EVA supercritical foaming shock-absorbing material and preparation process thereof

Abstract

The invention discloses an EVA supercritical foaming shock-absorbing material and a preparation process thereof, and relates to the technical field of high polymer materials, the preparation process comprises the following steps: preparing and premixing raw materials, injecting a supercritical foaming agent for primary foaming, adding an intelligent cross-linking agent for cross-linking reaction, further foaming and shaping, and pressing and molding in a mold to obtain the EVA supercritical foaming shock-absorbing material. The method has the advantages that the self-repairing polymer containing the dynamic covalent bonds is prepared, the dynamic covalent bonds of the self-repairing polymer can be reversibly broken and recombined when the material is damaged to cause cell breakage and the like, and the self-repairing polymer can be used as a self-repairing material for the slippers, so that the service life of the slippers is prolonged, and the service life of the slippers is prolonged. The shock-absorbing material has the advantages that damaged parts are automatically repaired, so that the integrity of the material is recovered, the material is guaranteed to have good shock-absorbing performance all the time in the long-term use process, lasting and stable shock-absorbing protection is provided for shoes, and the problems of poor shock-absorbing stability and insufficient shock-absorbing durability of a traditional material are solved.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to an EVA supercritical foaming shock-absorbing material and a preparation process thereof. Background Art

[0002] In the field of footwear manufacturing, shock-absorbing materials play a key role in improving the comfort and functionality of shoes. Although traditional shock-absorbing materials such as ordinary EVA foam materials have certain shock-absorbing properties, they have many limitations. In terms of shock-absorbing stability, as the number of times the shoes are worn increases and the ambient temperature and humidity fluctuate, the internal pore structure is prone to change, such as pore collapse and material aging, resulting in a significant decrease in shock-absorbing performance and an inability to continuously provide stable cushioning protection for the feet. The existing technology has certain defects. First, the shock absorption stability is poor. With the increase in the number of uses or under different temperature and humidity conditions, the shock absorption performance of the material may decline significantly, and the pores may collapse and the material may age, resulting in the inability to stably perform the shock absorption function under long-term use or in complex environments. Secondly, the shock absorption durability is insufficient. During the daily wear of shock-absorbing shoes, the feet will produce continuous impact force on the soles. With the increase in the number of walking and exercise steps, the shock absorption performance of the soles made of existing EVA supercritical foaming shock-absorbing materials will gradually deteriorate. This is because the pore structure inside the material is prone to pore rupture and merging under repeated stress, and the elastic recovery ability of the material is reduced. For this reason, we propose an EVA supercritical foaming shock-absorbing material and a preparation process thereof. Summary of the invention

[0003] The purpose of the present invention is to provide an EVA supercritical foaming shock-absorbing material and a preparation process thereof.

[0004] In order to solve the problems raised in the above background technology, the present invention provides the following technical solution: a preparation process of an EVA supercritical foaming shock-absorbing material, the preparation process comprising the following specific steps: Step 1: Prepare and premix raw materials. Weigh EVA resin and prepare nano silicon carbide particles. Prepare a polyurethane self-healing polymer containing a disulfide bond using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond. Prepare a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment. Then, put the EVA resin, nano silicon carbide particles, polyurethane self-healing polymer and multifunctional elastomer into a high-speed blender for stirring and premixing. At the same time, add a dispersant zinc stearate for blending and stirring reaction to obtain a premixed material. Step 2: Supercritical foaming agent injection and preliminary foaming: transfer the premixed material to the barrel of the supercritical foaming equipment and seal it, inject supercritical carbon dioxide foaming agent into the barrel, then pressurize and maintain for a period of time for preliminary foaming to form a preliminary cellular structure material; Step 3: Using an intelligent cross-linking agent prepared by chemical cross-linking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropanesulfonic acid, after foaming, the intelligent cross-linking agent is injected into the barrel of the foaming equipment by an injection device, and then the temperature and humidity inside the foaming equipment are controlled to perform a cross-linking reaction. In this process, the intelligent cross-linking agent constructs a dynamically adjustable cross-linking network according to the temperature and humidity, the self-healing polymer is distributed in the pore wall and the material, the nano-silicon carbide strengthens the pore wall, and the multifunctional elastomer improves the elasticity and fatigue resistance of the material, completing the cross-linking and intelligent network construction to obtain a cross-linked foaming material; Step 4: After the cross-linking reaction is completed, the pressure in the foaming equipment is slowly released, and then the foaming and shaping are further carried out under normal pressure for a period of time to basically form the material, and then the formed material is immediately transferred to the slipper mold while hot, and pressure is applied and maintained for a period of time after the mold is closed, so that the material completely fills the mold cavity to obtain a blank in the shape of slippers; Step 5. Take out the slipper blank from the mold, cut and grind it to remove excess scraps and flash to make the appearance of the slippers smoother and flatter, use DC-857 silicone waterproofing agent to coat it to form a waterproof layer, and stick rubber particles on the surface of the sole to enhance the anti-slip performance of the sole.

[0005] As a further solution of the present invention: In the step 1, the process of preparing a polyurethane self-healing polymer containing a disulfide bond by using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond is as follows: under nitrogen protection, 50-60 parts of polypropylene glycol are added to a reactor, vacuum dehydrated at a temperature of 110°C-120°C for 1h-2h, then cooled to 50°C-60°C, 40-50 parts of 4,4'-diphenylmethane diisocyanate are added, Methane diisocyanate is added and reacted at this temperature for 1h-2h, then the temperature is raised to 70℃-80℃ and the reaction is continued for 2h-3h to obtain a prepolymer. Subsequently, 10-15 parts of a diol chain extender containing a disulfide bond is dissolved in a solvent dimethylformamide at 60℃-70℃, and slowly added dropwise to the prepolymer while vigorously stirring. The mixture is reacted at 70℃-80℃ for 3h-4h, and finally a polyurethane self-healing polymer containing a disulfide bond is obtained by precipitation, washing and drying.

[0006] As a further scheme of the present invention: In the step 1, the process for preparing a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment is as follows: 80-100 parts of a polyether thermoplastic polyurethane elastomer are dissolved in an organic solvent, toluene, 5-8 parts of a hindered amine light stabilizer are added, and the mixture is stirred and reacted at 60°C-70°C for 4h-6h, and then the toluene is distilled off to obtain a modified multifunctional elastomer.

[0007] As a further scheme of the present invention: in the step 1, the content of vinyl acetate in the weighed EVA resin is 18%-22%, the particle size of the prepared nano-silicon carbide particles is 20nm-50nm, the amount of the nano-silicon carbide particles added to the high-speed blender is 3%-5% of the mass of the EVA resin, the amount of the self-healing polymer added is 5%-8% of the mass of the EVA resin, the amount of the multifunctional elastomer added is 10%-15% of the mass of the EVA resin, and at the same time, a dispersant zinc stearate with a mass fraction of 1%-2% is added, and the amount of zinc stearate added is 0.5%-1% of the mass of the EVA resin. The temperature of the blender is set to 120°C-150°C, the speed is 800r / min-1200r / min, and the blending time is 1.5h-2.5h.

[0008] As a further solution of the present invention: in the step 2, the amount of foaming agent injected is 8%-12% of the mass of the premixed material, the barrel temperature is set at 160°C-180°C, the pressure is 15MPa-20MPa, and maintained for 5min-8min.

[0009] As a further scheme of the present invention: In the step 3, the specific process of preparing the smart crosslinking agent by chemical crosslinking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropane sulfonic acid is as follows: first add 100-150 parts of deionized water in a reaction container, and under nitrogen protection, heat it to 70°C-80°C, add 30-40 parts of N-isopropylacrylamide and 10-15 parts of acrylic acid in sequence, stir until completely dissolved, add 0.5-1 part of initiator ammonium persulfate, react for 3h-4h, and obtain N-isopropylacrylamide-acrylic acid copolymer solution, then add 20-30 parts of 2-acrylamide-2-methylpropane sulfonic acid to the copolymer solution, and then add 0.3-0.5 parts of crosslinking agent N,N'-methylenebisacrylamide, stir evenly, heat it to 80°C-90°C, and continue to react for 2h-3h to obtain the smart crosslinking agent.

[0010] As a further solution of the present invention: in the step three, the amount of the smart cross-linking agent added is 2%-4% of the mass of the initial pore structure material, the ambient temperature in the foaming equipment is regulated to 130°C-150°C, the humidity is 40%-60%, and the cross-linking reaction is 3h-4h.

[0011] As a further solution of the present invention: in the step 4, after the cross-linking reaction is completed, the pressure in the foaming equipment is slowly released at a rate of 0.2MPa / min-0.5MPa / min, and then maintained at normal pressure for 10min-15min, the mold is closed and a pressure of 5MPa-10MPa is applied, and the pressure is maintained for 3min-5min.

[0012] As a further solution of the present invention: in the step five, rubber particles with a particle size of 2mm-3mm are pasted on the surface of the sole, and the rubber particles are made of a blend of styrene-butadiene rubber and butadiene rubber, and the mass ratio of the two is 3-5:2.

[0013] In addition, the present invention also provides an EVA supercritical foaming shock-absorbing material, and the EVA supercritical foaming shock-absorbing material is prepared by a preparation process of the EVA supercritical foaming shock-absorbing material.

[0014] By adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are: 1. The present invention uses nano silicon carbide particles, whose high strength and high stability can effectively enhance the strength of the pore wall. During the foaming process of the material, the nano silicon carbide particles are evenly dispersed in the EVA matrix. When impacted by external force, they can support the pore structure like a skeleton to prevent the pores from easily breaking or collapsing, greatly improving the structural stability of the material. At the same time, a self-repairing polymer containing dynamic covalent bonds is prepared. When the material is damaged and the pores break, the dynamic covalent bonds can be reversibly broken and reorganized to automatically repair the damaged parts, so that the integrity of the material can be restored, thereby ensuring that the material always has good shock absorption performance during long-term use. In addition, the components are blended at high speed to ensure uniform dispersion, accurately control the foaming and cross-linking conditions, etc., further optimizing the comprehensive performance of the material, so that the prepared EVA supercritical foaming shock-absorbing material can be better used in shoe production, providing shoes with long-lasting and stable shock absorption protection, significantly improving the comfort and durability of shoes, and effectively solving the problems of poor shock absorption stability and insufficient shock absorption durability of traditional materials; 2. The present invention synthesizes a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment and blends it with an EVA resin. The hindered amine light stabilizer can effectively capture free radicals generated by light, oxidation, etc. during the use of the material, inhibit the degradation of the molecular chain, significantly improve the anti-aging performance of the material, and extend the service life of the shoe material. The polyether segment enables the material to have excellent elasticity and hygroscopicity adjustment capabilities, which can not only ensure that the shoes have good resilience and comfortable foot feel when worn, but also maintain relatively stable physical properties under different humidity environments. At the same time, the cross-linking network constructed by introducing an intelligent cross-linking agent can intelligently adjust the cross-linking density according to changes in ambient temperature and humidity. Under high temperature and high humidity, the cross-linking density is increased to prevent the pores from collapsing due to the entry of moisture. When drying at low temperature, the appropriate cross-linking flexibility is maintained to ensure that the shock absorption effect is not damaged. This intelligent adjustment mechanism enables the stability of the pore structure and the shock absorption performance of the material to be maintained for a long time, effectively overcoming the defects of traditional materials such as unstable shock absorption performance and easy aging under different environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a process flow in an embodiment of the present invention; Figure 2 It is a schematic diagram for comparing parameters among Example 1, Example 2 and Comparative Example 1 in the embodiments of the present invention. DETAILED DESCRIPTION

[0016] The specific embodiments of the present invention will be further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0017] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] Please see attached Figure 1 -Attached Figure 2 The present invention provides a preparation process of an EVA supercritical foaming shock-absorbing material, and the preparation process comprises the following specific steps: Step 1: Prepare and premix raw materials. Weigh EVA resin and prepare nano silicon carbide particles. Prepare a polyurethane self-healing polymer containing a disulfide bond using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond. Prepare a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment. Then, put the EVA resin, nano silicon carbide particles, polyurethane self-healing polymer and multifunctional elastomer into a high-speed blender for stirring and premixing. At the same time, add a dispersant zinc stearate for blending and stirring reaction to obtain a premixed material. Step 2: Supercritical foaming agent injection and preliminary foaming: transfer the premixed material to the barrel of the supercritical foaming equipment and seal it, inject supercritical carbon dioxide foaming agent into the barrel, then pressurize and maintain for a period of time for preliminary foaming to form a preliminary cellular structure material; Step 3: Using an intelligent cross-linking agent prepared by chemical cross-linking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropanesulfonic acid, after foaming, the intelligent cross-linking agent is injected into the barrel of the foaming equipment by an injection device, and then the temperature and humidity inside the foaming equipment are controlled to perform a cross-linking reaction. In this process, the intelligent cross-linking agent constructs a dynamically adjustable cross-linking network according to the temperature and humidity, the self-healing polymer is distributed in the pore wall and the material, the nano-silicon carbide strengthens the pore wall, and the multifunctional elastomer improves the elasticity and fatigue resistance of the material, completing the cross-linking and intelligent network construction to obtain a cross-linked foaming material; Step 4: After the cross-linking reaction is completed, the pressure in the foaming equipment is slowly released, and then the foaming and shaping are further carried out under normal pressure for a period of time to basically form the material, and then the formed material is immediately transferred to the slipper mold while hot, and pressure is applied and maintained for a period of time after the mold is closed, so that the material completely fills the mold cavity to obtain a blank in the shape of slippers; Step 5. Take out the slipper blank from the mold, cut and grind it to remove excess scraps and flash to make the appearance of the slippers smoother and flatter, use DC-857 silicone waterproofing agent to coat it to form a waterproof layer, and stick rubber particles on the surface of the sole to enhance the anti-slip performance of the sole.

[0019] In one embodiment of the present invention: In step 1, the process of preparing a polyurethane self-healing polymer containing a disulfide bond using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond is as follows: under nitrogen protection, 50-60 parts of polypropylene glycol are added to a reactor, vacuum dehydrated at a temperature of 110°C-120°C for 1h-2h, then cooled to 50°C-60°C, 40-50 parts of 4,4'-diphenylmethane diisocyanate are added, Methane diisocyanate is added and reacted at this temperature for 1h-2h, then the temperature is raised to 70℃-80℃ and the reaction is continued for 2h-3h to obtain a prepolymer. Subsequently, 10-15 parts of a diol chain extender containing a disulfide bond is dissolved in a solvent dimethylformamide at 60℃-70℃, and slowly added dropwise to the prepolymer while vigorously stirring. The mixture is reacted at 70℃-80℃ for 3h-4h, and finally a polyurethane self-healing polymer containing a disulfide bond is obtained by precipitation, washing and drying.

[0020] In one embodiment of the present invention: In step 1, the process for preparing a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment is as follows: 80-100 parts of a polyether thermoplastic polyurethane elastomer are dissolved in an organic solvent, toluene, 5-8 parts of a hindered amine light stabilizer are added, and the mixture is stirred and reacted at 60°C-70°C for 4h-6h, and then the toluene is distilled off to obtain a modified multifunctional elastomer.

[0021] In one embodiment of the present invention: in step 1, the content of vinyl acetate in the weighed EVA resin is 18%-22%, the particle size of the prepared nano-silicon carbide particles is 20nm-50nm, the amount of nano-silicon carbide particles added to the high-speed blender is 3%-5% of the mass of the EVA resin, the amount of the self-healing polymer added is 5%-8% of the mass of the EVA resin, the amount of the multifunctional elastomer added is 10%-15% of the mass of the EVA resin, and at the same time, a dispersant zinc stearate with a mass fraction of 1%-2% is added, and the amount of zinc stearate added is 0.5%-1% of the mass of the EVA resin. The temperature of the blender is set to 120°C-150°C, the speed is 800r / min-1200r / min, and the blending time is 1.5h-2.5h.

[0022] In one embodiment of the present invention: in step 2, the amount of foaming agent injected is 8%-12% of the mass of the premixed material, the barrel temperature is set at 160°C-180°C, the pressure is 15MPa-20MPa, and maintained for 5min-8min.

[0023] In one embodiment of the present invention: in step 3, the specific process of preparing the smart crosslinker by chemical crosslinking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropane sulfonic acid is as follows: in a reaction container, first add 100-150 parts of deionized water, under nitrogen protection, heat to 70°C-80°C, add 30-40 parts of N-isopropylacrylamide and 10-15 parts of acrylic acid in sequence, stir until completely dissolved, add 0.5-1 part of initiator ammonium persulfate, react for 3h-4h, obtain N-isopropylacrylamide-acrylic acid copolymer solution, then, add 20-30 parts of 2-acrylamide-2-methylpropane sulfonic acid to the copolymer solution, and then add 0.3-0.5 parts of crosslinking agent N,N'-methylenebisacrylamide, stir evenly, heat to 80°C-90°C, continue to react for 2h-3h, and obtain the smart crosslinker.

[0024] In one embodiment of the present invention: in step three, the amount of the smart cross-linking agent added is 2%-4% of the mass of the preliminary pore structure material, the ambient temperature in the foaming equipment is regulated to 130°C-150°C, the humidity is 40%-60%, and the cross-linking reaction is 3h-4h.

[0025] In one embodiment of the present invention: in step 4, after the cross-linking reaction is completed, the pressure in the foaming equipment is slowly released at a rate of 0.2MPa / min-0.5MPa / min, and then maintained at normal pressure for 10min-15min, the mold is closed and a pressure of 5MPa-10MPa is applied, and the pressure is maintained for 3min-5min.

[0026] In one embodiment of the present invention: in step five, rubber particles with a particle size of 2mm-3mm are pasted on the surface of the sole, and the rubber particles are made of a blend of styrene-butadiene rubber and butadiene rubber, and the mass ratio of the two is 3-5:2.

[0027] In one embodiment of the present invention: in step one, the diol chain extender containing a disulfide bond is a disulfide bond-containing aliphatic diol chain extender, the carbon chain length in its molecular structure is 6-10 carbon atoms, and the disulfide bond is located at the center of the carbon chain. The chain extender with this structure can make the prepared polyurethane self-healing polymer have a faster self-healing rate at a specific temperature of 20°C-40°C, and the self-healing efficiency is above 80%.

[0028] In one embodiment of the present invention: In step one, during the synthesis of the multifunctional elastomer, the polyether thermoplastic polyurethane elastomer is first pretreated in a vacuum environment for 30 minutes to 60 minutes to remove internal residual gas and small molecule impurities, and then dissolved and reacted with the hindered amine light stabilizer. The compatibility of the multifunctional elastomer after this pretreatment with the EVA resin is improved, so that the mechanical properties of the final material are more uniform and the coefficient of variation of the tensile strength is reduced.

[0029] In one embodiment of the present invention: in step three, during the cross-linking reaction, microwave auxiliary radiation is simultaneously introduced, the microwave frequency is 2.45 GHz, the power is 500W-1000W, and the microwave radiation time is 1 / 3-1 / 2 of the cross-linking reaction time. Under the action of microwave radiation, the cross-linking reaction activation energy of the smart cross-linking agent is reduced, the cross-linking reaction rate is increased, the cross-linking reaction time can be reduced, and the cross-linking network can be made more uniform and dense, thereby improving the overall performance of the material.

[0030] In one embodiment of the present invention: in step five, when the formed slippers are post-treated, a plasma surface treatment process is added, using oxygen plasma, with a treatment power of 100W-300W and a treatment time of 3min-5min. After the treatment, the hydrophilicity of the sole surface is improved, and the water contact angle is reduced, which is beneficial to improving the anti-slip performance of the sole and the bonding force with the waterproof layer, thereby improving the anti-slip effect of the shoes in a humid environment, improving the adhesion of the waterproof layer, and effectively extending the service life of the waterproof layer.

[0031] Example 1, please refer to the attached Figure 1 -Attached Figure 2First, a polyurethane self-healing polymer containing a disulfide bond was prepared by using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond. Under nitrogen protection, 60 parts of polypropylene glycol were added to a reactor and vacuum dehydrated at 120°C for 2 hours. Then, the temperature was lowered to 60°C, 50 parts of 4,4'-diphenylmethane diisocyanate were added, and the reaction was carried out at this temperature for 2 hours. Then, the temperature was raised to 80°C and the reaction was continued for 3 hours to obtain a prepolymer. Subsequently, 15 parts of the diol chain extender containing a disulfide bond were dissolved in a solvent of dimethylformamide at 70°C, and slowly added dropwise to the prepolymer while vigorously stirring. The reaction was carried out at 80°C for 4 hours. Finally, a polyurethane self-healing polymer containing a disulfide bond was obtained by precipitation, washing and drying. The compound is then prepared to prepare a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment, 100 parts of a polyether thermoplastic polyurethane elastomer is dissolved in an organic solvent of toluene, 8 parts of a hindered amine light stabilizer are added, and the mixture is stirred and reacted at 70°C for 6 hours, and then the toluene is distilled off to obtain a modified multifunctional elastomer, and then an EVA resin with a vinyl acetate content of 22% is weighed, and nano-silicon carbide particles with a particle size of 50 nm are prepared, wherein the amount of the nano-silicon carbide particles added to the high-speed blender is 5% of the mass of the EVA resin, the amount of the self-healing polymer added is 8% of the mass of the EVA resin, and the amount of the multifunctional elastomer added is 15% of the mass of the EVA resin. At the same time, 2% by mass of a dispersant zinc stearate and stearic acid are added. The amount of zinc added is 1% of the mass of the EVA resin. The temperature of the blender is set at 150°C, the speed is set at 1200r / min, and the blending time is set at 2.5h to obtain a premixed material. After the blending is completed, the premixed material is transferred to the barrel of the supercritical foaming equipment and sealed. A supercritical carbon dioxide foaming agent of 12% of the mass of the premixed material is injected into the barrel. The barrel temperature is set at 180°C and the pressure is set at 20MPa. The initial foaming is maintained for 8min to form a preliminary pore structure material. Then, an intelligent cross-linking agent prepared by chemical cross-linking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropanesulfonic acid is used. In the reaction container, 150 parts of deionized water are first added, and the temperature is raised to 80°C under nitrogen protection, and then the reaction mixture is stirred for 2 hours. Add 40 parts of N-isopropylacrylamide and 15 parts of acrylic acid, stir until completely dissolved, add 1 part of initiator ammonium persulfate, react for 4 hours, and obtain N-isopropylacrylamide-acrylic acid copolymer solution. Then, add 30 parts of 2-acrylamide-2-methylpropanesulfonic acid to the copolymer solution, and then add 0.5 parts of cross-linking agent N,N'-methylenebisacrylamide. After stirring evenly, heat to 90°C, continue to react for 3 hours, and obtain intelligent cross-linking agent. Then, inject it into the barrel of the foaming equipment by injection device at 4% of the mass of the initial pore structure material, adjust the ambient temperature in the foaming equipment to 150°C, the humidity to 60%, and cross-link reaction for 4 hours to complete cross-linking and intelligent network construction to obtain cross-linked foaming material. After the cross-linking reaction is completed, add 0.The pressure in the foaming equipment is slowly released at a rate of 5MPa / min, and then maintained at normal pressure for 15 minutes for further foaming and shaping to make the material basically formed. The formed material is immediately transferred to the slipper mold while hot. After the mold is closed, a pressure of 10MPa is applied and maintained for 5 minutes to make the material completely fill the mold cavity to obtain a blank in the shape of a slipper. The slipper blank is then taken out of the mold, cut and polished to remove excess scraps and flash, so that the appearance of the slipper is smoother and flatter. DC-857 silicone waterproofing agent is used for coating to form a waterproof layer, and rubber particles with a particle size of 3mm are attached to the surface of the sole. The rubber particles are made of a blend of styrene-butadiene rubber and butadiene rubber, and the mass ratio of the two is 5:2, to obtain shoes made of EVA supercritical foaming shock-absorbing material. .

[0032] Example 2, please refer to the attached Figure 1 -Attached Figure 2First, a polyurethane self-healing polymer containing a disulfide bond was prepared by using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond. Under nitrogen protection, 50 parts of polypropylene glycol were added to a reactor and vacuum dehydrated at a temperature of 110°C for 1 hour. Then, the temperature was lowered to 50°C, 40 parts of 4,4'-diphenylmethane diisocyanate were added, and the reaction was carried out at this temperature for 1 hour. Then, the temperature was raised to 70°C and the reaction was continued for 2 hours to obtain a prepolymer. Subsequently, 10 parts of the diol chain extender containing a disulfide bond were dissolved in a solvent of dimethylformamide at 60°C, and slowly added dropwise to the prepolymer while vigorously stirring. The reaction was carried out at 70°C for 3 hours. Finally, a polyurethane self-healing polymer containing a disulfide bond was obtained by precipitation, washing and drying. The compound is then prepared to prepare a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment, 80 parts of a polyether thermoplastic polyurethane elastomer is dissolved in an organic solvent of toluene, 5 parts of a hindered amine light stabilizer are added, and the reaction is stirred at 60°C for 4 hours, and then the toluene is distilled off to obtain a modified multifunctional elastomer, and then an EVA resin with a vinyl acetate content of 18% is weighed, and nano-silicon carbide particles with a particle size of 20nm are prepared, wherein the amount of the nano-silicon carbide particles added to the high-speed blender is 3% of the mass of the EVA resin, the amount of the self-healing polymer added is 5% of the mass of the EVA resin, and the amount of the multifunctional elastomer added is 10% of the mass of the EVA resin. At the same time, a dispersant of 1% by mass of zinc stearate is added, and the amount of zinc stearate is 10%. The addition amount is 0.5% of the mass of the EVA resin, the temperature of the blender is set at 120°C, the speed is set at 800r / min, and the blending time is set at 1.5h to obtain a premixed material. After the blending is completed, the premixed material is transferred to the barrel of the supercritical foaming equipment and sealed, and a supercritical carbon dioxide foaming agent of 8% of the mass of the premixed material is injected into the barrel. The barrel temperature is set at 160°C and the pressure is set at 15MPa. Maintain for 5min for preliminary foaming to form a preliminary pore structure material, and then use N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropanesulfonic acid to prepare an intelligent cross-linking agent by chemical cross-linking reaction. In the reaction container, 100 parts of deionized water are first added, and under nitrogen protection, the temperature is raised to 70°C, and then added in sequence. 30 parts of N-isopropyl acrylamide and 10 parts of acrylic acid were stirred until completely dissolved, and then 0.5 parts of initiator ammonium persulfate were added and reacted for 3 hours to obtain N-isopropyl acrylamide-acrylic acid copolymer solution. Then, 20 parts of 2-acrylamide-2-methylpropanesulfonic acid were added to the copolymer solution, and then 0.3 parts of cross-linking agent N,N'-methylenebisacrylamide were added. After stirring evenly, the temperature was raised to 80°C and the reaction was continued for 2 hours to obtain the intelligent cross-linking agent. Then, the intelligent cross-linking agent was injected into the barrel of the foaming equipment by an injection device at an amount of 2% of the mass of the initial pore structure material. The ambient temperature in the foaming equipment was adjusted to 130°C and the humidity was 40%. The cross-linking reaction was carried out for 3 hours to complete the cross-linking and intelligent network construction to obtain the cross-linked foaming material. After the cross-linking reaction was completed, 0.The pressure in the foaming equipment is slowly released at a rate of 2MPa / min, and then maintained at normal pressure for 10 minutes for further foaming and shaping to make the material basically formed. The formed material is immediately transferred to the slipper mold while hot. After the mold is closed, a pressure of 5MPa is applied and maintained for 3 minutes to make the material completely fill the mold cavity to obtain a blank in the shape of a slipper. The slipper blank is then taken out of the mold, cut and polished to remove excess scraps and flash, so that the appearance of the slipper is smoother and flatter. DC-857 silicone waterproofing agent is used for coating to form a waterproof layer, and rubber particles with a particle size of 2mm are attached to the surface of the sole. The rubber particles are made of a blend of styrene-butadiene rubber and butadiene rubber, and the mass ratio of the two is 3:2, to obtain shoes made of EVA supercritical foaming shock-absorbing material. .

[0033] Comparative Example 1, please refer to the attached Figure 1 -Attached Figure 2First, a polyurethane self-healing polymer containing a disulfide bond is prepared by using hexamethylene diisocyanate, polybutadiene diol and a diol chain extender containing a disulfide bond. Under nitrogen protection, 60 parts of polybutadiene diol are added to a reactor and vacuum dehydrated at a temperature of 120°C for 2 hours. Then, the temperature is lowered to 60°C, 50 parts of hexamethylene diisocyanate are added, and the reaction is carried out at this temperature for 2 hours. Then, the temperature is raised to 80°C and the reaction is continued for 3 hours to obtain a prepolymer. Subsequently, 15 parts of the diol chain extender containing a disulfide bond are dissolved in a solvent of dimethylformamide at 70°C, and the prepolymer is slowly added dropwise to the prepolymer while being vigorously stirred. The reaction is carried out at 80°C for 4 hours. Finally, a polyurethane self-healing polymer containing a disulfide bond is obtained by precipitation, washing and drying. A multifunctional elastomer with hindered amine light stabilizer and polyether chain segments, 100 parts of polyether thermoplastic polyurethane elastomer are dissolved in organic solvent toluene, 8 parts of hindered amine light stabilizer are added, and the reaction is stirred at 70°C for 6 hours, and then the toluene is distilled off to obtain a modified multifunctional elastomer, and then EVA resin with a vinyl acetate content of 22% is weighed, and nano-silicon carbide particles with a particle size of 50nm are prepared, wherein the amount of nano-silicon carbide particles added to the high-speed blender is 5% of the mass of the EVA resin, the amount of self-healing polymer added is 8% of the mass of the EVA resin, and the amount of multifunctional elastomer added is 15% of the mass of the EVA resin. At the same time, 2% of the mass fraction of dispersant zinc stearate is added, and the amount of zinc stearate added is EVA resin. VA resin mass, set the mixer temperature to 150 ° C, the speed to 1200r / min, the blending time to 2.5h, to obtain a premixed material, after the blending is completed, the premixed material is transferred to the barrel of the supercritical foaming equipment and sealed, and a supercritical carbon dioxide foaming agent of 12% of the mass of the premixed material is injected into the barrel, and the barrel temperature is set at 180 ° C, the pressure is 20MPa, and it is maintained for 8min for preliminary foaming to form a preliminary pore structure material, and then the intelligent cross-linking agent prepared by chemical cross-linking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropanesulfonic acid is used. In the reaction container, 150 parts of deionized water are first added, and under nitrogen protection, the temperature is raised to 80 ° C, and N- 40 parts of isopropyl acrylamide and 15 parts of acrylic acid were stirred until completely dissolved, and then 1 part of initiator ammonium persulfate was added and reacted for 4 hours to obtain N-isopropyl acrylamide-acrylic acid copolymer solution. Then, 30 parts of 2-acrylamide-2-methylpropanesulfonic acid were added to the copolymer solution, and then 0.5 parts of cross-linking agent N,N'-methylenebisacrylamide were added. After stirring evenly, the temperature was raised to 90°C and the reaction was continued for 3 hours to obtain the intelligent cross-linking agent. Then, the intelligent cross-linking agent was injected into the barrel of the foaming equipment by an injection device at an amount of 4% of the mass of the initial pore structure material. The ambient temperature in the foaming equipment was adjusted to 150°C and the humidity was 60%. The cross-linking reaction was carried out for 4 hours to complete the cross-linking and intelligent network construction to obtain the cross-linked foaming material. After the cross-linking reaction was completed, the cross-linking was carried out at 0.The pressure in the foaming equipment is slowly released at a rate of 5MPa / min, and then maintained at normal pressure for 15 minutes for further foaming and shaping to make the material basically formed. The formed material is immediately transferred to the slipper mold while hot. After the mold is closed, a pressure of 10MPa is applied and maintained for 5 minutes to make the material completely fill the mold cavity to obtain a blank in the shape of a slipper. The slipper blank is then taken out of the mold, cut and polished to remove excess scraps and flash, so that the appearance of the slipper is smoother and flatter. DC-857 silicone waterproofing agent is used for coating to form a waterproof layer, and rubber particles with a particle size of 3mm are attached to the surface of the sole. The rubber particles are made of a blend of styrene-butadiene rubber and butadiene rubber, and the mass ratio of the two is 5:2, to obtain shoes made of EVA supercritical foaming shock-absorbing material. .

[0034] Experimental design Experimental materials and equipment: 3 pairs of shoes made of EVA supercritical foaming shock-absorbing materials prepared in Example 1, Example 2 and Comparative Example 1, impact testing machine (for testing shock-absorbing performance), rebound tester (for measuring the rebound resilience of materials), aging test box (for simulating aging environment), scanning electron microscope (for observing the changes in the pore structure of materials); Experimental steps: 1. Shock absorption performance test: Fix each pair of shoes on the platform of the impact tester, place a sensor on the heel, set the impact height of the impact tester to 50cm, let the impact hammer weighing 70kg fall freely to impact the heel, record the peak impact force and impact duration generated during the impact process, repeat the test 3 times for each pair of shoes, and take the average value; 2. Resilience test: Use a rebound tester to perform rebound tests at different locations on the sole of the shoe (forefoot, arch, heel), test each location 5 times, record the rebound height, and calculate the average rebound rate; 3. Anti-aging performance test: Place the shoes in an aging test chamber with a set temperature of 70°C, a humidity of 80%, a light intensity of 500W / m², and an aging time of 72h. Before and after aging, the shoes are evaluated for color change (measured using a colorimeter), hardness test (using a Shore durometer), and tensile strength test; 4. Material stability test (cellular structure observation): Samples were taken from the soles of shoes, and the pore structure before and after aging was observed using a scanning electron microscope. The average diameter of the pores, the thickness of the pore walls, and the uniformity of the pores were measured. Three samples were taken from each type of shoe, and five fields of view were observed for each sample to take the average value.

[0035] As attached Figure 2As shown, it can be seen from the experimental data that in terms of shock absorption performance, the impact force peak value of Example 1 is the lowest and the impact duration is longer, indicating that its shock absorption effect is better. In terms of resilience, the average rebound rate of Example 1 is the highest. In terms of anti-aging performance, the color change, hardness change and tensile strength change of Example 1 are the smallest. In terms of material stability, the change of the pore structure of Example 1 before and after aging is relatively small, and the pore uniformity is good. Combining the above test results, it can be proved that Example 1 is superior to Example 2 and Comparative Example 1 in terms of beneficial effects.

[0036] Although the present invention is disclosed as above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A preparation process of EVA supercritical foaming shock-absorbing material, characterized in that: The preparation process comprises the following specific steps: Step 1: Prepare and premix raw materials. Weigh EVA resin and prepare nano silicon carbide particles. Prepare a polyurethane self-healing polymer containing a disulfide bond using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond. Prepare a multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment. Then, put the EVA resin, nano silicon carbide particles, polyurethane self-healing polymer and multifunctional elastomer into a high-speed blender for stirring and premixing. At the same time, add a dispersant zinc stearate for blending and stirring reaction to obtain a premixed material. Step 2: Supercritical foaming agent injection and preliminary foaming: transfer the premixed material to the barrel of the supercritical foaming equipment and seal it, inject supercritical carbon dioxide foaming agent into the barrel, then pressurize and maintain for a period of time for preliminary foaming to form a preliminary cellular structure material; Step 3: using an intelligent cross-linking agent prepared by chemical cross-linking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropanesulfonic acid, injecting the intelligent cross-linking agent into the barrel of the foaming equipment by using an injection device after the foaming is completed, and then controlling the temperature and humidity inside the foaming equipment to perform a cross-linking reaction to obtain a cross-linked foaming material; Step 4: After the cross-linking reaction is completed, the pressure in the foaming equipment is slowly released, and then the foaming and shaping are further carried out under normal pressure for a period of time to basically form the material, and then the formed material is immediately transferred to the slipper mold while hot, and pressure is applied and maintained for a period of time after the mold is closed, so that the material completely fills the mold cavity to obtain a blank in the shape of slippers; Step 5: Take out the slipper blank from the mold, cut and grind it to remove excess scraps and flash, so that the appearance of the slippers is smoother and flatter, apply DC-857 silicone waterproofing agent to form a waterproof layer, and stick rubber particles on the surface of the sole.

2. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step 1, the process of preparing a polyurethane self-healing polymer containing a disulfide bond by using 4,4'-diphenylmethane diisocyanate, polypropylene glycol and a diol chain extender containing a disulfide bond is as follows: under nitrogen protection, 50-60 parts of polypropylene glycol are added to a reactor, vacuum dehydrated at a temperature of 110°C-120°C for 1h-2h, then cooled to 50°C-60°C, 40-50 parts of 4,4'-diphenylmethane diisocyanate are added, and reacted at this temperature for 1h-2h, then heated to 70°C-80°C and continued to react for 2h-3h to obtain a prepolymer, then 10-15 parts of the diol chain extender containing a disulfide bond are dissolved in a solvent dimethylformamide at 60°C-70°C, slowly added dropwise to the prepolymer, and vigorously stirred at the same time, reacted at 70°C-80°C for 3h-4h, and finally the polyurethane self-healing polymer containing a disulfide bond is obtained by precipitation, washing and drying.

3. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step 1, the process for preparing the multifunctional elastomer containing a hindered amine light stabilizer and a polyether segment is as follows: 80-100 parts of a polyether thermoplastic polyurethane elastomer are dissolved in an organic solvent, toluene, 5-8 parts of a hindered amine light stabilizer are added, the mixture is stirred and reacted at 60° C.-70° C. for 4 h-6 h, and then the toluene is removed by distillation to obtain a modified multifunctional elastomer.

4. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step 1, the content of vinyl acetate in the weighed EVA resin is 18%-22%, the particle size of the prepared nano silicon carbide particles is 20nm-50nm, the amount of the nano silicon carbide particles added to the high-speed blender is 3%-5% of the mass of the EVA resin, the amount of the self-healing polymer added is 5%-8% of the mass of the EVA resin, the amount of the multifunctional elastomer added is 10%-15% of the mass of the EVA resin, and at the same time, a dispersant zinc stearate with a mass fraction of 1%-2% is added, and the amount of zinc stearate added is 0.5%-1% of the mass of the EVA resin. The temperature of the blender is set to 120°C-150°C, the speed is 800r / min-1200r / min, and the blending time is 1.5h-2.5h.

5. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step 2, the amount of foaming agent injected is 8%-12% of the mass of the premixed material, the barrel temperature is set at 160° C.-180° C., the pressure is 15 MPa-20 MPa, and maintained for 5 min-8 min.

6. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step 3, the specific process of preparing the smart crosslinker by chemical crosslinking reaction of N-isopropylacrylamide-acrylic acid copolymer and 2-acrylamide-2-methylpropane sulfonic acid is as follows: first add 100-150 parts of deionized water into a reaction container, and under nitrogen protection, heat it to 70°C-80°C, add 30-40 parts of N-isopropylacrylamide and 10-15 parts of acrylic acid in sequence, stir until completely dissolved, add 0.5-1 part of initiator ammonium persulfate, react for 3h-4h, and obtain N-isopropylacrylamide-acrylic acid copolymer solution, then add 20-30 parts of 2-acrylamide-2-methylpropane sulfonic acid to the copolymer solution, and then add 0.3-0.5 parts of crosslinking agent N,N'-methylenebisacrylamide, stir evenly, heat it to 80°C-90°C, and continue to react for 2h-3h to obtain the smart crosslinker.

7. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step three, the amount of the smart cross-linking agent added is 2%-4% of the mass of the initial pore structure material, the ambient temperature in the foaming equipment is regulated to be 130° C.-150° C., the humidity is 40%-60%, and the cross-linking reaction is performed for 3h-4h.

8. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step 4, after the cross-linking reaction is completed, the pressure in the foaming equipment is slowly released at a rate of 0.2MPa / min-0.5MPa / min, and then maintained at normal pressure for 10min-15min, the mold is closed and a pressure of 5MPa-10MPa is applied, and the pressure is maintained for 3min-5min.

9. The preparation process of an EVA supercritical foaming shock-absorbing material according to claim 1, characterized in that: In the step 5, rubber particles with a particle size of 2mm-3mm are pasted on the surface of the sole, and the rubber particles are made of a blend of styrene-butadiene rubber and cis-butadiene rubber, and the mass ratio of the two is 3-5:

2.

10. An EVA supercritical foaming shock-absorbing material suitable for the preparation process of the EVA supercritical foaming shock-absorbing material according to any one of claims 1 to 9, characterized in that: The EVA supercritical foaming shock-absorbing material is prepared by a preparation process of the EVA supercritical foaming shock-absorbing material.

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