Highly flame-retardant rubber for conveyor belt and method for preparing the same

Abstract

This invention belongs to the field of high flame-retardant compound rubber preparation technology, and relates to a high flame-retardant compound rubber for conveyor belts and its preparation method. Styrene-butadiene rubber, flame-retardant additives, modified fillers, initiators, plasticizers, vulcanizing crosslinking agents, and vulcanizing agents are mixed in an internal mixer and then heat-treated to obtain the high flame-retardant compound rubber. The flame-retardant additive molecular chain contains phosphenanthrene groups and siloxane structures, which work synergistically to improve the material's flame-retardant ability. Simultaneously, the cage-like polysilsesquioxane structure on the molecular chain provides a dense organic-inorganic hybrid network structure for the material, which works synergistically with the rigid benzene ring to resist external forces and improve the material's wear resistance. The modified filler contains a high-hardness nano-silicon nitride core, which enhances the material's surface scratch and wear resistance. The outer coating of ammonium phosphate chitosan promotes the formation of a dense and stable carbonized layer on the material surface under high-temperature combustion.

Description

Technical Field

[0001] This invention relates to the field of high flame retardant compound rubber preparation technology, specifically to a high flame retardant compound rubber for conveyor belts and its preparation method. Background Technology

[0002] Conveyor belts, as key components of continuous material conveying equipment, are widely used in industries such as coal mining, power, ports, and chemicals. In these high-dust, high-risk operating environments, conveyor belts not only need excellent physical and mechanical properties to resist long-term impact and wear from materials, but also must meet stringent flame-retardant safety standards to prevent fires caused by frictional heat or external ignition sources. Currently, most flame-retardant conveyor belts on the market achieve their flame-retardant purpose by adding large amounts of halogenated or phosphorus-based flame retardants to the rubber matrix. However, in practical applications, existing technologies have significant performance bottlenecks. The core problem lies in the poor interfacial compatibility between inorganic flame retardants or highly polar flame-retardant additives and the non-polar rubber matrix. This incompatibility makes it difficult for the additives to achieve uniform dispersion in the rubber compound, easily leading to agglomeration and the formation of localized stress concentration points. These microstructural defects directly lead to contradictions in macroscopic performance: First, in terms of flame retardancy, agglomerated flame retardants cannot form a continuous and dense char layer or release flame-retardant gases on the material surface, resulting in low flame retardant efficiency; second, in terms of wear resistance, agglomerated particles disrupt the continuity of the rubber matrix, causing the wear points to preferentially expand from these weak interfaces when the cover rubber is subjected to material impact and friction, resulting in premature peeling of the cover rubber. Therefore, how to simultaneously optimize the flame retardant efficiency and wear resistance of the material while improving the compatibility between the flame retardant and the rubber matrix has become a core technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to provide a high flame-retardant compound rubber for conveyor belts, so as to solve the problems of weak resistance to material wear and low flame-retardant efficiency caused by poor component compatibility of traditional conveyor belt rubbers.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for preparing a high flame-retardant compound rubber for conveyor belts specifically includes the following steps: Styrene-butadiene rubber, flame retardant additives, modified fillers, initiators, plasticizers, vulcanizing crosslinking agents, and vulcanizing agents are placed in an internal mixer and mixed under pressure at a temperature of 80-90℃ and a pressure of 0.6-1.0MPa for 6-10 minutes to obtain a compound. The compound is then heat-treated at a temperature of 70-80℃ under nitrogen purging for 2-3 hours, and then sheeted in an open mill to obtain a high flame retardant compound rubber for conveyor belts.

[0005] Furthermore, the weight ratio of styrene-butadiene rubber, flame retardant additive, modified filler, initiator, plasticizer, vulcanizing crosslinking agent, and vulcanizing agent mentioned in the step is 60-80:20-35:5-10:0.2-0.4:0.1-0.2:0.6-0.8:0.4-0.6. The initiator is 1-hydroxycyclohexylphenyl ketone, the plasticizer is acetylated tributyl citrate, the vulcanizing crosslinking agent is triallyl isocyanurate, and the vulcanizing agent is 2,5-dimethyl-2,5-dihexane.

[0006] Furthermore, the flame retardant additive is prepared by the following steps: Step A1: Allyl alcohol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diphenyl ether are mixed evenly and reacted for 3-5 hours under the conditions of 130-150 r / min, 120-160℃ and nitrogen gas to obtain intermediate 1. Step A2: Mix intermediate 1, nadic anhydride, toluene and triethylamine evenly, and react for 4-8 hours at a speed of 100-120 r / min and a temperature of 60-80℃ to obtain intermediate 2. Mix styrene, butadiene and toluene evenly, and stir and add azobisisobutyronitrile at a speed of 110-140 r / min and a temperature of 50-60℃, and react for 2-3 hours. Add intermediate 2 and react for 1-2 hours to obtain the pretreatment additive. Step A3: Mix 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid evenly, and react for 20-24 hours at a speed of 80-100 r / min and a temperature of 40-50℃ to obtain cage-like polysilsesquioxane. Mix cage-like polysilsesquioxane, pretreatment additive and xylene evenly, and stir and add 1-methylimidazole at a speed of 150-170 r / min and a temperature of 100-120℃ to obtain flame retardant additive.

[0007] Furthermore, the molar ratio of allyl alcohol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A1 is 1 mmol:1.2 mmol.

[0008] Furthermore, in step A2, the ratio of intermediate 1, nadic anhydride, and triethylamine is 1 mmol: 1.1 mmol: 5 mL, and the ratio of styrene, butadiene, intermediate 2, toluene, and azobisisobutyronitrile is 1 g: 0.35 g: 0.2 g: 4 mL: 0.05 g.

[0009] Furthermore, in step A3, the ratio of 3-glycidyl etheroxypropyltrimethoxysilane, acetone, and hydrochloric acid is 1 mL:2 mL:0.8 mL, the mass fraction of hydrochloric acid is 20%, and the ratio of cage-type polysilsesquioxane, pretreatment additive, xylene, and 1-methylimidazole is 1.2 g:1.8 g:5 mL:0.04 g.

[0010] Furthermore, the modified filler is prepared by the following steps: Step B1: Disperse nano-silicon nitride in pure water and sonicate for 10-12 minutes at a frequency of 30-40 Hz and a pH of 2-3 to obtain a silicon nitride dispersion. Mix aluminum hydroxide, deionized water and phosphoric acid solution evenly, stir and add the silicon nitride dispersion at a speed of 200-300 r / min, react for 30-50 minutes, adjust the pH to 5, and obtain the pretreated filler. Step B2: Mix mercaptopropionic acid and N-hydroxysuccinimide evenly, stir and add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and deionized water at a speed of 100-120 r / min and a temperature of 20-30℃, and react for 1-2 h. Add acetic acid solution of chitosan and react for 20-24 h to obtain pretreated chitosan. Mix pretreated chitosan, pyridine, dichloromethane and 2,4-dinitrofluorobenzene evenly, and react for 3-5 h at a speed of 120-150 r / min and a temperature of 20-25℃ to obtain pretreated chitosan. Melt urea at a temperature of 140-150℃ under nitrogen gas to obtain pretreated urea. Step B3: Mix pretreated chitosan and phosphorous acid evenly. Stir and add pretreated urea at 200-300 r / min and 160-180℃ for 3-5 hours. Adjust the pH to 7 with ammonia to obtain ammonium phosphate chitosan. Mix ammonium phosphate chitosan, 2-mercaptoethanol and dichloromethane evenly. React at 120-130 r / min and 40-50℃ for 2-4 hours to obtain modified chitosan. Disperse the pretreated filler in deionized water. Stir and add modified chitosan at 150-180 r / min, 20-25℃ and pH 6-6.5 for 20-24 hours to obtain the modified filler.

[0011] Furthermore, in step B1, the ratio of nano-silicon nitride to pure water is 1g:15mL, and the ratio of aluminum hydroxide, deionized water, phosphoric acid solution, and silicon nitride dispersion is 0.58g:10mL:4.33g:40mL.

[0012] Further, the chitosan in step B2 has a weight-average molecular weight of 2000-3000 and a degree of deacetylation of 90-95%. The ratio of mercaptopropionic acid, N-hydroxysuccinimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, deionized water, and acetic acid solution of chitosan is 5 mmol:4.2 mmol:4.2 mmol:20 mL:50 mL. The acetic acid solution of chitosan is prepared by adding 2 mmol of chitosan to 50 mL of 2% acetic acid solution. The ratio of pretreated chitosan, pyridine, dichloromethane, and 2,4-dinitrofluorobenzene is 10 mmol:15 mmol:15-20 mL:11 mmol.

[0013] Furthermore, in step B3, the ratio of pretreated chitosan, phosphorous acid, and pretreated urea is 1g:5g:8g; the ratio of ammonium phosphate chitosan, 2-mercaptoethanol, and dichloromethane is 1g:4.2g:12mL; and the ratio of pretreated filler, deionized water, and modified chitosan is 3g:40mL:2g.

[0014] The beneficial effects of this invention are as follows: Styrene-butadiene rubber, flame retardant additives, modified fillers, initiators, plasticizers, vulcanizing crosslinking agents, and vulcanizing agents are mixed in an internal mixer. Because the molecular chain segments of the flame retardant additives are similar and compatible with styrene-butadiene rubber, and the modified fillers are coated with a chitosan structure, the compatibility between the matrix rubber and the fillers is improved. Therefore, the components can be uniformly dispersed to obtain a compound. In the subsequent heat treatment process, the carbon-carbon double bonds on the compound react with the thiol groups on the modified fillers via a "thiol-alkene click reaction," establishing a crosslinking network to obtain a highly flame-retardant compound rubber for conveyor belts.

[0015] Flame retardant additive: The phosphorus atom of the phosphorus-hydrogen bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide acts as a nucleophile, attacking the β-carbon atom of the double bond in allyl alcohol to obtain intermediate 1. The carboxyl group on intermediate 1 reacts with the anhydride on Nadic anhydride to generate carboxyl and ester groups, obtaining intermediate 2. Styrene and butadiene undergo free radical copolymerization under the action of an initiator to form molecular chain segments identical to the matrix rubber. Then, intermediate 2 is added to participate in copolymerization and form blocks, obtaining a pretreatment additive. Using 3-glycidyl etheroxypropyltrimethoxysilane as a raw material, cage-like polysilsesquioxane is prepared under acidic conditions via anionization. The epoxy groups on the cage-like polysilsesquioxane react with the carboxyl groups on the pretreatment additive to obtain a flame retardant additive.

[0016] Modified filler: Silicon nitride is dispersed in pure water to obtain a silicon nitride dispersion. Aluminum phosphate precipitate, formed by the neutralization reaction of phosphoric acid and aluminum hydroxide, coats the surface of nano-silicon nitride particles to obtain a pretreated filler. The carboxyl groups on mercaptopropionic acid are activated and then amidated with the amino groups on chitosan, introducing thiol groups into the chitosan molecular chain to obtain pretreated chitosan. Then, Sanger's reagent 2,4-dinitrofluorobenzene is added to undergo a nucleophilic aromatic substitution reaction, thereby protecting the thiol groups and obtaining pretreated chitosan. Urea, under nitrogen purging and high-temperature melting, generates isocyanate. Isocyanate reacts with phosphorous acid to form a phosphate intermediate. This phosphate intermediate reacts with the hydroxyl groups on the pretreated chitosan, and after neutralization with ammonia water, generates an ammonium phosphate group O=P(H)O. - NH4 ﹢ Ammonium phosphate-modified chitosan was prepared. 2-Mercaptoethanol was used as a deprotecting agent to "replace" the 2,4-dinitrophenyl group on the ammonium phosphate-modified chitosan, thus obtaining modified chitosan. The pretreated filler was dispersed in deionized water, and the modified chitosan was added. Under a weakly acidic environment, the two interacted through positive and negative charge attraction, forming a structure where the modified chitosan coated the pretreated filler, thus obtaining the modified filler.

[0017] Flame retardant additives contain phosphenanthrene and siloxane structures in their molecular chains, which work synergistically to enhance the flame retardancy of the material. The phosphenanthrene structure decomposes upon heating to generate phosphorus-containing free radicals, which efficiently capture free radicals and interrupt the combustion chain reaction. The siloxane structure migrates to the material surface and cross-links under high-temperature combustion, forming a silica protective layer. The cage-like polysilsesquioxane structure provides a dense organic-inorganic hybrid network structure for the material, working synergistically with the rigid benzene ring to resist external forces and improve the material's wear resistance. A pretreated filler is prepared by coating aluminum phosphate onto the surface of nano-silicon nitride using a heterogeneous precipitation method. Then, modified chitosan is coated onto the surface of the pretreated filler through positive and negative charge attraction to obtain the modified filler. The ultra-hard nano-silicon nitride core serves as a rigid support, directly enhancing the material's surface resistance to scratches and wear. The synergistic effect of aluminum phosphate and ammonium phosphate chitosan promotes the formation of a dense and stable carbonized layer on the material surface at high temperatures. Meanwhile, substances such as polyphosphoric acid released during combustion can capture free radicals in the gas phase, significantly inhibiting smoke production and playing a dual role of highly efficient flame retardancy and smoke suppression. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: A method for preparing a high flame-retardant compound rubber for conveyor belts, specifically including the following steps: Styrene-butadiene rubber, flame retardant additives, modified fillers, initiators, plasticizers, vulcanizing crosslinking agents, and vulcanizing agents are placed in an internal mixer and mixed under pressure at 80°C and 0.6MPa for 6 minutes to obtain a compound. The compound is then heat-treated at 70°C with nitrogen gas for 2 hours and then sheeted in an open mill to obtain a high flame retardant compound rubber for conveyor belts.

[0020] The weight ratio of styrene-butadiene rubber, flame retardant additive, modified filler, initiator, plasticizer, vulcanizing crosslinking agent, and vulcanizing agent mentioned in the step is 60:25:5:0.2:0.1:0.6:0.4. The initiator is 1-hydroxycyclohexylphenyl ketone, the plasticizer is acetyl tributyl citrate, the vulcanizing crosslinking agent is triallyl isocyanurate, and the vulcanizing agent is 2,5-dimethyl-2,5-dihexane.

[0021] The flame retardant additive is prepared by the following steps: Step A1: Allyl alcohol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diphenyl ether are mixed evenly and reacted for 3 hours at a speed of 130 r / min, a temperature of 120 °C and a nitrogen atmosphere to obtain intermediate 1. Step A2: Mix intermediate 1, nadic anhydride, toluene and triethylamine evenly, and react for 4 hours at 100 r / min and 60°C to obtain intermediate 2. Mix styrene, butadiene and toluene evenly, and stir and add azobisisobutyronitrile at 110 r / min and 50°C, and react for 2 hours. Add intermediate 2 and react for 1 hour to obtain the pretreatment additive. Step A3: Mix 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid evenly, and react for 20 h at a speed of 80 r / min and a temperature of 40 °C to obtain cage-type polysilsesquioxane. Mix cage-type polysilsesquioxane, pretreatment additive and xylene evenly, and stir and add 1-methylimidazole at a speed of 150 r / min and a temperature of 100 °C to obtain flame retardant additive.

[0022] The molar ratio of allyl alcohol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A1 is 1 mmol: 1.2 mmol.

[0023] In step A2, the ratio of intermediate 1, nadic anhydride, and triethylamine is 1 mmol: 1.1 mmol: 5 mL, and the ratio of styrene, butadiene, intermediate 2, toluene, and azobisisobutyronitrile is 1 g: 0.35 g: 0.2 g: 4 mL: 0.05 g, with styrene accounting for 1 g.

[0024] The ratio of 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid in step A3 is 1 mL:2 mL:0.8 mL, the mass fraction of hydrochloric acid is 20%, and the ratio of cage-type polysilsesquioxane, pretreatment additive, xylene and 1-methylimidazole is 1.2 g:1.8 g:5 mL:0.04 g.

[0025] The modified filler is prepared by the following steps: Step B1: Disperse nano-silicon nitride in pure water and sonicate for 10 min at a frequency of 30 Hz and a pH of 2 to obtain a silicon nitride dispersion. Mix aluminum hydroxide, deionized water and phosphoric acid solution evenly, stir and add silicon nitride dispersion at a speed of 200 r / min, react for 30 min, adjust pH to 5, and obtain pretreated filler. Step B2: Mix mercaptopropionic acid and N-hydroxysuccinimide evenly, stir at 100 r / min and 20°C, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and deionized water, react for 1 h, add acetic acid solution of chitosan, react for 20 h to obtain pretreated chitosan. Mix pretreated chitosan, pyridine, dichloromethane and 2,4-dinitrofluorobenzene evenly, react at 120 r / min and 20°C for 3 h to obtain pretreated chitosan. Melt urea at 140°C under nitrogen atmosphere to obtain pretreated urea. Step B3: Mix pretreated chitosan and phosphorous acid evenly, stir and add pretreated urea at 200 r / min and 160℃, and react for 3 h. Add ammonia to adjust the pH to 7 to obtain ammonium phosphate chitosan. Mix ammonium phosphate chitosan, 2-mercaptoethanol and dichloromethane evenly, and react at 120 r / min and 40℃ for 2 h to obtain modified chitosan. Disperse the pretreated filler in deionized water, stir and add modified chitosan at 150 r / min, 20℃ and pH 6, and react for 20 h to obtain modified filler.

[0026] In step B1, the ratio of nano-silicon nitride to pure water is 1g:15mL, and the ratio of aluminum hydroxide, deionized water, phosphoric acid solution and silicon nitride dispersion is 0.58g:10mL:4.33g:40mL.

[0027] The chitosan described in step B2 has a weight-average molecular weight of 2000 and a degree of deacetylation of 90%. The ratio of mercaptopropionic acid, N-hydroxysuccinimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, deionized water, and acetic acid solution of chitosan is 5 mmol:4.2 mmol:4.2 mmol:20 mL:50 mL. The acetic acid solution of chitosan is prepared by adding 2 mmol of chitosan to 50 mL of 2% acetic acid solution. The ratio of pretreatment chitosan, pyridine, dichloromethane, and 2,4-dinitrofluorobenzene is 10 mmol:15 mmol:15 mL:11 mmol.

[0028] In step B3, the ratio of pretreated chitosan, phosphorous acid, and pretreated urea is 1g:5g:8g; the ratio of ammonium phosphate chitosan, 2-mercaptoethanol, and dichloromethane is 1g:4.2g:12mL; and the ratio of pretreated filler, deionized water, and modified chitosan is 3g:40mL:2g.

[0029] Example 2, a method for preparing a high flame-retardant compound rubber for conveyor belts, specifically includes the following steps: Styrene-butadiene rubber, flame retardant additives, modified fillers, initiators, plasticizers, vulcanizing crosslinking agents, and vulcanizing agents are placed in an internal mixer and mixed under pressure at 85°C and 0.8MPa for 8 minutes to obtain a compound. The compound is then heat-treated at 75°C with nitrogen gas for 2 hours and then sheeted in an open mill to obtain a high flame retardant compound rubber for conveyor belts.

[0030] The weight ratio of styrene-butadiene rubber, flame retardant additive, modified filler, initiator, plasticizer, vulcanizing crosslinking agent, and vulcanizing agent mentioned in the step is 60:30:5:0.2:0.1:0.6:0.4. The initiator is 1-hydroxycyclohexylphenyl ketone, the plasticizer is acetyl tributyl citrate, the vulcanizing crosslinking agent is triallyl isocyanurate, and the vulcanizing agent is 2,5-dimethyl-2,5-dihexane.

[0031] The flame retardant additive is prepared by the following steps: Step A1: Allyl alcohol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diphenyl ether are mixed evenly and reacted for 4 hours at a speed of 140 r / min, a temperature of 140 °C and a nitrogen atmosphere to obtain intermediate 1. Step A2: Mix intermediate 1, nadic anhydride, toluene and triethylamine evenly, and react for 6 hours at 110 r / min and 70°C to obtain intermediate 2. Mix styrene, butadiene and toluene evenly, and stir and add azobisisobutyronitrile at 120 r / min and 55°C, and react for 2 hours. Add intermediate 2 and react for 1 hour to obtain the pretreatment additive. Step A3: Mix 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid evenly, and react for 22 h at a speed of 90 r / min and a temperature of 40 °C to obtain cage-type polysilsesquioxane. Mix cage-type polysilsesquioxane, pretreatment additive and xylene evenly, and stir and add 1-methylimidazole at a speed of 160 r / min and a temperature of 110 °C to obtain flame retardant additive.

[0032] The molar ratio of allyl alcohol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A1 is 1 mmol: 1.2 mmol.

[0033] In step A2, the ratio of intermediate 1, nadic anhydride, and triethylamine is 1 mmol: 1.1 mmol: 5 mL, the ratio of styrene, butadiene, intermediate 2, toluene, and azobisisobutyronitrile is 1 g: 0.35 g: 0.2 g: 4 mL: 0.05 g, and the amount of styrene is 2 g.

[0034] The ratio of 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid in step A3 is 1 mL:2 mL:0.8 mL, the mass fraction of hydrochloric acid is 20%, and the ratio of cage-type polysilsesquioxane, pretreatment additive, xylene and 1-methylimidazole is 1.2 g:1.8 g:5 mL:0.04 g.

[0035] The modified filler is prepared by the following steps: Step B1: Disperse nano-silicon nitride in pure water and sonicate for 11 min at a frequency of 35 Hz and a pH of 2 to obtain a silicon nitride dispersion. Mix aluminum hydroxide, deionized water and phosphoric acid solution evenly, stir and add silicon nitride dispersion at a speed of 250 r / min, react for 40 min, adjust pH to 5, and obtain pretreated filler. Step B2: Mix mercaptopropionic acid and N-hydroxysuccinimide evenly, stir at 110 r / min and 25°C, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and deionized water, react for 1 h, add acetic acid solution of chitosan, react for 22 h to obtain pretreated chitosan. Mix pretreated chitosan, pyridine, dichloromethane and 2,4-dinitrofluorobenzene evenly, react at 130 r / min and 22°C for 4 h to obtain pretreated chitosan. Melt urea at 145°C under nitrogen atmosphere to obtain pretreated urea. Step B3: Mix pretreated chitosan and phosphorous acid evenly, stir and add pretreated urea at 250 r / min and 170℃, and react for 4 h. Add ammonia to adjust the pH to 7 to obtain ammonium phosphate chitosan. Mix ammonium phosphate chitosan, 2-mercaptoethanol and dichloromethane evenly, and react for 3 h at 125 r / min and 45℃ to obtain modified chitosan. Disperse the pretreated filler in deionized water, stir and add modified chitosan at 160 r / min, 2℃ and pH 6, and react for 22 h to obtain modified filler.

[0036] In step B1, the ratio of nano-silicon nitride to pure water is 1g:15mL, and the ratio of aluminum hydroxide, deionized water, phosphoric acid solution and silicon nitride dispersion is 0.58g:10mL:4.33g:40mL.

[0037] The chitosan described in step B2 has a weight-average molecular weight of 2000 and a degree of deacetylation of 90%. The ratio of mercaptopropionic acid, N-hydroxysuccinimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, deionized water, and acetic acid solution of chitosan is 5 mmol:4.2 mmol:4.2 mmol:20 mL:50 mL. The acetic acid solution of chitosan is prepared by adding 2 mmol of chitosan to 50 mL of 2% acetic acid solution. The ratio of pretreatment chitosan, pyridine, dichloromethane, and 2,4-dinitrofluorobenzene is 10 mmol:15 mmol:15 mL:11 mmol.

[0038] In step B3, the ratio of pretreated chitosan, phosphorous acid, and pretreated urea is 1g:5g:8g; the ratio of ammonium phosphate chitosan, 2-mercaptoethanol, and dichloromethane is 1g:4.2g:12mL; and the ratio of pretreated filler, deionized water, and modified chitosan is 3g:40mL:2g.

[0039] Example 3: A method for preparing a high flame-retardant compound rubber for conveyor belts, specifically including the following steps: Styrene-butadiene rubber, flame retardant additives, modified fillers, initiators, plasticizers, vulcanizing crosslinking agents, and vulcanizing agents are placed in an internal mixer and mixed under pressure at 90°C and 1.0 MPa for 10 minutes to obtain a compound. The compound is then heat-treated at 80°C with nitrogen gas for 3 hours and then sheeted in an open mill to obtain a high flame retardant compound rubber for conveyor belts.

[0040] The weight ratio of styrene-butadiene rubber, flame retardant additive, modified filler, initiator, plasticizer, vulcanizing crosslinking agent, and vulcanizing agent mentioned in the step is 60:35:5:0.2:0.1:0.6:0.4. The initiator is 1-hydroxycyclohexylphenyl ketone, the plasticizer is acetyl tributyl citrate, the vulcanizing crosslinking agent is triallyl isocyanurate, and the vulcanizing agent is 2,5-dimethyl-2,5-dihexane.

[0041] The flame retardant additive is prepared by the following steps: Step A1: Allyl alcohol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diphenyl ether are mixed evenly and reacted for 5 hours at a speed of 150 r / min, a temperature of 160 °C and a nitrogen atmosphere to obtain intermediate 1. Step A2: Mix intermediate 1, nadic anhydride, toluene and triethylamine evenly, and react for 8 hours at 120 r / min and 80 °C to obtain intermediate 2. Mix styrene, butadiene and toluene evenly, and stir and add azobisisobutyronitrile at 140 r / min and 60 °C, and react for 3 hours. Add intermediate 2 and react for 2 hours to obtain the pretreatment additive. Step A3: Mix 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid evenly, and react for 24 h at a speed of 100 r / min and a temperature of 50 °C to obtain cage-type polysilsesquioxane. Mix cage-type polysilsesquioxane, pretreatment additive and xylene evenly, and stir and add 1-methylimidazole at a speed of 170 r / min and a temperature of 120 °C, and react for 5 h to obtain flame retardant additive.

[0042] The molar ratio of allyl alcohol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A1 is 1 mmol: 1.2 mmol.

[0043] In step A2, the ratio of intermediate 1, nadic anhydride, and triethylamine is 1 mmol: 1.1 mmol: 5 mL, the ratio of styrene, butadiene, intermediate 2, toluene, and azobisisobutyronitrile is 1 g: 0.35 g: 0.2 g: 4 mL: 0.05 g, and the amount of styrene is 3 g.

[0044] The ratio of 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid in step A3 is 1 mL:2 mL:0.8 mL, the mass fraction of hydrochloric acid is 20%, and the ratio of cage-type polysilsesquioxane, pretreatment additive, xylene and 1-methylimidazole is 1.2 g:1.8 g:5 mL:0.04 g.

[0045] The modified filler is prepared by the following steps: Step B1: Disperse nano-silicon nitride in pure water and sonicate for 12 min at a frequency of 40 Hz and a pH of 3 to obtain a silicon nitride dispersion. Mix aluminum hydroxide, deionized water and phosphoric acid solution evenly, stir and add silicon nitride dispersion at a speed of 300 r / min, react for 50 min, adjust pH to 5, and obtain pretreated filler. Step B2: Mix mercaptopropionic acid and N-hydroxysuccinimide evenly, stir at 120 r / min and 30 °C, add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and deionized water, react for 2 h, add acetic acid solution of chitosan, react for 24 h to obtain pretreated chitosan. Mix pretreated chitosan, pyridine, dichloromethane and 2,4-dinitrofluorobenzene evenly, react at 150 r / min and 25 °C for 5 h to obtain pretreated chitosan. Melt urea at 150 °C under nitrogen gas to obtain pretreated urea. Step B3: Mix pretreated chitosan and phosphorous acid evenly, stir and add pretreated urea at 300 r / min and 80℃, and react for 5 h. Add ammonia to adjust the pH to 7 to obtain ammonium phosphate chitosan. Mix ammonium phosphate chitosan, 2-mercaptoethanol and dichloromethane evenly, and react for 4 h at 130 r / min and 50℃ to obtain modified chitosan. Disperse the pretreated filler in deionized water, stir and add modified chitosan at 180 r / min, 25℃ and pH 6.5, and react for 24 h to obtain modified filler.

[0046] In step B1, the ratio of nano-silicon nitride to pure water is 1g:15mL, and the ratio of aluminum hydroxide, deionized water, phosphoric acid solution and silicon nitride dispersion is 0.58g:10mL:4.33g:40mL.

[0047] The chitosan described in step B2 has a weight-average molecular weight of 2000 and a degree of deacetylation of 90%. The ratio of mercaptopropionic acid, N-hydroxysuccinimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, deionized water, and acetic acid solution of chitosan is 5 mmol:4.2 mmol:4.2 mmol:20 mL:50 mL. The acetic acid solution of chitosan is prepared by adding 2 mmol of chitosan to 50 mL of 2% acetic acid solution. The ratio of pretreatment chitosan, pyridine, dichloromethane, and 2,4-dinitrofluorobenzene is 10 mmol:15 mmol:15 mL:11 mmol.

[0048] In step B3, the ratio of pretreated chitosan, phosphorous acid, and pretreated urea is 1g:5g:8g; the ratio of ammonium phosphate chitosan, 2-mercaptoethanol, and dichloromethane is 1g:4.2g:12mL; and the ratio of pretreated filler, deionized water, and modified chitosan is 3g:40mL:2g.

[0049] Comparative Example 1: This comparative example uses propanol instead of intermediate 1 compared to Example 1, with the other steps remaining the same.

[0050] Comparative Example 2: This comparative example uses a pretreatment additive instead of a flame retardant additive, while the other steps are the same as in Example 1.

[0051] Comparative Example 3: This comparative example uses pretreated filler instead of modified filler, but the other steps are the same as in Example 1.

[0052] Comparative Example 4: This comparative example uses pretreated chitosan instead of modified chitosan compared to Example 1, while the other steps are the same.

[0053] The high flame-retardant compound rubbers for conveyor belts prepared in Examples 1-3 and Comparative Examples 1-4 were tested for volumetric wear rate according to GB / T1689-2014 "Determination of abrasion resistance of vulcanized rubber (using Akron abrasion tester)". The test results are shown in Table 1. The mass of the sample before testing and the mass after bearing a load of 26.5 N and traveling 1.61 km were recorded.

[0054] The high flame-retardant compound rubbers for conveyor belts prepared in Examples 1-3 and Comparative Examples 1-4 were tested for oxygen index and vertical burning time according to GB / T10707-2008 "Determination of Burning Performance of Rubber". The test results are shown in Table 1. The minimum oxygen concentration required to sustain combustion of the sample was recorded using the limiting oxygen index method of Method A. The sample was 100 mm long, 6.5 mm wide, and 3 mm thick. The flaming burning time and flameless burning time of the sample were recorded using the vertical burning method of Method B. The sample was 130 mm long, 13 mm wide, and 3 mm thick.

[0055] Table 1

[0056] Table 1 shows that the volumetric wear rate of the high flame-retardant compound rubber for conveyor belts prepared in Examples 1-3 is 0.17-0.19 cm. 3 Within a 1.61km range, the vertical burning time is in the range of 3.7-4.8s, and the oxygen index is in the range of 31-33%, indicating that the present invention has good flame retardancy and wear resistance.

[0057] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high flame-retardant compound rubber for conveyor belts, characterized in that: Specifically, the steps include the following: Styrene-butadiene rubber, flame retardant additives, modified fillers, initiators, plasticizers, vulcanizing crosslinking agents and vulcanizing agents are placed in an internal mixer and mixed under pressure to obtain a compound. The compound is then heat-treated and placed in an open mill for sheeting to obtain a high flame retardant compound rubber for conveyor belts. The weight ratio of styrene-butadiene rubber, flame retardant additive, modified filler, initiator, plasticizer, vulcanizing crosslinking agent and vulcanizing agent mentioned in the steps is 60-80:20-35:5-10:0.2-0.4:0.1-0.2:0.6-0.8:0.4-0.

6.

2. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 1, characterized in that: The flame retardant additive is prepared by the following steps: Step A1: Allyl alcohol, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diphenyl ether are mixed evenly and reacted to obtain intermediate 1; Step A2: Mix intermediate 1, nadic anhydride, toluene and triethylamine evenly and react to obtain intermediate 2. Mix styrene, butadiene and toluene and stir, then add azobisisobutyronitrile and react. Add intermediate 2 and react to obtain the pretreatment additive. Step A3: Mix 3-glycidyl etheroxypropyltrimethoxysilane, acetone and hydrochloric acid evenly and react to obtain cage-type polysilsesquioxane. Mix the cage-type polysilsesquioxane, pretreatment additive and xylene and stir, then add 1-methylimidazole and react to obtain flame retardant additive.

3. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 2, characterized in that: The molar ratio of allyl alcohol and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A1 is 1 mmol:1.2 mmol.

4. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 2, characterized in that: The ratio of intermediate 1, nadic anhydride and triethylamine used in step A2 is 1 mmol: 1.1 mmol: 5 mL, and the ratio of styrene, butadiene, intermediate 2, toluene and azobisisobutyronitrile used is 1 g: 0.35 g: 0.2 g: 4 mL: 0.05 g.

5. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 2, characterized in that: In step A3, the ratio of 3-glycidyl etheroxypropyltrimethoxysilane, acetone, and hydrochloric acid is 1 mL:2 mL:0.8 mL, and the ratio of cage-type polysilsesquioxane, pretreatment additive, xylene, and 1-methylimidazole is 1.2 g:1.8 g:5 mL:0.04 g.

6. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 1, characterized in that: The modified filler is prepared by the following steps: Step B1: Disperse nano-silicon nitride in pure water and sonicate to obtain silicon nitride dispersion. Mix aluminum hydroxide, deionized water and phosphoric acid solution and stir, then add to silicon nitride dispersion to react and adjust pH to obtain pretreated filler. Step B2: Mix mercaptopropionic acid and N-hydroxysuccinimide and add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and deionized water to react. Add acetic acid solution of chitosan and react to obtain pretreated chitosan. Mix pretreated chitosan, pyridine, dichloromethane and 2,4-dinitrofluorobenzene evenly and react to obtain pretreated chitosan. Melt urea to obtain pretreated urea. Step B3: Mix and stir pretreated chitosan and phosphorous acid, add pretreated urea, and react. Add ammonia to adjust the pH to obtain ammonium phosphate chitosan. Mix ammonium phosphate chitosan, 2-mercaptoethanol and dichloromethane evenly and react to obtain modified chitosan. Disperse the pretreated filler in deionized water, stir and add modified chitosan, and react to obtain modified filler.

7. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 6, characterized in that: In step B1, the ratio of nano-silicon nitride to pure water is 1g:15mL, and the ratio of aluminum hydroxide, deionized water, phosphoric acid solution and silicon nitride dispersion is 0.58g:10mL:4.33g:40mL.

8. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 6, characterized in that: In step B2, the ratio of mercaptopropionic acid, N-hydroxysuccinimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, deionized water, and acetic acid solution of chitosan is 5 mmol:4.2 mmol:4.2 mmol:20 mL:50 mL, and the ratio of pretreatment chitosan, pyridine, dichloromethane, and 2,4-dinitrofluorobenzene is 10 mmol:15 mmol:15-20 mL:11 mmol.

9. The method for preparing a high flame-retardant compound rubber for conveyor belts according to claim 6, characterized in that: In step B3, the ratio of pretreated chitosan, phosphorous acid, and pretreated urea is 1g:5g:8g; the ratio of ammonium phosphate chitosan, 2-mercaptoethanol, and dichloromethane is 1g:4.2g:12mL; and the ratio of pretreated filler, deionized water, and modified chitosan is 3g:40mL:2g.

10. A high flame-retardant compound rubber for conveyor belts, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.

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