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

Abstract

The purpose of the present invention is to provide an artificial leather that achieves both surface hue uniformity and good texture even when a polymer elastic body (polyurethane) having a hydrophilic group is used. An artificial leather according to the present invention includes a fibrous base material and polyurethane. The fibrous base material includes a nonwoven fabric comprising polyester ultrafine fibers having an average single fiber diameter of 1.0-10.0 μm. The polyurethane has a hydrophilic group, and further contains a black pigment and / or a chromatic pigment. In the pigment, the average particle diameter of the pigment is 0.01-0.10 μm, and the average degree of irregularity of the pigment is 0.50-1.00. When the artificial leather is equally divided into three layers in the thickness direction, the coefficient of variation of the mass ratio of the polyurethane in each layer is 5-30%.

Description

Artificial leather, its manufacturing method and uses

[0001] The present invention relates to artificial leather, a method for producing the same, and clothing, furniture, miscellaneous goods, vehicle interior materials, and automobile parts containing the same.

[0002] Artificial leather, which is made primarily of a fibrous substrate such as a nonwoven fabric made primarily of ultrafine fibers and polyurethane, has excellent characteristics not found in natural leather, such as high durability and uniformity, and is used not only as a material for clothing but also in a variety of fields, including vehicle interior materials, furniture and interior materials, and building materials. In producing such artificial leather, a more environmentally friendly method using water-dispersed polyurethane, in which a polyurethane resin having hydrophilic groups is dispersed in water, is being considered as an alternative to the conventional method using organic solvent-based polyurethane.

[0003] For example, Patent Document 1 proposes a method for producing a sheet-like material by impregnating a fiber material substrate made of nonwoven fabric with an aqueous dispersion containing a nonionic self-emulsifying polyurethane having a specific heat-sensitive gelation temperature and a water-dispersible inorganic pigment, and describes that this method produces a sheet-like material that has a good appearance and is environmentally friendly.

[0004] Patent Document 2 proposes a method for producing suede-like artificial leather, which includes the steps of: producing a fiber-entangled nonwoven fabric composed of a specific resin-based ultrafine fiber-developing fiber containing a specific amount of a pigment having a specific average particle size; applying a polymer elastomer dispersion containing a specific amount of a water-dispersed polymer elastomer and a specific amount of a pigment having a specific average particle size to the interior of the fiber-entangled nonwoven fabric so that the mass ratio of the polymer elastomer derived from the water-dispersed polymer elastomer to the three-dimensional entangled fiber is within a specific range; and obtaining ultrafine fibers by a specific method. It is described that this method results in excellent color development and fastness, such as lightfastness, in a variety of colors, and also in excellent sensory aspects, such as suede feel, surface touch, and texture, as well as good physical properties, such as surface strength, tear strength, and tensile strength.

[0005] Patent Document 3 also discloses a first polymeric elastomer precursor impregnation step in which a fibrous substrate made of ultrafine fiber-developing fibers is impregnated with an aqueous dispersion containing a polymeric elastomer precursor having a hydrophilic group, a monovalent cation-containing inorganic salt, and a crosslinking agent, and then the temperature of the fibrous substrate impregnated with the aqueous dispersion is set within a specific range and a heat drying treatment is performed to form a polymeric elastomer, the first polymeric elastomer precursor impregnation step being such that the aqueous dispersion contains a specific amount of the monovalent cation-containing inorganic salt; an ultrafine fiber development step in which ultrafine fibers are developed from the ultrafine fiber-developing fibers to form a fibrous substrate made of the ultrafine fibers; and a second polymeric elastomer precursor impregnation step in which a polymeric elastomer precursor having a hydrophilic group and a monovalent cation-containing inorganic salt are impregnated with the fibrous substrate made of the ultrafine fibers. A method for producing a sheet-like material has been proposed, which includes: impregnating a fibrous substrate with an aqueous dispersion containing a monovalent cation-containing inorganic salt and a crosslinking agent, followed by heating and drying the fibrous substrate at a temperature within a specific range, and then forming a polymeric elastomer (a second polymeric elastomer precursor impregnation step), in which the content of the monovalent cation-containing inorganic salt in the aqueous dispersion is adjusted to fall within a specific range. It is also disclosed that this method produces a sheet-like material with excellent flexibility, chemical resistance, and dye resistance.

[0006] JP 2008-184707 A JP 2004-143654 A International Publication No. 2021 / 125029

[0007] In the methods disclosed in Patent Documents 1 and 2, the pigment is uniformly dispersed in a polymeric elastomer and a fibrous substrate is impregnated with the aqueous dispersion, thereby improving the uniformity of the surface hue to some extent. However, if left as is, the polymeric elastomer tends to be biased toward the surface layer of the sheet when it solidifies, and the polymeric elastomer tends to cover the periphery of the fibers, creating a structure that strongly restricts their movement, so the texture tends to be hard and there is room for improvement.

[0008] In the method disclosed in Patent Document 3, when applying the water-dispersible polyurethane, an aqueous dispersion containing a specific amount of a monovalent cation-containing inorganic salt is used, and then a heat treatment is carried out at a specific temperature, thereby achieving a good texture. However, there is room for improvement in terms of the uniformity of the hue of the artificial leather surface.

[0009] In view of the above problems, an object of the present invention is to provide an artificial leather that achieves both uniformity in surface hue and good texture, even when a polymeric elastomer (polyurethane) having hydrophilic groups is used.

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems and have found that an artificial leather obtained by impregnating a fibrous substrate with an aqueous dispersion containing a hydrophilic polyurethane, an inorganic pigment, and an inorganic salt, and adding a specific amount of a nonionic surfactant, has a specific range of average irregularity of the pigment contained in the polyurethane, and a specific coefficient of variation of the mass proportion of the polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction.The inventors have also found that an artificial leather falling within this range has both uniform surface hue and good texture.

[0011] The present invention has been completed based on these findings, and provides the following inventions.

[0012] [1] An artificial leather comprising a fibrous base material and polyurethane, wherein the fibrous base material comprises a nonwoven fabric made of polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less, the polyurethane has a hydrophilic group and further comprises a black pigment and / or a chromatic pigment, the pigment having an average particle diameter of 0.01 μm or more and 0.10 μm or less, an average irregularity degree of the pigment being 0.50 or more and 1.00 or less, and when the artificial leather is divided into three equal parts in the thickness direction, the coefficient of variation of the mass proportion of the polyurethane in each layer is 5% or more and 30% or less.

[0013] [2] The artificial leather according to [1], wherein the total content of the pigment in the polyurethane is 0.01% by mass or more and 2.00% by mass or less.

[0014] [3] The artificial leather according to [1] or [2], wherein at least one surface has a nap of 200 μm or more and 500 μm or less.

[0015] [4] The artificial leather according to [3], wherein the nap coverage on the surface having the nap is 80% or more and 99% or less.

[0016] [5] Clothing comprising the artificial leather according to any one of [1] to [4].

[0017] [6] Furniture comprising the artificial leather according to any one of [1] to [4].

[0018] [7] Miscellaneous goods comprising the artificial leather according to any one of [1] to [4].

[0019] [8] A vehicle interior material comprising the artificial leather according to any one of [1] to [4].

[0020] [9] An automobile part comprising the artificial leather according to any one of [1] to [4].

[0021]

[10] A method for producing an artificial leather, comprising the steps of: forming a fibrous substrate containing a nonwoven fabric made of ultrafine fiber-developing fibers; impregnating the fibrous substrate with an aqueous dispersion, followed by heat-drying to form an impregnated sheet; and developing polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less from the ultrafine fiber-developing fibers of the impregnated sheet to form an ultrafine fiber sheet, wherein the aqueous dispersion contains: a precursor of polyurethane having a hydrophilic group; 1.0% by mass or more and 10.0% by mass or less of an inorganic salt relative to the aqueous dispersion; a black pigment and / or a chromatic pigment; and 0.001% by mass or more and 0.300% by mass or less of a nonionic surfactant relative to the aqueous dispersion, A method for producing an artificial leather, comprising: forming an artificial leather in which the average particle size of the pigment in the polyurethane is 0.01 μm or more and 0.10 μm or less, the average irregularity of the pigment is 0.50 or more and 1.00 or less, and when the artificial leather is divided into three equal layers in the thickness direction, the coefficient of variation of the mass ratio of the polyurethane in each layer is 5% or more and 30% or less.

[0022]

[11] The method for producing an artificial leather according to

[10] , wherein the nonionic surfactant is a copolymer made from two or more types of alkylene oxides.

[0023] According to the present invention, it is now possible to obtain artificial leather that combines uniformity in surface hue with a good texture, even when using a polymeric elastomer (polyurethane) having hydrophilic groups. As a result, the artificial leather of the present invention has less visible color unevenness due to the color difference between the polyurethane and the fiber, and has an elegant appearance and supple texture similar to natural leather, making it suitable for a wide range of applications, from clothing, furniture, miscellaneous goods, and vehicle interior materials to automobile parts.

[0024] Fig. 1 is a diagram for explaining how to measure and calculate the average particle size and average irregularity of the pigment for the artificial leather of the present invention. Fig. 2 is a diagram for explaining how to measure and calculate the average irregularity of the pigment for the artificial leather of the present invention.

[0025] The artificial leather of the present invention is an artificial leather comprising a fibrous substrate and polyurethane, wherein the fibrous substrate comprises a nonwoven fabric composed of polyester ultrafine fibers having an average single fiber diameter of 1.0 μm to 10.0 μm, the polyurethane having a hydrophilic group and further comprising a black pigment and / or a chromatic pigment, the pigment having an average particle diameter of 0.01 μm to 0.10 μm, the average irregularity of the pigment being 0.50 to 1.00, and the coefficient of variation of the mass proportion of the polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction is 5% to 30%. Here, in the present invention, "chromatic color" refers to a color with a hue such as red, blue, green, or yellow, and specifically, a color according to CIE 1976L ＊ a ＊ b ＊ In color space, saturation (C ＊ ) is 10 or more. The chroma is measured by a method conforming to JIS Z 8781-4:2013 for a pigment uniformly applied to a white substrate.

[0026] 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.

[0027] [Polyester Ultrafine Fibers] The artificial leather of the present invention includes a nonwoven fabric in which a fibrous substrate, one of its constituent elements, is composed of polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less. Here, polyester ultrafine fibers refer to fibers composed of a polyester-based resin and having a single fiber diameter of 20.0 μm or less, measured and calculated by the method described below. In the present invention, "polyester-based resin" refers to a resin in which the molar fraction of the polyester unit in the repeating units is 80 mol % or more and 100 mol % or less. Unless otherwise specified, the term "...-based resin" has the same meaning.

[0028] In general, polyester resins can be obtained from, for example, dicarboxylic acids and / or their ester-forming derivatives and diols.

[0029] Among these, in the present invention, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and mixtures and copolymers of these polyester resins are preferred, as they can be used to produce artificial leather with excellent heat resistance, light resistance, etc.

[0030] Therefore, examples of the dicarboxylic acid and / or its ester-forming derivative used in the polyester resin include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, and its ester-forming derivative. The ester-forming derivative referred to in the present invention refers to lower alkyl esters, acid anhydrides, acyl chlorides, and the like of dicarboxylic acids. Specifically, methyl esters, ethyl esters, hydroxyethyl esters, and the like are preferably used. A more preferred embodiment of the dicarboxylic acid and / or its ester-forming derivative used in the present invention is terephthalic acid and / or its dimethyl ester.

[0031] Examples of diols used in the polyester resin include ethylene glycol, 1,3-propanediol, 1,4-butanediol, cyclohexanedimethanol, etc. Among these, ethylene glycol is preferably used.

[0032] The polyester resin may contain inorganic particles such as titanium oxide particles, lubricants, pigments, dyes, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, and the like depending on various purposes.

[0033] The cross-sectional shape of the polyester ultrafine fibers may be either a round cross section or an irregular cross section. Specific examples of irregular cross sections include oval, flat, polygonal such as triangular (including those with rounded corners), sector, cross, etc.

[0034] In the present invention, the average single fiber diameter of the polyester ultrafine fibers is 1.0 μm or more and 10.0 μm or less. When the average single fiber diameter of the polyester ultrafine fibers is 10.0 μm or less, preferably 7.0 μm or less, and more preferably 5.0 μm or less, the artificial leather becomes softer. In addition, the quality of the nap can be improved. On the other hand, when the average single fiber diameter of the polyester ultrafine fibers is 1.0 μm or more, preferably 1.5 μm or more, and more preferably 2.0 μm or more, the artificial leather becomes excellent in color development after dyeing. In addition, 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.

[0035] In the present invention, the single fiber diameter and average single fiber diameter of polyester ultrafine fibers are measured and calculated by the following method. That is, (1) The 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 single fiber diameters of 50 polyester ultrafine fibers arbitrarily selected within the observation surface are measured on the cross section of each polyester ultrafine fiber, and this operation is carried out three times in total at different locations. However, when polyester ultrafine fibers with a modified cross section are used, the cross section area of ​​the polyester ultrafine fiber is first measured, and the diameter of the circle corresponding to this cross section area is calculated by the following formula. The diameter obtained is the single fiber diameter of the single fiber. Single fiber diameter (μm) = (4 × (cross section 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.

[0036] [Fibrous substrate] The fibrous substrate of the artificial leather according to the present invention includes a nonwoven fabric made of the polyester ultrafine fibers. That is, this fibrous substrate may be a nonwoven fabric made of the polyester ultrafine fibers, or may include a nonwoven fabric made of the polyester ultrafine fibers and a woven or knitted fabric. The woven or knitted fabric referred to here is a general term for woven fabrics and knitted fabrics. In the case of a substrate including a nonwoven fabric and a woven or knitted fabric, it is more preferable that these are entangled and integrated by a method such as needle punching or water jet punching.

[0037] The nonwoven fabric may be in the form of either a long-fiber nonwoven fabric such as a spunbonded nonwoven fabric or a melt-blown nonwoven fabric, or a short-fiber nonwoven fabric such as a papermaking nonwoven fabric. However, a short-fiber nonwoven fabric is preferred because it has a large number of raised fibers on the product surface and is therefore likely to give an elegant appearance.

[0038] In the case of a short-fiber nonwoven fabric, the fiber length of the polyester ultrafine fibers is preferably 25 mm or more and 90 mm or less. When the fiber length of the polyester ultrafine fibers is 25 mm or more, preferably 35 mm or more, more preferably 40 mm or more, the artificial leather has an elegant appearance. On the other hand, when the fiber length of the polyester ultrafine fibers is 90 mm or less, preferably 80 mm or less, more preferably 70 mm or less, the artificial leather has good surface quality and texture.

[0039] Examples of the woven or knitted fabric include plain weave, twill weave, satin weave, etc., and examples of knitted fabric include warp knitted fabrics such as tricot knit and raschel knit, and weft knitted fabrics such as plain knit and rib knit. Of these, plain weave fabrics are less likely to wrinkle or lose their shape during use or washing, i.e., they provide artificial leather with excellent shape stability.

[0040] The fibers constituting the woven or knitted fabric are preferably multifilaments. Examples of components constituting the filaments of this multifilament include polyester-based resins and polyamide-based resins. Among these, polyester-based resins, which have excellent durability and heat resistance, are preferred. Specific examples of polyester-based resins include polyalkylene terephthalates such as polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate, as well as mixtures and copolymers of these polyester-based resins.

[0041] Next, the average single fiber diameter of the filaments (single yarns) of the multifilament is preferably 0.3 μm or more and 10.0 μm or less. By keeping it in this range, the artificial leather will have better strength and feel.

[0042] In the present invention, the average single fiber diameter of the multifilament filaments constituting the woven or knitted fabric is measured and calculated by the following method. That is, (1) The 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 cross-sectional areas of 10 arbitrary filaments within the observation surface are measured, and the diameter of a circle corresponding to the cross-sectional area is calculated using the following formula. The diameter obtained is the single fiber diameter of the filament. Single fiber diameter (μm) = (4 × (cross-sectional area of ​​single fiber (μm ２ )) / π) １／２ (3) The arithmetic mean value (μm) of the 30 points obtained is calculated and rounded off to one decimal place.

[0043] The total fineness of the multifilaments is preferably 30 dtex or more and 170 dtex or less, which results in an artificial leather with better flexibility and shape stability.

[0044] In the present invention, the total fineness of the multifilament is measured and calculated according to "8.3.1 Correct fineness b) Method B (simplified method)" of "8.3 Fineness" of JIS L1013:2010 "Testing methods for chemical fiber filament yarns."

[0045] The number of filaments contained in the multifilament is preferably 30 to 300. When the number is within this range, the artificial leather has better flexibility and shape stability.

[0046] In the present invention, the number of filaments contained in a multifilament is measured and calculated by the following method. That is, (1) A cross section obtained by cutting the obtained artificial leather in the thickness direction is observed using a scanning electron microscope (SEM, "VHX-D500 / D510" manufactured by Keyence Corporation, or a scanning electron microscope with equivalent performance). (2) The number of filaments contained in the cross section of any 10 multifilaments within the observation surface is measured. (3) The arithmetic mean value (number) of the obtained 10 points is calculated and rounded off to one decimal place.

[0047] [Polyurethane] The artificial leather of the present invention contains polyurethane. This polyurethane can serve as a binder that holds the ultrafine fibers together in the artificial leather, and the inclusion of polyurethane gives the artificial leather a rich feel, a leather-like appearance, and physical properties that are durable enough for practical use.

[0048] The polyurethane according to the present invention has a hydrophilic group. Here, "having a hydrophilic group" refers to "having a group having active hydrogen," and specific examples of the group having active hydrogen include a hydroxyl group, a carboxyl group, a sulfonic acid group, and an amino group. 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.

[0049] First, this polyurethane having a hydrophilic group 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.

[0050] (1) Polymer Polyols Polymer polyols that can be preferably used in the present invention include polyether polyols, polyester polyols, polycarbonate polyols, and the like.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The number-average molecular weight of the polymer polyol preferably used in the present invention is preferably 500 or more and 5000 or less. When the number-average molecular weight of the polymer polyol is 500 or more, preferably 1500 or more, the artificial leather has a soft feel. When the number-average molecular weight is 5000 or less, preferably 4000 or less, the strength of the polyurethane having hydrophilic groups as a binder can be easily maintained.

[0058] (2) Organic Diisocyanate The organic diisocyanate used in the present invention includes aromatic diisocyanates having 6 to 20 carbon atoms (excluding carbon atoms in NCO groups, the same applies hereinafter), aliphatic diisocyanates having 2 to 18 carbon atoms, alicyclic diisocyanates having 4 to 15 carbon atoms, araliphatic diisocyanates having 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.

[0059] Specific examples of the aromatic diisocyanate having 6 or more and 20 or less carbon atoms include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4'-diphenylmethane diisocyanate, 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.

[0060] 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.

[0061] 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, 2,5-norbornane diisocyanate, and 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.

[0062] 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.

[0063] (3) Active hydrogen component-containing compound having a hydrophilic group The active hydrogen component-containing compound having a hydrophilic group preferably used in the present invention includes a compound containing active hydrogen and one or more functional groups selected from a nonionic group, an anionic group, and a cationic group. These active hydrogen component-containing compounds can also be used in the form of a salt neutralized with a neutralizing agent. The use of this active hydrogen component-containing compound having a hydrophilic group can improve the stability of the aqueous dispersion used in the manufacturing method of artificial leather.

[0064] 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 in a side chain, and triols such as trimethylolpropane and trimethylolbutane.

[0065] 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.

[0066] 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.

[0067] (4) Chain Extender Examples of chain extenders for use in the present invention 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.

[0068] 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.

[0069] (5) Constitution of Polyurethane Precursor As described above, the polyurethane precursor used in the present invention is prepared by reacting the above-mentioned high molecular weight polyol, an organic diisocyanate, and an active hydrogen component-containing compound having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting a chain extender.

[0070] (6) Crosslinking Agent The crosslinking agent used in the present invention may 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, oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, etc. One type of crosslinking agent may be used alone, or two or more types may be used in combination.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] Among these, it is particularly preferable to use a carbodiimide compound, which gives a polyurethane having a hydrophilic group obtained after the reaction with excellent durability and flexibility.

[0076] (7) Constituents of Polyurethane Having Hydrophilic Groups The polyurethane having hydrophilic groups 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.

[0077] From the viewpoint of flexibility, polyether polyurethane is preferable. When the polyurethane having a hydrophilic group is a polyether polyurethane, that is, when it contains a constituent 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, and therefore the polyurethane having a hydrophilic group has excellent flexibility.

[0078] On the other hand, from the viewpoint of durability, polycarbonate-based polyurethanes are preferred. When the polyurethane having a hydrophilic group is a polycarbonate-based polyurethane, that is, when it contains a constituent component derived from a polycarbonate-based polyol, the high cohesive force of the carbonate group can be used to provide a polyurethane having a hydrophilic group that is excellent in water resistance, heat resistance, weather resistance, and mechanical properties.

[0079] The constitution of the polyurethane having a hydrophilic group can be adjusted appropriately depending on the required properties, and polyether polyurethane or polycarbonate polyurethane may be used alone or in combination.

[0080] The constituent components of the polyurethane having hydrophilic groups can be confirmed (that the polyurethane having hydrophilic groups contains a constituent component derived from polyether polyol, and that the polyurethane having hydrophilic groups further contains a constituent component derived from polycarbonate polyol) by dissolving the fibrous substrate that constitutes the artificial leather and analyzing the insoluble matter (polyurethane having hydrophilic groups) by infrared spectroscopic analysis (using an analytical instrument such as the "FT / IR 4000 series" manufactured by JASCO Corporation or an infrared spectroscopic analyzer with equivalent performance) or pyrolysis GC / MS analysis (using an analytical instrument such as the "GCMS-QP5050A" manufactured by Shimadzu Corporation or a pyrolysis GC / MS analyzer with equivalent performance).

[0081] To elute the fibrous base material constituting the artificial leather, it is sufficient to dissolve it in a solvent that dissolves the polymer constituting the fibrous base material but does not dissolve the polyurethane component. For example, m-cresol or hexafluoroisopropanol can be used as a solvent that can elute polyester, but hexafluoroisopropanol, which can be handled at room temperature, is preferably used.

[0082] 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.

[0083] 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).

[0084] (8) Black pigment, chromatic pigment The polyurethane according to the present invention has the hydrophilic group described above and further contains a black pigment and / or a chromatic pigment. By containing such a pigment, the color difference between the ultrafine fibers of the artificial leather and the polyurethane can be reduced when dyeing, resulting in an artificial leather with a uniform surface hue.

[0085] Examples of such black pigments include carbon black, iron oxide black, acetone black, phthalocyanine black, and azo black.

[0086] Examples of chromatic pigments include inorganic pigments such as blue pigments such as ultramarine blue and Prussian blue (potassium iron ferrocyanide), red pigments such as red lead and iron oxide red, and yellow pigments such as yellow lead and zinc yellow (zinc yellow type 1, zinc yellow type 2), as well as organic pigments such as various colors of phthalocyanine-based, anthraquinone-based, quinacridone-based, dioxazine-based, isoindolinone-based, isoindoline-based, indigo-based, quinophthalone-based, diketopyrrolopyrrole-based, perinone-based, benzimidazolone-based, condensed azo-based, and azomethine azo-based pigments.

[0087] The pigment (here, a general term for black pigments and chromatic pigments) contained in the polyurethane has an average particle size of 0.01 μm or more and 0.10 μm or less, and an average irregularity of 0.50 or more and 1.00 or less. By using such a pigment, color unevenness in the polyurethane can be suppressed, resulting in artificial leather with a more uniform surface hue.

[0088] The average particle size of the pigment is 0.01 μm or more and 0.10 μm or less. The average particle size here refers to the average particle size of the pigment in an aggregated state when the pigment is present in polyurethane, as measured by the method described below.

[0089] When the average particle size of the pigment contained in the polyurethane having hydrophilic groups of the present invention is 0.01 μm or more, preferably 0.02 μm or more, and more preferably 0.03 μm or more, the pigment is held within the polyurethane, thereby preventing the pigment from falling off from the polyurethane. On the other hand, when the average particle size of the pigment contained in the polyurethane having hydrophilic groups is 0.10 μm or less, preferably 0.09 μm or less, and more preferably 0.08 μm or less, the pigment is prevented from settling, thereby providing excellent dispersibility when an aqueous dispersion of the polyurethane having hydrophilic groups containing the pigment is impregnated into a nonwoven fabric.

[0090] In the present invention, the average particle size of the pigment is measured and calculated by the following method. That is, (1) an ultrathin section having a thickness of 5 to 10 μm is prepared in the cross-sectional direction of a surface perpendicular to the longitudinal direction of the artificial leather. (2) Three random locations on the cross section of the polyurethane in the ultrathin section are observed at 40,000x magnification using a transmission electron microscope (TEM, Hitachi High-Technologies Corporation's "HT7700" or a transmission electron microscope with equivalent performance). (3) As shown in Figure 1, a line (1) is drawn on the TEM image along the outermost periphery of the pigment. (4) Using image analysis software (Keyence Corporation's "VW-9000 Album" or image analysis software with equivalent performance), 10 randomly selected points on the pigment in three observation images with a field of view of 0.6 μm x 0.6 μm are measured for their cross-sectional areas, and the diameter of the circle corresponding to the cross-sectional area (circle-equivalent diameter) is calculated using the following formula: However, if there are less than 10 pigment particles in the three observation images of a 0.6 μm × 0.6 μm field of view, measure the circle-equivalent diameter of all the pigment particles present. Circle-equivalent diameter (μm) = (4 × (cross-sectional area of ​​pigment (μm ２ )) / π) １／２ ... (formula) (5) Calculate the arithmetic mean (μm) of the 10 points obtained. However, if there are fewer than 10 pigment particles in the three observation images of a 0.6 μm x 0.6 μm field of view, calculate the arithmetic mean from the circle equivalent diameters of all the pigment particles present. (6) Five experts who have been engaged in technological development related to artificial leather for more than one year and specialize in said technological development are used as evaluators. Each evaluator performs the above steps (3) to (5), calculates the arithmetic mean (μm) of the 5 points obtained, and rounds off to three decimal places.

[0091] Next, the average irregularity of the pigment is 0.50 or more and 1.00 or less. The irregularity here refers to the irregularity of the pigment in an aggregated state, measured by the method described below, when the pigment is present in polyurethane.

[0092] By setting the average irregularity of the pigment to 0.50 or more, preferably 0.55 or more, more preferably 0.60 or more, the unevenness of the pigment surface can be reduced and diffused reflection on the pigment surface can be suppressed, thereby making it possible to obtain artificial leather with a uniform surface hue. Furthermore, the upper limit of the average irregularity of the pigment is 1.00, and at 1.00, the cross section of the pigment becomes a perfect circle.

[0093] In the present invention, the irregularity of the pigment is measured and calculated by the following method. That is, (1) an ultrathin section having a thickness of 5 to 10 μm is prepared in the cross-sectional direction of a surface perpendicular to the longitudinal direction of the artificial leather. (2) Three random locations on the cross section of the polyurethane in the ultrathin section are observed at 40,000x magnification using a transmission electron microscope (TEM, Hitachi High-Technologies Corporation's "HT7700" or a transmission electron microscope with equivalent performance). (3) As shown in Figures 1 and 2, a line (1) is drawn on the TEM image along the outermost periphery of the pigment. (4) Using image analysis software (Keyence Corporation's "VW-9000 Album" or image analysis software with equivalent performance), 10 randomly selected points on the pigment in three observation images with a field of view of 0.6 μm x 0.6 μm are measured, and the corresponding irregularity is calculated using the following formula. However, if there are fewer than 10 pigment particles in three observation images of a 0.6 μm x 0.6 μm field of view, the irregularity of all pigment particles present is measured. Irregularity (unitless) = pigment inscribed circle diameter (μm) / pigment circumscribed circle diameter (μm) ... (formula). (5) Calculate the arithmetic mean (unitless) of the total 10 points obtained. However, if there are fewer than 10 pigment particles in three observation images of a 0.6 μm x 0.6 μm field of view, calculate the arithmetic mean from the irregularities of all pigment particles present. (6) Five experts who have been engaged in technological development related to artificial leather for more than one year and specialize in this technology were selected as evaluators. Each evaluator performed the above steps (3) to (5), calculated the arithmetic mean (unitless) of the total 5 points obtained, and rounded off to three decimal places.

[0094] The average particle size and irregularity of the pigment can be adjusted to fall within the above ranges by adjusting the amount of nonionic surfactant or inorganic salt added to the aqueous dispersion when the aqueous dispersion described below is impregnated into a fibrous substrate.

[0095] The total content of the pigments contained in the polyurethane used in the present invention is preferably 0.01% by mass or more and 2.00% by mass or less, based on the mass of the polyurethane. This total content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, so that when dyeing, the color difference between the ultrafine fibers and the polyurethane of the artificial leather is small, resulting in an artificial leather with excellent surface hue uniformity. On the other hand, a total content of preferably 2.00% by mass or less, more preferably 1.50% by mass, can suppress shedding due to dyeing, washing, friction, etc., resulting in an artificial leather with excellent fastness.

[0096] In the present invention, the total content of the pigment in the polyurethane is measured and calculated by the following method. That is, (1) Two 5 cm x 5 cm test pieces are cut out from the artificial leather. (2) One test piece is immersed in hexafluoroisopropanol to dissolve the ultrafine fibers, and the polyurethane is collected. (3) The collected polyurethane is dissolved using N,N-dimethylformamide or the like, and only the pigment is extracted. (4) The extracted pigment is subjected to evolved gas analysis using a method such as gas chromatography, and a calibration curve for the evolved gas derived from the pigment is created. (5) Using the other test piece, the polyurethane contained in the artificial leather is dissolved using N,N-dimethylformamide or the like, and the N,N-dimethylformamide or the like is then removed, and the polyurethane is solidified again. (6) Perform evolved gas analysis on the polyurethane obtained in (5), and calculate the total pigment content (mass%) in the polyurethane from the detected intensity of evolved gas derived from the pigment and the calibration curve prepared in (4), and round off to two decimal places.

[0097] The total content of the pigment in the polyurethane can be adjusted to the above range by adjusting the amount of the pigment added to the aqueous dispersion described below. Although the total content of the pigment in the polyurethane can be measured by the above method, if it can be determined from the amounts of polyurethane and pigment charged, a value calculated from these can be used instead.

[0098] [Artificial Leather] First, the artificial leather of the present invention contains the above-mentioned fibrous base material and the above-mentioned polyurethane.

[0099] The artificial leather of the present invention has a coefficient of variation of the mass proportion of the polyurethane in each layer when the layer is divided into three equal parts in the thickness direction, of 5% to 30%. A coefficient of variation of this mass proportion of 30% or less, preferably 25% or less, and more preferably 20% or less, results in an artificial leather with a good texture. On the other hand, a coefficient of variation of this mass proportion of 5% or more, preferably 7% or more, and more preferably 9% or more, results in an artificial leather with excellent abrasion resistance.

[0100] The coefficient of variation of the mass proportion of the polyurethane in each layer can be set within the above range by adjusting the heat-sensitive coagulation temperature of the aqueous dispersion containing the precursor, so that the coagulation of the polyurethane precursor proceeds before the water evaporates from the fibrous substrate during heating, thereby suppressing the uneven distribution of polyurethane on the surface of the fibrous substrate. The heat-sensitive coagulation temperature here refers to the temperature at which the fluidity of the aqueous dispersion decreases and the dispersion solidifies when heated.

[0101] In the present invention, when the artificial leather is divided into three equal parts in the thickness direction, the coefficient of variation of the mass proportion of polyurethane in each layer is measured and calculated by the following method: (1) The thickness (mm) of the artificial leather is measured based on JIS L 1096 A method, and the artificial leather is sliced ​​into three equal parts in the thickness direction. (2) From the sample of each layer sliced ​​into three equal parts, a 10 cm square test piece is randomly cut out, and the mass (M Ａ１ , M Ａ２ , M Ａ３) and heat in a dryer at 180°C for a certain period of time. (3) After the heat treatment, each test piece is immersed overnight in a solvent in which the polyurethane dissolves (for example, N,N-dimethylformamide). (4) The insoluble component (fibrous substrate) is removed, washed with water, and then heated in a dryer at 100°C. (5) The weight (M Ｂ１ , M Ｂ２ , M Ｂ３ ) is measured, and the mass percentage (mass%) of the polyurethane in each layer is calculated using the following formula. Here, X below corresponds to 1, 2, or 3. Mass percentage (mass%) of polyurethane = (M ＡＸ -M ＢＸ ) / M ＡＸ (6) For the measured mass proportion of polyurethane in each layer, the coefficient of variation (%) is calculated using the following formula, and the result is rounded to one decimal place: Coefficient of variation (%) of mass proportion of polyurethane in each layer = (standard deviation of mass proportion of polyurethane in each layer) / (arithmetic mean of mass proportion of polyurethane in each layer) × 100 (formula).

[0102] The artificial leather of the present invention preferably has a polyurethane mass percentage of 15% by mass or more and 25% by mass or less. A mass percentage of 15% by mass or more, more preferably 18% by mass or more, results in an artificial leather with excellent abrasion resistance. On the other hand, a mass percentage of 25% by mass or less, more preferably 22% by mass or less, results in an artificial leather with a soft feel.

[0103] In the present invention, the mass ratio of polyurethane is measured and calculated by the following method: (1) Randomly cut out 10 cm square test pieces from the artificial leather, and measure the mass (M α ) and heat in a dryer at 180°C for a certain period of time. (2) After the heat treatment, each test piece is immersed overnight in a solvent in which the polyurethane dissolves (for example, N,N-dimethylformamide). (3) The insoluble component (fibrous substrate) is removed, washed with water, and then heated in a dryer at 100°C. (4) The weight (M β) is measured, and the mass percentage (mass%) of the polyurethane is calculated using the following formula, and the result is rounded to the first decimal place. Mass percentage (mass%) of polyurethane = (M α -M β ) / M α ×100...(formula).

[0104] The artificial leather of the present invention preferably has an abrasion loss of 25 mg or less when measured under a pressure load of 12 kPa and 20,000 abrasion cycles in the Martindale abrasion test specified in "8.19.5 Method E (Martindale method)" of "8.19 Abrasion resistance and discoloration due to friction" of JIS L1096:2005 "Testing methods for woven and knitted fabrics." This abrasion loss is preferably 25 mg or less, more preferably 20 mg or less, and even more preferably 15 mg or less, which can prevent contamination due to fluff shedding during actual use and results in an artificial leather that is less susceptible to change in appearance.

[0105] The artificial leather of the present invention preferably has at least one surface with nap of 200 μm to 500 μm. The length of this nap (hereinafter sometimes simply referred to as "napped length") is preferably 200 μm or more, more preferably 250 μm or more, resulting in an artificial leather with excellent touch. On the other hand, the nap length is preferably 500 μm or less, more preferably 450 μm or less, which can suppress deterioration of surface quality due to fluffing of the nap, resulting in an artificial leather with an elegant suede-like surface quality.

[0106] Furthermore, the artificial leather of the present invention preferably has a nap coverage of 80% or more and 99% or less on the nap-bearing surface. This range improves the surface smoothness of the artificial leather, resulting in an artificial leather with excellent touch.

[0107] The nap length and nap coverage can be set within the above ranges by adjusting the grit size of the sandpaper used in the process of forming a napped surface, the amount of lubricant such as silicone emulsion, etc.

[0108] In the present invention, the nap length of the artificial leather is measured and calculated by the following method. That is, (1) A lint brush or the like is used to make the nap of the artificial leather stand upright, and a thin section having a thickness of 1 mm is prepared in the cross-sectional direction perpendicular to the longitudinal direction of the artificial leather. (2) A cross-section of the artificial leather is observed at 80x magnification using a scanning electron microscope (SEM, Keyence Corporation's "VHX-D500 / D510" or a scanning electron microscope with equivalent performance). (3) In the SEM image, the height of the napped portion (layer consisting only of ultrafine fibers) is measured at 10 points at 200 μm intervals in the width direction of the cross-section of the artificial leather. (4) The arithmetic mean value of the heights of the napped portion (layer consisting only of ultrafine fibers) measured at the 10 points is calculated and rounded to the nearest decimal place, and this is the nap length (μm).

[0109] The nap coverage rate was measured by enlarging the nap surface by 30 to 90 times to observe the presence of naps using an SEM, and analyzing the image data of a total area of ​​9 mm2 using image analysis software (ImageJ of the National Institutes of Health (NIH) or image analysis software with equivalent capabilities, which has the function of identifying necessary areas in the captured image and performing pixel analysis). ２ The ratio of the total area of ​​the napped portion per unit area is calculated and is taken as the napped coverage rate (%). The ratio of the total area can be calculated by using image analysis software to photograph the SEM image, and binarizing the napped portion and the non-napped portion by setting a threshold value of 128 out of 256 gradations, with white being 255 and black being 0. At this time, the white areas are the napped portions and the black areas are the non-napped portions. In addition, in the calculation of the napped coverage rate, if a material that is not napped is calculated as napped and has a large influence on the napped coverage rate, the image is manually edited, and the color tone of the material that is not napped is set to 0 (black), and the part is calculated as a non-napped portion.

[0110] [Method for manufacturing artificial leather] The method for manufacturing artificial leather of the present invention comprises the steps of: forming a fibrous substrate containing a nonwoven fabric composed of ultrafine fiber-developing fibers; impregnating the fibrous substrate with an aqueous dispersion, followed by a heat-drying treatment to form an impregnated sheet; and developing polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less from the ultrafine fiber-developing fibers of the impregnated sheet to form an ultrafine fiber sheet, wherein the aqueous dispersion contains: a polyurethane precursor having a hydrophilic group; an inorganic salt in an amount of 1.0% by mass or more and 10.0% by mass or less relative to the aqueous dispersion; a black pigment and / or a chromatic pigment; and a nonionic surfactant in an amount of 0.001% by mass or more and 0.300% by mass or less relative to the aqueous dispersion. An artificial leather is formed in which the average particle size of the pigment in the polyurethane is 0.01 μm or more and 0.10 μm or less, the average irregularity of the pigment in the polyurethane is 0.50 or more and 1.00 or less, and when the artificial leather is divided into three equal layers in the thickness direction, the coefficient of variation of the mass ratio of the polyurethane in each layer is 5% or more and 30% or less.

[0111] Details are explained below.

[0112] <Step of forming a fibrous substrate> In this step, a fibrous substrate including a nonwoven fabric made of ultrafine fiber development type fibers is formed.

[0113] As the ultrafine fiber-forming fiber in the present invention, it is preferable to use an islands-in-sea type composite fiber in which the sea part and island parts are made of two thermoplastic resin components (two or three components when the island fiber is a core-sheath composite fiber) having different solvent solubility, and the sea part is converted into ultrafine fibers by dissolving and removing it using a solvent or the like, because this can provide appropriate voids between the island parts, i.e., between the ultrafine fibers inside the fiber bundle, when the sea part is removed. This is because, from the viewpoint of the texture and surface quality of the artificial leather, appropriate voids can be provided between the island parts, i.e., between the ultrafine fibers inside the fiber bundle.

[0114] Here, "different solvent solubility" means that the solubility of one thermoplastic resin in a solvent such as an organic solvent or an aqueous solution such as an alkaline aqueous solution used to remove the other thermoplastic resin from the ultrafine fiber-forming fiber is 100 times or more different. Because of this difference, for example, an alkali-soluble resin that is easily soluble in an alkaline aqueous solution will dissolve within 5 minutes when immersed in a 5% sodium hydroxide aqueous solution, whereas the other thermoplastic resin used in combination will not dissolve in the above solution for 10 minutes or more. This makes it easy to obtain ultrafine fibers.

[0115] 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.

[0116] The alkali-soluble resin used for the sea part of the islands-in-sea type composite fiber is preferably a copolymer polyester from the viewpoints of spinnability and ease of dissolution by alkali treatment. Furthermore, by using a copolymer polyester for the sea part, the frictional force between the islands-in-sea type composite fibers is reduced and the flexibility of the fibers is improved, which enables efficient entanglement of the fibers when entangled by needle punching or the like.

[0117] When a copolymer polyester is used, the copolymerization amount of sodium 5-sulfoisophthalate is preferably 3 mol % or more and 15 mol % or less, when the total amount of dicarboxylic acid components is taken as 100 mol %. By having the copolymerization amount of sodium 5-sulfoisophthalate be preferably 3 mol % or more, more preferably 5 mol % or more, sufficient alkali elution properties can be obtained. On the other hand, by having the copolymerization amount of sodium 5-sulfoisophthalate component be preferably 15 mol % or less, more preferably 13 mol % or less, thickening of the polyester can be suppressed, and the effect of preventing yarn breakage during spinning of islands-in-the-sea type composite fibers can be achieved.

[0118] The alkali-soluble resin is preferably a copolymer polyester copolymerized with a polyalkylene glycol. When the content is in this range, the flexibility of the islands-in-sea type composite fiber is improved, and efficient entanglement of the fibers can be achieved when the fibers are entangled by needle punching or the like.

[0119] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, and polybutylene glycol, with polyethylene glycol being preferred due to its ease of use and its ability to be reduced in weight in an alkaline aqueous solution.

[0120] The copolymer polyester preferably contains a polyethylene terephthalate polyester having ethylene terephthalate units as a main repeating unit as one component, and may be a polyester in which a portion of the terephthalic acid component is replaced with another bifunctional carboxylic acid component, or a polyester in which a portion of the ethylene glycol component is replaced with another polyol component.

[0121] Preferred examples of the difunctional carboxylic acid other than terephthalic acid used in the present invention include aromatic, aliphatic, and alicyclic difunctional carboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, adipic acid, sebacic acid, and 1,4-cyclohexanedicarboxylic acid. Preferred examples of the polyol compound other than ethylene glycol include aliphatic, alicyclic, and aromatic polyol compounds such as tetramethylene glycol, hexamethylene glycol, cyclohexane-1,4-dimethanol, neopentyl glycol, bisphenol A, and bisphenol S.

[0122] The alkali-soluble resin used for the sea part of the islands-in-sea type composite fiber may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, and the like, depending on various purposes.

[0123] Regarding the mass ratio of the sea component to the island component in the islands-in-sea type composite fiber used in the present invention, the mass ratio of the sea component to the islands-in-sea type composite fiber is preferably 10% by mass or more and 80% by mass or less. When this mass ratio is preferably 10% by mass or more, more preferably 15% by mass or more, the island component fibers can be sufficiently ultrafine-thinned. On the other hand, when the mass ratio is preferably 80% by mass or less, more preferably 70% by mass or less, the proportion of eluted components is reduced, and productivity is improved.

[0124] As described above, the nonwoven fabric of the present invention can be in the form of either a long-fiber nonwoven fabric or a short-fiber nonwoven fabric. However, a short-fiber nonwoven fabric is preferred because it results in a nonwoven fabric with more fibers oriented in the thickness direction of the artificial leather than a long-fiber nonwoven fabric, resulting in a high fiber density and excellent uniformity of fiber orientation, which makes it possible to obtain a highly dense feel on the surface of the artificial leather when it is brushed.

[0125] When a staple fiber nonwoven fabric is used as the nonwoven fabric, 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 processing and cutting processing can be carried out by known methods.

[0126] Next, the obtained raw cotton is made into a fiber web by a carding process, a cross-wrapping process, etc. 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, water jet punching, etc. can be used, but in order to set the average pile length and surface coverage within the above-mentioned ranges, needle punching, which has a high entanglement efficiency, is preferred.

[0127] When entanglement is performed by needle punching, needles having barbs (notches) capable of holding 5 to 15 ultrafine fiber-developing fibers are used, and the punch density is 2000 / cm. ２ Over 4000 strands / cm ２ By setting the thickness within this range, not only can a dense nonwoven fabric be obtained, but also fiber damage and a decrease in strength can be prevented, making it possible to obtain artificial leather with an even better feel and strength.

[0128] <Step of Forming an Impregnated Sheet> In this step, the fibrous substrate is impregnated with an aqueous dispersion, followed by a heat-drying treatment to form an impregnated sheet. The aqueous dispersion contains a polyurethane precursor having a hydrophilic group, an inorganic salt in an amount of 1.0% by mass to 10.0% by mass relative to the aqueous dispersion, a black pigment and / or a chromatic pigment, and a nonionic surfactant in an amount of 0.001% by mass to 0.300% by mass relative to the aqueous dispersion. By using such an aqueous dispersion, artificial leather with a uniform surface hue and a good texture can be obtained. The polyurethane precursor having a hydrophilic group, the black pigment, and the chromatic pigment can be those described above. The inorganic salt and the nonionic surfactant are as described below.

[0129] In the method for producing an artificial leather of the present invention, the coagulation after application of the aqueous dispersion can be performed using coagulation methods commonly used in the art, such as dry heat coagulation and wet heat coagulation. When using the dry heat coagulation method, it is preferable to apply the aqueous dispersion to a fibrous substrate, then heat treat the fibrous substrate at a temperature of 120°C or higher and 180°C or lower, and perform dry heat coagulation to provide a polyurethane having hydrophilic groups to the fibrous substrate. When using the wet heat coagulation method, it is preferable to apply the aqueous dispersion to the fibrous substrate, then heat treat the fibrous substrate at a temperature of 55°C or higher and 200°C or lower, and perform wet heat coagulation to provide a polyurethane having hydrophilic groups to the fibrous substrate.

[0130] 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. This concentration is preferably 3% by mass or more, more preferably 5% by mass or more, so that 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, the concentration is preferably 30% by mass or less, more preferably 15% by mass or less, so that the storage stability of the aqueous dispersion can be improved.

[0131] The heat-sensitive coagulation temperature of the aqueous dispersion is preferably 55° C. or higher and 80° C. or lower. By setting this heat-sensitive coagulation temperature to preferably 55° C. or higher, more preferably 60° C. or higher, gelation of the aqueous dispersion can be suppressed during preparation and storage. On the other hand, by setting the heat-sensitive coagulation temperature to preferably 80° C. or lower, more preferably 70° C. or lower, coagulation of the polyurethane precursor proceeds before water evaporates from the fibrous substrate, forming a structure similar to that obtained by wet coagulation of a solvent-based polyurethane, i.e., a structure in which the polyurethane does not strongly constrain the fibers, and achieving good flexibility and rebound feel.

[0132] In the method for producing an artificial leather of the present invention, the aqueous dispersion contains 1.0% by mass or more and 10.0% by mass or less of an inorganic salt relative to the aqueous dispersion. Specific examples of this inorganic salt include sodium chloride, sodium sulfate, sodium nitrate, sodium carbonate, ammonium sulfate, calcium chloride, calcium sulfate, calcium nitrate, calcium carbonate, magnesium chloride, and magnesium sulfate. Among these, monovalent cation-containing inorganic salts such as sodium chloride and sodium sulfate are more preferred. This is because 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.

[0133] By setting the inorganic salt content in the aqueous dispersion to 1.0% by mass or more, preferably 2.0% by mass or more, and more preferably 3.0% by mass or more, the ions present in large quantities in the aqueous dispersion act uniformly on the polyurethane precursor, allowing for rapid coagulation at a specific thermosensitive coagulation temperature. This allows for the formation of an adhesive structure of the polyurethane to the fibrous substrate that is very similar to that obtained by wet coagulation of a solvent-based polyurethane, achieving a good texture, in the process of proceeding with coagulation of the polyurethane precursor in a state where the fibrous substrate contains a large amount of water, as described above. On the other hand, by setting the inorganic salt content to 10.0% by mass or less, preferably 9.0% by mass or less, and more preferably 8.0% by mass or less, the stability of the aqueous dispersion can be maintained, resulting in a uniform quality.

[0134] In the method for producing an artificial leather of the present invention, the aqueous dispersion contains a black pigment and / or a chromatic pigment.

[0135] In the method for producing an artificial leather of the present invention, the aqueous dispersion contains 0.001% by mass or more and 0.300% by mass or less of a nonionic surfactant. The nonionic surfactant suppresses aggregation of the pigment and maintains uniform dispersion even in the presence of a large amount of salt in the aqueous dispersion. As a result, color unevenness of the polyurethane in the artificial leather can be reduced, resulting in an artificial leather with a uniform surface hue.

[0136] Here, "nonionic" refers to the fact that the substance itself "has the property of not dissociating into ions in water (nonionic)." Specific examples of functional groups that have the property of not dissociating into ions in water include hydroxyl groups, ether groups, and ester groups. From the viewpoint of solubility in water, it is preferable to have an ether group.

[0137] In the method for producing an artificial leather of the present invention, the nonionic surfactant is preferably a copolymer made from two or more types of alkylene oxides, thereby making it possible to obtain an artificial leather having a uniform surface hue.

[0138] Specific examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, glycidol, hexaethylene glycol diepoxide, pentaerythritol oxide, ethylene glycol monoethyl ether, butylene glycol monobutyl ether, decylene oxide, and trimethylene glycol monobutyl ether. Of these, the use of ethylene oxide and propylene oxide is preferred because they enable the production of artificial leather having a uniform surface hue.

[0139] The structure of the nonionic surfactant can be confirmed (confirmed to be a copolymer made from two or more types of alkylene oxides) by dissolving the nonionic surfactant in a heavy solvent (e.g., heavy water) in which it can be dissolved, and then subjecting the solution to NMR analysis (the analytical instrument used is the "JNM-ECZ400S" manufactured by JEOL Ltd. or an NMR analyzer with equivalent performance), or pyrolysis GC / MS analysis (the analytical instrument used is the "GCMS-QP5050A" manufactured by Shimadzu Corporation or a pyrolysis GC / MS analyzer with equivalent performance).

[0140] The content of the nonionic surfactant in the aqueous dispersion is 0.001% by mass or more, preferably 0.003% by mass or more, and more preferably 0.005% by mass or more, so that the nonionic surfactant present in the aqueous dispersion acts uniformly on the pigment, allowing the pigment to be uniformly dispersed in water. This allows the pigment to be uniformly dispersed in the polyurethane during the coagulation process of the polyurethane precursor, even in a state where a large amount of inorganic salt is contained in the aqueous dispersion. This allows the formation of an adhesive structure of polyurethane to the fibrous substrate that is very similar to that obtained by wet coagulation of a solvent-based polyurethane, achieving a uniform surface hue and a good texture. On the other hand, a content of 0.300% by mass or less, preferably 0.250% by mass or less, and more preferably 0.200% by mass or less, allows the artificial leather to have a uniform surface hue.

[0141] In the method for producing an artificial leather of the present invention, a crosslinking agent can be added 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.

[0142] 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 crosslinking agent concentration to preferably 1% by mass or more, more preferably 2% by mass or more, the crosslinking agent can introduce a larger amount of three-dimensional network structure into the polyurethane precursor, resulting in an artificial leather with excellent abrasion resistance, etc. On the other hand, by setting the crosslinking agent concentration to 10% by mass or less, more preferably 7% by mass or less, the inhibition of coagulation of the polyurethane precursor by an excess of crosslinking agent is suppressed, and deterioration of physical properties such as abrasion resistance is more easily suppressed.

[0143] Furthermore, the crosslinking agent 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. This allows a three-dimensional crosslinked structure to be imparted to the polyurethane molecules in the artificial leather by N-acylurea bonds and / or isourea bonds, which provide excellent physical properties such as light resistance, heat resistance, and abrasion resistance, as well as flexibility, thereby dramatically improving physical properties such as durability and abrasion resistance while maintaining the flexibility of the artificial leather.

[0144] The fibrous base material is then impregnated with the aqueous dispersion and then subjected to a heat drying treatment to form an impregnated sheet.

[0145] The temperature of the heat drying treatment after impregnation with the aqueous dispersion is preferably 110° C. or higher and 180° C. or lower. By setting this temperature to preferably 110° C. or higher, more preferably 120° C. or higher, not only can the drying efficiency of the sheet be increased, but also the progress of the crosslinking reaction can be promoted, thereby improving the physical properties of the artificial leather, such as durability and abrasion resistance. On the other hand, by setting the temperature to preferably 180° C. or lower, more preferably 170° C. or lower, thermal degradation of the polyurethane can be suppressed.

[0146] The heat drying treatment time is preferably 5 to 30 minutes. By setting this time to preferably 5 minutes or more, more preferably 10 minutes or more, it is possible to promote the progress of the crosslinking reaction, thereby improving the physical properties of the artificial leather, such as durability and abrasion resistance. On the other hand, by setting the time to preferably 30 minutes or less, more preferably 25 minutes or less, it is possible to suppress thermal degradation of the polyurethane due to excessive heating.

[0147] <Step of Obtaining Ultrafine Fiber Sheet> In this step, polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less are developed from the ultrafine fiber-developing fibers of the impregnated sheet to form an ultrafine fiber sheet.

[0148] When an islands-in-sea type composite fiber is used as the ultrafine fiber-producing fiber, the ultrafine fiber treatment (sea component removal treatment) can be carried out, for example, by immersing the islands-in-sea type composite fiber 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 the sea component, and when the sea component is a copolymer polyester, an aqueous alkali solution such as sodium hydroxide can be used.

[0149] 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 3.0 mol / L or less in order to prevent excessive deterioration of the polyurethane.

[0150] During this sea component removal process, inorganic salts, nonionic surfactants, and solids derived from silicone and non-silicone textile oils that have adhered to the fibrous base material usually fall off together with the sea component.

[0151] <Heat Treatment Step> In the method for producing the artificial leather of the present invention, the product obtained by completing the above steps may be directly subjected to processing such as dyeing, but it is preferable to subject the ultrafine fiber sheet to heat treatment in order to improve the abrasion resistance and flexibility of the artificial leather. As a method for this heat treatment, it is preferable to use a hot air dryer such as a floater dryer, a drum dryer, or a pin tenter.

[0152] First, it is preferable that the atmospheric temperature during the heat treatment be 150° C. or higher and 200° C. or lower. By setting this atmospheric temperature to preferably 150° C. or higher, more preferably 155° C. or higher, not only can the adhesion between the ultrafine fibers and the polyurethane be improved, improving the abrasion resistance of the artificial leather, but also the molecular weight of a portion of the polyurethane can be reduced, thereby increasing the flexibility of the artificial leather. On the other hand, by setting the atmospheric temperature to preferably 200° C. or lower, more preferably 190° C. or lower, and even more preferably 180° C. or lower, the molecular weight of a portion of the polyurethane can be reduced gradually.

[0153] Next, the heating time is preferably set to 5 minutes or more and 20 minutes or less. By setting this heating time to preferably 5 minutes or more, more preferably 6 minutes or more, the adhesion between the ultrafine fibers and the polyurethane can be improved, and the abrasion resistance of the artificial leather can be improved. On the other hand, by setting the heating time to preferably 20 minutes or less, more preferably 15 minutes or less, and even more preferably 12 minutes or less, it is possible to prevent a deterioration in the physical properties of the artificial leather due to excessive reduction in the molecular weight of the polyurethane.

[0154] This heat treatment is preferably carried out after the step of forming the ultrafine fiber sheet, but more preferably carried out subsequent to the step of forming the ultrafine fiber sheet (immediately after the step of forming the ultrafine fiber sheet) in order to prevent deterioration in quality due to elongation during the step.

[0155] <Finishing Step> The artificial leather obtained by the above steps has an average particle size of the pigment in the polyurethane of 0.01 μm or more and 0.10 μm or less, an average irregularity of the pigment of 0.50 or more and 1.00 or less, and when the artificial leather is divided into three equal parts in the thickness direction, the coefficient of variation of the mass proportion of polyurethane in each layer is 5% or more and 30% or less.

[0156] In the method for producing an artificial leather of the present invention, the product that has undergone the above steps may be used as is as an artificial leather, but it is preferable to carry out various finishing steps, as with general artificial leathers. Of course, it goes without saying that artificial leather that has undergone post-processing is also considered to be an artificial leather in the present invention.

[0157] First, the method for producing an artificial leather of the present invention preferably includes a step of dyeing the ultrafine fiber sheet (including the heat-treated ultrafine fiber sheet) with a disperse dye. This dyeing process can be performed using any of the methods commonly used in the art, including jet dyeing using a jigger dyeing machine or jet dyeing machine, dip dyeing using a continuous dyeing machine, such as thermosol dyeing, or printing on the napped surface using roller printing, screen printing, inkjet printing, sublimation printing, and vacuum sublimation printing. Jet dyeing machines are particularly 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. If necessary, various resin finishing processes can be performed after dyeing.

[0158] When the ultrafine fiber sheet (including the heat-treated ultrafine fiber sheet) is dyed with a disperse dye, or after dyeing, it may be subjected to a finishing agent treatment using, for example, a softener such as silicone, an antistatic agent, a water repellent, a flame retardant, a light-resistant agent, an antibacterial agent, or the like.

[0159] In the method for producing the artificial leather of the present invention, it is also preferable to cut the ultrafine fiber sheet in half in the thickness direction from the viewpoint of production efficiency, regardless of whether it is before or after the step of dyeing the ultrafine fiber sheet with a disperse dye.

[0160] Furthermore, in the method for producing an artificial leather of the present invention, it is also preferable to perform a nap raising treatment to form naps on at least one surface of the ultrafine fiber sheet, regardless of whether it is before or after the step of dyeing the ultrafine fiber sheet with a disperse dye. The method for the nap raising treatment is not particularly limited, and various methods commonly used in the field, such as buffing with sandpaper, can be used.

[0161] 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.

[0162] 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.

[0163] [Various applications such as clothing, furniture, miscellaneous goods, vehicle interior materials, and automobile parts] The artificial leather of the present invention has excellent surface hue uniformity and texture, and is therefore suitable for a variety of applications, including fashion and vehicle applications. Therefore, clothing containing the artificial leather is one preferred embodiment, as it can take advantage of these properties. Examples of such clothing include tops such as T-shirts, polo shirts, dress shirts, blouses, wrap tops, cut-and-sew tops, sweaters, vests, hoodies, sweatshirts, turtlenecks, cardigans, tank tops, and tube tops; outerwear such as coats, blazers, jackets, windbreakers, cloaks, capes, aprons, and mantles; trousers such as slacks, jeans, and shorts; skirts; dresses such as cocktail dresses, one-piece dresses, and gowns; formal wear, suits, uniforms, and underwear. It is preferable that at least a portion of the front, back, sleeves, collar, facing, hem, inseam, lining, and the like of these clothing items, or at least a portion of the clothing materials and accessories such as buttons, interlining, and pockets, be made of the above-mentioned artificial leather.

[0164] Another preferred embodiment is furniture containing the artificial leather. Examples of such furniture include chairs, sofas, stools, etc. It is preferable that at least a portion of the seat, back, etc. of such furniture is made of the artificial leather.

[0165] Furthermore, miscellaneous goods containing the artificial leather are also one of the preferred embodiments, including accessories such as shoes, hats, bags, belts, scarves, ties, and wallets, and interior goods such as cushions, armrests, and neck pillows.

[0166] The shoes include sneakers, pumps, loafers, boots, sandals, slippers, and spikes. Preferably, at least a portion of the upper, lining, insole, shoelaces, etc. of such shoes is made of the artificial leather.

[0167] Examples of the bag include handbags, tote bags, shoulder bags, Boston bags, waist pouches, briefcases, attaché cases, school bags, etc. It is preferable that at least a part of the handle, inner bag, base leather, gusset, bottom, etc. of such bags be made of the artificial leather.

[0168] On the other hand, vehicle interior materials containing the artificial leather are particularly preferred because they can utilize the properties of achieving a high level of both fine and elegant surface quality, a good touch, and tensile strength while reducing the environmental impact. Such vehicle 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 these automobile parts contain the artificial leather. In the present invention, the term "vehicle" includes automobiles, aircraft, railway vehicles, and ships, as well as carriages, carriages, rickshaws, and other vehicles, and also some industrial, construction, and agricultural machinery capable of carrying humans or animals, such as excavators, cranes, tractors, and combines.

[0169] 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.

[0170] [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.

[0171] (1) Average Single Fiber Diameter (μm) of Polyester Ultrafine Fibers: 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.

[0172] (2) Mass percentage (mass %) of polyurethane in artificial leather: The mass percentage of polyurethane in the artificial leather was measured and calculated by the above-mentioned method.

[0173] (3) Average particle size (μm) of pigment in polyurethane, average irregularity of pigment in polyurethane (no unit): The average particle size and average irregularity of pigment in polyurethane were measured and calculated by the above-mentioned methods using a transmission electron microscope (TEM) "HT7700" manufactured by Hitachi High-Technologies Corporation and image analysis software "VW-9000 Album" manufactured by Keyence Corporation.

[0174] (4) Total content of pigments in polyurethane (mass %): The total content of pigments in polyurethane was measured and calculated by the above-mentioned method.

[0175] (5) Coefficient of variation (%) of the mass proportion of polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction: The coefficient of variation of the mass proportion of polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction was measured and calculated using the method described above.

[0176] (6) Pile Length (μm): The pile length was measured and calculated by the above-mentioned method using a scanning electron microscope (SEM) "VHX-D500 / D510" manufactured by Keyence Corporation.

[0177] (7) Nap Coverage Ratio (%): The nap coverage ratio was measured and calculated by the above-mentioned method using a scanning electron microscope "VHX-D500 / D510" manufactured by Keyence Corporation and image analysis software "ImageJ".

[0178] (8) Abrasion loss (mg): In the Martindale abrasion test specified in "8.19 Abrasion resistance and friction discoloration" of "8.19.5 E method (Martindale method)" of the above-mentioned JIS L1096:2005 "Testing methods for woven and knitted fabrics," the abrasion loss (mg) was measured and calculated at a pressure load of 12 kPa and 20,000 abrasion cycles using a James H. Heal & Co. "Model 406" Martindale abrasion tester and the company's "ABRASTIVE CLOTH SM25" as the standard friction cloth. The abrasion loss (mg) was calculated using the following formula and rounded to the nearest decimal place. Abrasion loss (mg) = mass before abrasion (mg) - mass after abrasion (mg) ... (formula).

[0179] (9) Texture: Texture was evaluated by 20 healthy adults who judged the following evaluations by touch, and the most common evaluation was taken as the texture. In the present invention, a good level is "A or B." A: No resistance when gripped, soft. B: Some resistance when gripped, but soft. C: High resistance when gripped, hard.

[0180] (10) Uniformity of surface hue: The uniformity of surface hue was evaluated by 20 healthy adults who visually judged the following evaluations, and the most common evaluation was taken as the uniformity of surface hue. In the present invention, a good level is "A or B". A: Uniform hue. B: Slight color unevenness, but uniform hue. C: Significant color unevenness, with large variation in hue.

[0181] [Polyurethane Precursor] The polyurethane precursor having a hydrophilic group used in the examples and comparative examples is as follows: High molecular weight polyol: polytetramethylene glycol, organic diisocyanate: MDI, active hydrogen component-containing compound having a hydrophilic group: 2,2-dimethylolpropionic acid, chain extender: ethylene glycol. The polyurethane precursor was prepared by reacting the high molecular weight polyol, organic diisocyanate, and active hydrogen component-containing compound having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting the chain extender.

[0182] Example 1 <Step of forming a fibrous substrate> A copolymer polyester copolymerized with 8 mol % of 5-sodium sulfoisophthalate was used as the sea component, and polyethylene terephthalate was used as the island component. An islands-in-sea type composite fiber was obtained with a mass ratio of the sea component to the islands-in-sea type composite fiber of 20 mass %, 16 islands / filament, and a single fiber fineness of 3.8 dtex. The obtained islands-in-sea type composite fiber was cut to a fiber length of 51 mm, and further subjected to a carding process and a cross-wrapping process to form a fiber web. This fiber web was then cut at 3,500 fibers / cm using needles equipped with barbs capable of holding up to 10 islands-in-sea type composite fibers. ２ The fibrous substrate was needle-punched at a punch density of 600 g / m2 to form a short-fiber nonwoven fabric. ２ , thickness 2.4 mm, apparent density 0.25 g / cm ３ It was.

[0183] <Step of forming an impregnated sheet> First, an aqueous dispersion containing the following was prepared: Polyurethane precursor: 11 mass% of the polyurethane precursor having hydrophilic groups described above; Carbodiimide crosslinking agent: 1 mass% of "Carbodilite V-02-L2" manufactured by Nisshinbo Chemical Inc.; Inorganic salt: 5.0 mass% of sodium sulfate; Surfactant: 0.170 mass% of a nonionic surfactant composed of a copolymer of two types of alkylene oxide, ethylene oxide and propylene oxide (abbreviated as "EO / PO copolymer" in Tables 1 to 4); Pigment: 0.17 mass% of carbon black (adjusted so that the total content of pigments in the polyurethane was 1.50 mass%). A fibrous substrate was then impregnated with this aqueous dispersion, and the amount applied was adjusted by squeezing with a mangle so that the mass proportion of the aqueous dispersion contained in the fibrous substrate was 200 mass% relative to the mass of the fibrous substrate. Thereafter, a heat drying treatment was carried out by blowing hot air at 120° C. for 20 minutes to obtain an impregnated sheet.

[0184] <Step of Obtaining Ultrafine Fiber Sheet> The impregnated sheet obtained was immersed in a 1.3 mol / L aqueous sodium hydroxide solution and then squeezed with a mangle so that the pick-up rate of the aqueous sodium hydroxide solution was 100%. Further, the impregnated sheet was heat-treated with steam at 95°C for 10 minutes to alkali-decompose the sea component of the islands-in-sea type composite fiber. Subsequently, the excess sodium hydroxide, surfactant, and sodium sulfate were washed away with water to produce polyester ultrafine fibers having an average single fiber diameter of 4.4 µm, and an ultrafine fiber sheet was obtained.

[0185] <Heat Treatment Step> Following the above step (immediately after the above step), the obtained ultrafine fiber sheet was heat treated for 10 minutes in a hot air dryer with the atmospheric temperature raised to 160°C, to obtain a heat-treated sheet.

[0186] <Finishing Step> The heat-treated ultrafine fiber sheet was cut in half perpendicular to the thickness direction, and the opposite side of the cut surface was ground with endless sandpaper of sandpaper size 150 to obtain a napped sheet.

[0187] This 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. The results are shown in Table 1. The obtained artificial leather had a good texture and a uniform hue on the surface.

[0188] [Example 2] Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the content of the nonionic surfactant in the aqueous dispersion was changed from 0.170% by mass to 0.002% by mass. The results are shown in Table 1. The obtained artificial leather had a good texture and a uniform hue on the surface, although there was some color unevenness.

[0189] [Example 3] Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the pigment content in the aqueous dispersion was changed from 0.17% by mass to 0.01% by mass (adjusted so that the total pigment content in the polyurethane was 0.10% by mass). The results are shown in Table 1. The obtained artificial leather had a good texture and a uniform hue on the surface.

[0190] [Example 4] Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the pigment content in the aqueous dispersion was changed from 0.17% by mass to 0.24% by mass (adjusted so that the total pigment content in the polyurethane was 2.10% by mass). The results are shown in Table 1. Compared to Example 1, the obtained artificial leather showed slightly greater color transfer to the standard friction cloth in the abrasion test, but this was within the practical range, and the artificial leather had a good texture and a uniform hue on the surface.

[0191] [Example 5] An artificial leather was obtained in the same manner as in Example 1, except that in the finishing step, the grit of the sandpaper used was changed from 150 to 120. The results are shown in Table 2. The artificial leather obtained had a surface quality with slightly more nap than in Example 1, but was within the practical range and had a good texture and a uniform hue on the surface.

[0192] Example 6 Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the pigment content in the aqueous dispersion was changed from 0.17% by mass to 0.0001% by mass (adjusted so that the total pigment content in the polyurethane was 0.001% by mass), and further, in the finishing step, the grit size of the sandpaper was changed from 150 to 120. The results are shown in Table 2. The artificial leather obtained had a surface quality with slightly more nap than in Example 1, but was within the practical range, and had a soft texture and a uniform hue on the surface.

[0193] [Example 7] Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the content of inorganic salt in the aqueous dispersion was changed from 5.0% by mass to 1.1% by mass. The results are shown in Table 2. The texture of the obtained artificial leather was somewhat stiff, but it was soft and had a uniform hue on the surface.

[0194] [Example 8] An artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the content of the inorganic salt in the aqueous dispersion was changed from 5.0% by mass to 9.9% by mass. The results are shown in Table 2. The obtained artificial leather had a good texture and a uniform hue on the surface.

[0195] [Example 9] Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the type of inorganic salt in the aqueous dispersion was changed from sodium sulfate to sodium chloride. The results are shown in Table 3. The obtained artificial leather had a soft texture and a uniform hue on the surface.

[0196] [Example 10] Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the type of inorganic salt in the aqueous dispersion was changed from sodium sulfate to ammonium sulfate. The results are shown in Table 3. The obtained artificial leather had a soft texture and a uniform hue on the surface.

[0197] [Example 11] An artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the content of the nonionic surfactant in the aqueous dispersion was changed from 0.170% by mass to 0.295% by mass. The results are shown in Table 3. The obtained artificial leather had a slight color unevenness on the surface compared to Example 1, but had a sufficiently uniform hue and good texture.

[0198] Example 12 Artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the type of nonionic surfactant in the aqueous dispersion was changed from one composed of a copolymer of two alkylene oxides, ethylene oxide and propylene oxide, to one composed of a copolymer of two alkylene oxides, ethylene oxide and butylene oxide. The results are shown in Table 3. The obtained artificial leather had a slight color unevenness on the surface compared to Example 1, but had a sufficiently uniform hue and good texture.

[0199] Comparative Example 1 An artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the content of the nonionic surfactant in the aqueous dispersion was 0.170% by mass, but no nonionic surfactant was contained in the aqueous dispersion. The results are shown in Table 4. The obtained artificial leather had a good texture, but the uniformity of the surface hue was significantly poor.

[0200] Comparative Example 2 An artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the nonionic surfactant in the aqueous dispersion was changed to a polycarboxylic acid-based anionic surfactant (abbreviated as PCA in Table 4). The results are shown in Table 4. The obtained artificial leather had a good texture, but was significantly inferior in the uniformity of the surface hue.

[0201] Comparative Example 3 An artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the content of inorganic salt in the aqueous dispersion was 5.0 mass %, but no inorganic salt was contained in the aqueous dispersion. The results are shown in Table 4. The artificial leather obtained had a uniform hue on the surface, but was significantly inferior in texture.

[0202] Comparative Example 4 An artificial leather was obtained in the same manner as in Example 1, except that in the step of forming an impregnated sheet, the content of the nonionic surfactant in the aqueous dispersion was changed from 0.170% by mass to 0.305% by mass. The results are shown in Table 4. The obtained artificial leather had a good texture, but was significantly inferior in the uniformity of the surface hue.

[0203]

[0204]

[0205]

[0206]

[0207] 1: A line drawn along the outermost periphery of the pigment. 2: The circle with the largest diameter that is contained within the line drawn along the outermost periphery of the pigment. 3: A circle drawn so that its diameter is the maximum distance between two points on the line drawn along the outermost periphery of the pigment.

Claims

1. An artificial leather comprising a fibrous base material and polyurethane, wherein the fibrous base material comprises a nonwoven fabric made of polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less, the polyurethane has a hydrophilic group and further comprises a black pigment and / or a chromatic pigment, the pigment having an average particle diameter of 0.01 μm or more and 0.10 μm or less, an average irregularity degree of the pigment of 0.50 or more and 1.00 or less, and when the artificial leather is divided into three equal parts in the thickness direction, the coefficient of variation of the mass proportion of the polyurethane in each layer is 5% or more and 30% or less.

2. The artificial leather according to claim 1, wherein the total content of the pigment in the polyurethane is 0.01% by mass or more and 2.00% by mass or less.

3. The artificial leather according to claim 1 or 2, wherein at least one surface has a nap of 200 μm or more and 500 μm or less.

4. The artificial leather according to claim 3, wherein the nap coverage of the surface having the nap is 80% or more and 99% or less.

5. Clothing comprising the artificial leather according to claim 1 or 2.

6. Furniture comprising the artificial leather according to claim 1 or 2.

7. Miscellaneous goods comprising the artificial leather according to claim 1 or 2.

8. A vehicle interior material comprising the artificial leather of claim 1 or 2.

9. An automobile part comprising the artificial leather of claim 1 or 2.

10. A method for producing artificial leather, comprising the steps of: forming a fibrous substrate containing a nonwoven fabric made of ultrafine fiber-developing fibers; impregnating the fibrous substrate with an aqueous dispersion, followed by a heat-drying treatment to form an impregnated sheet; and developing polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less from the ultrafine fiber-developing fibers of the impregnated sheet to form an ultrafine fiber sheet, wherein the aqueous dispersion contains: a polyurethane precursor having a hydrophilic group; an inorganic salt in an amount of 1.0% by mass to 10.0% by mass relative to the aqueous dispersion; a black pigment and / or a chromatic pigment; and a nonionic surfactant in an amount of 0.001% by mass to 0.300% by mass relative to the aqueous dispersion. A method for producing an artificial leather, comprising: forming an artificial leather in which the average particle size of the pigment in the polyurethane is 0.01 μm or more and 0.10 μm or less, the average irregularity of the pigment is 0.50 or more and 1.00 or less, and when the artificial leather is divided into three equal layers in the thickness direction, the coefficient of variation of the mass ratio of the polyurethane in each layer is 5% or more and 30% or less.

11. The method for producing artificial leather according to claim 10, wherein the nonionic surfactant is a copolymer made from two or more types of alkylene oxides.

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