Process for preparing sodium perborate hydrate pellets

Sodium perborate hydrate pellets having an active oxygen content of 14 to 18% by weight, especially 15 to 16% by weight, an abrasion index in the ISO test 5937 of not more than 10%, a dissolving time of less than 1.5 minutes, preferably less than 1.0 minute (1 g/500 cm of water, 15 DEG C) and a bulk density from more than 0.6 to 1.2 kg/dm can be produced by compacting spray-dried, substantially amorphous sodium perborate hydrate, which has a bulk density below that of the pellets and a particle size of 90% smaller than 100 mu m and loses 0.2 to 2.0 of its weight by storage at 60 DEG C and 100 Pa in 30 minutes, between rollers at a contact pressure of 5 x 10 to 2 x 10 N/cm, comminuting the flakes and subjecting the pellets, if appropriate after rounding them by mechanical stressing, to grain fractionation. The advantage of the process is that pellets having the said physical data desired by the market can be obtained in this way in a simple manner and without a thermal stress of the perborate.