JP2000119974A - Manufacture of leather like sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a leather like sheet having soft feeling and satisfactory in fluff binding by forming a paraffin coated layer on the surface of a nonwoven cloth, immersing in and coating with solutions of an elastic polymer having a respectively specific viscosity and coagulating after forming a paraffin coated layer on the surface of a nonwoven fabric. SOLUTION: This leather like sheet is obtained by applying 5 to 50 g/m2 on solid base of paraffin emulsion to the surface of a nonwoven fabric of super fine fibers having 0.18 to 0.42 g/m2 of apparent density, performing fluff binding by pressing with a heating roll and forming the paraffin layer, impregnating the elastic polymer solution such as dimethylformamide solution of a polyurethane having viscosity <=20 poise or the like, applying the prescribed polymer solution having viscosity <=40 poise on the coated surface, coagulating in a liquid including non-solvent for the polyurethane, for example in water, and drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a method for producing a leather-like sheet having a grain surface layer, a nonwoven fabric is impregnated with a solution of an elastic polymer represented by polyurethane, and the surface is further coated with an elastic polymer solution. A method of wet coagulation is known. The leather-like sheet obtained by this method will have a porous layer on the surface, but generally the fluff composed of the constituent fibers of the non-woven fabric is present on the surface of the non-woven fabric. The fluff penetrates the porous layer, and the fluff greatly impairs the surface smoothness of the leather-like sheet.

In order to obtain a leather-like sheet with less fluff,
A method of applying a resin for a porous layer on the surface after smoothing the fibrous base layer is known. For example,
Japanese Patent Publication No. 52-18241 discloses a method of gluing and fixing a fibrous base material with a polyvinyl alcohol solution, buffing the surface, and smoothing the surface, and applying a resin solution after thermally fusing the fibers on the surface of the nonwoven fabric. Japanese Patent Publication No. 53-22121 discloses a method of coagulating and solidifying a resin. Further, a resin is applied to the surface of the non-woven fabric, dried by pressing against a drum, and smoothed. A method of impregnation or coating is proposed in Japanese Patent Publication No. 57-29590. A method is also known in which a polyurethane emulsion is applied to the surface of a nonwoven fabric to make the fluff lie down.

[0004] However, in the case of the buffing method in the above-mentioned prior art, although a leather-like sheet having a smooth surface can be obtained, the tensile strength of the leather-like sheet becomes weak because the surface fibers are cut. In addition, there is a problem that the peel strength between the coating layer and the base layer (nonwoven fabric layer) is reduced. On the other hand, in the case of the method of fusing the surface fibers, 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. In the case of a method of fuzz pressing by using a resin, if a resin that is insoluble or has a small degree of swelling in the coating resin liquid is used as the fuzz holding resin, the adhesion between the fuzz holding resin and the coating resin layer becomes insufficient, resulting in high peeling. There is a problem that it is difficult to obtain high strength. Further, in the case of the fluff holding method using a polyurethane emulsion, if the tackiness of the polyurethane coating applied to the surface of the nonwoven fabric is low, the elasticity of the fluff can overcome the fluff and the fluff cannot be completely laid down. In the case where the material dissolves in the polyurethane solution used as the above, the fluff laid down during the formation of the silver surface layer rises again and the purpose of completely laying down the fluff cannot be achieved.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a film having good flexibility and good surface smoothness in a fluffy state. The purpose of the present invention is to provide an excellent leather-like sheet.

[0006]

According to the present invention, a paraffin emulsion is applied to the surface of a non-woven fabric, and the coated surface is pressed by a heating roll. A method for producing a leather-like sheet, comprising applying a solution and coagulating the solution. Preferably, in the above method, a non-woven fabric coated with a paraffin emulsion to form a paraffin coating layer on a surface thereof is impregnated with a dimethylformamide solution of polyurethane having a viscosity of 20 poise or less, Is a polyurethane dimethylformamide solution having a viscosity of 40 poise or more, and the above method of coagulating and drying an impregnated or applied polyurethane solution in a solution containing a polyurethane non-solvent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The nonwoven fabric used in the method of the present invention is obtained by adding a natural fiber or a regenerated fiber to a synthetic fiber composed of a single polymer or a plurality of polymers, if necessary, and further three-dimensionally entangled. It is a nonwoven fabric, and may be provided with a needle punch or a binder resin. The synthetic fibers constituting the nonwoven fabric may be fibers composed of a single polymer or fibers obtained by mixing or spinning several kinds of polymers. In the case of using a fiber obtained by mixing or spinning several kinds of polymers, at least one of the polymers constituting the fiber may be extracted or decomposed and removed to make the fiber ultrafine or porous. The non-woven fabric used in the above method may be a fiber after ultrafine or porous fiber, or may be ultrafine or porous during or after the method of the present invention.

[0008] Examples of the polymer used for the fiber include polyamide, polyester, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, and polyurethane. In particular, as the polymer used for the single polymer fiber, polyesters such as polyethylene terephthalate and polyethylene terephthalate, and polyesters such as copolyesters obtained by copolymerizing an aromatic or aliphatic dicarboxylic acid or glycol with these polyesters And polyamide-based polymers such as polymers, 6-nylon and 66-nylon. In particular, a polyester-based polymer among these polymers is melt-spun, and then 60-65
High shrinkable fibers obtained by stretching 1.5 to 3.0 times in hot water at 65 ° C. and drying at 65 ° C. or lower, and melt-spun these polyester-based polymers.
It is stretched 2 to 4 times in hot water at ~ 65 ° C,
A latent spontaneously extensible fiber obtained by heat-treating in warm water at 5 ° C. and drying at 100 ° C. or less is preferred.

The fibers comprising a plurality of polymers include fibers spun or mixed with polyethylene and polyamide (especially nylon-6), fibers spun or mixed with polyethylene and polyethylene terephthalate, and fibers with polyurethane and terminal amino groups. Fibers obtained by composite spinning of a blocked polyamide are preferred, and among them, multicomponent fibers having a sea-island cross-sectional structure containing polyamide or polyester as an island component are preferred.

The preferred apparent density of the nonwoven fabric to which the method of the present invention is applied is 0.18 to 0.42 g / cm ³ , more preferably 0.20 to 0.35 g / cm ³ ,
Perform three-dimensional entanglement treatment by needle punching or applying high-pressure liquid or gas, and if necessary, further shrink the non-woven fabric constituent fibers in warm water or a dryer, or heat the non-woven fabric, and then press with a roll. Shrink processing. If the density of the nonwoven fabric is less than 0.18 g / cm ^3, the method hardly completely erase the unevenness of the surface may be applied to the present invention, it is greater than 0.42 g / cm ³ Conversely, products This is not preferred because the texture becomes harder and productivity is impaired such as a reduction in processing speed.

Next, paraffin is applied to the surface of the nonwoven fabric. The paraffin to be applied is an aqueous paraffin emulsion at room temperature. Examples of such paraffin include water-dispersible paraffin emulsified and dispersed in water and ionic colloid-dispersed paraffin.
They can be used alone or in combination of two or more. By using a paraffin emulsion, it is possible to focus paraffin on the surface of the nonwoven fabric.

The paraffin has a 100% elongation stress of 10 kg / cm ^{2 to} 100 kg, especially when formed into a film.
/ Cm ² is preferable, and if less than 10 kg / cm ² of paraffin is used, the tackiness of the coated surface increases,
Affects workability during application and post-processing. Also one
It is not preferable to use paraffin having a 00% elongation stress exceeding 100 kg / cm ² , because the texture becomes hard and the bending resistance becomes poor.

When the paraffin is applied to the surface of the nonwoven fabric, it can be used in the form of an emulsion containing a penetrating agent, an antifoaming agent, a thickener and the like. The amount applied to the nonwoven fabric surface is
It is determined by the constituent fibers of the nonwoven fabric, the basis weight, the specific gravity and the purpose of use of the obtained substrate, but it is important that most of the surface is covered with a paraffin film by drying. , 5 to 50 g / m in solid content
² , more preferably 10 to 30 g / m ² . In the present invention, the formed paraffin film is preferably partially dissolved by a solvent constituting the impregnating liquid or the coating liquid during impregnation or coating of the nonwoven fabric with the elastic polymer liquid, and partially The dissolution increases the peel strength between the nonwoven fabric layer and the coat layer. To partially dissolve,
The above coating amount is preferred.

When the area of the paraffin coating is less than 50% of the surface of the nonwoven fabric, fuzz holding is poor, and when it exceeds 95%, impregnation of the resin liquid into the nonwoven fabric in a later step becomes difficult, resulting in a decrease in peel strength and processing. It is not preferable because productivity is impaired such as a decrease in speed. For this reason, the paraffin 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 substantially uniform. As a method of applying the paraffin to the surface of the nonwoven fabric, a predetermined amount is applied by gravure coating, followed by drying and smoothing with a heat drum, or after applying a predetermined amount on a release paper film by a comma coater or the like, and then in a wet state. A method of drying after bonding and pressing the nonwoven fabric, spraying,
There is a method in which a non-woven fabric is directly applied to the surface of a non-woven fabric by a reverse coater or the like, and is dried and smoothed by a hot roll press, a hot drum, a stainless steel belt machine, or the like. In this case, when the surface of a hot roll press, a heat drum or the like is coated with a resin having good releasability such as silicone or Teflon, it is more effective in obtaining a smooth surface.

Next, the nonwoven fabric is preferably impregnated with a solution or emulsion of an elastic polymer. As the resin to be impregnated, a polyurethane resin is most preferable because the nonwoven fabric can satisfy the mechanical strength, flex resistance and texture required as a base material for artificial leather. The polyurethane resin used in the present invention comprises a polymer glycol having a molecular weight of 600 to 5000, an organic diisocyanate and a molecular weight of 5
A polyurethane obtained from a low molecular compound having less than 00 and having two active hydrogen atoms, and can be produced by polymerizing by a usual method. As a solvent for the polyurethane resin, dimethylformamide (abbreviated as DMF), diethylformamide, dimethylacetamide, tetrahydrofuran, dioxane, dimethylsulfoxide and the like can be used, but DMF is most preferred.

Examples of the impregnation method include a normal double-sided impregnation method and a method of rubbing and impregnating the impregnating solution from the surface opposite to the surface of the fluffed-down non-woven fabric using a flat roll, a trapezoidal or hatched gravure roll. Is used. As the impregnating solution, a solution having a viscosity of 20 poise or less at the temperature of the impregnating solution is preferable, and a solution having a viscosity of 15 poise or less is more preferable. Further, a solution containing at least 50% by weight or more of DMF as a solvent is preferable. Solution viscosity is 20
When the poise is exceeded, the immersion wetting resistance increases because the viscosity is too high, and impregnation becomes difficult. DMF as a solvent
Is less than 50%, the dissolution of the paraffin coating applied to the nonwoven fabric surface becomes insufficient, the adhesion between the base layer and the paraffin coating resin becomes poor, and the peeling strength decreases. The reason why the coating area of the paraffin coating is preferably 50 to 95% in the nonwoven fabric is also due to the impregnating workability from the lower surface. That is, if the coverage area is 5
If it is less than 0%, the fluffing effect is small, and if it exceeds 95%, the escape of air contained in the base layer at the time of impregnation becomes poor,
It is necessary to lengthen the impregnation time, and as a result, the coating film is excessively dissolved and the whole is fuzzed.

An elastic polymer solution is applied to the surface of the nonwoven fabric on which the paraffin coating layer is formed, and solidified. Polyurethane is preferred as the elastic polymer for surface coating, and the polyurethane used for this is obtained from 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. Polyurethane is preferred,
It can be produced by changing the composition according to the required performance and polymerizing by a known means. As a solvent for the polyurethane elastomer, DMF, diethylformamide, diethylacetamide, tetrahydrofuran, dioxane,
Although dimethyl sulfoxide and the like are preferred, DMF is most preferred. As the coating liquid, a solution having a viscosity at the liquid temperature at the time of coating of 40 poise or more, more preferably 100 poise
It is preferable to use a solution having a poise or more and containing at least 50% or more of DMF as a solvent. If the viscosity is less than 40 poise, the viscosity is too low, and the resin is sunk into the substrate layer, and it is difficult to obtain a smooth surface having a uniform thickness. If the DMF as a solvent is less than 50%, the paraffin coating applied to the surface of the nonwoven fabric is extremely poorly dissolved, the adhesion between the applied elastic polymer layer and the nonwoven fabric layer becomes poor, and the peel strength decreases. As a method of applying the elastic polymer liquid, a usual application method such as a knife coater, a comma coater, and a reverse coater can be adopted. Further, additives such as various coagulation regulators, pigments, antioxidants, and light stabilizers may be added to the impregnation liquid or the coating liquid according to the purpose.

The amount of the coating solution to be applied may be arbitrarily selected depending on the product to be applied. In the method of the present invention, the surface smoothness of the polyurethane-impregnated nonwoven fabric is improved due to the effect of the paraffin coating. Since there is little penetration into the nonwoven fabric layer, the amount of application can be reduced. For this reason, the thickness of the coat layer can be reduced, rubber rebound caused by the thickness of the coat layer can be reduced, and a product with silver having a texture very similar to natural leather can be obtained.
A preferable amount of the coating liquid is 400 to 700 in terms of resin.
A range of g / m ² is used.

A wet coagulation method is used as a method of coagulating the applied or impregnated resin liquid, and a non-solvent of a polymer which is at least partially miscible with a solvent of the polymer is used as the coagulation liquid. 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, a mixture containing a polymer solvent is also suitable as a coagulation bath. Therefore, it is preferable to use a mixture of water and DMF. The obtained leather-like sheet is subjected to ultrafine or porous treatment of the fibers as necessary, that is, dissolution or decomposition removal of one component of the fibers, and finishing treatments such as coloring, applying a finishing layer, embossing, and embossing. To produce a leather-like sheet.

As described above, in the present invention, the nonwoven fabric fluffed with a thin paraffin layer is preferably impregnated with an impregnating liquid having a specific viscosity from the opposite surface, and wet-solidified. The paraffin 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, but a smooth and high-viscosity paraffin layer is provided as a lower layer, and the fluff is sufficiently suppressed.Thus, by applying a thin coat layer, the surface smoothness, particularly the fluff is reduced. Fewer leather-like sheets are obtained. Moreover, since the paraffin coating layer for fluff binding is appropriately dissolved by the solvent contained in the impregnating liquid and the coating liquid, the compatibility between the coating layer and the impregnating layer is good, the adhesion is good, and the leather has high peeling strength. A sheet is obtained.

[0021]

The present invention will be specifically described below with reference to examples. Parts and percentages in the examples are by weight unless otherwise indicated. 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, and a sample length is 5c.
It is a quotient obtained by dividing the tensile strength at 100% elongation by the thickness and width of the sample, where the tensile strength is 10 cm / min. (2) DMF solubility: A dry film having a thickness of about 100 μm
The dissolution rate when immersed in MF (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 surface of the nonwoven fabric was determined by actual measurement. (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 fuzz 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 ×: Many fuzz defects, severe unevenness

(6) Peeling strength: A urethane-based adhesive is coated up to ／ of the coated surface of the rubber plate whose surface has been washed and a test piece of 220 (length) × 25 (width) mm, and then press-bonded after bonding. The tip of the sample was bent at 180 degrees, pulled at a pulling speed of 100 mm / min, peeled off, and the average value was read. (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 The island component is 6-nylon and the sea component is polyethylene having high fluidity. The weight ratio of the sea island is 50/50 and the single fineness is 4.
After passing through each process of card, cross wrapper, and needle punch, using staple fiber of 5 denier, 51 mm fiber length, ultra-fine fiber bundle fiber-generating sea-island cross-section multicomponent fiber (hereinafter referred to as multicomponent fiber), heating was performed. To fix the sea component polyethylene by melting and heat, and the apparent density is 0.285 g / cm
The fiber entangled nonwoven fabric of No. ³ was used. A paraffin emulsion soluble in DMF at room temperature is placed on one side of this fiber entangled nonwoven fabric.
After applying a 10% aqueous dispersion of [KRC-103 manufactured by Takemoto Yushi Co., Ltd.] with a 50 mesh oblique gravure roll,
By pressing and drying on a hot drum at 60 ° C., a fibrous substrate having a smooth surface having a paraffin coating (application amount (solid content): 20 g / m ² , surface coverage: 85%) on the nonwoven fabric surface was obtained.

Next, the polyurethane elastomer (I) was placed with the paraffin-coated side of the obtained fibrous substrate facing upward.
Impregnating liquid obtained by adding 10 parts of a black pigment for coloring to 100 parts of a 7.5% DMF solution (a viscosity of 1.0 poise at 30 ° C.)
Was prepared. The substrate having the paraffin coating is immersed in this solution to impregnate the polyurethane elastomer solution, and then immersed in a 50% aqueous dimethylformamide solution at a temperature of 35 ° C. in a coagulation bath for wet coagulation.
The substrate was passed through a hot cylinder roll process at ℃ to heat-fix the surface. Then, a coating liquid (viscosity 66 poise at 30 ° C.) of 10 parts of a black pigment for coloring added to 100 parts of a dimethylformamide solution of the same 20% solution of the same polyurethane elastomer as above was applied to the upper surface at a coating amount of 1000 g / m ² . 20% dimethylformamide aqueous solution, temperature 35 ° C
In a coagulation bath for wet coagulation, and further thoroughly washed with warm water at 70 ° C. to obtain a porous sheet.

The polyethylene component in the multicomponent fiber of this sheet is extracted and removed with hot toluene, dried with a hot air drier at 120 ° C., and porous polyurethane is contained in the entangled nonwoven fabric comprising 6-nylon ultrafine fiber bundle fibers. On the substrate layer
A sheet having a smooth porous polyurethane layer was obtained. The obtained base layer had no dents or cracks based on the nonwoven fabric, had good smoothness, and had a sense of fulfillment. Then, the surface was colored by gravure and embossed to give a leather-like sheet (A). This had extremely good adhesion between the nonwoven fabric layer and the coating layer.

Example 2, Comparative Example 1 Instead of the paraffin solution used in Example 1, a concentration of 15 was used.
% Of paraffin aqueous dispersion using 30% solid content
/ M ^2, except that the surface coverage of 80%, was treated in the same manner as in Example 1 to obtain a porous sheet (B) and leather-like sheet (B). This had good smoothness and adhesiveness between the nonwoven fabric layer and the coating layer as in the leather-like sheet (A).
On the other hand, a porous sheet (C) was obtained in the same manner as described above except that the paraffin solution treatment in Example 1 was omitted, and then a finishing treatment was performed in the same manner as above to obtain a leather-like sheet (C). However, it was dented and fluffy.

Comparative Example 2 In Example 1, polyurethane 1 was used instead of paraffin.
Except for using a 0% DMF solution, the same treatment as in Example 1 was performed to obtain a porous sheet (D). In the obtained base layer, dents or fuzz were recognized based on the nonwoven fabric. Subsequently, the surface was subjected to finishing treatment such as gravure and embossing in the same manner as in Example 1 to obtain a leather-like sheet (D). This product had sufficient adhesiveness between the nonwoven fabric layer and the coating layer, but had a hard texture. Table 1 shows the values of the surface smoothness and the peel strength between the coating layer and the base layer of the leather-like sheet obtained by the above Examples and Comparative Examples.

[0029]

[Table 1]

As is clear from the results in the above table, the leather-like sheet of the present invention has good surface smoothness, few fuzz defects, and high peel strength, whereas the leather-like sheet of the comparative example has a high surface smoothness. Poor smoothness and peel strength.

[0031]

According to the method of the present invention, the nonwoven fabric is fluffed with a specific paraffin layer. Preferably, after performing such fluffing, a resin liquid having a specific viscosity is impregnated.
Further, thereafter, a resin liquid having a specific viscosity is applied. According to the method of the present invention, the fluffing effect on the surface of the nonwoven fabric is high and the sinking of the coating liquid into the base layer is small, and the coating layer to be applied is made thinner. However, a leather-like sheet with excellent surface smoothness and less fuzz can be obtained rationally. Also,
The paraffin 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 a stable peeling strength. A leather-like sheet is obtained.

Claims (4)

[Claims] 1. A paraffin emulsion is applied to the surface of a non-woven fabric, and the coated surface is pressed by a heating roll.
A method for producing a leather-like sheet, further comprising applying a solution of a high molecular polymer mainly composed of an elastic polymer to the surface and solidifying the solution. 2. The method according to claim 1, wherein a non-woven fabric coated with a paraffin emulsion and having a paraffin coating layer formed on the surface is impregnated with a solution of polyurethane having a viscosity of 20 poise or less in dimethylformamide of polyurethane. 3. A solution of a high molecular weight polymer having a viscosity of 40
2. The method according to claim 1, wherein the solution is a solution of polyurethane at or above poise in dimethylformamide. 4. The method according to claim 2, wherein the impregnated or applied polyurethane solution is coagulated and dried in a solution containing a polyurethane non-solvent.