1.000~1.100, preferably 1.000~1.030.