Cooking cellulose material with high alkali concentrations and/or high pH
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United States of America Patent
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Jun 3, 1997
Grant Date -
N/A
app pub date -
Nov 13, 1995
filing date -
Nov 13, 1995
priority date (Note) -
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Abstract
Chemical (typically kraft) pulp having enhanced intrinsic fiber strength and bleachability compared to pulp produced using conventional or modified kraft cooking is produced by using high alkali and/or pH cooking. After being impregnated with a first cooking liquor (e.g. white liquor) having low effective alkali, the first liquor is extracted from the pulp, and it is impregnated with a second cooking liquor having an effective alkali concentration of at least 25 g/l and cooked at cooking temperature (e.g. 140.degree.-190.degree. C.) to produce a spent second cooking liquor having a residual effective alkali concentration of at least about 15 g/l, which is then extracted from the pulp. The spent second liquor may be used to preheat incoming white liquor, and then flashed and used as the first liquor. The pH of the first liquor is typically less than about 13.0, and the residual pH of the spent second liquor is about 13.0 or more.
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