Date of Award
Bachelor of Science
Pulp and Paper Technology
Dr. Robert A. Diehm
Survey of Literature
Since the development of cold soda pulping in the early 1950's, the search for suitable bleaching methods has been of primary concern. Cold soda pulp is dark brown in color and resists the bleaching action of most chemicals. Marton (1) suggests that this brown discoloration of hardwood cold soda pulp is due to a material in the cells of the wood, primarily in the heartwood. These substances, which have not been identified, are not the same as lignin but probably develop in a similar manner.
The chemicals most often used in bleaching hardwood cold soda pulps have been peroxides, hypochlorites, hydrosulfites, and most recently borohydrides. A satisfactory bleaching procedure should meet the following objectives:
1. Development of high brightness
2. Retention of the initial high yield
3. Low cost
In order to achieve these objectives Giertz (2) states that the pulping process should be performed in such a manner that colored lignins do not form and that the bleaching agent should destroy only the coloring material and not react with the lignin. These requirements would eliminate all chlorine compounds which form colored lignin complexes as bleaching agents.
Estes, Valerie A. S., "Two Stage Peroxide-Borohydride Bleaching of Cold Soda Pulp" (1962). Paper Engineering Senior Theses. 152.