Lightweight high-elasticity EVA shoe sole and preparation method thereof

Abstract

This invention relates to an EVA shoe material, and more particularly to a lightweight, high-elasticity EVA shoe sole and its preparation method. The raw materials include the following components: 60-75 parts EVA, 10-20 parts POE, 5-18 parts EPDM rubber, 0.45-0.7 parts crosslinking agent, 5-6.5 parts foaming agent, and 0.5-0.8 parts lubricant. The finished product is prepared through a process of intensive mixing, open milling and sheeting, granulation, granule cooling, settling, vulcanization and foaming, molding, semi-finished product polishing, secondary vulcanization, and final molding. The technical solution of this invention achieves an EVA shoe sole density of less than 0.15 g / cm³. 3 With a compression deformation rate of around 25%, it is lightweight and convenient while also possessing good softness and elasticity, high resistance to deformation, high shock absorption (i.e., high cushioning performance), and strong toughness; making it suitable for high-intensity rebound environments such as long-distance running and fast running.

Description

Technical Field

[0001] This invention relates to an EVA shoe material, and more particularly to a white, lightweight, high-elastic EVA shoe sole and its preparation method. Background Technology

[0002] EVA resin is an ethylene-vinyl acetate copolymer, typically containing 5% to 40% vinyl acetate (VA). Compared to polyethylene, EVA, due to the introduction of vinyl acetate monomers into its molecular chain, exhibits reduced crystallinity and improved flexibility, impact resistance, filler compatibility, and heat-sealing properties, making it widely used in the field of foamed shoe materials. Ethylene-vinyl acetate copolymer (EVA) foamed shoe soles are widely used in the manufacture of various shoe soles due to their numerous advantages, including lightweight, good flexibility, comfortable wear, wrinkle resistance, and good elasticity.

[0003] The main advantage of EVA soles is their light weight. Even without air cushioning, they still provide some shock absorption. With the increasing popularity of EVA soles, their lighter weight and greater resilience have become highly sought after. The density and compression deformation rate of the sole greatly determine its weight and lasting softness and elasticity.

[0004] Foaming agent is the main factor controlling the performance of foamed materials. The amount of foaming agent used in conventional EVA shoe soles is generally 2%-3%, and at most no more than 5%. The higher the amount of foaming agent, the lower the density of the sole, and the lighter it is. However, excessive foaming agent can cause bubble coalescence, resulting in uneven cell size distribution. Furthermore, the amount of foaming agent has a significant impact on the degree of vulcanization; excessive amounts lead to over-vulcanization, resulting in larger pores within the material, poorer performance, and yellowing of the material, particularly hindering the proper color matching of white and light-colored materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a lightweight, high-elastic EVA shoe sole with a large amount of foaming agent and its preparation method.

[0006] This invention is implemented as follows:

[0007] A lightweight, highly elastic EVA shoe sole, the raw materials of which include the following components:

[0008] EVA 60-75 parts

[0009] 10-20 copies of POE

[0010] 5-18 parts of EPDM rubber

[0011] Crosslinking agent 0.45-0.7 parts

[0012] 5.5-6.5 parts foaming agent

[0013] Lubricant 0.5-0.8 parts.

[0014] Preferably, the total weight of all raw material components is 100 parts.

[0015] Furthermore, the lubricant includes stearic acid.

[0016] Furthermore, the foaming agent is a low-temperature foaming agent or a high-temperature foaming agent.

[0017] Furthermore, the low-temperature foaming agent is a low-temperature AC foaming agent (decomposition temperature 135°C).

[0018] Furthermore, the crosslinking agent is an odorless crosslinking agent.

[0019] Furthermore, the odorless crosslinking agent is bis-tert-butylperoxyisopropylbenzene.

[0020] The method for preparing the EVA shoe sole includes the following steps:

[0021] (1) Internal mixing mixture:

[0022] Set the internal mixer temperature to 80±1℃; put EVA, POE, EPDM rubber and lubricant into the heating cylinder of the internal mixer for internal mixing, control the air pressure at 0.6-0.8MPA, and when the temperature rises to the range of 85±1℃-95±1℃, turn the material over once every 5℃ increase in temperature.

[0023] When the internal mixer temperature reaches 95±1℃, pour in the foaming agent and crosslinking agent, control the air pressure at 0.6-0.8MPA, and perform 3 turnings when the internal mixer temperature rises from 95±1℃ to 100±1℃. Discharge the material when the set temperature of 100±1℃ is reached.

[0024] (2) Open milling and tableting:

[0025] The temperature of the open mill wheel table is set to 65±5℃ and the roller spacing is 6-8mm. Keep the temperature of the open mill wheel table at 65±5℃, press the material from step (1) into a sheet through the open mill rollers, and press the sheet again through the rollers 2-4 times.

[0026] (3) Granulation:

[0027] The thin film prepared in step (2) is granulated;

[0028] (4) Cooling and settling of the granules:

[0029] After the temperature of the granules drops to 50℃, the material is discharged and allowed to stand for at least 24 hours.

[0030] (5) Vulcanization foaming and molding:

[0031] Vulcanizing foaming machine pressure setting: 150-180 kg / cm 2Machine temperature: 180-185℃; the granules are vulcanized in the mold of the machine for 550-600 seconds, and after cooling and removal, the semi-finished shoe sole is obtained;

[0032] (6) Polishing of semi-finished products:

[0033] After comparing and verifying the semi-finished product with the sample, use a cloth wheel to remove the surface skin and impurities.

[0034] (7) Secondary vulcanization and molding:

[0035] After secondary vulcanization and molding, the machine temperature is 175±5℃ and the holding time is 600s to ensure that the sole is fully vulcanized again. After cooling and molding, the finished product can be obtained.

[0036] Furthermore, the mold ratio of the machine tool in step (5) is 1:1.85.

[0037] Furthermore, the mold ratio of the machine tool in step (7) is 1:1.005.

[0038] The present invention has the following advantages: The technical solution of the present invention produces a white, lightweight, highly elastic EVA shoe sole with a density of less than 0.15 g / cm³. 3 With a compression deformation rate of around 25%, it is lightweight and convenient while also possessing good softness and elasticity, high resistance to deformation, high shock absorption (i.e., high cushioning performance), and strong toughness; making it suitable for high-intensity rebound environments such as long-distance running and fast running. Detailed Implementation

[0039] (1) Internal mixing mixture:

[0040] Set the internal mixer temperature to 80±1℃; put EVA (7350 or 5110 or 6110, 7350 is used in the following examples), POE (8150), EPDM (3745) and stearic acid into the heating cylinder of the internal mixer and internally mix them. Press the heating cylinder with 6-8KG air pressure. When the temperature rises to the range of 85±1℃-95±1℃, turn the material over once every 5℃ increase in temperature.

[0041] When the internal mixer temperature reaches 95±1℃, pour in the foaming agent and odorless crosslinking agent (DCP), and press the material into the heating cylinder with 6-8KG air pressure. When the internal mixer temperature rises from 95±1℃ to 100±1℃, the material is turned over 3 times. When the temperature reaches the set temperature of 100±1℃, the material is discharged.

[0042] (2) Open milling and tableting:

[0043] The temperature of the open mill roller table is set to 65±5℃ and the roller spacing is 6-8mm. The temperature of the open mill roller table is kept at 65±5℃. The material from step 1 is pressed into a sheet by the open mill rollers. The sheet is then pressed three more times by the rollers.

[0044] (3) Granulation:

[0045] Set the temperature of the granulator: the die head temperature is 85±5℃, the first stage of electric heating is 80±5℃, the second stage of electric heating is 80±5℃, the third stage of electric heating is 80±5℃, and the fourth stage of electric heating is 80±5℃; set the pelletizing speed: the spindle speed is 40-45 rpm, and the cutter speed is 15-25 rpm; granulate the sheet made in step (2) through a fan and a vibrating screen, a press and a pelletizer, and make particles of the size of a trapezoid.

[0046] (4) Cooling and settling of the granules:

[0047] The granules are diverted to the mixing tank via a vibrating screen. The cooling circulating water in the mixing tank is turned on, and the mixture is stirred for 25-30 minutes. After the temperature of the granules drops to 50℃, the material is discharged and allowed to stand for more than 24 hours.

[0048] (5) Weighing materials, vulcanization and foaming, molding:

[0049] The weighing error is ±0.05g. The vulcanizing foaming machine pressure setting is 150-180kg / cm². 2 Machine temperature: 180-185℃; the granules vulcanize in the machine mold (mold ratio: 1:1.85) for 550-600 seconds, and after natural cooling for 20-30 minutes, the semi-finished shoe sole is obtained. The length is compared (error ±3MM), and the weight is checked (error ±4g).

[0050] (6) Polishing of semi-finished products:

[0051] After comparing and verifying the semi-finished product with the sample, use a cloth wheel to remove the surface skin and impurities.

[0052] (7) Secondary vulcanization and molding:

[0053] After secondary vulcanization and molding, the mold (mold ratio: 1:1.005) is heated to 175±5℃ and held for 600s to allow the sole to be fully vulcanized again. After cooling for 550s and removing the molded sole, an ultra-lightweight, highly elastic and wear-resistant (please provide the wear data of the sole) finished sole is obtained.

[0054] This invention uses four embodiments to optimize the components, and the specific raw material components are as follows:

[0055]

[0056]

[0057] The resulting shoe soles were tested using GB21536-2008, a common method in the footwear material industry. The test results are as follows:

[0058] Test content Example 1 Example 2 Example 3 Example 4 <![CDATA[Density (Mg / cm 3 )]]> 0.13 0.11 0.115 0.111 Compression deformation (%) 33 28 25 19

[0059] While specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments described are merely illustrative and not intended to limit the scope of the present invention. Equivalent modifications and variations made by those skilled in the art in accordance with the spirit of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A lightweight, highly elastic EVA shoe sole, characterized in that: The raw material consists of the following components: 60 EVA 20 copies of POE 12.5 parts of EPDM rubber 0.45 parts crosslinking agent 6.5 parts foaming agent 0.55 parts lubricant; The EVA is EVA 7350. The POE is POE 8150. The EPDM rubber is EPDM 3745. The lubricant is stearic acid. The crosslinking agent is DCP; The preparation method of the lightweight, high-elastic EVA shoe sole is as follows: (1) Internal mixing mixture: Set the internal mixer temperature to 80±1℃; put EVA7350, POE8150, EPDM3745 and stearic acid into the heating cylinder of the internal mixer and mix them. Press the heating cylinder with 6-8KG air pressure. When the temperature rises to the range of 85±1℃-95±1℃, turn the material over once every 5℃ increase in temperature. When the internal mixer temperature reaches 95±1℃, pour in the foaming agent and odorless crosslinking agent DCP, and press the material into the heating cylinder with 6-8KG air pressure. When the internal mixer temperature rises from 95±1℃ to 100±1℃, the material is turned over 3 times. When the set temperature of 100±1℃ is reached, the material is discharged. (2) Open milling and tableting: The temperature of the open mill roller table is set to 65±5℃ and the roller spacing is 6-8mm. The temperature of the open mill roller table is kept at 65±5℃. The material from step 1 is pressed into a sheet by the open mill rollers. The sheet is then pressed three more times by the rollers. (3) Granulation: Set the temperature of the granulator: the die head temperature is 85±5℃, the first stage of electric heating is 80±5℃, the second stage of electric heating is 80±5℃, the third stage of electric heating is 80±5℃, and the fourth stage of electric heating is 80±5℃; set the pelletizing speed: the spindle speed is 40-45 rpm, and the cutter speed is 15-25 rpm; granulate the sheet made in step (2) through a fan and a vibrating screen, a press and a pelletizer, and make particles of the size of a trapezoid. (4) Cooling and settling of the granules: The granules are diverted to the mixing tank via a vibrating screen. The cooling circulating water in the mixing tank is turned on, and the mixture is stirred for 25-30 minutes. After the temperature of the granules drops to 50℃, the material is discharged and allowed to stand for more than 24 hours. (5) Weighing materials, vulcanization and foaming, molding: The weighing error is ±0.05g, and the vulcanizing foaming machine pressure is set at 150-180kg / cm². 2 Machine temperature: 180-185℃; the granules are vulcanized in the mold of the machine with a mold ratio of 1:1.85 for 550-600 seconds, and after natural cooling for 20-30 minutes, the semi-finished shoe sole is obtained. The length is compared with the template according to an error of ±3MM, and the weight is checked according to an error of ±4g. (6) Polishing of semi-finished products: After comparing and verifying the semi-finished product with the sample, use a cloth wheel to remove the surface skin and impurities. (7) Secondary vulcanization and molding: After secondary vulcanization and molding, the mold ratio is 1:1.005, the temperature is 175±5℃, and the holding time is 600s, so that the sole can be fully vulcanized again. After cooling for 550s, the ultra-lightweight, high-elasticity and wear-resistant sole is obtained.

2. A method for preparing a lightweight, high-elasticity EVA shoe sole as described in claim 1, characterized in that: Includes the following steps: (1) Internal mixing mixture: Set the internal mixer temperature to 80±1℃; put EVA7350, POE8150, EPDM3745 and stearic acid into the heating cylinder of the internal mixer and mix them. Press the heating cylinder with 6-8KG air pressure. When the temperature rises to the range of 85±1℃-95±1℃, turn the material over once every 5℃ increase in temperature. When the internal mixer temperature reaches 95±1℃, pour in the foaming agent and odorless crosslinking agent DCP, and press the material into the heating cylinder with 6-8KG air pressure. When the internal mixer temperature rises from 95±1℃ to 100±1℃, the material is turned over 3 times. When the set temperature of 100±1℃ is reached, the material is discharged. (2) Open milling and tableting: The temperature of the open mill roller table is set to 65±5℃ and the roller spacing is 6-8mm. The temperature of the open mill roller table is kept at 65±5℃. The material from step 1 is pressed into a sheet by the open mill rollers. The sheet is then pressed three more times by the rollers. (3) Granulation: Set the temperature of the granulator: the die head temperature is 85±5℃, the first stage of electric heating is 80±5℃, the second stage of electric heating is 80±5℃, the third stage of electric heating is 80±5℃, and the fourth stage of electric heating is 80±5℃; set the pelletizing speed: the spindle speed is 40-45 rpm, and the cutter speed is 15-25 rpm; granulate the sheet made in step (2) through a fan and a vibrating screen, a press and a pelletizer, and make particles of the size of a trapezoid. (4) Cooling and settling of granules: The granules are diverted to the mixing tank via a vibrating screen. The cooling circulating water in the mixing tank is turned on, and the mixture is stirred for 25-30 minutes. After the temperature of the granules drops to 50℃, the material is discharged and allowed to stand for more than 24 hours. (5) Weighing materials, vulcanization and foaming, molding: The weighing error is ±0.05g. The vulcanizing foaming machine pressure setting is 150-180kg / cm². 2 Machine temperature: 180-185℃; the granules are vulcanized in the mold of the machine with a mold ratio of 1:1.85 for 550-600 seconds, and after natural cooling for 20-30 minutes, the semi-finished shoe sole is obtained. The length is compared with the template according to an error of ±3MM, and the weight is checked according to an error of ±4g. (6) Polishing of semi-finished products: After comparing and verifying the semi-finished product with the sample, use a cloth wheel to remove the surface skin and impurities. (7) Secondary vulcanization and molding: After secondary vulcanization and molding, the mold ratio is 1:1.005, the temperature is 175±5℃, and the holding time is 600s, so that the sole can be fully vulcanized again. After cooling for 550s, the ultra-lightweight, high-elasticity and wear-resistant sole is obtained.

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