KR100204349B1 - Process for preparation of artificial leather - Google Patents

Abstract

The present invention is a three-dimensional articulated nonwoven fabric capable of microfiberization is calendered at a pressure of 1Kg / ㎠ ~ 5Kg / ㎠ with a thermal calender having a surface temperature of 140 ° C to 200 ° C and then treated with a water-soluble polymer, impregnated with polyurethane Subsequently, a step of ultrafine fibers and a surface buffing step are sequentially performed to provide a method of manufacturing artificial leather, characterized in that a thin film is coated on a polyurethane elastic body. According to the present invention, the structure is compact, flexible, and has excellent bending characteristics. In addition, it is possible to obtain an artificial leather with excellent surface appearance during post-processing.

Description

Manufacturing method of artificial leather

The present invention relates to a method of manufacturing artificial leather, and more specifically, after processing a three-dimensional roughly nonwoven fabric with a water-soluble polymer, calendering with a thermal calender, and performing a polyurethane impregnation process, a fiber miniaturization, and a surface buffing process. It is related to the manufacturing method of artificial leather which is characterized by the coating of urethane thin film, the structure is compact, flexible and excellent in the bending property as well as the surface appearance at the end of processing.

In general, in the manufacture of artificial leather, the card is made of three-dimensional nonwoven fabric by carding and needle punching a special fiber that can be micronized, and then impregnated with a microporous polyurethane elastomer, a polymer elastomer, by wet or dry processing. To produce a leather sheet.

Here, when the leather sheet is buffed, dyed and post-processed, it becomes a suede-type artificial leather, and wet coating and embossing a polyurethane solution, which is a polymer elastomer, or laminating a polyurethane film, results in a silver artificial leather. Silver-type artificial leather is widely used as a substitute material for natural leather, although it is used for the outer surface of sneakers, such as a ball shell and a seat cover. In particular, nonwoven type artificial leather using microfiber is similar to natural leather in terms of its structure, possibility, and flexibility, but it is widely used as a substitute material for natural leather because it has excellent advantages to compensate for the shortcomings of natural leather.

In the conventional manufacturing method of artificial leather, microfiber-composite composite fibers (splitting or island-like short fibers) are opened, carded and cross-wrapped to form a web, and then needle punched to produce a three-dimensional entangled nonwoven fabric. After filling with water-soluble polymer such as vinyl alcohol or carboxymethyl cellulose to stabilize the form of the nonwoven fabric, it is impregnated with a dimethylformamide solution (hereinafter referred to as DMF), which is a polyurethane elastomer, and solidified and washed in water to form a polyurethane elastomer inside the nonwoven fabric. Charge it.

After filling the nonwoven fabric with water-soluble polymer, the fiber may be first subjected to a micronization step and then the polyurethane impregnation step may be performed. Here, the former is called a preliminary elution method (a pole ultrafine process), and the latter is called a post elution method (a post ultrafine process). On the other hand, in the case of a composite fiber having a sea component as a copolyester, it is common to sequentially perform a water-soluble polymer pretreatment step, a polyurethane impregnation step, and a fiber ultrafine step, which corresponds to a post-dissolution method.

In the case of manufacturing artificial leather by the above-described manufacturing method of artificial leather, there is a limit to increase the density of three-dimensional interwoven nonwoven fabric only by needle punching, and thus the nonwoven fabric has a low density of 0.22 g / cm 3 or less. It becomes

When impregnated with a low-density nonwoven fabric, polyurethane, which is a high molecular elastomer, the amount of polyurethane is greater than that of the high-density nonwoven fabric, which gives a rubber-like feel to the final product.

In addition, since the surface of the nonwoven fabric is excessively generated by excessive needle punching, and the surface irregularities remain after the polyurethane impregnation processing, the surface smoothness is reduced, there is a problem that excessive surface buffing with sandpaper to obtain surface smoothness. Moreover, because of the wool layer formed by such excessive surface buffing, it is difficult to form a thin film in the secondary processing (silver surface processing). When processing the silver surface, a thick polyurethane coating or a thick lamination should be used, which causes a problem that the touch is hard to manufacture a flexible artificial leather.

An object of the present invention is to solve the above-described problems, to provide a method for producing artificial leather having a compact structure, smooth surface, smooth and flexible.

In other words, the three-dimensional entanglement nonwoven fabric capable of microfiber can be calendered with a thermal calender, water soluble polymer treatment, impregnating polyurethane, and then finely fiberizing and surface buffing are performed sequentially, followed by coating a polyurethane elastomer thin film. It is to provide a method of manufacturing artificial leather characterized by.

The present invention is briefly described as follows.

In the case of manufacturing artificial leather by the method of the present invention, first, the nonwoven fabric is manufactured by needle punching a composite fiber staple fiber containing copolyester as a sea component, and then using a heating roller of 140 to 200 ° C, After calendering under pressure, a conventional water-soluble polymer is padded on the nonwoven fabric, dried and heat treated to stabilize the form of the nonwoven fabric.

At this time, if the temperature of the heating roller exceeds 200˚C, the composite fiber is fused to the heating roller, resulting in poor processability, and the fused composite fiber is unevenly formed during buffing to form a coarse wool layer, resulting in poor appearance of artificial leather. Become. When the temperature of the heating roller is less than 140 ° C. After the calendering, the heat fixation of the composite fiber is incomplete and the elasticity is restored again, so that the effect of reducing the thickness of the nonwoven fabric is weak, and thus the object of the present invention cannot be achieved.

In the present invention, when the pressure of the heating roller exceeds 5Kg / ㎠, the nonwoven fabric is excessively calendered so that the impregnated content of the polymer elastomer is relatively reduced, the tear strength of the artificial leather is lowered. In contrast, when the pressure of the heating furnace is less than 1 Kg / cm 2, the effect of improving the density of the nonwoven fabric does not appear.

Next, the sea component is removed by a conventional alkali reduction process to perform a fiber miniaturization step, followed by impregnating a DMF solution of a polyester-based polyurethane, coagulating in water and washing with water to fill about 20 to 50% by weight of the fiber. To be. The surface of the bubble is then buffed with sandpaper to trim the wool. When measuring physical properties by molding on a dry film, the polyester-based polyurethane having a modulus of 5-20 Kg / cm 2 at 100% elongation is coated with a thickness of 3-15 microns and dried. The polyurethane thin film coating thickness is more preferably 5 to 12 microns. In the case of manufacturing silver-faced artificial leather, film lamination is performed, and in the case of suede artificial leather, buffing is performed.

When the modulus at 100% elongation of the polyurethane thin film exceeds 20 kg / cm 2, the wrinkles become large and the appearance becomes poor. In addition, when the thickness of the polyurethane thin film coating exceeds 15 microns, the flexibility is reduced in the case of silver surface processing and the bending wrinkles occur due to bending, and when the suede-like artificial leather is manufactured by buffing, the thin film is coated on the brushed surface. Too much of the polyurethane is formed to form a coarse wool layer.

When the thickness of the polyurethane thin coating is less than 3 microns, it is difficult to have smoothness for film laminating and it is difficult to have sufficient peel strength when laminating the film. In addition, when manufactured by suede artificial leather by buffing process, the polyurethane coating thin film lacks the role of holding the ultrafine fibers, the length of gathering is long, and irregular shaping length is formed to have a crude appearance.

The present invention is described in detail by process as follows.

First, the composite fiber used in the present invention is a composite spinning or mixed spinning of two kinds of high molecular materials capable of forming filaments in the form of sea / island (sea island) as a conventional component of nylon-6, polyethylene terephthalate (Hereinafter referred to as PET) and the like, co-polyester, polystyrene, polyethylene, and the like, which have different solvent and solvent solubility, may be used as the sea component, but co-polyester may be particularly useful for the purpose of the present invention.

Because polystyrene and polyethylene are used as sea components, toluene and perchloroethylene are used as solvents, so preliminary elution is possible even if a conventional water-soluble polymer such as polyvinyl alcohol is used as a filler. This is because it is possible to apply the ester-based polyurethane even if it is adopted.

On the other hand, the composite fiber used in the present invention is advantageous in obtaining the flexibility, strength and denseness of the bubbles when the fineness after the micronization is 0.5 denier or less, especially 0.1 denier or less. The composite fiber is opened and carded by a conventional nonwoven fabric manufacturing method, a web is laminated to a desired nonwoven fabric weight, and needle punched to produce a three-dimensional entangled nonwoven fabric.

Needle punching process is an important process to determine the density and appearance of nonwoven fabric. The physical properties and density are greatly influenced by the type of needle, speed of felt and depth of immersion.

On the other hand, in the artificial leather manufacturing process, the needle punched nonwoven fabric is usually shrunk by hot water, steam, or dry heat. Again, the nonwoven fabric is calendered at a pressure of 1-5Kg / cm 2 with a heating roller at 140-200 ° C. to reduce the thickness of the nonwoven fabric by 10-30%.

Next, the fiber is subjected to a micronization step, but the marine copolyester is completely decomposed and removed, and the polyurethane binder is not affected because of its excellent alkali hydrolysis resistance. At this time, the nonwoven fabric has some thickness reduction due to the removal of sea components, but the shape is maintained, and the elongation in the longitudinal direction due to mechanical tension is not large.

Next, the polyurethane wet impregnation process is performed to the ultrafine nonwoven fabric bubble.

Polyurethane elastomers used in this process are linear polymers composed of macroglycols of 500 to 3,000 molecular weight, diisocyanates and low molecular weight diols and are usually readily soluble in dimethylformamide.

Polyurethane elastomer that can be used in the present invention is applicable to polyether glycol, polyester glycol, polyether polyester copolymer glycol, polycarbonate glycol, etc. as a macro glycol, diisocyanate is composed of a polyurethane elastomer, the structure is dense It is a flexible, flexible, low elastic rubber and excellent bending property for artificial leather. Subsequently, the surface is buffed to even the surface, and then a 3 to 5 micron thin film polyether-based polyurethane having a modulus of 5 to 20 Kg / cm 2 at 100% elongation is coated. Then, film lamination may be performed according to the type of manufactured artificial leather to manufacture a silver artificial leather or a buffing process to manufacture a suede artificial leather.

In the present invention, after the three-dimensional twisted composite fiber calendering the nonwoven fabric at a constant pressure with a heating roller to reduce the thickness of the nonwoven fabric by 10 to 30% by reducing the amount of polyurethane impregnation during polyurethane impregnation Not only can it reduce the feeling of rubber, but the density of the nonwoven fabric can be made dense, and the surface is smoothed by thermal calendering, so that there is no need to perform excessive surface buffing as in the prior art. In addition, by performing a polyurethane thin film coating can be given flexibility in the surface processing and can have an excellent appearance during buffing processing.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited by the following examples.

Example 1

65 parts of nylon-6 and 35 parts of copolyester as sea components were used to prepare a composite fiber staple having a length of 2 inches, a fineness of 3 deniers, and Grips 12 to 18 pieces / inch. At this time, the number of island components was set to 36 pieces per filament. This fiber was opened and carded, and needle punched mainly with needle 40 to produce a three-dimensional entangled nonwoven fabric having a weight of 550 g / m 2, a thickness of 2.6 mm, and an apparent density of 0.212 g / cm 3. When the nonwoven fabric was shrunk with steam at 100 ° C. for 5 minutes, the area shrinkage was 12%. This nonwoven fabric was calendered at a pressure of 3Kg / cm 2 in a cylindrical cylinder type leaf calender with a surface temperature of 150 ° C and a diameter of 1500mm to smooth the surface and reduce the thickness to 2.2mm. The thermal calender used in the present invention has a structure in which at least half of the cylindrical cylinder is calendered with a rotary belt so that the nonwoven fabric can contact it.

Subsequently, a 5% aqueous polyvinyl alcohol solution having an average degree of polymerization of 500 and a degree of saponification of 80 to 90% was padded with a nonwoven fabric and dried. Next, when 100% elongation, 13% DMF solution of polyether polyurethane 13% having a modulus of 60Kg / cm 2 was impregnated into the nonwoven fabric, padded with 90% gap of the thickness of the nonwoven fabric, solidified with water, and washed with water in the usual manner. It was. The treated DMF solution was added with a surfactant to control the coagulation rate and an organic pigment suitable for the final artificial leather product.

Next, the solution was padded in a 10% aqueous solution of caustic soda and squeezed, followed by alkaline reduction for 5 minutes in a steam at 105 ° C., washed with water and dried.

At this time, the fibers were micronized to about 0.05 denier. At this time, the thickness of the forge was 1.7 mm, the weight was 610 g / cm 2, the density was 0.316 g / cm 3, and the density was very dense, and the content ratio of fiber to polyurethane was 58 to 42. The forge was buffed with 240 mesh sandpaper to give a thickness of 1.6 mm.

Next, when the 100% elongation, 20% DMF solution of polyether-based polyurethane having a modulus of 10Kg / cm 2 was coated with a thin film using a comma coater and dried to prepare a sheet-like structure which is an intermediate of artificial leather for shoes.

The surface coating area of this product was observed by electron microscopy, and an ultra-thin polyurethane film having a thickness distribution of 5 to 10 microns was formed. When the sheet-like structure is secondarily processed by a conventional silver-type artificial leather processing method, that is, a polyurethane laminating method (film layer thickness of 30 microns, adhesive layer thickness of 60 microns), the touch is flexible and has a dense silver artificial leather. As a substitute material for natural leather, it is suitable for sports shoes and shoes.

Comparative Example 1

When the nonwoven fabric used in Example 1 was subjected to water-soluble polymer treatment, polyurethane impregnation, and fiber miniaturization in the same manner as in Example 1 without thermal calendering, the thickness of the forge was 1.8 mm, weight 640 g / cm 2, and fiber-to-poly Urethane was 52 to 48. This was surface-buffed in the same manner as in Example 1 to prepare a leather-like sheet having a thickness of 1.6 mm.

In the case of this intermediate paper, the density was similar to that of Example 1, but the content of polyurethane was relatively high, resulting in a tactile rubber feeling, and the needle punching irregularities on the surface remained, requiring a large amount of back reduction in buffing (0.2 mm reduction). ).

In the case of secondary processing by laminating the polyurethane film layer according to a conventional method without the thin film polyurethane coating process treated in the following Example 1 (film layer thickness of 30 microns, contact layer thickness of 120 microns) lack of denseness and buffing Due to the formed fiber wool layer, the thickness of the polyurethane adhesive layer should be about twice that of Example 1, so the touch is hard, so when folded, the wrinkles become large, which is not suitable for high quality artificial leather for shoes.

Example 2

The leather sheet prepared in Example 1 was dyed at 100 ° C. for 50 minutes with a metal dye, followed by soaping and drying.

The surface was then lightly buffed with a sandpaper mounted buffer of 320 mesh to form a surface wool layer. At this time, the surface wool was very short because the coated polyurethane plays the role of a binder, and it took up more than half of the surface and became a nubuck-like artificial leather, which was suitable for the exterior of casual shoes and sports shoes.

Comparative Example 2

In Example 1, the leather-like sheet treated to finer fibers and surface buffing was dyed without surface polyurethane thin film coating treated in Example 1 and subjected to surface buffing. In this method, the surface wool did not cut short but fell out into a suede-like pattern and thus did not form the appearance of natural nubuck.

Claims (1)

A three-dimensional interwoven nonwoven fabric capable of microfiberization is calendered at a pressure of 1Kg / cm 2 to 5Kg / cm 2 with a thermal calender having a surface temperature of 140 to 200 ° C, and then treated with a water-soluble polymer, impregnated with polyurethane, and then microfiberized. And a thin film coating so as to have a thickness of 3 to 5 u with a polyether-based polyurethane elastomer having a modulus of 5 to 20 Kg / cm 2 at 100% elongation after the surface buffing step is sequentially performed.