| 摘要 |
PURPOSE:To obtain the subject composite porous body having various colors, etc., to give a good appearance, by removing a pore-forming material from a product prepared by reacting a salt aqueous solution-impregnated polyvinyl acetal porous body with a specific reaction raw solution having approximately the same specific gravity as the apparent specific gravity of the porous material in the presence of a catalyst. CONSTITUTION:A reaction raw solution comprising polyvinyl alcohol having an average polymerization degree of 300-30000 and a saponification degree of 80mol%, a pore-forming material preferably comprising starch extracted from a plant and a crosslinking agent such as formaldehyde is mixed with a catalyst such as hydrochloric acid and subsequently with a polyvinyl acetal porous body sufficiently impregnated with a salt aqueous solution such as sodium sulfate aqueous solution and having a specific gravity (specific gravity of 1.01-1.20) approximately the same or slightly higher as or than that of the reaction raw solution. The mixture is thermally subjected to a crosslinking reaction and the reaction product is taken out and washed with water to provide the objective composite porous body. |
