JPS62101203A - Production of shoes having shoe sole with microfoam structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing shoes having soles having a microfoamed structure.

(Prior art) Conventionally, as shown in Japanese Patent Publication No. 56-17288, a commonly used rubber compounding agent, a foaming agent, and an organic peroxide having a crosslinking effect on both Baum and polyethylene were added to a mixture of rubber and high-density polyethylene. An uncrosslinked foamable shoe sole molding material that has been melt-mixed above the melting temperature of the foaming agent and below the decomposition temperature of the foaming agent and the organic peroxide is weighed, introduced into a shoe sole mold, sealed, and mixed with the foaming agent. A method (referred to as a direct crosslinking and foaming method) of forming a sole having a microfoamed structure that is foamed and crosslinked by heating and pressurizing the organic peroxide at a temperature higher than the decomposition temperature of the organic peroxide has generally been adopted. Shoe soles molded using this method have excellent appearance and dimensional stability. However, this method requires a complicated molding process, and moreover, it is necessary to prepare a large number of expensive molds depending on the size of the sole, which significantly increases the manufacturing cost of the sole. In addition, since the soles formed using this method are already cross-linked, the surface that contacts the shoe cover must be puffed and roughened before being bonded to the shoe cover during the shoe assembly process. , the bonding work was also inefficient.

Therefore, as shown in Japanese Patent Publication No. 56-13642, a mixture of rubber and high-density polyethylene to which commonly used rubber compounding agents, crosslinking agents, and blowing agents are added is heated above the melting temperature of polyethylene and above the decomposition temperature of the blowing agent. The melt-mixed uncrosslinked foamed shoe sole molding material is rolled with a design roll and a design is applied to one side of the dough, which is then punched and cut into the shape of a shoe sole to form an uncrosslinked foamed shoe sole. In the shoe assembly process, the assembled shoes are put into a vulcanizing can with the designed side facing the ground surface and heated to a temperature above the decomposition temperature of the foaming agent. We investigated various methods of foaming and cross-linking shoe soles (indirect cross-linking foaming method), but the surface skin of the shoe soles became rough and the appearance deteriorated, and the dimensional stability after molding was poor, resulting in warped soles. The problem was that the shoes would become deformed.

(Problems to be Solved by the Invention) An object of the present invention is to provide a lightweight shoe sole that is inexpensive and has good appearance and dimensional stability after molding.

(Means for Solving the Problems) This invention uses 1 to 20 parts by weight of low-density polyethylene powder of 5 to 50 microns per 100 parts by weight of rubber, and other ordinary rubber compounding chemicals, blowing agents, and crosslinking agents. This is mixed at a temperature below the softening temperature of low-density polyethylene powder to form a dough, which is then cut into the shape of a shoe sole and the formed shoe sole 1 is adhered to the shoe cover 2. The gist of the invention is a method of manufacturing a shoe having a micro-foamed sole, which is characterized by heating and melting low-density polyethylene powder and foaming and cross-linking the sole 1 using an indirect vulcanization method. .

In this invention, the rubber includes one or more synthetic rubbers such as natural rubber, imprene rubber, styrene butadiene rubber, high styrene rubber, acrylonitrile rubber, chloroprene rubber, ethylene propylene rubber, chlorinated polyethylene, and chlorosulfonated polyethylene. A mixture is used. In this invention, low density polyethylene includes not only ethylene homopolymers having a density of 0.910 to 0.940, but also copolymers of ethylene and other monomers. Examples of such copolymers include copolymers of ethylene and vinyl acetate, ethylene and methacrylic acid, and ethylene and propylene. These low-density polyethylenes have more side chains and are less crystalline and softer than high-density polyethylenes, so they are added at a certain ratio to rubber-based shoe sole materials and foam-molded. A shoe sole having a foam structure with low shrinkage can be obtained without impeding combustibility. In this invention, the particle size of the low-density polyethylene powder is limited to 5 to 50 microns.If the particle size is smaller than this, the dispersibility in rubber will be better, but the dimensional foam structure and stability after foam crosslinking of the shoe sole will be affected. However, if the particle size is larger than that, the physical properties of the shoe sole after foaming and cross-linking will deteriorate, and the sole reforming effect will not be seen. . In addition, in this invention, the content of low density polyethylene powder is limited to 1 to 20 parts by weight per 100 parts by weight of rubber.
If the blending amount is less than this, the dimensional stability after sole molding will be poor, and the sole modification effect will not be observed. This is because the strength decreases, deformation of the uncrosslinked sole occurs, and the rubber elasticity of the crosslinked sole decreases.

In this invention, the crosslinking agents include sulfur, sulfur compounds, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethylhexane-2,5-di( peroxybenzoate),
Organic peroxides such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane-3 are used. Examples of the blowing agent include nitroso compounds such as dinitrosopentamethylenetetramine, azo compounds such as azodicarbonamide, and sulfonyl hydrazide compounds such as benzenesulfonyl hydrazide and toluenesulfonyl hydrazide derivatives. In addition, commonly used compounded chemicals for rubber such as crosslinking aids, crosslinking accelerators, fillers, pigments, and stabilizers are added.
The components prepared in this way are uniformly mixed and sheeted using a general mixer such as a Banbury mixer, a Henschel mixer, a mixing roll, or a kneader. It is carried out at a temperature below the softening temperature of the powder, that is, from 80°C to 110°C, preferably at a temperature of 50°C to 60°C.

During seating, an appropriate anti-slip design is engraved on the ground surface of the sole. The shoe sole molding material sheeted in this manner is punched and cut into a shoe sole shape. After the sole 1 prepared in this way is poorly adhered to the bottom of the shoe cover 2 during the shoe manufacturing process, it is heated in a vulcanizer using an indirect vulcanization method at an air pressure of 3 to 5. Crosslinking and foaming is performed by heating at 110°C to 140°C for 50 to 90 minutes.

Example A shoe sole molding material having the composition shown in Table 1 was heated to a temperature below the melting temperature of low-density polyethylene powder, specifically at a surface temperature of X850 to X60.
Knead with a mixed wire roll at ℃, and then mix with a design roll to a thickness of about 3
After rolling out the dough on the shoulders and adding a shoe sole design to one side, the rolled and assembled shoes are introduced into a vulcanizing can and exposed to hot air.
Foaming and crosslinking was carried out by heating and pressurizing at 45° C. for 50 minutes using an air pressure bundle.

#! As can be seen from Table 2, the sole of the example has a good appearance, the foaming is uniform, there is no dimensional change in the vertical and horizontal directions, and the sole is foamed 1.25 times in the thickness direction only. The shoes had excellent dimensional stability, no warpage was observed, and no deformation of the completed shoes was observed.

(Effects of the Invention) As described above, the present invention can provide a foamed shoe sole that has a good appearance, uniform foaming, excellent dimensional stability, and is extremely lightweight. The cause of this is that the low density polyethylene powder is dispersed in a non-melted state in the uncrosslinked rubber in the uncrosslinked foam sole, so the low density polyethylene powder melts during the heat foam crosslinking process. Even if heat shrinkage occurs in the vertical and horizontal directions, it is offset by the foaming of the foaming agent, and it is thought that this contributes to the dimensional stability of the sole after molding.

In addition, since the shoe sole of this case is manufactured using an indirect cross-linking foaming method, it is cheaper and suitable for mass-produced shoes compared to lightweight shoe soles made using a direct cross-linking foaming method.

Table 1 Note 1 HIZEX #50nQSSR (Bellet shape) Manufactured by Mitsui Petrochemicals Co., Ltd. Note 2 Frozen trlF-1,51M Manufactured by Tetsu Kagaku Co., Ltd. Table 2

[Brief explanation of drawings]

The drawing is a cross-sectional view of a main part of a shoe manufactured according to the present application. Explanation of symbols 1. Sole λ cover

Claims (1)

[Claims] To 100 parts by weight of rubber, 1 to 20 parts by weight of low-density polyethylene powder of 5 to 50 microns, and other ordinary rubber compounding chemicals, foaming agents, and crosslinking agents are added, and this is adjusted to the softening temperature of the low-density polyethylene powder. The dough is mixed below, the dough is cut into the shape of a shoe sole, the formed shoe sole 1 is adhered to the shoe cover 2, and then the shoe sole 1 is heated to melt the low-density polyethylene powder and the shoe A method for manufacturing shoes having a sole having a microfoam structure, characterized in that the sole 1 is foamed and cross-linked by an indirect vulcanization method.