JPS61206108A - Insulating material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an electrical insulating material having excellent breakdown strength against impact voltage.

(b) Prior Art Conventionally, various plastic materials have been used as electrical insulating materials such as electrical cables. In particular, olefin polymers have excellent properties such as electrical properties, mechanical properties, and chemical stability. Among them, low-density polyethylene produced by high-pressure radical polymerization is inexpensive, has low dielectric loss, has good processability, and can be crosslinked to greatly improve its heat resistance. It is widely used for electric wires and cables because it has many advantages such as less concern about tree phenomenon due to contamination.

The current problem with such insulating materials for power cables is that as the power transmission voltage increases due to the anticipated increase in the power transmission capacity, the thickness of the insulator must be made thicker to match the upper R voltage. This is something you have to do. That is, with current materials such as polyethylene, dielectric breakdown will occur if the insulating layer is not made very thick in response to high voltages.

Various improvement methods have been proposed to address this problem.

For example, several methods have been proposed in which styrene is graft-polymerized to polyethylene in order to improve the breakdown strength against Ij lightning voltage, especially in a high temperature range. Special Public Service 1974-1
One such method is disclosed in Japanese Patent No. 8760, but this method has the problem that crosslinking of polyethylene is unavoidable and the impulse strength in the low temperature range is reduced.

Also, a method of blending aromatic polymers such as borisdyrene with polyethylene or olefin polymers (Japanese Patent Publication No. 38-20
No. 717, JP-A-50-142651, JP-A-52-
No. 54187) has been proposed, but it has the drawback of poor compatibility between polyethylene or olefin polymers and styrene polymers.

A method of blending a block copolymer of styrene and conjugated dienes with polyethylene has also been proposed (Japanese Unexamined Patent Publication No. 52-41884), but this method results in a decrease in heat resistance and extrusion processability.

Other methods include impregnating polyethylene with electrical insulating oil (
Japanese Patent No. 171-33938) has been proposed, but this method has the disadvantage that the electrical insulating oil mixed in bleeds out due to long-term use or changes in the environment, resulting in loss of effectiveness.

(c) Problems to be Solved by the Invention As a result of intensive studies to solve the above-mentioned problems, the present invention has been found to be free from the drawbacks of the prior art as described above. The present invention provides an electrical insulating material with increased breakdown strength against voltage.

(d) Means for solving the problem The present invention contains a unit having an aromatic ring in a proportion of 0.005 to 1 mole per 100 moles of ethylene in the polymer chain, and An electrical insulating material made of an ethylene polymer having a crystallization content of 30% or more is provided.

The unit having an aromatic ring used in the present invention is derived from a saturated or unsaturated aromatic compound having a single ring or polycycles (fused type or non-fused type). Preferably it is an aromatic compound having 1 to 3 rings. in particular,
Representative examples include benzene, indane, indene, naphthalene, biphenyl, diarylalkane, arenaphthylene, anthracene, phenanthrene, terphenyl, triarylsialkane, triarylalkane, aralkylnaphthalene, etc., or their partially hydrogenated or dehydrogenated products. It is a compound having a saturated or unsaturated aromatic ring skeleton. Furthermore, as the Xi WJ form of these compounds having an aromatic ring skeleton, an alkyl group, a cycloalkyl group, a hydrocarbon group having a double bond or a triple bond; a group containing a halogen atom such as chlorine or bromine; Methoxy group, carboxyl group, ether bond, ester bond, phenolic water I
Oxygen-containing with L-alcoholic hydroxyl groups, etc.! 1 Unsaturated carboxylic acids or derivatives thereof such as niacrylic acid, methacrylic acid, maleic acid, fumaric acid; vinyl ester group;
Examples include those in which one or more substituents such as a group having one atom; a group having a nitrogen atom; and the like are bonded to the above-mentioned hydrocarbon compound having an aromatic ring skeleton.

In the present invention, it is an essential requirement that the ethylene polymer chain contains a predetermined amount of units that form an aromatic ring so that the ethylene polymer chain can be redistributed. In principle, the specific chemical structure of the compound does not matter.

Methods for introducing aromatic rings into the ethylene polymer chain are not particularly limited, but include copolymerization, chain transfer, graft modification, etc. Polymerization methods include radical polymerization, Both ion and ion polymerizations are possible. High-pressure radical polymerization has no residual catalyst that adversely affects electrical properties, and aromatic rings can be reliably introduced into the polymer chain by either copolymerization or chain transfer, so there are no restrictions due to the chemical structure of the aromatic compound. It is particularly preferable because it does not cause gel formation, which is often observed in graft modification.

Typical polymerization methods are shown below.

First, in ionic polymerization using a Ziegler type catalyst, solid catalyst components containing at least magnesium and titanium, such as total magnesium, magnesium hydroxide, magnesium carbonate, magnesium oxide, and magnesium chloride, and a metal selected from silicon, aluminum, and calcium are used. Double salts and double oxides containing magnesium atoms,
Inorganic materials containing magnesium such as carbonates, chlorides, hydroxides, etc., and those obtained by treating or reacting these inorganic solid compounds with oxygen-containing compounds, sulfur-containing compounds, aromatic compounds, or halogen-containing substances. A titanium compound is supported on a solid compound by a known method, and the polymerization is carried out in the same manner as the polymerization reaction of A-refine using a normal Ziegler type catalyst in the presence of a catalyst in which an organoaluminum compound is combined with a titanium compound. It will be done.

That is, all reactions are carried out in a gas phase, in the presence of an inert solvent, or using the monomer itself as a solvent in a state in which oxygen, water, etc. are substantially excluded. Polymerization conditions are temperature 20-30
The temperature is 0°C, preferably 40 to 200°C, and the pressure is normal pressure to 70Kg/al-9, preferably 2 to 60K9.
/ ci・ri desu. Although the molecular weight can be adjusted to some extent by changing polymerization conditions such as polymerization temperature and catalyst molar ratio, it is effectively carried out by adding hydrogen to the polymerization system. In addition, two or more stages of polymerization reactions with different conditions such as hydrogen concentration and polymerization temperature can be carried out without any hindrance. In particular, the ethylene polymer of the present invention is preferably produced by radical polymerization under high pressure! ! It will be built. In other words, the radical polymerization method under high pressure is a polymerization pressure of 500 to 4000 kg/
cIi, preferably 1000 to 3500 Kg/cal,
Reaction temperature 50-400°C, preferably 100-350°C
Ethylene and aromatics, and optionally other monomers, are simultaneously or stepwise reacted in a vessel wall or tube reactor in the presence of a free radical catalyst and a chain transfer agent, and if necessary auxiliaries. This refers to a method in which polymerization is interrupted by contact with other substances. When the aromatic compound is solid, it is dissolved in a solvent and supplied.

The free radical catalysts include the customary initiators such as peroxides, hydroperoxides, azo compounds, amine oxide compounds, vi elements, and the like.

In addition, as a chain transfer agent, hydrogen, propylene, butene-1
, C-02o or higher saturated aliphatic hydrocarbons and halogen-substituted hydrocarbons, such as methane, ethane, propane, butane, isobutane, n-hexane, n-hebutane, cycloparaffins, chloroform and carbon tetrachloride, C1-C2° or higher saturated aliphatic alcohols such as methanol, ethanol, propatool and isopropanol; C-C20 or higher saturated open aliphatic carbonyl compounds such as acetone and methyl ethyl ketone; Examples include compounds.

Polyethylene, which has traditionally been widely used as an insulating material for power cables, has lower breakdown strength against impact voltage (impulse breakdown strength) when its crystallinity is lowered, and workability becomes worse when its crystallinity is increased. It has its drawbacks. It is generally known that when other components are introduced into the polyethylene chain, the degree of crystallinity decreases due to steric hindrance. However, the present inventors have found that when an extremely small and specific proportion of aromatic rings is contained in a polymer chain, there is a range in which the impulse rupture strength increases even if the degree of crystallinity decreases. In other words, it has been found that there is a range in which the impulse rupture strength can be improved depending on the ratio of aromatic rings contained in the ethylene polymer chain and the crystallinity of the ethylene polymer. This improvement effect is observed in a wide temperature range from low to high temperatures, and is particularly remarkable in the high temperature range.

In the present invention, in J3, the aromatic ring unit in the ethylene polymer chain is 0 per 100 moles of ethylene units.
．． 0.005 to 1 mol, preferably 0.01 to 0.7 mol.

If the unit having an aromatic ring is less than 0.005 mole per 100 moles of ethylene units, little improvement effect will be seen, and if it exceeds 1 mole, the improvement will be better than when it does not contain an aromatic ring. Impulse rupture strength is rather reduced, and high-pressure radical polymerization consumes a large amount of initiator and requires the use of large amounts of expensive aromatic compounds, which is uneconomical. Further, in the present invention,
The crystallinity of the ethylene polymer as determined by X-ray diffraction is 30% or more. Preferably, the reduction in crystallinity of an ethylene homopolymer containing no aromatic ring obtained under substantially the same conditions as the ethylene polymer is suppressed to 25%. The upper limit of the crystallinity is naturally determined to be less than or equal to the crystallinity of an ethylene homopolymer obtained under substantially the same conditions as the ethylene polymer. Also, the crystallinity is 30
% or less, the ethylene homopolymer has a lower specific vane pulse rupture strength and a lower specific volume resistivity. In the present invention, it is necessary to satisfy both the content of units having an aromatic ring and the crystallinity at the same time.

The density of the ethylene polymer of the present invention is preferably in the range of 0.890 to 0.950 g/a3. Further, the melt index (hereinafter abbreviated as Ml) is preferably 0.05 to 50 g/10 min, more preferably 0.
It is in the range of 1 to 20 g/10 minutes.

The ethylene polymer of the present invention contains other unsaturated hanging bodies in addition to ethylene, and these unsaturated hanging bodies include butene-1, butene-1, Penten
Examples include 1, hexene-1,4-methylpentene-1, octene-1, decene-1, vinyl acetate, ethyl acrylate, methacrylic acid, esters thereof, and mixtures thereof.

The content of unsaturated suspension bodies in the above ethylene polymer is 0 to
It is preferably 3 mol% or less, particularly 1 mol% or less.

The ethylene polymer of the present invention can be used in combination with an ethylene polymer that does not contain other aromatic units. Compositions containing other ethylene polymers are also preferred practical IM embodiments of the present invention, and when the content of aromatic units in the composition is within the above range, the impulse rupture strength of the composition is improved.

Other ethylene polymers to be blended with the ethylene-1 polymer of the present invention include ethylene single polymer, ethylene and propylene, budene-1, pentene-1, hexene-1,4-
Copolymers with α-olefins having 3 to 12 carbon atoms such as methylpentene-1, ocvun-1, and decene-1, ethylene and vinyl acetate, acrylic acid, ethyl acrylate, methacrylic acid, ethyl methacrylate, maleic acid , a copolymer with a polar group-containing monomer such as maleic anhydride, or a polymer obtained by modifying the above-mentioned ethylene single polymer or ethylene and α-olefin copolymer with an unsaturated carboxylic acid or a derivative thereof such as acrylic acid or maleic acid. etc. and mixtures thereof.

(B) Functions and Effects of the Invention The ethylene polymer of the present invention has excellent dielectric strength as an electrical insulating material, and particularly has excellent breakdown strength against impact voltage in a high temperature range, so it is an insulating material for ultra-high voltage electrical cables. Very useful as a material.

In the present invention, olefin polymers (including copolymers), polyacrylonitrile, polyamide, polycarbonate, ABS resin, polystyrene, polyphenylene oxide, polyvinyl alcohol-based Resin, thermoplastic resin such as vinyl chloride resin, vinylidene chloride resin, polyester resin, petroleum resin, coumaron-indene resin, ethylene-propylene copolymer rubber (EPRlEPDM, etc.), 5BRSNBR, butadiene rubber, +1R, Chloroprene rubber, isoprene rubber, styrene-butadiene
It can be used by heating with at least one synthetic rubber such as a styrene block copolymer or natural rubber.

On the other hand, in the present invention, organic/inorganic fillers, antioxidants, lubricants, various organic/inorganic pigments, ultraviolet inhibitors, dispersants, copper damage inhibitors, neutralizing agents, blowing agents, plasticizers, bubbles, etc. Additives such as inhibitors, flame retardants, crosslinking agents, flowability improvers, weld strength improvers, and nucleating agents may be added to the extent that they do not significantly impair the effects of the present invention.

Further, the ethylene polymer of the present invention may be used as is without crosslinking, or may be used after being crosslinked if necessary. A normal crosslinking method is applied to the crosslinking method.

(f) Example Examples are shown below.

Examples 1 to 11 A predetermined amount of ethylene, an aromatic compound, and n-hebutane as a chain transfer agent were charged into a metal autoclave equipped with a stirrer that was sufficiently purged with nitrogen and ethylene, and a di-tertiary polymerization initiator was charged. - butyl peroxide was injected and polymerization was carried out under the following polymerization conditions: pressure 1900, 9/ci, polymerization temperature 180° C., polymerization time 40 minutes (Production method 1).

A part of the produced polymer was dissolved in heated carbon tetrachloride, and a large amount of the polymer was poured into a tonne to reprecipitate it. This operation was repeated several times to purify and then vacuum dry.

The purified polymer was molded into a sheet with a thickness of 500 μm by heating and compression, and each produced polymer was analyzed by infrared spectroscopy using a compensation method using an ethylene polymer sheet of the same thickness without aromatic compounds as a control. The units derived from aromatic compounds were quantified.

The amount of units derived from the aromatic compound contained in each produced polymer was determined mainly from the absorbance of the absorption attributed to the 夛'J aromatic ring around 1600Ca-'. In addition, the measurement of the melt index of each produced polymer is based on JIS
The crystallinity was measured by X-ray diffraction method. The impulse destruction test was conducted as follows, and the results are shown in Table 1.

The sample was made into a sheet with a thickness of 50 μm by heat compression molding.

A fixed electrode, a so-called Matsuon electrode (Fig. 1), was used as the electrode system. The electrode system substrate 4 is made of polymethyl methacrylate and has a hole of 1/2 inch in diameter in its center. A 1/2 inch stainless steel bulb 1 was used as the electrode.

Sample 2 was cut into approximately 8 to 10 shoe angles and was sandwiched between electrodes. Degassed EVO: 1 and resin 3 are placed between the sample 2 and the electrode.
was filled and hardened. The Matsukeon electrode was immersed in a container filled with silicone oil, and then placed in thermostats at 20°C and 80°C for measurements.

The voltage waveform used for destruction was a negative polarity, 1 x 40 μs impulse waveform. The waveform was observed with an oscilloscope, and the data that broke at the wave front was taken as data, and the average value of 20 points or more was taken.

Ethylene homopolymer was prepared under the same polymerization conditions as in Production Method 1 above without injecting an aromatic compound, and the same measurements were carried out. The results are shown in Table 1.

An ethylene-based polymer was prepared using the polymerization conditions of Process 1 and F1 above, and the content of units having an aromatic ring was outside the scope of the present invention, and the same measurements were carried out. It is shown in Table 1.

Yotsumugi'L Once, polymerization was carried out using propylene instead of n-hebutane as the chain transfer agent in Production Method 1 above, but under the same conditions as above (Production Method 2), an ethylene polymer was prepared, and the same measurements were carried out. The results are shown in Table 1.

As is clear from the evaluation results in Table 1, in Examples 1 to 11, the polymers of the present invention had better fracture resistance at low and high temperatures than the ethylene homopolymer (Comparative Example 1), and especially? This shows that it is excellent in the 3-starvation area.

On the other hand, in Comparative Example 2.3, when the aromatic compound content was set outside the range of the present invention, no improvement effect was observed.

Further, in Comparative Example 3, when the crystallinity was set outside the range of the present invention, no improvement effect was similarly observed.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the m& for impulse destruction test according to the present invention. 1... Stainless steel bulb 2... Sample 3... Epoxy resin 4... Polymethyl methacrylate substrate Figure 1

Claims (3)

[Claims] (1) In the polymer chain, per 100 moles of ethylene units,
An electrical insulating material comprising an ethylene polymer containing units having an aromatic ring in a proportion of 0.005 to 1 mole and having a crystallinity of 30% or more as determined by X-ray diffraction. (2) The electrical insulating material according to claim 1, wherein the ethylene polymer is a polymer obtained by high-pressure radical polymerization. (3) The electrical insulating material according to claim 1 or 2, wherein the ethylene polymer contains another monomer.