Virginia Chemicals Inc.

Mearl A Kise

Leonard C Ellis

Robert W Barton

Joseph A Cannizzaro

Sodium dithionite bleaching solutions for groundwood pulps which require no additional chemicals for pH adjustment prior to direct application to the pulps, based on zinc-derived or formate-derived sodium dithionite and containing small percentages of at least four additives selected from the following: a chelating agent, zinc dithionite, zinc sulfate, sodium carbonate, sodium hydroxide, sodium tripolyphosphate, sodium phosphate, and sodium metaborate. Tested chelating agents are nitrilotriacetic acid (NTA) trisodium salt and ethylenediaminetetraacetic acid (EDTA) tetrasodium salt. The solutions are cool-stable (50.degree.F. or 10.degree.C) for at least 5 days with less than 5% decomposition of the sodium dithionite, and several exhibit similar stability at storage temperatures of 70.degree.-75.degree.F. (21.degree.-24.degree.C.) A method of preparation of the solutions is also provided. Bleaching performance was proved in laboratory and field trials to be comparable to the performance of solutions prepared from dry, commercially available sodium dithionite blends or commercial zinc dithionite when compared on a basis of pounds of bleaching agent per ton of pulp per point brightness gain.

Stabilized sodium dithionite solutions

Apparatus and method are disclosed for continuously handling sodium hydrosulfite for use in textile dyeing including means for receiving the pure dry chemical in semi-bulk returnable containers, for dissolving the same in a caustic solution and for storing the resulting solution in low inventory automatic make-up tanks. The novel resulting solution is stabilized against decomposition and may be metered to specified locations in the textile mill.

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Portsmouth, VA, United States of America

Mearl A Kise