KR102555314B1 - A foaming composition for eco-friendly shoe parts - Google Patents

Abstract

One aspect of the present invention is a foamable resin 100 parts by weight; 1 to 35 parts by weight of filler; 1 to 30 parts by weight of recycled filler obtained by pulverizing waste shoes; And 0.1 to 10 parts by weight of a foaming agent; and a composition for a shoe member comprising a shoe member manufactured by foaming the same.

Description

Foaming composition for eco-friendly shoe members {A FOAMING COMPOSITION FOR ECO-FRIENDLY SHOE PARTS}

The present invention relates to an eco-friendly foam composition for shoe members and a shoe member manufactured by foaming the same.

Shoes are worn to protect the feet of the human body, and are manufactured and sold in various shapes and types. However, they are usually made by increasing friction with the ground while protecting the upper and soles that cover and protect the instep and ankle. It is composed of a sole that improves gaitability and at the same time alleviates the impact applied to the sole of the foot during walking.

The shoe sole is attached to a midsole made of rubber, foamed resin, or sponge material having excellent buffering power to elastically distribute and support the load of the human body during walking and is attached to the bottom surface of the midsole to provide frictional force during walking. It consists of an outsole made of rubber material for

In general, midsoles are generally manufactured using ethylene vinyl acetate (EVA) or polyurethane as a main material. The ethylene vinyl acetate has excellent light weight, is inexpensive, and has a soft and cushiony feeling, but has low restoring force, so that the cushion may be turned off over time. The polyurethane has relatively less cushioning than ethylene vinyl acetate, but has excellent durability and elasticity, quick recovery even when pressure is applied for a long time, and excellent processability and moldability. However, polyurethane is prone to breakage due to hydrolysis over time, and since the material itself is heavy, it may increase user's foot fatigue when worn for a long time.

In order to solve this problem, a technique for improving recovery and durability by including a metal oxide in the ethylene vinyl acetate has been proposed, but when a large amount of metal oxide is included, the manufacturing cost may increase, and the lightness of the shoe In addition to deterioration, there is a problem that durability, restoring force, etc. imparted to the shoe member immediately after manufacture cannot be maintained for a long period of time and deteriorated within a short period of time. Therefore, there is a demand for technical development of a composition for a shoe member having excellent light weight while improving resilience and durability by including a small amount of metal oxide.

On the other hand, while environmental issues have recently emerged throughout society, polymer and rubber materials used for various household items, automobile parts, and electrical and electronic product parts do not rot and cause environmental pollution problems. is causing

In particular, among these industrial wastes, rubber wastes generated by rubber products, which are widely used in tires and the like, do not decompose naturally, so they are a major cause of environmental pollution such as water, soil and air pollution. If this is done, serious environmental destruction may be caused by rapidly increasing rubber waste.

Studies on recycling methods for shoes, which generate as much rubber waste as tires, are insufficient. This is considered to be due to the characteristics of shoes composed of various components in a complex manner, unlike tires entirely composed of a rubber matrix and various additives.

The present invention is to solve the problems of the prior art described above, an object of the present invention is to provide an eco-friendly foaming composition for a shoe member that is environmentally friendly and has excellent physical properties, including recycled components derived from waste shoes, and a shoe member manufactured by foaming the same. is to do

One aspect of the present invention, 100 parts by weight of a foamable resin; 1 to 35 parts by weight of filler; 1 to 30 parts by weight of recycled filler obtained by pulverizing waste shoes; and 0.1 to 10 parts by weight of a foaming agent.

In one embodiment, the foamable resin may include ethylene vinyl acetate and a crystalline polymer.

In one embodiment, the ethylene vinyl acetate may include two or more ethylene vinyl acetates having different vinyl acetate contents.

In one embodiment, the ethylene vinyl acetate is the first ethylene vinyl acetate content of 20 to 30% by weight of vinyl acetate; and a second ethylene vinyl acetate having a vinyl acetate content of 5 to 20% by weight.

In one embodiment, the content of the crystalline polymer in the foamable resin may be 5 to 30% by weight.

In one embodiment, the crystalline polymer may include one selected from the group consisting of polyolefin, polyester, polycarbonate, polyamide, polyimide, and combinations of two or more thereof.

In one embodiment, the filler may be at least one of carbon black and silica.

In one embodiment, the average particle size of the reclaimed filler is 10 to 1,000 μm, and the surface of the reclaimed filler may be organosilane-modified.

In one embodiment, the composition for shoe members may further include one selected from the group consisting of a metal oxide, a lubricant, a crosslinking agent, a crosslinking aid, and a combination of two or more thereof.

Another aspect of the present invention provides a shoe member manufactured by foaming the composition for a shoe member.

An eco-friendly foam composition for a shoe member and a shoe member using the same according to an aspect of the present invention are environmentally friendly by replacing some of the fillers included in the conventional composition for a shoe member with recycled filler derived from waste shoes, and a shoe member including the same. While improving the durability, resilience and light weight of the shoe member, these properties given during manufacture can be maintained for a long period of time.

The effects of the present invention are not limited to the above effects, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the configuration of the invention described in the claims.

Hereinafter, the present invention will be described. However, the present invention may be embodied in many different forms and, therefore, is not limited to the embodiments described herein.

Throughout the specification, when a part is said to be "connected" to another part, this includes not only the case where it is "directly connected" but also the case where it is "indirectly connected" with another member interposed therebetween. . In addition, when a part "includes" a certain component, it means that it may further include other components without excluding other components unless otherwise stated.

One aspect of the present invention, 100 parts by weight of a foamable resin; 1 to 35 parts by weight of filler; 1 to 30 parts by weight of recycled filler obtained by pulverizing waste shoes; and 0.1 to 10 parts by weight of a foaming agent.

The foamable resin is a soft or hard polyolefin elastomer, an ethylene-based copolymer, a styrenic copolymer, polyethylene, polypropylene, polyurethane, polyester, nylon, polybutylene terephthalate, polycarbonate, polylactic acid, polymethyl methacryl rate, polyoxymethylene, and one selected from the group consisting of a combination of two or more thereof.

In particular, the foamable resin may be a thermoplastic elastomer, preferably an ethylene-based copolymer. For example, the ethylene-based copolymer may be one selected from the group consisting of ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and a combination of two or more of them, preferably ethylene vinyl acetate, It is not limited to this.

Conventional shoe members, for example, shoe midsoles, are manufactured using ethylene vinyl acetate and/or polyurethane as a main resin. Polyurethane is relatively superior to ethylene vinyl acetate in terms of durability, processability, moldability, and resilience, but the material itself is heavy, so the weight of shoes increases, and users who wear them inevitably feel fatigue within a short period of time. Ethylene vinyl acetate has excellent light weight, but has a problem in that resilience and durability are lower than polyurethane.

In contrast, the foamable resin of the composition for a shoe member includes two types of ethylene vinyl acetate, that is, a first ethylene vinyl acetate, a second ethylene vinyl acetate having a monomer composition different from that of the first ethylene vinyl acetate, and a crystalline polymer. By including it, resilience, durability, mechanical properties, and durability of these properties, which are lacking in conventional ethylene vinyl acetate, can be adequately supplemented.

While the ethylene vinyl acetate itself has excellent light weight, flexibility and adhesiveness of the resin may be determined by the degree of polymerization and the content of vinyl acetate. For example, when the content of vinyl acetate in the ethylene vinyl acetate is increased, flexibility and adhesiveness may be improved. However, as the content of vinyl acetate increases, there is a problem in that processability decreases due to increased adhesiveness during processing.

In addition, it is difficult to sufficiently implement durability and mechanical properties with ethylene vinyl acetate alone, and in particular, since tensile strength and the like decrease when used in a foam form, mechanical properties can be improved by partially crosslinking with a crosslinking agent.

The ethylene vinyl acetate may be prepared by emulsion polymerization, solution polymerization and/or suspension polymerization of monomers.

The emulsion polymerization is a method of emulsifying oil-soluble monomers in water with a surfactant and polymerizing them using a water-soluble initiator. can be obtained

The solution polymerization is a method in which an oil-soluble monomer is dissolved in a solvent, for example, an organic solvent, and then polymerized using an initiator.

The suspension polymerization is carried out in the micelle of the monomers suspended by dispersing the monomers in a medium in which the monomers are hardly soluble and using a polymerization initiator that is not soluble in the medium but is well soluble in the monomers. Polymerization can proceed as follows.

The content of vinyl acetate in the first ethylene vinyl acetate may be 20 to 30% by weight. If the content of vinyl acetate in the first ethylene vinyl acetate is less than 20% by weight, flexibility and adhesiveness may be deteriorated, and if it is greater than 30% by weight, processability may be deteriorated.

The content of vinyl acetate in the second ethylene vinyl acetate may be 5 to 20% by weight. If the content of vinyl acetate in the second ethylene vinyl acetate is less than 5% by weight, resilience may be reduced, and if it is greater than 20% by weight, workability may be reduced.

The content of the first ethylene vinyl acetate in the foamable resin may be 40 to 90% by weight. If the content of the first ethylene vinyl acetate in the foamable resin is less than 40% by weight, the restoring force may be reduced, and if it is greater than 90% by weight, durability and mechanical properties may be reduced.

The foamable resin may further include a crystalline polymer. The crystalline polymer not only partially improves the physical properties of the shoe member manufactured using the shoe member composition, for example, durability, resilience, and mechanical properties, but also can maintain these properties for a long period of time. However, since these crystalline polymers generally have a high processing temperature, for example, a melting point, a softening point, etc., it is difficult to process at about 100 to 150 ° C., which is the processing temperature of the ethylene vinyl acetate. there is

Therefore, when the crystalline polymer has a relatively low processing temperature and thus has good or excellent miscibility and compatibility with the ethylene vinyl acetate, these problems can be appropriately solved.

The crystalline polymer may be a thermoplastic polymer, and the thermoplastic polymer may be, for example, one selected from the group consisting of polyolefin, polyester, polycarbonate, polyamide, polyimide, and combinations of two or more thereof. It may include, preferably, may be polyolefin, but is not limited thereto.

The weight average molecular weight (Mw) of the polyolefin may be 1,000 to 100,000 g/mol, preferably 1,000 to 50,000 g/mol, and more preferably 1,000 to 30,000 g/mol. When the weight average molecular weight of the polyolefin is less than 1,000 g/mol, the melt viscosity is excessively low, resulting in extremely low dispersibility of other components included in the composition for shoe members, and in some cases, phase separation between the polyolefin and the other components. Alternatively, layer separation may occur. On the other hand, when the weight average molecular weight of the polyolefin is greater than 100,000 g/mol, the melt viscosity increases and processability decreases, which may cause uneven kneading during kneading.

The molecular weight distribution (Mw/Mn) of the polyolefin may be 3 to 7. If the molecular weight distribution of the polyolefin is less than 3, the dispersibility with the other components is lowered, and the physical properties of the manufactured shoe member may become non-uniform for each part and region, and if it exceeds 7, the mechanical properties of the shoe member may be lowered.

The polyolefin is, for example, one selected from the group consisting of polyethylene, polypropylene, polybutylene, polymethylpentene, ethylene vinyl acetate, ethylene butyl acrylate, ethylene ethyl acrylate, and combinations or copolymers of two or more thereof It may be, preferably, polyethylene, more preferably, low density polyethylene (LDPE), but is not limited thereto. Since the low-density polyethylene has a melting point of about 100 to 120° C., miscibility and compatibility with the ethylene vinyl acetate can be appropriately secured.

The content of the crystalline polymer in the foamable resin may be 5 to 30% by weight. If the content of the crystalline polymer in the foamable resin is less than 5% by weight, it is difficult to maintain the physical properties of the shoe member for a certain period of time or more, and if it exceeds 30% by weight, the rebound elasticity of the shoe member and the restoring force thereof may be reduced.

The content of the filler is 1 to 35 parts by weight, for example, 1 part by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight based on 100 parts by weight of the foamable resin. , 35 parts by weight or a range between two of these values. The filler may be at least one of carbon black and silica, preferably, silica, but is not limited thereto.

The content of the recycled filler is 1 to 30 parts by weight, for example, 1 part by weight, 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight based on 100 parts by weight of the foamable resin. It may be negative or a range between two of these values. The reclaimed filler is manufactured by crushing waste shoes, and may include foam, rubber, fabric, filler, and a very small amount of adhesive components. In this way, since the recycled filler is a mixture of a material having excellent affinity with the expandable resin and a material having excellent affinity with the filler, the compatibility of the composition for shoe members can be improved by using an appropriate amount of the recycled filler.

The total content of the filler and the recycled filler is 10 to 35 parts by weight, for example, 10 parts by weight, 15 parts by weight, 20 parts by weight, 30 parts by weight, 35 parts by weight or two of these based on 100 parts by weight of the foamable resin. It can be a range between values. If the total content of the filler and recycled filler is out of the above range, processability may deteriorate or mechanical properties may be unsuitable for shoe members.

Unless there is a separate surface treatment, the weight ratio of the recycled filler in the total content of the filler and the recycled filler may be 90% or less. If the ratio of the reclaimed filler is out of the above range without a separate treatment, the processability of the composition for a shoe member may deteriorate, and mechanical properties may deteriorate due to poor dispersibility in the foamable resin.

In addition, when the filler is silica, the surface of the recycled filler may be modified with organosilane. Foams, rubbers, etc. included in the regenerated filler may have insufficient compatibility with silica, but can significantly improve mechanical properties of final products by modifying them with organosilane to improve affinity with hydrophilic silica. Such organic silane modification may be performed by forming a hydroxy group (-OH) or carboxy group (-COOH) on the surface through surface treatment such as plasma treatment or UV treatment, and then reacting with aminoalkoxysilane or the like, but is not limited thereto. .

The average particle size of the recycled filler is 10 to 1,000 μm, for example, 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm. μm, 600 μm, 650 μm, 700 μm, 750 μm, 800 μm, 850 μm, 900 μm, 950 μm, 1,000 μm, and may range between two values thereof. If the average particle size of the recycled filler is out of the above range, fine pulverization may be substantially impossible or the size of the recycled filler may be excessively large, resulting in deterioration in dispersibility in the expandable resin matrix. The particle size can be realized by grinding the waste shoes one or more times by milling after washing, heat treatment before and/or after grinding, and/or removing metal components, and as a result, compatibility with the expandable resin matrix and filler is improved. can do.

The composition for a shoe member may further include one selected from the group consisting of a metal oxide, a lubricant, a crosslinking agent, a crosslinking aid, and a combination of two or more thereof.

When the composition for a shoe member is prepared by including only ethylene vinyl acetate, weight reduction can be realized, but durability and mechanical properties are lowered, which not only increases the defect rate of the shoe, but also reduces the user's fit and comfort. However, when a large amount of metal oxide is included, compatibility and processability with the foamable resin are lowered, and as the content of the metal component increases, the weight of the shoe member becomes heavy, which can also act as a factor deteriorating the user's comfort. there is.

Therefore, by including a small amount of a metal oxide in the first and second ethylene vinyl acetate and the crystalline polymer having different monomer compositions, the weight of the shoe can be finally realized, and the durability and resilience of the shoe member can be improved. .

The content of the metal oxide may be 1 to 10 parts by weight based on 100 parts by weight of the foamable resin. If the content of the metal oxide in the composition for a shoe member is less than 1 part by weight, durability and mechanical properties of the shoe may be reduced, and if it is more than 10 parts by weight, a large amount of metal oxide is included in the composition, and thus the lightness of the shoe may be reduced. there is.

The metal oxide may include zinc oxide, titanium oxide, or a combination thereof.

The zinc oxide may be included or dispersed in the foamable resin to control a crosslinking rate and promote foaming. The titanium oxide may be included in the composition for a shoe member together with the zinc oxide to further promote crosslinking and foaming.

The composition for shoe members may include a lubricant, and the lubricant may be, for example, stearic acid, but is not limited thereto. The stearic acid may play a role of uniformly dispersing the composition for shoe members. Specifically, the stearic acid is included in the composition for a shoe member to micronize large particles or agglomerated particles in the composition into smaller particles and uniformly disperse them, thereby preventing aggregation of the particles.

The amount of the lubricant may be 0.1 to 5 parts by weight based on 100 parts by weight of the foamable resin. If the content of the lubricant is less than 0.1 parts by weight, the dispersing effect may be weak, and if it exceeds 5 parts by weight, the viscosity of the composition for shoe members may be excessively lowered, resulting in deterioration in processability.

The composition for a shoe member may contain a foaming agent. The blowing agent may include, for example, one selected from the group consisting of azodicarbonamide, dinitrosopentamethyltetraamine, azobisisobutylnitrile, p-toluenesulfonylhydrazide, and combinations of two or more thereof. Yes, preferably, it may be azodicarbonamide, but is not limited thereto.

The amount of the foaming agent may be 0.1 to 10 parts by weight based on 100 parts by weight of the foamable resin. If the content of the foaming agent is less than 0.1 parts by weight, lightness may be reduced, and if it is greater than 10 parts by weight, durability of the shoe member may be reduced.

The composition for a shoe member may further include additives such as a crosslinking agent, a crosslinking aid, a pigment, and a dye.

The crosslinking agent may be a peroxide-based crosslinking agent. The crosslinking agent is, for example, dicumyl peroxide, t-butylperoxylaurylate, t-dibutylperoxymaleic acid, t-butylhydroperoxide, 2,5-dimethyl-2,5-di(t- butyl peroxy) nucleic acid, di-t-butyl peroxide and 1,3-bis (t-butyl peroxy isopropylene) benzene, and may be one selected from the group consisting of combinations of two or more thereof, preferably dicu It may be milperoxide, but is not limited thereto.

The content of the crosslinking agent may be 0.1 to 5 parts by weight based on 100 parts by weight of the foamable resin. If the content of the crosslinking agent is less than 0.1% by weight, durability and mechanical properties of the shoe member may decrease, and if it exceeds 5 parts by weight, flexibility and resilience of the shoe member may decrease.

The cross-linking aid may serve as a cross-linking accelerator that promotes a cross-linking reaction together with the cross-linking agent. The crosslinking aid is, for example, triallyl cyanurate, triallyl isocyanurate, trimethylol, polybutadiene, propane trimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, butyl may include one selected from the group consisting of len glycol acrylate, butylene glycol dimethacrylate, metal-acrylate, metal-methacrylate, and a combination of two or more of them, preferably, triallyl cyanurate It may be, but is not limited thereto.

The content of the crosslinking aid may be 0.1 to 2 parts by weight based on 100 parts by weight of the foamable resin. If the content of the cross-linking aid is less than 0.1 parts by weight, durability and mechanical properties of the shoe member may be reduced, and if it exceeds 2 parts by weight, flexibility and resilience of the shoe member may be reduced.

Another aspect of the present invention provides a shoe member manufactured by foam molding the composition for a shoe member. The manufacturing method of the shoe member may be a press method or an injection method. The shoe member may be manufactured by a press method or an injection method using the composition for a shoe member, and may be selected in consideration of desired purposes, facilities, effects, and the like.

The press method separately foams and expands the composition for shoe members, uses a press to form a sheet, cuts it into the size required for manufacturing, puts it in a press mold, pressurizes it at high temperature and pressure, and cools it to manufacture a shoe member. . In addition, the injection method can manufacture a shoe member through injection molding in which a composition for a shoe member is made into a pellet-type compound through an extruder, and the composition is put into an injection mold to proceed with crosslinking and foaming while maintaining a heated state.

The manufacturing method of the shoe member may include a step of mixing the composition for a shoe member before including the step of foam molding. The composition of the composition for shoe members is the same as described above. The composition for a shoe member may be put into a mixer and mixed, and the mixer may be a kneader, a ban-bury mixer, or an open roll mill, but is not limited thereto. no.

Mixing in the kneader may be performed at 50 to 100 ° C. If the temperature is less than 50 ° C, uniform mixing may be difficult, and if the temperature exceeds 100 ° C, additives such as a crosslinking agent and a foaming agent may be decomposed, resulting in a decrease in physical properties. It can be.

The extruder may be a single screw extruder or a twin screw extruder. As used herein, the terms "single-screw extruder" and "twin-screw extruder" refer to a screw-type extruder having one and two screws, respectively.

The single-screw extruder is suitable for extrusion molding of most thermoplastic resins, and the twin-screw extruder is mainly used for manufacturing pipes having a large diameter, for example, polyvinyl chloride (PVC) pipes. The twin-screw extruder has a more complicated structure than the single-screw extruder, so the equipment is expensive, but it is widely used because it is possible to perform constant and stable extrusion with a large amount of extrusion even at a slow screw driving speed.

The extrusion temperature may be carried out at 100 ~ 150 ℃. The extrusion temperature of the extruder may be differently adjusted according to the type of the composition, in consideration of the possibility of destruction of the mixture due to the pressure and temperature applied to the mixture during the extrusion process.

On the other hand, the length of the extruder: the ratio of the diameter may be 25 to 50: 1. The “length: diameter ratio” of the extruder means the ratio of the length (L) and diameter (D) of the screw, which is one of the factors determining the extrusion performance of the extruder. In general, as the "length: diameter ratio" value of the screw increases, the kneading effect and product quality improve, and the deviation of the extrusion amount can be reduced. can be adjusted differently.

If the length:diameter ratio of the extruder is less than 25:1, the kneading effect of the required level cannot be realized, and if it exceeds 50:1, the size of the extruder and the capacity of the driving motor may be affected, thereby reducing process efficiency.

In addition, the driving speed of the extruder may be 50 to 500 rpm. The drive speed of the extruder means the rotation speed of the screw provided in the extruder, and if the drive speed of the extruder is less than 50 rpm, the kneading effect of the required level cannot be implemented, and if it exceeds 500 rpm, the rotation of the motor compared to the number of rotations of the screw. Because the number is so large, they can cause damage by applying excessive loads to motors and gearboxes.

The shoe member may satisfy the following conditions. In addition, the shoe member may have a hardness (Asker, C) of 40 to 55, a specific gravity of 0.2 to 0.3 g/cc, and tensile strength and tear strength of 15 to 25 MPa and 10 to 20 N/mm, respectively.

<expression>

B/A ≥ 0.9

In the above formula, A is the rebound elasticity (%) measured immediately after manufacturing the shoe member, and is 40 or more, and B is the rebound elasticity (%) measured 7 days after the shoe member is manufactured.

Hereinafter, embodiments of the present invention will be described in detail.

Preparation Example 1

The first crushing of the washed shoe waste was performed using a milling grinder. The primary pulverized material was transferred to a magnetic conveyor, and metal components located on reinforcing materials and labels were removed. A recycled filler (1) was prepared by performing secondary grinding using a freeze mill.

Preparation Example 2

The first crushing of the washed shoe waste was performed using a milling grinder. The primary pulverized material was transferred to a magnetic conveyor, and metal components located on reinforcing materials and labels were removed. Secondary grinding was performed using a freeze mill. The recycled filler 2 was produced by compressing the pulverized material in a rotary tableting machine to pelletize.

Preparation Example 3

The first crushing of the washed shoe waste was performed using a milling grinder. The primary pulverized material was transferred to a magnetic conveyor, and metal components located on reinforcing materials and labels were removed. After performing secondary grinding using a freeze mill, the surface was treated with plasma to form a hydroxyl group, and then reacted with 3-aminopropyltriethoxysilane to prepare a regenerated filler (3).

When the metal component is not removed, fine grinding was impossible, but as in the above Preparation Example, after the first grinding, the metal component was removed, and the second grinding was performed, so that fine grinding was possible to a size of ㎛ unit.

Production Example 4

The first crushing of the washed shoe waste was performed using a milling grinder. The recycled filler 4 was prepared by heat-treating the primary pulverized material in an oven at 200° C. for 2 hours.

Examples and Comparative Examples

First ethylene vinyl acetate (EVA1) containing 28% by weight of vinyl acetate, second ethylene vinyl acetate (EVA2) containing 18% by weight of vinyl acetate, and low density polyethylene (LDPE, Tm = 110 ° C.) Foaming resin, silica , The recycled filler obtained in Preparation Examples 1 to 4, zinc oxide, stearic acid, dicumyl peroxide, triallyl cyanurate, and azodicarbonamide were mixed in a kneader according to the mixing ratio (unit: parts by weight) of Table 1 below. The mixture was added and kneaded at 70° C. for 10 minutes to prepare a composition for shoe members.

The composition for shoe members is first pressed at 90°C, 140kgf/cm2, for 8 minutes using a pouring foam molding method to make a preform in the form of a sheet, and then put it in a mold and press the second at 160°C, 150kgf/cm2, 15 minutes. After the press work, it was cooled in a cooling press for 10 minutes to prepare a shoe midsole.

division Example 1 Example 2 Example 3 Example 4 Example 5 EVA1 50 45 43 40 45 EVA2 45 45 42 30 45 LDPE 5 10 15 30 10 silica 25 20 15 5 15 Regeneration Filler(1) 5 - - - - Regeneration Filler(2) - 10 - - - Regeneration Filler(3) - - 15 30 - Regeneration Filler(4) - - - - 15 zinc oxide 3 3 3 3 3 stearic acid One One One One One Dicumyl Peroxide One One One One One Triallyl cyanurate One One One One One azodicarbonamide 6 6 6 6 6

(unit: parts by weight)

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 EVA1 50 50 35 45 45 EVA2 50 46 33 45 45 LDPE 0 4 32 10 10 silica - - - 35 5 Regeneration Filler(1) 30 - - - - Regeneration Filler(2) - 30 - - - Regeneration Filler(3) - - 30 - - Regeneration Filler(4) - - - - 35 zinc oxide 3 3 3 3 3 stearic acid One One One One One Dicumyl Peroxide One One One One One Triallyl cyanurate One One One One One azodicarbonamide 6 6 6 6 6

(unit: parts by weight)

Experimental Example: Evaluation of physical properties of shoe midsole

The physical properties of the shoe midsoles manufactured according to the above Examples and Comparative Examples were evaluated, and the results are shown in Tables 3 and 4 below. The physical property evaluation method is as follows.

-Hardness (Asker, C): measured using an Asker C type hardness tester according to KS M 6660

-Specific gravity (g/cc): Measured 5 times using Ueshima's automatic specific gravity measuring device according to KS M 6660 and expressed as an average value

-Tensile strength (MPa): Measured using Zwick's universal testing machine according to KS M ISO 1798

-Tear strength (N/mm): Measured using Zwick's universal testing machine according to KS M ISO 7214

-Resilient elasticity (%): Measured using a rebound elasticity tester from Daesung Science in accordance with KS M ISO 8307

division Hardness importance tensile strength tear strength Example 1 46 0.2 19 11 Example 2 48 0.2 18 13 Example 3 51 0.2 16 10 Example 4 53 0.3 15 12 Example 5 50 0.2 21 14 Comparative Example 1 45 0.2 19 8 Comparative Example 2 46 0.2 18 9 Comparative Example 3 53 0.2 18 7 Comparative Example 4 54 0.3 20 10 Comparative Example 5 57 0.4 19 9

division Resilience immediately after manufacturing (A) Resilience after 7 days (B) B/A Example 1 43.9 40.1 0.914 Example 2 41.8 38.6 0.924 Example 3 40.1 37.4 0.933 Example 4 41.1 38.1 0.927 Example 5 44.8 41.2 0.920 Comparative Example 1 43.4 38.0 0.877 Comparative Example 2 41.5 37.1 0.895 Comparative Example 3 35.9 35.1 0.977 Comparative Example 4 39.3 37.8 0.962 Comparative Example 5 44.6 39.7 0.891

Referring to Table 3, the hardness (Asker, C) of the shoe midsole according to Examples 1 to 5 was 40 to 55, specific gravity was 0.2 to 0.3 g/cc, and tensile strength and tear strength were 15 to 25 MPa, respectively. and 10 to 20 N/mm, indicating that hardness, lightness, and mechanical properties were implemented in a well-balanced manner, whereas, in the case of the shoe midsoles according to Comparative Examples 1 to 5, at least one of them did not satisfy the above range.

In addition, referring to Table 4, shoe midsoles (Examples 1 to 5) prepared by foaming a composition containing two types of ethylene vinyl acetate having different monomer compositions and a certain amount of a crystalline polymer (low density polyethylene) It can be seen that the hardness is 45 or more, and the rebound elasticity immediately after manufacture is 40% or more, so that durability, resilience, and cushioning characteristics are implemented in a balanced manner. In particular, in the case of shoe midsoles according to Examples 1 to 5, the ratio of the rebound elasticity measured after 7 days to the rebound elasticity measured immediately after manufacture was 0.9 or more, and the change in the rebound elasticity over time was relatively small. It is expected that the restoring force given to the midsole of the shoe will not deteriorate and can be maintained for a long period of time.

On the other hand, shoe midsoles (Comparative Examples 1 and 2) prepared by foaming a composition containing a relatively small amount of crystalline polymer (low density polyethylene) have a relatively high content of ethylene vinyl acetate in the foamable resin, so the rebound elasticity immediately after manufacture is It was measured at 40% or more, but after 7 days, it appeared that the rebound elasticity decreased sharply to less than 90% immediately after manufacture, and in general, considering that the deterioration of the rebound elasticity was further accelerated thereafter, the shoe member and the restoring force of the shoe including the same expected to significantly decrease.

In addition, the shoe midsole (Comparative Example 3) prepared by foaming a composition containing a relatively large amount of crystalline polymer (low density polyethylene) has a relatively high content of crystalline polymer in the foamable resin, so the rebound elasticity immediately after manufacture is 40%. Not only is it difficult to impart a suitable restoring force to the shoe member in the manufacturing stage, but also, as an excessive amount of crystalline polymer is mixed, the formability and processability during mixing and foaming are significantly deteriorated.

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims (10)

100 parts by weight of a foamable resin containing ethylene vinyl acetate and a polyolefin having a molecular weight distribution (Mw/Mn) of 3 to 7;
1 to 35 parts by weight of filler;
1 to 30 parts by weight of recycled filler obtained by heat treatment after crushing waste shoes; and
0.1 to 10 parts by weight of a foaming agent;
It is prepared by foaming a composition for shoe members,
Tensile strength measured according to KS M ISO 1798 is 21~25MPa,
The tear strength measured by KS M ISO 7214 is 14~20N/mm,
absence of shoes. delete According to claim 1,
The ethylene vinyl acetate includes two or more ethylene vinyl acetates having different vinyl acetate contents,
absence of shoes. According to claim 3,
The ethylene vinyl acetate is a first ethylene vinyl acetate having a vinyl acetate content of 20 to 30% by weight; and
A second ethylene vinyl acetate having a vinyl acetate content of 5 to 20% by weight; containing,
absence of shoes. According to claim 1,
The content of the polyolefin in the foamable resin is 5 to 30% by weight,
absence of shoes. delete According to claim 1,
The filler is at least one of carbon black and silica,
absence of shoes. According to claim 1,
The average particle size of the recycled filler is 10 to 1,000 μm,
The surface of the recycled filler is organosilane-modified,
absence of shoes. According to claim 1,
The composition for a shoe member further comprises one selected from the group consisting of a metal oxide, a lubricant, a crosslinking agent, a crosslinking aid, and a combination of two or more thereof,
absence of shoes. delete