Date of Award

4-1996

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

First Advisor

Dr. Ellsworth Shriver

Abstract

The final brightness of a bleached high-yield pulp paper product is a very important factor in determining the quality of the pulp and the product. If the brightness of this product tends to revert in time, then the quality of the product could be viewed lesser than before. Brightness reversion of high-yield pulps is the one flaw which is keeping the high-yield pulp market from really expanding in the paper industry.

High-yield pulps show economical and environmental advantages with their use in the high quality printing and copy papers market. Much research has been done to find ways to reduce and control brightness reversion, however, no concrete methodology of solving the problem has been derived. The following study takes a spruce CTMP pulp from Canada and sets up an experiment to try and show whether or not washing between hydrogen peroxide bleaching stages can help reduce and control brightness reversion. Two bleaching concentration levels of 2% and 4%, with and without washing, are used as part of the bleaching sequence. The data defining the conclusions of this study are before and after ageing brightness values taken from brightness pads made by the bleached CTMP pulp.

This study, based on the data obtained, concludes that a washing stage implemented into the two-stage bleaching sequence was not effective in reducing brightness reversion. The trend in the reduction of brightness reversion shows no significant reduction taking place. It is concluded that the chromophoric structure in the pulp, which aid in causing brightness reversion, are not water soluble and can not be easily washed out of the bleached CTMP pulp. Suggestions for future studies would be to use hot water washing stages and a more industry-based ageing technique.

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