KR100339197B1 - Method of manufacturing artificial leather - Google Patents

Abstract

PURPOSE: Provided is an artificial leather which involves excellent softness and fullness, and is well adapted for use in making shoes. CONSTITUTION: An artificial leather is manufactured by dispersing a micro-porous polyurethane elastomer in a three-dimensional non-woven fabric where microfibers are interlaced. After the fabric is dipped in the solvent of polyurethane, the solidification thereof is made at 45-80 deg.C for 5-30 minutes. The concentration of solidification DMF/H2O is established to be 20-40%.

Description

Manufacturing method of artificial leather

The present invention relates to a method for manufacturing artificial leather, and more particularly, in the manufacture of artificial leather by impregnating a polyurethane elastic body inside a three-dimensional entangled nonwoven fabric in which an ultrafine fiber bundle is entangled, solidification after polyurethane impregnation is performed at or above room temperature. The present invention relates to a method for producing a flexible and faithful artificial leather, characterized in that to form micropores in the polyurethane structure.

Artificial leather is made of non-woven fabric and mainly wetted or coated with polyurethane resin. It is similar to natural leather in terms of its structure, functionality, and flexibility, but rather poor launder resistance, instability, antibacterial, deodorization, and dyeing. It has an excellent merit that compensates for the shortcomings of natural leather, such as low fastness, and is in the spotlight as an alternative material for natural leather.

In general, artificial leather is carded and cross-wrapped special composite fibers that can be micronized, and then needle punched to create a three-dimensional entangled nonwoven fabric, and then filled with a microporous polyurethane elastic body therein. It is made by preparing water.

Such artificial leather is roughly divided into suede artificial leather and silver artificial leather. Suede artificial leather is manufactured by buffing the leather-like sheet, raising the surface layer, 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 sheet and then embossing or laminating a polyurethane film made on a release paper having a pattern. It is mainly used for outer shell, ball outer shell, seat cover, etc.

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. Subsequently, the density is increased by shrinking in steam or hot water, followed by filling with a water-soluble polymer such as polyvinyl alcohol or carboxymethyl cellulose to stabilize the nonwoven fabric. Next, the dimethylformamide (DMF) solution of the polyurethane elastomer is impregnated, coagulated and washed in water to fill the microporous polyurethane elastomer inside the nonwoven fabric. Subsequently, the temperature is raised to completely remove the filled water-soluble polymer, and then dried to remove the sea component to make the fiber fine. Finally, the sandpaper is buffed with a buffing machine, and dyed and post-processed to form a wool layer on the surface.

In the manufacture of artificial leather, the process of microfiber and polyurethane impregnation can be reversed depending on the characteristics required for the final product. In addition, the method of performing a polyurethane impregnation process first is called a post-eluting process method (post-micron fine process method).

In the polyurethane impregnation process of the conventional artificial leather manufacturing process, it is common to use the polytetramethylene glycol (PTMG) type as a soft cement, and to solidify at room temperature after solvent polyurethane impregnation.

However, the polytetramethylene glycol (PTMG) type is ether-based, and thus, hydrophobicity is higher than that of ester-based, and thus, coagulation is poor, resulting in poor flexibility and poor polyurethane filling. This is because the micropores were not formed in the filled polyurethane by solidifying at room temperature.

An object of the present invention is to overcome the problems of the prior art as described above, by forming the micropores in the polyurethane structure by solidifying after the polyurethane impregnation at room temperature or more to produce a flexible yet faithful artificial leather To provide.

That is, the present invention provides a method for producing artificial leather, characterized in that the solidification after polyurethane impregnation is carried out in the manufacture of artificial leather by impregnating a polyurethane elastic body inside a three-dimensional entangled nonwoven fabric in which an ultrafine fiber bundle is entangled. To provide.

Solidification Temperature: 45 ~ 80 ℃

Solidification time: 5 minutes or more

Coagulation concentration (DMF / H ₂ O): 20% or more

Hereinafter, the present invention will be described in 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 / island. 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 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 It is possible to use As the sea component, co-polyester, polystyrene, polyethylene, etc., which have different degree of control and solubility, may be used.

On the other hand, the composite fiber used in the present invention is advantageous to obtain the flexibility, strength, and fidelity of the bubbles when the fineness after the micronization is 0.5 denier or less, particularly 0.1 denier or less. 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, an area shrinkage of about 10% occurs. In the case of a PET / copolymer polyester nonwoven fabric, an area shrinkage of about 20% occurs. The apparent density of 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 carboxymethyl cellulose at a concentration of 3-15%, drying and giving 5-10% by weight of the fiber. 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, a polyurethane wet impregnation is performed on the nonwoven fabric. The polyurethane elastomers used in this process are readily dissolved in dimethyl formamide (DMF) as linear polymers composed of macroglycols, diisocyanates and low molecular weight diols having a molecular weight of 500 to 3,000. As the polyurethane elastomer used in the present invention, polyether glycol, polyester glycol, polyether polyester copolymer glycol, polycarbonate glycol, and the like are applicable as macroglycol, and as diisocyanate, usually 4,4'-diphenylmethane Diisocyanate, tolylene diisocyanate, hexamethylene diisocyate or 4,4'-dicyclohexyl methane diisocyanate. In the present invention, as the low molecular weight diol, 4,4'-butanediol, ethylene glycol, and the like are used, and a diamine-based chain extension agent is also applicable. A surfactant, a coloring pigment, an antioxidant, and the like are added to the DMF solution of the polyurethane elastomer to be used as an impregnation solution. After impregnation, the polyurethane is solidified, washed with hot water at 50 to 70 ° C., and the dried water-soluble polymer is completely removed and then dried. At this time, the solidification conditions should be maintained at the solidification temperature of 45 ~ 80 ℃, solidification time 5 minutes or more, coagulation concentration (DMF / H ₂ O) 20% or more.

When solidified under the above conditions, microcells are formed in the polyurethane structure, and artificial leather having micropores is more flexible in the case of artificial leather without micropores because the polyurethane content is not increased while the polyurethane is uniformly filled. The floor feel has an advantage.

In the present invention, if the solidification temperature is less than 45 ℃ micropores are not formed in the filled polyurethane, the flexibility and polyurethane filling is poor, on the contrary, if the solidification temperature exceeds 80 ℃ due to degradation of the polyurethane There is a risk of adversely affecting the physical properties of the final product.

In addition, in the present invention, if the solidification time is less than 5 minutes or the concentration of the coagulation bath is less than 20%, micropores are not formed in the filled polyurethane as in the case where the solidification temperature is low, so that the effect of the present invention can be obtained. Since there will be no solidification conditions in the present invention, it is essential to be within the above range.

The polyurethane content in the polyurethane impregnation process depends on the concentration of the impregnation solution, the gap between the padding rolls, 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 35-100 parts.

Subsequently, the sea component is removed by an alkali weight loss method to perform an ultrafine fiber process. In this case, if the sea component is a copolymerized polyester, the sea component is decomposed by 5 to 15% aqueous solution of caustic soda in a continuous or batch manner, and if the sea component is polyethylene or polystyrene, the sea component is removed with toluene or perchloroethylene. . For example, sea component copolyester is completely decomposed and removed by treatment with a 5% aqueous caustic soda solution 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.

Next, the surface of the leather-like sheet thus obtained is buffed by a buffer equipped with sandpaper of appropriate roughness to prepare surface wool. Subsequently, when the fiber used is nylon-6, it is usually dyed with a metal-containing dye or millipper acid dye, and in the case of polyethylene terephthalate, it is dyed in a high-pressure rapid dyeing machine. Finally, by treating the functional preparations such as softeners, water repellents, antistatic agents and the like, artificial leather is produced with dense bubbles and beautiful appearance.

As can be seen through the scanning electron micrograph of FIG. 1, the artificial leather manufactured according to the present invention has a number of fine pores formed in the polyurethane structure, so that the resistance to bending is reduced, so that the flexibility and fidelity are excellent. Therefore, it is very suitable as a shoe material that requires thick and coincidental.

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, 35 parts of copolyester as a sea component, and a composite fiber staple having a length of 2 inches, a fineness of 3 deniers and a crimp number of 12 to 18 pieces / inch were prepared. 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 to produce a three-dimensional entangled nonwoven fabric, which was then shrunk with steam at 100 ° C. At this time, the area shrinkage was 10%. Subsequently, polyvinyl alcohol 5% aqueous solution was padded with a nonwoven fabric and dried to form a stabilizer.

Next, a dimethylformamide solution of 13% polyether-based polyurethane elastomer having a 100% modulus of 100 kg / cm 2 was impregnated into a nonwoven fabric sheet filled with polyvinyl alcohol, and a mangle of 90% of the thickness of the fabric was removed. After passing through, the product was coagulated, washed with water and dried. At this time, the solidification conditions were set at a solidification temperature of 60 ° C., a solidification time of 5 minutes, and a solidification concentration (DMF / H ₂ O) of 20% to perform solidification. Subsequently, the aqueous 15% caustic soda solution was padded and squeezed, followed by continuous alkali reduction process with steam at 100 ° C, followed by washing with water and drying to make the fiber extremely fine.

The micronized pores were then dyed under normal conditions and buffed first with 240 mesh sandpaper to uniform the thickness and then buffed twice in succession. Finally, the artificial leather of the present invention was prepared by treating the softening agent and the antistatic agent, and the physical properties thereof were shown in Table 1 below.

Examples 2-4

Except for changing the coagulation conditions as shown in Table 1, artificial leather was prepared in the same manner as in Example 1 and the physical properties thereof were evaluated and the results are shown in Table 1 together.

Comparative Examples 1 to 5

Except for changing the coagulation conditions outside the scope of the present invention as shown in Table 1, artificial leather was produced in the same manner as in Example 1 and the physical properties thereof were evaluated and the results are shown in Table 1 below.

Table 1

[Measurement Method]

(1) Bending Moment: Measured using a Kawabata Evaluation System, the smaller the value, the more flexible it is.

(2) The presence of micropores was evaluated by reading a scanning electron microscope (SEM) photograph.

1 is a scanning electron micrograph of the artificial leather produced by the present invention.

Claims (1)

A method for producing artificial leather, characterized in that coagulation after polyurethane impregnation is carried out under the following conditions in the manufacture of artificial leather by impregnating a polyurethane elastic body inside a three-dimensional entangled nonwoven fabric in which an ultrafine fiber bundle is entangled. Solidification Temperature: 45 ~ 80 ℃ Solidification time: 5-30 minutes Coagulation Concentration (DMF / H ₂ O): 20 ~ 40%