KR20150119658A - Artificial Leather Using Aqueous Polyurethane, and Method for Manufacturing the Same - Google Patents

Abstract

The present invention relates to artificial leather having excellent elasticity and voluminosity which is eco-friendly manufactured using aqueous polyurethane and expandable microcapsule and a manufacturing method thereof. The method for manufacturing the artificial leather according to the present invention does not use an organic solvent, thereby being eco-friendly and harmless to a human body. The method increases compression rate and restoration rate of the artificial leather by the action of the expandable microcapsule in the artificial leather manufacturing process, thereby providing excellent elasticity. The method provides excellent strength and durability and shows regular physical properties over all the artificial leather, thereby replacing natural leather and providing comparable or better performance as compared with the natural leather.

Description

Technical Field [0001] The present invention relates to an artificial leather using a water-based polyurethane and a method for manufacturing the same,

The present invention relates to an artificial leather having excellent elasticity and bulkiness while being produced environmentally using an aqueous polyurethane and an expandable microcapsule, and a method for producing the same.

Natural leather obtained from animal raw hide has been widely used as a raw material for a long time, but natural leather is limited in resources, and not only does it not meet the demand, but also has a tendency to decrease production in terms of animal protection as well as various environmental problems .

As a result, artificial leather is naturally replaced by artificial leather, and has a similar texture and appearance to natural leather and is widely used in various fields such as shoes, clothes, gloves, miscellaneous goods, furniture, automobile interior materials and the like.

Many artificial and synthetic leather products such as nylon leather, PVC leather, and PU dry type leather have been introduced as artificial leather. Nonwoven fabrics made of microfine fibers include poly Urethane resin, amino resin, etc., alone or in copolymerized form, can be used as a substitute for natural leather, as well as to compensate for the disadvantages of natural leather. It is expanding.

Such artificial leather is largely manufactured by a wet method, a dry method and a paper method. The dry method is a method in which a composition comprising toluene, acetone, isopropyl, alcohol, polyurethane, etc. is applied on a release paper and then adhered to a textile fabric using an adhesive And a wet method is a method of applying a composition containing polyurethane, dimethyl formaldehyde and the like to a textile fabric to form a leather layer and passing it through water at a high temperature to cure the paper.

However, conventional artificial leather has a limitation in realizing physical strength, structure, performance, appearance and the like as natural leather, such as a lack of durability and a stiff feeling because the leather itself is not soft, and since organic chemicals are used, There is a risk of occurrence of odor and pollution as well as a separate treatment facility is required.

The leather produced by the dry method and the paper method has a problem of poor breathability and moisture permeability because the leather layer and the fabric are adhered with an adhesive agent. However, artificial leather manufactured by the wet method has some degree of breathability and moisture permeability, And other physical properties, so that polyurethane which is suitable as a material of artificial leather and can impart a bulk feeling to artificial leather has been mainly used.

Polyurethane artificial leather is produced by polymerizing polyol, isocyanate, chain extender, etc., which are urethane raw materials, in an organic solvent such as dimethylformamide (DMF) The microporous structure allows the artificial leather to exhibit the bulkiness and the pore size can be controlled by changing the rate of the substitution reaction, The volume feeling can be improved.

Conventional solvent-based polyurethane, which is the main material of polyurethane artificial leather, has been conventionally prepared by solution polymerization due to the hydrophobicity of raw materials. Since dimethylformamide, which is an organic solvent, is used as a reaction medium or used as a diluting solvent, It causes environmental problems such as air pollution and water pollution caused by the release of harmful DMF solvent, and adversely affects the human body.

In addition, the solvent-type polyurethane generally has poor hydrolysis resistance to water, and when exposed to water for a long time, the polyurethane is hydrolyzed as well as the friction fastness is lowered. Due to the steady increase in the solvent price, Type polyurethane is gradually replaced by an aqueous polyurethane.

The aqueous polyurethane has attracted attention as environmentally friendly material because it does not use dimethylformamide, which is an organic solvent, but it has disadvantages such as insufficient adhesive force and mechanical properties, low drying speed and storage stability, The high solid content required for the improvement of the speed lowers the stability of the particles and causes a problem of agglomeration among the particles.

To solve this problem, Korean Patent Registration No. 10-0535871 discloses a resin composition obtained by reacting a polyol, a silicone additive and an isocyanate with water, dispersing the resin composition, impregnating the nonwoven fabric with the resin composition, The present invention relates to a process for producing artificial leather through which a water-soluble polyurethane is used, which is similar to artificial leather produced by using an oil-based polyurethane and solves environmental problems caused by odor and organic solvents which are problematic when using oily polyurethane, Is advantageous in manufacturing cost.

However, in the above method, since water is evaporated by heat during drying and the aqueous polyurethane migrates to the surface of the nonwoven fabric, and the fiber and the polyurethane adhere to the surface to form a film layer, a nonporous structure may appear, There is a difference in the physical properties inside, so that appearance defects such as fuzz occurrence and deformation in the artificial leather may occur.

As a method for solving this problem, Korean Patent Laid-Open Publication No. 10-2013-0128955 discloses a reaction polymer of a urethane prepolymer formed by reacting a polyol and an isocyanate and containing a hydroxyl group (-OH) group at both terminals and an isocyanate compound A method of manufacturing artificial leather using a solventless urethane binder is proposed.

The present invention improves molding processability and production efficiency by eliminating the use of a solvent and eliminates the problem of defective appearance. However, the artificial leather is not soft and stiff, and the feeling of fullness and volume, which are advantages of polyurethane synthetic leather, There is a disadvantage that the quality is deteriorated.

In order to realize the volume feeling of such polyurethane artificial leather, Korean Patent Registration No. 10-1266009 discloses a method of manufacturing a double-woven fabric type artificial leather in which a water-soluble urethane resin composition is coated on a double-woven fabric, It is not only breathable but also has excellent waterproofness and moisture permeability and can provide a smooth and natural feel and appearance such as natural suede.

However, the artificial leather of the present invention has disadvantages that voids are not formed between the fibers constituting the fabric and the urethane resin, so that the elasticity and elasticity are insufficient and the physical strength performance of natural leather is not achieved.

A problem to be solved by the present invention is to provide an environmentally-friendly artificial leather manufacturing method and a method of manufacturing an artificial leather which are produced by using an aqueous polyurethane resin and which have physical strength and appearance similar to those of natural leather, To provide an artificial leather.

In order to solve the above problems, the present invention provides a method for producing an aqueous polyurethane resin composition, comprising: preparing an aqueous polyurethane resin composition comprising 10 to 30% by weight of an aqueous polyurethane; 3 to 7% by weight of an expandable microcapsule; Impregnating the resin composition with the fiber substrate or applying the resin composition to the fiber substrate; And curing the fiber base material to which the resin composition is added by infrared ray.

At this time, the aqueous polyurethane preferably has a particle size of 1 탆 or less and a viscosity of 300 mPa s or less, and the microcapsule preferably has an average particle diameter of 10 to 30 탆.

The expandable microcapsule may be particles containing carbon dioxide in an outer wall formed of a copolymer of vinylidene chloride or acrylonitrile.

The curing is preferably carried out at a temperature of 70 to 200 DEG C for 2 to 20 minutes, and the infrared ray is preferably a medium infrared ray having a wavelength range of 2.5 to 25 mu m.

In addition, the present invention provides an artificial leather made by using the aqueous polyurethane produced by the above method.

The process for producing artificial leather according to the present invention is environmentally friendly and harmless to the human body because it does not use a volatile organic solvent, and the compressibility and recovery rate of artificial leather are increased by the action of the expandable microcapsule in the process of producing artificial leather, .

In addition, since it has excellent strength and durability and exhibits uniform physical properties throughout the artificial leather, it can provide equivalent or superior performance by replacing conventional natural leather.

Artificial leather is generally produced by impregnating a fiber base material such as a nonwoven fabric with a polyurethane resin or by applying a polyurethane resin to a fiber base material and curing the fiber base material.

In the present invention, by using an aqueous polyurethane resin as the polyurethane resin and using water as a solvent instead of an organic solvent such as dimethylformamide, it is possible to eliminate environment and harmful factors to the human body, and an expandable microcapsule microcapsule) is added to increase the elasticity and volume of the artificial leather by the expansion of the microcapsules during the curing process, thereby improving the emotional quality.

Polyurethane is a generic name of a polymer having a urethane bond in the central part constituting the main chain, and is produced by bonding two or more isocyanates with an active hydrogen compound such as a polyol. Since the polyurethane is easily elongated as an elastic body, , The elongation of the synthetic leather can be improved.

The aqueous polyurethane used in the present invention is a water-soluble polyurethane, a self-emulsifying polyurethane having an anionic, cationic or nonionic hydrophilic group introduced into a polyurethane resin skeleton, a forced- emulsifier type) polyurethane, or a mixture of a hydrophilic polyurethane resin and a large amount of emulsifier and emulsified and dispersed by mechanical shear force.

The aqueous polyurethane exhibits elasticity, elasticity and flexibility possessed by the water-insoluble polyurethane, and imparts properties such as elasticity, stretchability and durability unique to polyurethane in artificial leather as a final product. Thereby forming a three-dimensional crosslinked structure so that the microcapsules are stably expanded in the fibrous substrate and are not desorbed.

The method for producing artificial leather according to the present invention comprises first preparing an aqueous polyurethane resin composition containing 10 to 30% by weight of an aqueous polyurethane, 3 to 7% by weight of an expandable microcapsule and the remainder of water, And then applying it to the fiber substrate and curing it.

The aqueous polyurethane is preferably a nonionic polymer having a particle size of 1 탆 or less and a viscosity of 300 mPa s or less in consideration of impregnation workability, and commercially available commercial products can be used.

If the content of the aqueous polyurethane in the resin composition is less than 10% by weight, the microcapsules are hardly easily adhered to the fiber substrate. If the content is more than 30% by weight, wrinkles may be generated in the artificial leather, .

The microcapsule is a thermally expansible polymer fine particle containing a hydrocarbon gas in a core of an outer shell. When heat is applied to the microcapsule, the size of the microcapsule increases to 30 times as the gas inside the polymer is expanded. Preferably, the hydrocarbon-based gas is carbon dioxide (CO ₂ ), and the material forming the outer wall is a copolymer of vinylidene chloride and acrylonitrile. However, the present invention is not limited thereto. It can be used if it is elastic and has a human-friendly material.

The microcapsules preferably have an average particle size of 10 to 30 占 퐉 in terms of adhesion to the fibrous substrate, workability and durability of the artificial leather. If it is less than 10 占 퐉, the microcapsules can not be uniformly adhered or impregnated into the fibrous substrate, The mechanical strength and durability may be deteriorated, and the microcapsule may be expanded on the surface of the artificial leather, resulting in deterioration of the surface quality such as dropping of the napped portion, which is not preferable.

When the content of the microcapsule is less than 3% by weight in the resin composition, the formation of the porous structure is insignificant in the artificial leather as the final product. When the content is more than 7% by weight, the porous structure is excessively formed, Which is undesirable.

The curing is a process of heating the resin composition to evaporate water and solidify the polyurethane. In this process, microcapsules expand to form voids in the solidified polyurethane, thereby forming a porous structure in artificial leather have.

However, when the heating is performed using a heating medium such as a heater or a heater, heat is transferred from the heating medium to the resin composition by the convection between the high temperature heat source and the resin composition and the thermal conduction in the resin composition, The expansion of the microcapsules proceeds in the inward direction with respect to the surface of the resin composition applied to the fiber substrate.

If the drying and curing of the resin composition can not proceed uniformly at the same time throughout the resin composition, water evaporation of the aqueous polyurethane and expansion of the microcapsules are not uniform, so that the shape of the cured aqueous polyurethane is distorted, And the physical and emotional properties of artificial leather are deteriorated and there is a problem of non-uniformity.

In order to prevent such a problem, in the present invention, as means for heating the resin composition, infrared rays which can uniformly heat the surface and the interior of the resin composition are used.

An infrared ray (IR) is an electromagnetic wave whose wavelength is longer than that of red light, which is visible light. It has a wavelength range of 0.75 ~ 0.8 ㎛ to 1 ㎜, and a wavelength range of usually 2.5 ㎛ or less is called near infrared ray (NIR) The wavelength range of 2.5 ~ 25 ㎛ is referred to as mid infrared ray (MIR), and the wavelength range of 25 ㎛ or more is called far infrared ray (FIR).

In the infrared region, many compounds are absorbed by the reference vibration. In the near-infrared region, the reference vibration generated in the mid-infrared region is absorbed by harmonics or coupling sounds. In the far-infrared region, appear.

If the gas contained in the microcapsule is carbon dioxide, the dipole efficiency of the carbon dioxide is 0 (zero). However, if the dipole efficiency of the molecule is zero or the dipole efficiency is changed due to the rotation, Because of the change of efficiency, infrared rays can be absorbed.

Since water (H ₂ O) is a polar molecule and a change in dipole efficiency occurs due to atomic vibration, water has a stronger infrared absorption power than carbon dioxide, and water as a solvent of a water-based resin composition can be efficiently heated. Thereby enabling efficient curing of the resin.

Infrared energy absorbed in the resin composition is converted into heat energy. Since infrared heat is easy to concentrate and disperse the energy to be emitted, the operating environment is clean, and no heat medium is required, direct infrared energy So that the entire resin composition is uniformly heated, so that deformation and uneven physical properties of the artificial leather do not occur.

The polyurethane component is partially dissolved and dissolved by the moisture in the resin composition during the heating by the infrared irradiation, and the polyurethane component is cured while forming a bonding point with the outer wall of the fiber base and the microcapsule, The bonding force is increased to suppress the peeling of artificial leather and the bonding force between the polyurethane component and the microcapsule in the resin composition increases so that the microcapsules are stably fixed in the cured polyurethane.

The heating by infrared rays is preferably carried out at a temperature of 70 to 200 DEG C for 2 to 20 minutes. When the moisture is evaporated by heating, the polyurethane solidifies and at the same time, the microcapsules expand and the poly The microcapsules are shrunk as the microcapsules are cooled down and the pores are formed in the artificial leather so that the porous structure is formed, thereby increasing the breathability and elasticity of the artificial leather.

If the temperature is less than 70 ° C or the drying time is less than 2 minutes, the microcapsules do not sufficiently expand to form a porous structure. When the temperature exceeds 200 ° C or exceeds 20 minutes, the microcapsules are excessively expanded, And the bonding strength between the microcapsule, the fiber substrate and the polyurethane is weakened, and the mechanical strength, durability and volume are lowered, which is undesirable.

In heating by infrared radiation, it is important to select an appropriate wavelength at which radiated energy is converted into heat from the heating target material. Water or an organic substance (aqueous polyurethane, microcapsule) which is a component of the resin composition has a strong absorption band And exhibits excellent energy transfer characteristics, it is more preferable to use the middle infrared ray as the heating means of the present invention.

Since the infrared ray has excellent drying time and drying efficiency, it occupies a small space of the facility, it can be dried at a high speed and high efficiency by using only the energy of the effective wavelength band, and thus energy can be saved. It is possible to reduce the drying period to less than half compared with the hot air drying method of convection and conduction method because the heat transfer rate is faster than that of the conventional method. Since it is a direct method, the same effect as that of the hot air drying method can be obtained even at a low temperature, have.

Hereinafter, the present invention will be described in more detail with reference to the following examples, comparative examples and test examples.

It is to be understood, however, that the invention is not to be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Will be apparent to those skilled in the art to which the present invention pertains.

≪ Examples 1 to 3 and Comparative Examples 1 and 2 >

A nonwoven fabric having a basis weight of 700 g / m < 2 >, a post-3.0 mm, and an apparent density of 0.3 g / m < 3 >

Next, a resin composition obtained by mixing aqueous polyurethane, carbon dioxide-containing expandable microcapsules (EXPANCEL 461 DE 20, Akzo Novel, Netherlands) and water in the proportions shown in Table 1 below was applied on one surface of the nonwoven fabric to a thickness of 1 mm .

The non-woven fabric coated with the resin composition was supplied to a medium-infrared drying system (MS 9108 H, Litzensa, Korea), heated at 80 캜 for 7 minutes using medium-wavelength infrared light having a wavelength of 5 탆, cooled to room temperature, .

Composition of resin composition (% by weight) Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Aqueous polyurethane 20 20 20 20 20 Microcapsule 3 5 7 0 10 water 77 75 73 80 70

≪ Test Example >

For each of the artificial leather prepared in Examples 1 to 3 and Comparative Examples 1 and 2, a sample was taken at three points, and the compressibility, the recovery rate, the tensile strength, the abrasion resistance and the fastness to rubbing were measured and the average value thereof is shown in Table 2 .

The compressive elasticity (thickness direction) of artificial leather can be grasped as a compressibility. The compressibility is measured by holding a circular impression cylinder at a load of 900 gf / cm < 2 > for 30 seconds, The maximum thickness (T1) of artificial leather at one point was measured up to 1/1000 mm.

The thickness (T3) of the artificial leather was measured to 1/1000 mm at 30 seconds after removing the initial load, measuring the thickness (T2) to 1/1000 mm after applying the initial load for 30 seconds, The compression ratio and the restoration ratio were calculated using the following equations.

Compression ratio (%) = (T1-T2) / T1100

Recovery rate = (T3-T2) / (T1-T2) x100

The tensile strength was measured according to the ASTM D 5035 test standard and measured using a tensile strength meter (Instron, USA) at a speed of 300 mm / min, a width of 50 mm, a length of 100 mm, a thickness of 0.8 mm and a warp direction .

The abrasion resistance of the specimen was measured by the color abrasion method (Martindale method) (ISO 12947-2: 1998 (E)), and the specimen was pressed with a load of 12 고 and rotated 35,000 cycles. The color discoloration of the friction area was judged to be gray scale And the rubbing fastness was measured in accordance with KS K ISO 105-X12 method.

Physical properties of artificial leather Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Compression rate (%) 15.7 16.2 17.6 13.2 18.5 Restoration rate (%) 99.2 99.5 99.6 96.6 99.5 Tensile strength (kgf / cm2) 8.3 7.9 7.5 8.8 6.9 Abrasion resistance (grade) 4.3 4.2 4.0 4.5 3.6 Friction fastness
(class) dry 4.7 4.5 4.1 4.9 3.7 wet 4.1 4.0 3.8 4.5 2.8

As a result of the above Table 2, it can be seen that as the content of the microcapsule increases, the elasticity of the artificial leather is improved by increasing the compression ratio and the restoration ratio, and in Comparative Example 1 in which the microcapsule is not contained, the compression ratio and the restoration ratio are very small, The elasticity and the quality of the sensibility are poor.

In addition, as the content of microcapsules increases, the tensile strength gradually decreases. In Comparative Example 2 containing 10% by weight, 6.9 kgf / cm 2 is exhibited. When the microcapsules are contained excessively, the mechanical properties of artificial leather are lowered and durability is lowered .

The abrasion resistance and the friction fastness decreased as the content of the microcapsules increased. As shown in Comparative Example 2, when the content of the microcapsules was too high, the artificial leather was quickly damaged by abrasion and friction.

Claims (7)

Preparing an aqueous polyurethane resin composition comprising 10 to 30% by weight of an aqueous polyurethane, 3 to 7% by weight of an expandable microcapsule and the remainder of water;
Impregnating the resin composition with the fiber substrate or applying the resin composition to the fiber substrate; And
And curing the fiber base material to which the resin composition is added by infrared ray. The method according to claim 1,
Wherein the aqueous polyurethane has a particle size of 1 占 퐉 or less and a viscosity of 300 mPa 占 퐏 or less. The method according to claim 1,
Wherein the expandable microcapsule is a particle in which carbon dioxide is contained in an outer wall formed of a copolymer of vinylidene chloride or acrylonitrile. The method according to claim 1,
Wherein the microcapsules have an average particle diameter of 10 to 30 占 퐉. The method according to claim 1,
Wherein the curing is carried out at a temperature of 70 to 200 DEG C for 2 to 20 minutes. The method according to claim 1,
Wherein the infrared ray is a medium infrared ray having a wavelength range of 2.5 to 25 占 퐉. 6. An artificial leather produced by the process according to any one of claims 1 to 6 using an aqueous polyurethane.