EP4786675A1

EP4786675A1 - Artificial leather and method for manufacturing same, vehicular interior material, vehicular component, miscellaneous goods, and furniture

Info

Publication number: EP4786675A1
Application number: EP24871983.3A
Authority: EP
Inventors: Tatsuya Hagiwara; Konosuke Yamamoto; Hajime Nishimura
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2023-09-29
Filing date: 2024-09-18
Publication date: 2026-08-05
Also published as: JPWO2025070191A1; CN121909313A; KR20260076196A; WO2025070191A1

Abstract

The present invention addresses the problem of providing an artificial leather having excellent moldability that allows the artificial leather to easily follow complicated shapes, and excellent surface quality after being molded. The present invention pertains to an artificial leather comprising: a base material part that includes a polymer elastic body and a fiber entangled body including a nonwoven fabric made of ultrafine fibers having an average monofilament diameter of 0.01-10.00 µm; and a napped part on at least one surface of the artificial leather. The mass proportion of the polymer elastic body in the artificial leather is 15-40 mass%. The area proportion of the polymer elastic body on the surface of the artificial leather on which the napped part is present is 0.01-3.00%. The area proportion of the polymer elastic body in a cross-section of the artificial leather is not less than 5% but less than 15%.

Description

TECHNICAL FIELD

The present invention relates to an artificial leather, a method for manufacturing the same, a vehicular interior material, a vehicular component, miscellaneous goods, and furniture.

BACKGROUND ART

An artificial leather including a fiber entangled body and a polymer elastic body such as polyurethane has excellent characteristics as compared with natural leather in terms of high durability, uniformity of quality, and the like. Therefore, the artificial leather is used in various fields including interior materials of vehicles such as automobiles, aircraft, and railway vehicles, interiors such as furniture, clothing, and miscellaneous goods such as shoes and bags. Among these, when the artificial leather is used as an interior material of a vehicle or a skin of an interior or the like, moldability that can easily follow a complicated shape is required, and various artificial leathers have been proposed.
For example, Patent Document 1 proposes a method for manufacturing a stretchable artificial leather in which an artificial leather composed of a fiber entangled body mainly containing fine fibers having a single yarn fineness of 1.1 dtex or less and polyurethane is stretched in a length direction in a heated state and shrunk in a width direction after or simultaneously with imparting a softener to the artificial leather. It is described that this can inexpensively provide an artificial leather having excellent stretchability in the width direction and excellent flexibility by a simple means.
In addition, Patent Document 2 proposes an artificial leather including a fibrous sheet and a polyurethane resin, in which in the fibrous sheet, a cross-sectional polyurethane resin area ratio in a cross section in a thickness direction of a fibrous layer (A) constituting a first outer surface of the artificial leather and a standard deviation of the cross-sectional polyurethane resin area ratio are in specific ranges. It is described that this provides the artificial leather with excellent hand (stiffness-softness value) and wrinkle resistance, and thus the artificial leather can be suitably used for skin materials or interior materials of sheets for interior use, automobile use, aircraft use, railway vehicle use, and the like, and for clothing products and the like.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

Patent Document 1: Japanese Patent Laid-open Publication No. 2005-76151
Patent Document 2: Japanese Patent Laid-open Publication No. 2021-70904

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

In the technique disclosed in Patent Document 1, stretchability is exhibited in the width direction of the artificial leather. This allows such artificial leather to be molded while the artificial leather is caused to follow a complicated shape such as a vehicular interior material or an interior in the width direction to some extent. However, such an artificial leather cannot sufficiently follow a complicated shape in its length direction. That is, the obtained artificial leather tends to have anisotropy, and thus a portion where the nap portions of the surface of the artificial leather are broken is likely to occur, and the polymer elastic body is exposed from the portion, which may lead to deterioration of surface quality.
In addition, in the technique as disclosed in Patent Document 2, the cross-sectional polyurethane resin area ratio and its standard deviation in the thickness direction of the fiber layer constituting the outer surface of the artificial leather are set within a predetermined range. This can achieve both a certain hand and wrinkle resistance despite using a water-dispersible polyurethane resin having characteristics of increasing the density of polyurethane having a film-shaped structure and easily forming a nonporous membrane. However, when the cross-sectional polyurethane resin area ratio is approximately 15% or more and 30% or less, an artificial leather is molded into a complicated shape, and then local stretch and tear of the artificial leather tend to occur. In this case, the polyurethane is exposed from a portion where the nap portions of the surface of the artificial leather are broken, which may also lead to deterioration of surface quality.
Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide an artificial leather excellent in moldability with easy followability to a complicated shape and further in surface quality after molding processing.

SOLUTIONS TO THE PROBLEMS

As a result of repeated studies by the present inventors to achieve the above object, the present inventors have found that the mass ratio of the polymer elastic body in the artificial leather and the area ratio of the polymer elastic body on the surface and the cross section of the artificial leather are within a specific range, thereby making it possible to obtain an artificial leather that can retain favorable moldability with followability to a complicated shape and a dense and smooth surface quality after molding processing, leading to the present invention.
The present invention has been completed based on these findings, and the present invention provides the following invention.

[1] An artificial leather including:
a base material part including:
- a fiber entangled body including a nonwoven fabric composed of fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less; and
- a polymer elastic body, and
- a nap portion on at least one surface, in which
- a mass ratio of the polymer elastic body in the artificial leather is 15 mass% or more and 40 mass% or less,
- an area ratio of the polymer elastic body on at least one surface of a side having the nap portion of the artificial leather is 0.01% or more and 3.00% or less, and
- an area ratio of the polymer elastic body in a cross section of the artificial leather is 5% or more and less than 15%.
[2] The artificial leather according to [1], in which a standard deviation of an area ratio of a polymer elastic body on at least one surface of the side having the nap portion of the artificial leather is 25% or less.
[3] The artificial leather according to [1] or [2], in which a standard deviation of an area ratio of a polymer elastic body in a cross section of the artificial leather is 25% or less.
[4] The artificial leather according to any one of [1] to [3], in which a thickness of the base material part t_A is 250 µm or more and 800 µm or less, and a ratio of the thickness t_A of the base material part to a thickness t_B of a nap portion, t_A/t_B, is 0.5 or more and 2.5 or less.
[5] The artificial leather according to [4], in which a coefficient of variation of the thickness t_A of the base material part is 50% or less.
[6] The artificial leather according to any one of [1] to [5], in which the fine fiber includes black pigment.
[7] A method for manufacturing the artificial leather, the method including:
- a step of imparting polyvinyl alcohol in an amount of 4 mass% or more and 40 mass% or less with respect to a mass of fine fiber-generating fibers to a fiber entangled body including a nonwoven fabric mainly composed of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet;
- a step of developing fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less from the fine fiber-generating fibers of the polyvinyl alcohol-imparted sheet to form a nonwoven sheet;
- a step of widening a width of the nonwoven sheet by 2% or more and 10% or less to form a widened sheet;
- a step of imparting a polymer elastic body to the widened sheet in an amount of 12 mass% or more and 64 mass% or less with respect to a mass of the widened sheet to form a polymer elastic body-imparted sheet;
- a step of removing the polyvinyl alcohol from the polymer elastic body-imparted sheet to form a base sheet; and
- a step of buffing at least one surface of the base sheet.
[8] A method for manufacturing the artificial leather, the method including:
- a step of imparting polyvinyl alcohol in an amount of 4 mass% or more and 40 mass% or less with respect to a mass of fine fiber-generating fibers to a fiber entangled body including a nonwoven fabric mainly composed of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet;
- a step of widening a width of the polyvinyl alcohol-imparted sheet by 2% or more and 10% or less to form a widened sheet;
- a step of developing fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less from the fine fiber-generating fibers of the widened sheet to form a nonwoven sheet;
- a step of imparting, to the nonwoven sheet, a polymer elastic body in an amount of 12 mass% or more and 64 mass% or less with respect to a mass of the nonwoven sheet to form a polymer elastic body-imparted sheet;
- a step of removing the polyvinyl alcohol from the polymer elastic body-imparted sheet to form a base sheet; and
- a step of buffing at least one surface of the base sheet.
[9] The method for manufacturing an artificial leather according to [7] or [8], in which polyethylene glycol is included in an amount of 0.01 mass% or more and 0.5 mass% or less with respect to a mass of the polyvinyl alcohol in the step of forming the polyvinyl alcohol-imparted sheet.
[10] A vehicular interior material including the artificial leather according to any one of [1] to [6].
[11] A vehicular component including the artificial leather according to any one of [1] to [6].
[12] Miscellaneous goods including the artificial leather according to any one of [1] to [6].
[13] Furniture including the artificial leather according to any one of [1] to [6].

EFFECTS OF THE INVENTION

The present invention can provide an artificial leather excellent in moldability with easy followability to a complicated shape and further in surface quality after molding processing. The artificial leather of the present invention can be used in a wide range of applications including vehicular interior materials, vehicular components, miscellaneous goods, furniture, and clothing, and is excellent in moldability with easy followability to a complicated shape as described above and in surface quality after molding processing, and thus can be suitably used particularly in applications such as vehicular interior materials, vehicular components, miscellaneous goods, and furniture.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a conceptual cross-sectional view of an artificial leather according to the present invention.
Fig. 2 is a conceptual cross-sectional view for explaining a method for measuring a thickness t_A of a base material part, a thickness t_B of a nap portion, and a coefficient of variation thereof according to the artificial leather of the present invention.

EMBODIMENTS OF THE INVENTION

The artificial leather of the present invention is an artificial leather including: a base material part including: a fiber entangled body including a nonwoven fabric composed of fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less; and a polymer elastic body, and a nap portion on at least one surface, in which
a mass ratio of the polymer elastic body in the artificial leather is 15 mass% or more and 40 mass% or less, an area ratio of the polymer elastic body on at least one surface of a side having the nap portion of the artificial leather is 0.01% or more and 3.00% or less, and an area ratio of the polymer elastic body in a cross section of the artificial leather is 5% or more and less than 15%. Hereinafter, these constituent elements will be described in detail, but the present invention is not limited to the scope described below without departing from the gist of the present invention, and various modifications can be made without departing from the gist of the present invention.

[Fiber entangled body]

The base material part according to the artificial leather of one embodiment (hereinafter, also referred to as "the present embodiment") of the present invention first includes a nonwoven fabric composed of fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less in a fiber entangled body.
The fine fibers according to the nonwoven fabric are preferably mainly composed of a melt-spinnable thermoplastic resin. Examples of the thermoplastic resin include: polyesters such as "polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, and polylactic acid"; polyamides such as "polyamide 6, polyamide 66, or polyamide 12"; acrylic; polyolefins such as "polyethylene, polypropylene"; polyphenylene sulfide (PPS); and thermoplastic cellulose. Among them, a polyester-based resin is preferably used from the viewpoint of strength, dimensional stability, and light resistance. In the present embodiment, the "main component" refers to a component in which the content of the component accounts for 50 mass% or more in the constituent element. For example, the "main component of the fine fiber is polyethylene terephthalate" means that 50 mass% or more of the component of the fine fiber is polyethylene terephthalate.
Examples of the polyester-based resin include polycyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, and polyethylene-1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, in addition to polyethylene terephthalate, polytrimethylene terephthalate, and polytetramethylene terephthalate. Among these, polyethylene terephthalate, which is most commonly used, or a polyester copolymer mainly containing an ethylene terephthalate unit is preferably used. In the present embodiment, the "polyester copolymer mainly containing an ethylene terephthalate unit" refers to a polyester copolymer in which the copolymerization component is isophthalic acid or bisphenol A and the ethylene terephthalate unit accounts for 80 mol% or more.
In addition, as the polyester-based resin, a single polyester may be used or two or more different polyesters may be used in combination, but when two or more different polyesters are used in combination, from the viewpoint of compatibility of the two or more components, a difference in intrinsic viscosity (IV value) between the polyesters to be used is preferably 0.50 or less, and more preferably 0.30 or less.
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 ortho-chlorophenol.
(2) Calculate a relative viscosity η_r by the following formula using an Ostwald viscometer at a temperature of 25°C and round off to the second decimal place. $η_{r} = η / η_{0} = (t \times d) / (t_{0} \times d_{0})$ $Intrinsic viscosity (IV value) = 0.0242 η_{r} + 0.2634$ (where η represents the viscosity of a polymer solution, η₀ represents the viscosity of ortho-chlorophenol, t represents a dropping time (seconds) of the solution, d represents the density (g/cm³) of the solution, t₀ represents the dropping time (seconds) of ortho-chlorophenol, and d₀ represents the density (g/cm³) of ortho-chlorophenol)

As the cross-sectional shape of the fine fiber, from the viewpoint of processing workability, it is preferable to have a round cross section (the cross-sectional shape is a perfect circle), but other shapes, for example, polygonal shapes (including shapes with rounded corners) such as an ellipse, a capsule, and a triangle, and cross-sectional shapes such as a fan shape, a cross shape, a hollow shape, a Y shape, a T shape, and a U shape can also be adopted in accordance with desired characteristics.
In the present embodiment, the fine fiber has an average monofilament diameter of 0.01 µm or more and 10.00 µm or less. The average monofilament diameter of the fine fiber is 0.01 µm or more, preferably 1.00 µm or more, thereby providing an artificial leather that exhibits excellent effects of color development after dyeing, color fastness to light and color fastness to rubbing, and stability during spinning. Meanwhile, the average monofilament diameter of the fine fiber is 10.00 µm or less, preferably 5.00 µm or less, thereby providing an artificial leather having smooth touch and dense surface quality.
In the present embodiment, the average monofilament diameter of the fine fiber is calculated by photographing an SEM image using a scanning electron microscope (SEM, for example, "VHX-D500/D510" manufactured by KEYENCE CORPORATION. Hereinafter, when the measurement device is exemplified in the description of the measurement method, the exemplified device or a device having performance equivalent thereto is used for the measurement) for an artificial leather cross section, randomly selecting 10 pieces of fine fibers having a circular shape or an elliptical shape close to a circular shape, measuring the monofilament diameters of the fine fibers, calculating the arithmetic average of 10 pieces of monofilament diameters, and rounding off the arithmetic average to the first decimal place. However, when fine fibers having a modified cross section are used, first, the cross-sectional area of the single fiber is measured, and the diameter of a hypothetical circle on the assumption that the cross section was circular is calculated to obtain the diameter of the single fiber.
To the resin forming the fine fiber, a black pigment described later, a chromatic fine-particle oxide pigment such as "iron oxyhydroxide or cobalt aluminate", inorganic particles such as titanium oxide particles, a lubricant, a heat stabilizer, an ultraviolet absorber, a conducting agent, a heat storage agent, and an antimicrobial can be added according to various purposes as long as the object of the present invention is not impaired.
In particular, in the present embodiment, the fine fiber preferably includes a black pigment in order to achieve both a dark color and uniform color developability. As this black pigment, carbon-based black pigments such as carbon black and graphite, and oxide-based black pigments such as triiron tetraoxide and composite oxides of copper and chromium can be used. Particularly, the black pigment is more preferably carbon black from the viewpoint of easily obtaining a black pigment having a small particle diameter and excellent dispersibility in a polymer.
When the fine fiber includes a black pigment, the average particle diameter of the black pigment is preferably 0.05 µm or more and 0.20 µm or less. The average particle diameter of the black pigment herein refers to an average particle diameter in a state where the black pigment is present in the fine fiber, and commonly refers to what is called a secondary particle diameter, that is, an average particle diameter in an aggregated state.
The average particle diameter of the black pigment is preferably 0.05 µm or more, more preferably 0.07 µm or more, whereby the black pigment is held inside the fine fibers, and thus the pigment is prevented from falling off from the fine fibers. Therefore, the artificial leather becomes excellent in fastness to rubbing. In addition, the average particle diameter of the black pigment is set to preferably 0.20 µm or less, more preferably 0.18 µm or less, and still more preferably 0.16 µm or less, making it possible to suppress the exposure of the pigment to the surface of the fine fiber, and to be excellent in stability during spinning and yarn strength, and thus the artificial leather becomes excellent in abrasion resistance and strength.
In addition, when the fine fiber includes a black pigment, the coefficient of variation (CV) in particle diameter of the black pigment is preferably 75% or less. When the coefficient of variation (CV) of the particle diameter of the black pigment is 75% or less, preferably 65% or less, more preferably 60% or less, still more preferably 55% or less, and most preferably 50% or less, the distribution of the particle diameter becomes small, thus suppressing the exposure of the pigment on the surface of the fine fibers, falling off of small particles from the surface, spinning faults due to significantly aggregated particles, a significant decrease in yarn strength, and the like. The lower limit of the coefficient of variation in the particle diameter in the present embodiment is not particularly limited, but is preferably 0.1% or more from the viewpoint of spinning operability and manufacturing cost.
In the present embodiment, the average particle diameter and the coefficient of variation (CV) of the black pigment are calculated by the following method.

(1) An ultrathin section having a thickness of 5 µm to 10 µm is prepared in a cross-sectional direction of a plane perpendicular to the longitudinal direction of the fine fiber. For the preparation of this ultrathin section, for example, an ultramicrotome "MT6000 type" manufactured by Sorvall can be used.
(2) A fiber cross section in the ultrathin section is observed with a transmission electron microscope (TEM, for example, "H7700 type" manufactured by Hitachi High-Tech Corporation) at a magnification of 10,000 times.
(3) Using image analysis software (for example, "WinROOF" manufactured by Mitani Corporation), the equivalent-circle diameter of the particle diameter of the black pigment contained in a visual field of 2.3 µm × 2.3 µm of the observation image is measured at 20 points. When the number of particles of the black pigment contained in a visual field of 2.3 µm × 2.3 µm is less than 20, the equivalent-circle diameters of the particle diameters of the existing particles of the black pigment are all measured.
(4) The average value (arithmetic average) and the coefficient of variation (CV) are calculated for the particle diameters at the measured 20 points. In the present embodiment, the coefficient of variation is calculated by the following equation.

Coefficient of variation of particle diameter (%) = (standard deviation of particle diameter)/(arithmetic average of particle diameter) × 100

In addition, when the fine fiber includes a black pigment, the content of the black pigment included in the resin that forms the fine fiber is preferably 0.1 mass% or more and 5.0 mass% or less, and more preferably 2.0 mass% or more and 5.0 mass% or less with respect to the mass of the fine fiber. When the proportion of the pigment is 0.1 mass% or more, preferably 1.0 mass% or more, more preferably 2.0 mass% or more, still more preferably 2.5 mass% or more, and most preferably 3.0 mass% or more, an artificial leather having dark color and excellent developability is obtained. When the proportion of the pigment is 5.0 mass% or less, preferably 4.5 mass% or less, and more preferably 4.0 mass% or less, an artificial leather having high physical properties such as strength and elongation can be obtained.
In the present embodiment, the content of the black pigment contained in the resin that forms the fine fiber is calculated by the following method.

(1) The artificial leather is immersed in a solution containing dimethylformamide or the like, and the polymer elastic body is removed to collect the fine fibers.
(2) The resin of the collected fine fibers is dissolved using a mixed solution of phenol and tetrachloroethane, and only the black pigment is then extracted.
(3) Generated gas analysis is performed on the extracted black pigment, and a calibration curve for generated gas derived from the black pigment is created.
(4) The artificial leather is subjected to de-dyeing treatment, the polymer elastic body is extracted with dimethylformamide or the like to leave only the fine fibers, and then the fine fibers are collected.
(5) Generated gas analysis is performed on the collected fine fibers, and the proportion of the black pigment contained in the fine fibers is calculated from the detection intensity of generated gas derived from the black pigment and the calibration curve created in (3).

The fiber entangled body according to the artificial leather of the present embodiment includes a nonwoven fabric composed of the fine fiber.
In the present embodiment, a "fiber entangled body including a nonwoven fabric" refers to an aspect in which the fiber entangled body is a nonwoven fabric, or an aspect in which the fiber entangled body is formed by entangling and integrating a nonwoven fabric and a woven fabric as described later, an aspect in which the fiber entangled body is formed by entangling and integrating a nonwoven fabric and a substrate other than a woven fabric, and the like.
Forming the fiber entangled body including a nonwoven fabric makes it possible to provide an appearance and a hand that are uniform and elegant when the surface is napped.
Examples of the form of this nonwoven fabric include a long fiber nonwoven fabric mainly composed of filaments as well as a short fiber nonwoven fabric mainly composed of fibers of 100 mm or less. When the short fiber nonwoven fabric is used, the number of fibers oriented in the thickness direction of the artificial leather can be increased as compared with the case where the long fiber nonwoven fabric is used. Then, the surface of the artificial leather when napped can have a high dense feeling and a favorable touch sensation.
The fiber length of the fine fibers in a case of using the short fiber nonwoven fabric is preferably 25 mm or more and 95 mm or less. The fiber length is preferably 95 mm or less, more preferably 85 mm or less, and still more preferably 75 mm or less, thereby providing an artificial leather excellent in hand and having a dense and smooth surface quality. In contrast, the fiber length is preferably 25 mm or more, more preferably 35 mm or more, and still more preferably 40 mm or more, thereby providing an artificial leather excellent in abrasion resistance.
In the artificial leather of the present embodiment, for improving the strength and shape stability of the artificial leather, it is possible to laminate, entangle and integrate a woven fabric inside or on one side of the nonwoven fabric.
As the type of fibers constituting the woven fabric used when the woven fabric is entangled and integrated, a filament yarn, a spun yarn, a mixed composite yarn of a filament yarn and a spun yarn, and the like are preferably used. Among these, from the viewpoint of durability, particularly mechanical strength and the like, it is more preferable to use a multifilament containing a polyester-based resin or a polyamide-based resin as a main component.
The average monofilament diameter of the fiber constituting the woven fabric is preferably 1.0 µm or more and 50.0 µm or less. The average monofilament diameter of the fiber constituting the woven fabric is preferably 50.0 µm or less, more preferably 15.0 µm or less, and still more preferably 13.0 µm or less, thereby providing an artificial leather excellent in flexibility. In addition, when the fibers of the woven fabric are exposed on the surface of the artificial leather, the hue difference from the fine fiber containing the pigment after dyeing is reduced, thus providing the artificial leather in which the uniformity of the hue of the surface is not impaired. Meanwhile, the average monofilament diameter of the fiber constituting the woven fabric is preferably 1.0 µm or more, more preferably 8.0 µm or more, and still more preferably 9.0 µm or more, thereby providing an artificial leather having higher product shape stability.
In the present embodiment, the average monofilament diameter of fibers constituting the woven fabric is calculated by photographing an SEM image of a cross section of the artificial leather with a scanning electron microscope (SEM, for example, "VHX-D500/D510" type manufactured by Keyence Corporation), randomly selecting 10 fibers constituting the woven fabric, measuring the single fiber diameters of the fibers, calculating the arithmetic average of the 10 fibers, and rounding off the arithmetic average to the first decimal place.
When the fibers constituting the woven fabric are multifilaments, a total fineness of the multifilaments is measured according to "8.3.1 Fineness based on corrected mass b) Method B (simple method)" in "8.3 Fineness" of JIS L 1013:2010 "Chemical fiber filament yarn test method", and is preferably 30 dtex or more and 170 dtex or less.
The total fineness of the thread constituting the woven fabric is 170 dtex or less, thereby providing an artificial leather excellent in flexibility. Meanwhile, the total fineness is 30 dtex or more, thereby providing the artificial leather having higher product shape stability. In addition, when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, fibers constituting the woven fabric are less likely to be exposed on the surface of the artificial leather, thus providing the artificial leather having a high surface quality. At this time, the total fineness of the multifilaments of warps and wefts is preferably the same.
Further, the thread constituting the woven fabric preferably has a number of twist of 1,000 T/m or more and 4,000 T/m or less. The number of twists is preferably 4,000 T/m or less, more preferably 3,500 T/m or less, and still more preferably 3,000 T/m or less, thereby providing an artificial leather excellent in flexibility. Meanwhile, the number of twists is preferably 1,000 T/m or more, more preferably 1,500 T/m or more, and still more preferably 2,000 T/m or more, thereby allowing damage to the fiber constituting the woven fabric to be prevented when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, thus providing an artificial leather having excellent mechanical strength.

[Polymer elastic body]

The base material part according to the artificial leather of the present embodiment further includes a polymer elastic body.
Examples of the polymer elastic body include polyurethane, polyurea, polyurethane-polyurea, and polyacryl. This polymer elastic body serves as a binder for gripping the fine fiber included in the artificial leather. Thus, in consideration of achieving a soft hand of the artificial leather of the present embodiment, the polymer elastic body to be used is preferably polyurethane.
This polyurethane is obtained by reaction of a polymer diol, an organic diisocyanate, and a chain extender. Either organic solvent-based polyurethane used in the state of being dissolved in an organic solvent or water-dispersible polyurethane used in the state of being dispersed in water can be used.
When the polymer elastic body is polyurethane, examples of the polymer diol include a polycarbonate-based diol, a polyester-based diol, a polyether-based diol, a silicone-based diol, and a fluorine-based diol. A copolymer obtained by combining these can also be used. Among these, it is a preferable aspect to use a polycarbonate-based diol from the viewpoint of hydrolysis resistance and wear resistance.
First, examples of the polycarbonate-based diol include a diol obtained by a transesterification reaction of an alkylene glycol and a carbonate ester or a reaction of phosgene or a chloroformate ester and an alkylene glycol.
In addition, examples of the alkylene glycol used for the polycarbonate-based diol 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 embodiment, either the polycarbonate-based diol obtained from a single alkylene glycol or the copolymerized polycarbonate-based diol obtained from two or more kinds of alkylene glycols can be adopted.
Examples of the polyester-based diol include diols obtained by condensing various low molecular weight polyols with a polybasic acid.
As the low molecular weight polyol used for the polyester-based diol, 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, cyclohexane-1,4-dimethanol, and adducts obtained by adding various alkylene oxides to bisphenol A can be used.
In addition, examples of the polybasic acid used in the polyester-based diol 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.
Further, examples of the polyether-based diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and a copolymerized diol combining these.
When the polymer elastic body is polyurethane, the number average molecular weight of the polymer diol is preferably in the range of 500 or more and 4,000 or less when the molecular weight of the polyurethane-based elastomer is constant. The number average molecular weight is preferably 500 or more, more preferably 1,500 or more, thereby allowing the artificial leather to be prevented from becoming hard, and providing a more flexible artificial leather. In addition, the number average molecular weight is preferably 4,000 or less, and more preferably 3,000 or less, thereby allowing the strength as polyurethane to be maintained, and providing an artificial leather having higher strength.
Then, when the polymer elastic body is polyurethane, examples of usable organic diisocyanates include aliphatic diisocyanates such as "hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate"; and aromatic diisocyanates such as "diphenylmethane diisocyanate and tolylene diisocyanate", which may be used in combination.
When the polymer elastic body is polyurethane, an amine-based chain extender such as "ethylenediamine or methylenebisaniline" and a diol-based chain extender such as "ethylene glycol" can be preferably used as the chain extender. In addition, a polyamine that is obtained by reacting polyisocyanate and water can be used as a chain extender.
Further, when the polymer elastic body is polyurethane, a crosslinker can be used in combination for the purpose of improving water resistance, abrasion resistance, hydrolysis resistance, and the like. The crosslinker may be either an external crosslinker to be added to polyurethane as a third component or an internal crosslinker that contains a reaction point acting as a crosslinking structure in the polyurethane molecular structure. It is preferable to use the internal crosslinker from a viewpoint that crosslinking points can be formed more uniformly in the polyurethane molecular structure and that a decrease in flexibility can be reduced.
A compound containing an isocyanate group, an oxazoline group, a carbodiimide group, an epoxy group, a melamine resin, or a silanol group can be used as the crosslinker.
In the present embodiment, the mass ratio of the polymer elastic body in the artificial leather is 15 mass% or more and 40 mass% or less. The mass ratio of the polymer elastic body is 15 mass% or more, preferably 18 mass% or more, and more preferably 21 mass% or more, thereby allowing the bonding by the polymer elastic body between fibers to be strengthened. Further, the artificial leather has high abrasion resistance. Meanwhile, the mass ratio of the polymer elastic body is 40 mass% or less, preferably 37 mass% or less, and more preferably 34 mass% or less, thereby providing an artificial leather that easily follows a complicated shape and has excellent moldability.
Note that the mass ratio of the polymer elastic body in the artificial leather is measured and calculated by the following method.

(1) Three test pieces having a length of 20 cm × a width of 20 cm are randomly collected from an artificial leather, and the mass of each test piece is measured.
(2) The test piece is immersed in a solution to dissolve the polymer elastic body (for example, when the polymer elastic body is polyurethane, dimethylformamide is used) to remove the polymer elastic body, and fine fibers are collected.
(3) The mass of the collected fine fibers is measured, and the mass ratio of the polymer elastic body in the test piece is calculated by the following formula. Mass ratio (%) of polymer elastic body in test piece = {(mass of test piece) - (mass of fine fiber)}/(mass of test piece) × 100
(4) The mass ratio (%) of the polymer elastic body in each of the three test pieces is calculated, and the arithmetic average value (%) thereof is rounded off to the nearest integer.

In addition, the polymer elastic body may contain various additives including pigments such as "inorganic and oxide-based pigments"; flame retardants such as "phosphorus, halogen, and inorganic flame retardants"; antioxidants such as "phenolic, sulfur, and phosphorus antioxidants"; ultraviolet absorbers such as "benzotriazole, benzophenone, salicylate, cyanoacrylate, and oxalic acid anilide ultraviolet absorbers"; light stabilizers such as "hindered amine and benzoate light stabilizers"; hydrolysis stabilizers such as polycarbodiimide; plasticizers; antistatic agents; surfactants; coagulation modifiers; and dyes according to the purpose.
In the artificial leather of the present embodiment, for example, in order to achieve both a dark color and uniform color developability, the polymer elastic body preferably includes a black pigment. As this black pigment, carbon-based black pigments such as carbon black and graphite, and oxide-based black pigments such as triiron tetraoxide and composite oxides of copper and chromium can be used. Particularly, the black pigment is more preferably carbon black from the viewpoint of easily obtaining a black pigment having a small particle diameter and excellent dispersibility in a polymer.
When this polymer elastic body includes a black pigment, the average particle diameter of the black pigment is more preferably 0.05 µm or more and 0.20 µm or less. The average particle diameter of the black pigment herein refers to an average particle diameter in a state where the black pigment is present in the polymer elastic body, and commonly refers to what is called a secondary particle diameter, that is, an average particle diameter in an aggregated state.
The average particle diameter of the black pigment is preferably 0.05 µm or more, more preferably 0.07 µm or more, whereby the black pigment is held inside the polymer elastic body, and thus the pigment is prevented from falling off from the polymer elastic body. Therefore, the artificial leather becomes excellent in fastness to rubbing. In addition, the average particle diameter of the black pigment is preferably 0.20 µm or less, preferably 0.18 µm or less, and more preferably 0.16 µm or less, thereby allowing excellent dispersibility to be obtained when the polymer elastic body is impregnated, and thus an artificial leather having small variations in hue is obtained.
In addition, when the polymer elastic body includes a black pigment, the coefficient of variation (CV) in particle diameter of the black pigment is preferably 75% or less.
When the coefficient of variation (CV) of the particle diameter of the black pigment is 75% or less, preferably 65% or less, more preferably 60% or less, still more preferably 55% or less, and most preferably 50% or less, a distribution of the particle diameter becomes small, and falling off of small particles from a surface of the polymer elastic body, precipitation of significantly aggregated particles in an impregnation tank, and the like are suppressed. The lower limit of the coefficient of variation in particle diameter in the present embodiment is not particularly limited, but is preferably 0.1% or more from the viewpoint of operability when the polymer elastic body is impregnated.
In the present embodiment, the average particle diameter and the coefficient of variation (CV) of the black pigment included in the polymer elastic body are calculated by the following method.

(1) An ultrathin section having a thickness of 5 µm to 10 µm is prepared in a cross-sectional direction of a plane perpendicular to a longitudinal direction of the artificial leather.
(2) A cross section of the polymer elastic body in the ultrathin section is observed with a transmission electron microscope (TEM, for example, "H7700 type" manufactured by Hitachi High-Tech Corporation) at a magnification of 10,000 times.
(3) Using image analysis software (for example, "WinROOF" manufactured by Mitani Corporation), the equivalent-circle diameter of the particle diameter of the black pigment contained in a visual field of 2.3 µm × 2.3 µm of the observation image is measured at 20 points. When the number of particles of the black pigment contained in a visual field of 2.3 µm × 2.3 µm is less than 20, the equivalent-circle diameters of the particle diameters of the existing particles of the black pigment are all measured.
(4) The average value (arithmetic average) and the coefficient of variation (CV) are calculated for the particle diameters at the measured 20 points. In the present embodiment, the coefficient of variation is calculated by the following equation.

In addition, when the polymer elastic body includes a black pigment, the content of the black pigment included in the polymer elastic body is preferably 0.01 mass% or more and 5.0 mass% or less with respect to the mass of the polymer elastic body. The mass ratio of the pigment is preferably 0.01 mass% or more, more preferably 0.1 mass% or more, and still more preferably 1.0 mass% or more, thereby providing an artificial leather excellent in dark color developability. Meanwhile, the mass ratio of the pigment is 5.0 mass% or less, preferably 4.5 mass% or less, and more preferably 4.0 mass% or less, thereby providing an artificial leather having high physical properties such as strength.
In the present embodiment, the content of the black pigment included in the polymer elastic body is calculated by the following method.

(1) An artificial leather is immersed in a mixed liquid of phenol and tetrachloroethane to dissolve fine fibers, and a polymer elastic body is collected.
(2) The collected polymer elastic body is dissolved in a solution using dimethylformamide or the like, and only the black pigment is extracted.
(3) Generated gas analysis is performed on the extracted black pigment, and a calibration curve for generated gas derived from the black pigment is created.
(4) The polymer elastic body included in the artificial leather is dissolved using dimethylformamide or the like, and then dimethylformamide or the like is removed to solidify the polymer elastic body again.
(5) The analysis of the gas generated is performed on the polymer elastic body obtained in (4), and the content of the black pigment included in the polymer elastic body constituting the artificial leather is calculated from the generated gas detection intensity derived from the black pigment and the calibration curve created in (3).

[Artificial leather]

The artificial leather of the present embodiment includes a base material part including the fiber entangled body and the polymer elastic body, and nap portions on at least one surface. Herein, the base material part is a part including the above-described fiber entangled body and the above-described polymer elastic body, and corresponds to a part in which the surface of a "base sheet" described in a method for manufacturing an artificial leather as described later is not buffed as viewed from a thickness direction. The nap portion refers to a portion in which the above-described fine fiber is dispersed without being gripped by the above-described polymer elastic body, and corresponds to a portion in which the surface of a "base sheet" described in the method for manufacturing an artificial leather as described later is buffed as viewed from a thickness direction.
As exemplified in Fig. 1, the artificial leather of the present embodiment has a nap portion on at least one surface. Both surfaces may be surfaces having nap portions. The form of the nap on the nap surface preferably has a length of the nap and directional flexibility to such an extent as to emit a so-called finger mark, in which a trace remains as the direction of the nap changes during trace with a finger, from the viewpoint of favorable surface quality after molding processing and designability.
First, for the artificial leather of the present embodiment, the area ratio of the polymer elastic body on the surface of the artificial leather on the side having at least one nap portion is 0.01% or more and 3.00% or less. That is, when both surfaces are surfaces having nap portions, at least one surface may satisfy this range.
The area ratio (hereinafter, may be abbreviated as "the area ratio of the polymer elastic body on the surface") of the polymer elastic body on the surface of the artificial leather on the side having at least one nap portion is 0.01% or more, preferably 0.05% or more, and more preferably 0.10% or more, thereby providing an artificial leather having excellent abrasion resistance in which the fine fiber present in the nap portion is moderately gripped by the polymer elastic body at the boundary line between the nap portion and the base material part of the artificial leather. Meanwhile, the area ratio of the polymer elastic body on the surface is 3.00% or less, preferably 2.00% or less, and more preferably 1.00% or less, thereby providing an artificial leather that retains a dense and smooth surface quality and a favorable touch sensation also after molding processing.
The area ratio of the polymer elastic body on the surface of the artificial leather can be set within a predetermined range by adjusting the widening ratio in the width direction of the polyvinyl alcohol-imparted sheet, the apparent density of polyvinyl alcohol included in the nonwoven sheet, the buffing conditions of the surface of the base sheet, and the ratio t_A/t_B of the thickness t_A of the base material part and the thickness t_B of the nap portion of the artificial leather.
In addition, the standard deviation (hereinafter, may be abbreviated as "standard deviation of the area ratio of the polymer elastic body on the surface") of the area ratio of the polymer elastic body on the surface of the artificial leather on the side having at least one nap portion is preferably 25% or less. That is, when both surfaces are surfaces having nap portions, at least one surface may satisfy this range. The standard deviation of the area ratio of the polymer elastic body on at least one surface of the artificial leather is preferably 25% or less, more preferably 23% or less, and still more preferably 20% or less, thereby providing an artificial leather that maintains a dense and smooth surface quality after molding processing at any place of the artificial leather. The lower limit of the standard deviation of the area ratio of the polymer elastic body in the cross section in the present embodiment is not particularly limited. However, it is preferably 1% or more.
The standard deviation of the area ratio of the polymer elastic body on the surface of the artificial leather can be set within a predetermined range by adjusting the widening ratio in the width direction of the polyvinyl alcohol-imparted sheet, the apparent density of polyvinyl alcohol included in the nonwoven sheet, and the buffing conditions of the surface of the base sheet.
In the present embodiment, the area ratio of the polymer elastic body on the surface of the artificial leather and the standard deviation of the area ratio of the polymer elastic body on the surface are calculated by the following method.

(1) A test piece having a length of 0.5 cm × a width of 0.5 cm is randomly collected from artificial leather, and is allowed to stand in saturated vapor of ruthenium tetroxide for 4 hours. As a result, the polyurethane exposed on the surface of the artificial leather is electronically dyed.
(2) The surface of the artificial leather is coated with osmium atoms in a thickness of 1 nm and subjected to a conductive treatment.
(3) The surface of the artificial leather is observed with a field emission scanning electron microscope (for example, "JSM-7800F Prime" manufactured by JEOL Ltd.) at a magnification of 100.
(4) For the obtained SEM image, for example, using image analysis software "ImageJ" or the like, the image is binarized by the following method, and the area ratio of the polymer elastic body on the surface of the artificial leather is calculated.
1. (i) The SEM image is filtered. If "ImageJ", the processing conditions are as follows.
  - Bilateral Filter of the Bilateral Filter Fije plugin spacial radius: 3
  - range radius: 50
  - Number of times of filter treatment: 5 times
2. (ii) The black portion in the SEM image after binarization performed by the MaxEntropy method
  is regarded as a polymer elastic body.
3. (iii) The obtained binarized image (2560 × 1920 pixels) is sectioned into 32 × 32 pixels (in this case, it is divided into 4800). Then, if "ImageJ", the total of the areas of the polymer elastic bodies distributed in each section is divided by the area of each section as the area ratio (%) of the polymer elastic bodies exposed on the surface of each section using the Analyze Particle function (a function of measuring a particle diameter and an area of particles. If "ImageJ", the condition is set as follows: Size = 0 to infinity, Circularity = 0.00 to 1.00).
4. (iv) The number of pixels of the x and y axes of the target image is read, the section size is designated by a pixel size, the number of divisions of the x and y axes is obtained, and the area ratio of the polymer elastic body in each divided region is calculated. The area ratio (%) of the polymer elastic body on the surface of the artificial leather is obtained by averaging the area ratio (%) of the polymer elastic body for all the sections, and its standard deviation is an index of variation from the average value for all the sections.

However, the standard deviation is calculated for all the sections obtained by dividing one image into sections, but when 100 images are prepared, the average value and the standard deviation of the area ratio (%) of the surface polymer elastic body are obtained for all the calculation results of all the sections of each of the 100 images (in the above case, (100 images) × (4800 sections) = 480,000).
As the image analysis software, the image analysis software "ImageJ" described above is exemplified, but the image analysis software is not limited to the image analysis software "ImageJ" as long as the image analysis software includes image processing software having a function of calculating a specified area ratio of pixels. Note that the image analyzing software "ImageJ" is common software, and was developed by the National Institutes of Health. The image processing software "ImageJ" has a function of specifying a necessary region and performing pixel analysis on the captured image.
Then, in the present embodiment, the area ratio of the polymer elastic body in the cross section of the artificial leather is 5% or more and less than 15%. The area ratio of the polymer elastic body in the cross section of the artificial leather (hereinafter, may be abbreviated as "the area ratio of the polymer elastic body in the cross section") is 5% or more, more preferably 7% or more, and still more preferably 9% or more, thereby providing an artificial leather having favorable strength and abrasion resistance while the polymer elastic body is sufficiently bonded between fibers and breakage of the artificial leather in molding processing is suppressed. Meanwhile, the area ratio of the polymer elastic body of the cross section is less than 15%, more preferably 14% or less, and still more preferably 13% or less, thereby providing the artificial leather excellent in moldability with easy followability to a complicated shape.
In addition, the standard deviation of the area ratio of the polymer elastic body in the cross section of the artificial leather is preferably 25% or less. The standard deviation of the area ratio of the polymer elastic body in the cross section of the artificial leather is preferably 25% or less, more preferably 23% or less, and still more preferably 20% or less, thereby providing an artificial leather in which every part of the artificial leather can uniformly follow a complicated shape during molding processing, and not only moldability is excellent but also a dense and smooth surface quality is maintained. The lower limit of the standard deviation of the area ratio of the polymer elastic body in the cross section in the present embodiment is not particularly limited. However, it is preferably 1% or more.
In the present embodiment, the area ratio of the polymer elastic body of the cross section of the artificial leather and the standard deviation of the area ratio of the polymer elastic body of the cross section are calculated by the following method.

(1) A test piece having a length of 0.5 cm × a width of 1.0 cm is randomly collected from an artificial leather, and the internal space is embedded with an epoxy-based resin.
(2) The resin-embedded test piece is cut in parallel with the thickness direction with a microtome.
(3) The test piece obtained by cutting is allowed to stand in saturated vapor of ruthenium tetroxide for 4 hours. As a result, the polymer elastic body of the cross section of the artificial leather is electronically dyed.
(4) The cross section of the artificial leather is coated with osmium atoms in a thickness of 1 nm and subjected to a conductive treatment.
(5) The cross section of the artificial leather is observed with a field emission scanning electron microscope (for example, "JSM-7800F Prime" manufactured by JEOL Ltd.) at a magnification of 500.
(6) For the obtained SEM image, for example, using image analysis software "ImageJ" or the like, the image is binarized by the following method, and the area ratio (%) of the polymer elastic body of the cross section of the artificial leather is calculated.
1. (i) The SEM image is filtered. If "ImageJ", the processing conditions are as follows.
  - "Bandpass filter processing" (this is processing for removing a high spatial frequency component and a low spatial frequency component)
  - Filter large structures down to 40 pixels
  - Filter small structures up to 3 pixels
  - Suppress stipes: None
  - Tolerance of direction: 5%
  - Autoscale after filtering: yes
  - Saturate image when autoscaling: yes
  - Number of times of filter treatment: once
  - "Median filter processing" (this is processing for reducing noise in an image by replacing each pixel value with a median value of pixel values in the vicinity thereof.)
  - Radius: 4.0
  - Number of times of filter treatment: once
2. (ii) The black portion in the SEM image after binarization performed by the MaxEntropy method
  is regarded as a polymer elastic body.
3. (iii) The obtained binarized image (1280 × 960 pixels) is sectioned into 32 × 32 pixels (in this case, it is divided into 1200). Then, if "ImageJ", the Analyze Particle function (a function of measuring the particle size and area of the particles. If "ImageJ", the condition is set as follows: Size = 0 to infinity, Circularity = 0.00 to 1.00) is used, and the total of the areas of the respective polymer elastic bodies distributed in each section is divided by the area of each section as the area ratio (%) of the polymer elastic bodies exposed to the cross section of each section.
4. (iv) The number of pixels of the x and y axes of the target image is read, the section size is designated by a pixel size, the number of divisions of the x and y axes is obtained, and the area ratio of the polymer elastic body in each divided region is calculated. The area ratio (%) of the polymer elastic body of the cross section of the artificial leather is obtained by averaging the area ratio (%) of the polymer elastic body for all the sections, and its standard deviation is an index of variation from the average value for all the sections.

However, the standard deviation is calculated for all the sections obtained by dividing one image into sections, but when 100 images are prepared, the average value and the standard deviation of the area ratio (%) of the cross-sectional polymer elastic body are obtained for all the calculation results of all the sections of each of the 100 images (in the above case, (100 images) × (1200 sections) = 120,000).
Further, it is preferable that a thickness of the base material part t_A is 250 µm or more and 800 µm or less, and a ratio of the thickness t_A of the base material part to a thickness t_B of a nap portion, t_A/t_B, is 0.5 or more and 2.5 or less. Satisfying these two requirements provides an artificial leather excellent in abrasion resistance while local breakage of the artificial leather is suppressed in molding processing and a dense and smooth surface quality is maintained.
First, the thickness t_A of the base material part is preferably 250 µm or more and 800 µm or less. The thickness t_A of the base material part is preferably 250 µm or more, more preferably 300 µm or more, thereby providing an artificial leather while local breakage of the artificial leather is suppressed in molding processing and a dense and smooth surface quality is maintained. Meanwhile, setting the thickness t_A of the base material part to preferably 800 µm or less, more preferably 700 µm or less, provides an artificial leather that can uniformly follow a complicated shape in molding processing.
Then, the ratio t_A/t_B of the thickness t_A of the base material part of the artificial leather to the thickness t_B of the nap portion is preferably 0.5 or more and 2.5 or less. The ratio t_A/t_B is preferably 0.5 or more, more preferably 0.7 or more, thereby providing an artificial leather excellent in abrasion resistance while uniform and dense surface quality is maintained. Meanwhile, setting the ratio t_A/t_B to preferably 2.5 or less, more preferably 2.2 or less can reduce the area ratio of the polyurethane exposed on the surface of the artificial leather while the touch sensation of the artificial leather is smoothed.
The coefficient of variation of the thickness t_A of the base material part is preferably 50% or less. The coefficient of variation of the thickness t_A of the base material part is preferably 50% or less, more preferably 25% or less, and still more preferably 10% or less, thereby providing an artificial leather that can uniformly follow a complicated shape and maintain a dense and smooth surface quality while local breakage of the artificial leather is suppressed in molding processing. The lower limit of the coefficient of variation of the thickness t_A of the base material part in the present embodiment is not particularly limited.
In addition, the thickness t_B of the nap portion is preferably 300 µm or more and 500 µm or less. The average length of the nap is preferably 300 µm or more, more preferably 350 µm or more, making it possible to reduce the area ratio of the polymer elastic body exposed on the surface of the artificial leather while the touch sensation of the artificial leather is smoothed. Meanwhile, the thickness t_B of the nap portion is preferably 500 µm or less, more preferably 450 µm or less, thereby providing an artificial leather excellent in abrasion resistance while uniform and dense surface quality is maintained.
Further, the coefficient of variation of the thickness t_B of the nap portion is preferably 50% or less. The coefficient of variation of the thickness t_B of the nap portion is preferably 50% or less, more preferably 40% or less, and still more preferably 30% or less, thereby providing an artificial leather in which the area ratio of the polymer elastic body exposed on the surface of the artificial leather is reduced to be easily in the above range, and both uniform and dense surface quality and a smooth touch sensation are achieved. The lower limit of the coefficient of variation of the thickness t_B of the nap portion in the present embodiment is not particularly limited. However, it is preferably 1% or more.
In the present embodiment, the thickness t_A of the base material part and its standard deviation, and the thickness t_B of the nap portion and its standard deviation are measured and calculated by the following method.

(1) A thin section with a thickness of 1 mm is prepared in a cross-sectional direction of a plane perpendicular to the longitudinal direction of the artificial leather in a state where the raised nap of the artificial leather is ruffed by using a lint brush or the like.
(2) The cross section of the artificial leather is photographed with a scanning electron microscope (SEM, for example, "VHX-D500/D510" manufactured by Keyence Corporation) at a magnification of 90 times.
(3) In the photographed SEM image, in accordance with the schematic view of the cross section of the artificial leather shown in Fig. 2, perpendicular lines are drawn, at intervals of 200 µm, on a line (L_A in Fig. 2) parallel to the bottom surface (L_B in Fig. 2) of the artificial leather.
(4) Points P₁ to P₁₀ are marked on a boundary line (L₀ in Fig. 2) between the nap portion (2 in Fig. 2) and the base material part (3 in Fig. 2).
(5) Normal lines (dashed-dotted lines in Fig. 2) are drawn from points P₁ to P₁₀ in the direction of the nap portion and the direction of the base material part, respectively, and points Q₁ to Q₁₀ intersecting the end of the nap portion and points S₁ to S₁₀ intersecting the end of the base material part are marked.
(6) A value obtained by setting a distance T₁ between the points P₁ and S₁, similarly obtaining up to T₁₀, and rounding off an average value (arithmetic average value) (µm) thereof to the nearest integer is set as a thickness t_A (µm) of the base material part. Then, the coefficient of variation (%) of the thickness t_A of the base material part is calculated by the following formula. Coefficient of variation (%) of thickness t_A of base material part = (standard deviation (µm) of thickness t_A (distance T₁ to distance T₁₀) of base material part)/(arithmetic average value (µm) of thickness t_A (distance T₁ to distance T₁₀) of base material part) × 100
(7) The distance R₁ between the points P₁ and Q₁ is similarly obtained up to R₁₀, and the average value (arithmetic average value) (µm) thereof is rounded off to the nearest integer to obtain the thickness t_B (µm) of the nap portion. The coefficient of variation (%) of thickness t_B of the nap portion is calculated by the following formula. Coefficient of variation (%) of thickness t_B of nap portion = (standard deviation (µm) of thickness t_B of nap portion (distance R₁ to distance R₁₀))/(arithmetic average value (µm) of thickness t_B of nap portion (distance R₁ to distance R₁₀)) × 100

In the present embodiment, the basis weight of the artificial leather is preferably 150 g/m² or more and 450 g/m² or less. The basis weight of the artificial leather is preferably 150 g/m² or more, more preferably 175 g/m² or more, thereby providing the artificial leather excellent in strength and abrasion resistance while breakage during molding processing is suppressed. Meanwhile, the basis weight of the artificial leather is preferably 450 g/m² or less, more preferably 400 g/m² or less, thereby providing the artificial leather that can uniformly follow a complicated shape in molding processing.
The basis weight of the artificial leather of the present embodiment is measured in accordance with "6.2 Mass per unit area (ISO method)" of JIS L 1913:2010 "Test methods for nonwovens", and is specifically measured and calculated as follows.

(1) Three test pieces having a length of 30 cm × a width of 30 cm are taken from the artificial leather.
(2) The mass of each test piece of (1) is measured.
(3) The mass per unit area of each test piece is calculated by the following equation. Mass per unit area (g/m²) = mass of test piece (g)/area of test piece (m²)
(4) A value obtained by rounding the arithmetic average (g/m²) of the mass per unit area obtained in (3) down to the nearest integer is employed as the weight per unit area of the artificial leather.

The artificial leather of the present embodiment preferably has a thickness of 0.5 mm or more and 1.2 mm or less as measured according to "6.1.1 A method" in "6.1 Thickness (ISO method)" of JIS L1913:2010 "Test methods for nonwovens". The thickness of the artificial leather is preferably 0.5 mm or more, more preferably 0.6 mm or more, thereby providing an artificial leather excellent in strength and abrasion resistance while local breakage of the artificial leather during molding processing is suppressed. Meanwhile, the thickness of the artificial leather is preferably 1.2 mm or less, more preferably 1.0 mm or less, thereby providing the artificial leather that can uniformly follow a complicated shape in molding processing.
In the artificial leather of the present embodiment, the fastness to rubbing measured by a "9.1 rubbing tester type I (clock meter) method" according to JIS L0849:2013 "The methods for color fastness to rubbing" and color fastness to light measured by a "7.2 Exposure method a) First exposure method" according to JIS L0843:2006 "The methods for color fastness to light of xenon arc lamp" are each preferably grade 3 or higher. The fastness to rubbing and color fastness to light are grade 3 or higher, thereby providing an artificial leather that is less likely to cause color loss and staining on clothing or the like in actual use. For the determination of the grade for each fastness, the gray scale for contamination specified in JIS L0805:2005 "Grey scale for assessing staining" is used for the fastness to rubbing of the artificial leather, and the gray scale for discoloration specified in JIS L0804:2004 "Grey scale for assessing change in color" is used for the color fastness to light of the artificial leather.
For the fastness to rubbing of the artificial leather, it is considered that the area ratio of the polymer elastic body exposed on the surface of the artificial leather, the thickness t_B of the nap portion on the surface of the artificial leather, and the coefficient of variation thereof are adjusted to specific ranges, thereby reducing friction between napped hairs, allowing falling of napped hairs to be suppressed, and improving the fastness to rubbing.
In addition, in the artificial leather of the present embodiment, the mass loss of the artificial leather after 20,000 times of abrasion under a pressing load of 12.0 kPa in an abrasion test measured in accordance with "8.19.5 Method E (Martindale method)" of "8.19 Abrasion strength and color change by rubbing" of JIS L 1096:2010 "Cloth experiment method of woven fabric and knitted fabric" is preferably 10 mg or less, more preferably 8 mg or less, still more preferably 6 mg or less. The mass loss is 10 mg or less, thereby allowing contamination due to fluff dropping during actual usage to be prevented.
For the abrasion strength of the artificial leather, in order to set the pressing load to 12.0 kPa and to set the mass loss of the artificial leather after 20,000 times of abrasion within a predetermined range, it is considered that the area ratio of the polymer elastic body of the surface of the artificial leather, the thickness t_B of the nap portion of the surface of the artificial leather, and the coefficient of variation thereof are adjusted to specific ranges, thereby reducing friction between napped hairs, and allowing the mass loss to be suppressed.
In the artificial leather of the present embodiment, the tensile strength as measured in accordance with "6.3.1 Tensile strength and elongation percentage (ISO method)" in "Test methods for nonwovens" of JIS L1913:2010 is preferably 25 N/cm or more and 100 N/cm or less in optional measurement direction.
The tensile strength is preferably 20 N/cm or more, more preferably 30 N/cm or more, thereby providing an artificial leather excellent in shape stability and durability. In addition, the tensile strength is preferably 90 N/cm or less, more preferably 80 N/cm or less, thereby providing the artificial leather that can uniformly follow a complicated shape in molding processing, and has a favorable hand.

[Method for manufacturing artificial leather]

The artificial leather of the present embodiment is preferably manufactured by any one of the following first manufacturing method and second manufacturing method.
That is, the <First manufacturing method>, which is one of preferable aspects, includes:

a step of imparting polyvinyl alcohol in an amount of 4 mass% or more and 40 mass% or less with respect to a mass of fine fiber-generating fibers to a fiber entangled body including a nonwoven fabric mainly composed of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet;
a step of developing fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less from the fine fiber-generating fibers of the polyvinyl alcohol-imparted sheet to form a nonwoven sheet;
a step of widening a width of the nonwoven sheet by 2% or more and 10% or less to form a widened sheet;
a step of imparting a polymer elastic body to the widened sheet in an amount of 12 mass% or more and 64 mass% or less with respect to a mass of the widened sheet to form a polymer elastic body-imparted sheet;
a step of removing the polyvinyl alcohol from the polymer elastic body-imparted sheet to form a base sheet; and
a step of buffing at least one surface of the base sheet.

In addition, the <Second manufacturing method>, which is another preferable aspect, includes:

a step of imparting polyvinyl alcohol in an amount of 4 mass% or more and 40 mass% or less with respect to a mass of fine fiber-generating fibers to a fiber entangled body including a nonwoven fabric mainly composed of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet;
a step of widening a width of the polyvinyl alcohol-imparted sheet by 2% or more and 10% or less to form a widened sheet;
a step of developing fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less from the fine fiber-generating fibers of the widened sheet to form a nonwoven sheet;
a step of imparting, to the nonwoven sheet, a polymer elastic body in an amount of 12 mass% or more and 64 mass% or less with respect to a mass of the nonwoven sheet to form a polymer elastic body-imparted sheet;
a step of removing the polyvinyl alcohol from the polymer elastic body-imparted sheet to form a base sheet; and
a step of buffing at least one surface of the base sheet.

The difference between the <First manufacturing method> and the <Second manufacturing method> lies in the timing of developing the fine fiber, and will be described in detail.

In this <First manufacturing method>, fine fibers are developed after a polyvinyl alcohol-imparted sheet described later is formed and before the sheet is widened in width. This can further reduce the equipment load of widening the sheet, more uniformly widen the sheet in the width direction, and provide an artificial leather that can easily follow a complicated shape and is excellent in surface quality and abrasion resistance after molding processing.

In this step, polyvinyl alcohol is added to a fiber entangled body including a nonwoven fabric mainly composed of fine fiber-generating fibers in an amount of 4 mass% or more and 40 mass% or less based on the mass of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet.
Herein, the fine fiber-generating fibers refer to a fiber that can be made into a fine fiber by the method described later. Specific examples thereof include: islands-in-the-sea fibers in which thermoplastic resins having different solvent solubility are used as a sea portion (easily soluble polymer) and an island portion (hardly soluble polymer), and the sea portion is dissolved and removed using a solvent or the like to form the island portion as fine fibers; and release type composite fibers in which two components of thermoplastic resins having different solvent solubility are alternately disposed radially or in multiple layers in a fiber cross section, and each component is separated and divided into fine fibers. Among these, from the viewpoint of the hand and surface quality of the artificial leather, the islands-in-the-sea fibers are more preferable because appropriate voids can be imparted between the island portions, that is, between the fine fibers inside the fiber bundle when the sea portion is removed. The manufactured fine fiber-generating fibers may be generally referred to as fiber.
As the method of spinning the fine fiber-generating fibers having an islands-in-the-sea fiber structure, a method using a mutually arranged polymer body in which a spinneret for islands-in-the-sea fibers is used and the fibers are spun by mutually arranging a sea portion and an island portion is preferred from the viewpoint that fine fibers having a uniform monofilament diameter are obtained.
In the present embodiment, for the purpose of achieving a balance between a dark color and uniform color developability, a black pigment may be included in a portion that becomes fine fibers of the fine fiber-generating fibers (portion corresponding to island portion in case of the islands-in-the-sea fibers). As a method therefor, a method of spinning using thermoplastic resin chips prepared by kneading a thermoplastic resin with a black pigment in advance in an amount of, for example, 0.1 mass% or more and 5.0 mass% or less relative to the mass of the thermoplastic resin, and a method of mixing thermoplastic resin chips with a masterbatch prepared by kneading a thermoplastic resin with a black pigment in an amount of, for example, 10.0 mass% or more and 40.0 mass% or less relative to the mass of the thermoplastic resin, and spinning using the mixture can be adopted. Among these, a method of mixing thermoplastic resin chips with a masterbatch is preferable because the amount of pigment contained in the fine fibers can be appropriately adjusted.
When the masterbatch is mixed with the thermoplastic resin chips, it is preferable to use a masterbatch in which the number average of primary particle diameters of the black pigment contained in the masterbatch to be 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 30.0% or less. When a masterbatch having a primary particle diameter within the above range is used, the particle diameter (secondary particle diameter) and the coefficient of variation (CV) in the fine fibers can be set within appropriate ranges.
As the sea portion of the islands-in-the-sea fibers, for example, polyethylene, polypropylene, polystyrene, a copolymerized polyester obtained by copolymerizing sodium sulfoisophthalic acid or polyethylene glycol, and polylactic acid can be used, but polystyrene or copolymerized polyester is preferably used from the viewpoint of yarn making property, easy elutability, and the like.
When the fine fiber-generating fibers are an islands-in-the-sea fibers, it is preferable to use an islands-in-the-sea fibers in which the tensile strength of the island portion (tensile strength of the fine fiber) is 2.2 cN/dtex or more. The tensile strength of the island portion is preferably 2.2 cN/dtex or more, more preferably 3.0 cN/dtex or more, still more preferably 4.0 cN/dtex or more, making it possible to improve the abrasion resistance of the artificial leather, and at the same time, to suppress reduction in the fastness to rubbing due to falling off of the fiber.
In the present embodiment, the tensile strength of the island portion of the islands-in-the-sea fiber (tensile strength of the fine fiber) is calculated by the following method.

(1) Ten islands-in-the-sea fibers having a length of 20 cm are bundled.
(2) The sea portion is dissolved and removed from the sample of (1), and an air drying is performed.
(3) A test is performed 10 times (N = 10) under conditions of a distance between chucks of 5 cm, a tensile speed of 5 cm/min, and a load of 2 N according to "8.5.1 Standard time test" in "8.5 Tensile strength and elongation percentage" of JIS L1013:2010 "Testing methods for man-made filament yarns".
(4) A value obtained by rounding off the arithmetic average (cN/dtex) of the test results of (3) to the first decimal place is employed as the tensile strength of the island portion of the islands-in-the-sea fiber, that is the tensile strength of the fine fiber.

In this step, the spun-out fine fiber-generating fibers are opened and passed through a cross wrapper, or the like to form a fiber web, and the fiber web is then entangled to obtain a nonwoven fabric. As the method for obtaining the nonwoven fabric by entangling the fiber web, needle punching, water jet punching, and the like can be used.
As a form of the nonwoven fabric, either a short fiber nonwoven fabric or a long fiber nonwoven fabric is used as described above. Among these, in the case of the short fiber nonwoven fabric, the number of fibers oriented in the thickness direction of the artificial leather is larger than that of the long fiber nonwoven fabric, and highly dense feeling can be obtained on the surface of the artificial leather when napped.
In a case where a short fiber nonwoven fabric is selected for the nonwoven fabric, the obtained fine fiber-generating fibers are preferably crimped, cut to a predetermined length to obtain a raw stock, then opened, layered, and entangled, thereby obtaining a short fiber nonwoven fabric. Generally known methods may be used for the crimping and cutting steps.
In addition, when the fiber entangled body related to the artificial leather includes the woven fabric, the obtained nonwoven fabric and the woven fabric are layered and then entangled and integrated. For the entanglement and integration of the nonwoven fabric and the woven fabric, the woven fabric can be layered on one surface or both surfaces of the nonwoven fabric, or fibers of the nonwoven fabric and the woven fabric can be entangled by needle punching, water jet punching, or the like after the woven fabric is sandwiched between a plurality of nonwoven fabric webs.
The apparent density of the nonwoven fabric including fine fiber-generating fibers after needle punching or water jet punching is preferably 0.15 g/cm³ or more and 0.35 g/cm³ or less. The apparent density is set to preferably 0.15 g/cm³ or more, more preferably 0.20 g/cm³ or more, thereby providing an artificial leather having sufficient shape stability and dimensional stability, and allowing local breakage during molding processing to be suppressed. Meanwhile, the apparent density is set to preferably 0.35 g/cm³ or less, and more preferably 0.30 g/cm³ or less, thereby allowing a sufficient space for imparting the polymer elastic body to be maintained, and allowing the area ratio of the polymer elastic body in the cross section of the artificial leather to be within a predetermined range.
It is also a preferable aspect for the nonwoven fabric to be subjected to heat shrinking treatment with warm water or steam to improve the dense feeling of the fibers.
Then, polyvinyl alcohol is added to the fiber entangled body in an amount of 4 mass% or more and 40 mass% or less based on the mass of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet. Imparting polyvinyl alcohol can provide an artificial leather in which the area ratio of the polymer elastic body in the cross section of the finally obtained artificial leather is within a predetermined range, and the moldability with easy followability to a complicated shape, dense and uniform surface quality, abrasion resistance, and hand are excellent. Examples of the imparting method include imparting polyvinyl alcohol by impregnating an aqueous solution of polyvinyl alcohol and drying.
In the present embodiment, it is preferable that polyvinyl alcohol is added to the fiber entangled body in an amount of 4 mass% or more and 40 mass% or less based on the mass of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet. The amount to be imparted is set to preferably 4 mass% or more, more preferably 8 mass% or more, and still more preferably 16 mass% or more, whereby in the step of forming the polymer elastic body-imparted sheet, dimensional stability is improved because polyvinyl alcohol fixes fibers, and the coefficient of variation of the thickness t_A of the base material part of the finally obtained artificial leather can be set within a predetermined range. Meanwhile, the amount of polyvinyl alcohol is set to be imparted to preferably 40 mass% or less, more preferably 32 mass% or less, and still more preferably 24 mass% or less, whereby in the step of imparting the polymer elastic body, the area ratio of the polymer elastic body in the cross section of the artificial leather is set within a predetermined range while the adhesion between the fiber and the polymer elastic body is appropriately relaxed due to the presence of polyvinyl alcohol, and the artificial leather can uniformly follow a complicated shape in molding processing and have a favorable hand.
In this step, polyethylene glycol is preferably included in an amount of 0.01 mass% or more and 0.5 mass% or less with respect to the mass of the polyvinyl alcohol. The content of polyethylene glycol is preferably 0.01 mass% or more and more preferably 0.1 mass% or more, thereby allowing foaming of the water-soluble resin to be suppressed and the preparation time to be shortened in preparation of the aqueous solution of the water-soluble resin. Meanwhile, the content of polyethylene glycol is preferably 0.5 mass% or less and more preferably 0.3 mass% or less, whereby polyvinyl alcohol is imparted to the fiber entangled body in a uniform size, and the area ratio of the polymer elastic body in the cross section of the finally obtained artificial leather can be within a predetermined range.

In this step, the fine fiber having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less is expressed from the fine fiber-generating fibers of the polyvinyl alcohol-imparted sheet to form a nonwoven sheet.
Expressing the fine fiber having an average monofilament diameter in the above range from the fine fiber-generating fibers of the polyvinyl alcohol-imparted sheet can be performed by, for example, immersing the polyvinyl alcohol-imparted sheet in a solvent. When the fine fiber-generating fiber is an islands-in-the-sea fiber, the expression is achieved by dissolving and removing the sea portion.
When the fine fiber-generating fibers are islands-in-the-sea fibers, and the sea portion is polyethylene, polypropylene, or polystyrene, an organic solvent such as toluene or trichloroethylene can be used as the solvent to dissolve and remove the sea portion. An aqueous alkali solution of sodium hydroxide or the like can be used when the sea portion is copolymerized polyester or polylactic acid. Hot water (70°C to 99°C) can be used when the sea portion is water-soluble thermoplastic polyvinyl alcohol-based resin.
In addition, repeatedly immersing the polyvinyl alcohol-imparted sheet in a solvent, and squeezing and compressing with a mangle allows fine fibers to be efficiently expressed from the fine fiber-generating fibers.
In addition, as the treatment of dispersing the developed fine fibers, it is also a preferable aspect to pass a water flow through the inside of the nonwoven sheet in a liquid. This water flow provides a mechanical impact to the bundled fine fiber, allowing the fine fiber to be dispersed. Specifically, apparatus such as a vibratory washer is used. This vibratory washer is preferable in that uniform dispersion treatment can be performed over the entire surface of the nonwoven sheet.

In this step, the width of the nonwoven sheet is widened by 2% or more and 10% or less to form a widened sheet.
The width of the nonwoven sheet is widened by preferably 2% or more, more preferably 3% or more, whereby the bonding state between the fine fiber and the polyvinyl alcohol is alleviated, and in the step of forming the polymer elastic body-imparted sheet described later, the bonding state between the fine fiber and the polymer elastic body can be adjusted. As a result, the artificial leather can uniformly follow a complicated shape in molding processing. Meanwhile, the width of the nonwoven sheet is widened by preferably 10% or less, more preferably 8% or less, allowing uniformly widening the nonwoven sheet in the width direction while the equipment load is reduced. Further, the apparent density of polyvinyl alcohol included in the nonwoven sheet can be appropriately reduced, and the area ratio of the polymer elastic body in the cross section and the surface of the finally obtained artificial leather can be within a predetermined range.

In this step, a polymer elastic body is imparted to the widened sheet by 12% or more and 64% or less of the mass of the widened sheet to form a polymer elastic body-imparted sheet. More specifically, it is preferable that the widened sheet is impregnated with a solution of a precursor of a polymer elastic body so as to be imparted in an amount of 12% or more and 64% or less with respect to the mass of the widened sheet, and the widened sheet is solidified to form a polymer elastic body-imparted sheet. Herein, the precursor of the polymer elastic body refers to a precursor (hereinafter, may be simply abbreviated as "precursor") that becomes a polymer elastic body by means such as coagulation and solidification described later. For example, when the polymer elastic body is polyurethane, each reaction component of the polyurethane, that is, a mixture of a polymer diol, an organic diisocyanate, a chain extender, and the like is a precursor of the polyurethane.
In the present embodiment, a polymer elastic body including a black pigment can also be imparted to the widened sheet for the purpose of further achieving a dark color and uniform color developability. Examples of the method include a method of including a black pigment in a precursor of a polymer elastic body. As the black pigment to be used, a black pigment in which the number average of primary particle diameters is 0.01 µm or more and 0.05 µm or less, and the coefficient of variation (CV) is 0.1% or more and 30.0% or less is preferable. When a black pigment having a primary particle diameter within the above range is used, the particle diameter (secondary particle diameter) and the coefficient of variation (CV) in the polymer elastic body can be set within appropriate ranges.
N,N'-dimethylformamide, dimethyl sulfoxide, or the like is preferably used as the solvent used when the polymer elastic body is imparted to the fiber entangled body. In addition, an aqueous dispersion in which a polymer elastic body is dispersed in water as an emulsion may be used.

In this step, the polyvinyl alcohol is removed from the polymer elastic body-imparted sheet to form a base sheet. Examples of the method include a method in which the polymer elastic body-imparted sheet is impregnated with water (hot water) heated to 65°C to 95°C, and the sheet is dried.
The step of forming the base sheet can also be performed simultaneously with the <Step of forming polymer elastic body-imparted sheet>. That is, in addition to the step of removing the solvent such as N,N'-dimethylformamide or dimethyl sulfoxide used when the polymer elastic body is imparted to the fiber entangled body, the polyvinyl alcohol can also be removed by performing impregnation with hot water. In the present embodiment, even in such a case, it is considered that both <Step of forming polymer elastic body-imparted sheet> and <Step of forming base sheet> have been performed.

In this step, at least one surface of the base sheet is buffed. Thus, the surface is provided with nap to form a nap portion. In this buffing, it is preferable to use a buffing means such as a sandpaper or a roll sander. Further, prior to this buffing, it is also a preferable aspect that the base sheet is cut into two sheets by half in the thickness direction from the viewpoint of manufacturing efficiency. This buffing can be performed only on one surface or both surfaces of the sheet, and in a case where a sheet cut into two halves in the thickness direction is buffed, it is preferable to buff a surface (half cut surface) newly formed by cutting into halves.
In the buffing of the base sheet, in order to obtain an artificial leather that maintains excellent surface quality even after molding processing, the number of times of buffing by the buffing means is set to preferably two or more times, and more preferably three or more times. Further, it is more preferable to make the count of the sandpaper or roll sander used for each stage finer in stages or at least the same.
The grain size of the sandpaper or roll sander for buffing the surface of the base sheet (corresponding to the surface of artificial leather) is preferably in the range of No. 100 or more and No. 320 or less specified in JIS R6610:2000 "Grain Size of Abrasive for Polishing Fabric". The particle size of the sandpaper or the roll sander is set to preferably 100 or more, more preferably 120 or more, thereby allowing the thickness t_B of the nap portion to be set within a predetermined range, and providing an artificial leather excellent in touch sensation. Meanwhile, the particle size of the sandpaper or roll sander is set to preferably No. 320 or less, more preferably No. 240 or less, thereby allowing an artificial leather to have a dense feeling and a uniform and elegant surface quality.
When at least one surface of the base sheet is buffed a plurality of times by a buffing means, the conveyance speed of the base sheet is preferably 10 m/min or more and 20 m/min. The conveyance speed of the base sheet is set to preferably 10 m/min or more, more preferably 13 m/min or more, thereby allowing the thickness t_B of the nap portion to be set within a predetermined range while favorable productivity is achieved. Meanwhile, the conveyance speed of the base sheet is set to preferably 20 m/min or less, more preferably 17 m/min or more, whereby the area ratio of the polymer elastic body on the surface of the artificial leather can be set within a predetermined range while equipment load is suppressed, and dense and uniform surface quality can be achieved even after molding processing. Herein, the conveyance speed of the base sheet is a speed at which the sheet is supplied to a roll or a roll sander rotating the sandpaper at a high speed.
In addition, the buffing speed is preferably 200 m/min or more and 1000 m/min or less. The buffing speed is set to preferably 200 m/min or more, more preferably 300 m/min or more, thereby allowing the thickness t_B of the nap portion to be set within a predetermined range while the equipment load is suppressed, and providing an artificial leather excellent in touch sensation. Meanwhile, the buffing speed is set to preferably 1000 m/min or less, more preferably 900 m/min or less, whereby the area ratio of the polymer elastic body on the surface of the artificial leather is set within a predetermined range, and a dense and uniform surface quality can be achieved even after molding processing. Herein, the buffing speed is a peripheral speed calculated from a rotation speed and a peripheral length of the sandpaper or the roll sander, and can be specifically calculated by the following formula. Buffing speed (m/min) = {rotation speed (rpm/min) of sandpaper or roll sander} × {circumferential length (m/rpm) of sandpaper or roll sander}
Prior to this buffing, a lubricant such as a silicone emulsion can be imparted to the surface of the base sheet. In addition, when an antistatic agent is imparted before the buffing, a powder generated from the artificial leather by buffing is less likely to be deposited on the sandpaper.
Herein, the basis weight of the buffed sheet-shaped product obtained after the buffing is preferably 150 g/m² or more and 450 g/m² or less. The basis weight of the sheet-shaped product obtained after buffing is set to preferably 150 g/m² or more, more preferably 175 g/m², thereby allowing an artificial leather to be excellent in strength and abrasion resistance while breakage during molding processing in addition to breakage of the sheet-shaped product in this step is suppressed. Meanwhile, the basis weight of the sheet-shaped product is set to preferably 450 g/m² or less, more preferably 400 g/m² or less, thereby providing an artificial leather that can uniformly follow a complicated shape in molding processing.

In this <second manufacturing method>, a polyvinyl alcohol-imparted sheet described later is formed, and then the sheet is widened in width to develop fine fibers. This can provide an artificial leather having the moldability with easy followability to a more complicated shape, excellent surface quality after molding processing, and further a soft hand.

This step is exactly the same as the first manufacturing method.

This step is basically the same as <Step of forming widened sheet> in <First manufacturing method>, but differs in that in <Step of forming widened sheet> in <First manufacturing method>, a nonwoven sheet in which fine fibers are expressed is widened, and in this step, the width of the polyvinyl alcohol-imparted sheet is widened by 2% or more and 10% or less to form a widened sheet. Details will be described by replacing the term "nonwoven sheet" in <Step of forming widened sheet> of <First manufacturing method> with "polyvinyl alcohol-imparted sheet".

This step is basically the same as <Step of forming nonwoven sheet> in <First manufacturing method>, but differs in that in <Step of forming nonwoven sheet> in <First manufacturing method>, the polyvinyl alcohol-imparted sheet before the fine fibers are expressed is widened, and in this step, fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less are expressed from the fine fiber-generating fibers of the above-described widened sheet to form a nonwoven sheet. Details will be described by replacing the term "polyvinyl alcohol-imparted sheet" in <Step of forming nonwoven sheet> of <First manufacturing method> with "widened sheet".

This step is basically the same as <Step of forming polymer elastic body-imparted sheet> in <First manufacturing method>, but differs in that in <Step of forming polymer elastic body-imparted sheet> in <First manufacturing method>, a polymer elastic body is imparted to a widened sheet, and in this step, a polymer elastic body is imparted to the nonwoven sheet by 12% or more and 64% or less with respect to the mass of the nonwoven sheet to form a polymer elastic body-imparted sheet. Details are described by replacing the term "widened sheet" in <Step of forming polymer elastic body-imparted sheet> of <First manufacturing method> with "nonwoven sheet".

This step is exactly the same as the first manufacturing method.

This step is exactly the same as the first manufacturing method.

Further, following <First manufacturing method> or <Second manufacturing method>, a sheet obtained by buffing at least one surface of the base sheet can be dyed.
As a dyeing method, for example, a jet dyeing treatment using a jigger dyeing machine or a jet dyeing machine, a dip dyeing treatment such as a thermosol dyeing process using a continuous dyeing machine, or a textile printing treatment on a nap surface by roller textile printing, screen textile printing, inkjet textile printing, sublimation printing, vacuum sublimation printing, or the like can be used. Among these, it is preferable to use a jet dyeing machine from the viewpoint of quality and surface appearance because the soft hand can be obtained. In addition, various resin finishing may be performed after dyeing, as necessary.
In addition, the sheet obtained as described above may be used as an artificial leather as it is, but the surface thereof may be further subjected to various types of processing as necessary to obtain an artificial leather excellent in design property. For example, post-processing including hole-forming processing such as perforation, emboss processing, laser processing, pinsonic processing, and print processing can be performed. In addition, various resin finishing processing can also be performed.

[Vehicular interior material, vehicular component, miscellaneous goods, and furniture]

The artificial leather of the present embodiment obtained by the manufacturing method exemplified above has both favorable moldability with followability to a complicated shape in molding processing and dense and smooth surface quality even after molding processing. Therefore, the artificial leather is a material particularly suitable for applications such as vehicular interior materials and interiors.
First, the vehicular interior material including the artificial leather is preferable because it can take advantage of the characteristic that the surface quality after molding processing is dense and smooth while easily following a complicated shape particularly in molding processing. Such a vehicular interior material is preferably used for vehicular components such as a steering wheel, a horn switch, a shift knob, a dashboard, an instrument panel, a glove box, a floor carpet, a floor mat, a ceiling lining, a sun visor, and an assist grip of an automobile or the like, and it is more preferable that these vehicular components include the artificial leather. The "vehicle" in the present embodiment includes not only automobiles, aircraft, railway vehicles, and ships, but also vehicles such as carriages, palanquins, and human-powered vehicles, and also some industrial machines, construction machines, and agricultural machines capable of carrying humans and animals, such as excavators, crane cars, tractors, and combines.
In addition, miscellaneous goods including the artificial leather are also one of preferable embodiments. Examples of such miscellaneous goods include accessories such as shoes, hats, bags, belts, scarves, ties, and wallets, and interior goods such as cushions, armrests, and neck pillows.
Examples of the shoes include sneakers, pumps, loafers, boots, sandals, slippers, and spikes. At least a part of the upper, lining, insole, shoelace, and the like of such shoes is preferably the artificial leather.
Examples of the bag include a handbag, a tote bag, a shoulder bag, a traveling bag, a waist pouch, a briefcase, an attaché case, and a school backpack. At least a part of a handle, an inner bag, an edge binding, a gusset, a bottom, and the like of such a bag is preferably the artificial leather.
Further, furniture including the artificial leather is also one of preferable aspects. Examples of such furniture include a chair, a sofa, and a stool. At least a part of the seating surface, the back surface, and the like of such furniture is preferably the artificial leather.

EXAMPLES

Then, the artificial leather of the present embodiment will be described more specifically with reference to Examples, but the present embodiment is not limited to these Examples.

[Measuring method and processing method for evaluation]

Then, an evaluation method used in Examples and measurement conditions thereof will be described. However, unless otherwise described, physical properties are measured based on the above methods.

(1) Average monofilament diameter (µm) of fine fibers:
In the measurement of the average monofilament diameter of the fine fibers, the fine fibers were observed using "VHX-D500/D510" type manufactured by Keyence Corporation as a scanning electron microscope (SEM), and the average monofilament diameter was calculated.
(2) Tensile strength of fine fiber (cN/dtex):
The tensile strength of the fine fiber was measured and calculated by the above-described method using a Tensilon universal material tester "RTC-1350A" manufactured by A&D Company, Limited.
(3) Thickness t_A (µm) of base material part of artificial leather and coefficient of variation (%) thereof:
In the measurement of the thickness t_A of the base material part of the artificial leather, the cross section of the artificial leather was observed using "VHX-D500/D510" manufactured by KEYENCE CORPORATION as a scanning electron microscope (SEM), and the thickness t_A of the base material part of the artificial leather and the coefficient of variation thereof were calculated.
(4) Thickness t_B (µm) of nap portion of artificial leather and coefficient of variation (%) thereof:
In the measurement of the thickness t_B of the nap portion of the artificial leather, a cross section of the artificial leather was observed using "VHX-D500/D510" manufactured by KEYENCE CORPORATION as a scanning electron microscope (SEM), and the thickness t_B of the nap portion of the artificial leather and the coefficient of variation thereof were calculated.
(5) Basis weight of artificial leather (g/m²):
In the measurement of the basis weight of the artificial leather, the basis weight was measured and calculated by the above-described method.
(6) Thickness of artificial leather (mm):
The thickness of the artificial leather was measured and calculated using "Peacock dial thickness gauge H" manufactured by OZAKI MFG. CO., LTD. as a thickness measuring instrument.
(7) Mass ratio (mass%) of polymer elastic body:
In the measurement of the mass ratio of the polymer elastic body, dimethylformamide was used as a solvent, and the mass ratio was measured and calculated.
(8) Area ratio (%) of polymer elastic body on surface of artificial leather having nap portion and standard deviation (%) thereof:
In the above measurement, measurement and calculation were performed using "JSM-7800F Prime" manufactured by JEOL Ltd. as a field emission scanning electron microscope and further using "ImageJ" as image analysis software.
(9) Area ratio (%) of polymer elastic body in cross section of artificial leather and its standard deviation (%):
In the above measurement, measurement and calculation were performed using "JSM-7800F Prime" manufactured by JEOL Ltd. as a field emission scanning electron microscope and further using "ImageJ" as image analysis software.
(10) Tensile strength of artificial leather (N/cm):
Two test pieces each having a size of 2 cm × 20 cm were collected in any direction of the artificial leather, and the tensile strength (N/cm) specified in accordance with "6.3.1 Tensile strength and elongation percentage (ISO method)" in "Test methods for nonwovens" of JIS L1913:2010 was measured. In the measurement, the average of the two test pieces was employed as the tensile strength of the artificial leather. In the measurement, a single column desktop tester "3343" manufactured by Instron was used.
(11) Fastness to rubbing for artificial leather (grade)
The degree of contamination of the sample after the rubbing test was determined according to the gray scale for contamination, and a sample of grade 4 or higher (color difference ΔE*_ab according to L*a*b* color system is 4.5 ± 0.3 or less) was rated as acceptable.
(12) Color fastness to light for artificial leather (grade)
The degree of discoloration of the sample after irradiation with xenon arc lamp light was graded using the gray scale for discoloration, and a sample of grade 4 or higher (color difference ΔE*_ab according to L*a*b* color system is 1.7 ± 0.3 or less) was rated as acceptable.
(13) Lightness (L* value, unitless) of artificial leather
The L* value defined by "3.3 CIE1976 lightness index" of JIS Z8781-4:2013 "Colorimetry - Part 4: CIE1976 L*a*b* color space" was measured using a spectrophotometer. The measurement was performed 10 times using "CM-M6" manufactured by KONICA MINOLTA, INC., and the average thereof was taken as the L* value of the artificial leather.
(14) Wear resistance of artificial leather (mg):
The abrasion resistance test described above was performed using a "Model 406" abrasion tester manufactured by James H. Heal & Co. Ltd., and "Abrastive CLOTH SM25" manufactured by the same company as a standard abradant cloth, in accordance with the abrasion resistance test measured by "8.19 Abrasion resistance and color fastness to rubbing", "8.19.5 Method E (Martindale method)" of JIS L 1096:2010 "Testing methods for woven and knitted fabrics", under a pressing load of 12.0 kPa, with the number of abrasion cycles being 20,000. An artificial leather in which weight loss of the artificial leather was 10 mg or less was determined to be acceptable.
(15) Touch sensation of artificial leather:
The touch sensation of the artificial leather was evaluated by sensory evaluation described below. That is, the surface having the nap portion of the artificial leather was discriminated according to the following evaluation criteria using a total of 20 people of 10 healthy adult men and 10 healthy adult women as evaluators, and the most frequent evaluation was used as the evaluation of the touch sensation of the artificial leather. In the case of a tie between ratings, a higher rating was employed as the touch sensation of the artificial leather. A favorable level of the embodiment was "A or B".
- · A: Even if the surface is stroked, the touch feeling is significantly smooth such that no catch is felt.
- · B: It is a smooth tactile sensation to such an extent that a slight catch is felt when the surface is stroked.
- · C: It is a rough tactile sensation that a catch is felt when the surface is stroked.
- · D: It is a significantly rough tactile sensation that a large catch is felt when the surface is stroked.
(16) Surface quality of artificial leather: The surface quality of the artificial leather was evaluated by sensory evaluation described below. That is, the following evaluations were visually discriminated using a total of 20 people of 10 healthy adult men and 10 healthy adult women as evaluators, and the most frequent evaluation was used as the evaluation of the surface quality of the artificial leather. In the case of a tie between ratings, a higher rating was employed as the rating of the surface quality of the artificial leather. A favorable level of the embodiment was "A or B".
- · A: significantly dense feeling and a uniform surface quality.
- · B: dense feeling and a uniform surface quality.
- · C: surface quality having poor dense feeling and large variation.
- · D: surface quality significantly having poor dense feeling and large variation.
(17) Coefficient of variation (%) in area change rate of artificial leather before and after molding processing:
As an index of the surface quality after molding processing when an artificial leather was used as a skin, the coefficient of variation in the area change rate before and after molding processing was evaluated by the following methods (i) to (viii). A smaller value indicates that the whole is uniformly deformed, and an artificial leather having a coefficient of variation of the area change rate of 30% or less was evaluated as an artificial leather having excellent uniform deformability and favorable surface quality.
1. (i) 10 pieces of A4 size (210 mm × 297 mm) evaluation samples were randomly collected from artificial leather.
2. (ii) 5 mm × 5 mm squares (grid lines) were drawn on the surface of the collected evaluation samples on the nap layer side.
3. (iii) A high density polyethylene (PE) film having a thickness of 500 µm was bonded to a surface on a side opposite to a surface on a nap layer side where squares were formed with a film-like olefinic hot-melt resin (thickness 50 µm, basis weight 20 g/m²).
4. (iv) The evaluation sample bonded to the film was disposed on a concave cylindrical mold having an area expansion ratio of 212% and having a diameter of 50 mm × a height of 14 mm with the surface on the nap layer side facing the mold side, and vacuum molding processing was performed at room temperature.
5. (v) The area of squares drawn on the nap surface side of the sample for evaluation obtained by vacuum molding processing was measured. For the measurement, "VHX-5000" manufactured by KEYENCE CORPORATION was used as a digital microscope, and the area was measured by adjusting the magnification to 20 times.
6. (vi) The area (mm²) of the measured squares was divided by the original area before molding (5 mm × 5 mm = 25 mm²) to obtain a percentage, and the area change rate (%) was calculated.
7. (vii) The arithmetic average value and standard deviation of the calculated area change rate (%) of each square were calculated.
8. (viii) The coefficient of variation (%) of the area change rate was calculated from the value calculated in (vii) by the following formula, and rounded off to the nearest integer. Coefficient of variation in area change rate (%) = standard deviation of area change rate/arithmetic average value of area change rate × 100
(18) Area rate (%) of polymer elastic body on surface of artificial leather having nap portion after molding processing:
As an index of the surface quality after molding processing when the artificial leather is used as a skin, the area ratio of the polymer elastic body on the surface of a side having the nap portion of the artificial leather after molding processing was evaluated. An artificial leather in which the area ratio of the polymer elastic body on the surface of the artificial leather on the side having the nap portion after molding processing was 3.00% or less was processed as a skin, and was evaluated as an artificial leather in which deterioration of surface quality due to an increase in exposure of the polymer elastic body was suppressed.
1. (i) The squares having an area change rate in the range of 145% to 155% were collected from the squares drawn on the surface on the nap portion side of the molded product obtained at the area change rate (%) of (17). When a square having an area change rate in the range of 145 to 155% was not present, a square having an area change rate in the range of 135% to 144% or 156% to 165% was collected.
2. (ii) Using the collected squares, the area ratio (%) of the polymer elastic body on the surface of the artificial leather on the side having the nap portion was measured in the same manner as in the "(8) Area ratio (%) of polymer elastic body on the surface of the artificial leather on the side having the nap portion".
(19) Surface quality (point) of artificial leather after molding processing:
Evaluation was performed using the evaluation sample after processing into a cylindrical shape according to the "(17) Coefficient of variation (%) in area change rate of artificial leather". The obtained molded product was subjected to vacuum molding processing, and the surface quality of the processed artificial leather was judged by the following 5-grade evaluation using a total of 20 people of 10 healthy adult men and 10 healthy adult women as evaluators. The surface quality of the processed artificial leather was evaluated by the total score of the scores determined by each evaluator. Therefore, the total score ranged from a minimum score of 20 points to a maximum score of 100 points, and a score of 80 points or more was determined to be acceptable.
- 5 points: Significantly favorable (the artificial leather can be shaped into a cylindrical shape, and there is no deterioration in quality due to an increase in exposure of the polymer elastic body on the surface of the artificial leather after processing)
- 4 points: Favorable (intermediate between 5 points and 3 points)
- 3 points: Normal (the artificial leather is not shaped into a cylindrical shape, or the exposure of the polymer elastic body on the surface of the artificial leather after processing is increased, and the quality is deteriorated)
- 2 points: Poor (intermediate between 3 points and 1 point)
- 1 point: Significantly poor (the artificial leather is not shaped into a cylindrical shape, and the exposure of the polymer elastic body on the surface of the artificial leather after processing greatly increases, and the quality is significantly deteriorated)

[Example 1]

Fine fiber-generating fibers having an islands-in-the-sea fiber structure composed of an island component and a sea component were melt-spun under the following conditions.

Island component: polyethylene terephthalate having an intrinsic viscosity (IV value) of 0.73
Sea component: polystyrene having an MFR (melt flow rate, measured by test method specified in ISO 1133:1997, and the same applies hereinafter) of 65 g/10 min
Spinneret: spinneret for islands-in-the-sea fibers having 16 islands/hole
Spinning temperature: 285°C
Mass ratio of island portion/sea portion: 80/20
Discharge rate: 1.2 g/(min · hole)
Spinning speed: 1,100 m/min.

Then, the fine fiber-generating fiber was drawn 2.7 times in a spinning oil solution bath at 90°C. Then, the drawn fibers were crimped using a stuffer box crimper, followed by cutting to a length of 51 mm to provide fiber of islands-in-the-sea fibers with a single fiber fineness of 4.2 dtex. The average monofilament diameter of the fine fibers obtained from the islands-in-the-sea fibers was 4.40 µm, and the strength of the fine fibers was 3.7 cN/dtex.
The fiber obtained as described above was used to form a layered web via carding and cross-lapper steps. Then, needle punching was performed with the number of punches of 2,500/cm² to obtain a fiber entangled body including a nonwoven fabric composed of fine fiber-generating fibers having a basis weight of 470 g/m², a width of 183 cm, and a thickness of 2.1 mm.
The fiber entangled body obtained as described above was shrunk with hot water at 96°C. Thereafter, a nonwoven fabric shrink-treated with hot water was impregnated with a polyvinyl alcohol aqueous solution (this aqueous solution contained 0.13 mass% of polyethylene glycol with respect to the mass of polyvinyl alcohol (hereinafter, may be abbreviated as PVA)) having a saponification degree of 88%, which was prepared so as to have a concentration of 12 mass%. Further, this was squeezed with a roll, and dried with hot air at a temperature of 120°C for 10 minutes to form a polyvinyl alcohol-imparted sheet having a PVA mass of 23 mass% with respect to the mass of the nonwoven fabric composed of the fine fiber-generating fibers.

The polyvinyl alcohol-imparted sheet thus obtained was impregnated with trichloroethylene, and then a step of compressing and squeezing by a mangle was performed 10 times. As a result, the sea portion of the fine fiber-generating fiber was dissolved and removed, and the sheet was compressed to form a nonwoven sheet having a width of 158 cm in which the fine fibers having a width of 158 cm and an average monofilament diameter of 4.40 µm were developed.

Further, this nonwoven sheet was widened to a width of 163 cm with a pin tenter, that is, the width of the nonwoven sheet was widened by 3% to form a widened sheet.

The widened sheet obtained as described above was immersed in a DMF (dimethylformamide) solution of polyurethane, which was obtained using a polycarbonate-based diol as a polymer diol and was prepared such that the concentration of a solid content mainly composed of polyurethane as a polymer elastic body was 13.0%. Thereafter, the widened sheet immersed in the DMF solution of polyurethane was squeezed with rollers. Then, this sheet was immersed in a DMF aqueous solution having a concentration of 30 mass% to coagulate the polyurethane. The amount of the polymer elastic body imparted with respect to the mass of the widened sheet at this time was 27 mass%. Thereafter, PVA and DMF were removed with hot water at 95°C and dried with hot air at a temperature of 100°C for 10 minutes. As a result, a base sheet having a width of 153 cm, a thickness of 1.7 mm, and a polyurethane mass of 35 mass% with respect to the mass of the fine fiber was obtained.

The base sheet obtained as described above was cut in half such that the thickness of each part was 1/2. Subsequently, the conveyance speed of the sheet object was set to 13 m/min, and the surface layer portion of the non-half cut surface was buffed by 0.30 mm to perform a napping treatment. At this time, the buffing speed was 900 m/min in the first stage and 700 m/min in the second stage, and endless sandpaper having a sandpaper count of 120 (in Tables 1 and 2, it is described as "#120". The same applies to other counts.) was used as the buffing means. As a result, a buffed sheet having an average monofilament diameter of fine fibers of 4.40 µm, a width of 153 cm, a basis weight of 200 g/m², and a thickness of 0.55 mm was obtained.

The buffed sheet was dyed with a jet dyeing machine and subjected to reduction cleaning to obtain a dyed sheet. In this dyeing, a recipe prepared using a black dye such that the L* value of the sheet after dyeing was 22 was used, and the temperature of the dyeing solution was set to 120°C. Thereafter, drying treatment was performed at 100°C for 7 minutes with a pin tenter to obtain an artificial leather having a thickness of 0.65 mm and a mass ratio of the polymer elastic body of 26 mass%.
The obtained artificial leather had a significant dense feeling, a uniform surface quality, a significant smooth touch feeling, and significantly excellent abrasion resistance. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 1 and 2.

[Example 2]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming widened sheet>, the nonwoven sheet having a width of 158 cm was widened to 161.5 cm, that is, the width of the nonwoven sheet was widened by 2% as shown in Table 1.
The obtained artificial leather had a dense feeling, a uniform surface quality, a significant smooth touch feeling, and significantly excellent abrasion resistance. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 1 and 2.

[Example 3]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming widened sheet>, the nonwoven sheet having a width of 158 cm was widened to 172 cm, that is, the width of the nonwoven sheet was widened by 9% as shown in Table 1.
The obtained artificial leather had a very dense feeling, a uniform surface quality, and a smooth touch. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 1 and 2.

[Example 4]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming polyvinyl alcohol-imparted sheet>, the conditions for melt-spinning the fine fiber-generating fibers having an islands-in-the-sea fiber structure consisting of an island component and a sea component were changed to the following conditions.

Island component: a mixture of the following components P1 and P2 at a mass ratio of 95:5
P1 polyethylene terephthalate having an intrinsic viscosity (IV value) of 0.73
P2 a masterbatch containing 20 mass% of carbon black (average particle diameter: 0.02 µm, coefficient of variation (CV) of particle diameter: 20%) as a black pigment relative to the mass of the masterbatch in the polyethylene terephthalate A
Sea component: polystyrene having an MFR (melt flow rate, measured by test method specified in ISO 1133:1997) of 65 g/10 min
Spinneret: spinneret for islands-in-the-sea fibers having 16 islands/hole
Spinning temperature: 285°C
Mass ratio of island portion/sea portion: 80/20
Discharge rate: 1.2 g/(min · hole)
Spinning speed: 1,100 m/min.

The obtained artificial leather had a significant dense feeling, a uniform surface quality, a significant smooth touch feeling, and excellent abrasion resistance. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 1 and 2.

[Example 5]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming polyvinyl alcohol-imparted sheet>, PVA was imparted in an amount of 4 mass% with respect to the mass of the nonwoven fabric composed of the fine fiber-generating fiber as shown in Table 3.
The obtained artificial leather had a dense feeling, a uniform surface quality, a smooth touch feeling, and significantly excellent abrasion resistance. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 3 and 4.

[Example 6]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming polyvinyl alcohol-imparted sheet>, PVA was imparted in an amount of 40 mass% with respect to the mass of the nonwoven fabric composed of the fine fiber-generating fiber as shown in Table 3.
The obtained artificial leather had a very dense feeling, a uniform surface quality, and a smooth touch. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 3 and 4.

[Example 7]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming polyvinyl alcohol-imparted sheet>, PVA was imparted in an amount of 48 mass% with respect to the mass of the nonwoven fabric composed of the fine fiber-generating fiber as shown in Table 3.
The obtained artificial leather had a dense feeling, a uniform surface quality, and a smooth touch. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 3 and 4.

[Example 8]

An artificial leather was obtained in the same manner as in Example 1 except that a nonwoven fabric shrink-treated with hot water was impregnated with a PVA aqueous solution (containing 0.60 mass% of polyethylene glycol with respect to the mass of PVA) having a saponification degree of 88% prepared so as to have a concentration of 12 mass% as shown in Table 3 in <Step of forming polyvinyl alcohol-imparted sheet>.
The obtained artificial leather had a dense feeling, a uniform surface quality, and a smooth touch. In addition, in the artificial leather after molding processing, the artificial leather was able to be shaped into a cylindrical shape, and the surface quality of the artificial leather was not deteriorated before and after molding processing. The results are shown in Tables 3 and 4.

[Comparative Example 1]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming widened sheet>, a nonwoven sheet having a width of 158 cm was not widened and a polymer elastic body was imparted as shown in Table 3.
The obtained artificial leather had a smooth touch, but had a high area ratio of a polymer elastic body on the surface, poor dense feeling, and a surface quality with large variations. In addition, in the artificial leather after molding processing, the coefficient of variation of the area change rate was large, the exposure of the polymer elastic body on the surface of the artificial leather increased, and the quality was deteriorated. The results are shown in Tables 5 and 6.

[Comparative Example 2]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming widened sheet>, the nonwoven sheet having a width of 158 cm was widened to 175 cm, that is, the width of the nonwoven sheet was widened by 11% as shown in Table 3. The obtained artificial leather had a smooth touch, but had a poor dense feeling, and a surface quality with large variations. In addition, local breakage occurred in molding processing, and the coefficient of variation of the area change rate of the artificial leather and the area ratio of the polymer elastic body on the surface of the artificial leather failed to be evaluated. The results are shown in Tables 5 and 6.

[Comparative Example 3]

An artificial leather was obtained in the same manner as in Example 1 except that in the <Step of forming nonwoven sheet>, a nonwoven sheet having a width of 158 cm was treated with a vibratory washer, a water flow was allowed to pass through the inside of the nonwoven sheet in water to disperse fine fibers, and in the <Step of forming widened sheet>, a polymer elastic body was imparted to the nonwoven sheet having a width of 158 cm without widening as shown in Table 3.
The obtained artificial leather had a smooth touch, but had a high area ratio of a polymer elastic body on the surface, poor dense feeling, and a surface quality with large variations. In addition, in the artificial leather after molding processing, the coefficient of variation of the area change rate was large, the exposure of the polymer elastic body on the surface of the artificial leather increased, and the quality was deteriorated. The results are shown in Tables 5 and 6.
As shown in Tables 1 to 4, in the artificial leather of Examples 1 to 8, in the step of forming a widened sheet, the nonwoven sheet to which PVA was imparted at a predetermined ratio was widened within a predetermined range, the adhesion state between the fine fiber and the PVA was moderately relaxed, then the polymer elastic body was imparted, and the sheet was buffed, thereby setting the area ratio of the polymer elastic body on the surface and the cross section of the artificial leather within a specific range, thereby achieving both favorable moldability with followability to a complicated shape and dense and smooth surface quality even after molding processing.
Meanwhile, as shown in Tables 5 and 6, in the artificial leather of Comparative Example 1, when the above-described widening was not performed in the step of forming a widened sheet, the area ratio of the polymer elastic body on the surface and the cross section of the artificial leather was out of the predetermined range, thus failing to achieve both moldability with followability to a complicated shape and dense and smooth surface quality even after molding processing.
In addition, as in the artificial leather of Comparative Example 2, even when the nonwoven sheet was widened by more than 10% in the step of forming a widened sheet, the area ratio of the polymer elastic body in the cross section of the artificial leather was out of the predetermined range, thus failing to achieve both moldability with followability to a complicated shape and a dense and smooth surface quality even after molding processing.
In addition, as in the artificial leather of Comparative Example 3, in the step of forming a nonwoven sheet, even when the fine fibers were subjected to a dispersion treatment with a vibratory washer, in the step of forming a widened sheet, when the widening was not performed, the area ratio of the polymer elastic body on the surface and the cross section of the artificial leather was out of the predetermined range, thus failing to achieve both moldability with followability to a complicated shape and dense and smooth surface quality even after molding processing.
While the present invention has been described in detail with reference to certain aspects, it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit and scope of the present invention. The present application is based on Japanese Patent Application (No. 2023-169362) filed on September 29, 2023 , which is incorporated herein by reference in its entirety. In addition, all references cited herein are incorporated in their entirety.

DESCRIPTION OF REFERENCE SIGNS

1: Artificial leather
2: Nap portion
3: Base material part
4: Surface on side having nap portion
5: Surface (bottom surface) opposite to surface having nap portion
L_A: Line parallel to bottom surface
L_B: Bottom surface
L₀: Boundary line between nap portion and base material part
P₁ to P₁₀: Point on boundary line between nap portion and base material part
Q₁ to Q₁₀: Point where perpendicular line intersects with end of nap portion
R₁ to R₁₀: Distance between point on boundary line between nap portion and base material part and point where perpendicular line intersects with end of nap portion
S₁ to S₁₀: Point where perpendicular line intersects with end of base material part
T₁ to T₁₀: Distance between point where perpendicular line intersects end of nap portion and point where perpendicular line intersects end of base material part

Claims

An artificial leather comprising:
a base material part including:
a fiber entangled body including a nonwoven fabric composed of fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less; and

a polymer elastic body, and

a nap portion on at least one surface, wherein

a mass ratio of the polymer elastic body in the artificial leather is 15 mass% or more and 40 mass% or less,

an area ratio of the polymer elastic body on at least one surface of a side having the nap portion of the artificial leather is 0.01% or more and 3.00% or less, and

an area ratio of the polymer elastic body in a cross section of the artificial leather is 5% or more and less than 15%.
The artificial leather according to claim 1, wherein a standard deviation of an area ratio of a polymer elastic body on at least one surface of the side having the nap portion of the artificial leather is 25% or less.
The artificial leather according to claim 1 or 2, wherein a standard deviation of an area ratio of a polymer elastic body in a cross section of the artificial leather is 25% or less.
The artificial leather according to claim 1 or 2, wherein a thickness of the base material part t_A is 250 µm or more and 800 µm or less, and a ratio of the thickness t_A of the base material part to a thickness t_B of a nap portion, t_A/t_B, is 0.5 or more and 2.5 or less.
The artificial leather according to claim 4, wherein a coefficient of variation of the thickness t_A of the base material part is 50% or less.
The artificial leather according to claim 1 or 2, wherein the fine fibers include a black pigment.
A method for manufacturing the artificial leather, the method comprising:
a step of imparting polyvinyl alcohol in an amount of 4 mass% or more and 40 mass% or less with respect to a mass of fine fiber-generating fibers to a fiber entangled body including a nonwoven fabric mainly composed of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet;

a step of developing fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less from the fine fiber-generating fibers of the polyvinyl alcohol-imparted sheet to form a nonwoven sheet;

a step of widening a width of the nonwoven sheet by 2% or more and 10% or less to form a widened sheet;

a step of imparting a polymer elastic body to the widened sheet in an amount of 12 mass% or more and 64 mass% or less with respect to a mass of the widened sheet to form a polymer elastic body-imparted sheet;

a step of removing the polyvinyl alcohol from the polymer elastic body-imparted sheet to form a base sheet; and

a step of buffing at least one surface of the base sheet.
A method for manufacturing the artificial leather, the method comprising:
a step of imparting polyvinyl alcohol in an amount of 4 mass% or more and 40 mass% or less with respect to a mass of fine fiber-generating fibers to a fiber entangled body including a nonwoven fabric mainly composed of the fine fiber-generating fibers to form a polyvinyl alcohol-imparted sheet;

a step of widening a width of the polyvinyl alcohol-imparted sheet by 2% or more and 10% or less to form a widened sheet;

a step of developing fine fibers having an average monofilament diameter of 0.01 µm or more and 10.00 µm or less from the fine fiber-generating fibers of the widened sheet to form a nonwoven sheet;

a step of imparting, to the nonwoven sheet, a polymer elastic body in an amount of 12 mass% or more and 64 mass% or less with respect to a mass of the nonwoven sheet to form a polymer elastic body-imparted sheet;

a step of removing the polyvinyl alcohol from the polymer elastic body-imparted sheet to form a base sheet; and

a step of buffing at least one surface of the base sheet.
The method for manufacturing an artificial leather according to claim 7 or 8, wherein polyethylene glycol is included in an amount of 0.01 mass% or more and 0.5 mass% or less with respect to a mass of the polyvinyl alcohol in the step of forming the polyvinyl alcohol-imparted sheet.
A vehicular interior material comprising the artificial leather according to claim 1 or 2.
A vehicular component comprising the artificial leather according to claim 1 or 2.
Miscellaneous goods comprising the artificial leather according to claim 1 or 2.
Furniture comprising the artificial leather according to claim 1 or 2.