KR980009647A - Artificial leather and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a process for producing artificial leather by impregnating a microporous water-based polyurethane elastomer into a three-dimensionally entangled nonwoven fabric entangled with microfine fibers, wherein the 30% solids liquid has a viscosity of 4000-20000 CPS / Is mixed with water at a mixing ratio of 100 / 130-170, diluted to a concentration of 10% -15% and stirred for 1 hour or more, and then impregnated into the nonwoven fabric using the diluted solution. , The artificial leather produced by the present invention has a flexural rigidity value of 0.500-0.650 gf · cm ² / cm, which is excellent in flexibility, and thus is well suited for use in bubbles for shoes, especially for shoe endings.

Description

Artificial leather and method for manufacturing the same

FIG. 1 is a photograph of equipment used for measuring bending stiffness of artificial leather in the present invention.

The present invention relates to a method for producing artificial leather, and more particularly, to a method for producing artificial leather by impregnating several microporous polyurethane elastomers into a three-dimensional interlocking nonwoven fabric entangled with microfine fibers, Was mixed with water at a mixing ratio of 100 / 130-170 at a concentration of 4000-20000 CPS / 25 ° C, diluted to a concentration of 10% -15%, stirred for 1 hour or more, and impregnated into the nonwoven fabric using the diluted solution And to a method for producing an aqueous polyurethane based artificial leather improved in flexibility.

Artificial leather is a material obtained by wet-impregnating and coating an aqueous polyurethane resin with a nonwoven fabric as a bubble, and is similar to natural leather in terms of its structure, functionality, and flexibility. Rather, it has poor washability, instability, And it has excellent merits that complement defects of natural leather such as low fastness of dyeing, and it is getting a spotlight as a substitute material of natural leather.

In general, artificial leather is made by carding, cross-lapping, and punching a special composite fiber capable of microfiberization to make a three-dimensional interlocking nonwoven fabric by needle punching, filling a microporous polyurethane elastomer therein, and then finely finishing the fiber (0.005-0.05 denier ) To produce a leather-like sheet.

Such artificial leather is largely classified into suede artificial leather and silver artificial leather. Suede artificial leather is manufactured by buffing the leather-like artificial leather, brushed the surface layer, dyeing and post-processing to form a mat layer on the surface , Clothes, gloves, and miscellaneous goods. For this purpose, cotton type artificial leather is produced by wet or dry coating of polyurethane solution on leather sheet, after forming a two-layer structure, by embossing, or by laminating a polyurethane film formed on a deformed paper having a pattern, It is mainly used as outer cover, outer cover of ball, seat cover and so on. Suede artificial leather is divided into a velor type which lengthens the length of the surface according to the buffing condition and a nuchal which shortens the length of the lure. In recent years, there has been a demand for nuchal vessels having a delicate and luxurious appearance .

The method of manufacturing artificial leather according to the related art will now be described in more detail. Firstly, split or sea-island staple fibers of 2 to 5 denier that can be made finer can be re-inserting, carding and cross-lapping to form a laminated web, . Followed by shrinking in steam or hot water to increase the density, and then filling with a water-soluble polymer such as polyvinyl alcohol (PVA) or carboxymethyl cellulose to stabilize the nonwoven fabric. Next to that. A water-dispersible polyurethane emulsion (water-based polyurethane: 30% polyurethane / H ₂ O 100/100 in solid content) is impregnated and coagulated and washed in water to fill the microporous polyurethane elastomer inside the nonwoven fabric. Then, the water-soluble polymer water charged is completely removed, dried, and then the sea component is removed to make the fiber finer and then main-buffered. Finally, final buffing is carried out with a buffing machine equipped with a sandpeter, and dyeing and post-processing are performed to form a layer on the surface.

However, since the aqueous polyurethane used in the aqueous polyurethane impregnation step of the prior art as described above is migrated to the surface upon impregnation and drying, the aqueous polyurethane is concentrated on the surface, and therefore, There is a hard problem. In addition, since the aqueous polyurethane can not easily escape from the water serving as a dispersion medium of the aqueous polyurethane during drying and is transferred to the surface, the drying time is increased accordingly.

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

That is, the present invention relates to a process for producing an artificial leather by impregnating a microporous water-based polyurethane elastomer into a three-dimensional entangled nonwoven fabric entangled with microfine fibers, wherein the aqueous polyol having a viscosity of 4000-20000 CPS / Wherein the urea solution is mixed with water at a mixing ratio of 100 / 130-170, diluted to a concentration of 10-15%, and stirred for at least 1 hour to thereby impregnate the nonwoven fabric with the solution. will be.

Hereinafter, the method of the present invention will be described in more detail as follows.

First, the highly water-repellent conjugated fiber which can be used in the present invention is a composite filament or mixed filament of two kinds of polymer materials capable of forming filaments in a sea / island form. As a component of the polyethylene terephthalate main chain

Modified polyesters in which the degree of crystallinity of the yarn is controlled to less than 35% by copolymerizing macromolecules composed of aromatic chains are used. As the copolymerization component, 2,2-bis- (4- (2-hydroxyethoxy) phenol) propane , 2- (4- (2- hydroxyethoxy) phenol) propane, or 2- (4- (2- (2-hydroxyethoxy) ethoxy) phenol) propane. As the sea component, copolymerized polyester, polystyrene, polyethylene or the like having different solubility in solvent may be used.

The composite fibers used in the present invention are advantageous in that flexibility, strength and fidelity of bubbles are obtained when the fineness after microfabrication is 0.005 denier to 0.05 denier. Such a composite fiber is opened and carded by a conventional nonwoven fabric manufacturing method, the web is laminated to a desired weight, and then needle punching is performed to produce a three-dimensionally entangled nonwoven fabric.

The needle punched nonwoven fabric is then shrunk by hot water, steam or dry heat, or passed through a thermal calender. For example, when a nylon-6 / copolymer polyester nonwoven fabric having a weight of 300 g / m ² is shrunk in hot water for 5 minutes, an area shrinkage of about 10% occurs and in the case of PET / copolymer polyester nonwoven fabric, So that the apparent density of the nonwoven fabric is improved, resulting in a more dense state.

The shrunk nonwoven fabric is then stabilized by imparting a water-soluble polymer solution such as polyvinyl alcohol or carboxymethylcellulose at a concentration of 3 to 15% to the nonwoven fabric bubbles, and drying the same at 5 to 10% of the fiber weight. This process is effective not only to stabilize the shape of the bubbles but also to prevent the subsequent wet-process polyurethane from being excessively adhered to the fibers to harden the feel.

The nonwoven fabric is then subjected to an aqueous polyurethane wet impregnation process. The polyurethane elastomer used in this process is prepared by mixing an aqueous polyurethane liquid having a viscosity of 4000-20000 CPS / 25 DEG C of an aqueous polyurethane liquid having a solid content of 30% with water at a mixing ratio of 100 / 130-170 for 1 hour or more So that the concentration of the aqueous polyurethane solution is about 10-15%.

In the present invention, polyester-based, polyether-based, and polycarbonate-based polyurethanes are preferably used for the water-based polyurethane impregnation treatment, but polyether-based or polycarbonate-based ones are preferable in order to ensure durability to some extent as a commodity.

In the present invention, the viscosity of the aqueous polyurethane liquid is related to the viscosity of the polyurethane. If the viscosity is less than 4000 CPS / 25 캜, the migration of the aqueous polyurethane occurs, and the drying time becomes longer and the sample becomes uneven. On the other hand, Exceeds 20000 CPS / 25 캜, the water-based polyurethane is densely packed in the center of the nonwoven fabric, so that the fixation of the fibers in the surface layer of the nonwoven fabric is unstable, and the flexibility of the synthetic oil leather is deteriorated. Therefore, in the present invention, it is essential that the viscosity of the aqueous polyurethane liquid having a solid content of 30% is maintained within the above range.

When the polyurethane resin and water are mixed, they are mixed so that the mixing ratio of the aqueous polyurethane solution and water is 100 / 130-170, and the mixture is diluted to a concentration of 10% -15% and stirred for 1 hour or longer. Is more than 15%, the feel becomes very hard and the amount of migration of the aqueous polyurethane increases. When the stirring time is less than 1 hour, the feeling may become hard.

The content of polyurethane to be added depends on the concentration of the impregnation solution, the gap of the padding roll, the density of the nonwoven fabric to be treated, and so on. 100 parts by weight.

In the present invention, immediately after the aqueous polyurethane impregnation, the pressure is overpressured so as to maintain a degree of 80-90% of the polyvinyl alcohol content through the mangles of the cap lower than that of the forge. By doing so, it is possible to prevent the migration of aqueous polyurethane

And the flexibility can be improved. At this time, when the interval of the squeezed mangles exceeds 90% of the polyvinyl alcohol foam degree, the impregnation amount of the aqueous polyurethane is increased, and the haying time becomes very long.

After the aqueous polyurethane impregnation process, the alkali component is removed by the alkali reducing process, and the microfibre process of the fiber is carried out. When the marine component is a copolymerized polyester, the marine component is decomposed by continuously or batchwise treatment with an aqueous solution of caustic soda of 5 to 15%, and if the marine component is polyethylene or polystyrene, it is removed with toluene or perchlorethylene do. For example, the sea component copolymer polyester is completely decomposed and removed by treatment with a 5% aqueous solution of caustic soda at 95 ° C for 20 to 50 minutes. At this time, although the thickness of the nonwoven fabric is slightly reduced due to the removal of the sea component, the shape is maintained and the elongation in the longitudinal direction due to the mechanical tension is not large.

Next, the surface of the leather-like sheet material thus obtained is buffed on the surface with the sandpaper No. 240 or 320, and the surface sand is further trimmed in the same direction with a finer sandpaper. Next, when the fiber used is Nylon-6, it is usually dyed with a mixed metal dye or a milling type acidic dye, and in the case of polyethylene terephthalate, it is dyed with a dispersion dye in a high pressure rapid dyeing machine. Finally, water-repellent and antistatic processing is performed to produce high-quality artificial leather excellent in flexibility.

The artificial leather produced by the present invention has a bending rigidity value of 0.500-0.650 gf · cm ² / cm and has a very excellent flexibility. Therefore, it can be applied directly to bubbles for shoes, If the bending stiffness of the artificial leather is less than 0.500 gf · cm ² / cm, the artificial leather is too flexible and is not suitable for use as a leather product because its form stability is poor. On the contrary, when the bending stiffness is 0.650 gf · cm ² / , The artificial leather is too hard and the bending property is lowered, so that the curved treatment is not smooth and it can not be applied to leather products such as shoes.

Further, according to the present invention, since the drying time of the aqueous polyurethane can be shortened, it is possible to obtain an advantage that artificial leather improved in productivity can be ultimately obtained.

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 conductive component and 35 parts of copolyester as a sea component to prepare a composite fiber staple having a length of 2 inches, a fineness of 3 deniers and a cream soup of 12-18 pieces per inch. At this time, the number of metallic components was 36 per single filament. The staple fibers thus obtained were carded and carded and needle punched with a needle of No. 40 to produce a three-dimensionally entangled nonwoven fabric having a weight of 500 g / m ^{2, a} length of 2.00 mm and an apparent density of 0.25 g / cm 3. When this nonwoven fabric was shrunk with steam at 100 ° C for 5 minutes, the area shrinkage was 9%. Next, a 5% aqueous solution of polyvinyl alcohol having an average degree of polymerization of 500 and a degree of saponification of 80 to 90% was padded onto a nonwoven fabric and dried. Subsequently, a water-based polyurethane having a viscosity of 5000 CPS / 25 ° C in a solid content of 30% by weight was diluted to 13% in water and stirred for 1 hour and 30 minutes. After the solution was mixed with the nonwoven fabric, an interval of 80% The mangles were passed through and dried. Subsequently, the polyurethane impregnation was poured and squeezed with a 13 wt% aqueous solution of caustic soda, followed by continuously reducing the alkali with steam at 100 ° C for 10 minutes, washing it with water and drying to make the fiber finer, Respectively. Subsequently, the surface of the porridge was buffed with a sandpaper of 240 mesh to homogenize the finish, and then buffed twice with a sandpaper sandpaper of 400 mesh at 0.05 mm. Finally, the artificial leather of the present invention was manufactured through the process of softening agent and anti-dying agent, and the physical properties thereof were evaluated. The results are shown in Table 1 below.

Examples 2 to 6

The artificial leather of the present invention was produced in the same manner as in Example 1 except that the composition and conditions of the aqueous polyurethane used in the polyurethane impregnation step were changed as shown in Table 1, 1.

Comparative Examples 1 to 5

An artificial leather was produced in the same manner as in Example 1 except that the composition and conditions of the aqueous polyurethane used in the polyurethane impregnation process were changed as shown in Table 1, and the properties were evaluated. The results are shown in Table 1 .

Property evaluation method

(1) Bending rigidity

The following measurements were made using a Pure Bend Tester as shown in Fig. 1 of Kawabata measurement system equipment. The smaller the value, the more flexible.

① Preparation of sample

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

② Measurement principle

Bending is applied only in the interval of 1cm in length of 5cm. As a result, the bending moment according to the curvature (k, ² cm) (M, ² gfcm /

cm), and its slope is the flexural stiffness (B, gf · cm ² / cm).

③ Calculation

The curvature K is changed to a constant rate of change between -2.5 and 2.5 cm ^-1 , and the average of these values is calculated by setting the slope at B = -0.5 to 1.5 at Bb and the slope at k = 0.5 to 1.5 at Bf . The bending stiffness (B) of the specimen is obtained by performing a total averaging on the horizontal direction and the vertical direction.

(2) Whether or not migration occurred: SEM (scanning electron microscope) photographs were taken.

Claims (3)

Aqueous polyurethane elastomer is impregnated into a three-dimensional interlocking nonwoven fabric in which microfiber fibers are entangled to produce an artificial leather, the water-based polyurethane liquid having a viscosity of 4000 to 20000 CPS / 25 ° C in a 30% 100 / 130-170, diluted to a concentration of 10% to 15%, and agitated for 1 hour or more, to thereby impregnate the nonwoven fabric with the diluted solution. The method of claim 1, wherein the method further comprises a step of passing over the mangles at intervals of 80-90% of the foam immediately after the aqueous polyurethane impregnation. Artificial leather having a bending stiffness value of 0.500-0.650 gf · cm ² / cm. ※ Note: It is disclosed by the original application.