JPH08214913A - Manufacture of foamed sole made of thermoplastic synthetic resin - Google Patents

Abstract

PURPOSE: To produce a foamed sole made of a thermoplastic synthetic resin by miniaturizing the apparatus and reducing the number of steps. CONSTITUTION: A foaming ratio is set so that the length and width of a foamed and hardened sole are equal to values which correspond to the final shape when a mold is formed for the first time. The molding is immediately put into the final mold having a three-dimensional industrial design or the like on the bottom while the molding is hot. The molding is pressed and cooled to obtain the sole having the three-dimensional industrial design on the under face which touches the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foam sole made of a thermoplastic synthetic resin which is easy to process and has no material loss.

[0002]

2. Description of the Related Art Thermoplastic synthetic resins such as ethylene-vinyl acetate copolymers have excellent physical properties such as weather resistance, chemical resistance and impact resistance, and when a foaming agent is used on them, they can be foamed relatively large. Since it can be formed, has a smaller shrinkage than other materials, and has many advantages such as obtaining uniform bubbles, it is often used for shoe soles.

A conventional method for producing a foamed shoe sole from such a synthetic resin is to fill a kneaded product containing a foaming agent into a mold having a wide cavity capable of obtaining a large number of shoe soles, and heat and pressurize at a crosslinking temperature to apply the mixture. Release the pressure state, obtain a sheet thicker than the thickness of the sole, slice the upper and lower surfaces of this sheet to be slightly thicker than the thickness of the sole, and then make the length and width the same as the sole Cut with a blade mold like this, fill in a mold with a shoe sole-shaped cavity, heat and press,
Then, it cooled and obtained the foam sole.

[0004]

In the conventional method of manufacturing a shoe sole, the upper and lower surfaces of the foamed sheet must be sliced so as to be slightly thicker than the thickness of the shoe sole in the intermediate step. In addition, it must be cut with a blade mold or the like so as to have the same length and width as the shoe sole, which requires a lot of equipment and labor, and a cutting layer is formed after cutting, which causes an increase in cost. Moreover, since the finished shoe sole is once cooled, it is modeled by the three-dimensional design of the bottom surface of the mold cavity, so it can be said that it is heated and pressed, but a sharply engraved design could not be produced clearly.

Furthermore, since the upper and lower surfaces are sliced and then molded, the skin is not formed on the surface, the appearance is inferior, and the abrasion resistance is not sufficient. The present invention aims to eliminate all of the above-mentioned drawbacks of conventional manufacturing methods.

[0006]

The present invention provides a method for producing a foamed sole made of a thermoplastic synthetic resin, which comprises the following steps (A) and (B). (A) A thermoplastic synthetic resin kneaded product containing a foaming agent is filled in a mold cavity having a smooth bottom surface, pressurized and heated, taken out from the cavity and foamed, and has the same length and width as the sole, Use a molded product with a large thickness. (B) While the molded body is hot, it is placed in a mold cavity having the same length, width, and thickness as the sole and having a three-dimensional design on the bottom surface, and is pressurized and cooled to form a three-dimensional design on the ground contact surface. The soles. Is the first feature.

The present invention also provides a method for producing a foam sole made of a thermoplastic synthetic fiber resin, which comprises the following steps (a) to (d). (a) Fill a mold having a cavity with a smooth bottom surface and smaller than a shoe sole shape with a thermoplastic synthetic resin kneaded product containing a foaming agent, (b) keep the cavity closed, and heat the thermoplastic synthetic resin to a crosslinking temperature. (C) After crosslinking, open the closed state after cross-linking and foam to make a molded product with the same length and width and a larger thickness than the specified sole shape,
Fill a mold at room temperature that has a three-dimensional design while it is hot and has the same length, width, and thickness as the sole of the shoe, and seal the mold cavity used in steps (d) and (c). After pressurizing and cooling, a three-dimensional design is formed on the ground contact surface to form the sole. Is the second feature.

In carrying out the present invention, ethylene-vinyl acetate copolymer or syndiotactic 1.2 polybutadiene is used as the thermoplastic synthetic resin. This is because the foam having excellent weather resistance, chemical resistance, and impact resistance can be foamed relatively large, uniform bubbles can be formed, and shrinkage is relatively small.

As the ethylene-vinyl acetate copolymer, one having a vinyl acetate content of 5 to 30% (according to JIS K6370 ethylene vinyl acetate test method, the same applies hereinafter) is used.
When it is less than 30%, the workability is deteriorated, the elasticity of the finished foam is insufficient, and when it exceeds 30%, it becomes too soft and sufficient physical properties cannot be obtained. Crosslinking and foaming conditions of thermoplastic synthetic resin containing a foaming agent in a mold with a smooth bottom surface and a cavity smaller than the shoe sole shape are as follows: temperature 150-170 ℃, time 10-
15 minutes.

Foaming ratio of foamed shoe sole obtained by using a mold having a three-dimensional design on the bottom surface using a thick material obtained under such conditions and having cavities of the same shape as the shoe sole. Is 2 to 5 times, and the specific gravity is 0.2 to 0.5.

[0011]

The operation and effect of the present invention is as follows.
Fill a mold with a cavity with a smooth bottom and smaller than the sole shape with thermoplastic synthetic resin containing a foaming agent, heat,
After crosslinking by pressurization, the pressurized state is removed, and foaming of the kneaded product to be filled is carried out so that the foamed molded product obtained at that time has a length and a width that are the same as the shape of the sole and is slightly thicker. Since the magnification is set in advance, it is not necessary to slice or cut the upper and lower surfaces, and the skin layer can be exposed as it is.

[0012] Therefore, the process is omitted, the manufacturing cost can be reduced, and the shoe sole having a good appearance and excellent physical properties can be obtained.
Further, the foamed molded product obtained in the above step is immediately hot-pressurized and cooled by a mold having a cavity having a three-dimensional design on the bottom surface while being hot to give a three-dimensional design to the ground contact surface, so that a deep and sharp design is obtained. can get.

[0013]

Example: Ethylene vinyl acetate copolymer (vinyl acetate content 15%) 30 parts by weight, the same copolymer (vinyl acetate content 26
%) 70 parts by weight, stearic acid 1 part by weight, blowing agent azodicarbonamide 4 parts by weight, cross-linking agent Perkmill D-40, 2.5
Knead the mixture consisting of parts by weight with a Banbury mixer,
Seat with a roll machine thicker than the thickness of the sole.

This was cut, put into a mold cavity having a smooth bottom, a length and a width smaller than the shoe sole and a large thickness, sealed with a lid mold, and crosslinked at 160 ° C. for 15 minutes. Remove the lid mold and allow it to foam. This foamed molded product is placed in a mold at room temperature having a cavity with the same length, width, and thickness as the shoe sole, which has a three-dimensional design on the bottom surface, and is sealed with a lid mold at room temperature and pressed,
Let stand for 10 minutes, remove the lid mold and get the soles.
The size of this shoe sole is 25.0 cm.

On the other hand, a sheet thicker than the sole obtained from the same kneaded product as the above was put into a flat plate mold having a size of about 500 × 850 mm so as to be filled, and crosslinked under the condition of 152 ° C. × 25 minutes. Take out and foam. The size of the foamed molded product at this time was about 700 × 1200 mm.

[0016] This sheet is sliced into upper and lower surfaces to be slightly thicker than the thickness of the sole, and cut with a blade mold so that the length and width of the sole are the same, and this is the same thickness and length as the sole. ， It has a width, and it is put so that it fills the mold of a cavity with a three-dimensional design on the bottom, heated and pressurized under the condition of 160 ℃ × 10 minutes, then cooled at room temperature as it is, fixed for 10 minutes, and fixed to the ground plane. Typed.

The size of the shoe sole thus obtained is 25.0 cm. The former method had two fewer steps than the latter method, no cutting layer was provided, the design of the grounding surface was clear, and the skin on the surface was smooth and beautiful.

Claims (5)

[Claims] 1. A method for producing a foam sole made of a thermoplastic synthetic resin, which comprises the following steps (A) and (B): (A) A thermoplastic synthetic resin kneaded product containing a foaming agent is filled in a mold cavity having a smooth bottom surface, pressurized and heated, taken out from the cavity and foamed, and has the same length and width as the sole, Use a molded product with a large thickness. (B) While the molded body is hot, it is placed in a mold cavity having the same length, width, and thickness as the sole and having a three-dimensional design on the bottom surface, and is pressurized and cooled to form a three-dimensional design on the ground contact surface. The soles. 2. A method for producing a foam sole made of a thermoplastic synthetic fiber resin, which comprises the following steps (a) to (d): (a) A thermoplastic synthetic resin kneaded product containing a foaming agent is filled in a mold having a cavity having a smooth bottom surface and smaller than a shoe sole shape. (b) The cavity is hermetically closed and heated and pressed at the crosslinking temperature of the thermoplastic synthetic resin. (c) After cross-linking, the closed state is opened and foaming is performed to form a molded body with the same length and width and a larger thickness than the prescribed shoe sole shape, and while it is hot, there is a three-dimensional design on the bottom and the length Fill a mold at room temperature with a cavity that has the same width and thickness as the sole. (d) The cavity of the mold used in steps (c) is hermetically sealed, pressurized and cooled to form a three-dimensional design on the ground contact surface to form the sole. 3. The foamed shoe made of thermoplastic synthetic resin according to claim 1, wherein the thermoplastic synthetic resin is any one of ethylene vinyl acetate copolymer and syndiotactic 1.2 polybutadiene. How to make the bottom. 4. The method for producing a foam sole made of a thermoplastic synthetic resin according to claim 3, wherein the vinyl acetate content of the ethylene vinyl acetate copolymer is 5 to 30%. 5. The method for producing a foam sole made of a thermoplastic synthetic resin according to claim 1, wherein the surface of the sole having the three-dimensional design is a skin layer.