Date of Award

6-1961

Degree Name

Bachelor of Science

Department

Pulp and Paper Technology

Abstract

Magazine papers which have a high groundwood content are deinked in large quantities by the deinking mills. For many uses deinked pulp produced from these papers must be bleached. The commonly practice industrial methods are not wholly satisfactory due to the high shrinkage and lack of brightness stability of the pulp they produce.

In this research project a high groundwood content magazine paper is deinked, washed and bleached. The following bleaching sequences are applied to the portions of the pulp: a single stage hydrogen peroxide treatment, a single stage zinc hydrosulphite treatment and a two-stage hydrogen peroxide-zinc hydrosulphite treatment. In order to determine the effect of acid pretreatment on pulp brightness, portions of the pulp are treated with sulfuric acid and washed before the previously mentioned sequences are applied. It is found that the acid pretreatment does not result in a significant increase in pulp brightness.

A sulfur dioxide post-treatment applied to the bleached pulps increases the brightness values up to 3.0 points.

Field values for each sequence show that there is little shrinkage due to bleaching.

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