JPS5935171B2 - multilayer electrolytic paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrolytic paper used as a dielectric in capacitors.

Currently, kraft paper made of sulfate pulp is mainly used as such electrolytic paper.

Although such kraft paper has the advantage of being relatively inexpensive, it is impossible to obtain it as an industrial product with a purity of 10%, and it always contains 2 to 3% of lignin and other substances such as dust and iron. However, impurities such as iron remain in the electrolyte, and these impurities migrate to the anode, which is usually made of aluminum foil, and attack the anode.

Furthermore, kraft paper has a problem in that it has very poor low temperature characteristics and frequency characteristics as an electrolytic paper at low temperatures (20 DEG C. to -45 DEG C.).

Compared to such kraft paper, Manila paper made from Manila hemp is a thin paper with high purity and fine fibers that does not contain lignin, and is known to be preferable as electrolytic paper for capacitors. Because it is more expensive than paper, it has not been widely used as an electrolytic paper instead of kraft paper.

Conventionally, considering the advantages and disadvantages of kraft paper and manila paper, attempts have been made to mix manila hemp fibers into sulfate pulp to obtain electrolytic paper that is intermediate in price and performance. Even if the impurities contained in the capacitor, such as lignin, start to attack the anode, even if it is only a small amount, once it begins to attack the anode, the attack will gradually spread, and if a hole occurs in one part of the electrode, the entire capacitor will become inoperable. Depending on the method of mixing Manila hemp fibers into sulfate pulp, it is difficult to obtain an improvement in electrolytic paper performance that is directly proportional to the amount of Manila hemp fibers mixed in.

- As a result of various studies on electrolytic paper, the present inventor found that even if it is made of the same sulfate pulp, instead of constructing electrolytic paper as a single layer paper, it can be constructed as a multilayer paper. It has been found that by doing so, a considerable improvement in corrosion of the anode can be obtained.

This is a type of buffer type in which impurities such as lignin contained in the sulfuric acid pulp and impurities such as iron contained in the electrolyte are captured at the interface between each layer of multilayer paper, and these interfaces capture the impurities. This is because, while acting as a filter, the liquid retention capacity is locally increased at the interface, thereby suppressing the progress of corrosion caused by impurities at the interface.

The present invention is based on the above-mentioned recognition regarding electrolytic paper for capacitors, and an object of the present invention is to provide an electrolytic paper that is improved from a comprehensive viewpoint considering price and performance.

Such an object, according to the invention, is a multi-layered electrolytic paper having at least two layers, at least one of said layers providing a solid surface of the electrolytic paper, such as a multi-layered electrolytic paper consisting of Manila hemp. Achieved by electrolytic paper.

The multilayer electrolytic paper of the present invention as described above is, in its most basic structure, a double electrolytic paper in which one kraft paper layer made of sulfuric acid pulp and one Manila paper layer made of Manila hemp are mutually polymerized. be.

Such electrolytic paper is of course used with the manila paper layer in contact with an anode body such as aluminum foil, and the kraft paper layer side in contact with a cathode body also made of aluminum foil or the like.

When such multilayer electrolytic paper is used, the electrolytic paper layer in contact with the anode is a high-purity paper layer made of Manila hemp, thereby greatly reducing corrosion of the anode due to impurities.

In addition, since the Manila paper layer generally has a larger liquid retention capacity than the kraft paper layer, the propagation speed of corrosion across the paper layer is slow, and as mentioned above, the liquid retention capacity is particularly high at the interface between the Manila paper layer and the kraft paper layer. Since regions of high capacity are formed, corrosion propagation is greatly suppressed even at such boundaries, and the extent to which corrosion propagates across the entire paper layer from the cathode to the anode is greatly reduced.

The multilayer electrolytic paper according to the present invention may, of course, be constructed by making each layer as a separate paper and simply stacking them together, but such a loose multilayer paper is inconvenient to handle, and it is difficult to handle the capacitor. Since there is a problem of complicating the manufacturing process, the multilayer electrolytic paper according to the present invention preferably uses a papermaking process in which each layer is combined simultaneously, so that a clear boundary is defined between each layer, and there is no mechanical separation between the two layers. Preferably, the paper is constructed as an integral multilayer paper with a sufficient degree of intertwining of the fibers to bind the fibers together.

One preferred embodiment of the multilayer electrolytic paper according to the present invention has the following properties.

In the accompanying figures, 1 is the kraft paper layer and 2 is the manila paper layer.

Overall density approximately 0.5 f/d Thickness 50 microns (Manila paper layer - 25 microns) (Kraft paper layer - 25 microns) Resistance value 50,000Ω/1 sheet or more Water absorption
Measured at the height of water rising over 50 minutes on a 1,411m wide paper. Specific gravity: 25g/m2 or higher. Tensile strength: Min. 1,700 (f/15M) in the papermaking direction.
Lateral direction minimum 514 (//) In the above basic configuration, the multilayer electrolytic paper according to the present invention was explained as consisting of one kraft paper layer and one manila paper layer, but at the boundary between the layers In order to further enhance the effect of trapping impurities and the effect of suppressing corrosion propagation, one or both of the kraft paper layer and the manila paper layer may each be further configured into two or more layers.

In addition, in the above, the present invention has been explained using the concept of a Manila paper layer, but in this case, the concept of a Manila paper layer is a paper layer consisting of high purity and fine fibers, which is the main characteristic of the paper layer. Therefore, if a paper layer made of fibers that is recognized to be equivalent or of the same quality as this from the viewpoint of such properties can be obtained, the idea of the present invention can be carried out using this.

Thus, according to the present invention, by constructing only a portion of the electrolytic paper from Manila hemp or fibers of the same or the same quality as those mentioned above, the price increase can be moderately suppressed, and the performance, especially the corrosion resistance of the anode electrode, can be improved. It is possible to obtain electrolytic paper having improved performance similar to or better than that of electrolytic paper consisting essentially of manila paper.

[Brief explanation of the drawing]

The attached figure is an illustrative cross-sectional view showing one embodiment of the multilayer electrolytic paper according to the present invention. 1...Kraft paper layer, 2...Manila paper layer.

Claims (1)

[Claims] 1 An electrolytic paper which is sandwiched between an anode body and a cathode body in a state containing an electrolytic solution to constitute a capacitor together with the anode body and the cathode body, and has a polymeric layer structure including a kraft paper layer and a manila paper layer. 1. A multilayer electrolytic paper having a polymeric layer structure, wherein one surface of the polymeric layer structure that provides a surface in contact with the anode body is a manila paper layer.