High-temperature-resistant mixed silicone rubber and preparation method thereof

Abstract

The invention relates to the technical field of silicone rubber, and particularly discloses high-temperature-resistant mixed silicone rubber and a preparation method thereof. Through the synergistic effect of the rigid group, the cross-linked network structure and the lignin nano-modified silicon dioxide, the main chain degradation reaction of the mixed silicon rubber caused by the influence of high temperature can be fully weakened, so that the mixed silicon rubber has better thermal stability, can maintain better mechanical properties after high-temperature treatment, and has a wide application range.

Description

Technical Field

[0001] The present application relates to the technical field of silicone rubber, and more specifically, to a high-temperature resistant mixed silicone rubber and a preparation method thereof. Background Art

[0002] Silicone rubber is a type of polymeric elastomeric material with repetitive silicon-oxygen bonds as its backbone and organic groups (primarily methyl, vinyl, or phenyl groups) attached to its side chains. Its unique molecular structure gives it excellent overall performance. Advantages of silicone rubber include exceptional flexibility and elasticity, a wide operating temperature range (typically -60°C to +200°C), excellent weather resistance (UV and ozone resistance), good electrical insulation, physiological inertness, and low surface tension.

[0003] Thanks to its inherently superior properties, silicone rubber has become an indispensable key material in numerous industrial fields and everyday life. In the aerospace sector, silicone rubber is used in engine compartment seals, hot air ducts, and gaskets. In the automotive industry, silicone rubber is used in engine peripheral seals (such as cylinder head gaskets), turbocharger hoses, and ignition cable jackets. In the electrical and electronics sector, silicone rubber is used in wire and cable insulation, connector seals, and thermally conductive gaskets. Silicone rubber also plays a key role in household appliances and medical devices.

[0004] Regarding the above-mentioned related technologies, the inventors believe that although silicone rubber has a certain tolerance to high temperatures, when the temperature exceeds 300°C, thermal degradation will have a serious impact on the structure of silicone rubber, resulting in a decrease in the mechanical properties of silicone rubber, thereby limiting the application scope of silicone rubber. Summary of the Invention

[0005] In the related art, when the temperature exceeds 300°C, thermal degradation will have a serious impact on the structure of silicone rubber, resulting in a decrease in the mechanical properties of silicone rubber and limiting the scope of application of silicone rubber. To improve this defect, the present application provides a high-temperature resistant compound silicone rubber and a preparation method thereof.

[0006] In the first aspect, the present application provides a high temperature resistant compound silicone rubber, which adopts the following technical solution:

[0007] A high-temperature resistant mixed silicone rubber comprises the following components in parts by weight: 40-45 parts of modified methyl vinyl silicone rubber, 10-15 parts of methyl phenyl silicone rubber, 10-15 parts of vinyl MQ silicone resin, 3-5 parts of a structuring control agent, 3.5-4.5 parts of a filler, and 2.0-2.5 parts of a vulcanizing agent; the modified methyl vinyl silicone rubber contains a polyimide group and a lignin group; and the filler comprises lignin-modified nano-silica.

[0008] By adopting the above technical solution, the present application uses modified methyl vinyl silicone rubber and methyl phenyl silicone rubber as the main components. The modified methyl phenyl silicone rubber contains lignin groups and polyimide groups with strong rigidity, and the methyl phenyl silicone rubber contains benzene rings with strong rigidity. These rigid groups can hinder the movement of the molecular chains of the mixed silicone rubber. Vinyl MQ silicone resin can be evenly dispersed in the mixed silicone rubber and can participate in vulcanization during the vulcanization process. Further cross-linking occurs on the basis of the silicone rubber. The new cross-linked network structure can cooperate with the rigid groups introduced into the mixed silicone rubber to hinder the movement of the mixed silicone rubber molecular chains. The lignin groups on the surface of the lignin-modified nano-silica in the filler can cooperate with the lignin groups in the modified methyl vinyl silicone rubber to hinder the movement of the mixed silicone rubber molecular chains, and the good thermal conductivity of the silica itself also promotes the uniform dispersion of heat, reducing the possibility of local accumulation of high temperature. Through the synergistic effect of rigid groups, cross-linked network structure and lignin nano-modified silica, the main chain degradation reaction of compounded silicone rubber caused by high temperature can be fully weakened, thereby having better thermal stability and being able to maintain good mechanical properties after high-temperature treatment, and has a wide range of applications.

[0009] Preferably, the structuring control agent is one of hydroxy silicone oil, dimethyldiethoxysilane and hexamethyldisilazane.

[0010] By adopting the above technical solution, the present application optimizes the type of structuring control agent. Compared with the other two structuring control agents, the more rigid hexamethyldisilazane can produce a good synergistic effect with the rigid groups in components such as modified methyl vinyl silicone rubber and methylphenyl silicone rubber, thereby effectively improving the high temperature resistance of the compounded silicone rubber, so that the compounded silicone rubber can maintain good mechanical properties after high temperature treatment.

[0011] Preferably, the vinyl mole fraction of the vinyl MQ silicone resin is 0.13-0.17%.

[0012] By adopting the above technical solution, the present application optimizes the vinyl mole fraction range of the vinyl MQ silicone resin, which can fully promote the cross-linking of the vinyl MQ silicone resin and the silicone rubber molecules, effectively improve the high temperature resistance of the compounded silicone rubber, and enable the compounded silicone rubber to maintain good mechanical properties after high temperature treatment.

[0013] Preferably, the modified methyl vinyl silicone rubber is prepared according to the following method:

[0014] (1) Methyl vinyl silicone rubber and toluene are stirred and mixed uniformly, dimethyl monochlorosilane is added to the mixture, the mixture is stirred and heated under nitrogen protection, a platinum catalyst is added, the mixture is kept warm for reaction, and then the temperature is lowered and the material is discharged, and the silicone rubber intermediate material is obtained through purification and post-treatment processes;

[0015] (2) Add the silicone rubber intermediate material into tetrahydrofuran and stir to dissolve, then add hydroxyethylated lignin, hydroxyl-containing polyimide and acid binding agent, stir and heat at constant temperature under nitrogen protection, discharge the material after the reaction is completed, and then wash and vacuum dry to obtain modified methyl vinyl silicone rubber.

[0016] By adopting the above technical solution, the present application first uses dimethyl monochlorosilane and methyl vinyl silicone rubber as reactants, and undergoes a hydrosilylation reaction under the catalysis of a platinum catalyst to obtain a chlorine-containing silicone rubber intermediate material. Then, in the presence of an acid binding agent, the silicone rubber intermediate material is subjected to a coupling grafting reaction with hydroxyethylated lignin and hydroxyl-containing polyimide. The chlorine atoms in the silicone rubber intermediate material are removed, and the lignin groups and polyimide groups are grafted onto the main chain of the silicone rubber, thereby obtaining a modified methyl vinyl silicone rubber.

[0017] Preferably, the hydroxyl-containing polyimide is prepared according to the following method:

[0018] After mixing a diamine monomer, a dianhydride monomer and m-cresol, isoquinoline is added dropwise to the mixture, and then heated under nitrogen protection to react to obtain a reaction liquid. The reaction liquid is cooled, and the reaction liquid is added to excess ethanol for precipitation. After reduced pressure filtration and washing, a hydroxyl-containing polyimide is obtained; the diamine monomer contains phenolic hydroxyl groups.

[0019] By adopting the above technical solution, the present application uses a diamine monomer containing a phenolic hydroxyl group to react with a dianhydride monomer to obtain a hydroxyl-containing polyimide.

[0020] Preferably, the diamine monomer is 3,3'-dihydroxybenzidine or 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.

[0021] By adopting the above technical solution, the present application preferably selects two hydroxyl-containing diamine monomers, which can be used to prepare hydroxyl-containing polyimide.

[0022] Preferably, the dianhydride monomer is 4,4'-(4,4'-isopropyldiphenoxy) diphthalic anhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride or 4,4'-oxydiphthalic anhydride.

[0023] By adopting the above technical solution, the present application preferably selects three dianhydride monomers, which can be used to prepare hydroxyl-containing polyimide.

[0024] Preferably, the hydroxyethylated lignin is prepared according to the following method:

[0025] Enzymatically hydrolyzed lignin, ethylene carbonate, and tetrabutylammonium iodide are mixed and stirred to obtain a reaction mixture, ethanol is added to the reaction mixture to obtain a diluted mixture, the diluted mixture is added to hydrochloric acid, and then reacted under freezing conditions. After the reaction is completed, the filter is filtered and the filter residue is collected. The filter residue is washed and freeze-dried to obtain hydroxyethylated lignin.

[0026] By adopting the above-mentioned technical solution, the present application uses ethylene carbonate as an alkylating agent and tetrabutylammonium iodide as an ionic liquid solvent and catalyst to hydroxyethylate enzymatically hydrolyzed lignin, resulting in hydroxyethylated lignin. In the hydroxyethylated lignin, some phenolic hydroxyl groups are converted to alcoholic hydroxyl groups, enabling more efficient coupling and grafting reactions with the silicone rubber intermediate material, thereby improving the high-temperature resistance of the compounded silicone rubber.

[0027] Preferably, the lignin-modified nano-silica is prepared according to the following method:

[0028] Sodium silicate, alkali lignin and deionized water are mixed, stirred and dissolved, and then deionized water, ethanol and polyethylene glycol are added, stirred first, and then sulfuric acid is added for acidification, and a nano-silica suspension is obtained after stirring; the nano-silica suspension is ultrasonically treated and preheated, and then sulfuric acid is added again for acidification, and then allowed to stand for treatment, and then a solid product is collected by vacuum filtration, and after acid washing and drying, lignin-modified nano-silica is obtained.

[0029] By adopting the above-mentioned technical solution, the present application uses sodium silicate as the silicon source and a two-step acid precipitation method to hybridize and modify lignin to prepare lignin-modified nano-silica. The lignin groups on the surface of the lignin-modified nano-silica can synergistically hinder the movement of the compounded silicone rubber molecular chains with the lignin groups in the modified methyl vinyl silicone rubber. Furthermore, the excellent thermal conductivity of the silica itself also promotes uniform heat dispersion, reducing the possibility of localized high temperature accumulation and improving the high-temperature resistance of the compounded silicone rubber.

[0030] In a second aspect, the present application provides a method for preparing high-temperature resistant compound silicone rubber, which adopts the following technical solution.

[0031] A method for preparing high-temperature resistant mixed silicone rubber comprises the following steps:

[0032] (1) placing modified methyl vinyl silicone rubber, methyl phenyl silicone rubber, a structural control agent and vinyl MQ silicone resin in a two-roll mill for mixing, adding fillers and vulcanizing agents during the mixing process, and thinning out sheets after the mixing is completed to form a mixed rubber;

[0033] (2) Add the mixed rubber into a flat vulcanizer for vulcanization, take it out and wait for it to cool naturally to obtain high-temperature resistant mixed silicone rubber.

[0034] By adopting the above technical solution, the present application first mixes the components evenly through mixing to obtain a rubber mix, and then further vulcanizes the rubber mix through a flat vulcanizer. During the vulcanization, the vinyl MQ silicone resin is further cross-linked on the basis of the silicone rubber. The new cross-linked network structure can cooperate with the rigid groups introduced into the mixed silicone rubber to hinder the movement of the mixed silicone rubber molecular chains, thereby obtaining a mixed silicone rubber with strong high-temperature resistance.

[0035] In summary, this application has the following beneficial effects:

[0036] 1. Through the synergistic effect of rigid groups, cross-linked network structure and lignin nano-modified silica, the main chain degradation reaction of compounded silicone rubber caused by high temperature can be fully weakened, thereby having better thermal stability and being able to maintain good mechanical properties after high temperature treatment, and has a wide range of applications.

[0037] 2. This application prefers the type of structured control agent, among which hexamethyldisilazane can produce a good synergistic effect with the rigid groups in components such as modified methyl vinyl silicone rubber and methylphenyl silicone rubber, thereby effectively improving the high temperature resistance of the compounded silicone rubber, so that the compounded silicone rubber can maintain good mechanical properties after high temperature treatment. DETAILED DESCRIPTION

[0038] The present application is further described in detail below with reference to the Examples, Preparation Examples and Comparative Examples. The raw materials involved in the present application can all be obtained commercially.

[0039] Preparation Example of Modified Methyl Vinyl Silicone Rubber

[0040] The following is an explanation using Preparation Example 1.

[0041] Preparation Example 1

[0042] In this preparation example, the methyl vinyl silicone rubber had a molecular weight of 550,000 and a vinyl content of 0.17 mol%. The platinum catalyst was chloroplatinic acid. The diamine monomer used was 3,3'-dihydroxybenzidine, and the dianhydride monomer was 4,4'-(4,4'-isopropyldiphenyloxy)diphthalic anhydride. The hydroxyl content of the enzymatically hydrolyzed lignin was 2.04 mmol / g, and the carboxyl content was 1.12 mmol / g.

[0043] In this preparation example, the hydroxyl-containing polyimide was prepared according to the following method:

[0044] After mixing 40 mmol of diamine monomer, 40 mmol of dianhydride monomer and 200 mL of meta-cresol, 2 mL of isoquinoline was added dropwise to the mixture, and then heated under nitrogen protection for reaction. During the reaction, the room temperature was first maintained for 2 hours, then the temperature was raised to 100°C and kept for 4 hours, and then the temperature was raised to 190°C and kept for 12 hours to obtain a reaction solution. The reaction solution was cooled to 100°C, and then the reaction solution was added to excess ethanol for precipitation. After reduced pressure filtration and washing, a hydroxyl-containing polyimide was obtained.

[0045] In this preparation example, hydroxyethylated lignin was prepared according to the following method:

[0046] 20 g of enzymatically hydrolyzed lignin, 12 g of ethylene carbonate, and 48 g of tetrabutylammonium iodide were mixed and stirred at 110° C. for 48 h to obtain a reaction mixture. After cooling, 200 mL of ethanol was added to the reaction mixture to obtain a diluted mixture. The diluted mixture was added to 700 mL of hydrochloric acid at a pH of 2, and then reacted under freezing conditions for 2 h. After the reaction was completed, the residue was filtered and collected. The residue was washed and freeze-dried to obtain hydroxyethylated lignin.

[0047] This preparation example provides a modified methyl vinyl silicone rubber, which is prepared according to the following method:

[0048] (1) 80 g of methyl vinyl silicone rubber and 150 g of toluene were stirred and mixed uniformly, 3 g of dimethyl monochlorosilane was added to the mixture, and the mixture was stirred and heated to 70°C under nitrogen protection. 0.1 g of a platinum catalyst was added, and the mixture was kept warm for 9 h before being cooled and discharged. The toluene was removed by vacuum distillation at -95 kPa and 65°C to obtain a silicone rubber intermediate material;

[0049] (2) 80 g of the silicone rubber intermediate material was added to 300 g of tetrahydrofuran and stirred to dissolve, and then 8 g of hydroxyethylated lignin and 5 g of hydroxyl-containing polyimide were added, and triethylamine was added as an acid binding agent. The mixture was stirred and heated at a constant temperature of 65 ° C under nitrogen protection for 6 h. After the reaction was completed, the material was discharged, washed and vacuum dried to obtain modified methyl vinyl silicone rubber.

[0050] Preparation Example 2

[0051] The difference between this preparation example and preparation example 1 is that 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane is used as the diamine monomer.

[0052] Preparation Example 3

[0053] The difference between this preparation example and preparation example 2 is that 4,4'-(hexafluoroisopropylene) diphthalic anhydride is selected as the dianhydride monomer.

[0054] Preparation Example 4

[0055] The difference between this preparation example and preparation example 3 is that 4,4'-oxydiphthalic anhydride is used as the dianhydride monomer.

[0056] Preparation example of lignin-modified nano-silica

[0057] The following is an explanation using Preparation Example 5 as an example.

[0058] Preparation Example 5

[0059] In this preparation example, lignin-modified nano-silica was prepared according to the following method:

[0060] 59 g of sodium silicate nonahydrate, 12.5 g of alkali lignin and 350 mL of deionized water were mixed, stirred and dissolved, and then 200 mL of deionized water, 200 mL of ethanol and 2.5 g of polyethylene glycol (PEG-2000) were added. The mixture was stirred first, and then 1 mol / L of sulfuric acid was added for acidification. After stirring, a nano-silica suspension with a pH of 9.5 was obtained; the nano-silica suspension was ultrasonically treated for 20 min, preheated at 70°C for 20 min, and then 1 mol / L of sulfuric acid was added again for acidification, and the pH was adjusted to 2. The mixture was then allowed to stand for 2 h, and the solid product was collected by vacuum filtration. After acid washing and drying, lignin-modified nano-silica was obtained.

[0061] Example

[0062] Examples 1-3

[0063] The following description will be made using Example 1 as an example.

[0064] Example 1

[0065] In this embodiment, modified methyl vinyl silicone rubber is prepared according to the method of Preparation Example 1, the molar ratio of phenyl to silicon atom in the methyl phenyl silicone rubber is 0.18, the molar fraction of vinyl in the vinyl MQ silicone resin is 0.10%, hydroxy silicone oil is selected as the structuring control agent, the filler is the lignin-modified nano-silica of Preparation Example 5, and the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0066] This embodiment provides a high-temperature resistant mixed silicone rubber, including the following components in parts by weight: 40g of modified methyl vinyl silicone rubber, 10g of methyl phenyl silicone rubber, 10g of vinyl MQ silicone resin, 3g of structuring control agent, 3.5g of filler, and 2.0g of vulcanizing agent.

[0067] This embodiment provides a method for preparing high-temperature resistant mixed silicone rubber, comprising the following steps:

[0068] (1) Modified methyl vinyl silicone rubber, methyl phenyl silicone rubber, structural control agent and vinyl MQ silicone resin are placed in a two-roll mill, mixed at 40°C for 4 hours, heated to 120°C and continued to mix for 2 hours, cooled to 40°C, and fillers and vulcanizing agents are added. The mixture is continued to be plasticized for 2 hours. After the mixing is completed, a thin sheet is formed to form a mixed rubber;

[0069] (2) Add the mixed rubber into a flat vulcanizing machine, set the pressure to 25 MPa and the temperature to 160°C, and then vulcanize it. After vulcanizing for 10 minutes, take it out and wait for it to cool naturally to obtain high-temperature resistant mixed silicone rubber.

[0070] As shown in Table 1, the differences between Examples 1-3 mainly lie in the different raw material ratios of the mixed silicone rubber.

[0071] Table 1 Ratio of raw materials for compounding silicone rubber

[0072]

[0073] Example 4

[0074] The difference between this embodiment and embodiment 3 is that the structuring control agent is dimethyldiethoxysilane.

[0075] Example 5

[0076] The difference between this embodiment and embodiment 4 is that the structuring control agent is hexamethyldisilazane.

[0077] Example 6

[0078] The difference between this embodiment and embodiment 5 is that the vinyl mole fraction of the vinyl MQ silicone resin is 0.13%.

[0079] Example 7

[0080] The difference between this embodiment and embodiment 5 is that the vinyl mole fraction of the vinyl MQ silicone resin is 0.15%.

[0081] Example 8

[0082] The difference between this embodiment and embodiment 5 is that the vinyl mole fraction of the vinyl MQ silicone resin is 0.17%.

[0083] Example 9

[0084] The difference between this embodiment and embodiment 8 is that the modified methyl vinyl silicone resin is prepared according to the method of preparation example 2.

[0085] Example 10

[0086] The difference between this embodiment and embodiment 8 is that the modified methyl vinyl silicone resin is prepared according to the method of preparation example 3.

[0087] Example 11

[0088] The difference between this embodiment and embodiment 8 is that the modified methyl vinyl silicone resin is prepared according to the method of preparation example 4.

[0089] Comparative Example

[0090] Comparative Example 1

[0091] In this comparative example, the molecular weight of the methyl vinyl silicone rubber is 550,000, and the vinyl content is 0.17 mol%. The structuring control agent is hydroxy silicone oil, the filler is nano-silica, and the vulcanizing agent is 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane.

[0092] This comparative example provides a mixed silicone rubber, comprising the following components in parts by weight: 60 g of methyl vinyl silicone rubber, 3 g of a structuring control agent, 3.5 g of a filler, and 2.0 g of a vulcanizing agent.

[0093] This comparative example provides a method for preparing a high-temperature resistant mixed silicone rubber, comprising the following steps:

[0094] (1) Methyl vinyl silicone rubber and a structural control agent are placed in a two-roll mill, mixed at 40°C for 4 hours, heated to 120°C and mixed for 2 hours, cooled to 40°C, and fillers and vulcanizing agents are added. The mixture is plasticized for 2 hours. After the mixing is completed, a thin sheet is formed to form a rubber compound;

[0095] (2) Add the mixed rubber into a flat vulcanizing press, set the pressure to 25 MPa and the temperature to 160°C, and then vulcanize. After vulcanization for 10 minutes, take it out and wait for natural cooling to obtain mixed silicone rubber.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that the modified methyl vinyl silicone rubber is replaced by the same methyl vinyl silicone rubber as that in Comparative Example 1.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 1 is that the methylphenyl silicone rubber is replaced by the same methylvinyl silicone rubber as that in Comparative Example 1.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that the vinyl MQ silicone resin is replaced by the same methyl vinyl silicone rubber as in Comparative Example 1.

[0102] Comparative Example 5

[0103] The difference between this comparative example and Example 1 is that the lignin-modified nano-silica is replaced by nano-silica that is not modified with lignin.

[0104] Performance testing methods

[0105] With reference to GB / T 528-2009, Vulcanized or Thermoplastic Rubber - Determination of Tensile Stress-Strain Properties, the compounded silicone rubber prepared in each Example and Comparative Example was cut into test samples that met the test specifications. The tensile strength of the samples was tested at room temperature and in a 350°C oven for 6 h, respectively. The tensile rate was set at 500 mm / min. The test results are shown in Table 2.

[0106] In addition to testing the tensile strength, the weight loss rate of the samples after high temperature treatment was also weighed and calculated. The results are shown in Table 2.

[0107] Table 2 Test results

[0108]

[0109]

[0110] Combining Examples 1-3 with Comparative Example 1 and Table 2, it can be seen that the compounded silicone rubbers of Examples 1-3 still have high tensile strength and minimal weight loss after high-temperature treatment. This is because, through the synergistic effects of the rigid groups, cross-linked network structure, and lignin nano-modified silica, Examples 1-3 can fully weaken the main chain degradation reactions that occur in the compounded silicone rubber under the influence of high temperature, thereby achieving better thermal stability and maintaining good mechanical properties after high-temperature treatment. Comparative Example 1, on the other hand, lacks this synergistic effect and, as a result, loses most of its tensile strength and suffers a significant weight loss after high-temperature treatment.

[0111] Combining Example 1 and Comparative Examples 2-5 with Table 2, it can be seen that the mixed silicone rubber of Example 1 still has a high tensile strength and a small weight loss after high-temperature treatment. This is because the rigid groups of Comparative Examples 2-3 are missing, the cross-linked network structure of Comparative Example 4 cannot be fully improved, and the filler of Comparative Example 5 cannot cooperate with the rigid groups to hinder the movement of the mixed silicone rubber molecular chains. As a result, the mixed silicone rubbers of Comparative Examples 2-5 generally experience severe thermal degradation and lose a lot of mechanical properties.

[0112] From Examples 3-5 and Table 2, it can be seen that the mixed silicone rubber of Example 5 still has a high tensile strength and a small weight loss after high-temperature treatment. This is because the hexamethyldisilazane with strong rigidity in Example 5 can produce a good synergistic effect with the rigid groups in the modified methyl vinyl silicone rubber, methylphenyl silicone rubber and other components, thereby effectively improving the high-temperature resistance of the mixed silicone rubber, so that the mixed silicone rubber can maintain good mechanical properties after high-temperature treatment.

[0113] From Examples 5-8 and Table 2, it can be seen that the compounded silicone rubbers of Examples 6-8 still have high tensile strength and little weight loss after high-temperature treatment. This is because when the vinyl mole fraction of the vinyl MQ silicone resin is 0.13-0.17%, the crosslinking of the vinyl MQ silicone resin and the silicone rubber molecules can be fully promoted, effectively improving the high-temperature resistance of the compounded silicone rubber, so that the compounded silicone rubber can maintain good mechanical properties after high-temperature treatment.

[0114] It can be seen from Examples 8-11 and Table 2 that after changing the composition of the polyimide group, the compounded silicone rubber can still maintain good heat resistance.

[0115] The above embodiments are merely explanations of the present application and are not limitations of the present application. After reading this specification, those skilled in the art may make modifications to the embodiments of the present application as needed without any creative contribution. However, as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A high temperature resistant mixed silicone rubber, characterized in that: The invention comprises the following components in parts by weight: 40-45 parts of modified methyl vinyl silicone rubber, 10-15 parts of methyl phenyl silicone rubber, 10-15 parts of vinyl MQ silicone resin, 3-5 parts of a structuring control agent, 3.5-4.5 parts of a filler, and 2.0-2.5 parts of a vulcanizing agent; the modified methyl vinyl silicone rubber contains a polyimide group and a lignin group; and the filler comprises lignin-modified nano-silica.

2. The high temperature resistant compounded silicone rubber according to claim 1, characterized in that: The structuring control agent is one of hydroxy silicone oil, dimethyldiethoxysilane and hexamethyldisilazane.

3. The high temperature resistant compounded silicone rubber according to claim 1, characterized in that: The vinyl MQ silicone resin has a vinyl mole fraction of 0.13-0.17%.

4. The high temperature resistant compounded silicone rubber according to claim 1, characterized in that: The modified methyl vinyl silicone rubber is prepared according to the following method: (1) Methyl vinyl silicone rubber and toluene are stirred and mixed uniformly, dimethyl monochlorosilane is added to the mixture, the mixture is stirred and heated under nitrogen protection, a platinum catalyst is added, the mixture is kept warm for reaction, and then the temperature is lowered and the material is discharged, and the silicone rubber intermediate material is obtained through purification and post-treatment processes; (2) Add the silicone rubber intermediate material into tetrahydrofuran and stir to dissolve, then add hydroxyethylated lignin, hydroxyl-containing polyimide and acid binding agent, stir and heat at constant temperature under nitrogen protection, discharge the material after the reaction is completed, and then wash and vacuum dry to obtain modified methyl vinyl silicone rubber.

5. The high temperature resistant compounded silicone rubber according to claim 4, characterized in that: The hydroxyl-containing polyimide is prepared according to the following method: After mixing a diamine monomer, a dianhydride monomer and m-cresol, isoquinoline is added dropwise to the mixture, and then heated under nitrogen protection to react to obtain a reaction liquid. The reaction liquid is cooled, and the reaction liquid is added to excess ethanol for precipitation. After reduced pressure filtration and washing, a hydroxyl-containing polyimide is obtained; the diamine monomer contains phenolic hydroxyl groups.

6. The high temperature resistant compounded silicone rubber according to claim 5, characterized in that: The diamine monomer is selected from 3,3'-dihydroxybenzidine or 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.

7. The high temperature resistant compounded silicone rubber according to claim 5, characterized in that: The dianhydride monomer is selected from 4,4'-(4,4'-isopropyldiphenoxy) diphthalic anhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride or 4,4'-oxydiphthalic anhydride.

8. The high temperature resistant compounded silicone rubber according to claim 4, characterized in that: The hydroxyethylated lignin is prepared according to the following method: Enzymatically hydrolyzed lignin, ethylene carbonate, and tetrabutylammonium iodide are mixed and stirred to obtain a reaction mixture, ethanol is added to the reaction mixture to obtain a diluted mixture, the diluted mixture is added to hydrochloric acid, and then reacted under freezing conditions. After the reaction is completed, the filter is filtered and the filter residue is collected. The filter residue is washed and freeze-dried to obtain hydroxyethylated lignin.

9. The high temperature resistant compounded silicone rubber according to claim 4, characterized in that: The lignin-modified nano-silica is prepared according to the following method: Sodium silicate, alkali lignin and deionized water are mixed, stirred and dissolved, and then deionized water, ethanol and polyethylene glycol are added, stirred first, and then sulfuric acid is added for acidification, and a nano-silica suspension is obtained after stirring; the nano-silica suspension is ultrasonically treated and preheated, and then sulfuric acid is added again for acidification, and then allowed to stand for treatment, and then a solid product is collected by vacuum filtration, and after acid washing and drying, lignin-modified nano-silica is obtained.

10. The method for preparing high temperature resistant compounded silicone rubber according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) placing modified methyl vinyl silicone rubber, methyl phenyl silicone rubber, a structural control agent and vinyl MQ silicone resin in a two-roll mill for mixing, adding fillers and vulcanizing agents during the mixing process, and thinning out sheets after the mixing is completed to form a mixed rubber; (2) Add the mixed rubber into a flat vulcanizer for vulcanization, take it out and wait for it to cool naturally to obtain high-temperature resistant mixed silicone rubber.

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