EP4223925A1

EP4223925A1 - Artificial leather, production method therefor, and artificial leather backing material

Info

Publication number: EP4223925A1
Application number: EP21875351.5A
Authority: EP
Inventors: Takahiro TSUCHIMOTO; Tatsuya Hagiwara; Atsushi Shinozaki
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 2020-09-29
Filing date: 2021-09-22
Publication date: 2023-08-09
Also published as: EP4223925A4; CN116018439A; WO2022071049A1; TW202223198A; US20230323594A1; JPWO2022071049A1; KR20230078990A

Abstract

An object of the present invention is to provide an artificial leather having excellent flame retardancy while having moderate air permeability and a flexible texture, and having feels like natural suede and an elegant appearance, the artificial leather including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a flame retardant surface having a flame retardant, and the following requirements 1 and 2 are satisfied. Requirement 1: At least the flame retardant surface has a plurality of opening portions. Requirement 2: The flame retardant has a tackiness of 0.1 N/cm<sup>2</sup> or more and 2.0 N/cm<sup>2</sup> or less.

Description

TECHNICAL FIELD

The present invention relates to an artificial leather which includes a fiber entanglement including ultrafine fibers, an elastomer, and a functional agent (flame retardant or the like), has moderate air permeability and a flexible texture, is excellent in flame retardancy, and has feels like natural suede and an elegant appearance. The present invention also relates to an artificial leather backing material used for obtaining the artificial leather, and having good formability of an opening portion.

BACKGROUND ART

Conventionally, an artificial leather including a fiber entanglement formed of ultrafine fibers and an elastomer and having raised nap has excellent characteristics in air permeability, durability, uniformity of quality, and the like as compared with natural leather, and is used not only as a clothing material but also in various fields such as interior materials of public transporters such as aircrafts, ships, and railroad vehicles, interior materials for vehicles, interior materials, building materials, and miscellaneous goods.
In the fields described above, artificial leather is often required to have high flame retardant performance, and in the fields where flame retardancy is required, it is common that the artificial leather includes a flame retardant. Among them, in order to cope with a ventilation system particularly in an interior material for vehicles, moderate air permeability is required by the density and material configuration of artificial leather and control of an opening portion.
Meanwhile, in order to develop the flame retardancy in the artificial leather, methods such as applying a flame retardant to ultrafine fibers, applying the flame retardant to the entire artificial leather, and coating and applying the flame retardant to one surface of the artificial leather are adopted.
However, in the artificial leather obtained by these methods, the elastomer such as polyurethane constituting the artificial leather and an ultrafine thermoplastic synthetic fiber constituting a nonwoven fabric, a woven fabric, or a knitted fabric are different from each other in a mechanism developing flame retardancy, and therefore, it is known that it is very difficult to make the entire artificial leather flame retardant.
In order to solve such a problem of flame retardancy, it has been proposed that an organic phosphorus component copolymerized polyester is used for ultrafine fibers of artificial leather (for example, see Patent Document 1), a polyurethane elastomer obtained by copolymerizing an organic phosphorus component is used for an elastomer of artificial leather (for example, see Patent Document 2), or a diaryl phosphoramidate-based flame retardant is attached to ultrafine fibers and exhausted (for example, see Patent Document 3).
In addition, there have been proposed a method in which a base formed of a flame-retardant heat-resistant fiber is stacked on a back surface and integrated by entanglement (for example, see Patent Document 4), a method in which a flame retardant is partially applied so as to have an area ratio of 60 to 90% in order to secure a certain air permeability when the flame retardant is applied to a back surface of artificial leather (for example, see Patent Document 5), and a method in which vent holes penetrating the artificial leather are formed (for example, see Patent Document 6).

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

Patent Document 1: Japanese Patent Laid-open Publication No. 2002-115183
Patent Document 2: Japanese Patent Laid-open Publication No. 2002-201574
Patent Document 3: Japanese Patent Laid-open Publication No. 2012-229508
Patent Document 4: Japanese Patent Laid-open Publication No. 2014-25156
Patent Document 5: Published Japanese Translation No. 2013-520581 of the PCT International Publication
Patent Document 6: International Publication 2014/097999

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

In the technique as disclosed in Patent Document 1, the organophosphorus component is copolymerized as compared with polyester usually used for ultrafine fibers, so that spinnability and dye dyeability at the time of production are deteriorated. In addition, since thread strength of ultrafine fibers and rubbing fastness of the artificial leather decrease, it is difficult to use the artificial leather for applications requiring high light resistance and high abrasion resistance.
In the technique as disclosed in Patent Document 2, the organophosphorus component is copolymerized with a polyurethane component that is an important constituent material for imparting strength and texture to the artificial leather without aged deterioration, and the design is such that texture and durability are lowered as compared with normal polyurethane.
In the technique as disclosed in Patent Document 3, when the diaryl phosphoramidate-based flame retardant is attached without using a binder, the flame retardant may fall off during use, and the flame retardancy becomes unstable. On the other hand, when the flame retardant is attached with a binder, a tactile sensation of a surface of the artificial leather becomes a hard feel. In addition, as disclosed in the background art of Patent Document 3, in a case where a water-soluble flame retardant such as guanidine phosphate is added to the entire artificial leather, when a napped surface is subjected to a process of absorbing moisture and then drying, there occurs a phenomenon that the guanidine phosphate is dissolved by the moisture and transferred to the surface to form a cyclic stain, that is, so-called "water spot", and there is a problem that designability of the artificial leather is significantly impaired.
In the technique as disclosed in Patent Document 4, it is necessary to have a sufficient basis weight of the flame-retardant heat-resistant fiber in order to secure a certain flame retardancy, and denseness of an entangled structure of the artificial leather is reduced, so that an elegant appearance and a flexible texture tend to be impaired. A method of integrating by entanglement by inserting into the inside and intertwining and integrating the flame-retardant heat-resistant fiber and a method of mixing flame-retardant heat-resistant fiber with constituent fiber also have the same problem.
In the technique as disclosed in Patent Document 5, since the flame retardant is applied in a dot shape, sufficient flame retardancy is not obtained, and a preliminary artificial leather does not have sufficient air permeability, so that it is not possible to achieve both denseness for an elegant appearance and air permeability that can be compatible with, for example, a ventilation system.
In the technique as disclosed in Patent Document 6, in the punching by a punching roll, a scrap after the punching is likely to clog a sheet or the punching roll, and mass production is difficult.
To summarize the above, in the techniques as disclosed in Patent Documents 1 to 6, in the artificial leather including a fiber entanglement formed of ultrafine fibers difficult to be made flame retardant and an elastomer, the artificial leather achieving both the flame retardancy and other important characteristics (in particular, moderate air permeability, flexible texture, feels like natural suede, and elegant appearance) cannot be provided.
Thus, the present invention has been made in view of the above circumstances, and an object thereof is to provide an artificial leather having excellent functionality (flame retardancy and the like) while having moderate air permeability and a flexible texture, and having feels like natural suede and an elegant appearance. Another object of the present invention is to provide an artificial leather backing material used for obtaining the artificial leather, and having good formability of an opening portion.

SOLUTIONS TO THE PROBLEMS

As a result of intensive studies by the present inventors to achieve the above object, it has been found that in an artificial leather including an ultrafine fiber entanglement, an elastomer, and a functional agent (flame retardant or the like), when the form of existence of the functional agent (flame retardant or the like) is within a specific range and tackiness of the functional agent (flame retardant or the like) is within a specific range, an artificial leather having good formability and achieving both functionality (flame retardancy or the like) and other important characteristics can be provided even if an opening portion is provided in the artificial leather.
The present invention has been completed based on these findings. The present invention provides the following inventions.
The artificial leather of the present invention is an artificial leather including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a flame retardant surface having a flame retardant, and the following requirements 1 and 2 are satisfied.

Requirement 1: At least the flame retardant surface has a plurality of opening portions.
Requirement 2: The flame retardant has a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less.

According to a preferred aspect of the artificial leather of the present invention, an opening ratio of the flame retardant surface is 1% or more and 40% or less.
According to a preferred aspect of the artificial leather of the present invention, the artificial leather has a plurality of opening portions in each of the napped surface and the flame retardant surface, and at least some of the opening portions are through opening portions formed to penetrate from the napped surface to the flame retardant surface.
According to a preferred aspect of the artificial leather of the present invention, the fiber entanglement is formed by integrating a fiber entanglement including the ultrafine fiber and a woven/knitted fabric (a).
According to a preferred aspect of the artificial leather of the present invention, the flame retardant surface is a surface formed by stacking a woven/knitted fabric (b).
According to a preferred aspect of the artificial leather of the present invention, a presence ratio of the flame retardant in a thickness direction satisfies the following formula: $0.001 \leq W / W_{0} \leq 0.7$
where W is a thickness (mm) from the flame retardant surface where the flame retardant is present, and W₀ is a thickness (mm) of the entire artificial leather.
According to a preferred aspect of the artificial leather of the present invention, the flame retardant contains a phosphorus-based compound.
According to a preferred aspect of the artificial leather of the present invention, the fiber entanglement including the elastomer has a density of 0.20 g/cm³ or more and 0.50 g/cm³ or less.
In a production method for an artificial leather of the present invention, a flame retardant having a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less is applied to one surface of a napped sheet-shaped article including a fiber entanglement including ultrafine fibers having an average single fiber diameter of 0.1 um or more and 10 um or less and an elastomer to form a flame retardant surface, and a plurality of opening portions are provided on at least the flame retardant surface.
An artificial leather backing material of the present invention is an artificial leather backing material including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a functional surface having a functional agent, and the functional agent has a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less. The artificial leather backing material can be used as the artificial leather of the present invention by forming an opening portion, and the artificial leather backing material itself can also be used as an artificial leather.
An artificial leather backing material of the present invention is an artificial leather backing material including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, and the other surface is a functional surface having a functional agent, the functional surface has a Kinetic friction coefficient of 0.15 or more and 0.60 or less, and the artificial leather backing material has a stiffness of 30 mm or more and 150 mm or less.
An artificial leather backing material of the present invention is an artificial leather backing material including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a functional surface having a functional agent, and an adhesion amount of the functional agent is 2 to 30% by mass with respect to the artificial leather backing material.

EFFECTS OF THE INVENTION

According to the present invention, it is possible to obtain an artificial leather having excellent functionality (flame retardancy and the like) while having moderate air permeability and a flexible texture, and having feels like natural suede and an elegant appearance. In addition, it is possible to obtain an artificial leather backing material used for obtaining the artificial leather, and having good formability of an opening portion.

EMBODIMENTS OF THE INVENTION

The artificial leather of the present invention is an artificial leather including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a flame retardant surface having a flame retardant, and the following requirements 1 and 2 are satisfied.

A ratio by weight of the ultrafine fiber contained in the fiber entanglement is preferably 60% or more, more preferably 80% or more.
An artificial leather backing material of the present invention is an artificial leather backing material including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a functional surface having a functional agent, and the functional agent has a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less.
An artificial leather backing material of the present invention is an artificial leather backing material including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, and the other surface is a functional surface having a functional agent, the functional surface has a Kinetic friction coefficient of 0.15 or more and 0.60 or less, and an artificial leather has a stiffness of 30 mm or more and 150 mm or less.
An artificial leather backing material of the present invention is an artificial leather backing material including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a functional surface having a functional agent, and an adhesion amount of the functional agent is 2 to 30% by mass with respect to the artificial leather backing material. Hereinafter, the constituent elements will be described in detail, but the present invention is not limited to the scope described below at all as long as the gist thereof is not exceeded.

[Fiber entanglement]

The fiber entanglement constituting the artificial leather of the present invention includes an ultrafine fiber, and the ultrafine fiber has an average single fiber diameter of 0.1 um or more and 10 um or less. When the average single fiber diameter of the ultrafine fiber is 0.1 um or more, preferably 1.5 um or more, an excellent effect of coloring property after dyeing, light resistance, fastness to rubbing, and stability during spinning is exhibited, and strength of the artificial leather that withstands practical use can be obtained. On the other hand, when the average single fiber diameter is 10.0 µm or less, preferably 6.0 µm or less, more preferably 4.5 µm or less, it is possible to obtain an artificial leather that has flexibility, and dense and soft-to-the-touch surface quality.
In the present invention, the average single fiber diameter of ultrafine fiber is calculated by taking a scanning electron microscope (SEM) photograph of a cross-section of the artificial leather, randomly selecting 10 ultrafine fibers having a circular shape or an elliptical shape close to a circular shape, measuring the single fiber diameters, calculating the arithmetic average of the 10 fibers, and rounding the arithmetic average off to the first decimal place. However, when ultrafine fibers having an irregular cross-section are used, first, the cross-sectional area of the single fiber is measured, and the diameter of a hypothetical circle on the assumption that the cross-section was circular is calculated to obtain the diameter of the single fiber.
As the ultrafine fiber of the fiber entanglement constituting the artificial leather of the present invention, various synthetic fibers including polyesters such as polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polycyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalenedicarboxylate, and polyethylene-1,2-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, polyamides such as polyamide 6 and polyamide 66, polymers such as acrylic polyethylene and polypropylene, and the like can be used. Among these, polyester fibers formed of polymers such as polyethylene terephthalate, polybutylene terephthalate and polytrimethylene terephthalate, and the like are excellent in strength, dimensional stability, light resistance and coloring properties and are thus preferably used. Ultrafine fibers formed of different materials can be mixed in the fiber entanglement as long as the object of the present invention is not impaired.
The cross-sectional shape of the ultrafine fiber is circular from the viewpoint of processing operability, and it is also possible to employ ultrafine fibers having a modified cross-sectional shape such as an ellipse, polygons such as a flattened polygon and a triangle, a fan shape, a cross shape, a hollow shape, a Y-shape, a T-shape, and a U-shape.
Inorganic particles such as titanium oxide particles, a lubricant, a pigment, a thermal stabilizer, a UV absorber, a conductive agent, a heat storage agent, an antibacterial agent, and the like can be added to the ultrafine fibers forming the fiber entanglement according to various purposes.
In order to achieve excellent deep color developability in the present invention, a resin constituting the ultrafine fiber may be a polyester-based resin, and the polyester-based resin may contain a pigment having an average particle diameter of 0.05 µm or more and 0.20 µm or less. The particle diameter referred to herein is a particle diameter in a state in which the pigment is present in the ultrafine fiber, and generally refers to a particle diameter referred to as a secondary particle diameter. When the average particle diameter is 0.05 µm or more, preferably 0.07 µm or more, the pigment is gripped inside the ultrafine fiber, and therefore, falling off from the ultrafine fiber is suppressed. When the average particle diameter is 0.20 um or less, preferably 0.18 um or less, more preferably 0.16 um or less, stability during spinning and yarn strength are excellent. The average particle diameter is calculated by the following method.

(1) An ultrathin slice having a thickness of 5 to 10 um is prepared in a cross-sectional direction of a plane perpendicular to a longitudinal direction of the ultrafine fiber.
(2) A fiber cross section in the ultrathin slice is observed with a transmission electron microscope (TEM) at a magnification of 10,000.
(3) Using image analysis software, an equivalent circle diameter of the particle diameter of the pigment contained in a visual field of 2.3 um × 2.3 um of an observation image is measured at 20 points. When the number of pigment particles contained in the visual field of 2.3 um × 2.3 um is less than 20, the equivalent circle diameter of the particle diameter of the existing pigment is all measured.
(4) An average value (arithmetic average) is calculated for the particle diameters at the measured 20 points.

In order to achieve excellent deep color developability in the present invention, when the resin constituting the ultrafine fiber is a polyester-based resin and a pigment is contained in the polyester-based resin, the content of the pigment contained in the polyester-based resin forming the ultrafine fiber is preferably 0.5% by mass or more and 2.0% by mass or less with respect to the mass of the ultrafine fiber. When the proportion of the pigment is 0.5% by mass or more, preferably 0.7% by mass or more, and more preferably 0.9% by mass or more, the deep color developability is excellent. When the proportion of the pigment is 2.0% by mass or less, preferably 1.8% by mass or less, and more preferably 1.6% by mass or less, an artificial leather having high physical properties such as strength can be obtained. As the pigment, carbon-based black pigments such as carbon black and graphite, and oxide-based black pigments such as triiron tetraoxide and composite oxides of copper and chromium can be used. The pigment is preferably carbon black from the viewpoint of easily obtaining a pigment having a small particle diameter and excellent dispersibility in a polymer. As a chromatic fine-particle oxide pigment, a known pigment close to the target color can be used, and examples thereof include iron oxyhydroxide (e.g., "TM Yellow 8170" produced by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), iron oxide (e.g., "TM Red 8270" produced by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and cobalt aluminate (e.g., "TM Blue 3490E" produced by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).
In the artificial leather of the present invention, a fiber entanglement including the ultrafine fiber is one of constituent elements. Examples of the fiber entanglement include a woven fabric, a knitted fabric, and a nonwoven fabric, and the fiber entanglement further includes an elastomer inside or outside, and these may be properly used depending on the cost and properties required for each application and purpose. Woven and knitted fabrics are preferably used from the viewpoint of cost, and nonwoven fabrics, fiber entanglements filled with an elastomer, and the like are preferably used from the viewpoint of texture with a sense of fulfillment and quality due to fine naps.
In the case of using a woven/knitted fabric as the fiber entanglement, examples of the woven fabric include plain woven fabrics, twill woven fabrics, satin woven fabrics, and various woven fabrics based on these weave structures. As the knitted fabric, any of warp knitted fabrics, weft knitted fabrics represented by tricot knit fabrics, lace knit fabrics, and various knitted fabrics based on these knitting structures may be adopted.
In the case of using a nonwoven fabric as the fiber entanglement, all nonwoven fabrics described in various categories may be applied, such as general short fiber nonwoven fabrics, long fiber nonwoven fabrics, needle punch nonwoven fabrics, papermaking nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, and electrospun nonwoven fabrics. Here, a nonwoven fabric is preferable from the viewpoint of the texture with a sense of fulfillment and the quality due to fine naps.
The inclusion of the elastomer inside or outside the fiber entanglement is more preferably used from the viewpoint of excellent durability and abrasion resistance of the artificial leather. In particular, it is preferable that the elastomer is contained in the fiber entanglement from the viewpoint of flexibility.
In addition, in the artificial leather of the present invention, it is preferable to integrate the fiber entanglement and a woven/knitted fabric (a) by entanglement from the viewpoint of excellent mechanical strength. More preferably, the fiber entanglement is a nonwoven fabric, and the woven/knitted fabric (a) is contained therein. Still more preferably, a balance of appearance, flexibility, and strength is optimized when the fiber entanglement is a nonwoven fabric and the woven/knitted fabric (a) is a woven fabric.
In the woven/knitted fabric (a) integrated with the fiber entanglement, as the yarn that constitutes the woven/knitted fabric (a), synthetic fibers formed of polyester, polyamide, polyethylene, polypropylene, copolymers thereof, or the like are preferably used. Among these, synthetic fibers formed of polyester, polyamide and copolymers thereof may be used singly or in combination or in mixture. As the yarn that constitutes the woven/knitted fabric (a), filament yarns, spun yarns, blended yarns of filaments and short fibers, and the like may be used. From the viewpoint of durability, particularly mechanical strength and the like, it is more preferable to use a multifilament including a polyester-based resin or a polyamide-based resin.
When the average single fiber diameter of the fibers that constitute the woven/knitted fabric (a) is 50.0 µm or less, more preferably 15.0 µm or less, and still more preferably 13.0 µm or less, not only an artificial leather excellent in flexibility is obtained, but also even when the fibers of the woven/knitted fabric are exposed on the surface of the artificial leather, a hue difference from the ultrafine fiber containing the pigment after dyeing is reduced, so that uniformity of a hue of the surface is not impaired. On the other hand, when the average single fiber diameter of the fibers that constitute the woven/knitted fabric (a) is 1.0 µm or more, more preferably 8.0 µm or more, and still more preferably 9.0 µm or more, shape stability of a product as an artificial leather is improved. The average single fiber diameter of the fibers that constitute the woven/knitted fabric (a) is calculated by taking a scanning electron microscope (SEM) photograph of the cross-section of the artificial leather, randomly selecting 10 fibers constituting the woven fabric, measuring the single fiber diameter of the fiber, calculating the arithmetic average of the 10 fibers, and rounding the arithmetic average off to the first decimal place. When the fibers that constitute the woven/knitted fabric (a) are multifilaments, a total fineness of the multifilaments is measured according to "8.3.1 Fineness based on corrected mass b) Method B (simple method)" in "8.3 Fineness" in JIS L 1013: 2010 "Chemical fiber filament yarn test method", and is preferably 30 dtex or more and 170 dtex or less. When the total fineness of the yarns that constitute the woven/knitted fabric (a) is 170 dtex or less, an artificial leather excellent in flexibility is obtained. On the other hand, when the total fineness is 30 dtex or more, not only the shape stability of a product as the artificial leather is improved, but also when the fiber entanglement is a nonwoven fabric, the fibers that constitute the woven/knitted fabric (a) are less likely to be exposed on the surface of the artificial leather when the woven/knitted fabric (a) is integrated by entanglement by needle punching or the like, which is preferable. When the woven/knitted fabric (a) is a woven fabric, the multifilaments of the warp and the weft preferably have the same total fineness. In addition, the yarns constituting the woven fabric preferably have a twist count of 1000 T/m or more and 4000 T/m or less. When the twist count is 4000 T/m or less, more preferably 3500 T/m or less, and still more preferably 3000 T/m or less, an artificial leather excellent in flexibility is obtained. When the twist count is 1000 T/m or more, more preferably 1500 T/m or more, and still more preferably 2000 T/m or more, in a case where a nonwoven fabric and a woven fabric are integrated by entanglement by needle punching or the like, damage to fibers constituting the woven fabric can be prevented, and the mechanical strength of the artificial leather is excellent, which is preferable.
As the woven/knitted fabric (a), a woven/knitted fabric containing a composite fiber (hereinafter, described as a side-by-side composite fiber in some cases) in which two or more kinds of polymers are combined in a side-by-side or eccentric sheath-core type may also be used. For example, in a side-by-side composite fiber formed of two or more kinds of polymers having different intrinsic viscosities (IV), different internal strains are generated between the two components by stress concentration on the high viscosity side during stretching. Because of this internal strain, the high viscosity side shrinks greatly by the difference in elastic recovery after stretching and the difference in thermal shrinkage in the heat treatment process, and strain is generated in the single fiber to develop a three-dimensional coil type crimp. By this three-dimensional coil type crimp, stretchability as artificial leather is developed.
When the fiber entanglement is a nonwoven fabric, a nonwoven fabric can provide an appearance and a texture that are uniform and elegant when the surface of the nonwoven fabric is napped. Examples of the form of the nonwoven fabric include a long fiber nonwoven fabric mainly composed of filaments and a short fiber nonwoven fabric mainly composed of fibers of 100 mm or less. When the long fiber nonwoven fabric is used as a fibrous substrate, an artificial leather having excellent strength can be obtained, which is preferable. On the other hand, in the case of the short fiber nonwoven fabric, the number of fibers oriented in the thickness direction of the artificial leather can be increased as compared with the case of the long fiber nonwoven fabric, and the surface of the artificial leather when napped can have a high dense feeling.
The fiber length of the ultrafine fibers in the case where a short fiber nonwoven fabric is used is preferably 25 mm or more and 90 mm or less. When the fiber length is 90 mm or less, more preferably 80 mm or less, and still more preferably 70 mm or less, good quality and texture are obtained. On the other hand, when the fiber length is 25 mm or more, more preferably 35 mm or more, and still more preferably 40 mm or more, an artificial leather with excellent abrasion resistance can be obtained.
The basis weight of the fiber entanglement including the ultrafine fiber that constitutes the artificial leather according to the present invention is measured according to "6.2 Mass per Unit Area (ISO method)" in "Test methods for nonwovens" of JIS L 1913: 2010, and is preferably in a range of 50 g/m² or more and 600 g/m² or less. When the basis weight of the nonwoven fabric is 50 g/m² or more, more preferably 100 g/m² or more, an artificial leather having a sense of fulfillment and an excellent texture can be obtained. On the other hand, when the basis weight is 600 g/m² or less, more preferably 450 g/m² or less, a soft artificial leather having excellent moldability can be obtained. Even when the woven/knitted fabric (a) is integrated by entanglement, the basis weight of the fiber entanglement is preferably in the above-described basis weight range.

[Elastomer]

Next, the artificial leather of the present invention has an elastomer. Preferably, the elastomer is contained in the fiber entanglement. By including the elastomer inside, the softness, shape stability, and abrasion resistance of the artificial leather are improved. Unlike a functional agent (flame retardant or the like) to be described later, the elastomer is required to have a purpose as a binder of the fiber entanglement.
As the elastomer, polyurethane, styrene-butadiene rubber (SBR), nitrile rubber (NBR), acrylic resin, and the like may be used, and it is a preferred aspect to use polyurethane as the main component among these. Use of polyurethane can afford an artificial leather having touch having feels like natural suede, an elegant appearance, and physical properties enough to endure actual use.
The polyurethane forming the elastomer preferably contains a black pigment (b) having an average particle diameter of 0.05 um or more and 0.20 um or less and a coefficient of variation (CV) of 75% or less.
The particle diameter referred to herein is a particle diameter in a state in which the black pigment (b) is present in the elastomer, and generally refers to a particle diameter referred to as a secondary particle diameter.
When the average particle diameter is 0.05 µm or more, preferably 0.07 µm or more, the black pigment (b) is gripped inside the elastomer, and therefore, falling off from the ultrafine fiber is suppressed. When the average particle diameter is 0.20 µm or less, preferably 0.18 um or less, more preferably 0.16 µm or less, dispersibility is excellent when the elastomer is impregnated.
When the coefficient of variation (CV) of the particle diameter is 75% or less, preferably 65% or less, more preferably 60% or less, still more preferably 55% or less, and most preferably 50% or less, a distribution of the particle diameter becomes small, and falling off of small particles from a surface of the elastomer, precipitation of significantly aggregated particles in an impregnation tank, and the like are suppressed.
In the present invention, the average particle diameter and the coefficient of variation (CV) are calculated by the following method.

(1) An ultrathin slice having a thickness of 5 to 10 um is prepared in a cross-sectional direction of a plane perpendicular to a longitudinal direction of the artificial leather.
(2) A cross section of the elastomer in the ultrathin slice is observed with a transmission electron microscope (TEM) at a magnification of 10,000.
(3) Using image analysis software, an equivalent circle diameter of the particle diameter of the black pigment (b) contained in a visual field of 2.3 µm × 2.3 µm of an observation image is measured at 20 points. When the number of particles of the black pigment (b) contained in the visual field of 2.3 µm × 2.3 µm is less than 20, the equivalent circle diameter of the particle diameter of the existing black pigment (b) is all measured.
(4) The average value (arithmetic average) and the coefficient of variation (CV) are calculated for the particle diameters at the measured 20 points. In the present invention, the coefficient of variation is calculated by the following equation: $\begin{array}{l} Coefficient of variation of particle diameter (%) = \\ (standard deviation of particle diameter) / (\begin{array}{l} arithmetic \\ average of particle diameter \end{array}) \times 100 . \end{array}$

As the black pigment (b) in the present invention, carbon-based black pigments such as carbon black and graphite, and oxide-based black pigments such as triiron tetraoxide and composite oxides of copper and chromium can be used. The black pigment is preferably carbon black from the viewpoint of easily obtaining a pigment having a small particle diameter and excellent dispersibility in a polymer.
As the polyurethane used in the present invention, either organic solvent-based polyurethane used in the state of being dissolved in an organic solvent or water-dispersible polyurethane used in the state of being dispersed in water can be used. Polyurethane obtained by reaction of a polymer diol, an organic diisocyanate, and a chain extender is preferably used as polyurethane to be used for the present invention.
For example, a polycarbonate-based diol, polyester-based diol, polyether-based diol, silicone-based diol, or fluorine-based diol can be used as the aforementioned polymer diol, and a copolymer of a combination of these diols can also be used. Among them, it is a preferred aspect to use a polycarbonate-based diol from the viewpoint of hydrolysis resistance and abrasion resistance.
A polycarbonate-based diol as described above can be produced, for example, through ester exchange reaction between alkylene glycol and ester carbonate or through reaction of phosgene or a chloroformate with alkylene glycol.
Examples of the alkylene glycol 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, aromatic diols such as bisphenol A, and glycerin, trimethylolpropane, and pentaerythritol. In the present invention, either a polycarbonate-based diol obtained from a single alkylene glycol or a copolymerized polycarbonate-based diol obtained from two or more alkylene glycols can be adopted.
Examples of the polyester-based diols include polyester diols produced by condensing one of various low molecular weight polyols and a polybasic acid.
For example, one or a plurality selected from the following can be used as the low molecular weight polyol described above: ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butane diol, 1,4-butane diol, 2,2-dimethyl-1,3-propane diol, 1,6-hexane diol, 3-methyl-1,5-pentane diol, 1,8-octane diol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol.
Adducts prepared by adding various alkylene oxides to bisphenol A are also usable.
Furthermore, for example, one or a plurality selected from the following can be used as the polybasic acid: succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecane dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydroisophthalic acid.
Examples of the polyether-based diols used in the present invention include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymerized diols which are formed by combining these substances.
The number average molecular weight of the polymer diol is preferably in a range of 500 or more and 4000 or less when the molecular weight of a polyurethane-based elastomer is constant. When the number average molecular weight is preferably 500 or more, more preferably 1,500 or more, it is possible to prevent the artificial leather from becoming hard. When the number average molecular weight is 4000 or less, or more preferably 3000 or less, the polyurethane can maintain its strength.
Examples of the organic diisocyanate used in the present invention include aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate, and aromatic diisocyanates such as diphenylmethane diisocyanate and tolylene diisocyanate. These compounds can also be used in combination.
As the chain extender, amine chain extenders such as ethylenediamine and methylenebisaniline, and diol chain extenders such as ethylene glycol can be preferably used. Furthermore, a polyamine which is obtained by reacting polyisocyanate and water can also be used as a chain extender.
The polyurethane used in the present invention may be used in combination with a crosslinker with the aim of improving waterproofness, abrasion resistance, hydrolysis resistance, and the like. The crosslinker may be an external crosslinker that is added as a third component to polyurethane, or an internal crosslinker that introduces reaction points to form a crosslinked structure in advance into the polyurethane molecular structure. It is preferable to use an internal crosslinker from the viewpoint that crosslinking points can be formed more uniformly in the polyurethane molecular structure and that the decrease in flexibility can be mitigated.
The crosslinking agent used may be a compound having an isocyanate group, an oxazoline group, a carbodiimide group, an epoxy group, a melamine resin, a silanol group and the like.
The elastomer may contain various additives including flame retardants such as "phosphorus, halogen, and inorganic flame retardants"; antioxidants such as "phenolic, sulfur, and phosphorus antioxidants"; ultraviolet absorbers such as "benzotriazole, benzophenone, salicylate, cyanoacrylate, and oxalic acid anilide UV absorbers"; light stabilizers such as "hindered amine and benzoate light stabilizers"; hydrolysis stabilizers such as polycarbodiimide; plasticizers; antistatic agents; surfactants; coagulation modifiers; and dyes according to purposes.
In general, the content of the elastomer in the artificial leather can be appropriately adjusted in consideration of the type of the elastomer to be used, a production method for the elastomer, and the texture and physical properties; however, in the present invention, the content of the elastomer is preferably 10% by mass or more and 60% by mass or less with respect to the mass of the fiber entanglement. When the content of the elastomer is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, the bonding between the fibers by the elastomer can be enhanced, and the abrasion resistance of the artificial leather can be improved. On the other hand, when the content of the elastomer is preferably 60% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less, the flexibility of the artificial leather can be further increased.
According to a preferred aspect of the artificial leather of the present invention, the density of the fiber entanglement including the elastomer, that is, the density of the fiber entanglement with the elastomer (the density of the woven/knitted fabric (b) described later and the artificial leather containing no flame retardant) is preferably 0.20 g/cm³ or more and 0.50 g/cm³ or less. When the density is 0.20 g/cm³ or more, preferably 0.25 cm³, the shape stability, dimensional stability, and strength of the artificial leather become sufficient. In addition, the artificial leather becomes dense, and the opening portion becomes a clean opening portion without fraying or the like. On the other hand, when the density is 0.50 g/cm³ or less, preferably 0.45 g/cm³ or less, the air permeability and flexibility of the artificial leather are improved.

[Functional agent (flame retardant or the like)]

The functional agent used in the present invention refers to an agent that imparts functionality such as flame retardancy, antifouling properties, yellowing resistance, NOx resistance, grip properties, water repellency, oil repellency, color migration resistance, abrasion resistance, odor resistance, durability, flexibility, and stretchability to a fibrous product. The functional agent (flame retardant or the like) used for the artificial leather of the present invention has tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less. When the tackiness of the functional agent (flame retardant or the like) is 0.10 N/cm² or more, preferably 0.15 N/cm² or more, and more preferably 0.20 N/cm² or more, the functional agent (flame retardant or the like) is secured to the fiber entanglement with sufficient adhesiveness during application and drying of the functional agent (flame retardant or the like), and the functional agent (flame retardant or the like) after drying does not fall off even in a high-temperature environment. When the tackiness is 2.00 N/cm² or less, preferably 1.60 N/cm² or less, and more preferably 1.00 N/cm² or less, after the formation of the opening, the fiber dusts composed of the fiber, the elastomer, and the functional agent (flame retardant or the like) are not clogged in the opening, and the formability of the opening portion is improved, and when the formation of the opening portion is punching, continuous processing can be performed without clogging the needle hole. In addition, a structure in which the functional agent (flame retardant or the like) is uniformly dispersed and bonded is obtained, and the texture of the artificial leather becomes flexible. In the present invention, the tackiness of the functional agent (flame retardant or the like) is a value obtained by measurement and calculation as follows.

(1) A functional agent (flame retardant or the like) is heated to 60°C.
(2) Using a tack meter, a stainless steel probe (contact pressure 24.5 N/cm²) is pressed against the functional agent (flame retardant or the like) at a speed of 6 mm/min, and held for 5 seconds.
(3) After (2), a maximum load at the time of peeling at 6 mm/min is read.
(4) (2) to (3) are repeated five times, and the arithmetic average of the resulting values is rounded off to the second decimal place.

In order to stably obtain the adhesiveness, opening properties, and softness even when there is a temperature change, the tackiness when the functional agent (flame retardant or the like) is heated to 40°C is preferably 0.05 N/cm² or more and 1.00 N/cm² or less, and the tackiness at 20°C is preferably 0.01 N/cm² or more and 0.50 N/cm² or less. In particular, the tackiness at 20°C is preferable when the stickiness of the surface of the functional surface (surface of the flame retardant or the like) is small as handleability such as molding or sewing of an artificial leather sheet at room temperature. When the tackiness of the functional agent is within the above range, resistance is reduced when the artificial leather is unwound from the roll shape, and the handleability of the artificial leather is improved in the work of the next step. When the functional agent (flame retardant or the like) is heated to 40°C or 20°C, the tackiness is measured in the same manner as described above except that the heating temperature in (1) is changed to 40°C or 20°C.
Although the functional agent (flame retardant or the like) may be a resin itself composed of a polymer compound having an active functional group, in addition to a low molecular compound having a functional component (flame retardant component or the like), it is preferable to contain a resin in order to obtain durability of functionality, and the resin is selected from, for example, an acrylic resin, a urethane resin, a polyester resin, a vinyl acetate resin, and the like, is not particularly limited, and is preferably an acrylic resin having a good balance from the viewpoint of adhesiveness to a fiber entanglement and a woven/knitted fabric, heat resistance, and adhesiveness. An amount of the binder resin to be blended is not limited to a specific value, and is preferably in a range of 5 to 50% by mass with respect to a total mass of the functional component (flame retardant component or the like) contained in the functional agent (flame retardant or the like). When the blending amount is 5% by mass or less, the flame retardant is likely to cause falling off of a powder component, and when the blending amount exceeds 50% by mass, the texture of the artificial leather may be impaired. From the viewpoint of the tackiness, for example, a resin having low rubber elasticity is preferably used. For example, regarding the acrylic resin, an acrylamide-based acrylic resin is more preferable than an acrylonitrile-based acrylic resin because the tackiness is better. In general, many resins have a hard texture, and the texture can be softened by reducing the blending amount of the resin. When an ethylene-vinyl acetate resin having high adhesiveness is used, the adhesiveness and the tackiness are enhanced even in a small amount; therefore, when it is desired to reduce the blending amount of the resin, it is preferable to contain ethylene-vinyl acetate.
When the functional agent is a flame retardant and a combustion mode is a carbonization type, as the resin of the flame retardant, other resins such as acrylic resins, SBR resins, and MBR resins may also be used, provided they do not affect the carbide formation of vinyl acetate, vinyl acetate copolymer resins, or the like. In particular, if the flame retardant is made to further include an acrylic resin, the advantages of softened texture and improved water resistance of the flame retardant are obtained.
The type of the flame retardant component of the flame retardant is not particularly limited, and the flame retardant component is preferably water-insoluble or sparingly water-soluble from the viewpoint of water spot. The "water spot" as used herein refers to a phenomenon in which, in the artificial leather to which a flame retardant is added, when moisture typified by water droplets adheres from either side of the front and back surfaces and the artificial leather is then naturally dried, the wet portion becomes a white spot or stain. From the viewpoint of adapting to recent environmental hormone regulations, it is preferable to use a dehalogenated flame retardant. Examples of the dehalogenated flame retardant include phosphorus-containing compounds, nitrogen-containing compounds, phosphorus-nitrogen compounds, sulfoamide-based compounds, phosphorus-sulfoamide-based compounds, and sulfur-containing nitrogen-based compounds, and these can be used alone or in combination of two or more thereof. From the viewpoint of the flame retardant performance, a phosphorus-based compound is preferable, and examples of the phosphorus-based compound include guanidine-based compounds, carbamate-based compounds, phosphate ester-based compounds, phosphate ester-amide-based compounds, ammonium polyphosphate compounds, and aromatic phosphate ester-based compounds such as triphenyl phosphate and trixylenyl phosphate. Particularly, an ammonium polyphosphate flame retardant having a high phosphorus content is preferable, and a type covered with a melamine resin or a silicon oxide resin is preferable for further making the flame retardant sparingly water-soluble. As the inorganic flame retardant, known flame retardants such as aluminum hydroxide, titanium oxide, zinc oxide, expandable graphite, magnesium hydroxide, calcium carbonate, zinc borate, ammonium polyphosphate, and red phosphorus can be used, and it is preferable to use a polyphosphate-based flame retardant excellent in processability and durability.
As the combustion mode of the flame retardant, there are a carbonization type for forming a carbonized film and a melting type for dropping a fire source, and although any mode is not limited, the melting type is preferable from the viewpoint of flame retardant stability in flame retardant evaluation in the case of sufficient flame retardancy.
In the artificial leather of the present invention, in the evaluation of the flame retardancy, based on burning test standard (horizontal burning rate) of automobile interior material of Federal Motor Vehicle Safety Standards (FMVSS) No. 302, a test piece (350 mm × 100 mm) is held horizontally, a 38 mm flame is allowed to remain for 15 seconds, and the flame retardancy is evaluated by a burning rate with respect to 254 mm between a gauge line A and a gauge line B according to the following criteria.

In the case where the flame self-extinguishes before reaching the gauge line A, a judgment classification is "non-combustible", and the product is judged as acceptable.
In the case where the flame self-extinguishes after the gauge line A, and the burning distance is within 50 mm and the burning time was within 60 seconds, the judgment classification is "self-extinguished", and the product is judged as acceptable.
In the case where the flame does not self-extinguish but the burning rate between the gauge lines is 4 inches/min (about 101.6 mm/min) or less, the judgment classification is "burning at rate not more than specified rate", and the product is judged as acceptable.
In the case where the flame does not self-extinguish and the burning rate between the gauge lines exceeds 4 inches/min (about 101.6 mm/min), the judgment classification is "burning at rate exceeding specified rate", and the composite sheet product is judged as unacceptable.

For example, when a carbonization type agent such as an antifouling agent is applied to the artificial leather, since the flame retardant is of the carbonization type, the carbonization amount increases, the flame retardancy improves, and the combustion mode can be selected according to the material configuration of the artificial leather. When the carbonization type is selected for the flame retardant, by selecting a resin that is easily carbonized for the resin of the flame retardant, the above-described flame retardant component can be reduced, which is preferable from the viewpoint of cost. For example, there is a vinyl group-containing resin that forms a carbonized skeleton during combustion.
It is preferable that the vinyl group-containing resin contains at least one selected from a vinyl acetate resin, an ethylene-vinyl acetate copolymer resin, an acrylic vinyl acetate copolymer resin, a vinyl acetate vinyl copolymer resin, and a branched fatty acid vinyl acetate copolymer resin, since the formation of a carbide by using the vinyl acetate resin or the vinyl acetate copolymer resin in combination with a phosphorus-based compound promotes flame retardancy, and particularly exhibits an effect of improving flame retardant properties for horizontal burning of the artificial leather.
An adhesion amount of the flame retardant is required to be determined from the viewpoint of securing necessary flame retardant performance and reducing texture curing, and increases or decreases depending on the basis weight, thickness, and ultrafine fiber of the artificial leather, the polymer type of the elastomer, and the fiber entanglement type; however, it is preferable to contain the flame retardant in an amount of 2 to 30% by mass with respect to the artificial leather from the viewpoint of achieving both the flame retardancy and the texture. An application amount of the flame retardant is preferably 10 to 200 g/m², and more preferably within a range of 20 to 100 g/m². Although the adhesion amount of the flame retardant can be calculated by, for example, mass after application - mass after application, when the adhesion amount is calculated from the artificial leather after application, the adhesion amount can also be calculated using elemental peak analysis such as fluorescent X-rays.
As a solution used for applying the flame retardant to the artificial leather, it is preferable that the viscosity is 500 to 10000 mPa·s at normal temperature from the viewpoint of coating permeability, and a viscosity modifier may be contained as necessary. The viscosity is more preferably 1500 to 9000 mPa-s, and still more preferably 2500 to 7000 mPa·s. In this way, a presence ratio of the flame retardant described later in the thickness direction falls within a suitable range, and an artificial leather that is more flexible and has high flame retardancy can be obtained. The method for measuring the viscosity of the solution is not particularly limited, but a measurement method using a commonly used rotational viscometer is used. The viscosity modifier used for adjusting the viscosity of the solution is preferably poorly soluble in water from the viewpoint of preventing occurrence of water spot, and is preferably, for example, an alkali-thickened acrylic resin or an ethylene oxide higher fatty acid ether.
In the present invention, in addition to the components described above, aluminum hydroxide, magnesium hydroxide, a metal oxide, and the like can also be used as a flame retardant aid for the flame retardant.
The adhesion amount of the functional agent (flame retardant or the like) is required to be determined from the viewpoint of securing necessary functional performance and reducing texture curing, and the opening properties of the artificial leather backing material, and increases or decreases depending on the basis weight, thickness, and ultrafine fiber of the artificial leather, the polymer type of the elastomer, and the fiber entanglement type; however, it is preferable to contain the functional agent in an amount of 2 to 30% by mass with respect to the artificial leather from the viewpoint of satisfying the above characteristics. An application amount of the functional agent (flame retardant or the like) is preferably 10 to 200 g/m², and more preferably within a range of 20 to 100 g/m².

[Woven/knitted fabric (b)]

In the artificial leather of the present invention, the functional surface (surface of flame retardant or the like) is preferably a surface formed by stacking the woven/knitted fabric (b). That is, by adopting an aspect in which the woven/knitted fabric (b) is further stacked to the fiber entanglement on the functional surface (surface of flame retardant or the like) side opposite to the napped surface of the artificial leather, the artificial leather has more strength and also has flexibility. In this case, the fiber entanglement may include the woven/knitted fabric (a) as described above, and a suitable woven/knitted fabric can be selected according to the purpose of each of the woven/knitted fabric (a) and the woven/knitted fabric (b).
As for the kind of the woven/knitted fabric (b) used in the present invention, it is possible to use any of various kinds of knitted fabrics such as warp knitted fabrics and weft knitted fabrics typified by tricot knitted fabrics, lace knitted fabrics, and knitted fabrics based on these knitting methods, and various kinds of woven fabrics such as plain weave fabrics, twill weave fabrics, satin weave fabrics, and woven fabrics based on these weaving methods. In a preferred aspect, a knitted fabric having high air permeability and high stretchability is used as the woven/knitted fabric (b).
As for the kind of the yarn that constitutes the woven/knitted fabric (b), for example, a filament yarn, a spun yarn, or a blended yarn of a filament yarn and short fibers can be used.
The density of the woven/knitted fabric (b) is preferably 0.10 g/cm³ or more and 0.60 g/cm³ or less. When the density of the woven/knitted fabric (b) is 0.10 g/cm³ or more, more preferably 0.15 g/cm³ or more, an artificial leather having good shape retention can be obtained. On the other hand, when the density of the woven/knitted fabric (b) is 0.60 g/cm³ or less, more preferably 0.50 g/cm³ or less, the functional agent (flame retardant or the like) can be penetrated to the inside, and an artificial leather excellent in flexibility can be obtained.
The thickness of the woven/knitted fabric (b) is preferably 0.10 to 2.50 mm, more preferably 0.15 to 1.50 mm, and still more preferably 0.20 to 1.00 mm. If the thickness of the woven/knitted fabric (b) is less than 0.10 mm, the processability and strength at the time of sticking with the fiber entanglement are deteriorated, and if the thickness exceeds 2.50 mm, the flexibility of the air permeability tends to be impaired.
The method of stacking the fiber entanglement and the woven/knitted fabric (b) is not limited, and a method of bonding the fiber entanglement and the woven/knitted fabric (b) with an adhesive interposed therebetween is common. Examples of the adhesive include thermoplastic resins such as a polyester resin, a copolymerized polyester resin, a nylon resin, and an acrylic resin, and moisture-curable resins such as a silicone rubber, a polystyrene rubber, and a polyurethane resin. A thermoplastic resin excellent in workability is preferably used and, in particular, a nylon resin excellent in hydrolysis resistance is preferably used. In the artificial leather including the ultrafine fiber, a moisture-curable resin capable of being processed with a low thermal history is preferable from the viewpoint of improving rubbing fastness.
A thickness of an adhesive layer is preferably 1 to 300 um as long as the adhesive layer has sufficient bondability and does not impair the flexibility and air permeability of the artificial leather.
In the case where a thermoplastic resin is used as the adhesive, the softening temperature of the thermoplastic resin is preferably 70 to 160°C, more preferably 80 to 120°C. If the softening temperature is lower than 70°C, the thermoplastic resin may be softened during the processing or actual use. If the softening temperature is higher than 160°C, the texture of the artificial leather and the rubbing fastness may be impaired by the softening treatment at the time of sticking.

[Artificial leather]

The artificial leather of the present invention includes the fiber entanglement and the elastomer, and one surface is a napped surface having a raised nap, and the other surface is a flame retardant surface having the flame retardant.
First, in the artificial leather of the present invention, one surface is the napped surface having the raised nap. That is, the raised nap may be provided only on the surface to be a product surface of the artificial leather, and is also allowed to be provided on both surfaces. As for the form of raised nap in the case where the artificial leather has raised nap on the surface to be the product surface, the raised nap preferably has a length and direction flexibility to such an extent that traces remain when the artificial leather is stroked with a finger, that is, a so-called finger mark remain due to the change of direction of the raised nap from the viewpoint of design effects. Examples of the form having raised nap on the other surface (back surface) with respect to the product surface of the artificial leather include imparting a flame retardant after forming raised nap on the back surface of the fiber entanglement. When the woven/knitted fabric (b) is stacked on the back surface of the fiber entanglement, the front and back surfaces of the fiber entanglement are napped, and the flame retardant is added to the surface of the stacked woven/knitted fabric (b), so that the flame retardant is present in the napped portion of the back surface of the fiber entanglement, and the flame retardant surface has raised nap.
More specifically, when the surface to be the product surface is the napped surface, the raised napped length on the surface is preferably 50 um or more and 500 um or less, and more preferably 100 um or more and 450 um or less. When the raised nap length is 50 um or more, the raised nap covers the elastomer, and the exposure of the elastomer on the product surface of the artificial leather is suppressed, so that an elegant appearance can be obtained. When the woven/knitted fabric (a) is entangled and integrated with the fiber entanglement constituting the artificial leather, or when the fiber entanglement itself includes a woven/knitted fabric, setting the raised nap length within the above range can sufficiently cover a tissue of the woven/knitted fabric in the vicinity of the product surface of the artificial leather, which is preferable in that a naturally-like and elegant appearance can be obtained. On the other hand, when the raised nap length is 500 um or less, an artificial leather excellent in design effect and abrasion resistance can be obtained.
In the present invention, the raised nap length of the artificial leather is calculated by the following method.

(1) A thin slice with a thickness of 1 mm in the cross-sectional direction of a plane perpendicular to the longitudinal direction of the artificial leather is prepared in the state of the raised nap of the artificial leather being ruffled by using a lint brush, etc.
(2) A cross-section of the artificial leather is observed at 90-fold magnification by means of a scanning electron microscope (SEM).
(3) In an SEM image photographed, the height of a raised nap portion (layer including only ultrafine fiber) is measured at 10 points at intervals of 200 um in the width direction of the cross-section of the artificial leather.
(4) With respect to the measured height of the raised nap portion (layer including only ultrafine fiber) at 10 points, the average value (arithmetic average) is calculated.

In the artificial leather of the present invention, it is important to have a plurality of opening portions in the functional surface (surface of flame retardant or the like). The "opening portion" in the present invention is not limited to a portion where a hole (through opening portion) formed by penetrating an artificial leather from the napped surface to the functional surface (surface of flame retardant or the like) is opened, and includes, for example, a case where the opening portion does not overlap the woven/knitted fabric (b) in a planar direction and is not the through opening portion. Examples of the latter include a form in which an opening portion is formed in advance in the woven/knitted fabric (b) containing the functional agent (flame retardant or the like) and the woven/knitted fabric (b) is stacked on the fiber entanglement. The shape of the opening portion can be any shape according to a desired design, and polygonal shapes such as a round shape, an elliptical shape, a flat shape, and a triangular shape, a fan shape, a cross shape, and deformed shapes such as a hollow shape, a Y shape, a T shape, and a U shape can be adopted. An arrangement pattern of the opening portion is not particularly limited, and the opening portion may be regularly provided or irregularly provided; however, from the viewpoint of exhibiting uniform air permeability and strength throughout the artificial leather, the opening portions are preferably regularly arranged at predetermined intervals. A hole diameter of the opening portion is preferably 0.1 to 3.0 mm and more preferably 0.5 to 2.5 mm from the viewpoint of achieving both air permeability and strength of the entire artificial leather.
In addition, in the artificial leather of the present invention, an opening ratio of the functional surface (surface of flame retardant or the like) is preferably 1% or more and 40% or less from the viewpoint of achieving both air permeability and strength of the entire artificial leather. That is, when the opening ratio is 1% or more, more preferably 2% or more, an artificial leather excellent in air permeability can be obtained. On the other hand, when the opening ratio is 40% or less, more preferably 20% or less, and still more preferably 150 or less, an artificial leather excellent in strength can be obtained.
The artificial leather of the present invention has a plurality of opening portions in each of the napped surface and the functional surface (surface of flame retardant or the like), and at least some of the opening portions are the through opening portions formed to penetrate from the napped surface to the functional surface (surface of flame retardant or the like). With this configuration, an artificial leather having more excellent air permeability can be obtained.
The shape of the through opening portion in the thickness direction may be, for example, a cylindrical through opening portion in which the hole diameters of the opening portion of the napped surface and the opening portion of the functional surface (surface of flame retardant or the like) are the same, or a mortar-shaped through opening portion in which the hole diameters of the opening portion of the napped surface and the opening portion of the functional surface (surface of flame retardant or the like) are different. That is, the shape of the through opening portion can be selected in consideration of the design and mechanical properties of the artificial leather.
In the artificial leather of the present invention, the presence ratio of the functional agent (flame retardant or the like) in the thickness direction preferably satisfies the following formula:
$0.001 \leq W / W_{0} \leq 0.7$
where W is the thickness (mm) from the functional surface (surface of flame retardant or the like) where the functional agent (flame retardant or the like) is present, and W₀ is the thickness (mm) of the entire artificial leather. When the presence ratio of the functional agent (flame retardant or the like) in the thickness direction is 0.001 or more, more preferably 0.01 or more, still more preferably 0.05 or more, an artificial leather excellent in functionality (flame retardancy or the like) can be obtained. On the other hand, when the presence ratio of the functional agent (flame retardant or the like) in the thickness direction is 0.7 or less, more preferably 0.5 or less, and still more preferably 0.3 or less, an artificial leather excellent in air permeability and flexibility can be obtained.
The presence ratio of the functional agent (flame retardant or the like) in the thickness direction is obtained by collecting and preparing three SEM measurement samples, randomly selecting five points in an observation image of each cross section, measuring W and W₀ at each point, and calculating W/W₀ using an arithmetic average value. When the functional agent (flame retardant or the like) cannot be specified from a normal SEM image, for example, calculation is performed using a method of determining a resin containing an element peak as the functional agent by SEM-EDX. For example, in the case of the flame retardant, calculation is performed using a method of determining a resin containing a phosphorus element peak as the flame retardant.
As a preferred form of the artificial leather, a form in which the woven/knitted fabric (b) is stacked on the fiber entanglement and the functional agent (flame retardant or the like) is unevenly distributed in the woven/knitted fabric (b) is preferable from the viewpoint of functionality (flame retardancy or the like).
As a preferable form of the functional surface (surface of flame retardant or the like) of the artificial leather, it is preferable that the functional agent (flame retardant or the like) is present on the surface of the functional surface (surface of flame retardant or the like), and an area ratio of the functional agent (flame retardant or the like) of the functional surface (surface of flame retardant or the like) is 10 to 100%. The area ratio is obtained by collecting and preparing three SEM measurement samples, randomly selecting five points in an observation image of 50 times of the surface of each functional surface (surface of flame retardant or the like), photographing a SEM image, binarizing the SEM image, and then performing calculation by using a value obtained by arithmetically averaging the area ratio in which the functional agent (flame retardant or the like) is present with respect to a total area obtained by excluding the opening portion from an image area of 50 times. When the area ratio is preferably 10% or more, more preferably 30% or more, an artificial leather excellent in functionality (flame retardancy or the like) and functional (flame retardant, etc.) stability can be obtained, and for example, when a polyurethane foam is laminated on the back surface of an artificial leather such as an interior material for vehicles, smoothness of the functional surface (surface of flame retardant or the like) increases, so that e peel strength with the polyurethane foam increases.
The artificial leather of the present invention preferably has a thickness of 0.2 mm or more and 2.5 mm or less as measured according to "6.1.1 A method" in "6.1 Thickness (ISO method)" in "Test methods for nonwovens" of JIS L 1913: 2010 When the thickness of the artificial leather is 0.2 mm or more, more preferably 0.3 mm or more, and still more preferably 0.4 mm or more, not only excellent processability at the time of production is obtained, but also a sense of fulfillment and excellent texture are obtained. On the other hand, when the thickness is 2.5 mm or less, more preferably 2.0 mm or less, and still more preferably 1.5 mm or less, a soft artificial leather having excellent moldability can be obtained.
In the artificial leather of the present invention, the rubbing fastness measured by a "9.1 friction tester type I (clock meter) method" according to JIS L 0849: 2013 "Test methods for color fastness to rubbing" and light fastness measured by a "7.2 Exposure method a) First exposure method" according to JIS L 0843: 2006 "Test method for color fastness to light of xenon arc lamp" are each preferably grade 3 or higher. When the rubbing fastness and the light fastness are grade 3 or higher, it is possible to prevent color loss and contamination of clothes and the like during actual use.
In the artificial leather of the present invention, the mass loss of the artificial leather after 20,000 times of abrasion under a pressing load of 12.0 kPa in an abrasion test measured in accordance with "8.19.5 Method E (Martindale method)" of "8.19 Abrasion strength and color change by rubbing" of JIS L 1096:2010 "Cloth experiment method of woven fabric and knitted fabric" is preferably 20 mg or less, more preferably 15 mg or less, still more preferably 10 mg or less. When the mass loss is 20 mg or less, fluff dropping during actual usage can be prevented.
In the artificial leather of the present invention, the tensile strength as measured in accordance with "6.3.1 Tensile strength and percentage elongation (ISO method)" in "Test methods for nonwovens" of JIS L 1913: 2010 is preferably from 20 to 400 N/cm in arbitrary measurement direction. When the tensile strength is 20 N/cm or more, more preferably 30 N/cm or more, and still more preferably 40 N/cm or more, the artificial leather is excellent in shape stability and durability, which is preferable. When the tensile strength is 400 N/cm or less, more preferably 300 N/cm or less, and still more preferably 250 N/cm or less, an artificial leather excellent in moldability is obtained.
The artificial leather of the present invention preferably has a stiffness of 30 to 150 mm as measured by a cantilever method in "8.21 Stiffness" of JIS L 1096:2010 "Cloth experiment method of woven fabric and knitted fabric", from the viewpoint of texture and flexibility, and more preferably 50 to 130 mm.
In the artificial leather of the present invention, the air permeability is preferably 1 to 400 cm³/cm²/sec, more preferably 20 to 300 cm³/cm²/sec, and still more preferably 70 to 250 cm³/cm²/sec in order to achieve both flame retardancy and air permeability in Method A (Frazier type method) of "8.26 Air permeability" of JIS L 1096: 2010 "Cloth experiment method of woven fabric and knitted fabric". In the present invention, the air permeability is greatly affected by the opening; however, when the fiber entanglement has air permeability, the fiber entanglement is better from the viewpoint of sweatiness and multiplication of bacteria. Therefore, the air permeability of the fiber entanglement having no opening portion is preferably 1 to 100 cm³/cm²/sec, more preferably 2 to 50 cm³/cm²/sec.
The basis weight of the artificial leather of the present invention is measured according to "6.2 Mass per Unit Area (ISO method)" in "Test methods for nonwovens" of JIS L 1913: 2010, and is preferably in a range of 50 g/m² or more and 800 g/m² or less. When the basis weight of the nonwoven fabric is 50 g/m² or more, more preferably 100 g/m² or more, still more preferably 150 g/m² or more, an artificial leather having a sense of fulfillment and an excellent texture can be obtained. On the other hand, when the basis weight is 800 g/m² or less, more preferably 600 g/m² or less, and still more preferably 500 g/m² or less, a soft artificial leather having excellent moldability can be obtained.
From the viewpoint of the texture and flexibility of the artificial leather after formation of the opening, the artificial leather backing material for producing the artificial leather having the opening portion according to the present invention preferably has a stiffness of 30 mm or more and 150 mm or less, more preferably 50 mm or more and 130 mm or less, as measured by the cantilever method in "8.21 Stiffness" of JIS L 1096: 2010 "Cloth experiment method of woven fabric and knitted fabric". When the stiffness is 30 mm or more and 150 mm or less, an opening portion is easily formed in the artificial leather backing material, and for example, when the opening portion is formed with a hollow punch such as a hole piercing punch, waste of the artificial leather backing material hollowed out at the opening portion tends to come out from the hollow portion of the punch, so that productivity of opening forming processing is improved.
In the artificial leather backing material of the present invention, the Kinetic friction coefficient of the functional surface is preferably 0.15 or more and 0.60 or less in terms of the formability of the opening portion and the productivity of opening forming processing. A friction coefficient affects slipperiness of the functional agent and an opening device (punch, hollow needle, drill, etc.), for example, in the case of an opening method is perforation (punch, hollow needle, etc.) and drilling.
In the artificial leather backing material of the present invention, the adhesion amount of the functional agent is preferably 2 to 30% by mass with respect to the artificial leather backing material in terms of the properties of the artificial leather described above, the formability of the opening, and the productivity of opening forming processing. When the adhesion amount of the functional agent is less than 2% by mass, fiber waste hollowed out at the opening portion of the artificial leather backing material is likely to be loosened, and for example, in the case of a punch, it is difficult to remove the fiber waste from the hollow portion. When the adhesion amount of the functional agent is more than 30% by mass, for example, in the case of the punch, the hollow portion is likely to be clogged with the waste. The adhesion amount can be calculated from a weight change before and after application similarly to the adhesion amount, and can also be calculated by chemical analysis such as fluorescent X-ray.

[Production method for artificial leather]

The artificial leather of the present invention is preferably produced by applying a flame retardant having a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less to one surface of a napped sheet-shaped article including a fiber entanglement including ultrafine fibers having an average single fiber diameter of 0.1 um or more and 10 um or less and an elastomer to form a flame retardant surface, and providing a plurality of opening portions on at least the flame retardant surface to have. Hereinafter, the details of each step will be described.

The ultrafine fiber constituting the artificial leather of the present invention can be produced by a conventionally known method, and examples of the method include a sea-island spinning method, a mixed spinning method, and a split type composite spinning method in synthetic fiber production. It is preferable to use ultrafine fiber-generating fibers including two or more kinds of polymer substances having different solubilities in a solvent in terms of productivity such as formation of the fiber entanglement.
In an ultrafine fiber generation step, an island portion formed of a resin to be an ultrafine fiber is formed, and an ultrafine fiber-generating fiber having a sea-island type composite structure in which an easily soluble polymer forms a sea portion is produced.
As the ultrafine fiber-generating fiber, an islands-in-the-sea fiber is used in which thermoplastic resins having different solvent solubilities are used as a sea portion (easily soluble polymer) and an island portion (hardly soluble polymer), and the sea portion is dissolved and removed using a solvent or the like to cause the island portion to form an ultrafine fiber. Use of the islands-in-the-sea fiber is favorable in view of the texture or surface quality of the artificial leather, because at the time of removing the sea portion, a suitable gap can be provided between island portions, that is, between ultrafine fibers inside a fiber bundle.
As the method of spinning the ultrafine fiber-generating fiber having a sea-island composite structure, a method using a mutually arranged polymer body in which a spinneret for sea-island composite fibers is used and the fiber is spun by mutually arranging a sea portion and an island portion is preferred from the viewpoint that ultrafine fibers having a uniform single fiber fineness are obtained.
As a method of incorporating the pigment into the island portion, even when spinning is performed using a resin chip obtained by kneading the pigment with the resin of the island portion, any method can be adopted in which a master batch obtained by kneading the pigment with the resin is prepared in advance, and the master batch and chips of another resin are mixed and spun.
As the sea portion of the islands-in-the-sea fibers, for example, a copolymerized polyester obtained by copolymerizing polyethylene, polypropylene, polystyrene, sodium sulfoisophthalic acid, polyethylene glycol or the like, and polylactic acid can be used, but polystyrene or copolymerized polyester is preferably used from the viewpoint of yarn making property, easy elutability, and the like.
In the production method for an artificial leather of the present invention, in the case of using the islands-in-the-sea fiber, an islands-in-the-sea fiber in which the strength of the island portion is 2.5 cN/dtex or more is preferably used. When the strength of the island portion is 2.5 cN/dtex or more, more preferably 2.8 cN/dtex or more, still more preferably 3.0 cN/dtex or more, the abrasion resistance of the artificial leather is enhanced, and at the same time, reduction in the rubbing fastness due to falling off of the fiber can be suppressed.
In the present invention, the strength of the island portion of the islands-in-the-sea fibers is calculated by the following method.

(1) 10 islands-in-the-sea fibers having a length of 20 cm are bundled.
(2) The sea portion is dissolved and removed from the sample of (1), and an air drying is performed.
(3) A test is performed 10 times (N=10) in accordance with "8.5.1 Standard time test" of "8.5 Tensile strength and percentage elongation" of JIS L 1013:2010 "Testing methods for man-made filament yarns" under the conditions of a grasp interval of 5 cm, a tensile speed of 5 cm/min, and a load of 2 N.
(4) A value obtained by rounding the arithmetic average value (cN/dtex) of the test results of (3) to the first decimal place is employed as the strength of the island portion of the islands-in-the-sea fiber.

A conventional production method for a fiber entanglement in which ultrafine fibers or islands-in-the-sea fibers are used as a woven/knitted fabric and a nonwoven fabric can be applied. Preferably, the spun-out ultrafine fiber-generating fiber is opened and passed through a cross wrapper, etc. to form a fiber web, and the fiber web is then entangled to obtain a nonwoven fabric. As the method for obtaining the nonwoven fabric by entangling the fiber web, a needle punching treatment, a water jet punching treatment, and the like can be used.
As for the form of the nonwoven fabric, either a short-fiber nonwoven fabric or a long-fiber nonwoven fabric may be used as described above, and in the case of the short-fiber nonwoven fabric, the number of fibers oriented in the thickness direction of the artificial leather is larger than that in the long-fiber nonwoven fabric, and the surface of the artificial leather at the time of being napped can give a highly dense feeling.
In the case where a short-fiber nonwoven fabric is used for the nonwoven fabric, the obtained ultrafine fiber-generating fibers are preferably crimped, cut to a predetermined length to obtain a raw cotton, then opened, stacked, and entangled, thereby obtaining a short-fiber nonwoven fabric. Generally known methods may be used for the crimping and cutting steps.
In addition, when the artificial leather includes the woven/knitted fabric (a), the obtained nonwoven fabric and the woven/knitted fabric (a) are stacked and then integrated by entanglement. For the entanglement and integration of the nonwoven fabric and the woven/knitted fabric (a), the woven/knitted fabric (a) is stacked on one surface or both surfaces of the nonwoven fabric, or the woven/knitted fabric (a) is sandwiched between a plurality of nonwoven fabric webs, and then the fibers of the nonwoven fabric and the woven/knitted fabric (a) can be interlaced by needle punching, water jet punching, or the like.
The apparent density of the nonwoven fabric including ultrafine fiber-generating fibers after needle punching or water jet punching is preferably 0.15 g/cm³ or more and 0.45 g/cm³ or less. Preferably, when the apparent density is 0.15 g/cm³ or higher, the sheet-shaped article should have sufficient shape stability and dimension stability. In addition, preferably, when the apparent density is 0.45 g/cm³ or lower, a sufficient space can be kept such that the elastomer is imparted.
It is also preferable for the nonwoven fabric to be subjected to heat shrinkage treatment with warm water or steam to improve the dense feeling of the fibers.
Then, the nonwoven fabric may be impregnated with an aqueous solution of a water-soluble resin and dried to add the water-soluble resin to the nonwoven fabric. Adding the water-soluble resin to the nonwoven fabric fixes the fibers and improves the dimensional stability.

When the islands-in-the-sea fiber is used, in this step, the obtained fibrous substrate is treated with a solvent to generate ultrafine fibers having an average single fiber diameter of single fibers of 0.1 um or more and 10 um or less.
The development of ultrafine fibers is carried out by immersing the nonwoven fabric formed of islands-in-the-sea fibers in a solvent to ensure dissolution and removal of the sea portion of the islands-in-the-sea fibers.
When the ultrafine fiber-generating fiber is an islands-in-the-sea fiber and the sea portion is polyethylene, polypropylene or polystyrene, an organic solvent such as toluene or trichloroethylene can be used as the solvent to dissolve and remove the sea portion. An aqueous alkali solution of sodium hydroxide or the like can be used when the sea portion is copolymerized polyester or polylactic acid. Hot water can be used when the sea portion is water-soluble thermoplastic polyvinyl alcohol-based resin.

In this step, a fiber entanglement including ultrafine fibers or ultrafine fiber-generating fibers as a main component is impregnated with a solution of an elastomer and solidified to add the elastomer. The method of fixing the elastomer to the fiber entanglement may be a method of impregnating a solution of the elastomer into the fiber entanglement and then subjecting the resultant to wet coagulation or dry coagulation, and these methods can be appropriately selected according to the kind of the used elastomer.
N,N'-dimethylformamide, dimethyl sulfoxide, or the like is preferably used as the solvent used when polyurethane is added as the elastomer. A water-dispersible polyurethane liquid in which polyurethane is dispersed as an emulsion in water may be used.
The elastomer may be applied to the fiber entanglement before generating ultrafine fibers from the ultrafine fiber-generating fibers, or after generating ultrafine fibers from the ultrafine fiber-generating fibers.

From the viewpoint of production efficiency, it is also a preferable aspect that after the completion of the step above, the fiber entanglement provided with the elastomer is cut in half in the thickness direction to form half-cut sheets as two fiber entanglements.
Furthermore, a napped surface can be formed by applying a napping treatment to the fiber entanglement provided with the elastomer or a half-cut sheet-shaped article obtained by cutting in half. The napping treatment can be performed by grinding the surface using sandpaper or a roll sander. The napping treatment can be applied to only one surface or both surfaces.
When the napping treatment is applied, a lubricant such as a silicone emulsion can be added to the surface of the fiber entanglement before the napping treatment. In addition, when an antistatic agent is applied before the napping treatment, a ground powder generated by grinding is less likely to deposit on sandpaper. In this way, a napped sheet-shaped article having a napped surface is formed.

It is preferable for the napped sheet-shaped article to be dyed. Examples of the dyeing treatment include jet dyeing treatment using a jigger dyeing machine or a jet dyeing machine, dip dyeing treatment such as thermosol dyeing treatment using a continuous dyeing machine, and printing treatment to the napped surface, such as roller printing, screen printing, inkjet printing, sublimation printing, and vacuum sublimation printing. In particular, a jet dyeing machine is preferably used from the viewpoint of quality and appearance from the viewpoint of obtaining a flexible texture. If necessary, the artificial leather may be subjected to various kinds of resin finishing after the dyeing.

It is preferable that the woven/knitted fabric (b) is stacked and integrated with an adhesive on a surface opposite to a napped surface (when both surfaces each have a napped surface, the napped surface on a side to be a product surface) of the napped sheet. Examples of the method of adding the adhesive include a method of applying a predetermined amount of the adhesive using a device such as a rotary screen, a knife roll coater, a gravure roll coater, a kiss roll coater, or a calender coater. In particular, it is preferable to form a discontinuous adhesive layer using a rotary screen or a gravure roll coater because the artificial leather has a good texture. Forming a discontinuous adhesive layer can prevent texture curing and reduction in air permeability of the artificial leather. The discontinuous adhesive layer means an adhesive layer including both a portion where an adhesive is present and a portion where an adhesive is absent with respect to an adhesion surface, that is, a horizontal surface of the woven/knitted fabric or raised nap sheet. For example, the discontinuous adhesive layer means an adhesive layer in which the adhesive is arranged in a dot pattern.
As a bonding method, when a thermoplastic resin is used as an adhesive, the adhesive can be integrated by thermocompression bonding. For the thermocompression bonding, a method such as heat rolls can be used. In the case where heat rolls are used, it is preferable to set the temperature of the heat roll on the woven/knitted fabric side higher than the temperature of the heat roll on the skin sheet side. When a wet-curable resin is used as an adhesive, adhesion is promoted under a suitable temperature and humidity environment called curing.
The roll temperature on the woven/knitted fabric side in thermocompression bonding with heat rolls is preferably 80 to 180°C, more preferably 100 to 160°C. If the roll temperature on the woven/knitted fabric side is lower than 80°C, adhesion takes time, and a large load is imposed on the process. If the roll temperature on the woven/knitted fabric side is higher than 180°C, the texture of the artificial leather becomes coarse and hard.

A functional agent (flame retardant or the like) is added to one surface of the napped sheet-shaped article to form a functional surface (surface of flame retardant or the like), thereby obtaining an artificial leather backing material. Here, the functional agent (flame retardant or the like) having a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less is applied to obtain the functional surface (surface of flame retardant or the like). Alternatively, the functional surface has a Kinetic friction coefficient (JIS K 7125) of 0.15 or more and 0.60 or less, and the artificial leather backing material has a stiffness of 30 mm or more and 150 mm or less. In this step, the functional surface (surface of flame retardant or the like) is formed on a surface opposite to the napped surface (when both surfaces each have a napped surface, the napped surface on the side to be a product surface) of the napped sheet-shaped article.
Examples of the method of forming the functional surface (surface of flame retardant or the like) include a method of applying the functional agent (flame retardant or the like) to a stacked sheet obtained by stacking the napped sheet-shaped article or the woven/knitted fabric (b) by using a device such as a rotary screen, a knife roll coater, a gravure roll coater, a kiss roll coater, or a calender coater. Although the functional agent (flame retardant or the like) may be applied by a padding treatment and migrated by drying to be unevenly distributed to a surface layer, stability of unevenly distributed to the surface layer is poor. The napping treatment may be further performed after the functional agent (flame retardant or the like) is applied and dried. Alternatively, the functional agent (flame retardant or the like) may be applied to the woven/knitted fabric (b) in advance, and then the woven/knitted fabric (b) may be stacked on the surface opposite to the napped surface (when both surfaces each have the napped surface, the napped surface on the side to be a product surface) of the napped sheet-shaped article to form a functional surface (surface of flame retardant or the like).
Since the functional agent (flame retardant or the like) permeates the inside after being applied, the functional agent (flame retardant or the like) is permeated while adjusting the viscosity of the functional agent (flame retardant or the like), a mesh of a gravure roll, the application amount, an immersion amount, and the like. As a drying method after the application of the functional agent (flame retardant or the like), the drying can be performed using a known dryer such as a tenter dryer.

Then, the functional (flame retardant or the like) sheet including the functional surface (surface of flame retardant or the like) has a plurality of opening portions at least on the functional surface (surface of flame retardant or the like). Examples of the means for providing the opening portion include methods such as boring such as perforation and drilling, and laser processing. The opening portion may be formed not only on the functional surface (surface of flame retardant or the like) but also on the other surface. The timing of opening is not limited, and for example, the fiber entanglement and the woven/knitted fabric (b) may be separately opened and then stacked and integrated. Preferably, the functional agent (flame retardant or the like) is applied to the stacked sheet, and a through opening portion is formed by a drill, a perforated needle, or a hole piercing punch. The artificial leather is obtained by forming the opening portion.
Since the artificial leather after the opening portion is formed has a smaller contact area than before the opening, the Kinetic friction coefficient of the functional surface decreases. For example, from the viewpoint of stacking a polyurethane foam on the functional surface by frame lamination or the like, or from the viewpoint of handleability in the next step, the Kinetic friction coefficient of the functional surface is preferably 0.10 to 0.55 as the artificial leather having the opening portion.

<Post-processing step>

In addition, in the artificial leather, it is also possible to provide an artificial leather in which a design may be applied to its surface as necessary. For example, the surface may be subjected to post processing such as embossing, laser processing, pinsonic processing, and printing processing.
The artificial leather of the present invention obtained by the production method exemplified above is excellent in functionality (flame retardancy and the like) while having moderate air permeability and a flexible texture, has feels like natural suede and an elegant appearance, and can be widely used for an interior material for vehicles, interior materials, building materials, and miscellaneous goods, and in particular, the artificial leather is suitably used for the interior material for vehicles because of its excellent functionality (flame retardancy and the like). In addition, the artificial leather backing material of the present invention obtained by the production method exemplified above is excellent in opening formability, and is suitably used for the production of the artificial leather.

EXAMPLES

Next, the artificial leather of the present invention will be described more specifically using Examples, but the present invention is not limited only to these Examples. Unless otherwise described, physical properties are measured based on the methods described above.

[Measuring methods and processing methods for evaluation]

(1) Average single-fiber diameter of ultrafine fiber (µm)

In the measurement of the average single fiber diameter of ultrafine fibers, the average single fiber diameter was calculated by observing the ultrafine fibers by means of a scanning electron microscope, Model "VW-9000", manufactured by Keyence Corp.

(2) Abrasion resistance of artificial leather

After 20,000 times of abrasion under a pressing load of 12.0 kPa in an abrasion test measured in accordance with "8.19.5 Method E (Martindale method)" of "8.19 Abrasion strength and color change by rubbing" of JIS L 1096:2010 "Cloth experiment method of woven fabric and knitted fabric", an abrasion state of the artificial leather surface was observed and compared with the surface state before the test, and a degree of abnormality was judged according to the following grade. In this evaluation, grades 3 to 5 were regarded as acceptable.

Grade 5: not recognized at all.
Grade 4: slightly recognized; however, hardly conspicuous.
Grade 3: apparently recognized; however, less conspicuous.
Grade 2: somewhat remarkable abnormality is recognized.
Grade 1: considerably remarkable abnormality is recognized.

(3) Tensile strength of artificial leather

Two specimen sheets of 2 cm × 20 cm were sampled in an arbitrary direction of the artificial leather, and the tensile strength specified in accordance with "6.3.1 Tensile strength and percentage elongation (ISO method)" in "Test methods for nonwovens" of JIS L 1913: 2010 was measured. In the measurement, the average of two sheets was employed as the tensile strength of the artificial leather.

(4) Appearance quality and feel of artificial leather

The appearance quality and feel of the artificial leather were evaluated by a total of 20 evaluators consisting of 10 healthy adult men and 10 healthy adult women and after visually deciding the following ratings, the most common rating was employed as the appearance quality and feel of the artificial leather. In the case of a tie between ratings, a higher rating was employed as the quality and feel of the artificial leather. The acceptance level of the present invention was "A, B, or C".

A: Elegant appearance like natural leather, dense surface touch, and premium luxurious feeling
B: Although inferior to natural leather, slightly elegant appearance, slightly dense surface touch, and moderate luxurious feeling
C: Artificial elegance and surface touch, and low luxurious feeling
D: Less elegant, rough surface touch, and felt as low-cost product

(5) Evaluation of air permeability of artificial leather

For each artificial leather to be measured, a 200 mm × 200 mm test piece was taken from five different positions and subjected to measurement according to Method A (Frazier type method) of "8.26 Air permeability" of JIS L 1096: 2010 "Cloth experiment method of woven fabric and knitted fabric", followed by calculating the quantity of air (cm³/cm²/sec) passing through the test piece based on the conversion table attached to the test apparatus. In addition, the five calculations thus obtained were averaged to give a value to be adopted as the air permeability (cm³/cm²/sec).

(6) Test of flexibility of artificial leather

Based on the cantilever method described in "8.21 Stiffness" of JIS L 1096: 2010 "Cloth experiment method of woven fabric and knitted fabric", the flexibility of the artificial leather was evaluated by preparing a test piece of 2 cm × 15 cm, placing the test piece on a horizontal table having a 45° slope, making the test piece to glide, and reading the scale when a middle point at one end of the test piece was in contact with the slope.

(7) Flame retardant performance test of artificial leather

As described above, evaluation was performed based on the burning test standard (horizontal burning rate) of the automobile interior material of Federal Motor Vehicle Safety Standards (FMVSS) No. 302. The size of the test piece at this time was 350 mm × 100 mm.

(8) Test of water spot properties of artificial leather

An artificial leather sample was placed, 3 cm³ of water was added dropwise onto the surface, the sample was allowed to stand until it was naturally dried, and then the occurrence of ring stain and the like on the sample surface was observed. A case where the ring stain and the like were visually clearly conspicuous was determined to be unacceptable.

(9) Opening ratio of artificial leather

The opening ratio refers to an area ratio of the opening portion in the entire area on one surface of the artificial leather, and refers to an area ratio on the surface. A 20 cm × 20 cm sample of the artificial leather was scanned by image photographing, an operation of calculating the area ratio by binarization processing was performed on the sample at 5 points, and the area ratio was determined by arithmetic average.

(10) Presence ratio of flame retardant in thickness direction

The presence ratio of the flame retardant in the thickness direction was calculated by the above method after observing the cross section of the artificial leather by using the scanning electron microscope (SEM), Model "VW-9000", manufactured by Keyence Corp.

(11) Density of fiber entanglement including elastomer

The density of the fiber entanglement including the elastomer (the density of the woven/knitted fabric (b) and the artificial leather containing no flame retardant) shown in Examples and Comparative Examples was calculated by measuring the basis weight of the fiber entanglement to which the elastomer was added (including the woven/knitted fabric (a) when there was the woven/knitted fabric (a)) according to "6.2 Mass per Unit Area (ISO method)" in "Test methods for nonwovens" of JIS L 1913: 2010 as described above, and dividing the basis weight by the thickness of the fiber entanglement to which the elastomer was added. Five samples were randomly taken out from the fiber entanglement sample including the elastomer, and the average value was taken as the density.
$\begin{array}{l} Density (g / {cm}^{3}) = basis weight (g / m^{2}) \div thickness \\ (mm) \div 1000 \end{array}) .$

(12) Tackiness of functional agent

Measurement and calculation were performed according to the following procedure.

(1) The functional agent was heated to 60°C.
(2) Using a tack meter (Tack Taster TA-500 manufactured by Universal Building Materials Co., Ltd.), a stainless steel probe (contact pressure 24.5 N/cm²) was pressed against the functional agent (flame retardant or the like) at a speed of 6 mm/min, and held for 5 seconds.
(3) After (2), a maximum load at the time of peeling at 6 mm/min was read.
(4) (2) to (3) were repeated five times, and the arithmetic average of the resulting values was rounded off to the second decimal place to obtain the tackiness at 60°C.

(13) Kinetic friction coefficient

Three test pieces of 80 mm × 200 mm were taken from the artificial leather, and the functional surface was measured at a test speed of 100 mm/min, with a sliding piece of 63 mm × 63 mm, and at a load of 1.92 N according to JIS K 7125, and the average value was taken as the Kinetic friction coefficient.

[Example 1]

While polyethylene terephthalate was used as the island component, polystyrene was used as the sea component, and the island component and the sea component were subjected to melt spinning using a sea-island composite spinneret having 16 islands under the conditions of an island/sea mass ratio of 80/20, a discharge rate of 1.2 g/(min-hole), and a spinning speed of 1,100 m/min, and then 2.7-fold stretching was performed in a spinning oil solution bath set at 90°C. Then, crimping was performed using a stuffer box crimper, followed by cutting to a length of 51 mm to provide raw stock of islands-in-the-sea fiber with a single fiber fineness of 3.8 dtex.

The raw stock obtained as described above was used to form a laminated web via carding and cross wrapper steps. The needle punching treatment was performed with a number of punches of 2,500 punches/cm² to obtain a nonwoven fabric having a basis weight of 540 g/m² and a thickness of 2.4 mm.

The nonwoven fabric obtained as described above was shrunk with hot water at 96°C. Thereafter, the nonwoven fabric shrunk with hot water was impregnated with a polyvinyl alcohol (hereinafter, may be abbreviated as PVA) aqueous solution having a saponification degree of 88%, which was prepared so as to have a concentration of 12% by mass. Furthermore, the nonwoven fabric was squeezed with rollers and dried by hot air having a temperature of 120°C for 10 minutes while allowing for migration of PVA, to obtain a PVA-impregnated sheet in which the mass of PVA was 25% by mass relative to the mass of a sheet base. The PVA-impregnated sheet thus obtained was immersed in trichloroethylene, and squeezed and compressed by a mangle ten times. Thus, dissolution removal of the sea portion and compression treatment of the PVA-impregnated sheet were performed to obtain a PVA-impregnated sheet in which the ultrafine fiber bundles to which PVA was applied were entangled. The average single fiber diameter of the ultrafine fiber was 4.4 um.

A dimethylformamide (hereinafter, may be abbreviated as DMF) solution of polyurethane prepared so that the concentration of a solid content mainly composed of polyurethane was 13% was immersed in the PVA-impregnated sheet obtained as described above. Thereafter, the sea-removing PVA-impregnated sheet immersed in DMF solution of polyurethane was squeezed with rollers. Then, the sheet was immersed in a DMF aqueous solution having a concentration of 30% by mass to solidify the polyurethane. After that, PVA and DMF were removed by hot water, and a silicone oil emulsion solution adjusted to a concentration of 1% by mass was impregnated, thereby applying a silicone-based lubricant such that the applied amount thereof was 0.5% by mass relative to the total mass of the mass of the fiber entanglement and the mass of the polyurethane, and drying was performed with hot air having a temperature of 110°C for ten minutes. As a result, a polyurethane-impregnated sheet having a thickness of 1.8 mm and a polyurethane mass of 33% by mass relative to the mass of the fiber entanglement was obtained. The density of the polyurethane-impregnated sheet which was the fiber entanglement including the elastomer was 0.35 g/cm³.

The polyurethane-impregnated sheet obtained as described above was cut in half such that the thickness of each part was 1/2. Subsequently, a napping treatment was performed by grinding the surface layer portion of the half-cut surface by 0.3 mm with an endless sandpaper having a sandpaper grit size of 180 to obtain a napped sheet having a thickness of 0.6 mm.

The napped sheet obtained as described above was dyed with a black disperse dye at 120°C using a jet dyeing machine, and reduction-cleaned. Thereafter, a drying treatment was performed at 100°C for 7 minutes to obtain a dyed sheet having an average single fiber diameter of the ultrafine fiber of 4.4 um, a basis weight of 220 g/m², and a thickness of 0.70 mm.

A flame retardant A was obtained by mixing 20 parts by mass of ammonium polyphosphate treated with a silicon oxide resin (manufactured by Wellchem. com, phosphorus content: 28%, nitrogen content: 14%) as a flame retardant main component of the flame retardant, 0.2 parts by mass of polyoxyethylene sorbitan monostearate (nonionic surfactant) as a surfactant, 11 parts of methyl acrylate resin having a nonvolatile content of 50% as a binder resin, and 4 parts by mass of melamine cyanurate (nitrogen content: 49.4%), and using hydroxyethyl cellulose as a thickener. Coating processing of applying a flame retardant processing agent solution (the viscosity was adjusted to 3000 mPa-s by the thickener) containing 70% by mass of the flame retardant A to one surface opposite to the product surface of the dyed sheet using a screen coater was performed, and then drying treatment was performed at a temperature of 100°C for 7 minutes to obtain a sheet with a flame retardant in which the adhesion amount of the flame retardant with respect to the mass of the artificial leather after drying was 20% by mass.

In the sheet with a flame retardant, a through opening portion was formed with a punching board in which needles were planted, thereby obtaining an artificial leather (needle diameter: 1.2 mm, longitudinal pitch: 5 mm, transverse pitch: 5 mm, opening ratio: 6%). The through opening portion after the punching was not clogged with fiber waste, the flame retardant did not stick to an edge of the opening portion, a clean opening portion was formed, and the fiber waste and the flame retardant did not adhere to the punching board after the punching in which dust was blown off by air. The obtained artificial leather had excellent flame retardancy while having moderate air permeability and a flexible texture, and had dense feels like natural suede and an elegant appearance. The tackiness of the flame retardant was 0.45 N/cm² at 60°C, 0.20 N/cm² at 40°C, and 0.14 N/cm² at 20°C. The basis weight of the artificial leather was 240 g/m², and the thickness was 0.72 mm. The results are shown in Table 1.

[Example 2]

An artificial leather was obtained in the same manner as in Example 1 except that an ultrafine fiber-generating fiber having a sea-island composite structure including an island component and a sea component was subjected to melt spinning using a sea-island composite spinneret having 16 islands under the conditions of an island/sea mass ratio of 55/45, a discharge amount of 1.0 g/(min-hole), and a spinning speed of 1100 m/min, and then the ratio of stretching in a spinning oil solution bath set at 90°C was 3.4 times. The density of the polyurethane-impregnated sheet was 0.360 g/cm³, which was higher than that in Example 1, and the immersion amount of the flame retardant was small, so that W/W₀ = 0.07. The average single fiber diameter of the ultrafine fiber was 2.9 um. The results are shown in Table 1.

[Example 3]

A laminated web was formed using the raw stock described in Example 1 via the carding and cross wrapper steps, and then a plain woven fabric (basis weight: 75 g/m²) having a warp density of 95 yarns/2.54 cm and a weft density of 76 yarns/2.54 cm, in which a twisted yarn obtained by twisting a multifilament (average single fiber diameter: 11 um, total fineness: 84 dtex, 72 filaments) containing polyethylene terephthalate having an intrinsic viscosity (IV value) of 0.65 at 2500 T/m was used for both wefts and warps, was stacked on and under the laminated web. Thereafter, an artificial leather in which the average single fiber diameter of the ultrafine fiber was 4.4 um, the basis weight was 360 g/m², and the thickness was 1.0 mm was obtained in the same manner as in Example 1 except that the needle punching treatment was performed with a number of punches of 2,500 punches/cm² to obtain a nonwoven fabric of a fiber entanglement having a basis weight of 700 g/m² and a thickness of 3.0 mm. A tough artificial leather having higher strength than that of Example 1 was obtained. The results are shown in Table 1.

[Example 4]

A tricot fabric was prepared with a multifilament (total fineness: 48 dtex, 18 filaments) containing polyethylene terephthalate by using a single tricot machine, and dyed with a black disperse dye to prepare a dyed tricot fabric having a warp density of 32 yarns/2.54 cm and a weft density of 48 yarns/2.54 cm, and a low-melting-point nylon resin (softening temperature: 90°C) as an adhesive was applied in an amount of 20 g/m² in the form of dots using a gravure roll coater, and then dried with hot air at a temperature of 100°C to obtain a tricot with an adhesive. The tricot side was thermocompression-bonded to the dyed sheet of Example 3 with a heat roll heated to a temperature of 150°C to obtain a composite sheet having a basis weight of 440 g/m² and a thickness of 1.1 mm. The composite sheet was subjected to flame retardant processing and punched in the same manner as in Example 3 to obtain an artificial leather having a basis weight of 490 g/m² and a thickness of 1.2 mm. An artificial leather having higher strength than that of Example 3 was obtained. The flame retardant adhered to the entire tricot, and the tricot as a single component had high flame retardancy, so that the artificial leather had high flame retardancy. The results are shown in Table 1.

[Example 5]

A circular knitted base fabric was knitted with a blister structure using an interlaced yarn containing a multifilament (84 dtex/25 f, average single fiber diameter of ultrafine fibers after sea removal: 9 um) using a sea-island composite yarn using polyethylene terephthalate as the island component and polystyrene as the sea component and a multifilament (33 dtex/12 f) of polyethylene terephthalate. An artificial leather including the fiber entanglement including the elastomer was obtained in the same manner as in Example 1 except that the fiber entanglement was a circular knitted base fabric. The basis weight of the artificial leather was 240 g/m², and the thickness was 0.72 mm. The artificial leather which had a luxurious feeling in a lower zone as compared with Example 1 and a relatively hard texture, and was excellent in water spot and punching processability was obtained. The results are shown in Table 1.

[Example 6]

An artificial leather having a basis weight of 490 g/m² and a thickness of 1.2 mm was obtained in the same manner as in Example 4 except that with respect to the flame retardant, 30 parts by mass of a dialkylphosphinic acid metal salt as a main component of the flame retardant and 15 parts by mass of an acrylic acid ester copolymer as a binder resin were used to obtain a flame retardant B, and a flame retardant processing agent solution containing 50% by mass of the flame retardant B was obtained. The tackiness of the flame retardant was 1.50 N/cm² at 60°C, 0.50 N/cm² at 40°C, and 0.30 N/cm² at 20°C. Since the flame retardant had high tackiness at room temperature, the immersion amount was smaller than that in Example 4, and the tackiness at 60°C was high, an artificial leather having excellent flame retardancy and appearance quality was obtained although holes and punching board needles were slightly clogged after punching. The results are shown in Table 1.

[Example 7]

An artificial leather was obtained in the same manner as in Example 4 except that the opening ratio was 14%. Since the number of opening portions was larger than that in Example 4, the flame retardancy was slightly inferior; however, an artificial leather excellent in flexibility and the like was obtained. The results are shown in Table 1.

[Comparative Example 1]

An artificial leather was obtained in the same manner as in Example 4 except that 5 parts by mass of a methyl acrylate resin and 10 parts by mass of an acrylonitrile resin were used as binder components for the flame retardant. The tackiness was high, the opening portion was clogged during punching, and the air permeability was poor. The results are shown in Table 1.

[Comparative Example 2]

An artificial leather was obtained in the same manner as in Example 4 except that the average single fiber diameter of the ultrafine fibers was 11 um. A rough surface touch quality with no elegance was obtained. The results are shown in Table 1.

[Table 1]

		Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7	Comparative Example 1	Comparative Example 2
Fiber entanglement	Average single fiber diameter of ultrafine fiber (µm)	4.4	2.9	4.4	4.4	9.0	4.4	4.4	4.4	11.0
	Fiber entanglement	Nonwoven fabric	Nonwoven fabric	Nonwoven fabric	Nonwoven fabric	Knitted fabric	Nonwoven fabric	Nonwoven fabric	Nonwoven fabric	Nonwoven fabric
	Woven/knitted fabric (a)	-	-	Woven fabric	Woven fabric	-	Woven fabric	Woven fabric	Woven fabric	Woven fabric
	Woven/knitted fabric (b)	-	-	-	Tricot	-	Tricot	Tricot	Tricot	Tricot
	Elastomer	Polyurethane
	Density of fiber entanglement including elastomer (g/cm³)	0.35	0.36	0.40	0.40	0.30	0.40	0.40	0.40	0.42
Flame retardant	Flame retardant main component	Ammonium polyphosphate					Dialkylphosp hinic acid metal salt	Ammonium polyphosphate
	Main resin	Methyl acrylate					Acrylic acid ester	Methyl acrylate	Acrylonitrile	Methyl acrylate
	Tackiness at 60° C (N/cm²)	0.45	0.45	0.45	0.45	0.45	1.5	0.45	2.1	0.45
Artificial leather backing material (before opening)	Kinetic friction coefficient	0.29	0.28	0.31	0.27	0.29	0.41	0.25	0.61	0.31
Artificial leather backing material (before opening)	Stiffness (mm)	70	75	80	95	90	90	90	105	125
Artificial leather	Thickness (mm)	0.72	0.72	1.0	1.2	0.72	1.2	1.2	1.2	0.72
	Basis weight (g/m² )	240	240	360	360	240	360	330	360	362
	W/W₀	0.10	0.07	0.15	0.21	0.31	0.17	0.21	0.25	0.28
	Opening ratio (%)	6	6	6	6	6	6	14	6	6
	Air permeability (cm³/cm²/sec)	110	105	100	90	110	95	140	65	95
	Flame retardancy (mm/min)	25	30	20	10	40	Self-extinguished	60	30	7
	Tensile strength (N/cm)	50	55	70	80	40	78	70	75	62
	Appearance quality and feel	A	A	A	A	C	A	A	A	D
	Abrasion resistance	5	4	5	5	3	5	4	5	5
	Stiffness (mm)	65	70	75	90	85	85	85	100	120
	Water spot	Acceptable	Acceptable	Acceptable	Acceptable	Acceptable	Acceptable	Acceptable	Acceptable	Acceptable
	Punching processability	Good	Good	Good	Good	Good	Slightly good	Good	Poor	Good

Particular embodiments have been used to detail the invention. However, it is evident to those skilled in the art that various alternations and modifications are allowed without departing from the spirit and scope of the invention.

Claims

An artificial leather comprising:
a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less; and

an elastomer,

wherein one surface is a napped surface having a raised nap, the other surface is a flame retardant surface having a flame retardant, and the following requirements 1 and 2 are satisfied:
requirement 1: at least the flame retardant surface has a plurality of opening portions, and

requirement 2: the flame retardant has a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less.
The artificial leather according to claim 1, wherein an opening ratio of the flame retardant surface is 1% or more and 40% or less.
The artificial leather according to claim 1 or 2, wherein the artificial leather has a plurality of opening portions in each of the napped surface and the flame retardant surface, and at least some of the opening portions are through opening portions formed to penetrate from the napped surface to the flame retardant surface.
The artificial leather according to any one of claims 1 to 3, wherein the fiber entanglement is formed by integrating a fiber entanglement including the ultrafine fiber and a woven/knitted fabric (a).
The artificial leather according to any one of claims 1 to 4, wherein the flame retardant surface is a surface formed by stacking a woven/knitted fabric (b).
The artificial leather according to any one of claims 1 to 5, wherein a presence ratio of the flame retardant in a thickness direction satisfies the following formula: $0.001 \leq {W/W}_{0} \leq 0.7$
wherein W is a thickness (mm) from the flame retardant surface where the flame retardant is present, and W₀ is a thickness (mm) of the entire artificial leather.
The artificial leather according to any one of claims 1 to 6, wherein the flame retardant contains a phosphorus-based compound.
The artificial leather according to any one of claims 1 to 7, wherein the fiber entanglement including the elastomer has a density of 0.20 g/cm³ or more and 0.50 g/cm³ or less.
A production method for the artificial leather according to any one of claims 1 to 8, comprising:
applying a flame retardant having a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less to one surface of a napped sheet-shaped article including a fiber entanglement including ultrafine fibers having an average single fiber diameter of 0.1 um or more and 10 um or less and an elastomer to form a flame retardant surface; and

providing a plurality of opening portions on at least the flame retardant surface.
An artificial leather or a backing material of the artificial leather comprising:
a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less; and

an elastomer,

wherein one surface is a napped surface having a raised nap, the other surface is a functional surface having a functional agent, and the functional agent has a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less.
An artificial leather or a backing material of the artificial leather comprising:
a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less; and

an elastomer,

wherein one surface is a napped surface having a raised nap, the other surface is a functional surface having a functional agent, the functional surface has a Kinetic friction coefficient of 0.15 or more and 0.60 or less, and the artificial leather or the backing material of the artificial leather has a stiffness of 30 mm or more and 150 mm or less.
An artificial leather or a backing material of the artificial leather comprising:
a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 um or more and 10 um or less; and

an elastomer,

wherein one surface is a napped surface having a raised nap, the other surface is a functional surface having a functional agent, and an adhesion amount of the functional agent is 2 to 30% by mass with respect to the artificial leather or the backing material of the artificial leather.