KR0126653B1 - Process for the preparation of artificial leather heaving excellent suppleness - Google Patents

Abstract

Manmade leather with good flexibility is manufactured by forming micro pores in a polyurethane elastomer. Synthetic fiber such as nylon 6, polyethylene terephthalate undergoes a padding process by contactingpolyvinyl alcohol of 3-15% concentration for softness contacted with the PU elastomer. DMF solution of a polyether PU elastomer of low molecular diol, macroglycol, and diisocyanate is mixed with silica powder with an average granule size of 2-10 micrometers as much as 5-10% of PU solids for a superfine fiber. Extraction of the silica from the elastomer provides a microporous manmade leather with good flexibility.

Description

Highly flexible artificial leather and its manufacturing method

The present invention relates to an artificial leather and a method for producing the same, which are flexible and have good bending characteristics.

BACKGROUND ART A leather sheet material impregnated with a polyurethane (hereinafter PU) elastic body by a wet processing method in a nonwoven fabric composed of a conventional ultrafine fiber bundle is widely used as a basic material of artificial leather.

Looking at the conventional manufacturing method of the foam for artificial leather consisting of a microfiber nonwoven fabric of less than 0.3 denier and a PU elastic body as follows.

First, microscopic splitting or island-like short fibers of 2 to 5 deniers are opened, carded and cross-wrapped to form a web, and then needle punched to produce a three-dimensional entangled nonwoven fabric, and then polyvinyl alcohol or carboxymethyl cellulose, etc. After filling the water-soluble polymer of to stabilize the form of the nonwoven fabric, it is impregnated with a solution of dimethylformamide (hereinafter referred to as DMF) of PU elastomer, coagulated in water and washed with water to fill a polyether PU nonwoven fabric in the nonwoven fabric.

Then, after heating, the water-soluble high molecular weight material is completely removed and dried, and then the sea component is removed under the solvent of the sea component to make the fiber fine. After that, if the surface of the surface of the wool is prepared with a buffing machine equipped with sandpaper, it becomes a leather-like sheet.

In other words, by forming a wool layer by buffing the surface of the leather sheet, dyeing and post-processing, it becomes a suede artificial leather, and after wet or dry coating the PU solution, embossing or laminating the PU film becomes a silver artificial leather.

Silver-type artificial leather is widely applied as a substitute material for natural leather, such as sneaker outer shell, ball outer shell and seat cover. Especially, nonwoven fabric type artificial leather using ultra-fine fibers has the structure, functionality, and flexibility. It is similar to natural leather or rather has the advantage of making up for the shortcomings of natural leather.

Microfibers, the main component of artificial leather, are rarely produced directly from the yarn stage of one component of fiber-forming polymers. In general, two-component fiber-forming polymers are manufactured by the island-in-the-sea composite spinning method, and then called the post-processing process. It is common to remove the sea component and to make it fine.

Therefore, what kind of fiber component (sea component) and matrix component (sea component) concentrating the fiber component of the island-in-the-sea composite fiber, that is, artificial according to the composition of the fiber used and the characteristics of the final product required The manufacturing method of leather will inevitably change.

For example, in the case of using island-in-the-sea composite fibers made of nylon-6 or polyethylene terephthalate as a component and polystyrene or polyethylene as a sea component, the nonwoven fabric is filled with a water-soluble polymer, followed by an ultrafine fiber process. Next, the PU impregnation process may be performed, or the PU impregnation process may be performed and the next PU impregnation process may be performed, or the PU impregnation process may be performed first, and the ultrafine fiber process may be performed later.

Here, the former eluting the sea component based on the PU impregnation process is called a preliminary elution method, and the latter eluting the sea component after PU impregnation is called a post elution method.

On the other hand, in the case of a composite fiber made of copolyester with sea component, it is common to sequentially perform a water-soluble polymer pretreatment process, a PU impregnation process, and an ultrafine fiber process.

If it is carried out by the preliminary elution method, the treated water-soluble polymer is dissolved and removed in the alkali gamma amount process, so the morphological stability of the nonwoven fabric is lost, and the nonwoven fabric is not only paper-like but also stretched under mechanical tension in the elution process. .

After all, in order to adopt the preliminary extraction method, it is necessary to devise a new pretreatment method that can fix the form of the non-woven fabric while it is stable to the solvent of the sea component, or adopt the post-employment method if it is not. The polyether-based PU elastomer having excellent hydrolysis resistance must be used since it should not be removed from the alkali reducing process.

This is because the alkali reduction process is a process of treating 5 to 15% of caustic soda solution at 95 ° C. for 20 to 50 minutes, so that the polyester-based PU is hydrolyzed in this process to deteriorate physical properties.

On the other hand, polyester-based PU is used a lot in the manufacture of leather-like sheets used for shoes, the reason is as follows.

Polyester-based PU is excellent in hydrolysis resistance and can be applied to any of the pre- and post-eluting methods, but the rubber-like elasticity is large, and micropores are not formed during wet impregnation processing.

On the other hand, polyester-based PU is poor in hydrolysis resistance, and is not applicable to the post-eluting method. However, micro-pores having a size of 5 to 10 µm are formed during wet impregnation, so that the non-woven fabric is evenly distributed in a small amount so that the flexibility and flexibility of the bubbles can be achieved. It has good advantages, and its rubber elasticity is small.

In the study of the present inventors for producing artificial leather having excellent flexibility and bending characteristics without the above-mentioned problems of the prior art, using a copolyester as a sea component of the composite fiber, here polyether-based polyurethane and silica powder After impregnating and filling the solution containing the mixture, the alkali treatment dissolves the silica particles and simultaneously forms the spherical micropores having a size of 5 to 10 μm inside the polyether-based PU elastomer. Artificial leather has been found to have excellent flexibility and bending characteristics.

Therefore, the main object of the present invention is to provide a new artificial leather that can solve the problems of the prior art as described above.

Still another object of the present invention is to provide a method of manufacturing artificial leather.

According to the present invention for achieving the above object, in the artificial leather consisting of a nonwoven fabric and a polyether-based polyurethane elastic body in which the ultrafine fiber bundle is entangled, the fine type of 5 to 10 ㎛ in diameter in the polyether-based polyurethane elastic body Excellent artificial leather is characterized in that the pores are formed.

In addition, according to the present invention, in the manufacture of artificial leather consisting of a nonwoven fabric and a microether-based polyurethane elastic body entangled the ultrafine fiber bundle, silica powder having an average particle diameter of 2 to 10㎛ to the polyether-based polyurethane elastomer 5 to 15 parts by weight of the mixed polyurethane elastomer solution was impregnated into the nonwoven fabric in which the micronized fibers were entangled and solidified, followed by treatment with an alkali solution to make the nonwoven fabric the microfiber and at the same time silica in the polyether polyurethane elastomer Provided is a method for producing artificial leather having excellent flexibility, characterized in that to form spherical micropores in the polyether-based polyurethane elastomer by extraction.

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

Artificial leather according to the present invention is produced by the following method. First, a silica having an appropriate particle size in a PU impregnation solution is filled with a water-soluble polymer in order to stabilize a nonwoven fabric formed by interweaving a composite fiber which can be micronized by alkali treatment and a polyether-based PU elastomer by a wet method. Mix the powder in the appropriate amount.

Thereafter, the water-soluble polymer is completely removed from the water washing process, followed by an alkali reduction process of the sea component to dissolve the silica particles as well as the sea component elution.

The silica used at this time is ultrafine anhydrous silica obtained by reacting silicon-containing volatile compounds in the gas phase.The particles are almost completely spherical, uniform in particle size, low in cohesiveness, and poor in dispersibility, so that they are used in paints, synthetic resins, pharmaceuticals, cosmetics industry, etc. Commercially available examples include Aerosil of Japan and Davidson of USA. Such silica is easily dissolved in an aqueous alkali solution such as caustic soda, and in the process of manufacturing artificial leather using island-in-the-sea microfibers, silica is also melted when hydrolyzing and extracting the copolyester, which is a sea component, using an aqueous alkali solution. At this time, pores are formed in the portion occupied by silica.

The leather-like sheet made in this way is an air bubbles for artificial leather, and exhibits excellent flexibility and bending characteristics, and becomes a product with reduced repulsion characteristics.

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

A needle punched nonwoven fabric is prepared from a composite fiber staple fiber containing copolyester as a sea component, followed by normal water-soluble polymer treatment to stabilize the nonwoven fabric.

Next, the impregnation solution obtained by dispersing and mixing the silica powder having an average particle diameter of 2 to 10 µm in the PU solution to 5 to 15 parts by weight based on the PU solid content is wet-impregnated by a conventional method.

At this time, if the average particle diameter of the silica is less than 2㎛, there is a problem that the pores formed after the alkali reduction are too fine, which lacks flexibility and does not relieve resilience.In the case of larger than 10㎛, the pores become too large and the bending characteristics are deteriorated. There is a drawback of poor fidelity.

In addition, if the silica content is less than 5 wt.% Based on the PU solid content, there is a problem of insufficient flexibility and excessive repulsive elasticity due to the lack of overall porosity. If the content is greater than 15 parts by weight, the overall porosity is so large that the bending property is deteriorated and the feeling of deterioration is poor. There is.

At this time, there are the following things to be noted, firstly, the silica powder mixing method, the silica powder must be dispersed in DMF in advance, and then mixed at high speed to the PU. If the dispersion or mixing of silica is not uniform, care should be taken because the large pores are formed after dissolution of the sea component, resulting in poor bending characteristics.

Secondly, since the sucked silica powder may delay the PU filling in the nonwoven fabric, it is preferable to prolong the impregnation time or to carry out nipping in the middle.

When the sea component is removed and the fiber is subjected to an ultrafine process using a conventional alkali reduction process using the above-described method, silica particles dispersed in the polyether-based PU elastomer are melted by alkali and silica particles are dispersed. Here, spherical micropores having a diameter of 5 to 10 µm are formed.

Next, sanding the surface with a sandpaper-buffer, and if necessary, water repellent, antifouling, and flexible processing, you can obtain artificial leather-like sheets with a sense of fidelity, flexible feel, excellent bending characteristics, and reduced repulsion characteristics. .

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

First, the composite fiber used in the present invention is composite spun or mixed spinning in two kinds of polymer material sea / island form that can form filament, and as the island component, conventional nylon-6, polyethylene terephthalate and the like are used As the co-polyester having different solvent content and solvent solubility, it is possible to use.

In particular, the fineness of the composite fibers after the fineness is 0.3 denier or less, especially 0.1 denier or less is advantageous to obtain the flexibility, strength and tightness of the bubble.

The composite fiber is opened and carded by a conventional nonwoven fabric manufacturing method, and a web is loaded with a desired nonwoven fabric weight, and then needle punched to produce a three-dimensional interwoven nonwoven fabric.

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

On the other hand, in the artificial leather manufacturing process, needle punching nonwoven fabric is usually contracted by hot water, steam or dry heat. When the nylon-6 / copolyester nonwoven fabric having a weight of 500 g / m ² is shrunk by hot water for 5 minutes, the area is about 8%. Shrinkage occurs and in the case of polyethylene terephthalate / copolymer polyester nonwovens, about 15% of area shrinkage occurs, resulting in an improved density of the nonwoven fabrics, resulting in a more compact state.

Next, a water-soluble polymer solution such as polyvinyl alcohol or carboxymethyl cellulose at a concentration of 3 to 15% is padded and dried to give an ultrafine nonwoven fabric 5 to 10% by weight of the fiber. This process is effective not only to stabilize the shape of the bubbles but also to prevent the PU from excessively adhering to the fiber bundle and hardening the touch during the subsequent wet processing.

The next step is PU wet impregnation processing.

The polyether-based PU elastomer used in this process is a linear polymer composed of macro glycols having a molecular weight of 500 to 3,000, diisocyanates and low molecular weight diols, and is usually easily dissolved in DMF.

As the solvent-type polyether PU elastomer used in the present invention, polyether glycol, polyether polyester copolymer glycol, polycarbonate glycol, polysiloxane glycol, and the like are applicable as macroglycol, and isocyanate, 4,4'-di Phenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexyl methane diisocyanate, and the like. Low molecular weight diols include 4,4'-butanediol, ethylene glycol, and the like, and diamine-based chain elongation is also possible.

In the DMF solution of such a polyether PU elastomer, silica powder having an average particle diameter of 2 to 10 µm is previously dissolved in DMF so as to be 5 to 15 parts by weight based on the PU solid content, uniformly dispersed and mixed, and then used as a surfactant, a coloring pigment, and an antioxidant. It is used as an impregnation solution by adding.

After impregnation, the PU is solidified in the non-solvent system of the PU or the non-solvent and solvent mixture system, washed with hot water at 60-80 ° C., and completely removed from the water-soluble polymer filled therein, and then dried. Denseness and the like are expressed. In this case, the amount of PU to be added depends on the concentration of the impregnation solution, the gap between the padding roll, and the density of the nonwoven fabric to be treated. It is preferable to make it negative.

Next, the fiber is finely processed. Since the sea component is a copolyester, it can be treated continuously or batchwise with 5 to 20% of caustic soda solution. For example, a solution of caustic soda at a concentration of 5% is 20 to 50 at 95 ° C. If it is treated for a minute, it is completely decomposed and removed because the polyether-based PU elastomer is not affected by the excellent alkali hydrolysis resistance.

However, since the silica particles mixed during the impregnation process are easily dissolved by strong alkali, the portions occupied by the silica particles in the polyether-based PU elastomer form a spherical micromachining having a diameter of 5 to 10 μm after the elution process. .

The surface of the leather-like sheet thus produced is buffed the surface with sandpaper Nos. 240-320 and again trims seedlings in the same direction using finer sandpaper.

The artificial leather sheet manufactured by the above-described method is composed of a fiber component of fineness of 0.3 to 0.001 denier and a polyether PU elastomer component having fine pores according to the manufacturing method of the present invention, so that physical properties, functionality and appearance are natural. It is similar to suede, and is a bubble for artificial leather with excellent flexibility, bending characteristics, and resilience.

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

% And parts used in the following Examples and Comparative Examples represent the weight percent and parts by weight, respectively.

Example 1

A composite fiber staple of 3 denier, 2 inches in length and 12 to 18 / inch crimp was prepared using 65 parts of nylon-6 as a island component and 35 parts of copolyester as a sea component. In this case, the number of island components was set to 36 pieces per filament. This was opened, carded and needle punched mainly with needle 40 to produce a three-dimensional entangled nonwoven fabric having a weight of 500 g / m ² and an apparent density of 0.20 g / cm ² .

When the nonwoven fabric was shrunk for 5 minutes in hot water at 95 ° C, the area shrinkage was 7%. Next, a 7% aqueous polyvinyl alcohol solution having an average degree of polymerization of 500 was padded with a nonwoven fabric and dried.

Next, the silica powder having an average particle diameter of 2.5 μm was dissolved in DMF in advance to 13 parts with respect to the PU solid content, impregnated with DMF solution of polytetramethylene glycol-based PU having a solid content of 13% of the mixed solid content, and solidified with water, and then Washed with water and dried.

Next, padded and squeezed in a 15% aqueous solution of caustic element, followed by alkali reduction processing for 5 minutes with steam at 105 ° C. to elute the sea component to make microfiber, and to elute the silica in the PU. After forming spherical micromachining in an elastic body, it washed with water and dried.

The surface was then trimmed with a buffing machine equipped with 320 mesh sandpaper.

As a result of observing the cross-section of the artificial leather sheet manufactured in this way, about 0.05 denier fibers were entangled in three dimensions while forming a fiber bundle, and wet-processed polyurethane was bonded between the fiber bundle and the fiber bundle. Or, it was filled in a non-bonded form, and spherical micromachining having a diameter of 5 to 10 µm was uniformly formed in the polyether-based PU elastomer.

The apparent density of the final product was 0.33g / cm ³ , and showed excellent flexibility and flexural characteristics, and artificial leather with reduced rubber elasticity.

Example 2

60 parts of nylon-6 as a island component and 40 parts of copolyester as a sea component were used to prepare 3.5 denier and 51 mm long-spun mixed staple fibers.

In this case, the number of island components was 100 to 200 per filament. When the nonwoven fabric was prepared in the same manner as in Example 1 and contracted under steam at 100 ° C., the area shrinkage was 11%.

Next, a 7% aqueous polyvinyl alcohol solution having an average degree of polymerization of 500 was padded with a nonwoven fabric and dried.

Next, the silica powder having an average particle diameter of 2.5 μm was dissolved in DMF in advance to 13 parts with respect to the PU solid content, impregnated with DMF solution of polytetramethylene glycol-based PU having a solid content of 13% of the mixed solid content, and solidified with water, and then Washed with water and dried.

Next, padded and squeezed in an aqueous solution of caustic soda at a concentration of 15%, followed by alkali reduction processing for 5 minutes with steam at 105 ° C. to elute the sea component to form microfibers, and to elute the silica in the PU to polyether-based PU. Spherical micropores were formed in the elastic body, and then washed with water and dried.

The surface was then trimmed with a buffing machine equipped with 320 mesh sandpaper.

As a result of observing the cross-section of the manufactured artificial leather sheet by electron micrograph, about 0.05 denier fibers were entangled in three dimensions while forming a fiber bundle, and wet processing polyurethane was bonded or bonded to the fiber bundle between the fiber bundle and the fiber bundle. Filled in a non-bonded form, the polyether-based PU elastomer had a uniform spherical micropores having a diameter of 5 to 10㎛.

The artificial leather thus obtained has excellent flexibility and flexural characteristics, consisting of 65% of the ultrafine fiber concentrator and 35% of the polyether-based PU elastomer, and exhibited reduced rubber elasticity.

Example 3

In the same manner as in Example 1, 12% polytetramethylene glycol-based poly (polyethylene) -based polystyrene was prepared by dissolving and mixing silica powder having an average particle diameter of 8.5 μm in 5 parts with respect to PU solids after manufacturing, shrinking, and water-soluble polymer padding. It was impregnated with a DMF solution of urethane, solidified in water, washed with water and dried in a conventional manner.

Thereafter, the process was performed in the same manner as in Example 1, and when the cross section of the artificial leather sheet was observed by electron micrographs, fibers of about 0.05 denier were entangled in three dimensions while forming a fiber bundle, and were present between the fiber bundle and the fiber bundle. In the polyether-based PU elastomer, spherical micropores having a diameter of 5 to 10 µm were uniformly distributed and formed. The elasticity and flexural characteristics of the polyether-based PU elastomers were excellent. Indicated.

Comparative Example 1

A nonwoven fabric was prepared in the same manner as in Example 1 and subjected to hydrothermal shrinkage. However, the silica powder used in Example 1 was not mixed, and other process conditions were the same. After processing, the density of the forge was 0.36g / cm ^{3, which} was very dense but the touch was somewhat hard and the wrinkle formation was not natural during bending.

Comparative Example 2

A nonwoven fabric was prepared in the same manner as in Example 1 and subjected to hydrothermal shrinkage. However, in the PU impregnation process, 5 parts of silica powder having an average particle diameter of 15 μm was mixed, and other process conditions were the same. After processing, the artificial leather top sheet has a large crease when it is bent, and a lack of fidelity.

Comparative Example 3

A nonwoven fabric was prepared in the same manner as in Example 1 and subjected to hydrothermal shrinkage. However, in the PU impregnation process, 20 parts of silica powder having an average particle diameter of 5 μm was mixed, and other process conditions were the same. At this time, the artificial leather sheet of the Forge was wrinkled during bending was large, lacking a sense of fidelity.

Claims (2)

An artificial leather composed of a nonwoven fabric and a polyether-based polyurethane elastic body in which an ultrafine fiber bundle is entangled, wherein the spherical micropores having a diameter of 5 to 10 μm are formed inside the polyether-based polyurethane elastic body. Leather. 5 to 15 parts by weight of silica powder having an average particle diameter of 2 to 10 μm in the polyether polyurethane elastomer is prepared in the artificial leather comprising a nonwoven fabric interwoven with an ultrafine fiber bundle and a polyether polyurethane elastomer. The mixed polyurethane elastomer solution is impregnated into a nonwoven fabric in which fine fibers are entangled and coagulated, and then treated with an alkali solution to make the nonwoven fabric microfiber and at the same time extracting the silica in the polyether polyurethane elastomer to extract a polyether-based poly A method of manufacturing artificial leather with excellent flexibility, characterized in that to form spherical micropores in the urethane elastic body.