Composite heat-resistant agent, high-temperature resistant silicone rubber and preparation method thereof

Abstract

The invention belongs to the technical field of silicone rubber, and provides a composite heat-resistant agent, which is used for silicone rubber resistant to high temperatures of 350°C, and the composite heat-resistant agent is composed of 15-40% cerium oxide, 50% methyl vinyl silicone rubber compound, 5-30% titanium dioxide, 3-19% zirconium oxide, and 1-10% GW heat-resistant additive by mass fraction. The composite heat-resistant agent of the invention can be used to improve the high temperature resistance of silicone rubber under high temperature conditions of 350°C, so that the silicone rubber still has good elasticity and mechanical properties.

Description

Technical Field

[0001] The invention belongs to the technical field of silicone rubber, and in particular relates to a composite heat-resistant agent, high-temperature resistant silicone rubber and a preparation method thereof. Background Art

[0002] Silicone rubber is a semi-organic and semi-inorganic polymer material with a main chain of Si-O-Si bonds and side chains composed of organic groups. Before vulcanization, silicone rubber is a high molecular weight linear polysiloxane, and after vulcanization, it is a network elastomer. This special structure gives silicone rubber the characteristics of high temperature resistance, low temperature resistance, high air permeability and weather resistance, and is widely used in the fields of automobiles, kitchen and bathroom, and aviation.

[0003] The Si-O bond energy in the main chain of silicone rubber is 444kJ / mol, while the main chain CC bond energy of commonly used organic polymers is 356kJ / mol and the CO bond energy is 339kJ / mol. The higher Si-O bond energy gives silicone rubber materials excellent thermal stability and can be used for a long time below 260°C. However, the application of silicone rubber is subject to certain restrictions after exceeding 300°C, especially when the temperature reaches 350°C, silicone rubber is prone to brittle fracture. Therefore, its application in the fields of kitchen, bathroom, aviation, etc. that need to withstand high temperature environments of 350°C and above is subject to certain restrictions. For example, the application of sealing rings for steam-bake all-in-one machines is limited. In order to broaden the application scope of silicone rubber in high temperature environments, it is necessary to further improve the high temperature resistance of silicone rubber and avoid thermal aging.

[0004] There are two types of thermal aging phenomena in silicone rubber: one is that the main chain of silicone rubber breaks to generate cyclosiloxane or oligomers, which reduces the hardness; the other is that the side chain methyl is oxidized, and the cross-linking points increase, which increases the hardness. At present, there are five main ways to improve the heat resistance or high temperature of silicone rubber: (1) change the main chain or side chain structure. Heat-resistant bulky segments such as cyclodisilazane, phenylene and carbon decaborane can be introduced into the main chain, and groups such as phenyl can be introduced into the side chain; (2) eliminate silanol groups. Trimethylsilyl can be used to end-cap the silicone rubber end silanol groups to reduce the end hydroxyl group unbuckling reaction. Hexamethyldisilazane can be used to reduce the surface silanol groups of silicone rubber and white carbon black; (3) Adding metal oxides such as SnO2, CeO2, Fe2O3 or metal oxides to the system can prevent the side chain methyl from being oxidized and improve the heat resistance; (4) Adding heat-resistant additives, such as introducing phenyl silicone resin, will inhibit the unbuckling degradation of the main chain; (5) Other methods, such as the positive ions after oxidation of bismaleimide can inhibit the oxidation of side chain methyl groups.

[0005] Patent CN111073057B uses nano zirconium hydroxide, nano yttrium oxide and hexaphenylcyclotrisilazane to improve heat resistance, but the quality loss of silicone rubber is large after aging. Patent CN113278290A uses polydimethylsiloxane, nano aluminum oxide, nano iron oxide, lanthanum oxide and cerium oxide as heat resistant agents, which can maintain certain mechanical and aging resistance within 300℃*(7-10)h, but does not mention aging resistance at 350℃ and above. Patent CN109401330A adds methyl vinyl polysiloxane containing phenyl, and the tensile strength reaches 4.6MPa and the elongation is 102% after aging at 350℃*24h. Although phenyl silicone rubber has good high temperature resistance, its easy sticking to rollers, high price and limited output limit its application. Patent CN111909525A adds oil-resistant additives such as diphenylsilanediol, methylphenylvinyl silicone oil and modified iron oxide to improve aging resistance. After aging at 315℃*24h, the tensile strength retention rate is 63.2% and the elongation retention rate is 52.7%, but it does not mention the aging performance under temperature conditions of 350℃ and above. Patent CN109867965A uses boron-based heat-resistant agents to study the aging of silicone rubber at high temperatures, but the quality loss of silicone rubber is relatively large.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is first to provide a composite heat-resistant agent, which can be used to improve the high temperature resistance of silicone rubber under high temperature conditions of 350°C, so that the silicone rubber still has good elasticity and mechanical properties.

[0008] In order to achieve the above technical effects, the basic concept of the technical solution of the present invention is as follows:

[0009] A composite heat-resistant agent for silicone rubber resistant to high temperatures of 350°C, wherein the composite heat-resistant agent is composed of 15-40% cerium oxide, 50% methyl vinyl silicone rubber compound, 5-30% titanium dioxide, 3-19% zirconium oxide, and 1-10% GW heat-resistant additive by mass fraction;

[0010] Wherein, the chemical structural formula of the GW heat-resistant additive is as follows:

[0011]

[0012] As an example, the preparation method of the heat-resistant auxiliary agent GW is as follows: 2-indolone and 2-(4-bromophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane are reacted in a mixed solution of potassium acetate, 1,4-dioxane and [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II), and after the reaction is completed, the organic part is washed with water, the obtained water layer is extracted with ethyl acetate, and the organic layer is combined, and the organic layer is dried over anhydrous sodium sulfate, filtered and concentrated to obtain a crude product, which is then purified by flash column chromatography to obtain a purified heat-resistant auxiliary agent GW;

[0013] Preferably, the reaction is carried out at 90°C for 24 hours.

[0014] The present invention provides a high temperature resistant silicone rubber, comprising any one of the composite heat resistant agents described above. The high temperature resistant silicone rubber still has certain elasticity and mechanical properties after aging at 350°C*5h, has good high temperature resistance, and can be used under high temperature conditions in the automotive field, household appliances, aviation and the like.

[0015] As an example, the high temperature resistant silicone rubber includes: 100 parts of methyl vinyl silicone rubber raw rubber, 30-50 parts of white carbon black, 0.2-10 parts of structuring control agent, 0.5-10 parts of composite heat resistant agent, and 0.05-0.3 parts of internal release agent.

[0016] As an example, the molar mass of the methyl vinyl silicone rubber raw rubber is between 500,000 and 750,000 g / mol, and the content of vinyl in molar percentage is 0.05-1.0%.

[0017] As an example, the white carbon black is fumed white carbon black, which has a specific surface area of ​​200-380m 2 / g of silica.

[0018] As an example, the internal release agent is one or more of zinc stearate, calcium stearate, barium stearate, magnesium stearate, zinc laurate, magnesium laurate, palmitic acid, lauric acid, and stearic acid.

[0019] As an example, the structuring control agent includes one or more of hydroxy silicone oil, vinyl hydroxy silicone oil, diphenyl dihydroxy silicone oil, dimethyl dimethoxy silane, dimethyl diethoxy silane, methyl phenyl dimethoxy silane, methyl phenyl diethoxy silane, diphenyl dimethoxy silane, diphenyl diethoxy silane, hexamethyl disilazane, vinyl silazane, vinyl trimethoxy silane, and vinyl triethoxy silane.

[0020] As an example, the purity of the methylphenyldimethoxysilane is ≥99%, and the refractive index (n 25D) is 1.469±0.005, and the polychlorinated biphenyl content is 0.

[0021] As an example, the viscosity of the vinyl hydroxy silicone oil (25°C), mm 2 / s: ≤35, hydroxyl content: (mol%) ≥6.0%, vinyl content: (mol%) 6.5-7.5.

[0022] The present invention further provides a method for preparing any of the above-mentioned high temperature resistant silicone rubbers, the preparation method comprising the following steps:

[0023] (1) placing methyl vinyl silicone rubber raw rubber, a structuring control agent and an internal release agent into a kneader to obtain a first mixed material;

[0024] (2) adding white carbon black to the first mixed material in batches, mixing evenly at 100° C., and standing for 4-8 hours to obtain a second mixed material;

[0025] (3) The second mixed material is kneaded at 0.04-0.08 MPa and 120-170° C. for 2-5 h to obtain a mixed base rubber, and then the composite heat-resistant agent is added to the mixed base rubber at a temperature of ≤100° C. to obtain a mixed rubber material, which can be discharged.

[0026] As an example, the mixed rubber material is further added with a vulcanizing agent for molding, and the vulcanizing agent is selected from one of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, diisopropylbenzene peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide or platinum vulcanizing agent.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The heat-resistant auxiliary agent GW used in the composite heat-resistant agent of the present invention is used in combination with metal oxides to significantly increase the thermal decomposition temperature of silicone rubber, improve thermal stability, effectively inhibit the unbuckling degradation of the main chain and the oxidation of the methyl group of the side chain, and improve the heat resistance of silicone rubber at a high temperature of 350°C, which is beneficial to broaden the application range of silicone rubber under high temperature conditions.

[0029] 2. The high temperature resistant silicone rubber of the present invention still has certain elasticity and mechanical properties after aging at 350°C*5h, has good high temperature resistance, and can be used under high temperature conditions in the automotive field, household appliances, aviation, etc.

[0030] 3. The composite heat-resistant agent of the present invention has good dispersibility in silicone rubber.

[0031] 4. The weight loss of the high temperature resistant silicone rubber of the present invention is small after aging at 350°C*5h. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a thermal gravimetric curve of the silicone rubber of Comparative Example 3 (Waters TGA Q50, room temperature to 800° C., 10° C. / min, nitrogen atmosphere).

[0033] Figure 2 This is a thermal gravimetric curve of the silicone rubber of Example 6 (Waters TGA Q50, room temperature to 800°C, 10°C / min, nitrogen atmosphere).

[0034] Figure 3 This is the thermal gravimetric curve of the silicone rubber of Example 9 (Waters TGA Q50, room temperature to 800° C., 10° C. / min, nitrogen atmosphere).

[0035] Figure 4 This is the nuclear magnetic hydrogen spectrum of the heat-resistant additive GW (using AVANCE400 or 500MHz nuclear magnetic resonance spectrometer from Bruker, Germany, and using deuterated chloroform solvent. The peak at 1.26ppm is the hydrocarbon in a, the peak at 7.2ppm is the hydrocarbon in b, the peak at 7.6ppm is the hydrocarbon in c, the peak at 3.49ppm is the hydrocarbon in d, the peak at 7.52ppm is the overlapping hydrocarbon in e and g, the peak at 6.88ppm is the hydrocarbon in f, and the peak at 7.04ppm is the hydrocarbon in h). DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The "parts" in the following embodiments are "parts by weight". The measurement units of "parts" or "parts by weight" in the same embodiment are unified, which is the same as the idea of ​​the technical solution defined by specific measurement units and does not affect its feasibility.

[0038] Unless otherwise specified, the meaning of "%" is "mol%" in relation to vinyl content, and "%" in relation to heat-resistant agents is "wt%".

[0039] Unless otherwise specified, the raw materials involved in the present invention can be obtained by purchasing from the market.

[0040] As an example, the preparation method of the heat-resistant additive GW is as follows:

[0041] 2-Indolone (4.4 g, 0.033 mol) and 2-(4-bromophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (9.4 g, 0.033 mol) were added to a round-bottom flask, and the mixture was heated to 90°C in a mixed solution of potassium acetate (7.0 g, 0.072 mol), 1,4-dioxane (20 mL) and [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (Pd(dppf)Cl2) (1.2 g, 1.64 mmol) for 24 h. The organic portion was washed with water (100 mL), and the aqueous layer was further extracted with ethyl acetate (240 mL). The organic layer was dried over anhydrous sodium sulfate, filtered and concentrated to obtain a crude product, which was then purified by flash column chromatography to obtain purified heat-resistant auxiliary agent GW.

[0042] As an example, the methyl vinyl silicone rubber compound is a 50HA silicone rubber compound made in the laboratory, and its preparation process is as follows:

[0043] (1) placing 100 parts of methyl vinyl silicone rubber raw rubber with an average molecular weight of 660,000 to 720,000 and an average vinyl content of 0.16 to 0.21 mol%, 3.0 to 4.0 parts of a structuring control agent and an appropriate amount of an internal release agent into a kneader to obtain a first mixed material;

[0044] (2) adding 32-38 parts of fumed silica to the first mixed material in 4-6 batches, mixing evenly at 100° C., and standing for 4-8 hours to obtain a second mixed material;

[0045] (3) The second mixed material is kneaded at 0.04-0.08 MPa and 120-170° C. for 2-5 h to obtain a 50HA silicone rubber compound having a secondary vulcanization hardness of 51±3HA, a secondary vulcanization tensile strength ≥8.5 MPa, a secondary vulcanization elongation at break ≥350%, and a secondary vulcanization tear strength ≥18.0 KN / m.

[0046] Of course, the methyl vinyl silicone rubber compound can be obtained through commercial purchase, which will not affect the basic beneficial effects to be achieved by the present invention.

[0047] Example 1

[0048] 100 parts of methyl vinyl silicone rubber with an average molecular weight of 685,000 and an average vinyl content of 0.193 mol% (including 75 parts of methyl vinyl silicone rubber with a molecular weight of 680,000 and a vinyl content of 0.09 mol%, and 25 parts of methyl vinyl silicone rubber with a molecular weight of 700,000 and a vinyl content of 0.5 mol%), 1.5 parts of hexamethyldisilazane (content ≥ 99%), 1.0 part of vinyl hydroxy silicone oil (viscosity (25°C), mm 2 / s:35, hydroxyl content: (mol%) 6.0, vinyl content: (mol%) 7.0), 2.5 parts of methylphenyldimethoxysilane (HY-PS-9116, Hangyu Technology Product Center), 1.2 parts of tetramethyldivinyldisilazane (Xinyaqiang Silicon Chemical Co., Ltd.), 0.4 parts of deionized water, 0.08 parts of zinc stearate (Hangzhou Oil Chemical Co., Ltd.) are put into a kneader to obtain a first mixed material; 34 parts of fumed silica (HL-300, Yichang Huifu Silicon Material Co., Ltd.) are added to the above materials in 5 times, mixed evenly at 100°C, and allowed to stand for 4 hours to obtain a second mixed material; then put it into a kneader and heat it to 165°C for high-temperature mixing, keep it warm, remove low-molecular substances, and wait for the rubber compound to cool below 100°C. Add 4.5 parts of heat-resistant agent (29% cerium oxide, 50% methyl vinyl silicone rubber compound, 12% titanium dioxide, 7% zirconium oxide, 2% GW) and continue kneading (cooling water is required and the temperature cannot exceed 100°C) for 30 minutes and then discharge the material to obtain high-temperature resistant silicone rubber. Divide the rubber into flaky rubber, cool for more than 30 minutes, and then open-mix, filter, weigh and package to obtain the finished high-temperature resistant silicone rubber.

[0049] Take 100 parts of the high temperature resistant silicone rubber product, mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane on a 150mm open mill to prepare a curable silicone rubber composition, and perform flat-plate vulcanization, i.e., first-stage vulcanization, on the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization, i.e., second-stage vulcanization, at 200°C for 2 hours, and test its mechanical properties.

[0050] Example 2

[0051] 100 parts of methyl vinyl silicone rubber with an average molecular weight of 706,000 and an average vinyl content of 0.183 mol% (including 5 parts of methyl vinyl silicone rubber with a molecular weight of 650,000 and a vinyl content of 0.03 mol%, 53 parts of methyl vinyl silicone rubber with a molecular weight of 700,000 and a vinyl content of 0.16 mol%, and 42 parts of methyl vinyl silicone rubber with a molecular weight of 720,000 and a vinyl content of 0.23 mol%), 0.8 parts of hydroxy silicone oil (viscosity of 25 mm at 25°C) were added. 2 / s, hydroxyl content of 8.5wt%), 1.2 parts of hexamethyldisilazane (content ≥ 99%), 0.5 parts of vinyl hydroxy silicone oil (viscosity (25°C), mm 2 / s:35, hydroxyl content: (mol%) 6.0, vinyl content: (mol%) 7.0), 2.0 parts of diphenyldimethoxysilane (DP-820, Guangzhou Shuangtao Fine Chemical Co., Ltd.), 1.5 parts of tetramethyldivinyldisilazane (Xinyaqiang Silicon Chemical Co., Ltd.), 0.5 parts of deionized water, 0.10 parts of polyethylene glycol distearate (Nantong Qianhe Chemical Co., Ltd.) are put into a kneader to obtain a first mixed material; 33 parts of fumed silica (XHG-300, Zhejiang Kaihua Synthetic Materials Co., Ltd.) are added to the above materials in 5 times, mixed evenly at 100°C, and allowed to stand for 4 hours to obtain a second mixed material; then put it into a kneader and heat it to 155°C for high-temperature mixing, keep it warm, remove low-molecular substances, and wait for the rubber to cool below 100°C.

[0052] Add 4.0 parts of heat-resistant agent (31% cerium oxide, 50% methyl vinyl silicone rubber compound, 13% titanium dioxide, 3% zirconium oxide, 3% GW) and continue kneading (cooling water is required and the temperature cannot exceed 100°C) for 30 minutes and then discharge the material to obtain high-temperature resistant silicone rubber. Divide the rubber into flaky rubber, cool for more than 30 minutes, and then open-mix, filter the rubber, weigh, and package to obtain the finished high-temperature resistant silicone rubber.

[0053] Take 100 parts of the high temperature resistant silicone rubber product, mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane on a 150mm open mill to prepare a curable silicone rubber composition, and perform flat-plate vulcanization, i.e., first-stage vulcanization, on the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization, i.e., second-stage vulcanization, at 200°C for 2 hours, and test its mechanical properties.

[0054] Example 3

[0055] 100 parts of methyl vinyl silicone rubber with an average molecular weight of 697,000 and an average vinyl content of 0.196 mol% (including 21 parts of methyl vinyl silicone rubber with a molecular weight of 680,000 and a vinyl content of 0.09 mol%, 73 parts of methyl vinyl silicone rubber with a molecular weight of 700,000 and a vinyl content of 0.16 mol%, and 6 parts of methyl vinyl silicone rubber with a molecular weight of 720,000 and a vinyl content of 1.0 mol%), 0.3 parts of hydroxy silicone oil (viscosity of 25 mm at 25°C) were added. 2 / s, hydroxyl content of 8.5wt%), 1.0 part hexamethyldisilazane (content ≥99%), 0.5 part vinyl hydroxy silicone oil (viscosity (25℃), mm 2 / s:35, hydroxyl content: (mol%) 6.0, vinyl content: (mol%) 7.0), 2.0 parts of diphenyldimethoxysilane (Hubei Ruishengxiang Technology Co., Ltd.), 0.8 parts of tetramethyldivinyldisilazane (Xinyaqiang Silicon Chemical Co., Ltd.), 0.3 parts of deionized water, 0.15 parts of stearic acid (Hangzhou Oil Chemical Co., Ltd.) are put into a kneader to obtain a first mixed material; 33 parts of fumed silica (XHG-200, Zhejiang Kaihua Synthetic Materials Co., Ltd.) are added to the above materials in 5 times, mixed evenly at 100°C, and allowed to stand for 4 hours to obtain a second mixed material; then put it into a kneader and heat it to about 170°C for high-temperature mixing, keep warm, remove low-molecular substances, and wait for the rubber to cool to below 100°C.

[0056] Add 5.0 parts of heat-resistant agent (27% cerium oxide, 50% methyl vinyl silicone rubber compound, 18% titanium dioxide, 4% zirconium oxide, 1% GW) and continue kneading (cooling water is required and the temperature cannot exceed 100°C) for 30 minutes and then discharge the material to obtain high-temperature resistant silicone rubber. Divide the rubber into flaky rubber, cool for more than 30 minutes, and then open-mix, filter, weigh and package to obtain the finished high-temperature resistant silicone rubber.

[0057] Take 100 parts of the high temperature resistant silicone rubber product, mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane on a 150mm open mill to prepare a curable silicone rubber composition, and perform flat-plate vulcanization, i.e., first-stage vulcanization, on the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization, i.e., second-stage vulcanization, at 200°C for 2 hours, and test its mechanical properties.

[0058] Example 4

[0059] 100 parts of methyl vinyl silicone rubber with an average molecular weight of 687,000 and an average vinyl content of 0.202 mol% (including 23 parts of methyl vinyl silicone rubber with a molecular weight of 700,000 and a vinyl content of 0.05 mol%, 72 parts of methyl vinyl silicone rubber with a molecular weight of 680,000 and a vinyl content of 0.23 mol%, and 5 parts of methyl vinyl silicone rubber with a molecular weight of 720,000 and a vinyl content of 0.5 mol%), 0.4 parts of hydroxy silicone oil (viscosity of 25 mm at 25°C) were added. 2 / s, hydroxyl content of 8.5wt%), 1.3 parts of hexamethyldisilazane (content ≥ 99%), 0.8 parts of vinyl hydroxy silicone oil (viscosity (25°C), mm 2 / s:35, hydroxyl content: (mol%) 6.0, vinyl content: (mol%) 7.0), 2.5 parts of methylphenyldiethoxysilane (Hubei Xinghengye Technology Co., Ltd.), 1.0 part of tetramethyldivinyldisilazane (Xinyaqiang Silicon Chemical Co., Ltd.), 0.3 parts of deionized water, 0.12 parts of palmitic acid (Nanjing Dongde Chemical Technology Co., Ltd.) are put into a kneader to obtain a first mixed material; 32 parts of fumed silica (Tokuyama QS-30, Tokuyama Co., Ltd., Japan) are added to the above materials in 5 times, mixed evenly at 100°C, and allowed to stand for 4 hours to obtain a second mixed material; then put into a kneader and heat to 160°C for high-temperature mixing, keep warm, remove low-molecular substances, and wait for the rubber compound to cool below 100°C.

[0060] Add 4.3 parts of heat-resistant agent (25% cerium oxide, 50% methyl vinyl silicone rubber compound, 10% titanium dioxide, 12% zirconium oxide, 3% GW) and continue kneading (cooling water is required and the temperature cannot exceed 100°C) for 30 minutes and then discharge the material to obtain high-temperature resistant silicone rubber. Divide the rubber into flaky rubber, cool for more than 30 minutes, and then open-mix, filter, weigh and package to obtain the finished high-temperature resistant silicone rubber.

[0061] Take 100 parts of the high temperature resistant silicone rubber product, mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane on a 150mm open mill to prepare a curable silicone rubber composition, and perform flat-plate vulcanization, i.e., first-stage vulcanization, on the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization, i.e., second-stage vulcanization, at 200°C for 2 hours, and test its mechanical properties.

[0062] Example 5

[0063] 100 parts of methyl vinyl silicone rubber with an average molecular weight of 682,000 and an average vinyl content of 0.194 mol% (including 13 parts of methyl vinyl silicone rubber with a molecular weight of 650,000 and a vinyl content of 0.03 mol%, 72 parts of methyl vinyl silicone rubber with a molecular weight of 680,000 and a vinyl content of 0.16 mol%, and 15 parts of methyl vinyl silicone rubber with a molecular weight of 720,000 and a vinyl content of 0.5 mol%), 0.1 parts of hydroxy silicone oil (viscosity of 25 mm at 25°C) were added. 2 / s, hydroxyl content of 8.5wt%), 0.6 parts of hexamethyldisilazane (content ≥99%), 0.5 parts of vinyl hydroxy silicone oil (viscosity (25°C), mm 2 / s:35, hydroxyl content: (mol%) 6.0, vinyl content: (mol%) 7.0), 2.0 parts of diphenyldimethoxysilane (Hubei Ruishengxiang Technology Co., Ltd.), 1.2 parts of tetramethyldivinyldisilazane (Xinyaqiang Silicon Chemical Co., Ltd.), 0.4 parts of deionized water, 0.08 parts of lauric acid (Nanjing Dongde Chemical Technology Co., Ltd.) are put into a kneader to obtain a first mixed material; 30 parts of fumed silica (Tokuyama DM-30S, Tokuyama Co., Ltd., Japan) are added to the above materials in 5 times, mixed evenly at 100°C, and allowed to stand for 4 hours to obtain a second mixed material; then put it into a kneader and heat it to 170°C for high-temperature mixing, keep it warm, remove low-molecular substances, and wait for the rubber to cool below 100°C.

[0064] Add 3.5 parts of heat-resistant agent (30% cerium oxide, 50% methyl vinyl silicone rubber compound, 11% titanium dioxide, 3% zirconium oxide, 6% GW) and continue kneading (cooling water is required and the temperature cannot exceed 100°C) for 30 minutes and then discharge the material to obtain high-temperature resistant silicone rubber. Divide the rubber into flaky rubber, cool for more than 30 minutes, and then open-mix, filter the rubber, weigh, and package to obtain the finished high-temperature resistant silicone rubber product.

[0065] Take 100 parts of the high temperature resistant silicone rubber product, mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane on a 150mm open mill to prepare a curable silicone rubber composition, and perform flat-plate vulcanization, i.e., first-stage vulcanization, on the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization, i.e., second-stage vulcanization, at 200°C for 2 hours, and test its mechanical properties.

[0066] Example 6

[0067] 100 parts of methyl vinyl silicone rubber with an average molecular weight of 689,000 and an average vinyl content of 0.193 mol% (including 25 parts of methyl vinyl silicone rubber with a molecular weight of 700,000 and a vinyl content of 0.05 mol%, 65 parts of methyl vinyl silicone rubber with a molecular weight of 680,000 and a vinyl content of 0.20 mol%, and 10 parts of methyl vinyl silicone rubber with a molecular weight of 720,000 and a vinyl content of 0.5 mol%), 0.2 parts of hydroxy silicone oil (viscosity of 25 mm at 25°C) were added. 2 / s, hydroxyl content of 8.5wt%), 0.5 parts of hexamethyldisilazane (content ≥99%), 0.8 parts of vinyl hydroxy silicone oil (viscosity (25°C), mm 2 / s:35, hydroxyl content: (mol%) 6.0, vinyl content: (mol%) 7.0), 2.4 parts of methylphenyldimethoxysilane (HY-PS-9116, Hangyu Technology Product Center), 1.3 parts of tetramethyldivinyldisilazane (Xinyaqiang Silicon Chemical Co., Ltd.), 0.4 parts of deionized water, 0.1 parts of calcium stearate (Hangzhou Oil Chemical Co., Ltd.) are put into a kneader to obtain a first mixed material; 37 parts of fumed silica (Tokuyama DM-20S, Tokuyama Co., Ltd., Japan) are added to the above materials in 5 times, mixed evenly at 100°C, and allowed to stand for 4 hours to obtain a second mixed material; then put it into a kneader and heat it to about 155°C for high-temperature mixing, keep it warm, remove low-molecular substances, and wait for the rubber to cool below 100°C.

[0068] Add 4.0 parts of heat-resistant agent (30% cerium oxide, 50% methyl vinyl silicone rubber compound, 15% titanium dioxide, 4% zirconium oxide, 1% GW) and continue kneading (cooling water is required and the temperature cannot exceed 100°C) for 30 minutes and then discharge the material to obtain high-temperature resistant silicone rubber. Divide the rubber into flaky rubber, cool for more than 30 minutes, and then open-mix, filter, weigh and package to obtain the finished high-temperature resistant silicone rubber.

[0069] Take 100 parts of the high temperature resistant silicone rubber product, mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane on a 150mm open mill to prepare a curable silicone rubber composition, and perform flat-plate vulcanization, i.e., first-stage vulcanization, on the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization, i.e., second-stage vulcanization, at 200°C for 2 hours, and test its mechanical properties.

[0070] Example 7

[0071] 100 parts of methyl vinyl silicone rubber with an average molecular weight of 678,000 and an average vinyl content of 0.181 mol% (including 24 parts of methyl vinyl silicone rubber with a molecular weight of 650,000 and a vinyl content of 0.05 mol%, 62 parts of methyl vinyl silicone rubber with a molecular weight of 680,000 and a vinyl content of 0.16 mol%, and 14 parts of methyl vinyl silicone rubber with a molecular weight of 720,000 and a vinyl content of 0.5 mol%), 0.2 parts of hydroxy silicone oil (viscosity of 25 mm at 25°C) were added. 2 / s, hydroxyl content of 8.5wt%), 0.8 parts of hexamethyldisilazane (content ≥ 99%), 0.5 parts of vinyl hydroxy silicone oil (viscosity (25°C), mm 2 / s:35, hydroxyl content: (mol%) 6.0, vinyl content: (mol%) 7.0), 2.0 parts of methylphenyldimethoxysilane (HY-PS-9116, Hangyu Technology Product Center), 0.8 parts of tetramethyldivinyldisilazane (Xinyaqiang Silicon Chemical Co., Ltd.), 0.3 parts of deionized water, 0.10 parts of polyethylene glycol distearate (Nantong Qianhe Chemical Co., Ltd.) are put into a kneader to obtain a first mixed material; 33 parts of fumed silica (Evonik Degussa R106, Evonik Degussa Co., Ltd.) are added to the above materials in 5 times, mixed evenly at 100°C, and allowed to stand for 4 hours to obtain a second mixed material; then put it into a kneader and heat it to about 170°C for high-temperature banburying, keep it warm, remove low-molecular substances, and wait for the rubber compound to cool below 100°C.

[0072] Add 4.0 parts of heat-resistant agent (28% cerium oxide, 50% methyl vinyl silicone rubber compound, 13% titanium dioxide, 4% zirconium oxide, 5% GW) and continue kneading (cooling water is required, and the temperature cannot exceed 100°C) for 30 minutes and then discharge the material to obtain high-temperature resistant silicone rubber. The rubber material is divided into sheet-like rubber materials, cooled for more than 30 minutes, and then open-mixed, filtered, weighed, and packaged to obtain a high-temperature resistant silicone rubber product. Take 100 parts of the high-temperature resistant silicone rubber product, use a 150mm open mill to mix and disperse 1 part of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane to prepare a curable silicone rubber composition, and perform flat vulcanization (i.e., first-stage vulcanization) of the curable silicone rubber composition at 170°C for 10 minutes, and also perform post-vulcanization (i.e., second-stage vulcanization) at 200°C for 2 hours, and test its mechanical properties.

[0073] Example 8

[0074] The difference from implementation 2 is that 4 parts of heat-resistant agent (50% methyl vinyl silicone rubber compound, 29% titanium dioxide, 18% zirconium oxide, 3% GW) are added.

[0075] Example 9

[0076] The difference from implementation 2 is that 4 parts of heat-resistant auxiliary agent GW mixture (80% methyl vinyl silicone rubber compound, 20% GW) are added.

[0077] Example 10

[0078] The difference from implementation 2 is that 4 parts of heat-resistant agent (30% cerium oxide, 50% methyl vinyl silicone rubber compound, 15% titanium dioxide, 5% zirconium oxide) are added.

[0079] Embodiment 11

[0080] The difference from implementation 2 is that 4 parts of heat-resistant agent (10% cerium oxide, 50% methyl vinyl silicone rubber compound, 13.5% titanium dioxide, 26% zirconium oxide, 0.5% GW) are added.

[0081] Comparative Example 1

[0082] The difference from Example 6 is that the heat-resistant agent is replaced by 5 parts of commercially available WACKER H6, and the rest is consistent with Example 6.

[0083] Comparative Example 2

[0084] The difference from Implementation 6 is that the heat-resistant agent is replaced with 5 parts of commercially available Dow RBM9012, and the rest is consistent with Implementation 6.

[0085] Comparative Example 3

[0086] The difference from Example 6 is that the heat-resistant agent is replaced with 3.0 parts of commercially available heat-resistant agent WACKER H6 and 2.0 parts of commercially available heat-resistant agent cerium oxide paste (JC-CeOC, Shenzhen Jingcai Chemical Co., Ltd.), and the rest is consistent with Example 6.

[0087] The silicone rubber data measured in the following table are respectively tested according to national standards for the Shore hardness, tensile strength, elongation at break, tear strength, resilience, and hot air aging of the silicone rubber prepared in the embodiments and comparative examples of the present invention. The specific test methods are as follows: Shore hardness is tested according to GB / T531.1-2008; tensile strength and elongation at break are tested according to GB / T528-2009; tear strength is tested according to GB / T529-2008; hot air aging is tested according to GB / T3512-2004. The experimental data obtained from the test refer to the secondary vulcanization and hot air aging properties of silicone rubber in Tables 1-2 below.

[0088] Table 1

[0089]

[0090] Table 2

[0091]

[0092] As can be seen from Table 1-2, in Comparative Example 1, the heat-resistant agent is replaced by commercially available WACKER H6; in Comparative Example 2, the heat-resistant agent is replaced by commercially available Dow RBM9012; in Comparative Example 3, the heat-resistant agent is replaced by commercially available WACKER H6 and commercially available cerium oxide paste. The hardness of the silicone rubber of Comparative Example 1 and Comparative Example 3 is significantly increased after 350℃*5h hot air aging. This is because the side chain groups of the silicone rubber are oxidized, which increases the crosslinking points and causes the hardness to rise. The samples are obviously brittle after aging and lose mechanical properties. Comparative Example 2 also has certain mechanical properties after 350℃*5h, but its appearance is yellow and its price is relatively high, which limits its application to a certain extent.

[0093] In Examples 1-7, the new heat-resistant agent of the present invention is used. After hot air aging at 350°C for 5h, the mass loss rate of the silicone rubber is relatively low, at about 11%, and good mechanical properties are still maintained. However, after adding the commercially available heat-resistant agent, the mass loss of the silicone rubber increases, and the rubber even becomes brittle and fractures and loses its mechanical properties.

[0094] Compared with Example 2, Example 8 lacks the synergistic heat-resistant effect of cerium oxide metal oxide, and the tensile strength and elongation at break decrease slightly after 350℃*5h hot air aging. Compared with Example 2, Example 9 only uses the heat-resistant auxiliary agent GW mixture, which will not become brittle after 350℃*5h hot air aging, and the aging strength decreases slightly, but the cost of the heat-resistant agent is relatively high. Compared with Example 2, Example 10 does not add the heat-resistant auxiliary agent GW, and the tensile strength decreases significantly. Compared with Example 2, the amounts of cerium oxide, zirconium oxide and GW used in Example 11 are not within the preferred range of the present invention, and the tensile strength decreases significantly after 350℃*5h aging.

[0095] As an example, the present invention provides the thermogravimetric performance test results of Example 6, Example 9 and Comparative Example 3 of the present invention. Figure 1 This is the thermal weight loss curve of the silicone rubber of Comparative Example 3 (adding 3.0 parts of H6 and 2.0 parts of cerium oxide paste), the temperature of 5% weight loss is 419.36°C, and the epitaxial starting temperature is 446.88°C. Figure 2 This is the thermal weight loss curve of the silicone rubber of Example 6 (adding 4.0 parts of a mixed heat-resistant agent consisting of 30% cerium oxide, 50% methyl vinyl silicone rubber compound, 15% titanium dioxide, 4% zirconium oxide, and 1% GW), the temperature of 5% weight loss is 451.73°C, and the epitaxial starting temperature is 486.67°C. Figure 3 This is the thermal weight loss curve of the silicone rubber of Example 9 (adding 4 parts of GW mixed heat-resistant agent composed of 80% methyl vinyl silicone rubber compound and 20% GW), the temperature of 5% weight loss is 433.58°C, and the epitaxial starting temperature is 457.04°C.

[0096] according to Figure 1-3 It can be seen from the thermal weight loss curve combined with the test data in Table 1-2 that the comparative example 3 becomes brittle and loses its usability after 350°C*5h hot air aging, while the examples 6 and 9 of the present invention have better mechanical properties after 350°C*5h hot air aging due to the use of the heat-resistant agent of the present invention.

Claims

1. A composite heat-resistant agent, characterized in that: Used for silicone rubber resistant to high temperature of 350°C, the composite heat-resistant agent is composed of 15-40% cerium oxide, 50% methyl vinyl silicone rubber compound, 5-30% titanium dioxide, 3-19% zirconium oxide, and 1-10% GW heat-resistant additive by mass fraction; Wherein, the chemical structural formula of the GW heat-resistant additive is as follows:

2. The composite heat-resistant agent according to claim 1, characterized in that: The preparation method of the heat-resistant auxiliary agent GW is as follows: 2-indolone and 2-(4-bromophenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane are reacted in a mixed solution of potassium acetate, 1,4-dioxane and [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II), and after the reaction is completed, the organic part is washed with water, the obtained water layer is extracted with ethyl acetate, and the organic layers are combined, and the organic layers are dried over anhydrous sodium sulfate, filtered and concentrated to obtain a crude product, which is then purified by flash column chromatography to obtain a purified heat-resistant auxiliary agent GW.

3. The composite heat-resistant agent according to claim 2, characterized in that: The reaction was carried out at 90°C for 24 h.

4. A high temperature resistant silicone rubber, characterized in that: Add the composite heat-resistant agent according to any one of claims 1 to 3.

5. The high temperature resistant silicone rubber according to claim 4, characterized in that: The high temperature resistant silicone rubber comprises: 100 parts of methyl vinyl silicone rubber raw rubber, 30-50 parts of white carbon black, 0.2-10 parts of a structural control agent, 0.5-10 parts of a composite heat resistant agent, and 0.05-0.3 parts of an internal release agent.

6. The high temperature resistant silicone rubber according to claim 5, characterized in that: The molar mass of the methyl vinyl silicone rubber raw rubber is between 500000-750000 g / mol, and the content of vinyl in molar percentage is 0.05-1.0%.

7. The high temperature resistant silicone rubber according to claim 5, characterized in that: The white carbon black is a fumed white carbon black with a specific surface area of ​​200-380m 2 / g of silica.

8. The high temperature resistant silicone rubber according to claim 5, characterized in that: The internal mold release agent is one or more of zinc stearate, calcium stearate, barium stearate, magnesium stearate, zinc laurate, magnesium laurate, palmitic acid, lauric acid, and stearic acid.

9. The high temperature resistant silicone rubber according to claim 5, characterized in that: The structuring control agent includes one or more of hydroxy silicone oil, vinyl hydroxy silicone oil, diphenyl dihydroxy silicone oil, dimethyl dimethoxy silane, dimethyl diethoxy silane, methyl phenyl dimethoxy silane, methyl phenyl diethoxy silane, diphenyl dimethoxy silane, diphenyl diethoxy silane, hexamethyl disilazane, vinyl silazane, vinyl trimethoxy silane, and vinyl triethoxy silane.

10. The high temperature resistant silicone rubber according to claim 9, characterized in that: The purity of the methylphenyldimethoxysilane is ≥99%; the refractive index is 1.469±0.005 at 25° C. with the helium yellow line having a wavelength of 587.56 nanometers as the incident light; and the polychlorinated biphenyl content is 0.

11. The high temperature resistant silicone rubber according to claim 9, characterized in that: The viscosity of the vinyl hydroxy silicone oil at 25°C is ≤35 mm 2 / s; hydroxyl content, calculated in mol%, ≥6.0%; vinyl content, calculated in mol%, 6.5-7.

5.

12. The method for preparing high temperature resistant silicone rubber according to any one of claims 4 to 11, characterized in that: The preparation method comprises the following steps: (1) placing methyl vinyl silicone rubber raw rubber, a structuring control agent and an internal release agent into a kneader to obtain a first mixed material; (2) adding white carbon black to the first mixed material in batches, mixing evenly at 100° C., and standing for 4-8 hours to obtain a second mixed material; (3) The second mixed material is kneaded at 0.04-0.08 MPa and 120-170° C. for 2-5 h to obtain a mixed base rubber, and then the composite heat-resistant agent is added to the mixed base rubber at a temperature of ≤100° C. to obtain a mixed rubber material, which can be discharged.

13. The method for preparing high temperature resistant silicone rubber according to claim 12, characterized in that: The mixed rubber material is further added with a vulcanizing agent for molding, and the vulcanizing agent is selected from one of 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane, diisopropylbenzene peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide or platinum vulcanizing agent.

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