JP2000235815A - Electric insulating material and electric insulating member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain superior electrical characteristics, and improve extrusion workability under low temperature condition by using a material containing syndiotactic polypropylene having a specified value of weight mean molecular weight to number mean molecular weight. SOLUTION: A copolymer material, which is composed of a homo polymer of polypropylene having a syndiotactic structure and other olefin and which can obtain the weight mean molecular weight to the number mean molecular weight at 2.5-5, is obtained by using two or more kinds of even group catalyst in the polymerization. Stereospecific polymerization catalyst of the organic metal complex such as metallocene compound is used. With this molecular weight distribution, an appearance defect when extruded onto a conductor at a low temperature, generation of drip, degradation of the electrical characteristics at a high temperature tan δ and lowering of the voltage resistance strength can be prevented. In order to prevent the lowering of melting point, lowering of the electrical breaking strength and mechanical strength, syndiotactic factor is set at 0.7 or more, and in order to obtain the high temperature flowing property, melt flow rate is desirably set at 0.1-20 g/10 min. Various additive can be added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating material and an electric insulating member using the same. More specifically, the present invention relates to an electric insulating material and an electric insulating member containing syndiotactic polypropylene having a certain molecular weight distribution.

[0002]

2. Description of the Related Art Syndiotactic polypropylene (hereinafter also referred to as "s-PP") is superior to existing insulators such as crosslinked polyethylene (XLPE) in a wide temperature range from room temperature to high temperature (120 ° C.). Electrical characteristics and high withstand voltage characteristics. Also, the polymer has a high melting point,
Even with non-crosslinking, it shows high mechanical strength at high temperatures and is promising as a next-generation electrical insulating material.

[0003]

However, sP
In the case of manufacturing a cable using P, a molded product obtained when extruded at a low temperature and a high speed on a conductor tends to have poor appearance (melt fracture), and when extruded at a high temperature, sagging is easily generated. At present, extrusion is performed at a low temperature to prevent sagging and at a low speed to suppress poor appearance, and there is a problem that the production speed is limited. An object of the present invention is to provide an electric insulating material and an electric insulating member in which the extrudability of s-PP at a low temperature is improved while maintaining excellent electric properties.

[0004]

That is, according to the present invention, the weight average molecular weight (Mw) / number average molecular weight (Mn) is 2.5 to 2.5.
5 relates to an electric insulating material containing the syndiotactic polypropylene and an electric insulating member using the electric insulating material.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The s-PP used in the present invention is:
The concept includes not only a homopolymer of polypropylene having a syndiotactic structure but also a copolymer of propylene and another olefin. In the following description, the term "s-PP" includes the copolymer. In the present invention, s-PP, which is a homopolymer, is preferred, but for applications requiring low-temperature brittleness resistance, a copolymer of s-propylene and olefin and an s-PP / polyolefin blend are preferred.

[0006] The molecular weight distribution of s-PP, that is, weight average molecular weight (Mw) / number average molecular weight (Mn) must be 2.5-5. When Mw / Mn is less than 2.5, when s-PP is extruded on a conductor at a low temperature during cable production,
Appearance defects are likely to occur. Conversely, when Mw / Mn exceeds 5, the amount of low molecular weight polymer increases, sagging is likely to occur even at low temperature extrusion, and the electrical characteristics or withstand voltage strength is reduced. In particular, the high temperature tan δ is significantly increased. s-PP
By adjusting Mw / Mn in the above range, a material extrudable at high speed and excellent in extrudability can be obtained, and the obtained molded article has excellent electric properties and high withstand voltage strength. A preferred range of Mw / Mn is 3.0 to 5, and a more preferred range is 4.0 to 4.8.

[0007] The Mw / Mn of s-PP can be adjusted to 2.5 to 5 by using two or more homogeneous catalysts used in polymerization. Alternatively, it is achieved by changing the polymerization temperature, pressure or the amount of a chain transfer agent such as hydrogen using one or more homogeneous catalysts. Furthermore, it can be achieved by blending two or more s-PPs having different molecular weights.

The catalyst used may be an organometallic complex having a symmetric or asymmetric molecular structure, for example, a stereospecific polymerization catalyst such as a metallocene compound. Also,
The polymerization conditions are not particularly limited, for example, a bulk polymerization method,
It can be produced by a method such as a gas phase polymerization method or a solution polymerization method using an inert solvent. In particular, a polymer obtained by coordination polymerization using a metallocene compound as a catalyst is preferable.

The s-PP used in the present invention has a syndiotactic pentad fraction (rrrr fraction) of 0.1.
It is necessary to be 7 or more. Here, the syndiotactic pentad fraction is measured at 67.8 MHz with a 1,2,4-trichlorobenzene solution at 135 ° C.13
In the C-NMR spectrum, the peak intensity at 20.2 ppm based on tetramethylsilane [peak intensity of the methyl group attributable to the syndiotactic pentad (rrrr) chain] is attributed to all the methyl groups of the propylene unit. Means the ratio of peak intensity. S-PP having a syndiotactic pentad fraction of less than 0.7 should not be used as the electrical insulating material of the present invention, because it has a low melting point and a low electrical breakdown strength and mechanical properties. The syndiotactic pentad fraction is preferably 0.8 to 0.95 in view of electric field resistance, and more preferably 0.83 to 0.95 in view of workability.

Further, the s-PP is ASTM-D-1
The melt flow rate (MFR) (load: 2.16 kgf, temperature: 230 ° C.) specified in 238 is 0.1 to 2
It is necessary to have a range of 0 g / 10 minutes. 20g /
An s-PP having an MFR of more than 10 minutes has too high a fluidity at a high temperature, and conversely, a M of less than 0.1 g / 10 minutes.
S-PP having FR has too little fluidity, and therefore, when any of them is used as the electrical insulating material of the present invention, there is a difficulty in workability. The preferred range of the MFR is 0.3 to 15 g / 10 minutes from the viewpoint of high temperature fluidity.
A more preferred range is 0.5 to 10 g / 10 minutes from the viewpoint of extrusion processability and moldability.

The preferred molecular weight (weight average molecular weight) of s-PP is from 3,000 to 400,000, more preferably from 10,000 to 200,000.

The s-PP may contain, if necessary, an antioxidant or stabilizer such as a hindered phenol, amine or thioether, a copper harm inhibitor such as an amide or hydrazide, a benzophenone or a benzoin. Usually used for plastics, such as UV-based anti-oxidants, lubricants such as higher fatty acids or their metal salts, processing aids, organic and inorganic pigments, organic and inorganic flame retardants, and fillers such as silica and clay. May be added.

[0013] The electric insulating member referred to in the present invention includes an electric insulating paper made of paper mixed with cellulose and an oil-immersed insulator obtained by combining the same with an insulating oil, as well as tapes, sheets, spacers, plugs, sockets, pipes, Examples include insulating rods, various electrical molded products, circuit components, and sealing materials. These members are each formed by a known method using the s-PP of the present invention.

The electric insulating material containing s-PP of the present invention is:
The impulse breakdown electric field strength at room temperature is 10 to 25% higher than that of conventional low density polyethylene (LDPE) and 110 to 140% higher than that of i-PP, and the AC breakdown electric field strength at room temperature is 2. 5-8.5%, crosslinked LDPE
14-20% higher than i-PP and 45-55% higher than i-PP.

[0015]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Example 1 A syndiotactic pentad fraction (rrrr) of 0.
83, s-PP having an MFR of 2.7 g / 10 min and an Mw / Mn of 3.0 was continuously extruded at 180 ° C. using a 50 mmφ extruder equipped with a T-die, and a 1 mm thick tape was obtained. I got In order to conduct a destructive test and an electrical property test of the obtained tape, the tape was subjected to a compression molding machine for 18 hours.
After melt molding at 0 ° C. (5 minutes), the mixture was left standing at room temperature and cooled, and finally a tape having a thickness of 0.3 mm was obtained as a tape for a destructive test, and a tape having a thickness of 0.5 mm was obtained as a tape for an electrical property test.

With respect to the obtained sample having a thickness of 0.3 mm, an impulse breakdown test and an AC breakdown test were performed using a Mackinon electrode system.

In the impulse breakdown test, JIS C 3
According to 005, a negative impulse standard wave of 1 × 40 μsec is set to 70% of an expected breakdown voltage as an initial value.
Electric power was applied by a step-up voltage boost method of 5 kV / 3 times application.

In the AC breakdown test, 70% of the expected breakdown voltage is set as an initial value in accordance with JIS C 3005, and 2%.
Electric power was applied by a step-up voltage boost method of kV / 1 minute application.
For both impulse and AC breakdown tests, data of 10 samples were collected per condition, and after Weibull analysis,
The breakdown value at a probability of failure of 63.3% was defined as the breakdown voltage of the sample.

In the high-temperature electrical property test, the dielectric loss tangent (tan δ:%) of a 0.5 mm thick sample was measured at 60 Hz, 1000 V and 120 ° C. Table 2 shows the test results.

The relationship between the extrusion temperature and the resin sagging was visually observed on the surface of a 0.3 mm thick tube extruded at a resin pressure of 100 kg / cm ² at the temperature shown in Table 3. The relationship between the resin pressure at the time of extrusion and the appearance was observed by visual observation of the surface of a 0.3 mm thick tube extruded at a temperature of 160 ° C. under the pressures shown in Table 3. ：: There is no roughness on the surface. X: The surface is rough (the difference between the upper and lower surfaces is 1 μm or more). Table 3 shows the results.

Examples 2 and 3 and Comparative Examples 1 to 3 Using s-PP or XLPE having the physical properties shown in Table 1, samples were prepared in the same manner as in Example 1, and destruction tests and electrical property tests were performed. And the appearance was observed. The results are shown in Tables 2 and 3.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

The electrical insulating material of the present invention has excellent electrical characteristics (such as AC breakdown characteristics, impulse breakdown characteristics, volume resistivity and dielectric constant) in a wide temperature range of s-PP, high withstand voltage characteristics, The extrusion processability is improved while maintaining high mechanical strength and flexibility enough to be used as an electrical insulating member. The effect of increasing the processing speed and improving production efficiency is obtained. That is, the production rate at a lower temperature can be twice or more higher than that of the conventional insulating material containing s-PP. Moreover, the obtained electrical insulation member is excellent in electrical characteristics, withstand voltage strength, and the like. In particular, a long-length object such as an electric cable can be a high-performance cable with high production efficiency.

 ──────────────────────────────────────────────────続 き Continuing from the front page (71) Applicant 590003331 Katsumi Yoshino 166-3 Oomachi, Kishiwada-shi, Osaka (72) Inventor Masayuki Kawato 8 Nishinomachi, Higashi-Mukojima, Amagasaki-shi, Hyogo Inside Mitsubishi Electric Wire Industry Co., Ltd. (72 Inventor Tsuyoshi Murakami 1008 Shinbori, Kumagaya-shi, Saitama Pref. Mitsubishi Electric Wire & Cable Co., Ltd. (72) Inventor Tadahiro Sunaga 1-6 Takasago, Takaishi-shi, Osaka Mitsui Chemicals Co., Ltd. (72) Inventor Masaru Abe Osaka 1-6-6 Takasago, Takaishi-shi Mitsui Chemicals, Inc. (72) Inventor Takuo Nagiri 3-3-22 Nakanoshima, Kita-ku, Osaka-shi Kansai Electric Power Co., Inc. (72) Katsumi Yoshino Oiocho, Kishiwada-shi, Osaka 166-3 F term (reference) 4F071 AA20 AA81 AA88 AF39A AH12 BA01 BB06 BC01 BC07 4J002 BB121 BB141 GQ01 4J100 AA03P CA01 CA04 CA12 DA04 DA42 DA55 JA44 5G305 AA02 AA14 AB36 BA12 BA26 BA29 CA01

Claims (4)

[Claims] 1. An electrically insulating material containing a syndiotactic polypropylene having a weight average molecular weight (Mw) / number average molecular weight (Mn) of 2.5 to 5. 2. A syndiotactic pentad fraction of 0.7 or more and a melt flow rate of 0.1 to 20 g / 1.
2. The electrically insulating material according to claim 1, wherein the time is 0 minutes. 3. An electric insulating member using the electric insulating material according to claim 1. 4. An electrically insulated cable using the electrically insulated member according to claim 3.