SU558081A1 - The method of obtaining fibrous cellulose semi-finished product - Google Patents

Description

one

The invention relates to the pulp and paper industry and can be used in the manufacture of pulp for various types of paper and cardboard.

The known method is that the wood bristles are impregnated with an aqueous solution of sodium carbonate to soften, then grind, boil with oxygen-containing gas (boiling with an oxidizing agent).

The disadvantages of this method are the production of a semi-finished product with insufficient mechanical parameters, as well as the need to carry out the process at high temperatures and pressures.

The aim of the invention is to increase the tenacity indicators of the semi-finished product and provide more favorable conditions of the process (carrying out the oxidation process without pressure).

The goal is achieved by the fact that before alkaline impregnation the starting material is subjected to aqueous gpdroliza at 120-140 ° C. Before the product is 90-95%, the subsequent alkaline impregnation is carried out at 10-140 ° C and the concentration of alkali in the solution 15-25 g / l , and the processing of i-ray fiber pulp with an oxidizing agent is carried out at 70-98 ° C and the consumption of oxidizer is 1.5-10% of the mass of absolutely dry fiber.

Hydrogen peroxide is used as an oxidizing agent.

In tab. 1 shows the strength of nsMeiseinni sulphate pulp strength during irpmeeeiip hydrolysis.

Table 1

Without IC

Indicators

hydrolysis I hydrolysis

As SPECIFIED from the table, the predprolysis does not increase the strength of sulphate pulp as a whole, but in terms of such an important indicator as the breaking length sharply reduces.

Studies have shown the opposite picture. The use of weak hydraulic oil before oxidizing with alkaline treatment leads to an increase in all the strength properties of semi-finished products. In tab. Figures 2 and 3 show the results of these studies.

table 2

Consequently, the cleavage of acetyl groups of hemicelluloses by the method of easy hydrolysis saves hemicelluloses to a greater extent than without hydrolysis during alkaline treatment due to the stabilization of a part of hemicelluloses, which entails preservation of strength, not only alkali treatment, but also during oxidation ligiiia.

In tab. 4 shows the actual characteristics of the semi-finished product obtained using aqueous hydrolysis compared with acid and hydrolysis.

Table 4

Table 3

For example, the alkaline mass after impregnation of irp without hydrolysis of an ir and a higher yield (97.4 versus 94.0%) when conducting hydrolysis has a breaking length of 5300 m, and with the use of water hydrolysis of 7400 m, as well as the number of double kinks - 71 against 325 using hydrolysis. This regularity is also preserved in the finished semi-finished product after alkaline oxidation (Table 3). The breaking length of the production of an oleaginated hydrolysis product was 5560 BJO m, and with a hydrolysis of 9420-10380 m. The number of double kinks increased from 277-311 to 880-1070 with hydrolysis. Thus, the conducted studies have shown the positive effect of hydrolysis on the erosiveness of the proposed semi-finished product for all indicators.

It is known that wood hemicelluloses contain acetyl groups. In hemicelluloses of foliage wood there are more of them, and in coniferous wood there are fewer. It is known that as a result of the cleavage of acetyl group and uronic acid residues, the stability of glucuronoxylaa and glucomannan, the main hemicellulose comionites, is increased.

These data demonstrate the indisputable advantage of water hydrolysis over acid for i-type and semi-finished products according to the method of the invention.

The proposed removal method is carried out as follows: outgoing wood raw material — softwood and hardwood wood — is subjected to aqueous hydrolysis of the iri at 120–140 ° C for 30–60 min until the wood leaves after the hydrolysis of 95–90%, then it is alkaline at 10–140 ° C and alkali concentrations 15-25 g / l Na2O, hydronic module 1: 4-1: 6

when circulating aperture liquor. Both hydrolysis and alkali impregnation can be carried out in either continuous or intermittent manner. The duration of the impregnation can vary from 30 to 120 minutes.

Proiitku lead to shrinkage output in the range of 80-92% of the original wood.

Then, the impregnated chips are directed to semi-milling in two stages. The resulting mass is concentrated on a pressure filter to

concentrations of 25–30% and is intended for oxidative treatment — delignification. Delignification of the obtained mass is carried out by treating it with an oxidizing agent, for example, hydrogen peroxide at a different consumption of 1.5-10% by weight of abs. dry fiber, depending on the purpose of the desired semi-finished product and the depth of delnification, at a water ratio of 1: 4-1.5 for 1.5-2.0 hours at a temperature of 70-98 C.

After oxidative treatment, the mass is tromped and used for various types of paper and cardboard. 11 get a semifinished product with high indicators of strength, discontinuous length of more than 9000 m, the number of double spirals more than 1000, co-razrydpypu 90 g.

Example 1. Cellulose and batch of birch wood. The hydrolysis is carried out for 60 minutes. The impregnation of hydrolyzed wood is scavenged and, with a concentration of 25 g / l, at 10 ° C for 120 min and water module 1; 6. The alkali-impregnated chips are subjected to semi-mass grinding in two steps to a grinding degree of 15–20 ° SH. This is followed by rinsing of the mass, which is then concentrated to a concentration of 25% and sent to the oxidative treatment of hydrogen overpowered at an oxidizer consumption of 10% of the fiber, processing time 1.5 hours at a temperature of 90 ° C.

As a result, the semi-finished product obtained is distinguished by high yield and mechanical properties (see Table 5).

T a b l and c a 5

Example 2. Cellulose and batch of birch wood. The hydrolysis is carried out under the same conditions as in Example 1. Impregnation nj is effected at 120-loO C for 60-30 minutes. The impregnated wood chips are ground to the degree of grinding 15 ° W. After washing, the mass is oxidized with hydrogen peroxide at a rate of 5% oxidant from the fiber at 70 ° C for 2 h. As a result, fepolfactory is obtained, the strength properties of which are given in Table. 6

T a b l and c a 6

ten

15

PRI me R 3. Cellulose is obtained from aspen wood according to the regime shown in example 1, with the exception of hydrogen peroxide consumption, which was 5 and 10% by weight of abs. dry fiber processing temperature of 98%, the duration of 2 hours.

As you can see, the strength of the fiber trap from aspen wood birch li (see Tables 6, 7) is 1: 1;

THAT indicates

- I have opportunities to combine aspen processing

Table 7

GO

1000 71 4.5

65

Table

PRI me R 4. Cellulose is produced from pine wood. The prehydrolysis is carried out at 140 ° C for 60 minutes. Alkaline impregnation is carried out at 120 and 140 ° C for 60 and 30 minutes, respectively. The grinding of the mass is carried out to the degree of grinding 15 ° SH. The resulting mass after washing and condensed is oxidized with a consumption of hydrogen peroxide of 10% of the fiber. Poluchepny semi-finished product has high strength (see table. 8).

Iirj data numbered in the tables, it is clear that the method is suitable for both deciduous and coniferous wood.

Table 9 shows the data on the optimal mode for different wood species (for modes see examples 1, 2, 3, 4).

As follows from the data in this table, the mechanical properties of the semi-finished products obtained according to the method of the invention greatly exceed the strength of the neutral sulphite semi-cellulose and approach the strength of sulphate numbly white cellulose.

The application of the method allows to significantly increase the technical and economic indicators of the production of semi-finished products due to the high yield of wood, low consumption of balances and steam for technological needs.

Table 9