A laminated rubber cover for high temperature material conveying and a manufacturing process thereof

Abstract

The application relates to the technical field of high polymer materials, and discloses a laminated rubber covering layer for high-temperature material conveying and a preparation process thereof, and aims to solve the problems of insufficient high-temperature resistance, easy peeling between layers and insufficient mechanical strength of the existing rubber covering layer. The covering layer adopts a three-layer composite laminated structure and sequentially comprises a heat-resistant outer layer, an aramid framework layer and a wear-resistant adhesive layer; the heat-resistant outer layer adopts a composite system of fluororubber and ceramic fillers with a mass fraction of 15% to 25%; the aramid framework layer is reinforced by aramid fabric; the wear-resistant adhesive layer adopts a nitrile rubber and kaolin reinforced system; and the three-layer structure realizes interlayer chemical bonding through a hot-pressing vulcanization process. Application shows that the laminated covering layer has a tensile strength retention rate of no less than 80% under a high-temperature environment of 200 DEG C, a peeling strength of 12 to 18 N / mm with the conveying belt framework, excellent wear resistance, significantly prolonged service life, and is suitable for large-scale application in high-temperature material conveying scenes.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a laminated rubber cover layer for high-temperature material conveying and its preparation process. Background Technology

[0002] Industrial material handling is a crucial link in modern process industry production, widely used in mining, metallurgy, building materials production, power energy, and chemical industries. In long-distance or high-intensity material handling operations, the conveyor belt, as the core load-bearing and transmission component, directly determines the operating efficiency, equipment lifespan, and production safety of the conveying system through the performance of its surface covering layer. Rubber coverings, with their excellent wear resistance, impact resistance, flexibility, and good compatibility with conveyor belt skeleton materials, have become the most mainstream covering material system in the material handling field.

[0003] High-temperature material conveying is one of the most demanding application scenarios in industrial conveying technology. In high-temperature operations such as ore sintering, cement clinker transfer, steel slag handling, boiler slag discharge, and coking, the conveyor belt surface must continuously withstand material impacts and heat radiation at temperatures ranging from 150°C to 500°C or even higher. Laminated rubber covers, by combining rubber layers with different functional properties, can achieve optimized configuration of functional areas such as heat-resistant layers, buffer layers, and adhesive layers within a single cover layer, representing a key technological development direction in the field of high-temperature material conveying.

[0004] Existing laminated rubber cover layers still have significant drawbacks in high-temperature material conveying applications. First, traditional rubber materials are highly susceptible to thermo-oxidative aging under sustained high temperatures, leading to increased hardness, decreased elasticity, and a sharp decline in wear resistance, potentially resulting in cracking, peeling, or even complete failure. Second, the significant differences in thermal expansion coefficients between the rubber layers in a laminated structure make them prone to interlayer delamination and debonding under repeated thermal cycling. Third, while some rubber cover layers modified with heat-resistant fillers can improve their heat resistance, this often comes at the cost of reduced processing fluidity and mechanical strength, resulting in a narrower manufacturing process window and lower product yield. Furthermore, existing laminated structure designs struggle to simultaneously achieve high-temperature resistance, thermal shock resistance, and durable adhesion to the conveyor belt frame, failing to meet the stringent comprehensive performance requirements of high-temperature material conveying. Therefore, developing a laminated rubber cover layer and its manufacturing process that can maintain structural stability and functional reliability under high-temperature conditions has become an urgent technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a laminated rubber cover layer for conveying high-temperature materials and its preparation process, which can effectively solve the problems in the background art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A laminated rubber cover layer for conveying high-temperature materials includes the following specific structure: the cover layer adopts a three-layer composite laminated structure, comprising a heat-resistant outer layer, an aramid skeleton layer, and a wear-resistant adhesive layer in sequence; the heat-resistant outer layer adopts a mixed system of fluororubber and ceramic filler, with the ceramic filler having a mass fraction of 15% to 25%; the aramid skeleton layer uses aramid cord fabric as a reinforcing material to provide tensile strength and tear resistance for the overall structure; the wear-resistant adhesive layer adopts a nitrile rubber combined with a kaolin reinforcement system to achieve reliable bonding with the conveyor belt skeleton; the three-layer structure achieves interlayer chemical bonding through a hot-press vulcanization process to form a complete laminated composite cover layer.

[0007] A process for preparing a laminated rubber cover layer for high-temperature material conveying includes the following specific steps: Step 1: Preparing a heat-resistant outer layer compound: Fluororubber, ceramic filler, crosslinking agent, and processing aids are added to a mixer in a preset ratio and mixed at 120°C to 140°C for 8 to 12 minutes. After sheeting, a heat-resistant outer layer compound is obtained. Step 2: Preparing a wear-resistant adhesive layer compound: Nitrile rubber, kaolin, plasticizer, and adhesive aids are added to a mixer in a preset ratio and mixed at 80°C to 100°C for 10 to 15 minutes. After sheeting, a wear-resistant adhesive layer compound is obtained. Step 3: Laying and skeleton bonding: The heat-resistant outer layer compound rubber sheet, aramid cord fabric and the wear-resistant adhesive layer compound rubber sheet are alternately laid in the order from top to bottom and placed in the lamination mold; Step 4: Hot pressing vulcanization: The mold with the layers laid is placed in a hot press and vulcanized for 20 to 30 minutes at 165 to 175 degrees Celsius and a pressure of 8 to 12 MPa, so that the three-layer structure forms a chemically bonded whole through cross-linking reaction; Step 5: Cooling and post-treatment: After vulcanization, cooling and shaping are carried out, and the edges are trimmed and shaped to obtain the finished laminated rubber cover layer.

[0008] Preferably, the formulation of the heat-resistant outer layer compound in step 1 is: 55% to 75% fluororubber, 15% to 25% ceramic filler, 2% to 4% crosslinking agent, and 3% to 6% processing aid, with the sum of the mass fractions of each component being 100%.

[0009] Preferably, the ceramic filler in step 1 is at least one of silicon carbide, alumina, or silicon nitride, and the filler particle size is controlled in the range of 0.5 micrometers to 3 micrometers, with a specific surface area of ​​8 square meters per gram to 15 square meters per gram.

[0010] Preferably, the formula of the wear-resistant adhesive layer compound in step 2 is: 65% to 75% nitrile rubber, 20% to 30% kaolin, 5% to 10% plasticizer, and 1% to 3% adhesive additive, with the sum of the mass fractions of each component being 100%.

[0011] Preferably, in step 2, the nitrile rubber has a Mooney viscosity of 45 to 65, an acrylonitrile content of 28% to 40%, and a kaolin particle size of 1 micrometer to 5 micrometers.

[0012] Preferably, in step 3, the aramid skeleton layer uses aramid fabric with a weight of 200 g / m² to 400 g / m², a cord breaking strength greater than or equal to 80 centineton-teks, and has 1 to 3 layers.

[0013] Preferably, the stacking order of the three-layer structure in step 3 is as follows: the heat-resistant outer compound rubber sheet is located in the upper layer, the aramid cord is arranged in the middle layer, and the wear-resistant adhesive compound rubber sheet is located in the lower layer; adhesive is pre-coated between each layer to enhance the interlayer bonding force.

[0014] Preferably, the adhesive is a mixture of isocyanate-modified resin and epoxy resin-modified resin, and the mass fraction of the silane coupling agent is 1% to 3%.

[0015] Preferably, the process parameters for hot-press vulcanization in step 4 are: temperature 168°C to 172°C, pressure 9 to 11 MPa, vulcanization time 22 to 28 minutes, and heating rate 1.5°C to 2.5°C per minute.

[0016] Preferably, during the hot-press vulcanization process in step 4, the mold temperature uniformity is controlled within ±2 degrees Celsius to ensure that the vulcanization degree of each area of ​​the cover layer is consistent.

[0017] Preferably, the cooling in step 5 adopts a segmented cooling method. First, the temperature is cooled to below 80 degrees Celsius in the mold cavity before demolding, and then it continues to be cooled to room temperature in ambient air. During the cooling process, internal stress concentration caused by rapid cooling is avoided.

[0018] Preferably, the overall thickness of the laminated rubber cover layer is 8 mm to 15 mm, the density is 1.35 g / cm³ to 1.55 g / cm³, and the Shore A hardness is 75 to 90.

[0019] Preferably, after the laminated rubber cover layer is subjected to an aging test at 200 degrees Celsius for 168 hours, the tensile strength retention rate is greater than or equal to 80%, the elongation at break retention rate is greater than or equal to 70%, and the hardness change is controlled within ±5 Shore A.

[0020] Preferably, the abrasion resistance of the surface layer of the laminated rubber cover is determined according to the Akron abrasion test method, and the abrasion amount is less than or equal to 0.15 cubic centimeters per 1.61 kilometers.

[0021] Preferably, the interlayer adhesion between the heat-resistant outer layer and the aramid skeleton layer is greater than or equal to 8 N / mm, and the peel strength between the wear-resistant adhesive layer and the conveyor belt skeleton is 12 N / mm to 18 N / mm.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. Excellent high-temperature resistance: The heat-resistant outer layer is prepared using a composite system of fluororubber and ceramic filler. The carbon-fluorine bond structure of fluororubber gives the material excellent heat resistance and stability, while the high heat capacity and low thermal expansion characteristics of ceramic filler effectively block heat transfer to the interior. The synergistic effect of the two ensures that the tensile strength retention rate of the cover layer is greater than or equal to 80% when used for a long time in a high-temperature environment of 200 degrees Celsius, and the hardness change is controlled within ±5 Shore A, which effectively delays the thermo-oxidative aging process and significantly extends the service life.

[0023] 2. Reliable interlayer bonding performance: By optimizing the gradient design of the thermal expansion coefficients of each layer in the three-layer structure, the thermal expansion coefficients of the heat-resistant outer layer, the aramid skeleton layer and the wear-resistant adhesive layer are distributed in a gradient, reducing the difference in thermal stress between the layers during thermal cycling; combined with the chemical bonding achieved by the hot-pressing vulcanization process, the interlayer adhesion force is greater than or equal to 8 N / mm, effectively preventing the interlayer peeling and debonding problems of the laminated structure under repeated thermal shock.

[0024] 3. Excellent tear resistance and mechanical strength: The introduction of the aramid skeleton layer provides a high-strength, high-modulus support skeleton with a cord breaking strength greater than or equal to 80 centinetonnes per minute tex, forming an effective stress transfer network with the rubber material; the interface between the aramid skeleton layer and the upper and lower rubber layers adopts a plasma pretreatment process, which enhances the interface wettability and bonding strength, and significantly improves the overall tear resistance of the cover layer.

[0025] 4. Excellent bonding reliability: The wear-resistant adhesive layer adopts a nitrile rubber and kaolin reinforcement system, and through the synergistic effect of isocyanate modified resin and epoxy resin modified resin, combined with silane coupling agent, the chemical bonding with the conveyor belt skeleton is further enhanced. This adhesive system enables the peel strength between the laminated cover layer and the conveyor belt skeleton to reach 12 N / mm to 18 N / mm, which is more than 40% higher than the traditional single-layer rubber cover layer, ensuring reliable bonding during long-term use.

[0026] 5. Good processing adaptability and yield: Both fluororubber and nitrile rubber systems have suitable Mooney viscosity ranges. With the synergistic adjustment of plasticizers and processing aids, the compound has good flowability and coating properties during calendering and layup. The hot-pressing vulcanization process has a wide window, with a temperature tolerance of ±2 degrees Celsius and a pressure fluctuation range of 2 MPa, providing stable process conditions for large-scale production and significantly improving the product yield.

[0027] 6. Balanced Comprehensive Performance: Through the functional design of the three-layer structure, a comprehensive and optimized balance of heat resistance, mechanical strength, wear resistance, and adhesion is achieved. The heat-resistant outer layer provides heat insulation, the aramid skeleton layer provides strength support, and the wear-resistant adhesive layer provides wear resistance and adhesion. The three work together to enable the cover layer to exhibit excellent comprehensive performance under the harsh conditions of high-temperature material transportation. Attached Figure Description

[0028] Figure 1 A schematic diagram of the overall process for the laminated rubber cover layer used for conveying high-temperature materials and its preparation process. Figure 2 A schematic diagram illustrating the design process of the core multi-layer structure for laminated rubber cover layers; Figure 3 This is a flowchart illustrating the main stages of the preparation process for a laminated rubber cover layer. Figure 4 This is a schematic diagram illustrating the process of laminated rubber covering layers in terms of high-temperature resistance and service life compared to existing technologies. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0032] This invention discloses a laminated rubber cover layer for high-temperature material conveying and its preparation process. The core of this invention lies in achieving comprehensive optimization of heat resistance, mechanical strength, wear resistance, and adhesion through a three-layer composite laminated structure. Structurally, this laminated rubber cover layer is divided into three functional layers: an upper heat-resistant outer layer, a middle aramid skeleton layer that acts as a reinforcing framework, and a lower wear-resistant adhesive layer that bonds with the conveyor belt. The three layers are chemically bonded together through a hot-press vulcanization process, forming a laminated composite cover layer with excellent comprehensive performance.

[0033] The overall structural design of the laminated rubber cover layer follows the basic principle of functional zoning. The heat-resistant outer layer, as the outermost surface of the cover layer, is directly exposed to the high-temperature material transport environment, undertaking the core functions of heat insulation and surface protection. This layer uses a hybrid system of fluororubber and ceramic filler as the main material. The carbon-fluorine bonds in the fluororubber molecular chain endow the material with excellent heat resistance and chemical inertness, while the introduction of ceramic filler provides a physical barrier effect with high heat capacity and low coefficient of thermal expansion. The two work synergistically to form a highly efficient heat insulation structure. An aramid skeleton layer is positioned between the heat-resistant outer layer and the wear-resistant adhesive layer, using high-strength aramid cord fabric as the reinforcing material. Its cord breaking strength is greater than or equal to 80 centinetonnes per tex, forming a continuous stress-supporting skeleton in the laminated structure, effectively dispersing and transferring external loads, significantly improving the tear resistance and overall structural stability of the cover layer. The wear-resistant adhesive layer serves as the interface between the cover layer and the conveyor belt skeleton. It adopts a nitrile rubber combined with a kaolin reinforcement system. This system has both excellent wear resistance and reliable adhesion characteristics, and can maintain a stable bond with the conveyor belt skeleton under high temperature conditions.

[0034] In its specific implementation, the preparation process of this invention includes the following five core steps: Step 1: Preparation of heat-resistant outer layer compound Fluororubber, ceramic fillers, crosslinking agents, and processing aids are added to an internal mixer according to a preset ratio for mixing. The internal mixer should be selected to meet the requirements of large-capacity, high-efficiency industrial production. The effective volume of the mixing chamber is determined according to the production batch, with a typical configuration ranging from 20 liters to 200 liters. During the mixing process, the rotor speed of the internal mixer is controlled within the range of 60 to 120 revolutions per minute. Through the forced extrusion, shearing, and tumbling action of the rotor, the components are fully dispersed and mixed.

[0035] In the formulation design of the heat-resistant outer layer compound, the mass fraction range of each component is as follows: fluororubber 55% to 75%, ceramic filler 15% to 25%, crosslinking agent 2% to 4%, and processing aids 3% to 6%, with the sum of the mass fractions of each component strictly controlled to 100%. Fluororubber, as the matrix material, is selected as a copolymer of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene, with its fluorine content controlled within the range of 65% to 70% to ensure excellent heat resistance and chemical corrosion resistance. The ceramic filler uses at least one of silicon carbide, alumina, or silicon nitride, with the filler particle size precisely controlled within a narrow distribution range of 0.5 micrometers to 3 micrometers, and the specific surface area measured is controlled between 8 square meters per gram and 15 square meters per gram. The ultrafine treatment of the ceramic filler is achieved through air jet milling; the uniformity of the particle size distribution directly affects the dispersion effect and reinforcing efficiency of the filler in the rubber matrix. The crosslinking agent is a compound system of bisphenol AF and benzyltriphenylphosphine chloride, and its dosage is calculated and added according to the mass of the fluororubber to ensure the formation of an appropriate crosslinking network density during vulcanization. The processing aids are a combination of fluorinated surfactants and stearate lubricants. Their function is to reduce the heat generation effect during the mixing process, improve the wetting and dispersion effect of fillers, and increase the flowability of the compound.

[0036] The mixing process parameters are set as follows: mixing temperature 120°C to 140°C, with an optimal range of 125°C to 135°C; mixing time 8 to 12 minutes, with an optimal range of 9 to 11 minutes. Temperature control employs a circulating oil heating system, with a temperature sensor on the mixing chamber wall providing real-time monitoring and feedback to ensure that mixing temperature fluctuations are controlled within ±2°C. After mixing, the sheeting device calenders the mixed rubber into uniformly thick sheets. The sheet thickness is determined according to the requirements of subsequent lamination processes, typically ranging from 2 mm to 4 mm. The heat-resistant outer layer mixed rubber sheet after sheeting requires cooling and setting. Cooling is achieved using circulating cooling water, with the cooling temperature controlled within the range of 20°C to 30°C, and the cooling time no less than 30 minutes to ensure complete setting of the sheet and elimination of internal residual stress.

[0037] Step 2: Preparation of wear-resistant adhesive layer compound Nitrile rubber, kaolin, plasticizer, and adhesive additives are added to an internal mixer in a predetermined ratio and mixed. The rotor speed of the internal mixer is set to 50 to 100 rpm, and the temperature of the mixing chamber is controlled within the range of 80 to 100 degrees Celsius. Nitrile rubber, as the matrix material, has a Mooney viscosity controlled within the range of 45 to 65, and an acrylonitrile content set at 28% to 40%. The synergistic optimization of Mooney viscosity and acrylonitrile content ensures that the material possesses both good processing fluidity and excellent oil resistance and adhesive properties. Kaolin, as a reinforcing filler, has a particle size controlled within the range of 1 to 5 micrometers. Its lamellar structure can form an effective stress dispersion network in the rubber matrix, improving wear resistance while enhancing adhesion.

[0038] The mass fraction range of each component in the wear-resistant adhesive layer compound is as follows: 65% to 75% nitrile rubber, 20% to 30% kaolin, 5% to 10% plasticizer, and 1% to 3% adhesive additive. The sum of the mass fractions of all components is strictly controlled to 100%. The plasticizer selected is dioctyl phthalate or adipate, which has good compatibility with nitrile rubber. Its function is to reduce the viscosity of the compound, improve processing performance, and impart good flexibility and low-temperature performance to the vulcanized rubber. The adhesive additive is a pre-condensate of resorcinol formaldehyde resin and rubber latex. The active hydroxyl groups in its molecular structure can form chemical bonds with the rubber molecular chains and simultaneously form an effective interfacial bond with the surface of the conveyor belt skeleton material.

[0039] The mixing process parameters are set as follows: mixing temperature 80°C to 100°C, preferably 85°C to 95°C; mixing time 10 to 15 minutes, preferably 11 to 13 minutes. After mixing, the sheeting device calenders the mixed rubber into a film of uniform thickness. The film thickness is determined according to the lamination structure design, typically 2 mm to 3 mm. Cooling is performed in the same manner as in step 1 to ensure complete film setting.

[0040] Step 3: Lamination and skeleton composite The heat-resistant outer compound film prepared in step 1, the wear-resistant adhesive layer compound film prepared in step 2, and the aramid cord fabric are layered and combined in a specific laying sequence to form a complete three-layer prefabricated structure. During the laying process, the wear-resistant adhesive layer compound film is first laid flat at the bottom of the lamination mold, and then the aramid cord fabric is laid flat on top of the wear-resistant adhesive layer compound film. The laying of the aramid cord fabric must ensure that it is wrinkle-free, bubble-free, and flat to meet the process requirements. Finally, the heat-resistant outer compound film is covered on top of the aramid cord fabric.

[0041] The specific technical parameters of the aramid skeleton layer are as follows: aramid cord fabric with a basis weight of 200 g / m² to 400 g / m², a cord breaking strength greater than or equal to 80 centinetonnes per minute (CdTx), and a layer count of 1 to 3. The basis weight of the aramid cord fabric is selected based on the strength requirements of the covering layer; a higher basis weight results in a more significant reinforcing effect, but also increases the difficulty of the lamination process and material costs. In typical applications involving high-temperature material conveying, the preferred basis weight of the aramid cord fabric is 280 g / m² to 350 g / m², and the preferred number of cord layers is 2, to achieve the best balance between strength and processability. Aramid cord fabric requires pretreatment before being laid up. The pretreatment process uses plasma treatment technology, in which argon plasma is used to bombard the surface of the cord fabric in a vacuum chamber. The plasma power is set to 200 watts to 500 watts, and the treatment time is 30 seconds to 120 seconds. This treatment can effectively remove organic pollutants from the surface of the cord fabric, and at the same time introduce oxygen- and nitrogen-containing polar functional groups into the fiber surface, which significantly improves the wettability and interfacial adhesion of the fiber surface.

[0042] The three-layer structure is laid out as follows: the heat-resistant outer compound film is on top, the aramid cord is in the middle layer, and the abrasion-resistant adhesive compound film is on the bottom layer. Each layer needs to be pre-coated with an adhesive to enhance interlayer bonding. The adhesive is a mixture of isocyanate-modified resin and epoxy-modified resin, with the mass fraction of silane coupling agent controlled between 1% and 3%. The adhesive is applied using a roller coating process, with the coating amount controlled between 10 grams per square meter and 30 grams per square meter. After coating, appropriate pre-curing treatment is required. The pre-curing temperature is set between 60°C and 80°C, and the pre-curing time is between 5 and 15 minutes to ensure that the active groups in the adhesive partially pre-react, avoiding defects such as flow or bubbles during subsequent hot pressing.

[0043] The design of the lamination mold must meet the following technical requirements: the mold material should be high-strength alloy tool steel, and the mold surface should be hard chrome plated with a plating thickness controlled between 15 and 25 micrometers to provide excellent wear resistance and demolding performance; the mold heating system should use an array of electric heating rods, and the heating power distribution should be optimized through thermodynamic simulation to ensure that the mold temperature uniformity is controlled within ±2 degrees Celsius; the mold cooling system should use a cooling water channel design, with the cooling water temperature controlled between 20 and 25 degrees Celsius, and the cooling water flow rate determined according to the heat capacity of the mold; the mold positioning mechanism should use a rectangular tenon and mortise structure, with positioning accuracy controlled within 0.05 millimeters to ensure the precise positioning of the multi-layer structure within the mold.

[0044] Step 4: Hot pressing vulcanization The mold with the laminated layers is placed in a hot press, where a vulcanization reaction is carried out under set temperature and pressure conditions. The hot press should be selected to meet the tonnage and stroke requirements of the lamination process; a typical configuration is a 500-ton to 2000-ton hot press, and the platen size is determined according to the product dimensions. The hot-press vulcanization process is the core step in the preparation of this laminated rubber cover layer. Through the dual action of hot pressing and vulcanization, the chemical bonding and physical shaping of the three-layer structure are achieved.

[0045] The hot-press vulcanization process parameters are set as follows: vulcanization temperature 168°C to 172°C, preferably 170°C; vulcanization pressure 9 to 11 MPa, preferably 10 MPa; vulcanization time 22 to 28 minutes, preferably 25 minutes; heating rate 1.5°C / min to 2.5°C / min, preferably 2.0°C / min. Precise temperature control is achieved through the hot press oil heating system, using high-pressure mineral oil as the heating medium, which has good thermal stability and high heat transfer efficiency. Stable pressure control is achieved through a hydraulic servo system, with pressure fluctuations controlled within ±0.5 MPa.

[0046] Temperature uniformity control during hot-press vulcanization is crucial for ensuring consistent product quality. During hot-press vulcanization, the mold temperature uniformity must be controlled within ±2 degrees Celsius. This is achieved through the following technical measures: 3 to 5 temperature measuring points are installed on each of the upper and lower pressure plates of the hot press, symmetrically arranged along the diagonal and center positions of the pressure plates; K-type thermocouples with an accuracy class of 0.5 and a response time of less than 1 second are used as temperature sensors; a PID algorithm is employed in the temperature control system to adjust the power output of each heating zone in real time based on temperature feedback from each measuring point; the temperature field distribution on the mold surface needs to be verified using a thermocouple grid method before formal production to ensure that the temperature uniformity meets the process requirements.

[0047] The main chemical reactions occurring during hot-press vulcanization include: fluororubber molecular chains undergo defluorination and cross-linking reactions under the action of a cross-linking agent, forming a three-dimensional cross-linked network structure; nitrile rubber molecular chains undergo vulcanization and cross-linking reactions under the action of a cross-linking agent, forming an elastomer cross-linked network; and the active functional groups on the surface of aramid fabric undergo interfacial chemical reactions with the active groups in the rubber molecular chains under hot-pressing conditions, forming covalent bonds. The conversion rate of the cross-linking reaction is a key indicator for measuring the degree of vulcanization. By adjusting the amount of cross-linking agent and vulcanization process parameters, the cross-linked network density distribution can be optimized, ensuring that the physical and mechanical properties of the coating layer meet design requirements.

[0048] During hot-press vulcanization, the pressurization, holding, and depressurization procedures of the hot press must be precisely controlled. The pressurization process employs a segmented approach: first, the pressure is increased from 0 MPa to 3 MPa within 30 seconds, then increased from 3 MPa to the target pressure of 10 MPa within 60 seconds, with simultaneous heating during the pressurization process. The holding process maintains stable temperature and pressure, with the holding time equal to the vulcanization time minus the heating and depressurization times. The depressurization process uses a slow depressurization method, gradually reducing the pressure from 10 MPa to 0 within 60 seconds to avoid interlayer delamination and internal defects caused by sudden pressure changes. The timing parameters of the pressurization, holding, and depressurization procedures are automatically executed through a preset program in the control system, ensuring the repeatability and consistency of the process parameters.

[0049] The temperature-time-pressure curve of the hot-press vulcanization process can be represented as:

[0050]

[0051]

[0052] in, Let be a function of temperature change over time. The initial temperature. For the heating rate, This is the end time of the heating process; Let the pressure be a function of time. For the rated working pressure, This represents the pressure increase end time. This formula precisely describes the temporal control relationship between temperature and pressure during hot-press vulcanization, providing a mathematical basis for optimizing process parameters.

[0053] Step 5: Cooling and Post-processing After vulcanization, the cover layer enters the cooling and setting stage. A segmented cooling method is used to avoid stress concentration and delamination defects caused by rapid cooling. The first stage is in-mold cooling: the vulcanized mold is placed in the cooling station, the heating system is turned off, and the mold cooling water circulation is turned on. The cooling water temperature is controlled between 20 and 25 degrees Celsius, and the cooling water flow rate is determined according to the mold's heat capacity. The mold temperature is monitored during cooling, and the mold opening operation can only be performed when the mold temperature drops below 80 degrees Celsius. Cooling to below 80 degrees Celsius before demolding ensures a uniform temperature field distribution inside the cover layer, avoiding temperature gradient stress caused by excessively low surface temperature while the internal temperature remains high. The second stage is room temperature air cooling: the demolded cover layer is placed in room temperature air to continue cooling to room temperature. During cooling, the cover layer must be placed flat on a flat support surface to avoid deformation due to its own weight or improper support. The room temperature air cooling time is no less than 2 hours to ensure that the internal temperature of the cover layer completely drops to room temperature and stress relaxation is completed.

[0054] After cooling, the coating undergoes trimming and shaping. The trimming process uses CNC cutting equipment to precisely cut according to the product design dimensions, with the trimming allowance controlled within the range of 1 to 2 millimeters. During trimming, the degree of vulcanization and interlayer bonding in each area of ​​the coating layer must be checked; defective products must be marked and isolated. The shaping process optimizes the surface quality of the coating layer, removing any flow marks, parting line burrs, or other defects. After surface treatment, the coating layer undergoes a final quality inspection, including: thickness uniformity, hardness distribution, surface quality, dimensional accuracy, and the interlayer bonding state.

[0055] After the above preparation process, the physical properties of the laminated rubber cover layer obtained by this invention are as follows: overall thickness of 8 mm to 15 mm, density of 1.35 g / cm³ to 1.55 g / cm³, and Shore A hardness of 75 to 90. After aging test at 200 degrees Celsius for 168 hours, the tensile strength retention rate is greater than or equal to 80%, the elongation at break retention rate is greater than or equal to 70%, and the hardness change is controlled within ±5 Shore A. The abrasion resistance of the surface layer is determined according to the Akron abrasion test method, and the abrasion amount is less than or equal to 0.15 cm³ per 1.61 km. The interlayer adhesion between the heat-resistant outer layer and the aramid skeleton layer is greater than or equal to 8 N / mm, and the peel strength between the abrasion-resistant adhesive layer and the conveyor belt skeleton is 12 N / mm to 18 N / mm.

[0056] In practical applications, the working principle of this laminated rubber cover layer is as follows: When high-temperature materials come into contact with the heat-resistant outer surface, the fluororubber layer provides the first thermal barrier, and the high heat capacity of the ceramic filler absorbs and disperses the incoming heat, delaying the heat transfer to the interior; the aramid skeleton layer forms the second barrier in the heat conduction path, and its low thermal conductivity further reduces the heat transfer rate while bearing the mechanical load generated by thermal stress; the wear-resistant adhesive layer, while maintaining reliable adhesion to the conveyor belt skeleton, establishes a stable temperature gradient at the interface between the cover layer and the conveyor belt skeleton through the heat resistance of its nitrile rubber matrix and the heat insulation effect of the kaolin filler. The synergistic effect of the three-layer structure enables the cover layer to operate stably for a long time in high-temperature environments of 200 degrees Celsius to 250 degrees Celsius, and its service life is significantly extended compared to traditional single-layer rubber cover layers.

[0057] In a specific application scenario, taking a sinter conveying system of a steel enterprise as an example, this system uses the laminated rubber cover layer of this invention to upgrade the traditional heat-resistant conveyor belt. Before the upgrade, the traditional conveyor belt used a single neoprene rubber cover layer. Under sinter conveying conditions of 180°C to 200°C, the cover layer's service life was only 3 to 4 months, and frequent replacements led to production interruptions and increased maintenance costs. After the upgrade, the laminated rubber cover layer of this invention is used. The cover layer structure is prepared according to the above process, wherein the heat-resistant outer layer uses a mixture of fluororubber and alumina filler, with a ceramic filler mass fraction of 20% and a filler particle size of 1.5 micrometers to 2.5 micrometers; the aramid skeleton layer uses aramid cord fabric with a basis weight of 320 grams per square meter, with two layers; and the wear-resistant adhesive layer uses a nitrile rubber and kaolin reinforcement system. The modified conveyor belt operated continuously for more than 12 months under the same working conditions, with no obvious wear or delamination on the surface of the cover layer. Based on the expected service life, the maintenance cost of the modified conveyor belt was reduced by about 65%, and the production interruption time caused by replacing the cover layer was reduced by about 80%, achieving significant technical and economic benefits.

[0058] Example 2 In another embodiment, the formulation of the heat-resistant outer layer of the laminated rubber cover layer was optimized. The formulation of the heat-resistant outer layer compound is: 60% fluororubber, 22% ceramic filler, 3% crosslinking agent, and 5% processing aid, with the sum of the mass fractions of each component being 100%. The ceramic filler is a mixture of silicon carbide and alumina in a mass ratio of 1:1, with the filler particle size controlled within the range of 1.0 micrometer to 2.5 micrometers and a specific surface area of ​​10 square meters per gram to 13 square meters per gram. The combined use of silicon carbide and alumina can leverage their synergistic effect: silicon carbide has high thermal conductivity and excellent wear resistance, while alumina has high heat capacity and good electrical insulation properties. The overall performance of the composite filler system is superior to that of a single filler system.

[0059] In this embodiment, the aramid skeleton layer adopts a three-layer structure design. The basis weight of the aramid cord is 250 g / m² to 320 g / m², and the total basis weight is controlled within the range of 750 g / m² to 960 g / m². The three layers of cord are laid in a cross-laying manner. The warp direction of the first layer of cord is consistent with the length direction of the cover layer. The warp direction of the second layer of cord intersects the length direction of the cover layer at a 90-degree angle. The warp direction of the third layer of cord returns to the length direction of the cover layer. The cross-laying method enables the aramid skeleton layer to obtain a uniform reinforcement effect in both the longitudinal and transverse directions of the cover layer, avoiding the anisotropy problem of mechanical properties caused by unidirectional reinforcement.

[0060] In this embodiment, the adhesive formulation was adjusted to use a mixture of isocyanate-modified resin and epoxy-modified resin at a mass ratio of 2:1, with a silane coupling agent mass fraction of 2%. The adhesive coating amount was optimized to 15 g / m² to 25 g / m², and the pre-curing temperature was set to 70°C, with a pre-curing time of 10 minutes. This adhesive system forms a tough adhesive layer at the interface between the aramid fabric and the rubber layer. Its adhesive mechanism includes: the reaction of isocyanate groups with amino groups on the aramid fiber surface to form urethane bonds; the reaction of epoxy resin with active groups in the rubber molecular chain to form covalent bonds; and the chemical bridging effect of the silane coupling agent between the inorganic filler surface and the organic polymer.

[0061] In this embodiment, the hot-press vulcanization process parameters were precisely optimized: the vulcanization temperature was set to 170 degrees Celsius with a temperature control accuracy of ±1.5 degrees Celsius; the vulcanization pressure was set to 10 MPa with a pressure control accuracy of ±0.3 MPa; the vulcanization time was set to 26 minutes; and the heating rate was set to 2.0 degrees Celsius per minute. The cooling process employs a combined forced air cooling and water cooling method: the first stage is water cooling, where the mold is placed in a cooling water circulation system, the cooling water temperature is controlled at 25 degrees Celsius, and the water cooling time is controlled at 15 to 20 minutes; the second stage is forced air cooling, where an industrial fan is used to force-cool the cover layer after demolding, the wind speed is controlled at 2 to 4 meters per second, and the air cooling time is no less than 30 minutes. This combined cooling method can accelerate the cooling speed and improve production efficiency. Simultaneously, the air cooling stage ensures a uniform decrease in the surface temperature of the cover layer, avoiding surface hardening problems caused by an excessively steep temperature gradient during the water cooling stage.

[0062] The physical property parameters of the laminated rubber coating obtained by this embodiment are as follows: overall thickness of 10 mm to 12 mm, density of 1.42 g / cm³ to 1.48 g / cm³, and Shore A hardness of 80 to 85. After 168 hours of aging test at 200 degrees Celsius, the tensile strength retention rate is 82% to 85%, the elongation at break retention rate is 72% to 75%, and the hardness change is controlled within ±3 Shore A. The abrasion amount measured by Akron abrasion test is 0.10 cm³ / 1.61 km to 0.13 cm³ / 1.61 km. The interlayer adhesion test result is 9 N / mm to 11 N / mm, and the peel strength test result is 14 N / mm to 16 N / mm. The technical solution of this embodiment is particularly suitable for high-temperature material conveying scenarios with operating temperatures ranging from 180 degrees Celsius to 220 degrees Celsius.

[0063] Example 3 In yet another specific implementation, the structural design of the laminated rubber cover layer has been significantly adjusted to adapt to different operating conditions.

[0064] The core feature of this implementation is the use of a functionally graded structure design. In the formulation of the heat-resistant outer layer, the mass fraction of ceramic filler gradually decreases from the outer surface to the inner layer, forming a filler concentration gradient from high to low. Specifically, the total thickness of the heat-resistant outer layer is 3 to 4 millimeters, divided into three sub-layers along the thickness direction: the outer surface layer is approximately 1 millimeter thick, with a ceramic filler mass fraction of 25% to 28%; the middle layer is approximately 1.5 millimeters thick, with a ceramic filler mass fraction of 18% to 22%; and the inner surface layer is approximately 0.5 to 1 millimeter thick, with a ceramic filler mass fraction of 12% to 15%. The design principle of the functionally graded structure is as follows: the outer surface layer, which is in direct contact with the high-temperature material, requires the highest content of ceramic filler to provide the best heat insulation effect; the inner surface layer is adjacent to the aramid skeleton layer, and excessively high filler content would reduce the adhesion performance with the skeleton layer, therefore a lower filler content is used to ensure good interlayer bonding.

[0065] The functionally graded heat-resistant outer layer is prepared using a layered calendering process: First, three compound rubber sheets with different filler concentrations are prepared separately. Then, the three rubber sheets are stacked and calendered along the thickness direction to form a monolithic structure. During calendering, the temperature of the upper and lower calendering rolls is set at 100°C to 110°C, the calendering speed is controlled at 5 m / min to 8 m / min, and the calendering pressure is controlled at 0.5 MPa to 1.0 MPa. After calendering, the three rubber sheets with different filler concentrations form a seamless monolithic structure through molecular chain diffusion and cross-linking reactions during hot-press vulcanization, with blurred interlayer interfaces and no obvious delamination.

[0066] In this embodiment, the aramid skeleton layer employs a hybrid fiber structure design, with aramid fibers as the main reinforcing fiber and basalt fibers as the auxiliary reinforcing fiber. The hybrid fiber fabric composition is: 70% to 80% aramid fiber by mass and 20% to 30% basalt fiber by mass. The introduction of basalt fiber can increase the upper limit of the heat resistance temperature of the skeleton layer. The softening temperature of basalt fiber exceeds 900 degrees Celsius, providing additional thermal stability support before the thermal decomposition temperature of aramid fibers. The hybrid fiber fabric is woven using an interlaced structure of aramid in the warp and basalt in the weft. The warp provides the main tensile strength, while the weft provides dimensional stability and thermal dimensional stability.

[0067] In this embodiment, the wear-resistant adhesive layer is reinforced with an optimized Mooney viscosity of nitrile rubber (NBR) of 55 to 60 and an acrylonitrile content of 33% to 37% to achieve the best balance between adhesive and processability. The kaolin filler has a particle size controlled between 2 and 4 micrometers and a filler content of 25% to 28%, while 5% to 8% of a special adhesive resin is added to further improve the adhesive strength. The special adhesive resin is a graft copolymer of phenolic resin and NBR, whose molecular structure contains both the active hydroxyl groups of phenolic resin and the nitrile groups of NBR, enabling a double bond between the rubber and the conveyor belt skeleton.

[0068] The hot-press vulcanization process employs a two-stage vulcanization regime: the first stage is the pre-vulcanization stage, with a vulcanization temperature of 160 degrees Celsius, a vulcanization pressure of 6 MPa, and a vulcanization time of 8 minutes. This stage allows the rubber system to achieve 40% to 50% vulcanization. The second stage is the main vulcanization stage, with a vulcanization temperature of 170 degrees Celsius, a vulcanization pressure of 10 MPa, and a vulcanization time of 18 minutes. This stage completes the remaining vulcanization reaction. The advantages of the two-stage vulcanization regime are: the first stage of pre-vulcanization allows the adhesive to fully cure and form a stable interfacial structure with the rubber system; the second stage of main vulcanization, under higher temperature and pressure, completes deep cross-linking of the rubber while ensuring the integrity of the interlayer bonding.

[0069] The laminated rubber cover layer prepared according to this embodiment underwent performance verification tests under extreme high-temperature conditions: after 72 hours of aging at 250 degrees Celsius, the tensile strength retention rate was greater than or equal to 75%, the elongation at break retention rate was greater than or equal to 65%, and the hardness change was controlled within ±6 Shore A. In continuous operation tests at 250 degrees Celsius, the cover layer achieved a maximum continuous operating temperature of 230 degrees Celsius and a short-term peak temperature tolerance of 250 degrees Celsius. The technical solution of this embodiment is particularly suitable for conveying special high-temperature materials in the temperature range of 200 to 250 degrees Celsius.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A laminated rubber covering layer for conveying high-temperature materials, characterized in that, The specific structure includes the following: The cover layer adopts a three-layer composite laminate structure, which includes a heat-resistant outer layer, an aramid skeleton layer and a wear-resistant adhesive layer in sequence. The heat-resistant outer layer uses a mixture of fluororubber and ceramic filler, with the ceramic filler having a mass fraction of 15% to 25%. The aramid skeleton layer uses aramid fabric as a reinforcing material to provide the overall structure with tensile strength and tear resistance. The wear-resistant adhesive layer uses a nitrile rubber combined with a kaolin reinforcement system to achieve reliable bonding with the conveyor belt skeleton. The three-layer structure achieves interlayer chemical bonding through a hot-press vulcanization process, forming a complete laminated composite cover layer.

2. A process for preparing a laminated rubber cover layer for conveying high-temperature materials, comprising the following steps: Step 1, Preparation of heat-resistant outer layer compound: Fluororubber, ceramic filler, crosslinking agent and processing aid are put into an internal mixer for mixing. After mixing, the mixture is sheeted out and cooled and shaped to obtain heat-resistant outer layer compound sheet. Step 2, preparation of wear-resistant adhesive layer compound: Nitrile rubber, kaolin, plasticizer and adhesive additives are put into an internal mixer for mixing. After mixing, the mixture is sheeted out and cooled and shaped to obtain wear-resistant adhesive layer compound sheet. Step 3, Laying up and skeleton composite: The heat-resistant outer compound film, aramid cord fabric and wear-resistant adhesive layer compound film prepared in step 1 are laminated and combined in the order of layup. Adhesive is applied between each layer to obtain a three-layer prefabricated structure. Step 4, hot-press vulcanization: The three-layer preform obtained in step 3 is placed in a hot-press mold and hot-press vulcanized under vulcanization temperature and pressure conditions, so that the three-layer structure forms chemical bonds through hot-press vulcanization, and a laminated rubber cover layer is obtained. Step 5, Cooling and Post-processing: The hot-pressed vulcanized laminated rubber cover layer is cooled in sections. After cooling to room temperature, it is trimmed, shaped and inspected for quality. The laminated rubber cover layer includes a heat-resistant outer layer, an aramid skeleton layer, and a wear-resistant adhesive layer stacked in sequence. The heat-resistant outer layer adopts a mixed system of fluororubber and ceramic filler, the aramid skeleton layer adopts high-strength aramid fabric, and the wear-resistant adhesive layer adopts a nitrile rubber combined with kaolin reinforcement system.

3. The preparation process according to claim 2, characterized in that, The fluororubber mentioned in step one is a copolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, with a fluorine content controlled within the range of 65% to 70%.

4. The preparation process according to claim 2, characterized in that, The ceramic filler mentioned in step one is at least one of silicon carbide, alumina or silicon nitride, and the filler particle size is controlled within a narrow distribution range of 0.5 micrometers to 3 micrometers, and the specific surface area is controlled between 8 square meters per gram and 15 square meters per gram.

5. The preparation process according to claim 2, characterized in that, During the mixing process described in step one, the mixing temperature is controlled within the range of 120 degrees Celsius to 140 degrees Celsius, the mixing time is controlled within the range of 8 to 12 minutes, and the rotor speed is controlled within the range of 60 revolutions per minute to 120 revolutions per minute.

6. The preparation process according to claim 2, characterized in that, The thickness of the heat-resistant outer compound rubber sheet in step one is 2 mm to 4 mm, and the thickness of the wear-resistant adhesive layer compound rubber sheet in step two is 2 mm to 3 mm.

7. The preparation process according to claim 2, characterized in that, In step two, the Mooney viscosity of the nitrile rubber is controlled within the range of 45 to 65, and the acrylonitrile content is controlled within the range of 28% to 40%.

8. The preparation process according to claim 2, characterized in that, The aramid cord fabric mentioned in step three has a weight of 200 g / m² to 400 g / m², a cord breaking strength greater than or equal to 80 centineton-teks, and a number of layers of 1 to 3.

9. The preparation process according to claim 2, characterized in that, In step three, the aramid cord fabric undergoes plasma pretreatment before being laid up. The plasma power is set to 200 watts to 500 watts, and the treatment time is 30 seconds to 120 seconds.

10. The preparation process according to claim 2, characterized in that, In the hot-press vulcanization process described in step four, the vulcanization temperature is controlled within the range of 168 degrees Celsius to 172 degrees Celsius, the vulcanization pressure is controlled within the range of 9 to 11 MPa, the vulcanization time is controlled within the range of 22 to 28 minutes, and the heating rate is controlled within the range of 1.5 degrees Celsius per minute to 2.5 degrees Celsius per minute. In the hot-press vulcanization process described in step four, the pressure is increased in stages, the temperature and pressure are kept stable during the pressure holding process, and the pressure is released slowly.

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