Artificial leather and its manufacturing method

Abstract

Provided are a synthetic leather achieving both wear resistance and a velvety texture, which is a texture typical of nubuck, and a method for producing the same. The synthetic leather according to the present invention comprises an entangled sheet and a polymer elastic body with which the entangled sheet is impregnated. The entangled sheet has a structure of at least two layers composed of a fiber layer (A) serving as a top face of the synthetic leather, and a scrim in contact with the fiber layer (A). An average diameter of the fibers constituting the fiber layer (A) is between 2 µm and 7 µm both inclusive. The following requirements (1) and (2) are satisfied: (1) a buffed portion area ratio (S) on the top face side of the synthetic leather satisfies the relationship 0.18 ≤ S ≤ 0.5; and (2) a peak material volume (Vmp) [mm3] of the top face side of the synthetic leather satisfies the relationship 1 ≤ Vmp ≤ 3.

Description

[Technical Field]

[0001] The present invention relates to an artificial leather and a method for producing the same. [Background technology]

[0002] Artificial leather, which is primarily composed of a nonwoven fabric (entangled sheet) formed by entangling fibers and a polymeric elastomer, has excellent properties that are difficult to achieve with natural leather, such as ease of care, functionality, and uniformity. It is therefore suitable for use in a variety of applications, including clothing, shoes, bags, and interior seat coverings and interior materials for automobiles, aircraft, and railway vehicles, as well as decorative materials such as ribbons and badge base materials.

[0003] Among artificial leathers, suede-like artificial leathers, which have a brushed outer surface, are known for their luxurious appearance and feel. Furthermore, suede-like artificial leathers with a denser, shorter, and more uniform nap than general suede-like artificial leathers are called nubuck-like artificial leathers because of their appearance and soft feel. Patent Document 1 below describes a method for obtaining nubuck-like artificial leather that has both the fluffy texture of nubuck and the fine wrinkles of natural leather by entangling a laminate of fiber webs made of fibers with a single fiber fineness of 0.0001 to 0.003 dtex. The following Patent Document 2 describes a method for obtaining nubuck-like artificial leather with a smooth surface by pressing the raised surface of a dyed and processed product made of fibers with an average fiber diameter of 1.9 μm or more and 4 μm or less using a heated roll. Patent Document 3 listed below describes a method for obtaining suede-like artificial leather with a good texture while maintaining surface properties and without deteriorating surface quality by integrating a fiber web composed of fibers with a single fiber fineness of 0.0001 to 0.5 dtex with a knitted scrim by needle punching, and adjusting the state of surface fiber presence and average nap fiber length. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-204863 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-186138 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-280643 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a demand for nubuck-like artificial leathers to have a more moist feel. The smoother the surface of the artificial leather is and the denser the nap is raised, the more moist the feel tends to be. However, if the smoothness is excessively increased by a resin coating or the like, the feel will be different from that of the artificial leather. Artificial leather also needs to be resistant to wear. To achieve the appearance and feel of nubuck, it is possible to reduce the diameter of the fibers constituting the nonwoven fabric and increase the fiber density, but it is difficult to achieve high wear resistance when using a nonwoven fabric made of thin fibers. In Patent Document 1, artificial leather with a dense outer surface is obtained by forming the artificial leather into a laminate including a fiber web composed of ultrafine fibers. However, since fine fibers of 0.0001 to 0.003 dtex are used, the abrasion resistance is insufficient. In Patent Document 2, a smooth artificial leather is obtained by hot pressing the surface of the artificial leather. However, simply hot pressing the surface leaves the fiber density sparse, and the moist feel required for nubuck-like artificial leather is not satisfied. In Patent Document 3, the polymeric elastomer that discontinuously covers the surface of an artificial leather is removed, the surface is smoothed, and then the surface is raised until the napped fibers account for 70 to 100% to obtain napped fibers. However, although the surface is sufficiently raised, the smoothness is insufficient, and therefore a sufficient moist feel cannot be obtained.

[0006] In view of these problems of the prior art, the problem that the present invention aims to solve is to provide an artificial leather that combines abrasion resistance with the moist feel that is characteristic of nubuck. [Means for solving the problem]

[0007] As a result of extensive research and experimentation conducted by the present inventors in order to solve the above-mentioned problems, they unexpectedly discovered that the problems could be solved by artificial leather having the following characteristics, and thus completed the present invention.

[0008] That is, the present invention is as follows. [1] An artificial leather comprising an entangled sheet and a polymeric elastomer filled in the entangled sheet, the entangled sheet has a two-layer or more structure composed of a fiber layer (A) that forms the front surface side of the artificial leather and a scrim that is in contact with the fiber layer (A), The average diameter of the fibers constituting the fiber layer (A) is 2 μm or more and 7 μm or less, The following requirements (1) and (2): (1) The raised area ratio (S) on the front surface side of the artificial leather satisfies the relationship 0.18≦S≦0.5; and (2) The actual volume of the protruding peaks on the front side of the artificial leather is (Vmp) [mm 3 ] satisfies the relationship 1≦Vmp≦3; An artificial leather characterized by satisfying the above. [2] The artificial leather according to [1], wherein the dispersion state (A) [μm] of the naps present on the outer surface of the artificial leather satisfies the relationship 20≦A≦60. [3] The artificial leather according to [1] or [2], wherein the polymeric elastomer is a water-dispersible polyurethane. [4] The artificial leather according to any one of the above [1] to [3], wherein the fiber constituting the fiber layer (A) is a polyester fiber. [5] The artificial leather according to any one of [1] to [4], wherein the difference between the static friction coefficient and the dynamic friction coefficient (μs-μk) of the front surface of the artificial leather is 0.25 or more and 0.5 or less. [6] The artificial leather according to any one of [1] to [5], wherein the evaluation result of an abrasion resistance test on the front surface of the artificial leather is grade 3 or higher. [7] The following steps: (1) forming a fiber web (A') from fibers having an average diameter of 2.0 μm or more and 7.0 μm or less; (2) a first hydroentangling step in which the obtained fiber web (A') is hydroentangled at a water pressure of 2 to 5 MPa and an entanglement coverage of 60% or more to obtain a fiber sheet (A"); (3) a second hydroentangling step of laminating at least the fiber sheet (A″) and a scrim, and hydroentangling the laminate at a water pressure of 5 to 15 MPa and an entanglement coverage of 80% or more to obtain an entangled sheet; (4) A step of pressing the entangled sheet using calender rolls, with an unheated roll in contact with the fiber sheet (A″) side of the entangled sheet and a roll with a surface temperature of 105 to 135°C in contact with the opposite side, at a press pressure of 6 to 14 N / cm and a base fabric running speed of 15 to 25 m / min or less; (5) A heat pressing process in which the sheet is pressed using a calender roll, with an unheated roll in contact with the front side of the product and a roll with a surface temperature of 105 to 135°C in contact with the opposite side, at a pressure of 6 to 14 N / cm and a base fabric running speed of 15 to 25 m / min or less; (6) optionally, raising the outer surface of the entangled sheet; (7) a step of filling the obtained entangled sheet with a polymeric elastomer to obtain a sheet-like product; (8) if the step (6) is not carried out, a step of raising the outer surface of the sheet-like material obtained in the step (7), or a step of carrying out the step (6) and further raising the outer surface of the sheet-like material; and (9) dyeing the obtained sheet-like product; A method for producing artificial leather, comprising: [Effects of the Invention]

[0009] According to the present invention, an artificial leather can be obtained that has both a moist, nubuck-like surface and good abrasion resistance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a conceptual diagram showing an example of the structure of artificial leather. The fiber layer (B) denoted by reference numeral 14 is optional. [Figure 2] FIG. 2 is a schematic diagram of the raised surface of artificial leather. [Figure 3] FIG. 3 is a schematic diagram showing the distribution of raised naps on the artificial leather. [Figure 4] FIG. 4 is a conceptual diagram illustrating how to determine the average diameter of the fibers that make up the fiber layer (A). [Figure 5] FIG. 5 is an explanatory diagram showing the locations where samples were collected. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Furthermore, unless otherwise specified, various values ​​in the present disclosure are values ​​obtained by the method described in the Examples section of the present disclosure or a method that would be understood by a person skilled in the art to be equivalent thereto.

[0012] <Artificial leather> The artificial leather of the present embodiment is an artificial leather including an entangled sheet and a polymeric elastomer filled in the entangled sheet, the entangled sheet has a two-layer or more structure composed of a fiber layer (A) that forms the front surface side of the artificial leather and a scrim that is in contact with the fiber layer (A), The average diameter of the fibers constituting the fiber layer (A) is 2 μm or more and 7 μm or less, The following requirements (1) and (2): (1) The total area ratio of the raised portion on the front side of the artificial leather is 0.18≦S≦0.5; and (2) The actual volume of the protruding peaks on the front surface of the artificial leather is 1≦Vmp≦3 [mm 3 ] is; It is an artificial leather that satisfies the above.

[0013] In this specification, "artificial leather" refers to "a material using a special nonwoven fabric (mainly a fiber layer with a random three-dimensional structure, impregnated with polyurethane (PU) resin or a similar flexible polymeric elastomer) as a substrate" in accordance with the Household Goods Quality Labeling Act. According to the definition of JIS-6601, artificial leathers are classified by appearance into "smooth," which has a grain-like appearance of leather, and "napped," which has the appearance of nubuck, suede, velour, or the like. The artificial leather of this embodiment relates to an artificial leather classified as "napped" (i.e., a brushed artificial leather with a brushed appearance). The brushed appearance can be achieved by buffing (brushing) the outer surface (also referred to as the front surface) of the fiber layer (A) with sandpaper or the like. In this specification, the outer surface of the artificial leather, the outer surface of the fiber layer (A), the outer surface of the entangled sheet, the outer surface of the fiber sheet, and the outer surface of the laminated sheet refer to surfaces that are exposed to the outside when used as artificial leather (for example, the surface that comes into contact with the human body in the case of a chair). In one embodiment, in the case of a raised artificial leather, the outer surface of the fiber layer (A) is raised or napped by buffing or the like.

[0014] The artificial leather has a two-layer or more structure consisting of at least a fiber layer (A) and a scrim in contact with the fiber layer (A). Having a two-layer or more structure including a scrim improves the mechanical properties of the artificial leather, particularly its tear strength and tensile strength. The artificial leather may be composed of, for example, three layers: the fiber layer (A), the scrim, and a fiber layer (B) that forms the back surface. A three-layer structure consisting of the fiber layer (A), the fiber layer (B), and the scrim sandwiched between them allows the fiber layer (A) and the fiber layer (B) to be individually designed, which is advantageous in that the diameter and type of the fibers that make up these layers can be freely customized to suit the functions and applications required of the artificial leather using the entangled sheet. For example, using ultrafine fibers in the fiber layer (A) and flame-retardant fibers in the fiber layer (B) can achieve both excellent surface quality and high flame retardancy. In addition, a three-layer structure of a fiber layer (A), a fiber layer (B), and a scrim sandwiched therebetween is also preferable in that the entanglement strength between the fiber layer (A) and the scrim tends to be high.

[0015] [Fibers that make up the fiber layer] Suitable fibers for the fiber layers (fiber layer (A), as well as optional fiber layer (B) and additional layers) that make up the artificial leather include polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate; and polyamide fibers such as nylon 6, nylon 66, and nylon 12. Among these, considering applications requiring durability, such as car seats, polyethylene terephthalate is preferred because the fiber itself does not yellow even when exposed to direct sunlight for long periods of time and has excellent color fastness. Furthermore, from the perspective of reducing the environmental impact, chemically recycled or material recycled polyethylene terephthalate, or polyethylene terephthalate made from plant-derived materials, is even more preferred.

[0016] The average diameter of the fibers constituting the fiber layer (A) of the artificial leather is 2 μm or more and 7 μm or less. An average diameter of 2 μm or more makes it easier to obtain sufficient abrasion resistance. On the other hand, if the average diameter is 7 μm or less, the distance between fibers is short and a dense sample is easily obtained, so that the raised nap is appropriately dispersed, making it easier to obtain a moist feel. The average diameter of the fibers constituting the fiber layer (A) of the artificial leather is preferably 2.5 μm or more and 6 μm or less, more preferably 3 μm or more and 5 μm or less.

[0017] As the raw material fibers for the fiber web constituting the fiber layers (fiber layer (A), optional fiber layer (B), additional fiber layer, etc.) constituting the artificial leather, directly spun fibers and ultrafine fibers extracted from ultrafine fiber-developing fibers are preferred. By using directly spun fibers and ultrafine fibers extracted from ultrafine fiber-developing fibers, the fibers in the fiber layers constituting the artificial leather are easily dispersed as single fibers.

[0018] At least in the fiber layer (A), the fibers are preferably dispersed as single fibers. For example, ultrafine fiber-producing fibers such as islands-in-sea composite fibers (e.g., those using a copolymer polyester as the sea component and a regular polyester as the island component) are used, and the fibers are entangled with a scrim to form a sheet, followed by a fiber-thinning treatment (removing the sea component of the islands-in-sea composite fiber by dissolving, decomposing, or the like). The resulting fibers exist as fiber bundles in the fiber layer (A) and are not dispersed as single fibers. For example, islands-in-sea composite staple fibers with island components having a single fiber fineness of 0.2 dtex (24 islands / 1f) are prepared, and the fiber layer (A) is formed from the islands-in-sea composite staple fibers. An entangled sheet with the scrim is then formed by needle punching or the like. PU resin is then filled into the three-dimensional entangled body, and the sea component is dissolved or decomposed, resulting in fibers with a single fiber fineness of 0.2 dtex. In this case, the fibers exist in the fiber layer (A) in the form of a fiber bundle with 24 single fibers (equivalent to 4.8 dtex in the bundled state).

[0019] As used herein, the phrase "single fiber dispersion" means that the fibers do not form fiber bundles, such as those obtained by removing the sea component of islands-in-sea composite fibers by dissolving, decomposing, or the like. When the fiber layer (A) is composed of fibers in which single fibers are dispersed, the surface is excellent in smoothness, and uniform nap formation is easily achieved when the outer surface of the fiber layer (A) is subjected to a nap raising treatment, such as buffing. Furthermore, even when the PU resin adhesion rate is relatively low, pilling, or a fuzz-like appearance, is unlikely to occur due to friction, resulting in an artificial leather with superior surface quality and abrasion resistance. Furthermore, when the fibers are dispersed in single fibers, the fiber spacing is likely to be narrow and uniform, and therefore good abrasion resistance is obtained even when the PU resin is attached in a fine form. Examples of methods for dispersing fibers into single fibers include a method in which ultrafine fibers produced by a direct spinning method are converted into a fiber web by a papermaking method, and a method in which the sea component of a fiber sheet or entangled sheet made of islands-in-sea type composite fibers is dissolved or decomposed to generate ultrafine fiber bundles, and then the fiber bundle surface is subjected to a water jet dispersion treatment to promote the disintegration of the fiber bundles into single fibers. Among the fiber layers constituting the entangled sheet, the fibers in the fiber layers other than the fiber layer (A) may or may not be monofilament dispersed, but in a preferred embodiment, the layers other than the fiber layer (A) are also composed of fibers in which monofilaments are dispersed. When the fibers constituting the layers other than the fiber layer (A) are monofilament dispersed, the thickness of the artificial leather using the entangled sheet becomes uniform, improving processing precision and stabilizing quality, which is preferable.

[0020] [Brushed area of ​​artificial leather] This embodiment is characterized in that the raised area ratio on the outer surface of the artificial leather is 0.18≦S≦0.5. The measurement method will be described later. By setting the raised area ratio to 0.18 or more, the raised naps are likely to catch on fingerprints when a sample is pressed against the surface with a finger, resulting in a high static friction coefficient. Furthermore, bridges due to the raised naps are likely to form in the gaps between the raised naps on the outer surface of the artificial leather, making it easier for the finger to slip when stroking the outer surface, reducing the dynamic friction force. On the other hand, if the raised area ratio is 0.5 or less, pilling is unlikely to occur and abrasion resistance is likely to be good. The raised area ratio is preferably 0.25 to 0.5, more preferably 0.32 μm to 0.5 μm. As will be described later, a moist feel like nubuck can be obtained by adjusting the difference between the static and dynamic friction coefficients of the artificial leather surface. In general suede-like artificial leather, both the static and dynamic friction coefficients are small, and the difference between them is also small, but by increasing the difference between the static and dynamic friction coefficients, a moist feel like nubuck can be obtained.

[0021] [Volume of protruding ridges of artificial leather] In this embodiment, the actual volume of the protruding peaks on the outer surface of the artificial leather is 1≦Vmp≦3 [mm 3 The actual volume of the protruding peaks indicates the flatness of the outer surface of the artificial leather. By setting the actual volume of the protruding peaks within the above range, the contact area between the finger and the sample when touching the sample with a finger increases, and the static friction coefficient also increases.

[0022] [Dispersion of raised nap on artificial leather (average diameter of virtual bubbles)] In this embodiment, the dispersion of the naps present on the outer surface of the artificial leather is preferably 20≦A≦60 μm. If the dispersion of the naps is 60 μm or less, the nap pitch is narrower than that of the fingerprint area, so that the naps are more likely to fill the fingerprint area when the sample is pressed against it, resulting in a higher static friction coefficient. On the other hand, if the dispersion of the naps is 20 μm or more, there is an appropriate distance between the naps, making pilling less likely to occur and improving abrasion resistance. The dispersion of the naps is preferably 20 μm or less and 45 μm or more, more preferably 20 μm or more and 40 μm or less.

[0023] [Difference between static and dynamic friction coefficients (moist feeling)] The difference (μs-μk) between the static friction coefficient (μs) and the dynamic friction coefficient (μk) calculated from a friction test of the artificial leather is preferably 0.25 or more and 0.5 or less. The difference between the static friction coefficient and the dynamic friction coefficient indicates the moist feel, which is an important tactile sensation of nubuck-like artificial leather. The difference between the static friction coefficient and the dynamic friction coefficient within the above range can be obtained by controlling the nap area ratio and the solid volume of the protruding ridges. Furthermore, the difference between the static friction coefficient and the dynamic friction coefficient is preferably 0.28 or more and 0.5 or less, more preferably 0.3 or more and 0.5 or less. The static friction coefficient is preferably 0.8 or more and 1.5 or less, more preferably 1.0 or more and 1.2 or less. The dynamic friction coefficient is preferably 0.5 or more and 1.3 or less, more preferably 0.6 or more and 1.0 or less.

[0024] When the entangled sheet is composed of two layers, a fiber layer (A) and a scrim, the basis weight of the fiber web (A') constituting the fiber layer (A) is preferably 10 g / m from the viewpoint of mechanical strength such as abrasion resistance. 2 More than 200g / m 2 Less than 30 g / m, more preferably 2 More than 170g / m 2 More preferably 60 g / m or less 2 More than 170g / m 2 The basis weight of the scrim is preferably 20 g / m from the viewpoint of mechanical strength and entanglement of the fiber layer with the scrim. 2 More than 150g / m 2 Less than 20 g / m, more preferably 2 More than 130g / m 2More preferably, 30 g / m or less 2 More than 110g / m 2 The weight of the artificial leather obtained by impregnating an entangled sheet composed of two layers of a fiber layer (A) and a scrim with a PU resin is preferably 50 g / m 2 More than 550g / m 2 Less than 60 g / m 2 More than 400g / m 2 More preferably, 70 g / m or less 2 More than 350g / m 2 The following is the result.

[0025] When the entangled sheet has a three-layer structure of a fiber layer (A), a scrim, and a fiber layer (B), the basis weight of the fiber web (A') constituting the fiber layer (A) is preferably 10 g / m from the viewpoint of mechanical strength such as abrasion resistance. 2 More than 200g / m 2 Less than 30 g / m, more preferably 2 or more and 170 g / m² or less, more preferably 60 g / m² 2 More than 170g / m 2 The basis weight of the fiber web (B') constituting the fiber layer (B) is preferably 10 g / m from the viewpoint of cost and ease of production. 2 More than 200g / m 2 Less than 20 g / m, more preferably 2 More than 170g / m 2 The basis weight of the scrim is preferably 20 g / m from the viewpoint of mechanical strength and entanglement of the fiber layer with the scrim. 2 More than 150g / m 2 Less than 20 g / m, more preferably 2 More than 130g / m 2 More preferably, 30 g / m or less 2 More than 110g / m 2 The weight of the artificial leather obtained by impregnating a PU resin into an entangled sheet having a three-layer structure of a fiber layer (A), a scrim, and a fiber layer (B) is preferably 60 g / m 2 More than 750g / m 2 or less, more preferably 80 g / m² or more and 570 g / m² or more 2 More preferably, 70 g / m or less2 More than 520g / m 2 The following is the result.

[0026] [Scrim] The scrim may be, for example, a woven or knitted fabric, and is preferably composed of fibers of the same polymer as the fibers constituting the fiber layer (A) in terms of color matching 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 fibers constituting the scrim are preferably polyamide-based. In the case of a knitted fabric, the scrim is preferably a single knit knitted with a gauge of 22 to 28. When the scrim is a woven fabric, higher dimensional stability and strength can be achieved than with a knitted fabric. The weave of the fabric may be plain weave, twill weave, satin weave, etc., but plain weave is preferred from the standpoint of cost and process aspects such as entanglement. The yarns constituting the woven fabric may be monofilaments or multifilaments. The single fiber fineness of the yarns is preferably 5.5 dtex or less, since this facilitates the production of soft artificial leather using an entangled sheet. The yarns constituting the woven fabric are preferably in the form of multifilament raw silk, such as polyester or polyamide, or textured yarn that has been false-twisted and twisted at a twist count of 0 to 3000 T / m. The multifilaments may be ordinary, and preferred examples include 33 dtex / 6f, 55 dtex / 24f, 83 dtex / 36f, 83 dtex / 72f, 110 dtex / 36f, 110 dtex / 48f, 167 dtex / 36f, and 166 dtex / 48f yarns made of polyester, polyamide, etc. The yarns constituting the woven fabric may be multifilament long fibers. The weave density of the threads in the woven fabric is preferably 30 threads / inch or more and 150 threads / inch or less, more preferably 40 threads / inch or more and 100 threads / inch or less, in order to obtain an artificial leather that is soft and has excellent mechanical strength. In order to provide good mechanical strength and a suitable feel, the weight of the woven fabric is 20 g / m 2 More than 150g / m 2The following are preferred: The presence or absence of false twist processing in the woven fabric, the number of twists, the single fiber fineness of the multifilament, the weave density, etc. contribute to the entanglement with the constituent fibers of the fiber layer (A) and the flexibility of the artificial leather, as well as to the mechanical properties such as seam strength, tear strength, tensile strength / elongation, and stretchability, and therefore may be appropriately selected depending on the target physical properties and application.

[0027] [Polymer elastic material] The polymeric elastomer constituting the artificial leather is preferably polyurethane (PU) resin. PU resin can be used in various forms, including solvent-based PU resin, in which the PU resin is dissolved in an organic solvent such as N,N-dimethylformamide, and water-dispersed PU resin, in which the PU resin is emulsified with an emulsifier and dispersed in water. In this embodiment, however, water-dispersed PU resin is preferred because it is easy to fill the entangled sheet with fine particles, and even a small amount of the PU resin can easily achieve the required properties of artificial leather, such as texture and mechanical properties, and it does not require the use of organic solvents, thereby reducing the environmental impact. In other words, water-dispersed PU resin can be impregnated into the entangled sheet in the form of a dispersion in which the PU resin is dispersed with a desired particle size. Therefore, the filling state of the PU resin in the entangled sheet can be well controlled by controlling the particle size. As the water-dispersible 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, or the like can be used. A crosslinking agent can be used in combination with the water-dispersible PU resin to improve durability, such as resistance to moist heat, abrasion, and hydrolysis. Adding a crosslinking agent is preferable to improve durability during jet dyeing, suppress fiber shedding, and obtain excellent surface quality. The crosslinking agent may be an external crosslinking agent added to the PU resin as an additive, or an internal crosslinking agent that pre-introduces reactive groups capable of forming a crosslinked structure into the PU resin structure. The water-dispersible PU resin used in artificial leather generally has a crosslinked structure to provide resistance to dyeing processes, and therefore tends to be difficult to dissolve in organic solvents such as N,N-dimethylformamide. Therefore, for example, if an artificial leather is immersed in N,N-dimethylformamide at room temperature for 12 hours to dissolve the PU resin, and then the cross section is observed with an electron microscope or the like, if a resinous material not having a fibrous shape remains, the resinous material can be determined to be a water-dispersible PU resin.

[0028] From the viewpoint of the flexibility and homogeneity required for artificial leather, it is preferable to fill the PU resin using a PU resin dispersion and to set the average primary particle size of the PU resin in the dispersion to 0.1 μm or more and 0.8 μm or less. The average primary particle size is a value obtained by measuring the PU resin dispersion using a laser diffraction particle size analyzer (HORIBA's "LA-920"). By setting the average primary particle size of the PU resin to 0.1 μm or more, the force with which the PU resin holds the fibers in the entangled sheet together (i.e., the binder strength) is improved, resulting in an artificial leather with excellent mechanical strength. Furthermore, setting the average primary particle size of the PU resin to 0.8 μm or less is advantageous in that it prevents the PU resin from aggregating or coarsening, thereby controlling the standard deviation of the cross-sectional PU resin area ratio to 25 or less. 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 constituting the artificial leather (particularly its surface layer) are able to grip each other at more points, resulting in a soft feel (bending resistance) and excellent mechanical strength (abrasion resistance, etc.). The average primary particle size of the PU resin is preferably 0.1 μm or more and 0.6 μm or less, and more preferably 0.2 μm or more and 0.5 μm or less.

[0029] [Solid content of PU resin dispersion] As described above, the PU resin is impregnated in the form of an impregnation liquid such as a solution (for example, in the case of a solvent-dissolved type) or a dispersion (for example, in the case of a water-dispersed type). For example, the solids concentration of the water-dispersed PU resin dispersion can be 3% by weight or more and 35% by weight or less, more preferably 4% by weight or more and 30% by weight or less, and even more preferably 5% by weight or more and 25% by weight or less. In one embodiment, the impregnation liquid is prepared and the entangled sheet is impregnated so that the ratio of PU resin to 100% by weight of the entangled sheet is 5% by weight or more and 50% by weight or less.

[0030] 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, or other diols can be used, and copolymers of two or more of these may also be used. From the viewpoint of hydrolysis resistance, polycarbonate-based, polyether-based, or combinations thereof diols are preferably used. Furthermore, from the viewpoint of light resistance and heat resistance, polycarbonate-based, polyester-based, or combinations thereof diols are preferably used. Furthermore, from the viewpoint of cost competitiveness, polyether-based, polyester-based, or combinations thereof diols are preferably used. Polycarbonate-based diols can be produced by, for example, transesterification of alkylene glycol with a carbonate ester, or reaction of phosgene or chloroformate with an alkylene glycol.

[0031] Examples of alkylene glycols include linear alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and 1,10-decanediol; branched alkylene glycols such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, and 2-methyl-1,8-octanediol; alicyclic diols such as 1,4-cyclohexanediol; and aromatic diols such as bisphenol A. 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 with polybasic acids. Examples of low-molecular-weight polyols that can be used include one or more selected from ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol. Also usable are adducts of bisphenol A with various alkylene oxides. Examples of polybasic acids include one or more selected from the group consisting of succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydroisophthalic acid.

[0032] Examples of polyether diols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymer diols obtained by combining these. The number average molecular weight of the polymer diol is preferably 500 to 4000. 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. Furthermore, by setting the number average molecular weight to 4000 or less, more preferably 3000 or less, it is possible to maintain good strength of the PU resin. 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 these may be used in combination. Among these, 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-based chain extender such as ethylenediamine or methylenebisaniline, or a diol-based chain extender such as ethylene glycol can be used. Also, a polyamine obtained by reacting a polyisocyanate with water can be used as the chain extender.

[0033] If necessary, additives such as stabilizers (ultraviolet absorbers, antioxidants, etc.), flame retardants, antistatic agents, and pigments (carbon black, etc.) may be added to the impregnation solution containing the PU resin (e.g., water-dispersible PU resin). The total amount of these additives present in the artificial leather may be, for example, 0.1 to 10.0 parts by mass, 0.2 to 8.0 parts by mass, or 0.3 to 6.0 parts by mass per 100 parts by mass of the PU resin. These additives are distributed throughout the PU resin of the artificial leather. In this disclosure, when referring to the mass ratio of the PU resin to the size and entangled sheet, this value includes the additives (if used).

[0034] <Manufacturing method for artificial leather> An example of a method for producing the artificial leather of this embodiment will be described below. The method for producing artificial leather of the present embodiment includes the following steps: The following steps: (1) forming a fiber web (A') from fibers having an average diameter of 2.0 μm or more and 7.0 μm or less; (2) a first hydroentangling step in which the obtained fiber web (A') is hydroentangled at a water pressure of 2 to 5 MPa and an entanglement coverage of 60% or more to obtain a fiber sheet (A); (3) a second hydroentangling step of laminating at least the fiber sheet (A) and a scrim, and hydroentangling the laminate at a water pressure of 5 to 15 MPa and an entanglement coverage of 80% or more to obtain an entangled sheet; (4) A step of pressing the entangled sheet using calender rolls, with an unheated roll in contact with the fiber sheet (A) side of the entangled sheet and a roll having a surface temperature of 105 to 135°C in contact with the opposite side, at a press pressure of 6 to 14 N / cm and a base fabric running speed of 15 to 25 m / min or less; (5) A heat pressing process in which the sheet is pressed using a calender roll, with an unheated roll in contact with the front side of the product and a roll with a surface temperature of 105 to 135°C in contact with the opposite side, at a pressure of 6 to 14 N / cm and a base fabric running speed of 15 to 25 m / min or less; (6) optionally, raising the outer surface of the entangled sheet; (7) a step of filling the obtained entangled sheet with a polymeric elastomer to obtain a sheet-like product; (8) if the step (6) is not carried out, a step of raising the outer surface of the sheet-like material obtained in the step (7), or a step of carrying out the step (6) and further raising the outer surface of the sheet-like material; and (9) dyeing the obtained sheet-like product; Includes:

[0035] As an example of a method for manufacturing artificial leather, the steps are carried out in the order shown above. Each step will be explained below in order. In this specification, the following terms are used to distinguish between fibers formed into a sheet in a web-forming process (fiber web), a fiber sheet formed by hydroentangling a fiber web in a preliminary hydroentangling process (fiber sheet), a laminated sheet formed by laminating a fiber sheet with a scrim and an optional additional fiber web or fiber sheet, an entangled sheet formed by hydroentangling a laminated sheet in a main hydroentangling process, a sheet-like material formed by filling an entangled sheet with a polymeric elastomer in a polymeric elastomer filling process, and an artificial leather formed by coloring a sheet-like material. The fiber layer constituting the artificial leather is not limited to being a single layer. For example, an artificial leather obtained using an entangled sheet having a three-layer structure consisting of a fiber layer (A), a scrim in contact with the fiber layer (A), and a fiber layer (B) in contact with the scrim is composed of two fiber layers separated by a scrim. Furthermore, when an artificial leather includes two or more fiber layers, the structures of these layers are not necessarily the same. For example, by forming the fiber layer on the outer surface side with ultrafine fibers that tend to provide a smooth feel, and forming the fiber layer on the opposite side of the outer surface with flame-retardant fibers that have a large diameter and are less likely to provide a smooth feel, it is possible to obtain artificial leather that is flame-retardant while maintaining the smooth feel of the outer surface.

[0036] [Web forming process] Methods for producing the fiber web (A'), optional fiber web (B'), additional fiber web, etc. that constitute each fiber layer (fiber layer (A), optional fiber layer (B), additional fiber layer, etc.) that constitutes the artificial leather include direct spinning methods (e.g., spunbonding and meltblown methods) and methods for forming a fiber web using staple fibers (e.g., dry methods such as carding and airlaid methods, and wet methods such as papermaking), and either method is preferably used. In particular, fiber webs produced using staple fibers have small and uniform basis weight variations and are easy to obtain uniform raised nap, and are therefore preferable in terms of improving the surface quality of the artificial leather.

[0037] As the raw material fibers for the fiber web constituting the fiber layers (fiber layer (A), optional fiber layer (B), additional fiber layers, etc.) constituting the artificial leather, directly spun fibers and ultrafine fibers extracted from ultrafine fiber-developing fibers are preferred. By using directly spun fibers and ultrafine fibers extracted from ultrafine fiber-developing fibers, the fibers in the fiber layers constituting the artificial leather are easily dispersed as single fibers.

[0038] When sea-island (SIF) staple fibers are used as staple fibers, it is preferable to use ultrafine fiber development fibers as a means for forming the fibers of the fiber web, as the use of ultrafine fiber development fibers allows for a stable entanglement of fiber bundles. Examples of ultrafine fiber-forming fibers that can be used include islands-in-sea fibers in which two thermoplastic resin components with different solvent solubility are used as a sea component and an island component, and the sea component is dissolved and removed using a solvent or the like to turn the island components into ultrafine fibers, and peel-type composite fibers in which two thermoplastic resin components are alternately arranged radially or in multiple layers on the fiber cross section and the components are peeled and split to form ultrafine fibers. Among these, islands-in-sea fibers are preferably used from the viewpoint of the flexibility and texture of sheet-like products, because the removal of the sea component can provide appropriate voids between the island components, i.e., between the fibers.

[0039] Island-in-sea type fibers include islands-in-sea type composite fibers produced by spinning two components, a sea component and an island component, in a mutual arrangement using an islands-in-sea type composite spinneret, and mixed spun fibers produced by mixing two components, a sea component and an island component, and spinning them. Island-in-sea type composite fibers are preferably used because they can produce fibers of uniform fineness and fibers of sufficient length, which contributes to the strength of the sheet-like product. The sea component of the islands-in-sea fiber can be polyethylene, polypropylene, polystyrene, copolymer polyester copolymerized with sodium sulfoisophthalic acid, polyethylene glycol, etc., polylactic acid, etc. Among them, from the viewpoint of environmental consideration, copolymer polyester copolymerized with sodium sulfoisophthalic acid, polyethylene glycol, etc., which are alkali-decomposable and can be decomposed without using organic solvents, and polylactic acid are preferred. When islands-in-sea type fibers are used, the sea-removal treatment is preferably carried out before the polymeric elastomer filling step. If the sea-removal treatment is carried out before the polymeric elastomer filling step, the polymeric elastomer will adhere directly to the fibers, and the fibers can be firmly held, resulting in good abrasion resistance of the sheet-like product.

[0040] When a method using short fibers (staple) is selected, the short fiber length is preferably 13 mm to 102 mm, more preferably 25 mm to 76 mm, and even more preferably 38 mm to 76 mm in dry methods (carding, airlaid, etc.), and is preferably 1 mm to 30 mm, more preferably 2 mm to 25 mm, and even more preferably 3 mm to 20 mm in wet methods (papermaking, etc.). For example, the aspect ratio (L / D), which is the ratio of length (L) to diameter (D) of short fibers used in wet methods (papermaking, etc.), is preferably 500 to 2,000, more preferably 700 to 1,500. Such an aspect ratio is preferable because it allows for good dispersibility and openability of the short fibers in the slurry when the short fibers are dispersed in water to prepare a slurry, provides good fiber layer strength, and is less likely to cause pilling, a fluff-like appearance caused by friction, since the fibers are shorter and easier to disperse as single fibers compared to those obtained by the dry method. For example, the fiber length of short fibers having a diameter of 4 μm is preferably 2 mm to 8 mm, more preferably 3 mm to 6 mm.

[0041] [Hydroentangling process] The hydroentangling step in the manufacturing process of artificial leather preferably includes a first hydroentangling step in which only the fiber web (A') constituting the fiber layer (A) of the artificial leather obtained in the web forming step is hydroentangled to obtain a fiber sheet (A"); and a second hydroentangling step in which at least two layers of the first hydroentangled fiber sheet (A") and a scrim are laminated together, and the laminated sheet of at least two layers is integrated by hydroentangling to obtain an entangled sheet. By hydroentangling only the fiber web (A') constituting the fiber layer (A) of the artificial leather, a sufficiently densified fiber sheet (A") can be obtained. In particular, to adjust the above-mentioned raised area ratio and average diameter of virtual bubbles within a specific range, it is preferable to set the water pressure in the first hydroentanglement step to 2 to 5 MPa and the water pressure in the second hydroentanglement step to 5 to 15 MPa. If the water pressure in the first hydroentanglement step is less than 2 MPa, insufficient entanglement can cause fiber peeling due to the water flow during dyeing. On the other hand, if it exceeds 5 MPa, the fiber density of the fibrous web (A') is low, so the degree of freedom of the fibers is high, and excessive hydroentanglement can cause fiber coarseness and density, resulting in a loss of smoothness. Furthermore, if the water pressure in the second hydroentanglement step is less than 5 MPa, insufficient entanglement can cause fiber peeling due to the water flow during dyeing. On the other hand, if it exceeds 15 MPa, excessive hydroentanglement can cause fiber coarseness and density, resulting in a loss of smoothness. Furthermore, in order to adjust the average diameter of the virtual bubbles to a specific range, it is preferable that the area to be hydroentangled relative to the area of ​​the fiber web (A') in the first hydroentanglement step (hereinafter referred to as the hydroentanglement coverage rate) is 60% or more, and that the hydroentanglement coverage rate is 80% or more in the second hydroentanglement step. If the first hydroentanglement coverage rate is less than 60%, the degree of freedom of the fibers will be high due to insufficient entanglement, and if the second hydroentanglement is carried out in this state, the fibers will vary in density and roughness, resulting in a loss of smoothness.

[0042] Furthermore, it is preferable to spray high-pressure water using multiple nozzles with a nozzle spacing of 1.0 mm or less. The nozzle spacing is the distance in the nozzle width direction between a nozzle hole and the nozzle hole closest to that nozzle hole in the nozzle width direction. By setting the nozzle spacing to 1.0 mm or less, it is possible to spray water streams with tight spacing onto the fiber sheet, and this treatment is referred to as first hydroentanglement and second hydroentanglement, and by performing each treatment multiple times, the entanglement coverage can be adjusted. The hole diameter of the high-pressure water spray nozzle is preferably 0.05 mm to 0.40 mm to promote dispersion of single fibers. More preferably, it is 0.05 mm to 0.30 mm, and even more preferably, it is 0.10 mm to 0.25 mm. Furthermore, the distance from the high-pressure water spray surface to the treated material can be preferably 5 mm to 100 mm in terms of application before the hydroentanglement and process passability during the hydroentanglement. It is more preferably 10 mm to 60 mm, and even more preferably, it is 20 mm to 40 mm. When the entangled sheet has a three-layer structure consisting of a fibrous layer (A), a scrim in contact with the fibrous layer (A), and a fibrous layer (B) in contact with the scrim, the fibrous layer (B) to be laminated as a laminate sheet is laminated in the state of a fibrous sheet (B") obtained by hydroentangling only the fibrous web (B'), or in the state of a fibrous web (B') that has not been pre-hydroentangled. In other words, the fibrous layer (B) to be laminated as a laminate sheet may be laminated in either the state of a fibrous sheet (B") obtained by hydroentangling only the fibrous web (B'), or in the state of a fibrous web (B') that has not been pre-hydroentangled. Furthermore, when the entangled sheet has a multilayer structure having a fibrous layer (C) or more on the fibrous layer (B) side in addition to the fibrous layer (B), the multilayer portion consisting of the fibrous layer (B) and the fibrous layer (C) or more may be laminated in the same way as the fibrous layer (B).

[0043] As a method for entangling, a method can be adopted in which the islands-in-sea fibers are cut to a predetermined fiber length to form staples, and the staples are passed through a card and a cross wrapper to form a fiber web, which is then entangled by a needle punching method. In one embodiment, however, a hydroentangling treatment is preferred.

[0044] In the hydroentanglement step, it is preferable to move the nozzle in a circular motion or a reciprocating motion perpendicular to the direction of the hydroentanglement step, since this allows the fibers to be entangled evenly, reduces water flow marks parallel to the direction of the hydroentanglement step, and improves surface quality.

[0045] [Heat pressing process] A hot press can be performed to smooth the surface of the bonded sheet, sheet-like material, or artificial leather. Examples of hot press methods include a flat press method and a calender roll method. The calender roll method is particularly preferred because it allows continuous pressing. In the calender method of the present application, an unheated roll is placed on the front side of the bonded sheet, sheet-like material, or artificial leather, and a roll with a surface temperature of 105 to 135°C is placed on the opposite side. To adjust the solid volume of the protruding peaks to a specific range, the roll temperature of the hot press is preferably 105°C to 135°C, and the pressing pressure is preferably 6 N / cm to 14 N / cm. The roll temperature is more preferably 110°C to 130°C, even more preferably 115°C to 125°C, and the pressing pressure is more preferably 7 N / cm to 13 N / cm, even more preferably 8 N / cm to 12 N / cm. To obtain sufficient processing stability or raised nap, it is desirable to press the base fabric at a running speed of 15 to 25 m / min or less and with a surface roughness Ra of the calender roll of 0.5 μm.

[0046] [Napping process] To form naps on the surface of the entangled sheet or sheet-like material, a nap raising treatment can be performed. The nap raising treatment can be performed by grinding using sandpaper, a roll sander, or the like. Furthermore, adding a silicone or other lubricant before the nap raising treatment makes it easy to perform the nap raising treatment by surface grinding, resulting in very good surface quality.

[0047] [Polymer elastomer filling process] In this step, the entangled sheet is impregnated with a polymeric elastomer and then dried to fill the sheet with the polymeric elastomer. In one embodiment, the polymeric elastomer is preferably a water-dispersible polyurethane (PU) resin. The water-dispersible PU resin is impregnated in the form of an impregnation liquid such as a dispersion. The concentration of the water-dispersible PU resin in the impregnation liquid can be, for example, 3 to 35% by mass. In one embodiment, the impregnation liquid is prepared and the entangled sheet is impregnated with the PU resin in a ratio of 5 to 50% by mass relative to 100% by mass of the entangled sheet.

[0048] Water-dispersible PU resins are classified into forced emulsification PU resins, which are forcibly dispersed and stabilized using a surfactant, and self-emulsification PU resins, which have a hydrophilic structure in the PU molecular structure and are dispersed and stabilized in water even in the absence of a surfactant. Either type may be used in this embodiment, but from the viewpoint of imparting heat-sensitive coagulation properties, which will be described later, it is preferable to use forced emulsification PU resins. The concentration of the water-dispersible PU resin (the content of the PU resin relative to the water-dispersible PU resin dispersion) is preferably from 3 to 35% by mass, more preferably from 4 to 30% by mass, and even more preferably from 5 to 30% by mass, in order to control the amount of adhesion of the water-dispersible PU resin and because a high concentration promotes aggregation of the PU resin.

[0049] Furthermore, the water-dispersed PU resin dispersion is preferably one that exhibits heat-sensitive coagulation properties. Using a water-dispersed PU resin dispersion with heat-sensitive coagulation properties allows the PU resin to be uniformly applied across the thickness of the entangled sheet. Heat-sensitive coagulation refers to the property of a PU resin dispersion that, when heated, reduces its fluidity and coagulates when it reaches a certain temperature (heat-sensitive coagulation temperature). In the production of a sheet-like material filled with PU resin, the PU resin dispersion is applied to an entangled sheet, coagulated by dry heat coagulation, wet heat coagulation, hot water coagulation, or a combination of these, and then dried to impart the PU resin to the entangled 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. However, this method can cause migration, in which the PU resin concentrates on the surface of the sheet, and the texture of the PU-filled sheet tends to become fixed. The heat-sensitive coagulation temperature of the aqueous PU resin dispersion is preferably 40°C or higher and 90°C or lower. By setting the heat-sensitive coagulation temperature to 40°C or higher, the PU resin dispersion has good stability during storage and can prevent adhesion of the PU resin to machines during operation. Furthermore, by setting the heat-sensitive coagulation temperature to 90°C or lower, migration of the PU resin in the entangled sheet can be prevented. To adjust the heat-sensitive coagulation temperature to the above range, a heat-sensitive coagulating agent may be added as needed. Examples of the heat-sensitive coagulating agent 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.

[0050] The aqueous PU resin dispersion can be impregnated or coated onto an entangled sheet, and the PU resin can be coagulated by dry heat coagulation, wet heat coagulation, hot water coagulation, or a combination of these. The wet heat coagulation temperature is set to be equal to or higher than the thermosensitive coagulation temperature of the PU resin, preferably between 40°C and 200°C. By setting the wet heat coagulation temperature at 40°C or higher, more preferably at 80°C or higher, the time until the PU resin coagulates can be shortened, thereby further suppressing migration. On the other hand, by setting the wet heat coagulation temperature at 200°C or lower, more preferably at 160°C or lower, thermal degradation of the PU resin and PVA resin can be prevented. The hot water coagulation temperature is set to be equal to or higher than the thermosensitive coagulation temperature of the PU resin, preferably between 40°C and 100°C. By setting the hot water coagulation temperature in hot water at 40°C or higher, more preferably at 80°C or higher, the time until the PU resin coagulates can be shortened, thereby further suppressing migration. The dry coagulation temperature and drying temperature are preferably between 80°C and 180°C. By setting the dry coagulation temperature and drying temperature to 80°C or higher, more preferably 90°C or higher, excellent productivity can be achieved. On the other hand, by setting the dry coagulation temperature and drying temperature to 180°C or lower, more preferably 160°C or lower, thermal degradation of the PU resin and PVA resin can be prevented.

[0051] [Dyeing process] The artificial leather is preferably dyed to enhance its aesthetic value (i.e., visual effect). The dye may be selected according to the type of fiber constituting the entangled sheet. For example, disperse dyes can be used for polyester fibers, and acid dyes or metal-containing dyes can be used for polyamide fibers, or a combination thereof can be used. When dyeing with disperse dyes, reduction washing may be performed after dyeing. Conventional dyeing methods well known to dyeing and processing companies can be used. A jet dyeing machine is preferably used for the dyeing method, since it can dye the sheet-like material while simultaneously providing a kneading effect to soften the sheet-like material. The dyeing temperature, although it depends on the type of fiber, is preferably 80°C or higher and 150°C or lower. By setting the dyeing temperature at 80°C or higher, more preferably 110°C or higher, efficient dyeing into the fibers can be achieved. On the other hand, by setting the dyeing temperature at 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 (i.e., washing in the presence of a chemical reducing agent) to remove excess dye. It is also a preferred embodiment to use a dyeing assistant during dyeing. The use of a dyeing assistant can improve the uniformity and reproducibility of the dyeing. Furthermore, finishing treatments using softeners such as silicone, antistatic agents, water repellents, flame retardants, lightfastness agents, antibacterial agents, etc. can be performed in the same bath as dyeing or after dyeing.

[0052] The artificial leather of this embodiment can be suitably used as an interior material with a very elegant appearance, such as a surface material for furniture, chairs, wall materials, seats, ceilings, and interior trims in vehicle cabins such as automobiles, trains, and airplanes; uppers and trims for shoes such as shirts, jackets, casual shoes, sports shoes, men's shoes, and women's shoes; clothing materials used in parts of bags, belts, wallets, and the like; and industrial materials such as wiping cloths, polishing cloths, and CD curtains. [Example]

[0053] The present invention will be described in detail below based on examples and comparative examples, but the examples are not intended to limit the scope of the present invention. The artificial leather samples according to the examples and comparative examples were evaluated for physical properties, quality, etc. according to the following procedures and methods.

[0054] (1-0) Sample collection location Figure 5 shows the locations where the samples were collected. First, two strips (sampling areas 1 and 2) in the machine direction (MD) of the fiber layer (A) or the artificial leather containing the fiber layer (A) were cut out (indicated by dotted lines). A cross section in the thickness (t) direction was prepared for each sampling area, and five approximately uniform positions were selected in the CD direction perpendicular to the MD direction on this cross section. A total of 10 selected positions were subjected to SEM measurement, and the average diameter (μm) of the single fibers constituting the fiber layer (A) was determined by the method described below.

[0055] (1-1) Average diameter (μm) of the single fibers constituting the fiber layer (A) The average diameter of the fibers constituting the fiber layer (A) was determined by photographing one of the cross sections of the fiber layer (A) of the artificial leather selected in (1-0) above using a scanning electron microscope (SEM, JEOL "JSM-5610") at a magnification of 1500x, randomly selecting 10 fibers constituting the cross section of the fiber layer (A) of the artificial leather, and measuring the cross-sectional diameter of each single fiber. Similar measurements were performed on all 10 cross sections selected in (1-0), and the arithmetic mean value of the measurements for a total of 100 fibers was taken as the average diameter of each single fiber. When the observed shape of the cross section of a single fiber is not circular, the fiber diameter is the distance between the outer peripheries on a line perpendicular to the midpoint of the longest diameter of the cross section of the single fiber. Fig. 4 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. 4, the fiber diameter is the distance c between the outer peripheries on a line b perpendicular to the midpoint P of the longest diameter a of the cross section A in the observed image.

[0056] (1-2) Raised area ratio (S) The raised area ratio is the ratio of the raised area to the total fibers on the outer surface of the artificial leather. A 20cm x 20cm sample was placed on the stage of an optical microscope (OPTELICS HYBRID, Lessertec) with the nap direction (the direction in which the nap lies when stroked) aligned with the depth direction. The nap was then aligned in one direction by brushing. The optical microscope measurement conditions were a 20x objective lens, 1024 x 1024 pixels, a z-step of 5 μm, a GREEN measurement channel, Fine Peek peak detection, a reduction ratio of 1 / 2, a 10 x 10 patchwork image, and overlapping imagery. One image was taken at any given location on the sample. The same measurement was repeated after changing the sample's location, resulting in a total of 10 images, all of which were taken at random locations more than 1 cm apart. These images were then processed using image processing software (LMeye7, Lessertec) after surface correction and processing with a 6000 μm high-pass filter, followed by binarization using discriminant analysis. The opening setting was then set to 3, and the opening process was performed. Then, to extract features, domains of 3000 pixels or less were removed. The area ratio of each raised area (highlighted in white) obtained in the final image was calculated using the following formula, and the average value was calculated. Brushed area ratio (S) = Number of pixels in the brushed highlighted area / Number of pixels in the entire image

[0057] (1-3) Protruding peak volume (Vmp) [mm 3 ] The 10 images taken in (1-2) were processed with a 6000 μm high-pass filter after surface correction using image processing software (LMeye7, Lessertec). Furthermore, surface shape analysis was performed on an area 0.8 x 0.8 times the image size at the center of each image obtained, and the volume of the protruding peaks defined by the surface roughness parameter (ISO25178-2:2012) was calculated, and the average value was calculated.

[0058] (1-4) Dispersion state of raised particles (A) [μm] The dispersion state of the raised naps refers to the distance between the raised naps on the outer surface of the artificial leather. In this embodiment, multiple virtual bubbles were placed between the raised fibers using the thickness method from the 10 final images obtained in (1-2), and the average diameter of the virtual bubbles (hereinafter referred to as the dispersed state of the raised fibers) was calculated, and the average value was calculated.

[0059] [Difference between static and dynamic friction coefficients (moist feeling) (μs-μk)] A measurement sample was taken from a randomly selected location on the artificial leather, measuring 50 mm x 250 mm, with the nap direction aligned longitudinally. One measurement sample was then fixed to the moving table of a static / dynamic friction tester (TL201Ts, Trinity Lab Co., Ltd.) so that the sliding direction of the moving table was parallel to the longitudinal direction of the measurement sample. An artificial finger model (skin model with fingerprint pattern, Trinity Lab Co., Ltd.) was used as the contactor of the static / dynamic friction tester. The friction coefficient was measured by two round trips with a load of 100 gf, a sliding speed of 30 mm / sec, and a travel distance of 100 mm. The static friction coefficient was calculated as the maximum value over a travel distance of 0 to 20 mm, and the kinetic friction coefficient was calculated from the average value over a travel distance of 20 to 80 mm. From these values, the difference between the static and kinetic friction coefficients (μs-μk) was calculated. Furthermore, the above sampling and measurement were carried out a total of 10 times, and the average value of the difference between the static and dynamic friction coefficients (μs-μk) was calculated.

[0060] [Wear resistance evaluation] The Martindale test (abrasion cloth: "ABRASIVECLOTH1575W" manufactured by James H. Heal) is carried out in accordance with the method described in JIS L1096 Fabric Testing Method for Woven and Knitted Fabrics, Method 8.19.5 E (Martindale method). The Martindale test conditions are as follows: Artificial leather weight 250g / m 2 Over: 50,000 friction cycles, load 12 kPa Artificial leather weight 250g / m 2 Less than: 20,000 friction cycles, load 9kPa. Next, the abrasion surface of the artificial leather after the test is visually evaluated by five healthy adults as evaluators, and judged into one of five levels according to the following evaluation criteria. [Evaluation criteria] Grade 5: The scrim is not exposed on the abraded surface, the fiber layer is not abraded, and no pilling is observed. Grade 4: The scrim is not exposed on the abraded surface and the fiber layer is not worn away, but pilling is observed. Grade 3: The scrim is not exposed on the worn surface and no pilling is observed, but the fiber layer is worn. Grade 2: The scrim is not exposed on the worn surface, but the fiber layer is worn and pilling is visible. Grade 1: The scrim is exposed on the worn surface and pilling is also visible. The abrasion resistance was determined as the average of 15 points (rounded to the nearest whole number) obtained by the five panelists for the three pieces of artificial leather. Grades 3 to 5 were considered to be good (passed).

[0061] [Example 1] Polyethylene terephthalate fibers with an average single fiber diameter of 4 μm were produced by melt spinning and cut to a length of 5 mm (hereinafter, the polyethylene terephthalate fibers cut to a length of 5 mm are also referred to as "PET ultrafine short fibers"). The PET ultrafine short fibers were dispersed in water and spun into a paper-making paper with a basis weight of 140 g / m. 2 A high-speed water jet (first hydroentanglement) using a straight-flow jet nozzle was sprayed onto the outer surface of the obtained fiber web (A') at a pressure of 2 MPa so as to give a coverage of 60%, and the web was dried at 100°C using an air-through pin tenter dryer to give a fiber sheet (A"). In the same way, PET ultra-fine short fibers were dispersed in water and made into a paper sheet with a basis weight of 80 g / m 2 The fiber web (B') was produced and used as the fiber layer (B) on the opposite side of the outer surface of the artificial leather. Between the fiber sheet (A″) and the fiber web (B′), a 95 g / m2 polyethylene terephthalate fiber sheet with a density of 166 dtex / 48 f is placed. 2 A scrim (plain weave fabric) was inserted to create a laminated sheet with a three-layer structure. Next, a high-speed water stream (second water stream entanglement) was sprayed onto the laminated sheet using a straight-flow spray nozzle at a pressure of 15 MPa from the outer surface side and 15 MPa from the opposite side of the outer surface so that the coverage was 80%, entangling the fiber layer with the scrim and integrating them into an entangled structure.Then, the sheet was dried at 100°C using an air-through pin tenter dryer to obtain an entangled sheet having a three-layer structure.

[0062] Next, the entangled sheet was pressed by a calendering method with an unheated roll in contact with the outer surface and a roll with a surface temperature of 120°C in contact with the opposite surface, with a press pressure of 10 N / cm, a base fabric running speed of 20 m / min, and a surface roughness Ra of the calender roll of 0.5 μm. Next, the outer surface of the entangled sheet was subjected to a nap raising treatment using #400 emery paper. The entangled sheet was then impregnated with a water-dispersible polyurethane resin impregnation solution having the composition shown in Table 1 below, then heated and dried at 130°C using a pin tenter dryer, and then immersed in hot water heated to 90°C and softened, followed by drying to extract and remove the anhydrous sodium sulfate, yielding a sheet-like material filled with the water-dispersible polyurethane resin. The ratio of the water-dispersible PU resin to the total mass of the fibers in this sheet-like material was 10% by mass. The sheet-like material was then dyed with a blue disperse dye (BlueFBL, manufactured by Sumitomo Chemical Co., Ltd.) at a dye concentration of 5.0% owf using a jet dyeing machine at 130°C for 15 minutes, followed by reduction washing.Then, it was dried at 100°C for 5 minutes using a pin tenter dryer to obtain an artificial leather having a three-layer structure.

[0063] [Examples 2 to 9] An artificial leather having a three-layer structure was obtained in accordance with the method of Example 1, except that the average diameter of the single fibers, the first hydroentanglement water pressure, the first hydroentanglement coverage ratio, the second hydroentanglement water pressure, the second hydroentanglement coverage ratio, the roll temperature, and the press pressure were changed as shown in Table 1 below.

[0064] [Comparative Examples 1 to 13] An artificial leather having a three-layer structure was obtained in accordance with the method of Example 1, except that the average diameter of the single fibers, the first hydroentanglement water pressure, the first hydroentanglement coverage ratio, the second hydroentanglement water pressure, the second hydroentanglement coverage ratio, the roll temperature, and the press pressure were changed as shown in Table 1 below. The various physical properties of the artificial leathers obtained in Examples 1 to 9 and Comparative Examples 1 to 13 are shown in Table 1 below.

[0065] [Table 1] [Industrial Applicability]

[0066] The artificial leather of the present invention is excellent in both moist feel and abrasion resistance, and is therefore suitable for use in interior seat coverings or interior trims for automobiles, aircraft, railway vehicles, etc., clothing products, etc. Specifically, the artificial leather of the present invention is suitable for use as an interior covering material with a very elegant appearance, such as covering materials for furniture, chairs, wall materials, seats, ceilings, interior trims, etc. in the interiors of vehicles such as automobiles, trains, and aircraft, uppers and trims, etc. for shirts, jackets, casual shoes, sports shoes, men's shoes, women's shoes, etc., clothing materials used in bags, belts, wallets, etc., and parts thereof, and industrial materials such as wiping cloths, polishing cloths, CD curtains, etc. [Explanation of symbols]

[0067] MD Process direction (machine direction) CD width (horizontal) direction 11 Entangled Sheet 12 Scrims 13 Fiber layer (A) 14 Fiber layer (B) A. Cross section of fiber when cross section is elliptical a Longest diameter of cross section A b A straight line that passes through the midpoint p of the longest diameter a and is perpendicular to the longest diameter a c Distance between the outer peripheries on line b P Midpoint of the longest diameter a

Claims

1. An artificial leather comprising an entangled sheet and a polymeric elastomer filled in the entangled sheet, the entangled sheet has a two-layer or more structure composed of a fiber layer (A) that forms the front surface side of the artificial leather and a scrim that is in contact with the fiber layer (A), the average diameter of the fibers constituting the fiber layer (A) is 2 μm or more and 7 μm or less, The following requirements (1) and (2): (1) The raised area ratio (S) on the front surface side of the artificial leather satisfies the relationship 0.18≦S≦0.5; and (2) The actual volume of the protruding peaks on the front side of the artificial leather (Vmp) [mm ３ ] satisfies the relationship 1≦Vmp≦3; An artificial leather characterized by satisfying the above.

2. 2. The artificial leather according to claim 1, wherein the dispersion state (A) [μm] of the raised particles present on the outer surface of the artificial leather satisfies the relationship 20≦A≦60.

3. 3. The artificial leather according to claim 1, wherein the polymeric elastomer is a water-dispersible polyurethane.

4. 3. The artificial leather according to claim 1, wherein the fibers constituting the fiber layer (A) are polyester fibers.

5. 3. The artificial leather according to claim 1, wherein the difference between the static friction coefficient and the dynamic friction coefficient (μs-μk) of the front surface of the artificial leather is 0.25 or more and 0.5 or less.

6. 3. The artificial leather according to claim 1, wherein the front surface of the artificial leather has an evaluation result of grade 3 or higher in an abrasion resistance test.

7. The following steps: (1) a step of forming a fiber web (A') from fibers having an average diameter of 2.0 μm or more and 7.0 μm or less; (2) a first hydroentangling step in which the obtained fiber web (A') is hydroentangled at a water pressure of 2 to 5 MPa and an entanglement coverage of 60% or more to obtain a fiber sheet (A"); (3) a second hydroentangling step in which at least the fiber sheet (A") and a scrim are laminated together, and hydroentangling is performed at a water pressure of 5 to 15 MPa and an entanglement coverage of 80% or more to obtain an entangled sheet; (4) A step of pressing the entangled sheet using calender rolls, with an unheated roll in contact with the fiber sheet (A") side of the entangled sheet and a roll having a surface temperature of 105 to 135°C in contact with the opposite side, at a press pressure of 6 to 14 N / cm and a base fabric running speed of 15 to 25 m / min or less; (5) A heat pressing step in which the sheet is pressed using a calender roll, with an unheated roll in contact with the front side of the product and a roll with a surface temperature of 105 to 135°C in contact with the opposite side, at a pressure of 6 to 14 N / cm and a base fabric running speed of 15 to 25 m / min or less; (6) optionally, raising the outer surface of the entangled sheet; (7) A step of filling the obtained entangled sheet with a polymeric elastomer to obtain a sheet-like product; (8) a step of raising the outer surface of the sheet-like material obtained in the step (7) when the step (6) is not performed, or a step of performing the step (6) and further raising the outer surface of the sheet-like material; and (9) dyeing the obtained sheet-like material; A method for producing artificial leather, comprising:

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