Flame-retardant wear-resistant conveying belt for coal mine and preparation method thereof

Abstract

The invention discloses a flame-retardant wear-resistant conveying belt for a coal mine and a preparation method thereof, and belongs to the technical field of wear-resistant conveying belts. Substances such as calcium nitrate tetrahydrate, ferric nitrate nonahydrate and antimony trioxide are subjected to hydrothermal coprecipitation to obtain multifunctional composite microspheres, the microspheres are aminated through a silane coupling agent KH-550 and then coated with silicon carbide, and coated composite microspheres are obtained; the preparation method comprises the following steps: carrying out graft copolymerization on nitrile rubber, octavinyl silsesquioxane and DOPO acrylate, compounding a quaternary phosphonium salt flame retardant to obtain modified nitrile rubber, carrying out three-stage mixing on the modified nitrile rubber, coated composite microspheres, conductive carbon black and other substances to obtain a rubber coating layer, carrying out double-sided calendering on the rubber coating layer and an epoxy resin plasticized aramid fiber skeleton layer, and carrying out vulcanization molding to obtain the composite material. And finally obtaining the flame-retardant wear-resistant conveying belt for the coal mine. The synergistic effect of high flame retardance, strong wear resistance and static electricity resistance is achieved, and the service life is prolonged.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wear-resistant conveying belt, and particularly relates to a flame-retardant wear-resistant conveying belt for coal mines and a preparation method thereof. BACKGROUND

[0002] There are a large amount of flammable and explosive gases and dust in the underground environment of coal mines. In order to reduce the occurrence of fire accidents, the flame-retardant performance of the conveying belt is strictly required. The conveying belt is subjected to great wear when transporting materials such as coal, and the wear resistance becomes another important performance of the conveying belt for coal mines. The conveying belt with strong wear resistance can prolong the service life, reduce the replacement frequency, and reduce the use cost.

[0003] The conveying belt, also known as a transport belt, is a rubber and fiber, metal composite product or a plastic and fabric composite product used in a belt conveyor to bear and transport materials. The components include a framework layer, a cover rubber layer, and edge rubber, etc. The framework layer provides strength and stiffness, the cover rubber layer can protect the framework material, transfer the conveying power and bear the materials, and the cover rubber can improve the friction to achieve wear resistance. The edge rubber mainly reduces the delamination of the belt core and reduces the influence of the medium on the framework material.

[0004] The flame-retardant wear-resistant conveying belt is a conveying belt with flame-retardant and wear-resistant performances, also known as a whole-core flame-retardant conveying belt, which is made of a whole belt core impregnated with a polyvinyl chloride impregnation paste and plasticized or vulcanized. The conveying belt has the characteristics of high strength and large capacity, and has good flame-retardant, anti-static, wear-resistant and other performances.

[0005] A Chinese patent application with the publication number CN116102825A discloses a halogen-free flame-retardant rubber conveying belt and a production method thereof. The halogen-free flame-retardant rubber conveying belt includes a cover rubber and a framework layer. The raw materials of the cover rubber include hydrogenated nitrile rubber, methyl vinyl phenyl silicone rubber, ethylene propylene diene rubber, polyethylene glycol, filler, microencapsulated aluminum hydroxide, crosslinking agent, adhesive, and anti-aging agent. The cover rubber raw materials are uniformly mixed to obtain the cover rubber. The cover rubber and the framework layer are directly laminated, and are subjected to calendering, flat plate vulcanization to obtain a high-temperature-resistant rubber conveying belt.

[0006] However, the coal mine environment is generally humid and dusty, the microencapsulated aluminum hydroxide is easy to absorb moisture and form lumps, which causes micro-cracks in the cover rubber due to expansion, and the lumps can reduce the local flame-retardant performance. The conductive filler is not added, and it is difficult to achieve the surface anti-static requirement by relying on the polymer itself only. The accumulation of friction static electricity may cause a fire. SUMMARY

[0007] The present application aims to solve the problems of micro-cracks in the cover rubber caused by moisture absorption and lumping of ordinary flame retardants in a humid coal mine environment, local flame-retardant failure, and accumulation of friction static electricity, and provides a flame-retardant wear-resistant conveying belt for coal mines and a preparation method thereof.

[0008] The present application obtains multifunctional composite microspheres by taking calcium nitrate tetrahydrate, iron nitrate nonahydrate and antimony trioxide as precursors and through hydrothermal co-precipitation, obtains coated composite microspheres by aminating the microspheres through silane coupling agent KH-550, polycarbosilane melt penetration and high-temperature pyrolysis in a molten salt bath, obtains modified nitrile rubber by graft copolymerization of nitrile rubber, octavinylsilsesquioxane and DOPO acrylate and compounding quaternary phosphonium salt flame retardant, and finally obtains a coal mine flame-retardant and wear-resistant conveyor belt by three-stage mixing of modified nitrile rubber, coated composite microspheres, conductive carbon black and zinc borate and the like, covering rubber layer, and plasticizing aramid skeleton layer through double-sided calendering and vulcanization.

[0009] The object of the present application can be achieved by the following technical solutions:

[0010] A coal mine flame-retardant and wear-resistant conveyor belt, comprising a covering rubber layer and a plasticized skeleton layer in the covering rubber layer; wherein the covering rubber layer is composed of covering rubber, and the plasticized skeleton layer is composed of aramid fiber cloth, and the covering rubber comprises the following component raw materials in parts by mass:

[0011] 90-100 parts of modified nitrile rubber, 1-2 parts of calcium stearate, 25-30 parts of coated composite microspheres, 10-15 parts of conductive carbon black, 3-5 parts of zinc borate, 1-1.5 parts of sulfur, 3-5 parts of zinc oxide and 1-1.5 parts of stearic acid;

[0012] The coated composite microspheres are obtained by coating the multifunctional composite microspheres with silicon carbide;

[0013] The multifunctional composite microspheres are obtained by the following steps:

[0014] Dissolve calcium nitrate, iron nitrate and antimony trioxide in nitric acid to obtain solution A; then prepare surfactant solution B, adjust the pH value, and then add solution A dropwise into solution B, stir, pour the mixed solution into a high-pressure reaction kettle lined with polytetrafluoroethylene, react, cool, wash the product with deionized water and anhydrous ethanol, centrifuge, and vacuum dry to obtain multifunctional composite microspheres.

[0015] Further, the modified nitrile rubber is prepared by the following steps:

[0016] Add nitrile rubber and toluene into a reaction kettle, stir at 50-60℃ for 30-40min, then add octavinylsilsesquioxane, DOPO acrylate and benzoyl peroxide, react at 60-75℃ under nitrogen protection for 3-4h, then add tetraphenylphosphonium bromide and zinc stearate, stir at 50-60℃ for 2-3h, transfer to 1000mL of methanol, stir for 5-10min, filter, wash the filter cake with deionized water and methanol for 3-5 times, and vacuum dry to obtain modified nitrile rubber.

[0017] Further, the use amount ratio of butyl nitrile rubber, toluene, octa-vinyl silsesquioxane, DOPO acrylate, benzoyl peroxide, tetraphenyl phosphonium bromide and zinc stearate is 90-100 g: 350-400 mL: 6-8 g: 5-6 g: 0.8-1 g: 4-5 g: 0.3-0.5 g.

[0018] Further, the coated composite microspheres are prepared by the following steps:

[0019] The multifunctional composite microspheres and 10wt% silane coupling agent KH-550 ethanol solution are ultrasonically immersed for 20-30 min, filtered, and dried to obtain pretreated microspheres; the pretreated microspheres and polycarbosilane are added into a reaction kettle, stirred for 1-2 h, sodium chloride and potassium chloride are further added, stirred for 15-30 min to obtain a mixed powder, which is transferred into a graphite crucible and placed in a tube furnace, heated to 400-500℃ at 5℃ / min under argon atmosphere, kept for 1-2 h, then heated to 1200-1300℃ at 3℃ / min, kept for 2-3 h, and cooled to room temperature with the furnace, the product is washed with hot water and ethanol for 3-5 times, and vacuum dried to obtain the coated composite microspheres.

[0020] Further, the use amount ratio of multifunctional composite microspheres and silane coupling agent KH-550 ethanol solution is 40-50 g: 90-100 mL.

[0021] Further, the mass ratio of pretreated microspheres, polycarbosilane, sodium chloride and potassium chloride is 40-50: 15-20: 130-150: 130-150.

[0022] Further, the multifunctional composite microspheres are prepared by the following steps:

[0023] Calcium nitrate tetrahydrate, ferric nitrate nonahydrate, antimony trioxide, concentrated nitric acid and deionized water are added into a reaction kettle, stirred for 30-40 min, sodium citrate is further added and stirred for 1-2 h to obtain solution A; cetyltrimethylammonium bromide and deionized water are added into a constant temperature water bath kettle, stirred at 50-60℃ for 30-40 min, diammonium hydrogen phosphate is further added and stirred for 30-40 min, the pH value is adjusted to 5 with nitric acid to obtain solution B; solution A is added dropwise into solution B, stirred for 30-40 min, the mixed solution is slowly poured into a high-pressure reaction kettle with a polytetrafluoroethylene liner, reacted at 130-150℃ for 20-24 h, cooled with ice water, the product is washed with deionized water and anhydrous ethanol, centrifuged for 3-5 times, and vacuum dried to obtain the multifunctional composite microspheres.

[0024] Further, the usage ratio of calcium nitrate tetrahydrate, ferric nitrate nonahydrate, antimony trioxide, concentrated nitric acid, deionized water and sodium citrate is 60-70 g: 15-20 g: 15-20 g: 15-20 mL: 2.5-3 L: 90-100 g.

[0025] Further, the usage ratio of cetyltrimethylammonium bromide, deionized water and diammonium hydrogen phosphate is 18-20 g: 3.5-4 L: 30-32 g.

[0026] Further, a preparation method of the flame-retardant wear-resistant conveying belt for coal mines comprises the following steps:

[0027] Step one: the modified butyl nitrile rubber and calcium stearate are added into a mixing machine, mixed at 60-70 DEG C for 8-10 min, the coated composite microspheres, conductive carbon black and zinc borate are added, mixed at 80-90 DEG C for 6-8 min, and then the sulfur, zinc oxide and stearic acid are added, mixed at 100-110 DEG C for 5-10 min, to obtain a covering rubber;

[0028] Step two: the aramid fiber cloth skeleton layer is immersed in the epoxy resin adhesive for 30-40 min to obtain a rubber impregnated skeleton layer, and the rubber impregnated skeleton layer is added into a plasticizing box and plasticized at 160-170 DEG C for 45-60 min to obtain a plasticized skeleton layer;

[0029] Step three: the covering rubber is preheated to 90-100 DEG C, the calender is adjusted, the upper and lower rollers are heated to 150-170 DEG C, the plasticized skeleton layer is first laid on the surface of the lower roller, and then the covering rubber is uniformly coated on the skeleton layer, the calender is started, and the upper and lower surfaces are rolled at the same time, the skeleton layer is wrapped in the covering rubber layer to complete double-sided calendering, and then transferred to a flat plate vulcanizing machine, vulcanized at 150-160 DEG C for 30-40 min to obtain the flame-retardant wear-resistant conveying belt for coal mines;

[0030] The thickness of the covering layer is 3 mm, the thickness of the plasticized skeleton layer is 3 mm, and the thickness of the conveying belt is 9 mm.

[0031] The beneficial effects of the present application are as follows:

[0032] The multifunctional composite microspheres in the application are catalytically carbonized, cooperated with zinc borate and modified rubber to form a triple flame-retardant barrier of "catalysis-carbonization-gas phase inhibition", improve the flame-retardant effect, avoid the risk of moisture absorption and caking, make the flame-retardant efficiency durable and stable, the silicon carbide ceramic shell improves the hardness of the microsphere surface, and the enhanced rubber network of octa-ethylene-vinyl silsesquioxane monomer makes the abrasion volume decrease, the strong interface bonding of the microsphere-rubber modified by silane coupling agent avoids the micro-cracks of the rubber coating layer caused by stress concentration; the silicon carbide coating layer isolates the water vapor erosion, the aramid skeleton layer maintains good tensile strength after plasticizing by epoxy resin, and the synergistic effect of high flame retardance, strong wear resistance and anti-static is realized, and the service life is prolonged.

[0033] 2、The multifunctional composite microspheres in the application realize flame retardance and wear resistance through the core-shell structure, wherein the nano-mesoporous of the multifunctional composite microspheres can absorb combustion free radicals, the released elements cooperatively catalyze carbonization, and a four-element synergistic system is formed with zinc borate in the rubber coating layer, the silicon carbide shell formed by molten salt cracking makes the microspheres pressure-resistant, and the strong interface bonding of the silane coupling agent makes the abrasion volume of the conveyor belt decrease, the compactness of the silicon carbide ceramic shell makes the water absorption rate decrease, and the micro-cracks of the rubber coating layer caused by moisture absorption and expansion in the humid environment are completely avoided.

[0034] 3、The coated composite microspheres in the application are modified by molten salt cracking and silane coupling agent, which improves the mechanical properties and stability of the conveyor belt rubber coating layer, the amino group constructed on the surface of the microspheres by silane coupling agent KH-550 forms a covalent bond bridge with the carboxyl group of modified nitrile rubber, the interface bonding energy is improved, the external force load is efficiently transferred to the silicon carbide hard shell layer, the mechanical properties are enhanced, and the stability of the conveyor belt is further improved.

[0035] 4、The modified nitrile rubber in the application is designed by molecular-level flame retardance and reinforcement integration, so that the conveyor belt rubber coating layer has high strength and toughness and high flame retardance, the cage-type siloxane core of octa-ethylene-vinyl silsesquioxane is embedded in the rubber network by covalent bond to form a nano-hybrid structure, which improves the tensile strength, maintains high elongation and tear strength; the DOPO acrylate is chemically grafted to the main chain, and the phosphorus group generates a free radical capture type gas phase flame retardant during combustion, which cooperatively catalyzes the dehydration and carbonization with tetraphenyl phosphonium bromide to achieve efficient flame retardance. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application will be clearly and completely described below in combination with the embodiments in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0037] Embodiment 1: A flame-retardant wear-resistant conveying belt for coal mine, comprising a rubber coating layer and a plasticized skeleton layer located in the rubber coating layer;

[0038] The rubber coating layer is composed of a covering rubber, and the covering rubber comprises the following component raw materials in parts by mass:

[0039] 90 parts of modified nitrile rubber, 1 part of calcium stearate, 25 parts of coated composite microspheres, 10 parts of conductive carbon black, 3 parts of zinc borate, 1 part of sulfur, 3 parts of zinc oxide and 1 part of stearic acid.

[0040] The plasticized skeleton layer is composed of aramid fiber cloth;

[0041] A preparation method of a flame-retardant wear-resistant conveying belt for coal mine, comprising the following steps:

[0042] Step one: add modified nitrile rubber and calcium stearate to a mixing machine, mix at 60°C for 8 min, add coated composite microspheres, conductive carbon black and zinc borate, mix at 80°C for 6 min, then add sulfur, zinc oxide and stearic acid, mix at 100°C for 5 min, to obtain a covering rubber;

[0043] Step two: immerse the aramid fiber cloth skeleton layer in an epoxy resin adhesive for 30 min to obtain a rubber-impregnated skeleton layer, and then add the rubber-impregnated skeleton layer to a plasticizing box and plasticize at 160°C for 45 min to obtain a plasticized skeleton layer;

[0044] Step three: preheat the covering rubber to 90°C, adjust the calender, and heat the upper and lower rollers to 150°C; first lay the plasticized skeleton layer on the surface of the lower roller, then evenly coat the covering rubber on top of the skeleton layer, start the calender, and roll the skeleton layer in the covering rubber layer to complete double-sided calendering, and then transfer to a flat vulcanizing machine and vulcanize at 150°C for 30 min to obtain a flame-retardant wear-resistant conveying belt for coal mine.

[0045] The thickness of the covering layer is 3 mm; the thickness of the plasticized skeleton layer is 3 mm; and the thickness of the conveying belt is 9 mm.

[0046] The modified nitrile rubber matrix, flame-retardant filler, antistatic agent and vulcanization system are compounded by sectional mixing, the aramid skeleton layer is impregnated and plasticized for reinforcement, and finally the flame-retardant wear-resistant conveying belt for coal mine is formed by calendering and flat vulcanization; the antimony-iron composite microspheres and the phosphorus-boron-nitrogen flame-retardant system cooperate to form a "gas phase inhibition-coagulation phase carbon formation-ceramic barrier" triple protection, so that the conveying belt realizes flame retardation, wear resistance, antistatic property and other properties in high-risk environments such as coal mines.

[0047] Specifically, in step one, the modified nitrile rubber is prepared by the following steps:

[0048] Put 90 g of nitrile rubber and 350 mL of toluene into a reaction kettle, stir at 50℃ for 30 min, then add 6 g of octavinylsilsesquioxane, 5 g of DOPO acrylate and 0.8 g of benzoyl peroxide, react at 60℃ under nitrogen protection for 3 h, then add 4 g of tetraphenylphosphonium bromide and 0.3 g of zinc stearate, stir at 50℃ for 2 h, transfer to 1000 mL of methanol, stir for 5 min, filter, wash the filter cake with deionized water and methanol 3 times, and vacuum dry to obtain modified nitrile rubber.

[0049] By free radical graft copolymerization, DOPO acrylate with flame retardancy and octavinylsilsesquioxane monomer with nano-enhancing effect are covalently grafted onto the main chain of nitrile rubber, and then physically mixed with quaternary phosphonium salt flame retardant and zinc stearate processing aid; by dual introduction of flame retardant through chemical grafting and physical mixing, synergistic effect is produced with subsequently added composite microspheres, etc., significantly improving the flame retardancy, and also maintaining the oil resistance and wear resistance of the rubber.

[0050] Specifically, in step one, the coated composite microspheres are prepared by the following steps:

[0051] Ultrasonic immersion for 20 min in 40 g of multifunctional composite microspheres and 90 mL of 10 wt% silane coupling agent KH-550 ethanol solution, filter and dry to obtain pretreated microspheres; add 40 g of pretreated microspheres and 15 g of polycarbosilane into a reaction kettle, stir for 1 h, then add 130 g of sodium chloride and 130 g of potassium chloride, stir for 15 min to obtain a mixed powder, transfer to a graphite crucible and place in a tube furnace, heat to 400℃ at 5℃ / min under argon atmosphere, keep for 1 h, then heat to 1200℃ at 3℃ / min, keep for 2 h, cool to room temperature with the furnace, wash the product with hot water and ethanol 3 times, and vacuum dry to obtain coated composite microspheres.

[0052] By molten salt method assisted polycarbosilane pyrolysis, a nanoscale silicon carbide coating layer is constructed on the surface of antimony-iron doped hydroxyapatite microspheres, the surface amino groups of the microspheres are modified by silane coupling agent KH-550, polycarbosilane is selectively adsorbed, molten salt provides an isostatic pressure environment, polycarbosilane penetrates into the mesopores of the microspheres, and pyrolysis in argon forms a dense ceramic shell; the multifunctional composite microsphere core catalyzes carbonization to improve flame retardancy, the silicon carbide shell not only improves hardness and wear resistance, but also blocks water / acid erosion, prolonging the service life.

[0053] Specifically, the multifunctional composite microspheres are prepared by the following steps:

[0054] 60g of calcium nitrate tetrahydrate, 15g of iron nitrate nonahydrate, 15g of antimony trioxide, 15mL of concentrated nitric acid and 2.5L of deionized water were added into a reaction kettle, stirred for 30min, then 90g of sodium citrate was added and stirred for 1h to obtain solution A; 18g of cetyltrimethylammonium bromide and 3.5L of deionized water were added into a constant temperature water bath, stirred at 50℃ for 30min, then 30g of diammonium hydrogen phosphate was added and stirred for 30min, and the pH value was adjusted to 5 with nitric acid to obtain solution B; solution A was added dropwise into solution B, stirred for 30min, and the mixed solution was slowly poured into a polytetrafluoroethylene lined high-pressure reaction kettle, reacted at 130℃ for 20h, cooled with ice water, and the product was washed with deionized water and anhydrous ethanol, centrifuged 3 times and vacuum dried to obtain multifunctional composite microspheres.

[0055] The multifunctional composite microspheres were synthesized by a hydrothermal templating method, cetyltrimethylammonium bromide micelles were used to construct mesoporous templates, sodium citrate complex was used to control the crystal morphology, and the calcium source, phosphorus source and doped antimony-iron ions were co-precipitated in an acidic hydrothermal environment to form crystals with regular channels and microsphere morphology; antimony ions capture gas phase free radicals, iron ions catalyze carbonization and oxidize and decompose smoke dust, significantly improving the flame retardant efficiency.

[0056] Embodiment 2: A flame-retardant and wear-resistant conveying belt for coal mines, comprising a rubber coating layer and a plasticized framework layer in the rubber coating layer.

[0057] The rubber coating layer is composed of a coating rubber, and the coating rubber comprises the following component raw materials in parts by mass:

[0058] 95 parts of modified nitrile rubber, 1.5 parts of calcium stearate, 27.5 parts of coated composite microspheres, 12.5 parts of conductive carbon black, 4 parts of zinc borate, 1.25 parts of sulfur, 4 parts of zinc oxide and 1.25 parts of stearic acid.

[0059] The plasticized framework layer is composed of aramid fiber cloth.

[0060] A preparation method of a flame-retardant and wear-resistant conveying belt for coal mines, comprising the following steps:

[0061] Step one: modified nitrile rubber and calcium stearate are added to a mixer, mixed at 65℃ for 9min, coated composite microspheres, conductive carbon black and zinc borate are added, mixed at 85℃ for 7min, sulfur, zinc oxide and stearic acid are added, mixed at 105℃ for 7.5min to obtain a coating rubber;

[0062] Step two: the aramid fiber cloth framework layer is immersed in an epoxy resin adhesive for 35min to obtain a rubber-impregnated framework layer, which is added to a plasticizing box and plasticized at 165℃ for 52.5min to obtain a plasticized framework layer.

[0063] Step three: after preheating the cover glue to 95℃, adjust the calender, and heat the upper and lower rollers to 160℃. First, lay the plastic skeleton layer on the surface of the lower roller, then evenly cover the cover glue on the skeleton layer, start the calender, and roll the skeleton layer in the cover glue layer at the same time. Complete double-sided calendering, transfer to a flat plate vulcanizing machine, and vulcanize at 155℃ for 30min to obtain a flame-retardant and wear-resistant conveyor belt for coal mines.

[0064] The thickness of the cover layer is 3mm; the thickness of the plastic skeleton layer is 3mm; and the thickness of the conveyor belt is 9mm.

[0065] Specifically, in step one, the modified nitrile rubber is prepared by the following steps:

[0066] 95g of nitrile rubber and 375mL of toluene were added to the reaction kettle, stirred at 55℃ for 35min, then 7g of octavinylsilsesquioxane, 5.5g of DOPO acrylate and 0.9g of benzoyl peroxide were added, and the reaction was carried out at 67.5℃ under nitrogen protection for 3.5h. Then 4.5g of tetraphenylphosphonium bromide and 0.4g of zinc stearate were added, and the mixture was stirred at 55℃ for 2.5h. Then it was transferred to 1000mL of methanol and stirred for 7.5min. The filter cake was washed with deionized water and methanol four times, and then vacuum dried to obtain the modified nitrile rubber.

[0067] Specifically, in step one, the coated composite microspheres are prepared by the following steps:

[0068] 45g of multifunctional composite microspheres and 95mL of 10wt% silane coupling agent KH-550 ethanol solution were ultrasonically immersed for 25min, filtered and dried to obtain pretreated microspheres. 45g of pretreated microspheres and 17.5g of polycarbosilane were added to a reaction kettle, stirred for 1.5h, then 140g of sodium chloride and 140g of potassium chloride were added and stirred for 22.5min to obtain a mixture powder. The mixture powder was transferred to a graphite crucible and placed in a tube furnace, heated to 450℃ at a rate of 5℃ / min under argon atmosphere, and kept at 450℃ for 1.5h. Then it was heated to 1250℃ at a rate of 3℃ / min and kept at 1250℃ for 2.5h. The furnace was cooled to room temperature, and the product was washed with hot water and ethanol four times and vacuum dried to obtain the coated composite microspheres.

[0069] Specifically, the multifunctional composite microspheres are prepared by the following steps:

[0070] 65g of calcium nitrate tetrahydrate, 17.5g of iron nitrate nonahydrate, 17.5g of antimony trioxide, 17.5mL of concentrated nitric acid and 2.75L of deionized water were added into a reaction kettle, stirred for 35min, then 95g of sodium citrate was added and stirred for 1.5h to obtain solution A; 19g of cetyltrimethylammonium bromide and 3.75L of deionized water were added into a constant temperature water bath, stirred at 55℃ for 35min, then 31g of diammonium hydrogen phosphate was added and stirred for 35min, and the pH value was adjusted to 5 with nitric acid to obtain solution B; solution A was added dropwise into solution B, stirred for 35min, and the mixed solution was slowly poured into a polytetrafluoroethylene lined high-pressure reaction kettle, reacted at 140℃ for 22h, cooled with ice water, and the product was washed with deionized water and anhydrous ethanol, centrifuged 4 times and vacuum dried to obtain multifunctional composite microspheres.

[0071] Example 3: A flame-retardant and wear-resistant conveying belt for coal mines, comprising a rubber coating layer and a plasticized framework layer located in the rubber coating layer.

[0072] The rubber coating layer is composed of a covering rubber, and the covering rubber comprises the following component raw materials in parts by mass:

[0073] 100 parts of modified nitrile rubber, 2 parts of calcium stearate, 30 parts of coated composite microspheres, 15 parts of conductive carbon black, 5 parts of zinc borate, 1.5 parts of sulfur, 5 parts of zinc oxide and 1.5 parts of stearic acid.

[0074] The plasticized framework layer is composed of aramid fiber cloth;

[0075] A preparation method of a flame-retardant and wear-resistant conveying belt for coal mines, comprising the following steps:

[0076] Step one: modified nitrile rubber and calcium stearate are added to a mixer, mixed at 70℃ for 10min, coated composite microspheres, conductive carbon black and zinc borate are added, mixed at 90℃ for 8min, sulfur, zinc oxide and stearic acid are added, mixed at 110℃ for 10min to obtain a covering rubber;

[0077] Step two: the aramid fiber cloth framework layer is immersed in an epoxy resin adhesive for 40min to obtain a rubber-impregnated framework layer, which is added to a plasticizing box and plasticized at 170℃ for 60min to obtain a plasticized framework layer;

[0078] Step three: the covering rubber is preheated to 100℃, the calender is adjusted, the upper and lower rollers are heated to 170℃, the plasticized framework layer is first laid on the surface of the lower roller, then the covering rubber is evenly coated on top of the framework layer, the calender is started, and the framework layer is wrapped in the rubber coating layer by rolling on both sides at the same time, and then transferred to a flat plate vulcanizing machine for vulcanization at 160℃ for 40min to obtain a flame-retardant and wear-resistant conveying belt for coal mines.

[0079] The covering layer has a thickness of 3 mm; the plasticizing framework layer has a thickness of 3 mm; and the conveying belt has a thickness of 9 mm.

[0080] Specifically, in step one, the modified nitrile rubber is prepared by the following steps:

[0081] 100 g of nitrile rubber and 400 mL of toluene were added to a reaction kettle, stirred at 60°C for 40 min, then 8 g of octavinylsilsesquioxane, 6 g of DOPO acrylate and 1 g of benzoyl peroxide were added, reacted at 75°C under nitrogen protection for 4 h, then 5 g of tetraphenylphosphonium bromide and 0.5 g of zinc stearate were added, stirred at 60°C for 3 h, transferred to 1000 mL of methanol, stirred for 10 min, filtered, and the filter cake was washed with deionized water and methanol for 5 times, and vacuum dried to obtain the modified nitrile rubber.

[0082] Specifically, in step one, the coated composite microspheres are prepared by the following steps:

[0083] 50 g of multifunctional composite microspheres and 100 mL of 10wt% silane coupling agent KH-550 ethanol solution were ultrasonically immersed for 30 min, filtered and dried to obtain pretreated microspheres; 50 g of pretreated microspheres and 20 g of polycarbosilane were added to a reaction kettle, stirred for 2 h, then 150 g of sodium chloride and 150 g of potassium chloride were added, stirred for 30 min to obtain a mixed powder, which was transferred to a graphite crucible and placed in a tube furnace, heated to 500°C at 5°C / min under argon atmosphere, kept for 2 h, then heated to 1300°C at 3°C / min, kept for 3 h, and cooled to room temperature with the furnace, and the product was washed with hot water and ethanol for 5 times and vacuum dried to obtain the coated composite microspheres.

[0084] Specifically, the multifunctional composite microspheres are prepared by the following steps:

[0085] 70 g of calcium nitrate tetrahydrate, 20 g of ferric nitrate nonahydrate, 20 g of antimony trioxide, 20 mL of concentrated nitric acid and 3 L of deionized water were added to a reaction kettle, stirred for 40 min, then 100 g of sodium citrate was added and stirred for 2 h to obtain solution A; 20 g of cetyltrimethylammonium bromide and 4 L of deionized water were added to a constant temperature water bath kettle, stirred at 60°C for 40 min, then 32 g of diammonium hydrogen phosphate was added and stirred for 40 min, and the pH value was adjusted to 5 with nitric acid to obtain solution B; solution A was added dropwise to solution B, stirred for 40 min, and the mixed solution was slowly poured into a high-pressure reaction kettle lined with polytetrafluoroethylene, reacted at 150°C for 24 h, cooled with ice water, and the product was washed with deionized water and anhydrous ethanol, centrifuged 5 times, and vacuum dried to obtain the multifunctional composite microspheres.

[0086] The raw materials used in the examples 1-3 of the present application are all commercially available, such as aramid fiber cloth selected from Zhejiang Xuantai New Material Co., Ltd.; octavinylsilsesquioxane selected from Guangdong Yuanfeng Chemical Reagent Co., Ltd. (Yuanfeng Chemical); DOPO acrylate selected from Guangzhou Mingshen New Material Co., Ltd. (DOPO); benzoyl peroxide selected from Jinan Shuangying Chemical Co., Ltd. (Shuangying); tetraphenylphosphonium bromide selected from Shandong Jinhe Chemical Co., Ltd. (Jinhe Chemical); diammonium hydrogen phosphate selected from Hebei Jiuyu Biological Technology Co., Ltd. (Diammonium hydrogen phosphate).

[0087] Comparative Example 1: The difference from Example 1 is that, in the process of preparing multifunctional composite microspheres, no iron nitrate nonahydrate and antimony trioxide are added, and the remaining steps remain unchanged to prepare a conveyor belt.

[0088] Comparative Example 2: The difference from Example 1 is that, without going through the step of preparing coated composite microspheres, multifunctional composite microspheres are used to replace the coated composite microspheres in step one, and the remaining steps remain unchanged to prepare a conveyor belt.

[0089] Comparative Example 3: The difference from Example 1 is that, without going through the step of preparing modified nitrile rubber, nitrile rubber is used to replace the modified nitrile rubber in step one, and the remaining steps remain unchanged to prepare a conveyor belt.

[0090] The coal mine flame-retardant and wear-resistant conveyor belts prepared in Examples 1-3 and Comparative Examples 1-3 are cut into 10 cm x 10 cm samples, the oxygen index of the samples is tested according to GB / T 10707-2008 “Determination of Combustion Behavior of Rubber”, the higher the material oxygen index, the higher the oxygen concentration required for ignition, the more difficult it is to be ignited, thereby the flame retardancy test is carried out; the relative volume abrasion of the conveyor belt is tested according to GB / T 9867-2008 “Determination of Abrasion Resistance of Vulcanized Rubber or Thermoplastic Rubber (Rotary Roller Abrasion Machine Method)”, thereby the wear resistance test is carried out; the tensile strength test is carried out according to GB / T 528-2009 “Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber”; the adhesion strength between the cover rubber and the skeleton layer of the conveyor belt is tested according to “GB / T 20021-2017 Canvas Core Heat-Resistant Conveyor Belt” by using 180° peeling method; and the surface resistivity of the conveyor belt is tested according to GB / T 1410-2006 “Test Method for Volume Resistivity and Surface Resistivity of Solid Insulating Materials”.

[0091] The results are shown in Table 1:

[0092] Table 1: Performance test results of a coal mine flame-retardant and wear-resistant conveyor belt

[0093] Item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Relative volume loss / mm 3 ]] 35 42 45 72.6 75.3 80.6 Tensile strength / MPa 29.9 29.3 28.8 25.2 24.3 20.6 Oxygen index % 68.8 67.4 66.9 48.1 59.4 53.0 Adhesion strength of covering rubber and skeleton layer N / mm 9.5 9.2 9.0 8.5 7.2 7.8 Surface resistivity Ω 6.2 x 10 6 ]]> 6.4 x 10 6 ]] 6.8 x 10 6 ]] 7.2 x 10 7 ]] 8.9 x 10 7 ]] 2.8 x 10 8 ]]>

[0094] As can be seen from Table 1, the flame-retardant wear-resistant conveying belt for coal mine prepared in Examples 1-3 is obviously superior to Comparative Examples 1-3; through the iron / sb elements in the multifunctional composite microspheres and zinc borate forming a high-efficiency flame-retardant synergistic system, promoting the generation of a dense carbon layer, and through octavinylsilsesquioxane and DOPO acrylate enhancing the thermal stability and flame retardance of the butyl rubber, the wear resistance, mechanical strength and flame-retardant capacity of the matrix are greatly improved, and the silicon carbide coating improves the dispersibility of the microspheres and the bonding strength at the rubber interface, strengthening the wear resistance and mechanical properties.

[0095] In Comparative Example 1, the oxygen index decreases significantly, which may be due to the absence of iron nitrate and antimony trioxide, and iron and antimony can form Fe-Sb-O compounds in the combustion process, which have a synergistic effect with DOPO acrylate and zinc borate in the coating layer, and the iron element promotes the formation of a dense and continuous carbon layer, which can act as a physical barrier to effectively isolate oxygen and heat, and zinc borate itself can play a flame-retardant role by dehydrating and absorbing heat to form a glassy barrier, but its effect alone is limited, and the absence of iron and antimony makes it lose the synergistic effect, resulting in a significant reduction in flame-retardant efficiency.

[0096] In Comparative Example 2, the adhesion strength of the coating and the skeleton layer decreases significantly, which may be due to the absence of silicon carbide coating and silane coupling agent modification, and the uncoated multifunctional composite microspheres are severely agglomerated due to the surface polarity, which destroys the homogeneity of the coating and causes stress concentration, and the absence of silane coupling agent KH-550 makes the filler and the matrix only have weak van der Waals force, which eventually leads to the failure of chemical bonding with the epoxy resin adhesive.

[0097] In Comparative Example 3, the tensile strength decreases significantly, and the relative volume loss and surface resistivity increase significantly, which may be due to the use of ordinary butyl rubber instead of modified butyl rubber, and the unmodified ordinary butyl rubber has low polarity, poor compatibility with fillers, and lacks the reinforcing structure introduced by modification, which causes the conductive carbon black and composite microspheres to be severely agglomerated and unevenly dispersed in the rubber matrix, and at the same time weakens the interfacial bonding force between the fillers and the matrix, and leads to a single and weak crosslinked network structure, and the combination of filler agglomeration and weak interface reduces the material's ability to resist tension and wear, and the poor dispersion and contact of conductive carbon black severely damages the continuity of the conductive network, ultimately resulting in the overall deterioration of mechanical properties, wear resistance and conductivity.

[0098] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application.

Claims

1. A fire-retardant and wear-resistant conveying belt for coal mines, comprising a rubberized layer and a plasticized skeleton layer located in the rubberized layer; characterized in that, The rubber coating layer is composed of rubber coating, and the plastic skeleton layer is composed of aramid fiber cloth. 90-100 parts of modified nitrile rubber, 1-2 parts of calcium stearate, 25-30 parts of coated composite microspheres, 10-15 parts of conductive carbon black, 3-5 parts of zinc borate, 1-1.5 parts of sulfur, 3-5 parts of zinc oxide and 1-1.5 parts of stearic acid; The coated composite microspheres are prepared by coating the multifunctional composite microspheres with silicon carbide; The multifunctional composite microspheres are prepared by the following steps: Dissolve calcium nitrate, iron nitrate and antimony trioxide in nitric acid to obtain solution A; then prepare surfactant solution B, adjust the pH value, and then add solution A dropwise into solution B, stir, pour the mixed solution into a high-pressure reaction kettle with a polytetrafluoroethylene liner, react, cool, wash the product with deionized water and anhydrous ethanol, centrifuge, and vacuum dry to obtain multifunctional composite microspheres.

2. The fire resistant, abrasion resistant conveyor belt for coal mines according to claim 1, characterized in that, The modified nitrile rubber is prepared by the following steps: Put nitrile rubber and toluene into a reaction kettle, stir at 50-60℃ for 30-40min, then add octavinylsilsesquioxane, DOPO acrylate and benzoyl peroxide, react under nitrogen protection at 60-75℃ for 3-4h, then add tetraphenylphosphonium bromide and zinc stearate, stir at 50-60℃ for 2-3h, transfer to 1000mL methanol, stir for 5-10min, filter, wash the filter cake with deionized water and methanol for 3-5 times, and vacuum dry to obtain modified nitrile rubber.

3. A fire resistant, abrasion resistant conveyor belt for coal mines according to claim 2, characterised in that, The amount ratio of nitrile rubber, toluene, octavinylsilsesquioxane, DOPO acrylate, benzoyl peroxide, tetraphenylphosphonium bromide and zinc stearate is 90-100g:350-400mL:6-8g:5-6g:0.8-1g:4-5g:0.3-0.5g.

4. The fire resistant, abrasion resistant conveyor belt for coal mines according to claim 1, characterized in that, The coated composite microspheres are prepared by the following steps: Ultrasonic immersion the multifunctional composite microspheres in 10wt% silane coupling agent KH-550 ethanol solution for 20-30min, filter and dry to obtain pretreated microspheres; Put the pretreated microspheres and polycarbosilane into a reaction kettle, stir for 1-2h, then add sodium chloride and potassium chloride, stir for 15-30min to obtain a mixed powder, transfer to a graphite crucible and place in a tube furnace, heat to 400-500℃ at 5℃ / min under argon atmosphere, keep for 1-2h, then heat to 1200-1300℃ at 3℃ / min, keep for 2-3h, cool to room temperature with the furnace, wash the product with hot water and ethanol for 3-5 times, and vacuum dry to obtain coated composite microspheres.

5. A fire resistant, abrasion resistant conveyor belt for coal mines according to claim 4, characterised in that, The amount ratio of multifunctional composite microspheres and silane coupling agent KH-550 ethanol solution is 40-50g:90-100mL.

6. A fire resistant, abrasion resistant conveyor belt for coal mines according to claim 4, characterized in that, The mass ratio of pretreated microspheres, polycarbosilane, sodium chloride and potassium chloride is 40-50:15-20:130-150:130-150.

7. The fire resistant, abrasion resistant conveyor belt for coal mines according to claim 4, characterized in that, The multifunctional composite microspheres are prepared by the following steps: Put calcium nitrate tetrahydrate, ferric nitrate nonahydrate, antimony trioxide, concentrated nitric acid and deionized water into a reaction kettle, stir for 30-40 min, then add sodium citrate and stir for 1-2 h to obtain solution A; Put cetyltrimethylammonium bromide and deionized water into a constant temperature water bath, stir for 30-40 min at 50-60℃, then add diammonium hydrogen phosphate and stir for 30-40 min, adjust the pH value to 5 with nitric acid to obtain solution B; Add solution A dropwise into solution B, stir for 30-40 min, slowly pour the mixed solution into a polytetrafluoroethylene lined high-pressure reaction kettle, react at 130-150℃ for 20-24 h, cool with ice water, wash the product with deionized water and anhydrous ethanol, centrifuge 3-5 times, and vacuum dry to obtain multifunctional composite microspheres.

8. A fire resistant, abrasion resistant conveyor belt for coal mines according to claim 7, characterised in that, The amount ratio of calcium nitrate tetrahydrate, ferric nitrate nonahydrate, antimony trioxide, concentrated nitric acid, deionized water and sodium citrate is 60-70g:15-20g:15-20g:15-20mL:2.5-3L:90-100g.

9. The fire resistant, abrasion resistant conveyor belt for coal mines according to claim 7, characterized in that, The amount ratio of cetyltrimethylammonium bromide, deionized water and diammonium hydrogen phosphate is 18-20g:3.5-4L:30-32g.

10. A method for preparing a flame-retardant and wear-resistant conveyor belt for coal mines according to any one of claims 1-9, characterized in that, The preparation method comprises the following steps: Step one: Put modified butyl nitrile rubber and calcium stearate into a mixer, mix at 60-70℃ for 8-10 min, add coated composite microspheres, conductive carbon black and zinc borate, mix at 80-90℃ for 6-8 min, then add sulfur, zinc oxide and stearic acid, mix at 100-110℃ for 5-10 min to obtain a covering rubber; Step two: Dip the aramid fiber cloth skeleton layer in an epoxy resin adhesive, dip for 30-40 min to obtain a dipped skeleton layer, and put the dipped skeleton layer into a plasticizing box and plasticize at 160-170℃ for 45-60 min to obtain a plasticized skeleton layer; Step three: Preheat the covering rubber to 90-100℃, adjust the calender, warm the upper and lower rollers to 150-170℃, first lay the plasticized skeleton layer on the surface of the lower roller, then evenly coat the covering rubber on top of the skeleton layer, start the calender, roll at the same time from both sides, complete double-sided calendering by wrapping the skeleton layer in the covering rubber layer, and transfer to a flat plate vulcanizer, vulcanize at 150-160℃ for 30-40 min to obtain a flame-retardant and wear-resistant conveyor belt for coal mines.