JP2013047405A - Substrate for artificial leather and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for artificial leather that has a material feeling excellent in mechanical properties, softness and texture, and has also lightness, and a method for producing the same.SOLUTION: There are provided: a substrate for artificial leather including a three-dimensionally entangled nonwoven fabric and an elastomer in which the three-dimensionally entangled nonwoven fabric includes a hollow filament and satisfies the following requirements (1) to (3); and a method for producing the same. Requirement (1) is that an average area of circles inscribed in voids, except areas of circles inscribed in voids of less than 350 μm, in a cross section parallel to a thickness direction of the substrate for artificial leather is 1250 μmor less. Requirement (2) is that the number of circles inscribed in voids of 350-3000 μmin a cross section parallel to a thickness direction of the substrate for artificial leather is 85% or more with respect to the total number of circles inscribed in voids. Requirement (3) is that the substrate for artificial leather has 15/mmor more of cut ends of fibers on at least one side of the substrate.

Description

  The present invention relates to a base material for artificial leather and a method for producing the same. Specifically, it is a base material for artificial leather composed of a three-dimensional entangled nonwoven fabric and a polymer elastic body, and has a mechanical feel, flexibility, a texture that is excellent in texture, and also has a lightweight property. The present invention relates to a material and a manufacturing method thereof.

In recent years, artificial leather has been widely used as a main material for shoes, bags, clothing parts, etc. Especially in the field of sports shoes, casual shoes, etc., it has only excellent mechanical properties such as adhesive peel strength and tear strength. There is a need for a product that is comfortable and is made of lightweight and flexible materials.
Many of the conventional methods for producing a base material for artificial leather consist of several steps as follows. Multi-component fibers spun from two types of polymers with different solubility and degradability are stapled into a desired weight web using a card, cross wrapper, random weber, etc., then needle punch, water jet, etc. After the fibers are entangled with each other to form an entangled nonwoven fabric, a solution or emulsion solution of a polymer elastic body represented by polyurethane is applied and solidified, and then one component in the multicomponent fiber is removed or It is a method of making ultrafine fibers by weight reduction, or a method of performing the above-described steps of impregnating and solidifying a polymer elastic body and making the multicomponent fibers ultrafine fibers in the reverse order.
By these methods, it is possible to obtain flexible artificial leather base materials in which the fibers constituting the entangled nonwoven fabric are made ultrafine, and by using various artificial leather materials based on these base materials, the products are unique to ultrafine fibers. It is widely recognized in various product markets that an excellent texture due to the texture and appearance can be obtained.

  However, in the manufacturing process of the conventional artificial leather substrate described above, when the multicomponent fiber is made into an ultrafine fiber, an external force such as tension or compression acts to reduce the thickness of the entangled nonwoven fabric. An increase in the apparent density of the substrate itself is unavoidable. For this reason, it is impossible to industrially obtain a material that has the required performance as a material and also has an advantage in the market as a lightweight material, and various methods have been proposed so far.

Various production methods using hollow fibers have been studied as artificial leather having excellent lightness. For example, an artificial leather using polyester fibers having a hollowness of more than 40% has been proposed (for example, see Patent Document 1). In addition, as an artificial leather having mechanical properties, flexibility, and lightness, it has an ultrafine fiber (A) of 0.5 dtex or less and 5 to 50 hollow parts in a cross section of 5 dtex or less, The total area ratio of the hollow portion is in the range of 25 to 50%, and the fiber (B) in which the area occupied by one hollow portion is 5% or less is 20/80 by weight ratio of (A) / (B). A non-woven fabric that is three-dimensionally intertwined at 80/20, an artificial leather base made of a polymer elastic body, and a method for producing the same have been proposed (for example, see Patent Document 2). Further, a method of impregnating a polymer elastic body after impregnating a non-woven fabric with a polyvinyl alcohol resin (hereinafter sometimes abbreviated as PVA) in order to prevent restraint of the polymer elastic body on hollow fibers or ultrafine fibers. (For example, refer to Patent Document 3) Furthermore, there is a method of adding PVA to an aqueous emulsion for the purpose of releasing the emulsion and fibers in impregnating the aqueous emulsion into a nonwoven fabric (for example, refer to Patent Document 4). ).
On the other hand, in recent years, the use of organic solvents has led to demand for solvent-free manufacturing processes due to concerns about adverse effects on the human body and the environment. For example, water-soluble resins are used as extraction components for hollow fiber-generating fibers. In the method for producing artificial leather, a polymer elastic aqueous dispersion is studied as a resin impregnated into the interior of a three-dimensional entangled nonwoven fabric.

Japanese Patent No. 3924360 JP 2002-242077 A Japanese Patent Publication No. 7-42652 Japanese Examined Patent Publication No. 6-55999 JP 2003-73924 A

  However, in the artificial leather disclosed in Patent Document 1, hollow fibers having a hollow ratio of more than 40% have a hollow portion due to insufficient rigidity derived from the cross-sectional shape in the spinning process, the nonwoven fabric manufacturing process, and the subsequent processes. It tends to be crushed and flattened, or the outer wall and partition walls for forming the hollow portion are easily destroyed. In addition, once flattened, it is very difficult to recover the original high-hollow cross-sectional shape, and once the wall of the hollow part is broken, the hollow part itself disappears, so that the fiber having a high hollow ratio of 40% or more Tends to lose its effect as a hollow fiber in the process of manufacturing non-woven fabric and artificial leather. Moreover, since the manufacturing method disclosed in Patent Document 2 has a structure in which hollow fibers are easily constrained by a polymer elastic body, it is necessary to set the ratio of ultrafine fibers high in order to increase mechanical properties and flexibility. In addition, the use of ultrafine fibers impairs the inherent lightness of the hollow fibers, and all of these cannot be satisfied.

  Further, in the production method disclosed in Patent Document 3, since the impregnated polyvinyl alcohol-based resin moves to the surface layer by migration during drying, the amount remaining in the nonwoven fabric is reduced, particularly from hollow fibers or directly spun fibers. The release property between the polymer elastic body and the fiber inside the nonwoven fabric could not be sufficiently secured, and a sufficient texture without cracking or the like could not be obtained. Moreover, since the manufacturing method disclosed in Patent Document 4 is based on suede, it is assumed that PVA once impregnated is extracted at the time of dyeing. If the fiber or the hollow fiber is a fiber that is expressed by solvent extraction, two extraction steps are required, and there is a problem that the production process becomes complicated due to an increase in processing steps. In addition, in the production method of impregnating the inside of a three-dimensional entangled nonwoven fabric with an aqueous dispersion of a polymer elastic body, when the polymer elastic body is applied in the form of an aqueous emulsion, the polymer elastic body adheres to the surface of the hollow fiber. In addition, not only is the decrease in flexibility and physical properties noticeable, but there is also a problem in that the production efficiency and lightness are reduced due to the decrease in extraction efficiency when extracting island components from hollow fiber generating fibers. .

  In addition, in the thickness range of 0.3 to 3.0 mm that is generally used in each field of artificial leather, there is a demand for flexible products that are lighter and have excellent mechanical properties. In particular, the product is flexible and lightweight, and has excellent mechanical properties, and a useless artificial leather base material that satisfies all these requirements has not yet been developed.

  Accordingly, an object of the present invention is to provide a base material for artificial leather having a material feeling excellent in mechanical properties, flexibility, and texture, and further lightweight, and a method for producing the same.

That is, this invention provides the following base material for artificial leather and its manufacturing method.
1. A base material for artificial leather comprising a three-dimensional entangled nonwoven fabric and a polymer elastic body, wherein the three-dimensional entangled nonwoven fabric is a hollow long fiber and satisfies the following requirements (1) to (3): A base material for artificial leather.
Requirement (1): The average of the void inscribed circle area excluding the void inscribed circle area of less than 350 μm ^{2 in the} cross section parallel to the thickness direction of the base material for artificial leather is 1250 μm ² or less.
Requirement (2): The number of void inscribed circles with a gap inscribed circle area of 350 to 3000 μm ² in a cross section parallel to the thickness direction of the base material for artificial leather is 85% or more with respect to the number of inscribed circles of all voids It is.
Requirement (3): At least one side of the base material for artificial leather has a fiber cut end of 15 pieces / mm ² or more.
2. 2. The base material for artificial leather as described in 1 above, wherein the average thickness of the outer peripheral part of the hollow long fiber or the partition wall of the hollow part is 7 μm or less.
3. The base material for artificial leather according to 1 or 2 above, wherein the hollow long fiber has a crack in the length direction of the fiber on the surface thereof.
4). The mass ratio of the polymer elastic body and the three-dimensional entangled nonwoven fabric constituting the base material for artificial leather (polymer elastic body / three-dimensional entangled nonwoven fabric) is 5/95 to 50/50 in terms of solid content. The base material for artificial leather according to any one of 1 to 3, which is a range.

5. A base material for artificial leather composed of a three-dimensional entangled nonwoven fabric and a polymer elastic body, including steps performed in the order of the following (Step 1) to (Step 5), and buffing before the following (Step 5) A method for producing a base material for artificial leather, comprising:
(Step 1): A step of obtaining a sea-island type composite long fiber having a poorly water-soluble resin as a sea component and a water-soluble resin (a) as an island component.
(Step 2): A step of obtaining a composite long fiber web from the sea-island composite long fibers obtained in Step 1 above.
(Process 3) The process of forming a three-dimensional entangled nonwoven fabric (a) by carrying out a needle punching process, after superposing | stacking 2 or more of the composite long fiber webs obtained at the said process 2. FIG.
(Step 4) After impregnating the three-dimensional entangled nonwoven fabric (a) obtained in Step 3 with a polymer elastic body solution containing a polymer elastic body to which a water-soluble resin (b) is added, the polymer elasticity The process of obtaining the three-dimensional entangled nonwoven fabric (b) which solidified the body.
(Step 5): A tertiary composed of hollow long fibers of a poorly water-soluble resin by dissolving and removing the water-soluble resin (a) and the water-soluble resin (b) from the three-dimensional entangled nonwoven fabric (b) obtained in Step 4 above. The process of forming a former entangled nonwoven fabric.
6). 6. The method for producing a substrate for artificial leather as described in 5 above, wherein the water-soluble resin (a) and / or the water-soluble resin (b) is polyvinyl alcohol.
7). In the process 4, the water-soluble resin (b) is added at a ratio of 2.0 to 40% by mass with respect to the solid content of the polymer elastic body. Production method.
8). 8. The method for producing a base material for artificial leather according to any one of 5 to 7, wherein in the step 4, the polymer elastic body solution is an aqueous emulsion.
9. In the sea-island type composite long fiber, the average of the shortest distance between the island components or the average of the shortest distance between the island component and the outer periphery of the sea-island type composite long fiber is 7 μm or less. A method for producing a base material for leather.

  The base material for artificial leather according to the present invention is such that the polymer elastic body has a constant release structure with the fiber and is discontinuously present on the fiber surface, and the polymer elastic body is uniformly dispersed inside, It is an artificial leather base material that has a uniform distribution of inter-fiber voids, is excellent in mechanical properties, is soft, lightweight, and has a good texture that is used in sports shoes and the like. Moreover, according to the manufacturing method of this invention, the said artificial leather base material can be obtained.

It is the photograph which observed the cross section of the base material for artificial leather obtained in Example 1 with the scanning electron microscope. It is the image which binarized the photograph which observed the cross section of the base material for artificial leather obtained in Example 1 with the scanning electron microscope by the dynamic threshold method. It is the image which binarized the photograph which observed the cross section of the base material for artificial leather obtained in Example 1 with the scanning electron microscope by the dynamic threshold method, and drawn the inscribed circle in the space | gap part.

[Base material for artificial leather]
The base material for artificial leather of the present invention comprises a three-dimensional entangled nonwoven fabric and a polymer elastic body, the three-dimensional entangled nonwoven fabric is a hollow long fiber, and satisfies the following requirements (1) to (3) It is characterized by.

(Requirements)
Requirement (1): The average gap inscribed circle area excluding the gap inscribed circle area of less than 350 μm ^{2 in the} cross section parallel to the thickness direction of the artificial leather substrate is 1250 μm ² or less, preferably 1240 μm ² or less, more preferably 1200 [mu] m ² or less, more preferably 1100 .mu.m ² or less. Further, the average lower limit value of the air gap inscribed circle area is preferably 350 μm ² or more, and more preferably 400 μm ² or more.
Requirement (2): The number of void inscribed circles with a gap inscribed circle area of 350 to 3000 μm ² in a cross section parallel to the thickness direction of the base material for artificial leather is 85% or more with respect to the number of inscribed circles of all voids. Preferably, it is 86% or more, more preferably 88% or more, and still more preferably 90% or more.
Requirement (3): It has 15 / mm ² or more fiber cutting ends on at least one side of the base material for artificial leather, preferably 20 / mm ² or more, more preferably 35 / mm ² or more.

In requirement (1), if the air gap inscribed circle average area exceeds 1250 μm ² , the lightness is impaired. In requirement (2), if the air gap inscribed circle area of 350 to 3000 μm ² is less than 85%, When the artificial leather base material is bent, the size of the leather becomes non-uniform, causing cracks and burrows and the like, causing problems in the texture.
In addition, "air gap inscribed circle" is a cross section parallel to the thickness direction of the base material for artificial leather is observed with a scanning electron microscope at a magnification of 30 times, and the obtained photograph is used image analysis software, The image is binarized by the dynamic threshold method, and is a circle drawn in the gap between the fiber and the fiber, the gap between the fiber attached with the polymer elastic body and the fiber or the fiber attached with the polymer elastic body, and the fiber Is a circle that touches two or more points. A specific method for measuring the inscribed circle area and the number of air gaps is the same as the measurement of the inter-fiber void area using a scanning electron microscope described later in Examples.

Furthermore, in the requirement (3), if the number of fiber cut ends on the surface of the substrate is less than 15 pieces / mm ² , the extraction rate is lowered, the lightness is impaired and the texture becomes hard. The upper limit of the fiber cutting fraction is preferably less than 500 pieces / mm ² , more preferably less than 300 pieces / mm ² , and still more preferably less than 100 pieces / mm ² . If it is less than 500 pieces / mm < ² >, there is no possibility of causing a physical-property fall without cutting a long fiber too much.
The “fiber cut end” refers to the tip of the cut fiber on the surface or the back surface of the artificial leather substrate. For example, the surface of the substrate is observed with a scanning electron microscope and the fiber cut ends are counted. be able to. In the present invention, the fiber cutting fraction (pieces / mm ² ) is specified by the measurement method described later in the examples.

Moreover, it is preferable that the base material for artificial leather of this invention has a discontinuous polymeric elastic body on the surface of the fiber which forms a three-dimensional entangled nonwoven fabric.
Here, the term “discontinuous” means that the polymer elastic body does not exist in a continuous state such as a band shape or a planar shape on the surface of the fiber, but a space such as a dot or spot on the surface of the fiber (high A portion where no molecular elastic body exists) regularly or irregularly and uniformly.

(Hollow long fiber)
The three-dimensional entangled nonwoven fabric constituting the base material for artificial leather of the present invention needs to be composed of long hollow fibers in order to improve the physical properties of the base material for artificial leather and to obtain light weight. Further, long fibers are excellent in mechanical properties. Here, the long fiber refers to a fiber that is not intentionally cut, such as a short fiber (fiber length: 10 to 50 mm).
In the case of long fibers, unlike the short fibers, since the exposure of the fiber cross-section is very small, in order to efficiently extract the water-soluble resin, which is preferably performed from the wall surface of the fiber, in Step 5 of the manufacturing method described later. The surface of the hollow long fiber preferably has a crack in the length direction of the fiber, and the average thickness of the outer peripheral portion of the hollow long fiber or the partition wall of the hollow portion is preferably 7 μm or less, more preferably 3 μm or less.

  In the step 5 of dissolving and removing the water-soluble resin from the sea-island composite fiber in the extraction step described later by setting the average thickness of the outer peripheral portion of the hollow long fiber or the partition wall of the hollow portion to 7 μm or less, from the cut surface or the damaged portion When the water-soluble resin swells with water, cracks (parts that become cracks generated in the length direction of the fiber on the surface of the hollow fiber) are likely to occur in the partition wall formed of the poorly water-soluble resin of the sea component. And when water permeates into the inside of the sea-island type composite fiber from the crack, the water-soluble resin further swells and dissolves, and the dissolution and removal efficiency of the water-soluble resin increases. Accordingly, by setting the average thickness of the outer peripheral portion of the hollow long fiber or the partition wall of the hollow portion to 7 μm or less, the three-dimensional formed using the long fiber (same as the filament) made of sea-island type composite fiber having a small fiber cross section. Even if it is an entangled nonwoven fabric, since the water-soluble resin can be extracted efficiently, the obtained base material for artificial leather is lightweight and excellent in flexibility.

  Here, although the hollow part of a hollow long fiber is mentioned later in detail in description of a manufacturing method, it forms by extracting the water-soluble resin which is an island part of a sea island type fiber. From this, the outer peripheral part of the hollow long fiber and the thickness of each partition of the hollow part are the island part in the image obtained by observing the transverse cross section of the sea-island fiber with a scanning electron microscope (SEM) at 2000 times. The thickness obtained by measuring the thickness t of the thinnest portion of the plurality of partition walls formed by the sea portion that separates the island portion and the outline of the sea-island fiber, and averaging the values.

(Mass ratio between polymer elastic body and three-dimensional entangled nonwoven fabric)
The mass ratio of the polymer elastic body and the three-dimensional entangled nonwoven fabric (polymer elastic body / three-dimensional entangled nonwoven fabric) constituting the base material for artificial leather of the present invention is preferably 5/95 to solids conversion. 50/50, more preferably 10/90 to 40/60, still more preferably 15/85 to 30/70.
As described later in the description of the production method, the three-dimensional entangled nonwoven fabric is composed of fibers formed from a poorly water-soluble resin, and the mass of the three-dimensional entangled nonwoven fabric in the mass ratio is the three-dimensional entanglement. It is the mass of the poorly water-soluble resin used to obtain the composite nonwoven fabric.
That is, from the above mass ratio, the amount of the polymer elastic body given to the three-dimensional entangled nonwoven fabric when used as the base material for artificial leather of the present invention is the amount of the polymer elastic nonwoven fabric and the three-dimensional Preferably, in terms of solid content, 5 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass with respect to a total of 100 mass of the fiber forming the entangled nonwoven fabric and the poorly water-soluble resin. is there.
If it is 5 mass% or more, a poorly water-soluble fiber can be fixed, no bending bends occur, and the shape stability and surface smoothness are improved. If it is 50% by mass or less, the texture will not be cured, and the elastic properties of the polymer elastic body and the low resilience flexibility of natural leather will be balanced, and the lightness will be good.

(thickness)
The thickness of the base material for artificial leather can be arbitrarily selected according to the use and is not particularly limited, but is preferably in the range of 0.3 to 3 mm, more preferably 0.7 to 1.8 mm. . If it is 0.3 mm or more, strength and uniformity that can withstand actual use can be obtained, and if it is 3 mm or less, the desired lightness can be obtained.

(Apparent density)
The apparent density of the artificial leather substrate is preferably less than 0.3 g / cm ³ . What is important in light weight is the weight of the product itself such as shoes and bags using an artificial leather-like base material, and the evaluation is relative and sensory based on the experience of the user. The weight of the artificial leather or the base material for artificial leather as a constituent material of the existing product is generally 280 to 800 when the apparent density is 0.35 to 0.5 g / cm ³ , that is, the thickness is 0.8 mm. It is about 400 g / m ² . In the case where at least 10% is lighter than 250 g / m ² than the image of the weight of general materials such as a base material for artificial leather and artificial leather with a thickness of 0.8 mm, that is, in terms of apparent density, 0.3 g / cm If it is a base material for artificial leather of less than ³ , it is easily felt light by ordinary consumers. Although it is difficult to combine light weight, high physical properties, and texture as a real problem with existing technology, according to the present invention, it has lightness with an apparent density of less than 0.3 g / cm ³ and mechanical properties required for applications. The base material for artificial leather having the texture and quality required for artificial leather can be stably produced.

[Manufacturing method of artificial leather base]
In the conventional method for producing an artificial leather base material, a method is adopted in which a binder resin dissolved in an organic solvent is impregnated into a fibrous sheet and treated with a non-solvent and wet coagulated. It was possible to form a foamed state, and to stabilize the form and give a natural leather-like texture with a small amount of binder resin. However, when an aqueous emulsion resin is used without using chemicals, a large amount of resin is required because the binder resin becomes a continuous structure, resulting in the hardening of the texture and the reduction in weight and physical properties. In addition, if the amount of water-based emulsion resin used is simply reduced, a continuous layer is partially formed instead of a uniform discontinuous state, resulting in a non-uniform structure as a whole, resulting in light weight. Even if it secured, the fall of texture, such as a broken part, was invited.
On the other hand, in order to ensure light weight, it is necessary to be a hollow long fiber generated from a hollow fiber generating fiber as described later as a fiber constituting the three-dimensional entangled nonwoven fabric. In order to make it easy to extract an extraction component from the inside by making it a hollow fiber generation type fiber, it leads also to softening a texture as a result, ensuring lightweightness by fully extracting an extraction component.

Therefore, in the present invention, when a polymer elastic body is applied to the three-dimensional entangled nonwoven fabric, the three-dimensional entangled nonwoven fabric is impregnated and solidified with a polymer elastic body solution composed of a polymer elastic body to which a water-soluble resin is added. . By adding a water-soluble resin to a polymer elastic body solution composed of a polymer elastic body, the water-soluble resin is dissolved and removed by a subsequent extraction step, and a hollow fiber generating fiber of a three-dimensional entangled nonwoven fabric is formed. A release structure in which a space is formed at the interface between the fiber, that is, the poorly water-soluble resin, and the polymer elastic body contained in the polymer elastic body solution is obtained, and the polymer elastic body is discontinuous on the fiber surface. It becomes possible to obtain a structure in which voids formed between the fibers are uniformly distributed. This makes it possible to obtain a sheet that is excellent in flexibility and has no burrows, so that the amount of the binder resin to be applied can be reduced, and the weight can be reduced.
In addition, buffing is performed before the step of dissolving and removing the water-soluble resin, and by increasing the number of fiber cut ends on the surface of the base material, extraction components containing the water-soluble resin can be easily extracted and removed from the hollow fiber generating fiber. In addition, the artificial leather base material of the present invention having the above-described characteristics can be manufactured based on the above, which can reduce the weight and improve the texture.

That is, the manufacturing method of the artificial leather base material which consists of the three-dimensional entangled nonwoven fabric of this invention and a polymeric elastic body includes the process performed in order of the following (process 1)-(process 5), and the following (process 5). The buffing process is performed before.
(Step 1): A step of obtaining a sea-island type composite long fiber having a poorly water-soluble resin as a sea component and a water-soluble resin (a) as an island component.
(Step 2): A step of obtaining a composite long fiber web composed of the sea-island type composite long fibers obtained in Step 1 above.
(Process 3) The process of forming a three-dimensional entangled nonwoven fabric (a) by carrying out a needle punching process, after superposing | stacking 2 or more of the composite long fiber webs obtained at the said process 2. FIG.
(Step 4) After impregnating the three-dimensional entangled nonwoven fabric (a) obtained in Step 3 with a polymer elastic body solution containing a polymer elastic body to which a water-soluble resin (b) is added, the polymer elasticity The process of obtaining the three-dimensional entangled nonwoven fabric (b) which solidified the body.
(Step 5): Three-dimensionally composed of poorly water-soluble resin hollow long fibers by dissolving and removing the water-soluble resin (a) and the water-soluble resin (b) from the three-dimensional entangled nonwoven fabric (b) obtained in Step 4 above. The process of forming an entangled nonwoven fabric.

(Process 1)
As described above, the fiber forming the three-dimensional entangled nonwoven fabric constituting the artificial leather substrate of the present invention is a hollow long fiber in order to improve the physical properties of the obtained artificial leather substrate and to obtain light weight. It is necessary. In addition, this hollow long fiber is composed of a polymer elastic body on a fiber made of one kind of polymer or a multicomponent fiber (composite fiber) made of at least two kinds of spinnable polymers having different chemical or physical properties. After impregnation, at least one kind of polymer is extracted and removed at an appropriate stage, and can be formed by changing the fiber form (hereinafter sometimes referred to as hollow fiber generating composite long fiber). It is preferable to generate from. This hollow fiber generation type composite long fiber is obtained by a method represented by a chip blend (mixed spinning) method or a composite spinning method. A typical fiber form of the hollow fiber generating fiber is a so-called sea-island type.
Therefore, in the manufacturing method of this invention, the process of obtaining a sea-island type | mold composite long fiber which uses a water-insoluble resin as a sea component and uses a water-soluble resin as an island component is performed as the process 1.

<Sea component>
The sea component is a poorly water-soluble resin that forms a hollow long fiber after Step 5 described later, and is not particularly limited as long as it is a known polymer, for example, a polyamide-based, polyester-based, or polyolefin-based resin.
In particular, the specific gravity is low and light weight is easily developed. When the polymer elastic polymer in Step 4 described later is impregnated with a water-based emulsion which is a preferred form of the polymer elastic solution, it is separated from the hollow long fibers. A polymer having a polyolefin-based fiber-forming ability is preferable in that it easily develops a mold structure, and a polypropylene-based resin is particularly preferable. When physical properties and hydrophilicity are desired, polyamide-based materials are preferable, and general-purpose nylon is preferable, and there is no particular limitation as long as melt spinning of nylon 6, nylon 11, nylon 12, or the like is possible.

Examples of the polypropylene resin include a propylene homopolymer, a crystalline random copolymer or a crystalline block copolymer of propylene and ethylene and / or an α-olefin having 4 to 20 carbon atoms. Specific α-olefins used as comonomers include ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-pentene-1, 4-methyl-hexene-1. 4,4-dimethylpentene-1 and the like.
These polypropylene resins can be used alone or in combination of two or more. A small amount of other olefin resin such as polyethylene can also be blended.

From the viewpoint of spinnability, the melt flow rate of the polypropylene resin used in the present invention (hereinafter sometimes abbreviated as MFR) is preferably 1 to 200 g / min, more preferably 5 to 100 g / min, and still more preferably. 10-50 g / min. Here, MFR is a value measured at 230 ° C. and a load of 21.1 N in accordance with JIS K6921-2 appendix.
The melting point of the polypropylene resin is preferably 140 to 180 ° C, more preferably 160 to 180 ° C, from the viewpoint of spinnability and heat resistance of the product.

The polypropylene resin used in the present invention can be obtained by polymerizing propylene using a highly stereoregular polymerization catalyst.
As the highly stereoregular polymerization catalyst, a so-called Ziegler-Natta catalyst using a titanium compound prepared using titanium chloride, alkoxy titanium or the like as a starting material, or a Kaminsky catalyst using a metallocene compound can be used. .

  As the polymerization mode of propylene using the catalyst as described above, any method can be adopted as long as the catalyst component and the monomer come into efficient contact. Specifically, the slurry method using an inert solvent, the bulk method using propylene as a solvent substantially without using an inert solvent, the solution polymerization method, or the monomers are substantially gaseous without using a liquid solvent substantially. It is possible to employ a vapor phase method or the like that keeps the temperature constant. Further, continuous polymerization and batch polymerization are also applied. In the case of slurry polymerization, a saturated aliphatic or aromatic hydrocarbon such as hexane, heptane, pentane, cyclohexane, benzene and toluene can be used alone or as a polymerization solvent.

In these polymerization methods, the MFR of polypropylene is adjusted by introducing hydrogen. In this case, the amount of hydrogen introduced may be constant from the start to the end of the polymerization or may be changed continuously or stepwise. .
In addition, the above polypropylene resins can be selected from commercially available products. Moreover, colorants such as dyes and pigments, ultraviolet absorbers, heat stabilizers, deodorants, fungicides, various stabilizers and the like may be added to the resin constituting the hollow long fibers.

<Island component>
An island component is water-soluble resin (a) which comprises the extraction component of the three-dimensional entangled nonwoven fabric (b) in the process 5 mentioned later.
The water-soluble resin (a) is a polymer that is different in solubility or decomposability with respect to a solvent or a decomposing agent from a polymer that forms a fiber after extracting and removing an extraction component, and has a low affinity with a sea component, Further, it is preferable that the polymer has a melt viscosity higher than that of the sea component under the spinning conditions or a polymer having a large surface tension. With such a polymer, it is possible to produce a base material for artificial leather that can be removed at the same time as a water-soluble resin (b) added to a polymer elastic body described later without using chemicals.

  As the water-soluble resin (a) constituting the extraction component of the hollow fiber generating fiber, a known polymer can be used as long as it is a water-soluble resin that can be spun and can be extracted with an aqueous solution. The water-soluble resin and polymer elastic body are not substantially decomposed during extraction, and the water-insoluble resin and polymer elastic body are not limited. Thermoplastic polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) is preferred.

The viscosity average polymerization degree of PVA (hereinafter simply referred to as polymerization degree) is preferably 200 to 500, more preferably 230 to 470, and further preferably 250 to 450. If the degree of polymerization is 200 or more, a stable composite can be obtained without the melt viscosity being too low. If the degree of polymerization is 500 or less, the melt viscosity is not too high, the resin from the spinning nozzle can be discharged well, and there is also an advantage that the dissolution rate is increased when dissolving with hot water. When the degree of polymerization is in the above range, the object of the present invention can be achieved more suitably.
The polymerization degree (P) of PVA here is measured according to JIS-K6726. That is, after re-saponifying and purifying PVA, it is obtained by the following equation from the intrinsic viscosity [η] measured in water at 30 ° C.
P = ([η] 10 ³ /8.29) ^{(1 / 0.62)}

  The saponification degree of PVA used in the present invention is preferably 90 to 99.99 mol%, more preferably 93 to 99.98 mol%, still more preferably 94 to 99.97 mol%, and particularly preferably 96 to 99. 96 mol%. If the degree of saponification is 90 mol% or more, the thermal stability is good, the thermal decomposition and the gelation are difficult to perform, and the melt spinning can be performed satisfactorily, and the biodegradability described later is not lowered. Furthermore, the water solubility of PVA does not decrease depending on the type of copolymerization monomer described later. Further, when the degree of saponification is 99.99 mol% or less, PVA can be stably produced.

  The PVA used in the present invention has biodegradability and is decomposed into water and carbon dioxide when activated sludge treatment or soil is buried. The activated sludge method is preferable for the treatment of the PVA-containing waste liquid after dissolving the PVA. When the PVA aqueous solution is continuously treated with activated sludge, it is decomposed in 2 days to 1 month. Moreover, since PVA used for this invention has low combustion heat and the load with respect to an incinerator is small, you may incinerate PVA by drying the waste_water | drain which melt | dissolved PVA.

160-230 degreeC is preferable, as for melting | fusing point (Tm) of PVA used for this invention, 170-227 degreeC is more preferable, 175-224 degreeC is further more preferable, 180-220 degreeC is especially preferable. If melting | fusing point is 160 degreeC or more, the crystallinity of PVA will not fall, fiber strength and the thermal stability of PVA can be maintained, and it can fiberize favorably. Also, if the melting point is 230 ° C. or lower, the melt spinning temperature will not be too high, and the PVA fiber production will not be unstable due to the spinning temperature approaching the PVA decomposition temperature.
The melting point of PVA was raised to 300 ° C. in nitrogen using a differential scanning calorimeter at a heating rate of 10 ° C./min, cooled to room temperature, and again up to 300 ° C. at a heating rate of 10 ° C./min. It means the temperature at the top of the endothermic peak indicating the melting point of PVA when the temperature is raised.

  The PVA used in the present invention can be obtained by saponifying a resin mainly composed of vinyl ester units. Vinyl compound monomers for forming vinyl ester units include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and Examples include vinyl versatate, and among these, vinyl acetate is preferable from the viewpoint of easily obtaining PVA.

In addition, the PVA used in the present invention may be a homopolymer or a modified PVA into which a copolymer unit is introduced. However, from the viewpoint of melt spinnability, water solubility, and fiber properties, the copolymer unit is introduced. It is preferable to use modified PVA.
As the kind of the comonomer, α-olefins having 4 or less carbon atoms such as ethylene, propylene, 1-butene and isobutene, methyl vinyl ether, Vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether and n-butyl vinyl ether are preferred. The unit derived from α-olefins having 4 or less carbon atoms and / or vinyl ethers preferably has 1 to 20 mol% of PVA constituent units in PVA, more preferably 4 to 15 mol%, and 6 More preferred is ˜13 mol%. Further, when the α-olefin is ethylene, it is preferable to use ethylene-modified PVA because the fiber properties are high, and the ethylene unit content in ethylene-modified PVA is particularly 4 to 15 mol%. It is preferable that ethylene modified PVA is introduced, more preferably 6 to 13 mol%.

The PVA can be produced by a known method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without solvent or in a solvent such as alcohol is usually employed.
Examples of alcohol used as a solvent during solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. Examples of the initiator used for copolymerization include a, a′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl-valeronitrile), benzoyl peroxide, n-propyl Known initiators such as azo initiators such as oxycarbonate or peroxide initiators may be mentioned. Although there is no restriction | limiting in particular about superposition | polymerization temperature, The range of 0 to 150 degreeC is suitable.

<Mass ratio of sea component / island component>
In the sea-island type composite long fiber, the mass ratio of the sea component / island component is preferably 10/90 to 60/40, more preferably 20/80 to 60/40, from the viewpoint of cross-sectional formability.

<Sea-island type composite continuous fiber>
The sea-island type composite long fiber composed of the sea component and the island component is discharged from the spinning nozzle hole, cooled by a cooling device, and then used to obtain a desired fineness using a suction device such as an air jet nozzle. In addition, the fiber is drawn and thinned by a high-speed air stream at a speed corresponding to a take-up speed of about 1000 to 6000 m / min.

In the present invention, the hollow fiber generating fiber, which is the sea-island type composite long fiber, is a long fiber, and in order to increase the extraction efficiency in step 5 described later, when the water swells, a crack is generated on the fiber wall surface. It is preferable to make it. Moreover, since it is preferable that the outer peripheral part of a hollow long fiber and the partition of a hollow part form specific thickness as mentioned above, in sea-island type composite long fiber, it is between island components of water-soluble resin which is an island component. The average of the shortest distance or the average of the shortest distance (the thinnest part) between the island component and the outer periphery of the sea-island composite long fiber is preferably 7 μm or less, and more preferably 3 μm or less.
The average of said thinnest part is as having demonstrated the thickness of the outer peripheral part of the said hollow long fiber, and the partition of a hollow part.

  In the process of extracting and removing the water-soluble resin with hot water from the three-dimensional entangled nonwoven fabric (b), which is a hollow fiber generating fiber, by forming the hollow fiber generating fiber as described above, a cut surface or damage When the water-soluble resin swells from the water, cracks are likely to occur in the partition walls formed from the poorly water-soluble resin of the sea component, and water penetrates into the hollow fiber generating fiber from the cracks, so that the water-soluble resin Further swells and dissolves. By applying mechanical force such as mangle at the time of extraction in this state, it becomes possible to form cracks on the wall surface of almost all the fibers, further improving the extraction efficiency and obtaining a lighter one. . Therefore, even if it is a three-dimensional entangled body formed using a filament made of sea-island fibers with a small fiber cross-section, it is water-soluble by increasing the fiber cutting fraction on the substrate surface by mechanical treatment such as buffing treatment. Resin can be extracted efficiently.

  The fineness of the hollow fiber generating fiber is preferably 5 dtex or less, and more preferably 3 dtex or less. In a fiber sheet such as artificial leather, generally, the smaller the fineness, the less the texture and the softer the texture. Also in the present invention, when the fineness exceeds 5 dtex, the texture of the base material is hard and the texture that is stiff is emphasized, which is not appropriate. However, if the fineness is too small, the fibers in the base material will be densely packed, so that the fineness is preferably 0.5 dtex or more, more preferably 1 dtex or more, in order to achieve the lightness of the present invention.

  Further, the number of island components present in the cross section of the fiber having a fineness of 5 dtex or less is preferably 1 or more, more preferably 5 to 50, and even more preferably 10 to 30. When the fiber is a hollow fiber-generating fiber, the hollow part satisfies the following formulas (1) and (2) simultaneously, and the hollow part is crushed and flattened by bending during use as a product, or wall Without being destroyed, it has excellent performance in the recovery of the hollow shape and can stably exhibit the light weight effect.

25 ≦ 100 × sm / S ≦ 50 (1)
100 × s / S ≦ 5 (2)
s: Area of one hollow part in the fiber cross section sm: Area of the total hollow part in the fiber cross section S: Area of the part surrounded by the fiber outer periphery

  The area hollow ratio represented by the above formula (1), that is, the ratio of the total area of the hollow portion in the cross section of the fiber is preferably 25 to 50%, more preferably 30 to 40%. If the area hollowness is 25% or more, a light weight effect can be obtained, and if it is 50% or less, the collapse of the hollow portion of the fiber cross section due to the tension and press applied after the island removal step can be minimized. It is possible to obtain a lightweight substrate without increasing the density of the substrate.

  Furthermore, it is preferable that the area occupied by one hollow generating portion in the cross section of the hollow fiber generating fiber is 5% or less. If it is 5% or less, it is possible to minimize the collapse of the hollow part of the fiber cross section due to the tension and press applied after the island removal process, and the hollow part is crushed and deformed by bending and compression after becoming a product. Is less likely to occur. In addition, if the area of one island part (hollow part) in the hollow long fiber is too small, the island component is removed by the tension and press applied after the island part removing step for generating the hollow part. Since it becomes a thing without a part, 1-4% is more preferable, and 2-4% is a more preferable range.

  Moreover, the fineness of the island component of the hollow fiber generating fiber is preferably 0.05 to 0.5 dtex, and more preferably 0.1 to 0.5 dtex of the hollow long fiber after the island component is removed. It is more preferable from the viewpoint of hollow shape stability. In addition, the area hollow ratio is the ratio of the area ratio between the part that forms the hollow long fiber and the island component part that becomes the hollow part after extraction and removal, and the form of the outer wall and partition wall made of the hollow long fiber component when the island component is removed Since it depends on maintainability, it is preferable to stabilize the hollow shape by appropriately combining the fineness of the island component and the sea-island hollow ratio.

(Process 2)
Step 2 is a step of obtaining a composite long fiber web from the sea-island composite long fibers obtained in Step 1.
The composite long fiber web is formed by depositing the sea-island type composite long fibers spun in step 1 on a collection surface such as a movable net while opening. Furthermore, when it is necessary to stabilize the form of the web for conveyance to the next step, the composite continuous fiber web may be manufactured by a method in which the form is stabilized by partially pressing the composite continuous fiber web with a press or the like. .
This method has a production advantage that a series of large equipment such as a raw cotton supply device, a fiber opening device, and a card machine, which are essential in a conventional method for producing a fiber web via short fibers, is not required. In addition, the obtained long fiber nonwoven fabric, or the base material for artificial leather using the same, is composed of long fibers having high continuity in the structure. Therefore, the short fiber nonwoven fabric that has been generally used in terms of physical properties such as strength, or There is an advantage that a high product can be obtained as compared with a base material for artificial leather using the same.
The basis weight of the composite long fiber web obtained in Step 2 is preferably 10 to 100 g / m ² , more preferably 20 to 60 g / m ² .

(Process 3)
Step 3 is a step of forming a three-dimensional entangled nonwoven fabric (a) by needle punching after two or more composite long fiber webs obtained in Step 2 are superposed.
In order to obtain a nonwoven fabric having a desired basis weight, a plurality of composite long fiber webs obtained in the above step 2 are overlapped, and the fibers are substantially cut by an entanglement process including the following needle punching step. The fibers can be entangled with each other while orienting the fibers in the thickness direction to obtain a three-dimensional entangled nonwoven fabric (a).

  The felt needle used in the needle punching process is a known one. However, in order to reliably entangle the fibers in the thickness direction of the fiber web, the resistance per needle when the needle is pierced into the web. Therefore, a thinner needle or a 1 barb needle with less barb is preferably used. Further, by increasing the apparent density of the surface layer region of the nonwoven fabric from the vicinity of the middle layer, in order to efficiently obtain a smooth and more dense surface state even with a small number of hollow long fibers, 3 barbs, 6 barbs, 9 Barbs and other needles are effective. Therefore, by using these needles in combination, even when using a fiber web that is difficult to be entangled, such as when the fibers are fused together, the surface layer is smooth after effectively entangled. It is also possible to obtain a three-dimensional entangled nonwoven fabric in a dense state.

In the needle punching process, the number of felt needles per unit area that pierce the fiber web varies depending on the shape of the needle used and the basis weight of the web, and the throat depth of the needle used is deep and the number of barbs penetrating the web is large. When the fabric weight is high, it is easy to effectively entangle the fibers with a small number, but conversely, the throat depth is shallow, the number of barbs penetrating the fiber web is small, and when the web fabric weight is low, the required number is increased. Generally, it is set in the range of 200 to 2500 / cm ² , preferably 500 to 2000 / cm ² . Generally, in the needle punching process of sea-island type fibers, if the needle punching conditions are too strong, the sea-island type fibers will be cut or damaged, making it difficult to entangle, and if the needle punching conditions are too weak, in the thickness direction The number of fibers arranged tends to be insufficient.
The basis weight of the three-dimensional entangled nonwoven fabric obtained by the needle punching step, preferably 100 to 3000 g / m ^2, more preferably 150~1500g / m ^2, more preferably from 200 to 1000 g / m ^2.

The needle punched non-woven fabric is preferably pressed, for example, for smoothing according to the present invention, and it is also preferable to adjust the thickness simultaneously with the smoothing by pressing.
As a pressing method, conventionally known methods such as a method of passing between a plurality of heating rolls and a method of passing a preheated nonwoven fabric between cooling rolls can be used. In this step, it is possible to add an adhesive such as PVA, starch, or resin emulsion for the purpose of adjusting the melt / compression condition of the fibers and suppressing the change in the shape of the step due to tension, press, or the like. The condition that the thickness of the nonwoven fabric is preferably reduced by 5 to 30%, more preferably 10 to 25% by pressing.

(Process 4)
In step 4, the three-dimensional entangled nonwoven fabric (a) obtained in step 3 is impregnated with a polymer elastic body solution containing a polymer elastic body to which a water-soluble resin (b) is added. This is a step of obtaining a three-dimensional entangled nonwoven fabric (b) that has been solidified.
Here, a water-soluble resin may be added to the nonwoven fabric in advance before performing step 4. In step 4, the polymer elastic body solution to which the water-soluble resin is added is impregnated to develop an appropriate release effect with the fiber formed of the poorly water-soluble polymer, but this effect is supplemented. As a method of adding the water-soluble resin to the nonwoven fabric in advance, a method such as impregnating the nonwoven fabric with a water-soluble resin aqueous solution may be adopted. However, in this case, the solid content concentration of the water-soluble resin aqueous solution is too high in viscosity. From the viewpoint of avoiding productivity deterioration such as poor permeability due to the fact that it is not possible to squeeze out in the adjustment of the applied amount, it is preferably 0.5 to 10% by mass, more preferably 1.0 to 9.0% by mass. is there. Moreover, the water-soluble resin solid content adhesion rate to the nonwoven fabric is preferably 0.5 to 20% by mass, more preferably 1.0 to 15% by mass, from the viewpoint of effectively exhibiting the release effect.

In the three-dimensional entangled nonwoven fabric (b) obtained in step 4, the polymer elastic body is discontinuously present on the surface of the fiber. Thus, in order to discontinuously exist the polymer elastic body on the surface of the fiber forming the three-dimensional entangled nonwoven fabric, the polymer elastic body is formed by adding a water-soluble resin to the inside of the three-dimensional entangled nonwoven fabric. The polymer elastic body solution is preferably an aqueous emulsion.
As the water-soluble resin (b) to be added to the polymer elastic body, a known polymer can be used as long as it is a component that can be extracted with an aqueous solution. However, it is easy to dissolve and remove with hot water, and hardly soluble in water during extraction. In addition, PVA is preferred from the viewpoint that the decomposition reaction of the polymer elastic body component does not substantially occur, the poorly water-soluble resin and the polymer elastic body are not limited, and the environment is considered. In addition, the water-soluble resin (b) here may be the same as the above-mentioned water-soluble resin (a) constituting the extraction component (island component) of the hollow fiber generating fiber, or different ones. It may be used.

The addition amount of the water-soluble resin (b) is preferably 2.0 to 40 with respect to the solid content of the polymer elastic body so that the viscosity of the water-based emulsion does not become too high and the release effect is effectively expressed. It is 7.0 mass%, More preferably, it is 7.0-35 mass%, More preferably, it is 8.0-30 mass%, Most preferably, it is 9.0-25 mass%. If the addition amount of PVA is 2.0% by mass or more, the mold release effect and the water-based emulsion can be effectively made discontinuous and uniformly dispersed on the fiber surface. Furthermore, there is an effect that moderate slippage occurs between the poorly water-soluble resin and the polymer elastic body to improve physical properties such as tear strength and peel strength, and the above effect is obtained in the hollow long fiber used in the present invention. Cheap. Moreover, if it is 40 mass% or less, by adding water-soluble resin (b), it can prevent that the viscosity of a water-based emulsion does not become high too much, and a texture becomes soft too much and a stiffness is lost.
Here, when water repellency is imparted by post-treatment using a known water repellency treatment agent, the water-based water repellency treatment agent itself has a hydrophilic group or an interface for the purpose of making it water-soluble. Since it contains an activator, the water repellency decreases during the process of impregnating, coagulating and drying the aqueous emulsion, making it difficult to stably obtain the intended release structure.

Examples of the resin constituting the polymer elastic body include polyvinyl chloride, polyamide, polyester, polyester ether copolymer, polyacrylate copolymer, polyurethane, neoprene, styrene butadiene copolymer, silicone resin, polyamino acid, polyamino acid polyurethane copolymer, and the like. Synthetic resins, natural polymer resins, and mixtures thereof.
Among them, polyurethane or a material obtained by adding other resin to the polyurethane is preferably used as a polymer elastic body because a soft texture can be obtained. If necessary, pigments, dyes, crosslinking agents, fillers, plasticizers, various stabilizers, surfactants, and the like may be added to the aqueous emulsion, but self-emulsifying emulsions are preferably used.

  As described above, the resin concentration in the water-based emulsion can be arbitrarily set as long as the ratio between the polymer elastic body and the poorly water-soluble resin of the fibers forming the three-dimensional entangled nonwoven fabric satisfies the preferable range. From the viewpoints of dispersibility, liquid stability, and additive stability when other additives are mixed, the content is preferably 1 to 60% by mass, more preferably 2 to 40% by mass. If it is in this range, it is easy to adjust the mass of the polymer elastic body with respect to the non-woven fabric after forming the hollow fiber generating fiber to 5 to 50% by mass in terms of solid content, and the balance between the fiber and the elastic polymer. Therefore, a sense of fulfillment and flexibility as a product are obtained, and lightness and physical properties are improved.

The method for impregnating the water-based emulsion composed of a polymer elastic body to which the water-soluble resin (b) has been added into the interior of the three-dimensional entangled nonwoven fabric (a) is not particularly limited. For example, the nonwoven fabric is uniformly impregnated by dipping or the like. And a method of applying to the front and back surfaces. In addition, a heat-sensitive gelling agent or the like may be used to prevent the impregnated aqueous emulsion from migrating to the front and back surfaces of the nonwoven fabric, and the aqueous emulsion may be solidified uniformly in the nonwoven fabric.
Further, the impregnated water-based emulsion may be migrated to the front and back surfaces of the nonwoven fabric and then solidified, so that the abundance of the polymer elastic body may be gradually gradient in the thickness direction. That is, the abundance of the polymer elastic body may be increased in the vicinity of both surface layer portions, rather than the central portion in the thickness direction. In order to obtain such a distribution gradient, after impregnating the aqueous emulsion, the front and back surfaces of the nonwoven fabric are preferably heated at 100 to 150 ° C., preferably 0.5 to 30 minutes, without taking any means for preventing migration. To do. With such heating, moisture evaporates from the front surface and the back surface, and the water content of the aqueous emulsion is transferred to both surface layers, and the aqueous emulsion coagulates in the vicinity of the front surface and the back surface. Heating for migration is preferably performed by blowing hot air on the front and back surfaces in a drying apparatus or the like.

(Process 5)
Step 5 is a three-dimensional entanglement composed of hollow long fibers of a poorly water-soluble resin by dissolving and removing the water-soluble resin (a) and the water-soluble resin (b) from the three-dimensional entangled nonwoven fabric (b) obtained in Step 4. This is a process (extraction process) for forming a composite nonwoven fabric.

In step 4 above, an aqueous emulsion comprising a polymer elastic body to which the water-soluble resin (b) was added was impregnated and coagulated (this was followed by a drying treatment, preferably a hollow fiberization treatment by a known method). Using a chemical from the three-dimensional entangled nonwoven fabric (b), the water-soluble resin (a) of the hollow fiber generating fiber forming the nonwoven fabric, and the water-soluble resin (b) added to the aqueous emulsion Remove hot water at the same time.
In this step, in addition to the water-soluble resin (a) and water-soluble resin (b) to be dissolved and removed, additives contained in the polymer elastic body solution and the like are also extracted and removed as an extraction component. can do.

For example, when the water-soluble resin (a) of the sea-island type composite long fiber is first extracted and removed and then impregnated with the aqueous emulsion, the hot water extraction and removal is performed again to remove the water-soluble resin (b) and additives contained in the aqueous emulsion. Since it is necessary to perform the operation, it is preferable to remove the hot water after impregnating the aqueous emulsion and remove all the water-soluble resins and additives at once in order to increase the production efficiency. Further, when the water-soluble resin (a) of the hollow fiber generating long fiber is extracted and removed before impregnating the water-based emulsion composed of the polymer elastic body to which the water-soluble resin (b) is added, the polymer elasticity The effect of reinforcing the nonwoven fabric by the body is insufficient, the overall thickness is large, the fibers constituting the nonwoven fabric are easy to collect hair, and the space specified by the inscribed circle of air gaps of 350 to 3000 μm ² is associated with them. By decreasing, the texture becomes more like paper.

  The fibers forming the three-dimensional entangled nonwoven fabric in the present invention are hollow long fibers formed from hollow fiber generating long fibers, and unlike short fibers, there is substantially no or little exposure of the fiber cross section. Before performing the process, it is necessary to perform buffing treatment to increase the number of fiber cut ends on the surface of the base fabric to promote water intrusion. By promoting the infiltration of water, extraction components including a water-soluble resin can be easily extracted and removed from the hollow fiber generating fiber, and the weight can be reduced and the texture can be improved.

The buffing treatment can be performed in any step before this step, but is preferably after impregnating the polymer elastic solution in step 4, and at least one side, preferably both sides of the surface of the base fabric. Perform buffing.
The buffing treatment can be performed, for example, by grinding the surface of the three-dimensional entangled nonwoven fabric with sandpaper or a needle cloth. Among them, 180-400 sandpaper is used, and the buffing treatment is about 3/100 to 20/100 mm. It is preferable to do.

  Furthermore, it is preferable to dissolve and remove a water-soluble resin represented by PVA from the wall surface of the fiber for the purpose of increasing the extraction efficiency. In this case, it is preferable that the average thickness of the thinnest part of each partition in the plural (outer peripheral part and hollow part) partition formed by the sea component as described above is 7 μm or less. Water swells the PVA that is an island component, so that it is easy to dissolve and remove PVA by generating minute cracks without reducing the physical properties on the fiber side surface.

  As an extraction method, a water temperature of about 80 to 95 ° C. is preferable, and a liquid dyeing machine, a dyeing machine such as a jigger, and a scouring machine such as an open soaper can be used. An extraction method capable of giving physical deformation to the long fiber is preferable, and it is preferable to use a liquid dyeing machine or a device in which a vibro washing machine and a squeezing device are combined in multiple stages. By the above extraction method, most or all of the water-soluble resin is extracted and removed.

[Uses of artificial leather substrates]
The base material for artificial leather of the present invention satisfying the requirements (1) to (3) can be obtained by a production method including steps 1 to 5, and is used in various applications, for example, artificial leather with silver having various appearances. It can be used as a substrate.
Specifically, a resin film with a leather-like appearance formed on a release paper is transferred to the surface of an artificial leather substrate via an adhesive, or a liquefied resin paint such as a resin emulsion, a resin solution, or a molten resin is applied. Surface finishing with continuous coating using gravure, comma coater, etc., embossing roll or mirror belt on the front and back of them, smoothing processing, and combining these processes. It is possible to obtain artificial leather products such as shoes and bags having the effects of the present invention by using artificial leather made as long as it does not impair the intended light weight as all or part of the main material. It is.

  Conventionally known resins such as a polyurethane resin, an acrylic resin, a polyamide resin, a polyester resin, and a polyolefin resin can be used as the resin that constitutes the finished surface portion of the surface that has been subjected to the surface finishing process, that is, the silver surface layer. It is possible to use polyurethane resin or acrylic resin to balance the texture and fullness of the base material for artificial leather and to balance the performance of surface wear resistance, flex resistance, surface touch, durability, etc. preferable.

  In addition, the structure of the silver surface layer is a porous structure or non-porous structure formed by a wet method or a dry method when a resin film is formed on the above-mentioned release paper or when a liquefied resin paint coated on the substrate surface is solidified. By adopting a quality structure, desired functions and textures can be obtained. The thickness of the silver surface layer does not impair the lightness of an apparent density of less than 0.3, has mechanical properties such as surface strength required for the application, and has a balance of texture with the substrate and the total amount of the substrate. As long as the thickness falls within the desired range, there is no particular limitation, but the standard is in the range of 20 to 500 μm. For example, it is smooth, flexible, and features a texture with a sense of unity. When it is desired to obtain artificial leather with improved air permeability and moisture permeability, 50 to 300 μm is preferable.

  EXAMPLES The present invention will be described with reference to examples, but the present invention is not limited to these examples. Moreover, the part and% which are described in an Example are related with mass unless there is particular notice. In the following examples and comparative examples, the melting point measurement, mechanical properties and other evaluations were performed according to the following methods.

[Measurement method of melting point of resin]
Using a differential scanning calorimeter (TA3000, manufactured by Mettler), the temperature was raised from room temperature to 300 ° C. in nitrogen at a heating rate of 10 ° C./min. When the temperature was raised to 300 ° C., the peak top temperature of the endothermic peak indicating the melting point of the resin was adopted.

[Extraction rate measurement]
The extraction rate was calculated by the following formula.
Extraction rate of nonwoven fabric after application of polymer elastic body (%) = (A−B) / (A × C / 100 × D) × 100
A: Weight of nonwoven fabric after application of polymer elastic body before extraction B: Mass of nonwoven fabric after application of polymer elastic body after extraction C: Mass ratio of hollow fiber generating fiber component of nonwoven fabric after application of polymer elastic body D: of hollow fiber generating fiber Water-soluble resin mass ratio

[Measurement of apparent density of base material for artificial leather]
The value obtained by dividing the mass (g / cm ² ) per unit area of the artificial leather base material by the thickness (cm) was used as the apparent density (g / cm ³ ), and measured at any 10 locations on the artificial leather base material. The value obtained by arithmetically averaging the apparent density was used as the apparent density of the base material for artificial leather. The thickness was measured at a load of 240 gf / cm ² according to JISL1096.

[Method of measuring peel strength of base material for artificial leather]
The surface of a polyurethane rubber plate 15cm long, 2.5cm wide and 5mm thick is lightly scraped with sandpaper, and a two-component cross-linking type polyurethane adhesive is evenly distributed within a range of about 10cm from either end. On the other hand, a test piece obtained by cutting a base material for artificial leather to a length of 25 cm and a width of 2.5 cm is similarly applied with a uniform application of an adhesive within a range of about 10 cm from either end. Then, they were bonded so that the ends to which the adhesive was applied overlapped.
The bonded specimen and rubber plate were pressed at a pressure of about ² to 4 kg / cm ² and then left at 25 ° C. for one day and night. Rubber that corresponds to the tensile time at a tensile speed of 10 cm / min by sandwiching the ends of the test piece and the rubber plate that are not coated with adhesive between the upper and lower chucks of a tensile tester set at an initial interval of 5 cm. The peel strength of the bonded portion between the plate and the test piece was measured and recorded on a chart. The average value of the portions where the peel strength in the tensile time-peel strength curve obtained on the chart was almost constant was read and taken as the peel strength value of the test piece. For one type of artificial leather substrate, the value obtained by arithmetically averaging the peel strength measurement values of three test pieces cut out from three arbitrary locations was taken as the peel strength value of the artificial leather substrate.

[Method of measuring tear strength of base materials for artificial leather]
A test piece cut to a length of 10 cm x a width of 4 cm is cut into the center of the short side (2 cm from both ends in the width direction) at a right angle to the short side (parallel to the length direction), and the tongue is peeled off strongly. The tear stress when tearing at a tensile speed of 10 cm / min was sandwiched between upper and lower chucks of a tensile tester set in the same manner as the measurement method, and recorded on a chart. The maximum value of the tear stress was read from the chart and used as the tear strength value of the test piece. For one type of artificial leather substrate, the value obtained by arithmetically averaging the measured tear strength values of three test pieces cut out from any three locations was taken as the tear strength value of the artificial leather substrate.

[Texture]
(1) At the time of bending The bent shape generated when the sample cut into a square of 20 cm × 20 cm was valley-folded so that the upper end and the lower end were matched was visually observed.
And it determined with the following references | standards.
Good: A fine and uniform fold wrinkle was generated on the surface, similar to the case where cowhide was folded.
Defect: Rough wrinkles such as corrugated cardboard were generated on the folded surface.

(2) Touch (flexibility)
A test piece of 20 cm × 20 cm was cut out from the obtained base material for artificial leather. And it judged by the tactile sensation when putting the test piece in the palm.

[Measurement of inter-fiber void area]
The cross section of all layers of the artificial leather substrate was observed with a scanning electron microscope at a magnification of 30 times. Using the image analysis software PopImaging (manufactured by Digital being kids. Co), the resulting image is binarized by a dynamic threshold method, and an inscribed circle is drawn in the void, and the inscribed circle area is inscribed in the gap It was measured as a circular area. In the drawn inscribed circle area, less than 350 μm ² is removed, and the average of the remaining inscribed circle area is the average of the void inscribed circle area, and the drawn inscribed circle area is 350 to 3000 μm ² . The ratio of the number of tangent circles to the number of circles inscribed in the entire gap was calculated.

[Fiber cutting edge measurement]
The surface of the artificial leather substrate was observed with a scanning electron microscope at a magnification of 50 times. On both sides of the substrate, the fiber cutting ends in the range of 1.46 mm × 1.75 mm were counted. The number per 1 mm ² was calculated from the average value of both surfaces and the visual field.

[Example 1]
(Process 1)
Nylon 6 (Ube Industries Co., Ltd. 1015BK) is used as a sea component, and water-soluble thermoplastic PVA (Kuraray Exval CP-4104MI, melting point 209 ° C., MFR measured by M method of JIS K7210: 80 g / min, viscosity average polymerization Using a melt compound spinning die that has 12 islands per island (sea island) with a sea level of 330 and a degree of saponification of 98.4 mol%). It was discharged from the die at 255 ° C. so that the mass ratio of the island components was 50/50.
Discharge from the base by adjusting the air in the air jet suction device installed directly below the base so that the spinning speed obtained indirectly from the ratio of the discharge amount per unit time and the fineness of the obtained long fibers is 2500 m / min. Nylon hollow fiber generating composite fibers having an average fineness of 2.53 dtex were spun by cooling while making the polymer polymerized into an index. The thickness of the wall separating PVA in the obtained nylon hollow fiber generating composite fiber was 1.10 μm.

(Process 2)
The nylon hollow fiber generating composite fiber is continuously collected on a mobile net installed immediately below the suction device, and then pressed at a linear pressure of 17 kg / cm using a metal roll having a surface temperature of room temperature to obtain a basis weight of 45 g / A composite long fiber web of m ² was obtained.

(Process 3)
The resulting composite long fiber web was uniformly applied to the web surface using a spray while overlapping the resulting composite long fiber web so as to have a basis weight corresponding to 8 webs using a cross wrapper. Next, using 9-barb and 6-barb felt needles with a distance of 5 mm from the tip of the needle to the barb, and alternating between both sides of the web with the setting so that the tip of the needle stabbed into the composite long fiber web protrudes up to 10 mm from the opposite side. The needle punching process was performed. A needle punching process was performed so that the total number of pierced needles was 1450 / cm ^2, and the composite long fibers were entangled with each other to obtain a three-dimensional entangled nonwoven fabric having a basis weight of 344 g / m ² .
(PVA pre-added)
A three-dimensional entangled nonwoven fabric obtained by impregnating the obtained nonwoven fabric with a PVA aqueous solution having a solid content concentration of 5.4% by mass so that the PVA solid content adhesion rate was 11.5% by mass was obtained.

(Process 4)
To a self-emulsifying aqueous polyurethane emulsion, 9.5% by mass of PVA (Pura-117, manufactured by Kuraray Co., Ltd.) of emulsion solid content is added to a three-dimensional entangled nonwoven fabric with a smooth surface, and the emulsion solid content concentration is 8.0 mass. After impregnation as a percentage, the polymer elastic body was impregnated by drying treatment with hot air at 100 ° C. for 30 minutes in a dryer.

(Buffing process)
Subsequently, 240th sandpaper was used and both sides were ground 10/100 mm and buffed.
(Process 5)
After the buffing treatment, the island component PVA was dissolved and removed from the composite fiber in the three-dimensional entangled nonwoven fabric by dip × nip method in 95 ° C. hot water so that the hot water immersion time was 20 minutes. The extraction rate is 92.0% by mass, and the obtained one has a thickness of 1.16 mm, a basis weight of 274 g / m ² , and a three-dimensional entangled nonwoven fabric of nylon hollow long fibers having twelve hollow portions in the cross section, A base material for artificial leather made of polyurethane was obtained.

The mass ratio of polyurethane to nylon hollow long fiber in the obtained base material for artificial leather is polyurethane / nylon hollow long fiber = 34.1 / 65.9, and the polyurethane is discontinuously present on the fiber. It was. The fiber cut fraction of the substrate surface was sides average 42.3 pieces / mm ^2. Further, according to the above-mentioned measurement of the inter-fiber void area, the cross section of the obtained artificial leather substrate was observed with an electron microscope at a magnification of 30 times, and the obtained photograph (FIG. 1) was image analysis software PopImaging (Digital being kids. Using Co), the image was binarized by the dynamic threshold method (FIG. 2), an inscribed circle was drawn in the gap (FIG. 3), and the inscribed circle area was measured as the inscribed circle area of the air gap. The air gap inscribed circle area, which is the number average of all inscribed circle areas drawn, is an average of 1238 μm ² , and the number of air gap inscribed circles having the number of drawn inscribed circle areas of 350 to 3000 μm ² The ratio to the number of yen was 90.2%.

This base material for artificial leather has a higher peel strength as the base fabric is cut at the time of peel strength measurement. The vertical tear strength is 4.5 kg, the horizontal tear strength is 7.9 kg, the peel strength is 7.9 kg / cm ² , and the apparent density is 0. 237 g / cm ³ , excellent mechanical properties, not only light, but also feels soft and soft to the touch, and fine wrinkles appear evenly when bent It was an excellent material as a base material for finishing artificial leather for men's shoes and sports shoes.

[Example 2]
Em amount change The same operation as Example 1 was carried out except that the water-based polyurethane emulsion was applied in the form of polyurethane / nylon hollow long fiber = 25.5 / 74.5 to obtain a base material for artificial leather.
The polyurethane in the obtained base material for artificial leather was discontinuously present on the fiber, and the average number of fiber cuts on the surface of the base material was 42.3 / mm ^{2 on the} front and back. The air gap inscribed circle area averaged 1038 μm ² and the ratio of the number of air gap inscribed circles of 350 to 3000 μm ² was 91.7%. In addition, the vertical tear strength is 4.9 kg, the horizontal tear strength is 5.4 kg, and the peel strength is high enough to cut the base material. The apparent density is 0.223 g / cm ^3, which is excellent in mechanical properties but only light. In addition, the texture is soft and soft to the touch, and when bent, fine wrinkles are evenly expressed, which is very good as a base material for finishing artificial leather for men's shoes and sports shoes. It was an excellent material.

[Example 3]
No PVA pre-addition A base material for artificial leather was obtained in the same manner as in Example 1 except that PVA was not added in advance to the three-dimensional entangled nonwoven fabric.
Polyurethane in the obtained base material for artificial leather is discontinuously present on the fiber, the fiber cutting edge number is 35.2 pieces / mm ² , and the air gap inscribed circle area is an average of 1141 μm ² and 350 to 3000 μm ² . The ratio of the number of circles inscribed in the air gap was 88.0%. In addition, the vertical tear strength is 5.7 kg, the horizontal tear strength is 5.3 kg, and the peel strength is high enough to cut the base material. The apparent density is 0.202 g / cm ^3. The texture is soft and soft to the touch, and when bent, fine wrinkles are evenly expressed, and it is excellent as a base material for finishing artificial leather for men's shoes and sports shoes. Material.

[Comparative Example 1]
No buffing treatment A base material for artificial leather was obtained in the same manner as in Example 1 except that no buffing treatment was performed before extraction.
Polyurethane in the obtained base material for artificial leather is discontinuously present on the fiber, but the fiber cut edge is 9.4 pieces / mm ^{2 and the} air gap inscribed circle area is an average of 1065 μm ² and 350 to 3000 μm ² . The ratio of the number of circles inscribed in the air gap was 93.1%, and the extraction rate was 81.3%. Also, it has a vertical tear strength of 5.9 kg, a horizontal tear strength of 4.5 kg, a peel strength of 8.5 kg / cm ² , and an apparent density of 0.235 g / cm ^3. The folds were conspicuous and the heels were inconspicuous at the time of bending, which was inferior as a base material for finishing artificial leather for men's shoes and sports shoes.

[Comparative Example 2]
No buffing treatment, no PVA pre-added, no Em-added PVA Same as Example 1 except that no PVA was added to the nonwoven fabric in advance, no PVA was added to the aqueous polyurethane emulsion, and no buffing treatment was performed before extraction. Operation was performed to obtain a base material for artificial leather.
Although the polyurethane in the obtained base material for artificial leather exists discontinuously on the fiber, the fiber cut fraction is 3.5 pieces / mm ² , and the air gap inscribed circle area is an average of 1108 μm ² and 350 to 3000 μm ^2. The ratio of the number of circles inscribed in the air gap was 89.4%, and the extraction rate was 80.3%. The vertical tear strength is 5.8 kg, the horizontal tear strength is 5.6 kg, the peel strength is 9.6 kg / 2.5 cm, and the apparent density is 0.233 g / cm ^{3. The} mechanical properties are strong, but the extraction rate is low, and the texture is Baki folds were conspicuous, and the heels were inconspicuous when bent, and were inferior as a base material for finishing artificial leather for men's shoes and sports shoes.

[Comparative Example 3]
Buffing treatment, PVA pre-added, No Em-added PVA The same procedure as in Example 1 was performed except that PVA was not added to the nonwoven fabric in advance and PVA was not added to the aqueous polyurethane emulsion. Got.
Although the polyurethane in the obtained artificial leather base material is discontinuously present on the fiber, the fiber cut edge is 48.5 pieces / mm ² , and the air gap inscribed circle area exceeds 1275 μm ² and 1250 μm ² on average. The ratio of the number of circles inscribed in the air gap of 350 to 3000 μm ² was 85.7%. Moreover, although the peel strength is higher as the base fabric is cut at the time of peel strength measurement, the vertical tear strength is 4.2 kg, the horizontal tear strength is 4.3 kg, the peel strength is 7.2 kg / 2.5 cm, and the apparent density is 0.225 g / cm ³ . Yes, the mechanical properties are high and light, but the texture is noticeably broken, and the heel is conspicuous and poor when bent, and it is inferior as a base material for finishing artificial leather for men's shoes and sports shoes. .

  The base material for artificial leather of the present invention has excellent mechanical properties, is flexible, lightweight, and has a texture that is excellent in texture, so it is extremely useful as a base material for finishing artificial leather for bags, men's shoes, and sports shoes. Useful.

Claims (9)

A base material for artificial leather comprising a three-dimensional entangled nonwoven fabric and a polymer elastic body, wherein the three-dimensional entangled nonwoven fabric is a hollow long fiber and satisfies the following requirements (1) to (3): A base material for artificial leather.
Requirement (1): The average of the void inscribed circle area excluding the void inscribed circle area of less than 350 μm ^{2 in the} cross section parallel to the thickness direction of the base material for artificial leather is 1250 μm ² or less.
Requirement (2): The number of void inscribed circles with a gap inscribed circle area of 350 to 3000 μm ² in a cross section parallel to the thickness direction of the base material for artificial leather is 85% or more with respect to the number of inscribed circles of all voids. It is.
Requirement (3): At least one side of the base material for artificial leather has a fiber cut end of 15 pieces / mm ² or more.   The base material for artificial leather according to claim 1, wherein an average thickness of an outer peripheral part of the hollow long fiber or a partition wall of the hollow part is 7 µm or less.   The base material for artificial leather according to claim 1 or 2, wherein a surface of the hollow long fiber has a crack in a length direction of the fiber.   The mass ratio of the polymer elastic body and the three-dimensional entangled nonwoven fabric constituting the base material for artificial leather (polymer elastic body / three-dimensional entangled nonwoven fabric) is 5/95 to 50/50 in terms of solid content. The base material for artificial leather according to any one of claims 1 to 3, which is a range. A base material for artificial leather composed of a three-dimensional entangled nonwoven fabric and a polymer elastic body, including steps performed in the order of the following (Step 1) to (Step 5), and buffing before the following (Step 5) A method for producing a base material for artificial leather, comprising:
(Step 1): A step of obtaining a sea-island type composite long fiber having a poorly water-soluble resin as a sea component and a water-soluble resin (a) as an island component.
(Step 2): A step of obtaining a composite long fiber web from the sea-island composite long fibers obtained in Step 1 above.
(Process 3) The process of forming a three-dimensional entangled nonwoven fabric (a) by carrying out a needle punching process, after superposing | stacking 2 or more of the composite long fiber webs obtained at the said process 2. FIG.
(Step 4) After impregnating the three-dimensional entangled nonwoven fabric (a) obtained in Step 3 with a polymer elastic body solution containing a polymer elastic body to which a water-soluble resin (b) is added, the polymer elasticity The process of obtaining the three-dimensional entangled nonwoven fabric (b) which solidified the body.
(Step 5): A tertiary composed of hollow long fibers of a poorly water-soluble resin by dissolving and removing the water-soluble resin (a) and the water-soluble resin (b) from the three-dimensional entangled nonwoven fabric (b) obtained in Step 4 above. The process of forming a former entangled nonwoven fabric.   The method for producing a base material for artificial leather according to claim 5, wherein the water-soluble resin (a) and / or the water-soluble resin (b) is polyvinyl alcohol.   The base for artificial leather according to claim 5 or 6, wherein the water-soluble resin (b) is added at a ratio of 2.0 to 40% by mass with respect to the solid content of the polymer elastic body in the step 4. A method of manufacturing the material.   In the said process 4, the manufacturing method of the base material for artificial leather of any one of Claims 5-7 whose polymer elastic body solution is a water-system emulsion.   In the sea-island type composite long fiber, the average of the shortest distance between the island components or the average of the shortest distance between the island component and the outer periphery of the sea-island type composite long fiber is 7 μm or less. The manufacturing method of the base material for artificial leather of description.