| 摘要 |
PROBLEM TO BE SOLVED: To provide a cork board having its original advantages as a natural product and display its outstanding color fastness to light by decoloring its contained natural coloring matter to make the cork board pale colored. SOLUTION: The cork board is made pale colored by decoloring its contained natural coloring matter and thereby the natural coloring matter is previously decomposed in the cork material. In order to realize this treatment, the cork board is treated by oxidation. For this oxidation, the cork board is soaked into a treating solution containing an oxidizing agent or is sprayed with the treating solution an thus is impregnated with the treating solution. After the lapse of a specified time, the cork board is water-washed and dried. As the oxidizing agent, various kind of peroxides or chlorides are used. Consequently, the cork board shows a superb original property as a natural product and also a high color fastness to light and its color hardly fades, even when it is used exposed to a direct sunshine. For these reasons, the cork board maintains a good outward appearance over a load time on account of its stably uniform color shade and is almost free from a difference in variable density of the color shade depending upon the degree of light exposure, as a product intended for the purpose.
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