Artificial leather, its manufacturing method, and its uses

Abstract

Even when using a polymer elastic material (polyurethane) having hydrophilic groups, in order to provide artificial leather that achieves both uniformity of surface hue and good texture, the present invention provides artificial leather comprising a fibrous base material and polyurethane, wherein the fibrous base material includes a nonwoven fabric composed of polyester ultrafine fibers with an average single fiber diameter of 1.0 μm or more and 10.0 μm or less, the polyurethane has hydrophilic groups and further includes a black pigment and / or a chromatic pigment, the pigment has an average particle diameter of 0.01 μm or more and 0.10 μm or less, the average degree of irregularity of the pigment is 0.50 or more and 1.00 or less, and the coefficient of variation of the mass ratio of the polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction is 5% or more and 30% or less.

Description

[Technical Field]

[0001] This invention relates to artificial leather, a method for manufacturing the same, and clothing, furniture, general merchandise, interior materials for vehicles, and automobile parts containing the same. [Background technology]

[0002] Artificial leather, which consists mainly of fibrous base materials such as nonwoven fabrics made of ultrafine fibers and polyurethane, possesses superior 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 various fields such as vehicle interior materials, furniture and interior materials, and building materials. In manufacturing such artificial leather, a more environmentally friendly method is being considered, which uses water-dispersible polyurethane in which a polyurethane resin with hydrophilic groups is dispersed in water, 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 fibrous material substrate made of nonwoven fabric with an aqueous dispersion containing a nonionic self-emulsifying polyurethane having a specific temperature for heat-sensitive gelling and a water-dispersible inorganic pigment. It is stated that this method yields a sheet-like material with a good appearance and is environmentally friendly.

[0004] Furthermore, Patent Document 2 proposes a method for manufacturing suede-like artificial leather, comprising the steps of: manufacturing a fiber-entangled nonwoven fabric composed of specific resin-based ultrafine fiber-generating fibers containing a specific amount of pigment with a specific average particle size; applying a polymer-elastic dispersion containing a water-dispersible polymer-elastic body and a specific amount of pigment with a specific average particle size to the interior of the fiber-entangled nonwoven fabric such that the mass ratio of the polymer-elastic body derived from the water-dispersible polymer-elastic body to the three-dimensional entanglement is within a specific range; and obtaining ultrafine fibers by a specific method. It is stated that this method yields excellent color development and lightfastness in a variety of colors, as well as good sensory aspects such as suede feel, surface touch, and texture, and good physical properties such as surface strength, tear strength, and tensile strength.

[0005] Furthermore, Patent Document 3 describes a first polymer elastic precursor impregnation step in which a fibrous substrate made of ultrafine fiber-forming fibers is impregnated with an aqueous dispersion containing a polymer elastic precursor having hydrophilic groups, a monovalent cation-containing inorganic salt, and a crosslinking agent, and then the fibrous substrate impregnated with the aqueous dispersion is subjected to a heat drying treatment within a specific temperature range to form a polymer elastic, wherein the first polymer elastic precursor impregnation step contains a specific amount of monovalent cation-containing inorganic salt in the aqueous dispersion, A process of generating ultrafine fibers from ultrafine fiber generating type fibers to form a fibrous substrate made of the ultrafine fibers, and further, a polymer elastic precursor having hydrophilic groups on the fibrous substrate made of ultrafine fibers. A second polymer elastic precursor impregnation step, comprising impregnating a fibrous substrate with an aqueous dispersion containing a monovalent cation-containing inorganic salt and a crosslinking agent, then performing a heat-drying treatment at a temperature within a specific range to form a polymer elastic body, wherein the content of the monovalent cation-containing inorganic salt in the aqueous dispersion is within a specific range, A method for producing a sheet-like material containing [the specified substance] has been proposed. It has been stated that this method yields a sheet-like material with excellent flexibility, chemical resistance, and stain resistance. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-184707 [Patent Document 2] Japanese Patent Publication No. 2004-143654 [Patent Document 3] International Publication No. 2021 / 125029 [Overview of the project] [Problems that the invention aims to solve]

[0007] In the methods disclosed in Patent Documents 1 and 2, while the uniformity of the surface hue is improved to some extent by uniformly dispersing the pigment in a polymeric elastic material and impregnating a fibrous substrate with an aqueous dispersion, there is still room for improvement. As the polymeric elastic material solidifies, it tends to be biased towards the surface layer of the sheet, and the polymeric elastic material tends to surround the fibers, strongly restricting their movement. As a result, the texture tends to be hard.

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

[0009] Therefore, in view of the above problems, the object of the present invention is to provide artificial leather that achieves both uniformity of surface hue and good texture, even when using a polymer elastic material (polyurethane) having hydrophilic groups. [Means for solving the problem]

[0010] The inventors, after diligent research to solve the above problems, have found that the average degree of irregularity of the pigment contained in the polyurethane of artificial leather obtained by impregnating a fibrous substrate with an aqueous dispersion containing hydrophilic polyurethane, inorganic pigment, and inorganic salt, with a specific amount of nonionic surfactant, and the coefficient of variation of the mass ratio of the polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction, fall within a specific range. Furthermore, they have found that artificial leather within this range achieves both uniformity of surface hue and a good texture.

[0011] This invention was completed based on these findings, and according to this invention, the following inventions are provided.

[0012] [1] Artificial leather comprising a fibrous base material and polyurethane, The fibrous base material includes a non-woven fabric composed of polyester ultra-fine 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 contains a black pigment and / or a colored pigment. The pigment is The average particle diameter of the pigment is 0.01 μm or more and 0.10 μm or less. The average of the degree of irregularity of the pigment is 0.50 or more and 1.00 or less. An artificial leather in which the coefficient of variation of the mass ratio of the polyurethane in each layer when the artificial leather is trisected in the thickness direction is 5% or more and 30% or less.

[0013] [2] The artificial leather according to [1], wherein the total content ratio 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 surface with raised hairs of 200 μm or more and 500 μm or less.

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

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

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

[0018] [7] Sundries containing the artificial leather according to any one of [1] to [4].

[0019] [8] Interior materials for vehicles containing the artificial leather according to any one of [1] to [4].

[0020] [9] Automobile parts containing the artificial leather according to any one of [1] to [4].

[0021]

[10] A step of forming a fibrous base material including a nonwoven fabric composed of ultrafine fiber-generating fibers, The process involves impregnating the fibrous base material with an aqueous dispersion, and then performing a heat drying treatment to form an impregnated sheet. A step of forming an ultrafine fiber sheet by generating polyester ultrafine fibers with an average single fiber diameter of 1.0 μm or more and 10.0 μm or less from the ultrafine fiber-generating fibers of the impregnated sheet, A method for manufacturing artificial leather having the following characteristics: The aforementioned aqueous dispersion is A precursor of polyurethane having a hydrophilic group, The aqueous dispersion contains 1.0% to 10.0% by mass of an inorganic salt, Black pigment, and / or chromatic pigment, 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, Includes, A method for producing artificial leather, wherein the average particle size of the pigment in the polyurethane is 0.01 μm or more and 0.10 μm or less, the average degree of irregularity of the pigment is 0.50 or more and 1.00 or less, and the coefficient of variation of the mass ratio of polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction is 5% or more and 30% or less.

[0022]

[11] The method for producing artificial leather according to

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

[0023] According to the present invention, even when using a polymeric elastic material (polyurethane) having hydrophilic groups, it is possible to obtain artificial leather that achieves both uniform surface color and a good texture. Therefore, the artificial leather of the present invention has a beautiful appearance and supple texture similar to natural leather, with color unevenness defects due to color differences between polyurethane and fibers being less noticeable, and can be used in a wide range of applications from clothing, furniture, general merchandise, and interior materials for vehicles to automobile parts. [Brief explanation of the drawing]

[0024] [Figure 1] Figure 1 is a diagram illustrating the method for measuring and calculating the average particle size and average degree of irregularity of pigments related to the artificial leather of the present invention. [Figure 2] Figure 2 is a diagram illustrating the method for measuring and calculating the average degree of deformation of pigments related to the artificial leather of the present invention. [Modes for carrying out the invention]

[0025] The present invention relates to artificial leather comprising a fibrous base material and polyurethane, wherein the fibrous base material comprises a nonwoven fabric composed of polyester ultrafine fibers having an average single fiber diameter of 1.0 μm or more and 10.0 μm or less, and the polyurethane has hydrophilic groups and further comprises a black pigment and / or a chromatic pigment, wherein the pigment has an average particle size of 0.01 μm or more and 0.10 μm or less. The average degree of irregularity of the pigment is 0.50 or more and 1.00 or less, and the coefficient of variation of the mass ratio of polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction is 5% or more and 30% or less. Here, in the present invention, "chromatic color" refers to a color with hue such as red, blue, green, and yellow, and specifically CIE1976L * a * b * In a color space, saturation (C * This refers to colors with a chroma value of 10 or higher. The above chroma values ​​were measured on pigments uniformly coated on a white substrate using a method compliant with JIS Z 8781-4:2013.

[0026] The components will be described in detail below, but the present invention is not limited in any way to the scope described below, as long as it does not exceed the spirit of the invention, and various modifications are possible without departing from the spirit of the invention.

[0027] [Polyester ultrafine fiber] The artificial leather of the present invention includes a nonwoven fabric in which a fibrous base material, one of the 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 resin, with a single fiber diameter of 20.0 μm or less, as measured and calculated by the method described later. Furthermore, in the present invention, "polyester resin" refers to a resin in which the mole fraction of the polyester unit in the repeating unit is 80 mol% or more and 100 mol% or less. Unless otherwise specified, the same applies to any mention of "...-type resin".

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

[0029] In this invention, polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and mixtures and copolymers of these polyester resins are preferred because they can be used to produce artificial leather with excellent heat resistance, light resistance, and other properties.

[0030] Therefore, examples of dicarboxylic acids and / or ester-forming derivatives used in the polyester resin include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid and its ester-forming derivatives. In this invention, ester-forming derivatives refer to lower alkyl esters, acid anhydrides, acyl chlorides, etc. of dicarboxylic acids. Specifically, methyl esters, ethyl esters, hydroxyethyl esters, etc., are preferably used. A more preferred embodiment of the dicarboxylic acid and / or ester-forming derivative used in this 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, and cyclohexanedimethanol. Among these, ethylene glycol is preferred.

[0032] Furthermore, the polyester resin may contain inorganic particles such as titanium dioxide particles, lubricants, pigments, dyes, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, and antibacterial agents, depending on the purpose.

[0033] Polyester ultrafine fibers can have either a round or irregular cross-sectional shape. Specific examples of irregular cross-sections include elliptical, flat, triangular polygons (including those with rounded corners), sectors, and cross shapes.

[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. An average single fiber diameter of 10.0 μm or less, preferably 7.0 μm or less, and more preferably 5.0 μm or less, results in a more flexible artificial leather. Furthermore, the quality of the nap can be improved. On the other hand, an average single fiber diameter of 1.0 μm or more, preferably 1.5 μm or more, and more preferably 2.0 μm or more, results in an artificial leather with excellent color development after dyeing. Furthermore, when performing a napping treatment by buffing, the ease of dispersing and separating the bundled polyester ultrafine fibers can be improved.

[0035] In this invention, the single fiber diameter and average single fiber diameter of polyester ultrafine fibers shall be 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 using a scanning electron microscope (SEM, Keyence Corporation "VHX-D500 / D510", or a scanning electron microscope with equivalent performance). (2) The diameter of any 50 polyester ultrafine fibers within the observation surface is measured at the cross-section of each polyester ultrafine fiber, and this operation is performed a total of three times at different locations. However, if polyester ultrafine fibers with irregular cross-sections are used, first measure the cross-sectional area of ​​the polyester ultrafine fiber, and calculate the diameter of the circle that gives that cross-sectional area using the following formula. The diameter obtained from this shall be taken as the diameter of the single fiber. Single fiber diameter (μm) = (4 × (cross-sectional area of ​​single fiber (μm) 2 )) / π) 1 / 2 ···(formula). (3) Calculate the arithmetic mean (μm) of the total of 150 points obtained and round it to two decimal places.

[0036] [Fibrous base material] The fibrous base material of the artificial leather according to the present invention includes a nonwoven fabric composed of the polyester ultrafine fibers. That is, this fibrous base material may be a nonwoven fabric composed of the polyester ultrafine fibers, or it may include a nonwoven fabric composed of the polyester ultrafine fibers and a woven or knitted fabric. Here, "woven or knitted fabric" is a general term for woven and knitted fabrics. Furthermore, in the case of including a nonwoven fabric and a woven or knitted fabric, it is more preferable that these are intertwined and integrated by methods such as needle punching or water jet punching.

[0037] The nonwoven fabric can be of any form, including long-fiber nonwoven fabrics such as spunbond nonwoven fabrics and meltblown nonwoven fabrics, or short-fiber nonwoven fabrics such as papermaking nonwoven fabrics. However, short-fiber nonwoven fabrics are preferred because they have a large number of upright fibers on the product surface, making it easier to obtain 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, and more preferably 40 mm or more, an artificial leather with an elegant appearance is obtained. On the other hand, when the fiber length of the polyester ultrafine fibers is 90 mm or less, preferably 80 mm or less, and more preferably 70 mm or less, an artificial leather with good surface quality and texture is obtained.

[0039] Examples of woven and knitted fabrics include plain weave, twill weave, and satin weave for woven fabrics, and warp knitted fabrics such as tricot knit and raschel knit, or weft knitted fabrics such as plain knit and rib knit for knitted fabrics. In particular, plain weave fabrics are less prone to wrinkles and deformation during use and washing, resulting in artificial leather with excellent shape retention.

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

[0041] Next, the average single fiber diameter of the filaments (single threads) in the multifilament is preferably between 0.3 μm and 10.0 μm. Being within this range results in artificial leather with superior strength and texture.

[0042] In this invention, the average single fiber diameter of the filaments of the multifilament constituting the woven fabric shall be 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 using a scanning electron microscope (SEM, Keyence Corporation "VHX-D500 / D510", or a scanning electron microscope with equivalent performance). (2) Measure the cross-sectional area of ​​any 10 filaments within the observation surface, and calculate the diameter of the circle that corresponds to that cross-sectional area using the following formula. The diameter obtained from this is taken as the single fiber diameter of that filament. Single fiber diameter (μm) = (4 × (cross-sectional area of ​​single fiber (μm) 2 )) / π) 1 / 2 ···(formula). (3) Calculate the arithmetic mean (μm) of the total of 30 points obtained and round it to two decimal places.

[0043] Furthermore, the total fineness of the multifilament is preferably between 30 dtex and 170 dtex. This range results in artificial leather with superior flexibility and dimensional stability.

[0044] In this invention, the total fineness of the multifilament shall be measured and calculated according to "8.3 Fineness" and "8.3.1 True Fineness b) Method B (Simplified Method)" of "8.3 Fineness" in JIS L1013:2010 "Test Methods for Chemical Fiber Filament Yarns".

[0045] Furthermore, the number of filaments in the multifilament is preferably between 30 and 300. Being within this range results in an artificial leather with superior flexibility and shape retention.

[0046] In this invention, the number of filaments included in the multifilament shall be 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 using a scanning electron microscope (SEM, Keyence Corporation "VHX-D500 / D510", or a scanning electron microscope with equivalent performance). (2) Measure the number of filaments contained in the cross-section of any 10 multifilaments within the observation plane. (3) Calculate the arithmetic mean (number of books) of the total of 10 points obtained and round it to the first decimal place.

[0047] [Polyurethane] First, the artificial leather of the present invention contains polyurethane. This polyurethane can act as a binder that holds the ultrafine fibers in the artificial leather, and by including polyurethane, the artificial leather has a substantial feel, a leather-like appearance, and physical properties that can withstand actual use.

[0048] Furthermore, the polyurethane according to the present invention has hydrophilic groups. Here, "having hydrophilic groups" means that the group itself "has a group having active hydrogen," and specific examples of such groups having active hydrogen include hydroxyl groups, carboxyl groups, sulfonic acid groups, amino groups, etc. From the viewpoint of reactivity with crosslinking agents having carbodiimide groups, which will be described later, it is preferable to have hydroxyl groups or carboxyl groups.

[0049] First, this hydrophilic polyurethane is obtained by reacting a high-molecular-weight polyol (described later), an organic diisocyanate, and a compound containing an active hydrogen component with hydrophilic groups to form a hydrophilic prepolymer, and then reacting the resulting polyurethane precursor with a crosslinking agent. These are explained in detail below.

[0050] (1) High molecular weight polyol Examples of polymeric polyols that are preferably used in the present invention include polyether-based polyols, polyester-based polyols, and polycarbonate-based polyols.

[0051] First, examples of polyether-based polyols include polyols obtained by addition-polymerization of monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin, and cyclohexylene using a polyhydric alcohol or polyamine as an initiator, as well as polyols obtained by ring-opening polymerization of the aforementioned monomers using a protic acid, Lewis acid, or cationic catalyst as a catalyst. Specifically, examples include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 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 opening polymerization of lactones.

[0053] Examples of low molecular weight polyols used in polyester polyols include one or more selected from 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 polybasic acids used in polyester polyols 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 the reaction of a polyol with a dialkyl carbonate, or a polyol with a diaryl carbonate, etc.

[0056] For polycarbonate-based polyols, low molecular weight polyols used for polyester-based polyols can be used. On the other hand, dimethyl carbonate and diethyl carbonate can be used as dialkyl carbonates, and diphenyl carbonate can be used as diaryl carbonates.

[0057] In this invention, the number-average molecular weight of the polymer polyol is preferably 500 or more and 5000 or less. A number-average molecular weight of 500 or more, preferably 1500 or more, results in a soft and flexible artificial leather. Furthermore, a number-average molecular weight of 5000 or less, preferably 4000 or less, makes it easier to maintain the strength of the polyurethane having hydrophilic groups as a binder.

[0058] (2) Organic diisocyanates The organic diisocyanates used in the present invention include aromatic diisocyanates having 6 to 20 carbon atoms (excluding carbon atoms in the NCO group; the same applies hereinafter), aliphatic diisocyanates having 2 to 18 carbon atoms, alicyclic diisocyanates having 4 to 15 carbon atoms, aromatic aliphatic diisocyanates having 8 to 15 carbon atoms, modified forms of these diisocyanates (carbodiimide modified forms, urethane modified forms, uretdione modified forms, etc.), and mixtures of two or more of these.

[0059] Specific examples of aromatic diisocyanates having 6 to 20 carbon atoms include 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, 2,4'-diphenylmethanediisocyanate, 4,4'-diphenylmethanediisocyanate (hereinafter abbreviated as MDI), 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 1,5-naphthylenediisocyanate, and the like. Among these, MDI is preferred because it exhibits excellent flexibility when used as a polyurethane with hydrophilic groups.

[0060] Specific examples of aliphatic diisocyanates having 2 to 18 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 diisocyanates 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, dicyclohexylmethane-4,4'-diisocyanate is preferred because it exhibits excellent durability when used as a polyurethane with hydrophilic groups.

[0062] Specific examples of aromatic aliphatic diisocyanates having 8 to 15 carbon atoms include m- and / or p-xylylene diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate.

[0063] (3) Compounds containing active hydrogen components having hydrophilic groups Examples of hydrophilic active hydrogen component-containing compounds preferably used in the present invention include compounds containing one or more functional groups selected from nonionic, anionic, and cationic groups, and active hydrogen. These active hydrogen component-containing compounds can also be used in the form of salts neutralized with a neutralizing agent. By using these hydrophilic active hydrogen component-containing compounds, the stability of the aqueous dispersion used in the method for manufacturing artificial leather can be improved.

[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 polyoxyethylene glycol groups with a molecular weight of 250 to 9000 in their side chains, and triols such as trimethylolpropane and trimethylolbutane.

[0065] Examples of compounds having anionic groups and active hydrogen include carboxyl group-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid, as well as their derivatives; compounds containing sulfonic acid groups such as 1,3-phenylenediamine-4,6-disulfonic acid and 3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid, as well as their derivatives; and salts obtained by neutralizing these compounds with a neutralizing agent.

[0066] Examples of compounds containing cationic groups and active hydrogen include tertiary amino group-containing compounds such as 3-dimethylaminopropanol, N-methyldiethanolamine, and N-propyldiethanolamine, as well as their derivatives.

[0067] (4) Chain extenders Examples of chain extenders used 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, dihydrazides such as hydrazine and adipic acid dihydrazide, and mixtures of two or more of these.

[0068] Among these, preferred chain elongators are water, low molecular weight diols, and aromatic diamines, and more preferably water, ethylene glycol, 1,4-butanediol, 4,4'-diaminodiphenylmethane, and mixtures of two or more of these.

[0069] (5) Composition 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 a compound containing an active hydrogen component having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting a chain extender.

[0070] (6) Crosslinking agents The crosslinking agent used in the present invention may have two or more reactive groups in its molecule that can react with the reactive groups introduced into the polyurethane precursor. Specifically, examples include polyisocyanate crosslinking agents such as water-soluble isocyanate compounds and blocked isocyanate compounds, oxazoline crosslinking agents, carbodiimide crosslinking agents, melamine crosslinking agents, and the like. The crosslinking agent may be used alone or in combination of two or more.

[0071] Water-soluble isocyanate compounds are those having two or more isocyanate groups in their molecule, and examples include the aforementioned compounds containing organic polyisocyanates. Commercially available examples include the "Bayhijur" (registered trademark) series and the "Desmodule" (registered trademark) series manufactured by Bayer Material Science Co., Ltd.

[0072] Blocked isocyanate compounds are those that have two or more blocked isocyanate groups in their molecule. Blocked isocyanate groups refer to organic polyisocyanate compounds that have been blocked with blocking agents such as amines, phenols, imines, mercaptans, pyrazoles, oximes, and active methylene compounds. Examples of commercially available products include the "Elastron" (registered trademark) series from Daiichi 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 their molecule. Commercially available examples include the "Epocross" (registered trademark) series manufactured by Nippon Shokubai Co., Ltd.

[0074] Examples of carbodiimide-based crosslinking agents include compounds having two or more carbodiimide groups in their molecule. Examples of 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 exhibits excellent durability and flexibility in the hydrophilic polyurethane obtained after the reaction.

[0076] (7) Structure of polyurethane having hydrophilic groups The hydrophilic polyurethane is preferably a polyether-based polyurethane containing components derived from a polyether-based polyol, and / or a polycarbonate-based polyurethane containing components derived from a polycarbonate-based polyol.

[0077] From the viewpoint of flexibility, polyether-based polyurethane is preferable. By using a polyether-based polyurethane, that is, by including components derived from polyether-based polyols, the high degree of freedom of its ether bonds results in a low glass transition temperature and weak cohesive force, thus enabling the creation of a highly flexible, hydrophilic polyurethane.

[0078] On the other hand, from the viewpoint of durability, polycarbonate-based polyurethane is preferable. By using a polycarbonate-based polyurethane, that is, by including components derived from polycarbonate-based polyols, the high cohesive force of the carbonate groups allows for a hydrophilic polyurethane with excellent water resistance, heat resistance, weather resistance, and mechanical properties.

[0079] The composition of the hydrophilic polyurethane can be adjusted as appropriate according to the required properties, and either polyether-based polyurethane or polycarbonate-based polyurethane may be used alone, or both may be used together.

[0080] Furthermore, to confirm the constituent components of hydrophilic polyurethane (confirming that hydrophilic polyurethane contains constituent components derived from polyether polyol, and that hydrophilic polyurethane further contains constituent components derived from polycarbonate polyol), the fibrous base material constituting the artificial leather is eluted, and the insoluble matter (hydrophilic polyurethane) is analyzed by infrared spectroscopy (using the FT / IR 4000 series from JASCO Corporation or an infrared spectrometer with equivalent performance) or pyrolysis GC / MS analysis (using the GCMS-QP5050A from Shimadzu Corporation or a pyrolysis GC / MS analyzer with equivalent performance).

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

[0082] Furthermore, the hydrophilic polyurethane used in the present invention preferably has N-acylurea bonds and / or isourea bonds. The N-acylurea bonds and / or isourea bonds are formed by the reaction of the hydrophilic group with a crosslinking agent having a carbodiimide group, and by forming a crosslinked structure in the hydrophilic polyurethane, the durability of the hydrophilic polyurethane can be increased.

[0083] Furthermore, the presence of the above-mentioned N-acylurea groups and isourea groups in hydrophilic polyurethanes can be analyzed by performing mapping processes such as time-of-flight secondary ion mass spectrometry (TOF-SIMS analysis) on a cross-section of artificial leather (for example, using an ION-TOF "TOF.SIMS 5" or a TOF-SIMS analyzer with equivalent performance) or infrared spectroscopy (for example, using a JASCO "FT / IR 4000 series" or an infrared spectrometer with equivalent performance).

[0084] (8) Black pigments, chromatic pigments Next, the polyurethane according to the present invention has the aforementioned hydrophilic group and further contains a black pigment and / or a chromatic pigment. By including such pigments, the color difference between the ultrafine fibers of the artificial leather and the polyurethane can be reduced when dyeing, resulting in 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] In addition, examples of chromatic pigments include inorganic pigments such as blue pigments like ultramarine blue and Prussian blue (potassium iron ferrocyanide), red pigments such as red lead and red iron oxide, and yellow pigments such as lead yellow and zinc yellow (zinc yellow type 1, zinc yellow type 2), as well as organic pigments of each color, such as phthalocyanine, anthraquinone, quinacridone, dioxazine, isoindolinone, isoindoline, indigo, quinophthalone, diketopyrrolopyrrole, perinone, benzimidazolon, condensed azo, and azomethine azo.

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

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

[0089] In the present invention, if the average particle size of the pigment contained in the hydrophilic polyurethane 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 suppressing the detachment of the pigment from the polyurethane. On the other hand, if the average particle size of the pigment contained in the hydrophilic polyurethane is 0.10 μm or less, preferably 0.09 μm or less, and more preferably 0.08 μm or less, the sedimentation of the pigment is suppressed, resulting in excellent dispersibility when impregnating a hydrophilic polyurethane aqueous dispersion containing the pigment onto a nonwoven fabric.

[0090] In this invention, the average particle size of the pigment is measured and calculated by the following method. That is, (1) Prepare an ultra-thin section with a thickness of 5 to 10 μm in the cross-sectional direction of a plane perpendicular to the longitudinal direction of the artificial leather. (2) Randomly observe three locations on the cross-section of the polyurethane in the ultra-thin section at a magnification of 40,000 using a transmission electron microscope (TEM, "HT7700" manufactured by Hitachi High-Tech Corporation, or a transmission electron microscope having equivalent performance). (3) As shown in Fig. 1, draw a line (1) on the TEM image along the outermost periphery of the pigment. (4) Using image analysis software ("VW-9000 Album" manufactured by Keyence Corporation, or image analysis software having equivalent performance), randomly select 10 points for the pigments included in three observation images with a field of view of 0.6 μm × 0.6 μm, measure their cross-sectional areas, and calculate the diameter (equivalent circle diameter) of the circle corresponding to the cross-sectional area using the following formula. However, if there are less than 10 pigment particles in the three observation images with a field of view of 0.6 μm × 0.6 μm, measure the equivalent circle diameters of all the existing pigments. Equivalent circle diameter (μm) = (4 × (cross-sectional area of pigment (μm 2 )) / π) 1 / 2 ···(Formula) (5) Calculate the arithmetic mean value (μm) of the total 10 points obtained. However, if there are less than 10 pigment particles in the three observation images with a field of view of 0.6 μm × 0.6 μm, calculate the arithmetic mean value from the equivalent circle diameters of all the existing pigments. (6) Five experts who have been engaged in the technical development of artificial leather for more than one year and are specialized in the technical development are used as evaluators. Each evaluator performs the operations in (3) to (5) above, calculates the arithmetic mean value (μm) of the total 5 points obtained, and rounds it to the third decimal place.

[0091] Next, the average of the irregularity of the pigment is 0.50 or more and 1.00 or less. Here, the irregularity refers to the irregularity of the pigment in the state where the pigment exists in the polyurethane, which is measured by the method described later and refers to the irregularity in the aggregated state.

[0092] When the average degree of irregularity of the pigment is 0.50 or higher, preferably 0.55 or higher, and more preferably 0.60 or higher, the surface irregularities of the pigment are reduced, and diffuse reflection of the pigment surface can be suppressed, thereby enabling the production of artificial leather with a uniform surface hue. Furthermore, the upper limit of the average degree of irregularity of the pigment is 1.00, at which point the cross-section of the pigment becomes perfectly circular.

[0093] In this invention, the degree of pigment irregularity shall be measured and calculated by the following method. That is, (1) Prepare ultrathin sections with a thickness of 5-10 μm in the cross-sectional direction of a surface perpendicular to the longitudinal direction of the artificial leather. (2) Using a transmission electron microscope (TEM, Hitachi High-Technologies Corporation "HT7700", or a transmission electron microscope with equivalent performance), three random locations on the cross-section of the polyurethane in the ultrathin section are observed at 40,000x magnification. (3) As shown in Figures 1 and 2, draw a line (1) on the TEM image along the outermost edge of the pigment. (4) Using image analysis software (Keyence Corporation's "VW-9000 Album" or image analysis software with equivalent performance), 10 points are randomly selected from the pigments contained in three observation images of a 0.6 μm × 0.6 μm field of view, and the circumscribed circle diameter and inscribed circle diameter are measured. The corresponding degree of irregularity is then calculated using the following formula. However, if there are fewer than 10 pigment particles contained in the three observation images of a 0.6 μm × 0.6 μm field of view, the degree of irregularity of all present pigments is measured. Degree of irregularity (unitless) = inscribed circle diameter of pigment (μm) / circumscribed circle diameter of pigment (μm) ... (formula). (5) Calculate the arithmetic mean (unitless) of the total of 10 points obtained. However, if there are fewer than 10 pigments in the three observation images of a 0.6 μm × 0.6 μm field of view, calculate the arithmetic mean from the heteromorphism of all the pigments present. (6) Five experts who have been engaged in the development of artificial leather technology for more than one year and specialize in such technology development shall be selected as evaluators. Each evaluator shall perform the operations described in (3) to (5) above, and the arithmetic mean (unitless) of the total score of 5 obtained shall be calculated and rounded to the third decimal place.

[0094] The average particle size and degree of irregularity of the pigment can be set to the above range by adjusting the amount of nonionic surfactant and inorganic salt added to the aqueous dispersion when impregnating the fibrous substrate with the aqueous dispersion described later.

[0095] In the present invention, it is preferable that the total content of the pigment in the polyurethane is 0.01% by mass or more and 2.00% by mass or less relative to the mass of the polyurethane. When the total content is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more, the color difference between the ultrafine fibers of the artificial leather and the polyurethane is small when dyeing is performed, resulting in artificial leather with excellent uniformity of surface hue. On the other hand, when the total content is preferably 2.00% by mass or less, and more preferably 1.50% by mass, it is possible to suppress shedding due to dyeing, washing, friction, etc., resulting in artificial leather with excellent durability.

[0096] In this invention, the total content of the pigment in the polyurethane shall be measured and calculated by the following method. That is, (1) Cut out two 5cm x 5cm test pieces from the artificial leather. (2) One test piece is immersed in hexafluoroisopropanol to dissolve the ultrafine fibers and collect the polyurethane. (3) The collected polyurethane is dissolved using N,N-dimethylformamide or the like, and only the pigment is extracted. (4) The extracted pigments are subjected to gas analysis using methods such as gas chromatography, and a calibration curve is created for the gases generated from the pigments. (5) Using the other test piece, the polyurethane contained in the artificial leather is dissolved using N,N-dimethylformamide, etc., and then the polyurethane is solidified again by removing the N,N-dimethylformamide, etc. (6) The polyurethane obtained in (5) is subjected to generated gas analysis, and the total percentage of pigment content (mass%) in the polyurethane is calculated from the detection intensity of the generated gas derived from the pigment and the calibration curve created in (4), and rounded to the third decimal place.

[0097] Furthermore, the total content of the pigment in the polyurethane can be set to the above range by adjusting the amount of the pigment added to the aqueous dispersion, as described later. In addition, although the total content of the pigment in the polyurethane can be measured by the above method, if it can be determined from the amount of polyurethane and pigment used, the value calculated from these can be used as a substitute.

[0098] [Artificial leather] First, the artificial leather of the present invention comprises the fibrous base material and the polyurethane.

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

[0100] The coefficient of variation of the mass ratio of polyurethane in each layer can be set to the above range by adjusting the heat-sensitive solidification temperature of the aqueous dispersion containing the precursor, thereby suppressing uneven distribution of polyurethane on the surface of the fibrous substrate by allowing the solidification of the polyurethane precursor to proceed before water evaporates from the fibrous substrate during heating. The heat-sensitive solidification temperature referred to here is the temperature at which the fluidity of the aqueous dispersion decreases and solidification occurs when the aqueous dispersion is heated.

[0101] In this invention, the coefficient of variation of the mass ratio of polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction shall be measured and calculated by the following method. That is, (1) Measure the thickness (mm) of the artificial leather according to JIS L 1096 Method A, and slice it into three equal parts in the thickness direction. (2) From each of the three sliced ​​layers of the sample, randomly cut out 10cm square test pieces, and measure the mass of each test piece (M A1 M A2 M A3 ) is measured and heated in a 180°C dryer for a set period of time. (3) After heat treatment, each test piece is immersed overnight in a solvent that dissolves the polyurethane (for example, N,N-dimethylformamide). (4) Remove the insoluble components (fibrous base material), wash them with water, and then heat them in a dryer at 100°C. (5) The weight (M) of each test specimen (fibrous base material) obtained B1 M B2 M B3 The following measurements are taken, and the mass percentage (mass%) of the polyurethane in each layer is calculated using the following formula. Here, X corresponds to 1, 2, and 3. Mass percentage of polyurethane (mass%) = (M AX -M BX ) / M AX ×100...(formula) (6) For the mass percentage of polyurethane in each measured layer, calculate the coefficient of variation (%) using the following formula and round it to the first decimal place. The coefficient of variation (%) of the mass percentage of polyurethane in each layer = (standard deviation of the mass percentage of polyurethane in each layer) / (arithmetic mean of the mass percentage of polyurethane in each layer) × 100 ... (formula).

[0102] In the present invention, the artificial leather preferably has a polyurethane mass ratio of 15% by mass or more and 25% by mass or less. When this mass ratio is preferably 15% by mass or more, and more preferably 18% by mass or more, the artificial leather has excellent abrasion resistance. On the other hand, when the polyurethane mass ratio is preferably 25% by mass or less, and more preferably 22% by mass or less, the artificial leather has a flexible texture.

[0103] In this invention, the mass percentage of polyurethane shall be measured and calculated by the following method. That is, (1) Randomly cut out 10cm square test pieces from the artificial leather, and measure the mass (M) of the test pieces. α ) is measured and heated in a 180°C dryer for a set period of time. (2) After heat treatment, each test piece is immersed overnight in a solvent that dissolves the polyurethane (for example, N,N-dimethylformamide). (3) Remove the insoluble components (fibrous base material), wash them with water, and then heat them in a dryer at 100°C. (4) Weight of the obtained test specimen (fibrous base material) (M β The following measurements are taken, and the mass percentage (mass%) of the polyurethane is calculated using the following formula, and rounded to the first decimal place. Mass percentage of polyurethane (mass%) = (M α -M β ) / M α ×100...(formula).

[0104] The artificial leather of the present invention preferably exhibits a wear loss of 25 mg or less when measured under a pressing load of 12 kPa and 20,000 cycles in the Martindale abrasion test specified in "8.19 Abrasion Strength and Friction Discoloration Resistance" of "8.19.5 Method E (Martindale Method)" of JIS L1096:2005 "Test Methods for Woven and Knitted Fabrics". A wear loss of 25 mg or less, more preferably 20 mg or less, and even more preferably 15 mg or less, prevents contamination due to shedding of fibers during actual use and results in an artificial leather with minimal changes in appearance.

[0105] The artificial leather of the present invention preferably has at least one surface having a pile of 200 μm or more and 500 μm or less. When the length of this pile (hereinafter sometimes simply referred to as "pile length") is preferably 200 μm or more, more preferably 250 μm or more, the artificial leather has excellent tactile properties. On the other hand, when the pile length is preferably 500 μm or less, more preferably 450 μm or less, the deterioration of surface quality due to the fluffing of the pile can be suppressed, resulting in an artificial leather with an elegant suede-like surface quality.

[0106] Furthermore, it is preferable that the artificial leather of the present invention has a pile coverage rate of 80% to 99% on the surface having a pile. This range improves the surface smoothness of the artificial leather, resulting in an artificial leather with excellent tactile properties.

[0107] The aforementioned pile length and pile coverage can be set to the above range by adjusting the grit of the sandpaper used in the process of forming the surface with pile, the amount of lubricant such as silicone emulsion applied, etc.

[0108] In this invention, the pile length of the artificial leather shall be measured and calculated by the following method. That is, (1) Using a lint brush or the like, raise the nap of the artificial leather and prepare a 1 mm thick thin section in the cross-sectional direction of a surface perpendicular to the longitudinal direction of the artificial leather. (2) Observe the cross-section of the artificial leather at 80x magnification using a scanning electron microscope (SEM, Keyence Corporation "VHX-D500 / D510", or a scanning electron microscope with equivalent performance). (3) In the captured SEM image, the height of the pile (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 of the heights of the 10 pile sections (layers consisting only of ultrafine fibers) is calculated, rounded to the first decimal place, and this is taken as the pile length (μm).

[0109] The coverage rate of the arrowing hairs was determined by magnifying the arrowing surface with a SEM at a magnification of 30x to 90x so that the presence of arrowing hairs could be seen, and then using image analysis software (such as the U.S. National Institutes of Health (NIH) "ImageJ" or equivalent image analysis software, which has the function to identify the necessary area in the captured image and perform pixel analysis) to analyze a total area of ​​9 mm². 2 The ratio of the total area of ​​the raised pile portion per unit area is calculated and expressed as the raised pile coverage rate (%). The ratio of the total area can be calculated by using image analysis software on the captured SEM image and binarizing it by setting the threshold to 128 out of 256 grayscale levels (white = 255, black = 0) for the raised pile portion and the non-raised pile portion. In this case, the white areas are the raised pile portion and the black areas are the non-raised pile portion. Furthermore, if non-raised material is calculated as raised pile and significantly affects the raised pile coverage rate, the image is manually edited to set the color tone of the non-raised material to 0 (black) so that area is calculated as the non-raised pile portion.

[0110] [Manufacturing method for artificial leather] The present invention provides a method for manufacturing artificial leather, comprising the steps of forming a fibrous base material including a nonwoven fabric composed of ultrafine fiber-generating fibers, The process involves impregnating the fibrous base material with an aqueous dispersion, and then performing a heat drying treatment to form an impregnated sheet. A step of forming an ultrafine fiber sheet by generating polyester ultrafine fibers with an average single fiber diameter of 1.0 μm or more and 10.0 μm or less from the ultrafine fiber-generating fibers of the impregnated sheet, A method for manufacturing artificial leather having the following characteristics: The aforementioned aqueous dispersion is A polyurethane precursor having a hydrophilic group, The aqueous dispersion contains 1.0% to 10.0% by mass of an inorganic salt, Black pigment, and / or chromatic pigment, 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, Includes, The present invention provides a method for forming 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 degree of irregularity of the pigment in the polyurethane is 0.50 or more and 1.00 or less, and the coefficient of variation of the mass ratio of the polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction is 5% or more and 30% or less.

[0111] Details are explained below.

[0112] <Process for forming a fibrous substrate> In this process, a fibrous substrate is formed, which includes a nonwoven fabric composed of ultrafine fiber-generating fibers.

[0113] In the present invention, as the ultrafine fiber-generating fiber, it is preferable to use a sea-island type composite fiber in which two thermoplastic resins with different solvent solubility (two or three components if the island fibers are core-sheath composite fibers) are used as the sea component and island component, and the sea component is dissolved and removed using a solvent or the like to form the island component into ultrafine fibers. This is preferable from the viewpoint of the texture and surface quality of the artificial leather because when the sea component is removed, appropriate voids can be provided between the island components, i.e., between the ultrafine fibers inside the fiber bundle.

[0114] Here, "different solvent solubility" means that the solubility of one thermoplastic resin in an aqueous solution, such as an organic solvent or alkaline aqueous solution, used to remove one thermoplastic resin from the ultrafine fiber-generating fibers described above differs by more than 100 times. Due to this difference, for example, an alkali-soluble resin that dissolves easily in an alkaline aqueous solution will dissolve within 5 minutes when immersed in a 5% sodium hydroxide aqueous solution, while the other thermoplastic resin used in combination will not dissolve in the same solution for more than 10 minutes. Therefore, ultrafine fibers can be easily obtained.

[0115] As for sea-island type composite fibers, a method using a polymer interconnected array that is spun by interconnecting two components (three components if the island fiber is a core-sheath composite fiber) of sea component and island component using a sea-island type composite spinneret is preferred from the viewpoint of obtaining ultrafine fibers with a uniform single fiber diameter.

[0116] For the marine component of sea-island composite fibers, copolymerized polyester is preferred as the alkali-soluble resin, from the viewpoint of ease of spinning and dissolution by alkali treatment. Furthermore, by using copolymerized polyester for the marine component, the frictional force between sea-island composite fibers is reduced, and the flexibility of the fibers is improved, enabling efficient fiber entanglement when the fibers are entangled by needle punching or the like.

[0117] When using copolymerized polyester, it is preferable that the copolymerized amount of sodium 5-sulfoisophthalate is 3 mol% to 15 mol% when the total amount of dicarboxylic acid components is 100 mol%. By having a copolymerized amount of sodium 5-sulfoisophthalate of preferably 3 mol% or more, and more preferably 5 mol% or more, sufficient alkali elution can be obtained. On the other hand, by having a copolymerized amount of sodium 5-sulfoisophthalate component of preferably 15 mol% or less, and more preferably 13 mol% or less, the thickening of the polyester is suppressed, resulting in the effect of reducing the likelihood of yarn breakage during spinning of sea-island type composite fibers.

[0118] Furthermore, it is preferable that the alkali-soluble resin is a copolymerized polyester in which polyalkylene glycol is copolymerized. Within this range, the flexibility of the sea-island type composite fiber is improved, and efficient fiber entanglement becomes possible when the fibers are entangled by needle punching or the like.

[0119] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, and polybutylene glycol, but polyethylene glycol is preferred due to its ease of use and its ability to reduce in alkaline aqueous solutions.

[0120] Furthermore, the copolymerized polyester preferably contains a polyethylene terephthalate-based polyester whose main component is a repeating unit composed primarily of ethylene terephthalate units, and may also be a polyester in which a portion of the terephthalic acid component is replaced with another bifunctional carboxylic acid component. Similarly, it may also be a polyester in which a portion of the ethylene glycol component is replaced with another polyol component.

[0121] In addition to terephthalic acid, other bifunctional carboxylic acids used in the present invention include, for example, aromatic, aliphatic, and alicyclic bifunctional carboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, adipic acid, sebacic acid, and 1,4-cyclohexanedicarboxylic acid. In addition, other polyol compounds besides ethylene glycol include, for example, aliphatic, alicyclic, and aromatic polyol compounds such as tetramethylene glycol, hexamethylene glycol, cyclohexane-1,4-dimethanol, neopentyl glycol, bisphenol A, and bisphenol S.

[0122] Furthermore, the alkali-soluble resin used in the marine component of the sea-island type composite fiber can contain inorganic particles such as titanium dioxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, and antibacterial agents, depending on the purpose.

[0123] In the sea-island type composite fiber used in the present invention, the mass ratio of the sea component to the island component is preferably 10% by mass or more and 80% by mass or less. When this mass ratio is preferably 10% by mass or more, and more preferably 15% by mass or more, the island component is easily made into ultrafine particles. On the other hand, when the mass ratio is preferably 80% by mass or less, and 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 either a long-fiber nonwoven fabric or a short-fiber nonwoven fabric. However, a short-fiber nonwoven fabric is preferable because, compared to a long-fiber nonwoven fabric, there are more fibers oriented in the thickness direction of the artificial leather, resulting in a nonwoven fabric with high fiber density and excellent uniformity of fiber orientation. This allows for a high level of density on the surface of the artificial leather when it is napped.

[0125] When using a short-fiber nonwoven fabric as the nonwoven material, the obtained ultrafine fiber-generating fibers are preferably crimped and cut to a predetermined length to obtain raw cotton. Known methods can be used for crimping and cutting.

[0126] Next, the obtained raw cotton is subjected to processes such as carding and cross-wrapping to form a fiber web. Then, the obtained fiber web is entangled to obtain a nonwoven fabric. As a method for entangling the fiber web to obtain a nonwoven fabric, needle punching and water jet punching can be used, but in order to keep the average pile length and surface coverage within the above range, it is preferable to use needle punching, which has high entanglement efficiency.

[0127] When performing entanglement by needle punching, a needle equipped with barbs (notches) capable of grasping 5 to 15 ultrafine fiber-generating fibers is used, and the punch density is 2000 fibers / cm². 2 Over 4000 strands / cm 2 The following is preferable. By keeping it within this range, not only is a dense nonwoven fabric formed, but fiber damage and strength reduction can be prevented, thus enabling the production of artificial leather with superior touch and strength.

[0128] <Process for forming an impregnated sheet> In this process, the fibrous substrate is impregnated with an aqueous dispersion, and then subjected to a heat-drying treatment to form an impregnated sheet. In this process, the aqueous dispersion contains a polyurethane precursor having hydrophilic groups, an inorganic salt in an amount of 1.0% 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% to 0.300% by mass relative to the aqueous dispersion. By using such an aqueous dispersion, artificial leather with a uniform surface hue and good texture can be obtained. Here, the polyurethane precursor having hydrophilic groups, the black pigment, and the chromatic pigment can be those described above. The inorganic salt and nonionic surfactant will be described later.

[0129] In the method for manufacturing artificial leather of the present invention, solidification after application of the aqueous dispersion can be carried out using solidification methods commonly used in this field, such as dry heat solidification or moist heat solidification. When using dry heat solidification, it is preferable to apply the aqueous dispersion to the fibrous substrate and then heat-treat it at a temperature of 120°C to 180°C to dry-heat solidification, thereby imparting polyurethane having hydrophilic groups to the fibrous substrate. When using moist heat solidification, it is preferable to apply the aqueous dispersion to the fibrous substrate and then heat-treat it at a temperature of 55°C to 200°C to moist-heat solidification, thereby imparting polyurethane having hydrophilic groups to the fibrous substrate.

[0130] It is preferable that the concentration of the polyurethane precursor in the aqueous dispersion (content of polyurethane precursor in 100% by mass of the aqueous dispersion) is 3% by mass or more and 30% by mass or less. When this concentration is preferably 3% by mass or more, and more preferably 5% by mass or more, the polyurethane precursor can be uniformly applied to the fibrous substrate even when the amount of polyurethane precursor applied is small. On the other hand, when the concentration is preferably 30% by mass or less, and more preferably 15% by mass or less, the storage stability of the aqueous dispersion can be improved.

[0131] Furthermore, it is preferable that the heat-sensitive solidification temperature of the aqueous dispersion is 55°C or higher and 80°C or lower. A heat-sensitive solidification temperature of preferably 55°C or higher, and more preferably 60°C or higher, can suppress gelation during the preparation and storage of the aqueous dispersion. On the other hand, a heat-sensitive solidification temperature of preferably 80°C or lower, and more preferably 70°C or lower, allows the solidification of the polyurethane precursor to proceed before the water evaporates from the fibrous substrate. This makes it possible to form a structure similar to that obtained by wet solidification of solvent-based polyurethane, i.e., a structure in which the polyurethane does not strongly restrain the fibers, thereby achieving good flexibility and resilience.

[0132] In the method for producing artificial leather of the present invention, the aqueous dispersion contains 1.0% to 10.0% by mass 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 low ionic charge have little effect on the stability of the aqueous dispersion, and by adjusting the amount added, the thermal solidification temperature can be precisely controlled while ensuring the stability of the aqueous dispersion.

[0133] Regarding the content of the inorganic salt in the aqueous dispersion, by setting this content 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 completion of solidification at a specific heat-sensitive solidification temperature. This makes it possible to form an adhesive structure of polyurethane to the fibrous substrate that is very similar to that obtained by wet solidification of solvent-based polyurethane, in the process of proceeding with the solidification of the polyurethane precursor while the fibrous substrate contains a large amount of water, as described above, and to achieve a good texture. On the other hand, by setting the 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 and a homogeneous quality can be achieved.

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

[0135] In the method for producing artificial leather of the present invention, the aqueous dispersion contains 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. The nonionic surfactant suppresses the 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, and artificial leather with a uniform surface hue can be obtained.

[0136] Here, "nonionic" refers to the property of "not dissociating into ions in water (nonionic)." Specific examples of functional groups that do not dissociate 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] Furthermore, in the method for producing artificial leather according to the present invention, the nonionic surfactant is preferably a copolymer made from two or more alkylene oxides. In this way, artificial leather with a uniform surface color can be obtained.

[0138] Specific examples of the alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, glycidol, hexaethylene glycol diepoxide, pentaerythritol oxide, ethylene glycol monoethyl ether, butylene glycol monobutyl ether, decylene oxide, trimethylene glycol monobutyl ether, and the like. Among these, ethylene oxide and propylene oxide are preferred because they allow for the production of artificial leather with a uniform surface color.

[0139] Furthermore, to confirm the structure of the nonionic surfactant (to confirm that it is a copolymer made from two or more alkylene oxides), the nonionic surfactant can be dissolved in a deuterated solvent in which it can dissolve (for example, heavy water), and the solution can be analyzed by NMR analysis (using JEOL Ltd.'s "JNM-ECZ400S" or an NMR analyzer with equivalent performance) or by pyrolysis GC / MS analysis (using Shimadzu Corporation's "GCMS-QP5050A" or a pyrolysis GC / MS analyzer with equivalent performance).

[0140] Regarding the content ratio of the nonionic surfactant in the aqueous dispersion, by setting this content ratio to 0.001% by mass or more, preferably 0.003% by mass or more, and more preferably 0.005% by mass or more, the nonionic surfactant present in the aqueous dispersion acts uniformly on the pigment, allowing the pigment to be uniformly dispersed in the water. As a result, in the process of proceeding with the coagulation of the polyurethane precursor with a large amount of inorganic salt contained in the aqueous dispersion as described above, the pigment is uniformly dispersed in the polyurethane, and an adhesive structure for polyurethane to a fibrous substrate is formed that is very similar to that obtained by wet coagulation of solvent-based polyurethane, achieving a uniform hue and good texture on the surface. On the other hand, by setting the content ratio to 0.300% by mass or less, preferably 0.250% by mass or less, and more preferably 0.200% by mass or less, an artificial leather with a uniform hue on the surface is obtained.

[0141] In the method for producing artificial leather of the present invention, a crosslinking agent can be included in the aqueous dispersion. By introducing a three-dimensional network structure into the polyurethane precursor using the crosslinking agent, physical properties such as abrasion resistance can be improved.

[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. When the concentration of the crosslinking agent is preferably 1% by mass or more, and more preferably 2% by mass or more, the crosslinking agent can introduce more three-dimensional network structures into the polyurethane precursor, resulting in artificial leather with excellent abrasion resistance and other properties. On the other hand, when the concentration of the crosslinking agent is 10% by mass or less, and more preferably 7% by mass or less, it is possible to suppress the inhibition of solidification of the polyurethane precursor by an excess of crosslinking agent, and thus suppress the deterioration of physical properties such as abrasion resistance.

[0143] Furthermore, the crosslinking agent in the method for manufacturing artificial leather of the present invention is preferably a carbodiimide-based crosslinking agent and / or a blocked isocyanate crosslinking agent. By doing so, a three-dimensional crosslinked structure can be imparted to the polyurethane molecules in the artificial leather by N-acylurea bonds and / or isourea bonds, which have excellent physical properties such as light resistance, heat resistance, and abrasion resistance, as well as flexibility. This makes it possible to dramatically improve physical properties such as durability and abrasion resistance while maintaining the flexibility of the artificial leather.

[0144] Then, the fibrous base material is impregnated with the aqueous dispersion, and subsequently 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 between 110°C and 180°C. By setting this temperature preferably above 110°C, and more preferably above 120°C, not only is the drying efficiency of the sheet increased, but the progress of the crosslinking reaction can be promoted, resulting in higher physical properties such as durability and abrasion resistance of the artificial leather. On the other hand, by setting the temperature preferably below 180°C, and more preferably below 170°C, thermal degradation of the polyurethane can be suppressed.

[0146] Furthermore, it is preferable to set the heating and drying time to 5 minutes or more and 30 minutes or less. By setting this time to preferably 5 minutes or more, and more preferably 10 minutes or more, it is possible to accelerate 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, and more preferably 25 minutes or less, it is possible to suppress thermal degradation of polyurethane due to excessive heating.

[0147] <Process for obtaining ultrafine fiber sheets> In this process, polyester ultrafine fibers with an average single fiber diameter of 1.0 μm to 10.0 μm are generated from the ultrafine fiber-generating fibers of the impregnated sheet, thereby forming an ultrafine fiber sheet.

[0148] When using sea-island composite fibers as ultrafine fiber-generating fibers, the fiber ultrafineization treatment (de-sea treatment) can be carried out, for example, by immersing the sea-island composite fibers in a solvent followed by heat treatment. The solvent used to dissolve the sea component can be appropriately selected depending on the type of sea component; if the sea component is copolymerized polyester, an alkaline aqueous solution such as sodium hydroxide can be used.

[0149] When using an alkaline aqueous solution as a solvent for desalination, it is preferable that the molar concentration of the alkaline aqueous solution be 3.0 mol / L or less in order to prevent excessive degradation of the polyurethane.

[0150] During this desalination process, inorganic salts, nonionic surfactants, and solid components derived from silicones and non-silicone fiber oils that were attached to the fibrous substrate are usually removed along with the marine components.

[0151] <Heat treatment process> In the method for manufacturing artificial leather of the present invention, dyeing or other processing may be performed directly on the product after the above steps have been completed. However, it is preferable to heat-treat the ultrafine fiber sheet in order to improve the abrasion resistance and flexibility of the artificial leather. As for the method of heat treatment, it is preferable to use a hot air dryer such as a floater dryer, drum dryer, or pin tenter.

[0152] First, it is preferable to set the ambient temperature in the heat treatment to 150°C or higher and 200°C or lower. By setting this ambient temperature to preferably 150°C or higher, and more preferably 155°C or higher, the adhesion between the ultrafine fibers and polyurethane is improved, which not only improves the abrasion resistance of the artificial leather but also reduces the molecular weight of a portion of the polyurethane, thereby increasing the flexibility of the artificial leather. On the other hand, by setting the ambient temperature to preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower, it is possible to gradually reduce the molecular weight of a portion of the polyurethane.

[0153] Next, it is preferable to set the heating time to 5 minutes or more and 20 minutes or less. By setting the heating time to preferably 5 minutes or more, more preferably 6 minutes or more, the adhesion between the ultrafine fibers and polyurethane is 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 decrease in the physical properties of the artificial leather due to excessive reduction of the molecular weight of the polyurethane.

[0154] This heat treatment is preferably performed after the process of forming the ultrafine fiber sheet, but it is even more preferable to perform it immediately after the process of forming the ultrafine fiber sheet (immediately after the process of forming the ultrafine fiber sheet) in order to suppress the deterioration of quality due to elongation during the process.

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

[0156] Furthermore, in the method for manufacturing artificial leather of the present invention, the product obtained after completing the above steps may be used as artificial leather as is, but it is preferable to perform various finishing processes, just as with general artificial leather. Of course, it goes without saying that artificial leather that has undergone post-processing is also treated as artificial leather in the present invention.

[0157] First, in the method for manufacturing artificial leather of the present invention, it is preferable to include a step of dyeing the ultrafine fiber sheet (including the heat-treated ultrafine fiber sheet) with a disperse dye. Various methods commonly used in this field can be used for this dyeing process. For example, immersion dyeing treatments such as liquid flow dyeing using a jigger dyeing machine or liquid flow dyeing machine, thermosol dyeing treatment using a continuous dyeing machine, or printing treatments on the napped surface using roller printing, screen printing, inkjet printing, sublimation printing, and vacuum sublimation printing can be used. In particular, it is preferable to use a liquid flow dyeing machine because it can soften the unnapped artificial leather or artificial leather by simultaneously providing a kneading effect while dyeing it. Furthermore, various resin finishing processes can be applied after dyeing as needed.

[0158] Furthermore, when dyeing the aforementioned ultrafine fiber sheet (including the heat-treated ultrafine fiber sheet) with a disperse dye, a finishing treatment using, for example, a softener such as silicone, an antistatic agent, a water repellent, a flame retardant, a lightfastener, and an antibacterial agent can be applied in the same bath or after dyeing.

[0159] Furthermore, in the method for manufacturing artificial leather of the present invention, it is also preferable to cut the ultrafine fiber sheet in half in the thickness direction, both before and after the step of dyeing it with a disperse dye, from the viewpoint of manufacturing efficiency.

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

[0161] When applying a napped finish, a lubricant such as a silicone emulsion can be applied to the surface of the artificial leather before the napping process. Additionally, applying an antistatic agent before the napping process reduces the accumulation of grinding dust on the sandpaper. In this way, the artificial leather is formed.

[0162] Furthermore, in the method for manufacturing artificial leather of the present invention, post-processing treatments such as perforation, embossing, laser processing, pin sonic processing, and printing can be applied to the artificial leather as needed.

[0163] [Various applications including clothing, furniture, general merchandise, vehicle interior materials, and automotive parts] The artificial leather of the present invention is suitable for a wide range of applications, including fashion and automotive, due to its excellent uniformity of surface color and texture. Therefore, clothing containing the aforementioned artificial leather is one preferred embodiment, as it can take advantage of these characteristics. 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 cloaks; trousers such as slacks, jeans, and shorts; skirts; dresses such as cocktail dresses, one-piece dresses, and gowns; ceremonial clothing, suits, uniforms, and underwear. It is preferable that at least a part of these garments, such as the front, back, sleeves, collar, facing, hem, inseam, and lining, or at least a part of the clothing materials and accessories such as buttons, interlining, and pockets, is made of the aforementioned artificial leather.

[0164] Furthermore, furniture containing the aforementioned artificial leather is also one of the preferred embodiments. Examples of such furniture include chairs, sofas, and stools. It is preferable that at least a part of such furniture, such as the seat or backrest, is made of the aforementioned artificial leather.

[0165] Furthermore, miscellaneous goods containing the aforementioned artificial leather are also a preferred embodiment. Examples of such miscellaneous goods include shoes, hats, accessories such as bags, belts, scarves, ties, and wallets, and interior items such as cushions, armrests, and neck pillows.

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

[0167] Furthermore, examples of the aforementioned bags include handbags, tote bags, shoulder bags, Boston bags, waist pouches, briefcases, attaché cases, and school bags. Preferably, at least a part of such bags, such as the handles, inner lining, base leather, gussets, and bottom, is made of the aforementioned artificial leather.

[0168] On the other hand, the interior materials for vehicles that include the aforementioned artificial leather are preferable because they can take advantage of the characteristics that allow for a high level of balance between a dense and elegant surface quality, a good touch, and tensile strength, while reducing the environmental burden. Such interior materials for vehicles are preferably used in automobile parts such as steering wheels, horn switches, shift knobs, dashboards, instrument panels, glove boxes, floor carpets, floor mats, headliners, sun visors, and assist grips, and it is more preferable that these automobile parts include the aforementioned artificial leather. In this invention, "vehicle" includes automobiles, aircraft, railway vehicles, ships, as well as carriages, palanquins, rickshaws, and other vehicles, and also includes some industrial machinery, construction machinery, and agricultural machinery that can carry people or animals, such as excavators, cranes, tractors, and combine harvesters. [Examples]

[0169] The artificial leather of the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

[0170] [Evaluation Method] The evaluation methods and measurement conditions used in the examples are described below. Unless otherwise specified, the measurements of each physical property were performed based on the methods described above.

[0171] (1) Average single fiber diameter of polyester ultrafine fibers (μm): The average single fiber diameter (μm) was measured and calculated using the method described above with a scanning electron microscope (SEM) manufactured by Keyence Corporation, specifically the "VHX-D500 / D510".

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

[0173] (3) Average particle size (μm) of pigments in polyurethane, average degree of pigment irregularity (unitless): The average particle size and average degree of irregularity of pigments in polyurethane were measured and calculated using the above method, with 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 percentage of pigment in polyurethane (mass): The total pigment content in the polyurethane was measured and calculated using the method described above.

[0175] (5) The coefficient of variation (%) of the mass ratio of polyurethane in each layer when artificial leather is divided into three equal parts in the thickness direction: The coefficient of variation of the mass ratio 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 length of the upright hair was measured and calculated using the method described above with a scanning electron microscope (SEM) manufactured by Keyence Corporation, specifically the "VHX-D500 / D510".

[0177] (7) Pile coverage rate (%): The pile coverage rate was measured and calculated using the method described above, with a scanning electron microscope, the "VHX-D500 / D510" manufactured by Keyence Corporation, and the image analysis software, "ImageJ".

[0178] (8) Weight loss due to wear (mg): In the Martindale abrasion test specified in "8.19 Abrasion Strength and Friction Discoloration" of "8.19.5 Method E (Martindale Method)" of the aforementioned JIS L1096:2005 "Test Methods for Woven and Knitted Fabrics," the abrasion loss (mg) measured with a pressing load of 12 kPa and 20,000 abrasion cycles was measured using James H. Heal & Co.'s "Model 406" as the Martindale abrasion tester and their "ABRASTIVE CLOTH SM25" as the standard friction cloth. The abrasion loss (mg) was then calculated using the following formula and rounded to the first decimal place. Weight loss due to wear (mg) = Mass before wear (mg) - Mass after wear (mg) ... (Formula).

[0179] (9) Texture: The texture was evaluated by 20 healthy adults who judged the following evaluations by touch, and the most frequent evaluation was defined as the texture. In this invention, a good level is "A or B". A: It's soft and doesn't offer any resistance when you grip it. B: It feels slightly resistant when you grip it, but it's soft. C: It feels very hard and has a lot of resistance when you grip it.

[0180] (10) Uniformity of surface hue: The uniformity of surface hue was assessed by 20 healthy adults who visually distinguished between the following evaluations. The most frequent evaluation was defined as the uniformity of surface hue. In this invention, a good level is "A or B". A: It has a uniform hue. B: There is some unevenness in color, but the hue is uniform. C: This hue has a lot of color unevenness and variation.

[0181] [Polyurethane precursor] The hydrophilic polyurethane precursors used in the examples and comparative examples are as follows: High molecular weight polyol: Polytetramethylene glycol Organic diisocyanates: MDI Compounds containing active hydrogen components with hydrophilic groups: 2,2-dimethylolpropionic acid Chain extender: Ethylene glycol. The above-mentioned polymeric polyol was reacted with an organic diisocyanate and a hydrophilic compound containing an active hydrogen component to form a hydrophilic prepolymer, and then the above-mentioned chain extender was added and reacted to prepare the product.

[0182] [Example 1] <Process for forming a fibrous substrate> A copolymer polyester obtained by copolymerizing 8 mol% sodium 5-sulfoisophthalate as the sea component and polyethylene terephthalate as the island component was used. A sea-island composite fiber was obtained with a sea component mass ratio of 20% by mass, 16 islands / filament, and a single fiber fineness of 3.8 dtex. The obtained sea-island composite fiber was cut to a fiber length of 51 mm, and then subjected to carding and cross-wrapping processes to form a fiber web. Furthermore, this fiber web was processed at a rate of 3500 fibers / cm using a needle equipped with barbs capable of gripping up to 10 sea-island composite fibers. 2 A fibrous base material, which is a short-fiber nonwoven fabric, was formed by needle punching at a punch density. The resulting fibrous base material had a basis weight of 600 g / m². 2 The thickness is 2.4 mm, and the apparent density is 0.25 g / cm³. 3 That was the case.

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

[0184] <Process for obtaining ultrafine fiber sheets> The resulting impregnated sheet was immersed in a 1.3 mol / L sodium hydroxide aqueous solution, and then squeezed with a mangle to achieve a 100% pick-up rate of the sodium hydroxide aqueous solution. Furthermore, the marine components of the sea-island type composite fiber were alkalinely decomposed by heat treatment with 95°C steam for 10 minutes. Subsequently, the excess sodium hydroxide, surfactant, and sodium sulfate were washed off with water to reveal polyester ultrafine fibers with an average single fiber diameter of 4.4 μm, thereby obtaining an ultrafine fiber sheet.

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

[0186] <Finishing Process> A heat-treated ultrafine fiber sheet was cut in half perpendicular to its thickness, and the opposite side of the cut surface was ground with 150-grit endless sandpaper to obtain a pile sheet.

[0187] This pile sheet was dyed using a disperse dye at a temperature of 120°C using a jet dyeing machine. Next, it was dried in a dryer to obtain 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 the content of the nonionic surfactant in the aqueous dispersion was changed from 0.170% by mass to 0.002% by mass in the <process of forming the impregnated sheet>. The results are shown in Table 1. The obtained artificial leather had a good texture and, although there was some unevenness in color, it had a uniform hue on the surface.

[0189] [Example 3] Artificial leather was obtained in the same manner as in Example 1, except that 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) in the <process of forming the impregnated sheet>. 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 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 polyurethane was 2.10% by mass) in the <process of forming the impregnated sheet>. 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 it was within a practical range, and it also had a good texture and a uniform hue on the surface.

[0191] [Example 5] In the finishing process, the sandpaper grit was changed from 150 to 120, but otherwise the process was the same as in Example 1 to obtain artificial leather. The results are shown in Table 2. The obtained artificial leather had a slightly higher nap and fluffiness on the surface compared to Example 1, but it was within a practical range and had a good texture and uniform color on the surface.

[0192] [Example 6] In the <process of forming the 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). Furthermore, in the <finishing process>, the grit of the sandpaper was changed from 150 to 120. The artificial leather was obtained in the same manner as in Example 1, except for these changes. The results are shown in Table 2. The obtained artificial leather had a surface quality with slightly more nap than Example 1, but it was within a practical range and had a flexible 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 the inorganic salt content in the aqueous dispersion was changed from 5.0% by mass to 1.1% by mass in the <process of forming the impregnated sheet>. The results are shown in Table 2. The obtained artificial leather had a slightly resistant texture but was flexible and had a uniform hue on the surface.

[0194] [Example 8] Artificial leather was obtained in the same manner as in Example 1, except that the inorganic salt content in the aqueous dispersion was changed from 5.0% by mass to 9.9% by mass in the <process of forming the impregnated sheet>. 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 the type of inorganic salt in the aqueous dispersion was changed from sodium sulfate to sodium chloride in the <process of forming the impregnated sheet>. The results are shown in Table 3. The obtained artificial leather had a flexible 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 the type of inorganic salt in the aqueous dispersion was changed from sodium sulfate to ammonium sulfate in the <process of forming the impregnated sheet>. The results are shown in Table 3. The obtained artificial leather had a flexible texture and a uniform hue on the surface.

[0197] [Example 11] In the process of forming the impregnated sheet, the content of the nonionic surfactant in the aqueous dispersion was changed from 0.170% by mass to 0.295% by mass, but otherwise the same procedure as in Example 1 was used to obtain artificial leather. The results are shown in Table 3. The obtained artificial leather had a sufficiently uniform hue and good texture, although it had some color unevenness on the surface compared to Example 1.

[0198] [Example 12] Artificial leather was obtained in the same manner as in Example 1, except that in the <step of forming the 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 sufficiently uniform hue and good texture, although there was some color unevenness on the surface compared to Example 1.

[0199] [Comparative Example 1] In the process of forming the impregnated sheet, the nonionic surfactant content in the aqueous dispersion was 0.170% by mass. In this case, artificial leather was obtained in the same manner as in Example 1, except that the nonionic surfactant was not included at all 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 inferior.

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

[0201] [Comparative Example 3] In the process of forming the impregnated sheet, the inorganic salt content in the aqueous dispersion was 5.0% by mass, but artificial leather was obtained in the same manner as in Example 1, except that the inorganic salt content in the aqueous dispersion was completely removed. The results are shown in Table 4. The obtained artificial leather had a uniform hue on the surface, but its texture was significantly inferior.

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

[0203] [Table 1]

[0204] [Table 2]

[0205] [Table 3]

[0206] [Table 4] [Explanation of symbols]

[0207] 1: A line drawn along the outermost edge of the pigment. 2: The circle with the largest diameter contained within a line drawn along the outermost edge of the pigment. 3: A circle drawn such that the maximum distance between two points on a line drawn along the outermost edge of the pigment becomes the diameter.

Claims

1. Artificial leather comprising a fibrous base material and polyurethane, The fibrous base material includes a nonwoven fabric composed of polyester ultrafine fibers with an average single fiber diameter of 1.0 μm or more and 10.0 μm or less. The polyurethane has hydrophilic groups and further comprises a black pigment and / or a chromatic pigment. The aforementioned pigment is The average particle size of the pigment is 0.01 μm or more and 0.10 μm or less. The average degree of irregularity of the pigment is 0.50 or more and 1.00 or less. Artificial leather in which the coefficient of variation of the mass ratio of polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction 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 pile of 200 μm or more and 500 μm or less.

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

5. Clothing comprising artificial leather as described in claim 1 or 2.

6. Furniture comprising artificial leather as described in claim 1 or 2.

7. A general merchandise item comprising artificial leather as described in claim 1 or 2.

8. A vehicle interior material comprising artificial leather as described in claim 1 or 2.

9. Automotive part comprising artificial leather according to claim 1 or 2.

10. A process of forming a fibrous base material including a nonwoven fabric composed of ultrafine fiber-generating fibers, The process involves impregnating the fibrous base material with an aqueous dispersion, and then performing a heat drying treatment to form an impregnated sheet. A step of forming an ultrafine fiber sheet by generating polyester ultrafine fibers with an average single fiber diameter of 1.0 μm or more and 10.0 μm or less from the ultrafine fiber-generating fibers of the impregnated sheet, A method for manufacturing artificial leather having the following characteristics: The aforementioned aqueous dispersion is A precursor of polyurethane having a hydrophilic group, The aqueous dispersion contains 1.0% to 10.0% by mass of an inorganic salt, Black pigment, and / or chromatic pigment, 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, Includes, A method for producing artificial leather, wherein the average particle size of the pigment in the polyurethane is 0.01 μm or more and 0.10 μm or less, the average degree of irregularity of the pigment is 0.50 or more and 1.00 or less, and the coefficient of variation of the mass ratio of polyurethane in each layer when the artificial leather is divided into three equal parts in the thickness direction 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 alkylene oxides.

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