JP2023140491A - Artificial leather and manufacturing method thereof - Google Patents

Abstract

To provide an artificial leather, which has uniform surface quality and good touch feeling and excellent abrasion resistance, and a manufacturing method thereof.SOLUTION: An artificial leather contains fibrous base material including a nonwoven fabric formed of ultra fine fibers having average single fiber diameter of 0.1 μm or more and 10.0 μm or less and water dispersion type elastomer as components thereof. Average fiber length of the ultra fine fiber is 25 mm or more and 90 mm or less. Fiber bundles composed of 5 pieces or more and 200 pieces or less of the ultra fine fibers are formed. In a scanning electron micrograph of a cut surface obtained by cutting vertically to a surface of the artificial leather, when equally dividing an observation area of the scanning electron micrograph into eight sections, variation coefficient of quantity of fiber cross sections existing in each section is 50% or less.SELECTED DRAWING: None

Description

The present invention relates to artificial leather and a method for manufacturing the same.

Artificial leather, which is mainly made of a fibrous base material such as nonwoven fabric and polyurethane, has excellent characteristics that natural leather does not have, such as excellent durability and ease of dyeing. In particular, artificial leather using a fibrous base material made of ultrafine fibers has excellent surface quality and touch feel, and is therefore being used year by year for applications such as clothing, miscellaneous goods, and automobile interior materials.

In manufacturing such artificial leather, a fibrous base material is impregnated with an organic solvent solution of polyurethane, and then the obtained fibrous base material is immersed in water or an aqueous organic solvent solution that is a non-solvent of polyurethane. A combination of steps in which polyurethane is wet-coagulated is generally employed. In this case, water-miscible organic solvents such as N,N-dimethylformamide are used as the organic solvent for polyurethane, but since organic solvents are generally highly harmful to the environment, artificial leather There is a strong demand for a manufacturing method that does not use organic solvents.

As a specific solution, for example, a method is disclosed in which a water-dispersed polyurethane in which a polyurethane resin is dispersed in water is used in place of the conventional organic solvent-based polyurethane (Patent Document 1).

JP2011-214210A

When applying a water-dispersed polyurethane by the method disclosed in Patent Document 1, a fibrous base material is impregnated in an aqueous dispersion of a precursor of the water-dispersed polyurethane, and then the precursor is coagulated. A method is used to obtain artificial leather coated with water-dispersed polyurethane. However, the distribution of the water-dispersed polyurethane after impregnation tends to depend on the density distribution of the fibrous base material itself before impregnation, and therefore tends to become non-uniform, resulting in a problem that the surface quality and touch feel are deteriorated. Furthermore, since the distribution of polyurethane becomes uneven, there are fibers to which polyurethane is not attached, and as a result, the abrasion resistance of the artificial leather decreases.

SUMMARY OF THE INVENTION In view of the background of the prior art described above, an object of the present invention is to provide an artificial leather having uniform surface quality, good touch feeling, and excellent abrasion resistance, and a method for manufacturing the same. be.

As a result of repeated studies by the present inventors in order to achieve the above object, the present inventors have found that before impregnating a specific fibrous base material with a solution of a water-dispersed polymeric elastomer precursor, etc., the fibrous base material is pre-impregnated with water. By allowing water to enter between the fibers, the dispersibility of the fibers is improved, and by subsequently impregnating the water-dispersible polymer elastomer precursor, the distribution of the water-dispersible polyurethane is made uniform. It was found that artificial leather with uniform surface quality, good touch feeling, and good abrasion resistance can be obtained.

That is, the present invention aims to solve the above problems, and the artificial leather of the present invention comprises a fibrous base material containing a nonwoven fabric made of ultrafine fibers having an average single fiber diameter of 0.1 μm or more and 10.0 μm or less. , an elastomer polymer having a hydrophilic group as a constituent element, wherein the average fiber length of the ultrafine fibers is 25 mm or more and 90 mm or less, and the number of the ultrafine fibers is 5 or more and 200 or less. In a scanning electron micrograph of a cross-section cut perpendicular to the surface of the artificial leather, the observation range of the scanning electron micrograph is equally divided into eight sections, and the inside of each section is The coefficient of variation of the number of fiber cross sections present in the fiber cross section is 50% or less.

Further, in the method for producing artificial leather of the present invention, preferably, a fibrous base material containing a nonwoven fabric made of ultrafine fiber-generating fibers is prepared such that the moisture content of the fibrous base material is 5% by mass or more and 300% or less. is impregnated with water, and further a solution or aqueous dispersion of a precursor of a polymeric elastomer having a hydrophilic group is added at a flow rate of 25 L/m ² ·min or more and 85 L/m ² ·min or less per unit area/unit time. The fibrous base material is impregnated by spraying it onto at least one surface of the fibrous base material.

According to a preferred embodiment of the method for producing artificial leather of the present invention, the temperature of the water when adding water is 60°C or more and 100°C or less.

According to a preferred embodiment of the method for producing artificial leather of the present invention, the above-mentioned injection is performed in a solution or an aqueous dispersion of the above-mentioned precursor.

According to a preferred embodiment of the method for producing artificial leather of the present invention, the above-mentioned spraying is carried out on both surfaces of the above-mentioned fibrous base material.

According to the present invention, artificial leather having uniform surface quality, good touch feeling, and good abrasion resistance can be obtained.

The artificial leather of the present invention includes as constituent elements a fibrous base material containing a nonwoven fabric made of ultrafine fibers with an average single fiber diameter of 0.1 μm or more and 10.0 μm or less, and an elastomer polymer having a hydrophilic group. Artificial leather, in which the average fiber length of the ultrafine fibers is 25 mm or more and 90 mm or less, the ultrafine fibers form a fiber bundle of 5 or more and 200 or less, and are perpendicular to the surface of the artificial leather. In a scanning electron micrograph of a cross-section cut into , when the observation range of the scanning electron micrograph is equally divided into eight sections, the coefficient of variation of the number of fiber cross sections present in each section is 50% or less. These components will be described in detail below, but the present invention is not limited to the scope described below unless it exceeds the gist thereof.

[Ultra-fine fiber]
In the artificial leather of the present invention, resins that can be used for the ultrafine fibers include polyester resins, polyamide resins, etc. from the viewpoints of excellent durability, particularly mechanical strength, heat resistance, and light resistance. can be mentioned. Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and the like. The polyester resin can be obtained from, for example, a dicarboxylic acid and/or its ester-forming derivative and a diol.

Examples of dicarboxylic acids and/or ester-forming derivatives thereof used in the polyester resin include terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid and ester-forming derivatives thereof. Examples include. The ester-forming derivatives used in the present invention include lower alkyl esters of dicarboxylic acids, acid anhydrides, and acyl chlorides. Specifically, methyl ester, ethyl ester, hydroxyethyl ester, etc. are preferably used. A more preferred embodiment of the dicarboxylic acid and/or its ester-forming derivative used in the present invention is terephthalic acid and/or its dimethyl ester.

Examples of the diol used in the polyester resin include ethylene glycol, 1,3-propanediol, 1,4-butanediol, and cyclohexanedimethanol. Among them, ethylene glycol is preferably used.

When a polyamide resin is used as the resin for the ultrafine fibers, polyamide 6, polyamide 66, polyamide 56, polyamide 610, polyamide 11, polyamide 12, copolyamide, etc. can be used.

The resin used for ultrafine fibers may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc., depending on various purposes. I can do it.

Further, it is preferable that the resin used for the ultrafine fiber contains a component derived from biomass resources.

When a polyester resin is used as the resin for ultrafine fibers, the component derived from biomass resources may be a component derived from biomass resources such as dicarboxylic acid or its ester-forming derivative, or diol. Although components derived from biomass resources may be used as the components, from the viewpoint of reducing environmental load, it is preferable to use components derived from biomass resources for both the dicarboxylic acid or its ester-forming derivative and the diol.

When polyamide resin is used as the resin for ultrafine fibers, the components derived from biomass resources include polyamide 56, polyamide 610, Polyamide 11 is preferably used.

As for the cross-sectional shape of the ultrafine fibers, either a round cross-section or an irregular cross-section can be adopted. Specific examples of the irregularly shaped cross section include an ellipse, a flattened shape, a polygon such as a triangle, a fan shape, a cross shape, and the like.

The average single fiber diameter of the ultrafine fibers is 0.1 μm or more and 10.0 μm or less. By setting the average single fiber diameter of the ultrafine fibers to be 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. Moreover, the quality of the raised hair can be improved. On the other hand, since the average single fiber diameter of the ultrafine fibers is 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.7 μm or more, it is possible to obtain artificial leather with excellent color development after dyeing. can do. Furthermore, when performing the raising treatment by buffing, it is possible to improve the ease of dispersing and sorting the ultrafine fibers present in bundles.

The average single fiber diameter as used in the present invention is measured by the following method. That is,
(1) A cross section of the artificial leather cut in the thickness direction is observed using a scanning electron microscope (SEM).
(2) Measure the fiber diameters of any 50 ultrafine fibers in the observation plane in three directions at the cross section of each ultrafine fiber. However, when ultrafine fibers with an irregular cross section are used, the cross-sectional area of the single fiber is first measured, and the diameter of the circle corresponding to the cross-sectional area is calculated using the following formula. The diameter obtained from this is the single fiber diameter of that single fiber Single fiber diameter (μm) = (4 x (cross-sectional area of single fiber (μm ² )) / π) ^1/2
(3) Calculate the arithmetic mean value (μm) of the total 150 points obtained and round to the second decimal place.

[Fibrous base material]
The fibrous base material used in the present invention includes a nonwoven fabric made of the ultrafine fibers described above. Note that it is permissible for the fibrous base material to contain a mixture of ultrafine fibers made from different raw materials.

As a specific form of the fibrous base material, a nonwoven fabric formed by intertwining each of the above-mentioned ultrafine fibers or a nonwoven fabric formed by entangled fiber bundles of ultrafine fibers can be used. Among these, a nonwoven fabric formed by intertwining fiber bundles of ultrafine fibers is preferably used from the viewpoint of the strength and texture of the artificial leather. From the viewpoint of flexibility and texture, it is particularly preferable to use a nonwoven fabric in which the ultrafine fibers forming the fiber bundle of ultrafine fibers are appropriately spaced from each other and have voids. In this way, a nonwoven fabric formed by entangling fiber bundles of ultrafine fibers can be obtained, for example, by entangling ultrafine fiber-expressing fibers in advance and then developing the ultrafine fibers. In addition, nonwoven fabrics in which the ultrafine fibers forming a fiber bundle of ultrafine fibers are appropriately spaced from each other and have voids are, for example, sea-island composite fibers that can create voids between island components by removing the sea component. It can be obtained by using

The above-mentioned nonwoven fabric is a nonwoven fabric made of ultrafine fibers having a certain fiber length. By doing so, the texture and quality of the artificial leather can be further improved.

Specifically, the average fiber length of the ultrafine fibers is in the range of 25 mm or more and 90 mm or less. When the average fiber length is 25 mm or more, more preferably 35 mm or more, and still more preferably 40 mm or more, the ultrafine fibers are sufficiently entangled, resulting in an artificial leather with more excellent wear resistance. In addition, when the average fiber length is 90 mm or less, more preferably 80 mm or less, and even more preferably 70 mm or less, the artificial leather has even better texture and quality.

In the present invention, the average fiber length of the ultrafine fibers is calculated by the following method. That is, slits are made at three arbitrary locations on the artificial leather using scissors, and tears are made by hand. Using tweezers, extract 10 ultrafine fibers from the cross section of each tear that has not been passed through the scissors, measure the fiber length, and calculate the number average (mm) of the 30 fiber lengths to one decimal place. Round off to the nearest whole number to obtain the average fiber length of the ultrafine fiber.

In the present invention, when a nonwoven fabric is used as the fibrous base material, a woven or knitted fabric may be inserted, laminated, or lined inside the nonwoven fabric for the purpose of improving strength or the like. The average single fiber diameter of the fibers constituting such a woven or knitted fabric is more preferably 0.3 μm or more and 10.0 μm or less, since damage during needle punching can be suppressed and strength can be maintained.

The fibers constituting the woven or knitted fabrics include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polylactic acid, synthetic fibers such as polyamides such as 6-nylon and 66-nylon, and cellulose polymers. Regenerated fibers, natural fibers such as cotton and linen, etc. can be used.

[Elastic polymer]
The artificial leather of the present invention includes an elastomer polymer having a hydrophilic group as a component. By doing so, artificial leather with excellent solvent resistance can be obtained. In the present invention, the term "polymer elastomer having a hydrophilic group" refers to a polymer elastomer having a hydrophilic group having active hydrogen in the main chain or side chain of the polymer elastomer. The term "hydrophilic group" used herein refers to a functional group that has a high affinity for water. Specific examples of hydrophilic groups include hydroxyl groups, carboxyl groups, sulfonic acid groups, and amino groups.

In the artificial leather of the present invention, examples of the polymer elastomer used as the polymer elastomer having a hydrophilic group include silicone resins, acrylic resins, polyurethane resins, and copolymers thereof. Among them, polyurethane resins are preferably used from the viewpoint of texture.

As the polyurethane resin having a hydrophilic group, a resin obtained by reacting a polymer polyol having a number average molecular weight of preferably 500 or more and 5000 or less, an organic polyisocyanate, and a chain extender is preferably used. Furthermore, in order to improve the stability of the aqueous polyurethane dispersion, it is preferable to use a hydrophilic group-containing active hydrogen component, which will be described later, in combination. By setting the number average molecular weight of the polymer polyol to 500 or more, more preferably 1500 or more, it is possible to easily prevent the texture from becoming hard. Further, by setting the number average molecular weight to 5,000 or less, more preferably 4,000 or less, the strength of the polyurethane as a binder can be easily maintained. A case where a polyurethane resin having a hydrophilic group is used as the polymer elastic body will be described below.

(1) Each reactive component of the polyurethane resin having a hydrophilic group First, each reactive component of the polyurethane resin having a hydrophilic group will be explained.

(1-1) Polymer polyol Examples of polymer polyols that can be used in the present invention include polyether polyols, polyester polyols, polycarbonate polyols, and the like.

Examples of polyether polyols include polyols obtained by adding and polymerizing monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin, and cyclohexylene using a polyhydric alcohol or polyamine as an initiator; Examples include polyols obtained by ring-opening polymerization of the above monomers using a protonic acid, a Lewis acid, a cationic catalyst, or the like as a catalyst. Specific examples include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene ether glycol, and copolymerized polyols that are combinations thereof.

Examples of polyester polyols include polyester polyols obtained by condensing various low molecular weight polyols and polybasic acids, polyols obtained by depolymerizing lactones, and the like.

Examples of low molecular weight polyols include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1.8-heptanediol. Linear alkylene glycols such as octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentane diols, branched alkylene glycols such as 2-methyl-1,8-octanediol, alicyclic diols such as 1,4-cyclohexanediol, and aromatic divalent diols such as 1,4-bis(β-hydroxyethoxy)benzene. One or more types selected from alcohols and the like can be mentioned. Further, adducts obtained by adding various alkylene oxides to bisphenol A can also be used as low molecular weight polyols.

Examples of polybasic acids include 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 hexahydrocarbonic acid. Examples include one or more selected from the group consisting of isophthalic acid and the like.

Examples of polycarbonate polyols include compounds obtained by reacting polyols with carbonate compounds such as dialkyl carbonates and diaryl carbonates.

As the polyol as a raw material for producing polycarbonate polyol, the polyols listed as raw materials for producing polyester polyol can be used. As the dialkyl carbonate, dimethyl carbonate, diethyl carbonate, etc. can be used, and as the diaryl carbonate, diphenyl carbonate, etc. can be used.

In the artificial leather of the present invention, it is preferable that the elastomer polymer having a hydrophilic group contains polyether diol as a constituent component. In addition, in this specification, "containing as a constituent component" means containing as a monomer component or oligomer component constituting the polymeric elastomer. Polyether diol has a low glass transition temperature due to its high degree of freedom in ether bonds, and has a weak cohesive force, making it easy to obtain polyurethane with excellent flexibility.

(1-2) Organic diisocyanate The organic diisocyanate used in the present invention includes aromatic diisocyanates having 6 to 20 carbon atoms (excluding carbon in the NCO group, the same applies hereinafter), and aromatic diisocyanates having 2 to 18 carbon atoms. Aliphatic diisocyanates, alicyclic diisocyanates having 4 to 15 carbon atoms, aromatic aliphatic diisocyanates having 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.

Specific examples of the aromatic diisocyanate having 6 to 20 carbon atoms include 1,3- and/or 1,4-phenylene diisocyanate, 2,4- and/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.

Specific examples of the aliphatic diisocyanate having 2 or more and 18 or less carbon atoms include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2, Examples include 6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexaate.

Specific examples of the alicyclic diisocyanate having 4 to 15 carbon atoms include isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, and bis(2-isocyanatoethyl). -4-cyclohexylene-1,2-dicarboxylate, and 2,5- and/or 2,6-norbornane diisocyanate.

Specific examples of the aromatic aliphatic diisocyanate having 8 or more and 15 or less carbon atoms include m- and/or p-xylylene diisocyanate, α, α, α', α'-tetramethylxylylene diisocyanate, and the like. It will be done.

Among these, preferred organic diisocyanates are alicyclic diisocyanates. Furthermore, a particularly preferred organic diisocyanate is dicyclohexylmethane-4,4'-diisocyanate.

(1-3) Chain extender Chain extenders used in the present invention include water, ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol and neopentyl glycol, etc., alicyclic diols such as 1,4-bis(hydroxymethyl)cyclohexane, aromatic diols such as 1,4-bis(hydroxyethyl)benzene, and ethylene diamine. aliphatic diamines such as isophorone diamine, aromatic diamines such as 4,4-diaminodiphenylmethane, aromatic aliphatic diamines such as xylene diamine, and alkanols such as ethanolamine. Examples include amines, hydrazine, dihydrazides such as "adipate dihydrazide," and mixtures of two or more of these.

Among these, preferred chain extenders are water, low-molecular diols, and aromatic diamines, and more preferred are water, ethylene glycol, 1,4-butanediol, 4,4'-diaminodiphenylmethane, and two or more of these. Mixtures may be mentioned.

(2) Additive for polyurethane resin having a hydrophilic group For reasons described later, it is preferable to add an inorganic salt containing a monovalent cation to a solution or aqueous dispersion containing a polyurethane having a hydrophilic group. In addition, if necessary, coloring agents such as titanium oxide, ultraviolet absorbers (benzophenone type, benzotriazole type, etc.), antioxidants [hinder such as 4,4-butylidene bis (3-methyl-6-1-butylphenol), etc. Various stabilizers such as dophenol; organic phosphites such as triphenyl phosphite and trichloroethyl phosphite], inorganic fillers (calcium carbonate, etc.), and the like can be contained.

(3) Component that causes polyurethane to contain a hydrophilic group In the polyurethane having a hydrophilic group used in the present invention, an example of a component that causes the polyurethane to contain a hydrophilic group is a hydrophilic group-containing active hydrogen component. Examples of the hydrophilic group-containing active hydrogen component include compounds containing a nonionic group and/or anionic group and/or cationic group and active hydrogen.

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 with a molecular weight of 250 to 9000 in 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 derivatives thereof; , 3-phenylenediamine-4,6-disulfonic acid, 3-(2,3-dihydroxypropoxy)-1-propanesulfonic acid and other compounds containing sulfonic acid groups and their derivatives, as well as neutralizing these compounds. Examples include salts neutralized with agents.

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.

The hydrophilic group-containing active hydrogen component can also be used in the form of a salt neutralized with a neutralizing agent.

The hydrophilic group-containing active hydrogen component used in the polyurethane molecule is 2,2-dimethylolpropionic acid, 2,2-dimethylolbutane, from the viewpoint of mechanical strength and dispersion stability of the polyurethane resin having a hydrophilic group. Preference is given to using acids and their neutralized salts.

The elastomer polymer having a hydrophilic group used in the present invention appropriately holds the fibers together in the artificial leather, and preferably has naps on at least one side of the artificial leather, so that the inside of the fibrous base material In a preferred embodiment, it is present in

[Artificial leather]
The artificial leather of the present invention includes the above-mentioned fibrous base material and the above-mentioned elastomer polymer having a hydrophilic group as constituent elements, and furthermore, in a cross section cut perpendicularly to the surface of the artificial leather, observation is made. It is important that the coefficient of variation of the number of ultrafine fiber cross sections present in each section when the range is divided into eight equal parts is 50% or less. The coefficient of variation of the number of ultrafine fiber cross sections is 50% or less, preferably 45% or less, more preferably 40% or less, achieving high uniformity of fiber dispersion, uniform surface quality, and good touch feeling. It is possible.

In the present invention, the coefficient of variation of the number of ultrafine fiber cross sections present in each section when the observation range is divided into eight equal parts is calculated by the following method. That is,
(1) A cross section of the artificial leather cut in the thickness direction is observed using a scanning electron microscope (SEM, such as "VHX-D500/D510" manufactured by Keyence Corporation). Note that the observation range conditions shall satisfy the following (a) to (c).
(a) The total number of ultrafine fiber cross sections facing toward the observation surface that exist in the observation range is 500 or more.
(b) If the sheet surface is treated with raised hair, the raised part should not be included in the observation range.
(c) If a woven or knitted fabric is inserted inside the nonwoven fabric, the cross section of the fibers that make up the woven or knitted fabric should not be included in the observation range.
(2) Draw a straight line to divide the observation range into 2 equal parts vertically and 4 equal parts horizontally to divide the observation range into 8 equal parts.
(3) Count the number of ultrafine fiber cross sections facing toward the observation surface that exist in each section. If the ultrafine fiber cross section spans multiple sections, it is counted as existing in the section containing the largest cross-sectional area of the ultrafine fiber.
(4) Find the number of cross-sectional areas of ultra-fine fibers for each of the eight sections, and calculate the coefficient of variation according to the following formula 1. (Coefficient of variation of the number of cross-sections of ultra-fine fibers in each section) sample standard deviation of the number of ultrafine fiber cross sections present in each section)/(average value of the number of ultrafine fiber cross sections present in each section) (Formula 1).

In the present invention, in the artificial leather, the ultrafine fibers form a fiber bundle of 5 or more and 200 or less. When the number of ultrafine fibers forming the fiber bundle is 5 or more, preferably 8 or more, and more preferably 10 or more, the ultrafine fiber generation type fibers can have a fiber diameter suitable for entanglement. In addition, by setting the number of ultrafine fibers forming the fiber bundle to 200 or less, preferably 130 or less, and more preferably 100 or less, it is possible to improve the dispersibility of the ultrafine fibers and provide a good touch feeling. Artificial leather can be obtained. Note that in the present invention, a "fiber bundle" refers to an aggregate of a plurality of ultrafine fibers that can be considered to be oriented in the same direction. Furthermore, in the present invention, the expression that the ultrafine fibers can be considered to be oriented in the same direction means that the cross sections of the ultrafine fibers can be considered to have substantially the same shape. For example, in the cross section of artificial leather, if 10 ultrafine fibers with the same circular cross section (an ellipse with an oblateness of 0) are clustered together, the aggregate is made up of 10 ultrafine fibers. It can be said that it is a fiber bundle.

The number of ultrafine fibers forming a fiber bundle as used in the present invention is calculated by the following method. That is, on a cross section of artificial leather cut in the thickness direction, a scanning electron microscope (SEM, such as "VHX-D500/D510" manufactured by Keyence Corporation) is used to detect ultra-fine particles that exist in the observation range and face toward the observation surface. Ten images are taken at a magnification of 1200 to 1700 times so that the total number of fiber cross sections is 200 or more. Then, for each of the 10 images, count all the number of ultrafine fibers that form what can be considered as one "fiber bundle", and round off the average value (number of fibers) per fiber bundle to one decimal place. is the number of ultrafine fibers forming the fiber bundle.

The artificial leather of the present invention preferably contains 10% by mass or more and 50% by mass or less of the above-mentioned type polymeric elastomer having a hydrophilic group. It is more preferable to contain 15% by mass or more, and even more preferably to contain 20% by mass or more from the viewpoint of suppressing breakage due to tension during the manufacturing process and shedding of fluff during actual use. In addition, by setting the content of the type polymeric elastomer having a hydrophilic group to 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less, the texture is prevented from becoming hard and good napping is achieved. You can gain dignity.

In addition, the artificial leather of the present invention has been tested in "8.19.5 E method (Martindale method)" in "8.19 Abrasion strength and friction discoloration" of JIS L1096:2010 "Testing methods for textiles and knitted fabrics". In the measured abrasion resistance test, the press load is 12.0 kPa, and the mass loss of the artificial leather after being worn 20,000 times is preferably 10 mg or less, more preferably 8 mg or less, and 6 mg or less. It is more preferable that When the weight loss is 10 mg or less, contamination due to fluff falling off during actual use can be prevented.

[Manufacturing method of artificial leather]
Next, a preferred method for producing the artificial leather of the present invention will be described.

In the present invention, as a means for obtaining ultrafine fibers, direct spinning or ultrafine fiber expression type fibers can be used. Among these, when using ultrafine fiber expression type fibers, the ultrafine fiber expression type fibers are entangled in advance to form a nonwoven fabric, and then the fibers are made ultrafine to obtain a nonwoven fabric in which ultrafine fiber bundles are entangled. I can do it.

The microfiber-expressing fiber is made of two thermoplastic resin components (two or three components if the island fiber is a core-sheath composite fiber) with different solvent solubility as a sea component and an island component, and the sea component is mixed with a solvent. By using a sea-island type composite fiber in which the island components are made into ultra-fine fibers by dissolving and removing them using, for example, the sea-island composite fibers, when removing the sea components, appropriate voids are created between the island components, that is, between the ultra-fine fibers inside the fiber bundle. Therefore, it is preferable from the viewpoint of the texture and surface quality of the artificial leather.

The sea-island type composite fiber is a polymer mutually arranged body in which two components (sea component and island component) (three components if the island fiber is a core-sheath composite fiber) are arranged and spun using a sea-island composite spinneret. The method used is preferable from the viewpoint that ultrafine fibers having a uniform single fiber diameter can be obtained.

As the sea component of the sea-island type composite fiber, polyethylene, polypropylene, polystyrene, copolymerized polyester made by copolymerizing sodium sulfoisophthalic acid, polyethylene glycol, etc., and polylactic acid can be used, but there may be problems with spinability, easy dissolution, etc. From this viewpoint, polystyrene and copolymerized polyester are preferably used.

As will be described later, it is a preferred embodiment that the sea component is dissolved and removed after the precursor of the elastomer polymer having a hydrophilic group is provided.

The mass ratio of the sea component to the island component in the sea-island composite fiber used in the present invention is preferably in the range of sea component: island component = 10:90 to 80:20. When the mass proportion of the sea component is 10% by mass or more, the island component can be sufficiently reduced in size. Moreover, when the mass proportion of the sea component is 80 mass or less, the proportion of eluted components is small, so that productivity is improved. 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.

In addition, it is preferable that the fiber entanglement takes the form of a nonwoven fabric, and as mentioned above, it can be used as either a short fiber nonwoven fabric or a long fiber nonwoven fabric. This is preferable because it has more fibers than a long-fiber nonwoven fabric, and a high density feeling can be obtained on the surface of the fibrous base material when raised.

When a short fiber nonwoven fabric is used as the fiber entanglement, the obtained ultrafine fiber-expressing fiber is preferably crimped and cut into a predetermined length to obtain raw cotton. A known method can be used for crimping and cutting.

Next, the obtained raw cotton is made into a fiber web using a cross wrapper or the like and entangled to obtain a short fiber nonwoven fabric. Needle punching, water jet punching, or the like can be used as a method for entangling fiber webs to obtain a short fiber nonwoven fabric.

Furthermore, the obtained short fiber nonwoven fabric and woven fabric may be laminated and entangled and integrated. To entangle and integrate the short fiber nonwoven fabric and the woven fabric, the woven fabric is laminated on one or both sides of the short fiber nonwoven fabric, or the fabric is sandwiched between multiple short fiber nonwoven fabric webs, and then needle punching or water jet treatment is performed. The fibers of the short fiber nonwoven fabric and the woven fabric can be entangled with each other by punching or the like.

The apparent density of the short fiber nonwoven fabric made of composite fibers (ultrafine fiber developed fibers) after needle punching or water jet punching is preferably 0.15 g/cm ³ or more and 0.45 g/cm ³ or less. By setting the apparent density to preferably 0.15 g/cm ³ or more, the fibrous base material can have sufficient morphological stability and dimensional stability. On the other hand, by setting the apparent density to preferably 0.45 g/cm ³ or less, sufficient space for providing the polymer elastic body can be maintained.

From the viewpoint of densification, it is preferable that the nonwoven fabric thus obtained is further densified by shrinking it by dry heat, wet heat, or both. Further, the nonwoven fabric can also be compressed in the thickness direction by calendering or the like.

In the method for producing artificial leather of the present invention, before applying a precursor of an elastic polymer having a hydrophilic group, which will be described later, the fibrous base material is adjusted to a moisture content of the fibrous base material. It is preferable to include water in an amount of 5% by mass or more and 300% or less. The moisture content of the fibrous base material is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, so that water penetrates into the fine details of the fibrous base material and the fibers are well dispersed. The state will be as follows. After this state is obtained, by impregnating a precursor of an elastic polymer having a hydrophilic group, the water contained in the fibrous base material is replaced with the solution or aqueous dispersion of the precursor, thereby forming a fiber. The precursor can sufficiently penetrate into the fine details of the textured substrate, and as a result, the dispersibility of the fibers after the precursor is solidified is improved, and an artificial leather having a uniform surface quality and a good touch feeling can be obtained. becomes possible. On the other hand, by setting the water content to 300% by mass or less, preferably 250% by mass or less, more preferably 230% by mass or less, the water contained in the fibrous base material can be replaced with the solution or aqueous dispersion of the precursor. It is possible to perform the process more efficiently and to reduce the decrease in the concentration of the precursor solution or aqueous dispersion during processing.

In this case, it is preferable that the temperature of the water when the water is added is 60°C or more and 100°C or less. When the temperature of the water is 60° C. or higher and 100° C. or lower, the nonwoven fabric of the fibrous base material is shrunk and becomes denser, and at the same time, by impregnating it with water, it becomes easier for water to penetrate into the inside of the nonwoven fabric. Fiber dispersibility is further improved.

In addition, after impregnating the fibrous base material with water and before impregnating it with the precursor, use a nip roll, dryer, suction device, blower, vacuum dehydrator, etc. to prevent the moisture content of the fibrous base material from falling below 5% by mass. It may be lowered to the extent that it does not. By lowering the water content after impregnating the fibrous base material with water, as mentioned above, the water contained in the fibrous base material can be more efficiently replaced with the precursor solution or aqueous dispersion. At the same time, it is possible to reduce the decrease in the concentration of the precursor solution or aqueous dispersion during processing.

In the method for producing artificial leather of the present invention, a fibrous base material is impregnated with a precursor of an elastic polymer having a hydrophilic group. When using a nonwoven fabric as a fibrous base material, the provision of a precursor of an elastic polymer having a hydrophilic group can be applied to either a nonwoven fabric made of ultrafine fiber-expressing fibers or a nonwoven fabric made into ultrafine fibers. It can be carried out. Here, the "precursor of an elastomeric polymer having a hydrophilic group" according to the present invention refers to a precursor that becomes an elastomer having a hydrophilic group by means such as coagulation or solidification described below (hereinafter simply referred to as (sometimes abbreviated as "precursor"). For example, when a polyurethane resin having a hydrophilic group is used as a polymeric elastomer having a hydrophilic group included as a component of artificial leather, each reactive component of the polyurethane resin having a hydrophilic group, i.e., A mixture of a molecular polyol, an organic diisocyanate, a chain extender, and a component containing a hydrophilic group is a precursor of an elastomer having a hydrophilic group.

When applying the precursor to the fibrous base material, a solution or an aqueous dispersion may be used depending on the characteristics of the precursor.

When impregnating the sheet with the precursor, it is also preferable to perform nipping in the aqueous dispersion of the precursor, generation of a liquid flow by stirring, or spraying the aqueous dispersion of the precursor onto the sheet by jetting. In the artificial leather manufacturing method of the present invention, since the fibrous base material contains water when the precursor is applied, it may be difficult to impregnate the precursor by simply immersing the sheet in the aqueous dispersion of the precursor. . Therefore, by using the above method, it is possible to more easily impregnate the fibrous base material with the precursor.

In particular, in the method for producing artificial leather of the present invention, when impregnating with the precursor, the solution or aqueous dispersion of the precursor is added at a rate of 25 L/(m ² ·min) or more to 85 L/unit area/unit time. It is preferable to spray onto at least one surface of the fibrous base material at a flow rate of (m ² ·min) or less. Furthermore, it is more preferable to spray this spray onto both surfaces of the fibrous base material. By doing so, it is possible to prevent unevenness in the content of the polymer elastic body having a hydrophilic group in the thickness direction of the artificial leather. By injecting this flow rate preferably at a flow rate of 25 L/(m ² ·min) or more, more preferably 35 L/(m ² ·min) or more, and even more preferably 40 L/(m ² ·min) or more, it is possible to The moisture contained in the base material can be efficiently replaced with the solution or aqueous dispersion of the precursor, making it easier to impregnate the fibrous base material with the precursor. In addition, by setting the flow rate to preferably 85 L/(m ² ·min) or less, more preferably 75 L/(m ² ·min) or less, and even more preferably 70 L/(m ² ·min) or less, the sheet during processing can be It is possible to suppress flapping and meandering and prevent deterioration of workability.

The injection of the solution or aqueous dispersion of the precursor may be carried out in the solution or aqueous dispersion of the precursor, or may be carried out in the air.

The concentration of the precursor solution or aqueous dispersion (the content of the precursor in the precursor solution or aqueous dispersion) is 10% by mass or more from the viewpoint of storage stability of the precursor solution or aqueous dispersion. It is preferably 50% by mass or less, more preferably 15% by mass or more and 40% by mass or less.

In addition, in order to improve storage stability and film forming properties of the precursor solution or aqueous dispersion used in the present invention, a water-soluble organic solvent is added to the precursor solution in addition to the aforementioned precursor and solvent water. The content may be 40% by mass or less based on the aqueous dispersion. From the viewpoint of preserving the film-forming environment, the content of the organic solvent is more preferably 1% by mass or less.

Furthermore, in the method for producing artificial leather of the present invention, it is also preferable that an inorganic salt containing a monovalent cation is contained in the aqueous dispersion of the precursor. By containing the monovalent cation-containing inorganic salt, heat-sensitive coagulability can be imparted to the solution or aqueous dispersion of the precursor. In the present invention, thermal coagulation property means that when a precursor solution or aqueous dispersion is heated, the fluidity of the precursor solution or aqueous dispersion decreases when a certain temperature (thermal coagulation temperature) is reached, and the precursor solution or aqueous dispersion decreases in fluidity. Refers to the property of solidifying a polymer to obtain an elastic polymer having hydrophilic groups.

Since the precursor has heat-sensitive coagulability, it is possible to suppress the phenomenon in which the precursor migrates to the sheet surface with the evaporation of water, that is, the occurrence of migration. Furthermore, as water evaporates, coagulation proceeds without the precursor being unevenly distributed around the microfibers, so in the resulting artificial leather, covering of the fibers with a hydrophilic group-containing elastic polymer is suppressed. This makes it difficult to create a structure in which the movement of fibers is strongly restricted. These can make the texture of the artificial leather softer.

The heat-sensitive coagulation temperature of the solution or aqueous dispersion of the precursor is preferably 55°C or more and 80°C or less. The stability of the precursor solution or aqueous dispersion during storage is improved, and the adhesion of the polymer elastomer having a hydrophilic group to the inside of the production equipment during operation can be suppressed, so the heat-sensitive temperature can be lowered to 60°C. It is more preferable that it is above. The migration phenomenon of the precursor to the surface layer of the fibrous base material can be suppressed, and the solidification of the precursor progresses before the water evaporates from the fibrous base material, making it possible to create a solvent-based polymer elastomer precursor. It is possible to form a structure similar to when an elastomer polymer is obtained by wet coagulating a body, that is, a structure in which the elastomer polymer does not strongly constrain the ultrafine fibers. Since it is possible to obtain artificial leather that is softer and has a more resilient feel, it is more preferable that the heat-sensitive coagulation temperature is 70° C. or lower.

In the present invention, it is preferable to use an inorganic salt containing a monovalent cation as the inorganic salt used as a heat-sensitive coagulant. The monovalent cation-containing inorganic salt is preferably sodium chloride and/or sodium sulfate. In conventional methods, inorganic salts containing divalent cations such as magnesium sulfate and calcium chloride have been suitably used as heat-sensitive coagulants; Depending on the type of precursor, it is difficult to strictly control the heat-sensitive gelation temperature by adjusting the amount added. There were issues such as concerns about the On the other hand, monovalent cation-containing inorganic salts with low ionic valences have little effect on the stability of the solution or aqueous dispersion, and by adjusting the amount added, the stability of the solution or aqueous dispersion can be improved. It is possible to strictly control the heat-sensitive coagulation temperature while ensuring the following.

In the method for producing artificial leather of the present invention, the coagulation after impregnation with the precursor may be carried out by a hot water coagulation method in which the precursor is coagulated in hot water to obtain an elastomer having a hydrophilic group, or by a method in which the precursor is precipitated with an acid. Although acid coagulation methods can also be used to obtain an elastic polymer having hydrophilic groups by coagulating the precursor, heat treatment is performed at a temperature of 100°C or higher and 180°C or lower to solidify the precursor to obtain hydrophilic groups. It is preferable to use a dry heat coagulation method to obtain an elastic polymer having the following properties. This dry heat coagulation method is a very simple method in which a sheet impregnated with a precursor is heat-treated using a hot air dryer, etc., and there is no concern that the elastic polymer having hydrophilic groups will fall off, resulting in improved workability. This is an excellent method.

In the method for producing artificial leather of the present invention, the heating temperature in the dry heat coagulation method is preferably 100°C or more and 180°C or less, more preferably 120°C or more and 160°C or less. By setting the heating temperature to 100°C or higher, the precursor is quickly solidified into an elastic polymer having hydrophilic groups, and due to its own weight, the elastic polymer having hydrophilic groups is unevenly distributed on the lower surface of the artificial leather. You can prevent this from happening. Furthermore, in the present invention, a crosslinking agent may be used when using a polyurethane resin having a hydrophilic group, and in such cases, by setting the above temperature, the crosslinking reaction is sufficiently promoted and the physical properties are improved. I can do it. Further, by setting the heating temperature to 180° C. or lower, thermal deterioration of the precursor or the elastic polymer having a hydrophilic group can be suppressed.

When a sea-island composite fiber is used as the microfiber-expressing fiber, the fiber ultrafine treatment (de-sea treatment) can be performed, for example, by immersing the sea-island composite fiber in a solvent and squeezing the liquid. As a solvent for dissolving the sea component, an alkaline aqueous solution such as sodium hydroxide or hot water can be used.

In the ultrafine fiber development step, devices such as a continuous dyeing machine, a vibrowasher type de-seaper, a jet dyeing machine, a wince dyeing machine, a jigger dyeing machine, etc. can be used.

After the ultrafine fiber development step, it is preferable to perform a sufficient washing step after the alkali treatment. By going through the cleaning process, the artificial leather can be processed without leaving any alkali or monovalent cation-containing inorganic salts on the sheet, and can be processed without affecting production equipment. In consideration of the environment and safety, it is preferable to use water as the cleaning liquid.

Regarding the drying temperature, if the temperature is too low, a long drying time will be required, and if the temperature is too high, thermal decomposition of the polyurethane will be accelerated, so it is preferable to dry at a temperature of 80°C or more and 200°C or less, more preferably The temperature is 120°C or more and 190°C or less, more preferably 150°C or more and 180°C or less.

In the present invention, at least one side of the artificial leather may be subjected to a napping treatment to form raised naps on the surface. The method for forming the nap is not particularly limited, and various methods commonly used in the art, such as buffing with sandpaper, etc., can be used. If the nap length is too short, it is difficult to obtain an elegant appearance, and if it is too long, pilling tends to occur. Therefore, the nap length is preferably 0.2 mm or more and 1 mm or less.

Furthermore, in one embodiment of the present invention, silicone or the like may be applied as a lubricant to the artificial leather before the napping treatment. By adding a lubricant, it becomes possible to easily raise the fluff by surface grinding, and the surface quality becomes very good, which is preferable. Further, an antistatic agent may be applied before the napping treatment. This is a preferred embodiment because the addition of an antistatic agent makes it difficult for grinding dust generated from the artificial leather to accumulate on the sandpaper during grinding.

Artificial leather can be dyed. As this dyeing process, various methods commonly used in this field can be adopted, such as jet dyeing process using a jigger dyeing machine or jet dyeing machine, thermosol dyeing process using a continuous dyeing machine, etc. Dip dyeing treatment, or printing treatment on the raised surface by roller printing, screen printing, inkjet printing, sublimation printing, vacuum sublimation printing, etc. can be used. Among these, it is preferable to use a jet dyeing machine because it is possible to soften the unraised artificial leather or artificial leather by imparting a rubbing effect to the unraised artificial leather or artificial leather at the same time as dyeing the unraised artificial leather or artificial leather. Moreover, various resin finishing processes can be applied after dyeing, if necessary.

The dyeing temperature is preferably 80°C or higher and 150°C or lower, although it depends on the type of fiber. By setting the dyeing temperature to 80°C or higher, more preferably 110°C or higher, the fibers can be dyed efficiently. On the other hand, by setting the dyeing temperature to 150° C. or lower, more preferably 130° C. or lower, deterioration of the polymer elastic body can be prevented.

The dye used in the present invention may be selected according to the type of fiber constituting the fibrous base material and is not particularly limited, but for example, a disperse dye can be used for polyester fiber, and a disperse dye can be used for polyester fiber. If so, acidic dyes and metal-containing dyes can be used, and combinations thereof can also be used. When dyeing with a disperse dye, reduction washing may be performed after dyeing.

It is also a preferred embodiment to use a dyeing aid during dyeing. By using a dyeing aid, the uniformity and reproducibility of dyeing can be improved. Further, in the same bath as dyeing or after dyeing, finishing agent treatment using, for example, a softening agent such as silicone, an antistatic agent, a water repellent, a flame retardant, a light-resistant agent, an antibacterial agent, etc. can be performed.

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

Furthermore, in one embodiment of the present invention, a design can be applied to the surface if necessary. For example, post-processing treatments such as perforation, embossing, laser processing, pinsonic processing, and printing can be performed.

Next, the artificial leather of the present invention will be explained in more detail using Examples. However, the present invention is not limited only to these examples. In addition, in the measurement of each physical property, unless otherwise specified, the measurement was performed based on the method described above.

[Evaluation method]
(1) Coefficient of variation (%) of the number of ultrafine fiber cross sections existing in each section when the observation range is divided into 8 equal parts
A cross section of the artificial leather cut in the thickness direction was photographed at a magnification of 500x using a scanning electron microscope (SEM) "VHX-D500/D510" manufactured by Keyence Corporation, satisfying the observation range conditions described above. Then, by the method described above, when the observation range was divided into eight equal parts, the coefficient of variation of the number of ultrafine fiber cross sections present in each division was measured and calculated. Hereinafter, the coefficient of variation of the number of ultrafine fiber cross sections existing in each section when the observation range is divided into eight equal parts will be simply referred to as the "coefficient of variation of the number of ultrafine fiber cross sections", including Tables 1 to 4. May be abbreviated.

(2) Average fiber length of ultrafine fibers (mm)
According to the above method, 10 ultrafine fibers were extracted from each of three arbitrary locations on the artificial leather using tweezers, the fiber length was measured, and the number average of the 30 measured fiber lengths was calculated.

(3) Number of ultrafine fibers forming a fiber bundle (pieces)
A cross section of the artificial leather cut in the thickness direction was examined using a scanning electron microscope (SEM) "VHX-D500/D510" manufactured by Keyence Corporation at a magnification of 1500x, satisfying the conditions of the observation range described above. The number of ultrafine fibers forming the fiber bundle was measured for each of the 10 images, and the average value was calculated.

(4) Surface quality Evaluated by sensory test of 11 subjects. The surface quality of the artificial leather was evaluated as described below, and the level evaluated by the largest number of people was determined as the surface quality of the artificial leather. In addition, in the case of the same number of evaluations, the higher evaluation was determined to be the surface quality of the artificial leather. In the present invention, a good level is "A or B".
-A: Very uniform surface quality.
-B: Uniform surface quality.
-C: Non-uniform surface quality.
-D: Very uneven surface quality.

(5) Touch Evaluated by sensory test of 11 subjects. The evaluation was performed as shown below, and the level that received the highest number of evaluations was defined as the touch of artificial leather. If the level with the largest number of evaluations was the same, and if the evaluations were the same, the surface quality of the artificial leather was determined to be higher. In the present invention, a good level is "A or B".
- A: Very good touch with good fiber dispersion.
-B: The dispersion state of the fibers is slightly good and the touch is good.
- C: The dispersion state of the fibers is somewhat poor and the touch is poor.
- D: Very poor touch due to poor fiber dispersion.

(6) Abrasion resistance Measured according to "8.19.5E method (Martindale method)" of "8.19 Abrasion strength and friction discoloration" of JIS L1096:2010 "Testing methods for woven and knitted fabrics" In the abrasion resistance test, the press load was set to 12.0 kPa (for furniture, carpets, etc.), and the weight loss of the sheet-like material after being worn 20,000 times was evaluated, and a weight loss of 9 mg or less was considered to be a pass. The results of this abrasion resistance test are simply expressed as "abrasion loss" in Tables 1 to 4.

[Example 1]
(Nonwoven fabric)
Using 8 mol% sodium 5-sulfoisophthalate (SSIA) copolyester as the sea component and polyethylene terephthalate as the island component, the number of islands was determined with a composite ratio of 20% by mass for the sea component and 80% by mass for the island component. A sea-island composite fiber having 16 islands/1 filament and an average single fiber diameter of 20 μm was obtained. The obtained sea-island composite fibers were cut into staples with a fiber length of 51 mm, passed through a card and a cross wrapper to form a fiber web, and then subjected to needle punching to produce a nonwoven fabric with a basis weight of 700 g/m ² and a thickness of 3.0 mm. I got it. The thus obtained nonwoven fabric was soaked in water at a temperature of 98° C. so that the water content was 40%. Specifically, after shrinking by immersing it in the water described above for 2 minutes, the water content was reduced using a vacuum dehydrator.

(Providing precursor of elastic polymer having hydrophilic group)
Precursor (polytetramethylene ether glycol with a number average molecular weight (Mn) of 2000 as a polymeric polyol, MDI as an organic diisocyanate, ethylene glycol and ethylene diamine as chain extenders, 2,2 as a component to add a hydrophilic machine to polyurethane - dimethylolpropionic acid and a mixture thereof), sodium sulfate as a heat-sensitive coagulant, a carbodiimide crosslinking agent, and water, the precursor is An aqueous dispersion containing a precursor was prepared, containing 5% by mass of the heat-sensitive coagulant and 0.6% by mass of the carbodiimide crosslinking agent. Then, the nonwoven fabric with a moisture content of 40% is immersed in this aqueous dispersion, and a flow rate of 55 L/(m ² min) per unit area/unit time is applied toward both sides of the nonwoven fabric in the aqueous dispersion. The aqueous dispersion was sprayed. Next, by drying with hot air at a temperature of 120°C for 20 minutes, the hydrophilic groups are removed so that when the sheet is made into a sheet, the elastomer polymer having hydrophilic groups accounts for 28% by mass in 100% by mass of the sheet. A nonwoven fabric having a thickness of 2.10 mm and having a polymer elastic body provided thereon was obtained.

(Ultra-fine fiber development treatment)
The obtained nonwoven fabric with a polymer elastic body was immersed in a sodium hydroxide aqueous solution with a concentration of 50 g/L heated to a temperature of 95°C and treated for 5 minutes to remove the sea component of the sea-island composite fiber (de-sea). By doing so, ultrafine fibers were developed. Thereafter, the aqueous sodium hydroxide solution adhering to the nonwoven fabric was immersed in water, washed for 30 minutes, and dried in a dryer at 160°C for 30 minutes to obtain a sheet consisting of ultrafine fibers and an elastic polymer having a hydrophilic group. Ta.

(dyeing/finishing)
The obtained sheet after sea removal was cut in half perpendicularly to the thickness direction, and the opposite side of the half-cut surface was ground with endless sandpaper of sandpaper grit No. 180, so that the surface with a thickness of 0.75 mm was raised. Got a sheet.

The obtained sheet was dyed with a black dye at a temperature of 120° C. using a jet dyeing machine, and then dried in a drier to obtain artificial leather. The results are shown in Table 1. The obtained artificial leather has a surface layer with uniform surface quality and a good touch feeling. The coefficient of variation in the number of fiber cross sections was 30%, and the number of ultrafine fibers forming the fiber bundle was 23. Further, the weight loss due to abrasion was 7.3 mg.

[Example 2]
Artificial leather was produced in the same manner as in Example 1 (nonwoven fabric) except that the number of islands of the sea-island composite fiber was changed to 36 islands/1 filament. The results are shown in Table 1. The water content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 50%. In addition, the obtained artificial leather has uniform surface quality and good touch, and the average single fiber diameter of the ultrafine fibers of the obtained artificial leather is 2.1 μm, the average fiber length of the ultrafine fibers is 51 mm, The coefficient of variation of the number of ultrafine fiber cross sections was 28%, the number of ultrafine fibers forming the fiber bundle was 23, and the loss by abrasion was 8.6 mg.

[Example 3]
In the (nonwoven fabric) of Example 1, the water content was reduced by a vacuum dehydrator after being immersed in water for 2 minutes to shrink, but the difference was that the water content was not reduced by the vacuum dehydrator. , Artificial leather was produced in the same manner. The results are shown in Table 1. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 200%. In addition, the obtained artificial leather has uniform surface quality and good touch, and the average single fiber diameter of the ultrafine fibers of the obtained artificial leather is 4.4 μm, the average fiber length of the ultrafine fibers is 51 mm, The coefficient of variation of the number of ultrafine fiber cross sections was 25%, the number of ultrafine fibers forming the fiber bundle was 14, and the abrasion loss was 7.6 mg.

[Example 4]
In Example 1 (non-woven fabric), the non-woven fabric had a basis weight of 700 g/m ² and a thickness of 3.0 mm, but the non-woven fabric had a basis weight of 670 g/m ² and a thickness of 2.5 mm. Artificial leather was produced in the same manner. The results are shown in Table 1. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 70%. In addition, the obtained artificial leather has uniform surface quality and good touch, and the average single fiber diameter of the ultrafine fibers of the obtained artificial leather is 4.4 μm, the average fiber length of the ultrafine fibers is 51 mm, The coefficient of variation of the number of ultrafine fiber cross sections was 40%, the number of ultrafine fibers forming the fiber bundle was 20, and the abrasion loss was 6.9 mg.

[Example 5]
Artificial leather was produced in the same manner as in Example 1 (nonwoven fabric) except that the temperature of the water was changed from 98°C to 25°C. The results are shown in Table 2. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 100%. Although the obtained artificial leather was slightly inferior to that of Example 1, it had uniform surface quality and good touch, and the average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm. The average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of cross sections of the ultrafine fibers was 33%, the number of ultrafine fibers forming the fiber bundle was 18, and the abrasion loss was 8.8 mg.

[Example 6]
In Example 1 (providing a precursor of an elastic polymer having a hydrophilic group), a nonwoven fabric was immersed in an aqueous dispersion, and the aqueous dispersion was sprayed toward both sides of the nonwoven fabric in the aqueous dispersion. Artificial leather was produced in the same manner as above, except that the nonwoven fabric was not immersed in the aqueous dispersion, but the aqueous dispersion was sprayed onto both sides of the nonwoven fabric in the air. The results are shown in Table 2. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 40%. Although the uniformity of the surface quality of the obtained artificial leather is slightly inferior to that of the artificial leather of Example 1, it has a good touch, and the average single fiber diameter of the ultrafine fibers of the obtained artificial leather is 4. .4 μm, the average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 40%, the number of ultrafine fibers forming the fiber bundle was 12, and the abrasion loss was 8.2 mg.

[Example 7]
In Example 1 (providing a precursor of an elastic polymer having a hydrophilic group), when the aqueous dispersion was being sprayed toward both sides of the nonwoven fabric, one side of the nonwoven fabric Artificial leather was produced in the same manner, except that the process was performed only on The results are shown in Table 2. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 40%. Although the obtained artificial leather is slightly inferior to that of Example 1, it has a uniform surface quality and good touch, and the average single fiber diameter of the ultrafine fibers of the obtained artificial leather is 4.4 μm, which is extremely fine. The average fiber length of the fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 46%, the number of ultrafine fibers forming the fiber bundle was 22, and the loss by abrasion was 7.5 mg. The evaluation of surface quality, touch, and abrasion loss was performed on the artificial leather on the side on which the aqueous dispersion was sprayed.

[Comparative example 1]
In the (nonwoven fabric) of Example 1, the nonwoven fabric was immersed in water at a temperature of 98°C for 2 minutes to shrink, and then the moisture content was lowered using a vacuum dehydrator, and water was added so that the moisture content was 40%. The nonwoven fabric was immersed in water at a temperature of 98°C for 2 minutes to shrink, and then dried at a temperature of 100°C for 5 minutes to lower the moisture content and impregnated with the aqueous dispersion of the precursor. Artificial leather was produced in the same manner except that the moisture content of the nonwoven fabric was 0%. The results are shown in Table 3. In addition, the obtained artificial leather had a surface quality in which the density of the nap was uneven, and the touch was also poor. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 65%, and the number of ultrafine fibers forming a fiber bundle. There were 21 pieces, and the weight loss from abrasion was 10.2 mg.

[Comparative example 2]
In the (nonwoven fabric) of Example 1, the nonwoven fabric was immersed in water at a temperature of 98°C for 2 minutes to shrink, and then the moisture content was lowered using a vacuum dehydrator, and water was added so that the moisture content was 40%. Except that the nonwoven fabric was not immersed in water and the moisture content was not lowered, and the moisture content of the nonwoven fabric was 0% before being impregnated with the aqueous dispersion of the precursor. produced artificial leather in the same manner. The results are shown in Table 3. In addition, the obtained artificial leather had a surface quality in which the density of the nap was uneven, and the touch was also poor. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 77%, and the number of ultrafine fibers forming a fiber bundle. There were 19 pieces, and the weight loss from abrasion was 13.8 mg.

[Comparative example 3]
Artificial leather was produced in the same manner as in Example 1 (nonwoven fabric) except that the number of islands of the sea-island composite fiber was 4 islands/1 filament. The results are shown in Table 3. The water content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 50%. In addition, the obtained artificial leather had a surface quality such that the distance between the raised naps was wide and the texture was less dense. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 33%, and the number of ultrafine fibers forming a fiber bundle. There were 3 pieces, and the weight loss from abrasion was 8.6 mg.

[Comparative example 4]
In Example 1 (providing a precursor of an elastic polymer having a hydrophilic group), 55 L/(m ² min) per unit area/unit time was applied to both sides of the nonwoven fabric in an aqueous dispersion. Artificial leather was produced in the same manner except that the aqueous dispersion was injected at a flow rate of 20 L/(m ² ·min) per unit area/unit time. The results are shown in Table 3. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 40%. In addition, the obtained artificial leather had a surface quality in which the density of the raised piles was uneven. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 62%, and the number of ultrafine fibers forming a fiber bundle. There were 9 pieces, and the weight loss from abrasion was 9.5 mg.

[Comparative example 5]
In Example 1 (providing a precursor of a polymeric elastomer having a hydrophilic group), a nonwoven fabric was immersed in an aqueous dispersion, and the aqueous dispersion was jetted toward both sides of the nonwoven fabric in the aqueous dispersion. Artificial leather was produced in the same manner as above, except that the nonwoven fabric was only immersed in the aqueous dispersion without spraying the aqueous dispersion. The results are shown in Table 4. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 40%. In addition, the obtained artificial leather had a surface quality in which the density of the raised piles was uneven. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 70%, and the number of ultrafine fibers forming a fiber bundle. There were 8 pieces, and the abrasion loss was 9.6 mg.

[Comparative example 6]
Artificial leather was produced in the same manner as in Example 1 (nonwoven fabric) except that the sea-island composite fibers were cut into staples with a fiber length of 51 mm, but were cut into fiber lengths of 20 mm. The results are shown in Table 4. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 40%. In addition, the obtained artificial leather had a surface quality such that the spacing between the naps was wide and the texture was less dense. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 20 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 31%, and the number of ultrafine fibers forming a fiber bundle. There were 25 pieces, and the weight loss from abrasion was 13.5 mg.

[Comparative Example 7]
Artificial leather was produced in the same manner as in Example 1 (nonwoven fabric) except that the sea-island composite fibers were cut into staples with a fiber length of 51 mm, but the fiber length was changed to 150 mm. The results are shown in Table 4. The moisture content of the nonwoven fabric before being impregnated with the aqueous dispersion of the precursor was 70%. In addition, the obtained artificial leather had long naps and rough surface quality, and in addition, the touch was also poor. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 150 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 44%, and the number of ultrafine fibers forming a fiber bundle. There were 28 pieces, and the weight loss from abrasion was 8.2 mg.

[Comparative example 8]
(Nonwoven fabric)
In Example 1 (nonwoven fabric), after obtaining a nonwoven fabric with a basis weight of 700 g/m ² and a thickness of 3.0 mm, the obtained nonwoven fabric was immersed in water at a temperature of 98° C. for 2 minutes to shrink. Water was being added to the product using a vacuum dehydrator to give a water content of 40%, but the process was changed to include the following.

That is, first, in the (nonwoven fabric) of Example 1, a nonwoven fabric with a basis weight of 700 g/m ² and a thickness of 3.0 mm was obtained, and then the obtained nonwoven fabric was immersed in water at 98° C. for 2 minutes to shrink. Ta. Thereafter, it was directly impregnated with a polyvinyl alcohol (PVA) aqueous solution having a saponification degree of 98% and a polymerization degree of 450, which was prepared to a concentration of 12% by mass. This was further squeezed with a roll, dried by heating with hot air at a temperature of 140°C for 10 minutes, and then heat treated at a temperature of 160°C for 5 minutes to obtain a PVA-coated sheet with a PVA mass of 25% by mass based on the mass of the nonwoven fabric. Obtained. The obtained PVA-coated sheet was immersed in a sodium hydroxide aqueous solution with a concentration of 80 g/L heated to a temperature of 60° C. and treated for 30 minutes to obtain a PVA-coated sheet from which the sea portion of the sea-island composite fibers had been removed.

(Providing precursor of elastic polymer having hydrophilic group)
In the same manner as in Example 1, an aqueous dispersion containing the precursor was prepared, the PVA-coated sheet obtained as described above was immersed in the aqueous dispersion, and both sides of the nonwoven fabric were coated in the aqueous dispersion. The aqueous dispersion was sprayed at a flow rate of 55 L/(m ² ·min) per unit area and unit time. Next, a sheet was obtained by drying with hot air at a temperature of 120° C. for 20 minutes. Then, the obtained sheet is immersed in water heated to 95°C for 10 minutes to remove the applied PVA. A polymer elastic material-added nonwoven fabric having a thickness of 2.10 mm was obtained, in which a polymer elastic material having a hydrophilic group was added so that the molecular elastic material amounted to 28% by mass.

(dyeing/finishing)
Artificial leather was produced in the same manner as in Example 1 (dying/finishing). The results are shown in Table 4. The obtained artificial leather had a surface quality with uneven nape density and poor touch. The average single fiber diameter of the ultrafine fibers of the obtained artificial leather was 4.4 μm, the average fiber length of the ultrafine fibers was 51 mm, the coefficient of variation of the number of ultrafine fiber cross sections was 82%, and the number of ultrafine fibers forming a fiber bundle. There were 22 pieces, and the weight loss from abrasion was 11.1 mg.

The artificial leathers of Examples 1 to 7 were produced by controlling the moisture content of the nonwoven fabric to 5% or more and 300% or less before immersing it in an aqueous dispersion containing a precursor of a polymeric elastomer having a hydrophilic group. It was possible to obtain artificial leather in which the elastomer and the polymeric elastomer were uniformly distributed, and had uniform surface quality and good touch. Among them, the artificial leather of Example 4 was able to obtain particularly excellent abrasion resistance by using a nonwoven fabric with higher density.

On the other hand, in the artificial leathers of Comparative Examples 1 and 2, since the nonwoven fabrics were not immersed in water before being immersed in the water dispersion, the distribution of the ultrafine fibers and the polymeric elastomer was uneven, resulting in raised naps. The artificial leather had a surface quality with uneven density and poor touch.

In addition, the artificial leather of Comparative Example 3 had a surface quality such that the spacing between the napped fibers was wide and the feeling of density was low by reducing the number of ultrafine fibers forming the fiber bundle.

In the artificial leathers of Comparative Examples 4 and 5, the flow rate of the polymeric elastic material sprayed onto the nonwoven fabric during impregnation with the polymeric elastic material was insufficient, so the polymeric elastic material was not applied to the inside of the artificial leather, resulting in raised naps. The resulting artificial leather has a surface quality with uneven density.

In addition, the artificial leather of Comparative Example 6 had a short fiber length of the ultrafine fibers, resulting in an artificial leather with a surface quality such that the spacing between the napped fibers was wide and the texture was less dense.

Furthermore, the artificial leather of Comparative Example 7 had a long nap length and rough surface quality by increasing the fiber length of the ultrafine fibers, and in addition, the artificial leather had poor touch.

Finally, because the artificial leather of Comparative Example 8 was coated with PVA before being immersed in the aqueous dispersion, the distribution of the polymeric elastic material was uneven, resulting in a surface quality with uneven nape density. The resulting artificial leather also had poor touch.

Claims (5)

An artificial leather comprising as constituent elements a fibrous base material including a nonwoven fabric made of ultrafine fibers with an average single fiber diameter of 0.1 μm or more and 10.0 μm or less, and an elastic polymer having a hydrophilic group, the artificial leather comprising: The average fiber length of the ultrafine fibers is 25 mm or more and 90 mm or less, the ultrafine fibers form a fiber bundle of 5 or more and 200 or less, and a scanning electron microscope of a cross section cut perpendicular to the surface of the artificial leather. In a photograph, an artificial leather having a variation coefficient of 50% or less in the number of fiber cross sections present in each division when the observation range of the scanning electron micrograph is equally divided into eight divisions. A fibrous base material containing a nonwoven fabric made of microfiber-generating fibers is impregnated with water such that the water content of the fibrous base material is 5% by mass or more and 300% or less, and further, a polymer having a hydrophilic group is added. A solution or aqueous dispersion of a precursor of an elastic body is applied to at least one surface of the fibrous base material at a flow rate of 25 L/(m ² ·min) to 85 L/(m ² ·min) per unit area and unit time. The method for producing artificial leather according to claim 1, wherein the method comprises impregnating the artificial leather by spraying the impregnated leather onto the material. The method for manufacturing artificial leather according to claim 2, wherein the water when impregnated with water is at a temperature of 60°C or more and 100°C or less. The method for producing artificial leather according to claim 2 or 3, wherein the injection is performed in a solution or an aqueous dispersion of the precursor. The method for producing artificial leather according to any one of claims 2 to 4, wherein the spraying is performed on both surfaces of the fibrous base material.