Macmillan Bloedel Limited

Marco Solinas

Thomas Howard Murphy

Yonghao Ni

Adriaan Reinhard Van Heiningen

Zheng Tan

Allan M Proust

A bleached pulp having a high viscosity for a given permanganate number is formed by pretreating never dried pulp with an organic solvent medium to produce a treated pulp composed of said never dried pulp in the medium and then bleaching that treated pulp using ozone at a pH of 1.5-5 to provide a bleached pulp while reducing the viscosity loss during the ozone bleaching step significantly compared to that what would occur if the medium used in the ozone bleaching were water.

Ozone bleaching with an organic solvent and mineral acid

An improved oxygen bleaching process wherein the pulp is bleached in an aqueous organic medium wherein a polyhydric alcohol constitutes between 10 and 70% by weight of the medium to produce a pulp having a viscosity at least 2.5 cp higher than a similar pulp bleached using the same conditions in an aqueous atmosphere to the same kappa no. of 8 ml.

Oxygen bleaching process for cellulocis pulps with a polyhydric alcohol

Cellulosic pulps are bleached with ozone in an ozone bleaching stage in an aqueous medium containing an additive in an effective amount not exceeding 5% weight concentration of the aqueous medium. The additive is selected from a group consisting of N-alkylated ureas, N-alkylated lactams and N-alkylated amides. pH in the Z stage is operated under conventional ozone bleaching conditions, but preferably at high consistency and at low temperature, below 5.degree. C.

Method of bleaching cellulosic pulps with ozone and a protective amount

A method of bleaching a chemical pulp by adjusting the pH of the pulp to 1.5-3.5, chelating the pulp and then treating the pulp in an N stage with nitric oxide (NO) in the amount of at least 1.5% by weight of the oven dried pulp at a consistency of between 30 and 55% and further treating the pulp in a Z stage with ozone to produce a bleach pulp having a higher viscosity for a given permanganate number compared with a similar pulp bleached without using the N stage.

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Marco Solinas