SU1449605A1 - Method of bleaching sulfate pulp - Google Patents

Abstract

This invention relates to the pulp and paper industry and reduces the chemical loss of fiber and reduces the consumption of chemicals. The method of cellulose bleaching involves the chlorination of unsteady cellulose in two steps with an intermediate alkali treatment, hot refining and hypochlorite treatment in one or two steps. Hot refining was carried out after hypochlorite treatment of prn 95-98 s for 85-90 minutes. Hot refining can be carried out in the presence of a surfactant in an amount of 1-5 kg per ton of pulp. 2 h, para. f-ly. SL C

Description

ABOUT)

The invention relates to the methods of: bleaching sulphide pulp and can be used in the production of pulp for various purposes, mainly for the manufacture of an absorbent layer of sanitary-hygienic products,

The purpose of the invention is to reduce chemical losses of the fiber and reduce the consumption of chemicals.

The method includes successive stages of chlorination of the original cellulose in two stages with an intermediate alkali treatment, hypochlorite treatment in one or two stages and I with subsequent hot refining.

I Hot refining is carried out 1 when 95-98 ° C for 85-90 min. I, preferably in the presence of top

| of the active substance, which I will choose in the amount of 1.0-5.0 kg per tone | of cellulose.

I Example, Unbleached pulp with a hardness of 65 permanganate units (lu) is subjected to chlorination. CONDITIONS of chlorination are as follows: mass concentration 3%, duration 30 minutes, temperature 20 ° С, consumption of active chlorine 20 kg / ton of cellulose, residual content of active ilor not more than 0.03 g / l.

After chlorination, the cellulose is washed and subjected to alkaline treatment, ke at a mass concentration of 10%, temperature 60 С, duration 60 min, caustic soda consumption 10 kg / ton of cellulose, pH not less than i1.

After alkaline treatment (step 1), the pulp is washed and sent to the second chlorination stage with a consumption of active chlorine of 15 kg / t, mass concentration 3.0%. The consumption of active chlorine on chlorination steps is 70% of the total consumption of active chlorine for bleaching.

After the second chlorination stage, the cellulose is subjected to alkaline treatment under the following conditions; caustic soda consumption 15 kg / t, temperature, duration 60 min.

Then, calcium hypochlorite bleaching is carried out under the following conditions: temperature 40 ° C, mass concentration 10%, duration 150 min, pH 9.0, consumption of active chlorine 12 kg / ton of cellulose. After bleaching with chlorite, cellulose is washed and

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give to the second step hypochlorite bleaching. The bleaching conditions are as follows: the consumption of active chlorine is 10 kg / ton of cellulose, the pH is not lower than 9.5, the temperature is 38 ° C, the mass concentration is 10%, the duration is 120 minutes. Next, the cellulose is fed for hot refinement. It is carried out at 95 ° C, consumption of caustic soda 6% (60 kg / t) to the mass of absolutely dry cellulose (a.s.c.) and a duration of 90 minutes. The cationic drug katamin AB (amylbenzyldimethylammonium chloride) in the amount of 1.0 kg / t.s.c.. in order to reduce the mass fraction of resins and fats to 0.40%, to reduce the density and strength of the folder. Absorption rate after aging 6 s.

The total chemical fiber loss during bleaching and refining is 10.7%, of which at the refining stage is 4.5%.

PRI mme R 2. Unbleached pulp hardness of 95 pu subjected to chlorination. Chlorination conditions are as follows: mass concentration 3.5%, temperature 18 ° C, duration 1. 30 minutes, consumption of active chlorine 25 kg / ton of pulp, residual content of active chlorine not more than 0.03 g / l.

Chlorinated cellulose is washed and subjected to alkaline treatment with concentrates of weight 10%, temperature 60-65 ° C, duration 60-65 minutes, consumption of caustic soda 10-12 kg / ton of pulp, pH not less than 11.

After alkaline treatment, the cellulose is washed and sent to the second chlorination stage with a consumption of active chlorine of 10–18 kg / t, mass concentration 3.5%. The consumption of active chlorine for chlorination is 70% of the total consumption of active chlorine for bleaching.

After the second chlorination stage, the cellulose is subjected to alkaline treatment with the following parameters: consumption of caustic soda 15 kg / ton, temperature 60 ° C, duration 60 minutes, and addition of sodium phosphate in an amount of 10 kg / ton of cellulose. Then, bleaching with sodium hypochlorite is carried out under the following conditions: consumption of active chlorine 10 kg / ton pulp, pH 9.5-9.8, temperature 40 ° C, mass concentration 10%, duration 120 minutes.

Then bleached pulp is subjected to hot beating at 98 s to the consumption of caustic soda 80 kg by May

ce a.s.p., surfactant consumption 5.0 kg / t and a duration of 85 min. As a result, cellulose is obtained with a sufficiently high absorption rate (4 s) with low resin and fat content (0.45%), high whiteness and alpha cellulose content (90.2%), Total chemical loss of fiber during bleaching and refining 12, 5%, including at the improvement stage of 6.0%.

PrimerZ (by a known method). Unbleached pulp stiffness 50 p. subjected to pre-treatment with chlorine dioxide. The treatment conditions are as follows: mass concentration 3.5%, temperature 30 ° C, consumption of 10 kg / ton pulp.

Chlorination is carried out at a concentration of 3.5%, a temperature of 20 ° C, a flow rate of 8.3 kg / ton. Chlorinated cellulose is washed and subjected to neutralization at a mass concentration of 9%, a temperature of 60 ° C, pH 11. The consumption of caustic soda is 10 kg / t.

The washed mass is subjected to refinement at a mass concentration of 13% temperature of 115 ° C, pressure in the tower 0.7 kPa, duration 150 minutes. Dp of resin reduction add trisodium phosphate 10 kg / t and PA

0.5% (5.0 kg / t as.ps.).

The washed mass enters the second chlorination stage. Chlorination conditions are as follows: mass concentration 3%, consumption of active chlorine 8 kg / t, duration 30 minutes.

After the second chlorination stage, the cellulose is subjected to bleaching with sodium hypochlorite with the following parameters: mass concentration 10%, temperature 50 ° C, pH 10.3, consumption of active chlorine 12 kg / t, duration 180 minutes.

Next, the washed pulp enters the second bleaching stage with sodium hypochlorite at a concentration of 10%, temperature, pH 11.5. The total chemical loss is 25.3%, of which 18.1% are at the refining stage.

The bleached pulp obtained according to a known method is characterized by the following parameters: whiteness 90.5%, mass fraction of resins and fats 0.38%, absorption rate after aging 6.8 s. The chemical losses are 25.3%, of which 18.1% are at the refining stage.

Thus, the proposed method allows to reduce the chemical losses of the fiber while reducing the consumption of chemicals.

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Invention Formula

Claims (2)

one . The method of bleaching sulfite pulp mainly for the adsorbent layer of sanitary-hygienic products, including chlorination of the original pulp in two stages with an intermediate alkali treatment, hot refining 30 and hypochlorite treatment in one or two steps, characterized in that, in order to reduce chemical fiber loss and reduce the consumption of chemicals, hotness is improved - 3g live wire after hypochlorite treatment. 2. A method according to claim I, characterized in that the hot bending is carried out at 95-98 ° C for 85-90 minutes. 3, the method according to claim 1, about tl and h ay i and so that the hot refining is carried out in the presence of a surfactant in the amount of 1.0-5.0 kg / ton of cellulose.