Rubber sealing material suitable for gas pipeline and preparation method thereof

Abstract

The invention discloses a rubber sealing material suitable for a gas pipeline and a preparation method of the rubber sealing material, and belongs to the technical field of rubber materials. The rubber sealing material is prepared from the following raw materials in parts by weight: 75 to 90 parts of modified nitrile rubber, 5 to 10 parts of carboxyl-terminated nitrile rubber, 5 to 20 parts of hydrogenated nitrile rubber, 40 to 80 parts of carbon black, 15 to 35 parts of silica powder, 15 to 28 parts of a plasticizer, 4.5 to 5 parts of zinc oxide, 0.8 to 1.2 parts of stearic acid, 1.2 to 2 parts of microcrystalline wax, 3.5 to 4 parts of an anti-aging agent, 2.5 to 3.5 parts of peroxide, 0.2 to 0.5 part of sulfur, 1.2 to 2.5 parts of an assistant vulcanizing agent and 0.6 to 2 parts of an accelerant. The modified nitrile rubber is prepared by grafting silane containing sulfydryl and amino bifunctional groups on nitrile rubber through sulfydryl-double bond click reaction. The rubber sealing material provided by the invention is high in low-temperature resistance, low in compression set value and good in dimensional stability.

Description

Technical Field

[0001] This invention belongs to the field of rubber material technology, specifically relating to a rubber sealing material suitable for gas pipelines and its preparation method. Background Technology

[0002] With the widespread adoption and popularization of natural gas in my country's industrial and residential sectors, gas pipeline systems have experienced continuous and rapid development. Due to the high pressure requirements of natural gas pipeline networks and the presence of trace impurities in the gas, including dust, unsaturated moisture, hydrogen sulfide, tar, benzene, and naphthalene, the pipeline medium exerts a strong impact on the machined surfaces of valve cavities and seals, thus placing higher demands on the sealing systems of gas pipeline valves, flanges, and instruments.

[0003] Sealing materials used in gas pipelines not only need to have good resistance to oil, gas media, and corrosion to meet the performance requirements of low-temperature environments in some cold regions during winter, but also need to have good compression set properties to ensure the long-term dimensional stability of the seal.

[0004] Chinese invention patent CN110128718A discloses a low compression set nitrile rubber and its preparation method. Under the premise of using a sulfur and DCP vulcanization system, a carbon black N990 and carbon black N330 filler system is used to significantly improve the final rebound and deformation resistance of the product, reduce the compression set of the nitrile rubber vulcanizate, and improve the sealing performance and service life during use. However, the presence of unsaturated bonds in nitrile rubber also makes it prone to embrittlement at low temperatures, i.e., increased low-temperature brittleness, which reduces its adaptability to extreme environments. The material in this patent is difficult to meet the high performance requirements of low temperature resistance and low compression set at the same time.

[0005] Therefore, only rubber sealing materials with good compression set, excellent oil resistance, corrosion resistance, and low-temperature resistance can meet the sealing requirements of gas transportation systems. Summary of the Invention

[0006] This invention provides a rubber sealing material suitable for gas pipelines and its preparation method, which can solve the problem of poor low-temperature resistance of existing rubber sealing materials for gas pipelines.

[0007] The objective of this invention can be achieved through the following technical solutions: A rubber sealing material suitable for gas pipelines, comprising the following raw materials by weight: Modified nitrile rubber 75-90 parts, carboxyl-terminated nitrile rubber 5-10 parts, hydrogenated nitrile rubber 5-20 parts, carbon black 40-80 parts, silicone powder 15-35 parts, plasticizer 15-28 parts, zinc oxide 4.5-5 parts, stearic acid 0.8-1.2 parts, microcrystalline wax 1.2-2 parts, antioxidant 3.5-4 parts, peroxide 2.5-3.5 parts, sulfur 0.2-0.5 parts, co-vulcanizing agent 1.2-2.5 parts, accelerator 0.6-2 parts; The modified nitrile rubber is obtained by grafting silanes containing thiol and amino bifunctional groups onto nitrile rubber via a thiol-double bond click reaction.

[0008] Conventional nitrile butadiene rubber (NBR) contains unsaturated double bonds and cyano groups. The unsaturated double bonds exhibit high chemical reactivity, and their corrosion resistance needs improvement. While hydrogenated NBR, obtained through hydrogenation, offers better corrosion resistance, it is more expensive, and direct large-scale use would increase costs. A solution involves grafting silanes onto NBR via a mercapto-double bond click reaction to increase saturation. The introduction of silane chains enhances molecular chain flexibility at low temperatures, improving low-temperature resistance. The reaction conditions are mild, and the reaction is highly efficient.

[0009] The compression set performance of rubber sealing materials significantly impacts their sealing performance, necessitating the addition of inorganic materials as fillers for reinforcement (such as carbon black). While nitrile rubber possesses a certain degree of polarity, its compatibility with inorganic materials is poor. Using carboxyl-terminated nitrile rubber as a bridge, the compatibility is improved by utilizing the binding effect of the carboxyl groups and the hydroxyl groups on the surface of the inorganic material. Simultaneously, silanes containing thiol and amino bifunctional groups are used as grafting reactants. The introduced amino groups can react with the carboxyl-terminated nitrile rubber, increasing the crosslinking density, improving mechanical strength, and enhancing compression set performance.

[0010] The ternary blend system constructed from modified nitrile butadiene rubber, carboxyl-terminated nitrile butadiene rubber, and hydrogenated nitrile butadiene rubber, through synergistic effects, endows rubber sealing materials with excellent media resistance, high and low temperature resistance, sealing performance, low compression set, high mechanical strength, and good processability.

[0011] Furthermore, the silane containing thiol and amino bifunctional groups is prepared as follows: The reaction solution was obtained by mixing the hydrolysate of mercaptopropyltrimethoxysilane and the hydrolysate of 3-aminopropyltrimethoxysilane, adding an alkaline catalyst, heating to 100-110℃ and stirring for 2-4 hours, adding a neutralizing agent while stirring, adjusting the pH to 6-7, removing low-boiling-point substances and water by vacuum distillation, and cooling to room temperature to obtain silanes containing thiol and amino bifunctional groups.

[0012] Silane hydrolysis forms silanol groups, which then polymerize under alkaline catalysis to form silanes containing thiol and amino bifunctional groups. The residual silanol groups can increase the bonding force with inorganic materials in rubber sealing materials and promote the uniform dispersion of the components of rubber sealing materials.

[0013] Furthermore, the hydrolysate is prepared as follows: Add mercaptopropyltrimethoxysilane or 3-aminopropyltrimethoxysilane at a mass concentration of 1-5% to an aqueous ethanol solution, and heat to 40-50℃ for 1-3 hours to hydrolyze and obtain the hydrolysate.

[0014] Furthermore, the mixing ratio of the reaction solution is n(mercaptopropyltrimethoxysilane):n(3-aminopropyltrimethoxysilane) = 1-3:1.

[0015] Furthermore, the alkaline catalyst is potassium hydroxide; The amount of alkaline catalyst added is 0.05-0.1% of the total mass of mercaptopropyltrimethoxysilane and 3-aminopropyltrimethoxysilane.

[0016] Furthermore, the neutralizing agent is one of acetic acid and hydrochloric acid.

[0017] Furthermore, the modified nitrile rubber is prepared as follows: Nitrile rubber was dissolved in acetone at a mass concentration of 2-5%. Silane containing thiol and amino bifunctional groups was added, and the mixture was stirred evenly. A photoinitiator was then added, and the mixture was stirred until homogeneous. The grafting reaction was carried out by irradiation with ultraviolet light for 20-30 minutes. After the reaction was completed, acetone was removed by vacuum distillation, and the modified nitrile rubber was obtained by vacuum drying.

[0018] Furthermore, the acrylonitrile content in the nitrile rubber (NBR) is 31% to 35%, and the Mooney viscosity is 65 to 79 mL (1+4) at 100°C.

[0019] Furthermore, the silane containing thiol and amino bifunctional groups is 10-30% of the mass of nitrile rubber.

[0020] Furthermore, the photoinitiator is one of 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-2-methylpropanone; the photoinitiator is 1-2% of the mass of nitrile rubber.

[0021] Furthermore, the acrylonitrile content of the end-carboxyl butadiene-acrylonitrile rubber is 28%–30%, and the carboxyl content is 0.3–1.2 mmol / g; The hydrogenated nitrile butadiene rubber (HNBR) contains 25% to 30% acrylonitrile and has a degree of hydrogenation of 90% to 96%.

[0022] Furthermore, the carbon black is a composition of high abrasion-resistant carbon black and semi-reinforcing carbon black in a mass ratio of 1:1 to 2.5.

[0023] Furthermore, the plasticizer is at least one selected from dioctyl adipate, di-n-hexyl adipate, dioctyl sebacate, and tributyl acetylcitrate.

[0024] Furthermore, the antioxidant is a combination of at least one of antioxidant RD, antioxidant BLE, and N-nitrosodiphenylamine, and at least one of antioxidant 4010NA, antioxidant 4020, and antioxidant AW.

[0025] Furthermore, the antioxidant is a composition of N-nitrosodiphenylamine and antioxidant 4010NA in a mass ratio of 1 to 2:1, or the antioxidant is a composition of N-nitrosodiphenylamine and antioxidant 4020 in a mass ratio of 1 to 2:1.

[0026] Furthermore, the peroxide is one of dicumyl peroxide (DCP), bis-tert-butylperoxyisopropylbenzene (BIPB), and 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane (BPMC).

[0027] Peroxides are used as the main crosslinking component. They decompose to generate free radicals, which capture active hydrogens from the rubber molecular chain (especially methylene hydrogen next to the acrylonitrile group, tertiary hydrogen on hydrogenated nitrile rubber, and silane ortho-hydrogen on modified nitrile rubber) to form macromolecular free radicals, which then combine to form CC crosslinking bonds.

[0028] Furthermore, the peroxide is bis-tert-butylperoxyisopropylbenzene.

[0029] Furthermore, the vulcanizing agent is a bismaleimide-based vulcanizing agent.

[0030] Furthermore, the vulcanizing agent is N,Nˊ-m-phenylenebismaleimide.

[0031] Furthermore, the accelerator is at least one of sulfenamide accelerators, thiazole accelerators, and thiuram accelerators.

[0032] Furthermore, the accelerator is at least one of accelerator CZ, accelerator NOBS, accelerator TMTD, and accelerator DPTT.

[0033] This invention also provides a method for preparing a rubber sealing material suitable for gas pipelines, comprising the following steps: S1. Weigh the required weight parts of modified nitrile rubber, carboxyl-terminated nitrile rubber and hydrogenated nitrile rubber according to the formula and add them to the open mill for plasticizing. Pass each material through a thin mill 3 to 5 times. The roller gap of the open mill is 0.8 to 1 mm. Then discharge the rubber and sheet it. Cool the rubber compound to room temperature and let it stand for more than 3 hours to obtain the pre-plasticized rubber. S2. The pre-plasticized modified nitrile rubber, carboxyl-terminated nitrile rubber, and hydrogenated nitrile rubber obtained in S1 are put into a mixer and mixed for 2-3 minutes. Then, carbon black, zinc oxide, stearic acid, microcrystalline wax, antioxidant, and half the weight of plasticizer are added in sequence according to the required weight ratio. Mixing continues for 1-1.5 minutes. Then, silicone powder and the remaining half the weight of plasticizer are added. Mixing continues for 3-5 minutes, and the rubber is discharged. S3. Add the rubber discharged from S2 to the open mill, and add peroxide, sulfur, vulcanizing agent and accelerator in sequence. Adjust the roller gap to 0.1 mm, pass through the mill twice, make two triangular swirls, adjust the roller gap to 0.5-1 mm, pass through the mill three times, make three triangular swirls, adjust the roller gap to about 3 mm, and then extrude the sheet. Let the compound rubber stand at 20-30℃ for at least 16 hours. S4. The compound rubber that has been left to stand in S3 is subjected to compression molding and vulcanization. The vulcanization pressure is 10-20 MPa, the vulcanization temperature is 155-180℃, and the vulcanization time is 5-10 min to obtain the rubber sealing material.

[0034] Furthermore, the glue discharge temperature in S2 is 130–145°C.

[0035] The beneficial effects of this invention are: (1) In this invention, silane containing thiol and amino bifunctional groups is grafted onto nitrile rubber through a mercapto-double bond click reaction. The reaction conditions are mild, which improves the saturation of nitrile rubber, introduces silane chains, and utilizes the crosslinking of amino and carboxyl-terminated nitrile rubber to participate in the vulcanization crosslinking network, improves the crosslinking density, improves the compression set performance, and enhances the low temperature resistance of the rubber sealing material.

[0036] (2) The present invention uses a combination of nitrile rubber with medium to high acrylonitrile content, a small amount of carboxyl-terminated nitrile rubber with medium acrylonitrile content and hydrogenated nitrile rubber, combined with a plasticizing system and a protective system with good cold resistance, to control material costs while significantly improving the aging resistance, oil resistance, media resistance and low temperature resistance of rubber materials.

[0037] (3) The present invention combines high abrasion-resistant carbon black and semi-reinforcing carbon black, taking into account the strength, abrasion resistance and dispersibility of the rubber sealing material. At the same time, the loose granular layered embedded structure of the silicone powder can improve the filling density of the rubber, reduce air bubbles and voids in the rubber particles, and reduce the heat generated by the movement of rubber molecular chains, thereby effectively reducing the dynamic compression permanent deformation of the product and ensuring the dimensional stability of the product under high temperature and high pressure.

[0038] (4) In this invention, peroxide is used for crosslinking, and a small amount of sulfur is used as a vulcanization regulator and a co-vulcanizing agent, bismaleimide, to form an auxiliary crosslinking network, which intertwines with the peroxide crosslinking network. The two networks penetrate each other, which further improves the aging resistance of the rubber compound, reduces compression set, and improves the tensile stress and tear strength of the material. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1

[0041] Preparation of silanes containing thiol and amino bifunctional groups: Step 1: Preparation of hydrolysate: Add mercaptopropyltrimethoxysilane at a mass concentration of 3% to an ethanol aqueous solution (ethanol-water volume ratio of 5:3), heat to 45℃ and hydrolyze for 2 hours to obtain mercaptopropyltrimethoxysilane hydrolysate. Prepare 3-aminopropyltrimethoxysilane hydrolysate under the same conditions.

[0042] Step 2: Mix the hydrolysate of mercaptopropyltrimethoxysilane and the hydrolysate of 3-aminopropyltrimethoxysilane to obtain a reaction solution with a mixing ratio of n(mercaptopropyltrimethoxysilane):n(3-aminopropyltrimethoxysilane) = 2:1. Add potassium hydroxide (0.06% of the total mass of mercaptopropyltrimethoxysilane and 3-aminopropyltrimethoxysilane), heat to 105℃ and stir for 3 hours. While stirring, add acetic acid to adjust the pH to 6.5. Remove low-boiling-point substances and water by vacuum distillation, and cool to room temperature to obtain silanes containing thiol and amino bifunctional groups.

[0043] Preparation of modified nitrile butadiene rubber: Acrylonitrile rubber (acrylonitrile content 31-35%, Mooney viscosity 65-79 mL (1+4) 100℃) was dissolved in acetone at a mass concentration of 4%. A silane containing thiol and amino bifunctional groups prepared above was added, with the silane containing thiol and amino bifunctional groups accounting for 20% of the mass of the nitrile rubber. After mixing evenly, 2,2-dimethoxy-2-phenylacetophenone was added at a mass of 1.5% of the nitrile rubber. The mixture was stirred evenly and subjected to grafting reaction by irradiation with ultraviolet light (365 nm) for 25 min. After the reaction was completed, acetone was removed by vacuum distillation, and the modified nitrile rubber was obtained by vacuum drying.

[0044] A rubber sealing material suitable for gas pipelines, comprising the following raw materials by weight: 75 parts modified nitrile rubber, 5 parts carboxyl-terminated nitrile rubber, 20 parts hydrogenated nitrile rubber, 27 parts high abrasion-resistant carbon black N330, 38 parts semi-reinforcing carbon black N774, 28 parts silicone powder N85, 22.5 parts plasticizer (dioctyl sebacate), 5 parts zinc oxide, 1 part stearic acid, 1.2 parts microcrystalline wax, 2 parts antioxidant N-nitrosodiphenylamine, 2 parts antioxidant 4010NA, 2.5 parts peroxide (di-tert-butylperoxyisopropylbenzene), 0.3 parts sulfur S-80, 2 parts co-curing agent (N,Nˊ-m-phenylenebismaleimide), and 1.5 parts accelerator CZ.

[0045] Among them, the acrylonitrile content of the carboxyl-terminated nitrile butadiene rubber is 28% to 30%, and the carboxyl content is 0.3 to 1.2 mmol / g; the acrylonitrile content of the hydrogenated nitrile butadiene rubber is 25% to 30%, and the degree of hydrogenation is 90% to 96%.

[0046] Preparation of rubber sealing materials suitable for gas pipelines: S1. Weigh the required weight parts of modified nitrile rubber, carboxyl-terminated nitrile rubber and hydrogenated nitrile rubber according to the formula and add them to the open mill for plasticizing. Pass each material through a thin mill 5 times. The roller gap of the open mill is 1 mm. Then discharge the rubber and sheet it. Cool the rubber compound to room temperature and let it stand for 6 hours to obtain the pre-plasticized rubber.

[0047] S2. The pre-plasticized modified nitrile rubber, carboxyl-terminated nitrile rubber, and hydrogenated nitrile rubber obtained in S1 are put into a mixer and mixed for 3 minutes. Then, according to the required weight parts, high abrasion-resistant carbon black N330, semi-reinforcing carbon black N774, zinc oxide, stearic acid, microcrystalline wax, antioxidant, and half the weight parts of plasticizer are added. Mixing is continued for 1.5 minutes. Then, silicone powder and the remaining half the weight parts of plasticizer are added. Mixing is continued for 4 minutes. The discharge temperature is controlled at 130-145℃ for discharge.

[0048] S3. Add the rubber discharged from S2 to the open mill, and add peroxide, sulfur, vulcanizing agent and accelerator in sequence. Adjust the roller gap to 0.1mm, pass through the mill twice, make 2 triangular swirls, adjust the roller gap to 0.8mm, pass through the mill three times, make 3 triangular swirls, adjust the roller gap to about 3mm, and then extrude the sheet. Let the compound rubber stand at 25℃ for 24 hours. S4. The compound rubber that has been left to stand in S3 is subjected to compression molding and vulcanization. The vulcanization pressure is 15MPa, the vulcanization temperature is 170℃, and the vulcanization time is 8min to obtain the rubber sealing material.

[0049] Examples 2-5

[0050] The only difference from Example 1 is the raw material ratio for preparing the rubber sealing material suitable for gas pipelines. All other preparation steps and conditions are the same as in Example 1, and the specific ratios are shown in Table 1. Table 1

[0051] Example 6

[0052] The only difference from Example 2 is that in the preparation of silanes containing thiol and amino bifunctional groups, the mixing ratio n(mercaptopropyltrimethoxysilane):n(3-aminopropyltrimethoxysilane) = 1:1 in step two, and the other conditions and steps are the same as in Example 1.

[0053] Example 7

[0054] The only difference from Example 2 is that in the preparation of silanes containing thiol and amino bifunctional groups, the mixing ratio n(mercaptopropyltrimethoxysilane):n(3-aminopropyltrimethoxysilane) = 3:1 in step two, while the other conditions and steps are the same as in Example 1.

[0055] Example 8

[0056] The only difference from Example 2 is that in the preparation of modified nitrile rubber, the silane containing thiol and amino bifunctional groups is 10% of the mass of nitrile rubber, and the other conditions and steps are the same as in Example 1.

[0057] Example 9

[0058] The only difference from Example 2 is that in the preparation of modified nitrile rubber, the silane containing thiol and amino bifunctional groups is 30% of the mass of nitrile rubber, and the other conditions and steps are the same as in Example 1.

[0059] Comparative Example 1

[0060] The only difference from Example 1 is that this comparative example directly replaces the modified nitrile rubber with nitrile rubber.

[0061] A rubber sealing material suitable for gas pipelines, comprising the following raw materials by weight: 75 parts of nitrile rubber, 5 parts of carboxyl-terminated nitrile rubber, 20 parts of hydrogenated nitrile rubber, 27 parts of high abrasion-resistant carbon black N330, 38 parts of semi-reinforcing carbon black N774, 28 parts of silicone powder N85, 22.5 parts of plasticizer (dioctyl sebacate), 5 parts of zinc oxide, 1 part of stearic acid, 1.2 parts of microcrystalline wax, 2 parts of antioxidant N-nitrosodiphenylamine, 2 parts of antioxidant 4010NA, 2.5 parts of peroxide (di-tert-butylperoxyisopropylbenzene), 0.3 parts of sulfur S-80, 2 parts of co-curing agent (N,Nˊ-m-phenylenebismaleimide), and 1.5 parts of accelerator CZ.

[0062] Among them, the acrylonitrile content of nitrile rubber is 31-35%, the Mooney viscosity is 65-79 mL (1+4) 100℃, the acrylonitrile content of carboxyl-terminated nitrile rubber is 28%-30%, the carboxyl content is 0.3-1.2 mmol / g, and the acrylonitrile content of hydrogenated nitrile rubber is 25%-30%, and the degree of hydrogenation is 90%-96%.

[0063] Preparation of rubber sealing materials suitable for gas pipelines: S1. Weigh the required weight parts of nitrile rubber, carboxyl-terminated nitrile rubber and hydrogenated nitrile rubber according to the formula and add them to the open mill for plasticizing. Pass each material through a thin mill 5 times. The roller gap of the open mill is 1 mm. Then discharge the rubber and sheet it. Cool the rubber compound to room temperature and let it stand for 6 hours to obtain the pre-plasticized rubber.

[0064] S2. The pre-plasticized nitrile rubber, carboxyl-terminated nitrile rubber, and hydrogenated nitrile rubber obtained in S1 are put into a mixer and mixed for 3 minutes. Then, according to the required weight parts, high abrasion-resistant carbon black N330, semi-reinforcing carbon black N774, zinc oxide, stearic acid, microcrystalline wax, antioxidant, and half the weight parts of plasticizer are added. Mixing continues for 1.5 minutes. Then, silicone powder and the remaining half the weight parts of plasticizer are added. Mixing continues for 4 minutes. The discharge temperature is controlled at 130-145℃ for discharge.

[0065] S3. Add the rubber discharged from S2 to the open mill, and add peroxide, sulfur, vulcanizing agent and accelerator in sequence. Adjust the roller gap to 0.1mm, pass through the mill twice, make 2 triangular swirls, adjust the roller gap to 0.8mm, pass through the mill three times, make 3 triangular swirls, adjust the roller gap to about 3mm, and then extrude the sheet. Let the compound rubber stand at 25℃ for 24 hours. S4. The compound rubber that has been left to stand in S3 is subjected to compression molding and vulcanization. The vulcanization pressure is 15MPa, the vulcanization temperature is 170℃, and the vulcanization time is 8min to obtain the rubber sealing material.

[0066] Comparative Example 2

[0067] The only difference from Example 1 is that this comparative example directly adds silane containing thiol and amino bifunctional groups to the preparation of rubber sealing material suitable for gas pipelines, and replaces modified nitrile rubber with nitrile rubber.

[0068] Preparation of silanes containing thiol and amino bifunctional groups: Step 1: Preparation of hydrolysate: Add mercaptopropyltrimethoxysilane at a mass concentration of 3% to an ethanol aqueous solution (ethanol-water volume ratio of 5:3), heat to 45℃ and hydrolyze for 2 hours to obtain mercaptopropyltrimethoxysilane hydrolysate. Prepare 3-aminopropyltrimethoxysilane hydrolysate under the same conditions.

[0069] Step 2: Mix the hydrolysate of mercaptopropyltrimethoxysilane and the hydrolysate of 3-aminopropyltrimethoxysilane to obtain a reaction solution with a mixing ratio of n(mercaptopropyltrimethoxysilane):n(3-aminopropyltrimethoxysilane) = 2:1. Add potassium hydroxide (0.06% of the total mass of mercaptopropyltrimethoxysilane and 3-aminopropyltrimethoxysilane), heat to 105℃ and stir for 3 hours. While stirring, add acetic acid to adjust the pH to 6.5. Remove low-boiling-point substances and water by vacuum distillation, and cool to room temperature to obtain silanes containing thiol and amino bifunctional groups.

[0070] A rubber sealing material suitable for gas pipelines, comprising the following raw materials by weight: The composition includes: 62.5 parts of nitrile rubber, 12.5 parts of silane containing thiol and amino bifunctional groups, 5 parts of carboxyl-terminated nitrile rubber, 20 parts of hydrogenated nitrile rubber, 27 parts of high abrasion-resistant carbon black N330, 38 parts of semi-reinforcing carbon black N774, 28 parts of silicone powder N85, 22.5 parts of plasticizer (dioctyl sebacate), 5 parts of zinc oxide, 1 part of stearic acid, 1.2 parts of microcrystalline wax, 2 parts of antioxidant N-nitrosodiphenylamine, 2 parts of antioxidant 4010NA, 2.5 parts of peroxide (di-tert-butylperoxyisopropylbenzene), 0.3 parts of sulfur S-80, 2 parts of co-curing agent (N,Nˊ-m-phenylenebismaleimide), and 1.5 parts of accelerator CZ.

[0071] Among them, the acrylonitrile content of nitrile rubber is 31-35%, the Mooney viscosity is 65-79 mL (1+4) 100℃, the acrylonitrile content of carboxyl-terminated nitrile rubber is 28%-30%, the carboxyl content is 0.3-1.2 mmol / g, and the acrylonitrile content of hydrogenated nitrile rubber is 25%-30%, and the degree of hydrogenation is 90%-96%.

[0072] Preparation of rubber sealing materials suitable for gas pipelines: S1. Weigh the required weight parts of nitrile rubber, carboxyl-terminated nitrile rubber, and hydrogenated nitrile rubber according to the formula and add them to the open mill for plasticizing. Pass each material through a thin mill 5 times. The roller gap of the open mill is 1 mm. Then discharge the rubber, sheet it, cool the rubber compound to room temperature and let it stand for 6 hours to obtain the pre-plasticized rubber.

[0073] S2. The pre-plasticized nitrile rubber, carboxyl-terminated nitrile rubber, and hydrogenated nitrile rubber obtained in S1 are put into a mixer and mixed for 3 minutes. Then, according to the required weight proportions, silane containing mercapto and amino bifunctional groups, high abrasion-resistant carbon black N330, semi-reinforcing carbon black N774, zinc oxide, stearic acid, microcrystalline wax, antioxidant, and half the weight proportion of plasticizer are added. Mixing is continued for 1.5 minutes. Then, silicone powder and the remaining half the weight proportion of plasticizer are added. Mixing is continued for 4 minutes. The discharge temperature is controlled at 130-145℃ for discharge.

[0074] S3. Add the rubber discharged from S2 to the open mill, and add peroxide, sulfur, vulcanizing agent and accelerator in sequence. Adjust the roller gap to 0.1mm, pass through the mill twice, make 2 triangular swirls, adjust the roller gap to 0.8mm, pass through the mill three times, make 3 triangular swirls, adjust the roller gap to about 3mm, and then extrude the sheet. Let the compound rubber stand at 25℃ for 24 hours. S4. The compound rubber that has been left to stand in S3 is subjected to compression molding and vulcanization. The vulcanization pressure is 15MPa, the vulcanization temperature is 170℃, and the vulcanization time is 8min to obtain the rubber sealing material.

[0075] Comparative Example 3

[0076] The only difference from Example 1 is that this comparative example does not add carboxyl-terminated nitrile butadiene rubber, but replaces the carboxyl-terminated nitrile butadiene rubber with an equal mass of hydrogenated nitrile butadiene rubber. The steps for preparing the silane containing thiol and amino bifunctional groups and preparing the modified nitrile butadiene rubber are the same as in Example 1.

[0077] A rubber sealing material suitable for gas pipelines, comprising the following raw materials by weight: 75 parts modified nitrile rubber, 25 parts hydrogenated nitrile rubber, 27 parts high abrasion-resistant carbon black N330, 38 parts semi-reinforcing carbon black N774, 28 parts silicone powder N85, 22.5 parts plasticizer (dioctyl sebacate), 5 parts zinc oxide, 1 part stearic acid, 1.2 parts microcrystalline wax, 2 parts antioxidant N-nitrosodiphenylamine, 2 parts antioxidant 4010NA, 2.5 parts peroxide (di-tert-butylperoxyisopropylbenzene), 0.3 parts sulfur S-80, 2 parts co-curing agent (N,Nˊ-m-phenylenebismaleimide), and 1.5 parts accelerator CZ.

[0078] The acrylonitrile content in hydrogenated nitrile rubber is 25%–30%, and the degree of hydrogenation is 90%–96%.

[0079] Preparation of rubber sealing materials suitable for gas pipelines: S1. Weigh the required weight parts of modified nitrile rubber and hydrogenated nitrile rubber according to the formula and add them to the open mill for plasticizing. Pass each material through the mill 5 times. The roller gap of the open mill is 1 mm. Then discharge the rubber and sheet it. Cool the rubber compound to room temperature and let it stand for 6 hours to obtain the pre-plasticized rubber.

[0080] S2. Add the pre-plasticized modified nitrile rubber and hydrogenated nitrile rubber obtained in S1 into a mixer and mix for 3 minutes. Then, add the required weight parts of high abrasion-resistant carbon black N330, semi-reinforcing carbon black N774, zinc oxide, stearic acid, microcrystalline wax, antioxidant, and half the weight part of plasticizer according to the formula. Continue mixing for 1.5 minutes. Then, add silicone powder and the remaining half the weight part of plasticizer and continue mixing for 4 minutes. Control the discharge temperature at 130-145℃ for discharge.

[0081] S3. Add the rubber discharged from S2 to the open mill, and add peroxide, sulfur, vulcanizing agent and accelerator in sequence. Adjust the roller gap to 0.1mm, pass through the mill twice, make 2 triangular swirls, adjust the roller gap to 0.8mm, pass through the mill three times, make 3 triangular swirls, adjust the roller gap to about 3mm, and then extrude the sheet. Let the compound rubber stand at 25℃ for 24 hours. S4. The compound rubber that has been left to stand in S3 is subjected to compression molding and vulcanization. The vulcanization pressure is 15MPa, the vulcanization temperature is 170℃, and the vulcanization time is 8min to obtain the rubber sealing material.

[0082] The rubber sealing material samples or specimens prepared in the above embodiments and comparative examples were tested, and the relevant test contents and test basis are as follows: The Shore A hardness was tested according to GB / T 531.1—2008; tensile strength was tested according to GB / T 528—2009, with a tensile rate of 500 mm / min; aging resistance was tested according to GB / T 3512—2014, with test conditions of 100℃×7d; high-temperature compression set was tested according to GB / T 7759.1—2015, with test conditions of 120℃×72h and a compression rate of 25%; low-temperature compression set was tested according to GB / T 7759.2—2014, with test conditions of -25℃×72h and a compression rate of 25%; oil resistance was tested according to GB / T The tests were conducted according to GB / T 1690—2010. The sample was immersed in liquid B (30% toluene, 70% isooctane) at 23°C for 7 days, and the volume change rate was measured. Then, it was aged in dry hot air at 70°C for 4 days, and the volume change rate was measured again. The sample was also immersed in standard oil No. 3 at 70°C for 7 days, and the volume change rate was measured. The ozone resistance test was conducted according to GB / T 7762—2014. The sample was pre-stretched by 20% at 40°C with an ozone concentration of 0.5ppm for 72 hours, and the cracking was observed. The low-temperature brittleness test was conducted according to GB / T 1682—2014, and the brittle temperature at which the sample failed was measured.

[0083] The test results are shown in Tables 2 and 3: Table 2

[0084] Table 3

[0085] As shown in Tables 2 and 3, this invention constructs a cross-linked network structure through a ternary blend system of modified nitrile rubber, carboxyl-terminated rubber, and hydrogenated nitrile rubber. Compared to pure nitrile rubber, this significantly improves the material's aging resistance, oil resistance, ozone resistance, and low-temperature resistance, reducing the brittle temperature to below -40℃. The design incorporating silicone powder and a peroxide vulcanization system gives the material excellent compression set and chemical resistance at both high and low temperatures, ensuring good dimensional stability even under high temperature and pressure. This makes it highly suitable for seals used in gas transportation environments.

[0086] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A rubber sealing material suitable for gas pipelines, characterized in that, By weight, it includes the following ingredients: Modified nitrile rubber 75-90 parts, carboxyl-terminated nitrile rubber 5-10 parts, hydrogenated nitrile rubber 5-20 parts, carbon black 40-80 parts, silicone powder 15-35 parts, plasticizer 15-28 parts, zinc oxide 4.5-5 parts, stearic acid 0.8-1.2 parts, microcrystalline wax 1.2-2 parts, antioxidant 3.5-4 parts, peroxide 2.5-3.5 parts, sulfur 0.2-0.5 parts, co-vulcanizing agent 1.2-2.5 parts, accelerator 0.6-2 parts; The modified nitrile rubber is obtained by grafting silanes containing thiol and amino bifunctional groups onto nitrile rubber via a thiol-double bond click reaction.

2. The rubber sealing material suitable for gas pipelines according to claim 1, characterized in that, The preparation of the silane containing thiol and amino bifunctional groups is as follows: The reaction solution was obtained by mixing the hydrolysate of mercaptopropyltrimethoxysilane and the hydrolysate of 3-aminopropyltrimethoxysilane, adding an alkaline catalyst, heating to 100-110℃ and stirring for 2-4 hours, adding a neutralizing agent while stirring, adjusting the pH to 6-7, removing low-boiling-point substances and water by vacuum distillation, and cooling to room temperature to obtain silanes containing thiol and amino bifunctional groups.

3. The rubber sealing material suitable for gas pipelines according to claim 2, characterized in that, The mixing ratio of the reaction solution is n(mercaptopropyltrimethoxysilane):n(3-aminopropyltrimethoxysilane) = 1-3:

1.

4. The rubber sealing material suitable for gas pipelines according to claim 1, characterized in that, The modified nitrile rubber is prepared as follows: Nitrile rubber was dissolved in acetone at a mass concentration of 2-5%. Silane containing thiol and amino bifunctional groups was added, and the mixture was stirred evenly. A photoinitiator was then added, and the mixture was stirred until homogeneous. The grafting reaction was carried out by irradiation with ultraviolet light for 20-30 minutes. After the reaction was completed, acetone was removed by vacuum distillation, and the modified nitrile rubber was obtained by vacuum drying.

5. A rubber sealing material suitable for gas pipelines according to claim 4, characterized in that, The acrylonitrile content in the nitrile rubber is 31% to 35%, and the Mooney viscosity is 65 to 79 mL (1+4) at 100°C.

6. A rubber sealing material suitable for gas pipelines according to claim 4, characterized in that, The silane containing thiol and amino bifunctional groups is 10-30% of the mass of nitrile rubber.

7. The rubber sealing material suitable for gas pipelines according to claim 1, characterized in that, The acrylonitrile content of the terminal carboxyl-terminated butadiene-acrylonitrile rubber is 28%–30%, and the carboxyl content is 0.3–1.2 mmol / g; The hydrogenated nitrile butadiene rubber contains 25% to 30% acrylonitrile and has a degree of hydrogenation of 90% to 96%.

8. The rubber sealing material suitable for gas pipelines according to claim 1, characterized in that, The carbon black is a composition of high abrasion-resistant carbon black and semi-reinforcing carbon black in a mass ratio of 1:1 to 2.

5.

9. A rubber sealing material suitable for gas pipelines according to claim 1, characterized in that, The antioxidant is a combination of at least one of antioxidant RD, antioxidant BLE, and N-nitrosodiphenylamine, and at least one of antioxidant 4010NA, antioxidant 4020, and antioxidant AW; The peroxide is one of dicumyl peroxide, bis-tert-butylperoxyisopropylbenzene, and 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane; the vulcanizing agent is a bismaleimide vulcanizing agent; and the accelerator is at least one of sulfenamide accelerators, thiazole accelerators, and thiuram accelerators.

10. A method for preparing a rubber sealing material suitable for gas pipelines as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Weigh the required weight parts of modified nitrile rubber, carboxyl-terminated nitrile rubber and hydrogenated nitrile rubber according to the formula and add them to the open mill for plasticizing. Pass each material through a thin mill 3 to 5 times. The roller gap of the open mill is 0.8 to 1 mm. Then discharge the rubber and sheet it. Cool the rubber compound to room temperature and let it stand for more than 3 hours to obtain the pre-plasticized rubber. S2. The pre-plasticized modified nitrile rubber, carboxyl-terminated nitrile rubber, and hydrogenated nitrile rubber obtained in S1 are put into a mixer and mixed for 2-3 minutes. Then, carbon black, zinc oxide, stearic acid, microcrystalline wax, antioxidant, and half the weight of plasticizer are added in sequence according to the required weight ratio. Mixing continues for 1-1.5 minutes. Then, silicone powder and the remaining half the weight of plasticizer are added. Mixing continues for 3-5 minutes, and the rubber is discharged. S3. Add the rubber discharged from S2 to the open mill, and add peroxide, sulfur, vulcanizing agent and accelerator in sequence. Adjust the roller gap to 0.1 mm, pass through the mill twice, make two triangular swirls, adjust the roller gap to 0.5-1 mm, pass through the mill three times, make three triangular swirls, adjust the roller gap to about 3 mm, and then extrude the sheet. Let the compound rubber stand at 20-30℃ for at least 16 hours. S4. The compound rubber that has been left to stand in S3 is subjected to compression molding and vulcanization. The vulcanization pressure is 10-20 MPa, the vulcanization temperature is 155-180℃, and the vulcanization time is 5-10 min to obtain the rubber sealing material.

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