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AssigneeWeyerhaeuser Company
InventorsRichard A. Jewell, Joseph Lincoln Komen, Yong Li, Bing Su
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The invention is directed to a method of making carboxylated cellulose fibers whose fiber strength and degree of polymerization is not significantly sacrificed. The method involves the use of TEMPO (2,2,6,6-tetramethylpiperidinyloxy free radical) as a primary oxidant and a hypohalite salt as a secondary oxidant in an aqueous environment. Preferably the oxidized cellulose is then stabilized against D.P. loss in alkaline environments and color reversion with a reducing agent such as sodium borohydride. Alternatively it may be treated with an oxidant such as sodium chlorite. The method results in a high percentage of carboxyl groups located at the fiber surface. The product is especially useful as a papermaking fiber where it contributes strength and has a higher attraction for cationic additives. The product is also useful as an additive to recycled fiber to increase strength. The method can be used to improve properties of either virgin or recycled fiber. It does not require high α-cellulose fiber but is suitable for regular market pulps.
A stable fibrous carboxylated cellulose having 5-100 meq/100 g of carboxyl substitution wherein the carboxyl groups are present as uronic acid moieties and at least about 20% of the substitution is located on the surface of the fibers.
A wood fiber based cellulose having less than about 90% α-cellulose and having 5-100 meq/100 g of carboxyl substitution wherein the carboxyl groups are present as uronic acid moieties and at least about 20% of the substitution is located on the surface of the fibers, said fiber being resistant to strength loss upon repeated recycling.
A cellulose sheet comprising from 0.5-100% by weight of a stable fibrous carboxylated cellulose having 5-100 meq/100 g of carboxyl substitution wherein the carboxyl groups are present as uronic acid moeties wherein at least 20% of the substitution is located on the surface of the carboxylated cellulose fibers.
A stable fibrous carboxylated cellulose having 5-100 eq/100 g of carboxyl substitution wherein the carboxyl groups are located at the C6 position of the anhydroglucose units and aldehyde groups are substantially absent.
Dependencies are inferred from the claim text.