JPH01124689A - Production of air-permeable artificial leather - Google Patents

Abstract

PURPOSE:To obtain an artificial leather outstanding in air permeability, by forming, on one surface of a porous flexible sheet material, a non-porous continuous film consisting of a polymer so as to result in parts differing in film thickness from each other followed by coating the film with a solvent soluble for said polymer to develop air-permeable pores. CONSTITUTION:A polymer (e.g. polyurethane elastomer) is coated on one surface of a porous flexible sheet material made up of nonwoven fabric consisting of natural or synthetic fiber and a polymeric binder (e.g. polyurethane elastomer) to form a non-porous continuous film consisting of parts 10-30mu thick and other parts >=80mu thick. Thence, the above film is coated with a solvent soluble for said polymer (e.g. dimethylformamide) by e.g. the gravure coating process to develop random air-permeable pores, thus obtaining the objective artificial leather excellent in air permeability.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing artificial leather with excellent breathability.

(Prior Art and its Problems) Conventionally, many artificial leathers and methods for producing the same have been proposed, and representative methods are listed below.

(1) Impregnating non-woven fabric or woven or knitted fabric with polymer solution
A method of filling the filling, applying a high molecular weight polymer directly on top of the filling, and performing wet coagulation.

(2) Create a base by impregnating and filling a non-woven fabric or woven or knitted fabric with a high-molecular polymer, and apply the high-molecular polymer to the support,
After wet solidification, it is bonded to the substrate using an adhesive.

The artificial leather obtained by these methods is given a grain by embossing or the like to improve the surface finish and become a product.

The above artificial leather has a porous silver surface and has better moisture permeability than conventional leather, but generally has a high surface strength,
Currently, it has a hard texture and almost no breathability.

(3) A substrate is created by impregnating and filling a nonwoven fabric or a woven or knitted fabric with a high molecular weight polymer, and on the other hand, a non-woven fabric of at least 211 different high molecular weight polymers consisting of a surface layer and an adhesive layer is placed on a textured release paper. A method of creating a porous layer and then bonding this coating to the substrate.

Artificial leather created by method (3) above maintains the flexibility of the base because it does not have a porous layer, but since the surface is a non-porous layer, the level of moisture permeability is low and there is no air permeability at all. The current situation is that there is no such thing.

In addition, Japanese Patent Publication No. 51-45648 proposes a method in which a substrate, a porous layer, and a non-porous layer are formed on top of the substrate, and mechanical deformation is applied to produce minute cracks on the surface. Since the cracks are only on the surface, the moisture permeability is improved, but it cannot be said that the air permeability is sufficient. Also special public service 1977-2584
Publication No. 8 describes a method of applying a liquid to a substrate and then bringing the polymer on the surface into contact with a heated surface to soften it to form a polymer film. A method has been proposed in which the surface of the substrate is impregnated with a liquid and brought into contact with a heating body to thermally melt the surface and form a surface layer, but in both cases the surface becomes film-like and it is difficult to obtain good flexibility. It can hardly be said that the breathability is sufficient. Furthermore, JP-A-60-84676 proposes a method for forming a highly air-permeable silver surface in which the surface of the substrate is thermally melted and rubbed. The thickness of the silver surface is determined by the temperature of the heating element, the pressure applied to the substrate, and the heating treatment time, which is extremely difficult to control.
It is difficult to say that products of constant quality can always be produced, and the development of cracks due to the rolling process also affects the thickness of the silver surface, and it can be said that it is extremely difficult to develop uniform cracks.

(Problems to be Solved by the Invention) The present inventors have overcome the drawbacks of the above-mentioned prior art, and as a result of intensive studies to obtain artificial leather that has excellent breathability and can be stably produced industrially, the inventors have found the following. The present inventors have discovered that a specific manufacturing method satisfies these requirements, and have completed the present invention.

(Means for solving the problem) That is, the present invention applies a solution or aqueous dispersion of a polymer to one side of a porous flexible sheet made of a nonwoven fabric and a polymer binder, and then dries the solution or aqueous dispersion of the polymer. A non-porous continuous film is formed with a polymer film thickness of 10 to 80 microns and a part larger than 80 microns, and then a solvent that can dissolve the polymer is applied to create ventilation holes. This is a method for producing breathable artificial leather, which is characterized by the ability to produce breathable artificial leather.

Examples of the polymer used in the present invention include solutions or aqueous dispersions of polyvinyl chloride, polyvinyl acetate, polyamide, polyester, polyurethane, polyacrylonitrile, polyamino acid, etc.;
Polyurethane is most preferable in terms of its tactile feel and physical properties such as flexibility.

A non-porous continuous film with a non-uniform thickness consisting of areas of 10 to 80 microns and areas larger than 30 microns is formed using the above polymer on a porous flexible sheet consisting of a nonwoven fabric and a polymer binder. This is achieved by the following method. A porous flexible sheet consisting of a nonwoven fabric and a polymeric binder has a surface that has various characteristics such as the density and density of the fibers forming the nonwoven fabric, the raised state, the unfilled areas of the polymeric binder, the porous pores of the polymeric binder, and the It is formed with one unevenness of about 5 to 40 microns due to needle punching marks or the like. The above-mentioned high molecular weight polymer is applied to one side of the sheet as a support, and the sheet is still fluid (wet).
After drying, peel off the support, or apply on this surface by gravure coating method, spray method, direct coating method using knife coater or reverse coater, press the base surface and coat the surface. This can be achieved by making it flat. In both cases, it is important to apply the polymer while it is fluid, and if it is not fluid, the polymer will not be sufficiently filled into the recesses on the surface of the porous sheet, and the film thickness will be 10%. This is because it does not form a continuous film consisting of a region of ~80 microns and a region larger than 80 microns.

In order to form a non-porous continuous film consisting of areas of 10 to 80 microns and areas larger than 80 microns, the coating amount is preferably 16 to 100,777 m2 in terms of solid content, although it varies depending on the type of polymer plate. More preferably 20~
50 l/m2. If it is less than 15 I/m2, the film will not form a continuous film and the appearance will be damaged.
When the amount is more than 00Ii/m2, the thinner part of the film exceeds 80 microns, and the subsequent solvent treatment does not form vent holes.
This results in a complete lack of breathability.

In addition, coloring agents such as dyes and pigments, gloss control agents, antistatic agents, antioxidants, mold deterioration inhibitors, and the like can be used in combination with the high molecular weight polymer, if necessary.

Solvents that can be used for solvent treatment include methanol, ethanol, propatool, IP, toluene, xylene,
Examples include acetone, MEK, formaldehyde, acetaldehyde, dioxane, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, anone, etc., but as long as it is a solvent that can easily dissolve a 80μ film of high molecular weight polymer at 20°C, it can be used alone or Can be used in combination.

Methods for applying the solvent include gravure coating, spray coating, etc., but gravure coating is industrially the most effective since it allows accurate coating of a small amount. The amount of solvent applied varies somewhat depending on the thickness of the thin part of the film, the type of polymer, and the dissolving power of the solvent, but is preferably 5 to 40 ji
/m2, more preferably 10-8 Q77/m
65J1/m which is 2! If the amount is less than 801/m2, the vent holes cannot be formed, whereas if the amount is more than 801/m2, the diameter of the vent holes becomes too large and the appearance deteriorates.

By performing the above two steps of forming a non-porous film and treating with a solvent, it was possible to create vents without damaging the appearance, and it became possible to achieve extremely high air permeability.

The nonwoven fabric used in the present invention is made of long fibers or short fibers such as natural fibers such as cotton, silk, and wool, recycled fibers such as rayon, and synthetic fibers such as polyester, nylon, and acrylic, either alone or in combination, and has a limited denier. It is not something that will be done. Using such fibers, a nonwoven fabric in which the fibers are three-dimensionally entangled is produced, by needle punching a single layer or multilayer web obtained by a known method such as carding, cross wrapper, or random unit. Make it into a sheet. In addition, the Mitt value of nonwoven fabric is 100 to 5001/m.
2, and the density is preferably about 0.10 to 0.8011/Cm''.The above nonwoven fabric is impregnated and filled with a polymer binder to obtain a porous flexible sheet. As the polymer binder used, one or more synthetic rubbers such as styrene butadiene rubber, nitrile butadiene rubber, polyurethane elastomer, polybutadiene rubber, and polyacrylic can be used.

Among these, polyurethane elastomer is the most preferred because its flexibility, texture, and feel are similar to those of natural materials.

The porous flexible sheet-like ladle obtained by this method has substantially irregularities, and has a surface suitable for forming a continuous film having an uneven thickness.

If necessary, various processes such as embossing, color finishing, softening, rolling, and dyeing can be added to one side of this porous flexible sheet. Such an addition step may be appropriately selected depending on the type of fiber or polymer used, the basis weight, density, intended use, etc. of the product.

(Effect of the invention) The artificial leather thus obtained has excellent appearance, flexibility, texture, and
It has a texture similar to natural leather, has high breathability that could not be achieved by any conventional method, and can be produced stably industrially, making it suitable for use as a material for shoes, bags, cases, clothing, and interior decoration. Can be done.

(Example) The method of the present invention will be explained in more detail with reference to Examples below. The air permeability was determined according to JI8-L-1096B method.

Example 1 Using a 6-nylon stable with a fineness of 1.5 denier and a fiber length of 51 mm, a web was created with a card and a cross wrapper, and the web was passed through a double needle locker room to produce 2000 pieces/c from the top and bottom. 2 needle punching, weight, ffi 2201/m2, thickness 1
．． A three-dimensional nonwoven fabric having a thickness of 2 mm and an apparent density of 0.181//Cm8 was obtained.

Polyethylene butylene with a molecular fi of 1500 (
1:1 mol) adipate glycoldiphenylmethane-
4,4-diisocyanate and ethylene glycol as a chain extender in dimethylformamide in a molar ratio of 1:5:
15% of the polyurethane elastomer obtained by reaction in step 4
The nonwoven fabric was impregnated with a dimethylformamide solution at an impregnation rate of 400X per N amount of the nonwoven fabric, and then coagulated in a coagulation bath at 40°C. Next, after removing the solvent in water, 12
Hot air drying was performed at 0°C to obtain a porous sheet material impregnated with polyurethane elastomer.

The weight of the porous sheet thus obtained was 850 I/m.
, thickness 1.25 mm1, apparent density 0.28, p
/am8, and the air permeability was 1.6 seconds.

Next, a solution of the same polyurethane elastomer as above was applied to one side of this porous sheet at a solid content of 4 0 l/m.
After coating with a knife coater and drying with hot air at 120°C, the surface was smoothed with a flat roll. The surface layer formed by this non-porous continuous film (hereinafter referred to as the surface layer)
The film thickness was 60μ in the thicker region and 15μ in the thinner region, and the air permeability was a, ooo seconds, meaning there was virtually no air permeability.

This surface layer is then coated with dimethylformamide (DMF).
was coated with a gravure coater at IQ l/m2 to form random ventilation holes. This surface was further colored and embossed using GC to give it a natural leather-like appearance. The air permeability of the artificial leather thus obtained was 82 seconds (Example 1).

For comparison, the surface layer was treated with toluene (Comparative Example 1).
, and methyl ethyl ketone (MEK1 Comparative Example 2), no vent holes were developed and no air permeability could be imparted.

(hereinafter referred to as thread/white) Examples 2 to 6, Comparative Examples 8 to 5 On one side of the porous sheet-like material obtained in the same manner as in Example 1,
A polyether type polyurethane obtained by reacting polytetramethylene ether glycol, diphenylmethane-4,4'-diisocyanate, and ethylene glycol at a molar ratio of about 8:10 was coated on a smooth metal support with a solid content of 5.
10,80,50°80.100,150. f/m, and then pressure-bonded to a porous sheet material in a fluid state, and after drying with hot air at 120° C., the support was peeled off.

Then dimethylformamide was added at 15. Coating was performed using a y/m2 gravure coating method to obtain artificial leather. The surface layer thickness was 10 to 80 μm at the thinner portion, and the appearance and air permeability were both good.

(Leaving space below) Examples 7 to 11, Comparative Examples 6 and 7 Polyether type polyurethane was coated on a metal support in a solid amount of 801.77 m2, and the amount of dimethylformamide applied in the subsequent solvent treatment was 8.5 m2. 10°20.80,4
0.50. Artificial leather was obtained by carrying out the same operation as in Example 2 except that F/m2 was used.

When the coating amount of dimethylformamide was 5 to 4011/m2, both appearance and air permeability could be achieved.

(The following are blank spaces) Example 12, Comparative Example 8 A web was created using a card cloth wrapper using a polyester stable with a fineness of 1.5 denier and a fiber length of 514 mm, and the web was processed using a needle machine at 2000 pieces/cm from the top and bottom directions. Needling was carried out at a needle density of 1.5 mm to obtain a three-dimensional nonwoven fabric having a weight of 40097 m2, a thickness of 1.7 mm%, and an apparent density of 0.2477/Cm.

The nonwoven fabric was impregnated with 80% styrene butadiene (mole ratio 1:6) emulsion in terms of solid content, and the impregnation rate was 850% per nonwoven fabric nail amount.
%, passed through a steamer heated to 100°C under normal pressure for 5 minutes to gel, and then
The product was washed with warm water at 0°C and dried with hot air at 120°C to obtain a porous sheet material impregnated with styrene-butadiene rubber. The porous sheet material thus obtained had a weight of 82,017 m2, a thickness of 1.75 mm, and an apparent density of 0.
．． It was 471/crn.

On one side of this porous sheet, N-alkoxymethyl-modified nylon was applied at a solid content of 8097 m by the subsea coating method, and the surface was smoothed using a flat roll. It was a non-porous continuous film with a thickness of 10μ and a thickness of 40μ at the thickest part, and the air permeability was 5,200 seconds, meaning there was virtually no air permeability.

Next, methanol was applied to this surface layer at a rate of 10 l/m2 using a gravure coating method to develop random ventilation holes. The surface of this artificial leather, which was embossing, dyed, and textured, was similar to natural leather on the outside, and had an air permeability of 52 seconds. (Example 12) For comparison, when solvent treatment was carried out with dimethylformamide, no vent holes were developed and the air permeability was 4.800 seconds (Comparative Example 8).

Par・＼ (hereinafter referred to as Umbrella/7 White)

Claims (1)

[Claims] A solution or aqueous dispersion of a polymer is coated on one side of a porous flexible sheet made of a nonwoven fabric and a polymer binder, and then dried to form a portion where the polymer has a film thickness of 10 to 80 microns. to form a non-porous continuous film consisting of portions larger than 80 microns, and then the polymer,
1. A method for producing breathable artificial leather, which comprises applying a solvent capable of dissolving the breathable artificial leather to create vents.