JPS61110907A - Electric 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 (Field of Industrial Application) The present invention relates to an electrical insulating material having excellent breakdown strength against impact voltage.

(Prior Art) Various plastic materials have been used as electrical insulating materials for power cables and the like. 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 lanocal polymerization is inexpensive, has low dielectric loss, has good processability, and can be crosslinked to greatly improve its heat resistance.Compared to ionic polymerization, low-density polyethylene is less susceptible to contamination by foreign substances such as catalyst residues. It is widely used for electric wires and cables because it has many advantages such as less concern about the tree phenomenon caused by electric wires.

The current problem with insulating materials for power cables is that as the power transmission voltage rises due to the expected future increase in power transmission capacity, the thickness of the insulator must be increased to match the increased voltage. It is. That is, with current materials such as preethylene, 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 impact voltage, especially in a high temperature range. Special Public Service 1977-18
One such method is disclosed in Japanese Patent No. 760, but this method requires crosslinking of 2-ethylene and has the problem that the in/f las strength in the low temperature range decreases. JP-A-57-80605 proposes a method of impregnating and polymerizing ethylene polymer particles with an aromatic vinyl monomer in an aqueous suspension, but this method has the disadvantage that the process is very complicated.

Also, a method of blending aromatic polymers such as polystyrene 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 has also been proposed in which a block copolymer of styrene and conjugated tsene compounds is blended with polyethylene (Japanese Patent Application Laid-Open 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 (
JP-A No. 49-33938) has been proposed, but
This method has the disadvantage that the insulated electrical insulating oil bleeds out when used for a long time or due to changes in the environment, impairing its effectiveness.

(Problems to be Solved by the Invention) As a result of intensive studies to solve the above-mentioned problems, the present invention has been developed to provide electrical insulation that does not have the above-mentioned drawbacks of the prior art and has increased breakdown strength against impact voltage. It provides materials.

(Means for Solving the Problems) The present invention provides ethylene or ethylene and other ethylene:
A copolymer of a / unsaturated monomer and a comonomer of the following formula (1) or a composition in which an ethylene polymer is blended with the copolymer, the comonomer content being 0.005 The present invention provides an electric material characterized in that the amount is in the range of 1 mol - 0.

The comonomer represented by the above formula (+) is benyl methacrylate, methylbennyl methacrylate, chlorobenzyl methacrylate, benzyl acrylate, methyl pencil acrylate, chlorobennyl acrylate, phenylbenzyl methacrylate, phenyl acrylate. It is at least one selected from the group such as benzyl, and benyl methacrylate and benyl acrylate are particularly preferred.

In a copolymer of ethylene and a comonomer represented by the above formula (1) of the present invention (hereinafter simply referred to as ethylene copolymer), or a composition in which an ethylene polymer is blended with the ethylene copolymer, The content of the comonomer is o, oos ~ 1.0
The molar ratio is preferably applied in the range of 0.01 to 0.7 molar ratio.

Further, the present invention includes an ethylene copolymer composition in which an ethylene polymer is blended with the above ethylene copolymer, but the comonomer content in the composition is still 0.005. -1.0 molar range.

When the comonomer content is less than 0.05 molar, there is almost no effect of modifying the ethylene copolymer, and when it exceeds 1.0 molar, the impulse rupture strength decreases.

The present invention aims to improve the dielectric strength by introducing the comonomer represented by the above formula (1) into the ethylene polymer, but if the comonomer content is too large, the in-ξ On the contrary, the breaking strength decreases. This is thought to be because the crystallinity of the ethylene copolymer is reduced due to steric hindrance of the comonomer.

Therefore, in order to improve the impulse rupture strength, the comonomer must be introduced within a range that does not significantly reduce the crystallinity of the ethylene copolymer.

The density of the above ethylene copolymer is generally 0.89 to 0.
．． 94? /crn range.

In addition, the melt index (hereinafter abbreviated as M, ■) is 0.05 to 50 r/10 minutes, preferably sail 1 to 2.
It is in the range of 07/10 minutes.

The ethylene copolymer of the present invention is a copolymer of ethylene or ethylene and an ethylenically unsaturated monomer, and the comonomer represented by the above formula (1), and the above ethylenically unsaturated monomer Examples include propylene, butene-1, pentene-1, hexene-1,4-methyl, ten-11octene-1, decene-1, vinyl acetate, ethyl acrylate, and mixtures thereof.

The content of the ethylenically unsaturated monomer in the ethylene copolymer is preferably 0 to 3 mol, particularly 1 mol or less.

The ethylene polymers to be blended into the above ethylene copolymer include ethylene homopolymer, ethylene and propylene, butene-1, intene-1, hexene-1,4-methylintene-1, octene-1, decene-1 etc. carbon number 3~
Copolymer of 12 α-olefins, ethylene and vinyl acetate, acrylic acid, ethyl acrylate, methacrylic acid,
A copolymer with a polar group-containing monomer such as ethyl methacrylate, maleic acid, or maleic anhydride; Examples include polymers modified with derivatives thereof and mixtures thereof.

For the production of the ethylene copolymer of the present invention, known methods such as ionic polymerization using a Ziegler type catalyst or radical polymerization under high pressure can be used, but high-pressure radical polymerization without residual catalyst is preferred.

For example, in ionic polymerization using a Ziegler type catalyst, a solid catalyst component containing at least magnesium and titanium, such as magnesium metal, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium chloride, etc., and a metal selected from silicon, aluminum, and calcium and magnesium atoms are used. Double salts and double oxides containing
Inorganic solid compounds containing magnesium, such as carbonates, chlorides, or hydroxides, and those obtained by treating or reacting these inorganic solid compounds with oxygen-containing compounds, sulfur-containing compounds, aromatic hydrocarbons, or halogen-containing substances. It is obtained by carrying out polymerization in the same manner as the polymerization reaction of olefins using ordinary Ziegler type catalysts in the presence of a catalyst in which a titanium compound is supported by a known method and an organoaluminum compound is combined.

That is, all reactions are carried out substantially in the absence of oxygen, water, etc., in a gas phase or in the presence of an inert solvent, or using the monomer itself as a solvent. The polymerization conditions for the above olefin are a temperature of 20 to 300°C, preferably 40 to 200'O, and a pressure of normal pressure to 70 Kf/crn2. , preferably 2 to 60 to 9/1. 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. Furthermore, two or more stages of polymerization reactions with different polymerization conditions such as hydrogen concentration and polymerization temperature can be carried out without any hindrance.

In particular, the ethylene copolymer of the present invention is preferably produced by a radical polymerization method under high pressure.

That is, the radical polymerization method under high pressure refers to a polymerization pressure of 500 to 4000 Kq/cn1, preferably 1000 Kq/cn1.
~3500K97cm, reaction temperature 50~400℃1
The monomers are contacted and polymerized simultaneously or in stages, preferably under conditions of 100 to 350° C., in the presence of a free radical catalyst, a chain transfer agent, and if necessary an auxiliary agent, in a seed or tubular reactor. It refers to the method of

The free radical catalysts include customary initiators such as peroxides, hydroberoquinides, azo compounds, amine oxide compounds, oxygen, and the like.

In addition, as a chain transfer agent, hydrogen, propylene, buteno-1
,01 to C2o or higher and halokene-substituted hydrocarbons, such as methane, ethane, propane, butane, isobutane, n-hexane, n-
Hebutane, Cyclono'7 (Class 7, Chloroform and Carbon Tetrachloride, CI-020'! or higher saturated aliphatic alcohols such as methanol, ethanol, pronognol and Inglo-Zononope CI"20 or higher) Mention may be made of the saturated aliphatic carbonyl compounds mentioned above, such as carbon dioxide, acetone and methyl ethyl ketone, as well as aromatic compounds such as evaluene, noethylbenzene and xylene.

(Actions and Effects of the Invention) The ethylene copolymer of the present invention produced as described above or the ethylene copolymer composition containing the ethylene copolymer has excellent dielectric strength as an electrical insulating material, and particularly, It is very useful as an insulating material for ultra-high voltage electrical cables because it has excellent breakdown strength against impact voltage in the high temperature range.

Further, the present invention is very superior in that it can be produced by a relatively simple process of copolymerization and does not require the conventional complicated grafting and blending steps.

In the present invention, olefin polymers (including copolymers) other than the ethylene polymer, polyacrylonitrile, polyamide, and Thermoplastic resins such as carbnate, ABSd resin, teristyrene, polyphenylene oxide, polyvinyl alcohol resin, vinyl chloride resin, vinylidene chloride resin, polyester resin, petroleum resin, coumaron-indene resin, ethylene-propylene copolymer Rubber (EPR.

EPDM, etc.), SBR, NBR, butanoene rubber, E-R1 chloroprene rubber, isoprene rubber, styrene rubber
It can be used in combination with at least one synthetic rubber such as butanoene-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 copolymer or ethylene copolymer composition 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.

(Example) Examples are shown below.

Examples 1 to 6 A predetermined amount of ethylene, various comonomers, and n-hexane as a chain transfer agent were charged into a metal autoclave equipped with a stirrer that was sufficiently purged with nitrogen, and further a di-tertiary polymerization initiator was charged. Inject butyl peroxide, pressure 1700
Various ethylene copolymers with different aromatic monomer contents as shown in Table i1 were prepared by carrying out polymerization under the following conditions: K9/cm, polymerization temperature: 170°C, 1 polymerization time:
The in-glass fracture strength of the ethylene copolymer was measured at temperatures of 200C and 80C, and the results are shown in Table 1.

Comparative Example 1 Commercially available high pressure low density polyethylene (LD) for power cables
Abbreviated as PK, product name: Nippon Sekishi Xuron W3100, manufactured by Japan Petrochemical Company, density 0.92297 cm, M, ■,
3.0 f710 minutes) was measured in the same manner as in Example 1, and the results are shown in Table 1.

In fact, the ethylene copolymers shown in Table 1 were prepared under the same polymerization conditions as in Example 1, and the in-glass fracture strength was measured. Table 1 shows the results.

Example 7 An ethylene-bennyl methacrylate copolymer having a benyl methacrylate content of 4 molt was prepared under the same polymerization conditions as in Example 1. 6 parts by weight of the ethylene copolymer and the low-density polyethylene used in Comparative Example 1÷94.0 parts by weight were kneaded using a plastograph, and the content of benyl methacrylate was 0.2.
A mulch ethylene copolymer composition was obtained. Table 1 shows the measurement results of the in- and -rus fracture strength of the above ethylene copolymer composition.

As is clear from Table 1 of the evaluation results, in Examples 1 to 7, the copolymer of the present invention was compared to conventional high-pressure process low-density 1-monitor polyethylene (comparative example 1).
This indicates that the fracture resistance is particularly poor in the high temperature region.

Further, as shown in Example 7, it can be seen that even an ethylene copolymer composition has an improvement effect as long as the benyl methacrylate content is within the range of the present invention.

On the other hand, in Comparative Examples 2 and 3, no improvement effect was observed when the benzyl methacrylate content was set outside the range of the present invention.

Note that the method for the in-gust destruction test is as follows.

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

Sample 3 was cut into approximately 8-10m square pieces and placed between the electrodes. The space between the sample and the electrode was filled with degassed resin 4 and cured. The Unamatsukeon electrode was immersed in a container filled with silicone oil, and then placed in a constant temperature bath for measurements. The voltage waveform used for destruction was negative polarity,
The waveform was observed with an oscilloscope using an impulse waveform of 1×40 μs, and the data broken at the wave front was used as data, and the average value of m points or more was taken.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing a Matsukeon electrode for impulse breakdown testing according to the present invention. ■・・・Polymethyl methacrylate substrate 2・・・
Stainless steel ball electrode 3... Sample 4... Epoxy resin patent applicant Nippon Petrochemical Co., Ltd. Figure 1

Claims (3)

[Claims] (1) Ethylene or ethylene and other ethylenically unsaturated monomers and the following formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [However, for Ar ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, where R_1 represents a hydrogen atom or a methyl group, R_2 and R_3 represent a hydrogen atom,
It represents a chlorine atom or a straight chain or branched alkyl group having 1 to 4 carbon atoms. ] In the copolymer with the comonomer shown in or the composition in which the copolymer is blended with an ethylene polymer, the content of the comonomer is in the range of 0.005 to 1 mol%. An electrical material characterized by (2) The comonomer according to claim 1, wherein the comonomer is at least one selected from the group of benzyl methacrylate, benzyl acrylate, phenylbenzyl methacrylate, and phenylbenzyl acrylate. electrical materials. (3) The pressure of the copolymer is 500 to 4000 Kg/cm
^2. The electrical insulating material according to claim 1 or 2, which is a copolymer obtained by high-pressure radical polymerization at a temperature of 50 to 400°C.