Rubber sealing element resistant to compression deformation and preparation method thereof

Abstract

The invention discloses a compressive deformation resistant rubber sealing element and a preparation method thereof, and belongs to the technical field of rubber sealing elements, the coating comprises the following components: modified graphene, aldehyde-terminated polybutadiene rubber, piperazine, hydrogenated nitrile rubber, fluororubber, white carbon black, calcium fluoride, carbon black and an auxiliary agent. The preparation method of the rubber sealing element comprises the following steps: S1, preparing modified graphene; s2, preparing a pre-dispersed rubber master batch; s3, preparing an elastomer; s4, performing segmented mixing on the raw materials to prepare a mixed rubber body; and S5, carrying out segmented vulcanization treatment on the rubber compound and annealing. According to the invention, an elastomer containing an imine bond is generated through aldehyde-terminated polybutadiene rubber and piperazine, irreversible slippage of a rubber molecular chain is limited in cooperation with a lamellar structure of graphene, and the characteristic of dynamic crosslinking is endowed to a rubber body due to the fact that the imine bond can be broken and reformed, so that the compression permanent deformation resistance of the rubber sealing element is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber seals, and in particular to a rubber seal resistant to compression deformation and a preparation method thereof. Background Art

[0002] Rubber seals are components primarily made of rubber. They are used to prevent the leakage of fluids (liquids, gases) or solid particles, while also preventing foreign matter (such as dust and moisture) from entering the equipment. Due to their low elastic modulus, high elongation, and excellent air permeability, they are widely used in various mechanical equipment.

[0003] Currently, rubber seals on the market primarily use nitrile rubber, fluororubber, and silicone rubber. These utilize the elasticity of the rubber material, squeezed against each other at the joints of equipment, to fill gaps and achieve a sealing function. Under high stress, compression, and high temperatures, rubber molecules are prone to slippage or breakage, causing permanent deformation of the rubber seal. This degrades the seal's cushioning and adaptive capabilities, reduces its fatigue resistance, and makes it more susceptible to breakage or tearing, compromising its sealing function. Summary of the Invention

[0004] The present invention provides a compression-deformation-resistant rubber seal and its preparation method, aiming to address the prior art problem of rubber molecules slipping or breaking under high-stress, extrusion, and high-temperature conditions, resulting in permanent deformation of the rubber seal. This can cause the rubber seal to lose its cushioning and adaptive capabilities, reduce its fatigue resistance, and easily break or tear, compromising its sealing function.

[0005] On the one hand, the present invention provides a rubber seal resistant to compression deformation, comprising the following components: 0.5-1.5 parts of graphene, 60-70 parts of hydrogenated nitrile rubber, 20-30 parts of fluororubber, and the balance being an elastomer containing an imine bond; wherein the elastomer containing an imine bond comprises 20-25 parts of aldehyde-terminated polybutadiene rubber and 0.7-1.6 parts of piperazine.

[0006] Furthermore, the rubber seal also includes: 8 to 12 parts of white carbon black, 2 to 4 parts of calcium fluoride, 8 to 12 parts of carbon black and additives, and the imine bonds of the elastomer containing imine bonds can be broken and reformed; wherein the additives include catalysts, vulcanizing agents, antioxidants and plasticizers.

[0007] In another aspect, the present application provides a method for preparing a compression-deformation-resistant rubber seal, comprising the following preparation steps: graphene modification pretreatment: graphene is oxidized by concentrated acid, and silanol is generated by hydrolysis of silane coupling agent, and condensation reaction occurs between silanol and carboxyl groups or defect sites on the surface of oxidized graphene to obtain modified graphene; preparation of elastomer: an elastomer containing an imine bond is generated by reaction of aldehyde-terminated polybutadiene rubber and piperazine; preparation of rubber compound and vulcanization treatment: the raw materials are subjected to stepwise mixing to obtain a rubber compound, and the rubber compound is subjected to stepwise vulcanization treatment, and the vulcanization temperature is gradiently increased.

[0008] Further, the method for preparing the modified graphene is as follows: concentrated sulfuric acid and concentrated nitric acid are mixed in a volume ratio of 3:1 to prepare a strong acid solution, graphene powder is taken and added to the strong acid solution for oxidation, silane coupling agent, anhydrous ethanol and deionized water are mixed in a volume ratio of 5:90:5 to generate a hydrolysis solution containing silanol, and the oxidized graphene: silane coupling agent is added to the hydrolysis solution in a ratio of 1:0.5-1, ultrasonic dispersion and stirring are performed, condensation reaction occurs between silanol and hydroxyl groups or defect sites on the surface of graphene, and the remaining silane coupling agent is removed by washing to obtain the modified graphene.

[0009] Further, before the step of preparing the rubber compound, a pre-dispersed masterbatch is prepared, and the method for preparing the pre-dispersed masterbatch is as follows: the modified graphene 0.5-1.5 parts, white carbon black 8-12 parts and carbon black 8-12 parts are placed in a disperser, mixed at a speed of 5000 rpm for 10 min, and the pre-dispersed masterbatch is prepared.

[0010] Further, the method for preparing the elastomer is as follows: 20-25 parts of aldehyde-terminated polybutadiene rubber and 8-16 parts of toluene solvent are mixed and placed in a prepared reaction container, after stirring, 0.7-1.6 parts of piperazine is added, the stirring is continued until the piperazine is completely dissolved, 0.1-0.5 parts of catalyst, 0.05-0.12 parts of antioxidant and 2-6 parts of carbon black are added, nitrogen is introduced to remove oxygen, the imine bond appears, the reaction is terminated by cooling to room temperature and adding methanol, and the remaining methanol solvent is removed by distillation to obtain the elastomer containing the imine bond.

[0011] Furthermore, the method for preparing the mixed colloid is as follows: 60-70 parts of hydrogenated nitrile rubber and 20-30 parts of fluororubber are put into an internal mixer, firstly, preliminary mixing is carried out at 60-80°C for 10-15 minutes, then 6-8 parts of plasticizer are added and mixing is continued at the same temperature for 5-8 minutes, then all the pre-dispersed masterbatch and 2-4 parts of calcium fluoride are added to the internal mixer, the roller spacing is gradually increased and the mixing temperature is controlled within 100°C, and mixing is continued for 5 minutes to complete the first stage mixing; 1-2.5 parts of vulcanizing agent and 0.5-1.5 parts of antioxidant are added to the colloid after the first stage mixing is completed, and mixing is further carried out at a temperature of 40-50°C for 5-8 minutes, and finally 5-15 parts of elastomer are added and mixing is continued at the same temperature for 5-8 minutes to complete the second stage mixing to obtain a mixed colloid, and the mixed colloid is injected into a prepared sealing mold for curing and molding.

[0012] Furthermore, the method for vulcanization treatment of the mixed colloid is as follows: a sealing mold filled with the mixed colloid is sealed and placed in a prepared flat-plate vulcanizing press, firstly subjected to a first-stage vulcanization treatment at 170-180° C. and a vulcanization pressure controlled at 12-15 MPa for 15-25 minutes to obtain a first-stage vulcanized colloid; the flat-plate vulcanizing press is cooled to 120° C., the first-stage vulcanized colloid is vulcanized in the flat-plate vulcanizing press at 120° C. for 0.8-1.2 hours, and at 150° C. for 0.6-1 hour, and the temperature is increased at a heating rate of no more than 5° C. / min, and then the temperature is increased to 200° C. for vulcanization for 1-1.5 hours, and finally vulcanized at 230° C. for 0.5-1 hour to complete the second-stage vulcanization treatment and obtain the vulcanized colloid.

[0013] Furthermore, the prepared vulcanized colloid is annealed. The annealing method of the vulcanized colloid is as follows: the seal is removed from the mold, placed in a forced air drying oven and annealed at 150° C. for 1 to 2 hours. After annealing, the seal is removed and naturally cooled to room temperature to obtain the rubber seal.

[0014] Furthermore, the hydrogenated nitrile rubber and fluororubber are both rubber bodies that have been placed at room temperature for at least 24 hours to reach room temperature.

[0015] The compression-set-resistant rubber seal provided by the present invention utilizes an aldehyde-terminated polybutadiene rubber and piperazine to form an elastomer containing imine bonds. The imine bonds can break and reform, imparting dynamic crosslinking properties to the rubber, further enhancing the compression set resistance of the rubber seal. The graphene's layered structure also limits irreversible slippage of the rubber molecular chains, increasing the crosslink density.

[0016] By dispersing the excellent thermal conductivity of graphene in the rubber body, the temperature transfer during the vulcanization and annealing of the rubber seal is increased, and the uniformity of the vulcanization and annealing is increased.

[0017] The rubber body is vulcanized by using the heat conduction of graphene and gradient temperature, so that the added additives can be fully activated at each temperature stage, and the overall performance of the rubber seal is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 is a preparation method flowchart of a compression deformation resistant rubber seal of the present application. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0021] The silane coupling agent used in each of the following examples and comparative examples is model KH-550, and the manufacturer is Wuhan Jiyue Shenghua Chemical Co., Ltd.

[0022] The catalyst used in each of the following examples and comparative examples is PTSA (toluene sulfonamide).

[0023] The vulcanizing agent used in each of the following examples and comparative examples is dicumyl peroxide.

[0024] The antioxidant used in each of the following examples and comparative examples is BHT (dibutyl hydroxytoluene).

[0025] The plasticizer used in each of the following examples and comparative examples is phthalate.

[0026] As described above, under the conditions of high stress extrusion and high temperature use, the rubber molecules are prone to slip or break between the rubber molecules, causing permanent deformation of the rubber seal. The rubber seal loses the buffering and self-adapting ability, reduces the fatigue resistance of the rubber seal, is prone to breakage or tearing, and affects the sealing function.

[0027] To this end, the present application provides a compression deformation resistant rubber seal, which can disperse graphene in the rubber body by virtue of the excellent heat conductivity of graphene, increase the temperature transfer during vulcanization and annealing of the rubber seal, and increase the uniformity of vulcanization and annealing. Moreover, the sheet structure of graphene can limit the irreversible slip of rubber molecular chains and increase the crosslinking density. The imine bond containing elastomer is prepared by using aldehyde-terminated polybutadiene rubber and piperazine, the imine bond can be broken and reformed, which gives the rubber body the dynamic crosslinking property, and further increases the compression permanent deformation resistance of the rubber seal. It comprises the following components by weight percentage: modified graphene 0.5-1.5 parts, aldehyde-terminated polybutadiene rubber 20-25 parts, piperazine 0.7-1.6 parts, hydrogenated nitrile rubber 60-70 parts, and fluororubber 20-30 parts, white carbon black 8-12 parts, calcium fluoride 2-4 parts, and the additives including catalyst, vulcanizing agent, antioxidant and plasticizer.

[0028] The modified graphene is dispersed in the rubber body by virtue of the excellent heat conductivity of graphene, which increases the temperature transfer during vulcanization and annealing of the rubber seal, and increases the uniformity of vulcanization and annealing. Moreover, the sheet structure of graphene can limit the irreversible slip of rubber molecular chains and increase the crosslinking density. The imine bond containing elastomer is prepared by using aldehyde-terminated polybutadiene rubber and piperazine, the imine bond can be broken and reformed, which gives the rubber body the dynamic crosslinking property, and further increases the compression permanent deformation resistance of the rubber seal. Calcium fluoride and fluororubber are used to increase the oil resistance of the rubber seal.

[0029] Based on the same overall inventive concept, the present application also protects a preparation method of a compression deformation resistant rubber seal. As shown in Figure 1 the preparation method can comprise the following steps: S1, preparing modified graphene; S2, preparing a pre-dispersed masterbatch by using the modified graphene; S3, performing nucleophilic addition reaction by using aldehyde-terminated polybutadiene rubber and piperazine to prepare an elastomer; S4, adding rubber raw materials, modifiers, pre-dispersed masterbatch and elastomer to perform segmented mixing to prepare a mixed rubber body; S5, performing segmented vulcanization treatment on the mixed rubber body, and injecting the rubber body after vulcanization treatment into a mold to form a rubber seal; S6, performing annealing treatment on the rubber seal, and performing turning finishing and inspection on the outer surface.

[0030] The above steps can comprise: Step one: graphene powder is added to a mixture of concentrated sulfuric acid and concentrated nitric acid and stirred thoroughly to oxidize. After removing the graphene powder, it is washed by centrifugation until neutral and dried in vacuum to obtain oxidized graphene powder. The oxidized graphene powder is put into a hydrolysis solution formed by mixing silane coupling agent, anhydrous ethanol and deionized water, and stirred thoroughly. The silane coupling agent is first hydrolyzed to form silanol bonds. The oxidized graphene powder is added to the hydrolysis solution, ultrasonically dispersed and stirred thoroughly. The silanol reacts with the hydroxyl groups or defect sites on the surface of the graphene to form Si-O-C covalent bonds. The unreacted silane coupling agent is removed by centrifugation with anhydrous ethanol, and the modified graphene is obtained after drying.

[0031] The structural formula of KH-550 type silane coupling agent is as follows: H2N(CH3)3Si(OCH2CH3)3; The alkoxyl group is hydrolyzed to form silanol: Si(OCH2CH3)3+ 3H2O Si(OH)3+ 3CH3CH2OH; The ethoxyl group (-OCH2CH3) undergoes nucleophilic substitution reaction with water molecules to form silanol (Si(OH)3), and the deionized water accounts for 5% of the total volume of the hydrolysis solution.

[0032] The silanol reacts with the hydroxyl groups on the surface of the graphene to form graphene-O-Si(OH)2 and H2O, forming Si-O-C covalent bonds to enhance the interfacial bonding force between the rubber body and the graphene. The sheet structure of the graphene can limit the irreversible slip of the rubber molecular chain and increase the crosslinking density.

[0033] Specifically, first, concentrated sulfuric acid and concentrated nitric acid are mixed in a volume ratio of 3:1 to form a mixed strong acid solution. Graphene powder is added to the strong acid solution and stirred at 60°C for 2 hours. The graphene is washed by centrifugation until neutral and dried in vacuum to obtain oxidized graphene. The silane coupling agent, anhydrous ethanol and deionized water are stirred and mixed in a volume ratio of 5:90:5 to form silanol. The oxidized graphene is added to the hydrolysis solution in a mass ratio of graphene:silane coupling agent = 1:0.5~1. The power of the ultrasonic disperser is adjusted to 500W and the frequency is 40kHz. The graphene is ultrasonically dispersed for 30 minutes, and then magnetically stirred at 80°C for 4 hours. After the condensation reaction between the silanol and the hydroxyl groups or defect sites on the surface of the graphene, the unreacted silane coupling agent is removed by centrifugation with anhydrous ethanol in a centrifugal washing machine at a speed of 8000 rpm for 10 minutes per time for 3 times. The modified graphene is obtained after drying.

[0034] Step two: take 0.5~1.5 parts of modified graphene, 8~12 parts of white carbon black, 8~12 parts of carbon black, and pre-mix them at a speed of 5000 rpm for 10 min to obtain a pre-dispersed masterbatch, and take 60~70 parts of hydrogenated nitrile rubber and 20~30 parts of fluorine rubber to make them completely reach room temperature.

[0035] Step three: take 20~25 parts of aldehyde-terminated polybutadiene rubber and 8~16 parts of toluene solvent and mix them in a reaction container, stir at a speed of 200~400 rpm and a temperature of 40~50℃, then add 0.7~1.6 parts of piperazine, stir for 30 min until the piperazine is completely dissolved, add 0.1~0.5 parts of PTSA, 0.05~0.12 parts of BHT, and 2~6 parts of carbon black, introduce nitrogen to remove oxygen, heat to 80~100℃, and keep the temperature constant for 18~24 h, monitor the reaction progress by FTIR, the aldehyde group peak 1720 cm -1 gradually weakens, and the imine bond 1640 cm -1 appears. After cooling to room temperature, add methanol to terminate the reaction, distill off the solvent at 60~80℃ under a vacuum of 0.1 MPa, obtain PAPB (polyaminopropyl biguanide) elastomer, and place the PAPB elastomer in a vacuum drying oven at 60℃ for 24 h to remove residual solvent. PTSA is used as the catalyst.

[0036] Further, the aldehyde group in the aldehyde-terminated polybutadiene rubber reacts with the primary amine group of piperazine under the catalysis of PTSA to form an imine bond. This reaction is reversible, and the imine bond can break and reform under high temperature or stress, giving the rubber dynamic crosslinking properties. The dynamic crosslinking of aldehyde-terminated polybutadiene rubber and piperazine can be represented as: ; wherein is a N-C-N bond, and piperazine is a crosslinking agent for aldehyde-terminated polybutadiene rubber.

[0037] Step four: Put 60-70 parts of hydrogenated nitrile rubber and 20-30 parts of fluoroelastomer which have reached room temperature into the internal mixer, first carry out low temperature mixing for 10-15 min, preliminarily mix the rubber matrix, and make the two kinds of rubber fully mixed and uniform to form a uniform rubber matrix. Then add 6-8 parts of plasticizer and continue to mix for 5-8 min to make the plasticizer fully melt into the rubber matrix. Then add all the pre-dispersed masterbatch and 2-4 parts of calcium fluoride into the internal mixer, gradually increase the roll gap and ensure the temperature control within 100℃, continue to mix for 5 min to complete the first stage mixing. Then add 1-2.5 parts of vulcanizing agent and 0.5-15 parts of antioxidant, mix at a temperature range of 40-50℃ for 5-8 min to make the antioxidant uniformly dispersed in the rubber matrix and fully play its anti-aging role, and obtain the mixed rubber body. Add 5-15 parts of PAPB elastomer to the mixed rubber body to complete the second stage mixing, and inject the mixed rubber body mixed with PAPB elastomer into the seal mold for curing and forming.

[0038] Step five: Ensure that the seal mold injected with the mixed rubber body is tightly closed and placed in the flat vulcanizing machine, the vulcanization temperature is controlled at 170-180℃, the vulcanization pressure is controlled at 12-15 MPa, and the first stage vulcanization treatment is carried out for 15-25 min to make the rubber molecular chain begin to crosslink and form a preliminary crosslinking structure. During this period, the temperature should be avoided to be too high to cause the aggregation of fillers and the rupture of rubber molecular chain, and the first stage vulcanization is completed. The vulcanization temperature is increased in gradient, the vulcanization treatment is carried out at 120℃ for 0.8-1.2 h, at 150℃ for 0.6-1 h, and the temperature is increased at a speed not more than 5℃ / min, the vulcanization treatment is carried out at 200℃ for 1-1.5 h, and then at 230℃ for 0.5-1 h. The vulcanization pressure remains unchanged to ensure the chemical bonding of calcium fluoride and the mixed rubber body, and the second stage vulcanization treatment is completed. The high temperature vulcanization stage makes the crosslinking reaction fully proceed to form a dense three-dimensional network structure, improves the elasticity and mechanical properties of the rubber, and further reduces the compression permanent deformation.

[0039] Step six: Take out the seal from the mold and place it in the air drying oven for annealing treatment to eliminate the internal stress generated during the vulcanization process, make the rubber molecular chain further adjust and relax, improve the shape recovery ability of the seal, and reduce the permanent deformation caused by internal stress. During the annealing process, the temperature in the drying oven should be uniform to avoid local temperature being too high or too low. After the annealing is completed, the seal is taken out and naturally cooled to room temperature. Then the seal is subjected to appearance inspection to remove burrs and burrs, and detect whether there are bubbles, cracks and other defects. The qualified seal is subjected to performance test including compression permanent deformation, tensile strength, oil resistance, high temperature resistance and the like to ensure that it meets the design requirements.

[0040] Example 1: (1) Put 60 parts of hydrogenated nitrile rubber and 20 parts of fluorine rubber which are at room temperature into the internal mixer, the roll gap is 1 mm, the roll temperature is controlled at 60°C, and mixing is carried out for 10 min, then 6 parts of phthalate is added, and mixing is continued for 5 min, so that the phthalate is fully mixed into the rubber matrix, then 2 parts of calcium fluoride is added to the internal mixer, the roll gap is gradually increased to 3 mm, the temperature does not exceed 100°C, and mixing is continued for 5 min, then 1 part of vulcanizing agent and 0.5 part of BHT are mixed at a temperature range of 40°C for 5 min to complete the second mixing, 5 parts of PAPB elastomer is added to the mixed rubber to obtain a mixed rubber, and the mixed rubber is injected into a mold for shaping; (3) The vulcanization pressure of the flat vulcanization machine is controlled at 12 MPa, and vulcanization is carried out at 170°C for 25 min to complete the first vulcanization, then the vulcanization temperature is lowered to 120°C for 1.2 h of vulcanization treatment, then 150°C for 1 h of vulcanization, 200°C for 1.5 h of vulcanization treatment, and then 230°C for 1 h of vulcanization to complete the second vulcanization treatment; (4) The sealing element is taken out of the mold and placed in a forced air drying oven for annealing at 150°C for 2 h, after annealing, the sealing element is taken out and naturally cooled to room temperature to obtain a finished sealing element.

[0041] Example 2: (1) 1.5 parts of modified graphene, 12 parts of white carbon black, and 12 parts of carbon black are pre-mixed at a speed of 5000 rpm for 10 min to prepare a pre-dispersed masterbatch, and 70 parts of hydrogenated nitrile rubber and 30 parts of fluorine rubber are placed at room temperature for at least 24 h to reach room temperature; (2) Put 70 parts of hydrogenated nitrile rubber and 30 parts of fluorine rubber which are at room temperature into the internal mixer, the roll gap is 2 mm, the roll temperature is controlled at 80°C, and mixing is carried out for 15 min to preliminarily mix the rubber matrix, then 8 parts of phthalate is added, and mixing is continued for 8 min, so that the phthalate is fully mixed into the rubber matrix, 4 parts of calcium fluoride is added to the internal mixer, the roll gap is gradually increased to 4 mm, the temperature does not exceed 100°C, and mixing is continued for 5 min to complete the first mixing, then 2.5 parts of dicumyl peroxide and 1.5 parts of BHT are mixed at a temperature range of 50°C for 8 min to complete the second mixing, and the mixed rubber is injected into a mold for shaping; (3) The vulcanization temperature of the flat vulcanization machine is controlled at 180°C, the vulcanization pressure is 15 MPa, and the vulcanization time is 15 min to complete the first vulcanization treatment, then the vulcanization temperature is lowered to 120°C for 0.8 h of vulcanization treatment, 150°C for 0.6 h of vulcanization, 200°C for 1 h of vulcanization treatment, and then 230°C for 0.5 h of vulcanization to complete the second vulcanization treatment; (4) The seal is removed from the mold and placed in a forced air drying oven for annealing at 150°C for 1.5 hours to eliminate the internal stress generated during the vulcanization process. After annealing, the seal is removed and naturally cooled to room temperature to obtain a finished seal.

[0042] Example 3: (1) Take 1 part of modified graphene, 10 parts of white carbon black, and 10 parts of carbon black, and pre-mix them at a speed of 5000 rpm for 10 minutes to prepare a pre-dispersed masterbatch. Then take 65 parts of hydrogenated nitrile rubber and 25 parts of fluororubber and place them at room temperature for at least 24 hours to allow them to reach room temperature; (2) 65 parts of hydrogenated nitrile rubber and 25 parts of fluororubber that have reached room temperature are put into an internal mixer, the roller spacing is 1.5 mm, the roller temperature is controlled at 70 ° C, and the mixing is carried out for 13 minutes to perform preliminary mixing of the rubber matrix. Then, 7 parts of phthalate are added and the mixing is continued for 6 minutes to allow the phthalate to be fully integrated into the rubber matrix. 3 parts of calcium fluoride are added to the internal mixer, the roller spacing is gradually increased to 3.5 mm, the temperature does not exceed 100 ° C, and the mixing is continued for 5 minutes. Then, 1.5 parts of diisopropylbenzene peroxide and 1 part of BHT are added and mixed at a temperature range of 45 ° C for 7 minutes. 10 parts of PAPB elastomer are added to the mixed colloid to obtain a mixed colloid, and the mixed colloid is injected into a mold for shaping; (3) The vulcanization temperature of the flat vulcanizer is controlled at 175°C, the vulcanization pressure is 13 MPa, and the vulcanization process is completed for 17 minutes. Then, the vulcanization temperature is lowered to 120°C for vulcanization for 0.9 hours, and then the temperature is raised to 150°C for vulcanization for 0.8 hours. Then, the temperature is raised to 200°C for vulcanization for 1.2 hours, and then the temperature is raised to 230°C for vulcanization for 0.6 hours to complete the second stage vulcanization process. (4) The seal is removed from the mold and placed in a forced air drying oven for annealing at 150°C for 1 hour. After annealing, the seal is removed and naturally cooled to room temperature to obtain a finished seal.

[0043] Comparative Example 1: (1) 9 parts of white carbon black and 10 parts of carbon black were pre-mixed and mixed at a speed of 5000 rpm for 10 minutes to prepare a pre-dispersed masterbatch. 62 parts of hydrogenated nitrile rubber and 24 parts of fluororubber were placed at room temperature for at least 24 hours to allow them to reach room temperature. (2) 63 parts of hydrogenated nitrile rubber and 23 parts of fluororubber that have reached room temperature are put into an internal mixer, the roller spacing is 2 mm, the roller temperature is controlled at 60 ° C, and the mixing is carried out for 15 minutes. Then, 7 parts of phthalate are added and the mixing is continued for 8 minutes to allow the phthalate to be fully integrated into the rubber matrix. 3 parts of calcium fluoride are added to the internal mixer, the roller spacing is gradually increased to 3 mm, and the mixing is continued for 5 minutes. Then, 1.5 parts of vulcanizing agent and 1 part of BHT are added and the mixing is carried out at a temperature range of 50 ° C for 8 minutes to obtain a mixed colloid, which is then injected into a mold for shaping; (3) The vulcanization temperature of the flat vulcanizer is controlled at 180°C, the vulcanization pressure is 15 MPa, the vulcanization time is 15 min, and the vulcanization temperature is gradually increased to 230°C at a rate of 15°C / h for vulcanization treatment for 4 h; (4) The seal is removed from the mold and placed in a forced air drying oven for annealing at 150°C for 2 hours. After annealing, the seal is removed and naturally cooled to room temperature to obtain a finished seal.

[0044] Comparative Example 2: (1) Pre-mix 10 parts of white carbon black and 11 parts of carbon black at 5000 rpm for 10 minutes to prepare a pre-dispersed masterbatch, and then take 65 parts of hydrogenated nitrile rubber and 30 parts of fluororubber and place them at room temperature for 24 hours to reach room temperature; (2) 60 parts of hydrogenated nitrile rubber and 30 parts of fluororubber that have reached room temperature are put into an internal mixer, the roller spacing is 2 mm, the roller temperature is controlled at 70°C, and the mixing is carried out for 13 minutes. Then, 7 parts of phthalate are added and the mixing is continued for 6 minutes to allow the phthalate to be fully integrated into the rubber matrix. 3 parts of calcium fluoride are added to the internal mixer, the roller spacing is gradually increased to 3 mm, the temperature is controlled within 100°C, and the mixing is continued for 5 minutes. Then, 1.5 parts of vulcanizing agent and 1 part of BHT are added and the mixing is carried out at a temperature range of 45°C for 7 minutes to obtain a mixed colloid, which is then injected into a mold for shaping; (3) The vulcanization temperature of the flat vulcanizer is controlled at 170°C, the vulcanization pressure is 13 MPa, and the vulcanization time is 13 min. The vulcanization temperature is gradually increased by vulcanizing at 120°C for 1 h, 200°C for 4 h, and then at 230°C for 2 h while the vulcanization pressure remains unchanged. The vulcanization time is 27 min, and the vulcanization treatment is completed. (4) The seal is removed from the mold and placed in a forced air drying oven for annealing at 150°C for 1.5 hours. After annealing, the seal is removed and naturally cooled to room temperature to obtain a finished seal.

[0045] Test Example 1: Tensile Strength Test (ASTM D412): The seal samples of each example and comparative example were cut into standard dumbbell-shaped test pieces with a thickness of 2 mm, and tested using a universal material testing machine at a tensile rate of 500 mm / min, and the maximum load and elongation at break were recorded. Five test pieces were tested in each group, and the average value was taken.

[0046] Test Example 2: Compression set test (ASTM D395): The test piece was compressed to 25% of the original height, kept at 150°C for 22 hours, and after the pressure was released, the residual deformation rate was measured after 30 minutes of recovery.

[0047] Test Example 3: Thermal conductivity test (ASTM E1461): The sample was processed into a round piece with a diameter of 10 mm and a thickness of 1 mm, and a laser thermal conductivity instrument was used to measure the thermal diffusivity and calculate the thermal conductivity.

[0048] Table 1: Test results of various properties of rubber seals

[0049] From the experimental data of Examples 1-3 and Comparative Examples 1-2 in Table 1, it can be found that the rubber seal prepared by the present application has higher tensile strength. The dynamic cross-linked elastomer of aldehyde-terminated polybutadiene rubber and piperazine is dynamically cross-linked, and under the action of high temperature or stress, the imine bond can break and reform, giving the rubber body the characteristic of dynamic cross-linking, increasing the overall permanent deformation resistance of the rubber seal. And the graphene can be dispersed in the rubber body, increasing the overall thermal conductivity of the rubber body, which is more conducive to the uniformity and temperature diffusion of vulcanization and annealing. Using a gradient heating method, the vulcanizing agent, plasticizer and antioxidant can be fully activated at each temperature stage, ensuring the overall performance of the rubber seal. The reaction between the silicon alcohol and the hydroxyl group on the surface of the graphene forms graphene-O-Si(OH)2 and H2O, forming a Si-O-C covalent bond, enhancing the interfacial bonding force between the rubber body and the graphene. And the lamellar structure of graphene can limit the irreversible slip of rubber molecular chains, increasing the crosslinking density.

[0050] By comparison, it can be found that Comparative Examples 1 and 2 and Example 1 do not add graphene, and without the assistance of graphene in thermal conductivity, the vulcanization and annealing time is longer, and the tensile strength is slightly weaker. Compared with Comparative Example 2, Comparative Example 1 does not use gradient heating for vulcanization treatment, and its tensile performance is poor. Compared with Comparative Examples 1 and 2, Examples 1 and 3 add PAPB elastomer to the rubber body, which can break and reform under the action of high temperature or stress, giving the rubber body the characteristic of dynamic cross-linking, and increasing the overall permanent deformation resistance of the rubber seal.

[0051] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A rubber seal resistant to compression deformation, characterized in that: The invention comprises the following components: 0.5-1.5 parts of graphene, 60-70 parts of hydrogenated nitrile rubber, 20-30 parts of fluororubber, and the balance being an elastomer containing an imine bond; The elastomer containing imine bonds comprises 20 to 25 parts of aldehyde-terminated polybutadiene rubber and 0.7 to 1.6 parts of piperazine.

2. The compression-deformation-resistant rubber seal according to claim 1, characterized in that: The rubber seal further comprises: 8-12 parts of white carbon black, 2-4 parts of calcium fluoride, 8-12 parts of carbon black and an additive, wherein the imine bond of the elastomer containing an imine bond can be broken and reformed; Wherein, the auxiliary agents include catalysts, vulcanizing agents, antioxidants and plasticizers.

3. A method for preparing a compression-deformation-resistant rubber seal according to claim 1 or 2, characterized in that: The method comprises the following preparation steps: Graphene modification pretreatment: Graphene is oxidized using concentrated acid, and the silane coupling agent is hydrolyzed to generate silanols. The silanols then react with the carboxyl groups or defect sites on the surface of the graphene oxide to obtain modified graphene. Preparation of elastomer: an elastomer containing imine bonds is generated by reacting aldehyde-terminated polybutadiene rubber with piperazine; Preparation of mixed colloid and vulcanization treatment: the raw materials are mixed in sections to obtain mixed colloid, and the mixed colloid is vulcanized in sections, and the vulcanization temperature is increased in a gradient manner.

4. The method for preparing a rubber seal resistant to compression deformation according to claim 3, characterized in that: The modified graphene preparation method comprises the following steps: mixing concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 to prepare a strong acid solution; adding graphene powder to the strong acid solution for oxidation; mixing a silane coupling agent, anhydrous ethanol, and deionized water in a volume ratio of 5:90:5 to generate a hydrolyzate containing silanols; adding graphene oxide:silane coupling agent in a ratio of 1:0.5-1 to the hydrolyzate; ultrasonically dispersing and stirring to allow condensation reaction between the silanols and hydroxyl groups or defect sites on the graphene surface; and washing and removing the remaining silane coupling agent to prepare the modified graphene.

5. The method for preparing a rubber seal resistant to compression deformation according to claim 3, characterized in that: Before the step of preparing the mixed colloid, a pre-dispersed masterbatch is prepared. The method for preparing the pre-dispersed masterbatch is as follows: 0.5-1.5 parts of modified graphene, 8-12 parts of white carbon black and 8-12 parts of carbon black are placed in a disperser, and mixed at a speed of 5000 rpm for 10 minutes to obtain the pre-dispersed masterbatch.

6. The method for preparing a rubber seal resistant to compression deformation according to claim 3, characterized in that: The preparation method of the elastomer comprises the following steps: taking 20 to 25 parts of aldehyde-terminated polybutadiene rubber and 8 to 16 parts of toluene solvent, mixing them and placing them in a prepared reaction container; adding 0.7 to 1.6 parts of piperazine after stirring; continuing to stir until the piperazine is completely dissolved; adding 0.1 to 0.5 parts of a catalyst, 0.05 to 0.12 parts of an antioxidant and 2 to 6 parts of carbon black; introducing nitrogen to expel oxygen; cooling to room temperature after the imine bond appears, adding methanol to terminate the reaction, and distilling off the remaining methanol solvent to obtain an elastomer containing imine bonds.

7. The method for preparing a rubber seal resistant to compression deformation according to claim 3, characterized in that: The method for preparing the mixed colloid comprises: adding 60-70 parts of hydrogenated nitrile rubber and 20-30 parts of fluororubber into an internal mixer, performing preliminary mixing at 60-80° C. for 10-15 minutes, then adding 6-8 parts of plasticizer and continuing mixing at the same temperature for 5-8 minutes, then adding all the pre-dispersed masterbatch and 2-4 parts of calcium fluoride into the internal mixer, gradually increasing the roller distance and controlling the mixing temperature within 100° C., and continuing mixing for 5 minutes to complete one stage of mixing; Add 1 to 2.5 parts of vulcanizing agent and 0.5 to 1.5 parts of antioxidant to the colloid after the first stage mixing, mix at a temperature of 40 to 50 ° C for 5 to 8 minutes for further mixing, and finally add 5 to 15 parts of elastomer, continue mixing at the same temperature for 5 to 8 minutes to complete the second stage mixing to obtain a mixed colloid, and inject the mixed colloid into the prepared sealing mold for curing and molding.

8. The method for preparing a rubber seal resistant to compression deformation according to claim 3, characterized in that: The mixed colloid vulcanization treatment method comprises: sealing a sealing mold filled with the mixed colloid and placing it in a prepared flat vulcanizing press, firstly performing a vulcanization treatment at 170-180° C. and a vulcanization pressure controlled at 12-15 MPa for 15-25 minutes to obtain a first-stage vulcanized colloid; The flat plate vulcanizer is cooled to 120°C, and the first stage vulcanized colloid is vulcanized at 120°C for 0.8-1.2h and at 150°C for 0.6-1h in the flat plate vulcanizer, and the temperature is increased at a heating rate not exceeding 5°C / min, and then the temperature is increased to 200°C for vulcanization for 1-1.5h, and finally vulcanized at 230°C for 0.5-1h to complete the second stage vulcanization treatment and obtain the vulcanized colloid.

9. The method for preparing a rubber seal resistant to compression deformation according to claim 8, characterized in that: The prepared vulcanized colloid is annealed. The annealing method of the vulcanized colloid is as follows: the seal is removed from the mold, placed in a forced air drying oven and annealed at 150° C. for 1 to 2 hours. After the annealing is completed, the seal is removed and naturally cooled to room temperature to obtain the rubber seal.

10. The method for preparing a rubber seal resistant to compression deformation according to claim 7, characterized in that: The hydrogenated nitrile rubber and fluororubber are both rubber bodies that have been placed at room temperature for at least 24 hours to reach room temperature.

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