SU1203160A1 - Method of bleaching pulp - Google Patents

Description

This invention relates to pulp bleaching processes and can be used in the pulp and paper industry.

The aim of the invention is to increase the viscosity of the pulp while maintaining its flourish.

In the proposed method, the bleaching of cellulose with a solution of hypochlorite is carried out in the presence of 3,6-di-t-butyl pyrocatechol added in an amount of 0.05-0.50% by weight of absolutely dry fiber.

Example}. Unbleached sulphate pulp from coniferous woods, after the chlorination and alkalization stage, with a delignification degree of 5.4 permanganate units and a viscosity index of 1% copper ammonia solution 71.5 mPa-s, is treated with sodium hypochlorite solution (2% but active chlorine absolutely dry fiber) 60 minutes at 60 ° C. Before the hypochlorite treatment, 3,6-di-t-butyl pyrocatechin in an amount of 0.05 is added to the reaction medium; 0.10; 0, 0.30 and 0.50% by weight of absolutely dry fiber. At the same time, under the same conditions, control bleaching is carried out without an additive, as well as with additives of urea and hydroquinone (by prototype) as inhibitors of cellulose destruction.

The results of analyzes of cellulose after hypochlorite bleaching are presented in table. one.

As can be seen from the table. 1, the bleaching of cellulose with sodium hypochlorite in the presence of 3, () - ditertbutylpyrocatechol, taken in an amount of 0.05-0.20% by weight of absolutely dry fiber, allows to increase the viscosity of the cellulose fiber without reducing the whiteness of the cellulose.

five

five

0 5

0

A further increase in the amount of 3,6-ditertbutylpyrocatechine additive leads to a slight decrease in whiteness, as a result of the sorption of the residual 3,6-ditertbutylcatechol and its oxidation products on the fiber.

An increase in viscosity also takes place in multi-stage bleaching of cellulose, including the hypochlorite bleaching stage of the proposed method. At the same time, the amount of added 3,6-ditertbutylpyrocatechol can be increased to 0.5% by weight of absolutely dry fiber, without a significant decrease in the whiteness of the pulp.

Example 2. Sulfate pulp from coniferous wood bleached according to the scheme X-Sch | -G-D | -Shch2-Do-K. The cellulose after the first stage of alkali and the stiffness of 4.4 permanganate units, the viscosity of 1% of the copper-ammonia solution is 77.9 MPa. with. The bleaching is carried out according to the specified scheme with the addition of 3,6-diterbutylpyrocatechine at the stage of hylochlorite treatment (consumption of NaCIO 1.5% to absolutely dry fiber). In parallel, control bleaching is carried out without an additive at the hypochlorite treatment stage. The results of the experiment are presented in table. 2

As can be seen from the table. 2, when multistage bleaching is added. 3,6-ditertbutylpyrocatechol up to 0.50% of the weight of absolutely dry fiber does not affect the whiteness of the pulp, increasing the viscosity of the finished pulp.

In tab. 3 shows the mechanical indicators of bleached pulp according to the proposed method, indicating high quality of the product obtained.

Table 1

Indicators

Additive 3,6-ditretbugilpyrokagehin,% by weight of absolutely dry fiber

Breaking length, m

7300

Resistance

pushing through

kPa

458

Tear resistance, mN

920

table 2

Table 3

7800

7800

8300

473

500

522

1000

1040

970

Claims (1)

METHOD FOR BELLING CELLULOSE, including treating it with a hypochlorite solution in the presence of an organic additive, characterized in that, in order to increase the viscosity of the cellulose while maintaining its whiteness, 3,6-ditretbutylpyrocatechol in the amount of 0.05-0.50% is used as an organic “additive” by weight of absolutely dry fiber.