C - Chemistry – Metallurgy – 12 – S
Patent
C - Chemistry, Metallurgy
12
S
C12S 3/08 (2006.01) D21C 5/00 (2006.01) D21C 9/16 (2006.01)
Patent
CA 2115881
The present invention relates to a process for the bleaching of kraft pulps with non-chlorine chemicals, employing a sequential reaction of oxidative enzymes and hydrogen peroxide. The kraft pulp can be from conventional or extended pulping, or from an oxygen delignification step. The enzyme reaction is monitored by methanol release which results from the demethylation of lignin. The process of the present invention essentially comprises three steps. The first step is the oxidation of kraft pulp either with manganese peroxidase enzyme in the presence of Mn(II) salts, hydrogen peroxide and chelator, or with laccase enzyme preferably in the presence of 2,2'-azinobis(3- ethylbenzothiazoline-6-sulfonic acid (ABTS), or a combination of both enzymes in a crude mixture as typically produced by certain fungi. The Mn(II) salts and chelator may already be present in sufficient amount in the pulp. This first step is performed at an acidic pH, and moderate temperatures for a period of time between 30 and 240 minutes. The two subsequent steps are the removal of metals from the pulp and the alkaline hydrogen peroxide treatment. These steps are performed under standard conditions as known by those skilled in the art. The resulting pulp is surprisingly brighter and of lower lignin content than would be obtained without the enzyme treatment.
Bourbonnais Robert E.
Paice Michael G.
Fpinnovations
Ogilvy Renault Llp/s.e.n.c.r.l.,s.r.l.
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