KR20220155467A - Composition for shoes midsole and manufacturing method of thermoplastic shoes midsole using the same - Google Patents

Abstract

The present invention relates to a shoe midsole composition and a method for manufacturing a thermoplastic shoe midsole using the same, and more specifically, to a shoe midsole composition in which the cooling properties of an injection material are improved by mixing TPU and SBR, the compatibility of TPU and SBR is improved and flowability is increased by mixing EVA, and foaming properties are improved by mixing talc as a foaming nucleating agent such that the cooling properties of TPU is efficiently improved so as to realize excellent physical properties and light weight at the same time while making it suitable for injection foam molding, and to a method for manufacturing a thermoplastic shoe midsole using the same.

Description

Composition for shoe midsole and manufacturing method of thermoplastic shoe midsole using the same

The present invention relates to a composition for a shoe midsole and a method for manufacturing a thermoplastic shoe midsole using the same, which improves the cooling properties of TPU so that it is suitable for injection foam molding and simultaneously realizes excellent physical properties and lightness.

In general, shoe midsoles are manufactured in an expansion type in which crosslinking and foaming are simultaneously performed in a mold, and related research is also being conducted mainly in this way.

More specifically, the midsole is usually manufactured by manufacturing a preform larger than the size of the mold and molding it through remolding. Usually, a preform is manufactured by primary molding of a compound and then cut into the shape of a shoe sole. And after grinding, it is molded by inserting it into the mold of the final midsole shape and applying appropriate temperature and pressure.

However, the conventional technology as described above has many disadvantages compared to injection molding having a finished product form after injection, since size stability due to shrinkage after molding is low and deformation characteristics are high in heat.

Furthermore, in the case of general pressurized foaming, there are many restrictions according to the flowability of the material as the foaming proceeds by being heated and pressurized in the mold and the material is supplied through the mold gate.

Therefore, as in Patent Documents 1 and 2, some research on midsole development through foaming in a mold (1: 1 foaming) is being conducted, but research is being conducted in a pressurized foaming method in which crosslinking and foaming must proceed together, leading to material development and commercialization. There are difficulties.

On the other hand, in relation to the material of the midsole, EVA material is generally used to secure light weight, but recently, development of a midsole made of TPU (thermoplastic polyurethane) having excellent physical properties has been actively carried out. However, as described above, the TPU-based material has a large change in heat (weak heat resistance), so there is a problem in that the flowability is not constant and the cooling is slow, resulting in defects during injection and foaming.

Patent Document 1: Republic of Korea Patent Publication No. 10-2018-0034074 "Method for manufacturing foam using foam composition suitable for in-mold foaming" Patent Document 2: Republic of Korea Patent Registration No. 10-1622710 "Mold structure for foam molding and method for manufacturing foam using the same"

The present invention is to solve the above problems, a composition for a shoe midsole and a thermoplastic shoe midsole using the same, which can simultaneously realize excellent physical properties and light weight while improving the cooling properties of TPU so that it is suitable for injection foam molding It is an object of the present invention to provide a manufacturing method.

In the present invention, in order to improve the cooling properties of TPU, the cooling properties of the injected material are improved by mixing SBR having a styrene content of 68% or more, but the VA content is 28% or more and the MI (melt index) is 25g/10min. EVA of ~ 60g/10min. is used to improve the compatibility of TPU and SBR, as well as to improve flowability, and by mixing talc with a particle size of 4㎛ or less as a foaming nucleating agent to improve foaming properties, the cooling properties of TPU are effectively improved. A composition for a shoe midsole and a method for manufacturing a thermoplastic shoe midsole using the same, which can be improved to be suitable for injection foam molding and simultaneously realize excellent physical properties and light weight, are a means of solving the problem.

In the present invention, TPU and SBR are mixed to improve the cooling properties of the injected material, and EVA is mixed to improve the compatibility of TPU and SBR, as well as to increase flowability and to improve foaming properties by mixing talc as a foaming nucleating agent, TPU It has the effect of realizing excellent physical properties and lightness at the same time while efficiently improving the cooling characteristics of the product to make it suitable for injection foam molding.

The present invention for achieving the above effects relates to a composition for a shoe midsole and a method for manufacturing a thermoplastic shoe midsole using the same. It should be noted that it will be omitted so as not to obscure the gist.

Hereinafter, the composition for a shoe midsole according to the present invention and the manufacturing method of a thermoplastic shoe midsole using the same will be described in detail.

The composition for a shoe midsole according to the present invention includes 100 parts by weight of a base material composed of 65 to 80% by weight of thermoplastic polyurethane (TPU), 5 to 15% by weight of styrene butadiene rubber (SBR), and 15 to 20% by weight of ethylene vinyl acetate (EVA). 2 to 5 parts by weight of talc, 0.3 to 4 parts by weight of calcium stearate, 0.2 to 1.5 parts by weight of an antioxidant, and 0.2 to 1.5 parts by weight of a UV (ultraviole) stabilizer.

Here, the TPU uses a hardness of 75 to 85A (asker A type), the SBR uses a styrene content of 68 to 90% by weight, and the EVA has a VA (vinyl acetate) content. 28 to 80% by weight and an MI (melt index) of 25g/10min. ~ 60g/10min., and the talc has a particle size of 0.1 ~ 4㎛.

That is, the cooling properties of the injected material are improved by mixing TPU and SBR, and the compatibility of TPU and SBR is improved by mixing EVA, the flowability is increased, and the foaming properties are improved by mixing talc as a foaming nucleating agent. Cooling characteristics are efficiently improved to make it suitable for injection foam molding.

At this time, if the contents of the TPU, SBR, EVA and talc are out of the above range, there is a concern about the degradation of the physical properties of the midsole, and also, the hardness of the TPU, the styrene content of SBR, the VA content and MI range of EVA, and the talc If the particle size is out of the above range, there is a concern that the physical properties of the midsole may deteriorate or the cooling characteristics may be insufficient.

On the other hand, the talc is used after surface treatment with a silane coupling agent in consideration of dispersibility and uniform foamed cells. The silane coupling agent is used alone or in combination with vinyltriethoxysilane, vinyltrimethoxysilane or vinyltri(2-methoxyethoxy)silane. . Here, when the content of the silane coupling agent is out of the above range, there is a concern that the dispersibility of talc is lowered.

In addition, the calcium stearate, antioxidant, and UV (ultraviole) stabilizer are known additives added for ease of molding, prevention of oxidation, and prevention of deterioration by UV. In the case of antioxidants, arylamine , Phosphite, thioester, and benzotriazole, benzophenone, triazine, etc. may be used as UV stabilizers, but are not limited thereto and are known in the art. Various types of additives can be used. In addition, the content is also not limited to the above range, and can be applied variably depending on the type of shoe or use environment.

In the method for manufacturing a thermoplastic shoe midsole using the composition for shoe midsole according to the present invention, 2 to 10 parts by weight of sodium bicarbonate and 1 to 3 parts by weight of thermally expandable microcapsules as a foaming agent are added to 100 parts by weight of the composition for shoe midsole as described above. After mixing, it is manufactured by injection molding. More specifically, after injecting the composition as described above, the temperature of the injector of the injection molding machine is set to 150 ~ 180 ℃ based on the die, and then injected, and the mold is 30 ℃ or less keep as Here, the mold is injected from a mold capable of core-back, injects the material into the mold, and then core-backs more than twice the thickness of the mold (eg, 5 mm -> 10 mm or more) to manufacture a midsole with a specific gravity of 0.3 or less. can do.

Here, the thermally expandable microcapsule is a material already known as a capsule foaming agent that expands by heat, and includes microspheres (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), cell powder (CELLPOWDER; manufactured by Eiwa Kasei Co.), and EXPANCEL (Akzo Co., Ltd.). Nobel Corporation), Microsphere (manufactured by Kureha), etc. may be used, and among them, it is preferable to use those having a foaming start temperature of 145 ° C. or higher and a foaming maximum temperature of 190 ° C. or higher in consideration of foaming efficiency.

On the other hand, if the content and injection conditions of sodium bicarbonate and thermally expandable microcapsules used as the foaming agent are out of the above ranges, there is a concern that moldability may be deteriorated, such as insufficient foaming.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited by the examples.

1. Manufacture of shoe midsole composition

(Production Example 1)

Based on 100 parts by weight of a substrate composed of 80% by weight of TPU (hardness: 75A), 5% by weight of SBR (styrene content: 68%), and 15% by weight of EVA (VA content: 28%, MI: 25g/10min.), talc (particle size) 4㎛) 2 parts by weight, calcium stearate 0.3 parts by weight, antioxidant (Songnox-1076, Songwon Chemical) 0.2 parts by weight and UV stabilizer (Zikozor, Zico) 0.2 parts by weight in a closed kneader kneader to 180 ° C. After mixing, it was extruded in an extruder to produce pellets. Here, the talc was surface-treated by mixing 1 part by weight of vinyltriethoxysilane with respect to 100 parts by weight of talc.

(Production Example 2)

Based on 100 parts by weight of a substrate composed of 65% by weight of TPU (hardness: 85A), 15% by weight of SBR (styrene content: 90%), and 20% by weight of EVA (VA content: 80%, MI: 60g/10min.), talc (particle size) 0.1 μm) 5 parts by weight, calcium stearate 4 parts by weight, antioxidant (Songnox-1076, Songwon Chemical) 1.5 parts by weight and UV stabilizer (Zikozor, Zico) 1.5 parts by weight in a closed kneader kneader to 180 ° C. After mixing, it was extruded in an extruder to produce pellets. Here, the talc was surface-treated by mixing 2 parts by weight of vinyltrimethoxysilane with respect to 100 parts by weight of talc.

2. Manufacture of shoe midsoles

(Example 1)

With respect to 100 parts by weight of the shoe midsole composition according to Preparation Example 1, 2 parts by weight of sodium bicarbonate and 1 part by weight of thermally expandable microcapsules (microspheres) were mixed, followed by injection molding, but at an injector temperature of 150 ° C. (based on die) After setting to , injection was performed, and the mold was maintained at 30 ° C or less. At this time, the mold was injected as a core-back mold, and after injecting the material into the mold, the mold was core-backed (eg, 5 mm -> 10 mm or more) to manufacture a midsole with a specific gravity of 0.3 or less.

(Example 2)

After mixing 10 parts by weight of sodium bicarbonate and 3 parts by weight of thermally expandable microcapsules (microspheres) with respect to 100 parts by weight of the shoe midsole composition according to Preparation Example 2, injection molding was performed, but the injector temperature was 180° C. (based on the die). After setting to , injection was performed, and the mold was maintained at 30 ° C or less. At this time, the mold was injected as a core-back mold, and after injecting the material into the mold, the mold was core-backed (eg, 5 mm -> 10 mm or more) to manufacture a midsole with a specific gravity of 0.3 or less.

(Comparative Example 1)

It was prepared in the same way as in Example 1, but TPU was used alone, and it was prepared by press molding.

(Comparative Example 2)

It was prepared in the same manner as in Example 2, but TPU was used alone, and it was prepared by injection molding.

3. Evaluation of shoe midsoles

The midsoles according to the above examples and comparative examples were tested with the following test items and methods, and the results are shown in [Table 1] below.

(1) hardness

According to KS M6518, it was measured using a Shore C-type hardness tester.

(2) specific gravity

In accordance with KS M6519, it was measured using Model DMA-3, an automatic specific gravity measuring device manufactured by Ueshima.

(3) Permanent compression set

After cutting the midsole specimen to a thickness of 10 mm, a test specimen manufactured in the form of a cylinder having a diameter of 30 ± 0.05 mm was measured according to KS M6660. After inserting the test piece between two parallel metal plates, inserting a spacer corresponding to 50% of the thickness of the test piece, compressing it, and heat-treating it in an open state maintained at 50 ± 0.1 ° C for 6 hours, releasing the compression state, and leaving it at room temperature for 30 minutes. The thickness of the test piece was measured, and the permanent compression set was calculated by Equation 1 below.

(Equation 1)

t ₀ : initial thickness of the test piece

t _f : thickness of the test piece when cooled after heat treatment

t _x : thickness of spacer

(4) Tensile strength and elongation

After making the specimen to a thickness of about 3 mm, a No. 2 type according to KS M6518 was prepared using a cutter, and the tensile strength was measured according to KS M6518.

(5) Tear strength and split tear strength

Measurements were made according to KS M6518.

(6) Resilience

Measured according to ASTM D2632.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Hardness
(Asker C) 34 34 45 injection molding
not become importance
(Sp. Gr.) 0.257 0.258 0.572 permanent compression set
(C/set, %) 55 54 68 The tensile strength
(kg/cm ² ) 25 22 12 Elongation (%) 245 245 225 tear strength
(kg/cm) 10 10 6 split tear strength
(kg/cm) 2.2 2.2 1.1 resilience
(%, 22℃) 62 60 55

As shown in [Table 1], it can be seen that the shoe midsole according to the embodiment of the present invention is suitable for injection foam molding, such as exhibiting excellent physical properties and light weight even during injection molding.

As described above, the composition for a shoe midsole according to the present invention and the manufacturing method of a thermoplastic shoe midsole using the same have been described through the above preferred examples and their superiority confirmed, but those skilled in the art It will be understood that various modifications and changes may be made to the present invention without departing from the spirit and scope of the described invention.

Claims (3)

In the composition for a shoe midsole,
2 to 5 parts by weight of talc, 0.3 to 4 parts by weight of calcium stearate, 0.2 to 1.5 parts by weight of an antioxidant, based on 100 parts by weight of a substrate composed of 65 to 80% by weight of TPU, 5 to 15% by weight of SBR, and 15 to 20% by weight of EVA A composition for a shoe midsole, characterized in that it consists of 0.2 to 1.5 parts by weight and a UV stabilizer.
According to claim 1,
The TPU uses a hardness of 75 ~ 85A,
The SBR uses a styrene content of 68 to 90% by weight,
The EVA has a VA content of 28 to 80% by weight, and an MI of 25 g/10 min. ~ 60g/10min.,
The talc has a particle size of 0.1 to 4 μm, and is used after surface treatment with a silane coupling agent. Surface treatment is performed by mixing 1 to 2 parts by weight of a silane coupling agent with respect to 100 parts by weight of talc.
The silane coupling agent is vinyltriethoxysilane, vinyltrimethoxysilane or vinyltri(2-methoxyethoxy)silane, characterized in that used alone or in combination, the composition for midsole shoes.
In the method for manufacturing a thermoplastic shoe midsole using the shoe midsole composition according to claim 1,
2 to 10 parts by weight of sodium bicarbonate and 1 to 3 parts by weight of thermally expandable microcapsules are mixed with 100 parts by weight of the shoe midsole composition according to claim 1, and then injection molded to produce a thermoplastic shoe midsole. Manufacturing method of.