Magnesium hydroxide and process for its production
AssigneeAsahi Glass Company, Limited
InventorsKeiichi Nakaya, Kunio Tanaka
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Abstract
Magnesium hydroxide of a fine plate-like particle form having an average particle size (d) of from 0.2 to 0.8 .mu.m as measured by a light transmission type liquid phase sedimentation method, wherein the proportion of particles having a particle size of d+0.5 .mu.m or larger is not higher than 50% by weight based on the weight of the total particles, and the particle thickness distribution is such that the proportion of particles having a thickness of 0.05 .mu.m or less is not higher than 5% by number and the proportion of particles having a thickness of 0.2 .mu.m or more is not higher than 20% by number.
Claims20
Magnesium hydroxide having a fine plate-shaped particle form with an average particle size (d) of from 0.2 to 0.8 ? m as measured by a light transmission liquid phase sedimentation method, wherein the proportion of particles having a particle size of d+0.5 .mu.m or larger is not greater than 50% by weight based on the weight of the total particles, and the particle thickness distribution is such that the proportion of particles having a thickness of 0.05 .mu.m or less is not greater than 5% by number and the proportion of particles having a thickness of 0.2 .mu.m or more is not greater than 20% by number;
- and wherein said magnesium hydroxide is produced by a process which comprises:
- (a) reacting an aqueous solution containing a water-soluble magnesium salt, with ammonia;
- and
- (b) precipitating the magnesium hydroxide formed thereby from the aqueous solution, wherein the precipitation of magnesium hydroxide is initiated when the concentration of magnesium hydroxide dissolved in the aqueous solution reaches a level equal to or greater than the value of C.sub.s, with C.sub.S being represented by the formula:
- C.sub.S =0.0293 C.sub.M.sup.1.78
- wherein C.sub.S is the concentration in g mol/liter of magnesium hydroxide dissolved in the aqueous solution at the initiation of the precipitation of magnesium hydroxide, and C.sub.M is the concentration in g mol/liter of magnesium ions in the aqueous solution containing the water-soluble magnesium salt to be reacted with ammonia.
Dependencies are inferred from the claim text.