JP3015130B2 - Method for producing a leather-like sheet having good surface smoothness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a leather-like sheet having good flexibility, excellent peeling strength, less fuzz defects and excellent surface smoothness.

[0002]

2. Description of the Related Art Conventionally, in the production of a leather-like sheet having a porous layer on the surface, in order to obtain a leather-like sheet having a smooth surface and a small amount of fluff (a fiber of a base layer is pushed up on a coat layer), a fiber-like sheet is used. There is known a method in which a porous substrate layer is smoothed and then a surface porous layer is subjected to a coating treatment or the like. For example, a method of gluing and fixing a fibrous substrate with PVA or the like and buffing the surface to smooth it is disclosed in JP-B-48-12962, JP-B-52-18241, and the fibers on the substrate surface are heat-sealed. After that, a method of impregnating and coagulating to obtain a smooth leather-like sheet is disclosed in JP-B-53-22121.
In Japanese Patent Application Laid-Open No. Sho 49-49, there is disclosed a method in which a resin is applied to the surface of a non-woven fabric, pressed and dried on a drum, smoothed, and then impregnated or coated with a resin dissolved in a non-solvent of the surface-coated resin.
No. 118303 and Japanese Patent Publication No. 57-29590.

[0003] However, in the prior art, in the smoothing by buffing, a leather-like sheet having a smooth surface can be obtained, but the tensile strength is weakened because the surface fibers are cut, or the coat layer and the base layer are not bonded to each other. There is a problem that the peel strength between the layers is low. On the other hand, when the surface fibers are fused, there is a problem that if the fusion point is too large, the fiber becomes hard, and if the fusion point is small, the surface smoothness becomes poor and the production is unstable. Also, in the fuzz pressing method using a resin, when a resin insoluble in the coating composition or having a small degree of swelling is used as the surface resin, the adhesion between the surface resin and the coating layer resin is insufficient, and high peel strength is obtained. Is difficult to obtain.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide good flexibility, excellent peeling strength, and few fluff defects. Another object of the present invention is to provide a leather-like sheet having excellent surface smoothness.

[0005]

According to the present invention, there is provided a method for producing a porous sheet having a porous layer of a high molecular polymer mainly composed of an elastic polymer laminated on the surface of a fibrous base material. The 100% elongation stress of a film formed on the surface of a nonwoven fabric having an apparent density of 0.15 to 0.40 g / cm ³ is 1
70 to 95% of the surface is coated with a polyurethane film by applying and drying a solution or dispersion mainly composed of polyurethane which is soluble in N, N-dimethylformamide at room temperature and is 5 to 85 kg / cm ^2. (2) With the fluffed surface of the nonwoven fabric as the upper surface, the solvent of the resin mainly composed of polyurethane is N,
A step of impregnating with a solution containing N-dimethylformamide having a viscosity of 30 poise or less, (3) a resin containing polyurethane as a main component from the upper surface of the fluffed nonwoven fabric,
A step of coating and coating a solution containing N-dimethylformamide having a viscosity of 80 poise or more, and (4) a step of coagulating and drying the impregnated and applied polyurethane solution in a solvent containing a non-solvent of polyurethane and sequentially performing the steps. This is a method for producing a leather-like sheet having good surface smoothness.

The nonwoven fabric used in the method of the present invention is a three-dimensionally entangled nonwoven fabric obtained by adding natural fibers or regenerated fibers to one or more components of synthetic fibers, as the case may be. The presence or absence of the binder resin does not matter. The synthetic fibers constituting the non-woven fabric are not limited to fibers having a single composition, but may be fibers obtained by mixing or spinning several kinds of polymers. In the case of using a microfiber-generating fiber obtained by mixing or spinning several types of polymers, the present method may be carried out on a nonwoven fabric obtained by ultrafine fibering. Good. A more flexible leather-like sheet can be obtained by subjecting the polyurethane to a fine fiber treatment after coagulation.

[0007] Examples of the polymer used for the fiber include polyamide, polyester, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, and polyurethane. As a fiber having a single composition, polyethylene terephthalate, polyester such as polybutylene terephthalate, or a copolyester obtained by copolymerizing an aromatic or aliphatic dicarboxylic acid or glycol with these polyesters is melt-spun, and then at 60 to 65 ° C. Highly shrinkable fibers obtained by stretching 1.5 to 3.0 times in warm water and drying at 65 ° C. or lower, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and aromatic or aliphatic polyesters Melt spinning copolyester copolymerized with dicarboxylic acid or glycol,
Polyester fibers such as latent spontaneously extensible fibers obtained by stretching by 2 to 4 times in warm water at 60 to 65 ° C, heat-treating in warm water at 85 to 95 ° C, and drying at 100 ° C or less. Polyamide fibers obtained from 6-nylon, 66-nylon and the like are preferred. Examples of the multicomponent fiber include a fiber obtained by spinning or composite spinning of polyethylene and polyamide (nylon-6), a fiber obtained by spinning or composite spinning of polyethylene and polyethylene terephthalate, or nylon-6 having a terminal amino group blocked with polyurethane. Composite spun fibers are preferred.

The density of the nonwoven fabric to which the method of the present invention is applied is 0.15 to 0.40 g / cm ³ , preferably 0.20 to 0.40 g / cm ³ .
0.35 g / cm ³ , needle punching, three-dimensional entanglement treatment by jetting liquid or gas, shrinking treatment in warm water if necessary, heating the sheet, and then pressing with a metal roll Thus, a predetermined density can be obtained. Density of the nonwoven fabric is hardly completely erase the unevenness of the surface may be applied to the method of the present invention is 0.15 g / cm ³ or less, is greater than 0.40 g / cm ^3, on the other hand, the texture of the product It is not preferable because it becomes hard and impregnating property in a post-process becomes poor, thereby impairing productivity such as reduction in processing speed.

Next, the polyurethane applied to the surface of the non-woven fabric has a 100% elongation stress of 15% when formed into a film.
８５85 kg / cm ² and the film must be a polyurethane soluble in DMF at room temperature. Examples of such a polyurethane include a substantially linear one-part solution type polyurethane, a water-dispersible polyurethane emulsified and dispersed in water, and a water-soluble urethane resin dispersed in an ionic colloid. A mixture of more than one species can be used.

[0010] If polyurethane having a 100% elongation stress of less than 15 kg / cm ² in the case of a film is used, the tackiness of the coated surface increases, which affects workability during coating and post-processing. Use of a polyurethane having a 100% elongation stress of more than 85 kg / cm ² is not preferred because the feeling becomes hard and the bending resistance becomes poor. In addition, as the polyurethane used, from the viewpoint of workability in the post-process,
A substantially linear one-pack type polyurethane is preferable, and when a two-pack type polyurethane or a self-cross-linking type polyurethane is used in combination, it is necessary to adjust the amount of the cross-linking agent so as to easily swell with DMF.

The polyurethane is applied to the surface of the nonwoven fabric in the form of a solvent solution of DMF, methyl ethyl ketone, toluene, isopropyl alcohol, ethyl acetate or the like, or an emulsion containing a penetrating agent, an antifoaming agent, a thickener and the like. be able to. The amount applied to the surface of the nonwoven fabric is determined by the constituent fibers of the nonwoven fabric, the basis weight, the specific gravity, and the purpose of use of the obtained base material. However, drying may cover 70 to 95% of the surface with a polyurethane film. It is important that the amount of coating is 10 g / m ²
５０50 g / m ² , more preferably 15 g / m ^{2 to} 35 g / m ²
It is. If the coating area of the polyurethane film is less than 70%, the fluff pressing becomes poor, and if it is 95% or more, impregnation in a subsequent step is difficult, and productivity is impaired such as a decrease in peel strength and a decrease in processing speed, which is not preferable.

The polyurethane coating is not a continuous coating having no pores but a discontinuous coating having the above-mentioned coverage or a continuous coating having openings, and the thickness of the coating is preferably uniform. The method of applying the polyurethane to the surface of the nonwoven fabric is a method of applying a predetermined amount on a release paper film with a comma coater or the like, bonding the nonwoven fabric in a wet state, pressing and drying, or a gravure coating, spray spraying, reverse coating, or the like. For example, there is a method in which the non-woven fabric is directly applied to the surface of the non-woven fabric by application and dried and smoothed by a hot roll press, a hot drum, a stainless steel belt machine, or the like. At this time, it is more effective to coat a surface of a hot roll press, a heat drum or the like with a resin having good releasability such as silicone or Teflon to obtain a smooth surface.

Next, as the resin impregnated in the nonwoven fabric, the mechanical strength required for the nonwoven fabric as a base material for artificial leather,
Polyurethane resins are most preferred in terms of satisfying flex resistance and texture. The polyurethane elastomer used in the present invention comprises a polymer glycol having a molecular weight of 600 to 5,000, an organic diisocyanate and a molecular weight of 500.
Is a low-molecular-weight compound having less than 2 and two active hydrogen atoms, and can be produced by polymerizing by a known means. As a solvent for the polyurethane elastomer, DMF, diethylformamide, dimethylacetamide, tetrahydrofuran, dioxane, dimethylsulfoxide and the like can be used, but DMF is most preferable.

In the case of using the usual double-sided impregnation method, the polyurethane coating applied to the surface of the nonwoven fabric is dissolved in the solvent of the impregnating solution and the surface becomes fluffy. The upper surface is the upper surface, and the impregnating liquid is preferably rubbed and impregnated from the opposite lower surface using a flat roll or a trapezoidal or hatched gravure roll. The impregnating liquid must be a solution having a viscosity of 30 poise or less at the temperature of the impregnating liquid, more preferably a solution having a viscosity of 20 poise or less, and must contain at least 50% or more of DMF as a solvent. If the viscosity exceeds 30 poise, the immersion wetting resistance increases because the viscosity is too high, and impregnation from the lower surface becomes difficult. DMF as solvent
If less than 50%, the dissolution of the polyurethane coating applied to the surface of the nonwoven fabric is insufficient, the adhesion between the substrate layer and the polyurethane coating resin becomes poor, and the peel strength decreases. In the nonwoven fabric, the coverage area of the polyurethane film is 70%.
It is also necessary to be 95% because of the similar impregnation workability from the lower surface. That is, if the coating area is less than 70%, the fluffing effect is small, and if it exceeds 95%, the escape of air contained in the base layer during impregnation becomes poor, and the impregnation time needs to be lengthened. The film will dissolve too much and will fluff all over.

The polyurethane for coating the surface coat is a polyurethane composed of a polymer glycol having a molecular weight of 600 to 5,000, an organic diisocyanate and a low molecular weight compound having a molecular weight of less than 500 and two active hydrogen atoms. It can be produced by changing the polymerization by a known means. As the solvent for the polyurethane elastomer, DMF, diethylformamide, dimethylacetamide, tetrahydrofuran, dioxane, dimethylsulfoxide and the like are preferable.
F is most preferred. The coating solution must be a solution having a viscosity of 80 poise or more at the temperature of the coating solution, more preferably a solution having a viscosity of 100 poise or more, and must contain at least 50% of DMF as a solvent.
If the viscosity is less than 80 poise, the viscosity is too low, and the resin is sunk into the base layer so strongly that a smooth surface having a uniform thickness cannot be obtained. If the DMF as a solvent is less than 50%, the polyurethane film applied on the surface of the nonwoven fabric is insufficiently dissolved,
The adhesion between the coat layer and the polyurethane film becomes poor,
Peel strength decreases. The coating of the coating liquid can be performed by a usual coating method such as a knife coater, a comma coater, and a reverse coater. Further, additives such as various coagulation regulators, pigments, antioxidants, and light stabilizers may be added to the impregnating composition liquid and the coating composition liquid according to the purpose.

The coating amount of the coating liquid may be arbitrarily selected depending on the product to be applied. In this method, the surface smoothness of the non-woven fabric impregnated with polyurethane is improved by the effect of the polyurethane coating, Since the penetration is small, the application amount can be reduced. For this reason, the thickness of the coat layer can be reduced, and a product with silver having a texture very similar to natural leather with little rubber rebound can be obtained.

As the coagulating liquid, a non-solvent of the polymer which is at least partially miscible with the solvent of the polymer is used. Water, methanol, ethanol, isopropanol, and the like can be used as the coagulation bath, but water is most advantageous from the viewpoint of economy. Further, those in which a polymer solvent is mixed are also suitable as a coagulation bath. The obtained leather-like sheet material is subjected to a fine treatment of fibers as necessary, and is subjected to finishing treatments such as coloring, application of a finishing layer, embossing, and embossing to finish the leather-like sheet.

[0018]

According to the present invention, the nonwoven fabric, which is mostly covered with a thin polyurethane layer and covered with fluff, is impregnated with an impregnating liquid having a specific viscosity from the lower surface, and then a coating liquid having a specific viscosity is applied and wet coagulated. is there. The polyurethane for fluff binding absorbs and dissolves DMF contained in the impregnating liquid impregnated from the lower surface, but does not have sufficient fluidity, and the fluff on the surface of the nonwoven fabric is still suppressed. Furthermore, a polyurethane solution having a specific viscosity is applied by coating.Since there is a smooth and high-viscosity polyurethane solution layer in the lower layer, a thin coat layer is applied to improve the surface smoothness, especially the leather-like sheet material with less fuzz. It can be obtained by a simple manufacturing method. In addition, since the polyurethane coating layer for fluff binding is appropriately dissolved by the common solvent contained in the impregnating liquid and the coating liquid for coating, the compatibility between the coating layer and the coating layer and the impregnating layer is good, the adhesiveness is good, and the peeling is performed. A leather-like sheet having high strength can be obtained.

[0019]

Next, embodiments of the present invention will be described with reference to specific examples. The parts and percentages in the examples relate to weight unless otherwise specified. In addition, the measuring method of the product in this invention is based on the following method. (1) 100% elongation stress: A dry film having a thickness of 50 to 100 μm is prepared, a sample is cut out to a width of 2.5 cm, the sample length is set to 5 cm, and the sample is pulled at a speed of 10 cm / min. And the quotient divided by the width. (2) DMF solubility: 50-100 μm dry coating was applied to DM
The dissolution rate when immersed in F (bath ratio about 1: 100) at room temperature for 15 minutes was evaluated according to the following criteria. …: Dissolution rate of 95% or more (undissolved solid content less than 5%) △: dissolution rate of 50% or more and less than 95% (undissolved solid content of 5% or more and less than 50%) ×: dissolution rate of less than 50% (undissolved solid content) (50% or more)

(3) Coverage: The surface-coated fibrous substrate was observed with a scanning electron microscope photograph, and the coverage of the nonwoven fabric surface was measured and measured. (4) Texture: Evaluated in three stages by sensory evaluation. …: Soft, small rubber feeling, △: slightly hard, ×: hard, large rubber feeling (5) Surface smoothness: The degree of fluff defect and unevenness were visually judged and evaluated on a three-point scale. ○: Almost no fuzz defects, good smoothness without unevenness △: Slight fuzz defects, slight unevenness ×: Frequent fuzz defects, severe unevenness

(6) Peeling strength: A urethane-based adhesive is coated up to ／ of the coated surface of a clean crepe rubber plate and a test piece of 220 (vertical) × 25 (width) mm, and then pressed after bonding. The tip of the crimped sample is bent at 180 degrees, pulled at a pulling speed of 100 mm / min, and peeled off.
Read the average value. (7) Impregnation: The permeation state of the impregnation liquid and the solubility of the coating film on the surface of the nonwoven fabric were visually judged, and evaluated by three grades of 段 階, Δ, and X (○ is the best). (8) Uniformity of coat application: The state of sinking of the coat application liquid onto the substrate and the uniformity of the thickness of the coat sponge were measured from the cross section after impregnation and solidification, and evaluated by three steps of △, Δ, × ( The best).

Example-1 Single component fineness: 4.5 denier, 5 parts: 50 parts of 6-nylon for the island component and 50 parts of high flowable polyethylene for the sea component.
Using staple fiber of 1mm extra-fine fiber bundle fiber-generating multi-component fiber (hereinafter referred to as multi-component fiber), pass through each process of card, cross wrapper and needle punch, then heat to melt polyethylene of sea component By heat setting, a fiber-entangled nonwoven fabric having an apparent density of 0.285 g / cm ³ was obtained. Hydran HW-312, which is an ionomer-type aqueous urethane resin soluble in DMF at room temperature, is provided on one surface of the fiber-entangled nonwoven fabric.
B (manufactured by Dainippon Ink and Chemicals, Inc., 100% elongation stress: 32 kg / cm ² ) was applied with a 50 mesh oblique gravure roll, and then dried on a 140 ° C. heat drum.
By pressing under pressure for 2 minutes, a fibrous substrate having a smooth surface having a polyurethane coating of 24 g / m ^{2 on the} surface of the nonwoven fabric was obtained.
When observing this fibrous substrate with a scanning electron microscope photograph,
85% of the nonwoven fabric surface was covered.

The average molecular weight of each of the obtained fibrous substrates was 2000
Mixed diol (mixing ratio, 60:40) of polytetramethylene glycol (hereinafter abbreviated as PTMG) and polybutylene adipate (hereinafter abbreviated as PBA), 4,
4'-diphenylmethane diisocyanate (hereinafter MDI
As a wet film-forming aid, in 100 parts of a 13% DMF solution of a 4.8% nitrogen-containing polyether polyurethane (I) composed of ethylene glycol (hereinafter abbreviated as EG) and ethylene glycol (hereinafter abbreviated as EG). SD-14
An impregnating solution (viscosity of 8.2 poise at 40 ° C.) to which 2 parts of Dainippon Ink and Chemicals, Inc. was added was impregnated to the surface of the fibrous base by a roll-in method, and then a polyether-based polyurethane was formed on the upper surface. (I) 100 parts of a 21% DMF solution was added with 1 part each of Chris Bon Assister SD-7 and SD-14 (manufactured by Dainippon Ink and Chemicals, Inc.) as a wet film forming aid (coating solution) (Viscosity of 105 poise at 40 ° C.) is 120 g / m ^{2 in} terms of solid matter.
After applying the coat, it was immersed in a coagulation bath having a DMF concentration of 30% and a temperature of 40 ° C. to perform wet coagulation and washed with water to obtain a porous sheet.

This sheet is treated in hot toluene,
The polyethylene component of the multicomponent fiber is dissolved and removed, further washed, immersed in a cationic treating agent dispersion and dried,
A porous sheet material having a smooth porous polyurethane wet sponge coat layer on a substrate layer containing porous polyurethane in an entangled nonwoven fabric of 6-nylon ultrafine fiber bundle fibers was obtained. Next, the surface was subjected to finishing treatment such as gravure and embossing to obtain a leather-like sheet. Table 1 shows the surface smoothness and peel strength of the leather-like sheet.

[0025]

[Table 1]

Examples 2 to 3 and Comparative Examples 1 to 4 Various water-dispersible polyurethane emulsions (manufactured by Dainippon Ink and Chemicals, Inc.) were used as nonwoven fabrics in place of the hydrane HW-312B of Example 1. Table 1 shows the results of evaluation of surface smoothness and peel strength by obtaining a porous sheet by treating in the same manner as in Example 1 except that the resin was used as a resin for surface coating. As is clear from the results in Table 1, the leather-like sheet of the present invention has good surface smoothness, few fuzz defects, and a stable and high peeling strength. A film having both smoothness and peel strength was not obtained.

Example-4 Polyethylene terephthalate fiber having a shrinkage factor of 30% in hot water at 70 ° C. (single yarn fineness: 1.9 denier, length: 38 m)
m), through a card and a random webber, and laminated by a cross lap method to obtain a fiber web having an average weight of 240 g / m ² , and a total punch density of 800 from both sides of the fiber web.
Perform a needle punch at a punch / cm2, and then
It was immersed in warm water of 2 ° C. for 2 minutes to shrink to 65% of the original area. Using a belt press drier,
Weight is 330 g / m ² , thickness is 1.2 mm, apparent density is 0.
A fiber entangled nonwoven fabric of 275 g / cm ³ was obtained.

A one-pack type solution polyurethane, Chrisbon NB-130 (manufactured by Dainippon Ink & Chemicals, Inc., 100% elongation stress 65 kg / c) is applied to an enamel-type release paper.
m ² ) (DMF / MEK = 2/1) with a comma coater to apply 100 g / m ^{2 of the} solution (3% in solid content).
0 g / m ² ), and in a wet state, the fiber-entangled nonwoven fabric obtained above is bonded to a polyurethane on release paper with a press roll using a laminating roll, and dried at 130 ° C. for 2 minutes to form a surface. A fibrous substrate having a polyurethane coating was obtained. Observation of the fibrous substrate with a scanning electron microscope photograph revealed that 78% of the surface of the nonwoven fabric was covered.

With the polyurethane-coated surface of the resulting fibrous substrate facing upward, 1,9-nonanediol and 2-methyl-1,8-octanediol are present in a molar ratio of 5 from the lower surface.
Polyester diol having an average molecular weight of 2,000 (hereinafter abbreviated as PNOA) obtained from a mixed diol and adipic acid mixed at a ratio of 0/50, and a polyester-based polyurethane composed of MDI and EG and having a nitrogen content of 3.2% ( An impregnating solution (40 ° C.) obtained by adding 2 parts of Chrisbon Assister SD-14 (manufactured by Dainippon Ink and Chemicals, Inc.) as a wet film forming aid to 100 parts of a 13% DMF solution of II).
9.5 poise) to the surface of the fibrous substrate by a roll-in method, and then, on the upper surface, a 21% DMF solution 10% of the polyether-based polyurethane (I).
0 parts, as a wet film forming aid, Chris Bon Aster S
D-7 and SD-14 (manufactured by Dainippon Ink and Chemicals, Inc.)
Is applied at 120 g / m ^{2 in} terms of solid content, and then immersed in a coagulation bath having a DMF concentration of 30% and a temperature of 40 ° C. for wet coagulation. After washing with water, immersion treatment in a dispersion of a cationic treating agent and drying are performed, and a porous sponge coat layer of a smooth porous polyurethane is provided on a base layer containing a porous polyurethane in an entangled nonwoven fabric of polyethylene terephthalate. A quality sheet was obtained. Next, the surface was subjected to finishing treatment such as gravure and embossing to obtain a leather-like sheet. Table 2 shows the surface smoothness and peel strength of this leather-like sheet.

[0030]

[Table 2]

Comparative Examples -5 to 7 In the same manner as in Example 4, the amount of Chrisbon NB-130 applied (solid content: 30 g / m ² ) was changed to 7 g / m ² for the non-coated and the applied amount (solid content). ² , treated in the same manner as in Example 4 except that it was changed to 70 g / m ² and used as a fibrous substrate having a polyurethane coating on its surface, to obtain a porous sheet-like product, and to have a surface smoothness and peel strength. Are shown in Table 2.

Examples 5 to 6 and Comparative Examples -8 to 10 In place of the Chrisbon NB-130 of Example 4, various solution-type polyurethanes (Dainippon Ink Chemical Industry Co., Ltd.)
Ex.) Was used as the resin for surface coating of the nonwoven fabric, and treated in the same manner as in Example-4 to obtain a porous sheet material.
Table 2 shows the results of evaluation of surface smoothness and peel strength.

As is evident from the results in Table 2, the leather-like sheet of the present invention has good surface smoothness, few fuzz defects, and a stable and high peeling strength. As for No., a material having both good texture, surface smoothness and peeling strength was not obtained.

Example 7, Comparative Examples 11 to 12 Polyurethane obtained from a raw material having the same composition as that of the polyester-based polyurethane (II) instead of the impregnating liquid (viscosity at 40 ° C. of 9.5 poise) of Example-4 The same procedure as in Example 4 was carried out except that an impregnating solution having the same concentration and a high viscosity (viscosity at 40 ° C. of 19 poise and 40 poise) was used to obtain a porous sheet material. On the other hand, instead of the coating solution of Example-4 (viscosity at 40 ° C. of 105 poise),
Example 1-Polyurethane obtained from a raw material having the same composition as the polyether-based polyurethane (I), except that a low-viscosity (65 poise at 40 ° C.) coating solution of the same concentration was used.
The same treatment as in Example 4 was carried out to obtain a porous sheet material, and the results of evaluating the surface smoothness and peel strength are shown in Table 3.

[0035]

[Table 3]

As is evident from the results in Table 3, the leather-like sheet of the present invention has good impregnating workability and coat coatability, good surface smoothness, few fuzz defects and stable peel strength. However, the leather-like sheet material of the comparative example was inferior in impregnating workability or coat applicability and could not obtain a material having both surface smoothness and peel strength.

Example -8 548 parts of a mixed diol of PTMG and PBA having an average molecular weight of 1500 (mixing ratio: 60:40), 95 parts of 1,4-butanediol and 357 parts of MDI were reacted.
Pellets of thermoplastic polyurethane having a nitrogen content of 4.0% based on isocyanate groups were obtained. The thermoplastic polyurethane and 6 having a terminal amino group concentration of 1.5 × 10 ⁻⁵ eq / g.
20 parts of a polyurethane stream using nylon as a spinning raw material,
The polymer streams extruded from separate extruders are mixed, split, and integrated so that 80 parts of the 6-nylon stream are merged, split, and integrated, and the number of islands is 50 (6-nylon is an island component) and the fineness is 10 denier. Thus, a polyurethane-based multicomponent fiber was obtained. The obtained multicomponent fiber is heated in hot water at 80 ° C. for 3 hours.
The fiber was drawn twice and heat-set to obtain a fiber having a fineness of 3.5 dr. After applying the oil agent, the fiber is mechanically crimped to obtain a fiber length of 5
Staple fibers were obtained by cutting to 1 mm.

Next, the obtained staple fiber was passed through a card and a random webber, laminated by a cross lap method to obtain a fiber web having an average weight of 400 g / m ² , and a total punch density of 980 punch / cm from both sides of the fiber web. Needle punching is performed in ² to obtain a fiber-entangled nonwoven fabric, impregnated with a 7.5% aqueous solution of polyvinyl alcohol, squeezed at a target squeezing rate of 150%, and dried to a weight of 390 g / m ² and a thickness of 1.5 m.
m, a fiber-entangled nonwoven fabric having an apparent density of 0.260 g / cm ³ was obtained. Hydran HW-111-, which is a DMF-soluble ionomer-type aqueous urethane resin, is added to this fiber-entangled nonwoven fabric.
H (manufactured by Dainippon Ink and Chemicals, Inc., 100% elongation stress: 26 kg / cm ² ) was coated with a 40-mesh diagonal gravure roll using a 40% aqueous dispersion.
By pressing under pressure for 2 minutes, a fibrous substrate having a smooth surface having a polyurethane coating on the nonwoven fabric surface of 22 g / m ² was obtained.
When observing this fibrous substrate with a scanning electron microscope photograph,
90% of the nonwoven fabric surface was covered.

With the polyurethane-coated surface of the obtained fibrous substrate facing upward, 100 parts of a 12% DMF solution of the above-mentioned polyester-based polyurethane (II) having a nitrogen content of 3.2% was wet-coated from the lower surface with 100 parts. Chris Bon Assister SD-14 (manufactured by Dainippon Ink and Chemicals, Inc.)
Partially added impregnation liquid (viscosity at 50 ° C. 5.8 poise)
Was impregnated to the surface of the fibrous substrate by a roll-in method to dissolve the polyurethane component of the multicomponent fiber. Next, on the upper surface, 21 of the polyether-based polyurethane (I) was used.
% DMF solution, 100 parts of Chrisbon Assister SD-7 and SD-14 (manufactured by Dainippon Ink and Chemicals, Inc.) were added as wet film-forming aids in an amount of 100 parts by weight, respectively.
(Viscosity at 0 ° C: 95 poise) is 120 g in terms of solid content.
/ M ² coating, DMF concentration 30%, temperature 40 ° C
Immersed in a coagulation bath and wet coagulated, washed with warm water to remove polyvinyl alcohol, immersed in a cationic treating agent dispersion and dried, and porous polyurethane contained in a 6-nylon ultrafine fiber entangled nonwoven fabric A porous sheet having a smooth porous polyurethane wet sponge coat layer on the base layer thus obtained was obtained. Next, the surface was subjected to finishing treatment such as gravure and embossing to obtain a leather-like sheet.
The leather-like sheet had good surface smoothness and high peel strength of 12.5 kg / inch.

[0040]

According to the present invention, the nonwoven fabric is fluffed off with a specific polyurethane thin film coating, the impregnating liquid having a specific viscosity is impregnated from the lower surface, and then a coating liquid having a specific viscosity is applied. It has a high downside effect, reduces the sinking of the coating liquid into the base layer, and has excellent surface smoothness even if the applied coating layer is thinner. Is obtained.
Therefore, a softer leather-like sheet can be obtained. Moreover, the polyurethane coating layer for fluff binding is appropriately dissolved by the common solvent contained in the impregnating liquid and the coating coating liquid, has high compatibility with the polyurethane of the coating layer and the impregnating layer, has good adhesiveness, and has high peeling strength. A leather-like sheet is obtained.

Claims (1)

(57) [Claims] 1. A method for producing a porous sheet having a porous layer of a high molecular polymer mainly composed of an elastic polymer laminated on a surface of a fibrous base material. (1) An apparent density of 0.15 to 0.1. The surface of a nonwoven fabric of 40 g / cm ³ has a 100% elongation stress of 1
70 to 95% of the surface is coated with a polyurethane film by applying and drying a solution or dispersion mainly composed of polyurethane which is soluble in N, N-dimethylformamide at room temperature and is 5 to 85 kg / cm ^2. (2) With the fluffed surface of the nonwoven fabric as the upper surface, the solvent of the resin mainly composed of polyurethane is N,
A step of impregnating with a solution containing N-dimethylformamide having a viscosity of 30 poise or less, (3) a resin containing polyurethane as a main component from the upper surface of the fluffed nonwoven fabric,
A step of coating and coating a solution containing N-dimethylformamide having a viscosity of 80 poise or more, and (4) a step of coagulating and drying the impregnated and applied polyurethane solution in a solvent containing a non-solvent of polyurethane and sequentially performing the steps. A method for producing a leather-like sheet having good surface smoothness, characterized by the following. [0001]