PURPOSE: To improve the powder properties, to prevent caking and to improve the flowability, etc., by incorporating a specified quantity of silicon dioxide in sodium silicofluoride.
CONSTITUTION: A 40% silicofluoric acid is put in a polyethylene-made reactor, incorporated with deionized water to dilute it, stirred thoroughly, while the outside of the reactor is cooled, and is gradually incorporated with an aqueous caustic soda solution to make its pH at about 2.6. After cooled, the produced precipitation is filtered and washed with deionized water and dried. Thus by such a process, sodium siliofluoride is produced. Consequently a 0.05-10wt.% silicon dioxide which is preferably noncrystal and has 50-350m2/g specific surface area, is incorporated into the obtained sodium silicofluoride to produce a sodium silicofluoride composition. The sodium silicofluoride composition does not generate degradation of flowability due to caking, and a clogging phenomenon in a hopper and a caking phenomenon during storage, etc.
Takenaga
Yukio Takahashi
Noboru Hatsuda
