JPH0357229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a leather-like sheet material having excellent surface smoothness.

Conventionally, the method for manufacturing leather-like sheets involves impregnating the voids of a fibrous base material with a solution of an elastic polymer such as polyurethane in a hydrophilic organic solvent.
The base material is immersed in a solvent such as water that dissolves the hydrophilic organic solvent but does not dissolve the high-molecular elastomeric polymer, and the organic solvent is dissolved and removed in the solvent such as water to wet-coagulate the elastomeric polymer, A method is known in which a solution of an elastomeric polymer such as polyurethane is then applied to the surface of the base material, and then the elastomeric polymer applied to the surface is wet coagulated to form a microporous layer. However, according to this method, water penetrates into the base material during the wet coagulation process during the formation of the microporous layer, and air bubbles in the base material are extruded and penetrate into the microporous layer during the solidification process, resulting in microporous Coarse bubbles occur in the layer, and a uniform, dense microporous layer of bubbles is not formed.
There was a drawback that the surface smoothness of the obtained sheet-like product was reduced.

On the other hand, it is also known to form a microporous layer by applying a solution of polyurethane or the like to the opposite side of the base material after water-repellent treatment on the back side of the base material, and then wet coagulating the polyurethane or the like. (Japanese Patent Application Laid-open No. 51-61605), in this method, only the back side of the base material is treated with water repellency, and the front side is not treated with water or oil repellency, 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 substrate is prevented, when a solution such as polyurethane is applied in the previous step, the solution such as polyurethane penetrates into the base material and replaces the air in the base material. The problem is that air bubbles are extruded 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 called water removal treatment, which complicates manufacturing. It was hot.

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, the present invention impregnates a fibrous base material with an elastomeric polymer solution containing a fluorine-containing urethane compound, and then immerses the base material in a coagulation bath to wet-coagulate the elastomeric polymer, Next, the excess coagulation bath solvent impregnated into the base material is removed, and at least one of the surfaces of the base material is brought into contact with the surface of the heating element to remove the coagulation bath solvent near the surface layer of the base material. An elastomeric polymer solution is applied to the side that is in contact with the surface of the heating element on one side, and then immersed in a coagulation bath to wet-coagulate the elastomeric polymer applied to one side of the base material to form a microporous layer. The gist of the present invention is a method for manufacturing a leather-like sheet material, which is characterized by:

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. The fibrous base material may also be impregnated with a water-soluble polymer such as polyvinyl alcohol, hydroxycellulose, or methylcellulose. In addition, examples of the elastic polymer containing a fluorine-containing urethane compound include polyurethane, polyacrylonitrile,
Examples include polyacrylic esters, but thermoplastic polyurethanes are most preferable in view of various physical properties such as wet film formability, bending resistance, and flexibility, and polyurethanes having a softening point of 140 to 220°C are particularly preferable.

In the method of the present invention, first, the above fibrous base material is
After impregnating with a solution of the above elastic polymer containing a fluorine-containing urethane compound, the fluorine-containing urethane compound and the elastic polymer are wet coagulated. At this time, as a solvent for the elastomeric polymer solution, an organic solvent that dissolves both the fluorine-containing urethane compound and the elastomeric polymer and has hydrophilic properties is used, such as dimethylformamide, dioxane, tetrahydrofuran, acetone, etc. dimethylformamide is most preferred. Further, as a coagulation solution solvent for wet-coagulating the elastic polymer, a solvent mainly composed of water is used, which dissolves the organic solvent but does not dissolve the elastic 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 prepolymers include polyester polyols such as polyethylene adipate, polybutylene adipate, poly-ε-caprolactone, polyethylene glycol, polypropylene glycol,
Polyether polyol such as polytetramethylene glycol, 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 Examples include compounds represented by the general formula R ₁・O・CH ₂ CH ₂ OH (where R ₁ is a perfluoroalkyl group and R ₂ is an alkyl group), but the perfluoroalkyl group has 6 to 6 carbon atoms. 18 is preferred.

For example, a urethane prepolymer having an isocyanate group at the end obtained by reacting 1 mole of polyethylene adipate with 2 moles of tolylene diisocyanate is further reacted with 2 moles of perfluorooctyl alcohol as a perfluoroalkyl group-containing compound having an active hydrogen group. The fluorine-containing urethane compound thus obtained has the following structure.

The above urethane prepolymer and the perfluoroalkyl group-containing compound have a fluorine content of 12
Urethane prepolymer, to be ~35% by weight
It is preferable to select and use the molecular weight, type, etc. of the perfluoroalkyl group-containing compound. In addition, 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 0.30% by weight, especially 0.03% by weight.
An amount of ~0.20% by weight is preferred. If the fluorine content of the fluorine-containing urethane compound is outside the range of 12 to 35% by weight, the water repellency of the fluorine-containing urethane compound may decrease, the fluorine-containing urethane compound may escape from the elastic polymer into the solvent, etc. Problems are likely to occur. Furthermore, if the content of the fluorine-containing urethane compound in the elastic 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 5% 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 elastic 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 and hydrolysis resistance of the elastic polymer, light resistance improvers such as hindered phenol, benzotriazole, benzophenone, and hindered amine, and hydrolysis inhibitors such as polycarbodiimide are used. There is no problem even if it is added and used as long as it does not cause a decrease in water repellency, 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 elastomer is removed from the excess coagulation bath solvent impregnated into the base material, but at this time, the solvent contained in the base material must be completely removed. It is preferable that the solvent is contained in the voids in the base material, and the amount of solvent contained in the base material is 30 to 200 when the dry weight of the base material filled with the solidified elastic polymer is 100. It is preferable that

Next, at least one surface of the base material is brought into contact with a heating body surface, preferably a heating body surface having a surface temperature equal to or higher than the boiling point of the coagulation bath solvent to remove the solvent near the base material surface layer, and then one side of the base material is removed. An elastomeric polymer solution is applied to the side that is in contact with the surface of the heating element. By bringing the surface of the base material into contact with the surface of the heating element and removing the solvent on the surface, the adhesive strength with the elastomeric polymer applied to the surface is improved, and the fibers protruding from the surface are collapsed, and the surface This has the effect of further improving the smoothness of the surface. In addition, the surface that is brought into contact with the surface of the heating element becomes hydrophobic, and therefore, not only the surface on which the elastomeric polymer solution that forms the microporous layer is applied, but also the surface on which the elastomeric polymer solution is not applied. It is preferable to bring the substrate into contact with the surface of the heating element to remove the solvent near the surface layer.By bringing both the front and back surfaces of the base material into contact with the heating element surface, hydrophobicity is further increased, resulting in a more uniform coating. A microporous layer with a dense cell structure is formed.

The elastomeric polymer applied to the surface 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, and Examples include polyester polyols such as -ε-caprolactone, polyether polyols such as polypropylene glycol and polytetramethylene ether glycol, low molecular weight glycols such as ethylene glycol, 1,4-butanediol and 1,3-butanediol, and polycarbonate polyols. It will be done. Examples of polyisocyanates include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate,
Examples include xylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate is particularly preferred. Examples of the solvent for the elastic polymer containing polyurethane elastomer as a main component include the same organic solvents used as the solvent for the elastic polymer impregnated into the base material,
After applying the elastomeric polymer solution to the surface of the base material,
By immersing the base material in a solvent whose main component is water, the elastomeric polymer applied to the surface of the base material is coagulated, forming a microporous layer and yielding a leather-like sheet material. .

As described above, according to the present invention, since the elastic polymer filled in the base material contains a fluorine-containing urethane compound, the entire base material has excellent water repellency, and therefore the polymer forming the microporous layer During wet coagulation of an elastomeric polymer, it is difficult for solvents such as water to penetrate into the base material. Since there is very little risk of being extruded into the microporous layer, coarse air bubbles are not contained in the formed microporous layer, and as a result, a microporous layer with a dense and uniform cell structure is formed, resulting in a smooth surface. An extremely smooth leather-like sheet material is obtained. In addition, the surface to which the elastomeric polymer solution that forms the microporous layer is applied is brought into contact with the surface of the heating element in advance to remove the solvent near the surface layer and to collapse the fibers on the surface. It has various effects such as improving the adhesive strength of the microporous layer and further improving the planar smoothness.

The present invention will be described in more detail below with reference to Examples and Comparative Examples.

Example 1 30% polyurethane terephthalate fiber with a fiber length of 38 mm and a fineness of 1.5 denier, and a fiber length of 51 mm and a fineness of 1.5 denier.
Consisting of 70% 1.5 denier 6-nylon fiber.
The base material is a short fiber entanglement with a thickness of 1.3 mm and a basis weight of 250 g/ ^m2 , and the base material is made of polyurethane polyurea (product name: Crisbon, manufactured by Dainippon Ink and Chemicals: softening point 194°C, 100% modulus 40 kg/ ^cm2 ) 19.8%,
Fluorine-containing urethane (fluorine content 32% by weight) 0.044%
The sample was immersed in a dimethyl formamide solution (the fluorine content in the total solid content of polyurethane polyurea and fluorine-containing urethane was approximately 0.070%). Then the ratio of substrate to dimethyl formamide solution was 100:
After squeezing the solution to 97%, the base material was immersed in a solvent at 20°C consisting of 97% water and 3% dimethyl formamide to coagulate the polyurethane polyurea containing fluorine-containing urethane. Next, when the weight of the solvent contained in the base material is set to the dry weight of the base material as 100,
After squeezing the liquid with a squeezing roll so that the temperature is 68, the surface of the base material is brought into contact with a metal roll with a surface temperature of 160°C, and then a polyurethane polyurea (product name: Samprene, manufactured by Sanyo Chemical Co., Ltd.: softening point) is applied to the surface. 198℃,
100% modulus 125Kg/ ^cm2 ) 23.5%, castor oil
A dimethyl formamide solution containing 0.65% polyethylene glycol lauryl ether and 1.3% polyethylene glycol lauryl ether was applied at a density of 1050 g/m ² , and the substrate was then immersed in water at 20° C. to coagulate the polyurethane polyurea. Thereafter, it was thoroughly washed with water and dried with ventilation at 120°C, to obtain a leather-like sheet material with a uniform, dense microporous layer and excellent surface smoothness.

The above fluorine-containing urethane ratio is perfluorooctyl obtained by reacting polyethylene diadipate (MV556), tolylene diisocyanate, and C ₈ F ₁₇ SO ₂ N (CH ₃ ) CH ₂ CH ₂ OH in dimethylformamide. It is a fluorine-containing urethane with a group at the end.

Comparative Example 1 A leather-like sheet material was obtained in exactly the same manner as in Example 1 except that fluorine-containing urethane was not used, but coarse air bubbles were contained in the microporous layer and the surface smoothness was poor. Ta.

Comparative Example 2 The same base material as in Example 1 was impregnated with a dimethyl formamide solution of polyurethane polyurea containing the same fluorine-containing urethane as in Example 1, and then the base material was immersed in water to coagulate the polyurethane polyurea. I forced it. Next, without bringing the surface of the substrate into contact with the surface of the heating element, a dimethyl formamide solution containing polyurethane polyurea as a main component similar to Example 1 was immediately applied, and then immersed in water to coagulate the polyurethane polyurea to form a microporous layer. A leather-like sheet material was obtained. The obtained sheet-like product had poor surface smoothness and also poor adhesive strength of the microporous layer.

Claims (1)

[Scope of Claims] 1. After impregnating a fibrous base material with an elastomeric polymer solution containing a fluorine-containing urethane compound, the base material is immersed in a coagulation bath to wet-coagulate the elastomeric polymer. After removing the excess coagulation bath solvent impregnated into the base material and bringing at least one of the surfaces of the base material into contact with the surface of the heating element to remove the coagulation bath solvent near the surface layer of the base material, An elastomeric polymer solution is applied to one side of the substrate that is in contact with the surface of the heating element, and then immersed in a coagulation bath to wet-coagulate the elastomeric polymer applied to one side of the substrate to form a microporous layer. A method for producing a leather-like sheet material, characterized by forming a leather-like sheet material. 2 The fluorine content in the fluorine-containing urethane compound is 12~
The method for producing a leather-like sheet material according to claim 1, wherein the content is 35% by weight. 3. Claims 1 or 2, wherein the elastic polymer containing a fluorine-containing urethane compound contains the fluorine-containing urethane compound in an amount such that the fluorine content in the polymer is 0.02 to 0.03% by weight. The method for producing the leather-like sheet material described above. 4. The method for producing a leather-like sheet material according to any one of claims 1 to 3, wherein the surfaces of the base material that are brought into contact with the heating body surface are both the front and back surfaces.