Global Patent Index - EP 0191756 B1

EP 0191756 B1 19890104 - MULTI PEROXIDE STAGE MECHANICAL PULP BLEACHING

Title (en)

MULTI PEROXIDE STAGE MECHANICAL PULP BLEACHING

Publication

EP 0191756 B1 19890104 (EN)

Application

EP 86890030 A 19860212

Priority

US 70200085 A 19850215

Abstract (en)

[origin: EP0191756A1] Bleaching of a mechanical pulp, such as chemimechanical pulp (CMP), chemithermomechanical pulp (CTMP), and the like, achieves high brightness. A lignocellulose mechanical pulp is subjected to two different peroxide (P) stages (12, 18), and a hydrosulfite (dithionite) (T) stage (20). A P-P-T sequence is preferred (although a P-T-P sequence also produces good results). Bleaching is typically accomplished in all stages at a consistency of between about 8-30%. Between the peroxide stages, the pulp is preferably pressed (19). Between a peroxide stage and a subsequent hydrosulfite stage the pulp is preferably pressed (19 min ), and the pH reduced to between about 5.5-6.0 when diluting with SO2 water (26). The P-P-T bleaching sequence results in pulp with unexpectedly high brightness, brightness levels of about 83% ISO, and greater, being possible.

IPC 1-7

D21C 9/10

IPC 8 full level

D21C 9/10 (2006.01); D21C 9/16 (2006.01)

CPC (source: EP)

D21C 9/1057 (2013.01)

Citation (examination)

EP 0187477 A1 19860716 - PULP PAPER RES INST [CA]

Designated contracting state (EPC)

AT DE FR

DOCDB simple family (publication)

EP 0191756 A1 19860820; EP 0191756 B1 19890104; AT E39714 T1 19890115; BR 8600637 A 19861104; DE 3661641 D1 19890209; FI 85729 B 19920214; FI 85729 C 19920525; FI 860688 A0 19860214; FI 860688 A 19860816; JP S61245392 A 19861031; NO 166244 B 19910311; NO 166244 C 19910619; NO 860546 L 19860818; SE 8600615 D0 19860212; SE 8600615 L 19860816

DOCDB simple family (application)

EP 86890030 A 19860212; AT 86890030 T 19860212; BR 8600637 A 19860214; DE 3661641 T 19860212; FI 860688 A 19860214; JP 3058286 A 19860214; NO 860546 A 19860214; SE 8600615 A 19860212