Flame-retardant and aging-resistant rubber sealing element and preparation method thereof

Abstract

The invention discloses a flame-retardant and aging-resistant rubber sealing element and a preparation method thereof, belongs to the technical field of rubber sealing element processing, and aims to solve the technical problem that flame retardance, aging resistance and mechanical properties need to be further improved in the prior art. The preparation method comprises the following steps: adding a rubber compound into a sulfur change instrument, heating to 150-170 DEG C, carrying out heat preservation reaction for 30-40 minutes, injecting into a mold to obtain the rubber sealing element, preparing the rubber compound by taking modified epoxy rubber and nitrile rubber as raw rubber, taking a modified reinforcing agent, a modified flame retardant and a cross-linking agent as reinforcing materials and taking an auxiliary additive as an auxiliary agent, vulcanizing, injecting into the mold, and carrying out heat preservation reaction to obtain the rubber sealing element. Not only are the flame retardant property and aging resistance of the rubber sealing element effectively improved, but also the mechanical property of the rubber sealing element is improved.

Description

Technical Field

[0001] The invention relates to the technical field of rubber seal processing, and in particular to a flame retardant and aging resistant rubber seal and a preparation method thereof. Background Art

[0002] With the rapid development of modern society, rubber products are widely used in daily life and industrial production. Rubber seals are widely used in machinery, automobiles, aerospace and other fields to prevent the leakage of liquids and gases and protect equipment from the external environment.

[0003] With the advancement of science and technology, sealing technology continues to develop. Rubber seals have become ideal sealing materials due to their excellent elasticity, wear resistance and sealing performance. However, many traditional rubber materials are easy to burn under high temperature or fire environment, and are prone to aging phenomena such as oxidation and cracking under the influence of ultraviolet rays, oxygen, moisture and other environments, resulting in reduced sealing performance. Especially in high temperature and high pressure environments such as automobile engines and chemical equipment, rubber seals have poor flame retardancy and fast aging speed, which may cause leakage, failure, and even cause safety hazards.

[0004] In the preparation of rubber seals, nitrile rubber is a commonly used material, but its performance is easily affected in harsh environments such as high load, high temperature and high pressure. The main reason is that there are a large number of double bonds in the nitrile rubber molecular chain, which are prone to double bond debonding and chain breaking. In order to enhance the aging resistance and mechanical properties of hydrogenated nitrile rubber, inorganic substances such as carbon black and talcum powder are usually added in the process of preparing rubber. These materials enhance the performance of rubber to a certain extent, but due to the problem of insufficient compatibility, the prepared rubber seals are difficult to use for a long time, and the molecular structure of rubber seals contains a large number of organic groups, such as hydrocarbon segments and double bonds. These groups are prone to oxidation reactions and free radical reactions at high temperatures, thereby accelerating the combustion process. In order to improve the flame retardant properties of rubber seals, flame retardant melamine is added, but as a single nitrogen-containing flame retardant, its flame retardant mechanism is usually flame retardant in the gas phase, and due to the lack of carbon source, its carbonization efficiency in the condensed phase is low, and it is difficult to block the transfer of heat.

[0005] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0006] The object of the present invention is to provide a flame retardant and aging resistant rubber seal and a preparation method thereof, so as to solve the technical problem that the flame retardant performance, aging resistance and mechanical properties of the rubber seal in the prior art need to be further improved.

[0007] The purpose of the present invention can be achieved by the following technical scheme: a flame retardant and aging resistant rubber seal, comprising the following raw material components in parts by weight: 95-100 parts of modified epoxy rubber, 20-30 parts of nitrile rubber, 10-15 parts of modified reinforcing agent, 15-20 parts of modified flame retardant, 4-6 parts of vulcanizing agent, 2-5 parts of cross-linking agent and 4-6 parts of auxiliary additives;

[0008] The modified epoxy rubber is prepared by the following steps:

[0009] A1. Place nitrile rubber and chlorobenzene in a reaction kettle, heat to 35-45°C, stir for 5-7 minutes, add m-chloroperbenzoic acid, keep warm for 5-7 hours, and post-treat to obtain epoxy nitrile rubber;

[0010] Preparation reaction principle of epoxy butyl rubber:

[0011] During the reaction, high temperature catalyzes the decomposition of m-chloroperbenzoic acid into oxidizing free radicals, which react with the double bond of olefins to form a new free radical. Then, oxygen molecules combine with the free radical to form an epoxy group to obtain epoxy nitrile rubber.

[0012] A2. Put epoxy nitrile rubber, chloroform and palladium carbon in a reaction kettle, catalytically hydrogenate, and post-treat to obtain modified epoxy rubber.

[0013] Preparation reaction principle of modified epoxy rubber:

[0014] Under high temperature and high pressure and the catalytic action of palladium carbon, the olefin double bonds of epoxy nitrile rubber are reduced to carbon-carbon single bonds to obtain modified epoxy rubber.

[0015] Further, in step A1, m-chloroperbenzoic acid is added at 0.15 times the molar amount of the carbon-carbon double bond in the nitrile rubber, and the amount ratio of the nitrile rubber to chlorobenzene is 200-300g:2500-3000mL, and the post-treatment step comprises: after the reaction is completed, the reaction liquid is cooled to room temperature, ethanol is added to the reaction liquid, stirred for 2-5min, filtered, and the filter cake is placed in a drying oven at a temperature of 40-60°C, and dried to constant weight to obtain epoxy nitrile rubber; in step A2, the amount ratio of the epoxy nitrile rubber, chloroform and palladium carbon is 100- 150g:1500-2000mL:4-6g, the operation of the catalytic hydrogenation is: after filling and discharging nitrogen and hydrogen three times into the reactor respectively, filling hydrogen until the pressure of the reactor is 3-3.5Mpa, heating the reactor to 140-160°C, and keeping the temperature for reaction for 3.5-4.5h, the post-treatment step includes: after the reaction is completed, cooling the reaction liquid to room temperature, exhausting at a low speed, adding ethanol to the reaction liquid, stirring for 2-5min, filtering, placing the filter cake in a drying oven at a temperature of 40-60°C, and drying to constant weight to obtain a modified epoxy rubber.

[0016] Furthermore, the modified reinforcing agent is prepared by the following steps:

[0017] B1. Place zinc chloride and deionized water in a reaction kettle, heat to 25-35°C, add dilute hydrochloric acid solution, adjust pH to 6±0.5, and obtain a mixed acid solution;

[0018] Preparation principle of mixed acid solution:

[0019] During the reaction, zinc chloride is easily hydrolyzed in deionized water, and an acidic environment is provided to inhibit the hydrolysis of zinc chloride.

[0020] B2. Place 3-methylcinnamic acid and deionized water in a reaction kettle, add sodium hydroxide solution, adjust pH to 8±0.3, dropwise add mixed acid solution, react at room temperature for 0.5-1h, and post-treat to obtain a modified reinforcing agent.

[0021] The preparation reaction principle of the modified reinforcing agent is:

[0022] During the reaction, 3-methylcinnamic acid reacts with sodium hydroxide to generate sodium 3-methylcinnamate. When sodium 3-methylcinnamate and zinc chloride are dissolved in water, sodium ions are separated from chloride ions, while 3-methylcinnamate ions are combined with zinc ions to form insoluble 3-methylcinnamate zinc precipitates, thereby obtaining a modified reinforcing agent.

[0023] Furthermore, in step B1, the concentration of the dilute hydrochloric acid is 1-2 mol / L, and the dosage ratio of the zinc chloride and deionized water is 20-50 g: 100-200 mL; in step B2, the dosage ratio of the 3-methylcinnamic acid, deionized water and mixed acid solution is 40-60 g: 500-700 mL: 100-150 mL, and the concentration of the sodium hydroxide solution is 0.5-1 mol / L. The post-treatment step includes: after the reaction is completed, standing for 30 minutes, filtering, washing the filter cake with deionized water and ethanol 1-2 times, transferring to a drying oven at a temperature of 35-45°C, and drying to constant weight to obtain a modified reinforcing agent.

[0024] Furthermore, the preparation method of the modified flame retardant is: placing melamine sodium salt, 1,4-dioxane and sodium methoxide in a reactor protected by a nitrogen atmosphere, stirring at room temperature for 5-8 minutes, adding tert-butyl dichlorophosphinoyl, reacting at room temperature for 15-30 minutes, heating to 80-90°C, condensing and reflux for 4-6 hours, and post-treating to obtain the modified flame retardant.

[0025] Preparation reaction principle of modified flame retardant:

[0026] During the reaction, the P-Cl bond on tert-butyl dichlorophosphoryl is broken to form an active intermediate, which is rapidly replaced by the nucleophilic amino group on the sodium salt of melamine to obtain a modified flame retardant.

[0027] Furthermore, the dosage ratio of melamine sodium salt, 1,4-dioxane, sodium methoxide and tert-butyl dichlorophosphoryl is 100-200g:800-1300mL:50-80g:45-75g, and the post-treatment step includes: after the reaction is completed, the reaction is cooled to room temperature, filtered, the filter cake is washed 1-2 times with deionized water, transferred to a drying oven at a temperature of 50-70°C, and dried to constant weight to obtain a modified flame retardant.

[0028] The present invention also provides a method for preparing a flame retardant and aging resistant rubber seal, comprising the following steps:

[0029] S1, adding modified epoxy rubber and nitrile rubber into an open mixing mill, heating to 40-50°C, and thinning through 4-6 times to obtain raw rubber;

[0030] S2, adding the raw rubber to an internal mixer, heating to 50-70°C, mixing for 1-5 minutes, adding a modified reinforcing agent, a modified flame retardant, a cross-linking agent and auxiliary additives, mixing for 10-15 minutes, adding a vulcanizing agent, mixing for 5-10 minutes, and obtaining a mixed rubber;

[0031] S3. Add the mixed rubber into the vulcanizer, heat it to 150-170°C, keep it warm for 30-40 minutes, and inject it into the mold to obtain the rubber seal.

[0032] Furthermore, in step S1, the roller speed ratio of the open mill is 25 / 18, and the roller spacing is 0.5 mm; in step S2, the cross-linking agent is tetraethylenetriamine, the vulcanizing agent is composed of diisopropylbenzene peroxide and sulfur in a mass ratio of 3:1, and the speed of the internal mixer is 60r / min, and the auxiliary additives are composed of lubricant, anti-ultraviolet agent, plasticizer and accelerator in a weight ratio of 5:2:10:3, the lubricant is one or more of silicone oil and stearic acid, the anti-ultraviolet agent is one or more of UV-531 and UV-328, the plasticizer is dibutyl phthalate, and the accelerator is one or more of aniline disulfide and sodium tetramethyldithiocarbamate.

[0033] The present invention has the following beneficial effects:

[0034] 1. A flame-retardant and aging-resistant rubber seal prepared by the present invention comprises the following steps: using modified epoxy rubber and nitrile rubber as raw rubber, using modified reinforcing agent, modified flame retardant and cross-linking agent as reinforcing materials, and using auxiliary additives as auxiliary agents to prepare a rubber mix; after the rubber mix is ​​vulcanized, it is injected into a mold to obtain a rubber seal; the modified epoxy rubber is prepared by catalytic hydrogenation of nitrile rubber modified by epoxidation of meta-chloroperbenzoic acid; the molecular structure of the hydrogenated nitrile rubber removes part of the unsaturated olefin double bonds, so that the configuration of the molecular chain is more orderly and the structure is more stable, thereby increasing the thermal stability and oxidation resistance of the nitrile rubber and further enhancing the aging resistance of the rubber seal; and in the subsequent process of preparing the seal, the modified epoxy rubber forms a chemical bond with the amino group in the cross-linking agent tetraethylenetriamine and the modified flame retardant to form a cross-linking network, thereby improving the mechanical properties and aging resistance of the rubber seal; in the vulcanization process of the rubber seal, the added nitrile rubber can react with the vulcanizing agent to form a chemical cross-linking, thereby improving the aging resistance of the rubber seal.

[0035] 2. A flame-retardant and aging-resistant rubber seal prepared by the present invention is prepared by using 3-methylcinnamic acid and zinc chloride as raw materials to obtain 3-methylcinnamic zinc. During the rubber vulcanization process, the CH bond of the hydrogen atom on α-C connected to the cyano functional group on the modified epoxy rubber and the nitrile rubber can be broken under the thermal oxidation condition of 150°C to generate free radicals. The 3-methylcinnamic zinc contains an olefin structure and can be grafted to the modified epoxy rubber and the nitrile rubber through a free radical reaction under the action of a vulcanizing agent to form an ionic bond and a covalent bond. The benzene ring group in the molecule increases the segment length between two adjacent cross-linking points, thereby reducing the flow resistance of the modified rubber, increasing the maximum torque, improving the cross-linking degree of the rubber seal, and further improving the aging resistance and mechanical properties of the rubber seal.

[0036] 3. A flame-retardant and aging-resistant rubber seal prepared by the present invention is prepared by a modified flame retardant through a phosphorylation reaction of melamine sodium salt and tert-butyl dichlorophosphinate. When the rubber seal burns, the melamine in the modified flame retardant is thermally decomposed to release non-combustible gases such as nitrogen oxides and ammonia, which can dilute oxygen and reduce the concentration of the combustion-supporting gas from the gas phase. The oxygen concentration is reduced and the flame is extinguished, while indirectly preventing the transfer of heat to achieve a flame retardant effect. The modified flame retardant contains phosphorus, which can form polyphosphate esters during the combustion process to cover the surface of the rubber seal. In a fire or high-temperature environment, it has a heat-insulating effect and further enhances the aging resistance of the rubber seal. The modified flame retardant contains amino groups, which form a cross-linked network by chemically bonding with the epoxy group in the modified epoxy rubber, thereby further increasing the mechanical properties of the rubber seal. The melamine in the modified flame retardant has a strong hardness and plays a skeleton support role in the rubber seal, thereby further enhancing the mechanical properties of the rubber seal. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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.

[0038] The alkaline silica sol used in the present invention is purchased from Shandong Huayunda New Materials Co., Ltd. and has a particle size of 10-20 nm.

[0039] Example 1

[0040] This embodiment provides a method for preparing a modified epoxy rubber for a flame retardant and aging resistant rubber seal, comprising the following steps:

[0041] Weigh: 200 g of nitrile rubber and 2500 mL of chlorobenzene are placed in a reaction kettle, heated to 35° C., stirred for 5 min, and m-chloroperbenzoic acid is added according to 0.15 times the molar amount of the carbon-carbon double bond in the nitrile rubber. The reaction is kept warm for 5 h. After the reaction is completed, wait for the reaction solution to cool to room temperature, add ethanol to the reaction solution, stir for 2 min, filter, and place the filter cake in a drying oven at 40° C. and dry to constant weight to obtain epoxy nitrile rubber;

[0042] Weigh: 100 g of epoxy nitrile rubber, 1500 mL of chloroform and 4 g of palladium carbon and put them in a reactor. After filling and exhausting nitrogen and hydrogen into the reactor three times and three times respectively, fill with hydrogen until the pressure of the reactor is 3 MPa, heat the reactor to 140°C, and keep the reaction warm for 3.5 hours. After the reaction is completed, wait for the reaction liquid to cool to room temperature, exhaust at a low speed, add ethanol to the reaction liquid, stir for 2 minutes, filter, place the filter cake in a drying oven at 40°C, and dry it to constant weight to obtain modified epoxy rubber.

[0043] Example 2

[0044] This embodiment provides a method for preparing a modified epoxy rubber for a flame retardant and aging resistant rubber seal, comprising the following steps:

[0045] Weigh: 250 g of nitrile rubber and 2700 mL of chlorobenzene are placed in a reactor, heated to 40° C., stirred for 6 min, and m-chloroperbenzoic acid is added according to 0.15 times the molar amount of the carbon-carbon double bond in the nitrile rubber. The reaction is kept warm for 6 h. After the reaction is completed, wait for the reaction solution to cool to room temperature, add ethanol to the reaction solution, stir for 3 min, filter, and place the filter cake in a drying oven at 50° C. and dry to constant weight to obtain epoxy nitrile rubber;

[0046] Weigh: 120g of epoxy nitrile rubber, 1700mL of chloroform and 5g of palladium carbon are placed in a reactor. After filling and exhausting nitrogen and hydrogen into the reactor three times and three times respectively, hydrogen is filled until the pressure of the reactor is 3.2Mpa. The reactor is heated to 150°C and kept warm for 4h. After the reaction is completed, the reaction liquid is cooled to room temperature, the exhaust is carried out at a low speed, ethanol is added to the reaction liquid, stirred for 3min, and filtered. The filter cake is placed in a drying oven at 50°C and dried to constant weight to obtain a modified epoxy rubber.

[0047] Example 3

[0048] This embodiment provides a method for preparing a modified epoxy rubber for a flame retardant and aging resistant rubber seal, comprising the following steps:

[0049] Weigh: 300 g of nitrile rubber and 3000 mL of chlorobenzene are placed in a reaction kettle, heated to 45° C., stirred for 7 min, and m-chloroperbenzoic acid is added according to 0.15 times the molar amount of the carbon-carbon double bond in the nitrile rubber. The reaction is kept warm for 7 h. After the reaction is completed, wait for the reaction liquid to cool to room temperature, add ethanol to the reaction liquid, stir for 5 min, filter, and place the filter cake in a drying oven at 60° C. and dry to constant weight to obtain epoxy nitrile rubber;

[0050] Weigh: 150 g of epoxy nitrile rubber, 2000 mL of chloroform and 6 g of palladium carbon, and place them in a reactor. After filling and exhausting nitrogen and hydrogen three times into the reactor respectively, fill with hydrogen until the pressure of the reactor is 3.5 MPa, heat the reactor to 160°C, and keep the reaction warm for 4.5 hours. After the reaction is completed, wait for the reaction liquid to cool to room temperature, exhaust at a low speed, add ethanol to the reaction liquid, stir for 5 minutes, filter, place the filter cake in a drying oven at 60°C, and dry it to constant weight to obtain a modified epoxy rubber.

[0051] Example 4

[0052] This embodiment provides a method for preparing a flame retardant and aging resistant modified reinforcing agent for rubber seals, comprising the following steps:

[0053] Weigh: 20 g of zinc chloride and 100 mL of deionized water, place in a reaction kettle, heat to 25°C, add 1 mol / L dilute hydrochloric acid solution, adjust pH to 6.3, and obtain a mixed acid solution;

[0054] Weigh: 40 g of 3-methylcinnamic acid and 500 mL of deionized water are placed in a reaction kettle, 0.5 mol / L sodium hydroxide solution is added, pH is adjusted to 8.1, 100 mL of mixed acid solution is added dropwise, and the reaction is carried out at room temperature for 0.5 h. After the reaction is completed, it is allowed to stand for 30 min, filtered, and the filter cake is washed twice with deionized water and ethanol, transferred to a drying oven at a temperature of 35°C, and dried to constant weight to obtain a modified reinforcing agent.

[0055] Example 5

[0056] This embodiment provides a method for preparing a flame retardant and aging resistant modified reinforcing agent for rubber seals, comprising the following steps:

[0057] Weigh: 35 g of zinc chloride and 150 mL of deionized water, place in a reaction kettle, heat to 30°C, add 1.5 mol / L dilute hydrochloric acid solution, adjust pH to 6.3, and obtain a mixed acid solution;

[0058] Weigh: 50 g of 3-methylcinnamic acid and 600 mL of deionized water are placed in a reaction kettle, 0.7 mol / L sodium hydroxide solution is added, pH is adjusted to 8.2, 125 mL of mixed acid solution is added dropwise, and the reaction is carried out at room temperature for 1 hour. After the reaction is completed, it is allowed to stand for 30 minutes, filtered, and the filter cake is washed twice with deionized water and ethanol, transferred to a drying oven at a temperature of 40°C, and dried to constant weight to obtain a modified reinforcing agent.

[0059] Example 6

[0060] This embodiment provides a method for preparing a flame retardant and aging resistant modified reinforcing agent for rubber seals, comprising the following steps:

[0061] Weigh: 50 g of zinc chloride and 200 mL of deionized water, place in a reaction kettle, heat to 35°C, add 2 mol / L dilute hydrochloric acid solution, adjust pH to 6.1, and obtain a mixed acid solution;

[0062] Weigh: 60 g of 3-methylcinnamic acid and 700 mL of deionized water are placed in a reaction kettle, 1 mol / L sodium hydroxide solution is added, pH is adjusted to 8.2, 150 mL of mixed acid solution is added dropwise, and the reaction is carried out at room temperature for 1 hour. After the reaction is completed, it is allowed to stand for 30 minutes, filtered, and the filter cake is washed twice with deionized water and ethanol, transferred to a drying oven at a temperature of 45°C, and dried to constant weight to obtain a modified reinforcing agent.

[0063] Example 7

[0064] This embodiment provides a method for preparing a modified flame retardant for a flame retardant and aging resistant rubber seal, comprising the following steps:

[0065] Weigh: 100 g of melamine sodium salt, 800 mL of 1,4-dioxane and 50 g of sodium methoxide, place in a reactor protected by nitrogen atmosphere, stir at room temperature for 5 min, add 45 g of tert-butyl dichlorophosphoryl, react at room temperature for 15 min, heat to 80 ° C, condense and reflux for 4 h. After the reaction is completed, wait for the reaction to cool to room temperature, filter, wash the filter cake twice with deionized water, transfer to a drying oven at a temperature of 50 ° C, and dry to constant weight to obtain a modified flame retardant.

[0066] Example 8

[0067] This embodiment provides a method for preparing a modified flame retardant for a flame retardant and aging resistant rubber seal, comprising the following steps:

[0068] Weigh: 150 g of melamine sodium salt, 1000 mL of 1,4-dioxane and 65 g of sodium methoxide, place in a reactor protected by nitrogen atmosphere, stir at room temperature for 7 min, add 60 g of tert-butyl dichlorophosphoryl, react at room temperature for 25 min, heat to 85 ° C, condense and reflux for 5 h. After the reaction is completed, wait for the reaction to cool to room temperature, filter, wash the filter cake twice with deionized water, transfer to a drying oven at a temperature of 60 ° C, and dry to constant weight to obtain a modified flame retardant.

[0069] Example 9

[0070] This embodiment provides a method for preparing a modified flame retardant for a flame retardant and aging resistant rubber seal, comprising the following steps:

[0071] Weigh: 200 g of melamine sodium salt, 1300 mL of 1,4-dioxane and 80 g of sodium methoxide, place in a reactor protected by nitrogen atmosphere, stir at room temperature for 8 min, add 75 g of tert-butyl dichlorophosphoryl, react at room temperature for 30 min, heat to 90°C, condense and reflux for 6 h. After the reaction is completed, wait for the reaction to cool to room temperature, filter, wash the filter cake twice with deionized water, transfer to a drying oven at 70°C, and dry to constant weight to obtain a modified flame retardant.

[0072] Example 10

[0073] This embodiment provides a method for preparing a flame retardant and aging resistant rubber seal, comprising the following steps:

[0074] Stearic acid, UV-531, dibutyl phthalate and aniline disulfide are uniformly mixed in a weight ratio of 5:2:10:3 to obtain an auxiliary additive for standby use;

[0075] Mix dicumyl peroxide and sulfur in a mass ratio of 3:1 to obtain a vulcanizing agent for later use;

[0076] Weigh by weight: 95 parts of the modified epoxy rubber prepared in Example 1 and 20 parts of nitrile rubber are added to an open mill, heated to 40°C, and thinned 4 times to obtain raw rubber, and the raw rubber is added to an internal mixer, heated to 50°C, and mixed for 1 minute, and then 10 parts of the modified reinforcing agent prepared in Example 4, 15 parts of the modified flame retardant prepared in Example 7, 2 parts of a cross-linking agent and 4 parts of auxiliary additives are added, and mixed for 10 minutes, and 4 parts of a vulcanizing agent are added, and mixed for 5 minutes to obtain a mixed rubber;

[0077] The mixed rubber was added into a vulcanizer, heated to 150°C, kept warm for 30 minutes, and injected into a mold to obtain a rubber seal.

[0078] Embodiment 11

[0079] This embodiment provides a method for preparing a flame retardant and aging resistant rubber seal, comprising the following steps:

[0080] Stearic acid, UV-531, dibutyl phthalate and aniline disulfide are uniformly mixed in a weight ratio of 5:2:10:3 to obtain an auxiliary additive for standby use;

[0081] Mix dicumyl peroxide and sulfur in a mass ratio of 3:1 to obtain a vulcanizing agent for later use;

[0082] Weigh by weight: 97 parts of the modified epoxy rubber prepared in Example 2 and 25 parts of nitrile rubber are added to an open mixer, heated to 45°C, and thinned 5 times to obtain raw rubber, and the raw rubber is added to an internal mixer, heated to 60°C, and mixed for 3 minutes, and then 12 parts of the modified reinforcing agent prepared in Example 5, 17 parts of the modified flame retardant prepared in Example 8, 4 parts of a cross-linking agent and 5 parts of an auxiliary additive are added, and mixed for 13 minutes, and 5 parts of a vulcanizing agent are added, and mixed for 7 minutes to obtain a mixed rubber;

[0083] The mixed rubber was added into a vulcanizer, heated to 160°C, kept warm for 35 minutes, and injected into a mold to obtain a rubber seal.

[0084] Example 12

[0085] This embodiment provides a method for preparing a flame retardant and aging resistant rubber seal, comprising the following steps:

[0086] Stearic acid, UV-531, dibutyl phthalate and aniline disulfide are uniformly mixed in a weight ratio of 5:2:10:3 to obtain an auxiliary additive for standby use;

[0087] Mix dicumyl peroxide and sulfur in a mass ratio of 3:1 to obtain a vulcanizing agent for later use;

[0088] Weigh by weight: 100 parts of the modified epoxy rubber prepared in Example 3 and 30 parts of nitrile rubber are added to an open mill, heated to 50°C, and thinned 6 times to obtain raw rubber, and the raw rubber is added to an internal mixer, heated to 70°C, and mixed for 5 minutes, and then 15 parts of the modified reinforcing agent prepared in Example 6, 20 parts of the modified flame retardant prepared in Example 9, 5 parts of a cross-linking agent and 6 parts of auxiliary additives are added, and mixed for 5 minutes, and 6 parts of a vulcanizing agent are added, and mixed for 10 minutes to obtain a mixed rubber;

[0089] The mixed rubber was added into a vulcanizer, heated to 170°C, kept warm for 40 minutes, and injected into a mold to obtain a rubber seal.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 12 is that an equal amount of nitrile rubber is used to replace the modified epoxy rubber.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 12 is that the modified reinforcing agent prepared in Example 6 is omitted.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 12 is that an equal amount of the melamine sodium salt prepared in Example 9 is used to replace the modified flame retardant.

[0096] Performance Test:

[0097] The flame retardant properties of the rubber seals prepared in Examples 10-12 and Comparative Examples 1-3 were measured with reference to the standard GB / T 10707-2008 "Determination of Rubber Combustion Performance";

[0098] The aging resistance of the rubber seals prepared in Examples 10-12 and Comparative Examples 1-3 was measured with reference to the standard GB / T 11206-2009 "Surface Cracking Method for Rubber Aging Test";

[0099] According to the standard GB / T 531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore hardness method (Shore hardness)", the rubber seal samples prepared in Examples 10-12 and Comparative Examples 1-3 are placed on the hardness tester, and then the measuring pointer is lightly pressed to measure at three different points, and the median of these three measurements is taken as the final test result;

[0100] The mechanical properties of the rubber seals prepared in Examples 10-12 and Comparative Examples 1-3 were measured with reference to standard HG / T 3868-2008 “Determination of high temperature tensile strength and elongation at break of vulcanized rubber”. Specific test data are shown in Table 1.

[0101] Table 1. Performance test data of samples

[0102]

[0103] Data Analysis:

[0104] Comparative analysis of the data in Table 1 above shows that the flame retardant and aging resistant rubber seal prepared by the present invention has a cracking grade of 0a, a vertical burning grade of FV-0, a Shore hardness of 83 Shore A, an elongation at break of 462%, and a tensile strength of 42.4 Mpa.

[0105] By comparing the data of Comparative Example 1 and Examples 10-12, it is found that the crack grade, Shore hardness, elongation at break and tensile strength of the rubber seal prepared in Comparative Example 1 are all reduced, indicating that the modified epoxy rubber prepared by the present invention is prepared by catalytic hydrogenation of the nitrile rubber modified by epoxidation of m-chloroperbenzoic acid, and the molecular structure of the hydrogenated nitrile rubber removes some unsaturated olefin double bonds, so that the configuration of the molecular chain is more orderly and the structure is more stable, so that the thermal stability and oxidation resistance of the nitrile rubber are increased, and the aging resistance of the rubber seal is further enhanced. In the subsequent process of preparing the seal, the epoxy group on the modified epoxy rubber forms a chemical bond with the cross-linking agent tetraethylenetriamine and the amino group of the modified flame retardant to form a cross-linked network, thereby improving the mechanical properties and aging resistance of the rubber seal.

[0106] By comparing the data of Comparative Example 2 and Examples 10-12, it is found that the crack grade, Shore hardness, elongation at break and tensile strength of the rubber seal prepared in Comparative Example 1 are all reduced, indicating that the rubber seal prepared by the present invention uses 3-methylcinnamic acid as a raw material and adopts a double decomposition method to prepare 3-methylcinnamic acid zinc. During the rubber vulcanization process, the CH bond of the hydrogen atom on the α-C connected to the cyano functional group on the modified epoxy rubber and the nitrile rubber can be broken under a thermal oxidation condition of 150°C to generate free radicals. The zinc 3-methylcinnamic acid contains an olefin structure and can be grafted to the modified epoxy rubber and the nitrile rubber through a free radical reaction under the action of a vulcanizing agent to form an ionic bond and a covalent bond. The benzene ring group in the molecule increases the segment length between two adjacent cross-linking points, thereby reducing the flow resistance of the modified rubber, increasing the maximum torque, improving the cross-linking degree of the rubber seal, and further improving the aging resistance and mechanical properties of the rubber seal.

[0107] By comparing the data of Comparative Example 3 and Examples 10-12, it is found that the cracking grade, vertical burning grade, Shore hardness, elongation at break and tensile strength of the rubber seal prepared in Comparative Example 1 are all reduced, indicating that the rubber seal prepared by the present invention is prepared by a modified flame retardant through a phosphorylation reaction of melamine sodium salt and tert-butyl dichlorophosphinoyl. When the rubber seal burns, the melamine in the modified flame retardant is thermally decomposed to release non-combustible gases such as nitrogen oxides and ammonia, which can dilute oxygen and reduce the concentration of the combustion-supporting gas from the gas phase. The oxygen concentration is reduced, the flame is extinguished, and the heat transfer is indirectly prevented to achieve a flame retardant effect. The prepared phosphoryl melamine contains phosphorus element, which can form polyphosphate esters during the combustion process to cover the surface of the rubber seal and have a heat-insulating effect. The modified flame retardant contains amino groups, which form chemical bonds with the epoxy groups in the modified epoxy rubber to form a cross-linked network, thereby further increasing the mechanical properties of the rubber seal.

[0108] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0109] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0110] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flame retardant and aging resistant rubber seal, characterized in that: The raw material composition includes the following parts by weight: 95-100 parts of modified epoxy rubber, 20-30 parts of nitrile rubber, 10-15 parts of modified reinforcing agent, 15-20 parts of modified flame retardant, 4-6 parts of vulcanizing agent, 2-5 parts of crosslinking agent and 4-6 parts of auxiliary additives; The modified epoxy rubber is prepared by the following steps: A1, placing nitrile rubber and chlorobenzene in a reaction kettle, heating to 35-45°C, stirring for 5-7 minutes, adding m-chloroperbenzoic acid, keeping the temperature for reaction for 5-7 hours, and post-treating to obtain epoxy nitrile rubber; A2. Put epoxy nitrile rubber, chloroform and palladium carbon in a reaction kettle, catalytically hydrogenate, and post-treat to obtain modified epoxy rubber.

2. The flame retardant and aging resistant rubber seal according to claim 1, characterized in that: In step A1, the amount of m-chloroperbenzoic acid is 0.15 times the molar amount of the carbon-carbon double bond in the nitrile rubber, and the amount ratio of the nitrile rubber to chlorobenzene is 200-300g:2500-3000mL; in step A2, the amount ratio of the epoxy nitrile rubber, chloroform and palladium carbon is 100-150g:1500-2000mL:4-6g.

3. The flame retardant and aging resistant rubber seal according to claim 1, characterized in that: The modified reinforcing agent is prepared by the following steps: B1. Place zinc chloride and deionized water in a reaction kettle, heat to 25-35°C, add dilute hydrochloric acid solution, adjust pH to 6±0.5, and obtain a mixed acid solution; B2. Place 3-methylcinnamic acid and deionized water in a reaction kettle, add sodium hydroxide solution, adjust pH to 8±0.3, dropwise add mixed acid solution, react at room temperature for 0.5-1h, and post-treat to obtain a modified reinforcing agent.

4. The flame retardant and aging resistant rubber seal according to claim 3, characterized in that: In step B1, the concentration of the dilute hydrochloric acid is 1-2 mol / L, and the dosage ratio of the zinc chloride to deionized water is 20-50 g:100-200 mL; in step B2, the dosage ratio of the 3-methylcinnamic acid, deionized water and mixed acid solution is 40-60 g:500-700 mL:100-150 mL, and the concentration of the sodium hydroxide solution is 0.5-1 mol / L.

5. The flame retardant and aging resistant rubber seal according to claim 1, characterized in that: The preparation method of the modified flame retardant is as follows: sodium melamine, 1,4-dioxane and sodium methoxide are placed in a reactor protected by a nitrogen atmosphere, stirred at room temperature for 5-8 minutes, tert-butyl dichlorophosphoryl is added, reacted at room temperature for 15-30 minutes, heated to 80-90° C., condensed and refluxed for 4-6 hours, and post-treated to obtain the modified flame retardant.

6. The flame retardant and aging resistant rubber seal according to claim 5, characterized in that: The usage ratio of the melamine sodium salt, 1,4-dioxane, sodium methoxide and tert-butyl dichlorophosphoryl is 100-200 g: 800-1300 mL: 50-80 g: 45-75 g.

7. A method for preparing a flame retardant and aging resistant rubber seal according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, adding modified epoxy rubber and nitrile rubber into an open mixing mill, heating to 40-50°C, and thinning through 4-6 times to obtain raw rubber; S2, adding the raw rubber to an internal mixer, heating to 50-70°C, mixing for 1-5 minutes, adding a modified reinforcing agent, a modified flame retardant, a cross-linking agent and auxiliary additives, mixing for 10-15 minutes, adding a vulcanizing agent, mixing for 5-10 minutes, and obtaining a mixed rubber; S3. Add the mixed rubber into the vulcanizer, heat it to 150-170°C, keep it warm for 30-40 minutes, and inject it into the mold to obtain the rubber seal.

8. The method for preparing a flame retardant and aging resistant rubber seal according to claim 7, characterized in that: In step S1, the roller speed ratio of the open mill is 25 / 18, and the roller spacing is 0.5 mm; in step S2, the cross-linking agent is tetraethylenetriamine, the vulcanizing agent is composed of diisopropylbenzene peroxide and sulfur in a mass ratio of 3:1, and the speed of the internal mixer is 60r / min, the auxiliary additives are composed of lubricant, anti-ultraviolet agent, plasticizer and accelerator in a weight ratio of 5:2:10:3, the lubricant is one or more of silicone oil and stearic acid, the anti-ultraviolet agent is one or more of UV-531 and UV-328, the plasticizer is dibutyl phthalate, and the accelerator is one or more of disulfide aniline and sodium tetramethyldithiocarbamate.

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