An aramid fiber reinforced impact and abrasion resistant conveyor belt and method of making

Abstract

The application belongs to the technical field of polymer material conveying belt, and discloses an aramid fiber reinforced impact resistance and wear resistance conveying belt and a preparation method. The conveying belt comprises a covering rubber, a core layer rubber and an aramid fiber cloth. The surface crystallinity of aramid short fibers is moderately reduced by dimethyl sulfoxide infiltration, and then GMA functional groups and carboxyl functional groups are used to penetrate the aramid short fibers, so as to enhance the activity of the aramid short fibers and promote the interaction between the modified aramid short fibers and the rubber, thereby greatly improving the tensile strength, wear resistance and shear impact resistance of the covering rubber. By using malic acid resin in the core layer rubber, the core layer rubber and the aramid fiber cloth are fully penetrated and bonded, the adhesion strength of the covering rubber and the aramid fiber cloth is enhanced, the structural strength and durability of the conveying belt are improved, the protective rubber layer is prevented from falling off, the aramid core layer skeleton is matched, the service life of the conveying belt is prolonged, and the long-distance heavy-load conveying belt demand is met.

Description

Technical Field

[0001] This invention belongs to the field of polymer material conveyor belt technology, and specifically relates to an aramid fiber reinforced impact-resistant and wear-resistant conveyor belt and its preparation method. Background Technology

[0002] Conveyor belts are generally made of a high-strength reinforcing material as the inner core, covered with a rubber layer after vulcanization. The inner core, serving as the conveyor belt's skeleton material, primarily bears the load during operation; commonly used inner core skeleton materials include nylon fiber, polyester fiber, and steel wire rope. The covering rubber layer mainly serves to prevent corrosion, provide wear resistance, and protect the inner core skeleton material.

[0003] With the development of heavy-load, long-distance transportation in ultra-large logistics, port material handling, and deep-sea mining, there is an urgent need for conveyor belts with high load-bearing capacity. Heavy-duty, long-distance conveyor belts not only require high strength and large load capacity but also must be adaptable to complex application environments, possessing excellent corrosion resistance, wear resistance, heat resistance, and aging resistance. In existing heavy-duty material transportation scenarios such as mines, power plants, and ports, conveyor belts mainly use high-strength steel wire rope as the core skeleton. However, steel wire core conveyor belts are thick, have a heavy weight for long-distance transport, require high motor power, have high energy consumption, and high operating costs. Moreover, the steel wire core has poor corrosion resistance and is prone to breakage after continuous bending during long-term operation, affecting its service life.

[0004] Aramid fiber (AF, also known as aromatic polyamide fiber) possesses excellent properties such as high strength, high modulus, light weight, high temperature resistance, corrosion resistance, low density, low thermal shrinkage, and good chemical stability. Its strength is comparable to that of steel wire, and its fiber density is 1.4 g / cm³. 3 Only one-fifth the weight of steel wire, aramid fiber is used as the core reinforcement material for conveyor belts. At the same strength, it is about 30% lighter than steel cord conveyor belts, significantly reducing belt thickness and overall weight. Lightweight conveyor belts, while maintaining strength and performance, reduce equipment load and energy consumption, lower operating and maintenance costs, and extend belt lifespan. Therefore, lightweight, high-strength, and low-elongation aramid fiber skeleton materials have become a hot topic in the development of high-performance conveyor belts. For example, Chinese patent CN107216560B discloses an aramid fiber solid core flame-retardant conveyor belt and its manufacturing method. The radial stress lines of the conveyor belt's integral core are made of aramid fiber, resulting in high strength, a thin belt body, and light weight. The finished belt weighs about 35% of a steel cord conveyor belt of equivalent strength, significantly reducing energy consumption during operation.

[0005] The cover rubber, as a protective layer of the conveyor belt's inner core skeleton, aims to protect the skeleton material from direct impact and abrasion by materials. Aramid core conveyor belts are used for long-distance, heavy-load conveyor belts due to their high strength, moderate flexibility, high impact resistance, and long service life. However, under harsh conditions such as long distances, high loads, high temperatures, and high-speed operation, the cover rubber is highly susceptible to wear, cracking, aging, and deformation. If the tensile strength and abrasion resistance of the cover rubber are not matched with the aramid core skeleton, premature fatigue, wear, or detachment may occur, failing to effectively protect the aramid core and severely impacting the conveyor belt's service life. Therefore, developing high-performance cover rubbers that match the aramid core skeleton is crucial.

[0006] Our engineers hope to use aramid short fibers in cover rubber to improve its strength, abrasion resistance, and impact resistance. However, the dispersion and compatibility of aramid short fibers in rubber are not ideal. This is mainly due to the smooth surface and high crystallinity of aramid short fibers, the steric hindrance effect of the benzene ring, and their chemical inertness, which result in poor bonding between aramid and rubber, thus affecting the performance of the composite material. Currently, there are published methods for modifying aramid short fibers for use in conveyor belt cover rubber. For example, Chinese patent CN109749153B discloses a cold- and heat-resistant conveyor belt and its preparation process. Aramid fibers are modified by immersing them in a tackifier composed of epoxy resin, terpene resin, hydrogenated rosin glycerol ester, 3-chloropropyltrimethoxysilane, and triethanolamine, increasing the bonding strength between the aramid fibers and rubber. Using this in conveyor belt cover rubber can improve its dispersion in rubber, increasing its compatibility and bonding strength. Chinese patent CN116640367A discloses a high wear-resistant conveyor belt cover compound. It uses the coupling agent Si-69 to modify aramid short fibers, which helps to improve their dispersion in rubber and can effectively improve the strength and wear resistance of the cover compound.

[0007] However, the high crystallinity of the aramid short fiber surface has remained unchanged, and coupled with its low functional group activity, the effect of aramid short fiber reinforced rubber composites is not significant. The cover rubber is prone to wear and cracking under high loads, affecting the service life of the aramid conveyor belt. Summary of the Invention

[0008] Aramid-core conveyor belts are characterized by high strength. Their cover rubber, acting as a protective layer for the aramid core, requires properties such as abrasion resistance, tensile strength, and tear resistance to match those of the aramid core skeleton. If the tensile strength and abrasion resistance of the cover rubber do not match the aramid core skeleton, premature fatigue, wear, or detachment will occur, failing to effectively protect the aramid core and severely impacting the conveyor belt's service life. To address these shortcomings, this invention proposes an aramid fiber-reinforced impact-resistant and abrasion-resistant conveyor belt and its preparation method. By modifying the aramid short fiber to reinforce the cover rubber, the conveyor belt is strengthened, extending its service life.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] This invention provides an aramid fiber-reinforced impact-resistant and abrasion-resistant conveyor belt, the conveyor belt comprising a cover rubber, a core rubber, and an aramid fiber cloth, wherein:

[0011] The raw material composition of the cover rubber by weight is as follows: 40-45 parts styrene-butadiene rubber, 30-35 parts chloroprene rubber, 15-20 parts butadiene rubber, 10-15 parts ethylene propylene diene monomer (EPDM) rubber, 10-15 parts carbon black, 2-3 parts zinc oxide, 6-8 parts modified aramid short fiber, 1-1.5 parts antioxidant, 1-2 parts accelerator, and 2.5-3.5 parts sulfur;

[0012] The core layer adhesive is composed of the following raw materials by weight: 50-60 parts of chloroprene rubber, 40-50 parts of EPDM rubber, 8-10 parts of zinc oxide, 3-5 parts of marinic resin, 3-5 parts of coumarone, 1-2 parts of zinc stearate, 1-1.5 parts of antioxidant, 1-2 parts of accelerator, and 2-3 parts of sulfur.

[0013] The modified aramid staple fiber was prepared by the following method:

[0014] Add 3-5% dimethyl sulfoxide by weight of aramid short fibers to aramid short fibers, mix thoroughly and impregnate, and let stand at 50-60℃ for 30-50 minutes; then add 30-40% glycidyl methacrylate modified vinyl elastomer and 10-20% carboxylated acrylonitrile rubber by weight of aramid short fibers, and then modify by internal mixing to obtain modified aramid short fibers.

[0015] The use of modified aramid short fibers in cover rubber can significantly improve its tensile strength, abrasion resistance, and shear impact resistance. This is mainly due to the fact that the surface hydrogen bonds of the aramid short fibers are moderately disrupted by the impregnation of dimethyl sulfoxide, reducing the fiber crystallinity. This, in turn, facilitates the penetration of the GMA functional groups of the glycidyl methacrylate-modified vinyl elastomer and the carboxyl functional groups of the carboxylated nitrile rubber into the aramid short fibers, enhancing the activity of the aramid short fibers and promoting compatibility with the rubber. This allows the modified aramid short fibers to interact with the rubber, forming a powerful abrasion-resistant reinforcing system.

[0016] Preferably, the content of GMA functional groups in the glycidyl methacrylate modified vinyl elastomer is ≥5%. The glycidyl methacrylate modified vinyl elastomer contains glycidyl methacrylate (GMA) functional groups and has a unique acrylate double bond and epoxy group structure.

[0017] Preferably, the carboxylated nitrile rubber has a room temperature viscosity of 10,000–50,000 mPa·s and an acrylonitrile content of 22–30%. Carboxylated nitrile rubber is formed by copolymerization of butadiene, acrylonitrile, and acrylic acid. Its molecular structure contains carboxyl functional groups, which possess polarity and reactivity, resulting in a viscous liquid. The carboxyl functional groups facilitate the permeation of aramid short fibers.

[0018] Preferably, the length of the aramid short fibers ranges from 1 to 5 mm. Aramid short fibers have a stronger fiber structure, and by reducing surface crystallinity and introducing active groups, they are dispersed in rubber to significantly improve tensile strength, impact resistance, and abrasion resistance.

[0019] The core layer adhesive, serving as a transition layer between the cover adhesive and the aramid fiber fabric, directly adheres to the fabric. This requires high bonding strength to prevent fatigue and delamination under heavy cyclic loads on the conveyor belt. By using marinic acid resin in the core layer adhesive, the presence of carboxylic acid groups introduced by maleic anhydride in its molecular structure promotes full penetration and bonding between the core layer adhesive and the aramid fiber fabric, thus enhancing the bonding strength between the cover adhesive and the aramid fiber fabric.

[0020] Preferably, the acid value of the marinic resin is 25-30 mg KOH / g.

[0021] Aramid fiber cloth, as the skeleton material of conveyor belts, is lightweight, high-strength, and has low elongation, bearing the main tensile strength of the conveyor belt.

[0022] Preferably, the aramid fiber cloth is one of aramid canvas, aramid cord fabric, or aramid straight warp and weft structure fabric.

[0023] More preferably, the aramid fiber cloth is aramid canvas.

[0024] Chloroprene rubber has good adhesion, especially good initial tack, which ensures that the core layer rubber fully covers the aramid fiber cloth during calendering and wrapping. On the other hand, chlorobutyl rubber contains halogens and has a good oxygen index, which gives the cover rubber a certain degree of flame retardancy.

[0025] Preferably, the carbon black is a combination of high abrasion-resistant carbon black and high resilience carbon black. More preferably, the carbon black is a combination of N220 and N774 in a 1:1 mass ratio.

[0026] Preferably, the antioxidant is at least one of antioxidant A, antioxidant D, and antioxidant 4010.

[0027] Preferably, the accelerator is at least one of a thiazole accelerator or a thiuram accelerator; more preferably, the accelerator is at least one of an accelerator DM or an accelerator TMTD.

[0028] Another object of the present invention is to provide a method for preparing an aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt, characterized by comprising the following steps:

[0029] S1. Preparation of modified aramid short fibers: Add 3-5% (by weight of aramid short fibers) of dimethyl sulfoxide to aramid short fibers, mix thoroughly and impregnate, and let stand at 50-60℃ for 30-50 min; then add 30-40% (by weight of aramid short fibers) of glycidyl methacrylate modified vinyl elastomer and 10-20% (by weight of aramid short fibers) of carboxylated acrylonitrile rubber, and modify by internal mixing to obtain modified aramid short fibers;

[0030] S2. Preparing the cover rubber: Styrene-butadiene rubber, chloroprene rubber, butadiene rubber, and ethylene propylene diene monomer (EPDM) rubber are put into an internal mixer and mixed at 110-120℃ for 3-6 minutes. Then, carbon black, zinc oxide, modified aramid short fiber, and antioxidant are added and mixed for 3-6 minutes. The mixture is then discharged to a two-roll mill. After plasticizing once in the two-roll mill and cooling down, accelerator and sulfur are added and the mixture is passed through a thin mill 3-4 times. The roll gap is adjusted according to the thickness requirements to obtain the cover rubber sheet. The sheet is then separated by a pad and wound up for later use.

[0031] S3. Preparation of core layer rubber: Chloroprene rubber and EPDM rubber are put into an internal mixer and mixed at 110-120℃ for 3-6 minutes. Then zinc oxide, marinic acid resin, coumarone, zinc stearate and antioxidant are added and mixed for 3-6 minutes. The material is discharged to a two-mill. After plasticizing once in the two-mill and cooling, accelerator and sulfur are added. The mixture is passed through a thin sheet 3-4 times and sheeted out. It is then stored in a louvered cart to obtain the core layer rubber.

[0032] S4. Laminating the core layer adhesive: The aramid fiber cloth placed on the guide frame is spread out by the drying roller and tension roller and then fed into the four-roll calender; the core layer adhesive is thermoplasticized by the open mill and transferred to the four-roll calender. The core layer adhesive is laminated and penetrated into the upper and lower surfaces of the aramid fiber cloth by the roller pressure to obtain the core body; the core body is cooled by the cooling roller and then rolled up with a pad cloth for later use.

[0033] S5. Applying cover adhesive: The cover adhesive film is applied to the upper and lower surfaces of the core obtained in step S4 by roller pressing on the roller bonding molding machine to obtain the strip blank;

[0034] S6. Vulcanization: The strip blank is hot vulcanized for 15-45 minutes at 150-160℃ and 5-8MPa pressure using a flat vulcanizing machine, trimmed, and wound to obtain an aramid fiber reinforced impact-resistant and wear-resistant conveyor belt.

[0035] Aramid fiber cloth serves as the inner core, with core adhesive adhering to both the upper and lower surfaces of the aramid fiber cloth as a transition to the cover adhesive. The cover adhesive is then bonded to both the upper and lower surfaces of the core, achieving a smooth transition, enhancing the adhesive strength of the cover adhesive, and constructing a conveyor belt with higher structural strength and durability.

[0036] Preferably, the mixing temperature range of the internal mixer in step S1 is 130–150°C, and the mixing time is 10–12 minutes. Higher temperatures and longer mixing times are beneficial for the dispersion and modification of staple fibers, but scorching of materials caused by prolonged high temperatures must be avoided.

[0037] Preferably, the roller temperature of the open mill in steps S2 and S3 is 50-60°C; the plasticizing process involves one cooling step to control the temperature of the rubber compound to below 80°C.

[0038] Preferably, the roller temperature of the four-roll calender is 115–120°C. This allows the core layer adhesive to fully melt and penetrate the upper and lower surfaces of the aramid fiber fabric under roller pressure.

[0039] More preferably, the roller spacing of the four-roll calender is adjusted so that the thickness of the core after bonding the core layer adhesive is 1.5 to 2.0 times the thickness of the aramid fiber cloth.

[0040] Preferably, the vulcanization time in step S6 is controlled according to the full thickness of the conveyor belt. A better choice is that the vulcanization time is 12 minutes for a conveyor belt with a thickness of 8 mm, 15 minutes for a conveyor belt with a thickness of 10 mm, 23 minutes for a conveyor belt with a thickness of 15 mm, and 30 minutes for a conveyor belt with a thickness of 20 mm.

[0041] The advantages and beneficial effects of this invention are as follows:

[0042] (1) In this invention, the surface crystallinity of aramid short fibers is moderately reduced by impregnating them with dimethyl sulfoxide, and then the GMA functional group and the carboxyl functional group of carboxylated nitrile rubber are used to penetrate the aramid short fibers to enhance the activity of the aramid short fibers. This allows the modified aramid short fibers to interact with the rubber to form an aramid short fiber reinforced cover rubber system, which greatly improves the tensile strength, wear resistance and shear impact resistance of the cover rubber.

[0043] (2) In this invention, a marinic resin containing carboxylic acid groups introduced by maleic anhydride is used in the core layer adhesive to promote full penetration and bonding between the core layer adhesive and the skeleton material aramid fiber cloth, enhance the bonding strength between the cover adhesive and the aramid fiber cloth, and the adhesive material is appropriately soft, thus constructing a conveyor belt with higher structural strength and durability, avoiding the peeling of the protective adhesive layer, achieving matching with the aramid core layer skeleton, extending the service life of the conveyor belt, and meeting the needs of long-distance heavy-duty conveyor belts.

[0044] (3) The conveyor belt preparation method of the present invention is simple and can be industrialized on existing mature internal mixers, open mills and calendering production lines. Detailed Implementation

[0045] The preferred embodiments of the present invention will now be described in detail so that the advantages of the present invention can be more readily understood by those skilled in the art.

[0046] The equipment involved in this invention, such as internal mixers, open mills, four-roll calenders, and flat vulcanizing machines, are conventional choices for those skilled in the art. No parameters are limited, and the choice can be made according to actual needs.

[0047] The terms used in this invention, such as "thin pass," "film output," and "lamination," are common knowledge that will be understood by those skilled in the art. Unless otherwise specified, all percentages (%) refer to mass percentages.

[0048] The specific implementation of this invention involves the following raw materials:

[0049] Styrene-butadiene rubber (SBR), provided by Nanjing Herun New Material Technology Co., Ltd.

[0050] Butadiene rubber, provided by Siliang Venture Group Co., Ltd.

[0051] Aramid canvas: 2.3mm thick, Jiangsu Jiaheng Chemical Fiber Co., Ltd.

[0052] Nylon canvas: 2.3mm thick, Jiangsu Jiaheng Chemical Fiber Co., Ltd.

[0053] Aramid staple fiber: Tepron® 1414 chopped fiber, 3mm in length, Taihe New Materials Group Co., Ltd.

[0054] Glycidyl methacrylate modified vinyl elastomer: LOTADER® AX8840 (E-GMA terpolymer), GMA content 8%, Arkema, France.

[0055] Glycidyl methacrylate modified vinyl elastomer: LOTADER® AX8900 (EMA-GMA terpolymer), GMA content 8%, Arkema, France.

[0056] Carboxylated nitrile rubber: XL2740, room temperature viscosity 20000 mPa·s, acrylonitrile content 26-28%, Hengshui Ruien Rubber & Plastics Technology Co., Ltd.

[0057] Marinic resin: acid value 25-30 mg KOH / g.

[0058] Antioxidants and accelerators: provided by Taizhou Huangyan Donghai Chemical Co., Ltd.

[0059] Example 1

[0060] S1. Preparation of modified aramid short fibers: Add 5% by weight of dimethyl sulfoxide to aramid short fibers, mix evenly and thoroughly impregnate, and let stand at 60℃ for 30 min; then add 40% by weight of AX8840 and 10% by weight of carboxylated acrylonitrile rubber to aramid short fibers, and internally mix at 135℃ for 10 min in an internal mixer, sheet out, and store in a louvered cart to obtain modified aramid short fibers;

[0061] S2. Preparation of Cover Rubber: By weight, add 45 parts of styrene-butadiene rubber, 30 parts of chloroprene rubber, 15 parts of butadiene rubber, and 10 parts of ethylene propylene diene monomer (EPDM) rubber to a mixer and mix at 120°C for 4 minutes. Then add 6 parts of carbon black N220, 6 parts of carbon black N774, 2 parts of zinc oxide, 8 parts of modified aramid staple fiber, 1.0 part of antioxidant A, and 0.5 parts of antioxidant D and mix for 6 minutes. Discharge the material to an open mill. After plasticizing once in the open mill and cooling, add 1.5 parts of accelerator DM and 3.0 parts of sulfur, and pass through a thin pass 3 times. Adjust the roller gap according to the thickness requirements to obtain cover rubber sheets with thicknesses of 6 mm and 3 mm. Separately roll them with a padding cloth for later use.

[0062] S3. Preparation of core layer rubber: By weight, 60 parts of chloroprene rubber and 40 parts of EPDM rubber are added to an internal mixer and mixed at 120°C for 3 minutes. Then, 10 parts of zinc oxide, 5 parts of marinic resin, 3 parts of coumarone, 1 part of zinc stearate, and 1.5 parts of antioxidant A are added and mixed for 6 minutes. The mixture is then discharged to a two-roll mill. After plasticizing once in the two-roll mill and cooling, 1.5 parts of accelerator TMTD and 3 parts of sulfur are added. The mixture is passed through a thin sheet 4 times and then sheeted out. The sheet is stored in a louvered cart to obtain the core layer rubber.

[0063] S4. Laminating the core layer adhesive: The aramid canvas placed on the guide frame is spread out by the drying roller and tension roller and then fed into a four-roll calender; the core layer adhesive is thermoplasticized by an open mill and transferred to the four-roll calender. The roller temperature of the four-roll calender is 120℃, which allows the core layer adhesive to fully melt and penetrate the upper and lower surfaces of the aramid canvas under the roller pressure, resulting in a core with a thickness of 4.5mm; after being cooled by the cooling roller, the core is separated by a pad and rolled up for later use;

[0064] S5. Applying cover adhesive: On the roller bonding molding machine, the cover adhesive film is applied to the upper and lower surfaces of the core obtained in step S4 by roller pressing. The upper surface is the material contact layer, with a cover adhesive film of 6mm thickness applied, and the lower surface is applied with a cover adhesive film of 3mm thickness to obtain the strip blank.

[0065] S6. Vulcanization: The strip blank is vulcanized for 21 minutes at 150℃ and 5MPa pressure using a flat vulcanizing machine, trimmed, and wound to obtain an aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt.

[0066] Example 2

[0067] S1. Preparation of modified aramid short fibers: Add 4% by weight of dimethyl sulfoxide to aramid short fibers, mix evenly and fully impregnate, and let stand at 60℃ for 40 min; then add 35% by weight of AX8900 and 15% by weight of carboxylated acrylonitrile rubber to aramid short fibers, and internally mix at 135℃ for 10 min in an internal mixer, sheet out, and store in a louvered cart to obtain modified aramid short fibers;

[0068] S2. Preparation of Cover Rubber: By weight, add 40 parts of styrene-butadiene rubber, 35 parts of chloroprene rubber, 15 parts of butadiene rubber, and 10 parts of ethylene propylene diene monomer (EPDM) rubber to a mixer and mix at 120°C for 6 minutes. Then add 8 parts of carbon black N220, 6 parts of carbon black N774, 2 parts of zinc oxide, 7 parts of modified aramid staple fiber, 1.0 part of antioxidant A, and 0.5 parts of antioxidant 4010 and mix for 6 minutes. Discharge the material to an open mill. After plasticizing once and cooling in the open mill, add 1.5 parts of accelerator DM and 3.0 parts of sulfur, and pass through a thin pass 3 times. Adjust the roller gap according to the thickness requirements to obtain cover rubber sheets with thicknesses of 6 mm and 3 mm. Separately roll them with a padding cloth for later use.

[0069] S3. Preparation of core layer rubber: By weight, 50 parts of chloroprene rubber and 50 parts of EPDM rubber are added to an internal mixer and mixed at 120°C for 3 minutes. Then, 8 parts of zinc oxide, 4 parts of marinic resin, 4 parts of coumarone, 1 part of zinc stearate, and 1.5 parts of antioxidant A are added and mixed for 6 minutes. The mixture is then discharged to a two-roll mill. After plasticizing once in the two-roll mill and cooling, 1.5 parts of accelerator TMTD and 3 parts of sulfur are added. The mixture is passed through a thin sheet 4 times and then sheeted out. The sheet is stored in a louvered cart to obtain the core layer rubber.

[0070] S4. Laminating the core layer adhesive: The aramid canvas placed on the guide frame is spread out by the drying roller and tension roller and then fed into a four-roll calender; the core layer adhesive is thermoplasticized by an open mill and transferred to the four-roll calender. The roller temperature of the four-roll calender is 120℃, which allows the core layer adhesive to fully melt and penetrate the upper and lower surfaces of the aramid canvas under the roller pressure, resulting in a core with a thickness of 4.5mm; after being cooled by the cooling roller, the core is separated by a pad and rolled up for later use;

[0071] S5. Applying cover adhesive: On the roller bonding molding machine, the cover adhesive film is applied to the upper and lower surfaces of the core obtained in step S4 by roller pressing. The upper surface is the material contact layer, with a cover adhesive film of 6mm thickness applied, and the lower surface is applied with a cover adhesive film of 3mm thickness to obtain the strip blank.

[0072] S6. Vulcanization: The strip blank is vulcanized for 21 minutes at 150℃ and 6MPa pressure using a flat vulcanizing machine, trimmed, and wound to obtain an aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt.

[0073] Example 3

[0074] S1. Preparation of modified aramid short fibers: Add 3% by weight of dimethyl sulfoxide to aramid short fibers, mix evenly and thoroughly impregnate, and let stand at 60℃ for 50 min; then add 30% by weight of AX8840 and 20% by weight of carboxylated acrylonitrile rubber to aramid short fibers, and internally mix at 135℃ for 10 min in an internal mixer, sheet out, and store in a louvered cart to obtain modified aramid short fibers;

[0075] S2. Preparation of Cover Rubber: By weight, add 40 parts of styrene-butadiene rubber, 30 parts of chloroprene rubber, 20 parts of butadiene rubber, and 10 parts of ethylene propylene diene monomer (EPDM) rubber to a mixer and mix at 120°C for 4 minutes. Then add 8 parts of carbon black N220, 7 parts of carbon black N774, 3 parts of zinc oxide, 6 parts of modified aramid staple fiber, 1.0 part of antioxidant D, and 0.5 parts of antioxidant 4010 and mix for 6 minutes. Discharge the material to an open mill. After plasticizing once in the open mill and cooling, add 1.5 parts of accelerator DM and 3.5 parts of sulfur, and pass through a thin pass 4 times. Adjust the roller gap according to the thickness requirements to obtain cover rubber sheets with thicknesses of 6 mm and 3 mm. Separately roll them with a padding cloth for later use.

[0076] S3. Preparation of core layer rubber: By weight, 55 parts of chloroprene rubber and 45 parts of EPDM rubber are added to an internal mixer and mixed at 120°C for 3 minutes. Then, 10 parts of zinc oxide, 3 parts of marinic resin, 5 parts of coumarone, 2 parts of zinc stearate, and 1.5 parts of antioxidant D are added and mixed for 6 minutes. The mixture is then discharged to a two-roll mill. After plasticizing once in the two-roll mill and cooling, 1.5 parts of accelerator TMTD and 3 parts of sulfur are added. The mixture is passed through a thin sheet 4 times and then sheeted out. The sheet is stored in a louvered cart to obtain the core layer rubber.

[0077] S4. Laminating the core layer adhesive: The aramid canvas placed on the guide frame is spread out by the drying roller and tension roller and then fed into a four-roll calender; the core layer adhesive is thermoplasticized by an open mill and transferred to the four-roll calender. The roller temperature of the four-roll calender is 120℃, which allows the core layer adhesive to fully melt and penetrate the upper and lower surfaces of the aramid canvas under the roller pressure, resulting in a core with a thickness of 4.5mm; after being cooled by the cooling roller, the core is separated by a pad and rolled up for later use;

[0078] S5. Applying cover adhesive: On the roller bonding molding machine, the cover adhesive film is applied to the upper and lower surfaces of the core obtained in step S4 by roller pressing. The upper surface is the material contact layer, with a cover adhesive film of 6mm thickness applied, and the lower surface is applied with a cover adhesive film of 3mm thickness to obtain the strip blank.

[0079] S6. Vulcanization: The strip blank is vulcanized for 21 minutes at 150℃ and 5MPa pressure using a flat vulcanizing machine, trimmed, and wound to obtain an aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt.

[0080] Comparative Example 1

[0081] Aramid staple fibers were treated with the conventional silane coupling agent KH560, replacing the modified aramid staple fibers in equal amounts. The remaining processes were the same as in Example 1.

[0082] Comparative Example 2

[0083] When processing modified aramid staple fibers, no dimethyl sulfoxide impregnation pretreatment was used; the remaining processes were the same as in Example 1. The penetration and activation of aramid staple fibers by glycidyl methacrylate-modified vinyl elastomer and carboxylated acrylonitrile rubber were not significant.

[0084] Comparative Example 3

[0085] Marinic acid resin was not used when preparing the core layer adhesive; the rest of the process was the same as in Example 1.

[0086] Comparative Example 4

[0087] The aramid canvas was replaced with a 2.3mm thick nylon canvas specifically for conveyor belts, and the rest of the process was the same as in Example 1. This serves as a reference.

[0088] Comparative Example 5

[0089] The steel wire rope core conveyor belt with an inner core steel wire rope thickness of 4mm and a total thickness of 13.5mm is used as a reference.

[0090] I. Performance Testing of Cover Adhesive

[0091] Covering films with a thickness of 6 mm obtained from Examples 1-3 and Comparative Examples 1-2 were vulcanized at 150°C and 5 MPa for 9 min; covering films with a thickness of 3 mm were vulcanized at 150°C and 5 MPa for 4.5 min to obtain vulcanized covering film samples, which were used to evaluate the tensile stress-strain properties, right-angle tear properties, and deformation fatigue resistance of the covering films. The test data are shown in Table 1 below.

[0092] (1) The tensile stress-strain properties of the cover rubber were determined in accordance with GB / T 528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber", with a sample thickness of 6 mm and a tensile speed of 500 mm / min.

[0093] (2) The right-angle tear performance of the cover rubber is in accordance with GB / T 529-2008 "Test for tear strength of vulcanized rubber or thermoplastic rubber", and the sample thickness is 6mm.

[0094] (3) The deformation fatigue resistance of the cover rubber is determined according to GB / T 1688-2008 "Determination of tensile fatigue of vulcanized rubber". The sample thickness is 3.0 mm. Under the action of repeated stretching deformation with an elongation of 15% at a frequency of 5 Hz in a rubber fatigue testing machine, until cracks and fractures occur, the fatigue life is determined by the number of stretching cycles.

[0095] Table 1: Performance of Cover Adhesive

[0096]

[0097] II. Conveyor Belt Performance Testing

[0098] (1) The abrasion resistance of the conveyor belt was determined in accordance with GB / T 9867-2008 "Determination of abrasion resistance of vulcanized rubber or thermoplastic rubber (rotary roller abrasion test method)". The test data are shown in Table 2 below.

[0099] (2) The tensile strength and elongation of the conveyor belt were determined in accordance with GB / T3690-2017 "Test methods for tensile strength, elongation at break and elongation at reference force of fabric core conveyor belts of full thickness". The test data are shown in Table 2 below.

[0100] (3) The adhesion strength between the conveyor belt cover rubber and the core was tested using a tensile testing machine in accordance with GB / T6759-2013 "Test Method for Interlayer Adhesion Strength of Conveyor Belts". The test data are shown in Table 2 below.

[0101] Table 2: Conveyor Belt Performance

[0102]

[0103] Table 1 compares the performance of the cover rubber, and Table 2 compares the performance of the conveyor belt. This invention reduces the crystallinity of aramid short fibers by impregnating them with dimethyl sulfoxide. GMA and carboxyl functional groups are infiltrated into the aramid short fibers, greatly enhancing the bonding activity between the aramid short fibers and rubber. The aramid short fiber-reinforced cover rubber system significantly improves the tensile strength, abrasion resistance, and shear-folding impact resistance of the cover rubber. The use of marinic acid resin in the core layer rubber increases adhesion and enhances the bonding strength between the cover rubber and the aramid fiber fabric. The excellent strength and abrasion resistance of the cover rubber protect the aramid core, preventing early fatigue, wear, or detachment, and actively extending the service life of the conveyor belt.

[0104] Compared to nylon canvas core conveyor belts, the tensile strength of the conveyor belt of this invention is increased several times over; compared with steel cord core conveyor belts of the same thickness, the strength increase is significant.

[0105] Obviously, the embodiments described above are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. An aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt, characterized in that, The conveyor belt comprises a cover rubber, a core rubber, and an aramid fiber cloth, wherein: The raw material composition of the cover rubber by weight is as follows: 40-45 parts styrene-butadiene rubber, 30-35 parts chloroprene rubber, 15-20 parts butadiene rubber, 10-15 parts ethylene propylene diene monomer (EPDM) rubber, 10-15 parts carbon black, 2-3 parts zinc oxide, 6-8 parts modified aramid short fiber, 1-1.5 parts antioxidant, 1-2 parts accelerator, and 2.5-3.5 parts sulfur; The core layer adhesive is composed of the following raw materials by weight: 50-60 parts of chloroprene rubber, 40-50 parts of EPDM rubber, 8-10 parts of zinc oxide, 3-5 parts of marinic resin, 3-5 parts of coumarone, 1-2 parts of zinc stearate, 1-1.5 parts of antioxidant, 1-2 parts of accelerator, and 2-3 parts of sulfur. The modified aramid staple fiber was prepared by the following method: Add 3-5% dimethyl sulfoxide by weight of aramid short fibers to aramid short fibers, mix thoroughly and impregnate, and let stand at 50-60℃ for 30-50 minutes; then add 30-40% glycidyl methacrylate modified vinyl elastomer and 10-20% carboxylated acrylonitrile rubber by weight of aramid short fibers, and then modify by internal mixing to obtain modified aramid short fibers.

2. The aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 1, characterized in that, The content of GMA functional groups in the glycidyl methacrylate modified vinyl elastomer is ≥5%.

3. The aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 1, characterized in that, The carboxylated nitrile rubber has a room temperature viscosity of 10,000–50,000 mPa·s and an acrylonitrile content of 22–30%.

4. The aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 1, characterized in that, The length of the aramid short fiber ranges from 1 to 5 mm.

5. The aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 1, characterized in that, The acid value of the marinic resin is 25-30 mg KOH / g.

6. The aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 1, characterized in that, The aramid fiber cloth is one of the following: aramid canvas, aramid cord fabric, or aramid straight warp and weft structure fabric.

7. A method for preparing an aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Preparation of modified aramid short fibers: Add 3-5% (by weight of aramid short fibers) of dimethyl sulfoxide to aramid short fibers, mix thoroughly and impregnate, and let stand at 50-60℃ for 30-50 min; then add 30-40% (by weight of aramid short fibers) of glycidyl methacrylate modified vinyl elastomer and 10-20% (by weight of aramid short fibers) of carboxylated acrylonitrile rubber, and modify by internal mixing to obtain modified aramid short fibers; S2. Preparing the cover rubber: Styrene-butadiene rubber, chloroprene rubber, butadiene rubber, and ethylene propylene diene monomer (EPDM) rubber are put into an internal mixer and mixed at 110-120℃ for 3-6 minutes. Then, carbon black, zinc oxide, modified aramid short fiber, and antioxidant are added and mixed for 3-6 minutes. The mixture is then discharged to a two-roll mill. After plasticizing once in the two-roll mill and cooling down, accelerator and sulfur are added and the mixture is passed through a thin mill 3-4 times. The roll gap is adjusted according to the thickness requirements to obtain the cover rubber sheet. The sheet is then separated by a pad and wound up for later use. S3. Preparation of core layer rubber: Chloroprene rubber and EPDM rubber are put into an internal mixer and mixed at 110-120℃ for 3-6 minutes. Then zinc oxide, marinic acid resin, coumarone, zinc stearate and antioxidant are added and mixed for 3-6 minutes. The material is discharged to a two-mill. After plasticizing once in the two-mill and cooling, accelerator and sulfur are added. The mixture is passed through a thin sheet 3-4 times and sheeted out. It is then stored in a louvered cart to obtain the core layer rubber. S4. Laminating the core layer adhesive: The aramid fiber cloth placed on the guide frame is spread out by the drying roller and tension roller and then fed into the four-roll calender; the core layer adhesive is thermoplasticized by the open mill and transferred to the four-roll calender. The core layer adhesive is laminated and penetrated into the upper and lower surfaces of the aramid fiber cloth by the roller pressure to obtain the core body; the core body is cooled by the cooling roller and then rolled up with a pad cloth for later use. S5. Applying cover adhesive: The cover adhesive film is applied to the upper and lower surfaces of the core obtained in step S4 by roller pressing on the roller bonding molding machine to obtain the strip blank; S6. Vulcanization: The strip blank is hot vulcanized for 15-45 minutes at 150-160℃ and 5-8MPa pressure using a flat vulcanizing machine, trimmed, and wound to obtain an aramid fiber reinforced impact-resistant and wear-resistant conveyor belt.

8. The method for preparing the aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 7, characterized in that, The mixing temperature range of the internal mixer in step S1 is 130-150℃, and the mixing time is 10-12 minutes.

9. The method for preparing the aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 7, characterized in that, In steps S2 and S3, the roller temperature of the open mill is 50-60°C; the plasticizing process involves one cooling step to control the temperature of the rubber compound to below 80°C.

10. The method for preparing the aramid fiber reinforced impact-resistant and abrasion-resistant conveyor belt according to claim 7, characterized in that, In step S4, the roller temperature of the four-roll calender is 115-120℃. The roller gap is adjusted so that the thickness of the core after bonding the core layer adhesive is 1.5-2.0 times the thickness of the aramid fiber cloth.

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