JP7438714B2 - Artificial leather that has a moist and dense feel with less noticeable staining spots, and its manufacturing method - Google Patents

Description

The present invention makes dyeing spots less noticeable (by dispersing the polyurethane resin that adheres to the fibers more finely than in conventional methods, the color difference between the fibers and the polyurethane resin is less noticeable), and provides an excellent moist and dense feel. Regarding artificial leather and its manufacturing method.

Artificial leather, which is mainly composed of fiber sheets such as non-woven fabric (fibrous base material) and polyurethane (hereinafter also referred to as PU) resin, has properties that cannot be achieved with natural leather, such as easy care, functionality, and uniformity. It has difficult and excellent characteristics, and is suitable for clothing, shoes, bags, interior materials, interior materials for seats for automobiles, aircraft, railway vehicles, etc., and clothing materials such as ribbons, patch base materials, etc. It is suitably used for.

Conventionally, the method for manufacturing such artificial leather is to impregnate a fiber sheet with an organic solvent solution of PU resin, and then immerse it in a non-solvent of the PU resin (for example, water or an organic solvent) to remove the PU resin. A wet coagulation method is generally employed. For example, in Patent Document 1 below, an organic solvent-based PU resin using N,N-dimethylformamide as an organic solvent that is a solvent for the PU resin is used. However, since organic solvents are generally highly harmful to the human body and the environment, there is a strong demand for a method that does not use organic solvents in the production of artificial leather.

Patent Document 2 below discusses a method of using a water-dispersed PU resin dispersion in which PU resin is dispersed in water instead of the conventional organic solvent-based PU resin; A sheet-like product obtained by impregnating a fiber sheet with a liquid and solidifying a PU resin has a problem in that it tends to have a hard texture. One of the main reasons for this is the difference in the coagulation method between the two. In other words, the coagulation method of the organic solvent-based PU resin dispersion is a "wet coagulation method" in which the organic solvent in which the PU molecules are dissolved is replaced with water to precipitate and coagulate the PU molecules. When viewed, it forms a porous membrane with low density. Therefore, even when the PU resin is impregnated into a fiber sheet and solidified, there are dotted bonding points between the fibers and the PU resin, and the PU resin tends to have a porous structure, resulting in a soft sheet-like product. On the other hand, water-dispersed PU resin uses a "dry heat coagulation method" in which the hydration state of PU molecules dispersed in water is disrupted by heating, and the PU molecules are coagulated by coagulation. The resulting PU membrane structure becomes a dense, non-porous membrane. Therefore, the adhesion between the fibers and the PU resin becomes tight, and the intertwined portions of the fibers are strongly gripped, resulting in a hard texture. In order to improve the texture by applying this water-dispersed PU resin, that is, to suppress the PU resin from grasping fiber entanglement points, a technology has been proposed in which the structure of the PU resin in the sheet-like object is made porous. A sheet-like product characterized in that a PU resin dispersion containing a water-dispersed PU resin, a blowing agent, an anionic surfactant, and/or an amphoteric surfactant is applied to a fiber sheet in recognition of the following. With this manufacturing method, the porous structure of the PU resin inside the sheet material can be expressed regardless of the type of blowing agent and PU, and the fiber has a uniform nap length similar to that of artificial leather made with organic solvent-based PU resin. It is disclosed that it is possible to produce a sheet-like article that has an elegant surface quality that is excellent in denseness, and a good texture that is flexible and has an excellent rebound feeling.
However, in the sheet-like product obtained by the method described in Patent Document 2, the voids between the ultrafine fiber bundle and the PU resin are large (the PU resin has a porous structure), and the PU resin is firmly attached to the ultrafine fiber bundle. Although some softening of the texture is observed as a result of the inhibition of adhesion to Dyeing spots (by dispersing the PU resin that adheres to the fibers more finely than in conventional methods, the color difference between the fibers and the PU resin is less noticeable) has not been studied.

In addition, in the following Patent Document 3, in the case of artificial leather made of ultrafine fibers and a polymeric elastic body, the color difference between the ultrafine fibers and PU resin is hard to stand out, it has a feeling of elasticity, is smooth to the touch, is uniform, and has excellent surface quality. In order to provide an artificial leather made of ultrafine fibers with an average single fiber fineness of 0.01 to 0.50 dtex and an elastic polymer, the elastic polymer is contained in a proportion of 10 to 50% by mass. A polymer having a size of 100 μm or more in the thickness direction and existing within 200 μm in the thickness direction from the surface of the artificial leather excluding the raised portion in a cross section when the artificial leather is cut perpendicular to the surface direction. An artificial leather is disclosed in which the number of elastic lumps per cross-sectional length in the surface direction is 0.1 to 2.5 pieces/mm, and as a manufacturing method thereof, the inside of a fiber sheet made of ultrafine fibers is A method is disclosed that includes a step of dispersing ultrafine fibers by passing a water stream through them. The same book states that in order to eliminate color spots on the surface of artificial leather caused by the difference in color tone between the ultrafine fibers and the polymeric elastic material, the ultrafine fibers are dispersed during the manufacturing process, and the polymeric elastic material that exists inside the artificial leather has to be dispersed. It is effective to keep the size of the body mass within an appropriate range, and as a treatment for dispersing the microfibers, it is preferable to use a method in which a water stream is passed inside the microfiber sheet in a liquid, and the microfibers are dispersed by the water stream. Ultrafine fibers can be dispersed by applying a mechanical impact to the bundle. Specifically, a device such as a vibro washer can be used, and a vibro washer performs a uniform dispersion process over the entire surface of the fiber sheet. However, methods such as water jet punching, which apply mechanical shock by localized high-pressure water flow outside the liquid bath, are not preferred because water jet punching only passes the liquid locally. This is because it is difficult to process uniformly, and even when the number of nozzles is increased, regular streak-like appearance defects tend to occur in the length direction, resulting in artificial leather with an artificial texture. It is stated that. In the example of Patent Document 3, as a dispersion treatment of ultrafine fibers, "a sea-removed fiber sheet in which the sea component of sea-island composite fibers has been removed and ultrafine fibers have been developed is treated with a vibro washer, and in water, Although there is a statement that ``a water stream was passed through the inside of the fiber sheet to perform a dispersion treatment of ultrafine fibers,'' the details of the treatment conditions are not described at all. In general dispersion treatment, fiber bundles still remain, and the fibers dispersed together with the fiber bundles during the napping treatment do not provide uniform denseness or denseness. In addition, Patent Document 3 states that "the number per cross-sectional length in the surface direction of clumps of polymeric elastic material having a size of 100 μm or more in the thickness direction that exist within 200 μm from the surface in the thickness direction" of the obtained artificial leather. 0.1 to 2.5 pieces/mm", the appearance quality (color tone) was more uniform, but the surface PU resin area ratio and its standard deviation were not studied, and even less The dispersibility of single fibers has not been studied.

Patent Document 4 below discloses that an average single fiber diameter is A fiber sheet comprising ultrafine fibers of 0.1 μm or more and 8 μm or less, wherein at least one side of the fiber structure has naps, a discontinuous resin layer is formed on the nap surface, and A sheet-like article is disclosed in which 50% or more and 100% or less of the total thickness of the resin layer is present in the fiber sheet. As described in the same book, natural nubuck leather (cowhide surface), unlike suede (pigskin floor surface), is obtained by applying a brushing treatment to the silver surface (surface) of leather. The invention described in Patent Document 4 aims to provide a nubuck-like sheet material. The same book also states that on the napped surface of the fiber structure, there is a discontinuous resin layer (i.e., resin parts are scattered in the form of islands on the surface of the sheet-like object, and napped parts are formed between the resin parts). It is important that a surface layer in which a It is described that it is preferably 10% or more and 90% or less, and that such a resin layer is applied and dried using a flat screen, gravure coating, or the like.
As described above, since the invention described in Patent Document 4 actively forms a PU resin layer on the surface of a sheet-like object, the surface PU resin area ratio, which is an index of the dispersion state of the surface PU resin lumps, The standard deviation, much less the dispersibility of single fibers, has not been studied.

The following Patent Document 5 discloses a leather-like sheet material having an average single fiber diameter of 0 in order to provide a sheet material having a uniform fiber length on the surface layer and a luxurious appearance, and a method for manufacturing the same. .A sheet-like material comprising a fibrous base material mainly composed of ultrafine fibers of 1 to 8 μm and a polymeric elastic material, the sheet-like material having napped on one or both sides, (1) the napped fibers are occupies 50 to 100% of the surface of the sheet-like object, and (2) the surface layer of the sheet-like object has 3 to 20 microfiber bundles with a major axis of 1 mm to 4 mm per ²⁵ mm unit. Disclosed is a sheet-like product characterized by the fact that: The same book describes a method for manufacturing such a sheet-like article in which, before the step of developing ultrafine fibers, the number of crimps in the ultrafine fiber-generating fibers is 10 to 30 crests/2.54 cm and the degree of crimp is 15 to 28%. The method includes a step of imparting crimps and entangling the crimped fibers to form a fibrous base material, and after the step of developing ultrafine fibers, the rotation speed of the vibro washer is 300 rpm or more and 400 rpm or less, and liquid flow is performed. A method including a process of performing a treatment has been proposed. In the same book, ultrafine fiber generation type fibers are highly crimped and highly entangled fibrous base material is subjected to liquid flow treatment at the same time as or after the ultrafine fibers are developed to form a sheet. The number of ultrafine fiber bundles with a long major axis generated on the surface layer of a sheet-like article is reduced, and the number of ultrafine fiber bundles with a major axis of 1 mm or more and 4 mm or less on the surface layer of a sheet ^- like article is 25 mm or more. It is disclosed that appearance quality can be obtained. In addition, the liquid flow treatment is preferably performed by applying a water stream under water using a vibro washer, and by setting the rotational speed of the vibro washer to preferably 300 rpm or more and 400 rpm or less, the ultrafine fiber bundles become entangled and become denser. It is possible to adjust the number of long ultrafine fiber bundles with a major axis of 1 mm or more and 4 mm or less that exist on the surface layer of the shaped object. The number of ultrafine fiber bundles with a long diameter of 1 mm or more and 4 mm or less on the surface layer of the object increases, making it difficult to obtain an elegant appearance.In addition, if the rotation speed of the vibro washer exceeds 400 rpm, the pressure caused by the liquid flow of the vibro washer will increase. It is described that the ultra-fine fiber bundles will break and pilling will occur more easily. In this way, in Patent Document 5, the vibro washer treatment is performed not to disperse single fibers but to entangle ultrafine fiber bundles.
Furthermore, although Patent Document 5 describes that appearance quality such as the occurrence of pilling and surface touchability such as feel are improved, staining spots are not investigated.

In this way, in the conventional technology, in artificial leather obtained by impregnating a fiber sheet using sea-island fibers with water-dispersible PU resin, dyeing spots can be reduced by increasing the dispersibility of the fibers and the dispersibility of the PU resin. Although various attempts have been made to provide artificial leather that is less conspicuous, moisturized, and dense (dispersibility of fiber bundles), the inconspicuousness of dyed spots, moisturized feel, and dense feel are still poor. At present, an artificial leather and a method for producing the same that can satisfy all of the characteristics of less conspicuous dyeing spots, a moist feel, and a dense feel have not yet been achieved.

Patent No. 4089324 Japanese Patent Application Publication No. 2014-25165 JP2016-69790A Japanese Patent Application Publication No. 2018-123444 Japanese Patent Application Publication No. 2017-133134 International Publication No. 2015/151873

In view of the problems of the prior art described above, the problem to be solved by the present invention is to make dyeing spots less noticeable (by dispersing the polyurethane resin that adheres to the fibers more finely than in the conventional method, and to improve the bond between the fibers and the polyurethane resin). An object of the present invention is to provide artificial leather that has a satisfactory level of a moist feeling (color difference is hardly noticeable), a moist feeling, and a dense feeling (dispersibility of fiber bundles).

As a result of intensive research and repeated experiments in order to solve the above-mentioned problem, the present inventors unexpectedly discovered that the problem could be solved by using artificial leather having the following characteristics, and thus completed the present invention. It is something that
That is, the present invention is as follows.
[1] Artificial leather comprising a fiber sheet and a polyurethane resin, wherein the fiber sheet includes at least a fiber layer (A) constituting the first outer surface of the artificial leather, and the thickness of the artificial leather is The k-neighborhood distance ratio value (k = 9, radius r = 20 μm) between single fiber cross sections constituting the fiber layer (A) in the direction cross section is 10% or more and 80% or less, and the fiber layer (A) ) has a surface polyurethane resin area ratio of 8% or more and 25% or less, and the standard deviation of the surface polyurethane resin area ratio of the fiber layer (A) is 25% or less.
[2] The fiber sheet has two or more layers composed of a fiber layer (A) constituting the first outer surface and a scrim and/or fiber layer (B) in contact with the fiber layer (A). The artificial leather according to [1] above, which has a structure.
[3] The artificial leather according to [1] or [2] above, wherein the average diameter of the single fibers constituting the fiber layer (A) is 1.0 μm or more and 8.0 μm or less.
[4] The artificial leather according to any one of [1] to [3] above, wherein the polyurethane resin is a water-dispersed polyurethane resin.
[5] The artificial leather according to any one of [1] to [4], wherein the adhesion rate of the polyurethane resin to the fiber sheet is 15% by mass or more and 50% by mass or less.
[6] The artificial leather according to any one of [1] to [5] above, which has staining spots of grade 4.0 or higher.
[7] The artificial leather according to any one of [1] to [6], wherein the fiber sheet is composed of polyester fibers.
[8] The artificial leather according to any one of [1] to [7] above, which has a moist feel of grade 4.0 or higher.
[9] The artificial leather according to any one of [1] to [8] above, which has a dense feel of grade 4.0 or higher.
[10] The following steps:
Forming a fiber web with sea-island short fibers, and then de-sea-removing the fiber sheet obtained by needle punching to obtain a fiber sheet in which the single fibers of the island component are exposed; and Water dispersion in the obtained fiber sheet. A process of performing treatment to obtain a fiber sheet in which single fibers are dispersed;
The method for producing artificial leather according to any one of [1] to [9] above, comprising:
[11] The following steps:
The fiber sheet in which the single fibers are dispersed is impregnated with a water-dispersed polyurethane resin dispersion containing hot water-soluble resin fine particles, and then the polyurethane resin is fixed by heating to form a sheet filled with polyurethane resin. a step of obtaining a product; and a step of removing the hot water-soluble resin fine particles from the obtained sheet-like product using hot water;
The manufacturing method according to [10] above, further comprising:
[12] The manufacturing method according to [10] or [11], wherein the hot water-soluble resin fine particles are polyvinyl alcohol resin.
[13] The water dispersion treatment is carried out using a plurality of nozzles having a nozzle hole interval of 1.0 mm or less and a nozzle hole diameter of 0.05 mm or more and 0.30 mm or less, [10] to The manufacturing method according to any one of [12].
[14] The manufacturing method according to any one of [10] to [13], wherein the water stream dispersion treatment is performed using a plurality of nozzles that discharge a water stream with a disturbance of 10% or more.
[15] The manufacturing method according to any one of [11] to [14], wherein the solid content concentration of the water-dispersed polyurethane resin dispersion is 10% by weight or more and 35% by weight or less.
[16] The production according to any one of [11] to [15] above, wherein the content of hot water-soluble resin fine particles in the water-dispersed polyurethane resin dispersion is 1% by weight or more and 20% by weight or less. Method.

The artificial leather according to the present invention has less noticeable staining spots and has an excellent moist and dense feel, so it can be used for clothing products such as the surface material or interior material of seats for interiors, automobiles, aircraft, railway vehicles, etc. It can be suitably used for, etc.

FIG. 1 is a conceptual diagram showing an example of the structure of artificial leather. Note that the scrim 11 and the fiber layer (B) 13 are optional, so when the artificial leather of this embodiment is a single fibrous layer (A) 12, the scrim 11 and the fibrous layer (B) 13 are optional. In the case of two layers including a scrim or fiber layer (B), there are cases in which there are three layers including the fiber layer (A), the scrim, and the fiber layer (B). FIG. 2 is a conceptual diagram illustrating how to determine the average diameter of single fibers constituting the fiber layer (A). FIG. 3 shows the single fiber cross section k neighborhood distance ratio (%) in the thickness direction cross section of the fiber layer (A), the cross section PU resin area ratio, the average diameter of the single fibers, the surface PU resin area ratio on the first outer surface, FIG. 3 is a conceptual diagram illustrating sample collection locations for each spatial size. FIG. 4 is an image showing a state in which each single fiber cross section within a predetermined image area is marked by a person in order to obtain the k neighborhood distance ratio value (%) of the single fiber cross section in the thickness direction cross section. FIG. 5 is a conceptual diagram for explaining how to obtain the k-neighborhood distance ratio value (%) of a single fiber cross section in a thickness direction cross section. FIG. 6 is a conceptual diagram for explaining how to obtain the cross-sectional or surface PU resin area ratio and its standard deviation. FIG. 7 is a conceptual diagram showing the nozzle hole spacing in the case where a plurality of nozzle holes used for water dispersion treatment are in one row or two or more rows.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the embodiments. Further, unless otherwise specified, various values of the present disclosure are values obtained by the method described in the [Examples] section of the present disclosure or a method understood by those skilled in the art to be equivalent thereto.

<Artificial leather>
One embodiment of the present invention is an artificial leather comprising a fiber sheet and a PU resin, wherein the fiber sheet includes at least a fiber layer (A) constituting a first outer surface of the artificial leather, and , the k-neighborhood distance ratio value (k = 9, radius r = 20 μm) between the single fiber cross sections constituting the fiber layer (A) in the thickness direction cross section of the artificial leather is 10% or more and 80% or less, and , characterized in that the surface polyurethane resin area ratio of the fiber layer (A) is 8% or more and 25% or less, and the standard deviation of the surface polyurethane resin area ratio of the fiber layer (A) is 25% or less. This is the artificial leather.

In this specification, "artificial leather" refers to "artificial leather" as defined in the Household Goods Quality Labeling Act. (impregnated with molecular elastomer)". In addition, according to the definition of JIS-6601, artificial leather is classified according to its appearance into "smooth", which has the appearance of leather like silver, and "nap", which has the appearance of suede, velor, etc. The artificial leather of the embodiment relates to one classified as "nap" (that is, suede-like artificial leather having a raised appearance). The suede-like appearance can be formed by buffing (raising) the outer surface of the fiber layer (A) (that is, the first outer surface of the artificial leather) with sandpaper or the like. In this specification, the first outer surface of the artificial leather is the surface that is exposed to the outside when the artificial leather is used (for example, the surface that comes into contact with the human body in the case of a chair application). (See Figures 1 and 3). In one embodiment, in the case of suede-like artificial leather, the first outer surface is raised or raised by buffing or the like.
In this specification, unless otherwise specified, the term "fibrous web" refers to the state of short fibers before they are entangled, and the term "fiber sheet" refers to the state after entangling and before filling with PU resin. The term "artificial leather" refers to the state of the product after filling with PU resin and before dyeing and finishing, and the term "artificial leather" refers to the state of the product after dyeing and finishing. In addition, the term "nonwoven fabric" includes "fiber web,""fibersheet,""sheet-likematerial," and "artificial leather," and the term "fibrous base material" includes the term "nonwoven fabric." In addition, it also includes woven and knitted fabrics.

[Surface PU resin area ratio and its standard deviation on the first outer surface of the fiber layer (A)]
In the artificial leather of this embodiment, the PU resin area ratio on the first outer surface of the artificial leather is 8% or more and 25% or less, and the standard deviation of the surface PU resin area ratio is 25% or less.
When the surface PU resin area ratio is 25% or less, since the PU resin is present in an appropriate amount on the surface, the product does not feel dry to the touch, provides a satisfying moist feeling, and suppresses staining spots. Furthermore, in this case, since the proportion of fibers present on the surface is higher than that of the PU resin, the fibers can be effectively raised, resulting in a satisfactory dense feel. On the other hand, if the surface PU resin area ratio is 8% or more, the PU resin is present in an appropriate amount on the surface, so that the fabric-like feel, that is, the feeling is not dry, and the moist feeling is satisfactory. The surface PU resin area ratio is preferably 9% or more and 22% or less, more preferably 10% or more and 20% or less.
As described later (see Figure 6), the surface PU resin area ratio is determined by binarizing the PU resin in the SEM image as a black part, and calculating the area of the polyurethane resin for each section using the section method from the obtained binarized image. The ratio is calculated and the surface PU resin area ratio (%) is averaged for all the sections, and the standard deviation is an index of the variation from the average for all the sections. If the standard deviation of the surface PU resin area ratio is 25% or less, there are few areas where the PU resin is unevenly distributed, and the areas where the PU resin and fibers are adjacent are small and small, so that staining spots are difficult to stand out. The standard deviation of the surface PU resin area ratio is preferably 22% or less, more preferably 20% or less.
As will be described later, for example, after forming a fiber web with sea-island short fibers and then de-seaing the fiber sheet obtained by needle punching, a fiber sheet with exposed single fibers of island components is obtained. By subjecting the obtained fiber sheet to the water dispersion treatment described below to obtain a fiber sheet in which single fibers are dispersed, as the single fibers are dispersed, the PU resin attached to the fibers is also dispersed. The standard deviation of the surface PU resin area ratio can be controlled to 25% or less. In addition, a water-dispersed PU resin dispersion containing hot water-soluble resin fine particles (for example, hot water-soluble fine resin particles) is impregnated, and then the PU resin is fixed by heating, so that the PU resin is filled. By carrying out the step of obtaining a sheet-like product, the surface PU resin area ratio can be controlled to 8% or more and 25% or less.

[K neighborhood distance ratio value between single fiber cross sections constituting the fiber layer (A) (k = 9, radius r = 20 μm)]
In this embodiment, the k-neighborhood distance ratio value (k = 9, radius r = 20 μm) between the single fiber cross sections constituting the fiber layer (A) in the thickness direction cross section of the artificial leather is 10% or more and 80% or less. It is a certain thing. The k-neighborhood distance ratio value (k = 9, radius r = 20 μm) indicates the degree of crowding of single fibers.
The measurement method will be described later, but the k-nearest neighbor method takes k single fiber cross sections close to any one single fiber cross section, and calculates the Euclidean distance (i.e., the square root of the sum of the squares of the distances in the X and Y directions (= This is a method in which the radius closest to the k-th point in the shortest distance) is set as the determination boundary. In this embodiment, a SEM image is taken, and k= Determine whether the ninth closest single fiber cross section exists. For all single fiber cross sections in one SEM image, the presence or absence of the single fiber cross section is determined, and the single fiber cross section k = 9 neighborhood distance ratio (%) is determined using the following formula:
Single fiber cross section (k = 9) neighborhood distance ratio (%) = {(Number of single fiber cross sections in which k = 9th closest single fiber cross section exists within a distance of 20 μm radius from the approximate center of the single fiber cross section) /(total number of single fiber cross sections in one SEM image)}×100.
If the k-neighborhood distance ratio value (k = 9, radius r = 20 μm) between the single fiber cross sections constituting the fiber layer (A) in the thickness direction cross section of the artificial leather is 10% or more, the single fibers are appropriately dispersed. As a result, the PU resin lumps of the fiber layer (A) also exist in a moderately dispersed state, and when you touch the artificial leather with your fingertips, you will come into contact with such moderately dispersed PU resin lumps. , the moist feeling (the size is similar to that of a PU resin lump) is satisfactory. On the other hand, if the k-neighborhood distance ratio value (k = 9, radius r = 20 μm) is 80% or less, the single fibers are moderately aggregated, resulting in a smooth texture with a high density (dispersibility of fiber bundles). becomes. The k-neighborhood distance ratio value (k=9, radius r=20 μm) is preferably 20% or more and 70% or less, more preferably 30% or more and 60% or less.

As described later, a fiber sheet obtained by forming a fiber web with sea-island staple fibers and then performing a needle punching treatment to obtain a fiber sheet in which single fibers of the island component are exposed is obtained. The k-neighborhood distance ratio value (k = 9, radius r = 20 μm) is controlled within a range of 80% or less by performing a water dispersion treatment on the fiber sheet to obtain a fiber sheet in which single fibers are dispersed. be able to. The water dispersion treatment is preferably carried out by jetting high-pressure water using a plurality of nozzles having a nozzle hole interval of 1.00 mm or less. As shown in FIG. 7, the nozzle spacing is the distance in the nozzle width direction between a nozzle hole and the nozzle hole that is closest to the nozzle hole in the nozzle width direction (even if there are two or more rows of nozzle holes, one row ). By setting the nozzle hole spacing to 1.00 mm or less, it is possible to discharge water streams at close intervals onto the fiber sheet, and by dispersing the single fibers in the form of single fiber bundles, the dense and moist feeling is improved. Easy to do. Furthermore, the water flow trajectory caused by the water flow dispersion treatment on the surface of the fiber sheet is less noticeable. The nozzle hole interval is preferably 0.60 mm or less, more preferably 0.30 mm or less.

Further, the number of nozzle hole rows opened in the width direction of the water dispersion treatment equipment may be one row or multiple rows of two or more rows. When performing water dispersion treatment, it is common to remove the water introduced into the fiber sheet by water dispersion treatment in order to maintain the uniformity and shape stability of the fiber sheet. dehydrated by such methods. In that case, for example, if the number of nozzle rows is one and the nozzle hole spacing is narrowed, the dewatering capacity will be insufficient for the amount of water input, and as a result, the uniformity and shape stability of the fiber sheet may deteriorate. On the other hand, reducing the amount of water input per nozzle hole row by increasing the number of rows and widening the nozzle spacing per nozzle hole row is a preferred mode because it is easy to balance the amount of water input and dewatering capacity. It is. For example, if dehydration failure occurs in a single row of nozzles with a nozzle hole spacing of 0.30 mm, use a two row nozzle with a nozzle hole spacing of 0.60 mm in the first row, and the phase difference between the second row and the first row is 0. If a nozzle row of 30 mm is arranged with a nozzle hole interval of 0.60 mm, the water flow trajectory (nozzle hole interval) will be 0.30 mm, and the effect of improving dehydration defects can be obtained. Further, it is preferable to widen the nozzle hole interval and form multiple rows because nozzle machining (hole drilling machining) becomes easier. It is preferable that the nozzle hole spacing (water flow trajectory) be equally spaced because it is easy to uniformly disperse the single fibers, the water flow trajectory is less noticeable, and the dense and moist feeling is easily improved.
When the number of nozzle rows is multiple, the distance between the nozzle rows is preferably set to a distance equivalent to the nozzle hole interval in one nozzle row, for example, from the viewpoint of dehydration.

The pore diameter of the high-pressure water injection nozzle in water flow dispersion treatment is 0.0 mm because it is easy to obtain high single fiber dispersion, the water flow trajectory is not noticeable, and furthermore, the amount of water input is not excessive and it is easy to balance with the dewatering capacity. It is preferably 0.05 mm or more and 0.30 mm or less, more preferably 0.05 mm or more and 0.20 mm or less, and even more preferably 0.08 mm or more and 0.13 mm or less.
Further, it is preferable that the water pressure in the water jet dispersion treatment is 1.0 to 10.0 MPa. By setting the water pressure in the water dispersion treatment to 1.0 MPa or more, single fiber bundles are not excessively dispersed, so that it is easy to control the k-nearby distance ratio value to 10% or more and 80% or less. In addition, single fibers in the form of single fiber bundles are easily dispersed, and by setting the water pressure in the water dispersion treatment to 10.0 Mpa or less, the single fibers in the form of single fiber bundles are dispersed, and the trajectory of the water flow is less noticeable. It's easy. When the water pressure of water dispersion treatment is high, the water flow may penetrate the fiber sheet, and it is not used as energy to disperse the single fiber bundles, and on the other hand, the dispersion effect of the single fiber bundles is lower than when processing with low water pressure. There are cases where Furthermore, when the water pressure of the water dispersion treatment is high, the fiber sheet tends to become denser and the texture (flexibility value) tends to deteriorate. The water pressure of the water dispersion treatment is more preferably 1.5 to 7.0 MPa, still more preferably 2.0 to 4.5 MPa.

Regarding the shape of the water stream discharged from the nozzle hole, it is also preferable to use a plurality of nozzles that discharge a water stream in which the disturbance of the water stream is 10% or more. Disturbance is a measure of variation in the diameter of water flow. The disturbance is preferably 12% or more, more preferably 15% or more, since the energy of the water stream can be efficiently converted into fiber dispersion. The disturbance is calculated using the following formula, where W is the average diameter of the water flow in the range from 25 mm to 35 mm from the discharge port of the nozzle hole, and σ is the standard deviation of the average diameter.
Disturbance (%) = σ (mm) / W (mm) × 100
Calculated by
Although the mechanism of dispersion of single fiber bundles due to disturbance is not clear, the present inventors found that when the disturbance is large compared to small cases, the water flow energy is directed not only vertically but also horizontally to the fiber sheet. We believe that by making it easier to disperse in multiple directions, the water flow energy can be efficiently converted into the dispersion energy of single fiber bundles, thereby increasing the dispersion effect. As an example, it is believed that at high water pressure, it is easy to capture water flow energy that would be wasted by penetrating the fiber sheet as dispersion energy.

In addition, it is preferable to move the high-pressure water jet nozzle in a circular motion or to move it back and forth at right angles to the process direction (machine direction) to promote single fiber dispersion and improve the dense and moist feeling. .
The distance from the high-pressure water jet surface to the object to be treated is preferably 5 mm or more and 100 mm or less, from the viewpoint of the dispersion effect of the single fiber bundle, the guiding cloth before water dispersion treatment, and the process passability during water dispersion treatment. The length is more preferably 10 mm or more and 60 mm or less, and even more preferably 20 mm or more and 40 mm or less.

[Adhesion rate of PU resin to fiber sheet]
In the artificial leather of this embodiment, the adhesion rate of the PU resin to the fiber sheet is preferably 15% by mass or more and 50% by mass or less, more preferably 22% by mass or more and 45% by mass or less, still more preferably 26% by mass. % or more and 40% by mass or less. The ratio of PU resin to the fiber sheet affects the above-mentioned surface PU resin area ratio. When the ratio of PU resin is low, the surface PU resin area ratio tends to be low. On the other hand, when the ratio of PU resin is high, the cross-sectional PU resin area ratio tends to be high. When the ratio of the PU resin to the fiber sheet is 15% by mass or more, the fibers are held well by the PU resin, and it is easy to obtain mechanical strength such as abrasion resistance that satisfies market needs. On the other hand, if the ratio of the PU resin to the fiber sheet is 50% by mass or less, it is easy to obtain artificial leather with a soft texture and a dense feel.

[Polyurethane (PU) resin]
The PU resin is preferably one obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender.
As the polymer diol, for example, polycarbonate-based, polyester-based, polyether-based, silicone-based, fluorine-based diols, etc. can be employed, and a copolymer of two or more of these may be used. From the viewpoint of hydrolysis resistance, polycarbonate-based diols, polyether-based diols, or a combination thereof are preferably used. Moreover, from the viewpoint of light resistance and heat resistance, polycarbonate-based, polyester-based diols, or a combination thereof are preferably used. Furthermore, from the viewpoint of cost competitiveness, polyether diols, polyester diols, or a combination thereof are preferably used.
Polycarbonate diols can be produced by transesterification of alkylene glycol and carbonate, reaction of phosgene or chloroformate, and alkylene glycol, and the like.

Examples of alkylene glycols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and 1,10-decanediol. Chain alkylene glycol; branched alkylene glycol such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-methyl-1,8-octanediol; 1, Alicyclic diols such as 4-cyclohexanediol; aromatic diols such as bisphenol A; etc., and these can be used alone or in combination of two or more.
Examples of polyester diols include polyester diols obtained by condensing various low molecular weight polyols and polybasic acids.
Examples of low molecular weight polyols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethyl-1,3-propane. Diol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, cyclohexane One or more types selected from -1,4-dimethanol can be used. Further, adducts obtained by adding various alkylene oxides to bisphenol A can also be used.
Examples of polybasic acids include succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydrocarbonic acid. One or more types selected from the group consisting of isophthalic acid can be mentioned.

Examples of the polyether diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymer diols that are a combination thereof.
The number average molecular weight of the polymer diol is preferably 500 to 4,000. By setting the number average molecular weight to 500 or more, more preferably 1500 or more, it is possible to prevent the texture from becoming hard. Further, by setting the number average molecular weight to 4000 or less, more preferably 3000 or less, the strength of the PU resin can be maintained well.
Examples of organic diisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate; aromatic diisocyanates such as diphenylmethane diisocyanate and tolylene diisocyanate; and combinations thereof. It may also be used. Among them, from the viewpoint of light resistance, aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate are preferably used.
As the chain extender, an amine chain extender such as ethylenediamine and methylenebisaniline, or a diol chain extender such as ethylene glycol can be used. Moreover, a polyamine obtained by reacting polyisocyanate and water can also be used as a chain extender.

PU resin is also used in the form of solvent-type PU resin in which PU resin is dissolved in an organic solvent such as N,N-dimethylformamide, and water-dispersed PU resin in which PU resin is emulsified with an emulsifier and dispersed in water. can. Among these, it is easy to fill fiber sheets with PU resin in a fine form, and even with a small amount of adhesion, it is easy to obtain the performance required for artificial leather such as texture and mechanical properties, and there is no need to use organic solvents, reducing environmental impact. A water-dispersed PU resin is preferable because it can reduce the amount of water. In other words, water-dispersed PU resin can be impregnated into a fiber sheet in the form of a dispersion (hereinafter also referred to as PU resin dispersion) in which PU resin is dispersed with a desired particle size, so the particle size can be controlled. Accordingly, the filling form of the PU resin in the fiber sheet can be well controlled.
As the water-dispersed PU resin, a self-emulsifying PU resin containing a hydrophilic group in the PU molecule, a forced emulsifying PU resin in which the PU resin is emulsified with an external emulsifier, etc. can be used.
A crosslinking agent can be used in combination with the water-dispersed PU resin for the purpose of improving durability such as heat and humidity resistance, abrasion resistance, and hydrolysis resistance. It is preferable to add a crosslinking agent in order to improve durability during jet dyeing, suppress fiber shedding, and obtain excellent surface quality. The crosslinking agent may be an external crosslinking agent that is added to the PU resin as an additive component, or an internal crosslinking agent that introduces a reactive group that can form a crosslinked structure into the PU resin structure in advance.
Water-dispersible PU resins used for artificial leather generally have a crosslinked structure to provide resistance to dyeing processes, so they tend to be difficult to dissolve in organic solvents such as N,N-dimethylformamide. . Therefore, for example, when artificial leather is immersed in N,N-dimethylformamide at room temperature for 12 hours to dissolve the PU resin, when the cross section is observed with an electron microscope, it is found that the resin does not have a fiber shape. If any substance remains, it can be determined that the resinous substance is a water-dispersed PU resin.

In a preferred embodiment, from the viewpoint of easily controlling the surface PU resin area ratio and its standard deviation, PU resin is filled using a PU resin dispersion, and at that time, the average primary order of the PU resin in the dispersion is The particle size is preferably 0.1 μm or more and 0.8 μm or less, more preferably 0.1 μm or more and 0.6 μm or less, and still more preferably 0.2 μm or more and 0.5 μm or less. The average primary particle diameter is a value obtained by measuring a PU resin dispersion using a laser diffraction particle size distribution analyzer ("LA-920" manufactured by Horiba, Ltd.). Artificial leather that has excellent mechanical strength by making the average primary particle size of the PU resin 0.1 μm or more and improving the force of gripping the fibers in the fiber sheet (i.e., the binder force) with the PU resin. is obtained. Furthermore, setting the average primary particle size of the PU resin to 0.8 μm or less is advantageous in that it suppresses the PU resin from agglomerating or coarsening, and the standard deviation of the surface PU resin area ratio can be controlled to 20% or less. It is. By setting the average primary particle size of the PU resin in the PU resin dispersion to 0.1 μm or more and 0.8 μm or less, the fibers that make up the artificial leather (especially its surface layer) will be held together at more points, making it more flexible. Provides excellent texture (flexibility value) and mechanical strength (abrasion resistance, etc.).

[Solid content concentration of PU resin dispersion]
As described below, in typical embodiments, the PU resin is impregnated in the form of an impregnating liquid such as a solution (for example, in the case of a solvent-dispersed type) or a dispersion (for example, in the case of a water-dispersed type). For example, the solid content concentration of the water-dispersed PU resin dispersion can be from 10% by weight to 35% by weight, more preferably from 15 to 30% by weight, and even more preferably from 15 to 25% by weight. In one embodiment, the impregnation liquid is prepared and impregnated into the fiber sheet so that the adhesion rate of the PU resin to 100 mass% of the fiber sheet is 15% by mass or more and 50% by mass or less.
The impregnating liquid containing PU resin (for example, water-dispersed PU resin) may contain stabilizers (ultraviolet absorbers, antioxidants, etc.), flame retardants, antistatic agents, pigments (carbon black, etc.) as necessary. Additives may be added. The total amount of these additives present in the artificial leather is, for example, 0.1 to 10.0 parts by weight, or 0.2 to 8.0 parts by weight, or 0.3 to 100 parts by weight, based on 100 parts by weight of the PU resin. It may be 6.0 parts by mass. Note that such additives will be distributed in the PU resin of the artificial leather. In this disclosure, when referring to the size and mass ratio of the PU resin to the fiber sheet, the values are intended to include additives (if used).

[Hot water soluble resin particles]
When filling a fiber sheet with PU resin by impregnating the fiber sheet with an impregnating liquid containing PU resin, the fiber sheet is impregnated with a water-dispersible PU resin dispersion containing hot water-soluble resin fine particles, and then A preferred embodiment is to perform a step of fixing the PU resin by heating to obtain a sheet-like article filled with the PU resin. In the post-process or dyeing process, the hot water-soluble resin particles are removed from the obtained fiber sheet using hot water, thereby dividing a part of the continuous layer of PU resin and making it porous, which prevents the adhesion of PU resin. The effect of refining the state can be obtained.
Examples of the hot water-soluble resin particles include partially saponified PVA resin particles and completely saponified PVA resin particles. Completely saponified PVA resin particles tend to be more difficult to dissolve in water at room temperature (20°C) than partially saponified PVA resin particles, so fully saponified PVA resin particles are used as hot water-soluble resin particles. It is preferable. From the viewpoint of being difficult to elute in water at room temperature (20° C.), the degree of saponification of the fully saponified PVA resin particles is preferably 95 mol% or more, more preferably 98 mol% or more. In order to achieve both the strength to bond and grip the fibers and the fineness of the adhesion state of the PU resin, the average particle diameter (size) of the hot water-soluble resin fine particles is preferably 1 μm or more and 8 μm or less, more preferably 2 μm or more and 6 μm or less. More preferably, the thickness is 2 μm or more and 4 μm or less. By setting the average particle size to 1 μm or more, the hot water-soluble resin fine particles are difficult to aggregate, and by setting the average particle size to 8 μm or less, the hot water-soluble resin fine particles can easily impregnate the fiber sheet. . "NL-05" manufactured by Mitsubishi Chemical Corporation can be used as the fine particles, and the fineness of the fine particles can be achieved by the method described in JP-A-7-82384.
The content of hot water-soluble resin fine particles in the water-dispersed PU resin dispersion is preferably 1% by weight or more and 20% by weight or less, more preferably 2% by weight or more and 15% by weight or less, and Preferably it is 3% by weight or more and 10% by weight or less. When the water-dispersed PU resin dispersion contains 1% by mass or more of hot water-soluble resin fine particles, the dispersion of the PU resin lumps is likely to be promoted. On the other hand, when the water-dispersible PU resin dispersion contains 20% by weight or less of hot water-soluble resin fine particles, the fine particles do not aggregate and the stability of the dispersion is easily maintained.
In addition, in this specification, "hot water soluble resin" refers to a resin that is hardly soluble in room temperature water, and specifically has a shedding rate of 25% or less in room temperature water at a temperature of 20 ± 2 ° C. .

[Hot water soluble resin]
When a fiber sheet is impregnated with a water-dispersed PU resin dispersion containing hot water-soluble resin fine particles, and then the PU resin is fixed by heating to obtain a sheet-like article filled with PU resin, the fiber sheet is Before impregnating the fiber sheet with a water-dispersible PU resin dispersion containing fine particles of hot water-soluble resin, a step of attaching hot water-soluble resin to the fiber sheet can also be performed. The hot water soluble resin (for example, PVA resin) can be attached by a method such as preparing an aqueous solution of the hot water soluble resin, impregnating the fiber sheet with the aqueous solution, and then drying it. In the post-process or dyeing process, the hot water-soluble resin is removed together with the hot water-soluble resin fine particles from the obtained fiber sheet using hot water, thereby inhibiting the adhesion between the fibers and the PU resin, The effect of dividing a part of the continuous layer of PU resin and making it porous to make the state of adhesion of the PU resin finer can be obtained, thereby easily improving the feel of the artificial leather.
Examples of the hot water-soluble resin include partially saponified PVA resin, completely saponified PVA resin, and the like. Since fully saponified PVA resin tends to be less eluted in water at room temperature (20° C.) than partially saponified PVA resin, it is preferable to use fully saponified PVA resin as the hot water-soluble resin. From the viewpoint of being difficult to elute in water at room temperature (20° C.), the degree of saponification of the fully saponified PVA resin is preferably 95 mol% or more, more preferably 98 mol% or more. Further, in order to increase the permeability of the hot water-soluble resin aqueous solution during impregnation, the degree of polymerization is preferably 1000 or less, more preferably 700 or less.

[Fiber sheet]
As shown in FIG. 1, the fiber sheet 1 includes at least a fiber layer (A) 12, and the scrim 11 and the fiber layer (B) 13 are optional and not essential elements. Therefore, in the case of a single layer of the fiber layer (A), in the case of two layers of the fiber layer (A) and the scrim or the fiber layer (B), the artificial leather of the present embodiment includes the fiber layer (A), the scrim and the fiber layer. There may be three layers (layer (B)).
When the scrim 11 and/or the fiber layer (B) 13 is not included, the fiber layer (A) may be a single-layer fiber sheet filled with PU resin cut in half, as described later. In one aspect, the fibrous sheet is a single layer structure that does not include a scrim. This is because cutting in half increases productivity.
In other embodiments, the fibrous sheet has a three layer structure and the scrim is the middle layer. For example, a scrim 11 that is a woven or knitted fabric is placed between the fiber layer (A) 12 that constitutes the first outer surface of the artificial leather and the fiber layer (B) 13 that constitutes the second outer surface of the artificial leather. A three-layer structure in which the fibers are sandwiched and intertwined between these layers is preferable in terms of dimensional stability, tensile strength, tear strength, and the like. Moreover, according to the three-layer structure of the fiber layer (A), the fiber layer (B), and the scrim sandwiched between them, the fiber layer (A) and the fiber layer (B) can be designed individually. This is preferable in that the diameter, type, etc. of the fibers constituting these layers can be freely customized according to the functions and uses required of the artificial leather. For example, if ultrafine fibers are used in the fiber layer (A) and flame-retardant fibers are used in the fiber layer (B), both excellent surface quality and high flame retardance can be achieved.

When the fiber sheet includes a scrim, the scrim, which is a woven or knitted fabric, is preferably made of the same polymer type as the fibers constituting the fiber layer (A) from the viewpoint of the same color property when dyed. For example, if the fibers constituting the fiber layer (A) are polyester-based, the fibers constituting the scrim are preferably polyester-based, and if the fibers constituting the fiber layer (A) are polyamide-based, the scrim is preferably polyester-based. It is preferable that the constituent fibers are also polyamide-based. In the case of a knitted fabric, the scrim is preferably a single knit knitted with a gauge of 22 or more and 28 or less. When the scrim is woven, greater dimensional stability and strength can be achieved than when knitted. The structure of the woven fabric may be plain weave, twill weave, satin weave, etc., but plain weave is preferred from the viewpoint of cost and process aspects such as interlacing properties.
The yarn constituting the fabric may be monofilament or multifilament. The single fiber fineness of the yarn is preferably 5.5 dtex or less, since flexible artificial leather can be easily obtained. As for the form of the yarn constituting the woven fabric, it is preferable to use multifilament raw silk of polyester, polyamide, etc., or textured yarn subjected to false twisting, twisted at a twist number of 0 to 3000 T/m. The multifilament may be a normal one, for example, 33dtex/6f, 55dtex/24f, 83dtex/36f, 83dtex/72f, 110dtex/36f, 110dtex/48f, 167dtex/36f, 166dtex/48f, etc. made of polyester, polyamide, etc. Preferably used. The threads constituting the fabric may be multifilament long fibers. The weaving density of the threads in the fabric is preferably 30 to 150 threads/inch, more preferably 40 to 100 threads/inch, in order to obtain artificial leather that is flexible and has excellent mechanical strength. In order to have good mechanical strength and appropriate texture, the basis weight of the fabric is preferably 20 to 150 g/m ² . In addition, the presence or absence of false twisting in the woven fabric, the number of twists, the single fiber fineness of the multifilament, the weaving density, etc. are determined by the entanglement with the fibers constituting the fiber layer (A) and the optional layer (B), In addition to the flexibility of the artificial leather, it also contributes to mechanical properties such as seam strength, tear strength, tensile strength and elongation, and elasticity, so it may be selected appropriately depending on the target physical properties and use.

From the viewpoint of obtaining artificial leather that has higher levels of wear resistance, dyeability, and surface quality, in the artificial leather of this embodiment, the fiber layer (A) is composed of fibers with an average diameter of 1 μm or more and 8 μm or less. It is preferably 2 μm or more and 6 μm or less, and even more preferably 2 μm or more and 5 μm or less. If the average diameter of the fibers is 1 μm or more, the abrasion resistance, color development by dyeing, and light fastness will be good. On the other hand, if the average diameter of the fibers is 8 μm or less, the number density of the fibers is high, so that it is easy to obtain artificial leather with a high density, smooth surface feel, and better surface quality.

The fibers constituting the fiber layers (fiber layer (A), optional fiber layer (B), and additional layers) constituting the artificial leather include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, etc. Synthetic fibers such as polyester fibers; polyamide fibers such as nylon 6, nylon 66, and nylon 12 are suitable. Among these, polyethylene terephthalate is preferable for applications that require durability, such as in the car seat field, because the fiber itself does not yellow even when exposed to direct sunlight for a long time, and has excellent color fastness. . Further, from the viewpoint of reducing environmental load, as the fibers constituting the fiber layer constituting the artificial leather, chemically recycled or material recycled polyethylene terephthalate, or polyethylene terephthalate using plant-derived raw materials, etc. are more preferable.

As used herein, the term "fibers are dispersed as single fibers" means that the fibers do not form fiber bundles such as the island components in the sea-island composite fibers described below. For example, ultrafine fiber generation fibers such as sea-island type composite fibers (for example, those using copolymerized polyester as a sea component and regular polyester as an island component) are used, and after forming a three-dimensional entanglement with a scrim, fine fibers are formed. The fibers obtained by chemical treatment (removal of the sea component of the sea-island composite fiber by dissolving, decomposing, etc.) exist as fiber bundles in the fiber layer (A), and are not dispersed as single fibers. As an example, sea-island type composite short fibers in which the island component is equivalent to a single fiber fineness of 0.2 dtex and 24 islands/1f are prepared, and after forming the fiber layer (A) with the sea-island type composite short fibers, needle punching etc. After forming a three-dimensional entangled body with the scrim and filling the three-dimensional entangled body with PU resin, the sea component is dissolved or decomposed to obtain ultrafine fibers with a single fiber fineness equivalent to 0.2 dtex. In this case, 24 single fibers are present in the fiber layer (A) in the form of a fiber bundle (equivalent to 4.8 dtex in the converged state).

When the fibrous layer (A) is composed of fibers in which single fibers are dispersed, it has excellent surface smoothness, and for example, when the outer surface of the fibrous layer (A) is raised by buffing or the like, uniform raising is achieved. It is easy to obtain, and even when the adhesion rate of PU resin is relatively low, a pill-like appearance called pilling is unlikely to occur due to friction, so artificial leather with better surface quality and abrasion resistance can be obtained. Furthermore, when the fibers are dispersed as single fibers, the fiber spacing tends to be narrow and uniform, so even if the PU resin is attached in a fine form, good abrasion resistance can be obtained. Methods for dispersing fibers into single fibers include a method in which fibers produced by a direct spinning method are made into a fiber sheet by a papermaking method, and a method in which the sea component of a fiber sheet made from sea-island composite fibers is dissolved or decomposed to form ultrafine fiber bundles. For example, a method of promoting the formation of a single fiber from the ultrafine fiber bundle by subjecting the surface of the ultrafine fiber bundle to the water dispersion treatment described above after generating the ultrafine fiber bundle.

In the fiber layers other than the fiber layer (A) among the fiber layers constituting the artificial leather, the fibers may or may not be dispersed as single fibers, but in a preferred embodiment, the layers other than the fiber layer (A) It is also composed of fibers that are dispersed in single fibers. It is preferable that the fibers constituting the layers other than the fiber layer (A) are dispersed in single fibers, so that the thickness of the artificial leather becomes uniform, processing accuracy improves, and quality is stabilized. It is also preferable from the viewpoint of making the appearance of the front and back sides of the artificial leather uniform.

When the artificial leather is composed only of the fiber layer (A), the basis weight of the fibers constituting the fiber layer (A) is preferably 40 g/m ² or more and 500 g/m ² from the viewpoint of mechanical strength such as abrasion resistance. Below, it is more preferably 50 g/m ² or more and 370 g/m ² or less, and still more preferably 60 g/m ² or more and 320 g/m ² or less.
When artificial leather is composed of a three-layer structure of a fiber layer (A), a scrim, and a fiber layer (B), the basis weight of the fibers constituting the fiber layer (A) is determined from the viewpoint of mechanical strength such as abrasion resistance. Preferably it is 10 g/m ² or more and 200 g/m ² or less, more preferably 30 g/m ² or more and 170 g/m ² or less, and even more preferably 60 g/m ² or more and 170 g/m ² or less. In addition, from the viewpoint of cost and ease of production, the basis weight of the fibers constituting the fiber layer (B) is preferably 10 g/m ² or more and 200 g/m ² or less, more preferably 20 g/m 2 or more and 170 g/m ² or less. It can be less than or equal to ² . The basis weight of the scrim is preferably 20 g/m ² or more and 150 g/m 2 or less, more preferably 20 g/m 2 or more and 130 g/m ^{2 or} less, and even more preferably from the viewpoint of mechanical strength and entanglement between ^{the fiber layer} and the scrim. is 30 g/m ² or more and 110 g/m ² or less.
The basis weight of the artificial leather filled with PU resin is preferably 50 g/m ² or more and 550 g/m ² or less, more preferably 60 g/m ² or more and 400 g/m ² or less, and even more preferably 70 g/m ² or more and 350 g/m 2 or less. ² or less.

In one embodiment, the inconspicuousness of dyed spots on the artificial leather is preferably 4.0 grade or higher, more preferably 5.0 grade or higher. The inconspicuousness of dyed spots is a value determined by visual evaluation of the difficulty in distinguishing the color difference between the fiber and the PU resin on a 7-level scale. By setting the inconspicuousness of dyed spots to grade 4.0 or higher, the quality as a surface material or interior material for seats of interiors, automobiles, aircraft, railway vehicles, etc. is improved, and dyed spots are difficult to stand out.

In one embodiment, the moist feel of the artificial leather is preferably grade 4.0 or higher, more preferably grade 5.0 or higher. The moist feeling is a value determined by a sensory evaluation based on tactile sensation, and the moist feeling when the first outer surface of the fibrous layer (A) is touched on a 7-grade scale. By setting the denseness to 4.0 grade or higher, the quality of the material as a surface material or interior material for seats in interiors, automobiles, aircraft, railway vehicles, etc. is improved.

In one embodiment, the dense feel (dispersibility of fiber bundles) of the artificial leather is preferably grade 4.0 or higher, more preferably grade 5.0 or higher. The denseness (dispersibility of fiber bundles) is the value of the denseness of the nap determined in 7 levels by visual and tactile sensory evaluation. By setting the denseness to 3.0 grade or higher, the quality as a surface material or interior material for seats of interiors, automobiles, aircraft, railway vehicles, etc. is improved.

<Manufacturing method of artificial leather>
An example of the method for manufacturing artificial leather of this embodiment will be described below.
An example of the method for manufacturing artificial leather of this embodiment includes the following steps:
Forming a fiber web with sea-island short fibers, and then de-sea-removing the fiber sheet obtained by needle punching to obtain a fiber sheet in which the single fibers of the island component are exposed; and Water dispersion in the obtained fiber sheet. A process of performing treatment to obtain a fiber sheet in which single fibers are dispersed;
The following steps may include:
The fiber sheet in which the single fibers are dispersed is impregnated with a water-dispersed PU resin dispersion containing hot water-soluble resin fine particles, and then the PU resin is fixed by heating to obtain a sheet-like product filled with PU resin. and a step of removing the hot water-soluble resin fine particles from the obtained sheet-like material using hot water;
may further include.
Each step will be explained in order below.

[Step of forming a fiber web with sea-island short fibers, and then de-sea-removing the fiber sheet obtained by needle punching to obtain a fiber sheet in which the single fibers of the island component are exposed]
The manufacturing method for each fiber layer (fiber layer (A), arbitrary fiber layer (B), etc.) constituting the fiber sheet of artificial leather includes a direct spinning method (for example, spunbond method and melt-blown method), or , a method of forming a fiber sheet using short fibers (for example, a dry method such as a carding method or an air-laid method, and a wet method such as a papermaking method). In embodiments, island-in-the-sea (SIF) staple fibers are used as the raw material. A fiber sheet manufactured using short fibers has small density spots and excellent uniformity, and is easy to obtain uniform napping, so it is suitable for improving the surface quality of artificial leather.

As the means for forming the ultrafine fibers of the fiber sheet, ultrafine fiber expression type fibers can be used. By using ultrafine fiber expression type fibers, a form in which ultrafine fiber bundles are entangled can be stably obtained.
The ultrafine fiber developing type fiber is a sea-island type fiber in which two thermoplastic resin components with different solvent solubility are used as a sea component and an island component, and the island component is made into ultrafine fiber by dissolving and removing the sea component using a solvent or the like. It is possible to employ peelable composite fibers in which fibers or two-component thermoplastic resins are arranged alternately in a radial or multilayered manner on the cross section of the fibers, and each component is peeled and split into ultrafine fibers. Among these, sea-island type fibers are preferably used from the viewpoint of the flexibility and texture of sheet-like products because by removing the sea component, it is possible to create appropriate voids between the island components, that is, between the ultrafine fibers. .
Sea-island composite fibers include sea-island composite fibers, which are spun using a sea-island composite spinneret by arranging two components, a sea component and an island component, and a sea-island composite fiber, which is spun by mixing two components, a sea component and an island component. There are mixed type fibers. Sea-island composite fibers are preferably used because they yield ultrafine fibers of uniform fineness and have sufficient length, contributing to the strength of the sheet-like product.
As the sea component of the sea-island type fiber, polyethylene, polypropylene, polystyrene, copolymerized polyester obtained by copolymerizing sodium sulfoisophthalic acid, polyethylene glycol, etc., and polylactic acid can be used. Among these, from the viewpoint of environmental consideration, copolymerized polyesters and polylactic acid, which are copolymerized with alkali-decomposable sodium sulfoisophthalic acid, polyethylene glycol, and the like, which can be decomposed without using an organic solvent, are preferable.
When sea-island type fibers are used, the sea removal treatment is preferably performed before applying the PU resin to the fiber sheet. If the sea removal treatment is performed before applying the PU resin, the structure will be such that the PU resin will adhere directly to the ultrafine fibers, and the ultrafine fibers can be strongly gripped, so that the abrasion resistance of the sheet-like material will be improved.

As a method for entangling the fibers or fiber bundles of the fibrous web, sea-island fibers are cut to a predetermined fiber length to form staples, a fibrous web is formed through a card and a cross wrapper, and a hydroentangling process called needle punching or spunlace method is used. A method of confounding can be adopted.
In the needle punch method, the number of needle barbs used is preferably 1 to 9. By setting the number of barbs to one or more, a confounding effect can be obtained and damage to the fibers can be suppressed. By setting the number of barbs to 9 or less, damage to the fibers can be reduced, and needle marks left on the artificial leather can be reduced, so that the appearance of the product can be improved.
Considering the entanglement of the fibers and the influence on the product appearance, the total depth of the barb (the length from the tip of the barb to the bottom of the barb) is preferably 0.05 mm or more and 0.10 mm or less. When the total depth of the barbs is 0.05 mm or more, good hooking on the fibers can be obtained, so that efficient fiber entanglement can be achieved. In addition, since the total depth of the barbs is 0.10 mm or less, needle marks left on the artificial leather are reduced and the quality is improved. Considering the balance between the strength of the barb portion and fiber entanglement, the total depth of the barb is more preferably 0.06 mm or more and 0.08 mm or less.
When fibers are entangled by ^the needle punch method, the punch density range is preferably 300 to 6000 fibers/cm ² , and 1000 to 6000 fibers/cm ^{2 .} is more preferable.
The fiber sheet obtained by needle punching can be immersed in water at a temperature of 98° C. for 2 minutes to shrink, and dried at a temperature of 100° C. for 5 minutes to obtain a fiber sheet before sea removal. .
The sea-removal treatment can be performed by immersing the sea-island type fibers in a solvent and draining the fibers. As the solvent for dissolving the sea component, when the sea component is copolymerized polyester or polylactic acid, an alkaline aqueous solution such as sodium hydroxide can be used. From the viewpoint of environmental considerations in the process, desalination treatment with an alkaline aqueous solution such as sodium hydroxide is preferred.

When selecting a method using short fibers (staples), the short fiber length is preferably 13 mm or more and 102 mm or less, more preferably 25 mm or more and 76 mm or less, and even more preferably It is 38 mm or more and 76 mm or less, and preferably 1 mm or more and 30 mm or less, more preferably 2 mm or more and 25 mm or less, and still more preferably 3 mm or more and 20 mm or less, by a wet method (paper making method, etc.). For example, the aspect ratio (L/D), which is the ratio of length (L) to diameter (D), of short fibers used in a wet method (paper-making method, etc.) is preferably 500 or more and 2000 or less, more preferably It is 700-1500. Such an aspect ratio is such that the short fibers have good dispersibility and spreadability in the slurry when the short fibers are dispersed in water to prepare the slurry, the fiber layer strength is good, Compared to the dry method, the fiber length is shorter and the single fibers are easily dispersed, so it is less likely to cause a pill-like appearance called pilling due to friction, which is preferable. For example, the fiber length of short fibers having a diameter of 4 μm is preferably 2 mm or more and 8 mm or less, more preferably 3 mm or more and 6 mm or less.

[Step of subjecting the obtained fiber sheet to water dispersion treatment to obtain a fiber sheet in which single fibers are dispersed]
By subjecting the obtained fiber sheet to the water dispersion treatment described above, a fiber sheet in which single fibers are dispersed can be obtained. By performing the above-mentioned water dispersion treatment after the sea removing step, the k-neighborhood distance ratio value (k = 9, radius r=20 μm) can be controlled to 80% or less.

[The fiber sheet in which the single fibers are dispersed is impregnated with a water-dispersed PU resin dispersion containing hot water-soluble resin fine particles, and then the PU resin is fixed by heating to form a sheet filled with PU resin. process of obtaining something]
In this step, the fiber sheet is impregnated with a water-dispersed PU resin dispersion containing hot water-soluble resin fine particles, and then the PU resin is fixed by heating to fill the fiber sheet with the PU resin. In typical embodiments, the PU resin is impregnated in the form of an impregnating liquid, such as a dispersion (eg, in the case of an aqueous dispersion). The concentration of PU resin in the impregnation liquid can be, for example, 10 to 35% by weight. In one embodiment, the impregnation liquid is prepared and the fiber sheet is impregnated so that the ratio of the PU resin to 100 mass% of the fiber sheet is 15 to 50 mass%.

Water-dispersed PU resins are forcibly dispersed and stabilized using surfactants, and forced emulsification-type PU resins, which have a hydrophilic structure in the PU molecular structure and can be used in water even in the absence of surfactants. It is classified as a self-emulsifying PU resin that is dispersed and stabilized. Although any one may be used in this embodiment, it is preferable to use a forced emulsification type PU resin from the viewpoint of imparting heat-sensitive coagulability, which will be described later.
In this embodiment, the fiber sheet is impregnated with a water-dispersible PU resin dispersion containing hot water-soluble resin fine particles, but it is not preferable that the hot water-soluble resin fine particles dissolve in the water-dispersible PU resin dispersion. On the other hand, since hot water-soluble resin particles are less soluble in an aqueous solution containing a surfactant than in water, a force-emulsified PU resin dispersion containing a surfactant is more likely to dissolve at the interface. This is a more preferred embodiment than a self-emulsifying PU resin dispersion containing no activator. The concentration of water-dispersed PU resin (the content of PU resin in the water-dispersed PU resin dispersion) controls the amount of attached water-dispersed PU resin, and a high concentration promotes the aggregation of PU resin. The content is preferably 10 to 35% by mass, more preferably 15 to 30% by mass, and even more preferably 15 to 25% by mass, since the stability of the impregnating liquid is reduced. It is.
Moreover, as the water-dispersed PU resin dispersion, one having heat-sensitive coagulability is preferable. By using a water-dispersed PU resin dispersion having heat-sensitive coagulability, the PU resin can be uniformly applied to the fiber sheet in the thickness direction. Thermal coagulability refers to the property that when a PU resin dispersion is heated, when a certain temperature (thermal coagulation temperature) is reached, the fluidity of the PU resin dispersion decreases and it coagulates. In the production of sheets filled with PU resin, a fiber sheet is impregnated with a PU resin dispersion, then coagulated by dry heat coagulation, wet heat coagulation, hot water coagulation, or a combination thereof, and dried to form fibers. Apply PU resin to the sheet. Dry coagulation is a practical method for coagulating water-dispersed PU resin dispersions that do not exhibit heat-sensitive coagulation properties in industrial production, but in this case, a migration phenomenon in which PU resin concentrates on the surface layer of a sheet material occurs. The texture of the sheet-like material filled with PU resin tends to harden.
The heat-sensitive coagulation temperature of the water-dispersed PU resin dispersion is preferably 40 to 90°C. By setting the heat-sensitive coagulation temperature to 40° C. or higher, the stability of the PU resin dispersion during storage becomes good, and adhesion of the PU resin to the machine during operation can be suppressed. Furthermore, by setting the heat-sensitive coagulation temperature to 90° C. or lower, it is possible to suppress the migration phenomenon of the PU resin in the fiber sheet.
In order to adjust the heat-sensitive coagulation temperature as described above, a heat-sensitive coagulant may be added as appropriate. Examples of heat-sensitive coagulants include inorganic salts such as sodium sulfate, magnesium sulfate, calcium sulfate, and calcium chloride, and radical reaction initiators such as sodium persulfate, potassium persulfate, ammonium persulfate, azobisisobutyronitrile, and benzoyl peroxide. Examples include agents.

A fiber sheet can be impregnated or coated with a water-dispersed PU resin dispersion, and the PU resin can be coagulated by dry heat coagulation, moist heat coagulation, hot water coagulation, or a combination thereof. The temperature of the wet heat coagulation is set to be higher than the heat-sensitive coagulation temperature of the PU resin, and is preferably 40 to 200°C. By setting the temperature of wet heat coagulation to 40° C. or higher, more preferably 80° C. or higher, it is possible to shorten the time until solidification of the PU resin and further suppress the migration phenomenon. On the other hand, by setting the wet heat coagulation temperature to 200° C. or lower, more preferably 160° C. or lower, thermal deterioration of the PU resin or PVA resin can be prevented. The temperature of hot water coagulation is preferably higher than the heat-sensitive coagulation temperature of the PU resin, and is preferably 40 to 100°C. By setting the temperature of hot water coagulation in hot water to 40° C. or higher, more preferably 80° C. or higher, it is possible to shorten the time until solidification of the PU resin and further suppress the migration phenomenon. The dry coagulation temperature and drying temperature are preferably 80 to 180°C. Productivity is excellent by setting the dry coagulation temperature and drying temperature to 80°C or higher, more preferably 90°C or higher. On the other hand, thermal deterioration of PU resin and PVA resin can be prevented by setting the dry coagulation temperature and drying temperature to 180° C. or lower, more preferably 160° C. or lower.

As described above, when impregnating a fiber sheet in which the single fibers are dispersed with a water-dispersed PU resin dispersion containing hot water-soluble resin fine particles, hot water dissolution in the water-dispersed PU resin dispersion is necessary. The content of the fine resin particles is preferably 1% by weight or more and 20% by weight or less, preferably 2% by weight or more and 15% by weight or less, and more preferably 3% by weight or more and 10% by weight or less. The inclusion of hot water-soluble resin fine particles in the water-dispersed PU resin dispersion facilitates further dispersion of the PU resin mass.

[Step of removing the hot water-soluble resin fine particles from the obtained sheet-like material using hot water]
Examples of methods for removing the hot water-soluble resin from the sheet-like material include immersion in hot water of 60°C or higher, preferably 80°C or higher, or immersion in hot water of 80°C or higher before dyeing in a jet dyeing machine. Examples include a method of removing hot water-soluble resin particles while circulating hot water. In particular, the method of removing hot water-soluble resin particles in a jet dyeing machine can omit the process of drying and winding up the sheet after removing the hot water-soluble resin particles, increasing production efficiency. It is preferable. In this embodiment, a flexible sheet-like product is obtained by removing hot water-soluble resin fine particles from the sheet-like product after applying the PU resin. The method for removing the hot water-soluble resin particles is not particularly limited, but it is preferable to dissolve and remove them by, for example, immersing the sheet in hot water at 60 to 100°C and, if necessary, squeezing the liquid with a mangle or the like. It is a mode.

[Post-process]
After filling the fiber sheet with PU resin and removing hot water-soluble resin fine particles, if no scrim is included, the sheet-like material filled with PU resin can be cut in half in the sheet thickness direction. Thereby, production efficiency can be improved.
Furthermore, a lubricant such as a silicone dispersion may be applied to the sheet-like material filled with the PU resin before the raising treatment described below. Furthermore, applying an antistatic agent before the napping treatment is a preferred embodiment in order to prevent grinding powder generated from the sheet material during grinding from being deposited on the sandpaper.
A napping treatment can be performed to form naps on the surface of the sheet-like article. The raising treatment can be performed by grinding using sandpaper, a roll sander, or the like. Further, by applying silicone or the like as a lubricant before the napping treatment, it becomes possible to easily raise the nap by surface grinding, and the surface quality becomes very good.
The artificial leather is preferably dyed for the purpose of increasing its sensory value (ie, visual effect). The dye may be selected according to the type of fibers constituting the fiber sheet; for example, disperse dyes can be used for polyester fibers, and acid dyes or metal-containing dyes can be used for polyamide fibers. can be used, and combinations thereof can also be used. When dyeing with a disperse dye, reduction washing may be performed after dyeing. As a dyeing method, a conventional method well known to dyeing processors can be used. As the dyeing method, it is preferable to use a jet dyeing machine because it is possible to dye the sheet-like material and at the same time impart a rolling effect to soften the sheet-like material. The dyeing temperature is preferably 80 to 150°C, although it depends on the type of fiber. By setting the dyeing temperature to 80°C or higher, more preferably 110°C or higher, the fibers can be dyed efficiently. On the other hand, by setting the dyeing temperature to 150°C or lower, more preferably 130°C or lower, deterioration of the PU resin can be prevented.
The artificial leather dyed in this manner is preferably subjected to soaping and, if necessary, reduction washing (that is, washing in the presence of a chemical reducing agent) to remove excess dye. It is also a preferred embodiment to use a dyeing aid during dyeing. By using a dyeing aid, the uniformity and reproducibility of dyeing can be improved. Further, in the same bath as dyeing or after dyeing, a finishing agent treatment using a softener such as silicone, an antistatic agent, a water repellent, a flame retardant, a light stabilizer, an antibacterial agent, etc. can be performed.

The artificial leather of this embodiment can be used as an interior material with a very elegant appearance as a surface material for furniture, chairs, wall materials, seats in the interior of vehicles such as automobiles, trains, and airplanes, ceilings, and interiors, shirts, jackets, and casual wear. Uppers and trims of shoes, sports shoes, men's shoes, women's shoes, etc., bags, belts, wallets, etc., clothing materials used in some of them, industrial materials such as wiping cloths, polishing cloths, CD curtains, etc. It can also be suitably used as

Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples, but the Examples do not limit the scope of the present invention. Each physical property, quality, etc. of the artificial leather samples according to Examples and Comparative Examples were evaluated using the following procedures and methods.

(1) Sample collection locations Figure 3 shows sample collection locations.
First, 10 locations (sampling areas 1, 2, . . . ) are cut into strips (indicated by dotted lines) approximately equally in the machine direction (MD) of the fiber layer (A) or the artificial leather containing the fiber layer (A). In each sampling region, a cross section in the thickness (t) direction is prepared, and in this cross section, the distance ratio value (%) near the single fiber cross section k and the average diameter (μm) of the single fibers constituting the fiber layer (A) are determined. For this purpose, SEM images are taken at ten locations approximately equally in the CD direction perpendicular to the MD direction. Furthermore, in each sampling region, in order to obtain the surface PU resin area ratio (%), SEM images of the first outer surface of the fiber layer (A) are taken at ten locations approximately equally in the CD direction. That is, each image used to determine the single fiber cross-section k neighborhood distance ratio value (%), the surface PU resin area ratio (%), and the average diameter (μm) of the single fibers constituting the fiber layer (A) is , prepare 100 sheets. In this case, the average value and standard deviation of each value are those for 100 images.

(2) Surface PU resin area ratio (%) and standard deviation/pretreatment Cut the sample on the first outer surface of the fiber layer (A) into 1 cm x 0.5 cm (horizontal (x) x vertical (y)) After that, the sample is left to stand in saturated ruthenium tetroxide vapor for 4 hours, and the PU resin attached to the sample is electronically stained with ruthenium. Next, conductive treatment is performed by coating with osmium atoms to a thickness of 1 nm.
- Observation Observe with a scanning electron microscope (SEM, Hitachi "SU8220"). The observation conditions are as follows.
Acceleration voltage: 10kV
Detector: YAG-BSE (circular scintillator type backscattered electron)
Imaging magnification: 100x/Image analysis The obtained SEM backscattered electron image was binarized using the image analysis software "ImageJ (version: 1.51j8) National Institutes of Health, USA) in the following manner, and then PU Determine the average size of the resin.
(i) Filtering the SEM image. The processing conditions are as follows:
Bilateral Filter Fije plugin's Bilateral Filter, spatial radius:3, range radius:50, filtering 5 times.
(ii) Binarization is performed using the MaxEntropy method, and the black part in the SEM image after the binarization is made into PU resin.
(iii) From the obtained binarized image, determine the area ratio of PU resin for each section.
As shown in Figure 6, the obtained binarized image (2560 x 1920 pixels is divided into 32 x 32 pixels (in this case, 4800 divisions), and the Analyze Particle function of ImageJ (conditions: Size=0-infinity, Circularity= 0.00-1.00), the total area of each PU resin distributed in each compartment is divided by the area of each compartment, and the value is the surface PU resin area ratio (%) of each compartment. .Read the number of pixels on the x and y axes of the target image, specify the section size in pixel size, find the number of divisions on the x and y axes, and calculate the PU resin area % in each divided area.
The surface PU resin area ratio (%) is the average of the surface PU resin area ratio (%) for all sections, and its standard deviation is calculated by the formula shown in FIG. 6.
However, in Figure 6, the standard deviation is calculated for all sections obtained by dividing one image into sections, but when preparing 100 images, the average value of the surface PU area ratio (%) and the standard deviation are , is calculated for all the sections per image multiplied by 100.

(3) Single fiber cross section k neighborhood distance ratio value (%)
As shown in FIG. 5, the k-nearest neighbor method is a method in which k single fiber cross sections close to an arbitrary single fiber cross section are taken, and the kth closest radius in Euclidean distance is set as the determination boundary.
In this embodiment, in one SEM image, a range of about 250 μm x about 186 μm is photographed with 640 x 480 pixels including a band at the bottom of the image (in this case, 1 pixel corresponds to about 0.40 μm x about 0.40 μm). ), it is determined whether the k=9th closest single fiber cross section exists within a distance of 20 μm radius from the approximate center of any one single fiber cross section. The presence or absence of all single fiber cross sections in one SEM image is determined, and the distance ratio (%) of single fiber cross sections k = 9 in the vicinity is determined using the following formula:
Single fiber cross section (k = 9) neighborhood distance ratio (%) = {(Number of single fiber cross sections in which k = 9th closest single fiber cross section exists within a distance of 20 μm radius from the approximate center of the single fiber cross section) /(total number of single fiber cross sections in one SEM image)}×100.
In addition, when the sample has a scrim, the deepest part of the fiber layer (A) (i.e., the part closest to the scrim) on the above-mentioned cut surface of the conductive-treated sample is set as the observation area, and the fibers constituting the scrim are observed. As a non-objective sample, it is observed using a scanning electron microscope (SEM, "JSM-5610" manufactured by JEOL). When the sample does not have a scrim, the central part of the cut surface of the conductive-treated sample in the thickness direction of the artificial leather is set as the center point of the observation area, and observed using the SEM.
As shown in FIG. 4, the presence of a single fiber cross section in a SEM image can be identified by marking it manually. The specific steps are as follows:
[Step 1]
In the SEM image (gray), a red (R) circle is placed on the cross section of the fiber, and then the coordinates of the cross section of the fiber are calculated.
<Detailed method>
(i) Load the image using OpenCV (cv2 module for Python).
(ii) Extract pixels whose R, G, and B values are 220 or more and 100 or less.
(iii) For noise processing, dilation processing (cv2.dilate with iteration=2) and contraction processing (cv2.erode with iteration=2) are performed on the detected round points.
(iv) Process the noise-processed image with cv2.connectedComponentsWithStats to obtain the centroid coordinates of the detected round points, which is the third result among the four obtained results.
(v) Let the above barycenter coordinates be the fiber cross-sectional position.
(vi) Furthermore, calculate the distance between specific positions on the coordinates. When the coordinates of fiber cross section A and fiber cross section B are (Ax, Ay) and (Bx, By), the Euclidean distance R between the two is R=√((Ax-Bx) ² +(Ay-By) ² ) is calculated.
[Step 2]
For all fiber cross sections, the Euclidean distance (k-neighborhood distance: matrix distance) to the kth nearest fiber cross section is calculated.
<Detailed method>
(i) Calculate the distance between the fiber cross section A and the coordinates of other cross sections.
(ii) Arrange the calculated distances in ascending order.
(iii) Let the kth distance in the array be the k-neighborhood distance.
[Step 3]
The number of cross-sections with a k-neighborhood distance of R or less is divided by the total number of fiber cross-sections, and this is taken as the k-neighborhood distance ratio value in the SEM image.
In addition, when the number of SEM images is large, images containing training data (correct labels) with red (R) round dots attached to the fiber cross section are used as learning data, and all are composed of convolutional layers. Network FCN (Fully Convolutional Networks) method (Jonathan Long, Evan Shelhamer, and Trevor Darrel (2015): Fully Convolutional Networks for Semantic Segmentation. In The IEEE Conference on Computer Vision and Pattern Recognition (CVPR) Machine learning (deep learning) that performs class classification based on level may be used to replace human marking and specify the position of the fiber cross section.

(4) Average diameter (μm) of single fibers constituting the fiber layer (A)
The average diameter of the fibers constituting the fiber layer (A) is determined by photographing a cross-section in the thickness direction of the artificial leather using a scanning electron microscope (SEM, "JSM-5610" manufactured by JEOL) at a magnification of 1500 times. 100 fibers forming a cross section in the thickness direction are randomly selected, the diameter of the cross section of the single fiber is measured, and the arithmetic mean value of the 100 measured values is obtained.
If the observed shape of the cross section of a single fiber is not circular, the distance between the outer circumferences on a straight line perpendicular to the midpoint of the longest diameter of the cross section of the single fiber is defined as the fiber diameter.
FIG. 2 is a conceptual diagram illustrating how to determine the fiber diameter. For example, when the cross section A of the fiber is elliptical as shown in FIG. 2, the fiber diameter is defined as the distance c between the outer circumferences on a straight line b perpendicular to the midpoint p of the longest diameter a of the cross section A in the observed image.

(5) Difficulty in conspicuousness of dyed spots Using a Hi-Di dyeing tester manufactured by Todoroki Sangyo Co., Ltd., artificial leather fabric measuring 15 cm long x 30 cm wide was treated with 5.0% owf of blue disperse dye (BlueFBL, manufactured by Sumitomo Chemical Co., Ltd.) at a bath ratio of 1. :20, dyed at 130°C for 30 minutes, and then subjected to reduction washing to obtain artificial leather. For each sample, a total of 20 evaluators, 10 each of adult men and women in good health, visually evaluated the samples using the following criteria. did. Regarding the inconspicuousness of staining spots, a grade of 4.0 to 5.0 is considered good (pass).
Grade 5: 9 or more people judged that the color difference between the fiber and the PU resin was not noticeable and the color spots were unrecognizable.
Grade 4: 8 or more people judged that the color difference between the fiber and the PU resin was not noticeable and the color spots were unrecognizable.
Grade 3: 5 to 7 people judged that the color difference between the fiber and the PU resin was not noticeable and the color spots were unrecognizable.
Grade 2: 3 to 4 people judged that the color difference between the fiber and the PU resin was not noticeable and the color spots were unrecognizable.
Grade 1: Two or fewer people judged that the color difference between the fiber and the PU resin was not noticeable and the color spots were unrecognizable.
Note that the evaluation value of staining spots is the average value for 10 samples.

(6) Moist feeling The samples were rated on a 7-point scale based on the criteria below using visual and sensory evaluation by a total of 20 evaluators, 10 each of adult men and women in good health. It felt moist. A moist feeling of 4.0 to 7.0 is considered good (pass).
Grade 7: The texture is very smooth (moist) and the appearance is very good.
6th grade: Rated between 7th grade and 5th grade.
Grade 5: The texture is smooth (moist) and the appearance is good.
Grade 4: Rated between grade 5 and grade 3.
Grade 3: No roughness to the touch and a leather-like appearance.
2nd grade: An evaluation between 3rd grade and 1st grade.
Grade 1: The texture is rough and the appearance is poor.
Note that the average value of the 10 samples is taken as the grade of moist feeling.

(7) Dense feeling (dispersibility of fiber bundles)
A total of 20 evaluators, 10 each of adult men and adult women in good health, evaluated the samples on a seven-point scale based on the following criteria through visual and sensory evaluation, and the most frequent evaluation was taken as denseness. The dense feeling (dispersibility of fiber bundles) is considered to be good (pass) if it is in the range of 4.0 to 7.0.
Grade 7: The nap is very dense and the appearance is very good.
6th grade: Rated between 7th grade and 5th grade.
Grade 5: The nap is dense and the appearance is good.
Grade 4: Rated between grade 5 and grade 3.
Grade 3: Uniform napping is present throughout, giving it a leather-like appearance.
2nd grade: An evaluation between 3rd grade and 1st grade.
Grade 1: The nap is mottled and the appearance is poor.
Note that the average value of the 10 samples is used as the grade of denseness.

(8) Adhesion rate of PU resin to fiber sheet The adhesion rate of PU resin to fiber sheet was measured by the following method.
Let A (g) be the mass of the fiber sheet before impregnation with PU resin. A fiber sheet is impregnated with the PU resin dispersion, then heated and dried at 130°C using a pin tenter dryer, then soaked in hot water heated to 90°C and made into a soft cloth, and then dried to remove the PU resin. A filled fiber sheet (hereinafter also referred to as "resin-filled fiber sheet") is obtained. Let the mass of the resin-filled fiber sheet be B1 (g). The adhesion rate (C1) of PU resin is calculated using the following formula.
C1=(B1-A)/A×100(wt%)

(9) Average primary particle diameter of PU resin in PU resin dispersion Measured using a laser diffraction particle size distribution analyzer (“LA-920” manufactured by Horiba, Ltd.) according to the equipment measurement manual, and the median diameter was determined. It was defined as the average primary particle diameter.

(10) Saponification degree of PVA resin fine particles contained in PU resin dispersion Measured according to JIS K 6726 (1994) 3.5.

(11) Degree of polymerization of PVA resin fine particles contained in PU resin dispersion It was measured according to JIS K 6726 (1994) 3.7.

(12) Average particle diameter (size) of PVA resin fine particles contained in the PU resin dispersion (μm)
"NL-05" manufactured by Mitsubishi Chemical Corporation can be used as the fine particles, and the fine particles of the hot water-soluble resin were made according to the method described in JP-A-7-82384.

(13) Disturbance of the water stream discharged from the nozzle in the water dispersion process The disturbance of the water stream discharged from the nozzle in the water stream dispersion process was measured by the following method.
The water stream discharged from the nozzle is photographed with a single-lens camera ("D600" manufactured by Nikon Corporation) equipped with a telecentric lens ("S5LPJ007/212" manufactured by Sill Optics GmbH & Co. KG) to obtain image data. The image data is loaded into a PC, a water stream is cut out within a range of 25 mm to 35 mm from the nozzle outlet, and the diameter of each pixel row (approximately 6 μm) in the width direction of the water stream is measured. From all the measured data, the average diameter W and standard deviation σ of the water flow in the range from 25 mm to 35 mm from the discharge port of the nozzle hole are calculated, and the disturbance is calculated using the following formula.
Disturbance (%) = σ (mm) / W (mm) × 100
Note that the disturbance is the average value of the values obtained from the five image data.

[Example 1]
As the sea component, polyethylene terephthalate copolymerized with 8 mol% of sodium 5-sulfoisophthalate was used, and as the island component, polyethylene terephthalate was used, with a composite ratio of 20% by mass of the sea component and 80% by mass of the island component. A sea-island composite fiber having several 16 islands/1f and an average fiber diameter of 18 μm was obtained. The obtained sea-island composite fibers were cut into staples with a fiber length of 51 mm, passed through a card and a cross wrapper to form a fiber web, and then subjected to needle punching to obtain a fiber sheet. The obtained fiber sheet was immersed in 95° C. hot water to shrink, and dried at 100° C. for 5 minutes using the pin tenter dryer to obtain a single-layer fiber sheet with a basis weight of 600 g/m ² .
The obtained fiber sheet was immersed in an aqueous sodium hydroxide solution with a concentration of 10 g/L heated to a temperature of 95° C. and treated for 25 minutes to perform a sea-removal treatment to remove the sea component of the sea-island composite fiber. The average diameter of the single fibers constituting the fiber sheet after sea removal was 4 μm.
Next, a high-speed water stream was injected at a pressure of 4 MPa from the upper layer side and 3 MPa from the lower layer side using three rows of straight flow injection nozzles with a nozzle hole interval of 0.25 mm, a disturbance of 7%, and a hole diameter of 0.10 mm to form a fiber bundle. This promoted the formation of single fibers.
Next, a polyether-based water-dispersed PU dispersion "AP-12" (manufactured by NICCA CHEMICAL CO., LTD.) (solid content concentration: 35% by mass) with an average primary particle diameter of 0.3 μm was added to the impregnation solution in an amount ( The amount of anhydrous sodium sulfate in the impregnating liquid as an impregnating aid (as a mass % of solid content) was 9.0%, and the amount of PVA resin fine particles "NL-" with an average particle size of 3 μm was The fiber sheet was impregnated with an impregnating solution containing "05" (manufactured by Mitsubishi Chemical Corporation), and then coagulated under wet heat at 100° C. for 5 minutes, and dried with hot air at 130° C. for 5 minutes using a hot air dryer.
Thereafter, it was immersed in hot water heated to 95° C. to extract and remove the impregnated anhydrous sodium sulfate and PVA resin fine particles, thereby obtaining a sheet filled with water-dispersed PU resin. The ratio of the water-dispersed PU resin to the total fiber mass of this sheet-like material was 30% by mass.
Thereafter, the sheet-like material was cut in half perpendicular to the thickness direction using a half-cutting machine with an endless band knife, and the uncut side was brushed with #400 emery paper, and the dye concentration was 5. It was dyed with .0% owf blue disperse dye ("BlueFBL" manufactured by Sumitomo Chemical Co., Ltd.) using a jet dyeing machine at 130° C. for 15 minutes, and then subjected to reduction cleaning. Thereafter, it was dried at 100° C. for 5 minutes using a hot air dryer to obtain a single layer of artificial leather.

[Example 2]
Artificial leather was obtained in the same manner as in Example 1, except that the water pressure from the upper layer side in the water dispersion treatment was changed to 4.0 MPa.

[Example 3]
Artificial leather was obtained in the same manner as in Example 2, except that the ratio of PU resin to the fiber sheet was 44% by mass.

[Example 4]
Artificial leather was obtained in the same manner as in Example 2, except that the ratio of PU resin to the fiber sheet was 47% by mass.

[Example 5]
Artificial leather was obtained in the same manner as in Example 2, except that the ratio of PU resin to the fiber sheet was 17% by mass.

[Example 6]
Artificial leather was obtained in the same manner as in Example 2, except that the nozzle hole interval in the water dispersion treatment was changed to 0.50 mm and the number of nozzle rows was changed to 2.

[Example 7]
Artificial leather was obtained in the same manner as in Example 2, except that the nozzle hole interval in the water dispersion treatment was changed to 0.50 mm and the number of nozzle rows was changed to 1.

[Example 8]
Artificial leather was obtained in the same manner as in Example 2, except that the nozzle hole interval in the water dispersion treatment was changed to 0.90 mm and the number of nozzle rows was changed to 1.

[Example 9]
Artificial leather was obtained in the same manner as in Example 2, except that the nozzle hole interval in the water dispersion treatment was changed to 0.50 mm, the nozzle hole diameter to 0.15 mm, and the number of nozzle rows to 2.

[Example 10]
Artificial leather was obtained in the same manner as in Example 2, except that the nozzle hole interval in the water dispersion treatment was changed to 0.50 mm, the nozzle hole diameter to 0.22 mm, and the number of nozzle rows to 2.

[Example 11]
Artificial leather was obtained in the same manner as in Example 2, except that the disturbance in the water dispersion treatment was 13%.

[Example 12]
Artificial leather was obtained in the same manner as in Example 2, except that the disturbance in the water dispersion treatment was 11%.

[Example 13]
Artificial leather was obtained in the same manner as in Example 2, except that the disturbance in the water dispersion treatment was 16%.

[Example 14]
Artificial leather was obtained in the same manner as in Example 2, except that the average primary particle diameter of the PVA particles in the PU resin impregnation was 5 μm, and the disturbance in the water dispersion treatment was 13%.

[Example 15]
Artificial leather was obtained in the same manner as in Example 2, except that the average primary particle diameter of the PVA particles in the PU resin impregnation was 7 μm, and the disturbance in the water dispersion treatment was 13%.

[Comparative example 1]
Artificial leather was obtained in the same manner as in Example 2, except that PVA resin fine particles were not added to the PU resin impregnation liquid.

[Comparative example 2]
Artificial leather was obtained in the same manner as in Example 2, except that PVA resin fine particles were not added to the PU resin impregnation liquid and the disturbance in the water dispersion treatment was set to 13%.

[Comparative example 3]
Artificial leather was obtained in the same manner as in Example 2, except that the water dispersion treatment was not performed.

[Comparative example 4]
Artificial leather was obtained in the same manner as in Example 2, except that the water pressure from the upper layer side in the water dispersion treatment was changed to 12.0 MPa.

[Comparative example 5]
Artificial leather was obtained in the same manner as in Example 2, except that the water pressure from the upper layer side in the water dispersion treatment was changed to 0.7 MPa.

[Comparative example 6]
Artificial leather was obtained in the same manner as in Example 2, except that the ratio of PU resin to the fiber sheet was 58% by mass.

[Comparative Example 7]
Artificial leather was obtained in the same manner as in Example 2, except that the ratio of PU resin to the fiber sheet was 13% by mass.

[Comparative example 8]
Artificial leather was obtained in the same manner as in Example 2, except that the average primary particle diameter of the PVA particles in the PU resin impregnation was 10 μm, and the disturbance in the water dispersion treatment was 13%.

The results of Examples 1 to 15 and Comparative Examples 1 to 8 are shown in Table 1 below.

From these results, in each example, the k-neighborhood distance ratio value (k = 9, radius r = 20 μm) between the single fiber cross sections constituting the fiber layer (A) is 10% or more and 80% or less, And, the surface PU resin area ratio in the thickness direction cross section is 8% or more and 25% or less, and the standard deviation of the surface PU resin area ratio is 25% or less, and the PU resin and single fibers are distributed in a specific structure. It can be seen that by doing this, it was possible to obtain artificial leather that has less noticeable staining spots, a dense feel, and a moist feel.

The artificial leather according to the present invention is excellent in the inconspicuousness of dyed spots, dense feel, and moist feel, so it can be used in clothing products such as surface materials or interior materials for seats for interiors, automobiles, aircraft, railway vehicles, etc. It can be suitably used for, etc. Specifically, the artificial leather of the present invention can be used as a surface material for furniture, chairs, wall materials, seats in vehicle interiors such as automobiles, trains, and airplanes, ceilings, and interior materials that have a very elegant appearance, and for shirts. , uppers and trims of shoes such as jackets, casual shoes, sports shoes, men's shoes, and women's shoes, bags, belts, wallets, etc., clothing materials used for some of them, wiping cloths, polishing cloths, CD curtains, etc. It can be suitably used as an industrial material.

1 Fiber sheet 11 Scrim (optional)
12 Fiber layer (A)
13 Fiber layer (B)
A Cross section a of the fiber when the cross section is elliptical Longest diameter b of cross section A Straight line c passing through the midpoint p of longest diameter a and orthogonal to longest diameter a Distance between outer circumferences p on straight line b Midpoint of longest diameter a MD Machine direction CD Width (horizontal) direction t Artificial leather thickness

Claims (15)

An artificial leather comprising a fiber sheet and a polyurethane resin, wherein the fiber sheet includes at least a fiber layer (A) constituting a first outer surface of the artificial leather, and in a cross section in the thickness direction of the artificial leather. The k-neighborhood distance ratio value (k = 9, radius r = 20 μm) between the cross sections of single fibers constituting the fiber layer (A) is 10% or more and 80% or less, and the surface of the fiber layer (A) An artificial leather having a polyurethane resin area ratio of 8% or more and 25% or less, and a standard deviation of the surface polyurethane resin area ratio of the fiber layer (A) of 25% or less. The fibrous sheet has a two or more layer structure consisting of a fibrous layer (A) constituting the first outer surface and a scrim and/or fibrous layer (B) in contact with the fibrous layer (A). , the artificial leather according to claim 1. The artificial leather according to claim 1 or 2, wherein the average diameter of the single fibers constituting the fiber layer (A) is 1.0 μm or more and 8.0 μm or less. The artificial leather according to any one of claims 1 to 3, wherein the polyurethane resin is a water-dispersed polyurethane resin. The artificial leather according to any one of claims 1 to 4, wherein the adhesion rate of the polyurethane resin to the fiber sheet is 15% by mass or more and 50% by mass or less. The artificial leather according to any one of claims 1 to 5, which has dyeing spots of grade 4.0 or higher. The artificial leather according to any one of claims 1 to 6, wherein the fiber sheet is made of polyester fiber. The artificial leather according to any one of claims 1 to 7, having a moist feel of grade 4.0 or higher. The artificial leather according to any one of claims 1 to 8, having a dense feel of grade 4.0 or higher. The following steps:
forming a fiber web with sea-island short fibers, and then de-sea-removing the fiber sheet obtained by needle punching to obtain a fiber sheet in which the single fibers of the island component are exposed ;
A step of subjecting the obtained fiber sheet to a water jet dispersion treatment with a water pressure of 1.0 to 10.0 MPa to obtain a fiber sheet in which single fibers are dispersed;
The fiber sheet in which the single fibers are dispersed is impregnated with a water-dispersed polyurethane resin dispersion containing hot water-soluble resin fine particles having an average particle diameter of 1 μm or more and 8 μm or less, and then, the polyurethane resin is fixed by heating. obtaining a sheet-like material filled with polyurethane resin; and
a step of removing the hot water-soluble resin fine particles from the obtained sheet-like material using hot water;
The method for producing artificial leather according to any one of claims 1 to 9, comprising: The manufacturing method according to claim 10, wherein the hot water-soluble resin fine particles are polyvinyl alcohol resin. 12. The water dispersion treatment according to claim 10 or 11 , wherein the water dispersion treatment is carried out using a plurality of nozzles having a nozzle hole interval of 1.0 mm or less and a nozzle hole diameter of 0.05 mm or more and 0.30 mm or less. Production method. The manufacturing method according to any one of claims 10 to 12 , wherein the water stream dispersion treatment is performed using a plurality of nozzles that discharge a water stream with a disturbance of 10% or more. The manufacturing method according to any one of claims 10 to 13 , wherein the solid content concentration of the water-dispersed polyurethane resin dispersion is 10% by weight or more and 35% by weight or less. The method according to any one of claims 10 to 14 , wherein the content of hot water-soluble resin fine particles in the water-dispersed polyurethane resin dispersion is 1% by weight or more and 20% by weight or less.

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