Light PU (polyurethane) foamed sole and preparation method thereof

Abstract

The invention discloses a light PU (polyurethane) foamed sole and a preparation method thereof, and belongs to the technical field of foamed soles, and the sole is remarkably improved in shock absorption and folding resistance by optimizing a material formula and a preparation process. The sole is composed of an ethylene-vinyl acetate copolymer, an ethylene-octylene copolymer, an SBS thermoplastic elastomer, polyether polyurethane and other raw materials, and a specific cushioning additive is introduced. The preparation method comprises the steps of banburying, mixing, foaming forming and the like, and uniform mixing of the materials and full proceeding of a cross-linking reaction are ensured by accurately controlling the temperature, the time and the turning frequency. Compared with the prior art, the sole disclosed by the invention is excellent in shock absorption and folding resistance, and has important practical application value and market prospect.

Description

Technical Field

[0001] The invention relates to the technical field of foamed soles, and in particular to a lightweight PU foamed sole and a preparation method thereof. Background Art

[0002] In the field of foam sole technology, especially in the preparation of lightweight PU foam soles, shock absorption and bending resistance are key indicators for measuring the quality of soles. Although the existing lightweight foam sole technology has met the market demand for lightness and comfort to a certain extent, it still has obvious shortcomings in high-performance application scenarios.

[0003] In the prior art, lightweight foam soles have limited performance in absorbing impact energy. For example, some traditional foam materials are prone to uneven energy transfer under high-energy impact, resulting in poor shock absorption. This problem is particularly prominent in scenarios that require high-intensity shock absorption, such as sports shoes and work shoes. In addition, traditional foam sole materials are prone to fatigue after multiple impacts, and the shock absorption performance gradually decreases, affecting the service life and wearing experience of the sole. In terms of folding resistance, existing foam soles are prone to cracks or breaks during repeated bending, especially in the forefoot and heel parts of the sole. These parts are subject to the greatest bending stress during walking and exercise, and insufficient bending resistance will cause premature damage to the sole, affecting the overall quality and service life of the shoe. The folding resistance of some foam materials will further decrease in high temperature or humid environments, limiting their application in complex environments.

[0004] The limitations of the existing technology are mainly reflected in the material formula and preparation process. Although a variety of additives have been added to the traditional material formula to improve performance, there is still a lot of room for improvement in shock absorption and folding resistance. For example, commonly used fillers and cross-linking agents often sacrifice flexibility and elasticity while improving material strength. In addition, the existing preparation process has deficiencies in the control of mixing uniformity and cross-linking reactions. For example, the control of temperature and time during mixing and kneading is not precise enough, resulting in uneven material properties. Traditional freeze-drying technology is rarely used in the preparation of shock-absorbing additives, which limits the further improvement of shock-absorbing performance.

[0005] Chinese patent publication number CN114891292A discloses a lightweight, oil-resistant, and anti-skid foamed sole and its preparation process. The sole is composed of raw materials such as ethylene-vinyl acetate copolymer, maleic anhydride grafted EVA, nitrile rubber, SBS thermoplastic elastomer, foaming agent, accelerator, cross-linking agent, nanofiller (composed of attapulgite, asbestos fiber, and mica powder in a specific proportion), zinc stearate, and cycloalkane oil. By combining ethylene-vinyl acetate copolymer, nitrile rubber, and SBS thermoplastic elastomer, and introducing maleic anhydride grafted EVA to enhance the compatibility and adhesion between the raw materials, the invention successfully improves the oil resistance and anti-skid properties of the foamed sole, while ensuring the overall mechanical properties of the sole. However, despite significant progress in oil resistance and anti-skid properties, the lightweight, oil-resistant, and anti-skid foamed sole prepared by the patent still needs to be further improved in terms of shock absorption and folding resistance.

[0006] In summary, the deficiencies of the prior art in shock absorption and folding resistance limit the application of lightweight foamed soles in high-performance application scenarios. Therefore, developing a lightweight PU foamed sole with excellent shock absorption and folding resistance and a preparation method thereof has important practical significance and market value. Summary of the invention

[0007] In order to solve the deficiencies in the prior art, the present invention aims to provide a lightweight PU foam sole and a preparation method thereof.

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: A lightweight PU foam sole comprises the following raw materials in parts by weight: 15~25 parts of ethylene-vinyl acetate copolymer, 10~20 parts of ethylene octene copolymer, 5~10 parts of SBS thermoplastic elastomer, 5~15 parts of polyether polyurethane, 4~6 parts of kaolin, 0.5~1 parts of calcium stearate, 2~4 parts of paraffin oil, 0.5~2 parts of azodicarbonamide, 1~2 parts of shock-absorbing additives, 0.5~1 parts of dimethyl silicone oil, and 0.5~1 parts of di-tert-butyl peroxide.

[0009] The preparation method of the shock-absorbing additive comprises the following steps: mixing an organic silicon compound and a functional organic silane, adding the mixture into water, heating and stirring, and obtaining a pre-treated product; then, dissolving polyacrylamide into water, heating and stirring evenly, and preparing an active solution; then, adding talcum powder, bentonite, boric oxide and ammonium dihydrogen phosphate into water and mixing, and forming a suspension; then, dropping the active solution into the pre-treated product, continuing to stir, and then mixing evenly with the suspension; and finally, freeze-drying, and obtaining the shock-absorbing additive.

[0010] A method for preparing a lightweight PU foam sole is as follows, in parts by weight: Step 1, 15-25 parts of ethylene-vinyl acetate copolymer, 10-20 parts of ethylene octene copolymer, 5-10 parts of SBS thermoplastic elastomer, and 5-15 parts of polyether polyurethane are mixed and put into a mixer, and the mixture is mixed for 8-12 minutes, and 4-6 parts of kaolin, 0.5-1 parts of calcium stearate, and 2-4 parts of paraffin oil are added, and the mixture is mixed and mixed, and the mixture is stirred once after the mixing temperature reaches 90-100°C and maintained for 3-5 minutes, and the mixture is stirred twice after the mixing temperature rises to 95-105°C, and the mixture is stirred three times after the mixing temperature rises to 100-110°C, and the mixture is stirred four times after the mixing temperature rises to 105-115°C, and the mixture is stirred five times after the mixing temperature rises to 110-120°C, and the mixture is mixed for 2-4 minutes, and the mixture is discharged, and the mixture is placed at room temperature for 10-48 hours to obtain a mixture; Step 2, adding the mixture prepared in step 1 to a double-roll mill, and then adding 0.5-2 parts of azodicarbonamide, 1-2 parts of a shock absorbing additive, 0.5-1 parts of dimethyl silicone oil, and 0.5-1 parts of di-tert-butyl peroxide, mixing, mixing evenly, and forming the evenly mixed material into a sheet; Step 3: Cut the sheet prepared in step 2 into the shape of a sole, put it into a sole mold for foaming, and after the foaming is completed, naturally cool it to room temperature to obtain a lightweight PU foam sole.

[0011] The temperature increase rate of the internal mixer in step 1 is 1-2°C / min.

[0012] In step 2, the mixing temperature is 100-130° C. and the mixing time is 5-15 minutes.

[0013] In step 2, the thickness of the sheet is controlled at 2-4 mm.

[0014] In step 3, the foaming temperature is between 130 and 170°C.

[0015] The preparation method of the shock absorbing additive is as follows, in parts by weight: 15-25 parts of an organic silicon compound and 5-10 parts of a functional organic silane are mixed and added to 120-180 parts of water, and the mixture is continuously stirred at a temperature of 70-80°C for 2-5 hours to prepare a pretreated product; 10-20 parts of polyacrylamide are dissolved in 200-400 parts of water, heated to 65-75°C and stirred evenly to prepare an active solution; then 5-10 parts of talc, 2-6 parts of bentonite, 4-8 parts of boric oxide and 4-6 parts of ammonium dihydrogen phosphate are added to 100-150 parts of water and mixed to form a suspension, and the active solution is dripped into the pretreated product at a dripping speed of 10-30 mL / min, and the mixture is continuously stirred at a temperature of 70-90°C for 1-3 hours, and then the mixture is uniformly mixed with the suspension, and freeze-dried to obtain a shock absorbing additive.

[0016] The organic silicon compound is at least one of tetramethoxysilane, tetra-sec-butoxysilane, bis(3-trimethoxysilylpropyl)amine and bis-[3-(triethoxysilyl)propyl]-tetrasulfide.

[0017] The functional organic silane is at least one of 3-glycidyloxypropylmethyldiethoxysilane and 1-(3-glycidyloxypropyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane.

[0018] The organosilicon compound forms a silica network in the shock-absorbing additive through hydrolysis and condensation reactions, providing the shock-absorbing additive with a high-strength and thermally stable skeleton, enhancing the overall mechanical properties while remaining stable in high-temperature environments.

[0019] Functional organosilicon undergoes cross-linking reactions with other ingredients through its reactive groups to form a complex three-dimensional network structure, which further enhances the toughness and elasticity of the material and improves its shock-absorbing performance.

[0020] As a cross-linking agent, polyacrylamide forms an active solution after dissolving in water, which can undergo cross-linking reactions with organosilicon compounds and functional organosilanes to form a uniform and tight network structure, significantly improving the elasticity and toughness of the shock-absorbing additive, while also improving the water absorption and biocompatibility of the material.

[0021] As an inorganic filler, talc can significantly improve the mechanical properties and thermal stability of shock-absorbing additives. Its flaky structure forms a physical barrier in the material, enhancing toughness and tear resistance, while reducing material costs and maintaining good processing performance.

[0022] Bentonite has good adsorption and expansion properties, and can form a uniformly distributed microporous structure in the shock-absorbing additive, effectively absorbing and dispersing impact energy, improving shock-absorbing performance, and enhancing the flexibility and fatigue resistance of the material.

[0023] Boric oxide can reduce the melting point and viscosity of the material, promote the hydrolysis and condensation reactions of organosilicon compounds and functional organosilanes, enable the material to form a stable network structure at a lower temperature, and enhance thermal and chemical stability.

[0024] Ammonium dihydrogen phosphate can adjust the pH value of the material, ensure that the reaction is carried out under suitable acid-base conditions, improve reaction efficiency and uniformity, and further enhance the network structure, improve mechanical properties and thermal stability.

[0025] The synergistic effect of these substances enables the cushioning additives to significantly improve the shock absorption and folding resistance of the soles, meeting the needs of high-performance soles.

[0026] Compared with the prior art, it has the following beneficial effects: 1) The lightweight PU foam sole of the present invention performs well in absorbing impact energy. The organosilicon compound and functional organosilane in the shock-absorbing additive can form a complex cross-linked network to effectively disperse the impact force, thereby significantly improving the shock-absorbing effect of the sole.

[0027] 2) The sole of the present invention can still maintain good structural integrity during repeated bending. The flexible structure and high-density cross-linked network in the shock-absorbing additive give the sole excellent elasticity and folding resistance, which can effectively extend the service life of the sole.

[0028] 3) The preparation method of the present invention ensures uniform mixing of materials and sufficient cross-linking reaction by precisely controlling the temperature, time and number of material turnings during the internal kneading and mixing process. In addition, the application of freeze-drying technology further improves the quality of the shock-absorbing additive, making it more evenly dispersed in the sole, thereby improving the overall performance of the sole. This optimized preparation process not only improves production efficiency, but also reduces production costs, and has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION

[0030] Main sources of substances: Ethylene-vinyl acetate copolymer, brand: 7470M, manufacturer (origin): Formosa Plastics Corporation.

[0031] Ethylene octene block copolymer, specification model: 8003, brand: Dow, USA.

[0032] SBS thermoplastic elastomer, brand: D1101JO, ​​manufacturer (origin): Kraton, USA.

[0033] Polyether polyurethane, item number: TPU 1185A, brand: BASF, Germany.

[0034] Kaolin, 800 mesh.

[0035] Paraffin oil, item number: 6-17, Chuangyida (Shandong) Biotechnology Co., Ltd.

[0036] Dimethyl silicone oil, model: 1PMX-200, brand: Dow Corning.

[0037] Polyacrylamide, mesh number: 60-80, item number: 05, Henan Chuangyi Environmental Protection Technology Co., Ltd.

[0038] Talc, 1250 mesh.

[0039] Bentonite, 800 mesh.

[0040] Boron oxide, specification: 1um.

[0041] The remaining raw materials in the examples and comparative examples of the present invention are all commercially available products.

[0042] The design idea of ​​the present invention is to develop a lightweight PU foam sole with excellent shock absorption and bending resistance by optimizing the formula and preparation process of the sole material. The core lies in the introduction of a specific shock-absorbing additive, and its preparation process involves the mixing of organic silicon compounds and functional organic silanes, the activation of polyacrylamide, and the synergistic effect of multiple inorganic fillers. This shock-absorbing additive can significantly improve the structural stability of the sole when absorbing impact energy and repeatedly bending, thereby meeting the needs of high-performance soles.

[0043] Example 1 A method for preparing a lightweight PU foam sole is as follows, in parts by weight: Step 1, 20 parts of ethylene-vinyl acetate copolymer, 15 parts of ethylene octene copolymer, 8 parts of SBS thermoplastic elastomer, and 10 parts of polyether polyurethane are mixed and put into an internal mixer, and the internal mixer is mixed for 10 minutes. The temperature of the internal mixer is increased at a rate of 1.5°C / min, and 5 parts of kaolin, 0.8 parts of calcium stearate, and 3 parts of paraffin oil are added, and the mixing and mixing is continued. When the internal mixer temperature reaches 95°C, the material is turned over once after being kept for 4 minutes, and the material is turned over twice after the internal mixer temperature rises to 100°C. When the internal mixer temperature rises to 105°C, the material is turned over three times, when the internal mixer temperature rises to 110°C, the material is turned over four times, when the internal mixer temperature rises to 115°C, the material is turned over five times, and the material is mixed for 3 minutes, the glue is discharged, and the material is placed at room temperature for 24 hours to obtain a mixture; Step 2, adding the mixture prepared in step 1 to a double-roll mill, and then adding 1 part of azodicarbonamide, 1.5 parts of a shock absorbing additive, 0.8 parts of dimethyl silicone oil, and 0.8 parts of di-tert-butyl peroxide, and mixing at a mixing temperature of 110° C. for 10 minutes, mixing evenly, and forming the evenly mixed material into a sheet with a thickness controlled at 3 mm; Step 3, cutting the sheet prepared in step 2 into the shape of a sole, placing it in a sole mold for foaming, the foaming temperature being 160° C., and after the foaming is completed, naturally cooling to room temperature to obtain a lightweight PU foam sole.

[0044] The preparation method of the shock absorbing additive is as follows, in parts by weight: 20 parts of di(3-trimethoxysilylpropyl)amine and 8 parts of 1-(3-glycidyl ether propyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane were mixed and added to 150 parts of water, and stirred continuously for 3 hours at a temperature of 75°C to prepare a pretreated material; 15 parts of polyacrylamide were dissolved in 300 parts of water, heated to 70°C and stirred uniformly to prepare an active solution; then 8 parts of talc, 4 parts of bentonite, 6 parts of boric oxide and 5 parts of ammonium dihydrogen phosphate were added to 120 parts of water and mixed to form a suspension, and the active solution was dripped into the pretreated material at a dripping speed of 20 mL / min, and continued to stir at a temperature of 80°C for 1.5 hours, then mixed uniformly with the suspension, and freeze-dried to obtain a shock absorbing additive.

[0045] Example 2 The preparation method of a lightweight PU foam sole is basically the same as that of Example 1, the only difference being that the preparation method of the shock absorbing additive is different.

[0046] The preparation method of the shock absorbing additive is as follows, in parts by weight: 20 parts of tetra-sec-butoxysilane and 8 parts of 1-(3-glycidyl ether propyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane are mixed and added to 150 parts of water, and stirred continuously for 3 hours at a temperature of 75°C to prepare a pretreated material; 15 parts of polyacrylamide are dissolved in 300 parts of water, heated to 70°C and stirred uniformly to prepare an active solution; then 8 parts of talc, 4 parts of bentonite, 6 parts of boric oxide and 5 parts of ammonium dihydrogen phosphate are added to 120 parts of water and mixed to form a suspension, and the active solution is dripped into the pretreated material at a dripping speed of 20 mL / min, and stirring is continued at a temperature of 80°C for 1.5 hours, and then mixed uniformly with the suspension, and freeze-dried to obtain a shock-absorbing additive.

[0047] Example 3 The preparation method of a lightweight PU foam sole is basically the same as that of Example 1, the only difference being that the preparation method of the shock absorbing additive is different.

[0048] The preparation method of the shock absorbing additive is as follows, in parts by weight: 20 parts of tetramethoxysilane and 8 parts of 1-(3-glycidyl ether propyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane are mixed and added to 150 parts of water, and stirred continuously for 3 hours at a temperature of 75°C to prepare a pretreated material; 15 parts of polyacrylamide are dissolved in 300 parts of water, heated to 70°C and stirred uniformly to prepare an active solution; then 8 parts of talc, 4 parts of bentonite, 6 parts of boron oxide and 5 parts of ammonium dihydrogen phosphate are added to 120 parts of water and mixed to form a suspension, and the active solution is dripped into the pretreated material at a dripping speed of 20 mL / min, and stirring is continued at a temperature of 80°C for 1.5 hours, and then mixed uniformly with the suspension, and freeze-dried to obtain a shock-absorbing additive.

[0049] Example 4 The preparation method of a lightweight PU foam sole is basically the same as that of Example 1, the only difference being that the preparation method of the shock absorbing additive is different.

[0050] The preparation method of the shock absorbing additive is as follows, in parts by weight: 20 parts of di(3-trimethoxysilylpropyl)amine and 8 parts of 3-glycidyloxypropylmethyldiethoxysilane were mixed and added to 150 parts of water, and stirred continuously for 3 hours at a temperature of 75°C to prepare a pretreated material; 15 parts of polyacrylamide were dissolved in 300 parts of water, heated to 70°C and stirred uniformly to prepare an active solution; then 8 parts of talc, 4 parts of bentonite, 6 parts of boric oxide and 5 parts of ammonium dihydrogen phosphate were added to 120 parts of water and mixed to form a suspension, and the active solution was dripped into the pretreated material at a dripping speed of 20 mL / min, and continued to stir at a temperature of 80°C for 1.5 hours, then mixed uniformly with the suspension, and freeze-dried to obtain a shock-absorbing additive.

[0051] Example 5 The preparation method of a lightweight PU foam sole is basically the same as that of Example 1, the only difference being that the preparation method of the shock absorbing additive is different.

[0052] The preparation method of the shock absorbing additive is as follows, in parts by weight: 20 parts of bis-[3-(triethoxysilyl)propyl]-tetrasulfide and 8 parts of 1-(3-glycidyl ether propyl)-1,1,3,3,3-pentaethoxy-1,3-disilpropane were mixed and added to 150 parts of water, and stirred continuously for 3 hours at a temperature of 75°C to prepare a pretreated material; 15 parts of polyacrylamide were dissolved in 300 parts of water, heated to 70°C and stirred uniformly to prepare an active solution; then 8 parts of talc, 4 parts of bentonite, 6 parts of boric oxide and 5 parts of ammonium dihydrogen phosphate were added to 120 parts of water and mixed to form a suspension, and the active solution was dripped into the pretreated material at a dripping speed of 20 mL / min, and continued to stir at a temperature of 80°C for 1.5 hours, then mixed uniformly with the suspension, and freeze-dried to obtain a shock-absorbing additive.

[0053] Comparative Example 1 The preparation method of a lightweight PU foam sole is basically the same as that of Example 1, the only difference being that the preparation method of the shock absorbing additive is different.

[0054] The preparation method of the shock absorbing additive is as follows, in parts by weight: 20 parts of propyl orthosilicate and 8 parts of 1-(3-glycidyl ether propyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane are mixed and added to 150 parts of water, and stirred continuously for 3 hours at a temperature of 75°C to prepare a pretreated material; 15 parts of polyacrylamide are dissolved in 300 parts of water, heated to 70°C and stirred uniformly to prepare an active solution; then 8 parts of talc, 4 parts of bentonite, 6 parts of boric oxide and 5 parts of ammonium dihydrogen phosphate are added to 120 parts of water and mixed to form a suspension, and the active solution is dripped into the pretreated material at a dripping speed of 20 mL / min, and stirring is continued at a temperature of 80°C for 1.5 hours, and then mixed uniformly with the suspension, and freeze-dried to obtain a shock-absorbing additive.

[0055] Comparative Example 2 The preparation method of a lightweight PU foam sole is basically the same as that of Example 1, the only difference being that the preparation method of the shock absorbing additive is different.

[0056] The preparation method of the shock absorbing additive is as follows, in parts by weight: 20 parts of di(3-trimethoxysilylpropyl)amine and 8 parts of 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane were mixed and added to 150 parts of water, and stirred continuously for 3 hours at a temperature of 75°C to prepare a pretreated material; 15 parts of polyacrylamide were dissolved in 300 parts of water, heated to 70°C and stirred uniformly to prepare an active solution; then 8 parts of talc, 4 parts of bentonite, 6 parts of boric oxide and 5 parts of ammonium dihydrogen phosphate were added to 120 parts of water and mixed to form a suspension, and the active solution was dripped into the pretreated material at a dripping speed of 20 mL / min, and continued to stir at a temperature of 80°C for 1.5 hours, then mixed uniformly with the suspension, and freeze-dried to obtain a shock-absorbing additive.

[0057] Comparative Example 3 The preparation method of a lightweight PU foam sole is basically the same as that of Example 1, the only difference being that the shock absorbing additive is not added.

[0058] Test Example 1 Shock absorption performance test The shock absorbing performance of the soles of Examples 1-5 and Comparative Examples 1-3 was tested according to the method described in GB / T 30907-2014 “Test method for shock absorbing performance of rubber shoes and sports shoes”, wherein the test part was the heel, and 7J of energy was applied to the sole. The test results are shown in Table 1.

[0059] Table 1 Experimental protocol Shock absorption performance (G value) Example 1 13.7 Example 2 14.5 Example 3 14.8 Example 4 14.9 Example 5 13.7 Comparative Example 1 15.6 Comparative Example 2 15.0 Comparative Example 3 19.8 Test Example 2 Folding test The soles of Examples 1-5 and Comparative Examples 1-3 were tested according to the method specified in GB / T 3903.1-2017 "Footwear Test Methods for Folding Resistance". Test conditions: flexion angle: 50°, flexion frequency: 230 times / min, flexion times: 40,000 times, cut length: 5 mm, and the test results are shown in Table 2.

[0060] Table 2 Experimental protocol Crack length mm Example 1 6.2 Example 2 6.9 Example 3 7.4 Example 4 7.0 Example 5 6.0 Comparative Example 1 7.5 Comparative Example 2 7.5 Comparative Example 3 7.9 It can be seen from the data of Test Example 1 that the lightweight PU foam sole prepared in Example 1 has the best shock absorption performance and excellent folding resistance.

[0061] The di(3-trimethoxysilylpropyl)amine used in Example 1 shows better shock absorption and folding resistance than the tetra-sec-butoxysilane of Example 2, the tetramethoxysilane of Example 3 and the orthosilicate propyl ester of Comparative Example 1, which is mainly due to its unique molecular structure. The di(3-trimethoxysilylpropyl)amine molecule contains two trimethoxysilane groups, which provides abundant cross-linking sites, promotes chemical bonding with other components, and forms a more complex and stable cross-linked network. This network structure can effectively absorb and disperse impact energy, thereby significantly improving shock absorption. At the same time, the high density and stability of its cross-linked network also enhance the bending resistance of the material, so that the sole can still maintain good structural integrity during repeated bending. In contrast, although tetra-sec-butoxysilane, tetramethoxysilane and orthosilicate propyl ester can also form cross-linked structures, they lack such abundant cross-linking sites, resulting in insufficient complexity and stability of the cross-linked network, which is slightly weaker in shock absorption and folding resistance.

[0062] The 1-(3-glycidyl ether propyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane used in Example 1 shows better shock absorption and folding resistance than the 3-glycidyl ether oxypropyl methyl diethoxy silane of Example 4 and the 3-[(2,3)-epoxypropyloxy]propyl methyl dimethoxy silane of Comparative Example 2, which is mainly due to its unique molecular structure. The 1-(3-glycidyl ether propyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane molecule contains a glycidyl ether group and a pentaethoxysilane group. This structure not only provides abundant cross-linking sites, but also promotes chemical bonding with other components such as polyacrylamide through the high reactivity of the glycidyl ether group, forming a more complex and stable cross-linking network. This network structure can effectively absorb and disperse impact energy, thereby significantly improving shock absorption performance. At the same time, the high density and stability of its cross-linked network also enhance the folding resistance of the material, allowing the sole to maintain good structural integrity during repeated bending. In contrast, although 3-glycidyloxypropylmethyldiethoxysilane and 3-[(2,3)-epoxypropyloxy]propylmethyldimethoxysilane can also form cross-linked structures, their reactive groups (glycidyloxy and epoxypropyloxy) are relatively few, resulting in insufficient complexity and stability of the cross-linked network, and thus slightly inferior in shock absorption and folding resistance.

[0063] The bis-[3-(triethoxysilyl)propyl]-tetrasulfide in Example 5 is more flexible due to the tetrasulfide chain, has better cross-linked network elasticity, and has stronger folding resistance. Its shock absorption performance is equivalent to that of Example 1 because the two have similar impact energy absorption capabilities. However, the bis(3-trimethoxysilylpropyl)amine in Example 1 lacks a flexible structure and has slightly weaker folding resistance.

Claims

1. A lightweight PU foam sole, characterized in that: The invention comprises the following raw materials in parts by weight: 15-25 parts of ethylene-vinyl acetate copolymer, 10-20 parts of ethylene octene copolymer, 5-10 parts of SBS thermoplastic elastomer, 5-15 parts of polyether polyurethane, 4-6 parts of kaolin, 0.5-1 parts of calcium stearate, 2-4 parts of paraffin oil, 0.5-2 parts of azodicarbonamide, 1-2 parts of shock absorbing additive, 0.5-1 parts of dimethyl silicone oil and 0.5-1 parts of di-tert-butyl peroxide; The preparation method of the shock-absorbing additive comprises the following steps: mixing an organosilicon compound and a functional organosilane, adding the mixture into water, heating and stirring, and obtaining a pretreated product; adding polyacrylamide into water, heating and stirring evenly, and preparing an active solution; adding talcum powder, bentonite, boric oxide and ammonium dihydrogen phosphate into water and mixing them to form a suspension; dropping the active solution into the pretreated product, continuing to stir, and then mixing evenly with the suspension; and finally, freeze-drying to obtain the shock-absorbing additive.

2. A method for preparing the lightweight PU foam sole as claimed in claim 1, characterized in that: The method is as follows, in parts by weight: Step 1, 15-25 parts of ethylene-vinyl acetate copolymer, 10-20 parts of ethylene octene copolymer, 5-10 parts of SBS thermoplastic elastomer, and 5-15 parts of polyether polyurethane are mixed and put into a mixer, and the mixture is mixed for 8-12 minutes, and 4-6 parts of kaolin, 0.5-1 parts of calcium stearate, and 2-4 parts of paraffin oil are added, and the mixture is mixed and mixed, and the mixture is stirred once after the mixing temperature reaches 90-100°C and maintained for 3-5 minutes, and the mixture is stirred twice after the mixing temperature rises to 95-105°C, and the mixture is stirred three times after the mixing temperature rises to 100-110°C, and the mixture is stirred four times after the mixing temperature rises to 105-115°C, and the mixture is stirred five times after the mixing temperature rises to 110-120°C, and the mixture is mixed for 2-4 minutes, and the mixture is discharged, and the mixture is placed at room temperature for 10-48 hours to obtain a mixture; Step 2, adding the mixture prepared in step 1 to a double-roll mill, and then adding 0.5-2 parts of azodicarbonamide, 1-2 parts of a shock absorbing additive, 0.5-1 parts of dimethyl silicone oil, and 0.5-1 parts of di-tert-butyl peroxide, mixing, mixing evenly, and forming the evenly mixed material into a sheet; Step 3: Cut the sheet prepared in step 2 into the shape of a sole, put it into a sole mold for foaming, and after the foaming is completed, naturally cool it to room temperature to obtain a lightweight PU foam sole.

3. The method according to claim 2, characterized in that The temperature increase rate of the internal mixer in step 1 is 1-2°C / min.

4. The method according to claim 2, characterized in that In step 2, the mixing temperature is 100-130° C. and the mixing time is 5-15 minutes.

5. The method according to claim 2, characterized in that In step 2, the thickness of the sheet is controlled at 2-4 mm.

6. The method according to claim 2, characterized in that In step 3, the foaming temperature is between 130 and 170°C.

7. The method according to claim 1 or 2, characterized in that: The preparation method of the shock absorbing additive is as follows, in parts by weight: 15-25 parts of an organic silicon compound and 5-10 parts of a functional organic silane are mixed and added to 120-180 parts of water, and the mixture is continuously stirred at a temperature of 70-80°C for 2-5 hours to prepare a pretreated product; 10-20 parts of polyacrylamide are dissolved in 200-400 parts of water, heated to 65-75°C and stirred evenly to prepare an active solution; then 5-10 parts of talc, 2-6 parts of bentonite, 4-8 parts of boric oxide and 4-6 parts of ammonium dihydrogen phosphate are added to 100-150 parts of water and mixed to form a suspension, and the active solution is dripped into the pretreated product at a dripping speed of 10-30 mL / min, and the mixture is continuously stirred at a temperature of 70-90°C for 1-3 hours, and then the mixture is uniformly mixed with the suspension, and freeze-dried to obtain a shock absorbing additive.

8. The method according to claim 7, characterized in that The organic silicon compound is at least one of tetramethoxysilane, tetra-sec-butoxysilane, bis(3-trimethoxysilylpropyl)amine and bis-[3-(triethoxysilyl)propyl]-tetrasulfide.

9. The method according to claim 7, characterized in that The functional organic silane is at least one of 3-glycidyloxypropylmethyldiethoxysilane and 1-(3-glycidyloxypropyl)-1,1,3,3,3-pentaethoxy-1,3-disiloxane.