KR100263040B1 - A artificial leather and fabrication thereof - Google Patents

Abstract

PURPOSE: The subject artificial leather prepared by impregnating nonwoven fabric with water-based polyurethane and a process for preparation thereof are provided. Whereby, the obtained leather has excellent flexibility such that it is suitable for in particular, the inside skin of shoes. CONSTITUTION: In manufacturing artificial leather by impregnating a fine porous water-based polyurethane elastomer into the inner part of three-dimensional textured nonwoven fabric, the water-based polyurethane liquid having a solid content of 30% by weight and a viscosity of 4,000 to 20,000CPS/25deg.C is mixed with water in a ratio of 100/130 - 170, agitated for more than 1 hr and impregnated into the nonwoven fabric.

Description

Artificial leather and its manufacturing method

1 is a photograph of the equipment used to measure the bending stiffness of artificial leather in the present invention.

The present invention relates to a method of manufacturing artificial leather, and more particularly, in manufacturing an artificial leather by impregnating a microporous water-based polyurethane elastic agent inside a three-dimensional entangled nonwoven fabric in which an ultrafine fiber bundle is entangled, a solid content of 30% by weight liquid The aqueous polyurethane solution having a viscosity of 4000 to 20000 CPS / 25 ° C. was mixed with water at a mixing ratio of 100/130 to 170, dilute to a concentration of 10 to 15% by weight, and stirred for at least 1 hour. It relates to a method for producing an aqueous polyurethane-based artificial leather with improved flexibility, characterized by impregnation.

Artificial leather is a material which is mainly impregnated with water-based polyurethane resin and coated with non-woven fabric, and its structure, functionality and flexibility are similar to those of natural leather, but rather poor laundering resistance, instability, antibacterial and deodorization, As it has excellent advantages to compensate for the shortcomings of natural leather such as low dye fastness, it is attracting the spotlight as a substitute material of natural leather.

In general, artificial leather is carded and cross-wrapped a special microfiber that can be micronized, needle punched to make a three-dimensional entangled nonwoven fabric, and then filled with a microporous polyurethane elastomer inside the microfiber (0.005 ~ 0.05 denier) ) To produce a leather-like sheet.

Such artificial leather is roughly divided into suede artificial leather and silver artificial leather. Suede artificial leather is manufactured by buffing the leather sheet and raising the surface layer, followed by dyeing and post-processing to form a wool layer on the surface. Mainly used for clothing, gloves, miscellaneous goods. Silver-type artificial leather is manufactured by forming a two-layer structure by wet or dry coating a polyurethane solution on a leather-like site and then embossing or laminating a polyurethane film made on a release paper having a pattern. It is mainly used as outer shell, ball outer shell, seat cover, etc. Suede-like artificial leather is divided into velour type, which has a long length of the surface of the wool according to the buffing condition, and a nubuck, which has a short length of the wool. Doing.

Looking at the manufacturing method of the conventional artificial leather in more detail, first, to form a laminated web by opening, carding and cross-lapping the split or island-like short fibers of 2 to 5 denier that can be micronized, and then punching the three-dimensional entangled nonwoven fabric To prepare. The film is then densified by shrinking in steam or hot water, and then filled with a water-soluble polymer such as polyvinyl alcohol (PVC) or carboxymethyl cellulose to stabilize the nonwoven fabric. Next, the water-dispersible polyurethane emulsion (water-based polyurethane: solid content 30% by weight polyurethane / H 2 O = 100/100) is impregnated, solidified in water, and washed with water to fill a microporous polyurethane elastomer inside the nonwoven fabric. Subsequently, the temperature is raised to completely remove the filled water-soluble polymer, and after drying, the sea component is removed to make the fiber main buffing fine. Finally, the final paper is buffed with a sandpaper-equipped buffer, and is manufactured by forming a layer of wool on the surface through dyeing and post-processing.

However, the water-based polyurethane used in the above-mentioned water-based polyurethane impregnation process in the prior art is migrated to the surface during drying after impregnation, so that the water-based polyurethane concentrates on the surface, so it is not applicable to artificial leather. There are some hard issues. In addition, there is a disadvantage in that the drying time is longer because the aqueous polyurethane is not easily released from the water, which serves as a dispersion medium of the aqueous polyurethane during drying, is transferred to the surface.

It is an object of the present invention to overcome these problems in the prior art, and to provide a method for producing an aqueous polyurethane-based artificial leather which is flexible and has a short drying time by changing each condition in the aqueous polyurethane impregnation process.

That is, in the present invention, in manufacturing artificial leather by impregnating a microporous water-based polyurethane elastomer inside a three-dimensional entangled nonwoven fabric in which an ultrafine fiber bundle is entangled, the water content has a viscosity of 4000-20000 CPS / 25 ° C. A method for producing artificial leather, characterized in that the polyurethane solution is mixed with water in a mixing ratio of 100 / 130-170, dilute to a concentration of 10 to 15% by weight, and impregnated into a nonwoven fabric using a lean solution prepared by stirring for 1 hour or more. To provide.

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

First, the high shrinkage composite fiber usable in the present invention is a composite spinning or mixed spinning of two kinds of polymer materials capable of forming filaments in the form of sea / doe (海 / 島). As a co-constituent, a modified polyester in which the crystallinity of the yarn is controlled to less than 35% by copolymerizing a macromolecular molecule composed of an aromatic chain in the polyethylene terephthalate backbone is used. As the copolymerizing component, 2,2-bis- (4- (2 -Hydroxyethoxy) phenol) propane, 2- (4- (2-hydroxyethoxy) phenol) propane, or 2- (4- (2- (2-hydroxyethoxy) ethoxy) phenol) propane It is possible to use As the sea component, copolyester, polystyrene, polyethylene, and the like, which have different solvent soluble properties and solvents, may be used.

The composite fiber used in the present invention is advantageous in obtaining the flexibility, strength, and fidelity of the bubbles when the fineness after the micronization is 0.005 denier to 0.05 denier. Such a composite fiber is opened and carded by a conventional nonwoven fabric manufacturing method, a web is laminated at a desired weight, and needle punched to produce a three-dimensional interwoven nonwoven fabric.

The needle punched nonwoven fabric is then shrunk by hot water, steam or dry heat or passed through a hot calender. For example, when a nylon-6 / copolymer polyester nonwoven fabric having a weight of 300 g / m2 is shrunk in hot water for 5 minutes, about 10% of area shrinkage occurs, and about 20% of area shrinkage occurs for PET / copolyester nonwoven fabrics. The apparent density of the nonwoven fabric is improved, resulting in a more compact state.

The contracted nonwoven fabric is then stabilized by padding the nonwoven fabric with a water-soluble polymer solution such as polyvinyl alcohol or cellulose at a concentration of 3 to 15% by weight and giving 5 to 10% by weight of the fiber weight. This process is effective not only to stabilize the shape of the bubbles, but also to prevent the subsequent wet processing polyurethane from excessively adhering to the fiber bundle and hardening the touch.

Next, an aqueous polyurethane wet impregnation is performed on the nonwoven fabric. The polyurethane elastomer used in this step is stirred and mixed for 1 hour or more with an aqueous polyurethane liquid having a viscosity of 4000 to 20000 CPS / 25 ° C of water-based polyurethane having a solid content of 30% by weight at a mixing ratio of water and 100/130 to 170. This resulted in overly thin so that the concentration of the aqueous polyurethane liquid was about 10 to 15% by weight.

In the present invention, a polyester-based, polyether-based, and polycarbonate-based polyurethane may be preferably used for the water-based polyurethane impregnation treatment, but polyether-based and polycarbonate-based are preferable in order to secure a certain degree of durability as a product.

In the present invention, the viscosity of the aqueous polyurethane liquid is related to the viscosity of the polyurethane, but if the viscosity is less than 4000 CPS / 25 ℃ transition of the aqueous polyurethane occurs, the drying time is long and the sample is uneven, on the contrary If the viscosity exceeds 20000 CPS / 25 ℃ water-based polyurethane is concentrated in the center of the nonwoven fabric, not only the fiber bundle of the surface layer of the nonwoven fabric is unstable, but also the flexibility of the artificial leather, there is a fear that the touch is hard. Therefore, in the present invention, it is essential that the viscosity of the aqueous polyurethane liquid having a solid content of 30% by weight is maintained within the above range.

In addition, when the polyurethane resin and water are mixed, the mixing ratio of the aqueous polyurethane liquid and water is 100/130 to 170, and the mixture is diluted to 10 to 15% by weight in a concentration of about 1 hour or longer. When the concentration of is greater than 15% by weight, the feel becomes very hard and the amount of transition of the aqueous polyurethane increases, and when the stirring time is less than 1 hour, the touch may become hard.

The amount of polyurethane given at this time depends on the concentration of the impregnation solution, the gap between the padding roll, and the density of the nonwoven fabric to be treated. Therefore, it is necessary to adjust it to suit the required characteristics of the final bubble. It is preferable to set it as 100 parts.

In the present invention, immediately after the aqueous polyurethane impregnation, through the mangle of the lower gap even after the forge is over-compressed to maintain a thickness of 80% to 90% of the thickness of the fabric impregnated with polyvinyl alcohol. By doing so, it is possible to prevent the migration of the water-based polyurethane and to improve the flexibility. If the spacing of the crimp mangle exceeds 90% after the polyvinyl alcohol, the impregnation amount of the water-based polyurethane increases and the drying time is very high. Longer

After the aqueous polyurethane impregnation process, the sea component is removed by an alkali weight reduction method to perform an ultrafine fiber process. In this case, if the sea component is a copolyester, the sea component is decomposed by 5 to 15% by weight aqueous solution of caustic soda in a continuous or batch manner, and if the sea component is polyethylene or polystyrene, the toluene or perchloroethylene Remove For example, the sea component copolyester is completely decomposed and removed by treatment with a 5% by weight aqueous solution of caustic soda at 95 ° C. for 20 to 50 minutes. At this time, the nonwoven fabric has some thickness reduction due to the removal of the sea component, but the shape is maintained and the elongation in the longitudinal direction due to the mechanical tension is not large.

The surface of the leather-like sheet thus obtained is then buffed with sandpaper 240 or 320 and again trimmed with the finer sandpaper in the same direction. Subsequently, when the fiber used is nylon-6, it is usually dyed with a metal-containing dye or milling type new dye, and in the case of polyethylene terephthalate, it is dyed with a high-speed rapid dyeing machine with a disperse dye. Finally, high-quality artificial leather with excellent water repellency and antistatic processing is produced.

The artificial leather manufactured by the present invention has a bending rigidity value of 0.500 to 0.650 gf · cm 2 / cm, which is very flexible, and thus is directly applied to shoes foam or particularly suitable for shoe endothelium. However, if the flexural rigidity of artificial leather is less than 0.500 gf · cm / cm, the artificial leather is too flexible and its shape stability is poor, making it unsuitable for use as leather products. On the contrary, the flexural rigidity of more than 0.650 gf · cm / cm In this case, the artificial leather is so hard that its flexural characteristics are deteriorated, so the curve is not smooth and cannot be applied to leather products such as shoes.

In addition, according to the method of the present invention, it is possible to shorten the drying time of the water-based polyurethane, and thus, it is possible to obtain an advantage of obtaining artificial leather with improved productivity.

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

Example 1

65 parts of nylon-6 as a island component and 35 parts of copolyester as a sea component were used to prepare a composite fiber staple having a length of 2 inches, a fineness of 3 deniers and a crimp number of 12-18 pieces / inch. At this time, the number of island components was set to 36 pieces per filament. The staple fibers thus obtained were opened, carded, and needle punched with needle No. 40 to produce a three-dimensional entangled nonwoven fabric having a weight of 500 g / m 2, a thickness of 2.00 mm, and an apparent density of 0.25 g / cm 3. When this nonwoven fabric was shrunk for 5 minutes at 100 ° C steam, the area shrinkage was 9%. Next, a 5% by weight aqueous solution of polyvinyl alcohol 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. Subsequently, the water-based polyurethane having a viscosity of 5000 CPS / 25 ° C. in a 30 wt% solids solution was diluted to 13 wt% in water, and the solution stirred for 1 hour and 30 minutes was impregnated into the nonwoven fabric, which corresponds to 80% of the fabric thickness. The gap was passed through a mangle and dried. Next, the polyurethane impregnated cloth was padded and squeezed with 13 wt% aqueous sodium hydroxide solution, followed by alkali reduction processing for 10 minutes with steam at 100 ° C., washed with water and dried to make fibers fine and dyed under normal conditions. . Subsequently, the surface of the paper was buffed with 240-mesh sandpaper to uniform the thickness, and then, after the grinding was made with 400-mesh sandpaper, the coating amount was 0.05 mm. Finally, the artificial leather of the present invention was manufactured through a softening agent and an antistatic agent treatment process, and the physical properties thereof were evaluated and the results are shown in Table 1 below.

[Examples 2 to 6]

Except for changing the composition and conditions of the water-based polyurethane used in the polyurethane impregnation process as shown in Table 1, the artificial leather of the present invention was prepared in the same manner as in Example 1, the physical properties were evaluated and the results are shown in Table 1 Together.

[Comparative Examples 1 to 5]

Except for changing the composition and conditions of the water-based polyurethane used in the polyurethane impregnation process as shown in Table 1, artificial leather was prepared in the same manner as in Example 1, the physical properties were evaluated and the results are shown in Table 1 together. It was.

[Property evaluation method]

(1) Banding Rigidity:

Kawabata measurement system equipment using the pure bending tester as shown in Figure 1 was measured as follows. Smaller values are more flexible.

① Preparation of Sample

A sample of 5 cm or more in length and 1 cm in width is attached to the bending tester. At this time, the distance between the fixed chuck and the moving chuck of the tester is 1 cm.

② Measuring principle

Bending is applied only to an interval of 1 cm of 5 cm in length. As a result, the bending moments (M, gf · cm / cm) change according to the curvature (k, cm) and the slope is the bending stiffness (B, gf · cm / cm / cm).

③ Calculation

The curvature k changes at a constant rate of change between -2.5 and 2.5 (cm ^-1 ), and the slope when k = -0.5 to -1.5 is B _b value and the slope when k = 0.5 to 1.5 is B _f value Calculate their average. When the results are collectively averaged in the transverse and longitudinal directions, the bending stiffness B of the sample is obtained.

(2) presence or absence of transition: It was read by SEM (scanning electron microscope) photograph.

Claims (3)

Microporous water system inside a three-dimensional entangled nonwoven fabric with microscopic fiber bundles intertwined In manufacturing artificial leather by impregnating a polyurethane elastic body, 10-15 weight by mixing the water-based polyurethane liquid whose viscosity of 30 weight% liquid of solid content is 4000-20000 CPS / 25 degreeC by mixing ratio of water and 100 / 130-170 A method of manufacturing artificial leather, characterized in that it is impregnated into a nonwoven fabric using a lean solution prepared by diluting at a% concentration and stirring for 1 hour or more. The method of claim 1, The method further comprises the step of over-compressing by passing the mangle of the interval corresponding to 80 to 90% of the post-treatment immediately after the aqueous polyurethane impregnation. An artificial leather comprising a polyurethane elastic body in a three-dimensional interwoven microfiber nonwoven fabric, wherein the artificial leather has a bending rigidity value of 0.500 to 0.650 gf · cm / cm.