JP2586007B2 - Capacitor - Google Patents

Description

The present invention relates to a capacitor using a biaxially oriented polypropylene film as a dielectric.

[Conventional technology]

Capacitors using a polypropylene film for the dielectric layer are commonly used because of their small dielectric loss tangent and excellent electrical properties such as dielectric strength.

[Problems to be Solved by the Invention] However, such conventional polypropylene films do not always have high insulation properties and do not sufficiently receive the excellent electrical characteristics inherent to polypropylene.

In view of such a problem, the present invention increases the breakdown voltage,
It is intended to provide a capacitor having a long life.

[Means for solving the problem]

The present invention relates to a capacitor including an electrode and a dielectric, wherein the dielectric has an ash content of 100 ppm or less, an isotacticity of 94% or more, and a crystallization peak temperature of a component extracted with 135 ° C boiling n-heptane of 85 ° C or more. The gist of the present invention is a capacitor characterized by using the biaxially oriented polypropylene film of (1).

The polypropylene (hereinafter abbreviated as PP) film in the present invention refers to a crystallization peak temperature (hereinafter abbreviated as Tmc) of 135 ° C. boiling n-heptane extractable component in a differential calorimeter (DSC) of 85 ° C. or higher. , More preferably 88
It is sufficient if the film is made of PP of at least ℃.
It is not necessary to consist of a homopolymer, and a small amount, preferably 5% by weight or less of another olefin may be mixed within the scope of the present invention. When Tmc is lower than 85 ° C., atactic portions and components having low crystallinity increase, and the dielectric strength is remarkably reduced. The film of the present invention may contain various known additives such as a stabilizer, a filler, an antioxidant, a withstand voltage improver, and the like. About 90 ash
It is the residual amount after incineration at 0 ° C. Since the inorganic component becomes a component and causes a decrease in the insulating power due to fish eyes or a dielectric, the content of the film of the present invention is
It must be below 100 ppm, preferably below 70 ppm. The lower limit is not particularly limited, but is about 5 ppm.
The degree of isotacticity (hereinafter abbreviated as II) is
It is expressed as a percentage by weight of the residue after extraction of n-heptane at 135 DEG C. for 12 hours, and its II is desirably 94% or more, preferably 97% or more. If II is less than 94%, the crystallinity of the film will be small, and not only will the dielectric strength decrease, but also the workability will tend to deteriorate due to the decrease in Young's modulus.

In the oil-impregnated condenser, the oil to be applied is not particularly limited, and any known oil for condensers may be used.

Next, an example of a method for producing a biaxially oriented polypropylene film will be described.

Polymerization in liquefied polpyrene without solvent using an ultra-high activation catalyst, II obtained by post-treatment, 97.5-99.6% II
PP is supplied to an extruder heated to 240 to 285 ° C., extruded from a T-die into a sheet shape equivalent to 350 to 750 μ, and a surface temperature of 20 to 90 μm.
It was cooled and solidified by contact with a chill roll at ℃. This sheet is lengthened 4.0-5.3 times at a temperature of 125-155 ° C, then
After stretching in the perpendicular direction at a temperature of 150 to 175 ° C to 7.0 to 11.0 times, heat-treating at a temperature of 140 to 160 ° C while slightly relaxing,
Next, the film surface is subjected to a surface activation treatment (corona discharge treatment) and wound up.

On the film formed as described above, metals such as aluminum and zinc are vapor-deposited in a vacuum so as to have a film resistance of 2 to 7 Ω / □ to form electrodes. Capacitor element. The dielectric may be the above film alone, or may be a laminate with another film or paper. Further, a metal foil may be used as the electrode.

The condenser of the present invention may be either a dry type or an oil impregnated type.

(Measurement method)

The characteristic value of the present invention is measured by the following measuring method.

(1) Ash content According to JIS.C-2111.

(2) Degree of isotacticity (II) A. A sample having a weight of W (g) is taken from a film and put into a thimble filter paper.

B. Put thimble filter paper containing the sample and 80 ml of n-heptane into an extractor, and perform extraction at 135 ° C. for 12 hours.

C. After the extraction, remove the thimble filter paper, measure the weight of the sample after drying for 5 hours with a vacuum dryer, and let the value be W '(g).

D. Calculate II (%) by the following formula.

II (%) = (W ′ / W) × 100 (3) Crystallization peak temperature (Tmc) After evaporating the extract obtained in the measurement of II to dryness, PERKIN
The differential temperature of DSC-II type manufactured by ELMER was measured using a scanning calorimeter, and the peak temperature at the time of cooling at a lower temperature obtained under the following measurement conditions was defined as the crystallization peak temperature (Tmc).

Sample amount: 5 mg Range: 5 mcal / sec Heating rate: 20 ° C / min Sensitivity: 10 mv Melting temperature / holding time: 280 ° C-5 minutes (4) Breakdown voltage of capacitor Film resistance of aluminum is 3.5 on film surface. Using a 7.5μ metallized film deposited to Ω / □,
Ten capacitors are wound with a designed capacity of 0 μF, metallicon is applied to the end face, and terminals are attached, and then heat-treated at 115 ° C. for 5 hours.

This capacitor is charged at an alternating voltage of 600V for 1 minute at room temperature. If no destruction occurs, the voltage is increased step by step by 50V, and the voltage is applied until the capacitor is destroyed, destroying the average value of the breakdown voltage of 10 capacitors. Defined as voltage.
The value obtained by dividing the breakdown voltage by the film thickness was defined as the dielectric breakdown strength.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on examples.

Examples 1-2 and Comparative Examples 1-4 Capacitor samples of Examples 1-2 and Comparative Examples 1-4 were made as follows.

PP having an II of 99.4% is supplied to an extruder heated to 250 ° C. and extruded from a T-die as a 375 μm molten sheet.
It was cooled and solidified by contact with a chill roll at ℃. This sheet was stretched 5.0 times in the length direction at a temperature of 135 ° C., stretched 10 times at a temperature of 163 ° C. in the perpendicular direction, and then stretched 3.0 times at a temperature of 155 ° C.
% Heat-treated with a 7.5% film. One side of this film was subjected to a corona discharge treatment with an energy amount of 4000 J / m ² . After slitting this film to a width of 530 mm, aluminum metal was vapor-deposited on the corona discharge treated surface with a film resistance of 3.5Ω / □ in a vacuum vapor deposition device. Margin width 3mm
After slitting to a film width of 100 mm containing, a capacitor element of 10 μF was formed by an element winding machine, a metallikon was heat-treated at 115 ° C. for 5 hours by a conventional method, and lead wires were attached. Using this capacitor, voltage was applied from 600 V for 1 minute, and the voltage was increased in steps of 50 V until breakdown was reached. The results are as shown in Table 1, where the ash content is
It can be seen that the capacitors having a concentration of 100 ppm or less, a II of 94% or more and a Tmc of 85 ° or more, that is, the capacitors of Examples 1 and 2 have clearly improved withstand voltage as compared with Comparative Examples 1 to 4.

[Effect of the Invention] As described above, the condenser of the present invention has an ash content of 10%.
Since the biaxially stretched film having an extraction component of n-heptane of 0 ppm or less and Tmc of 85 ° C. or more was used as the dielectric layer, the breakdown voltage was improved as compared with the conventional product.

Therefore, the life characteristics in the accelerated test are expected to be improved by about 30%, and the withstand voltage can be greatly increased.

Claims (1)

(57) [Claims] 1. A capacitor provided with an electrode and a dielectric material, wherein the dielectric material has an ash content of 100 ppm or less, an isotacticity of 94% or more, and a crystallization peak temperature of a component extracted with n-heptane boiling at 135 ° C. of 85. A condenser characterized by using a biaxially oriented polypropylene film at a temperature of at least ℃.