Artificial leather and method for producing artificial leather

Abstract

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

Description

Artificial leather and method for manufacturing artificial leather

[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 required to satisfy not only sensory 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 (color clarity and depth), but also physical property requirements such as light resistance, pilling resistance, and abrasion resistance at a high level. 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 entanglement body. ２ The patent document 2 describes a leather-like sheet in which the ultrafine long fiber bundles have a cross-sectional area of ​​170 to 700 μm. The patent document 2 also describes a substrate for artificial leather made of a nonwoven fabric structure of ultrafine long fiber bundles. The ultrafine long fiber bundles have a cross-sectional area of ​​170 to 700 μm. ２ , the aspect ratio is 4.0 or less, and the cross section of the ultrafine long fiber bundle is 1500 to 3000 pieces / mm in any cross section parallel to the thickness direction of the nonwoven fabric structure. ２ The article describes a substrate for artificial leather that exists within a range of 100%. The substrate for artificial leather is described as having high levels of both sensory performance and physical performance, which have been conventionally recognized as contradictory performances.

[0004] International Publication No. 2007 / 040144 Japanese Patent Application Laid-Open No. 2008-308784

[0005] As described in Patent Documents 1 and 2, artificial leathers are generally produced by a method in which multicomponent fibers spun from two types of polymers differing in solubility and degradability are stapled, and the stapled fibers are formed into a web of a desired weight using a card, cross wrapper, random weber, or the like. The fibers are then entangled with one another using a needle punch, water jet, or the like to form an entangled nonwoven fabric, which is then coagulated by applying a solution or emulsion of a polymeric elastomer such as polyurethane, and then one component of the multicomponent fibers is removed or reduced in weight to form ultrafine fibers; alternatively, the above-mentioned steps of impregnating and coagulating the polymeric elastomer and converting the multicomponent fibers into ultrafine fibers are carried out in the reverse order.

[0006] Although the techniques described in Patent Documents 1 and 2 improve the quality of artificial leather, they have problems such as the tendency for fibers to come off and unsatisfactory surface abrasion resistance and pilling resistance, etc., and artificial leather that satisfies the sensory and physical property requirements at an even higher level has been desired. Furthermore, applying an organic solvent or a polymeric elastomer to the surface of the artificial leather can inhibit the fibers from coming off and improve the surface abrasion resistance and pilling resistance to some extent, but this increases the cost, and the use of organic solvents has problems of adverse effects on the human body and the environment.

[0007] The present invention aims to solve the above-mentioned problems and to provide an artificial leather that has excellent texture, surface abrasion resistance, and pilling resistance, and a method for producing the artificial leather.

[0008] As a result of various investigations, the present inventors have found that the above-mentioned problems can be solved by ensuring that, in a cut surface when cut at a depth of 0.3 mm from the surface, the maximum area of ​​the cut surface of the ultrafine fiber bundles is a predetermined value or more and that the number ratio of the ultrafine fiber bundles is a predetermined value or more, and have arrived at the present invention. That is, the present invention encompasses the following inventions.

[0009] [1] An artificial leather containing ultrafine fibers, wherein the maximum area of ​​the cut surface of the ultrafine fiber bundles when cut at a depth of 0.3 mm from the surface is 4500 μm ２ or more, and the area of ​​the cut surfaces relative to the total number of cut surfaces of the ultrafine fiber bundle is 500 μm ２[2] The total area of ​​the ultrafine fiber bundles on the cut surface is 50,000 μm or more. ２ / mm ２ [3] The artificial leather according to the above [1] or [2], wherein the average diameter of the ultrafine fibers is 7.5 μm or less. [4] The artificial leather according to any one of the above [1] to [3], wherein the average fineness of the ultrafine fibers is 0.5 dtex or less. [5] The artificial leather according to any one of the above [1] to [4], wherein the ultrafine fibers are long fibers. [6] The artificial leather according to any one of the above [1] to [5], wherein the polymer elastomer is contained in an amount of 45% by mass or less. [7] A method for producing an artificial leather according to any one of [1] to [6] above, comprising the steps of: preparing a fiber web formed from ultrafine fiber-generating fibers; crimping the fiber web to form a crimped fiber web; stacking a plurality of the crimped fiber webs to form a web laminate; entangling the web laminate to form an entangled fiber sheet; and removing at least one component from the ultrafine fiber-generating fibers. [8] A method for producing an artificial leather according to [7] above, further comprising the step of impregnating the entangled fiber sheet with the polymer elastomer.

[0010] According to the present invention, it is possible to provide an artificial leather having excellent texture, surface abrasion resistance, and pilling resistance, and a method for producing the artificial leather. Furthermore, according to the present invention, it is possible to obtain an artificial leather having the above-mentioned effects without applying an organic solvent or a polymer elastomer to the surface of the artificial leather.

[0011] This is a scanning electron microscope (SEM) image of the remaining cut surface of the artificial leather according to the present invention, which was sliced ​​off at a depth of 0.3 mm from the surface with a single-edged razor, taken at 100x magnification. The image in Figure 1 was printed, the printed surface was placed under a flat panel light, light was applied from the printed surface side to make the image visible through to the back surface, and the cut surface portions of the ultrafine fiber bundles present on the cut surface were painted black and transferred from the back surface (an image in which the left and right sides of Figure 1 are reversed).

[0012] 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'').

[0013] [Artificial Leather] The artificial leather of this embodiment is an artificial leather containing ultrafine fibers, and when cut at a depth of 0.3 mm from the surface, the maximum area of ​​the cut surface of the ultrafine fiber bundles is 4500 μm ２ or more, and the area of ​​the cut surfaces relative to the total number of cut surfaces of the ultrafine fiber bundle is 500 μm ２ The proportion of the number of ultrafine fiber bundles having a fiber count of 60% or more is 60% or more. When the artificial leather is cut at a depth of 0.3 mm from the surface, the maximum area of ​​the cut surface of the ultrafine fiber bundles is a predetermined value or more, and the proportion of the number of ultrafine fiber bundles is a predetermined value or more, so that the artificial leather has excellent texture, surface abrasion resistance, and pilling resistance. The artificial leather of the present invention means an artificial leather having 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 state. In this specification, "a cut surface when cut at a depth of 0.3 mm from the surface" means, in the case of napped artificial leather, a cut surface obtained by slicing at a position where the difference between the thickness of the napped artificial leather and the thickness from the surface opposite the fiber-raised surface to the cut surface is 0.3 mm. In the case of grain-finish artificial leather, it means a cut surface obtained by slicing at a position where the difference between the thickness of the fiber layer constituting the grain-finish artificial leather and the thickness from the surface opposite the surface of the fiber layer in contact with the resin layer to the cut surface is 0.3 mm. Note that this cut surface is a plane parallel to the surface direction of the artificial leather and perpendicular to the thickness direction. Furthermore, in this specification, "excellent texture" means excellent density, flexibility, and the like, and a good feel, which is similar to the texture of natural leather.

[0014] The thickness of the artificial leather of this embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather that is superior in texture, surface abrasion resistance, and pilling resistance, it is preferably 0.1 to 2.0 mm, more preferably 0.3 to 1.5 mm, and even more preferably 0.5 to 1.2 mm. The "thickness" is a value measured in accordance with JIS L1096 (2010) (Method A).

[0015] The apparent density of the artificial leather of this embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather that is superior in texture, surface abrasion resistance, and pilling resistance, it is preferably 0.1 to 1.0 g / cm ３ , more preferably 0.2 to 0.9 g / cm ３ , more preferably 0.3 to 0.8 g / cm ３ The "apparent density" is a value measured in accordance with JIS L1096 (2010) (Method A).

[0016] The basis weight of the artificial leather of this embodiment is not particularly limited, but from the viewpoint of obtaining an artificial leather that is superior in texture, surface abrasion resistance, and pilling resistance, 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).

[0017] The artificial leather of the present embodiment is not particularly limited, but is preferably a napped artificial leather having a napped surface, from the viewpoint of more easily achieving the effects of the present invention.

[0018] <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 having different chemical or physical properties. The ultrafine fiber bundle referred to in the present invention is a bundle of a plurality of ultrafine fibers, which is formed by gathering three or more closely spaced ultrafine fibers with a distance between the ultrafine fibers of 6 μm or less, and the total cross-sectional area of ​​the gathered ultrafine fibers is 60 μm.２ It refers to an aggregate of ultrafine fibers.

[0019] The ultrafine fibers of this embodiment are preferably long fibers from the viewpoint of obtaining artificial leather with superior texture, surface abrasion resistance, and pilling resistance. 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 producible and is 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. Note that, during the production process, needle punching or surface buffing during entanglement can unavoidably cut some of the long fibers to short fibers.

[0020] Examples of resins constituting the ultrafine fibers of this embodiment include modified PET such as polyethylene terephthalate (hereinafter sometimes referred to as "PET"), isophthalic acid-modified PET, sulfoisophthalic acid-modified PET, and cationic dye-dyeable PET; aromatic polyesters such as polybutylene terephthalate and polyhexamethylene terephthalate; aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalerate resin; nylons such as nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, and nylon 6-12; and fibers of polypropylene, polyethylene, polybutene, polymethylpentene, and chlorinated polyolefins. The modified PET is a PET in which at least a portion of the ester-forming dicarboxylic acid monomer units or diol monomer units of unmodified PET are replaced with substitutable monomer units. Specific examples of the modified monomer units that substitute for the dicarboxylic acid-based monomer units include units derived from isophthalic acid, sodium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, adipic acid, etc., that substitute for the terephthalic acid unit. Specific examples of the modified monomer units that substitute for the diol-based monomer units include units derived from diols such as butanediol and hexanediol that substitute for the ethylene glycol unit. Among these, polyester-based resins such as aromatic polyesters and aliphatic polyesters are preferred from the viewpoint of obtaining artificial leathers that are excellent in colorability, surface abrasion resistance, and pilling resistance.Furthermore, from the viewpoint of productivity during spinning, mechanical strength, and the like, preferred are modified PET such as polyethylene terephthalate (PET), isophthalic acid-modified PET, sulfoisophthalic acid-modified PET, and PET dyeable with cationic dyes; aromatic polyesters such as polybutylene terephthalate and polyhexamethylene terephthalate; aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalerate resin; nylons such as nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, and nylon 6-12; and polyolefins such as polypropylene, polyethylene, polybutene, polymethylpentene, and chlorinated polyolefins.

[0021] 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.

[0022] The artificial leather of this embodiment has a maximum area of ​​4500 μm on the cut surface of the ultrafine fiber bundle when cut at a depth of 0.3 mm from the surface. ２ The maximum area of ​​the cut surface of the ultrafine fiber bundle is preferably 5000 μm from the viewpoint of obtaining an artificial leather having better texture, surface abrasion resistance, and pilling resistance. ２ More preferably, 5500 μm or more ２ More preferably, 6000 μm or more ２ From the viewpoint of ease of production and obtaining artificial leather with excellent appearance, it is preferable that the thickness is 30,000 μm or more. ２ Less than or equal to 25,000 μm, more preferably 25,000 μm ２ More preferably, 20,000 μm or less ２ That is, the maximum area of ​​the cut surface of the ultrafine fiber bundle is preferably 5,000 to 30,000 μm ２ , more preferably 5500 to 25000 μm ２ , more preferably 6000 to 20000 μm ２The "maximum area of ​​the cut surface of the ultrafine fiber bundle" is a value calculated based on a photograph of the cut surface when the artificial leather is cut at a depth of 0.3 mm from the surface, taken with a scanning electron microscope (SEM) at 100x magnification, and is specifically measured by the procedure described in the Examples.

[0023] The artificial leather of this embodiment has a cross section of 500 μm with respect to the total number of cross sections of the ultrafine fiber bundles when cut at a depth of 0.3 mm from the surface. ２ The ratio of the number of the ultrafine fiber bundles having an area of ​​500 μm or more to the total number of the cut surfaces of the ultrafine fiber bundles is 60% or more. ２ The number ratio of the ultrafine fiber bundles is preferably 61% or more, more preferably 63% or more, and even more preferably 65% ​​or more, from the viewpoint of obtaining an artificial leather that is more excellent in texture, surface abrasion resistance, and pilling resistance, and when the artificial leather has a fiber-raised surface, from the viewpoint of preventing deterioration in appearance due to the base being visible through gaps in the napped fibers, the number ratio is preferably 95% or less, more preferably 93% or less, and even more preferably 90% or less. That is, the number ratio is preferably 61 to 95%, more preferably 63 to 93%, and even more preferably 65 to 90%. Note that, in the case of the artificial leather having a fiber-raised surface, the area of ​​the cut surface relative to the total number of cut surfaces of the ultrafine fiber bundles is 500 μm ２ The "number ratio of ultrafine fiber bundles" is a value calculated based on a photograph of a cross section of the artificial leather cut at a depth of 0.3 mm from the surface, taken with a scanning electron microscope (SEM) at 100x magnification, and is specifically measured by the procedure described in the Examples.

[0024] The total area of ​​the cut surfaces of the ultrafine fiber bundles when cut at a depth of 0.3 mm from the surface (the total area of ​​the cut surfaces of the ultrafine fiber bundles is ２ From the viewpoint of obtaining artificial leather that is superior in texture, surface abrasion resistance, and pilling resistance, the surface roughness is preferably 25,000 μm ２ / mm ２ More preferably, 40,000 μm or more ２ / mm ２ More preferably, 50,000 μm or more ２ / mm ２From the viewpoint of ease of production and obtaining artificial leather having good tear strength, it is preferably 200,000 μm ２ / mm ２ Less than or equal to 180,000 μm, more preferably 180,000 μm ２ / mm ２ or less, more preferably 150,000 μm ２ / mm ２ That is, the total area of ​​the cut surfaces of the ultrafine fiber bundle is preferably 25,000 to 200,000 μm ２ / mm ２ , more preferably 40,000 to 180,000 μm ２ / mm ２ , more preferably 50,000 to 150,000 μm ２ / mm ２ The "total area of ​​the cut surfaces of the ultrafine fiber bundles" is a value calculated based on a photograph of the cut surfaces of the artificial leather cut at a depth of 0.3 mm from the surface, taken with a scanning electron microscope (SEM) at 100x magnification, and is specifically measured by the procedure described in the Examples.

[0025] From the viewpoint of obtaining artificial leather having superior texture, surface abrasion resistance, and pilling resistance, 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 still more preferably 5.0 μm or less. There is no particular lower limit, but from the viewpoint of ease of production and color development, it is, for example, 1.0 μm or more, or 1.5 μm or more. In other words, the average diameter of the ultrafine fibers of this embodiment is preferably 1.0 to 7.5 μm, and more preferably 1.5 to 6.0 μm.

[0026] 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 that is superior in texture, surface abrasion resistance, and pilling resistance. There is no particular lower limit, but from the viewpoint of ease of production and color development, it is, for example, 0.01 dtex or more, or 0.02 dtex or more. In other words, the average fineness of the ultrafine fibers of this embodiment is preferably 0.01 to 0.50 dtex, and more preferably 0.01 to 0.40 dtex. The above-mentioned "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 by the procedure described in the Examples.

[0027] <Polymer elastomer> The artificial leather of this embodiment may 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 and ethylenediamine in a predetermined molar ratio, and polymerizing these in one or multiple stages by melt polymerization, bulk polymerization, solution polymerization, etc. The content of the polymer polyol component in the polyurethane elastomer is preferably 15 to 90% by mass.

[0028] 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.

[0029] 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 in multiple installments. 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.

[0030] The content of the polymeric elastomer in the artificial leather is preferably 5 to 45% by mass, more preferably 7 to 40% by mass, and even more preferably 8 to 30% by mass, from the viewpoint of obtaining an artificial leather having an excellent feel.

[0031] <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 body fluid, as described in step (4) below. The other components may be encapsulated in at least one of the ultrafine fibers and the polymeric elastomer. The content of the other components is preferably 0.5 to 10.0% 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 realization of the desired effects of the other components and of water absorbency, water repellency, stain resistance, etc.

[0032] [Method for manufacturing artificial leather] The artificial leather according to this embodiment is preferably manufactured by a manufacturing method including the following steps (1) to (4) and (6): Step (1): A step of preparing a fiber web formed from ultrafine fiber-generating fibers; Step (2): A step of crimping the fiber web to form a crimped fiber web; Step (3): A step of stacking a plurality of the crimped fiber webs to form a web laminate; Step (4): A step of entangling the web laminate to form an entangled fiber sheet; Step (6): A step of removing at least one component from the ultrafine fiber-generating fibers.

[0033] Furthermore, from the viewpoint of imparting texture and shape stability similar to that of natural leather, the method may include the following step (5), and from the viewpoint of achieving an even better texture, the method may include the following step (7): Step (5): Impregnating the entangled fiber sheet with the polymeric elastomer Step (7): Dyeing the artificial leather Step (5) is preferably carried out between steps (4) and (6), and step (7) is preferably carried out after step (6).

[0034] By including the step (2) in the production method according to the present embodiment, the maximum area of ​​the cut surface of the ultrafine fiber bundle when cut at a depth of 0.3 mm from the surface is 4500 μm ２ or more, and the area of ​​the cut surfaces relative to the total number of cut surfaces of the ultrafine fiber bundle is 500 μm ２ It is therefore easy to obtain an artificial leather having the above-mentioned ultrafine fiber bundle number ratio of 60% or more. As a result, it is easy to obtain an artificial leather having excellent texture, surface abrasion resistance, and pilling resistance. Each step will be described below.

[0035] <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.

[0036] 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.

[0037] 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%.

[0038] The mass ratio of the sea component to the island component in the islands-in-sea type composite fiber is not particularly limited, but preferably falls within 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, making it easier to ensure industrial productivity. Furthermore, when a polymeric elastomer is added, voids of a required size are more likely to be formed between the ultrafine fiber bundles and the polymeric elastomer after the sea component is removed, making it easier to achieve a fluffy feel, a solid feel, a dense surface feel, and the like. On the other hand, when the sea component polymer ratio is 60% 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, making it easier to prevent a decrease in quality stability.

[0039] 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 net without cutting, to form a fiber web of long fibers that are continuous fibers.

[0040] Specifically, a conjugate spinning die having a large number of nozzle holes arranged in a predetermined pattern is used to continuously extrude molten strands of islands-in-sea type conjugate fibers from a spinning nozzle at a predetermined extrusion speed, and the strands are substantially cooled and solidified by cooling air at some stage between 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 conjugate fibers to the desired diameter or fineness. The high-speed air stream is applied so that the average spinning speed, which corresponds to the mechanical take-up speed in normal spinning, falls within the range of 1,000 to 6,000 m / min. Furthermore, a fiber web of long fibers can be produced by a spunbonding method in which, depending on the texture of the resulting fiber web, the conjugate fibers are opened by a collision plate or air stream, and then collected and deposited on a collecting surface such as a conveyor belt-like moving net while being suctioned from the opposite side of the net to form a long-fiber web. The fiber web may be subjected to a heat press treatment to impart shape stability, and the fiber web may be fused in association with this.

[0041] If the basis weight or thickness of the obtained fiber web is insufficient, it can be adjusted to the desired basis weight and thickness by wrapping (supplying a single fiber web perpendicular to the flow direction of the process and folding it in the width direction (horizontal direction), or by folding a web supplied parallel to the flow direction of the process in its length direction (vertical direction)) or stacking (overlapping multiple fiber webs). When adjusting the shape stability, fiber density, and thickness direction orientation of islands-in-the-sea fibers, a mechanical entanglement treatment is performed by a known method such as needle punching. This three-dimensionally entangles the fibers constituting the fiber web, particularly the fibers between adjacent layers of wrapped or stacked layered fiber webs. 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).

[0042] The entanglement treatment may be performed by needle punching or high-pressure water jet treatment under conditions in which at least one barb penetrates from both sides simultaneously or alternately. The punch density of the needle punching treatment is 1500 to 5500 punches / cm. ２ , and further, 2000 to 5000 punches / cm ２ If 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.

[0043] <Step (2)> Step (2) is a step of crimping the fiber web to form a crimped fiber web. Examples of crimping methods include physical and mechanical crimping methods such as passing the fiber between two gears, using a press roll (press crimping), rubbing the fiber against a knife edge while bending it, air injection, and twisting, as well as latent crimping methods using multicomponent fibers or hollow fibers with different thermal shrinkage, and combinations of these methods. For the crimping method, physical and mechanical methods that can stably crimp the fiber over a wide range are preferred, and press crimping is more preferred from the viewpoint of imparting an appropriate crimp rate to the fiber. Among press crimping methods, press crimping using a roll with an uneven surface is preferred from the viewpoint of obtaining artificial leather that is easy to process and has better texture, surface abrasion resistance, and pilling resistance. From the viewpoint of obtaining an artificial leather that is superior in texture, surface abrasion resistance, and pilling resistance, the uneven shape is preferably a periodic uneven shape, and the average height difference between the recesses and the protrusions is preferably 1 to 30 mm, more preferably 1.5 to 25 mm, and even more preferably 2 to 20 mm. The distance between the recesses and the distance between the protrusions are preferably 1 to 30 mm, more preferably 1.5 to 25 mm, and even more preferably 2 to 20 mm.

[0044] The crimp percentage when a fiber web is crimped by pressing it with a roll having a periodic uneven surface is preferably 120% or more, more preferably 150% or more, and even more preferably 170% or more from the viewpoint of obtaining an artificial leather having excellent texture, surface abrasion resistance, and pilling resistance, and is preferably 300% or less, more preferably 250% or less, and even more preferably 220% or less from the viewpoint of ease of production. That is, the crimp percentage is preferably 120 to 300%, more preferably 150 to 250%, and even more preferably 170 to 220%. The "crimp percentage" is the ratio of the length along the uneven surface of the uneven roll to the length of the fiber web before crimping (length along the uneven surface of the uneven roll / length of the fiber web before crimping × 100 (%)). Furthermore, after crimping, a dusting oil and a finishing oil can be applied to the crimped fiber web within a range that does not adversely affect the crimping.

[0045] <Step (3)> Step (3) is a step of stacking multiple crimped fiber webs to form a web laminate. Multiple crimped fiber webs can be stacked by all crimping the fiber webs in the same direction, or by a cross-wrapping method in which the conveying direction of the crimped fiber web is changed by 90° and folded back. Cross-wrapping is preferred as a method of stacking multiple crimped fiber webs, as it allows for easy adjustment of the width of the entangled fiber sheet and suppresses unevenness in the width direction of the entangled fiber sheet, i.e., suppresses unevenness in basis weight. The number of layers of the fiber webs to be stacked is not particularly limited, but is preferably two or more, more preferably three or more, from the viewpoints of reducing unevenness in basis weight and mechanical strength of the entangled fiber sheet. From the viewpoint of ease of production, it is preferably 30 or less, more preferably 25 or less. That is, the number of layers of the fiber webs to be stacked is preferably 2 to 30, more preferably 3 to 25.

[0046] <Step (4)> Step (4) is a step of entangling the web laminate to form an entangled fiber sheet. In step (4), the web laminate is subjected to a mechanical entanglement treatment using a known method such as 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 wrapped or stacked layered fiber webs. When the entanglement treatment is performed using 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.), the number of needle punches (needle punch treatment density per unit area obtained by multiplying the density of needles implanted in a needle board by the number of strokes the board applies to the fiber web per unit area), and the needle punch depth (depth at which the needles apply to the fiber web). When a web laminate having a crimped fiber web laminated thereon is entangled by a needle punching method, the crimped fiber web is caught on the barbs, and the moving fibers move, dragging many of the surrounding fibers along with them, increasing the amount of fibers oriented in the thickness direction and improving the degree of entanglement. This suppresses fiber slippage during surface friction and improves abrasion resistance and pilling resistance. Therefore, it is preferable to use a web laminate having a crimped fiber web laminated thereon and perform entanglement by a needle punching method.

[0047] The punch density of the needle punching process is 1500 to 5500 punches / cm ２ , and further, 2000 to 5000 punches / cm ２ If 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.

[0048] 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-forming fibers, fiber web, crimped fiber web, web laminate, entangled fiber sheet, etc. Furthermore, if necessary, the ultrafine fiber-forming fibers, fiber web, crimped fiber web, web laminate, 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 entangled state dense in advance.

[0049] The basis weight of the entangled fiber sheet obtained by entanglement is 100 to 2000 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.

[0050] <Step (5)> Step (5) is a step of impregnating the entangled fiber sheet with the polymer elastomer. In step (5), the entangled fiber sheet is impregnated with the polymer elastomer at least at one of the stages before and after the removal of the sea part. 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 impregnate the entangled fiber sheet with the polymer elastomer before removing the sea part. By impregnating the entangled fiber sheet with the polymer elastomer before removing the sea part in this way, voids formed by removing the sea part are formed between the ultrafine fibers that form the fiber bundles after the removal of the sea part. As a result, the ultrafine fibers inside the fiber bundles are less likely to be restrained by the polymer elastomer, i.e., the ultrafine bundles are less likely to be affected by 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 fibers 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, thereby producing an artificial leather with a hard texture.

[0051] 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.

[0052] 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.

[0053] Details of the polymeric elastomer used in step (5) are as explained above in the section "polymeric elastomer."

[0054] 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.

[0055] <Step (6)> Step (6) is a step of removing at least one component from the ultrafine fiber-forming fibers. 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.

[0056] 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.

[0057] When the sea part is removed, it is preferable to carry out a dip-nip treatment in parallel. Furthermore, during the period from when the islands-in-sea type composite fiber is melt-spun to obtain a web until when the sea part is removed, the fibers may be densified by subjecting them to a heat shrinkage treatment (fiber shrinkage treatment) using steam, hot water, dry heat, or the like.

[0058] <Step (7)> ​​Step (7) is a step of dyeing the artificial leather. Step (7) can be performed at any stage after the islands-in-sea fibers are converted into ultrafine fiber bundles.

[0059] In step (7), any dyeing method can be employed using a known dyeing machine typically used for dyeing conventional artificial leathers such as padder, jigger, circular, wince, etc., using a dye selected appropriately depending on the type of fiber and mainly consisting of disperse dyes, reactive dyes, acid dyes, metal complex dyes, sulfur dyes, sulfur vat dyes, etc. In addition to dyeing, finishing treatments such as mechanical kneading in a dry state, relaxation treatment in a wet state using a dyeing machine or washing machine, softener treatment, treatment to impart functionality such as a flame retardant, antibacterial agent, deodorizer, or water / oil repellent, treatment to impart a tactile feel such as a silicone resin, a silk protein-containing treatment, or a grip-imparting resin, and treatment to impart a design by applying a resin other than the above-mentioned resins, such as a colorant or an enamel-like coating resin, may also be carried out as necessary.

[0060] 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.

[0061] 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, after the nap-raising treatment, the above-described step (7) may be performed to produce a dyed artificial leather.

[0062] 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.

[0063] First, the measurement and evaluation methods used in the examples and comparative examples described below will be summarized below.

[0064] <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 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 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)

[0065] <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 the fiber 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.

[0066] <Content of Polymeric Elastomer> The mass C of the artificial leather cut into a size having a mass of 1 g or more was measured. When the polymeric elastomer is soluble in N,N-dimethylformamide (DMF), the artificial leather was immersed in 300 mL of DMF at room temperature for 5 hours, then squeezed to remove the DMF. The squeezed DMF was then added to water, and the process of immersing the artificial leather in DMF and squeezing was repeated under the same conditions, while replacing the DMF, until the water no longer became cloudy, thereby removing the polymeric elastomer from the artificial leather. The polyester fibers remaining after removing the polymeric elastomer from the artificial leather were dried to remove the DMF, and the mass D of the dried polyester fibers was measured. The content of the polymeric elastomer in the artificial leather was then calculated based on the following formula (2): Polymer elastomer content (mass%)=(C-D) / C×100...Equation (2) When the polymer elastomer does not dissolve in DMF, the artificial leather was immersed in 300 mL of hexafluoro-2-propanol (HFIP) at room temperature (25°C) for 12 hours to dissolve the polyester fibers, and the remaining solids were filtered out, washed with HFIP, and then dried to remove the HFIP. The mass E of the resulting solids was measured. The polymer elastomer content in the artificial leather was then calculated based on the following equation (3): Polymer elastomer content (mass%)=E / C×100...Equation (3) Note that "solids" refers to components excluding the solvent and liquid dispersant. In other words, it refers to components excluding the liquid.

[0067] <Thickness, basis weight and apparent density> According to JIS L1096 (2010) (Method A), the thickness (mm) and basis weight (g / m2) of the obtained artificial leather were measured using a thickness measuring instrument (measuring probe diameter: 10 mm) under a constant pressure of 23.5 kPa for 5 seconds. ２ ) was measured, and from these values, the apparent density (g / cm ３ ) was calculated.

[0068] <Measurement of Area and Number of Ultrafine Fiber Bundles> A small piece of artificial leather was prepared, and the back surface (the side on which no nap or resin layer was formed) was fixed to a base with double-sided adhesive tape. The artificial leather was sliced ​​at a depth of 0.3 mm from the surface with a single-edged razor, the front surface side was removed, and a scanning electron microscope (SEM) photograph of the cut surface of the remaining side was taken at 100x magnification. This was printed (see Figure 1), and the printed surface was placed under a flat panel light. Light was applied from the printed surface side to make the image transparent to the back surface. The cut surfaces of the ultrafine fiber bundles present on the cut surface from the back surface were painted black (see Figure 2). The area of ​​the cut surfaces of the ultrafine fiber bundles and the number of cut surfaces of the ultrafine fiber bundles were measured using Image-Pro Premier ver. 9.1 (manufactured by Nippon Rover Co., Ltd.). The maximum value of the area of ​​the cut surfaces of the ultrafine fiber bundles was defined as the maximum area of ​​the cut surfaces of the ultrafine fiber bundles. The total value of the area of ​​the cut surfaces of the ultrafine fiber bundles was defined as 1 mm. ２ The total area of ​​the ultrafine fiber bundle was calculated as the area of ​​the cut surfaces per 500 μm. ２ The proportion of the number of ultrafine fiber bundles above this level was calculated.

[0069] <20% Strength> A test specimen measuring 16 cm length x 2.5 cm width was cut from the obtained artificial leather. The test specimen was clamped between the chucks of a tensile tester, adjusted to 10 cm intervals, so that the artificial leather was stretched in the longitudinal direction (the flow direction in step (3)), and an S-S curve was measured using an autograph at a tensile speed of 100 mm / min. This procedure was repeated three times. From the obtained S-S curve, the strength at an elongation of 20% was read, and the average value of the three measurements was taken as the 20% strength in the longitudinal direction (kgf / 2.5 cm). The 20% strength in the transverse direction (kgf / 2.5 cm) was calculated in the same manner as above, except that the test specimen was clamped between the chucks of the tensile tester so that the artificial leather was stretched in the transverse direction (a direction turned 90° from the flow direction in step (3)), which was perpendicular to the longitudinal direction.

[0070] <Weight Loss Due to Abrasion> In accordance with JIS L 1096 (2020) (8.19.5 Method E, Martindale Method), a test was conducted using a Martindale abrasion tester under conditions of a pressure load of 12 kPa (gf / cm) and a number of abrasion cycles of 350 million, and the weight loss due to abrasion on the surface of the artificial leather was calculated.

[0071] <Pilling> According to JIS L 1096 (2020) (8.19.5 E Method, Martindale Method), a pressure load of 12 kPa (gf / cm ２ ), the test was carried out using a Martindale abrasion tester for the number of abrasions shown in Table 1, and the pilling on the surface of the artificial leather after the test was judged visually and by touch according to the following criteria: A: No collected pills were observed, and the feel was smooth and silky. B: Some collected pills were observed, but no pills were felt, and the feel was slightly rough. C: Some collected pills were observed, and the feel was rough.

[0072] <Texture> The texture of the obtained artificial leather after bending was judged visually and by touch according to the following criteria: A: Feels full, does not break (occurs due to buckling), and has excellent flexibility. B: Lacks fullness, does not break (occurs due to buckling), and has a texture that corresponds to one or more of the following: hard.

[0073] <Appearance> The appearance of the obtained artificial leather was visually inspected and judged according to the following criteria: A: The fibers are not clumped together and are finely separated, and have a uniform length. B: The fibers are clumped together and are coarsely separated, and have an uneven length.

[0074] Example 1 A water-soluble thermoplastic polyvinyl alcohol resin as a sea component and an isophthalic acid-modified polyethylene terephthalate (polyethylene phthalate modified with 6 mol% isophthalic acid) as an island component were extruded at 270°C from a melt conjugate spinning die (number of islands: 25 / fiber) so that the sea component / island component ratio was 25 / 75 (mass ratio), and spun at a spinning speed of 3,500 m / min to obtain a fiber web containing islands-in-sea type composite fibers with an average fineness of 2.95 dtex. The web was then heat-pressed with a calendar roll and then pressed with a roll having an irregular shape to impart an irregular shape to the width direction of the fiber web (crimping treatment) so that the crimp rate was 200%. The crimped fiber web was then folded lengthwise and cross-lap laminated so that seven fiber webs overlapped with each other to form a laminate web. The laminate web was then punched using 1-barb and 6-barb needles at a punch density of 3,500 punches / cm. ２ By needle punching, the basis weight is 385 g / m ２ The entangled fiber sheet was then subjected to a steam treatment under conditions of 110°C and 23.5% RH. After drying in an oven at 90 to 110°C, it was further heat-pressed at 120°C to form an entangled fiber sheet with a basis weight of 755 g / m. ２ , specific gravity 0.65g / cm ３A 1.16 mm thick heat-pressed fiber sheet was obtained. The heat-pressed fiber sheet was then impregnated with a 52% pick-up emulsion of a non-yellowing polycarbonate polyurethane (polyurethane (1)) as a polymeric elastomer. The emulsion consisted of 1.5 parts by mass of a carbodiimide crosslinking agent and 2.7 parts by mass of ammonium sulfate per 100 parts by mass of the polymeric elastomer, resulting in a polymeric elastomer solids content of 16% by mass. The polymeric elastomer solids content was adjusted to 10% by mass relative to the total weight of the polyester fiber and polymeric elastomer in the heat-shrinkable fiber sheet. The emulsion-impregnated heat-pressed fiber sheet was then subjected to a moist heat treatment at 110°C and 29% RH, followed by drying at 150°C to obtain a heat-pressed fiber sheet impregnated with a polymeric elastomer. The hot-pressed fiber sheet to which the polymer elastomer had been added was then 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 composite fiber, and form ultrafine fibers of isophthalic acid-modified polyethylene terephthalate with an average diameter of 3.02 μm and an average fineness of 0.1 dtex. After drying, the back surface was ground with #320 paper, and the main surface was ground with #320 and #400 paper to form a napped surface, thereby obtaining an artificial leather with a napped surface. The resulting artificial leather was dyed with a disperse dye at 120°C to a basis weight of 439 g / m. ２ , apparent density 0.499 g / cm ３ A dyed artificial leather having a thickness of 0.88 mm was obtained. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0075] [Example 2] A dyed artificial leather was obtained in the same manner as in Example 1, except that the crimping treatment was carried out so that the crimp rate was 175%. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0076] [Example 3] A dyed artificial leather was obtained in the same manner as in Example 1, except that the thickness of the artificial leather was 0.68 mm. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0077] [Example 4] A dyed artificial leather was obtained in the same manner as in Example 3, except that the crimping treatment was carried out so that the crimp rate was 175%. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0078] [Example 5] A dyed artificial leather was obtained in the same manner as in Example 3, except that the fiber webs crimped in the width direction were laminated in the direction of travel of the entangled fiber sheet (the direction of the process flow) to form a laminated web, and the entangled fiber sheet was crimped in the transverse direction to form an entangled fiber sheet. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0079] [Example 6] A dyed artificial leather was obtained in the same manner as in Example 1, except that polyethylene was used as the sea component, the fiber-entangled sheet was shrunk in hot water at 90°C and pressed with a cooled roll to obtain a heat-shrunk web-entangled sheet, a DMF solution (solids content 18.5 mass%) of polycarbonate-based polyurethane (polyurethane (2)) was used as the polymer elastomer, the solids content of the polymer elastomer was adjusted to 30 mass% based on the total of the polyethylene terephthalate fiber and polymer elastomer in the heat-pressed fiber sheet, toluene was used to dissolve and remove the polyethylene sea component, and the thickness was adjusted to 0.78 mm. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0080] [Example 7] A dyed artificial leather was obtained in the same manner as in Example 6, except that the crimping treatment was carried out so that the crimp rate was 175%. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0081] [Example 8] A dyed artificial leather was obtained in the same manner as in Example 7, except that a DMF solution (solid content 18.5% by mass) of an ether-based polyurethane (polyurethane (3)) was used as the polymer elastomer. The measurement and evaluation results of the obtained artificial leather are shown in Table 1.

[0082] Comparative Example 1 A dyed artificial leather was obtained in the same manner as in Example 1, except that the crimping treatment was not carried out. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[0083] Comparative Example 2 A dyed artificial leather was obtained in the same manner as in Example 3, except that the crimping treatment was not carried out. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[0084] Comparative Example 3 A dyed artificial leather was obtained in the same manner as in Example 5, except that the crimping treatment was not performed and the thickness was set to 0.80 mm. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[0085] Comparative Example 4 A dyed artificial leather was obtained in the same manner as in Example 6, except that the crimping treatment was not carried out. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[0086] [Comparative Example 5] An islands-in-sea type composite fiber was obtained in the same manner as in Example 6, except that spinning was performed at a spinning speed of 800 m / min. The islands-in-sea type composite fiber was then drawn in a warm water bath at a draw ratio of 2.7 to obtain a 4.0 dtex islands-in-sea type composite fiber. Subsequently, a crimper was used to impart an irregular shape (crimping) to the 4.0 dtex islands-in-sea type composite fiber so that the crimp rate was 9.0%, and a carding machine was used to produce a fiber web made of the crimped islands-in-sea type composite fiber. Next, the fiber web was folded in the length direction, and seven fiber webs were cross-lap laminated so as to overlap each other, to produce a laminate web. The laminate web was then punched using a 1-barb needle at a punch density of 2,500 punches / cm. ２ By needle punching, the basis weight is 1128 g / cm ２ An entangled fiber sheet of the above formula was formed. Subsequently, a heat-pressed fiber sheet was obtained in the same manner as in Example 6, and a polymeric elastomer was imparted to the heat-pressed fiber sheet, the sea component of the islands-in-sea composite fiber was dissolved and removed, and a fiber-raised surface was formed, thereby obtaining an artificial leather having a fiber-raised surface. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[0087] [Comparative Example 6] In Comparative Example 5, the fiber web made of the obtained short fibers was hot-pressed with a calendar roll, and then pressed with a roll having an uneven shape to impart an uneven shape to the width direction of the fiber web so that the crimp rate was 200% (to impart a crimping treatment). As a result, the short fiber web broke, and subsequent processing could not be carried out.

[0088] [Comparative Example 7] In Comparative Example 3, needle punching was performed at a punch density of 5900 punches / cm ２ A dyed artificial leather was obtained in the same manner as above, except that the diameter was increased to 100 mm. The measurement and evaluation results of the obtained artificial leather are shown in Table 2.

[0089]

[0090]

[0091] From Table 1, it can be seen that the artificial leathers obtained in Examples 1 to 8 are excellent in texture, surface abrasion resistance, and pilling resistance. On the other hand, when cut at a depth of 0.3 mm from the surface, the maximum area of ​​the cut surface of the ultrafine fiber bundles is 4500 μm ２ It can be seen that the artificial leathers (Comparative Examples 1, 2 and 4) that do not have the above maximum area do not have excellent texture, excellent surface abrasion resistance and pilling resistance. ２ Even if the area of ​​the cut surfaces relative to the total number of cut surfaces of the ultrafine fiber bundle is 500 μm ２ It can be seen that the artificial leather (Comparative Example 3) in which the proportion of ultrafine fiber bundles by number is less than 60% is inferior in feel. ２ The artificial leather (Comparative Example 7) in which the entanglement of the fiber web was enhanced by increasing the cross section area to 500 μm ２ The proportion of ultrafine fiber bundles equal to or greater than this is less than 60%, which indicates that the texture and appearance quality are poor.

Claims

1. An artificial leather containing ultrafine fibers, in which the maximum area of ​​the cut surface of the ultrafine fiber bundles is 4500 μm when cut at a depth of 0.3 mm from the surface. ２ or more, and the area of ​​the cut surfaces relative to the total number of the cut surfaces of the ultrafine fiber bundle is 500 μm ２ The artificial leather has a ratio of the number of the ultrafine fiber bundles of 60% or more.

2. The total area of ​​the ultrafine fiber bundle on the cut surface is 50,000 μm ２ / mm ２ The artificial leather according to claim 1 .

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

4. The artificial leather according to any one of claims 1 to 3, wherein the average fineness of the ultrafine fibers is 0.5 dtex or less.

5. The artificial leather according to any one of claims 1 to 4, wherein the ultrafine fibers are long fibers.

6. The artificial leather according to any one of claims 1 to 5, which contains 45% by mass or less of a polymer elastomer.

7. A method for producing an artificial leather according to any one of claims 1 to 6, comprising the steps of: preparing a fiber web formed from ultrafine fiber generating fibers; subjecting the fiber web to a crimping treatment to form a crimped fiber web; stacking a plurality of the crimped fiber webs to form a web laminate; entangling the web laminate to form an entangled fiber sheet; and removing at least one component from the ultrafine fiber generating fibers.

8. The method for producing an artificial leather according to claim 7, further comprising the step of impregnating the entangled fiber sheet with a polymeric elastomer.

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