Claims
- 1. A process for bleaching kraft pulp comprising:
- (a) treating an aqueous slurry of kraft pulp with a bleaching effective amount of chlorine and a cellulose protective amount of chlorine dioxide;
- (b) extracting the pulp of step (a) above at an acidic pH and at a temperature range of from about 30.degree. C. to about 77.degree. C. with an effective amount of a chlorinated lignin solubilizing agent comprising an aqueous solution of a sulfite ion;
- (c) treating the pulp from step (b) above with an effective amount of chlorine dioxide or sodium hypochlorite;
- (d) extracting the pulp from step (c) above with an effective amount of an aqueous solution of an alkali metal hydroxide or a chlorinated lignin solubilizing agent as defined in step (b) above; and
- (e) treating the pulp from step (d) above with an effective amount of chlorine dioxide.
- 2. A process as defined in claim 1 wherein the treatment in step (d) is with an aqueous solution of an alkali metal hydroxide.
- 3. A process as defined in claim 2 wherein the alkali metal hydroxide is sodium hydroxide.
- 4. A process as defined in claim 1 wherein the treatment in step (d) is with a chlorinated lignin solubilizing agent.
- 5. A process as defined in claim 1 wherein the aqueous solution of sulfite ion has a pH of from about 3 to about 5.
- 6. A process as defined in claim 5 wherein the aqueous solution of sulfite ion contains counter ions derived from sodium.
Parent Case Info
This application is a continuation of application Ser. No. 546,263, filed Oct. 28, 1983, now abandoned.
Foreign Referenced Citations (2)
Number |
Date |
Country |
537738 |
Mar 1957 |
CAX |
523971 |
Mar 1972 |
SUX |
Non-Patent Literature Citations (3)
Entry |
Histed; Pulp and Paper Canada; "Bleachery Simplification in CIP"; vol. 81, No. 11, pp. 54-58, 11-1980. |
Richter; TAPPI, vol. 38, No. 3, "Production of High Alpha-Cellulose Wood Pulps and Their Properties", 3-1955, pp. 129-150. |
Singh, "The Bleaching of Pulp", pp. 82-100, Standard Press Inc., Atlanta, Ga., 1979. |
Continuations (1)
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Number |
Date |
Country |
Parent |
546263 |
Oct 1983 |
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