Preparation method of shoe foam sheet containing regenerated polyurethane waste powder

Abstract

The invention relates to a preparation method of a foam sheet for shoes containing regenerated PU (polyurethane) waste powder, and provides the preparation method of the foam sheet for shoes containing regenerated PU waste powder, which comprises the following steps: for an environment-friendly PU foam composition formed by water foaming, mixing regenerated PU waste powder and polyhydric alcohol for the first time, and then adding the regenerated PU waste powder and the polyhydric alcohol for the second time, so as to obtain the foam sheet for shoes containing regenerated PU waste powder. According to the present invention, the conditions and the processing speed in the process are adjusted by means of a side-feeder, and the regenerated PU waste powder is reacted while being added for the second time, thereby preventing the viscosity of the raw material from increasing, and thus, even if a larger amount (within 60 wt%) of the regenerated material is used compared to the prior art, the viscosity of the raw material can be increased. According to the present invention, a foam sheet for shoes, such as a foam composite for insoles or vamps, having the same quality as the existing level can be formed, and thus the cost of raw materials can be saved and the carbon emission can be significantly reduced.

Description

Technical Field

[0001] The present invention relates to a method for preparing a shoe foam sheet containing recycled polyurethane (PU) waste powder, and more specifically, to a method for preparing a shoe foam sheet containing recycled PU waste powder as follows: for an environmentally friendly polyurethane foam composition formed by water foaming, the recycled PU waste powder is mixed with polyol for the first time, and then the recycled PU waste powder is added for the second time through a side-feeder and reacted simultaneously, so that even if a larger amount of recycled materials than before is used, the quality of shoe foam sheet products such as insoles or foam composites for uppers is good. Background Art

[0002] Generally, various shoes such as leather shoes, sports shoes, and hiking shoes are composed of an upper that forms the appearance of the shoe, an outer sole that contacts the ground, a midsole that is installed on the upper side of the outer sole, and an inner sole that contacts the sole of the foot (hereinafter referred to as "shoe insole"). In this case, the shoe insole is formed to be installed on the inner bottom surface of the shoe to reduce the impact force from the ground acting on the sole of the foot during walking and improve the fit and hygiene.

[0003] Based on the research results that the health of the foot is a very important factor for the human body, various functions are added to the insoles as described above. For example, the insoles are formed into an ergonomic structure that can effectively absorb impact, or materials for improving sweat absorption function, antibacterial function and deodorization function have been developed. Recently, a technology has been proposed that can prevent winter frostbite by providing a heating function by building a heating wire into the insole.

[0004] Furthermore, polyurethane (PU), ethylene-vinyl acetate (EVA), polyethylene (PE), latex, and the like, which are often used as materials for the insoles, are foamed and molded into foam sheets, which are usually bonded to fabrics woven from natural or artificial fibers using adhesives or hot-melt films.

[0005] The advantage of this bonding process is that after the liquid adhesive is applied to the adherend, it is bonded to the fabric in a state where the solvent or water is evaporated by drying. Compared with the sewing process, the process time and the number of operators can be reduced. However, in order to minimize costs, processes that use thermoplastic hot melt films instead of liquid adhesives to bond fabrics are being used more frequently. The foam sheet bonded to the fabric as described above can usually be cut into foam sheet products for shoes such as insoles or foam composites for upper leather, or placed in a mold and formed and cut by a heat press.

[0006] As a prior art for preparing the above-mentioned foam sheet for shoes, Korean Patent Publication No. 10-2009-0086791 (Shin Seungwook) relates to an adhesive leather shoe insole using high-density polyurethane foam, characterized in that it is formed by stacking the following components in order to adhere to the surface of the leather shoe sole to prevent the foot from slipping and have excellent cushioning and restoring force: a cushion layer 10, having a thickness of 0.8 g / cm 3 Up to 1.0 g / cm 3 The high-density polyurethane foam is heat-treated, pressurized by a cold press, and sliced ​​and molded into the shape of an insole; an adhesive layer 20, wherein the surface of the cushion layer 10 attached to the adherend is coated with polyacrylate, natural rubber or synthetic rubber adhesive, or hot-melt adhesive; and a release paper layer 30, which protects the adhesive layer 20.

[0007] In addition, Korean Patent No. 10-1569659 (Nike Innovations Limited Partnership) discloses a method for molding a foamed article, the method comprising the steps of placing a desired amount of thermoplastic polyurethane foam beads in a compression mold having the shape of an article, wherein the thermoplastic polyurethane foam beads have a particle size of 0.01 g / cm 3 Up to 0.3 g / cm 3 density; closing the mold; bringing the mold to a peak temperature of between 130°C and 180°C for a period of time between 300 seconds and 1500 seconds; within 30 seconds after reaching the peak temperature, cooling the mold to a temperature of 5°C to 80°C for a period of time between 300 seconds and 1500 seconds; and removing the article.

[0008] In addition, Korean Patent No. 10-2096984 (BASF SE) relates to a combination foam comprising a matrix composed of polyurethane foam and thermoplastic polyurethane foam particles contained in the matrix, wherein the matrix and the particles are each composed of a polyol component and a polyisocyanate component, wherein at least 50% by weight of the basic building blocks of the polyol component used to form the matrix and the particles are the same, and at least 50% by weight of the basic building blocks of the polyisocyanate component used to form the matrix and the particles are the same, whereby the matrix is ​​completely open-celled and at least a portion of the foamed particles in the matrix are closed-celled.

[0009] Furthermore, according to Korean Patent No. 10-2131606 developed by the inventors, a point-bonded insole using an adhesive resin containing hydrophobic nano-silica and a preparation method thereof, nano-silica containing a hydrophobic functional group is included in the adhesive resin to improve dispersibility in the adhesive resin, enhance water resistance and increase tensile strength. In addition, the adhesive resin is transferred to any surface of foam and fabric using a transfer roller formed in a mesh-type intaglio dot pattern in the shape of the insole and molded to prevent overflow, thereby not only having excellent bonding performance, but also having the following effects even if the adhesive resin is coated with a thinner thickness (10 μm to 40 μm): ensuring more uniform bonding strength and excellent durability than existing products, and reducing product weight and material costs while presenting a soft touch.

[0010] In the patent No. 10-2131606, by removing the adhesive resin in the area other than the gravure dot pattern from the adhesive resin applied to the surface of the transfer roller, and transferring the adhesive resin applied to the surface of the transfer roller in which the gravure dot pattern is formed in a mesh-type within the shape of the insole to any surface of the foam and the fabric and pressurizing it, 35% to 40% of waste generated after cutting out the shape of the insole is easily separated into the respective foams and fabrics and recycled, thereby having the advantages of being environmentally friendly and being able to achieve cost reduction.

[0011] In addition, in the past, polyurethane foam compositions containing a large amount of recycled materials were prepared using adhesives, which caused problems such as lumps in the product and reduced elasticity due to the solidified adhesive inside the foam sheet. However, in the present invention, for an environmentally friendly polyurethane foam composition formed by water foaming, recycled polyurethane PU waste powder and polyol are mixed for the first time, and then the recycled PU waste powder is added for the second time through a side-feeder and reacted simultaneously. Therefore, a method for preparing a shoe foam sheet is developed in which the quality of shoe foam sheet products such as insoles or foam composites for uppers is good even if more recycled materials are used than before.

[0012] [Prior art literature] [Patent Literature] (Patent Document 1) Korean Patent Publication No. 10-2009-0086791 (Publication Date: August 14, 2009) (Patent Document 2) Korean Patent Gazette No. 10-1569659 (Published on November 16, 2015) (Patent Document 3) Korean Patent Gazette No. 10-2096984 (Published on April 3, 2020) (Patent Document 4) Korean Patent Gazette No. 10-2131606 (Published on July 8, 2020) Summary of the invention

[0013] The purpose of the present invention for solving the above-mentioned problems is to provide a method for preparing a foam sheet for shoes containing recycled PU waste powder. For an environmentally friendly polyurethane (PU: Polyurethane) foam composition formed by water foaming, after the recycled PU waste powder and polyol are mixed for the first time, the process conditions and processing speed are adjusted by a side feeder, and the recycled PU waste powder is reacted while being added for the second time, thereby preventing the viscosity of the raw materials from increasing. According to this, even if a larger amount of recycled materials (within 60 weight %) than before is used, a foam sheet for shoes such as an insole or a foam composite for a shoe upper with the same product quality as the existing level can be formed, thereby saving raw material costs and significantly reducing carbon emissions.

[0014] The method for preparing a shoe foam sheet containing recycled PU waste powder according to the present invention is characterized in that, in the process of using polyol, isocyanate, chain extender and The invention discloses a method for preparing a foam sheet for shoes from a polyurethane foam composition comprising a polyol (polyol extender) and water (water) as a foaming agent in a ratio of 0.1 wt % to 2 wt %, comprising the following steps: preparing the polyurethane foam composition (S100), mixing recycled PU waste powder in a ratio of 10 wt % to 20 wt % relative to the polyol, based on the total weight of the polyurethane foam composition; preparing a polyurethane unit foam (S200), adding recycled PU waste powder in a ratio of 10 wt % to 40 wt % based on the total weight of the polyurethane foam composition through a side-feeder and then reacting the powder; forming a polyurethane foam sheet (S300), cutting the polyurethane unit foam into a desired thickness; bonding the polyurethane foam sheet cut into the desired thickness and a fabric (S400); cutting the polyurethane foam sheet bonded to the fabric into a product of a specific shape, or putting the polyurethane foam sheet bonded to the fabric into a mold, forming the product by a heat press and cutting the product into a specific shape (S500).

[0015] According to a preferred embodiment of the present invention, it is characterized in that the recycled PU waste powder is crushed into an average particle size of 50 μm to 300 μm, the adhesive used in the step (S400) of bonding the polyurethane foam sheet to the fabric is a liquid adhesive or a hot-melt film composed of any one resin composition selected from thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA), and the product of the specific shape is any one of a foam composite for an insole or an upper.

[0016] According to the preparation method of the shoe foam sheet containing TPU powder and recycled PU waste powder of the present invention, for the environmentally friendly polyurethane (PU: Polyurethane) foam composition formed by water foaming, the recycled PU waste powder is mixed with polyol for the first time, and then the processing speed in the process is appropriately adjusted by a side feeder, and the recycled PU waste powder is reacted while being added for the second time, thereby preventing the viscosity of the raw materials from increasing. Therefore, even if a larger amount of recycled materials (within 60 weight %) than before is used, a shoe foam sheet such as a foam composite for insole or upper with the same product quality as the existing level can be formed, thereby having the effect of saving raw material costs and significantly reducing carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 11 is a process flow chart showing a method for preparing a foam sheet for shoes according to the present invention. DETAILED DESCRIPTION

[0018] Hereinafter, the preparation method of the shoe foam sheet containing recycled PU waste powder of the present invention is described with reference to the accompanying drawings. This is intended to illustrate the extent to which ordinary technicians in the technical field to which the present invention belongs can easily implement the present invention, and is not meant to limit the technical concept and scope of the present invention.

[0019] Generally, polyurethane resin is a resin generated based on the urethane bond generated by the reaction of isocyanate group (-NCO) and hydroxyl group (-OH) in the polymer. Its raw materials include polyol, isocyanate, chain extender, etc. By adjusting the ratio of soft segment and hard segment constituting polyurethane, a variety of molecular designs can be achieved, ranging from elastic products such as rubber to hard products such as plastic.

[0020] Since this polyurethane resin is characterized by excellent film strength and adhesive strength, a thinner coating can be prepared, and since the coating has sufficient elasticity, it can be prepared into a porous film or sheet with a soft touch, thereby imparting moisture permeability and air permeability while having excellent cold resistance. Since it is processed without using a plasticizer, there are fewer workability problems caused by plasticizers.

[0021] In addition, the polyol is an active hydrogen compound used to react with isocyanate to prepare polyurethane, and refers to a substance having two or more active hydrogen groups such as hydroxyl groups, carboxyl groups, and amine groups in the molecule. Various types are used according to the molecular structure, molecular weight, functionality, and OH value, which directly affects the physical properties of polyurethane.

[0022] For example, compared with polyurethane using polyether polyol, polyurethane using polyester polyol has higher tensile strength, hardness and elongation, excellent flame retardancy, and excellent chemical resistance, drug resistance, strong oxidation resistance, and excellent adhesion to various fabrics woven from polyester fiber or nylon, etc. On the contrary, unlike polyether polyol, it has hydrolysis properties, so it has a disadvantage of weak water resistance. However, since polyurethane using polyether polyol has excellent elasticity, can be used even in high temperature and high humidity environments, and shows excellent durability against acids and alkalis, it is preferred to use them alone or in combination according to the application.

[0023] In the preparation of the polyurethane (PU) resin, if a polyether prepared by polymerization of ethylene oxide and a diisocyanate are mixed, polyurethane is generated. Polyurethane is a mixed ester amine-ester generated when an alcohol group reacts with an isocyanate. If a triol is used instead of a diol, cross-coupling occurs to generate a thermosetting polyurethane.

[0024] Accordingly, the present invention utilizes a polyurethane foam composition composed of polyol, isocyanate, chain extender as raw materials and water as a foaming agent in a ratio of 0.1 wt % to 2 wt % to prepare a shoe foam sheet, characterized in that the polyurethane foam composition contains recycled PU waste powder with an average particle size of 50 μm to 300 μm in a ratio of 20 wt % to 60 wt % based on the total weight of the polyurethane foam composition.

[0025] In the present invention, based on the total weight of the polyurethane foam composition, water is included as a foaming agent in a range of 0.1 wt % to 2 wt %, thereby preparing a polyurethane foam composition having a hardness (ASKERC-Type) of 8 to 40 and a density of 0.05 g / cm 3 Up to 0.35 g / cm 3 In the foam sheet for shoes within the scope of the present invention (for example, insoles, foam composites for uppers, etc.), water as a blowing agent can be mixed with the polyol component in advance, or mixed with the polyol component at the same time as being mixed with the isocyanate component later.

[0026] Taking into account operability and environmental protection, the foaming agent contains a predetermined amount of water as a low-carbon source, so that a polyurethane foam molded body of a desired density can be prepared while minimizing carbon emissions (water reacts with isocyanate compounds to produce carbon dioxide gas). As a foaming agent currently widely used, the present invention uses carbon dioxide, fluorocarbons such as chlorofluorocarbons, hydrocarbons such as pentane and cyclopentane, fluorinated hydrocarbons or a gas pressure loading device to pre-disperse air or nitrogen into the polyol component. The method is not only poor in operability, but also considered the environmental hazards of carbon emissions and high energy costs, etc., and therefore has been determined to be undesirable through research.

[0027] The recycled PU waste used in the present invention, for example, comes from the preparation method of point-bonded insoles using an adhesive resin containing hydrophobic nano-silica in Patent No. 10-2131606 developed by the inventor. Of course, the 35% to 40% waste generated after the insole shape in the composite package bonded with foam 10 and fabric 30 is cut out can be easily separated into respective foams and fabrics and recycled.

[0028] As described above, the PU waste separated from the fabric is subjected to the pulverization process in each step, and the recycled PU waste powder pulverized into an average particle size of 50 μm to 300 μm is mixed into the raw material (polyol) so that it is evenly mixed with the raw material. Due to its good moldability and elasticity, it is conducive to stably ensuring the quality of the product.

[0029] The particle size or content of the recycled PU waste powder can be adjusted within a specific range according to the required hardness and density of the molded body. When the average particle size is less than 50 μm, the miscibility with the polyurethane foam composition deteriorates, and when the average particle size is greater than 300 μm, the dispersibility deteriorates, so the defective rate of the product prepared after molding may increase.

[0030] Accordingly, the present invention, for an environmentally friendly polyurethane (PU) foam composition formed by water foaming, after the recycled PU waste powder and polyol are mixed for the first time, the process conditions and processing speed are adjusted by a side-feeder, and the recycled PU waste powder is added for the second time while being reacted, thereby preventing the viscosity of the raw materials from increasing. Even if a larger amount of recycled materials than before is used, a shoe foam sheet such as an insole or a foam composite for a shoe upper with the same product quality as the existing level can be formed.

[0031] like Figure 1 As shown, according to the method for preparing a shoe foam sheet containing recycled PU waste powder of the present invention, the polyol (Polyol), isocyanate (Isocyanate), chain extender (Chain The invention discloses a method for preparing a foam sheet for shoes from a polyurethane foam composition comprising a polyol (polyol extender) and water (water) as a foaming agent in a ratio of 0.1 wt % to 2 wt %, comprising the following steps: preparing the polyurethane foam composition (S100), mixing recycled PU waste powder in a ratio of 10 wt % to 20 wt % relative to the polyol, based on the total weight of the polyurethane foam composition; preparing a polyurethane unit foam (S200), adding recycled PU waste powder in a ratio of 10 wt % to 40 wt % based on the total weight of the polyurethane foam composition through a side-feeder and then reacting the powder; forming a polyurethane foam sheet (S300), cutting the polyurethane unit foam into a desired thickness; bonding the polyurethane foam sheet cut into the desired thickness and a fabric (S400); cutting the polyurethane foam sheet bonded to the fabric into a product of a specific shape, or putting the polyurethane foam sheet bonded to the fabric into a mold, forming the polyurethane foam sheet by a heat press and cutting the product into a specific shape (S500).

[0032] First, in the step (S100) of preparing the polyurethane foam composition, the polyol in the raw materials consisting of polyol, isocyanate, chain extender and water as a foaming agent in a ratio of 0.1 wt % to 2 wt % is first mixed at a ratio of 10 wt % to 20 wt % based on the total weight of the polyurethane foam composition. However, when the recycled PU waste powder exceeds 20 wt %, the viscosity of the raw materials increases, making it difficult to perform kneading for the subsequent foam reaction, thereby causing poor reactivity.

[0033] For the reasons described above, in the past, the content of recycled PU waste powder mixed in the polyurethane foam composition was limited to 20% by weight, which was considered to be the usual limit value of recycled waste. However, in the present invention, a separate side feeder capable of secondary feeding of the recycled PU waste powder is provided to easily adjust the reaction rate according to the raw material ratio, thereby ensuring a process technology that can contain up to 60% by weight of recycled PU waste powder based on the total weight of the polyurethane foam composition.

[0034] Accordingly, in the present invention, by adjusting the process conditions and processing speed by a side feeder provided in the step (S200) of preparing the polyurethane unit foam, and adding recycled PU waste powder at a ratio of 10 wt % to 40 wt % based on the total weight of the polyurethane foam composition, the viscosity of the raw materials is prevented from increasing, thereby confirming the fact that even if more recycled materials than before are used, a foam sheet for shoes such as insoles or foam composites for uppers with the same product quality as the existing level can be formed.

[0035] Since the polyurethane unit foam formed as described above is cut into a desired thickness within a range of 1 mm to 10 mm (usually 2 mm, 4 mm, 5 mm, 6 mm, etc.) to form a polyurethane foam sheet (S300) and the polyurethane foam sheet cut into the desired thickness and the fabric are bonded (S400), the adhesive used in the step (S300) of bonding the polyurethane foam sheet and the fabric is most preferably a liquid adhesive or a hot melt film formed by any one resin composition selected from thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA) having excellent compatibility with the polyurethane foam sheet.

[0036] Since the adhesive formed by the thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA) does not use solvents, it is not only environmentally friendly, but also has good operability and productivity and soft material properties, which is conducive to ensuring adhesion to various fabrics. In particular, it can ensure excellent durability by maintaining strong adhesion to the polyurethane foam sheet for a long time.

[0037] Next, the polyurethane foam sheet bonded to the fabric is cut into a product of a specific shape, or is placed in a mold, formed by a heat press, and cut into a product of a specific shape (S500) to prepare a foam sheet for shoes. At this time, when the polyurethane foam sheet bonded to the fabric is placed in a mold and formed by a heat press, the temperature is 150°C to 200°C and the pressure is 40 kgf / cm 2 Up to 60 kgf / cm 2 When using a heat press to form the insole, it usually takes about 100 seconds more to form the insole and about 40 seconds more to form the upper foam composite.

[0038] The core feature of the five steps (S100), (S200), (S300), (S400), and (S500) described above is that, based on the total weight of the polyurethane foam composition, the recycled PU waste powder with an average particle size of 50 μm to 300 μm is mixed with polyol for the first time, and then the processing speed in the process is adjusted by a side feeder, and the recycled PU waste powder is added for the second time while being reacted, thereby preventing the viscosity of the raw materials from increasing. Even if more recycled materials are used than before, the moldability will not decrease, and the quality of the product, such as insoles or foam composites for shoe uppers, can be formed. Therefore, by recycling the PU foam waste generated in large quantities during the preparation of insoles, etc., environmental protection and cost reduction can be achieved.

[0039] The recycled PU waste powder not only has excellent chemical miscibility with the polyurethane foam composition of the same polymer resin, but also has excellent moldability using a heat press as it is dispersed into a particle size with the most suitable kneading property. When the average particle size is less than 50 μm, the kneading property with the polyurethane foam composition deteriorates, and when the average particle size exceeds 300 μm, the dispersibility deteriorates, so the quality (moldability, elasticity) of the product prepared after molding may be reduced. In addition, for the same reason as mentioned above, the maximum particle size contained in the particles of the recycled PU waste powder is preferably not more than 500 μm.

[0040] Hereinafter, the method for preparing the shoe foam sheet containing recycled PU waste powder according to the present invention will be specifically described, and the present invention will be explained through preferred embodiments that can be easily implemented by ordinary technicians in the technical field to which the present invention belongs.

[0041] [Example 1] Preparation of insoles The insole prepared according to the present invention is prepared by polymerizing a polyurethane foam composition composed of polyol, isocyanate, chain extender as raw materials and water as a foaming agent, and the preparation method consists of the following five steps.

[0042] The first step: based on the total weight of the polyurethane foam composition containing polyol as raw materials, isocyanate and water as a foaming agent in a range of 0.1 wt % to 2 wt %, a polyurethane foam composition is prepared by mixing recycled PU waste powder with an average particle size of 150 μm in a ratio of 10 wt % to 20 wt % with respect to the polyol.

[0043] The second step: adding recycled PU waste powder having an average particle size of 150 μm at a ratio of 10 wt % to 40 wt % based on the total weight of the polyurethane foam composition through a side-feeder and reacting the powder to prepare a polyurethane cell foam.

[0044] The third step: cutting the polyurethane unit foam into a thickness of 4 mm to form a polyurethane foam sheet.

[0045] Step 4: The polyurethane foam sheet cut into a thickness of 4 mm and the polyester fiber fabric were bonded using a thermoplastic polyurethane (TPU) hot melt film.

[0046] The fifth step is to cut the polyurethane foam sheet bonded with the fabric into products of a specific shape, thereby preparing an insole.

[0047] When preparing an insole as described in Example 1, the average value of the results of several evaluations of the moldability and appearance of the polyurethane foam sheet bonded to the fabric processed into the shape of an insole in the fifth step by a heat press is shown in [Table 1] according to the ratio of the recycled PU waste powder contained in the polyurethane foam composition in the first step and the second step.

[0048]

Table 1

[0049] The first step: based on the total weight of the polyurethane foam composition containing polyol as raw materials, isocyanate and water as a foaming agent in a range of 0.1 wt % to 2 wt %, a polyurethane foam composition is prepared by mixing recycled PU waste powder with an average particle size of 150 μm in a ratio of 10 wt % to 20 wt % with respect to the polyol.

[0050] The second step: adding recycled PU waste powder having an average particle size of 150 μm at a ratio of 10 wt % to 40 wt % based on the total weight of the polyurethane foam composition through a side-feeder and reacting the powder to prepare a polyurethane cell foam.

[0051] The third step: cutting the polyurethane unit foam into a thickness of 2 mm to form a polyurethane foam sheet.

[0052] Step 4: The polyurethane foam sheet cut into a thickness of 2 mm and the PU film fabric are bonded using a thermoplastic polyurethane (TPU) hot melt film.

[0053] The fifth step is to cut the polyurethane foam sheet bonded with the fabric into products of a specific shape, thereby preparing a foam composite part for a shoe upper.

[0054] When preparing a foam composite for a shoe upper as in Example 2, the average value of the results of several evaluations of the moldability and appearance of the polyurethane foam sheet bonded to the fabric into the shape of a foam composite for a shoe upper by a heat press is shown in [Table 2] according to the proportion of recycled PU waste powder contained in the polyurethane foam composition in the first step and the second step.

[0055]

Table 2

[0056] As described above, the present invention has confirmed the following effect: in a polyurethane foam composition, after the recycled PU waste powder of a predetermined particle size is mixed with polyol for the first time, the process conditions and the processing amount are adjusted by a side-feeder, and the recycled PU waste powder is added for the second time and reacted, thereby preventing the viscosity of the raw materials from increasing. Therefore, even if more recycled materials are used than before, a shoe foam sheet such as an insole or a foam composite for a shoe upper can be formed with the same product quality as the existing level.

[0057] [Experimental example] In order to confirm the exemplary properties of the polyurethane foam composition according to the present invention, within the range of hardness and density required by the present invention, as shown in Examples 1-5 and 2-5, under the same conditions as the existing hot press (temperature of 150° C. to 200° C., pressure of 40 kgf / cm 2 Up to 60 kgf / cm 2 ) prepared two types of polyurethane foam sheets (foam composites for insoles and uppers) containing 50% by weight of recycled PU waste powder with an average particle size of about 150 μm. The results of several tests on their physical properties are shown in [Table 3] below.

[0058]

Table 3

[0059] Therefore, the shoe foam sheet containing recycled PU waste powder prepared by the present invention can be replaced, deformed and changed in various forms without departing from the technical idea of ​​the present invention. It is particularly environmentally friendly, has good productivity and can reduce preparation costs. Therefore, it can not only be used for various insoles and foam composites for uppers (decorations) that require uniform formability and durability, but also can be used for various uses that require functions such as molding materials, cushioning materials, and filling materials for internal use in clothing, bags, sporting goods or daily necessities, industrial products, etc. made of fiber or natural leather and synthetic leather, plastic, etc.

Claims

1. A method for preparing a shoe foam sheet containing recycled PU waste powder, characterized in that: In preparing a foam sheet for shoes using a polyurethane foam composition composed of polyol, isocyanate, chain extender as raw materials and water as a foaming agent in a ratio of 0.1 wt % to 2 wt %, the method comprises the following steps: preparing a polyurethane foam composition (S100), mixing recycled PU waste powder in a ratio of 10 wt % to 20 wt % relative to the polyol, based on the total weight of the polyurethane foam composition; preparing a polyurethane unit foam (S200), for which recycled PU waste powder is added at a ratio of 10 wt % to 40 wt % based on the total weight of the polyurethane foam composition through a side feeder and then reacted; forming a polyurethane foam sheet (S300), cutting the polyurethane unit foam into a desired thickness; Bonding the polyurethane foam sheet and the fabric cut to the desired thickness (S400); The polyurethane foam sheet bonded to the fabric is cut into products of a specific shape, or is put into a mold, formed by a hot press, and cut into products of a specific shape (S500).

2. The method for preparing a shoe foam sheet containing recycled PU waste powder according to claim 1, characterized in that: The recycled PU waste powder is crushed into a size with an average particle size of 50 μm to 300 μm.

3. The method for preparing a shoe foam sheet containing recycled PU waste powder according to claim 1, characterized in that: The adhesive used in the step of bonding the polyurethane foam sheet to the fabric ( S400 ) is a liquid adhesive or a hot melt film consisting of any one resin composition selected from thermoplastic polyurethane and ethylene vinyl acetate.

4. The method for preparing a shoe foam sheet containing recycled PU waste powder according to claim 1, characterized in that: The product of the specific shape is any one of a shoe insole and a foam composite part for a shoe upper.

5. A shoe foam sheet containing recycled PU waste powder, characterized in that: The method is formed by the preparation method according to any one of claims 1 to 4.

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