Artificial leather, method for producing same, and use of same

Abstract

This artificial leather comprises: a fibrous base material composed of a nonwoven fabric and a woven fabric entangled and integrated together; and polyurethane including a hydrophilic group. The non-woven fabric is composed of polyester ultrafine fibers having an average single fiber diameter between 0.1 µm and 10.0 µm inclusive. The woven fabric is composed of a multifilament with 30 to 300 filaments inclusive. An average single fiber diameter of the filaments constituting the multifilament is between 1 µm and 30 µm inclusive. The content ratio of the polyurethane in the artificial leather is between 15 mass% and 25 mass% inclusive.　Provided are: an artificial leather comprising a fibrous base material composed of a nonwoven fabric and a woven fabric entangled and integrated together, and a water-dispersible polyurethane, the artificial leather having high strength and excellent flexibility and abrasion resistance; a method for producing the same; and a use of the same.

Description

Artificial leather, its manufacturing method and uses

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

[0002] Artificial leathers, which are primarily made of a fibrous substrate such as nonwoven fabric and polyurethane, have excellent characteristics not found in natural leather, such as high durability and uniformity, and in particular, so-called suede-like artificial leathers, in which the surface is buffed to form a nap of ultrafine fibers, are used not only as clothing materials but also in a variety of fields, such as vehicle interior materials, furniture interior materials, and building materials. In particular, from the perspective of environmental considerations, methods using water-dispersed polyurethanes, in which polyurethane resins are dispersed in water, instead of methods using conventional organic solvent-based polyurethanes as polyurethanes, are being widely studied.

[0003] When suede-like artificial leather is used as a covering material for vehicle interiors, etc., repeated use over a long period of time can cause distortion in the covering material. Therefore, methods are being investigated for integrating woven fabric into the interior or one side of a nonwoven fabric to produce artificial leather that is strong and can withstand long-term use.

[0004] However, artificial leathers made by entangling and integrating woven fabrics inside or on one side of nonwoven fabrics generally have the problem of being stiff in texture, one of the main reasons for which is that the added polyurethane tightly grips the intertwining points of the woven fabric, reducing the flexibility of the woven fabric.

[0005] In particular, when a water-dispersible polyurethane is used as the polyurethane and the polyurethane emulsion is coagulated by heating to aggregate, the polyurethane membrane structure becomes a dense, non-porous membrane, resulting in a tight bond between the woven fabric and the polyurethane, which tightly grips the intertwined portions of the fibers that make up the woven fabric, resulting in a significantly harder texture.

[0006] In response to these circumstances, several methods have been proposed for applying water-dispersible polyurethane to artificial leather in which a woven fabric is entangled and integrated inside or on one side of a nonwoven fabric, thereby obtaining artificial leather with high strength and excellent flexibility.

[0007] For example, Patent Documents 1 and 2 propose a method in which a specific amount of polyvinyl alcohol having a specific degree of saponification and polymerization is applied to a fibrous substrate, then a water-dispersible polyurethane is applied, and then the polyvinyl alcohol is removed. It is described that this method achieves an elegant appearance and a soft feel, and also allows the production of a sheet-like product having good abrasion resistance.

[0008] Furthermore, Patent Document 3 describes that by setting the ratio of polyurethane resin to 100% by mass of the fiber sheet to 20% by mass or less, it is possible to achieve a soft texture even in artificial leather that contains a scrim, which is a woven or knitted fabric, and uses a water-dispersible polyurethane resin.

[0009] JP 2013-234409 A International Publication No. 2014 / 042241 International Publication No. 2020 / 054256

[0010] In the methods disclosed in Patent Documents 1 and 2, polyvinyl alcohol is applied to the woven or knitted fabric before applying polyurethane, coating the fabric, and is removed after applying polyurethane, thereby preventing direct adhesion between the polyurethane and the woven or knitted fabric and achieving a soft texture. However, since a polyvinyl alcohol elution treatment is required, there is room for improvement in terms of production efficiency.

[0011] In the method disclosed in Patent Document 3, the amount of polyurethane applied is small, so it is difficult to say that the level required by the market in terms of abrasion resistance is satisfied.

[0012] In view of the above, an object of the present invention is to provide an artificial leather containing a fiber-entangled body made of a nonwoven fabric and a woven fabric as a constituent component, which is produced by an environmentally friendly process that does not use organic solvents, and which combines a soft texture with excellent abrasion resistance, and a method for producing the same.

[0013] In order to solve the above problems, the present invention has the following configuration: [1] An artificial leather comprising a fibrous substrate formed by entanglement and integration of a nonwoven fabric and a woven fabric, and a polyurethane having a hydrophilic group, wherein the nonwoven fabric is composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm, the woven fabric is composed of a multifilament having 30 to 300 filaments, and the average single fiber diameter of the filaments constituting the multifilament is 1 μm to 30 μm, the content of the polyurethane in the artificial leather is 15% by mass to 25% by mass, and the proportion of the filaments to which the polyurethane is attached is 10% to 80% of the outermost filaments of the multifilament.

[0014] [2] The artificial leather according to [1], wherein the polyurethane is a polyether-based polyurethane and / or a polycarbonate-based polyurethane.

[0015] [3] A method for producing the artificial leather according to [1], comprising the following steps (1) to (3) in this order: (1) a step of entangling and integrating a nonwoven fabric made of ultrafine fiber-developing fibers with a woven fabric to form a fibrous substrate, (2) a step of impregnating the fibrous substrate with an aqueous dispersion of polyurethane having hydrophilic groups, and then coagulating the polyurethane to obtain a sheet, the sheet having a width of 0.85L to 0.95L, where L is the width of the fibrous substrate before impregnation, and (3) a step of developing polyester ultrafine fibers from the ultrafine fiber-developing fibers of the shrunk sheet.

[0016] [4] The method for producing an artificial leather according to [3], wherein the entanglement and integration means in the step (1) is needle punching.

[0017] [5] The method for producing an artificial leather according to [3] or [4], wherein the means for obtaining the shrink sheet in the step (2) is a dry heat treatment at an atmospheric temperature of 100°C or higher and 180°C or lower.

[0018] [6] The method for producing an artificial leather according to any one of [3] to [5], wherein the means for developing the polyester ultrafine fibers in the step (3) is an alkali treatment.

[0019] [7] An automobile interior material comprising the artificial leather according to [1] or [2].

[0020] [8] An automobile part comprising the artificial leather according to [1] or [2].

[0021] [9] A seat comprising the artificial leather according to [1] or [2].

[0022] According to the present invention, an artificial leather having high strength, excellent flexibility and abrasion resistance can be obtained by a simple process, which artificial leather is made of a fibrous base material in which a nonwoven fabric and a woven fabric are entangled and integrated, and a water-dispersible polyurethane.

[0023] This is a schematic cross-sectional view of a scanning electron microscope (SEM) photograph of an artificial leather cross section taken to measure and calculate the proportion of filaments to which polyurethane is attached among the outermost filaments of a multifilament.

[0024] The artificial leather of the present invention is an artificial leather comprising a fibrous substrate formed by entanglement of a nonwoven fabric and a woven fabric, and a polyurethane having a hydrophilic group, wherein the nonwoven fabric is composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm, the woven fabric is composed of a multifilament having 30 to 300 filaments, and the average single fiber diameter of the filaments constituting the multifilament is 1 μm to 30 μm, the content of the polyurethane in the artificial leather is 15% by mass to 25% by mass, and the proportion of the outermost filaments of the multifilament to which the polyurethane is attached is 10% to 80%.

[0025] These components will be described in detail below, but the present invention is not limited to the scope described below as long as it does not go beyond the gist of the present invention, and various modifications are possible within the scope of the present invention.

[0026] [Polyester Ultrafine Fibers] The artificial leather of the present invention has a fibrous substrate, which is one of its constituent elements, composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less. Note that "polyester ultrafine fibers" refers to "ultrafine fibers made of polyester resin" described below, and ultrafine fibers refer to "fibers having a single fiber diameter of 0.1 μm or more and 10.0 μm or less" measured and calculated by the method described below.

[0027] In this invention, "polyester-based resin" refers to a resin in which the molar fraction of the polyester units in the repeating units is 80 mol% to 100 mol%. Unless otherwise specified, the term "...-based resin" has the same meaning. This polyester-based resin can be used to make artificial leather with excellent heat resistance, light resistance, etc. Specific examples include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and mixtures and copolymers of these polyester resins. Polyester-based resins can be obtained, for example, from dicarboxylic acids and / or their ester-forming derivatives and diols.

[0028] Examples of dicarboxylic acids and / or ester-forming derivatives thereof used in the polyester resin include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, and ester-forming derivatives thereof. The ester-forming derivatives referred to in the present invention include lower alkyl esters, acid anhydrides, and acyl chlorides of dicarboxylic acids. Specifically, methyl esters, ethyl esters, and hydroxyethyl esters are preferably used. Terephthalic acid and / or its dimethyl esters are more preferred as dicarboxylic acids and / or ester-forming derivatives thereof used in the present invention.

[0029] Examples of diols that can be used in the polyester resin include ethylene glycol, 1,3-propanediol, 1,4-butanediol, cyclohexanedimethanol, etc. Among these, ethylene glycol is preferably used.

[0030] The polyester resin may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc., depending on various purposes.

[0031] The cross-sectional shape of the polyester ultrafine fiber may be either a round cross section or an irregular cross section. Specific examples of irregular cross sections include an oval, a flattened shape, a polygonal shape such as a triangle, a sector shape, and a cross shape.

[0032] In the present invention, the average single fiber diameter of the polyester ultrafine fibers is 0.1 μm or more and 10.0 μm or less. By making the average single fiber diameter of the polyester ultrafine fibers 10.0 μm or less, preferably 7.0 μm or less, and more preferably 5.0 μm or less, the artificial leather can be made softer. Furthermore, the quality of the nap can be improved. On the other hand, by making the average single fiber diameter of the polyester ultrafine fibers 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.7 μm or more, the artificial leather can be made to have excellent color development after dyeing. Furthermore, when performing a nap raising treatment by buffing, the ease of dispersion and handling of the polyester ultrafine fibers present in bundles can be improved.

[0033] The single fiber diameter and average single fiber diameter of polyester ultrafine fibers referred to in the present invention are measured and calculated by the following method. That is, (1) A cross section of the obtained artificial leather cut in the thickness direction is observed with a scanning electron microscope (SEM, "VHX-D500 / D510" manufactured by Keyence Corporation or a scanning electron microscope with equivalent performance). (2) The fiber diameters of 50 polyester ultrafine fibers arbitrarily selected within the observation surface are measured in three directions on the cross section of each polyester ultrafine fiber. However, when polyester ultrafine fibers with an irregular cross section are used, the cross-sectional area of ​​the single fiber is first measured, and the diameter of a circle corresponding to that cross-sectional area is calculated using the following formula. The diameter thus obtained is the single fiber diameter of the single fiber.

[0034] Single fiber diameter (μm) = (4 × (cross-sectional area of ​​single fiber (μm ２ )) / π) １／２(3) The arithmetic mean value (μm) of the 150 points obtained is calculated and rounded off to one decimal place to obtain the average single fiber diameter (μm) of the polyester ultrafine fiber.

[0035] [Woven Fabric] It is important that the woven fabric used in the artificial leather of the present invention is composed of multifilaments. As the component constituting the multifilaments, polyester-based resins or polyamide-based resins can be used, but polyester-based resins, which have excellent durability and heat resistance, are preferably used.

[0036] It is important that the average single fiber diameter of the filaments constituting the multifilament is 1 μm or more and 30 μm or less. By setting the average single fiber diameter to 30.0 μm or less, more preferably 15.0 μm or less, and even more preferably 13.0 μm or less, the artificial leather will have excellent flexibility. On the other hand, by setting the average single fiber diameter to 1.0 μm or more, more preferably 8.0 μm or more, and even more preferably 9.0 μm or more, the shape stability of the artificial leather product will be improved.

[0037] In the present invention, the average single fiber diameter of the filaments constituting the multifilament is calculated by taking a scanning electron microscope (SEM) photograph of the cross section of the artificial leather, randomly selecting 10 filaments from the multifilament constituting the woven fabric, measuring the single fiber diameters of the selected filaments, calculating the arithmetic average of the 10 filaments, and rounding off to the nearest tenth. However, when a filament with a modified cross section is used, the cross-sectional area (μm ２ ) is measured, and the diameter when the cross section is regarded as a circle, that is, the circle equivalent diameter, is calculated to determine the diameter (μm) of the filament.

[0038] It is important that the number of single fibers contained in the multifilament constituting the woven fabric, i.e., the number of filaments, is 30 to 300. By setting the number of filaments to 30 or more, more preferably 50 or more, not only is the shape stability of the product as an artificial leather improved, but also the fibers constituting the woven fabric are less likely to be exposed on the surface of the artificial leather when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, which is preferable. On the other hand, by setting the number of filaments to 300 or less, more preferably 250 or less, and even more preferably 100 or less, the artificial leather has excellent flexibility. In this case, the number of filaments in the warp and the number of filaments in the weft may be the same or different.

[0039] Furthermore, the twist number of the multifilament is preferably 1,000 to 4,000 T / m. By setting the twist number to 4,000 T / m or less, more preferably 3,500 T / m or less, and even more preferably 3,000 T / m or less, an artificial leather with excellent flexibility can be obtained, while by setting the twist number to 1,000 T / m or more, more preferably 1,500 T / m or more, and even more preferably 2,000 T / m or more, damage to the fibers constituting the woven fabric can be prevented when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, and the mechanical strength of the artificial leather can be excellent, which is preferable.

[0040] The basic weave of the fabric may be twill or satin, but plain weave, which is less likely to cause misalignment, is preferably used.

[0041] The weave density of the woven fabric is preferably adjusted so that both the warp and weft threads in the artificial leather are 40 threads / 2.54 cm to 200 threads / 2.54 cm. By adjusting the weave density of the woven fabric constituting the artificial leather to 40 threads / 2.54 cm or more, more preferably 60 threads / 2.54 cm or less, an artificial leather with excellent shape stability can be obtained. On the other hand, by adjusting the weave density of the woven fabric constituting the artificial leather to 200 threads / 2.54 cm or less, more preferably 150 threads / 2.54 cm or less, not only can the texture of the artificial leather be made softer, but the entanglement of the fibers of the nonwoven fabric is not hindered when the nonwoven fabric and the woven fabric are entangled and integrated, and as a result, fiber shedding from the artificial leather can be suppressed.

[0042] [Fibrous Substrate] The fibrous substrate used in the present invention is formed by entangling and integrating the nonwoven fabric made of the polyester ultrafine fibers and the woven fabric.

[0043] [Polyurethane Having Hydrophilic Group] The artificial leather of the present invention contains a polyurethane having a hydrophilic group as a constituent element, which will be described in further detail below.

[0044] (1) Polyurethane Having a Hydrophilic Group First, in the present invention, "having a hydrophilic group" refers to "having a group having active hydrogen". Specific examples of the group having active hydrogen include a hydroxyl group, a carboxyl group, a sulfonic acid group, an amino group, etc. From the viewpoint of reactivity with a crosslinking agent having a carbodiimide group, which will be described later, it is preferable that the polyurethane has a hydroxyl group or a carboxyl group.

[0045] This polyurethane having hydrophilic groups can be obtained by reacting a polymer polyol (described later), an organic diisocyanate, and an active hydrogen-containing compound having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting a chain extender to obtain a polyurethane precursor, which is then reacted with a crosslinking agent. These will be described in detail below.

[0046] (1-1) Polymer Polyols Examples of polymer polyols that are preferably used in the synthesis of the polyurethane include polyether polyols, polyester polyols, and polycarbonate polyols.

[0047] First, examples of polyether polyols include polyols obtained by addition polymerization of monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin, and cyclohexylene using polyhydric alcohols or polyamines as initiators, and polyols obtained by ring-opening polymerization of the above-mentioned monomers using protonic acids, Lewis acids, cationic catalysts, etc. as catalysts. Specific examples include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and copolymer polyols combining these.

[0048] Next, examples of polyester polyols include polyester polyols obtained by condensing various low molecular weight polyols with polybasic acids, and polyols obtained by open polymerization of lactones.

[0049] Examples of low molecular weight polyols used in polyester polyols include linear alkylene glycols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; branched alkylene glycols such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, and 2-methyl-1,8-octanediol; alicyclic diols such as 1,4-cyclohexanediol; and aromatic dihydric alcohols such as 1,4-bis(β-hydroxyethoxy)benzene. Adducts obtained by adding various alkylene oxides to bisphenol A can also be used as low molecular weight polyols.

[0050] On the other hand, examples of the polybasic acid used in the polyester polyol include one or more selected from the group consisting of succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydroisophthalic acid.

[0051] Examples of polycarbonate-based polyols include compounds obtained by reacting a polyol with a carbonate compound, such as a polyol with a dialkyl carbonate or a polyol with a diaryl carbonate.

[0052] The polyol used in the polycarbonate polyol can be a low-molecular-weight polyol used in the polyester polyol. On the other hand, the dialkyl carbonate can be dimethyl carbonate or diethyl carbonate, and the diaryl carbonate can be diphenyl carbonate.

[0053] The number-average molecular weight of the polymer polyol preferably used in the present invention is preferably 500 or more and 5,000 or less. By setting the number-average molecular weight of the polymer polyol to 500 or more, more preferably 1,500 or more, it is possible to easily prevent the texture of the artificial leather from becoming hard. Furthermore, by setting the number-average molecular weight to 5,000 or less, more preferably 4,000 or less, it is possible to easily maintain the strength of the polyurethane having hydrophilic groups as a binder.

[0054] (1-2) Organic Diisocyanate Examples of organic diisocyanates preferably used in the synthesis of the polyurethane include aromatic diisocyanates having from 6 to 20 carbon atoms (excluding carbon atoms in NCO groups, the same applies hereinafter), aliphatic diisocyanates having from 2 to 18 carbon atoms, alicyclic diisocyanates having from 4 to 15 carbon atoms, araliphatic diisocyanates having from 8 to 15 carbon atoms, modified products of these diisocyanates (carbodiimide modified products, urethane modified products, uretdione modified products, etc.), and mixtures of two or more of these.

[0055] Specific examples of the aromatic diisocyanate having 6 or more and 20 or less carbon atoms include 1,3- and / or 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as MDI), 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, and 1,5-naphthylene diisocyanate. Among these, it is preferable to use MDI, which has excellent flexibility when made into a polyurethane having a hydrophilic group.

[0056] Specific examples of the aliphatic diisocyanate having 2 or more and 18 or less carbon atoms include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl)carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexaate.

[0057] Specific examples of the alicyclic diisocyanate having 4 to 15 carbon atoms include isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, and 2,5- and / or 2,6-norbornane diisocyanate. Among these, it is preferable to use dicyclohexylmethane-4,4'-diisocyanate, which has excellent durability when made into a polyurethane having a hydrophilic group.

[0058] Specific examples of the aromatic aliphatic diisocyanate having 8 to 15 carbon atoms include m- and / or p-xylylene diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate.

[0059] (1-3) Active hydrogen component-containing compound having a hydrophilic group Examples of the active hydrogen component-containing compound having a hydrophilic group that is preferably used in the synthesis of the polyurethane include compounds containing a nonionic group and / or anionic group and / or cationic group and active hydrogen. These active hydrogen component-containing compounds can also be used in the form of a salt neutralized with a neutralizing agent. Use of this active hydrogen component-containing compound having a hydrophilic group can improve the stability of the aqueous dispersion used in the production method of artificial leather.

[0060] Examples of compounds having a nonionic group and active hydrogen include compounds containing two or more active hydrogen components or two or more isocyanate groups and having a polyoxyethylene glycol group or the like having a molecular weight of 250 to 9,000 on the side chain, and triols such as trimethylolpropane and trimethylolbutane.

[0061] Examples of the compound having an anionic group and active hydrogen include carboxyl group-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid, and derivatives thereof; sulfonic acid group-containing compounds such as 1,3-phenylenediamine-4,6-disulfonic acid and 3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid, and derivatives thereof; and salts of these compounds neutralized with a neutralizing agent.

[0062] Examples of compounds containing a cationic group and active hydrogen include tertiary amino group-containing compounds such as 3-dimethylaminopropanol, N-methyldiethanolamine, and N-propyldiethanolamine, and derivatives thereof.

[0063] (1-4) Chain Extender Examples of chain extenders preferably used in the synthesis of the polyurethane include water, low-molecular-weight diols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and neopentyl glycol, alicyclic diols such as 1,4-bis(hydroxymethyl)cyclohexane, aromatic diols such as 1,4-bis(hydroxyethyl)benzene, aliphatic diamines such as ethylenediamine, alicyclic diamines such as isophoronediamine, aromatic diamines such as 4,4-diaminodiphenylmethane, aromatic aliphatic diamines such as xylenediamine, alkanolamines such as ethanolamine, hydrazine, dihydrazides such as adipic acid dihydrazide, and mixtures of two or more of these.

[0064] Of these, preferred chain extenders are water, low molecular weight diols and aromatic diamines, and more preferred are water, ethylene glycol, 1,4-butanediol, 4,4'-diaminodiphenylmethane and mixtures of two or more of these.

[0065] (1-5) Structure of Polyurethane Precursor As described above, the polyurethane precursor preferably used for synthesizing the polyurethane is prepared by reacting the polymer polyol, the organic diisocyanate, and the active hydrogen component-containing compound having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting a chain extender.

[0066] (1-6) Crosslinking Agent The crosslinking agent preferably used in the synthesis of the polyurethane can be one having two or more reactive groups in the molecule that can react with the reactive group introduced into the polyurethane precursor, and specific examples include polyisocyanate-based crosslinking agents such as water-soluble isocyanate compounds and blocked isocyanate compounds, melamine-based crosslinking agents, carbodiimide-based crosslinking agents, etc. One type of crosslinking agent can be used alone, or two or more types can be used in combination.

[0067] The water-soluble isocyanate compound has two or more isocyanate groups in the molecule, and examples thereof include the above-mentioned organic polyisocyanate-containing compounds. Commercially available products include the "Bayhydur" (registered trademark) series and the "Desmodur" (registered trademark) series manufactured by Bayer MaterialScience Co., Ltd.

[0068] A blocked isocyanate compound has two or more blocked isocyanate groups in the molecule. The blocked isocyanate group refers to an organic polyisocyanate compound blocked with a blocking agent such as an amine, a phenol, an imine, a mercaptan, a pyrazole, an oxime, or an active methylene. Commercially available products include the "Elastron" (registered trademark) series from Dai-ichi Kogyo Seiyaku Co., Ltd., the "Duranate" (registered trademark) series from Asahi Kasei Corporation, and the "Takenate" (registered trademark) series from Mitsui Chemicals, Inc.

[0069] Examples of oxazoline crosslinking agents include compounds having two or more oxazoline groups (oxazoline skeletons) in the molecule. Commercially available products include the "Epocross" (registered trademark) series manufactured by Nippon Shokubai Co., Ltd.

[0070] Examples of carbodiimide crosslinking agents include compounds having two or more carbodiimide groups in the molecule. Commercially available products include the "Carbodilite" (registered trademark) series manufactured by Nisshinbo Chemical Inc.

[0071] Among these, it is particularly preferable to use a carbodiimide compound, which gives a polyurethane having a hydrophilic group obtained after the reaction that is particularly excellent in durability and flexibility.

[0072] (1-7) Constitution of Polyurethane Having Hydrophilic Group The polyurethane having a hydrophilic group is preferably a polyether-based polyurethane containing a constituent component derived from a polyether-based polyol and / or a polycarbonate-based polyurethane containing a constituent component derived from a polycarbonate-based polyol.

[0073] From the viewpoint of flexibility, it is preferable that the polyurethane having a hydrophilic group contains a component derived from a polyether polyol. When the polyurethane contains a component derived from a polyether polyol, the degree of freedom of the ether bond is high, and therefore the glass transition temperature is low and the cohesive force is weak, resulting in a water-dispersible polyurethane having excellent flexibility.

[0074] On the other hand, from the viewpoint of durability, it is preferable that the polyurethane having a hydrophilic group contains a component derived from a polycarbonate-based polyol. When the polyurethane having a hydrophilic group contains a component derived from a polycarbonate-based polyol, the high cohesive force of the carbonate group can result in a polyurethane having a hydrophilic group that is excellent in water resistance, heat resistance, weather resistance, and mechanical properties.

[0075] The constitution of the polyurethane having a hydrophilic group can be adjusted appropriately depending on the required properties, and a polyether-based polyurethane containing a constituent component derived from a polyether-based polyol or a polycarbonate-based polyurethane containing a constituent component derived from a polycarbonate-based polyol may be used alone or both may be used.

[0076] The components of the polyurethane having hydrophilic groups can be confirmed (that the polyurethane having hydrophilic groups contains a component derived from a polyester polyol, and that the polyurethane having hydrophilic groups further contains a component derived from a polycarbonate polyol) by dissolving the polyester that constitutes the artificial leather and analyzing the insoluble matter (polyurethane having hydrophilic groups) using infrared spectroscopic analysis (the analytical instrument used is an FT / IR 4000 series manufactured by JASCO Corporation or an infrared spectroscopic analyzer with equivalent performance) or pyrolysis GC / MS analysis (the analytical instrument used is a GCMS-QP5050A manufactured by Shimadzu Corporation or a pyrolysis GC / MS analyzer with equivalent performance). While m-cresol and hexafluoroisopropanol can be used as solvents capable of dissolving the polyester that constitutes the artificial leather, it is preferable to use hexafluoroisopropanol, which can be handled at room temperature.

[0077] The polyurethane having a hydrophilic group used in the present invention preferably has an N-acylurea bond and / or an isourea bond. The N-acylurea bond and / or the isourea bond is formed by the reaction of the hydrophilic group with a crosslinking agent having a carbodiimide group, and by forming a crosslinked structure in the polyurethane having a hydrophilic group, the durability of the polyurethane having a hydrophilic group can be improved.

[0078] The presence of the N-acylurea group or isourea group in the polyurethane having a hydrophilic group can be analyzed by subjecting a cross section of the artificial leather to, for example, a mapping process such as time-of-flight secondary ion mass spectrometry (TOF-SIMS analysis) (the analytical instrument used is, for example, the "TOF.SIMS 5" manufactured by ION-TOF or a TOF-SIMS analyzer having equivalent performance) or infrared spectroscopic analysis (the analytical instrument used is, for example, the "FT / IR 4000 series" manufactured by JASCO Corporation or an infrared spectroscopic analyzer having equivalent performance).

[0079] [Artificial Leather] First, the artificial leather of the present invention has a content of polyurethane having a hydrophilic group of 15% by mass or more and 25% by mass or less. By setting the content to 15% by mass or more, preferably 18% by mass or more, the artificial leather has excellent abrasion resistance. On the other hand, by setting the content to 25% by mass or less, preferably 22% by mass or less, the artificial leather has a soft texture.

[0080] In the present invention, the content of polyurethane having a hydrophilic group is measured and calculated by the following method: (1) A test piece of 5 cm x 5 cm is cut out from the artificial leather, and the mass (M Ｘ (2) The test piece is immersed in hexafluoroisopropanol to elute the polyester ultrafine fibers from the artificial leather. (3) The insoluble component (polyurethane having hydrophilic groups) in (2) is dried in a dryer at 100°C, and the mass (M Ａ ) is measured, and then the content (mass %) of polyurethane having a hydrophilic group is calculated using the following formula.

[0081] Content of polyurethane having hydrophilic groups=(M Ａ / MＸ ) x 100.

[0082] In the present invention, it is important that polyurethane is attached to 10% to 80% of the outermost filaments of the multifilament constituting the woven fabric.

[0083] By having polyurethane adhere to 10% or more, more preferably 15% or more, and even more preferably 20% or more of the outermost filaments of the multifilament, artificial leather with excellent shape stability can be obtained.

[0084] On the other hand, when polyurethane is attached to 80% or less, more preferably 60% or less, and even more preferably 50% or less of the outermost filaments of the multifilament, the artificial leather has excellent flexibility.

[0085] In the present invention, the ratio of the outermost filaments of the multifilament to which polyurethane is attached is measured and calculated by the following method: (1) A scanning electron microscope (SEM) photograph of the cross section of the artificial leather is taken, and the number of outermost filaments (N Ｍ ) is calculated, and then the number of filaments to which polyurethane is attached among the outermost filaments of the multifilament (N ｐ ) is calculated, and the percentage of filaments to which polyurethane is attached is calculated using the following formula.

[0086] Percentage of filaments to which polyurethane is attached (%) = (N ｐ / N Ｍ ) x 100 (2) The measurement in (1) is carried out for 20 multifilaments, and the average value is the percentage of filaments to which polyurethane is attached.

[0087] The apparent density of the artificial leather of the present invention is 0.30 g / cm ３ 0.40g / cm or more ３ The apparent density of the artificial leather is preferably 0.30 g / cm or less. ３ More preferably, 0.32 g / cm ３ More preferably, 0.34 g / cm ３By setting the value to 0.40 g / cm or more, the abrasion resistance of the artificial leather becomes excellent. ３ or less, preferably 0.38 g / cm ３ By doing as follows, it is possible to obtain artificial leather with a soft feel.

[0088] In the present invention, the apparent density of the artificial leather is calculated using the following formula, after measuring the thickness and mass per unit area of ​​the artificial leather using the methods specified in JIS L 1913:2010 "Testing methods for general nonwoven fabrics" 6.1.1 (thickness, method A) and 6.2 (mass per unit area).

[0089] Apparent density of artificial leather (g / cm ３ ) = mass per unit area of ​​artificial leather (g / cm ２ ) / Thickness of artificial leather (cm).

[0090] The artificial leather of the present invention has a bending resistance of 150 mm or less in the longitudinal direction of the sheet, as defined by Method A (45° cantilever method) described in "8.21 Bending resistance" of JIS L 1096:2010 "Testing methods for woven and knitted fabrics." By setting the bending resistance in this range, an artificial leather with excellent flexibility can be obtained. By setting the bending resistance to 150 mm or less, more preferably 100 mm or less, an artificial leather with even greater flexibility can be obtained.

[0091] The artificial leather of the present invention preferably has an abrasion loss of 30 mg or less when measured after 50,000 abrasion cycles in the Martindale abrasion test specified in "8.19.5 Method E (Martindale method)" of "8.19 Abrasion resistance and friction discoloration" of JIS L 1096:2005 "Testing methods for woven and knitted fabrics." The abrasion loss is more preferably 25 mg or less, from the viewpoint of suppressing deterioration of the appearance of the artificial leather.

[0092] Furthermore, the artificial leather of the present invention preferably exhibits an abrasion loss of 10 mg or less when measured after 10,000 abrasion cycles in a Martindale abrasion test specified in "8.19.5 Method E (Martindale method)" of "8.19 Abrasion resistance and friction discoloration" of "Testing methods for woven and knitted fabrics" after xenon irradiation specified in "7.2 Exposure method a) First exposure method" of JIS L 0843:2006 "Testing methods for color fastness to xenon arc lamp light." Having an abrasion loss of 10 mg or less after xenon irradiation provides an artificial leather with durability suitable for long-term use in areas exposed to sunlight, such as automobile seats.

[0093] [Method for Producing Artificial Leather] The method for producing an artificial leather of the present invention comprises the following steps (1) to (3) in this order: (1) a step of entangling and integrating a nonwoven fabric made of ultrafine fiber-developing fibers with a woven fabric to form a fibrous substrate, (2) a step of impregnating the fibrous substrate with an aqueous dispersion of polyurethane having hydrophilic groups and then coagulating the polyurethane to obtain a sheet, where L is the width, to obtain a shrunk sheet having a width of 0.85L to 0.95L, and (3) a step of developing polyester ultrafine fibers from the ultrafine fiber-developing fibers of the shrunk sheet.

[0094] Details are explained below.

[0095] <Step of forming a fibrous substrate> In this step, a nonwoven fabric made of ultrafine fiber-developing fibers and a woven fabric are subjected to an entanglement treatment to form a fibrous substrate.

[0096] As the ultrafine fiber-forming fiber, it is preferable to use an islands-in-sea type composite fiber in which the sea part and island part are made of two thermoplastic resin components (two or three components when the island fiber is a core-sheath composite fiber) with different solvent solubility, and the sea part is dissolved and removed using a solvent or the like to convert the island part into ultrafine fibers, because when the sea part is removed, appropriate gaps can be imparted between the island part components, i.e., between the ultrafine fibers inside the fiber bundle, which is preferable from the viewpoint of the texture and surface quality of the artificial leather.

[0097] As for the islands-in-sea type composite fiber, a method using a polymer mutually aligned body in which two components, a sea component and an island component, are mutually aligned and spun using an islands-in-sea type composite spinneret (three components when the island components are core-sheath composite fibers) is preferred from the viewpoint of obtaining ultrafine fibers with a uniform single fiber diameter.

[0098] As the sea component of the islands-in-sea type composite fiber, polyethylene, polypropylene, polystyrene, copolymer polyesters copolymerized with sodium sulfoisophthalic acid, polyethylene glycol, etc., and polylactic acid, etc. can be used, but from the viewpoints of spinnability, ease of elution, etc., polystyrene and copolymer polyesters are preferably used.

[0099] The mass ratio of the sea component to the island component in the islands-in-sea type composite fiber preferably used in the present invention is preferably in the range of 10:90 to 80:20 (sea component:island component). When the mass ratio of the sea component is 10% by mass or more, the island component fibers are easily and sufficiently ultrafine. When the mass ratio of the sea component is 80% by mass or less, the proportion of eluted components is small, thereby improving productivity. The mass ratio of the sea component to the island component is more preferably in the range of 20:80 to 70:30 (sea component:island component).

[0100] As described above, either short fiber nonwoven fabric or long fiber nonwoven fabric can be used as the nonwoven fabric constituting the fibrous substrate. However, short fiber nonwoven fabric is preferred because it has more fibers oriented in the thickness direction of the artificial leather than long fiber nonwoven fabric, and can provide a highly dense feel to the surface of the artificial leather when raised.

[0101] When a staple fiber nonwoven fabric is used as the fibrous substrate, the obtained ultrafine fiber-developing fibers are preferably subjected to crimping processing and then cut to a predetermined length to obtain raw cotton. The crimping and cutting processes can be carried out by known methods.

[0102] Next, the obtained raw cotton is made into a fiber web using a cross wrapper or the like. The obtained fiber web is then entangled to obtain a nonwoven fabric. As a method for entangling the fiber web to obtain a nonwoven fabric, needle punching treatment, water jet punching treatment, etc. can be used, but needle punching treatment, which has high entanglement efficiency, is preferred.

[0103] The nonwoven fabric and the woven fabric are then laminated and entangled together. The entanglement of the nonwoven fabric and the woven fabric can be achieved by laminating the woven fabric on one or both sides of the nonwoven fabric, or by sandwiching the woven fabric between multiple nonwoven fabric webs and then entangling the fibers of the nonwoven fabric and the woven fabric by needle punching, water jet punching, or the like. From the viewpoint of production efficiency, it is preferable to laminate the woven fabric on both sides of the nonwoven fabric and then perform needle punching.

[0104] The apparent density of the nonwoven fabric made of the composite fiber (ultrafine fiber development type fiber) after the entanglement treatment and the fibrous base material made of the woven fabric is 0.20 g / cm ３ 0.30g / cm or more ３ It is preferable that the apparent density is 0.20 g / cm or less. ３ More preferably, 0.23 g / cm ３ By adjusting the apparent density to 0.30 g / cm or more, the fibrous base material can obtain sufficient shape stability and dimensional stability. ３ or less, more preferably 0.28 g / cm ３ By setting the above, it is possible to maintain a sufficient space for applying the polyurethane having a hydrophilic group.

[0105] The fibrous base material can be subjected to a heat shrinkage treatment using warm water or steam in order to improve the denseness of the fibers. However, in the present invention, since the sheet is shrunk after being impregnated with the aqueous dispersion containing the polyurethane precursor, it is preferable not to perform the shrinkage treatment before being impregnated with the aqueous dispersion containing the polyurethane precursor.

[0106] <Step of forming an impregnated sheet and shrinking it in the width direction> In this step, the fibrous base material is impregnated with an aqueous dispersion containing a polyurethane precursor, and then a heat drying treatment is performed to form an impregnated sheet containing the fibrous base material and polyurethane having a hydrophilic group as components.After that, when the width of the fibrous base material before impregnation with the sheet is L, a shrunk sheet is obtained with a width of 0.85L or more and 0.95L or less.

[0107] In the method for producing an artificial leather of the present invention, coagulation after application of the aqueous dispersion can be performed using coagulation methods commonly used in the field, such as dry heat coagulation and submerged coagulation. When using the dry heat coagulation method, it is preferable to apply the aqueous dispersion to a fibrous substrate, followed by heat treatment at a temperature of 120°C to 180°C and dry heat coagulation to impart a polyurethane having hydrophilic groups to the fibrous substrate. Furthermore, submerged coagulation can be performed using an acid coagulation method in which coagulation treatment is performed using a coagulation solvent with a pH of 1 to 3, or a hot water coagulation method in which coagulation treatment is performed using hot water at 80°C to 100°C.

[0108] The concentration of the polyurethane precursor in the aqueous dispersion (the content of the polyurethane precursor in 100% by mass of the aqueous dispersion) is preferably 3% by mass or more and 30% by mass or less. By setting it to 3% by mass or more, more preferably 5% by mass or more, the polyurethane precursor can be uniformly applied to the fibrous substrate even when the amount of the polyurethane precursor applied is small. On the other hand, by setting it to 30% by mass or less, more preferably 15% by mass or less, the storage stability of the aqueous dispersion can be improved.

[0109] When the dry heat coagulation method is used as the coagulation method, the coagulation temperature is preferably adjusted to 55° C. or higher and 80° C. or lower. By setting the coagulation temperature to 55° C. or higher, more preferably 60° C. or higher, gelation can be suppressed when preparing or storing the aqueous dispersion. On the other hand, by setting the temperature to 80° C. or lower, more preferably 70° C. or lower, coagulation of the polyurethane precursor proceeds before water evaporates from the fibrous substrate, and a structure similar to that obtained by wet coagulation of a solvent-based polyurethane can be formed, i.e., a structure in which the polyurethane does not strongly constrain the fibers that make up the nonwoven fabric or woven fabric, thereby achieving good flexibility and resilience.

[0110] In the method for producing an artificial leather of the present invention, when a dry heat coagulation method is used, an inorganic salt can be contained in the aqueous dispersion. By containing an inorganic salt, the aqueous dispersion can be imparted with heat-sensitive coagulation properties. In the present invention, heat-sensitive coagulation properties refer to the property that when the aqueous dispersion is heated, the fluidity of the aqueous dispersion decreases and the dispersion coagulates when the temperature reaches a certain temperature (coagulation temperature).

[0111] In the present invention, when an inorganic salt is used as a heat-sensitive coagulant, it is preferable to use a monovalent cation-containing inorganic salt. The monovalent cation-containing inorganic salt is preferably sodium chloride and / or sodium sulfate. Monovalent cation-containing inorganic salts with a small ionic valence have little effect on the stability of the aqueous dispersion, and by adjusting the amount added, the heat-sensitive coagulation temperature can be strictly controlled while ensuring the stability of the aqueous dispersion.

[0112] Furthermore, in the present invention, the content of the monovalent cation-containing inorganic salt in the aqueous dispersion is preferably 10% by mass or more and 50% by mass or less relative to the polyurethane precursor. By setting the content to 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, the ions present in large quantities in the aqueous dispersion act uniformly on the polyurethane precursor particles, allowing for rapid completion of coagulation at a specific heat-sensitive coagulation temperature. This provides a more significant effect when promoting coagulation of the polyurethane precursor in a fibrous substrate containing a large amount of water, as described above. As a result, a structure very similar to that obtained by wet coagulation of a solvent-based polyurethane can be formed, achieving good flexibility and resilience. Furthermore, by adding the inorganic salt in the above-mentioned amount, the inorganic salt acts as an inhibitor of the fusion of polyurethane precursor particles and can also suppress the hardening of the polyurethane precursor due to the formation of a continuous coating. On the other hand, setting the content to 50% by mass or less allows the polyurethane precursor to maintain an appropriate continuous coating structure, preventing deterioration of physical properties. The stability of the aqueous dispersion can also be maintained.

[0113] In the method for producing an artificial leather of the present invention, it is also preferable to add a crosslinking agent to the aqueous dispersion. The crosslinking agent introduces a three-dimensional network structure into the polyurethane precursor, thereby improving physical properties such as abrasion resistance.

[0114] The concentration of the crosslinking agent in the aqueous dispersion is preferably 1% by mass or more and 10% by mass or less relative to the mass of the polyurethane precursor. By setting the concentration of the crosslinking agent in the aqueous dispersion to 1% by mass or more, more preferably 2% by mass or more, the crosslinking agent can introduce a larger amount of a three-dimensional network structure into the polyurethane precursor, thereby producing an artificial leather with excellent abrasion resistance, etc. On the other hand, by setting the concentration to 10% by mass or less, more preferably 7% by mass or less, it is possible to prevent excessive crosslinking agent from inhibiting the coagulation of the polyurethane precursor when it is formed, and it is easier to prevent a decrease in physical properties such as abrasion resistance.

[0115] The crosslinking agent preferably used in the method for producing an artificial leather of the present invention is preferably a carbodiimide crosslinking agent and / or a blocked isocyanate crosslinking agent. By using this method, a three-dimensional crosslinked structure can be imparted to the molecules of the polymeric elastomer in the artificial leather by N-acylurea bonds and / or isourea bonds, which have excellent physical properties such as light resistance, heat resistance, and abrasion resistance, as well as flexibility, and the physical properties such as durability and abrasion resistance can be dramatically improved while maintaining the flexibility of the artificial leather.

[0116] After impregnation and coagulation with the aqueous dispersion, a shrunken sheet is obtained with a width of 0.85L to 0.95L, where L is the width of the fibrous substrate before impregnation. Methods for shrinking the sheet in the width direction include dry heat treatment at a temperature of 100°C to 180°C, and hot water treatment using hot water at a temperature of 80°C to 100°C. Examples of dry heat treatment include treatment in which hot air is applied to one or both sides of the sheet using a floater dryer, drum dryer, pin tenter dryer, etc., and examples of hot water treatment include treatment in which the sheet is immersed in hot water at a temperature of 80°C to 100°C, squeezed with a mangle, and then dried in a dryer.

[0117] From the viewpoint of production efficiency, it is preferable that the coagulation method and the shrinkage method of the aqueous dispersion are the same.

[0118] Shrinking the sheet in the width direction can increase the density of the artificial leather surface. In particular, shrinking the sheet in the width direction after impregnation and coagulation of the aqueous polyurethane dispersion can prevent the polyurethane from strongly adhering to the woven fabric, thereby softening the texture of the artificial leather.

[0119] The degree of shrinkage in the width direction of the sheet can be adjusted by the heat treatment temperature and heat treatment time, and the above-mentioned effect can be made sufficient by making the shrinkage 5% or more, more preferably 10% or more, of the width of the fibrous base material before impregnation.

[0120] On the other hand, by making the width 15% or less of the width of the fibrous base material before impregnation, quality defects such as wrinkles in the sheet can be prevented.

[0121] When dry heat treatment is used as the shrinkage treatment, the shrinkability of the sheet can be increased by setting the temperature of the dry heat treatment to 100° C. or higher, preferably 120° C. or higher, and more preferably 130° C. or higher. On the other hand, by setting the temperature of the dry heat treatment to 180° C. or lower, preferably 160° C. or lower, the deterioration of the durability of the artificial leather due to decomposition of the polyurethane can be suppressed.

[0122] When dry heat treatment is used as the shrinkage treatment, the dry heat treatment time is preferably 5 minutes or more and 30 minutes or less. Heating for 5 minutes or more, more preferably 10 minutes or more, can increase the shrinkage of the sheet. Dry heat treatment time of 30 minutes or less, preferably 25 minutes or less, can suppress deterioration of the durability of the artificial leather due to decomposition of polyurethane.

[0123] <Step of expressing polyester ultrafine fibers> In this step, polyester ultrafine fibers are expressed from the ultrafine fiber-expressing fibers of the shrink sheet, and a sheet containing, as components, a fibrous base material composed of polyester ultrafine fibers and woven fabric, and polyurethane having hydrophilic groups.

[0124] When islands-in-sea type composite fibers are used as the ultrafine fiber-producing fibers, the ultrafine fiber treatment (sea component removal treatment) can be carried out, for example, by immersing the islands-in-sea type composite fibers in a solvent and then performing a heat treatment. The solvent for dissolving the sea component can be appropriately selected depending on the type of sea component. When the sea component is a copolymer polyester, an aqueous alkali solution such as sodium hydroxide can be used, but it is preferable to carry out the alkali treatment using an aqueous alkali solution, which is expected to have the effect of reducing the adhesion between the woven fabric and the polyurethane.

[0125] When an aqueous alkaline solution is used as a solvent for the sea-removal treatment, the molar concentration of the aqueous alkaline solution is preferably 3 mol / L or less in order to prevent excessive deterioration of the polyurethane having hydrophilic groups.

[0126] <Finishing Step> In the method for producing the artificial leather of the present invention, it is preferable to carry out various finishing steps, as in the case of general artificial leathers.

[0127] First, the method for producing an artificial leather of the present invention preferably includes a dyeing step for dyeing the artificial leather. This dyeing process can be performed using any of the methods commonly used in the art, including, for example, jet dyeing using a jigger dyeing machine or jet dyeing machine, dip dyeing such as thermosol dyeing using a continuous dyeing machine, or printing on the napped surface using roller printing, screen printing, inkjet printing, sublimation printing, vacuum sublimation printing, etc. Among these, jet dyeing machines are preferred because they can impart a kneading effect to the unbrushed artificial leather or artificial leather while dyeing it, thereby softening the unbrushed artificial leather or artificial leather. Furthermore, various resin finishing processes can be performed after dyeing, if necessary.

[0128] In addition, finishing treatment using a softener such as silicone, an antistatic agent, a water repellent, a flame retardant, a lightfastness agent, an antibacterial agent, etc. can be carried out in the same bath as dyeing or after dyeing.

[0129] In the present invention, regardless of whether it is before or after the dyeing step, from the viewpoint of production efficiency, it is also a preferred embodiment to cut the film in half in the thickness direction.

[0130] In the method for producing the artificial leather of the present invention, it is also preferable to include a nap raising step, whether before or after the dyeing step. The method for forming nap is not particularly limited, and various methods commonly used in the art, such as buffing with sandpaper, can be used.

[0131] When performing the nap raising treatment, a lubricant such as a silicone emulsion can be applied to the surface of the artificial leather before the nap raising treatment. Also, by applying an antistatic agent before the nap raising treatment, grinding dust generated from the artificial leather during grinding is less likely to accumulate on the sandpaper. In this way, the artificial leather is formed.

[0132] Furthermore, in the method for producing an artificial leather of the present invention, the artificial leather can be subjected to post-processing such as perforation, embossing, laser processing, pinsonic processing, and printing, as needed.

[0133] [Uses of Vehicle Interior Materials, Vehicle Parts, Seats, etc.] The artificial leather obtained by the present invention can be suitably used as an interior material having a very elegant appearance, such as a covering material for furniture, chairs, and wall materials, and for seats, ceilings, and interiors in the cabins of vehicles such as automobiles, trains, and airplanes; uppers and trims of shoes such as shirts, jackets, casual shoes, sports shoes, men's shoes, and women's shoes; bags, belts, wallets, etc.; clothing materials used in parts of these; and industrial materials such as wiping cloths, polishing cloths, and CD curtains.

[0134] For example, automobile interior materials containing the artificial leather are preferred because they can take advantage of the properties of high strength, excellent flexibility, and excellent abrasion resistance. Such automobile interior materials are preferably used for automobile parts such as steering wheels, horn switches, shift knobs, dashboards, instrument panels, glove boxes, floor carpets, floor mats, ceiling linings, sun visors, and assist grips, and it is more preferable that at least a portion of these automobile parts is made of the artificial leather. Note that the term "automobile" in this invention is not limited to so-called ordinary passenger cars, but also includes some industrial, construction, and agricultural machinery that can carry people or animals, such as excavators, crane trucks, tractors, and combine harvesters.

[0135] Seats containing the artificial leather are also preferred because they can take advantage of the properties of high strength, excellent flexibility, and excellent abrasion resistance. It is more preferable that at least a portion of the covering material of the headrest, seat, armrest, footrest, etc., for example, the portion that comes into direct contact with the seated person, is made of the artificial leather. Of course, the seat of the present invention can be used not only for vehicles such as automobiles, airplanes, railway vehicles, and ships, but also for homes, offices, and stores. The term "seat" as used in the present invention also includes chairs, benches, sofas, couches, stools, and floor chairs.

[0136] The artificial leather of the present invention will be explained in more detail using examples, but the present invention is not limited to these examples.

[0137] [Evaluation Methods] The evaluation methods and measurement conditions used in the examples are described below. Unless otherwise specified, the measurements of each physical property were carried out according to the above-mentioned methods.

[0138] (1) Average Single Fiber Diameter (μm): The average single fiber diameter (μm) was measured and calculated by the above-mentioned method using a scanning electron microscope (SEM) "VHX-D500 / D510" manufactured by Keyence Corporation.

[0139] (2) Content (mass %) of polyurethane having hydrophilic group: The content (mass %) of polyurethane having hydrophilic group was measured and calculated by the above-mentioned method.

[0140] (3) Percentage (%) of filaments to which polyurethane is attached among the outermost filaments of a multifilament: The percentage (%) of filaments to which polyurethane is attached among the outermost filaments of a multifilament was measured and calculated by the method described above.

[0141] (4) Bending resistance of artificial leather: Based on Method A (45° cantilever method) described in 8.21 “Bending resistance” 8.21.1 of JIS L 1096:2010 “Testing methods for woven and knitted fabrics,” five test pieces of 2 cm × 30 cm were prepared in the longitudinal direction of the sheet and placed on a horizontal table with a 45° inclined surface. The test pieces were slid and the scale was read when the center point of one end of the test piece came into contact with the inclined surface, and the average value of the five pieces was calculated.

[0142] (5) Abrasion loss (mg) of artificial leather: When measuring and calculating the abrasion loss (mg) of the artificial leather, a Martindale abrasion tester "Model 406" manufactured by James H. Heal & Co. was used as the abrasion tester, and "ABRASTIVE CLOTH SM25" manufactured by the same company was used as the standard friction cloth. A load of 12 kPa was applied to the artificial leather, and measurements were carried out after 50,000 abrasion cycles. The abrasion loss was calculated using the mass of the artificial leather before and after abrasion according to the following formula.

[0143] Abrasion loss (mg) = mass before abrasion (mg) - mass after abrasion (mg) The abrasion loss (mg) was rounded off to one decimal place.

[0144] (6) Abrasion loss (mg) of artificial leather after xenon irradiation: When measuring and calculating the abrasion loss (mg) of artificial leather after xenon irradiation, irradiation was performed as specified in "7.2 Exposure method a) First exposure method" of JIS L 0843:2006 "Test method for color fastness to xenon arc lamp light," and then a Martindale abrasion tester "Model 406" manufactured by James H. Heal & Co. and a standard friction cloth "ABRASTIVE CLOTH SM25" manufactured by the same company were used. A load of 12 kPa was applied to the artificial leather, and measurements were performed after 10,000 abrasion cycles. The abrasion loss was calculated using the mass of the artificial leather before and after abrasion according to the following formula.

[0145] Abrasion loss (mg) = mass before abrasion (mg) - mass after abrasion (mg) The abrasion loss (mg) was rounded off to one decimal place.

[0146] [Polyurethane Precursor] The polyurethane precursors used in the examples and comparative examples are as follows.

[0147] PU-A (polyether-based polyurethane precursor containing a component derived from a polyether-based polyol): A polyurethane precursor consisting of polytetramethylene glycol as a polymer polyol, MDI as an organic diisocyanate, 2,2-dimethylolpropionic acid as an active hydrogen component-containing compound having a hydrophilic group, and ethylene glycol as a chain extender.

[0148] PU-B (polycarbonate-based polyurethane precursor containing a component derived from a polycarbonate-based polyol): A polyurethane precursor consisting of polyhexamethylene carbonate diol as a polymer polyol, MDI as an organic diisocyanate, 2,2-dimethylolpropionic acid as an active hydrogen component-containing compound having a hydrophilic group, and ethylene glycol as a chain extender.

[0149] [Woven Fabrics] The woven fabrics used in the Examples and Comparative Examples are as follows.

[0150] Fabric A: A plain weave fabric (weight 75 g / m) with a warp density of 95 warp threads / 2.54 cm and 76 weft threads / 2.54 cm, in which twisted yarns obtained by twisting multifilament consisting of 72 filaments with an average single fiber diameter of 11 μm made of polyethylene terephthalate having an intrinsic viscosity of 0.65 at 2,500 T / m were used for both the weft and the warp. ２ ).

[0151] Fabric B: A plain weave fabric (basis weight 75 g / m) with a warp density of 95 warp threads / 2.54 cm and a weft density of 76 weft threads / 2.54 cm, in which twisted yarns obtained by twisting multifilament consisting of 40 filaments with an average single fiber diameter of 15 μm made of polyethylene terephthalate having an intrinsic viscosity of 0.65 at 2,500 T / m were used for both the weft and the warp. ２ ).

[0152] Fabric C: A plain weave fabric (weight 75 g / m) with a warp density of 190 threads / 2.54 cm and a weft density of 152 threads / 2.54 cm, in which twisted yarns obtained by twisting multifilament consisting of 68 filaments with an average single fiber diameter of 8 μm made of polyethylene terephthalate having an intrinsic viscosity of 0.65 at 2,500 T / m were used for both the weft and the warp. ２ ).

[0153] [Example 1] <Step of forming a fibrous substrate> A polyester copolymerized with 8 mol % of 5-sodium sulfoisophthalate was used as the sea component, and polyethylene terephthalate having an intrinsic viscosity of 0.73 was used as the island component. Using an islands-in-sea composite spinneret with an island number of 16 per hole, melt spinning was performed under the conditions of a spinning temperature of 285°C, an islands / sea mass ratio of 80 / 20, a throughput of 1.6 g / min per hole, and a spinning speed of 1,100 m / min. The resulting fiber was then stretched 3.7 times in an oil bath and cut to a length of 51 mm to obtain raw fiber for islands-in-sea composite fiber with a single fiber fineness of 3.8 dtex. The raw fiber for the islands-in-sea composite fiber was then subjected to carding and cross-wrapping processes to obtain an apparent density of 0.09 g / cm. ３ After forming the laminated web, the woven fabric A was laminated thereon, and the laminated web was 3,500 threads / cm ２ The fabric was needle punched at a punch density of 690 g / m ２ The thickness is 3.0 mm, the width is 170 cm, and the apparent density is 0.23 g / cm ３A fibrous substrate consisting of a nonwoven fabric made of sea-island composite fibers and a woven fabric was obtained.

[0154] <Step of forming an impregnated sheet and shrinking it in the width direction> An aqueous dispersion containing 12 parts by mass of PU-A, a polyether-based polyurethane precursor, 1 part by mass of a carbodiimide-based crosslinking agent ("Carbodilite" (registered trademark) V-02-L2, manufactured by Nisshinbo Chemical Inc.), 5 parts by mass of sodium sulfate, and 82 parts by mass of water was prepared as a polyurethane precursor. After impregnating a fibrous base material with the aqueous dispersion, the dispersion was squeezed with a mangle so that the pickup rate of the aqueous dispersion was 200% by mass relative to the fibrous base material. The sheet was then heated with hot air at 100°C for 10 minutes to solidify the polyurethane precursor, and then heated with hot air at 150°C for 10 minutes to shrink the sheet in the width direction by 12% relative to the width L of the fibrous base material before impregnation, thereby obtaining an impregnated sheet having a width of 150 cm (0.88 L) and consisting of a nonwoven fabric of islands-in-sea composite fiber, a woven fabric, and a polyurethane having hydrophilic groups.

[0155] <Step of Developing Polyester Ultrafine Fibers> The obtained impregnated sheet was immersed in a 5% aqueous solution of sodium hydroxide, and then squeezed with a mangle so that the pick-up rate of the aqueous sodium hydroxide solution became 100%, and then heat-treated with steam at 95°C for 10 minutes to alkali-decompose the sea component of the islands-in-sea type composite fibers. Next, the excess sodium hydroxide was washed away with water, and a sheet comprising polyester ultrafine fibers, a woven fabric, and a polyurethane having hydrophilic groups was obtained.

[0156] <Finishing Step> The obtained sheet was cut in half perpendicular to the thickness direction, and the cut surfaces were ground with endless sandpaper of sandpaper size 180 to obtain a napped sheet having a thickness of 0.9 mm.

[0157] The resulting napped sheet was dyed with a disperse dye at 120°C using a jet dyeing machine. It was then dried in a dryer to obtain an artificial leather containing 23% by mass of polyurethane with hydrophilic groups and an average single fiber diameter of 4.4 μm. The proportion (%) of polyurethane-attached filaments in the outermost filaments of the multifilament woven fabric of the resulting artificial leather was 30%, and the artificial leather had a soft texture and excellent durability. The results are shown in Table 1.

[0158] [Example 2] An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass% of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming a fibrous substrate>, the woven fabric was changed to woven fabric B. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation, to 150 cm (0.88 L).

[0159] The percentage (%) of the outermost filaments of the multifilament composing the resulting artificial leather fabric to which polyurethane had adhered was 45%, and although the artificial leather was slightly inferior in flexibility compared to Example 1, it had a soft texture and excellent durability. The results are shown in Table 1.

[0160] [Example 3] An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass% of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming a fibrous substrate>, the woven fabric was changed to woven fabric C. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation, to 150 cm (0.88 L).

[0161] The percentage (%) of the outermost filaments of the multifilament constituting the resulting artificial leather fabric to which polyurethane had adhered was 65%, and although the artificial leather was slightly inferior in flexibility compared to Example 1, it had a soft texture and excellent durability. The results are shown in Table 1.

[0162] [Example 4] An artificial leather containing ultrafine fibers with an average single fiber diameter of 4.4 μm and 23 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the heating conditions after solidifying the polyurethane precursor were changed to 10 minutes with hot air at 120° C. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 160 cm (0.94 L), which was shrunk by 6% in the width direction compared to the width L of the fibrous base material before impregnation.

[0163] The percentage (%) of the outermost filaments of the multifilament composing the obtained artificial leather fabric to which polyurethane had adhered was 39%, and although the artificial leather was slightly inferior in flexibility compared to Example 1, it had a soft texture and excellent durability. The results are shown in Table 1.

[0164] [Example 5] An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet and shrinking it in the width direction, a polycarbonate-based polyurethane precursor, PU-B, was used as the polyurethane precursor. The width of the impregnated sheet obtained in the step of forming an impregnated sheet and shrinking it in the width direction was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous base material before impregnation.

[0165] Of the outermost filaments of the multifilament composing the resulting artificial leather fabric, the percentage (%) of filaments to which polyurethane was attached was 32%, and although the artificial leather was slightly inferior in flexibility compared to Example 1, it had a soft texture and extremely excellent durability. The results are shown in Table 1.

[0166] [Example 6] An artificial leather containing ultrafine fibers with an average single fiber diameter of 4.4 μm and 18 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet and shrinking it in the width direction, the pickup rate of the aqueous dispersion was 140% by mass of the fibrous substrate. The width of the impregnated sheet obtained in the step of forming an impregnated sheet and shrinking it in the width direction was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation.

[0167] The percentage of filaments to which polyurethane was attached among the outermost filaments of the multifilament composing the obtained artificial leather fabric was 22%, and the artificial leather had a soft feel and excellent durability. The results are shown in Table 1.

[0168] [Example 7] An artificial leather containing ultrafine fibers with an average single fiber diameter of 4.4 µm and 23 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the heating conditions for coagulating the polyurethane precursor and after coagulation were changed to steam at 98°C. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 162 cm (0.95 L), which was shrunk by 5% in the width direction compared to the width L of the fibrous base material before impregnation.

[0169] Of the outermost filaments of the multifilament composing the resulting artificial leather fabric, the percentage (%) of filaments to which polyurethane was attached was 47%, and although the artificial leather was slightly inferior in flexibility compared to Example 1, it had a soft texture and excellent durability. The results are shown in Table 1.

[0170] [Example 8] An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the <step of developing polyester ultrafine fibers>, the concentration of sodium hydroxide was changed to 3% and the pickup rate was changed to 200%. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 12% in the width direction compared to the width L of the fibrous base material before impregnation, to 150 cm (0.88 L).

[0171] Of the outermost filaments of the multifilament composing the resulting artificial leather fabric, the percentage (%) of filaments to which polyurethane was attached was 40%, and although the artificial leather was slightly inferior in flexibility compared to Example 1, it had a soft texture and extremely excellent durability. The results are shown in Table 1.

[0172] [Comparative Example 1] An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the fibrous substrate was shrunk in the width direction to 150 cm with hot water at 97°C before impregnating with the aqueous dispersion, and no shrinkage in the width direction was performed after coagulation of the polyurethane precursor. Note that the width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> did not shrink in the width direction compared to the width L of the fibrous substrate before impregnation, and remained at 150 cm (1.00 L).

[0173] The percentage of fibers to which polyurethane was attached among the outermost filaments of the multifilament constituting the filaments of the obtained artificial leather was 95%, and the obtained artificial leather had excellent durability, but the texture was hard. The results are shown in Table 1.

[0174] [Comparative Example 2] An artificial leather containing ultrafine fibers with an average single fiber diameter of 4.4 μm and 13 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the pickup rate of the aqueous dispersion was set to 100% by mass of the fibrous substrate. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation.

[0175] The percentage (%) of the outermost filaments of the multifilament composing the resulting artificial leather fabric to which polyurethane had adhered was 8%, and although the resulting artificial leather had an excellent feel, it was significantly inferior in durability. The results are shown in Table 1.

[0176] [Comparative Example 3] An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 29 mass% of polyurethane having hydrophilic groups was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the pickup rate of the aqueous dispersion was set to 250% by mass of the fibrous substrate. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation.

[0177] The percentage (%) of the outermost filaments of the multifilament composing the artificial leather fabric to which polyurethane had adhered was 82%, and the artificial leather obtained had excellent durability but a hard feel. The results are shown in Table 1.

[0178] [Comparative Example 4] In the <step of forming an impregnated sheet and shrinking it in the width direction>, before impregnating the fibrous substrate with the aqueous dispersion, the fibrous substrate was shrunk in the width direction to 150 cm with hot water at 97°C, and at the same time, polyvinyl alcohol with a saponification degree of 98% was added in an amount of 10 mass% relative to the mass of the fibrous substrate, thereby obtaining an artificial leather containing ultrafine fibers with an average single fiber diameter of 4.4 μm and 23 mass% of polyurethane having hydrophilic groups. Note that the width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> did not shrink in the width direction compared to the width L of the fibrous substrate before impregnation, and remained at 150 cm (1.00 L).

[0179] The proportion (%) of fibers to which polyurethane was attached among the outermost filaments of the multifilament constituting the filaments of the obtained artificial leather was 95%, and the obtained artificial leather had excellent durability but a hard feel. The results are shown in Table 1. <Step of forming a fibrous substrate> A fibrous substrate consisting of a nonwoven fabric made of sea-island composite fiber and a woven fabric was obtained in the same manner as in Example 1.

[0180] <Step of forming an impregnated sheet and shrinking it in the width direction> Before impregnating the fibrous substrate with the aqueous dispersion, the fibrous substrate was shrunk in the width direction to 150 cm with hot water at 97°C, and at the same time, polyvinyl alcohol having a saponification degree of 98% was added in an amount of 10 mass% relative to the mass of the fibrous substrate, and the fibrous substrate was dried with hot air at 100°C, thereby obtaining a fibrous substrate with polyvinyl alcohol. Next, an aqueous dispersion containing 12 parts by mass of PU-A, which is a polyether polyurethane precursor, 1 part by mass of a carbodiimide crosslinking agent ("Carbodilite" (registered trademark) V-02-L2, manufactured by Nisshinbo Chemical Inc.), 5 parts by mass of sodium sulfate, and 82 parts by mass of water was prepared as a polyurethane precursor. After impregnating a fibrous base material with the aqueous dispersion, the dispersion was squeezed with a mangle so that the pickup rate of the aqueous dispersion was 200% by mass relative to the fibrous base material. The mixture was then heated with hot air at 100°C for 10 minutes to solidify the polyurethane precursor, and then heated with hot air at 150°C for 10 minutes to obtain an impregnated sheet comprising a nonwoven fabric of islands-in-sea composite fibers, a woven fabric, a polyurethane having a hydrophilic group, and polyvinyl alcohol.

[0181] <Step of Developing Polyester Ultrafine Fibers> The obtained impregnated sheet was subjected to an alkali treatment in the same manner as in Example 1 to develop polyester ultrafine fibers, and the polyvinyl alcohol was removed with hot water at 100°C to obtain a sheet comprising polyester ultrafine fibers, a woven fabric, and polyurethane having hydrophilic groups.

[0182] <Finishing Process> The obtained sheet was subjected to a finishing process in the same manner as in Example 1 to obtain an artificial leather having an average single fiber diameter of 4.4 μm of ultrafine fibers and containing 23 mass% of polyurethane having hydrophilic groups. Of the outermost filaments of the multifilament composing the obtained artificial leather fabric, the percentage (%) of filaments to which polyurethane was attached was 3%. Although the artificial leather had a soft texture and excellent durability, the use of polyvinyl alcohol resulted in a higher process load compared to Example 1. The results are shown in Table 1.

[0183]

[0184] The artificial leather obtained by the present invention can be suitably used as an interior material having a very elegant appearance as a surface material for furniture, chairs, and wall materials, and for seats, ceilings, and interior trims in the interiors of vehicles such as automobiles, trains, and airplanes; uppers and trims for shoes such as shirts, jackets, casual shoes, sports shoes, men's shoes, and women's shoes; bags, belts, wallets, and the like; and industrial materials used in parts of these items, such as wiping cloths, polishing cloths, and CD curtains.

[0185] 1: Multifilament that makes up the fabric 2: Polyurethane 3: Filament with polyurethane attached 4: Filament without polyurethane attached

Claims

1. An artificial leather comprising a fibrous base material formed by entanglement of a nonwoven fabric and a woven fabric, and a polyurethane having a hydrophilic group, wherein the nonwoven fabric is composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm, the woven fabric is composed of a multifilament having 30 to 300 filaments, and the average single fiber diameter of the filaments constituting the multifilament is 1 μm to 30 μm, the content of the polyurethane in the artificial leather is 15% by mass to 25% by mass, and the proportion of the filaments to which the polyurethane is attached among the outermost filaments of the multifilament is 10% to 80%.

2. The artificial leather according to claim 1, wherein the polyurethane is a polyether-based polyurethane and / or a polycarbonate-based polyurethane.

3. A method for producing the artificial leather according to claim 1, comprising the steps of (1) to (3) below in this order: (1) A process for forming a fibrous base material by entangling and integrating a nonwoven fabric made of ultrafine fiber-developing fibers with a woven fabric. (2) A process for obtaining a shrunk sheet having a width of 0.85L to 0.95L, where L is the width of the fibrous base material before impregnation, from the sheet obtained by impregnating the fibrous base material with an aqueous dispersion of polyurethane having hydrophilic groups. (3) A process for developing polyester ultrafine fibers from the ultrafine fiber-developing fibers of the shrunk sheet.

4. The method for producing an artificial leather according to claim 3, wherein the entanglement and integration means in the step (1) is a needle punching process.

5. The method for producing an artificial leather according to claim 3 or 4, wherein the means for obtaining the shrink sheet in the step (2) is a dry heat treatment at an atmospheric temperature of 100° C. or higher and 180° C. or lower.

6. The method for producing an artificial leather according to claim 3 or 4, wherein the means for developing the polyester ultrafine fibers in the step (3) is an alkali treatment.

7. An automobile interior material comprising the artificial leather according to claim 1 or 2.

8. An automobile part comprising the artificial leather according to claim 1 or 2.

9. A seat comprising the artificial leather according to claim 1 or 2.

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