SU779470A1 - Method of treating sulphite pulp after digesting - Google Patents

Description

The invention relates to the pulp and paper industry and relates to a method for sulfite polynueni: viscose pulp for chemical processing. A known method of bleaching cellulose by treating it with sulfuric anhydride in an amount of 0.1-3.0% by weight of absolutely dry fiber and subsequent chlorination l3 "However, this method does not allow to reduce the resin content in the target product. There is also known a method of bleaching sulfite pulp by treating cellulose with chlorine dioxide and chlorine, followed by washing with water and alkali, single or multiple treatments with chlorine dioxide or hypochlorite, water and alkali 2. The disadvantage of this method is the complexity of the design process and the insufficient quality of the target product. The purpose of the invention is to improve the conditions of the pulp bleaching process and improve the quality of the target product. This goal is achieved by the fact that, prior to chlorination, the initial unbleached pulp is sequentially treated with a solution of a surfactant (surfactant) in an amount of 0.02-0.1% by weight of absolutely dry pulp, an aqueous solution of dioxin series KPK sulfuric acid in an amount of 0.2- 0.5% by weight of absolutely dry cellulose to pH 4.0-5.5 and sodium hypochlorite in an amount of 0.3-0.6% by weight of absolutely dry cellulose for 30-60 minutes. Example 1. DP experiments are used, unbleached sulphite pulp with the following parameters: alpha cellulose content 88%, viscosity 40 MPa-s, resin content 1.24%. Unbleached cellulose in the amount of 78 g with a moisture content of 36.2%, concentration of the mass of 3% is treated with stirring with a surface-active substance, which is the product of oxyethylation of synthetic fatty alcohols (DS-20 synthanol), added in the amount of 0, 35 by weight of absolutely dry cellulose, and then with an aqueous solution of sulfur dioxide. Obra779470

Cellulose pulping with sodium hypochlorite is carried out in an acidic medium at pH 4.8 for 30 minutes. The oxidizing potential of the reaction mass is equal to illOO MB. The consumption of hypochlorite is 0.6% of the mass of absolutely dry cellulose.

After treatment, the pulp is bleached according to the following scheme: chlorination — hot refining — chlorination — hypochlorite bleaching of the first stage — hypochloric; bleaching of the second stage — sour. Indicators of the quality of cellulose are presented in table. one.

Table 1

. Famous 92,60,38

Prototype method92, 50,29

Proposed 92,40,24

1d &YOI; 7a:, 1 - - --- --- ------ - - ----- - - -.-J- .- 1-i1 ---- - ..--. -... jJ..j, i -t i-y - ii --J-Example 2. For experience using unprocessed pulp with the same .. quality indicators, -that and. in example 1.-

The mode of processing and bleaching is the same as in example 1.

Example 3. For experiments using unbleached sulphite pulp

in the amount of 50 g with the following:

indications: alpha-cellulose content 88%; viscosity .44 MPa-s, resin content 1.49%, humidity 9.1%. The cellulose is soaked for 3 hours in water, the concentration of the mass of carbon; 3%. Then to the pulp. 5 ml of a 1% aqueous solution of the surfactant DSA-3-methanol, that is 0.1% by weight of absolutely dry cellulose, are added to the mass with constant mixing for 15 minutes. The pulp treatment is carried out for a pH of 5.5. To create the required pH in the reaction medium

7.0-7.5

17.2

25.4

91 .24,5.

7.0-7.5 17.5 91 25.7 5.5-6.5 16.5

Instead of an aqueous solution of sulfur dioxide, sulfuric acid is used in the amount of 0.4% of absolutely dry cellulose to treat unbleached pulp, Berol T1, -0.22 as surfactant. The quality indicators of cellulose after the alkalization stage are presented in table. 2

table 2

3.8 ml of a 3.9% aqueous solution of sulfur dioxide in an amount of 0, the mass of absolutely dry cellulose is added, after which b ml of an aqueous solution of sodium hypochlorite is added to the pulp with a content of 24.8 g / l of active chlorine. The consumption of hypochlorite is 0.3% of; the mass of absolutely dry cellulose, while the oxidation potential of the system is 1150 mV. After pretreatment, the pulp is bleached in the usual manner indicated in Example 1, the refining is carried out at a caustic sludge consumption of 40 kg / ton.

The results obtained are presented in Table. 3. T a b i c a 3

The data in Tables 1-3 show that the proposed method improves the reactivity of the pulp to subsequent bleaching and ensures the production of finished pulp with high whiteness, uniform viscosity and lower content of resins and fats and improves the process conditions.

Claims (2)

1. Author's certificate of the USSR 284599, cl. O 21 C 9/14, 1969. 2.Patent of the USSR .№ 196679, cl. D 21 C 9/10, 1965 Gprotioty).