JP2017008478A - Substrate for artificial leather - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for an artificial leather that has a material feeling excellent in mechanical properties, softness and texture, and has also lightness.SOLUTION: There is provided a substrate for an artificial leather including a three-dimensionally entangled nonwoven fabric and an elastomer. The substrate for the artificial leather satisfies the following requirements (1) to (3) and has an apparent density of less than 0.3 g/cm, in which a mass ratio (the elastomer/fibers forming the three-dimensionally entangled nonwoven fabric) of the elastomer to the fibers forming the three-dimensionally entangled nonwoven fabric is 15/85 to 30/70. Requirement (1) is that the elastomer discontinuously exists on a surface of the fibers forming the three-dimensionally entangled nonwoven fabric. Requirement (2) is that an average area of incircles between voids, except areas of incircles between voids of less than 350 μm, in a cross section parallel to a thickness direction of the substrate for the artificial leather is 1250 μmor less. Requirement (3) is that the number of incircles between voids of areas of incircles between voids of 400 to 3000 μmin a cross section parallel to a thickness direction of the substrate for the artificial leather is 85% or more with respect to the total number of incircles between voids.SELECTED DRAWING: None

Description

  The present invention relates to a base material for artificial leather. Specifically, it is a base material for artificial leather consisting of a three-dimensional entangled nonwoven fabric and a polymer elastic body, and has a mechanical feel, flexibility, texture, and a lightweight feel. About.

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, there has been a demand for a solvent-free manufacturing process for the use of organic solvents because of the concern of adverse effects on the human body and the environment. (For example, refer to Patent Document 5), and in a method for producing artificial leather, a polymer elastic water 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.

  Then, an object of this invention is to provide the base material for artificial leather which has the mechanical property, the softness | flexibility, the material feeling excellent in the texture, and also the lightness.

That is, this invention provides the following base material for artificial leather.
1. A base material for artificial leather comprising a three-dimensional entangled nonwoven fabric and a polymer elastic body, which satisfies the following requirements (1) to (3).
Requirement (1): The polymer elastic body exists discontinuously on the surface of the fiber forming the three-dimensional entangled nonwoven fabric.
Requirement (2): 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 base material for artificial leather is 1250 μm ² or less.
Requirement (3): 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 all indented circle inscribed circles It is.
2. 2. The artificial leather substrate according to 1, wherein the polymer elastic body is formed by impregnating and solidifying a three-dimensional entangled nonwoven fabric with an aqueous emulsion resin.
3. The base material for artificial leather as described in 1 or 2 above, wherein the fibers forming the three-dimensional entangled nonwoven fabric are hollow fiber generating long fibers.
4). In the base material for artificial leather, the mass ratio of the polymer elastic body and the poorly water-soluble polymer component of the fiber forming the three-dimensional entangled nonwoven fabric (polymer elastic body / water fragility of the fiber forming the three-dimensional entangled nonwoven fabric) The base material for artificial leather according to any one of 1 to 3, wherein the soluble polymer component) is in the range of 5/95 to 50/50 in terms of solid content.

  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.

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.

The base material for artificial leather of the present invention is a base material for artificial leather comprising a three-dimensional entangled nonwoven fabric and a polymer elastic body, and satisfies the following requirements (1) to (3).
Requirement (1): The polymer elastic body exists discontinuously on the surface of the fiber forming the three-dimensional entangled nonwoven fabric.
Requirement (2): 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 base material for artificial leather is 1250 μm ² or less.
Requirement (3): 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 all indented circle inscribed circles It is.

In the base material for artificial leather of the present invention, requirement (1): the elastic polymer is discontinuously present on the surface of the fiber forming the 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.

  Conventionally, a method has been adopted in which a fibrous resin is impregnated with a binder resin dissolved in an organic solvent, and wet-solidified by treatment with a non-solvent. It was possible to stabilize the form and give a natural leather-like texture with the 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. End up. In addition, simply reducing the amount of water-based emulsion resin used resulted in a partially continuous layer rather than a uniform discontinuous state, resulting in a non-uniform structure as a whole, and as a result, it was possible to secure light weight. However, it will cause a decrease in texture such as cracks.

  Therefore, in the present invention, when a polymer elastic body is imparted to a three-dimensional entangled nonwoven fabric, a three-dimensional entangled nonwoven fabric is impregnated with a water-based emulsion resin composed of a polymer elastic body added with a water-soluble polymer component, and solidified. It is preferable to perform a drying process. By adding a water-soluble polymer component to a water-based emulsion resin made of a polymer elastic body, the water-soluble polymer component is extracted and removed by an extraction step described later, and a hollow fiber generating fiber of a three-dimensional entangled nonwoven fabric is obtained. A release structure in which a space is formed at the interface between the constituent fibers, that is, the poorly water-soluble polymer component and the polymer elastic body contained in the water-based emulsion resin, is obtained, and the polymer elastic body is not present on the fiber surface. It becomes possible to exist continuously, and a structure in which voids formed between fibers are uniformly distributed is obtained. 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 order to exhibit the above effects, requirement (2): the 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 base material for artificial leather average may be 1250 micrometers ² or less, preferably 1240Myuemu ² or less, more preferably 1200 [mu] m ² or less, still more preferably at 1100 .mu.m ² or less. 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. At the same time, Requirement (3): The number of void inscribed circles with a gap inscribed circle area of 350 to 3000 μm ^{2 in} the cross section parallel to the thickness direction of the artificial leather substrate is 85 with respect to the number of all inscribed void inscribed circles. % Or more, preferably 86% or more, more preferably 88% or more, and further preferably 90% or more.
When the air gap inscribed circle average area exceeds 1250 μm ² , the lightness is impaired, and when the air gap inscribed circle area of 350 to 3000 μm ² is less than 85%, the size of the air gap becomes non-uniform and for artificial leather When the base material is bent, it breaks, creating a burrowing pit and the like, causing a problem 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.

  In the base material for artificial leather of the present invention, the mass ratio of the polymer elastic body and the hardly water-soluble polymer component of the fiber forming the three-dimensional entangled nonwoven fabric (polymer elastic body / poor water-soluble polymer component) is a solid content. It is preferably 5/95 to 50/50 in terms of conversion, more preferably 10/90 to 40/60, and even more preferably 15/85 to 30/70. That is, as the amount of the polymer elastic body imparted to the three-dimensional entangled nonwoven fabric when used as a base material for artificial leather, the polymer elastic nonwoven fabric and the three-dimensional entangled nonwoven fabric are formed after the water-insoluble fiber is formed. Preferably it is 5-50 mass% in conversion of solid content, More preferably, it is 10-40 mass%, More preferably, it is 15-30 mass% with respect to a total of 100 mass with the poorly water-soluble polymer component of a fiber. 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.

  The thickness of the base material for artificial leather of the present invention can be arbitrarily selected according to the use and is not particularly limited, but is preferably 0.3 to 3 mm, more preferably 0.7 to 1.8 mm. It is a range. 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.

Moreover, it is preferable that the apparent density of the base material for artificial leather is 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 existing products is generally 280 to 800 for an apparent density of 0.35 to 0.5 g / cm ³ , that is, a thickness of 0.8 mm. It is about 400 g / m ² . In the case of at least 10% lighter than 250 g / m ² from the image of the weight of general materials such as artificial leather base materials 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 lightly by general consumers. In existing technology, it was difficult to combine light weight, high physical properties, and texture as real problems, but 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 use. The base material for artificial leather having the texture and quality required for artificial leather can be stably produced.

The base material for artificial leather of the present invention is composed of a three-dimensional entangled nonwoven fabric and a polymer elastic body, and the fibers forming the three-dimensional entangled nonwoven fabric are fibers composed of one kind of polymer, or chemically or physically. After impregnating a polymer elastic body into a multicomponent fiber (composite fiber) composed of at least two kinds of spinnable polymers having different properties, at least one kind of polymer is extracted and removed at an appropriate stage to obtain a fiber form. It is a fiber that can be formed by changing.
As the above-mentioned composite fiber, any of sea-island type fiber typified by sea-island type composite spun fiber, sea-island type mixed spun fiber, etc., and multi-component type composite fiber such as petal type and laminated type fiber can be used. A hollow fiber generating fiber is preferable. The hollow fiber generating composite 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 fiber.

  In the case of hollow fiber generating fiber, the polymer that forms the fiber after the extraction step described later (corresponding to the sea component in the sea-island type) is a known polymer that is a poorly water-soluble polymer, for example, polyamide-based, polyester-based And if it is polyolefin type etc., it will not specifically limit. Of these, nylon is preferred as the polyamide system. In particular, the specific gravity of the polymer is low and light weight is easily developed, and when the polymer elastic polymer is impregnated in the form of an aqueous emulsion, a release structure with the hollow fiber is exhibited. Polymers having polyolefin-based fiber-forming ability are preferred from the viewpoint of easy formation, and polypropylene resins are particularly preferred from the viewpoint of physical properties and spinning stability.

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. In addition, 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 fiber.

  The polymer constituting the extraction component of the hollow fiber generating fiber (corresponding to the island component in the sea-island type) is a water-soluble polymer, and the polymer forming the fiber after extraction is soluble in a solvent or a decomposing agent. Alternatively, a polymer having a different decomposability and a low affinity with the sea component and having a melt viscosity higher than the melt viscosity of the sea component under the spinning conditions or a polymer having a large surface tension is preferable. With such a polymer, it becomes possible to produce a base material for artificial leather that can be removed simultaneously with a water-soluble polymer component added to a polymer elastic body described later without using chemicals.

  As the polymer constituting the extraction component of the hollow fiber generating fiber, a known polymer can be used as long as it is a water-soluble polymer that can be spun and can be extracted with an aqueous solution, but it can be easily dissolved and removed with hot water. Yes, from the point that decomposition reaction of poorly water-soluble polymer components and polymer elastic bodies during extraction does not occur substantially, and poorly water-soluble polymer components and polymer elastic bodies are not limited. Water-soluble 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.

In addition, 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.
In order to produce the description for artificial leather of the present invention, PVA is added to the water-based emulsion resin to be impregnated to develop an appropriate mold release effect with the fiber formed of the poorly water-soluble polymer, but this effect is supplemented. Therefore, PVA may be added to the nonwoven fabric in advance before the nonwoven fabric is impregnated with the aqueous emulsion resin. In this case, the solid content concentration of the PVA aqueous solution is preferably 0.5 to 10 masses from the viewpoint of avoiding the poor permeability due to the viscosity being too high, or the productivity reduction such as being unable to be fully squeezed in the adjustment of the applied amount. %, More preferably 1.0 to 9.0% by mass, and the PVA solid content adhesion rate to the nonwoven fabric is preferably 0.5 to 20% by mass from the viewpoint of effectively expressing the mold release effect. Preferably it is 1.0-15 mass%.

As described above, the hollow fiber generating fiber suitable in the present invention is preferably a long fiber because of excellent mechanical properties. 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, the exposure of the fiber cross section is very small, and it is preferable to extract the water-soluble polymer from the fiber wall surface in the extraction step described later. Therefore, in order to increase the extraction efficiency, it is preferable to generate cracks in the fiber wall surface when swollen with water, the distance between the island components of the water-soluble polymer that is the island component of the hollow fiber generating fiber, or the island component The average of the shortest distance between the outer periphery of the hollow fiber generating fiber and the outer periphery of the hollow fiber generating fiber is preferably 7 μm or less, and more preferably 3 μm or less.
Here, the average thickness of the thinnest part of each partition refers to each island component, and each island component and island component and sea-island fiber in an image obtained by observing a cross section of the sea-island fiber at a magnification of 2000 with a scanning electron microscope (SEM). It is the thickness obtained by measuring the thickness t of the thinnest part and averaging the values in the plurality of partition walls formed by the sea component that separates the outline of the sea wall.

  When the PVA is swollen from the cut surface or the damaged part in the process of extracting and removing PVA from the hollow fiber generating fiber in the extraction process described later by hot water by forming the hollow fiber generating fiber as described above. , Cracks are likely to occur in the partition walls made of a sea component polyolefin-based resin (poorly water-soluble polymer). And when water permeates into the sea-island fiber from the crack, PVA further swells and dissolves, and the extraction efficiency of PVA increases. Therefore, PVA can be efficiently extracted even if it is a three-dimensional entangled body formed using filaments made of sea-island fibers with a small fiber cross section.

  The fineness of the hollow fiber generating fiber suitable in the present invention 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, when the area of one island part (hollow part) in the hollow fiber is too small, the hollow part is removed even though the island component is removed by the tension or press applied after the island part removing step for generating the hollow part. Therefore, 1 to 4% is more preferable, and 2 to 4% is a more preferable range.

  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, after the island component is removed. More preferable in terms of shape stability. In addition, the area hollowness ratio is the area ratio between the portion forming the hollow fiber and the island component portion that becomes the hollow portion after extraction and removal, and the form maintaining property of the outer wall and partition wall made of the hollow fiber component when the island component is removed Therefore, it is preferable to stabilize the hollow shape by appropriately combining the fineness of the island component and the sea-island hollow ratio.

The hollow fiber generating fiber suitable for the present invention is any fiber after spinning, drawing and crimping to the desired fineness, as most commonly practiced in conventional artificial leather substrates. The composite fiber web may be produced by cutting into long pieces to form staples, and using a card, a cross wrapper, a random weber or the like.
Alternatively, after the hollow fiber generating fiber discharged from the spinning nozzle hole is cooled by a cooling device, a suction device such as an air jet nozzle is used to achieve a desired fineness of about 1000 to 6000 m / min. After pulling and thinning with a high-speed air stream at a speed corresponding to the take-off speed, the fiber web is formed by depositing on a collection surface such as a mobile net while opening the fiber, and then the web to be transported to the next process In the case where it is necessary to stabilize the form, the fiber web may be subsequently produced by a method in which the form is stabilized by partially pressing 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 fiber web obtained as described above is overlapped in order to obtain a target non-woven fabric, and the thickness is substantially cut by entanglement processing including the following needle punching step, without substantially cutting the fiber. It can be set as the three-dimensional entangled nonwoven fabric which entangled the fibers while orienting the fibers in the direction.

  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. In addition, by increasing the apparent density of the surface layer region of the three-dimensional entangled nonwoven fabric from the vicinity of the middle layer, in order to efficiently obtain a smooth and dense surface state even with a small number of hollow fibers, 3 barbs with a large amount of 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. If 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 if the web 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 preferred basis weight of the three-dimensional entangled nonwoven fabric obtained by the needle punching step 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 at the same time as 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 is such that the thickness of the nonwoven fabric is preferably reduced by 5 to 30%, more preferably 10 to 25% by pressing.

In order to make a polymer elastic body discontinuously exist on the surface of the fiber forming the three-dimensional entangled nonwoven fabric, an aqueous system comprising a polymer elastic body with a water-soluble polymer component added to the inside of the three-dimensional entangled nonwoven fabric. It is preferable to impregnate and solidify the emulsion resin.
As the water-soluble polymer component 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. PVA is preferred from the viewpoint that the decomposition reaction of the component and the elastic polymer component does not substantially occur, the poorly water-soluble polymeric component and the elastic polymer are not limited, and the environment is considered. The water-soluble polymer component used here may be the same as or different from the water-soluble polymer constituting the extraction component of the hollow fiber generating fiber.

The amount of PVA added is preferably 7.0 to 35% by mass, more preferably based on the solid content of the polymer elastic body, in order that the viscosity of the water-based emulsion does not become too high and the release effect is effectively expressed. It is 8.0-30 mass%, More preferably, it is 9.0-25 mass%. If the amount of PVA added is 7.0% by mass or more, the release effect and the water-based emulsion resin can be effectively discontinuously and uniformly dispersed on the fiber surface. There is an effect of improving the physical properties such as tear strength and peel strength by causing moderate slip between the component and the polymer elastic body, and when the hollow fiber generating fiber which is a suitable combination in the present invention is a long fiber The above effects are easily obtained. Moreover, if it is 35 mass% or less, by adding PVA, it can prevent that the viscosity of water-based emulsion resin does not become high too much, and a texture becomes soft too much and a firmness is lose | eliminated.
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 step of impregnating, coagulating and drying the aqueous emulsion binder resin, making it difficult to stably obtain the desired 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 liquid, but self-emulsifying emulsions are preferably used.

  The resin concentration in the water-based emulsion can be arbitrarily set as long as the ratio of the poorly water-soluble polymer component of the fiber forming the polymer elastic body and the fiber entanglement satisfies the preferable range as described above, but the dispersibility From the viewpoint of the stability of the liquid and the additive stability when other additives are mixed, it 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 of impregnating the aqueous emulsion resin composed of a polymer elastic body to which a water-soluble polymer component has been added into the interior of the three-dimensional entangled nonwoven fabric is not particularly limited, for example, a method of uniformly impregnating the nonwoven fabric by immersion or the like, The method etc. which apply | coat to the surface and a back surface are mentioned. 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 resin may be uniformly solidified in the nonwoven fabric.
Alternatively, the impregnated water-based emulsion resin may migrate (migrate) to the front and back surfaces of the nonwoven fabric, and then coagulate, so that the abundance of the polymer elastic body may be inclined substantially continuously 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 in the thickness direction center portion. In order to obtain such a distribution gradient, the surface and the back surface of the nonwoven fabric are preferably at 100 to 150 ° C., preferably 0.5 to 30 minutes, without impregnating migration after impregnating the aqueous emulsion resin. Heat. By such heating, moisture evaporates from the front surface and the back surface, and the water content of the water-based emulsion resin moves to both surface layers, and the water-based emulsion resin solidifies near 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.

Three-dimensional entanglement impregnated with a water-based emulsion resin composed of a polymer elastic body to which the above-mentioned water-soluble polymer component is added, solidified and dried (preferably followed by hollow fiberization by a known method) A water-soluble polymer component of a suitable hollow fiber-generating fiber forming the nonwoven fabric, a water-soluble polymer component added to the water-based emulsion resin, and a water-based emulsion resin from the beginning. At the same time, hot water extraction and removal of the additive is performed without using chemicals.
For example, when the water-soluble polymer component of the hollow fiber generating fiber is first extracted and removed, and then impregnated with the aqueous emulsion resin, the hot water extraction and removal is performed again to remove the water-soluble polymer component and additives contained in the aqueous emulsion resin. Since it becomes necessary to perform the operation, hot water extraction removal is performed after impregnating the aqueous emulsion resin, and it is preferable to remove all the water-soluble polymer components and additives at once in order to increase production efficiency. . In addition, when the water-soluble polymer component of the hollow fiber generating fiber is first extracted and removed before impregnating the water-based emulsion resin composed of the polymer elastomer added with the water-soluble polymer component, The effect of reinforcing the nonwoven fabric is insufficient, the overall thickness is large, the fibers constituting the nonwoven fabric are easily collected, and the space specified by the inscribed circle of air gaps of 350 to 3000 μm ² is reduced accordingly. As a result, the texture is more likely to be paper-like.

  When the suitable hollow fiber generating fiber forming the three-dimensional entangled nonwoven fabric in the present invention is a suitable long fiber, unlike the short fiber, there is substantially no or little exposure of the fiber cross section, and therefore, from the fiber wall surface. It is necessary to extract a water-soluble polymer component typified by PVA. For this purpose, it is preferable that the average thickness of the thinnest part of each partition in the plurality of partitions formed by the sea component is 7 μm or less, and in this range, the hot water swells the PVA which is the island component. Thus, it is easy to extract and remove PVA by generating minute cracks on the fiber side surface without reducing the physical properties.

  As a method for extracting and removing, a water temperature of 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 hollow 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 polymer component is extracted and removed.

The base material for artificial leather of the present invention described above can be used as a base material for artificial leather with silver having various appearances in various applications.
Transfer the leather-like resin film formed on the release paper to the surface of the artificial leather substrate via an adhesive, or apply liquefied resin paint such as resin emulsion, resin solution, molten resin, gravure, comma coater, etc. Originally intended for surface finish processing, such as continuous coating using, embossing rolls and mirror belts on the front and back, embossing and smoothing processing, or a combination of these processing By using artificial leather made within a range that does not impair the lightness as all or part of the main material, it is possible to obtain artificial leather products such as shoes and bags having the effects of the present invention.

  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 polymer component mass ratio

[Measurement of apparent density of base material for artificial leather]
The value obtained by dividing the mass per unit area (g / cm ² ) of the artificial leather base material by the thickness (cm) was used as the apparent density (g / cm ³ ), and measurements were made 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. 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. Of the drawn inscribed circle areas, those less than 350 μm ² were removed, and the number of all the drawn inscribed circle areas was averaged to be the average of the void inscribed circle areas. Further, the ratio of the number of inscribed circles with an inscribed circle area of 350 to 3000 μm ^{2 to} the number of inscribed circles with all the gaps was calculated.

[Example 1]
Polypropylene (Prime Polymer Pro-Prime Y-2005GP, melting point 162 ° C., MFR measured by M method of JIS K7210: 20 g / min) was used as a sea component, and water-soluble thermoplastic PVA (Kuraray Exval CP-4104MI, Melting point 209 ° C, MFR measured by JIS K7210 M method: 80 g / min, viscosity average polymerization degree 330, saponification degree 98.4 mol%) as island components, and the number of islands per sea-island type multicomponent fiber Using a melt compound spinning die having 12 (islands), the mixture was discharged from the die at 240 ° C. so that the mass ratio of sea component / island component 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. The resulting polymer was cooled while being indexed to spin a polypropylene hollow fiber generating composite fiber having an average fineness of 2.81 dtex. The thickness of the wall separating the PVA of the obtained polypropylene hollow fiber generating composite fiber was 1.24 μm. The composite fiber is continuously collected on a mobile net installed just below the suction device, and then pressed with a metal roll having a surface temperature of room temperature at a linear pressure of 17 kg / cm to provide a composite fiber having a basis weight of 45 g / m ² . Got the web.

The resulting composite fiber web was uniformly applied to the web surface using a spray while overlapping the resulting composite fiber web so as to have a basis weight equivalent to 8 webs using a cross wrapper. Next, using a 9-barb and 6-barb felt needle with a distance of 5 mm from the tip of the needle to the barb, alternately on both sides of the web with the setting so that the tip of the needle pierced the composite fiber web protrudes up to 10 mm from the opposite side Needle punching was performed. A needle punching process was performed so that the total number of pierced needles was 1450 / cm ^2, and the composite fibers were entangled with each other, thereby obtaining a three-dimensional entangled nonwoven fabric having a basis weight of 298 g / m ² . After impregnating the nonwoven fabric with a PVA aqueous solution having a solid content concentration of 1.8% by mass so as to have a PVA solid content adhesion rate of 2.8% by mass, the thickness was pressed between metal rolls having a smooth surface at 145 ° C. A three-dimensional entangled nonwoven fabric having a smooth surface at 1.62 mm and density of 0.194 g / cm ³ was obtained.

  To a self-emulsifying water-based polyurethane emulsion (100% modulus: 27 MPa), 9.3 mass% of PVA (Kuraray Co., PVA-117) is added to a three-dimensional entangled nonwoven fabric with a smooth surface, and the interface After adding 3.5 g / L of activator BK90NM (manufactured by Nikka Chemical Co., Ltd.) and impregnating it with an emulsion solid content concentration of 10.8% by mass, it was dried in a dryer with hot air at 100 ° C. for 30 minutes. The polymer elastic body was impregnated.

Then, hot water immersion time of 20 minutes in hot water at 95 ° C. containing 0.5 g / L of HLB9, a nonionic surfactant having a cloud point of 57 ° C. (manufactured by Nikka Chemical Co., Ltd., Sunmol BK-90NM) The island component PVA was dissolved and removed from the composite fiber in the three-dimensional entangled nonwoven fabric by the dip × nip method. The extraction rate is 96.8% by mass, and the obtained is 1.06 mm in thickness, 218 g / m ² in weight, and three-dimensional entangled nonwoven fabric of polyurethane hollow fibers having 12 hollow portions in the cross section and polyurethane A base material for artificial leather consisting of

The mass ratio of polyurethane and polypropylene hollow fiber in the obtained base material for artificial leather was polyurethane / polypropylene hollow fiber = 24.3 / 75.7, and the polyurethane was discontinuously present on the fiber. In addition, according to the 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 inscribed circle area of less than 350 μm ² was removed from the drawn inscribed circle area, and the inscribed circle area of the air gap that averaged the number of all the inscribed circle areas that were drawn was 1222 μm ^{2 on} average. The ratio of the number of air gap inscribed circles with an area of 350 to 3000 μm ^{2 to} the number of air gap inscribed circles was 87.9%.

This base material for artificial leather has 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 4.8 kg, and the apparent density is 0.206 g / cm ^3. It is excellent in physical properties but not only light, but also has a soft texture with a soft texture, and fine wings are evenly expressed when bent, and is an artificial material for men's shoes and sports shoes. It was an extremely excellent material as a base material for finishing leather.

[Example 2]
Change in PVA / Em amount The same procedure as in Example 1 was performed except that PVA was not added to the three-dimensional entangled nonwoven fabric in advance, and 12.4 mass% of PVA was added to the aqueous polyurethane emulsion. A leather substrate was obtained.
The polyurethane in the obtained base material for artificial leather is discontinuously present on the fiber, and the air gap inscribed circle area is an average of 1044 μm ² and the ratio of air gap inscribed circles of 350 to 3000 μm ² is 92.4. %Met. In addition, it has a vertical tear strength of 4.0 kg, a horizontal tear strength of 3.1 kg, and an apparent density of 0.218 g / cm ^3, which is excellent in mechanical properties but not only light, but also has a soft texture and a soft feel. In addition, when bent, fine wrinkles uniformly appear and are good, and it is an excellent material as a base material for finishing artificial leather for men's shoes and sports shoes.

[Example 3]
Change in PVA / Em amount The same procedure as in Example 1 was performed except that PVA was not added to the three-dimensional entangled nonwoven fabric in advance, and 18.6% by mass of PVA having an emulsion solid content was added to the aqueous polyurethane emulsion. A leather substrate was obtained.
The polyurethane in the obtained base material for artificial leather is discontinuously present on the fiber, and the air gap inscribed circle area has an average of 1089 μm ² and the ratio of air gap inscribed circles of 350 to 3000 μm ² is 91.7. %Met. In addition, it has a vertical tear strength of 3.0 kg, a horizontal tear strength of 3.7 kg, and an apparent density of 0.229 g / cm ^3. In addition, when bent, fine wrinkles uniformly appear and are good, and it is an excellent material as a base material for finishing artificial leather for men's shoes and sports shoes.

[Example 4]
PP fiber → NY fiber change Nylon 1015BK (manufactured by Ube Industries) was changed as a sea component, and the same operation as in Example 1 was carried out except that the surfactant was not added to the aqueous emulsion. Obtained.
Polyurethane in the obtained base material for artificial leather is discontinuously present on the fiber, and the air gap inscribed circle area is an average of 1175.5 μm ² and the ratio of air gap inscribed circles of 350 to 3000 μm ² is 88. 8%. In addition, the peel strength is higher as the base fabric is cut at the time of peel strength measurement. The vertical tear strength is 4.9 kg, the horizontal tear strength is 4.6 kg, and the apparent density is 0.223 g / cm ^3. In addition, the texture is soft and soft to the touch, and when bent, fine wrinkles are evenly expressed and are good, and it is a base material for finishing artificial leather for men's shoes and sports shoes It was an extremely excellent material.

[Example 5]
Suede fiber Water-soluble thermoplastic PVA as sea component (manufactured by Kuraray Co., Ltd., EXVAL CP-4104MI, melting point 209 ° C., MFR measured by M method of JIS K7210: 80), isophthalic acid-modified polyethylene having 6 mol% modification as island component Using a terephthalate resin (melting point: 240 ° C.) and using a fusion compound spinning die having 25 islands (islands) per sea-island type multi-component fiber, a sea component / island component mass ratio of 25 / No. 75, and the same procedure as in Example 1 was carried out except that the mass ratio of polyurethane to polyethylene terephthalate fiber in the substrate was polyurethane / polyethylene terephthalate = 25.1 / 74.9. Got.

The polyurethane in the obtained base material for artificial leather is discontinuously present on the fiber, and the air gap inscribed circle area has an average of 959.6 μm ² and a ratio of air gap inscribed circles of 350 to 3000 μm ² is 92. .5%. In addition, the vertical tear strength is 4.2 kg, the horizontal tear strength is 4.3 kg, the apparent density is 0.454 g / cm ³ , and the mechanical properties are excellent, but the texture is not only soft, but also has a soft touch. At the time of bending, fine wrinkles were evenly expressed and good, and it was an excellent material as a base material for finishing artificial leather for men's shoes and sports shoes.

[Comparative Example 1]
No PVA Addition A base material for artificial leather was obtained in the same manner as in Example 1 except that PVA was not added to the aqueous polyurethane emulsion.
Although the polyurethane in the obtained artificial leather base material is discontinuously present on the fiber, the air gap inscribed circle area has an average of 1255 μm ² and the ratio of air gap inscribed circles of 350 to 3000 μm ² is 84. It was 6%. Although the peel strength increases as the base fabric is cut at the time of peel strength measurement, the vertical tear strength is 3.0 kg, the horizontal tear strength is 2.1 kg, the apparent density is 0.215 g / cm ³ , and the mechanical properties are low and light. The texture was notable as a base material for finishing artificial leather for men's shoes and sports shoes.

[Comparative Example 2]
Addition of a large amount of PVA A base material for artificial leather was obtained in the same manner as in Example 1 except that 30.0% by mass of PVA having an emulsion solid content was added to the aqueous polyurethane emulsion.
When the nonwoven fabric impregnated with PVA-added water-based emulsion, the viscosity was too high to be handled, and the nonwoven fabric was elongated. The polyurethane in the obtained base material for artificial leather is discontinuously present on the fibers and is light, but the air gap inscribed circle area has an average of 1263 μm ² and the ratio of air gap inscribed circles of 350 to 3000 μm ² is 90. 7%. Although the peel strength is higher as the base fabric is cut at the time of peel strength measurement, the vertical tear strength is 3.9 kg, the horizontal tear strength is 3.7 kg, the apparent density is 0.218 g / cm ³ , and the mechanical properties are high and light. The texture was too soft and firm, and was inferior as a base material for finishing artificial leather for men's shoes and sports shoes.

[Comparative Example 3]
Addition of a small amount of PVA A base material for artificial leather was obtained in the same manner as in Example 1, except that PVA having an emulsion solid content of 3.1% by mass was added to the aqueous polyurethane emulsion.
The polyurethane in the obtained base material for artificial leather is discontinuously present on the fiber, but the air gap inscribed circle area averages 1300 μm ² and the ratio of air gap inscribed circles of 350 to 3000 μm ² is 84. 3%. Moreover, although the peel strength is higher as the base fabric is cut at the time of peel strength measurement, the tear tear strength is 2.9 kg, the horizontal tear strength is 2.1 kg, the apparent density is 0.207 g / cm ³ , and the mechanical properties are low and light. The texture was notable as a base material for finishing artificial leather for men's shoes and sports shoes.

[Comparative Example 4]
Pre-extraction impregnation After extracting the extraction component of the non-woven fabric using the sea component / island component mass ratio 60/40 as the fiber of Example 1 before impregnation with the PVA-added aqueous emulsion, the PVA and the emulsion additive are then removed. Therefore, the same operation as in Example 1 was performed except that the material was extracted and removed again to obtain a base material for artificial leather.
Although the polyurethane in the obtained artificial leather base material is discontinuously present on the fiber, the air gap inscribed circle area averages 1359 μm ² , and the ratio of air gap inscribed circles of 350 to 3000 μm ² is 83. It was 9%. In addition, the peel strength is higher as the base fabric is cut at the time of peel strength measurement. The vertical tear strength is 6.0 kg, the horizontal tear strength is 6.7 kg, the apparent density is 0.288 g / cm ³ , and the mechanical properties are high and light. The resulting artificial leather base material tends to be slightly heavier than those not previously extracted, and because the extracted components of the nonwoven fabric are extracted first, the warp elongation and thickness of the nonwoven fabric due to the extraction process are increased. Remained, wrinkled, and paper-like inferior in texture.

  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 (3)

A base material for artificial leather consisting of a three-dimensional entangled nonwoven fabric and a polymer elastic body, which satisfies the following requirements (1) to (3),
The apparent density is less than 0.3 g / cm ³ ,
In the base material for artificial leather, the mass ratio of the polymer elastic body and the poorly water-soluble polymer component of the fiber forming the three-dimensional entangled nonwoven fabric (polymer elastic body / water fragility of the fiber forming the three-dimensional entangled nonwoven fabric) The base material for artificial leather whose soluble polymer component is in the range of 15/85 to 30/70 in terms of solid content.
Requirement (1): The polymer elastic body exists discontinuously on the surface of the fiber forming the three-dimensional entangled nonwoven fabric.
Requirement (2): 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 base material for artificial leather is 1250 μm ² or less.
Requirement (3): The number of void inscribed circles with a space inscribed circle area of 400 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.   The method for producing a base material for artificial leather according to claim 1, further comprising a step of impregnating and solidifying a three-dimensional entangled nonwoven fabric with an aqueous emulsion resin to form a polymer elastic body. It is a method for producing a base material for artificial leather having a step of impregnating and solidifying an aqueous emulsion resin in which polyvinyl alcohol is added to a three-dimensional entangled nonwoven fabric to form a polymer elastic body,
The manufacturing method of the base material for artificial leather with which the said base material for artificial leather satisfy | fills the following requirements (1)-(3).
Requirement (1): The polymer elastic body exists discontinuously on the surface of the fiber forming the three-dimensional entangled nonwoven fabric.
Requirement (2): 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 base material for artificial leather is 1250 μm ² or less.
Requirement (3): 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 all indented circle inscribed circles It is.