WO2025187710A1 - Artificial leather and method for producing artificial leather - Google Patents

Abstract

This artificial leather includes ultrafine fibers containing a polyester-based resin. In a longitudinal cross-section of the artificial leather, an area ratio A occupied by ultrafine fibers that are oriented in a range of -30° to +30° in the thickness direction is 4.5% or less. In a lateral cross-section of the artificial leather, the area ratio A and an area ratio B occupied by ultrafine fibers that are oriented in a range of -30° to +30° in the thickness direction satisfy A/B ≤ 0.9.

Description

Artificial leather and method for manufacturing artificial leather

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

BACKGROUND 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.
Artificial leathers are also required to satisfy, at a high level, requirements in terms of physical properties such as light resistance, pilling resistance, and abrasion resistance, as well as sensory requirements such as appearance (a surface texture closer to that of natural leather), texture (a soft feel combined with a moderate sense of fullness and fullness), and color development (vividness and depth of color), and various proposals have been made to meet these requirements.

For example, Patent Document 1 describes a leather-like sheet comprising an ultrafine fiber entanglement body made of ultrafine fiber bundles and a polymeric elastomer provided inside the ultrafine fiber bundles, wherein the ultrafine fiber bundles are composed of ultrafine individual fibers having an average cross-sectional area of 0.1 to 30 ^μm2 , and the average cross-sectional area is 40 to 400 ^μm2 , and the ultrafine fiber bundles are present at a density of 600 to 4,000 fibers/ ^mm2 in any cross section parallel to the thickness direction of the ultrafine fiber entanglement body. The leather-like sheet is also described as having excellent flexibility.

International Publication No. 2007/040144

Artificial leather is generally dyed to impart design and satisfy aesthetic demands, but the dyeing process requires a large amount of water, which is a problem. Also, from the perspective of sustainability, there is a growing demand for reducing water consumption.
On the other hand, thermosol dyeing is a dyeing method that uses less water, but artificial leather dyed by thermosol dyeing has the problem of having a strong rebound feeling and poor flexibility.

The present invention aims to solve the above-mentioned problems and provide artificial leather that has a soft feel and little rebound even without softening treatment, as well as a method for manufacturing the same.

After extensive investigation, the inventors discovered that the above-mentioned problems could be solved by setting the area proportions of ultrafine fibers oriented within specific ranges in the longitudinal and transverse cross sections of the artificial leather to specific values and ratios, respectively, and arrived at the present invention. In other words, the present invention encompasses the following inventions:

[1] An artificial leather comprising ultrafine fibers containing a polyester-based resin,
In the longitudinal cross section of the artificial leather, the area ratio A occupied by the ultrafine fibers oriented in the thickness direction in the range of −30° to +30° is 4.5% or less,
An artificial leather, wherein an area ratio B occupied by ultrafine fibers oriented at an angle of −30° to +30° in the thickness direction in a transverse cross section of the artificial leather and the area ratio A satisfy A/B≦0.9.
[2] The artificial leather according to the above [1], wherein the average diameter of the ultrafine fibers is 7.5 μm or less.
[3] The artificial leather according to the above [1] or [2], wherein the average fineness of the ultrafine fibers is 0.50 dtex or less.
[4] The artificial leather according to any one of the above [1] to [3], wherein the ultrafine fibers are long fibers.
[5] The artificial leather according to any one of [1] to [4] above, wherein the polyester resin is polyethylene terephthalate.
[6] The artificial leather according to any one of the above [1] to [5], wherein the intrinsic viscosity of the polyester resin is 0.63 dl/g or less.
[7] The artificial leather according to the above [5], wherein the polyethylene terephthalate contains dicarboxylic acid units and diol units, and 94 mol % or more of the dicarboxylic acid units are structural units derived from terephthalic acid.
[8] The artificial leather according to the above [7], wherein the polyethylene terephthalate is recycled polyethylene terephthalate.
[9] A method for producing an artificial leather according to any one of [1] to [8] above,
Providing a fiber web formed from ultrafine fiber-generating fibers;
forming an entangled fiber sheet using the fiber web;
a step of shrinking the entangled fiber sheet and removing at least one component from the ultrafine fiber-forming fiber to obtain an artificial leather substrate;
and a step of dyeing the artificial leather substrate.
A method for producing an artificial leather, wherein the ratio (Y/X) of the strength X at the yield point in the transverse direction of the fiber web to the maximum strength Y after the yield point is 4.0 or less.
[10] The method for producing an artificial leather according to the above [9], wherein the ultrafine fiber-forming fiber is not impregnated with a polymeric elastomer before one component is extracted from the ultrafine fiber-forming fiber.

The present invention provides artificial leather that has a soft feel and little rebound, even without softening treatment, and a method for producing the same.

The following describes the artificial leather according to an embodiment of the present invention and the method for manufacturing the artificial leather according to an embodiment of the present invention (hereinafter, sometimes referred to as "artificial leather according to this embodiment" or "method for manufacturing the artificial leather according to this embodiment").

[Artificial leather]
The artificial leather of this embodiment is an artificial leather containing ultrafine fibers containing a polyester resin, and in a longitudinal cross section of the artificial leather, an area ratio A occupied by ultrafine fibers oriented at an angle of −30° to +30° in the thickness direction is 4.5% or less, and an area ratio B occupied by ultrafine fibers oriented at an angle of −30° to +30° in the thickness direction in a transverse cross section of the artificial leather and the area ratio A satisfy A/B≦0.9.

The artificial leather of the present embodiment has the above-described configuration, and therefore the crossing of the ultrafine fibers in the artificial leather is moderate, and the artificial leather can have a soft texture with little resilience even without softening treatment.
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, grain-finish artificial leather, etc. Furthermore, raised artificial leather includes suede-like, velour-like, nubuck-like, etc., which are variations depending on the raised surface condition.

In this specification, the direction in which the artificial leather has the smallest extensibility when pulled is referred to as the "longitudinal direction" of the artificial leather, and the direction perpendicular to that direction is referred to as the "lateral direction" of the artificial leather. Also, the flow direction of the artificial leather during production is referred to as the "longitudinal direction" of the artificial leather.
In this specification, "area ratio A" and "area ratio B" are values calculated from a photograph of the cross section obtained by cutting the artificial leather in the longitudinal thickness direction or the transverse thickness direction and taking the photograph at 150x magnification using a scanning electron microscope (SEM).
More specifically, the area ratio A and the area ratio B are measured by the procedures described in the Examples.

From the viewpoint of obtaining an artificial leather having less resilience and a softer feel, the area ratio A is 4.5% or less, preferably 4.2% or less, more preferably 4.0% or less, and even more preferably 3.8% or less, and from the viewpoint of mechanical properties such as tensile strength, tensile elongation, and tear strength, the area ratio A is preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.3% or more. Suitable ranges include preferably 0.1 to 4.5%, more preferably 0.2 to 4.2%, even more preferably 0.3 to 4.0%, and even more preferably 0.3 to 3.8%, etc.
The area ratio A can be adjusted to a desired value by adjusting the number of intersections between fibers in the fiber web.

A/B, the ratio of area proportion A to area proportion B, is A/B≦0.9. From the viewpoint of obtaining artificial leather with less resilience and a softer feel, it is preferably A/B≦0.8, more preferably A/B≦0.7, and even more preferably A/B≦0.6. From the viewpoint of mechanical properties such as tensile strength, tensile elongation, and tear strength, it is preferably A/B≧0.1, more preferably A/B≧0.2, and even more preferably A/B≧0.3. Suitable ranges include preferably 0.1≦A/B≦0.9, more preferably 0.1≦A/B≦0.8, even more preferably 0.2≦A/B≦0.7, and even more preferably 0.3≦A/B≦0.6.

From the viewpoint of obtaining an artificial leather having less repulsion and a softer texture, the area ratio B is preferably 5.5% or less, more preferably 5.4% or less, and even more preferably 5.3% or less, and from the viewpoint of obtaining an artificial leather having a desired width, the area ratio B is preferably 1.0% or more, more preferably 2.0% or more, and even more preferably 3.0% or more. Suitable ranges include preferably 1.0 to 5.5%, more preferably 2.0 to 5.4%, and even more preferably 3.0 to 5.3%, etc.
The area ratio B can be adjusted by the ratio of widening the width of the artificial leather after dyeing, and the higher the ratio of widening the width of the artificial leather, the more it can be reduced, and the smaller the ratio of widening the width of the artificial leather, the more it can be increased.

The thickness of the artificial leather of the present embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather having less repulsion and a softer texture, 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 "thickness" is a value measured in accordance with JIS L1096 (2010) (Method A).

The apparent density of the artificial leather of this embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather with less resilience and a softer feel, it is preferably 0.10 to 1.00 g/cm ³ , more preferably 0.20 to 0.80 g/cm ³ , even more preferably 0.30 to 0.60 g/cm ³ , and still more preferably 0.35 to 0.48 g/cm ³ .
The "apparent density" is a value measured in accordance with JIS K6505 (1995) 5.2.2.

The basis weight of the artificial leather of this embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather with less repulsion and a softer texture, 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 "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 perspective of more easily achieving the effects of the present invention, it is preferable that the artificial leather be an artificial leather with a napped surface, i.e., a napped artificial leather.

<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 spinnable polymers with different chemical or physical properties. Furthermore, the ultrafine fiber bundle is a bundle of a plurality of ultrafine fibers.

The ultrafine fibers of the present embodiment are preferably long fibers from the viewpoint of obtaining artificial leather having less repulsion and a softer feel.
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, for example. The fiber length of the islands-in-sea type composite fiber before being converted into ultrafine fibers, as described below, is preferably 100 mm or more, and more preferably 200 mm or more. As long as it is technically possible to produce the long fibers and they are not inevitably cut during the production process, the long fibers may be continuous fibers that are produced, for example, by a spunbonding method and continuously spun, and have a fiber length of several meters, several hundred meters, several kilometers, or even longer. Note that needle punching during entanglement or surface buffing can unavoidably cut some of the long fibers into short fibers during the production process.

The ultrafine fibers of this embodiment contain a polyester-based resin. Examples of polyester-based resins 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; and aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalerate resin. In this specification, the polyester-based resin contains dicarboxylic acid-based monomer units and diol-based monomer units, and modified PET is PET in which at least a portion of the ester-forming dicarboxylic acid-based monomer units or diol-based monomer units of unmodified PET have been replaced with substitutable monomer units. Specific examples of the modified monomer unit substituting the dicarboxylic acid monomer unit include units derived from isophthalic acid, sodium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, adipic acid, etc., which substitute for the terephthalic acid unit. Specific examples of the modified monomer unit substituting the diol monomer unit include units derived from diols such as butanediol and hexanediol, which substitute for the ethylene glycol unit.
The polyester resin of the present embodiment is preferably PET from the viewpoint of obtaining artificial leather with less repulsion and a softer feel.
Furthermore, from the viewpoint of recyclability and of obtaining artificial leather having less repulsion and a softer texture, the PET preferably contains 94 mol % or more of dicarboxylic acid monomer units as terephthalic acid units, more preferably 95 mol % or more, even more preferably 96 mol % or more, and may even contain 100 mol %.
Furthermore, from the viewpoint of recyclability and of obtaining artificial leather having less repulsion and a softer texture, the PET preferably contains 94 mol % or more of diol-based monomer units as ethylene glycol units, more preferably 95 mol % or more, even more preferably 96 mol % or more, and may contain 100 mol %.

The polyester resin of the present embodiment is preferably unmodified PET from the viewpoint of sustainability and from the viewpoint of suppressing adhesion of fibers and obtaining artificial leather with less repulsion and a softer texture.
Moreover, the polyester resin of the present embodiment is preferably recycled PET from the viewpoint of sustainability.

The intrinsic viscosity of the polyester resin of this embodiment is preferably 0.63 dl/g or less, more preferably 0.625 dl/g or less, and even more preferably 0.62 dl/g or less, from the viewpoint of cross-section formability of the ultrafine fiber-forming fiber, and is preferably 0.55 dl/g or more, more preferably 0.56 dl/g or more, and even more preferably 0.57 dl/g or more, from the viewpoint of mechanical properties such as tensile strength, tensile elongation, and tear strength. Suitable ranges include preferably 0.55 to 0.63 dl/g, more preferably 0.56 to 0.625 dl/g, and even more preferably 0.57 to 0.62 dl/g.
The "intrinsic viscosity" is a value measured using a phenol/tetrachloroethane (volume ratio 1/1) mixed solvent as a solvent at a measurement temperature of 30°C using an Ubbelohde viscometer, and specifically, is measured by the procedure described in the Examples.

The ultrafine fibers of the present embodiment may or may not contain a resin other than the polyester-based resin.
Examples of resins other than polyester-based resins include 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 chlorinated polyolefins.
From the viewpoint of recyclability, it is preferable that the ultrafine fibers contain no resin other than the polyester-based resin.

The resin that constitutes the ultrafine fibers of this embodiment may contain various additives, provided that the effects of the present invention are 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, and inorganic fine particles.

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 less resilience and a softer feel. There is no particular lower limit, but from the viewpoint of ease of production and color development, it may be 1.0 μm or more, or even 1.5 μm or more. Suitable ranges include preferably 1.0 to 7.5 μm, more preferably 1.0 to 6.0 μm, even more preferably 1.0 to 5.5 μm, and even more preferably 1.5 to 5.0 μm.

From the viewpoint of obtaining an artificial leather having less resilience and a softer feel, 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 may be, for example, 0.01 dtex or more, or 0.02 dtex or more. Suitable ranges include preferably 0.01 to 0.50 dtex, more preferably 0.01 to 0.40 dtex, and even more preferably 0.02 to 0.30 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.

<Polymeric elastomer>
The artificial leather of this embodiment may or may not contain a polymeric elastomer.
Any polymeric elastomer that has conventionally been used in artificial leathers can be used. Specific examples include polyurethane elastomers, acrylonitrile elastomers, olefin elastomers, polyester elastomers, and acrylic elastomers, with polyurethane elastomers and acrylic elastomers being preferred.
Examples of polyurethane elastomers 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 with 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 melt polymerization, bulk polymerization, solution polymerization, or the like.
The content of the polymer polyol component in the polyurethane elastomer is preferably 15 to 90% by mass.

Furthermore, the acrylic elastomer may comprise at least one soft component selected from the group consisting of a monomer whose homopolymer has a glass transition temperature in the range of -90 to -5°C and is preferably non-crosslinkable, such as methyl acrylate, n-butyl acrylate, isobutyl acrylate, isopropyl acrylate, n-hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and a monomer whose homopolymer has a glass transition temperature in the range of 50 to 250°C and is preferably non-crosslinkable, such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, or cyclohexyl 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, acrylic acid, and (meth)acrylic acid with a monofunctional or polyfunctional ethylenically unsaturated monomer unit capable of forming a crosslinked structure, or a compound capable of forming a crosslinked structure by reacting with an ethylenically unsaturated monomer unit introduced into a polymer chain, such as at least one ethylenically unsaturated monomer comprising 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 elastomer are preferred because they have an excellent balance of texture and mechanical properties, and if the type is appropriately selected, they also have an excellent 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 polyurethane elastomers and are poor at fixing the nap during nap formation, but are particularly preferred for forming grain-finish 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 separate batches. Furthermore, in addition to the above-mentioned polymer elastomers such as polyurethane elastomers, acrylonitrile elastomers, olefin elastomers, polyester elastomers, and acrylic elastomers that serve as the main component, a polymer elastomer such as synthetic rubber may be added as needed to form a polymer elastomer composition.

When the artificial leather of this embodiment contains a polymeric elastomer, its content 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 an artificial leather with an 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 various additives that can be added to the polymeric elastomer liquid used to impregnate the ultrafine fibers. 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% by mass, more preferably 1.0 to 5.0% by mass, and even more preferably 1.5 to 3.0% by mass, relative to the mass of the artificial leather, from the viewpoints of water absorbency, water repellency, stain resistance, etc., as well as making it easier for the other components to exhibit their intended effects.

[Manufacturing method of artificial leather]
From the viewpoint of obtaining an artificial leather having less resilience and a softer texture, the artificial leather according to the present embodiment is preferably produced by a production method comprising the following steps (1) to (4), in which the ratio (Y/X) of the strength X at the yield point in the lateral direction of the fiber web prepared in the following step (1) to the maximum strength Y after the yield point is 4.0 or less.
Step (1): A step of preparing a fiber web formed from ultrafine fiber-generating fibers. Step (2): A step of forming an entangled fiber sheet using the fiber web. Step (3): A step of obtaining an artificial leather substrate by shrinking the entangled fiber sheet and removing at least one component from the ultrafine fiber-generating fibers. Step (4): A step of dyeing the artificial leather substrate.

The manufacturing method according to the present embodiment includes a step (step (1)) of preparing a fiber web in which the ratio (Y/X) of the strength X at the yield point in the lateral direction to the maximum strength Y after the yield point is 4.0 or less, thereby making it easier to obtain the artificial leather of the present embodiment.
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 have been made ultrafine by removing at least one component from a multicomponent fiber (composite fiber) made of at least two or more types of spinnable polymers that differ in chemical or physical properties, and the multicomponent fiber that generates these ultrafine fibers is an ultrafine fiber-generating fiber. Typical examples of ultrafine fiber-generating fibers include islands-in-sea type composite fibers, multilayer laminated composite fibers, and radial laminated composite fibers, which are obtained using methods such as chip blending (mixed spinning) and composite spinning. Among these, islands-in-sea type composite fibers are preferred from the viewpoints of increasing productivity through high-speed spinning and of 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-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 by removing the sea component, ultrafine fibers in the form of fiber bundles are generated.
Hereinafter, a method for obtaining a fiber web by melt-spinning islands-in-sea type composite fibers, using islands-in-sea type composite fibers as ultrafine fiber-forming fibers, will be described in more detail.

Examples of the island component resins contained in the islands-in-sea type composite fibers and later to become the ultrafine fibers include the same resins as those constituting the ultrafine fibers in the above-mentioned "ultrafine fibers."
The sea component resin contained in the islands-in-sea type composite fiber and removed by extraction, decomposition, etc. is preferably a resin that has a solubility or decomposability different from that of the island component resin and has low compatibility with it. Such a resin is preferably selected appropriately depending on the type of island component resin and the production method.
Examples of the resin for the sea component include olefin-based resins such as polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer, as well as 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 using only water without using a solvent, such as polyvinyl alcohol-based resins, water-soluble polyester resins, easily alkali-decomposable modified polyester resins, polyacrylamide resins, and carboxymethyl cellulose resins. Among these, polyethylene and polyvinyl alcohol-based resins are preferred from the viewpoints of melt spinnability, water solubility, and fiber properties (fiber strength), and more preferred are 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 fibers, 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 copolymerization unit is ethylene, the fiber properties are improved, and therefore ethylene-modified polyvinyl alcohol is more preferred. 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 to the island component in the islands-in-sea composite fiber is not particularly limited, but preferably falls within the range of 5:95 to 80:20 (sea component:island component). If the sea component polymer ratio in the islands-in-sea composite fiber is 5% by mass or more, the spinning stability of the islands-in-sea fiber is less likely to decrease, making it easier to ensure industrial productivity. Furthermore, when a polymer elastomer is added, voids of the required size are more likely to form between the ultrafine fiber bundles and the polymer elastomer after the sea component is removed, making it easier to achieve a fluffy, full, dense surface. On the other hand, if the sea component polymer ratio is 80% by mass or less, the shape and distribution of the island component in the cross section of the islands-in-sea fiber are stable, making it easier to prevent a decrease in quality stability.

The preferred method for producing a fiber web is to use the so-called spunbond method, in which ultrafine fiber-generating fibers are melt-spun and collected on a conveyor belt without cutting, to form a fiber web of continuous long 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 composite fibers from a spinning nozzle at a predetermined extrusion speed, and the strands are substantially cooled and solidified by cooling air at any stage between just below the nozzle holes and the suction device described below. A high-velocity air stream is applied using a suction device such as an air jet nozzle, and the islands-in-sea type composite fibers are uniformly drawn and attenuated to a desired diameter or fineness.
The high-speed air stream may be applied so that the average spinning speed, which corresponds to the mechanical take-up speed in normal spinning, is any speed in the range of 1,000 to 6,000 m/min. Furthermore, a fiber web can be produced by a spunbonding method in which, depending on the texture of the resulting fiber web, the islands-in-sea type composite fibers are opened by an impingement plate, an air stream, or the like, and then collected and deposited on a collecting surface such as a conveyor belt that moves in the longitudinal direction while being sucked from the opposite side of the conveyor belt to form a long-fiber web.
From the viewpoint of efficiently achieving the effects of the present invention, the distance between the air jet nozzle and the collection surface is preferably 10 to 100 cm, more preferably 30 to 80 cm, and even more preferably 40 to 70 cm. The suction speed to the collection surface is preferably 5 to 35 m/sec, more preferably 10 to 25 m/sec. The movement speed of the collection surface is preferably 20 to 150 m/min, more preferably 50 to 120 m/min.
The degree of spreading and the number of intersections of the islands-in-sea type composite fibers collected on the collecting surface can be appropriately adjusted by adjusting the average spinning speed, the distance between the air jet nozzle and the collecting surface, the suction speed onto the collecting surface, the movement speed of the collecting surface, etc. As a result, an artificial leather with less repulsion and a softer feel can be obtained.

In the step of preparing a fiber web, the greater the spread of the islands-in-sea type composite fibers collected on a collecting surface such as a conveyor belt, the greater the number of intersections between the fibers. The greater the number of intersections between the fibers, the greater the residual strain associated with longitudinal elongation when the entangled fiber sheet is shrunk and at least one component is removed from the ultrafine fiber-generating fibers, making it more difficult to elongate in the transverse direction, and therefore the area ratio A increases.
Furthermore, the smaller the spread when the fibers land on the belt, the fewer the number of intersections between the fibers. The fewer the number of intersections between the fibers, the easier it is for the fibers to be properly pulled out as they stretch in the longitudinal direction when at least one component is removed from the ultrafine fiber-generating fiber, making it less likely that residual strain will remain and making them more likely to stretch in the transverse direction, thereby reducing the area ratio A.

The fiber web may be subjected to a heat press treatment to impart shape stability, and the fiber web may be fused as a result.

When the ratio (Y/X) of the strength X at the yield point in the transverse direction of the fiber web obtained in step (1) to the maximum strength Y after the yield point is 4.0 or less, the number of fiber intersections becomes appropriate, and the artificial leather of this embodiment becomes easy to obtain. In step (3), such a fiber web shrinks in the transverse direction (width direction), which not only relieves the tension of the fibers in the transverse direction but also allows the fibers to be appropriately passed through in the longitudinal direction, thereby relieving the tension in the longitudinal direction, and thickness collapse is suppressed, making it easy to obtain an artificial leather that is less likely to increase in apparent density and has a soft texture.
From the viewpoint of obtaining an artificial leather having less repulsion and a softer feel, Y/X is preferably 3.9 or less.

<Step (2)>
Step (2) is a step of forming an entangled fiber sheet using the fiber web.
In step (2), a plurality of layers of the fiber web obtained in step (1) are superimposed on one another, and then subjected to an entanglement treatment such as needle punching or hydroentanglement treatment to obtain an entangled web in which the long fibers are entangled in the thickness direction.
As a method for stacking a plurality of fiber webs, the fiber webs may be stacked in the same direction, or the fiber webs may be stacked by changing the conveying direction of the fiber web to a 90° direction and folding it back by a cross-lapping method. The method for stacking a plurality of fiber webs is preferably cross-lapping lamination, from the viewpoints that it is easy to adjust the width of the entangled fiber sheet as desired and it can suppress the occurrence of unevenness in the width direction of the fiber web, i.e., it can suppress unevenness in the basis weight.
The number of layers of the web to be superimposed is not particularly limited, but from the viewpoint of mechanical strength, it is preferably 4 layers or more, more preferably 8 layers or more, and from the viewpoint of ease of production, it is preferably 20 layers or less, more preferably 16 layers or less.

A fiber web made up of multiple layers is subjected to a mechanical entanglement process 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 entanglement is performed by needle punching, various processing conditions are appropriately selected, such as the type of needles (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).
In the step of obtaining an artificial leather substrate, when the component to be removed from the ultrafine fiber-forming fiber is a water-soluble polymer, it is preferable to carry out the entanglement treatment by the needle punch method from the viewpoint of suppressing elution of the water-soluble polymer during the entanglement treatment.

The punch density for needle punching is preferably 1500 to 5500 punches/cm ² , more preferably 2000 to 5000 punches/cm ² , from the viewpoint of easily 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, and also preventing fiber breakage from occurring, preventing a decrease in the degree of entanglement.

Furthermore, at any stage from the spinning of the islands-in-sea composite fiber to the entanglement process, an oil or antistatic agent may be applied to the ultrafine fiber-generating fiber, fiber web, fiber web laminate, entangled fiber sheet, etc. Furthermore, if necessary, the ultrafine fiber-generating fiber, fiber web, fiber web laminate, entangled fiber sheet, etc. may be immersed in warm water at a temperature of 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 1000 g/ ^m2 . Furthermore, the entangled fiber sheet may be subjected to a treatment to further increase the fiber density and degree of entanglement by heat shrinking as needed. Furthermore, the entangled fiber sheet densified by the heat shrinking treatment may be further densified, and the fiber density may be further increased by heat pressing as needed for the purposes of fixing the shape of the entangled fiber sheet and smoothing the surface.

<Step (3)>
In step (3), the entangled fiber sheet is shrunk and at least one component is removed from the ultrafine fiber-forming fibers to obtain an artificial leather substrate. 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-forming fibers can be converted into a fiber bundle of ultrafine fibers.

Methods for shrinking an entangled fiber sheet include heat shrinkage (fiber shrinkage) using steam, hot water, dry heat, etc. When an entangled fiber sheet is heat shrinked, it shrinks in the horizontal direction (width direction), relaxing the tension in the horizontal fibers. In addition, the process of removing at least one component allows the fibers to be pulled out appropriately in the vertical direction, relaxing the tension in the vertical direction and suppressing an increase in apparent density. As a result, an artificial leather with less resilience and a softer texture can be obtained.

As a method for removing the sea part resin, for example, a method using a solvent or decomposing agent capable of selectively removing only the sea part resin can be mentioned.
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 that dissolves and removes 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.

From the viewpoint of efficiently obtaining the effects of the present invention, it is preferable to simultaneously shrink the entangled fiber sheet and remove at least one component from the ultrafine fiber-generating fibers, and when the sea component is a water-soluble resin, it is preferable to use hot water to shrink the entangled fiber sheet and remove the water-soluble resin.
When removing the sea component, a dip-nip treatment may be carried out in parallel.

<Step (4)>
Step (4) is a step of dyeing the artificial leather substrate.
Step (4) can be carried out at any stage after the islands-in-the-sea fibers are converted into ultrafine fiber bundles.

In the step (4), any dyeing method can be employed using a known dyeing machine that is usually used for dyeing conventional artificial leathers such as padder, jigger, circular, and wince, using a dye mainly composed 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.
On the other hand, conventional artificial leathers dyed by thermosol dyeing have had the problem of having a strong resilience and poor flexibility. However, even if an artificial leather substrate manufactured by a manufacturing method comprising the steps (1) to (3) in which the ratio (Y/X) of the strength X at the yield point in the lateral direction of the fiber web prepared in step (1) to the maximum strength Y after the yield point is 4.0 or less is dyed by thermosol dyeing, an artificial leather having a soft texture and a low resilience can be obtained. Furthermore, thermosol dyeing can significantly reduce the amount of water used compared to dyeing methods used for general artificial leathers, thereby reducing the environmental impact. Therefore, from the perspective of reducing the environmental impact, it is preferable to dye the artificial leather substrate by thermosol dyeing.

<Step (5)>
The method for producing an artificial leather according to this embodiment may further include step (5) of impregnating the entangled fiber sheet with the polymeric elastomer, from the viewpoint of imparting texture and shape stability similar to those of natural leather.
Step (5) may be carried out between step (2) and step (3), or between step (3) and step (4).
In the production of 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 carry out step (5) between steps (2) and (3). That is, it is preferable to impregnate the artificial leather with a polymeric elastomer before removing the sea component.
By impregnating the ultrafine fibers forming the fiber bundle with a polymeric elastomer before removing the sea part in this way, voids are formed between the ultrafine fibers that form the fiber bundle after removing the sea part, 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 polymeric elastomer, i.e., the ultrafine bundle is less likely to be affected by the polymeric elastomer, making it easier to obtain an artificial leather with excellent flexibility. Note that when the ultrafine fibers forming the fiber bundle after removing the sea part from the islands-in-sea type composite fiber are impregnated with a polymeric elastomer, the polymeric elastomer penetrates into the voids in the fiber bundle, and the ultrafine fibers forming the fiber bundle are restrained by the polymeric elastomer, making it easier to obtain an artificial leather with a hard texture.

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

The concentration of the polymeric elastomer body fluid, that is, 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, such as colorants such as dyes and pigments, coagulation regulators, antioxidants, ultraviolet absorbers, fluorescent agents, antifungal agents, penetrating agents, antifoaming agents, lubricants, water repellents, oil repellents, thickeners, bulking agents, hardening accelerators, foaming agents, and water-soluble polymer compounds such as polyvinyl alcohol and carboxymethyl cellulose, within the range that does not impair the properties of the artificial leather that is finally obtained.

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

The polymeric elastomer may be fixed within the entangled fiber sheet by impregnating the entangled fiber sheet with the polymeric elastomer and then coagulating the polymeric elastomer using a conventional dry or wet method. The dry method here refers to any method for fixing a polymeric elastomer within a fiber sheet structure by removing solvents, dispersants, etc. by drying or other methods. The wet method here refers to any method for temporarily or completely fixing a polymeric elastomer within the entangled fiber sheet structure prior to removing the dispersant by treating an entangled fiber sheet structure impregnated with a polymeric elastomer liquid with a non-solvent or coagulant for the polymeric elastomer, or by using an aqueous polymeric elastomer liquid containing a heat-sensitive gelling agent or other additive to heat-treat the impregnated entangled fiber sheet.

The artificial leather of this embodiment has a texture similar to that of natural leather, even without the polymer elastomer, so it is preferable not to impregnate it with the polymer elastomer. In other words, it is preferable not to include step (5).

In addition to the above steps (1) to (5), finishing treatments such as mechanical kneading in a dry state, relaxation treatment in a wet state using a dyeing machine or washing machine, treatment with softeners, functionalization treatments such as flame retardants, antibacterial agents, deodorizers, water and oil repellents, treatments to add texture modifiers such as silicone resins, silk protein-containing treatments, and grip-imparting resins, and design-imparting treatments using resins other than those mentioned above, such as colorants and enamel-like coating resins, may also be performed as needed.

As with conventional artificial leather manufacturing, the artificial leather of this embodiment can be sliced into multiple pieces in the thickness direction as needed, 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.

The artificial leather of this embodiment may have a napped surface.
To form a napped surface, any of the known methods, such as buffing with sandpaper or card cloth, or brushing, can be used. Furthermore, before or after such nap-raising treatment, a solvent capable of dissolving or swelling the polymeric elastomer or ultrafine fiber bundles, such as a treatment liquid containing dimethylformamide (DMF) or a treatment liquid containing a phenolic compound such as resorcinol, may be applied to the surface to be napped. This allows for 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 raising treatment, the above-mentioned step (4) may be carried out.

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

First, the evaluation methods used in the examples and comparative examples described below will be summarized below.

<Intrinsic viscosity>
A phenol/tetrachloroethane (volume ratio 1/1) mixed solvent was used as the solvent, and the measurement was carried out at a measurement temperature of 30° C. using an Ubbelohde viscometer "HRK-3" (manufactured by Hayashi Seisakusho).

<Spreading of islands-in-the-sea composite fiber on the conveyor belt (collection surface)>
The islands-in-sea type composite fiber was discharged from the air jet nozzle onto the stationary conveyor belt for 2 seconds, and the spread (length) of the islands-in-sea type composite fiber in the direction in which the conveyor belt was moving was measured.

<Yield strength X in the fiber web transverse direction and maximum strength Y after the yield point>
The fiber web was cut into a size of 16 cm x 16 cm, and then folded in quarters lengthwise (first folded in half to reduce the area, and then folded again to reduce the area to a quarter) to give a test specimen width of 4 cm. Using a precision universal testing machine (Shimadzu Corporation, Autograph AG-X plus), the specimens were elongated at a gripping distance of 10 cm and a constant-rate extension tensile tester at a tension rate of 200 mm/min, and an SS curve plotting the relationship between strength (kg) and elongation (%) was measured. From the obtained SS curve, the yield point strength X (kg) and the maximum strength Y (kg) after the yield point (maximum value of strength after the yield point) were read.

<Content of polymer elastomer>
The weight C of the artificial leather cut into a size having a mass of 1 g or more was measured. Next, the artificial leather was immersed in hexafluoro-2-propanol (HFIP) at room temperature (25°C) for 12 hours to dissolve the polyester fibers, and the remaining solid content was filtered and washed with HFIP, and then dried to remove the HFIP. The weight D of the resulting solid was measured. The content of the polymer elastomer in the artificial leather was then calculated based on the following formula (2).
Content of polymer elastomer (mass%)=D/C×100 Equation (2)
The term "solid content" refers to components excluding solvents and dispersants.

<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 3000x magnification. Ten cross sections of fibers were randomly selected from the SEM photograph, and their cross-sectional areas were measured. The arithmetic mean 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 fiber was measured as follows.
A scanning electron microscope (SEM) photograph of the cross section of the artificial leather was taken at 3000x magnification. Ten cross sections of fibers were randomly selected from the SEM photograph, and the cross-sectional areas were measured and the arithmetic mean value of the cross-sectional areas was calculated. The mean value of the cross-sectional areas was then converted into an average fineness using the density of the resin.

<Measurement of area ratio A and area ratio B>
The artificial leather was cut in the longitudinal thickness direction using a single-edged razor, and the resulting cross section was photographed in multiple sections from the front side to the back side using a scanning electron microscope (SEM) at 150x magnification. The multiple images were printed on paper and connected so that the cross section of the artificial leather was continuous from the front side to the back side, and a straight line was drawn evenly across the boundary between the artificial leather substrate and the base of the napped fibers on the printed surface. Furthermore, a rectangle equivalent to 400 μm (depth direction) x 700 μm (direction perpendicular to the depth direction) was drawn in the center of the cross section of the artificial leather on the printed surface. A transparent polyethylene terephthalate film (PET film) was placed on the printed surface to cover the rectangle, and the surface of the PET film in the rectangular area was painted black. The area of the blackened portion of the PET film was analyzed using image analysis software "Image-Pro Premier ver. 9.1" (manufactured by Nippon Rover Co., Ltd.), and the area of the longitudinal cross section of the artificial leather was measured. Next, the rectangular portion of the PET film was replaced with a new transparent PET film placed on the printed surface so as to cover the rectangle. The straight line was defined as 0°, and the angle (±90° or less) between the straight line and the ultrafine fibers was defined as the angle in the thickness direction. The surface of the PET film in the portion where the ultrafine fibers were oriented in the thickness direction within a range of -30° to +30° was painted black. The area of the ultrafine fibers oriented in the thickness direction within a range of -30° to +30° was measured using the image analysis software in the same manner as in measuring the area of the longitudinal cross section of the artificial leather. From the area of the obtained longitudinal cross section of the artificial leather and the area of the ultrafine fibers oriented in the thickness direction within a range of -30° to +30°, the area ratio A (%) of the ultrafine fibers oriented in the thickness direction within a range of -30° to +30° was calculated. Next, the artificial leather was cut in the thickness direction in the lateral direction using a single-edged razor, and the area ratio B (%) of the ultrafine fibers oriented in the thickness direction in the lateral cross section of the artificial leather was calculated using the same procedure as in calculating the area ratio A (%).

<Thickness, basis weight and apparent density>
The obtained artificial leather was cut into a size of 16 cm x 16 cm (256 cm ² ). The mass (g) of the cut artificial leather was measured, and the basis weight (g/m ² ) of the cut artificial leather was calculated using the following formula (3).
Basis weight = mass / 256 × 10000 Formula (3)
In accordance with JIS L1096 (2010) (Method A), the thickness (mm) of the cut artificial leather was 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/cm ³ ) of the artificial leather was calculated using the following formula (4) in accordance with JIS K6505 (1995) 5.2.2.
Apparent density = basis weight / thickness / 1000 Formula (4)

<Young's modulus>
Three sheets of the artificial leathers obtained in the Examples and Comparative Examples were stacked together and compressed in the thickness direction using a YAWASA (YWS-5N-1-SL) (manufactured by Tech Gihan Co., Ltd.) with a pressing tool having a diameter of 1 mm at a speed of 0.2 m/sec up to a maximum pressing force of 0.2 N, and Young's modulus was measured.

Texture
The texture of the resulting artificial leather after bending was judged visually and by touch according to the following criteria.
A: The texture was solid, had little resilience, was bendable without large buckling wrinkles, and had excellent flexibility.
B: The texture fell into one or more of the following categories: lacking in a sense of fullness, having a sense of resilience, having large buckling wrinkles, and being hard.

[Example 1]
A water-soluble thermoplastic polyvinyl alcohol resin (modified polyvinyl alcohol modified by ethylene copolymerization) was used as the sea component, and recycled polyethylene terephthalate (dicarboxylic acid units, of which constitutional units derived from terephthalic acid account for 100 mol %) having an intrinsic viscosity of 0.60 dl/g was used as the island component. Islands-in-sea type composite fibers were extruded from a melt conjugate spinning nozzle (number of islands: 25/fiber) at 270°C so that the sea component/island component ratio was 25/75 (mass ratio).
Next, an air jet nozzle was installed at a position 55 cm above the conveyor belt (the collection surface of the islands-in-sea type composite fibers), and spinning was performed while pulling and attenuating at a spinning speed of 3,279 m/min, and islands-in-sea type composite fibers with an average fineness of 3.05 dtex were collected on the conveyor belt, thereby obtaining an islands-in-sea type composite fiber sheet. Under the above collection conditions, the spread (length) of the islands-in-sea type composite fibers on the conveyor belt (collection surface) was measured and found to be 24.5 cm.
The resulting islands-in-sea composite fiber sheet was hot-pressed using a calender roll at a roll surface temperature of 58°C and a linear pressure of 36 kg/cm to obtain a fiber web. The resulting fiber web had a strength X of 0.6 kg at the yield point in the transverse direction, an elongation of 6%, a maximum strength Y after the yield point of 1.73 kg, and an elongation at the maximum strength Y of 190%, so that Y/X = 2.9.
The fiber webs were then cross-lap laminated to form a laminate web, which was then needle-punched using 6-barb needles to form an entangled fiber sheet having a basis weight of 292 g/ ^m2 and longitudinal crimping.
Next, the entangled fiber sheet was immersed in hot water at 95°C for 10 minutes while undergoing dip-nip treatment and high-pressure water jet treatment to dissolve and remove the water-soluble thermoplastic polyvinyl alcohol resin, which is the sea component of the islands-in-sea type composite fiber, and form polyethylene terephthalate ultrafine fibers with an average diameter of 3.02 µm and an average fineness of 0.101 dtex. The resulting product was then dried to obtain an artificial leather substrate.
The resulting artificial leather substrate was then thermosol dyed with a disperse dye and raised to obtain an artificial leather with a napped surface. The resulting artificial leather had a basis weight of 436 g/ ^m2 , an apparent density of 0.451 g/ ^cm3 , and a thickness of 0.97 mm. The resulting artificial leather had a solid feel with little rebound, was bendable without large buckling wrinkles, and had excellent flexibility.

[Example 2]
A dyed artificial leather was obtained in the same manner as in Example 1, except that a sheet of islands-in-sea type composite fibers was obtained by adjusting the air jet nozzle so that the measured spread of the islands-in-sea type composite fibers on the conveyor belt (collection surface) was 26.0 cm. The results are shown in Table 1.

[Example 3]
A dyed artificial leather was obtained in the same manner as in Example 1, except that a sheet of islands-in-sea type composite fibers was obtained by adjusting the air jet nozzle so that the measured spread of the islands-in-sea type composite fibers on the conveyor belt (collection surface) was 27.0 cm. The results are shown in Table 1.

[Example 4]
Dyed artificial leather was obtained in the same manner as in Example 1, except that the artificial leather substrate was dyed by circular dyeing instead of thermosol dyeing. The results are shown in Table 1.

[Example 5]
In Example 3, the artificial leather substrate was impregnated with a mixture of acrylic emulsion Kasesol ARS-2 (manufactured by Nicca Chemical Co., Ltd.) and water in a mass ratio of 30:70 (acrylic emulsion content: approximately 18 mass%), pickled 40%, dried at 140°C for 4 minutes, and then thermosol dyed. Dyed artificial leather was obtained in the same manner as in Example 3. The results are shown in Table 1.

[Comparative Example 1]
A dyed artificial leather was obtained in the same manner as in Example 1, except that a sheet of islands-in-sea type composite fibers was obtained by adjusting the air jet nozzle so that the measured spread of the islands-in-sea type composite fibers on the conveyor belt (collection surface) was 23.0 cm. The results are shown in Table 1.

[Comparative Example 2]
Dyed artificial leather was obtained in the same manner as in Example 1, except that isophthalic acid-modified polyethylene terephthalate (polyethylene phthalate modified with 6 mol% isophthalic acid) was used instead of the recycled polyethylene terephthalate having an intrinsic viscosity of 0.60 dl/g, and the air jet nozzle was adjusted so that the measured spread of the islands-in-sea type composite fiber on the conveyor belt (collection surface) was 27.0 cm to obtain a sheet of islands-in-sea type composite fiber. The results are shown in Table 1.

[Comparative Example 3]
Dyed artificial leather was obtained in the same manner as in Comparative Example 2, except that circular dyeing was used instead of thermosol dyeing. The results are shown in Table 1.

[Comparative Example 4]
A dyed artificial leather was obtained in the same manner as in Example 1, except that a sheet of islands-in-sea type composite fibers was obtained by adjusting the air jet nozzle so that the measured spread of the islands-in-sea type composite fibers on the conveyor belt (collection surface) was 23.2 cm. The results are shown in Table 1.

It can be seen from Table 1 that the artificial leathers obtained in Examples 1 to 5 have a soft feel with little rebound.
On the other hand, the artificial leathers obtained in Comparative Examples 1, 2, and 4, which do not have the configuration of the present invention, have a strong resilience and are inferior in texture, and the artificial leather obtained in Comparative Example 3, which does not have the configuration of the present invention, has a strong resilience.

Claims (10)

An artificial leather including ultrafine fibers containing a polyester resin,
In the longitudinal cross section of the artificial leather, the area ratio A occupied by the ultrafine fibers oriented in the thickness direction in the range of −30° to +30° is 4.5% or less,
An artificial leather, wherein an area ratio B occupied by ultrafine fibers oriented at an angle of −30° to +30° in the thickness direction in a transverse cross section of the artificial leather and the area ratio A satisfy A/B≦0.9. The artificial leather described in claim 1, wherein the average diameter of the ultrafine fibers is 7.5 μm or less. The artificial leather according to claim 1 or 2, wherein the average fineness of the ultrafine fibers is 0.50 dtex or less. The artificial leather according to claim 1 or 2, wherein the ultrafine fibers are long fibers. The artificial leather according to claim 1 or 2, wherein the polyester resin is polyethylene terephthalate. The artificial leather according to claim 1 or 2, wherein the intrinsic viscosity of the polyester resin is 0.63 dl/g or less. The artificial leather described in claim 5, wherein the polyethylene terephthalate contains dicarboxylic acid units and diol units, and 94 mol % or more of the dicarboxylic acid units are structural units derived from terephthalic acid. The artificial leather described in claim 7, wherein the polyethylene terephthalate is recycled polyethylene terephthalate. A method for producing the artificial leather according to claim 1 or 2,
Providing a fiber web formed from ultrafine fiber-generating fibers;
forming an entangled fiber sheet using the fiber web;
a step of shrinking the entangled fiber sheet and removing at least one component from the ultrafine fiber-forming fiber to obtain an artificial leather substrate;
and a step of dyeing the artificial leather substrate.
A method for producing an artificial leather, wherein the ratio (Y/X) of the strength X at the yield point in the transverse direction of the fiber web to the maximum strength Y after the yield point is 4.0 or less. The method for producing an artificial leather according to claim 9, wherein the ultrafine fiber-forming fibers are not impregnated with a polymeric elastomer before one component is extracted from the ultrafine fiber-forming fibers.