JP5601886B2 - Substrate for artificial leather, method for producing the same, and artificial leather - Google Patents

Description

  The present invention relates to a substrate for artificial leather, a synthetic leather, and a method for producing the same, including a three-dimensional entangled nonwoven fabric and a polymer elastic body.

  Conventionally, artificial leather has been widely used as a surface material for footwear, bags, clothing, furniture, and the like. Artificial leather is required to be lightweight in addition to mechanical properties and texture. As artificial leather with improved lightness, artificial leather including a fiber base material formed from ultrafine fibers is known.

  The fiber base material formed from the ultrafine fibers is formed, for example, by selectively dissolving and removing only the sea components from the fiber base material formed from the sea-island type composite fiber. According to such a method, it is possible to obtain a lightweight fiber substrate made of ultrafine fibers. However, the fiber base material obtained by such a method has a problem in that sufficient lightness cannot be obtained because the gap between the fibers is greatly reduced by the press treatment for adjusting the thickness. In order to solve such a problem, a method of using a fiber base material formed from hollow fibers as a base material for artificial leather is known.

  For example, Patent Document 1 below discloses a fiber structure excellent in lightness including hollow fibers made of a thermoplastic polymer having an equilibrium moisture content of 2% or less.

  Moreover, for example, the following Patent Document 2 discloses an artificial leather containing polyester fibers having a hollow ratio of 40 to 85%.

  Further, for example, Patent Document 3 below discloses a nonwoven fabric made of hollow fibers, in which the hollow ratio of the hollow fibers has a gradient from one side to the other in the thickness direction.

  Further, for example, Patent Document 4 below has an ultrafine fiber (A) of 0.5 dtex or less and 5 to 50 dtex in a transverse section, and the total area ratio of the hollow portions is 25. The fiber (B) in which the area occupied by one hollow part is 5% or less is in the range of ~ 50%, and (A) / (B) is 20/80 to 80/20 by weight ratio and is three-dimensionally entangled An artificial leather base material comprising a nonwoven fabric and a polymer elastic body is disclosed.

Japanese Patent Laid-Open No. 2002-220741 Japanese Patent No. 3924360 Japanese Patent No. 3361967 Japanese Patent Laid-Open No. 2002-242077

  In recent years, artificial leather used for sports shoes and the like has been required to be both durable and light weight capable of withstanding intense exercise. Examples of durability include peel strength between a shoe sole rubber portion and artificial leather, tear strength, and the like. Further, there is a demand for an appearance that does not cause buckling wrinkles during use, flexibility, and the like.

  A relatively thin base material is used for artificial leather such as that used in sports shoes. Therefore, there is a demand for artificial leather having excellent durability, mechanical characteristics, and appearance even when used in such a thin thickness. However, a base for artificial leather that has all these characteristics is still required. The material was not obtained.

  An object of this invention is to provide the base material for artificial leather which is excellent in durability, lightness, and buckling resistance, and has a soft texture.

  One aspect of the present invention is a base material for artificial leather comprising a three-dimensional entangled nonwoven fabric and a polymer elastic body impregnated in the three-dimensional entangled nonwoven fabric, wherein the three-dimensional entangled nonwoven fabric has a fineness of 0.5. It consists of polyolefin hollow filaments of -5 dtex, and the cross section of the polyolefin hollow filament has 5 to 50 hollow portions with a total hollowness of 25 to 50% and a hollowness of 1 to 5% per piece. And the content rate of a polymeric elastic body is the range of 15-50 mass% with respect to the total amount of a three-dimensional entangled nonwoven fabric and a polymeric elastic body, and is 0-30 of the outer periphery of the cross section of a polyolefin hollow filament. % Is a base material for artificial leather bonded to a polymer elastic body.

The apparent density is preferably in the range of 0.20 to 0.25 g / cm ³ .

  The polymer elastic body is preferably polyurethane.

  Another aspect of the present invention is an artificial leather including the artificial leather base material and a resin skin layer formed on the surface thereof.

Further, another aspect of the present invention, a polyolefin resin as a sea component, and polyolefin resin and chemical or physical properties different selectively extracted removable polyolefin resin other than the resin island component fibers A step of producing a sea-island type composite filament having a fineness of 0.5 to 5 dtex in which the number of island components in the cross section is 5 to 50 and the area ratio per island component is 1 to 5% (step 1); A step of producing a spunbond sheet made of sea-island type composite filament (step 2) and a step of forming an entangled web by needle punching an overlapped body of two or more spunbond sheets (step 3). dry When a heating press the entangled web (step 4), the heat-pressed entangled web was impregnated with an aqueous resin solution of the elastic polymer, the elastic polymer A step (step 5) to coagulation of, after step 5, a polyolefin hollow filaments by dissolving and removing the resin other than the polyolefin resin from the sea island type composite filaments while applying a physical deformation to the sea-island type composite filament And a step of forming a three-dimensional entangled nonwoven fabric (step 6), wherein the ratio of the resin other than the polyolefin-based resin in the sea-island composite filament is in the range of 25 to 60% by mass, and the total hollowness of the polyolefin hollow filament is The amount of impregnation with the aqueous resin liquid is within the range of 25 to 50%, and the amount of the polymer elastic body is 15 to 50% by mass with respect to the total amount of the polyolefin hollow filament and the polymer elastic body. It is a manufacturing method of the base material for leather.

  The aqueous resin liquid containing the polymer elastic body is preferably an aqueous polyurethane emulsion.

Further, resins other than the polyolefin-based resin has an average polymerization degree of 200-500, saponification degree 90 to 99.99 mol%, and Ri Oh water-soluble thermoplastic polyvinyl alcohol having a melting point of 160 to 230 ° C., the step 6 It is preferable to provide a step of dissolving and removing water-soluble thermoplastic polyvinyl alcohol with hot water containing a nonionic surfactant .

  ADVANTAGE OF THE INVENTION According to this invention, the base material and artificial leather for artificial leather excellent in lightweight property, durability, buckling resistance, and a softness | flexibility are obtained.

It is a model longitudinal cross-sectional view of the artificial leather 10 of this embodiment. It is a model expansion longitudinal cross-sectional view of the base material 3 for artificial leather of this embodiment.

One embodiment of a base material for artificial leather and artificial leather according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view of an artificial leather 10 of the present embodiment. The artificial leather 10 includes a three-dimensional entangled nonwoven fabric 1 made of a polyolefin hollow filament 1a having a fineness of 0.5 to 5 dtex, and a polymer elastic body 2 impregnated in the three-dimensional entangled nonwoven fabric 1. It has the material 3 and the resin skin layer 4 formed in the surface of the base material 3 for artificial leather. The content ratio of the polymer elastic body 2 is in the range of 15 to 50% by mass with respect to the total amount of the three-dimensional entangled nonwoven fabric 1 and the polymer elastic body 2.

  FIG. 2 is a schematic enlarged vertical sectional view of the base material 3 for artificial leather. As shown in FIG. 2, the polyolefin hollow filament 1 a has 5 to 50 hollow portions v having a hollow ratio of 1 to 5% per piece in its cross section. Moreover, the total hollow ratio in the cross section of the polyolefin hollow filament 1a is in the range of 25 to 50%. And the range of 0-30% of the outer periphery of the cross section of the polyolefin hollow filament 1a is bonded to the polymer elastic body 2, that is, 70-100% of the outer periphery is not bonded to the polymer elastic body 2.

  Here, the hollow ratio per piece is the ratio of the area per hollow portion v to the total area inside the outer peripheral contour of the cross section of the polyolefin hollow filament 1a. Moreover, the said total hollow ratio is a ratio of the total area of all the hollow parts v with respect to the total area inside the outline of the outer periphery of the cross section of the polyolefin hollow filament 1a.

The polyolefin hollow filament 1a will be described in detail.
The polyolefin resin that forms the polyolefin hollow filament 1a is not particularly limited, and specific examples include polypropylene resins and polyethylene resins. These may be used alone or in combination of two or more. Among these, polypropylene resins are preferable because they are excellent in stability of melt spinning and particularly excellent in mechanical properties and buckling resistance.

  Specific examples of the polypropylene resin include a propylene homopolymer and a copolymer of propylene and an ethylenically unsaturated monomer. Examples of the copolymer type include a random copolymer having crystallinity and a crystalline block copolymer. Examples of the ethylenically unsaturated monomer include ethylene; 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-pentene-1, 4-methyl-hexene-1, 4, Examples include α-olefins having 4 to 20 carbon atoms such as 4-dimethylpentene-1.

  The polyolefin-based resin may contain a colorant such as a dye or a pigment, an ultraviolet absorber, a heat stabilizer, a deodorant, a fungicide, various stabilizers, and the like as necessary.

  The fineness of the polyolefin hollow filament 1a is in the range of 0.5 to 5 dtex, and preferably in the range of 1 to 3 dtex. When the fineness exceeds 5 dtex, the texture of the resulting artificial leather becomes hard and the tactile sensation becomes harsh. On the other hand, if the fineness is less than 0.5 dtex, the fiber density tends to be high during production, and it becomes difficult to obtain a lightweight artificial leather.

  The polyolefin hollow filament 1a has, in its transverse cross section, 5 to 50 hollow portions v having a total hollow rate of 25 to 50% and a hollow rate of 1 to 5% per piece.

  The hollowness per hollow portion v in the cross section of the polyolefin hollow filament 1a is 1 to 5%, preferably 2 to 4%. When the hollowness ratio per hollow portion v exceeds 5%, the hollow portion is easily crushed when subjected to an external force such as bending or compression, and the lightness is reduced or the buckling resistance is reduced. It tends to decrease. Moreover, when the hollow ratio per one hollow part v is less than 1%, it becomes difficult to form a filament with a total hollow ratio of 25 to 50% industrially.

  The number of the hollow portions v in the cross section of the polyolefin hollow filament 1a is 5 to 50, preferably 9 to 50. When the number of hollow portions is less than 5, it becomes difficult to form a hollow structure having homogeneous partition walls. Moreover, when the number of hollow parts exceeds 50, in order to adjust to the range of the total hollowness of 25 to 50%, the hollowness per piece becomes too low. Also in this case, the hollow portion is easily crushed.

  The total hollow ratio of the hollow part v in the cross section of the polyolefin hollow filament 1a as described above is 25 to 50%, preferably 30 to 40%. When the total hollowness is less than 25%, it is difficult to obtain a sufficiently lightweight artificial leather, and when it exceeds 50%, the hollow portion is easily crushed by receiving external force such as bending and compression. As a result, the lightness is reduced and the buckling resistance is reduced.

  The polyolefin hollow filament 1a is a long fiber. The long fibers are continuous long fibers, and are distinguished from so-called staples, which are short fibers cut to a predetermined fiber length.

  The three-dimensional entangled nonwoven fabric 1 is a nonwoven fabric in which polyolefin hollow filaments 1a are entangled three-dimensionally. For example, as described later, it is formed by selectively dissolving and removing a resin component that forms an island component from a three-dimensional entangled nonwoven fabric made of sea-island type composite filaments.

The density of the three-dimensional entangled nonwoven fabric 1 is not particularly limited, but is preferably about 0.08 to 0.18 g / cm ³ from the viewpoint of excellent balance between entanglement and lightness.
Further, the three-dimensional entangled nonwoven fabric 1 of the basis weight, 100 to 1000 g / m ^2, more preferred in view of uniformity and light weight of 200 to 600 g / m ² and it is obtained for artificial leather substrate.

Next, the polymer elastic body 2 impregnated with the three-dimensional entangled nonwoven fabric 1 will be described in detail.
As shown in FIGS. 1 and 2, the polymer elastic body 2 is applied to the voids present inside the three-dimensional entangled nonwoven fabric 1. The content ratio of the polymer elastic body 2 is 15 to 50% by mass with respect to the total amount of the three-dimensional entangled nonwoven fabric 1 and the polymer elastic body 2. And the range of 0-30% of the outer periphery of the cross section of the polyolefin hollow filament 1a is bonded to the polymer elastic body 2, that is, 70-100% of the outer periphery is not bonded to the polymer elastic body 2.

  Specific examples of the resin forming the polymer elastic body 2 include, for example, polyurethane, polyvinyl chloride, polyamide, polyester, polyester ether copolymer, polyacrylate copolymer, neoprene, styrene butadiene copolymer, silicone resin, polyamino acid, poly An amino acid polyurethane copolymer etc. are mentioned. These may be used alone or in combination of two or more. Among these, polyurethane is particularly preferable from the viewpoint of obtaining a soft texture. Moreover, the polymer elastic body 2 may contain a pigment, a dye, a crosslinking agent, a filler, a plasticizer, various stabilizers, and the like as necessary.

  The content ratio of the polymer elastic body 2 is 15 to 50% by mass, preferably 20 to 45% by mass, based on the total amount of the three-dimensional entangled nonwoven fabric 1 and the polymer elastic body 2. When the content of the polymer elastic body 2 is less than 15% by mass, durability, form stability, and surface smoothness are lowered, buckling resistance is lowered, and bending and wrinkles are likely to occur. . Moreover, when the content rate of the polymeric elastic body 2 exceeds 50 mass%, the artificial leather obtained becomes a hard texture and the lightness falls.

In the cross section in the thickness direction of the artificial leather 10, 0-30%, preferably 1-20%, more preferably 2-10% of the outer circumference of the cross section of the polyolefin hollow filament 1a is bonded to the polymer elastic body 2. doing. That is, the outer peripheral surface of the polyolefin hollow filament 1a has 70 to 100% of a region where the polymer elastic body 2 is not attached. Thus, when 70% or more of the outer peripheral surface of the polyolefin hollow filament 1a is not bonded and fixed by the polymer elastic body 2, the polyolefin hollow filament 1a and the polymer elastic body 2 may be firmly fixed. It is possible to deviate moderately from each other. Thereby, an artificial leather having a soft texture is obtained, and even when folded, the occurrence of buckling wrinkles that occur due to the difference in elongation characteristics between the polyolefin hollow filament 1a and the polymer elastic body 2 is suppressed. When the ratio of the bonded part exceeds 30%, the resulting artificial leather has a hard texture.
The ratio of the elastic polymer adhered to the outer periphery of the transverse cross section of the polyolefin hollow filament 1a is determined by observing the cross section in the thickness direction of the artificial leather 10 with an electron microscope and with respect to the axial direction of the polyolefin hollow filament in the observation field. For example, 50 cross sections that are perpendicular to each other are selected, and the outer peripheral length of each cross section and the length of the outer periphery of each cross section to which the polymer elastic body is bonded to the outer periphery are measured. It is obtained by calculating the ratio of the length of the portion where the polymer elastic body is bonded to the entire length of the outer periphery.

  The thickness of the base material 3 for artificial leather is not particularly limited, but is preferably in the range of 0.3 to 3 mm, more preferably 0.7 to 1.8 mm. When the thickness of the base material 3 for artificial leather is too thin, durability and mechanical properties that can withstand practicality tend to be difficult to obtain, and when it is too thick, the lightness tends to be reduced.

The apparent density of the base material 3 for artificial leather is preferably 0.15 to 0.3 g / cm ³ , more preferably 0.20 to 0.25 g / cm ³ . If the apparent density is too high, the resulting artificial leather tends to be reduced in lightness, and if the apparent density is too low, the mechanical properties tend to be reduced.

  A resin skin layer 4 is formed on the surface of the base material 3 for artificial leather. Such a resin skin layer 4 is a layer for protecting and decorating the surface of the artificial leather 10.

  The resin forming the resin skin layer 4 is not particularly limited. Specifically, a polyurethane resin, an acrylic resin, a polyamide resin, a polyester resin, a polyolefin resin, etc. are mentioned, for example. Among these, a polyurethane resin or an acrylic resin is preferable because it is excellent in surface wear resistance, flex resistance, surface touch property, durability, and the like.

  Although the thickness of the resin skin layer 4 is not specifically limited, It is preferable that it is 20-500 micrometers, Furthermore, it is 50-300 micrometers. When the thickness of the resin skin layer 4 is too thick, the feeling of lightness tends to be lowered, and when the thickness is too thin, the surface of the artificial leather tends not to be sufficiently protected and decorated.

  The resin skin layer 4 may be a silver-like one having a smooth surface or a surface decorated by embossing or the like. Moreover, a desired function, texture, etc. can also be provided by setting it as a porous structure or a non-porous structure.

  The base material 3 for artificial leather according to the present embodiment has, for example, a peel strength of 8 kg / 2.5 cm or more, further 10 kg / 2.5 cm or more, and a tear strength per 1 mm thickness of 7 kg or more, more preferably 8 Excellent mechanical properties such as 5 kg or more. Therefore, the artificial leather using the artificial leather base material of the present embodiment can be preferably used for applications such as sports shoes that require durability, lightness, buckling resistance, and flexibility.

Next, an example of the manufacturing method of the artificial leather 10 of this embodiment will be described in detail.
The manufacturing method of the base material 3 for artificial leather of this embodiment uses a polyolefin-based resin as a sea component, and a resin other than a polyolefin-based resin that can be selectively extracted and removed with a chemical or physical property different from that of the polyolefin-based resin. A step of producing a sea-island composite filament having a fineness of 0.5 to 5 dtex as a component (step 1), a step of producing a spunbond sheet made of a sea-island composite filament (step 2), and two or more spunbonds A process of forming an entangled web by needle punching the overlapped body on which the sheets are stacked (process 3), a process of heating and pressing the entangled web (process 4), and a hot pressed entangled web. After impregnating the molecular elastic body with the aqueous resin solution, solidifying the polymer elastic body (step 5), and after step 5, the sea-island type composite filaments are treated with polio. Forming a three-dimensional entangled nonwoven fabric composed of polyolefin hollow filaments by dissolving and removing the resin other than the fin-based resin (step 6), and the ratio of the resin other than the polyolefin-based resin in the sea-island composite filament is The amount of impregnation of the aqueous resin liquid is within the range of 25 to 60% by mass, and the amount of the polymer elastic body is 15 to 50% by mass with respect to the total amount of the polyolefin hollow filament and the polymer elastic body. Is the method.

First, step 1 and step 2 will be described in detail.
A spunbond sheet made of sea-island composite filaments is formed using a so-called spunbond method. Specifically, a polyolefin resin for forming a sea component, a polyolefin resin for forming an island component, and a resin other than a polyolefin resin that can be selectively extracted and removed with different chemical or physical properties The sea-island type composite fiber strand is obtained from the spinning nozzle hole by melt-combining. Subsequently, after the obtained sea-island type composite fiber strand is cooled by a cooling device, a high-speed air current is generated at a speed corresponding to a take-up speed of, for example, 1000 to 6000 m / min by using a suction device such as an air jet nozzle. A sea-island type composite filament is obtained by stretching and thinning. A spunbond sheet is formed by depositing the sea-island type composite filament on a collection surface such as a movable net while opening the sea-island composite filament.

  Sea-island composite filaments have a sea-island cross-section with a polyolefin resin as the sea component and a resin other than the polyolefin resin with a chemical or physical property that is different from the polyolefin resin and can be selectively extracted and removed. It is a composite fiber of long fibers. And the polyolefin hollow fiber filament which has polyolefin resin as a main component is formed by selectively extracting and removing the resin of an island component from such a sea-island type composite filament.

Examples of the polyolefin resin include various polyolefin resins as described above. Among various polyolefin-based resins, the specific gravity is low and the lightness is easily developed, and the water-based resin liquid is particularly easily water-repellent when impregnated with the water-based resin liquid of the polymer elastic body in the subsequent process. Polypropylene resins are preferred.
The melt flow rate (MFR) of the polypropylene resin is preferably 1 to 200 g / min, more preferably 5 to 100 g / min. In addition, MFR is the value measured by 230 degreeC and the load 21.1N based on JIS-K6921-2 appendix.

  In addition, the resin that can be extracted and removed to form the island component is a resin that is different in solubility with respect to the solvent with the polyolefin resin that forms the sea component or decomposability with respect to the decomposing agent, and has low compatibility with the polyolefin resin. Any resin that can be melt-spun can be used without particular limitation. Specific examples of such a resin include, for example, a water-soluble thermoplastic polyvinyl alcohol resin (hereinafter also simply referred to as PVA), polystyrene having a solvent solubility different from that of a polyolefin resin, an ethylene propylene copolymer, and ethylene. A vinyl acetate copolymer, a styrene ethylene copolymer, a styrene acrylic copolymer, etc. are mentioned. Among these, PVA dissolves easily in hot water with almost no swelling of the polyolefin resin, which is a sea component, and the hollow part formed by the influence of the organic solvent is crushed and flattened. This is particularly preferable because the outer wall and the partition wall forming the portion are not easily destroyed. Furthermore, PVA is preferable from the viewpoint of low environmental load. In this embodiment, the case where PVA is used as a sea component will be described in detail as a representative example.

  PVA is polyvinyl alcohol that can be dissolved in hot water by saponifying a polymer containing a vinyl ester unit derived from a fatty acid vinyl ester monomer and another copolymer unit included as necessary. can get.

  Specific examples of the fatty acid vinyl ester monomer include, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, and versatha. Examples thereof include vinyl tick acid.

  Further, specific examples of the monomer that forms other copolymer units included as necessary include, for example, α-olefins having 4 or less carbon atoms such as ethylene, propylene, 1-butene, and isobutene; methyl vinyl ether , Vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, and the like. Among these, ethylene is particularly preferable from the viewpoint of excellent mechanical properties of the obtained artificial leather. As a content rate of the other copolymerization unit in PVA, it is preferable to contain 1-20 mol%, further 4-15 mol%, especially 6-13 mol%.

  As PVA, a modified PVA obtained by saponifying a polymer mainly containing vinyl ester units derived from vinyl acetate containing 4 to 15 mol%, further 6 to 13 mol% of ethylene units is commonly used. This is particularly preferable from the viewpoint of excellent polymerizability, melt spinnability and water solubility of the fiber.

  The degree of polymerization of PVA is preferably 200 to 500, more preferably 230 to 470, and particularly preferably 250 to 450 from the viewpoint of excellent melt spinning stability and dissolution / removability to hot water.

In addition, the said polymerization degree (P) means the viscosity average polymerization degree measured according to JIS-K6726. Specifically, after re-saponification and purification of PVA, the intrinsic viscosity [η] measured in water at 30 ° C. is obtained by the following formula.
P = ([η] 10 ³ /8.29) ^{(1 / 0.62)}

  The degree of saponification of PVA is from 90 to 99.99 mol%, more preferably from 93 to 99.98 mol%, especially from 94 to 99.97 mol%, in particular from 96 to 99.96 mol%. Preferably there is. If the degree of saponification is too low, melt spinnability tends to decrease or water solubility tends to decrease.

  The melting point (Tm) of PVA is preferably in the range of 160 to 230 ° C., more preferably 170 to 227 ° C., and particularly preferably 175 to 224 ° C., more preferably 180 to 220 ° C. When the melting point is too low, the thermal stability of PVA is lowered, and thus fiberization tends to be difficult. Further, when the melting point is too high, the melting point and the decomposition temperature are close to each other, so that there is a tendency that stable spinning cannot be performed.

  The melting point of PVA is that when DSC is used, the temperature is raised to 300 ° C. in nitrogen at a heating rate of 10 ° C./min, cooled to room temperature, and then heated again to 300 ° C. at a heating rate of 10 ° C./min. It means the temperature at the peak top of the endothermic peak indicating the melting point of PVA.

  PVA is obtained by radical polymerization using a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, or the like. Among these, a bulk polymerization method in which polymerization is performed without solvent and a solution polymerization in which polymerization is performed in a polar solvent such as alcohol are preferably used. Specific examples of the polar solvent used in the solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. Specific examples of radical polymerization initiators include azo initiators such as a, a′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), Examples thereof include peroxide initiators such as benzoyl oxide and n-propyl peroxycarbonate. Moreover, although superposition | polymerization temperature is not specifically limited, For example, the range of 0-150 degreeC is mentioned.

In the melt composite spinning, the number of islands is preferably 5 to 50 islands / fiber cross section, more preferably 9 to 50 islands / fiber cross section.
Moreover, the thickness of the partition wall having a hollow structure formed by the sea component is preferably about 0.5 to 5 μm. In such a range, it is preferable because the extraction and removal processing of island components is easy.
Furthermore, the ratio of the resin other than the polyolefin-based resin in the sea-island composite filament is preferably in the range of 25 to 60% by mass, more preferably 30 to 55% by mass. When the proportion of the resin other than the polyolefin-based resin is too high, the proportion of the formed hollow portion tends to be too high, and when it is too low, the proportion of the formed hollow portion tends to be too low. .

  After the sea-island type composite strand formed by melt composite spinning is cooled by a cooling device, it has a speed corresponding to a take-up speed of 1000 to 6000 m / min so as to achieve a desired fineness using a suction device such as an air jet nozzle. Stretched by high-speed airflow. Then, the spunbond sheet is formed by depositing the stretched sea-island type composite fiber on the movable collection surface. At this time, the spunbond sheet may be partially crimped as necessary.

The fineness of the sea-island composite filament is preferably in the range of 0.7 to 12.5 dtex, and more preferably in the range of 2.5 to 8 dtex, from the viewpoint of excellent island component extraction and removal.
Moreover, it is preferable from the point of stability of the hollow structure of the hollow fiber obtained that the fineness of the island part which forms a sea-island type composite filament is 0.5-5 dtex, Furthermore, it is the range of 2-5 dtex.
Further, the basis weight of the spunbond sheet is preferably in the range of ^{20 to} 50 g / m ² from the viewpoint of excellent productivity.

Next, the process (process 3) of superposing two or more spunbond sheets obtained as described above and forming an entangled web by a needle punching process will be described in detail.
Step 3 is a step of obtaining an entangled web in which fibers are entangled in the thickness direction by superimposing a plurality of spunbond sheets obtained as described above and then performing an entanglement process by needle punching. It is.
The number of spunbond sheets to be superimposed is not particularly limited, but is preferably 4 or more, and more preferably 8 or more.

An entangled web is formed by performing an entanglement process by needle punching on an overlapped body obtained by overlapping a plurality of spunbond sheets.
The type of felt needle used for needle punching is not particularly limited. In order to sufficiently increase the entanglement of the fibers in the thickness direction, it is preferable to use a thin felt needle or a felt needle with few barbs such as a 1 barb needle. Moreover, it is preferable to use felt needles, such as 3 barb, 6 barb, and 9 barb, from the point which suppresses the cutting | disconnection of a sea island type composite filament.
Further, the number of felt needles used in needle punching per unit area is not particularly limited, but a range of 200 to 2500 / cm ² is preferable.
The basis weight of the entangled web thus obtained is preferably 100 to 3000 g / m ² , more preferably 200 to 1000 g / m ² .

Next, the process (process 4) of heat-pressing the entangled web will be described.
The obtained entangled web is smoothed by a hot press, and its thickness is adjusted. By heating, the polyolefin resin is melted or softened, and the fibers are pressure-bonded.

Examples of the heating press method include a method of passing between a plurality of heating rolls, a method of passing a preheated entangled web between cooling rolls, and the like. During pressing, an adhesive such as polyvinyl alcohol, starch, or resin emulsion may be applied to the entangled web. Thus, by apply | coating an adhesive agent, the press-fit state of a fiber and the form of an entanglement web are controllable. By such a heating press, the surface of the entangled web is smoothed and the thickness is adjusted.
The rate of decrease in the thickness of the entangled web after pressing relative to the thickness of the entangled web before pressing is preferably 5 to 30%, and more preferably 10 to 25%.

Next, the step (Step 5) of solidifying the polymer elastic body after impregnating the hot-pressed entangled web with the aqueous resin liquid of the polymer elastic body will be described.
In this step, first, an entangled web after pressing is impregnated with an aqueous resin liquid of a polymer elastic body. A polyolefin resin having high water repellency is present on the surface of the sea-island composite filament forming the entangled web. Therefore, when such an entangled web is impregnated with an aqueous resin liquid of a polymer elastic body, the aqueous resin liquid of the polymer elastic body is less likely to contact the surface of the sea-island composite filament. When the polymer resin aqueous resin liquid impregnated in such an entangled web is dried and solidified, the polymer elastic body adheres only in the range of 0 to 30% of the outer periphery of the sea-island composite filament. Such a structure can be easily formed.

  Examples of the aqueous resin liquid include an aqueous emulsion and an aqueous suspension containing a resin for forming a polymer elastic body. The aqueous resin liquid preferably contains as little surfactant as possible to reduce the water repellency of the polyolefin resin. Accordingly, a self-emulsification type emulsion is particularly preferable as the aqueous emulsion.

  The resin concentration in the aqueous resin liquid is preferably about 20 to 60% by mass. When the aqueous resin liquid having such a resin concentration is used, the content ratio of the polymer elastic body is adjusted to 15 to 50% by mass with respect to the total amount of the three-dimensional entangled nonwoven fabric and the polymer elastic body. It becomes easy.

  In addition, since polyolefin resin has high water repellency, an entangled web may be impregnated with the aqueous resin liquid nonuniformly. In such a case, the elastic polymer to be dried and solidified is unevenly distributed. In order to suppress the non-uniform presence of the polymer elastic body, the following method is exemplified. Specifically, for example, as a pre-treatment before impregnating the aqueous resin liquid, uniformity is achieved by impregnating with a water-soluble compound such as polyvinyl alcohol or starch that is removed by the island component extraction and removal treatment described later. Can be improved. Moreover, you may use the aqueous resin liquid with a high viscosity, or may use the aqueous resin liquid containing a gelatinizer. Specific examples of the gelling agent include a heat-sensitive gelling agent that gels at a constant temperature.

  Examples of the method for impregnating the entangled web with the aqueous resin liquid include a method using a knife coater, a bar coater, or a roll coater, or a dipping method.

  The polymer elastic body can be solidified by drying the entangled web impregnated with the aqueous polymer liquid of the polymer elastic body. As a drying method, a method of heat treatment in a drying apparatus at 50 to 200 ° C., a method of heat treatment in a dryer after infrared heating, a method of heat treatment in a dryer after steam treatment, or drying after ultrasonic heating Examples thereof include a method of performing heat treatment with a machine, a method of combining these, and the like.

  Next, the process (process 6) of forming the three-dimensional entangled nonwoven fabric which consists of polyolefin hollow filaments by melt | dissolving and removing resin other than polyolefin resin from a sea island type composite filament is demonstrated. By this step, all or most (for example, 95% or more) of the resin that forms the island component contained in the sea-island composite filament is extracted and removed to form a polyolefin hollow filament.

  By treating the entangled web provided with the polymer elastic body in hot water containing a surfactant, the water-soluble thermoplastic polyvinyl alcohol is dissolved and removed from the sea-island composite filament forming the entangled web.

  Examples of the hot water treatment method include a method of treating at a water temperature of 80 to 95 ° C. using a dyeing machine such as a liquid dyeing machine or a jigger, or a scouring machine such as an open soaper. In particular, in order to improve the extraction efficiency, it is preferable to use a liquid flow dyeing machine that can physically deform the hollow fiber, or a device that combines a vibro washing machine and a squeezing device in multiple stages.

  Moreover, in order to improve the wettability of polyolefin resin, nonionic surfactant represented by poly (oxyethylene) alkyl ethers, etc., or hot water containing a known anionic surfactant may be used. preferable. As such a surfactant, the HLB (Hydrophile-Lipophile Balance) is preferably in the range of 4-16.

  And after extracting and removing all or most of PVA contained in a sea-island type composite filament, the base material for artificial leather of this embodiment is obtained by drying.

  The base material for artificial leather thus obtained is usually subjected to post-processing such as silver surface treatment, raising treatment, softening treatment, two-division treatment, molding treatment, and dyeing treatment according to various applications. .

  For example, in the case of producing silver-tone artificial leather, a resin skin layer containing a polymer elastic body is formed on the surface of a base material for artificial leather.

  As a method for forming a resin skin layer, a method of forming a dispersion or solution of a polymer elastic body directly on the surface of a base material for artificial leather, or a resin skin layer formed on a release paper for artificial leather A method of bonding to the surface of the substrate is used. As the polymer elastic body used for forming the resin skin layer, a polymer elastic body conventionally used for the production of silver surface artificial leather can be used without any particular limitation.

The apparent density of the artificial leather obtained as described above is not particularly limited, but the range of 0.25 to 0.35 g / cm ³ is a balance between durability, light weight, and buckling resistance. From the point which is excellent in it. The thickness of the artificial leather is not particularly limited, but is preferably in the range of about 0.3 to 4 mm.

  EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples. Moreover, the part and% which are described in an Example are related with mass unless there is particular notice.

First, the measurement method and the evaluation method used in this example will be described together.
[Measurement of total hollowness of cross section of polyolefin hollow filament and hollowness per hollow part]
Twenty cross-sections of polyolefin hollow filaments in the thickness direction of the obtained artificial leather base material were photographed with a scanning electron microscope at a magnification of about 1000 to 2000 times. In addition, 20 pieces were selected so as not to be biased so as to be averaged as much as possible.
And for each of the cross sections perpendicular to the axial direction of the 20 polyolefin hollow filaments observed in the selected image, the area within the outer contour (total cross-sectional area: S1), included in the cross section The total cross-sectional area of all the hollow portions (total hollow area: S2) and the area per hollow portion included in each cross-section (hollow area per piece: S3) were determined. And the total hollow rate of each cross section of a polyolefin hollow filament and the hollow rate per hollow part were computed by the following formula | equation (1) and Formula (2).
・ Total hollowness (%) = S2 / S1 × 100 (1)
・ Hollow rate per hollow part (%) = S3 / S1 × 100 (2)
And the total hollow rate and the hollow rate per hollow part in the cross section of 20 polyolefin hollow filaments were averaged.
In addition, although the measurement of each area of S1-S3 was performed with the image processing apparatus, you may calculate based on the weight of the photographic paper measured by cutting out each part from an image photograph.

[Ratio of the length of the portion adhering to the polymer elastic body to the length of the outer periphery of the cross section of the polyolefin hollow filament]
A cross section in the thickness direction of the obtained base material for artificial leather was observed at a magnification of about 500 to 1000 using a scanning electron microscope. Then, a plurality of images of the observation field of view having 1 to 10 cross sections perpendicular to the axial direction of the polyolefin hollow filament were taken.
Then, from each of the obtained images, a total of 50 cross sections were selected so as not to be biased so as to be averaged as much as possible. Then, the outer peripheral length of each cross section and the length of the outer peripheral portion bonded to the polymer elastic body in each cross section are measured, and the polymer elastic body is bonded to the entire length of the outer periphery for each cross section. The ratio of the length of the outer peripheral part which is doing was calculated. And the arithmetic average of the value of the ratio of the length of the part which the polymer elastic body has adhere | attached with respect to the full length of the outer periphery of 50 cross sections was computed.

[Measurement of apparent density of base material for artificial leather]
The apparent density (g / cm ³ ) was obtained by dividing the mass (g / cm ² ) per unit area of the obtained base material for artificial leather by the thickness (cm). The result is the arithmetic average value of the apparent density measured for any 10 locations. The thickness was measured under a load of 240 gf / cm ² according to JISL1096.

[Method of measuring peel strength of base material for artificial leather]
After lightly shaving the surface of a 15 mm long, 2.5 cm wide, 5 mm thick polyurethane rubber plate with sandpaper, a two-part cross-linked polyurethane adhesive is uniformly applied to the surface within a range of about 10 cm in width from one end. Applied. On the other hand, the same adhesive was uniformly applied in the range of about 10 cm in width from one end to the surface of a test piece of a base material for artificial leather cut out to a length of 25 cm and a width of 2.5 cm. The ends of the polyurethane rubber plate and the artificial leather base material coated with the adhesives were bonded together and pressed at a pressure of about ² to 4 kg / cm ² , and then at 25 ° C. for one day and night. I left it alone.
Then, one end of each of the test pieces of the polyurethane rubber plate and the artificial leather base material on which the adhesive was not applied was sandwiched between chucks of a tensile tester, and a peel strength test was performed at a tensile speed of 10 cm / min. . The initial chuck distance was 50 mm.
In the tensile test, the value when the peel strength exceeding the slope of the rising of the tensile time-peel strength curve was almost constant was defined as the peel strength. About one type of base material for artificial leather, measurement was performed at n = 3, and the arithmetic average value of the peel strength was obtained.

[Method of measuring tear strength of base materials for artificial leather]
The obtained base material for artificial leather was cut into a length of 10 cm and a width of 4 cm to prepare a test piece. Then, in the center of the short side of the obtained test piece (2 cm from both ends in the width direction), a 5 cm cut is made perpendicular to the short side (parallel to the length direction), and each tongue piece is the same as the peel strength measurement method. Was sandwiched between chucks of a tensile tester. And the tearing stress when tension | pulling at a tension speed of 10 cm / min was measured. The maximum value of the tear stress read from the chart obtained by the measurement was taken as the tear strength. About one type of base material for artificial leather, measurement was performed at n = 3, and the arithmetic average value of the peel strength was obtained.

[Buckling resistance test]
A bent shape generated when the sample cut into a 200 × 200 mm square was folded so that the upper end and the lower end were aligned was visually observed. And it determined with the following references | standards.
Good: A fine and uniform fold wrinkle was generated on the surface, similar to the case where cowhide was folded.
Defect: Rough wrinkles such as corrugated cardboard were generated on the folded surface.

[Flexibility test]
A test piece of 20 cm × 20 cm was cut out from the obtained base material for artificial leather. And it judged by the tactile sensation when putting the test piece in the palm.

[Example 1]
Polypropylene as sea component, water-soluble thermoplastic PVA as island component, sea island type composite fiber strand of 12 islands with sea component / island component mass ratio of 60/40 is ejected from melt compound spinning die at 240 ° C did. In addition, Prime Polypro Y-2005GP (melting point: 162 ° C., MFR measured by M method of JIS K7210: 20) is used as polypropylene, and Exeval CP-4104MI (melting point: 209 ° C.) manufactured by Kuraray is used as the water-soluble thermoplastic PVA. , MFR measured by M method of JIS K7210: 80) was used.
The resin strand discharged from the die was cooled while being stretched and thinned by an air jet suction device installed directly below the die, thereby spinning a sea-island composite filament having an average fineness of 2.5 dtex. The suction force of the air jet suction device was adjusted so that the spinning speed obtained indirectly from the ratio of the discharge amount per unit time and the fineness of the obtained long fibers was 3000 m / min. Then, the sea-island type composite filament is continuously collected on a mobile net installed just under the air jet suction device, and pressed at a linear pressure of 25 kg / cm using a metal roll having a surface temperature of 50 ° C. A spunbond sheet of / m ² was obtained.

The spunbond sheets were overlapped using a cross wrapper so as to have a basis weight equivalent to eight sheets. Further, the needle breakage preventing oil was uniformly applied to the surface of the spunbond sheet using a spray. Next, using a 1-barb felt needle with a distance of 5 mm from the needle tip to the barb, the needle tip stabbed into the spunbond sheet protrudes up to 10 mm from the opposite side, and the needles are alternately placed on both sides of the spunbond sheet. A punching process was performed. A needle punching process was performed so that the total number of pierced needles was 1200 / cm ^2, and the sea-island composite filaments were entangled with each other, thereby obtaining an entangled web having a basis weight of 350 g / m ² . The entangled web was heated with hot air at 140 ° C. to soften the polypropylene, and then immediately pressed with a pair of smooth metal rolls having a surface temperature of 145 ° C. to compress the thickness to 85% before pressing. . In this way, an entangled web having a thickness of 1.6 mm, a density of 0.205 g / cm ³ and a smooth surface was obtained.

  Next, the entangled web after pressing was impregnated with an aqueous polyurethane emulsion having a solid content of 35% by mass (Evaphanol APC-48 manufactured by Nikka Chemical Co., Ltd.). The polymer elastic body was solidified by performing a drying process and a curing process with hot air at 150 ° C.

Next, using a flow dyeing machine, entangled in 95 ° C hot water containing 0.1% nonionic surfactant (Sunmol BK-57NM manufactured by Nikka Chemical Co., Ltd.) with an HLB of 5.5. PVA as an island component was dissolved and removed from the sea-island type composite filament in the web. And by carrying out a drying process, a base material for artificial leather comprising a polyurethane hollow filament three-dimensional entangled nonwoven fabric having a thickness of 1.45 mm and a basis weight of 350 g / m ² and having 12 hollow portions in the cross section and polyurethane is obtained. Obtained.

The mass ratio of the polypropylene hollow filament and polyurethane of the obtained base material for artificial leather was polypropylene hollow filament / polyurethane = 60/40. The total hollowness of the cross section of the polypropylene hollow filament was 35%, and the hollowness per hollow part was about 2.9%. Further, there is a space at the interface between the outer periphery of the cross-section of the polypropylene hollow filament and the polyurethane, and the ratio of the length of the portion bonded to the polyurethane to the outer peripheral length of the cross-section of the polyolefin hollow filament is 19%. Met.
The artificial leather substrate thus obtained was evaluated by the method described above. The results are shown in Table 1.

[Examples 2 to 4]
Except for changing the number of islands of the sea-island composite fiber strand, the sea component / island component mass ratio, and the fineness of the filament as shown in Table 1, under the spinning conditions of the sea-island composite filament of Example 1, Example 1 and Similarly, a base material for artificial leather was obtained. The base material for artificial leather thus obtained was evaluated. The results are shown in Table 1.

[Examples 5 to 6]
A base material for artificial leather was obtained in the same manner as in Example 1 except that the solid content concentration of the aqueous polyurethane emulsion was changed as shown in Table 1 in the production of the base material for artificial leather of Example 1. The base material for artificial leather thus obtained was evaluated. The results are shown in Table 1.

[Example 7]
Manufacture of the artificial leather substrate of Example 1 was performed in the same manner as in Example 1 except that an aqueous acrylic emulsion (Casesol ARS-2 manufactured by Nikka Chemical Co., Ltd.) was used instead of the aqueous polyurethane emulsion. A leather substrate was obtained. The base material for artificial leather thus obtained was evaluated. The results are shown in Table 1.

[Comparative Example 1]
A base material for artificial leather was obtained in the same manner as in Example 1 except that the number of islands of the sea-island composite fiber strand was changed to 1 as shown in Table 1 under the spinning conditions of the sea-island composite filament of Example 1. . The base material for artificial leather thus obtained was evaluated. The results are shown in Table 1.

[Comparative Example 2]
A base material for artificial leather was obtained in the same manner as in Example 1 except that the solid content concentration of the aqueous polyurethane emulsion was changed as shown in Table 1 in the production of the base material for artificial leather of Example 1. The base material for artificial leather thus obtained was evaluated. The results are shown in Table 1.

[Comparative Example 3]
In the same manner as in Example 1, the sea-island type composite fiber strand discharged from the die was wound up at 3000 m / min. The obtained fiber was crimped and cut to obtain a staple having a length of 2.5 dtex and a cut length of 51 mm. And the entangled sheet | seat of 30 g / m < ² > of fabric weights was obtained by making the obtained staple entangled using a card | curd. Then, instead of using the spunbonded sheet having a basis weight of 30 g / m ^2, except for using an entangled sheet obtained basis weight 30 g / m ^2, to obtain an artificial leather substrate for in the same manner as in Example 1. The base material for artificial leather thus obtained was evaluated. The results are shown in Table 1.

[Comparative Example 4]
Instead of using polypropylene as the sea component, nylon 6 (UBE nylon 1015B manufactured by Ube Industries) was used, and instead of pressing with a metal roll at 145 ° C., pressing with a metal roll at 180 ° C. was performed as in Example 1. Thus, a base material for artificial leather was obtained. The base material for artificial leather thus obtained was evaluated. The results are shown in Table 1.

From the results shown in Table 1, all of the artificial leather substrates of Examples 1 to 7 had an apparent density of 0.24 g / cm ³ or less and were excellent in lightness. Further, the peel strength is 11.9 kg / 2.5 cm or more, the tear strength is 11.0 kg or more, and it can be seen that both have excellent durability. Furthermore, in the buckling resistance test, fine wrinkles were uniformly expressed at the time of bending and wrinkles disappeared after the bending was eliminated. Moreover, in the flexibility test, the flexibility was maintained even though there was a waist.
On the other hand, the base material for artificial leather of Comparative Example 1 has only one hollow portion with a hollowness ratio of 35%. According to such a hollow structure, the apparent density was 0.31 g / cm ³ and the lightness was poor. Further, in the buckling resistance test, rough and deep wrinkles were generated at the time of bending, and wrinkles remained even after the bending was eliminated.
In addition, the base material for artificial leather of Comparative Example 2 is soft to the touch, but has a low quality in which wrinkles generated on the surface of the base material remain during processing. Even after it was resolved, it remained a habit.
The base material for artificial leather of Comparative Example 3 includes a three-dimensional entangled nonwoven fabric made of polyolefin hollow fiber staples. When such a three-dimensional entangled nonwoven fabric made of staples is used, the peel strength and tear strength are remarkably lowered, so that it does not have the durability required for artificial leather for sports shoes.
The base material for artificial leather of Comparative Example 4 includes a three-dimensional entangled nonwoven fabric made of hollow filaments made of nylon 6. In the base material for artificial leather including such a three-dimensional entangled nonwoven fabric made of nylon 6 made of nylon 6, a large amount of polyurethane was adhered to the surface of the hollow filament, and there were few voids on the surface of the hollow filament. . Thereby, the texture was extremely hard. In the buckling resistance test, rough and deep creases occurred during bending, and the creases remained after the bending was resolved.

  The base material for artificial leather of the present invention has excellent lightness, durability, flexible texture and buckling resistance required for uses such as sports shoes and bags. Therefore, it is preferably used as a base material for footwear such as sports shoes and men's shoes, and a base material for bags and the like.

    DESCRIPTION OF SYMBOLS 1 Three-dimensional entangled nonwoven fabric, 1a Polyolefin hollow filament, 2 Polymer elastic body, 3 Base material for artificial leather, 4 Resin skin layer, v Hollow part

Claims (7)

A base material for artificial leather comprising a three-dimensional entangled nonwoven fabric and a polymer elastic body impregnated in the three-dimensional entangled nonwoven fabric,
The three-dimensional entangled nonwoven fabric comprises a polyolefin hollow filament having a fineness of 0.5 to 5 dtex,
The cross section of the polyolefin hollow filament has 5 to 50 hollow portions having a total hollow ratio of 25 to 50% and a hollow ratio of 1 to 5% per piece,
The content ratio of the polymer elastic body is in a range of 15 to 50 mass% with respect to the total amount of the three-dimensional entangled nonwoven fabric and the polymer elastic body,
A base material for artificial leather, wherein a ratio of a portion adhering to the polymer elastic body is in a range of 0 to 30% on an outer periphery of the cross section. The base material for artificial leather according to claim 1, wherein the apparent density is in the range of 0.20 to 0.25 g / cm ³ .   The base material for artificial leather according to claim 1 or 2, wherein the polymer elastic body is polyurethane.   The artificial leather containing the base material for artificial leather according to any one of claims 1 to 3, and a resin skin layer formed on the surface thereof. A polyolefin resin is used as a sea component, and a resin other than a polyolefin resin that can be selectively extracted and removed that is different in chemical or physical properties from the polyolefin resin is used as an island component, and the number of island components in the fiber cross section is 5 to 50. A step of producing a sea-island type composite filament having a fineness of 0.5 to 5 dtex , wherein the area ratio per piece of the island component is 1 to 5%, and a spunbond comprising the sea-island type composite filament A step of producing a sheet (step 2), a step of forming an entangled web by needle punching an overlapped body of two or more spunbond sheets (step 3), and the entangled web heat pressing to process (step 4), the heat pressed the entangled web was impregnated with an aqueous resin solution of the elastic polymer, coagulating dried elastic polymer A step of (step 5), wherein after the step 5, the polyolefin hollow filaments by dissolving and removing the resin other than the polyolefin resin before Symbol island composite filament while providing physical deformation to the sea-island type composite filament Forming a three-dimensional entangled nonwoven fabric comprising (step 6),
The ratio of the resin other than the polyolefin-based resin in the sea-island composite filament is in the range of 25 to 60% by mass , and the total hollowness of the polyolefin hollow filament is in the range of 25 to 50% .
The amount of impregnation of the aqueous resin liquid is an amount that makes the polymer elastic body 15 to 50% by mass with respect to the total amount of the polyolefin hollow filament and the polymer elastic body. Method for manufacturing a substrate.   The resin other than the polyolefin-based resin is a water-soluble thermoplastic polyvinyl alcohol having an average polymerization degree of 200 to 500, a saponification degree of 90 to 99.99 mol%, and a melting point of 160 to 230 ° C.
  The said process 6 is a manufacturing method of the base material for artificial leather of Claim 5 provided with the process of melt | dissolving and removing the said water-soluble thermoplastic polyvinyl alcohol with the hot water containing a nonionic surfactant. The method for producing a base material for artificial leather according to claim 5 or 6 , wherein the aqueous resin liquid is an aqueous polyurethane emulsion.

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