Method of increasing the wet strength of a fibrous sheet

• US 6,579,415 B2
• Filed: 09/27/2002
• Issued: 06/17/2003
• Est. Priority Date: 12/29/1998
• Status: Expired due to Fees

• Current Assignee: Weyerhaeuser Company (Weyerhauser)
• Original Assignee: Weyerhaeuser Company (Weyerhauser)
• Inventors: Jewell, Richard A.
• Primary Examiner(s): Fortuna, Jose A.
• Application Number:
  US10/260,876
• Publication Number:
  US 20030029586A1
• Time in Patent Office: 263 Days
• Field of Search: 162/157.6, 162/157.1, 162/146, 162/141, 162/158, 162/164.3, 162/164.6, 162/168.2, 162/175, 162/169, 162/9, 162/182, 811/551-115, 811/61, 818/1, 811/9, 812/0, 812/9
• US Class Current: 162/157.6
• CPC Class Codes: D06M 13/192 Polycarboxylic acids; Anhydrides, halides or salts thereof D06M13/1845 takes precedence
• CPC Class Codes: D06M 15/263 of unsaturated carboxylic acids; Salts or esters thereof
• CPC Class Codes: D21C 9/005 organic compounds
• CPC Class Codes: D21H 11/20 Chemically or biochemically modified fibres

Abstract

Carboxylated cellulosic fibers are disclosed. The fibers include a polycarboxylic acid covalently coupled to the fibers. Methods for producing the fibers and for producing fibrous products that incorporate the fibers are also disclosed.

Claims

1. A method for increasing the wet strength of a fibrous sheet, comprising:

forming a fibrous slurry, wherein the slurry comprises individualized carboxylated cellulosic fibers, the fibers comprising cellulosic fibers covalently coupled to a carboxylating agent through an ester bond, wherein the carboxylating agent provides a carboxyl group to the fibers, and wherein the carboxylating agent is a polycarboxylic acid having one carboxyl group separated from a second carboxyl group by either two or three atoms, wherein the carboxylated fibers have a water retention value greater than or equal to the water retention value of the fibers from which the carboxylated fibers are formed;

depositing the fibrous slurry on a foraminous support;

dewatering the deposited slurry to provide a wet composite; and

drying the wet composite to provide a fibrous sheet having a wet strength greater than a fibrous sheet formed from a fibrous slurry lacking carboxylated cellulosic fibers.

2. The method of claim 1 wherein the polycarboxylic acid is selected from the group consisting of a dicarboxylic acid, an organic acid having three or more carboxyl groups, a polymeric polycarboxylic acid, and mixtures thereof.

3. The method of claim 1 wherein the fibrous slurry further comprises a catalyst.

4. The method of claim 1 wherein the fibrous slurry further comprises a cationic additive.

5. The method of claim 1 wherein the fibrous slurry comprises fibers selected from the group consisting of carboxymethylated fibers, carboxyethylated fibers, crosslinked fibers, untreated cellulosic fibers, thermomechanical fibers, chemithermomechanical fibers, cellulose acetate fibers, polyester fibers, thermobondable fibers, and mixtures thereof.