Artificial leather base material, napped artificial leather, and grain-finished artificial leather

Abstract

This artificial leather base material comprises: non-woven fabric obtained by tying microfibers together; and polyurethane that the non-woven fabric is impregnated with. The polyurethane contains the following with respect to all of the polymeric polyol units: 60-95% of condensed polyester polyol units; and 5-25% of polyether polyol units selected from the group consisting of polyethylene glycol units and polypropylene glycol units. The condensed polyester polyol units do not include a ring structure, and have repeating units each containing 5-7 carbon atoms on average, excluding the carbon in ester bonds. The porosity of a polyurethane region including the polyurethane and vacancies surrounded by the polyurethane is 30% or less. The area of the polyurethane region accounts for 10-30% of the entire cross-sectional area.

Description

Artificial leather base material, raised artificial leather and grained artificial leather

[0001] The present invention relates to an artificial leather that is preferably used as a material for clothing, bags, shoes, furniture, car seats, miscellaneous goods, etc.

[0002] Artificial leathers are known, such as suede-like raised artificial leathers that use an artificial leather substrate containing a nonwoven fabric impregnated with polyurethane, and grain-finish artificial leathers that have a grain-finish resin layer formed on the surface. These artificial leathers are required to have a supple texture, as well as mechanical properties and durability that can withstand practical use.

[0003] For example, the following techniques are known for improving artificial leather containing polyurethane.

[0004] Patent Document 1 below discloses a method for producing polyurethane-containing artificial leather, which uses an impregnation solution mainly composed of a hydrophobic polyurethane containing at least one soft segment selected from polytetramethylene ether, polypropylene ether, polycaprolactone, polyvalerolactone, polyβ-methyl-δ valerolactone, and polyhexamethylene adipate, and adds to the impregnation solution at least one solidification regulator selected from higher alcohols having 8 or more carbon atoms, alcohol-modified silicone oil, polyoxyalkylphenyl ether, and sorbitan fatty acid ester.

[0005] Furthermore, Patent Document 2 listed below discloses a method for producing a sheet-like material, which comprises impregnating and / or coating a fibrous substrate with a polyurethane elastomer composition liquid, which comprises (a) a polyester diol obtained by condensation polymerization of a diol containing 1,9-nonanediol and / or 2-methyl-1,8-octanediol as the main component with a dicarboxylic acid, a polyoxyalkylene glycol, an organic diisocyanate, and a chain extender, (b) a polyether-modified silicone oil, (c) a polyoxyethylene-polyoxypropylene block copolymer, and (d) a solvent, wherein the total amount of components (b) and (c) is 0.5 to 50 wt % relative to component (a), and the weight ratio of component (b) to component (c) is 1 / 20 to 5 / 1, and the liquid is then coagulated with a non-solution of the polyurethane elastomer.

[0006] Furthermore, Patent Document 3 listed below discloses a napped artificial leather that is a sheet-like material containing polyurethane inside a fiber substrate comprising ultrafine fibers with an average single fiber diameter of 0.3 to 7 μm and having napped portions on at least one surface, the sheet-like material having a compressibility P of 7 to 14% and a compressive modulus Pe of 30 to 70% under an initial load of 0.5 kPa and a constant load of 30 kPa, as measured by the method of JIS L1913.

[0007] Furthermore, Patent Document 4 listed below discloses a method for producing an artificial leather, which comprises adhering an elastic sheet stretched by 15% or more in the longitudinal and / or transverse directions to an artificial leather substrate composed of polyurethane and a nonwoven fabric containing ultrafine fibers with a single fiber fineness of 0.9 dtex or less, and then relaxing the stretch of the elastic sheet to shrink the artificial leather substrate, and then removing the elastic sheet.

[0008] Furthermore, Patent Document 5 listed below discloses an artificial leather made substantially of a fibrous material, in which an ultrafine fiber nonwoven fabric having an average fiber fineness of 0.001 to 0.5 dtex is entangled and integrated with a woven fabric, one surface of the artificial leather is made of entangled ultrafine fibers that are continuous in the surface direction, and the other surface is made of discontinuous ultrafine fibers that form a surface, and the artificial leather has a drape coefficient of 0.35 to 0.5 and an elongation rate of 10 to 35% in at least one of the warp and weft directions.

[0009] Japanese Patent Laid-Open No. 1-239177 Japanese Patent Laid-Open No. 2-264086 International Publication No. 2016-031694 Pamphlet Japanese Patent Laid-Open No. 2004-197282 Japanese Patent Laid-Open No. 2007-197889

[0010] Polyurethanes used in the production of artificial leather include polyester-based polyurethanes, polyether-based polyurethanes, and polycarbonate-based polyurethanes, depending on the type of polymeric polyol unit. Polyester-based polyurethanes tend to produce artificial leather with excellent mechanical properties due to their excellent adhesion to fibers, but they have poor hydrolysis resistance. Polyether-based polyurethanes tend to produce artificial leather with a supple texture, but they are prone to poor recovery when deformed by force during use and to leaving dents when stretched or compressed. Another problem is that they result in artificial leather with poor resistance to oxidation and deterioration. Polycarbonate-based polyurethanes tend to produce artificial leather with excellent hydrolysis resistance and durability, but tend to produce artificial leather with a hard texture due to their high resilience. Thus, artificial leathers produced using each polyurethane have their own advantages and disadvantages.

[0011] Furthermore, when polyurethane with a low modulus is used, it is easy to obtain artificial leather with a soft feel, but there are problems such as the artificial leather being difficult to recover when deformed by the application of force during use, leaving dents when stretched or compressed, and having low durability in terms of hydrolysis resistance and resistance to oxidative degradation.

[0012] For example, Patent Document 1 discloses that artificial leather with improved texture and hydrolysis resistance can be obtained by using a polyurethane containing polytetramethylene ether, polypropylene ether, and a ring-opening polyester polyol whose repeating units have an average carbon number of 4 to 6, excluding the carbon atoms in the ester bonds, and by selecting a coagulation regulator. However, polyurethanes using ring-opening polyester polyols whose repeating units have an average carbon number of 4 to 6, excluding the carbon atoms in the ester bonds, tend to be more crystalline than polyurethanes containing condensation polyester polyols obtained by the condensation reaction of a diol and a dicarboxylic acid. In this case, the polyurethane solution tends to coagulate quickly, coagulating before the polyurethane has fully coagulated, resulting in artificial leather with a hard, rough texture. Furthermore, polyurethanes containing polyester polyol units whose repeating units have an average carbon number of 4, excluding the carbon atoms in the ester bonds, tend to have poor hydrolysis resistance. Furthermore, polyurethanes obtained by combining polyester polyol units having an average carbon number of 4 in the repeating units, excluding the carbon atoms of the ester bonds, with polytetramethylene ether units or polypropylene ether units in a polymer polyol amounting to 40% by mass or more were prone to oxidative degradation due to the ether bonds.

[0013] Furthermore, Patent Document 2 discloses a method for producing artificial leather, which uses a polyurethane containing condensation polyester polyol units and polytetramethylene ether units, each of which has an average carbon number between ester bonds in the repeating units of 6.5 (diol component: 9, dicarboxylic acid component: 4), excluding the carbon atoms in the ester bonds, and selects a coagulation regulator to be incorporated into the polyurethane solution. This production method is disclosed to improve the texture and hydrolysis resistance of the artificial leather. However, because the condensation polyester polyol units, each of which has an average carbon number between ester bonds in the repeating units of 6.5, excluding the carbon atoms in the ester bonds, are also highly crystalline, they tend to coagulate before the polyurethane has fully coagulated, resulting in a problem of a hard texture and a rough feel in the resulting artificial leather. Furthermore, polyurethanes obtained by combining condensation polyester polyol units, each of which has an average carbon number between ester bonds in the repeating units of 6.5, excluding the carbon atoms in the ester bonds, with 40% or more by mass of polytetramethylene ether in the polymer polyol, were also susceptible to oxidative degradation due to the ether bonds.

[0014] The present invention aims to provide an artificial leather that solves the above-mentioned problems, which contains polyurethane and has excellent resistance to hydrolysis and oxidation degradation, and also has a supple texture, a smooth feel, and mechanical properties that allow the leather to easily recover from deformation caused by force during use.

[0015] In the production of artificial leather, by impregnating a nonwoven fabric with a polyurethane containing polyester polyol units as high molecular weight polyol units, the polyurethane has excellent adhesion to fibers, resulting in artificial leather with excellent mechanical properties. However, the present inventors recognized that polyurethanes containing polyester polyol units as high molecular weight polyol units have poor hydrolysis resistance.

[0016] The present inventors also recognized that if the average number of carbon atoms in the repeating units of the polyester polyol units, excluding the carbon atoms in the ester bonds between the ester bonds, is too small, the proportion of ester bonds becomes relatively high, and the hydrolysis resistance of the polyurethane tends to be particularly reduced. Furthermore, if the average number of carbon atoms is too large, the hydrolysis resistance of the polyurethane improves, but the hydrophobicity and crystallinity become high, resulting in rapid coagulation. Therefore, the polyurethane does not sufficiently aggregate and coagulate, which can lead to the problem of a hard texture and a rough feel in the resulting artificial leather.

[0017] The present inventors have discovered that an artificial leather substrate obtained by impregnating a nonwoven fabric with a polyurethane containing, in the polymer polyol units, 60 to 95% by mass of condensation polyester polyol units having an average carbon number of 5 to 7 between the ester bonds in the repeating units, excluding the carbon atoms in the ester bonds, and 5 to 25% by mass of one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, can provide a polyurethane in a highly cohesive state and easily recover from deformation. Furthermore, the present inventors have discovered that such polyurethane provides artificial leather with excellent resistance to hydrolysis and oxidation degradation, as well as a supple feel, a smooth touch, and an excellent balance of mechanical properties, such as easy recovery from deformation under force, which led to the completion of the present invention.

[0018] That is, one aspect of the present invention is an artificial leather substrate comprising a nonwoven fabric in which ultrafine fibers having an average fiber diameter of 0.1 to 7 μm are entangled, and polyurethane impregnated into the nonwoven fabric, wherein the polyurethane contains, based on the total amount of high molecular weight polyol units, 60 to 95 mass% of condensation polyester polyol units and 5 to 25 mass% of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, wherein the condensation polyester polyol units do not contain a ring structure and the average number of carbon atoms between ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, is 5 to 7, and in a cross section in the thickness direction of the artificial leather substrate, the porosity of a polyurethane region, which includes the polyurethane and voids surrounded by the polyurethane, is 30 area % or less, and the area ratio of the polyurethane region to the total cross-sectional area of ​​the cross section in the thickness direction is 10 to 30 area %. Such an artificial leather substrate can provide an artificial leather that has excellent resistance to hydrolysis and oxidation degradation due to the polyurethane contained therein, as well as a supple texture, a smooth feel, and mechanical properties that allow it to easily recover when deformed by the application of force during use.

[0019] Furthermore, it is preferable that the 100% modulus of the polyurethane is 5 to 15 MPa, since the state of aggregation of the polyurethane solidified in an appropriate state of aggregation is easily maintained through each step in the production process and in actual use.

[0020] In addition, it is preferable that the content of polyurethane in the artificial leather substrate is 15 to 55 mass %, since this makes it easier to obtain artificial leather in which, in a cross section in the thickness direction, the porosity of the polyurethane region, which includes polyurethane and voids surrounded by polyurethane, is 30 area % or less, and the area ratio of the polyurethane region to the total cross-sectional area in the thickness direction is 10 to 30 area %.

[0021] Furthermore, the polyurethane may contain, for example, 0 to 35 mass% of polyether polyol units having an average carbon number of 4 or more in the repeating unit, within a range that does not impair the effects of the present invention, based on the total amount of high molecular weight polyol units. Note that, for example, an expression such as 0 to 35 mass% means 0 mass% or more and 35 mass% or less, and includes 0 mass%.

[0022] Furthermore, it is preferable that the artificial leather substrate has a compressibility P of 15 to 35% and a compressive modulus Pe of 85% or more when subjected to a constant load of 30 kPa against an initial load of 0.5 kPa, as measured in accordance with the method described in 6.14 of JIS L 1913:2010, since this facilitates the production of an artificial leather that is highly deformable and recovers easily, resulting in an excellent luxurious feel.

[0023] The artificial leather substrate also has a 30% elongation modulus E, which is the recovery rate of elongation after 30% elongation, measured in accordance with the method described in 8.15.1A of JIS L 1096:2010. 30 It is preferable that the elastic modulus is 65 to 90% in order to obtain an artificial leather that easily returns to its original shape after stress is applied, has excellent dimensional stability, and excels in a luxurious feel.

[0024] Another aspect of the present invention is a napped artificial leather comprising any one of the above artificial leather substrates and having at least one surface of the artificial leather substrate with a napped surface formed by raising ultrafine fibers. Such a napped artificial leather has a supple texture and a smooth feel due to the napped surface, and is also preferable because it has pilling resistance sufficient for practical use, and in particular, due to the excellent hydrolysis resistance and oxidative degradation resistance of polyurethane, it is easy to obtain a napped artificial leather that combines pilling resistance with wet heat durability and dry heat durability.

[0025] Another aspect of the present invention is a grain-finish artificial leather comprising any one of the above-described artificial leather substrates and a resin layer laminated on the artificial leather substrate. Such grain-finish artificial leather is easily resilient to deformation, has excellent crease resistance, and is also excellent in hydrolysis resistance.

[0026] That is, the present disclosure includes the following aspects.

[0027] [1] An artificial leather substrate comprising a nonwoven fabric formed by entanglement of ultrafine fibers having an average fiber diameter of 0.1 to 7 μm, and a polyurethane impregnated into the nonwoven fabric, wherein the polyurethane comprises, based on the total amount of high molecular weight polyol units, 60 to 95% by mass of condensation polyester polyol units and 5 to 25% by mass of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, wherein the condensation polyester polyol units do not contain a ring structure and the average number of carbon atoms between ester bonds in the repeating units is 5 to 7, excluding the carbon atoms of the ester bonds, wherein, in a cross section in the thickness direction of the artificial leather substrate, a polyurethane region comprising the polyurethane and voids surrounded by the polyurethane has a porosity of 30 area % or less, and wherein the area ratio of the polyurethane region to the total cross-sectional area in the thickness direction is 10 to 30 area %. [2] The artificial leather substrate according to [1] above, wherein the 100% modulus of the polyurethane is 5 to 15 MPa. [3] The artificial leather substrate according to [1] or [2], wherein the content of the polyurethane in the artificial leather substrate is 15 to 55% by mass. [4] The artificial leather substrate according to any one of [1] to [3], wherein the compressibility P is 15 to 35% and the compressive modulus Pe is 85% or more when the initial load is 0.5 kPa and the constant load is 30 kPa, as measured in accordance with the method described in JIS L 1913:2010, 6.14. [5] The artificial leather substrate according to [1] or [2], wherein the compressibility P is 15 to 35% and the compressive modulus Pe is 85% or more when the initial load is 0.5 kPa and the constant load is 30 kPa, as measured in accordance with the method described in JIS L 1096:2010, 8.15.1A. 30[6] The artificial leather substrate according to any one of [1] to [4] above, wherein the polyurethane contains 0 to 35 mass% of polyether polyol units, the repeating units of which have an average carbon number of 4 or more, based on the total amount of the high molecular weight polyol units. [7] A napped artificial leather comprising the artificial leather substrate according to any one of [1] to [6] above, and having a napped surface on at least one side of the artificial leather substrate, in which the ultrafine fibers are napped. [8] A grain-finish artificial leather comprising the artificial leather substrate according to any one of [1] to [6] above, and a resin layer laminated on the artificial leather substrate.

[0028] According to the present invention, an artificial leather can be obtained which contains polyurethane with excellent resistance to hydrolysis and oxidation degradation, has a supple texture and smooth feel, and has mechanical properties that allow it to easily recover from deformation caused by the application of force during use.

[0029] FIG. 1 is an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate obtained in Example 1, taken with a scanning electron microscope (SEM) at 200x magnification. FIG. 2 shows an image based on the image of FIG. 1, in which polyurethane regions containing polyurethane and voids surrounded by the polyurethane are blackened. FIG. 3 shows an image based on the image of FIG. 1, in which voids contained in the polyurethane regions are blackened. FIG. 4 is an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate obtained in Comparative Example 1, taken with an SEM at 200x magnification. FIG. 5 shows an image based on the image of FIG. 4, in which polyurethane regions containing polyurethane and voids surrounded by the polyurethane are blackened. FIG. 6 shows an image based on the image of FIG. 4, in which voids contained in the polyurethane regions are blackened. FIG. 7 is an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate obtained in Example 1, taken with an SEM at 500x magnification. FIG. 8 is an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate obtained in Comparative Example 1, taken with an SEM at 500x magnification.

[0030] The artificial leather substrate, the raised artificial leather, and the grain-finish artificial leather of the present embodiment will be described in detail below.

[0031] The artificial leather substrate of this embodiment includes a nonwoven fabric formed by entanglement of ultrafine fibers having an average fiber diameter of 0.1 to 7 μm, and polyurethane impregnated into the nonwoven fabric. The polyurethane contains, based on the total amount of high molecular weight polyol units, 60 to 95 mass% of condensation polyester polyol units and 5 to 25 mass% of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units. The condensation polyester polyol units do not contain a ring structure, and the average number of carbon atoms between ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, is 5 to 7. The artificial leather substrate has, in a cross section in the thickness direction, a porosity of a polyurethane region, including polyurethane and voids surrounded by the polyurethane, of 30 area% or less, and an area ratio of the polyurethane region to the total cross-sectional area in the thickness direction of the cross section of the artificial leather substrate of 10 to 30 area%.

[0032] The nonwoven fabric in this embodiment is an entangled nonwoven fabric in which ultrafine fibers having an average fiber diameter of 0.1 to 7 μm are entangled. The nonwoven fabric may also be a fiber structure in which a nonwoven fabric is the main component and, as necessary, a woven fabric, a knitted fabric, or the like is combined.

[0033] The type of resin from which the ultrafine fibers are formed is not particularly limited. Specific examples include nylons such as nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, and nylon 6-12; polyethylene terephthalate (PET); modified PETs such as isophthalic acid-modified PET, sulfoisophthalic acid-modified PET, and modified PET dyeable with cationic dyes; aromatic polyesters such as polybutylene terephthalate and polyhexamethylene terephthalate; aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalerate resin; and polyolefins such as polypropylene, polyethylene, polybutene, polymethylpentene, and chlorinated polyolefins. Among these, nylon is particularly preferred because it allows for the production of artificial leather with a supple texture. Modified PET is PET in which at least a portion of the ester-forming dicarboxylic acid monomer units or diol monomer units of unmodified PET are replaced with substitutable monomer units. Specific examples of the modifying monomer units that replace the dicarboxylic acid monomer units include units derived from isophthalic acid, sodium sulfoisophthalic acid, sodium sulfonaphthalenedicarboxylic acid, adipic acid, etc., which replace terephthalic acid units. Specific examples of the modifying monomer units that replace diol monomer units include units derived from diols such as butanediol and hexanediol, which replace ethylene glycol units.

[0034] The ultrafine fibers have an average fiber diameter of 0.1 to 7 μm, preferably 0.2 to 5 μm. The use of ultrafine fibers with such a fiber diameter allows for the production of artificial leather with a supple feel. Furthermore, this is preferred because it facilitates the production of raised-pile artificial leather with a smooth feel. The average fiber diameter can be obtained by taking a scanning electron microscope (SEM) image of the cross section of the artificial leather substrate or the artificial leather substrate forming the artificial leather at 200 to 500 magnifications, randomly selecting 10 cross sections of the ultrafine fibers perpendicular to the cross section, measuring the cross-sectional area, and calculating the average cross-sectional area using the following formula: Average fiber diameter (μm) = (4 × (average cross-sectional area (μm^2)) / π)^1 / 2

[0035] Examples of methods for producing a nonwoven fabric made of entangled ultrafine fibers include melt-spinning ultrafine fiber-generating fibers such as islands-in-sea (matrix-domain) composite fibers to produce a web of the ultrafine fiber-generating fibers, entangling the web, and then forming ultrafine fibers from the ultrafine fiber-generating fibers. Alternatively, a method may be used in which ultrafine fibers are directly spun and entangled without using ultrafine fiber-generating fibers. In this embodiment, a detailed description will be given of a case in which a nonwoven fabric made of ultrafine fibers is produced by entangling islands-in-sea composite fibers and selectively removing the sea component from the islands-in-sea composite fibers to produce ultrafine fibers.

[0036] Examples of the island component resins for forming islands-in-sea type composite fibers include the resins for forming ultrafine fibers described above. Specific examples of the sea component resins for forming islands-in-sea type composite fibers include polyethylene, polypropylene, polystyrene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, styrene-ethylene copolymers, styrene-acrylic copolymers, and polyvinyl alcohol.

[0037] Furthermore, the resin for forming the ultrafine fibers may contain, as necessary, various stabilizers such as coloring pigments, antioxidants, ultraviolet absorbers, fluorescent agents, and heat stabilizers, deodorizers, mildew inhibitors, lubricants, water repellents, oil repellents, extenders, inorganic fine particles, and conductive agents.

[0038] Examples of methods for producing a web of islands-in-sea type composite fibers include a method in which long-fiber islands-in-sea type composite fibers spun by a spunbonding method or the like are collected on a net without cutting them to form a long-fiber web, and a method in which the long fibers are cut into staples to form a short-fiber web.

[0039] The entanglement treatment may be, for example, a method in which a plurality of layers of the web are superimposed in the thickness direction using a cross wrapper or the like, and then needle punched or subjected to a high-pressure water jet treatment under conditions in which at least one or more barbs penetrate simultaneously or alternately from both sides. The punch density of the needle punch is 1500 to 5500 punches / cm. 2 , and further, 2000 to 5000 punches / cm 2This is preferred because it is easy to obtain a nonwoven fabric with a rich feel and excellent surface physical properties.

[0040] An oil or an antistatic agent may be applied to the web at any stage from the spinning process of the islands-in-sea type composite fiber to the entanglement treatment. Furthermore, if necessary, the web may be subjected to a shrinkage treatment in which the web is immersed in warm water at about 70 to 150°C to previously make the entanglement state of the web dense. Furthermore, the entangled web may be subjected to a treatment to increase the fiber density and the degree of entanglement by heat shrinking, if necessary. Furthermore, the entangled web densified by the heat shrinkage treatment may be further densified, and the fiber density may be further increased by a heat press treatment, if necessary, for the purposes of fixing the shape of the web, smoothing the surface, etc.

[0041] The basis weight of the entangled web thus obtained is 100 to 2000 g / m 2 It is preferable that the range is about the same.

[0042] A nonwoven fabric having ultrafine fibers entangled therein is formed by removing the sea component resin from the islands-in-sea composite fibers of a nonwoven fabric having entangled islands-in-sea composite fibers. The method for removing the sea component resin from the islands-in-sea composite fibers can be any conventional method for forming ultrafine fibers, such as treating a nonwoven fabric having entangled islands-in-sea composite fibers with a solvent or decomposing agent capable of selectively removing only the sea component resin. For example, when polyethylene is used as the sea component resin, it is preferable to extract and remove the polyethylene by treating it in toluene at 85 to 100°C until the polyethylene removal rate reaches about 95 to 100%. Repeated dip-nip treatment allows the sea component to be efficiently extracted and removed.

[0043] The basis weight of the nonwoven fabric thus obtained is 140 to 3000 g / m 2 , and further 200 to 2000 g / m 2 It is preferable that:

[0044] In the production of the artificial leather substrate of this embodiment, a nonwoven fabric formed by entangling islands-in-sea composite fibers or a nonwoven fabric of ultrafine fibers formed by removing the sea component resin from islands-in-sea composite fibers is impregnated with polyurethane.

[0045] Examples of a method for impregnating a nonwoven fabric with polyurethane include a method in which a polyurethane solution prepared by dissolving polyurethane in an organic solvent capable of dissolving polyurethane is used as an impregnation liquid, and the nonwoven fabric is impregnated with the impregnation liquid by dip-nipping or coating, and then the nonwoven fabric is immersed in a poor solvent for the polyurethane to coagulate the polyurethane in the nonwoven fabric.

[0046] The polyurethane can be obtained by reacting urethane raw materials containing, for example, a polymer polyol, an organic polyisocyanate compound, a chain extender, and optionally other monofunctional or polyfunctional compounds. The polyurethane of this embodiment contains a polymer polyol unit as described below.

[0047] The polyurethane of this embodiment contains, based on the total amount of high molecular weight polyol units, 60 to 95 mass% of condensation polyester polyol units and 5 to 25 mass% of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units. The condensation polyester polyol units do not contain a ring structure and have an average of 5 to 7 carbon atoms between ester bonds in the repeating units, excluding the carbon atoms of the ester bonds.

[0048] Condensation polyester polyols are polyols obtained by the condensation reaction of a diol having a number-average molecular weight (Mn) of less than 500 with a dicarboxylic acid or its ester-forming derivative (such as an acid anhydride, a lower alkyl ester having 1 to 4 carbon atoms, or an acid halide), and are distinguished from ring-opening polyester polyols that form polymeric polyol units by ring-opening. Polyurethanes containing condensation polyester polyol units coagulate more slowly from a polyurethane solution and tend to coagulate in a highly aggregated state than polyurethanes containing ring-opening polyester polyol units. In the following description, the phrase "not containing a ring structure" may be omitted for simplicity.

[0049] The condensation polyester polyol unit, which does not contain a ring structure and has an average carbon number of 5 to 7 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, is a constituent unit of a high molecular weight polyol unit of a polyurethane, derived from a condensation polyester polyol, which does not contain a ring structure and has an average carbon number of 5 to 7 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds.

[0050] Condensation polyester polyols having an average carbon number of 5 to 7 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, are shown, for example, as follows:

[0051] (In formula (I), R １ is a group obtained by removing an ester bond from a unit derived from a dicarboxylic acid compound not containing a ring structure, R is a group obtained by removing an ester bond from a unit derived from a diol compound not containing a ring structure, and R １ and R2 have an average carbon number of 5 to 7, and n1 is, for example, an integer of 23 or less.

[0052] The average number of carbon atoms between ester bonds in the repeating unit of the condensation polyester polyol unit, excluding the carbon atoms of the ester bonds, is R １ and the average number of carbon atoms contained in R2. １ Alternatively, when at least one of R2 consists of two or more types, the number of carbon atoms is calculated according to the molar ratio of each type.

[0053] The average number of carbon atoms between the ester bonds in the repeating units of the condensation polyester polyol units, excluding the carbon atoms of the ester bonds, is 5 to 7, preferably 5.5 to 6.5. When the average number of carbon atoms between the ester bonds in the repeating units of the condensation polyester polyol units, excluding the carbon atoms of the ester bonds, is less than 5, the number of ester bonds becomes relatively large, resulting in reduced hydrolysis resistance. Furthermore, when the average number of carbon atoms between the ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, exceeds 7, the hydrophobicity and crystallinity become too high, resulting in rapid solidification, making it difficult for the polyurethane to aggregate. This makes it difficult to form a region in the thickness direction cross section of the artificial leather substrate in which the porosity of the polyurethane region containing the polyurethane and the voids surrounded by the polyurethane is 30 area% or less, and the area ratio of the polyurethane region to the total cross-sectional area in the thickness direction is 10 to 30 area%, resulting in a hard texture. Furthermore, when producing a napped artificial leather, it is easy to obtain a napped artificial leather with a rough feel.

[0054] Examples of such condensation polyester polyols that do not contain a ring structure and have an average carbon number of 5 to 7 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, include the following condensation polyester polyols.

[0055] Specific examples of condensation polyester polyols having an average carbon number of 5 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, include polyethylene sebacate diol (R １ The number of carbon atoms is 8, R ２ carbon number 2), poly(3-methyl-1,5-pentylene adipate)diol (R １ The number of carbon atoms is 4, R ２ (carbon number: 6), poly(3-methyl-1,5-pentylene)(2-methyl-1,3-glutarate)diol (R １ The number of carbon atoms is 4, R ２ (carbon number: 6), polyhexylene adipate diol (R １ The number of carbon atoms is 4, R ２ (6 carbon atoms) and the like.

[0056] Specific examples of condensation polyester polyols that do not contain a ring structure and have an average carbon number of 5.5 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, include polypropylene sebacate diol (R １ The number of carbon atoms is 8, R ２ (R carbon number: 3), polyhexylene piperate diol (R １ The number of carbon atoms is 5, R ２ (carbon number: 6), poly(3-methyl-1,5-pentylenepiperate)diol (R １ The number of carbon atoms is 5, R ２ (carbon number: 6), poly(1,8-octylene succinate)diol (R １ The number of carbon atoms is 2, R ２ (carbon number: 9), polynonamethylene succinate diol (R １ The number of carbon atoms is 2, R ２ (having 9 carbon atoms)

[0057] Specific examples of condensation polyester polyols that do not contain a ring structure and have an average carbon number of 6 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, include polyethylene 1,10-decamethylene diol (R １ R has 10 carbon atoms, R has 2 carbon atoms), polybutylene sebacate diol (R １ R has 8 carbon atoms, R has 4 carbon atoms), polydecamethylene succinate diol (R １ and R has 2 carbon atoms, and R has 10 carbon atoms.

[0058] Specific examples of condensation polyester polyols that do not contain a ring structure and have an average carbon number of 6.5 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, include polypropylene 1,10-decamethylene diol (R １ The number of carbon atoms is 10, R ２ (carbon number: 3), poly(1,8-octylene adipate)diol (R １ The number of carbon atoms is 4, R ２ (carbon number: 9), polynonamethylene adipate diol (R １ The number of carbon atoms is 4, R ２ (carbon number: 9), polydecamethylene glutarate diol (R １The number of carbon atoms is 3, R ２ (having 10 carbon atoms)

[0059] Specific examples of condensation polyester polyols that do not contain a ring structure and have an average carbon number of 7 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, include polyethylene 1,12-dodecamethylene diol (R １ carbon number 12, R ２ carbon number 2), poly(3-methyl-1,5-pentylene sebacate)diol (R １ The number of carbon atoms is 8, R ２ (R carbon number: 6), polyhexylene sebacate diol (R １ The number of carbon atoms is 8, R ２ (carbon number: 6), polydecamethylene (1,3-methylglutarate) diol (R １ The number of carbon atoms is 4, R ２ (carbon number: 10), polydecamethylene adipate diol (R １ The number of carbon atoms is 4, R ２ (C10), polydodecamethylene succinate diol (R １ The number of carbon atoms is 2, R ２ (having 12 carbon atoms)

[0060] Among these, polyhexylene adipate diol (average carbon number: 5), polyethylene 1,10-decamethylene diol (average carbon number: 6), polypropylene sebacate diol (average carbon number: 5.5), polypropylene 1,10-decamethylene diol (average carbon number: 6.5), polybutylene sebacate diol (average carbon number: 6), poly(1,8-octylene adipate) diol (average carbon number: 6.5), polynonamethylene adipate diol (average carbon number: 6), which are linear condensation polyester polyols that do not contain a ring structure and do not have a side chain structure in which the average number of carbon atoms between the ester bonds in the repeating unit is 5 to 7, excluding the carbon atoms of the ester bonds, are particularly preferred. Poly(3-methyl-1,5-pentylene)(2-methyl-1,3-glutarate)diol (average carbon number: 5), poly(3-methyl-1,5-pentylene adipate)diol (average carbon number: 5), poly(3-methyl-1,5-pentylene sebacate)diol (average carbon number: 7), polydecamethylene glutarate diol (average carbon number: 6.5), polyhexylene sebacate diol (average carbon number: 7), and polydecamethylene(1,3-methylglutarate)diol (average carbon number: 7), which have an average carbon number of 5 to 7 and have a methyl branched structure in the side chain, are particularly preferred.

[0061] These condensation polyester polyols which do not contain a ring structure and have an average carbon number of 5 to 7 between ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds, may be used either alone or in combination of two or more.

[0062] By using a polyurethane obtained by reacting such a condensation polyester polyol in combination with at least one polyether polyol selected from the group consisting of polyethylene glycol and polypropylene glycol, it becomes easier to form a polyurethane region as described below. Furthermore, when producing a napped artificial leather, it becomes easier to obtain a good napped artificial leather that has a supple texture and a smooth feel, and also has pilling resistance that can withstand practical use, particularly pilling resistance with both wet heat durability and dry heat durability. Furthermore, when these are condensation polyester diols obtained from biomass raw materials, this is particularly preferred because it can reduce the environmental impact.

[0063] The high molecular weight polyol units constituting the polyurethane of the present embodiment may contain polyester polyol units other than the above-described condensation polyester polyol units having an average carbon number of 5 to 7, as long as the effects of the present invention are not impaired.

[0064] In order to incorporate polyester polyol units other than the above-mentioned condensation type polyester polyol units having an average carbon number of 5 to 7, known polyester polyols such as those shown below are used.

[0065] Such known polyester polyols are produced by reacting a dicarboxylic acid or its ester-forming derivative with a polyol through a direct esterification reaction or an ester exchange reaction, or by ring-opening polymerization of a cyclic ester.

[0066] Specific examples of dicarboxylic acids include aliphatic dicarboxylic acids having 4 to 12 carbon atoms, such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, methylsuccinic acid, 2-methylglutaric acid, 3,8-dimethyl-3-methylglutaric acid, trimethyladipic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, and 3,7-dimethyldecanedioic acid; alicyclic dicarboxylic acids, such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids, such as terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid. These dicarboxylic acids or their ester-forming derivatives may be used alone or in combination of two or more.

[0067] Specific examples of polyols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butylene glycol, 1,4-butanediol, 2-methyl-1,4-hexamethylene glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8 Examples of the diol include aliphatic diols having 2 to 15 carbon atoms, such as 1,4-octanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 1,9-nonanediol, 2,8-dimethyl-1,9-nonanediol, and 1,10-decanediol; alicyclic diols, such as 1,4-cyclohexanediol, cyclohexanedimethanol, and dimethylcyclooctanedimethanol; and aromatic dihydric alcohols, such as 1,4-bis(β-hydroxyethoxy)benzene. These may be used alone or in combination of two or more.

[0068] Furthermore, a polyol having three or more hydroxyl groups may be used together with the diol, if necessary. Specific examples of such polyols having three or more hydroxyl groups include glycerin, trimethylolethane, trimethylolpropane, trimethylolbutane, butanetriol, hexanetriol, and pentaerythritol. These may be used alone or in combination of two or more.

[0069] Specific examples of cyclic esters include ε-caprolactone, β-methyl-δ-valerolactone, polyvalerolactone, polyβ-methyl-δ-valerolactone, etc. These may be used alone or in combination of two or more.

[0070] The polyurethane of this embodiment contains 5 to 25 mass% of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, based on the total amount of high molecular weight polyol units. The polyethylene glycol units contain ethylene glycol units as repeating units, and the polypropylene glycol units contain propylene glycol units as repeating units. Furthermore, the poly(ethylene glycol-propylene glycol) units contain copolymerized units of ethylene glycol units and propylene glycol units as repeating units, and such polyether polyol units are also included in the at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units. These may be used alone or in combination of two or more.

[0071] At least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units slows down the coagulation of polyurethane, thereby coagulating the polyurethane from the polyurethane solution in a highly coagulated state. As a result, the texture of the resulting artificial leather and, in the case of napped artificial leather, the surface touch are improved. Furthermore, if these polyether polyols are obtained from biomass raw materials, this is particularly preferred from the viewpoint of reducing the environmental impact.

[0072] Furthermore, the polymer polyol units constituting the polyurethane of this embodiment may contain polyether polyol units having an average carbon number of 4 or more in the repeating units, as long as the effects of the present invention are not impaired. When polyether polyol units having an average carbon number of 4 or more in the repeating units are contained, it is preferable that the polyether polyol units having an average carbon number of 4 or more in the repeating units account for, for example, 0 to 35 mass%, or even 15 to 30 mass%, of the total amount of polymer polyol units.

[0073] Specific examples of polyether polyol units having an average carbon number of 4 or more in the repeating unit include units derived from polytetramethylene glycol, polyhexamethylene ether glycol, poly(methyltetramethylene glycol), and the like.

[0074] The polyurethane contains 60 to 95% by mass of condensation polyester polyol units that do not contain a ring structure and have an average carbon number of 5 to 7 between ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, and 5 to 25% by mass of polyether polyol units that contain at least one polyether polyol unit selected from the group consisting of polyethylene glycol units, polypropylene glycol units, and poly(ethylene glycol-propylene glycol) units.

[0075] The content of condensation polyester polyol units, which do not contain a ring structure and have an average carbon number of 5 to 7 between ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, in the polymer polyol units constituting the polyurethane is 60 to 95% by mass, preferably 65 to 90% by mass. If the content of these condensation polyester polyol units having an average carbon number of 5 to 7 is less than 60% by mass, the mechanical properties of the resulting artificial leather substrate, which are easily recoverable when deformed by force during use, are reduced. Furthermore, if the content of these condensation polyester polyol units having an average carbon number of 5 to 7 is more than 95% by mass, the content of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, which is used in combination with the condensation polyester polyol unit, is 5% by mass or less, which accelerates coagulation and makes the polyurethane more likely to coagulate in a low-aggregation state, making it difficult to obtain an artificial leather substrate with a supple feel and a raised-pile artificial leather with a smooth feel.

[0076] Furthermore, the content of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units in the high molecular weight polyol units constituting the polyurethane is 5 to 25% by mass, preferably 10 to 20% by mass. If the content of these polyether polyol units is less than 5% by mass, coagulation will be rapid and the polyurethane will tend to coagulate in a low coagulation state, making it difficult to obtain an artificial leather substrate with a supple feel, and when used in the production of napped artificial leather, it will be difficult to obtain a smooth feel. If the content of these polyether polyol units exceeds 25% by mass, the polyurethane will have an increased number of ether bonds, making it more susceptible to oxidative degradation due to the ether bonds, and the polyurethane's resistance to oxidative degradation will be reduced.

[0077] The slowing of coagulation due to at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units is believed to be due to the moderate hydrophilicity of these polyether polyol units. Furthermore, coagulating polyurethane in a moderately aggregated state, as described below, facilitates the formation of polyurethane regions, as described below. As a result, an artificial leather substrate is obtained that has a supple texture, easily recovers after deformation, and also has excellent resistance to hydrolysis and oxidation degradation. Furthermore, it is easy to obtain a napped artificial leather with a smooth surface feel.

[0078] Furthermore, the high molecular weight polyol units constituting the polyurethane may contain polycarbonate diol units within the range that does not impair the effects of the present invention. Specific examples of polycarbonate diols for forming the polycarbonate diol unit include polycarbonate diols such as polypropylene carbonate diol, poly(2-methyl-1,3-propylene carbonate) diol, polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyhexamethylene carbonate diol, poly(3-methyl-1,5-pentylene carbonate) diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol, polyoctamethylene carbonate diol, poly(2-methyl-1,8-octylene carbonate) diol, polynonamemethylene carbonate diol, polydecamethylene polycarbonate diol, and polydodecamethylene polycarbonate diol, or copolymers thereof. These may be used alone or in combination of two or more. Furthermore, when these are polycarbonate diols obtained from biomass raw materials, it is particularly preferable from the viewpoint of reducing the environmental load.

[0079] The number average molecular weight (Mn) of the polymer polyol for forming the polymer polyol unit is not particularly limited, but is preferably 400 to 5000, more preferably 800 to 4000, from the viewpoint of achieving an excellent balance between mechanical properties and soft texture.

[0080] Specific examples of organic polyisocyanates for forming the organic polyisocyanate units constituting polyurethane include aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, and hexamethylene diisocyanate; 1,2-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, norbornene diisocyanate, 4,4'-methylenebiscyclohexyl diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, and the like. alicyclic diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 1,3-bis(isocyanatomethylbenzene), 1,4-bis(isocyanatomethylbenzene), and the like; polyfunctional isocyanates, which are polyfunctional compounds that give branched structures such as isocyanurate-type, biuret-type, and adduct-type trifunctional and tetrafunctional isocyanates, and their isocyanate-blocked products. These may be used alone or in combination of two or more.

[0081] The chain extender units constituting the polyurethane are derived from a chain extender, which is a low molecular weight compound having two or more functional groups with active hydrogen, such as a hydroxyl group or an amino group. Specific examples of chain extenders include diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, and bisphenol A; triols such as glycerin and trimethylolpropane; aminoalcohols such as aminoethyl alcohol and aminopropyl alcohol; hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, metaxylylenediamine, paraxylylenediamine, isophoronediamine, piperazine, and piperazine derivatives; diamines such as adipic acid dihydrazide and isophthalic acid dihydrazide; triamines such as diethylenetriamine; and tetramines such as triethylenetetramine. These may be used alone or in combination of two or more.

[0082] Polyurethane can be obtained, for example, by solution polymerization of a urethane raw material containing the above-mentioned high molecular weight polyol, organic polyisocyanate compound, chain extender, and other polyfunctional compounds used as needed, in the presence of a solvent through a urethanization reaction using a known prepolymer method or one-shot method.

[0083] The blending ratio of each component is adjusted appropriately depending on the desired properties. For example, it is preferable to blend the isocyanate groups contained in the organic polyisocyanate compound in a ratio of 0.95 to 1.3 mol, preferably 0.96 to 1.10 mol, and particularly preferably 0.97 to 1.05 mol per 1 mol of active hydrogen contained in the high molecular weight polyol and chain extender.

[0084] The 100% modulus of the polyurethane of the present embodiment obtained in this manner is not particularly limited, but if it is 5 to 20 MPa, or even more preferably 5 to 15 MPa, it is a relatively hard polyurethane, and therefore the polyurethane solidified in a moderately aggregated state is likely to maintain its shape even after passing through each step in the production, and polyurethane regions as described below are likely to be formed.

[0085] To impregnate the nonwoven fabric, the polyurethane is dissolved in, for example, an organic solvent in which the polyurethane is soluble, to prepare a polyurethane solution of a predetermined concentration.

[0086] Specific examples of polyurethane-soluble organic solvents include N,N-dimethylformamide (DMF), dimethylacetamide, N-methylpyrrolidone, toluene, ethyl acetate, methyl ethyl ketone, and tetrahydrofuran.

[0087] Furthermore, the polyurethane solution may further contain, within the scope of not impairing the effects of the present invention, colorants such as pigments (e.g., carbon black) and dyes, coagulation regulators, antioxidants, ultraviolet absorbers, flame retardants, fluorescent agents, antioxidants, ultraviolet absorbers, antifungal agents, penetrating agents, antifoaming agents, lubricants, water repellents, oil repellents, thickeners, extenders, hardening accelerators, foaming agents, water-soluble polymer compounds such as polyvinyl alcohol and carboxymethyl cellulose, inorganic fine particles, conductive agents, and the like.

[0088] In particular, it is preferable to blend an appropriate coagulation regulator into the polyurethane solution to regulate the aggregation state. Specific examples of such coagulation regulators include higher alcohols having 8 or more carbon atoms, sorbitan fatty acid esters, polyoxyethylene compounds, and hydrophilic-group-modified organopolysiloxanes.

[0089] Specific examples of higher alcohols having 8 or more carbon atoms include octanol, nonanol, decyl alcohol, undecyl alcohol, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol, ceryl alcohol, and myricyl alcohol.

[0090] Specific examples of sorbitan fatty acid esters include monoesters, diesters, and triesters obtained by reacting sorbitan with higher fatty acids such as lauric acid, stearic acid, oleic acid, and palmitic acid.

[0091] Specific examples of polyoxyethylene compounds include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene phenyl ethers, polyoxyethylene alkylamines, polyoxyethylene polyoxyalkylene ethers, and polyoxyethylene fatty acid esters.

[0092] Specific examples of hydrophilic group-modified organopolysiloxanes include polyoxyethylene-modified organopolysiloxanes, polyoxyalkylene-modified organopolysiloxanes, amino-modified organopolysiloxanes, alcohol-modified hydroxyl group-containing organopolysiloxanes, glyceryl-modified organopolysiloxanes, polyglyceryl-modified organopolysiloxanes, and sugar-modified organopolysiloxanes, which are obtained by modifying methyl groups or the like of unmodified organopolysiloxanes such as dimethylorganopolysiloxanes and methylphenylorganopolysiloxanes with hydrophilic organic groups.

[0093] Among these, hydrophilic group-modified organopolysiloxanes, particularly relatively highly hydrophobic polyoxyethylene-modified organopolysiloxanes (e.g., polyethylene glycol-modified silicone oil), alcohol-modified hydroxyl group-containing organopolysiloxanes (e.g., alcohol-modified hydroxyl group-containing silicone oil), glyceryl-modified organopolysiloxanes, and polyglyceryl-modified organopolysiloxanes, are preferred because they slow down coagulation and allow the polyurethane to coagulate in an appropriate aggregated state, facilitating the formation of polyurethane regions as described below.

[0094] The proportion of the coagulation regulator added is preferably 0.1 to 10% by mass, more preferably 1 to 5% by mass, based on the solid content of the polyurethane.

[0095] The solids concentration of polyurethane in the polyurethane solution is not particularly limited, but is preferably 10% by mass or more, and more preferably 10 to 30% by mass, from the viewpoint of easily adjusting the aggregation state of the polyurethane. If the solids concentration of polyurethane in the polyurethane solution is too high, the polyurethane tends to coagulate quickly, making it difficult to form polyurethane regions containing polyurethane and voids surrounded by polyurethane, as described below.

[0096] When impregnating a nonwoven fabric with polyurethane, wet coagulation is preferred, in which the nonwoven fabric is impregnated with a polyurethane solution by dip-nipping or coating, and then immersed in a coagulation liquid to coagulate. According to this method, by immersing the nonwoven fabric impregnated with the polyurethane solution in the coagulation liquid, the solvent in the polyurethane solution is gradually replaced by the coagulation liquid, and voids are formed in the parts where the solvent has phase-separated, making it easier to form polyurethane regions as described below.

[0097] Examples of coagulation liquids for coagulating polyurethane from a polyurethane solution include water and a mixture of a polyurethane-soluble organic solvent such as DMF and water. In the case of a mixture of a polyurethane-soluble organic solvent and water, the content of the polyurethane-soluble organic solvent is preferably 5 to 60% by mass, and more preferably 10 to 50% by mass, in order to obtain an appropriate aggregation state. Furthermore, the temperature of the coagulation liquid is preferably 10 to 60°C, and more preferably 20 to 55°C. The aggregation state can be adjusted by adjusting the type and temperature of the coagulation liquid.

[0098] As described above, the aggregation state of the polyurethane can be controlled by using the polyurethane described above and adjusting conditions such as the solids concentration of the polyurethane solution when wet coagulating the polyurethane solution, the addition of a coagulation regulator, the type and temperature of the coagulation liquid, etc.

[0099] The content of polyurethane impregnated into the nonwoven fabric is preferably 15 to 55 mass%, more preferably 20 to 50 mass%, relative to the total of the nonwoven fabric and polyurethane, since this makes it easier to form polyurethane regions as described below.

[0100] Furthermore, the nonwoven fabric may contain polymeric elastomers other than polyurethane, such as acrylic elastomers, olefin elastomers, polyester elastomers, polyamide elastomers, and acrylonitrile elastomers, as long as the effects of the present invention are not impaired.

[0101] The polyurethane-impregnated nonwoven fabric is sliced ​​in the thickness direction or buffed as necessary to adjust the thickness to the desired value, thereby obtaining an artificial leather substrate.

[0102] The artificial leather substrate may be subjected to a shrinking treatment or a kneading softening treatment to impart flexibility in order to further adjust the texture, or may be subjected to finishing treatments such as reverse seal brushing treatment, stain-resistant treatment, hydrophilic treatment, lubricant treatment, softener treatment, antioxidant treatment, ultraviolet absorber treatment, fluorescent agent treatment, and flame retardant treatment.

[0103] In the production of the artificial leather substrate of this embodiment, as described above, the nonwoven fabric is impregnated with polyurethane, so that the porosity of the polyurethane region, which includes the polyurethane and voids surrounded by the polyurethane, in the cross section in the thickness direction of the artificial leather substrate is adjusted to 30 area % or less, and the area ratio of the polyurethane region to the total cross-sectional area in the cross section in the thickness direction of the artificial leather substrate is adjusted to 10 to 30 area %. Note that the morphology of the polyurethane in the artificial leather substrate is maintained even when the artificial leather is finished into a napped artificial leather or a grain-finish artificial leather.

[0104] The porosity of the polyurethane region containing polyurethane and voids surrounded by polyurethane refers to the area ratio of the total area of ​​voids contained in the polyurethane region containing polyurethane and voids surrounded by polyurethane in an SEM image of an artificial leather substrate or a cross section of an artificial leather taken with a scanning electron microscope (SEM) at 200x magnification. Furthermore, the area ratio of the polyurethane region to the total cross-sectional area of ​​the cross section in the thickness direction of the artificial leather substrate refers to the ratio of the total cross-sectional area of ​​the polyurethane region to the total cross-sectional area of ​​the cross section in the above-mentioned SEM image. It is preferable to take an SEM image so that the cross section including the middle layer of the artificial leather substrate occupies the entire image. The middle layer of the artificial leather substrate is defined as a range of 30 to 70% in the thickness direction of the artificial leather substrate.

[0105] The porosity of the polyurethane region and the area ratio of the polyurethane region are determined as follows: A cross section of the artificial leather substrate in the thickness direction is photographed using an SEM, preferably at a magnification of 200x so that the cross section including the middle layer of the artificial leather substrate occupies the entire image. Photographs are taken at three evenly selected locations across the cross section of the artificial leather substrate in the thickness direction. The images of the three locations are then printed on A4-size paper.

[0106] A transparent sheet such as an overhead projector (OHP) sheet is then placed on each printed sheet. A polyurethane region containing polyurethane and voids surrounded by polyurethane is then transferred onto each transparent sheet by painting it black. At this time, large voids containing fibers were determined to be voids formed when the sea component was removed from the islands-in-sea composite fiber, and were not voids surrounded by polyurethane. The transparent sheets with the polyurethane regions painted black in this way are then scanned with a scanner to form an image of the polyurethane region.

[0107] Similarly, a transparent sheet is placed on each of the same printed papers used to form the images of the polyurethane regions. Then, the voids surrounded by polyurethane contained in the polyurethane regions are transferred to each transparent sheet by painting them black. The transparent sheets with the voids surrounded by polyurethane painted black are then scanned with a scanner to form images of the voids surrounded by polyurethane.

[0108] Then, using an image processing device, noise of 10 dots or less is removed from each image of the voids surrounded by polyurethane, and the total area of ​​the blackened portions is calculated as the total cross-sectional area (A) of the voids contained in the polyurethane region. Similarly, noise of 10 dots or less is removed from each image of the polyurethane region, and the total area of ​​the blackened portions is calculated as the total cross-sectional area (B) of the polyurethane region. In addition, the total cross-sectional area (C) of the cross section in the thickness direction of the artificial leather substrate is calculated. The image processing device used is configured by installing image processing software on a computer. A specific example of image processing software is image-pro plus from Media Cybernetics.

[0109] The porosity (area %) of the polyurethane region is then calculated using the formula (A) / (B) x 100. The area ratio (area %) of the total cross-sectional area (B) of the polyurethane region to the total cross-sectional area (C) of the cross section in the thickness direction of the artificial leather substrate is also calculated using the formula (B) / (C) x 100.

[0110] In the artificial leather substrate of this embodiment, the porosity of the polyurethane region calculated in this manner is 30 area % or less, preferably 2 to 28 area %, and the area ratio of the polyurethane region to the total cross-sectional area of ​​the cross section of the artificial leather substrate is 10 to 30 area %, preferably 12 to 29 area %. By using an artificial leather substrate having such a cross-sectional structure, it is possible to produce an artificial leather that has a supple feel and mechanical properties that allow it to easily recover when deformed by force applied during use.

[0111] If the porosity of the polyurethane region exceeds 30% by area, the polyurethane will adhere too much to the ultrafine fibers, resulting in a hard texture, and when a raised-pile artificial leather is produced, the surface will feel rough to the touch.

[0112] If the area ratio of the polyurethane region to the total cross-sectional area of ​​the cross-section of the artificial leather substrate is less than 10 area %, the artificial leather substrate will have a reduced solid feel and reduced pilling resistance.If the area ratio of the polyurethane region to the total cross-sectional area of ​​the cross-section of the artificial leather substrate is more than 30 area %, the artificial leather substrate will have an excessively high resilience and reduced suppleness, and when a raised-pile artificial leather is produced, the surface will have a rough feel to the touch.

[0113] When a polyurethane containing polyester polyol units having an average carbon number of 5 or more between the ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, is used alone as the high molecular weight polyol unit, coagulation tends to be rapid, the porosity of the polyurethane region increases, suppleness decreases, and the surface tends to feel rough when produced as a napped artificial leather. As in the polyurethane of this embodiment, a polyester polyol unit having an average carbon number of 5 or more between the ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, is used in combination with at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, and an artificial leather substrate having the above-described cross-sectional structure is prepared, thereby providing a supple texture, and when a napped artificial leather is produced, a napped artificial leather having a smooth surface touch and sufficient pilling resistance is easily obtained.

[0114] It is preferable that such an artificial leather substrate has an average compressibility P of 15 to 35% when a constant load of 30 kPa is applied to an initial load of 0.5 kPa in the thickness direction of a test piece measuring 50 mm in length and 50 mm in width, measured according to the method described in 6.14 of JIS L 1913:2010, and an average compressive modulus Pe of 85% or more when the constant load is removed. By using an artificial leather substrate having such characteristics, it becomes easier to obtain an artificial leather that combines a supple texture that is easily deformed with mechanical properties that allow for easy recovery after deformation due to the application of force during use.

[0115] Here, the compressibility P is the deformation rate when a constant load of 30 kPa is applied in the thickness direction of the artificial leather substrate, and as described below, it is calculated from the following formula: Compressibility P (%) = (T0 - T1) / T0 x 100 ... (Formula 1), where T0 (mm) is the thickness when an initial load of 0.5 kPa is applied to a 50 mm x 50 mm test piece, and T1 (mm) is the thickness when a load of 30 kPa is applied.

[0116] The compressive elastic modulus Pe indicates the recovery rate of thickness when a load of 30 kPa applied to the artificial leather substrate is removed, and is calculated from the compressive elastic modulus Pe (%) = (T0' - T1) / (T0 - T1) x 100 (Equation 2), where T0' (mm) is the thickness when the load of 30 kPa is removed.

[0117] If the compression ratio P of the artificial leather substrate is less than 15%, the texture and surface feel will tend to become hard, and the luxurious feel will be reduced. If the compression ratio P of the artificial leather substrate is more than 35%, the feeling of fullness will be low, and the leather will be prone to breaking and the luxurious feel will be reduced. It is preferable that the compression ratio P of the artificial leather substrate is 15 to 35%, more preferably 15 to 30%, and particularly 16 to 28%, in order to easily obtain an artificial leather that has an excellent balance between a supple texture and recovery from deformation.

[0118] Furthermore, if the compressive elastic modulus Pe of the artificial leather substrate is less than 85%, creases are likely to remain when the material is bent, reducing the luxurious feel. The compressive elastic modulus Pe of the artificial leather substrate is 85% or more, preferably 85 to 99%, and more preferably 86 to 98%.

[0119] The elongation modulus E at 30% elongation of the artificial leather substrate measured in accordance with the method described in 8.15.1A of JIS L 1096:2010 ３０ The average is preferably 65 to 90%, more preferably 70 to 85%.

[0120] Here, the elongation modulus E at 30% elongation ３０ indicates the recovery rate after the artificial leather substrate is stretched 30% in the planar direction and the stretching load is removed, and as will be described later, the elongation modulus E at 30% elongation ３０ (%) = (L - L1) / L × 100 (Equation 3), where L (mm) is the constant elongation at 30% elongation, and L1 (mm) is the residual elongation L1 (mm) measured from the recorded load-elongation curve when the grip spacing is returned to the constant elongation after the elongation load is removed.

[0121] Elongation modulus E of artificial leather substrate at 30% elongation ３０ If the elongation modulus E of the artificial leather substrate at 30% elongation is less than 65%, the substrate will be difficult to return to its original shape after deformation, and the dimensional stability before and after deformation will tend to decrease. ３０ If the elastic modulus exceeds 90%, the resilience upon deformation tends to increase and the supple feel tends to decrease.

[0122] The apparent density of the artificial leather substrate of the present embodiment obtained in this manner is 0.25 to 0.7 g / cm ３ , and further 0.3 to 0.6 g / cm ３ It is preferable that the apparent density of the artificial leather substrate is too low, because it can provide an artificial leather that is well-balanced between a firm feel that does not break and a soft texture. If the apparent density of the artificial leather substrate is too low, the firm feel is low and the leather is prone to breaking. Furthermore, when a napped artificial leather is produced, the fibers are easily pulled out by rubbing the napped surface, which tends to reduce the surface properties. On the other hand, if the apparent density of the artificial leather substrate is too high, the soft texture tends to be reduced.

[0123] The thickness of the artificial leather substrate is not particularly limited, but is preferably about 0.1 to 3 mm, more preferably about 0.3 to 2 mm, in view of good mechanical properties and surface properties.

[0124] The artificial leather substrate described above is used by being dyed and finished into raised artificial leather, or by being finished into grain-finished artificial leather by laminating a resin layer on the surface.

[0125] By buffing one or both sides of the artificial leather substrate, an artificial leather substrate having a napped surface in which the surface layer fibers are raised can be obtained. The artificial leather substrate is raised by buffing using sandpaper or emery paper, preferably having a count of 120 to 600, more preferably about 320 to 600. In this way, an artificial leather substrate having a napped surface in which the napped fibers are present on one or both sides can be obtained.

[0126] The artificial leather substrate having a napped surface is dyed to produce a napped artificial leather. An appropriate dye is selected depending on the type of ultrafine fiber. For example, an artificial leather substrate including a nonwoven fabric containing ultrafine fibers made of nylon is preferably dyed with various dyes having an acidic ionic group, such as metal complex dyes (abbreviated as metal-containing dyes), acid dyes, and acid printing dyes.

[0127] Furthermore, artificial leather substrates containing nonwoven fabrics containing ultrafine polyester fibers are preferably dyed with, for example, disperse dyes or cationic dyes. Specific examples of disperse dyes include benzene azo dyes (monoazo, disazo, etc.), heterocyclic azo dyes (thiazole azo, benzothiazole azo, quinoline azo, pyridine azo, imidazole azo, thiophene azo, etc.), anthraquinone dyes, and condensation dyes (quinophthaline, styryl, coumarin, etc.). These are commercially available as dyes with the prefix "Disperse." These dyes may be used alone or in combination of two or more.

[0128] As the dyeing method, there are no particular limitations on the dyeing method, and dyeing methods such as high pressure liquid jet dyeing, jigger dyeing, thermosol continuous dyeing machine method, and sublimation printing method can be used.

[0129] The napped artificial leather of this embodiment has a supple texture, a smooth surface touch, and sufficient pilling resistance, particularly the wet heat durability and dry heat durability of the pilling resistance.

[0130] Specifically, for example, a softness tester (leather softness measuring device ST300: manufactured by MSA Engineering Systems, UK) is used to measure the softness using a ring with a diameter of 25 mm and a metal pin with a diameter of 5 mm, thereby obtaining a napped artificial leather with a suppleness of 4.1 mm or more.

[0131] Furthermore, a napped artificial leather having high pilling resistance, for example, a pilling grade of 4 or higher in a pilling resistance test according to ISO12945-2 (Martindale method, friction cloth: wool, load: 415±2 g, number of times: 5,000 times), can be obtained.

[0132] In particular, a napped artificial leather having excellent pilling resistance and wet heat durability and dry heat durability can be obtained. Specifically, a napped artificial leather having excellent pilling resistance and wet heat durability can be obtained, such that the drop in the grade in the pilling resistance test before and after the wet heat treatment described below is 1 grade or less, or even 0.5 grade or less. Furthermore, a napped artificial leather having excellent pilling resistance and dry heat durability can be obtained, such that the drop in the grade in the pilling resistance test before and after the dry heat durability test described below, which indicates the degree of oxidative degradation of polyurethane, is 1 grade or less, or even 0.5 grade or less.

[0133] Furthermore, grain-finish artificial leather can be produced by laminating a grain-finish resin layer on at least one surface of an artificial leather substrate.

[0134] Methods for forming a resin layer on the surface of an artificial leather substrate include the dry surfacing method, in which a polymeric elastomer is coated onto release paper and then laminated to the surface of the artificial leather substrate; the wet surfacing method, in which a solution of polymeric elastomer is applied to the surface of the artificial leather substrate and then immersed in a solvent or water to solidify; the film lamination method, in which a polymeric elastomer film is laminated to the surface of the artificial leather substrate; and the direct coating method, in which a polymeric elastomer is directly coated onto the surface of the artificial leather substrate and then dried.

[0135] The thickness of the resin layer is preferably 10 to 400 μm, and more preferably 30 to 300 μm. The resin layer may have a grain pattern formed by embossing or the like. The resin layer may have a single-layer structure or a multi-layer structure including a surface layer and an adhesive layer.

[0136] The resin for forming the resin layer may be any polymeric elastomer conventionally used to form resin layers in grain-finish artificial leathers, without any particular limitations. Specific examples include polyurethane, acrylic elastomer, diene rubber, nitrile rubber, silicone rubber, olefin rubber, fluorine-containing rubber, polystyrene elastomer, acrylonitrile-styrene copolymer or their hydrogenated or epoxidized products, polyolefin elastomer, polyester elastomer, nylon elastomer, and halogenated elastomer. These may be used alone or in combination of two or more. Among these, polyurethane and acrylic elastomer are preferred. The grain surface layer may also contain additives such as colorants, softeners, hair conditioners, antifouling agents, hydrophilizing agents, lubricants, anti-degradants, UV absorbers, and flame retardants, as needed.

[0137] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0138] First, the evaluation methods used in the present examples will be summarized below.

[0139] (Measurement of porosity of polyurethane region and area ratio of polyurethane in thickness direction cross section of artificial leather substrate) A cross section of the thickness direction of the artificial leather substrate was photographed using an SEM at a magnification of 200x at three evenly selected locations so that the entire image was occupied by the cross section of the artificial leather substrate and the middle layer portion was included, and each image was printed on A4 size paper.

[0140] A transparent sheet (OHP (Overhead Projector) sheet) was then placed on top of the paper on which the obtained SEM image was printed, and polyurethane regions containing polyurethane and numerous voids surrounded by polyurethane were painted black and transferred onto the OHP sheet.

[0141] The pattern on the transparent sheet in which the polyurethane regions were painted black was scanned to form an image, and an image processing device consisting of a personal computer with image processing software (Image-Pro Plus) installed was used to remove noise of 10 dots or less from the obtained image, after which the total area (B) of the painted black portions was determined.

[0142] Similarly, a transparent sheet was placed on the paper on which the SEM image was printed, and the voids contained in the polyurethane region were blackened and transferred to the transparent sheet. Since the voids containing the ultrafine fibers were voids formed when the sea component was removed from the islands-in-sea composite fiber, they were determined not to be voids surrounded by polyurethane in the polyurethane region and were not blackened. The pattern on the transparent sheet with the blackened voids was then scanned to form an image. An image processor was then used to remove noise with an area of ​​10 dots or less from the resulting image, after which the total area (A) of the blackened portions was determined.

[0143] The porosity (area %) of the polyurethane region was then calculated using the formula "(A) / (B) x 100".

[0144] Furthermore, the total area (B) of the polyurethane region after removing noise of 10 dots or less from an image captured by a scanner of a transparent sheet in which the polyurethane region was painted black and the total cross-sectional area (C) including pores and voids in the cross section in the thickness direction of the artificial leather substrate were determined.

[0145] Then, the area ratio (area %) of the total area (B) of the polyurethane regions to the total cross-sectional area (C) of the cross section in the thickness direction of the artificial leather substrate was calculated using the formula "(B) / (C) x 100".

[0146] Figure 1 shows an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate of Example 1, photographed with an SEM at 200x magnification. Figure 2 shows an image based on the image of Figure 1, in which polyurethane regions containing polyurethane and voids surrounded by polyurethane are shaded in black. Figure 3 shows an image based on the image of Figure 1, in which voids surrounded by polyurethane contained in the polyurethane regions are shaded in black.

[0147] Fig. 4 shows an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate of Comparative Example 1 photographed with an SEM at 200x magnification. Fig. 5 shows an image based on the image of Fig. 4, in which polyurethane regions containing polyurethane and voids surrounded by polyurethane are shaded in black. Fig. 6 shows an image based on the image of Fig. 4, in which voids contained in the polyurethane regions are shaded in black.

[0148] Furthermore, Fig. 7 shows an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate of Example 1 photographed with an SEM at a magnification of 500 times, and Fig. 8 shows an example of an image of a cross section parallel to the thickness direction of the artificial leather substrate of Comparative Example 1 photographed with an SEM at a magnification of 500 times.

[0149] (Measurement of compressibility P and compressive modulus Pe of artificial leather substrate) The compressibility P and compressive modulus Pe of the artificial leather substrate were measured according to the method described in 6.14 of JIS L1913:2010 (Testing methods for general nonwoven fabrics). Specifically, five test pieces measuring approximately 50 mm x 50 mm were randomly cut from the artificial leather substrate. Using a compression elasticity tester, the thickness when an initial load of 0.5 kPa was applied was defined as T0 (mm), and the thickness when a load of 30 kPa was applied was defined as T1 (mm). First, a load of 30 kPa was applied to the test piece and held for 1 minute. Then, the load of 30 kPa was removed and the piece was left for 1 minute. The thickness when an initial load of 0.5 kPa was again applied was defined as T0' (mm). The compressibility P and compressive modulus Pe were then calculated using the following formulas 1 and 2. Compressibility P (%) = (T0 - T1) / T0 x 100 (Equation 1) Compressive elastic modulus Pe (%) = (T0' - T1) / (T0 - T1) x 100 (Equation 2)

[0150] (Elongation Modulus of Artificial Leather Substrate at 30% Elongation) The elongation modulus of the artificial leather substrate at 30% elongation was determined according to the measurement method for elongation modulus at a constant rate of elongation described in 8.15.1A of JIS L1096:2010 (Testing Methods for Woven and Knit Fabrics). Specifically, three test specimens (25 x 30 cm) were taken in each of the warp and weft directions. Then, using a constant-rate extension tensile tester with a self-recording device (Shimadzu Corporation, Autograph), the specimens were stretched to 30% (constant elongation L) at a grip distance of 200 mm and a pulling rate of 20 mm / min, and then held for 1 minute. Next, the load was removed at a pulling rate of 20 mm / min, the grip distance was returned to 200 mm, and the specimen was held for 3 minutes. The specimen was then again stretched to the constant elongation L at the same speed. The residual elongation L1 (mm) was then measured from the recorded load-elongation curve. The elongation modulus at 30% elongation was calculated using the following formula 3: E 30 (%)=(L-L1) / L×100...(Formula 3)

[0151] (Softness of Raised Artificial Leather) The softness of the raised artificial leather was measured using a softness tester (Leather Softness Measuring Device ST300: manufactured by MSA Engineering Systems, UK). Specifically, a predetermined ring with a diameter of 25 mm was set in the lower holder of the device, and then the raised artificial leather was set in the lower holder. Then, a metal pin (diameter 5 mm) fixed to the upper lever was pressed down toward the raised artificial leather. The upper lever was then pressed down and the value read when the upper lever locked. The value represents the penetration depth, and the larger the value, the more flexible the leather.

[0152] (Measurement of 100% Modulus of Polyurethane) A polyurethane solution was applied to release paper using a knife coater with an adjusted clearance to achieve a film thickness of approximately 250 μm after drying, and then dried for 10 minutes in a thermostatic oven at 60°C. The film was then left to stand for 24 hours in an atmosphere of 20°C and 65% RH to condition it, thereby preparing a polyurethane film with a thickness of approximately 250 μm. The strength and elongation of the film cut to a width of 2.5 cm were measured using a precision universal testing machine (Shimadzu Autograph) at a grip distance of 200 mm and a tensile speed of 200 mm / min. The strength at 100% elongation of the resulting SS curve was read. The 100% modulus was calculated by dividing the strength at 100% by the cross-sectional area obtained from the film thickness and the 2.5 cm width.

[0153] (Measurement of Polyurethane Content of Artificial Leather Substrate) The mass of the artificial leather substrate was measured. The artificial leather substrate was then immersed in dimethylformamide for 12 hours and pressed. The substrate was then immersed in N,N-dimethylformamide for another 5 minutes and pressed, and this process was repeated five times to solvent-extract the polyurethane. The nonwoven fabric remaining after the solvent extraction of the polyurethane was then dried and its weight was measured. The polyurethane content (mass %) of the artificial leather substrate was calculated using the formula (mass of artificial leather substrate - mass of nonwoven fabric) / mass of artificial leather substrate x 100.

[0154] (Pilling resistance of artificial leather substrate) Four test pieces of artificial leather substrate were subjected to an abrasion weight loss test in accordance with ISO12945-2 (Martindale method, friction cloth: wool, load: 415±2 g, number of times: 5,000). The pilling grade of each test piece was then determined. The pilling resistance of each test piece was then evaluated according to the following pilling evaluation criteria based on the ISO12945-2 method. The average grade of all test pieces was used as the evaluation value. Grade 5: No change. Grade 4: Clean fluffing, but small pilling in a very small area. Grade 3: Small pilling in some areas. Grade 2: Obvious pilling in the majority of the area. Grade 1: Pilling occurred throughout, with dense pilling.

[0155] (Pilling resistance after moist heat treatment) Four test pieces of artificial leather substrate were prepared. Each test piece was subjected to moist heat treatment (jungle test treatment) by leaving it in an atmosphere of 70°C and 95% RH for 4 weeks. The artificial leather substrates after the moist heat treatment were then evaluated in the same manner as in the "Pilling resistance of raised nap artificial leather" above.

[0156] (Pilling resistance after dry heat treatment (oxidation degradation resistance)) Four test pieces of artificial leather substrate were prepared. Each test piece was then hung in a circulation dryer so that the distance between each test piece and the inner wall of the circulation dryer was 100 mm or more, the test pieces did not contact each other, and clean air at 130°C was circulating around each test piece, and the test pieces were left for 5 days for dry heat treatment. Each test piece of the artificial leather substrate after the dry heat treatment was then evaluated in the same manner as in the above-mentioned "Pilling resistance of napped artificial leather."

[0157] (Touch and Appearance of Raised Artificial Leather) A 20 cm x 20 cm test piece was cut out from the raised artificial leather. The touch and appearance of the raised surface of the test piece were evaluated according to the following criteria: A: Smooth touch and elegant appearance with a luxurious feel. No color spots were observed. B: The ultrafine fibers were bundled together, giving a rough touch. C: Color spots were observed in the appearance.

[0158] (Wrinkles of grain-finish artificial leather) A 20 cm x 20 cm test piece was cut out from the grain-finish artificial leather. The test piece was then bent into a semicircle with a curvature radius of 6 cm, and the wrinkles of the grain-finish artificial leather that occurred were evaluated according to the following criteria: A: Fine wrinkles, no wrinkles remaining. B: Large wrinkles remaining when bent, lacking a luxurious feel. C: Large wrinkles, lacking a luxurious feel.

[0159] [Example 1] Polyethylene (PE; sea component) and nylon 6 (island component) were extruded at a single-hole output rate of 1.0 g / min from a melt-mixing spinning die at 260°C so that the sea component / island component ratio was 50 / 50 (mass ratio), and the extruded fibers were stretched and cut to produce multicomponent staple fibers. The resulting multicomponent staple fibers were then cut into 1000 mm² sheets. 2 The stacked bodies were then punched at 2500 punches / cm using needles. ２The web was then heated to 140°C and pressed with a cooled roll to obtain a web having a basis weight of 750 g / m. ２ , apparent density 0.28 g / cm ３ A surface-smoothed web having a thickness of 2.7 mm was obtained.

[0160] Next, the smoothed web was impregnated with a DMF solution of polyurethane so that the polyurethane content of the artificial leather substrate was approximately 40% by mass, and then the web was immersed in a 30% DMF aqueous solution at 40°C, which served as a coagulation liquid, to coagulate the polyurethane.

[0161] The polyurethane contained in the DMF solution contained 85% by mass of polypropylene sebacate diol (PPS), a condensation type polyester polyol unit having an average carbon number of 5.5 between ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, and 15% by mass of polyethylene glycol (PEG) as high molecular weight polyol units, 4,4'-diphenylmethane diisocyanate (MDI) as isocyanate units, and ethylene glycol (EG) as chain extender units, resulting in a polyurethane with a 100% modulus of 9 MPa. The polyurethane DMF solution had a polyurethane solids concentration of approximately 14% by mass, and the polyurethane DMF solution also contained 4% by mass of polyethylene glycol-modified silicone oil (PEGSi) as a coagulation regulator, based on the polyurethane solids.

[0162] Next, the smoothed web to which the polyurethane had been applied was immersed in toluene at 90°C for 180 minutes while undergoing nip treatment and immersion treatment to dissolve and remove the PE, and then dried. In this way, a nonwoven fabric containing the polyurethane impregnated into the nonwoven fabric and having a basis weight of 645 g / m was obtained. ２ , apparent density 0.39 g / cm ３ The average fiber diameter of the ultrafine fibers forming the nonwoven fabric of the fiber substrate was 0.3 μm (0.008 dtex).

[0163] The fiber substrate was then cut in half, and the sliced ​​surface was ground with #120 paper, while the non-sliced ​​surface was buffed with #240, #400, and #600 paper to form napped surfaces on both sides.

[0164] The buffed fiber substrate was then subjected to a relaxation treatment at 90 to 95°C for 30 minutes. ２ , apparent density 0.36 g / cm ３ The artificial leather substrate was then evaluated according to the above evaluation methods.

[0165] (Production of raised-pile artificial leather) The artificial leather substrate was dyed with a metal complex dye at 90 to 95°C. ２ , apparent density 0.35 g / cm ３ The resulting suede-like napped artificial leather was 0.70 mm thick. The napped artificial leather was evaluated according to the above-described evaluation method.

[0166] (Production of grain-finish artificial leather) A solvent-based polymeric elastomer solution containing polyurethane and pigment was applied onto a release paper to form a resin layer with a thickness of 100 μm. The resin layer on the release paper was then pressed onto the surface of the artificial leather substrate to adhere it, and after leaving it for a predetermined time, the release paper was peeled off to form a grain-finish artificial leather with a basis weight of 355 g / m. ２ , apparent density 0.44 g / cm ３ The grain-finish artificial leather was obtained, and the grain-finish artificial leather was evaluated according to the above-mentioned evaluation methods.

[0167] The results are shown in Table 1 below.

[0168]

[0169] [Examples 2 to 7 and Comparative Examples 1 to 9] Artificial leather substrates, raised artificial leathers, and grain-finish artificial leathers were obtained in the same manner as in Example 1, except that the type of web, the type of polyurethane, the solids concentration of the impregnation solution, the content of polyurethane, and the coagulation regulator were changed or adjusted.

[0170] The condensation type polyester polyols or polyether polyols used in the examples are as follows:・PBA: Polybutylene adipate diol, a condensation type polyester polyol having an average of 4 carbon atoms between the ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds. ・PHA: Polyhexylene adipate diol, a condensation type polyester polyol having an average of 5 carbon atoms between the ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds. ・PPS: Polypropylene sebacate diol, a condensation type polyester polyol having an average of 5.5 carbon atoms between the ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds. ・PHS: Polyhexylene sebacate diol, a condensation type polyester polyol having an average of 7 carbon atoms between the ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds. ・P3MPDD: Poly3-methylpentane dodecane diol, a condensation type polyester polyol having an average of 8 carbon atoms between the ester bonds in the repeating unit, excluding the carbon atoms of the ester bonds. ・PEG: Polyethylene glycol ・PPG: Polypropylene glycol ・PTMG: Polytetramethylene ether glycol ・PHMG: Polyhexamethylene ether glycol

[0171] The coagulation regulators used in each example are as follows: PEGSi: polyethylene glycol-modified silicone oil SA: stearyl alcohol LA: higher alcohol having 16 to 18 carbon atoms AOHSi: alcohol-modified hydroxyl group-containing silicone oil

[0172] The results are shown in Table 1.

[0173] Fig. 7 is an image of a cross section parallel to the thickness direction of the artificial leather substrate of Example 1, taken with an SEM at 500x magnification. Fig. 8 is an image of a cross section parallel to the thickness direction of the artificial leather substrate of Comparative Example 1, taken with an SEM at 500x magnification. Referring to these images, it can be seen that the polyurethane impregnated into the artificial leather substrate of Example 1 has fewer voids in the polyurethane region than the polyurethane impregnated into the artificial leather substrate of Comparative Example 1, and that the polyurethane impregnated into the artificial leather substrate of Example 1 has better cohesion.

[0174] Referring to Table 1, the artificial leather substrates and napped artificial leathers obtained in Examples 1 to 7, in which the polyurethane contained 60 to 95% by mass of condensation polyester polyol units having an average carbon number of 5 to 7 between the ester bonds in the repeating units, excluding the carbon atoms in the ester bonds, and 5 to 25% by mass of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, as polymer polyol units, had a porosity of 30% by area or less in the polyurethane region, and the area ratio of the polyurethane region to the total cross-sectional area in the thickness direction was 10 to 30% by area, had a softness in the range of 4.1 to 5.2 mm, a supple texture, a smooth feel and appearance, and pilling resistance of grades 4 to 4.5. Furthermore, the artificial leather substrates and napped artificial leathers obtained in Examples 1 to 7 also had pilling resistance of grade 4 after wet heat treatment and dry heat treatment, demonstrating excellent resistance to hydrolysis and oxidation degradation. Furthermore, no color unevenness was observed after dyeing. Furthermore, the grain-finish artificial leather was less likely to develop creases.

[0175] On the other hand, as shown in Comparative Example 1, the artificial leather substrate of Comparative Example 1 was produced in the same manner as in Example 1, except that stearyl alcohol was added as the coagulation regulator instead of polyethylene glycol-modified silicone oil. The porosity of the polyurethane region was 45% by area, and the area ratio of the polyurethane region to the total cross-sectional area in the thickness direction was 50% by area. Furthermore, the compressibility P was low, and as a result, the raised-pile artificial leather had a hard texture and a rough feel. Furthermore, the grain-finish artificial leather was prone to creases.

[0176] Furthermore, as shown in Comparative Example 2, an artificial leather substrate obtained using only 100% by mass of a condensation polyester polyol having an average carbon number of 5.5 in the repeating units excluding the ester bonds between the ester bonds in the repeating units as the high molecular weight polyol constituting the polyurethane, and a polyurethane not containing at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units, had a porosity of 40 area % in the polyurethane region and an area ratio of 45 area % in the polyurethane region. The compressibility P was low, and as a result, the softness of the raised artificial leather was low and the texture was hard. Furthermore, the raised surface of the raised artificial leather had a rough feel and noticeable color unevenness.

[0177] Furthermore, as shown in Comparative Example 3, an artificial leather substrate using a polyurethane containing 85% by mass of a condensation polyester polyol in which the repeating units, excluding the ester bonds between the ester bonds in the repeating units, have an average carbon number of 4, and 15% by mass of polyethylene glycol as the high molecular weight polyol constituting the polyurethane, and using a higher alcohol having 16 to 18 carbon atoms as the coagulation regulator, had a porosity of 28 area % in the polyurethane region and an area ratio of 26 area %, but had a pilling resistance of grade 2.5 after moist heat treatment and poor hydrolysis resistance.

[0178] Furthermore, as shown in Comparative Example 4, an artificial leather substrate using a polyurethane containing 85% by mass of condensation polyester polyol units, in which the repeating units excluding the ester bonds between the ester bonds in the repeating units have an average carbon number of 8, and 15% by mass of polyethylene glycol as the high molecular weight polyol constituting the polyurethane, had a porosity of 46% by area and an area ratio of 55% by area of ​​the polyurethane region. The compressibility P was low, and as a result, the softness of the raised-napped artificial leather was low and the texture was hard. The raised surface of the raised-napped artificial leather also had a rough feel. Creases were also likely to remain in the grain-finish artificial leather.

[0179] Furthermore, as shown in Comparative Example 5, an artificial leather substrate obtained using only a condensation polyester polyol in which the average number of carbon atoms in the repeating units, excluding the ester bonds between the ester bonds in the repeating units, was 8 as the high molecular weight polyol constituting the polyurethane had a porosity of 48 area % in the polyurethane region and an area ratio of 52 area % in the polyurethane region. The compressibility P was low, and as a result, the softness of the raised artificial leather was low and the texture was hard. Furthermore, the raised surface of the raised artificial leather had a rough feel and noticeable color unevenness.

[0180] In addition, as shown in Comparative Example 6, the artificial leather substrate of Comparative Example 6, which was produced in the same manner as in Example 1 except that the polyurethane content was 13%, had a porosity of 12% by area in the polyurethane region and an area ratio of the polyurethane region to the total cross-sectional area in the thickness direction of 9%. Although the softness was high, the elongation modulus E at 30% elongation was 0.01%. 30 The compressive elastic modulus was low, and the grain-finish artificial leather was prone to creases. The pilling resistance was also low.

[0181] Furthermore, as shown in Comparative Example 7, an artificial leather substrate and a raised artificial leather using a polyurethane having a 100% modulus of 6 MPa, which contained 50% by mass of condensation polyester polyol units, in which the average number of carbon atoms in the repeating units excluding the ester bonds between the ester bonds in the repeating units was 5.5, and 50% by mass of polyethylene glycol units, as the high molecular weight polyol constituting the polyurethane, had a porosity of 6 area% in the polyurethane region and an area ratio of 12 area% in the polyurethane region. Although the compressibility and softness were high, the pilling resistance after dry heat treatment was low and the grain-finish artificial leather was prone to wrinkles.

[0182] Furthermore, as shown in Comparative Example 8, an artificial leather substrate using a polyurethane containing 85% by mass of condensation polyester polyol units, the repeating units of which have an average carbon number of 5.5 excluding ester bonds, and 15% by mass of polytetramethylene ether glycol units as the high molecular weight polyol constituting the polyurethane, had a porosity of 44% by area and an area ratio of 47% by area in the polyurethane region. As a result, the compressibility P was low and the texture was hard. Furthermore, the raised surface of the raised artificial leather had a rough feel and noticeable color unevenness.

[0183] The artificial leather substrate of Comparative Example 9 was produced in the same manner as in Example 6, except that stearyl alcohol was added as a coagulation regulator instead of the polyurethane solution of Example 6 to which polyethylene glycol-modified silicone oil was added as a coagulation regulator. The porosity of the polyurethane region was 43% by area, and the area ratio of the polyurethane region to the total cross-sectional area in the thickness direction was 22% by area. The compressibility P was also low, and the softness was also low. As a result, the raised-pile artificial leather had a hard texture and a rough feel.

Claims

1. An artificial leather substrate comprising: a nonwoven fabric formed by entangling ultrafine fibers having an average fiber diameter of 0.1 to 7 μm; and polyurethane impregnated into the nonwoven fabric; wherein the polyurethane contains, based on the total amount of high molecular weight polyol units, 60 to 95% by mass of condensation polyester polyol units and 5 to 25% by mass of at least one polyether polyol unit selected from the group consisting of polyethylene glycol units and polypropylene glycol units; wherein the condensation polyester polyol units do not contain a ring structure and the average number of carbon atoms between ester bonds in the repeating units, excluding the carbon atoms of the ester bonds, is 5 to 7; wherein, in a cross section in the thickness direction of the artificial leather substrate, a polyurethane region comprising the polyurethane and voids surrounded by the polyurethane has a porosity of 30 area % or less; and wherein the area ratio of the polyurethane region to the total cross-sectional area of ​​the cross section in the thickness direction is 10 to 30 area %.

2. The artificial leather substrate according to claim 1, wherein the 100% modulus of said polyurethane is 5 to 15 MPa.

3. The artificial leather substrate according to claim 1, wherein the content of said polyurethane in said artificial leather substrate is 15 to 55% by mass.

4. The artificial leather substrate according to claim 1, wherein the compressibility P of the artificial leather substrate is 15 to 35% and the compressive modulus Pe is 85% or more when a constant load of 30 kPa is applied to an initial load of 0.5 kPa, as measured in accordance with the method described in 6.14 of JIS L 1913:2010.

5. The artificial leather substrate has a 30% elongation modulus E, which is the recovery rate of elongation after 30% elongation, measured in accordance with the method described in 8.15.1A of JIS L 1096:2010. 30 2. The artificial leather substrate according to claim 1, wherein the content of the polymer is 65 to 90%.

6. The artificial leather substrate according to claim 1, wherein the polyurethane contains 0 to 35 mass % of polyether polyol units having an average carbon number of 4 or more in the repeating unit, based on the total amount of the high molecular weight polyol units.

7. A napped artificial leather comprising the artificial leather substrate according to any one of claims 1 to 6, and having a napped surface on at least one side of the artificial leather substrate where the ultrafine fibers are napped.

8. A grain-finish artificial leather comprising the artificial leather substrate according to any one of claims 1 to 6 and a resin layer laminated on the artificial leather substrate.

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