Alkoxy-terminated polysiloxane and preparation method thereof

Abstract

The invention provides alkoxy-terminated polysiloxane and a preparation method thereof.107 silicone rubber, a platinum catalyst and an end-capping reagent are mixed and stirred at the room temperature for a dehydrogenation reaction, and the alkoxy-terminated polysiloxane is obtained. The end-capping reagent is obtained by mixing hydrogen-containing double end caps, vinyl siloxane and a platinum complex catalyst and then reacting at the temperature of 20-35 DEG C. The preparation process of the terminated 107 silicone rubber is carried out at room temperature, the raw material cost is low, the process is simple, the condition is mild, and the method is safe and energy-saving. The prepared terminated 107 silicone rubber is colorless transparent liquid, and has the advantages of controllable viscosity, high product termination rate, no viscosity peak and good storage stability. In addition, the reaction endpoint is easy to judge, and the reaction endpoint can be determined according to whether a viscosity peak exists or not.

Description

Technical Field

[0001] This invention relates to the field of organosilicon polymer technology, and more specifically to a method for preparing alkoxy-terminated polysiloxanes. Background Technology

[0002] Silicone rubber, due to its excellent weather resistance, high and low temperature resistance, electrical insulation, and physiological compatibility, has wide applications in aerospace, electronics, construction, and medical fields. Based on its cross-linking and vulcanization method, it can be divided into heat-cured silicone rubber and room-temperature vulcanized silicone rubber; it can also be divided into addition-type silicone rubber and condensation-type silicone rubber. Condensation-type silicone rubber, based on the byproducts released during vulcanization, can be further divided into products such as de-alcoholized, de-acidified, de-ketoxime, de-acetone, and de-amided types. Among them, the de-alcoholized RTV-1 silicone rubber has no irritating acidic odor or corrosiveness compared to the deacetic acidized RTV-1 silicone rubber, and compared to the de-ketoximeized RTV-1 silicone rubber, it does not crack during vulcanization, has good adhesion, and maintains good physical and electrical properties in harsh environments. Therefore, it is one of the best-performing single-component RTV-1 silicone rubbers in terms of overall performance.

[0003] Traditional dealcoholized silicone rubber is generally made by using 107 silicone rubber as the base rubber, combined with fillers, crosslinking agents, catalysts, coupling agents, plasticizers, etc. Because organotin catalysts are used, they easily generate monoalkoxy polymers without crosslinking activity, resulting in poor storage stability. If titanate is used as a catalyst, the reaction between the titanate and the terminal hydroxyl groups of 107 silicone rubber forms a pseudo-crosslinked state, leading to viscosity peaks that severely affect production efficiency.

[0004] Alkoxy-terminated polydimethylsiloxane can solve the above problems. Even when using titanate catalysts in the production of alcohol-based adhesives, viscosity peaks will not occur, improving production efficiency and storage stability. Furthermore, the compounded and vulcanized product is transparent and not cloudy.

[0005] Currently, there are three main methods for producing alkoxy-terminated polysiloxanes: condensation reaction, cyclic polymerization, and hydrosilylation reaction. Patents CN111333843B, CN112961358A, CN113881049A, CN117801281A, and CN118440329, among others, use condensation reactions to prepare alkoxy-terminated polysiloxanes. This method suffers from the tendency for depolymerization, a cumbersome preparation process, and low end-capping rates, resulting in residual terminal hydroxyl groups and poor storage performance of sealants made from alkoxy-terminated polysiloxanes. Patent CN104479132B uses cyclic polymerization to prepare alkoxy-terminated polysiloxanes, but this method involves multiple reactions such as hydrolysis, condensation, and prepolymerization, making the process complex. Patents CN110878142A, CN109593510A, and CN118994588A, among others, use the hydrosilylation method to prepare alkoxy-terminated polysiloxanes. However, this method has problems such as the difficulty in obtaining raw materials and high costs. Summary of the Invention

[0006] To address the above problems, this invention provides a polysiloxane end-capping agent with the following structural formula: ; Wherein, R1 is one of methyl, ethyl or propyl; R2 and R3 are independently selected from any one of methyl, ethyl, propyl, methoxy, ethoxy or propoxy.

[0007] The present invention also provides a method for preparing the above-mentioned polysiloxane end-capping agent, comprising the following steps: mixing hydrogen-containing dual-end-capped vinylsiloxane with a platinum complex catalyst containing 0.1-5 ppm platinum of 1%-3%, and reacting at 20-35°C; after the reaction is completed, performing vacuum distillation to obtain the end-capping agent.

[0008] Furthermore, the reaction time is 3-6 hours; the vacuum distillation temperature is 45-75°C.

[0009] Furthermore, the mass ratio of the hydrogen-containing dual-endogen to vinylsiloxane is (2-20):1, and the hydrogen-containing dual-endogen is 1,1,3,3-tetramethyldisiloxane.

[0010] Furthermore, the vinylsiloxane includes at least one of vinyltrimethoxysilane, vinyltriethoxysilane, methylvinyldimethoxysilane, or methylvinyldiethoxysilane.

[0011] This invention also provides an alkoxy-terminated polysiloxane with the following structural formula: ; Where n = 50-4000; R1 is one of methyl, ethyl or propyl, and R2 and R3 are independently selected from any one of methyl, ethyl, propyl, methoxy, ethoxy or propoxy.

[0012] The present invention also provides a method for preparing the above-mentioned alkoxy-terminated polysiloxane, comprising the following steps: mixing 107 silicone rubber, platinum catalyst and the above-mentioned capping agent, stirring to carry out a dehydrogenation reaction, and obtaining alkoxy-terminated polysiloxane.

[0013] Furthermore, the mass ratio of the 107 silicone rubber to the end-capping agent is 100:(1-10), the amount of the platinum catalyst is 1-10 ppm of a platinum complex catalyst with a platinum content of 1%-3%, and the dehydrogenation reaction temperature is 20-35℃.

[0014] Furthermore, the method for determining the endpoint of the dehydrogenation reaction is as follows: take out a portion of the reaction sample by mass, add titanate ester to it and stir. If no "viscosity peak" appears, it means that the reaction is over. The titanate includes at least one of tetraisopropyl titanate, tetrabutyl titanate, or tetraoctyl titanate. The mass ratio of the extracted reaction sample to the titanate ester is (30-50):1.

[0015] The above-mentioned alkoxy-terminated polysiloxanes or the alkoxy-terminated polysiloxanes obtained by the above preparation methods are used in the preparation of silicone.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The process of preparing the 107-terminated silicone rubber of this invention is carried out at room temperature, with low raw material costs, simple processes, mild conditions, and is safe and energy-saving. The prepared 107-terminated silicone rubber is a colorless and transparent liquid with controllable viscosity, high end-capping rate, no viscosity peak, and good storage stability.

[0017] 2. The reaction endpoint of this invention is easy to determine; the reaction endpoint can be determined based on whether there is a viscosity peak.

[0018] 3. After the reaction between the hydrogen-containing double end cap and the siloxane is completed, the excess hydrogen-containing double end cap is removed by vacuum distillation. The catalyst remains in the end capping agent, which can reduce the amount of catalyst used when the end capping agent reacts with 107 glue.

[0019] 4. The hydrogen-containing alkoxysilanes prepared by the method of the present invention can be used as raw materials for the preparation of other alkoxysilane oils, or they can be sold separately as products. Detailed Implementation

[0020] The embodiments of the present invention will be described in detail below with reference to the examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0021] This invention provides a polysiloxane end-capping agent with the following structural formula: ; Wherein, R1 is one of methyl, ethyl or propyl; R2 and R3 are independently selected from any one of methyl, ethyl, propyl, methoxy, ethoxy or propoxy.

[0022] The present invention also provides a method for preparing the above-mentioned polysiloxane end-capping agent, comprising the following steps: mixing hydrogen-containing dual-end-capped vinylsiloxane with a platinum complex catalyst containing 0.1-5 ppm platinum of 1%-3%, and reacting at 20-35°C; after the reaction is completed, performing vacuum distillation to obtain the end-capping agent.

[0023] Furthermore, the reaction time is 3-6 hours; the vacuum distillation temperature is 45-75°C.

[0024] Furthermore, the mass ratio of the hydrogen-containing dual-endogen to vinylsiloxane is (2-20):1, and the hydrogen-containing dual-endogen is 1,1,3,3-tetramethyldisiloxane.

[0025] Furthermore, the vinylsiloxane includes at least one of vinyltrimethoxysilane, vinyltriethoxysilane, methylvinyldimethoxysilane, or methylvinyldiethoxysilane.

[0026] This invention also provides an alkoxy-terminated polysiloxane with the following structural formula: ; Where n = 50-4000; R1 is one of methyl, ethyl or propyl, and R2 and R3 are independently selected from any one of methyl, ethyl, propyl, methoxy, ethoxy or propoxy.

[0027] The present invention also provides a method for preparing the above-mentioned alkoxy-terminated polysiloxane, comprising the following steps: mixing 107 silicone rubber, platinum catalyst and the above-mentioned capping agent, stirring to carry out a dehydrogenation reaction, and obtaining alkoxy-terminated polysiloxane.

[0028] Furthermore, the mass ratio of the 107 silicone rubber to the end-capping agent is 100:(1-10), the amount of the platinum catalyst is 1-10 ppm of a platinum complex catalyst with a platinum content of 1%-3%, and the dehydrogenation reaction temperature is 20-35℃.

[0029] Furthermore, the method for determining the endpoint of the dehydrogenation reaction is as follows: take out a portion of the reaction sample by mass, add titanate ester to it and stir. If no "viscosity peak" appears, it means that the reaction is over. The titanate includes at least one of tetraisopropyl titanate, tetrabutyl titanate, or tetraoctyl titanate. The mass ratio of the extracted reaction sample to the titanate ester is (30-50):1.

[0030] The platinum complex catalysts used in the following examples and comparative examples were purchased from Shanghai Neutron Star Chemical Technology Co., Ltd. (KP22).

[0031] Example 1 (1) Preparation of capping agent: 1000g of hydrogen-containing dual-terminated siloxane (1,1,3,3-tetramethyldisiloxane) and 100g of vinyltrimethoxysilane were added to a reaction flask and mixed thoroughly. Then, 2.5ppm of a platinum complex catalyst with a platinum content of 2% was added. The reaction was carried out at room temperature for 4 hours. After the reaction was completed, excess hydrogen-containing dual-terminated siloxane was removed by vacuum distillation at 65℃ (which can be recycled) to obtain the hydrogen-containing alkoxy-terminated agent with a yield of 99.6%. Gas chromatography analysis showed that the product purity was 96.2%.

[0032] (2) Preparation of alkoxy-terminated polysiloxanes: At room temperature, 100 parts of 107 silicone rubber were mixed evenly with 2 ppm of platinum complex catalyst containing 2% platinum. Then, 2 parts of hydrogen-containing alkoxy end-capping agent were added. After stirring and reacting for a period of time, 20g of sample was taken and 0.5g of tetraisopropyl titanate was added and stirred rapidly. If there was no "viscosity peak", the reaction was terminated, and trimethoxy-terminated 107 silicone rubber with a viscosity of 2110 cp was obtained.

[0033] Example 2 (1) Preparation of capping agent: 2000g of hydrogen-containing dual-terminated siloxane (1,1,3,3-tetramethyldisiloxane) and 100g of vinyltriethoxysilane were added to a reaction flask and mixed thoroughly. Then, 2ppm of a platinum complex catalyst with a platinum content of 2% was added, and the reaction was carried out at room temperature for 2 hours. After the reaction was completed, excess hydrogen-containing dual-terminated siloxane was removed by vacuum distillation at 55℃ (which can be recycled) to obtain a hydrogen-containing alkoxy-terminated agent with a yield of 99.0%. Gas chromatography analysis showed that the product purity was 93.4%.

[0034] (2) Preparation of alkoxy-terminated polysiloxanes: At room temperature, 100 parts of 107 silicone rubber were mixed evenly with 3 ppm of a platinum complex catalyst containing 2% platinum. Then, 2 parts of a hydrogen-containing alkoxy end-capping agent were added. After stirring and reacting for a period of time, 20g of sample was taken and 0.5g of tetraisopropyl titanate was added and stirred rapidly. If there was no "viscosity peak", the reaction was terminated, and triethoxy-terminated 107 silicone rubber with a viscosity of 5010 cp was obtained.

[0035] Example 3 (1) Preparation of capping agent: 200g of hydrogen-containing dual-terminated siloxane (1,1,3,3-tetramethyldisiloxane) and 100g of methylvinyldimethoxysilane were added to a reaction flask and mixed thoroughly. Then, 1ppm of a platinum complex catalyst with a platinum content of 2% was added. The reaction was carried out at room temperature for 6 hours. After the reaction was completed, excess hydrogen-containing dual-terminated siloxane was removed by vacuum distillation at 60℃ (which can be recycled) to obtain the hydrogen-containing alkoxy-terminated agent with a yield of 98.7%. Gas chromatography analysis showed that the purity of the product was 92.8%.

[0036] (2) Preparation of alkoxy-terminated polysiloxanes: At room temperature, 100 parts of 107 silicone rubber were mixed evenly with a 2% platinum complex catalyst containing 3 ppm platinum. Then, 2 parts of hydrogen-containing alkoxy end-capping agent were added. After stirring and reacting for a period of time, 20g of sample was taken and 0.5g of tetraisopropyl titanate was added and stirred rapidly. If there was no "viscosity peak", the reaction was terminated, and dimethoxy-terminated 107 silicone rubber with a viscosity of 20300cp was obtained.

[0037] Example 4 (1) Preparation of capping agent: 600g of hydrogen-containing dual-terminated siloxane (1,1,3,3-tetramethyldisiloxane) and 100g of methylvinyldiethoxysilane were added to a reaction flask and mixed thoroughly. Then, 1.5ppm of a platinum complex catalyst with a platinum content of 2% was added. The reaction was carried out at room temperature for 5 hours. After the reaction was completed, excess hydrogen-containing dual-terminated siloxane was removed by vacuum distillation at 70℃ (which can be recycled) to obtain the hydrogen-containing alkoxy-terminated agent with a yield of 99.4%. Gas chromatography analysis showed that the purity of the product was 95.8%.

[0038] (2) Preparation of alkoxy-terminated polysiloxanes: At room temperature, 100 parts of 107 silicone rubber were mixed evenly with 3 ppm of a platinum complex catalyst containing 2% platinum. Then, 2 parts of a hydrogen-containing alkoxy end-capping agent were added. After stirring and reacting for a period of time, 20g of sample was taken and 0.5g of tetraisopropyl titanate was added and stirred rapidly. If there was no "viscosity peak", the reaction was terminated, and diethoxy-terminated 107 silicone rubber with a viscosity of 79820cp was obtained.

[0039] Comparative Example 1 Unlike Example 1, step (2) involves adding 15 ppm of a platinum complex catalyst with a platinum content of 2%, while the rest is the same as in Example 1.

[0040] Comparative Example 2 (1) Preparation of capping agent 1000g of hydrogen-containing double-ended (1,1,3,3-tetramethyldisiloxane) and 100g of vinyltrimethoxysilane were added to a reaction flask and mixed evenly. Then, 2ppm of a platinum complex catalyst with a platinum content of 2% was added, and the mixture was refluxed at 90℃ for 2h. After the reaction was completed, the mixture was distilled under reduced pressure at 80℃ to obtain the hydrogen-containing alkoxy end-capping agent.

[0041] (2) Preparation of alkoxy-terminated polysiloxanes: At room temperature, 100 parts of 2000cp 107 silicone rubber were mixed evenly with 2 ppm of platinum complex catalyst containing 2% platinum. Then, 2 parts of hydrogen-containing alkoxy end-capping agent were added and stirred. 20g samples were taken periodically and 0.5g of tetraisopropyl titanate were added and stirred rapidly. There was a viscosity peak that was always present, which indicates that the hydroxyl silicone oil was not completely end-capped.

[0042] The pressure of vacuum distillation in the above embodiments and comparative examples is <10 kPa.

[0043] The alkoxy-terminated 107 silicone rubber prepared in the above examples and comparative examples was mixed with titanate, and the presence of viscosity peaks was observed. The viscosity of the alkoxy-terminated 107 silicone rubber was measured after being stored at room temperature, in a dry and sealed condition for 6 months. The results are shown in Table 1.

[0044] Table 1

[0045] This invention prepares hydrogen-containing alkoxysilanes at room temperature, avoiding the risk of flash explosion of hydrogen-containing double-ended heads under high-temperature conditions. The excess hydrogen-containing double-ended head in this invention acts as a diluent, preventing the prepared end-capping agent from being a byproduct with alkoxy groups at both ends, thus avoiding the presence of difficult-to-remove small molecules in the prepared end-capped 107 silicone rubber, which would affect the performance of the rubber compound. Furthermore, the excess hydrogen-containing double-ended head can be recovered by vacuum distillation and reused.

Claims

1. A polysiloxane end-capping agent, characterized in that, The structural formula is: ； Wherein, R1 is one of methyl, ethyl or propyl; R2 and R3 are independently selected from any one of methyl, ethyl, propyl, methoxy, ethoxy or propoxy.

2. The method for preparing a polysiloxane end-capping agent according to claim 1, characterized in that, The process includes the following steps: mixing hydrogen-containing double-ended end caps, vinylsiloxane, and a platinum complex catalyst with a platinum content of 1%-3% (0.1-5 ppm), and reacting at 20-35°C; after the reaction is completed, vacuum distillation is performed to obtain the end capping agent.

3. The method for preparing a polysiloxane end-capping agent according to claim 2, characterized in that, The reaction time is 3-6 hours; the vacuum distillation temperature is 45-75°C.

4. The method for preparing a polysiloxane end-capping agent according to claim 2, characterized in that, The mass ratio of the hydrogen-containing double end cap to vinylsiloxane is (2-20):1, and the hydrogen-containing double end cap is 1,1,3,3-tetramethyldisiloxane.

5. The method for preparing a polysiloxane end-capping agent according to claim 2, characterized in that, The vinylsiloxane includes at least one of vinyltrimethoxysilane, vinyltriethoxysilane, methylvinyldimethoxysilane, or methylvinyldiethoxysilane.

6. An alkoxy-terminated polysiloxane, characterized in that, The structural formula is: ； Where n = 50-4000; R1 is one of methyl, ethyl or propyl, and R2 and R3 are independently selected from any one of methyl, ethyl, propyl, methoxy, ethoxy or propoxy.

7. The method for preparing an alkoxy-terminated polysiloxane according to claim 6, characterized in that, The process includes the following steps: mixing 107 silicone rubber, platinum catalyst and end-capping agent, stirring to carry out dehydrogenation reaction, and obtaining alkoxy-terminated polysiloxane; The capping agent is the capping agent according to claim 1 or the capping agent obtained by the preparation method according to any one of claims 2-5.

8. The method for preparing an alkoxy-terminated polysiloxane according to claim 7, characterized in that, The mass ratio of the 107 silicone rubber to the end-capping agent is 100:(1-10), the amount of the platinum catalyst is 1-10 ppm, and the platinum complex catalyst has a platinum content of 1%-3%; the dehydrogenation reaction temperature is 20-35℃.

9. The method for preparing an alkoxy-terminated polysiloxane according to claim 7, characterized in that, The method for determining the endpoint of the dehydrogenation reaction is as follows: take out a portion of the reaction sample by mass, add titanate ester and stir. If no "viscosity peak" appears, the reaction is considered to be complete. The titanate includes at least one of tetraisopropyl titanate, tetrabutyl titanate, or tetraoctyl titanate. The mass ratio of the extracted reaction sample to the titanate ester is (30-50):

1.

10. The alkoxy-terminated polysiloxane of claim 6 or the alkoxy-terminated polysiloxane obtained by any one of claims 7-9 is used in the preparation of silicone.

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