artificial leather

Abstract

To provide an artificial leather for a material for clothing excellent in touch feeling, glossy feeling, color fastness, and color rendering property while having deep and even color development.SOLUTION: An artificial leather comprises: a fiber-entangled body including a nonwoven fabric comprising an ultrafine fiber having an average single fiber diameter of 0.01 μm or more and 3.0 μm or less as a constitution component; and a polymer elastomer, where the artificial leather satisfies the following requirements. Requirement 1: the ultrafine fiber is composed of a polyester-based resin containing a black pigment (a). Requirement 2: the average particle size of the black pigment (a) is 0.05 μm or more and 0.20 μm or less, and the variation coefficient (CV) of the average particle size is 75% or more. Requirement 3: an average distance between the most neighboring black pigments (a) is 0.1 μm or more and 0.7 μm or less. Requirement 4: the polymer elastomer contains a black pigment (b).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an artificial leather comprising a fiber-entangled body containing a nonwoven fabric made of polyester ultrafine fibers as a component and a polymeric elastomer, which has deep, uniform color development, while also exhibiting excellent touch, gloss, and color fastness. [Background technology]

[0002] Artificial leathers with a natural leather look, which are made of a fiber-entangled body containing a nonwoven fabric mainly made of polyester ultrafine fibers as a component, and a polymeric elastomer, have superior characteristics compared to natural leather, such as high durability and uniform quality, and are used not only as clothing materials but also in a variety of fields, such as vehicle interior materials, interior goods, shoes, and clothing. When artificial leathers are used as clothing materials, etc., they are required to have a good feel, as well as uniform color development in dark colors such as black, an elegant luster, and color fastness sufficient for practical use.

[0003] By using a nonwoven fabric made of polyester ultrafine fibers with an average single fiber diameter of 0.01 μm to 10.0 μm and improving the surface smoothness of the artificial leather, it is possible to obtain artificial leather with a consistent touch and luster. However, polyester fibers have a high refractive index and poor color development compared to other synthetic fibers such as acetate fibers, acrylic fibers, and nylon fibers, making them difficult to dye in dark colors. This tendency is particularly pronounced for ultrafine fibers, as the specific surface area increases as the fiber diameter decreases. In response to this, attempts have been made to increase the dye concentration to achieve uniform dark color development, but this results in a decrease in the color fastness of the artificial leather, such as lightfastness and abrasion fastness. Therefore, there has long been a need for a method for achieving both a good touch and elegant luster in artificial leather made from polyester ultrafine fibers, as well as uniform dark color development and color fastness.

[0004] To address the above-mentioned issues, a method of adding a pigment to ultrafine fibers, i.e., a method of using so-called dyed fibers, has been proposed as a means of achieving both deep, uniform color development and dye fastness in artificial leather using ultrafine fibers (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2004-143654 [Patent Document 2] Japan Special Publication No. 2011-523985 [Patent Document 3] International Publication No. 2018 / 124524 [Patent Document 4] Japanese Patent Application Publication No. 2018-178297 Summary of the Invention [Problem to be solved by the invention]

[0006] The techniques disclosed in Patent Documents 1 to 4 use pigments that have superior lightfastness compared to dyes, which makes it possible to some extent to achieve darker colors without reducing lightfastness. However, the pigments are partially exposed on the surface of the ultrafine fibers and absorb light, which can result in the loss of the elegant luster desired for clothing materials.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an artificial leather for use as a material for clothing, which comprises a fiber-entangled body containing a nonwoven fabric made of polyester ultrafine fibers as a constituent element and a polymeric elastomer, and which has deep, uniform color development, while also exhibiting excellent touch, gloss, and dye fastness. [Means for solving the problem]

[0008] In order to achieve the above object, the inventors conducted extensive research and found that by setting the average particle size of the black pigment in the ultrafine fibers within a specified range and reducing the variation in the average particle size, processing is possible without impairing spinning operability. Further research revealed that by setting the distance between adjacent black pigment particles within a specific range and suppressing the exposure of the pigment on the surface of the ultrafine fibers, it is possible to produce artificial leather that has a deep, uniform color development while also having excellent touch, gloss, and dye fastness. Furthermore, it was also found that this artificial leather has excellent color rendering properties.

[0009] The present invention has been completed based on these findings, and provides the following inventions.

[0010] The artificial leather of the present invention is an artificial leather comprising a fiber-entangled body containing, as a constituent element, a nonwoven fabric made of ultrafine fibers having an average single fiber diameter of 0.01 μm or more and 3.0 μm or less, and a polymeric elastomer, and satisfies the following requirements:

[0011] Requirement 1: The ultrafine fibers are made of a polyester resin containing a black pigment (a). Requirement 2: The average particle size of the black pigment (a) is 0.05 μm or more and 0.20 μm or less, and the coefficient of variation (CV) of the average particle size is 75% or less. Requirement 3: The average distance between the black pigments (a) nearest to each other is 0.15μm or more and 0.50μm or less is Requirement 4: The polymeric elastomer contains a black pigment (b).

[0012] According to a preferred embodiment of the artificial leather of the present invention, the content (A) of the black pigment (a) contained in the ultrafine fibers is 0.1% by mass or more and 5.0% by mass or less.

[0013] According to a preferred embodiment of the artificial leather of the present invention, the nap coverage of the nap-bearing surface of the artificial leather is 60% or more and 100% or less.

[0014] According to a preferred embodiment of the artificial leather of the present invention, the artificial leather has a nap length of 200 μm or more and 500 μm or less.

[0015] According to a preferred embodiment of the artificial leather of the present invention, the black pigment (b) has an average particle size of 0.05 μm or more and 0.20 μm or less, and the coefficient of variation (CV) of the average particle size is 75% or less.

[0016] According to a preferred embodiment of the artificial leather of the present invention, the content (B) of the black pigment (b) contained in the polymeric elastomer is 0.01% by mass or more and 5.0% by mass or less.

[0017] According to a preferred embodiment of the artificial leather of the present invention, the polymeric elastomer is polyurethane. [Effects of the Invention]

[0018] According to the present invention, it is possible to obtain artificial leather that has deep, uniform color development and high color rendering properties, is excellent in touch and gloss, and has excellent color fastness to light irradiation, friction, etc. DETAILED DESCRIPTION OF THE INVENTION

[0019] The artificial leather of the present invention is an artificial leather comprising a fiber-entangled body containing, as a constituent element, a nonwoven fabric made of ultrafine fibers having an average single fiber diameter of 0.01 μm or more and 3.0 μm or less, and a polymeric elastomer, and satisfies the following requirements: Requirement 1: The ultrafine fibers are made of a polyester resin containing a black pigment (a). Requirement 2: The average particle size of the black pigment (a) is 0.05 μm or more and 0.20 μm or less, and the coefficient of variation (CV) of the average particle size is 75% or less. Requirement 3: The average distance between the black pigments (a) nearest to each other is 0.15μm or more and 0.50μm or less is Requirement 4: The polymeric elastomer contains a black pigment (b). These components will be described in detail below, but the present invention is not limited to the scope of the following description as long as it does not deviate from the gist of the invention.

[0020] [Fiber entanglement] The ultrafine fibers constituting the fiber-entangled structure used in the present invention are made of a polyester resin from the viewpoints of durability, particularly mechanical strength and heat resistance.

[0021] Examples of the polyester resin include polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polycyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, and polyethylene-1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate. Among these, polyethylene terephthalate, which is the most widely used, or a polyester copolymer containing mainly ethylene terephthalate units is preferably used.

[0022] Furthermore, as the polyester-based resin, a single polyester or two or more different polyesters may be used. When two or more different polyesters are used, from the viewpoint of compatibility between the two or more components, the difference in intrinsic viscosity (IV value) of the polyesters used is preferably 0.50 or less, and more preferably 0.30 or less.

[0023] In the present invention, the intrinsic viscosity is calculated by the following method. (1) Dissolve 0.8 g of sample polymer in 10 mL of orthochlorophenol. (2) Relative viscosity η measured using an Ostwald viscometer at 25°C r Calculate using the formula below and round off to the third decimal place.

[0024] η r =η / η0=(t×d) / (t0×d0) Intrinsic viscosity (IV value) = 0.0242η r +0.2634 (where η is the viscosity of the polymer solution, η0 is the viscosity of orthochlorophenol, t is the solution drop time (seconds), and d is the solution density (g / cm 3 ), t0 is the fall time of orthochlorophenol (seconds), and d0 is the density of orthochlorophenol (g / cm3 ) respectively.

[0025] From the viewpoint of processing operability, the cross-sectional shape of the ultrafine fibers is preferably a round cross-section. However, cross-sectional shapes such as an oval, a polygonal shape (e.g., a flat or triangular shape), a sector shape, a cross shape, a hollow shape, a Y shape, a T shape, and a U shape can also be used depending on the desired properties.

[0026] The average single fiber diameter of the ultrafine fibers is 0.01 μm or more and 3.0 μm or less. By making the average single fiber diameter of the ultrafine fibers 0.01 μm or more, preferably 0.5 μm or more, excellent effects are achieved in color development after dyeing, light fastness and friction fastness, and stability during spinning. On the other hand, by making the average single fiber diameter of the ultrafine fibers 3.0 μm or less, preferably 2.5 μm or less, a dense artificial leather with an excellent feel, particularly suitable for clothing applications, can be obtained.

[0027] In the present invention, the average single fiber diameter of ultrafine fibers is calculated by taking a scanning electron microscope (SEM) photograph of the cross section of the artificial leather, randomly selecting 10 circular or elliptical ultrafine fibers, measuring the single fiber diameters, calculating the arithmetic average of the 10 fibers, and rounding off to one decimal place. However, when ultrafine fibers with a modified cross section are used, the diameter of the single fiber is determined by first measuring the cross-sectional area of the single fiber and calculating the diameter when the cross section is considered to be circular.

[0028] In order to achieve both deep and uniform color development and an elegant luster in the artificial leather of the present invention, the ultrafine fibers of the artificial leather of the present invention are made of a polyester resin containing a black pigment (a), and the average particle size of this black pigment (a) is 0.05 μm or more and 0.20 μm or less, and the coefficient of variation (CV) of the particle size is 75% or less.

[0029] The average particle size of the black pigment (a) referred to here is the average particle size of the black pigment (a) when it is present in the ultrafine fibers, and is generally referred to as the secondary particle size.

[0030] By setting the average particle size of the black pigment (a) to 0.05 μm or more, preferably 0.07 μm or more, the black pigment (a) is retained inside the ultrafine fibers, thereby preventing the pigment from falling off from the ultrafine fibers. Also, by setting the average particle size of the black pigment (a) to 0.20 μm or less, preferably 0.18 μm or less, more preferably 0.16 μm or less, the pigment is prevented from being exposed to the surface of the ultrafine fibers, and excellent stability during spinning and yarn strength are achieved.

[0031] When the coefficient of variation (CV) of the particle size of the black pigment (a) is 75% or less, preferably 65% or less, more preferably 60% or less, even more preferably 55% or less, and most preferably 50% or less, the particle size distribution becomes narrow, and exposure of the pigment on the surface of the ultrafine fiber, falling off of small particles from the surface, poor spinning due to significant particle aggregation, and a significant decrease in yarn strength are suppressed. Note that there is no particular lower limit for the coefficient of variation of the particle size in the present invention, but from the viewpoint of spinning operability and production costs, it is preferably 0.1% or more.

[0032] In the present invention, the average particle size and coefficient of variation (CV) of the black pigment (a) are calculated by the following method. (1) Prepare ultrathin sections with a thickness of 5 to 10 μm in the cross-sectional direction perpendicular to the longitudinal direction of the ultrafine fibers. (2) Observe the cross section of the fiber in the ultrathin section using a transmission electron microscope (TEM) at 10,000x magnification. (3) Using image analysis software, measure the circle-equivalent diameter of the particle size of black pigment (a) at 20 points within a 2.3 μm × 2.3 μm field of view of the observed image. If there are fewer than 20 particles of black pigment (a) within the 2.3 μm × 2.3 μm field of view, measure the circle-equivalent diameter of all particles of black pigment (a) present. (4) Calculate the average value (arithmetic mean) and coefficient of variation (CV) for the particle diameters measured at 20 points. In the present invention, the coefficient of variation is calculated using the following formula: Coefficient of variation of particle size (%) = (standard deviation of particle size) / (arithmetic mean of particle size) × 100.

[0033] In the present invention, in order to achieve both deep, uniform color development and an elegant luster, it is important that the average distance between the most adjacent black pigments (a) is 0.1 μm or more and 0.7 μm or less. By setting the average distance to 0.1 μm or more, preferably 0.15 μm or more, the coefficient of variation of the average particle size of the black pigment (a) becomes smaller. Furthermore, by setting the average distance to 0.60 μm or less, preferably 0.50 μm or less, more preferably 0.40 μm or less, the exposure of the pigment to the surface of the ultrafine fiber can be suppressed.

[0034] In the present invention, the average distance between the most adjacent black pigments (a) is calculated by the following method. (1) Prepare ultrathin sections with a thickness of 5 to 10 μm in the cross-sectional direction perpendicular to the longitudinal direction of the ultrafine fibers. (2) Observe the cross section of the fiber in the ultrathin section using a transmission electron microscope (TEM) at 10,000x magnification. (3) Using image analysis software, measure the distance between the nearest black pigment (a) particles at 20 points within a 2.3 μm × 2.3 μm field of view of the observed image. If there are fewer than 20 particles of black pigment (a) within the 2.3 μm × 2.3 μm field of view, measure the distance between all of the black pigments (a) that are present and their nearest neighbors. (4) Calculate the average (arithmetic mean) of the particle diameters measured at 20 points.

[0035] The content (A) of the black pigment (a) contained in the polyester resin forming the ultrafine fibers is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 2.0% by mass or more and 5.0% by mass or less, based on the mass of the ultrafine fibers. By setting the pigment content to 0.1% by mass or more, preferably 1.0% by mass or more, more preferably 2.0% by mass or more, even more preferably 2.5% by mass or more, and most preferably 3.0% by mass or more, artificial leather with excellent dark color development can be obtained. By setting the pigment content to 5.0% by mass or less, preferably 4.5% by mass or less, and more preferably 4.0% by mass or less, artificial leather with excellent physical properties such as strength and elongation can be obtained.

[0036] In the present invention, the content (A) of the black pigment (a) contained in the polyester resin forming the ultrafine fibers is calculated by the following method. (1) The artificial leather is immersed in a solution containing dimethylformamide or the like to remove the polymeric elastomer and extract ultrafine fibers. (2) The polyester resin in the collected ultrafine fibers is dissolved using a mixture of phenol and tetrachloroethane, and only the black pigment (a) is extracted. (3) The extracted black pigment (a) is subjected to evolved gas analysis, and a calibration curve for evolved gas from the black pigment (a) is prepared. (4) After the artificial leather is de-dyed, the polymeric elastomer is extracted using dimethylformamide or the like to leave only the ultrafine fibers, and the ultrafine fibers are then collected. (5) Perform evolved gas analysis on the collected ultrafine fibers, and calculate the proportion of black pigment (a) contained in the ultrafine fibers from the detected intensity of evolved gas derived from black pigment (a) and the calibration curve created in (3).

[0037] The black pigment (a) in the present invention may be a carbon-based black pigment such as carbon black or graphite, or an oxide-based black pigment such as triiron tetroxide, a composite oxide of copper and chromium, etc. From the viewpoints of easily obtaining a black pigment with a small particle size and excellent dispersibility in polymers, it is preferable that the black pigment (a) be carbon black.

[0038] In addition to the black pigment and the chromatic fine particle oxide pigment, inorganic particles such as titanium oxide particles, lubricants, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, and the like can be added to the polyester resin forming the ultrafine fibers according to various purposes, within the range that does not impair the object of the present invention.

[0039] The artificial leather of the present invention has as one of its constituent elements a fiber-entangled body containing, as a constituent element, a nonwoven fabric made of ultrafine fibers made of the polyester-based resin.

[0040] In the present invention, the term "a fiber-entangled body containing a nonwoven fabric as a component" refers to an embodiment in which the fiber-entangled body is a nonwoven fabric, an embodiment in which a nonwoven fabric and a woven fabric are entangled and integrated as described below, and an embodiment in which a fiber-entangled body is entangled and integrated with a nonwoven fabric and a substrate other than a woven fabric.

[0041] By forming a fiber-entangled body containing a nonwoven fabric as a constituent element, it is possible to obtain a uniform and elegant appearance and texture when the surface is raised.

[0042] Nonwoven fabrics come in two forms: long-fiber nonwoven fabrics composed mainly of filaments, and short-fiber nonwoven fabrics composed mainly of fibers 100 mm or less. Long-fiber nonwoven fabrics are preferred as fibrous substrates, as they produce artificial leathers with excellent strength. Short-fiber nonwoven fabrics, on the other hand, allow for more fibers to be oriented in the thickness direction of the artificial leather than long-fiber nonwoven fabrics, resulting in a highly dense surface for the artificial leather after nap raising.

[0043] When using a short-fiber nonwoven fabric, the fiber length of the ultrafine fibers is preferably 25 mm or more and 90 mm or less. By setting the fiber length to 90 mm or less, more preferably 80 mm or less, and even more preferably 70 mm or less, good quality and texture can be achieved. On the other hand, by setting the fiber length to 25 mm or more, more preferably 35 mm or more, and even more preferably 40 mm or more, artificial leather with excellent abrasion resistance can be obtained.

[0044] The basis weight of the nonwoven fabric constituting the artificial leather of the present invention is measured according to "6.2 Mass per unit area (ISO method)" of JIS L1913:2010 "General nonwoven fabric testing method", and is 50 g / m 2 More than 400g / m 2 The weight of the nonwoven fabric is preferably in the range of 50 g / m 2 More preferably, 80 g / m 2 By setting the weight of the nonwoven fabric to 400 g / m or more, an artificial leather having a rich feel and excellent texture can be obtained. 2 Less than 300 g / m2 By doing as follows, it is possible to obtain a flexible artificial leather with excellent moldability.

[0045] In the artificial leather of the present invention, a woven fabric may be laminated inside or on one side of the nonwoven fabric to be entangled and integrated, in order to improve its strength and shape stability.

[0046] The type of fiber used to form the woven fabric when entangling and integrating the above-mentioned woven fabrics is preferably a filament yarn, a spun yarn, a composite yarn made of a filament yarn and a spun yarn, or the like. From the viewpoint of durability, particularly mechanical strength, it is more preferable to use a multifilament made of a polyester resin or a polyamide resin.

[0047] By setting the average single fiber diameter of the fibers constituting the woven fabric to preferably 50.0 μm or less, more preferably 15.0 μm or less, and even more preferably 13.0 μm or less, not only can an artificial leather with excellent flexibility be obtained, but even if the fibers of the woven fabric are exposed on the surface of the artificial leather, the hue difference with the pigment-containing ultrafine fibers after dyeing is small, so the uniformity of the surface hue is not impaired. On the other hand, by setting the average single fiber diameter to preferably 1.0 μm or more, more preferably 8.0 μm or more, and even more preferably 9.0 μm or more, the dimensional stability of the artificial leather product is improved.

[0048] In the present invention, the average single fiber diameter of the fibers constituting the woven fabric is calculated by taking a scanning electron microscope (SEM) photograph of the cross section of the artificial leather, randomly selecting 10 fibers constituting the woven fabric, measuring the single fiber diameter of the selected fibers, calculating the arithmetic average value of the 10 fibers, and rounding off to one decimal place.

[0049] When the fibers constituting the woven fabric are multifilaments, the total fineness of the multifilaments is preferably 30 dtex or more and 170 dtex or less, as measured by "8.3.1 Correct fineness b) Method B (simplified method)" of "8.3 Fineness" in JIS L1013:2010 "Testing methods for chemical fiber filament yarns."

[0050] By setting the total fineness of the yarns constituting the woven fabric to 170 dtex or less, an artificial leather with excellent flexibility can be obtained. On the other hand, by setting the total fineness to 30 dtex or more, not only is the shape stability of the artificial leather product improved, but also the fibers constituting the woven fabric are less likely to be exposed on the surface of the artificial leather when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, which is preferable. In this case, it is preferable that the total fineness of the warp and weft multifilaments be the same.

[0051] Furthermore, the twist number of the yarns constituting the woven fabric is preferably 1000 T / m or more and 4000 T / m or less. By setting the twist number to 4000 T / m or less, more preferably 3500 T / m or less, and even more preferably 3000 T / m or less, an artificial leather with excellent flexibility can be obtained, while by setting the twist number to 1000 T / m or more, more preferably 1500 T / m or more, and even more preferably 2000 T / m or more, damage to the fibers constituting the woven fabric can be prevented when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, and the mechanical strength of the artificial leather can be excellent, which is preferable.

[0052] [Polymer elastic material] The polymeric elastomer that constitutes the artificial leather of the present invention is a binder that holds the ultrafine fibers that constitute the artificial leather, and therefore, in consideration of the soft texture of the artificial leather of the present invention, it is preferable that the polymeric elastomer used be polyurethane.

[0053] The polyurethane used in the present invention can be either an organic solvent-based polyurethane, which is used in a state dissolved in an organic solvent, or a water-dispersed polyurethane, which is used in a state dispersed in water. Furthermore, the polyurethane used in the present invention is preferably a polyurethane obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender.

[0054] As the polymer diol, for example, polycarbonate-based diol, polyester-based diol, polyether-based diol, silicone-based diol, and fluorine-based diol can be used, and copolymers of these can also be used. Among them, from the viewpoint of hydrolysis resistance and abrasion resistance, it is preferable to use polycarbonate-based diol.

[0055] The polycarbonate diol can be produced by the transesterification reaction of alkylene glycol with a carbonate ester, or by the reaction of phosgene or a chloroformate with an alkylene glycol.

[0056] Examples of alkylene glycols include linear alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 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, aromatic diols such as bisphenol A, glycerin, trimethylolpropane, and pentaerythritol. In the present invention, either a polycarbonate-based diol obtained from a single alkylene glycol or a copolymer polycarbonate-based diol obtained from two or more alkylene glycols can be used.

[0057] Examples of polyester diols include polyester diols obtained by condensing various low molecular weight polyols with polybasic acids.

[0058] Examples of low molecular weight polyols that can be used include one or more selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol.

[0059] Also usable are adducts of bisphenol A with various alkylene oxides.

[0060] Examples of polybasic acids 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.

[0061] Examples of the polyether diols used in the present invention include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymer diols obtained by combining these.

[0062] When the molecular weight of the polyurethane elastomer is constant, the number-average molecular weight of the polymer diol is preferably in the range of 500 to 4000. By setting the number-average molecular weight to preferably 500 or more, more preferably 1500 or more, it is possible to prevent the artificial leather from becoming hard. Furthermore, by setting the number-average molecular weight to preferably 4000 or less, more preferably 3000 or less, it is possible to maintain the strength of the polyurethane.

[0063] Examples of the organic diisocyanate used in the present invention include aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate, and aromatic diisocyanates such as diphenylmethane diisocyanate and tolylene diisocyanate, and these can also be used in combination.

[0064] As the chain extender, an amine-based chain extender such as ethylenediamine or methylenebisaniline, or a diol-based chain extender such as ethylene glycol can be preferably used. Also, a polyamine obtained by reacting polyisocyanate with water can be used as the chain extender.

[0065] The polyurethane used in the present invention can be used in combination with a crosslinking agent to improve water resistance, abrasion resistance, hydrolysis resistance, etc. The crosslinking agent may be an external crosslinking agent added to the polyurethane as a third component, or an internal crosslinking agent that pre-introduces reactive points that form a crosslinked structure within the polyurethane molecular structure. From the viewpoint of being able to form crosslinking points more uniformly within the polyurethane molecular structure and reducing loss of flexibility, it is preferable to use an internal crosslinking agent.

[0066] As the crosslinking agent, a compound having an isocyanate group, an oxazoline group, a carbodiimide group, an epoxy group, a melamine resin, a silanol group, or the like can be used.

[0067] Furthermore, the polymeric elastomer may contain various additives depending on the purpose, such as flame retardants such as "phosphorus-based, halogen-based, and inorganic" antioxidants, "phenol-based, sulfur-based, and phosphorus-based" antioxidants, ultraviolet absorbers such as "benzotriazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, and oxalic acid anilide-based" ultraviolet absorbers, light stabilizers such as "hindered amine-based and benzoate-based" stabilizers, hydrolysis-resistant stabilizers such as polycarbodiimide, plasticizers, antistatic agents, surfactants, coagulation adjusters, and dyes.

[0068] Generally, the content of the polymeric elastomer in the artificial leather can be adjusted appropriately taking into consideration the type of polymeric elastomer used, the manufacturing method of the polymeric elastomer, and the texture and physical properties. In the present invention, however, the content of the polymeric elastomer is preferably 10% by mass or more and 60% by mass or less relative to the mass of the fiber-entangled material. By setting the content of the polymeric elastomer to 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, the bonding between the fibers by the polymeric elastomer can be strengthened, thereby improving the abrasion resistance of the artificial leather. On the other hand, by setting the content of the polymeric elastomer to 60% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, the artificial leather can be made more flexible.

[0069] In the artificial leather of the present invention, the polymeric elastomer contains a black pigment (b), which more preferably has an average particle size of 0.05 μm to 0.20 μm and a coefficient of variation (CV) of 75% or less.

[0070] The average particle size of the black pigment (b) referred to here is the average particle size of the black pigment (b) when it is present in the polymer elastomer, and is generally referred to as the secondary particle size.

[0071] By setting the average particle size of the black pigment (b) to 0.05 μm or more, preferably 0.07 μm or more, the black pigment (b) is held within the polymeric elastomer, thereby preventing the pigment from falling off from the polymeric elastomer. By setting the average particle size to 0.20 μm or less, preferably 0.18 μm or less, more preferably 0.16 μm or less, the black pigment (b) can be easily dispersed when impregnated into the polymeric elastomer.

[0072] When the coefficient of variation (CV) of the particle size of the black pigment (b) is 75% or less, preferably 65% or less, more preferably 60% or less, even more preferably 55% or less, and most preferably 50% or less, the particle size distribution becomes narrow, and the detachment of small particles from the surface of the polymeric elastomer and the precipitation of significantly aggregated particles in the impregnation tank are suppressed. Note that, although there is no particular lower limit for the coefficient of variation of the particle size in the present invention, it is preferably 0.1% or more from the viewpoint of operability when impregnating the polymeric elastomer.

[0073] In the present invention, the average particle size and coefficient of variation (CV) are calculated by the following methods. (1) Prepare ultrathin sections of 5 to 10 μm in thickness in the cross-sectional direction perpendicular to the longitudinal direction of the artificial leather. (2) The cross section of the polymeric elastomer in the ultrathin section is observed at 10,000x magnification using a transmission electron microscope (TEM). (3) Using image analysis software, measure the circle-equivalent diameter of the particle diameter of black pigment (b) at 20 points within a 2.3 μm × 2.3 μm field of view of the observed image. If there are fewer than 20 particles of black pigment (b) within a 2.3 μm × 2.3 μm field of view, measure the circle-equivalent diameter of all particles of black pigment (b) present. (4) Calculate the average (arithmetic mean) and coefficient of variation (CV) for the particle diameters measured at 20 points. In the present invention, the coefficient of variation is calculated using the following formula:

[0074] Coefficient of variation of particle size (%) = (standard deviation of particle size) / (arithmetic mean of particle size) × 100.

[0075] The content (B) of the black pigment (b) contained in the polymeric elastomer is preferably 0.01% by mass or more and 5.0% by mass or less, based on the mass of the polymeric elastomer. By setting the pigment content to 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 1.0% by mass or more, artificial leather can be obtained that has excellent dark color development. By setting the pigment content to 5.0% by mass or less, preferably 4.5% by mass or less, and more preferably 4.0% by mass or less, artificial leather can be obtained that has excellent physical properties such as strength.

[0076] In the present invention, the content (B) of the black pigment (b) contained in the polymeric elastomer is calculated by the following method. (1) The artificial leather is immersed in a mixture of phenol and tetrachloroethane to dissolve the ultrafine fibers and extract a polymeric elastomer. (2) The collected polymeric elastomer is dissolved in dimethylformamide or the like, and only the black pigment (b) is extracted. (3) The extracted black pigment (b) is subjected to evolved gas analysis, and a calibration curve for evolved gas from the black pigment (b) is prepared. (4) The polymeric elastomer contained in the artificial leather is dissolved in dimethylformamide or the like, and then the dimethylformamide or the like is removed, thereby solidifying the polymeric elastomer again. (5) The polymer elastomer obtained in (4) is subjected to evolved gas analysis, and the content (B) of black pigment (b) contained in the polymer elastomer constituting the artificial leather is calculated from the detected intensity of evolved gas derived from black pigment (b) and the calibration curve prepared in (3).

[0077] The black pigment (b) in the present invention may be a carbon-based black pigment such as carbon black or graphite, or an oxide-based black pigment such as triiron tetroxide or a composite oxide of copper and chromium. From the viewpoints of easily obtaining a black pigment with a small particle size and excellent dispersibility in polymers, it is preferable that the black pigment (b) be carbon black.

[0078] [Artificial leather] The artificial leather of the present invention has nap on the surface. The nap may be on only one side of the artificial leather, or on both sides. From the viewpoint of design effect, the nap shape on the surface preferably has such a nap length and directional flexibility that when the surface is napped, the direction of the nap changes when the surface is traced with a finger, leaving a mark, that is, a so-called finger mark.

[0079] More specifically, the surface nap length is preferably 200 μm or more and 500 μm or less, and more preferably 250 μm or more and 450 μm or less. By setting the nap length to 200 μm or more, the surface smoothness of the artificial leather is improved, and artificial leather with excellent touch and gloss can be obtained. On the other hand, by setting the nap length to 500 μm or less, artificial leather with excellent design effect and wear resistance can be obtained.

[0080] In the present invention, the nap length of the artificial leather is calculated by the following method. (1) Using a lint brush or the like, raise the nap of the artificial leather and prepare a thin section 1 mm thick in the cross-sectional direction perpendicular to the longitudinal direction of the artificial leather. (2) Observe the cross section of the artificial leather using a scanning electron microscope (SEM) at 90x magnification. (3) In the SEM image, the height of the napped portion (layer consisting only of ultrafine fibers) is measured at 10 points at 200 μm intervals across the width of the cross section of the artificial leather. (4) The average (arithmetic mean) of the height of the napped portion (layer consisting only of ultrafine fibers) measured at 10 points is calculated.

[0081] In the artificial leather of the present invention, the proportion of the surface covered by the nap of the artificial leather (napped coverage) is preferably 60% to 100%, more preferably 70% to 100%. By making the nap coverage 60% or more, more preferably 70% or more, the surface smoothness of the artificial leather is improved, and an artificial leather with excellent touch and gloss can be obtained. In the present invention, by setting the average particle size and coefficient of variation (CV) of the black pigment (a) contained in the nap (ultrafine fibers) within specified ranges, the yarn strength of the nap (ultrafine fibers) can be increased, and therefore, an artificial leather in which fibers are less likely to fall off due to friction can be obtained even when the nap coverage is as high as 60% or more.

[0082] The nap coverage rate was measured by magnifying the nap surface by 30 to 90 times to see the presence of nap using SEM, and measuring the total area of 9 mm2 using image analysis software. 2The ratio of the total area of the nap-standing part per unit area was calculated and used as the nap-standing coverage rate. The total area ratio can be calculated by binarizing the captured SEM image using the image analysis software "ImageJ" with the nap-standing part and non-napped part set as a threshold of 100. In addition, when calculating the nap-standing coverage rate, if a substance that is not nap-standing is calculated as nap-standing and has a large impact on the nap-standing coverage rate, the image is manually edited and that part is calculated as a non-napped part.

[0083] An example of an image analysis system is the image analysis software "ImageJ," but the image analysis system is not limited to the image analysis software "ImageJ" as long as it is image processing software with the function of calculating the area ratio of specified pixels. Note that the image processing software "ImageJ" is a commonly used software and was developed by the National Institutes of Health in the United States. The image processing software "ImageJ" has the function of identifying necessary areas in an imported image and performing pixel analysis.

[0084] The artificial leather of the present invention preferably has a thickness of 0.2 mm or more and 1.2 mm or less, as measured by "6.1.1 Method A" of "6.1 Thickness (ISO Method)" in JIS L1913:2010 "Testing Methods for General Nonwoven Fabrics." By making the thickness of the artificial leather 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more, it not only has excellent processability during manufacturing, but also has a rich feel and excellent texture. On the other hand, by making the thickness 1.2 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less, it is possible to obtain a flexible artificial leather with excellent moldability.

[0085] The artificial leather of the present invention preferably has a rub fastness of Grade 4 or higher as measured by "9.1 Rub Tester Type I (Crockmeter) Method" of JIS L0849:2013 "Test Method for Color Fastness to Rub" and a light fastness of Grade 4 or higher as measured by "7.2 Exposure Method a) First Exposure Method" of JIS L0843:2006 "Test Method for Color Fastness to Xenon Arc Lamp Light." Having rub fastness and light fastness of Grade 4 or higher prevents color fading and staining of clothing during actual use. The rub fastness of the artificial leather is determined using the stain gray scale specified in JIS L0805:2005 "Gray Scale for Staining," and the light fastness of the artificial leather is determined using the discoloration gray scale specified in JIS L0804:2004 "Gray Scale for Discoloration."

[0086] Furthermore, in an abrasion resistance test for the artificial leather of the present invention measured according to "8.19.5 Method E (Martindale method)" in "8.19 Abrasion resistance and discoloration due to friction" of JIS L1096:2010 "Testing methods for woven and knitted fabrics," the artificial leather is abraded 20,000 times at a pressure load of 12.0 kPa, and the weight loss of the artificial leather after abrasion is preferably 10 mg or less, more preferably 8 mg or less, and even more preferably 6 mg or less. A weight loss of 10 mg or less can prevent contamination due to fluff shedding during actual use.

[0087] In addition, the artificial leather of the present invention has a surface brightness (L * The value) is preferably 35 or less, more preferably 30 or less, and even more preferably 25 or less. The surface lightness is measured by laying the nap on the surface of the artificial leather using a lint brush or the like, in accordance with JIS Z8781-4:2013 "Colorimetry - Part 4: CIE1976L" * a * b * L defined in "3.3 CIE1976 Lightness Index" of "Color Space" * In the present invention, L *The value was measured 10 times using a spectrophotometer, and the arithmetic average of the measurement results was used as the L value of the artificial leather. * value.

[0088] Furthermore, the artificial leather of the present invention preferably has a color rendering index of 90 or higher, more preferably 92 or higher, and even more preferably 95 or higher. Color rendering index refers to the property that causes the color of the same object to appear differently depending on the wavelength spectrum of the illuminating light, and is a numerical representation of the magnitude of color difference when the same object is illuminated with a standard light source and an evaluation light source.

[0089] In the present invention, the color rendering index of the artificial leather is calculated by the following method. (1) L of artificial leather irradiated with a standard light source and an evaluation light source using a spectrophotometer * value, a * value, b * The values were measured 10 times each, and the arithmetic mean of the measurement results was used as the L value of the artificial leather irradiated with the standard light source or the evaluation light source. * value, a * value, b * This is adopted as the value. * value, b * The value is measured on the surface of the artificial leather that has raised nap, with the raised nap laid down using a lint brush or similar, according to JIS Z8781-4:2013 "Colorimetry - Part 4: CIE1976L * a * b * "3.4 CIELAB1976 a" in "Color Space" * ,b * It is a numerical value specified in "Coordinates". (2) JIS Z8781-4:2013 “Color measurement-Part 4: CIE1976L * a * b * "3.12 CIELAB1976 L" in "Color Space" * a * b * In accordance with the "Color Difference" standard, the L of artificial leather irradiated with a standard light source * value, a * value, b * L value of artificial leather irradiated with an evaluation light source * value, a* value, b * Using the values, the color difference (ΔE) is calculated using Equation 1.

[0090]

number

[0091] where: L * S : L of artificial leather irradiated with a standard light source * value(-) a * S : a of artificial leather irradiated with a standard light source * value(-) b * S : b of artificial leather irradiated with standard light source * value(-) L * N : L of artificial leather irradiated with the evaluation light source * value(-) a * N : a of artificial leather irradiated with the evaluation light source * value(-) b * N : b of artificial leather irradiated with the evaluation light source * value(-) is. (3) In accordance with "6.10 Calculation of color rendering index" of JIS Z8726:1990 "Evaluation method of color rendering of light source", calculate the color rendering index of artificial leather using the following formula: (Color rendering index of artificial leather) = 100 - 4.6 x ΔE In the present invention, the color rendering properties of artificial leather are evaluated using the D65 light source specified in "5. Standard light source and common light source" of JIS Z8720:2012 "Standard illuminants (standard light) and standard light sources for colorimetry."

[0092] The artificial leather of the present invention also has an elegant gloss, and the specular gloss of the artificial leather is preferably 5% to 60%, more preferably 15% to 50%. A specular gloss of 5% or more is preferred because it provides an elegant gloss and achieves a luxurious surface quality. A specular gloss of 60% or less is also preferred because it can suppress excessive light reflection.

[0093] The specular gloss of the artificial leather of the present invention is measured as follows in accordance with the method specified in JIS Z8741:1997 "Specular gloss - measuring method." (1) Take three 60mm x 60mm samples from the artificial leather. (2) A light beam with a specified divergence angle (60°) is incident on a glass surface with a refractive index of 1.567 across the entire visible wavelength range at an incident angle of 60°, and the light beam A reflected in the direction of specular reflection at the specified divergence angle (60°) is measured with a photodetector. This light beam A is the standard for 100% specular gloss. (3) A light beam with a specified divergence angle (60°) is incident on the three sample surfaces at an incident angle of 60°, and the light beam B with a specified divergence angle (60°) reflected in the direction of specular reflection is measured with a photodetector. (4) Calculate the specular gloss using the following formula, find the arithmetic average value, and round off the average value to three significant digits. (Specular gloss (%)) = (Luminous flux B) / (Luminous flux A) x 100.

[0094] Furthermore, the artificial leather of the present invention preferably has a tensile strength of 20 N / cm to 200 N / cm in any measurement direction as measured in accordance with "6.3.1 Tensile strength and elongation (ISO method)" of JIS L1913:2010 "General nonwoven fabric testing methods."

[0095] A tensile strength of 20 N / cm or more, more preferably 30 N / cm or more, and even more preferably 40 N / cm or more is preferred because the artificial leather will have excellent shape stability and durability. A tensile strength of 200 N / cm or less, more preferably 180 N / cm or less, and even more preferably 150 N / cm or less will result in an artificial leather with excellent moldability.

[0096] [Manufacturing method for artificial leather] The artificial leather of the present invention is preferably produced by the following steps (1) to (4). Step (1): A step of producing an ultrafine fiber-forming fiber having an islands-in-sea composite structure in which islands made of a polyester resin containing a black pigment (a) are formed in the fiber cross section and a sea made of an easily soluble polymer is formed. Step (2): A step of producing a fibrous base material having ultrafine fiber-developing fibers as the main component Step (3): A step of producing ultrafine fibers having an average single fiber diameter of 0.01 μm or more and 3.0 μm or less from a fibrous base material having ultrafine fiber-producing fibers as a main component. Step (4): A step of providing a polymeric elastomer to a fibrous substrate mainly composed of ultrafine fibers or ultrafine fiber-forming fibers. Each step will be described in detail below.

[0097] <Process for producing ultrafine fiber-developing fibers> In this step, ultrafine fiber-forming fibers are produced that have an islands-in-sea composite structure in which islands made of a polyester resin containing black pigment (a) are formed in the fiber cross section and a sea made of an easily soluble polymer.

[0098] As the ultrafine fiber-forming fiber, an islands-in-sea type composite fiber is used, in which thermoplastic resins with different solvent solubilities are used as a sea portion (easily soluble polymer) and an island portion (slightly soluble polymer), and the sea portion is converted into ultrafine fibers by dissolving and removing it using a solvent, etc. The use of islands-in-sea type composite fiber is preferred from the viewpoint of the texture and surface quality of the artificial leather, because it is possible to provide appropriate gaps between the island portions, i.e., between the ultrafine fibers within the fiber bundle, when the sea portion is removed.

[0099] As a method for spinning ultrafine fiber-producing fibers having an islands-in-sea composite structure, a method using a spinneret for islands-in-sea composite fibers and a polymer mutually aligned structure in which sea parts and island parts are mutually aligned and spun is preferred from the viewpoint of obtaining ultrafine fibers with a uniform single fiber fineness.

[0100] The method of incorporating the black pigment (a) into the island portions can be either spinning using polyester resin chips that have been kneaded in advance with the black pigment (a) in an amount of, for example, 0.1% by mass to 5.0% by mass relative to the mass of the polyester resin, or mixing a masterbatch prepared by kneading the black pigment (a) into the polyester resin in an amount of, for example, 10% by mass to 40% by mass relative to the mass of the polyester resin, with the polyester resin chips, and spinning the mixture. Among these, the method of using a masterbatch to mix with the polyester resin chips is preferred because it allows the amount of pigment contained in the ultrafine fibers to be appropriately adjusted.

[0101] When a masterbatch is used to mix with polyester resin chips, it is preferable to use a masterbatch in which the number average primary particle size of the black pigment (a) contained in the masterbatch used is 0.01 μm or more and 0.05 μm or less and the coefficient of variation (CV) is 0.1% or more and 30% or less. By using a masterbatch with a primary particle size within the above range, the particle size (secondary particle size) and coefficient of variation (CV) in the ultrafine fibers can be kept within appropriate ranges.

[0102] For the sea portion of the islands-in-sea type composite fiber, polyethylene, polypropylene, polystyrene, copolymer polyesters copolymerized with sodium sulfoisophthalic acid, polyethylene glycol, etc., and polylactic acid, etc. can be used. From the viewpoints of spinnability, ease of elution, etc., polystyrene and copolymer polyesters are preferably used.

[0103] In the method for producing an artificial leather of the present invention, when an islands-in-sea type composite fiber is used, it is preferable to use an islands-in-sea type composite fiber whose island portion has a strength of 2.2 cN / dtex or more. By using an island portion having a strength of 2.2 cN / dtex or more, more preferably 2.5 cN / dtex or more, and even more preferably 3.0 cN / dtex or more, the abrasion resistance of the artificial leather can be improved and a decrease in friction fastness due to fiber shedding can be suppressed.

[0104] In the present invention, the strength of the island parts of the islands-in-sea type composite fiber is calculated by the following method. (1) Ten 20cm long islands-in-the-sea composite fibers are bundled together. (2) After dissolving and removing the sea area from the sample (1), air dry it. (3) According to JIS L1013:2010 "Testing methods for chemical fiber filament yarns", "8.5 Tensile strength and elongation", "8.5.1 Standard time test", the test shall be carried out 10 times (N=10) under the conditions of grip length 5 cm, pulling speed 5 cm / min, and load 2 N. (4) The arithmetic mean value (cN / dtex) of the test results obtained in (3) shall be rounded to one decimal place to obtain the strength of the island portion of the islands-in-sea type composite fiber.

[0105] <Process for producing a fibrous base material> In this process, the spun ultrafine fiber-developing fibers are opened and then formed into a fiber web using a cross wrapper or the like, and the web is entangled to obtain a nonwoven fabric. Methods that can be used to entangle the fiber web to obtain a nonwoven fabric include needle punching and water jet punching.

[0106] As for the form of the nonwoven fabric, either a short fiber nonwoven fabric or a long fiber nonwoven fabric can be used as described above. However, when using a short fiber nonwoven fabric, the number of fibers oriented in the thickness direction of the artificial leather is greater than that of a long fiber nonwoven fabric, and a highly dense feel can be achieved on the surface of the artificial leather when it is raised.

[0107] When the nonwoven fabric is a staple fiber nonwoven fabric, the obtained ultrafine fiber-developing fibers are preferably subjected to crimping processing, cut to a predetermined length to obtain raw cotton, and then opened, laminated, and entangled to obtain a staple fiber nonwoven fabric. Known methods can be used for crimping and cutting.

[0108] Furthermore, when the artificial leather contains a woven fabric, the obtained nonwoven fabric and the woven fabric are laminated and then entangled together. The entanglement and integration of the nonwoven fabric and the woven fabric can be achieved by laminating the woven fabric on one or both sides of the nonwoven fabric, or by sandwiching the woven fabric between multiple nonwoven fabric webs and then entangling the fibers of the nonwoven fabric and the woven fabric by needle punching, water jet punching, or the like.

[0109] The apparent density of the nonwoven fabric made of ultrafine fiber-developing fibers after needle punching or water jet punching is 0.15 g / cm 3 More than 0.45g / cm 3 The apparent density is preferably 0.15 g / cm or less. 3 By adjusting the apparent density to 0.45 g / cm or more, the artificial leather can have sufficient shape stability and dimensional stability. 3 By setting the above, it is possible to maintain a sufficient space for providing the polymeric elastomer.

[0110] It is also a preferred embodiment that the nonwoven fabric is subjected to a heat shrinking treatment using hot water or steam in order to improve the denseness of the fibers.

[0111] Next, the nonwoven fabric can be impregnated with an aqueous solution of a water-soluble resin and then dried to impart the water-soluble resin to the nonwoven fabric. By imparting the water-soluble resin to the nonwoven fabric, the fibers are fixed and the dimensional stability is improved.

[0112] <Process for producing ultrafine fibers> In this step, the obtained fibrous base material is treated with a solvent to produce ultrafine fibers having an average single fiber diameter of 0.01 μm or more and 3.0 μm or less.

[0113] The treatment for developing ultrafine fibers can be carried out by immersing a nonwoven fabric made of islands-in-sea type composite fibers in a solvent to dissolve and remove the sea portion of the islands-in-sea type composite fibers.

[0114] When the ultrafine fiber-producing fiber is an islands-in-sea type composite fiber, the solvent for dissolving and removing the sea portion can be an organic solvent such as toluene or trichloroethylene when the sea portion is made of polyethylene, polypropylene, or polystyrene. Alternatively, an aqueous alkali solution such as sodium hydroxide can be used when the sea portion is made of a copolymer polyester or polylactic acid. Alternatively, hot water can be used when the sea portion is made of a water-soluble thermoplastic polyvinyl alcohol resin.

[0115] <Step of providing polymeric elastomer> In this process, a fibrous substrate primarily composed of ultrafine fibers or ultrafine fiber-developing fibers is impregnated with a solution of a polymeric elastomer containing a black pigment (b) and solidified to form a polymeric elastomer. Methods for fixing the polymeric elastomer containing the black pigment (b) to the nonwoven fabric include impregnating the nonwoven fabric (fiber-entangled body) with a solution of the polymeric elastomer containing the black pigment (b) and then wet or dry coagulating the solution. These methods can be selected appropriately depending on the type of polymeric elastomer used. The black pigment (b) used preferably has a number-average primary particle size of 0.01 μm to 0.05 μm and a coefficient of variation (CV) of 0.1% to 30%. Using a black pigment (b) with a primary particle size within the above range ensures that the particle size (secondary particle size) and coefficient of variation (CV) in the polymeric elastomer are within appropriate ranges.

[0116] Preferred solvents used when applying polyurethane as a polymeric elastomer to a fibrous substrate include N,N'-dimethylformamide and dimethyl sulfoxide. Alternatively, a water-dispersed polyurethane liquid in which polyurethane is dispersed in water as an emulsion may be used.

[0117] The polymeric elastomer may be applied to the fibrous substrate before generating ultrafine fibers from the ultrafine fiber-producing fiber, or after generating ultrafine fibers from the ultrafine fiber-producing fiber.

[0118] <The process of cutting the artificial leather in half and grinding it> From the viewpoint of production efficiency, it is also a preferred embodiment that the artificial leather to which the polymeric elastomer has been added after the above steps is cut in half in the thickness direction to form two pieces of artificial leather.

[0119] Furthermore, the surface of the artificial leather to which the polymeric elastomer has been applied or the surface of the artificial leather cut in half is subjected to a nap raising treatment. The nap raising treatment can be carried out by a method such as grinding using sandpaper or a roll sander. The nap raising treatment can be carried out on only one surface of the artificial leather or on both surfaces.

[0120] When performing the nap raising treatment, a lubricant such as a silicone emulsion can be applied to the surface of the artificial leather before the nap raising treatment. Also, by applying an antistatic agent before the nap raising treatment, grinding dust generated from the artificial leather during grinding is less likely to accumulate on the sandpaper. In this way, the artificial leather is formed.

[0121] <Artificial leather dyeing process> The artificial leather is preferably dyed with a dye of the same color as the black pigment or chromatic fine-particle oxide pigment. Examples of dyeing methods include jet dyeing using a jigger dyeing machine or jet dyeing machine, thermosol dyeing using a continuous dyeing machine, and other dip dyeing processes, as well as roller printing, screen printing, inkjet printing, sublimation printing, and vacuum sublimation printing. Jet dyeing machines are preferred for achieving a soft texture and ensuring high quality and elegance. If necessary, various resin finishing processes can be applied after dyeing.

[0122] <Post-processing process> Furthermore, the surface of the above-mentioned artificial leather can be given a design, if necessary, by post-processing such as perforation, embossing, laser processing, pinsonic processing, and printing.

[0123] The artificial leather of the present invention obtained by the above-exemplified production method has deep and uniform coloring, and is excellent in touch, gloss and color fastness, and is suitable for use as a material for clothing. [Example]

[0124] Next, 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. Next, the evaluation methods and measurement conditions used in the examples will be described. However, in measuring each physical property, unless otherwise specified, the measurement was carried out based on the above-mentioned method.

[0125] [Measurement method and evaluation processing method] (1) Average single fiber diameter of ultrafine fibers (μm): In measuring the average single fiber diameter of the ultrafine fibers, the ultrafine fibers were observed using a scanning electron microscope "VW-9000" manufactured by Keyence Corporation, and the average single fiber diameter was calculated.

[0126] (2) Average particle size (μm) and coefficient of variation (CV) (%) of black pigment (a) contained in ultrafine fibers: Ultrathin cross-sectional sections perpendicular to the longitudinal direction of the ultrafine fibers were prepared using a Sorvall ultramicrotome (model MT6000). The sections were then observed using a transmission electron microscope (model H7700, Hitachi High-Technologies). The particle size of the pigment was then measured using image analysis software (WinROOF, Mitani Corporation).

[0127] (3) Average particle size (μm) and coefficient of variation (CV) (%) of black pigment (b) contained in polymer elastomer: Ultrathin cross-sectional sections perpendicular to the longitudinal direction of the artificial leather were prepared using a Sorvall ultramicrotome (model MT6000). The sections were then observed using a transmission electron microscope (model H7700, Hitachi High-Technologies). The particle size of the pigment was then measured using image analysis software (WinROOF, Mitani Corporation).

[0128] (4) Average distance (μm) between the nearest black pigments (a) contained in the ultrafine fibers: Ultrathin cross-sectional sections perpendicular to the longitudinal direction of the ultrafine fibers were prepared using a Sorvall ultramicrotome, model MT6000. The sections were then observed using a transmission electron microscope (Hitachi High-Technologies Corporation, model H7700). The average distance between the nearest black pigments (a) was then measured using image analysis software (Mitani Corporation, WinROOF).

[0129] (5) Content (A) (%) of black pigment (a) contained in ultrafine fibers: The content (A) of the black pigment (a) contained in the ultrafine fibers was measured using a gas chromatograph mass spectrometer "GCMS-QP2010" manufactured by Shimadzu Corporation.

[0130] (6) Content (B) of black pigment (b) contained in polymer elastomer (%): The content (B) of the black pigment (b) contained in the polymeric elastomer was measured using a gas chromatograph mass spectrometer "GCMS-QP2010" manufactured by Shimadzu Corporation.

[0131] (7) Artificial leather nap coverage (%): In measuring the nap coverage, a scanning electron microscope "VW-9000" manufactured by Keyence Corporation and "ImageJ" were used as image analysis software.

[0132] (8) Artificial leather nap length (μm): In measuring the nap length of the artificial leather, a scanning electron microscope "VW-9000" manufactured by Keyence Corporation was used.

[0133] (9) Lightness of artificial leather (L * value): Using a spectrophotometer, the above-mentioned JIS Z8781-4:2013 "Colorimetry - Part 4: CIE1976L * a * b * L defined in "3.3 CIE1976 Lightness Index" of "Color Space" * The measurement was carried out 10 times using a Konica Minolta "CM-M6" and the average was used to measure the L value of the artificial leather. * The value was set as

[0134] (10) Color rendering of artificial leather: The reference illuminant was the D65 illuminant specified in "5. Standard and common illuminants" of JIS Z8720:2012 "Standard illuminants (standard light) and standard illuminants for colorimetry." The evaluation illuminants were the A illuminant specified in "5. Standard and common illuminants" of JIS Z8720:2012 "Standard illuminants (standard light) and standard illuminants for colorimetry." The evaluation illuminants were the F2, F6, F8, and F11 illuminants specified in "Appendix 1" of JIS Z8719:1996 "Metameric index - Evaluation method for illuminant metamerism." The measurements were performed using a spectrophotometer according to the above-mentioned JIS Z8781-4:2013 "Colorimetry - Part 4: CIE1976L * a * b * L defined in "3.3 CIE1976 Lightness Index" of "Color Space" * Value and "3.4 CIELAB1976 a * ,b * a specified by the "coordinates" * value, b * The measurement was carried out 10 times using a Konica Minolta "CM-M6" and the average was used as the L value of the artificial leather irradiated with the standard light source or the evaluation light source. * value, a * value, b * Next, the above-mentioned JIS Z8781-4:2013 "Colorimetry - Part 4: CIE1976L * a * b * "3.12 CIELAB1976 L" in "Color Space"* a * b * The color rendering index of the artificial leather was calculated in accordance with "Color Difference" and "6.10 Calculation of Color Rendering Index" of JIS Z8726:1990 "Method for Evaluating the Color Rendering of Light Sources," and artificial leather with a score of 95 or higher was deemed to have passed.

[0135] (11) Abrasion resistance of artificial leather: The degree of contamination of the sample after the friction test was judged using the gray scale for contamination specified in JIS L0805:2005 "Gray scale for contamination" and was rated as Grade 4 or higher (L * a * b * Color difference ΔE according to color system * ab A value of 4.5±0.3 or less was considered acceptable.

[0136] (12) Light fastness of artificial leather: After irradiating the sample with xenon arc light, the degree of discoloration was graded using the gray scale for discoloration specified in JIS L0804:2004 "Gray scale for discoloration." Grades were 4 or higher (L * a * b * Color difference ΔE according to color system * ab A value of 1.7±0.3 or less was considered acceptable.

[0137] (13) Abrasion resistance of artificial leather (mg): The abrasion resistance test was conducted using a James H. Heal & Co. Ltd. "Model 406" abrasion tester and the same company's "Abrastive Cloth SM25" as the standard friction cloth, and artificial leather with an abrasion loss of 10 mg or less was deemed to have passed.

[0138] (14) Tensile strength of artificial leather (N / cm): Two 2cm x 20cm test pieces were taken from the artificial leather in any direction, and the tensile strength (N / cm) was measured as specified in "6.3.1 Tensile strength and elongation (ISO method)" of JIS L1913:2010 "General nonwoven fabric test methods." The average of the two pieces was taken as the tensile strength of the artificial leather.

[0139] (15) Mirror gloss of artificial leather (%): The specular gloss (%) of the artificial leather was measured using a Konica Minolta "GM-268Plus" gloss meter in accordance with "Specular gloss - measuring method" of JIS Z8741:1997.

[0140] (16) Color development of artificial leather: The color development of the artificial leather was evaluated by a total of 20 evaluators, 10 healthy adult males and 10 healthy adult females, who visually judged the following evaluations, and the color development of the artificial leather was determined to be the evaluation with the highest number of evaluations. In the case of a tie, the color development of the artificial leather was determined to be the evaluation with the highest number of evaluations. The good level of the present invention was determined to be "A or B." A: Very uniform color development. B: Uniform color development. C: Color development varies greatly. D: Color development varies greatly.

[0141] (17) Artificial leather feel: The touch of the artificial leather was evaluated by a total of 20 evaluators, 10 healthy adult males and 10 healthy adult females, who visually judged the following evaluations, and the most common evaluation was taken as the color development of the artificial leather. In the case of a tie, the higher evaluation was taken as the touch of the artificial leather. The good level of the present invention was rated as "A or B." A: It has a dense texture and is very smooth to the touch. B: Dense and smooth to the touch. C: Lacks density and feels rough to the touch. D: Poor density and very rough texture.

[0142] [Example 1] <Process for manufacturing raw cotton> Ultrafine fiber-forming fibers having an island-in-sea composite structure consisting of island and sea components were melt-spun under the following conditions. Island component: A mixture of the following components P1 and P2 in a mass ratio of 85:15 P1 Polyethylene terephthalate A with an intrinsic viscosity (IV value) of 0.73 P2 A masterbatch in which carbon black (average particle size: 0.02 μm, coefficient of variation (CV) of particle size: 20%) is contained as a black pigment (a) in the polyethylene terephthalate A in an amount of 20 mass% relative to the mass of the masterbatch. Sea component: Polystyrene with an MFR (melt flow rate, measured according to the test method specified in ISO 1133:1997) of 65 g / 10 min Spinneret: Spinneret for islands-in-sea composite fiber with 36 islands / hole Spinning temperature: 285℃ Island / sea mass ratio: 55 / 45 Discharge rate: 1.2g / min (hole) Spinning speed: 1280m / min.

[0143] The ultrafine fiber-forming fibers were then stretched 3.5 times in a spinning oil bath at 90°C. They were then crimped using a push-type crimper and cut to a length of 51 mm to obtain raw cotton for islands-in-sea composite fibers with a single fiber fineness of 3.2 dtex. The average single fiber diameter of the ultrafine fibers obtained from these islands-in-sea composite fibers was 2.1 μm, the strength of the ultrafine fibers was 2.7 cN / dtex, the average particle size of the carbon black in the ultrafine fibers was 0.13 μm, and the coefficient of variation (CV) of particle size was 30%. most The average distance between adjacent carbon black particles was 0.15 μm.

[0144] <Process for producing a fibrous base material> First, the raw cotton obtained as described above was subjected to carding and cross-wrapping processes to form a laminated web. 2 The fabric is needle punched with the number of punches, and the weight is 630g / m 2 Thus, a nonwoven fabric (fibrous base material) with a thickness of 2.8 mm was obtained.

[0145] <Process for producing ultrafine fibers> The nonwoven fabric obtained as described above was shrunk in hot water at 96°C. The hot-water-shrunk nonwoven fabric was then impregnated with an aqueous solution of polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) with a saponification degree of 88%, adjusted to a concentration of 12% by mass. The nonwoven fabric was then squeezed with a roll and dried with hot air at 120°C for 10 minutes while allowing the PVA to migrate, yielding a PVA-coated sheet with a PVA mass of 25% by mass relative to the mass of the sheet substrate. The PVA-coated sheet thus obtained was immersed in trichloroethylene and subjected to a process of squeezing and compressing using a mangle 10 times. This process dissolved and removed the sea portion and compressed the PVA-coated sheet, yielding a PVA-coated sheet composed of entangled ultrafine fiber bundles to which PVA had been applied.

[0146] <Step of providing polymeric elastomer> The PVA-coated sheet obtained as described above was immersed in a DMF (dimethylformamide) solution of polyurethane containing carbon black (average primary particle diameter: 0.02 μm, coefficient of variation (CV) of particle diameter: 20%) as a black pigment (b) at a solids concentration of 10.5%. The sea-free PVA-coated sheet immersed in the DMF solution of polyurethane was then squeezed with a roll. The sheet was then immersed in a 30% by weight DMF aqueous solution to coagulate the polyurethane. The PVA and DMF were then removed with hot water, and the sheet was impregnated with a silicone oil emulsion adjusted to a concentration of 1% by weight. A silicone-based lubricant was added so that the amount of added lubricant was 0.5% by weight relative to the total weight of the fibrous base material and polyurethane, and the sheet was dried with hot air at a temperature of 110°C for 10 minutes. This resulted in a polyurethane sheet with a thickness of 1.5 mm, in which the polyurethane mass was 31% by mass relative to the mass of the fibrous substrate, and the carbon black content in the polyurethane was 1.5% by mass relative to the total mass of the polyurethane and carbon black. The average particle size (secondary particle size) of the carbon black in the polyurethane was 0.1 μm, and the coefficient of variation (CV) of the particle size was 30%.

[0147] <Cutting in half and raising the nap> The polyurethane-coated sheet obtained as described above was cut in half so that each half had a thickness of 1 / 2. The surface of the cut half was then ground by 0.3 mm with endless sandpaper of sandpaper count 180, and the nap was removed to obtain a sheet with an average single fiber diameter of 2.1 μm and a basis weight of 180 g / m. 2 The resulting artificial leather had a thickness of 0.45 mm, a nap coverage of 90%, and a nap length of 330 μm. The resulting artificial leather had a deep, uniform color, and was excellent in touch, color fastness, gloss, and color rendering. The results are shown in Tables 1 and 2.

[0148] [Example 2] The artificial leather obtained by the raising process is dyed with black dye in a liquid flow dyeing machine. * An artificial leather was obtained in the same manner as in Example 1, except that the fabric was dyed at 120°C using a recipe adjusted to give a dyeing value of 22, and then dried at 100°C for 7 minutes. The ultrafine fibers constituting this artificial leather had an average single fiber diameter of 2.1 μm and a basis weight of 180 g / m 2 The thickness was 0.55 mm, the nap coverage was 90%, and the nap length was 330 μm. The artificial leather obtained had a deep, very uniform color, and was excellent in touch, color fastness, gloss, and color rendering. The results are shown in Tables 1 and 2.

[0149] [Example 3] An artificial leather was produced in the same manner as in Example 2, except that island components P1 and P2 were mixed so that the ratio of carbon black contained in the ultrafine fibers as black pigment (a) was 1.0 mass% based on the mass of the ultrafine fibers. The ultrafine fibers constituting this artificial leather had an average single fiber diameter of 2.1 μm, a strength of 4.3 cN / dtex, an average particle size of the carbon black in the ultrafine fibers of 0.07 μm, a coefficient of variation (CV) of particle size of 30%, and most The average distance between adjacent carbon black particles was 0.2 μm. The resulting artificial leather had a deep, uniform color and was excellent in touch, color fastness, gloss, and color rendering. The results are shown in Tables 1 and 2.

[0150] [Example 4] An artificial leather was obtained in the same manner as in Example 2, except that ultrafine fiber-developing fibers having an islands-in-sea composite structure consisting of island parts and sea parts were melt-spun under the following conditions, and then the ultrafine fiber-developing fibers were stretched 3.4 times in a spinning oil bath set to 90°C. The ultrafine fibers constituting this artificial leather had an average single fiber diameter of 2.9 μm, an ultrafine fiber strength of 3.4 cN / dtex, an average particle diameter of carbon black in the ultrafine fibers of 0.12 μm, a coefficient of variation (CV) of particle diameter of 30%, and most The average distance between adjacent carbon black particles was 0.25 μm. The resulting artificial leather had a slightly lower gloss, but a deep, very uniform color, and excellent touch, color fastness, and color rendering. The results are shown in Tables 1 and 2. Island component: A mixture of the following components P1 and P2 in a mass ratio of 95:5 P1 Polyethylene terephthalate A with an intrinsic viscosity (IV value) of 0.73 P2 A masterbatch in which carbon black (average particle size: 0.025 μm, coefficient of variation (CV) of particle size: 20%) is contained as a black pigment (a1) in the polyethylene terephthalate A in an amount of 20 mass% relative to the mass of the masterbatch. Sea component: Polystyrene with an MFR (melt flow rate, measured according to the test method specified in ISO 1133:1997) of 65 g / 10 min Spinneret: Spinneret for islands-in-sea composite fiber with 16 islands per hole Spinning temperature: 285℃ Island / sea mass ratio: 55 / 45 Discharge rate: 1.0g / min (hole) Spinning speed: 1100m / min.

[0151] [Example 5] An artificial leather was obtained in the same manner as in Example 1, except that the silicone-based lubricant was applied in an amount of 0.2% by mass relative to the total mass of the fibrous base material and polyurethane, and the surface of the half-cut surface was ground 0.3 mm with endless sandpaper (#240) to give a nap-raising treatment. The obtained artificial leather had a slightly inferior gloss, but had a deep, uniform color development and excellent touch, color fastness, and color rendering properties. The results are shown in Tables 1 and 2.

[0152] [Example 6] An artificial leather was obtained in the same manner as in Example 1, except that the surface of the half-cut surface was ground 0.4 mm with endless sandpaper (grit #150) and then brushed. The obtained artificial leather had a slightly inferior gloss, but had a deep, very uniform color development, and was excellent in touch, color fastness, and color rendering. The results are shown in Tables 1 and 2.

[0153] [Example 7] An artificial leather was obtained in the same manner as in Example 2, except that the proportion of carbon black contained in the polyurethane as the black pigment (b) was 3.1% by mass relative to the total mass of the polyurethane and carbon black. The average particle size (secondary particle size) of the carbon black in the polyurethane was 0.21 μm, and the coefficient of variation (CV) of particle size was 90%. Although the resulting artificial leather had slightly inferior gloss, it had a deep, very uniform color development, and was excellent in touch, color fastness, and color rendering. The results are shown in Tables 1 and 2.

[0154] [Example 8] An artificial leather having an average particle size (secondary particle size) of carbon black in polyurethane of 0.05 μm and a coefficient of variation (CV) of 30% was obtained in the same manner as in Example 2, except that island components P1 and P2 were mixed so that the ratio of carbon black contained in ultrafine fibers as black pigment (a) was 0.5 mass% based on the mass of the ultrafine fibers, and the ratio of carbon black contained in polyurethane as black pigment (b) was 0.1 mass% based on the total mass of polyurethane and carbon black. The ultrafine fibers constituting this artificial leather had an average single fiber diameter of 2.1 μm, a strength of 4.5 cN / dtex, an average particle size of carbon black in ultrafine fibers of 0.06 μm and a coefficient of variation (CV) of 30%. most The average distance between adjacent carbon black particles was 0.3 μm. The resulting artificial leather had a deep, uniform color and was excellent in touch, color fastness, gloss, and color rendering. The results are shown in Tables 1 and 2.

[0155] [Table 1]

[0156] [Table 2]

[0157] [Comparative Example 1] An artificial leather was produced in the same manner as in Example 2, except that the island component P2 was a masterbatch containing, in polyethylene terephthalate A, carbon black (average particle size: 0.06 μm, coefficient of variation (CV) of particle size: 60%) as a black pigment (a) at 20 mass% relative to the mass of the masterbatch. The ultrafine fibers constituting this artificial leather had an average single fiber diameter of 2.1 μm, an ultrafine fiber strength of 2.0 cN / dtex, an average particle size of the carbon black in the ultrafine fibers of 0.27 μm, and a coefficient of variation (CV) of particle size of 80%. mostThe average distance between adjacent carbon black particles was 0.08 μm. The resulting artificial leather had excellent lightfastness and color rendering properties, and a deep, very uniform color development, but was poor in abrasion fastness and gloss. The results are shown in Tables 3 and 4.

[0158] Comparative Example 2 An artificial leather was obtained in the same manner as in Example 2, except that only island component P1 was melt-spun. The ultrafine fibers constituting this artificial leather had an average single fiber diameter of 2.1 μm and a strength of 4.9 cN / dtex. The obtained artificial leather was excellent in touch, gloss, and friction fastness, but was poor in lightfastness, color development, and color rendering. The results are shown in Tables 3 and 4.

[0159] Comparative Example 3 An artificial leather was obtained in the same manner as in Example 2, except that the sample was immersed in a DMF (dimethylformamide) solution of polyurethane, prepared so that the solids concentration was 13%, and the polyurethane was the main component and did not contain carbon black (average particle size: 0.02 μm, coefficient of variation (CV) of particle size: 20%) as the black pigment (b). The artificial leather obtained was excellent in touch, gloss, dyeing fastness, and color rendering, but had poor color development. The results are shown in Tables 3 and 4.

[0160] [Table 3]

[0161] [Table 4]

[0162] As shown in Tables 1 and 2, the artificial leathers of Examples 1 to 8 have an average particle size of the carbon black (black pigment (a)) contained in the ultrafine fibers constituting the artificial leather within a specified range, and the coefficient of variation (CV) of the particle size is reduced, thereby suppressing exposure of the pigment on the surface of the ultrafine fibers. As a result, the artificial leathers obtained have excellent touch, gloss, dyeing fastness, and color rendering properties in addition to deep, uniform color development.

[0163] On the other hand, as shown in Tables 3 and 4, when the average particle size of the carbon black (black pigment (a)) contained in the ultrafine fibers constituting the artificial leather is outside the specified range, or when the coefficient of variation (CV) of the particle size of the carbon black (black pigment (a)) is outside the specified range, as in the artificial leather of Comparative Example 1, the pigment is exposed on the surface of the ultrafine fibers, resulting in an artificial leather inferior in gloss and friction resistance.

[0164] Furthermore, when the ultrafine fibers did not contain the black pigment (a), as in the artificial leather of Comparative Example 2, the dye deteriorated due to light exposure, causing a significant change in the hue of the ultrafine fibers, resulting in an artificial leather with poor lightfastness.

[0165] In addition, when the polyurethane did not contain carbon black (black pigment (b)), as in the artificial leather of Comparative Example 3, the polyurethane was not dyed with the dye and remained white, resulting in artificial leather with variable color development.

Claims

1. An artificial leather comprising a fiber-entangled body containing, as a constituent element, a nonwoven fabric made of ultrafine fibers having an average single fiber diameter of 0.01 μm or more and 3.0 μm or less, and a polymeric elastomer, and which satisfies the following requirements: Requirement 1: The ultrafine fibers are made of a polyester resin containing a black pigment (a). Requirement 2: The average particle size of the black pigment (a) is 0.05 μm or more and 0.20 μm or less, and the coefficient of variation (CV) of the average particle size is 75% or less. Requirement 3: The average distance between the black pigments (a) nearest to each other is 0.15 μm or more and 0.50 μm or less. Requirement 4: The polymeric elastomer contains a black pigment (b).

2. 2. The artificial leather according to claim 1, wherein the content (A) of the black pigment (a) contained in the ultrafine fibers is 0.1% by mass or more and 5.0% by mass or less.

3. 3. The artificial leather according to claim 1, wherein the nap coverage of the surface of the artificial leather having nap is 60% or more and 100% or less.

4. The artificial leather according to any one of claims 1 to 3, wherein the nap length of the artificial leather is 200 µm or more and 500 µm or less.

5. The artificial leather according to any one of claims 1 to 4, wherein the black pigment (b) has an average particle size of 0.05 µm or more and 0.20 µm or less, and the coefficient of variation (CV) of the average particle size is 75% or less.

6. The artificial leather according to any one of claims 1 to 5, wherein the content (B) of the black pigment (b) contained in the polymeric elastomer is 0.01% by mass or more and 5.0% by mass or less.

7. The artificial leather according to any one of claims 1 to 5, wherein the polymeric elastomer is polyurethane.

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