JPS6354833B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synthetic leather sheet material with excellent light resistance and hydrolysis resistance, and a method for producing the same.

Conventionally, polyurethane-based synthetic leather (artificial leather) has excellent texture and appearance, and has been widely used as a material for bags, bags, shoes, belts, clothing, and the like. However, in most cases, polyurethane, whose polyol component is a polyester of a glycol with 2 to 4 carbon atoms and a dibasic acid such as adipic acid, has been used as the raw material for this product. Furniture, vehicle seats,
For products that require long-term use, such as high-quality clothing, it is impossible to withstand use.

Of course, some improvement can be achieved by adding a hydrolysis inhibitor, such as polycarbodiimide, to the components, but no substantial improvement can be expected.

On the other hand, polycarbonate-based polyurethane elastomers are known as polyurethane elastomers with excellent light resistance and hydrolysis resistance. For all laminates of (artificial leather), especially those with a porous covering layer, it is substantially difficult to form this layer with a polycarbonate-based polyurethane elastomer.

The present inventors have discovered that the light resistance and hydrolysis resistance of the entire synthetic leather sheet can be improved by substantially blocking the supply of air to the porous coating layer provided on the synthetic leather sheet.

Polyether polyurethane inherently has poor light resistance. Here, the polyether polyurethane refers to a polyurethane containing polypropylene ether glycol and/or polytetramethylene ether glycol as a polyol component. In particular, when the surface area is large, such as a porous layer, the contact area between the components and air increases, and the layer becomes significantly susceptible to oxidative deterioration and deterioration due to ultraviolet rays.

Therefore, at least the light resistance of polyether-based polyurethane can be improved by blocking the supply of air into the porous coating layer as much as possible. Hydrolysis resistance can be improved by using a polyether polyurethane that does not have groups.

The following three methods can be considered for restricting the supply of air into the porous coating layer.

The first method is to form a continuous film between a fibrous base material and a porous coating layer. However, when using this method, the texture becomes hard and it is not possible to obtain a texture similar to natural leather.

The second method is to provide a coating on the surface of the porous coating layer. In most conventional synthetic leathers, especially those commonly called artificial leathers, except for so-called enamel type ones, the surface of the porous coating layer is colored by the gravure method.

However, it is known that even if finished by gravure treatment, the light resistance is hardly improved.

The surface of gravure-coated artificial leather appears uniform to the naked eye, but when observed under an electron microscope, a large number of pores remain on the surface of the porous coating layer, and a large amount of air is supplied into the porous coating layer through these pores. It is presumed that it will deteriorate due to This fact shows that in order to improve light resistance and hydrolysis resistance, it is necessary to laminate a continuous film having a certain thickness on the surface of the porous coating layer.

The third method is to make the wet cells formed in the wet porous coating layer as small as possible. For example, dimethyl formamide (DMF), a synthetic resin polymer whose main component is polyurethane elastomer, is used for this method.
A method of performing initial coagulation in a highly concentrated aqueous solution is used, but when this method is used, knitted fabrics,
When textiles are used as a base material, dyes are leached into the water bath, lowering the quality of the product, resulting in poor durability and causing contamination.

Therefore, in order to employ this method, it is necessary to select a coagulation modifier whose durability is not affected by contamination of the coagulation tank.

The present invention applies the second and third methods described above to obtain a synthetic leather sheet with excellent light resistance and hydrolysis resistance. That is, the present invention consists of a fibrous base material impregnated with a polyether-based polyurethane elastomer, a porous coating layer made of the polyether-based polyurethane elastomer and having fine pores, and a polycarbonate-based polyurethane elastomer or a polyether-based polyurethane elastomer. This is an integrated lamination of at least one continuous bond coat and a continuous top coat made of polycarbonate-based polyurethane elastomer. The structure of each layer will be explained below.

A knitted fabric, woven fabric, nonwoven fabric, etc. is used as the fibrous base material, and this base material is impregnated with a polyether-based polyurethane elastomer. The impregnation amount of polyurethane elastomer is within 200%.

A polyether polyurethane elastomer is used as the porous coating layer. Polyether-based polyurethane elastomers containing polypropylene ether glycol as a main component are extremely widely used, economically advantageous, and do not have hydrolyzable groups. The proportion of polypropylene ether glycol in the polyether polyol in the polyether polyurethane elastomer is 10 to 100%. This porous coating layer is formed on the surface of the substrate by wet processing. Palmitic acid monostearate is generally known to be the most effective coagulation regulator for forming micropores in the wet cells formed in the porous coating layer.

However, in order to use this in the production of the sheet material of the present invention, a considerable amount is required, and even after the solvent is removed and the water washing process is repeated several times, a considerable amount of the component remains in the porous coating layer. During drying, this migrates to the surface and forms an oil film, which is unsuitable as it significantly impairs the adhesion to the bond coat. As a result of conducting a wide variety of tests including natural oils and fats, it was found that castor oil is a coagulation modifier that is satisfactory in all respects. In addition,
Fine cellulose powder, pigments, calcium carbonate, ultraviolet absorbers, antioxidants, etc. can be added to improve the wet film formability and texture of this polyether-based polyurethane elastomer.
The type of additive and the amount added must be carefully determined in relation to the light resistance and hydrolysis resistance of the sheet material.

A polyether-based polyurethane elastomer solution containing these additives is applied to a fibrous base material impregnated with the polyether-based polyurethane elastomer, coagulated in a water bath, the solvent removed, and then washed repeatedly in warm water. It is dried to form a porous coating layer having micropores.

The top coat and bond coat must be processed into a continuous coating without pinholes.

The top coat is an important coating layer that affects light resistance and hydrolysis resistance. Generally, Totubcoat is made by adding an aliphatic or alicyclic diisocyanate to a polyester polyol obtained by reacting a glycol having 2 to 6 carbon atoms with a dibasic acid such as adipic acid, and adding a polycarbodiimide or the like to the resulting polyurethane elastomer. Products containing hydrolysis inhibitors, benzimidazole-based, benzofunone-based UV absorbers, and phenol-based antioxidants can be used, but durability is required for furniture, vehicle seats, luxury clothing, etc. It is inappropriate for things.

If only the hydrolysis resistance is to be improved, polytetramethylene, ether glycol and/or polypropylene ether glycol can be used as the polyol component, but it cannot be used as a top coat because the light resistance is extremely poor. . By the way, the porous coating layer has excellent hydrolysis resistance and poor light resistance due to the characteristics of its components, but there are various raw materials for the top coat that can completely compensate for the deterioration of the porous coating layer. As a result of our investigation, we found that polycarbonate-based polyurethane elastomer was the best choice and completely met our needs.

For the bond coat, either or both of a polycarbonate-based polyurethane elastomer and a polyether-based polyurethane elastomer can be used. However, when using a polyether-based polyurethane elastomer, a radical scavenger, ultraviolet absorber, and antioxidant are added in consideration of light resistance. In addition to agents, pigments and the like may also be added as necessary.

The top coat and tie coat are processed into an integral laminate by the following steps. That is, a polycarbonate-based polyurethane elastomer solution forming the top coat is applied onto a release body such as release paper, a metal belt, a plastic sheet, etc., and then dried to form a continuous film without pinholes, and then a bond coat is formed. A continuous coating is formed by applying a polycarbonate-based or polyether-based polyurethane solution. The bonding coat of this laminate is pressed onto the porous coating layer to complete the synthetic leather sheet, but the bonding coat and the porous coating layer are integrated by utilizing the adhesive state after the organic solvent has evaporated. It is preferable to carry out this process from the viewpoint of maintaining surface smoothness and texture.

The thickness of both the top coat and the bonding coat is preferably within the range of 2 to 40 microns, particularly the thickness of the top coat is preferably within the range of 10 to 25 microns. If the thickness is less than 2μ, it will not be possible to sufficiently suppress the deterioration of the porous coating layer of polyether-based polyurethane, and if it is more than 40μ, it will not be possible to obtain a texture similar to natural leather even if the top coat and bond coat are flexible coatings. become unable.

Additionally, antifoaming agents may be added to the component solutions to actively inhibit the formation of pinholes in the top coat and bond coat.

By configuring the present invention as described above, it is possible to obtain a natural leather-like synthetic leather sheet having excellent light resistance and hydrolysis resistance. Examples of the present invention will be described below.

(Example) 6-nylon of 1.5 denier and fiber length of 51 m/m was processed into 200 g/cm ² by carding machine and cross wrapper.
A web with a basis weight of 1.5 m/m was obtained through a needle punching process.

Then polypropylene ether glycol 70
%, polytetramethylene ether glycol 30%
This wet was impregnated with a dimethyl formamide solution containing a polyether polyurethane elastomer having a solid content of 12%, and squeezed with a squeeze roll to a resin solid content of 45% based on the weight of the fibers, and then placed in a water tank. The resulting nonwoven fabric was immersed in water at 20°C, coagulated, desolvated, dehydrated, dried under ventilation at 120°C, and then passed between heated rolls. did.

Next, the following compounded solution was prepared as a coating solution for forming a porous coating layer, and this was applied to the fibrous base material at 1.0 m/m.
It was applied to a thick layer.

Coating liquid formulation Weight part Γ Polyether polyurethane elastomer solution (same as that impregnated into the fibrous base material)
(Solid content 30%) 100 Γ Pigment (Dairatsuku Color) (manufactured by Dainippon Ink)
5 Γ Castor oil (coagulation modifier) 2.5 Γ Cellulose fine powder 5 Γ DMF 40 After applying the above coating solution to the fibrous base material, coagulate and remove the solvent in water at 20°C, and thoroughly soak in warm water at 55°C. After repeated washing, dehydration, and drying at 120° C., a porous coating layer with a thickness of 1.5 m/m and extremely excellent surface smoothness was obtained.

On the other hand, on release paper (manufactured by Dai Nippon Printing), the solid content was 15%.
A polycarbonate-based polyurethane elastomer solution colored dark brown was applied to a solid content of 20 g/cm ² and dried with continuous ventilation in a dryer with a temperature gradient of 80°C to 120°C. A continuous top coat without holes was obtained.

Furthermore, 15% solids content is added as a bond coat on top of this.
A triene solution of a two-component polypropylene glycol-based polyurethane adhesive was applied to a solid content of 18 g/cm ² and dried at 100°C for 2 minutes. It was integrated by pressing onto the surface of the porous coating layer.

The obtained synthetic leather sheet material had a feel extremely similar to natural leather.

This synthetic leather sheet material showed no change in appearance, physical properties, or texture even after 20 weeks in an atmosphere with a relative humidity of 90% and a temperature of 70°C.

Furthermore, no change in appearance was observed even after an ultraviolet irradiation test using a fade meter at 63°C.

Claims (1)

[Scope of Claims] 1. A fibrous base material impregnated with a polyether polyurethane elastomer, a porous coating layer made of the polyether polyurethane elastomer and having fine pores, a polycarbonate polyurethane elastomer, and a polyether polyurethane elastomer. A synthetic leather sheet material having excellent light resistance and hydrolysis resistance, characterized in that a bond coat, which is a continuous film made of at least one side of an elastomer, and a top coat, which is a continuous film made of a polycarbonate polyurethane elastomer, are laminated and integrated. 2 The thickness of the top coat and bond coat is 2
A synthetic leather sheet material having excellent light resistance and hydrolysis resistance according to claim 1, wherein the particle diameter is within the range of ~40μ. 3. A polyurethane elastomer solution to which castor oil is added as a coagulation modifier is applied to a fibrous base material impregnated with a polyether-based polyurethane elastomer, a porous coating layer is formed on the fibrous base material by wet processing, and then the porous coating layer is formed on the fibrous base material by wet processing. A bond coat made of a continuous film made of at least one of a polycarbonate-based polyurethane elastomer and a polyether-based polyurethane elastomer and a top coat made of a continuous film made of a polycarbonate-based polyurethane elastomer are laminated and integrated on the surface of the quality coating layer. A method for producing synthetic leather sheet material with excellent light resistance and hydrolysis resistance.