SU1125323A1 - Method of preparing paper pulp for manufacturing electric insulating paper - Google Patents

Abstract

METHOD FOR PREPARING PAPER PULP FOR MANUFACTURING Insulating By VlAGI comprising cellulose dissolution, predrazmol weight fractionation and grinding the coarse fraction, characterized in that, in order to improve the electrical properties of paper predrazmol fractionation are at least two stages, where in the first stage predismol leads to the degree of grinding between 30 and 35 ° C. SR, and on the second, to a degree of grinding of 35-40 ° A and SR, and at each stage of the fractionation, the masas is washed with deionized water.

Description

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The invention relates to a process for the stock preparation of paper pulp for the manufacture of electrical insulation, preferably

capacitor, paper, and can be used in the pulp and paper and electrical industries.

A known method for the preparation of paper pulp for the manufacture of electrically insulating paper, including the dissolution of cellulose, predismol pulp with fractionation and the grinding of coarse fraction 1.

The main disadvantage of this method is that the paper obtained does not sufficiently satisfy the requirements of the electrical industry.

The purpose of the invention is to improve the electrical properties of the paper.

The goal is achieved in that according to the method of preparing paper pulp for the manufacture of electrically insulating paper, including pulp dissolution, predrammol mass with fractionation and grinding of a large fraction, the predismunt with fractionation is carried out in at least two steps, and at the first stage, the predirrmol is reduced to the degree of grinding 30-35 ° СР, and on the second - up to the grinding stage 35-40 ° СР, and at each stage of fractionation the mass is washed with deionized water.

Paper pulp in stages I and II circulates through pre-grinding mills and a machine for simultaneous washing and fractionation for 3-5 hours (depending on the type of paper produced, the productivity of paper machines, etc.). The number of cellulosic fiber passes through the system. Basin - grinding apparatus - washing and fractionation unit - the pool is 3-4. The pulp recovered after the second stage of fractionation with washing is subjected to grinding at the main grinding plant, and a small fraction of the fiber, together with washing water, is directed to the production of less important types of paper (KOH, ODP, etc.).

In tab. Figure 1 shows the sizes of the outgoing fine and isolated (long-fiber) fractions of cellulose fibers.

As can be seen from the results table. 1, the proposed method for the preparation of paper pulp makes it possible to obtain and direct to the main grinding a uniform length fraction of cellulose fiber free from fine fibers.

Examples 1-3 are carried out under laboratory conditions.

Example 1. Cellulose brand E-2 (GOST 5186-74) after the breakdown, in a mixer, is subjected to preliminary grinding to

30 ° SH. Then the cellulose fiber is subjected to fractionation (separation of the fine fiber fraction) with simultaneous washing on a sieve with φ 1.8 mm holes. After

This mass is rolled in a roll up to 35 ° SR and again subjected to fractionation by washing on a sieve with φ 1.6 mm holes. The number of cellulosic fiber passes through the fine fiber separation and washing apparatus 3. The sieve fraction passed through the sieve and was separated, and the remaining washed coarse fraction was ground to 97.6 ° SR and the weighted average fiber length of 45 dg. From the resulting paper pulp, a paper is produced on a sheet-cutting apparatus, which is tested for basic quality characteristics.

The results of the test paper are given in Table. 2

Example 2. Cellulose brand e-2 after

breakdowns in the mixer are pre-ground in a roll to 40 ° ShR. Then the pulp mass is subjected to fractionation with washing on a sieve with 0 holes of 1.6 mm. After that, the pulp is domayut to 45 ° SR and subjected to fractionation with washing on a sieve with f holes of 0.8 mm. The number of passes is 2. The fine fraction of fiber passing through the sieve is removed, and the large washed fraction of fiber, after stage II of the fractionation, is grinded to a grinding degree of 97.2 ° SR and the index of weighted average fiber length 41 dg. From the resulting paper pulp on a sheet-making apparatus, paper is made, which is tested for the main quality characteristics.

The test results are given in Table. 2

Example 3. Cellulose brand E-2, after breaking up in a mixer, is preliminarily diluted in a roll to 50 ° ShR, then subjected to fractionation by washing on a sieve with 0 openings of 1.2 mm. After that, the pulp is kept at 55 ° SR and fractionated with washing.

5 on a sieve with 0 holes of 0.6 mm. The number of cellulose fiber passes through the apparatus for separating the fine fraction of the fiber and washing 3. The fine cellulosic fraction passed through the sieve is removed, and the long fiber fraction is ground to 98.2 ° SR and the weighted average fiber length of 37 dg. From the obtained paper pulp on a sheet-making apparatus, they make a paper, which is tested for basic quality characteristics. In order to obtain comparative data, a mass is prepared in parallel in a manner known per se and in the usual manner without the stage of fractionation of cellulose fiber.

When carrying out the process under production conditions, unbleached sulphate pulp of grade E-2 (GOST 5186-74) is dissolved in a pulper, accumulated in a 25 m pool at a concentration of 3.8-42%, after which the pulp is directed to circulate through a closed contour: three pre-grinding mills - a device for separating a fine fraction of the fiber with simultaneous washing - a basin. The degree of grinding of paper pulp 34 ° SR. The circulation time was 4 hours, the diameter of the sieve holes of the sieve separator was 1.4 mm. After 4 hours, the mass is pumped to the second pool, from where it is fed for circulation through the pre-razmol stage II mill, the apparatus for separating the fine fraction of the fiber with washing and the pool. The circulation time is 4 hours, the degree of grinding is 40 ° SHR, the diameter of the holes of the sieve of the apparatus of the second stage is 0.6 mm, the number of mass passes through the apparatus of the fine fraction and washing 3.

In tab. 2 summarizes the results of tests of paper obtained by the proposed and known methods. If a known method improves the electrical strength of the paper on

Paper weight

15%, and the dielectric loss tangent at t 120 ° С by 10%, the proposed method improves these indicators, respectively

by 32 and 28%.

Table 1

ten

15

20

table 2

Claims (1)

METHOD FOR PREPARING PAPER PAPER FOR PREPARATION OF ELECTRIC INSULATION PAPER, including pulp dissolution, mass pre-grinding with fractionation and grinding of a large fraction, characterized in that, in order to improve the electrical properties of the paper, pre-grinding with fractionation is carried out at least two steps, and the first lead to a grinding degree of 30–35 ° SR, and in the second to a grinding degree of 35–40 ° SR, and at each stage of fractionation, the mass is washed with deionized water. SU, 1125323> I