TECHNICAL FIELD

The present invention relates to a grain-finished artificial leather having a combination of fine fold creases, suppleness, surface smoothness, and a texture with fullness, similar to those of a grain-finished leather.

BACKGROUND ART

Conventionally, a grain-finished artificial leather is known in which a grain-like resin layer (hereinafter also simply referred to as “grain layer”) is stacked on an artificial leather base material obtained by impregnating an elastic polymer into voids inside a fiber-entangled body. The grain-finished artificial leather has been used as an alternative to a grain-finished leather for the skin materials of shoes, clothing, gloves, bags, balls, and the like, and the interior finishing materials for buildings and vehicles.

A grain-finished leather using a natural leather as a raw material includes dense collagenous fibers, and thus has both suppleness and a high level of fullness (voluminousness). When a grain-finished leather is bent, its high level of fullness allows the formation of fine fold creases with roundness and luxurious quality. In addition, a grain-finished leather has excellent surface flatness, and unevenness is less likely to be conspicuous even when a grain surface is formed, so that the surface smoothness is high. However, it has been difficult to obtain a grain-finished leather with stable quality. Moreover, collagenous fibers have low heat resistance and low water resistance. Therefore, it has been difficult to use a grain-finished leather in applications for which heat resistance and water resistance are required. To increase the heat resistance and the water resistance of the grain-finished leather, a method is available in which a thick grain layer is formed. However, when a thick grain layer is formed, the suppleness, which is an advantage of a grain-finished leather, is reduced.

On the other hand, the grain-finished artificial leather is superior to a grain-finished leather in quality stability, heat resistance, water resistance, and abrasion resistance, and is also easier to maintain. However, voids that are not filled with the elastic polymer remain inside the fiber-entangled body of the grain-finished artificial leather. Accordingly, when bent, the grain-finished artificial leather does not bend with roundness as in the case of a grain-finished leather, and, instead, forms buckled creases or large fold creases, resulting in the problem that it is inferior in luxurious quality. When the number of voids is decreased by increasing the content ratio of the elastic polymer in the fiber-entangled body, the resilience of the elastic polymer increases, resulting in a rubber-like, rigid texture. As a grain-finished artificial leather having a texture similar to that of a grain-finished leather, for example, PTL 1 listed below discloses a grain-finished artificial leather with a high level of fullness that is obtained by stacking a grain-like resin layer on an artificial leather base material containing a filler, a liquid non-volatile oil, and an elastic polymer. However, the grain-finished artificial leather described in PTL 1 does not form sufficiently fine fold creases as compared with a grain-finished leather.

CITATION LIST

Patent Literature

[PTL 1] WO 2014/132630

SUMMARY OF INVENTION

Technical Problem

It is an object of the present invention to provide a grain-finished artificial leather having a combination of the formability of fine fold creases, suppleness, surface smoothness, and a texture with fullness, similar to those of a grain-finished leather.

Solution to Problem

One aspect of the present invention is directed to a grain-finished artificial leather including an artificial leather base material, and a grain layer stacked on the artificial leather base material. The artificial leather base material includes a fiber-entangled body including ultrafine fibers having an average fineness of 0.4 dtex or less, an elastic polymer, and fine particles having an average particle size of 10 μm or less, and a content ratio of the fine particles is 10 to 40 mass %, and a ratio of the elastic polymer to a total amount of the elastic polymer and the fine particles is 20 to 80 mass %, and a total of an apparent density of the elastic polymer and an apparent density of the fine particles is 0.23 to 0.55 g/cm3. Such a grain-finished artificial leather has a combination of the formability of fine fold creases, suppleness, surface smoothness, and a texture with fullness.

It is preferable that the artificial leather base material has a content ratio of the fiber-entangled body of 30 to 80 mass %, and a content ratio of the elastic polymer of 10 to 40 mass %, because a grain-finished artificial leather that is particularly well-balanced in formability of fine fold creases, suppleness, surface smoothness, and a texture with fullness can be easily obtained.

It is preferable that the fine particles are attached to the elastic polymer, because the detachment of the fine particles is suppressed.

It is preferable that the elastic polymer includes a polyurethane and an acrylic elastic polymer, because a grain-finished artificial leather that is particularly well-balanced in formability of fine fold creases, suppleness, surface smoothness, and a texture with fullness can be easily obtained.

It is preferable that the fine particles have a Mohs hardness of 1 to 4, because a grain-finished artificial leather having further excellent suppleness can be obtained.

It is preferable that the fine particles include at least one selected from the group consisting of talc, magnesium silicate, calcium sulfate, aluminum silicate, calcium carbonate, magnesium oxide, magnesium carbonate, magnesium hydroxide, aluminum hydroxide, and mica.

It is preferable that the artificial leather base material further includes a plasticizer, because the texture having both suppleness and fullness of the grain-finished artificial leather can be easily further enhanced. It is particularly preferable that the plasticizer is liquid at 23° C.

It is preferable that the artificial leather base material has an apparent density of 0.45 to 0.8 g/cm3, because a grain-finished artificial leather that is particularly well-balanced in suppleness, surface smoothness, and a texture with fullness can be easily obtained.

It is preferable that the ultrafine fibers having an average fineness of 0.4 dtex or less include nylon ultrafine fibers having an average fineness of 0.025 dtex or less, because a grain-finished artificial leather having particularly excellent suppleness can be easily obtained.

It is preferable that an arithmetic mean height Saof a surface of the grain layer is 30 μm or less when the grain-finished artificial leather is caused to extend in a semicircular shape along an outer surface of a cylindrical mandrel having an outer radius of 8.7 mm, with the grain layer located on an inner side. Such a grain-finished artificial leather has a combination of fine fold creases, suppleness, surface smoothness, and a texture with fullness, similar to those of a grain-finished leather.

Another aspect of the present invention is directed to a method for producing a grain-finished artificial leather, including the steps of: preparing an artificial leather base material; and forming a grain layer on a surface of the artificial leather base material by direct coating, wherein the artificial leather base material includes a fiber-entangled body including ultrafine fibers having an average fineness of 0.4 dtex or less, an elastic polymer, and fine particles having an average particle size of 10 μm or less, a content ratio of the fine particles is 10 to 40 mass %, and a ratio of the elastic polymer to a total amount of the elastic polymer and the fine particles is 20 to 80 mass %, and a total of an apparent density of the elastic polymer and an apparent density of the fine particles is 0.23 to 0.55 g/cm3.

It is preferable that the step of forming a grain layer on a surface of the artificial leather base material by direct coating includes the steps of: forming an undercoat layer by applying a solution of an undercoat layer-forming elastic polymer to a surface of the artificial leather base material, followed by drying; and forming a skin layer by applying a resin solution including a skin layer-forming elastic polymer to a surface of the undercoat layer, because a thin grain layer can be formed.

It is preferable that a water absorption time when 3 cc of water droplets are dripped to the surface of the undercoat layer is 3 minutes or more, because a resin solution including a skin layer-forming elastic polymer does not excessively permeate into the artificial leather base material when the resin solution is applied.

Advantageous Effects of Invention

According to the present invention, it is possible to obtain a grain-finished artificial leather having a combination of the formability of fine fold creases, suppleness, surface smoothness, and a texture with fullness, similar to those of a grain-finished leather.

