Silicone rubber heat stabilizer and preparation method thereof

Abstract

The invention relates to the technical field of silicone rubber, and particularly discloses a silicone rubber heat stabilizer and a preparation method thereof. According to the silicone rubber heat stabilizer, a liquid organic cerium source serves as a core of the heat stabilizer, liquid organic cerium salt is added into silicone rubber, the proportion of the liquid organic cerium salt in the silicone rubber is 0.01%-10% (weight), the heat stability of the silicone rubber can be remarkably improved, and meanwhile other excellent performance of the silicone rubber can be kept. The preparation method can solve the problem of poor dispersibility of the cerium oxide powder heat-resistant agent in the silicone rubber, widens the application field of the silicone rubber in a high-temperature environment, and provides a new scheme for research and development and performance optimization of a high-performance silicone rubber material.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber, and in particular to a silicone rubber heat stabilizer and a preparation method thereof. Background Art

[0002] Silicone rubber is widely popular in the fields of aerospace, automotive electronics, medical and sealing due to its excellent high and low temperature resistance, electrical insulation, chemical stability and physiological inertness. Especially in high temperature environments, silicone rubber can maintain good elasticity and mechanical strength, becoming the preferred material in many high temperature working scenarios. However, with the advancement of science and technology and industrial development, higher requirements are placed on the heat resistance of silicone rubber.

[0003] In order to improve the heat resistance of silicone rubber, researchers have tried to add heat stabilizers, such as cerium oxide powder heat stabilizers, to silicone rubber. Cerium oxide powder heat stabilizers have improved the heat resistance of silicone rubber to a certain extent, but their dispersion effect is poor during use, and they are prone to form large clusters of particles in silicone rubber, which in turn affects the performance of silicone rubber; at the same time, it will also lead to a decrease in transparency and processing performance, and an increase in cost. Therefore, how to prepare a heat stabilizer with better dispersibility without sacrificing other key properties of silicone rubber has become a technical challenge that needs to be solved urgently.

[0004] In view of this, developing a silicone rubber heat stabilizer that can significantly improve the heat resistance of silicone rubber, maintain its original excellent physical properties and processing performance, and has good dispersibility is of great significance for broadening the application areas of silicone rubber and meeting higher standards of industrial needs. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes a silicone rubber heat stabilizer and a preparation method thereof. The stabilizer uses a liquid organic cerium source as the core of the heat stabilizer, and adds a liquid organic cerium salt to the silicone rubber to improve its thermal stability. After systematic research, it is found that when a liquid organic cerium salt such as cerium isooctanoate solution is used as an additive, it has good dispersibility and can significantly improve the thermal stability and mechanical properties of silicone rubber. At the same time, the addition of a small amount of liquid organic cerium salt can maintain the color of the silicone rubber.

[0006] In some embodiments of the present invention, a silicone rubber heat stabilizer is proposed in the present invention, and the raw materials involved in the application of the heat stabilizer include: methyl vinyl silicone rubber premix as a base material, an appropriate amount of 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane and gas-phase silica powder are evenly mixed into a paste vulcanizing agent, cerium isooctanoate solution is used as a heat-resistant additive, cerium isooctanoate solution and silica are mixed into a paste-like heat-resistant agent, and cerium isooctanoate solution and silicone rubber are mixed into a paste-like heat-resistant agent.

[0007] In some embodiments of the present invention, the present invention proposes a method for improving the heat resistance of silicone rubber, and the specific steps of the method are as follows: First, 0.5 parts of 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane and 0.125 parts of fumed silica were mixed in a high-speed mixer at a ratio of 4:1 to form a paste vulcanizing agent for later use; The cerium isooctanoate solution and silicon dioxide are mixed in a mass ratio of 1:9 by a kneader to form a uniform paste-like heat-resistant agent; The cerium isooctanoate solution and silicone rubber are mixed in a mass ratio of 1:9 by a kneader to form a uniform paste-like heat-resistant agent; 100 parts of methyl vinyl silicone rubber premix were mixed on an open mill for 5 minutes to remove the structure; Add the mixed paste curing agent into the methyl vinyl silicone rubber premix three times and mix evenly for 10 minutes to make the curing agent evenly dispersed; 0.1 parts of cerium isooctanoate solution or 1 part of paste-like heat-resistant agent is added to the silicone rubber and mixed evenly for 15 minutes to obtain a silicone rubber compound.

[0008] The silicone rubber compound obtained above was cured in a flat vulcanizer at 165° C. for 15 minutes to obtain a silicone rubber sheet, and the silicone rubber sheet was placed in a blast oven at 200° C. for 4 hours for two-stage vulcanization to obtain a silicone rubber sample.

[0009] The silicone rubber samples were subjected to thermogravimetric analysis, aging test and mechanical property test to verify the heat resistance and stability of the silicone rubber prepared by the method of the present invention in a high temperature environment.

[0010] The temperature at which the silicone rubber loses 5% of its thermal weight by the above additional technical features is greatly increased, and at the same time, the tensile strength and elongation at break after thermal aging have a good retention rate.

[0011] In some embodiments of the present invention, the present invention provides a silicone rubber heat stabilizer and a preparation method thereof, and the heat stabilizer has the following specific characteristics for improving the heat resistance of silicone rubber: The temperature at which the weight loss of 5% in the thermogravimetric analysis of silicone rubber with the addition of cerium isooctanoate heat-resistant additive increased by 26 to 40°C; The mechanical properties of silicone rubber added with cerium isooctanoate heat-resistant additive have no obvious changes at room temperature; The silicone rubber to which the cerium isooctanoate heat-resistant additive is added has a tensile strength retention rate of 25.3% to 28.9% and a break elongation retention rate of 35.8% to 40.8% before and after 250°C / 72h thermal oxidation aging. The control rubber without the additive becomes completely brittle after aging.

[0012] The beneficial effects of the present invention are as follows: a silicone rubber heat stabilizer and a preparation method thereof are invented, which can significantly improve the heat resistance of silicone rubber, solve the problem of poor dispersibility of cerium oxide powder, and meet higher industrial requirements; the heat stabilizer can maintain the original performance while improving the heat resistance, maintains the original excellent physical properties and processing performance of silicone rubber, and the additive cost is relatively low; the silicone rubber prepared by the present invention is suitable for applications in higher temperature environments, such as high-temperature seals and insulating materials in the fields of aerospace, automotive electronics, etc. DETAILED DESCRIPTION

[0013] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0014] Example 1 Raw material formula: 100 g of methyl vinyl silicone rubber premix, 0.5 g of 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, 0.125 g of fumed silica, and 0.1 g of cerium isooctanoate solution.

[0015] Preparation method: 2,5-Dimethyl-2,5-bis-(tert-butylperoxy)hexane (hereinafter referred to as bis(2,5-dimethyl)) and fumed silica were mixed in a high-speed mixer at 2000 rpm for 2 minutes, and mixed 3 times until the mixture was uniform, to obtain a bis(2,5-dimethyl) curing agent paste; the methyl vinyl silicone rubber premix was mixed in an open mill for 5 minutes to remove the structure, and then the bis(2,5-dimethyl) curing agent paste was added to the methyl vinyl silicone rubber premix in 3 times and mixed for 10 minutes until the curing agent was uniformly dispersed; cerium isooctanoate solution was added to the silicone rubber as a heat-resistant agent, and mixed on an open mill for 15 minutes until the mixture was uniform to obtain a silicone rubber compound; the silicone rubber compound was placed in a flat-plate vulcanizer mold, and vulcanized for 15 minutes at a temperature of 165°C and a pressure of 18 MPa in the flat-plate vulcanizer to obtain a silicone rubber film; the silicone rubber film was hung in a blast oven at 200°C for 4 hours for two-stage vulcanization to obtain a silicone rubber sample A1.

[0016] Example 2 Raw material formula: 100 g of methyl vinyl silicone rubber premix, 0.5 g of 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, 0.125 g of fumed silica, 10 g of cerium isooctanoate solution, and 90 g of fumed silica powder.

[0017] Preparation method: Mix 10g of cerium isooctanoate solution and 90g of silicon dioxide powder in a kneader, mix at 90°C for 2h, and prepare 100g of a paste heat-resistant agent 1 containing 10% cerium isooctanoate, and take 1g of it as standby; the remaining steps are the same as Example 1, wherein the paste heat-resistant agent 1 is used as a silicone rubber heat-resistant agent to obtain a silicone rubber sample A2.

[0018] Example 3 Raw material formula: 100 g of methyl vinyl silicone rubber premix, 0.5 g of 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, 0.125 g of fumed silica, 10 g of cerium isooctanoate solution, and 90 g of methyl vinyl silicone rubber premix.

[0019] Preparation method: Mix 10g of cerium isooctanoate solution and 90g of methyl vinyl silicone rubber premix in a kneader, mix at 90°C for 2h, and prepare 100g of paste heat-resistant agent 2 containing 10% cerium isooctanoate, and take 1g of it as standby; the remaining steps are the same as Example 1, wherein the paste heat-resistant agent 2 is used as a silicone rubber heat-resistant agent to obtain silicone rubber sample A3.

[0020] Comparative Example 1 Raw material formula: 100 g of methyl vinyl silicone rubber premix, 0.5 g of 2,5-dimethyl-2,5-bis-(tert-butylperoxy)hexane, and 0.125 g of fumed silica.

[0021] Preparation method: 2,5-Dimethyl-2,5-bis-(tert-butylperoxy)hexane and fumed silica were mixed in a high-speed mixer at 2000 rpm for 2 minutes, mixed 3 times until mixed evenly, to obtain a di-2,5 paste vulcanizer; the methyl vinyl silicone rubber premix was mixed in an open mill for 5 minutes to remove the structure, and then the di-2,5 paste vulcanizer was added to the methyl vinyl silicone rubber premix in 3 times and mixed for 10 minutes until the vulcanizer was evenly dispersed to obtain a silicone rubber compound; the silicone rubber compound was placed in a flat-plate vulcanizer mold, and vulcanized for 15 minutes at a temperature of 165°C and a pressure of 18 MPa in the flat-plate vulcanizer to obtain a silicone rubber sheet; the silicone rubber sheet was hung in a blast oven at 200°C for 4 hours for two-stage vulcanization to obtain a silicone rubber sample A0.

[0022] The silicone rubber samples A1, A2, A3 and A0 obtained by the above preparation method were subjected to thermogravimetric tests in air atmosphere. The thermogravimetric test results showed that the temperature at which the thermal weight loss was 5% was as follows: A1: The temperature when thermal weight loss is 5% is 396℃; A2: The temperature when thermal weight loss is 5% is 407℃; A3: The temperature when thermal weight loss is 5% is 410℃; A0: The temperature when thermal weight loss is 5% is 370℃; A1, A2, A3 and A0 were placed in a hot air aging box at 250°C for 72 hours, and the film hardness, tensile strength and elongation at break were tested before and after aging. The results are as follows:

[0023] Note: A0 has cracked after being hot-air aged at 250℃ for 72 hours.

[0024] Conclusion: It can be seen from the above results that, compared with the control example, the silicone rubber prepared in the embodiment of the present invention has a temperature increase of 26 to 40°C when the thermal weight loss is 5%; the tensile strength retention rate after hot air aging reaches 25.3% to 28.9%, and the elongation at break retention rate reaches 35.8% to 40.8%, while the control example has completely cracked after hot air aging; the above two points both reflect that the present invention has a significant effect of improving the heat resistance of silicone rubber.

[0025] In summary, the present invention successfully improves the heat resistance of silicone rubber and the thermal stability of silicone rubber by adding liquid organic cerium salt to silicone rubber, solves the impact of poor dispersibility of cerium oxide powder heat-resistant agent, and maintains the original excellent physical properties and processing performance of silicone rubber, broadens its application range, especially the potential for use in high temperature environments; the preparation operation of the heat stabilizer is simple and low-cost, provides a new technical approach for optimizing the performance of silicone rubber materials, and has significant economic and social benefits.

[0026] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A silicone rubber heat stabilizer and a preparation method thereof, characterized in that: Liquid organic cerium source is the core of the thermal stabilizer. Adding liquid organic cerium salt into silicone rubber can improve its thermal stability.

2. The silicone rubber heat stabilizer according to claim 1, characterized in that: The components of silicone rubber heat stabilizer are mainly liquid organic cerium salt, and the liquid organic cerium salt is one or more of the following: cerium isooctanoate, cerium octanoate, cerium acetate, cerium oxalate, etc.

3. The silicone rubber heat stabilizer according to claims 1 to 2, characterized in that: The preparation method includes one or more of the following methods: a. Adding liquid organic cerium salt directly into silicone rubber as a heat stabilizer; b. The liquid organic cerium salt and silica are physically mixed in a mass ratio of 1:1 to 1:100 to form a paste-like additive as a silicone rubber heat stabilizer; c. Physically mix the liquid organic cerium salt and silicone rubber in a mass ratio of 1:1 to 1:100 to form a paste additive as a silicone rubber heat stabilizer.

4. The silicone rubber heat stabilizer according to claims 1 to 3, characterized in that: The amount of heat stabilizer added to silicone rubber is 0.01%~10% by weight.

5. The silicone rubber heat stabilizer according to claims 1 to 4, characterized in that: The addition methods of heat stabilizers include one or more of the following: physical mixing (direct addition or addition through a carrier), chemical combination, dissolution and dispersion, layered composite, electrostatic adsorption, etc.

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