Method for Reducing the Extractives Content of High-Yield Pulps and Method for Producing Bleached High-Yield Pulps

• US 20070272378A1
• Filed: 02/23/2005
• Published: 11/29/2007
• Est. Priority Date: 02/24/2004
• Status: Abandoned Application

• Current Assignee: Kemira Oyj
• Original Assignee: Kemira Oyj
• Inventors: Jakara, Jukka, Paren, Aarto
• Application Number:
  US10/590,297
• Publication Number:
  US 20070272378A1
• Time in Patent Office: Days
• US Class Current: 162/78
• CPC Class Codes: D21C 9/08 Removal of fats, resins, pitch or waxes; Chemical or physical purification, i.e. refining, of crude cellulose by removing non-cellulosic contaminants, optionally combined with bleaching fats, waxes C11B; natural resins C09F1/00; hemicellulose C08B37/14; purification by mechanical means D21D5/00
• CPC Class Codes: D21C 9/1036 Use of compounds accelerating or improving the efficiency of the processes
• CPC Class Codes: D21C 9/163 with peroxides

Abstract

The invention relates to a method for reducing the content of extractives of a high-yield pulp in a peroxide bleaching stage, said stage including peroxide bleaching and a subsequent dewatering or washing, said method comprising contacting the pulp in the peroxide bleaching with an organic stabilizer and in or after the peroxide bleaching with a surfactant, and thereafter subjecting the bleached pulp to said dewatering or washing for removing extractives along with the aqueous phase. The invention also relates to a method for producing bleached high-yield pulp.

Claims

1. A method for treating pulp, said method comprising:

peroxide bleaching the pulp;

contacting the pulp with an organic stabilizer before or during the peroxide bleaching;

contacting the pulp with a surfactant before, during or after the peroxide bleaching;

said dewatering and/or washing the peroxide bleached pulp containing the organic stabilizer and the surfactant to remove extractives along with the aqueous phase.

2. The method according to claim 1 wherein the organic stabilizer and the surfactant are added to the pulp during the peroxide bleaching.

3. The method according to claim 1 wherein the organic stabilizer and the surfactant are added to the pulp before the peroxide bleaching.

4. The method according to claim 1 wherein the surfactant is added to the pulp after the peroxide bleaching.

5. The method according to claim 1 wherein dilution water is added to the pulp between the peroxide bleaching and the dewatering or washing.

6. The method according to claim 5 wherein the surfactant is added to the dilution water.

7. The method according to claim 1 wherein the organic stabilizer comprises a polymeric stabilizer.

8. The method according to claim 1 wherein the amount of the organic stabilizer is from 0.1 kg to 5 kg per ton dry pulp.

9. The method according to claim 1 wherein the surfactant comprises an anionic surfactant.

10. The method according to claim 1 wherein the amount of the surfactant is from 0.005 kg to 2 kg per ton dry pulp.

21. The method according to claim 1 wherein the organic stabilizer is a poly-alpha-hydroxyacrylic acid, a salt thereof, the corresponding polylactone, a homopolymer of acrylic acid, a homopolymer of methacrylic acid, a homopolymer of maleic acid, a copolymer of acrylic acid with an unsaturated dicarboxylic acid, a copolymer of methacrylic acid with an unsaturated dicarboxylic acid, or a mixture comprising at least one of the foregoing polymers.

22. The method according to claim 1 wherein the surfactant comprises naphthalene sulphonate, naphthalene lignosulphonate, an oil-in-water emulsifier, a fatty alcohol ethoxylate, an alkyl phenol ethoxylate, or a combination comprising at least one of the foregoing surfactants.

11. A method for producing a bleached having a reduced content of extractives, comprising:

bleaching a pulp with a peroxide;

contacting the pulp with an organic, polymeric stabilizer before or during the peroxide bleaching, in an amount of 0.1 kg to 5 kg) per ton dry pulp, wherein the stabilizer comprises a poly-alpha-hydroxyacrylic acid, a salt thereof, the corresponding polylactone, a homopolymer of acrylic acid, a homopolymer of methacrylic acid, a homopolymer of malcic acid, a copolymer of acrylic acid with an unsaturated dicarboxylic acid, a copolymer of methacrylic acid with an unsaturated dicarboxylic acid, or a combination comprising at least one of the foregoing organic stabilizers;

contacting the pulp with an anionic or nonionic surfactant before the peroxide bleaching, during the peroxide bleaching, or after the peroxide bleaching in an amount of 0.1 kg to 5 kg per ton dry pulp, wherein the surfactant comprises naphthalene sulphonate, naphthalene lignosulphonate, an oil-in-water emulsifier, a fatty alcohol ethoxylate, an alkyl phenol ethoxylate, or a combination comprising at least one of the foregoing surfactants; and

dewatering and/or washing the bleached pulp to remove extractives along with the aqueous phase, to produce a bleached pulp having a reduced content of extractives.

12. The method according to claim 11 wherein the organic stabilizer and the surfactant are added to the pulp during the peroxide bleaching.

13. The method according to claim 11 wherein the organic stabilizer and the surfactant are added to the pulp before the peroxide bleaching.

14. The method according to claim 11 wherein the surfactant is added to the pulp after the peroxide bleaching.

15. The method according to claim 11 wherein dilution water is added to the pulp between the peroxide bleaching and the dewatering or washing.

16. The method according to claim 15 wherein the surfactant is added to the dilution water.

18. The method according to claim 11 wherein the amount of the organic stabilizer is from 0.25 kg to 3 kg per ton of dry pulp.

20. The method according to claim 11 wherein the amount of the surfactant is from 0.05 kg t o 1 kg per ton dry pulp.

17. (canceled)

19. (canceled)