JPH0418643B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrically insulating materials having excellent electrical properties. More specifically, the present invention relates to an electrical insulating material using a biaxially stretched polypropylene film having specific physical properties.

Biaxially oriented polypropylene film has excellent electrical, mechanical, and chemical properties and is therefore widely used in electrical insulation materials such as capacitors. One of the important electrical properties in this field is dielectric breakdown voltage. This indicates the voltage per unit thickness of the film when the insulation resistance decreases and a relatively large current flows. Therefore, if a biaxially stretched film with a high dielectric breakdown voltage can be produced, the film thickness can be reduced, which is extremely useful for industrial production.

In view of this, the inventors of the present invention have made extensive studies and have discovered that a biaxially stretched film using polypropylene having specific physical properties has a very high dielectric breakdown voltage, and have arrived at the present invention.

The present invention is characterized in that polypropylene completely dissolved in tetralin at 160°C and then cooled and precipitated has a boiling diethyl ether soluble content of 1.8% by weight or less,
Dielectric breakdown made of polypropylene in which the boiling n-hexane soluble content in the boiling diethyl ether insoluble content is 1.0% by weight or less, and the boiling toluene soluble content in the boiling n-hexane insoluble content is 5.0% by weight or less. It is an electrically insulating material made of high voltage biaxially stretched polypropylene film.

These physical property values are the same even when the molded film is measured. Here, the target value of the dielectric breakdown voltage is 620V/μ or more.

In the present invention, if polypropylene that does not satisfy the above physical property values is used, the target dielectric breakdown voltage cannot be obtained.

The polypropylene used as a raw material in the present invention preferably has a load of 2.16 at a temperature of 230°C.
The melt index ratio between kg and 10 kg is 22 or more, and the ratio between weight average molecular weight and number average molecular weight is 5.5.
As above, the content insoluble in boiling n-heptane is 99.0% by weight or more, and after conditioning the press sheet made from the raw material polypropylene at 50°C for 20 hours and 23°C for 24 hours, the JIS K-7112 density gradient tube method was applied. The ^density measured according to
Melt index (MI, unit: g/10 min) at a temperature of 230°C with a load of 2.16 kg and intrinsic viscosity ([η], unit: dl/10 min) measured in tetralin at 135°C.
It also has the property that the relationship with g) is 20≦logMI+5.20log[η]≦22.

In the present invention, the content of various solvent-soluble parts in the polypropylene used is determined as follows. In addition, in the present invention, the polypropylene sample is divided into the following components in order of decreasing crystallinity:
In addition, the following operations were carried out to extract and separate components in descending order of molecular weight, starting with the lowest molecular weight.

That is, after completely dissolving 5 g of polypropylene pellets in 500 ml of tetralin at 160°C, the temperature was lowered to 20°C in 3 hours, and 1.5 g of methanol was added.
After the entire amount of polypropylene has been precipitated, it is filtered and dried. This was subjected to Soxhlet extraction with boiling diethyl ether for 13 hours and separated into an extraction residue and an extract.
This extract is used as a boiling diethyl ether soluble content, and the extraction residue is used as a boiling diethyl ether insoluble content. Next, this boiling diethyl ether insoluble matter is
Soxhlet extraction was performed with boiling n-hexane for 13 hours to separate the extraction residue and extract. This extract was made into boiling n-hexane soluble portion, and the extraction residue was boiled into n-hexane.
- Consider the hexane insoluble portion. Furthermore, this boiling n-hexane insoluble matter is subjected to Soxhlet extraction with boiling toluene for 13 hours to separate it into an extraction residue and an extract. This extract is made into boiling toluene soluble content.

In the present invention, dielectric breakdown voltage was measured by the following method.

According to JIS-2330, using a DC withstand voltage tester manufactured by Kasuga Denki Co., Ltd., set the range to 20KV and set the range to 100V/
Even with a voltage increase of sec, voltage was applied to the film, the breakdown voltage was measured, the micrometer thickness when 10 films were stacked was converted to the thickness per film, and the withstand voltage characteristics were determined using the following formula.

Dielectric breakdown voltage = Breakdown voltage (V) / Micrometer film thickness (μ) The film required for measurement was a biaxially stretched film manufactured by the method described in Example 1, 150 mm × 150 mm.
Sample 5 blocks from a stack of 10 films of size . That is, a total of 50 test pieces were used, and the measurement location of each test piece was limited to one location. The electrodes used were as follows.

The upper electrode is 25mmφ with a 3mm radius around it.
A well-polished brass cylinder is used as the (+) electrode, and the lower electrode is approximately 150 mm x 150 mm and is placed on an elastic plate with a rubber shore of 60 to 70 degrees on a 30 mm thick metal plate.
An aluminum foil having a thickness of 0.007 mm or more and a width of 80 mm as specified in H-4160 was wrapped around it, and this was used as a (-) electrode.

In the present invention, polypropylene powder contains
Various commonly used stabilizers are added, mixed, extruded and pelletized by conventional methods.

Next, the polypropylene pellets are extruded into a meat shape by a conventional method and biaxially stretched to obtain a film.

In the present invention, inorganic fine particles such as kaolin, kaolinite, silica, zeolite, titanium oxide, alumina, calcium carbonate, calcium silicate, etc., or organic fine particles such as dibutyl phthalate,
Mixing hydroxybenzophenone, amino stearate, alkylamine ethylene adduct, monoglyceride stearate, dimethylsiloxane, etc., or using polypropylene other than the present invention, polyethylene, poly-4-methyl-pentene-1, etc. A desired dielectric breakdown voltage can also be obtained by combining a seed polymer.

In the present invention, a capacitor is formed by winding a so-called metallized biaxially stretched polypropylene film in which a metal such as aluminum is vapor-deposited on at least one side of a biaxially stretched polypropylene film that has a high dielectric breakdown voltage determined by the above-mentioned measurement method. ,
Alternatively, whether it is an oil-immersed capacitor used in an oil-immersed state or a hybrid capacitor of these methods, the voltage at which the final product is charged and the capacitor breaks down, the so-called breakdown voltage, is the dielectric breakdown voltage defined in the text. As the voltage increases, the breakdown voltage of the capacitor also increases, making it a superior product.

Hereinafter, in order to explain the present invention more specifically,
An example will be given.

Example 1 618 mmol of diethylaluminum chloride, ^31.2 mmol of triphenyl phosphite, and a titanium trichloride solid catalyst (tetrachloride Titanium reduced with an organic aluminum compound and further activated) 30.2
After charging 300 kg of liquefied propylene and hydrogen gas, the temperature of the autoclave was raised. Polymerization was continued with stirring at an autoclave internal temperature of 60°C for 5 hours. After 5 hours, the liquefied propylene and hydrogen were purged. Subsequently, 165 methanol, 300 n-heptane, and 42 mol of methyl acetoacetate were charged,
After decalcifying for 2 hours at 112℃, 200
of water at 65°C four times. After filtering and drying, 212 kg of polypropylene powder was obtained.
For 100 parts by weight of this polypropylene powder,
After adding and mixing 0.1 part by weight of 2,6-di-t-butyl-p-cresol, 0.01 part by weight of calcium stearate, and 0.2 part by weight of Irganox 1330 (trade name, manufactured by Ciba Geigy), extrusion at 250 ° C. Turned into pellets. Approximately 5 g of the polypropylene pellets obtained in this manner were accurately weighed, and tetralin
The mixture was added to 500 ml and heated to 160°C to completely dissolve. The temperature of this solution was lowered to 20° C. over 3 hours, 1.5 liters of methanol was added, and after the entire amount of polypropylene was precipitated, it was filtered and dried. This was extracted with boiling diethyl ether using a Soxhlet extractor for 13 hours to separate it into a boiling diethyl ether soluble fraction and a boiling diethyl ether insoluble fraction. Next, this boiling diethyl ether insoluble matter was extracted with boiling n-hexane in a Soxhlet extractor for 13 hours.
-Separated into a hexanated soluble fraction and a boiling n-hexane insoluble fraction. Next, this boiling n-hexane insoluble matter was extracted with boiling toluene in a Soxhlet extractor for 13 hours to separate it into a boiling toluene soluble matter and a boiling toluene insoluble matter. The content soluble in boiling diethyl ether was 1.4% by weight, the content soluble in boiling n-hexane was 0.53% by weight or less, and the content soluble in boiling toluene was 3.7% by weight.

Next, the polypropylene pellets were heated to 270°C.
A sheet-like film with a thickness of 600 μm was obtained.
This film is processed using a TM long biaxial stretching machine.
At 150° C., the film was first stretched 5 times in the MD direction and then 8 times in the TD direction to produce a biaxially stretched film with a thickness of 15 μm. The breakdown voltage of this biaxially stretched film is
It was 664V/μ.

Example 2 In Example 1, triphenyl phosphite
using 100 mmol of diethylene glycol monoisopropyl ether instead of 31.2 mmol;
The same procedure as in Example 1 was conducted except that the polymerization temperature was 56°C. The boiling diethyl ether soluble content of polypropylene pellets measured in the same manner as in Example 1 was 1.5% by weight, and the boiling n-hexane soluble content was 1.5% by weight.
The content was 0.60% by weight, and the boiling toluene soluble content was 3.8% by weight.

Also, the dielectric breakdown voltage of biaxially stretched film is
It was 657V/μ.

Comparative example 1 Internal volume 100 after thoroughly drying and replacing with nitrogen gas
A reactor was charged with 50 g of dehydrated and degassed n-heptane, 155 mmol of diethylaluminium chloride, and 13 g of a titanium trichloride solid catalyst which had been activated by reducing titanium tetrachloride with metallic aluminum, and then charged with hydrogen gas. After entering, the temperature was raised to 68℃ and the weight was 5Kg/
Charge propylene gas to maintain cm ³ -G,
Polymerization was carried out. After 8 hours, the propylene gas charge was stopped. The obtained polypropylene slurry was transferred to a post-treatment container with an internal volume of 500, and 26 methanol and 760 mmol of methyl acetoacetate were charged therein.
After deashing at 93°C for 2 hours, it was washed 4 times with 25 parts of water each time at 63°C. After drying, 27.3
Kg of polypropylene powder was obtained. Physical properties were evaluated in the same manner as in Example 1 using this powder. The boiling diethyl ether soluble content of polypropylene pellets is 2.0% by weight, the boiling n-hexane soluble content is 1.0% by weight, and the boiling toluene soluble content is
It was 7.3% by weight.

Also, the dielectric breakdown voltage of biaxially stretched film is
It was 581V/μ.

Claims (1)

[Claims] 1 Polypropylene completely dissolved in tetralin at 160°C and then cooled and precipitated has a boiling diethyl ether soluble content of 1.8% by weight or less, and a boiling n-hexane soluble content of the boiling diethyl ether insoluble content is 1.0% by weight. % or less, and its boiling n-
An electrical insulating material made of a biaxially stretched polypropylene film with a high dielectric breakdown voltage and made of polypropylene in which the boiling toluene soluble content in the hexane insoluble content is 5.0% by weight or less.