Preparation method of high-elastic damping foaming material

Abstract

The invention discloses a preparation method of a high-elastic damping foaming material, which comprises the following steps: S1, melting and blending raw materials comprising a basic elastomer, a hydrogenated styrene thermoplastic elastomer, brominated butyl rubber, a foaming agent and a cross-linking agent to form a homogeneous precursor composition; s2, synchronously carrying out chemical foaming and cross-linking reaction on the precursor composition to form a foaming material with a continuous network foam structure; wherein the basic elastomer comprises at least one of an ethylene-vinyl acetate copolymer and a polyolefin elastomer; moreover, in parts by weight, the dosage of the basic elastomer is 50-70 parts, the dosage of the hydrogenated styrene thermoplastic elastomer is 15-35 parts, and the dosage of the brominated butyl rubber is 10-25 parts. By adopting the technical scheme, the foaming material with high resilience, high damping performance and excellent durability can be prepared.

Description

Technical Field

[0001] The invention relates to the technical field of foam materials, and in particular to a method for preparing a high-elasticity shock-absorbing foam material. Background Art

[0002] In the manufacture of high-performance footwear, especially athletic shoes, the midsole is a core component that provides cushioning protection and energy return. Its performance directly impacts the wearer's comfort and athletic performance. Currently, the industry widely adopts a technology approach to producing foam materials using a compression molding (MD) process using thermoplastic elastomers such as ethylene-vinyl acetate copolymer (EVA) and polyolefin elastomer (POE) as primary raw materials.

[0003] However, such foam materials in the prior art generally have the following defects:

[0004] First, there's an inherent and difficult-to-reconcile technical contradiction between a material's shock absorption and rebound performance. Shock absorption requires the material to absorb and dissipate impact energy to the greatest extent possible, which manifests itself macroscopically as a low rebound rate. Rebound performance, on the other hand, requires the material to efficiently store and return energy after being compressed, which manifests macroscopically as a high rebound rate. Existing technologies typically only focus on optimizing one aspect of performance. For example, materials pursuing extreme shock absorption often experience a sluggish feedback, while materials aiming for high rebound lack cushioning and protection.

[0005] Secondly, the physical durability of existing materials, particularly their resistance to compression set, needs to be improved. Many foam materials are unable to effectively recover their original dimensions and properties after repeated stress impacts, shortening the product's lifespan. Their cushioning and resilience properties rapidly degrade with age. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects or problems existing in the background technology and provide a method for preparing a high-elastic shock-absorbing foam material, which can prepare a foam material with both high rebound and high shock-absorbing properties and excellent durability.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] Technical Solution 1: A method for preparing a high-elastic shock-absorbing foam material, comprising: S1: melt-blending raw materials comprising a base elastomer, a hydrogenated styrene thermoplastic elastomer, brominated butyl rubber, a foaming agent, and a cross-linking agent to form a homogeneous precursor composition; S2: simultaneously subjecting the precursor composition to chemical foaming and cross-linking reactions to form the foam material having a continuous network pore structure; wherein the base elastomer comprises at least one of ethylene-vinyl acetate copolymer and a polyolefin elastomer; and, in parts by weight, the amount of the base elastomer is 50-70 parts, the amount of the hydrogenated styrene thermoplastic elastomer is 15-35 parts, and the amount of the brominated butyl rubber is 10-25 parts.

[0009] Technical solution 2 based on technical solution 1: In step S2, the following steps are included: Step S21: The precursor composition formed in step S1 is subjected to initial foaming and cross-linking reaction to obtain a foamed embryo; Step S22: The foamed embryo is placed in a mold and molded and heated to perform foaming and cross-linking reaction again to obtain the foamed material.

[0010] Technical solution three based on technical solution two: in step S21, the foaming ratio of the precursor composition is 180%-190%; and in step S22, the compression ratio applied to the foamed embryo is 140%-150%.

[0011] Technical solution 4 based on technical solution 3: In step S22, the molding heating temperature is 175°C-181°C, the heating time is 520-580 seconds, and then cooling is performed, and the cooling time is 470-530 seconds.

[0012] Technical solution 5 based on technical solution 1: the foaming agent is azodicarbonamide, and the usage is 3-5 parts; the cross-linking agent is an organic peroxide cross-linking agent, and the usage is 0.5-1.0 parts.

[0013] Technical solution six based on technical solution three: the base elastomer comprises an ethylene-vinyl acetate copolymer having a vinyl acetate content of 20-30%.

[0014] Technical solution 7 based on technical solution 6: the base elastomer also includes the polyolefin elastomer, and the polyolefin elastomer is an ethylene-octene copolymer, and its density is 0.86-0.88 g / cm 3 ; In the base elastomer, the amount of the ethylene-vinyl acetate copolymer is 40-50 parts by weight, and the amount of the polyolefin elastomer is 10-20 parts by weight.

[0015] Technical solution eight based on technical solution one: in step S1, the raw materials further include at least one selected from fillers, reinforcing agents and processing aids.

[0016] Technical solution nine based on technical solution eight: the filler is talcum powder, the reinforcing agent is zinc oxide, and the processing aid contains stearic acid and zinc stearate.

[0017] Technical Solution 10 based on Technical Solution 1: In step S1, the following steps are included: S11: the base elastomer, hydrogenated styrene thermoplastic elastomer and brominated butyl rubber are melt-blended in a first stage in an internal mixer; S12: the materials after the first stage blending are melt-blended with the foaming agent and cross-linking agent in an open mixer in a second stage to form a homogeneous precursor composition.

[0018] From the above description of the present invention, it can be seen that compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a method for preparing a high-elastic shock-absorbing foam material. By improving the formula and the preparation method, the problem of balancing the shock-absorbing performance and the rebound performance of the foam material is effectively improved, and on this basis, the physical durability of the foam material to cope with long-term repeated stress impact is ensured.

[0020] Among them, the formula of the present invention mainly includes a basic elastomer that provides basic elasticity, a hydrogenated styrene thermoplastic elastomer that provides core shock absorption function, and brominated butyl rubber that provides key durability and structural stability. In the system of the present invention, the functions of each component are clear and mutually supportive: the basic elastomer constitutes the continuous phase skeleton of the foam material and is the fundamental source of the material's macroscopic elasticity. Its polymer chain network undergoes reversible deformation to store mechanical energy when subjected to force, which is the physical basis for achieving high resilience. The hydrogenated styrene thermoplastic elastomer is dispersed in the matrix in the form of a microphase. When impacted, internal friction and friction occur between its molecular chain segments, and a portion of the mechanical energy is irreversibly converted into heat energy and dissipated, thereby achieving efficient energy absorption, i.e. shock absorption. The extremely low gas permeability of brominated butyl rubber can effectively slow down the escape of gas inside the closed-cell foam material to the outside world, thereby maintaining the structural integrity and internal pressure of the pores for a long time, ensuring that the mechanical properties of the material will not decay rapidly due to physical aging or collapse of the pores during use. At the same time, the high damping properties of butyl rubber itself also synergistically enhance the energy absorption capacity of the entire system.

[0021] Among them, the present invention precisely defines the content of these three core functional components, which is the key to achieving the ultimate performance balance. The amount of base elastomer is limited to 50-70 parts. This is because as a continuous phase, it needs a sufficient amount to ensure the structural integrity and basic resilience of the entire material. If it is less than 50 parts, the matrix will not be able to form a stable continuous network, resulting in weak rebound and insufficient structural strength of the material; if it is higher than 70 parts, the relative content of the shock-absorbing component and the durability component is too low, and the high shock absorption and high durability technical effects pursued by the present invention will not be achieved. In addition, the amount of hydrogenated styrene thermoplastic elastomer and brominated butyl rubber used in the present invention is significantly increased and different from the amount used in the conventional formula in the prior art. Specifically, the hydrogenated styrene thermoplastic elastomer in the conventional formula can be used to improve the overall shock absorption performance of the foam material, but its addition amount should not be too much, because too much hydrogenated styrene thermoplastic elastomer will make the material too soft, resulting in good shock absorption performance but greatly reduced rebound performance. In the present invention, the amount of hydrogenated styrene thermoplastic elastomer is specifically increased. On this basis, brominated butyl rubber is added and the amount of this component is precisely limited. Through its own high damping and poor fluidity, the influence of excessive hydrogenated styrene thermoplastic elastomer on the rebound performance is reduced, while the durability of the foamed material is improved.

[0022] In addition, the preparation method of the present invention is not a universal process, but is closely coupled with the above-mentioned specific chemical formula.

[0023] First, the present invention preferably limits the base elastomer to be composed of EVA with a specific VA content and ethylene-octene copolymer (POE) with a specific density in a specific weight ratio. The introduction of ethylene-octene copolymer (POE) can significantly improve the strength and toughness of the blend in a molten state, so that when the precursor composition is subjected to an extreme compression ratio of up to 140%-150% during the subsequent secondary molding process, its cell walls will not undergo brittle fracture and structural collapse, thereby achieving the orderly densification to be achieved by the present invention. Among them, EVA, as the main component, provides the basic elasticity and framework of the system. And POE, as a toughening modifier, its dosage must be within a suitable range to play the best role. If the dosage of POE is less than 10 parts, its improvement effect on the mechanical properties of the entire matrix, especially the improvement effect on the melt strength, will not be obvious, and the resulting matrix material toughness is insufficient and cannot withstand the harsh conditions of the subsequent high compression ratio process. If the amount of POE is higher than 20 parts, the excessive POE may affect the compatibility of the blending system, and also reduce the rigidity and resilience of the matrix material to a certain extent, deviating from the technical goal of high rebound and high shock absorption of the present invention.

[0024] Secondly, after the raw materials are melt-mixed to form a precursor composition, the present invention simultaneously performs chemical foaming and cross-linking reactions in step S2. Because the formulation of the present invention contains a relatively high content of hydrogenated styrene thermoplastic elastomer and brominated butyl rubber, the uniform dispersion of these two components in the matrix is ​​crucial to the final performance. The simultaneous foaming and cross-linking reactions can fix the polymer network through cross-linking within the same time window of gas generation and cell expansion to form the final physical form. This process can effectively fix functional phases such as hydrogenated styrene thermoplastic elastomer and brominated butyl rubber uniformly in their dispersed positions in the matrix, effectively suppressing phase domain aggregation or unevenness that may be caused by thermal effects. This ensures that every part of the final material has the shock absorption and durability properties required by the design on a macroscopic scale, avoiding the problem of uneven performance distribution. During the heating process, the foaming agent decomposes to produce gas, causing the material to have a tendency to expand; at the same time, the cross-linking agent decomposes to trigger chemical bonding between polymer chains, increasing the viscosity and strength of the material. The rates of these two reactions are matched by using specific blowing agents and crosslinking agents in a precisely defined weight ratio, ensuring they proceed simultaneously. If the crosslinking reaction is too rapid, the polymer matrix solidifies before the gas has fully expanded, inhibiting the formation and growth of cells, resulting in insufficient expansion ratio and excessive material density. Conversely, if the foaming reaction is too rapid, the excessive amount of gas before the matrix has built up sufficient strength can cause excessive expansion, rupture, or merging of cells, ultimately forming a coarse and uneven cell structure, and even causing the foamed product to collapse, seriously affecting the material's mechanical properties.

[0025] Furthermore, in step S2, a secondary molding process is used to further ensure the balance between the shock absorption and resilience properties of the final foamed material. In the first step, a high-rate primary foaming process is used to prefabricate a large foamed preform with relatively weak cell walls and a loose internal structure. This preform serves as an intermediate for the subsequent structural remodeling, providing ample internal space for compression. In the second step, this loose foamed preform is subjected to a compression ratio of 140%-150%. Under specific heating temperature and molding time control, the physical structure of the preform is altered. During this process, the loose cell network is strongly compressed, trapping gas within the cells and applying high pressure. Under high pressure, the cell walls fold, buckle, and densify. Ultimately, the compacted, thickened, and toughened cell walls serve as supporting beams, forming a three-dimensional, highly tough, continuous network. Simultaneously, a dense, non-porous skin forms on the material surface. The entire cross-linking reaction is fully completed in this highly compressed state, thereby fixing this high-strength microstructure.

[0026] Therefore, an inseparable synergy is generated between the formula and preparation process defined by the present invention. The high-toughness material foundation achieved by the combination of ethylene-vinyl acetate copolymer and polyolefin elastomer in the base elastomer is a necessary condition for achieving high compression ratio physical molding in the subsequent secondary molding process. The foam material thus obtained has good shock absorption and rebound effects. The strong and dense cell wall network in the foam material can quickly undergo elastic deformation and quickly recover when impacted by external forces, storing and returning most of the energy, thereby contributing to excellent high rebound performance. At the same time, when the entire porous network structure is compressed, the compression and flow of the gas in the cells, as well as the internal friction of the polymer material itself, efficiently absorb and dissipate the impact energy, achieving high shock absorption performance. In addition, the densified, high-strength pore network formed by the high compression ratio process improves the material's fatigue resistance and structural stability, reduces the material's permanent compression deformation rate under long-term, repeated stress cycles, improves the problem of rapid performance degradation of existing materials due to structural fatigue, and ensures that the material can maintain its excellent rebound and shock absorption properties throughout its service life. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are preferred embodiments of the present invention and should not be considered as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] In the claims and description of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" is for distinguishing different objects rather than for describing a specific order.

[0029] In the claims and description of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0030] The present invention relates to a method for preparing a high-elastic shock-absorbing foam material, which comprises:

[0031] S1: melt-blending raw materials including a base elastomer, a hydrogenated styrene-based thermoplastic elastomer, brominated butyl rubber, a foaming agent, and a cross-linking agent to form a homogeneous precursor composition;

[0032] S2: simultaneously subjecting the precursor composition to chemical foaming and cross-linking reactions to form the foamed material having a continuous network cell structure;

[0033] The base elastomer comprises at least one of ethylene-vinyl acetate copolymer and polyolefin elastomer; and, in parts by weight, the base elastomer is used in an amount of 50-70 parts, the hydrogenated styrene thermoplastic elastomer is used in an amount of 15-35 parts, and the brominated butyl rubber is used in an amount of 10-25 parts.

[0034] Furthermore, in step S1, the following steps are included:

[0035] S11: melt blending the base elastomer, hydrogenated styrene-based thermoplastic elastomer and brominated butyl rubber in an internal mixer in a first stage;

[0036] S12: melt-blending the materials after the first stage blending with the foaming agent and the cross-linking agent in a second stage in an open mill to form a homogeneous precursor composition.

[0037] Wherein, the specific mode of the first section melt blending and the second section melt blending in steps S11 and S12 can be: in step S11, adopt internal mixer to carry out the melt blending of the first stage. First, preheat the internal mixer with a set temperature of 110 ℃ -120 ℃, and then add the basic elastomer, hydrogenated styrene thermoplastic elastomer, brominated butyl rubber and other auxiliary agents (such as filler, reinforcing agent, etc.) except foaming agent and cross-linking agent in sequence according to the formula amount. Close the top bolt, melt blend under the condition of rotor speed of 30-40 rpm, and mix for 8-10 minutes. The purpose of this step is to utilize the powerful shearing and kneading action of internal mixer to forcibly evenly disperse the polymer components with large differences in molecular weight, polarity and viscosity to form a macroscopically uniform masterbatch. The higher temperature and longer mixing time are selected to ensure that all polymer components are fully plasticized and interpenetrate, particularly to allow the hydrogenated styrene thermoplastic elastomer and bromobutyl rubber to form a microscopically uniformly dispersed phase structure within the base elastomer, laying the foundation for subsequent performance. After mixing is completed, the lower ejector bolt is opened to discharge the material, resulting in the first-stage blend. In step S12, an open mill is used for the second stage of melt blending. The flaky blend obtained in the first stage is fed into an open mill with a roller temperature controlled at 90°C-100°C and a roller pitch set at 1.5-2.5 mm. Multiple triangular wrapping and thinning operations are performed to further homogenize the material and reduce its temperature. Once the material temperature drops below 100°C, the foaming agent and crosslinking agent are added to the rubber mixer. Adding the foaming agent and crosslinking agent at a lower temperature prevents premature decomposition of these two heat-sensitive additives during the mixing stage, thereby ensuring that they can precisely function within the set time and temperature in the subsequent foaming molding step. After adding the blowing agent and crosslinking agent, mixing is continued for 3-5 minutes to ensure their uniform dispersion throughout the system. The product is then discharged from the sheet to obtain the final precursor composition. This staged blending process ensures sufficient dispersion of the polymer components at high temperatures while preventing premature failure of heat-sensitive additives at low temperatures, which is crucial for achieving uniform and stable performance in the final product.

[0038] In step S2, the following steps are included:

[0039] Step S21: subjecting the precursor composition formed in step S1 to a primary foaming and cross-linking reaction to obtain a foamed primary embryo;

[0040] Step S22: placing the foamed preform in a mold and performing compression heating to perform foaming and cross-linking reactions again to obtain the foamed material.

[0041] In step S21, the precursor composition has a foaming ratio of 180%-190%; and in step S22, the foamed embryo is compressed at a compression ratio of 140%-150%. In step S22, the temperature of the mold pressing and heating is 175-181°C, the heating time is 520-580 seconds, and then cooling is performed, with a cooling time of 470-530 seconds.

[0042] In step S21 and step S22, the foaming and crosslinking can be performed as follows: in step S21, primary foaming is performed. The precursor composition obtained in step S1 is precisely weighed and placed in a large-sized primary foaming mold. The mold is placed on a flat vulcanizing machine and heated at a temperature of 160-170°C for 10-15 minutes. At this temperature, the foaming agent and the crosslinking agent in the precursor composition decompose synchronously, a large amount of gas generated by the foaming reaction causes the material to expand rapidly, and the crosslinking reaction forms a preliminary network structure of the polymer chain, thereby trapping the gas and forming uniform and fine cells. This process causes the material to expand to a foaming ratio of 180%-190% compared to its original volume, thereby obtaining a foamed embryo with a large size and loose structure. After the primary foaming is completed, the foamed embryo is taken out and cooled to prepare for subsequent secondary mold pressing. In step S22, secondary mold pressing is performed. The cooled foamed embryo is cut to the desired size and then placed in a precision sizing mold with a size smaller than that of the foamed embryo but consistent with the size of the final product. The mold is closed, and the foamed embryo is pressed in the mold cavity at a compression ratio of 140%-150%. Then, the sizing mold is placed again on the flat vulcanizing machine, and mold pressing and heating are performed at a temperature of 175-181°C for 520-580 seconds. Under the action of high temperature and high pressure, the cell walls of the foamed embryo are further compacted and densified, and the crosslinking reaction is fully completed, thereby permanently fixing the high-strength microstructure. After heating is completed, the mold is immediately cooled for 470-530 seconds to rapidly cool and size the product, and a foamed material with high resilience and high shock absorption performance is finally obtained.

[0043] In addition, the foaming agent is azodicarbonamide, and the amount used is 3-5 parts; the crosslinking agent is an organic peroxide crosslinking agent, and the amount used is 0.5-1.0 parts. The base elastomer comprises an ethylene-vinyl acetate copolymer with a vinyl acetate content of 20-30%. The base elastomer further comprises the polyolefin elastomer, which is an ethylene-octene copolymer with a density of 0.86-0.88 g / cm 3 ; and in the base elastomer, the amount of the ethylene-vinyl acetate copolymer is 40-50 parts, and the amount of the polyolefin elastomer is 10-20 parts by weight.

[0044] Furthermore, in step S1, the raw materials further include at least one selected from the group consisting of a filler, a reinforcing agent, and a processing aid. Specifically, the filler is talc, the reinforcing agent is zinc oxide, and the processing aid includes stearic acid and zinc stearate.

[0045] The present invention provides a method for preparing a high-elastic shock-absorbing foam material. By improving the formula and the preparation method, the problem of balancing the shock-absorbing performance and the rebound performance of the foam material is effectively improved, and on this basis, the physical durability of the foam material to cope with long-term repeated stress impact is ensured.

[0046] Among them, the formula of the present invention mainly includes a basic elastomer that provides basic elasticity, a hydrogenated styrene thermoplastic elastomer that provides core shock absorption function, and brominated butyl rubber that provides key durability and structural stability. In the system of the present invention, the functions of each component are clear and mutually supportive: the basic elastomer constitutes the continuous phase skeleton of the foam material and is the fundamental source of the material's macroscopic elasticity. Its polymer chain network undergoes reversible deformation to store mechanical energy when subjected to force, which is the physical basis for achieving high resilience. The hydrogenated styrene thermoplastic elastomer is dispersed in the matrix in the form of a microphase. When impacted, internal friction and friction occur between its molecular chain segments, and a portion of the mechanical energy is irreversibly converted into heat energy and dissipated, thereby achieving efficient energy absorption, i.e. shock absorption. The extremely low gas permeability of brominated butyl rubber can effectively slow down the escape of gas inside the closed-cell foam material to the outside world, thereby maintaining the structural integrity and internal pressure of the pores for a long time, ensuring that the mechanical properties of the material will not decay rapidly due to physical aging or collapse of the pores during use. At the same time, the high damping properties of butyl rubber itself also synergistically enhance the energy absorption capacity of the entire system.

[0047] Among them, the present invention precisely defines the content of these three core functional components, which is the key to achieving the ultimate performance balance. The amount of base elastomer is limited to 50-70 parts. This is because as a continuous phase, it needs a sufficient amount to ensure the structural integrity and basic resilience of the entire material. If it is less than 50 parts, the matrix will not be able to form a stable continuous network, resulting in weak rebound and insufficient structural strength of the material; if it is higher than 70 parts, the relative content of the shock-absorbing component and the durability component is too low, and the high shock absorption and high durability technical effects pursued by the present invention will not be achieved. In addition, the amount of hydrogenated styrene thermoplastic elastomer and brominated butyl rubber used in the present invention is significantly increased and different from the amount used in the conventional formula in the prior art. Specifically, the hydrogenated styrene thermoplastic elastomer in the conventional formula can be used to improve the overall shock absorption performance of the foam material, but its addition amount should not be too much, because too much hydrogenated styrene thermoplastic elastomer will make the material too soft, resulting in good shock absorption performance but greatly reduced rebound performance. In the present invention, the amount of hydrogenated styrene thermoplastic elastomer is specifically increased. On this basis, brominated butyl rubber is added and the amount of this component is precisely limited. Through its own high damping and poor fluidity, the influence of excessive hydrogenated styrene thermoplastic elastomer on the rebound performance is reduced, while the durability of the foamed material is improved.

[0048] In addition, the preparation method of the present invention is not a universal process, but is closely coupled with the above-mentioned specific chemical formula. First, the present invention preferably limits the base elastomer to be composed of EVA with a specific VA content and ethylene-octene copolymer (POE) with a specific density in a specific weight ratio. The introduction of ethylene-octene copolymer (POE) can significantly improve the strength and toughness of the blend in the molten state, so that when the precursor composition is subjected to an extreme compression ratio of up to 140%-150% during the subsequent secondary molding process, its cell walls will not undergo brittle fracture and structural collapse, thereby achieving the orderly densification to be achieved by the present invention. Among them, EVA, as the main component, provides the basic elasticity and framework of the system. And POE, as a toughening modifier, its dosage must be within an appropriate range to play the best role. If the dosage of POE is less than 10 parts, its improvement effect on the mechanical properties of the entire matrix, especially the improvement effect on the melt strength, will not be obvious, and the resulting matrix material will not be tough enough to withstand the harsh conditions of the subsequent high compression ratio process. If the amount of POE is higher than 20 parts, the excessive POE may affect the compatibility of the blending system, and also reduce the rigidity and resilience of the matrix material to a certain extent, deviating from the technical goal of high rebound and high shock absorption of the present invention.

[0049] Secondly, after the raw materials are melt-mixed to form a precursor composition, the present invention simultaneously performs chemical foaming and cross-linking reactions in step S2. Because the formulation of the present invention contains a relatively high content of hydrogenated styrene thermoplastic elastomer and brominated butyl rubber, the uniform dispersion of these two components in the matrix is ​​crucial to the final performance. The simultaneous foaming and cross-linking reactions can fix the polymer network through cross-linking within the same time window of gas generation and cell expansion to form the final physical form. This process can effectively fix functional phases such as hydrogenated styrene thermoplastic elastomer and brominated butyl rubber uniformly in their dispersed positions in the matrix, effectively suppressing phase domain aggregation or unevenness that may be caused by thermal effects. This ensures that every part of the final material has the shock absorption and durability properties required by the design on a macroscopic scale, avoiding the problem of uneven performance distribution. During the heating process, the foaming agent decomposes to produce gas, causing the material to have a tendency to expand; at the same time, the cross-linking agent decomposes to trigger chemical bonding between polymer chains, increasing the viscosity and strength of the material. The rates of these two reactions are matched by using specific blowing agents and crosslinking agents in a precisely defined weight ratio, ensuring they proceed simultaneously. If the crosslinking reaction is too rapid, the polymer matrix solidifies before the gas has fully expanded, inhibiting the formation and growth of cells, resulting in insufficient expansion ratio and excessive material density. Conversely, if the foaming reaction is too rapid, the excessive amount of gas before the matrix has built up sufficient strength can cause excessive expansion, rupture, or merging of cells, ultimately forming a coarse and uneven cell structure, and even causing the foamed product to collapse, seriously affecting the material's mechanical properties.

[0050] Furthermore, in step S2, a secondary molding process is used to further ensure the balance between the shock absorption and resilience properties of the final foamed material. In the first step, a high-rate primary foaming process is used to prefabricate a large foamed preform with relatively weak cell walls and a loose internal structure. This preform serves as an intermediate for the subsequent structural remodeling, providing ample internal space for compression. In the second step, this loose foamed preform is subjected to a compression ratio of 140%-150%. Under specific heating temperature and molding time control, the physical structure of the preform is altered. During this process, the loose cell network is strongly compressed, trapping gas within the cells and applying high pressure. Under high pressure, the cell walls fold, buckle, and densify. Ultimately, the compacted, thickened, and toughened cell walls serve as supporting beams, forming a three-dimensional, highly tough, continuous network. Simultaneously, a dense, non-porous skin forms on the material surface. The entire cross-linking reaction is fully completed in this highly compressed state, thereby fixing this high-strength microstructure.

[0051] Therefore, an inseparable synergy is generated between the formula and preparation process defined by the present invention. The high-toughness material foundation achieved by the combination of ethylene-vinyl acetate copolymer and polyolefin elastomer in the base elastomer is a necessary condition for achieving high compression ratio physical molding in the subsequent secondary molding process. The foam material thus obtained has good shock absorption and rebound effects. The strong and dense cell wall network in the foam material can quickly undergo elastic deformation and quickly recover when impacted by external forces, storing and returning most of the energy, thereby contributing to excellent high rebound performance. At the same time, when the entire porous network structure is compressed, the compression and flow of the gas in the cells, as well as the internal friction of the polymer material itself, efficiently absorb and dissipate the impact energy, achieving high shock absorption performance. In addition, the densified, high-strength pore network formed by the high compression ratio process improves the material's fatigue resistance and structural stability, reduces the material's permanent compression deformation rate under long-term, repeated stress cycles, improves the problem of rapid performance degradation of existing materials due to structural fatigue, and ensures that the material can maintain its excellent rebound and shock absorption properties throughout its service life.

[0052] In order to further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to examples and comparative examples.

[0053] The raw materials used in the embodiments and comparative examples have the following specific brands or models:

[0054] Ethylene vinyl acetate copolymer (EVA): Plastics Industry Co., Ltd., brand 7350M, VA content of 28%.

[0055] Polyolefin elastomer (POE): Dow Chemical Company, brand Engage TM 8180, an ethylene-octene copolymer with a density of 0.863 g / cm 3 .

[0056] Hydrogenated styrenic thermoplastic elastomer (SEBS): Kraton Polymers, brand name Kraton TM G1652, a linear styrene-ethylene / butylene-styrene block copolymer.

[0057] Bromobutyl rubber (BIIR): ExxonMobil Chemical Company, brand Exxon TM Bromobutyl 2222.

[0058] Foaming agent (ADC): azodicarbonamide, Hebei Jianxin Chemical Co., Ltd., model AC-3000.

[0059] Crosslinking agent (DCP): dicumyl peroxide, Arkema, brand DC.

[0060] Zinc oxide (ZnO): industrial grade, indirect method, purity 99.7%.

[0061] Stearic acid: industrial grade, type 1801.

[0062] Talc: 1250 mesh.

[0063] Low-density polyethylene (LDPE): China Petrochemical Corporation, brand 2426H.

[0064] Example 1

[0065] (1) Step S1: melt blending

[0066] Step S11: Preheat the internal mixer to 115°C, add 45 parts by weight of EVA (7350M), 15 parts by weight of POE (Engage TM 8180), 25 parts by weight of SEBS (Kraton TM G1652), 15 parts by weight of BIIR (Exxon TM 2222), 5 parts by weight of talc, 3 parts by weight of zinc oxide and 1 part by weight of stearic acid. Close the top plug and melt blend for 9 minutes at a rotor speed of 35 rpm to obtain a first-stage blended material.

[0067] Step S12: The first-stage blended material is thinned and passed on an open mill. When the material temperature drops to 95° C., 4 parts by weight of a foaming agent ADC and 0.8 parts by weight of a cross-linking agent DCP are added and mixed for 4 minutes to obtain a final precursor composition.

[0068] (2) Step S2: Foaming

[0069] Step S21: The precursor composition is weighed and placed in a primary foaming mold, heated on a flat vulcanizer at 165° C. for 12 minutes to foam it to a foaming ratio of 185%, thereby obtaining a foamed embryo. The embryo is then taken out and cooled to set.

[0070] Step S22: Cut the foamed preform and place it in a precision shaping mold, close the mold to achieve a compression ratio of 145%, then place the mold on a flat vulcanizer, heat the mold at 178°C for 550 seconds, then water-cool for 500 seconds, and then open the mold to remove the finished product.

[0071] Example 2

[0072] The formula and preparation method are basically the same as those in Example 1, except that the amount of hydrogenated styrene-based thermoplastic elastomer (SEBS) is 35 parts by weight and the amount of brominated butyl rubber (BIIR) is 10 parts by weight. The other components and process parameters remain unchanged.

[0073] Example 3

[0074] The formula and preparation method are basically the same as those in Example 1, except that the primary expansion ratio is 180%, the secondary compression ratio is 140%, and the other components and process parameters remain unchanged.

[0075] Comparative Example 1

[0076] The material formula is exactly the same as that of Example 1, but the conventional preparation process described below is adopted:

[0077] (1) Melt blending: All components of the formula of Example 1, including the base elastomers (EVA, POE), functional elastomers (SEBS, BIIR), additives (talc, zinc oxide, stearic acid), foaming agent (ADC) and crosslinking agent (DCP), were added to an internal mixer at one time and melt blended at 115°C for 12 minutes to form a homogeneous material.

[0078] (2) Foaming molding: The above blended material is extruded and foamed in a single-screw extruder with the barrel temperature set at 170°C and the die temperature set at 175°C to obtain a single-foamed sheet.

[0079] (3) Pressing and shaping: The foamed sheet is placed in a mold of a flat vulcanizer and pressed and shaped at 170°C and 15 MPa for 5 minutes to obtain the final product. This step is intended to simulate the compaction treatment of the foamed material in the conventional process.

[0080] Comparative Example 2

[0081] The same preparation process as in Example 1 was used, except that the polyolefin elastomer (POE) was not included in the material formulation. The base elastomer was 60 parts of EVA (7350M). The remaining components and process parameters remained unchanged from Example 1.

[0082] Comparative Example 3

[0083] The same preparation process as in Example 1 was used, except that the amount of hydrogenated styrene thermoplastic elastomer (SEBS) in the material formulation was increased to 40 parts by weight, which exceeded the range defined in the present invention. The remaining components and process parameters remained unchanged from those in Example 1.

[0084] Comparative Example 4

[0085] This comparative example adopts an existing technical solution, and its formula and preparation process are as follows:

[0086] (1) Material formula (parts by weight): 30 parts of ethylene-vinyl acetate copolymer (EVA), 8 parts of low-density polyethylene (LDPE), 8 parts of hydrogenated styrene elastomer (SEBS), 8 parts of brominated butyl rubber (BIIR), and various other fillers and additives.

[0087] (2) Preparation process:

[0088] Step 1 (multi-stage mixing): According to the multi-stage mixing method of the prior art, different components are mixed in batches in an internal mixer to obtain a mixture containing a base resin, a functional additive, a foaming agent and a cross-linking agent.

[0089] Step 2 (extrusion foaming): the mixed material is extruded and foamed through an extruder to obtain a primary foaming material.

[0090] Step 3 (high-pressure molding): The primary foaming material is mixed with a polyethylene modified material, and then subjected to banbury molding at 170°C and 45 MPa under high pressure to obtain the final product.

[0091] The foam materials prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests according to the following Chinese national standards.

[0092] Hardness (Shore C): Tested in accordance with GB / T 531.1-2008.

[0093] Density (g / cm 3 ):Tested in accordance with GB / T 533-2008 standard.

[0094] Rebound rate (%): tested in accordance with GB / T 6670-2008 standard.

[0095] Tear strength (N / mm): tested in accordance with GB / T 529-2008 standard.

[0096] Compression set (%): According to GB / T 6669-2008, the test is carried out after compressing 50% at 70°C and holding for 22 hours.

[0097] The test results are shown in the following table:

[0098]

[0099] According to the above test results:

[0100] Comparative Example 1 uses exactly the same preferred chemical formula as Example 1, but uses a conventional preparation process. Although its test results are acceptable in some aspects, there is still a huge gap compared with Example 1. Its rebound rate is only 58% (far lower than 72% of Example 1), and the compression permanent deformation rate is as high as 45% (far worse than 25% of Example 1). This comparison strongly proves that only using the chemical formula of the present invention is not enough to achieve the ultimate technical effect. The unique process path of "high-ratio primary foaming-high compression ratio secondary molding" of the present invention, and the synergistic cooperation between the formulas, achieve the final required high rebound, high shock absorption and high durability.

[0101] Comparative Example 2 uses the process of the present invention, but lacks polyolefin elastomer (POE) in its formula. Its tear strength is only 8.2N / mm, which is much lower than the 12.5N / mm of Example 1, and the compression set rate is also as high as 48%. This shows that the lack of the high toughness given by POE means that the basic elastomer material cannot effectively maintain the integrity of its cell structure under the high compression ratio of the secondary molding, causing the cell wall to be damaged at the microscopic level. Although the rebound rate is acceptable, the structural strength and durability (tear resistance, compression deformation resistance) of the material are seriously weakened. This proves that the various components in the formula of the present invention, especially the introduction of POE, have an inseparable synergistic effect with the preparation process.

[0102] Comparative Example 3 increased the SEBS content to 40 parts, outside the claimed range. The results showed a significant decrease in hardness, making the material too soft. The rebound rate plummeted to 55%, and the compression set also deteriorated to 52%. This indicates that excessively high levels of the shock-absorbing component can impair the material's rebound performance and structural stability, failing to achieve the desired balance of "high resilience, high shock absorption, and high durability" sought by the present invention.

[0103] As can be seen from the data in Table 1, the foam materials produced in Examples 1-3 significantly outperformed Comparative Example 4 in three key properties: rebound rate, tear strength, and compression set. The rebound rate of Example 1 was as high as 72%, significantly higher than the 45% of Comparative Example 4; at the same time, the compression set was as low as 25%, significantly better than the 68% of Comparative Example 4. This demonstrates that the technical solution of the present invention successfully resolves the conflict between shock absorption and rebound, and significantly improves the durability of the material. However, the solution of Comparative Example 4, due to its complex formulation, low content of functional components, and conventional processing, was unable to form the unique microstructure described in the present invention, resulting in poor performance.

[0104] The above description and embodiments are intended to explain the scope of protection of the present invention, but do not constitute a limitation thereto. Modifications, equivalent substitutions, or other improvements to the embodiments of the present invention or portions thereof that can be obtained by a person of ordinary skill in the art through logical analysis, reasoning, or limited experimentation based on the teachings of the present invention or the above embodiments, combined with common knowledge, ordinary technical knowledge in the field, and / or prior art, should all be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-elastic shock-absorbing foam material, characterized in that: include: S1: melt-blending raw materials including a base elastomer, a hydrogenated styrene-based thermoplastic elastomer, brominated butyl rubber, a foaming agent, and a cross-linking agent to form a homogeneous precursor composition; S2: simultaneously subjecting the precursor composition to chemical foaming and cross-linking reactions to form the foamed material having a continuous network cell structure; The base elastomer comprises at least one of ethylene-vinyl acetate copolymer and polyolefin elastomer; and, in parts by weight, the base elastomer is used in an amount of 50-70 parts, the hydrogenated styrene thermoplastic elastomer is used in an amount of 15-35 parts, and the brominated butyl rubber is used in an amount of 10-25 parts.

2. The method for preparing a high-elastic shock-absorbing foam material according to claim 1, wherein: In step S2, the following steps are included: Step S21: subjecting the precursor composition formed in step S1 to a primary foaming and cross-linking reaction to obtain a foamed primary embryo; Step S22: placing the foamed embryo in a mold and pressing and heating it to perform foaming and cross-linking reactions again to obtain the foamed material.

3. The method for preparing a high-elastic shock-absorbing foam material according to claim 2, wherein: In step S21, the foaming ratio of the precursor composition is 180%-190%; Furthermore, in step S22, the compression ratio applied to the foamed preform is 140%-150%.

4. The method for preparing a high-elastic shock-absorbing foam material according to claim 3, wherein: In step S22, the molding is heated at a temperature of 175°C-181°C for 520-580 seconds, followed by cooling for 470-530 seconds.

5. The method for preparing a high-elastic shock-absorbing foam material according to claim 1, wherein: The foaming agent is azodicarbonamide, and the usage amount is 3-5 parts; the cross-linking agent is an organic peroxide cross-linking agent, and the usage amount is 0.5-1.0 parts.

6. The method for preparing a high-elastic shock-absorbing foam material according to claim 3, wherein: The base elastomer comprises ethylene-vinyl acetate copolymer having a vinyl acetate content of 20-30%.

7. The method for preparing a high-elastic shock-absorbing foam material according to claim 6, wherein: The base elastomer also includes the polyolefin elastomer, which is an ethylene-octene copolymer with a density of 0.86-0.88 g / cm 3 ; In the base elastomer, the amount of the ethylene-vinyl acetate copolymer is 40-50 parts by weight, and the amount of the polyolefin elastomer is 10-20 parts by weight.

8. The method for preparing a high-elastic shock-absorbing foam material according to claim 1, wherein: In step S1, the raw materials further include at least one selected from fillers, reinforcing agents and processing aids.

9. The method for preparing a high-elastic shock-absorbing foam material according to claim 8, wherein: The filler is talc powder, the reinforcing agent is zinc oxide, and the processing aid comprises stearic acid and zinc stearate.

10. The method for preparing a high-elastic shock-absorbing foam material according to claim 1, wherein: In step S1, the following steps are included: S11: melt blending the base elastomer, hydrogenated styrene-based thermoplastic elastomer and brominated butyl rubber in an internal mixer in a first stage; S12: melt-blending the materials after the first stage blending with the foaming agent and the cross-linking agent in a second stage in an open mill to form a homogeneous precursor composition.

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