Yong Y Li

US Patent:

6379494, Apr 30, 2002

Filed:

Oct 15, 1999

Appl. No.:

09/418909

Inventors:

Richard A. Jewell - Bellevue WA
Joseph Lincoln Komen - Bothell WA
Yong Li - Tacoma WA
Bing Su - Federal Way WA

Assignee:

Weyerhaeuser Company - Federal Way WA

International Classification:

D21H 1120

US Classification:

162 9, 1621576, 8181, 81161, 811551

Abstract:

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.

US Patent:

6524348, Feb 25, 2003

Filed:

Aug 17, 2000

Appl. No.:

09/641276

Inventors:

Richard A. Jewell - Bellevue WA
Joseph Lincoln Komen - Bothell WA
Bing Su - Federal Way WA
S. Ananda Weerawarna - Seattle WA
Yong Li - Tacoma WA

Assignee:

Weyerhaeuser Company - Federal Way WA

International Classification:

D06M 2300

US Classification:

81161, 8181, 162 9

Abstract:

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 cyclic nitroxide free radical compounds 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.