WO2025023132A1 - Artificial leather and method for producing artificial leather - Google Patents

Abstract

The present invention addresses the problem of providing: an artificial leather having excellent texture, surface wear resistance, and pilling resistance; and a method for producing the artificial leather.　This artificial leather contains ultrafine fibers. With respect to cut surfaces when the artificial leather is cut at a depth of 0.3mm from the surface, the maximum area of the cut surfaces of the ultrafine fiber bundles is 4500 μm² or more, and the ratio of the number of ultrafine fiber bundles for which the area of the cut surfaces thereof are at least 500 μm² to the total number of cut surfaces of the ultrafine fiber bundles is 60% or more.

Description

Artificial leather and method for manufacturing artificial leather

The present invention relates to artificial leather and a method for manufacturing artificial leather.

2. Description of the Related Art Leather-like sheets such as artificial leather have flexibility and functionality not found in natural leather and are therefore used in a variety of applications such as clothing and materials.
Moreover, artificial leathers are required to satisfy not only sensory requirements such as appearance (a surface texture closer to that of natural leather), feel (a combination of a soft touch and a moderate sense of fullness and solidity), and color development (vividness and depth of color), but also physical property requirements such as light fastness, pilling resistance, and abrasion resistance at a high level. To meet these requirements, various proposals have been made.

For example, Patent Document 1 describes a leather-like sheet including an ultrafine fiber entangled body made of ultrafine fiber bundles and a polymeric elastomer provided inside the ultrafine fiber bundles, in which the ultrafine fiber bundles are made of ultrafine single fibers having an average cross-sectional area of 0.1 to 30 ^μm2 , the average cross-sectional area of which is 40 to 400 ^μm2 , and the ultrafine fiber bundles are present at a density of 600 to 4000 pieces/ ^mm2 in any cross section parallel to the thickness direction of the ultrafine fiber entangled body. The leather-like sheet is described as having a luxurious appearance, good quality stability such as robustness and surface abrasion resistance, and excellent practicality.
Also, for example, Patent Document 2 describes an artificial leather substrate made of a nonwoven fabric structure of ultrafine long fiber bundles, in which the ultrafine long fiber bundles have a cross-sectional area of 170 to 700 μm ² and an aspect ratio of 4.0 or less, and in any cross section parallel to the thickness direction of the nonwoven fabric structure, the cross sections of the ultrafine long fiber bundles are present in a range of 1500 to 3000 pieces/mm ^2. The above artificial leather substrate is described as having high levels of both sensory performance and physical property performance, which have been conventionally recognized as mutually exclusive performances.

International Publication No. 2007/040144 JP 2008-308784 A

As described in Patent Documents 1 and 2, artificial leather is generally produced by stapling multicomponent fibers spun from two types of polymers with different solubilities and degradability, forming a web of the desired weight using a card, cross wrapper, random weber, etc., and then entangling the fibers with each other using a needle punch, water jet, etc. to form an entangled nonwoven fabric. After that, a solution or emulsion of a polymeric elastomer such as polyurethane is applied to the fabric to coagulate it, and then one of the components in the multicomponent fibers is removed or reduced to form ultrafine fibers, or by performing the above process of impregnating and coagulating the polymeric elastomer and the process of forming the multicomponent fibers into ultrafine fibers in the reverse order.

Although the techniques described in Patent Documents 1 and 2 improve the quality of artificial leather, they have problems such as the tendency for fibers to come off and unsatisfactory surface abrasion resistance and pilling resistance, and so on. Thus, there has been a demand for artificial leather that can satisfy sensory and physical property requirements at an even higher level.
In addition, when an organic solvent or a polymeric elastomer is applied to the surface of the artificial leather, it is possible to suppress the fiber from coming off and to improve the abrasion resistance and pilling resistance of the surface to some extent. However, this increases the cost, and the use of an organic solvent has a problem of adverse effects on the human body and the environment.

The present invention aims to solve the above-mentioned problems and provide artificial leather that has excellent texture, surface abrasion resistance, and pilling resistance, as well as a manufacturing method for the artificial leather.

After extensive investigation, the inventors discovered that the above problems could be solved by ensuring that the maximum area of the cut surface of the ultrafine fiber bundles is equal to or greater than a specified value, and that the percentage of the number of ultrafine fiber bundles is equal to or greater than a specified value, when the cut surface is cut at a depth of 0.3 mm from the surface, and thus arrived at the present invention. In other words, the present invention encompasses the following inventions.

[1] An artificial leather containing ultrafine fibers,
An artificial leather, wherein, in a cut surface when cut at a depth of 0.3 mm from the surface, the maximum area of the cut surface of the ultrafine fiber bundle is 4,500 ^µm2 or more, and the proportion of the number of the ultrafine fiber bundles having a cut surface area of 500 µm2 or ^more to the total number of the cut surfaces of the ultrafine fiber bundles is 60% or more.
[2] The artificial leather according to the above-mentioned [1], wherein the total area of the ultrafine fiber bundles in the cut surface is 50,000 µm ² /mm ² or more.
[3] The artificial leather according to the above [1] or [2], wherein the average diameter of the ultrafine fibers is 7.5 μm or less.
[4] The artificial leather according to any one of the above [1] to [3], wherein the average fineness of the ultrafine fibers is 0.5 dtex or less.
[5] The artificial leather according to any one of the above [1] to [4], wherein the ultrafine fibers are long fibers.
[6] The artificial leather according to any one of the above [1] to [5], containing 45% by mass or less of a polymer elastomer.
[7] A method for producing an artificial leather according to any one of [1] to [6] above,
Providing a fibrous web formed from microfiber-generating fibers;
A step of subjecting the fiber web to a crimping treatment to form a crimped fiber web;
forming a web laminate by stacking a plurality of the crimped fiber webs;
entangling the web laminate to form an entangled fiber sheet;
and removing at least one component from the ultrafine fibers.
[8] The method for producing an artificial leather according to the above [7], further comprising a step of impregnating the entangled fiber sheet with the polymer elastomer.

The present invention can provide artificial leather that is excellent in texture, surface abrasion resistance, and pilling resistance, and a method for producing the artificial leather. Furthermore, the present invention can provide artificial leather that has the above-mentioned effects without applying an organic solvent or a polymer elastomer to the surface of the artificial leather.

This is a scanning electron microscope (SEM) image taken at 100x magnification of the cut surface of the remaining side of the artificial leather according to the present invention, which was sliced off at a depth of 0.3 mm from the surface with a single-edged razor. The image in Figure 1 was printed, the printed side was placed under a flat panel light, and light was shone from the printed side, allowing the image to be seen through to the back side. The cut surfaces of the ultrafine fiber bundles present on the cut surface were then painted black from the back side, resulting in a transferred image (an image in which the left and right sides of Figure 1 are reversed).

The artificial leather according to the embodiment of the present invention and the manufacturing method of the artificial leather according to the embodiment of the present invention (hereinafter, sometimes referred to as "artificial leather according to the present embodiment" or "manufacturing method of the artificial leather according to the present embodiment") will be described below.

[Artificial leather]
The artificial leather of the present embodiment is an artificial leather containing ultrafine fibers, and in a cut surface when cut at a depth of 0.3 mm from the surface, the maximum area of the cut surface of the ultrafine fiber bundles is 4,500 ^µm2 or more, and the proportion of the number of the ultrafine fiber bundles having a cut surface area of 500 µm2 ^or more to the total number of the cut surfaces of the ultrafine fiber bundles is 60% or more.
The above-mentioned artificial leather has a maximum area of the cut surface of the ultrafine fiber bundles that is a predetermined value or more, and the number ratio of the ultrafine fiber bundles that is a predetermined value or more, when cut at a depth of 0.3 mm from the surface, so that the artificial leather has excellent texture, surface abrasion resistance, and pilling resistance.
The artificial leather of the present invention means an artificially produced leather having a texture similar to that of natural leather, and includes raised artificial leather with a raised surface, grained artificial leather, etc. Furthermore, raised artificial leather includes suede-like, velour-like, nubuck-like, etc., as variations depending on the raised surface state.
In this specification, "a cut surface when cut at a depth of 0.3 mm from the surface" means, in the case of napped artificial leather, a cut surface when sliced at a position where the difference between the thickness of the napped artificial leather and the thickness from the surface opposite to the fiber napped surface to the cut surface is 0.3 mm, and in the case of grain-finished artificial leather, means a cut surface when sliced at a position where the difference between the thickness of the fiber layer constituting the grain-finished artificial leather and the thickness from the surface of the fiber layer opposite to the surface in contact with the resin layer to the cut surface is 0.3 mm. Note that this cut surface is a surface parallel to the surface direction of the artificial leather and perpendicular to the thickness direction.
In addition, in this specification, "excellent texture" means that the texture is close to that of natural leather, such as excellent density, flexibility, and a good feel.

The thickness of the artificial leather of the present embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, it is preferably 0.1 to 2.0 mm, more preferably 0.3 to 1.5 mm, and even more preferably 0.5 to 1.2 mm.
The above "thickness" is a value measured in accordance with JIS L1096 (2010) (Method A).

The apparent density of the artificial leather of the present embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, it is preferably 0.1 to 1.0 g/cm ³ , more preferably 0.2 to 0.9 g/cm ³ , and even more preferably 0.3 to 0.8 g/cm ³ .
The above "apparent density" is a value measured in accordance with JIS L1096 (2010) (Method A).

The basis weight of the artificial leather of the present embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, it is preferably 100 to 1000 g/m ² , more preferably 150 to 800 g/m ² , and even more preferably 200 to 600 g/m ² .
The above "basis weight" is a value measured in accordance with JIS L1096 (2010) (Method A).

The artificial leather of this embodiment is not particularly limited, but from the viewpoint of more easily obtaining the effects of the present invention, it is preferable that the artificial leather is a napped artificial leather having a napped surface.

<Ultrafine fibers>
The ultrafine fibers contained in the artificial leather of this embodiment are ultrafine fibers obtained by removing at least one component from a multicomponent fiber (composite fiber) made of at least two or more kinds of spinnable polymers having different chemical or physical properties. The ultrafine fiber bundle in the present invention is a bundle of a plurality of ultrafine fibers, and refers to an assembly of ultrafine fibers in which three or more ultrafine fibers are gathered together and are adjacent to each other with a distance between the ultrafine fibers of 6 μm or less, and the total area of the cut surfaces of the gathered ultrafine fibers is 60 ^μm2 or more.

The ultrafine fibers of the present embodiment are preferably long fibers from the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance.
In this specification, "long fibers" means continuous fibers that are not short fibers intentionally cut after spinning. More specifically, it means filaments or continuous fibers that are not short fibers intentionally cut to a fiber length of about 3 to 80 mm. The fiber length of the islands-in-the-sea type composite fiber before being made into ultrafine fibers, which will be described later, is preferably 100 mm or more, and more preferably 200 mm or more. As long as it is technically possible to produce it and it is not unavoidably cut in the production process, the long fibers may be continuous fibers having a fiber length of several meters, several hundred meters, several kilometers, or more that are produced, for example, by a spunbonding method and continuously spun. Note that, in some cases, the long fibers are inevitably cut into short fibers in the production process due to needle punching during entanglement or surface buffing.

Examples of resins constituting the ultrafine fibers of this embodiment include modified PET such as polyethylene terephthalate (hereinafter sometimes referred to as "PET"), isophthalic acid modified PET, sulfoisophthalic acid modified PET, and cationic dye dyeable PET; aromatic polyesters such as polybutylene terephthalate and polyhexamethylene terephthalate; aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalerate resin; nylons such as nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, and nylon 6-12; and fibers such as polypropylene, polyethylene, polybutene, polymethylpentene, and chlorine-based polyolefins. The modified PET is a PET in which at least a part of the ester-forming dicarboxylic acid monomer units or diol monomer units of unmodified PET is replaced with a substitutable monomer unit. Specific examples of modified monomer units substituting dicarboxylic acid monomer units include units derived from isophthalic acid, sodium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, adipic acid, etc., which substitute terephthalic acid units. Specific examples of modified monomer units substituting diol monomer units include units derived from diols such as butanediol and hexanediol, which substitute ethylene glycol units.
Among these, from the viewpoint of obtaining an artificial leather excellent in colorability, surface abrasion resistance, and pilling resistance, polyester-based resins such as aromatic polyesters and aliphatic polyesters are preferred. Also, from the viewpoint of productivity during spinning, mechanical strength, etc., preferred are modified PET such as polyethylene terephthalate (PET), isophthalic acid-modified PET, sulfoisophthalic acid-modified PET, and cationic dye-dyeable PET, aromatic polyesters such as polybutylene terephthalate and polyhexamethylene terephthalate, aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalerate resin, nylons such as nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, and nylon 6-12, and polyolefins such as polypropylene, polyethylene, polybutene, polymethylpentene, and chlorine-based polyolefins.

The resin constituting the ultrafine fibers of this embodiment may contain various additives to the extent that the effect of the present invention is not impaired. Examples of additives include catalysts, colorants, heat resistance agents, flame retardants, lubricants, stain-resistant agents, fluorescent brighteners, matting agents, gloss improvers, antistatic agents, fragrances, deodorizers, antibacterial agents, anti-mite agents, inorganic fine particles, etc.

In the artificial leather of the present embodiment, the maximum area of the cut surface of the ultrafine fiber bundles when cut at a depth of 0.3 mm from the surface is 4,500 μm2 or ^more .
From the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, the maximum area of the cut surface of the ultrafine fiber bundle is preferably 5000 μm ² or more, more preferably 5500 μm ² or more, and even more preferably 6000 μm ² or more, and from the viewpoint of obtaining an artificial leather having ease of production and excellent appearance, the maximum area of the cut surface of the ultrafine fiber bundle is preferably 30000 μm ² or less, more preferably 25000 μm ² or less, and even more preferably 20000 μm ² or less. That is, the maximum area of the cut surface of the ultrafine fiber bundle is preferably 5000 to 30000 μm ² , more preferably 5500 to 25000 μm ² , and even more preferably 6000 to 20000 μm ² .
The "maximum area of the cut surface of the ultrafine fiber bundle" is a value calculated based on a photograph of the cut surface when the artificial leather is cut at a depth of 0.3 mm from the surface thereof, taken with a scanning electron microscope (SEM) at 100 times magnification, and specifically, is measured by the procedure described in the Examples.

In the artificial leather of this embodiment, in a cut surface when cut at a depth of 0.3 mm from the surface, the ratio of the number of ultrafine fiber bundles having a cut surface area of 500 µm2 or ^more to the total number of cut surfaces of the ultrafine fiber bundles is 60% or more.
The ratio of the number of the ultrafine fiber bundles having a cut surface area of 500 ^μm2 or more to the total number of the cut surfaces of the ultrafine fiber bundles is preferably 61% or more, more preferably 63% or more, and even more preferably 65% or more, from the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, and when the artificial leather has a fiber-raised surface, from the viewpoint of deterioration in appearance due to the base being visible through gaps in the napped fibers, is preferably 95% or less, more preferably 93% or less, and even more preferably 90% or less. That is, the ratio of the number is preferably 61 to 95%, more preferably 63 to 93%, and even more preferably 65 to 90%.
The above-mentioned "proportion of the number of ultrafine fiber bundles having a cut surface area of 500 ^µm2 or more relative to the total number of cut surfaces of the ultrafine fiber bundles" is a value calculated based on a photograph of a cut surface when the artificial leather is cut at a depth of 0.3 mm from the surface thereof, taken with a scanning electron microscope (SEM) at 100 times magnification, and specifically, is measured by the procedure described in the Examples.

The total area of the cut surfaces of the ultrafine fiber bundles at a cut surface at a depth of 0.3 mm from the surface (the value obtained by converting the total value of the areas of the cut surfaces of the ultrafine fiber bundles ^per mm2) is preferably 25,000 ^μm2 /mm2 or ^more , more preferably 40,000 ^μm2 /mm2 or ^more , and even more preferably 50,000 μm2/mm2 or more, from the viewpoint of obtaining an artificial leather having excellent texture, surface abrasion resistance, and pilling resistance, and is preferably 200,000 ^μm2 /mm2 ^or less, more preferably 180,000 ^μm2 /mm2 ^{or less} , and even more preferably ^{150,000 μm2 /} mm2 or ^less , from the viewpoint of obtaining an artificial leather having ease of production and good tear strength. That is, the total area of the cut surfaces of the ultrafine fiber bundle is preferably 25,000 to 200,000 μm ² /mm ² , more preferably 40,000 to 180,000 μm ² /mm ² , and even more preferably 50,000 to 150,000 μm ² /mm ² .
The "total area of the cut surfaces of the ultrafine fiber bundles" is a value calculated based on a photograph of the cut surfaces when the artificial leather is cut at a depth of 0.3 mm from the surface thereof, taken with a scanning electron microscope (SEM) at 100 times magnification, and specifically, is measured by the procedure described in the Examples.

The average diameter of the ultrafine fibers of this embodiment is preferably 7.5 μm or less, more preferably 6.0 μm or less, even more preferably 5.5 μm or less, and even more preferably 5.0 μm or less, from the viewpoint of obtaining artificial leather with better texture, surface abrasion resistance, and pilling resistance. There is no particular lower limit, but from the viewpoint of ease of production and color development, it is, for example, 1.0 μm or more, or 1.5 μm or more. In other words, the average diameter of the ultrafine fibers of this embodiment is preferably 1.0 to 7.5 μm, and more preferably 1.5 to 6.0 μm.

From the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, the average fineness of the ultrafine fibers of this embodiment is preferably 0.50 dtex or less, more preferably 0.40 dtex or less, and even more preferably 0.30 dtex or less. There is no particular lower limit, but from the viewpoint of ease of production and color development, it is, for example, 0.01 dtex or more, or 0.02 dtex or more. In other words, the average fineness of the ultrafine fibers of this embodiment is preferably 0.01 to 0.50 dtex, and more preferably 0.01 to 0.40 dtex.
The "average diameter" and "average fineness" are values calculated based on the cross-sectional areas of a plurality of ultrafine fibers randomly selected from an enlarged photograph of the cross sections of the ultrafine fibers, and are specifically measured by the procedure described in the Examples.

<Polymer elastomer>
The artificial leather of the present embodiment may contain a polymer elastomer.
The polymer elastomer may be any that has been conventionally used in artificial leathers. Specific examples include polyurethane elastomers, acrylonitrile elastomers, olefin elastomers, polyester elastomers, and acrylic elastomers, with polyurethane elastomers and acrylic elastomers being preferred.
Examples of the polyurethane elastomer include various polyurethane elastomers obtained by combining, as main components, at least one polymer polyol having an average molecular weight of 500 to 3000 selected from polyester diols, polyether diols, polyether ester diols, polycarbonate diols, polycarbonate ether diols, polycarbonate ester diols, and the like, and at least one polyisocyanate selected from aromatic, alicyclic, and aliphatic diisocyanates, such as 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate, and further combining at least one low molecular weight compound having two or more active hydrogen atoms, such as ethylene glycol and ethylenediamine, in a predetermined molar ratio, and polymerizing these in one stage or multiple stages by a melt polymerization method, a bulk polymerization method, a solution polymerization method, or the like.
The content of the polymer polyol component in the polyurethane elastomer is preferably 15 to 90% by mass.

The acrylic elastomer may be a monomer having a homopolymer glass transition temperature in the range of -90 to -5°C, preferably a non-crosslinkable monomer, such as at least one soft component selected from the group consisting of methyl acrylate, n-butyl acrylate, isobutyl acrylate, isopropyl acrylate, n-hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and a monomer having a homopolymer glass transition temperature in the range of 50 to 250°C, preferably a non-crosslinkable monomer, such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, or 2-ethylhexyl methacrylate. Examples of such acrylic elastomers include various acrylic elastomers obtained by polymerizing at least one hard component selected from the group consisting of acrylic acid, (meth)acrylic acid, and a monofunctional or polyfunctional ethylenically unsaturated monomer unit capable of forming a crosslinked structure, or an ethylenically unsaturated monomer unit introduced into a polymer chain that can react to form a crosslinked structure, such as at least one ethylenically unsaturated monomer that is a crosslinkable component selected from the group consisting of ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate.

Artificial leathers obtained by using polyurethane elastomers as the main polymeric elastomers are preferred because they have a good balance of texture and mechanical properties, and if the type is appropriately selected, they also have a good balance including durability. Artificial leathers obtained by using acrylic elastomers are unsuitable for forming napped artificial leathers because the acrylic elastomers have lower adhesion to ultrafine fiber bundles than the polyurethane elastomers and are poor in the nap fixing effect during nap formation, but are particularly preferred for forming grain-finished artificial leathers because the degree of hardening of the texture relative to the content is suppressed.
As the polymer elastomer, different types may be mixed and contained, or different types may be contained in multiple batches. Furthermore, in addition to the above-mentioned polyurethane elastomer, acrylonitrile elastomer, olefin elastomer, polyester elastomer, acrylic elastomer, etc. that serve as the main polymer elastomer, a polymer elastomer such as synthetic rubber may be added as necessary to form a polymer elastomer composition.

The content of the polymer elastomer in the artificial leather is preferably 5 to 45% by mass, more preferably 7 to 40% by mass, and even more preferably 8 to 30% by mass, from the viewpoint of obtaining artificial leather with excellent texture.

<Other Ingredients>
The artificial leather of this embodiment may or may not contain components other than the ultrafine fibers and the polymeric elastomer. Such other components include the other components contained in the ultrafine fibers described above and the same as the various additives that can be added to the polymeric elastomer body fluid described in step (4) below. The other components may be encapsulated in at least one of the ultrafine fibers and the polymeric elastomer.
The content of the other components is preferably 0.5 to 10.0 mass %, more preferably 1.0 to 5.0 mass %, and even more preferably 1.5 to 3.0 mass %, relative to the mass of the artificial leather, from the viewpoints of water absorbency, water repellency, stain resistance, and the like, while making it easier for the other components to exert their intended effects.

[Manufacturing method of artificial leather]
The artificial leather according to the present embodiment is preferably produced by a production method including the following steps (1) to (4) and (6).
Step (1): A step of preparing a fiber web formed from ultrafine fiber generating fibers. Step (2): A step of subjecting the fiber web to a crimping treatment to form a crimped fiber web. Step (3): A step of stacking a plurality of the crimped fiber webs to form a web laminate. Step (4): A step of entangling the web laminate to form an entangled fiber sheet. Step (6): A step of removing at least one component from the ultrafine fiber generating fibers.

In addition, from the viewpoint of imparting a texture and shape stability similar to that of natural leather, the method may include the following step (5), and from the viewpoint of providing an even better texture, the method may include the following step (7).
Step (5): A step of impregnating the entangled fiber sheet with the polymer elastomer. Step (7): A step of dyeing the artificial leather. The step (5) is preferably carried out between the step (4) and the step (6), and the step (7) is preferably carried out after the step (6).

The production method according to the present embodiment, which includes the above-mentioned step (2), makes it easy to obtain an artificial leather in which, when cut at a depth of 0.3 mm from the surface, the maximum area of the cut surface of the ultrafine fiber bundle is 4500 ^μm2 or more, and the proportion of the number of the ultrafine fiber bundles having a cut surface area of 500 μm2 or ^more to the total number of the cut surfaces of the ultrafine fiber bundles is 60% or more. As a result, it makes it easy to obtain an artificial leather that is excellent in texture, surface abrasion resistance, and pilling resistance.
Each step will be described below.

<Step (1)>
Step (1) is a step of preparing a fiber web formed from ultrafine fiber generating fibers.
As described above, ultrafine fibers are fibers that are made ultrafine by removing at least one component from a multicomponent fiber (composite fiber) made of at least two or more kinds of spinnable polymers that differ in chemical or physical properties, and the multicomponent fiber that generates ultrafine fibers is an ultrafine fiber-generating fiber. Representative examples of ultrafine fiber-generating fibers include islands-in-the-sea type composite fibers, multilayer laminated composite fibers, radial laminated composite fibers, etc., which are obtained by using a method such as a chip blend (mixed spinning) method or a composite spinning method. Among these, islands-in-the-sea type composite fibers are preferred from the viewpoint of increasing productivity by high-speed spinning and obtaining artificial leather that is excellent in surface abrasion resistance and pilling resistance, and from the same viewpoint, it is preferred to obtain a fiber web by melt spinning islands-in-the-sea type composite fibers.
When the ultrafine fiber-generating fiber is an islands-in-sea type composite fiber, island components are dispersed in a sea component that serves as a matrix in the fiber cross section, and ultrafine fibers in the form of fiber bundles are generated by removing the sea component.
Hereinafter, a method of using islands-in-sea type composite fibers as ultrafine fiber-forming fibers and obtaining a fiber web by melt spinning the islands-in-sea type composite fibers will be described in more detail.

Examples of the island component resins contained in the islands-in-sea type composite fibers and which later become the ultrafine fibers include the same resins as those constituting the ultrafine fibers in the above-mentioned "ultrafine fibers."
As the sea component resin contained in the islands-in-sea type composite fiber and removed by extraction, decomposition, etc., it is preferable to use a resin that has a different solubility or decomposability from the island component resin and has low compatibility with it. It is preferable to appropriately select such a resin depending on the type of the island component resin and the production method.
Examples of the resin for the sea component include olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer, and resins that are soluble in organic solvents and can be dissolved and removed by organic solvents, such as polystyrene, styrene-acrylic copolymer, and styrene-ethylene copolymer. Other examples include resins that can be removed with water alone without using a solvent, such as polyvinyl alcohol resins, water-soluble polyester resins, modified polyester resins that are easily decomposable by alkali, polyacrylamide resins, and carboxymethyl cellulose resins. Among these, from the viewpoints of melt spinnability, water solubility, and fiber properties (fiber strength), it is preferable to use polyethylene and polyvinyl alcohol resins, and more preferably polyethylene and modified polyvinyl alcohol.

As the type of copolymerization monomer used in the modified polyvinyl alcohol, from the viewpoints of copolymerizability, melt spinnability, and water solubility of the fiber, preferred are α-olefins having 4 or less carbon atoms, such as ethylene, propylene, 1-butene, and isobutene; and vinyl ethers, such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, and n-butyl vinyl ether.
The content of copolymerized units in polyvinyl alcohol is preferably from 1 to 20 mol %, more preferably from 4 to 15 mol %, and even more preferably from 6 to 13 mol %.
Furthermore, since the fiber properties are improved when the copolymerization unit is ethylene, ethylene-modified polyvinyl alcohol is more preferable. The ethylene unit content in the ethylene-modified polyvinyl alcohol is preferably 4 to 15 mol %, more preferably 6 to 13 mol %.

The mass ratio of the sea component and the island component in the islands-in-sea composite fiber is not particularly limited, but is preferably in the range of, for example, sea component:island component = 5:95 to 80:20. If the sea component polymer ratio in the islands-in-sea composite fiber is 5 mass% or more, the spinning stability of the islands-in-sea fiber is unlikely to decrease, and industrial productivity is easily ensured. In addition, when a polymer elastomer is added, voids of the required size are likely to be formed between the ultrafine fiber bundles and the polymer elastomer after the sea component is removed, and as a result, a sense of volume, fullness, dense surface, etc. are easily obtained. On the other hand, if the sea component polymer ratio is 60 mass% or less, the shape and distribution state of the island component in the cross section of the islands-in-sea fiber are stable, making it easy to prevent a decrease in quality stability.

The preferred method for producing a fiber web is to use the so-called spunbond method to collect ultrafine fiber-generating fibers that have been melt-spun onto a net without cutting them, and form a fiber web of long continuous fibers.

Specifically, a conjugate spinning die having a large number of nozzle holes arranged in a predetermined pattern is used to continuously extrude molten strands of islands-in-sea type conjugate fibers from a spinning nozzle at a predetermined extrusion speed, and the strands are substantially cooled and solidified by cooling air at some stage between just below the nozzle holes and the suction device described below. At the same time, a high-velocity air stream is applied to the strands using a suction device such as an air jet nozzle, and the conjugate fibers are uniformly pulled and thinned to a desired diameter or fineness.
The high-speed air stream is applied so that the average spinning speed, which corresponds to the mechanical take-up speed in normal spinning, falls within the range of 1000 to 6000 m/min. Furthermore, a long-fiber fiber web can be produced by a spunbonding method in which the composite fibers are opened by a collision plate, air stream, or the like depending on the texture of the resulting fiber web, and then collected and deposited on a collecting surface such as a conveyor belt-like moving net while being sucked from the opposite side of the net to form a long-fiber web. The fiber web may be subjected to a heat press treatment to impart shape stability, and the fiber web may be fusion-bonded accordingly.

If the basis weight or thickness of the obtained fiber web is insufficient, it is adjusted by wrapping (supplying one fiber web perpendicular to the flow direction of the process and folding it almost in the width direction (horizontal direction), or folding a web supplied parallel to the flow direction of the process in its length direction (vertical direction)) or stacking (stacking a plurality of fiber webs) to obtain the desired basis weight and thickness. When adjusting the shape stability, fiber density, and orientation of islands-in-the-sea fibers in the thickness direction, a mechanical entanglement treatment is performed by a known method such as a needle punch method. This three-dimensionally entangles the fibers constituting the fiber web, particularly the fibers between adjacent layers of wrapped or stacked layered fiber webs.
When the entanglement process is performed by the needle punching method, various process conditions are appropriately selected, such as the type of needle (needle shape and count, barb shape and depth, number and position of barbs, etc.), the number of needle punches (needle punch processing density per unit area obtained by multiplying the density of needles implanted in a needle board by the number of strokes that the board applies to a unit area of a fiber web), and the needle punch depth (depth at which the needles apply to the fiber web).

The entanglement treatment may be performed by needle punching or high-pressure water jet treatment under conditions where at least one or more barbs penetrate simultaneously or alternately from both sides. The punch density of the needle punching treatment is preferably 1500 to 5500 punches/ ^cm2 , more preferably 2000 to 5000 punches/ ^cm2 , in view of the ease of obtaining high abrasion resistance. If the punch density is within the above range, insufficient entanglement is suppressed, preventing the surface of the artificial leather from becoming rough due to fraying of the fibers on the surface, and also preventing fiber breakage from occurring, preventing a decrease in the degree of entanglement.

<Step (2)>
The step (2) is a step of subjecting the fiber web to a crimping treatment to form a crimped fiber web.
Examples of the crimping process include physical and mechanical crimping methods such as passing between two gears, using a press roll (press crimping), rubbing against a knife edge while bending, air injection, and twisting, as well as latent crimping methods using multicomponent fibers or hollow fibers with different thermal shrinkage, and methods using these in combination. The crimping process is preferably a physical and mechanical method that can apply stable crimping to the fibers over a wide range, and press crimping is more preferable from the viewpoint of imparting an appropriate crimp rate to the fibers. Among the press crimping methods, press crimping with a roll having an uneven shape is preferable from the viewpoint of obtaining an artificial leather that has good processability, texture, surface abrasion resistance, and pilling resistance. From the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, the uneven shape is preferably a periodic uneven shape, and the average height difference between the recesses and the protrusions is preferably 1 to 30 mm, more preferably 1.5 to 25 mm, and even more preferably 2 to 20 mm. The distance between the recesses and the distance between the protrusions are preferably 1 to 30 mm, more preferably 1.5 to 25 mm, and even more preferably 2 to 20 mm.

The shrinkage ratio when the fiber web is pressed with a roll having a periodic uneven shape to impart a shrinkage treatment is preferably 120% or more, more preferably 150% or more, and even more preferably 170% or more from the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance, and is preferably 300% or less, more preferably 250% or less, and even more preferably 220% or less from the viewpoint of ease of production. That is, the shrinkage ratio is preferably 120 to 300%, more preferably 150 to 250%, and even more preferably 170 to 220%.
The "shrinkage rate" is the ratio of the length along the uneven shape of the uneven roll to the length of the fiber web before the crimping treatment (length along the uneven shape of the uneven roll/length of the fiber web before the crimping treatment x 100 (%)).
Furthermore, after the crimping treatment, a spray oil and a finishing oil can be applied to the crimped fiber web as long as they do not have an adverse effect.

<Step (3)>
The step (3) is a step of forming a web laminate by stacking a plurality of the crimped fiber webs.
As a method for stacking a plurality of crimped fiber webs, the crimped fiber webs may be stacked with all the crimp directions in the same direction, or the crimped fiber web may be stacked while changing the conveying direction to a 90° direction and folding back by a cross-wrapping method. As a method for stacking a plurality of crimped fiber webs, cross-wrapping lamination is preferred from the viewpoint of easily adjusting the width of the entangled fiber sheet as desired and suppressing the occurrence of unevenness in the width direction of the entangled fiber sheet, i.e., suppressing unevenness in the basis weight.
The number of layers of the fiber web to be laminated is not particularly limited, but from the viewpoints of reducing the basis weight unevenness of the entangled fiber sheet and mechanical strength, it is preferably 2 layers or more, more preferably 3 layers or more, and from the viewpoint of ease of production, it is preferably 30 layers or less, more preferably 25 layers or less. That is, the number of layers of the fiber web to be laminated is preferably 2 to 30 layers, more preferably 3 to 25 layers.

<Step (4)>
Step (4) is a step of entangling the web laminate to form an entangled fiber sheet.
In step (4), the web laminate is subjected to a mechanical entanglement treatment using a known method such as a needle punching method or a high-pressure water jet treatment method, thereby three-dimensionally entangling the fibers constituting the fiber web, particularly the fibers between adjacent layers of a wrapped or stacked layered fiber web.
When the entanglement process is performed by the needle punching method, various process conditions are appropriately selected, such as the type of needle (needle shape and count, barb shape and depth, number and position of barbs, etc.), the number of needle punches (needle punch processing density per unit area obtained by multiplying the density of needles implanted in a needle board by the number of strokes at which the board acts on the fiber web per unit area), and the needle punch depth (depth at which the needles act on the fiber web).
When a web laminate having a crimped fiber web laminated thereon is used and an entanglement treatment is performed by a needle punching method, the crimped fiber web is caught by the barbs, and the moving fibers move with many surrounding fibers, increasing the amount of fibers oriented in the thickness direction and improving the degree of entanglement. This suppresses the fibers from coming off during surface friction, improving the abrasion resistance and pilling resistance. Therefore, it is preferable to use a web laminate having a crimped fiber web laminated thereon and perform an entanglement treatment by a needle punching method.

From the viewpoint of easily obtaining high abrasion resistance, the punch density in the needle punching treatment is preferably 1500 to 5500 punches/cm ² , and more preferably 2000 to 5000 punches/cm ^2. If the punch density is within the above range, insufficient entanglement is suppressed, preventing the surface of the artificial leather from becoming rough due to fraying of the fibers on the surface, and also preventing fiber breakage from causing a decrease in the degree of entanglement.

In addition, at any stage from the spinning of the islands-in-the-sea composite fiber to the entanglement treatment, an oil agent or an antistatic agent may be applied to the ultrafine fiber-generating fiber, fiber web, crimped fiber web, web laminate, entangled fiber sheet, etc. Furthermore, if necessary, the ultrafine fiber-generating fiber, fiber web, crimped fiber web, web laminate, entangled fiber sheet, etc. may be immersed in hot water at about 70 to 150°C for shrinkage treatment to make the entanglement dense in advance.

The basis weight of the entangled fiber sheet obtained by entanglement is preferably in the range of about 100 to 2000 g/ ^m2 . Furthermore, the entangled fiber sheet may be subjected to a treatment to further increase the fiber density and the degree of entanglement by heat shrinking as necessary. In addition, the entangled fiber sheet densified by the heat shrinking treatment may be further densified, and the fiber density may be further increased by a heat press treatment as necessary for the purpose of fixing the shape of the entangled fiber sheet and smoothing the surface.

<Step (5)>
The step (5) is a step of impregnating the entangled fiber sheet with the polymeric elastomer.
In the step (5), the entangled fiber sheet is impregnated with a polymeric elastomer at least at one of the stages before and after the removal of the sea component.
In producing the artificial leather of this embodiment, in order to impart a texture and shape stability similar to those of natural leather as well as flexibility, it is preferable to impregnate the entangled fiber sheet with the polymer elastomer before removing the sea component.
In this way, by impregnating the ultrafine fibers with a polymer elastomer before removing the sea part, voids are formed between the ultrafine fibers that form the fiber bundle after the sea part is removed, which are formed by removing the sea part. As a result, the ultrafine fibers inside the fiber bundle are less likely to be restrained by the polymer elastomer, i.e., the ultrafine bundle is less likely to be affected by the polymer elastomer, making it easier to obtain an artificial leather with excellent flexibility. Note that when the ultrafine fibers that form the fiber bundle after the sea part is removed from the islands-in-sea type composite fiber are impregnated with a polymer elastomer, the polymer elastomer penetrates into the voids in the fiber bundle, and the ultrafine fibers that form the fiber bundle are restrained by the polymer elastomer, thereby obtaining an artificial leather with a hard texture.

When applying the polymer elastomer to the entangled fiber sheet, a non-aqueous polymer elastomer liquid in which the polymer elastomer is dissolved or dispersed in a solvent may be used, or an aqueous polymer elastomer liquid in which the polymer elastomer is dispersed in an aqueous medium together with a dispersant as necessary may be used. In the former case, a uniform polymer elastomer liquid is easily obtained, and in the latter case, it is easy to reduce the amount of organic solvent used.

The concentration of the polymeric elastomer body fluid, ie, the content of the polymeric elastomer in the polymeric elastomer body fluid, is preferably 0.1 to 60% by mass.
The polymer elastic body fluid may contain various additives as appropriate, provided that the additives do not impair the properties of the artificial leather that is finally obtained. These additives include colorants such as dyes and pigments, coagulation regulators, antioxidants, ultraviolet absorbers, fluorescent agents, antifungal agents, penetrating agents, defoamers, lubricants, water repellents, oil repellents, thickeners, bulking agents, hardening accelerators, foaming agents, and water-soluble polymer compounds such as polyvinyl alcohol and carboxymethyl cellulose.

Details of the polymer elastomer used in step (5) are as explained in the "Polymer elastomer" section above.

The polymer elastomer may be impregnated into the entangled fiber sheet, and then solidified by a conventional dry or wet method to fix the polymer elastomer in the entangled fiber sheet. The dry method here refers to any method in which a solvent, dispersant, etc. are removed by drying or the like to fix the polymer elastomer in a fiber sheet structure. The wet method here refers to any method in which a polymer elastomer is temporarily or completely fixed in the entangled fiber sheet structure prior to removing the dispersant by treating the entangled fiber sheet structure impregnated with a polymer elastomer liquid with a non-solvent or coagulant for the polymer elastomer, or by using an aqueous polymer elastomer liquid containing a heat-sensitive gelling agent or the like to heat the impregnated entangled fiber sheet.

<Step (6)>
Step (6) is a step of removing at least one component from the ultrafine fiber. The one component is preferably a sea component resin contained in the islands-in-sea composite fiber. By removing the sea component, the ultrafine fiber can be converted into a fiber bundle of ultrafine fibers.

As a method for removing the sea part resin, for example, there can be mentioned a method in which only the sea part resin is removed using a solvent or decomposing agent capable of selectively removing only the sea part resin.
When the sea component is a water-soluble resin such as a polyvinyl alcohol resin, a water-soluble polyester resin, an easily alkali-decomposable modified polyester resin, a polyacrylamide resin, or a carboxymethyl cellulose resin, the sea component can be removed with water.
When the sea component is insoluble in water but soluble in organic solvents and the island component resin is a polyamide resin or a polyester resin, examples of the organic solvent for dissolving and removing the sea component include toluene, trichloroethylene, and tetrachloroethylene.
In this embodiment, from the viewpoint of environmental friendliness, it is preferable to use water, and for resins that are poorly soluble in water, it is preferable to use toluene, which has a high resin dissolving power.

When removing the sea component, it is preferable to carry out a dip nip treatment in parallel.
In addition, after the islands-in-sea type composite fiber is melt-spun to obtain a web, and before the sea component is removed, the fibers may be densified by subjecting them to a heat shrinkage treatment (fiber shrinkage treatment) using steam, hot water, dry heat, or the like.

<Step (7)>
The step (7) is a step of dyeing the artificial leather.
Step (7) can be carried out at any stage after the islands-in-the-sea fibers are converted into ultrafine fiber bundles.

In the step (7), any dyeing method using a known dyeing machine that is usually used for dyeing conventional artificial leathers such as padder, jigger, circular, and wince, can be used, using a dye mainly consisting of a disperse dye, a reactive dye, an acid dye, a metal complex dye, a sulfur dye, or a sulfur vat dye, which is appropriately selected depending on the type of fiber.
In addition to dyeing, finishing treatments such as mechanical kneading in a dry state, relaxation treatment in a wet state using a dyeing machine or washing machine or the like, treatment with a fabric softener, treatment to impart functionality such as a flame retardant, antibacterial agent, deodorant, water repellent or oil repellent, treatment to impart a texture modifier such as a silicone resin, a silk protein-containing treatment agent or a gripping resin, and design imparting treatment by applying a resin other than the above-mentioned resins, such as a colorant or an enamel-like coating resin, may be performed as necessary.

The artificial leather of this embodiment can be sliced into multiple pieces in the thickness direction as required, and the thickness can be adjusted by grinding the back surface, or a solvent capable of dissolving or swelling the polymer elastomer or ultrafine fiber bundles can be applied to the back surface, in the same manner as in conventional artificial leather manufacturing.

The artificial leather of the present embodiment may have a napped surface.
To form a fiber-raised surface, any of the known methods such as buffing with sandpaper or card cloth, brushing, etc. may be used. In addition, before or after such nap raising, a solvent capable of dissolving or swelling the polymeric elastomer or ultrafine fiber bundles, for example, a treatment liquid containing dimethylformamide (DMF) or the like when the polymeric elastomer is a polyurethane elastomer, or a treatment liquid containing a phenolic compound such as resorcinol, may be applied to the surface to be nap-raised. This allows fine adjustment of the restraint state of the ultrafine fiber bundles due to adhesion of the polymeric elastomer or ultrafine fiber bundles, the nap length of the ultrafine fibers of the artificial leather, the surface friction durability, etc.
After the above-mentioned raising treatment, the above-mentioned step (7) may be carried out to produce a dyed artificial leather.

The present invention will be explained in more detail below with reference to examples. Note that the scope of the present invention is not limited in any way by the contents of the examples.

First, the measurement and evaluation methods used in the examples and comparative examples described below are summarized below.

Average diameter
The average diameter of the polyester fibers was measured as follows.
A scanning electron microscope (SEM) photograph of the cross section of the artificial leather was taken at 3000 times. Then, ten cross sections of the fibers were randomly selected from the SEM photograph, and the cross-sectional area was measured. The arithmetic average value of the cross-sectional areas was calculated, and the average diameter of the fibers was calculated based on the following formula (1).
Average diameter = (average cross-sectional area/π) ^1/2 ×2...Formula (1)

Average fineness
The average fineness of the polyester fibers was measured as follows.
A scanning electron microscope (SEM) photograph of the cross section of the artificial leather was taken at 3000 times. Then, ten cross sections of the fibers were randomly selected from the SEM photograph, and the cross-sectional area was measured and the arithmetic average value of the cross-sectional area was calculated. The average value of the cross-sectional area was converted into the average fineness using the density of the resin.

<Content of polymer elastomer>
The mass C of the artificial leather cut into a size having a mass of 1 g or more was measured.
In the case where the polymeric elastomer is soluble in N,N-dimethylformamide (DMF), the artificial leather was immersed in 300 mL of DMF at room temperature for 5 hours, squeezed to remove the DMF, and the squeezed DMF was poured into water. The process of immersing in DMF and squeezing was repeated under the same conditions while replacing the DMF until the water became clear, thereby removing the polymeric elastomer from the artificial leather. The polyester fiber, which was the residue after removing the polymeric elastomer from the artificial leather, was dried to remove the DMF, and the mass D of the polyester fiber after drying was measured. The content of the polymeric elastomer in the artificial leather was then calculated based on the following formula (2).
Content of polymer elastomer (mass%)=(C−D)/C×100 Equation (2)
When the polymer elastomer was not dissolved in DMF, the artificial leather was immersed in 300 mL of hexafluoro-2-propanol (HFIP) at room temperature (25° C.) for 12 hours to dissolve the polyester fibers, and the remaining solid was filtered out and washed with HFIP, and then dried to remove the HFIP, and the mass E of the obtained solid was measured. Then, the content of the polymer elastomer in the artificial leather was calculated based on the following formula (3).
Content of polymer elastomer (mass%)=E/C×100 Equation (3)
The term "solid content" refers to components excluding solvents and liquid dispersants, i.e., components excluding liquids.

<Thickness, basis weight and apparent density>
In accordance with JIS L1096 (2010) (Method A), the thickness (mm) and basis weight (g/ ^m2 ) of the obtained artificial leather were measured using a thickness gauge (measuring probe diameter: 10 mm) under a constant pressure of 23.5 kPa for 5 seconds, and the apparent density (g/ ^cm3 ) of the artificial leather was calculated from these values.

<Measurement of area and number of ultrafine fiber bundles>
A small piece of artificial leather was prepared, and the back side (the side on which no nap or resin layer was formed) was fixed to a base with double-sided adhesive tape. The artificial leather was sliced at a depth of 0.3 mm from the surface with a single-edged razor, the front side was removed, and a scanning electron microscope (SEM) photograph of the cut surface of the remaining side was taken at 100 times. It was printed (see FIG. 1), the printed surface was placed on a flat panel light, and light was applied from the printed surface side to make the image transparent to the back side, and the cut surface part of the ultrafine fiber bundle present on the cut surface from the back side was painted black (see FIG. 2), and the area of the cut surface of the ultrafine fiber bundle and the number of cut surfaces of the ultrafine fiber bundle were measured using Image-Pro Premier ver. 9.1 (manufactured by Nippon Rover Co., Ltd.). The maximum value of the area of the cut surfaces of the ultrafine fiber bundle was taken as the maximum area of the cut surfaces of the ultrafine fiber bundle. In addition, the total value of the area of the cut surfaces of the ultrafine fiber bundle was converted to per 1 ^mm2 to take the total area of the ultrafine fiber bundle. Furthermore, the ratio of the number of ultrafine fiber bundles having a cut surface area of 500 μm2 ^or more to the total number of cut surfaces of the ultrafine fiber bundles was calculated.

<20% Strength>
A test piece measuring 16 cm length x 2.5 cm width was cut out from the obtained artificial leather. The test piece was clamped between the chucks of a tensile tester adjusted to 10 cm intervals so that the artificial leather was stretched in the longitudinal direction (the flow direction of the process in step (3)), and an S-S curve was measured using an autograph at a tensile speed of 100 mm/min. The above procedure was carried out three times. In the obtained S-S curve, the strength at an elongation of 20% was read, and the average value of the three measurements was taken as the 20% strength in the longitudinal direction (kgf/2.5 cm).
In addition, the 20% strength (kgf/2.5 cm) in the horizontal direction was calculated in the same manner as above, except that the artificial leather was clamped in the chuck of the tensile tester so that it was stretched in the horizontal direction perpendicular to the longitudinal direction of the artificial leather (the direction rotated 90° from the flow direction of the process in step (3)).

<Wear loss>
In accordance with JIS L 1096 (2020) (8.19.5 E Method, Martindale Method), a test was conducted using a Martindale abrasion tester under conditions of a pressure load of 12 kPa (gf/cm2) and 350 million abrasion cycles, and the abrasion loss on the surface of the artificial leather was calculated.

<pilling>
The test was conducted using a Martindale abrasion tester in accordance with JIS L 1096 (2020) (8.19.5 E Method, Martindale Method) with a pressure load of 12 kPa (gf/ ^cm2 ) and the number of abrasion cycles shown in Table 1. The pilling on the artificial leather surface after the test was judged visually and by touch according to the following criteria.
A: No collected hairballs were visible, and the texture was smooth and silky.
B: Although there is some feeling of hair gathering, no pilling is noticeable and the texture is a little rough.
C: Hair balls were observed and the texture was rough.

Texture
The texture of the resulting artificial leather after bending was judged visually and by touch according to the following criteria.
A: It has a rich feel, is not easily broken (does not buckle or wrinkle), and has excellent flexibility.
B: The texture falls into one or more of the following categories: lacking in solidity, easily breaking (creases due to buckling), and hard.

<exterior>
The appearance of the resulting artificial leather was visually observed and judged according to the following criteria.
A: The fibers are not clumped together, but are finely separated and have a uniform length.
B: The fibers are loosely packed and have uneven lengths.

[Example 1]
A water-soluble thermoplastic polyvinyl alcohol-based resin as the sea component and an isophthalic acid-modified polyethylene terephthalate (polyethylene phthalate modified with isophthalic acid by 6 mol %) as the island component were extruded from a melt conjugate spinning die (number of islands: 25 islands/fiber) at 270° C. so that the sea component/island component ratio was 25/75 (mass ratio), and spun at a spinning speed of 3,500 m/min to obtain a fiber web containing islands-in-sea type conjugate fibers having an average fineness of 2.95 dtex.
Next, the fiber web was hot-pressed with a calendar roll, and then pressed with a roll having an uneven shape to impart an uneven shape to the width direction of the fiber web (to impart a crimping treatment) so that the crimping rate was 200%.
Next, the crimped fiber web was folded in the length direction, and seven sheets of the fiber web were cross-lapped and laminated to form a laminated web. The laminated web was then needle-punched using 1-barb and 6-barb needles at a punch density of 3500 punches/ ^cm2 to form a longitudinally crimped entangled fiber sheet with a basis weight of 385 g/ ^m2 .
Next, the entangled fiber sheet was subjected to steam treatment under conditions of 110° C. and 23.5% RH, and then dried in an oven at 90 to 110° C., and then further heat-pressed at 120° C. to obtain a heat-pressed fiber sheet having a basis weight of 755 g/m ² , a specific gravity of 0.65 g/cm ³ , and a thickness of 1.16 mm.
Next, the heat-pressed fiber sheet was impregnated with an emulsion of a polycarbonate-based non-yellowing polyurethane (polyurethane (1)) as a polymeric elastomer, in which 1.5 parts by mass of a carbodiimide-based crosslinking agent and 2.7 parts by mass of ammonium sulfate were added to 100 parts by mass of the polymeric elastomer, and the solid content of the polymeric elastomer was 16% by mass. The solid content of the polymeric elastomer was adjusted to 10% by mass relative to the total of the polyester fiber and the polymeric elastomer in the heat-shrinkable fiber sheet. The heat-pressed fiber sheet impregnated with the emulsion was subjected to a wet heat treatment at 110°C and 29% RH atmosphere, and further dried at 150°C to obtain a heat-pressed fiber sheet impregnated with a polymeric elastomer.
The hot-pressed fiber sheet to which the polymer elastomer had been applied was then immersed in hot water at 95°C for 10 minutes while being subjected to a dip nip treatment and a high-pressure water jet treatment, thereby dissolving and removing the water-soluble thermoplastic polyvinyl alcohol resin, which is the sea component of the islands-in-sea type composite fiber, and forming ultrafine fibers of isophthalic acid-modified polyethylene terephthalate having an average diameter of 3.02 µm and an average fineness of 0.1 dtex. After drying, the back surface was ground with #320 paper, and the main surface was ground with #320 and #400 papers to form a fiber-raised surface, thereby obtaining an artificial leather having a fiber-raised surface.
The obtained artificial leather was dyed with a disperse dye at 120° C. to obtain a dyed artificial leather having a basis weight of 439 g/m ² , an apparent density of 0.499 g/cm ³ and a thickness of 0.88 mm. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[Example 2]
A dyed artificial leather was obtained in the same manner as in Example 1 in Table 1, except that the shrink treatment was carried out so that the shrink rate became 175%. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[Example 3]
A dyed artificial leather was obtained in the same manner as in Example 1, except that the thickness of the artificial leather was 0.68 mm. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[Example 4]
A dyed artificial leather was obtained in the same manner as in Example 3, except that the shrink treatment was carried out so that the shrink rate became 175%. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[Example 5]
A dyed artificial leather was obtained in the same manner as in Example 3, except that the fiber webs crimped in the width direction were laminated in the traveling direction of the entangled fiber sheet (the flow direction of the process) to form a laminated web, and an entangled fiber sheet crimped in the transverse direction was formed. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[Example 6]
A dyed artificial leather was obtained in the same manner as in Example 1, except that polyethylene was used as the sea component, the fiber-entangled sheet was shrunk in hot water at 90°C and pressed with a cooled roll to obtain a heat-shrunk web entangled sheet, a DMF solution (solid content 18.5 mass%) of polycarbonate-based polyurethane (polyurethane (2)) was used as the polymer elastomer, the solid content of the polymer elastomer was adjusted to 30 mass% relative to the total of the polyethylene terephthalate fiber and the polymer elastomer in the heat-pressed fiber sheet, toluene was used to dissolve and remove the polyethylene as the sea component, and the thickness was adjusted to 0.78 mm. Measurement and evaluation results 1 of the obtained artificial leather are shown in Table 1.

[Example 7]
A dyed artificial leather was obtained in the same manner as in Example 6, except that the shrink treatment was carried out so that the shrink rate became 175%. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[Example 8]
A dyed artificial leather was obtained in the same manner as in Example 7, except that a DMF solution (solid content 18.5% by mass) of an ether-based polyurethane (polyurethane (3)) was used as the polymer elastomer. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[Comparative Example 1]
A dyed artificial leather was obtained in the same manner as in Example 1, except that the shrink treatment was not carried out. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[Comparative Example 2]
A dyed artificial leather was obtained in the same manner as in Example 3, except that the shrink treatment was not carried out. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[Comparative Example 3]
A dyed artificial leather was obtained in the same manner as in Example 5, except that the shrink treatment was not performed and the thickness was set to 0.80 mm. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[Comparative Example 4]
A dyed artificial leather was obtained in the same manner as in Example 6, except that the shrink treatment was not carried out. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[Comparative Example 5]
An islands-in-sea type composite fiber was obtained in the same manner as in Example 6, except that spinning was performed at a spinning speed of 800 m/min, and then the islands-in-sea type composite fiber was drawn in a warm water bath at a draw ratio of 2.7 times to obtain an islands-in-sea type composite fiber of 4.0 dtex. Next, an uneven shape was imparted to the 4.0 dtex islands-in-sea type composite fiber using a crimper so that the crimp rate was 9.0% (crimping treatment was imparted), and then a fiber web was produced from the islands-in-sea type composite fiber that had been crimped using a carding machine.
Next, the fiber web was folded in the length direction, and seven sheets of the fiber web were cross-lapped and laminated to form a laminated web. The laminated web was then subjected to needle punching treatment using a 1-barb needle at a punch density of 2500 punches/ ^cm2 to form an entangled fiber sheet with a basis weight of 1128 g/ ^cm2 .
Subsequently, a heat-pressed fiber sheet was obtained in the same manner as in Example 6, and a polymeric elastomer was imparted to the heat-pressed fiber sheet, the sea component of the islands-in-sea type composite fiber was dissolved and removed, and a fiber napped surface was formed, thereby obtaining an artificial leather having a fiber napped surface. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[Comparative Example 6]
In Comparative Example 5, when the fiber web made of the obtained short fibers was hot-pressed with a calendar roll and then pressed with a roll having an uneven shape to impart an uneven shape in the width direction of the fiber web so that the crimp rate was 200% (i.e., crimping treatment was performed), the short fiber web broke and subsequent processing could not be performed.

[Comparative Example 7]
A dyed artificial leather was obtained in the same manner as in Comparative Example 3, except that the needle punching treatment was performed at a punch density of 5,900 punches/ ^cm2 . The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

It can be seen from Table 1 that the artificial leathers obtained in Examples 1 to 8 are excellent in texture, surface abrasion resistance, and pilling resistance.
On the other hand, it is clear that the artificial leathers (Comparative Examples 1, 2, and 4) in which the maximum area of the cut surface of the ultrafine fiber bundles when cut at a depth of 0.3 mm from the surface is not 4,500 µm2 or ^more do not have excellent texture, excellent surface abrasion resistance, and excellent pilling resistance.
In addition, it is also found that the artificial leather (Comparative Example ³ ) in which the ratio of the number of ultrafine fiber bundles having a cut surface area of 500 μm2 ^or more to the total number of cut surfaces of the ultrafine fiber bundles is less than 60% even when the maximum area is 4,500 μm2 or more is inferior in texture.
In addition, in the artificial leather (Comparative Example 7) in which the fiber web was not subjected to a crimping treatment and the needle punching treatment was performed to increase the punch density to 5,900 punches/ ^cm2 to increase the entanglement of the fiber web, the proportion of ultrafine fiber bundles having a cut surface area of 500 ^μm2 or more was less than 60%, and it is clear that the artificial leather was inferior in texture and appearance quality.

Claims (8)

An artificial leather containing ultrafine fibers,
An artificial leather, wherein, in a cut surface when cut at a depth of 0.3 mm from the surface, the maximum area of the cut surface of the ultrafine fiber bundle is 4,500 ^µm2 or more, and the proportion of the number of the ultrafine fiber bundles having a cut surface area of 500 µm2 or ^more to the total number of the cut surfaces of the ultrafine fiber bundles is 60% or more. The artificial leather according to claim 1 , wherein the total area of the ultrafine fiber bundles on the cut surface is 50,000 μm ² /mm ² or more. The artificial leather according to claim 1 or 2, wherein the average diameter of the ultrafine fibers is 7.5 μm or less. The artificial leather according to any one of claims 1 to 3, wherein the average fineness of the ultrafine fibers is 0.5 dtex or less. The artificial leather according to any one of claims 1 to 4, wherein the ultrafine fibers are long fibers. The artificial leather according to any one of claims 1 to 5, containing 45% by mass or less of a polymeric elastomer. A method for producing an artificial leather according to any one of claims 1 to 6,
Providing a fibrous web formed from microfiber-generating fibers;
A step of subjecting the fiber web to a crimping treatment to form a crimped fiber web;
forming a web laminate by stacking a plurality of the crimped fiber webs;
entangling the web laminate to form an entangled fiber sheet;
and removing at least one component from the ultrafine fibers. The method for producing an artificial leather according to claim 7 , further comprising a step of impregnating the entangled fiber sheet with a polymeric elastomer.

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