JP4869462B2 - Artificial leather base - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a suede-like artificial leather having a very good appearance and excellent mechanical properties, lightweight and flexible, and a method for producing the same.
[0002]
[Prior art]
In various fields of artificial leather, lightweight, flexible products with excellent mechanical properties are demanded. Conventionally, it has been known that a non-woven fabric is formed using a multi-component fiber having a sea-island structure from which sea components can be eluted, for example, a fiber having a sea-island structure in which the sea component is made of polyethylene, and is used as an artificial leather. Such a sea-island structure fiber is obtained by removing sea components in any process until it becomes a final product, thereby obtaining a very fine fiber. Such products have a unique texture of fine fibers and a good suede appearance, and have a certain reputation in the market. However, an increase in specific gravity due to a decrease in thickness at the time of forming ultrafine fibers is unavoidable, and it does not have light weight performance.
Further, mixing different types of fibers according to the purpose to form an entangled nonwoven fabric is a conventional method. Japanese Patent Publication No. 48-11925 discloses an entangled body in which two or more kinds of webs and sheets are laminated and entangled, and a method of impregnating and solidifying these entangled bodies with a polymer elastic body solution. Some of them are leather-like and have excellent mechanical properties, but they do not have good suede appearance and light weight performance.
Further, polyester and nylon hollow fibers are generally used for clothing products and the like from the viewpoints of light weight and heat retention. In the field of synthetic leather and artificial leather, Japanese Patent Application Laid-Open Nos. 47-28104 and 50-5502 describe light-weight synthetic leather with good air permeability using hollow fibers. Japanese Patent Application Laid-Open No. 1-292188 discloses a synthetic leather in which minute hollow particles are mixed to reduce weight and improve heat retention. As described above, techniques for using a material having a hollow structure including fibers for synthetic leather and artificial leather are known, but these have light weight performance, but have an insufficient appearance as a suede. Even those having light weight performance and necessary mechanical performance are insufficient in terms of flexibility and surface appearance, which have been strongly demanded in recent years, and not all of them.
[0003]
[Problems to be solved by the invention]
In each field of artificial leather, a substrate having a thickness of 0.5 to 1.3 mm is generally used. Within this range of thickness, there is a demand for flexible products that are lighter and have excellent mechanical properties. Especially in suede-like artificial leather, they have excellent mechanical properties and light and flexible suede. Therefore, an artificial leather substrate that satisfies all of these requirements has not been developed yet.
As described above, in each field of artificial leather, an improvement in luxury is demanded, and among them, a high-quality appearance and lightweight performance are most strongly desired. On the other hand, the mechanical properties according to the application, especially the artificial leather for sports, the peel strength between the shoe sole rubber part and the artificial leather product, the tear strength required during exercise are the most important characteristics, It is extremely important to combine this mechanical property with a light and excellent appearance as a product.
[0004]
As a solution to the problem, a method of increasing the ratio of components that are made of multi-component fibers that can be made ultrafine by extraction or the like, for example, is removed from the sea-island structure fiber sheet by extraction or the like is considered. The thickness is reduced by the treatment, the weight cannot be reduced, and the mechanical properties are insufficient. In addition, although the weight can be reduced by the method of reducing the fiber amount itself of the artificial leather product, there is a problem that various physical properties are insufficient.
In addition, the method of using these hollow fibers as a base material for artificial leather by utilizing the bulkiness of hollow fiber staples can surely achieve a reduction in weight, but it is necessary to form a hollow in the fibers. In addition, the fiber decitex becomes large, and the surface is not smooth. Especially, the appearance as a suede application cannot be secured, and the texture is not flexible.
An object of the present invention is to solve such problems, and to provide a suede-like artificial leather substrate that has a very good appearance and excellent mechanical properties, and is lightweight and flexible.
[0005]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present inventors have conducted intensive research. As a result, the present invention has a hollow portion in the cross section of the fine fiber bundle of 0.1 decitex or less, and the fiber is three-dimensionally entangled. The present inventors have found that a suede-like artificial leather having a very good appearance, light weight and softness can be obtained by using a non-woven fabric. That is, the present invention provides an artificial leather base composed of a nonwoven fabric in which ultrafine fiber bundles are three-dimensionally entangled and a polymer elastic body impregnated therein, and the ultrafine fiber bundles constituting the nonwoven fabric are 0.1 decitex. A converging body composed of the following ultrafine fibers, and the ultrafine fiber converging body is a hollow portion in which a sheath portion in a core-sheath cross-sectional structure has an ultrafine fiber and a core portion has substantially no ultrafine fiber. An artificial leather base characterized in that the cross-sectional shape of the ultrafine fiber focusing body is a hollow ratio in the range of 6 to 20% represented by the following formula: is there.
Hollow ratio (%) = (A / B) × 100
A = area of the space surrounded by the inner periphery of the ultrafine fiber bundle B = area of the portion surrounded by the outer circumference of the ultrafine fiber bundle Further, the artificial leather substrate of the present invention has the following (1) to (3) It can manufacture by performing these processes sequentially.
(1) According to the following step (3), the bundle of ultrafine fibers of 0.1 decitex or less has an ultrafine fiber in the sheath portion in the core-sheath cross-sectional structure, and the ultrafine fiber is substantially in the core portion. process of manufacturing a nonwoven fabric from the core-sheath type microfine fiber-forming fibers to be able to have a hollow portion that does not exist,
(2) impregnating the non-woven fabric with a polymer elastic body solution or dispersion to solidify the polymer elastic body;
(3) In the sheath portion of the core-sheath microfine fiber-forming fibers after the process of generating ultrafine fibers, a process for generating a hollow portion in the microfine fiber bundle of section, you to microfine fiber bundle of section And a step of generating an ultrafine fiber bundle having a hollow portion in which the ultrafine fiber is present in the sheath portion in the core-sheath type cross-sectional structure, and the ultrafine fiber is not substantially present in the core portion ,
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The ultrafine fiber-generating fiber that allows the hollow portion to be present in the cross-section of the bundle of ultrafine fibers having a fineness of 0.1 dtex or less used in the present invention is composed of three or more types that are not compatible. It is obtained by complex spinning a thermoplastic polymer. A typical form of the fiber is a so-called core-sheath fiber.
The sheath portion of the fiber has a two-component sea-island structure, and the core portion may be at the center portion of the fiber cross section or may be offset from the center portion, and the shape of the core portion is somewhat within the fiber cross section. It may be indefinite as long as it forms an area, or it may have a geometric form such as a circle, an ellipse, a square, or a triangle.
[0007]
Further, the sheath portion is composed of two or more thermoplastic polymers that are not compatible, and these polymers form a sea-island structure. The polymer constituting the island component is a polymer that can be melt-spun and exhibits sufficient fiber properties such as strength, and has a higher melt viscosity and higher surface tension than the sea component polymer under the spinning conditions. Preferably, for example, polyamide-based polymers such as 6-nylon and 66-nylon, and copolymers mainly composed thereof, polyester-based polymers such as polyethylene terephthalate and polybutylene terephthalate, and copolymers mainly composed thereof. Preferably used.
The sea component polymer has a lower melt viscosity than the island component polymer, has different solubility and decomposability from the island component, and has solubility in a solvent or decomposing agent used for dissolving or removing sea components. A component that is large (the island component polymer is not substantially dissolved or decomposed and removed upon removal of the sea component polymer) and has a low compatibility with the island component is preferable. For example, polyethylene, modified polyethylene, polypropylene, polystyrene, modified polyester and the like are preferably used.
[0008]
In the present invention, the preferred sea-island volume ratio of the sea-island fiber in the sheath portion that generates ultrafine fibers having a fineness of 0.1 dtex or less is in the range of sea / island = 30/70 to 70/30. If the sea component is less than 30%, there are too few components to be dissolved or decomposed with a solvent or a decomposing agent, so that the softening effect cannot be sufficiently exerted. If the sea component exceeds 70%, the island component after dissolution or decomposition is removed. It is inappropriate from the viewpoint of productivity that the absolute amount of the fibers made of the material becomes small, and sufficient physical properties as a leather-like sheet cannot be secured, and that many components are dissolved or decomposed and removed.
[0009]
The average fiber thickness of a suitable island component after dissolving and removing the sea component of the sea-island structure forming the sheath portion in the present invention is 0.1 dtex or less, preferably 0.05 dtex or less. In general, a nonwoven fabric made of a thick dtex fiber entanglement tends to easily lose fibers. Even in the present invention, when the fiber thickness of the island exceeds 0.1 dtex, the removal of the ultrafine fibers after removal of the sea component is eliminated. The phenomenon becomes prominent, the flexibility of the substrate is lost, and the texture becomes harsh, and the surface aesthetics as a suede tone are lacking. The thickness (fineness) of the ultrafine fiber referred to in the present invention is determined by taking a cross-section perpendicular to the fiber axis direction of the ultrafine fiber bundle with a microscope and obtaining the total decitex of the ultrafine fiber bundle from the micrograph. It is obtained by dividing by the number of fibers.
[0010]
The polymer that forms the core part is different in solubility or decomposability from the solvent or decomposing agent used for dissolving or removing the sea component of the sea-island structure that forms the sheath part. Is not dissolved or decomposed), and the island component of the sea-island structure forming the sheath portion is also different in solubility or decomposability (when the core component is removed, the island component polymer is not substantially dissolved or decomposed). For example, a polymer, which can be eluted with a dilute alkali or is water-soluble, a polyester copolymer, a water-soluble and thermoplastic modified polyvinyl alcohol, and the like are preferably used.
[0011]
When generating an ultrafine fiber bundle having a hollow portion in the cross section of the ultrafine fiber bundle from the ultrafine fiber generating fiber of the present invention, after first dissolving or decomposing and removing only the sea component of the sea-island structure part forming the sheath part, Dissolve or decompose the core component.
For example, when a sea component is removed from a sea-island structure fiber sheet obtained by impregnating a non-woven fabric with a polymer elastic body solution or dispersion and solidifying the polymer elastic body, the thickness may be increased by tension or pressing in the manufacturing process. Reduced and cannot be reduced in weight. In other words, when removing the sea component of the ultrafine fiber-generating fiber, fiber wrinkles are generated due to the removal of the sea component, and the polymer elastic body impregnated in the nonwoven fabric is swelled and softened, so that it passes through the tension and press processing steps. This is because of a decrease.
[0012]
The present invention eliminates the sea component of the sea-island structure fiber portion of the sheath portion from the ultrafine fiber-generating fiber of the present invention by extraction or the like, and generates the ultrafine fiber without being affected by the solvent, drug, etc. This is because the component part can withstand and acts to reduce or alleviate the thickness reduction caused by the tension or pressing in the manufacturing process. Then, different from the solvent or decomposing agent used for dissolving or removing the sea component of the sea-island structure forming the sheath part, the island component of the sea-island structure forming the sheath part may be substantially dissolved or decomposed. Without removing the core component by treating with a solvent or a decomposing agent that dissolves or decomposes the core component, leaving an island component of the sheath portion, a hollow portion in the cross section of the fine fiber bundle having a fineness of 0.1 dtex or less Can be produced.
[0013]
This core component removal step can be removed by removing the sea component from the sheath, followed by washing with hot water when removing the used solvent and decomposing agent remaining in the substrate, or blanching before dyeing and washing after dyeing. Is preferred. For example, water-soluble and thermoplastic modified polyvinyl alcohol containing 5 to 10 mol% of ethylene units, having a polymerization degree of 200 to 500 and a saponification degree of 90 to 99 mol% is easily dissolved in hot water of 50 to 80 ° C. It is particularly preferable because it dissolves in
[0014]
The area ratio of the core part that generates the hollow part in the cross section of the core-sheath type fiber of the ultrafine fiber generation type fiber in which the hollow part is present in the cross section part of the ultrafine fiber bundle having a fineness of 0.1 dtex or less used in the present invention is 7-30. % Range is preferred. If the area ratio of the core is less than 7%, the effect of weight reduction is insufficient, and if it exceeds 30%, the hollow portion of the fiber cross-section becomes prominently crushed by the tension in the core removal process and the pressing process. It is difficult to obtain a lightweight substrate. In general, the thickness of the core portion is preferably in the range of 0.3 to 1.3 dtex in terms of the shape stability of the ultrafine fiber converging body having the hollow portion after the core component is removed.
In addition, the hollowness ratio of the sea-island fiber of the sheath part that generates the ultrafine fiber, the sea-island volume ratio, the thickness of the ultrafine fiber, and the polymer that constitutes the ultrafine fiber have different shape maintainability at the time of removal of the core part, so the combination is appropriate It is preferable to do this. Generally, the island ratio of the sheath portion is small, and when the denier is thin, the hollow portion tends to be crushed.
[0015]
As described above, the hollow ratio generated in the actual cross-section portion of the ultrafine fiber bundle is different from the area ratio of the core portion of the core-sheath fiber, but is generally preferably adjusted to be 6 to 20%. If the hollow ratio generated in the cross section of the ultrafine fiber bundle is less than 6%, the effect of weight reduction is insufficient, and if it exceeds 20%, the fluff on the surface of the substrate becomes rough and the appearance as a suede In addition, the mechanical properties are inferior.
[0016]
In the stretching treatment of the core-sheath type multicomponent fiber of the present invention, it is preferable to stretch at a temperature below the softening point of the sea component polymer of the sheath portion, more preferably the sea component polymer in terms of preventing fiber sticking at the time of stretching. The temperature is 5 to 10 ° C. lower than the softening temperature.
Subsequently, this sea-island type multicomponent fiber is made into a fiber having a fineness of 2 to 10 dtex through processing steps such as crimping, drying and cutting.
[0017]
The core-sheath type multicomponent fiber is opened with a card, a random web or a cross-wrap web is formed through a web, and the obtained fiber web is laminated to a desired weight and thickness. Subsequently, a entanglement process is performed by a known method such as a needle punch or a high-speed fluid flow process to obtain a nonwoven fabric. For the purpose of improving the sense of unity of the product and the smoothness of the surface, it is permissible to use a plurality of cards and wrappers as a non-woven fabric. In the present invention, as a part of the fibers constituting the nonwoven fabric, fibers other than the core-sheath type multicomponent fiber can be blended within a range not impairing the object of the present invention.
[0018]
As the felt needle of the needle punch in the present invention, a well-known felt needle is used, but a 1 barb needle which is less likely to cause fiber breakage is suitably used for sewing in the thickness direction of the web. In order to increase the specific gravity of the surface of the nonwoven fabric, needles of multiple barbs such as 3 barbs, 6 barbs, and 9 barbs can be used. These needles may be combined depending on the purpose.
[0019]
The number of punches in the needle punching process varies depending on the shape of the needle used and the thickness of the web, but is set in the range of 200 to 2500 punches / cm ² . Generally, in the needle punch of the ultra fine fiber generating fiber, if the needle punch condition is too strong, the ultra fine fiber generating fiber is cut or broken, the entanglement is not improved, and the needle punch condition is too weak. In such a case, the entanglement is not improved due to insufficient number of fibers arranged in the thickness direction.
[0020]
The needle punched nonwoven fabric is then preferably pressed in the thickness direction in order to smooth the surface and regulate the thickness. 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 as a pressing method, and a sea component in a fiber, ie, a low melt viscosity component such as polyethylene is melted and pressed. By this, smoothing of the nonwoven fabric can be achieved more. In this step, it is possible to add an adhesive such as polyvinyl alcohol, starch, or resin emulsion for the purpose of suppressing a change in the shape of the step due to tension or pressing.
[0021]
The nonwoven fabric having a smooth surface is then impregnated with a polymer elastic body solution or dispersion and solidified in a sponge form. As the polymer elastic body, a resin conventionally used for producing a leather-like sheet is preferably used. That is, a polyurethane resin, a polyvinyl chloride resin, a polyacrylic acid resin, a polyamino acid resin, a silicon resin, a copolymer thereof, and a mixture thereof are suitable. These resins are impregnated into the nonwoven fabric as an aqueous emulsion or an organic solvent solution, and then solidified in a sponge form by wet coagulation or the like. In the present invention, it is preferable to impregnate and solidify the polymer elastic body before removing the sea component in the fiber sheath portion from the viewpoint of shape stabilization of the ultrafine fiber converging body having a hollow portion.
[0022]
The fibrous base material impregnated and solidified with the polymer elastic body solution or dispersion is then a non-solvent of the core component polymer, the island component polymer of the sheath portion and the polymer elastomer impregnated with the core component polymer, and the sea component polymer of the sheath portion. By dissolving or decomposing and removing the sea component with a liquid that is a solvent or a decomposing agent, an extra fine fiber of 0.1 decitex or less is generated around the core component fiber, and then a non-solvent of the extra fine fiber and the polymer elastic body is used. A fiber bundle having a hollow portion in the cross-section of a fine core fiber of 0.1 decitex or less and polymer elasticity by dissolving or decomposing and removing the core component polymer with a solvent or a decomposing agent for the core component fiber An artificial leather substrate consisting of a body is obtained.
[0023]
Next, as a method for obtaining a suede-like artificial leather, the artificial leather base is sliced into a plurality of sheets in the thickness direction as necessary, and at least one surface of the surface is raised to raise a fiber raised surface mainly composed of ultrafine fibers. To form. As a method for forming the fiber raised surface, a known method such as buffing with sandpaper or the like is used. Next, the dyed suede-like fibrous base material is subjected to finishing treatments such as kneading, softening treatment, and brushing to obtain a product of suede-like artificial leather that has an elegant appearance and does not fall off fluff.
According to the present invention, a lightweight suede-like artificial leather having excellent mechanical properties such as a density of 0.3 g / cm ³ or less, a peel strength of 8 kg / 2.5 cm or more, and a tear strength per 1 mm of thickness of 6 kg or more can be obtained.
[0024]
The thickness of the artificial leather substrate can be arbitrarily selected according to the use and is not particularly limited, but is preferably in the range of 0.3 mm to 3 mm, particularly preferably 0.7 mm to 1.8 mm. The weight ratio between the ultrafine fiber and the polymer elastic body is preferably 35/65 to 65/35 by weight. If it is out of this range, the balance between the fiber and the elastic polymer is deteriorated, and a sense of fulfillment and flexibility as a product cannot be obtained.
[0025]
The density of the artificial leather substrate in the present invention is preferably 0.3 g / cm ³ or less. Heavy in various fields, mild relative of a person using is a sensory element, the density of a typical artificial leather is 0.35~0.5g / cm ^3, density of 0.3 g / cm ³ The following substrate is clearly a light range from the feeling of the conventional artificial leather substrate, and according to the present invention, the density of the artificial leather substrate can be surely made 0.3 g / cm ³ or less.
[0026]
The artificial leather substrate of the present invention can also be suitably used in the field of silver-tone artificial leather. In other words, the surface of this artificial leather substrate is finished with adhesion of leather-like film, resin emulsion, resin solution, molten resin coating, gravure, embossing, combinations of these, etc. Artificial leather is obtained.
[0027]
【Example】
Next, although execution of the present invention is concretely explained with an example, the present invention is not limited to these examples. In the examples, “part” and “%” relate to weight unless otherwise specified. In the following examples and comparative examples, the hollowness ratio, specific gravity measurement, mechanical properties, and other evaluations were in accordance with the following methods.
[0028]
[Method of measuring tear strength of artificial leather base]
A test piece of 10 cm in length and 4 cm in width is cut out, a 5 cm cut is made in the center of the short side at right angles to the side, each tongue piece is sandwiched between chucks, and teared at a speed of 100 mm / min with a tensile tester. The maximum tearing load is obtained and divided by the thickness of the test piece obtained in advance, and is expressed as an average value of three test pieces.
[0029]
[Density measurement]
A number obtained by dividing the weight (g / cm ² ) per unit area of the artificial leather substrate by the thickness (cm) is defined as density (g / cm ³ ). The thickness is measured according to JISL1096.
[0030]
[Core-sheath ratio of core-sheath composite fiber]
The area ratio of the core sheath of the composite fiber is calculated from the average fiber diameter and the average diameter of the core by taking an enlarged photograph of the yarn cross section 500 times with an electron microscope.
[Hollowness in cross section of ultrafine fiber converging body]
The hollow ratio in the cross section of the ultrafine fiber converging body is obtained by taking an enlarged photograph of the cross section of the product 500 times with an electron microscope and calculating the hollow ratio by the following formula.
Hollow ratio (%) = (A / B) × 100
A = area of the space surrounded by the inner periphery of the ultrafine fiber bundle B = area of the portion surrounded by the outer circumference of the ultrafine fiber bundle
Example 1
Using a core-sheath type composite spinning and spinning apparatus, a polymer stream melted in two extruder melt systems contains 7 mol% of ethylene units, has a polymerization degree of 300, and a saponification degree of 97 mol%. In addition, a thermoplastic modified polyvinyl alcohol, and the sheath part is a sea-island fiber in which the island component is 6-nylon and the sea component is a high-fluidity low-density polyethylene (sea component / island component ratio = 40/60). A core-sheath type composite fiber made of The ratio of the core-sheath component of the core-sheath composite fiber was core / sheath = 25/75.
The obtained yarn was drawn, crimped and cut to obtain staple fibers having 3.5 decitex and a cut length of 51 mm.
This staple fiber was passed through a card, made into a web by a cross wrapper method, and laminated. Next, a non-woven fabric having a weight per unit area of 450 g / m ² was obtained by needle punching with a needle penetration density of 980 P / cm ² using a felt needle with one barb on the needle. This non-woven fabric is dried by heating, pressed to smooth the surface, impregnated with 13% polyurethane DMF solution, coagulated with DMF aqueous solution, washed with water, dried and extracted with hot toluene, which is the sea component of the sheath. Then, a substrate made of impregnated polyurethane and fibers in a state where 6-nylon ultrafine fibers covered the core modified polyvinyl alcohol was obtained. Thereafter, the substrate obtained was treated with a wine dyeing machine at 80 ° C. for 30 minutes with a Wins dyeing machine, and a 6-nylon ultrafine fiber converging body having a hollow portion and a polyurethane base having a thickness of 1.2 mm and a basis weight of 310 g / m ² were obtained. Obtained.
[0032]
When the cross section of the ultrafine fiber bundle of the fibrous base was observed with an electron microscope, the hollowness was 17% and the average fineness of the ultrafine fiber was 0.007 dtex. After buffing one side of this substrate to adjust the thickness to 1.0 mm, the other side is treated with an emery buffing machine to form a fine fiber raised surface, and further using Irgalan Brown 2BLN (Chiba Geigy) Stained at a concentration of 4% owf. The finished suede-like artificial leather has a tear strength of 9kg / 2.5cm, a specific gravity of 0.26, and is very strong. It has a good appearance, texture and touch, and is light with almost no fluff falling off. It was.
[0033]
Comparative Example 1
The same procedure as in Example 1 was performed except that the fiber of Example 1 was replaced with the mixed spun fiber consisting only of the sheath component of Example 1 and the core component was removed, to obtain a suede-like artificial leather. . This suede-like artificial leather was good in appearance, texture and touch, and had almost no fluff falling off. However, when the cross section of the ultrafine fiber bundle was observed with an electron microscope, there was no hollow part and a tear strength of 9 kg / 2 Although it was 0.5 cm, the density was 0.39 g / cm ³ , which was lacking in lightness.
[0034]
Comparative Example 2
Using a core-sheath compound spinning machine, the polymer stream melted in the two extruder melt systems is a high-fluidity low-density polyethylene whose core component is 6-nylon and the sheath component is 6-nylon. A core-sheath type composite fiber composed of sea-island type fibers composed of high-fluidity low-density polyethylene (sea component / island component ratio = 40/60) was spun. The ratio of the core-sheath component of the core-sheath composite fiber was core / sheath = 25/75 as in Example 1.
After making into a non-woven fabric by the same operation as in Example 1, heat drying, pressing to smooth the surface, impregnating with 13% polyurethane DMF solution, coagulating with DMF aqueous solution, washing with water, hot toluene with core part and The polyethylene, which is a sea component in the sheath, was extracted and removed. When the cross section of the ultrafine fiber bundle of the obtained substrate was observed with an electron microscope, there was no hollow portion in the ultrafine fiber bundle, the tear strength was 8 kg / 2.5 cm, and the density was 0.36 g / cm ³ . It was lacking in lightness.
[0035]
【Effect of the invention】
According to the present invention, a lightweight and flexible suede-like artificial leather substrate having mechanical properties that can withstand applications such as sports shoes can be obtained. In addition, the surface layer of the artificial leather substrate obtained by the present invention is finished by combining leather-like film adhesion, resin emulsion, resin solution, melted resin coating, gravure, embossing, etc., and finishing with silver-finished artificial leather I can do it.

Claims (3)

In an artificial leather base composed of a nonwoven fabric in which ultrafine fiber bundles are three-dimensionally entangled and a polymer elastic body impregnated therein, the ultrafine fiber bundles constituting the nonwoven fabric are made of ultrafine fibers of 0.1 decitex or less. And the ultrafine fiber bundle has a hollow portion in which the ultrafine fibers are present in the sheath portion and the ultrafine fibers are not substantially present in the core portion in the core-sheath type cross-sectional structure. An artificial leather base characterized by the above. 2. The artificial leather substrate according to claim 1, wherein the cross-sectional shape of the ultrafine fiber bundle is a hollow ratio in the range of 6 to 20% represented by the following formula.
Hollow ratio (%) = (A / B) × 100
A = area of the space surrounded by the inner periphery of the ultrafine fiber bundle B: area of the portion surrounded by the outer circumference of the ultrafine fiber bundle Steps (1) to (3) below (1) By the following step (3), the bundle of ultrafine fibers of 0.1 decitex or less has ultrafine fibers in the sheath portion in the core-sheath cross-sectional structure. a step of producing a nonwoven fabric from the core-sheath type microfine fiber-forming fibers to be able to have a hollow portion which is substantially free of ultrafine fibers in the core part,
(2) impregnating the non-woven fabric with a polymer elastic body solution or dispersion to solidify the polymer elastic body;
(3) In the sheath portion of the core-sheath microfine fiber-forming fibers after the process of generating ultrafine fibers, a process for generating a hollow portion in the microfine fiber bundle of section, you to microfine fiber bundle of section And a step of generating an ultrafine fiber bundle having a hollow portion in which the ultrafine fiber is present in the sheath portion in the core-sheath type cross-sectional structure, and the ultrafine fiber is not substantially present in the core portion ,
A method for producing an artificial leather substrate, characterized in that