Date of Award

4-1996

Degree Name

Bachelor of Science

Department

Paper Science and Engineering

Abstract

In the attempt to find improved bleaching chemicals for the bleaching of high-yield pulps, dioxiranes may prove to be the solution. Unlike hydrogen peroxide, which has been introduced to a refiner environment in the past, dimethyldioxirane (DMD) does not require the use of sodium silicates. This is very beneficial due to the fact that silicates have a highly undesirable side effect of causing excessive refiner plate wear.

The experimentation was constructed to determine the exact feasibility of the use of dimethyldioxirane as a refiner bleaching agent. This was completed through the comparison of the pulp strength and brightness values of refiner bleached stock using a PFI mill to simulate refiner action. Hydrogen peroxide and dimethyldioxirane generated in-situ were used as the bleaching agents.

Dimethyldioxirane was found to produce a brightness increase of 8.5 points in comparison to the reference pulp. Low concentrations of DMD were found to be sufficient, with a charge of 2.0% DMD producing equivalent brightness values to higher concentrations. A 17 brightness point increase was obtained while utilizing a 2-stage refiner bleaching sequence, with the first stage being 3.0% DMD, and the second being 2.5% hydrogen peroxide without silicates.

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