US-12617916-B2 - Manufacturing method of foam sheet for shoes with TPU powder and recycled PU scrap powder

Abstract

The present invention relates to a manufacturing method for a foam sheet for shoes containing Thermoplastic polyurethane (TPU) powder and recycled Polyurethane (PU) scrap powder, the foam sheet manufactured by the method thereof, and the foam sheet produced an eco-friendly polyurethane foam composition by water foam, where the method includes firstly the recycled PU scrap powder is mixed with polyol, and then the processing speed in a process is controlled through a side-feeder to react while adding the TPU powder and recycled PU scrap powder secondarily, thereby preventing a rise in viscosity of the raw material, so that even if a larger amount of recycled materials is used than before, it is possible to form foam sheets for shoes, such as shoe insoles or foam packages for shoe uppers, with the same level of product quality as conventional products.

Inventors

• Heedae Park

Assignees

• SAM BU FINE CHEMICAL CO., LTD.

Dates

Publication Date

20260505

Application Date

20241113

Priority Date

20230323

Claims (4)

1. 1 . A foam sheet for shoes comprising: a polyurethane (PU) foam sheet bonded to a fabric, wherein the PU foam sheet has a thickness and a face surface formed by cutting, and the PU foam sheet comprises: a cured PU foam composition comprising the reaction product of a polyol, an isocyanate, a chain extender and 0.1 to 2 wt % of water as a foaming agent, based on the total weight of the PU foam composition, 20 to 50 wt % recycled PU scrap powder having an average particle size of 50 to 300 μm, and 5 to 30 wt % un-foamed thermoplastic polyurethane (TPU) powder, wherein the recycled PU scrap powder and the un-foamed TPU powder are dispersed in the cured PU foam composition, wherein the PU foam sheet bonded to the fabric has a predetermined shape of a product formed by cutting.
2. 2 . The foam sheet for shoes containing TPU powder and recycled PU scrap powder of claim 1 , wherein the un-foamed TPU powder is used anyone selected from the group consisting of virgin TPU with an average particle size of 50 to 300 μm and recycled TPU with an average particle size of 50 to 300 μm or a combination thereof.
3. 3 . The foam sheet for shoes containing TPU powder and recycled PU scrap powder of claim 1 , wherein an adhesive agent used for bonding the polyurethane foam sheet with the fabric is a liquid adhesive or hot melt film made of one resin composition selected from the group consisting of thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA).
4. 4 . The foam sheet for shoes containing TPU powder and recycled PU scrap powder of claim 1 , wherein the predetermined shape of the product corresponds to a foam package for a shoe upper or a shoe insole.

Description

CROSS-REFERENCES TO RELATED APPLICATION The present application is a divisional application of U.S. application Ser. No. 18/616,061 filed Mar. 25, 2024, which claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2023-0037864 filed on Mar. 23, 2023, and Korean Patent Application No. 10-2023-0112717 filed on Aug. 28, 2023, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by references in their entireties. TECHNICAL FIELD The present invention relates to a method for the manufacture of a foam sheet for shoes containing TPU powder and recycled PU scrap powder, and more specifically, for an eco-friendly polyurethane foam composition by water foam, recycled PU scrap powder is mixed with polyol, and then TPU powder and recycled PU scrap powder are added through a side-feeder, so that even if a larger amount of recycled material is used than conventionally, the quality of the shoe foam sheet products such as shoe insoles or foam packages for shoe uppers is good, It relates to the manufacturing method of foam sheet for shoes containing TPU powder and recycled PU scrap powder, which can reduce the molding time in the process of processing by heat press by half due to the addition of the TPU powder. BACKGROUND OF THE INVENTION In general, various types of shoes such as shoes, sneakers, and hiking boots may include an upper leather that forms the exterior of the shoe, an outsole that contacts the ground, a midsole that is installed on the upper side of the outsole, and an insole that contacts a sole (Insole, hereinafter referred to as ‘insole’). At this time, the insole is installed on the inner bottom surface of the shoes to mitigate the impact force applied from the ground to the sole of the foot during walking and is formed to improve comfort and hygiene. Various functions have been added to the shoe insole as described above based on the research result that foot health is a very important factor for the human body. For example, insoles are molded into an ergonomic structure that can effectively absorb shock, or materials to improve sweat absorption, antibacterial and deodorizing functions are being developed. Recently, a technology has been proposed to prevent frostbite in the winter by providing a heating function by embedding a heat wire in a shoe insole. In addition, as materials widely used for the shoe insole, polyurethane (PU), ethylene-vinyl acetate (EVA), polyethylene (PE), latex material, etc. are foam-molded and manufactured in a form of a foam sheet. They are usually bonded to fabrics woven from natural or artificial fibers using adhesives or hot melt films. This bonding process has an advantage of reducing the process time and number of workers compared to the sewing process by applying a liquid adhesive to the adherend and bonding it to the fabric in a state where the solvent or moisture is volatilized through drying. However, in order to maximize cost reduction, instead of using a liquid adhesive, a process of bonding the fabric with a heat press using a thermoplastic hot melt film is widely applied. As described above, it is common to go through a molding process in which the foam sheet combined or bonded with the fabric is processed into a shoe insole shape by a high-temperature heat press. A related art of manufacturing an insole for shoes using the foam sheet as described above, Korea Patent Publication No. 10-2009-0086791, titled “ADHESION-TYPE SHOES CUSHIN USING HIGH DENSITY POLYURETHANE FOAM AND MANUFACTURING METHOD,” an adhesive shoes cushion using high density polyurethane foam, provided is a related art a method for manufacturing an insole for shoes by using the foam sheet, comprising: a cushion layer which is formed by cutting and molding a high density polyurethane foam having a density of 0.8-1.0 g/cm3 into a shape of a shoes cushion by heat-treating the high density polyurethane foam and pressurizing the same with a cooling press in order to prevent slipping of a foot by being attached to the bottom surface of the shoes and to have excellent impact absorption and restoring force; an adhesive layer coated with polyacrylate, natural rubber or synthetic rubber adhesive, and heat-melting adhesive on a surface to which the cushion layer is attached to an object; a release layer protecting the adhesive layer, wherein the cushion layer, an adhesive layer, and the release paper layer are sequentially stacked. In addition, in Korean patent No. 10-1569659, titled “BEAD FOAM COMPRESSION MOLDING METHOD FOR LOW DENSITY PRODUCT,” a method for molding a foamed article, comprising: placing a desired amount of thermoplastic polyurethane foam beads in a compression mold in the shape of an article, wherein the thermoplastic polyurethane foam beads have a density of from about 0.01 to about 0.3 g/cm3; closing the mold; bringing the mold to a peak temperature of from about 130° C. to about 180° C. over a period of from about 300 to about 1500