Preparation method of ultralow-viscosity vinyl methoxy-terminated silicone oil

Abstract

The invention provides a preparation method of ultralow-viscosity vinyl methoxy-terminated silicone oil, which is mainly applied to a structure control agent in the field of silicone rubber.The preparation method comprises the steps that a polydimethylsiloxane linear body serves as a raw material, dimethyl vinyl methoxy silane serves as an end-capping reagent, a base catalyst is added, a polymerization reaction is conducted till the viscosity is stable, and the ultralow-viscosity vinyl methoxy-terminated silicone oil is obtained. And adding phosphoric acid gel for neutralization, carrying out gradient heating to 90 DEG C, and carrying out devolatilization under a vacuum condition to obtain the methoxy hydroxyl-terminated silicone oil. The technological process is simple and easy to operate, and the product is uniform in molecular weight distribution and high in flash point, has the advantages of improving the processability and the mechanical property as a structure control agent, and can improve the molecular crosslinking density and improve the strength of a silica gel product in the product vulcanization technological process.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for preparing an ultra-low viscosity vinyl methoxy-terminated silicone oil, which is mainly applied in the field of silicone rubber structure control agents. Background Technology

[0002] Vinyl-terminated silicone oil is an important organosilicon material, widely used in silicone rubber, liquid silicone rubber, and textile auxiliaries due to the presence of vinyl groups at the ends of its molecular chains that can participate in addition reactions. Methoxysilanes exhibit high reactivity, and the byproduct methanol is easily removed. Therefore, developing a method for preparing vinyl-methoxy-terminated silicone oil using methoxysilanes as end-capping agents, with mild reaction conditions, simple process, and environmental friendliness, is of great significance.

[0003] Structure control agents primarily function to resist structural degradation, resulting in silicone rubber compounds with good stiffness and excellent reprocessing and molding properties. Their main role is to inhibit the formation of interparticle hydrogen bonds by interacting with the Si-OH groups on the surface of silica, while also improving the storage stability of silicone rubber. Currently, hydroxyl-based and alkoxy-based silicone oils are commonly used structure control agents, which have replaced traditional diphenylsilanediol or dimethyldimethoxysilane due to their superior anti-structural properties and safety. However, existing structure control agents do not provide additional benefits to the mechanical properties of silicone rubber and can negatively impact aging resistance. Introducing vinyl groups helps improve processing and mechanical properties, and can increase molecular crosslinking density during the vulcanization process, thereby increasing the strength of silicone rubber products. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing an ultra-low viscosity vinyl methoxy-terminated silicone oil, which has the advantages of low viscosity, environmental friendliness, high flash point, and superior mechanical properties. The vinyl methoxy-terminated silicone oil is mainly used in the field of silicone rubber structure control agents. The preparation method of the structure control agent includes the following steps: (1) Under nitrogen protection, stir the polydimethylsiloxane linear body and the end-capping agent evenly; (2) Material heating: Add alkaline catalyst and heat the mixture until the viscosity stabilizes; (3) Neutralization: Neutralize by adding an acidic neutralizing agent; (4) Degradation: The neutralized material is placed in a negative pressure environment for the first step of degradation. After the degradation collection device has no obvious flow of liquid, the temperature is gradually increased for the second step of degradation. After the temperature is increased again for the third step of degradation, the material is filtered to obtain clear and transparent vinyl methoxy-terminated silicone oil.

[0005] Preferably, the viscosity of the polydimethylsiloxane lineare is 50-100 mPa·s, and the end-capping agent is dimethylvinylmethoxysilane, or methylvinyldimethoxysilane, or a combination of dimethylvinylmethoxysilane and methyltrimethoxysilane, or a combination of methylvinyldimethoxysilane and dimethyldimethoxysilane. Preferably, the mass ratio of the added polydimethylsiloxane linear body to the end-capping agent in step (1) is (1~5):1; the blending speed is 100~300 rpm.

[0006] Preferably, the catalyst in step (2) comprises one of KOH alcohol solution or KOH alkaline gel, NaOH alcohol solution or NaOH alkaline gel; wherein the alcohol is methanol or ethanol.

[0007] More preferably, the amount of catalyst used in step (2) is 100 to 500 ppm of the amount of polydimethylsiloxane linear body.

[0008] Preferably, in step (2), the mixture is heated to 60-80°C and the reaction time is 2-6 hours.

[0009] Preferably, the neutralizing agent in step (3) is any one of linear silanized phosphate, an alcoholic solution of phosphoric acid, or acetic acid, wherein the alcohol is methanol or ethanol.

[0010] Preferably, the neutralization time in step (3) is 0.5-1h.

[0011] Preferably, the negative pressure in step (4) is -0.1 to -0.09 MPa, and the total time for de-pressure is 1 hour. Preferably, in step (4), the neutralized material is placed in a negative pressure environment of 55-65℃ for the first step of desliming. After the desliming collection device has no obvious flowing liquid, the temperature is gradually raised to 66-75℃ for the second step of desliming. After the obvious flowing liquid has no more, the temperature is raised to 80℃ for the third step of desliming. Preferably, the neutralized material is placed in a negative pressure environment of 60℃ for the first step of desliming. After the desliming collection device has no obvious flowing liquid, the temperature is gradually raised to 70℃ for the second step of desliming. After the obvious flowing liquid has no more, the temperature is raised to 80℃ for the third step of desliming.

[0012] The beneficial effects of this invention are as follows: 1. The low-molecular-weight polymers extracted by this invention do not require waste disposal and can be reused. Furthermore, the reaction process does not generate wastewater or pollutants, making it low-cost and environmentally friendly. The generated low-molecular-weight polymers can be reused without affecting the refining effect.

[0013] 2. Using low-viscosity polydimethylsiloxane lineare as raw material and highly active methoxy end-capping agent, no high-temperature reaction is required, the conditions are mild, and the risk of yellowing due to reaction at temperatures above 100°C is avoided.

[0014] 3. Using low-viscosity polydimethylsiloxane lineare as raw material, the prepared product has a more uniform molecular weight distribution.

[0015] 4. Use a gradual de-lowering method at 60℃-80℃ and low temperature to avoid azeotropic removal of effective chain segment components during the de-lowering process of ultra-low viscosity silicone oil.

[0016] 5. The structure control agent obtained by the present invention is a hybrid end-capping structure control agent, which has the anti-structural advantages of methoxy silicone oil and the mechanical property improvement advantages of vinyl groups.

[0017] 6. The operation process of this invention is not complicated, and the molecular weight is controllable. Detailed Implementation

[0018] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be construed as limiting the present invention. The scope of protection of the present invention should be determined by the contents of the claims. Modifications and substitutions made by those skilled in the art to the technical solution of the present invention without creative effort all fall within the scope of protection of the present invention.

[0019] Example 1 Under nitrogen protection, 1000 g of 70 mPa·s linear polydimethylsiloxane, 400 g of methylvinyldimethoxysilane, and 500 g of dimethyldimethoxysilane were stirred evenly at 300 rpm. The mixture was heated to 80°C, and then 5% (m / m) KOH alkali colloid was added, with the KOH addition amount being 200 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 1.96 cSt. Then, 5% (m / m) linear silanized phosphate ester with a phosphoric acid content was added, with the phosphoric acid addition amount being 1.25 times the amount of KOH added. After neutralization for 0.5 hours, the material was placed at 60°C and -0.095 MPa for descaling, with the temperature increased by 10°C every 20 minutes, finally reaching 80°C for descaling. After filtration, a colorless and transparent vinyl methoxy-terminated silicone oil was obtained with a viscosity of 2.82 cst, a vinyl content of 4.3%, a methoxy content of 12.3%, a yellowness index (YI) of 1.66, and a polydispersity of 1.08 as determined by GPC testing.

[0020] Example 2 Under nitrogen protection, 1000 g of 70 mPa·s polydimethylsiloxane linear polymer, 400 g of dimethylvinylmethoxysilane, and 500 g of methyltrimethoxysilane were stirred evenly at 200 rpm. The mixture was heated to 80°C, and then a 5% (m / m) KOH methanol solution was added, with the KOH addition amount being 200 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 1.88 cSt. A 5% (m / m) phosphoric acid ethanol solution was then added, with the phosphoric acid addition amount being 1.25 times the amount of KOH added. After neutralization for 0.5 hours, the material was placed at 60°C and -0.095 MPa for descaling, with the temperature increased by 10°C every 20 minutes, finally reaching 80°C for descaling. After filtration, a colorless and transparent vinyl methoxy-terminated silicone oil was obtained with a viscosity of 2.75 cst, a vinyl content of 3.9%, a methoxy content of 13.9%, a yellowness index (YI) of 1.74, and a polydispersity of 1.05 according to GPC testing.

[0021] Example 3 Under nitrogen protection, 1000 g of 70 mPa·s linear polydimethylsiloxane and 500 g of methyl vinyl dimethoxysilane were stirred evenly at 200 rpm. The mixture was heated to 80℃, and then 5% (m / m) of KOH alkali gum was added, with the KOH addition amount being 150 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 3.0 cSt. Then, 5% (m / m) of linear silanol phosphate was added, with the phosphoric acid addition amount being 1.25 times the KOH addition amount. After neutralization for 0.5 hours, the material was placed at 60℃ and -0.095 MPa for degradation, with the temperature increased by 10℃ every 20 minutes, finally reaching 80℃ for further degradation. After filtration, a colorless and transparent vinyl methoxy-terminated silicone oil was obtained, with a viscosity of 3.60 cSt, a vinyl content of 4.5%, a methoxy content of 8.4%, and a yellowness YI of 1.83.

[0022] Example 4 Under nitrogen protection, 1000 g of 70 mPa·s polydimethylsiloxane lineare, 400 g of methylvinyldimethoxysilane, and 500 g of dimethyldimethoxysilane were stirred evenly at 300 rpm. The mixture was heated to 70℃, and then 5% (m / m) KOH alkali gel was added, with the KOH addition amount being 200 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 2.02 cSt. Then, 5% (m / m) phosphoric acid ethanol solution was added, with the phosphoric acid addition amount being 1.25 times the KOH addition amount. After neutralization for 0.5 hours, the material was placed at 60℃ and -0.095 MPa for degradation, with the temperature increased by 10℃ every 20 minutes, finally reaching 80℃ for further degradation. After filtration, a colorless and transparent vinylmethoxy-terminated silicone oil was obtained, with a viscosity of 3.21 cSt, a vinyl content of 3.2%, a methoxy content of 10.6%, and a yellowness YI of 1.46.

[0023] Example 5 Under nitrogen protection, 1000 g of 70 mPa·s linear polydimethylsiloxane, 370 g of methylvinyldimethoxysilane, and 400 g of low-molecular-weight polymers collected after degradation were stirred at 300 rpm until homogeneous. The mixture was heated to 80°C, and then a 5% (m / m) NaOH methanol solution was added, with the NaOH addition amount being 200 ppm of the total material. After reacting for 3 hours, the viscosity stabilized at 2.05. Then, a 5% (m / m) phosphoric acid methanol solution was added, with the phosphoric acid addition amount being 1.25 times the NaOH addition amount. After neutralization for 0.5 hours, the material was placed at 60°C and -0.095 MPa for degradation, with the temperature increased by 10°C every 20 minutes, finally reaching 80°C for degradation. After filtration, a colorless and transparent vinylmethoxy-terminated silicone oil was obtained, with a viscosity of 3.10 cst, a vinyl content of 4.2%, a methoxy content of 10.9%, and a yellowness (YI) of 1.66.

[0024] Comparative Example 1 Under nitrogen protection, 1000g of DMC (dimethylsiloxane mixed cyclic compound), 400g of methylvinyldimethoxysilane, and 500g of dimethyldimethoxysilane were stirred evenly at 300 rpm. The mixture was heated to 80℃, and then 5% (m / m) of KOH alkaline colloid was added, with the KOH addition amount being 200 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 1.93 cSt. Then, 5% (m / m) of linear silanized phosphate ester was added, with the phosphoric acid addition amount being 1.25 times the amount of KOH added. After neutralization for 0.5 hours, the material was placed at 60℃ and -0.095 MPa for descaling, with the temperature increased by 10℃ every 20 minutes, finally reaching 80℃ for descaling. After filtration, a colorless and transparent vinyl methoxy-terminated silicone oil was obtained with a viscosity of 2.86 cSt, a vinyl content of 4.2%, a methoxy content of 11.8%, a yellowness index (YI) of 1.68, and a polydispersity of 1.34 according to GPC testing. Comparative Example 1 shows that the silicone oil prepared using DMC as a raw material has a worse molecular weight distribution.

[0025] Comparative Example 2 Under nitrogen protection, 1000 g of 70 mPa·s linear polydimethylsiloxane, 400 g of methylvinyldimethoxysilane, and 500 g of dimethyldimethoxysilane were stirred uniformly under reflux conditions at 300 rpm. The mixture was heated to 110℃, and then 5% (m / m) KOH alkali gel was added, with the KOH addition amount being 200 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 1.89 cst. Then, 5% (m / m) phosphoric acid ethanol solution was added, with the phosphoric acid addition amount being 1.25 times the KOH addition amount. After neutralization for 0.5 hours, the material was placed at 60℃ and -0.095 MPa for descaling, with the temperature increased by 10℃ every 20 minutes, finally reaching 80℃ for descaling. After filtration, a pale yellow, transparent vinyl methoxy-terminated silicone oil was obtained, with a viscosity of 2.82 cSt; vinyl content of 3.8%, methoxy content of 12.3%, yellowness YI of 2.78, and GPC polydispersity of 1.02. Comparative Example 2 shows that the high-temperature reaction causes the product to turn yellow.

[0026] Comparative Example 3 Under nitrogen protection, 1000 g of 70 mPa·s linear polydimethylsiloxane, 400 g of methylvinyldimethoxysilane, and 500 g of dimethyldimethoxysilane were stirred evenly at 300 rpm. The mixture was heated to 80℃, and then 5% (m / m) KOH alkali gel was added, with the KOH addition amount being 200 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 1.96 cst. Then, 5% (m / m) phosphoric acid ethanol solution was added, with the phosphoric acid addition amount being 1.25 times the KOH addition amount. After neutralization for 0.5 hours, the material was placed at 85℃ and -0.095 MPa to reduce the viscosity to the range of 2.8-2.9 cs. After filtration, a colorless and transparent vinyl methoxy-terminated silicone oil was obtained with a viscosity of 2.85 cst; vinyl content of 4.5%, methoxy content of 11.9%, yellowness YI of 1.83, and GPC polydispersity of 1.26. Comparative Example 3 shows that after the product is degraded to the target viscosity at high temperature, the molecular weight distribution is deviated and the low molecular weight is not completely removed. In the preparation of ultra-low viscosity silicone oil, a gradual degradation process should be adopted to avoid azeotropy of the product.

[0027] Comparative Example 4 Preparation of methoxysilicone oil: Under inert gas protection, 1000g of 70 mPa·s linear polydimethylsiloxane and 900g of dimethyldimethoxysilane were stirred evenly at 300 rpm. The mixture was heated to 80℃, and then 5% (m / m) of KOH alkali gum was added, with the KOH addition amount accounting for 200 ppm of the total material. After reacting for 4 hours, the viscosity stabilized at 1.94 cst. Then, 5% (m / m) of linear silanol phosphate was added, with the phosphoric acid addition amount being 1.25 times the KOH addition amount. After neutralization for 0.5 hours, the material was placed at 60℃ and -0.095 MPa for descaling, with the temperature increased by 10℃ every 20 minutes, finally reaching 80℃ for further descaling. After filtration, a pale yellow transparent methoxysilicone oil was obtained, with a viscosity of 2.85 cst, a methoxy content of 13%, a yellowness YI of 1.56, and a GPC polydispersity of 1.04.

[0028] Using the methoxylated silicone oil prepared in Comparative Example 4 as a comparative example, an application evaluation was conducted together with Example 3 by preparing a compound. The main evaluation indicators were the number of back-mixing cycles, hardness, ML, MH, and tc90. The preparation ratios of the base rubber were: 140g of methyl vinyl silicone rubber; 70g of precipitated silica; and 5g of structure control agent. The evaluation results are shown in Table 1 below: Table 1

[0029] The results showed that the number of re-mixing times for methoxy silicone oil and vinyl methoxy silicone oil was not significantly different. The rubber compounds had high transparency, good stiffness, and were not sticky; vinyl methoxy silicone oil had better mechanical properties.

[0030] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations; therefore, any obvious variations or modifications derived therefrom remain within the scope of protection of this invention.

Claims

1. A method for preparing an ultra-low viscosity vinyl methoxy-terminated silicone oil, characterized in that, Includes the following steps: (1) Under nitrogen protection, stir the polydimethylsiloxane linear body and the end-capping agent evenly; (2) Material heating: Add alkaline catalyst and heat the mixture until the viscosity stabilizes; (3) Neutralization: Neutralize by adding an acidic neutralizing agent; (4) De-lowering: The neutralized material is placed in a negative pressure environment for the first step of de-lowering. After the de-lowering collection device has no obvious flowing liquid, the temperature is raised for the second step of de-lowering. After the temperature is raised again for the third step of de-lowering, the material is filtered to obtain clear and transparent vinyl methoxy-terminated silicone oil.

2. The method for preparing ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: The viscosity of the polydimethylsiloxane lineare is 50-100 mPa·s, and the end-capping agent is dimethylvinylmethoxysilane, or methylvinyldimethoxysilane, or a combination of dimethylvinylmethoxysilane and methyltrimethoxysilane, or a combination of methylvinyldimethoxysilane and dimethyldimethoxysilane.

3. The method for preparing ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: The mass ratio of the added polydimethylsiloxane linear body to the end-capping agent in step (1) is (1~5):1; the blending speed is 100~300 rpm.

4. The method for preparing the ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: The catalyst in step (2) comprises one of KOH alcohol solution or KOH alkaline gel, NaOH alcohol solution or NaOH alkaline gel; the alcohol is methanol or ethanol.

5. The method for preparing the ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 4, characterized in that: The amount of catalyst used in step (2) is 100~500 ppm of the amount of polydimethylsiloxane linear body.

6. The method for preparing the ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: Step (2) Heat the mixture to 60-80℃ and react for 2-6 hours.

7. The method for preparing ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: The neutralizing agent in step (3) is any one of linear silanized phosphate, an alcoholic solution of phosphoric acid, or acetic acid, wherein the alcohol is methanol or ethanol.

8. The method for preparing the ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: The neutralization time in step (3) is 0.5-1h.

9. The method for preparing the ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: The negative pressure mentioned in step (4) is -0.1~-0.09MPa, and the total time for de-pressure is 1 hour.

10. The method for preparing the ultra-low viscosity vinyl methoxy-terminated silicone oil according to claim 1, characterized in that: Step (4): The neutralized material is placed in a negative pressure environment at 55-65℃ for the first step of desliming. After the desliming collection device shows no obvious flow of liquid, the temperature is raised to 66-75℃ for the second step of desliming. After the obvious flow of liquid is no longer visible, the temperature is raised to 80℃ for the third step of desliming. Preferably, the neutralized material is placed in a negative pressure environment at 60℃ for the first step of desliming. After the desliming collection device shows no obvious flow of liquid, the temperature is raised to 70℃ for the second step of desliming. After the obvious flow of liquid is no longer visible, the temperature is raised to 80℃ for the third step of desliming.

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