Producing method of foam sheet for shoe with recycled PU scrap powder

Abstract

The present invention relates to a method of manufacturing a foam sheet for shoes containing recycled PU scrap powder, the method of manufacturing the foam sheet, including eco-friend Polyurethane (PU) foam composition prepared by water foam, is provided by first mixing recycled PU scrap powder with polyol and then reacting with the secondary addition of recycled PU scrap powder by controlling the process conditions and processing speed through a side-feeder, it is possible to prevent the viscosity of the raw material from rising, so that even if a larger amount (less than 60 wt %) of recycled material is used than before, the quality of the product is equivalent to that of conventional shoe insoles or shoe uppers.

Claims

1. A method of producing foam sheet containing recycling polyurethane (PU) scrap powder for shoes using a polyurethane foam composition comprising: as raw materials polyol, isocyanate, a chain extender, and water as a foaming agent in a ratio of 0.1 to 2 wt %, the method comprising: a step of mixing in a ratio of 10-20 wt % recycled PU scrap powder based on the total weight of the polyurethane foam composition with the polyol to form a polyol mixture; a mixing step of the isocyanate, the chain extender, and in a range of 0.1 to 2 wt % of water as a foaming agent based on the total weight of the polyurethane foam composition to the polyol mixture to form the polyurethane foam composition; a step of preparing a polyurethane block foam by adding the recycled PU scrap powder in a ratio of 10-40 wt % based on the total weight of the polyurethane foam composition to the polyurethane foam composition through a side feeder; a step of cutting the polyurethane block foam to a predetermined thickness to form a polyurethane foam sheet; a step of combining the polyurethane foam sheet cut to the predetermined thickness with a fabric; and a step of cutting the polyurethane foam sheet combined with the fabric into a predetermined shape of product, or placing it in a mold and molding and cutting it into a predetermined shape of product by using heat pressing.

2. The method of producing foam sheet containing recycled PU scrap powder for shoes of claim 1, wherein the recycling PU scrap powder is an average particle size in a range of 50 300 m.

3. The method of producing foam sheet containing recycled PU scrap powder for shoes of claim 1, wherein an adhesive used in a step combining polyurethane foam sheet with the fabric is a liquid adhesive or hot melt film comprising a resin composition of at least one selected from the group consisting of thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA).

4. The method of producing foam sheet containing recycled PU scrap powder for shoes of claim 1, wherein the predetermined shape of product is any one of a shoe insole foam package or a shoe upper foam package.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a process flow diagram showing a method for manufacturing a foam sheet for shoes according to the present invention.

(2) FIG. 2 is a foam sheet for shoes according to an aspect of the present invention.

(3) FIG. 3 is an insole for shoes according to an aspect of the present invention.

(4) FIG. 4 illustrates an apparatus for producing polyurethane foam sheet according to an aspect of the present invention.

DETAILED DESCRIPTION

(5) Hereinafter, a method for producing a foam sheet for shoes containing recycled PU scrap powder of the present invention is to be described with reference to the drawings. However, this is to illustrate the invention to be easily carried out by a person with ordinary skills in the art to which the present invention belongs, and does not imply that the technical ideas and categories of the present invention are limited.

(6) In general, polyurethane resin is a resin produced based on a urethane bond generated by the reaction of an isocyanate group (NCO) and a hydroxyl group (OH) in a polymer, and its raw materials may include polyol, isocyanate, and a chain extender, etc. By adjusting the ratio of soft and hard segments that make up polyurethane, it is possible to design a variety of fields, from elastic products such as rubber to hard products such as plastic.

(7) The polyurethane resin has excellent film strength and adhesive strength, thereby being able to manufacture a thin coating film. The coating film has excellent elasticity, thereby being able to be manufactured into a soft porous film or a film sheet, thereby imparting moisture permeability and air permeability. In addition, the polyurethane resin has excellent cold resistance, and is processed without using a plasticizer, thereby having less workability problems caused by the plasticizer.

(8) In addition, the polyol is an active hydrogen compound used to react with isocyanate to prepare polyurethane, wherein the polyol has two or more active hydrogen groups such as hydroxyl groups, carboxyl groups, and amine groups in the molecule, and has a direct effect on the physical properties of the polyurethane by using various types according to the molecular structure, molecular weight, functionalities, and OH-value.

(9) For example, a polyurethane using a polyester polyol is a polyether compared to polyurethane using polyol, it has higher tensile strength, hardness, and elongation, and has excellent flame retardancy, as well as excellent chemical resistance and chemical resistance, so it is resistant to oxidation and has excellent adhesion to various fabrics made of polyester or nylon. unlike polyether polyol, it has a property of hydrolysis, so its water resistance is weak. However, since polyurethane using polyether polyol has excellent elasticity, can be used in high temperature and high humidity environments, and shows excellent durability against acids and alkalis, it is preferable to use them alone or in combination depending on the application.

(10) Polyurethane (PU) is produced when polyether made by polymerization of ethylene oxide is mixed with diisocyanate, and urethane is a mixed amide-ester produced when an alcohol group reacts with isocyanate, and when triol is used instead of diol, cross-linking occurs to produce thermosetting polyurethane.

(11) Accordingly, in a preparing a foam sheet for shoe using the polyurethane foam composition containing polyol, isocyanate, chain extender, and 0.12 wt % of water as a foaming agent as raw materials according to the present invention, the polyurethane foam composition may contain recycled polyurethane (PU) powder having an average particle size of 50 to 300 m in an amount of 20 to 60 wt % based on the total weight of the polyurethane foam composition.

(12) According to aspects of the present invention, by including in a range of 0.1 to 2 wt % of water as a foaming agent based on the total weight of the polyurethane foam composition, the hardness (ASKER C-Type) has a range of 8 to 40 and a density of 0.05 to 0.35 g/cm.sup.3 foam moldings (for example shoe insoles, shoe upper foam packages, etc.) can be manufactured. Water as a foaming agent may be mixed with the polyol component in advance or mixed with the polyol component at the same time as mixing with the isocyanate component later.

(13) The foaming agent, water-blown agent, may contain a predetermined amount of water, which is a low carbon source, in consideration of workability and eco-friendliness, thereby minimizing carbon emission and producing a polyurethane foam molded body having a predetermined density, and water reacts with an isocyanate compound to produce carbon dioxide gas. The present invention has been researched in view the fact that conventionally used foaming agents, such as carbon dioxide, fluorocarbons etc. such as chlorofluorocarbons, hydrocarbons such as pentane and cyclopentane, fluorinated hydrocarbons, or air or nitrogen gas pre-dispersed in the polyol components using an air loading device, are undesirable due to poor workability, environmental harmfulness such as carbon emissions, and high energy costs.

(14) The recycled PU scrap used in the present invention can be recycled by easily separating the scrap of about 35% to 40% generated after cutting the shoe insole shape from the package comprising the foam 10 and fabric 30 in the method of manufacturing a dot bonded shoe insole using an adhesive resin mixed with hydrophobic nanosilica of Korean Patent No. 10-2131606 invented by the same inventor of the present application.

(15) As mentioned above, PU scraps separated from fabrics go through a step-by-step crushing process, and recycled PU scrap powder crushed to an average particle size of 50300 m is mixed with raw materials (polyols) to ensure that it is uniformly mixed with raw materials, which is advantageous for securing stable product quality due to good moldability and elasticity.

(16) The particle size or content of the recycled PU scrap powder can be adjusted within a certain range depending on the hardness and density of the desired molded body, but if the average particle size is less than 50 m, the compatibility with the polyurethane foam composition is poor, and if it exceeds 300 m, the dispersibility is poor, which may increase the defect rate of the manufactured product after molding.

(17) Accordingly, an aspect of the present invention provides an eco-friendly polyurethane (PU) foam composition composed of water foam, which is mixed with polyol as a first step, and then reacted by adding recycled PU scrap powder as a second step by controlling the process conditions and processing speed through a side-feeder to prevent the viscosity of the raw material from rising, thereby forming a foam sheet for footwear, such as a foam package for shoe insoles or shoe uppers, whose product quality is equivalent to that of conventional products even when a larger amount of recycled material is used.

(18) As shown in FIG. 1, a method for manufacturing a foam sheet for footwear containing recycled PU scrap powder according to aspects of the present invention may include: a polyurethane foam composition comprising as raw materials a polyol, an isocyanate, a chain extender, and in a ratio of 0. 1 to 2 wt % of water as a foaming agent, i.e., water-blown agent, based on the total weight of the polyurethane foam composition, a first step of preparing a polyurethane foam composition in which the polyol is mixed with in a ratio of 10 to 20 wt % of recycled PU scrap powder based on the total weight of the polyurethane foam composition, and then isocyanate, a chain extender, and in a ratio of 0. 1 to 2 wt % of water as a foaming agent and the resultant are mixed for reaction S100; a second step of adding recycled PU scrap powder via a side-feeder at a ratio of 10 to 40 wt % based on the total weight of said polyurethane foam composition to the resultant composition of the polyurethane foam composition of the first step S100, a third step of cutting the polyurethane block foam to a predetermined thickness to form a polyurethane foam sheet S300; a fourth step of compounding the polyurethane foam sheet cut to the predetermined thickness with a fabric S400; and a fifth step of cutting the fabric-compounded polyurethane foam sheet into a product of a particular shape or, alternatively, placing it in a mold and forming and cutting it into a predetermined product shape by heat pressing S500.

(19) First, in the first step S100 of preparing the above polyurethane foam composition, the polyurethane foam composition is composed of polyol, isocyanate, chain extender, and in a ratio of 0.1 to 2 wt % of water as a foaming agent. The polyol in the raw materials is first mixed with in a range 10 to 20 wt % of recycled PU scrap powder based on the total weight of the polyurethane foam composition, but if the recycled PU scrap powder exceeds 20 wt %, the viscosity of the raw material rises, making it difficult to knead for further foam reaction, resulting in poor reactivity.

(20) For the above reasons, limiting the content of recycled PU scrap powder mixed into the polyurethane foam composition to within 20 wt % has been recognized as a conventional limit for recycling waste, but aspects of the present invention provides a process technology that can include up to 60 wt % of recycled PU scrap powder based on the total weight of the polyurethane foam composition by providing a separate side-feeder for secondary input of the recycled PU scrap powder to facilitate adjustment of the reaction rate according to the composition of the raw materials.

(21) Accordingly, the present invention has confirmed that by adjusting the process conditions and processing speed through a side-feeder provided in the second step S200 of manufacturing the polyurethane block foam, recycled PU scrap powder is added at a ratio of 10 to 40 wt % based on the total weight of the polyurethane foam composition, and by preventing the viscosity of the raw material from rising, it is possible to form a foam sheet for footwear, such as a foam package for a shoe insole or a foam package for a shoe upper, with a product quality equivalent to that of a conventional shoe, despite using a larger amount of recycled material than conventionally.

(22) The third step S300 of forming a polyurethane foam sheet by cutting the polyurethane block foam formed as above to a predetermined thickness in a range of about 1 to about 10 mm (typically 2, 4, 5, 6 mm, etc.); and a fourth step S400 of bonding using the polyurethane foam sheet cut to the predetermined thickness with a fabric. The adhesive used in the step of bonding the polyurethane foam sheet with the fabric of the step S300 is most preferably a liquid adhesive or a hot melt film comprising a resin composition of at least one of thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA) having good compatibility with the polyurethane foam sheet.

(23) The adhesive made of the thermoplastic polyurethane (TPU) or ethylene vinyl acetate (EVA) is eco-friendly because a solvent is not used, and is advantageous in securing adhesion to various fabrics due to properties of a flexible material having good workability and productivity. In particular, excellent durability can be secured by maintaining strong adhesion to the polyurethane foam sheet for a long period of time.

(24) Next, the polyurethane foam sheet is made by cutting the polyurethane foam sheet into a specific shape, or putting the polyurethane foam sheet into a mold and molding and cutting the polyurethane foam sheet into a specific shape by a heat press with a temperature of 150200 C. and a pressure of 4060 kgf/cm in step S500. When the polyurethane foam sheet is put into the mold and molded by the heat press, when molding by the heat press, it may take about 100 seconds for the shoe insole foam package and about 40 seconds for the shoe upper foam package, respectively.

(25) The one of features of the five-steps, S100S500, process as described above is that recycled PU scrap powder with an average particle size of 50300 m based on the total weight of the polyurethane foam composition is mixed with polyol in the first step, and then recycled PU scrap powder is added in the second step through a side-feeder by controlling the processing speed of the process to prevent the viscosity of the raw material from rising, it is possible to form a foam sheet for footwear, such as a foam package for shoe insoles or shoe uppers, with a product quality equivalent to that of conventional products without deterioration in moldability despite using a larger amount of recycled material than conventional products.

(26) The recycled PU scrap powder has very good chemical miscibility with polyurethane foam compositions, which are polymer resins of the same type, as well as very good molding properties by heat pressing because it is dispersed into particle sizes having the most suitable miscibility, and if the average particle size is less than 50 m, the miscibility with the polyurethane foam compositions is poor, and if it exceeds 300 m, the dispersibility is poor, and there is a possibility that the quality (moldability, elasticity) of the product manufactured after molding may be reduced. For the same reason, it is preferred that the maximum particle size of the particles included in the recycled PU scrap powder does not exceed 500 m.

(27) Hereinafter, a method for manufacturing a foam sheet for shoes containing recycled PU scrap powder according to aspects of the present invention will be described in detail, and aspects of the present invention will be described through preferred embodiments that can be easily performed by a person with ordinary skills in the art to which the present invention belongs.

Example 1

Manufacture of Shoe Insoles

(28) The shoe insole manufactured according to aspects of the present invention is manufactured by polymerizing a polyurethane foam composition composed of, as a raw material, polyol, isocyanate, a chain extender, and water as a foaming agent, and may include the following five steps. Step 1: a polyurethane foam composition, which include polyol, isocyanate, a chain extender and the range of 0.1 to 2% wt % of water as a foaming agent based on the total weight of the polyurethane foam composition as raw materials, the polyurethane foam composition is prepared by mixing in a range of 10 to 20 wt % recycled PU scrap powder with an average particle size of 150 m based on the total weight of the polyurethane foam composition to the polyol. Step 2: A polyurethane block foam is prepared by adding about 10 to about 40 wt % of recycled PU scrap powder having an average particle size of 150 m based on the total weight of the above polyurethane foam composition through a side-feeder and reacting it. Step 3: The polyurethane block foam is cut to a thickness of about 4 mm to form a polyurethane foam sheet. Step 4: The polyurethane foam sheet cut to a thickness of about 4 mm is bonded, i.e., combined, with polyester fiber fabric using a thermoplastic polyurethane (TPU) hot melt film. Step 5: The polyurethane foam sheet bonded with the above fabric is cut into a product of a specific shape to manufacture a shoe insole.

(29) In manufacturing a shoe insole as in Example 1 above, the average values of the results of multiple evaluations of the moldability and appearance of a polyurethane foam sheet bonded with a fabric by heat pressing into a shoe insole shape in a fifth step according to the proportion of recycled PU scrap powder included in the polyurethane foam composition in the first and second steps are shown in Table 1 below.

(30) TABLE-US-00001 TABLE 1 example example example example example example Comparative category 1-1 1-2 1-3 1-4 1-5 1-6 example 1 (1step) PU Scrap 10 10 15 15 20 20 30 Powder(w %) (2step) PU Scrap 10 15 20 25 30 40 0 Powder(w %) Formability and good good good good good good poor appearance

Example 2

Manufacture of Foam Package for Shoe Upper

(31) The foam package for shoe uppers manufactured according to the present invention is manufactured by polymerizing a polyurethane foam composition including polyol, isocyanate, chain extender, and water as a foaming agent as raw materials, in the following five steps. Step 1: polyurethane foam composition including, as raw materials, a polyol and isocyanate and water as a foaming agent in the range of 0.1, to 2 wt % was prepared by mixing the polyol with recycled PU scrap powder having an average particle size of 150 m in a ratio of 10 to 20 wt % based on the total weight of the polyurethane foam composition. Step 2: polyurethane block foam is prepared by adding about 10 to about 40 wt % of recycled PU scrap powder with an average particle size of 150 m based on the total weight of the polyurethane foam composition through a side-feeder. Step 3: The polyurethane block foam was cut to a thickness of about 2 mm to form a polyurethane foam sheet. Step 4: The polyurethane foam sheet cut to a thickness of about 2 mm was bonded with PU skin film fabric using a thermoplastic polyurethane (TPU) hot melt film.

(32) Step 5: The polyurethane foam sheet bonded with the above fabric is cut into a product of a specific shape to manufacture a foam package for shoe uppers.

(33) When manufacturing a foam package for a shoe upper as in example 2 above, the average values of the results of multiple evaluations of the moldability and appearance of a polyurethane foam sheet compounded with a fabric by heat pressing into a foam package for a shoe upper according to the proportion of recycled PU scrap powder included in the polyurethane foam composition in the first and second steps are shown in [Table 2] below.

(34) TABLE-US-00002 TABLE 2 example example example example example example Comparative category 2-1 2-2 2-3 2-4 2-5 2-6 example 2 (1 step) 10 10 15 15 20 20 30 PU Scrap Powder(wt %) (2 step) 10 15 20 25 30 40 0 PU Scrap Powder(wt %) Formability good good good good good good poor and appearance

(35) As shown in [Table 1] and [Table 2] above, the foam packages for shoe insoles prepared by Examples 1-1 to 1-6 and for shoe uppers prepared by Examples 2-1 to 2-6 were found to have excellent quality, such as moldability, adhesion between the fabric and the polyurethane foam sheet, and appearance, it was found that when the amount of recycled PU scrap powder mixed into the polyurethane foam composition in the first step of comparative examples 1 and 2 exceeds 20 wt. %, the viscosity of the raw material increases, making it difficult to knead for further foam reaction and resulting in uneven density and hardness of the product due to poor reactivity.

(36) As described above, The polyurethane foam composition is made by first mixing recycled PU scrap powder of a certain particle size with polyol, and then reacting with the second addition of recycled PU scrap powder by controlling the process conditions and throughput through a side-feeder to prevent the viscosity of the raw material from rising, so it is possible to form a foam sheet for footwear, such as a foam package for shoe insoles or shoe uppers, with a product quality equivalent to that of conventional products despite using a larger amount of recycled material than conventional products.

Experimental Examples

(37) In order to confirm the exemplary properties of the polyurethane foam composition by the present invention, within the range of hardness and density required by the present invention, two kinds of polyurethane foam sheet (shoe insoles, foam package for shoe upper) containing recycled PU scrap powder with an average particle size of about 150 m in the range of 50% by weight as shown in Example 1-5 and Example 2-5 were manufactured under the same conditions as the conventional heat press (temperature 150200 C. & pressure 4060 kgf/cm), The results of several physical properties tests are shown in Table 3 below.

(38) TABLE-US-00003 TABLE 3 Foam package Properties unit Shoe insoles for shoe upper hardness(ASKER C) 21/25/28/29/27 19/19/19/20/20 density g/cm.sup.3 0.18/0.16/0.16 0.14/0.15/0.15 Tear Strength kgf/cm 2.5/2.3/2.1 1.8/1.8/2.0 Tensile strength kgf/cm.sup.2 4.6/4.6/4.8 3.8/3.5/3.6 Elongation rate % 105/109/101 123/110/118 Shrinkage rate % 0.10/0.25/0.30 0.09/0.15/0.20 hardness: ASKER C Type Durometer based on JIS K 7312

(39) As shown in [Table 3], the foam sheet for shoes containing recycled PU scrap powder according to the present invention is obtained by first mixing the recycled PU scrap powder with polyol and then by reacting with secondary addition of recycled PU scrap powder through a side-feeder, the overall physical properties such as tear strength, tensile strength, elongation, and shrinkage can be manufactured to the same level as conventional polyurethane foam sheets that do not contain recycled PU scrap powder. It was confirmed that 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/cm.sup.3.

(40) FIG. 4 illustrates an apparatus for producing polyurethane foam sheet in accordance with an aspect of the present invention.

(41) Referring to FIG. 4, an apparatus for producing polyurethane foam sheet in accordance with an aspect of the present invention may include an isocyanate tank, a polyol tank, a recycled power tank, a chamber, and a side-feeder. However, it is not limited thereto.

(42) Therefore, the shoe foam sheet containing recycled PU scrap powder manufactured by aspects of the present invention can be replaced, modified, and changed in various forms without departing from the technical spirit of the present invention, and is especially environmentally friendly and improves productivity and foam packages for various shoe insoles and shoe uppers (decoration) that have the advantage of reducing manufacturing costs and require uniform formability and durability, as well as clothing, bags, and sporting goods made of fiber, natural and synthetic leather, plastic, etc. It can be applied to a variety of applications that require functions such as molding materials, cushioning materials, and fillers used inside household goods, industrial products, etc.