Napped Artificial Leather and Manufacturing Method Therefor

The present invention relates to a napped artificial leather and a method for manufacturing the same.

Napped artificial leathers having a suede-like appearance which are used as surface materials of clothes, shoes, furniture, car seats, general merchandise, and the like have a napped surface which is formed by fluffing microfine fibers through a raising treatment. Such napped artificial leathers are generally colored for use. Heretofore, dyeing with dyestuffs of various colors ranging from a pale color to a dark color has been frequently performed.

A conventional napped artificial leather has a problem in that when the napped artificial leather including polyester fibers serving as microfine fibers and a polyurethane resin serving as a high-molecular elastic body is dyed with a disperse dyestuff and then reduced and cleaned, color unevenness occurs in the napped artificial leather, resulting in deterioration in appearance.

In order to deal with this problem, for example, PTL 1 has proposed an artificial leather in which within 200 μm in the thickness direction from the surface except for a napped portion of the artificial leather in a cross section obtained by cutting the artificial leather perpendicularly to the surface direction, the number of high-molecular elastic body blocks each having a size of 100 μm or more in the thickness direction per the cross-sectional length in the surface direction is 0.1 to 2.5 pcs/mm.

PTL 2 has proposed a substrate for an artificial leather in which the average value for the area of a high-molecular elastic body exposed to a sheet surface is 0.1 mmor less.

The conventional napped artificial leather also has a problem in that the color tone and the color density are restricted and the artificial leather is difficult to color with various color tones at various color densities.

In order to deal with this problem, PTL 3 has proposed a suede-finished artificial leather including fibers colored with a pigment and a high-molecular elastic body colored with a pigment and having an average napped fiber length of 10 to 200 μm.

For napped artificial leathers, a texture close to that of natural leather, such as excellent denseness and softness and a good feeling are required.

In response to this requirement, for example, PTL 4 has proposed a nubuck-finished leather-like sheet-shaped product which includes a staple fiber nonwoven fabric having a single fiber fineness of 0.0001 to 0.5 dtex and an apparent density of 0.300 to 0.700 g/cm, has a napped fiber length of 5 to 500 μm, and does not include a film-shaped substance formed from an elastic polymer.

PTL 5 has proposed an artificial leather including a napped layer in which the average fiber length of microfine fibers is 250 μm or more and 500 μm or less and the surface coverage rate of the microfine fibers is 60% or more and 100% or less.

Further, PTL 6 has proposed a leather-like fabric in which a resin layer is intermittently formed on a napped surface, the area ratio of a resin portion in a fabric surface is 10 to 90%, and the resin layer is composed of two or more layers.

In the artificial leathers described in PTL 1 and PTL 2, the occurrence of color unevenness is suppressed, but mechanical strength such as frictional wear property and tensile strength is insufficient, and there remains a need for improvement.

The artificial leathers described in PTL 3, PTL 4, and PTL 6 do not sufficiently have mechanical strength such as tensile strength, and there remains a need for improvement.

The leather described in PTL 5 does not have a sufficiently satisfactory skin feeling, that is, have a rough skin feeling, and there remains a need for improvement.

On the other hand, as a method for suppressing dyeing unevenness unlike methods described in PTL 1 and PTL 2, a method in which color unevenness is concealed by increasing a napped fiber length has been also investigated. However, this method has a problem in that the skin feeling is deteriorated and the denseness is reduced. Use application in which a person touches, such as furniture and a car seat, have caused problems such as excessive lighting and ununiform appearance.

Conventionally, the use of filaments in a napped artificial leather has been investigated to enhance the mechanical strength of the napped artificial leather. However, the use of filaments enhances the mechanical strength such as tensile strength, but results in a problem in that color unevenness more easily occurs than a napped artificial leather including staple fibers.

In view of the circumstances, the present invention is made, and an object of the present invention is to provide a napped artificial leather in which the occurrence of color unevenness is suppressed and which has a high mechanical strength and an excellent texture.

The term “excellent texture” as used herein means a texture close to that of natural leather, such as excellent denseness and softness and a good feeling.

The present invention is based on a finding that when the content of a high-molecular elastic body attached to a nonwoven fabric, the area ratio of the high-molecular elastic body present on a napped surface, and the napped fiber length are set to predetermined values, a napped artificial leather in which the occurrence of color unevenness is suppressed and which has a high mechanical strength and an excellent texture is obtained.

The present invention provides the following procedures.

[1] A napped artificial leather including: a nonwoven fabric containing microfine fibers and a high-molecular elastic body, the napped artificial leather having a napped surface, in which a content of the high-molecular elastic body is 15 to 35 mass %, an area ratio of the high-molecular elastic body present on the napped surface is 17% or less, and a napped fiber length is 250 μm or less.

[2] The napped artificial leather according to [1], in which the microfine fibers are polyester-based fibers.

[3] The napped artificial leather according to [1] or [2], in which the microfine fibers have an average fineness of 0.01 to 1.0 dtex.

[4] The napped artificial leather according to any one of [1] to [3], in which the nonwoven fabric is a spun-bond nonwoven fabric.

[5] A method for manufacturing the napped artificial leather according to any one of [1] to [4], the method including a step of removing a sea component from an entangled web containing the high-molecular elastic body, to obtain a nonwoven fabric containing the high-molecular elastic body.

[6] The method for manufacturing the napped artificial leather according to [5], the method including a step of melt-spinning a sea/island type composite fiber to obtain a web.

[7] The method for manufacturing the napped artificial leather according to [6], in which the step of obtaining a nonwoven fabric containing the high-molecular elastic body includes removing the sea component through dissolution in an organic solvent.

[8] The method for manufacturing the napped artificial leather according to any one of [5] to [7], the method including a step of forming the entangled web containing the high-molecular elastic body through use of a solvent-based polyurethane.

The present invention provides a napped artificial leather in which the occurrence of color unevenness is suppressed and which has a high mechanical strength and an excellent texture, and a method for manufacturing the same.

The following description is based on an example of embodiments of the present invention (hereinafter also referred to as “the present embodiment”). However, embodiments described below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following description.

The description shows preferred aspects of embodiments, but a combination of two or more of individual preferred aspects is also a preferred aspect. Regarding the matters indicated by the numerical ranges, in a case where there are several numerical ranges, it is possible to selectively combine the lower limit value and the upper limit value of the numerical ranges to obtain a preferred aspect.

In the description, when there is a description of a numerical range of “XX to YY”, it means “XX or more and YY or less”.

A napped artificial leather of an embodiment is a napped artificial leather including: a nonwoven fabric containing microfine fibers and a high-molecular elastic body, the napped artificial leather having a napped surface, in which the content of the high-molecular elastic body is 15 to 35 mass %, the area ratio of the high-molecular elastic body present on the napped surface is 17% or less, and the napped fiber length is 250 μm or less.

In the napped artificial leather of the embodiment, the occurrence of color unevenness is suppressed, and a high mechanical strength and an excellent texture are achieved.

The term “napped fiber length” as used herein means the length of napped fibers present on a napped surface of a napped artificial leather, and the term “color unevenness” means color unevenness caused during colorization of the napped artificial leather.

Although the reason that the aforementioned effects can be produced by the aforementioned configuration of the napped artificial leather of the embodiment is not clear, it is considered that the reason is as follows.

In general, different components are used for the fibers and the high-molecular elastic body constituting the nonwoven fabric of the napped artificial leather. For example, polyester-based fibers may be used as the fibers, and a polyurethane-based resin may be used as the high-molecular elastic body. When such a napped artificial leather is colored with a colorant such as a disperse dyestuff, there may be differences in the color tone and the color density between the fibers and the high-molecular elastic body due to a difference in colorability between the fibers and the high-molecular elastic body. In particular, when there are differences in the color tone and the color density between the high-molecular elastic body exposed to the napped surface and the fibers present on the napped surface, the differences are considered to be recognized as color unevenness.

In the napped artificial leather of the present invention, the content of the high-molecular elastic body is 15 to 35 mass % and the area ratio of the high-molecular elastic body present on the napped surface is 17% or less, and therefore it is considered that exposure of the high-molecular elastic body to the napped surface is suppressed, resulting in suppression of color unevenness.

In the napped artificial leather of the embodiment, the content of the high-molecular elastic body is 15 to 35 mass %, and therefore the color unevenness is suppressed, and excellent denseness and softness, a good feeling, and a texture similar to that of natural leather are further achieved. That is, the napped artificial leather has a good texture.

From the viewpoint of obtaining a napped artificial leather having a better texture, the content of the high-molecular elastic body is preferably 16 to 34 mass %, more preferably 16.5 to 33.5 mass %, further preferably 17 to 33 mass %.

In the napped artificial leather of the embodiment, the area ratio of the high-molecular elastic body present on the napped surface is 17% or less. When the area ratio of the high-molecular elastic body is 17% or less, exposure of the high-molecular elastic body to the napped surface is suppressed, and the high-molecular elastic body cannot be completely viewed or can be extremely slightly viewed, resulting in suppression of color unevenness. From the viewpoint of further suppressing color unevenness, the area ratio of the high-molecular elastic body is preferably 15% or less, more preferably 14% or less, and further preferably 13% or less. From the viewpoint of obtaining a napped artificial leather having more excellent softness and elasticity, the area ratio of the high-molecular elastic body is preferably 5% or more, more preferably 6% or more, and further preferably 7% or more.

The “area ratio of the high-molecular elastic body present on the napped surface” as used herein is measured and calculated by the following method.

Three different portions of the napped surface of the napped artificial leather are photographed with a scanning electron microscope (SEM) at a magnification of 50. From each of the resultant images, the total area of a region where the high-molecular elastic body is present is determined with an image processing apparatus and the like, and from the determined total area and the total area of the entire region of each of the images, the area ratio of the high-molecular elastic body is calculated by the following expression.

Area ratio of high-molecular elastic body=total area of region where high-molecular elastic body is present/total area of entire region of image×100(%)

Specifically, the measurement and the calculation follow methods described in Examples below.

In the napped artificial leather of the embodiment, the napped fiber length is 250 μm or less. When the napped fiber length is 250 μm or less, napped fibers are finely dispersed and have a uniform length, and therefore a napped surface having excellent softness and a smooth feeling can be formed. From the viewpoint of forming a napped surface having more excellent softness and a smooth feeling, the napped fiber length is preferably 150 μm or less, more preferably 120 μm or less, and further preferably 100 μm or less. From the viewpoint of preventing the exposure of the high-molecular elastic body at the lower portion of the napped fibers, which results in a deterioration in appearance, and keeping a soft feeling of the microfine fibers, the napped fiber length is preferably 40 μm or more, more preferably 50 μm or more, and further preferably 60 μm or more.

The thickness of the napped artificial leather of the embodiment is not particularly limited, but from the viewpoint of obtaining a napped artificial leather having a high mechanical strength and an excellent texture, it is preferably 0.1 to 1.5 mm, and more preferably 0.3 to 1.0 mm.

The basis weight of the napped artificial leather is not particularly limited, but from the viewpoint of obtaining a napped artificial leather having a high mechanical strength and an excellent texture, it is preferably 100 to 1,000 g/m, and further preferably 150 to 800/m.

The apparent density of the napped artificial leather of the embodiment is preferably 0.35 g/cmor more, more preferably 0.37 g/cmor more, and further preferably 0.38 g/cmor more, and preferably 0.70 g/cmor less, more preferably 0.50 g/cmor less, and further preferably 0.48 g/cmor less. When the apparent density is 0.35 g/cmor more, the napped artificial leaser has excellent elasticity, the fibers are prevented from dragging and protruding during rubbing of the napped surface, and elegant appearance of the napped fibers is easily achieved. When the apparent density is 0.70 g/cmor less, the napped artificial leaser has excellent softness.