EP 0520140 A1 19921230 - Ozone-alkaline extraction bleaching without intermediate washing.

Title (en)

Ozone-alkaline extraction bleaching without intermediate washing.

Title (de)

Bleiche durch Ozon-Alkaline Gewinnung ohne Zwischenwaschung.

Title (fr)

Blanchiment par ozone-extraction alcaline sans lavage intermédiaire.

Publication

EP 0520140 A1 19921230 (EN)

Application

EP 92103706 A 19920304

Priority

US 72178091 A 19910628

Abstract (en)

Enhanced brightness pulp, decreased color, and decreased COD discharge, are obtained during the bleaching of chemical cellulose (e.g. kraft) pulp by using a combined (ZE) stage, that is without washing between ozonation and alkaline extraction. Ozonation takes place preferably at acidic conditions and proceeds rapidly, while caustic extraction is at a pH of about 10-13. The (ZE)stage (29, 33) is preferably used in a bleaching sequence containing no more than five stages (25, 29, 31, 33 and 35), preferably (ZE)P(ZE)P, or (ZE)D(ZE)D, which may be preceded by a C/D stage, an O stage, an acid washing stage, or a nitrogen dioxide stage. The pulp produced can have a brightness of greater than 90 ISO, and ozonation can take place at a high consistency (greater than 25%), a medium consistency (about 6-18%), or low consistency (about 3% or less). If ozonation (10, 17) is at low consistency, dewatering (at 18) is effected prior to alkaline extraction (13,21). <IMAGE>

IPC 1-7

D21C 9/10; D21C 9/153

IPC 8 full level

D21C 9/10 (2006.01); D21C 9/153 (2006.01)

CPC (source: EP)

D21C 9/1057 (2013.01); D21C 9/153 (2013.01)

Citation (search report)

[A] FR 2265908 A1 19751024 - SCOTT PAPER CO [US]
[A] CA 1112813 A 19811124 - INT PAPER CO
[A] CA 1178756 A 19841204 - INT PAPER CO
[A] ABSTRACT BULLETIN OF THE INSTITUTE OF PAPER CHEMISTRY vol. 55, no. 6, December 1984, APPLETON US page 705 RUTKOWSKI, J. 'Use of ozone in bleaching kraft pulp.'

Designated contracting state (EPC)

AT BE CH DE DK ES FR GB GR IT LI LU MC NL PT SE

DOCDB simple family (publication)

EP 0520140 A1 19921230; AU 1282692 A 19930107; BR 9202472 A 19930209; FI 922945 A0 19920625; FI 922945 A 19921229; MX 9203191 A 19921201; NO 922526 D0 19920626; NO 922526 L 19921229; ZA 921843 B 19921230

DOCDB simple family (application)

EP 92103706 A 19920304; AU 1282692 A 19920312; BR 9202472 A 19920707; FI 922945 A 19920625; MX 9203191 A 19920624; NO 922526 A 19920626; ZA 921843 A 19920312