JPH10241988A - Polyolefine based film for oil-impregnated capacitor, and capacitor comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve extended heat/electricity resistance by winding a specific polyolefine based film together with a both-sided vapor-deposition capacitor paper which is an electrode, which is used as a part of dielectrics. SOLUTION: Relating to a polyolefine based film, the content of cyclic aliphatic epoxy based resin is 0.005-0.100wt.% while surface roughness Ra being 0.08μm or less on both sides. As a polymer which constitutes a polyolefine based film, a polymer of polypropylene is used. The polyolefine based film is wound together with a both-sided vapor-deposition capacitor paper which is an electrode, to function as a dielectrics. Here, the both-sided capacitor paper which is an electrode refers to the one where a metal layer is provide on a capacitor paper by vacuum vapor deposition method, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin film used as a part of or the whole of a dielectric material of an oil-impregnated capacitor when wound together with a double-sided deposited capacitor paper as an electrode, and a capacitor using the film. is there.

[0002]

2. Description of the Related Art Paper and film capacitors, electrolytic capacitors and ceramic capacitors have been known as capacitors, but oil-impregnated film capacitors are made of polyolefin-based films having good electric characteristics for electric power (for high pressure). ) Is often used. When a long-term heating application test is performed on a capacitor using such a polyolefin-based film, the dielectric strength characteristics of the polyolefin-based film decrease over time,
Eventually, dielectric breakdown will occur. Therefore, improvements have been made to the electrical properties of the polyolefin-based film and the oil itself to be impregnated, and the additives to be added to the impregnated oil have been studied.

[0003]

However, as the demand for extending the life of capacitors on the market has increased, these conventional techniques have not always been able to provide a satisfactory product.

Accordingly, an object of the present invention is to provide an oil-impregnated capacitor which improves the long-term heat application durability of the polyolefin-based film itself, and further provides excellent long-term stability.

[0005]

In order to achieve the above object, a polyolefin film for an oil-impregnated capacitor according to the present invention comprises 0.005% by weight of a cycloaliphatic epoxy resin.
A polyolefin-based film containing 0.100 wt% or less and having a surface roughness Ra on both sides of 0.08 μm or less, and wound together with a double-sided vapor-deposited capacitor paper as an electrode, and at least a part of a dielectric material It is characterized by being used as.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, cyclic aliphatic epoxy resins include 3,4 epoxycyclohexylmethyl, 3,4 epoxycyclohexanecarboxylate,
2- (3 ", 4" -epoxycyclohexyl) -1,3
-Dioxane-5-spiro-3 ', 4'-epoxycyclohexane, 3,4-epoxy, 6, methylcyclohexyl adipate and the like.

[0007] The content of the cycloaliphatic epoxy resin must be not less than 0.005 wt% and not more than 0.100 wt%. When the content is less than 0.005 wt%, the deterioration rate of the withstand voltage characteristics of the film is increased, and the life of the capacitor is short. If the content exceeds 0.100 wt%, the epoxy resin bleeds out from the film surface during the production of the polyolefin film, and the various roll surfaces used in the film production process are stained and re-adhered to the film surface. Occurs. Preferably 0.005 wt%
As described above, the content is 0.070 wt% or less, and more preferably 0.005 wt% or more and 0.050 wt% or less.

The surface roughness Ra of the polyolefin film of the present invention must be not more than 0.08 μm on both sides.
If the surface roughness Ra exceeds 0.08 μm, the surface is excessively roughened to substantially reduce the thickness and lower the dielectric breakdown voltage. It is preferably at most 0.05 μm, more preferably at most 0.03 μm.

The polymer constituting the polyolefin film of the present invention includes polypropylene, polyethylene, polybutene and the like. These polymers may be used alone, in combination or in combination. A copolymer may be used. In particular, polypropylene is preferable from the viewpoints of easy film formation (stretching) and swelling property against oil. From the viewpoint of dimensional stability, a polymer having an isotacticity of 93% or more is preferable.

The polyolefin film of the present invention contains tetrakis [methylene-3] other than the epoxy resin.
(3,5-Di-tert-butyl-4-hydroxyphenyl) propionate] methane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene and the like May be contained within a range that does not adversely affect the electrical properties.

Further, the polyolefin-based film of the present invention may be obtained by a tenter method or an inflation method. The stretching formulation may be any of unstretched, uniaxially stretched, and biaxially stretched, but the tenter method and biaxial stretching are preferred from the viewpoint of the uniformity of the thickness of the obtained film and the swelling property to oil.

The polyolefin film of the present invention functions as a dielectric when wound together with a double-sided vapor-deposited capacitor paper as an electrode.

The double-sided vapor-deposited capacitor paper, which is an electrode,
A metal layer provided on a capacitor paper by a vacuum evaporation method or the like.

In this case, the metal to be applied includes, but is not limited to, aluminum, zinc or a mixture thereof.

Examples of the impregnating oil for the capacitor include phenylxylylethane and alkylbenzene, and phenylxylylethane is particularly preferred in terms of good electrical characteristics.

Other configurations of the capacitor such as the capacitor case and the bushing are not particularly limited as long as they are conventionally used.

Next, an example of a preferred method for producing a film and a capacitor according to the present invention will be described, but is not particularly limited.

The cycloaliphatic epoxy resin is 0.005w
The polyolefin resin added with t% to 0.100 wt% is supplied to an extruder at a temperature of 200 to 280 ° C. to be melted and extruded into a sheet from a slit T die.
It is cooled and solidified by a cooling roll at a temperature of 20 to 80 ° C. At this time, the higher the cooling roll temperature, the greater the surface roughness. Next, it is stretched 3 to 7 times in the length direction at a temperature of 100 to 155 ° C. Also in this case, the surface roughness can be adjusted by selecting the stretching temperature. Next, the film is stretched 5 to 12 times in the width direction at a temperature of 140 to 165 ° C. After that, 140 ~
Heat treatment is performed at a temperature of 170 ° C. The thus obtained polyolefin film is wound up by a winder.

Thereafter, the polyolefin film is wound together with a double-sided vapor-deposited capacitor paper to form a capacitor element, which is placed in a metal case and impregnated with impregnating oil.

Next, the measurement method and the evaluation method used in the present invention will be described.

(1) Epoxy Content of Film The equivalent weight per kg was determined by the perchloric acid method of JIS-K-7236 and expressed as a percentage. (2) Surface roughness Ra According to JIS-B-0601, cutoff 0.25 mm
It is expressed by the center line average roughness obtained in the above. For the measurement, a three-dimensional roughness measuring device ET-30HK manufactured by Kosaka Laboratory Co., Ltd. was used.

(3) Capacitor heating durability The sample film is wound together with a 6 μm-thick double-sided evaporated capacitor paper which has been double-side evaporated with zinc, and has a double-sided evaporated capacitor paper / film / double-sided evaporated capacitor paper / film structure. A capacitor element was prepared, placed in a metal case at a clamping rate of 110%, and impregnated with phenylxylylethane to produce a capacitor. The capacitance of the capacitor was 0.5 μF. This capacitor was subjected to an AC voltage of 2.7 kV at an ambient temperature of 60 ° C. for 30 minutes.
00hrs, and measure the insulation resistance before and after the application according to JIS-C-
4908 8.5.

Here, the higher the insulation resistance before the application of electric power, the higher the insulation breakdown voltage, and the smaller the change in the insulation resistance before and after the application of the electric power, the higher the durability against heating.

In addition, the insulation resistance before application measured under the conditions described above is 1 × 10 ⁶ MΩ or more, and the insulation resistance after application is 5
× 10 ⁵ MΩ or more is regarded as a pass standard in the examples.

Next, the present invention will be described based on examples.

[0026]

【Example】

Example 1 A polypropylene having an isotacticity of 97% to which 3,4 epoxycyclohexylmethyl, 3,4 epoxycyclohexanecarboxylate was added in an amount of 0.03% by weight was added.
It is melted by an extruder heated to a temperature of 80 ° C., extruded through a gap in a die, wound around a cooling roll of 40 ° C., solidified by cooling, and then stretched 5 times in the length direction at a temperature of 135 ° C. C to a tenter heated to
The film was stretched twice and heat-treated at 150 ° C. while relaxing by 5% to obtain a biaxially stretched polypropylene film (thickness: 20 μm) for an oil-impregnated capacitor. Surface roughness R of this film
a was 0.02 μm. This film was wound together with a 6μ-thick double-sided vapor-deposited capacitor paper to form a phenylxylylethane-impregnated model capacitor. At this time, the capacitance of the capacitor was 0.5 μF. The heat application durability was evaluated using this capacitor. Table 1 shows the physical properties and heat application durability of the obtained film.

The insulation resistance before the application of the electric power was high, and no change in the insulation resistance before and after the application of the electric power was observed. Example 2 The surface roughness Ra was set to 0.0 by setting the temperature of the cooling roll to 70 ° C.
Same as Example 1 except that the thickness was 7 μm. Table 1 shows the physical properties and heat application durability of the obtained film.

Compared with Example 1, the insulation resistance before application of electric power was slightly lower, and the insulation resistance before and after application of electric power was slightly changed. However, it was sufficient for practical use.

Example 3 Example 1 except that the amount of epoxy added was 0.01 wt%.
Same as Table 1 shows the physical properties and heat application durability of the obtained film.

As in Example 1, the insulation resistance before application of electric power was excellent, and the insulation resistance before and after application of electric power was changed, but it was sufficient for practical use.

Comparative Example 1 A film was produced in the same manner as in Example 1 except that the amount of epoxy added was changed to 0.200 wt%. However, the roll surface during film production was severely stained and could not be produced stably. .

Comparative Example 2 Same as Example 1 except that the amount of epoxy added was 0.003 wt%. Table 1 shows the physical properties and heat application durability of the obtained film.

In Comparative Example 2, since the epoxy content in the film was low, the insulation resistance after application of electricity was remarkably reduced, and the long-term heat application durability was lacking.

Comparative Example 3 The surface roughness Ra of the cooling roll was set to 90 ° C. and the surface roughness Ra was set to 0.1.
Same as Example 1 except that the thickness was set to 0 μm. Table 1 shows the physical properties and heat application durability of the obtained film.

In Comparative Example 3, since the surface roughness Ra was large, the insulation resistance before power application was low, and the object of the present invention was not achieved.

[0036]

[Table 1]

[0037]

The polyolefin film for an oil-impregnated capacitor of the present invention has excellent long-term heat application durability, and has a long-term stability by being wound together with a double-sided deposited capacitor paper and used as a dielectric for the oil-impregnated capacitor. A capacitor excellent in quality can be obtained.

Claims (4)

[Claims] 1. The method according to claim 1, wherein the cycloaliphatic epoxy resin is 0.005 watts.
a polyolefin-based film containing at least t% and not more than 0.100 wt%, and having a surface roughness Ra on both sides of not more than 0.08 μm, respectively. A polyolefin film for an oil-impregnated capacitor, which is used as a part. 2. The polyolefin film for an oil-impregnated capacitor according to claim 1, wherein the polyolefin film is a polypropylene film. 3. An oil-impregnated capacitor wherein at least a part of a dielectric is a polyolefin-based film and wound together with a double-sided deposited capacitor paper as an electrode,
An oil-impregnated capacitor, characterized in that the polyolefin-based film contains 0.005% by weight or more and 0.100% by weight or less of cycloaliphatic epoxy-based resin, and the surface roughness Ra of both surfaces is 0.08 μm or less. 4. The oil-impregnated capacitor according to claim 3, wherein the polyolefin-based film is a polypropylene film.