High-temperature-resistant rubber-based elbow and preparation method thereof

Abstract

The invention relates to the technical field of rubber, in particular to a high-temperature-resistant rubber-based elbow and a preparation method thereof. The preparation method comprises the following steps: blending a flexible flame-retardant acrylic copolymer and fluororubber, stirring, dissolving, demulsifying, washing with water, and drying in vacuum to obtain the modified fluororubber. Mixing butyl rubber, vinyl modified white carbon black, sulfur, activating agent zinc oxide and accelerating agent 2-mercaptobenzimidazole, and performing mixing and calendering to obtain an inner rubber layer; mixing modified fluororubber, vinyl modified white carbon black, bisphenol AF, an activator calcium hydroxide and an accelerant benzyl triphenyl phosphorus chloride, and carrying out mixing and calendering to obtain an outer rubber layer; an inner rubber layer, a nylon fabric layer and an outer rubber layer are sequentially laid, steel wires are wound after vulcanization, and the rubber-based elbow is obtained; and then the connecting piece and the rubber-based elbow are assembled and formed, and a finished product is obtained. The finished product prepared by the invention has good high-temperature resistance, flame retardance and mechanical properties, so that the finished product has a wide application prospect in the technical field of rubber.

Description

Technical Field

[0001] The invention relates to the technical field of rubber, in particular to a high-temperature resistant rubber-based elbow and a preparation method thereof. Background Art

[0002] In the field of rubber technology, rubber-based elbows, with their unique properties, demonstrate multi-dimensional value in modern industry. In the construction sector, rubber-based elbows are widely used in water supply and drainage systems. They can easily cope with pipe deformation caused by factors such as building settlement and temperature fluctuations, ensuring smooth water supply and drainage. In earthquake-prone areas, the shock-absorbing properties of rubber-based elbows can effectively absorb seismic energy, prevent pipe ruptures during earthquakes, and ensure water safety for residents and the overall stability of buildings. Rubber-based elbows also play a vital role in the transportation industry. In the cooling and fuel systems of automotive engines, rubber-based elbows can adapt to complex operating environments, ensure the normal delivery of coolant and fuel, and improve engine efficiency and reliability. In ship water supply, drainage, ventilation, and other systems, rubber-based elbows' seawater corrosion resistance and sealing properties provide strong guarantees for safe navigation.

[0003] However, in the industrial field, the medium transported by pipelines may have extremely high temperatures, and ordinary rubber-based elbows are prone to softening, deformation, or even decomposition at high temperatures, resulting in a decrease in sealing performance and causing medium leakage. This not only wastes resources but also poses a safety hazard. Rubber-based elbows with good high-temperature resistance can ensure the stable operation of the pipeline system, reduce the occurrence of failures, and ensure the continuity and safety of production. Improving flame retardant properties is also crucial. In some flammable environments, such as coal mines and chemical warehouses, once a fire occurs, ordinary rubber-based elbows may become fuel for the spread of fire, exacerbating the hazards of the fire. Rubber-based elbows with good flame retardant properties can effectively suppress the spread of fire when encountering a fire source, buying valuable time for personnel evacuation and fire fighting and rescue, and reducing loss of life and property.

[0004] In order to overcome the defects of the prior art, the present invention provides a high-temperature resistant rubber-based elbow and a preparation method thereof. Summary of the Invention

[0005] The object of the present invention is to provide a high-temperature resistant rubber-based elbow and a preparation method thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for preparing a high-temperature resistant rubber-based elbow comprises the following steps: Step 1: adding a flexible flame-retardant acrylic copolymer and fluororubber to acetone, stirring and dissolving to obtain a rubber emulsion; adding the rubber emulsion to a 3-5wt% calcium chloride solution, breaking the emulsion, washing with water, and vacuum drying to obtain a modified fluororubber; Step 2: Butyl rubber, vinyl modified silica, sulfur, activator zinc oxide, and accelerator 2-mercaptobenzimidazole are mixed, and the mixture is kneaded and calendered to obtain an inner rubber layer; modified fluororubber, vinyl modified silica, bisphenol AF, activator calcium hydroxide, and accelerator benzyltriphenylphosphine chloride are mixed, and the mixture is kneaded and calendered to obtain an outer rubber layer; the inner rubber layer, nylon fabric layer, and outer rubber layer are then laid in sequence, and the mixture is vulcanized at 170-180°C for 15-20 minutes, and then wrapped with steel wire to obtain a rubber-based elbow; the connector is assembled with the rubber-based elbow to obtain a finished product.

[0007] More optimally, in step one, the mixing ratio of the flexible flame-retardant acrylic copolymer and fluororubber is (1.3-1.5):4.

[0008] More optimally, in step 2, the contents of the components of the inner rubber layer are: by mass, 90-100 parts of butyl rubber, 25-35 parts of vinyl-modified silica, 2-3 parts of sulfur, 3-5 parts of activator zinc oxide, and 1-2 parts of accelerator 2-mercaptobenzimidazole; the contents of the components of the outer rubber layer are: by mass, 90-100 parts of modified fluororubber, 25-30 parts of vinyl-modified silica, 3-5 parts of bisphenol AF, 3-5 parts of activator calcium hydroxide, and 1.0-1.3 parts of accelerator benzyltriphenylphosphine chloride; the connecting parts are made of 316 stainless steel.

[0009] More optimally, the preparation process of the flexible flame retardant acrylic copolymer is: Step S1: adding anhydrous potassium carbonate and p-hydroxybenzaldehyde to tetrahydrofuran and stirring uniformly to obtain a p-hydroxybenzaldehyde solution; adding ethyl 2-chloromethylacrylate to tetrahydrofuran and stirring uniformly to obtain an ethyl 2-chloromethylacrylate solution; then adding the ethyl 2-chloromethylacrylate solution dropwise to the p-hydroxybenzaldehyde solution, heating to 65-70° C. and stirring to react for 25-30 hours; after the reaction is completed, washing, concentrating, precipitating a solid, filtering, and recrystallizing to obtain aldehyde-modified acrylic acid; Step S2: Under a nitrogen atmosphere, melamine is added to dimethyl sulfoxide, the temperature is raised to 130-140° C., and stirring is continued to obtain a uniform melamine solution; aldehyde-modified acrylic acid is added to the dimethyl sulfoxide, stirred uniformly, and then added dropwise to the melamine solution, the temperature is raised to 180-190° C., and refluxed for reaction for 70-75 hours. After the reaction is completed, the mixture is filtered, washed, and vacuum-dried to obtain a flame-retardant modified acrylic acid; Step S3: Under a nitrogen environment, methoxyethyl acrylate, butyl acrylate, flame-retardant modified acrylic acid, an emulsifier, and deionized water are mixed, pre-emulsified for 25-35 minutes, and then heated to 50-55° C., and then potassium persulfate-sodium bisulfite initiator is added dropwise. After the addition is completed, the reaction is continued by keeping the temperature for 6-7 hours to obtain a copolymer emulsion; the copolymer emulsion is then added to a 3-5wt% calcium chloride solution, demulsified, washed with water, and vacuum dried to obtain a flexible flame-retardant acrylic copolymer.

[0010] More optimally, in step S1, the reaction molar ratio of p-hydroxybenzaldehyde to ethyl 2-chloromethylacrylate is (1.1-1.2):1.

[0011] More optimally, in step S2, the reaction molar ratio of melamine to aldehyde-modified acrylic acid is (1.3-1.5):1.

[0012] More optimally, in step S3, the emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mixing ratio is (2.3-2.5):1; the reaction mass ratio of methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, emulsifier, deionized water, and potassium persulfate-sodium bisulfite initiator is (6-7):2:(1.5-2.0):0.1:(18-20):(0.3-0.5).

[0013] More optimally, the preparation process of vinyl modified silica is: Step S1: adding silica to anhydrous ethanol, ultrasonically dispersing for 1.5-2.5 hours, then adding 3-chloropropyltrimethoxysilane, and reacting at a constant temperature of 80-85°C for 0.5-1.0 hours, then adding 3-5 wt% hydrochloric acid, and continuing to stir and react for 4-6 hours. After the reaction is completed, the modified silica is obtained by centrifugation, alcohol washing, and drying. Step S2: adding modified silica, melamine, and triethylamine to toluene, stirring and reacting at 80-85° C. for 10-15 hours, and after the reaction is completed, centrifuging, washing, and drying to obtain flame-retardant silica; then adding flame-retardant silica, methylvinyldichlorosilane, and triethylamine to toluene, stirring and reacting at 80-85° C. for 10-15 hours, and after the reaction is completed, centrifuging, washing, and drying to obtain vinyl-modified silica.

[0014] More optimally, the mass volume ratio of silica, 3-chloropropyltrimethoxysilane, and hydrochloric acid is 1 g: (0.4-0.5) g: (8-10) mL; the reaction mass ratio of modified silica, melamine, and methylvinyldichlorosilane is (1.0-1.2): 0.25: 0.40.

[0015] Beneficial effects of the present invention: The present invention is characterized in that, in step 1, a substitution reaction is generated by adding p-hydroxybenzaldehyde, ethyl 2-chloromethylacrylate, and tetrahydrofuran to produce aldehyde-modified acrylic acid. Flame-retardant modified acrylic acid is then prepared using the aldehyde-modified acrylic acid and melamine as primary raw materials. Flexible acrylic monomers (methoxyethyl acrylate and butyl acrylate) are mixed with the flame-retardant modified acrylic acid and copolymerized in the presence of an initiator to produce a flexible flame-retardant acrylic copolymer. The prepared flexible flame-retardant acrylic copolymer is then blended with fluororubber, dissolved by stirring, demulsified, washed with water, and vacuum dried to produce the modified fluororubber.

[0016] Fluororubber contains a large number of highly electronegative fluorine atoms, resulting in high fluorine-carbon bond energies and short, stable bond lengths. This unique chemical bond structure imparts excellent thermal stability to the fluororubber backbone, maintaining molecular integrity at high temperatures and resisting thermal decomposition or thermal oxidation. This results in the modified fluororubber's excellent high-temperature resistance. Furthermore, the flame-retardant modified acrylic acid introduced during the preparation of the modified fluororubber contains melamine, a component that undergoes an endothermic decomposition reaction at high temperatures, thereby lowering the system temperature and slowing the thermal aging of the fluororubber in high-temperature environments. Furthermore, the decomposition gases form a heat-insulating and oxygen-isolating layer on the rubber surface, further preventing heat and oxygen from reaching the rubber and enhancing the modified fluororubber's high-temperature resistance. Furthermore, methoxyethyl acrylate and butyl acrylate, as flexible acrylic monomers, possess long side chains and ether groups, making the molecular chains more susceptible to relative sliding and deformation. When external forces act on the modified fluororubber, the chain segments formed by the flexible acrylic monomers provide a degree of flexibility, allowing the material to undergo significant elastic deformation without breaking. The melamine flame retardant component in the flame retardant modified acrylic acid will decompose and produce non-combustible gases such as ammonia when heated. These gases can dilute the concentration of oxygen and combustible gases, inhibit the progress of combustion, and improve the flame retardant properties of the material.

[0017] The present invention is characterized by the following: in step 2, the surface of the silica reinforcing filler is first modified using a silane coupling agent to obtain modified silica. Melamine, triethylamine, modified silica, and toluene are then blended to undergo a nucleophilic substitution reaction, introducing the melamine onto the silica surface to obtain flame-retardant silica. Flame-retardant silica, methylvinyldichlorosilane, and triethylamine are then added to the toluene. The chlorine atoms in the methylvinyldichlorosilane react with the remaining amino groups on the flame-retardant silica surface, thereby introducing carbon-carbon double bonds onto the silica surface to obtain vinyl-modified silica. Surface modification of silica with a silane coupling agent improves its dispersibility in the rubber matrix. The uniformly dispersed silica can more effectively exert its reinforcing effect, further enhancing the mechanical properties of the rubber material. Furthermore, silica itself has a certain flame retardant effect and can form a siliceous layer that isolates heat and oxygen during combustion. After combining with melamine, the two may produce a synergistic flame retardant effect, further improving the flame retardant properties of vinyl-modified silica, so that butyl rubber and modified fluororubber added with this filler also have better flame retardant ability.

[0018] Furthermore, the introduction of the carbon-carbon double bond from methylvinyldichlorosilane onto the surface of silica improves the compatibility of vinyl-modified silica with butyl rubber and modified fluororubber. The presence of vinyl groups can also participate in the rubber's vulcanization reaction. During the vulcanization process, the vinyl groups can cross-link with sulfur (used in butyl rubber vulcanization) or other vulcanizing agents (such as bisphenol AF used in modified fluororubber vulcanization), promoting the formation of a three-dimensional network structure between rubber molecules. This not only strengthens the bonding between the rubber and silica, but also allows for a more complete vulcanization reaction, thereby improving the performance stability and durability of the rubber material.

[0019] Finally, butyl rubber, vinyl-modified silica, sulfur, activator zinc oxide, and accelerator 2-mercaptobenzimidazole are mixed, kneaded, and calendered to form the inner rubber layer. Modified fluororubber, vinyl-modified silica, bisphenol AF, activator calcium hydroxide, and accelerator benzyltriphenylphosphonium chloride are mixed, kneaded, and calendered to form the outer rubber layer. The inner rubber layer, nylon fabric layer, and outer rubber layer are then laid in sequence, vulcanized, and wrapped with steel wire to form the rubber-based elbow. The connector is then assembled with the rubber-based elbow to form the finished product. In terms of structural design, the inner rubber layer combines butyl rubber with vinyl-modified silica to impart strength and flexibility to the elbow. The outer rubber layer, modified fluororubber and vinyl-modified silica, further enhance strength and wear resistance. Furthermore, the outer rubber layer is resistant to high temperatures, weathering, and chemical corrosion, protecting the internal structure from harsh external environments. The nylon fabric layer further enhances the overall tear and tensile strength, while the steel wire wrapping significantly improves pressure resistance. This enables the elbow to withstand complex external forces, maintain a stable shape under different working conditions, and not be easily damaged. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] Source of raw materials: Nonylphenol polyoxyethylene ether, provided by Guangzhou Huining Chemical Raw Materials Co., Ltd., model NP-10; fluororubber, provided by Shanghai Manhua Plastic Raw Materials Co., Ltd., model FKM N 215; white carbon black, provided by Jinan Baoda Dye Chemical Co., Ltd., model 300; butyl rubber, provided by Shenzhen Masini Elastomer Co., Ltd., model LIIR; nylon fabric layer, provided by Ningguo Zhongdian New Materials Co., Ltd., thickness of 1.1 mm; in parts by mass, one part is 1 g.

[0022] Example 1: Step 1: Step S1: adding anhydrous potassium carbonate and p-hydroxybenzaldehyde to tetrahydrofuran and stirring uniformly to obtain a p-hydroxybenzaldehyde solution; adding ethyl 2-chloromethylacrylate to tetrahydrofuran and stirring uniformly to obtain a 2-chloromethylacrylate solution; then adding the 2-chloromethylacrylate solution dropwise to the p-hydroxybenzaldehyde solution, heating to 70° C. and stirring to react for 30 hours. After the reaction is completed, washing, concentrating, precipitating a solid, filtering, and recrystallizing to obtain aldehyde-modified acrylic acid; the reaction molar ratio of p-hydroxybenzaldehyde to ethyl 2-chloromethylacrylate is 1.15:1; Step S2: Under a nitrogen atmosphere, melamine is added to dimethyl sulfoxide, the temperature is raised to 140° C., and stirring is continued to obtain a uniform melamine solution; aldehyde-modified acrylic acid is added to the dimethyl sulfoxide, stirred uniformly, and then added dropwise to the melamine solution, the temperature is raised to 190° C., and refluxed for reaction for 75 hours. After the reaction is completed, the mixture is filtered, washed, and vacuum-dried to obtain a flame-retardant modified acrylic acid; the reaction molar ratio of melamine to aldehyde-modified acrylic acid is 1.4:1; Step S3: Under a nitrogen environment, methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, an emulsifier, and deionized water are mixed, pre-emulsified for 35 minutes, and then heated to 55°C. Potassium persulfate-sodium bisulfite initiator is then added dropwise, and the reaction is continued for 7 hours after the addition is completed to obtain a copolymer emulsion; the copolymer emulsion is then added to a 3wt% calcium chloride solution, demulsified, washed with water, and vacuum dried to obtain a flexible flame retardant acrylic copolymer; the emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mixing ratio is 2.4:1; the reaction mass ratio of methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, emulsifier, deionized water, and potassium persulfate-sodium bisulfite initiator is 6.5:2:1.7:0.1:19:0.4; Step S4: adding a flexible flame-retardant acrylic copolymer and fluororubber to acetone, stirring and dissolving to obtain a rubber emulsion; adding the rubber emulsion to a 3 wt % calcium chloride solution, breaking the emulsion, washing with water, and vacuum drying to obtain a modified fluororubber; the mixing ratio of the flexible flame-retardant acrylic copolymer and the fluororubber is 1.4:4; Step 2: Step S1: Add silica to anhydrous ethanol and ultrasonically disperse for 2.5 hours, then add 3-chloropropyltrimethoxysilane, react at 85°C for 1.0 hour, then add 3wt% hydrochloric acid, continue stirring and react for 6 hours, and after the reaction is completed, centrifuge, wash with alcohol, and dry to obtain modified silica; the mass volume ratio of silica, 3-chloropropyltrimethoxysilane, and hydrochloric acid is 1g:0.45g:9mL; Step S2: adding modified silica, melamine, and triethylamine to toluene, stirring and reacting at 85° C. for 15 hours, centrifuging, washing, and drying after the reaction to obtain flame-retardant silica; then adding flame-retardant silica, methylvinyldichlorosilane, and triethylamine to toluene, stirring and reacting at 85° C. for 15 hours, centrifuging, washing, and drying after the reaction to obtain vinyl-modified silica; the reaction mass ratio of modified silica, melamine, and methylvinyldichlorosilane is 1.1:0.25:0.40; Step S3: 90g of butyl rubber, 25g of vinyl-modified silica, 2g of sulfur, 3g of activator zinc oxide, and 1g of accelerator 2-mercaptobenzimidazole are mixed, and the mixture is kneaded and calendered to obtain an inner rubber layer; 90g of modified fluororubber, 25g of vinyl-modified silica, 3g of bisphenol AF, 3g of activator calcium hydroxide, and 1.0g of accelerator benzyltriphenylphosphonium chloride are mixed, and the mixture is kneaded and calendered to obtain an outer rubber layer; the inner rubber layer, nylon fabric layer, and outer rubber layer are then laid in sequence, and the mixture is vulcanized at 180°C for 20min, followed by winding with steel wire to obtain a rubber-based elbow; the connecting piece is assembled with the rubber-based elbow to obtain a finished product; the connecting piece is made of 316 stainless steel.

[0023] Example 2: Step 1: Step S1: adding anhydrous potassium carbonate and p-hydroxybenzaldehyde to tetrahydrofuran and stirring uniformly to obtain a p-hydroxybenzaldehyde solution; adding ethyl 2-chloromethylacrylate to tetrahydrofuran and stirring uniformly to obtain an ethyl 2-chloromethylacrylate solution; then adding the ethyl 2-chloromethylacrylate solution dropwise to the p-hydroxybenzaldehyde solution, heating to 67° C. and stirring to react for 27 hours. After the reaction is completed, washing, concentrating, precipitating a solid, filtering, and recrystallizing to obtain aldehyde-modified acrylic acid; the reaction molar ratio of p-hydroxybenzaldehyde to ethyl 2-chloromethylacrylate is 1.15:1; Step S2: Under a nitrogen atmosphere, melamine is added to dimethyl sulfoxide, the temperature is raised to 135° C., and stirring is continued to obtain a uniform melamine solution; aldehyde-modified acrylic acid is added to the dimethyl sulfoxide, stirred uniformly, and then added dropwise to the melamine solution, the temperature is raised to 185° C., and refluxed for reaction for 72 hours. After the reaction is completed, the mixture is filtered, washed, and vacuum-dried to obtain a flame-retardant modified acrylic acid; the reaction molar ratio of melamine to aldehyde-modified acrylic acid is 1.4:1; Step S3: Under a nitrogen environment, methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, an emulsifier, and deionized water are mixed, pre-emulsified for 30 minutes, and then heated to 52° C., and then potassium persulfate-sodium bisulfite initiator is added dropwise. After the addition is completed, the reaction is continued by keeping warm for 6.5 hours to obtain a copolymer emulsion; the copolymer emulsion is then added to a 3wt% calcium chloride solution, demulsified, washed with water, and vacuum dried to obtain a flexible flame retardant acrylic copolymer; the emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mixing ratio is 2.4:1; the reaction mass ratio of methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, emulsifier, deionized water, and potassium persulfate-sodium bisulfite initiator is 6.5:2:1.7:0.1:19:0.4; Step S4: adding a flexible flame-retardant acrylic copolymer and fluororubber to acetone, stirring and dissolving to obtain a rubber emulsion; adding the rubber emulsion to a 3 wt % calcium chloride solution, breaking the emulsion, washing with water, and vacuum drying to obtain a modified fluororubber; the mixing ratio of the flexible flame-retardant acrylic copolymer and the fluororubber is 1.4:4; Step 2: Step S1: Add silica to anhydrous ethanol and ultrasonically disperse for 2 hours, then add 3-chloropropyltrimethoxysilane, react at 82°C for 0.7 hours, then add 3wt% hydrochloric acid, continue stirring and react for 5 hours, and after the reaction is completed, centrifuge, wash with alcohol, and dry to obtain modified silica; the mass volume ratio of silica, 3-chloropropyltrimethoxysilane, and hydrochloric acid is 1g:0.45g:9mL; Step S2: adding modified silica, melamine, and triethylamine to toluene, stirring and reacting at 82° C. for 12 hours, centrifuging, washing, and drying after the reaction to obtain flame-retardant silica; then adding flame-retardant silica, methylvinyldichlorosilane, and triethylamine to toluene, stirring and reacting at 82° C. for 12 hours, centrifuging, washing, and drying after the reaction to obtain vinyl-modified silica; the reaction mass ratio of modified silica, melamine, and methylvinyldichlorosilane is 1.1:0.25:0.40; Step S3: 90g of butyl rubber, 25g of vinyl-modified silica, 2g of sulfur, 3g of activator zinc oxide, and 1g of accelerator 2-mercaptobenzimidazole are mixed, and the mixture is kneaded and calendered to obtain an inner rubber layer; 90g of modified fluororubber, 25g of vinyl-modified silica, 3g of bisphenol AF, 3g of activator calcium hydroxide, and 1.0g of accelerator benzyltriphenylphosphonium chloride are mixed, and the mixture is kneaded and calendered to obtain an outer rubber layer; the inner rubber layer, nylon fabric layer, and outer rubber layer are then laid in sequence, and the mixture is vulcanized at 175°C for 17 minutes, followed by winding with steel wire to obtain a rubber-based elbow; the connecting piece is assembled with the rubber-based elbow to obtain a finished product; the connecting piece is made of 316 stainless steel.

[0024] Example 3: Step 1: Step S1: adding anhydrous potassium carbonate and p-hydroxybenzaldehyde to tetrahydrofuran and stirring uniformly to obtain a p-hydroxybenzaldehyde solution; adding ethyl 2-chloromethylacrylate to tetrahydrofuran and stirring uniformly to obtain an ethyl 2-chloromethylacrylate solution; then adding the ethyl 2-chloromethylacrylate solution dropwise to the p-hydroxybenzaldehyde solution, heating to 65° C. and stirring to react for 25 hours. After the reaction is completed, washing, concentrating, precipitating a solid, filtering, and recrystallizing to obtain aldehyde-modified acrylic acid; the reaction molar ratio of p-hydroxybenzaldehyde to ethyl 2-chloromethylacrylate is 1.15:1; Step S2: Under a nitrogen atmosphere, melamine is added to dimethyl sulfoxide, the temperature is raised to 130-140° C., and stirring is continued to obtain a uniform melamine solution; aldehyde-modified acrylic acid is added to the dimethyl sulfoxide, stirred uniformly, and then added dropwise to the melamine solution, the temperature is raised to 180° C., and refluxed for reaction for 70 hours. After the reaction is completed, the mixture is filtered, washed, and vacuum-dried to obtain a flame-retardant modified acrylic acid; the reaction molar ratio of melamine to aldehyde-modified acrylic acid is 1.4:1; Step S3: Under a nitrogen environment, methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, an emulsifier, and deionized water are mixed, pre-emulsified for 25 minutes, and then heated to 50°C, and then potassium persulfate-sodium bisulfite initiator is added dropwise. After the addition is completed, the reaction is continued by keeping the temperature for 6 hours to obtain a copolymer emulsion; the copolymer emulsion is then added to a 3wt% calcium chloride solution, demulsified, washed with water, and vacuum dried to obtain a flexible flame retardant acrylic copolymer; the emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mixing ratio is 2.4:1; the reaction mass ratio of methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, emulsifier, deionized water, and potassium persulfate-sodium bisulfite initiator is 6.5:2:1.7:0.1:19:0.4; Step S4: adding a flexible flame-retardant acrylic copolymer and fluororubber to acetone, stirring and dissolving to obtain a rubber emulsion; adding the rubber emulsion to a 3 wt % calcium chloride solution, breaking the emulsion, washing with water, and vacuum drying to obtain a modified fluororubber; the mixing ratio of the flexible flame-retardant acrylic copolymer and the fluororubber is 1.4:4; Step 2: Step S1: Add silica to anhydrous ethanol, ultrasonically disperse for 1.5 hours, then add 3-chloropropyltrimethoxysilane, react at 80°C for 0.5 hours, then add 3wt% hydrochloric acid, continue stirring and react for 4 hours, and after the reaction is completed, centrifuge, wash with alcohol, and dry to obtain modified silica; the mass volume ratio of silica, 3-chloropropyltrimethoxysilane, and hydrochloric acid is 1g:0.45g:9mL; Step S2: adding modified silica, melamine, and triethylamine to toluene, stirring and reacting at 80° C. for 10 hours, centrifuging, washing, and drying after the reaction to obtain flame-retardant silica; then adding flame-retardant silica, methylvinyldichlorosilane, and triethylamine to toluene, stirring and reacting at 80° C. for 10 hours, centrifuging, washing, and drying after the reaction to obtain vinyl-modified silica; the reaction mass ratio of modified silica, melamine, and methylvinyldichlorosilane is 1.1:0.25:0.40; Step S3: 90g of butyl rubber, 25g of vinyl-modified silica, 2g of sulfur, 3g of activator zinc oxide, and 1g of accelerator 2-mercaptobenzimidazole are mixed, and the mixture is kneaded and calendered to obtain an inner rubber layer; 90g of modified fluororubber, 25g of vinyl-modified silica, 3g of bisphenol AF, 3g of activator calcium hydroxide, and 1.0g of accelerator benzyltriphenylphosphonium chloride are mixed, and the mixture is kneaded and calendered to obtain an outer rubber layer; the inner rubber layer, nylon fabric layer, and outer rubber layer are then laid in sequence, and the mixture is vulcanized at 170°C for 15min, followed by winding with steel wire to obtain a rubber-based elbow; the connecting piece and the rubber-based elbow are assembled to obtain a finished product; the connecting piece is made of 316 stainless steel.

[0025] Comparative Example 1: The flexible flame-retardant acrylic copolymer was removed, and the rest was the same as in Example 1, and the specific steps were as follows: Step 1: Step S1: Add silica to anhydrous ethanol, ultrasonically disperse for 2.5 hours, then add 3-chloropropyltrimethoxysilane, and react at a constant temperature of 85°C for 1.0 hour, then add 3wt% hydrochloric acid, continue stirring and react for 6 hours, and after the reaction is completed, centrifuge, wash with alcohol, and dry to obtain modified silica; the mass volume ratio of silica, 3-chloropropyltrimethoxysilane, and hydrochloric acid is 1g:0.45g:9mL; Step S2: adding modified silica, melamine, and triethylamine to toluene, stirring and reacting at 85° C. for 15 hours, centrifuging, washing, and drying after the reaction to obtain flame-retardant silica; then adding flame-retardant silica, methylvinyldichlorosilane, and triethylamine to toluene, stirring and reacting at 85° C. for 15 hours, centrifuging, washing, and drying after the reaction to obtain vinyl-modified silica; the reaction mass ratio of modified silica, melamine, and methylvinyldichlorosilane is 1.1:0.25:0.40; Step S3: 90g of butyl rubber, 25g of vinyl-modified silica, 2g of sulfur, 3g of activator zinc oxide, and 1g of accelerator 2-mercaptobenzimidazole are mixed, and the mixture is kneaded and calendered to obtain an inner rubber layer; 90g of fluororubber, 25g of vinyl-modified silica, 3g of bisphenol AF, 3g of activator calcium hydroxide, and 1.0g of accelerator benzyltriphenylphosphine chloride are mixed, and the mixture is kneaded and calendered to obtain an outer rubber layer; the inner rubber layer, nylon fabric layer, and outer rubber layer are then laid in sequence, and the rubber-based elbow is obtained after being vulcanized at 180°C for 20min. The rubber-based elbow is then wound with steel wire to obtain a rubber-based elbow; the connector is assembled with the rubber-based elbow to obtain a finished product; the connector is made of 316 stainless steel.

[0026] Comparative Example 2: Vinyl-modified silica was replaced with silica, and the rest was the same as Example 1, with the following specific steps: Step 1: Step S1: Anhydrous potassium carbonate and p-hydroxybenzaldehyde were added to tetrahydrofuran, and stirred evenly to obtain a p-hydroxybenzaldehyde solution; ethyl 2-chloromethylacrylate was added to tetrahydrofuran, and stirred evenly to obtain an ethyl 2-chloromethylacrylate solution; the ethyl 2-chloromethylacrylate solution was then added dropwise to the p-hydroxybenzaldehyde solution, and the temperature was raised to 70° C. and stirred for 30 hours. After the reaction was completed, the solid was washed, concentrated, filtered, and recrystallized to obtain aldehyde-modified acrylic acid; the reaction molar ratio of p-hydroxybenzaldehyde to ethyl 2-chloromethylacrylate was 1.15:1; Step S2: Under a nitrogen atmosphere, melamine is added to dimethyl sulfoxide, the temperature is raised to 140° C., and stirring is continued to obtain a uniform melamine solution; aldehyde-modified acrylic acid is added to the dimethyl sulfoxide, stirred uniformly, and then added dropwise to the melamine solution, the temperature is raised to 190° C., and refluxed for reaction for 75 hours. After the reaction is completed, the mixture is filtered, washed, and vacuum-dried to obtain a flame-retardant modified acrylic acid; the reaction molar ratio of melamine to aldehyde-modified acrylic acid is 1.4:1; Step S3: Under a nitrogen environment, methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, an emulsifier, and deionized water are mixed, pre-emulsified for 35 minutes, and then heated to 55°C. Potassium persulfate-sodium bisulfite initiator is then added dropwise, and the reaction is continued for 7 hours after the addition is completed to obtain a copolymer emulsion; the copolymer emulsion is then added to a 3wt% calcium chloride solution, demulsified, washed with water, and vacuum dried to obtain a flexible flame retardant acrylic copolymer; the emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mixing ratio is 2.4:1; the reaction mass ratio of methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, emulsifier, deionized water, and potassium persulfate-sodium bisulfite initiator is 6.5:2:1.7:0.1:19:0.4; Step S4: adding a flexible flame-retardant acrylic copolymer and fluororubber to acetone, stirring and dissolving to obtain a rubber emulsion; adding the rubber emulsion to a 3 wt % calcium chloride solution, breaking the emulsion, washing with water, and vacuum drying to obtain a modified fluororubber; the mixing ratio of the flexible flame-retardant acrylic copolymer and the fluororubber is 1.4:4; Step 2: Mix 90g of butyl rubber, 25g of white carbon black, 2g of sulfur, 3g of activator zinc oxide, and 1g of accelerator 2-mercaptobenzimidazole, and obtain an inner rubber layer through mixing and calendering; mix 90g of modified fluororubber, 25g of white carbon black, 3g of bisphenol AF, 3g of activator calcium hydroxide, and 1.0g of accelerator benzyltriphenylphosphine chloride through mixing and calendering to obtain an outer rubber layer; then lay the inner rubber layer, nylon fabric layer, and outer rubber layer in sequence, vulcanize at 180°C for 20min, and then wrap steel wire to obtain a rubber-based elbow; then take the connecting piece and the rubber-based elbow and assemble them into a finished product; the connecting piece is stainless steel 316.

[0027] Detection test: Flame retardant performance test: The outer rubber layer prepared in the present invention was cut into samples of 120×6×3 mm, and the oxygen index of the samples was tested according to ASTM D2863-97.

[0028] Mechanical properties testing: Referring to GB / T 528-2009, "Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties," the cover prepared in this invention was cut into specimens measuring 115 x 25 x 3 mm. The gripper was moved at a speed of 500 mm / min. The results are shown in the following table:

[0029] Conclusion: The dosages used in Examples 1 to 3 remained unchanged, and only some reaction parameters were modified. The experimental data show that there was no significant fluctuation in the performance of the samples.

[0030] Comparative Example 1: The flexible flame-retardant acrylic copolymer was removed, and the rest was the same as in Example 1. From the experimental data, it can be seen that compared with Example 1, the oxygen index was reduced to 28.7%, the tensile strength was reduced to 17.7 MPa, and the elongation at break was reduced to 231%. The reasons for this are analyzed as follows: the flexible flame-retardant acrylic copolymer contains multiple flexible segments, which allow the material to undergo a large degree of elastic deformation without breaking. Therefore, after removing them, the tensile strength will be reduced, and the elongation at break will be significantly reduced; in addition, the copolymer contains a large amount of flame-retardant nitrogen elements, so it has good flame retardant properties. Therefore, after removing them, the flame retardant oxygen index is reduced.

[0031] Comparative Example 2: Vinyl-modified silica is replaced by silica, and the rest is the same as Example 1. It can be seen from the experimental data that, compared with Example 1, the oxygen index is reduced to 31.6%, the tensile strength is reduced to 16.1 MPa, and the elongation at break is reduced to 271%. The reason for this is that vinyl-modified silica is obtained by improving the dispersibility and flame retardant modification of silica, so after removing it, the oxygen index is reduced and the mechanical properties are reduced.

[0032] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0033] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant rubber-based elbow, characterized in that: The following steps are involved: Step 1: adding a flexible flame-retardant acrylic copolymer and fluororubber to acetone, stirring and dissolving to obtain a rubber emulsion; adding the rubber emulsion to a 3-5wt% calcium chloride solution, breaking the emulsion, washing with water, and vacuum drying to obtain a modified fluororubber; Step 2: Butyl rubber, vinyl modified silica, sulfur, activator zinc oxide, and accelerator 2-mercaptobenzimidazole are mixed, and the mixture is kneaded and calendered to obtain an inner rubber layer; modified fluororubber, vinyl modified silica, bisphenol AF, activator calcium hydroxide, and accelerator benzyltriphenylphosphine chloride are mixed, and the mixture is kneaded and calendered to obtain an outer rubber layer; the inner rubber layer, nylon fabric layer, and outer rubber layer are then laid in sequence, and the mixture is vulcanized at 170-180°C for 15-20 minutes, and then wrapped with steel wire to obtain a rubber-based elbow; the connector is assembled with the rubber-based elbow to obtain a finished product.

2. The method for preparing a high-temperature resistant rubber-based elbow according to claim 1, characterized in that: In step 1, the mixing ratio of the flexible flame-retardant acrylic copolymer and the fluororubber is (1.3-1.5):

4.

3. The method for preparing a high-temperature resistant rubber-based elbow according to claim 1, characterized in that: In step 2, the contents of the components of the inner rubber layer are: by mass, 90-100 parts of butyl rubber, 25-35 parts of vinyl-modified silica, 2-3 parts of sulfur, 3-5 parts of activator zinc oxide, and 1-2 parts of accelerator 2-mercaptobenzimidazole; the contents of the components of the outer rubber layer are: by mass, 90-100 parts of modified fluororubber, 25-30 parts of vinyl-modified silica, 3-5 parts of bisphenol AF, 3-5 parts of activator calcium hydroxide, and 1.0-1.3 parts of accelerator benzyltriphenylphosphine chloride; the connecting piece is made of 316 stainless steel.

4. The method for preparing a high-temperature resistant rubber-based elbow according to claim 1, characterized in that: The preparation process of flexible flame retardant acrylic copolymer is as follows: Step S1: adding anhydrous potassium carbonate and p-hydroxybenzaldehyde to tetrahydrofuran and stirring uniformly to obtain a p-hydroxybenzaldehyde solution; adding ethyl 2-chloromethylacrylate to tetrahydrofuran and stirring uniformly to obtain an ethyl 2-chloromethylacrylate solution; then adding the ethyl 2-chloromethylacrylate solution dropwise to the p-hydroxybenzaldehyde solution, heating to 65-70° C. and stirring to react for 25-30 hours; after the reaction is completed, washing, concentrating, precipitating a solid, filtering, and recrystallizing to obtain aldehyde-modified acrylic acid; Step S2: Under a nitrogen atmosphere, melamine is added to dimethyl sulfoxide, the temperature is raised to 130-140° C., and stirring is continued to obtain a uniform melamine solution; aldehyde-modified acrylic acid is added to the dimethyl sulfoxide, stirred uniformly, and then added dropwise to the melamine solution, the temperature is raised to 180-190° C., and refluxed for reaction for 70-75 hours. After the reaction is completed, the mixture is filtered, washed, and vacuum-dried to obtain a flame-retardant modified acrylic acid; Step S3: Under a nitrogen environment, methoxyethyl acrylate, butyl acrylate, flame-retardant modified acrylic acid, an emulsifier, and deionized water are mixed, pre-emulsified for 25-35 minutes, and then heated to 50-55° C., and then potassium persulfate-sodium bisulfite initiator is added dropwise. After the addition is completed, the reaction is continued by keeping the temperature for 6-7 hours to obtain a copolymer emulsion; the copolymer emulsion is then added to a 3-5wt% calcium chloride solution, demulsified, washed with water, and vacuum dried to obtain a flexible flame-retardant acrylic copolymer.

5. The method for preparing a high-temperature resistant rubber-based elbow according to claim 4, characterized in that: In step S1, the reaction molar ratio of p-hydroxybenzaldehyde to ethyl 2-chloromethylacrylate is (1.1-1.2):

1.

6. The method for preparing a high-temperature resistant rubber-based elbow according to claim 4, characterized in that: In step S2, the reaction molar ratio of melamine to aldehyde-modified acrylic acid is (1.3-1.5):

1.

7. The method for preparing a high-temperature resistant rubber-based elbow according to claim 4, characterized in that: In step S3, the emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium lauryl sulfate, and the mixing ratio is (2.3-2.5):1; the reaction mass ratio of methoxyethyl acrylate, butyl acrylate, flame retardant modified acrylic acid, emulsifier, deionized water, and potassium persulfate-sodium bisulfite initiator is (6-7):2:(1.5-2.0):0.1:(18-20):(0.3-0.5).

8. The method for preparing a high-temperature resistant rubber-based elbow according to claim 1, characterized in that: The preparation process of vinyl modified silica is as follows: Step S1: adding silica to anhydrous ethanol, ultrasonically dispersing for 1.5-2.5 hours, then adding 3-chloropropyltrimethoxysilane, and reacting at a constant temperature of 80-85°C for 0.5-1.0 hours, then adding 3-5 wt% hydrochloric acid, and continuing to stir and react for 4-6 hours. After the reaction is completed, the modified silica is obtained by centrifugation, alcohol washing, and drying. Step S2: adding modified silica, melamine, and triethylamine to toluene, stirring and reacting at 80-85° C. for 10-15 hours, and after the reaction is completed, centrifuging, washing, and drying to obtain flame-retardant silica; then adding flame-retardant silica, methylvinyldichlorosilane, and triethylamine to toluene, stirring and reacting at 80-85° C. for 10-15 hours, and after the reaction is completed, centrifuging, washing, and drying to obtain vinyl-modified silica.

9. The method for preparing a high-temperature resistant rubber-based elbow according to claim 8, characterized in that: The mass volume ratio of white carbon black, 3-chloropropyltrimethoxysilane and hydrochloric acid is 1g: (0.4-0.5)g: (8-10)mL; the reaction mass ratio of modified white carbon black, melamine and methylvinyldichlorosilane is (1.0-1.2): 0.25: 0.

40.

10. A high temperature resistant rubber-based elbow, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 9.

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