Patent ID: 7919066

Claim:
A process for preparing calcium carbonate hydroxodialuminates which have a hexagonal platelet-shaped crystal habit and are of the formula (A): Ca m Al 2 (OH) 6+2(m-1) An* n H 2 O (A) where m=3.5 to 4.5 and An=carbonate which may be partly replaced by perchlorate and/or trifluoromethanesulfonate and n=0 to 6, comprising the steps of: (a) reacting calcium oxide or calcium hydroxide with optionally activated aluminum oxohydroxide or aluminum hydroxide and simultaneously or subsequently with a carbonate source consisting of carbon dioxide or alkali metal carbonate or bicarbonate; and (b1) optionally further reacting the product obtained in step (a) with perchloric acid and/or trifluoromethanesulfonic acid; or (b2) optionally calcining the product obtained in step (a) at 200° C. to 900° C. and subsequently exchanging ions in the presence of a perchlorate and/or trifluoromethanesulfonate salt, optionally in the presence of alkali metal carbonate or bicarbonate, in water, wherein the reaction in step (a) is performed at temperatures of 25-180° C. at ambient pressure or under an elevated pressure of up to 12 bar.