TOWARDS A SELECTIVE OZONE BLEACHING STAGE BY ADDITION OF ORGANIC OXYGENATES - TERT-BUTYL ALCOHOL HAS AN OUTSTANDING EFFECT

Instead of chlorinated agents, oxygen, ozone and hydrogen peroxide mak e up the new bleaching-sequence roots. In this research field, the rep orted investigations are devoted to ozone-stage improvements by adding organic oxygenates. Many alcohols and acids known as radical scavenge rs succeed in increasing ozone reactivity, efficiency and selectivity at low consistency. Among the tested additives, tert-butyl alcohol sho ws an outstanding effect due to its hydrodynamic role in the ozone tra nsfer. Even if the tert-butyl alcohol concentration is reduced to a la rge extent, the ozone transfer rise involves better access to the lign in, and the efficiency and selectivity increase. Finally, the bleachin g sequences OZEZP and EZEZP including the modified Z stage carried out with a reasonable ozone charge, manage to reach high brightness value s with good carbohydrate protection.