Abitibi-price, Inc.

Abitibi Paper Company, Ltd.

Arnold E Willoughby

Philip Whiting

Martin G Fairbank

Fraser McLellan

Adele M Rhodes

Hollis D MacEwen

Stanley H Baldwin

A process is provided for the bleaching of wood pulp with hydrogen or sodium peroxide. The process includes the steps of adding to a wood pulp a bleach liquor having an effective amount of hydrogen or sodium peroxide bleaching agent and, by weight of the diluted wood pulp, 0.5 to 6% sodium hydroxide, 0 to 5% sodium silicate, 0 to 1%, preferably 0.02 to 0.05%, magnesium sulphate, and a chelating agent in an amount sufficient to sequester heavy metal ions in the pulp, to produce a pulp consistency of 1 to 16% at a temperature in the range of the bleach liquor freezing point to 25.degree. C., uniformly mixing the bleach liquor with the wood pulp, and immediately thickening the diluted wood pulp to a consistency in the range of 20 to 70% for bleaching of the thickened wood pulp. The wood pulp can be subjected to a preliminary treatment by the addition of a chelating agent in an amount sufficient to sequester chelatable heavy metals including manganese at a pulp consistency of 1 to 10%, and dewatering said pulp to a consistency of 20 to 70% to remove the sequestered manganese to less than 10 ppm.

High consistency peroxide bleaching

Pressed fiberboard is produced in an S-1-S type process at much shorter than normal (prior art) press cycles. The process includes the use of fiber furnish having preselected shrinkage characteristics. This furnish is wet formed into a mat either with or without a paper overlay, which overlay may be decorated or undecorated, depending on the desired end use and pressed wet as in the S-1-S process, using control means, such as stop bars in the hot press, to limit the final separation distance between the hot plates in each press opening to provide full caliper reduced density board. By using a fiber furnish having selected shrinkage characteristics it has been found that the pressed board can be safely removed from the press in a semi-cured, moist condition, at unusually short press cycles. The use of said fiber furnish also permits the use of higher than normal (prior art) press temperatures without incurring discloration of the paper overlays. The board is then baked and humidified to complete the curing process.

Short cycle pressed fiberboard manufacturing process

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Mississauga, Canada

Arnold E Willoughby