Flame-retardant rubber containing bismuth-based flame retardant and preparation method of flame-retardant rubber

Abstract

The invention provides flame-retardant rubber containing a bismuth-based flame retardant and a preparation method of the flame-retardant rubber, and belongs to the technical field of flame-retardant rubber. Natural rubber, nitrile rubber, butadiene styrene rubber and chloroprene rubber are adopted as main base materials, and at least one of bismuth oxide, bismuth oxychloride, bismuth hydroxide and bismuth subcarbonate is introduced as an environment-friendly flame retardant, so that the flame-retardant effect of the product is ensured; meanwhile, the use of complex solvents and the discharge of potential byproducts are reduced, and the method is an important way for realizing ideal green life. Carbon black, stearic acid, zinc oxide, decabromodiphenyl ethane, aluminum diethylphosphinate, diethyl phthalate, paraffin oil, a coupling agent, insoluble sulfur, an accelerant, an anti-aging agent and other substances are also added, and through multiple times of mixing and banburying, the tensile property of the product is guaranteed, meanwhile, the fireproof performance of the product is effectively improved, ignition is delayed, and the flame propagation speed is reduced; and the use safety of the product is improved.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant rubber, and in particular to a flame retardant rubber containing a bismuth-based flame retardant and a preparation method thereof. Background Art

[0002] The molecular structure of most rubber composites is composed of carbon and hydrogen elements, which can lead to highly flammable properties, with flames spreading rapidly and producing large amounts of toxic smoke. The combustion behavior is based on free radical chain reactions, where oxidation is an autocatalytic process leading to uncontrolled destruction.

[0003] According to the International Rubber Research Group, the global annual rubber consumption is expected to exceed 30 million tons. As one of the most important biopolymers, natural rubber extracted directly from plants and its composites have a series of unique properties such as elasticity, wear resistance, impact resistance and low-temperature ductility. Their comprehensive properties make them indispensable in daily life, transportation and industrial systems. However, since most widely used rubber composites are combustible, their rapid burning when ignited will greatly accelerate the destruction of the entire system, and the toxic fumes may also pose a great threat to life. The toxic gases produced by traditional halogen-based flame retardants cause serious pollution to the environment and have been widely banned in recent years. Bionic flame retardants, halogen-free flame retardants and flame retardants from sustainable sources have attracted more and more attention, but due to their limited flame retardant efficiency, large additions often affect the overall performance of the composites. Therefore, how to design green and efficient flame retardant systems and expand the advanced applications of rubber composites remains a huge challenge. Summary of the invention

[0004] In order to solve the above-mentioned problems existing in the background technology, an embodiment of the present invention provides a flame retardant rubber containing a bismuth-based flame retardant, which includes the following components by weight: 60-100 parts of natural rubber, 10-20 parts of nitrile rubber, 10-20 parts of styrene-butadiene rubber, 10-20 parts of chloroprene rubber, 30-60 parts of carbon black, 3-12 parts of stearic acid, 5-10 parts of zinc oxide, 3-50 parts of decabromodiphenylethane, 5-30 parts of diethyl aluminum phosphinate, 0.8-3 parts of diethyl phthalate, 2-18 parts of paraffin oil, 1-3 parts of coupling agent, 2-6 parts of insoluble sulfur, 1.5-2.5 parts of accelerator, 1.5-3 parts of antioxidant, and 30-100 parts of bismuth-based flame retardant.

[0005] According to one aspect of an embodiment of the present invention, the accelerator is at least one of tetramethylthiuram disulfide, tetramethylthiuram tetrasulfide, methylenediphenyldiamine, diphenylguanidine, N,N'-diethyl-2-benzobenzothiazolesulfonamide, hexamethylenetetramine, tetramethylthiourea, 2-thiolbenzothiazole, and dibenzothiazole disulfide.

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

[0007] According to one aspect of an embodiment of the present invention, the coupling agent is at least one of isopropyl distearate acyloxyaluminate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl dioleate acyloxy (dioctyl phosphate acyloxy) titanate, isopropyl trioleate acyloxy titanate, Si-69, vinyl trimethoxy silane, and vinyl triethoxy silane.

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

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

[0010] S1: taking a bismuth-based flame retardant and decabromodiphenylethane and mixing them evenly in anhydrous ethanol, then adding paraffin oil and a coupling agent for ultrasonic homogenization, mechanically stirring at room temperature, and drying to obtain a modified bismuth-based flame retardant powder;

[0011] S2: natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber are put into an internal mixer for mixing; carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder, diethyl aluminum phosphinate, and diethyl phthalate are sequentially added for mixing; an antioxidant, an accelerator, and insoluble sulfur are sequentially added for mixing to obtain a mixed rubber;

[0012] S3: placing the mixed rubber at room temperature, making triangular packages on an open mixing mill, thinning the packages several times, pressing the sheets, and letting the mixed rubber stand to obtain a mixed sheet;

[0013] S4: The mixed rubber sheet is subjected to primary vulcanization using a flat vulcanizer, and then subjected to secondary vulcanization using an oven, to obtain the mixed rubber sheet.

[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 the embodiment of the present invention, in step S2, the mixing time of the three mixing stages is 0.5 to 30 minutes, 5 to 40 minutes, and 2 to 20 minutes, respectively.

[0016] According to one aspect of the embodiments of the present invention, in step S3, the standing time is 0.5 to 3 hours; the thin pass is repeated 5 to 15 times, and the mixture is left standing 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 scheme of the present invention has the following beneficial effects:

[0019] (1) The present invention uses natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber as main base materials, and introduces at least one of bismuth oxide, bismuth oxychloride, bismuth hydroxide, and bismuth subcarbonate as an environmentally friendly flame retardant, thereby ensuring 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 further adds carbon black, stearic acid, zinc oxide, decabromodiphenylethane, aluminum diethylphosphinate, diethyl phthalate, paraffin oil, coupling agent, insoluble sulfur, accelerator, antioxidant and the like, and through multiple mixing and kneading, effectively improves the fire resistance of the product while ensuring the tensile properties of the product, delays ignition, reduces the flame propagation speed, and improves the safety of product use. DETAILED DESCRIPTION

[0021] In order to make the technical problems to be solved, technical solutions and advantages of the present invention more clear, they are described in detail below in conjunction with specific embodiments.

[0022] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

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

[0024] In view of the existing problems, the invention provides a flame retardant rubber containing a bismuth-based flame retardant. The flame retardant rubber comprises the following components in parts by weight: 60-100 parts of natural rubber, 10-20 parts of nitrile rubber, 10-20 parts of styrene-butadiene rubber, 10-20 parts of chloroprene rubber, 30-60 parts of carbon black, 3-12 parts of stearic acid, 5-10 parts of zinc oxide, 3-50 parts of decabromodiphenylethane, 5-30 parts of diethyl aluminum phosphinate, 0.8-3 parts of diethyl phthalate, 2-18 parts of paraffin oil, 1-3 parts of a coupling agent, 2-6 parts of insoluble sulfur, 1.5-2.5 parts of an accelerator, 1.5-3 parts of an antioxidant and 30-100 parts of a bismuth-based flame retardant.

[0025] According to one aspect of an embodiment of the present invention, the accelerator is at least one of tetramethylthiuram disulfide, tetramethylthiuram tetrasulfide, methylenediphenyldiamine, diphenylguanidine, N,N'-diethyl-2-benzobenzothiazolesulfonamide, hexamethylenetetramine, tetramethylthiourea, 2-thiolbenzothiazole, and dibenzothiazole disulfide.

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

[0027] According to one aspect of an embodiment of the present invention, the coupling agent is at least one of isopropyl distearate acyloxyaluminate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl dioleate acyloxy (dioctyl phosphate acyloxy) titanate, isopropyl trioleate acyloxy titanate, Si-69, vinyl trimethoxy silane, and vinyl triethoxy silane.

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

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

[0030] S1: taking a bismuth-based flame retardant and decabromodiphenylethane and mixing them evenly in anhydrous ethanol, then adding paraffin oil and a coupling agent for ultrasonic homogenization, mechanically stirring at room temperature, and drying to obtain a modified bismuth-based flame retardant powder;

[0031] S2: natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber are put into an internal mixer for mixing; carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder, diethyl aluminum phosphinate, and diethyl phthalate are sequentially added for mixing; an antioxidant, an accelerator, and insoluble sulfur are sequentially added for mixing to obtain a mixed rubber;

[0032] S3: placing the mixed rubber at room temperature, making triangular packages on an open mixing mill, thinning the packages several times, pressing the sheets, and letting the mixed rubber stand to obtain a mixed sheet;

[0033] S4: The mixed rubber sheet is subjected to primary vulcanization using a flat vulcanizer, and then subjected to secondary vulcanization using an oven, to obtain the mixed rubber sheet.

[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 the embodiment of the present invention, in step S2, the mixing time of the three mixing stages is 0.5 to 30 minutes, 5 to 40 minutes, and 2 to 20 minutes, respectively.

[0036] According to one aspect of the embodiments of the present invention, in step S3, the standing time is 0.5 to 3 hours; the thin pass is repeated 5 to 15 times, and the mixture is left standing 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 explain in detail through specific implementation methods.

[0039] Example 1

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

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

[0042] The method for preparing the flame retardant rubber containing bismuth flame retardant comprises the following steps:

[0043] Step 1: Dissolve bismuth nitrate pentahydrate and potassium chloride in water in a 1:1 ratio, stir for 30 minutes, then drop sodium hydroxide aqueous solution into the resulting solution and stir for 3 hours. Then transfer the mixture to a hydrothermal reactor, keep it at 180°C for 16 hours, and cool it to obtain a precipitate; wash the resulting precipitate with water and anhydrous ethanol for 3-5 times, respectively, and dry it at 60-80°C for 8-10 hours to obtain bismuth oxychloride;

[0044] Step 2: bismuth oxychloride and decabromodiphenylethane are mixed evenly in anhydrous ethanol, paraffin oil and a coupling agent are added, and after ultrasonic homogenization for 30 minutes, mechanical stirring is performed at room temperature at a stirring speed of 300 rpm for 60 minutes, and then dried at 80° C. for 8 hours to obtain a modified bismuth-based flame retardant powder;

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

[0046] Step 4: placing the mixed rubber obtained in step 3 at room temperature for 2 hours, then making triangle packages on an open mixing mill, passing through the mixture 5-15 times, pressing the mixture into sheets, and standing the mixture for 10 hours to obtain a mixed sheet;

[0047] Step 5: The mixed rubber obtained in step 4 is vulcanized using a flat vulcanizer at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100° C., and a vulcanizing time of 12 minutes. Afterwards, a secondary vulcanization is performed using an oven at a vulcanizing temperature of 100° C. and a vulcanizing time of 3 hours.

[0048] Example 2

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

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

[0051] The method for preparing the flame retardant rubber containing bismuth flame retardant comprises the following steps:

[0052] Step 1: After stirring pentahydrate nitric acid and ethylene glycol at a mass ratio of 3:2 at room temperature for 30 minutes, sodium carbonate and water are evenly mixed at a mass ratio of 1:2, and sodium carbonate aqueous solution is added dropwise to the mixed solution of pentahydrate nitric acid and ethylene glycol. After continuing to stir for 3 hours, the mixture is washed with water and anhydrous ethanol for 3-5 times respectively, and dried at 60°C for 12 hours to obtain bismuth subcarbonate;

[0053] Step 2: Mix bismuth subcarbonate and decabromodiphenylethane in anhydrous ethanol, add paraffin oil and a coupling agent, perform ultrasonic homogenization for 30 minutes, and then perform mechanical stirring at room temperature at a stirring speed of 300 rpm for 80 minutes, and then dry at 50° C. for 12 hours to obtain a modified bismuth-based flame retardant powder;

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

[0055] Step 4: placing the mixed rubber obtained in step 3 at room temperature for 2 hours, then making triangle packages on an open mixing mill, passing through the mixture 5-15 times, pressing the mixture into sheets, and standing the mixture for 10 hours to obtain a mixed sheet;

[0056] Step 5: The mixed rubber obtained in step 4 is vulcanized using a flat vulcanizer at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 70° C., and a vulcanizing time of 10 minutes. Afterwards, a secondary vulcanization is performed using an oven at a vulcanizing temperature of 70° C. and a vulcanizing time of 3 hours.

[0057] Example 3

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

[0059] The accelerator consists of tetramethylthiuram tetrasulfide, methylenediphenylenediamine, diphenylguanidine and N,N'-diethyl-2-benzoylbenzothiazolesulfonamide; and the antioxidant consists of polymethyleneaniline, polycarbodiimide and p-tert-butylphenol.

[0060] The method for preparing the flame retardant rubber containing bismuth flame retardant comprises the following steps:

[0061] Step 1: Dissolve bismuth nitrate pentahydrate and potassium chloride in water in a 1:1 ratio, stir for 30 minutes, then drop sodium hydroxide aqueous solution into the resulting solution and stir for 3 hours. Then transfer the mixture to a microwave reactor, place it in a microwave high-pressure synthesizer, keep it warm at 120°C for 0.5 hours, and cool it to obtain a precipitate. Wash the resulting precipitate with water and anhydrous ethanol three times each, and dry it at 60°C for 12 hours to obtain bismuth oxychloride;

[0062] Step 2: Mix bismuth oxychloride and decabromodiphenylethane in anhydrous ethanol, add paraffin oil and a coupling agent, perform ultrasonic homogenization for 30 minutes, and then perform mechanical stirring at room temperature at a stirring speed of 300 rpm for 90 minutes, and then dry at 60° C. for 12 hours to obtain a modified bismuth-based flame retardant powder;

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

[0064] Step 4: placing the mixed rubber obtained in step 3 at room temperature for 2 hours, then making triangle packages on an open mixing mill, passing through the mixture 5-15 times, pressing the mixture into sheets, and standing the mixture for 10 hours to obtain a mixed sheet;

[0065] Step 5: The mixed rubber obtained in step 4 is vulcanized using a flat vulcanizer at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 80° C., and a vulcanizing time of 15 minutes. Afterwards, a secondary vulcanization is performed using an oven at a vulcanizing temperature of 80° C. and a vulcanizing time of 6 hours.

[0066] Example 4

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

[0068] The accelerator is composed of hexamethylenetetramine, tetramethylthiourea and 2-thiolbenzothiazole; the antioxidant is 3-methyl-6-tert-butylphenol and 3,5'-di-tert-butyl-4-hydrogen benzyl diethyl phosphate.

[0069] The method for preparing the flame retardant rubber containing bismuth flame retardant comprises the following steps:

[0070] Step 1: using bismuth hydroxide powder as a raw material, grinding the raw material in a mortar, heating to 400-800°C for 2-4 hours at a heating rate of 5-10°C / min, cooling to obtain bismuth oxide, and then mechanically crushing to obtain bismuth oxide;

[0071] Step 2: Mix bismuth oxide and decabromodiphenylethane in anhydrous ethanol, add paraffin oil and a coupling agent, perform ultrasonic homogenization for 40 minutes, and then perform mechanical stirring at room temperature at a stirring speed of 300 rpm for 80 minutes, and then dry at 80° C. for 10 hours to obtain a modified bismuth-based flame retardant powder;

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

[0073] Step 4: placing the mixed rubber obtained in step 3 at room temperature for 2 hours, then making triangle packages on an open mixing mill, passing through the mixture 5-15 times, pressing the mixture into sheets, and standing the mixture for 10 hours to obtain a mixed sheet;

[0074] Step 5: The mixed rubber obtained in step 4 is vulcanized using a flat vulcanizer at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100° C., and a vulcanizing time of 20 minutes. Afterwards, a secondary vulcanization is performed using an oven at a vulcanizing temperature of 100° C. and a vulcanizing time of 4 hours.

[0075] Example 5

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

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

[0078] The method for preparing the flame retardant rubber containing bismuth flame retardant comprises the following steps:

[0079] Step 1: Add sodium hydroxide solution dropwise to bismuth nitrate solution, adjust pH value to 11; heat in a water bath at 60°C, stir and react for 3 hours; use centrifugal equipment to separate the solid and liquid of the reaction product, wash the solid precipitate with deionized water 3 times and anhydrous ethanol 2 times. Dry the above precipitate at 60°C for 12 hours under air atmosphere to obtain bismuth hydroxide;

[0080] Step 2: Mix bismuth hydroxide and decabromodiphenylethane in anhydrous ethanol, add paraffin oil and a coupling agent, perform ultrasonic homogenization for 40 minutes, and then perform mechanical stirring at room temperature at a stirring speed of 350 rpm for 60 minutes, and then dry at 60° C. for 10 hours to obtain a modified bismuth-based flame retardant powder;

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

[0082] Step 4: placing the mixed rubber obtained in step 3 at room temperature for 2 hours, then making triangle packages on an open mixing mill, passing through the mixture 5-15 times, pressing the mixture into sheets, and standing the mixture for 10 hours to obtain a mixed sheet;

[0083] Step 5: vulcanize the mixed rubber obtained in step 4 using a flat vulcanizer at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 110° C., and a vulcanizing time of 5 minutes. Afterwards, perform secondary vulcanization in an oven at a vulcanizing temperature of 110° C. and a vulcanizing time of 5 hours.

[0084] Example 6

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

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

[0087] The method for preparing the flame retardant rubber containing bismuth flame retardant comprises the following steps:

[0088] Step 1: bismuth oxide, bismuth hydroxide and decabromodiphenylethane are mixed evenly in anhydrous ethanol, paraffin oil and a coupling agent are added, and after ultrasonic homogenization for 25 minutes, mechanical stirring is performed at room temperature at a stirring speed of 350 rpm for 50 minutes, and then dried at 60° C. for 12 hours to obtain a modified bismuth-based flame retardant powder;

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

[0090] Step 3: placing the mixed rubber obtained in step 2 at room temperature for 2 hours, then making triangle packages on an open mixing mill, passing through the mixture 5-15 times, pressing the mixture into sheets, and letting it stand for 12 hours to obtain a mixed sheet;

[0091] Step 4: The mixed rubber obtained in step 3 is vulcanized using a flat vulcanizer at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100° C., and a vulcanizing time of 10 minutes. Afterwards, a secondary vulcanization is performed using an oven at a vulcanizing temperature of 100° C. and a vulcanizing time of 5 hours.

[0092] Example 7

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

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

[0095] The method for preparing the flame retardant rubber containing bismuth flame retardant comprises the following steps:

[0096] Step 1: bismuth subcarbonate, bismuth oxychloride and decabromodiphenylethane are mixed evenly in anhydrous ethanol, paraffin oil and a coupling agent are added, and after ultrasonic homogenization for 40 minutes, mechanical stirring is performed at room temperature at a stirring speed of 250 rpm for 80 minutes, and then dried at 60° C. for 12 hours to obtain a modified bismuth-based flame retardant powder;

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

[0098] Step 3: placing the mixed rubber obtained in step 2 at room temperature for 2 hours, then making triangle packages on an open mixing mill, passing through the mixture 5-15 times, pressing the mixture into sheets, and letting it stand for 12 hours to obtain a mixed sheet;

[0099] Step 4: The mixed rubber obtained in step 3 is vulcanized using a flat vulcanizer at a vulcanizing pressure of 10 MPa, a vulcanizing temperature of 100° C., and a vulcanizing time of 10 minutes. Afterwards, a secondary vulcanization is performed using an oven at a vulcanizing temperature of 100° C. and a vulcanizing time of 5 hours.

[0100] Comparative Example 1

[0101] The difference from Example 1 is that the content of bismuth oxychloride is replaced by 6 parts from 60 parts, and the other steps and parameters are the same as those 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 from isopropyl distearate acyloxyaluminate, and the other steps and parameters are the same as those in Example 2.

[0104] Comparative Example 3

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

[0106] Comparative Example 4

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

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

[0109] Table 1 Performance test table of flame retardant rubber prepared by Examples 1-7 and Comparative Examples 1-4

[0110]

[0111]

[0112] As can be seen from Table 1 above, the bismuth oxide, bismuth oxychloride, bismuth hydroxide and bismuth subcarbonate introduced in the present invention are used as environmentally friendly flame retardants, which effectively improve the fire resistance of the product while ensuring the tensile performance of the product, delay ignition, reduce the flame propagation speed, and improve the safety of product use.

[0113] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A flame retardant rubber containing a bismuth-based flame retardant, characterized in that: The invention comprises the following components in parts by weight: 60-100 parts of natural rubber, 10-20 parts of nitrile rubber, 10-20 parts of styrene-butadiene rubber, 10-20 parts of chloroprene rubber, 30-60 parts of carbon black, 3-12 parts of stearic acid, 5-10 parts of zinc oxide, 3-50 parts of decabromodiphenylethane, 5-30 parts of diethyl aluminum phosphinate, 0.8-3 parts of diethyl phthalate, 2-18 parts of paraffin oil, 1-3 parts of coupling agent, 2-6 parts of insoluble sulfur, 1.5-2.5 parts of accelerator, 1.5-3 parts of antioxidant and 30-100 parts of bismuth flame retardant.

2. The flame retardant rubber containing bismuth flame retardant according to claim 1, characterized in that: The accelerator is at least one of tetramethylthiuram disulfide, tetramethylthiuram tetrasulfide, methylenediphenyldiamine, diphenylguanidine, N,N'-diethyl-2-benzobenzothiazolesulfenamide, hexamethylenetetramine, tetramethylthiourea, 2-mercaptobenzothiazole, and dibenzothiazole disulfide.

3. The flame retardant rubber containing bismuth flame retardant according to claim 1, characterized in that: The antioxidant is at least one of octylated diphenylamine, polymethylene aniline, polycarbodiimide, p-tert-butylphenol, 3-methyl-6-tert-butylphenol, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, and 3,5'-di-tert-butyl-4-hydrogen benzyl diethyl phosphate.

4. The flame retardant rubber containing bismuth flame retardant according to claim 1, characterized in that: The coupling agent is at least one of isopropyl distearate acyloxyaluminate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl dioleate acyloxy (dioctyl phosphate acyloxy) titanate, isopropyl trioleate acyloxy titanate, Si-69, vinyl trimethoxy silane, and vinyl triethoxy silane.

5. The flame retardant rubber containing bismuth flame retardant according to claim 1, characterized in that: The bismuth-based flame retardant is at least one of bismuth oxide, bismuth oxychloride, bismuth hydroxide and bismuth subcarbonate.

6. The method for preparing a flame retardant rubber containing a bismuth flame retardant according to any one of claims 1 to 5, characterized in that: The steps include: S1: taking a bismuth-based flame retardant and decabromodiphenylethane and mixing them evenly in anhydrous ethanol, then adding paraffin oil and a coupling agent for ultrasonic homogenization, mechanically stirring at room temperature, and drying to obtain a modified bismuth-based flame retardant powder; S2: natural rubber, nitrile rubber, styrene-butadiene rubber, and chloroprene rubber are put into an internal mixer for mixing; carbon black, zinc oxide, stearic acid, the modified bismuth-based flame retardant powder, diethyl aluminum phosphinate, and diethyl phthalate are added in sequence for mixing; then, an antioxidant, an accelerator, and insoluble sulfur are added in sequence for mixing to obtain a mixed rubber; S3: placing the mixed rubber at room temperature, making triangular packages on an open mixing mill, thinning the packages several times, pressing the sheets, and letting the mixed rubber stand to obtain a mixed sheet; S4: The mixed rubber sheet is subjected to primary vulcanization using a flat vulcanizer, and then subjected to secondary vulcanization using an oven, to obtain the mixed rubber sheet.

7. The method for preparing a flame retardant rubber containing a bismuth-based flame retardant according to claim 6, characterized in that: 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.

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

9. The method for preparing a flame retardant rubber containing a bismuth-based flame retardant according to claim 6, characterized in that: In step S3, the standing time is 0.5 to 3 hours; the mixture is passed through 5 to 15 times and allowed to stand for 5 to 24 hours.

10. The method for preparing a flame retardant rubber containing a bismuth-based flame retardant according to claim 6, characterized in that: 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.

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