KR890003171B1 - Method of synthetic leather - Google Patents

Abstract

The method for smooth type synthetic leather comprises (i) wet finishing a leather-like sheet with the mixt. of polyurethane resin 50-95 wt.% and polyamino acid resin 50-5 wt.% to form a fine porous layer of 20-200 micron thickness, and (ii) dry finishing the above sheet to form a nonporous layer of 5-50 micron thickness over the first layer.

Description

Manufacturing method of upper artificial leather

The present invention relates to a method for manufacturing an upper artificial leather, and in particular, to improve the surface processing method of a leather upper sheet composed of a nonwoven fabric structure and a polyurethane elastic body, the upper artificial leather having excellent wettability. It relates to a manufacturing method.

Conventional manufactured smooth type artificial leather is formed by continuously forming a microporous layer and a non-porous layer composed solely of polyurethane elastomer on the surface of the leather-like sheet, for example, JP 58-120871 or SO 60 -71777 describes the formation of upper artificial leather by forming a porous layer wet coated with polyurethane on a leather-like sheet material and a non-porous layer dried on polyurethane, and also described in British Patent No. 1,464,223. Artificial leather is manufactured in the same manner as in the following, but the technology of changing the type and characteristics of polyurethane according to its use is introduced.

However, the artificial leather manufactured only from the leather sheet material and the polyurethane has the disadvantage of fundamentally low moisture permeability when used for its main purpose of shoemaking. Generally, the moisture permeability of natural leather for shoemaking is 2,000 g / m 2 · 24hr. Should be above, the artificial leather manufactured by the conventional method has a room for improvement because the moisture permeability is only 300 to 500g / ㎡ · 24hr or so.

As described above, the upper upper artificial leather has a low moisture permeability due to the non-porous structure during dry processing, but above all, the present inventors have shown that the polyurethane elastomer exhibits hydrophobicity. It is noted that polyamino acid resin having a high moisture permeability, and by applying them to the production of artificial leather, it is to fundamentally solve the moisture permeability of artificial leather.

That is, an object of the present invention is to provide a method for manufacturing an upper artificial leather with improved moisture permeability.

Hereinafter, the present invention will be described in detail.

In the present invention, a microporous layer and a nonporous layer are sequentially formed on the surface of a leather sheet to prepare an upper artificial leather, wherein a mixture of 50 to 95% by weight of polyurethane resin and 5 to 50% by weight of polyamino acid resin is mixed. The wet is treated on the surface of the leather sheet to form a microporous layer having a thickness of 20 to 200 µ, and thereafter, the mixture is subjected to dry processing again to form a porous layer having a thickness of 5 to 50 µ. It is a method of manufacturing artificial leather.

In this case, the polyamino acid resin may be used for both the microporous layer and the nonporous layer, or may be used only for any one of them.

Hereinafter, the present invention will be described in more detail.

The leather sheet used as the fabric of artificial leather in the present invention is filled with a polyurethane elastomer in a nonwoven fabric, and can be prepared according to a conventional method. The nonwoven fabric is mainly polyethylene terephthalate or polyamide or viscose rayon or their Carding short fibers of the mixture, cross-wrapping and needle punching to make the staple fibers intertwined with each other in three dimensions to form a shape stability and processability. In addition, the polyurethane elastomer is a one-component linear polymer that can be dissolved in dimethylformamide, and the polyurethane elastomer is impregnated into the nonwoven fabric by a wet processing method in which a solvent is extracted from water, which is a non-solvent, to coagulate the polymer. In this way, the polyurethane elastic body acts as a binder between the short fibers to form a continuous microporous hole, the leather-like sheet material is made to have moisture permeability and breathability.

On the other hand, as the fibers used in the nonwoven fabric, when the polymer inter-array fiber that can be specifically refined is used, the manufactured leathery sheet material has excellent flexibility and feel. Here, the polymer inter-array fiber is a composite fiber of two kinds of polymers having different solubility in a solvent and capable of forming continuous filaments through special detention, also known as island-in-the-sea fibers. Forms continuous fibrils and acts as a binder to bond fibrils of another type of high molecular material (hereinafter, sea component). As such a component, conventional polyethylene terephthalate or nylon-6 may be used, and as the sea component, polystyrene, polyethylene, polyester, or the like may be used.

In this way, impregnating polyurethane into a nonwoven fabric made of polymer inter-array fibers and extracting and removing sea component using a suitable solvent results in ultrafine fibrils having a fineness of 0.5 to 0.005 denier.

The leather-like sheet produced in this way has a structure and physical properties very similar to those of natural leather, compared to the conventional one having fineness of 3 to 7 denier, and the moisture permeability is also good at 4,000 to 5,000 g / m 2 · 24hr.

Subsequently, a wet porous layer is formed on the surface of the leather sheet. Conventionally, as described above, a polyurethane elastomer comprising dimethylformamide as a solvent is coated on the surface of the leather sheet together with a suitable pigment and a surfactant for wet processing. Coated with a knife coater and coagulated with water or 50% or less of dimethylformamide solution to form a microporous layer having a thickness of 50-300μ, the pore size and wet processing conditions are used. The shapes could be different and the density of the coating layer was usually about 0.2-0.5 g / cm 3.

However, in the present invention, 5 to 50% by weight of the polyamino acid solution is mixed with respect to 50 to 95% by weight of the polyurethane elastomer solution, and the wet sheet is wet-molded using the same, but the thickness of the coating film is 20 to 200 mu, in particular ultrafine In the case of fibrous leather-like sheets, the microporous layer is formed to have a thickness of 30 to 100 µ, thereby greatly improving the feel, moisture permeability, and flexibility.

As the polyurethane elastomer used in the present invention, ether type, ester type, ether and ester copolymer type, etc. may be used. However, ether and ester copolymer type are preferred because of good compatibility with polyamino acid resins, hydrolysis resistance and light resistance. The best.

The physical properties of the polyurethane elastomer is a one-component polymer having 100% modulus of 40-80kg / cm 2, tensile strength of 300-600kg / cm 2, elongation of 450-700%, and soluble in dimethylformamide. On the other hand, the polyamino acid resin according to the present invention is a polyalkyl glutamate-based polymer mainly polycondensed methyl glutamate, and has similar characteristics in terms of molecular structure and collagen fibers of natural leather and its components. Is used as a dimethylformamide solution having a 200 to 400 poise.

At this time, since the polymethyl glutamate contains hydrophilic ester group and amide group, it has excellent moisture permeability and has excellent properties such as light resistance, hydrolysis resistance, heat resistance, etc. than polyurethane alone.

In addition, since dimethylformamide is used as the solvent, it has excellent compatibility with polyurethane, as well as excellent wet and dry processability alone. In particular, when the film is formed by dry, 100% modulus 50-80 kg / cm 2, tensile strength 300-500 kg / cm 2 and elongation 250-500%, showing a tendency similar to or somewhat harder than that of conventional polyurethanes.

In the present invention, the use of the polyamino acid resin alone and branded with the polyurethane resin in the dimethylformamide solvent is used to maintain the stiffness balance, that is, the modulus balance and the bonding strength between the layers of the leather material To increase the sense of unity.

Finally, a non-porous film layer is formed on the wet microporous layer thus formed. This process is to ensure that the manufactured artificial leather has sufficient surface wear strength, flexibility, pattern, and color to be used for shoemaking. In the same manner as when forming the wet porous layer, 50 to 95% by weight of polyurethane elastomer and 5 to 50% by weight of polyamino acid resin are mixed and used to form a film layer having a thickness of 5 to 50μ, and then adhesive When the wet porous layer is laminated with the upper artificial leather of the present invention is manufactured.

At this time, in the present invention, both the microporous layer and the nonporous layer may use a mixture of a polyurethane elastomer and a polyamino acid resin, or the mixture may be used only for any one of them, and only the polyurethane elastomer may be used alone. You may use it.

Next, the moisture permeability of the conventional polyurethane resin and the polymyonic acid resin used in the present invention will be compared for each processing condition.

TABLE 1

* Water vapor transmission rate (g / m 2 · 24hr) is measured according to JIS K6549.

In Table 1, the polyamino acid resin is about 3 times higher than the polyurethane in the case of the wet molded film, and about 1.5 to 2 times higher moisture permeability in the case of the dry molded film.

Hereinafter, examples of the present invention will be described.

Example 1

50% by weight of nylon-6 having a fineness of 3 denier, 51 mm in length and 50% by weight of polyethylene terephthalate with a fineness of 1.5 denier and 38 mm in length are given to a machine crimp of 10-20 pieces / inch to form staple fibers. After making it well mixed, carding, cross-tapping and needle punching to make a three-dimensional entangled nonwoven fabric weighing 800g / ㎡, and then shrink it sufficiently in the heat flux and polyurethane elastomer solution with a soft block of polyethylene adipate glycol Impregnation process.

Subsequently, the pickle is adjusted so that the solid content of the polyurethane elastomer to the fiber is 80% by weight, the resin is solidified in water and sliced in a direction perpendicular to the thickness through a squirrel machine to make two sheets of the same leather material. A dimethylformamide solution of 30% polytetramethylene ether glycol / polycaprolactonediol copolymer-based polyurethane elastomer and a dimethylformamide solution of polymethylglutamate having a concentration of 20% were mixed at a weight ratio of 60/40 The slicing surface of the leather sheet is coated.

Next, solidify it in water and dry it with water to form a wet porous layer having a thickness of 150 μ. Then, the dimethylformamide solution of ether-type polyurethane and the dimethylformamide solution of polymethylglutamate are mixed so as to have a solid ratio of 70/30. After coating on the sheet and evaporating the solvent therefrom to form a non-porous film layer having a thickness of 20 mu, laminating it with a one-component polyurethane adhesive and peeling off the release paper becomes an upper artificial leather.

Comparative Example 1

In Example 1, except that polymethyl glutamate is not used, the same procedure as in Example 1 is performed except that the wet and dry processing layers are continuously formed by the polyurethane elastomer alone.

Example 2

In Example 1, the wet processing layer is processed as in Example 1, and the dry processing layer is processed with polyurethane alone.

Example 3

In Example 1, the wet processing layer is processed by polyurethane alone, and the dry film layer is processed as in Example 1.

Example 4

A polymer inter-array fiber having 3 deniers and 51 mm in length using 50 weight% nylon-6 as a sea component and 50 weight% polystyrene as a sea component is prepared. The island component is composed of 16 fibrils in the sea component and forms a continuous filament in the longitudinal direction. The two-stage fiber with 15-25 pieces / inch of machine crimp is then cut, cross-wrapped, and needle punched to form a high-density nonwoven fabric weighing 1,000 g / m2, which is then impregnated with polyester-based polyurethane resin and solidified, washed, and dried. Subsequently, more than 99% of sea component polystyrene is extracted from perchloroethylene to form ultrafine nylon fiber fibrils having a fineness of 0.1 denier. The leather sheet thus prepared was sliced into two sheets, and the slicing surface was coated with a mixed solution of poly / polymethylglutamate mixed at a solid ratio of 50/50, and solidified in water to obtain 100 μm in thickness. A porous layer is formed. Subsequently, a mixture of ether-type polyurethane and polymethylglutamate at 80/20 in solid content is coated on a release paper and dried to form a non-porous film layer coating film having a thickness of 10 μ, followed by laminating with a wet coating layer using an adhesive. .

For the upper artificial leather manufactured according to the above Examples and Comparative Examples, the moisture permeability, cold resistance, and light resistance were measured, and the results are shown in Table 2 below.

TABLE 2

At this time, the moisture permeability was measured by the JISK 6549 evaluation method, and the cold resistance bend was measured according to the JISK 6545 evaluation method.

As can be seen in Table 2, the artificial leather manufactured by the conventional method has a water vapor transmission rate of only 350 g / m 2 · 24 hr, whereas the upper artificial leather according to the present invention appears to be 800 to 1200 g / m 2 · 24 hr. The moisture permeability has been improved by about 2 to 3 times. Therefore, when the upper artificial leather according to the present invention is used for shoemaking, it is possible to greatly improve the product quality and product value.

Claims (5)

In forming the upper artificial leather by forming a microporous layer and a nonporous layer on the surface of the leather sheet, a mixture of 50 to 95 weight percent polyurethane resin and 5 to 50 weight percent polyamino acid resin is mixed. Wet processing on the surface to form a microporous layer having a thickness of 20 to 200μ, and then a non-porous layer having a thickness of 5 to 50μ by dry processing the mixture thereon to form an upper artificial leather . The method of claim 1, wherein the leather sheet comprises a nonwoven fabric and a polyurethane resin filled therein, wherein the raw material of the nonwoven fabric is polyethylene terephthalate, polyamide or viscose rayon, or a mixture thereof. The method according to claim 1 or 2, wherein the polyurethane resin is a one-component linear polymer which can be dissolved in dimethylformamide as ether type or ester type or copolymer of ether and ester. The polyamino acid resin according to claim 1, wherein the polyamino acid resin is polymethyl glutamate, polyethyl glutamate, polypropyl glutamate using dimethylformamide as a solvent, or a mixture thereof, and the 100% modulus of the dry forming film is 50 to 80 kg / cm 2. , Elongation is 250 to 500%. The method according to claim 1, wherein the polyamino acid resin is used for both the microporous layer and the nonporous layer, or only one of them.