MANUFACTURE OF CRYSTALLINE ALKALI METAL ALUMINUM PHOSPHATE

A process for the production of crystalline alkali metal aluminum phosphate represented by the formula NaaKbHcAld(PO4)e.xH2O wherein a has a value of from 0.5 to 1.5, b has a value of from 0 to 0.5, c has a value of from 12 to 16, d has a value of from 2.7 to 3.3, e has a value of from 7 to 9 and x has a value of from 3 to 6, and wherein a+b+c+3d=3e, comprises mixing phosphoric acid, sodium hydroxide or sodium carbonate and potassium hydroxide or potassium carbonate in aqueous solution with aluminum hydroxide, potassium oxide or aluminum oxide hydrate in amounts defined by the above formula, with a content of free water in solution ranging from 5 to 44%. The reaction mixture is then heated at a temperature of from 80 DEG to 200 DEG C. (if necessary, under elevated pressure) such that partial crystallization takes place. The free water is thereafter completely removed, if necessary under reduced pressure, at a temperature between about 60 DEG to 130 DEG C., and the crystallization is completed.