Lightweight wear-resistant anti-slip silencing sole material and preparation method thereof

Abstract

The invention relates to the technical field of soles, in particular to a lightweight recyclable thermoplastic elastomer-based sole foaming material and a preparation process thereof. The formula of the sole material mainly comprises the following components: 50-80 parts of thermoplastic polyester elastomer; 20 to 50 parts of rubber; 3-5 parts of a compatilizer and 5-15 parts of a plasticizer; 20 to 40 parts of filler; 1-2 parts of stearic acid; 1-2 parts of an anti-aging agent; 0.1-0.2 part of an accelerant (zinc oxide, zinc chloride and stannous chloride); 1-4 parts of a cross-linking agent (bio-based dicarboxylic acid, sebacic acid and maleic acid), and 0.05-0.2 part of an initiator (peroxide). The sole material is prepared by blending the thermoplastic polyester elastomer and the rubber, and the density of the material is adjusted by adopting a supercritical foaming process according to requirements, so that better mechanical properties can be ensured, excellent wear resistance and slip resistance can be achieved, and meanwhile, the sole material can be recycled.

Description

Technical Field

[0001] This invention relates to the field of shoe sole technology, and in particular to a lightweight thermoplastic elastomer-based shoe sole foam material and its preparation process. Background Technology

[0002] In modern footwear design, the choice of outsole material is crucial to the overall performance of the shoe. Traditionally, most soles are made of rubber, especially in athletic shoes. While rubber soles are widely used due to their excellent abrasion and water resistance, their inherent weight cannot meet the modern consumer demand for lightweight footwear. Furthermore, rubber soles tend to generate noise on smooth surfaces, affecting the user experience, especially noticeable on smooth indoor floors or in gyms.

[0003] Currently, the main materials for athletic shoe outsoles include rubber and thermoplastic polyurethane (TPU), both with a hardness generally higher than 65A. While this high hardness helps improve abrasion resistance, it results in a small contact area and low deformation capacity, leading to poor grip and noise reduction. Although the hardness can be adjusted to some extent by changing the ratio of reinforcing agents and softening oils, this method sacrifices the mechanical properties of the rubber while reducing hardness, thus failing to meet the practical requirements of footwear. Furthermore, attempts to increase contact area and improve friction noise through small, shallow outsole patterns, while theoretically feasible, often have limited effectiveness in practice, especially as the patterns wear down easily after long-term use, reducing their practical effect. In addition, the need for lightweight outsole materials is one of the goals of modern athletic and casual shoe design. According to sports biomechanics, for every gram of weight added to the sole, the energy required to swing the leg during running or walking increases accordingly. Lightweight outsoles significantly reduce the swing load on the lower limbs, making strides lighter and more energy-efficient, thereby extending exercise time and increasing speed. Therefore, the "balance of wear resistance, slip resistance, and lightweight" is the core challenge in footwear outsole design.

[0004] This invention aims to address the limitations of traditional rubber and TPU soles in terms of weight, noise, softness, grip, and abrasion resistance. Specifically, it seeks a novel sole material and manufacturing method that not only possesses lightweight and softness but also effectively reduces noise when walking on smooth surfaces and provides excellent slip resistance. Furthermore, this new sole material should have sufficient abrasion resistance to meet the needs of daily use, overcoming the problem of sacrificing mechanical properties due to reduced hardness in existing technologies. Simultaneously, this material should be recyclable, representing an important step towards sustainable development for the footwear and apparel industry. Summary of the Invention

[0005] In order to achieve the above-mentioned objectives and address the aforementioned technical problems, This invention provides a lightweight, wear-resistant, non-slip, and noise-absorbing shoe sole material, wherein the shoe sole material comprises, by weight: 50-80 parts of thermoplastic polyester elastomer; 15-55 parts of rubber composition; 8-15 parts of plasticizer; 0-5 parts of compatibilizer; 5-20 parts of reinforcing filler; 1-2 parts of stearic acid; 1-2 parts of antioxidant; 1-2 parts of accelerator; 2-4 parts of crosslinking agent; 0.03-0.1 parts of initiator.

[0006] Preferably, the thermoplastic polyester elastomer is selected from one or more combinations of TPU, TPEE, and PEBAX.

[0007] Preferably, the rubber composition is selected from two or more combinations of natural rubber, epoxidized natural rubber, styrene-butadiene rubber, ethylene propylene diene monomer (EPDM) rubber, brominated butyl rubber, and polynorbornene.

[0008] Preferably, the plasticizer is selected from one or more of paraffin oil, naphthenic oil, C5 resin, and phenolic resin.

[0009] Preferably, the reinforcing filler is selected from one or more of carbon black and silica.

[0010] Preferably, the compatibilizer is maleic anhydride-grafted EPDM rubber.

[0011] Preferably, the crosslinking agent is one of bio-based dicarboxylic acid, sebacic acid, and maleic acid.

[0012] Preferably, the antioxidant is selected from one or more of antioxidant 264, antioxidant RD, and antioxidant 2246; Preferably, the accelerator is selected from one or more of stannous chloride and zinc chloride; Preferably, the initiator is a peroxide.

[0013] The present invention also provides a preparation process for the lightweight, wear-resistant, non-slip, and noise-absorbing shoe sole material described above, the process comprising the following steps: Step S1: Place the thermoplastic polyester elastomer and rubber composition in a 140-170℃ internal mixer and mix for 3-8 minutes. Add antioxidant, plasticizer, reinforcing filler and stearic acid in sequence and continue mixing for 5-8 minutes. Then add compatibilizer. After the torque stabilizes, discharge the material and let it stand for 24 hours to obtain rubber masterbatch. Step S2: Place the rubber masterbatch in a 110-130℃ internal mixer and mix for 3-5 minutes. Add the accelerator, initiator and crosslinking agent in sequence, and continue mixing for 1-3 minutes. After the torque is stable, discharge the material to obtain the final rubber. Step S3: Shape the final compound into sheets; Step S4: The sheet is foamed under supercritical nitrogen conditions at a temperature of 80-160℃, a pressure of 20-30MPa, and a time of 1.5-2 hours to obtain a pre-foamed sheet. Step S5: After cutting the initial foamed sheet, place it in a patterned shoe sole mold and hot press it at 120-140℃ for 8-10 minutes. Open the mold to obtain the micro-foamed shoe sole.

[0014] Preferably, the sheet in step S3 is obtained in the following manner: Flat vulcanization: The final compound is placed in a flat vulcanizing machine and hot-pressed at 150-170℃ for 4-8 minutes to obtain a cross-linked sheet.

[0015] Preferably, the cross-linked sheet in step S3 is obtained in the following manner: Extrusion granulation followed by injection molding into sheets: The final compound is extruded and granulated in a single-screw extruder at 120-140℃ to obtain blend particles; the blend particles are fed into an injection molding machine, with the temperature of each zone of the screw and barrel of the injection molding machine at 110-130℃, the screw speed at 50-80 rpm, the mold temperature at 160-180℃, the back pressure at 0.3-1.0 MPa, and the holding time at 6-10 min. After mold opening, cross-linked sheets are obtained.

[0016] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: 1. Formulation System Design: Primarily composed of thermoplastic TPU, TPEE, and PEBAX, providing excellent wear resistance and good mechanical strength, while also offering flexibility for recycling. In addition to commonly used NR, EPDM, and SBR, the rubber phase incorporates ENR, polynorbornene, and brominated butyl rubber for improved damping performance, resulting in superior anti-slip properties and quieter operation. The crosslinking system utilizes bio-based dicarboxylic acids as crosslinking agents, combined with specific accelerators and initiators, to form a covalent crosslinking network. This not only makes the rubber phase easier to control during processing and supercritical foaming but also allows for rapid and efficient exchange reactions of dynamic bonds during recycling, achieving excellent reshaping and solving the recycling dilemma of traditional vulcanized rubber shoe outsoles.

[0017] 2. Achieving a balance between lightweight and performance: By employing supercritical foaming technology, the density of the material can be flexibly adjusted, reducing the weight of the sole while ensuring the material retains the necessary mechanical properties. TPU outsoles have a relatively high hardness, resulting in less deformation capacity compared to softer rubber. Consequently, their hysteresis effect on smooth, wet surfaces is weaker, compromising slip resistance. This invention, through micro-foaming, reduces the material's hardness, providing better deformation and grip, thus giving the sole material both excellent wear resistance and slip resistance.

[0018] 3. Environmental friendliness and sustainability: The main material is made of thermoplastic polymer, and the formulation can include bio-based crosslinking agents, which makes the entire sole material recyclable and meets the requirements of green manufacturing and circular economy. Attached Figure Description

[0019] Figure 1 This is a SEM image from Embodiment 1 of the present invention; Figure 2 This is a SEM image of the product after friction in Example 1 of the present invention; Figure 3 This is a SEM image from Embodiment 2 of the present invention; Figure 4 This is a SEM image from Embodiment 3 of the present invention; Figure 5 This is a SEM image from Embodiment 4 of the present invention; Figure 6 This is a SEM image from Embodiment 5 of the present invention; Figure 7 This is a SEM image of Embodiment 6 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Example 1 This embodiment provides a lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material and its preparation method.

[0022] 1. The lightweight, wear-resistant, non-slip, and noise-absorbing sole material comprises, by weight: Thermoplastic elastomer: 60 parts TPU, 20 parts PEBAX; Rubber composition: 10 parts EPDM, 10 parts polynorbornene; Compatibilizer: 2 parts EPDM-GMA; Plasticizer: 10 parts paraffin oil, 2 parts phenolic resin; Reinforcing filler: 20 parts silica; Stearic acid: 1 part; Antioxidant: Antioxidant 2246 1 part; Initiator: 0.03 parts DCP; Accelerator: 2 parts stannous chloride; Crosslinking agent: 2 parts adipic acid.

[0023] 2. Preparation method Step S1: Preparation of rubber masterbatch The rubber composition was fed into an internal mixer, the mixing temperature was set to 150°C, and the mixture was mixed for 6 minutes. Then, add antioxidants, plasticizers, reinforcing fillers and stearic acid in sequence, and continue mixing for 7 minutes. Add a compatibilizer and continue mixing until the torque stabilizes, then discharge the material. The discharged material was left to stand for 24 hours to obtain the compound rubber; After the torque stabilizes, the material is discharged to obtain rubber masterbatch.

[0024] Step S2: Final Refinement The rubber masterbatch is fed into an internal mixer, the temperature is set to 130°C, and the mixture is mixed for 4 minutes. Add the accelerator, zinc oxide, initiator and crosslinking agent in sequence, and continue mixing for 2 min; After the torque stabilizes, discharge the material to obtain the final rubber compound.

[0025] Step S3: Molding to obtain cross-linked sheet material (flat vulcanization) The final rubber compound was placed in a flat vulcanizing press, and the hot-pressing temperature was set to 180°C for 6 minutes. Cross-linked sheets are obtained.

[0026] Step S4: Supercritical nitrogen foaming The cross-linked sheet was placed in a supercritical nitrogen foaming device. The foaming temperature was set to 105℃, the pressure to 25MPa, and the foaming time to 1.8h. After foaming is completed, the initial foamed sheet is obtained.

[0027] Step S5: Embossing and Shaping The pre-foamed sheet is cut and placed in a patterned shoe sole mold. Set the hot-pressing temperature to 140℃, hot-press for 8 minutes, then open the mold. A micro-foamed shoe sole was obtained.

[0028] Examples 2-8 Prepared according to the same formulation and preparation method as in Example 1, except as shown in Table 1: Table 1. Differences in Formulation and Process between Examples (Formulation: Parts)

[0029] Comparative Example 1 Prepared according to the same formulation and preparation method as in Example 1, except that only thermoplastic elastomer TPU is used, and nothing else is added. The process only includes step S5, with a hot pressing temperature of 150°C and a time of 8 minutes.

[0030] Comparative Example 2 Prepared according to the same formulation and preparation method as in Example 2, except that foaming is not performed.

[0031] Comparative Example 3 Prepared according to the same formulation and preparation method as in Example 5, except that the vulcanizing agent is sulfur; the rubber composition is 20 parts ENR, 10 parts EPDM, and 10 parts SBR; the compatibilizer is 5 parts EPDM-GMA; the plasticizer is 10 parts paraffin oil and 2 parts phenolic resin; the reinforcing filler is 10 parts silica and 2 parts carbon black; the accelerator is 1.5 parts CBS and 5 parts ZnO; the crosslinking agent is 1.5 parts sulfur; the foaming temperature in step S4 is 80°C, and the hot pressing temperature in step S5 is 120°C.

[0032] Comparative Example 4 An anti-slip composite thermoplastic elastomer comprises the following components in parts by weight: butyl rubber 15 parts, liquid nitrile rubber 5 parts, surface-modified needle-shaped wollastonite obtained in Preparation Example 1 5.263 parts, vulcanizing agent phenolic resin 1 part, vulcanizing aid stannous chloride 0.3 parts, thermoplastic polyurethane elastomer particles 85 parts, compatibilizer POE grafted maleic anhydride 3 parts.

[0033] A method for preparing an anti-slip composite thermoplastic elastomer includes the following steps: (1) At room temperature, 1000g of surface-modified needle-shaped wollastonite obtained in Preparation Example 1, 3000g of butyl rubber, 1000g of liquid nitrile rubber, 200g of phenolic resin and 60g of stannous chloride were put into a 6L internal mixer for blending to obtain a compound; the material temperature was controlled below 70°C during the blending process. (2) The compound is placed in a rubber granulator with a conical twin-screw forced feeding, and while pelletizing, 1% by weight of the surface-modified needle-shaped wollastonite obtained in Preparation Example 1 is mixed in and isolated to prepare compound granules. (3) The compounded granules, thermoplastic polyurethane elastomer granules, and POE-grafted maleic anhydride were fed into a twin-screw extruder in a ratio of 26.563:85:3 using a loss-in-weight weigher. The temperature of each section of the twin-screw extruder was set to 160°C. Dynamic vulcanization and granulation are carried out at 190℃ and screw speed of 400 rpm. After cooling, the anti-slip composite thermoplastic elastomer is obtained.

[0034] Experimental test: 1. Apparent density: in accordance with GB / T6343-2009.

[0035] 2. Shore A hardness: in accordance with GB / T10807-2006.

[0036] 3. Tensile strength and tear strength: GB / T 6344-2008.

[0037] 4. Dry and wet slip resistance: Tested according to standard GB / T3903.6-2017 respectively.

[0038] 5. Wear volume test: Tested according to GB / T9867-2008.

[0039] Table 2 Test Data

[0040] As can be seen from Table 2, Examples 2-4 use the same formula, but different foaming processes are used to obtain outsole materials with different densities. It can be seen that within this density range, density has little effect on anti-slip performance, but a significant effect on abrasion resistance. The lower the density, the worse the abrasion resistance, but all of them still meet the general abrasion-resistant outsole requirement of <80 V / mm3.

[0041] Table 2 shows that the outsole of the sports shoe made of pure TPU material in Comparative Example 1, although possessing high mechanical strength and excellent wear resistance, has high hardness and poor dry and wet slip resistance. Comparing Example 2 and Comparative Example 2, both have the same formula, but Comparative Example 2 does not foam. It can be seen that Comparative Example 2 has high strength and hardness, but its slip resistance is still worse than Example 2. Example 5 and Comparative Example 3 have the same rubber matrix formula, but different vulcanization systems. Under the same molding and foaming processes, the density of Example 5 did not decrease significantly after foaming. This is because the sulfur vulcanization system reacts quickly, rapidly forming a network structure, which hinders the formation and growth of cells during foaming, thus preventing proper foaming. Furthermore, with a high rubber ratio, the blend of the sulfur vulcanization system cannot be recycled. Compared with Comparative Example 4, it can be seen that without micro-foaming, Comparative Example 4 has a Shore A hardness of 71, which is higher than the required Shore A hardness of 65.

[0042] The above description is only a preferred embodiment of the present invention and is 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 lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material, characterized in that, The sole material comprises, by weight: 50-80 parts of thermoplastic polyester elastomer; 20-40 parts of rubber composition; 8-15 parts of plasticizer; 0-5 parts of compatibilizer; 5-20 parts of reinforcing filler; 1-2 parts of stearic acid; 1-2 parts of antioxidant; 1-2 parts of accelerator; 2-4 parts of crosslinking agent; 0.03-0.1 parts of initiator.

2. The lightweight, wear-resistant, non-slip, and sound-absorbing sole material according to claim 1, characterized in that, The thermoplastic polyester elastomer is selected from one or more combinations of TPU, TPEE, and PEBAX.

3. The lightweight, wear-resistant, non-slip, and noise-absorbing sole material according to claim 1, characterized in that, The rubber composition is selected from two or more of the following: natural rubber, epoxidized natural rubber, styrene-butadiene rubber, ethylene propylene diene monomer (EPDM) rubber, brominated butyl rubber, and polynorbornene.

4. The lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material according to claim 1, characterized in that, The plasticizer is selected from one or more of paraffin oil, naphthenic oil, C5 resin, and phenolic resin.

5. The lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material according to claim 1, characterized in that, The reinforcing filler is selected from one or more of carbon black and silica.

6. The lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material according to claim 1, characterized in that, The compatibilizer is maleic anhydride-grafted EPDM rubber.

7. The lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material according to claim 1, characterized in that, The crosslinking agent is one of oxalic acid, sebacic acid, or maleic acid in bio-based dicarboxylic acids.

8. The lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material according to claim 1, characterized in that, The antioxidant is selected from one or more of antioxidant 264, antioxidant RD, and antioxidant 2246; The accelerator is selected from one or more of stannous chloride, zinc oxide, and zinc chloride; The initiator is a peroxide.

9. The preparation process of the lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material according to any one of claims 1-8, characterized in that, The process includes the following steps: Step S1: The thermoplastic polyester elastomer, rubber composition, antioxidant, plasticizer, reinforcing filler and stearic acid are placed in an internal mixer and mixed in sequence, and then a compatibilizer is added and mixed to obtain rubber masterbatch. Step S2: Place the rubber masterbatch in a mixer and mix, then add the accelerator, initiator and crosslinking agent in sequence and continue mixing to obtain the final rubber. Step S3: Shape the final compound into sheets; Step S4: The sheet is foamed under supercritical nitrogen conditions to obtain a pre-foamed sheet; Step S5: After cutting the initial foamed sheet, place it in the shoe sole mold for embossing and shaping to obtain the micro-foamed shoe outsole.

10. The preparation process of the lightweight, wear-resistant, non-slip, and sound-absorbing shoe sole material according to claim 9, characterized in that, The sheet material in step S3 is obtained in any of the following ways: (1) Flat vulcanization: The final compound is placed in a flat vulcanizing machine and hot-pressed to obtain a sheet; (2) After extrusion granulation, injection molding into sheets: The final rubber compound is placed in an extruder for extrusion and granulation to obtain blended particles; the blended particles are then fed into an injection molding machine for injection molding to obtain sheets.

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