JPH0145210B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing capacitor paper used as the main material of the dielectric of paper capacitors and metallized paper capacitors.

Capacitor paper, which is the main dielectric material, has a strictly rated value, but in the past, paper was made from sulfite pulp, kraft pulp, etc. using water as a medium, and the paper was dried and used as capacitor paper. I was using it. For this reason, it is not possible to obtain a paper with excellent properties required for capacitor paper, such as moisture and dielectric loss tangent (tan δ), which has a serious impact on subsequent processes such as the element winding process, drying, and impregnation. It was supposed to have an impact.

As a result of various long-term studies, we have found that the characteristics of capacitor paper are significantly influenced by paper making, subsequent processing, drying methods, etc.

In other words, paper is simply made using water as a medium as before,
If this is dried by normal means, the fibers may collapse due to the surface tension of water during the drying process, resulting in a significant reduction in the internal surface area of the paper and a large tan δ.

The object of the present invention is to provide a paper for capacitors with excellent properties, in particular a very small tan δ.

Examples of the present invention will be described.

First, the basic idea of the present invention is to prevent the collapse of fibers due to the surface tension of water during drying, to obtain paper with a large internal surface area, and to reduce the tan δ of the capacitor.
The goal is to improve. The methods for this purpose include: a. Making paper using a solvent with a lower surface tension than water, such as n-hexane, without using water as a solvent, and drying it; and b. Paper produced by conventional means. means for swelling paper produced by conventional means in a first solvent having a surface tension lower than that of water and then drying the paper, or c. The above-mentioned effects due to the surface tension of the solvent can also be prevented by d) freeze-drying, which involves immersing it in a solvent with a surface tension lower than that of the first solvent in an undried state, replacing the solvent, and then drying it. After paper is made using water as a medium or paper manufactured by conventional means is swollen, it is frozen in liquefied gas such as liquid nitrogen, and then dried in air or in a stream of nitrogen gas. There are methods such as freeze-drying as a drying treatment in a, b, and c above, and to give specific examples of the above, as an example of a, paper is made using n-hexane as a solvent and dried by normal means. .

As an example of b, paper (Manila hemp) manufactured by conventional means was immersed in n-hexane to swell, and then dried by conventional means.

As an example of c, paper (Manila hemp) manufactured by conventional means was immersed in methanol to swell it, then immersed in n-hexane, which has a lower surface tension than methanol, and then dried by conventional means.

As an example of d, paper manufactured by conventional means was immersed in methanol to swell, then frozen in liquid nitrogen, and then dried in air.

Any of the capacitor papers manufactured by above a to d can achieve almost the same purpose. For example, for the capacitor paper produced by above b, 100wv, conventional capacitor paper,
Comparing the tanδ of a 2.2μF capacitor, it was: ● Conventional paper capacitor: 0.05 ● Paper capacitor based on b: 0.023.

By using capacitor paper with a significantly increased internal surface area according to the present invention, the capacitor's tan δ
is extremely small and can improve frequency characteristics, high-speed characteristics, linearity, etc., and can significantly improve the characteristics of paper capacitors and metallized paper (MP) capacitors.

Claims (1)

[Claims] 1. A method for producing capacitor paper, which comprises immersing paper in a normal hexane solvent with low surface tension to swell it and drying it.