JPH0529709B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing leather-like products, and more specifically to a method for manufacturing a leather-like product that has a soft texture that does not sag and has excellent moisture permeability. This relates to a manufacturing method. (Prior Art) For leather-like products, it has been desired to have a silver surface that is lightweight and has a soft texture. The most commonly used method for this purpose is to reduce the thickness of the silver surface and make it lightweight, and the so-called dry release paper method is one in which a resin material for the grain surface is coated on a textured release paper and then dried and transferred to the base material. It was standard. However, with this method, a microporous silver surface having moisture permeability cannot be obtained, and the functionality of high moisture permeability must be sacrificed. On the other hand, a method has been widely used in which a thick wet microporous silver surface is formed on the base material (often 300 to 500 microns thick) and then textured from behind using strong heat and pressure. Ta. With this method, the silver surface is heavy and has a hard texture, and the silver surface is weakened by the heat and pressure during embossing, resulting in an even harder surface texture, so it has no choice but to limit its uses. It was hot. On the other hand, even with the same microporous silver surface, thin layered silver surfaces of 300 microns or less, especially 200 cyclones or less, cannot be coated substantially uniformly on the substrate using conventional silver surface processing techniques such as doctor coating and reverse roll coating. It was something I didn't have. Even if it were possible, the surface would be very disturbed due to the unevenness of the base material or fiber pieces, and the fine grains, especially the calf-like grains, would have a lot of settling. Steam coagulation is a method that attempts to relatively effectively overcome these technical drawbacks. For example, Tokkosho
This method is disclosed in Japanese Patent Nos. 37-4434 and 42-56499, and is a technique related to the so-called steam solidification method in which steam is directly applied to an unsolidified silver surface to solidify it while maintaining a smooth horizontal surface. These methods coat a relatively large amount of resin material on the silver surface, and smoothness is easily obtained due to the horizontal plane principle of the liquid, but the thickness of the silver surface is usually 300 to 500 microns, and if it is less than 200 microns, the above-mentioned I was unable to obtain a stable silver surface. As described above, although an easy and stable method for producing a thin microporous silver surface with high moisture permeability and clearly showing desired grains is desired, it has not yet been realized. (Problems to be Solved by the Invention) The present invention aims to obtain a grained wet microporous silver surface, which can be obtained only by conventional dry processing methods. (a) Provides a new method for manufacturing a grained wet microporous thin layer silver surface, and (b) Provides a soft and lightweight grain surface that is highly moisture permeable and does not sag due to no post-texturing process. The goal is to provide leather-like products that have the same characteristics. Of course, most of the fiber aggregates or those treated with a binder can be used as the base material for the grain surface, and it is possible to obtain a smooth grain surface without the need for any special surface smoothness processing of the base material. That's what I was aiming for. As a result of intensive research in view of the problems of the above-mentioned conventional technology, the present inventors first coated a grained release belt with a silver surface forming solution, then superimposed a water-wetted base material on top of the grained release belt. We have discovered a stable method for processing silver surfaces, which is a very simple operation of heating the substrate from above and releasing the belt after a certain timing period, and have arrived at the present invention.
The key point is that in the conventional steam coagulation method, steam treatment is applied from above the grain-faced raw material, whereas in the present invention, the method coagulates only by the water vapor or moisture within the base material, and one of the grain-faced raw materials is The biggest feature is that the shape is retained by a textured release belt. That is, the present invention was completed using a method that is difficult for anyone to imagine, in which the coagulation action is applied from the back side of the base material, which is completely opposite to the conventional method. (Means for solving the problem) The above-mentioned purpose is to coat a substrate with a microporous silver surface having an average grain thickness of 200 microns or less, first with a grain pattern that is reversely engraved with respect to the desired grain pattern. A release belt is coated with a water-miscible solvent solution mainly composed of polyurethane elastomer, one side of the base material moistened with water is placed on top of the release belt, and then the other side of the base material is heated to release the base material. Achieved by a method for producing a textured thin-layer microporous silver surface, which is characterized in that the polyurethane elastomer is substantially coagulated by saturated water vapor generated within the elastomer, and then released from a textured release belt and washed and dried with water. be done. The base material as used in the present invention refers to fibers made of synthetic fibers, natural fibers, knitted fabrics, raised products thereof, fiber aggregates themselves such as nonwoven fabrics, and those fiber aggregates processed with a binder. Usually, fibers such as cotton, rayon, nylon, and polyester, which are easily available industrially, are often used. Generally, the density of the base material is 0.15~
0.50g/ ^cm3 is good, and the particularly preferable range is 0.25-0.45
g/ ^cm3 . A polymer elastomer is most suitable as the binder, and polyacrylic acid ester, polyurethane, polystyrene butadiene rubber, polyacrylonitrile butaene rubber, or a copolymer thereof is used. A wet coagulation method, a dry coagulation method, etc. are adopted as the binder processing method, and the weight ratio of fiber and binder is adjusted to a range that is preferable for artificial leather (leather-like products) such as texture and elasticity. In the case of fiber alone, it has a soft texture but lacks stiffness and is difficult to post-process when turning into a secondary product, so a base material treated with a binder is usually preferred. The surface of the base material may be treated with a binder as it is, or may be sliced or sanded to make it relatively smooth. The most preferred base material for artificial leather is a nonwoven fabric made of short nylon fibers impregnated with a solution of polyurethane elastomer in N,N-dimethylformamide, wet-coagulated, washed with water, and dried. If necessary, it can be further softened and water-repellent treated. This is what I did. Next, the textured release belt, which is one of the main features of the present invention, will be described. It is preferable to use a continuous belt that is reversely engraved or embossed with the desired grain, but it may of course be a single piece.
Relatively inexpensive textured release paper may be used, but
In this case, it cannot withstand continuous use. Preferred materials for the endless type are stainless steel, a polymer elastomer composite belt reinforced with fibers, or glass cloth. Polyfluoroethylene, NBR, SBR, ethylene propylene diene rubber, silicone rubber, etc. are used as the polymer elastomer, but in all cases, one side of the belt to be processed must be engraved to obtain the desired texture. is a necessary condition. The effects of the present invention can be fully exhibited only by using a textured belt. That is, in view of the requirements of the present invention, when the wet microporous thin layer silver surface is peeled off from the textured release belt, in other words, it has already been textured. Therefore, the concept is fundamentally different from the conventional method of forming a wet grain surface without grain and then graining it with strong heat and pressure (referred to as post-graining or post-embossing). It is. In the post-texturing process, the silver surface weakens due to heat and pressure, resulting in a hard texture and reduced moisture permeability. In contrast, the present invention eliminates all the negative effects of post-texturing, and this is one of the most important reasons for employing the above-mentioned textured release belt. As an example, a release belt that has been embossed to give a suede look has been successfully transferred, and a useful leather-like product can be obtained by simply coloring or clearing the surface. In any case, the textured release belt needs to be made of a material that does not swell in water or the water-miscible solvent of the polyurethane elastomer described below, and preferably has a certain degree of elasticity. Next, a water-miscible solvent solution mainly composed of a polyurethane elastomer to be coated on the smooth release belt will be described. A polyurethane elastomer is a polymer composed of a polyol, an organic diisocyanate, and a chain extender, which is made into a polymer mainly through urethane bonds. This polymer may be used as a main component, and a small amount of other polymers, for example, 5 to 30 wt %, may be mixed therein. Various other polymers may be used depending on the purpose, but the essential condition is that the polymer be dissolved in the solvent in which the polyurethane-based polymer is dissolved. Furthermore, inorganic or organic fillers, colorants, and other additives may be mixed. The components constituting the polyurethane elastomer will be described in more detail. First of all, polyols mainly have hydroxyl groups at both ends and have a molecular weight of 500 to 500.
There are about 3000 compounds. There are polyether types and polyester types, and polyether types include polypropylene glycol ether, polytetramethylene glycol ether, etc., and copolymers of these functionalities may also be used. Polyester types include those obtained by polycondensation reaction of low-molecular glycols such as ethylene glycol, 1,4 butylene glycol, 1,6 hexane glycol, etc. and dicarboxylic acids such as adipic acid, sebacic acid, isophthalic acid, etc., or polyester types. -There are polylactone types such as caprolactone. The organic diisocyanate is an organic compound having two isocyanate groups, and includes, for example, 2,4 tolylene diisocyanate, 4,4' diphenylmethane diisocyanate, 1,6 hexane diisocyanate, and isophorone diisocyanate. Furthermore, the last component, a chain extender, is a compound having two active hydrogens, and is mainly a low-molecular compound. Examples include glycols such as ethylene glycol and butylene glycol, diamines such as hydrazine, ethylene diamine, 1,2 propylene diamine, and m-tolylene diamine, and amino alcohols. Methods for polymerizing polyurethane elastomers include solution polymerization, bulk polymerization, powder polymerization, etc., but for the purposes of the present invention, solution polymerization conducted in a solvent as described below is preferred. This is because the polymerization method used allows the viscosity, concentration, etc. to be precisely controlled since the solution is coated on the belt. Among the above-mentioned polyurethane elastomers, the most preferred and standard ones are those consisting of polybutylene adipate as the polyol, 4,4' diphenyl diisocyanate as the organic diisocyanate, and ethylene glycol as the chain extender. Another feature of polyurethane elastomers is that the hardness and softness of the polyurethane can be changed relatively freely by changing the molar ratio of polyol and organic diisocyanate. Although there are various solvents for these polyurethane elastomers, a water-miscible solvent is required for the method for producing the microporous silver surface of the present invention. Examples include N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, tetramethylurea, and N-methylpyrrolidone. Dioxane, methyl ethyl ketone, tetrahydrofuran, etc. can also be used as a partial dilution solvent. The solvent solution is a polymer mainly composed of the aforementioned polyurethane elastomer, and the polymer concentration is generally 15 to 40 wt%, preferably 15 to 30 wt%, and more preferably 20 to 25 wt%.
It is. The viscosity also varies depending on the density of the substrate to which it is applied, but is from 5,000 centipoise to 30,000 centipoise. The most preferred solvent is N,N-dimethylformamide from the standpoint of being industrially inexpensive and a good solvent for polyurethane elastomers. The important constitution of the present invention is to coat the above-mentioned textured release belt with the polyurethane solution, to superimpose one side of the water-wetted base material thereon, and then to overlay the other side of the base material ( (hereinafter also referred to as the back side)
It means heating it up more. The appropriate degree of water wetting of the base material is 30 to 150% in terms of squeezing rate. ,
If it is lower than 30%, it is similar to simply stacking dry base materials, and if one side is heated, the solvent will dry, and it is exactly the same as performing dry binder processing with the polyurethane elastomer on the surface of the base material. As a result, the texture is hard and a thin microporous silver surface cannot be obtained. On the other hand, if it exceeds 150%, free water partially appears on the surface of the substrate, and the polyurethane solution immediately gels due to the free water, making it impossible to obtain adhesion between the substrate and the silver surface. It is not possible to make products with surfaces. At a drawing ratio of 30% to 150%, which is exactly in between these, the grain surface coagulation by water vapor from the back side proceeds smoothly, a good grain is fixed, and the softness and adhesion are also good. Next, the method of heating from the back side is to utilize the principle of heat: heat movement and radiation. In other words, there may be a method in which the back surface of the water-moistened base material is brought into contact with a heating element, a method in which it is exposed to heated air, a method in which it is irradiated with heat rays, and the like. Generally, the heating temperature and time are
Approximately 0.1 to 10 minutes at 50 to 150°C is sufficient, but the appropriate conditions can be determined after thorough consideration of the following conditions. This is because it is influenced by the moisture content due to the thickness, density and squeezing ratio of the base material, the conduction of heat due to the heating method, the resulting vaporization of moisture, and the amount of coating of the solution mainly consisting of polyurethane elastomer. This will be illustrated in examples, but the preferred range of conditions is
The processing conditions should be selected at around 60-90°C and for 1-2 minutes. If the temperature is too low, it will take a long time for the elastomer to coagulate, which is unfavorable from an industrial standpoint, and if it exceeds 100°C, the rate of moisture loss in the base material during drying will be high, making coagulation control difficult. As for the time, as mentioned above, it is sufficient to adopt a minimum time sufficient to substantially solidify the elastomer, but from an industrial standpoint, it is advantageous to shorten the time to some extent, and it is also possible to achieve stable wet microporous formation. It will be done. Next, when the polyurethane elastomer is substantially solidified on the substrate, it is released from the textured release belt, washed with water, and dried to obtain a thin microporous silver surface with excellent smoothness. The microporous structure is completed at the stage of release from the mold, but because it retains a large amount of water-miscible solvent solution inside, it is difficult to remove the solvent by washing thoroughly with water, which is different from the conventional wet coagulation method. The method is the same as that of If the elastomer is dried without sufficient solvent removal, the microporous elastomer will re-dissolve and become similar to a mere dry film, which will not develop a soft texture and will also have poor moisture permeability. (Effects of the Invention) The greatest feature of the present invention is that the wet process microporous film has a thin layer of grained silver and can be easily processed onto any base material in just one step. It is. We think it is surprising that it is possible to process grain surfaces with a thickness of 30 to 50 microns, which was previously said to be impossible using methods other than the dry release paper method. Furthermore, even for polyurethane elastomers, such as polyether type and polycarbonate type, which are extremely difficult to remove by conventional wet methods, the process of coagulating them with saturated steam works effectively, and the solvent can be removed by washing with water. One of its major features is that it progresses very smoothly. (Example) Next, the present invention will be described in more detail with reference to Examples. Example 1 A nonwoven fabric (F) of polyester fiber was impregnated with a butylene adipate-based ester type polyurethane elastomer (R), and the thickness was 1.30 mm, the basis weight was 470 g/m ² , the apparent density was 0.35, and the weight ratio of F/R was 60/40. A base material was obtained (the surface of the base material is somewhat uneven due to needle marks from needling, etc.). Next, this base material is squeezed to 80%
Water wet processing was performed. A 50/50 weight percent mixture of butylene ester type/polytetramethylene ether type ether type polyurethane elastomer for silver surfaces was prepared, and an N,N dimethylformamide solution having a solid content concentration of 25% was prepared. This product was colored with 0.5% by weight of carbon black based on the polyurethane elastomer, and had a viscosity of 12,000 cps/30°C. The above polyurethane elastomer solution was cast at a rate of 100 g/m ² onto a stainless steel belt whose surface had been reversely engraved with hard grains and which had also been thinly coated with polyethylene fluoride, and the above water-wetted substrate was immediately poured onto the stainless steel belt. The materials were stacked uniformly and heated from above (back side of the base material) using a far-infrared heater. When heated for 4 minutes, the temperature of the moistened back side of the device was 70°C, with only a slight amount of water vapor rising from that side. Next, after contacting the cooling roll surface and cooling it to 40°C, the silver-finished base material was peeled off from the engraved stainless steel belt and further heated for 60°C.
After washing with hot water at ℃ for 90 minutes to completely remove the solvent, it was dried. The average thickness of the microporous silver surface obtained here is 50 microns, and the adhesive surface with the base material has partially penetrated into the recesses of the base material, and the surface of the silver surface has a wonderfully sharp shading. The deep grain was fixed. Moreover, the texture and lux of the finished product with black gravure ink according to conventional methods was similar to that of natural hard leather. Moreover, its peel strength was 9.5 kg/inch, and its Gurley bending strength, which is a measure of softness, was 630 mg, making it flexible and satisfying. As a comparative example, a silver surface was prepared in exactly the same manner except that a flat stainless steel release belt was used instead of a textured one, and then pressed with an embossing roll with hard grains engraved at a surface temperature of 160°C to a thickness of 30 kg/m, 3
When embossed at a speed of m/min and then similarly finished with gravure, the thickness of the silver surface was flat at 30 microns, and the texture was hard (Comparative Example 1). As a further comparison, the process was carried out in exactly the same manner as in Example 1, except that a substrate without water wetting was used. The obtained silver surface is like a dry film and is fixed to the surface of the base material.
It had a very hard texture (Comparative Example 2). Table 1 shows the properties of the product obtained here. Regarding the measurement of physical properties, moisture permeability is determined according to the JIS K-6549 method, and the higher the number, the better the moisture permeability. Regarding Gurley stiffness, the smaller the number, the softer the texture. Furthermore, in terms of peel strength, after bonding the silver surfaces together with a urethane-based two-component adhesive,
The strength is measured in inch width according to JIS K-6500.

[Table] Example 2 In order to faithfully reproduce the grain of goat natural leather, a 1.5 mm release belt-shaped silicone sheet with goat-like grain reversely engraved was created by pouring a hardening silicone liquid onto its surface. did. 50, 150, 300, 400 as a silver surface polyurethane solution on the sheet
Example 1 except that each g/m ² was coated.
In exactly the same manner as above, an artificial leather having a black color was obtained. The physical properties of the artificial leather coated with 50 to 300 g/m ² are as listed in Table 2, and the softness and goat-like lux were sufficiently satisfactory. The 500g/ ^m2 coated material was heat-treated at 70℃ for 10 minutes to ensure sufficient solidification, but the average grain thickness on the substrate was 340μ, and the water vapor solidification balance did not proceed well. The Gurley value was 1400 mg, and the goat-like grain was somewhat unclear.

[Table] Example 3 A brown-dyed fabric made of Tetron/Rayon = 65/35 mixed yarn, brushed on one side, 0.9 mm in thickness, and 200 g/m ² in area weight was subjected to water wet treatment at a squeezing rate of 90%. On the other hand, the molar ratio of polytetramethylene ether glycol (molecular weight 1500), 4,4 diphenylmethane isodicyanate, and ethylene glycol was 1:
A solution of polyurethane elastomer polymerized from 4:3 in N,N dimethylformamide having a solid content of 28% and a viscosity of 21000 CPS/30°C was used as a polyurethane elastomer for silver surfaces. Furthermore, this product is colored with a brown pigment. Next, the goat-like textured silicone sheet used in Example 2 was coated with the above polyurethane elastomer solution for silver surfaces at a rate of 100 g/m ² .
Immediately, the water-wetted fabric was evenly layered.
In this case, they were stacked so that the side opposite to the raised side was treated with a silver surface. The silicone sheet and the raised fabric were stacked on top of the iron plate surface at a surface temperature of 95°C, and the raised side was brought into contact with the silicone sheet for 3 minutes for heat treatment.Then, it was peeled off from the silicone sheet, introduced into water at 60°C, and thoroughly washed with water. Dry. The resulting leather-like material obtained by clear processing on the goat-like grain had a total thickness of 1.05 mm, and had a soft, grain-free lux with deep shading. Its permeability is also 12.8mg/
² cm2, making it a very desirable shoe for women.

Claims (1)

[Claims] 1. In coating a microporous silver surface with an average grain surface thickness of 200 microns or less on a substrate, first, a water-mixture containing polyurethane elastomer as a main component is placed on a textured release belt that has been reversely engraved to the desired texture. The polyurethane elastomer is coated with a polyurethane elastomer solution, one side of the water-wetted base material is placed on top of the coated base material, and then heated from the other side of the base material so that the saturated water vapor generated within the base material substantially dissolves the polyurethane elastomer. A method for producing a grained thin-layer microporous silver surface, which comprises solidifying, releasing from a grained release belt, washing with water and drying.