Polymeric aluminum silicate-sulphate and process for producing same

A process for producing polynucleate basic aluminum hydroxy silicate sulfates having an average chemical composition indicated by the formula:

• Al.sub.A (OH).sub.B (SO.sub.4).sub.C (SiO.sub.x).sub.D (H.sub.2 O).sub.E
• wherein:
• A is the number 1.0;
• B is a number from 0.75 to 2.0;
• C is a number from 0.30 to 1.12;
• D is a number from 0.005 to 0.1;
• x is a number greater than 2 but less than or equal to 4, such that 3=B+2C+2D (x-2);
• and
• E is a number greater than 8 for products in solution form and less than 8 for products in solid form;
• said polynucleate compounds having a basicity defined by B/3A.times.100 in the range of 25-66%;
• with the provisos that up to 10 molar % of the amount of Al indicated in the above formula may be replaced by an equivalent amount of another multi-valent cation and up to 10 molar % of the amount of sulfate indicated in the above formula may be replaced by another anion, and that the solution may also contain up to 10 molar % of a weak acid or a salt thereof;
• which process comprises:
• mixing an alkali metal silicate and an alkali metal aluminate in water to form an alkaline intermediate mixture;
• and
• adding the alkaline intermediate mixture to an acidic aluminum sulfate solution under high shear mixing conditions to form a stable solution;
• the relative amounts of said alkali metal silicate, said alkali metal aluminate and said aluminum sulfate being such that said values of A, B, C and D in the formula above are satisfied.