EVA secondary MD shoe insole formula and production process

Abstract

The invention relates to an EVA secondary MD shoe insole formula and a production process. The formula comprises main materials of EVA 6110, POE 8003 and TPEE and auxiliary agents of stearic acid, a cross-linking agent and the like. According to the technology, through two times of vulcanization (first-stage foaming crosslinking, second-stage deep crosslinking and bottom sheet fusion) and gradient temperature control material preparation, the produced shoe insole is high in rebound rate, small in compression deformation and light in specific gravity, and the problems that a traditional insole is insufficient in elasticity and large in specific gravity are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a shoe midsole formula and production process. BACKGROUND

[0002] The shoe midsole is a functional interlayer structure between the upper and the outsole, and is the core functional component of the sole, which can buffer the impact force of the ground to protect the joints of the foot, provide elastic feedback to improve the efficiency of movement, maintain the arch support and gait stability. However, the existing shoe midsole has the following defects: 1. Low resilience and fast decay, which cannot meet the energy feedback needs of high-intensity sports scenarios. 2. Large compression deformation, which leads to permanent deformation of the shoe midsole after repeated compression, resulting in "collapse" and "soft collapse" phenomenon, affecting the supportability and service life of the shoe. 3. Large specific gravity, insufficient lightweight, poor wearing comfort, and heavy shoe midsole increases the burden on the foot and reduces the wearing comfort, especially not meeting the lightweight requirements of running shoes and sports shoes. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide an EVA secondary MD shoe midsole formula and production process, so that the prepared shoe midsole has excellent properties of lightweight, high elasticity and fatigue resistance, and solves the problems of insufficient elasticity and large specific gravity of traditional midsoles.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: The EVA secondary MD shoe midsole formula comprises a main material and an additive, and is characterized in that: The main material comprises 35kg - 45kg of EVA6110, 20kg - 30kg of POE8003, and 20kg - 30kg of TPEE. The additive comprises 0.2kg - 0.4kg of stearic acid, 0.4kg - 0.6kg of zinc stearate, 0.8kg - 1.2kg of zinc oxide, 0.4kg - 0.6kg of odorless crosslinking agent, and 4.0kg - 5.0kg of AC foaming agent.

[0005] EVA (ethylene-vinyl acetate copolymer) is the basic material of the shoe midsole, and the model 6110 refers to a "VA" content of 25%-28%, with good foaming performance and processing fluidity. EVA6110 (35kg-45kg) as the main material framework provides basic elasticity, flexibility and processing adaptability for the shoe midsole, with the highest proportion (35%-45%) of the total amount, directly affecting the stability and cost control of the shoe midsole. POE (polyolefin elastomer) is a copolymer of ethylene and alpha-olefin, and the model 8003 is a low-crystallinity elastomer with excellent low-temperature elasticity and weather resistance. After mixing POE8003 with EVA6110, the elasticity and deformation resistance of the shoe midsole can be greatly improved, and by adjusting the amount (20%-30%), the hardness of the shoe midsole can be moderate, avoiding the "soft collapse" of pure EVA foaming material. TPEE (thermoplastic polyester elastomer) is a block copolymer of rigid and flexible chain segments, with high resilience, fatigue resistance and high temperature stability. After mixing with EVA and POE, the resilience and compression deformation of the midsole can be significantly improved, and the aging of the shoe midsole can be delayed. Stearic acid is a fatty acid lubricant, and zinc stearate is a metal soap lubricant and release agent. After mixing stearic acid and zinc stearate, the melt viscosity can be reduced, the processing fluidity can be improved, and the sticking or scorching during mixing can be prevented; zinc stearate can also activate the crosslinking agent, improving the vulcanization efficiency. Zinc oxide is an inorganic oxide, which is used as a vulcanization activator and crosslinking promoter. It reacts with odorless crosslinking agent (such as DCP) to generate active intermediates, accelerates the crosslinking reaction of EVA molecular chain, improves the crosslinking density, and ensures the structural strength and compression resistance of the shoe midsole. Odorless crosslinking agent is a modified product of dicumyl peroxide (DCP), with a decomposition temperature of 120°C-140°C, high crosslinking efficiency and no irritating odor. Odorless crosslinking agent can initiate the crosslinking reaction of EVA, POE and TPEE molecular chains, form a three-dimensional network structure, convert linear molecules into bulk structures, and improve the elastic modulus and tear strength of the shoe midsole. AC foaming agent (azodicarbonamide) has a decomposition temperature of 160-200°C and produces a large amount of nitrogen gas, resulting in uniform cell structure, controlled foaming ratio, reduced shoe midsole specific gravity, and light weight while maintaining elasticity. In summary, the formula realizes the advantages of "light weight, high elasticity and fatigue resistance" of the shoe midsole by optimizing the selection and ratio of raw materials, solving the problems of "insufficient elasticity" and "excessive specific gravity" of traditional EVA shoe midsoles.

[0006] The production process of the EVA secondary MD shoe midsole, characterized by comprising the following steps, S1: preparing an injection mold for injection molding of the shoe midsole and foaming material made of the EVA secondary MD shoe midsole formula of claim 1; S2: clean the oil stains and impurities on the surfaces of the shoe midsole involved in the injection molding, and preheat the injection mold to 125-135°C by electromagnetic induction heating furnace; S3: quickly pour the foaming material into the forming cavity of the injection mold, and then close the mold; S4: start the equipment and perform one-stage vulcanization treatment; S5: after opening the mold, take out the one-stage shoe midsole within two seconds and place it flat for setting, and the adjacent one-stage shoe midsoles should not be overlapped; S6: remove the skin, hold the one-stage shoe midsole with the left hand, and use a cloth wheel polisher with a rotation speed of 1500-2000r / min to lightly sweep the one-stage shoe midsole, and roughen and smooth the skin on the bottom periphery; S7: prepare the insole under each shoe midsole to form a two-stage shoe midsole, and blow clean the two-stage shoe midsole with an air gun; S8: place the two-stage shoe midsole into the injection mold and press tightly to close the mold, and push it into the machine hole for heating and cooling setting; S9: perform two-stage vulcanization treatment, automatically open the mold and take out the shoe midsole, and place the shoe midsole into the freezer for cooling; S10: take out the shoe midsole from the freezer, and take the shoe midsole from front to back, and then straighten and set the shoe midsole after taking it out; S11: after inspection and examination, pack according to the standard requirements.

[0007] By adopting the above technical scheme, the process adopts "two-stage vulcanization", the first vulcanization realizes foaming and crosslinking, and the second vulcanization realizes deep crosslinking and fusion of the insole and the one-stage shoe midsole, so that the finally produced shoe midsole has excellent properties of high resilience, low deformation and fatigue resistance. This process innovation prolongs the service life of the EVA two-stage MD shoe midsole in the sports scene, and at the same time meets the multifunctional requirements of lightness, high elasticity and wear resistance.

[0008] The production process of the above-mentioned EVA two-stage MD shoe midsole can be further set as follows: the one-stage vulcanization treatment in step S4 includes the following contents, The set value of the material amount of the left mold is 222.0g, the injection time of the left mold is 19.0s, the injection speeds of the first to fifth stages of the left mold are 75%, 70%, 60%, 55% and 50% respectively, and the pressures of the first to fifth stages of the left mold are 100bar, 95bar, 90bar, 85bar and 80bar respectively; The set value of the material amount of the right mold is 300.0g, the injection time of the right mold is 26.6s, the injection speeds of the first to fifth stages of the right mold are 60%, 55%, 50%, 45% and 40% respectively, and the pressures of the first to fifth stages of the right mold are 100bar, 95bar, 90bar, 85bar and 80bar respectively.

[0009] With the above technical solution, the one-stage vulcanization realizes the dynamic balance of precise feeding, uniform foaming and preliminary crosslinking through the regulation of feeding amount, time, speed and pressure to match the filling needs of different cavity volumes. The left mold is set to a feeding amount of 222.0 g and an injection time of 19.0 s, and through the stepwise decrease of the five-stage injection speed and pressure, the mold cavity is first filled quickly at high speed and high pressure to avoid cold material blockage, and then the speed and pressure are gradually reduced to reduce the melt turbulence and prevent bubble generation. The right mold is set to a feeding amount of 300.0 g and an injection time of 26.6 s, and a lower initial speed and pressure are adopted to ensure the slow flow of the melt in the large-volume cavity and sufficient exhaust, avoiding the problems of air trapping or material shortage caused by too fast filling. The melt front is stably advanced, the nitrogen gas generated by the decomposition of the foaming agent is uniformly distributed in the EVA matrix in the early crosslinking stage, and a closed-cell structure with a pore size of 50-100 μm is formed, laying a uniform cell foundation for subsequent secondary vulcanization.

[0010] The production process of the EVA secondary MD shoe midsole described above can be further set as follows: the two-stage vulcanization treatment in step S9 includes the following contents, the vulcanization time is 420 s, the vulcanization temperature is 125-135°C, and the vulcanization pressure is 40-50 bar.

[0011] With the above technical solution, the secondary vulcanization needs to complete the interfacial molecular diffusion of the semi-finished product and the bottom sheet and the deep crosslinking of EVA / POE / TPEE. The time of 420 s ensures that the crosslinking agent is fully decomposed and initiates molecular chain crosslinking, avoiding incomplete crosslinking due to insufficient time. 125-135°C is the best decomposition temperature interval of EVA crosslinking agent, at this temperature, the decomposition rate of the crosslinking agent is moderate (avoiding too fast decomposition at high temperature leading to "scorching"), and at the same time, the TPEE flexible chain segment (melting point about 160°C) is in a high-elastic state, which can fully move and entangle with the EVA / POE molecular chain segment, improving the integrity of the elastic network, and the shoe midsole has high rebound rate.

[0012] The production process of the EVA secondary MD shoe midsole described above can be further set as follows: the foaming material prepared from the EVA secondary MD shoe midsole formula of claim 1 in step S1 includes the following steps, F1: mixing in an internal mixer, sequentially adding 35-45 kg of EVA6110, 20-30 kg of POE8003, and 20-30 kg of TPEE into the internal mixer; then adding 0.2-0.4 kg of stearic acid, 0.4-0.6 kg of zinc stearate, 0.8-1.2 kg of zinc oxide, 0.4-0.6 kg of odorless crosslinking agent, and 4.0-5.0 kg of AC foaming agent; F2: Stepwise temperature control mixing, after the temperature of the internal mixer is raised to 85℃, the first mixing is carried out, lasting for 15 minutes; then the temperature of the internal mixer is raised to 95℃, the second mixing is carried out, lasting for 10 minutes; then the temperature of the internal mixer is raised to 105℃, the third mixing is carried out, lasting for 8 minutes; then the temperature of the internal mixer is raised to 115℃, the fourth mixing is carried out, lasting for 12 minutes; then the temperature of the internal mixer is raised to 120℃, the fifth mixing is carried out, lasting for 15 minutes, and then the material is discharged; F3: roll pressing by an open mill, the mixed material prepared in F2 is roll pressed by the open mill, the roller temperature is 60-70℃; the roller gap is controlled, the roller gap is adjusted to 8-10mm for the first time, the mixed material is roll pressed into uniform sheet; the gap is adjusted to 0.3-0.5mm for the second time, the sheet thickness is uniform and has no bubbles; the gap is adjusted to 6-8mm for the third time, the re-mixing enhances the uniformity of the material; the fourth roll pressing: the gap is kept at 6-8mm, the dispersion degree of the mixed material is ensured to be greater than or equal to 95%, and there is no visible particle; F4: granulation by a granulator, firstly, the parameters of the granulator are set, the first section is heated to 85±5℃, the second section is heated to 90±5℃, the third section is heated to 95±5℃, and the fourth section is heated to 100±5℃; the die temperature is 105℃; the cold water circulation and air cooling system are started; secondly, the sheet after roll pressing in F3 is put into the granulator, and cylindrical granules with a diameter of 3-5mm are prepared; F5: the granules after granulation are sent into a cooling conveying belt through a vibrating screen to remove broken granules, and the granules after cooling are packaged.

[0013] By adopting the above technical scheme, step F2 adopts 85-120℃ stepwise temperature control and five times of mixing, so that the raw materials are fully dispersed, and the crosslinking agent and the foaming agent are prevented from reacting too early; step F3 is roll pressed by the open mill in four stages, so that the bubbles and particles are eliminated by strong shear force, and uniform sheet is formed; steps F4-F5 are cooled by the gradient temperature control, cold water and air cooling of the granulator, so that the stability of the granules is ensured, and finally the foaming material is prepared for the subsequent two times of injection molding vulcanization, so that the shoe midsole prepared has the advantages of light weight, high elasticity and fatigue resistance.

[0014] The beneficial effects of the present application are as follows: I. TPEE and POE composite elastic system, and two times of vulcanization, the rebound rate is greatly improved, the compression deformation is small, and it is better than the traditional MD shoe midsole.

[0015] II. The foaming ratio of AC foaming agent is accurately controlled, and the two times of vulcanization densifies the bubbles, and the specific gravity of the finished product is reduced, which is more than 20% lighter than the traditional EVA midsole.

[0016] III. The two times of vulcanization strengthens the bottom sheet and combines with the one-stage shoe midsole, and the TPEE fatigue resistance characteristics increase the compression resistance of the shoe midsole, and prolong the service life in the sports scene.

[0017] It should be noted that "MD" mentioned in this invention is an abbreviation for midsole.

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 These are schematic diagrams of the production process of Embodiments 2 and 4 of the present invention; Figure 2 These are exploded schematic diagrams of the injection molds in Embodiments 2 and 4 of the present invention; Figure 3 This is a schematic diagram of the shoe midsole structure that can be produced according to Embodiments 2 and 4 of the present invention. Figure 1 ; Figure 4 This is a schematic diagram of the shoe midsole structure that can be produced according to Embodiments 2 and 4 of the present invention. Figure 2 . Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: 1. EVA secondary MD shoe midsole formula, including main materials and additives, The main ingredients include 40kg of EVA6110, 25kg of POE8003, and 25kg of TPEE; The additives include 0.3 kg of stearic acid, 0.5 kg of zinc stearate, 1.0 kg of zinc oxide, 0.5 kg of odorless crosslinking agent, and 4.5 kg of AC foaming agent.

[0022] Example 2: Figure 1 The manufacturing process of the EVA secondary MD shoe midsole shown includes the following steps: S1: Prepare materials for injection-molded shoe midsoles, such as... Figure 2 The injection mold shown is made of foam material prepared using the EVA secondary MD shoe midsole formula of Example 1; The preparation process of foamed rice is as follows: F1: Mixing in an internal mixer. 40kg of EVA6110, 25kg of POE8003, 25kg of TPEE, 0.3kg of stearic acid, 0.5kg of zinc stearate, 1.0kg of zinc oxide, 0.5kg of odorless crosslinking agent, and 4.5kg of AC foaming agent are added to the internal mixer in sequence. F2: Stepwise temperature control mixing, after heating the internal mixer to 85°C, the first material turning is carried out for 15 minutes; then the internal mixer is heated to 95°C, the second material turning is carried out for 10 minutes; then the internal mixer is heated to 105°C, the third material turning is carried out for 8 minutes; then the internal mixer is heated to 115°C, the fourth material turning is carried out for 12 minutes; then the internal mixer is heated to 120°C, the fifth material turning is carried out for 15 minutes, and then the material is discharged; F3: Roller pressing of the open mill, the mixed material prepared in F2 is pressed by the open mill, the roller temperature is 65°C; the roller gap is controlled, the roller gap is adjusted to 9mm for the first time, the mixed material is pressed into uniform sheet; the gap is adjusted to 0.4mm for the second time, the sheet thickness is uniform and has no bubbles; the gap is adjusted to 7mm for the third time to improve the uniformity of the re-mixed material; the fourth roller pressing: the gap is kept at 7mm to ensure that the dispersion degree of the mixed material is ≥95% and there is no visible particle; F4: Granulator granulation, first, set the parameters of the granulator, the first section is heated to 85°C, the second section is heated to 90°C, the third section is heated to 95°C, and the fourth section is heated to 100°C; the die temperature is 105°C; turn on the cold water circulation and air cooling system; secondly, put the sheet after roller pressing in F3 into the granulator to prepare cylindrical granules with a diameter of 3-5mm; F5: The granules after granulation are removed by a vibrating screen, sent to a cooling conveyor, air-cooled to 45°C, and the cooled granules are packaged.

[0023] S2: Clean the oil stains and impurities on the surfaces of the shoe midsole involved in injection molding, preheat the injection mold to 130°C by electromagnetic induction heating furnace; S3: Pour the foaming material into the forming cavity of the injection mold, and then close the mold; S4: Start the equipment and perform one-stage vulcanization treatment; The set value of the material amount of the left mold is 222.0g, the injection time of the left mold is 19.0s, the injection speed of the first to fifth sections of the left mold is 75%, 70%, 60%, 55%, and 50% respectively, and the pressure of the first to fifth sections of the left mold is 100bar, 95bar, 90bar, 85bar, and 80bar respectively; The set value of the material amount of the right mold is 300.0g, the injection time of the right mold is 26.6s, the injection speed of the first to fifth sections of the right mold is 60%, 55%, 50%, 45%, and 40% respectively, and the pressure of the first to fifth sections of the right mold is 100bar, 95bar, 90bar, 85bar, and 80bar respectively.

[0024] S5: After the mold is opened, take out the one-stage shoe midsole and place it to be shaped within two seconds, and the adjacent one-stage shoe midsoles cannot be overlapped and placed; S6: remove the skin, left hand holding a stage shoe midsole, right hand auxiliary speed 1750r / min cloth wheel polisher will be a stage shoe midsole mouth light sweep, the bottom of the rough circle of the skin, clean; S7: under each shoe midsole with the bottom, thus constituting a two-stage shoe midsole, with air gun clean two-stage shoe midsole; S8: the two-stage shoe midsole into the injection mold as Figure 2 shown, and make a tight pressure to close the mold, push into the machine hole heating and cooling; S9: two-stage vulcanization, two-stage vulcanization in step S9 includes the following content, vulcanization time is 420s, vulcanization temperature 130°C, vulcanization pressure 45bar.

[0025] Automatic mold opening and take out the shoe midsole, the shoe midsole into the freezer to cool; S10: take out the shoe midsole from the freezer, take the shoe from front to back, the shoe midsole needs to be taken out and need to be right, shaping; S11: product inspection, check qualified, according to the standard requirements of packing.

[0026] Example one formula combined with the production process of example two, the shoe midsole has the core advantages of high resilience (70%±2%), low compression deformation (≤38%), lightweight (specific gravity 0.11±0.01g / cm³), two vulcanization and dense pore structure guarantee the fatigue resistance, at the same time, environmental protection, no odor, size stable, suitable for running shoes and other sports scenes, solve the problem of traditional EVA midsole elasticity, specific gravity.

[0027] Example three: EVA two MD shoe midsole formula, including main material and auxiliary agent, The main material includes 38kg of EVA6110, 23kg of POE8003, 28kg of TPEE; Auxiliary agent includes 0.25kg of stearic acid, 0.45kg of zinc stearate, 0.9kg of zinc oxide, 0.45kg of odorless crosslinking agent, 4.8kg of AC foaming agent.

[0028] Example four: the production process of EVA two MD shoe midsole as Figure 1 shown, including the following steps, S1: prepare the injection mold for injection molding shoe midsole as Figure 2 shown, foaming material prepared by the EVA two MD shoe midsole formula of example three; The preparation process of foaming material is as follows: F1: mixing in an internal mixer, 8 kg of EVA6110, 23 kg of POE8003, 28 kg of TPEE, 0.25 kg of stearic acid, 0.45 kg of zinc stearate, 0.9 kg of zinc oxide, 0.45 kg of odorless crosslinking agent, 4.8 kg of AC foaming agent were sequentially put into the internal mixer; F2: mixing by controlling temperature in stages, after the internal mixer was heated to 85°C, the first mixing was carried out, lasting for 15 minutes; then the internal mixer was heated to 95°C, the second mixing was carried out, lasting for 10 minutes; then the internal mixer was heated to 105°C, the third mixing was carried out, lasting for 8 minutes; then the internal mixer was heated to 115°C, the fourth mixing was carried out, lasting for 12 minutes; then the internal mixer was heated to 120°C, the fifth mixing was carried out, lasting for 15 minutes, and then the material was discharged; F3: roller pressing in an open mill, the material prepared in F2 was roller pressed in an open mill, the roller temperature was 68°C; the roller gap was controlled, the roller gap was first adjusted to 9.5 mm, the material was roller pressed into uniform thin sheets; the gap was secondly adjusted to 0.35 mm, the thickness of the sheets was uniform and had no bubbles; the gap was thirdly adjusted to 7.5 mm, the uniformity of the material was enhanced by re-mixing; the fourth roller pressing: the gap was kept at 7.5 mm, the dispersion of the material was ensured to be ≥95%, and there were no visible particles; F4: granulation in a granulator, first, the parameters of the granulator were set, the first section was heated to 80°C, the second section was heated to 85°C, the third section was heated to 90°C, and the fourth section was heated to 95°C; the die temperature was 105°C; the cold water circulation and air cooling system were turned on; secondly, the sheets after roller pressing in F3 were put into the granulator, and cylindrical granules with a diameter of 3-5 mm were prepared; F5: the granules after granulation were sent to a cooling conveyor belt through a vibrating screen to remove broken granules, and the cooled granules were packaged after cooling to below 40°C.

[0029] S2: clean the oil stains and impurities on the surfaces of the shoe midsole involved in injection molding, preheat the injection mold to 132°C by electromagnetic induction heating furnace; S3: quickly pour the foaming material into the molding cavity of the injection mold, and then close the mold; S4: start the equipment and perform one-stage vulcanization treatment; The set value of the material amount of the left mold was 222.0 g, the injection time of the left mold was 19.0 s, the injection speed of the first to fifth sections of the left mold was 75%, 70%, 60%, 55%, and 50% respectively, and the pressure of the first to fifth sections of the left mold was 100 bar, 95 bar, 90 bar, 85 bar, and 80 bar respectively; The right mold material setting value is 300.0 g, the right mold injection time is 26.6 s, the right mold injection speed of the first to fifth sections is 60%, 55%, 50%, 45%, and 40% respectively, and the pressure of the first to fifth sections of the right mold is 100 bar, 95 bar, 90 bar, 85 bar, and 80 bar respectively.

[0030] S5: After the mold is opened, the one-stage shoe insole is taken out within two seconds and placed flat for setting, and the adjacent one-stage shoe insole cannot be overlapped and placed; S6: Skin removal, left hand holding one-stage shoe insole, right hand assisting with a speed of 1900 r / min cloth polishing machine to lightly sweep the one-stage shoe insole mold port, roughening the skin on the bottom periphery to be round and smooth and clean; S7: Prepare the bottom sheet under each shoe insole to form a two-stage shoe insole, and blow clean the two-stage shoe insole with an air gun; S8: Place the two-stage shoe insole into the injection mold as shown in Figure 2 , and tightly press to close the mold, and push into the machine hole for heating and cooling setting; S9: Perform two-stage vulcanization treatment, which includes the following contents, vulcanization time is 420 s, vulcanization temperature is 132°C, and vulcanization pressure is 48 bar.

[0031] Automatic mold opening and shoe insole taking out, placing the shoe insole into the freezer for cooling; S10: Take out the shoe insole from the freezer, and take the shoe insole from front to back when taking out, and need to be straightened and set after taking out; S11: After inspection and examination, pack according to the standard requirements.

[0032] The shoe insole prepared by the formula of Example Three combined with the process of Example Four has the core advantages of super-high rebound (72%±3%), ultra-low compression deformation (≤35%), and extreme lightweight (specific gravity 0.105±0.005 g / cm³), realizes dispersion ≥98%, cell diameter 40-60 μm, and dense cell wall with 48 bar vulcanization pressure, dynamic fatigue resistance up to 180,000 times, and also has the advantages of low temperature elasticity (-20°C) (rebound rate ≥65%), and size shrinkage rate ≤0.3%.

[0033] Compared with Example 2, the following differences exist in Example 4: the amount of TPEE in the formulation of Example 4 is increased by 3 kg to improve the elasticity of the shoe midsole, the amount of AC foaming agent is increased by 0.3 kg to improve the foaming ratio, and the amounts of EVA and POE are each reduced by 2 kg to further improve the elasticity. The vulcanization temperature and pressure of Example 4 are both higher than those of Example 2, which can promote deep crosslinking, the roller spacing is smaller, the cloth wheel speed is faster, and the granulation temperature is lower, thereby improving the dispersion uniformity and avoiding the premature activation of the foaming agent. In summary, the shoe midsole produced in Example 4 is superior to that of Example 2 in terms of resilience, lightweight, and fatigue resistance, and is more suitable for high-end sports shoes, while Example 2 focuses more on the balance between cost and performance and is suitable for mass leisure shoes or entry-level sports shoes.

Claims

1. An EVA secondary MD shoe midsole formula, comprising a main material and an additive, characterized in that: the main material comprises 35-45 kg of EVA6110, 20-30 kg of POE8003, and 20-30 kg of TPEE; and the additive comprises 0.2-0.4 kg of stearic acid, 0.4-0.6 kg of zinc stearate, 0.8-1.2 kg of zinc oxide, 0.4-0.6 kg of odorless crosslinking agent, and 4.0-5.0 kg of AC foaming agent.

2. A production process of an EVA secondary MD shoe midsole, comprising the following steps, S1: preparing an injection mold for injection molding of a shoe midsole and foaming material made of the EVA secondary MD shoe midsole formula according to claim 1; S2: cleaning the oil stains and impurities on the surfaces of the injection mold involved in injection molding of the shoe midsole, and preheating the injection mold to 125-135°C by electromagnetic induction heating furnace; S3: quickly pouring the foaming material into the forming cavity of the injection mold, and then closing the mold; S4: starting the equipment and performing one-stage vulcanization treatment; S5: after opening the mold, taking out the one-stage shoe midsole within two seconds and placing it flat for setting, and the adjacent one-stage shoe midsoles cannot be overlapped; S6: removing the skin, using a left hand to hold the one-stage shoe midsole and a right hand to assist in polishing the one-stage shoe midsole with a cloth wheel polisher at a speed of 1500-2000 r / min to lightly sweep the one-stage shoe midsole, and roughening and smoothing the skin on the bottom periphery; S7: placing the bottom sheet under each shoe midsole to form a two-stage shoe midsole, and blowing the two-stage shoe midsole clean with an air gun; S8: placing the two-stage shoe midsole into the injection mold and tightly pressing it to close the mold, and pushing it into the machine hole for heating and cooling setting; S9: performing two-stage vulcanization treatment, automatically opening the mold and taking out the shoe midsole, and placing the shoe midsole into a freezer for cooling; S10: taking out the shoe midsole from the freezer, and taking the shoe midsoles from front to back, and straightening and setting the shoe midsoles after taking them out; S11: after inspection and examination, packing according to the standard requirements. The one-stage vulcanization treatment in step S4 includes the following contents, the set value of the material amount of the left mold is 222.0 g, the injection time of the left mold is 19.0 s, the injection speeds of the first to fifth stages of the left mold are 75%, 70%, 60%, 55%, and 50% respectively, and the pressures of the first to fifth stages of the left mold are 100 bar, 95 bar, 90 bar, 85 bar, and 80 bar respectively; 3. The process for producing an EVA secondary MD shoe midsole according to claim 2, characterized by: the set value of the material amount of the right mold is 300.0 g, the injection time of the right mold is 26.6 s, the injection speeds of the first to fifth stages of the right mold are 60%, 55%, 50%, 45%, and 40% respectively, and the pressures of the first to fifth stages of the right mold are 100 bar, 95 bar, 90 bar, 85 bar, and 80 bar respectively. The two-stage vulcanization treatment in step S9 includes the following contents, the vulcanization time is 420 s, the vulcanization temperature is 125-135°C, and the vulcanization pressure is 40-50 bar. ​ 4. The process for producing an EVA secondary MD shoe midsole according to claim 2, characterized in that: ​ 5. The process for producing EVA secondary MD shoe midsole according to claim 2, characterized in that: The foamed material made of the EVA secondary MD shoe midsole formula of claim 1 in step S1 comprises the following steps, F1: mixing in an internal mixer, 35kg - 45kg of EVA6110, 20kg - 30kg of POE8003, and 20kg - 30kg of TPEE are sequentially added into the internal mixer; then 0.2kg - 0.4kg of stearic acid, 0.4kg - 0.6kg of zinc stearate, 0.8kg - 1.2kg of zinc oxide, 0.4kg - 0.6kg of odorless crosslinking agent, and 4.0kg - 5.0kg of AC foaming agent are added; F2: temperature-controlled mixing in stages, after the internal mixer is heated to 85℃, the first mixing is performed for 15 minutes; then the internal mixer is heated to 95℃, the second mixing is performed for 10 minutes; then the internal mixer is heated to 105℃, the third mixing is performed for 8 minutes; then the internal mixer is heated to 115℃, the fourth mixing is performed for 12 minutes; then the internal mixer is heated to 120℃, the fifth mixing is performed for 15 minutes, and then the material is discharged; F3: roll pressing in an open mill, the mixed material made in F2 is roll pressed in an open mill, the roll temperature is 60 - 70℃; the roll gap is controlled, the roll gap is first adjusted to 8 - 10mm, the mixed material is roll pressed into uniform sheets; the gap is secondly adjusted to 0.3 - 0.5mm, the sheet thickness is uniform and free of bubbles; the gap is thirdly adjusted to 6 - 8mm, the material uniformity is enhanced by re-mixing; the fourth roll pressing: the gap is kept at 6 - 8mm, the dispersion degree of the mixed material is ≥95%, and no visible particles are present; F4: granulation in a granulator, first, the parameters of the granulator are set, the first electric heating section is 85±5℃, the second section is 90±5℃, the third section is 95±5℃, and the fourth section is 100±5℃; the die temperature is 105℃; the cold water circulation and air cooling system are turned on; secondly, the sheets after roll pressing in F3 are put into the granulator to obtain cylindrical granules with a diameter of 3 - 5mm; F5: the granules after granulation are sent to a cooling conveyor through a vibrating screen to remove broken granules, and the granules after cooling to below 50℃ are packaged.

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