Synthetic magnesium silicate

A process for the preparation of synthetic magnesium silicates having a layered crystalline structure of the formula

• [Mg3−x−LixSi4O10(OH)2−yFy]x− x/zMz+
• where 0.1≦x≦0.4 and 0<y≦2,
• M is an alkali metal ion having a valency z and in which the relationship of the fluorine molar content (CF) to the silicon molar content (Csi) in the final product is
• CF[mols]=−1.92 Csi[mols]+b
• where b=2.18 to 2.02
• said process, which comprises
• reacting an aqueous MgSO4 solution with an aqueous solution containing lithium ions and fluoride ions, subsequently adding a silicon compound to form a reaction mixture before crystallization, and after said addition of silicon compound, heating at autogenous pressures at from at from 100° to 320° C. for from 2 to 24 hours, then cooling, and separating said magnesium silicate from byproducts, then washing said magnesium silicate, wherein before crystallization the atomic ratios in said reaction mixture are:
• Mg/Si=0.7144 to 0.6405;
• Li/Si=0.02464 to 0.09854;
• Si/F=2.04 to 2.49;
• Na/Si=0.9514 to 2.0298;
• and the ratio of H2O to SiO2 is from about 14:1 to 43:1 with the proviso that the ratio of Li/Mg is from 0.079 to 0.096.

A synthetic, purified magnesium silicate having a layered crystalline structure of the formula

• [Mg3−x−LixSi4O10(OH)2−yFy]x− x/zMz+
• where 0.21≦x≦0.33 and 0<y≦2,
• M is an alkali metal ion having a valency z and in which the molar relationship of the fluorine mole content (CF) to the silicon mole content (Csi) in the final product resulting from said reaction mixture is
• CF[mols]=−1.92 Csi[mols]+b
• where b=2.18 to 2.02
• said magnesium silicate exhibiting a high yield point in solutions containing low electrolyte concentration, and wherein said magnesium silicate is derived from a reaction mixture, before crystallization, having atomic ratios of constituents in said reaction mixture of:
• Mg/Si=0.6750 to 0.6849;
• Li/Si=0.05420 to 0.06405;
• Si/F=2.04 to 2.49;
• Na/Si=0.9514 to 2.0298;
• and the ratio of H2O to SiO2 is from about 14:1 to 43:1 with the proviso that the ratio of Li/Mg is from 0.079 to 0.096.

A synthetic, purified magnesium silicate having a layered crystalline structure of the formula

• [Mg3−x−LixSi4O10(OH)2−yFy]x− x/zMz+
• where 0.21≦x≦0.33 and 0<y≦2,
• M is an alkali metal ion having a valency z and in which the molar relationship of the fluorine mole content (CF) to the silicon mole content (Csi) in said reaction mixture is
• CF[mols]=−1.92 Csi[mols]+b
• where b=2.18 to 2.02
• said magnesium silicate exhibiting pseudoplasticity in solutions containing high or low electrolyte concentration, and wherein said magnesium silicate is derived from a reaction mixture, before crystallization having atomic ratios of constituents in said reaction mixture of:
• Mg/Si=0.6528 to 0.6627;
• Li/Si=0.0764 to 0.0862;
• Si/F=2.04 to 2.49;
• Na/Si=0.9514 to 2.0298;
• and the ratio of H2O to SiO2 is from about 14:1 to 43:1 with the proviso that the ratio of Li/Mg is from 0.079 to 0.096.14