Foam composition, for shoe midsole, having bio-based polymer applied thereto, and production method thereof

Abstract

The present invention pertains to a composition for producing a foamed body using a bio-based polyolefin elastomer and a bio-based polyethylene vinyl acetate, which are low-carbon / environmentally friendly materials, and is characterized by comprising: a polymer base material comprising 55-65 wt. % of a bio-based polyethylene vinyl acetate, 15-25 wt. % of a bio-based polyolefin elastomer, and 15-25 wt. % of a thermoplastic elastomer; and an additive which is added to the polymer base material and which comprises, relative to 100 parts by weight of the polymer base material, 1.5-2.5 parts by weight of zinc p-toluenesulfonate, 0.5-1.4 parts by weight of a processing aid, 3-9 parts by weight of titanium oxide, 6-14 parts by weight of a foaming agent, 0.1-0.5 parts by weight of a co-crosslinking agent, and 0.3-1.0 parts by weight of a crosslinking agent.

Description

Foam composition for shoe midsole using bio-based polymer and method for producing the same

[0001] The present invention relates to a method for manufacturing a foam composition for a shoe midsole and a composition manufactured thereby, and relates to a novel foam composition for a shoe midsole and a method for manufacturing the same, which can prevent environmental destruction by increasing the bio-content of a polymer using a bio-based polymer.

[0002]

[0003] Most polymer materials are derived from petrochemical resources, which will eventually face depletion, and environmental protection issues will become increasingly serious. Against this backdrop, the development of bio-based polymer materials and their applications as alternatives to petrochemical-derived polymers is urgent.

[0004] Bio-based thermoplastic materials are a product that emerged in response to the demand for non-renewable energy sources. They are polymers manufactured by extracting raw materials from plants such as castor oil and rapeseed flowers and through chemical refining, and their main components are basically polyester, nylon, polyether, and polyurethane.

[0005]

[0006] In conventional technology, shoe midsoles are manufactured by adding foaming agents to various synthetic resins and then injection foaming them.

[0007] Meanwhile, most of the synthetic resin materials used in shoe midsoles are petrochemical-derived (petrochemical-based) synthetic resins.

[0008]

[0009] Meanwhile, ethylene vinyl acetate (EVA) is known as a polymer plastic with excellent flexibility, impact strength, adhesiveness, and processability. Bio-based EVA, which has similar properties to petrochemical-derived EVA but is manufactured from ethylene extracted from biomass, is also known.

[0010] The present invention aims to produce excellent shoe products by using bio-based EVA in the manufacture of shoe midsoles while simultaneously achieving carbon reduction effects and environmental non-destructive effects.

[0011] Ethylene vinyl acetate, which has excellent flexibility, adhesiveness, and processability, has the disadvantage that as the content increases, the hardness decreases and the durability and shock absorption properties decrease, so it is generally used together with a rigid polyethylene-based material such as poly α-olefin elastomer, which is a material for reinforcing properties.

[0012]

[0013] The present invention aims to produce a shoe midsole composition having the same properties as existing ones while increasing the bio content by using a bio-based polyolefin elastomer (Bio-Poly α-olefin elastomer) to produce a polymer raw material with excellent properties.

[0014]

[0015] The present invention aims to improve the shortcomings of bio-based ethylene vinyl acetate by using a bio-based polyolefin elastomer instead of a rigid petrochemical-derived polyolefin elastomer.

[0016]

[0017] Bio-based polymers have a molecular structure similar to that of petrochemical-derived polymers, but their physical properties and moldability are not the same. The present invention relates to the manufacture of a compound for a shoe midsole for pressure injection molding.

[0018]

[0019] The present invention has been devised to solve the problems of the prior art as described above, and in order to manufacture a more environmentally friendly polymer composition while maintaining the properties and processability of a foam manufactured from a conventional petrochemical-derived polymer, the technical task of this task is to manufacture a foam composition having similar properties and processability to the existing one while simultaneously conducting research on additives to improve the deterioration of properties while using a bio-based polymer instead of a petrochemical-derived polymer.

[0020] More specifically, the present invention aims to manufacture a foam composition using bio-based polyethylene vinyl acetate as the main raw material and adding bio-based polyolefin elastomer to it, thereby maintaining the properties of conventional shoes while applying a more environmentally friendly bio-based polymer.

[0021]

[0022] The present invention relates to a composition design for a polymer substrate with bio-based ethylene vinyl acetate as the main component and the components of the substrate including the necessary additives to maximize eco-friendly properties and non-irritating elements.

[0023]

[0024] In order to solve the above problems, the present invention is characterized by comprising: a polymer substrate comprising 55 to 65 wt% of bio-based polyethylene vinyl acetate, 15 to 25 wt% of bio-based polyolefin elastomer, and 15 to 25 wt% of thermoplastic elastomer; and an additive added to the polymer substrate, comprising 1.5 to 2.5 wt% of zinc p-toluenesulfonate, 0.5 to 1.4 wt% of a processing aid, 6 to 14 wt% of a foaming agent, 0.1 to 0.5 wt% of a co-crosslinking agent, and 0.3 to 1.0 wt% of a crosslinking agent, with respect to 100 wt% of the polymer substrate.

[0025]

[0026] In another aspect of the present invention, a method for manufacturing a shoe midsole compound using a bio-based polymer is provided, comprising: a first mixing step of preparing a polymer substrate comprising 55 to 65 wt% of bio-based polyethylene vinyl acetate, 15 to 25 wt% of bio-based polyolefin elastomer, and 15 to 25 wt% of thermoplastic elastomer, and adding 1.5 to 2.5 wt% of zinc p-toluenesulfonate and 0.5 to 1.4 wt% of a processing aid to 100 wt% of the polymer substrate, and mixing the mixture in a kneader at a temperature of 100 to 120 degrees; It is characterized by comprising: a second mixing step in which, after the first mixing step, 6 to 14 parts by weight of a foaming agent, 0.1 to 0.5 parts by weight of a co-crosslinking agent, and 0.3 to 1.0 parts by weight of a crosslinking agent are added to 100 parts by weight of the first mixed polymer base, and mixing is further performed for 1.5 to 2.5 minutes; a dispersion step in which, after the second mixing step, the second mixed polymer is dispersed using an open roll; and a pelletization step in which, after the dispersion step, the dispersed polymer is pelletized using an extruder to produce a compound (pellet) for a shoe midsole.

[0027]

[0028] As described above, the composition for manufacturing a foam of the present invention can manufacture a shoe midsole with excellent properties that is low-carbon and environmentally friendly by replacing a petrochemical-derived polymer with a bio-based polymer while maintaining the physical properties of a conventional shoe midsole, thereby reducing the use of petrochemical-derived polymers and increasing the use of natural-derived polymers.

[0029]

[0030] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. In the drawings, irrelevant parts have been omitted for clarity of description, and similar reference numerals have been assigned to similar parts throughout the specification.

[0031] Throughout the specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0032]

[0033] First, the composition of the present invention will be described.

[0034] The composition of the present invention comprises a polymer substrate and an additive.

[0035]

[0036] A. Polymer substrate

[0037] The polymer substrate comprises 55 to 65 wt% bio-based polyethylene vinyl acetate, 15 to 25 wt% bio-based polyolefin elastomer, and 15 to 25 wt% thermoplastic elastomer styrene-ethylene-butylene-styrene (SEBS).

[0038]

[0039] (1) Bio-Ethylene Vinyl Acetate

[0040] Bio-based ethylene vinyl acetate has a structure in which vinyl groups are attached in the form of branches to the linear structure of ethylene. The vinyl groups repel each other, resulting in elasticity. The polarity of the vinyl groups allows for high adhesiveness to other substances. Cross-linking, which allows the vinyl groups to be linked to each other through radical reactions, makes it useful in manufacturing elastomers.

[0041] In the present invention, a product group having a bio-content of 60 to 74% is used.

[0042] Meanwhile, among the physical properties of bio-based ethylene vinyl acetate, the vinyl acetate content (VA%, the vinyl acetate content within EVA) significantly influences the properties. A higher VA% results in more vinyl groups, increasing molecular weight and density. This increases overall polarity, resulting in enhanced adhesiveness, increased elasticity, and increased cross-linking, but also lower melting point. A higher molecular weight improves toughness, plasticity, and impact resistance, but at the expense of formability and surface gloss. By adjusting the VA% of ethylene vinyl acetate, a variety of resins can be produced, ranging from rigid to flexible.

[0043]

[0044] (2) Bio-based polyolefin elastomer

[0045] Olefin refers to a chain-shaped hydrocarbon compound with one double bond. Polyalphaolefin is a polymer compound produced by the polymerization of α-olefins with double bonds such as polyethylene, polypropylene, and polyisobutylene. It is a lightweight plastic with excellent transparency and low density. An olefin with elastomer properties, that is, rubber-like properties, is called a polyolefin elastomer. It is a relatively new type of polymer that emerged with the development of metallocene polymerization catalysts. The biggest feature of polyolefin elastomers is that they are compatible with most olefin materials (PE, PP, EVA, EPDM, SBC, PVC, etc.), are excellent impact modifiers for plastics, and impart unique performance to the finished product.

[0046]

[0047] (3) Thermoplastic elastomer: Styrene-ethylene-butylene-styrene (SEBS)

[0048] Styrene-Ethylene-Butylene-Styrene is a thermoplastic elastomer with heat stability, weather resistance, and oil resistance. It is a material that behaves like rubber without vulcanization. It is suitable for injection molding or extrusion molding when compounded, and has excellent flexibility, so it is used in many products. In the present invention, styrene-ethylene-butylene-styrene is mixed with other resins and molded, and the soft phase melts and plasticizes, exhibiting unique molding processability. After molding is complete, it hardens and functions as a component that prevents plastic deformation.

[0049]

[0050] B. Additives

[0051] As additives, 1.5 to 2.5 parts by weight of zinc p-toluenesulfonate, 0.5 to 1.4 parts by weight of processing aid, 3 to 9 parts by weight of titanium oxide, 6 to 14 parts by weight of foaming agent, 0.1 to 0.5 parts by weight of crosslinking agent, and 0.3 to 1.0 parts by weight of crosslinking agent are added to the polymer substrate per 100 parts by weight of the polymer substrate.

[0052]

[0053] (1) Zinc p-toluenesulfonate (zinc p-toluenesulfonate)

[0054] In the present invention, as a special additive to improve the deterioration of physical properties, zinc p-toluenesulfonate is added in an amount of 1.5 to 2.5 parts by weight per 100 parts by weight of the weight base material.

[0055] Zinc p-toluenesulfonate is a type of foaming activator that acts as a stabilizer and lubricant.

[0056]

[0057] Zinc p-toluenesulfonate, an alkylaromatic zinc compound, serves as an activator in foaming reactions. Its high dispersibility lowers the foaming decomposition temperature, thereby facilitating a stable crosslinking foaming reaction. Its excellent compatibility makes it ideal for use with PE, PVC, PP, nylon, ABS, and butyl rubber, and it boasts excellent UV and thermal stability and transparency.

[0058]

[0059] (2) Processing agent: Stearic acid

[0060] As a processing aid, stearic acid is added in an amount of 0.5 to 1.4 parts by weight per 100 parts by weight of the weight base material.

[0061] Processing aids are additives that prevent stickiness between the mold or extruder surface and the resin and improve slipperiness. When mixed with the resin, they lower melt viscosity and facilitate molding and processing. In particular, the vinyl group of ethylene vinyl acetate is polar, resulting in strong adhesiveness. Therefore, a lubricant, which is a substance that lubricates the metal surface that comes into contact during processing and promotes fluidity, is required. The most commonly used lubricants for plastic resins include wax, oil, zinc-stearate, and stearic acid. Stearic acid and zinc-stearate are most preferred for application to the present invention.

[0062]

[0063] (3) Titanium oxide (TiO2)

[0064] Titanium oxide (TiO2) is added in an amount of 3 to 9 parts by weight per 100 parts by weight of the weight base material.

[0065] Titanium oxide is used to improve the whiteness of the foam.

[0066]

[0067] (4) Pigment

[0068] Add pigment in an amount of 1 to 4 parts by weight per 100 parts by weight of the weight base material.

[0069] Many polymer materials are colorless or transparent, but are often colored to enhance their visual appeal. Representative colorants include pigments and dyes. Pigments are insoluble in water, solvents, and other solvents, while dyes are soluble in water and other solvents.

[0070]

[0071] (5) Foaming agent: Azodicarbonamide / sodium bicarbonate (NaHCO3)

[0072] In the present invention, the foaming agent is added in an amount of 6 to 14 parts by weight per 100 parts by weight of the weight base material.

[0073] Blowing agents should be selected based on the type, properties, and intended use of the polymer. Generally, considerations include the particle size of the blowing agent, its decomposition temperature and decomposition temperature control, its effect on polymer properties, compatibility with crosslinking reactions, and toxicity during decomposition.

[0074] Azodicarbonamide (AZO) is an organic foaming agent with a relatively distinct decomposition temperature, an exothermic reaction, and the generation of harmless N2 gas upon decomposition. Compared to other foaming agents, this gas production is relatively large. Furthermore, N2 gas has low resin permeability, enabling the formation of closed cells. Its foaming decomposition temperature of 160-200°C ensures excellent compatibility with EVA and crosslinking agents, along with a half-life.

[0075] Sodium bicarbonate (NaHCO3), commonly known as baking soda, is a type of physical foaming agent. Used alongside organic foaming agents, it offers a synergistic effect, offering environmental friendliness and low-irritation properties.

[0076]

[0077] (6) Co-crosslinker: Triallylicyanourate (TAC) or Triallyisocyanurate (TAIC)

[0078] In the present invention, the cross-linking agent is added in an amount of 0.1 to 0.5 parts by weight per 100 parts by weight of the weight base material.

[0079] Cross-linking agents are highly reactive monomers that increase cross-linking density and are additives that facilitate rapid curing in free-radical polymerization. They are generally used to accelerate cross-linking and improve physical properties.

[0080] Types of co-crosslinkers include methacrylate-based crosslinkers such as TMPTMA (Trimethylopropane Trimethacrylate) or EDMA (Ethylene dimethacrylate); TAC (triallyl cyanurate) and TAIC (triallyl isocyanurate), which have excellent heat aging resistance and scorch stability and are suitable for peroxide crosslinking; and oxime-based crosslinkers such as Quinone dioxime and Diphenozoyl-P-quonone dioxime, which are mainly used in butyl rubber. The present invention includes TAC (triallyl cyanurate) and TAIC (triallyl isocyanurate).

[0081]

[0082] (7) Cross-linking agent: Di(tert-butylperoxyisopropyl)benzene (BIPB)

[0083] In the present invention, a crosslinking agent is added in an amount of 0.3 to 1.0 parts by weight per 100 parts by weight of a weight base material.

[0084] Crosslinking agents are substances that, by applying energy to peroxides and using the radicals generated, initiate a polymerization reaction, transforming linear resins (such as PE and EVA) into a network structure. They are used as additives to fix the shape of plastic resins or improve their mechanical and chemical properties.

[0085] Commonly used crosslinking agents include Perbutyl peroxide (PB) and Dicumyl peroxide (DCP), which are used as crosslinking agents in the polymerization reaction of various polymers such as polyester, polystyrene, ABS, EVA, and PE.

[0086] In the present invention, Di(tert-butylperoxyisopropyl)benzene is used as a crosslinking agent.

[0087]

[0088] The following describes a method for manufacturing a composition for manufacturing a foam using a bio-based polymer according to one embodiment of the present invention.

[0089] (1) 1st mixing stage

[0090] First, a polymer substrate is prepared, and zinc p-toluenesulfonate, a processing aid, and titanium oxide are added to the prepared polymer substrate, and kneaded in a kneader at a temperature of 100 to 120 degrees.

[0091] Specifically, the polymer substrate comprises 55 to 65 wt% bio-based polyethylene vinyl acetate, 15 to 25 wt% bio-based polyolefin elastomer, and 15 to 25 wt% thermoplastic elastomer.

[0092] Additionally, 1.5 to 2.5 parts by weight of zinc p-toluenesulfonate, 0.5 to 1.4 parts by weight of processing aid, and 3 to 9 parts by weight of titanium oxide are added to 100 parts by weight of the polymer substrate.

[0093]

[0094] (2) Second mixing stage

[0095] After the first mixing step, a foaming agent, a co-crosslinking agent, and a crosslinking agent are added to the first mixed polymer base material and mixed for an additional 1.5 to 2.5 minutes.

[0096] Specifically, 6 to 14 parts by weight of a foaming agent, 0.1 to 0.5 parts by weight of a crosslinking agent, and 0.3 to 1.0 parts by weight of a crosslinking agent are added to 100 parts by weight of a polymer substrate.

[0097]

[0098] (3) Dispersion stage

[0099] After the second mixing step, the second-mixed polymer is dispersed using an open roll.

[0100]

[0101] (4) Pelletization stage

[0102] After the dispersion step, the dispersed polymer is pelletized using an extruder to manufacture a compound for a shoe midsole.

[0103]

[0104] The compound manufactured in this way can be used to manufacture a foam by going through a pressurized injection molding process and putting it in a mold at a temperature of 160 to 180 degrees for 7 to 8 minutes.

[0105]

[0106] Below, examples according to the present invention and comparative examples 1 to 3 are compared.

[0107]

[0108] (Example)

[0109] 100 kg of polymer base material (60 kg of bio-based ethylene vinyl acetate / 20 kg of bio-based polyolefin elastomer / 20 kg of thermoplastic elastomer) is fed into a kneader, and 2 kg of zinc p-toluenesulfonate, 0.8 kg of stearic acid as a processing aid, 5 kg of titanium oxide, and 2 kg of pigment are mixed and kneaded at approximately 110°C for 10 minutes. To the polymer sufficiently kneaded in the kneader, 38 kg of blowing agent ADCA / NaHCO, 0.25 kg of co-crosslinking agent TAC, and 0.6 kg of crosslinking agent BIPB are additionally added and kneaded for approximately 2 minutes. The kneaded polymer is dispersed three times through an open roll. After the open-roll process, the polymer is pelletized through an extruder at approximately 90°C using an extrusion die and a cutter (pelletizing machine) to produce a compound. The compound thus produced is then pressurized and injected into a 10mm-thick mold at 170°C for 7 minutes using a pressure-blown injection molding machine to produce a foam.

[0110]

[0111] (Comparative Example 1)

[0112] 100 kg of polymer base material (70 kg of petrochemical-based ethylene vinyl acetate / 15 kg of petrochemical-based polyolefin / 15 kg of thermoplastic elastomer) is fed into a kneader, and 0.8 kg of stearic acid as a processing aid, 5 kg of titanium oxide, and 2 kg of pigment are mixed and kneaded at approximately 110°C for 10 minutes. 8 kg of blowing agent ADCA / NaHCO3, 0.25 kg of co-crosslinking agent TAC, and 0.6 kg of crosslinking agent BIPB are further added to the polymer sufficiently kneaded in the kneader, and kneading is performed for approximately 2 minutes. The kneaded polymer is dispersed three times through an open roll. The polymer after the open roll process is pelletized through an extrusion die and a cutter (pelletizing machine) at approximately 90°C in an extruder to produce a compound. The compound manufactured in this way is pressurized and injected into a mold with a thickness of 10 mm using a pressurized foam injection molding machine at 170℃ for 7 minutes to manufacture a foam.

[0113]

[0114] (Comparative Example 2)

[0115] 100 kg of polymer base material (70 kg of bio-based ethylene vinyl acetate / 15 kg of bio-based polyolefin elastomer / 15 kg of thermoplastic elastomer) is fed into a kneader, and 0.8 kg of stearic acid as a processing aid, 5 kg of titanium oxide, and 2 kg of pigment are mixed and kneaded at approximately 110°C for 10 minutes. 8 kg of blowing agent ADCA / NaHCO3, 0.25 kg of co-crosslinking agent TAC, and 0.6 kg of crosslinking agent BIPB are further added to the polymer sufficiently kneaded in the kneader, and kneading is performed for approximately 2 minutes. The kneaded polymer is dispersed three times through an open roll. The polymer after the open roll process is pelletized through an extrusion die and a cutter (pelletizing machine) at approximately 90°C in an extruder to produce a compound. The compound manufactured in this way is pressurized and injected into a mold with a thickness of 10 mm using a pressurized foam injection molding machine at 170℃ for 7 minutes to manufacture a foam.

[0116]

[0117] (Comparative Example 3)

[0118] 100 kg of polymer base material (70 kg of bio-based ethylene vinyl acetate / 15 kg of bio-based polyolefin elastomer / 15 kg of thermoplastic elastomer) is fed into a kneader, and 3 kg of zinc p-toluenesulfonate, 0.8 kg of stearic acid as a processing aid, 5 kg of titanium oxide, and 2 kg of pigment are mixed and kneaded at approximately 110°C for 10 minutes. 8 kg of blowing agent ADCA / NaHCO3, 0.25 kg of co-crosslinking agent TAC, and 0.6 kg of crosslinking agent BIPB are additionally added to the polymer sufficiently kneaded in the kneader, and kneading is performed for approximately 2 minutes. The kneaded polymer is dispersed three times through an open roll. After the open-roll process, the polymer is pelletized through an extruder at approximately 90°C using an extrusion die and a cutter (pelletizing machine) to produce a compound. The compound thus produced is then pressurized and injected into a 10mm-thick mold at 170°C for 7 minutes using a pressure-blown injection molding machine to produce a foam.

[0119]

[0120] The compositions of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 1 below. The unit is kg.

[0121] Composition Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Ethylene vinyl acetate 6070 (petrochemical-based) 7070 Polyolefin elastomer 2015 (petrochemical-based) 1515 Thermoplastic elastomer 2015 1515 Polymer substrate 100 100 100 100 Zinc p-toluenesulfonate 2-3 Stearic acid 0.8 0.8 0.8 0.8 Titanium oxide 55 55 Pigment 22 2 Blowing agent 88 8 Co-crosslinker 0.25 0.25 0.25 0.25 Crosslinker 0.6 0.6 0.6

[0122] Comparative Example 1 is a formulation using a petrochemical-derived polymer, and Comparative Example 2 applies a bio-based polymer to the same formulation as Comparative Example 1. In the practical example, the content of the polymer in Comparative Example 2 was adjusted and 2% of Zinc p-toluenesulfonate was added.

[0123] Comparative Example 3 increased the amount of zinc p-toluenesulfonate added to 3% in the example.

[0124]

[0125] < Physical property evaluation >

[0126] The physical properties of the foams manufactured by the above examples and comparative examples 1 to 3 were evaluated according to the following authorized method, and the results are shown in Table 2.

[0127] Hardness: According to the method of KS M 6660:2016, a specimen with a thickness of 6 mm or more is measured at 5 different points with a load of 1.0 kg using Asker's hardness tester (CL-150) and the average result is calculated.

[0128] Specific gravity: It is defined as the ratio of the mass of a substance to the mass of a standard substance (water) with the same volume, and is measured using an automatic hydrometer according to the method of KS M 6660:2016.

[0129] Compression set: This is a value that indicates the strain that occurs when a load is applied to a material and it is measured according to the method of KS M 6518:2016 (50±1℃, 6h, 50% compression). In this evaluation, the thickness of the specimen is compressed to 50% in a fixture, left at 50℃ for 6 hours, then removed from the fixture, cooled for 30 minutes, the thickness is measured, and the compression set is calculated.

[0130] Tensile strength: The maximum tensile load a material receives is divided by the cross-sectional area at break, and is measured according to the test method of KS M ISO 1798 (2012).

[0131] Tear strength: It is defined as the maximum force that tears a material from a cut mark divided by the thickness at the peak, and is measured according to the standards of KS M ISO 7214.

[0132] Resilience: Measure the average of the last three values ​​out of a total of six tests using a pendulum rebound device according to the method of KS M ISO 8307:2013.

[0133] Physical properties Comparative example 1 Comparative example 2 Comparative example 3 Hardness (Asker C) 52-53 52-53 50-51 55-56 Specific gravity (g / ㎤) 0.194 0.195 0.194 0.193 Permanent compression set (%) 34.7 35.44 2.32 9.5 Tensile strength (㎏ / ㎠) 26.4 25.72 2.72 8.8 Tear strength (㎏ / ㎝) 14.3 13.8 11.0 15.1 Rebound elasticity (%) 27-28 28-29 30-31 30-31

[0134] As confirmed in Table 2, Comparative Example 2 shows different physical property results compared to the conventional formulation (Comparative Example 1). In other words, the physical property difference between petrochemical-derived polymers and bio-based polymers can be confirmed.

[0135] In Example 3 and Comparative Example 3, zinc p-toluenesulfonate was additionally added, and the physical property results of Example 3 were most similar to those of Comparative Example 1.

[0136] That is, when comparing Comparative Example 2 and the Example using a bio-based polymer to which Zinc p-toluenesulfonate was not added, it was confirmed that the physical properties of the existing foam (Comparative Example 1) were exhibited by the addition of Zinc p-toluenesulfonate.

[0137] Comparative Example 3 confirms that as the amount of zinc p-toluenesulfonate added increases, the physical properties such as the permanent compression set ratio become different.

[0138]

[0139] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0140] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

[0141]

[0142] The foam composition for a shoe midsole of the present invention can be used to manufacture a shoe midsole.

Claims

A shoe midsole foam composition comprising: a polymer substrate comprising 1.55 to 65 wt% of bio-based polyethylene vinyl acetate, 15 to 25 wt% of bio-based polyolefin elastomer, and 15 to 25 wt% of thermoplastic elastomer; and, with respect to 100 wt% of the polymer substrate, 1.5 to 2.5 wt% of zinc p-toluenesulfonate, 0.5 to 1.4 wt% of a processing aid, 6 to 14 wt% of a foaming agent, 0.1 to 0.5 wt% of a co-crosslinking agent, and 0.3 to 1.0 wt% of a crosslinking agent; and an additive added to the polymer substrate; A first mixing step of preparing a polymer substrate comprising 2.55 to 65 wt% of bio-based polyethylene vinyl acetate, 15 to 25 wt% of bio-based polyolefin elastomer, and 15 to 25 wt% of thermoplastic elastomer, adding 1.5 to 2.5 parts by weight of zinc p-toluenesulfonate and 0.5 to 1.4 parts by weight of a processing aid to 100 parts by weight of the polymer substrate and mixing the mixture in a kneader at a temperature of 100 to 120 degrees; After the first mixing step, a second mixing step of adding 6 to 14 parts by weight of a blowing agent, 0.1 to 0.5 parts by weight of a co-crosslinking agent, and 0.3 to 1.0 parts by weight of a crosslinking agent to 100 parts by weight of the first-mixed polymer substrate and further mixing the mixture for 1.5 to 2.5 minutes; A method for manufacturing a shoe midsole compound using a bio-based polymer, characterized in that it comprises: a dispersion step for dispersing the second-mixed polymer using an open roll after the second mixing step; and a pelletizing step for manufacturing a shoe midsole compound (pellet) by pelletizing the dispersed polymer using an extruder after the dispersion step.

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