Temperature-resistant, pressure-resistant and corrosion-resistant 90-degree rubber expansion joint elbow and preparation method thereof

Abstract

The invention discloses a temperature-resistant, pressure-resistant and corrosion-resistant 90-degree rubber expansion joint elbow and a preparation method thereof, and relates to the technical field of rubber elbows. The 90-degree rubber expansion joint elbow provided by the invention has relatively high pressure resistance, temperature resistance and corrosion resistance. The vinyl modified silicone rubber is coated outside the composite layer, so that the high-temperature resistance and the mechanical property of the rubber expansion joint elbow can be improved. And then the steel wire is wound to obtain the rubber elbow base body, so that the pressure resistance of the rubber expansion joint elbow is enhanced. The nylon fibers and the steel wires are combined, so that the tensile strength and the pressure resistance of the rubber expansion joint elbow are improved. Vinyl modified silicone rubber coats the outer surface of the composite layer through an extruder and is vulcanized, so that the problem that the rubber expansion joint elbow is easy to age and deform is further solved, and the sealing performance of the rubber expansion joint elbow is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber elbows, and specifically to a heat-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbow and a preparation method thereof. Background Art

[0002] In industrial pipeline systems, rubber expansion joint elbows, as key components for compensating axial, lateral and angular displacements of pipelines caused by thermal expansion and contraction or mechanical vibration, absorbing vibration and reducing stress, are widely used in pipeline systems such as petrochemical, electric power, ship and heat supply pipe networks. Expansion joints usually consist of rubber and a reinforcing layer, and have good flexibility and pressure resistance. However, existing expansion joints are prone to aging and deformation in high-pressure or high-temperature environments, resulting in a decrease in sealing performance and a shortening of service life. Moreover, when used in seawater or corrosive media, their corrosion resistance is poor and their service life is short.

[0003] In order to solve the above problems and improve the heat resistance and corrosion resistance of rubber expansion joint elbows, the present invention provides a heat-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbow and a preparation method thereof. Summary of the Invention

[0004] The purpose of the present invention is to provide a heat-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbow and a preparation method thereof to solve the problems raised in the prior art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of a heat-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbow, comprising the following steps: Step 1: Mix acrylonitrile-butadiene rubber, plasticizer, anti-aging agent, light stabilizer, accelerator evenly to obtain an acrylonitrile-butadiene rubber mixture, inject it into a 90° elbow mold, and vulcanize and form at 130-150 °C to form a rubber main body material; bond nylon fiber on the rubber main body material and hot press to obtain a composite material; Step 2: Coat the outer surface of the composite material with vinyl-modified silicone rubber through an extruder and vulcanize; then wind steel wires to obtain a rubber elbow matrix; take stainless steel flanges and unions, assemble and form, and vulcanize to obtain a 90° rubber expansion joint elbow; Step 3: Spray anti-corrosion paint on the surface of the 90° rubber expansion joint elbow, dry for 10-20 min, and then cure with ultraviolet light to obtain a heat-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbow.

[0006] Preferably, the preparation method of the vinyl-modified silicone rubber is as follows: Take vinyl-terminated dimethylsiloxane and hydrogen-containing silicone oil, mix them evenly at 0 °C, add vinyl-POSS, stir for 1-2 h, then add a Kaster catalyst, continue stirring for 15-20 min, defoam and dry to obtain the vinyl-modified silicone rubber.

[0007] Preferably, the preparation method of the anticorrosive coating is as follows: Take epoxy resin, polyurethane, corrosion-resistant chitosan powder, and absolute ethanol, and stir evenly to obtain the anticorrosive coating.

[0008] Preferably, the preparation method of the corrosion-resistant chitosan powder is as follows: Take sodium gluconate and deionized water, stir evenly to obtain a sodium gluconate aqueous solution; take sodium molybdate, sodium gluconate, and deionized water, stir evenly to obtain a sodium molybdate mixed solution; add chitosan powder to the sodium gluconate aqueous solution, stir for 3-4 h, perform low-pressure adsorption in a vacuum drying oven at 25-28 °C for 10-14 h, filter by suction, then disperse the filter residue in the sodium molybdate mixed solution, stir for 3-4 h, perform low-pressure adsorption in a vacuum drying oven at 25-28 °C for 10-14 h, filter by suction, dry, and grind to obtain the corrosion-resistant chitosan powder.

[0009] Preferably, the preparation method of the chitosan powder is as follows: Take acetic acid and deionized water, stir evenly, add chitosan, and stir evenly to obtain a chitosan solution; take emulsifier Span-80 and paraffin, mix evenly to obtain a paraffin mixed solution; drop the chitosan solution into the paraffin mixed solution, stir for 2-3 h, then adjust the pH value to 8.5-9 with a sodium hydroxide solution, stir for 30-40 min to obtain a mixed solution; take 4-mercaptobenzaldehyde and ethanol, stir evenly to obtain a 4-mercaptobenzaldehyde solution, then slowly drop the 4-mercaptobenzaldehyde solution into the mixed solution, stir for 7-8 h, centrifuge for 5-10 min, wash, dry, and grind to obtain the chitosan powder.

[0010] Preferably, the nitrile rubber mixture includes the following components by weight: 95-110 parts of nitrile rubber, 32-38 parts of plasticizer, 4-7 parts of antioxidant, 2-4 parts of light stabilizer, and 1-3 parts of accelerator.

[0011] Preferably, the antioxidant is any one or more of antioxidant 445 and antioxidant RD; the accelerator is tetramethylthiuram disulfide; the plasticizer is diisobutyl nylonate; the light stabilizer is epoxy soybean oil.

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention provides a 90° rubber expansion joint elbow with high pressure resistance, temperature resistance and corrosion resistance. The present invention coats the composite layer with vinyl modified silicone rubber to improve the high temperature resistance and mechanical properties of the rubber expansion joint elbow. Then, the steel wire is wound to obtain the rubber elbow matrix, which enhances the pressure resistance of the rubber expansion joint elbow. The nylon fiber and the steel wire are combined to improve the tensile strength and pressure resistance.

[0013] 2. The vinyl modified silicone rubber is coated on the outer surface of the composite layer through an extruder and vulcanized, which further improves the aging and deformation problems of the rubber expansion joint elbow under high pressure or high temperature environment, and improves the sealing performance of the rubber expansion joint elbow.

[0014] 3. The present invention adds 4-mercaptobenzaldehyde when preparing chitosan powder. The aldehyde group on 4-mercaptobenzaldehyde can react with the amino group on chitosan to form a Schiff base, thereby generating porous chitosan. Then, sodium gluconate and sodium molybdate are loaded on the chitosan by impregnation to improve its corrosion resistance.

[0015] 4. The surface of the 90° rubber expansion joint elbow of the present invention is sprayed with an anti-corrosion coating to improve the corrosion resistance of the 90° rubber expansion joint elbow. The anti-corrosion coating contains corrosion-resistant chitosan powder with a thiol group, which can react with the vinyl on the surface of the 90° rubber expansion joint elbow to improve the adhesion of the coating, thereby improving the corrosion resistance of the 90° rubber expansion joint elbow. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0017] The sources and models of the substances involved in the present invention are not particularly limited, and exemplarily include: vinyl-terminated dimethylsiloxane: model: V741916, which can be purchased from McLean; vinyl POSS: model: P815521, which can be purchased from McLean; hydrogen-containing silicone oil: model: 63148-57-2, which can be purchased from Nantong Runfeng Petrochemical Co., Ltd.; 4-mercaptobenzaldehyde: which can be purchased from Beijing Bailingwei Technology Co., Ltd.; epoxy resin: model: E44, which can be purchased from Jinan Chuangshi Chemical Co., Ltd.; polyurethane: model: AH650, which can be purchased from BASF; nitrile rubber: model: 226, which can be purchased from Wuhan Jiyesheng Chemical Co., Ltd.

[0018] Embodiment 1: A method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow, comprising the following steps: Step 1: Preparation of 90° rubber expansion joint elbow: Mix acrylonitrile-butadiene rubber, plasticizer, antioxidant, light stabilizer, and accelerator evenly to obtain acrylonitrile-butadiene rubber mixture, inject it into a preheated 90° elbow mold, and vulcanize and form at 140 °C to form a rubber main body material; bond nylon fiber on the rubber main body material and hot press to obtain a composite material; The acrylonitrile-butadiene rubber mixture includes the following components by weight: 100 parts of acrylonitrile-butadiene rubber, 36 parts of plasticizer, 6 parts of antioxidant, 3 parts of light stabilizer, and 2 parts of accelerator; The antioxidant is any one or more of antioxidant 445 and antioxidant RD; the accelerator is tetramethylthiuram disulfide; the plasticizer is diisobutyl nylonate; the light stabilizer is epoxy soybean oil; Coat the outer surface of the composite material with vinyl-modified silicone rubber through an extruder and vulcanize; then wind steel wire to obtain a rubber elbow matrix; take stainless steel flange and union, assemble and form, and vulcanize to obtain a 90° rubber expansion joint elbow; Step 2: Preparation of vinyl-modified silicone rubber: Take 80 g of vinyl-terminated dimethylsiloxane and 28 g of hydrogen-containing silicone oil, mix evenly at 0 °C, add 30 g of vinyl POSS, stir for 1.5 h, then add 0.7 g of Karstedt catalyst, continue to stir for 18 min, defoam and dry to obtain vinyl-modified silicone rubber; Step 3: Preparation of corrosion-resistant chitosan powder: Take 2 mL of acetic acid and 100 mL of deionized water, stir evenly, add 1 g of chitosan, and stir evenly to obtain a chitosan solution; take 2 mL of emulsifier Span-80 and 100 mL of paraffin wax, mix evenly to obtain a paraffin wax mixture; drop 32 mL of chitosan solution into 100 mL of paraffin wax mixture, stir for 2.5 h, then use 1 mol / L sodium hydroxide solution to adjust the pH value to 8.9, stir for 35 min to obtain a mixed solution; take 15 g of 4-mercaptobenzaldehyde and 30 mL of ethanol, stir evenly to obtain a 4-mercaptobenzaldehyde solution, and then slowly drop 30 g of 4-mercaptobenzaldehyde solution into 10 g of mixed solution, stir for 7.5 h, centrifuge for 7 min, wash, dry and grind to obtain chitosan powder; Take 12 g of sodium gluconate and 100 mL of deionized water, stir evenly to obtain a sodium gluconate aqueous solution; take 1 g of sodium molybdate, 12 g of sodium gluconate, and 100 mL of deionized water, stir evenly to obtain a sodium molybdate mixture; add 3 g of chitosan powder to the sodium gluconate aqueous solution, stir for 3.5 h, adsorb under low pressure in a vacuum drying oven at 26 °C for 12 h, filter by suction, then disperse the filter residue in the sodium molybdate mixture, stir for 3.5 h, adsorb under low pressure in a vacuum drying oven at 27 °C for 12 h, filter by suction, dry and grind to obtain corrosion-resistant chitosan powder; Step 4: Preparation of anticorrosive coating: Take 50 g of epoxy resin, 50 g of polyurethane, 10 g of corrosion-resistant chitosan powder, and 40 mL of absolute ethanol, stir evenly to obtain an anticorrosive coating; Step 5: Preparation of a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance: Spray the anticorrosive coating on the surface of the 90° rubber expansion joint elbow, with a coating thickness of 70 μm, dry for 15 min, and then cure with ultraviolet light to obtain a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance.

[0019] Example 2: A method for preparing a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance, comprising the following steps: Step 1: Preparation of a 90° rubber expansion joint elbow: Mix acrylonitrile-butadiene rubber, plasticizer, antioxidant, light stabilizer, and accelerator evenly to obtain an acrylonitrile-butadiene rubber mixture, inject it into a preheated 90° elbow mold, and vulcanize and mold it at 130 °C to form a rubber main body material; bond nylon fiber on the rubber main body material and hot press to obtain a composite material; The acrylonitrile-butadiene rubber mixture comprises the following components by weight: 95 parts of acrylonitrile-butadiene rubber, 32 parts of plasticizer, 4 parts of antioxidant, 2 parts of light stabilizer, and 1 part of accelerator; The antioxidant is any one or more of antioxidant 445 and antioxidant RD; the accelerator is tetramethylthiuram disulfide; the plasticizer is diisobutyl nylonate; the light stabilizer is epoxy soybean oil; Coat the outer surface of the composite material with vinyl-modified silicone rubber through an extruder and vulcanize; then wind steel wires to obtain a rubber elbow matrix; take stainless steel flanges and nipples, assemble and mold, and vulcanize to obtain a 90° rubber expansion joint elbow; Step 2: Preparation of vinyl-modified silicone rubber: Take 80 g of vinyl-terminated dimethylsiloxane and 28 g of hydrogen-containing silicone oil, mix evenly at 0 °C, add 30 g of vinyl POSS, stir for 1 h, then add 0.7 g of Kaster catalyst, continue to stir for 15 min, defoam and dry to obtain vinyl-modified silicone rubber; Step 3: Preparation of corrosion-resistant chitosan powder: Take 2 mL of acetic acid and 100 mL of deionized water, stir evenly, add 1 g of chitosan, and stir evenly to obtain a chitosan solution; take 2 mL of emulsifier Span-80 and 100 mL of paraffin, mix evenly to obtain a paraffin mixture; drop 32 mL of the chitosan solution into 100 mL of the paraffin mixture, stir for 2 h, then use a sodium hydroxide solution with a concentration of 1 mol / L to adjust the pH value to 8.5, stir for 30 min to obtain a mixed solution; take 15 g of 4-mercaptobenzaldehyde and 30 mL of ethanol, stir evenly to obtain a 4-mercaptobenzaldehyde solution, then slowly drop 30 g of the 4-mercaptobenzaldehyde solution into 10 g of the mixed solution, stir for 7 h, centrifuge for 5 min, wash, dry, and grind to obtain chitosan powder; Take 12 g of sodium gluconate and 100 mL of deionized water, stir evenly to obtain an aqueous sodium gluconate solution; take 1 g of sodium molybdate, 12 g of sodium gluconate, and 100 mL of deionized water, stir evenly to obtain a sodium molybdate mixture; add 3 g of chitosan powder to the aqueous sodium gluconate solution, stir for 3 h, perform low-pressure adsorption in a vacuum drying oven at 25°C for 10 h, filter by suction, then disperse the filter residue in the sodium molybdate mixture, stir for 3 h, perform low-pressure adsorption in a vacuum drying oven at 25°C for 10 h, filter by suction, dry, and grind to obtain corrosion-resistant chitosan powder; Step Four: Preparation of the anti-corrosion coating: Take 50 g of epoxy resin, 50 g of polyurethane, 10 g of corrosion-resistant chitosan powder, and 40 mL of absolute ethanol, stir evenly to obtain an anti-corrosion coating; Step Five: Preparation of the 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance: Spray the anti-corrosion coating on the surface of the 90° rubber expansion joint elbow, with a coating thickness of 70 μm, dry for 10 min, and then cure with ultraviolet light to obtain the 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance.

[0020] Example 3: A method for preparing a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance, comprising the following steps: Step One: Preparation of the 90° rubber expansion joint elbow: Mix nitrile rubber, plasticizer, anti-aging agent, light stabilizer, and accelerator evenly to obtain a nitrile rubber mixture, inject it into a preheated 90° elbow mold, and vulcanize and form at 150°C to form a rubber main body material; bond nylon fiber on the rubber main body material and perform hot pressing to obtain a composite material; The nitrile rubber mixture includes the following components by weight: 110 parts of nitrile rubber, 38 parts of plasticizer, 7 parts of anti-aging agent, 4 parts of light stabilizer, and 3 parts of accelerator; The antioxidant is any one or more of antioxidant 445 and antioxidant RD; the accelerator is tetramethylthiuram disulfide; the plasticizer is diisobutyl nylonate; the light stabilizer is epoxy soybean oil; Coat the vinyl-modified silicone rubber on the outer surface of the composite material through an extruder and vulcanize it; then wind steel wires to obtain a rubber elbow matrix; take a stainless steel flange and an oil elbow, assemble and form, and vulcanize to obtain a 90° rubber expansion joint elbow; Step two: Preparation of vinyl-modified silicone rubber: Take 80 g of vinyl-terminated dimethylsiloxane and 28 g of hydrogen-containing silicone oil, mix evenly at 0 °C, add 30 g of vinyl POSS, stir for 2 h, then add 0.7 g of Kaster catalyst, continue to stir for 20 min, defoam and dry to obtain vinyl-modified silicone rubber; Step three: Preparation of corrosion-resistant chitosan powder: Take 2 mL of acetic acid and 100 mL of deionized water, stir evenly, add 1 g of chitosan, and stir evenly to obtain a chitosan solution; take 2 mL of emulsifier Span-80 and 100 mL of paraffin wax, mix evenly to obtain a paraffin wax mixture; drop 32 mL of the chitosan solution into 100 mL of the paraffin wax mixture, stir for 3 h, then adjust the pH value to 9 with a 1 mol / L sodium hydroxide solution, stir for 40 min to obtain a mixed solution; take 15 g of 4-mercaptobenzaldehyde and 30 mL of ethanol, stir evenly to obtain a 4-mercaptobenzaldehyde solution, and then slowly drop 30 g of the 4-mercaptobenzaldehyde solution into 10 g of the mixed solution, stir for 8 h, centrifuge for 10 min, wash, dry and grind to obtain chitosan powder; Take 12 g of sodium gluconate and 100 mL of deionized water, stir evenly to obtain an aqueous sodium gluconate solution; take 1 g of sodium molybdate, 12 g of sodium gluconate and 100 mL of deionized water, stir evenly to obtain a sodium molybdate mixture; add 3 g of chitosan powder to the aqueous sodium gluconate solution, stir for 4 h, adsorb under low pressure in a vacuum drying oven at 28 °C for 14 h, filter by suction, then disperse the filter residue in the sodium molybdate mixture, stir for 4 h, adsorb under low pressure in a vacuum drying oven at 28 °C for 14 h, filter by suction, dry and grind to obtain corrosion-resistant chitosan powder; Step four: Preparation of anticorrosive coating: Take 50 g of epoxy resin, 50 g of polyurethane, 10 g of corrosion-resistant chitosan powder, and 40 mL of absolute ethanol, stir evenly to obtain an anticorrosive coating; Step five: Preparation of a 90° rubber expansion joint elbow with temperature resistance, pressure resistance and corrosion resistance: Spray the anticorrosive coating on the surface of the 90° rubber expansion joint elbow, with a coating thickness of 70 μm, dry for 20 min, and then cure with ultraviolet light to obtain a 90° rubber expansion joint elbow with temperature resistance, pressure resistance and corrosion resistance.

[0021] Comparative Example 1: Sodium molybdate was not added, and the rest was the same as in Example 1: Step 1: Preparation of a 90° rubber expansion joint elbow: Nitrile rubber, plasticizer, antioxidant, light stabilizer, and accelerator were kneaded evenly to obtain a nitrile rubber mixture, which was injected into a preheated 90° elbow mold and vulcanized at 140°C to form a rubber main body material. Nylon fiber was adhered to the rubber main body material and hot-pressed to obtain a composite material; The nitrile rubber mixture included the following components by weight: 100 parts of nitrile rubber, 36 parts of plasticizer, 6 parts of antioxidant, 3 parts of light stabilizer, and 2 parts of accelerator; The antioxidant was any one or more of antioxidant 445 and antioxidant RD; the accelerator was tetramethylthiuram disulfide; the plasticizer was diisobutyl nylonate; the light stabilizer was epoxy soybean oil; Vinyl-modified silicone rubber was coated on the outer surface of the composite material through an extruder and vulcanized; then steel wires were wound to obtain a rubber elbow matrix; a stainless steel flange and an oil nipple were taken and assembled and vulcanized to obtain a 90° rubber expansion joint elbow; Step 2: Preparation of vinyl-modified silicone rubber: 80 g of vinyl-terminated dimethylsiloxane and 28 g of hydrogen-containing silicone oil were mixed evenly at 0°C, 30 g of vinyl POSS was added, and the mixture was stirred for 1.5 h. Then 0.7 g of Kaster catalyst was added, and stirring was continued for 18 min. After degassing and drying, vinyl-modified silicone rubber was obtained; Step 3: Preparation of corrosion-resistant chitosan powder: 2 mL of acetic acid and 100 mL of deionized water were stirred evenly, 1 g of chitosan was added and stirred evenly to obtain a chitosan solution; 2 mL of emulsifier Span-80 and 100 mL of paraffin were mixed evenly to obtain a paraffin mixture; 32 mL of the chitosan solution was dropped into 100 mL of the paraffin mixture and stirred for 2.5 h. Then the pH value was adjusted to 8.9 using a 1 mol / L sodium hydroxide solution and stirred for 35 min to obtain a mixed solution; 15 g of 4-mercaptobenzaldehyde and 30 mL of ethanol were stirred evenly to obtain a 4-mercaptobenzaldehyde solution, and then 30 g of the 4-mercaptobenzaldehyde solution was slowly dropped into 10 g of the mixed solution and stirred for 7.5 h. After centrifugation for 7 min, washing, drying, and grinding were carried out to obtain chitosan powder; Take 12 g of sodium gluconate and 100 mL of deionized water, stir evenly to obtain an aqueous sodium gluconate solution; add 3 g of chitosan powder to the aqueous sodium gluconate solution, stir for 3.5 h, perform low-pressure adsorption in a vacuum drying oven at 26 °C for 12 h, filter by suction, then redisperse the filter residue in the aqueous sodium gluconate solution, stir for 3.5 h, perform low-pressure adsorption in a vacuum drying oven at 27 °C for 12 h, filter by suction, dry, and grind to obtain corrosion-resistant chitosan powder; Step Four: Preparation of the anti-corrosion coating: Take 50 g of epoxy resin, 50 g of polyurethane, 10 g of corrosion-resistant chitosan powder, and 40 mL of absolute ethanol, stir evenly to obtain an anti-corrosion coating; Step Five: Preparation of the 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance: Spray the anti-corrosion coating on the surface of the 90° rubber expansion joint elbow, with a coating thickness of 70 μm, dry for 15 min, and then cure with ultraviolet light to obtain a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance.

[0022] Comparative Example 2: Without adding 4-mercaptobenzaldehyde, the rest is the same as in Example 1: Step One: Preparation of the 90° rubber expansion joint elbow: Mix acrylonitrile-butadiene rubber, plasticizer, anti-aging agent, light stabilizer, and accelerator evenly to obtain an acrylonitrile-butadiene rubber mixture, inject it into a preheated 90° elbow mold, and vulcanize and form at 140 °C to form a rubber main body material; bond nylon fiber to the rubber main body material and hot press to obtain a composite material; The acrylonitrile-butadiene rubber mixture includes the following components by weight: 100 parts of acrylonitrile-butadiene rubber, 36 parts of plasticizer, 6 parts of anti-aging agent, 3 parts of light stabilizer, and 2 parts of accelerator; The anti-aging agent is any one or more of anti-aging agent 445 and anti-aging agent RD; the accelerator is tetramethylthiuram disulfide; the plasticizer is diisobutyl nylonate; the light stabilizer is epoxy soybean oil; Coat the outer surface of the composite material with vinyl-modified silicone rubber through an extruder and vulcanize; then wind steel wires to obtain a rubber elbow matrix; take stainless steel flanges and nipples, assemble and form, and vulcanize to obtain a 90° rubber expansion joint elbow; Step Two: Preparation of vinyl-modified silicone rubber: Take 80 g of vinyl-terminated dimethylsiloxane and 28 g of hydrogen-containing silicone oil, mix evenly at 0 °C, add 30 g of vinyl POSS, stir for 1.5 h, then add 0.7 g of Kaster catalyst, continue to stir for 18 min, defoam and dry to obtain vinyl-modified silicone rubber; Step Three: Preparation of corrosion-resistant chitosan powder: Take 2 mL of acetic acid and 100 mL of deionized water, stir evenly, add 1 g of chitosan, and stir evenly to obtain a chitosan solution; take 2 mL of emulsifier Span-80 and 100 mL of paraffin, mix evenly to obtain a paraffin mixture; drop 32 mL of the chitosan solution into 100 mL of the paraffin mixture, stir for 2.5 h, then use a sodium hydroxide solution with a concentration of 1 mol / L to adjust the pH value to 8.9, stir for 35 min to obtain a mixed solution; take 15 g of vanillin and 30 mL of ethanol, stir evenly to obtain a vanillin solution, and then slowly drop 30 g of the vanillin solution into 10 g of the mixed solution, stir for 7.5 h, centrifuge for 7 min, wash, dry, and grind to obtain chitosan powder; Take 12 g of sodium gluconate and 100 mL of deionized water, stir evenly to obtain an aqueous sodium gluconate solution; take 1 g of sodium molybdate, 12 g of sodium gluconate, and 100 mL of deionized water, stir evenly to obtain a sodium molybdate mixture; add 3 g of chitosan powder to the aqueous sodium gluconate solution, stir for 3.5 h, perform low-pressure adsorption in a vacuum drying oven at 26 °C for 12 h, filter by suction, then disperse the filter residue in the sodium molybdate mixture, stir for 3.5 h, perform low-pressure adsorption in a vacuum drying oven at 27 °C for 12 h, filter by suction, dry, and grind to obtain corrosion-resistant chitosan powder; Step Four: Preparation of the anticorrosive coating: Take 50 g of epoxy resin, 50 g of polyurethane, 10 g of corrosion-resistant chitosan powder, and 40 mL of absolute ethanol, stir evenly to obtain an anticorrosive coating; Step Five: Preparation of the 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance: Spray the anticorrosive coating on the surface of the 90° rubber expansion joint elbow, with a coating thickness of 70 μm, dry for 15 min, and then cure with ultraviolet light to obtain a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance.

[0023] Comparative Example 3: Do not coat the vinyl-modified silicone rubber on the outer surface of the composite layer through an extruder, and the rest is the same as in Example 1: Step One: Preparation of the 90° rubber expansion joint elbow: Mix nitrile rubber, plasticizer, antioxidant, light stabilizer, and accelerator evenly to obtain a nitrile rubber mixture, inject it into a preheated 90° elbow mold, and vulcanize and form at 140 °C to form a rubber main body material; bond nylon fiber to the rubber main body material and perform hot pressing to obtain a composite material; The nitrile rubber mixture includes the following components by weight: 100 parts of nitrile rubber, 36 parts of plasticizer, 6 parts of antioxidant, 3 parts of light stabilizer, and 2 parts of accelerator; The antioxidant is any one or more of antioxidant 445 and antioxidant RD; the accelerator is tetramethylthiuram disulfide; the plasticizer is diisobutyl nylonate; the light stabilizer is epoxy soybean oil; Wind steel wires around the outer surface of the composite material to obtain a rubber elbow matrix; take a stainless steel flange and oil fittings, assemble and form, and vulcanize to obtain a 90° rubber expansion joint elbow; Step two: Preparation of corrosion-resistant chitosan powder: Take 2 mL of acetic acid and 100 mL of deionized water, stir evenly, add 1 g of chitosan, and stir evenly to obtain a chitosan solution; take 2 mL of emulsifier Span-80 and 100 mL of paraffin, mix evenly to obtain a paraffin mixture; drop 32 mL of the chitosan solution into 100 mL of the paraffin mixture, stir for 2.5 h, then use a sodium hydroxide solution with a concentration of 1 mol / L to adjust the pH value to 8.9, stir for 35 min to obtain a mixed solution; take 15 g of 4-mercaptobenzaldehyde and 30 mL of ethanol, stir evenly to obtain a 4-mercaptobenzaldehyde solution, and then slowly drop 30 g of the 4-mercaptobenzaldehyde solution into 10 g of the mixed solution, stir for 7.5 h, centrifuge for 7 min, wash, dry, and grind to obtain chitosan powder; Take 12 g of sodium gluconate and 100 mL of deionized water, stir evenly to obtain a sodium gluconate aqueous solution; take 1 g of sodium molybdate, 12 g of sodium gluconate, and 100 mL of deionized water, stir evenly to obtain a sodium molybdate mixture; add 3 g of chitosan powder to the sodium gluconate aqueous solution, stir for 3.5 h, perform low-pressure adsorption in a vacuum drying oven at 26°C for 12 h, filter by suction, then disperse the filter residue in the sodium molybdate mixture, stir for 3.5 h, perform low-pressure adsorption in a vacuum drying oven at 27°C for 12 h, filter by suction, dry, and grind to obtain corrosion-resistant chitosan powder; Step three: Preparation of the anticorrosive coating: Take 50 g of epoxy resin, 50 g of polyurethane, 10 g of corrosion-resistant chitosan powder, and 40 mL of absolute ethanol, stir evenly to obtain an anticorrosive coating; Step four: Preparation of a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance: Spray the anticorrosive coating on the surface of the 90° rubber expansion joint elbow, with a coating thickness of 70 μm, dry for 15 min, and then cure with ultraviolet light to obtain a 90° rubber expansion joint elbow with temperature resistance, pressure resistance, and corrosion resistance.

[0024] Experiment: The temperature-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbows prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests. "X"-shaped marks were evenly drawn on the surface of the temperature-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbows, and then the elbows after scratching were immersed in a sodium chloride solution with a concentration of 3.5 wt% for several hours, taken out, and the corrosion morphology at the scratched area was observed. The data obtained are shown in Table 1 below: Table 1

[0025] Conclusion: It can be seen from the comparison of the data in the table that in Comparative Example 1, sodium molybdate was not added, and the corrosion resistance of the 90° rubber expansion joint elbow deteriorated. After taking out the rubber expansion joint elbow immersed in hydrochloric acid after 1410 h, corrosion occurred at the scratched area and the coating peeled off. In Comparative Example 2, 4-mercaptobenzaldehyde was not added, and the loading amounts of sodium gluconate and sodium molybdate on chitosan decreased, and the corrosion resistance of the 90° rubber expansion joint elbow decreased significantly. In Comparative Example 3, vinyl-modified silicone rubber was not coated on the outer surface of the composite layer through an extruder, the coating adhesion decreased, and the corrosion resistance decreased. In Examples 1-3 of the present invention, 4-mercaptobenzaldehyde was added during the preparation of chitosan powder. The aldehyde group on 4-mercaptobenzaldehyde can undergo a Schiff base reaction with the amino group on chitosan, thereby generating porous chitosan; then sodium gluconate and sodium molybdate were loaded on chitosan by impregnation to improve its corrosion resistance effect. An anti-corrosion coating was sprayed on the surface of the 90° rubber expansion joint elbow to improve the corrosion resistance of the 90° rubber expansion joint elbow. The anti-corrosion coating contains corrosion-resistant chitosan powder with a mercapto group, which can react with the vinyl group on the surface of the 90° rubber expansion joint elbow to improve the coating adhesion, thereby improving the corrosion resistance of the 90° rubber expansion joint elbow. After taking out the rubber expansion joint elbow immersed in hydrochloric acid after 1452 h, there was no corrosion at the scratched area and the coating did not peel off.

[0026] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow, characterized in that: The following steps are involved: Step 1: Evenly mix nitrile rubber, plasticizer, antioxidant, light stabilizer and accelerator to obtain a nitrile rubber mixture, inject it into a 90° elbow mold, and vulcanize it at 130-150°C to form a rubber main body material; laminate nylon fiber on the rubber main body material, and heat press it to obtain a composite material; Step 2: coating the vinyl modified silicone rubber on the outer surface of the composite material through an extruder and vulcanizing; Then, the steel wire is wound to obtain the rubber elbow matrix; the stainless steel flange and the oil are assembled and formed, and vulcanized to obtain the 90° rubber expansion joint elbow; Step 3: Spray the anti-corrosion coating on the surface of the 90° rubber expansion joint elbow, dry it for 10-20 minutes, and then use ultraviolet light to cure it to obtain a temperature-resistant, pressure-resistant and corrosion-resistant 90° rubber expansion joint elbow.

2. The method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow according to claim 1, characterized in that: The preparation method of the vinyl modified silicone rubber is as follows: vinyl terminated dimethylsiloxane and hydrogen-containing silicone oil are mixed uniformly at 0° C., vinyl POSS is added, stirred for 1-2 hours, and then Custer catalyst is added, stirring is continued for 15-20 minutes, degassing and drying are performed to obtain the vinyl modified silicone rubber.

3. The method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow according to claim 1, characterized in that: The preparation method of the anti-corrosion coating is as follows: epoxy resin, polyurethane, corrosion-resistant chitosan powder and anhydrous ethanol are taken and stirred evenly to obtain the anti-corrosion coating.

4. The method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow according to claim 3, characterized in that: The preparation method of the corrosion-resistant chitosan powder is as follows: sodium gluconate and deionized water are taken and stirred evenly to obtain a sodium gluconate aqueous solution; sodium molybdate, sodium gluconate and deionized water are taken and stirred evenly to obtain a sodium molybdate mixed solution; chitosan powder is added to the sodium gluconate aqueous solution, stirred for 3-4 hours, low-pressure adsorption in a vacuum drying oven at 25-28° C. for 10-14 hours, suction filtered, and then the filter residue is dispersed in the sodium molybdate mixed solution, stirred for 3-4 hours, low-pressure adsorption in a vacuum drying oven at 25-28° C. for 10-14 hours, suction filtered, dried and ground to obtain the corrosion-resistant chitosan powder.

5. The method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow according to claim 4, characterized in that: The preparation method of the chitosan powder is as follows: taking acetic acid and deionized water, stirring evenly, adding chitosan, stirring evenly, and obtaining a chitosan solution; taking an emulsifier Span-80 and paraffin, mixing evenly, and obtaining a paraffin mixed solution; dropping the chitosan solution into the paraffin mixed solution, stirring for 2-3 hours, and then adjusting the pH value to 8.5-9 with a sodium hydroxide solution, stirring for 30-40 minutes, and obtaining a mixed solution; taking 4-mercaptobenzaldehyde and ethanol, stirring evenly, and obtaining a 4-mercaptobenzaldehyde solution; and then slowly dropping the 4-mercaptobenzaldehyde solution into the mixed solution, stirring for 7-8 hours, centrifuging for 5-10 minutes, washing, drying, and grinding, and obtaining chitosan powder.

6. The method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow according to claim 1, characterized in that: The nitrile rubber mixture comprises the following components, by weight: 95-110 parts of nitrile rubber, 32-38 parts of plasticizer, 4-7 parts of antioxidant, 2-4 parts of light stabilizer, and 1-3 parts of accelerator.

7. The method for preparing a temperature-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow according to claim 6, characterized in that: The antioxidant is any one or more of antioxidant 445 and antioxidant RD; the accelerator is tetramethylthiuram disulfide; the plasticizer is diisobutyl nylonate; and the light stabilizer is epoxidized soybean oil.

8. A heat-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow prepared according to the method for preparing a heat-resistant, pressure-resistant, and corrosion-resistant 90° rubber expansion joint elbow according to any one of claims 1 to 7.

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