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US 10,000,890 B2Granted
Low viscosity kraft fiber having reduced yellowing properties and methods of making and using the same
AssigneeGP Cellulose GmbH
InventorsArthur J. Nonni, Charles E. Courchene, Phillip R. Campbell, Steven C. Dowdle, Joel Mark Engle
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Abstract
A bleached softwood kraft pulp fiber with high alpha cellulose content and improved anti-yellowing is provided. Methods for making the kraft pulp fiber and products from it are also described.
Claims15
A method for making an oxidized kraft pulp comprising:
- digesting and oxygen delignifying a softwood cellulose pulp to a kappa number of less than 8;
- bleaching the cellulosic kraft pulp using a multi-stage bleaching process;
- and
- oxidizing the kraft pulp during at least one stage of the multi-stage bleaching process with a peroxide and a catalyst under acidic condition, wherein the multi-stage bleaching process comprises at least one bleaching stage following the oxidation stage, wherein the catalyst is an iron catalyst added in an amount of from about 25 ppm to about 100 ppm Fe2+based on the dry weight of the kraft pulp and wherein the peroxide is hydrogen peroxide added in an amount from about 0.1% to about 0.5% based on the dry weight of the pulp,
- wherein the cellulose kraft pulp comprises a 0.5% Capillary CEP viscosity of less than about 6 mPa·s and a carbonyl content of less than about 2.0 meq/100 g at the end of the multi-stage bleaching process.
2 more elements
A softwood kraft pulp having improved anti-yellowing characteristics made by a method which does not include a pre-hydrolysis step comprising:
- digesting and oxygen delignifying a softwood cellulose kraft pulp to a kappa number of less than 8;
- bleaching the cellulosic kraft pulp using a multi-stage bleaching process;
- and
- oxidizing the kraft pulp during at least one stage of the multi-stage bleaching process with a peroxide and a catalyst under acidic condition, wherein the multi-stage bleaching process comprises at least one bleaching stage following the oxidation stage, wherein the catalyst is an iron catalyst added in an amount of from about 25 ppm to about 100 ppm Fe2+based on the dry weight of the kraft pulp and wherein the peroxide is hydrogen peroxide added in an amount from about 0.1% to about 0.5% based on the dry weight of the pulp,
- wherein the cellulose kraft pulp comprises a 0.5% Capillary CEP viscosity of less than about 6 mPa·s and a carbonyl content of less than about 2.0 meq/100 g at the end of the multi-stage bleaching process.
2 more elements
Dependencies are inferred from the claim text.