JP7770786B2 - Artificial leather and its manufacturing method - Google Patents

Description

The present invention relates to artificial leather and its manufacturing method.

Artificial leathers are suitable for use in a wide range of applications, including clothing, shoes, bags, interior decoration, furniture, seat coverings and interior materials for automobiles, railway vehicles, aircraft, ships, etc., and as base materials for emblems. These applications require not only good appearance and texture, but also flame retardancy and resistance to physical loads such as abrasion.
The mainstream of artificial leather materials is a nonwoven fabric structure that has been impregnated with and attached with a polymeric elastomer resin. If the constituent fibers are simply physically entangled by needle punching or water jet processing without impregnating the elastomer resin, the resulting material will not be strong enough to withstand the load of the dyeing liquid flow and will easily break when used as artificial leather.

Manufacturing companies commonly use a technique called "applying a polymeric elastomer such as polyurethane to impart a good texture and abrasion resistance." For example, artificial leathers impregnated with polyurethane are commercially available under names such as Ecsaine (trademark) and Alcantara (trademark). However, because polymeric elastomers such as polyurethane are highly flammable, adding them to the leather can easily reduce the flame retardancy of the artificial leather itself.

Patent Document 1 below discloses an example of supplementing flame retardancy by back-coating a flame retardant on polyurethane-impregnated artificial leather. While this method provides good flame retardancy, it has the drawback of making the nonwoven fabric extremely stiff, preventing it from achieving a good feel when used as artificial leather. Another drawback is that the manufacturing process becomes complicated due to the need to apply the flame retardant, which can easily increase costs.

In addition to impregnating and adhering a polymeric elastomer such as polyurethane, a method has been investigated in the past for obtaining a binder effect to impart strength to artificial leather. This method involves mixing heat-fusible fibers into the nonwoven fabric for artificial leather during its production and melting them to bond the main fibers together. For example, in the examples of Patent Document 2 listed below, thick, sheath-core heat-fusible fibers are used. Since the fusion points of the main fibers are connected via the core fibers, the nonwoven fabric has the drawback of being stiff and of poor quality.
In addition, in the method disclosed in Patent Document 3 below, since the method includes a step of thermally shrinking the nonwoven fabric, the molten agglomerates of the heat-fusible fibers tend to become large, which is likely to result in a defect of poor surface quality. Furthermore, since the molten fibers are generated from ultrafine fiber-generating composite fibers, such as islands-in-sea fibers, the molten agglomerates tend to concentrate at the original composite fiber locations. This also makes the method prone to the defect of the molten agglomerates becoming large.

Furthermore, Patent Document 4 below proposes a leather-like material constructed with a laminated structure including a fused fiber nonwoven fabric. This leather-like material has a laminated structure in which the surface layer is made of ultrafine fibers and a nonwoven fabric layer containing fused fibers is placed underneath. Sheets with such a laminated structure have the disadvantage that, because the fibers on the outermost surface of the surface layer are not held together by fusion or other means, they do not have the abrasion resistance required for practical use as artificial leather.

Furthermore, in Patent Document 5 below, in order to provide artificial leather that combines good feel, high abrasion resistance, ease of cutting, and shape stability without impregnation with a polymer elastomer such as polyurethane resin, heat-fusible staple fibers are mixed in a specific ratio with at least the surface fiber layer of a nonwoven fabric having a multilayer structure of at least two layers, consisting of a surface fiber layer and a woven/knitted scrim layer, and then heat-fusible staple fibers are subjected to a heat-fusible treatment to produce artificial leather. Because the resulting artificial leather does not contain polyurethane resin, it has improved resistance to artificial sebum. Furthermore, if it is made of polyester fibers, it is highly recyclable. However, there is still room for improvement in terms of abrasion resistance (more than 20,000 cycles in a Martindale abrasion test) and feel (flexural strength less than 26 cm in a KES forward bending test). Furthermore, because the artificial leather is entangled by spraying with high-velocity water, followed by heat treatment at 200°C using a pin tenter dryer, the shape stability is good but the stretchability is poor.

Furthermore, in the following Patent Document 6, the invention described in Patent Document 5 is improved in abrasion resistance (more than 40,000 cycles in a Martindale abrasion test) and feel (a bending value of less than 24 cm in a KES pure bending test) by exposing a portion of the thermoplastic resin formed by melting the heat-fusible staple fibers to the surface of the surface fiber layer in the form of chunks of a specified size. However, as in Patent Document 5, the fabric is entangled by spraying a high-speed water stream, and then heat-treated at 190°C using a pin tenter dryer, simultaneously heat-fusing the heat-fusible staple fibers, resulting in low stretchability. Furthermore, Patent Document 6 discloses that the flame retardancy of the resulting artificial leather is improved by using a polyester-based main fiber and heat-fusible staple fibers.

Furthermore, Patent Document 7 listed below describes a fiber laminated sheet consisting of at least two layers including an upper layer base paper and a base fiber layer, wherein the upper layer base paper is a synthetic fiber paper made by a wet papermaking process, the main component of which is polyester staple fiber and which contains polyester-based binder staple fiber including a copolymer polyester having a melting point in the range of 210 to 250°C, the constituent fibers of the upper layer base paper are partially temporarily bonded by the polyester-based binder staple fiber during papermaking, but are dissociated by hydroentanglement, and after entanglement, are heated at a temperature higher than the drying temperature during papermaking, thereby partially softening and bonding the entangled points, the base fiber layer is selected from at least one of a nonwoven fabric, a nonwoven web, and a woven or knitted fabric, and the upper layer base paper and the base fiber layer are laminated together, and the fibers constituting both layers are entangled with each other to form an integrated fiber laminate. Patent Document 7 also describes that the present invention provides a novel fiber laminate sheet that has a soft surface texture and moderate firmness, stiffness, and breathability when not impregnated with an elastic polymer, and that the present invention provides a fiber laminate sheet that can be made into artificial leather with a texture more similar to that of natural leather when impregnated with an elastic polymer, as well as artificial leather using the same, and synthetic fiber paper used for the same that allows single fibers to be easily separated and entangled during hydroentangling, all at low cost.Therefore, the artificial leather described in Patent Document 7 is limited to one that contains a polymer elastomer such as water-based polyurethane.
Patent Document 7 also describes that the synthetic fiber paper of the present invention is (1) a synthetic fiber paper in which fibers are weakly bonded to each other by agglutination, (2) a synthetic fiber paper in which the agglutination is released by the pressure of mechanical entanglement and the fibers are redispersed in the thickness direction to form a three-dimensional entanglement, and (3) a synthetic fiber paper in which the binder short fibers soften, shrink, and deform during heat treatment after entanglement, bonding the entangled points and thereby improving the interlayer peel strength compared to when entangled. In order to achieve the series of actions (1) to (3), the synthetic fiber paper contains polyester short fibers as the main component fiber, and is wet-processed synthetic fiber paper containing binder short fibers that are partially bonded to the main component fiber by weak agglutination at the drying temperature during papermaking (100 to 120°C), and then further soften, shrink, and exhibit a bonding effect when heated at a temperature of 150 to 180°C, which is higher than the drying temperature during papermaking.
According to these descriptions, the substance that softens and shrinks is the binder short fiber, and therefore Patent Document 7 does not teach that a part of the thermoplastic resin formed by melting the heat-fusible short fiber is exposed on the surface of the surface fiber layer in the form of lumps of a predetermined size, as described in Patent Document 6, nor does it describe that abrasion resistance or texture are improved.

Special Publication No. 03-080914 Japanese Patent Application Publication No. 07-216756 Special Publication No. 03-016427 Patent No. 4835181 Patent No. 5685003 Patent No. 6118174 Patent No. 4708494

In light of the state of the art described above, the problem that the present invention aims to solve is to provide a recyclable artificial leather that combines good texture, high stretchability, high abrasion resistance, and flame retardancy, and a method for producing the same.

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

[1] An artificial leather including at least a surface fiber layer constituting a first surface, having the following characteristics:
(1) The surface fiber layer contains at least one type of main fiber and a thermoplastic resin having a melting point that is 20°C or more and 170°C or less lower than the melting point of the main fiber;
(2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less;
(3) The thermoplastic resin bonds the main fibers together, and at least a portion of the thermoplastic resin is exposed on the surface of the surface fiber layer in the form of resin lumps, with an average projected area of 0.66 × 10 ^-9 m ² or more and 5.0 × 10 ^-9 m ² or less per resin lump;
(4) The surface fiber layer is entangled with a scrim layer which is a woven fabric; and (5) In the artificial leather, when the sum of the 500 gf/cm constant load elongation (%) in the MD direction and the 500 gf/cm constant load elongation (%) in the CD direction is (A), the sum of the weave density (counts/2.54 cm) in the MD direction and the weave density (counts/2.54 cm) in the CD direction of the scrim layer is (B), and the fineness (denier) of the weaving yarn constituting the scrim layer is (C), the following formula is satisfied:
220000≦(A)×(B)×(C)≦600000
and the 500 gf/cm constant load elongation in the MD direction is 3% or more;
Artificial leather having the above structure.
[2] The artificial leather according to [1], wherein the main fiber is a polyester fiber.
[3] The artificial leather according to [1] or [2], wherein the thermoplastic resin is a polyester resin.
[4] The artificial leather according to any one of [1] to [3], wherein the scrim layer is made of polyester-based resin fibers.
[5] the following steps:
(1) subject fibers and heat-fusible fibers made of a thermoplastic resin having a melting point 20°C to 170°C lower than the melting point of the subject fibers are mixed so that the weight ratio of the heat-fusible fibers is 3% to 25%, and then the mixture is entangled on a scrim layer by wet papermaking, and then a surface fiber web entangled with the scrim layer is formed by hydroentangling or needle punching; and (2) the entangled structure of the obtained surface fiber web is relaxed by thermal annealing shrinkage at a temperature equal to or higher than the melting point of the heat-fusible fibers and lower than the melting point of the subject fibers to form a surface fiber layer.
The method for producing an artificial leather according to any one of [1] to [4] above,
[6] The manufacturing method according to [5], wherein the length of the subject fiber in the step (1) is 2.5 mm or more and 90 mm or less.
[7] The manufacturing method according to [5] or [6], wherein the fineness of the heat-fusible fiber in the step (1) is 0.5 dtex or more and 2.2 dtex or less.
[8] The artificial leather according to any one of [1] to [4] above, which has a bending stiffness per unit width in a KES pure bending measurement of 1.0 gfcm ² /cm or less.
[9] The artificial leather according to any one of [1] to [4], wherein when the surface is abraded with a pressing load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method), the scrim is not exposed when the abrasion number is less than 50,000.

In the artificial leather of the present invention, the thermoplastic resin bonds the main fibers having a fineness of 0.01 dtex or more and 0.5 dtex or less together in a relaxed intertwined structure, and at least a portion of the thermoplastic resin is exposed in the form of resin blocks of a predetermined size on the surface of the surface fiber layer. This results in excellent feel, high stretchability, and high abrasion resistance. Furthermore, if the artificial leather of the present invention uses polyester fibers as the main fibers and thermoplastic resin and does not contain elastic polymers such as water-based polyurethane, it will have excellent recyclability and excellent flame resistance in that it can suppress gas generation during combustion. Furthermore, because the artificial leather of the present invention has high stretchability, it has excellent moldability, particularly for use as a car seat or ceiling material, making it suitable for use as a car interior material.

FIG. 2 is a diagram showing an example of the state of clumped resin in a surface fiber layer. FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. FIG. 10 is a diagram showing another example of the state of lump resin in the surface fiber layer. FIG. 1 is a conceptual diagram of a dry heat shrinkage method. 1 is a photograph in place of a drawing showing a state in which the thermoplastic resin bonds the main fibers together and the thermoplastic resin is present on the surface of the surface fiber layer in the form of a lump resin. FIG. 1 is a diagram showing an example of a vehicle roof panel test piece.

Hereinafter, embodiments of the present invention will be described in detail.
One embodiment of the present invention is an artificial leather including at least a surface fiber layer constituting a first surface, the artificial leather having the following characteristics:
(1) The surface fiber layer contains at least one type of main fiber and a thermoplastic resin having a melting point that is 20°C or more and 170°C or less lower than the melting point of the main fiber;
(2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less;
(3) The thermoplastic resin bonds the main fibers together, and at least a portion of the thermoplastic resin is exposed on the surface of the surface fiber layer in the form of resin lumps, with an average projected area of 0.66 × 10 ^-9 m ² or more and 5.0 × 10 ^-9 m ² or less per resin lump;
(4) The surface fiber layer is entangled with a scrim layer which is a woven fabric; and (5) In the artificial leather, when the sum of the 500 gf/cm constant load elongation (%) in the MD direction and the 500 gf/cm constant load elongation (%) in the CD direction is (A), the sum of the weave density (counts/2.54 cm) in the MD direction and the weave density (counts/2.54 cm) in the CD direction of the scrim layer is (B), and the fineness (denier) of the weaving yarn constituting the scrim layer is (C), the following formula is satisfied:
220000≦(A)×(B)×(C)≦600000
and the 500 gf/cm constant load elongation in the MD direction is 3% or more;
It is an artificial leather having the above structure.

The main fibers contained in the surface fiber layer are fibers that account for 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on 100% by mass of the surface fiber layer. The upper limit is not particularly limited, but may be 99% by mass or less.
The main fiber contained in the surface fiber layer is preferably a polyester fiber, a polyamide fiber, an acrylic fiber, or a polyolefin fiber from the viewpoints of strength, availability, etc., but as described above, polyester fiber is particularly preferred from the viewpoint of providing a recyclable artificial leather that is also flame retardant.

Preferably, polyester fibers serving as the main fibers constituting the surface fiber layer include polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, and copolymers thereof. Suitable polyamide fibers include nylon, meta-aramid, para-aramid, and copolymers thereof. Suitable acrylic fibers include acrylic acid ester or methacrylic acid ester polymers and copolymers thereof. Suitable polyolefin fibers include polyethylene, polypropylene, polybutene, polystyrene, and copolymers thereof.

If the main fibers are made of a thermoplastic resin with a melting point 20°C or more lower than that of the main fibers contained in the surface fiber layer described below, and the scrim is made of a polyester-based resin, then, for example, used PET can be recovered from clothing and beverage bottles, processed into recycled PET resin, and used to manufacture artificial leather. Furthermore, used (end-of-life) artificial leather can be recycled and processed into, for example, insulation material or filter material, and PET can be recovered from the used insulation material or filter material, resulting in recyclable artificial leather that is suitable for a circular economy.

The main fiber preferably has a fineness of 0.5 dtex or less, more preferably 0.35 dtex or less, and even more preferably 0.2 dtex or less, from the viewpoint of easily obtaining a texture similar to that of natural leather or a suede-like or nubuck-like surface feel. From the viewpoint of production efficiency and production stability during fiber production, the fineness is preferably 0.01 dtex or more, and even more preferably 0.03 dtex or more.
The main fiber may be a fiber directly spun by a melt spinning method, a fiber obtained by a wet spinning method, or an ultrafine fiber obtained by removing the sea component from a sea-island composite fiber in which a copolyester is used as the sea component and a regular polyester is used as the island component.

The main fiber does not necessarily have to be made of fibers made of a single polymer, but may be a mixture of fibers made of other types of polymers.The main fiber does not necessarily have to be made of fibers having a single fineness, but may be a mixture of fibers having multiple finenesses.
The main fiber may contain or have attached thereto additives, such as titanium oxide, various antioxidants, light fasteners, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, and dyes, as long as the desired effect is achieved.

The thermoplastic resin that constitutes the surface fiber layer and has a melting point 20°C to 170°C lower than that of the main fiber is preferably a polyester resin, polyamide resin, acrylic resin, or polyolefin resin, due to its availability. Suitable polyester resins include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, and copolymers thereof. Suitable polyamide resins include nylon and its copolymers. Suitable acrylic resins include polymers of acrylic esters or methacrylic esters, and their copolymers. Suitable polyolefin resins include polyethylene, polypropylene, polybutene, polystyrene, and their copolymers.

The thermoplastic resin does not necessarily have to be made of only a single polymer, and may be a mixture of multiple types of polymers.
The thermoplastic resin may contain or have attached thereto additives, such as titanium oxide, various antioxidants, light stabilizers, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, and dyes, as long as the desired effect is achieved.
The thermoplastic resin has a melting point that is 20°C to 170°C lower than that of the subject fiber. When two or more types of subject fiber are used, the melting point must be 20°C to 170°C lower than that of the subject fiber with the lowest melting point. When the thermoplastic resin is a mixture of multiple polymers, the thermoplastic resin with the highest melting point must have a melting point that is 20°C to 170°C lower than that of the subject fiber with the lowest melting point. Regarding the melting point range, the stretchability, abrasion resistance, and appearance quality described in the present application can be achieved within the above range, but from the perspective of maintaining particularly good appearance quality, the melting point is preferably 40°C to 150°C lower, more preferably 40°C to 100°C lower.

The thermoplastic resin must be in the form of chunks and exposed on the surface of the surface fiber layer. If it is not exposed on the surface, the main fibers present on the surface will not be sufficiently held by the resin fusion, and the fibers will be prone to falling off and breakage, resulting in an artificial leather that does not have sufficient abrasion resistance.
It is also preferable that part or all of the thermoplastic resin bonds the main fibers together. If the thermoplastic resin does not bond the main fibers together, the main fibers will not be held together sufficiently, and the fibers will be prone to falling off or breakage, resulting in an artificial leather that does not have sufficient abrasion resistance or strength.

In this embodiment, the thermoplastic resin must bond the main fibers together, and at least a portion of the thermoplastic resin must be exposed on the surface of the surface fiber layer in the form of resin lumps, with an average projected area per resin lump of 0.66× ^{10−9 m2} or more and 5.0× ^{10−9 m2} or less, preferably 0.66× ^{10−9 m2} or more and 3.0× ^{10−9 m2} or less.

When observing the surface fiber layer from the front, the average projected area of the thermoplastic resin in a lumpy form is preferably 5.0× ^{10 m2} or less. If the average projected area is greater than 5.0× ^{10 m2} , the resin lumps present on the surface will be too large relative to the main fibers, impairing the appearance quality and feel. Furthermore, the density of fusion points between the main fibers will be reduced, resulting in insufficient bonding between the main fibers and inferior abrasion resistance of the surface layer. The average projected area is preferably 3.0× ^{10 m2} or less, more preferably 1.5× ^{10 m2} or less. On the other hand, from the viewpoint that the resin lumps must be large enough to bond the main fibers together, the average projected area is preferably 0.66× ^{10 m2} or more.

Another embodiment of the present invention is a method for producing a method of manufacturing a semiconductor device comprising the steps of:
(1) subject fibers and heat-fusible fibers made of a thermoplastic resin having a melting point 20°C to 170°C lower than the melting point of the subject fibers are mixed so that the weight ratio of the heat-fusible fibers is 3% to 25%, and then the mixture is entangled on a scrim layer by wet papermaking, and then a surface fiber web entangled with the scrim layer is formed by hydroentangling or needle punching; and (2) the entangled structure of the obtained surface fiber web is relaxed by thermal annealing shrinkage at a temperature equal to or higher than the melting point of the heat-fusible fibers and lower than the melting point of the subject fibers to form a surface fiber layer.
The method for producing the artificial leather comprises the steps of:

In this embodiment, the blend ratio of thermoplastic resin in the surface fiber layer is preferably 3% or more and 25% or less. The blend ratio is the percentage of the weight of thermoplastic resin relative to the total weight of the main fiber and thermoplastic resin. If the blend ratio is less than 3%, sufficient fusion strength cannot be obtained, making it difficult to achieve good abrasion resistance and shape stability. On the other hand, if the blend ratio exceeds 25%, the feel becomes hard, which is undesirable. This blend ratio is more preferably 4% or more and 20% or less, and even more preferably 6% or more and 15% or less.

The scrim layer constituting the artificial leather of this embodiment is a woven fabric, and the woven fabric is preferably made of untwisted processed yarn or twisted yarn of 400 to 1200 T/m. The material of the scrim layer is preferably made of the same polymer system as the main fiber in terms of color matching when dyed.

The weave density of the scrim layer in the MD and CD directions (threads/2.54 cm) is preferably 40 to 100, more preferably 45 to 80, and even more preferably 50 to 70. The MD direction in which the scrim layer is produced and wound up into a roll and the CD direction perpendicular to the MD direction can be determined from the manufacturing process of artificial leather by looking at the direction in which the artificial leather is wound in the case of a full-width roll and the pin marks left on the edges by the pin tenter dryer. In the case of cut-out scraps, the nap is aligned in the MD direction when the surface is stroked, taking into account the characteristics of the artificial leather manufacturing process.

From the viewpoint of achieving good stretchability and mechanical strength, the fineness of the woven yarns constituting the scrim layer is preferably 60 dtex or more and 200 dtex or less, more preferably 65 dtex or more and 170 dtex or less, and even more preferably 70 dtex or more and 150 dtex or less.

The length of the subject fibers in step (1) is preferably 2.5 mm or more and 90 mm or less. If the length of the subject fibers is within this range, hydroentanglement with the scrim layer is sufficient. If the length of the subject fibers is 2.5 mm or less, the entanglement effect with the scrim layer is not sufficiently achieved during the entanglement step, and relative peeling between the subject fiber layer and the scrim layer is likely to occur, which may cause quality defects such as poor adhesion and poor appearance. The length of the subject fibers is more preferably 2.5 mm or more and 20 mm or less, and even more preferably 3 mm or more and 10 mm or less.

The artificial leather of this embodiment can include at least a surface fiber layer constituting a first surface. For example, in the case of an artificial leather consisting of a surface fiber layer and a scrim layer, the first surface (upper surface) becomes the surface (front surface), and the back surface of the scrim layer becomes the second surface (lower surface). Also, in the case of an artificial leather of this embodiment consisting of three layers, namely, a surface fiber layer/scrim layer/back fiber layer, the back surface of the back fiber layer becomes the second surface.
Furthermore, when a surface fiber layer/scrim layer/back fiber layer configuration is adopted as one aspect of this embodiment, the material constituting the back fiber layer is not particularly limited, but from the viewpoint of achieving good recyclability, it is preferably the same as the main fiber and/or thermoplastic resin of the surface fiber layer.
The scrim layer functions as a core material, and can stabilize the production of the papermaking sheet in the papermaking process and increase the mechanical strength of the resulting artificial leather.
Furthermore, when a back surface fibrous layer is included, it may be made of a material different from that of the surface fibrous layer, for example, by adding a flame retardant, so that desired properties can be added.

A preferred method for producing the artificial leather of this embodiment involves heat-treating a nonwoven fabric structure having a surface fiber layer formed by mixing at least one type of main fiber with fully fusible heat-fusible fibers having a melting point that is 20° C. to 170° C. lower than the melting point of the main fiber, thereby melting the heat-fusible fibers and forming a mass of thermoplastic resin in the surface fiber layer.
The heat-fusible fibers are preferably full-fusible fibers so that the fused bulk resin has a sufficient number of points at which the fused main fibers are bonded together after melting. Compared with sheath-core fibers using a low-melting-point thermoplastic resin in the sheath or side-by-side fibers using a low-melting-point thermoplastic resin on only one side, full-fusible fibers have more points at which the main fibers are bonded together and a large amount of fusible components in the fused parts, so that the fusion strength is sufficient. Furthermore, since the fusion points are not continuously located in the vicinity of each other via the heat-fusible fibers, the full-fusible fibers are also preferred because they tend to have a softer feel.

The heat-fusible fibers (heat-melt yarns) that make up the surface fiber layer and have a melting point 20°C to 170°C lower than the melting point of the main fiber are preferably polyester fibers, polyamide fibers, acrylic fibers, or polyolefin fibers, due to their availability. Suitable polyester fibers include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, and copolymers thereof. Suitable polyamide fibers include nylon and its copolymers. Suitable acrylic fibers include polymers of acrylic esters or methacrylic esters, and their copolymers. Suitable polyolefin fibers include polyethylene, polypropylene, polybutene, polystyrene, and their copolymers.

The heat-fusible fiber does not necessarily have to be made of only a single polymer, and may be made of a mixture of multiple polymers. From the viewpoint of high fusible strength and uniformity in dyeing, it is preferable that the polymer system be the same as that of the main fiber.
The heat-fusible fibers can be fibers directly spun by a melt spinning method, fibers obtained by a wet spinning method, or ultrafine fibers obtained by removing the sea component from a sea-island composite fiber in which a copolymer polyester is used as the sea component and a regular polyester is used as the island component.
The fineness of the heat-fusible fiber is preferably 0.5 dtex or more and 2.2 dtex or less in view of the size of the molten block of thermoplastic resin. If the fineness is 2.2 dtex or less, the molten block of thermoplastic resin is uniformly dispersed on the surface of the surface fiber layer, resulting in excellent appearance and feel. The fineness of the heat-fusible fiber is more preferably 0.6 dtex or more and 2.0 dtex or less, and even more preferably 0.7 dtex or more and 1.5 dtex or less.

Additives may be mixed into or attached to the heat-sealable fibers as long as the desired effect is achieved. Additives include titanium oxide, various antioxidants, light-resistant agents, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, and dyes.

Examples of methods for forming the surface fiber layer include methods in which the main fibers and/or heat-fusible fibers are used in the form of short fibers and the fibers are entangled by a papermaking method, a carding method, an air-laying method, or the like to form a nonwoven structure.
From the viewpoint of uniform dispersion of the constituent fibers and ease of use of ultrafine fibers, it is particularly preferred that the surface fiber layer be formed by a papermaking method.

In addition, in this embodiment, the inter-layer entanglement can be achieved using a hydroentanglement method known as the spunlace method, a needle punch method, or other methods, but hydroentanglement is preferred as it does not destroy the structure of the woven or knitted fabric that forms the scrim layer.

The artificial leather of this embodiment has high stretchability, and is particularly excellent in stretch suitability for use as a car ceiling material. Specifically, the artificial leather of this embodiment satisfies the following formula: (A) where the sum of the 500 gf/cm constant load elongation (%) in the MD direction and the 500 gf/cm constant load elongation (%) in the CD direction is (A), the sum of the weave density (counts/2.54 cm) in the MD direction and the weave density (counts/2.54 cm) in the CD direction of the scrim layer is (B), and the fineness (denier) of the weaving yarn constituting the scrim layer is (C).
220000≦(A)×(B)×(C)≦600000
It is necessary for the material to satisfy the above requirements and for the 500 gf/cm constant load elongation in the MD direction to be 3% or more. Such high stretchability can be achieved by thermal bonding (also referred to as "thermal annealing shrinkage" in this specification) while the entangled structure is relaxed, as described below. (A) x (B) x (C) is preferably 230,000 to 500,000, more preferably 240,000 to 400,000. The 500 gf/cm constant load elongation in the MD direction is preferably 4% to 15%, more preferably 4.5% to 7%. The MD and CD directions of the artificial leather can be determined by the manufacturing characteristics of the artificial leather, in the case of a full-width roll, based on the direction in which the artificial leather is wrapped and the pin marks left on the edges by the pin tenter dryer, and in the case of cut scraps, the raised nap is aligned in the MD direction when the surface is stroked.

"Heat fusion in a relaxed state of intertwined structure (thermal annealing shrinkage)"
In this embodiment, the heat fusion treatment can be performed using a drum dryer, a contact dryer such as a calendar roll, a biaxially stretching film stretcher, or an air-through dryer such as a pin tenter dryer. The treatment temperature is at least 5°C higher, preferably at least 10°C higher, than the melting point of the thermoplastic resin that constitutes the surface fiber layer and has a melting point 20°C to 170°C lower than that of the main fiber. The upper limit of the treatment temperature is preferably 240°C or lower. If the difference between the treatment temperature and the melting point of the thermoplastic fiber is less than 5°C, sufficient heat fusion may not be achieved. If the treatment temperature exceeds 240°C, the polyester fiber may melt, resulting in insufficient surface quality and abrasion resistance.

FIG. 9 is a conceptual diagram of thermal annealing shrinkage.
In the artificial leather of this embodiment, when the sum of the 500 gf/cm constant load elongation (%) in the MD direction and the 500 gf/cm constant load elongation (%) in the CD direction is (A), the sum of the weave density (counts/2.54 cm) in the MD direction and the weave density (counts/2.54 cm) in the CD direction of the scrim layer is (B), and the fineness (denier) of the weaving yarn constituting the scrim layer is (C), the following formula can be calculated:
220000≦(A)×(B)×(C)≦600000
In order to satisfy the above requirement and to achieve a 500 gf/cm constant load elongation in the MD direction of 3% or more, it is necessary to bond the main fibers to each other with a molten thermoplastic resin in a state in which the entangled structure of the main fibers is relaxed during heat fusion (thermal bonding).
The mechanism by which the stretchability of the artificial leather of this embodiment manifests can be explained by the complex correlation between the suppleness and elongation of the artificial leather during elastic deformation and its surface quality. The suppleness and elongation of the artificial leather during elastic deformation are largely dependent on how the elastic deformation behavior of the scrim, which serves as the core material at the center of the artificial leather, is affected by the front and back ultrafine fiber layers and the size and number of fusion points of the heat-sealed fibers that bind them. To attach artificial leather to complex and wide areas, such as the ceiling of a car seat, while maintaining surface quality, it is necessary for the artificial leather to undergo appropriate elastic deformation and maintain that quality even after lamination. From this perspective, the inventors conducted extensive research and found that the intended effect can be explained by evaluating the elastic deformation behavior of the artificial leather as the product of the scrim layer's fineness (denier) and the weave density in the MD and CD directions, and further multiplying this by the artificial leather's constant-load elongation. The value of (A) x (B) x (C) derived from this concept is affected by the density of the fusion points of the entangled heat-fusible fibers. If the value of (A) x (B) x (C) is less than 220,000, the scrim layer will not have sufficient elasticity, making it difficult to bond the layers together without wrinkles. If the value of (A) x (B) x (C) is more than 600,000, although the scrim layer will have sufficient elasticity, the density of the ultrafine fibers in the surface layer will be reduced, and the luxurious surface quality of artificial leather may not be achieved when the layers are bonded together.

By performing the above-mentioned heat fusion while slackening and shrinking the surface fiber web entangled with the scrim layer in the MD and CD directions, the entangled structure as shown in Figure 9 becomes relaxed, i.e., the main fibers are fixed in a non-tensioned state. Therefore, compared to the conventional method in which heat fusion is performed while tensioning and shrinking using a pin tenter, an artificial leather with the desired stretchability and flexibility can be obtained.
In Table 1 below, "+" in "thermal annealing shrinkage" means that the heat fusion treatment was performed in a shrunk state of the nonwoven fabric, "0" means that the heat fusion treatment was performed without stretching or shrinking the nonwoven fabric, and "-" means that the heat fusion treatment was performed in a stretched state of the nonwoven fabric.

The nonwoven fabric for artificial leather obtained by the above method can be used as suede- or nubuck-like artificial leather by raising the surface of the surface fiber layer and dyeing it. The raising can be done by known methods such as buffing with sandpaper. In this case, if the raising is done before the heat-fusible fibers of the surface fiber layer are heat-fused, a suede-like surface texture can be obtained. On the other hand, if the raising is done after the heat-fusible fibers are heat-fused, a nubuck-like surface texture can be obtained.

There are no particular restrictions on the dyeing process. For example, when the main fiber is polyester-based, disperse dyes are generally used. The dyeing method can be a conventional method well known to dyeing and processing companies, and for artificial leather, a liquid jet dyeing machine is preferably used in order to achieve even dyeing. The artificial leather dyed in this way is reduced and washed by soaping or in the presence of a chemical reducing agent to remove excess dye. There are no particular restrictions on the conditions for the reduction and washing, and basic or acidic reducing agents can be used in accordance with conventional methods, without any particular restrictions.

The thickness of the artificial leather of this embodiment is preferably 0.40 mm to 1.50 mm. By ensuring a thickness within the range of 0.40 mm to 1.50 mm, the thickness of the ultrafine fiber layer can be sufficiently ensured while maintaining sufficient fusion points per unit area and entanglement between the fibers in the surface ultrafine fiber layer, thereby achieving both a supple feel and sufficient stretchability.

The weight per unit area of the artificial leather of this embodiment is preferably 100 g/m ² to 400 g/m ^2. By setting the weight per unit area to 100 g/m ² to 400 g/m ² , it is possible to achieve both a supple feel and appropriate hardness.

The artificial leather of this embodiment preferably exhibits a feel value (flexural rigidity per unit width in KES pure bending measurement) measured by the method described below as a substitute for feel, of less than 1.0 ^gfcm2 /cm or less, to ensure a good feel for use as an artificial leather. Although there are no particular limitations on the method for measuring the feel value, a suitable method is to use a 20 cm wide sample, evaluate it using a commercially available KES pure bending tester, and convert the resulting flexural rigidity per unit width. By achieving a feel value of less than 1.0 ^gfcm2 /cm, the good quality characteristic of artificial leather can be obtained.

The artificial leather of this embodiment preferably has good abrasion resistance for use as artificial leather, in that when the surface is abraded with a pressure load of 12 kPa in accordance with JIS-L-1096 Method E (Martindale method), the scrim is not exposed after less than 50,000 abrasion cycles.

The artificial leather of this embodiment preferably exhibits flame retardancy of Grade 4 or higher in a flammability test conforming to the U.S. Federal Motor Vehicle Safety Standard "FMVSS No. 302." By maintaining flame retardancy of Grade 4 or higher, the artificial leather can meet the flame resistance standards used in automobiles, aircraft, and other applications, thereby expanding the range of applications for which it can be used as artificial leather.

The present invention will be explained in detail below based on examples and comparative examples, but the present invention is not limited to these examples. The physical properties used in the examples were measured using the following methods.

(1) Average value of projected area of lump resin One hundred randomly selected points on the surface of the sample nonwoven fabric were photographed using a scanning electron microscope at a magnification of 250x to obtain one hundred images. The areas of 100 lump resin points were calculated using each image, and the average was used as the average projected area of the lump resin. If 100 lump resin points were not photographed in the 100 images, additional photographs were taken.

A JSM-5610 scanning electron microscope manufactured by JEOL Ltd. was used for the photography. ImageJ was used as image processing software to calculate the area of the lump resin. The area obtained by outlining the lump resin in the image at 250x magnification was calculated by converting the area to the scale of the photographed image. The area obtained by outlining was rounded to the nearest 0.001 x ^{10-9 m2} . The average area of 100 lump resins was rounded to the nearest 0.01 x ^{10-9 m2} .
To identify clumped resin, we used the following criteria: clumped resin adheres the main fibers and clumped resin is exposed on the surface of the surface fiber layer. "Clumped resin adheres the main fibers" refers to a state in which the clumped resin is in contact with and integrated with two or more main fibers. "Clumped resin is exposed on the surface of the surface fiber layer" refers to a state in which the entire clumped resin is exposed on the surface in the image without being hidden by the main fibers. Figures 1 to 8 are schematic diagrams showing the state of clumped resin in the surface fiber layer. Using these figures, we will explain the state of clumped resin and how to determine its presence. Figure 1 shows an example in which clumped resin is exposed on the surface of the surface fiber layer but does not adhere the main fibers. Figure 2 shows an example in which clumped resin is exposed on the surface and adheres the main fibers. Figure 3 shows an example in which clumped resin is not exposed on the surface but adheres the main fibers. Figure 4 shows an example in which clumped resin is exposed on the surface and adheres the main fibers. Figure 5 shows an example in which clumped resin is exposed on the surface but does not adhere the main fibers. Figure 6 shows an example in which the heat-fusible fibers are unmelted, and is not considered clumped resin. Figure 7 shows an example in which sheath-core fibers are used as heat-sealed fibers. Heat-sealed fibers retain their fibrous shape and are not called "lump resin." Figure 8 shows an example in which the main fibers are exposed on the surface but are not bonded together. In the figure, 1 is the main fiber, 2 is the lump resin, 3 is the unmelted resin, and 4 is the sheath-core fiber.
Here, "the main fibers are bonded together" means that at least two main fibers penetrate the interior of the block resin (thermoplastic resin) and are physically bonded together.

(2) Fineness Ten randomly selected points on the front or back fiber layer sample of the artificial leather were photographed using a microscope at a magnification of 2500 times, and the diameters of the fibers at 50 points were measured. The average value of these measurements was calculated as the average fiber diameter. The fineness [dtex] of the main fiber was calculated from the average fiber diameter thus obtained and the density of the heat-fusion resin.
In addition, artificial leather was immersed in ethanol, wrapped in a gelatin capsule, and freeze-dried in liquid nitrogen. The capsule was then cut with a knife, and the cut cross section of the sample returned to room temperature was observed using a scanning electron microscope (JSM-5610 manufactured by JEOL Ltd.) under conditions of WD = 10 mm and a magnification of 200x. The thickness of the woven yarns constituting the scrim layer was measured at five points on each of the 20 obtained images, and the fineness of the woven yarns constituting the scrim layer was determined by measuring the thickness.
The fineness of the heat-fusible yarn is the fineness of the raw short fibers, and was evaluated using a scanning electron microscope. Specifically, adhesive carbon tape was attached to an evaluation stage, 0.05 g of the raw short fibers was placed on the tape, and excess heat-fusible yarn was removed with an air duster to prepare a sample. The sample was observed under conditions of WD = 10 mm and a magnification of 200 times, and the thickness was determined by measuring five points on each of 20 images obtained.

(3) Feel The feel test was carried out using a KES pure bending tester, KES FB2-A, an automated forward bending tester manufactured by KATO TECH, and measurements were carried out under the conditions of SENS 4 using samples of 20 cm width and 20 cm length. The evaluation criteria are as follows: A feel value of 1.0 gf ^cm2 or less was considered to be acceptable.
(Evaluation criteria)
×: Feeling value is greater than 1.0 gf·cm ² .
Good: The feel value is 1.0 gf·cm ² or less.

(4) Abrasion Resistance The sample surface was abraded at a pressure load of 12 kPa according to the method specified in JIS-L-1096 Method E (Martindale method). The evaluation criteria for this test method were the number of abrasions until the sample surface layer was abraded and the scrim was exposed, and the evaluation was divided into the following evaluation criteria (grades).
(Evaluation criteria)
XX: After 5,000 abrasion cycles, significant fiber loss occurred, making it impossible to evaluate.
x: The scrim is exposed after less than 30,000 abrasion cycles.
△: The scrim is exposed after 30,000 or more and less than 40,000 abrasion cycles.
Good: The scrim is exposed after 40,000 or more and less than 50,000 abrasion cycles.
⊚: The scrim is exposed after 50,000 or more abrasion cycles.

(5) Surface fiber layer/scrim entanglement strength (N/cm)
The resulting artificial leather sample was cut into two pieces measuring 2.5 cm in the MD and 25 cm in the CD, ensuring that the pieces were perpendicular to each other. A 2.5 cm wide, 20 cm long hot melt tape (Harness Co., Ltd., Hot Melt Tape S1297-1X10-FT) was sandwiched between the front and back surfaces of the sample, and the pieces were pressed with a Hariron presser at 105°C for 2 minutes. After confirming that the adhesive surface was sufficiently strong (>20 N/cm), a cutter knife was used to make an incision on the adhesive surface of the sample where the hot melt tape was not attached, creating a sample in which the scrim layer and the surface were the peeling surface. This was then subjected to a 10 cm tensile test using a Tensilon universal testing machine (RTF-2410) at a tensile speed of 1.0 cm/sec and a load cell of 50 N. The maximum tensile strength per unit width measured at this time was averaged, and this procedure was repeated three times to obtain the average value, which was then used as the surface fiber layer/scrim entanglement strength.
The evaluation was based on the following criteria.
×: The strength is less than 4 N/cm.
Good: Strength of 4 N/cm or more.

(6) 500 gf/cm Constant Load Elongation The elongation of the artificial leather was measured at a load of 500 g/cm using a test piece with a width of 2.5 cm, a grip spacing of 10 cm, and a constant rate of extension of 10 cm/min in accordance with JIS-L-1096 (2015 edition): 8-14 “Tensile strength and elongation” (Method A: strip method).

(7) Stretchability of Automotive Headliner Material An adhesive solution having the following composition was applied to the back of the obtained artificial leather using a comma coater, and dried at 120°C for 2 minutes to obtain an artificial leather having a polyurethane resin adhesive layer.
(Adhesive Solution Composition)
Polycarbonate-based polyurethane resin solution (35% solids, 65% water): 100 parts Carbodiimide-based crosslinking agent (functional group number 3 or more): 10 parts Thickener (polyacrylamide): 1 part Antifoaming agent: 0.1 part

The artificial leather with the adhesive layer thus obtained was placed on a vehicle roof panel test piece (made of PET) shown in Figure 11 and bonded by thermocompression using a metal nip roll heated to 120°C. Next, aging was carried out for 72 hours at 60°C to firmly bond the artificial leather and test piece. The artificial leather with the polyurethane resin adhesive layer attached to the two blank holes of the obtained test piece was punched out using a Thomson punching machine and evaluated for stretchability of the automobile headliner material according to the following evaluation criteria.
(Evaluation criteria)
x: Wrinkles were formed, the edges were pulled, and the film was turned up from the hole, so that the film could not be satisfactorily bonded.
◯: Good adhesion was achieved.

[Example 1]
Polyethylene terephthalate fibers with a single fiber fineness of 0.15 dtex and a melting point of 255°C were produced by the direct spinning method and cut to a length of 5 mm to form the main fiber. Fully melt-type heat-fusible fibers (Casven 8000 manufactured by Unitika Ltd.) with a single fiber fineness of 0.7 dtex and a length of 5 mm and made of a polyethylene terephthalate copolymer with a melting point of 178°C were used as the heat-fusible fibers. These short fibers were dispersed in water at a weight ratio of main fiber to heat-fusible yarn of 90:10 to form a slurry. A surface fiber sheet with a basis weight of 130 g/ ^m2 was produced from this slurry by a papermaking method. Polyethylene terephthalate fibers with a single fiber fineness of 0.15 dtex and a melting point of 255°C were also produced by the direct spinning method and cut to a length of 5 mm to form the main fiber. The heat-fusible fibers used were fully fusible heat-fusible fibers (Casven 8000 manufactured by Unitika Co., Ltd.) made of polyethylene terephthalate copolymer with a melting point of 178°C, a single fiber fineness of 0.7 dtex, and a length of 5 mm. These short fibers were dispersed in water at a weight ratio of main fiber to heat-fusible fiber of 97:3 to prepare a slurry. A papermaking sheet for backside fiber with a basis weight of 50 g/ ^m2 was produced from this slurry by a papermaking method. These two layers were laminated with a woven scrim to form a three-layer structure consisting of a surface fiber layer, a scrim layer, and a backside fiber layer. The resulting three-layer laminate was entangled by spraying high-speed water using a straight-flow spray nozzle, and then dried at 130°C for 5 minutes using an air-through dryer to obtain a three-layer nonwoven fabric. The scrim layer was made of a woven fabric having a basis weight of 100 g/m ² and made of polyethylene terephthalate fiber of 166 dtex/48f, with a sum of the weave density in the MD direction and the weave density in the CD direction being 120 (threads/2.54 cm).
The surface of the surface fiber layer of the resulting nonwoven fabric was buffed with 400-mesh sandpaper to give a raised texture. The nonwoven fabric was then placed in a Toyo Seiki Seisaku-sho (Toyo Seiki Seisaku-sho) biaxial stretching tester X4HDHT, with the fabric loosened to a shrinkage of 5% in both the MD and CD directions, and the center and four corners of both sides were secured with compressed air grips. The nonwoven fabric was then thermally annealed at 190°C for 5 minutes in a chamber to obtain a nonwoven fabric for artificial leather. The fabric was then dyed at 130°C using a blue disperse dye (BlueFBL, manufactured by Sumitomo Chemical) in a jet dyeing machine and reduced at 80°C to obtain a suede-like artificial leather. The manufacturing conditions and evaluation results of the resulting artificial leather are shown in Table 1 below.

[Example 2]
Suede-like artificial leather 2 was obtained in the same manner as in Example 1, except that the weight ratio of main fiber:thermofusible fiber in the back surface fiber layer was set to 95:5. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 3]
The same procedure as in Example 1 was repeated except that the basis weight of the surface fiber sheet was 110 g/ ^m² , thereby obtaining suede-like artificial leather 3. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 4]
Suede-like artificial leather 4 was obtained in the same manner as in Example 1, except that the weight ratio of the surface fiber sheet was main fiber: heat-fusible fiber = 80:20 and the weight ratio of the back fiber sheet was main fiber: heat-fusible yarn = 96:4. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 5]
Suede-like artificial leather 5 was obtained in the same manner as in Example 1, except that the short fiber fineness of the polyethylene terephthalate fiber was 0.1 dtex, the fineness of the heat-fusible fiber was 1.1 ^dtex , and the basis weight of the surface fiber sheet was 150 g/m. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 6]
Suede-like artificial leather 6 was obtained in the same manner as in Example 1, except that the fineness of the heat-fusible fibers was 1.1 dtex, the weight ratio of the surface fiber sheet was main fiber:heat-fusible yarn = 96:4, and the weight ratio of the back fiber sheet was main fiber:heat-fusible fiber = 93:7. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 7]
Suede-like artificial leather 7 was obtained in the same manner as in Example 1, except that the heat-fusible fibers were changed to fully fusible heat-fusible fibers (Melty 4000 manufactured by Unitika Ltd.) made of polyethylene terephthalate copolymer with a melting point of 110°C, having a single fiber fineness of 2.2 dtex and a length of 5 mm, the surface fiber sheet had a basis weight of 150 g/ ^m2 , the back fiber sheet had a basis weight of 50 g/ ^m2 , and the thermal annealing temperature was 125°C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 8]
Suede-like artificial leather 8 was obtained in the same manner as in Example 1, except that the fineness of the weaving yarn of the scrim layer was changed to 75 denier, the basis weight of the surface fiber sheet was changed to 90 g/ ^m² , and the weight ratio of the back fiber sheet was changed to main fiber:thermofusible fiber = 95:5. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 9]
Suede-like artificial leather 9 was obtained in the same manner as in Example 1, except that the fineness of the woven yarns in the scrim layer was 75 denier, the sum of the weave densities of the scrim layers was 100 threads/2.54 cm, the basis weight of the surface fiber sheet was 80 g/ ^m² , the weight ratio of the surface fiber sheet was 92:8 (main fiber:thermofusible fiber), and the weight ratio of the back fiber sheet was 95:5 (main fiber:thermofusible fiber). The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 10]
Suede-like artificial leather 10 was obtained in the same manner as in Example 1, except that the fineness of the woven yarns of the scrim layer was 75 denier, the total weave density of the scrim layer was 130 threads/2.54 cm, the heat-fusible fibers were all-melt type heat-fusible fibers (Melty 4000 manufactured by Unitika Ltd.) made of polyethylene terephthalate copolymer with a melting point of 110°C, having a single fiber fineness of 2.2 dtex and a length of 5 mm, the weight ratio of the surface fiber sheet to the heat-fusible fiber was 95:5, the basis weight of the surface fiber sheet was 80 g/ ^m² , the weight ratio of the back fiber sheet to the main fiber to the heat-fusible fiber was 97:3, and the thermal annealing temperature was 125°C. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 11]
Suede-like artificial leather 11 was obtained in the same manner as in Example 1, except that the fineness of the woven yarns in the scrim layer was 75 denier, the sum of the weave densities of the scrim layers was 140 threads/2.54 cm, the weight ratio of the surface fiber sheet was 96: ⁴ (main fiber:thermofusible fiber), the basis weight of the surface fiber sheet was 65 g/m², and the weight ratio of the back fiber sheet was 97:3 (main fiber:thermofusible fiber). The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 12]
Suede-like artificial leather 12 was obtained in the same manner as in Example 1, except that the sum of the weave densities of the scrim layers was 140 threads/2.54 cm, the weight ratio of the surface fiber sheet was 95:5 (main fiber:thermofusible fiber), the basis weight of the surface fiber sheet was 200 g/ ^m² , and the weight ratio of the back fiber sheet was 97:3 (main fiber:thermofusible fiber). The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 1]
Suede-like artificial leather 13 was obtained in the same manner as in Example 1, except that the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 2]
Suede-like artificial leather 14 was obtained in the same manner as in Example 1, except that the surface fiber sheet had a basis weight of 140 g/ ^m² , the base fabric was heated in a pin tenter dryer at 190°C for 5 minutes without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 3]
Suede-like artificial leather 15 was obtained in the same manner as in Example 1, except that the length of the main fiber was 2 mm, the single fiber fineness of the heat-fusible fiber was 1.1 dtex, the basis weight of the surface fiber sheet was 140 g/ ^m² , the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 4]
Suede-like artificial leather 16 was obtained in the same manner as in Example 1, except that the surface fiber sheet had a basis weight of 150 g/ ^m² and was stretched by 3% in both the MD and CD directions instead of shrinking by thermal annealing. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 5]
Suede-like artificial leather 17 was obtained in the same manner as in Example 1, except that the surface fiber sheet had a basis weight of 20 g/ ^m² , the weight ratio of main fiber to heat-melting fiber was 70:30, and the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 6]
Suede-like artificial leather 18 was obtained in the same manner as in Example 1, except that the surface fiber sheet had a basis weight of 125 g/ ^m² , the weight ratio of main fiber to heat-melting fiber was 97.5:2.5, and the base fabric was heated at 190°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions, and no thermal annealing shrinkage was performed. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 7]
Suede-like artificial leather 19 was obtained in the same manner as in Example 1, except that the surface fiber sheet had a basis weight of 115 g/ ^m² , the back fiber sheet had a weight ratio of main fiber to heat-melting fiber of 95:5, and instead of thermal annealing shrinkage, the sheet was stretched by 3% in each of the MD and CD directions. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 8]
Suede-like artificial leather 20 was obtained in the same manner as in Example 1, except that the heat-fusible fibers were sheath-core type heat-fusible fibers (Melty 4080 manufactured by Unitika Ltd.) made of polyethylene terephthalate copolymer with a melting point of 110°C, having a single fiber fineness of 2.2 dtex and a length of 5 mm, the surface fiber sheet had a basis weight of 139 g/ ^m2 , and the heat treatment was carried out at a temperature of 125°C while elongating by 3% in each of the MD and CD directions instead of thermal annealing shrinkage. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 9]
Suede-like artificial leather 21 was obtained in the same manner as in Example 1, except that the fineness of the weaving yarns in the scrim layer was 75 denier, the sum of the weave densities of the scrim layers was 75 threads/2.54 cm, the basis weight of the surface fiber sheet was 100 g/ ^m² , and the weight ratio of the back fiber sheet was main fiber: heat-melt fiber = 95:5, and instead of thermal annealing shrinkage, the sheet was stretched by 3% in each of the MD and CD directions. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 10]
In Example 1, the weaving yarn fineness of the scrim layer was 100 denier, the sum of the weave densities of the scrim layer was 120 threads/2.54 cm, the fineness of the heat-fusible fibers was 1.1 dtex, the basis weight of the surface fiber sheet was 220 g/ ^m² , the weight ratio of the surface fiber sheet to the main fiber:heat-fusible fiber was 80:20, and the fabric was heated at 130°C for 5 minutes using a pin tenter dryer without slackening the base fabric in the MD and CD directions. Suede-like artificial leather 22 was obtained. No formation of molten resin was observed. The manufacturing conditions and evaluation results of the resulting artificial leather are shown in Table 1 below.

[Comparative Example 11]
In Example 1, the heat-fusible fibers were polyethylene terephthalate copolymers with a melting point of 110°C, sheath-core type heat-fusible fibers with a single fiber fineness of 2.2 dtex and a length of 5 mm (Melty 4080 manufactured by Unitika Co., Ltd.). The fineness of the weaving yarns in the scrim layer was 75 denier, the sum of the weave densities of the scrim layers was 120 threads/2.54 cm, the basis weight of the surface fiber sheet was 180 g/ ^m² , the weight ratio of the surface fiber sheet was 85:15 (main fiber:heat-fusible fiber), and the weight ratio of the back fiber sheet was 96:4 (main fiber:heat-fusible fiber). The same procedure was used to obtain suede-like artificial leather 22, except that the base fabric was heated at 80°C for 5 minutes using a pin tenter dryer without slackening in the MD and CD directions. No molten resin formation was observed. The manufacturing conditions and evaluation results of the resulting artificial leather are shown in Table 1 below.

In the artificial leather of the present invention, the thermoplastic resin bonds the main fibers having a fineness of 0.01 dtex to 0.5 dtex together in a relaxed intertwined structure, and at least a portion of the thermoplastic resin is exposed in the form of resin blocks at a predetermined size on the surface of the surface fiber layer. This results in excellent feel, high stretchability, and high abrasion resistance. Furthermore, if the main fibers and thermoplastic fibers used in the artificial leather of the present invention are polyester-based fibers and do not contain elastic polymers such as water-based polyurethane, the artificial leather of the present invention will have excellent recyclability and excellent flame resistance due to the suppression of gas generation during combustion. Because the artificial leather of the present invention has high stretchability, it is particularly suitable for stretching as a car ceiling material and is suitable for use as a car interior material. Furthermore, the artificial leather of the present invention can be used in fields other than car interior materials, such as seat coverings and interior materials for railway vehicles, aircraft, and ships, as well as clothing, shoes, bags, smartphone cases, interior decoration, and furniture.

1 Main fiber 2 Lump resin 3 Unmelted resin (heat-melting yarn)
4. Sheath-core fibers

Claims (6)

An artificial leather comprising at least a surface fiber layer constituting a first surface, the artificial leather having the following characteristics:
(1) The surface fiber layer contains at least one type of main fiber and a thermoplastic resin having a melting point that is 20°C or more and 170°C or less lower than the melting point of the main fiber;
(2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less;
(3) The thermoplastic resin bonds the main fibers together, and at least a portion of the thermoplastic resin is exposed on the surface of the surface fiber layer in the form of resin lumps, with an average projected area of 0.66 × 10 ^-9 m ² or more and 5.0 × 10 ^-9 m ² or less per resin lump;
(4) The surface fiber layer is entangled with a scrim layer which is a woven fabric; and (5) In the artificial leather, when the sum of the 500 gf/cm constant load elongation (%) in the MD direction and the 500 gf/cm constant load elongation (%) in the CD direction is (A), the sum of the weave density (counts/2.54 cm) in the MD direction and the weave density (counts/2.54 cm) in the CD direction of the scrim layer is (B), and the fineness (denier) of the weaving yarn constituting the scrim layer is (C), the following formula is satisfied:
220000≦(A)×(B)×(C)≦600000
and the 500 gf/cm constant load elongation in the MD direction is 3% or more;
and
The main fiber is a polyester fiber, and
The thermoplastic resin is a polyester-based resin, and
The scrim layer is made of polyester resin fibers, and
The warp and weft yarns constituting the scrim layer have the same fineness. The following steps:
(1) subject fibers and heat-fusible fibers made of a thermoplastic resin having a melting point 20°C to 170°C lower than the melting point of the subject fibers are mixed so that the weight ratio of the heat-fusible fibers is 3% to 25%, and then the mixture is entangled on a scrim layer by wet papermaking, and then a surface fiber web entangled with the scrim layer is formed by a hydroentanglement treatment or a needle punching method; and (2) the entangled structure of the obtained surface fiber web is relaxed by thermal annealing shrinkage at a temperature equal to or higher than the melting point of the heat-fusible fibers and lower than the melting point of the subject fibers to form a surface fiber layer.
The method for producing the artificial leather according to claim 1, comprising: The manufacturing method described in claim 2, wherein the length of the main fiber in step (1) is 2.5 mm or more and 90 mm or less. The manufacturing method described in claim 2 or 3, wherein the fineness of the heat-fusible fibers in step (1) is 0.5 dtex or more and 2.2 dtex or less. 2. The artificial leather according to claim 1, wherein the bending stiffness per unit width in a KES pure bending measurement is 1.0 gfcm ^<2> /cm or less. The artificial leather of claim 1, wherein when the surface is abraded with a pressure load of 12 kPa in accordance with JIS-L-1096 Method E (Martindale method), the scrim is not exposed after less than 50,000 abrasion cycles.