Method for whitening of sulfate pulp

FIELD: pulp-and-paper industry, in particular method for pulp whitening.

SUBSTANCE: pulp mass with concentration of 5-10 % after oxygen-alkaline treatment in step I is treated with sulfuric acid in consumption of 5 % based on dry cellulose mass and pH 2.6-3.0. In step II peroxide treatment is carried out in alkali consumption of 1.0-1.3 % based on dry cellulose mass, and in step III pulp is treated with chlorine dioxide in consumption of 1.0-1.6 % based on dry cellulose mass at 70°C.

EFFECT: pulp with increased whiteness.

1 tbl, 17 ex

 

The invention relates to the field of pulp and can be used to produce bleached pulp (pulp after oxygen-alkali treatment) without the use of molecular chlorine.

Known three-step method of bleaching pulp, comprising processing pulp 1 stage nitrogen-containing polycarboxylic acid at a temperature of 70-90°, 2 stage (hydrogen peroxide) with a flow rate of 1.3 to 2.0% by weight of the abs. dry. cellulose in an alkaline medium at a concentration of mass 10%, a temperature of 90°C for 120 min and 3-speed - chlorine dioxide with a flow rate of 1.3 to 2.4% by weight of the abs. dry. cellulose at a concentration of mass 10%, the processing time of 120 min at a temperature of 50-60°WITH (EN 2044808, class D 21 9/10, op).

The proposed method differs from the known fact that instead of the polycarboxylic acid using sulfuric acid and treatment of this acid is subjected to a pulp after oxygen-alkali treatment, the second stage of peroxide treatment is carried out with alkali consumption of 1.0 to 1.3% by weight of the abs. dry. cellulose and 3-speed use of chlorine dioxide when the flow rate of 1.0-1.6% and a temperature of 70°C.

This difference improves pulp quality by increasing its whiteness.

The technical result, which is in causal connection with the essential features of the invention is poluchenii white hardwood pulp and 88.5% in the initial stiffness of 10.2 Kapp due process of oxidation, the initiator of which is oxygen remaining in the fiber after the oxygen-alkali treatment in the residual alkalinity and flow which depends on the value of pH at 1 stage processing acid and, accordingly, the consumption of acid.

The essential features of the invention: method of bleaching of unbleached pulp, comprising alternating acid and alkali treatments, characterized in that the pulp after oxygen-alkali treatment on 1 stage leached in sulphuric acid with a concentration of 5-10 weight%, the consumption of sulphuric acid 5% by weight of the abs. dry. pulp pH of 2.6-3.0, 2-stage peroxide treatment is carried out with alkali consumption of 1.0 to 1.3% by weight of the abs. dry cellulose and stage 3 is carried out by treatment of the pulp with chlorine dioxide in its consumption of 1.0 to 1.6% by weight of the abs. dry. pulp at a temperature of 70°C.

Example 1.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT treated with sulfuric acid with a flow rate of 4% by weight VSC., with a mass concentration of 10% and maintaining the pulp slurry at 90°C for 30 minutes. Then the pulp was separated and dried. The white pulp is 52.0%, the yield of 98.2.

Example 2.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed chamois is th acid with a flow rate of 5% by weight VSC., with the mass concentration of 2.5% while maintaining the pulp slurry at 90°C for 30 minutes. Then the pulp was separated and dried. The white pulp is 54.2%, viscosity at 46.6 MPa, the yield of 98.2.

Example 3.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT treated with sulfuric acid with a flow rate of 5% by weight VSC., with the mass concentration of 2.5% and maintaining the pulp slurry at 90°C for 60 minutes. Then the pulp was separated and dried. White pulp 57,0%, output 98,0.

Example 4.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT treated with sulfuric acid with a flow rate of 3% by weight VSC., with a mass concentration of 10% while maintaining the pulp slurry at 80°C for 30 minutes, then the pulp mass is separated, washed and treated with hydrogen peroxide at the same concentration mass (expenses N2About22.0% of sodium hydroxide was 1.3%, a pH of 10.9) at 90°and duration 120 min, and then the pulp is separated, washed and dried. White pulp 66,4%, the yield of 96.5.

Example 5.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT treated with sulfuric acid with a flow rate of 5% by weight VSC., with the concentration of the th mass to 7% while maintaining the pulp slurry at 80° C for 30 minutes, then the pulp mass is separated, washed and treated with hydrogen peroxide at the same concentration mass (expenses N2About22.0% of sodium hydroxide was 1.3%, a pH of 10.9) at 90°and duration 120 min, and then the pulp is separated, washed and dried. The white pulp of 74.0%, the viscosity of 45.3 MPa·exit 96,0.

Example 6.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT treated with sulfuric acid at a rate of 2.5% by weight VSC., with the mass concentration of 2.5% while maintaining the pulp slurry at 90°C for 30 minutes, then the pulp mass is separated, washed and treated with hydrogen peroxide at the same concentration mass (expenses N2About22.0% of sodium hydroxide was 1.3%, a pH of 10.9) at 90°and duration 120 min, and then the pulp is separated, washed and treated with chlorine dioxide at a temperature of 70°with a flow rate of 1.0% at a concentration of mass, the duration of treatment is similar to the second stage, then the pulp is washed and dried. White pulp 85,8%, the viscosity of 45.7 MPa·exit 95,0%.

Example 7.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6, increasing for the first STU is Yeni processing time up to 60 min, then the pulp is washed and dried. The white pulp of 86.1%, viscosity 46,58 MPa·exit 95,0%.

Example 8.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 5%, then the pulp is washed and dried. White pulp 85,6%, viscosity 29,93 MPa·exit 95,0%.

Example 9.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 5%, increasing the processing time up to 60 min, and then the pulp is washed and dried. White pulp 86,5%, viscosity 30.20mm MPa·exit 95,0%.

Example 10.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 7% and the consumption of acid 7% by weight VSC., then the pulp is washed and dried. White pulp 85,8%, viscosity 22,82 MPa·exit 95,0%.

Example 11.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 3 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 7% and the consumption of the acid 7% by weight VSC., increasing the processing time up to 60 min, and then the pulp is washed and dried. White pulp 86,3%, viscosity 37,69 MPa·exit 95,0%.

Example 12.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 10%, the consumption of acid 10% by weight VSC., then the pulp is washed and dried. The white pulp of 85.4%, viscosity 22,69 MPa·exit 95,0%.

Example 13.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 10%, the consumption of acid 10% by weight VSC., increasing the processing time up to 60 min, and then the pulp is washed and dried. The white pulp of 85.1%, viscosity 27,35 MPa·exit 95,0%.

Example 14.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 10%, increasing the processing time up to 60 min, with a flow rate of hydrogen peroxide on the second level of 1.5% by weight VSC., washed and dried. White pulp and 82.2%, output 95,0%.

Example 15.

Unbleached pulp from hardwood rigidity 10,2 Kappa, vaskos the d 48,0 MPa· with white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first level of 10%, increasing the processing time up to 60 min, with a flow rate of hydrogen peroxide on the second level of 1.0% by weight VSC., washed and dried. The white pulp of 80.9%, output 95,0%.

Example 16.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 6 at a concentration of mass at the first stage and 10% with the consumption of acid 5% and processing time of 60 min, while the third stage was treated with chlorine dioxide at a flow rate of 1.5% by weight VSC., then the pulp is washed and dried. The white pulp is 88.1%, viscosity 22,1 MPa·C, the output of 94.5%.

Example 17.

Unbleached pulp from hardwood rigidity 10,2 Kappa, viscosity 48,0 MPa·C, white 48% after AAT processed under the conditions of example 16, and the third stage was treated with chlorine dioxide at a rate of 1.6% by weight VSC., then the pulp is washed and dried. White pulp and 88.5%, the viscosity of 22.0 MPa·C, the output of 94.5%.

METHOD of BLEACHING CELLULOSE

Table
№ p/pstage 1The consumption of H2About2, %The flow ClO2 , %Indicators cellulose
Acid consumption %τ, minCm,% conc. weightWhite, %Viscosity, MPa·Output %
1.4301090--52,0-of 98.2
2.5302,590--54,246,6of 98.2
3.5602,590--57,0-98,0
4.33010802,0-66,4-96,5
5.5307802,0-74,045,3096,0
6.2,5302,5902,01,085,845,7395,0
7.2,5602,5902,0 1,086,146,5895,0
8.5305902,01,085,629,9395,0
9.5605902,01,086,530.20mm95,0
10.7307902,01,085,822,8295,0
11.7607902,01,086,337,6995,0
12.103010902,01,085,422,6595,0
13.106010902,01,085,127,3595,0
14.56010901,51,082,2-95,5
15.56010901,01,0 80,9-95,5
16.56010902,01,5at 88.122,194,5
17.56010902,01,688,522,094,5

Method of bleaching of unbleached pulp, comprising alternating acid and alkali treatments, characterized in that the pulp after oxygen-alkali treatment on 1 stage leached in sulphuric acid with a concentration of 5-10 weight%, the consumption of sulphuric acid 5% by weight of absolutely dry pulp, the pH of 2.6-3.0, 2-stage peroxide treatment is carried out with alkali consumption of 1.0-1.3% of the mass of absolutely dry pulp and stage 3 is carried out by treatment of the pulp with chlorine dioxide in its consumption of 1.0 to 1.6% of the mass of absolutely dry pulp at a temperature of 70°C.



 

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EFFECT: reduced consumption of whitening agents.

1 tbl, 9 ex

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1 tbl, 9 ex

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EFFECT: reduced consumption of whitening agents.

1 tbl, 9 ex

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