JPH042717B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing synthetic leather using a urethane resin foam as an intermediate layer. Conventional technology Conventionally, methods for foaming resin used as an intermediate layer in synthetic leather include (1) a method in which gas spheres are dispersed in the resin and the spheres are broken and foamed by heating, (2) dimethylformamide (DMF), etc. Wet coagulation is carried out on a solution of a hydrophilic organic solvent, (3) mechanical foaming is carried out by mechanically foaming the emulsion resin, and (4) thermally decomposable blowing agent is dispersed in the resin. Foaming agent method that uses gas to foam;
(5) Isocyanate reaction methods that utilize gas generated by the reaction between isocyanate groups and water are well known. Problems to be Solved by the Invention Among these, the wet coagulation method uses an organic solvent, so there is a problem in wastewater treatment. The mechanical foaming method requires a foaming device such as a high-performance mixer to obtain fine bubbles, and foams obtained from emulsion resins may lack mechanical strength or the foaming agent may reach the surface of the synthetic leather. Problems such as seepage remain. In the method using gas spheres or a foaming agent, it is difficult to control the foaming temperature, and there are also problems with the form of the foam, such as large cell diameters and low cell density. The reaction between isocyanate groups and water is easily affected by humidity and temperature during processing, and the morphology of the foam is also poor, similar to methods using gas spheres or blowing agents. In view of the current situation, the present inventors conducted repeated research to improve the conventional problems in the isocyanate reaction method, and as a result, they arrived at the present invention. Means for Solving the Problems That is, the present invention provides a foamable adhesive for use in the production of synthetic leather made from polyester or polyether urethane having an isocyanate group at the polymer terminal group, water-containing microcapsules, and a catalyst. The present invention provides a method for producing synthetic leather, which is characterized by using a foamable composition and adding aluminum hydroxide thereto. Conventionally, as a method for obtaining urethane resin foam,
A method of heating and foaming in the presence of a polymer having an isocyanate group as a polymer terminal group, a thermally decomposable microcapsule containing water, and a catalyst has been carried out industrially. However, in the conventional method,
The foamed form was spherical and the foaming process was unsafe. In addition, calcium carbonate and the like have been used as a bulking agent, but this is nothing more than a bulking agent. By adding aluminum hydroxide to the above composition, the present inventors changed the foam form from the conventional spherical closed foam (cell diameter: approximately 100μ) to fine, dense, flat, independent foam. In addition to changing it into a foam with bubbles (cell diameter: 50μ or less),
We have discovered various advantages associated with this. That is, the first advantage of adding aluminum hydroxide is that the time required for heating and foaming can be significantly shortened due to its reaction promoting effect, resulting in a significant improvement in productivity. In addition, the filling effect of inexpensive aluminum hydroxide and the effect of saving urethane can be obtained by increasing the thickness of the foam layer. Furthermore, the softening of the texture due to the fine foam structure is also a major advantage of the present invention. The suitable type of aluminum hydroxide is one with an average particle size of 1 to 30μ;
If it is 30μ or more, coating unevenness and coating streaks will occur, which is not preferable. As for the amount added, polyurethane
A range of 15 to 50 parts by weight per 100 parts by weight is appropriate; if it is less than 15 parts by weight, the effect of shortening the heat foaming time cannot be obtained, and if it is more than 50 parts by weight, the adhesive strength with the base fabric will decrease. There is. Examples Hereinafter, the present invention will be further explained with reference to Examples. On the release paper, apply a skin layer polyurethane resin paint with the following formulation to 100g/ ^m2 , and
It was dried at ℃ for 2 minutes to form a skin layer. Next, a foam layer polyurethane resin paint having the following formulation was applied onto this surface layer at a coating weight of 200 g/m ² . This was heat-foamed at 140°C for 30 seconds, a base fabric was immediately attached, and then heat treated at 120°C for 2 minutes. After cooling or aging at 60°C for 12 hours, the release paper was peeled off to obtain synthetic leather. Skin layer resin composition Luxkin U-2216 [Seiko Kasei Co., Ltd.: Urethane polymer] ...100 parts by weight Methyl ethyl ketone ...30 parts by weight Pigment ...14 parts by weight Foam layer resin composition Ecole-7100 [Toyo Polymer Co., Ltd.: Urethane polymer] ...100 parts by weight EP-620 [Toyo Polymer Co., Ltd.: Microcapsule]
...4 parts by weight AD-D-14G [Toyo Polymer Co., Ltd.: Catalyst]
...1 part by weight C-308 [Sumitomo Aluminum Co., Ltd.: Aluminum hydroxide] ...30 parts by weight Methyl ethyl ketone ...2 parts by weight The average particle size of the aluminum hydroxide was 8 μm. As comparative examples, synthetic leather was prepared by removing aluminum hydroxide from the above foam layer resin composition as Comparative Example 1, and using calcium carbonate (average particle size 5μ) instead of aluminum hydroxide as Comparative Example 2. Created. Measuring the physical properties of the synthetic leather of the present invention example and comparative example,
The results are shown in Table 1.

[Table] By adding aluminum hydroxide, effects such as shortening the foaming time, increasing the thickness of the foam layer, and softening the texture were obtained, and better synthetic leather was obtained than in the comparative example. The cross-sectional structure of the synthetic leather obtained in the above example is shown in FIG. 1, and the cross-sectional structure of the synthetic leather obtained in Comparative Example 1 is shown in FIG.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the cross-sectional structure of synthetic leather obtained by adding aluminum hydroxide according to the present invention, and Figure 2 is a schematic diagram showing the cross-sectional structure of synthetic leather obtained by adding aluminum hydroxide. It is a cross-sectional schematic diagram. 1: skin layer, 2: bubbles, 3: foam layer, 4: base fabric.

Claims (1)

[Scope of Claims] 1. Synthetic leather consisting of a skin layer, a foam adhesive layer, and a base fabric, in which a polyester or polyether polyurethane having an isocyanate group at the polymer end group, a water-containing micro A method for producing synthetic leather, which comprises using a foamable composition comprising a capsule and a catalyst, and adding aluminum hydroxide thereto. 2 The particle size of the aluminum hydroxide to be added is 1~
30μ. The method according to claim 1, wherein 3 The amount of aluminum hydroxide added to polyurethane
The method according to claim 1, characterized in that the amount is 15 to 50 parts by weight per 100 parts by weight.