Modified material for starting area of rubber runway and preparation method of modified material

Abstract

The invention discloses a modified material for a starting area of a rubber runway and a preparation method of the modified material, and belongs to the field of rubber runway materials, the modified material is prepared from the following raw materials by weight: 100 parts of blend rubber of nitrile rubber and butadiene rubber, the mass ratio of nitrile rubber to butadiene rubber being 6: 4-4: 6; 35 to 55 parts of a polyurethane prepolymer with high NCO content; 8 to 18 parts of pretreated glass fiber; 90 to 130 parts of composite reinforcing filler; 1.5 to 2.5 parts of a vulcanizing agent; 1.5 to 3 parts of a composite vulcanization accelerator; 15-30 parts of a plasticizer and a softener; 2-4 parts of an antioxidant and an anti-aging agent; and 3-6 parts of pigment and ultraviolet light absorber. The preparation method comprises the following steps: pretreating glass fibers; plasticating and combining the rubber; first-stage mixing; carrying out second-stage mixing and modification; final smelting and sulfur adding; and carrying out compression molding and post-vulcanization. The runway material is modified through the glass fiber, and the impact resistance, tear resistance and fatigue resistance of a local area of the runway material are greatly improved on the premise that the elasticity and the buffering function required by the runway are not remarkably damaged.

Description

Technical Field

[0001] This invention belongs to the field of rubber track materials, specifically relating to a modified material for the starting area of ​​a rubber track and its preparation method. Background Technology

[0002] As a standard feature of modern sports venues, synthetic running tracks have rapidly replaced traditional cinder and sand tracks since their introduction in the mid-20th century due to their superior cushioning performance, stable physical properties, good anti-slip properties, and aesthetically pleasing colors. They have become the preferred surface material for international track and field events and school stadiums at all levels. Their core value lies in providing athletes with an all-weather, high-performance surface that maximizes their athletic performance while effectively reducing sports injuries. A typical synthetic running track system is a multi-layered composite structure, usually consisting of a base layer, an elastic cushioning layer, an adhesive layer, and an anti-slip and wear-resistant surface layer. Its performance directly depends on the chemical composition and manufacturing process of each layer.

[0003] Currently, the most widely used material systems in the industry for the surface layer and elastic layer of plastic running tracks are mainly based on the following categories: 1. Polyurethane (PU) based elastomer system: This system produces runways with good integrity, excellent elasticity, and strong design flexibility, but it is more expensive and sensitive to the purity of raw materials and the construction environment (temperature and humidity). If a TDI system is used, there may be a risk of releasing free monomers, raising environmental and health concerns.

[0004] 2. Precast or on-site installation system using EPDM granules: Precast EPDM rolls are finished products manufactured through high-temperature vulcanization in the factory, offering stable performance, but requiring complex installation and stringent joint treatment. More commonly, EPDM granules are mixed with polyurethane adhesives on-site to create a brightly colored, wear-resistant surface. However, pure EPDM granules have high hardness and limited cushioning performance, often requiring the use of an elastic layer.

[0005] 3. Thermoplastic elastomers (such as SBS) and waste rubber recycling system: The recycled rubber powder has a complex composition, containing various aging products, metal impurities and uncertain additives; its molecular chains have been broken and oxidized to varying degrees, resulting in the mechanical strength, elastic recovery rate and fatigue resistance of the recycled material being significantly lower than those of the virgin material.

[0006] While the aforementioned commonly used material systems meet requirements in conventional application areas, their inherent material defects are drastically amplified when applied to special functional areas of sports fields—especially the starting area. This makes this area the weakest and most likely to fail in the entire track system. The starting area is not subjected to uniformly distributed static loads, but rather to extremely dynamic, localized impact-fatigue composite loads. When athletes start, the starting blocks generate a tremendous backward push-off force on the track surface, which reaches its peak instantaneously, creating intense shear and compressive stress concentrations.

[0007] To address the unique damage patterns of the starting area, the industry has attempted several improvements, such as increasing the thickness of the surface layer, using higher-hardness EPDM granules, or employing polyurethane-rubber composite castings. However, these methods are mostly quantitative improvements, achieving temporary wear resistance by increasing material usage or sacrificing some elasticity, without fundamentally addressing the strengthening and toughening mechanisms of the material. How to significantly improve the impact resistance, tear resistance, and fatigue resistance of localized areas without significantly compromising the required elasticity and cushioning function of the track has become a long-standing and critical problem in synthetic running track material technology. Based on this, this invention proposes a modified material for the starting area of ​​a rubber running track and its preparation method. Summary of the Invention

[0008] To address the aforementioned technical problems in existing technologies, this invention proposes a modified material for the starting area of ​​a rubber running track and its preparation method, overcoming the shortcomings of the prior art. By modifying the running track material with glass fiber and pretreating the glass fiber, the impact resistance, tear resistance, and fatigue resistance of its local areas are significantly improved without significantly compromising the required elasticity and cushioning function of the running track.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A modified material for the starting area of ​​a rubber running track, characterized in that it is made from raw materials comprising the following parts by weight: Acrylonitrile rubber and butadiene rubber blend: 100 parts, wherein the mass ratio of acrylonitrile rubber to butadiene rubber is 6:4 to 4:6; high NCO content polyurethane prepolymer: 35-55 parts; pretreated glass fiber: 8-18 parts; composite reinforcing filler: 90-130 parts; vulcanizing agent: 1.5-2.5 parts; composite vulcanization accelerator: 1.5-3 parts; plasticizer and softener: 15-30 parts; antioxidant and anti-aging agent: 2-4 parts; pigment and ultraviolet absorber: 3-6 parts; The method for preparing the pretreated glass fiber is as follows: a) Cleaning and dewaxing: Place the chopped alkali-free glass fibers in a muffle furnace and heat-treat them at 380℃-420℃ for 25-35 minutes to completely remove the textile-type sizing agent from their surface; b) Preparation of coupling agent treatment solution: Mix γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water at a mass ratio of 5:90:5, and mechanically stir at a rate of 300-500 rpm for 30-45 minutes at room temperature until the solution is uniform and transparent. Adjust the pH value to 4-5 and let it stand for hydrolysis for 1-2 hours before use. c) Impregnation treatment: Immerse the glass fiber treated in step a into the treatment solution prepared in step b, ensuring complete immersion, and soak for 8-12 minutes; d) Drying and curing: Take out the glass fiber and place it in a forced-air drying oven at 110℃-130℃ for 20-30 minutes to dry and cure it, so as to obtain pretreated glass fiber. Seal it for later use. The composite reinforcing filler is a mixture of nano-calcium carbonate, precipitated silica, and silica powder, with a mass ratio of 4:4:2 to 3:5:2.

[0010] Preferably, the acrylonitrile content of the nitrile rubber is 28%-34%; and the cis-1,4 structure content of the cis-butadiene rubber is greater than 96%.

[0011] Preferably, the high NCO content polyurethane prepolymer is prepared by reacting toluene diisocyanate with polyether polyol, and its NCO mass percentage content is 12%-16%.

[0012] Preferably, the vulcanizing agent is one of sulfur or DCP peroxide.

[0013] Preferably, the plasticizer and softener are a mixture of dioctyl phthalate and liquid coumarone resin in a mass ratio of 1:1; the composite vulcanization accelerator is a compound of accelerator CZ, accelerator DM and accelerator TRA in a mass ratio of 1.5:1:0.5.

[0014] A method for preparing a modified material for the starting area of ​​a rubber running track includes the following steps: S1. Rubber plasticizing and blending: Nitrile rubber and butadiene rubber are plasticized separately on a two-roll mill and then mixed in proportion to obtain blended rubber masterbatch; S2. First stage of compounding: Put the combined rubber masterbatch into an internal mixer, heat it to 70-85℃, add 2 / 3 of the amount of composite reinforcing filler, all plasticizers and softeners, antioxidants and anti-aging agents in sequence, mix for 8-12 minutes until the temperature reaches 125-135℃, discharge the rubber, cool and stand for more than 12 hours to obtain the first stage of compounding. S3. Two-stage mixing and modification: Put the first-stage compound back into the internal mixer, add the high NCO content polyurethane prepolymer at 80-95℃, and mix for 3-5 minutes to initially disperse it; then add the pretreated glass fiber and the remaining 1 / 3 of the composite reinforcing filler, and mix for 5-8 minutes until the temperature reaches 105-115℃. S4. Final Vulcanization: Transfer the two-stage compound to the open mill, control the roller temperature at 50-60℃, and add vulcanizing agent, compound vulcanization accelerator, pigment and ultraviolet absorber in sequence. Pass through the mill 6-8 times and make triangular wraps 4-6 times to obtain the final compound. S5. Compression molding and post-curing: Fill the preheated starting area mold with the final compound and perform compression curing at 165-175℃ and 10-15MPa pressure for 18-25 minutes; after demolding, perform post-curing in an oven at 100-110℃ for 2-4 hours to obtain the final product.

[0015] Preferably, the modified material is prefabricated to the appropriate size and then bonded to the main structure of the runway with structural adhesive.

[0016] The beneficial technical effects of this invention are as follows: By modifying the runway material with glass fiber and pretreating the glass fiber, the impact resistance, tear resistance and fatigue resistance of the local area can be greatly improved without significantly compromising the elasticity and cushioning function required by the runway. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a modified material for the starting area of ​​a rubber track and its preparation method, according to the present invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Example

[0019] like Figure 1 As shown, a modified material for the starting area of ​​a rubber running track is characterized by being made from raw materials comprising the following parts by weight: Acrylonitrile rubber and butadiene rubber blend: 100 parts, wherein the mass ratio of acrylonitrile rubber to butadiene rubber is 6:4 to 4:6; high NCO content polyurethane prepolymer: 35-55 parts; pretreated glass fiber: 8-18 parts; composite reinforcing filler: 90-130 parts; vulcanizing agent: 1.5-2.5 parts; composite vulcanization accelerator: 1.5-3 parts; plasticizer and softener: 15-30 parts; antioxidant and anti-aging agent: 2-4 parts; pigment and ultraviolet absorber: 3-6 parts; The method for preparing the pretreated glass fiber is as follows: a) Cleaning and dewaxing: Place the chopped alkali-free glass fibers in a muffle furnace and heat-treat them at 380℃-420℃ for 25-35 minutes to completely remove the textile-type sizing agent from their surface; b) Preparation of coupling agent treatment solution: Mix γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water at a mass ratio of 5:90:5, and mechanically stir at a rate of 300-500 rpm for 30-45 minutes at room temperature until the solution is uniform and transparent. Adjust the pH value to 4-5 and let it stand for hydrolysis for 1-2 hours before use. c) Impregnation treatment: Immerse the glass fiber treated in step a into the treatment solution prepared in step b, ensuring complete immersion, and soak for 8-12 minutes; d) Drying and curing: Take out the glass fiber and place it in a forced-air drying oven at 110℃-130℃ for 20-30 minutes to dry and cure it, so as to obtain pretreated glass fiber. Seal it for later use. The composite reinforcing filler is a mixture of nano-calcium carbonate, precipitated silica, and silica powder, with a mass ratio of 4:4:2 to 3:5:2.

[0020] Preferably, the acrylonitrile content of the nitrile rubber is 28%-34%; and the cis-1,4 structure content of the cis-butadiene rubber is greater than 96%.

[0021] Preferably, the high NCO content polyurethane prepolymer is prepared by reacting toluene diisocyanate with polyether polyol, and its NCO mass percentage content is 12%-16%.

[0022] Preferably, the vulcanizing agent is one of sulfur or DCP peroxide.

[0023] Preferably, the plasticizer and softener are a mixture of dioctyl phthalate and liquid coumarone resin in a mass ratio of 1:1; the composite vulcanization accelerator is a compound of accelerator CZ, accelerator DM and accelerator TRA in a mass ratio of 1.5:1:0.5.

[0024] A method for preparing a modified material for the starting area of ​​a rubber running track includes the following steps: S1. Rubber plasticizing and blending: Nitrile rubber and butadiene rubber are plasticized separately on a two-roll mill and then mixed in proportion to obtain blended rubber masterbatch; S2. First stage of compounding: Put the combined rubber masterbatch into an internal mixer, heat it to 70-85℃, add 2 / 3 of the amount of composite reinforcing filler, all plasticizers and softeners, antioxidants and anti-aging agents in sequence, mix for 8-12 minutes until the temperature reaches 125-135℃, discharge the rubber, cool and stand for more than 12 hours to obtain the first stage of compounding. S3. Two-stage mixing and modification: Put the first-stage compound back into the internal mixer, add the high NCO content polyurethane prepolymer at 80-95℃, and mix for 3-5 minutes to initially disperse it; then add the pretreated glass fiber and the remaining 1 / 3 of the composite reinforcing filler, and mix for 5-8 minutes until the temperature reaches 105-115℃. S4. Final Vulcanization: Transfer the two-stage compound to the open mill, control the roller temperature at 50-60℃, and add vulcanizing agent, compound vulcanization accelerator, pigment and ultraviolet absorber in sequence. Pass through the mill 6-8 times and make triangular wraps 4-6 times to obtain the final compound. S5. Compression molding and post-curing: Fill the preheated starting area mold with the final compound and perform compression curing at 165-175℃ and 10-15MPa pressure for 18-25 minutes; after demolding, perform post-curing in an oven at 100-110℃ for 2-4 hours to obtain the final product.

[0025] Preferably, the modified material is prefabricated to the appropriate size and then bonded to the main structure of the runway with structural adhesive. Example

[0026] like Figure 1 As shown, the core of this invention lies in constructing a composite material system that can withstand instantaneous huge shear force, repeated impact and fatigue through interface engineering and multiphase synergy.

[0027] The underlying mechanism of glass fiber pretreatment is to fundamentally change the physical bond between glass fiber and organic rubber matrix into a strong chemical bond.

[0028] a) Cleaning and Dewaxing: Place the chopped alkali-free glass fibers in a muffle furnace and heat-treat at 380℃-420℃ for 25-35 minutes to completely remove the textile-type sizing agent on its surface. The "textile-type sizing agent" on commercially available glass fibers is designed for textile processes and severely hinders its adhesion to rubber. Heat treatment at 380℃-420℃ completely decomposes and volatilizes this agent, exposing a pure fiber surface rich in silanol groups (-Si-OH), providing active sites for subsequent chemical reactions.

[0029] b) Preparation of coupling agent treatment solution: Mix γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water at a mass ratio of 5:90:5, and mechanically stir at a rate of 300-500 rpm for 30-45 minutes at room temperature until the solution is uniform and transparent. Adjust the pH value to 4-5 and let it stand for hydrolysis for 1-2 hours before use. c) Impregnation treatment: Immerse the glass fibers treated in step a into the treatment solution prepared in step b, ensuring complete immersion, for 8-12 minutes; KH-550 (γ-aminopropyltriethoxysilane) is the key "molecular bridge". Its ethoxy group (-OC2H5) hydrolyzes in water to highly active silanol groups (-Si-OH). Under acidic (pH 4-5) and heating conditions, these silanol groups undergo dehydration condensation with the silanol groups on the fiber surface to form strong Si-O-Si covalent bonds, allowing the coupling agent to be chemically grafted onto the fiber surface in monolayer form.

[0030] d) Drying and curing: Take out the glass fiber and place it in a forced-air drying oven at 110℃-130℃ for 20-30 minutes to obtain pretreated glass fiber. Seal it for later use; promote complete grafting reaction and remove moisture to form a stable pretreated layer.

[0031] The treated fibers are coated with a layer of KH-550 molecules with amino groups (-NH2) at the end. These amino groups can react rapidly and strongly with the isocyanate groups (-NCO) of the polyurethane prepolymer with high NCO content in the formulation to form urea bonds (-NH-CO-NH-). At the same time, the amino groups also have a strong polar interaction with the cyano groups (-CN) of the nitrile rubber. This achieves a qualitative change from "mechanical anchoring" to "chemical welding" between the fiber and the matrix, which is the core of improving impact resistance and peel resistance. Example

[0032] like Figure 1 As shown, a nitrile butadiene rubber (NBR) / butadiene rubber blend is used: this unconventional combination aims to create a matrix that balances rigidity and elasticity. Medium-to-high acrylonitrile content NBR provides high strength, high abrasion resistance, and good polar compatibility with polyurethane; high-cis-butadiene rubber (BR) contributes excellent elasticity and dynamic fatigue properties. The two are combined in a microscopically separated but macroscopically homogeneous structure through compatibilizers.

[0033] The high proportion and high activity of polyurethane prepolymer have three functions: (1) Common matrix: It forms an interpenetrating / semi-interpenetrating network with the rubber matrix, which greatly improves the overall modulus and strength.

[0034] (2) Super coupling agent: Its -NCO group is the most active reaction point in the system. One end reacts with -NH2 on the surface of pretreated glass fiber, and the other end reacts with or self-polymerizes with rubber molecular chain, becoming the core chemical link connecting inorganic fiber and organic matrix.

[0035] (3) Interface compatibilizer: improves the compatibility between polar NBR and non-polar BR, and serves as a dispersion medium for fillers (such as silica). Example

[0036] like Figure 1 As shown, a multi-scale enhancement network is constructed by processing various materials. Macroscopic scale - pretreated glass fiber: as the main load-bearing skeleton, it directly bears and disperses impact stress.

[0037] Microscale - Composite Reinforcing Filler: Silica and silane coupling agents interact to form a strong reinforcing network; nano-calcium carbonate and silica powder fill the network voids, making the material denser. This filler network interpenetrates with the PU-rubber IPN network, providing fundamental strength.

[0038] Interface Scale - KH-550 and PU Prepolymer: Ensures efficient stress transfer between macroscopic fibers and microscopic matrix, preventing the interface from becoming a weak point and crack origin.

[0039] Through a rigorous and operable "interfacial chemical pretreatment process," general-purpose glass fibers are transformed into reinforcements that can form strong chemical bonds with specific high-performance rubber matrices (NBR / BR / PU). The entire material system addresses the extreme mechanical conditions of the starting zone through a "multi-scale network of chemically bonded structures," thereby systematically solving the technical challenges of fragility and spalling in the starting zone.

[0040] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified material for the starting area of ​​a rubber running track, characterized in that, Made from the following ingredients in parts by weight: 100 parts of nitrile rubber and butadiene rubber blend, wherein the mass ratio of nitrile rubber to butadiene rubber is 6:4 to 4:6; 35-55 parts of high NCO content polyurethane prepolymer. Pretreated glass fiber: 8-18 parts; composite reinforcing filler: 90-130 parts; vulcanizing agent: 1.5-2.5 parts; composite vulcanization accelerator: 1.5-3 parts; plasticizer and softener: 15-30 parts; antioxidant and anti-aging agent: 2-4 parts; pigment and ultraviolet absorber: 3-6 parts; The method for preparing the pretreated glass fiber is as follows: a) Cleaning and dewaxing: Place the chopped alkali-free glass fibers in a muffle furnace and heat-treat them at 380℃-420℃ for 25-35 minutes to completely remove the textile-type sizing agent from their surface; b) Preparation of coupling agent treatment solution: Mix γ-aminopropyltriethoxysilane, anhydrous ethanol and deionized water at a mass ratio of 5:90:5, and mechanically stir at a rate of 300-500 rpm for 30-45 minutes at room temperature until the solution is uniform and transparent. Adjust the pH value to 4-5 and let it stand for hydrolysis for 1-2 hours before use. c) Impregnation treatment: Immerse the glass fiber treated in step a into the treatment solution prepared in step b, ensuring complete immersion, and soak for 8-12 minutes; d) Drying and curing: Take out the glass fiber and place it in a forced-air drying oven at 110℃-130℃ for 20-30 minutes to dry and cure it, so as to obtain pretreated glass fiber. Seal it for later use. The composite reinforcing filler is a mixture of nano-calcium carbonate, precipitated silica, and silica powder, with a mass ratio of 4:4:2 to 3:5:

2.

2. The modified material for the starting area of ​​a rubber running track according to claim 1, characterized in that, The acrylonitrile content of the nitrile rubber is 28%-34%; the cis-1,4 structure content of the cis-butadiene rubber is greater than 96%.

3. The modified material for the starting area of ​​a rubber running track according to claim 1, characterized in that, The high NCO content polyurethane prepolymer is prepared by reacting toluene diisocyanate with polyether polyol, and its NCO mass percentage is 12%-16%.

4. The modified material for the starting area of ​​a rubber running track according to claim 1, characterized in that, The vulcanizing agent is either sulfur or DCP peroxide.

5. The modified material for the starting area of ​​a rubber running track according to claim 1, characterized in that, The plasticizer and softener are a mixture of dioctyl phthalate and liquid coumarone resin in a mass ratio of 1:1; the composite vulcanization accelerator is a compound of accelerator CZ, accelerator DM and accelerator TRA in a mass ratio of 1.5:1:0.

5.

6. A method for preparing a modified material for the starting area of ​​a rubber running track, characterized in that, Includes the following steps: S1. Rubber plasticizing and blending: Nitrile rubber and butadiene rubber are plasticized separately on a two-roll mill and then mixed in proportion to obtain blended rubber masterbatch; S2. First stage of compounding: Put the compounded rubber masterbatch into an internal mixer, heat it to 70-85℃, add 2 / 3 of the amount of composite reinforcing filler, all plasticizers and softeners, antioxidants and anti-aging agents in sequence, mix for 8-12 minutes until the temperature reaches 125-135℃, discharge the rubber, cool and stand for more than 12 hours to obtain the first stage of compounded rubber. S3. Two-stage mixing and modification: Put the first-stage compound back into the internal mixer, add the high NCO content polyurethane prepolymer at 80-95℃, and mix for 3-5 minutes to initially disperse it; then add the pretreated glass fiber and the remaining 1 / 3 of the composite reinforcing filler, and mix for 5-8 minutes until the temperature reaches 105-115℃. S4. Final Vulcanization: Transfer the two-stage compound to the open mill, control the roller temperature at 50-60℃, and add vulcanizing agent, compound vulcanization accelerator, pigment and ultraviolet absorber in sequence. Pass through the mill 6-8 times and make triangular wraps 4-6 times to obtain the final compound. S5. Compression molding and post-curing: Fill the preheated starting area mold with the final compound and perform compression curing at 165-175℃ and 10-15MPa pressure for 18-25 minutes; after demolding, perform post-curing in an oven at 100-110℃ for 2-4 hours to obtain the final product.

7. A method for preparing a modified material for the starting area of ​​a rubber running track according to claim 6, characterized in that, The modified material is prefabricated to the appropriate size and then bonded to the main structure of the runway with structural adhesive.

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