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:
Sep. 12, 1995
Filed:
Mar. 01, 1993
Applicant:
Inventors:
Lucien Bourson, Bois-Colombes, FR;
Michel Devic, Sainte-Foy les Lyons, FR;
Assignee:
Atochem, Puteaux, FR;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
D21C / ; D21C / ;
U.S. Cl.
CPC ...
162-6 ; 162-7 ; 162 78 ; 162 84 ;
Abstract
Deinked paper/wood pulps are improvedly bleached to high levels of whiteness by conjointly treating such pulps with a sulfite bleaching agent, e.g., Na.sub.2 SO.sub.3, NaHSO.sub.3 or mixture thereof, or SO.sub.2 and NaOH, and a reducing agent more electronegative than the sulfite ion, e.g., thiourea dioxide, sodium borohydride or sodium dithionite, in a reaction medium having an initial pH ranging from 6 to 12, advantageously followed by washing sulfite and reducing agent values from the bleached pulp and then treating the washed pulp with hydrogen peroxide in an aqueous alkaline medium.