| 摘要 |
PROBLEM TO BE SOLVED: To provide a practical composition for a heat insulating material, which uses as a reaction raw material a crystalline calcium silicate (including its hydrate) such as xonotlite, tobermorite, gyrolite and wollastonite, wherein even if the crystalline calcium silicate exceeding an amount of 90 wt.% is reacted, the drying shrinkage of a molding for a heat insulating material and the decrease in the mechanical strength thereof are suppressed; the heat insulation is better than that of conventional products; and the composition is obtained by a manufacture method which is simple and poses no problem of calcium salts waste water.SOLUTION: A composition for a heat insulating material is obtained by stirring a mixture under heating at 50°C or higher during mixing and after mixing of an aqueous slurry containing at least one crystalline calcium silicate selected from the group consisting of xonotlite, tobermorite. gyrolite and wollastonite, and phosphoric acid to react with an amount of >90 wt.% of the crystalline calcium silicate, wherein (1) the addition of the phosphoric acid to the aqueous slurry is rapidly carried out at such an addition rate that the pH of the mixture at least temporarily becomes <7 during the mixing; and (2) the composition contains a calcium phosphate salt and amorphous silica, and the amount of unreacted crystalline calcium silicate is <10 wt.% of the amount of the crystalline calcium silicate before the reaction. |
