Elimination of alum yellowing of aspen thermomechanical pulp through pulp washing
AssigneeInternational Paper Company
InventorsRobin R. Kilgannon, Robert J. Kane, Eileen M. Joy, Anil K. Dewan
Life of this patent
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Abstract
This invention relates to an improved process for manufacturing bleached thermomechanical aspen pulp having reduced yellow after treatment with aluminum based chemicals such as alum which are used in paper making processes. In this improved process the pulp is washed prior to, after or between the bleaching stages or a combination of the foregoing.
Claims23
1) A process for forming bleached thermomechanical bleached aspen pulp having reduced yellowing when subsequently treated with aluminum based chemicals, said process comprising the steps of:
- (a) a thermomechanical refining stage wherein aspen wood chips are thermomechnically refined to form thermomechanical refined aspen wood pulp;
- and
- (b) a bleaching stage wherein said thermomechanical refined aspen wood pulp is bleached in one or more bleaching stages to form a first bleached thermomechanical refined aspen wood pulp;
- the improvement comprising a washing stage subsequent to said thermomechanical refining stage wherein said thermomechanical refined aspen wood pulp, bleached thermomechanical refined aspen wood or a combination thereof is washed at least once with an aqueous liquid composition, wherein on subsequent treatment of said bleached thermomechanical refined aspen wood pulp with at least one aluminum based chemical said first bleached thermomechanical refined aspen wood pulp has a higher ISO brightness than a second bleached thermomechanical aspen wood pulp formed by the same or substantially the same process as said first bleached thermomechanical refined aspen wood pulp in the absence of said washing stage.
22) A pulping and paper making process which comprises the steps of:
- (a) a thermomechanical refining stage wherein aspen wood chips are thermomechanically refined to form thermomechanical refined aspen wood pulp,
- (b) a bleaching stage wherein said thermomechanically refined aspen wood pulp is bleached in one or more bleaching stages to form bleached thermomechanical refined aspen wood pulp,
- (c) a furnish forming stage wherein an aqueous paper making stock furnish comprising said bleached thermomechanical refined aspen wood pulp and one or more aluminum based chemicals is formed;
- (d) a furnish depositing stage wherein said furnish is deposited on a forming wire of a paper making machine to form a wet paper web;
- and
- (e) a wet paper web drying stage wherein said wet paper web to form a first dried paper web,
- the improvement comprising a washing stage subsequent to said thermomechanical refining stage wherein said thermomechanical refined aspen wood pulp, bleached thermomechanical refined aspen wood or a combination thereof is washed at least once with an aqueous liquid composition, wherein said first dried paper web has a higher ISO brightness than a second dried paper web formed by the same or substantially the same process as said first dried paper web in the absence of said washing stage.
23) A paper web formed by the process of claim 23.
Dependencies are inferred from the claim text.