JP7703362B2 - Artificial leather and its manufacturing method - Google Patents

Description

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

Artificial leather is widely accepted on the market as an alternative material to natural leather, and is available in a wide variety of products such as grain and suede finishes. It can also be dyed to produce a wide range of colors not found in natural leather, and is therefore widely used as a highly functional design material. In particular, suede-finished artificial leather with a brushed outer surface is suitable for use in clothing, shoes, bags, furniture, and seat coverings and interior materials for automobiles, railway vehicles, aircraft, and ships. In these fields, there is a demand for a combination of good appearance quality, a supple feel, and resistance to physical loads such as abrasion resistance over long periods of use.

According to the definition of JIS-6601, artificial leathers are classified according to their appearance into "smooth" which has a grain-like appearance of leather, and "napped" which has an appearance of leather such as nubuck, suede, or velour. The artificial leather of this embodiment relates to one classified as "napped" (i.e., brushed artificial leather with a brushed appearance). The brushed appearance can be formed by buffing (brushing) the outer surface (also called the front surface) of the main fiber layer with sandpaper or the like. In this specification, the outer surface of the artificial leather, the outer surface of the main fiber layer, the outer surface of the fiber sheet, and the outer surface of the laminated sheet refer to the surfaces exposed to the outside when used as artificial leather (for example, the surface that comes into contact with the human body in the case of chair use). In one embodiment, in the case of brushed artificial leather, the outer surface of the main fiber layer is brushed or raised by buffing or the like.

The mainstream material for artificial leather is a nonwoven fabric structure made of entangled ultrafine fibers made of materials such as polyethylene terephthalate and nylon, which is impregnated with and adhered to a polymeric elastomer resin such as polyurethane. If the fibers are simply left physically entangled by needle punching or hydroentanglement without being impregnated with a polymeric elastomer resin, it will not have sufficient abrasion resistance when actually used, will lack the supple feel of artificial leather, and will suffer from frequent shedding of threads during the dyeing process, resulting in manufacturing defects.

In the manufacturing process of artificial leather, a method is widely used in which a polymeric elastomer such as polyurethane is attached to give the leather a good texture and abrasion resistance. For example, polyurethane-impregnated artificial leather is commercially available under the names of Lamous (trademark), Ecsaine (trademark), and Alcantara (trademark). However, polymeric elastomers such as polyurethane have a high tendency to bleed out dyes, and if sufficient reduction washing treatment is not used, they are prone to problems such as poor washing fastness, vulnerability to ultraviolet rays, and susceptibility to deterioration due to long-term use, resulting in color changes and deterioration when used for a long time. In addition, they cannot be decomposed under reaction conditions that cause polyester to depolymerize, making them difficult to recycle when combined with polyester fibers, which are the most widely used main fibers in artificial leather.

In the following Patent Document 1, in order to provide an artificial leather that combines a good texture, high abrasion resistance, ease of cutting, and shape stability without impregnation with a polymer elastomer such as polyurethane resin, artificial leather is produced by mixing heat-fusible short fibers in a specific ratio with at least the surface fiber layer of a nonwoven fabric having a multilayer structure of at least two layers, a surface fiber layer and a scrim layer that is a woven or knitted fabric, and then subjecting it to a heat fusion treatment. Although the artificial leather obtained does not contain polyurethane resin and therefore has improved resistance to artificial sebum, its abrasion resistance is more than 20,000 times in an abrasion resistance test using the Martindale method, and its texture value is less than 26 cm in a flexibility test, leaving room for improvement in terms of specific applications such as car seats, which require both high abrasion resistance and a supple texture.

In addition, in the following Patent Document 2, the invention described in Patent Document 1 is improved in abrasion resistance (40,000 or more times in an abrasion resistance test using the Martindale method) and feel (bending value of less than 24 cm in a KES pure bending test) by exposing part of the thermoplastic resin formed by melting the heat-fusible short fibers to the surface of the surface fiber layer in the form of chunks of a specified size. However, as with Patent Document 1, there is room for improvement in terms of specific applications such as car seats, which require both high abrasion resistance and a supple feel.

Furthermore, Patent Document 3 listed below describes that the present invention provides a novel fiber laminate sheet that has a soft surface texture and appropriate firmness, stiffness, and breathability when not impregnated with an elastic polymer, and that the present invention provides a fiber laminate sheet that can be used to make artificial leather with a texture closer 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 can easily dissociate and entangle single fibers during hydroentanglement, all at low cost. Therefore, the artificial leather described in Patent Document 3 is limited to one that contains a polymer elastomer such as a water-based polyurethane. Patent Document 3 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 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, thereby improving the peel strength between layers 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-formed and contains binder short fibers that are partially bonded to the main component fiber by weak agglutination at the drying temperature (100 to 120° C.) during papermaking, and then further soften, shrink, and have a bond-developing 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 3 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, nor does it state that abrasion resistance or texture is improved.

Patent No. 5685003 Patent No. 6118174 Patent No. 4708494

In view of the state of the prior art described above, the problem that the present invention aims to solve is to provide an artificial leather that combines a good feel and high abrasion resistance without the addition of a polyurethane resin, and a method for producing the same.

In order to solve the above problems, the inventors conducted extensive research and experiments and unexpectedly discovered that an artificial leather having the following characteristics could solve the above problems, which led to the completion of 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, the artificial leather having the following characteristics:
(1) The surface fiber layer contains a main fiber and a thermoplastic resin;
(2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less;
(3) At least a portion of the thermoplastic resin bonds the main fibers;
(4) The thermoplastic resin in the surface fiber layer is one in which, in measurement by an atomic force microscope, a probe is pressed in with a cantilever at a load of 200 nN, and the distance the probe is pressed in from the contact initiation point to the maximum load is 20 nm or more and 200 nm or less; and (5) the number average volume of the thermoplastic resin in the surface fiber layer is 3,500 ^μm3 or more and 24,000 ^μm3 or less;
This artificial leather has the following properties.
[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-based resin.
[4] The artificial leather according to [1] or [2], wherein the thermoplastic resin is a polyamide resin.
[5] The artificial leather according to any one of [1] to [4], wherein the volumetric particle density of the thermoplastic resin per unit volume in the surface fiber layer is 0.5× ¹⁰ particles/m ^or more and 5.0× ¹⁰ particles/m or ^less .
[6] The artificial leather according to any one of [1] to [5], wherein the average quotient of the major axis divided by the minor axis when the thermoplastic resin in the surface fiber layer is approximated as an ellipse is 100 or less.
[7] The artificial leather according to any one of [1] to [6], wherein the surface fiber layer is entangled with a scrim layer which is a woven fabric.
[8] The artificial leather described in [7], wherein the scrim layer is made of polyester-based resin fibers.
[9] The artificial leather according to any one of [1] to [8], 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 count is less than 50,000.
[10] The artificial leather according to any one of the above [1] to [8], wherein when the surface is abraded with a pressing load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method), the abrasion loss is 21 mg or less after 50,000 abrasion cycles.
[11] the steps of:
(1) a step of mixing a subject fiber with a heat-fusible fiber produced using a thermoplastic resin, the heat-fusible fiber being produced using a thermoplastic resin in which a probe is pushed in from the contact initiation point to the maximum load of 20 nm or more and 200 nm or less when a probe is pushed in with a cantilever under a load of 200 nN in measurement by an atomic force microscope, so that the weight ratio of the heat-fusible fiber is 3% or more and 25% or less, and entangling the mixture by wet papermaking, and then forming a surface fiber web produced by a hydroentanglement treatment or a needle punching method; and (2) a step of forming a surface fiber layer by thermal annealing the entangled structure of the obtained surface fiber web at a temperature equal to or more than the melting point of the heat-fusible fiber and less than the melting point of the subject fiber.
The method for producing the artificial leather according to any one of [1] to [10] above, comprising:
[12] The method according to [11] above, wherein the fiber length of the heat-fusible fiber made of the thermoplastic resin is 2 mm or more and 90 mm or less.
[13] The method according to [11] or [12], wherein the fiber diameter of the heat-sealable fiber produced using the thermoplastic resin is 0.5 dtex or more and 2.2 dtex or less.
[14] The method according to any one of [11] to [13], wherein the heat-fusible fiber made of the thermoplastic resin is produced by melt spinning.
[15] The method according to any one of [11] to [14], wherein 95% by weight or more of the resin contained in the heat-fusible fiber is a copolymer of polyester and aliphatic polyether.
[16] The method according to any one of [11] to [15], wherein the melting point of the thermoplastic resin is 130° C. or higher and is 20° C. or higher lower than the melting point of the subject fiber.

The artificial leather of the present invention has excellent texture due to improved flexibility of the thermoplastic resin that bonds the main fibers having a fineness of 0.01 dtex or more and 0.5 dtex or less, while maintaining mechanical strength by keeping the size of the heat fusion points within a specified range, achieving both texture and abrasion resistance.

FIG. 2 is a diagram showing an example of the state of lump resin in a surface fiber layer. FIG. 11 is a diagram showing another example of the state of lump resin in a surface fiber layer. FIG. 11 is a diagram showing another example of the state of lump resin in a surface fiber layer. FIG. 11 is a diagram showing another example of the state of lump resin in a surface fiber layer. FIG. 11 is a diagram showing another example of the state of lump resin in a surface fiber layer. FIG. 11 is a diagram showing another example of the state of lump resin in a surface fiber layer. FIG. 11 is a diagram showing another example of the state of lump resin in a surface fiber layer. FIG. 11 is a diagram showing another example of the state of lump resin in a surface fiber layer. FIG. 2 is a schematic diagram of a force curve of an atomic force microscope. FIG. 2 is a diagram showing an example of an image obtained by cutting the artificial leather according to the embodiment and measuring it with an atomic force microscope. FIG. 2 is a diagram showing an example of a cross-sectional image obtained by cutting an artificial leather according to an embodiment and evaluating it by X-ray CT.

Hereinafter, an embodiment 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 a main fiber and a thermoplastic resin;
(2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less;
(3) At least a portion of the thermoplastic resin bonds the main fibers;
(4) The thermoplastic resin in the surface fiber layer is one in which, in measurement by an atomic force microscope, a probe is pressed in with a cantilever at a load of 200 nN, and the distance the probe is pressed in from the contact initiation point to the maximum load is 20 nm or more and 200 nm or less; and (5) the number average volume of the thermoplastic resin in the surface fiber layer is 3,500 ^μm3 or more and 24,000 ^μm3 or less;
It is an artificial leather having the following properties.

The main fibers contained in the surface fiber layer are fibers contained in an amount of 60% by mass or more, more preferably 70% by mass or more, and further 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, ease of manufacturing ultrafine fibers, general market availability, etc., but as described above, in consideration of applications requiring durability such as the field of car seats, polyethylene terephthalate is preferred because the fiber itself does not yellow even when exposed to direct sunlight for a long period of time and has excellent color fastness. Furthermore, from the viewpoint of reducing the environmental load, chemically recycled or material recycled polyethylene terephthalate, polyethylene terephthalate using plant-derived raw materials, etc. are even more preferred.

As the polyester fibers serving as the main fibers constituting the surface fiber layer, polyethylene terephthalate (PET), polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, copolymers thereof, etc. are preferably used. As the polyamide fibers, nylon, meta-aramid, para-aramid, copolymers thereof, etc. are preferably used. As the acrylic fibers, polymers of acrylic acid esters or methacrylic acid esters, copolymers thereof, etc. are preferably used. As the polyolefin fibers, polyethylene, polypropylene, polybutene, polystyrene, copolymers thereof, etc. are preferably used. These fibers can be used alone, or fibers of various polymers can be mixed in any ratio.

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, in order to easily obtain a texture similar to that of natural leather and a suede-like or nubuck-like surface texture. From the viewpoints of production efficiency, production stability, and abrasion resistance during fiber production, the fineness is preferably 0.01 dtex or more, and even more preferably 0.03 dtex or more.
The subject 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 part from a sea-island fiber in which a copolymer polyester is used as the sea part and a regular polyester is used as the island part.

Additives may be mixed into or attached to the main fiber as long as the desired effect is achieved. Additives include titanium oxide, various oxidation inhibitors, light resistance agents, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, dyes, etc.

When a method using short fibers is selected as the manufacturing method for the main fiber, the short fiber length is preferably 13 mm to 102 mm, more preferably 25 mm to 76 mm, and even more preferably 38 mm to 76 mm, in dry methods (carding method, airlaid method, etc.), and is preferably 1 mm to 30 mm, more preferably 2 mm to 25 mm, and even more preferably 3 mm to 20 mm, in wet methods (papermaking method, etc.). For example, the aspect ratio (L/D), which is the ratio of length (L) to diameter (D) of short fibers used in wet methods (papermaking method, etc.), is preferably 500 to 2000, more preferably 700 to 1500. Such an aspect ratio is preferable because the short fibers have good dispersibility and openability in the slurry when the short fibers are dispersed in water to prepare the slurry, the fiber layer strength is good, and the fiber length is shorter and the fibers are easier to disperse as single fibers compared to the dry method, so that the fibers are less likely to develop a pilling-like appearance due to friction. For example, the fiber length of a short fiber with a diameter of 4 μm is preferably 2 mm or more and 8 mm or less, more preferably 3 mm or more and 6 mm or less.

The higher the flexibility of the thermoplastic resin that bonds the main fibers, the higher the flexibility of the artificial leather and the better the texture. In order to obtain artificial leather with a good texture, the thermoplastic resin must have a probe-inserted distance of 20 nm or more and 200 nm or less when the probe is pressed in with a load of 200 nN using a cantilever in an atomic force microscope. If the probe is pressed in from the contact start point to the maximum load by 20 nm or more, the flexibility of the thermoplastic resin increases and the texture of the artificial leather improves. In order to obtain artificial leather with a better texture, the distance is preferably 30 nm or more, and more preferably 40 nm or more. On the other hand, if the probe is pressed in from the contact start point to the maximum load by more than 200 nm, the flexibility of the thermoplastic resin is too high, mechanical strength cannot be obtained, and the spinnability of the resin is poor. From the viewpoint of spinnability, the distance is preferably 170 nm or less, and more preferably 150 nm or less.

From the viewpoint of availability, the thermoplastic resin constituting the surface fiber layer is preferably a polyester resin, a polyamide resin, an acrylic resin, a polyolefin resin, or the like. As the polyester resin, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, or copolymers thereof, or the like, is preferably used. As the polyamide resin, nylon or its copolymers, or the like, is preferably used. As the acrylic resin, polymers of acrylic acid esters or methacrylic acid esters, or their copolymers, or the like, are preferably used. As the polyolefin resin, polyethylene, polypropylene, polybutene, polystyrene, or their copolymers, or the like, is preferably used.

The thermoplastic resin does not necessarily have to be composed of only a single polymer, and may be a mixture of multiple types of polymers.
In addition, this thermoplastic resin may contain or have attached thereto additives, such as titanium oxide, various antioxidants, light resistance agents, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, dyes, etc., as long as the desired effect is achieved.

The thermoplastic resin preferably has a melting point of 130°C or higher, and is at least 20°C lower than the melting point of the main fiber. Considering the detachment of the thermoplastic resin from the artificial leather during dyeing, the melting point of the thermoplastic resin is preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. When bonding the main fibers together with the thermoplastic resin, the melting point of the thermoplastic resin must be lower than that of the main fiber. In addition, when the thermoplastic resin is a mixture of multiple polymers, it is preferable that the thermoplastic resin with the highest melting point has a melting point that is 20°C or lower than the melting point of the main fiber with the lowest melting point. Regarding the range of the melting point, if it is within the above range, the abrasion resistance and appearance quality described in this application can be achieved, but from the viewpoint of maintaining particularly good appearance quality, it is preferable that the melting point is 30°C or lower, and more preferably 40°C lower.

The composition of the thermoplastic resin is not particularly limited as long as the distance the probe is pushed from the contact start point to the maximum load when the probe is pushed in with a load of 200 nN using a cantilever is 20 nm or more and 200 nm or less. From the viewpoint of combining the texture of artificial leather with high abrasion resistance, elastomers made of copolymers of polyester and aliphatic polyether and nylon-based elastomers can be used. Among them, polyester-based resins are preferred from the viewpoint of abrasion resistance, and it is preferable to use copolymers of polybutylene phthalate and aliphatic polyether, copolymers of polybutylene phthalate and polytetramethylene ether glycol, and in particular block copolymers of polybutylene phthalate and polytetramethylene ether glycol. Here, the form of the copolymer is not particularly limited, and it is particularly preferable to use a block copolymer in order to allow the soft segment and the hard segment to coexist appropriately and for the simplicity of the manufacturing method. The ratio of the soft segments can be calculated by the following calculation formula.
Presence ratio of soft segments (%)=number of monomer units of soft segments×100/(total number of monomer units of soft segments and hard segments)
The soft segment ratio (%) can be calculated using 1H-NMR, and is preferably from 40% to 85%, particularly preferably from 50% to 75%.
In the copolymer of polybutylene phthalate and polytetramethylene ether glycol, polybutylene phthalate is the hard segment and polytetramethylene ether glycol is the soft segment.

It is preferable that the thermoplastic resin is exposed on the surface of the surface fiber layer in a block shape. When it is exposed on the surface, the main fibers present on the surface are sufficiently held by resin fusion, and the fibers are less likely to fall off or break, improving the abrasion resistance of the artificial leather. It is also preferable that part or all of the thermoplastic resin bonds the main fibers together. When the thermoplastic resin bonds the main fibers together, the main fibers can be held together, the fibers are less likely to fall off or break, and the artificial leather has satisfactory abrasion resistance and strength.

It is also preferable that the thermoplastic resin is present in a block shape in the cross section of the surface fiber layer. When it is present only on the surface and also in a block shape in the cross section, the main fibers are sufficiently held together by the resin fusion, the abrasion resistance of the artificial leather is improved, the density of the surface fiber layer is increased, and the luxurious, moist texture characteristic of artificial leather can be expressed.

In this embodiment, the thermoplastic resin must bond the main fibers together, and the number-average volume of the thermoplastic resin must be 3500 μm ³ or more and 24000 μm ³ or less. If the number-average volume of the thermoplastic resin exceeds 24000 μm ³ , the resin masses present on the surface of the main fibers are too large, impairing the appearance quality and the feel, and the density of the number of fusion points between the main fibers becomes small, and the main fibers are not sufficiently held together, resulting in poor abrasion resistance of the surface layer. On the other hand, if the volume is less than 3500 μm ³ on average, the size is not sufficient to bond the main fibers together, and abrasion resistance cannot be achieved. The number-average volume is preferably 4000 μm ³ or more and 22000 μm ³ or less, more preferably 6000 μm ³ or more and 20000 μm ³ or less.

The volumetric density per unit volume in the surface fiber layer is preferably 0.5×10 ¹² pieces/m ³ or more and 5.0×10 ¹² pieces/m ³ or less. When the number of thermoplastic resins per unit volume is 0.5×10 ¹² pieces/m ³ or more, a plurality of main fibers can be bonded with a plurality of heat fusion point resins, and the fiber bundles are less likely to fall off when worn, and wear resistance can be exhibited. On the other hand, when the thermoplastic resin per unit volume is 5.0×10 ¹² pieces/m ³ or less, the surface fiber layer does not become too hard, and a supple, luxurious feel required for artificial leather can be obtained. The volumetric density per unit volume in the surface fiber layer is preferably 0.6×10 ¹² pieces/m ³ or more and 3.0×10 ¹² pieces/m ³ or less, and more preferably 0.8×10 ¹² pieces/m ³ or more and 1.5×10 ¹² pieces/m ³ or less.

It is preferable that the thermoplastic resin isotropically bonds the main fibers when viewed from any angle in three dimensions. Specifically, it is preferable that the average value of the quotient obtained by dividing the major axis by the minor axis when the thermoplastic resin in the surface fiber layer is approximated as an ellipse is 100 or less. If the average value of the quotient obtained by dividing the major axis by the minor axis when the thermoplastic resin is approximated as an ellipse is 100 or less, the heat-sealing resin is sufficiently melted when bonding the main fibers, the adhesive strength is high, and high abrasion resistance can be obtained. The average value of the quotient obtained by dividing the major axis by the minor axis when the thermoplastic resin is approximated as an ellipse is more preferably 30 or less, and even more preferably 10 or less. Since it is preferable that the thermoplastic resin is close to a perfect sphere (quotient value 1), there is no particular limitation, but the average value of the quotient obtained by dividing the major axis by the minor axis when the thermoplastic resin is approximated as an ellipse may be 1 or more.

Another embodiment of the present invention is a method for producing a process comprising the steps of:
(1) a step of mixing a subject fiber with a heat-fusible fiber produced using a thermoplastic resin, the heat-fusible fiber being produced using a thermoplastic resin in which a probe is pushed in from the contact initiation point to the maximum load of 20 nm or more and 200 nm or less when a probe is pushed in with a cantilever under a load of 200 nN in measurement by an atomic force microscope, so that the weight ratio of the heat-fusible fiber is 3% or more and 25% or less, and entangling the mixture by wet papermaking, and then forming a surface fiber web produced by a hydroentanglement treatment or a needle punching method; and (2) a step of forming a surface fiber layer by thermal annealing the entangled structure of the obtained surface fiber web at a temperature equal to or more than the melting point of the heat-fusible fiber and less than the melting point of the subject fiber.
The method for producing the artificial leather includes the steps of:

The artificial leather of this embodiment may include a scrim layer. The scrim layer used functions as a core material, and is preferably a woven or knitted fabric from the viewpoint of stabilizing the production of the papermaking sheet in the papermaking process and increasing the mechanical strength of the obtained artificial leather. The material of the scrim layer is preferably the same polymer system as the main fiber in terms of color uniformity in dyeing, and in the case of knitted fabrics, single knits knitted with a gauge of 22 to 28 are preferable. In the case of woven fabrics, higher dimensional stability and strength can be achieved than in knitted fabrics, so they are even more suitable. The yarns constituting the woven fabric may be monofilament or multifilament. The single fiber fineness of the yarns is preferably 5.5 dtex or less in terms of ease of obtaining a flexible artificial leather using an entangled sheet. As the form of the yarns constituting the woven fabric, raw multifilament yarns such as polyester and polyamide, or textured yarns that have been subjected to false twist processing, etc., are preferably twisted with a twist number of 0 to 3000 T/m. The multifilament may be a normal one, and for example, 33 dtex/6f, 55 dtex/24f, 83 dtex/36f, 83 dtex/72f, 110 dtex/36f, 110 dtex/48f, 167 dtex/36f, 166 dtex/48f, etc. of polyester, polyamide, etc. are preferably used. The threads constituting the woven fabric may be long multifilament fibers. In order to obtain an artificial leather that is soft and has excellent mechanical strength, the weaving density of the threads in the woven fabric is preferably 30 threads/inch or more and 150 threads/inch or less, more preferably 40 threads/inch or more and 100 threads/inch or less. In order to provide good mechanical strength and a suitable texture, the basis weight of the woven fabric is preferably 20 g/ ^m2 or more and 150 g/ ^m2 or less. In addition, the presence or absence of false twist processing in the woven fabric, the number of twists, the single fiber fineness of the multifilament, the weaving density, etc. contribute to the entanglement with the constituent fibers of the main fiber layer, the flexibility of the artificial leather, as well as mechanical properties such as seam strength, tear strength, tensile strength/elongation, and stretchability, and may be appropriately selected depending on the target physical properties and applications.

The length of the main fiber in step (1) is not particularly limited, but is preferably 2.5 mm or more and 90 mm or less. When a scrim layer is used, if the length of the main fiber is within this range, hydroentanglement with the scrim layer will be sufficient. If the length of the main fiber is 2.5 mm or less, the entanglement effect with the scrim layer in the entanglement step will not be fully expressed, and relative peeling will easily occur between the main fiber layer and the scrim layer, which may cause quality defects such as poor adhesion and poor appearance. The length of the main fiber 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 length of the heat-sealing fibers made of a thermoplastic resin is preferably 2.0 mm or more and 90 mm or less. When a scrim layer is used, if the length of the heat-sealing fibers is within this range, water flow entanglement with the scrim layer is sufficient, and adhesion between the main fiber and the scrim is also possible when the heat-sealing fibers are melted. If the length of the heat-sealing fibers is less than 2.0 mm, the entanglement effect with the scrim layer is not fully expressed in the entanglement process, and adhesion between the main fiber and the scrim cannot be achieved when the heat-sealing fibers are melted, which may cause quality defects such as poor adhesion and poor appearance.

The artificial leather of this embodiment can include at least a surface fiber layer that constitutes the 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). In addition, in the case of an artificial leather of this embodiment consisting of three layers, a surface fiber layer/scrim layer/back fiber layer, the back surface of the back fiber layer becomes the second surface.

In addition, when adopting a surface fiber layer/scrim layer/back fiber layer configuration 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 preferable that it is the same as the main fiber and/or thermoplastic resin of the surface fiber layer. In addition, when a back fiber layer is included, it may be made of a material different from that of the surface fiber layer, for example, by adding a flame retardant, to add desired properties.

A preferred method for producing the artificial leather of this embodiment is to heat treat a nonwoven fabric structure having a surface fiber layer formed by mixing main fibers and fully meltable heat-fusible fibers, thereby melting the heat-fusible fibers and forming a lump of thermoplastic resin in the surface fiber layer.
The heat-fusible fibers are preferably full-melt fibers so that the molten resin has a sufficient number of points at which the main fibers are fused together. Compared with sheath-core fibers using a low-melting thermoplastic resin in the sheath or side-by-side fibers using a low-melting thermoplastic resin on only one side, full-melt fibers have many points at which the main fibers are bonded together and a large amount of fusion components in the fusion parts, so that the fusion strength is sufficient. In addition, the fusion points are not continuously present in the vicinity of each other via the heat-fusible fibers, so that the feel is likely to be soft.
The resin component contained in the heat-sealable fiber is preferably 95% or more, but additives may be mixed in or attached to the fiber as long as the desired effect is achieved. Additives include titanium oxide, various oxidation inhibitors, light resistance agents, antistatic agents, flame retardants, softeners, fastness improvers, pigments such as carbon black, dyes, etc. The resin component contained in the heat-sealable fiber is preferably 96% or more, more preferably 97% or more.

From the viewpoint of availability, the heat-fusible fibers (heat-melting yarns) constituting the surface fiber layer are preferably polyester fibers, polyamide fibers, acrylic fibers, or polyolefin fibers. As polyester fibers, polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactate, copolymers thereof, etc. are preferably used. As polyamide fibers, nylon and copolymers thereof are preferably used. As acrylic fibers, polymers of acrylic acid esters or methacrylic acid esters, copolymers thereof, etc. are preferably used. As polyolefin fibers, polyethylene, polypropylene, polybutene, polystyrene, copolymers thereof, etc. are preferably used.

In this embodiment, the weight mixing ratio of the heat-fusible fibers is preferably 3% or more and 25% or less. The mixing ratio is the percentage of the weight of the heat-fusible fibers relative to the total weight of the main fiber and the thermoplastic fiber. If the weight mixing ratio is less than 3%, sufficient fusion strength cannot be obtained, making it difficult to obtain good abrasion resistance and shape stability. On the other hand, if the weight mixing ratio exceeds 25%, the texture becomes hard, which is not preferable. This weight mixing ratio is more preferably 4% or more and 20% or less, and even more preferably 6% or more and 15% or less.

In this specification, the melting points of the main fiber, heat-fused fiber, etc. refer to values measured by DSC (differential scanning calorimeter). The differential scanning calorimeter measures the difference in heat between the measurement sample and the reference material, and calculates the melting point of the measurement sample. Specifically, the top of the endothermic peak observed when the temperature was raised from 25°C to 250°C at 10°C/min was taken as the melting point.

The heat-fusible fiber does not necessarily have to be composed of a single polymer, and may be a mixture of multiple polymers. In terms of high fusion strength and uniformity in dyeing, it is preferable to use the same polymer system as the main fiber. The heat-fusible 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 fiber using a copolymer polyester as the sea component and a regular polyester as the island component. In terms of the size of the lump-shaped thermoplastic resin after melting, the fineness of the heat-fusible fiber is preferably 0.5 dtex or more and 2.2 dtex or less. If the fineness is 2.2 dtex or less, the lump-shaped thermoplastic resin after melting is uniformly dispersed on the surface of the surface fiber layer, and the appearance quality and feel are excellent. 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.
In addition, the heat-fusible fibers 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, dyes, etc., as long as the desired effects are achieved.

Methods for forming the surface fiber layer include using the main fibers and/or heat-fusible fibers in the form of short fibers and entangling the fibers to form a nonwoven structure using a papermaking method, a carding method, an air-laying method, or the like.
From the viewpoints 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 performed using a hydroentanglement method called the spunlace method, a needle punch method, or the like, but the hydroentanglement method is preferred because it does not destroy the structure of the woven or knitted fabric that is the scrim layer.

The above-mentioned thermoplastic resin can be evaluated by cutting the artificial leather vertically and observing it with an optical microscope or electron microscope, or by measuring three-dimensional images with CT or MRI. It is necessary to accurately evaluate the position, density, shape, and size of the heat-sealed resin not only on the surface of the surface fiber layer, but also inside it. This can be accurately analyzed and evaluated by performing continuous image analysis of the cross section in X-ray CT as described in the examples, taking the steps to properly process the images, and then performing mathematical analysis.

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 performed by a known method such as buffing with sandpaper. In this case, if the raising is performed before the heat-fusible fibers of the surface fiber layer are heat-fusible, a suede-like surface texture can be obtained. On the other hand, if the raising is performed after the heat-fusible fibers are heat-fusible, a nubuck-like surface texture can be obtained.

There are no particular limitations on the dyeing process. For example, when the main fiber is a polyester fiber, disperse dyes are generally used. The dyeing method can be a conventional method well known to dye processing companies, and for artificial leather, a liquid flow dyeing machine is preferably used in terms of uniform 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 limitations on the conditions for reduction and washing, and basic reducing agents and acidic reducing agents can be used without any particular limitations in accordance with conventional methods.

In the present embodiment, the heat fusion treatment (heat annealing shrinkage) 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 (heat annealing temperature) is at least 5°C higher than the melting point of the thermoplastic resin, preferably at least 10°C higher, and at most 240°C. If the difference between the treatment temperature and the melting point of the thermoplastic fiber is less than 5°C, a sufficient heat fusion effect may not be obtained. If the treatment temperature exceeds 240°C, the polyester fiber may melt, and the surface quality and abrasion resistance may not be fully expressed.

When thermally annealing, it is preferable to relax the nonwoven fabric structure. By performing the above heat fusion while sagging and shrinking the surface fiber web entangled with the scrim layer in the MD and CD directions, the entangled structure is in a relaxed state, i.e., the main fibers are fixed in a non-tensioned state. This makes it possible to obtain artificial leather with high abrasion resistance and texture compared to the conventional technology method in which heat fusion is performed while tensing and shrinking using a pin tenter.

The thickness of the artificial leather of this embodiment is preferably 0.40 mm to 1.50 mm. By making the thickness of the artificial leather 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 ultrafine fiber layer on the surface, thereby achieving both a soft 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 soft feel and appropriate hardness.

The artificial leather of the present embodiment preferably has good abrasion resistance for use as an artificial leather in that, 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 count is less than 50,000 times.
Similarly, when the surface is abraded with a pressure load of 12 kPa according to JIS-L-1096 E method (Martindale method), the abrasion loss is preferably 21 mg or less after 50,000 abrasion cycles.

The present invention will be specifically described 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 by the following methods.

(1) Force curve measurement pretreatment The artificial leather was cut into a width of 5 mm and a length of 10 mm to prepare a sheet-like sample. This sheet was mixed with 9.7 ml of Quetol 812, 3.7 ml of MNA, 6.6 ml of DDSA, and 0.34 ml of DMP-30 manufactured by Nissin EM to prepare a resin composition, which was then vacuum degassed. The epoxy resin prepared with the sample was then filled into a silicon embedding plate and cured in a thermostatic chamber at 60°C for 3 days. The composite of the obtained sample and the cured epoxy resin was removed, and a precise cross section of the sample was prepared using a cryomicrotome (Ultracut-UCT manufactured by Leica).

(2) Force curve measurement The deformation amount of the thermoplastic resin can be measured in the force curve mode of an atomic force microscope. The cantilever of the atomic force microscope is pressed against the thermoplastic resin of the sample cross section created by a cryomicrotome in a direction perpendicular to the surface and then released, to obtain a force curve as shown in Figure 9.
The atomic force microscope used was a Dimension Icon manufactured by Bruker Corporation, which is equipped with a force curve measurement function, and the probe used was an RTESPA type silicon single crystal probe manufactured by Bruker Corporation.
The probe was calibrated before the measurement. First, the warp sensitivity of the cantilever was measured on a sapphire plate. Next, the spring constant of the cantilever was measured by the thermal vibration method, and AFM image measurement of the cross section of the sample prepared by a cryomicrotome was performed under conditions that allowed quantification of the tip-sample distance and load by performing calibration, and the location of the thermoplastic resin was identified from the shape characteristics. At this time, the epoxy resin was observed as the matrix with the largest area, and the cross section of the main fiber was observed as a certain shape such as a circle or ellipse, but the thermoplastic resin component was observed as an area of indeterminate shape. When measuring the force curve of the thermoplastic resin, in order to avoid the influence of the hardness of the epoxy resin or the thread, the measurement was performed by selecting a location 1 μm or more away from the interface between the thermoplastic resin and the epoxy resin, and from the interface between the thermoplastic resin and the main fiber. The force curve measurement was performed with a load of 200 nN and a measurement frequency of 1 Hz. 9, the horizontal axis represents the tip-sample distance, and the vertical axis represents the load, and in this force curve, when the probe is brought close to the sample, A represents the state before contact, B represents the point at which the load becomes negative due to the jump-in at the start of contact, C represents the point at which the load becomes 0 as the load increases, and D represents the point at which the load reaches 200 nN. The distance between C and D was taken as the deformation amount of the thermoplastic resin. Different thermoplastic resin regions were selected and this force curve measurement was performed 15 times, and the arithmetic average of the obtained deformation amounts of the thermoplastic resin was taken as the measured value.

(3) Number average volume (μm ³ ), volume number density (10 ¹² particles/m ³ )
[Image measurement using X-ray CT]
The observation of the mass of the heat fusion point was performed using an X-ray CT device (Rigaku Corporation's "High Resolution 3D X-ray Microscope Nano3DX"), with the entire thickness direction of the artificial leather being the observation area, and a three-dimensional image was taken so that the center of the thickness direction cross section was the center point of the observation area. The image measurement was performed using copper as the X-ray target, under conditions of an X-ray tube voltage of 40 kV, a tube current of 30 mA, an exposure time of 12 seconds/sheet, and a spatial resolution of 1.08 μm/pixel. Using the same operation, 1000 images were taken per 180 degrees of rotation angle to obtain three-dimensional measurement data.

[Image processing method, analysis method, and method for calculating the additive average value of the quotient obtained by dividing the major axis by the minor axis when approximating an ellipse]
The detailed process of processing and analyzing the three-dimensional measurement data obtained above will be described below. The image analysis software used was ImageJ (version: 1.51j8) (National Institutes of Health, USA).
(i: Image rotation) The three-dimensional image is rotated so that the plane direction of the artificial leather coincides with the plane direction consisting of the xz axes, and the thickness direction of the artificial leather coincides with the y axis.
(ii: Trimming) Trim the three-dimensional image into a rectangular parallelepiped. In this case, the y-axis is set to a range that includes the entire thickness and does not include excessive space outside the film. Regarding the x-axis and z-axis, after the y-axis range is determined, the maximum range is taken so that no pixels outside the measurement field of view are included within the trimmed rectangular parallelepiped.
(iii: Setting of axes) The number of pixels in the x-axis direction of the trimmed image is set to x0, the number of pixels in the y-axis direction to y0, and the number of pixels in the z-axis direction to z0.
(iv: Filtering) A median filter is applied with a radius of 2 pix.
(v: Region division) The Otsu method is applied to divide the regions. At this time, in order to clarify the difference between light and dark, the pixel brightness value is set so that the air portion not containing the artificial leather is set to 0 and the main fiber portion constituting the artificial leather is set to 255.
(vi: Segmentation) The image processing method segmentation is applied to pixels with a brightness value of 255. A structure in which the number of pixels (pix) of a three-dimensionally connected region with a brightness value of 255 is 10,000 or less is regarded as noise, and its brightness value is changed to 0 and removed.
(vii: Noise Removal) Of the pixels with a luminance value of 0, pixels with a luminance value of 0 that are three-dimensionally surrounded by pixels with a luminance value of 255 are regarded as noise, and their luminance values are changed to 255 and removed.
(viii: Calculation of porosity) A two-dimensional original image of the xz plane is cut out from the three-dimensional image at a thickness of 1 pix in the thickness direction, and the porosity on that plane is calculated using the following formula:
The porosity is calculated as the number of pixels with a brightness value of 0 divided by the total number of pixels.
(ix: Thickness distribution of porosity) The above (viii) is carried out for all y data to obtain the distribution of porosity in the y-axis direction.
(x: Calculation of the size of high-luminance pixels) The size of a pixel with a luminance value of 255 is calculated by the Thickness method. This results in a three-dimensional image in which the luminance value of each pixel is the diameter value of the largest sphere that fits in that location. The Thickness method is a method described in the literature "A new method for the model-independent assessment of thickness in three-dimensional images" by T. Hildebrand and P. Ruesgsegger, J. of Microscopy, 185 (1996) 67-75, and can be executed, for example, by BoneJ Thickness, a plug-in for the image analysis software ImageJ. Furthermore, in the image obtained here, structures of 12 μm or less are regarded as main fibers and are removed as objects of analysis, so the image brightness value of the brightness value of the number of pixels corresponding to 12 μm or less is changed to 0.
(xi: binarization) The image obtained in (x) above is binarized by setting all pixels whose luminance value is not 0 to 255 and leaving pixels whose luminance value is 0 as 0.
(xii: Particle analysis) A three-dimensional particle analysis is performed on the image obtained in (xi) above. A three-dimensional continuous part with a brightness value of 255 is considered to be one particle, and the central coordinates (XC, YC, ZC) of each particle and the number of pixels of the continuous structure are calculated.
(xiii: Definition of the front surface, scrim layer, and back surface) In the data of the porosity distribution obtained in (ix) above, a range of 95% is used for analysis (the outermost surfaces of the front surface and back surface are excluded from the analysis), so the y-axis value on the surface of the artificial leather where the porosity is 0.95 or more is the furthest from the front side is defined as y1. In the case where a scrim layer is included, the portion where the porosity value in (viii) and fibers with a fineness of 100 dtex or more appear is defined as the end of the front side, and its coordinate is y2.
(xiv: Calculation of the sum of the number of pixels and data analysis) Of all the particles found in (xii) above, for particles whose coordinate values satisfy y1<YC<y2, the number of particles and the sum of the number of pixels of the particles are found.
Number average volume (μm ³ )=sum of pixel numbers of particles*p*p*p÷number of particles Volume number density (10 ¹² particles/m ³ )=number of particles÷(|y2-y1|*p*x0*p*z0*p)
Here, p is the pixel size (m/pix), which is the actual size (m) of one pixel (pix).
(xv: Calculation of the average value of the quotient (major axis/minor axis ratio) obtained by dividing the major axis by the minor axis when approximating an ellipse and data analysis) Three-dimensional particle analysis is performed on the image obtained in (xi) above. A three-dimensionally continuous part with a brightness value of 255 is regarded as one particle, and each particle is approximated as an elliptical sphere. The three axes of the elliptical sphere are designated as the major axis, middle axis, and minor axis in order of length. The average value of the quotient obtained by dividing the major axis by the minor axis when approximating each particle as an ellipse is calculated using the following formula:
The calculation was made by dividing the major axis by the minor axis = major axis length/minor axis length.
However, when the major axis of the approximated ellipsoid is greater than the minimum axis of the rectangular parallelepiped to be analyzed, it is excluded as an error and the aspect ratio is set to 0. The average aspect ratio is calculated using the following formula:
Average major axis divided by minor axis = sum of major axis divided by minor axis of particles ÷ (total number of particles - total number of particles excluded)
The calculation was done as follows.

(4) Melting point The melting point of the heat-fusible fiber was determined by placing 3 mg of the heat-fusible fiber in a nitrogen atmosphere, heating it from 25° C. to 250° C. at a rate of 10° C./min using aluminum as a reference substance with a DSCQ100 manufactured by TA Instruments, and then rapidly cooling it. The fiber was then heated for the second time under the same conditions, and the top of the endothermic peak that appeared was taken as the melting point.

(5) Explanation of the structure of heat fusion points The state of the lump resin and its determination will be explained with reference to the drawings. FIG. 1 is an example where the lump resin is exposed on the surface of the surface fiber layer but does not bond the main fibers, and FIG. 2 is an example where the lump resin is exposed on the surface and bonds the main fibers. FIG. 3 is an example where the lump resin is not exposed on the surface but bonds the main fibers, FIG. 4 is an example where the lump resin is exposed on the surface and bonds the main fibers, and FIG. 5 is an example where the lump resin is exposed on the surface but does not bond the main fibers. FIG. 6 is an example where the heat fusion fiber is not melted, and is not called lump resin. FIG. 7 is an example where sheath-core fiber is used as the heat fusion fiber, and the heat fusion fiber retains its fibrous shape, and is not called lump resin. FIG. 8 is an example where the lump resin is exposed on the surface but does not bond the main fibers. In the drawings, 1 is the main fiber, 2 is lump resin, 3 is unmelted resin, and 4 is sheath-core fiber.
The phrase "the main fibers are bonded to each other" used herein means that at least two main fibers penetrate the interior of the block resin (thermoplastic resin) and are physically bonded to each other.

(6) Fineness Ten randomly selected points on the front or back fiber layer sample of the artificial leather were photographed with a microscope at a magnification of 2500 times, and the diameters of the fibers at 50 points were measured, and the average value thereof was calculated as the average fiber diameter. The fineness [dtex] of the main fiber was calculated by converting the obtained average fiber diameter and the density of the main fiber.
In addition, artificial leather was immersed in ethanol, wrapped in a gelatin capsule, and freeze-dried in liquid nitrogen. The capsule was 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 magnification of 200 times. 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-fused fiber is the fineness of the raw short fiber, and was evaluated using a scanning electron microscope. Specifically, an adhesive carbon tape was attached on an evaluation stage, 0.05 g of the raw short fiber was placed on the tape, and the excess heat-fused fiber was removed with an air duster to prepare a sample. The sample was observed under conditions of WD = 10 mm and magnification of 200 times, and the thickness was measured at five points on each of 20 images obtained.

(7) Abrasion resistance and abrasion loss The sample surface was abraded with a pressure load of 12 kPa according to the method specified in JIS-L-1096 E method (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 and evaluation was not possible.
x: The scrim is exposed after less than 30,000 abrasion cycles.
Δ: The scrim is exposed after 30,000 or more and less than 40,000 abrasion cycles.
◯: 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.
In addition, a specimen of artificial leather (a perfect circle with a diameter of 40 mm) specified in JIS-L-1096 E method (Martindale method) was subjected to a pressure load of 12 kPa and abraded 50,000 times, and the weight change [mg] was evaluated as the abrasion loss. The measurement was carried out three times, and the arithmetic average was used as the result.

(8) Texture Evaluation The dyed artificial leather samples obtained were cut into 25 cm squares, arranged on a table with the surface facing up, and 20 subjects (10 men and 10 women, 2 subjects each in their 20s to 60s) were blindfolded and asked to test the texture by moving the brushed surface. At the same time, a similar texture test was also conducted on natural suede, and a sensory evaluation was conducted on the suppleness and luxurious feel of the surface on a 5-point scale (suede being 5 points), with the scores rounded off to the nearest 1 decimal place.
◯: The average score of the sensory evaluation was 4.0 points or more. Δ: The average score of the sensory evaluation was 3.0 points or more and less than 4.0. ×: The average score of the sensory evaluation was less than 3.0 points.

(9) Reduced Viscosity 0.35 g of the resin that is the raw material of the thermally fused fiber was added to 0.25 deciliters of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), and stirred at room temperature for 3 hours using a magnetic stirrer to prepare a diluted solution. The obtained diluted solution was added to an Ubbelohde viscosity tube (tube diameter: 0.03), and the falling time of the diluted solution and the HFIP solvent was measured in a water bath adjusted to 25°C ± 0.1°C to obtain the specific viscosity (ηsp). After the measurement, the diluted solution was weighed and dried in an oven at 120°C for 1 hour, and the polymer concentration C (g/dl) was calculated from the obtained solid content. The specific viscosity (ηsp) was divided by the polymer concentration C (g/dl) to obtain the reduced viscosity ηsp/c. The solvent and the amount of solvent may be changed depending on the type of resin that is the raw material of the thermally fused fiber.

The method for producing the resin used in the production of the heat-fusible fibers will be described below.
[Resin Production Example 1]
Polycondensation reaction was carried out using dimethyl terephthalate, 1,4-butanediol, and polytetramethylene glycol to obtain a polyester polyether block copolymer elastomer. Specific experimental conditions are shown below. 1000g of dimethyl terephthalate, 650g of 1,4-butanediol, and 8.3g of tetrabutoxytitanium (IV) were added to a 5L autoclave reactor equipped with a dispensing machine manufactured by Shibata Chemical Industry Co., Ltd., and after sufficient nitrogen replacement, the reactor was pressurized to 2 atm with nitrogen, and then the reactor was reacted at 250°C for 5 hours under a rotating condition of 50 rpm to carry out a polycondensation reaction, thereby obtaining a prepolymer. Next, 1210g of polytetramethylene glycol having a number average molecular weight of 2000 was added, and the polycondensation reaction was continued at 250°C for 2 hours while reducing the pressure to 0.01 atm. The reactor was returned to room temperature and pressure, and then removed from the reactor to obtain a polyester polyether block copolymer elastomer resin 1. This polyester polyether block copolymer elastomer resin 1 had a melting point of 182° C. and a reduced viscosity of 3.0 dl/g.

[Resin Production Example 2]
Polycondensation reaction was carried out using dimethyl terephthalate, dimethyl isophthalate, 1,4-butanediol, and polytetramethylene glycol to obtain a polyester polyether block copolymer elastomer. Specific experimental conditions are shown below. 780 g of dimethyl terephthalate, 220 g of dimethyl isophthalate, 650 g of 1,4-butanediol, and 8.3 g of tetrabutoxytitanium (IV) were added to a 5L autoclave reactor equipped with a dispensing machine manufactured by Shibata Chemical Industry Co., Ltd., and after sufficient nitrogen replacement, the reactor was pressurized to 2 atm with nitrogen, and then reacted at 250°C for 5 hours under a rotating condition of 50 rpm to carry out a polycondensation reaction to obtain a prepolymer. Next, 500 g of polytetramethylene glycol having a number average molecular weight of 2000 was added, and the polycondensation reaction was continued at 250°C for 2 hours while reducing the pressure to 0.01 atm. The temperature and pressure were returned to normal temperature and normal pressure, and the reactor was removed from the reactor to obtain a polyester polyether block copolymer elastomer resin 2. This polyester polyether block copolymer elastomer had a melting point of 170° C. and a reduced viscosity of 2.3 dl/g.

[Resin Production Example 3]
Polycondensation reaction was carried out using dimethyl terephthalate, dimethyl isophthalate, 1,4-butanediol, and polytetramethylene glycol to obtain a polyester polyether block copolymer elastomer. Specific experimental conditions are shown below. 740 g of dimethyl terephthalate, 260 g of dimethyl isophthalate, 650 g of 1,4-butanediol, and 8.3 g of tetrabutoxytitanium (IV) were added to a 5L autoclave reactor equipped with a suction machine manufactured by Shibata Chemical Industry Co., Ltd., and after sufficient nitrogen replacement, the reactor was pressurized to 2 atmospheres with nitrogen and reacted at 250°C for 5 hours under 50 rpm suction conditions to obtain a prepolymer. Next, 750 g of polytetramethylene glycol with a number average molecular weight of 2000 was added, and polycondensation reaction was continued at 250°C for 2 hours while reducing the pressure to 0.01 atmosphere, and the temperature and pressure were returned to normal temperature and normal pressure, and the reactor was removed to obtain a polyester polyether block copolymer elastomer resin 3. This polyester polyether block copolymer elastomer resin 3 had a melting point of 155° C. and a reduced viscosity of 3.0 dl/g.

[Resin Production Example 4]
Polycondensation reaction was carried out using dimethyl terephthalate, dimethyl isophthalate, 1,4-butanediol, and polytetramethylene glycol to obtain a polyester polyether block copolymer elastomer. Specific experimental conditions are shown below. 770 g of dimethyl terephthalate, 230 g of dimethyl isophthalate, 650 g of 1,4-butanediol, and 8.3 g of tetrabutoxytitanium (IV) were added to a 5L autoclave reactor equipped with a centrifuge manufactured by Shibata Chemical Industry Co., Ltd., and after sufficient nitrogen replacement, the reactor was pressurized to 2 atm with nitrogen and reacted at 250°C for 5 hours under 50 rpm centrifuge conditions to carry out a polycondensation reaction to obtain a prepolymer. Next, 1120 g of polytetramethylene glycol having a number average molecular weight of 2900 was added, and polycondensation reaction was continued to obtain a polyester polyether block copolymer elastomer resin 4. The melting point of this polyester polyether block copolymer elastomer resin 4 was 163°C and the reduced viscosity was 2.9 dl/g.

[Resin Production Example 5]
Polybutylene succinate was obtained by polycondensation reaction of succinic anhydride and 1,4-butanediol. 500g of succinic anhydride, 500g of 1,4-butanediol, 1.3g of tetrabutoxytitanium (IV) as catalyst, and 0.8g of toluene-4-sulfonic acid were added to a 2L autoclave reactor equipped with a pump (Shibata Chemical Co., Ltd.), pressurized to 2 atm with nitrogen, and reacted at 270°C for 6 hours under pumping conditions of 50 rpm to obtain polybutylene succinate resin 7. The obtained polybutylene succinate resin 7 had a melting point of 115°C and a reduced viscosity of 1.9 dl/g.

The method for producing the heat-fusible fibers will now be described.
[Fiber manufacturing example 1]
Resin 1 produced in Resin Production Example 1 was dried in a dehumidifying dryer at a drying temperature of 80°C for 8 hours, and then melt-extruded in a single-screw extruder at an extrusion temperature of 230°C. The resin was extruded from a spinneret having 400 nozzles and a nozzle diameter of 0.15 mm at a spinning temperature of 250°C and an output rate of 0.05 g/min per hole. The filaments were cooled by applying cooling air at 20°C and a wind speed of 0.5 m/s to a position approximately 100 mm to 900 mm below the spinneret, and then wound at a winding speed of 1000 m/min to obtain a multifilament having a fineness of 200 dtex/400 filaments.
50 of the obtained multifilaments were bundled together to form a tow, which was then cut to a fiber length of 5 mm with a rotary cutter at a cutting speed of 80 m/min and a cutting tension of 0.01 g/d to obtain a heat-fusible fiber made of resin 1 having a fineness of 0.5 dtex.

[Fiber manufacturing example 2]
Except for discharging at a discharge rate of 0.07 g/min per hole, a multifilament having a fineness of 280 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Resin 1 having a fineness of 0.7 dtex.

[Fiber manufacturing example 3]
Except for discharging at a discharge rate of 0.11 g/min per hole, a multifilament having a fineness of 440 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Resin 1 having a fineness of 1.1 dtex.

[Fiber Production Example 4]
Except for discharging at a discharge rate of 0.11 g/min per hole, a multifilament having a fineness of 440 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1, except for a fiber length of 8 mm, to obtain a heat-fused fiber made of Resin 1 having a fineness of 1.1 dtex.

[Fiber Production Example 5]
Except for discharging at a discharge rate of 0.18 g/min per hole, a multifilament having a fineness of 720 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Resin 1 having a fineness of 1.8 dtex.

[Fiber Production Example 6]
Except for setting the extrusion rate per hole of Resin 2 produced in Resin Production Example 2 to 0.10 g/min, a multifilament having a fineness of 400 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Resin 2 having a fineness of 1.0 dtex.

[Fiber Production Example 7]
Except for using Resin 3 produced in Resin Production Example 3 and setting the discharge rate per hole to 0.10 g/min, a multifilament having a fineness of 400 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Resin 3 having a fineness of 1.0 dtex.

[Fiber Manufacturing Example 8]
A multifilament having a fineness of 400 dtex/400 filaments was obtained in the same manner as in Production Example 1, except that Resin 3 produced in Resin Production Example 3 was used and the extrusion rate per hole was set to 0.10 g/min. The obtained multifilament was cut under the same cutting conditions as in Production Example 1, except that the fiber length was 3 mm, to obtain a heat-fused fiber made of Resin 3 having a fineness of 1.0 dtex.

[Fiber Production Example 9]
Except for using Resin 4 produced in Resin Production Example 4 and setting the discharge rate per hole to 0.10 g/min, a multifilament having a fineness of 400 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Resin 4 having a fineness of 1.0 dtex.

[Fiber Manufacturing Example 10]
A multifilament having a fineness of 560 dtex/400 filaments was obtained in the same manner as in Production Example 1, except that Resin 4 produced in Resin Production Example 4 was used and the extrusion rate per hole was set to 0.14 g/min. The obtained multifilament was cut under the same cutting conditions as in Production Example 1, except that the fiber length was set to 7 mm, to obtain a heat-fused fiber made of Resin 4 having a fineness of 1.4 dtex.

[Fiber Manufacturing Example 11]
A polyamide copolymer (Arkema Co., Ltd. Pebax 4033SP-01) was dried in a dehumidifying dryer at a drying temperature of 80°C for 8 hours, and then melt-extruded in a single-screw extruder at an extrusion temperature of 250°C, and discharged from a spinneret with 400 nozzles and a nozzle diameter of 0.15 mm at a spinning temperature of 260°C and an output rate of 0.10 g/min per hole. The filaments were cooled by applying cooling air at 20°C and a wind speed of 0.5 m/s at a position about 100 mm to 900 mm below the spinneret, and wound at a winding speed of 1000 m/min to obtain a multifilament having a fineness of 400 dtex/400 filaments. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Pebax 4033SP-01 having a fineness of 1.0 dtex.

[Fiber Production Example 12]
A multifilament having a fineness of 400 dtex/400 filaments was obtained in the same manner as in Production Example 11, except that a polyamide copolymer (Arkema Co., Ltd. Pebax 6333SP-01) was used. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Pebax 6333SP-01 having a fineness of 1.0 dtex.

[Fiber Manufacturing Example 13]
Except for discharging at a discharge rate of 0.50 g/min per hole and cooling the filaments by applying cooling air at a speed of 0.9 m/s, a multifilament having a fineness of 2000 dtex/400 filaments was obtained in the same manner as in Production Example 1. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of Resin 1 having a fineness of 5.0 dtex.

[Fiber Manufacturing Example 14]
Resin 5 produced in Resin Production Example 5 was used, dried in a dehumidifying dryer at a drying temperature of 60 ° C. for 8 hours, then melt-extruded in a single-screw extruder at an extrusion temperature of 180 ° C., extruded from a spinneret with 400 nozzles and a nozzle diameter of 0.15 mm at a spinning temperature of 190 ° C. and an output of 0.10 g / min per hole, and cooled by applying cooling air at 20 ° C. and a wind speed of 0.5 m / s at a position about 100 mm to 900 mm below the spinneret, and wound at a winding speed of 1000 m / min to obtain a multifilament with a fineness of 400 dtex / 400 filaments. The obtained multifilament was cut under the same cutting conditions as in Production Example 1 to obtain a heat-fused fiber made of polybutylene succinate of 1.0 dtex.

[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. The fibers produced in Fiber Production Example 1 (resin 1, fineness of 0.5 dtex, fiber length of 5 mm) were used as the heat-sealed fibers. These short fibers were dispersed in water to a weight ratio of main fiber: heat-sealed fiber = 90:10 to form a slurry. A papermaking sheet for surface fiber with a basis weight of 130 g/ ^m2 was produced from this slurry by a papermaking method. In addition, 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. These short fibers were dispersed in water to a weight ratio of main fiber: heat-sealed fiber = 97:3 to form 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 with a basis weight of 100 g/ ^m2 made of polyethylene terephthalate fiber of 166 dtex/48f, with the sum of the weave density in the MD direction and the weave density in the CD direction being 120 (lines/2.54 cm), to form a three-layer structure of a surface fiber layer/scrim layer/backside fiber layer. The obtained three-layer laminate was entangled and intertwined by spraying a high-speed water stream using a straight-flow spray nozzle, and then dried at 130°C for 5 minutes using an air-through type dryer to obtain a three-layer nonwoven fabric.
The surface of the surface fiber layer of the obtained nonwoven fabric was buffed with 400 mesh sandpaper to raise the nap, and then the nonwoven fabric was slackened in a biaxial stretching tester X4HDHT manufactured by Toyo Seiki Seisakusho so that the shrinkage rate in the MD and CD directions was 5%, and the center and four corners of both sides were fixed 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. Next, the fabric was dyed at 130°C using a blue disperse dye (BlueFBL: manufactured by Sumitomo Chemical) in a liquid flow dyeing machine and reduced and washed at 80°C to obtain a suede-like artificial leather. The manufacturing conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 2]
A suede-like artificial leather 2 was obtained in the same manner as in Example 1, except that the heat-fusible fiber was the fiber (resin 1, fineness 0.7 dtex, fiber length 5 mm) produced in Fiber Production Example 2. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 3]
A suede-like artificial leather 3 was obtained in the same manner as in Example 1, except that the thermally fusible fiber was changed to the fiber (resin 1, fineness 1.1 dtex, fiber length 5 mm) produced in Fiber Production Example 3 and the basis weight of the surface fiber sheet was changed to 140 g/ ^m2 . 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 heat-fusible fiber was changed to the fiber (resin 1, fineness 1.1 dtex, fiber length 8 mm) produced in Fiber Production Example 4, the weight ratio of the surface fiber sheet was main fiber: heat-fusible fiber = 94: ⁶ , and the basis weight of the surface fiber sheet was 130 g/m2. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 5]
A suede-like artificial leather 5 was obtained in the same manner as in Example 1, except that the fibers (resin 1, fineness 1.8 dtex, fiber length 5 mm) produced in Fiber Production Example 5 were used as the heat-fusible fibers and the basis weight of the surface fiber sheet was 80 g/ ^m2 . 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 fibers (resin 2, fineness 1.0 dtex, fiber length 5 mm) produced in Fiber Production Example 6 were used as the heat-fusible fibers, the basis weight of the surface fiber sheet was 110 g/ ^m2 , the weight ratio of the surface fiber layer was main fiber:heat-fusible fiber = 92:8, and the thermal annealing temperature was 180° C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 7]
A suede-like artificial leather 7 was obtained in the same manner as in Example 1, except that the fibers (resin 3, fineness 1.0 dtex, fiber length 5 mm) produced in Fiber Production Example 7 were used as the heat-fusible fibers, the basis weight of the surface fiber sheet was 120 g/ ^m2 , and the thermal annealing temperature was 165° 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 fibers (resin 3, fineness 1.0 dtex, fiber length 3 mm) produced in Fiber Production Example 8 were used as the heat-fusible fibers, the weight ratio of the surface fiber layer was main fiber:heat-fusible fiber = 91:9, and the thermal annealing temperature was 165° C. 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 fibers (resin 4, fineness 1.0 dtex, fiber length 5 mm) produced in Fiber Production Example 9 were used as the heat-fusible fibers, the weight ratio of the surface fiber layer was main fiber:heat-fusible fiber = 95:5, and the thermal annealing temperature was 170° C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 10]
Suede-like artificial leather 9 was obtained in the same manner as in Example 1, except that the fibers (resin 4, fineness 1.4 dtex, fiber length 7 mm) produced in Fiber Production Example 10 were used as the heat-fusible fibers, the basis weight of the surface fiber sheet was 110 g/ ^m2 , the weight ratio of the surface fiber layer was main fiber:heat-fusible fiber = 93:7, and the thermal annealing temperature was 170° C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 11]
A suede-like artificial leather 11 was obtained in the same manner as in Example 1, except that the fiber (Pebax 4033SP01, fineness 1.0 dtex, fiber length 5 mm) produced in Fiber Production Example 11 was used as the heat-fusible fiber and the thermal annealing temperature was set to 170° C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Example 12]
A suede-like artificial leather 12 was obtained in the same manner as in Example 1, except that the fiber produced in Fiber Production Example 11 (Pebax 4033SP01, fineness 1.0 dtex, fiber length 5 mm) was used as the heat-fusible fiber, the basis weight of the surface fiber sheet was 110 g/ ^m2 , the weight ratio of the surface fiber layer was main fiber: heat-fusible fiber = 93:7, and the thermal annealing temperature was 170 ° C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 1]
A suede-like artificial leather 13 was obtained in the same manner as in Example 1, except that the heat-fusible fibers were all-fusible type heat-fusible staple fibers Casven 8000 (manufactured by Unitika Ltd.) having a single fiber fineness of 0.7 dtex and a length of 5 mm. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 2]
A suede-like artificial leather 14 was obtained in the same manner as in Example 1, except that the heat-fusible fibers were fully fusible heat-fusible staple fibers Casven 8000 (manufactured by Unitika Ltd.) having a single fiber fineness of 1.1 dtex and a length of ⁵ mm, and the surface fiber sheet had a basis weight of 110 g/m2. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 3]
A suede-like artificial leather 15 was obtained in the same manner as in Example 1, except that the fiber (Pebax 6333SP-01, fineness 1.0 dtex, fiber length 5 mm) produced in Fiber Production Example 12 was used as the heat-fusible fiber, the basis weight of the surface fiber sheet was 110 g/ ^m2 , and the thermal annealing temperature was 180° C. 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 3, except that the thermal annealing temperature was 130° C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 5]
A suede-like artificial leather 17 was obtained in the same manner as in Example 1, except that the fibers (resin 1, fineness 5.0 dtex, fiber length 5 mm) produced in Fiber Production Example 13 were used as the heat-fusible fibers and the basis weight of the surface fiber sheet was 140 g/ ^m2 . The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below.

[Comparative Example 6]
A suede-like artificial leather 18 was obtained in the same manner as in Example 1, except that the fibers (polybutylene succinate, fineness 1.0 dtex, fiber length 5 mm) produced in Fiber Production Example 14 were used as the heat-fusible fibers and the heat annealing temperature was set to 130° C. The production conditions and evaluation results of the obtained artificial leather are shown in Table 1 below. No heat-fusible points were detected in the artificial leather.

In the artificial leather of the present invention, the thermoplastic resin bonding the main fibers having a fineness of 0.01 dtex to 0.5 dtex has a deformation amount of 20 nm to 200 nm as measured by force curve measurement with an atomic force microscope, and the lump size of the thermoplastic resin is 3500 μm ³ to 24000 μm ³ as the number average volume of the thermoplastic resin in the first surface fiber layer as measured by X-ray-CT, and the artificial leather has excellent feel and high abrasion resistance even without adding a polyurethane resin. Therefore, the artificial leather of the present invention can be suitably used not only as a material for car interiors, but also in fields such as seat covering materials and interior materials for railway cars, aircraft, ships, etc., clothing, shoes, bags, smartphone cases, interiors, furniture, etc.

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

Claims (13)

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 a main fiber and a thermoplastic resin;
(2) The fineness of the main fiber is 0.01 dtex or more and 0.5 dtex or less;
(3) At least a portion of the thermoplastic resin bonds the main fibers;
(4) The thermoplastic resin in the surface fiber layer is such that, in measurement by an atomic force microscope, a probe is pressed in with a cantilever at a load of 200 nN, and the distance the probe is pressed in from the contact initiation point to the maximum load is 20 nm or more and 200 nm or less; and (5) the number-average volume of the thermoplastic resin in the surface fiber layer is 3,500 ^μm3 or more and 24,000 ^μm3 or less ; and
The volumetric particle density of the thermoplastic resin per unit volume in the surface fiber layer is 0.5×10 ^particles /m ^or more and 5.0×10 ^particles /m or ^less , and
The thermoplastic resin is an elastomer made of a copolymer of polyester and aliphatic polyether or a nylon-based elastomer.
The artificial leather has the following properties. The artificial leather according to claim 1, wherein the main fiber is a polyester fiber. Old 6
3. The artificial leather according to claim 1, wherein the thermoplastic resin in the surface fiber layer is approximated as an ellipse, and an average quotient of the major axis divided by the minor axis is 100 or less. The artificial leather according to any one of claims 1 to 3 , wherein the surface fiber layer is intertwined with a scrim layer which is a woven fabric. The artificial leather according to claim 4 , wherein the scrim layer is made of polyester-based resin fibers. The artificial leather according to any one of claims 1 to 5 , 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. The artificial leather according to any one of claims 1 to 6 , wherein when the surface is abraded with a pressing load of 12 kPa in accordance with JIS-L-1096 E method (Martindale method), the abrasion loss is 21 mg or less after 50,000 abrasion cycles. The following steps:
(1) a step of mixing a subject fiber with a heat-fusible fiber produced using a thermoplastic resin, the heat-fusible fiber being produced using a thermoplastic resin in which a probe is pushed in from the contact initiation point to the maximum load of 20 nm or more and 200 nm or less when a probe is pushed in with a cantilever under a load of 200 nN in measurement by an atomic force microscope, so that the weight ratio of the heat-fusible fiber is 3% or more and 25% or less, and entangling the mixture by wet papermaking, and then forming a surface fiber web produced by a hydroentanglement treatment or a needle punching method; and (2) a step of forming a surface fiber layer by thermal annealing the entangled structure of the obtained surface fiber web at a temperature equal to or more than the melting point of the heat-fusible fiber and less than the melting point of the subject fiber.
The method for producing the artificial leather according to any one of claims 1 to 7 , comprising: The method according to claim 8 , wherein the fiber length of the heat-fusible fiber made of the thermoplastic resin is 2 mm or more and 90 mm or less. The method according to claim 8 or 9 , wherein the fiber diameter of the heat-sealable fiber produced by using the thermoplastic resin is 0.5 dtex or more and 2.2 dtex or less. The method according to any one of claims 8 to 10 , wherein the heat-bondable fibers made of the thermoplastic resin are produced by melt spinning. The method according to any one of claims 8 to 11 , wherein 95% by weight or more of the resin contained in the heat-sealable fibers is a copolymer of polyester and aliphatic polyether. The method according to any one of claims 8 to 12 , wherein the melting point of the thermoplastic resin is 130°C or higher and is 20°C or higher lower than the melting point of the main fiber.

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