Manufacturing method for foam sheet for shoe containing recycled PU scrap powder

Abstract

The present invention relates to a manufacturing method for a foam sheet for a shoe, the foam sheet containing recycled polyurethane (PU) scrap powder. The present invention provides a method for manufacturing a foam sheet for a shoe, the foam sheet containing recycled PU scrap powder, in which with respect to an eco-friendly polyurethane (PU) foam composition made of water foam, by first mixing recycled PU scrap powder with polyol and then reacting by secondly adding recycled PU scrap powder by controlling the process conditions and processing speed through a side feeder, the viscosity of raw materials can be prevented from increasing, and accordingly, by forming a foam sheet for a shoe, such as a foam package for shoe insoles or shoe uppers, having product quality equivalent to that of existing products even when using a larger amount (60 wt% or less) of recycled materials than is conventional, raw material costs can be reduced and carbon emissions can be drastically reduced.

Description

Method for manufacturing a shoe foam sheet containing recycled PU scrap powder

[0001] The present invention relates to a method for manufacturing a shoe foam sheet containing recycled PU scrap powder, and more particularly, to a method for manufacturing a shoe foam sheet containing recycled PU scrap powder, which comprises first mixing recycled PU scrap powder with polyol in an eco-friendly polyurethane foam composition made of water-blown foam and then secondarily adding recycled PU scrap powder through a side-feeder while reacting, thereby enabling the quality of shoe foam sheet products, such as shoe insoles or shoe upper foam packages, to be good even when a larger amount of recycled material is used than in the past.

[0002]

[0003] Typically, shoes, sneakers, hiking boots, and other footwear are made up of an upper leather that forms the exterior of the shoe, an outsole that comes into contact with the ground, a midsole that is installed on top of the outsole, and an insole (hereinafter referred to as "insole") that comes into contact with the sole of the foot. The insole is installed on the inner bottom of the shoe to cushion the impact force exerted from the ground to the sole of the foot during walking and to enhance comfort and hygiene.

[0004] Insoles, such as the above, are being equipped with various functions based on research findings showing that the health of the insole is a crucial factor in the human body. For example, insoles are being molded with ergonomic structures that effectively absorb shock, and materials are being developed to enhance sweat absorption, antibacterial properties, and deodorizing functions. Recently, technology has been proposed that incorporates heating wires into shoe insoles to provide warmth and prevent frostbite in winter.

[0005] And the materials widely used for the shoe insoles are polyurethane (PU), ethylene-vinyl acetate (EVA), polyethylene (PE), latex, etc., which are manufactured in the form of foam sheets by foam molding, and these are usually bonded to a fabric woven from natural or artificial fibers using an adhesive or hot melt film.

[0006] This bonding process has the advantage of reducing process time and manpower compared to the sewing process by applying a liquid adhesive to the adherend and then bonding it to the fabric after drying to evaporate the solvent or moisture. However, in order to maximize cost reduction, a process that bonds the fabric using a thermoplastic hot melt film instead of a liquid adhesive is widely applied. The foam sheet that is combined with the fabric as described above is typically cut into shoe foam sheet products such as shoe insoles or shoe upper foam packages, or is molded and cut using a heat press in a mold.

[0007] As a prior art for manufacturing a shoe foam sheet as described above, Korean Patent Publication No. 10-2009-0086791 (Shin Seung-wook) relates to an adhesive shoe cushion using high-density polyurethane foam, characterized in that the cushion layer (10) is formed by heat-treating high-density polyurethane foam having a density of 0.8 to 1.0 g / cm3 and then pressing it with a cooling press to cut and shape it into the shape of a shoe cushion, in order to prevent the foot from slipping when attached to the sole of the shoe and to have excellent shock absorption and resilience; an adhesive layer (20) having a polyacrylate, natural rubber or synthetic rubber adhesive, or a heat-melting adhesive coated on the surface where the cushion layer (10) is attached to the adherend; and a release layer (30) that protects the adhesive layer (20).

[0008] Also, the same patent No. 10-1569659 (Nike Innovate C.V.) discloses a method for molding a foamed article, comprising the steps of 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 0.01 to 0.3 g / cm3, closing the mold, bringing the mold to a maximum temperature of 130° C. to 180° C. over a period of 300 to 1,500 seconds, cooling the mold to a temperature of 5° C. to 80° C. over a period of 300 to 1,500 seconds immediately after reaching the maximum temperature or within 30 seconds therefrom, and removing the article.

[0009] In addition, the same patent No. 10-2096984 (BASF SE) relates to a combination foam comprising a matrix composed of polyurethane foam and foam particles of thermoplastic polyurethane contained therein, wherein the matrix and the particles are each composed of a polyol component and a polyisocyanate component, and at least 50 wt% of the basic building blocks forming the polyol component of the matrix and the particles are the same, and at least 50 wt% of the basic building blocks forming the polyisocyanate component of the matrix and the particles are the same, whereby the matrix is ​​completely open-celled and the foam particles within the matrix are at least partially closed-celled.

[0010] And according to the dot-laminated shoe insole and the manufacturing method thereof using an adhesive resin containing hydrophobic nano-silica of Korean Patent No. 10-2131606 developed by the present inventor, nano-silica containing a hydrophobic functional group is mixed into the adhesive resin to improve dispersibility within the adhesive resin, reinforce water resistance, and increase tensile strength, and further, the adhesive resin is formed by transferring a mesh-type negative dot pattern formed within the shoe insole shape onto one side of the foam or fabric, thereby preventing an overflow phenomenon and providing excellent adhesive performance. In addition, even when applying an adhesive resin having a thinner thickness (10 to 40 μm), it has the effect of ensuring more uniform adhesive strength and superior durability than conventional products, exhibiting a soft feel, and reducing the weight of the product and material costs.

[0011] The above patent No. 10-2131606 has the advantage of being environmentally friendly and reducing costs by removing adhesive resin other than the negative dot pattern applied to the surface of the transfer roller, and transferring the adhesive resin applied to the surface of the transfer roller, in which the negative dot pattern is formed in a mesh type within the shape of the shoe insole, to one side of foam or fabric and pressing it, thereby allowing about 35 to 40% of the scrap generated after cutting the shape of the shoe insole to be easily separated into each foam and fabric and recycled.

[0012] Meanwhile, in the past, when a polyurethane foam composition containing a large amount of recycled materials was manufactured using a binder, there was a problem that hard parts were generated in the product and elasticity was reduced due to the hardened binder inside the foam sheet. However, in the present invention, a method for manufacturing a shoe foam sheet having good quality, such as a shoe insole or a shoe upper foam package, was developed by first mixing recycled PU scrap powder with polyol in an eco-friendly polyurethane foam composition made of water foam and then secondarily adding recycled PU scrap powder through a side-feeder while reacting, even if a large amount of recycled materials is used compared to the past, for a shoe foam sheet product.

[0013]

[0014] The purpose of the present invention to solve the above problems is to provide a method for manufacturing a shoe foam sheet containing recycled PU scrap powder, which can prevent an increase in the viscosity of raw materials by first mixing recycled PU scrap powder with polyol in an eco-friendly polyurethane (PU) foam composition made of water-blown foam, and then adding recycled PU scrap powder secondarily while controlling the process conditions and processing speed through a side-feeder to react, thereby forming a shoe foam sheet, such as a shoe insole or a shoe upper foam package, with the quality of the product equivalent to that of the existing product even when a larger amount (within 60 wt%) of recycled materials is used than before, thereby reducing the cost of raw materials and drastically reducing carbon emissions.

[0015]

[0016] A method for manufacturing a shoe foam sheet containing PU scrap powder according to the present invention comprises the steps of: manufacturing a shoe foam sheet using a polyurethane foam composition comprising polyol as raw materials, isocyanate, a chain extender, and 0.1 to 2 wt% of water as a blowing agent; comprising the steps of: manufacturing a polyurethane foam composition by mixing 10 to 20 wt% of recycled PU scrap powder with the polyol based on the total weight of the polyurethane foam composition (S100); adding 10 to 40 wt% of recycled PU scrap powder based on the total weight of the polyurethane foam composition to the polyurethane foam composition through a side-feeder and reacting the mixture to manufacture a polyurethane block foam (S200); cutting the polyurethane block foam to a desired thickness to form a polyurethane foam sheet (S300); It is characterized by comprising a step (S400) of combining a polyurethane foam sheet cut to the desired thickness with a fabric; a step (S500) of cutting the polyurethane foam sheet combined with the fabric into a product of a specific shape, or putting it into a mold and forming and cutting it into a product of a specific shape by heat pressing.

[0017] According to a preferred embodiment of the present invention, the recycled PU scrap powder is ground to an average particle size of 50 to 300 μm, and the adhesive used in the step (S400) of bonding the polyurethane foam sheet with the fabric is a liquid adhesive or a hot melt film made of any one resin composition selected from thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA), and the product of the specific shape is characterized in that it is any one of a shoe insole or a shoe upper foam package.

[0018]

[0019] The method for manufacturing a shoe foam sheet containing TPU powder and recycled PU scrap powder according to the present invention comprises the steps of first mixing recycled PU scrap powder with polyol in an eco-friendly polyurethane (PU) foam composition made of water foam, and then adding recycled PU scrap powder secondarily while appropriately controlling the processing speed in the process through a side-feeder to allow the mixture to react, thereby preventing an increase in the viscosity of the raw materials. Accordingly, even if a larger amount (within 60 wt%) of recycled materials is used than in the past, a shoe foam sheet such as a shoe insole or a shoe upper foam package having the same level of product quality as in the past is formed, thereby reducing the cost of raw materials and drastically reducing carbon emissions.

[0020]

[0021] Figure 1 is a process flow diagram showing a method for manufacturing a shoe foam sheet according to the present invention.

[0022]

[0023] Hereinafter, a method for manufacturing a shoe foam sheet containing recycled PU scrap powder of the present invention will be described with reference to the drawings. However, this is intended to be an example to the extent that a person having ordinary knowledge in the technical field to which the present invention pertains can easily carry out the invention, and does not mean that the technical idea and scope of the present invention are limited thereby.

[0024] In general, polyurethane resin is a resin created based on urethane bonds generated by the reaction of isocyanate groups (-NCO) and hydroxyl groups (-OH) in the polymer, and its raw materials include polyol, isocyanate, chain extender, etc. By adjusting the ratio of soft segments and hard segments that make up polyurethane, various molecular designs are possible, from elastic products like rubber to hard products like plastic.

[0025] The characteristics of this polyurethane resin are that it has excellent film strength and adhesive strength, so it can be used to manufacture a thin coating film, and the elasticity of the coating film allows it to be manufactured into a soft-to-the-touch porous film or sheet, so it can provide moisture permeability and ventilation, and it has excellent cold resistance, and because it is processed without using a plasticizer, there are few workability problems caused by the plasticizer.

[0026] In addition, the polyol is an active hydrogen compound used to manufacture polyurethane by reacting with isocyanate, and has two or more active hydrogen groups such as hydroxyl group, carboxyl group, and amine group in the molecule, and by using various types depending on the molecular structure, molecular weight, functionality, and OH-value, it directly affects the physical properties of polyurethane.

[0027] For example, polyurethane using polyester polyol has higher tensile strength, hardness, and elongation than polyurethane using polyether polyol, and has excellent flame retardancy, as well as superior chemical and pharmaceutical resistance, so it is resistant to oxidation and has excellent adhesion to various fabrics woven with polyester or nylon, but unlike polyether polyol, it has the disadvantage of having poor water resistance due to its tendency to hydrolyze. However, polyurethane using polyether polyol has excellent elasticity, can be used in high temperature and humid environments, and shows excellent durability against acids and alkalis, so it is desirable to use them alone or in combination depending on the purpose.

[0028] The above polyurethane (PU) resin is manufactured by mixing polyether, which is made by polymerizing ethylene oxide, with diisocyanate to produce polyurethane. Urethane is a mixed amide-ester produced when an alcohol group reacts with isocyanate. When a triol is used instead of a diol, cross-linking occurs to produce a thermosetting polyurethane.

[0029] Accordingly, the present invention is characterized in that, in manufacturing a shoe foam sheet using a polyurethane foam composition comprising polyol, isocyanate, a chain extender, and 0.1 to 2 wt% of water as raw materials, the composition contains 20 to 60 wt% of recycled PU scrap powder having an average particle size of 50 to 300 μm based on the total weight of the polyurethane foam composition.

[0030] In the present invention, by including water as a foaming agent in a range of 0.1 to 2 wt% based on the total weight of the polyurethane foam composition, a shoe foam sheet (e.g., a shoe insole, a shoe upper foam package, etc.) having a hardness (ASKER C-Type) of 8 to 40 and a density of 0.05 to 0.35 g / cm3 can be manufactured. The water as a foaming agent can be mixed with a polyol component in advance or mixed with an isocyanate component at the same time as mixing with the polyol component.

[0031] The above-mentioned foaming agent can manufacture a polyurethane foam molded body having a desired density while minimizing carbon emissions by including a certain amount of water, a low-carbon source, in consideration of workability and environmental friendliness (water reacts with an isocyanate compound to generate carbon dioxide gas). In the present invention, it has been studied that the method of pre-dispersing air or nitrogen gas into a polyol component using a foaming agent widely used in the past, such as carbon dioxide, fluorocarbons such as chlorofluorocarbons, hydrocarbons such as pentane and cyclopentane, fluorinated hydrocarbons, or an air loading device, not only has poor workability, but is also undesirable in consideration of environmental hazards such as carbon emissions and high energy costs.

[0032] The recycled PU scrap used in the present invention can be easily separated into each foam and fabric and recycled by easily separating the scraps, which amount to about 35 to 40%, generated after cutting the shape of the shoe insole from the package in which the foam and fabric are combined, for example, from the method for manufacturing a dot-laminated shoe insole using an adhesive resin containing hydrophobic nano-silica, as described in Patent No. 10-2131606 developed by the inventor of the present invention.

[0033] As described above, the PU scrap separated from the fabric is subjected to a step-by-step crushing process, and the recycled PU scrap powder is crushed to an average particle size of 50 to 300 μm. This is mixed with the raw material (polyol) to ensure uniform mixing with the raw material, resulting in good formability and elasticity, which is advantageous in stably securing product quality.

[0034] The above recycled PU scrap powder can have its particle size or content adjusted within a specific range depending on the hardness and density of the desired molded body. If the average particle size is less than 50㎛, the mixing property with the polyurethane foam composition deteriorates, and if it exceeds 300㎛, the dispersibility deteriorates, so there is a concern that the defect rate of the product manufactured after molding may increase.

[0035] Accordingly, the present invention prevents an increase in the viscosity of raw materials by mixing recycled PU scrap powder with polyol in the first stage and then adding recycled PU scrap powder in the second stage while controlling the process conditions and processing speed through a side-feeder to an eco-friendly polyurethane (PU) foam composition made of foam foam, thereby forming a shoe foam sheet, such as a shoe insole or a shoe upper foam package, having a product quality equivalent to that of the existing product even when a larger amount of recycled material is used than before.

[0036] As illustrated in FIG. 1, a method for manufacturing a shoe foam sheet containing recycled PU scrap powder according to the present invention comprises the steps of: manufacturing a shoe foam sheet using a polyurethane foam composition comprising polyol as raw materials, isocyanate, a chain extender, and 0.1 to 2 wt% of water as a blowing agent; comprising the steps of: manufacturing a polyurethane foam composition by mixing 10 to 20 wt% of recycled PU scrap powder with the polyol based on the total weight of the polyurethane foam composition (S100); adding 10 to 40 wt% of recycled PU scrap powder based on the total weight of the polyurethane foam composition to the polyurethane foam composition through a side-feeder and reacting the mixture to manufacture a polyurethane block foam (S200); cutting the polyurethane block foam to a desired thickness to form a polyurethane foam sheet (S300); It consists of a step (S400) of combining a polyurethane foam sheet cut to the desired thickness with a fabric; a step (S500) of cutting the polyurethane foam sheet combined with the fabric into a product of a specific shape, or putting it into a mold and forming and cutting it into a product of a specific shape by heat pressing.

[0037] First, in the step (S100) of manufacturing the polyurethane foam composition, the polyol among the raw materials consisting of polyol, isocyanate, chain extender, and 0.1 to 2 wt% of water as a foaming agent is first mixed with 10 to 20 wt% of recycled PU scrap powder based on the total weight of the polyurethane foam composition. If the recycled PU scrap powder exceeds 20 wt%, the viscosity of the raw material increases, making it difficult to mix for a later foam reaction, resulting in poor reactivity.

[0038] For the above reasons, limiting the content of recycled PU scrap powder mixed into a polyurethane foam composition to within 20 wt% has been conventionally recognized as a typical limit for recycling waste, but in the present invention, a separate side-feeder capable of secondary input of the recycled PU scrap powder is provided to easily control the reaction speed according to the mixing of raw materials, thereby securing a process technology that can include the content of recycled PU scrap powder up to a maximum of 60 wt% based on the total weight of the polyurethane foam composition.

[0039] Accordingly, in the present invention, by controlling the process conditions and processing speed through the side-feeder provided in the step (S200) of manufacturing a polyurethane block foam, and adding recycled PU scrap powder at a ratio of 10 to 40 wt% based on the total weight of the polyurethane foam composition, an increase in the viscosity of the raw material is prevented, and it has been confirmed that a shoe foam sheet, such as a shoe insole or a shoe upper foam package, can be formed with the same level of product quality as the existing product despite using a larger amount of recycled material than the existing one.

[0040] The polyurethane block foam formed as described above is cut into a desired thickness of 1 to 10 mm (typically 2, 4, 5, 6 mm) to form a polyurethane foam sheet (S300); and a polyurethane foam sheet cut into the desired thickness is combined with a fabric (S400). In the step of combining the polyurethane foam sheet with the fabric (S300), it is most preferable to use a liquid adhesive or hot melt film made of any one resin composition selected from thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA) having excellent compatibility with the polyurethane foam sheet (PU foam sheet).

[0041] The adhesive made of the above thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA) is not only environmentally friendly because it does not use a solvent, but also has good workability and productivity, and is advantageous in securing adhesive strength with various fabrics due to its flexible material properties, and in particular, it can secure excellent durability by maintaining strong adhesive strength with the polyurethane foam sheet for a long period of time.

[0042] Next, a step (S500) is taken to manufacture a shoe foam sheet by cutting the polyurethane foam sheet combined with the fabric into a product of a specific shape, or by putting it in a mold and molding and cutting it into a product of a specific shape by heat pressing. In this case, when the step of putting the polyurethane foam sheet combined with the fabric in a mold and molding it by heat pressing is taken, when molding it by heat pressing at a temperature of 150 to 200°C and a pressure of 40 to 60 kgf / ㎠, a separate molding time of about 100 seconds is typically required for a shoe insole and about 40 seconds for a shoe upper foam package.

[0043] The most crucial feature of the above 5-step (S100 to S500) process is that recycled PU scrap powder having an average particle size of 50 to 300 μm based on the total weight of the polyurethane foam composition is mixed with polyol in the first stage, and then the processing speed is controlled through a side-feeder to add recycled PU scrap powder in the second stage while reacting, thereby preventing an increase in the viscosity of the raw material, so that even though a larger amount of recycled material is used than before, the moldability is not reduced and the product quality is equivalent to that of the existing one, and a shoe foam sheet such as a shoe insole or a shoe upper foam package can be formed. Therefore, by recycling PU foam scrap generated in large quantities during the manufacturing process of shoe insoles, etc., it is possible to realize environmental friendliness and cost reduction.

[0044] The above-mentioned recycled PU scrap powder has excellent chemical compatibility with a polyurethane foam composition, which is a polymer resin of the same type, and is dispersed in a particle size having the most suitable mixing property, so that the moldability by heat press is very good. However, if the average particle size is less than 50㎛, the mixing property with the polyurethane foam composition deteriorates, and if it exceeds 300㎛, the dispersibility becomes poor, so there is a concern that the quality (moldability, elasticity) of the product manufactured after molding may deteriorate. In addition, for the same reason, it is preferable that the maximum particle size among the particles included in the above-mentioned recycled PU scrap powder does not exceed 500㎛.

[0045]

[0046] Below, a method for manufacturing a shoe foam sheet containing recycled PU scrap powder according to the present invention will be specifically examined, and the present invention will be described through preferred embodiments that can be easily carried out by a person having ordinary knowledge in the technical field to which the present invention pertains.

[0047] [Example 1] Manufacturing of shoe insoles

[0048] The shoe insole manufactured according to the present invention is manufactured by polymerizing a polyurethane foam composition comprising polyol, isocyanate, a chain extender, and water as raw materials, and a foaming agent, in the following five steps.

[0049] ▶ Step 1: A polyurethane foam composition was prepared by mixing 10 to 20 wt% of recycled PU scrap powder having an average particle size of 150 μm with respect to the polyol based on the total weight of the polyurethane foam composition containing polyol, isocyanate, chain extender, and water as a blowing agent in the range of 0.1 to 2 wt% as raw materials.

[0050] ▶ Step 2: 10 to 40 wt% of recycled PU scrap powder having an average particle size of 150 μm based on the total weight of the polyurethane foam composition was added through a side-feeder and then reacted to produce a polyurethane block foam.

[0051] ▶ Step 3: The polyurethane block foam was cut to a thickness of 4 mm to form a polyurethane foam sheet.

[0052] ▶ Step 4: The polyurethane foam sheet cut to a thickness of 4 mm was combined with a polyester fiber fabric using a thermoplastic polyurethane (TPU) hot melt film.

[0053] ▶ Step 5: The polyurethane foam sheet combined with the above fabric was cut into a product of a specific shape to manufacture a shoe insole.

[0054] When manufacturing a shoe insole as in Example 1, the average values ​​of the results of evaluating the formability and appearance of the fabric and polyurethane foam sheet in the fifth step by heat pressing according to the ratio of recycled PU scrap powder included in the polyurethane foam composition in the first and second steps are shown in [Table 1] below.

[0055]

[0056] Classification Example 1-1 Example 1-2 Example 1-3 Example 1-4 Example 1-5 Example 1-6 Comparative Example 1 (Stage 1) PU scrap powder (w%) 10 10 15 15 20 20 30 (Stage 2) PU scrap powder (w%) 10 15 20 25 30 400 Formability and appearance Good Good Good Good Good Good Poor

[0057]

[0058] [Example 2] Manufacturing of foam package for shoe upper

[0059] The shoe upper foam package manufactured according to the present invention is manufactured by polymerizing a polyurethane foam composition comprising polyol, isocyanate, a chain extender, and water as raw materials, and a foaming agent, and is made in the following five steps.

[0060] ▶ Step 1: A polyurethane foam composition was prepared by mixing 10 to 20 wt% of recycled PU scrap powder having an average particle size of 150 μm with respect to the polyol based on the total weight of the polyurethane foam composition containing polyol, isocyanate, chain extender, and water as a blowing agent in the range of 0.1 to 2 wt% as raw materials.

[0061] ▶ Step 2: 10 to 40 wt% of recycled PU scrap powder having an average particle size of 150 μm based on the total weight of the polyurethane foam composition was added through a side-feeder and then reacted to produce a polyurethane block foam.

[0062] ▶ Step 3: The polyurethane block foam was cut to a thickness of 2 mm to form a polyurethane foam sheet.

[0063] ▶ Step 4: The polyurethane foam sheet cut to a thickness of 2 mm was combined with a PU skin film fabric using a thermoplastic polyurethane (TPU) hot melt film.

[0064] ▶ Step 5: The polyurethane foam sheet combined with the above fabric was cut into a product of a specific shape to manufacture a foam package for shoe uppers.

[0065] When manufacturing a shoe upper foam package as in Example 2, the average values ​​of the results of evaluating the formability and appearance of the polyurethane foam sheet combined with the fabric by heat pressing into the shape of the shoe upper foam package according to the ratio of recycled PU scrap powder included in the polyurethane foam composition in the first and second steps are shown in [Table 2] below.

[0066] Classification Example 2-1 Example 2-2 Example 2-3 Example 2-4 Example 2-5 Example 2-6 Comparative Example 2 (Stage 1) PU scrap powder (w%) 10 10 15 15 20 20 30 (Stage 2) PU scrap powder (w%) 10 15 20 25 30 400 Formability and appearance Good Good Good Good Good Good Poor

[0067]

[0068] As shown in the above [Table 1] and [Table 2], the shoe insoles manufactured by Examples 1-1 to 1-6 and the shoe upper foam packages manufactured by Examples 2-1 to 2-6 were found to have excellent qualities such as moldability, adhesion between the fabric and the polyurethane foam sheet, and appearance. As in Comparative Examples 1 and 2, it was confirmed that when the recycled PU scrap powder mixed into the polyurethane foam composition in the first step exceeds 20 wt%, the viscosity of the raw material increases, making subsequent mixing for foam reaction difficult and the reactivity being poor, the density and hardness of the product becoming uneven.

[0069] As described above, the present invention prevents an increase in the viscosity of raw materials by first mixing recycled PU scrap powder of a certain particle size with polyol in a polyurethane foam composition and then adding recycled PU scrap powder secondarily while controlling the process conditions and throughput through a side-feeder to react, thereby confirming that a shoe foam sheet, such as a shoe insole or a shoe upper foam package, having a product quality equivalent to that of a conventional product can be formed even though a larger amount of recycled material is used than in the past.

[0070] [Experimental Example]

[0071] In order to confirm exemplary characteristics of the polyurethane foam composition according to the present invention, two types of polyurethane foam sheets (foam packages for shoe insoles and shoe uppers) containing 50 wt% of recycled PU scrap powder having an average particle size of about 150 ㎛, as in Examples 1-5 and 2-5, within the range of hardness and density required by the present invention were manufactured under the same conditions as the conventional heat press (temperature 150 to 200°C & pressure 40 to 60 kgf / cm2), and the physical properties thereof were tested several times, and the results are shown in [Table 3] below.

[0072] Property UnitShoe InsoleFoam Package for Shoe UpperHardness (ASKER C)-21 / 25 / 28 / 29 / 2719 / 19 / 19 / 20 / 20Densityg / cm30.18 / 0.16 / 0.160.14 / 0.15 / 0.15Tear Strengthkgf / cm2.5 / 2.3 / 2.11.8 / 1.8 / 2.0Tensile Strengthkgf / cm24.6 / 4.6 / 4.83.8 / 3.5 / 3.6Elongation%105 / 109 / 101123 / 110 / 118Shrinkage%0.10 / 0.25 / 0.300.09 / 0.15 / 0.20

[0073]

[0074] - Hardness: ASKER C-type Durometer based on JIS K 7312

[0075] As shown in the above [Table 3], it was confirmed that the shoe foam sheet containing recycled PU scrap powder according to the present invention can be manufactured at a level equivalent to that of a conventional polyurethane foam sheet containing no recycled PU scrap powder in terms of overall physical properties such as tear strength, tensile strength, elongation, and shrinkage by first mixing recycled PU scrap powder with polyol and then secondarily adding recycled PU scrap powder through a side-feeder to cause a reaction, and the polyurethane foam molded body has a hardness (ASKER C-Type) of 8 to 40 and a density of 0.05 to 0.35 g / cm3.

[0076]

[0077] The shoe foam sheet containing recycled PU scrap powder manufactured by the present invention can be substituted, modified and changed in various forms within the scope that does not depart from the technical spirit of the present invention, and in particular, has the advantages of being environmentally friendly and reducing productivity and manufacturing costs, and can be applied to various uses that require functions such as molding materials, cushioning materials and filling materials used in the interior of clothing, bags, sports goods, household goods, industrial goods, etc. made of fibers, natural and synthetic leather, plastics, etc., as well as foam packages for various shoe insoles and shoe uppers (decorations) that require uniform moldability and durability.

[0078]

[0079] [Prior Art Literature]

[0080] (Patent Document 0001) Republic of Korea Patent Publication No. 10-2009-0086791 (Publication Date: August 14, 2009)

[0081] (Patent Document 0002) Republic of Korea Patent Publication No. 10-1569659 (Publication Date: November 16, 2015)

[0082] (Patent Document 0003) Republic of Korea Patent Publication No. 10-2096984 (Publication Date: April 3, 2020)

[0083] (Patent Document 0004) Republic of Korea Patent Publication No. 10-2131606 (Published on July 8, 2020)

Claims

1. In manufacturing a foam sheet for shoes using a polyurethane foam composition comprising polyol, isocyanate, chain extender as raw materials, and 0.1 to 2 wt% of water as a foaming agent, A step (S100) of manufacturing a polyurethane foam composition by mixing 10 to 20 wt% of recycled PU scrap powder with the polyol based on the total weight of the polyurethane foam composition; A step (S200) of manufacturing a polyurethane block foam by adding 10 to 40 wt% of recycled PU scrap powder based on the total weight of the polyurethane foam composition through a side-feeder and then reacting the same; A step (S300) of cutting the above polyurethane block foam to a desired thickness to form a polyurethane foam sheet; Step (S400) of combining a polyurethane foam sheet cut to the desired thickness with a fabric; A step (S500) of cutting the polyurethane foam sheet combined with the above fabric into a product of a specific shape, or putting it into a mold and forming and cutting it into a product of a specific shape by heat pressing; A method for manufacturing a shoe foam sheet containing recycled PU scrap powder characterized by being composed of:

2. In paragraph 1, A method for manufacturing a shoe foam sheet containing recycled PU scrap powder, characterized in that the recycled PU scrap powder is ground to an average particle size of 50 to 300 ㎛.

3. In paragraph 1, A method for manufacturing a shoe foam sheet containing recycled PU scrap powder, characterized in that the adhesive used in the step (S400) of combining the polyurethane foam sheet with the fabric is a liquid adhesive or hot melt film made of any one resin composition selected from thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA).

4. In paragraph 1, A method for manufacturing a shoe foam sheet containing recycled PU scrap powder, characterized in that the product of the above-mentioned specific shape is any one of a shoe insole or a shoe upper package.

5. A shoe foam sheet containing recycled PU scrap powder, characterized in that it is formed by the manufacturing method of any one of claims 1 to 4.

Images