KR20030026374A - cross foam polyolefine composition for shoes - Google Patents

Abstract

PURPOSE: Provided is a crosslinked polyolefin foam composition for shoes, which is excellent in specific gravity, hardness, tensile strength, elongation, rupture tearing strength, permanent compressibility, and restoration force and has light weight, therefore it can be used for insoles, midsoles, covers or reinforcements, and lining for shoes. CONSTITUTION: The crosslinked polyolefin foam composition comprises 30-90pts.wt. of a low density polyethylene(LDPE), 10-70pts.wt. of ethylene vinyl acetate(EVA) containing 15-22pts.wt. of vinyl acetate, 3-25pts.wt. of a foaming agent, and additionally 0.2-2pts.wt. of dicumyl peroxide(DCP) as a crosslinking agent, wherein the foaming agent is one selected from the group consisting of azodicarbonamide(ADCA), dinitroso penta-methyl tetra-amine(DPT), azobisiso-butyl nitrile(ABBN), and p-toluene sulfonyl hydrazide(TSH). The crosslinked polyolefin foam composition has a melting point of 60-120deg.C, a density of 0.9-1.0g/cm3, and a melt index of 0.3-20g/10min.

Description

Cross foam polyolefine composition for shoes

The present invention relates to a crosslinked foam polyolefin composition for shoes, and more particularly, to a crosslinked foam polyolefin composition for shoes having excellent mechanical strength and resilience and light weight.

In general, the insole and midsole of the shoe absorbs or cushions shocks and pressures transmitted by the weight of the body when walking or activities while wearing shoes, and absorbs sweat and facilitates breathability. It has been manufactured using materials such as rubber or thermosetting resin.

However, the insole and midsole of the shoe as described above has been used to produce a foam that is heavy in the weight of the material itself and also has a poor function in shock absorption or cushioning action.

As a method for manufacturing a foam used as an insole and midsole of a conventional shoe, a composition in which a foaming agent, a crosslinking agent, and other additives are mixed with ethylene vinyl acetate resin or polyurethane resin is prepared in a sheet, and then put into a closed mold. After forming, the foam molding method by press molding method which processes under high temperature and pressure using a press machine, decomposes a crosslinking agent and a foaming agent, and opens a metal mold | die instantaneously and removes a pressure and expands rapidly using a pressure difference is proposed.

In addition, a method of using a foam using ethylene vinyl acetate or ultra low density polyetherene (VLDPE) as a matrix resin has been proposed, but the foams have not been expected to have a product quality and economy, and a solution for this has been required.

The present invention has been made to solve the above problems, the polyolefin is extracted through the pyrolysis of gas and methane propane generated during petroleum refining process, or pyrolysis by extraction of methane, propane in natural gas, or pyrolysis of light oil. It is manufactured by using ethylene as a raw material. Continuously crosslinked polyolefin has its material characteristics different according to different molecular structures. It is possible to manufacture products suitable for special purposes by controlling the molecular structure and adjusting the material properties using blowing agents and additives. have.

Such continuous crosslinked foamed polyolefin is not only easy to process but also has excellent mechanical strength and resilience, light weight, excellent shock absorption and buffering effect, and provides a crosslinked foamed polyolefin composition for footwear that can produce a product of uniform quality. It aims to do it.

This object of the present invention is not only easy to process, but also high strength and light low density polyethylene (LDPE) and ethylene vinyl acetate (ethylene vinyl acetate, EVA) is produced by mixing the foam to the optimum composition ratio It is achieved by providing, the foam for footwear of the present invention is economical and easy to continuous processing, excellent physical properties such as specific gravity, hardness, tensile strength, elongation, tear tear strength and the like.

The composition of the present invention is 30 to 90 parts by weight of low density polyethylene (LDPE), 10 to 70 parts by weight of ethylene vinyl acetate (EVA) containing 15 to 22 parts by weight of vinyl acetate (VA Content), and 3 to 25 parts by weight of blowing agent It is a foaming composition for shoes comprised by mixing a part and 0.2-2 weight part of crosslinking agents.

The polyolefin resin of the present invention is mixed with low density polyethylene (LDPE) and ethylene vinyl acetate (EVA) so as to have physical properties of melting point 60 ~ 120 ℃, density 0.9 ~ 1.0g / cm 3, melt index (MI) 0.3 ~ 20g / 10min do.

In this case, when the resin density is less than 0.9 g / cm 3, the crystallinity is low and mechanical properties are lowered. When the resin density exceeds 1.0 g / cm 3, the flexibility is lowered, which is not preferable. That is, by having a range of density proposed in the present invention, the mechanical properties of the resin are good due to the moderate degree of crystallinity.

In addition, when the melt index (MI) of the resin of the present invention is less than 0.3g / 10min, the fluidity of the resin decreases, so that the work is difficult. When the melt index (MI) of the resin of the present invention exceeds 20g / 10min, the strength, elongation, impact resistance, abrasion resistance, etc. of the obtained molded article are This lowers and is not preferable.

Foaming agents used to expand the composition of the present invention, azo-based compounds such as azodicarbonamide (ADCA), nitroso-based compounds such as dinitroxo penta-methyl tetra-amine (DPT) , Azobisisobutyl nitrile (ABBN), p-tolune sulfonyl hydrazid (TSH), and the like, and most preferred are azodicarbonamides.

At this time, when the content of the crosslinking agent is less than 0.2 parts by weight, the crosslinked gel (gel)% is low, the foaming is poor, when the content exceeds 2 parts by weight, the surface is broken during foam molding and the molding itself becomes difficult.

Examples of the crosslinking method usable in the present invention include a chemical crosslinking method in which an organic peroxide is added to the composition and heated to generate free radicals, and an electron beam crosslinking method in which a polyfunctional compound and a monofunctional monomer are added to the composition and irradiated with an electron beam. .

Dicumyl peroxide (DCP) and t-butyl peroxy laurate when performing the chemical crosslinking method of the said crosslinking method. t-dibutylperoxymaleic acid, t-butylhydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) nucleic acid, di-t-butylperoxide and 1,3-bis (t Organic peroxides, such as -butyl peroxy isopropylene) benzene, are added. Most preferably, dicumyl peroxide (DCP) is added. In the electron beam crosslinking method, a crosslinking agent is not added or a very small amount is added. .

Hereinafter, the manufacturing method of the foam for use as a shoe insole or for the skin (covering), the midsole using the composition according to the present invention.

30 to 90 parts by weight of low density polyethylene (LDPE) constituting the composition of the present invention, 10 to 70 parts by weight of ethylene vinyl acetate (EVA) containing 15 to 22 parts by weight of vinyl acetate (VA Content), and 3 to 3 foaming agents. 25 parts by weight and 0.2 to 2 parts by weight of the crosslinking agent are blended in a molten state at a temperature below the decomposition temperature of the blowing agent and the crosslinking agent using a mixer, and then the blended composition is molded into a solid sheet using a special extruder or the crosslinking agent. Irradiated electron beams with absorbed doses of 3 to 10 Mrad were applied to the solid city formed without the addition of a solid state, and the solid sheet was foamed by atmospheric pressure or pressure in a special foam oven.

At this time, the preferred extrusion temperature is 90 ~ 135 ℃, foaming temperature is 150 ~ 270 ℃.

The sheet foam prepared as described above is a shoe insole, midsole, which is formed by vacuum-forming or thermo-compression molding a thin PVC sheet, cloth or non-woven fabric by dry-laminate or frane-laminate. It can be used in various ways depending on the application such as front, rear, side skin or reinforcement and lining.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the described embodiments.

Example 1

40 parts by weight of low-density polyethylene (LDPE), 60 parts by weight of ethylene vinyl acetate (EVA), 6 parts by weight of blowing agent azodicarbonamide and 0.6 parts by weight of crosslinking agent dicumylperoxide were subjected to chemical crosslinking to obtain a solid in an extruder at a temperature of 90-135 ° C. After molding into a sheet (solid sheet) using a special foam oven was foamed at a foaming temperature of 150 ~ 270 ℃ to prepare a sheet foam for shoe insole having a thickness of 5.5㎜.

Example 2

60 parts by weight of low-density polyethylene (LDPE), 40 parts by weight of ethylene vinyl acetate (EVA), 6 parts by weight of blowing agent azodicarbonamide and 0.5 parts by weight of crosslinking agent dicumylperoxide were subjected to chemical crosslinking to obtain a solid in an extruder at a temperature of 90-135 ° C. After molding into a sheet (solid sheet) using a special foam oven was foamed at a foaming temperature of 150 ~ 270 ℃ to prepare a sheet foam for a shoe insole having a thickness of 5㎜.

Example 3

Solid sheet formed by molding 80 parts by weight of low density polyethylene (LDPE), 20 parts by weight of ethylene vinyl acetate (EVA), 22 parts by weight of blowing agent azodicarbonamide and 0.2 parts by weight of crosslinking agent dicumyl peroxide in an extruder at a temperature of 90 to 135 ° C. ) Was irradiated with an electron beam of 3 ~ 10Mrad and foamed in a special foam oven (foaming temperature 150 ~ 270 ℃) to prepare a sheet foam for the cover of the shoe 10 mm thick.

Comparative Example 1

100 parts by weight of ethylene vinyl acetate (EVA), 6 parts by weight of azodicarbonamide, and 0.8 parts by weight of dicumyl peroxide were chemically crosslinked and blended in an extruder at a temperature of 90 to 110 ° C. Using to expand the foam temperature to 140 ~ 180 ℃ to prepare a flank (plank) foam.

The foam compositions prepared according to Examples 1 to 3 and Comparative Example 1 were molded into shoe insoles, and then physical properties thereof were measured and shown in Table 1 below.

Compounding ratio (part by weight) Example 1 Example 2 Example 3 Comparative example L D P E 40 60 80 － E V A 60 40 20 100 Foaming Agent (Azodicarbonamide) 6 6 22 6 Crosslinking Agent (Dicumyl Peroxide) 0.6 0.6 0.2 0.8 Electron beam dosage － － 3 ~ 10Mrad － Properties Specific gravity (g / cm 3) 0.128 0.121 0.028 0.136 ShoreC 44 46 18 42 Tensile Strength (㎏ / ㎠) 9.8 7.0 6.6 6.4 % Elongation 400 325 275 255 Rupture Tear Strength (㎏ / ㎝) 2.8 2.6 2.0 1.8 Permanent Compression Rate (%) 60.5 62.8 70 68.2

When the foaming composition for footwear of the present invention is compared with Comparative Example 1 as shown in Table 1, the specific physical properties, hardness, tensile strength, elongation, tear tear strength, and permanent compression ratio, which are important physical properties as foaming composition for footwear, are very excellent. In addition, it is economical and light in weight due to its easy continuous processing, and has excellent mechanical properties and resilience, so it can be used in various insoles, midsoles, front, rear, side skins, reinforcements, linings, etc. Can be.

Claims (6)

Melting Point 60 ~ 120 Consisting of 30 ~ 90 parts by weight of low density polyethylene (LDPE), 10 ~ 70 parts by weight of ethylene vinyl acetate (EVA) containing 3 ~ 25 parts by weight of vinyl acetate (VA Content) A crosslinked foamed polyolefin composition for footwear having physical properties of ℃, density of 0.9 to 1.0 g / cm 3 and melt index of 0.3 to 20 g / 10 min. The crosslinked foamed polyolefin composition for shoes according to claim 1, wherein 0.2 to 2 parts by weight of the crosslinking agent is further mixed. The method of claim 1, wherein the blowing agent is azodicarbonamide (ADPA), dinitroxo penta-methyl tetra-amine (DPT), azobisisobutylnitrile (azobisiso-butyl nitrile, ABBN) and p-toluenesulfonylhydrazid (p-tolune sulfonyl hydrazid, TSH) is one kind selected from the group consisting of shoes, cross-linked foamed polyolefin composition for shoes. The method of claim 2, wherein the crosslinking agent is dicumyl peroxide (DCP) cross-linked foam polyolefin shoe insole composition for shoes, characterized in that. The method according to any one of claims 1 to 2, The crosslinked foamed polyolefin composition for shoes is crosslinked foamed polyolefin composition for shoes, characterized in that used as a shoe insole. The method according to any one of claims 1 to 2, The crosslinked foamed polyolefin composition for shoes is crosslinked foamed polyolefin composition for shoes, characterized in that used as a shoe scalp.