RU2266992C1 - Method for pulp whitening - Google Patents

Abstract

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

SUBSTANCE: craft pulp mass with concentration of 2.5-5.0 % after oxygen-alkaline treatment is treated with potassium permanganate in consumption of 0.01-0.1 % based on dry cellulose at 40-80°C and pH 1.6-3.0 or with sulfuric acid solution in consumption of 1.0-1.5 % at 90°C for 30 min. In steps II and IV cellulose with concentration of 10 % is treated with hydrogen peroxide in consumption of 2 % based on mass of dry cellulose for 120 min at 80-90°C and pH 9.5-10.5 wherein consumption of sodium alkali and sodium silicate is 1.3 % and 2.5 %, respectively. In step III cellulose is treated with potassium permanganate in consumption of 0.01-0.4 % under step I conditions.

EFFECT: reduced consumption of whitening agents.

1 tbl, 9 ex

Description

The invention relates to the field of pulp production and can be used to produce bleached pulp without chlorine-containing reagents (TCF cellulose).

The known method of TCF bleaching of cellulose, in which cellulose with a hardness of 83 permanganate units, is subjected to alternating treatment with oxygen-containing reagents in five stages, hydrogen peroxide in an alkaline medium at stages I, III and V and potassium permanganate in a sulfuric solution at II and IV, while the cellulose is bleached hydrogen peroxide was carried out at 70-100 ° C with a flow rate of 2% and a concentration of pulp 2-7%, and treatment with potassium permanganate (flow rate of 0.01-0.8%) at 18-25 ° C was carried out until it was completely absorbed (RU 2142529, CL D 21 C 9/16, op. 10.12.1999). The technical result consists in obtaining cellulose whiteness in an environmentally friendly way without the use of chlorine-containing reagents with cellulose whiteness of 83-85%.

The disadvantage of this method is the high consumption of potassium permanganate, resulting in a decrease in the mechanical properties of cellulose.

The objective of the present invention is to develop a TCF technology for the production of cellulose after oxygen-alkaline treatment (BSC) using potassium permanganate and hydrogen peroxide to obtain a technical result, which consists in reducing the cost of these reagents.

This technical result is achieved by the fact that in the method of bleaching cellulose, including processing unbleached pulp, alternating acid and alkaline treatments in the first stage, the pulp after oxygen-alkaline treatment with a mass concentration of 2.5-5% is treated with potassium permanganate with a flow rate of 0.01-0 , 1% by weight of absolutely dry cellulose at a temperature of 40-80 ° C, pH 1.6-3.0, or with a solution of sulfuric acid with a flow rate of 1.0-1.5% at 90 ° C for 30 minutes, II and Stage IV carry out the processing of cellulose with a mass concentration of 10% hydrogen peroxide with rac in the course of 2% of the mass of absolutely dry cellulose for 120 min, pH 9.5-10.5 at 80-90 ° С and sodium alkali consumption of 1.3%, and sodium silicate 2.5%, and stage III is carried out by processing cellulose with potassium permanganate with 0.01-0.4% in the conditions of the first stage.

The proposed method allows to reduce the consumption of bleaching reagents.

This is the technical result, which is in a causal relationship with the essential features of the invention.

The essential features of the invention is the processing of unbleached pulp in the first stage after oxygen-alkaline treatment with a mass concentration of 2.5-5% potassium permanganate with a flow rate of 0.01-0.1% by weight of absolutely dry cellulose at a temperature of 40-80 ° C. pH 1 , 6-3.0 or a solution of sulfuric acid with a flow rate of 1.0-1.5% at 90 ° for 30 minutes, at stages II and IV, the pulp is treated with a concentration of 10% hydrogen peroxide with a flow rate of 2% by weight dry cellulose for 120 min, pH = 9.5-10.5 at 80-90 ° C and with a consumption of sodium alkali of 1.3%, and silicate n Tria 2.5%, and stage III is carried out by treating cellulose with potassium permanganate costs 0.01-0.4% under the conditions of step I. The invention is illustrated by the following examples.

Example 1

Hardwood pulp after oxygen-alkaline treatment with a hardness of 53.2 permanganate units, a viscosity of 48.2 cP, a whiteness of 48.7% is subjected to treatment with a solution of potassium permanganate in an acidic environment with a flow rate of 0.1% by weight of absolutely dry cellulose (molar ratio sulfuric acid / potassium permanganate 100: 1), mass concentration 2.5%, at a temperature of 40 °, until complete absorption of potassium permanganate (pH = 1.85). In the second and fourth stages, the cellulose is treated with hydrogen peroxide under conditions: mass concentration 10%, temperature 80 ° C, duration 120 min, pH = 10.0) and the following costs: 2.0% H ₂ O ₂ , 1.3% NaOH , 2.5% Na ₂ SiO ₃ . In the third stage, the cellulose is treated with a solution of potassium permanganate under conditions similar to the first stage, with a consumption of KMnO _{4 of} 0.4%. After each stage, the pulp is washed, after the last - dried.

Cellulose whiteness is 84.51%, viscosity 25.6 cP, yield 93%.

Example 2

The cellulose is subjected to processing analogously to example 1, with a consumption of potassium permanganate in stage 1 of 0.01%.

Cellulose whiteness is 81.0%, viscosity 27.2 cP, yield 94%.

Example 3

The cellulose is subjected to treatment with a solution of potassium permanganate in an acidic medium at stage 1 with a flow rate of 0.1% by weight of absolutely dry cellulose (molar ratio sulfuric acid / potassium permanganate 100: 1), mass concentration 2.5%, at a temperature of 40 °, until complete absorption of potassium permanganate (pH = 1.85), and in the second stage with hydrogen peroxide under conditions and costs similar to the second stage of example 1.

Cellulose whiteness is 71.6%, yield 98%.

Example 4

The cellulose is subjected to processing as in example 4, at a temperature of 1 stage of treatment with potassium permanganate 80 ° C.

Cellulose whiteness is 75.2%, yield 94.5%.

Example 5

The cellulose is subjected to processing as in example 4, at a mass concentration of 5%.

Cellulose whiteness is 69.8%, yield 98.2%.

Example 6

The cellulose is subjected to processing as in example 4, at a temperature of 1 stage of treatment with potassium permanganate 80 ° C.

Cellulose whiteness is 71.6%, yield 98%.

Example 7

Cellulose is subjected to treatment with filtrates obtained after the first stage of treatment with potassium permanganate of Example 1 at a temperature of 90 ° for 30 minutes, in the second stage, treatment with hydrogen peroxide is carried out - similarly also to example 1.

Cellulose whiteness is 77.3%, viscosity 37.5 cP, yield 98%.

Example 8

The cellulose is subjected to treatment with sulfuric acid (flow rate of 1.5%) and at a temperature of 90 ° for 30 minutes, in the second stage, treatment with hydrogen peroxide is carried out similarly as in example 1.

Cellulose whiteness is 75.0%, viscosity 36.9 cP, yield 98%.

Example 9

Cellulose is subjected to treatment with filtrates obtained after the first stage of treatment with potassium permanganate of Example 1 at a temperature of 90 ° for 30 minutes, in the second stage, treatment with hydrogen peroxide is carried out similarly to Example 1 and the treatment with filtrates of permanganate treatment and hydrogen peroxide is repeated.

Cellulose whiteness is 80.3%, viscosity 35.7 cP, yield 95.8%.

Table The method of bleaching pulp No. 1 stage 2 stage 3 step 4 step Pulp performance KMnO ₄ ,% Costs,%: H ₂ O ₂ , NaOH, Na ₂ SiO ₃ KMnO ₄ ,% Costs,%: H ₂ O ₂ , NaOH, Na ₂ SiO ₃ White,% Viscosity, cP Exit % 1. 0.1 2.0; 1.3; 2,5 0.4 2.0; 1.3; 2,5 84.5 25.60 93.0 2. 0.01 2.0; 1.3; 2,5 0.4 2.0; 1.3; 2,5 81.0 27,2 94.0 3. 0.1 2.0; 1.3; 2,5 - - 71.6 - 98 4. 0.1 2.0; 1.3; 2,5 - - 75,2 - 94.5 5. 0.1 2.0; 1.3; 2,5 69.8 - 98.2 6. filtrate 2.0; 1.3; 2,5 - - 77.3 38.3 98 7. H ₂ SO ₄ 2.0; 1.3; 2,5 - - 75.0 - 97.8 8. filtrate 2.0; 1.3; 2,5 filtrate 2.0; 1.3; 2,5 80.3 35.7 95.8

Claims (1)

The method of bleaching cellulose, including processing unbleached pulp by alternating acid and alkaline treatments, in the first stage, the pulp after oxygen-alkaline treatment with a mass concentration of 2.5-5% is treated with potassium permanganate with a flow rate of 0.01-0.1% by weight of absolutely dry cellulose at a temperature of 40-80 ° C, a pH of 1.6-3.0 or a solution of sulfuric acid with a flow rate of 1.0-1.5% at 90 ° C for 30 minutes, stage II and IV carry out the processing of cellulose with a concentration of 10 % hydrogen peroxide with a consumption of 2% by weight of absolutely dry cellulose for 120 min H 9.5-10.5 at 80-90 ° C and with a consumption of sodium alkali of 1.3% and sodium silicate 2.5%, and stage III is carried out by treating cellulose with potassium permanganate with a flow rate of 0.01-0.4% in the conditions of stage I.