SU749964A1 - Pulp bleaching method - Google Patents

Description

(54) PULSE BLEACHING METHOD

The invention relates to the pulp and paper industry and can be used in the production of cellulose.

A known method of bleaching cellulose by treating it with molecular oxygen in an alkaline medium at elevated temperature and pressure i and 23 When processing the cellulose, this method divides and improves the whiteness of the cellulose, but there is a destruction of the cellulose.

In order to intensify the bleaching of cellulose with molecular oxygen in an alkaline medium and reduce the destruction of cellulose, the process is carried out in the presence of an additive of a water-soluble salt; metal of variable valency in the form of a divalent salt, for example, manganese sulfate in the amount of O, 27-1.1% by weight of absolutely dry cellulose.

There is also known a method of bleaching cellulose by treating it with molecular oxygen in an alkaline medium while increasing

temperature and pressure in the presence of magnesium compounds 33.

However, this method makes it possible to achieve a certain limit on the content of alpha-de-lulose and viscosity. Increasing the content of alpha-41cellulose viscosity above this limit by changing processing conditions or increasing the consumption of magnesium compounds is not possible.

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The purpose of the invention is to increase the viscosity and alpha-cellulose content in the target product.

This goal is achieved by the fact that the pulp mass additionally

15, nickel compounds are introduced at a nickel to magnesium ratio of 0.05: 1 to 1: 1.

In the course of research, it was found that the additional introduction of a compound of a kel metal of variable valence, in the presence of magnesium compounds, gives an unexpected effect: a significant increase in the content of alpha-cellulose and in h. ,:.: 7

bones while maintaining other quality indicators and high cellulose. {The increase of nickel concentrations in the absence of magnesium compounds gives a much smaller effect. Magnesium and nickel compounds mutually reinforce the aru g effect of a friend,

Lab test method.

Example 1. Nebelento sulfite cellulose is mixed with sodium hydroxide solution, heated to and held for 50 minutes, then treated with oxygen under a pressure of 0.5 MPa for 12O minutes. The quality indicators of the treated pulp are given in table, 1,

Example 2 Unbleached sulphite pulp is mixed with magnesium sulphate solution, mixed with caustic soda solution and trisodium phosphate and then treated as in Example 1. The quality indicators of the treated pulp are shown in Table 2, sample 2.

Example 3 Unbleached sulphite pulp is mixed with a solution

Original unbleached pulp

Without additives

h ./,. -, ,, ..:.,: .. -,. ;;. . ,

The ratio of additives of nickel and magnesium is 0.5: 1.

99644

nickel chloride in the amount of O, Of3 by weight of absolutely dry fiber, and with a solution of sodium nitric oxide and further processed as in example 1, the quality indicators of cellulose are given in table. 1, sample 3,

Example 4 Unbleached sulphite pulp is mixed with magnesium sulphate solution, then nickel chloride is added to the pulp at a ratio with magnesium of 0.5: 1. After that, the pulp mass is mixed with a solution of sodium hydroxide and trisodium phosphate and treated as in. example 1. The quality indicators of the treated pulp are given in table. 1 sample 4 (proposed method).

Example 5 The treatment of unbleached sulphite pulp was carried out as in Example 4, but in the absence of trisodium phosphate. Indicators of the quality of cellulose are given in table. 1, sample 5 (the proposed method).

-. one

Table 1

87.3 49.6 59.0 83.692.1 26.4 74.9

The data in the table indicate that the additional introduction of soycinenne nickel provides cellulose with an alpha cellulose content of 93.9% and a viscosity of 43.2, t, e, 0.74% and 1.4 MPa, respectively, higher than during processing by a known method.

The use of the nickel compound in the bleaching process ensures

Unbleached pulp

cellulose with the same content of alpha cellulose in it, as in the known method, but with a lower viscosity.

Example 6 Unbleached sulphite pulp was treated with molecular oxygen in an alkaline medium, as in Example 4, at various ratios of nickel and magnesium compounds from 0, O5: 1 to 5.0: 1. The results of the experiments are presented in table. 2. Table 2

87.3

49,6

59.0

Claims (1)

The claims 50 The method of bleaching cellulose by treating the pulp with molecular oxygen in an alkaline medium at elevated temperature in the presence of a magnesium compound, characterized in that, in order to increase the viscosity and content of alpha-cellulose in the target product, nickel compounds in an additional ratio of nickel are added to the pulp and magnesium from 0.05: 1 to 1: 1.