Halogen-free rubber conveyor belt and preparation process thereof

Abstract

The invention provides a halogen-free rubber conveyor belt and a preparation process thereof, belonging to the technical field of rubber conveyor belts. The invention comprises the following steps: mixing n-hexyl phosphoric acid, ethanol and a magnesium hydroxide suspension, cooling and drying to obtain modified magnesium hydroxide; grinding steel slag powder, adding anhydrous ethanol and a sorbic acid solution, stirring and reacting, centrifuging to obtain a precipitate, and drying to obtain modified steel slag; adding rubber, modified steel slag, carbon black, modified magnesium hydroxide and an auxiliary agent into a double-roll mill, mixing, thinning, calendering to produce a sheet, and pressing the surface-treated aramid fiber cloth and a steel wire rope into a sheet, and vulcanizing to obtain a halogen-free rubber conveyor belt, which can improve the flame retardant property of the rubber conveyor belt while improving the mechanical strength and high-temperature resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber conveyor belts, and in particular to a halogen-free rubber conveyor belt and a preparation process thereof. Background Art

[0002] Steel cord conveyor belts are often used for transporting heavy, long-distance materials. Currently, steel cord conveyor belts are primarily divided into two categories: general-purpose steel cord conveyor belts and flame-retardant steel cord conveyor belts specifically designed for coal mining. Industries such as metallurgy, building materials, and chemicals often transport high-temperature materials such as sintered ore, pellets, cement clinker, lime, coke, and fertilizers, which are prone to fire during transportation. Consequently, these industries place even stricter demands on steel cord conveyor belts, requiring them to possess both flame-retardant properties and excellent high-temperature resistance to prevent ignition or damage under high-temperature conditions.

[0003] Traditional flame-retardant conveyor belts mostly use halogen elements as flame retardants, which have a strong flame retardant effect and improve the flame retardant properties of the material. However, when the conveyor belt catches fire under high temperature or fire conditions, the halogen reacts with the chemicals produced by thermal decomposition, releasing large amounts of toxic gases accompanied by thick smoke. This not only pollutes the air but can also have serious impacts on worker health, equipment and facilities, and the environment. To avoid the use of halogen flame retardants and reduce the impact on the environment and human health, researchers have developed a variety of halogen-free flame retardants suitable for conveyor belts. These halogen-free flame retardants are generally composed of environmentally friendly materials such as metal hydroxides, phosphates, and inorganic compounds. They absorb heat during combustion, forming a carbonized layer that hinders the spread of flames, effectively reducing the risk of fire and preventing the release of toxic gases.

[0004] Patent application publication number CN117183500B discloses an antimony-free, highly wear-resistant, flame-retardant conveyor belt and its preparation method. The belt comprises a rubber layer and a skeleton layer. The rubber layer is made of nitrile rubber, a composite flame retardant, fillers, sulfur, stearic acid, zinc oxide, and an antioxidant. The composite flame retardant is composed of magnesium hydroxide, borate, and phosphate esters. The skeleton layer is made of aramid fiber cloth. This technical solution addresses the problems of existing nitrile rubber conveyor belts, such as poor flame retardancy, poor adhesion between the rubber layer and the skeleton layer, and the environmental impact of using antimony-containing flame retardants. However, the magnesium hydroxide flame retardant has poor dispersion in the body, which affects mechanical properties.

[0005] Therefore, it is necessary to provide a halogen-free rubber conveyor belt and a preparation process thereof to solve the problems existing in the above-mentioned prior art. Summary of the Invention

[0006] In view of this, the present invention provides a halogen-free rubber conveyor belt and a preparation process thereof, which can improve the flame retardant properties of the rubber conveyor belt while improving the mechanical strength and high temperature resistance.

[0007] To achieve the above object, the present invention provides a process for preparing a halogen-free rubber conveyor belt, comprising the following steps:

[0008] S1. Mix n-hexyl phosphoric acid and ethanol, add dropwise to a magnesium hydroxide suspension, stir, cool, wash, and vacuum dry to obtain modified magnesium hydroxide;

[0009] S2, grinding the steel slag powder, adding anhydrous ethanol and stirring, adding sorbic acid solution, stirring to react, centrifuging to obtain a precipitate, washing, and drying to obtain modified steel slag;

[0010] S3, immersing the pretreated aramid fiber cloth in a KH-560 solution to obtain a surface-treated aramid fiber cloth;

[0011] S4. Rubber, modified steel slag, carbon black, modified magnesium hydroxide, stearic acid, zinc oxide, cross-linking agent and sulfur are added into a double-roll mill and mixed evenly. The mixture is thinly passed through the mill, and the sheet is pressed into shape with the surface-treated aramid fiber cloth, and vulcanized to obtain a halogen-free rubber conveyor belt.

[0012] The present invention modifies the surface of magnesium hydroxide by esterification with n-hexyl phosphoric acid. Magnesium hydroxide absorbs heat from the surrounding environment through an endothermic decomposition reaction and releases water vapor / carbon dioxide, thereby protecting the matrix from the influence of oxygen. However, due to its hydrophilic surface, the magnesium hydroxide particles have poor dispersibility in hydrophobic rubber, are prone to aggregation, and poorly bonded to the rubber matrix, which affects the mechanical properties of the rubber matrix and weakens the flame retardant effect. By introducing n-hexyl phosphoric acid, the hydrophobic group of n-hexyl phosphoric acid can improve the compatibility of magnesium hydroxide with rubber, thereby improving dispersibility; and the phosphate group in n-hexyl phosphoric acid has a free radical stabilizing effect by capturing free radicals during the combustion of hydrocarbons, so that it can slow down the OH reaction at high temperatures. - The release rate of n-hexyl phosphate and magnesium hydroxide creates a synergistic effect on thermal stability, delaying the decomposition temperature of magnesium hydroxide, allowing it to function at higher temperatures and improving high-temperature resistance. The phosphate group forms a P-Mg-O bond with magnesium hydroxide, synergistically promoting the formation of a dense carbon layer and enhancing the flame retardant effect.

[0013] The present invention uses sorbic acid to treat the steel slag surface to organicize it, producing a modified steel slag that can replace most carbon black. Steel slag itself contains metal oxides, making it suitable for use as a reinforcing filler. However, its hydrophilic surface makes it difficult to bond with rubber. Sorbic acid contains carboxylic acid groups that form chemical bonds with the metal oxides on the steel slag surface, enhancing interfacial bonding. The modified steel slag disperses better in rubber, providing a more effective reinforcement. Furthermore, the CaO / SiO2 components in the steel slag form a calcium silicate network at high temperatures, which improves the overall high-temperature resistance.

[0014] The present invention utilizes aramid fiber and steel wire rope as the reinforcing layer of the halogen-free rubber conveyor belt. The steel wire rope provides high-rigidity longitudinal tensile strength, while the aramid fiber, with its high modulus and low density, can form a tear-resistant network structure in the transverse direction to prevent local fracture caused by stress concentration. In addition, the steel wire rope and aramid fiber have good high-temperature resistance and can maintain good physical properties in high-temperature environments. The addition of aramid fiber can also effectively block the spread of flames. Here, after the aramid fiber cloth is treated with KH-560 silane coupling agent, a stable silane layer is formed on the fiber surface. This layer not only improves the bonding strength between the aramid fiber and the rubber matrix, but also improves its interface compatibility, thereby significantly improving the overall mechanical properties of the composite material.

[0015] Optionally, the magnesium hydroxide suspension is prepared by mixing magnesium hydroxide particles and anhydrous ethanol and subjecting the mixture to ultrasonic treatment for 5 to 10 minutes.

[0016] Optionally, in step S1, n-hexyl phosphoric acid and ethanol are mixed and stirred for 10 to 15 minutes, added dropwise to the magnesium hydroxide suspension, vacuumed, stirred at 2000 r / min for 10 to 20 minutes, heated to 170° C., stirred at 300 r / min for 6 hours, cooled to room temperature, rinsed with anhydrous ethanol 2 to 3 times, and vacuum dried at room temperature for 8 to 12 hours to obtain modified magnesium hydroxide.

[0017] In the process of preparing the modified magnesium hydroxide of the present invention, washing with anhydrous ethanol helps to remove unreacted solvent, impurities remaining on the surface and by-products, thereby ensuring the purity and performance of the modified magnesium hydroxide.

[0018] Optionally, in step S2, the mixing stirring speed is 500 r / min, the time is 10 min, the stirring reaction temperature is 80-150° C., the time is 2-3 h, anhydrous ethanol is used for washing 2-3 times, and the drying temperature is 100-120° C., and the time is 6 h.

[0019] Preferably, in step S2, the steel slag is ground to a particle size of less than 100 mesh.

[0020] The present invention grinds the steel slag powder to a particle size of less than 100 meshes, which can significantly increase its surface activity and reaction rate with other chemical substances, thereby improving the modification effect.

[0021] Optionally, the mass concentration of the sorbic acid solution in step S2 is 14%.

[0022] Optionally, the pretreated aramid fiber cloth is prepared by ultrasonically cleaning the aramid fiber cloth with acetone for 1 hour, washing it with deionized water for 3 to 5 times, immersing it in a 5% CaCl2 ethanol solution for 5 hours, immersing it in a 10% NaOH aqueous solution at 65°C for 3 to 5 hours, rinsing it with deionized water for 2 to 3 times, and drying it.

[0023] The present invention utilizes CaCl2 ethanol solution to increase surface roughness, and uses NaOH solution to hydrolyze aromatic fibers and destroy amide bonds on molecular chains, thereby forming carboxylic acid groups and primary amines, thereby increasing the surface activity of aramid fibers and enhancing their ability to combine with other materials.

[0024] Optionally, in step S3, the pretreated aramid fiber cloth is immersed in a KH-560 solution with a mass concentration of 10% at 40° C. for 3 to 5 hours to obtain the surface-treated aramid fiber cloth.

[0025] Optionally, in step S4, the rubber is natural rubber, silicone rubber and carboxylated styrene-butadiene rubber, the cross-linking agent is di-tert-butyl peroxide, and an antioxidant 1010 is also added when the cross-linking agent is added.

[0026] Optionally, the mixing in step S4 is performed at 45-70° C., the number of thin passes is 5-7 times, the vulcanization temperature is 160° C., and the time is 30-50 min.

[0027] Optionally, the halogen-free rubber conveyor belt includes the following raw materials in parts by mass: 100 parts of rubber, 20-30 parts of modified steel slag, 10-20 parts of carbon black, 10-15 parts of modified magnesium hydroxide, 8-10 parts of stearic acid, 2-3 parts of zinc oxide, 0.3-0.5 parts of cross-linking agent, 5-7 parts of sulfur, and 1-2 parts of antioxidant 1010.

[0028] The present invention adopts the above-mentioned mass fraction matching ratio to improve the overall performance of the halogen-free rubber conveyor belt in multiple aspects.

[0029] The above technical solution of the present invention includes at least the following beneficial effects:

[0030] 1. The present invention modifies the surface of magnesium hydroxide by esterifying it with n-hexyl phosphate, thereby improving its compatibility with the rubber matrix and enhancing its dispersibility. The hydrophobic group of n-hexyl phosphate strengthens the binding of magnesium hydroxide to rubber and reduces aggregation. Magnesium hydroxide protects the matrix through endothermic decomposition reaction, and the phosphate group in n-hexyl phosphate stabilizes free radicals, delaying OH - In addition, the phosphoric acid group forms a P-Mg-O bond with magnesium hydroxide, promoting the formation of a dense carbon layer and further enhancing the flame retardant effect.

[0031] 2. This invention modifies steel slag by treating it with sorbic acid, organicizing its surface and enhancing the interfacial bonding between the slag and rubber. The carboxylic acid groups of sorbic acid form chemical bonds with metal oxides on the surface of the slag, improving the slag's dispersibility and reinforcing properties. Furthermore, the CaO / SiO2 components in the slag form a calcium silicate network at high temperatures, enhancing the rubber's high-temperature resistance.

[0032] 3. This invention utilizes aramid fiber and steel cord as the reinforcement layer of the halogen-free rubber conveyor belt. The steel cord provides longitudinal tensile strength, while the aramid fiber forms a tear-resistant network, enhancing transverse strength. Both exhibit excellent high-temperature resistance and can block flame spread. Treatment with KH-560 silane coupling agent forms a stable silane layer on the aramid fiber surface, enhancing the bond strength and interfacial compatibility between the fiber and the rubber matrix, significantly improving the mechanical properties of the composite material. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0034] Example 1

[0035] 50 parts of magnesium hydroxide particles and 500 parts of anhydrous ethanol were mixed and ultrasonically treated for 10 minutes to prepare a magnesium hydroxide suspension; 16 parts of n-hexyl phosphoric acid and 100 parts of ethanol were mixed and stirred for 15 minutes, and then added dropwise to the magnesium hydroxide suspension. The mixture was vacuumed and stirred at a speed of 2000 r / min for 20 minutes. The mixture was heated to 170°C and stirred at a speed of 300 r / min for 6 hours. The mixture was cooled to room temperature, rinsed with anhydrous ethanol three times, and vacuum dried at room temperature for 12 hours to prepare modified magnesium hydroxide.

[0036] 100 parts of steel slag powder were ground to a particle size of less than 100 mesh, poured into a 250-part three-necked flask, added with 100 parts of anhydrous ethanol, stirred at 500 r / min for 10 minutes, and slowly added with 300 parts of sorbic acid solution with a mass concentration of 14%. The mixture was stirred at 150°C for 3 hours, centrifuged to obtain the precipitate, washed with anhydrous ethanol three times, and dried at 120°C for 6 hours to obtain the modified steel slag.

[0037] The aramid fiber cloth was ultrasonically cleaned with acetone for 1 hour, washed with deionized water 5 times, immersed in a 5% CaCl2 ethanol solution for 5 hours, immersed in a 10% NaOH aqueous solution at 65°C for 5 hours, rinsed with deionized water 3 times, and dried to obtain the pretreated aramid fiber cloth; the pretreated aramid fiber cloth was immersed in a 10% KH-560 solution at 40°C for 5 hours to obtain the surface-treated aramid fiber cloth.

[0038] On a double-roll mill, add 10 parts of natural rubber, 30 parts of silicone rubber, and 60 parts of carboxylated styrene-butadiene rubber, control the mill roll temperature at 50°C, add 30 parts of modified steel slag, 10 parts of carbon black, 15 parts of modified magnesium hydroxide, 10 parts of stearic acid, 3 parts of zinc oxide, 2 parts of antioxidant 1010 in sequence, and finally add 0.5 parts of cross-linking agent di-tert-butyl peroxide and 7 parts of sulfur, control the mill roll temperature at 70°C, mix evenly on the mill, then adjust the mill roll distance to 1 mm, the roll temperature to 50°C, and pass through thinly 7 times to obtain a rubber mixture.

[0039] The mixed rubber is put into an open mixing mill for re-mixing, and then placed in a calender to calender out a sheet to obtain a covering layer. The covering layer, the surface-treated aramid fiber cloth and the steel wire rope are pressed into shape on a molding machine according to the structure of covering layer-surface-treated aramid fiber cloth-steel wire rope-surface-treated aramid fiber cloth-covering layer, and then placed in a flat vulcanizer for vulcanization at 160°C for 50 minutes to obtain a halogen-free rubber conveyor belt.

[0040] Example 2

[0041] 30 parts of magnesium hydroxide particles and 500 parts of anhydrous ethanol were mixed and ultrasonically treated for 5 minutes to prepare a magnesium hydroxide suspension; 16 parts of n-hexyl phosphoric acid and 100 parts of ethanol were mixed and stirred for 10 minutes, and then added dropwise to the magnesium hydroxide suspension. The mixture was vacuumed and stirred at a speed of 2000 r / min for 10 minutes. The mixture was heated to 170°C and stirred at a speed of 300 r / min for 6 hours. The mixture was cooled to room temperature, rinsed twice with anhydrous ethanol, and vacuum dried at room temperature for 8 hours to prepare modified magnesium hydroxide.

[0042] 100 parts of steel slag powder were ground to a particle size of less than 100 mesh, poured into a 250-part three-necked flask, added with 100 parts of anhydrous ethanol, stirred at 500 r / min for 10 minutes, and slowly added with 300 parts of sorbic acid solution with a mass concentration of 14%. The mixture was stirred at 80°C for 3 hours, centrifuged to obtain the precipitate, washed twice with anhydrous ethanol, and dried at 100°C for 6 hours to obtain the modified steel slag.

[0043] The aramid fiber cloth was ultrasonically cleaned with acetone for 1 hour, washed with deionized water three times, immersed in a 5% CaCl2 ethanol solution for 5 hours, immersed in a 10% NaOH aqueous solution at 65°C for 3 hours, rinsed twice with deionized water, and dried to obtain the pretreated aramid fiber cloth; the pretreated aramid fiber cloth was immersed in a 10% KH-560 solution at 40°C for 3 hours to obtain the surface-treated aramid fiber cloth.

[0044] On a double-roll mill, add 20 parts of natural rubber, 30 parts of silicone rubber, and 50 parts of carboxylated styrene-butadiene rubber, control the mill roll temperature at 30°C, add 20 parts of modified steel slag, 20 parts of carbon black, 10 parts of modified magnesium hydroxide, 8 parts of stearic acid, 2 parts of zinc oxide, 1 part of antioxidant 1010 in sequence, and finally add 0.3 parts of cross-linking agent di-tert-butyl peroxide and 5 parts of sulfur, control the mill roll temperature at 45°C, mix evenly on the mill, then adjust the mill roll distance to 0.5 mm, the roll temperature to 40°C, and pass through thinly 5 times to obtain a rubber compound.

[0045] The mixed rubber is placed in an open mixing mill for re-mixing, and then placed in a calender for calendering to produce a covering layer. The covering layer, the surface-treated aramid fiber cloth and the steel wire rope are pressed into shape on a molding machine according to the structure of covering layer-surface-treated aramid fiber cloth-steel wire rope-surface-treated aramid fiber cloth-covering layer, and the halogen-free rubber conveyor belt is produced by vulcanizing the halogen-free rubber conveyor belt at 160°C for 30 minutes.

[0046] Example 3

[0047] 35 parts of magnesium hydroxide particles and 500 parts of anhydrous ethanol were mixed and ultrasonically treated for 6 minutes to prepare a magnesium hydroxide suspension; 16 parts of n-hexyl phosphoric acid and 100 parts of ethanol were mixed and stirred for 12 minutes, and then added dropwise to the magnesium hydroxide suspension. The mixture was vacuumed and stirred at a speed of 2000 r / min for 18 minutes. The mixture was heated to 170°C and stirred at a speed of 300 r / min for 6 hours. The mixture was cooled to room temperature, rinsed with anhydrous ethanol three times, and vacuum dried at room temperature for 10 hours to prepare modified magnesium hydroxide.

[0048] 100 parts of steel slag powder were ground to a particle size of less than 100 mesh, poured into a 250-part three-necked flask, added with 100 parts of anhydrous ethanol, stirred at 500 r / min for 10 minutes, and slowly added with 300 parts of sorbic acid solution with a mass concentration of 14%. The mixture was stirred at 120°C for 2.5 hours, centrifuged to obtain the precipitate, washed three times with anhydrous ethanol, and dried at 100°C for 6 hours to obtain the modified steel slag.

[0049] The aramid fiber cloth was ultrasonically cleaned with acetone for 1 hour, washed with deionized water 4 times, immersed in a 5% CaCl2 ethanol solution for 5 hours, immersed in a 10% NaOH aqueous solution at 65°C for 4 hours, rinsed with deionized water 3 times, and dried to obtain the pretreated aramid fiber cloth; the pretreated aramid fiber cloth was immersed in a 10% KH-560 solution at 40°C for 4 hours to obtain the surface-treated aramid fiber cloth.

[0050] On a double-roll mill, add 15 parts of natural rubber, 30 parts of silicone rubber, and 55 parts of carboxylated styrene-butadiene rubber, control the mill roll temperature at 40°C, add 28 parts of modified steel slag, 12 parts of carbon black, 14 parts of modified magnesium hydroxide, 9 parts of stearic acid, 2.7 parts of zinc oxide, 1.8 parts of antioxidant 1010 in sequence, and finally add 0.4 parts of cross-linking agent di-tert-butyl peroxide and 6 parts of sulfur, control the mill roll temperature at 70°C, mix evenly on the mill, then adjust the mill roll distance to 1 mm, the roll temperature to 50°C, and pass through thinly 6 times to obtain a rubber mixture.

[0051] The mixed rubber is put into an open mixing mill for re-mixing, and then placed in a calender to calender out a sheet to obtain a covering layer. The covering layer, the surface-treated aramid fiber cloth and the steel wire rope are pressed into shape on a molding machine according to the structure of covering layer-surface-treated aramid fiber cloth-steel wire rope-surface-treated aramid fiber cloth-covering layer, and then placed in a flat vulcanizer for vulcanization at 160°C for 45 minutes to obtain a halogen-free rubber conveyor belt.

[0052] Example 4

[0053] 35 parts of magnesium hydroxide particles and 500 parts of anhydrous ethanol were mixed and ultrasonically treated for 8 minutes to prepare a magnesium hydroxide suspension; 16 parts of n-hexyl phosphoric acid and 100 parts of ethanol were mixed and stirred for 11 minutes, and then added dropwise to the magnesium hydroxide suspension. The mixture was vacuumed and stirred at a speed of 2000 r / min for 15 minutes. The temperature was raised to 170°C and stirred at a speed of 300 r / min for 6 hours. The mixture was cooled to room temperature, rinsed with anhydrous ethanol three times, and vacuum dried at room temperature for 8 hours to prepare modified magnesium hydroxide.

[0054] 100 parts of steel slag powder were ground to a particle size of less than 100 mesh, poured into a 250-part three-necked flask, added with 100 parts of anhydrous ethanol, stirred at 500 r / min for 10 minutes, and slowly added with 300 parts of sorbic acid solution with a mass concentration of 14%. The mixture was stirred at 110°C for 2 hours, centrifuged to obtain the precipitate, washed three times with anhydrous ethanol, and dried at 110°C for 6 hours to obtain the modified steel slag.

[0055] The aramid fiber cloth was ultrasonically cleaned with acetone for 1 hour, washed with deionized water three times, immersed in a 5% CaCl2 ethanol solution for 5 hours, immersed in a 10% NaOH aqueous solution at 65°C for 3 hours, rinsed with deionized water twice, and dried to obtain the pretreated aramid fiber cloth; the pretreated aramid fiber cloth was immersed in a 10% KH-560 solution at 40°C for 3.5 hours to obtain the surface-treated aramid fiber cloth.

[0056] On a double-roll mill, add 15 parts of natural rubber, 30 parts of silicone rubber, and 55 parts of carboxylated styrene-butadiene rubber, control the mill roll temperature at 40°C, add 22 parts of modified steel slag, 18 parts of carbon black, 11 parts of modified magnesium hydroxide, 8 parts of stearic acid, 3 parts of zinc oxide, 1.2 parts of antioxidant 1010 in sequence, and finally add 0.3 parts of cross-linking agent di-tert-butyl peroxide and 5.5 parts of sulfur, control the mill roll temperature at 60°C, mix evenly on the mill, then adjust the mill roll distance to 0.5 mm, the roll temperature to 40°C, and pass through thinly 6 times to obtain a rubber compound.

[0057] The mixed rubber is placed in an open mixing mill for re-mixing, and then placed in a calender for calendering to obtain a covering layer. The covering layer, the surface-treated aramid fiber cloth and the steel wire rope are pressed into a structure of covering layer-surface-treated aramid fiber cloth-steel wire rope-surface-treated aramid fiber cloth-covering layer on a molding machine, and then placed in a flat vulcanizer for vulcanization at 160°C for 35 minutes to obtain a halogen-free rubber conveyor belt.

[0058] Example 5

[0059] 40 parts of magnesium hydroxide particles and 500 parts of anhydrous ethanol were mixed and ultrasonically treated for 6 minutes to prepare a magnesium hydroxide suspension; 16 parts of n-hexyl phosphoric acid and 100 parts of ethanol were mixed and stirred for 12 minutes, and then added dropwise to the magnesium hydroxide suspension. The mixture was vacuumed and stirred at a speed of 2000 r / min for 15 minutes. The mixture was heated to 170°C and stirred at a speed of 300 r / min for 6 hours. The mixture was cooled to room temperature, rinsed twice with anhydrous ethanol, and vacuum dried at room temperature for 9 hours to prepare modified magnesium hydroxide.

[0060] 100 parts of steel slag powder were ground to a particle size of less than 100 mesh, poured into a 250-part three-necked flask, added with 100 parts of anhydrous ethanol, stirred at 500 r / min for 10 minutes, and slowly added with 300 parts of sorbic acid solution with a mass concentration of 14%. The mixture was stirred at 90°C for 3 hours, centrifuged to obtain the precipitate, washed with anhydrous ethanol three times, and dried at 110°C for 6 hours to obtain the modified steel slag.

[0061] The aramid fiber cloth was ultrasonically cleaned with acetone for 1 hour, washed with deionized water 4 times, immersed in a 5% CaCl2 ethanol solution for 5 hours, immersed in a 10% NaOH aqueous solution at 65°C for 4.5 hours, rinsed with deionized water 3 times, and dried to obtain the pretreated aramid fiber cloth; the pretreated aramid fiber cloth was immersed in a 10% KH-560 solution at 40°C for 4 hours to obtain the surface-treated aramid fiber cloth.

[0062] On a double-roll mill, add 11 parts of natural rubber, 30 parts of silicone rubber, and 59 parts of carboxylated styrene-butadiene rubber, control the mill roll temperature at 50°C, add 20 parts of modified steel slag, 20 parts of carbon black, 15 parts of modified magnesium hydroxide, 9 parts of stearic acid, 2.6 parts of zinc oxide, 1.4 parts of antioxidant 1010 in sequence, and finally add 0.5 parts of cross-linking agent di-tert-butyl peroxide and 6 parts of sulfur, control the mill roll temperature at 60°C, mix evenly on the mill, then adjust the mill roll distance to 0.5 mm, the roll temperature to 50°C, and pass through thinly 7 times to obtain a rubber compound.

[0063] The mixed rubber is put into an open mixing mill for re-mixing, and then placed in a calender to calender out a sheet to obtain a covering layer. The covering layer, the surface-treated aramid fiber cloth and the steel wire rope are pressed into shape on a molding machine according to the structure of covering layer-surface-treated aramid fiber cloth-steel wire rope-surface-treated aramid fiber cloth-covering layer, and then placed in a flat vulcanizer for vulcanization at 160°C for 40 minutes to obtain a halogen-free rubber conveyor belt.

[0064] Example 6

[0065] 40 parts of magnesium hydroxide particles and 500 parts of anhydrous ethanol were mixed and ultrasonically treated for 5 minutes to prepare a magnesium hydroxide suspension; 16 parts of n-hexyl phosphoric acid and 100 parts of ethanol were mixed and stirred for 15 minutes, and then added dropwise to the magnesium hydroxide suspension. The mixture was vacuumed and stirred at a speed of 2000 r / min for 17 minutes. The mixture was heated to 170°C and stirred at a speed of 300 r / min for 6 hours. The mixture was cooled to room temperature, rinsed with anhydrous ethanol three times, and vacuum dried at room temperature for 11 hours to prepare modified magnesium hydroxide.

[0066] 100 parts of steel slag powder were ground to a particle size of less than 100 mesh, poured into a 250-part three-necked flask, added with 100 parts of anhydrous ethanol, stirred at 500 r / min for 10 minutes, and slowly added with 300 parts of sorbic acid solution with a mass concentration of 14%. The mixture was stirred at 150°C for 3 hours, centrifuged to obtain the precipitate, washed twice with anhydrous ethanol, and dried at 120°C for 6 hours to obtain the modified steel slag.

[0067] The aramid fiber cloth was ultrasonically cleaned with acetone for 1 hour, washed with deionized water three times, immersed in a 5% CaCl2 ethanol solution for 5 hours, immersed in a 10% NaOH aqueous solution at 65°C for 5 hours, rinsed twice with deionized water, and dried to obtain the pretreated aramid fiber cloth; the pretreated aramid fiber cloth was immersed in a 10% KH-560 solution at 40°C for 3 hours to obtain the surface-treated aramid fiber cloth.

[0068] On a double-roll mill, add 14 parts of natural rubber, 30 parts of silicone rubber, and 56 parts of carboxylated styrene-butadiene rubber, control the mill roll temperature at 40°C, add 28 parts of modified steel slag, 12 parts of carbon black, 13 parts of modified magnesium hydroxide, 10 parts of stearic acid, 2 parts of zinc oxide, 1 part of antioxidant 1010 in sequence, and finally add 0.3 parts of cross-linking agent di-tert-butyl peroxide and 5 parts of sulfur, control the mill roll temperature at 70°C, mix evenly on the mill, then adjust the mill roll distance to 1 mm, the roll temperature to 40°C, and pass through thinly 6 times to obtain a rubber compound.

[0069] The mixed rubber is put into an open mixing mill for re-mixing, and then placed in a calender to calender out a sheet to obtain a covering layer. The covering layer, the surface-treated aramid fiber cloth and the steel wire rope are pressed into shape on a molding machine according to the structure of covering layer-surface-treated aramid fiber cloth-steel wire rope-surface-treated aramid fiber cloth-covering layer, and then placed in a flat vulcanizer for vulcanization at 160°C for 40 minutes to obtain a halogen-free rubber conveyor belt.

[0070] The present invention also carried out comparative examples and related tests.

[0071] Comparative Example 1

[0072] Compared with Example 1, the only difference is that modified magnesium hydroxide is not prepared, magnesium hydroxide is directly added, and other preparation steps and components remain unchanged, and a halogen-free rubber conveyor belt is finally prepared.

[0073] Comparative Example 2

[0074] Compared with Example 1, the only difference is that modified steel slag is not prepared, and steel slag is directly added. Other preparation steps and components remain unchanged, and a halogen-free rubber conveyor belt is finally prepared.

[0075] Comparative Example 3

[0076] Compared with Example 1, the only difference is that the surface-treated aramid fiber cloth is not prepared, and the aramid fiber cloth is directly added. The other preparation steps and components remain unchanged, and a halogen-free rubber conveyor belt is finally prepared.

[0077] Performance testing

[0078] The halogen-free rubber conveyor belts prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were tested for relevant properties according to the national standard MT / T668-2019 flame-retardant steel cord conveyor belts for coal mines, GB / T528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber, and GB / T3512-2014 hot air accelerated aging and heat resistance test of vulcanized rubber or thermoplastic rubber. The specific test results are shown in Tables 1 and 2.

[0079] Table 1

[0080]

[0081] It can be seen from Table 1 that the relevant mechanical properties of the halogen-free rubber conveyor belt prepared by the present invention all meet the national standard requirements of MT / T668-2019 for steel cord flame-retardant conveyor belts for coal mines.

[0082] Combined with the data in Table 1, it can be seen that in Example 1, the bonding strength of the steel wire rope and the bonding strength between the covering layer and the aramid fiber layer are significantly improved due to the treatment of the aramid fiber surface, and the overall bonding strength is increased after the magnesium hydroxide and steel slag are modified, which also significantly improves the overall tensile strength, tear strength and elongation at break.

[0083] Table 2

[0084]

[0085] Combined with the data in Table 2, it can be seen that compared with the comparative example, the present invention uses n-hexyl phosphoric acid to modify magnesium hydroxide, thereby improving the flame retardant efficiency. The addition of modified steel slag and modified magnesium hydroxide significantly improves its high temperature resistance and smoke suppression effect, and can maintain good tensile strength and flame retardant properties even at 150°C.

[0086] The above is a preferred embodiment of the present invention. Those skilled in the art may make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for preparing a halogen-free rubber conveyor belt, characterized in that: The steps include: S1. Mix n-hexyl phosphoric acid and ethanol, add dropwise to a magnesium hydroxide suspension, stir, cool, wash, and vacuum dry to obtain modified magnesium hydroxide; S2, grinding the steel slag powder, adding anhydrous ethanol and stirring, adding sorbic acid solution, stirring to react, centrifuging to obtain a precipitate, washing, and drying to obtain modified steel slag; S3, immersing the pretreated aramid fiber cloth in a KH-560 solution to obtain a surface-treated aramid fiber cloth; S4, adding rubber, modified steel slag, carbon black, modified magnesium hydroxide, stearic acid, zinc oxide, a crosslinking agent and sulfur into a two-roll mill, mixing, thinning, and rolling out a sheet to obtain a covering layer; On a molding machine, the covering layer, the surface-treated aramid fiber cloth and the steel wire rope are pressed and formed in a structure of covering layer - surface-treated aramid fiber cloth - steel wire rope - surface-treated aramid fiber cloth - covering layer, and then placed in a flat vulcanizing press for vulcanization to produce a halogen-free rubber conveyor belt; In step S2, the steel slag is ground to a particle size of less than 100 mesh; The pretreated aramid fiber cloth is prepared by ultrasonically cleaning the aramid fiber cloth with acetone for 1 hour, washing it with deionized water for 3 to 5 times, immersing it in a 5% CaCl2 ethanol solution for 5 hours, immersing it in a 10% NaOH aqueous solution at 65°C for 3 to 5 hours, rinsing it with deionized water for 2 to 3 times, and drying it. In step S4, the rubber is natural rubber, silicone rubber and carboxylated styrene-butadiene rubber, the crosslinking agent is di-tert-butyl peroxide, and an antioxidant 1010 is added when the crosslinking agent is added.

2. The process for preparing a halogen-free rubber conveyor belt according to claim 1, characterized in that: The magnesium hydroxide suspension is prepared by mixing magnesium hydroxide particles and anhydrous ethanol and subjecting the mixture to ultrasonic treatment for 5 to 10 minutes.

3. The process for preparing a halogen-free rubber conveyor belt according to claim 1, characterized in that: In the step S1, n-hexyl phosphoric acid and ethanol are mixed and stirred for 10-15 minutes, added dropwise to the magnesium hydroxide suspension, vacuumed, stirred at a speed of 2000 r / min for 10-20 minutes, heated to 170° C., stirred at a speed of 300 r / min for 6 hours, cooled to room temperature, rinsed with anhydrous ethanol 2-3 times, and vacuum dried at room temperature for 8-12 hours to obtain modified magnesium hydroxide.

4. The process for preparing a halogen-free rubber conveyor belt according to claim 1, characterized in that: In step S2, the mixing and stirring speed is 500 r / min, the time is 10 minutes, the stirring reaction temperature is 80-150° C., the time is 2-3 hours, and the product is washed 2-3 times with anhydrous ethanol, and the drying temperature is 100-120° C., and the time is 6 hours.

5. The process for preparing a halogen-free rubber conveyor belt according to claim 1, characterized in that: The mass concentration of the sorbic acid solution in step S2 is 14%.

6. The process for preparing a halogen-free rubber conveyor belt according to claim 1, characterized in that: In step S3, the pretreated aramid fiber cloth is immersed in a KH-560 solution with a mass concentration of 10% at 40° C. for 3 to 5 hours to obtain a surface-treated aramid fiber cloth.

7. The process for preparing a halogen-free rubber conveyor belt according to claim 1, characterized in that: In step S4, the mixing is performed at 45-70° C., the number of thin passes is 5-7 times, the vulcanization temperature is 160° C., and the time is 30-50 minutes.

8. A halogen-free rubber conveyor belt, prepared by the process for preparing a halogen-free rubber conveyor belt according to any one of claims 1 to 7, characterized in that: The invention comprises the following raw materials in parts by mass: 100 parts of rubber, 20-30 parts of modified steel slag, 10-20 parts of carbon black, 10-15 parts of modified magnesium hydroxide, 8-10 parts of stearic acid, 2-3 parts of zinc oxide, 0.3-0.5 parts of cross-linking agent, 5-7 parts of sulfur, and 1-2 parts of antioxidant 1010.

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