A method for in-situ rapid repair of a mine conveyor belt

Abstract

This invention discloses a method for rapid in-situ repair of mining conveyor belts, belonging to the field of conveyor belt repair technology. The method includes selecting a damaged area on the surface of the mining conveyor belt as the repair area; cleaning, grinding, and drying the surface of the repair area; spraying an interface activator to activate the interface of the repair area; applying filler to the longitudinal tear on the conveyor belt surface and smoothing it; applying a primer and drying with hot air; applying polyurea in layers; and using an electric heating blanket to cover the repair area for constant temperature curing. This process enables rapid repair of damaged parts of the conveyor belt, reducing downtime. The repair layer of this invention has a long service life and is suitable for in-situ repair of various faults such as longitudinal tears, surface wear, and localized damage to conveyor belts under complex underground mining conditions, effectively reducing downtime and lowering maintenance costs.

Description

Technical Field

[0001] This invention relates to the field of conveyor belt repair technology, specifically to mining conveyor belts, and is applicable to in-situ repair of damaged steel wire rope core conveyor belts and fabric core conveyor belts in mining scenarios such as coal mines and metal mines. Background Technology

[0002] In mining operations, mining conveyor belts are core components of the mine's material conveying system. They are constantly subjected to impacts, wear, corrosion, and material abrasion, making them prone to longitudinal tears, surface rubber wear, and localized damage. Failure to repair these issues promptly can cause the company's transportation system to shut down, resulting in economic losses.

[0003] Patent CN121919625A discloses an integrated online quality inspection and defect repair process for rubber conveyor belts, aiming to solve the problems of fragmented inspection and repair, delayed response, and inability to intervene in situ in existing technologies. This process integrates four key stages: multi-source heterogeneous data synchronous acquisition, defect feature extraction and classification, adaptive repair strategy generation and execution, and real-time verification and recording of repair effects. By deeply integrating detection perception, intelligent decision-making, precise execution, and effect verification within the same spatiotemporal framework, it completely eliminates the inherent drawbacks of traditional offline repair methods, such as production interruptions, reliance on manual labor, and delayed response. In the adaptive repair strategy generation and execution stage, the central collaborative controller calls the corresponding repair strategy template based on the discrimination results, driving the track-type mobile platform and its mounted repair execution mechanism to move to the defect location. The multi-functional end effector head sequentially performs grinding, glue injection, hot pressing, and cooling operations to complete the in-situ repair of the defect. The duration of the repair operation is less than or equal to the single-pitch passage time of the conveyor belt. The entire process is fully automated, requiring no human intervention. It can identify micron-level defects and perform millimeter-level repairs while the conveyor belt is running at full speed, significantly improving the availability, safety, and intelligence of the conveyor system. Its disadvantages include high implementation difficulty and cost, stringent requirements on the conveyor belt's operating conditions, and difficulty in stable implementation in complex underground environments.

[0004] Patent CN117841417A discloses a method and apparatus for rapid and continuous hot repair of conveyor belts, belonging to the field of conveyor belt repair technology. The technical solution involves: loading an appropriate amount of hot-melt elastomer granules into a hopper, conveying it through a screw to a barrel for heating and melting into a molten elastomer adhesive; grinding the surface of the conveyor belt to be repaired; applying the molten elastomer adhesive to the new surface of the conveyor belt; and allowing it to cool and solidify naturally, thus completing the repair. The process is simple and convenient, and it is mainly used for repairing damaged conveyor belts.

[0005] Patent CN120118265A discloses a formulation for castable polyurethane materials and its application in conveyor belt repair. The formulation includes: 100 parts of component A; 8-20 parts of component B; 5-25 parts of component C; 0.5-10 parts of component D; and 102-106 parts of component E. Component C is a flame retardant, specifically expandable graphite powder; and component D is an antistatic liquid. The application process for castable polyurethane materials in conveyor belt repair includes the following steps: 1. Grinding the damaged areas of the conveyor belt requiring repair; 2. Applying component E; 3. Mixing components A, B, C, and D together; 4. Pouring and leveling the mixture; 5. Surface curing within 15 minutes and meeting requirements within 60 minutes. The present invention has the following advantages: it meets the requirements of MT / T113-1995 "Rules", can be cast in one piece, and its curing speed, physical properties and adhesion can meet the needs of various types of damage repair on coal mine conveyor belts.

[0006] Patent CN103419384A discloses a method and device for repairing damaged conveyor belts, belonging to the field of conveyor belt repair technology. The method for repairing damaged conveyor belts comprises the following steps: First, a suitable amount of molten elastomer is placed into a glue cylinder, and the molten elastomer inside the cylinder is heated by electricity to a temperature of 120℃-230℃ for 10-60 minutes until the molten elastomer melts into a molten elastomer adhesive; Second, the surface of the conveyor belt to be repaired is polished to expose a new surface; Third, the valve on the glue cylinder is opened, and the molten elastomer adhesive flows out automatically, or the glue cylinder is mounted on a glue gun and sprayed onto the new surface of the conveyor belt to be repaired; Fourth, the molten elastomer adhesive cools and solidifies naturally, completing the repair.

[0007] In existing technologies, hot-melt repair requires heating the material to 120-230℃, which takes a long time to cool naturally. Furthermore, high-temperature operation poses safety hazards and is unsuitable for the flammable and explosive environment of underground coal mines. While cast-in-place polyurethane can achieve rapid curing, it requires specialized casting equipment, strict control of ambient temperature and humidity before construction, poor adaptability to high humidity and dust conditions underground, and a long waiting period for complete curing after construction, resulting in limited repair efficiency. Due to the special nature of mining operations, daily downtime for maintenance is very short, averaging between 2 and 4 hours. The above methods generally suffer from insufficient adhesion strength between the repair layer and the substrate, limited wear resistance and tear resistance, leading to a short service life after repair. Frequent maintenance increases maintenance costs and downtime. Summary of the Invention

[0008] This invention aims to solve the technical problems existing in the repair methods of mining conveyor belts, such as low repair efficiency, insufficient bonding strength, poor wear and corrosion resistance, and weak on-site adaptability. It provides a polyurea repair method and supporting structure that can be constructed in situ quickly, with stable repair quality and long service life.

[0009] The technical solution adopted in this invention is as follows.

[0010] A method for rapid in-situ repair of mining conveyor belts, characterized by the following steps: Step 1: Surface Pretreatment Select a damaged area on the conveyor belt surface as the repair area and remove the aging layer and debris. Step 2: Interface Activation Treatment Spray the interface activator onto the repair area and let it stand for 5-8 minutes to form an active reaction layer; apply filler to the longitudinal tear on the conveyor belt surface and smooth it out. Step 3: Primer application Apply the primer, dry it with a hot air blower, and cure it for 25-30 minutes; Step 4: Polyurea spraying Polyurea material is sprayed multiple times on the surface of the active reaction layer. The polyurea material incorporates a flame retardant system and an antistatic system. There is an interval of 8-12 minutes between two adjacent sprays. During the interval, the previous coating layer is checked for defects such as bubbles and sagging. If any are found, they are repaired in time with a scraper to finally form a polyurea repair layer. Step 5: Constant temperature curing The repair area is covered with an electric heating blanket and kept warm for 25-30 minutes, with the temperature controlled at 70-80℃. After the heating blanket is removed, the in-situ repair of the repair area is completed. The ambient temperature during repair is 15-35℃ and the relative humidity does not exceed 80%. The conveyor belt is a steel wire rope core rubber conveyor belt or a fabric core rubber conveyor belt.

[0011] Its beneficial effects are as follows.

[0012] 1. High repair efficiency: In-situ repair eliminates the need to disassemble the conveyor belt, avoiding potential deformation or damage during disassembly. This preserves the original structural integrity of the conveyor belt to the greatest extent possible, ensuring stable operation after repair. Compared to traditional hot vulcanization repair, which requires several hours to tens of hours of curing and large heating equipment, the entire repair process can be controlled within 2 hours. It ensures a strong bond between the repair layer and the conveyor belt substrate, exhibiting excellent tensile and abrasion resistance, guaranteeing immediate operation of the conveyor belt after repair. This significantly reduces downtime and production interruption losses. Its advantages are even more pronounced in emergency scenarios involving sudden conveyor belt damage, enabling rapid production recovery and minimizing additional economic losses from emergency shutdowns.

[0013] 2. High safety. The polyurea material incorporates flame-retardant and antistatic systems, eliminating the need for large heating and pressurizing equipment. It can be applied using a portable sprayer, making it suitable for in-situ repairs in confined spaces underground in mines. The application process is simple and requires minimal technical expertise from operators. Furthermore, the polyurea material emits no volatile organic compounds during application, avoiding the harmful gas pollution of the underground working environment produced by traditional repair materials.

[0014] 3. Excellent performance of the repair layer. High bonding strength between layers; through the compatibility of the epoxy primer, the bonding strength between the polyurea repair layer and the conveyor belt body is far higher than that of cold bonding, ensuring the repair layer will not detach. The polyurea repair layer possesses excellent wear resistance, corrosion resistance, and impact resistance. Through gradient-interval spraying and constant-temperature curing, the polyurea repair layer can be put into use immediately after curing, adapting to the harsh environment of damp, dusty, and corrosive gases in underground mines. The service life of the repair layer can reach 1-2 years.

[0015] The filler is a two-component filler material composed of polyurethane elastomer, carbon black reinforcing agent, crosslinking agent, and silane coupling agent. The polyurethane filler exhibits excellent impact resistance and abrasion resistance, effectively filling pits formed by longitudinal tears in the conveyor belt. It also demonstrates good compatibility with interface activators and primer materials, ensuring a robust, integrated structure between the filled portion and the conveyor belt body and subsequent polyurea repair layer.

[0016] As a preferred technical solution, the components of the interface activator, by weight percentage, include 3%-5% silane coupling agent (KH-550), 15%-20% nitrile rubber resin, 1%-2% dibutyltin dilaurate, 0.5%-1% antioxidant RD, and the remainder is ethyl acetate.

[0017] This activator can effectively wet the surface of the conveyor belt rubber substrate, open the rubber molecular chain, and form a stable chemical bond with the subsequent primer and polyurea layer, significantly improving the interfacial adhesion strength. It has good weather resistance and anti-aging properties, and can adapt to the complex environment of high temperature, high humidity and dust in mines, ensuring long-term stable adhesion of the repair layer.

[0018] As a preferred technical solution, the primer is a solvent-free epoxy primer, which comprises, by mass ratio, 25%-35% polyamide curing agent, 10%-15% propylene oxide butyl ether, 0.5%-1% 2-methylimidazole, 1%-3% fumed silica, 0.3%-0.8% anti-settling agent, and the remainder being bisphenol A epoxy resin.

[0019] This primer is free of volatile organic solvents, environmentally friendly and odorless. It can quickly penetrate into the tiny pores of the conveyor belt's rubber substrate, forming a tight mechanical and chemical bond with the surface of the rubber after interface activation treatment. This significantly enhances the adhesion between the primer and the substrate, as well as the subsequent polyurea repair layer. The cured coating has excellent wear resistance, impact resistance, and chemical corrosion resistance, effectively resisting the effects of ore friction, oil erosion, and acid and alkali media in the mining environment. It also has good high-temperature resistance, adapting to the constant-temperature curing conditions during the repair process, ensuring the stability of the repair layer structure and extending the service life of the conveyor belt.

[0020] As a preferred technical solution, in step 1, a high-pressure water gun is used to wash away surface debris from the damaged area of ​​the repair area; the surface of the repair area is polished to make it smooth, and a hot air blower is used to dry the surface of the polished repair area until the moisture content is ≤1%.

[0021] In step 4, the polyurea material is a two-component polyurea material, which includes component A and component B.

[0022] Component A is an isocyanate prepolymer comprising 30% to 40% of the total mass of the polyurea material.

[0023] The B component comprises the following components in the total mass ratio of the polyurea material: 25%–35% amino-terminated polyether, 5.5%–9.5% m-phenylenediamine (MPDA), 1%–2.5% fast-reacting aromatic chain extender, 0.05%–0.2% tertiary amine catalyst, 5%–10% reactive phosphorus-nitrogen flame retardant, 5%–8% nano-wear-resistant filler; 1%–3% flame retardant synergist; 2%–5% conductive carbon black; 1%–2% conductive fiber; 0.5%–1.5% antistatic agent; 1%–2% silane coupling agent; 0.1%–0.5% latent catalyst; 0.5%–1% antioxidant; and 0.1%–0.3% defoamer.

[0024] As a preferred technical solution, the isocyanate prepolymer is an MDI-type isocyanate prepolymer; the amino-terminated polyether is a compound of polyetheramine D2000 and T5000, wherein the compounding ratio is 1:1.2-1.8 by weight; the fast-reacting aromatic chain extender is methylcyclohexanediamine; the tertiary amine catalyst is triethylenediamine; the reactive phosphorus-nitrogen flame retardant is aluminum diethylphosphinate; and the nano-wear-resistant filler is a compound system of nano-alumina and nano-silica, wherein... Nano-alumina accounts for 60%–70% of the total mass of nano-wear-resistant filler, and nano-silica accounts for 30%–40%; the flame retardant synergist is antimony trioxide; the conductive carbon black is acetylene black; the conductive fiber is conductive carbon fiber; the antistatic additive is a quaternary ammonium salt cationic surfactant; the silane coupling agent is KH550 silane coupling agent; the latent catalyst is dibutyltin dilaurate; the antioxidant is 1010 antioxidant; and the defoamer is a polyether-modified siloxane defoamer.

[0025] A polyurea core material is constructed using a compound system of MDI-type isocyanate prepolymer and polyetheramine D2000 / T5000. This system ensures that the material maintains excellent mechanical properties, including tensile strength ≥18MPa and elongation at break ≥400%, even after the addition of flame-retardant and antistatic components, thus adapting to the fatigue conditions of conveyor belt dynamic operation. A highly efficient flame-retardant effect with a limiting oxygen index ≥28% is achieved through a combination of reactive phosphorus-nitrogen flame retardant (aluminum diethylphosphonate), inorganic expandable flame-retardant filler (magnesium hydroxide / aluminum hydroxide 1:1 compound), and antimony trioxide synergist. The reactive flame retardant is covalently bonded to the polyurea molecular chain, avoiding the decrease in material elasticity caused by traditional additive flame retardants. Simultaneously, a dense carbon layer is formed during combustion to inhibit flame spread. A composite conductive system of acetylene black and short-cut carbon fibers (0.5–1 mm), combined with quaternary ammonium salt antistatic additives, is used. By optimizing the filler particle size and dispersion process, the surface resistivity of the material is stabilized at 10 Ω·cm. 6 -10 9 Within the Ω range, it effectively releases static charge; simultaneously ensuring wear resistance of ≤0.08cm³ / 1.61km, balancing safety and durability. The addition of silane coupling agent KH550 promotes chemical bonding between the polyurea material and the conveyor belt rubber matrix, increasing interfacial tensile shear strength to ≥3MPa, preventing peeling or cracking of the repair layer, and ensuring the long-term stability of the repair structure. Precise dosage control of dibutyltin dilaurate catalyst allows the material to reach its service strength after isothermal curing, meeting the needs of rapid in-situ repair in downhole environments. The compound filler fully utilizes the high hardness of nano-alumina, significantly improving the wear resistance of the repair layer; simultaneously, the hydroxyl groups on the surface of nano-silica form hydrogen bonds with polyurea molecules, enhancing the interfacial bonding between the filler and the polyurea matrix, preventing filler detachment during long-term friction. In addition, the particle size of the compound filler is controlled at 50-100nm, which can be uniformly dispersed in the polyurea material without affecting the flowability and density of the coating during spraying, ensuring a smooth surface of the repair layer, and further reducing the adhesion and friction damage of ore particles to adapt to the high-load wear conditions of mining conveyor belts.

[0026] m-Phenylenediamine (MPDA) is a conventional aromatic chain extender that undergoes an addition reaction with amino-terminated polyethers and isocyanate prepolymers, introducing a rigid aromatic ring structure into the polyurea molecular chain. This effectively improves the regularity and crosslinking density of the molecular chain, constructing a denser three-dimensional crosslinked network. It significantly enhances the tensile strength, tear strength, and impact resistance of the polyurea repair layer, maintaining structural stability under fatigue conditions caused by ore impact and dynamic conveyor belt operation. It also imparts superior thermal stability and aging resistance, reducing the degradation effects of high-temperature and humid environments in underground mines on the repair layer and extending its service life. Its good compatibility with the polyurea system ensures uniform reaction, avoiding local performance differences and guaranteeing the overall consistency of the repair layer's quality. Specifically, one of m-phenylenediamine (MPDA) or m-phenylenediamine (MPDA) with a purity of not less than 99.5% can be used. The MPDA is vacuum-dried to a moisture content ≤0.05% to prevent side reactions between moisture and the isocyanate prepolymer, which could lead to defects such as pinholes and bubbles in the coating. This aromatic chain extender exhibits highly compatible reactivity with amino-terminated polyethers and MDI-type isocyanate prepolymers, enabling it to rapidly participate in the cross-linking reaction during spraying. This results in a well-organized and dense three-dimensional molecular network structure, significantly enhancing the tensile strength (≥18MPa), tear strength (≥50kN / m), and thermal stability (heat distortion temperature ≥120℃) of the polyurea repair layer. This allows it to withstand the continuous impact, friction, and high-temperature environment of underground mine ore, ensuring long-term stable operation of the repair layer. Its excellent compatibility with the polyurea system ensures uniform reaction, avoiding local performance fluctuations and improving the overall quality consistency of the repair layer. The fast-reacting aromatic chain extender accelerates the addition reaction rate between amino groups and isocyanates, while the tertiary amine catalyst lowers the activation energy and shortens the gel time. The synergistic effect of these two components allows the polyurea material to complete early cross-linking shortly after spraying, significantly improving the early strength of the repair layer and achieving early strength without causing spray gun clogging.

[0027] The addition of antioxidant 1010 delays material aging, while polyether-modified siloxane defoamer eliminates air bubbles during application, ensuring a continuous and dense repair layer. This enhances the long-term stability of the material and the quality of the finished product, making it suitable for complex mining conditions. The curing process releases no harmful volatile substances, meeting mining environmental safety requirements.

[0028] As a preferred technical solution, during downhole operations, in step 1, the working pressure of the high-pressure water gun should be controlled at 8-10MPa. During the rinsing process, local ventilation equipment should be turned on to avoid the risk of slipping due to the accumulation of sewage and debris. Grinding should be done with an explosion-proof angle grinder, equipped with a dust mask and goggles. Dust should be collected by a negative pressure dust collection device to prevent the concentration from exceeding the standard. Drying should be done with an explosion-proof hot air gun at a temperature ≤80℃ to ensure that the surface moisture content is ≤1% and to avoid contact with flammable and explosive substances. The grinding area should extend 50-100mm beyond the edge of the damage, and the surface roughness should be Ra25-50μm.

[0029] In step 2, before spraying the interface activator, confirm that the gas concentration is <0.5%, control the spraying amount to 30-50g / ㎡, and maintain ventilation to prevent the accumulation of volatiles; apply the filler with an anti-static scraper, smoothing it without bubbles or depressions. In step 3, an antistatic scraper is used to apply the primer, with a coating amount of 120-160 g / m² and a thickness of 20-30 μm. The temperature of the explosion-proof hot air blower is 45-50℃, and the distance from the surface is ≥30 cm. The primer status is monitored in real time until it is "not sticky to the touch and has no drips" to meet the curing requirements of extended humidity in the well.

[0030] In step 4, the polyurea spraying equipment is explosion-proof. Specifically, component A is heated to 60-70℃ and component B is heated to 55-65℃ to ensure that the material maintains good fluidity in the underground environment. The spraying pressure is controlled at 15-20MPa, the atomization is uniform and there is no splashing, the thickness of a single spray does not exceed 1.0mm, and the cumulative thickness reaches 3mm to meet the requirements of wear resistance and tear resistance. During spraying, the equipment is kept 30-50cm away from the repair area, and the equipment is moved at a uniform speed to avoid local coatings being too thick or too thin. Continuous ventilation is used to prevent the accumulation of atomized particles.

[0031] In step 5, the electric blankets are explosion-proof, with a power of 500-800W and a heat preservation temperature of 70-80℃. Dedicated personnel are assigned to monitor the area to prevent electrical sparks. A gas monitor is used throughout the work process; work is immediately stopped if the gas concentration exceeds 0.5%. Construction personnel wear anti-static clothing, and the use of open flames and non-explosion-proof equipment is strictly prohibited to ensure safety during underground operations. The entire in-situ repair process takes no more than 2 hours. By strictly regulating the safety parameters and process details of each stage of underground operations, construction safety in the complex environment of the mine is effectively guaranteed: high-pressure water gun pressure control, the selection of explosion-proof equipment, and the coordination of local ventilation and negative pressure dust collection devices significantly reduce the risk of slipping due to sewage accumulation, the hazards of excessive dust concentration, and the fire hazards caused by electrical sparks. Real-time monitoring of gas concentration and setting of safety thresholds, combined with the use of anti-static tools and personal protective equipment, prevents major safety accidents such as gas explosions from occurring at the source. Precise control of process parameters at each step ensures the uniformity and density of the repair layer, avoids repair defects caused by process deviations, improves the stability and reliability of repair quality, and is fully compatible with the stringent safety and working conditions requirements of underground mines.

[0032] As a preferred technical solution, step 4 further includes placing a fiber reinforcement mesh on the surface of the polyurea material during one of the polyurea material cooling processes.

[0033] Fiber-reinforced mesh can form a tight composite reinforcement structure with the polyurea repair layer, improving the tensile and tear resistance and overall structural strength of the repair layer. It effectively disperses local stress caused by ore impact and material friction during conveyor belt operation, preventing crack propagation or localized damage to the repair layer. The three-dimensional mesh support structure of the fiber-reinforced mesh optimizes the internal stress distribution of the polyurea material, enhancing the impact resistance and fatigue resistance of the repair layer, ensuring its stability under harsh conditions of high load and multiple impacts in underground mines, and extending the service life of the repair layer. The fiber-reinforced mesh is embedded during the polyurea cooling stage, exhibiting good compatibility with the polyurea layer and primer, without affecting spraying construction and curing efficiency, ensuring a firm overall bond to the repair layer without the risk of delamination, and guaranteeing the long-term operational reliability of the repaired conveyor belt.

[0034] As a preferred technical solution, the fiber-reinforced mesh is one of glass fiber reinforced mesh, basalt fiber reinforced mesh, aramid fiber reinforced mesh, and ultra-high molecular weight polyethylene fiber reinforced mesh.

[0035] As a preferred technical solution, the mining conveyor belt is one of the following: rubber steel wire conveyor belt, rubber fiber conveyor belt, PVC conveyor belt, and PVG conveyor belt. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the polyurea repair method for mining conveyor belts according to the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments.

[0038] Example 1. A 1.2m × 0.4m wear area appeared on the surface of a fabric-core conveyor belt in an iron ore mine, with a wear depth of 2mm. Locally, longitudinal tears caused by falling ore were observed, with a depth of 4mm. Figure 1 As shown, the repair method includes the following steps.

[0039] Step 1: Surface Pretreatment Select a damaged area on the conveyor belt surface as the repair area and remove the aging layer and debris. Step 2: Interface Activation Treatment Spray the interface activator onto the repair area and let it stand for 5 minutes to form an active reaction layer; apply filler to the longitudinal tear on the conveyor belt surface and smooth it out. Step 3: Primer application Apply the primer, dry it with a hot air blower, and cure it for 25 minutes; Step 4: Polyurea spraying The polyurea material is sprayed onto the surface of the active reaction layer several times. The polyurea material is introduced into the flame retardant system and the antistatic system. There is an 8-minute interval between two consecutive sprays. During the interval, the previous coating layer is checked for defects such as bubbles and sagging. If there are any, they are repaired in time with a scraper to finally form a polyurea repair layer. Step 5: Constant temperature curing The repair area is covered with an electric heating blanket and kept warm for 25 minutes at a temperature of 70°C. After the heating blanket is removed, the in-situ repair of the repair area is completed. The ambient temperature during repair is 15°C and the relative humidity does not exceed 80%. The conveyor belt is a steel cord rubber conveyor belt or a fabric rubber conveyor belt.

[0040] In step 1, a high-pressure water gun can be used to rinse the surface of the damaged area to remove debris and aging layer. The surface of the repair area is then polished to make it smooth, and a hot air blower is used to dry the surface until the moisture content is ≤1%. Specifically, during surface pretreatment, the surface of the damaged area is cleaned to remove dust, gravel particles, and oil. Then, an angle grinder with a diamond grinding disc is used to polish the damaged area to remove the aged adhesive layer, debris, and oxide layer. The polishing area extends 50mm beyond the edge of the damage, and the surface roughness is controlled at Ra25μm after polishing. Finally, a hot air gun (temperature 60℃) is used to dry the polished surface for 20 minutes to ensure that the surface moisture content is ≤1%.

[0041] During the interface activation treatment, an interface activator is evenly sprayed onto the dried surface at a rate of 30 g / m². This allows the activator to fully penetrate the rubber surface and form an active reaction layer, ensuring an increase in interfacial adhesion strength with subsequent primer and polyurea materials of over 30%. Filler is applied to longitudinal tears on the conveyor belt surface and then smoothed.

[0042] The interface activator, by weight percentage, comprises 3% silane coupling agent (KH-550), 15% nitrile rubber resin, 1% dibutyltin dilaurate, 0.5% antioxidant RD, and the remainder is ethyl acetate. This activator effectively wets the surface of the conveyor belt rubber substrate, opens the rubber molecular chains, and forms stable chemical bonds with subsequent primer materials and polyurea layers, significantly improving interfacial adhesion strength. It possesses excellent weather resistance and anti-aging properties, enabling it to adapt to the complex environment of high temperature, high humidity, and high dust in mines, ensuring long-term stable adhesion of the repair layer.

[0043] The filler is a two-component filler material composed of polyurethane elastomer, carbon black reinforcing agent, crosslinking agent, and silane coupling agent. Specifically, the mass percentages of each component are as follows: polyurethane elastomer 65%, carbon black reinforcing agent 15%, diphenylmethane diisocyanate (MDI) crosslinking agent 6%, silane coupling agent KH-560 1.5%, and antioxidant RD 0.5%. This filler has a well-balanced composition. The polyurethane elastomer provides excellent elasticity and adhesion; the carbon black reinforcing agent enhances the filler's abrasion and tear resistance; the crosslinking agent improves the structural stability after curing; the silane coupling agent optimizes the interfacial bonding with the conveyor belt rubber substrate and subsequent coatings; and the antioxidant extends the filler's anti-aging life in mining environments, enabling it to effectively fill longitudinal tears on the conveyor belt surface and form a smooth transition base layer with the surrounding substrate, providing favorable conditions for subsequent primer and polyurea layer application.

[0044] For the primer application, a solvent-free epoxy primer compatible with the rubber activation layer and polyurea material is selected. It is applied evenly to the activated surface using a toothed scraper, with a coating amount controlled at 120g / ㎡, ensuring complete coverage of the damaged area and a 20mm perimeter, forming a dense transition layer with a thickness of 20μm. The surface drying time of the epoxy primer is 25 minutes; the hot air blower temperature must be controlled at 50℃. The primer is a solvent-free epoxy primer, comprising, by weight, 25% polyamide curing agent, 10% propylene oxide butyl ether, 0.5% 2-methylimidazole, 1% fumed silica, 0.3% anti-settling agent, and the remainder being bisphenol A epoxy resin. The hot air blower should be kept at least 30cm away from the primer surface, blowing evenly over the repaired area to prevent uneven heating; the auxiliary drying time is until the primer surface reaches a state of "not sticky to the touch and without drips". Keep the hot air blower at least 30cm away from the primer surface and blow it evenly over the repair area to prevent uneven heating. The auxiliary drying time is based on the primer surface reaching a state where it is "not sticky to the touch and has no drips".

[0045] In step 4, the polyurea material is a two-component polyurea material, which includes component A and component B.

[0046] Component A is an isocyanate prepolymer comprising 40% of the total mass of the polyurea material.

[0047] The B component comprises the following components in the total mass ratio of the polyurea material: 34.25% amino-terminated polyether, 5.5% m-phenylenediamine (MPDA), 1% fast-reacting aromatic chain extender, 0.05% tertiary amine catalyst, 5% reactive phosphorus-nitrogen flame retardant, 8% nano-wear-resistant filler; 1% flame retardant synergist; 2% conductive carbon black; 1% conductive fiber; 0.5% antistatic agent; 1% silane coupling agent; 0.1% latent catalyst; 0.5% antioxidant; and 0.1% defoamer.

[0048] Is the sum of component A and component B 100%? The defoamer is an organosilicon defoamer; the antioxidant is 1010 antioxidant; the silane coupling agent is KH550 silane coupling agent; the isocyanate prepolymer is MDI type isocyanate prepolymer; the amino-terminated polyether is a compound of polyetheramine D2000 and T5000, with a compounding ratio of 1:1.2 by weight; the fast-reacting aromatic chain extender is methylcyclohexanediamine; the tertiary amine catalyst is triethylenediamine; the reactive phosphorus-nitrogen flame retardant is aluminum diethylphosphinate; and the nano-wear-resistant filler is nano... The composite system of nano-alumina and nano-silica comprises 60% nano-alumina and 40% nano-silica by mass of the total mass of nano-wear-resistant filler; antimony trioxide is used as the flame retardant synergist; acetylene black is used as the conductive carbon black; carbon fiber is used as the conductive fiber; quaternary ammonium salt cationic surfactant is used as the antistatic agent; KH550 silane coupling agent is used as the silane coupling agent; dibutyltin dilaurate is used as the latent catalyst; 1010 antioxidant is used as the antioxidant; and polyether-modified siloxane defoamer is used as the defoamer.

[0049] The modified MDI prepolymer was prepared by reacting 4,4'-diphenylmethane diisocyanate (MDI-100) and polypropylene glycol (PPG-1000) at a mass ratio of 3:1 at 70°C for 2 hours. This prepolymer, modified with short-chain polypropylene glycol, retains the high reactivity of MDI while improving its compatibility with component B, enabling rapid reaction with component B and providing a foundation for the material's early strength properties.

[0050] During polyurea spraying, component A is heated to 60℃ and component B to 55℃, then sprayed using a spraying machine. The spraying pressure is adjusted to 15MPa, and the spraying is performed in three coats: the first coat is 1mm thick, with a 10-minute cooling interval; the second coat is 1mm thick, for a total thickness of 3mm; the repair layer extends 40mm beyond the damaged edge. The edges are beveled for a smooth transition.

[0051] Post-treatment and constant temperature curing: Immediately after the third spraying, cover the repair area with a flexible electric heating blanket (500W), set the temperature to 70℃, and keep it at that temperature for 25 minutes. After the insulation period, allow it to cool naturally to room temperature. Use 80-grit sandpaper to sand the edges of the repair layer to ensure a transition, ensuring the height difference with the original conveyor belt surface is ≤0.5mm. If defects such as pinholes or bubbles exist, use polyurea repair agent for touch-up treatment. In step 4, while the polyurea material is cooling, a fiber reinforcement mesh is also placed on the surface of the polyurea material.

[0052] The entire repair process was completed within 2 hours.

[0053] The fiber-reinforced mesh is made of basalt fiber. Basalt fiber possesses excellent high-temperature resistance (withstanding temperatures above 600℃), high tensile strength (approximately 30% higher than glass fiber), and good chemical corrosion resistance, making it suitable for the harsh working conditions of underground mines, characterized by high temperatures, high humidity, and corrosive gases. Its interfacial adhesion to polyurea materials is strong; embedding it into the polyurea repair layer significantly improves the tensile and impact resistance of the repair layer, extending its service life to over 3 years. Furthermore, basalt fiber is an inorganic material, posing no risk of aging or degradation, and its performance remains stable over long-term use. Aramid fiber possesses extremely high tear strength (2-3 times that of glass fiber) and excellent impact resistance, effectively resisting the severe impacts and friction from ore during mine conveyor belt operation. Its low density and light weight mean that embedding it into the polyurea layer will not increase the additional load on the conveyor belt. Aramid fiber is resistant to acid and alkali corrosion and aging, making it suitable for the complex underground environment.

[0054] The polyurea repair layer, after being cured at a constant temperature using a gradient-interval spraying process, reaches 62% of its maximum strength. The Shore A hardness of the repair layer, measured with a Shore hardness tester, is 70, and the tensile strength is 15.5 MPa. The bond strength between the repair layer and the conveyor belt body, measured using a portable bond strength tester, is 3.5 MPa. The flame retardant and antistatic properties meet mining safety requirements, with an oxygen index ≥30% and a surface resistivity ≤108 Ω. The Taber abrasion test shows an abrasion rate of less than 35 mg / 1000 rpm. The tear strength test shows a value of 15.5 kN / m, fully meeting the requirements for conveyor use. No tear propagation or repair layer detachment has been observed in the conveyor belt after 24 months of use.

[0055] This embodiment achieves rapid in-situ repair through five steps: surface pretreatment, interface activation, primer application, layered polyurea spraying, and constant-temperature curing. The entire repair time is less than 2 hours, significantly reducing downtime. The repair layer uses polyurea material and incorporates flame-retardant and antistatic systems. While meeting the safety requirements of underground coal mines, it possesses excellent wear resistance, tear resistance, and aging resistance. The repair layer has high adhesion strength to the conveyor belt substrate, resulting in a long service life. The process is simple and easy to operate, requiring no large specialized equipment. It is highly adaptable to ambient temperatures (15-35℃) and humidity (relative humidity not exceeding 80%), making it suitable for in-situ repair of longitudinal tears, surface wear, and localized damage to various conveyor belts, such as steel wire rope core rubber conveyor belts and fabric core rubber conveyor belts, in mining scenarios such as coal mines and metal mines. Compared with traditional methods, it has lower maintenance costs and more reliable operation.

[0056] Example 2. A longitudinal tear with a length of 2.0m and a width of 0.3m appeared on the steel wire rope conveyor belt of a certain iron mine, with a tear depth of 3mm. The repair method differs from that in Example 1 in that it includes the following steps.

[0057] Step 1: Surface Pretreatment Select a section of the conveyor belt surface as the repair area, use a high-pressure water gun to wash away surface debris from the damaged part of the repair area, and remove the aging layer and debris; grind the surface of the repair area to make it smooth, and use a hot air blower to dry the ground surface of the repair area.

[0058] Step 2: Interface Activation Treatment Spray the interface activator onto the repair area and let it stand for 8 minutes to form an active reaction layer; apply filler to the longitudinal tear on the conveyor belt surface and smooth it out.

[0059] Step 3: Primer application Apply the primer, dry it with a hot air blower, and cure for 30 minutes.

[0060] Step 4: Polyurea spraying Polyurea material is sprayed twice on the surface of the active reaction layer. The polyurea material incorporates a flame retardant system and an antistatic system. There is a 12-minute interval between the two sprays. During the interval, the previous coating is checked for defects such as bubbles and sagging. If any are found, they are repaired in time with a scraper to finally form a polyurea repair layer.

[0061] Step 5: Constant temperature curing The repair area is covered with an electric heating blanket and kept warm for 30 minutes at a temperature of 80°C. After the heating blanket is removed, the in-situ repair of the repair area is completed. The entire in-situ repair time shall not exceed 2 hours. The ambient temperature during the repair is 35°C and the relative humidity shall not exceed 80%.

[0062] Specifically, during surface pretreatment, a high-pressure water gun (working pressure 8-10MPa) is first used to rinse the surface of the damaged parts of the conveyor belt to remove dust, gravel particles, and oil stains. Then, an angle grinder with diamond grinding discs is used to grind the damaged area to remove the aged adhesive layer, debris, and oxide layer. The grinding area extends 100mm beyond the edge of the damage, and the surface roughness is controlled at Ra50μm after grinding. Finally, a hot air gun (temperature 80℃) is used to dry the ground surface for 20 minutes to ensure that the surface moisture content is ≤1%.

[0063] During the interface activation treatment, an interface activator is uniformly sprayed onto the dried surface at a rate of 50 g / m².

[0064] The activator is allowed to fully penetrate the rubber surface and form an active reaction layer, ensuring that the interfacial adhesion strength with subsequent primer and polyurea materials is increased by more than 30%. The longitudinal tear on the conveyor belt surface is then filled with filler and smoothed.

[0065] The interface activator comprises, by weight percentage, 5% silane coupling agent (KH-550), 20% nitrile rubber resin, 2% dibutyltin dilaurate, 1% antioxidant RD, and the remainder being ethyl acetate. The filler is a two-component filler material composed of polyurethane elastomer, carbon black reinforcing agent, crosslinking agent, and silane coupling agent. Specifically, the mass percentage of each component in the filler is: 70% polyurethane elastomer, 18% carbon black reinforcing agent, 8% diphenylmethane diisocyanate (MDI) crosslinking agent, 2.5% silane coupling agent (KH-560), 1% antioxidant RD, and the remainder being ethyl acetate.

[0066] For the primer application, a solvent-free epoxy primer compatible with the rubber activation layer and polyurea material is selected. It is applied evenly to the activated surface using a toothed scraper, with a coating amount controlled at 160 g / m², ensuring complete coverage of the damaged area and a 20 mm perimeter, forming a dense transition layer of 30 μm thickness. The epoxy primer surface-drying curing time is 35 minutes; the hot air gun temperature must be controlled at 45℃. The primer is a solvent-free epoxy primer, comprising, by mass ratio: 25% polyamide curing agent, 15% propylene oxide butyl ether, 1% 2-methylimidazole, 3% fumed silica, 0.8% anti-settling agent, and the remainder being bisphenol A epoxy resin. The hot air gun should be kept at least 30 cm away from the primer surface, blowing evenly onto the repaired area to prevent uneven heating; the auxiliary drying time is until the primer surface reaches a state of "not sticky to the touch and without drips". Keep the hot air gun at least 30cm away from the base coat surface and blow it evenly over the repair area to prevent uneven heating. The drying time should be based on the base coat surface reaching a state where it is "not sticky to the touch and has no drips".

[0067] In step 4, the polyurea material is a two-component polyurea material, which includes component A and component B; Component A is an isocyanate prepolymer comprising 32.5% of the total mass of the polyurea material. The B component comprises the following components in the total mass ratio of the polyurea material: 25% amino-terminated polyether, 9.5% m-phenylenediamine (MPDA), 2.5% fast-reacting aromatic chain extender, 0.2% tertiary amine catalyst, 10% reactive phosphorus-nitrogen flame retardant, 5% nano-wear-resistant filler; 3% flame retardant synergist; 5% conductive carbon black; 2% conductive fiber; 1.5% antistatic agent; 2% silane coupling agent; 0.5% latent catalyst; 1% antioxidant; and 0.3% defoamer.

[0068] Step 4 also includes placing a fiber reinforcement mesh on the surface of the polyurea material during the cooling process.

[0069] The defoamer is an organosilicon defoamer; the antioxidant is 1010 antioxidant; the silane coupling agent is KH550 silane coupling agent; the amino-terminated polyether is a compound of polyetheramine D2000 and T5000, and the compounding ratio is 1:1.8 by weight. The isocyanate prepolymer is an MDI-type isocyanate prepolymer; the amino-terminated polyether is a compound of polyetheramine D2000 and T5000 in a weight ratio of 1:1.8; the reactive phosphorus-nitrogen flame retardant is aluminum diethylphosphinate; the nano-wear-resistant filler is a compound system of nano-alumina and nano-silica, wherein nano-alumina accounts for 70% of the total mass of the nano-wear-resistant filler and nano-silica accounts for 30%; the flame retardant synergist is antimony trioxide; the conductive carbon black is acetylene black; the conductive fiber is conductive carbon fiber; the antistatic additive is a quaternary ammonium salt cationic surfactant; the silane coupling agent is KH550 silane coupling agent; the latent catalyst is dibutyltin dilaurate; the antioxidant is 1010 antioxidant; the defoamer is a polyether-modified siloxane defoamer; the fast-reacting aromatic chain extender is methylcyclohexanediamine; the tertiary amine catalyst is triethylenediamine.

[0070] The modified MDI prepolymer was prepared by reacting 4,4'-diphenylmethane diisocyanate (MDI-100) and polypropylene glycol (PPG-1000) at a mass ratio of 3:1 at 80°C for 3 hours. The NCO content of the prepolymer was controlled at 22%. This prepolymer, modified with short-chain polypropylene glycol, retains the high reactivity of MDI while improving its compatibility with component B, allowing for rapid reaction with component B and providing a foundation for the early strength performance of the material.

[0071] During polyurea spraying, component A is heated to 70℃ and component B to 65℃, then sprayed using a spraying machine. The spraying pressure is adjusted to 20MPa, and the spraying is performed in three coats: the first coat is 1mm thick, with a 10-minute cooling interval; the second coat is 1mm thick, for a total thickness of 2mm; the repair layer extends 40mm beyond the damaged edge. The edges are treated with a beveled transition.

[0072] Post-treatment and constant temperature curing: Immediately after the third spraying, cover the repair area with a flexible electric heating blanket (800W), set the temperature to 70℃, and keep it at that temperature for 25 minutes. After the insulation period, allow it to cool naturally to room temperature. Use 80-grit sandpaper to sand the edges of the repair layer to ensure a transition, ensuring the height difference between the repair layer and the original conveyor belt surface is ≤0.5mm. If defects such as pinholes or bubbles exist, apply a polyurea repair agent for touch-up treatment. In step 4, while the polyurea material is cooling, a fiber reinforcement mesh is also placed on the surface of the polyurea material.

[0073] Post-treatment and constant-temperature curing: Immediately after the third spraying, a flexible electric heating blanket (800W) is used to cover the repair area, setting the temperature to 80℃ and the curing time to 25 minutes. After the curing period, the area is allowed to cool naturally to room temperature. The edges of the repair layer are then sanded with 80-grit sandpaper to ensure a height difference of ≤0.5mm with the original conveyor belt surface. The fiber reinforcement mesh is glass fiber reinforced mesh. In step 4, during the first cooling of the polyurea material, a step of placing a fiber reinforcement mesh on the surface of the polyurea material is also included. The fiber reinforcement mesh is glass fiber reinforced mesh. Glass fiber possesses excellent chemical corrosion resistance and high-temperature stability, making it suitable for the harsh environments of mines, which are humid, dusty, and contain corrosive gases. It will not degrade or experience performance degradation due to long-term contact with mineral dust, acidic or alkaline media. Glass fiber reinforced mesh exhibits excellent interfacial compatibility with polyurea materials and primers. When embedded during the polyurea cooling stage, it can form a tight physical bond and chemical bond with polyurea molecules, eliminating the risk of delamination or detachment. Glass fiber reinforced mesh is relatively inexpensive, easy to process and shape, and can be flexibly cut to fit different sizes of repair needs according to the shape of the damaged area of ​​the conveyor belt.

[0074] The entire repair process was completed within 2 hours.

[0075] The polyurea repair layer, after being cured at a constant temperature using a gradient-interval spraying process, reaches 70% of its maximum strength. The repair layer's hardness (Shore A) is 75, and its tensile strength is 18.1 MPa. The bond strength between the repair layer and the conveyor belt body is 3.8 MPa, measured using a portable bond strength tester. Its flame retardant and antistatic properties meet mining safety requirements, with an oxygen index ≥30% and surface resistivity ≤108 Ω. The Taber abrasion test shows an abrasion rate below 28 mg / 1000 rpm. The tear strength test shows a value of 15.9 kN / m, fully meeting the requirements for conveyor use. No tear propagation or repair layer detachment has been observed in the conveyor belt after 24 months of use.

[0076] Example 3. A longitudinal tear measuring 3.0m in length and 0.3m in width, with a tear depth of 3mm, occurred on a steel wire rope conveyor belt in an underground coal mine. The repair method differs from that in Example 1 in that it includes the following steps.

[0077] Step 1: Surface Pretreatment Select a damaged area on the conveyor belt surface as the repair area, use a high-pressure water gun to wash away surface debris from the damaged part of the repair area, and remove the aging layer and debris; grind the surface of the repair area to make it smooth, and use a hot air blower to dry the surface of the ground repair area until the moisture content is ≤1%; the conveyor belt is a steel wire rope core rubber conveyor belt or a fabric core rubber conveyor belt.

[0078] Step 2: Interface Activation Treatment Spray the interface activator onto the repair area and let it stand for 7 minutes to form an active reaction layer; apply filler to the longitudinal tear on the conveyor belt surface and smooth it out.

[0079] Step 3: Primer application Apply the primer, dry it with a hot air blower, and cure for 28 minutes.

[0080] Step 4: Polyurea spraying Polyurea material is sprayed onto the surface of the active reaction layer several times. The polyurea material incorporates a flame retardant system and an antistatic system. There is a 12-minute interval between two consecutive sprays. During the interval, the previous coating layer is checked for defects such as bubbles and sagging. If any are found, they are promptly repaired with a scraper to finally form a polyurea repair layer.

[0081] Step 5: Constant temperature curing The repair area is covered with an electric heating blanket and kept warm for 28 minutes at a temperature of 75°C. After the heating blanket is removed, the in-situ repair of the repair area is completed. The ambient temperature during the repair is 20°C and the relative humidity does not exceed 80%.

[0082] Specifically, in step 1, the working pressure of the high-pressure water gun needs to be controlled at 9MPa. During the rinsing process, local ventilation equipment should be turned on to avoid the risk of slipping due to the accumulation of sewage and debris. For grinding, an explosion-proof angle grinder should be used, equipped with a dust mask and goggles. Dust should be collected through a negative pressure dust collection device to prevent the concentration from exceeding the standard. For drying, an explosion-proof hot air gun should be used, with a temperature ≤80℃, to ensure that the surface moisture content is ≤1% and to avoid contact with flammable and explosive substances. The grinding area should extend 100mm beyond the edge of the damage, and the surface roughness should be Ra50μm.

[0083] In step 2, before spraying the interface activator, confirm that the gas concentration is <0.5%, control the spraying amount to 50g / ㎡, and maintain ventilation to prevent the accumulation of volatiles; apply the filler with an anti-static scraper, smoothing it without bubbles or depressions. In step 3, an antistatic scraper is used to apply the primer, with a base coat amount of 140g / ㎡ and a base coat thickness of 30μm; the temperature of the explosion-proof hot air blower is 50℃, and the distance from the surface is ≥30cm. The condition of the primer is monitored in real time until it is "not sticky to the touch and has no drips", which is suitable for the curing requirements of extended humidity in the well. In step 4, the polyurea spraying equipment is explosion-proof. Specifically, component A is heated to 65°C and component B is heated to 60°C to ensure the material maintains good fluidity in the underground environment. The spraying pressure is controlled at 18MPa, ensuring uniform atomization without splashing. The thickness of a single spray does not exceed 1.0mm, and the cumulative thickness reaches 3mm to meet the requirements for wear resistance and tear resistance. During spraying, the equipment is kept 50cm away from the repair area, and the equipment moves at a uniform speed to avoid local coatings being too thick or too thin. Continuous ventilation is maintained to prevent the accumulation of atomized particles. In step 4, when the polyurea material is cooling, a fiber reinforcement mesh is also placed on the surface of the polyurea material.

[0084] In step 5, the electric blanket is an explosion-proof electric blanket with a power of 600W and a heat preservation temperature of 75℃. A dedicated person is on duty to prevent electrical sparks. A gas monitor is provided throughout the process. If the gas concentration is higher than 0.5%, the work must be stopped immediately. Construction personnel must wear anti-static clothing, and open flames and non-explosion-proof equipment are strictly prohibited to ensure the safety of underground operations. The entire in-situ repair time shall not exceed 2 hours.

[0085] The interface activator comprises, by weight percentage, 3%–5% silane coupling agent (KH-550), 15%–20% nitrile rubber resin, 1%–2% dibutyltin dilaurate, 0.5%–1% antioxidant RD, and the remainder being ethyl acetate.

[0086] The primer is a solvent-free epoxy primer, which comprises, by mass ratio, 30% polyamide curing agent, 12% propylene oxide butyl ether, 1% 2-methylimidazole, 2% fumed silica, 0.5% anti-settling agent, and the remainder is bisphenol A epoxy resin.

[0087] In step 4, the polyurea material is a two-component polyurea material, which includes component A and component B; Component A is an isocyanate prepolymer comprising 30% of the total mass of the polyurea material.

[0088] The B component comprises the following components in the total mass ratio of the polyurea material: 35% amino-terminated polyether, 8.1% m-phenylenediamine (MPDA), 2.5% fast-reacting aromatic chain extender, 0.2% tertiary amine catalyst, 8% reactive phosphorus-nitrogen flame retardant, 6% nano-wear-resistant filler; 2% flame retardant synergist; 3% conductive carbon black; 1.5% conductive fiber; 1% antistatic agent; 1.5% silane coupling agent; 0.3% latent catalyst; 0.7% antioxidant; and 0.2% defoamer.

[0089] The isocyanate prepolymer is an MDI-type isocyanate prepolymer; the amino-terminated polyether is a compound of polyetheramine D2000 and T5000 in a weight ratio of 1:1.6; the reactive phosphorus-nitrogen flame retardant is aluminum diethylphosphinate; the nano-wear-resistant filler is a compound system of nano-alumina and nano-silica, wherein nano-alumina accounts for 65% of the total mass of the nano-wear-resistant filler and nano-silica accounts for 35%; the flame retardant synergist is antimony trioxide; the conductive carbon black is acetylene black; the conductive fiber is conductive carbon fiber; the antistatic additive is a quaternary ammonium salt cationic surfactant; and the silane coupling agent is KH550. The coating consists of a silane coupling agent, a latent catalyst (dibutyltin dilaurate), an antioxidant (1010 antioxidant), and a defoamer (polyether-modified siloxane defoamer). This defoamer exhibits excellent dispersibility in high-viscosity polyurea systems, rapidly eliminating microbubbles generated during the high-speed mixing and high-pressure atomization of components A and B during spraying. It does not interfere with the crosslinking reaction process of the polyurea material, and does not leave pinholes or fisheye defects on the repair layer surface. It also exhibits good high-temperature stability and does not decompose or volatilize during the isothermal curing stage, ensuring that the density and mechanical properties of the repair layer remain unaffected. This makes it suitable for the stringent coating quality requirements of mining conveyor belt repair. The fast-reacting aromatic chain extender is methylcyclohexanediamine; the tertiary amine catalyst is triethylenediamine. The modified MDI prepolymer was prepared by reacting 4,4'-diphenylmethane diisocyanate (MDI-100) and polypropylene glycol (PPG-1000) at a mass ratio of 3:1 at 80°C for h, with the NCO content of the prepolymer controlled at 22%. This prepolymer, modified with short-chain polypropylene glycol, retains the high reactivity of MDI and significantly improves its compatibility with component B, enabling rapid reaction with component B and providing a foundation for the early strength performance of the material.

[0090] The fiber-reinforced mesh is made of aramid fiber. Aramid fiber has extremely high tear strength (2-3 times that of glass fiber) and excellent impact resistance, which can effectively resist the severe impact and friction of ore during the operation of mine conveyor belts; it has low density and light weight, and will not increase the extra load on the conveyor belt after being embedded in the polyurea layer; aramid fiber is resistant to acid and alkali corrosion and aging, making it suitable for complex underground environments and improving the fatigue resistance of the repair layer.

[0091] The polyurea repair layer, after being cured at a constant temperature using a gradient-interval spraying process, reaches 75% of its maximum strength. The repair layer's hardness (Shore A) is 82, and its tensile strength is 18.9 MPa. The bond strength between the repair layer and the conveyor belt body is 3.55 MPa, measured using a portable bond strength tester. Its flame retardant and antistatic properties meet mining safety requirements, with an oxygen index ≥30% and a surface resistivity ≤108 Ω. The Taber abrasion test shows an abrasion rate below 30 mg / 1000 rpm. The tear strength test shows a value of 16.5 kN / m, fully meeting the requirements for conveyor use. No tear propagation or repair layer detachment has been observed in the conveyor belt after 24 months of use.

[0092] Example 4. A longitudinal tear measuring 3.0m in length and 0.4m in width, with a tear depth of 4mm, occurred on a fiber core conveyor belt in an underground coal mine. The repair method differs from that in Example 1 in that it includes the following steps.

[0093] Step 1: Surface Pretreatment Select a damaged area on the conveyor belt surface as the repair area, use a high-pressure water gun to wash away surface debris from the damaged part of the repair area, and remove the aging layer and debris; grind the surface of the repair area to make it smooth, and use a hot air blower to dry the surface of the ground repair area until the moisture content is ≤1%; the conveyor belt is a steel wire rope core rubber conveyor belt or a fabric core rubber conveyor belt.

[0094] Step 2: Interface Activation Treatment Spray the interface activator onto the repair area and let it stand for 5-8 minutes to form an active reaction layer; apply filler to the longitudinal tear on the conveyor belt surface and smooth it out.

[0095] Step 3: Primer application Apply the primer, dry it with a hot air blower, and cure for 25 minutes.

[0096] Step 4: Polyurea spraying Polyurea material is sprayed onto the surface of the active reaction layer several times. The polyurea material incorporates a flame retardant system and an antistatic system. There is a 10-minute interval between two consecutive sprays. During the interval, the previous coating layer is checked for defects such as bubbles and sagging. If any defects are found, they are promptly repaired with a scraper to finally form a polyurea repair layer.

[0097] Step 5: Constant temperature curing The repair area is covered with an electric heating blanket and kept warm for 30 minutes at a temperature of 75°C. After the heating blanket is removed, the in-situ repair of the repair area is completed. The ambient temperature during the repair is 30°C and the relative humidity does not exceed 80%.

[0098] Specifically, in step 1, the working pressure of the high-pressure water gun needs to be controlled at 9MPa. During the rinsing process, local ventilation equipment should be turned on to avoid the risk of slipping due to the accumulation of sewage and debris. For grinding, an explosion-proof angle grinder should be used, equipped with a dust mask and goggles. Dust should be collected through a negative pressure dust collection device to prevent the concentration from exceeding the standard. For drying, an explosion-proof hot air gun should be used, with a temperature ≤80℃, to ensure that the surface moisture content is ≤1% and to avoid contact with flammable and explosive substances. The grinding area should extend 100mm beyond the edge of the damage, and the surface roughness should be Ra50μm.

[0099] In step 2, before spraying the interface activator, confirm that the gas concentration is <0.5%, control the spraying amount to 40g / ㎡, and maintain ventilation to prevent the accumulation of volatiles; apply the filler with an anti-static scraper, smoothing it without bubbles or depressions.

[0100] In step 3, an antistatic scraper is used to apply the primer, with a base coat amount of 160g / ㎡ and a base coat thickness of 30μm; the temperature of the explosion-proof hot air blower is 50℃, and the distance from the surface is ≥30cm. The condition of the primer is monitored in real time until it is "not sticky to the touch and has no drips", which is suitable for the curing requirements of extended humidity in the well.

[0101] In step 4, the polyurea spraying equipment is explosion-proof. Specifically, component A is heated to 70°C and component B is heated to 55°C to ensure the material maintains good fluidity in the downhole environment. The spraying pressure is controlled at 20MPa, ensuring uniform atomization without splashing. The thickness of a single spray does not exceed 1.0mm, and the cumulative thickness reaches 3mm to meet the requirements for wear resistance and tear resistance. During spraying, the equipment is kept 50cm away from the repair area, and the equipment moves at a uniform speed to avoid local coatings being too thick or too thin. Continuous ventilation is maintained to prevent the accumulation of atomized particles. In step 4, when the polyurea material is cooling, a fiber reinforcement mesh is also placed on the surface of the polyurea material.

[0102] In step 5, the electric blanket is an explosion-proof electric blanket with a power of 800W and a heat preservation temperature of 70℃. A dedicated person is on duty to prevent electrical sparks. A gas monitor is provided throughout the process. If the gas concentration is higher than 0.5%, the work must be stopped immediately. Construction personnel must wear anti-static clothing, and open flames and non-explosion-proof equipment are strictly prohibited to ensure the safety of underground operations. The entire in-situ repair time shall not exceed 2 hours.

[0103] The components of the interface activator, by weight percentage, include 5% silane coupling agent (KH-550), 15% nitrile rubber resin, 1% dibutyltin dilaurate, 1% antioxidant RD, and the remainder is ethyl acetate.

[0104] The primer is a solvent-free epoxy primer, which comprises, by mass ratio, 35% polyamide curing agent, 15% propylene oxide butyl ether, 0.5% 2-methylimidazole, 3% fumed silica, 0.8% anti-settling agent, and the remainder is bisphenol A epoxy resin.

[0105] In step 4, the polyurea material is a two-component polyurea material, which includes component A and component B; Component A accounts for 35% of the total mass of the polyurea material and is an isocyanate prepolymer; The components of component B, by mass ratio, comprise the following: 30% amino-terminated polyether, 7.4% m-phenylenediamine (MPDA), 2% fast-reacting aromatic chain extender, 0.2% tertiary amine catalyst, 5% reactive phosphorus-nitrogen flame retardant, 8% nano-wear-resistant filler, 3% flame retardant synergist, 5% conductive carbon black, 1% conductive fiber, 1.5% antistatic agent, 1% silane coupling agent, 0.1% latent catalyst, 0.5% antioxidant, and 0.3% defoamer.

[0106] The isocyanate prepolymer is an MDI-type isocyanate prepolymer; the amino-terminated polyether is a compound of polyetheramine D2000 and T5000 in a weight ratio of 1:1.5; the reactive phosphorus-nitrogen flame retardant is aluminum diethylphosphinate; the nano-wear-resistant filler is a compound system of nano-alumina and nano-silica, wherein nano-alumina accounts for 70% of the total mass of the nano-wear-resistant filler and nano-silica accounts for 30%; the flame retardant synergist is antimony trioxide; the conductive carbon black is acetylene black; the conductive fiber is conductive carbon fiber; the antistatic agent is a quaternary ammonium salt cationic surfactant; the silane coupling agent is KH550 silane coupling agent; the latent catalyst is dibutyltin dilaurate; the antioxidant is 1010 antioxidant; the defoamer is a polyether-modified siloxane defoamer; the fast-reacting aromatic chain extender is methylcyclohexanediamine; the tertiary amine catalyst is triethylenediamine. The modified MDI prepolymer was prepared by reacting 4,4'-diphenylmethane diisocyanate (MDI-100) and polypropylene glycol (PPG-1000) at a mass ratio of 3:1 at 70°C for 2 hours. This prepolymer, modified with short-chain polypropylene glycol, retains the high reactivity of MDI while improving its compatibility with component B, enabling rapid reaction with component B and providing a foundation for the material's early strength properties.

[0107] The fiber-reinforced mesh is made of ultra-high molecular weight polyethylene (UHMWPE) fiber. UHMWPE fiber has outstanding abrasion resistance (abrasion loss is only 1 / 5 that of glass fiber) and excellent impact resistance, which can significantly reduce frictional loss between the mining conveyor belt and the ore; its good flexibility allows it to closely conform to irregular damaged areas on the surface of the conveyor belt, ensuring a complete bond between the repair layer and the substrate; this fiber is resistant to chemical corrosion, has low water absorption, and maintains stable performance in the humid underground environment, with no risk of hydrolysis.

[0108] The polyurea repair layer, after being cured at a constant temperature using a gradient-interval spraying process, reaches 70% of its maximum strength. The Shore A hardness of the repair layer, measured with a Shore A hardness tester, is 81, and the tensile strength is 18.3 MPa. The bond strength between the repair layer and the conveyor belt body, measured using a portable bond strength tester, is 3.7 MPa. The flame retardant and antistatic properties meet mining safety requirements, with an oxygen index ≥30% and a surface resistivity ≤108 Ω. The Taber abrasion test shows an abrasion rate of less than 35 mg / 1000 rpm. The tear strength test shows a value of 16.9 kN / m, fully meeting the requirements for conveyor use. No tear propagation or repair layer detachment has been observed in the conveyor belt after 24 months of use.

Claims

1. A method for in-situ rapid repair of mining conveyor belts, characterized in that, Includes the following steps: Step 1: Surface Pretreatment Select a damaged area on the conveyor belt surface as the repair area and remove the aging layer and debris. Step 2: Interface Activation Treatment Spray the interface activator onto the repair area and let it stand for 5-8 minutes to form an active reaction layer; apply filler to the longitudinal tear on the conveyor belt surface and smooth it out. Step 3: Primer application Apply the primer, dry it with a hot air blower, and cure it for 25-30 minutes; Step 4: Polyurea spraying The polyurea material is sprayed onto the surface of the active reaction layer several times. The polyurea material is introduced into the flame retardant system and the antistatic system. There is an interval of 8-12 minutes between two adjacent sprays. During the interval, the previous coating layer is checked for defects such as bubbles and sagging. If there are any, they are repaired in time with a scraper to finally form a polyurea repair layer. Step 5: Constant temperature curing The repair area is covered with an electric heating blanket and kept warm for 25-30 minutes, with the temperature controlled at 70-80℃. After the heating blanket is removed, the in-situ repair of the repair area is completed. The ambient temperature during repair is 15-35℃ and the relative humidity does not exceed 80%. The conveyor belt is a steel wire rope core rubber conveyor belt or a fabric core rubber conveyor belt.

2. The in-situ rapid repair method for mining conveyor belts as described in claim 1, characterized in that: The filler is a two-component filler material composed of polyurethane elastomer, carbon black reinforcing agent, crosslinking agent and silane coupling agent.

3. The in-situ rapid repair method for mining conveyor belts as described in claim 1, characterized in that: The interface activator comprises, by weight percentage, 3%–5% silane coupling agent, 15%–20% nitrile rubber resin, 1%–2% dibutyltin dilaurate, 0.5%–1% antioxidant RD, and the remainder being ethyl acetate.

4. The in-situ rapid repair method for mining conveyor belts as described in claim 1, characterized in that: The primer is a solvent-free epoxy primer, which comprises, by mass ratio, 25%-35% polyamide curing agent, 10%-15% propylene oxide butyl ether, 0.5%-1% 2-methylimidazole, 1%-3% fumed silica, 0.3%-0.8% anti-settling agent, and the remainder is bisphenol A epoxy resin.

5. The in-situ rapid repair method for mining conveyor belts as described in claim 1, characterized in that: In step 1, a high-pressure water gun is used to rinse away surface debris from the damaged area of ​​the repair area; the surface of the repair area is polished to make it smooth, and a hot air blower is used to dry the polished surface of the repair area until the moisture content is ≤1%; In step 4, the polyurea material is a two-component polyurea material, which includes component A and component B; Component A is an isocyanate prepolymer comprising 30%–40% of the total mass of the polyurea material; The B component comprises the following components in the total mass ratio of the polyurea material: 25%–35% amino-terminated polyether, m-phenylenediamine, 1%–2.5% fast-reacting aromatic chain extender, 0.05%–0.2% tertiary amine catalyst, 5%–10% reactive phosphorus-nitrogen flame retardant, 5%–8% nano-wear-resistant filler; 1%–3% flame retardant synergist; 2%–5% conductive carbon black; 1%–2% conductive fiber; 0.5%–1.5% antistatic agent; 1%–2% silane coupling agent; 0.1%–0.5% latent catalyst; 0.5%–1% antioxidant; and 0.1%–0.3% defoamer.

6. The in-situ rapid repair method for mining conveyor belts as described in claim 5, characterized in that: The isocyanate prepolymer is an MDI-type isocyanate prepolymer; the amino-terminated polyether is a compound of polyetheramine D2000 and T5000, with a weight ratio of 1:1.2-1.8; the fast-reacting aromatic chain extender is methylcyclohexanediamine; the tertiary amine catalyst is triethylenediamine; the reactive phosphorus-nitrogen flame retardant is aluminum diethylphosphinate; the nano-wear-resistant filler is a compound system of nano-alumina and nano-silica, wherein nano-alumina accounts for 60%-70% of the total mass of the nano-wear-resistant filler and nano-silica accounts for 30%-40%; the flame retardant synergist is antimony trioxide; the conductive carbon black is acetylene black; the conductive fiber is conductive carbon fiber; the antistatic agent is a quaternary ammonium salt cationic surfactant; the silane coupling agent is KH550 silane coupling agent; the latent catalyst is dibutyltin dilaurate; the antioxidant is 1010 antioxidant; and the defoamer is a polyether-modified siloxane defoamer.

7. The in-situ rapid repair method for mining conveyor belts as described in claim 5, characterized in that: During underground operations, in step 1, the working pressure of the high-pressure water gun must be controlled at 8-10MPa. Local ventilation equipment should be turned on during rinsing to prevent the accumulation of sewage and debris that could cause slipping. For grinding, an explosion-proof angle grinder should be used, equipped with a dust mask and goggles. Dust should be collected using a negative pressure dust collection device to prevent excessive concentration. Drying should be done using an explosion-proof hot air gun at a temperature ≤80℃, ensuring a surface moisture content ≤1%, and avoiding contact with flammable and explosive substances. The grinding area should extend 50-100mm beyond the damaged edge, with a surface roughness Ra of 25-50μm. In step 2, before spraying the interface activator, confirm that the gas concentration is <0.5%, control the spraying amount to 30-50g / ㎡, and maintain ventilation to prevent the accumulation of volatiles; apply the filler with an anti-static scraper, smoothing it without bubbles or depressions. In step 3, an antistatic scraper is used to apply the primer, with a base coat amount of 120-160 g / m² and a base coat thickness of 20-30 μm. The temperature of the explosion-proof hot air blower is 45-50℃, and the distance from the surface is ≥30 cm. The condition of the primer is monitored in real time until it is "not sticky to the touch and has no drips" to meet the curing requirements of extended humidity in the well. In step 4, the polyurea spraying equipment is explosion-proof. Specifically, component A is heated to 60-70℃ and component B is heated to 55-65℃ to ensure that the material maintains good fluidity in the underground environment. The spraying pressure is controlled at 15-20MPa, with uniform atomization and no splashing. The thickness of a single spray does not exceed 1.0mm, and the cumulative thickness reaches 3mm to meet the requirements of wear resistance and tear resistance. During spraying, the equipment is kept 30-50cm away from the repair area, and the equipment is moved at a uniform speed to avoid local coatings being too thick or too thin. Continuous ventilation is maintained to prevent the accumulation of atomized particles. In step 5, the electric blanket is an explosion-proof electric blanket with a power of 500-800W and a heat preservation temperature of 70-80℃. It is monitored by a dedicated person to prevent electrical sparks. The entire process is equipped with a gas monitoring device. Work must be stopped immediately if the gas concentration exceeds 0.5%. Construction personnel must wear anti-static clothing, and open flames and non-explosion-proof equipment are strictly prohibited to ensure safety during underground operations. The entire in-situ repair time shall not exceed 2 hours.

8. The in-situ rapid repair method for mining conveyor belts as described in claim 1, characterized in that: In step 4, during one of the cooling processes of the polyurea material, a step of placing a fiber reinforcement mesh on the surface of the polyurea material is also included.

9. The in-situ rapid repair method for mining conveyor belts as described in claim 8, characterized in that: The fiber-reinforced mesh is one of the following: glass fiber reinforced mesh, basalt fiber reinforced mesh, aramid fiber reinforced mesh, and ultra-high molecular weight polyethylene fiber reinforced mesh.

10. The in-situ rapid repair method for mining conveyor belts as described in claim 1, characterized in that: Mining conveyor belts are one of the following: rubber steel wire conveyor belts, rubber fiber conveyor belts, PVC conveyor belts, and PVG conveyor belts.

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