RU2266993C1 - Method for whitening of sulfate pulp - Google Patents

Abstract

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

Description

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

A known three-stage method of bleaching cellulose, including processing the pulp in 1 step with nitrogen-containing polycarboxylic acid at a temperature of 70-90 ° C, in 2 steps with hydrogen peroxide with a flow rate of 1.3-2.0% by weight of abs. dry cellulose in an alkaline medium at a mass concentration of 10%, a temperature of 90 ° C for 120 minutes and at 3 steps with chlorine dioxide with a flow rate of 1.3-2.4% by weight of abs. dry cellulose at a mass concentration of 10%, a treatment time of 120 minutes at a temperature of 50-60 ° C (RU 2044808, class D 21 C 9/10, op. 1995).

The proposed method differs from the known one in that instead of polycarboxylic acid, sulfuric acid is used and cellulose is treated with this acid after oxygen-alkali treatment, in the second stage, peroxide treatment is carried out with an alkali consumption of 1.0-1.3% by weight of abs. dry cellulose and 3 stages use chlorine dioxide at a flow rate of 1.0-1.6% and a temperature of 70 ° C.

This difference improves the quality of cellulose by increasing its whiteness.

The technical result, which is causally connected with the essential features of the invention, is to obtain a whiteness of hardwood pulp 88.5% with an initial hardness of 10.2 Kappa units due to the auto-oxidation process, the initiator of which is the oxygen remaining in the fiber after oxygen-alkaline treatment in residual alkalinity and the course of which depends on the pH of the medium at 1 stage of acid treatment and, accordingly, acid consumption.

Salient features of the invention: a method for bleaching unbleached pulp, comprising alternating acid and alkaline treatments, characterized in that the pulp after oxygen-alkaline treatment in 1 step is treated with sulfuric acid with a mass concentration of 5-10%, sulfuric acid consumption of 5% by weight of abs. dry cellulose, pH 2.6-3.0, per 2 stages peroxide treatment is carried out with an alkali consumption of 1.0-1.3% by weight of abs. dry cellulose and stage 3 is carried out by treating cellulose with chlorine dioxide at a flow rate of 1.0-1.6% by weight of abs. dry cellulose at a temperature of 70 ° C.

Example 1

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after an ash treatment, is treated with sulfuric acid with a consumption of 4% by weight of high-purity clay, with a mass concentration of 10% and while maintaining a cellulosic suspension at 90 ° C for 30 minutes. Then the pulp was separated and dried. Cellulose whiteness 52.0%, yield 98.2.

Example 2

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after an ash treatment, is subjected to treatment with sulfuric acid with a flow rate of 5% by weight w.c.c., with a mass concentration of 2.5% upon aging cellulosic suspension at 90 ° C for 30 minutes. Then the pulp was separated and dried. Cellulose whiteness 54.2%, viscosity 46.6 MPa s, yield 98.2.

Example 3

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after an ash treatment, is treated with sulfuric acid with a consumption of 5% by weight of high-purity clay, with a mass concentration of 2.5% and withstanding cellulose suspension at 90 ° C for 60 minutes. Then the pulp was separated and dried. Cellulose whiteness 57.0%, yield 98.0.

Example 4

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after a BWC is subjected to treatment with sulfuric acid with a flow rate of 3% by weight of SCC, with a mass concentration of 10% while maintaining the cellulosic suspension at 80 ° C for 30 minutes, then the pulp is separated, washed and treated with hydrogen peroxide at the same mass concentration (with a flow rate of H ₂ O ₂ 2.0% and sodium hydroxide 1.3%, pH 10.9) at 90 ° C and a duration of 120 minutes, then the pulp is separated, washed and dried. Cellulose whiteness 66.4%, yield 96.5.

Example 5

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after an ash treatment, is subjected to treatment with sulfuric acid with a consumption of 5% by weight of centrifugal grade, with a mass concentration of 7% while maintaining the cellulosic suspension at 80 ° C for 30 minutes, then the pulp is separated, washed and treated with hydrogen peroxide at the same mass concentration (with a flow rate of H ₂ O ₂ 2.0% and sodium hydroxide 1.3%, pH 10.9) at 90 ° C and a duration of 120 minutes, then the pulp is separated, washed and dried. Cellulose whiteness 74.0%, viscosity 45.3 MPa · s, yield 96.0.

Example 6

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after an ash treatment, is subjected to treatment with sulfuric acid with a flow rate of 2.5% by weight of centrifugal grade, with a mass concentration of 2.5% while keeping the cellulose suspension at 90 ° C for 30 minutes, then the pulp is separated, washed and treated with hydrogen peroxide at the same mass concentration (with a flow rate of H ₂ O ₂ 2.0% and sodium hydroxide 1.3%, pH 10, 9) at 90 ° C and a duration of 120 minutes, then the cellulose is separated, washed and treated with chlorine dioxide at a temperature of 70 ° C a flow rate of 1.0% when the mass concentration, the processing time is similar to the second stage, then the pulp is washed and dried. The cellulose whiteness is 85.8%, the viscosity is 45.7 MPa · s, the yield is 95.0%.

Example 7

The unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 MPa · s, a whiteness of 48% after BWC is treated under the conditions of Example 6, increasing the processing time to 60 minutes in the first step, then the pulp is washed and dried. Cellulose whiteness 86.1%, viscosity 46.58 MPa · s, yield 95.0%.

Example 8

The unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after BWC is treated under the conditions of Example 6 with a mass concentration of 5% in the first stage, then the pulp is washed and dried. Cellulose whiteness is 85.6%, viscosity is 29.93 MPa · s, yield 95.0%.

Example 9

The unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after KSCH is treated under the conditions of Example 6 with a mass concentration in the first stage of 5%, increasing the processing time to 60 minutes, then the pulp is washed and are dried. Cellulose whiteness 86.5%, viscosity 30.20 MPa · s, yield 95.0%.

Example 10

The unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after BWC is subjected to treatment under the conditions of Example 6 with a mass concentration in the first stage of 7% and an acid flow rate of 7% by weight w.s. ., then the cellulose is washed and dried. The cellulose whiteness is 85.8%, the viscosity is 22.82 MPa · s, the yield is 95.0%.

Example 11

The unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 3 mPa · s, a whiteness of 48% after BWC is subjected to treatment under the conditions of Example 6 with a mass concentration in the first stage of 7% and an acid consumption of 7% by weight of V.c. c., increasing the processing time to 60 minutes, then the pulp is washed and dried. Cellulose whiteness 86.3%, viscosity 37.69 MPa · s, yield 95.0%.

Example 12

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after KSChO is subjected to treatment under the conditions of Example 6 at a mass concentration in the first stage of 10%, an acid consumption of 10% by weight ., then the cellulose is washed and dried. The cellulose whiteness is 85.4%, the viscosity is 22.69 MPa · s, the yield is 95.0%.

Example 13

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after KSChO is subjected to treatment under the conditions of Example 6 at a mass concentration in the first stage of 10%, an acid consumption of 10% by weight ., increasing the processing time to 60 minutes, then the pulp is washed and dried. Cellulose whiteness is 85.1%, viscosity is 27.35 mPa · s, yield 95.0%.

Example 14

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after KSCO is treated under the conditions of Example 6 with a mass concentration of 10% in the first stage, increasing the processing time to 60 min, with a consumption of hydrogen peroxide at the second stage, 1.5% of the mass of v.c.ts., washed and dried. Cellulose whiteness 82.2%, yield 95.0%.

Example 15

Unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after KSCO is treated under the conditions of Example 6 with a mass concentration of 10% in the first stage, increasing the processing time to 60 min, with a consumption of hydrogen peroxide in the second stage, 1.0% of the weight of the SCC, washed and dried. Cellulose whiteness 80.9%, yield 95.0%.

Example 16

The unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after KSCH is subjected to treatment under the conditions of Example 6 at a mass concentration in the first stage of 10% with an acid consumption of 5% and a treatment time of 60 minutes, and at the third stage, they were treated with chlorine dioxide with a flow rate of 1.5% by weight of SCC, then the pulp was washed and dried. Cellulose whiteness 88.1%, viscosity 22.1 MPa · s, yield 94.5%.

Example 17

The unbleached hardwood pulp with a hardness of 10.2 Kappa, a viscosity of 48.0 mPa · s, a whiteness of 48% after BWC was treated under the conditions of Example 16, and in the third stage it was treated with chlorine dioxide with a flow rate of 1.6% by weight w.s. c., then the pulp is washed and dried. Cellulose whiteness 88.5%, viscosity 22.0 MPa · s, yield 94.5%.

CELLULOSE BLEACHING METHOD

Table No. p / p 1 stage Consumption of N ₂ About ₂ ,% ClO ₂ consumption,% Pulp performance Acid consumption,% τ min See,% conc. masses T ° C White,% Viscosity, MPa · s Exit, % 1. 4 thirty 10 90 - - 52.0 - 98.2 2. 5 thirty 2,5 90 - - 54,2 46.6 98.2 3. 5 60 2,5 90 - - 57.0 - 98.0 4. 3 thirty 10 80 2.0 - 66,4 - 96.5 5. 5 thirty 7 80 2.0 - 74.0 45.30 96.0 6. 2,5 thirty 2,5 90 2.0 1,0 85.8 45.73 95.0 7. 2,5 60 2,5 90 2.0 1,0 86.1 46.58 95.0 8. 5 thirty 5 90 2.0 1,0 85.6 29.93 95.0 9. 5 60 5 90 2.0 1,0 86.5 30,20 95.0 10. 7 thirty 7 90 2.0 1,0 85.8 22.82 95.0 eleven. 7 60 7 90 2.0 1,0 86.3 37.69 95.0 12. 10 thirty 10 90 2.0 1,0 85,4 22.65 95.0 thirteen. 10 60 10 90 2.0 1,0 85.1 27.35 95.0 14. 5 60 10 90 1,5 1,0 82,2 - 95.5 fifteen. 5 60 10 90 1,0 1,0 80.9 - 95.5 16. 5 60 10 90 2.0 1,5 88.1 22.1 94.5 17. 5 60 10 90 2.0 1,6 88.5 22.0 94.5

Claims (1)

A method of bleaching unbleached pulp, including alternating acid and alkaline treatments, characterized in that the pulp after oxygen-alkaline treatment at 1 step is treated with sulfuric acid with a mass concentration of 5-10%, sulfuric acid consumption of 5% by weight of absolutely dry cellulose, pH 2, 6-3.0, in 2 steps, peroxide treatment is carried out with an alkali consumption of 1.0-1.3% by weight of absolutely dry cellulose and 3 steps are carried out by treating cellulose with chlorine dioxide at a flow rate of 1.0-1.6% by weight absolutely dry pulp at a temperature of 70 ° .