There are disclosed co-granules coated with hydroxymethyl cellulose and containing: b1) cyclic sulfonimine, b2) bleach activator selected from the group consisting of tetraacetylethylenediamine, decanoyloxybenzoic acid or mixtures thereof, and b3) carboxymethyl cellulose as binder, wherein the binder consists of the carboxymethyl cellulose of component b)3 which has a solubility of at least 1 g of carboxymethyl cellulose in 1 L of water at 25° C. and wherein the coating comprises hydroxymethyl cellulose in an amount of from 5 to 20 wt. % of the coated co-granules.