A runway material and its preparation method

Abstract

This invention relates to the field of polymer materials, and provides a running track material and its preparation method, solving the problems of traditional running track materials relying on chemical vulcanization, which leads to serious environmental pollution and difficulty in recycling after disposal, as well as the poor compatibility and easy softening and deformation at high temperatures of physical blending systems; comprising the following raw materials in parts by weight: 100-200 parts calcium carbonate, 30-70 parts polyethylene, 30-70 parts styrene-ethylene-propylene-styrene block copolymer, 0.05-0.5 parts peroxide initiator, 0.1-0.5 parts antioxidant, and 0.1-0.3 parts ultraviolet absorber.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and more particularly to a runway material and its preparation method. Background Technology

[0002] As a crucial component of sports facilities, the performance of running track materials directly impacts athletes' experience and safety. Currently, the mainstream running track materials on the market are mainly divided into two categories: vulcanized rubber and thermoplastic elastomers.

[0003] Vulcanized rubber track materials are represented by ethylene propylene diene monomer (EPDM) rubber and styrene-butadiene rubber (SBR). These materials form a three-dimensional chemical cross-linking network through sulfur or peroxide vulcanization systems, giving the materials excellent elasticity, resilience and aging resistance. However, vulcanized rubber tracks have the following inherent defects: (1) Non-recyclability: The chemical cross-linking bonds formed by vulcanization are irreversible covalent bonds. After the material is used, it cannot be recycled by melt processing and can only be downgraded or landfilled, resulting in serious waste of resources and environmental pollution; (2) Production pollution: The vulcanization process requires the addition of various additives such as sulfur, accelerators, and activators. During the production process, irritating odors and harmful gases are released, which does not meet the requirements of green environmental protection; (3) High recycling cost: The recycling of waste vulcanized rubber requires desulfurization treatment, which is complex, energy-intensive, and the performance of recycled materials is greatly reduced.

[0004] Thermoplastic elastomer track materials are mainly prepared by physical blending of styrene-based thermoplastic elastomers (such as SBS, SEBS, and SEPS) with polyolefins. These materials do not require vulcanization, can be melt-processed and molded, and have the advantage of being recyclable. However, the physical blending system has the following shortcomings: (1) compatibility problem: the compatibility between thermoplastic elastomers and polyolefins is limited, and the blending system is prone to phase separation, resulting in insufficient mechanical properties and long-term stability of the material; (2) insufficient heat resistance: the high-temperature performance of physical blends is poor, and they are prone to softening and deformation in hot climates; (3) weak elasticity retention: after multiple recycling, the mechanical properties of physical blends decay significantly, making it difficult to achieve true closed-loop recycling.

[0005] Chinese Patent Publication No. CN116426114A discloses a plastic composition, a plastic composite material, a prefabricated plastic running track, and a preparation method thereof, comprising: 5-35 parts of styrene-butadiene rubber, 5-30 parts of natural rubber, 5-30 parts of ethylene propylene diene monomer (EPDM) rubber, 15-45 parts of polyurethane elastomer, 10-40 parts of filler, 0-10 parts of anti-aging agent, 0-10 parts of colorant, 1-10 parts of vulcanizing agent, 0-6 parts of accelerator, and 0-25 parts of softener. The monomers of the polyurethane elastomer include polybutylene terephthalate (PET), diisocyanate, and hydroxyl-terminated polybutadiene. The plastic composition of this application uses styrene-butadiene rubber, natural rubber, EPDM rubber, and polyurethane elastomer as main materials. By optimizing the proportions of the above components, a plastic composition with good tensile strength, solvent resistance, and acid and alkali resistance is obtained. However, it cannot be recycled through melt processing; recycling requires desulfurization treatment; the vulcanization process releases irritating odors and harmful gases.

[0006] Chinese Patent Publication No. CN115197524A discloses a polymer roll material and its preparation method and application, comprising: 7-12 parts of a polyolefin polymer, 20-30 parts of a multi-block polymer, 5-10 parts of a thermoplastic elastomer, 5-10 parts of a silicone material, 0.2-0.5 parts of a benzophenone compound, and 0.5-1 parts of a hydroxyl compound. This invention, while meeting environmental protection and recyclability requirements, produces a polymer roll material with excellent resilience, good wear resistance, low density, and excellent mechanical strength, which can be applied to plastic running tracks. However, the compatibility between the thermoplastic elastomer and the polyolefin is limited, and it is prone to softening and deformation at high temperatures.

[0007] Therefore, developing a new type of track material that combines the excellent mechanical properties of vulcanized rubber, the recyclability of thermoplastic elastomers, and a green and environmentally friendly production process is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0008] Therefore, in view of the above problems, the present invention provides a runway material and its preparation method, which solves the problems of traditional runway materials relying on chemical vulcanization, resulting in serious environmental pollution and difficulty in recycling after disposal, as well as the poor compatibility of physical blending systems and easy softening and deformation at high temperatures.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A running track material comprising the following raw materials in parts by weight: 100-200 parts calcium carbonate, 30-70 parts polyethylene, 30-70 parts styrene-ethylene-propylene-styrene block copolymer, 0.05-0.5 parts peroxide initiator, 0.1-0.5 parts antioxidant, and 0.1-0.3 parts ultraviolet absorber.

[0010] Furthermore, the polyethylene is one or a mixture of two or more of linear low-density polyethylene, low-density polyethylene, or ultra-low-density polyethylene in any proportion.

[0011] Furthermore, the polyethylene has a melt index of 2 g / 10 min to 10 g / 10 min at 190 °C and 2.16 kg to ensure a balance between grafting reaction efficiency and processing fluidity.

[0012] Furthermore, the styrene-ethylene-propylene-styrene block copolymer has a melt index of 0.5 g / 10 min to 15 g / 10 min at 230°C and 2.16 kg to ensure good compatibility and dispersibility with the polyethylene matrix during melt blending.

[0013] Furthermore, in the styrene-ethylene-propylene-styrene block copolymer, the styrene segment mass percentage is 10%-20% to form a moderately and uniformly distributed physical crosslinking network, replacing the traditional chemical crosslinking system.

[0014] Furthermore, the peroxide initiator is any one of di-tert-butyl peroxide, dicumyl peroxide, or 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0015] The above-described method for preparing a runway material includes the following steps: S1. Preparation of the premix: Polyethylene, styrene-ethylene-propylene-styrene block copolymer, peroxide initiator, antioxidant and ultraviolet absorber are mixed according to the weight parts to obtain the premix; S2. The premix obtained in step S1 is added to an extruder or internal mixer and melt-blended at a temperature of 180°C to 240°C. Under high-temperature shearing, the peroxide initiator initiates chain scission of the styrene-ethylene-propylene-styrene block copolymer to form free radicals. The free radicals are grafted onto the main chain of the polyethylene. After grafting, a preliminary grafted copolymer is obtained. S3. The initial graft copolymer obtained in step S3 is extruded and granulated to obtain the graft copolymer. S4. Preparation of runway materials: The graft copolymer obtained in step S3 is prepared into prefabricated runway rolls or cast-in-place runway layers. The free radicals include SEP· free radicals and / or EP· free radicals.

[0016] The chain-severing products of the styrene-ethylene-propylene-styrene block copolymer are SEP segments and EP segments. After grafting, the styrene blocks in the SEP segments aggregate to form physical crosslinking points, giving the primary graft copolymer thermoplastic elastomer behavior. Furthermore, the preparation process of the primary graft copolymer does not require chemical vulcanization, and the product can be recycled and reused after use.

[0017] Compared to traditional EPDM and SBR runway materials that require chemical vulcanization, the graft copolymer does not generate vulcanization pollution throughout its entire production and use lifecycle, and can be recycled without desulfurization.

[0018] The physical crosslinking points formed by the styrene blocks can reversibly dissociate at high temperatures and reform after cooling, thereby enabling the graft copolymer to be repeatedly melt-processed without loss of mechanical properties, achieving closed-loop recycling of the material.

[0019] After the track material reaches the end of its service life, it can be cleaned, crushed, melted and granulated, and reused to produce track materials or other thermoplastic elastomer products, thus achieving a green recycling of the material throughout its entire life cycle.

[0020] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows: 1. This technical solution completely avoids the use of traditional vulcanization system additives such as sulfur, accelerators, and activators, and no irritating odor is generated during the melt blending process; 2. The graft copolymer prepared by this invention achieves mechanical reinforcement through physical crosslinking of styrene blocks. These physical crosslinking points can reversibly dissociate at processing temperatures and reform upon cooling. After the product reaches the end of its service life, it can be directly cleaned, crushed, melted, and regranulated for reuse in the production of runway materials or other thermoplastic elastomer products without the need for complex desulfurization treatment, thus achieving a green recycling of the material throughout its entire life cycle. 3. By chemically grafting SEP segments and / or EP segments onto the polyethylene backbone, the poor compatibility of physical blends is overcome. The styrene blocks in the grafted SEP segments separate into microphases, forming uniformly distributed physical crosslinking points. This endows the material with elasticity, resilience, and mechanical strength similar to vulcanized rubber. Key indicators such as tensile strength, elongation at break, and resilience can reach or exceed those of traditional vulcanized EPDM and SBR track materials. 4. Styrene blocks have a high glass transition temperature (about 90-100℃), and the physical cross-linking points formed can still maintain the integrity of the structure at high temperatures, making the material less prone to softening and deformation under hot climate conditions (such as summer sun exposure), and its stability is better than that of conventional thermoplastic elastomer blends. 5. The one-step high-temperature melt blending process is adopted, which completes the SEPS chain breaking, grafting reaction and physical cross-linking network construction in an extruder or internal mixer in one go. The process is short, easy to operate and suitable for large-scale industrial production. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the grafting reaction in Embodiment 1 of the present invention. Detailed Implementation

[0022] Example 1

[0023] A running track material comprising the following raw materials in parts by weight: 100 parts calcium carbonate, 70 parts polyethylene, 30 parts styrene-ethylene-propylene-styrene block copolymer, 0.1 parts peroxide initiator, 0.3 parts antioxidant, and 0.2 parts ultraviolet absorber.

[0024] The polyethylene is linear low-density polyethylene (LLDPE); the melt index of the polyethylene is 5 g / 10 min at 190°C and 2.16 kg to ensure a balance between grafting reaction efficiency and processing fluidity.

[0025] The styrene-ethylene-propylene-styrene block copolymer (SEPS) has a melt index of 8 g / 10 min at 230°C and 2.16 kg to ensure good compatibility and dispersibility with the polyethylene matrix during melt blending.

[0026] In the styrene-ethylene-propylene-styrene block copolymer, the styrene segments have a mass percentage of 15% to form a moderately and uniformly distributed physical crosslinking network, replacing the traditional chemical crosslinking system; the peroxide initiator is di-tert-butyl peroxide (DTBP).

[0027] The above-described method for preparing a runway material includes the following steps: S1. Preparation of the premix: Polyethylene, styrene-ethylene-propylene-styrene block copolymer and peroxide initiator are mixed according to the weight parts to obtain the premix; S2. The premix obtained in step S1 is added to an extruder and melt-blended at 180°C. Under high-temperature shearing, the peroxide initiator initiates chain scission of the styrene-ethylene-propylene-styrene block copolymer to form free radicals. The free radicals are grafted onto the main chain of the polyethylene. After grafting, a preliminary grafted copolymer is obtained. S3. The initial graft copolymer obtained in step S3 is extruded and granulated to obtain the graft copolymer. S4. Preparation of runway materials: The graft copolymer obtained in step S3 is prepared into prefabricated runway rolls or cast-in-place runway layers. Among them, reference Figure 1 The free radicals include SEP· free radicals and EP· free radicals.

[0028] The chain-severing products of the styrene-ethylene-propylene-styrene block copolymer are SEP segments and EP segments. After grafting, the styrene blocks in the SEP segments aggregate to form physical crosslinking points, giving the primary graft copolymer thermoplastic elastomer behavior. Furthermore, the preparation process of the primary graft copolymer does not require chemical vulcanization, and the product can be recycled and reused after use.

[0029] Compared to traditional EPDM and SBR runway materials that require chemical vulcanization, the graft copolymer does not generate vulcanization pollution throughout its entire production and use lifecycle, and can be recycled without desulfurization.

[0030] The physical crosslinking points formed by the styrene blocks can reversibly dissociate at high temperatures and reform after cooling, thereby enabling the graft copolymer to be repeatedly melt-processed without loss of mechanical properties, achieving closed-loop recycling of the material.

[0031] After the track material reaches the end of its service life, it can be cleaned, crushed, melted and granulated, and reused to produce track materials or other thermoplastic elastomer products, thus achieving a green recycling of the material throughout its entire life cycle.

[0032] Example 2 The difference from Example 1 is as follows: A running track material comprises the following raw materials in parts by weight: 150 parts calcium carbonate, 60 parts polyethylene, 40 parts styrene-ethylene-propylene-styrene block copolymer, and 0.2 parts peroxide initiator; The polyethylene is ultra-low density polyethylene (ULLDPE); the peroxide initiator is dicumyl peroxide (DCP).

[0033] Other technical solutions are the same as in Example 1.

[0034] Example 3 The difference from Example 1 is as follows: A running track material comprises the following raw materials in parts by weight: 200 parts calcium carbonate, 50 parts polyethylene, 50 parts styrene-ethylene-propylene-styrene block copolymer, and 0.3 parts peroxide initiator; The polyethylene is low-density polyethylene (LDPE); the peroxide initiator is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (Bis25).

[0035] Other technical solutions are the same as in Example 1.

[0036] Comparative Example 1 The difference from Example 1 is that no oxide initiator is added to the raw materials.

[0037] Other technical solutions are the same as in Example 1.

[0038] Comparative Example 2 The difference from Example 1 is as follows: Instead of using the raw materials described in this technical solution, commercially available EPDM is used as the raw material, and a vulcanization process is employed to prepare the runway material. The raw materials include the following parts by weight: 100 parts EPDM, 300 parts calcium carbonate, 25 parts softening oil, 2.5 parts sulfur, 3.0 parts vulcanization auxiliaries, 1.5 parts antioxidant RD, and 3 parts silane coupling agent Si-69. The vulcanization process includes the following steps in sequence: mixing, hot pressing and vulcanizing into sheets, crushing the sheets, and using polyurethane adhesive to form the runway material.

[0039] Other technical solutions are the same as in Example 1.

[0040] The primary graft copolymers prepared in Examples 1 to 3 and the copolymers prepared in Comparative Examples 1 to 2 were granulated by twin-screw extrusion and then injection molded. Tensile properties were tested according to GB / T 528-2009, and impact absorption properties were tested according to GB / T14833-2020. The test results are shown in Table 1.

[0041] Table 1

[0042] As can be seen from the test results in Table 1, the polyethylene graft copolymers in Examples 1-3 exhibit better impact absorption compared to the EPDM + vulcanized system. Example 1, compared to Comparative Example 1, demonstrates that the mechanical properties of the graft copolymer are superior to those of the blend (ungrafted).

[0043] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A running track material, characterized in that, It includes the following raw materials by weight: 100-200 parts calcium carbonate, 30-70 parts polyethylene, 30-70 parts styrene-ethylene-propylene-styrene block copolymer, 0.05-0.5 parts peroxide initiator, 0.1-0.5 parts antioxidant, and 0.1-0.3 parts ultraviolet absorber.

2. The track material according to claim 1, characterized in that, The polyethylene is one or a mixture of two or more of linear low-density polyethylene, low-density polyethylene, or ultra-low-density polyethylene in any proportion.

3. The track material according to claim 1, characterized in that, The polyethylene has a melt index of 2 g / 10 min to 10 g / 10 min at 190 °C and 2.16 kg.

4. The track material according to claim 1, characterized in that, The styrene-ethylene-propylene-styrene block copolymer has a melt index of 0.5 g / 10 min to 15 g / 10 min at 230 °C and 2.16 kg.

5. A track material according to claim 1, characterized in that, In the styrene-ethylene-propylene-styrene block copolymer, the mass percentage of styrene segments is 10%-20%.

6. A runway material according to claim 1, characterized in that, The peroxide initiator is any one of di-tert-butyl peroxide, dicumyl peroxide, or 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

7. The method for preparing a runway material according to claim 1, characterized in that, Includes the following steps: S1. Preparation of the premix: Polyethylene, styrene-ethylene-propylene-styrene block copolymer, peroxide initiator, antioxidant and ultraviolet absorber are mixed according to the weight parts to obtain the premix; S2. The premix obtained in step S1 is added to an extruder or internal mixer and melt-blended at a temperature of 180°C to 240°C. Under high-temperature shearing, the peroxide initiator initiates chain scission of the styrene-ethylene-propylene-styrene block copolymer to form free radicals. The free radicals are grafted onto the main chain of the polyethylene. After grafting, a preliminary grafted copolymer is obtained. S3. The initial graft copolymer obtained in step S3 is extruded and granulated to obtain the graft copolymer. S4. Preparation of runway materials: The graft copolymer obtained in step S3 is prepared into prefabricated runway rolls or cast-in-place runway layers. The free radicals include SEP· free radicals and / or EP· free radicals.

Images