SU834298A1 - Fibrous mass for making electric insulation cardboard - Google Patents

Description

(54) FIBROUS MASS FOR THE MANUFACTURE OF ELECTRICAL INSULATION CARDBOARD

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The invention relates to the pulp and paper industry, in particular to the manufacture and operation of electrical insulating materials with enhanced heat resistance and can be used as insulation for high voltage transformers, turbine generators and other electrical products. Cellulose insulation is one of the oldest and most common electrical insulation materials. However, low heat resistance and intense heat aging under the influence of the elevated temperature, air oxygen, decomposition products of impregnating masses limit the use of cellulose-based insulation. Therefore, increasing the heat resistance of cellulose insulation will significantly increase the service life of electrical products (transformer tube generators, etc.). The most effective way to increase the heat resistance of cellulose materials is to treat a sheet of paper or cardboard with various nitrogen-containing compounds l, 2 and. The disadvantage of the method is the use of toxic substances (nitrogen-containing compounds) for paper processing, which makes it difficult to handle them. In addition, when the surface of the insulation paper insulation paper solutions of nitrogen-containing. compounds (impregnation or spraying them) an important condition for increasing the heat resistance is the uniform distribution of the stabilizer over the thick web. If this is achievable during the processing of a sheet of paper, then it is difficult to produce electrically insulating cardboard having a greater thickness and density. The known method of improving the heat resistance of electrically insulating materials by introducing a stabilizer directly into the composition of the material (.43, However, the heat resistance of paper with polyethyleneimine in the process of thermal aging is not much higher than for paper made from pure cellulose. The purpose of the invention is to increase the thermal resistance of electrically insulating material I based on cellulose while maintaining high physicomechanical and dielectric indices, use environmentally friendly chemical compounds. It is achieved by the fact that the stabilizer composition comprises copper acetylamino tsetonaty Ca () and iron Fe {Cj-H-, O2) T iri the following components ratio, May. %: Unbleached sulphate cellulose 95-99.9 Copper or iron acetylacetonate 0.1-5 Laboratory specimens of elementary layers of electrical insulating cardboard with a thickness of 0–8-1, O g / cm are made on a laboratory sheet-shedding machine LOA-2 from unbleached electrical sulphate pulp EK-2 as follows. The pulp mass of grinding in the 20-liter roller and before casting of the elementary layers is introduced acetylacetonates of iron or copper at the rate of 0, 15% by weight of absolute dry fiber. Cardboard samples were prepared, containing, by mass, OD, O, 6j 1.0, 3, 9;; 6, O% acetyl acetate of iron and 99.9} 99.49.99, 0; 96.1 and 95.0% unbleached sulphate pulp EK-2, respectively, and samples containing O, 1; 0.4; 1, O; 5, O% copper acetylacetonate and, respectively, 99.9; 99.6; 99.0; 95.9; 95% sulphate unbleached pulp. The content of metal complexes in the samples is determined by pyrolytic analysis on a PPE derivatograph. At the same time, elementary layers of 100% EC-2 cellulose are cast. Cardboard corresponding to cardboard grade G with a thickness of 0.5 mm is obtained by subsequent pressing of elementary layers on a cold press PSU-5O at a specific pressure of Denoin 4O kg / cm, dried on a drying cylinder to constant mass at 10О ± 2:. The obtained samples of electrical insulating cardboard are tested in the initial state and after thermal aging for physical-mechanical and dielectric indices and determine the degree of polymerization (SP). Thermal aging of the laboratory samples of the board was carried out using 155 ± 2 C gp in the T-75O transformer oil .4.4 (GOST 5.171О72) using the existing procedure. Heat resistance is determined in accordance with the method according to the degree of SP change during thermal aging. Aging shows that the electric cardboard made from 100% cellulose and cardboard stabilized with polyethyleneimine is destroyed much faster than cardboard samples containing additives of acetylacetonate metals. After 10 days of aging, cardboard from 100% cellulose loses 28.6% of its strength, and the joint venture decreases by 37.5%. Cardboard stabilized with polyethyleneimine already after 3.5 days loses 38% strength in the limit, SP decreases by 7 O%. For 10 days of aging, cardboard stabilized by acetyl-cetonates of metals (1% by weight) loses 14–16% of tensile strength in the limit of aging, and SP decreases by 2–8%. The results of the test paperboard samples show that the addition of metal acetylacetates does not cause a deterioration in the physicomechanical and dielectric parameters of the paperboard compared with the sample stabilized with polyethyleneimine and the control one. At the same burden, there is an increase in the heat resistance of the cellulosic insulation material, which is expressed in higher values of the limit of moisture and SP for samples that have undergone thermal aging. Thus, the obtained data confirm the feasibility of using copper or iron acetylacetonates in cellulose-based electrical insulation materials in the composition to increase their heat resistance without compromising the physicomechanical and dielectric properties. Copper and iron acetylacetonates are fundamentally new stabilizers for the thermal degradation of cellulosic materials. V formula of the invention Fiber pulp for the manufacture of electrical insulating cardboard, containing unbleached sulphate pulp and a stabilizer, characterized in that, in order to improve the heat resistance of the cardboard, copper or iron acetylacetonates in the following ratio of components, May. %:

Nebelien sulfate

cellulose9 5-99.9

Copper acetylacetonate

or ironOD-5

Sources of information taken into account in the examination

1. USSR author's certificate N9 293901, CL. H 21 H 3/01, 1969.

834298

2. USSR author's certificate number 536274, cl. and 21 H 5 / GS, 1975.

3. US patent number 3510346, cl. 117-154, 1971.

4. USSR author's certificate number 456870, cl. TE 21 H 3/38, 1972 (prototype).

Claims (1)

Claim A fibrous mass for the manufacture of electrical insulating board, containing unbleached sulfate cellulose and a stabilizer, characterized in that, in order to increase the heat resistance of the board, the mass contains copper or iron acetylacetonates as a stabilizer in the following ratio of components, May. %: Unbleached Sulphate Pulp 95-99, '0 Copper or Iron Acetylacetonate 0.1-5