Shoe outsole composition for eva injection, and manufacturing method thereof

Abstract

The purpose of the present invention is to develop a raw material for a shoe outsole, for EVA injection, so as to improve upon the problems of low friction and low abrasion resistance that occur with ordinary EVA, and thus achieve the same level as a rubber outsole, the present invention being characterized by comprising: a polymer base material comprising 80-90 wt % of ethylene vinyl acetate and 10-20 wt % of a polyolefin elastomer; and an additive that is added to the polymer base material and that comprises, relative to 100 parts by weight of the polymer base material, 1-3 parts by weight of HVPBD (high vinyl 1,2-polybutadiene), 1-2 parts by weight of a processing aid, 2-4 parts by weight of a silicone anti-abrasion agent, 0.1-0.2 parts by weight of a co-crosslinking agent, and 0.5-1.0 parts by weight of a crosslinking agent.

Description

Composition for shoe outsole for EVA injection application and method for manufacturing the same

[0001] The present invention relates to a method for manufacturing a compound for a shoe outsole for EVA injection application and a composition manufactured thereby, and more particularly, to a method for manufacturing a compound for manufacturing a shoe outsole of various colors using ethylene vinyl acetate (EVA) as a main raw material by an injection technique.

[0002]

[0003] The present invention is to manufacture an injection shoe outsole based on ethylene vinyl acetate (EVA) to replace a conventional rubber outsole.

[0004] Conventional shoe outsoles made from rubber have raised concerns about manpower, process time, and the environment due to crosslinking through vulcanization and the use of the CMP (compression molding) process.

[0005] The reason why rubber is widely used in the manufacture of shoe outsoles is that the core functions of outsoles can be seen as traction and anti-abrasion functions, and natural rubber and butadiene rubber have been widely used because they are excellent in these functions.

[0006] However, rubber is not easy to handle due to its sticky nature, has a strong odor due to the vulcanization process, and has a short usable lifespan after manufacturing.

[0007]

[0008] Meanwhile, EVA IP outsole (IPO) utilizes an injection machine for continuous production of raw materials and product extraction, and uses a peroxide cross-linking method based on EVA, providing a relatively good working environment.

[0009] Ethylene vinyl acetate (EVA) is a polymer plastic with excellent flexibility, impact strength, adhesiveness, and processability. It is an elastic polymer that produces rubber-like materials with softness and flexibility. This material is particularly known for its excellent adhesive and waterproofing properties, and this project aims to use it as a raw material for shoe outsoles.

[0010] In addition, to reinforce the EVA properties, we aim to implement properties similar to those of conventional shoe outsoles by using poly α-olefin elastomers. Ethylene vinyl acetate, which has excellent flexibility, adhesion, and processability, has the disadvantage of lowering hardness and durability and shock absorption characteristics as the content increases. Therefore, we aim to reinforce the properties by using a rigid polyethylene-based material, such as poly α-olefin elastomer, which is a rigid material reinforcing the properties.

[0011] However, conventional EVA-based injection outsoles have the disadvantage of deteriorating physical properties, such as increased slipperiness and reduced wear resistance, after crosslinking reaction.

[0012]

[0013] The present invention has been devised to solve the problems of the prior art as described above, and aims to develop a raw material for a shoe outsole for injection of ethylene vinyl acetate (EVA), thereby improving the low friction performance and low wear resistance, which are problems of general EVA, to make it equivalent to a rubber outsole, and to improve the disadvantage of EVA that it sticks to a mold and is difficult to remove.

[0014] In addition, the present invention has as a technical solution the task of providing an EVA-based shoe outsole capable of injection and exhibiting friction performance and wear resistance at a level that can replace existing rubber outsoles.

[0015]

[0016] In order to solve the above problem, the present invention is characterized by comprising a composition for a shoe outsole for EVA injection application, comprising: a polymer substrate comprising 80 to 90 wt% of ethylene vinyl acetate and 10 to 20 wt% of polyolefin elastomer; and, with respect to 100 wt% of the polymer substrate, 1 to 3 wt% of HVPBD (high vinyl 1,2-polybutadiene), 1 to 2 wt% of a processing aid, 2 to 4 wt% of a silicone wear-resistant agent, 0.1 to 0.2 wt% of a co-crosslinking agent, and 0.5 to 1.0 wt% of a crosslinking agent; and an additive added to the polymer substrate.

[0017]

[0018] In another aspect of the present invention, there is provided a method for manufacturing a compound for a shoe outsole for EVA injection application: a first mixing step in which a polymer substrate composed of 80 to 90 wt% of ethylene vinyl acetate and 10 to 20 wt% of polyolefin elastomer is prepared, and 1 to 3 wt% of HVPBD (high vinyl 1,2-polybutadiene), 1 to 2 wt% of a processing aid, and 2 to 4 wt% of a silicone wear-resistant agent are added to 100 wt% of the polymer substrate and kneaded in a kneader at a temperature of 100 to 120 degrees; after the first mixing step, a second mixing step in which 0.1 to 0.2 wt% of a co-crosslinking agent and 0.5 to 1.0 wt% of a crosslinking agent are added to 100 wt% of the first-mixed polymer substrate and kneaded for an additional 2 to 4 minutes; It is characterized by including, after the second mixing step, a dispersing step of dispersing the second-mixed polymer using an open roll; and, after the dispersing step, a pelletizing step of pelletizing the dispersed polymer using an extruder to produce a compound (pellet) for a shoe outsole.

[0019]

[0020] As described above, the present invention develops a raw material for a shoe outsole for injection of ethylene vinyl acetate (EVA), thereby improving the low friction performance and low wear resistance, which are problems of general EVA, to make it equivalent to a rubber outsole, and can improve the disadvantage of EVA that it is difficult to remove by sticking to a mold.

[0021] In addition, the present invention can improve the problems of conventional rubber outsoles that require vulcanization reaction and have a strong odor.

[0022] In addition, the present invention has the effect of producing an excellent shoe outsole composition that is easy to manufacture and has excellent workability, such as improving the manufacturing environment, having the advantage of a short cycle time, and having the production of raw materials and the extraction of products being performed in a continuous process.

[0023]

[0024] 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.

[0025] 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.

[0026]

[0027] First, the composition of the present invention will be described.

[0028] The composition of the present invention comprises a polymer substrate and an additive.

[0029]

[0030] A. Polymer substrate

[0031] The polymer substrate is composed of 80 to 90 wt% ethylene vinyl acetate and 10 to 20 wt% polyolefin elastomer.

[0032]

[0033] (1) Ethylene Vinyl Acetate

[0034] 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. Due to the polarity of the vinyl groups, it has high adhesiveness to other substances. In addition, cross-linking, which allows the vinyl groups to be linked to each other through radical reactions, is possible, making it useful in manufacturing elastomers.

[0035] In particular, among the physical properties of ethylene vinyl acetate, the vinyl acetate content (VA%, the content of vinyl acetate in EVA) has a significant impact on the physical properties. A higher VA% increases the number of vinyl groups, resulting in a higher molecular weight and higher density. The overall polarity increases, resulting in higher adhesiveness, increased elasticity, and increased cross-linking, but the melting point decreases. A higher molecular weight improves toughness, plasticity, and impact resistance, but reduces formability and surface gloss. By adjusting the VA% of ethylene vinyl acetate, a variety of resins can be produced, ranging from hard to soft.

[0036] In the present invention, a product group having a vinyl acetate content (VA%) of 16 to 40% is used.

[0037]

[0038] (2) Polyolefin Elastomer

[0039] 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. Polyolefin elastomers, that is, olefins with rubber properties, are called polyolefin elastomers. They are 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 finished products.

[0040]

[0041] B. Additives

[0042] As additives, for 100 parts by weight of a polymer substrate, 1 to 3 parts by weight of HVPBD (high vinyl 1,2-polybutadiene), 1 to 2 parts by weight of a processing aid, 2 to 4 parts by weight of an abrasion-resistant agent, 0.1 to 0.2 parts by weight of a co-crosslinking agent, 0.5 to 1.0 parts by weight of a crosslinking agent, and 0.1 to 0.3 parts by weight of a pigment are added to the polymer substrate.

[0043]

[0044] (1) HVPBD (high vinyl 1,2-polybutadiene)

[0045] In the present invention, in order to improve physical properties, HVPBD (high vinyl 1,2-polybutadiene) is added in an amount of 1 to 3 parts by weight per 100 parts by weight of the weight base material.

[0046] HVPBD acts as a type of cross-linking agent to form a smooth cross-linking network.

[0047] HVPBD is mainly used to enhance the cross-linking effect of peroxides, and is particularly effective in improving modulus.

[0048] HVPBD has low polarity and high compatibility, which improves dispersibility, and has stable chemical properties that stop homopolymerization (aggregation).

[0049] HVPBD is a very stable material with low volatility, non-toxicity, high boiling point and low Tg.

[0050] In particular, due to the addition of HVPBD in the present invention, the shoe outsole compound of the present invention has rubber-like properties. In particular, the addition of HVPBD enhances friction performance, enabling the production of an EVA injection outsole having properties close to those of a general rubber outsole.

[0051]

[0052] (2) Processing agent: Stearic acid

[0053] As a processing aid, stearic acid is added in an amount of 1 to 2 parts by weight per 100 parts by weight of the weight base material.

[0054] 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.

[0055]

[0056] (3) Silicon anti-abrasion agent

[0057] As a wear-resistant agent, a silicone wear-resistant agent is added in an amount of 2 to 4 parts by weight per 100 parts by weight of the weight base material.

[0058] Silicone is added to thermoplastic resins and has excellent properties for improving wear resistance and coefficient of friction. Since silicone has the property of migrating to the surface, it forms a continuous silicone layer on the surface of the product.

[0059] Silicone anti-abrasion agents not only improve wear resistance but also enhance traction performance, thereby complementing the shortcomings of ethylene vinyl acetate.

[0060]

[0061] (4) Co-crosslinking agent: TMPTMA (Trimethylolpropane trimetacrylate)

[0062] In the present invention, the cross-linking agent is added in an amount of 0.1 to 0.2 parts by weight per 100 parts by weight of the weight base material.

[0063] 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.

[0064] Types of co-crosslinkers include methacrylate-based crosslinkers such as TMPTMA (Trimethylopropane Trimethacrylate) and EDMA (Ethylene dimethacrylate); TAC (triallyl cyanurate) and TAIC (triallyl isocyanurate), which have excellent heat aging resistance, 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.

[0065] In the present invention, TMPTMA (Trimethylopropane Trimethacrylate) is used.

[0066]

[0067] (5) Cross-linking agent: DCP (Dicumyl peroxide)

[0068] In the present invention, a crosslinking agent is added in an amount of 0.5 to 1.0 parts by weight per 100 parts by weight of a weight base material.

[0069] 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.

[0070] 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.

[0071] In the present invention, DCP (Dicumyl peroxide) is used as a crosslinking agent.

[0072]

[0073] (6) Pigment

[0074] Add pigment in an amount of 0.1 to 0.3 parts by weight per 100 parts by weight of the weight base material.

[0075] 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.

[0076]

[0077] The following describes a method for manufacturing a composition for a shoe outsole for EVA injection application according to one embodiment of the present invention.

[0078] (1) 1st mixing stage

[0079] First, a polymer substrate is prepared, and HVPBD (high vinyl 1,2-polybutadiene), processing aid, silicone wear-resistant agent, and pigment are added to the prepared polymer substrate and kneaded in a kneader at a temperature of 100 to 120 degrees.

[0080] Specifically, the polymer substrate comprises 80 to 90 wt% ethylene vinyl acetate and 10 to 20 wt% polyolefin elastomer.

[0081] In addition, 1 to 3 parts by weight of HVPBD (high vinyl 1,2-polybutadiene) per 100 parts by weight of the above polymer substrate,

[0082] 1 to 2 parts by weight of processing aid, 2 to 4 parts by weight of silicone wear-resistant agent, 0.1 to 0.2 parts by weight of co-crosslinking agent, 0.5 to 1.0 parts by weight of crosslinking agent, and 0.1 to 0.3 parts by weight of pigment are added.

[0083]

[0084] (2) Second mixing stage

[0085] After the first mixing step, a co-crosslinking agent and a crosslinking agent are added to the first mixed polymer substrate and mixed for an additional 2 to 4 minutes.

[0086] Specifically, 0.1 to 0.2 parts by weight of a co-crosslinking agent and 0.5 to 1.0 parts by weight of a crosslinking agent are added to 100 parts by weight of a polymer substrate.

[0087]

[0088] (3) Dispersion stage

[0089] After the second mixing step, the second-mixed polymer is dispersed using an open roll.

[0090]

[0091] (4) Pelletization stage

[0092] After the dispersion step, the dispersed polymer is pelletized using an extruder to manufacture a compound (pellet) for a shoe outsole.

[0093]

[0094] The compound manufactured in this way can be used to manufacture an outsole by going through a pressurized injection molding process and putting it in a mold at a temperature of 160 to 180 degrees for 5 to 6 minutes.

[0095]

[0096] Below, Examples 1 and 2 of the present invention and Comparative Examples 1 and 2 are compared.

[0097]

[0098] (Example 1)

[0099] 100 kg of polymer base material (90 kg of ethylene vinyl acetate / 10 kg of polyolefin elastomer) is fed into a kneader, and 2 kg of HVPBD, 1 kg of stearic acid as a processing aid, 3 kg of silicone wear-resistant agent, and 0.2 kg of pigment are mixed and kneaded at approximately 110°C for 10 minutes. 0.2 kg of co-crosslinking agent TMPTMA and 0.7 kg of crosslinking agent DCP are additionally added to the polymer sufficiently kneaded in the kneader, and kneading is performed for approximately 3 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 100°C in an extruder to produce a compound. The compound manufactured in this way was pressurized and injected into a mold with a thickness of 4 mm using a pressure injection machine at 180°C for 5 minutes to manufacture a shoe outsole specimen.

[0100]

[0101] (Example 2)

[0102] 100 kg of polymer base material (80 kg of ethylene vinyl acetate / 20 kg of polyolefin elastomer) is fed into a kneader, and 3 kg of HVPBD, 1 kg of stearic acid as a processing aid, 3 kg of silicone wear-resistant agent, and 0.2 kg of pigment are mixed and kneaded at approximately 110°C for 10 minutes. 0.2 kg of co-crosslinking agent TMPTMA and 0.7 kg of crosslinking agent DCP are additionally added to the polymer sufficiently kneaded in the kneader, and kneading is performed for approximately 3 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 100°C in an extruder to produce a compound. The compound manufactured in this way was pressurized and injected into a mold with a thickness of 4 mm using a pressure injection machine at 180°C for 5 minutes to manufacture a shoe outsole specimen.

[0103]

[0104] (Comparative Example 1)

[0105] 100 kg of polymer base material (80 kg of ethylene vinyl acetate / 20 kg of polyolefin elastomer) is fed into a kneader, and 1 kg of stearic acid as a processing aid, 3 kg of silicone wear-resistant agent, and 0.2 kg of pigment are mixed and kneaded at approximately 110°C for 10 minutes. 0.2 kg of co-crosslinking agent TMPTMA and 0.7 kg of crosslinking agent DCP are additionally added to the polymer sufficiently kneaded in the kneader, and kneading is performed for approximately 3 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 100°C in an extruder to produce a compound. The compound manufactured in this way was pressurized and injected into a mold with a thickness of 4 mm using a pressure injection machine at 180°C for 5 minutes to manufacture a shoe outsole specimen.

[0106]

[0107] (Comparative Example 2)

[0108] Butyl rubber material was fed into a kneader and kneaded for approximately 10 minutes. Sulfur was added to the kneaded rubber material and dispersed through open rolls to form a sheet. The processed sheet was then cut into a uniform 94g weight using a 4mm CMP mold through a compression molding process and heated at 180℃ for 10 minutes in a press machine and cooled at 20℃ for 10 minutes to produce a shoe outsole specimen.

[0109] Comparative Example 2 is a method for manufacturing butyl rubber, and is a method for manufacturing a general rubber outsole.

[0110]

[0111] The compositions of Examples 1 and 2 and Comparative Example 1 are summarized in Table 1 below. The unit is kg.

[0112] Composition Example 1 Example 2 Comparative Example 1 Ethylene vinyl acetate 908080 Polyolefin elastomer 102020 Polymer substrate 100100100 HYPBD23 - Processing aid 111 Silicone wear-resistant agent 333 Pigment 0.20.20.2 Co-crosslinker 0.20.20.2 Crosslinker 0.70.70.7

[0113] Example 2 and Comparative Example 1 have the same amount of polymer base material and the same amount of additives other than HVPBD. However, Comparative Example 1 did not contain HVPBD, whereas Example 2 was compounded with 3% HVPBD added. In Examples 1 and 2, the physical properties were confirmed by changing the mixing amount of ethylene vinyl acetate and polyolefin elastomer, and also by changing the amount of HVPBD added.

[0114]

[0115] < Physical property evaluation >

[0116] The physical properties of the specimens manufactured by the above Examples 1 and 2 and Comparative Examples 1 and 2 were evaluated according to the following authorized method, and the results are shown in Table 2.

[0117] Hardness: Hardness was measured in Shore A according to the method of KS M ISO 7619-1.

[0118] 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.

[0119] Tensile strength: The maximum 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).

[0120] Elongation: This refers to the permanent deformation until the specimen breaks under load, and is measured according to KS M 6518.

[0121] 300% Modulus: A unit of force applied when a specimen is stretched to a certain length. 100% elongation is expressed as 100% modulus, and 300% elongation is expressed as 300% modulus.

[0122] 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.

[0123] Abrasion (Din Abrasion): This indicates the measurement of abrasion resistance, and the volume loss of the specimen caused by sliding is measured using the method of D5963:2010.

[0124] Traction: This is a performance evaluation for anti-slip performance and is measured according to the method of ASTM D 1894-11.

[0125] Physical propertiesExample 1Example 2Comparative example 1Comparative example 2Hardness (Shore A) 67-6862-6367-6869-70Specific gravity (g / ㎤) 0.9480.9460.9411.157Tensile strength (㎏ / ㎠) 118.1109.292.1113.1Elongation (%) 601559478602300%Modulus (㎏ / ㎠) 34.031.421.744.5Tear strength (㎏ / ㎝) 46.844.219.753.1Abrasion resistance (㎣) 119123137117Frictional force (μ) 3.063.061.781.65

[0126] From the results in Table 2, it can be confirmed that the physical properties of the shoe outsole made of conventional rubber material of Comparative Example 2 and the general EVA injection outsole of Comparative Example 1 are completely different.

[0127] In particular, it can be confirmed that the tensile strength, tear strength, elongation, and wear resistance of Comparative Example 1 are significantly reduced compared to Comparative Example 2.

[0128] In this regard, it was confirmed that the EVA injection outsole with HVPBD added as in Examples 1 and 2 could obtain results similar to those in Comparative Example 2.

[0129] In addition, when comparing Example 1 and Example 2, it was confirmed that the physical properties slightly changed depending on the mixing ratio of the polymer substrate and the amount of HVPBD added.

[0130]

[0131] 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.

[0132] 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.

[0133]

[0134] The present invention can be used to manufacture a shoe outsole.

Claims

A composition for a shoe outsole for EVA injection application, characterized in that it comprises: a polymer substrate comprising 1.80 to 90 wt% of ethylene vinyl acetate and 10 to 20 wt% of polyolefin elastomer; and, with respect to 100 wt% of the polymer substrate, 1 to 3 wt% of HVPBD (high vinyl 1,2-polybutadiene), 1 to 2 wt% of a processing aid, 2 to 4 wt% of a silicone wear-resistant agent, 0.1 to 0.2 wt% of a co-crosslinking agent, and 0.5 to 1.0 wt% of a crosslinking agent, and additives added to the polymer substrate; A first mixing step of preparing a polymer substrate composed of 2.80 to 90 wt% of ethylene vinyl acetate and 10 to 20 wt% of polyolefin elastomer, adding 1 to 3 wt% of HVPBD (high vinyl 1,2-polybutadiene), 1 to 2 wt% of a processing aid, and 2 to 4 wt% of a silicone wear-resistant agent to 100 wt% of the polymer substrate and mixing the mixture in a kneader at a temperature of 100 to 120 degrees Celsius; After the first mixing step, a second mixing step is performed in which 0.1 to 0.2 parts by weight of a co-crosslinking agent and 0.5 to 1.0 parts by weight of a crosslinking agent are added to 100 parts by weight of the first-mixed polymer base material and mixing is performed for an additional 2 to 4 minutes; After the second mixing step, a dispersion step of dispersing the second-mixed polymer using an open roll; After the above dispersion step, a pelletizing step of pelletizing the dispersed polymer using an extruder to manufacture a compound (pellet) for a shoe outsole; A method for manufacturing a compound for a shoe outsole for EVA injection application, characterized in that it includes: