Flame-retardant rubber containing a bismuth-based flame retardant and a method for producing the same

Abstract

This invention provides a flame-retardant rubber containing a bismuth-based flame retardant and its preparation method, belonging to the field of flame-retardant rubber technology. This invention uses natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber as the main base materials, while introducing at least one of bismuth oxide, bismuth oxychloride, bismuth hydroxide, and bismuth subcarbonate as an environmentally friendly flame retardant, ensuring the product's flame-retardant effect; it also reduces the use of complex solvents and potential by-product emissions, which is an important way to achieve an ideal green lifestyle. Carbon black, stearic acid, zinc oxide, decabromodiphenyl ethane, aluminum diethylphosphinate, diethyl phthalate, paraffin oil, coupling agents, insoluble sulfur, accelerators, antioxidants, and other substances are also added. Through multiple mixing and intensive kneading processes, the product's tensile properties are guaranteed while effectively improving its fire resistance, delaying ignition, reducing flame propagation speed, and enhancing the safety of product use.

Description

Technical Field

[0001] This invention relates to the field of flame retardant rubber technology, and in particular to a flame retardant rubber containing a bismuth-based flame retardant and its preparation method. Background Technology

[0002] Most rubber composites are composed of carbon and hydrogen in their molecular structure, which can result in highly flammable properties, with flames spreading rapidly and producing large amounts of toxic fumes. The combustion behavior is based on free radical chain reactions, where oxidation is an autocatalytic process that leads to uncontrollable destruction.

[0003] According to data from the International Rubber Research Group, global rubber consumption is projected to exceed 30 million tons annually. Natural rubber and its composites, extracted directly from plants, are among the most important biopolymers, possessing a range of unique properties such as elasticity, abrasion resistance, impact resistance, and low-temperature ductility. Their comprehensive performance makes them indispensable in daily life, transportation, and industrial systems. However, since most widely used rubber composites are flammable, their rapid combustion upon ignition significantly accelerates the destruction of the entire system, while toxic fumes can also pose a significant threat to life. Traditional halogenated flame retardants produce toxic gases that cause severe environmental pollution and have been widely banned in recent years. Biomimetic flame retardants, halogen-free flame retardants, and sustainably sourced flame retardants are receiving increasing attention, but their limited flame-retardant efficiency and high addition amounts often negatively impact the overall performance of composite materials. Therefore, designing green and efficient flame-retardant systems to expand the advanced applications of rubber composites remains a significant challenge. Summary of the Invention

[0004] To address the aforementioned problems in the background art, embodiments of the present invention provide a flame-retardant rubber containing a bismuth-based flame retardant, comprising the following components by weight: 60-100 parts natural rubber, 10-20 parts nitrile rubber, 10-20 parts styrene-butadiene rubber, 10-20 parts chloroprene rubber, 30-60 parts carbon black, 3-12 parts stearic acid, 5-10 parts zinc oxide, 3-50 parts decabromodiphenyl ethane, 5-30 parts aluminum diethylphosphinate, 0.8-3 parts diethyl phthalate, 2-18 parts paraffin oil, 1-3 parts coupling agent, 2-6 parts insoluble sulfur, 1.5-2.5 parts accelerator, 1.5-3 parts antioxidant, and 30-100 parts bismuth-based flame retardant.

[0005] According to one aspect of an embodiment of the present invention, the accelerator is at least one selected from tetramethylthiuram disulfide, tetrathiotetramethylthiuram, methylene diphenyl diamine, diphenylguanidine, N,N'-diethyl-2-benzo[a]benzothiazole sulfenamide, hexamethylenetetramine, tetramethylthiourea, 2-thiol benzo[a]benzothiazole, and dibenzo[a]benzothiazole disulfide.

[0006] According to one aspect of the present invention, the antioxidant is at least one selected from octyl diphenylamine, polymethylene aniline, polycarbodiimide, p-tert-butylphenol, 3-methyl-6-tert-butylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and diethyl 3,5'-di-tert-butyl-4-hydrobenzyl phosphate.

[0007] According to one aspect of the present invention, the coupling agent is at least one of isopropyl distearate aluminoacrylate, bis(dioctyloxypyrophosphate) ethylene titanate, isopropyl dioleoyloxy(dioctylphosphoyloxy) titanate, isopropyl trioleoyloxy titanate, Si-69, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0008] According to one aspect of the present invention, the bismuth-based flame retardant is at least one selected from bismuth oxide, bismuth oxychloride, bismuth hydroxide, and bismuth subcarbonate.

[0009] Based on a general inventive concept, embodiments of the present invention provide a method for preparing a flame-retardant rubber containing a bismuth-based flame retardant, comprising the following steps:

[0010] S1: Mix bismuth-based flame retardant and decabromodiphenyl ethane evenly in anhydrous ethanol, then add paraffin oil and coupling agent and homogenize by ultrasonication. Stir mechanically at room temperature and dry to obtain modified bismuth-based flame retardant powder.

[0011] S2: Natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber are put into a mixer for mixing; carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder, aluminum diethylphosphinate, and diethyl phthalate are added in sequence for mixing; antioxidant, accelerator, and insoluble sulfur are added in sequence for mixing to obtain the compound rubber.

[0012] S3: Place the compounded rubber at room temperature, form triangular bags on a two-roll mill and pass through them in thin strips multiple times, press them into sheets, and let them stand to obtain mixed rubber sheets;

[0013] S4: The mixed film is vulcanized once using a flat vulcanizing machine and then vulcanized a second time using an oven to obtain the final product.

[0014] According to one aspect of an embodiment of the present invention, in step S1, the ultrasonic homogenization time is 5 to 60 minutes; the mechanical stirring speed is 250 to 400 rpm, and the stirring time is 5 to 240 minutes; the drying temperature is 50 to 80°C, and the drying time is 1 to 15 hours.

[0015] According to one aspect of an embodiment of the present invention, in step S2, the mixing times for the three mixing stages are 0.5 to 30 minutes, 5 to 40 minutes, and 2 to 20 minutes, respectively.

[0016] According to one aspect of an embodiment of the present invention, in step S3, the placement time is 0.5 to 3 hours; the tube is passed through 5 to 15 times, and then left to stand for 5 to 24 hours.

[0017] According to one aspect of an embodiment of the present invention, in step S4, the primary vulcanization pressure is 10 MPa, the vulcanization temperature is 70–130°C, and the vulcanization time is 3–25 minutes; the secondary vulcanization temperature is 80–150°C, and the vulcanization time is 3–8 hours.

[0018] The above-described solution of the present invention has the following beneficial effects:

[0019] (1) This invention uses natural rubber, nitrile rubber, styrene-butadiene rubber and chloroprene rubber as the main base materials, and introduces at least one of bismuth oxide, bismuth oxychloride, bismuth hydroxide and bismuth subcarbonate as an environmentally friendly flame retardant to ensure the flame retardant effect of the product; at the same time, it reduces the use of complex solvents and potential by-product emissions, which is an important way to achieve an ideal green life.

[0020] (2) The present invention also adds carbon black, stearic acid, zinc oxide, decabromodiphenyl ethane, aluminum diethylphosphinate, diethyl phthalate, paraffin oil, coupling agent, insoluble sulfur, accelerator, antioxidant and other substances. Through multiple mixing and intensive mixing, the product's fire resistance is effectively improved while ensuring its tensile properties, delaying ignition and reducing the speed of flame propagation, thereby improving the safety of the product. Detailed Implementation

[0021] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.

[0022] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0024] This invention addresses existing problems by providing a flame-retardant rubber containing a bismuth-based flame retardant, comprising the following components by weight: 60-100 parts natural rubber, 10-20 parts nitrile rubber, 10-20 parts styrene-butadiene rubber, 10-20 parts chloroprene rubber, 30-60 parts carbon black, 3-12 parts stearic acid, 5-10 parts zinc oxide, 3-50 parts decabromodiphenyl ethane, 5-30 parts aluminum diethylphosphinate, 0.8-3 parts diethyl phthalate, 2-18 parts paraffin oil, 1-3 parts coupling agent, 2-6 parts insoluble sulfur, 1.5-2.5 parts accelerator, 1.5-3 parts antioxidant, and 30-100 parts bismuth-based flame retardant.

[0025] According to one aspect of an embodiment of the present invention, the accelerator is at least one selected from tetramethylthiuram disulfide, tetrathiotetramethylthiuram, methylene diphenyl diamine, diphenylguanidine, N,N'-diethyl-2-benzo[a]benzothiazole sulfenamide, hexamethylenetetramine, tetramethylthiourea, 2-thiol benzo[a]benzothiazole, and dibenzo[a]benzothiazole disulfide.

[0026] According to one aspect of the present invention, the antioxidant is at least one selected from octyl diphenylamine, polymethylene aniline, polycarbodiimide, p-tert-butylphenol, 3-methyl-6-tert-butylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and diethyl 3,5'-di-tert-butyl-4-hydrobenzyl phosphate.

[0027] According to one aspect of the present invention, the coupling agent is at least one of isopropyl distearate aluminoacrylate, bis(dioctyloxypyrophosphate) ethylene titanate, isopropyl dioleoyloxy(dioctylphosphoyloxy) titanate, isopropyl trioleoyloxy titanate, Si-69, vinyltrimethoxysilane, and vinyltriethoxysilane.

[0028] According to one aspect of the present invention, the bismuth-based flame retardant is at least one selected from bismuth oxide, bismuth oxychloride, bismuth hydroxide, and bismuth subcarbonate.

[0029] Based on a general inventive concept, embodiments of the present invention provide a method for preparing a flame-retardant rubber containing a bismuth-based flame retardant, comprising the following steps:

[0030] S1: Mix bismuth-based flame retardant and decabromodiphenyl ethane evenly in anhydrous ethanol, then add paraffin oil and coupling agent and homogenize by ultrasonication. Stir mechanically at room temperature and dry to obtain modified bismuth-based flame retardant powder.

[0031] S2: Natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber are put into a mixer for mixing; carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder, aluminum diethylphosphinate, and diethyl phthalate are added in sequence for mixing; antioxidant, accelerator, and insoluble sulfur are added in sequence for mixing to obtain the compound rubber.

[0032] S3: Place the compounded rubber at room temperature, form triangular bags on a two-roll mill and pass through them in thin strips multiple times, press them into sheets, and let them stand to obtain mixed rubber sheets;

[0033] S4: The mixed film is vulcanized once using a flat vulcanizing machine and then vulcanized a second time using an oven to obtain the final product.

[0034] According to one aspect of an embodiment of the present invention, in step S1, the ultrasonic homogenization time is 5 to 60 minutes; the mechanical stirring speed is 250 to 400 rpm, and the stirring time is 5 to 240 minutes; the drying temperature is 50 to 80°C, and the drying time is 1 to 15 hours.

[0035] According to one aspect of an embodiment of the present invention, in step S2, the mixing times for the three mixing stages are 0.5 to 30 minutes, 5 to 40 minutes, and 2 to 20 minutes, respectively.

[0036] According to one aspect of an embodiment of the present invention, in step S3, the placement time is 0.5 to 3 hours; the tube is passed through 5 to 15 times, and then left to stand for 5 to 24 hours.

[0037] According to one aspect of an embodiment of the present invention, in step S4, the primary vulcanization pressure is 10 MPa, the vulcanization temperature is 70–130°C, and the vulcanization time is 3–25 minutes; the secondary vulcanization temperature is 80–150°C, and the vulcanization time is 3–8 hours.

[0038] The following will describe the specific implementation methods.

[0039] Example 1

[0040] A flame-retardant rubber containing bismuth-based flame retardants comprises the following raw materials in parts by weight: 80 parts natural rubber, 10 parts nitrile rubber, 10 parts styrene-butadiene rubber, 10 parts chloroprene rubber, 40 parts carbon black, 3 parts stearic acid, 5 parts zinc oxide, 10 parts decabromodiphenyl ethane, 10 parts aluminum diethylphosphinate, 0.8 parts diethyl phthalate, 3 parts paraffin oil, 3 parts insoluble sulfur, 1.5 parts accelerator, 1.5 parts antioxidant, 1 part silane coupling agent (Si-69), and 60 parts bismuth oxychloride.

[0041] The accelerator consists of tetramethylthiuram disulfide and dibenzothiazole disulfide; the antioxidant is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

[0042] The preparation method of the above-mentioned flame-retardant rubber containing bismuth-based flame retardants includes the following steps:

[0043] Step 1: Dissolve bismuth nitrate pentahydrate and potassium chloride in water at a 1:1 molar ratio and stir for 30 minutes. Then, add sodium hydroxide aqueous solution dropwise to the resulting solution and stir for 3 hours. Transfer the mixture to a hydrothermal reactor and maintain the temperature at 180°C for 16 hours. After cooling, a precipitate is obtained. Wash the precipitate 3-5 times with water and anhydrous ethanol, and dry it at 60-80°C for 8-10 hours to obtain bismuth oxychloride.

[0044] Step 2: Mix bismuth oxychloride and decabromodiphenyl ethane evenly in anhydrous ethanol, add paraffin oil and coupling agent, homogenize by ultrasonication for 30 minutes, then mechanically stir at room temperature at a stirring speed of 300 rpm for 60 minutes, and then dry at 80°C for 8 hours to obtain modified bismuth-based flame retardant powder.

[0045] Step 3: Mix natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber in a mixer for 0.5-30 minutes to obtain a mixed rubber compound; continue to add carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder obtained in Step 1, aluminum diethylphosphinate, and diethyl phthalate in sequence and mix in a mixer for 10 minutes. Then, continue to add antioxidant, accelerator, and insoluble sulfur in sequence and mix in a mixer for 8 minutes to obtain a compound rubber.

[0046] Step 4: Place the rubber compound obtained in Step 3 at room temperature for 2 hours, then roll it into triangular pieces and pass it through a thin mill 5-15 times, press it into sheets, and let it stand for 10 hours to obtain the mixed rubber sheet.

[0047] Step 5: Vulcanize the mixed film obtained in Step 4 using a flat vulcanizing machine at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100℃, and a vulcanizing time of 12 minutes. Then, perform a secondary vulcanization in an oven at a vulcanizing temperature of 100℃ for 3 hours.

[0048] Example 2

[0049] A flame-retardant rubber containing bismuth-based flame retardants comprises the following raw materials in parts by weight: 60 parts natural rubber, 20 parts nitrile rubber, 20 parts styrene-butadiene rubber, 10 parts chloroprene rubber, 40 parts carbon black, 8 parts stearic acid, 5 parts zinc oxide, 10 parts decabromodiphenyl ethane, 20 parts aluminum diethylphosphinate, 1.2 parts diethyl phthalate, 8 parts paraffin oil, 4 parts insoluble sulfur, 1.5 parts accelerator, 1.5 parts antioxidant, 1-3 parts isopropyl distearate coupling agent, and 50 parts bismuth subcarbonate.

[0050] The accelerator consists of tetramethylthiuram disulfide and dibenzothiazole disulfide; the antioxidant is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

[0051] The preparation method of the above-mentioned flame-retardant rubber containing bismuth-based flame retardants includes the following steps:

[0052] Step 1: Stir nitric acid pentahydrate and ethylene glycol at a mass ratio of 3:2 at room temperature for 30 minutes. Then mix sodium carbonate and water at a mass ratio of 1:2. Add sodium carbonate aqueous solution dropwise to the mixed solution of nitric acid pentahydrate and ethylene glycol. Continue stirring for 3 hours. Wash with water and anhydrous ethanol 3-5 times respectively. Dry at 60°C for 12 hours to obtain bismuth subcarbonate.

[0053] Step 2: Mix bismuth subcarbonate and decabromodiphenyl ethane evenly in anhydrous ethanol, add paraffin oil and coupling agent, sonicate for 30 minutes, then mechanically stir at room temperature at a speed of 300 rpm for 80 minutes, and then dry at 50°C for 12 hours to obtain modified bismuth-based flame retardant powder.

[0054] Step 3: Mix natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber in a mixer for 0.5-30 minutes to obtain a mixed rubber compound; continue to add carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder obtained in Step 1, aluminum diethylphosphinate, and diethyl phthalate in sequence and mix in a mixer for 10 minutes. Then, continue to add antioxidant, accelerator, and insoluble sulfur in sequence and mix in a mixer for 8 minutes to obtain a compound rubber.

[0055] Step 4: Place the rubber compound obtained in Step 3 at room temperature for 2 hours, then roll it into triangular pieces and pass it through a thin mill 5-15 times, press it into sheets, and let it stand for 10 hours to obtain the mixed rubber sheet.

[0056] Step 5: Vulcanize the mixed film obtained in Step 4 using a flat vulcanizing machine at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 70°C, and a vulcanizing time of 10 minutes. Then, perform a secondary vulcanization in an oven at a vulcanizing temperature of 70°C for 3 hours.

[0057] Example 3

[0058] A flame-retardant rubber containing bismuth-based flame retardants comprises the following raw materials in parts by weight: 60 parts natural rubber, 15 parts nitrile rubber, 15 parts styrene-butadiene rubber, 20 parts chloroprene rubber, 45 parts carbon black, 5 parts stearic acid, 10 parts zinc oxide, 20 parts decabromodiphenyl ethane, 15 parts aluminum diethylphosphinate, 1.8 parts diethyl phthalate, 5 parts paraffin oil, 3 parts insoluble sulfur, 1.5 parts accelerator, 1.5 parts antioxidant, 1-2 parts silane coupling agent (Si-69), and 50 parts bismuth oxychloride.

[0059] The accelerator is composed of tetrathiotetramethylthiuram, methylene diphenyl diamine, diphenylguanidine, and N,N'-diethyl-2-benzo[3]benzo[4]thiazole sulfenamide; the antioxidant is composed of polymethylene aniline, polycarbodiimide, and p-tert-butylphenol.

[0060] The preparation method of the above-mentioned flame-retardant rubber containing bismuth-based flame retardants includes the following steps:

[0061] Step 1: Bismuth nitrate pentahydrate and potassium chloride were mixed in a 1:1 molar ratio and dissolved in water. After stirring for 30 minutes, sodium hydroxide aqueous solution was added dropwise to the resulting solution, and the mixture was stirred for 3 hours. The mixture was then transferred to a microwave reactor and placed in a microwave high-pressure synthesizer. It was kept at 120°C for 0.5 hours, and then cooled to obtain a precipitate. The precipitate was washed three times each with water and anhydrous ethanol, and dried at 60°C for 12 hours to obtain bismuth oxychloride.

[0062] Step 2: Mix bismuth oxychloride and decabromodiphenyl ethane evenly in anhydrous ethanol, add paraffin oil and coupling agent, homogenize by ultrasonication for 30 minutes, then mechanically stir at room temperature at a stirring speed of 300 rpm for 90 minutes, and then dry at 60°C for 12 hours to obtain modified bismuth-based flame retardant powder.

[0063] Step 3: Mix natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber in a mixer for 0.5-30 minutes to obtain a mixed rubber compound; continue to add carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder obtained in Step 1, aluminum diethylphosphinate, and diethyl phthalate in sequence and mix in a mixer for 10 minutes. Then, continue to add antioxidant, accelerator, and insoluble sulfur in sequence and mix in a mixer for 8 minutes to obtain a compound rubber.

[0064] Step 4: Place the rubber compound obtained in Step 3 at room temperature for 2 hours, then roll it into triangular pieces and pass it through a thin mill 5-15 times, press it into sheets, and let it stand for 10 hours to obtain the mixed rubber sheet.

[0065] Step 5: Vulcanize the mixed film obtained in Step 4 using a flat vulcanizing machine at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 80°C, and a vulcanizing time of 15 minutes. Then, perform a secondary vulcanization in an oven at a vulcanizing temperature of 80°C for 6 hours.

[0066] Example 4

[0067] A flame-retardant rubber containing bismuth-based flame retardants comprises the following raw materials in parts by weight: 70 parts natural rubber, 10 parts nitrile rubber, 15 parts styrene-butadiene rubber, 15 parts chloroprene rubber, 45 parts carbon black, 5 parts stearic acid, 5 parts zinc oxide, 15 parts decabromodiphenyl ethane, 15 parts aluminum diethylphosphinate, 2 parts diethyl phthalate, 9 parts paraffin oil, 3.5 parts insoluble sulfur, 2 parts accelerator, 2 parts antioxidant, 1-2 parts bis(dioctyloxypyrophosphate)ethylene titanate coupling agent, and 60 parts bismuth oxide.

[0068] The accelerator consists of hexamethylenetetramine, tetramethylthiourea and 2-thiol benzothiazole; the antioxidant is 3-methyl-6-tert-butylphenol and 3,5'-di-tert-butyl-4-hydrobenzyl phosphate diethyl ester.

[0069] The preparation method of the above-mentioned flame-retardant rubber containing bismuth-based flame retardants includes the following steps:

[0070] Step 1: Using bismuth hydroxide powder as raw material, the raw material is ground in a mortar and pestle, heated to 400-800℃ and kept at that temperature for 2-4 hours, with a heating rate of 5-10℃ / minute. After cooling, bismuth oxide is obtained, and then mechanically crushed to obtain bismuth oxide.

[0071] Step 2: Mix bismuth oxide and decabromodiphenyl ethane evenly in anhydrous ethanol, add paraffin oil and coupling agent, homogenize by ultrasonication for 40 minutes, then mechanically stir at room temperature at a stirring speed of 300 rpm for 80 minutes, and then dry at 80°C for 10 hours to obtain modified bismuth-based flame retardant powder.

[0072] Step 3: Mix natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber in a mixer for 0.5-30 minutes to obtain a mixed rubber compound; continue to add carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder obtained in Step 1, aluminum diethylphosphinate, and diethyl phthalate in sequence and mix in a mixer for 15 minutes. Then, continue to add antioxidant, accelerator, and insoluble sulfur in sequence and mix in a mixer for 10 minutes to obtain a compound rubber.

[0073] Step 4: Place the rubber compound obtained in Step 3 at room temperature for 2 hours, then roll it into triangular pieces and pass it through a thin mill 5-15 times, press it into sheets, and let it stand for 10 hours to obtain the mixed rubber sheet.

[0074] Step 5: Vulcanize the mixed film obtained in Step 4 using a flat vulcanizing machine at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100℃, and a vulcanizing time of 20 minutes. Then, perform a secondary vulcanization in an oven at a vulcanizing temperature of 100℃ for 4 hours.

[0075] Example 5

[0076] A flame-retardant rubber mat with good flame-retardant effect comprises the following raw materials in parts by weight: 70 parts natural rubber, 20 parts nitrile rubber, 10 parts styrene-butadiene rubber, 10 parts chloroprene rubber, 40 parts carbon black, 4 parts stearic acid, 7 parts zinc oxide, 15 parts decabromodiphenyl ethane, 10 parts aluminum diethylphosphinate, 3 parts diethyl phthalate, 5 parts paraffin oil, 2.8 parts insoluble sulfur, 1.5 parts accelerator, 2.5 parts antioxidant, 1-2 parts isopropyl dioleoyl oxy(dioctyl phosphate oxy) titanate coupling agent, and 60 parts bismuth hydroxide.

[0077] The accelerator consists of tetramethylthiuram disulfide and hexamethylenetetramine; the antioxidant is diethyl 3,5'-di-tert-butyl-4-hydrobenzyl phosphate.

[0078] The preparation method of the above-mentioned flame-retardant rubber containing bismuth-based flame retardants includes the following steps:

[0079] Step 1: Add sodium hydroxide solution dropwise to bismuth nitrate solution to adjust the pH to 11; heat in a 60°C water bath and stir for 3 hours; use a centrifuge to separate the reaction product into solid and liquid phases, wash the solid precipitate three times with deionized water and twice with anhydrous ethanol. Dry the precipitate in air at 60°C for 12 hours to obtain bismuth hydroxide;

[0080] Step 2: Mix bismuth hydroxide and decabromodiphenyl ethane evenly in anhydrous ethanol, add paraffin oil and coupling agent, sonicate for 40 minutes, then mechanically stir at room temperature at a speed of 350 rpm for 60 minutes, and then dry at 60°C for 10 hours to obtain modified bismuth-based flame retardant powder.

[0081] Step 3: Mix natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber in a mixer for 0.5-30 minutes to obtain a mixed rubber compound; continue to add carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder obtained in Step 1, aluminum diethylphosphinate, and diethyl phthalate in sequence and mix in a mixer for 10 minutes. Then, continue to add antioxidant, accelerator, and insoluble sulfur in sequence and mix in a mixer for 8 minutes to obtain a compound rubber.

[0082] Step 4: Place the rubber compound obtained in Step 3 at room temperature for 2 hours, then roll it into triangular pieces and pass it through a thin mill 5-15 times, press it into sheets, and let it stand for 10 hours to obtain the mixed rubber sheet.

[0083] Step 5: Vulcanize the mixed rubber obtained in Step 4 using a flat vulcanizing machine at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 110℃, and a vulcanizing time of 5 minutes. Then, perform a secondary vulcanization using an oven at a vulcanizing temperature of 110℃ for 5 hours.

[0084] Example 6

[0085] A flame-retardant rubber containing bismuth-based flame retardants comprises the following raw materials in parts by weight: 70 parts natural rubber, 15 parts nitrile rubber, 15 parts styrene-butadiene rubber, 10 parts chloroprene rubber, 50 parts carbon black, 4 parts stearic acid, 7 parts zinc oxide, 20 parts decabromodiphenyl ethane, 10 parts aluminum diethylphosphinate, 3 parts diethyl phthalate, 5 parts paraffin oil, 2.8 parts insoluble sulfur, 1.5 parts accelerator, 2.5 parts antioxidant, 1-2 parts isopropyl dioleoyl oxy(dioctyl phosphoyl oxy) titanate coupling agent, 20 parts bismuth oxide, and 30 parts bismuth hydroxide.

[0086] The accelerator consists of tetramethylthiuram disulfide and dibenzothiazole disulfide; the antioxidant is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

[0087] The preparation method of the above-mentioned flame-retardant rubber containing bismuth-based flame retardants includes the following steps:

[0088] Step 1: Mix bismuth oxide, bismuth hydroxide and decabromodiphenyl ethane evenly in anhydrous ethanol, add paraffin oil and coupling agent, sonicate for 25 minutes, then mechanically stir at room temperature at a speed of 350 rpm for 50 minutes, and then dry at 60°C for 12 hours to obtain modified bismuth-based flame retardant powder.

[0089] Step 2: Mix natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber in a mixer for 15 minutes to obtain a mixed rubber compound; then add carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder obtained in Step 1, aluminum diethylphosphinate, and diethyl phthalate in sequence and mix in a mixer for 20 minutes. Then add antioxidant, accelerator, and insoluble sulfur in sequence and mix in a mixer for 20 minutes to obtain a compound rubber.

[0090] Step 3: Place the rubber compound obtained in Step 2 at room temperature for 2 hours, then roll it into a triangular shape and pass it through a thin sheet 5-15 times on a two-roll mill, press it into a sheet, and let it stand for 12 hours to obtain the mixed rubber sheet.

[0091] Step 4: Vulcanize the mixed film obtained in Step 3 using a flat vulcanizing machine at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100℃, and a vulcanizing time of 10 minutes. Then, perform a secondary vulcanization in an oven at a vulcanizing temperature of 100℃ for 5 hours.

[0092] Example 7

[0093] A flame-retardant rubber containing bismuth-based flame retardants comprises the following raw materials in parts by weight: 80 parts natural rubber, 10 parts nitrile rubber, 10 parts styrene-butadiene rubber, 10 parts chloroprene rubber, 40 parts carbon black, 3 parts stearic acid, 10 parts zinc oxide, 20 parts decabromodiphenyl ethane, 10 parts aluminum diethylphosphinate, 1.5 parts diethyl phthalate, 6 parts paraffin oil, 2.8 parts insoluble sulfur, 1.8 parts accelerator, 1.8 parts antioxidant, 1-2 parts silane coupling agent (Si-69), 10 parts bismuth subcarbonate, and 30 parts bismuth oxychloride.

[0094] The accelerator consists of tetramethylthiuram disulfide and dibenzothiazole disulfide; the antioxidant is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

[0095] The preparation method of the above-mentioned flame-retardant rubber containing bismuth-based flame retardants includes the following steps:

[0096] Step 1: Mix bismuth subcarbonate, bismuth oxychloride and decabromodiphenyl ethane evenly in anhydrous ethanol, add paraffin oil and coupling agent, homogenize by sonication for 40 minutes, then mechanically stir at room temperature at a speed of 250 rpm for 80 minutes, and then dry at 60°C for 12 hours to obtain modified bismuth-based flame retardant powder.

[0097] Step 2: Mix natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber in a mixer for 15 minutes to obtain a mixed rubber compound; then add carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder obtained in Step 1, aluminum diethylphosphinate, and diethyl phthalate in sequence and mix in a mixer for 20 minutes. Then add antioxidant, accelerator, and insoluble sulfur in sequence and mix in a mixer for 20 minutes to obtain a compound rubber.

[0098] Step 3: Place the rubber compound obtained in Step 2 at room temperature for 2 hours, then roll it into a triangular shape and pass it through a thin sheet 5-15 times on a two-roll mill, press it into a sheet, and let it stand for 12 hours to obtain the mixed rubber sheet.

[0099] Step 4: Vulcanize the mixed film obtained in Step 3 using a flat vulcanizing machine at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100℃, and a vulcanizing time of 10 minutes. Then, perform a secondary vulcanization in an oven at a vulcanizing temperature of 100℃ for 5 hours.

[0100] Comparative Example 1

[0101] The difference from Example 1 is that the bismuth oxychloride content is replaced with 6 parts instead of 60 parts, while the other steps and parameters are the same as in Example 1.

[0102] Comparative Example 2

[0103] The difference from Example 2 is that the coupling agent is replaced by γ-(2,3-epoxypropoxy)propyltrimethoxysilane instead of isopropyldistearate. All other steps and parameters are the same as in Example 2.

[0104] Comparative Example 3

[0105] The difference from Example 6 is that bismuth hydroxide is not added, but the other steps and parameters are the same as in Example 6.

[0106] Comparative Example 4

[0107] The difference from Example 7 is that bismuth oxychloride is not added, but the other steps and parameters are the same as in Example 7.

[0108] The flame-retardant rubbers prepared in Examples 1-7 and Comparative Examples 1-4 were used as samples for performance testing. The tensile strength of the samples was determined according to GB / T528-2009 for physical and mechanical properties. The limiting oxygen index was tested using a JF-3 oxygen index tester, following the standard GB-T10707-2008. The test results are shown in Table 1 below.

[0109] Table 1. Performance test results of the flame-retardant rubbers prepared in Examples 1-7 and Comparative Examples 1-4.

[0110]

[0111]

[0112] As shown in Table 1 above, the bismuth oxide, bismuth oxychloride, bismuth hydroxide, and bismuth subcarbonate introduced in this invention are environmentally friendly flame retardants. While ensuring the tensile properties of the product, they effectively improve its fire resistance, delay ignition, reduce the flame propagation speed, and enhance the safety of the product.

[0113] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flame-retardant rubber containing a bismuth-based flame retardant, characterized in that, The composition, by weight, includes the following components: 60-100 parts natural rubber, 10-20 parts nitrile rubber, 10-20 parts styrene-butadiene rubber, 10-20 parts chloroprene rubber, 30-60 parts carbon black, 3-12 parts stearic acid, 5-10 parts zinc oxide, 3-50 parts decabromodiphenyl ethane, 5-30 parts aluminum diethylphosphinate, 0.8-3 parts diethyl phthalate, 2-18 parts paraffin oil, 1-3 parts coupling agent, 2-6 parts insoluble sulfur, 1.5-2.5 parts accelerator, 1.5-3 parts antioxidant, and 40-100 parts bismuth-based flame retardant. The bismuth-based flame retardant is at least one of bismuth oxychloride and bismuth subcarbonate; The coupling agent is at least one of isopropyl distearate aluminoacrylate and Si-69.

2. The flame-retardant rubber containing a bismuth-based flame retardant according to claim 1, characterized in that, The accelerator is at least one of tetramethylthiuram disulfide and dibenzothiazole disulfide.

3. The flame-retardant rubber containing a bismuth-based flame retardant according to claim 1, characterized in that, The antioxidant is a 2,2,4-trimethyl-1,2-dihydroquinoline polymer.

4. A method for preparing a flame-retardant rubber containing a bismuth-based flame retardant as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Mix bismuth-based flame retardant and decabromodiphenyl ethane evenly in anhydrous ethanol, then add paraffin oil and coupling agent and homogenize by ultrasonication. Stir mechanically at room temperature and dry to obtain modified bismuth-based flame retardant powder. S2: Natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber are put into a mixer for mixing; carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder, aluminum diethylphosphinate, and diethyl phthalate are added in sequence for mixing; then, antioxidant, accelerator, and insoluble sulfur are added in sequence for mixing to obtain the compound rubber. S3: Place the compounded rubber at room temperature, form triangular bags on a two-roll mill and pass through them in thin strips multiple times, press them into sheets, and let them stand to obtain mixed rubber sheets; S4: The mixed film is vulcanized once using a flat vulcanizing machine and then vulcanized a second time using an oven to obtain the final product.

5. The method for preparing a flame-retardant rubber containing a bismuth-based flame retardant according to claim 4, characterized in that, In step S1, the ultrasonic homogenization time is 5-60 minutes; the mechanical stirring speed is 250-400 rpm and the stirring time is 5-240 minutes; the drying temperature is 50-80℃ and the drying time is 1-15 hours.

6. The method for preparing a flame-retardant rubber containing a bismuth-based flame retardant according to claim 4, characterized in that, In step S2, the mixing times for the three mixing stages are 0.5~30 minutes, 5~40 minutes, and 2~20 minutes, respectively.

7. The method for preparing a flame-retardant rubber containing a bismuth-based flame retardant according to claim 4, characterized in that, In step S3, the placement time is 0.5 to 3 hours; the tube is passed through 5 to 15 times, and then left to stand for 5 to 24 hours.

8. The method for preparing a flame-retardant rubber containing a bismuth-based flame retardant according to claim 4, characterized in that, In step S4, the primary vulcanization pressure is 10 MPa, the vulcanization temperature is 70~130℃, and the vulcanization time is 3~25 minutes; the secondary vulcanization temperature is 80~150℃, and the vulcanization time is 3~8 hours.

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