JPH08311268A - Polypropylene resin for capacitor-insulating film and method for evaluating the same - Google Patents

Abstract

PURPOSE: To obtain a polypropylene resin for capacitor-insulating film which satisfies specific conditions and exhibits excellent performance by stretching a specific polypropylene resin under specified conditions. CONSTITUTION: A polypropylene resin comprising a crystalline propylene homopolymer having an isotactic pentad fraction according to<13> C-NMR spectrometry of 0.94 or higher and a melt flow index measured at 230 deg.C under a load of 2.16kg of 10-0.1g10/min melt molded into a 150μm-thick sheet and stretched 5×7-fold at 145 deg.C at a deformation rate of 300%/sec to give a polypropylene resin for capacitor-insulating film which has a thickness of 4μm and contains at most one void having the major axis of 50μm or higher, at most two voids having the major axes of 30-50μm, and at most five voids having the major axes of 30μm or lower. The voids are measured by detecting the light reflected from the film with an apparatus equipped with a microscope XY stage and a line sensor camera.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polypropylene resin suitable for use as a capacitor insulating film. More specifically, the present invention relates to a polypropylene resin in which a film stretched under specific conditions satisfies the specific conditions and exhibits good physical properties when molded for a capacitor insulating film.

[0002]

2. Description of the Related Art Polypropylene has excellent stretching properties and can be made into a uniform thin film, and it is widely used for capacitor insulating films by taking advantage of its excellent electrical properties. As a polypropylene resin having excellent properties as a capacitor insulating film, it is necessary to improve the stereoregularity of the base polypropylene (JP-A-56-131921), to reduce the catalyst residue as much as possible, and to reduce the chlorine content as much as possible. That (JP-A-6
236709) and various other studies have been made, and those having excellent characteristics have been proposed.

[0003]

When it is evaluated as a capacitor insulating film even if it is adjusted so that stereoregularity, molecular weight, molecular weight distribution, catalyst residue, chlorine content, etc. become constant as is conventionally known. Often have different characteristics,
There is a problem in that a polypropylene resin showing good performance for a capacitor cannot be identified by a simple test, for example, as it is first known whether the resin used for a capacitor is excellent for a capacitor.

[0004]

[Means for Solving the Problems] The present inventors have completed the present invention by solving the above problems and earnestly searching for a polypropylene resin that exhibits excellent performance when used as a capacitor insulating film.

That is, the present invention comprises a crystalline propylene homopolymer having an isotactic pentad fraction of ¹³ C-NMR of 0.94 or more, at 230 ° C. and 2.16 k.
Melt flow index measured by g-load is 10
A polypropylene resin having a weight of 0.1 g / 10 minutes,
The polypropylene resin is melt-molded at 250 ° C. to a thickness of 1
In a film having a thickness of 4 μm obtained by obtaining a sheet having a thickness of 50 μm and further stretching at a deformation rate of 300% / sec 5 × 7 times at 145 ° C.,
A polypropylene resin for a capacitor insulating film, wherein one void having a major axis of 50 μm or more, one void or less, 2 voids or less of 30 μm to less than 50 μm, and 5 voids or less of 30 μm or less among voids formed per 15 square centimeters. is there. The present invention also provides a sheet having a thickness of 150 μm obtained by melt-molding the above polypropylene resin at 250 ° C., and further stretching a film having a thickness of 4 μm at 145 ° C. with a deformation rate of 300% / sec to 5 × 7 times. When measuring a void using an inspection apparatus equipped with an XY stage and a line sensor camera, light is emitted from the line sensor camera side, and the video signal obtained by detecting the reflected light from the film with the line sensor camera is subjected to image processing. This is a method for evaluating a polypropylene resin for a capacitor insulating film, which detects the size and number of voids.

In the present invention, it is preferable that the base crystalline propylene homopolymer has a catalyst residue of 40 ppm or less and a chlorine content of 2 ppm or less as measured by the ashing method. An example of such polypropylene is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-236709, but even if it has such a composition, a large number of voids are generated when formed into a film by the above method. In some cases, such a product had poor physical properties when actually evaluated as a capacitor. On the other hand, the polypropylene resin of the present invention does not have a problem that a large number of voids are generated when it is formed into a film, and exhibits good performance for capacitors.

In order to obtain the polypropylene resin of the present invention, a solid titanium catalyst component containing titanium, magnesium, halogen and an internally added electron donating compound and a group 1, 2 or 3 of the periodic table are selected. It is preferable to use polypropylene obtained by polymerizing propylene in the presence of a polymerization catalyst composed of an organometallic compound containing a metal and an externally added electron donating compound.

As the polymerization catalyst, more specifically, a catalyst usually used for industrially producing polypropylene is used. For example, an organoaluminum compound and titanium trichloride or titanium tetrachloride supported on a carrier such as magnesium halide are used. Among them, it is particularly preferable to use a catalyst having a high activity and originally having a small titanium component.

Above all, a transition metal catalyst component in which a compound containing a C--O or C--N bond as an internally added electron donating compound and a tetravalent titanium compound having at least one halogen are supported on a magnesium halide carrier. A catalyst composed of an organoaluminum compound and an externally added electron donating compound is preferred.

In the polymerization, the temperature is usually from room temperature to 150 ° C., and the pressure is from normal pressure to 100 kg / cm ² .
As the polymerization method, a conventional polymerization method such as a solvent polymerization method, a bulk polymerization method or a gas phase polymerization method is used, but the bulk polymerization method or the gas phase polymerization method is preferable.

The crystalline propylene homopolymer of the present invention needs to be subjected to a post-treatment to remove the catalyst residue when the amount of the polymer obtained per unit amount of the catalyst is low. Further, even when the activity of the catalyst is high and the amount of the polymer obtained is large, it is preferable to perform a post-treatment to remove the catalyst residue. As a post-treatment method, polypropylene obtained by polymerization is washed with liquid propylene, butane, hexane or heptane. At this time, water, alcohol compound, ketone compound, ether compound, ester compound,
An amine compound, an organic acid compound, an inorganic acid compound or the like may be added to solubilize catalyst components such as titanium and magnesium to facilitate extraction. It is also preferable to wash with a polar compound such as water or alcohol.

Further, by subjecting the polypropylene obtained by the above-mentioned polymerization method to dehalogenation, the polypropylene resin of the present invention which is particularly preferable can be obtained.

Among the above dehalogenation treatments, the dehalogenation treatment using an epoxy compound is particularly preferable. Here, as the epoxy compound, alkylene oxides such as ethylene oxide, propylene oxide, butene oxide, and cyclohexene oxide, glycidyl alcohol, glycidyl acid, and glycidyl ester are preferably used. When dechlorinating a polymer using these epoxy compounds, it is very effective to use a compound having an OH group in the same mole or more as the epoxy compound. Examples of the compound having an OH group include water and alcohol compounds.

As a method for quantifying the catalyst residue and chlorine content in the polypropylene resin in the present invention, known methods can be used.

In the present invention, polypropylene resin is ¹³ C
-The isotactic pentad fraction in NMR is 0.94 or more, the melt flow index (hereinafter referred to as MI) at 230 ° C under a load of 2.16 kg is 1.
A sheet having a thickness of 0 to 0.1 g / 10 minutes and a thickness of 150 μm formed at 250 ° C. has a deformation rate of 30 at 5 × 7 times at 145 ° C.
In the film having a thickness of 4 μm stretched at 0% / sec, one void having a major axis of 50 μm or more is formed from 15 μm or more, and 30 μm to 50 μm.
It is necessary to have a property that the number of particles having a size of less than m is 2 or less and the number of particles having a size of less than 30 μm is 5 or less.

For practical use as a capacitor insulating film, for example, 2,6-di-t-butyl-p-, due to its stability against thermal decomposition during molding and stability during use, although its amount is small. A stabilizer such as cresol is added, and the mixture is heated and melt-mixed to form pellets, which are then molded into a capacitor insulating film. It is important whether the polypropylene resin for the capacitor insulating film has specific characteristics.

When the polypropylene resin of the present invention is molded for a capacitor insulating film, specifically,
First, using a 20-mmφ two-layer T-die, at 250 ° C., thickness 1
Create a 50 μm sheet. The sheet thus obtained was preheated at 145 ° C. for 1 minute and then at 145 ° C., the deformation ratio was 30.
A film having a thickness of 4 μm is obtained by sequentially stretching the film in the machine direction at a rate of 0% / sec 5 times and the transverse direction 7 times. The number and size of voids formed in the film obtained by the above method were determined by the following method.

The film obtained by the above method is framed (15 cm).
(15 cm) and applied to a void inspection apparatus equipped with a microscope XY stage (Central Seiki SD-P sample) and a line sensor camera, and a range of 15 cm 2 (T)
Three points are measured within a range of 1 cm in the D direction and 5 cm in the MD direction. ) The number and size of voids were measured.

In the present invention, the video signal detected by the line sensor camera is an image processing device (SCANTEC-40).
00), and after being converted into a video signal, it is displayed on a monitor. Line sensor camera resolution (minimum pixel)
Depends on the magnification of the objective lens of the camera. For example, when the magnification of the objective lens is 5, the resolution is 1 μm and 1
A void having a size of μm or more can be detected.

In the present invention, the voids in the film are identified by the light and shade of the image. As a result of examining various measuring methods, it was found that the voids can be efficiently identified by looking at the reflected light instead of the transmitted light. In other words, even if the transmitted light is observed, the voids in the film cannot be detected due to the contrast of the image, but it becomes possible only by observing the reflected light.

[0021]

EXAMPLES The present invention will be further described below with reference to examples.

Example 1 [Preparation of catalyst] 300 g of anhydrous magnesium chloride, 1.6 liter of kerosene, 2-ethylhexyl alcohol
5 liters were heated at 140 ° C. for 3 hours to obtain a uniform solution. To this solution was added 70 grams of phthalic anhydride,
After stirring at 0 ° C. for 1 hour to dissolve, the mixture was cooled to room temperature.
Further, the above solution was slowly added dropwise to 8.5 liters of titanium tetrachloride cooled to -20 ° C. After completion of dropping 11
The temperature was raised to 0 ° C., 215 ml of diisobutyl phthalate was added, and the mixture was further stirred for 2 hours. The solid was separated by hot filtration, and the obtained solid was suspended again in 10 liters of titanium tetrachloride and stirred again at 110 ° C. for 2 hours. The solid was separated by hot filtration, and the obtained solid was washed with n-heptane until titanium was not substantially detected in the washing liquid. The obtained solid catalyst component was titanium 2.2 wt.
%, Diisobutyl phthalate 11.0 wt. %.

[Polymerization] A fully dried autoclave having an internal volume of 70 liters and having been purged with nitrogen was prepared. 150 mg of propylene was added, 20 kg of propylene and 17 Nl of hydrogen were added, and polymerization was carried out at 70 ° C. for 2 hours. After the polymerization, unreacted propylene was separated by decantation, and the polymerization product was washed with liquefied propylene three times. Then, 0.2 g of water and 10 ml of propylene oxide were added to the product, further treated at 90 ° C. for 15 minutes, and dried under reduced pressure for 5 minutes. This treatment with propylene oxide was repeated 3 times, and the produced polymer was taken out and weighed to obtain 14.50 kg of polypropylene. With this polymerization, the acquisition amount per titanium was 4.39 million g-
It was PP / g-Ti.

Boiling n measured with a Soxhlet extractor
-Heptane extraction residual amount (weight of unextracted polymer / weight of unextracted polymer expressed as a percentage. Hereinafter, II
It is written. ) Is 97.8, and the isotactic pentad fraction (hereinafter referred to as mmmm) measured by ¹³ C-NMR is 0.97, and 1,2,4-trichlorobenzene at 135 ° C. by gel permeation chromatography. Was used as a solvent, and the ratio of the weight average molecular weight to the number average molecular weight (hereinafter, referred to as Mw / Mn) was 5.2.

0.002 parts by weight of calcium stearate, Irganox-1330 (trade name, manufactured by Ciba-Geigy) based on 100 parts by weight of the obtained polypropylene.
A polypropylene resin was obtained by mixing 0.2 parts by weight and pelletizing at 250 ° C. The MI of this polypropylene resin was 4.1 g / 10 minutes, and when the catalyst residue and chlorine content were measured, they were 14 ppm and 1 ppm or less, respectively.

[Evaluation of Film] Next, using this polypropylene resin, a two-layer T die of 20 mmφ was used to measure 25
A sheet having a thickness of 150 μm was prepared at 0 ° C. The obtained sheet was subjected to 1 at 145 ° C. using a TM Long biaxial stretching machine.
After preheating for 5 minutes, the film was stretched at 145 ° C. at a deformation rate of 300% / sec in the longitudinal direction by 5 times and in the transverse direction by 7 times to obtain a film having a thickness of 4 μm.

The film obtained by the above method is framed (15 cm).
X 15 cm) and applied to a void inspection device equipped with a microscope XY stage and a line sensor camera, and the number and size of voids were measured.
Of the voids formed per 15 square centimeters, those with a major axis of 50 μm or more are 0, 30 μm or more to 5
One was less than 0 μm and three were less than 30 μm. The dielectric breakdown voltage of this film is 550V.
/ Μm.

Comparative Example 1 [Polymerization] The procedure of Example 1 was repeated except that the catalyst obtained in Example 1 was used and decyltrimethoxysilane was used instead of dinormalpropyldimethoxysilane.
0.10 kilogram of polypropylene was obtained. By this polymerization, the acquisition amount per titanium was 2.93 million g-PP / g-.
It was Ti. The polypropylene II is 98.1,
mmmm was 0.92 and Mw / Mn was 5.3.

The MI of polypropylene resin is 3.8.
g / 10 min, and the catalyst residue and chlorine content were 17 ppm and 1 ppm, respectively.

[Evaluation of Film] The same procedure as in Example 1 was performed. In a biaxially stretched film having a thickness of 4 μm,
One of the voids formed per 15 square centimeters having a major axis of 50 μm or more, 30 μm or more to 5
The number of particles less than 0 μm was 3 and the number of particles less than 30 μm was 8. The dielectric breakdown voltage of this film is 500V.
/ Μm.

Comparative Example 2 At the time of film evaluation in Example 1, an attempt was made to identify a void by transmitted light instead of reflected light, but the void could not be detected.

[0032]

The polypropylene resin of the present invention has very good physical properties when it is used for a capacitor insulating film. Further, the resin having good performance can be specified by a simple evaluation method, which is extremely valuable industrially.

Front page continuation (72) Inventor Tadashi Asanuma 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. A crystalline propylene homopolymer having an isotactic pentad fraction of 0.94 or more in ¹³ C-NMR and having a melt flow index of 10 to 0.30 measured at 230 ° C. under a load of 2.16 kg. A polypropylene resin having a weight of 1 g / 10 minutes, the polypropylene resin being melt-molded at 250 ° C. to obtain a sheet having a thickness of 150 μm, and further stretched 5 × 7 times at 145 ° C. with a deformation rate of 300% / sec. In the film of 4 μm in length, the major axis is 50 μm among the voids formed per 15 cm 2.
A polypropylene resin for a capacitor insulating film, in which the number of the above is 1 or less, the number of 2 or less is 30 μm or more and less than 50 μm, and the number of 5 or less is less than 30 μm. 2. A film having a thickness of 4 μm stretched 5 × 7 times at 145 ° C. at a deformation rate of 300% / sec according to claim 1 by using an inspection device equipped with an XY stage for a microscope and a line sensor camera. When measuring voids, a capacitor insulating film that detects the size and number of voids by irradiating light from the line sensor camera side and processing the image signal of the reflected light from the film detected by the line sensor camera Method for evaluating polypropylene resin for automobiles.