JPH0367149B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a leather-like sheet material with excellent surface smoothness. Conventionally, a method for manufacturing leather-like sheets involves impregnating the voids of a fibrous base material with a hydrophilic organic solvent solution of an elastomeric polymer such as polyurethane, and then immersing the base material in, for example, water to absorb the organic solvent. The elastic polymer is wet-coagulated by dissolving and removing it in water, and then a solution of an elastomeric polymer such as polyurethane is applied to the surface of this base material, and the elastomeric polymer applied to the surface is wet-coagulated. A method of providing a microporous layer is known. However, according to this method, water etc. permeate into the base material during the wet coagulation process during the formation of the microporous layer, causing air bubbles in the base material to be pushed out and enter the microporous layer during the solidification process, resulting in microporous There was a drawback that coarse air bubbles were formed in the porous layer, a microporous layer with uniform and dense air bubbles was not formed, and the surface smoothness of the obtained sheet-like product was reduced. On the other hand, a method is also known in which the back surface of the base material is water-repellent treated, a solution of polyurethane or the like is applied to the surface opposite to the treated surface, and the polyurethane or the like is wet coagulated to form a microporous layer. However, in this method, only the back side of the base material is treated to be water repellent, and the front side is not treated to be water or oil repellent, so it is difficult to use the base material in the wet coagulation process. Although penetration of water, etc. from the back side of the material is prevented, when a solution such as polyurethane is applied in the previous process, the solution penetrates into the base material and replaces the air in the base material. Air bubbles are forced out and invade the polyurethane film applied to the surface, making it difficult to form a microporous layer with excellent smoothness, and requiring a new process of water repellent treatment, which complicates manufacturing. There was a problem. The present invention was made in view of the above points, and it is possible to form a microporous layer with a dense and uniform cell structure without the bubbles in the base material transferring to the microporous layer during the solidification process when forming the microporous layer. An object of the present invention is to provide a method for producing a leather-like sheet material that can obtain a leather-like sheet material with excellent surface smoothness. That is, in the method for producing a leather-like sheet material of the present invention, after impregnating a fibrous base material with an elastic polymer solution containing a fluorine-containing urethane compound,
The base material is immersed in a non-solvent mainly composed of water to wet-coagulate the elastomeric polymer, and then dried, and then an elastomeric polymer solution is applied to the surface,
Thereafter, the elastic polymer coated on the surface is wet-solidified by immersing it in a non-solvent mainly containing water to form a microporous layer. Examples of the fibrous base material used in the present invention include base materials having voids inside, such as woven fabrics, knitted fabrics, and nonwoven fabrics. Note that the fibrous base material impregnated or coated with a water-soluble polymer compound such as polyvinyl alcohol, hydroxymethyl cellulose, methyl cellulose, etc. can also be used. In addition, examples of elastomeric polymers containing fluorine-containing urethane compounds include polyurethane, polyacrylonitrile, polyacrylic acid ester, etc.; Most preferred are plastic polyurethanes. In the method of the present invention, the fibrous base material is first impregnated with a solution of the elastomeric polymer containing a fluorine-containing urethane compound, and then the fluorine-containing urethane compound and the elastomeric polymer are wet-coagulated. urge At this time, as a solvent for the elastomeric polymer solution, an organic solvent that can dissolve both the fluorine-containing urethane compound and the elastomeric polymer and has hydrophilic properties is used, such as dimethylformamide, dioxane, tetrahydrofuran, acetone, etc. , dimethyl sulfoxide, dimethyl acetamide and the like, dimethyl formamide is most preferred. In order to wet-coagulate the elastomeric polymer, a non-solvent mainly composed of water is used which dissolves the organic solvent but does not dissolve the elastomeric polymer. In the present invention, examples of the fluorine-containing urethane compound contained in the elastic polymer include addition reaction products of a urethane prepolymer having an isocyanate group at the end and a perfluoroalkyl group-containing compound having an active hydrogen group. It will be done. The above urethane prepolymer is composed of polyester polyols such as polyethylene adipate, polybutylene adipate, and poly-ε-caprolactone, polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and 2,4-tolylene diisocyanate, 2,6 -tolylene diisocyanate, 4,
4'-Diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, 4,4'-
It is obtained by reacting with polyisocyanate such as dicyclohexylmethane diisocyanate,
Urethane prepolymers using polyols such as polyester polyols and polyether polyols having a molecular weight of 400 to 4,000 are preferred. Examples of the perfluoroalkyl group-containing compound having an active hydrogen group that can undergo an addition reaction with the urethane prepolymer include R ₁ OH, R ₁ SO ₂ NH ₂ ,

【formula】

[Formula] R ₁ OCH ₂ CH ₂ OH (wherein, R ₁ is a C ₆ to _{C 18} perfluoroalkyl group, and R ₂ is a C ₁ to _{C 3} alkyl group). Can be mentioned. The above urethane prepolymer and the perfluoroalkyl group-containing compound have a fluorine content in the fluorine-containing urethane compound obtained by the reaction of the two.
It is preferable to select the molecular weight, type, etc. of the urethane prepolymer and perfluoroalkyl group-containing compound so that the amount is 12 to 35% by weight. The amount of the fluorine-containing urethane compound added to the elastic polymer is such that the fluorine content in the elastic polymer and the fluorine-containing urethane compound is 0.02 to 0.3.
An amount of 0.03 to 0.2% by weight is preferred. The fluorine content of the fluorine-containing urethane compound is 12
If it is out of the range of ~35% by weight, the water repellency of the fluorine-containing urethane compound may decrease, or the fluorine-containing urethane compound may escape from the elastomeric polymer into a non-solvent mainly composed of water. Problems are likely to occur. Furthermore, if the content of the fluorine-containing urethane compound in the elastomeric polymer is such that the fluorine content is less than 0.02% by weight, it is difficult to obtain sufficient water repellency.
Even if the fluorine-containing urethane compound is contained in an amount exceeding 0.3% by weight, the effect of the addition of the fluorine-containing urethane compound will be in an equilibrium state, and no further improvement can be expected. It is preferable that the elastomeric polymer solution containing the fluorine-containing urethane compound does not contain a surfactant. When a surfactant is added to the base material, it is preferable to wet-coagulate the elastomeric polymer and then thoroughly wash the base material with water to remove the surfactant remaining in the base material. In addition, in order to improve the light resistance, hydrolysis resistance, etc. of the elastic polymer, light resistance improvers such as benzophenone compounds, benzotriazole compounds, hindered phenol compounds, and hindered amine compounds, and polycarbodiimide are added. Even if a hydrolysis inhibitor such as the like is added and used, there is no problem as long as the water repellency is not reduced, and if necessary, a pigment or the like for coloring the fibrous base material can also be used in combination. The base material filled with the wet-coagulated elastomeric polymer is dried so that the non-solvent mainly composed of water in the base material is completely removed. Next, an elastic polymer is applied to the base material,
This is wet solidified. At this time, since the base material is dried, it has the effect of improving the adhesive strength with the elastic polymer applied to the surface. In addition, since the above-mentioned base material has been dried and has increased hydrophobicity, even when an elastic polymer is applied to the base material and wet-coagulated in a non-solvent mainly composed of water, the hydrophobicity of the aqueous solvent is increased. It prevents air (in the base material) from penetrating into the base material and prevents the migration of air (in the base material) into the elastomeric polymer during the solidification process, which is caused by the penetration of water-based non-solvents into the base material. It is possible to form a microporous layer with excellent smoothness and a uniform fine cell structure. When the base material is brought into contact with a heating body such as a hot roll or a hot plate before or after drying, the fibers protruding on the surface of the base material can be brought down, and the surface smoothness can be further improved. I can do it. The elastomeric polymer applied to the surface of the base material is preferably an elastomeric polymer containing polyurethane elastomer as a main component, and polyols constituting the polyurethane elastomer include polyethylene adipate, polyethylene butylene adipate, polybutylene adipate, Polyester polyols such as poly-ε-caprolactone, polyether polyols such as polypropylene glycol, polytetramethylene ether glycol, or ethylene glycol, 1,4-butadiol,
Examples include low molecular weight glycols such as 1,3-butanediol, polycarbonate polyols, and the like.
Examples of the polyisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc. However, 4,4'-diphenylmethane diisocyanate is particularly preferred. As a solvent for these elastic polymers whose main component is polyurethane elastomer,
The same organic solvent used as the solvent for the elastomeric polymer impregnated into the base material may be used. By dipping the material, the elastomeric polymer applied to the surface of the substrate is solidified, thereby forming a microporous layer, and a leather-like sheet material is obtained. As described above, according to the present invention, since the high molecular elastic polymer filled in the base material contains a fluorine-containing urethane compound, the entire base material has excellent water repellency. During wet coagulation of a molecular elastic polymer, it is difficult for water to penetrate into the base material, and as water penetrates into the base material, air bubbles in the base material are pushed out into the high molecular elastic polymer during the solidification process. A leather-like sheet with an extremely smooth surface as a result of the formation of a microporous layer with a dense and uniform cell structure without the inclusion of coarse air bubbles in the formed microporous layer. A similar product is obtained. In addition, since the non-solvent mainly composed of water is completely removed from the surface to which the elastomeric polymer solution that forms the microporous layer is applied, it has the effect of improving the adhesive strength between the base material and the microporous layer. play. The present invention will be explained in more detail below by giving Examples and Comparative Examples. In Examples and Comparative Examples, % indicates weight %. Example Thickness 1.2 consisting of 10% polyethylene terephthalate fiber with a fiber length of 76 mm and a fineness of 6 denier, 30% polyethylene terephthalate fiber with a fiber length of 51 mm and a fineness of 2 denier, and 60% polyethylene terephthalate fiber with a fiber length of 29 mm and a fineness of 1.5 denier. mm, basis weight 300 g/m ² as a base material, 12% polyurethane polyurea (product name: Crisbon, manufactured by Dainippon Ink & Chemicals) and fluorine-containing urethane (

Synthesized from [formula], tolylene diisocyanate, and polyethylene adipate with a molecular weight of 500: Fluorine content 31
%) was immersed in a dimethyl formamide solution containing 0.048% (the fluorine content in the solid content of the total of polyurethane polyurea and fluorine-containing urethane was 0.124%). Next, the liquid was squeezed through squeezing rolls whose roll spacing was adjusted to 1.1 mm, and then immersed in water at 20°C to coagulate the polyurethane polyurea containing fluorine-containing urethane. After washing this thing with water
After drying with ventilation at 125°C, a 25% dimethyl formamide solution of polyurethane polyurea (product name: Crisbon, manufactured by Dainippon Ink Chemical) was applied to the surface.
It was coated at a weight of 800 g/m ² and then immersed in water at 20° C. to coagulate the polyurethane polyurea. Thereafter, the material was thoroughly washed with water and dried with ventilation at 120° C. to obtain a leather-like sheet material having a uniform, dense microporous layer and excellent surface smoothness. Comparative Example A leather-like sheet material was obtained in the same manner as in the example except that fluorine-containing urethane was not used, but coarse air bubbles were contained in the microporous layer and the surface smoothness was poor. .

Claims (1)

[Scope of Claims] 1. After impregnating a fibrous base material with a high-molecular elastomer solution containing a fluorine-containing urethane compound, the base material is immersed in a non-solvent mainly composed of water. After wet-coagulating a molecular elastic polymer and then drying it, an elastic polymer solution is applied to the surface, and then immersed in a non-solvent mainly composed of water and applied to the surface. A method for producing a leather-like sheet material, which comprises wet-coagulating a polymer to form a microporous layer. 2 The fluorine content in the fluorine-containing urethane compound is
The method for producing a leather-like sheet material according to claim 1, wherein the content is 12 to 35% by weight. 3. The elastic polymer containing the fluorine-containing urethane compound has a fluorine content of 0.02 to 0.02.
A method for producing a leather-like sheet material according to claim 1 or 2, which contains a fluorine-containing urethane compound in an amount of 0.3% by weight.