Patent ID: 7371356

Claim:
A process for the preparation of calcium carbonate with high brightness by reductive bleaching by means of one sulfinic and/or sulfonic acid derivative, which comprises treating calcium carbonate and/or the milk of lime used for its preparation by reacting milk of lime with carbon dioxide, and/or at least one of the calcium-containing preliminary products used for the preparation of the milk of lime before, during and/or after this reaction with a bleaching agent which comprises at least one compound of the formula (I): A[(CR 1 R 2 )SO p M (1/q) ] r (I) where the variables have the following meanings: A is NR 3 R 4 , NR 3 , N or OH; R 1 , R 2 , R 3 , R 4 , independently of one another, are hydrogen or an organic radical; M is ammonium or metal p is 2 or 3; q is the valency of M; and r is 1 when A = OH or NR 3 R 4 , is 2 when A = NR 3 and is 3 when A = N;. and where variables, if a mixture of compounds is used and/or r=2 or 3, are chosen independently of one another for each individual compound and/or for each [(CR 1 R 2 )SO p M (1/q) ] group.