Artificial leather, method for producing same, interior material for vehicle, automobile component, and seat

Abstract

The present invention addresses the problem of providing an artificial leather that achieves a fine and elegant surface quality, a pleasant feel, and tensile strength.　This artificial leather is composed of a polymer elastic body and a non-woven fabric comprising ultrafine fibers, and the artificial leather has at least one napped layer. The average single fiber diameter of the ultrafine fibers is 0.1-10.0 μm. The non-woven fabric includes fiber bundles comprising the ultrafine fibers. The number of cross sections of the ultrafine fibers oriented in the thickness direction in a transverse cross section at half the thickness of a base layer excluding the napped layer is 1000 cross sections / mm2 or more and no more than 5000 cross sections / mm2. The porosity in the transverse cross section is 5-65%.

Description

Artificial leather and its manufacturing method, as well as interior materials for vehicles, automobile parts, and seats

[0001] The present invention relates to an artificial leather comprising a nonwoven fabric made of ultrafine fibers and a polymeric elastomer, and having at least one napped layer.

[0002] Artificial leather with a natural leather look, made from a nonwoven fabric of ultrafine fibers and a polymeric elastomer, offers superior characteristics compared to natural leather, such as excellent mechanical properties and uniform quality. For this reason, it is used in a wide range of applications, including automotive interiors, consumer electronics, and clothing, and its use is expanding year by year. When used in automotive interiors, artificial leather must have excellent surface quality, as well as a pleasant feel and high mechanical properties that can withstand practical use.

[0003] Furthermore, with the recent increase in environmental awareness, environmentally friendly manufacturing processes for artificial leather that use less organic solvents have been attracting attention. For example, various studies have been conducted on attempts to use copolymerized polyester polymers that can be treated with an alkaline aqueous solution instead of an organic solvent when producing ultrafine fibers.

[0004] For example, Patent Document 1 proposes a method for producing artificial leather in which the sea part polymer is removed from a fiber-entangled structure containing islands-in-sea type composite fibers, the sea part polymer being a specific copolymer polyester. This method produces ultrafine fibers with a specific average single fiber diameter. This method produces artificial leather in which specific grooves are formed on the surfaces of at least some of the ultrafine fibers. It also describes that this method produces artificial leather that has high strength, excellent abrasion resistance, and a good texture.

[0005] Furthermore, Patent Document 2 proposes a method for producing ultrafine fiber-generating fibers, in which polyalkylene glycol is added to a sea part polymer during melt spinning of an islands-in-sea type composite fiber composed of a sea part polymer and an island part polymer, and the resulting composite fiber is spun. It also describes that the ultrafine fibers obtained by this method can be used to obtain artificial leather having good surface quality and abrasion resistance.

[0006] JP 2021-155885 A JP 2014-231650 A

[0007] In the technology disclosed in Patent Document 1, at least some of the ultrafine fibers constituting the artificial leather have grooves on their surfaces, which makes it easier for the ultrafine fibers to grip the polymeric elastomer, thereby achieving a soft feel and excellent abrasion resistance. However, because the ultrafine fibers have grooves, there is room for improvement in the mechanical properties of the artificial leather compared to when ultrafine fibers without grooves are used.

[0008] In the technology disclosed in Patent Document 2, by adding polyalkylene glycol to the sea part polymer during melt spinning of islands-in-sea type composite fibers and spinning them, highly rigid ultrafine fibers having a specific range of crystallinity and mobile amorphous content are obtained, and entanglement efficiency is increased, resulting in artificial leather with good surface quality and excellent abrasion resistance. However, because polyalkylene glycol with a relatively large number average molecular weight is added during spinning, the dispersibility of the polyalkylene glycol in the sea part polymer tends to be insufficient, making it difficult to achieve a uniform and sufficient sea-removal effect during alkali treatment, leaving room for improvement in surface quality and touch.

[0009] Therefore, an object of the present invention is to provide an artificial leather that has a fine and elegant surface quality, a good touch feeling, and tensile strength.

[0010] As a result of extensive research conducted to achieve the above object, it has been found that by stretching ultrafine fiber-patterning fibers formed from a readily soluble resin containing a polyalkylene glycol of a specific number-average molecular weight as a copolymer component, and then heating the stretched ultrafine fiber-patterning fibers at a specific temperature to shrink the ultrafine fiber-patterning fibers, it is possible to obtain artificial leather with a specific porosity in which the ultrafine fibers are oriented in the thickness direction of the artificial leather. It has also been found that it is possible to obtain artificial leather with a dense and elegant surface quality that combines a good feel with tensile strength.

[0011] The present invention has been completed based on these findings and has the following features: (1) An artificial leather comprising a nonwoven fabric made of ultrafine fibers and a polymeric elastomer, and having at least one napped layer, wherein the ultrafine fibers have an average single fiber diameter of 0.1 μm or more and 10.0 μm or less, the nonwoven fabric contains fiber bundles made of the ultrafine fibers, and the number of cross sections of the ultrafine fibers oriented in the thickness direction is 1,000 / mm in a cross section at half the thickness of the base layer excluding the napped layer. ２ More than 5000 pieces / mm ２(2) An artificial leather according to (1) above, wherein the ratio B / A of the diameter B (μm) of the cross section of the fiber bundle to the diameter A (μm) of the cross section of the ultrafine fiber in the longitudinal section of the artificial leather is 5 to 10. (3) An artificial leather according to (1) or (2) above, wherein the polymer elastomer is polyurethane having a hydrophilic group, and the content of the polyurethane having a hydrophilic group in the artificial leather is 10 to 50 mass%. (4) An artificial leather according to (3) above, wherein the polyurethane having a hydrophilic group contains a component derived from a polyether-based polyol and / or a component derived from a polycarbonate-based polyol. (5) An artificial leather according to (1) or (2) above, wherein the nap length of the ultrafine fibers in the napped layer is 200 to 500 μm. (6) The artificial leather according to (1) or (2) above, wherein the porosity is 45% or more and 60% or less. (7) A vehicle interior material comprising the artificial leather according to (1) or (2) above. (8) An automobile part comprising the artificial leather according to (1) or (2) above. (9) A seat comprising the artificial leather according to (1) or (2) above. (10) A method for producing an artificial leather, comprising the steps of: drawing ultrafine fiber-producing fibers formed from an easily soluble resin, which is a copolymer polyester copolymerized with a polyalkylene glycol having a number average molecular weight of 500 to 3500, and a poorly soluble resin; heating the drawn ultrafine fiber-producing fibers under conditions such that the surface temperature of the fibers becomes 40°C to 80°C, and then crimping the fibers to obtain crimped conjugate fibers; forming a fiber web from the crimped conjugate fibers and entangling the fiber web to form a nonwoven fabric; developing ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm from the nonwoven fabric to form an ultrafine fiber sheet; imparting a polymeric elastomer to the nonwoven fabric or the ultrafine fiber sheet to obtain an impregnated sheet; and grinding at least one surface of the impregnated sheet to develop a napped layer, The artificial leather has a cross section of the ultrafine fibers oriented in the thickness direction at half the thickness of the base layer excluding the napped layer of 1000 pieces / mm ２ More than 5000 pieces / mm ２(11) The method for producing an artificial leather according to (10), wherein in the step of forming the napped layer, the napped layer has a length of 200 μm to 500 μm.

[0012] According to the present invention, an artificial leather can be obtained that has a dense and elegant surface quality, a good touch, and tensile strength. The artificial leather of the present invention can be used in a wide range of applications, such as automobile interior materials and interiors, consumer electronics, and clothing, but because of the above-mentioned properties, it is particularly suitable for use in automobile interior materials and interiors.

[0013] Fig. 1 is a schematic perspective view illustrating the longitudinal section and transverse section of the artificial leather of the present invention. Fig. 2 is a diagram illustrating the fiber bundle of the present invention using an SEM image taken of the longitudinal section of the artificial leather of the present invention. Fig. 3 is a diagram illustrating the fiber bundle of the present invention and the circumscribed circle of the line surrounding its periphery. Fig. 4 is a diagram illustrating the fiber bundle of the present invention and the inscribed circle of the line surrounding its periphery. Fig. 5 is a conceptual cross-sectional view illustrating a method for measuring and calculating the number of cross sections of ultrafine fibers in the artificial leather of the present invention.

[0014] The artificial leather of the present invention is an artificial leather that is composed of a nonwoven fabric made of ultrafine fibers and a polymeric elastomer, and has at least one napped layer, wherein the nonwoven fabric contains fiber bundles made of the ultrafine fibers, and the number of cross sections of the ultrafine fibers oriented in the thickness direction in a cross section at half the thickness of the base layer excluding the napped layer is 1000 pieces / mm ２ More than 5000 pieces / mm ２ The porosity in the cross section is 5% or more and 65% or less. These components will be described in detail below, but the present invention is not limited to the scope described below as long as it does not deviate from the gist of the present invention, and various modifications are possible within the scope of the gist of the present invention.

[0015] In the present invention, the "longitudinal section" of the artificial leather refers to a section observed from the direction of the arrow (12) indicating the direction in which the longitudinal section is observed, as exemplified in FIG. 1, i.e., a section perpendicular to both surfaces of the artificial leather, and the "transverse section" of the artificial leather refers to a section observed from the direction of the arrow (11) indicating the direction in which the transverse section is observed, as exemplified in FIG. 1, i.e., a section parallel to both surfaces of the artificial leather.

[0016] [Nonwoven Fabric Made of Ultrafine Fibers] The artificial leather of the present invention first contains a nonwoven fabric made of ultrafine fibers as a constituent element.

[0017] As the type of ultrafine fiber used in the artificial leather of the present invention, synthetic fibers are preferably used from the viewpoint of durability, particularly mechanical strength, heat resistance and light resistance.

[0018] When synthetic fibers are used as the ultrafine fibers, examples of thermoplastic resins constituting the ultrafine fibers include polyester, polyamide, polyolefin, acrylic, and polyphenylene sulfide. Examples of polyesters include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polylactic acid. Examples of polyamides include polyamide 6, polyamide 66, polyamide 610, and polyamide 12. Examples of polyolefins include polyethylene and polypropylene. Preferably, polyester is used for the ultrafine fibers, which can easily achieve both a good touch and high tensile strength.

[0019] In the present invention, examples of dicarboxylic acids and / or ester-forming derivatives thereof used in the polyester include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, and ester-forming derivatives thereof. The ester-forming derivatives referred to in the present invention include lower alkyl esters, acid anhydrides, acyl chlorides, etc. of these dicarboxylic acids, and specifically, methyl esters, ethyl esters, hydroxyethyl esters, etc. are preferably used. A more preferred embodiment of the dicarboxylic acid and / or ester-forming derivatives thereof used in the present invention is terephthalic acid and / or its dimethyl ester.

[0020] In the present invention, examples of diols used in the polyester include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and cyclohexanedimethanol, with ethylene glycol being preferred.

[0021] When synthetic fibers are used as the ultrafine fibers, the thermoplastic resin forming the ultrafine fibers may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, and the like, depending on various purposes.

[0022] From the viewpoint of processing operability, it is preferable that the cross-sectional shape of the ultrafine fibers is round. However, it is also possible to use fibers having irregular cross sections such as oval, polygonal such as flat and triangular, sectoral and cross-shaped, hollow, Y-shaped, T-shaped and U-shaped.

[0023] The ultrafine fibers preferably have an average single fiber diameter of 0.1 μm or more and 10.0 μm or less. By having an average single fiber diameter of 0.1 μm or more, more preferably 1.0 μm or more, an artificial leather can be obtained that exhibits excellent color development and fastness after dyeing. On the other hand, by having an average single fiber diameter of 10.0 μm or less, more preferably 6.0 μm or less, an artificial leather can be obtained that is dense, soft to the touch, and has excellent surface quality.

[0024] The average single fiber diameter of ultrafine fibers in the present invention refers to a value measured and calculated by the following procedure. That is, in a longitudinal section of an artificial leather, the single fiber diameters of 50 randomly selected ultrafine fibers oriented perpendicular to the cross section are measured, and the procedure is repeated in two different cross sections to calculate the average value of the single fiber diameters of a total of 150 fibers. To calculate the single fiber diameter, first, the cross section of the single fiber is observed with a scanning electron microscope (SEM, for example, "VHX-D500" manufactured by Keyence Corporation), and the cross-sectional area is measured using analysis software (for example, "VHX-H2V2" chamber view software for "VHX-D500" manufactured by Keyence Corporation), and the diameter of a circle corresponding to the cross-sectional area is calculated using the following formula.

[0025] Single fiber diameter (μm) = (4 × (cross-sectional area of ​​single fiber (μm ２ )) / π) １／２ Furthermore, the nonwoven fabric according to the present invention includes a fiber bundle made of the ultrafine fibers. In the present invention, a "fiber bundle" made of ultrafine fibers refers to an aggregate of a plurality of ultrafine fibers that can be considered to be oriented in the same direction, and refers to an aggregate of ultrafine fibers that is surrounded by a circle with a non-circularity of 2 or less when the longitudinal or transverse section of the artificial leather is observed at 1000x magnification using an SEM. Here, "non-circularity" refers to the value obtained by drawing a line (21) around the periphery of the aggregate of ultrafine fibers on an SEM image as shown in Figure 2, and dividing the diameter of the circumscribed circle (22) of the line (21) by the diameter of the inscribed circle (23) of the line (21).

[0026] The artificial leather of the present invention is in the form of a nonwoven fabric containing fiber bundles made of ultrafine fibers, and therefore, when the surface is raised by the method described below, an artificial leather having a uniform and elegant appearance and texture can be obtained.

[0027] The nonwoven fabric according to the present invention preferably has a structure in which fiber bundles are entangled. The tensile strength of the artificial leather is improved by entangling ultrafine fibers in a bundle state. A nonwoven fabric of this type can be obtained, for example, by first entangling ultrafine fiber-generating fibers with each other and then generating ultrafine fibers.

[0028] The nonwoven fabric may be either a long fiber nonwoven fabric or a short fiber nonwoven fabric, but a short fiber nonwoven fabric is preferred because it has a large number of naps on the product surface and tends to give an elegant appearance.

[0029] In the case of a short-fiber nonwoven fabric, the fiber length of the ultrafine fibers is preferably 25 mm or more and 90 mm or less. When the fiber length of the ultrafine fibers is preferably 25 mm or more, more preferably 35 mm or more, and even more preferably 40 mm or more, the artificial leather has excellent tensile strength. On the other hand, when the fiber length of the ultrafine fibers is preferably 90 mm or less, more preferably 80 mm or less, and even more preferably 70 mm or less, the artificial leather has good surface quality and texture.

[0030] In the artificial leather of the present invention, it is also preferable that the molecular orientation degree of the ultrafine fibers is 6.5 or more and 9.0 or less. By making the molecular orientation degree of the ultrafine fibers preferably 6.5 or more, more preferably 6.7 or more, and even more preferably 7.0 or more, the ultrafine fibers have sufficient strength, resulting in an artificial leather with high tenacity and excellent tensile strength. On the other hand, by making the molecular orientation degree of the ultrafine fibers preferably 9.0 or less, more preferably 8.8 or less, and even more preferably 8.5 or less, the ultrafine fibers do not become too rigid, improving processability during the production of the artificial leather and resulting in an artificial leather with excellent moldability and touch.

[0031] In the present invention, the degree of molecular orientation of ultrafine fibers is measured by laser Raman spectroscopy and calculated by the following method. Here, Raman scattering is strong when the vibration direction of the molecular chain coincides with the polarization direction of the incident light. Therefore, the scattering intensity of the Raman band belonging to the vibration mode parallel to the molecular chain changes in correlation with the degree of orientation. Therefore, measurements are performed in a polarization direction parallel to the fiber axis and a polarization direction perpendicular to the fiber axis, and the ratio of these intensities is calculated as a parameter (degree of molecular orientation) that correlates with the degree of orientation in the fiber axis direction. This parameter increases as the degree of molecular orientation increases, and is 1 when there is no orientation. (1) Ten ultrafine fibers are sampled from artificial leather, and laser light is irradiated onto the fiber surfaces of the ultrafine fibers using a laser Raman spectrometer (e.g., Jobin Yvon's "Ramanor T64000"). The degree of orientation is measured under polarized conditions. (2) When the polarization direction is parallel to the fiber axis, it is considered a parallel condition, and when it is perpendicular to the fiber axis, it is considered a perpendicular condition. From the ratio of the Raman band intensities obtained, calculate the degree of orientation using the following formula, and round the value to one decimal place to obtain the degree of molecular orientation in the ultrafine fibers. Molecular orientation degree = I 平行 / I 垂直 Here, I 平行 : Intensity of the Raman band attributed to the vibration mode parallel to the molecular chain in a deflection configuration parallel to the fiber axis direction I 垂直 : The intensity of the Raman bands attributable to vibration modes parallel to the molecular chains in a deflection configuration perpendicular to the fiber axis.

[0032] The degree of molecular orientation in the ultrafine fibers can be adjusted to fall within the above range by adjusting, for example, the spinning speed, draw ratio, draw temperature, heat treatment temperature, and the like.

[0033] Furthermore, in the present invention, it is preferable that the thermoplastic resin is a polyester resin, and the crystalline orientation degrees of the (010) plane and the (100) plane in the fiber structure are 0.80 or more and 0.95 or less. When the crystalline orientation degrees of the (010) plane and the (100) plane in the fiber structure of the ultrafine fibers are preferably 0.80 or more, more preferably 0.82 or more, the resulting artificial leather has high strength and excellent tensile strength. On the other hand, when the crystalline orientation degrees of the (010) plane and the (100) plane in the fiber structure of the ultrafine fibers are preferably 0.95 or less, more preferably 0.90 or less, the resulting artificial leather has excellent moldability and feel.

[0034] In the present invention, the degrees of crystal orientation of the (010) plane and the (100) plane in the fiber structure of ultrafine fibers refer to values ​​measured and calculated using wide-angle X-ray diffraction as follows: (1) Ultrafine fibers are sampled from artificial leather, and a diffraction intensity curve is drawn using an X-ray diffractometer (e.g., an X-ray generator "SmartLab" manufactured by Rigaku Corporation) by performing continuous scanning at diffraction angles 2θ from 5° to 60°. (2) In the diffraction intensity curve, the crystal diffraction peaks (reflection planes) detected at 2θ = approximately 17° and 2θ = approximately 25° are designated as the (010) plane and the (100) plane, respectively. Continuous scanning is performed in the azimuthal (circumferential) direction from 90° to 270° with respect to each reflection plane, and the half-width of the diffraction peaks in the diffraction intensity curve is calculated. (3) From the half-width, the degrees of crystal orientation of the (010) plane and the (100) plane are calculated using the following formula, and the value rounded to one decimal place is used as the degrees of crystal orientation of the (010) plane and the (100) plane in the fiber structure of the ultrafine fibers: Crystal orientation degree = (180 - half-width) / 180 (formula).

[0035] The crystal orientation degrees of the (010) and (100) planes in the fiber structure of the ultrafine fibers can be adjusted to fall within the above ranges by, for example, adjusting the spinning speed, draw ratio, draw temperature, heat treatment temperature, etc.

[0036] Furthermore, in the present invention, it is preferable that the thermoplastic resin is a polyester resin, and the crystallite size of the (010) plane in the fiber structure is 2.0 nm or more and 5.0 nm or less, and the crystallite size of the (100) plane is 1.0 nm or more and 4.0 nm or less. When the crystallite size of the (010) plane in the fiber structure of the ultrafine fibers is preferably 2.0 nm or more, more preferably 2.5 nm or more, or when the crystallite size of the (100) plane is preferably 1.0 nm or more and more preferably 1.5 nm or more, the artificial leather has excellent tensile strength. On the other hand, when the crystallite size of the (010) plane in the fiber structure of the ultrafine fibers is preferably 5.0 nm or less, more preferably 4.5 nm or less, or when the crystallite size of the (100) plane is preferably 4.0 nm or less, more preferably 3.5 nm or less, the ultrafine fibers can exhibit good shrinkage, resulting in an artificial leather with high surface quality.

[0037] In the present invention, the crystallite sizes of the (010) and (100) planes in the fiber structure of ultrafine fibers refer to values ​​measured and calculated using wide-angle X-ray diffraction as follows: (1) Ultrafine fibers are collected from artificial leather, and a continuous scan is performed using an X-ray diffractometer (e.g., an X-ray generator "SmartLab" manufactured by Rigaku Corporation) at diffraction angles 2θ of 5° to 60° to plot a diffraction intensity curve. (2) In the diffraction intensity curve, the crystal diffraction peaks (reflection planes) detected at 2θ = approximately 17° and 2θ = approximately 25° are designated as the (010) and (100) planes, respectively, and the half-widths of the diffraction peaks of each reflection plane are calculated. (3) From the half-width, the crystallite sizes of the (010) plane and the (100) plane are calculated using the following formula, and the value rounded to one decimal place is used as the crystallite size (nm) of the (010) plane and the (100) plane in the fiber structure of the ultrafine fiber: Crystallite size (nm) = 0.9 × λ / (β × cos θ) β = (β ｅ ２ -β ０ ２ ) １／２ where λ is the wavelength of the X-ray (nm), θ is the Bragg angle, and β ｅ : half-width of diffraction peak, β ０: Half-value width correction value (0.46° in the present invention).

[0038] The crystallite sizes of the (010) and (100) planes in the fiber structure of the ultrafine fibers can be adjusted to fall within the above ranges by, for example, adjusting the spinning speed, draw ratio, draw temperature, heat treatment temperature, etc.

[0039] [Elastomer] The artificial leather of the present invention contains an elastomer as a component. This elastomer acts as a binder in the artificial leather, which not only prevents the ultrafine fibers from falling out of the artificial leather but also makes it possible to impart an appropriate resilience.

[0040] Examples of the polymeric elastomer include polyurethane, polyurea, polyacrylic acid, etc., and polyurethane is preferably used from the viewpoint of durability and flexibility. The polymeric elastomer may contain a plurality of types of polymeric elastomers.

[0041] In the present invention, from the viewpoint of environmental consideration, it is preferable that the polymeric elastomer employs a polyurethane having a hydrophilic group. In the present invention, the polyurethane having a hydrophilic group refers to a polyurethane obtained by reacting a polymer polyol (described later), an organic diisocyanate, and an active hydrogen component-containing compound having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting a chain extender to obtain a polyurethane precursor, and then reacting the polyurethane precursor with a crosslinking agent. These will be described in detail below.

[0042] (a) Polymer Polyols Polymer polyols preferably used in the present invention include polyether polyols, polyester polyols, polycarbonate polyols, and the like.

[0043] First, examples of polyether polyols include polyols obtained by addition polymerization of monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin, and cyclohexylene using polyhydric alcohols or polyamines as initiators, and polyols obtained by ring-opening polymerization of the above-mentioned monomers using protonic acids, Lewis acids, cationic catalysts, etc. as catalysts. Specific examples include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and copolymer polyols combining these.

[0044] Next, examples of polyester polyols include polyester polyols obtained by condensing various low molecular weight polyols with polybasic acids, and polyols obtained by open polymerization of lactones.

[0045] Examples of low molecular weight polyols used in polyester polyols include linear alkylene glycols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; branched alkylene glycols such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, and 2-methyl-1,8-octanediol; alicyclic diols such as 1,4-cyclohexanediol; and aromatic dihydric alcohols such as 1,4-bis(β-hydroxyethoxy)benzene. Adducts obtained by adding various alkylene oxides to bisphenol A can also be used as low molecular weight polyols.

[0046] On the other hand, examples of the polybasic acid used in the polyester polyol include one or more selected from the group consisting of succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydroisophthalic acid.

[0047] Examples of polycarbonate-based polyols include compounds obtained by reacting a polyol with a carbonate compound, such as a polyol with a dialkyl carbonate or a polyol with a diaryl carbonate.

[0048] The polyol used in the polycarbonate polyol can be a low-molecular-weight polyol used in the polyester polyol. On the other hand, the dialkyl carbonate can be dimethyl carbonate or diethyl carbonate, and the diaryl carbonate can be diphenyl carbonate.

[0049] The number-average molecular weight of the polymer polyol preferably used in the present invention is preferably 500 or more and 5000 or less. By setting the number-average molecular weight of the polymer polyol to preferably 500 or more, more preferably 1500 or more, it is possible to easily prevent the texture of the artificial leather from becoming hard. On the other hand, by setting the number-average molecular weight to preferably 5000 or less, more preferably 4000 or less, it is possible to easily maintain the strength of the polyurethane having hydrophilic groups as a binder.

[0050] (b) Organic Diisocyanate Examples of organic diisocyanates preferably used in the present invention include aromatic diisocyanates having from 6 to 20 carbon atoms (excluding carbon atoms in isocyanate (NCO) groups; the same applies hereinafter), aliphatic diisocyanates having from 2 to 18 carbon atoms, alicyclic diisocyanates having from 4 to 15 carbon atoms, araliphatic diisocyanates having from 8 to 15 carbon atoms, modified products of these diisocyanates (carbodiimide-modified products, urethane-modified products, uretdione-modified products, etc.), and mixtures of two or more of these.

[0051] Specific examples of aromatic diisocyanates having 6 to 20 carbon atoms include 1,3- and / or 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate, 2,4'- and / or 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as MDI), 4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, and 1,5-naphthylene diisocyanate. Of these, it is preferable to use MDI, which has excellent flexibility when made into a polyurethane having a hydrophilic group.

[0052] Specific examples of aliphatic diisocyanates having 2 to 18 carbon atoms include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl)carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexaate.

[0053] Specific examples of alicyclic diisocyanates having 4 to 15 carbon atoms include isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, and 2,5- and / or 2,6-norbornane diisocyanate. Of these, it is preferable to use dicyclohexylmethane-4,4'-diisocyanate, which has excellent durability when made into a polyurethane having a hydrophilic group.

[0054] Specific examples of aromatic aliphatic diisocyanates having 8 to 15 carbon atoms include m- and / or p-xylylene diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate.

[0055] (c) Active hydrogen component-containing compound having a hydrophilic group The active hydrogen component-containing compound having a hydrophilic group preferably used in the present invention includes compounds containing a nonionic group and / or anionic group and / or cationic group and active hydrogen. These active hydrogen component-containing compounds can also be used in the form of a salt neutralized with a neutralizing agent. The use of this active hydrogen component-containing compound having a hydrophilic group can improve the stability of the aqueous dispersion used in the manufacturing method of artificial leather.

[0056] Examples of compounds having a nonionic group and active hydrogen include compounds containing two or more active hydrogen components or two or more isocyanate groups and having a polyoxyethylene glycol group or the like having a molecular weight of 250 to 9,000 in a side chain, and triols such as trimethylolpropane and trimethylolbutane.

[0057] Examples of the compound having an anionic group and active hydrogen include carboxyl group-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid, and derivatives thereof; sulfonic acid group-containing compounds such as 1,3-phenylenediamine-4,6-disulfonic acid and 3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid, and derivatives thereof; and salts of these compounds neutralized with a neutralizing agent.

[0058] Examples of compounds containing a cationic group and active hydrogen include tertiary amino group-containing compounds such as 3-dimethylaminopropanol, N-methyldiethanolamine, and N-propyldiethanolamine, and derivatives thereof.

[0059] (d) Chain Extender Examples of chain extenders preferably used in the present invention include water, low molecular weight diols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and neopentyl glycol, alicyclic diols such as 1,4-bis(hydroxymethyl)cyclohexane, aromatic diols such as 1,4-bis(hydroxyethyl)benzene, aliphatic diamines such as ethylenediamine, alicyclic diamines such as isophoronediamine, aromatic diamines such as 4,4-diaminodiphenylmethane, araliphatic diamines such as xylenediamine, alkanolamines such as ethanolamine, hydrazine, and dihydrazides such as adipic acid dihydrazide, as well as mixtures of two or more of these.

[0060] Of these, preferred chain extenders are water, low molecular weight diols and aromatic diamines, and more preferred are water, ethylene glycol, 1,4-butanediol, 4,4'-diaminodiphenylmethane and mixtures of two or more of these.

[0061] (e) Structure of Polyurethane Precursor As described above, the polyurethane precursor preferably used in the present invention is prepared by reacting a high molecular weight polyol, an organic diisocyanate, and an active hydrogen component-containing compound having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting a chain extender.

[0062] (f) Crosslinking Agent The crosslinking agent used in the present invention may be one having two or more reactive groups in the molecule that can react with the reactive group introduced into the polyurethane precursor, and specific examples include polyisocyanate-based crosslinking agents such as water-soluble isocyanate compounds and blocked isocyanate compounds, melamine-based crosslinking agents, carbodiimide-based crosslinking agents, etc. One type of crosslinking agent may be used alone, or two or more types may be used in combination.

[0063] The water-soluble isocyanate compound has two or more isocyanate groups in the molecule, and examples thereof include compounds containing organic polyisocyanate.

[0064] A blocked isocyanate compound has two or more blocked isocyanate groups in the molecule. The blocked isocyanate group refers to an organic polyisocyanate compound blocked with a blocking agent such as an amine, a phenol, an imine, a mercaptan, a pyrazole, an oxime, or an active methylene.

[0065] Examples of the oxazoline-based crosslinking agent include compounds having two or more oxazoline groups (oxazoline skeletons) in the molecule.

[0066] The carbodiimide crosslinking agent may be a compound having two or more carbodiimide groups in the molecule.

[0067] Among these, it is preferable to use a carbodiimide compound, which gives a polyurethane having a hydrophilic group obtained after the reaction that is particularly excellent in durability and flexibility.

[0068] (g) Structure of Hydrophilic Group-Containing Polyurethane From the viewpoint of flexibility and durability, the hydrophilic group-containing polyurethane preferably used in the present invention preferably contains a component derived from a polyether polyol and / or a component derived from a polycarbonate polyol. When the hydrophilic group-containing polyurethane contains a component derived from a polyether polyol, the degree of freedom of the ether bond is high, resulting in a low glass transition temperature and weak cohesive strength, making it possible to obtain a hydrophilic group-containing polyurethane with excellent flexibility. Furthermore, when the hydrophilic group-containing polyurethane contains a component derived from a polycarbonate polyol, the high cohesive strength of the carbonate group makes it possible to obtain a hydrophilic group-containing polyurethane with excellent water resistance, heat resistance, weather resistance, and mechanical properties.

[0069] The constituent components of the polyurethane having hydrophilic groups can be confirmed (that the polyurethane having hydrophilic groups contains a component derived from a polyester polyol and / or that the polyurethane having hydrophilic groups contains a component derived from a polycarbonate polyol) by dissolving the polyester that constitutes the artificial leather and analyzing the insoluble matter (polyurethane having hydrophilic groups) using infrared spectroscopy (analytical equipment such as the FT / IR 4000 series manufactured by JASCO Corporation) or pyrolysis GC / MS analysis (analytical equipment such as the GCMS-QP5050A manufactured by Shimadzu Corporation). Examples of solvents that can be used to dissolve the polyester that constitutes the artificial leather include m-cresol and hexafluoroisopropanol, but it is preferable to use hexafluoroisopropanol, which can be handled at room temperature.

[0070] The polyurethane having a hydrophilic group used in the present invention preferably has an N-acylurea bond and / or an isourea bond. The N-acylurea bond and / or the isourea bond is formed by the reaction of a hydrophilic group with a crosslinking agent having a carbodiimide group, and by forming a crosslinked structure in the polyurethane having a hydrophilic group, the durability of the polyurethane having a hydrophilic group can be improved.

[0071] The presence of the N-acylurea group or isourea group in the polyurethane having a hydrophilic group can be analyzed by subjecting a cross section of the artificial leather to, for example, a mapping process such as time-of-flight secondary ion mass spectrometry (TOF-SIMS analysis) (an analytical instrument such as the "TOF.SIMS 5" manufactured by ION-TOF Corporation) or infrared spectroscopy (an analytical instrument such as the "FT / IR 4000 series" manufactured by JASCO Corporation).

[0072] In general, the content of the polymeric elastomer in the artificial leather can be adjusted appropriately taking into consideration the type of polymeric elastomer used, the manufacturing method of the polymeric elastomer, and the texture and physical properties. In the present invention, the content of the polymeric elastomer in the artificial leather, particularly the content of polyurethane having hydrophilic groups in the artificial leather, is preferably 10% by mass or more and 50% by mass or less. By setting the content of the polymeric elastomer to preferably 10% by mass or more, more preferably 15% by mass or more, the artificial leather can have excellent tensile strength. On the other hand, by setting the content of polyurethane having hydrophilic groups in the artificial leather to preferably 50% by mass or less, more preferably 35% by mass or less, the artificial leather can have a soft texture.

[0073] In the present invention, the content of polyurethane having a hydrophilic group in the artificial leather is a value measured and calculated by the following method: (1) A test piece of 5 cm x 5 cm is cut out from the artificial leather, and the mass (M Ｘ (2) The test piece is immersed in hexafluoroisopropanol to elute the polyester ultrafine fibers from the artificial leather. (3) The insoluble component (polyurethane having hydrophilic groups) in (2) is dried in a dryer at 100°C, and the mass (M Ａ After measuring (g), the content (mass %) of polyurethane having a hydrophilic group is calculated using the following formula.

[0074] Content of polyurethane having hydrophilic groups=(M Ａ / M Ｘ ) × 100 Furthermore, the polymeric elastomer may contain various additives depending on the purpose, such as "inorganic or oxide-based" pigments, "phosphorus-based, halogen-based, or inorganic" flame retardants, "phenol-based, sulfur-based, or phosphorus-based" antioxidants, "benzotriazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, or oxalic acid anilide-based" ultraviolet absorbers, "hindered amine-based or benzoate-based" light stabilizers, hydrolysis-resistant stabilizers such as polycarbodiimide, plasticizers, antistatic agents, surfactants, coagulation adjusters, and dyes.

[0075] [Artificial Leather] The artificial leather of the present invention is composed of the nonwoven fabric and a polymeric elastomer. Furthermore, the artificial leather of the present invention has at least one napped layer (Fig. 1, 10a). The napped layer is present on the surface of the artificial leather, and is present on one surface or both surfaces.

[0076] In the present invention, the "raised layer" refers to a layer in which ultrafine fibers that are not held by the polymeric elastomer and are not intertwined with each other are raised toward the outside of the nonwoven fabric. The remaining portion of the artificial leather excluding the "raised layer" is referred to as the "base layer."

[0077] The nap length of the ultrafine fibers in the napped layer, i.e., the nap length, is preferably 200 μm or more and 500 μm or less. A nap length of preferably 200 μm or more, more preferably 220 μm or more, results in an artificial leather with an excellent touch. On the other hand, a nap length of preferably 500 μm or less, more preferably 450 μm or less, results in an artificial leather with an elegant suede-like surface quality, in which deterioration of the surface quality due to entanglement of the ultrafine fibers is suppressed.

[0078] The nap length of the present invention can be measured by the method disclosed in JP-A-2019-112744.

[0079] Furthermore, in the artificial leather according to the present invention, the number of cross sections of the ultrafine fibers oriented in the thickness direction is 1000 pieces / mm in a cross section at half the thickness of the base layer. ２ More than 5000 pieces / mm ２ The porosity in the cross section is 5% or more and 65% or less. By simultaneously satisfying these two requirements, an artificial leather having a fine and elegant surface quality, a good feel, and tensile strength can be obtained.

[0080] Regarding these, first, in a cross section at half the thickness of the base layer, the number of cross sections of ultrafine fibers oriented in the thickness direction (hereinafter, sometimes simply abbreviated as "the number of cross sections of ultrafine fibers in the thickness direction") is 1000 pieces / mm ２ More than 1500 pieces / mm ２ More preferably, 2500 pieces / mm ２By setting the number of cross sections of the ultrafine fibers in the thickness direction to 5,000 pieces / mm or more, voids oriented in the thickness direction are formed in the artificial leather, and good breathability can be obtained. ２ Preferably 4500 pieces / mm or less ２ Less than or equal to 4000 pieces / mm ２ When the thickness is below 100 mm, the fibers oriented in the planar direction remain to a moderate extent, resulting in an artificial leather having excellent mechanical properties such as tensile strength.

[0081] In the present invention, the number of cross sections of ultrafine fibers in the thickness direction is a value measured and calculated as follows: (1) Cool the water-soaked artificial leather to -10°C. (2) Use a microtome (e.g., the "RX-860" microtome manufactured by Yamato Koki Kogyo Co., Ltd.) to grind the artificial leather in the thickness direction, as shown in Figure 3, from just below the napped layer to a grinding amount of between one-third and one-half of the thickness of the base layer (Figure 1, 10b). The final grinding amount (µm) is determined by taking a vertical cross-sectional SEM image of the artificial leather and measuring the distance (Figure 5, 31a) from the surface excluding the napped layer to the grinding end position (Figure 5, 31b) (Figure 5, 31). If the base layer contains a woven or knitted fabric, grinding is performed to a depth of between one-third and one-half of the thickness from just below the napped layer to the woven or knitted fabric. After grinding, dry the artificial leather at room temperature for 24 hours. (3) Metal is sputtered onto the ground artificial leather to avoid charging and vibration of the observation surface in the electron beam. For example, using an auto fine coater "JEC-3000FC" manufactured by JEOL Ltd., gold or platinum is used as a target and sputtering is performed for 240 seconds at a sputtering current of 20 mA. (4) The ground cross section is observed at 500x magnification using an SEM, and the number of cross sections of ultrafine fibers that form an angle of 90° with the observation surface is counted. Here, "ultrafine fibers that form an angle of 90° with the observation surface" refers to ultrafine fibers whose side faces in the depth direction cannot be seen from the observation surface. (5) The actual area of ​​the field of view is calculated using a scale, and the area is counted by 1 mm. ２ The number of cross sections per one point is calculated. The number of cross sections per one point is calculated, and the average value (number / mm ２ ) and round to the nearest tenth.

[0082] The number of cross sections of the ultrafine fibers in the thickness direction can be adjusted by, for example, needle punching or water jet punching in the process of obtaining a nonwoven fabric, or the ratio B / A of the diameter B (μm) of the cross section of the fiber bundle to the diameter A (μm) of the cross section of the ultrafine fiber, which will be described later.

[0083] Furthermore, the artificial leather of the present invention has a porosity in the cross section of 5% or more and 65% or less. A porosity in the cross section of 5% or more, preferably 15% or more, and more preferably 45% or more results in an artificial leather that is flexible and has excellent moldability. On the other hand, a porosity in the cross section of 65% or less, preferably 60% or less, results in an artificial leather that has a good surface density and excellent mechanical properties such as tensile strength. In particular, a porosity of 45% or more and 60% or less is particularly preferred because it can achieve both excellent touch, surface quality, and tensile strength.

[0084] In the present invention, the porosity of the cross section is a value measured and calculated as follows: (1) The cross section is observed at 200x magnification using an SEM, and an image is cut out to have actual dimensions of 2 mm x 2 mm. (2) For the captured SEM image, a histogram of the number of pixels at each of 256 gradations, with white being 255 and black being 0, is obtained using, for example, "ImageJ," an image analysis software developed by the National Institutes of Health (NIH). (3) The histogram is binarized, with the gradation with the most pixels between 20 and 235 being black, and the gradation with the most pixels being one gradation lighter than the gradation with the most pixels being white, from 255 to 255. (3) The ratio of the number of black pixels to the total number of pixels is calculated, and this is the porosity (%). (4) The porosity of 20 locations is determined, and the average (%) is rounded off to the nearest decimal point.

[0085] The void ratio in the cross section can be adjusted by, for example, needle punching or water jet punching in the process of obtaining a nonwoven fabric, or the ratio B / A of the diameter B (μm) in the cross section of the fiber bundle to the diameter A (μm) in the cross section of the ultrafine fiber, which will be described later.

[0086] Furthermore, in the artificial leather of the present invention, the ratio B / A of the diameter B (μm) of the cross section of the fiber bundle to the diameter A (μm) of the cross section of the ultrafine fiber in the longitudinal section of the artificial leather is preferably 5 or more and 10 or less. When this ratio B / A is preferably 5 or more, more preferably 5.5 or more, a large number of ultrafine fibers are oriented in the thickness direction of the artificial leather, resulting in an artificial leather with high tensile strength. On the other hand, when the ratio B / A is preferably 10 or less, more preferably 8 or less, the artificial leather has a denser raised nap layer and excellent surface quality.

[0087] In the present invention, the ratio B / A is a value measured and calculated as follows. (1) The longitudinal section of the artificial leather is observed at 1000x magnification using a scanning electron microscope (SEM, for example, "VHX-D500" manufactured by Keyence Corporation). (2) Ten locations are randomly observed, and five or more fibers in each location are selected, for a total of 100 fiber bundles. (3) The mode of the number of ultrafine fibers constituting the fiber bundle is determined. (4) For the fiber bundle with the mode of the number of ultrafine fibers, the diameter A (μm) of the cross section of the ultrafine fiber is calculated. Here, the diameter A (μm) of the cross section of the ultrafine fiber is calculated by using analysis software (for example, chamber view software "VHX-H2V2" for "VHX-D500" manufactured by Keyence Corporation) to calculate the cross-sectional area (μm) of the ultrafine fiber in the fiber bundle. ２ ) is measured, and the diameter (μm) of the circle having the cross-sectional area is calculated using the following formula: Diameter A (μm) of the cross section of the ultrafine fiber = (4 × (cross-sectional area of ​​the single fiber (μm) ２ )) / π) １／２ (5) For fiber bundles with the most frequent number of ultrafine fibers, calculate the diameter B (μm) of the cross section of the fiber bundle. Specifically, the area inside the line surrounding the periphery of the fiber bundle for which the diameter A of the cross section of the ultrafine fibers was calculated in (4) is measured using the analysis software described in (4), and the diameter B is calculated using the following formula: Diameter B (μm) of the cross section of the fiber bundle = (4 × (area surrounded by the line surrounding the periphery of the fiber bundle (μm) ２ )) / π) １／２(6) For each fiber bundle, the diameter B (µm) of the cross section of the fiber bundle calculated in (5) is divided by the diameter A (µm) of the cross section of the ultrafine fiber calculated in (4) to calculate the ratio B / A (unitless), and the arithmetic average value (unitless) of all the fiber bundles is rounded to one decimal place.

[0088] The ratio B / A can be adjusted by the number of ultrafine fibers constituting the composite fiber and the ratio of the easily soluble resin and the sparingly soluble resin constituting the ultrafine fiber-developing fiber.

[0089] The artificial leather of the present invention preferably has a thickness of 0.2 mm or more and 1.5 mm or less, as measured by "6.1.1 Method A" of "6.1 Thickness (ISO Method)" of JIS L1913:2010 "Testing Methods for General Nonwoven Fabrics." When the thickness of the artificial leather is preferably 0.2 mm or more, more preferably 0.3 mm or more, the artificial leather not only has excellent processability during production but also has a rich feel and excellent texture. On the other hand, when the thickness of the artificial leather is preferably 1.5 mm or less, more preferably 1.2 mm or less, the artificial leather has excellent moldability and flexibility.

[0090] [Method for producing artificial leather] The method for producing artificial leather of the present invention includes the steps of: drawing an ultrafine fiber-producing fiber formed from an easily soluble resin, which is a copolymer polyester copolymerized with a polyalkylene glycol having a number average molecular weight of 500 to 3500, and a poorly soluble resin, to obtain a drawn conjugate fiber; heating the drawn conjugate fiber under conditions such that the surface temperature of the drawn conjugate fiber becomes 40°C to 80°C, and then imparting crimping to obtain a crimped conjugate fiber; forming a fiber web from the crimped conjugate fiber and entangling the fiber web to form a nonwoven fabric; developing ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm from the nonwoven fabric to form an ultrafine fiber sheet; and imparting a polymeric elastomer to the nonwoven fabric or the ultrafine fiber sheet to obtain an impregnated sheet. and grinding one or both surfaces of the impregnated sheet to form a napped layer having a nap length of 200 μm or more and 500 μm or less on at least one surface. The details of the preferred embodiments will be described below, but the scope of the following description is not intended to limit the scope of the present invention, and various modifications are possible within the scope of the present invention.

[0091] <Step of Obtaining Crimped Conjugate Fiber> In this step, an ultrafine fiber-developing fiber formed from a soluble resin, which is a copolymer polyester copolymerized with a polyalkylene glycol having a number-average molecular weight of 500 to 3500, and a slightly soluble resin is first drawn, and the drawn ultrafine fiber-developing fiber is heated under conditions such that the surface temperature of the ultrafine fiber-developing fiber is 40°C to 80°C, thereby obtaining a crimped crimped conjugate fiber. In the present invention, the term "ultrafine fiber-developing fiber" refers to a fiber in which the soluble resin, as described below, is removed and the remaining slightly soluble resin becomes ultrafine fibers, such as islands-in-sea conjugate fibers and sheath-core conjugate fibers. The term "easily soluble resin" refers to a resin that has a solubility 100 times or more greater than that of the slightly soluble resin in solvents such as organic solvents or aqueous solutions such as alkaline aqueous solutions used to remove the soluble resin from the ultrafine fiber-developing fiber. Due to this difference, for example, a readily soluble resin that dissolves easily in an alkaline aqueous solution will dissolve within 5 minutes when immersed in a 5% aqueous sodium hydroxide solution, whereas a sparingly soluble resin used in combination will not dissolve in the above solution for 10 minutes or more.As a result, ultrafine fibers can be easily obtained.

[0092] (1) Readily Soluble Resin Examples of readily soluble resins for ultrafine fiber development fibers include polylactic acid and copolymer polyesters. From the viewpoints of spinnability and ease of dissolution by alkali treatment, copolymer polyesters are preferably used.

[0093] When a copolymerized polyester is used, a copolymerized polyester obtained by copolymerizing 3 mol % to 15 mol % of sodium 5-sulfoisophthalate as a copolymerization component is preferred. By setting the copolymerization amount of the sodium 5-sulfoisophthalate component to preferably 3 mol % or more, more preferably 5 mol % or more, sufficient alkali elution properties can be obtained. On the other hand, by setting the copolymerization amount of the sodium 5-sulfoisophthalate component to preferably 15 mol % or less, more preferably 13 mol % or less, thickening of the polyester is suppressed, and the effect of reducing the occurrence of yarn breakage during spinning of ultrafine fiber-forming fibers is achieved.

[0094] The copolymer polyester is preferably copolymerized with a polyalkylene glycol having a number-average molecular weight of 500 or more and 3500 or less, more preferably 700 or more and 3000 or less. By setting the number-average molecular weight of the polyalkylene glycol within the above range, the dispersibility of the polyalkylene glycol in the easily soluble resin is improved, which has the effect of improving the spinnability and alkali elution properties of the ultrafine fiber-developing fiber, and achieving a uniform and sufficient sea-removal effect during alkali treatment.

[0095] The copolymerization amount of polyalkylene glycol in the easily soluble resin is preferably 0.1% by mass or more and 15% by mass or less. By setting the copolymerization amount of polyalkylene glycol to preferably 0.1% by mass or more, more preferably 1.5% by mass or more, the alkali elution property is improved. On the other hand, by setting the copolymerization amount of polyalkylene glycol to preferably 15% by mass or less, more preferably 12% by mass or less, the effect of reducing the occurrence of yarn breakage during spinning of ultrafine fiber-producing fibers is achieved.

[0096] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, and polybutylene glycol, with polyethylene glycol being preferred due to its ease of use and its ability to be reduced in weight in an alkaline aqueous solution.

[0097] The readily soluble resin constituting the ultrafine fiber-forming fiber preferably contains a polyethylene terephthalate polyester having ethylene terephthalate units as a main repeating unit as one component, or may be a polyester in which a portion of the terephthalic acid component is replaced with another bifunctional carboxylic acid component, or similarly, a polyester in which a portion of the ethylene glycol component is replaced with another polyol component.

[0098] Preferred examples of the difunctional carboxylic acid other than terephthalic acid used in the present invention include aromatic, aliphatic, and alicyclic difunctional carboxylic acids such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, adipic acid, sebacic acid, and 1,4-cyclohexane dicarboxylic acid. Preferred examples of the polyol compound other than ethylene glycol include aliphatic, alicyclic, and aromatic polyol compounds such as tetramethylene glycol, hexamethylene glycol, cyclohexane-1,4-dimethanol, neopentyl glycol, bisphenol A, and bisphenol S.

[0099] Furthermore, the easily soluble resin constituting the ultrafine fiber-forming fiber and the sparingly soluble resin described below may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, and the like, depending on various purposes, within the scope of not interfering with the object of the present invention.

[0100] (2) Hardly Soluble Resin Examples of the hardly soluble resin for the ultrafine fiber-forming fibers include polyester resins, polyamide resins, polyolefin resins, acrylic resins, polyphenylene sulfide resins, etc., which are listed as examples of the thermoplastic resins constituting the ultrafine fibers. Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polylactic acid, and mixtures and copolymers of these polyester resins. Examples of polyamide resins include polyamide 6, polyamide 66, polyamide 610, polyamide 12, and mixtures and copolymers of these polyamide resins. Examples of polyolefin resins include polyethylene and polypropylene, and mixtures and copolymers of these polyolefin resins. Among these, polyester resins are preferred from the viewpoints of strength, dimensional stability, and heat resistance.

[0101] (3) Ultrafine fiber-developing fibers Ultrafine fiber-developing fibers include a method using an islands-in-sea composite spinneret or a sheath-core composite spinneret to spin two components, an easily soluble resin and a slightly soluble resin, in a mutually aligned polymer matrix, and a mixed spinning method to spin a mixture of two components, an easily soluble resin and a slightly soluble resin, in a mutually aligned polymer matrix. From the viewpoint of obtaining ultrafine fibers with a uniform single fiber fineness, islands-in-sea composite fibers or sheath-core composite fibers using a method using an mutually aligned polymer matrix are preferred.

[0102] The ultrafine fiber-developing fibers used in the artificial leather of the present invention can be obtained by using a general composite spinneret in which a group of pipes is arranged, or a composite spinneret capable of forming various cross-sectional shapes, as described in JP 2011-174215 A, which is configured by combining a metering plate having a plurality of metering holes for metering the polymer streams of each component and a confluence groove that confluences the polymer streams discharged from the plurality of metering holes with a distribution plate having a plurality of distribution holes.

[0103] The ratio of the easily soluble resin to the hardly soluble resin in the ultrafine fiber development type fiber is preferably 20% or more and 95% or less by mass of the hardly soluble resin to the ultrafine fiber development type fiber. By setting the mass ratio of the hardly soluble resin to preferably 20% or more, more preferably 30% or more, the removal rate of the easily soluble resin can be reduced, further improving productivity. On the other hand, by setting the mass ratio of the hardly soluble resin to preferably 95% or less, more preferably 90% or less, it is possible to prevent the hardly soluble resins from joining together and suppress deterioration of surface quality.

[0104] The spinning speed when obtaining ultrafine fiber-developing fibers is preferably 500 m / min or more and 3000 m / min or less. By setting the spinning speed to preferably 500 m / min or more, more preferably 800 m / min or more, ultrafine fiber-developing fibers having an average single fiber diameter of 10 μm or less can be easily obtained, and artificial leather with a fine surface quality and excellent feel can be obtained. On the other hand, by setting the spinning speed to preferably 3000 m / min or less, more preferably 2000 m / min or less, the frequency of yarn breakage can be reduced and productivity can be further improved.

[0105] (4) Drawing of Ultrafine Fiber-Developing Fiber In this step, the ultrafine fiber-developing fiber is first drawn to obtain a drawn ultrafine fiber-developing fiber (hereinafter sometimes simply referred to as drawn conjugate fiber). In this case, the draw ratio is preferably 2.0 times or more and 4.5 times or less. By setting the draw ratio to preferably 2.0 times or more, more preferably 2.3 times or more, an ultrafine fiber-developing fiber with sufficient strength can be obtained. On the other hand, by setting the draw ratio to preferably 4.5 times or less, more preferably 4.2 times or less, excellent stability during drawing processing can be achieved.

[0106] The drawing temperature during the above-mentioned drawing is preferably 50°C or higher and 80°C or lower. Here, the drawing temperature refers to the temperature of the heat source with which the ultrafine fiber development-type fiber comes into contact during drawing processing, and specifically refers to the surface temperature of the roller in the case of roller drawing, the liquid temperature of the liquid bath in the case of liquid bath drawing, and the atmospheric temperature inside the steam box in the case of steam drawing. By setting the drawing temperature to 50°C or higher, ultrafine fiber development-type fiber with little orientation unevenness can be obtained. On the other hand, by setting the drawing temperature to 80°C or lower, elution of the easily soluble resin during drawing processing can be suppressed.

[0107] (5) Crimped Conjugate Fibers In the final step of this process, the drawn conjugate fibers are heated under conditions such that the surface temperature of the drawn conjugate fibers is 40° C. or higher and 80° C. or lower, and then crimped to obtain crimped conjugate fibers. In addition to adjusting the conditions such as the draw ratio and the draw temperature, by carrying out this heat treatment, it is possible to control the degree of molecular orientation in the ultrafine fibers that make up the artificial leather, and it is possible to obtain an artificial leather that has a dense and elegant surface quality, a good touch, and tensile strength, which is the object of the present invention.

[0108] In the present invention, the surface temperature of the drawn conjugate fiber during heating is preferably 40° C. or higher and 80° C. or lower, more preferably 45° C. or higher and 70° C. or lower. By setting the heating temperature within this range, it is possible to suppress the elution of the easily soluble resin, and the ultrafine fiber-developing fiber has appropriate strength and elongation and shrinkage, which has the effect of providing excellent processability in subsequent steps. In addition, it is possible to set the degree of molecular orientation in the ultrafine fibers, which is a feature of the present invention, within a specific range.

[0109] In the present invention, the method of imparting crimps can be a known method, such as a method using a push-in crimper.

[0110] In the method for producing an artificial leather of the present invention, the tensile strength of the hardly soluble resin portion of the drawn conjugate fiber or crimped conjugate fiber is preferably 3.0 cN / dtex or more. By making the tensile strength of the hardly soluble resin portion preferably 3.0 cN / dtex or more, more preferably 3.2 cN / dtex or more, the tensile strength of the artificial leather can be improved and a decrease in friction fastness due to fiber shedding can be suppressed.

[0111] In the present invention, the tensile strength of the hardly soluble resin portion of a drawn or crimped conjugate fiber is calculated by the following method: (1) Ten drawn or crimped conjugate fibers, each 20 cm long, are bundled together. (2) The readily soluble resin is dissolved and removed from the sample obtained in (1), and then the sample is air-dried. (3) The test is conducted 10 times according to "8.5.1 Standard Time Test" in "8.5 Tensile Strength and Elongation" of JIS L1013:2010 "Test Methods for Chemical Fiber Filament Yarns" under the conditions of a grip length of 5 cm, a pulling speed of 5 cm / min, and a load of 2 N. (4) The arithmetic mean value (cN / dtex) of the test results obtained in (3) is rounded to one decimal place.

[0112] <Step of forming nonwoven fabric> In this step, a fiber web is formed from the crimped conjugate fibers, and the fiber web is entangled to form a nonwoven fabric. More specifically, the nonwoven fabric can be obtained by opening the crimped conjugate fibers, forming them into a fiber web using a cross wrapper or the like, and then entangling the fiber web.

[0113] As a method for forming a fiber web and entangling the fiber web to obtain a nonwoven fabric, needle punching, water jet punching, etc. can be used, but among them, needle punching, which has a high entanglement efficiency, is preferred.

[0114] As for the form of the nonwoven fabric, either a short fiber nonwoven fabric or a long fiber nonwoven fabric can be used as described above. However, when a short fiber nonwoven fabric is used, the fibers oriented in the thickness direction of the artificial leather are more numerous than in a long fiber nonwoven fabric, and a highly dense feel can be obtained on the surface of the artificial leather when it is raised.

[0115] When a short fiber nonwoven fabric is to be produced, the obtained crimped conjugate fibers are cut to a predetermined length, and then opened, laminated, and entangled to obtain a short fiber nonwoven fabric. The cutting process can be carried out by a known method.

[0116] The needles used in the needle punching process preferably have 1 to 9 needle barbs (notches). Having 1 or more needle barbs allows for efficient fiber entanglement. Having 9 or fewer needle barbs can prevent fiber damage.

[0117] The number of ultrafine fiber-developing fibers caught on the barbs is determined by the shape of the barbs and the diameter of the ultrafine fiber-developing fibers. Therefore, the barb shape of the needles used in the needle punching process preferably has a kick-up of 0 μm to 50 μm, an undercut angle of 0° to 40°, a throat depth of 40 μm to 80 μm, and a throat length of 0.5 mm to 1.0 mm.

[0118] The number of needle punches in the needle punching process is 1000 / cm ２ Over 8000 strands / cm ２ The number of punches is preferably 1000 / cm or less. ２ By setting the number of punches at 8000 / cm or more, a dense nonwoven fabric can be obtained. ２ By setting the content below, it is possible to prevent deterioration of processability, damage to the fibers, and a decrease in the tensile strength of the artificial leather.

[0119] Furthermore, when performing water jet punching, it is preferable to perform the water jet punching in the form of a columnar flow. Specifically, it is preferable to eject water from a nozzle having a diameter of 0.05 mm or more and 1.0 mm or less at a pressure of 2 MPa or more and 60 MPa or less.

[0120] The apparent density of the nonwoven fabric made of ultrafine fiber development type fibers after needle punching treatment is 0.15 g / cm ３ 0.40g / cm or more ３ The apparent density of the nonwoven fabric is preferably 0.15 g / cm or less. ３ More preferably, 0.20 g / cm ３ By setting the apparent density of the nonwoven fabric to 0.40 g / cm or more, an artificial leather having excellent durability and tensile strength can be obtained. ３ or less, more preferably 0.35 g / cm ３ By setting the above, it is possible to maintain space for applying the polymeric elastomer, so that the polymeric elastomer is applied uniformly, and an artificial leather with excellent resilience can be obtained.

[0121] The weight of the nonwoven fabric is 200 g / m ２ 900g / m or more ２ The basis weight of the nonwoven fabric is preferably 200 g / m or less. ２ More preferably, 250 g / m ２ By setting the weight of the nonwoven fabric to 900 g / m or more, an artificial leather having excellent tensile strength can be obtained. ２ or less, more preferably 800 g / m ２ By setting the following, it is possible to obtain a flexible artificial leather with excellent moldability.

[0122] It is also a preferred embodiment to subject the nonwoven fabric to a heat shrinking treatment using hot water or steam in order to improve the denseness of the fibers.

[0123] Next, the nonwoven fabric can be impregnated with an aqueous solution of the water-soluble resin and then dried to impart the water-soluble resin to the nonwoven fabric. By imparting the water-soluble resin to the nonwoven fabric, the fibers are fixed and the dimensional stability is improved.

[0124] <Step of Forming Ultrafine Fiber Sheet> In this step, ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less are produced from the nonwoven fabric to form an ultrafine fiber sheet.

[0125] The ultrafine fiber development treatment used in the present invention does not require the use of an organic solvent. More specifically, if the readily soluble resin is polylactic acid or a copolymer polyester, the treatment can be carried out by immersing a nonwoven fabric made of ultrafine fiber development fibers in an alkaline aqueous solution to dissolve and remove the readily soluble resin from the ultrafine fiber development fibers. As the alkaline aqueous solution, a sodium hydroxide aqueous solution is preferably used because it makes it easier to treat the salt generated by neutralization during wastewater treatment.

[0126] <Step of applying polymeric elastomer> In this step, the polymeric elastomer is applied to the nonwoven fabric or the ultrafine fiber sheet to obtain an impregnated sheet. Specifically, it is more preferable to apply the polymeric elastomer by impregnating the nonwoven fabric or the ultrafine fiber sheet in a solution of the polymeric elastomer and solidifying the polymeric elastomer.

[0127] Methods for fixing the polymeric elastomer to the nonwoven fabric or ultrafine fiber sheet include a wet coagulation method in which the nonwoven fabric or ultrafine fiber sheet is impregnated with a solution of the polymeric elastomer and then immersed in a coagulation bath to fix it, and a dry coagulation method in which the nonwoven fabric or ultrafine fiber sheet is dried to fix it. Either method can be selected as appropriate depending on the type of polymeric elastomer to be applied.

[0128] Preferred solvents used when providing polyurethane as the polymeric elastomer include N,N'-dimethylformamide, dimethyl sulfoxide, and the like, as well as a polyurethane liquid having hydrophilic groups in which polyurethane is dispersed as an emulsion in water, etc. Among these, from the viewpoint of environmental consideration, a polyurethane liquid having hydrophilic groups is preferably used.

[0129] Although the case where a polymeric elastomer is applied to the ultrafine fiber sheet after the step of forming the ultrafine fiber sheet by expressing the ultrafine fibers has been described above, a polymeric elastomer may also be applied to the nonwoven fabric after the step of forming the nonwoven fabric and before expressing the ultrafine fibers. In this case, ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less are expressed from the obtained impregnated sheet to form an ultrafine fiber sheet, and the details of this process are the same as those described in the step of forming the ultrafine fiber sheet.

[0130] <Step of developing nap layer> In this step, at least one surface of the impregnated sheet is ground to develop a nap layer. In this grinding, the method for forming nap is not particularly limited, and various methods commonly used in this field, such as buffing with sandpaper, can be used. Of course, it goes without saying that the grinding can be applied to only one surface or both surfaces of the impregnated sheet.

[0131] In the method for producing an artificial leather of the present invention, it is preferable that the nap length of the napped layer be 200 μm or more and 500 μm or less in this step.

[0132] When buffing with sandpaper is used, the grit size of the sandpaper is preferably in the range of 120 (P120) or more and 600 (P600) or less as specified in JIS R6010:2000 "Grain size of abrasives for coated abrasives." By setting the paper grit size to preferably 600 or less, more preferably 400 or less, the nap length can be set within the above range. Furthermore, by setting the paper grit size to preferably 120 or more, more preferably 150 or more, a more uniform nap length can be achieved.

[0133] Furthermore, in this process, a lubricant such as a silicone emulsion can be applied to the surface of the artificial leather before grinding. Also, by applying an antistatic agent before grinding, grinding dust generated from the artificial leather during grinding is less likely to accumulate on the sandpaper.

[0134] By going through the steps described above, the number of cross sections of ultrafine fibers oriented in the thickness direction in the cross section at half the thickness of the base layer is 1000 pieces / mm ２ More than 5000 pieces / mm ２ The resulting artificial leather has a void ratio of 5% to 65% in cross section.

[0135] <Other Finishing Steps> However, in the method for producing the artificial leather of the present invention, it is preferable to further carry out various finishing steps, as in the case of general artificial leathers. Of course, in the present invention, the artificial leather obtained by carrying out these finishing steps is also considered to be the artificial leather of the present invention.

[0136] It is also preferable to include a dyeing step for dyeing the artificial leather. This dyeing process can be performed using various methods commonly used in the art, such as jet dyeing using a jigger dyeing machine or jet dyeing machine, dip dyeing such as thermosol dyeing using a continuous dyeing machine, or printing on the surface (raised surface) of the fabric using roller printing, screen printing, inkjet printing, sublimation printing, vacuum sublimation printing, etc. Among these, jet dyeing machines are preferred because they can soften artificial leathers without a raised nap layer or artificial leathers with a raised nap layer by applying a kneading effect simultaneously with dyeing. The dyeing step can be performed before or after the step of developing the raised nap layer. If necessary, various resin finishing processes can be performed after dyeing.

[0137] In addition, finishing treatment using a softener such as silicone, an antistatic agent, a water repellent, a flame retardant, a lightfastness agent, an antibacterial agent, etc. can be carried out in the same bath as dyeing or after dyeing.

[0138] In the present invention, regardless of whether it is before or after the dyeing step, from the viewpoint of production efficiency, it is also a preferred embodiment to cut the film in half in the thickness direction.

[0139] <Vehicle interior materials, automobile parts, seats> The artificial leather of the present invention has high tensile strength and excellent shape stability, and is therefore suitable for a wide range of uses, including clothing, miscellaneous goods, shoe bags, vehicle interior materials, seats, CD curtains, DVD curtains, substrates for polishing pads, various polishing cloths, and industrial materials such as wiping cloths.

[0140] Among these, vehicle interior materials made using artificial leather are preferred because they can utilize the properties of achieving a fine and elegant surface quality, a good touch, and high levels of tensile strength while reducing the environmental impact. Such vehicle interior materials are preferably used for automobile parts such as steering wheels, horn switches, shift knobs, dashboards, instrument panels, glove boxes, floor carpets, floor mats, ceiling linings, sun visors, and assist grips, and it is more preferable that at least a portion of these automobile parts is made of artificial leather. In the present invention, the term "vehicle" includes automobiles, aircraft, railway vehicles, and ships, as well as carriages, carriages, rickshaws, and other vehicles, as well as some industrial, construction, and agricultural machinery capable of carrying humans or animals, such as excavators, cranes, tractors, and combine harvesters.

[0141] Alternatively, seats made of artificial leather are also preferred, as they can utilize the properties of fine and elegant surface quality, a pleasant touch, and high levels of tensile strength, while particularly reducing the environmental impact. It is more preferable that at least a portion of the covering material of the headrest, seat, armrest, footrest, etc., for example, the portion that comes into direct contact with the seated person, is made of artificial leather. Of course, the seat of the present invention can be used not only for vehicles such as automobiles, airplanes, railway vehicles, and ships, but also for homes, offices, and stores. The term "seat" as used in the present invention also includes chairs, benches, sofas, couches, stools, and floor chairs.

[0142] Next, the artificial leather of the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

[0143] [Measurement Methods] The evaluation methods and measurement conditions used in the examples are explained below, except that, in the measurement of each physical property, unless otherwise specified, the measurement was carried out based on the above-mentioned method.

[0144] (1) Average Single Fiber Diameter of Ultrafine Fibers: In measuring the average single fiber diameter (μm) of ultrafine fibers, ultrafine fibers were observed using a scanning electron microscope (SEM) "VHX-D500" manufactured by Keyence Corporation, and the average single fiber diameter was calculated.

[0145] (2) Molecular orientation degree in ultrafine fibers: The molecular orientation degree (unitless) in ultrafine fibers was measured using a laser Raman spectrometer "Ramanor T64000" manufactured by Jobin Yvon under the following conditions: Measurement mode: Microscopic Raman Objective lens: ×100 Beam diameter: 1 μm Light source: Ar+ laser / 514.5 nm Laser power: 50 mW Diffraction grating: Spectrograph 1800 gr / mm Slit: 100 μm Detector: CCD (manufactured by Jobin Yvon) 1024 × 256

[0146] (3) Crystalline Orientation of Ultrafine Fibers: The crystalline orientation of ultrafine fibers (unitless) was measured using an X-ray generator "SmartLab" manufactured by Rigaku Corporation under the following conditions: X-ray generator: SmartLab (sealed tube type) X-ray source: CuKα ray (using Ni filter) Output: 40 kV 50 mA Detector: D / teX one-dimensional detector Receiving Soller slit: 2.5° Scanning method: β continuous scan Entrance slit: 0.5 mmh × 0.55 mmw Receiving slit: 5 mm-5 mm Measurement range (β): 90° to 270° Measurement step (β): 0.5° Scanning speed: 15° / min Diffraction peaks: (010) plane 2θ = approximately 17°, (100) plane 2θ = approximately 25°.

[0147] (4) Crystallite Size of Ultrafine Fibers: The crystallite size (nm) of ultrafine fibers was measured using an X-ray generator "SmartLab" manufactured by Rigaku Corporation under the following conditions: X-ray generator: SmartLab (sealed tube type) X-ray source: CuKα ray (using Ni filter) Output: 40 kV 50 mA Detector: D / teX one-dimensional detector Receiving solar slit: 2.5° Scanning method: 2θ-θ continuous scanning Entrance slit: 0.5 mmh × 0.55 mmw Receiving slit: 15 mm-20 mm Measurement range (2θ): 5° to 60° Measurement step (2θ): 0.02° Scanning speed: 1.5° / min Measurement direction: equator line.

[0148] (5) Number of cross sections of ultrafine fibers oriented in the thickness direction, porosity in the cross section, diameter A of the cross section of the ultrafine fibers in the longitudinal section of the artificial leather, diameter B in the cross section of the fiber bundle, ratio B / A: number of cross sections of ultrafine fibers oriented in the thickness direction (pieces / mm ２ ), the porosity (%) in the cross section, the diameter A (μm) of the cross section of the ultrafine fiber in the longitudinal section of the artificial leather, the diameter B (μm) of the cross section of the fiber bundle, and the ratio B / A (unitless) were measured according to the above-mentioned methods using a microtome "RX-860" manufactured by Yamato Koki Kogyo Co., Ltd. as the microtome, a "JEC-3000FC" manufactured by JEOL Ltd. as the sputter, and a "VHX-D500" manufactured by Keyence Corporation as the scanning electron microscope (SEM).

[0149] (6) Content of Polyurethane Having Hydrophilic Group in Artificial Leather: The content (mass %) of polyurethane having hydrophilic groups was measured by the method described above.

[0150] (7) Pile Length in Napped Layer: The pile length (μm) in the napped layer was measured by the method described above.

[0151] (8) Tensile strength of artificial leather: Four test pieces, each 20 mm wide and 200 mm long, were cut from the artificial leather so that the angle between them was 45°. The test pieces were tested in accordance with JIS L1913:2010 "General Nonwoven Fabric Testing Methods" 6.3 "Tensile Strength and Elongation (ISO Method)" 6.3.1 "Standard Time" using an Instron tensile tester (Instron single-column tabletop tester "3343") at a grip distance of 100 mm and a pulling speed of 200 mm / min. The strength at break was taken as the tensile strength (N / cm). The test piece with the highest strength was determined as the vertical direction, and the test piece at a 90° angle to it was determined as the horizontal direction. A test piece with a tensile strength of 50 N / cm or more in both the vertical and horizontal directions was considered to have a good tensile strength.

[0152] (9) Touch of artificial leather: Twenty healthy adults were used as evaluators to judge the following evaluations by touch, and the most common evaluation was taken as the touch of the artificial leather. In the case of a tie, the higher evaluation was taken as the color development of the artificial leather. In the present invention, a satisfactory level was rated as "A or B." A: No unevenness felt when touched, very smooth touch. B: Slight unevenness felt when touched, smooth touch. C: Unevenness felt when touched, rough touch. D: Significant unevenness felt when touched, very rough touch.

[0153] (10) Surface quality of artificial leather: Twenty healthy adults were used as evaluators to visually judge the following evaluations, and the most common evaluation was taken as the surface quality of the artificial leather. In the event of a tie, the higher evaluation was taken as the surface quality of the artificial leather. In the present invention, a good level was defined as "A or B." A: The surface nap had no gaps, was dense, and had very good surface quality. B: The surface nap had a few gaps, but had a dense feel and had good surface quality. C: The surface nap had gaps, was not dense, and had poor surface quality. D: The surface nap had large gaps, was not dense, and had very poor surface quality.

[0154] [Copolymer Polyesters] The copolymer polyesters used in the examples and comparative examples are as follows. Copolymer PET-A: A copolymer polyester obtained by copolymerizing 6 mol % of 5-sodium sulfoisophthalate and 9 mass % of polyethylene glycol having a number average molecular weight of 2000. Copolymer PET-B: A copolymer polyester obtained by copolymerizing 8 mol % of 5-sodium sulfoisophthalate and 9 mass % of polyethylene glycol having a number average molecular weight of 1000. Copolymer PET-C: A copolymer polyester obtained by copolymerizing 8 mol % of 5-sodium sulfoisophthalate (polyethylene glycol was not copolymerized).

[0155] Example 1 (Step of Obtaining Crimped Conjugate Fiber) Using polyethylene terephthalate (abbreviated as "PET" in Table 1) having an intrinsic viscosity of 0.73 as the poorly soluble resin (island component), and a copolymer polyester "copolymerized PET-A" as the readily soluble resin (sea component), melt spinning was performed using an islands-in-sea type conjugate spinneret with 16 islands per hole under the following conditions: spinning temperature: 285°C, poorly soluble resin / ready soluble resin mass ratio: 90 / 10, throughput rate: 1.4 g / min per hole, and spinning speed: 1,100 m / min. The resulting fiber was then drawn 3.8 times in an oil bath set at 65°C to obtain a drawn ultrafine fiber-developing fiber (drawn conjugate fiber).

[0156] The drawn conjugate fiber was then heated under conditions such that the surface temperature of the drawn conjugate fiber reached 45° C. The drawn conjugate fiber after the heat treatment was crimped using a push-in crimper to obtain a crimped conjugate fiber.

[0157] (Step of forming nonwoven fabric) The crimped composite fiber was cut to a length of 51 mm to obtain raw cotton of islands-in-sea type composite fiber (crimped composite fiber) having a single fiber fineness of 4.4 dtex. Next, the raw cotton was used to form a fiber web through carding and cross-wrapping processes, and the fiber web was further formed into a fiber web having a density of 3,500 fibers / cm. ２ By needle punching with the number of punches, the fabric is entangled to a weight of 650 g / m. ２ The thickness is 2.5 mm and the apparent density is 0.26 g / cm ３ A nonwoven fabric was formed.

[0158] The nonwoven fabric thus formed was immersed in hot water at 98° C. for 2 minutes to cause shrinkage treatment.

[0159] (Step of Applying Polymeric Elastomer) An aqueous dispersion was prepared containing 11 parts by mass of a polyurethane precursor composed of polytetramethylene glycol as a polymer polyol, MDI as an organic diisocyanate, 2,2-dimethylolpropionic acid as an active hydrogen component-containing compound having a hydrophilic group, and ethylene glycol as a chain extender, 1 part by mass of a carbodiimide-based crosslinking agent, 5 parts by mass of sodium sulfate, and 83 parts by mass of water. A shrunk nonwoven fabric was impregnated with this aqueous dispersion, squeezed with a mangle, and dried with hot air at 120°C for 20 minutes to coagulate the polyurethane precursor, thereby solidifying the polyurethane, and an impregnated sheet was obtained to which polyurethane having a crosslinked structure composed of N-acylurea bonds and / or isourea bonds was applied.

[0160] (Step of generating ultrafine fibers) The impregnated sheet was immersed in a 5% aqueous sodium hydroxide solution and then heat-treated with steam at 95° C. for 10 minutes to alkaline-decompose the sea component of the islands-in-sea type composite fiber. Next, the excess sodium hydroxide and sodium sulfate were washed away with water, and the sheet was dried in a dryer at 160° C. for 10 minutes to obtain an impregnated sheet made of ultrafine fibers to which polyurethane had been applied.

[0161] (Step of forming napped layer) The impregnated sheet made of ultrafine fibers to which polyurethane was applied was cut in half perpendicular to the thickness direction, and then the surface opposite to the surface formed by cutting in half (non-cut surface) was ground using endless sandpaper with a grit size of 120 to obtain a napped sheet with a thickness of 0.70 mm.

[0162] (Other Finishing Steps) The napped sheet obtained as described above was dyed at 120°C using a jet dyeing machine and then dried in a dryer to obtain an artificial leather. The results are shown in Table 1. The obtained artificial leather had a dense and elegant surface quality, a good touch, and excellent tensile strength.

[0163] [Example 2] An artificial leather was obtained in the same manner as in Example 1, except that in the step of obtaining crimped conjugated fibers, the drawing temperature was changed from 65°C to 75°C, and heating was changed from 45°C to 70°C, resulting in a surface temperature of the drawn conjugated fibers. The results are shown in Table 1. The obtained artificial leather had a dense and elegant surface quality, a good feel, and excellent tensile strength.

[0164] [Example 3] An artificial leather was obtained in the same manner as in Example 1, except that in the step of obtaining crimped conjugated fibers, "copolymerized PET-A" was used as the sea component, but "copolymerized PET-B" was used instead. The results are shown in Table 1. The obtained artificial leather had a dense and elegant surface quality, a good touch, and excellent tensile strength.

[0165] Example 4 An artificial leather was obtained in the same manner as in Example 1, except that in the step of obtaining crimped composite fibers, the islands-in-sea composite spinneret with 16 islands / hole was changed to a sea-island composite spinneret with 9 islands / hole, and the throughput rate was changed from 1.4 g / min·hole to 1.2 g / min·hole. The results are shown in Table 1. The surface quality and touch of the obtained artificial leather were slightly inferior to those of Example 1, but it had a tensile strength superior to that of Example 1.

[0166] Example 5 An artificial leather was obtained in the same manner as in Example 1, except that in the step of obtaining crimped composite fibers, an islands-in-sea composite spinneret with 16 islands / hole was used instead of an islands-in-sea composite spinneret with 36 islands / hole, the mass ratio of sparingly soluble resin to readily soluble resin was changed from 90 / 10 to 55 / 45, and the throughput rate was changed from 1.4 g / min·hole to 1.2 g / min·hole. The results are shown in Table 1. The obtained artificial leather had a dense and elegant surface quality and a good feel, but its tensile strength was slightly inferior to that of the artificial leather of Example 1.

[0167] [Example 6] In the step of forming a nonwoven fabric, the number of punches was 3,500 / cm ２ 4000 strands / cm ２An artificial leather was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed to the following. The results are shown in Table 1. The obtained artificial leather had a dense and elegant surface quality, a good feel to the touch, and excellent tensile strength.

[0168] [Example 7] In the step of forming a nonwoven fabric, the number of punches was 3,500 / cm ２ 2500 strands / cm ２ An artificial leather was obtained in the same manner as in Example 1, except that the temperature was changed to 100°C. The results are shown in Table 1. The obtained artificial leather had excellent tensile strength, but the surface quality and touch were slightly inferior to those of the artificial leather of Example 1.

[0169] Comparative Example 1 An artificial leather was obtained in the same manner as in Example 1, except that in the step of obtaining crimped conjugated fibers, "copolymerized PET-A" was used as the sea component, but "copolymerized PET-C" was used instead. The results are shown in Table 2. The obtained artificial leather had a dense and elegant surface quality and a good touch, but was inferior in tensile strength to the artificial leather of Example 1.

[0170] Comparative Example 2 An artificial leather was obtained in the same manner as in Example 1, except that in the step of obtaining crimped composite fibers, an islands-in-sea composite spinneret with 9 islands / hole was used instead of the 16 islands / hole spinneret used, and the throughput rate was changed from 1.4 g / min·hole to 0.79 g / min·hole. The results are shown in Table 2. The obtained artificial leather had excellent tensile strength, but was inferior to the artificial leather of Example 1 in surface quality and touch.

[0171] Comparative Example 3 An attempt was made to obtain artificial leather in the same manner as in Example 1, except that in the step of obtaining crimped conjugated fibers, the drawing temperature was changed from 65°C to 90°C, and heating was changed from 45°C to 90°C. However, when an attempt was made to impart crimping to the obtained drawn conjugated fibers, the sea component eluted, preventing crimping using a push-in crimper, and the subsequent steps could not be carried out. The results are shown in Table 2.

[0172] Comparative Example 4 An attempt was made to obtain an artificial leather in the same manner as in Example 1, except that in the (step of obtaining crimped conjugate fiber), the drawn conjugate fiber was heated under conditions that would bring the surface temperature to 45°C, but heating was not performed, and the drawn conjugate fiber without being heated was directly subjected to a crimping process using a push-type crimper. However, no crimp was observed in the drawn conjugate fiber, and the raw cotton obtained by cutting it wrapped around the rollers in the carding process, making it impossible to continue with the steps subsequent to (the step of forming a conjugate fiber-entangled body). The results are shown in Table 2.

[0173] [Comparative Example 5] In the step of forming the nonwoven fabric, the number of punches was 3,500 / cm ２ 800 strands / cm ２ An artificial leather was obtained in the same manner as in Example 1, except that the above-mentioned conditions were changed. The results are shown in Table 2. The obtained artificial leather was inferior to the artificial leather of Example 1 in tensile strength, surface quality, and touch.

[0174] [Comparative Example 6] In the step of forming the nonwoven fabric, the number of punches was 3,500 / cm ２ 8200 strands / cm ２ An artificial leather was obtained in the same manner as in Example 1, except that the temperature was changed to 100°C. The results are shown in Table 2. The obtained artificial leather had a dense and elegant surface quality and a good feel, but was inferior in tensile strength to the artificial leather of Example 1.

[0175]

[0176]

[0177] 10 Artificial leather 10a Raised layer 10b Base layer 10c Raised layer 11 Arrow indicating the direction for observing a cross section 12 Arrow indicating the direction for observing a longitudinal section 21 Line surrounding the outer periphery of the fiber bundle 22 Circumscribed circle of the line surrounding the outer periphery of the fiber bundle 23 Inscribed circle of the line surrounding the outer periphery of the fiber bundle 31 Grinding amount 31a Surface position excluding the raised layer 31b Grinding end position

Claims

1. An artificial leather comprising a nonwoven fabric made of ultrafine fibers and a polymeric elastomer, and having at least one napped layer, wherein the average single fiber diameter of the ultrafine fibers is 0.1 μm or more and 10.0 μm or less, the nonwoven fabric contains fiber bundles made of the ultrafine fibers, and the number of cross sections of the ultrafine fibers oriented in the thickness direction in a cross section at half the thickness of the base layer excluding the napped layer is 1,000 / mm ２ More than 5000 pieces / mm ２ The artificial leather according to claim 1, wherein the following are present:

2. The artificial leather according to claim 1, wherein the ratio B / A of the diameter B (μm) of the cross section of the ultrafine fibers to the diameter A (μm) of the cross section of the fiber bundle in the longitudinal section of the artificial leather is 5 or more and 10 or less.

3. An artificial leather according to claim 1 or 2, wherein the polymeric elastomer is a polyurethane having a hydrophilic group, and the content of the polyurethane having a hydrophilic group in the artificial leather is 10% by mass or more and 50% by mass or less.

4. The artificial leather according to claim 3, wherein the polyurethane having a hydrophilic group contains a component derived from a polyether polyol and / or a component derived from a polycarbonate polyol.

5. The artificial leather according to claim 1 or 2, wherein the nap length of the ultrafine fibers in the napped layer is 200 μm or more and 500 μm or less.

6. The artificial leather according to claim 1 or 2, wherein the porosity is 45% or more and 60% or less.

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

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

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

10. A method for producing artificial leather, comprising the steps of: drawing ultrafine fiber-producing fibers formed from a soluble resin, which is a copolymer polyester copolymerized with a polyalkylene glycol having a number average molecular weight of 500 to 3500, and a sparingly soluble resin; heating the drawn ultrafine fiber-producing fibers under conditions such that the surface temperature of the fibers becomes 40°C to 80°C, and then crimping the fibers to obtain crimped composite fibers; forming a fiber web from the crimped composite fibers and entangling the fiber web to form a nonwoven fabric; developing ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm from the nonwoven fabric to form an ultrafine fiber sheet; applying a polymeric elastomer to the nonwoven fabric or the ultrafine fiber sheet to obtain an impregnated sheet; and grinding at least one surface of the impregnated sheet to develop a napped layer, The artificial leather has a cross section of the ultrafine fibers oriented in the thickness direction at half the thickness of the base layer excluding the napped layer of 1000 pieces / mm ２ More than 5000 pieces / mm ２ The method for producing an artificial leather according to claim 1, wherein the porosity in the cross section is 5% or more and 65% or less.

11. The method for producing an artificial leather according to claim 10, wherein in the step of developing the napped layer, the napped length of the napped layer is set to 200 μm or more and 500 μm or less.

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