Claims
- 1. A process for pulping lignocellulosic material comprising;
- a. treating lignocellulosic material with an aqueous cyanide ion-containing solution at a temperature between room temperature and 130.degree.C. at a pH between 7 and 12 until cyanohydrin groups are formed, withdrawing any excess cyanide ion-containing solution.
- b. digesting the thus treated lignocellulosic material with an alkali metal pulping solution containing hydroxy ions at a conventional pulping temperature until a Kappa Number from 60 to 160 is obtained, and
- c. treating the thus digested lignocellulosic material with 1% to 12% by weight sodium hydroxide, as sodium oxide based on the o.d. pulp from the alkaline stage, and an excess of oxygen at a partial pressure of 100 - 200 p.s.i.g. and temperature between 95.degree.C. and 130.degree.C. until a Kappa Number between 15 and 70 is obtained.
- 2. The process of claim 1 wherein said lignocellulosic material is in the form of softwood chips.
- 3. The process of claim 1 wherein said alkali metal pulping solution contains sodium sulfide.
- 4. The process of claim 1 wherein said alkali metal pulping solution contains sodium sulfite.
- 5. The process of claim 1 wherein said cyanide treatment is conducted at a temperature below 95.degree.C., and the pH of said cyanide ion-containing solution is between 8.5 and 10.5.
- 6. The process of claim 1 wherein the lignocellulosic material of step (c) is treated until a Kappa Number between 20 and 40 is obtained.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of copending application, Ser. No. 416,923, filed Nov. 19, 1973, now abandoned.
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Number |
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3384533 |
Robert et al. |
May 1968 |
|
3532596 |
Bills et al. |
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3652386 |
Noreus et al. |
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3663358 |
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3691008 |
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|
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
416923 |
Nov 1973 |
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