JP7648011B1 - Artificial leather, its manufacturing method and its uses - Google Patents

Abstract

An artificial leather comprising a fibrous base material formed by entangling and integrating a nonwoven fabric and a woven fabric, and a polyurethane having a hydrophilic group,
The nonwoven fabric is composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less,
The woven fabric is composed of a multifilament having 30 to 300 filaments, and the average single fiber diameter of the filaments constituting the multifilament is 1 μm to 30 μm,
The content of the polyurethane in the artificial leather is 15% by mass or more and 25% by mass or less,
and the ratio of the filaments to which the polyurethane is attached among the outermost filaments of the multifilament is 10% or more and 80% or less.
Artificial leather.
The present invention provides an artificial leather made of a fibrous base material in which a nonwoven fabric and a woven fabric are entangled and integrated, and a water-dispersible polyurethane, which has high strength, excellent flexibility and abrasion resistance, a production method thereof, and uses thereof.

Description

The present invention relates to artificial leather, its manufacturing method, and its uses.

Artificial leather, which is mainly made of a fibrous base material such as nonwoven fabric and polyurethane, has excellent characteristics not found in natural leather, such as high durability and uniformity, and in particular, so-called suede-like artificial leather, in which the surface is buffed to form a nap of ultra-fine fibers, is used not only as a material for clothing, but also in a variety of fields such as vehicle interior materials, furniture interior materials, and building materials. In particular, from the perspective of environmental considerations, a method of using water-dispersed polyurethane, in which polyurethane resin is dispersed in water, instead of the method of using conventional organic solvent-based polyurethane as the polyurethane, is being widely studied.

When suede-like artificial leather is used as a covering material for vehicle interiors, etc., repeated long-term use can cause distortion in the covering material. Therefore, methods are being investigated for making artificial leather that is strong and can withstand long-term use by entangling and integrating woven fabric inside the nonwoven fabric or on one side of it.

However, artificial leather made by entangling and integrating a woven fabric inside or on one side of a nonwoven fabric generally has the problem of being stiff in texture. One of the main reasons for this is that the added polyurethane tightly grips the intertwining points of the woven fabric, reducing the flexibility of the woven fabric.

In particular, when a water-dispersed polyurethane is used as the polyurethane and the polyurethane emulsion is heated to coagulate and solidify, the polyurethane membrane structure becomes a dense, non-porous membrane, so the adhesion between the fabric and the polyurethane becomes dense and the intertwined parts of the fibers that make up the fabric are tightly gripped, resulting in a significantly harder texture.

In response to these circumstances, several methods have been proposed for applying water-dispersible polyurethane to artificial leather in which a woven fabric is entangled and integrated inside or on one side of a nonwoven fabric, thereby obtaining artificial leather that is strong and has excellent flexibility.

For example, Patent Documents 1 and 2 propose a method in which a specific amount of polyvinyl alcohol with a specific degree of saponification and polymerization is applied to a fibrous substrate, then a water-dispersible polyurethane is applied, and then the polyvinyl alcohol is removed. It is described that this method achieves an elegant appearance and soft feel, and also makes it possible to obtain a sheet-like material with good abrasion resistance.

Furthermore, Patent Document 3 describes that by setting the ratio of polyurethane resin to 100% by mass of the fiber sheet to 20% by mass or less, it is possible to achieve a soft texture even in artificial leather that contains a scrim, which is a woven or knitted fabric, and uses a water-dispersible polyurethane resin.

JP 2013-234409 A International Publication No. 2014/042241 International Publication No. 2020/054256

In the methods disclosed in Patent Documents 1 and 2, polyvinyl alcohol is applied before polyurethane is applied to coat the woven or knitted fabric, and is removed after polyurethane is applied, thereby preventing direct adhesion between the polyurethane and the woven or knitted fabric and achieving a soft texture. However, since a process for eluting the polyvinyl alcohol is required, there is room for improvement in terms of production efficiency.

In the method disclosed in Patent Document 3, the amount of polyurethane applied is small, so it is difficult to say that the method satisfies the level of abrasion resistance required by the market.

In view of the above problems, the object of the present invention is to provide an artificial leather containing a fiber entanglement consisting of a nonwoven fabric and a woven fabric as a constituent component, which is manufactured using an environmentally friendly process that does not use organic solvents, and which combines a soft feel with excellent abrasion resistance, and a manufacturing method thereof.

In order to solve the above problems, the present invention has the following configuration.
[1] An artificial leather comprising a fibrous base material formed by entangling and integrating a nonwoven fabric and a woven fabric, and a polyurethane having a hydrophilic group,
The nonwoven fabric is composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less,
The woven fabric is composed of a multifilament having 30 to 300 filaments, and the average single fiber diameter of the filaments constituting the multifilament is 1 μm to 30 μm,
The content of the polyurethane in the artificial leather is 15% by mass or more and 25% by mass or less,
and the ratio of the filaments to which the polyurethane is attached among the outermost filaments of the multifilament is 10% or more and 80% or less.
Artificial leather.

[2] The artificial leather described in [1], wherein the polyurethane is a polyether-based polyurethane and/or a polycarbonate-based polyurethane.

[3] A method for producing an artificial leather according to [1], comprising the following steps (1) to (3) in this order:
(1) A process for forming a fibrous base material by entangling a nonwoven fabric made of ultrafine fiber-developing fibers with a woven fabric. (2) A process for impregnating the fibrous base material with an aqueous dispersion of polyurethane having hydrophilic groups, and then coagulating the polyurethane to obtain a sheet. The width of the fibrous base material before impregnation is defined as L, and the sheet is then obtained by shrinking the width of the sheet to be 0.85L or more and 0.95L or less. (3) A process for developing polyester ultrafine fibers from the ultrafine fiber-developing fibers of the shrink sheet.

[4] A method for producing an artificial leather as described in [3], in which the entanglement and integration means in step (1) is needle punch processing.

[5] A method for producing artificial leather as described in [3] or [4], in which the means for obtaining the shrink sheet in step (2) is a dry heat treatment at an atmospheric temperature of 100°C or higher and 180°C or lower.

[6] A method for producing an artificial leather according to any one of [3] to [5], wherein the means for producing polyester ultrafine fibers in step (3) is an alkali treatment.

[7] Automotive interior material comprising the artificial leather described in [1] or [2].

[8] An automobile part comprising the artificial leather described in [1] or [2].

[9] A seat comprising the artificial leather described in [1] or [2].

According to the present invention, an artificial leather having high strength, excellent flexibility and abrasion resistance can be obtained by a simple process using a fibrous base material in which a nonwoven fabric and a woven fabric are entangled and integrated, and water-dispersible polyurethane.

This is a schematic cross-sectional view of a scanning electron microscope (SEM) photograph of an artificial leather cross section taken to measure and calculate the proportion of filaments to which polyurethane is attached among the outermost filaments of a multifilament.

The artificial leather of the present invention is an artificial leather comprising a fibrous base material formed by entangling and integrating a nonwoven fabric and a woven fabric, and a polyurethane having a hydrophilic group,
The nonwoven fabric is composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less,
The woven fabric is composed of a multifilament having 30 to 300 filaments, and the average single fiber diameter of the filaments constituting the multifilament is 1 μm to 30 μm,
The content of the polyurethane in the artificial leather is 15% by mass or more and 25% by mass or less,
Furthermore, the ratio of filaments to which the polyurethane is attached to the outermost filaments of the multifilament is 10% or more and 80% or less.

These components are described in detail below, but the present invention is not limited to the scope described below as long as it does not exceed the gist of the invention, and various modifications are possible without departing from the gist of the invention.

[Polyester ultrafine fiber]
The artificial leather of the present invention is made of a fibrous base material, which is one of the components, composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm to 10.0 μm. Note that "polyester ultrafine fibers" refers to "ultrafine fibers made of polyester resin" described below, and ultrafine fibers refer to "fibers having a single fiber diameter of 0.1 μm to 10.0 μm" measured and calculated by the method described below.

In this invention, "polyester resin" refers to a resin in which the molar fraction of the polyester units in the repeating units is 80 mol% to 100 mol%. Unless otherwise specified, the term "polyester resin" has the same meaning. This polyester resin can be used to make artificial leather with excellent heat resistance and light resistance, and specific examples include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and mixtures and copolymers of these polyesters. Polyester resins can be obtained, for example, from dicarboxylic acids and/or their ester-forming derivatives and diols.

Examples of dicarboxylic acids and/or ester-forming derivatives thereof used in the polyester resin 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, and acyl chlorides of dicarboxylic acids. Specifically, methyl esters, ethyl esters, hydroxyethyl esters, and the like are preferably used. A more preferred embodiment of the dicarboxylic acid and/or ester-forming derivatives thereof used in the present invention is terephthalic acid and/or dimethyl esters thereof.

Diols used in the polyester resins include ethylene glycol, 1,3-propanediol, 1,4-butanediol, cyclohexanedimethanol, etc. Among these, ethylene glycol is preferably used.

The polyester resin may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, UV absorbers, conductive agents, heat storage agents, antibacterial agents, etc., depending on various purposes.

The cross-sectional shape of the polyester microfibers can be either round or irregular. Specific examples of irregular cross-sections include ovals, flats, polygons such as triangles, sectors, and crosses.

In the present invention, the average single fiber diameter of the polyester ultrafine fibers is 0.1 μm or more and 10.0 μm or less. By making the average single fiber diameter of the polyester ultrafine fibers 10.0 μm or less, preferably 7.0 μm or less, and more preferably 5.0 μm or less, the artificial leather can be made more flexible. In addition, the quality of the nap can be improved. On the other hand, by making the average single fiber diameter of the polyester ultrafine fibers 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.7 μm or more, the artificial leather can be made to have excellent color development after dyeing when dyeing. In addition, when performing a nap raising process by buffing, the ease of dispersion and ease of handling of the polyester ultrafine fibers present in a bundle can be improved.

The single fiber diameter and average single fiber diameter of the polyester ultrafine fiber in the present invention are measured and calculated by the following method.
(1) The cross section of the obtained artificial leather cut in the thickness direction is observed under a scanning electron microscope (SEM, Keyence Corporation's "VHX-D500/D510" or a scanning electron microscope having equivalent performance).
(2) The fiber diameters of 50 polyester ultrafine fibers randomly selected within the observation area are measured in three directions on the cross section of each polyester ultrafine fiber. However, when polyester ultrafine fibers with an irregular cross section are used, the cross-sectional area of a single fiber is first measured, and the diameter of a circle having the cross-sectional area is calculated by the following formula. The diameter thus obtained is regarded as the single fiber diameter of the single fiber.

Single fiber diameter (μm)=(4×(cross-sectional area of single fiber (μm ² ))/π) ^1/2
(3) The arithmetic mean value (μm) of the total 150 points obtained is calculated and rounded off to one decimal place to obtain the average single fiber diameter (μm) of the polyester ultrafine fiber.

[fabric]
It is important that the woven fabric used in the artificial leather of the present invention is composed of multifilaments. As the component constituting the multifilaments, polyester-based resins or polyamide-based resins can be used, but it is preferable to use polyester-based resins, which are excellent in durability and heat resistance.

It is important that the average single fiber diameter of the filaments constituting the multifilament is 1 μm or more and 30 μm or less. By making the average single fiber diameter 30.0 μm or less, more preferably 15.0 μm or less, and even more preferably 13.0 μm or less, the artificial leather has excellent flexibility. On the other hand, by making the average single fiber diameter 1.0 μm or more, more preferably 8.0 μm or more, and even more preferably 9.0 μm or more, the shape stability of the product as artificial leather is improved.

In the present invention, the average single fiber diameter of the filaments constituting the multifilament is calculated by taking a scanning electron microscope (SEM) photograph of the cross section of the artificial leather, randomly selecting 10 filaments from the multifilament constituting the woven fabric, measuring the single fiber diameters of the filaments, calculating the arithmetic average of the 10 filaments, and rounding off to the first decimal place. However, when a filament with a modified cross section is used, the cross-sectional area ( ^μm2 ) of the filament is first measured, and the diameter when the cross section is regarded as a circle, i.e., the circle equivalent diameter, is calculated to obtain the filament diameter (μm).

It is important that the number of single fibers contained in the multifilament constituting the woven fabric, i.e., the number of filaments, is 30 or more and 300 or less. By making the number of filaments 30 or more, more preferably 50 or more, not only does the shape stability of the product as artificial leather improve, but also the fibers constituting the woven fabric are less likely to be exposed on the surface of the artificial leather when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, which is preferable. On the other hand, by making the number of filaments 300 or less, more preferably 250 or less, and even more preferably 100 or less, the artificial leather has excellent flexibility. In this case, the number of filaments in the warp thread and the number of filaments in the weft thread may be the same or different.

Furthermore, it is preferable that the twist number of the multifilament is 1,000 to 4,000 T/m. By setting the twist number to 4,000 T/m or less, more preferably 3,500 T/m or less, and even more preferably 3,000 T/m or less, an artificial leather with excellent flexibility can be obtained, while by setting the twist number to 1,000 T/m or more, more preferably 1,500 T/m or more, and even more preferably 2,000 T/m or more, damage to the fibers constituting the woven fabric can be prevented when the nonwoven fabric and the woven fabric are entangled and integrated by needle punching or the like, and the mechanical strength of the artificial leather is excellent, which is preferable.

The basic weave of the fabric may be twill or satin, but a flat weave is preferable as it is less prone to uneven weave.

It is preferable to adjust the weave density of the woven fabric so that both the warp and weft threads in the artificial leather are 40 threads/2.54 cm to 200 threads/2.54 cm. By setting the weave density of the woven fabric constituting the artificial leather to 40 threads/2.54 cm or more, more preferably 60 threads/2.54 cm or less, an artificial leather with excellent shape stability can be obtained. On the other hand, by setting the weave density of the woven fabric constituting the artificial leather to 200 threads/2.54 cm or less, more preferably 150 threads/2.54 cm or less, not only can the texture of the artificial leather be made soft, but the entanglement of the fibers of the nonwoven fabric is not hindered when the nonwoven fabric and the woven fabric are entangled and integrated, and as a result, fiber shedding of the artificial leather can be suppressed.

[Fiber base material]
The fibrous base material used in the present invention is formed by entangling and integrating the nonwoven fabric made of the above-mentioned polyester ultrafine fibers and the above-mentioned woven fabric.

[Polyurethane having hydrophilic groups]
Next, the artificial leather of the present invention contains polyurethane having a hydrophilic group as a constituent element. The details of this will be described in further detail below.

(1) Polyurethane Having a Hydrophilic Group First, in the present invention, "having a hydrophilic group" refers to "having a group having active hydrogen". Specific examples of the group having active hydrogen include a hydroxyl group, a carboxyl group, a sulfonic acid group, an amino group, etc., and from the viewpoint of reactivity with a crosslinking agent having a carbodiimide group described later, it is preferable that the polyurethane has a hydroxyl group or a carboxyl group.

This polyurethane with hydrophilic groups can be obtained by reacting a polymer polyol (described below), an organic diisocyanate, and an active hydrogen component-containing compound with hydrophilic groups to form a hydrophilic prepolymer, and then adding and reacting a chain extender to obtain a polyurethane precursor, which is then reacted with a crosslinking agent. These are explained in detail below.

(1-1) Polymer Polyol Examples of the polymer polyol preferably used in the synthesis of the polyurethane include polyether polyols, polyester polyols, and polycarbonate polyols.

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 that combine these.

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.

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.

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

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.

As the polyol used in the polycarbonate polyol, a low molecular weight polyol used in the polyester polyol can be used. On the other hand, as the dialkyl carbonate, dimethyl carbonate, diethyl carbonate, etc. can be used, and as the diaryl carbonate, diphenyl carbonate, etc. can be used.

The number average molecular weight of the polymer polyol preferably used in the present invention is preferably 500 or more and 5,000 or less. By making the number average molecular weight of the polymer polyol 500 or more, more preferably 1,500 or more, it is possible to easily prevent the texture of the artificial leather from becoming hard. In addition, by making the number average molecular weight 5,000 or less, more preferably 4,000 or less, it is possible to easily maintain the strength of the polyurethane having hydrophilic groups as a binder.

(1-2) Organic Diisocyanate Examples of organic diisocyanates preferably used in the synthesis of the polyurethane include aromatic diisocyanates having a carbon number of 6 to 20 (excluding carbons in NCO groups, the same applies below), aliphatic diisocyanates having a carbon number of 2 to 18, alicyclic diisocyanates having a carbon number of 4 to 15, araliphatic diisocyanates having a carbon number of 8 to 15, modified products of these diisocyanates (carbodiimide modified products, urethane modified products, urethodione modified products, etc.), and mixtures of two or more of these.

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.

Specific examples of the 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.

Specific examples of the alicyclic diisocyanates having 4 to 15 carbon atoms include isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexylene-1,2-dicarboxylate, 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 hydrophilic groups.

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

(1-3) Active hydrogen component-containing compound having hydrophilic group The active hydrogen component-containing compound having a hydrophilic group that is preferably used in the synthesis of the polyurethane 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. By using this active hydrogen component-containing compound having a hydrophilic group, the stability of the aqueous dispersion used in the manufacturing method of artificial leather can be improved.

Examples of compounds having a nonionic group and active hydrogen include compounds that contain two or more active hydrogen components or two or more isocyanate groups and have a polyoxyethylene glycol group with a molecular weight of 250 to 9,000 on the side chain, and triols such as trimethylolpropane and trimethylolbutane.

Examples of compounds 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 their derivatives; sulfonic acid group-containing compounds such as 1,3-phenylenediamine-4,6-disulfonic acid and 3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid, and their derivatives; and salts of these compounds neutralized with a neutralizing agent.

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 their derivatives.

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

Among 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.

(1-5) Constitution of Polyurethane Precursor As described above, the polyurethane precursor preferably used for synthesizing the polyurethane is prepared by reacting the polymer polyol, the organic diisocyanate, and the active hydrogen component-containing compound having a hydrophilic group to form a hydrophilic prepolymer, and then adding and reacting a chain extender.

(1-6) Crosslinking Agent As the crosslinking agent preferably used in the synthesis of the polyurethane, one having two or more reactive groups in the molecule that can react with the reactive group introduced into the polyurethane precursor can be used, and specific examples thereof include polyisocyanate-based crosslinking agents such as water-soluble isocyanate compounds and blocked isocyanate compounds, melamine-based crosslinking agents, carbodiimide-based crosslinking agents, etc. The crosslinking agents can be used alone or in combination of two or more types.

Water-soluble isocyanate compounds have two or more isocyanate groups in the molecule, and examples of such compounds include the organic polyisocyanate-containing compounds mentioned above. Commercially available products include the Bayhydur (registered trademark) series and Desmodur (registered trademark) series manufactured by Bayer MaterialScience Co., Ltd.

Blocked isocyanate compounds have two or more blocked isocyanate groups in the molecule. Blocked isocyanate groups refer to the organic polyisocyanate compounds blocked with blocking agents such as amines, phenols, imines, mercaptans, pyrazoles, oximes, and active methylenes. Commercially available products include the "Elastron" (registered trademark) series from Daiichi Kogyo Seiyaku Co., Ltd., the "Duranate" (registered trademark) series from Asahi Kasei Corporation, and the "Takenate" (registered trademark) series from Mitsui Chemicals, Inc.

Oxazoline crosslinking agents include compounds that have two or more oxazoline groups (oxazoline skeletons) in the molecule. Commercially available products include the "Epocross" (registered trademark) series manufactured by Nippon Shokubai Co., Ltd.

Carbodiimide crosslinking agents include compounds that have two or more carbodiimide groups in the molecule. Commercially available products include the "Carbodilite" (registered trademark) series manufactured by Nisshinbo Chemical Inc.

Among these, it is particularly preferable to use carbodiimide compounds, which give polyurethanes having hydrophilic groups after the reaction that are particularly excellent in terms of durability and flexibility.

(1-7) Constitution of Polyurethane Having Hydrophilic Group The polyurethane having a hydrophilic group is preferably a polyether-based polyurethane containing a component derived from a polyether-based polyol and/or a polycarbonate-based polyurethane containing a component derived from a polycarbonate-based polyol.

From the viewpoint of flexibility, it is preferable to include a component derived from a polyether-based polyol. When a polyurethane having a hydrophilic group includes a component derived from a polyether-based polyol, the degree of freedom of the ether bond is high, so that the glass transition temperature is low and the cohesive force is weak, so that a water-dispersible polyurethane having excellent flexibility can be obtained.

On the other hand, from the viewpoint of durability, it is preferable to include a component derived from a polycarbonate-based polyol. When a polyurethane having a hydrophilic group includes a component derived from a polycarbonate-based polyol, the high cohesive force of the carbonate group can result in a polyurethane having a hydrophilic group that is excellent in water resistance, heat resistance, weather resistance, and mechanical properties.

The composition of the polyurethane having hydrophilic groups can be adjusted appropriately depending on the required properties, and polyether-based polyurethanes containing components derived from polyether-based polyols and polycarbonate-based polyurethanes containing components derived from polycarbonate-based polyols may be used alone or both may be used.

In addition, the components of the polyurethane having hydrophilic groups can be confirmed (that the polyurethane having hydrophilic groups contains a component derived from polyester polyol, and that the polyurethane having hydrophilic groups further contains a component derived from polycarbonate polyol) by dissolving the polyester that constitutes the artificial leather and analyzing the insoluble matter (polyurethane having hydrophilic groups) by infrared spectroscopy (analytical equipment: JASCO Corporation's "FT/IR 4000 series" or an infrared spectroscopy analyzer with equivalent performance) or pyrolysis GC/MS analysis (analytical equipment: Shimadzu Corporation's "GCMS-QP5050A" or a pyrolysis GC/MS analyzer with equivalent performance). In addition, m-cresol and hexafluoroisopropanol can be used as solvents that can dissolve the polyester that constitutes the artificial leather, but it is preferable to use hexafluoroisopropanol, which can be handled at room temperature.

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

The presence of the above-mentioned N-acylurea groups and isourea groups in polyurethane having hydrophilic groups can be analyzed by performing, for example, a mapping process such as time-of-flight secondary ion mass spectrometry (TOF-SIMS analysis) on a cross-section of the artificial leather (analytical equipment such as the ION-TOF "TOF.SIMS 5" or a TOF-SIMS analyzer having equivalent performance) or infrared spectroscopy (analytical equipment such as the JASCO "FT/IR 4000 series" or an infrared spectroscopy analyzer having equivalent performance).

[Artificial leather]
First, the artificial leather of the present invention has a content ratio of polyurethane having a hydrophilic group of 15% by mass or more and 25% by mass or less. By making the content ratio 15% by mass or more, preferably 18% by mass or more, the artificial leather has excellent abrasion resistance. On the other hand, by making the content ratio 25% by mass or less, preferably 22% by mass or less, the artificial leather has a soft feel.

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

Content of polyurethane having hydrophilic group=(M _A /M _X )×100.

In the present invention, it is important that polyurethane is attached to 10% to 80% of the outermost filaments of the multifilament constituting the woven fabric.

By having polyurethane attached to 10% or more of the outermost filaments of the multifilament, more preferably 15% or more, and even more preferably 20% or more, the artificial leather has excellent shape stability.

On the other hand, by having polyurethane attached to 80% or less, more preferably 60% or less, and even more preferably 50% or less of the outermost filaments of the multifilament, an artificial leather with excellent flexibility is obtained.

In the present invention, the ratio of the filaments to which polyurethane is attached among the outermost filaments of the multifilament is measured and calculated by the following method.
(1) A scanning electron microscope (SEM) photograph of the cross section of the artificial leather is taken, and the number (N _M ) of the outermost filaments of the multifilament constituting the woven fabric is calculated. Then, the number (N _p ) of the outermost filaments of the multifilament to which polyurethane is attached is calculated, and the proportion of the filaments to which polyurethane is attached is calculated using the following formula.

Percentage of filaments to which polyurethane is attached (%)=(N _p /N _M )×100
(2) The measurement in (1) is carried out on 20 multifilaments, and the average value is the percentage of filaments to which polyurethane is attached.

The apparent density of the artificial leather of the present invention is preferably 0.30 g/ ^cm3 or more and 0.40 g/ ^cm3 or less. By making the apparent density of the artificial leather 0.30 g/ ^cm3 or more, more preferably 0.32 g/ ^cm3 or more, and even more preferably 0.34 g/ ^cm3 or more, the abrasion resistance of the artificial leather becomes excellent. On the other hand, by making the apparent density 0.40 g/cm3 or ^less , preferably 0.38 g/ ^cm3 or less, the artificial leather can have a soft feel.

In the present invention, the apparent density of the artificial leather is determined by measuring the thickness and mass per unit area of the artificial leather using the methods specified in JIS L 1913:2010 "General nonwoven fabric testing methods" 6.1.1 (thickness, method A) and 6.2 (mass per unit area), and calculating using the following formula.

Apparent density of artificial leather (g/cm ³ )=mass per unit area of artificial leather (g/cm ² )/thickness of artificial leather (cm).

The artificial leather of the present invention has a bending resistance of 150 mm or less in the longitudinal direction of the sheet as defined by Method A (45° cantilever method) described in "8.21 Bending resistance" of JIS L 1096:2010 "Fabric testing methods for woven and knitted fabrics." By setting the bending resistance in this range, an artificial leather with excellent flexibility can be obtained. By setting the bending resistance to 150 mm or less, more preferably 100 mm or less, an artificial leather with greater flexibility can be obtained.

The artificial leather of the present invention preferably has an abrasion loss of 30 mg or less when measured after 50,000 abrasion cycles in the Martindale abrasion test specified in "8.19.5 E method (Martindale method)" of "8.19 Abrasion resistance and discoloration due to friction" of JIS L 1096:2005 "Testing methods for woven and knitted fabrics". It is more preferable that the abrasion loss is 25 mg or less from the viewpoint of suppressing deterioration of the appearance of the artificial leather.

Furthermore, the artificial leather of the present invention preferably has a wear loss of 10 mg or less when measured after 10,000 wear cycles in a Martindale abrasion test specified in "8.19.5 E method (Martindale method)" of "8.19 Abrasion resistance and friction discoloration" of "Testing methods for woven and knitted fabrics" of JIS L 1096:2005, after xenon irradiation specified in "7.2 Exposure method a) First exposure method" of "Testing methods for color fastness to xenon arc lamp light". By having a wear loss of 10 mg or less after xenon irradiation, the artificial leather has durability that allows it to be used for a long period of time in areas exposed to sunlight, such as automobile seats.

[Manufacturing method of artificial leather]
The method for producing an artificial leather of the present invention is a method for producing an artificial leather comprising the following steps (1) to (3) in this order.
(1) A process for forming a fibrous base material by entangling a nonwoven fabric made of ultrafine fiber-expressing fibers with a woven fabric. (2) A process for impregnating the fibrous base material with an aqueous dispersion of polyurethane having hydrophilic groups, and then coagulating the polyurethane to obtain a sheet, the sheet having a width of 0.85L or more and 0.95L or less, where L is the width. (3) A process for expressing polyester ultrafine fibers from the ultrafine fiber-expressing fibers of the shrunken sheet.

Details are explained below.

<Step of forming fibrous base material>
In this process, a nonwoven fabric made of ultrafine fiber development type fibers and a woven fabric are subjected to an entanglement treatment to form a fibrous base material.

As for ultrafine fiber-producing fibers, it is preferable to use sea-island composite fibers in which the sea component and island component are made of two thermoplastic resin components with different solvent solubility (two or three components if the island fiber is a core-sheath composite fiber), and the sea component is dissolved and removed using a solvent or the like to turn the island components into ultrafine fibers, because the removal of the sea component can provide appropriate gaps between the island components, i.e., between the ultrafine fibers inside the fiber bundle, from the perspective of the texture and surface quality of the artificial leather.

For islands-in-sea composite fibers, a method using a polymer mutual alignment body in which two components, a sea component and an island component (three components if the island fiber is a core-sheath composite fiber), are mutually aligned and spun using an islands-in-sea composite spinneret is preferred from the viewpoint of obtaining ultrafine fibers with a uniform single fiber diameter.

As the sea component of islands-in-the-sea composite fibers, polyethylene, polypropylene, polystyrene, copolymer polyesters copolymerized with sodium sulfoisophthalic acid or polyethylene glycol, and polylactic acid can be used, but polystyrene and copolymer polyesters are preferred from the standpoint of spinnability and ease of leaching.

The mass ratio of the sea component to the island component in the islands-in-sea type composite fiber preferably used in the present invention is preferably in the range of sea component:island component=10:90 to 80:20. When the mass ratio of the sea component is 10% by mass or more, the island component is easily and sufficiently ultra-fine. When the mass ratio of the sea component is 80% by mass or less, the proportion of eluted components is small, thereby improving productivity. The mass ratio of the sea component to the island component is more preferably in the range of sea component:island component=20:80 to 70:30.

As mentioned above, either short fiber nonwoven fabric or long fiber nonwoven fabric can be used as the nonwoven fabric constituting the fibrous base material. However, short fiber nonwoven fabric is preferred because it has more fibers oriented in the thickness direction of the artificial leather than long fiber nonwoven fabric, and this allows the artificial leather to have a highly dense surface when brushed.

When a staple fiber nonwoven fabric is used as the fibrous substrate, the resulting ultrafine fiber-developing fiber is preferably subjected to a crimping process and then cut to a predetermined length to obtain raw cotton. The crimping and cutting processes can be carried out by known methods.

Next, the obtained raw cotton is made into a fiber web using a cross wrapper or the like. The obtained fiber web is then entangled to obtain a nonwoven fabric. Methods for entangling the fiber web to obtain a nonwoven fabric include needle punching and water jet punching, but needle punching, which has high entanglement efficiency, is preferred.

The nonwoven fabric and woven fabric obtained are then laminated and entangled. The nonwoven fabric and woven fabric can be entangled by laminating the woven fabric on one or both sides of the nonwoven fabric, or by sandwiching the woven fabric between multiple nonwoven fabric webs and then entangling the fibers of the nonwoven fabric and woven fabric by needle punching, water jet punching, or the like. From the viewpoint of production efficiency, however, it is preferable to laminate the woven fabric on both sides of the nonwoven fabric and then perform needle punching.

The apparent density of the nonwoven fabric made of the composite fiber (ultrafine fiber development type fiber) after the entanglement treatment and the fibrous substrate made of the woven fabric is preferably 0.20 g/cm ³ or more and 0.30 g/cm ³ or less. By making the apparent density 0.20 g/cm ³ or more, more preferably 0.23 g/cm ³ or more, the fibrous substrate can obtain sufficient shape stability and dimensional stability. On the other hand, by making the apparent density 0.30 g/cm ³ or less, more preferably 0.28 g/cm ³ or less, it is possible to maintain sufficient space for providing polyurethane having a hydrophilic group.

The fibrous base material can be subjected to a heat shrinkage treatment using warm water or steam to improve the denseness of the fibers. However, in the present invention, the sheet is shrunk after being impregnated with an aqueous dispersion containing a polyurethane precursor, so it is preferable not to perform a shrinkage treatment before impregnating with an aqueous dispersion containing a polyurethane precursor.

<Step of forming an impregnated sheet and shrinking it in the width direction>
In this process, the fibrous base material is impregnated with an aqueous dispersion containing a polyurethane precursor, and then a heating and drying process is performed to form an impregnated sheet containing the fibrous base material and a polyurethane having a hydrophilic group as components. When the width of the fibrous base material before the sheet is impregnated is L, a shrunken sheet is obtained having a width of 0.85L to 0.95L.

In the method for producing the artificial leather of the present invention, the coagulation after the application of the aqueous dispersion can be performed by applying a coagulation method commonly used in the field, such as a dry heat coagulation method or a liquid coagulation method. When using a dry heat coagulation method, it is preferable to apply the aqueous dispersion to the fibrous substrate, heat treat the substrate at a temperature of 120°C to 180°C, and perform dry heat coagulation to provide a polyurethane having hydrophilic groups to the fibrous substrate. In addition, as the liquid coagulation, an acid coagulation method in which a coagulation process is performed using a coagulation solvent having a pH of 1 to 3, or a hot water coagulation method in which a coagulation process is performed using hot water having a pH of 80°C to 100°C can be used.

The concentration of the polyurethane precursor in the aqueous dispersion (content of the polyurethane precursor in 100% by mass of the aqueous dispersion) is preferably 3% by mass or more and 30% by mass or less. By making it 3% by mass or more, more preferably 5% by mass or more, the polyurethane precursor can be applied uniformly to the fibrous substrate even when the amount of the polyurethane precursor applied is small. On the other hand, by making it 30% by mass or less, more preferably 15% by mass or less, the storage stability of the aqueous dispersion can be improved.

When the dry heat coagulation method is used as the coagulation method, it is preferable to adjust the coagulation temperature to 55°C or higher and 80°C or lower. By setting the coagulation temperature to 55°C or higher, more preferably 60°C or higher, gelation during preparation and storage of the aqueous dispersion can be suppressed. On the other hand, by setting the temperature to 80°C or lower, more preferably 70°C or lower, coagulation of the polyurethane precursor proceeds before water evaporates from the fibrous base material, and a structure similar to that obtained by wet coagulation of a solvent-based polyurethane, that is, a structure in which the polyurethane does not strongly bind the fibers that make up the nonwoven fabric or woven fabric, can be formed, thereby achieving good flexibility and resilience.

In the manufacturing method of the artificial leather of the present invention, when the dry heat coagulation method is used, an inorganic salt can be contained in the aqueous dispersion. By containing an inorganic salt, the aqueous dispersion can be given heat-sensitive coagulation properties. In the present invention, heat-sensitive coagulation properties refer to the property that when the aqueous dispersion is heated, the fluidity of the aqueous dispersion decreases and the aqueous dispersion coagulates when a certain temperature (coagulation temperature) is reached.

In the present invention, when an inorganic salt is used as a heat-sensitive coagulant, it is preferable to use a monovalent cation-containing inorganic salt. The monovalent cation-containing inorganic salt is preferably sodium chloride and/or sodium sulfate. A monovalent cation-containing inorganic salt with a small ionic valence has little effect on the stability of the aqueous dispersion, and by adjusting the amount added, the heat-sensitive coagulation temperature can be strictly controlled while ensuring the stability of the aqueous dispersion.

Furthermore, in the present invention, the content of the monovalent cation-containing inorganic salt in the aqueous dispersion is preferably 10% by mass or more and 50% by mass or less with respect to the polyurethane precursor. By making the content 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, the ions present in large quantities in the aqueous dispersion act uniformly on the polyurethane precursor particles, so that the coagulation can be completed quickly at a specific heat-sensitive coagulation temperature. This makes it possible to obtain a more remarkable effect in proceeding with the coagulation of the polyurethane precursor in a state in which a large amount of moisture is contained in the fibrous base material as described above. As a result, it is possible to form a structure very similar to that obtained by wet coagulation of a solvent-based polyurethane, thereby achieving good flexibility and resilience. Furthermore, by making the amount added as described above, the inorganic salt acts as an inhibitor in the fusion of the polyurethane precursor particles, and it is also possible to suppress the hardening of the polyurethane precursor due to the formation of a continuous coating. On the other hand, by making the content 50% by mass or less, it is possible to leave a moderate continuous coating structure of the polyurethane precursor and suppress the deterioration of the physical properties. It is also possible to maintain the stability of the aqueous dispersion.

In the method for producing the artificial leather of the present invention, it is also preferable to include a crosslinking agent in the aqueous dispersion. By using the crosslinking agent to introduce a three-dimensional network structure into the polyurethane precursor, physical properties such as abrasion resistance can be improved.

The concentration of the crosslinking agent in the aqueous dispersion is preferably 1% by mass or more and 10% by mass or less relative to the mass of the polyurethane precursor. By setting the concentration of the crosslinking agent in the aqueous dispersion to 1% by mass or more, more preferably 2% by mass or more, the crosslinking agent can introduce more three-dimensional network structures into the polyurethane precursor, and artificial leather with excellent abrasion resistance and the like can be obtained. On the other hand, by setting the concentration to 10% by mass or less, more preferably 7% by mass or less, it is possible to prevent excess crosslinking agent from inhibiting the coagulation of the polyurethane precursor when the polyurethane precursor is formed, and to easily prevent deterioration of physical properties such as abrasion resistance.

In addition, the crosslinking agent preferably used in the method for producing artificial leather of the present invention is preferably a carbodiimide-based crosslinking agent and/or a blocked isocyanate crosslinking agent. In this way, a three-dimensional crosslinking structure can be imparted to the molecules of the polymeric elastomer in the artificial leather by N-acylurea bonds and/or isourea bonds, which have excellent physical properties such as light resistance, heat resistance, and abrasion resistance, as well as flexibility, and the physical properties such as durability and abrasion resistance can be dramatically improved while maintaining the flexibility of the artificial leather.

After impregnating and solidifying the aqueous dispersion, a shrunken sheet is obtained with a width of 0.85L to 0.95L, where L is the width of the fibrous substrate before impregnation. Methods for shrinking the sheet in the width direction include dry heat treatment at a temperature of 100°C to 180°C, and hot water treatment with hot water at 80°C to 100°C. Dry heat treatment includes treatment in which hot air is applied to one or both sides of the sheet using a floater dryer, drum dryer, pin tenter dryer, etc., and hot water treatment includes treatment in which the sheet is immersed in hot water at 80°C to 100°C, squeezed with a mangle, and then dried in a dryer.

From the viewpoint of manufacturing efficiency, it is preferable that the coagulation method and shrinkage method of the aqueous dispersion are the same.

By shrinking the sheet in the width direction, it is possible to increase the density of the artificial leather surface. In particular, by shrinking the sheet in the width direction after impregnating and solidifying an aqueous polyurethane dispersion, it is possible to prevent the polyurethane from adhering strongly to the woven fabric and to soften the texture of the artificial leather.

The degree of shrinkage of the sheet in the width direction can be adjusted by the heat treatment temperature and heat treatment time, and the above-mentioned effect can be sufficiently achieved by making it 5% or more, more preferably 10% or more, of the width of the fibrous base material before impregnation.

On the other hand, by making the thickness 15% or less of the width of the fibrous base material before impregnation, quality defects such as wrinkling of the sheet can be prevented.

When dry heat treatment is used as the shrinkage treatment, the temperature of the dry heat treatment is 100°C or higher, preferably 120°C or higher, and more preferably 130°C or higher, to increase the shrinkage of the sheet. On the other hand, by setting the temperature of the dry heat treatment to 180°C or lower, and preferably 160°C or lower, the deterioration of the durability of the artificial leather due to the decomposition of the polyurethane can be suppressed.

When dry heat treatment is used as the shrinkage treatment, the dry heat treatment time is preferably 5 minutes or more and 30 minutes or less. Heating for 5 minutes or more, more preferably 10 minutes or more, can increase the shrinkage of the sheet. By setting the dry heat treatment time to 30 minutes or less, preferably 25 minutes or less, it is possible to suppress a decrease in the durability of the artificial leather due to decomposition of the polyurethane.

<Step of forming polyester ultrafine fibers>
In this process, polyester ultrafine fibers are developed from the ultrafine fiber-developing fibers of the shrink sheet, and a sheet is formed containing, as components, a fibrous base material composed of polyester ultrafine fibers and woven fabric, and polyurethane having hydrophilic groups.

When islands-in-sea composite fibers are used as the ultrafine fiber-producing fibers, the ultrafine fiber processing (sea-removal processing) can be carried out, for example, by immersing the islands-in-sea composite fibers in a solvent and then performing a heat treatment. The solvent for dissolving the sea component can be appropriately selected depending on the type of sea component. When the sea component is a copolymer polyester, an alkaline aqueous solution such as sodium hydroxide can be used, but it is preferable to carry out the alkaline processing using an alkaline aqueous solution, which is expected to have the effect of reducing the adhesion between the woven fabric and the polyurethane.

When an alkaline aqueous solution is used as a solvent for the sea-removal process, it is preferable that the molar concentration of the alkaline aqueous solution be 3 mol/L or less to prevent excessive deterioration of the polyurethane having hydrophilic groups.

<Finishing process>
In the method for producing the artificial leather of the present invention, it is preferable to carry out various finishing steps, as in the case of general artificial leathers.

First, the method for producing the artificial leather of the present invention preferably includes a dyeing step for dyeing the artificial leather. As the dyeing process, various methods commonly used in the field can be adopted, such as a liquid flow dyeing process using a jigger dyeing machine or a liquid flow dyeing machine, a dip dyeing process such as a thermosol dyeing process using a continuous dyeing machine, or a printing process on the napped surface by roller printing, screen printing, inkjet printing, sublimation printing, vacuum sublimation printing, etc. Among them, it is preferable to use a liquid flow dyeing machine, since it is possible to soften the unbrushed artificial leather or artificial leather by giving a kneading effect at the same time as dyeing the unbrushed artificial leather or artificial leather. In addition, various resin finishing processes can be applied after dyeing, if necessary.

In addition, finishing treatments can be applied in the same bath as dyeing or after dyeing, for example, using softeners such as silicone, antistatic agents, water repellents, flame retardants, light fasteners and antibacterial agents.

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

In the manufacturing method of the artificial leather of the present invention, it is also preferable to include a nap raising step, whether before or after the dyeing step. The method for forming the nap is not particularly limited, and various methods commonly used in the field, such as buffing with sandpaper, can be used.

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

Furthermore, in the manufacturing method of the artificial leather of the present invention, if necessary, the artificial leather can be subjected to post-processing such as hole-making such as perforation, embossing, laser processing, pinsonic processing, and printing.

[Uses for vehicle interior materials, vehicle parts, seats, etc.]
The artificial leather obtained by the present invention can be suitably used as an interior material having a very elegant appearance as a surface material for furniture, chairs, and wall materials, and for seats, ceilings, and interiors in vehicle cabins such as automobiles, trains, and aircraft; uppers, trims, and the like of shoes such as shirts, jackets, casual shoes, sports shoes, men's shoes, and women's shoes; bags, belts, wallets, and the like; and industrial materials used in parts of these materials, such as wiping cloths, polishing cloths, and CD curtains.

For example, automobile interior materials containing the artificial leather are preferred because they can take advantage of the characteristics of high strength, excellent flexibility, and excellent abrasion resistance. Such automobile 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 part of these automobile parts is the artificial leather. In the present invention, the term "automobile" is not limited to so-called general passenger cars, but also includes some industrial, construction, and agricultural machinery that can carry humans or animals, such as excavators, cranes, tractors, and combines.

Seats containing the above-mentioned artificial leather are also preferred because they can take advantage of the characteristics of high strength, excellent flexibility, and excellent abrasion resistance. For such seats, it is more preferable that at least a portion of the covering material of the headrest, seat surface, armrest, footrest, etc., for example, the portion that comes into direct contact with the seated person, is made of the above-mentioned artificial leather. Of course, the seat of the present invention can be used not only for vehicles such as automobiles, aircraft, railway cars, and ships, but also for homes, offices, and stores. Note that the "seat" referred to in this invention also includes chairs, benches, sofas, couches, stools, and zaisu chairs.

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

[Evaluation method]
The evaluation methods and measurement conditions used in the examples are described below. Unless otherwise specified, the measurements of each physical property were performed according to the above-mentioned methods.

(1) Average single fiber diameter (μm):
The average single fiber diameter (μm) was measured and calculated by the above-mentioned method using a scanning electron microscope (SEM) "VHX-D500/D510" manufactured by Keyence Corporation.

(2) Content of polyurethane having hydrophilic group (mass%):
The content (mass %) of the polyurethane having a hydrophilic group was measured and calculated by the above-mentioned method.

(3) Percentage (%) of the outermost filaments of the multifilament to which polyurethane is attached:
The percentage (%) of the filaments to which polyurethane was attached among the outermost filaments of the multifilament was measured and calculated by the above-mentioned method.

(4) Bending resistance of artificial leather:
Based on Method A (45° cantilever method) described in 8.21.1 of "Bending resistance" in JIS L 1096:2010 "Testing methods for woven and knitted fabrics," five test pieces measuring 2 cm x 30 cm were prepared in the longitudinal direction of the sheet and placed on a horizontal table having a 45° inclined surface. The test pieces were slid and the scale was read when the center point of one end of the test piece came into contact with the inclined surface, and the average value of the five pieces was calculated.

(5) Abrasion loss of artificial leather (mg):
In measuring and calculating the abrasion loss (mg) of the artificial leather, a Martindale abrasion tester "Model 406" manufactured by James H. Heal & Co. was used as the abrasion tester, and "ABRASTIVE CLOTH SM25" manufactured by the same company was used as the standard friction cloth. A load of 12 kPa was applied to the artificial leather, and measurements were performed after 50,000 abrasion cycles. The abrasion loss was calculated using the mass of the artificial leather before and after abrasion according to the following formula.

Abrasion loss (mg) = mass before abrasion (mg) - mass after abrasion (mg)
The abrasion loss (mg) was calculated by rounding off the value to the first decimal place.

(6) Abrasion loss (mg) of artificial leather after xenon irradiation:
In measuring and calculating the abrasion loss (mg) of the artificial leather after xenon irradiation, irradiation was performed as specified in "7.2 Exposure method a) First exposure method" of JIS L 0843:2006 "Test method for color fastness to xenon arc lamp light", and then a Martindale abrasion tester "Model 406" manufactured by James H. Heal & Co. was used as the standard friction cloth, and "ABRASTIVE CLOTH SM25" manufactured by the same company was used as the standard friction cloth. A load of 12 kPa was applied to the artificial leather, and measurements were performed after 10,000 abrasion cycles. The abrasion loss was calculated by the following formula using the mass of the artificial leather before and after abrasion.

Abrasion loss (mg) = mass before abrasion (mg) - mass after abrasion (mg)
The abrasion loss (mg) was calculated by rounding off the value to the first decimal place.

[Polyurethane precursor]
The polyurethane precursors used in the examples and comparative examples are as follows.

PU-A (polyether-based polyurethane precursor containing components derived from polyether-based polyol): A polyurethane precursor consisting of polytetramethylene glycol as a polymeric 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.

PU-B (polycarbonate-based polyurethane precursor containing components derived from polycarbonate-based polyol): A polyurethane precursor consisting of polyhexamethylene carbonate diol as a polymeric 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.

[fabric]
The woven fabrics used in the examples and comparative examples are as follows.

Fabric A: A plain weave fabric (weight 75 g/m2) with a warp and warp density of 95 warp threads/2.54 cm and 76 weft threads/2.54 cm, in which a twisted yarn made of a multifilament consisting of 72 filaments with an average single fiber diameter of 11 μm made of polyethylene terephthalate with an intrinsic viscosity of 0.65 and twisted at 2,500 T/m was used for ^both the weft and warp.

Fabric B: A plain weave fabric (weight 75 g/m2) with a warp and warp density of 95 warp threads/2.54 cm and 76 weft threads/2.54 cm, in which a twisted yarn made of a multifilament consisting of 40 filaments with an average single fiber diameter of 15 μm made of polyethylene terephthalate with an intrinsic viscosity of 0.65 and twisted at 2,500 T/m is used for ^both the weft and warp.

Fabric C: A plain weave fabric (weight 75 g/m2) with a warp and weft density of 190 threads/2.54 cm and 152 threads/2.54 cm, using twisted yarns for both the weft and warp, each twisted at 2,500 T/m and made of multifilament consisting of 68 filaments of polyethylene terephthalate with an intrinsic viscosity of 0.65 and an average single fiber diameter of ^{8 μm} .

[Example 1]
<Step of forming fibrous base material>
A polyester copolymerized with 8 mol % of sodium 5-sulfoisophthalate was used as the sea component, and a polyethylene terephthalate having an intrinsic viscosity of 0.73 was used as the island component, and melt spun using an islands-in-sea composite spinneret with 16 islands/hole under the conditions of a spinning temperature of 285° C., an islands/sea mass ratio of 80/20, a throughput of 1.6 g/min/hole, and a spinning speed of 1,100 m/min. The fiber was then stretched 3.7 times in an oil bath and cut to a length of 51 mm to obtain raw islands-in-sea composite fiber with a single fiber fineness of 3.8 dtex. Next, using the raw cotton of the islands-in-sea type composite fiber, a laminated web having an apparent density of 0.09 g/ ^cm3 was formed through carding and cross-wrapping processes, and then woven fabric A was laminated thereon and needle punched at a punch density of 3,500 threads/ ^cm2 to obtain a fibrous base material consisting of a nonwoven fabric made of the islands-in-sea composite fiber and a woven fabric, having a basis weight of 690 g/ ^m2 , a thickness of 3.0 mm, a width of 170 cm and an apparent density of 0.23 g/ ^cm3 .

<Step of forming an impregnated sheet and shrinking it in the width direction>
As the polyurethane precursor, an aqueous dispersion was prepared containing 12 parts by mass of PU-A, which is a polyether polyurethane precursor, 1 part by mass of a carbodiimide crosslinking agent ("Carbodilite" (registered trademark) V-02-L2 manufactured by Nisshinbo Chemical Inc.), 5 parts by mass of sodium sulfate, and 82 parts by mass of water. After impregnating a fibrous base material, the aqueous dispersion was squeezed with a mangle so that the pickup rate of the aqueous dispersion was 200% by mass of the fibrous base material, and the polyurethane precursor was solidified by heating for 10 minutes with hot air at 100°C, and then heated for 10 minutes with hot air at 150°C. The sheet was shrunk in the width direction by 12% compared to the width L of the fibrous base material before impregnation, and an impregnated sheet having a width of 150 cm (0.88 L) and consisting of a nonwoven fabric of islands-in-the-sea composite fiber, a woven fabric, and a polyurethane having a hydrophilic group was obtained.

<Step of forming polyester ultrafine fibers>
The obtained impregnated sheet was immersed in a 5% aqueous sodium hydroxide solution, and then squeezed with a mangle so that the pick-up rate of the aqueous sodium hydroxide solution became 100%, and then heat-treated with steam at 95° C. for 10 minutes to alkali-decompose the sea component of the islands-in-sea type composite fibers. Next, the excess sodium hydroxide was washed away with water, and a sheet composed of polyester ultrafine fibers, a woven fabric, and a polyurethane having hydrophilic groups was obtained.

<Finishing process>
The obtained sheet was cut in half perpendicular to the thickness direction, and the cut surface was ground with endless sandpaper of sandpaper size 180 to obtain a napped sheet having a thickness of 0.9 mm.

The resulting napped sheet was dyed with a disperse dye at a temperature of 120°C using a liquid flow dyeing machine. It was then dried in a dryer to obtain an artificial leather containing 23% by mass of polyurethane with hydrophilic groups and an average single fiber diameter of 4.4 μm of ultrafine fibers. Of the filaments on the outermost periphery of the multifilaments constituting the woven fabric of the resulting artificial leather, the proportion (%) of filaments to which polyurethane was attached was 30%, and the artificial leather had a soft texture and excellent durability. The results are shown in Table 1.

[Example 2]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming a fibrous base material>, the woven fabric was changed to woven fabric B. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 12% in the width direction compared to the width L of the fibrous base material before impregnation, and was 150 cm (0.88 L).

The percentage (%) of the filaments to which polyurethane was attached among the outermost filaments of the multifilament constituting the obtained artificial leather fabric was 45%, and although the artificial leather was slightly less flexible than that of Example 1, it had a soft texture and excellent durability. The results are shown in Table 1.

[Example 3]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming a fibrous base material>, the woven fabric was changed to woven fabric C. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 12% in the width direction compared to the width L of the fibrous base material before impregnation, and was 150 cm (0.88 L).

The percentage (%) of the filaments to which polyurethane was attached among the outermost filaments of the multifilament constituting the obtained artificial leather fabric was 65%, and although the artificial leather was slightly less flexible than that of Example 1, it had a soft feel and excellent durability. The results are shown in Table 1.

[Example 4]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the heating conditions after solidifying the polyurethane precursor were changed to 10 minutes with hot air at 120° C. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 6% in the width direction compared to the width L of the fibrous base material before impregnation, to 160 cm (0.94 L).

The percentage (%) of the filaments to which polyurethane was attached among the outermost filaments of the multifilament constituting the obtained artificial leather fabric was 39%, and although the artificial leather was slightly less flexible than that of Example 1, it had a soft texture and excellent durability. The results are shown in Table 1.

[Example 5]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the polyurethane precursor was changed to PU-B, which is a polycarbonate-based polyurethane precursor. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous base material before impregnation.

The percentage (%) of the filaments to which polyurethane was attached among the outermost filaments of the multifilament constituting the obtained artificial leather fabric was 32%, and although the artificial leather was slightly less flexible than that of Example 1, it had a soft feel and extremely excellent durability. The results are shown in Table 1.

[Example 6]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 18 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the pickup rate of the aqueous dispersion was set to 140% by mass of the fibrous substrate. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation.

The percentage of filaments to which polyurethane was attached was 22% of the outermost filaments of the multifilament composing the obtained artificial leather fabric, and the artificial leather had a soft feel and excellent durability. The results are shown in Table 1.

[Example 7]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the coagulation of the polyurethane precursor and the heating conditions after coagulation were changed to steam at 98° C. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 5% in the width direction compared to the width L of the fibrous base material before impregnation, to 162 cm (0.95 L).

The percentage of filaments to which polyurethane was attached was 47% of the outermost filaments of the multifilament composing the obtained artificial leather fabric. Although the artificial leather was slightly less flexible than that of Example 1, it had a soft texture and excellent durability. The results are shown in Table 1.

[Example 8]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of developing polyester ultrafine fibers>, the concentration of sodium hydroxide was changed to 3% and the pickup rate was changed to 200%. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was shrunk by 12% in the width direction compared to the width L of the fibrous base material before impregnation, and was 150 cm (0.88 L).

The percentage (%) of the filaments to which polyurethane was attached among the outermost filaments of the multifilament constituting the obtained artificial leather fabric was 40%, and although the artificial leather was slightly less flexible than that of Example 1, it had a soft feel and extremely excellent durability. The results are shown in Table 1.

[Comparative Example 1]
In the <step of forming an impregnated sheet and shrinking it in the width direction>, the fibrous substrate was shrunk in the width direction to 150 cm with hot water at 97°C before impregnating with the aqueous dispersion, and no shrinkage in the width direction after solidification of the polyurethane precursor was performed in the same manner as in Example 1, to obtain an artificial leather containing ultrafine fibers with an average single fiber diameter of 4.4 µm and 23 mass% of polyurethane having a hydrophilic group. Note that the width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was not shrunk in the width direction compared to the width L of the fibrous substrate before impregnation, and remained at 150 cm (1.00 L).

The percentage of fibers to which polyurethane was attached was 95% of the outermost filaments of the multifilament constituting the filament of the obtained artificial leather, and the obtained artificial leather had excellent durability, but the texture was hard. The results are shown in Table 1.

[Comparative Example 2]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 13 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the pickup rate of the aqueous dispersion was set to 100% by mass of the fibrous substrate. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation.

The percentage (%) of the filaments to which polyurethane was attached among the outermost filaments of the multifilament composing the obtained artificial leather fabric was 8%, and the obtained artificial leather had an excellent feel, but was significantly inferior in durability. The results are shown in Table 1.

[Comparative Example 3]
An artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 29 mass % of polyurethane having a hydrophilic group was obtained in the same manner as in Example 1, except that in the <step of forming an impregnated sheet and shrinking it in the width direction>, the pickup rate of the aqueous dispersion was set to 250% by mass of the fibrous substrate. The width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was 150 cm (0.88 L), which was shrunk by 12% in the width direction compared to the width L of the fibrous substrate before impregnation.

The percentage of filaments to which polyurethane was attached was 82% of the outermost filaments of the multifilament composing the artificial leather fabric obtained, and the artificial leather obtained had excellent durability, but the texture was hard. The results are shown in Table 1.

[Comparative Example 4]
In the <step of forming an impregnated sheet and shrinking it in the width direction>, before impregnating the fibrous substrate with the aqueous dispersion, the fibrous substrate was shrunk in the width direction to 150 cm with hot water at 97°C, and at the same time, 10 mass% of polyvinyl alcohol having a saponification degree of 98% was added relative to the mass of the fibrous substrate, to obtain an artificial leather having an average single fiber diameter of ultrafine fibers of 4.4 μm and containing 23 mass% of polyurethane having a hydrophilic group. Note that the width of the impregnated sheet obtained in the <step of forming an impregnated sheet and shrinking it in the width direction> was not shrunk in the width direction relative to the width L of the fibrous substrate before impregnation, and remained at 150 cm (1.00 L).

The ratio (%) of fibers to which polyurethane was attached among the outermost filaments of the multifilament constituting the filament of the obtained artificial leather was 95%, and the obtained artificial leather had excellent durability, but the feel was hard. The results are shown in Table 1.
<Step of forming fibrous base material>
In the same manner as in Example 1, a fibrous base material composed of a nonwoven fabric made of sea-island composite fibers and a woven fabric was obtained.

<Step of forming an impregnated sheet and shrinking it in the width direction>
Before impregnating the fibrous substrate with the aqueous dispersion, the fibrous substrate was shrunk in the width direction to 150 cm with hot water at 97°C, and at the same time, polyvinyl alcohol having a saponification degree of 98% was added in an amount of 10 mass% relative to the mass of the fibrous substrate, and the fibrous substrate was dried with hot air at 100°C to obtain a fibrous substrate with polyvinyl alcohol. Next, an aqueous dispersion consisting of 12 parts by mass of PU-A, which is a polyether polyurethane precursor, 1 part by mass of a carbodiimide crosslinking agent ("Carbodilite" (registered trademark) V-02-L2 manufactured by Nisshinbo Chemical Inc.), 5 parts by mass of sodium sulfate, and 82 parts by mass of water was prepared as a polyurethane precursor. After impregnating a fibrous base material, the aqueous dispersion was squeezed with a mangle so that the pickup rate of the aqueous dispersion was 200% by mass of the fibrous base material, and the polyurethane precursor was solidified by heating for 10 minutes with hot air at 100°C, and then heated for 10 minutes with hot air at 150°C to obtain an impregnated sheet consisting of a nonwoven fabric of islands-in-the-sea composite fibers, a woven fabric, a polyurethane having a hydrophilic group, and polyvinyl alcohol.

<Step of forming polyester ultrafine fibers>
The obtained impregnated sheet was subjected to an alkali treatment in the same manner as in Example 1 to develop polyester ultrafine fibers, and the polyvinyl alcohol was removed with hot water at 100°C to obtain a sheet composed of polyester ultrafine fibers, woven fabric, and polyurethane having hydrophilic groups.

<Finishing process>
The obtained sheet was subjected to a finishing process in the same manner as in Example 1 to obtain an artificial leather having an average single fiber diameter of 4.4 μm and containing 23 mass % of polyurethane having a hydrophilic group. The ratio (%) of filaments to which polyurethane was attached among the outermost filaments of the multifilament constituting the woven fabric of the obtained artificial leather was 3%, and although the artificial leather had a soft feel and excellent durability, polyvinyl alcohol was used, and the process load was higher than that of Example 1. The results are shown in Table 1.

The artificial leather obtained by the present invention can be suitably used as an interior material with a very elegant appearance as a covering material for furniture, chairs and wall materials, seats, ceilings and interiors in vehicle cabins such as automobiles, trains and aircraft, uppers and trims for shoes such as shirts, jackets, casual shoes, sports shoes, men's shoes and women's shoes, bags, belts, wallets, etc., clothing materials used in some of these, and industrial materials such as wiping cloths, polishing cloths and CD curtains.

1: Multifilament constituting the woven fabric 2: Polyurethane 3: Filament with polyurethane attached 4: Filament without polyurethane attached

Claims (9)

An artificial leather comprising a fibrous base material formed by entangling and integrating a nonwoven fabric and a woven fabric, and a polyurethane having a hydrophilic group,
The nonwoven fabric is composed of polyester ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less,
The woven fabric is composed of a multifilament having 30 to 300 filaments, and the average single fiber diameter of the filaments constituting the multifilament is 1 μm to 30 μm,
The content of the polyurethane in the artificial leather is 15% by mass or more and 25% by mass or less,
and the ratio of the filaments to which the polyurethane is attached among the outermost filaments of the multifilament is 10% or more and 80% or less.
Artificial leather. The artificial leather according to claim 1, wherein the polyurethane is a polyether-based polyurethane and/or a polycarbonate-based polyurethane. The method for producing the artificial leather according to claim 1, comprising the following steps (1) to (3) in this order:
(1) A process for forming a fibrous base material by entangling and integrating a nonwoven fabric made of ultrafine fiber-developing fibers with a woven fabric. (2) A process for obtaining a shrunk sheet having a width of 0.85L to 0.95L, where L is the width of the fibrous base material before impregnation. (3) A process for developing polyester ultrafine fibers from the ultrafine fiber-developing fibers of the shrunk sheet. The method for producing artificial leather according to claim 3, wherein the entanglement and integration means in step (1) is needle punch processing. The method for producing artificial leather according to claim 3 or 4, wherein the means for obtaining the shrink sheet in step (2) is a dry heat treatment at an atmospheric temperature of 100°C or higher and 180°C or lower. The method for producing artificial leather according to claim 3 or 4, wherein the means for producing polyester ultrafine fibers in step (3) is an alkali treatment. An automobile interior material comprising the artificial leather according to claim 1 or 2. An automobile part comprising the artificial leather according to claim 1 or 2. A seat comprising the artificial leather of claim 1 or 2.