JPH0313685B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel insulating paper for electrical equipment. More specifically, we aim to prevent the generation of static electricity in forced oil-cooled electrical equipment, by coexisting with a specific nitrogen-containing organic compound that negatively charges the electrical insulating fluid. Regarding insulating paper for equipment. When a solid and a liquid come into contact, an uneven distribution of positive and negative charges occurs at the interface, but when the liquid flows at the interface, static electricity is generated. The amount of charge of the liquid is closely related to the electrical resistance of the liquid, 10 ¹¹ ~
It is known that the volume resistivity becomes significantly large in the range of 10 ¹⁵ Ω·cm. In the case of forced oil-cooled electrical equipment, if the insulating oil becomes significantly charged, this can sometimes lead to accidents. Conventionally, in order to avoid the above-mentioned volume resistivity range because the generation of static electricity is unavoidable, in the field of petrochemical industry, a method has been used to reduce the volume resistivity by adding a static eliminator made of an ionic substance that is already commercially available. has been adopted. Many commercially available insulating oils fall within the volume resistivity range described above. However, in the case of electrical insulating oil, the method used in the petrochemical industry is not preferred because it impairs electrical characteristics. On the other hand, with strict purification processing, ^the
It is difficult to maintain a volume resistivity of cm or more. It is difficult to suppress electrostatic charging by controlling the electrical resistance of the insulating oil in this way. The inventors of the present invention have conducted intensive research to overcome the above-mentioned drawbacks, and have found that electrical equipment made of cellulose insulating paper to which 1,2,3-benzotriazole, indazole, methylbenzotriazole, or benzimidazole is added. They arrived at insulating paper and completed the present invention. In general, when a liquid is charged due to some imbalance of positive and negative ions due to ions generated by thermal lysis of some of the liquid's molecules or ionic impurities contained in it, the net charge is the difference between the positive and negative ions. The charge is observed as static electricity. The reason for this is that the solid more selectively adsorbs one of the positive and negative ions in the liquid at the interface between the solid and the liquid. Therefore, at the interface, an electric double layer is formed between the solid fixed layer and the other ion layer of the opposite sign diffused into the liquid at a small distance. This is a phenomenon that occurs when a solid and a liquid come into contact, but as mentioned above, if flow occurs at the interface, the ions in the diffusion layer in the liquid are separated from the electric double layer, causing the generation of static electricity. Ru. This charge separation increases as the flow rate increases, so in the chemical industry, static electricity damage is also suppressed by controlling the transport speed of liquid petroleum products. However, according to the insulating paper for electrical equipment of the present invention,
As mentioned above, instead of suppressing static electricity by controlling electrical resistance or flow velocity, which is generally known,
Static electricity can be suppressed by controlling physicochemical adsorption phenomena. Generally, kraft pulp,
Natural fibers such as linen or cotton are in practical use. The polar groups of these fibers mainly consist of hydroxyl groups, but some of them also contain aldehyde groups and carboxyl groups generated by oxidation. Hydrogen in these polar groups is positively polarized due to the influence of oxygen, which has a high electronegativity. Since these hydrogens are thought to cover the fiber surface, the insulating oil is positively charged in order to selectively adsorb negative ions in the oil and form a fixed layer at the interface. Therefore, in order to selectively adsorb positive ions in oil, by introducing an active moiety with an excess of electrons into electrically insulating paper, the positive ions can be absorbed by their interaction. It is possible to create a fixed layer of That is, the present invention was completed based on the knowledge that by adjusting the amount of the excess electron portion, equal amounts of positive and negative ions are generated, thereby suppressing the generation of static electricity. Among organic compounds, the nitrogen atom of a nitrogen compound has a pair of unpaired electrons. Compounds having this unpaired electron pair generally exhibit chemical unsaturation, and therefore are expected to have great affinity with positive ions lacking electrons. Therefore, the generation of static electricity can be suppressed by mixing, adding or coating such a nitrogen compound to electrically insulating paper. In the present invention, 1,2,3-benzotriazole, indazole, methylbenzotriazole or benzimidazole is used as the nitrogen-containing organic compound. The chemical structural formulas of these are shown below.

【formula】

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[Formula] Since these are nonionic compounds, they have the effect of suppressing static electricity without impairing electrical properties, and can be used effectively in practice. Note that many petroleum-based hydrocarbons such as fuel and lubricating oil have electrical resistance comparable to that of electrical insulating oil. As a result, accidents such as fires and explosions occur due to static electricity generated during pipe transportation. The insulating paper for electrical equipment of the present invention, which is capable of suppressing static electricity, can also be used in transport pipes for liquids with high electrical resistance and in areas where such liquids easily flow. Next, the insulating paper for electrical equipment of the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples. Reference example 1 Kraft paper for electrical insulation with an inner diameter of 3 mm and a length of 310 mm.
A 300 mm long grounded back electrode is installed around the outer circumference of the pipe, and insulating oil is allowed to flow down inside the pipe at a flow rate of 10 cm/sec. The flowing oil was received by a Faraday gauge and the flowing current was measured. As a result, the charging potential, which is the product of the flowing current and the volume resistivity of the insulating oil, was 110 Ω·cm-A. Example 1 Electrical insulation kraft paper was impregnated with 1,2,3-benzotriazole dissolved in alcohol,
The dried product was made into a pipe shape, and the charging potential was measured in the same manner as in the reference example. The measurement results are shown in Figure 1. That is, FIG. 1 is a graph showing the relationship between the amount of 1,2,3-benzotriazole added to electrically insulating kraft paper and the degree of charging potential. As is clear from Figure 1, the greater the amount of 1,2,3-benzotriazole added, the greater the suppression of static electricity generation;
- It can be seen that the polarity of the generated static electricity is reversed when the amount of benzotriazole added is about 0.6% (wt%, the same applies hereinafter). Therefore, under the conditions using the electrically insulating kraft paper and 1,2,3-benzotriazole used here, the generation of static electricity can be ignored when the amount of 1,2,3-benzotriazole added is approximately 0.6%. be able to. However, it is difficult to define the amount of 1,2,3-benzotriazole added because it depends on conditions such as the measurement temperature and flow rate, as well as the raw material and degree of purification of the electrically insulating kraft paper. It is. From FIG. 1, the findings obtained in Example 1 are satisfied. Example 2 As described above, the flow charging phenomenon is an interface phenomenon between a solid and a liquid. Therefore, as in Example 1,
It is not necessary to impregnate the static electricity suppressant uniformly. Therefore, in Example 1, an alcoholic solution of 1,2,3-benzotriazole was applied in an amount that would cause negligible generation of static electricity on the surface of electrically insulating kraft paper, and the dried product was shaped into a pipe, and the process was carried out in the same manner as in the reference example. The charging potential was measured. The measurement result is 3
The charging potential was Ω·cm−A, and the generation of static electricity was negligible compared to the reference example. Example 3 1.0% indazole on kraft paper for electrical insulation
The added material was made into a pipe shape, and the charging potential was measured in the same manner as in the reference example, and the result was 10 Ω·cm-A. Example 4 A kraft paper for electrical insulation with 1.0% methylbenzotriazole added was made into a pipe shape, and the charging potential was measured in the same manner as in the reference example.
It was Ω・cm−A. Example 5 A kraft paper for electrical insulation with 1% benzimidazole added was made into a pipe shape, and the charging potential was measured in the same manner as in the reference example. As a result, it was 18 Ω cm-A.
It was hot.

[Brief explanation of the drawing]

Figure 1 shows 1, added to kraft paper for electrical insulation.
It is a graph showing the relationship between the amount of 2,3-benzotriazole added and the charging potential.

Claims (1)

[Claims] 1 An insulating paper for electrical equipment made of cellulose insulating paper to which 1,2,3-benzotriazole, indazole, methylbenzotriazole, or benzimidazole is added.