Artificial leather with raised pile and method for manufacturing the same

Abstract

To provide a napped artificial leather that is manufactured by a step using eco-friendly aqueous polyurethane and has appearance with less color unevenness on the napped surface, high-quality feeling, soft texture and high anti-pilling property.SOLUTION: On a cross section in thickness direction of a napped artificial leather, percentage of the number of first fiber bundles in which half or more of ultra fine fibers are converged with aqueous polyurethane (A1) to total amount of fiber bundles on a surface layer region (T1) is 20 to 60%, while percentage of the number of second fiber bundles that are not infiltrated with aqueous polyurethane and are bonded or contacted with a second continuous region at the length of one fourth or more of outer periphery of fiber bundle (B2) to total amount of fiber bundles on a non-surface layer region (T2) is 10 to 40%.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a napped artificial leather having a napped surface with fibers raised, similar to suede leather. [Background technology]

[0002] Artificial leather with a napped surface similar to suede is preferably used as a surface material for bags, shoes, clothing, furniture, car seats, and general merchandise. Artificial leather with a napped surface comprises a fiber entanglement body such as a nonwoven fabric and polyurethane impregnated into the fiber entanglement body, and has a napped surface on at least one side in which fibers are raised.

[0003] In recent years, water-based polyurethane has been used in the manufacture of piled artificial leather to reduce environmental impact. However, piled artificial leather manufactured using water-based polyurethane has been found to be inferior in terms of luxurious appearance, softness of texture, and resistance to pilling compared to piled artificial leather manufactured using solvent-based polyurethane, which has been widely used in the past and is solidified from a polyurethane organic solvent solution.

[0004] Regarding improvements to pile-textured artificial leather manufactured using water-based polyurethane, the following techniques are known, for example:

[0005] Patent Document 1 below discloses an artificial leather comprising an entanglement formed from ultrafine fiber bundles and polyurethane impregnated into the interior of the entanglement, wherein a portion of the polyurethane penetrates into the interior of the fiber bundles, and the penetration rate of the polyurethane is in the range of 1 to 30% in area ratio in any cross section perpendicular to the length direction of the fiber bundles. Patent Document 1 discloses that by controlling the solubility of the water-soluble polymer component, which is the marine component of the sea-island type composite fiber removed to form the fiber bundles, and by manufacturing the artificial leather so that a portion of the water-based polyurethane penetrates into the interior of the fiber bundles during the drying process after impregnating the entanglement of sea-island type composite fibers with a polyurethane aqueous dispersion, an artificial leather can be obtained in which a soft texture is maintained and fiber shedding is suppressed.

[0006] Furthermore, Patent Document 2 discloses a piled artificial leather having piles of ultrafine fibers on at least one surface, comprising a nonwoven fabric made of fiber bundles of ultrafine long fibers and polyurethane optionally contained in the nonwoven fabric, wherein the fiber bundles of ultrafine long fibers are formed by removing the water-soluble resin from composite long fibers containing a water-soluble resin, and a water-based polyurethane obtained from a polyurethane aqueous dispersion is present at the base of the piles and in its vicinity, thereby providing excellent anti-pilling properties.

[0007] Furthermore, Patent Document 3 below describes a sheet-like material in which a porous polyurethane is applied as a binder to a fibrous base material consisting of ultrafine fibers and / or bundles of ultrafine fibers, wherein in a cross-section cut in the thickness direction of the sheet-like material, of the polyurethane observed within the cut surface, 50 μm independently 2 The present invention discloses a sheet-like material in which the proportion of the portion having the above cross-sectional area is 0.1% to 5.0% of the area of ​​the artificial leather cross-section within the observation field. Furthermore, it is disclosed that in such a sheet-like material, in the cross-section cut in the thickness direction, 1% to 35% of the outer circumference of the ultrafine fibers and / or ultrafine fiber bundle cross-sections is covered with a polyurethane coating. Patent Document 3 discloses that such a sheet-like material is obtained by an environmentally conscious manufacturing process, has a uniformity comparable to artificial leather manufactured using solvent-based polyurethane, and possesses an elegant quality and good texture on the napped surface.

[0008] Furthermore, Patent Document 4 discloses a sheet-like material made of a fibrous base material and porous aqueous polyurethane, wherein the aqueous polyurethane contains polysaccharides and has pores of 1 to 200 μm. Patent Document 4 discloses that such a sheet-like material can be obtained through an environmentally conscious manufacturing process and has an elegant appearance and good texture regardless of the type of aqueous polyurethane used. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2007 / 099951 [Patent Document 2] Japanese Patent Publication No. 2011-074541 [Patent Document 3] International Publication No. 2015 / 129602 [Patent Document 4] Japanese Patent Publication No. 2019-112742 [Overview of the project] [Problems that the invention aims to solve]

[0010] According to the method for manufacturing artificial leather disclosed in Patent Document 1, the penetration of the aqueous polyurethane into the fiber bundles is limited because the polyurethane aqueous dispersion is impregnated into the entangled sea-island type composite fiber before the sea components are removed. As a result, it was difficult to obtain artificial leather that could sufficiently reduce fiber shedding. Furthermore, the texture tended to become hard because the aqueous polyurethane dispersion was impregnated into the fiber bundles throughout the thickness direction. In addition, when water-soluble polyvinyl alcohol is used as the sea component and the aqueous polyurethane contains ether-based polyurethane, the aqueous polyurethane swells and mixes with the water-soluble polyvinyl alcohol during the drying process after impregnation with the polyurethane aqueous dispersion. Therefore, the ether-based polyurethane tends to detach during the process of extracting and removing the sea components and the process of dyeing the ultrafine fibers, and the quality of the resulting artificial leather is difficult to stabilize due to variations in the amount of ether-based polyurethane detached.

[0011] Furthermore, according to the method for manufacturing artificial leather disclosed in Patent Document 2, in order to form a continuous or discontinuous polyurethane layer on the surface of the nonwoven fabric, the polyurethane tends to be exposed on the pile surface, which tends to result in uneven coloring, insufficient fluffing, and other issues that degrade the overall appearance and sense of luxury.

[0012] Furthermore, according to the method for manufacturing a sheet-like material disclosed in Patent Document 3, a sheet-like material is obtained in which the adhesive strength between the outer circumference of the fiber bundle and the water-based polyurethane is low, and the water-based polyurethane contains small clumps formed by the aggregation of water-based polyurethane particles. Although such a sheet-like material has a soft texture due to the low gripping force of the water-based polyurethane on the fiber bundle, the quality and physical properties of the pile surface are poor because the ultrafine fibers tend to slip out. In addition, because the aggregated water-based polyurethane particles form discontinuous aggregates with many voids, for example, with a diameter of about 0.5 to 10 μm, the texture tends to lack body when the polyurethane content is low. Also, when the water-based polyurethane content is increased in order to give the texture body, the water-based polyurethane tends to be exposed on the pile surface, making color unevenness noticeable and reducing the luxurious feel of the pile surface.

[0013] Furthermore, according to the method for manufacturing a sheet-like material disclosed in Patent Document 4, the texture becomes soft because it contains porous aqueous polyurethane having pores of 1 to 200 μm. However, because the gripping force of the aqueous polyurethane on the fiber bundle is low, ultrafine fibers tend to slip out easily, resulting in a sheet-like material with poor quality and physical properties on the pile surface. Also, because the aqueous polyurethane has pores of 1 to 200 μm, the texture does not develop well when the content of aqueous polyurethane is low. Moreover, when the content of aqueous polyurethane is increased in order to give the texture more body, the aqueous polyurethane tends to be more exposed on the pile surface, making color unevenness noticeable and reducing the luxurious feel of the pile surface.

[0014] The present invention aims to provide a napped artificial leather manufactured using environmentally friendly water-based polyurethane, which combines a smooth appearance with minimal color unevenness on the napped surface, a luxurious feel, a soft texture, and high anti-pilling properties. [Means for solving the problem]

[0015] One aspect of the present invention includes a fiber bundle complex including a fiber bundle composed of 5 to 75 ultrafine fibers, and 5 to 20% by mass of an aqueous polyurethane impregnated and applied to the fiber bundle complex. It has a flocked surface with ultrafine fibers standing on at least one surface thereof, and in a cross-section cut in the thickness direction, a continuous region of the aqueous polyurethane having a straight length of 50 μm or more is 0.04 mm 2 At least one on average per area, and when the region from the flocked surface to a virtual line at a distance of 100 μm in the thickness direction is defined as the surface layer region and the region to the back surface excluding the surface layer region is defined as the non-surface layer region, in the surface layer region, the ratio (A1 / T1×100) of the number (A1) of the first fiber bundles in which more than half of the ultrafine fibers are aggregated by the aqueous polyurethane to the total number of fiber bundles (T1) in the surface layer region is 20 to 60%, and in the non-surface layer region, the ratio (A2 / T2×100) of the number (A2) of the first fiber bundles in which more than half of the ultrafine fibers are aggregated by the aqueous polyurethane to the total number of fiber bundles (T2) in the non-surface layer region is 0 to 10%. It is a flocked artificial leather. Such flocked artificial leather, in the surface layer region, by having a large amount of aqueous polyurethane inside the fiber bundle, suppresses the occurrence of color unevenness due to the difference in color from the ultrafine fibers by exposing the aqueous polyurethane on the surface, while moderately restraining the ultrafine fibers in the surface layer region. As a result, it is possible to achieve both high anti-pilling property and suppression of the occurrence of color unevenness on the flocked surface. Also, in the non-surface layer region, since the ratio of the fiber bundles in which the aqueous polyurethane penetrates into the ultrafine fibers to restrain them is low, the ultrafine fibers are not overly restrained. Therefore, the soft texture of the flocked artificial leather can be maintained. Further, by including a continuous region of the aqueous polyurethane having a straight length of 50 μm or more, it becomes easier for a plurality of fiber bundles to be mutually restrained through one continuous region, so that an appropriate restraining force can be maintained with a small amount of aqueous polyurethane to suppress the pulling out of the ultrafine fibers. As a result, a flocked artificial leather having a surface appearance with little color unevenness, a soft texture, and high anti-pilling property can be obtained.

[0016] In addition, for the raised-pile artificial leather, the ratio (B2 / T2×100) of the number (B2) of the second fiber bundles that do not allow the aqueous polyurethane to penetrate therein and are adhesively bonded or in contact with the continuous region at a length of 1 / 4 or more of the outer periphery of the fiber bundles to the total number of fiber bundles (T2) is preferably 10 to 40%.

[0017] In addition, it is preferable that the continuous region adhesively bonds two or more fiber bundles. This is because multiple fiber bundles are more strongly constrained through the continuous region, making it difficult for the ultrafine fibers to slip through.

[0018] In addition, it is preferable that the continuous region does not have a particle interface derived from the contour of the dispersed particles of the aqueous polyurethane dispersion. This is because the aqueous polyurethane forms a strong continuous film with high continuity, making it difficult for the aqueous polyurethane to fall off or deform, and resulting in a raised-pile artificial leather with better quality and physical properties on the raised-pile surface.

[0019] In addition, the aqueous polyurethane forming the continuous region preferably has a heat softening temperature of 170°C or higher and a weight swelling ratio with respect to hot water at 90°C of 1 to 8%. This is preferable because it is easy to form the continuous region as described above by heating and drying.

[0020] In addition, the aqueous polyurethane includes a self-emulsifying type polyurethane having an anionic hydrophilic group, including a polymer diol unit, an organic diisocyanate unit, and a chain extender unit, and including a urethane skeleton into which an acid group is introduced. The polymer diol unit includes a polycarbonate diol unit containing 50 to 100 mol% of a diol unit having a methyl branch in 60 to 100 mol%, and the organic diisocyanate unit includes an organic diisocyanate unit containing at least one selected from 70 to 100 mol% of an alicyclic diisocyanate unit having no methyl branch in the alicyclic structure and a 4,4'-diphenylmethane diisocyanate unit. This is preferable because it is easy to form a continuous region due to excellent film-forming properties, has excellent quality stability because it is difficult to cause shedding in manufacturing processes such as the process of extracting and removing the sea component and the process of dyeing ultrafine fibers, and is easy to appropriately bundle the ultrafine fibers by penetrating into the inside of the fiber bundles.

[0021] Another aspect of the present invention is a method for manufacturing the above-described piled artificial leather, comprising the steps of: preparing a sea-island type composite fiber comprising a water-soluble PVA resin as a sea component and a water-insoluble resin as an island component, wherein the entanglement of sea-island type composite fibers has 5 to 75 islands; impregnating the entanglement of sea-island type composite fibers with a first polyurethane aqueous dispersion, and then heating and drying the first polyurethane aqueous dispersion at a temperature at which the dispersed particles fuse to produce a fiber base material impregnated with a first aqueous polyurethane; forming an artificial leather base material by removing the water-soluble PVA resin from the sea-island type composite fibers of the fiber base material; and buffing at least one surface of the artificial leather base material to raise the ultrafine fibers on its surface to form a piled surface. , a person who has formed a hair-raised surface Artificial leather raw machine on the raised pile surface The process includes the step of applying a second aqueous polyurethane dispersion and then heating and drying it at a temperature that fuses the dispersed particles to impart a second aqueous polyurethane to the interior of the surface fiber bundle, wherein the first aqueous polyurethane dispersion and the second aqueous polyurethane dispersion are emulsions of aqueous polyurethane in which the average dispersed particle diameter of the aqueous polyurethane dispersion particles is 30 to 200 mm, and the first aqueous polyurethane and the second aqueous polyurethane contain polymer diol units, organic diisocyanate units, and chain extension units, and also contain an anionic hydrophilic urethane skeleton into which acid groups have been introduced. Preferably, the method for producing a napped artificial leather is one in which a self-emulsifying polyurethane having a property group is used, the polymer diol unit comprises 60 to 100 mol% of polycarbonate diol units containing 50 to 100 mol% of methyl-branched diol units, and the organic diisocyanate unit comprises 70 to 100 mol% of organic diisocyanate units containing at least one selected from alicyclic diisocyanate units without methyl branching in the alicyclic structure and 4,4'-diphenylmethane diisocyanate units, the heat softening temperature is 170°C or higher, and the weight swelling rate in hot water is 1 to 8%. Such polymer diols are preferable because they have excellent film-forming properties, do not easily create particle interfaces due to the contours of dispersed particles, thus easily forming continuous regions, have excellent resistance to hot water swelling in the dyeing process, and have excellent adhesion to ultrafine fibers, making it easy to obtain a water-based polyurethane that easily forms continuous regions.

[0022] Furthermore, it is preferable that at least one thickener selected from polyacrylic acid-based polymer-type thickeners and polyurethane-based association-type thickeners is added to the second polyurethane aqueous dispersion in an amount of 0.1 to 8% by mass, as this provides excellent penetration into the interior of the fiber bundle, making it easier to appropriately bundle the ultrafine fibers that form the surface fiber bundle.

[0023] Furthermore, it is preferable to include a step of applying at least one compound selected from surfactants and hydrophilic compounds to the artificial leather material in a step prior to applying the second polyurethane aqueous dispersion, as this controls the permeability, allowing the second polyurethane aqueous dispersion to penetrate appropriately into the fiber bundles of the surface region, making it easier to obtain a napped artificial leather that has an appearance with less color unevenness, a luxurious feel, and high anti-pilling properties.

[0024] Furthermore, the second polyurethane aqueous dispersion was prepared Person who formed a hair surface When 0.05 ml is dropped onto the napped surface of the raw leather fabric, a penetration time of 1 to 60 seconds is preferable because it allows the second polyurethane to penetrate appropriately into the fiber bundles in the surface region, making it easier to achieve both high pilling resistance and a flexible texture. [Effects of the Invention]

[0025] According to the present invention, a piled artificial leather can be produced by a process using environmentally friendly water-based polyurethane, which has an appearance with minimal color unevenness on the piled surface, a luxurious feel, a soft texture, and excellent anti-pilling properties. [Brief explanation of the drawing]

[0026] [Figure 1] Figure 1 is a scanning electron microscope (SEM) image at 70x magnification of a region in a cross-section of the artificial napped leather of Example 1, cut in the thickness direction. [Figure 2] Figure 2 is a 200x magnification SEM image of the surface area of ​​a cross-section of the artificial leather used in Example 1, cut in the thickness direction. [Figure 3]Figure 3 is a 500x magnification SEM image of a cross-section of the piled artificial leather of Example 1, cut in the thickness direction, illustrating the continuous region near the surface. [Figure 4] Figure 4 is a 500x magnification SEM image of a cross-section of the piled artificial leather of Example 1, cut in the thickness direction, to illustrate the fiber bundles near the surface. [Figure 5] Figure 5 is a 500x magnification SEM image of a cross-section of the piled artificial leather of Example 1, cut in the thickness direction, illustrating the continuous region of the non-surface area. [Figure 6] Figure 6 is a 500x magnification SEM image of a cross-section of the piled artificial leather of Example 1, cut in the thickness direction, to illustrate the fiber bundles in the non-surface region. [Figure 7] Figure 7 is a 500x magnification SEM image of the surface region of a cross-section of the piled artificial leather of Comparative Example 1, cut in the thickness direction. [Figure 8] Figure 8 is a 500x magnification SEM image of the non-surface region in a cross-section cut in the thickness direction of the piled artificial leather of Comparative Example 6. [Modes for carrying out the invention]

[0027] The piled artificial leather of this embodiment comprises a fiber bundle containing 5 to 75 ultrafine fibers and 5 to 20% by mass of water-based polyurethane impregnated into the fiber bundle. It has a piled surface on at least one side in which the ultrafine fibers are raised.

[0028] The fiber bundle entanglement is formed by removing the island component from an entanglement of sea-island type composite fibers, which are ultrafine fiber-generating fibers having a cross-section containing both sea and island components. Examples of entanglements include nonwoven fabrics, woven fabrics, knitted fabrics, or entanglements combining these. Among these, nonwoven fabrics are preferred because they yield a high-quality artificial leather with an excellent surface appearance.

[0029] The number of ultrafine fibers forming the fiber bundle derived from the islands of the sea-island type composite fiber is preferably 5 to 75, with 7 to 70, and even more preferably 9 to 50. If the number of ultrafine fibers forming the fiber bundle is less than 5, it becomes difficult to obtain a high-quality surface appearance with an elegant fluffy texture due to the raised fibers, and pilling in the form of lint balls is more likely to occur due to friction with other articles. On the other hand, if the number of ultrafine fibers forming the fiber bundle exceeds 75, the color development by dyeing decreases, making it difficult to obtain dark colors, and the mechanical properties of the ultrafine fibers decrease, making them more prone to shedding due to friction with other articles.

[0030] The average fiber diameter of the ultrafine fibers being 1-8 μm, and more specifically 1.5-6 μm, is preferable because it easily produces a luxurious, high-quality napped surface with an elegant fluffiness due to the raised fibers, and also reduces pilling, provides excellent color development, and minimizes shedding.

[0031] The number of ultrafine fibers forming a fiber bundle, the average fiber diameter of the ultrafine fibers, and the average fiber bundle diameter can be determined from 500x scanning electron microscope (SEM) images taken at 15 locations evenly selected from a cross-section cut parallel to the thickness direction of the bristled artificial leather. Specifically, the average fiber diameter of the ultrafine fibers cut perpendicular to the fiber axis direction is measured in each SEM image and calculated as the average value of 15 evenly selected locations. The fiber diameter and fiber bundle diameter are calculated as the diameter when converted to circles with the same area.

[0032] The piled artificial leather contains 5-20% by mass of water-based polyurethane impregnated into the fiber bundle composite. By containing water-based polyurethane at a relatively low proportion, the piled artificial leather makes it less likely for color unevenness to appear on the pile surface due to the color difference between the water-based polyurethane and the ultrafine fibers, and also maintains a soft texture. If the water-based polyurethane content exceeds 20% by mass, color unevenness is more likely to appear on the pile surface, and it becomes more difficult to maintain a soft texture. Furthermore, if the water-based polyurethane content is less than 5% by mass, the continuous regions described later become less likely to form, and the ultrafine fibers are more likely to fall out, reducing the anti-pilling properties.

[0033] Furthermore, the pile artificial leather, in a cross-section cut in the thickness direction, contains a continuous region of aqueous polyurethane having a linear length of 50 μm or more, formed from an aqueous polyurethane dispersion. The continuous region of aqueous polyurethane is formed by agglomerating and fusing dispersed particles of aqueous polyurethane in the aqueous dispersion. Then, as will be described later, in a cross-section cut in the thickness direction of the pile artificial leather, the continuous region is 0.04 mm 2 Each region contains an average of one or more particles. Referring to Figure 3, the continuous region has a continuous straight length of 50 μm or more, as indicated by the lengths of the equivalent arrows. In such a continuous region, it is preferable that, in a 500x SEM image of the cross-section taken by SEM, numerous voids with an average diameter of 0.5 to 10 μm that remain when the dispersed particles are incompletely fused, and interfaces formed by the contours of the dispersed particles are not substantially observed on the surface. Specifically, for example, it is preferable that 10 or more, more than 5, and especially 3 or more, voids with an average diameter of 0.5 to 10 μm are not observed. Furthermore, because the continuous region is sufficiently heat-fused and film-formed by the water-based polyurethane so that it does not have interfaces formed by the contours of the dispersed particles, the water-based polyurethane becomes less likely to detach or deform, thereby improving the quality and physical properties of the pile surface.

[0034] Furthermore, in a cross-section cut in the thickness direction, if the region from the pile surface to a virtual line at a distance of 100 μm in the thickness direction is defined as the surface region, and the region excluding the surface region up to the back surface is defined as the non-surface region, then continuous regions of fiber bundles and aqueous polyurethane exist in the following specific form.

[0035] In the surface region, the ratio of the number of first fiber bundles (A1) in which more than half of the ultrafine fibers forming the fiber bundles are concentrated by water-based polyurethane to the total number of fiber bundles (T1) in the surface region is 20-60%. Here, "concentrated ultrafine fibers" means that multiple ultrafine fibers forming a fiber bundle are bonded together by water-based polyurethane. Note: 0.04 mm 2 The area of ​​this region roughly matches the field of view observed at 500x magnification using a scanning electron microscope (SEM).

[0036] Furthermore, in the non-surface region, the ratio of the number of first fiber bundles (A2) in which more than half of the ultrafine fibers that form fiber bundles by penetrating the interior of the water-based polyurethane are concentrated, to the total number of fiber bundles (T2) in the non-surface region, is 0-10%.

[0037] Referring to an SEM image of a cross-section of the piled artificial leather 10 obtained in Example 1, described later, cut in the thickness direction, the morphology of the fiber bundles and water-based polyurethane present in the surface and non-surface regions will be explained in more detail.

[0038] Figure 1 is a 70x magnification SEM image of a region in a cross-section of the piled artificial leather 10 obtained in Example 1, cut in the thickness direction. Figure 2 is a 200x magnification SEM image of the area near the surface of the cross-section of the piled artificial leather 10 cut in the thickness direction. Figure 3 is a 500x magnification SEM image of the cross-section of the piled artificial leather 10 cut in the thickness direction to illustrate the continuous area near the surface. Figure 4 is a 500x magnification SEM image of the cross-section of the piled artificial leather from Example 1 cut in the thickness direction to illustrate the fiber bundles near the surface. Similarly, Figure 5 is a 500x magnification SEM image of the cross-section of the piled artificial leather from Example 1 cut in the thickness direction to illustrate the continuous area of ​​the non-surface region. Figure 6 is a 500x magnification SEM image of a cross-section of the piled artificial leather of Example 1, cut in the thickness direction, illustrating the fiber bundles in the non-surface region.

[0039] Referring to Figures 1 and 2, the napped artificial leather 10 includes a fiber bundle entanglement of fiber bundles 1 consisting of 5 to 75 ultrafine fibers 1a, and a water-based polyurethane 2 that forms a continuous region attached to the fiber bundle entanglement of fiber bundles 1. Also referring to Figure 1, the napped artificial leather 10 has a napped surface N formed by raising the nap of the ultrafine fibers on the surface.

[0040] Referring to Figure 2, which is a 200x magnification SEM image of the surface area of ​​the piled artificial leather 10, the region from the piled surface to the imaginary line L, located 100 μm away in the thickness direction, is defined as the surface region S, and the region excluding the surface region up to the back surface is defined as the non-surface region M. Furthermore, the surface region S is defined as the region from the curve connecting the upper surfaces of the fiber bundles at the base of the piled ultrafine fibers to the imaginary line L, which is 100 μm away. The piled surface is the surface used as the surface of the piled artificial leather. The imaginary line L is an imaginary curve located 100 μm away from the curve connecting the upper surfaces of the fiber bundles forming the piled surface.

[0041] Referring to Figures 3 and 4, which are SEM images of the surface region at a magnification of 500x, the morphology of the fiber bundles and aqueous polyurethane observed in the cross-section of the piled artificial leather of this embodiment will be explained.

[0042] (A) First fiber bundle We define a first fiber bundle as one in which water-based polyurethane has penetrated the interior of the fiber bundle, and more than half of the ultrafine fibers contained in the fiber bundle are bound together by water-based polyurethane. In Figure 4, this is enclosed by a circle labeled "A1".

[0043] (B) Second fiber bundle A second fiber bundle is defined as one in which the water-based polyurethane has not penetrated the interior of the fiber bundle to the extent that it has gathered more than half of the ultrafine fibers contained within the fiber bundle, but the ultrafine fibers are adhered to or in contact with the continuous region for a length of 1 / 4 or more of the outer circumference of the fiber bundle. In Figure 4, this is enclosed by a circle labeled "B1". Whether or not a fiber bundle is adhered to or in contact with the continuous region is determined by identifying the outer circumference by connecting the surfaces of the ultrafine fibers that form the outer circumference of the fiber bundle based on SEM images taken at 500 to 1000x magnification, and then determining whether or not the ultrafine fibers forming the outer circumference are adhered to or in contact with the continuous region.

[0044] (C) Third fiber bundle Fiber bundles other than the first and second fiber bundles are defined as the third fiber bundle. Specifically, a third fiber bundle is defined as a fiber bundle in which the water-based polyurethane has not penetrated the interior of the fiber bundle to the extent that more than half of the ultrafine fibers contained in the fiber bundle are concentrated, and in which the ultrafine fibers are not bonded or in contact with each other in a continuous region and for more than 1 / 4 of the length of their outer circumference. In Figure 4, this is enclosed by a circle labeled "C1".

[0045] (D) Continuous region of water-based polyurethane A continuous region of aqueous polyurethane is defined as a cross-section of a continuous film of aqueous polyurethane with a straight length of 50 μm or more. A continuous region with a straight length of 50 μm or more means that the maximum straight distance between the ends of a continuous film formed by continuously depositing aqueous polyurethane is 50 μm or more. In Figure 3, these are labeled R1, R2, and R3.

[0046] Figure 3, an SEM image of the surface region, shows continuous regions R1, R2, and R3 with a linear length of 50 μm or more. Specifically, continuous region R1 has a linear length of 195 μm, continuous region R2 has a linear length of 125 μm, and continuous region R3 has a linear length of 70 μm. The maximum length of a continuous region in this image is 195 μm.

[0047] The continuous region adheres to or contacts two or more fiber bundles, making it easier to restrain them, thus supporting the water-based polyurethane and preventing it from falling off. Furthermore, the inclusion of the continuous region in the napped artificial leather improves the luxurious quality and anti-pilling properties of the napped surface, maintaining a firm texture. The continuous region measures 240 μm × 180 μm (0.04 mm) at 500x magnification. 2 On average, one or more are included in the field of view of the SEM image.

[0048] The continuous region has a linear length of 50 μm or more, preferably 75 μm or more, and more preferably 100 μm or more. While there is no particular upper limit, within the observation field, it is preferably about 600 μm, and more preferably about 300 μm. If the water-based polyurethane does not form a continuous region, the restraining force on the fiber bundle weakens, and the effect of improving anti-pilling properties decreases.

[0049] Furthermore, the continuous region is formed by thermal fusion of dispersed particles in such a way that it leaves almost no voids. When the cross-section of such a continuous region is observed at 500x magnification with a SEM, it is preferable that it contains almost no voids with an average diameter of 0.5 to 10 μm that remain when dispersed particles are incompletely fused, and more preferably contains 10 or fewer voids, even 5 or fewer, especially 3 or fewer, and most preferably 0 voids.

[0050] Furthermore, it is preferable that the continuous region does not have interfaces formed by the contours of the dispersed particles. This is preferable because the water-based polyurethane forming the continuous region is sufficiently heat-fused to create a film, making it less likely for the water-based polyurethane to detach or deform, and thus improving the quality and physical properties of the pile surface.

[0051] (Morphology of the surface region) Referring to Figure 4, in the surface region S, there are three fiber bundles: a first fiber bundle A1, a second fiber bundle B1, and a third fiber bundle C1. A fiber bundle is defined as a bundle of ultrafine fibers originating from a single ultrafine fiber-generating fiber. Furthermore, fiber bundles in which the ultrafine fibers constituting the fiber bundle have opened up and have not yet formed a cohesive fiber bundle are also classified into one of the fiber bundles according to the definition above.

[0052] The classification of each fiber bundle described above is determined by identifying the boundaries of the fiber bundles based on the number of ultrafine fibers forming each bundle, as can be seen in Figure 4. The boundaries of the fiber bundles can be determined based on SEM images taken at 500 to 1000x magnification. If it is difficult to determine the boundaries of the fiber bundles, the boundaries can be determined based on the average number of ultrafine fibers forming the bundle.

[0053] Furthermore, in this embodiment of the pile artificial leather, the proportion of first fiber bundles A1 (A1) in which more than half of the ultrafine fibers forming the fiber bundles are bundled with water-based polyurethane that has penetrated into the interior of the fiber bundles is 20-60% of the total number of fiber bundles (T1) in the surface region.

[0054] Here, the total number of fiber bundles in the surface region (T1) is calculated from the sum of the number of first fiber bundles A1 (A1), the number of second fiber bundles B1 (B1), and the number of third fiber bundles C1 (C1) present in the surface region, which is (A1) + (B1) + (C1). Therefore, the ratio of the number of first fiber bundles (A1) to the total number of fiber bundles in the surface region (T1) is calculated from the formula (A1) / {((A1)+(B1)+(C1))} × 100 (%). Also, the ratio of the number of second fiber bundles (B1) to the total number of fiber bundles in the surface region (T1) is calculated from the formula (B1) / {(A1)+(B1)+(C1))} × 100 (%).

[0055] The proportion of each fiber bundle is calculated from the number of first, second, or third fiber bundles identified in a 240 μm × 180 μm field-of-view SEM image at 500x magnification in a cross-section of the bristled artificial leather cut in the thickness direction. The value for each proportion is the average calculated from 15 SEM images.

[0056] Specifically, for example, in Figure 4, which is an SEM image of a cross-section of the surface region, the number of first fiber bundles A1 (A1) in the surface region S is 19, the number of second fiber bundles B1 (B1) is 2, and the number of third fiber bundles C1 (C1) is 15. Therefore, the ratio of the number of first fiber bundles A1 (A1) to the total number of fiber bundles in the surface region (T1), as determined from Figure 4, is calculated as {19 / (19+2+15)}×100=53%. Also, the ratio of the number of second fiber bundles B1 (B1) to the total number of fiber bundles in the surface region (T1) is calculated as {2 / (19+2+15)}×100=6%.

[0057] In this embodiment, the piled artificial leather has a ratio of 20-60% of the number of first fiber bundles (A1) to the total number of fiber bundles (T1) in the surface region. If the ratio of the number of first fiber bundles (A1) in the surface region is less than 20%, the ultrafine fibers tend to fall out easily, reducing the anti-pilling properties. If it exceeds 60%, the ultrafine fibers that are concentrated on the piled surface tend to be exposed, resulting in a rough surface texture.

[0058] Furthermore, in the SEM image of the surface region shown in Figure 3, continuous regions R1, R2, and R3 with a linear length of 50 μm or more are visible. These continuous regions R1, R2, and R3 are each attached to, in contact with, or in close proximity to numerous fiber bundles.

[0059] (Morphology of the non-surface region) Referring to Figures 5 and 6, in the non-surface region M of the piled artificial leather of this embodiment, water-based polyurethane has hardly penetrated into the fiber bundles, and many of the ultrafine fibers forming the fiber bundles have separated.

[0060] Referring to Figure 6, even in the non-surface region, there is a first fiber bundle A2 in which more than half of the ultrafine fibers are concentrated, a second fiber bundle B2 in which the ultrafine fibers are separated but more than 1 / 4 of the length of the outer circumference of the fiber bundle is adhered to or in contact with the continuous region, and a third fiber bundle C2 other than the first fiber bundle A2 and the second fiber bundle B2.

[0061] Furthermore, in this embodiment of the pile artificial leather, the ratio of the number of first fiber bundles A2 (A2) in which water-based polyurethane has penetrated into the interior of the fiber bundles so as to concentrate more than half of the ultrafine fibers is 0 to 10% of the total number of fiber bundles (T2) in the non-surface region.

[0062] The total number of fiber bundles in the non-surface region (T2) is calculated from the sum of the number of first fiber bundles A2 (A2), the number of second fiber bundles B2 (B2), and the number of third fiber bundles C2 (C2) present in the non-surface region: (A2) + (B2) + (C2). Therefore, the ratio of the number of second fiber bundles (A2) to the total number of fiber bundles in the non-surface region (T2) is calculated from the formula (A2) / {(A2)+(B2)+(C2)} × 100(%). Similarly, the ratio of the number of second fiber bundles (B2) to the total number of fiber bundles in the non-surface region (T2) is calculated from the formula (B2) / {(A2)+(B2)+(C2))} × 100(%).

[0063] Specifically, for example, in Figure 6, which is an SEM image of a cross-section of a non-surface region, the number of first fiber bundles A2 (A2) is 3, the number of second fiber bundles B2 (B2) is 14, and the number of third fiber bundles C2 (C2) is 30. Therefore, the ratio of the number of first fiber bundles A2 (A2) to the total number of fiber bundles in the non-surface region (T2), as determined from Figure 6, is calculated as {3 / (3+14+30)}×100=6%. Also, the ratio of the number of second fiber bundles B2 (B2) to the total number of fiber bundles in the non-surface region (T2) is calculated as {14 / (3+14+30)}×100=30%.

[0064] In the napped artificial leather of this embodiment, the ratio of the number of first fiber bundles (A2) to the total number of fiber bundles (T2) in the non-surface region is 0 to 10%, preferably 0 to 8%. If the ratio of the number of first fiber bundles (A2) in the non-surface region exceeds 10%, the texture becomes hard.

[0065] Furthermore, a ratio of 10-40% to 15-35% of the number of second fiber bundles (B2) relative to the total number of fiber bundles in the non-surface region (T2) is particularly preferable, as it provides an excellent balance between pilling resistance and a soft texture.

[0066] Furthermore, even in the non-surface region, there is a 0.04 mm area corresponding to 240 μm × 180 μm. 2Within the field of view of this area, an average of one or more continuous regions with a linear length of 50 μm or more are observed. In the SEM image of Figure 5, a continuous region R4 with a linear length of 140 μm and a continuous region R5 with a linear length of 70 μm can be identified. The longest continuous region in this image is continuous region R4 at 140 μm.

[0067] Furthermore, the continuous regions R4 and R5 are each adhered to, in contact with, or in close proximity to numerous fiber bundles.

[0068] Next, the method for manufacturing the piled artificial leather of this embodiment described above will be explained in detail below. The piled artificial leather of this embodiment is manufactured, for example, by the following process.

[0069] First, a sea-island type composite fiber entanglement is manufactured, containing a water-soluble polyvinyl alcohol-based resin (water-soluble PVA) as the sea component and a water-insoluble resin that forms ultrafine fibers as the island component. Then, the sea-island type composite fiber entanglement is impregnated with a first polyurethane aqueous dispersion with high film-forming properties. Next, a fiber base material to which the first aqueous polyurethane is applied is manufactured by heating and drying at a temperature at which the dispersed particles of the first aqueous polyurethane in the first polyurethane aqueous dispersion fuse together to form a film. Finally, an artificial leather base material is obtained from which the water-soluble PVA, which is the sea component, has been removed from the sea-island type composite fiber forming the fiber base material. Finally, the ultrafine fibers on the surface of the artificial leather base material are raised by buffing on at least one surface to manufacture a napped artificial leather base material having a napped surface.

[0070] Then, a second polyurethane aqueous dispersion with high film-forming properties is applied to the napped surface of the napped artificial leather fabric to impregnate the fiber bundles of the surface layer, and the fabric is heated and dried at a temperature at which the dispersed particles of the second aqueous polyurethane in the second polyurethane aqueous dispersion fuse together, thereby producing napped artificial leather fabric in which the second aqueous polyurethane has permeated the fiber bundles of the surface layer. Then, post-treatment such as dyeing the napped artificial leather fabric is performed as needed. In the above-described process, as the first polyurethane aqueous dispersion with high film-forming properties and the second polyurethane aqueous dispersion, for example, a self-emulsifying polyurethane having a high heat softening temperature, low hot water swelling properties, and an anionic hydrophilic group containing an acid group-introduced urethane skeleton, as described later, is preferably used because it easily forms a continuous region without particle interfaces due to the contours of the dispersed particles. Through these steps, the napped artificial leather of this embodiment is obtained. Each step will be described in detail below.

[0071] [Manufacturing of intertwined sea-island type composite fibers] This section describes the manufacturing process for sea-island composite fiber entanglements. The sea-island composite fiber entanglement is produced by melt-spinning a water-insoluble resin to form the island components (which will become ultrafine fibers) and a water-soluble PVA to form the sea components, using methods such as spunbonding, so that the cross-section has a sea-island structure. The melt-spun fibers are then collected on a net to form a web, which is then entangled using methods such as needle punching or water-flow entanglement. In this way, the sea-island composite fiber entanglement is manufactured.

[0072] Methods for manufacturing sea-island composite fiber webs include collecting the sea-island composite fibers on a net without cutting them to form a web of long fibers, or cutting the long fibers into staples to form a web of short fibers. The formed web may also be subjected to a fusion treatment to impart morphological stability. Furthermore, in any of the steps from removing the marine component of the sea-island composite fiber to forming ultrafine fibers, the sea-island composite fiber may be densified by fiber shrinkage treatment such as heat shrinkage treatment using steam, hot water, or dry heat. Note that "long fibers" refer to continuous fibers, not short fibers intentionally cut after spinning. The fiber length of the sea-island composite fiber before ultrafine fiber formation is preferably 100 mm or more, but it may be several meters, several hundred meters, several kilometers, or even longer, provided it is technically feasible and not inevitably cut during the manufacturing process.

[0073] Specific examples of resins used as island components for forming ultrafine fibers include, for example, aromatic polyesters such as polyethylene terephthalate (PET), isophthalic acid-modified PET, sulfoisophthalic acid-modified PET dyeable with cationic dyes, polybutylene terephthalate, and polyhexamethylene terephthalate; aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and polyhydroxybutyrate-polyhydroxyvalate copolymer; nylons such as nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, and nylon 6-12; polyolefins such as polypropylene, polyethylene, polybutene, polymethylpentene, and chlorinated polyolefins; modified polyvinyl alcohols such as modified polyvinyl alcohol containing 25-70 mol% ethylene units; and thermoplastic resins such as polyurethane elastomers, polyamide elastomers, and polyester elastomers. These may be used individually or in combination of two or more types. Among these, polyester is preferred because it is easy to dye, has little change in water absorption, and has excellent durability. Furthermore, the resin for forming the ultrafine fibers may contain, as necessary, coloring pigments, antioxidants, ultraviolet absorbers, fluorescent agents, various stabilizers such as heat stabilizers, deodorants, antifungal agents, lubricants, water repellents, oil repellents, fillers, inorganic fine particles, conductive agents, etc., to the extent that it does not impair the effects of the present invention.

[0074] Furthermore, water-soluble PVA is used to form the marine components. Water-soluble PVA is preferable because it has a low environmental impact, as it can be dissolved and removed by an aqueous medium such as hot water without using organic solvents.

[0075] The number of islands in the sea-island composite fiber is 5 to 75, preferably 7 to 70. The average fiber diameter of the island components is not particularly limited, but is preferably 1 to 10 μm, taking into account the average fiber diameter of the final fiber bundle. Furthermore, the average fiber diameter of the sea-island composite fiber for forming a fiber bundle consisting of ultrafine fibers is preferably 1 to 8 μm, and more preferably 1.5 to 6 μm, taking into account the average fiber bundle diameter of the final fiber bundle.

[0076] [Manufacturing of a fiber substrate impregnated with a first aqueous polyurethane] As described above, a fiber substrate to which the first aqueous polyurethane is applied is produced by impregnating the entangled sea-island type composite fiber with a first polyurethane aqueous dispersion that has high film-forming properties, adhesive properties, and permeability, and then heating and drying it at a temperature at which the dispersed particles of the first aqueous polyurethane in the first polyurethane aqueous dispersion fuse together.

[0077] Water-based polyurethane refers to polyurethane derived from polyurethane aqueous dispersions such as emulsions and dispersions, in which water-based polyurethane or its prepolymer is dispersed in an aqueous medium such as water. Examples of polyurethane aqueous dispersions include emulsions or dispersions containing self-emulsifying polyurethanes with anionic hydrophilic groups introduced by acidic groups such as carboxyl groups into the urethane skeleton, cationic hydrophilic groups introduced by ionic groups such as ammonium groups into the urethane skeleton, or nonionic hydrophilic groups into the urethane skeleton; emulsions of forced-emulsifying polyurethanes obtained by forcibly emulsifying polyurethanes without hydrophilic groups with an emulsifier; and emulsions or dispersions using both self-emulsifying and forced-emulsifying polyurethanes. Among these, emulsions of self-emulsifying polyurethanes having anionic hydrophilic groups introduced by acidic groups into the urethane skeleton, emulsions of forced-emulsifying polyurethanes without hydrophilic groups, or combinations thereof are preferred due to their excellent dispersion stability. Furthermore, due to its good film-forming properties and high adhesion to fiber bundles, an emulsion of self-emulsifying polyurethane having anionic hydrophilic groups with acid groups introduced into the urethane skeleton is particularly preferred.

[0078] Furthermore, the average particle size of the dispersed particles of the aqueous polyurethane in the polyurethane aqueous dispersion is preferably 10 to 250 nm, and more preferably 30 to 200 nm, because it provides good film-forming properties, high adhesion to fiber bundles, and facilitates the formation of the cross-sectional structure containing fiber bundles as described above. If the average particle size is too large, film-forming properties tend to decrease, and it becomes difficult to form continuous regions.

[0079] In this embodiment, it is preferable to use an aqueous dispersion of water-based polyurethane that has excellent film-forming properties, adhesion, and resistance to hot water swelling during the dyeing process. If an aqueous dispersion of water-based polyurethane with poor film-forming properties, poor adhesion, or susceptibility to hot water swelling is used, a water-based polyurethane without continuous regions will be formed, which will have numerous pores with an average diameter of 0.5 to 10 μm. Water-based polyurethane without continuous regions will have poor film-forming properties, adhesion, and resistance to hot water swelling during the dyeing process.

[0080] Water-based polyurethanes can be obtained by reacting urethane raw materials, such as an organic diisocyanate compound having two isocyanate groups, a polymeric diol, a chain extender, and, if necessary, a polyfunctional compound or an acid group-containing compound.

[0081] Organic diisocyanate compounds are compounds having two isocyanate groups. Specific examples include aliphatic diisocyanates such as hexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and 1,4-bis(isocyanatomethyl)cyclohexane; aromatic diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), and xylylene diisocyanate; and polyfunctional compounds that give branched structures such as trifunctional and tetrafunctional isocyanates of the isocyanurate, biuret, and adduct types, as well as polyfunctional isocyanates and their isocyanate blocks. These can be used individually or in combination of two or more types.

[0082] Among these, it is preferable that 70 to 100 mol% of the organic diisocyanate compound contains at least one organic diisocyanate compound selected from alicyclic diisocyanates without methyl branching in the alicyclic structure and 4,4'-diphenylmethane diisocyanate, because a strong pseudo-crystalline structure is easily formed by the aggregation of hard segments. These organic diisocyanate compounds are preferred because they easily suppress hydrothermal swelling and thus easily form continuous regions.

[0083] Among the organic diisocyanate compounds mentioned above, it is particularly preferable that the mixture contains 70 to 100 mol%, and more preferably 80 to 100 mol%, of an organic diisocyanate compound selected from 4,4'-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, and 4,4'-diphenylmethane diisocyanate, relative to the total diisocyanate components.

[0084] Furthermore, polymeric diols are polymeric diols that have two hydroxyl groups. Specific examples include, for instance, 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, polynonamethylene carbonate diol, polydecamethylene polycarbonate diol, and polydodecamethylene polycarbonate diol. Examples include polycarbonate diols such as poly(methyltetramethylene glycol), poly(methyltetramethylene glycol), polyether diols, and poly(methyltetramethylene glycol), and their copolymers; polyester diols, and their copolymers, such as polybutylene adipate diol, polybutylene sebacate diol, polyhexamethylene adipate diol, poly(3-methyl-1,5-pentylene adipate) diol, poly(3-methyl-1,5-pentylene sebacate) diol, and polycaprolactone diol; and polymeric diols such as polyester carbonate diols. These may be used individually or in combination of two or more.Among these, for example, if the ultrafine fibers are polyester fibers, it is preferable that the polymer diol contains at least one selected from polypropylene carbonate diol, polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyhexamethylene carbonate diol, poly(2-methyl-1,3-propylene 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, polynonanemethylene carbonate diol, polynonamethylene polycarbonate diol, and polydecamethylene polycarbonate diol.

[0085] In particular, it is preferable that 60 to 100 mol%, and more preferably 70 to 100 mol%, of the polymer diol is polycarbonate diol. Furthermore, it is preferable that 50 to 100 mol% of the polycarbonate diol contains methyl-branched polycarbonate diol. Examples of methyl-branched polycarbonate diols include poly(2-methyl-1,3-propylene carbonate)diol, poly(3-methyl-1,5-pentylene carbonate)diol, and poly(2-methyl-1,8-octylene carbonate)diol. Such polymer diols are preferred because they have excellent film-forming properties, excellent resistance to hot water swelling in the dyeing process, and excellent adhesion to ultrafine fibers, making it easier to obtain a water-based polyurethane that easily forms continuous regions.

[0086] Furthermore, it is preferable to use a low molecular weight diol containing an acid group to introduce anionic hydrophilic groups into the polyurethane backbone, as an acid group-containing compound that imparts self-emulsifying properties to the polyurethane and reacts with a crosslinking agent to form a self-crosslinked structure. In addition, the polymer diol may be used in combination with a polyfunctional low molecular weight diol such as a triol such as trimethylolpropane or a pentaol such as pentaerythritol, as a polyfunctional compound that gives the polyurethane a branched structure to form an internal crosslinked structure. When an internal crosslinked structure is formed, it is easier to reduce the hot water swelling rate and to improve the heat softening temperature.

[0087] Specific examples of low molecular weight diols containing acidic groups include, for example, carboxyl group-containing diols such as 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, 2,2-bis(hydroxymethyl)heptanoic acid, and 2,2-bis(hydroxymethyl)octanoic acid; sulfonic acid group-containing diols such as 2-(2,3-hydroxypropoxy)-1-propanesulfonic acid; sulfamic acid group-containing diols such as N,N-bis(2-hydroxyalkyl)sulfamic acid and its alkyl ether adducts, or salts of these compounds. As salts of each compound, for example, ammonium salts, amine salts, alkali metal salts, etc., can be used without particular limitation. Examples of amine salts include salts of primary monoamines such as methylamine, ethylamine, propylamine, and octylamine; salts of secondary monoamines such as dimethylamine, diethylamine, and dibutylamine; and salts of tertiary monoamines such as trimethylamine, triethylamine, triethanolamine, N-methyldiethanolamine, N,N-dimethylethanolamine, N-methylpiperidine, N-methylmorpholine, benzyldimethylamine, α-methylbenzyldimethylamine, and N-dimethylaniline. Examples of alkali metal salts include sodium salts, potassium salts, and lithium salts. Low molecular weight diol compounds having acidic groups may be used alone or in combination of two or more. Among these, carboxyl group-containing diols are preferred because they have excellent self-emulsifying and film-forming properties, excellent reactivity with crosslinking agents, and especially when the ultrafine fibers are polyester fibers, they are preferred because they do not cause significant deterioration in physical properties or shape changes even under high-temperature, high-pressure hot water conditions for dyeing polyester or under subsequent alkaline washing conditions, thus facilitating the formation of the aforementioned adhesion state to the fiber bundle and continuous regions without particle interfaces derived from the contours of dispersed particles.

[0088] Furthermore, chain extenders are low-molecular-weight compounds having two functional groups with active hydrogen, such as hydroxyl groups or amino groups. Specific examples of chain extenders include, for example, hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and their derivatives; diamines such as adipic acid dihydrazide and isophthalic acid dihydrazide; triamines such as diethylenetriamine; tetramines such as triethylenetetramine; diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, and 1,4-cyclohexanediol; and amino alcohols such as aminoethyl alcohol and aminopropyl alcohol. These may be used individually or in combination of two or more. Among these, triamines such as hydrazine, ethylenediamine, hexamethylenediamine, piperazine, isophoronediamine and their derivatives; and diethylenetriamine are preferred because they exhibit excellent light resistance and mechanical properties, and especially when the ultrafine fibers are polyester fibers, they show little deterioration in physical properties or change in shape even under high-temperature, high-pressure hot water conditions for dyeing polyester and subsequent alkaline washing conditions, thus facilitating the formation of the aforementioned adhesive state and continuous regions to the fiber bundle.

[0089] Furthermore, the chain extender may also be a polyfunctional low molecular weight diol such as triols like trimethylolpropane, pentaols like pentaerythritol, triamines like diethylenetriamine, or tetramines like triethylenetetramine, which are polyfunctional compounds used to give branched structures that allow for the formation of internal crosslinking structures in aqueous polyurethanes. When an internal crosslinking structure is formed, it becomes easier to reduce the hot water swelling rate and to improve the heat softening temperature.

[0090] Furthermore, monoamines such as ethylamine, propylamine, and butylamine; carboxyl group-containing monoamine compounds such as 4-aminobutanoic acid and 6-aminohexanoic acid; and monools such as methanol, ethanol, propanol, and butanol may be used in combination as chain extenders to adjust the molecular weight or the amount of functional groups.

[0091] Furthermore, to impart self-emulsifying properties to polyurethane by introducing anionic hydrophilic groups and to form a self-crosslinked structure by reacting with a crosslinking agent, a crosslinking agent that reacts with acidic groups may be added to the polyurethane aqueous dispersion. As the crosslinking agent that reacts with acidic groups, it is preferable to use a crosslinking agent that has two functional groups that react with acidic groups in its molecule. Specific examples of such crosslinking agents include, for example, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, and aziridine-based crosslinking agents. Among these, carbodiimide-based crosslinking agents and epoxy-based crosslinking agents are particularly preferred because they have excellent film-forming properties for dispersed particles in the polyurethane aqueous dispersion, easily form continuous regions without particle interfaces derived from the contours of the dispersed particles, have excellent adhesion between water-based polyurethane and ultrafine fibers, and are less susceptible to shedding and deformation during dyeing.

[0092] For water-based polyurethanes, a 100% modulus of 1 to 8 MPa, and more preferably 2 to 7 MPa, is preferable because it facilitates the formation of a continuous region.

[0093] Furthermore, for water-based polyurethanes, a heat softening temperature of 170°C or higher, and more preferably 175°C or higher, is preferable because it facilitates the formation of continuous regions. If the heat softening temperature of the water-based polyurethane is too low, the heat received during the drying process, the process of removing water-soluble PVA, the dyeing process, etc., during the manufacturing process can easily cause the water-based polyurethane to detach or deform.

[0094] Furthermore, the thermal softening temperature of water-based polyurethane is determined by preparing a dry film of water-based polyurethane with a thickness of 100-400 μm and measuring the storage modulus in dynamic viscoelasticity, which is 1 × 10⁻⁶. 6This can be obtained by measuring the temperature at which MPa is reached. A water-based polyurethane having such a thermosoftening temperature can be obtained by selecting the preferred monomer composition described above.

[0095] Furthermore, it is preferable that the water-based polyurethane has a weight swelling rate of 1-8%, or even 1-7%, in response to hot water at 90°C, because the water-based polyurethane is less likely to deform during each of the heat-exposed processes described above, thus facilitating the formation of continuous regions.

[0096] The water-based polyurethane contained in the pile-covered artificial leather of this embodiment has continuous regions with a linear length of 50 μm or more. Compared to porous or short, discontinuous water-based polyurethanes containing numerous voids, water-based polyurethanes with such continuous regions exhibit superior adhesion to the ultrafine fibers forming the outer periphery of the fiber bundle. Such water-based polyurethanes with continuous regions are formed using a polyurethane aqueous dispersion with high film-forming properties.

[0097] An example of a polyurethane aqueous dispersion that readily forms a continuous structure without particle interfaces derived from the contours of dispersed particles and exhibits high film-forming properties is an aqueous polyurethane in which the average dispersed particle diameter is approximately 30-200 nm, the aqueous polyurethane is a self-emulsifying polyurethane having an anionic hydrophilic group such as a urethane skeleton into which acid groups have been introduced, the polymer diol units of the polyurethane include 60-100 mol% of polycarbonate diol units containing 50-100 mol% of methyl-branched diol units, and the organic diisocyanate units of the polyurethane include 70-100 mol% of at least one organic diisocyanate unit selected from alicyclic diisocyanate units without methyl branching in the alicyclic structure and 4,4'-diphenylmethane diisocyanate units. Furthermore, an aqueous polyurethane can be mentioned in which the heat softening temperature is 170°C or higher and the weight swelling rate in 90°C hot water is 1-8%. Other examples include aqueous dispersions of water-based polyurethanes with minimum film formation temperatures (MFTs) of 0-50°C, or even 0-30°C. MFTs are measured according to ASTM D2354 or ISO 2115.

[0098] The polyurethane aqueous dispersion may contain, to the extent that it does not impair the effects of the present invention, colorants such as pigments and dyes such as carbon black, coagulation regulators, antioxidants, ultraviolet absorbers, fluorescent agents, antifungal agents, penetrating agents, defoaming agents, lubricants, water repellents, oil repellents, thickeners, bulking agents, curing accelerators, foaming agents, water-soluble polymer compounds such as polyvinyl alcohol and carboxymethylcellulose, inorganic fine particles, conductive agents, etc.

[0099] The viscosity of the first polyurethane aqueous dispersion is not particularly limited, but is preferably 1 to 10 cps, and more preferably 2 to 6 cps, in order to facilitate penetration into the entanglement of sea-island type composite fibers. The solution viscosity is measured using a B-type viscometer at 20°C.

[0100] Methods for applying aqueous polyurethane to entangled sea-island composite fibers include applying an aqueous polyurethane dispersion to the internal voids of the entangled sea-island composite fibers by means of dip-nip treatment, knife coater, bar coater, roll coater, etc., and then heating and drying at a temperature at which the dispersed particles fuse together. Drying methods include heat treatment in a dryer at 50-200°C, heat treatment in a dryer after infrared heating, heat treatment in a dryer after treatment in a humid atmosphere or steam, heat treatment in a dryer after ultrasonic heating, or a combination of these methods.

[0101] Furthermore, when a polyurethane aqueous dispersion is impregnated into the internal voids of a sea-island composite fiber entanglement and then dried, the polyurethane aqueous dispersion may migrate to the surface layer of the sea-island composite fiber entanglement, resulting in uneven application of the aqueous polyurethane. Methods to suppress migration include the following: for example, adjusting the particle size of the aqueous polyurethane dispersion; adjusting the type and amount of ionic groups in the aqueous polyurethane; reducing dispersion stability by using ammonium salts whose pH changes with temperature (around 40-100°C); and reducing dispersion stability at around 40-100°C by using monovalent or divalent alkali metal salts, alkaline earth metal salts, nonionic emulsifiers, associated water-soluble thickeners, associated heat-sensitive gelling agents such as water-soluble silicone compounds, or water-soluble polyurethane compounds in combination. Furthermore, by performing a curing treatment at approximately 120-170°C after impregnation with an aqueous polyurethane dispersion, followed by gelation, solidification, or drying, it is possible to suppress swelling and detachment of the aqueous polyurethane during the dyeing process and other steps.

[0102] Among these methods, the method that adjusts the particle size of dispersed particles in the aqueous polyurethane dispersion of water-based polyurethane by the self-emulsifying properties of carboxyl groups, and further reduces the dispersion stability by using an ammonium salt whose pH changes with temperature of about 40 to 100°C, is preferred because it facilitates the formation of continuous regions, as it easily creates an adhesive state to the fiber bundle that does not have particle interfaces due to the contours of the dispersed particles of the aqueous polyurethane as described above. The method of applying the aqueous polyurethane dispersion and then immersing it in water, acidic water, alkaline water, or hot water to gel is undesirable because it makes it difficult to form continuous regions.

[0103] [A process for manufacturing artificial leather material by removing water-soluble PVA, a marine component, from sea-island type composite fibers in a fiber base material.] By dissolving and removing water-soluble PVA, which is a marine component contained in the entanglement of sea-island type composite fibers, an entanglement of fiber bundles made of ultrafine fibers is formed. One method for removing the marine component is to repeatedly perform a dip-nip treatment in hot water at 85-100°C until substantially all of the water-soluble PVA is dissolved and removed.

[0104] In this way, a raw material for artificial leather is obtained, comprising a fiber bundle containing 5 to 75 ultrafine fibers and a water-based polyurethane having a continuous region of 5 to 20% by mass impregnated into the fiber bundle. The apparent density of such a raw material for artificial leather is 0.50 to 0.95 g / cm³. 3 It is preferable that it be such. Furthermore, the thickness is preferably 0.1 to 3 mm.

[0105] [A process of buffing at least one side of an artificial leather raw material to raise the nap of the ultrafine fibers on the surface and form a napped surface.] The napped artificial leather of this embodiment has a suede-like or nubuck-like napped surface on at least one side, where ultrafine fibers are raised. Such a napped surface is formed by buffing the surface of the artificial leather with a contact buff or emery buff. Buffing is preferably performed using sandpaper or emery paper with a grit of approximately 120 to 600.

[0106] [Process for manufacturing a piled artificial leather fabric in which a second water-based polyurethane is applied to the surface layer of the piled artificial leather fabric] A second polyurethane aqueous dispersion with high film-forming properties is applied to the napped surface of a napped artificial leather fabric, allowing it to penetrate the fiber bundles of the surface layer. By heating and drying the fabric at a temperature at which the dispersed particles of the second aqueous polyurethane in the second polyurethane aqueous dispersion fuse together, a napped artificial leather fabric with the second aqueous polyurethane applied to its surface is manufactured.

[0107] For the purpose of suppressing the bare fiber of the raised fibers on the surface layer of the raised artificial leather base fabric and improving the appearance quality and surface physical properties of the raised surface, it is preferable to apply the second aqueous polyurethane so as to penetrate into the ultra-fine fiber bundles of the surface layer and restrain the root of the raised hair. As a method of applying the second aqueous polyurethane so as to restrain the root of the raised hair, for example, a method of applying the second polyurethane aqueous dispersion from the raised surface side, a method of impregnating the second polyurethane aqueous dispersion from the raised surface side, a method of impregnating the entire layer of the raised artificial leather base fabric with the second polyurethane aqueous dispersion, and then strongly drying from the raised surface side to migrate the second polyurethane aqueous dispersion near the surface layer, etc. can be mentioned.

[0108] The type of the second aqueous polyurethane may be the same as or different from that of the first aqueous polyurethane.

[0109] When applying the polyurethane aqueous dispersion to the surface layer of the raised surface of the raised artificial leather base fabric, the application amount, as a solid content, is 0.2 to 4.0 g / m 2 , and further preferably 0.5 to 3.0 g / m 2 is applied so as to be excellent in the balance between the high-class feeling of the appearance of the raised surface and the anti-pilling property. The content ratio of the second aqueous polyurethane in the surface layer of the raised surface is preferably 0.1 to 1.0% by mass, and further preferably 0.15 to 0.8% by mass in terms of the excellent balance between the high-class feeling of the appearance of the raised surface and the anti-pilling property. In addition, the second aqueous polyurethane can penetrate into the fiber bundles without forming a layer in the thickness direction of the raised artificial leather and exist in a large amount, so that a raised artificial leather with particularly excellent high-class feeling of the appearance of the raised surface can be obtained.

[0110] In order to make the second aqueous polyurethane exist in a large amount inside the fiber bundles on the surface layer of the raised surface, it is preferable to add a thickener to the second polyurethane aqueous dispersion to adjust the liquid viscosity and control the permeability.

[0111] Examples of thickening agents include: association-type thickening agents such as acrylic, urethane-modified polyether, and silicone-based thickening agents having hydrophobic and hydrophilic groups; polymer-type thickening agents which are water-soluble polymer compounds such as polyacrylic acid, carboxyvinyl polymer, polyurethane, acrylic, polyvinyl alcohol, polyamide, and polyvinylpyrrolidone; cellulose-based thickening agents; and polysaccharide-based thickening agents.

[0112] The amount of thickener added is not particularly limited, but it is preferable to include about 0.1 to 5% by mass relative to the second polyurethane aqueous dispersion, as this exhibits thixotropy, allowing it to remain on the surface and penetrate more easily into the interior of the fiber bundle.

[0113] The viscosity of the second polyurethane aqueous dispersion is preferably 5 to 300 cps, and more preferably 10 to 200 cps, as this allows it to penetrate more easily into the fiber bundle.

[0114] Furthermore, in order to ensure that a large amount of the second aqueous polyurethane is present inside the fiber bundle, it is preferable to remove the water-soluble PVA from the sea-island type composite fiber, and then leave a small amount of water-soluble PVA on the surface of the ultrafine fibers to make the surface of the ultrafine fibers hydrophilic. The hydrophilicity of the ultrafine fiber surface allows the second polyurethane aqueous dispersion to penetrate into the fiber bundle more easily through capillary action. The water-soluble PVA content in the napped artificial leather material is preferably 0.05 to 1% by mass, and more preferably 0.1 to 0.4% by mass.

[0115] Furthermore, the permeability may be controlled by applying surfactants or hydrophilic compounds to the napped artificial leather material before applying the second polyurethane aqueous dispersion. By applying surfactants or hydrophilic compounds in this way, the second polyurethane aqueous dispersion penetrates appropriately into the fiber bundles of the surface region, making it easier to obtain napped artificial leather that has an appearance with less color unevenness, a luxurious feel, and high anti-pilling properties.

[0116] Specific examples of such hydrophilic compounds include silicone-based hydrophilic compounds, polyurethane-based hydrophilic compounds, acrylic-based hydrophilic compounds, fluorine-based hydrophilic compounds, and water-soluble polymer compounds.

[0117] Examples of anionic surfactants include carboxylates such as octanoates, decanoates, laurylates, and oleates; sulfonates such as alkylbenzene sulfonates, alkanesulfonates, and alkylnaphthalene sulfonates; phosphate esters such as lauryl phosphates, polyoxyethylene alkyl phosphates, and polyoxyethylene alkylallyl phosphates; and sulfate esters such as lauryl sulfates and polyoxyethylene alkylphenol sulfonates.

[0118] Specific examples of cationic surfactants include quaternary ammonium salts such as dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, tetramethylammonium hydroxide, tetramethylammonium chloride, and tetradecyldimethylbenzylammonium chloride; and alkylamine salts such as monomethylamine hydrochloride, dimethylamine acetate, and trimethylamine hydrochloride.

[0119] Specific examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene oxypropyl block polymers, polyoxyethylene polysiloxane block polymers, polyethylene glycol fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.

[0120] Furthermore, in order to allow a large amount of water-based polyurethane to penetrate into the interior of the fiber bundle, it is also preferable to adjust the particle size of the water-based polyurethane dispersion in the polyurethane aqueous dispersion. The average particle size of the polyurethane aqueous dispersion is preferably 10 to 250 nm, and more preferably 30 to 200 nm.

[0121] Regarding the permeability of the second polyurethane aqueous dispersion, for example, when 0.05 ml of the second polyurethane aqueous dispersion is dropped onto the napped surface of a napped artificial leather fabric from a height of 1 cm, it is preferable that the permeation time is 1 to 60 seconds, more preferably 3 to 60 seconds, especially 5 to 60 seconds, and even more preferably 10 to 30 seconds. This is because the second polyurethane penetrates appropriately into the fiber bundles of the surface layer, making it easier to achieve both high pilling resistance and a flexible texture. Furthermore, the diameter of the liquid that spreads at that time is preferably 5 to 50 mm, and more preferably 10 to 20 mm.

[0122] In this manner, the second polyurethane aqueous dispersion is permeated into the fiber bundles on the surface of the piled artificial leather fabric to form the first fiber bundles.

[0123] [Process for dyeing artificial leather fabric] The napped artificial leather may be dyed as needed. The type of dye used is not particularly limited, and specific examples include disperse dyes, acid dyes, cationic dyes, sulfur dyes, metal-containing dyes, or vat dyes. The dyeing method used is appropriately selected depending on the type of fiber and the type of dye, and specific examples include high-pressure liquid flow dyeing, jigger dyeing, thermosol continuous dyeing, and Wins dyeing.

[0124] [Post-processing steps] The napped artificial leather may be further subjected to shrinkage processing or kneading softening processing to add flexibility and adjust the texture, or to finishing treatments such as reverse seal brushing, stain-resistant treatment, hydrophilic treatment, lubricant treatment, softener treatment, antioxidant treatment, UV absorber treatment, fluorescent agent treatment, and flame retardant treatment.

[0125] In this way, the piled artificial leather of this embodiment is obtained. The piled artificial leather of this embodiment is manufactured using an environmentally conscious process and is a piled artificial leather that has an appearance with little color unevenness on the pile surface, a luxurious feel, a soft texture, and high anti-pilling properties. [Examples]

[0126] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited in any way to these examples.

[0127] First, the evaluation method for the napped artificial leather used in this embodiment is summarized below.

[0128] (Average fiber diameter, average fiber bundle diameter, classification of each fiber bundle, identification of the continuous region of aqueous polyurethane, and calculation of the proportion of each fiber bundle) A cross-section of the piled artificial leather, cut parallel to its thickness, was imaged with a scanning electron microscope (SEM) at 200x magnification, capturing the entire surface. Additionally, 15 randomly selected locations near the surface, including the surface layer up to a virtual line L located 100 μm away in the thickness direction, were imaged with SEM at 500x magnification. Furthermore, 15 randomly selected locations in the non-surface region, extending from that virtual line to the back surface, were also imaged with SEM at 500x magnification.

[0129] Then, in each 500x magnification SEM image of the surface region and each 500x magnification SEM image of the non-surface region, the boundaries of the fiber bundles were determined based on the number of ultrafine fibers forming the fiber bundles. The fiber diameter of the ultrafine fibers cut perpendicular to the fiber axis direction was measured. The fiber bundle diameter of the fiber bundles cut perpendicular to the fiber axis direction was also measured. The average fiber diameter of the ultrafine fibers or the average fiber bundle diameter of the fiber bundles was calculated as the average value of 15 locations. Note that the fiber diameter and fiber bundle diameter were converted to the diameter when converted to a circle with the same area.

[0130] Also, 500 times larger, 240 μm × 180 μm (0.043 mm) 2In each SEM image of the field of view, fiber bundles in which the water-based polyurethane penetrated the interior of the fiber bundle to focus more than half of the ultrafine fibers forming the fiber bundle were determined to be the first fiber bundle A. Fiber bundles in which the water-based polyurethane did not penetrate the interior of the fiber bundle to focus more than half of the ultrafine fibers contained in the fiber bundle, but were adhered to or in contact with a continuous region for a length of 1 / 4 or more of the outer circumference of the fiber bundle were determined to be the second fiber bundle B. Fiber bundles in which the ultrafine fibers were not adhered to or in contact with the water-based polyurethane were determined to be the third fiber bundle C. When ultrafine fibers were adhered to each other within a fiber bundle, it was determined that the water-based polyurethane had penetrated into the fiber bundle and was adhering to it. Furthermore, if a determination could not be made with a 500x SEM image, it was confirmed by further magnification to 600 to 1000x.

[0131] Furthermore, the presence or absence of continuous regions was determined by identifying areas where the film was formed without containing five or more pores in the diameter range of 0.5 to 10 μm in each SEM image of a 240 μm × 180 μm field of view at 500x magnification. Among these areas, regions with a linear length of 50 μm or more were determined to be continuous regions. In addition, it was confirmed whether particle interfaces based on the contours of dispersed particles could be recognized in the continuous regions. Finally, it was determined whether the continuous regions had two or more fiber bundles adhered to or in contact with each other.

[0132] Figure 1 is an example of a 200x magnification SEM image of the piled artificial leather obtained in Example 1. Figure 4 is an image showing the determination of the types of fiber bundles observed in the SEM image of the piled artificial leather obtained in Example 1, including the surface region S. Figure 6 is an image showing the determination of the types of fiber bundles observed in the SEM image of the piled artificial leather obtained in Example 1, including the non-surface region M. In Figure 4, the first fiber bundle is labeled A1, the second fiber bundle B1, and the third fiber bundle C1. In Figure 6, the first fiber bundle is labeled A2, the second fiber bundle B2, and the third fiber bundle C2.

[0133] Then, for each 500x SEM image, the number of first, second, and third fiber bundles was counted. The average number of first fiber bundles A1, second fiber bundles B1, and third fiber bundles C1 in the surface region S was denoted as (A1), and the ratio was calculated using the following formula. The ratio of the number of first fiber bundles (A1) to the total number of fiber bundles (T1) in the surface region S = (A1) / {(A1)+(B1)+(C1)}×100(%)

[0134] Furthermore, when the average number of first fiber bundles A2 in the counted non-surface region M was denoted as (A2), the average number of second fiber bundles B2 as (B2), and the average number of third fiber bundles C2 as (C2), the proportion was calculated using the following formula.

[0135] The ratio (%) of the number of first fiber bundles (A2) to the total number of fiber bundles (T2) in the non-surface region M is (A2) / {(A2)+(B2)+(C2)}×100(%) The ratio (%) of the number of second fiber bundles (B2) to the total number of fiber bundles (T2) in the non-surface region M is (B2) / {(A2)+(B2)+(C2)}×100(%) Then, the ratio of the number of first fiber bundles (A1) to the total number of fiber bundles (T1) in the surface region S, the ratio of the number of first fiber bundles (A2) to the total number of fiber bundles (T2) in the non-surface region M, and the ratio of the number of second fiber bundles (B2) to the total number of fiber bundles (T2) in the non-surface region M were averaged, based on the results obtained from the 15 images.

[0136] (Percentage of water-based polyurethane content) During the manufacturing of the piled artificial leather, the total weight of water-based polyurethane was calculated by tracing the weight changes due to the shedding of water-based polyurethane as the entangled sea-island composite fibers, which had been impregnated with water-based polyurethane during the manufacturing process, went through each process after the PVA removal step in the sea-island composite fibers. Then, the weight of water-based polyurethane remaining in the piled artificial leather was determined by subtracting the total weight of the shedding water-based polyurethane from the weight of the water-based polyurethane impregnated into the entangled sea-island composite fibers during manufacturing. Based on the weight of the remaining water-based polyurethane, the percentage of water-based polyurethane in the obtained piled artificial leather was calculated. Note that the weight of PVA that was left in place without removal, and the weight of the ultrafine fibers that were shed at each process were far smaller than the weight of the shedding water-based polyurethane, so these were ignored in the calculation. The percentage of water-based polyurethane in pile-napped artificial leather can also be determined by the following method: Using a scanning electron microscope (SEM), take three average images of a section of the pile-napped artificial leather parallel to its thickness at a magnification of 500x, and print each image on A4 size paper. Place the printed paper on a transparent sheet such as an OHP (Overhead Projector) sheet, and transfer the water-based polyurethane portion to the transparent sheet by blackening it. Transfer the ultrafine fiber portion in the same manner as the water-based polyurethane portion. Then, scan the patterns of the transparent sheet with the water-based polyurethane portion blackened and the transparent sheet with the ultrafine fiber portion blackened separately to form images. After removing noise with an area of ​​10 dots or less from the obtained images using an image processing device, determine the total area of ​​water-based polyurethane and the total area of ​​ultrafine fibers. Then, the value (α) obtained by dividing the total surface area of ​​the water-based polyurethane by the polymer density of the water-based polyurethane, and the value (β) obtained by dividing the total surface area of ​​the ultrafine fibers by the polymer density constituting the ultrafine fibers, are determined, and the content ratio of water-based polyurethane is calculated using (α) / ((α)+(β))×100. The image processing device used is one that consists of a computer with image processing software installed. A specific example of image processing software is, for example, Media Cybernetics' image-pro plus.

[0137] (Thermal softening temperature of water-based polyurethane) A 250 μm thick film was prepared by air-drying an aqueous dispersion of water-based polyurethane. The film was then heat-treated at 120°C for 30 minutes. After cooling, a 4 × 0.5 cm test specimen was cut from the film. The test specimen was then placed in a dynamic viscoelasticity analyzer (DVE-V4FT Rheospectra, Rheology Inc.) and the storage modulus was measured under the following conditions: starting temperature: -120°C, measurement mode: tensile, heating rate: 3°C / min, frequency: 11 Hz. The storage modulus was found to be 1 × 10⁻⁶. 6 The temperature at which the pressure reaches MPa was defined as the thermal softening temperature (°C).

[0138] (Hot water swelling rate of water-based polyurethane) A 250 μm thick film was prepared by air-drying an aqueous dispersion of water-based polyurethane. The film was then heat-treated at 120°C for 30 minutes. After cooling, a 5 × 10 cm test specimen was cut out and conditioned by leaving it in a 23°C 50% RH atmosphere for 24 hours. The weight of the test specimen was then measured. The test specimen was then immersed in 90°C hot water for 60 minutes, after which the hot water was cooled to 60°C. The test specimen was then removed from the water. The weight of the test specimen was measured immediately after wiping off the water from its surface. The hot water swelling rate (%) of the water-based polyurethane was then calculated using the following formula. • Swelling rate of water-based polyurethane in hot water (%) = ((Weight after hot water immersion - Weight before hot water immersion)) / (Weight before hot water immersion) × 100

[0139] (Penetration time of the second polyurethane aqueous dispersion on the pile surface of a pile artificial leather fabric) The penetration time (in seconds) was measured when 0.05 ml of a second polyurethane aqueous dispersion was dropped onto the napped surface of a napped artificial leather machine from a height of 1 cm. The measurement was repeated 5 times, and the average value was taken as the penetration time (in seconds).

[0140] (Percentage of water-soluble PVA content in artificial leather raw materials) A 20 x 20 cm test piece was cut from the raw material of artificial leather. The weight (a) was measured after leaving it at 25°C and 60% RH for 12 hours. The weight (b) was then measured after immersing the test piece in 95°C hot water for 60 minutes, drying it at 100°C for 30 minutes, and leaving it at 25°C and 60% RH for 12 hours. From the weights before and after treatment, the percentage of water-soluble PVA content (%) was calculated as ((a) - (b)) / (a) × 100.

[0141] (Tactile feel and appearance of the pile surface) A 20cm x 20cm test piece was cut from the piled artificial leather. The tactile feel and appearance of the piled surface of the test piece were then evaluated according to the following criteria. A: It had a smooth texture and a luxurious, elegant appearance. Furthermore, there were no color inconsistencies. B: The ultrafine fibers were clustered together, resulting in a rough texture, or there were color inconsistencies in the appearance. C: The color development was poor.

[0142] (Texture) A 20cm x 20cm test piece was cut from the pile artificial leather. The texture of the test piece was then evaluated according to the following criteria. A: It had a soft texture. B: It had a hard texture. C: It lacked rigidity and broke with a cracking sound.

[0143] (Anti-pilling properties) In accordance with ISO 12947-2, anti-pilling properties were measured using a Martindale testing machine under the following conditions: pressing load: 12kPa, friction fabric: wool friction fabric, piled artificial leather: diameter 38mm, number of cycles: 2000. The pilling was then judged based on the following pilling judgment criteria of ISO 12945-2. Grade 5: No change. Grade 4: The nap was fine, but there was some very slight pilling in a few places. Grade 3: There was some minor pilling in places. Grade 2: There was obvious pilling in most areas. Grade 1: The entire surface was covered in pilling, and the pilling was densely concentrated.

[0144] [Example 1] Water-soluble thermoplastic polyvinyl alcohol (PVA) was prepared as the sea component, and isophthalic acid-modified polyethylene terephthalate (IPA-modified PET) with a modification degree of 6 mol% was prepared as the island component. The sea component and island component were then supplied to a composite spinning die set to a die temperature of 260°C, with nozzle holes arranged in parallel to form a cross-section in which 25 island components with a uniform cross-sectional area were distributed within the sea component resin. Molten strands were then discharged from the nozzle holes. During this process, the pressure was adjusted so that the mass ratio of sea component to island component was sea component / island component = 25 / 75.

[0145] The molten strand was then stretched by suction using a suction device to achieve an average spinning speed of 3700 m / min, and sea-island composite fibers with a fineness of 2.9 dtex were spun. The sea-island composite fibers were continuously deposited on a movable net and lightly pressed with a metal roll at 42°C to suppress surface fuzzing. The sea-island composite fibers were then peeled from the net and passed between a grid-patterned metal roll and a back roll at a surface temperature of 55°C and a linear pressure of 200 N / mm. In this way, a basis weight of 32 g / m was obtained. 2 They manufactured the web.

[0146] Next, the web was processed using a cross-wrapper to achieve a total basis weight of 380 g / m². 2 A stacked web was created by layering 12 layers, and then sprayed with a needle breakage prevention lubricant. Then, using a 6-barb needle with a distance of 3.2 mm from the needle tip to the first barb, the stacked web was punched alternately from both sides at a needle depth of 8.3 mm at 3300 punches / cm. 2 By using needle punching, the weight reaches 500g / m². 2 A sea-island type composite fiber entanglement was manufactured. Then, the sea-island type composite fiber entanglement was subjected to moist heat shrinkage treatment under the conditions of a temperature of 70°C, a humidity of 50%RH, and a duration of 30 seconds.

[0147] Then, a first polyurethane aqueous dispersion, which is an emulsion containing 15% by mass of solids and a liquid viscosity of 2 cps, was impregnated into a tangle of sea-island type composite fibers that had been treated with moist heat shrinkage, and the dispersion particles had an average dispersion particle diameter of 150 nm. The dispersion was then dried at 150°C to cause aggregation and film formation. The average dispersion particle diameter of the emulsion was measured using a Microtrac particle size analyzer by the laser diffraction particle size distribution method, and the central particle diameter (D) of the dispersion particle size distribution was measured. 50 )

[0148] The aqueous polyurethane was a self-emulsifying polyurethane containing a carboxyl group and a urethane skeleton that included a urethane backbone containing a urethane skeleton with a carboxyl group, a urethane backbone containing a urethane backbone with a urethane backbone containing

[0149] Then, the intertwined sea-island type composite fibers, impregnated with water-based polyurethane, were repeatedly immersed in 95°C hot water and subjected to a dip-nip treatment to dissolve and remove the PVA, which is a marine component, and then dried. In this way, an artificial leather material was created containing a nonwoven fabric which is a fiber bundle intertwined composite in which a fiber bundle consisting of 25 ultrafine long fibers of isophthalic acid-modified polyethylene terephthalate is three-dimensionally intertwined. The proportion of polyurethane in the artificial leather material was 10% by mass, and the proportion of water-soluble PVA was 0.12% by mass.

[0150] Then, the raw artificial leather was sliced ​​and cut in half, and both sides were buffed to raise the ultrafine fibers on the surface and form a napped surface, thereby obtaining raw artificial leather with a thickness of 0.6 mm.

[0151] Next, a second polyurethane aqueous dispersion with a viscosity of 100 cps was prepared by adding 1.0% by mass of a polyacrylic acid-based polymer thickener to an emulsion (40% by mass) containing a self-emulsifying aqueous polyurethane with an average dispersed particle size of 150 nm. The second polyurethane aqueous dispersion and the first aqueous polyurethane dispersion are of the same type, but differ from the first polyurethane aqueous dispersion in that they contain a thickener and have different solid content concentrations. The second polyurethane aqueous dispersion was then gravure-coated onto the pile surface of a pile artificial leather machine and dried at 135°C. The penetration time of the second polyurethane aqueous dispersion on the pile surface was 20 seconds. The application amount of the second polyurethane aqueous dispersion was 1.5 g / m² in terms of solid content. 2 The proportion of the additive applied to the spongy artificial leather was 0.3% by mass.

[0152] Then, the napped artificial leather fabric, to which the second water-based polyurethane had been applied, was heat-treated in a liquid flow dyeing machine at a temperature of 120°C for 60 minutes to dye it, dried, impregnated with a softening agent, and dried again. After dyeing, the napped artificial leather fabric was subjected to a shrinkage treatment at a drum temperature of 120°C and a conveying speed of 10 m / min to shrink it by 5.0% in the longitudinal direction (length direction), and then the napped surface was sealed to obtain napped artificial leather with a suede-like napped surface. In this way, a thickness of 0.66 mm and a basis weight of 310 g / m² was obtained. 2 We obtained artificial leather with a raised pile texture.

[0153] The obtained artificial napped leather was then evaluated according to the evaluation method described above. The results are shown in Table 1 below.

[0154] [Table 1]

[0155] [Examples 2-6, Comparative Examples 2-3] Artificial napped leather was manufactured and evaluated in the same manner as in Example 1, except that the number of islands in the ultrafine fiber island component, the content ratio of water-based polyurethane, the average dispersed particle size of water-based polyurethane in the polyurethane aqueous dispersion, the type and blending ratio of polymeric thickener contained in the second polyurethane aqueous dispersion, the viscosity of the second polyurethane aqueous dispersion, the application ratio of the second water-based polyurethane, and the type of water-based polyurethane were changed as shown in Table 1. The results are shown in Table 1.

[0156] [Example 7] After preparing a pile artificial leather base in the same manner as in Example 1, an aqueous solution containing a polyurethane-based hydrophilic compound with a solid content of 4% by mass was applied to the surface of the pile artificial leather base. Then, pile artificial leather was manufactured and evaluated in the same manner as in Example 1, except that the second aqueous polyurethane dispersion shown in Table 1 was applied. The results are shown in Table 1.

[0157] [Comparative Example 1] The pile-napped artificial leather was manufactured and evaluated in the same manner as in Example 1, except that the application rate of the first aqueous polyurethane was changed from 10% by mass to 30% by mass, the material was immersed in a hot water bath to gel after impregnation with the first aqueous polyurethane dispersion, and then dried at 150°C, and the second aqueous polyurethane dispersion was not applied. The structure of the obtained artificial leather is shown in Figure 7. The polyurethane did not form a continuous film. The results are shown in Table 1.

[0158] [Comparative Example 4] Artificial napped leather was manufactured and evaluated in the same manner as in Example 1, except that the content of the polyacrylic acid-based polymer thickener in the second polyurethane aqueous dispersion was changed to 10% by mass, the liquid viscosity was set to 500 cps, the penetration time to 60 seconds or more, and the mixture was stirred in a homomixer and mechanically foamed before the second polyurethane aqueous dispersion was applied. However, the second polyurethane aqueous dispersion did not penetrate sufficiently into the artificial napped leather material. The results are shown in Table 1.

[0159] [Comparative Example 5] The artificial napped leather was manufactured and evaluated in the same manner as in Example 1, except that the number of ultrafine fiber islands was changed from 25 to 100 islands, and the first and second polyurethane aqueous dispersions were changed from an anionic self-emulsifying polyurethane with an average dispersion particle size of 150 nm to an anionic self-emulsifying polyurethane emulsion with a different composition and an average dispersion particle size of 25 nm. The results are shown in Table 1. The aqueous polyurethane was a self-emulsifying polyether urethane containing a urethane skeleton comprising a 100 mol% diisocyanate unit of isophorone diisocyanate, an alicyclic diisocyanate having a methyl group in its alicyclic structure, a 100 mol% polyether unit, a polymeric diol unit, and a chain extension agent unit, and having a carboxyl group. The first aqueous polyurethane dispersion contained 15% by mass of aqueous polyurethane, 2.5% by mass of ammonium sulfate as a heat-sensitive gelling agent, and 2.5% by mass of a carbodiimide-based crosslinking agent, while the second aqueous polyurethane dispersion contained 1.0% by mass of a polyacrylic acid-based polymeric thickener.

[0160] [Comparative Example 6] A pile-napped artificial leather was manufactured in the same manner as in Example 1, except that the first and second polyurethane aqueous dispersions were changed from an anionic self-emulsifying polyurethane with a particle size of 150 nm to a nonionic forced-emulsifying polyurethane emulsion with a different composition and an average dispersion particle size of 400 nm. The aqueous polyurethane contained a urethane skeleton comprising 100 mol% 4,4'-diphenylmethane diisocyanate (MDI) units, 100 mol% polymeric diol units including polycarbonate units with an average of 6 carbon atoms, and chain extension units, and was a forced-emulsification type polycarbonate urethane without carboxyl groups. The first aqueous polyurethane dispersion contained 15% by mass of aqueous polyurethane and 2.5% by mass of sodium sulfate, a heat-sensitive gelling agent. The results are shown in Table 1. The structure of the obtained artificial leather is shown in Figure 8. The polyurethane had numerous pores ranging from 1 to 5 μm.

[0161] From the 500x magnification SEM images, it was found that the water-based polyurethane contained in the pile-napped artificial leather obtained in Examples 1-7 had continuous regions, and each continuous region was adhered to multiple fiber bundles. Furthermore, referring to the results in Table 1, the following can be seen.

[0162] Referring to the results in Table 1, the artificial napped leather obtained in Examples 1 to 7, which included a fiber bundle entanglement body containing 5 to 75 ultrafine fibers and 5 to 20% by mass of aqueous polyurethane impregnated into the fiber bundle entanglement body, and contained a continuous region of aqueous polyurethane having a linear length of 50 μm or more, with A1 / T1 × 100 being 20 to 60% in the surface region and A2 / T2 × 100 being 0 to 10% in the non-surface region, exhibited excellent luxurious feel on the napped surface, a soft texture, and excellent anti-pilling properties on the napped surface.

[0163] On the other hand, the artificial leather obtained in Comparative Example 1, in which the first aqueous polyurethane was linked in a particulate manner and the aqueous polyurethane content was 30% by mass and the second aqueous polyurethane was not added, had noticeable surface unevenness and lacked firmness in texture, and also had poor anti-pilling properties due to the excessively low content of aqueous polyurethane inside the fiber bundles.

[0164] The first water-based polyurethane has a content of 21% by mass, and the second water-based polyurethane does not contain a polyacrylic acid-based polymer thickener, with an application amount of 3 g / m². 2 The artificial napped leather obtained in Comparative Example 2 had a rough texture, noticeable color unevenness, and a hard feel due to an excessively high proportion of water-based polyurethane within the fiber bundles.

[0165] The fiber bundle has 4 islands, the content of the first aqueous polyurethane is 3% by mass, and the amount of the second aqueous polyurethane added is 5 g / m². 2 The artificial napped leather obtained in Comparative Example 3 had a rough texture on the surface and noticeable color unevenness.

[0166] In Comparative Example 4, the artificial leather obtained, which had a porous structure with numerous voids in which the second aqueous polyurethane did not form continuous regions, had poor anti-pilling properties due to an insufficient amount of aqueous polyurethane inside the fiber bundles.

[0167] In Comparative Example 5, where the number of fiber bundles was 100 islands and the first and second polyurethane aqueous dispersions were emulsions of self-emulsifying polyurethanes with different compositions and an average dispersion particle size of 25 nm, the resulting artificial leather had significant unevenness in appearance and a hard, brittle texture due to the softening of the water-based polyurethane and its penetration into the fiber bundles.

[0168] In Comparative Example 6, where the first and second polyurethane aqueous dispersions were forced-emulsified nonionic polyurethane emulsions with an average dispersion particle size of 400 nm, and the first aqueous polyurethane had pores and did not form continuous regions, the resulting artificial leather lacked color development and also exhibited poor anti-pilling properties.

Claims

1. The material comprises a fiber bundle containing a fiber bundle of 5 to 75 ultrafine fibers, and 5 to 20% by mass of aqueous polyurethane impregnated into the fiber bundle, and having at least one surface on which the ultrafine fibers are arranged to form a pile surface. In the cross-section cut in the thickness direction, A continuous region of the aqueous polyurethane having a straight length of 50 μm or more is 0.04 mm ２ Each contains an average of one or more, If the region from the raised pile surface to the imaginary line at a distance of 100 μm in the thickness direction is defined as the surface region, and the region excluding the surface region up to the back surface is defined as the non-surface region, In the aforementioned surface region, The ratio (A1 / T1 × 100) of the number of first fiber bundles (A1) in which more than half of the ultrafine fibers are bundled with the aqueous polyurethane to the total number of fiber bundles (T1) in the surface region is 20 to 60%. In the aforementioned non-surface region, A pile artificial leather characterized in that the ratio (A2 / T2 × 100) of the number of first fiber bundles (A2) in which more than half of the ultrafine fibers are bundled with the water-based polyurethane to the total number of fiber bundles (T2) in the non-surface region is 0 to 10%.

2. The artificial napped leather according to claim 1, wherein in the non-surface region, the ratio (B2 / T2 × 100) of the number of second fiber bundles (B2) that are bonded to or in contact with the continuous region for a length of 1 / 4 or more of the outer circumference of the fiber bundles without the water-based polyurethane penetrating into the interior, to the total number of fiber bundles (T2), is 10 to 40%.

3. The artificial leather with raised fibers according to claim 1 or 2, wherein the continuous region has two or more fiber bundles bonded together.

4. The artificial leather according to any one of claims 1 to 3, wherein the continuous region does not have a particle interface derived from the contour of the dispersed particles of the aqueous dispersion of the aqueous polyurethane.

5. The artificial napped leather according to any one of claims 1 to 4, wherein the water-based polyurethane has a heat softening temperature of 170°C or higher and a weight swelling rate of 1 to 8% in hot water at 90°C.

6. The aforementioned aqueous polyurethane includes a self-emulsifying polyurethane having an anionic hydrophilic group, comprising a polymeric diol unit, an organic diisocyanate unit, a chain extension agent unit, and a urethane skeleton into which an acid group has been introduced. The polymer diol unit comprises a polycarbonate diol unit containing 60 to 100 mol% of methyl-branched diol units and 50 to 100 mol% of methyl-branched diol units. The artificial leather according to any one of claims 1 to 5, wherein the organic diisocyanate units comprise 70 to 100 mol% of organic diisocyanate units, which include at least one selected from alicyclic diisocyanate units that do not have methyl branching in their alicyclic structure and 4,4'-diphenylmethane diisocyanate units.

7. A method for producing artificial leather with raised pile according to claim 1, A sea-island type composite fiber comprising a water-soluble PVA resin which is the sea component and a water-insoluble resin which is the island component, comprising the step of preparing an entanglement of sea-island type composite fibers having 5 to 75 islands, A process for producing a fiber substrate impregnated with a first aqueous polyurethane by impregnating the entangled sea-island type composite fiber with a first aqueous polyurethane, and then heating and drying the first aqueous polyurethane dispersion at a temperature at which the dispersed particles fuse together, A step of forming artificial leather material by removing the water-soluble PVA resin from the sea-island type composite fibers of the fibrous base material, The process of buffing at least one surface of the artificial leather raw material to raise the nap of the ultrafine fibers on its surface and form the napped surface, The process includes the step of applying a second aqueous polyurethane dispersion to the raised surface of the artificial leather machine having formed the raised surface, and then heating and drying it at a temperature that fuses the dispersed particles to impart a second aqueous polyurethane to the interior of the fiber bundles of the surface layer, The first polyurethane aqueous dispersion and the second polyurethane aqueous dispersion are An emulsion of aqueous polyurethane in which the average dispersed particle size of the aqueous polyurethane is 30 to 200 nm, The first aqueous polyurethane and the second aqueous polyurethane include a self-emulsifying polyurethane having an anionic hydrophilic group, comprising a polymer diol unit, an organic diisocyanate unit, a chain extension agent unit, and a urethane skeleton into which an acid group has been introduced. A method for producing artificial napped leather, characterized in that the polymer diol unit comprises 60 to 100 mol% of polycarbonate diol units containing 50 to 100 mol% of methyl-branched diol units, and the organic diisocyanate unit comprises 70 to 100 mol% of organic diisocyanate units containing at least one selected from alicyclic diisocyanate units without methyl branching in the alicyclic structure and 4,4'-diphenylmethane diisocyanate units, and the heat softening temperature is 170°C or higher and the weight swelling rate in hot water is 1 to 8%.

8. The method for producing artificial napped leather according to claim 7, wherein at least one thickener selected from polyacrylic acid-based polymer-type thickeners and polyurethane-based association-type thickeners is added to the second polyurethane aqueous dispersion in an amount of 0.1 to 8% by mass.

9. A method for producing a pile artificial leather according to claim 7 or 8, comprising the step of applying at least one compound selected from surfactants and hydrophilic compounds to the artificial leather material before applying the second polyurethane aqueous dispersion.

10. A method for producing a piled artificial leather according to any one of claims 7 to 9, wherein the penetration time when 0.05 ml of the second polyurethane aqueous dispersion is dropped onto the piled surface of the artificial leather raw material having formed the piled surface is 1 to 60 seconds.

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