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:
Aug. 19, 1997
Filed:
Sep. 16, 1994
Lennart Andersson, Goteborg, SE;
Jiri Basta, Partille, SE;
Lillemor Holtinger, Nodinge, SE;
Jan Hook, Lilla Edet, SE;
Eka Nobel AB, Bohus, SE;
Abstract
A process for delignification and bleaching of chemically digested lignocellulose-containing pulp, where the pulp is treated with a complexing agent at a pH between 3.1 and 9.0, whereupon the pulp is bleached with ozone. The initial treatment with a complexing agent removes the ions of certain metals detrimental to the subsequent ozone bleaching, while retaining in the pulp the desirable ions, primarily of alkaline earth metals. Thereby, the selectivity in the delignification is increased and the strength of the pulp maintained. The pulp can be bleached with peroxide before the ozone step and/or after the treatment according to the invention, to obtain the desired final brightness and completely avoid formation and discharge of chlorinated organic compounds.