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:
Nov. 05, 2002
Filed:
Jun. 05, 1996
Jian Er Jiang, Queensbury, NY (US);
Kaj O. Henricson, Helsinki, FI;
Andritz Inc., Glens Falls, NY (US);
Abstract
The production of chemical (e.g., kraft) cellulose pulp much more suited to totally chlorine free or elemental chlorine free bleaching is produced by reducing the bleaching chemical consumability of the produced pulp. The effective alkalinity of the pulp during at least the majority of the cooking stage is maintained at about 15 g/l or above (e.g., about 18-25 g/l), expressed as sodium hydroxide, so as to reduce the charged acid groups (including hexeneuronic acids) by at least 30% (e.g., at least about 50%) compared with pulp cooked at conventional alkalinity. Instead—or in addition to—the cellulosic material which produces the pulp may be heated to a temperature (at least about 100° C., preferably at least about 130° C.) to release significant quantities of the transition metals within it, and preferably while it has this elevated temperature and a dissolved organic solids concentration of about 120 g/l or less, a chelating agent (such as EDTA) is added to combine with a significant quantity of the released transition metals to produce complexes. At least a majority of the complexes are preferably removed (e.g., using an extraction screen in a digester) before the pulp is bleached.