The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 03, 1990
Filed:
Feb. 23, 1989
Philip Whiting, Milton, CA;
Adele M Rhodes, Oakville, CA;
Arnold E Willoughby, Mississauga, CA;
Martin G Fairbank, Milton, CA;
Hollis D MacEwen, Mississauga, CA;
Fraser McLellan, Campbellville, CA;
Abitibi-Price Inc., Toronto, CA;
Abstract
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.