BLEACHING OF LIGNIN-CONTAINING CELLULOSE MATERIALS SUCH AS PULP

• US 3,661,699 A
• Filed: 12/21/1970
• Issued: 05/09/1972
• Est. Priority Date: 12/21/1970
• Status: Expired due to Term

• Current Assignee: Charles Edward Farley
• Original Assignee: Charles Edward Farley
• Inventors: Farley, Charles Edward
• Primary Examiner(s): Caine, Howard R.
• Application Number:
  US05/100,474
• Time in Patent Office: 505 Days
• Field of Search: 162/65,80,85 8/111
• US Class Current: 162/65
• CPC Class Codes: D21C 9/1036 Use of compounds accelerating or improving the efficiency of the processes

Abstract

Digester pulp is brightened and delignified by contacting the pulp with an aqueous medium containing oxygen and trisodium phosphate. The oxygen liberates the lignin substituents and the trisodium phosphate carries the lignin substituents into solution while minimizing degradation of the polymeric structure of the cellulose.

Claims

2. A process according to claim 1 wherein said aqueous medium has a temperature between about 75* and 150* C.

3. A process according to claim 1, wherein the oxygen is pure oxygen under an absolute pressure of 50-150 lb./in.2.

4. A process according to claim 1 wherein the water is a part of the aqueous medium which is separated from said fibers is evaporated, leaving a residue of a sodium phosphate and a sodium salt of oxidized lignin, said salt is burned, and the residue from said burning is returned to the process, the amount of aqueous medium thus separated being sufficient to maintain the concentration of said salt in said process substantially constant.