JPH11268145A - Electrically insulating film and capacitor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a voltage resistance and to prolong its lifetime with a small size by forming an electrically insulating film of a polymer resin containing a polyolefin resin polymerized by using a metallocene catalyst as a main component, incorporating a specific ratio of an organic compound having a chlorine capturing performance, and setting a surface roughness to a specific value, thereby improving the voltage resistance. SOLUTION: The electrically insulating film is formed of a polymer resin containing a polyolefin resin polymerized by using a metallocene catalyst, contained with 0.02 to 0.15 wt.% of an organic compound having a chlorine capturing capacity, and set with a surface roughness Ra to 0.03 to 0.30 μm. The metallocene catalyst is a bis-metal compound in which a metal atom is bonded to a cyclopentadiphenyl ring by a strong covalent bond or its derivative. Particularly, a compound of a structure in which a transition metal such as Zr or the like is held by a π-electron unsaturated cyclic compound as a metallic atom is excellent. Generally, it is used as a combination of an assistant medium of methylalmoxane or the like. As the compound having the chlorine capturing performance, an epoxy compound is particularly preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrically insulating film for a capacitor and a capacitor comprising the same, and more particularly to a metal-deposited film and a capacitor comprising the same.

[0002]

2. Description of the Related Art A metallized film capacitor (hereinafter, referred to as an MF capacitor) having an electrode made of a vapor-deposited metal layer made of Al, Zn or the like has a self-healing function, and a withstand voltage can be increased by winding the metallized film together. Therefore, it is widely used because it can be downsized.

As a film used for the MF capacitor, a biaxially stretched polypropylene film is often used because of its good temperature characteristics of dielectric loss. For oil-impregnated capacitor applications, especially oil-impregnated metallized film capacitors using metallized film as a dielectric, a film whose surface is roughened to secure an oil layer between film layers is used. Mineral oils, vegetable oils, aromatic hydrocarbon oils and the like are often used.

However, when the above-mentioned oil-impregnated metallized polypropylene film capacitor is subjected to a long-term voltage application, there have been problems such as a decrease in the dielectric strength of the polypropylene film over time and a decrease in the power factor due to an increase in tan δ. .

For example, Japanese Patent Application Laid-Open No. 7-278226 discloses a high-crystalline polypropylene composition having a high melting point, high crystallization temperature, excellent heat resistance and excellent mechanical strength, characterized by being polymerized using a metallocene polymerization catalyst. However, films made from these resins have not solved the above problems.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, to obtain a practical MF capacitor capable of improving withstand voltage, achieving a small size and achieving a long life.

[0007]

According to the present invention, there is provided an organic compound comprising a polymer resin having a polyolefin resin as a main component polymerized by using a metallocene catalyst and having a chlorine-trapping ability in an amount of 0.02 to 0.15% by weight. And a surface roughness Ra of 0.03 to 0.30 μm.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The metallocene catalyst in the present invention is a catalyst comprising a compound or a derivative of a bis (diclopentadiphenyl) metal compound in which a metal atom and a diclopentadiphenyl ring are connected by a strong covalent bond. Among them, a compound having a structure in which a transition metal such as Zr (or Zrcl ₂ ) is sandwiched between π-electron unsaturated cyclic compounds as a metal atom is excellent. Methylalumoxane (MAO)
Is generally used in combination with a co-catalyst such as

The polyolefin resin polymerized using the metallocene catalyst of the present invention is a polymer of polypropylene, polyethylene or polystyrene. In the present invention, in addition to the homopolymer, propylene and other olefin polymers (ethylene and butene) are used. Copolymerization, copolymerization of styrene with other olefin polymers (ethylene, butene), blends of propylene with other olefin polymers, and styrene with other olefin polymers may be used. Any film may be used as long as it is biaxially stretched using the above-mentioned polymer either simultaneously or sequentially.

In the case of the present invention, a homopolymer is particularly preferred, and various additives known in the art, such as a heat stabilizer, an antioxidant and a crystal nucleating agent, can be added to the compound having a chlorine trapping ability.

The organic compound having a chlorine-capturing ability of the present invention is not particularly limited as a compound which reacts with and captures chlorine, but is preferably an epoxy-based compound or an organic compound having a glycidyl group or an unsaturated group, particularly preferably an epoxy-based compound. Is more preferred.

[0012] The content of the organic compound having a chlorine-capturing ability is 0.1%.
It is necessary to be 02 to 0.15% by weight, preferably 0.04 to 0.1% by weight.

[0013] If the content is less than 0.02% by weight, the withstand voltage is reduced under long-term power application, sometimes leading to dielectric breakdown. When the content is more than 0.15%, the film surface becomes sticky.

In the film of the present invention, the average roughness Ra of the film surface is 0.02 to 0.30 μm, preferably 0.04 to 0.12 μm. 0.02μm roughness
If it is smaller than this, the film has poor slipperiness and tends to wrinkle. If it exceeds 0.30 μm, the surface becomes rough, the actual thickness of the film decreases, the breakdown voltage decreases, and the capacity decreases.

When the resin of the present invention is polypropylene, its isotactic pentad fraction is preferably at least 97%, more preferably at least 99%. If the isotactic pentad fraction is low, the stereoregularity of the polypropylene is low, and the crystallinity of the biaxially stretched film is low. That is, the ratio of the insulating defect portions may increase, leading to a decrease in the dielectric strength.

The pentad fraction of the polypropylene film is, for example, as described in T.W. Report of Hayashi et al. [Polyme
r, 29, 138 to 143 (1988)], the ratio of the segments having each of the above-mentioned conformations is ¹³ C-
It can be determined from NMR. Among these, the ratio of the conformation of mmmm to the absorption intensity of all methyl groups, that is, the isotactic pentad fraction (hereinafter sometimes abbreviated as mmmm) is m (mmmm) m, m (mmm
m) defined as the sum of three heptad fractions, r and r (mmmm) r.

In the present invention, the film resistance of the metal film is not particularly limited, but is preferably in the range of 2 to 30 Ω / □, more preferably 5 to 15 Ω / □. If the film resistance value is smaller than 2Ω / □, the thickness of the deposited film is so large that heat loss occurs during the deposition, which may cause an avatar-shaped surface defect.
If the film resistance exceeds 30 Ω / □, when the deposited film clears during the application of electricity, the film is apt to disappear and the change in capacitance may increase. The metals to be deposited are Al, Z
n, Cu or their alloys are optimal but not limited to these. Specific examples of alloys include Al /
Examples include Zn and Zn / Cu, but are not limited thereto.

In order to be wound into a capacitor, a part of these metallized films has an electric insulating portion (margin portion).
A portion where no vapor deposition is performed is required.

The capacitor using the metallized film of the present invention has a higher withstand voltage by using an impregnating agent.
Examples of the impregnating agent include an oil solidifying impregnating agent and a gas.

In the present invention, examples of the excellent oil impregnating agent include a mixed oil of an electrically insulating compound having two aromatic rings, which is liquid at normal temperature, and rapeseed oil. For example, typical aromatic impregnants include diarylalkanes, alkylbiphenyls, and alkylnaphthalenes. A wax is an example of a solidifying impregnating agent. Still another excellent impregnating agent is a gas, of which SF ₆ having a high withstand voltage is excellent.

It is needless to say that the film of the present invention can be formed as a capacitor by laminating or winding electrode portions without using metal deposition. Also in this case, the use of the impregnating agent further increases the pressure resistance, and examples of the impregnating agent include an oil-solidified impregnating agent and a gas.

A method for producing a metallized film of biaxially oriented polypropylene for a capacitor which is an example of the present invention will be described below. However, the present invention is not limited to the following manufacturing method.

A polypropylene resin containing an epoxy compound having an isotactic pentad fraction of 97.5 to 99.6% polymerized by using a metallocene catalyst and having an epoxy compound content of 220 to 2 is used.
It is fed to an extruder heated to 90 ° C, extruded into a sheet from a T-die, cooled and solidified by a cooling roll at 30 to 97 ° C, and then stretched in the longitudinal direction 3 to 6 times at a temperature of 130 to 150 ° C. And then 6-1 to 1 in the width direction at a temperature of 155 to 173 ° C.
The film is stretched twice and heat-treated while relaxing at a temperature of 150 to 160 ° C. by several percent to obtain a biaxially stretched film for a capacitor. Thereafter, a corona discharge treatment is performed on the film surface at 5 to 50 W / m ² / min in air or various gases. When making a composite film, a method of laminating a plurality of pieces in a short tube or a die using two or more extruders and co-extrusion and stretching, or stretching in the longitudinal direction, extrusion laminating and stretching in the width direction There are methods. The above-mentioned 6 with corona discharge on the surface
C on the corona discharge treated surface of 30 mm x 28000 m product
u metal was used as a nucleation metal, and Zn metal was vapor-deposited to obtain a metallized film.

Next, the terms used in the present invention and the measuring method will be described.

(1) Isotactic Pentad Fraction A sample was dissolved in o-dichlorobenzene / benzene-D6, and ¹³ C-NMR was measured at a resonance frequency of 67.93 MHz using a JNM-GX270 apparatus manufactured by JEOL. For the assignment of the obtained spectra and the calculation of the pentad fraction, see T.W. The method performed by Hayashi et al. [Poly
mer, 29, 138-143 (1988)].
The peak was assigned to 21.855 ppm, each peak was assigned, the peak area was determined, and the ratio to the total peak area derived from the methyl group was expressed as a percentage. Detailed measurement conditions are as follows.

Measurement concentration: 15 to 20% by weight Measurement solvent: o-dichlorobenzene (90% by weight) / benzene-D6 (10% by weight) Measurement temperature: 120 to 130 ° C. Resonance frequency: 67.93 MHz Pulse width: 10 μsec (45 ° pulse) ) Pulse repetition time: 7.091 sec Data point: 32K Integration count: 8168 Measurement mode: Noise decoupling

(2) Surface roughness (Ra) According to JIS B0601-1976. However, the cutoff at that time was 0.25 mm.

(3) Evaporation loss rate After adjusting the film resistance to 10 Ω / □ and cutting the Zn-evaporated product to a width of 75 mm × 6000 m, the product loss rate due to wrinkle defects is determined by the following equation. Was. Wrinkle loss rate (%) = number of wrinkles generated / number of all reels x 100

(4) Sheet Vt Destruction Rate A film having a thickness of 6 μm is sampled in a size of 150 mm × 150 mm, and AC is manufactured by Kasuga Electric Co., Ltd.
Withstand pressure tester Use a 15 kv withstand pressure machine and apply 50 mm
Three pieces of 9 μm Al foil are laminated on a 3 mm-thick silicone rubber as a φ brass electrode and a cathode. Next, a film is placed between the anode and the cathode, 1 kv of electric power is applied by alternating current, and the time from the application of the electric power to the destruction is measured. Sheet Vt destruction rate (%) = (number of destruction in 60 sec or less / total number of measurements) × 100

(5) Withstand Voltage A 5 μF capacitor element was prepared using a metal vapor-deposited film, impregnated with oil under vacuum, and then packaged with an epoxy-cured resin. This impregnated capacitor element was placed in a 95 ° C.
Under a voltage of 44 kv, a continuous power application test for 2000 hours was performed at a rate of 5 pieces / 1 level. The capacitor after the application of power is disassembled, the film sheet is taken out, the film sample is placed on a copper plate, and a DC voltage is applied using the copper plate as an anode and the deposition surface as a cathode, and the same voltage is applied for 30 seconds. Thereafter, the voltage is increased by 500 V, and the number of locations where dielectric breakdown occurs at each voltage is counted. The voltage generated at 5 pieces / m ² was defined as the dielectric breakdown voltage value.

◎: Destruction of the capacitor was 0 in the power application test for 2000 hours, and the breakdown voltage was 70% of that of the uncharged product.
% Or more. ：: No destruction of capacitor in 2000 hours of power application test
And the breakdown voltage is less than 40% to less than 70% of the uncharged product ratio. Δ: One capacitor destroyed in a 2000-hour power application test, or a breakdown voltage of 30 to 40 for an uncharged product
%. ×: Two or more capacitors were destroyed in the 2000-hour power application test, or the breakdown voltage was 20% of the uncharged product
It is as follows.

(6) tan δ The above-mentioned capacitor after power application was set to a tan δ value at a frequency of 60 Hz and a voltage of 200 V using an automatic sharing bridge DAC-PSC-20W manufactured by SOKEN.

(7) ΔC The above-mentioned capacitor after the power application was measured at a voltage of 200 V using an automatic shaking bridge DAC-PSC-20W manufactured by SOKEN Corporation, and calculated by the following equation.

ΔC (%) = (C ₀ −C ₁ ) / C ₀ × 100 C ₀ (μF): Capacitance of the capacitor when no power is applied C ₁ (μF): Capacity of the capacitor after 2000 hours of application

[0035]

EXAMPLES Example 1 Irganox 1010 was added as an antioxidant to a polypropylene powder having an isotactic pendant fraction of 99.0% polymerized using a metallocene catalyst at 5000 pp.
m, 4000 ppm of BHT as a heat stabilizer and 800 of cycloaliphatic epoxy resin CY179 (manufactured by Ciba-Geigy).
ppm were blended, melted and kneaded with an extruder and pelletized.
The MFR of the pellet was 1.6 g / 10 min.

The polypropylene resin was supplied to an extruder heated to 275 ° C., and extruded from a T-die into a sheet.
The molten sheet was wound around a chill roll at 93 ° C. and solidified by cooling to obtain an unstretched film equivalent to 320 μm. The unstretched film is stretched 4.8 times in the longitudinal direction by a roll heated to 143 ° C., then stretched 11.2 times in the width direction in a tenter heated to 170 ° C., and 5% at 150 ° C.
A heat treatment was performed while relaxing, to obtain a film having a thickness of 6 μm.
The surface of this film was subjected to corona treatment, and the wound film was cut into 620 mm × 28000 m to obtain a product. The surface roughness of this film was 0.08 μm.

This product is coated with Zn metal and has a film resistance of 10Ω / □.
And deposited on the corona treated surface. This vapor-deposited product was cut into a width of 75 mm × 6000 m to obtain a vapor-deposited product. The vapor deposition reel was wound by two sheets to make a 10 μF capacitor element. This capacitor element was impregnated with crystallin wax and packaged with an epoxy cured resin to form a capacitor. The number of the produced impregnated capacitors was 5.

An AC voltage of 0.44 kv was applied to each capacitor in an oven maintained at 95 ° C.
Long-term power application was performed for 000 hours. As shown in Table 1, there was no breakdown of the capacitor at the time of power application, and the breakdown voltage value after the application of the voltage was 90% of that of the uncharged product, indicating excellent breakdown voltage characteristics. Tan δ and ΔC also had excellent characteristics.

Example 2 Example 1 was followed except that the chill roll temperature was 89 ° C. and the transverse stretching temperature was 168 ° C. As shown in Table 1, the results were excellent as in Example 1.

Comparative Example 1 Example 1 was repeated except that the cycloaliphatic epoxy resin CY179 was not added to the raw polypropylene powder used in Example 1.
According to. As shown in Table 1, the film was inferior in withstand voltage. Also, the breaking rate of the sheet Vt is inferior,
Insulation performance under long-term power application decreased significantly.

Comparative Example 2 The content of cycloaliphatic epoxy resin CY179 was 1700
Example 1 was repeated except that the amount was increased to ppm. Table 1 shows the results
As shown in (1), although the capacitor characteristics were excellent, a large amount of processing loss occurred due to surface dirt and wrinkles.

Comparative Example 3 The procedure of Example 1 was followed except that the temperature of the chill roll was 97 ° C. and the transverse stretching temperature was 175 ° C. As shown in Table 1, the surface roughness was 0.32 μm. Due to the large roughness and the substantial decrease in film thickness, the destruction rate of the sheet Vt was inferior, and the insulation performance under long-term power application was significantly reduced.

Comparative Example 4 The procedure of Example 1 was followed except that the temperature of the chill roll was 45 ° C. As shown in Table 1, the film had a surface roughness of 0.01.
μm. The surface was smooth, the film slipped poorly, and wrinkles were apt to occur.

Comparative Example 5 The procedure of Example 1 was followed except that a polypropylene resin obtained using a conventional Ziegler-Natta catalyst was used. As shown in Table 1, the sheet Vt destruction rate was large and the withstand voltage was reduced.

Example 3 800 ppm of a blend of 5% by weight of an ethylene polypropylene copolymer and a cyclic aliphatic epoxy resin CY179 (manufactured by Ciba Geigy) were blended with syndiotactic polystyrene (weight average molecular weight: 25,000) polymerized using a metallocene catalyst. Then, the mixture was melted, kneaded and pelletized by an extruder.

The polystyrene resin was supplied to an extruder heated to 290 ° C., and extruded from a T-die into a sheet. The molten sheet was brought into close contact with a chill roll at 50 ° C. by electrostatic application to be cooled and solidified to obtain an unstretched film equivalent to 70 μm. After pre-heating a roll heated to 100 ° C., the unstretched film is stretched 3.3 times in the longitudinal direction at a temperature of 135 ° C.,
Then, the film was stretched 3.5 times in the width direction in a tenter heated to a temperature of 150 ° C. to obtain a film having a thickness of 6 μm. The surface of this film was subjected to corona treatment, and Zn metal was deposited and evaporated on the treated surface so that the film resistance became 10 Ω / □.

The vapor-deposited product was wound in two layers to prepare a 5 μF capacitor element. This capacitor element was impregnated with crystallin wax and packaged with an epoxy cured resin to form a capacitor. The number of the produced impregnated capacitors was 5.

An AC voltage of 0.44 kv was applied to each capacitor in an oven maintained at 95 ° C.
Long-term power application was performed for 000 hours. As shown in Table 1, there was no breakdown of the capacitor at the time of power application, and the breakdown voltage value after the application of the voltage was 90% of that of the uncharged product, indicating excellent breakdown voltage characteristics. Tan δ and ΔC also had excellent characteristics.

[0049]

[Table 1]

[0050]

As described above, the metallized film of the present invention has the following effects.

A metallized film polymerized with a metallocene catalyst and containing an epoxy-based additive is excellent in withstand voltage, has a small decrease in insulation performance due to long-term application under high temperature and high voltage, and has tanδ and ΔC characteristics. And an excellent capacitor can be obtained.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08L 23/10 C08L 25/04 25/04 H01G 4/22 B29K 23:00

Claims (7)

[Claims] An organic compound having a chlorine-trapping ability, which is composed of a high-molecular resin mainly composed of a polyolefin resin polymerized using a metallocene catalyst, is contained in an amount of 0.02 to 0.15% by weight.
And a surface roughness Ra of 0.03 to 0.30 [mu] m. 2. A film for electrical insulation, wherein the polyolefin resin according to claim 1 is polypropylene or polystyrene. 3. The film for electrical insulation according to claim 1, wherein the organic compound having a chlorine trapping ability is an epoxy compound or an organic compound having a glycidyl group or an unsaturated group. 4. A metal-deposited film obtained by vapor-depositing a metal on the electrical insulating film according to claim 1. 5. A laminated metal vapor-deposited film according to claim 4,
Or a wound capacitor. 6. The capacitor according to claim 5, comprising an oil, a solid organic compound, or a gas as an impregnating agent. 7. A capacitor characterized by laminating or winding an electrical insulating film and an electrode according to any one of claims 1 to 3, and using an oil, a solid organic compound or a gas as an impregnating agent.