Morton Thiokol Inc.

Stephen H Levis

Thomas Joachimides

Bert A Edstrom

Hans B Moldenius

A paper pulp refining and bleaching process wherein the pulp is treated in one or more refiners with a sodium hydrosulfite bleach liquor in the presence of a strong alkali such as NaOH, whereby the bleaching solution has an alkaline pH, preferably 10 to 12, and the pulp is discharged from the refiner at a pH of from about 5 to 6. The bleaching produces a brightness gain of at least 8 to 13 ISO points in the refiners. The process is preferably carried out by passing the pulp successively through a primary refiner at elevated pressure, a secondary refiner at atmospheric pressure and a bleaching tower, an alkaline hydrosulfite solution being fed to each.

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Haverhill, MA, United States of America

Stephen H Levis