OZONE BLEACHING OF EUCALYPT KRAFT PULPS

Kraft pulps from plantation and mature eucalypt wood samples were blea ched with the sequences OZ and OZQ(PO). The ozone stage was done at hi gh pulp concentration. The aim of the study was to bleach pulps to a b rightness oi 90% ISO without reducing their strength properties. pulps prepared by conventional and extended delignification procedures were used. The use of xylanase with the OZ sequence gave higher pulp brigh tness levels (about 2% ISO) but with the OZQ(PO)sequence the increase was much smaller The bleaching yield was about 1-3%, units lower depen ding on the wood sample and the pulping procedure Conventional pulps w ere bleached to about 88% ISO brightness with the OZQ(PO) sequence:The tearing resistance was equal to that of he unbleached pulp The extend ed delignification pulps were bleached to levels in the range 89,5-90. 5% ISO but tearing resistances were slightly lower.