A method for preparing an ultraviolet aging resistant silicone rubber

Abstract

The application relates to the technical field of silicone rubber, and discloses a preparation method of ultraviolet aging-resistant silicone rubber; methyl vinyl silicone rubber, sulfonated organosilicon polyimide, nano zinc oxide, an accelerator, a vulcanizing agent and the like are mixed and vulcanized to obtain the ultraviolet aging-resistant silicone rubber. The sulfonated organosilicon polyimide contains the same siloxane structure as the methyl vinyl silicone rubber, improves the compatibility between the sulfonated organosilicon polyimide and the silicone rubber, is beneficial to improving the Shore A hardness, the tear strength and the thermal decomposition temperature of the silicone rubber, has higher mechanical properties and high-temperature resistance, the sulfonated organosilicon polyimide can form interaction on the surface of the nano zinc oxide, improves the compatibility and dispersibility between the nano zinc oxide and the silicone rubber, and enhances the ultraviolet aging resistance of the silicone rubber.

Description

Technical Field

[0001] This invention relates to the field of silicone rubber technology, specifically to a method for preparing silicone rubber resistant to ultraviolet aging. Background Technology

[0002] Silicone rubber exhibits excellent high and low temperature resistance, superior elasticity, high electrical insulation, and strong hydrophobicity, making it widely used in wire and cable manufacturing, medical devices, and automobile production. Adding nanofillers to silicone rubber can improve its mechanical properties and UV aging resistance. Nano zinc oxide is a non-toxic, environmentally friendly, inexpensive, and readily available nanomaterial that can absorb ultraviolet light, improving the UV aging resistance of plastics and rubber materials. Chinese patent CN116426215B discloses a composite coating and its preparation method, a silicone rubber protective sleeve, and an insulator. Using silicone rubber adhesive as a coating, it embeds hydrophobically modified tetra-needle-shaped zinc oxide powder and nano-metal oxide powder, both acting as inorganic UV shielding agents. The resulting composite coating exhibits good UV shielding and anti-aging effects. However, this patent does not improve the tear strength or high-temperature resistance of silicone rubber. Polyimide possesses advantages such as high mechanical strength, good high-temperature resistance, and excellent insulation properties, and can be used as a structural or functional material to improve the overall performance of silicone rubber materials. Summary of the Invention

[0003] (I) Technical problem to be solved: The present invention provides a method for preparing silicone rubber with UV resistance, which improves the UV resistance and mechanical properties of silicone rubber.

[0004] (II) Technical Solution: A method for preparing UV-resistant silicone rubber, comprising the following steps:

[0005] Step A: Add N,N-dimethylformamide, dianhydride compound, aromatic diamine compound, and silicon-containing diamine monomer to the reaction vessel. Stir and react at room temperature under a nitrogen atmosphere for 18-24 hours. Pour the solution onto the surface of a glass mold and place it in a heating oven. Heat the mold sequentially to 100-120℃ for 1-2 hours, 140-160℃ for 1.5-2 hours, 200-220℃ for 1-1.5 hours, 240-260℃ for 1-1.5 hours, and 280-300℃ for 1-1.5 hours. Cool the mold to obtain organosilicon polyimide.

[0006] Step B: In an ice bath under a nitrogen atmosphere, add concentrated sulfuric acid and organosilicon polyimide to the reaction vessel, stir, and heat to 40-55℃ for sulfonation reaction for 12-18 hours. After cooling, pour the solution into ice water, filter, wash with water, and dry to obtain sulfonated organosilicon polyimide.

[0007]

[0008] Step C: Place methyl vinyl silicone rubber, sulfonated organosilicon polyimide, and nano zinc oxide in a two-roll mill for plasticizing. Then add accelerator, antioxidant, and crosslinking agent for mixing. Next, add vulcanizing agent for mixing. Finally, place the material in a flat vulcanizing machine and vulcanize it at 160-170℃ and 10-12MPa pressure for 20-30 minutes. Then vulcanize it at 170-175℃ under normal pressure for 2-3 hours. Cool and discharge the material to obtain UV-resistant silicone rubber.

[0009] Furthermore, in step A, the molar ratio of the dianhydride compound, the aromatic diamine compound, and the silanediamine monomer is 100:(60-90):(10-40).

[0010] Furthermore, the dianhydride compound is pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, or 4,4'-biphenyl ether dianhydride, and the aromatic diamine compound is p-phenylenediamine, 4,4-biphenyl ether diamine, or 4,4'-diaminodiphenylmethane.

[0011] Furthermore, the preparation method of the silanediamine monomer is as follows:

[0012] (1) Add ethanol, sodium ethoxide in a molar ratio of (2-2.2)::1:(2.2-2.6), 1,3-bis(3-chloropropyl)-1,1,3,3-tetramethyldisiloxane, and 4-nitrodiphenylamine to a reaction vessel, heat to 70-80℃, reflux for 4-6 hours, filter after cooling, distill the filtrate under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain a silicon-containing dinitro monomer.

[0013] (2) Add ethanol to the reaction vessel, purge with nitrogen gas, and add a silicon-containing dinitro monomer, palladium on carbon catalyst, and hydrazine hydrate in a mass ratio of 100:(5.8-6.6):(32-42). Heat to 70-80℃, reflux for 6-8 hours, filter, distill under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain a silicon-containing diamine monomer. The reaction formula is:

[0014]

[0015] Furthermore, in step C, the mass ratio of methyl vinyl silicone rubber, sulfonated organosilicon polyimide, and nano zinc oxide is 100:(15-30):(2-8).

[0016] Furthermore, the accelerator is 2-mercaptobenzothiazole, the antioxidant is N-phenyl-2-naphthylamine, the crosslinking agent is dicumyl peroxide, and the vulcanizing agent is sulfur.

[0017] (III) Technical effects of the present invention: A silicon-containing dinitro compound containing phenyl groups is polymerized with a dianhydride compound and an aromatic diamine compound to obtain an organosilicon polyimide with a benzene ring in the side chain. Then, the benzene ring in the side chain is sulfonated with concentrated sulfuric acid to obtain a sulfonated organosilicon polyimide with a higher sulfonic acid content. Then, it is mixed with methyl vinyl silicone rubber, nano zinc oxide, antioxidant, vulcanizing agent, etc., and vulcanized to obtain a silicone rubber resistant to ultraviolet aging.

[0018] The sulfonated organosilicon polyimide of the present invention contains the same siloxane structure as methyl vinyl silicone rubber, which improves its compatibility with silicone rubber and helps to improve the Shore A hardness, tear strength and thermal decomposition temperature of silicone rubber, resulting in higher mechanical properties and high temperature resistance.

[0019] The side chains of the organosilicon polyimide of the present invention contain a large number of sulfonic acid groups, which can interact with the surface of nano zinc oxide, coat the surface of nano zinc oxide, reduce the agglomeration of nano zinc oxide, and improve the compatibility between nano zinc oxide and silicone rubber. The uniformly dispersed nano zinc oxide has excellent reinforcing effect, and at the same time improves the UV resistance of silicone rubber. After UV aging test, the decrease in Shore A hardness and tear strength of silicone rubber is small and the retention rate is high. Detailed Implementation

[0020] To facilitate a better understanding of the technical solution of this invention by those skilled in the art, the invention will be further described below with reference to specific embodiments, but the invention is not limited thereto. Palladium on carbon catalyst: Product number YB54681, CAS No.: 7440-05-3, Hunan Yunbang Biotechnology Co., Ltd. Concentrated sulfuric acid: Concentration 98.3wt%.

[0021] Example 1: (1) Add 200 mL of ethanol, 60 mmol of sodium ethoxide, 30 mmol of 1,3-bis(3-chloropropyl)-1,1,3,3-tetramethyldisiloxane and 66 mmol of 4-nitrodiphenylamine to a reaction vessel, heat to 80 °C, reflux for 4 h, filter after cooling, distill under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain a silicon-containing dinitro monomer.

[0022] (2) Add 120 mL of ethanol to the reaction vessel, introduce nitrogen gas, add 10 g of silicon-containing dinitro monomer, 0.66 g of palladium on carbon catalyst, and 3.2 g of hydrazine hydrate with a mass fraction of 80%. Heat to 80 °C, reflux for 6 h, filter, distill the filtrate under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain silicon-containing diamine monomer.

[0023] (3) Add 250 mL of N,N-dimethylformamide, 100 mmol of 4,4'-biphenyl ether dianhydride, 90 mmol of p-phenylenediamine, and 10 mmol of silanediamine monomer to the reaction vessel. Stir the reaction at room temperature under a nitrogen atmosphere for 18 h. Pour the solution onto the surface of a glass mold and place it in a heating box. Heat the mold sequentially to 100 °C for 2 h, 140 °C for 2 h, 200 °C for 1.5 h, 260 °C for 1 h, and 300 °C for 1 h. Cool the mold to obtain organosilicon polyimide.

[0024] (4) In an ice bath under a nitrogen atmosphere, add 800 mL of concentrated sulfuric acid and 50 g of organosilicon polyimide to the reaction vessel, stir and heat to 45 °C for sulfonation reaction for 18 h. After cooling, pour the solution into ice water, filter, wash with water and dry to obtain sulfonated organosilicon polyimide.

[0025] (5) Place 1 kg of methyl vinyl silicone rubber, 150 g of sulfonated organosilicon polyimide, and 20 g of nano zinc oxide (average particle size 30 nm) in a two-roll mill and plasticize for 40 min. Then add 20 g of accelerator 2-mercaptobenzothiazole, 16 g of antioxidant N-phenyl-2-naphthylamine, and 22 g of crosslinking agent diisopropylbenzene peroxide and mix for 40 min. Then add 12 g of vulcanizing agent sulfur and mix for 10 min. Finally, put the material in a flat vulcanizing machine and vulcanize it at 170 °C and 10 MPa for 20 min. Then vulcanize it at 175 °C for 2 h under normal pressure. Cool and discharge the material to obtain silicone rubber resistant to ultraviolet aging.

[0026] Example 2: (1) Add 250 mL of ethanol, 66 mmol of sodium ethoxide, 30 mmol of 1,3-bis(3-chloropropyl)-1,1,3,3-tetramethyldisiloxane and 72 mmol of 4-nitrodiphenylamine to a reaction vessel, heat to 75 °C, reflux for 6 h, filter after cooling, distill under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain a silicon-containing dinitro monomer.

[0027] (2) Add 120 mL of ethanol to the reaction vessel, introduce nitrogen gas, add 10 g of silicon-containing dinitro monomer, 0.58 g of palladium on carbon catalyst, and 4.2 g of hydrazine hydrate with a mass fraction of 80%. Heat to 70 °C, reflux for 6 h, filter, distill the filtrate under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain silicon-containing diamine monomer.

[0028] (3) Add 300 mL of N,N-dimethylformamide, 100 mmol of pyromellitic anhydride, 75 mmol of 4,4-diphenyl ether diamine, and 25 mmol of silanediamine monomer to the reaction vessel. Stir the reaction at room temperature under a nitrogen atmosphere for 24 h. Pour the solution onto the surface of a glass mold and place it in a heating box. Heat the mold sequentially to 100 °C for 2 h, 160 °C for 1.5 h, 220 °C for 1 h, 260 °C for 1 h, and 280 °C for 1 h. Cool the mold to obtain organosilicon polyimide.

[0029] (4) In an ice bath under a nitrogen atmosphere, add 800 mL of concentrated sulfuric acid and 50 g of organosilicon polyimide to the reaction vessel, stir and heat to 55 °C for sulfonation reaction for 12 h. After cooling, pour the solution into ice water, filter, wash with water and dry to obtain sulfonated organosilicon polyimide.

[0030] (5) Place 1 kg of methyl vinyl silicone rubber, 220 g of sulfonated organosilicon polyimide, and 50 g of nano zinc oxide (average particle size 30 nm) in a two-roll mill and plasticize for 60 min. Then add 18 g of accelerator 2-mercaptobenzothiazole, 13 g of antioxidant N-phenyl-2-naphthylamine, and 24 g of crosslinking agent diisopropylbenzene peroxide and mix for 40 min. Then add 8 g of vulcanizing agent sulfur and mix for 10 min. Finally, put the material in a flat vulcanizing machine and vulcanize it at 160 °C and 12 MPa for 30 min. Then vulcanize it at 170 °C for 3 h under normal pressure. Cool and discharge the material to obtain silicone rubber resistant to ultraviolet aging.

[0031] Example 3: (1) Add 250 mL of ethanol, 66 mmol of sodium ethoxide, 30 mmol of 1,3-bis(3-chloropropyl)-1,1,3,3-tetramethyldisiloxane and 78 mmol of 4-nitrodiphenylamine to a reaction vessel, heat to 70 °C, reflux for 6 h, filter after cooling, distill under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain a silicon-containing dinitro monomer.

[0032] (2) Add 150 mL of ethanol to the reaction vessel, introduce nitrogen gas, add 10 g of silicon-containing dinitro monomer, 0.64 g of palladium on carbon catalyst, and 3.8 g of hydrazine hydrate with a mass fraction of 80%. Heat to 75 °C, reflux and condense for 8 h. After filtration, distill the filtrate under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain silicon-containing diamine monomer.

[0033] (3) Add 300 mL of N,N-dimethylformamide, 100 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 60 mmol of 4,4'-diaminodiphenylmethane, and 40 mmol of silanediamine monomer to the reaction vessel. Stir the reaction at room temperature under a nitrogen atmosphere for 24 h. Pour the solution onto the surface of a glass mold and place it in a heating box. Heat the mold sequentially to 120 °C for 1 h, 150 °C for 2 h, 200 °C for 1.5 h, 240 °C for 1.5 h, and 280 °C for 1.5 h. Cool the mold to obtain organosilicon polyimide.

[0034] (4) In an ice bath under a nitrogen atmosphere, add 800 mL of concentrated sulfuric acid and 50 g of organosilicon polyimide to the reaction vessel, stir and heat to 40 °C for sulfonation reaction for 18 h. After cooling, pour the solution into ice water, filter, wash with water and dry to obtain sulfonated organosilicon polyimide.

[0035] (5) Place 1 kg of methyl vinyl silicone rubber, 300 g of sulfonated organosilicon polyimide, and 80 g of nano zinc oxide (average particle size 30 nm) in a two-roll mill and plasticize for 60 min. Then add 22 g of accelerator 2-mercaptobenzothiazole, 18 g of antioxidant N-phenyl-2-naphthylamine, and 20 g of crosslinking agent diisopropylbenzene peroxide and mix for 40 min. Then add 12 g of vulcanizing agent sulfur and mix for 10 min. Finally, put the material in a flat vulcanizing machine and vulcanize it at 160 °C and 10 MPa for 30 min. Then vulcanize it at 170 °C for 3 h under normal pressure. Cool and discharge the material to obtain silicone rubber resistant to ultraviolet aging.

[0036] The difference between Comparative Example 1 and Example 1 is that sulfonated organosilicon polyimide is not added.

[0037] (1) Place 1 kg of methyl vinyl silicone rubber and 20 g of nano zinc oxide (average particle size 30 nm) in a two-roll mill and plasticize for 40 min. Then add 20 g of accelerator 2-mercaptobenzothiazole, 16 g of antioxidant N-phenyl-2-naphthylamine, and 22 g of crosslinking agent diisopropylbenzene peroxide and mix for 40 min. Then add 12 g of vulcanizing agent sulfur and mix for 10 min. Finally, put the material in a flat vulcanizing machine and vulcanize it at 170 °C and 10 MPa for 20 min. Then vulcanize it at 175 °C for 2 h under normal pressure. Cool and discharge the material to obtain silicone rubber resistant to ultraviolet aging.

[0038] The difference between Comparative Example 2 and Example 1 is that organosilicon polyimide was used instead of sulfonated organosilicon polyimide.

[0039] (1) Place 1 kg of methyl vinyl silicone rubber, 150 g of organosilicon polyimide, and 20 g of nano zinc oxide (average particle size 30 nm) in a two-roll mill and plasticize for 40 min. Then add 20 g of accelerator 2-mercaptobenzothiazole, 16 g of antioxidant N-phenyl-2-naphthylamine, and 22 g of crosslinking agent diisopropylbenzene peroxide and mix for 40 min. Then add 12 g of vulcanizing agent sulfur and mix for 10 min. Finally, put the material in a flat vulcanizing machine and vulcanize it at 170 °C and 10 MPa for 20 min. Then vulcanize it at 175 °C for 2 h under normal pressure. Cool and discharge the material to obtain silicone rubber resistant to ultraviolet aging.

[0040] The difference between Comparative Example 3 and Example 1 is that no silanediamine monomer is added when preparing the polyimide.

[0041] (1) Add 250 mL of N,N-dimethylformamide, 100 mmol of 4,4'-biphenyl ether dianhydride, and 100 mmol of p-phenylenediamine to the reaction vessel. Stir the reaction at room temperature under a nitrogen atmosphere for 18 h. Pour the solution onto the surface of a glass mold and place it in a heating box. Heat the mold sequentially to 100 °C for 2 h, 140 °C for 2 h, 200 °C for 1.5 h, 260 °C for 1 h, and 300 °C for 1 h. Cool the mold to obtain polyimide.

[0042] (2) In an ice bath under a nitrogen atmosphere, 800 mL of concentrated sulfuric acid and 50 g of polyimide were added to the reaction vessel. After stirring, the mixture was heated to 45 °C and sulfonated for 18 h. After cooling, the solution was poured into ice water, filtered, washed with water, and dried to obtain sulfonated polyimide.

[0043] (3) Place 1 kg of methyl vinyl silicone rubber, 150 g of sulfonated polyimide, and 20 g of nano zinc oxide (average particle size 30 nm) in a two-roll mill and plasticize for 40 min. Then add 20 g of accelerator 2-mercaptobenzothiazole, 16 g of antioxidant N-phenyl-2-naphthylamine, and 22 g of crosslinking agent diisopropylbenzene peroxide and mix for 40 min. Then add 12 g of vulcanizing agent sulfur and mix for 10 min. Finally, put the material in a flat vulcanizing machine and vulcanize it at 170 °C and 10 MPa for 20 min. Then vulcanize it at 175 °C for 2 h under normal pressure. Cool and discharge the material to obtain silicone rubber resistant to ultraviolet aging.

[0044] The difference between Comparative Example 4 and Example 1 is that, in the preparation of polyimide, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was used instead of the silane-containing diamine monomer.

[0045] (1) Add 250 mL of N,N-dimethylformamide, 100 mmol of 4,4'-biphenyl ether dianhydride, 90 mmol of p-phenylenediamine, and 10 mmol of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane to the reaction vessel. Stir the reaction at room temperature under a nitrogen atmosphere for 18 h. Pour the solution onto the surface of a glass mold and place it in a heating box. Heat the mold sequentially to 100 °C for 2 h, 140 °C for 2 h, 200 °C for 1.5 h, 260 °C for 1 h, and 300 °C for 1 h. Cool the mold to obtain organosilicon polyimide.

[0046] (2) In an ice bath under a nitrogen atmosphere, 800 mL of concentrated sulfuric acid and 50 g of organosilicon polyimide were added to the reaction vessel. After stirring, the mixture was heated to 45 °C and sulfonated for 18 h. After cooling, the solution was poured into ice water, filtered, washed with water, and dried to obtain sulfonated organosilicon polyimide.

[0047] (3) Place 1 kg of methyl vinyl silicone rubber, 150 g of sulfonated organosilicon polyimide, and 20 g of nano zinc oxide (average particle size 30 nm) in a two-roll mill and plasticize for 40 min. Then add 20 g of accelerator 2-mercaptobenzothiazole, 16 g of antioxidant N-phenyl-2-naphthylamine, and 22 g of crosslinking agent diisopropylbenzene peroxide and mix for 40 min. Then add 12 g of vulcanizing agent sulfur and mix for 10 min. Finally, put the material in a flat vulcanizing machine and vulcanize it at 170 °C and 10 MPa for 20 min. Then vulcanize it at 175 °C for 2 h under normal pressure. Cool and discharge the material to obtain silicone rubber resistant to ultraviolet aging.

[0048] The sulfonated polyimide was dried, weighed, and placed in 50 mL of a 3 mol / L sodium chloride solution. The solution was stirred for 48 h to remove H+. + with Na + After thorough exchange, filter the solution and titrate it with a 5 mmol / L sodium hydroxide solution using phenolphthalein as an indicator until the solution turns red. Calculate the acidity value W. The higher the acidity value, the higher the sulfonic acid content.

[0049] W = (C × V) / M, where C is the concentration of the sodium hydroxide solution, V is the titration volume of the sodium hydroxide solution, and M is the mass of the sulfonated polyimide.

[0050] Table 1 Acidity Value Test

[0051] Acidity value (mmol / L) Example 1 0.82 Example 2 1.16 Example 3 1.37 Comparative Example 3 0.66 Comparative Example 4 0.58

[0052] As shown in Table 1, compared with Comparative Examples 3 and 4, the polyimide side chains of Examples 1-3 contain benzene ring structures, which are prone to sulfonation reaction with concentrated sulfuric acid, thereby generating more sulfonic acid groups.

[0053] The Shore A hardness of the silicone rubber composite material was tested according to the national standard GB / T 531.1-2008. The tear resistance was tested according to the national standard GB / T529-2008.

[0054] The silicone rubber was placed in a UV aging test chamber and subjected to a UV aging test for 1440 hours. The main wavelength of the UV lamp was 340nm and the total power of the UV lamp was 320W. Then, the Shore A hardness and tear performance were tested.

[0055] 5 mg of the modified silicone rubber composite material was weighed and placed in a thermogravimetric analyzer. The thermogravimetric properties were analyzed under a nitrogen atmosphere at a heating rate of 10 °C / min.

[0056] Table 2. Performance test of silicone rubber.

[0057]

[0058] Compared to Comparative Example 1, the silicone rubbers in Examples 1-3 incorporated sulfonated organosilicon polyimide. This polyimide contains the same siloxane structure as methyl vinyl silicone rubber, improving its compatibility with silicone rubber and enhancing its Shore A hardness, tear strength, and thermal decomposition temperature, resulting in higher mechanical properties and high-temperature resistance. Simultaneously, the side chains of the organosilicon polyimide contain a large number of sulfonic acid groups, which can interact with the surface of nano-zinc oxide, coating it and reducing its agglomeration. This also improves the compatibility between nano-zinc oxide and silicone rubber. The uniformly dispersed nano-zinc oxide provides excellent reinforcement and enhances the UV resistance of the silicone rubber. After UV aging tests, the decrease in Shore A hardness and tear strength of the silicone rubber was small, with high retention rates.

[0059] Compared to Example 1, Comparative Example 2 used organosilicon polyimide instead of sulfonated organosilicon polyimide. Organosilicon polyimide exhibits good compatibility with silicone rubber, improving its Shore A hardness, tear strength, and thermal decomposition temperature. However, organosilicon polyimide lacks sulfonic acid groups, preventing interaction with nano-zinc oxide and its ability to coat the surface of nano-zinc oxide. This fails to reduce the aggregation of nano-zinc oxide and improve the compatibility between nano-zinc oxide and silicone rubber, resulting in lower Shore A hardness and tear strength compared to Example 1. Furthermore, the dispersion of nano-zinc oxide in the silicone rubber matrix is ​​poor, failing to significantly improve its UV aging resistance. UV aging tests revealed a large decrease in Shore A hardness and tear strength, with low retention rates.

[0060] In Comparative Example 3, no silane-containing diamine monomer was added during the preparation of the polyimide. The polyimide lacks a siloxane structure, resulting in poor compatibility with methyl vinyl silicone rubber. This leads to lower Shore A hardness and tear strength in the silicone rubber, and poor dispersion of nano-zinc oxide in the silicone rubber matrix, failing to significantly improve its UV aging resistance. UV aging tests showed a large decrease in Shore A hardness and tear strength, with low retention rates.

[0061] In Comparative Example 4, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane was used instead of the silanediamine monomer in the preparation of the polyimide. The resulting organosilicon polyimide did not contain side-chain phenyl groups, and after sulfonation, the content of sulfonic acid groups was low, resulting in a lower surface interaction force with nano-zinc oxide. This led to poor compatibility and dispersibility between nano-zinc oxide and silicone rubber, and the Shore A hardness, tear strength, and UV aging resistance of the silicone rubber were lower than those in Example 1.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing UV-resistant silicone rubber, characterized in that, The preparation method includes the following steps: Step A: Add N,N-dimethylformamide, dianhydride compound, and aromatic diamine compound (with the following structural formula) to the reaction vessel. The silicon-containing diamine monomer was reacted with stirring at room temperature under a nitrogen atmosphere for 18-24 hours. The solution was poured onto the surface of a glass mold and placed in a heating chamber. The mold was heated sequentially to 100-120℃ for 1-2 hours, 140-160℃ for 1.5-2 hours, 200-220℃ for 1-1.5 hours, 240-260℃ for 1-1.5 hours, and 280-300℃ for 1-1.5 hours. After cooling, organosilicon polyimide was obtained. Step B: In an ice bath under a nitrogen atmosphere, add concentrated sulfuric acid and organosilicon polyimide to the reaction vessel, stir to carry out the sulfonation reaction, cool and pour the solution into ice water, filter, wash with water, and dry to obtain sulfonated organosilicon polyimide. Step C: Place methyl vinyl silicone rubber, sulfonated organosilicon polyimide, and nano zinc oxide in a two-roll mill for plasticizing. Then add accelerator, antioxidant, and crosslinking agent for mixing. Add vulcanizing agent for mixing. Finally, perform two-stage vulcanization in a flat vulcanizing machine, cool and discharge the material to obtain UV-resistant silicone rubber.

2. The method for preparing UV-resistant silicone rubber according to claim 1, characterized in that, In step A, the molar ratio of the dianhydride compound, the aromatic diamine compound, and the silanediamine monomer is 100:(60-90):(10-40).

3. The method for preparing UV-resistant silicone rubber according to claim 2, characterized in that, The dianhydride compound is pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, or 4,4'-biphenyl ether dianhydride, and the aromatic diamine compound is p-phenylenediamine, 4,4-biphenyl ether diamine, or 4,4'-diaminodiphenylmethane.

4. The method for preparing UV-resistant silicone rubber according to claim 2, characterized in that, The method for preparing the silanediamine monomer is as follows: (1) Add ethanol, sodium ethoxide, 1,3-bis(3-chloropropyl)-1,1,3,3-tetramethyldisiloxane and 4-nitrodiphenylamine to the reaction vessel, heat to 70-80℃, reflux for 4-6 hours, filter after cooling, distill the filtrate under reduced pressure, wash with water, and recrystallize the product in ethanol to obtain silicon-containing dinitro monomer. (2) Add ethanol to the reaction vessel, introduce nitrogen gas, add silicon-containing dinitro monomer, palladium on carbon catalyst, hydrazine hydrate, heat to 70-80℃, reflux for 6-8 hours, filter, distill the filtrate under reduced pressure, wash with water, recrystallize the product in ethanol to obtain silicon-containing diamine monomer.

5. The method for preparing UV-resistant silicone rubber according to claim 4, characterized in that, The molar ratio of sodium ethoxide, 1,3-bis(3-chloropropyl)-1,1,3,3-tetramethyldisiloxane, and 4-nitrodiphenylamine in (1) is (2-2.2):1:(2.2-2.6).

6. The method for preparing UV-resistant silicone rubber according to claim 5, characterized in that, The mass ratio of silicon dinitro compound, palladium on carbon catalyst, and hydrazine hydrate in (2) is 100:(5.8-6.6):(32-42).

7. The method for preparing UV-resistant silicone rubber according to claim 1, characterized in that, The sulfonation reaction in step B is carried out at a temperature of 40-55℃ for 12-18 hours.

8. The method for preparing UV-resistant silicone rubber according to claim 1, characterized in that, In step C, the mass ratio of methyl vinyl silicone rubber, sulfonated organosilicon polyimide, and nano zinc oxide is 100:(15-30):(2-8).

9. The method for preparing UV-resistant silicone rubber according to claim 1, characterized in that, In step C, the two-stage vulcanization process involves first vulcanizing at 160-170℃ and 10-12MPa pressure for 20-30 minutes, and then vulcanizing at 170-175℃ under normal pressure for 2-3 hours.

10. The method for preparing UV-resistant silicone rubber according to claim 1, characterized in that, In step C, the accelerator is 2-mercaptobenzothiazole, the antioxidant is N-phenyl-2-naphthylamine, the crosslinking agent is dicumyl peroxide, and the vulcanizing agent is sulfur.

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