Artificial leather and method for producing artificial leather

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

[0001] The present invention relates to an artificial leather and a method for producing the artificial leather.

[0002] 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, including clothing and materials. Artificial leathers are also required to satisfy high levels of physical property requirements, such as light resistance, pilling resistance, and abrasion resistance, as well as aesthetic requirements, such as appearance (surface texture closer to that of natural leather), texture (soft feel combined with a moderate sense of fullness and fullness), and color development (vividness and richness of color), and various proposals have been made to address these requirements.

[0003] For example, Patent Document 1 discloses 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 have an average cross-sectional area of ​​0.1 to 30 μm ２ The average cross-sectional area of ​​the fiber is 40 to 400 μm. ２ The ultrafine fiber bundles have a density of 600 to 4000 pieces / mm in any cross section parallel to the thickness direction of the ultrafine fiber entangled body. ２ The leather-like sheet is described as having excellent flexibility.

[0004] International Publication No. 2007 / 040144

[0005] Artificial leather is generally dyed to impart design and satisfy aesthetic requirements, but the dyeing process requires a large amount of water. Furthermore, from the perspective of sustainability, there is a growing demand for reduced water consumption. Thermosol dyeing is a method that requires less water, but artificial leather dyed by thermosol dyeing has the disadvantage of being too resilient and lacking in flexibility.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide an artificial leather which solves the above-mentioned problems, has little repulsion and a soft feel even without softening treatment, and a method for producing the same.

[0007] As a result of extensive investigations, the present inventors have found that the above-mentioned problems can be solved by setting the area proportions of ultrafine fibers oriented within specific ranges in the longitudinal cross section and the transverse cross section of the artificial leather to specific values ​​and ratios, respectively, and have arrived at the present invention. That is, the present invention encompasses the following inventions.

[0008] [1] An artificial leather comprising ultrafine fibers containing a polyester-based resin, wherein the area ratio A of the ultrafine fibers oriented at an angle of -30° to +30° in the thickness direction in the longitudinal cross section of the artificial leather is 4.5% or less, and the area ratio B of the ultrafine fibers oriented at an angle of -30° to +30° in the thickness direction in the transverse cross section of the artificial leather to the area ratio A satisfies A / B ≦ 0.9. [2] The artificial leather according to [1] above, wherein the average diameter of the ultrafine fibers is 7.5 μm or less. [3] The artificial leather according to [1] or [2] above, wherein the average fineness of the ultrafine fibers is 0.50 dtex or less. [4] The artificial leather according to any one of [1] to [3] above, wherein the ultrafine fibers are long fibers. [5] The artificial leather according to any one of [1] to [4] above, wherein the polyester-based resin is polyethylene terephthalate. [6] The artificial leather according to any one of [1] to [5] above, wherein the intrinsic viscosity of the polyester resin is 0.63 dL / g or less. [7] The artificial leather according to [5] above, 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 [7] above, wherein the polyethylene terephthalate is recycled polyethylene terephthalate. [9] A method for producing the artificial leather according to any one of [1] to [8] above, comprising the steps of: preparing a fiber web formed from ultrafine fiber-forming fibers; forming an entangled fiber sheet using the fiber web; shrinking the entangled fiber sheet and removing at least one component from the ultrafine fiber-forming fibers to obtain an artificial leather substrate; and dyeing the artificial leather substrate, 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.

[0009] According to the present invention, it is possible to provide an artificial leather that has a soft feel with little rebound even without softening treatment, and a method for producing the same.

[0010] Below, we will explain the artificial leather of an embodiment of the present invention and the manufacturing method of the artificial leather of an embodiment of the present invention (hereinafter sometimes referred to as ``artificial leather of this embodiment'' or ``manufacturing method of the artificial leather of this embodiment'').

[0011] [Artificial Leather] The artificial leather of the present embodiment is an artificial leather containing ultrafine fibers containing a polyester-based resin, in which an area ratio A occupied by ultrafine fibers oriented at an angle of −30° to +30° in the thickness direction in a longitudinal cross section of the artificial leather 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.

[0012] The artificial leather of this embodiment has the above-described structure, which allows the crossing of the ultrafine fibers in the artificial leather to be moderate, resulting in an artificial leather with a soft texture and little rebound, even without softening treatment. The artificial leather of the present invention refers to an artificial leather with a texture similar to that of artificially produced natural leather, and includes raised-nap artificial leather with a raised surface, grain-finish artificial leather, etc. Furthermore, raised-nap artificial leather includes suede-like, velour-like, nubuck-like, etc., as variations depending on the raised surface condition.

[0013] In this specification, the direction in which the stretchability of the artificial leather is smallest when the artificial leather is pulled refers to the "longitudinal direction" of the artificial leather, and the direction perpendicular to this direction refers to the "lateral direction" of the artificial leather. The flow direction of the artificial leather during production is also referred to as the "longitudinal direction" of the artificial leather. In this specification, "area ratio A" and "area ratio B" are values ​​calculated from photographs of the cross sections obtained by cutting the artificial leather in the longitudinal thickness direction or the lateral thickness direction and taking them at 150x magnification using a scanning electron microscope (SEM). More specifically, area ratio A and area ratio B are measured by the procedures described in the Examples.

[0014] 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, it 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%. The area ratio A can be adjusted to a desired value by adjusting the number of intersections between fibers in the fiber web, etc.

[0015] The ratio A / B of the area proportion A to the area proportion B is A / B≦0.9, and from the viewpoint of obtaining an artificial leather having 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, and 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.

[0016] From the viewpoint of obtaining an artificial leather having a less resilient feel 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, it 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%. The area ratio B can be adjusted by the ratio by which the width of the artificial leather is expanded after dyeing; the higher the ratio by which the width of the artificial leather is expanded, the more the area ratio B can be reduced, and the smaller the ratio by which the width of the artificial leather is expanded, the more the area ratio B can be increased.

[0017] The thickness 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 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).

[0018] The apparent density of the artificial leather of this embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather having less resilience and a softer texture, it is preferably 0.10 to 1.00 g / cm ３ , more preferably 0.20 to 0.80 g / cm ３ , more preferably 0.30 to 0.60 g / cm ３ , and even more preferably 0.35 to 0.48 g / cm ３ The above "apparent density" is a value measured in accordance with JIS K6505 (1995) 5.2.2.

[0019] 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 , more preferably 200 to 600 g / m ２ The "basis weight" is a value measured in accordance with JIS L1096 (2010) (Method A).

[0020] 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 preferably an artificial leather having a napped surface, that is, a napped artificial leather.

[0021] <Ultrafine Fibers> The ultrafine fibers contained in the artificial leather of this embodiment 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. Also, the ultrafine fiber bundle is a bundle of multiple ultrafine fibers.

[0022] The ultrafine fibers of this embodiment are preferably long fibers from the viewpoint of obtaining an artificial leather with less resilience and a softer feel. In this specification, "long fibers" refers to continuous fibers that are not short fibers intentionally cut after spinning. More specifically, it refers to filaments or continuous fibers that are not short fibers intentionally cut to a fiber length of, for example, about 3 to 80 mm. The fiber length of the islands-in-sea 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 with a fiber length of several meters, several hundred meters, several kilometers, or even longer that are produced by, for example, a spunbonding method and continuously spun. It should be noted that needle punching during entanglement or surface buffing can unavoidably cut some of the long fibers into short fibers during the production process.

[0023] 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 units that substitute for the dicarboxylic acid monomer units 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 units that substitute for the diol monomer units include units derived from diols such as butanediol and hexanediol, which substitute for the ethylene glycol unit. The polyester resin of this embodiment is preferably PET from the viewpoint of obtaining an artificial leather having a softer texture and a lower repulsion feeling. Furthermore, from the viewpoint of recyclability and obtaining an artificial leather having a softer texture, the PET preferably contains 94 mol % or more of the 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 %.

[0024] The polyester-based 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. Also, the polyester-based resin of the present embodiment is preferably recycled PET from the viewpoint of sustainability.

[0025] 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. From the viewpoint of mechanical properties such as tensile strength, tensile elongation, and tear strength, the intrinsic viscosity 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. 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 (1 / 1 by volume) mixed solvent at 30°C using an Ubbelohde viscometer, and is specifically measured according to the procedure described in the Examples.

[0026] The ultrafine fibers of this embodiment may or may not contain a resin other than a 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; polypropylene, polyethylene, polybutene, polymethylpentene, and chlorinated polyolefins. From the viewpoint of recyclability, it is preferable that the ultrafine fibers do not contain any resin other than a polyester-based resin.

[0027] The resin constituting the ultrafine fibers of this embodiment may contain various additives within the range that does not impair the effects of the present invention. Examples of the additives include catalysts, colorants, heat stabilizers, flame retardants, lubricants, antifouling agents, fluorescent brighteners, matting agents, gloss improvers, antistatic agents, fragrances, deodorizers, antibacterial agents, anti-mite agents, and inorganic fine particles.

[0028] 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 repulsion 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 may be 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.

[0029] 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, 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, 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 in an enlarged photograph of the cross section of the ultrafine fibers, and are specifically measured according to the procedures described in the Examples.

[0030] <Polymer elastomer> The artificial leather of this embodiment may or may not contain a polymer elastomer. Any polymer elastomer conventionally used in artificial leathers can be used as the polymer elastomer. 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 the main component, at least one polymer polyol having an average molecular weight of 500 to 3,000 selected from polyester diols, polyether diols, polyether ester diols, polycarbonate diols, polycarbonate ether diols, polycarbonate ester diols, etc., with 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 or ethylenediamine, in a predetermined molar ratio, and polymerizing these in one 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.

[0031] The acrylic elastomer may be a mixture of 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, and cyclohexyl methacrylate. and (meth)acrylic acid, and 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 an ethylenically unsaturated monomer comprising at least one crosslink-forming 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.

[0032] Artificial leathers obtained using polyurethane elastomers as the main polymeric elastomer are preferred because they offer an excellent balance of texture and mechanical properties, and if the appropriate type is selected, they also offer an excellent balance, including durability. Artificial leathers obtained using acrylic elastomers are unsuitable for producing napped artificial leathers because the acrylic elastomers have lower adhesion to ultrafine fiber bundles than polyurethane elastomers and are less effective at fixing the nap during nap formation. However, they are particularly preferred for producing grain-finish artificial leathers because the degree of hardening of the texture relative to the content is suppressed. Different types of polymeric elastomers may be mixed or added multiple times. In addition to the aforementioned main polymeric elastomers such as polyurethane elastomers, acrylonitrile elastomers, olefin elastomers, polyester elastomers, and acrylic elastomers, polymeric elastomers such as synthetic rubbers may also be added as needed to form polymeric elastomer compositions.

[0033] When the artificial leather of the present embodiment contains a polymeric elastomer, the content thereof 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 having an excellent texture.

[0034] <Other Components> The artificial leather of this embodiment may or may not contain components other than the ultrafine fibers and the polymeric elastomer. Examples of 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 polymeric elastomer. 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 facilitating the desired effects of the other components and of water absorbency, water repellency, stain resistance, etc.

[0035] [Method for manufacturing artificial leather] From the viewpoint of obtaining an artificial leather with less resilience and a softer texture, the artificial leather according to this embodiment is preferably manufactured by a manufacturing 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 step (1) to the maximum strength Y after the yield point is 4.0 or less: Step (1): preparing a fiber web formed from ultrafine fiber-generating fibers; Step (2): forming an entangled fiber sheet using the fiber web; Step (3): shrinking the entangled fiber sheet and removing at least one component from the ultrafine fiber-generating fibers to obtain an artificial leather substrate; and Step (4): dyeing the artificial leather substrate.

[0036] The manufacturing method according to the present embodiment includes a step (step (1)) of preparing a fiber web having a ratio (Y / X) of the strength at the yield point X in the transverse direction to the maximum strength after the yield point Y of 4.0 or less, which makes it easier to obtain the artificial leather of the present embodiment. Each step will be described below.

[0037] <Step (1)> Step (1) is a step of preparing a fiber web formed from ultrafine fiber-forming 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 with different chemical or physical properties. The multicomponent fiber that generates these ultrafine fibers is an ultrafine fiber-forming fiber. Typical examples of ultrafine fiber-forming fibers include islands-in-sea composite fibers, multilayer laminated composite fibers, and radial laminated composite fibers obtained using methods such as chip blending (mixed spinning) and composite spinning. Among these, islands-in-sea composite fibers are preferred from the viewpoints of improving productivity through high-speed spinning and of obtaining artificial leather that is excellent in surface abrasion resistance and pilling resistance. From the same viewpoint, it is preferable to melt-spin the islands-in-sea composite fiber to obtain a fiber web. When the ultrafine fiber-forming fiber is an islands-in-sea composite fiber, island components are dispersed in a sea component that forms a matrix in the fiber cross section, and removing the sea component generates ultrafine fibers in the form of fiber bundles. 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.

[0038] Examples of island component resins contained in islands-in-sea composite fibers and later becoming ultrafine fibers include resins similar to those constituting the ultrafine fibers in the above-mentioned "ultrafine fibers." The sea component resin contained in islands-in-sea composite fibers and removed by extraction, decomposition, or the like is preferably a resin that differs in solubility or decomposition from the island component resin and has low compatibility. Such a resin is preferably selected appropriately depending on the type of island component resin and the manufacturing method. Examples of sea component resins 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 with 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-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 physical properties (fiber strength), and polyethylene and modified polyvinyl alcohol are more preferred.

[0039] 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 copolymerization units in the polyvinyl alcohol is preferably 1 to 20 mol%, more preferably 4 to 15 mol%, and even more preferably 6 to 13 mol%. Furthermore, since the fiber properties are improved when the copolymerization units are ethylene, ethylene-modified polyvinyl alcohol is more preferred. The content of ethylene units in the ethylene-modified polyvinyl alcohol is preferably 4 to 15 mol%, and more preferably 6 to 13 mol%.

[0040] The mass ratio of the sea component to the island component in the islands-in-sea type composite fiber is not particularly limited, but is preferably in the range of 5:95 to 80:20 (sea component:island component). When the sea component polymer ratio in the islands-in-sea type composite fiber is 5% by mass or more, the spinning stability of the islands-in-sea type fiber is less likely to decrease, and industrial productivity is easily ensured. Furthermore, when a polymeric elastomer is added, voids of a required size are easily formed between the ultrafine fiber bundles and the polymeric elastomer after the sea component is removed, and as a result, a fluffy feel, a solid feel, a dense surface feel, and the like are easily obtained. On the other hand, when 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 type fiber are stable, and a decrease in quality stability is easily prevented.

[0041] As a method for producing a fiber web, it is preferable to employ a method in which ultrafine fiber-generating fibers melt-spun using a so-called spunbonding method are collected on a conveyor belt without being cut, to form a fiber web of long fibers that are continuous fibers.

[0042] 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 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 directly below the nozzle holes and the suction device described below. A high-speed air stream is applied using a suction device such as an air jet nozzle to uniformly draw and attenuate the islands-in-sea composite fibers 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 ordinary spinning, falls within 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 composite fibers are opened by a collision plate, an air stream, or the like, and then collected and deposited on a collecting surface such as a conveyor belt moving in the longitudinal direction while being suctioned 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 collecting surface is preferably 10 to 100 cm, more preferably 30 to 80 cm, and even more preferably 40 to 70 cm. The suction speed onto the collecting surface is preferably 5 to 35 m / sec, more preferably 10 to 25 m / sec. The movement speed of the collecting surface is preferably 20 to 150 m / min, more preferably 50 to 120 m / min. 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, and the like, it is possible to appropriately adjust the degree of spreading and the number of intersections of the islands-in-sea type composite fibers collected on the collecting surface. As a result, an artificial leather with a softer feel and less repulsive feeling can be obtained.

[0043] In the process 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 stretching when the entangled fiber sheet is shrunk and at least one component is removed from the ultrafine fiber-forming fiber, making it more difficult to stretch in the lateral direction, and thus increasing the area ratio A. Furthermore, the smaller the spread when landing on the belt, the fewer the number of intersections between the fibers. The smaller the number of intersections between the fibers, the easier it is for the fibers to properly slip through as they stretch in the longitudinal direction when at least one component is removed from the ultrafine fiber-forming fiber, making it less likely that residual strain will remain and making it easier to stretch in the lateral direction, and thus decreasing the area ratio A.

[0044] The fibrous web may be subjected to a heat press treatment to impart shape stability, and the fibrous web may be fused in the process.

[0045] 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, making it easier to obtain the artificial leather of this embodiment. In step (3), such a fiber web shrinks in the transverse direction (width direction), relaxing the tension in the transverse fibers. Furthermore, the fibers are appropriately removed in the longitudinal direction, relaxing the tension in the longitudinal direction. This also suppresses thickness collapse, making it easier to obtain an artificial leather with a soft texture and a less increase in apparent density. Y / X is preferably 3.9 or less from the viewpoint of obtaining an artificial leather with a softer texture and less resilience.

[0046] <Step (2)> Step (2) is a step of forming an entangled fiber sheet using the fiber web. In step (2), multiple layers of the fiber web obtained in step (1) are stacked together, and then an entanglement treatment such as needle punching or hydroentanglement is performed to obtain an entangled web in which the long fibers are entangled in the thickness direction. As a method for stacking multiple fiber webs, the fiber webs may be stacked in the same direction, or the fiber webs may be stacked by a cross-wrapping method, in which the transport direction of the fiber web is changed to a 90° direction and folded back. Cross-wrapping is preferred as a method for stacking multiple fiber webs, as it allows for easy adjustment of the width of the entangled fiber sheet and can suppress unevenness in the width direction of the fiber web, i.e., can suppress unevenness in basis weight. The number of layers of the stacked webs is not particularly limited, but is preferably 4 or more, more preferably 8 or more, from the viewpoint of mechanical strength, and preferably 20 or less, more preferably 16 or less, from the viewpoint of ease of production.

[0047] A multi-layered fiber web is subjected to a mechanical entanglement treatment by a known method such as needle punching or high-pressure water jet treatment, 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 treatment is performed by the needle punching method, various treatment conditions are appropriately selected, such as the type of needle (needle shape and count, barb shape and depth, number and position of barbs, etc.), needle punch count (needle punch treatment density per unit area obtained by multiplying the density of needles implanted on a needle board by the number of strokes the board applies to the fiber web per unit area), and needle punch depth (depth at which the needles apply to the fiber web). When the component to be removed from the ultrafine fiber-generating fiber in the process of obtaining an artificial leather substrate is a water-soluble polymer, the entanglement treatment is preferably performed by the needle punching method in order to suppress the elution of the water-soluble polymer during the entanglement treatment.

[0048] The punch density of the needle punching process is 1500 to 5500 punches / cm ２ , and further, 2000 to 5000 punches / cm ２If the punch density is within the above range, insufficient entanglement is suppressed, and the surface of the artificial leather is prevented from becoming rough due to fraying of the fibers, and further, cutting of the fibers is suppressed, and a decrease in the degree of entanglement is prevented.

[0049] In addition, at any stage from the spinning of the islands-in-sea type composite fiber to the entanglement treatment, an oil or an antistatic agent may be applied to the ultrafine fiber-generating fiber, the fiber web, the fiber web laminate, the entangled fiber sheet, etc. Furthermore, if necessary, the ultrafine fiber-generating fiber, the fiber web, the fiber web laminate, the entangled fiber sheet, etc. may be subjected to a shrinkage treatment by immersing them in hot water at about 70 to 150°C to make the entanglement state dense in advance.

[0050] The basis weight of the entangled fiber sheet obtained by entanglement is 100 to 1000 g / m ２ It is preferable that the fiber density is in the range of about 1 / 2000. 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. 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 heat pressing as needed for the purposes of fixing the shape of the entangled fiber sheet and smoothing the surface.

[0051] <Step (3)> Step (3) is a step of obtaining an artificial leather substrate by shrinking the entangled fiber sheet and removing at least one component from the ultrafine fiber-forming fibers. The one component is preferably a sea component resin contained in islands-in-sea composite fibers. By removing the sea component, the ultrafine fiber-forming fibers can be converted into a fiber bundle of ultrafine fibers.

[0052] Methods for shrinking the entangled fiber sheet include heat shrinkage treatment (fiber shrinkage treatment) using steam, hot water, dry heat, etc. When the entangled fiber sheet is heat shrinked, it shrinks in the transverse direction (width direction), which relieves the tension of the fibers in the transverse direction. In addition, in the process of removing at least one component, the fibers are appropriately pulled out in the longitudinal direction, which also relieves the tension in the longitudinal direction and suppresses an increase in apparent density. As a result, an artificial leather with less resilience and a softer texture can be obtained.

[0053] Examples of methods for removing the sea component resin include a method using a solvent or decomposing agent capable of selectively removing only the sea component 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 an organic solvent and the island component resin is a polyamide resin or a polyester resin, examples of organic solvents 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.

[0054] 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-forming fibers, and when the sea component is a water-soluble resin, it is preferable to shrink the entangled fiber sheet and remove the water-soluble resin by using hot water. Furthermore, when removing the sea component, a dip-nip treatment may be carried out in parallel.

[0055] <Step (4)> Step (4) is a step of dyeing the artificial leather substrate. Step (4) can be performed at any stage after the islands-in-sea fibers are converted into ultrafine fiber bundles.

[0056] In step (4), any dyeing method using a known dyeing machine typically used for dyeing conventional artificial leathers such as padder, jigger, circular, and wince leathers can be employed, using dyes based on disperse dyes, reactive dyes, acid dyes, metal complex dyes, sulfide dyes, sulfide vat dyes, etc., selected appropriately depending on the type of fiber. Meanwhile, conventional artificial leathers dyed by thermosol dyeing have had problems with strong resilience and poor flexibility. However, even if an artificial leather substrate manufactured by a manufacturing method comprising steps (1) to (3) and in which the ratio (Y / X) of the strength X at the yield point in the transverse direction of the fiber web prepared in step (1) to the maximum strength Y after the yield point is 4.0 or less, an artificial leather with low resilience and a soft texture can be obtained by thermosol dyeing. Furthermore, thermosol dyeing can significantly reduce water consumption compared to dyeing methods used for general artificial leathers, thereby reducing environmental impact. Therefore, dyeing the artificial leather substrate by thermosol dyeing is preferred from the perspective of reducing environmental impact.

[0057] <Step (5)> The method for producing an artificial leather according to this embodiment may further include step (5), which is a step of impregnating the entangled fiber sheet with the polymer elastomer, from the viewpoint of imparting texture and dimensional stability similar to those of natural leather. Step (5) may be performed between steps (2) and (3), or between steps (3) and (4). In the production of the artificial leather according to this embodiment, in order to impart texture and dimensional stability similar to those of natural leather as well as flexibility, it is preferable to perform step (5) between steps (2) and (3). That is, it is preferable to impregnate the entangled fiber sheet with the polymer elastomer before removing the sea component. By impregnating the entangled fiber sheet with the polymer elastomer before removing the sea component, voids formed by removing the sea component are formed between the ultrafine fibers that form the fiber bundles after removing the sea component. As a result, the ultrafine fibers within the fiber bundles are less likely to be restrained by the polymer elastomer, i.e., the ultrafine fiber bundles are less susceptible to the influence of the polymer elastomer, making it easier to obtain an artificial leather with excellent flexibility. When the ultrafine fibers forming the fiber bundles after the sea component has been removed from the islands-in-sea type composite fiber are impregnated with a polymeric elastomer, the polymeric elastomer penetrates into the voids in the fiber bundles, and the ultrafine fibers forming the fiber bundles are bound by the polymeric elastomer, making it easier to obtain an artificial leather with a hard texture.

[0058] 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 easily obtained, while in the latter case, the amount of organic solvent used can be easily reduced.

[0059] The concentration of the polymeric elastomer body fluid, i.e., the content of the polymeric elastomer in the polymeric elastomer body fluid, is preferably 0.1 to 60% by mass. The polymeric elastomer 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 final artificial leather.

[0060] Details of the polymeric elastomer used in step (5) are as explained above in the section "polymeric elastomer."

[0061] The polymeric elastomer may be fixed in the entangled fiber sheet by impregnating the entangled fiber sheet with the polymeric elastomer and then coagulating the polymeric elastomer by a conventionally known dry or wet method. The dry method here refers to any method for fixing the polymeric elastomer in a fiber sheet structure by removing the solvent, dispersant, etc. by drying or the like. The wet method here refers to any method for temporarily or completely fixing the polymeric elastomer in the entangled fiber sheet structure prior to removing the dispersant by treating the entangled fiber sheet structure impregnated with a polymeric elastomer liquid with a non-solvent or coagulant for the polymeric elastomer, or by subjecting the impregnated entangled fiber sheet to a heat treatment or the like using an aqueous polymeric elastomer liquid containing a thermosensitive gelling agent or the like.

[0062] Since the artificial leather according to this embodiment has a texture similar to that of natural leather even without the polymer elastomer, it is preferable not to impregnate the artificial leather with the polymer elastomer, i.e., it is preferable not to include step (5).

[0063] In addition to the above steps (1) to (5), finishing treatments such as mechanical kneading treatment in a dry state, relaxation treatment in a wet state using a dyeing machine or washing machine, treatment with a softener, treatment to impart functionality such as a flame retardant, antibacterial agent, deodorizer, or water / oil repellent, treatment to impart a texture modifier such as a silicone resin, a silk protein-containing treatment agent, or a grip-imparting 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 needed.

[0064] As in the case of conventional artificial leather production, the artificial leather of this embodiment may be sliced ​​into multiple pieces in the thickness direction, and the thickness may be adjusted by grinding the surface that will become the back surface, or a solvent that can dissolve or swell the polymer elastomer or ultrafine fiber bundles may be applied to the surface that will become the back surface.

[0065] The artificial leather of this embodiment may have a napped surface. Formation of the napped surface can be achieved by any known method, such as buffing with sandpaper or card cloth, or brushing. Furthermore, before or after such nap-raising treatment, a solvent capable of dissolving or swelling the elastomer polymer 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 elastomer polymer or ultrafine fiber bundles, the nap length of the ultrafine fibers, and the surface friction durability of the artificial leather. Furthermore, the above-mentioned step (4) may be performed after the nap-raising treatment.

[0066] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to the contents of the examples.

[0067] First, the evaluation methods used in the examples and comparative examples described below will be summarized below.

[0068] <Intrinsic Viscosity> Using a phenol / tetrachloroethane (volume ratio 1 / 1) mixed solvent as the solvent, the intrinsic viscosity was measured at a measurement temperature of 30° C. using an Ubbelohde viscometer "HRK-3" (manufactured by Hayashi Seisakusho).

[0069] <Spread of islands-in-sea type composite fiber on the conveyor belt (collection surface)> An islands-in-sea type composite fiber was discharged from an air jet nozzle onto a 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.

[0070] <Yield strength X and maximum strength Y after yield point in the transverse direction of the fiber web> A fiber web was cut into a size of 16 cm x 16 cm and folded in quarters in the longitudinal direction (first folded in half to reduce the area, and then folded again to reduce the area to one-quarter) to obtain a test specimen with a width of 4 cm. The specimen was elongated using a precision universal testing machine (Shimadzu Corporation, Autograph AG-X Plus) with a grip spacing 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. The yield strength X (kg) and the maximum strength Y after yield point (maximum value of strength after yield point) were read from the obtained SS curve.

[0071] <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 polymer elastomer in the artificial leather was then calculated based on the following formula (2): Polymer elastomer content (mass%) = D / C × 100 (Formula (2)). Note that "solid content" refers to components excluding solvents and dispersants.

[0072] <Average Diameter> The average diameter of 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 fiber cross sections 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 result calculated based on the following formula (1) was taken as the average diameter of the fibers. Average diameter = (average cross-sectional area / π) １／２ ×2...Formula (1)

[0073] <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 fiber cross sections were randomly selected from the SEM photograph, and the cross-sectional areas were measured to calculate the arithmetic mean value of the cross-sectional areas. The average value of the cross-sectional areas was then converted into an average fineness using the density of the resin.

[0074] 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. A straight line was drawn evenly across the boundary between the artificial leather substrate and the roots of the napped fibers on the printed surface. Furthermore, a rectangle equivalent to 400 μm (depth direction) × 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 (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 this PET film was analyzed using image analysis software "Image-Pro Premier ver. 9.1" (manufactured by Nippon Rover Co., Ltd.) to measure the area of ​​the longitudinal cross section of the artificial leather. Next, the PET film with the blackened rectangular portion was replaced with a new transparent PET film placed on the printed surface so as to cover the rectangle. When the straight line was taken as 0° and the angle (±90° or less) formed by the straight line and the ultrafine fibers was taken as the angle in the thickness direction, the PET film surface in the portion where the ultrafine fibers were oriented in the thickness direction within a range of -30° to +30° was painted black. In the same manner as in measuring the area of ​​the longitudinal cross section of the artificial leather, the image analysis software was used to measure the area of ​​the ultrafine fibers oriented in the thickness direction within a range of -30° to +30°. From the area of ​​the longitudinal cross section of the obtained artificial leather and the area of ​​the ultrafine fibers oriented in the range of -30° to +30° in the thickness direction, the area percentage A (%) occupied by the ultrafine fibers oriented in the range of -30° to +30° in the thickness direction in the longitudinal cross section of the artificial leather was calculated. Next, the artificial leather was cut in the transverse thickness direction with a single-edged razor, and the area percentage B (%) occupied by the ultrafine fibers oriented in the range of -30° to +30° in the thickness direction in the transverse cross section of the artificial leather was calculated using the same procedure as in calculating the area percentage A (%).

[0075] <Thickness, basis weight and apparent density> The obtained artificial leather was cut into a 16 cm x 16 cm size (256 cm ２The mass (g) of the cut artificial leather was measured, and the basis weight (g / m) of the cut artificial leather was calculated using the following formula (3). ２ The thickness (mm) of the cut artificial leather was measured under a constant pressure of 23.5 kPa for 5 seconds using a thickness gauge (measuring probe diameter: 10 mm) in accordance with JIS L1096 (2010) (Method A), 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. ３ Apparent density = basis weight / thickness / 1000 (Equation 4)

[0076] <Young's modulus> Three sheets of the artificial leathers obtained in the Examples and Comparative Examples were stacked together using a YAWASA (YWS-5N-1-SL) (manufactured by Tech Gihan Co., Ltd.), and compressed in the thickness direction using a pressing tool with a diameter of 1 mm at a speed of 0.2 m / sec up to a maximum pressing force of 0.2 N, thereby measuring the Young's modulus.

[0077] <Texture> The texture of the obtained artificial leather after bending was judged visually and by touch according to the following criteria: A: The texture was full, had little resilience, was free of large buckling wrinkles, and was easy to bend and flexible. B: The texture fell into one or more of the following categories: lacked fullness, had resilience, had large buckling wrinkles, and was hard.

[0078] Example 1 An islands-in-sea composite fiber was extruded from a melt conjugate spinning die (number of islands: 25 per fiber) at 270°C using a water-soluble thermoplastic polyvinyl alcohol resin (modified polyvinyl alcohol modified by ethylene copolymerization) as the sea component and recycled polyethylene terephthalate (dicarboxylic acid units, 100 mol% of which are structural units derived from terephthalic acid) with an intrinsic viscosity of 0.60 dl / g as the island component, so that the sea component / island component ratio was 25 / 75 (mass ratio). An air jet nozzle was then installed 55 cm above the conveyor belt (collection surface of the islands-in-sea composite fiber), and spinning was performed while pulling and attenuating the fibers at a spinning speed of 3,279 m / min. Islands-in-sea composite fibers with an average fineness of 3.05 dtex were collected on the conveyor belt, yielding an islands-in-sea composite fiber sheet. Under the above collection conditions, the spread (length) of the islands-in-sea composite fiber 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 strength X at the yield point in the transverse direction of the resulting fiber web was 0.6 kg, the elongation was 6%, the maximum strength Y after the yield point was 1.73 kg, and the elongation at the maximum strength Y was 190%, resulting in a Y / X = 2.9. The fiber webs were then cross-lap laminated to form a laminate web. The laminate web was then needle-punched using 6-barb needles to obtain a basis weight of 292 g / m ２ An entangled fiber sheet with longitudinal crimping was formed. 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, thereby dissolving and removing the water-soluble thermoplastic polyvinyl alcohol resin, which is the sea component of the islands-in-sea composite fiber, and forming polyethylene terephthalate ultrafine fibers with an average diameter of 3.02 µm and an average fineness of 0.101 dtex. The sheet was then dried to obtain an artificial leather substrate. Next, the obtained artificial leather substrate was thermosol dyed using a disperse dye and subjected to a nap-raising treatment to obtain an artificial leather with a napped surface. The obtained artificial leather had a basis weight of 436 g / m ２ , apparent density 0.451 g / cm ３The resulting artificial leather had a solid feel with little rebound, was free of large buckling wrinkles, and was easily bent and had excellent flexibility.

[0079] [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.

[0080] [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.

[0081] [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.

[0082] [Example 5] Dyed artificial leather was obtained in the same manner as in Example 3, except that 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%), picked up 40%, dried at 140°C for 4 minutes, and then thermosol dyed. The results are shown in Table 1.

[0083] 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.

[0084] Comparative Example 2 A 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.

[0085] 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.

[0086] 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.

[0087]

[0088] It can be seen from Table 1 that the artificial leathers obtained in Examples 1 to 5 have a soft texture with little repulsion. 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 repulsion and poor texture, and the artificial leather obtained in Comparative Example 3, which does not have the configuration of the present invention, has a strong repulsion.

Claims

1. An artificial leather containing ultrafine fibers containing a polyester resin, wherein the area ratio A of ultrafine fibers oriented at an angle of -30° to +30° in the thickness direction in the longitudinal cross section of the artificial leather is 4.5% or less, and the area ratio B of ultrafine fibers oriented at an angle of -30° to +30° in the thickness direction in the transverse cross section of the artificial leather and the area ratio A satisfy A / B≦0.

9.

2. The artificial leather according to claim 1, wherein the average diameter of the ultrafine fibers is 7.5 μm or less.

3. The artificial leather according to claim 1 or 2, wherein the average fineness of the ultrafine fibers is 0.50 dtex or less.

4. The artificial leather according to claim 1 or 2, wherein the ultrafine fibers are long fibers.

5. The artificial leather according to claim 1 or 2, wherein the polyester resin is polyethylene terephthalate.

6. The artificial leather according to claim 1 or 2, wherein the intrinsic viscosity of the polyester resin is 0.63 dl / g or less.

7. The artificial leather according to 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.

8. The artificial leather according to claim 7, wherein the polyethylene terephthalate is recycled polyethylene terephthalate.

9. A method for producing an artificial leather according to claim 1 or 2, comprising the steps of: preparing a fiber web formed from ultrafine fiber-generating fibers; forming an entangled fiber sheet using said fiber web; shrinking said entangled fiber sheet and removing at least one component from said ultrafine fiber-generating fibers to obtain an artificial leather substrate; and dyeing said artificial leather substrate, wherein the ratio (Y / X) of the strength X at the lateral yield point of said 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 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.