Claims
- 1. In a process for the delignification and bleaching of at least one cellulosic pulp selected from the group consisting of chemical cellulosic pulps and semi-chemical cellulosic pulps in which the pulp is subjected to a treatment with oxygen in an alkaline medium and a subsequent treatment with peroxide, the improvement comprising:
- (a) subjecting the pulp to the treatment with oxygen in the alkaline medium and then to the treatment with peroxide at a basic pH without immediate treatment, and
- (b) recycling between 5 and 70% by weight of the effluents resulting from the treatment with peroxide to the treatment with oxygen to avoid an excess depolymerization of cellulose.
- 2. In a process for the delignification and bleaching of at least one cellulosic pulp selected from the group consisting of chemical cellulosic pulps and semi-chemical cellulosic pulps in which the pulp is subjected to a treatment with oxygen in an alkaline medium and a subsequent treatment with peroxide at a basic pH, the treatment comprising:
- (a) subjecting the pulp to at least one intermediate treatment selected from among washings, concentrations, dilutions, a bleaching treatment with a carboxylic peracid, and a bleaching treatment with ozone, after the pulp is subjected to the treatment with oxygen in alkaline medium and before it is subject to the treatment with peroxide, and
- (b) recycling between 5 and 70% by weight of the effluents resulting from the treatment with peroxide to the treatment with oxygen to avoid an excess depolymerization of cellulose.
- 3. Process according to claim 1 or 2, wherein the treatment with oxygen is carried out under a partial oxygen pressure of between 200 kPa and 2 MPa.
- 4. Process according to claim 1 or 2, wherein the oxygen treatment is carried out in the presence of from 1 to 15% of an alkali, relative to the weight of the dry pulp.
- 5. Process according to claim 1 or 2, wherein the alkaline medium comprises sodium hydroxide.
- 6. Process according to claims 1 or 2, wherein the treatment with oxygen is carried out on a pulp having a consistency of between 5 and 40%.
- 7. Process according to claim 1 or 2, wherein the treatment with peroxide is carried out with from 0.2 to 5% of a peroxidic compound calculated as 100% strength hydrogen peroxide.
- 8. Process according to claim 1 or 2, wherein the peroxide employed in the treatment with peroxide is selected from the group consisting of sodium peroxide, hydrogen peroxide, and mixtures thereof.
- 9. Process according to claim 1 or 2, wherein during the treatment with peroxide, the pH of the treatment is maintained at a value between 9 and 13.
- 10. Process according to claim 1 or 2, wherein the treatment with peroxide is carried out on pulp having a consistency of between 2 and 25%.
- 11. Process according to claim 1 or 2 in which the pulp is subjected after the peroxide treatment of step (b) to at least one final treatment selected from among the treatments with peroxide, with chlorine dioxide, with hypochlorite, with carboxylic peracids, with chlorine, and alkaline extractions.
- 12. Process according to claim 1 or 2 in which the pulp is subjected to the treatment with oxygen under a pressure of between 200 kPa and 2 MPa in an alkaline medium at a temperature of between 353.degree. and 423.degree. K.
Priority Claims (1)
Number |
Date |
Country |
Kind |
79 13554 |
May 1979 |
FRX |
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CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation application of applicants' copending U.S. application Ser. No. 152,676 filed May 23, 1980, now abandoned.
US Referenced Citations (3)
Non-Patent Literature Citations (2)
Entry |
"Pulping Processes", Rydholm, Interscience Publishing, N.Y., 1967, pp. 1118-1121. |
Soteland, "Bleaching of Chemical Pulps with Oxygen and Ozone", Pulp and Paper Mag. of Canada, vol. 75, No. 4, pp. 91-96, (1974). |
Continuations (1)
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Number |
Date |
Country |
Parent |
152676 |
May 1980 |
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