JPS6345705A - Electrically insulating material - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has excellent breakdown strength against impact voltage,
This invention relates to electrical insulating materials with excellent crosslinking properties.

[Prior Art] Various plastic materials have been used as insulating materials for power cables. In particular, low-density polyethylene produced by high-pressure radical polymerization is inexpensive, has low dielectric loss and has good processability, and can be crosslinked to improve heat resistance.Compared to ionic polymerization, low-density polyethylene is produced by the tree phenomenon caused by the contamination of foreign substances such as catalyst residues. It is widely used for power cables because it has many advantages, such as fewer concerns.

One of the problems with such cross-linked polyethylene electrical cables is the lack of dielectric strength, which results in thickening of the insulation layer of high-voltage electrical cables, which means an increase in the outer diameter of the cable, making it difficult to transport and install the cable. This poses a major obstacle.

As an attempt to improve the above-mentioned dielectric strength, a method of introducing an aromatic ring into an ethylene polymer has been proposed.

For example, 1) A method of blending an aromatic polymer such as polystyrene with polyethylene or an olefin polymer (Japanese Patent Publication No. 38-2
No. 0717, JP 50-142651@, JP 52 A.
2) A method of blending a block copolymer of styrene and conjugated dienes with polyethylene (Japanese Patent Laid-Open No. 52-41884)
3) A method of graft polymerizing styrene to polyethylene (Japanese Patent Publication No. 18760/1982), 4) A method of soaking electrical insulating oil into polyethylene (Japanese Patent Publication No. 1876/1983)
No. 938), and many others have been disclosed.

However, none of the above methods has been able to sufficiently improve dielectric strength.
In method 1), the compatibility between polyethylene or polyolefin and styrene polymer is poor. Method 2) results in a decrease in heat resistance and deterioration in extrusion processability. Method 3) not only requires complicated equipment and processes for graft polymerizing styrene onto pre-crosslinked polyethylene in order to improve the breaking strength of polyethylene against impact voltage in the high temperature range, but also It has the disadvantage that its breaking strength under impact voltage is inferior to that of untreated raw material polyethylene.

When method 4) is used for a long time -1 or due to changes in the environment, the kneaded electrical insulating oil may bleed, or the effect is inferior to the above three methods, so none of the methods is sufficient. No, it is stable over a long period of time,
The emergence of insulating materials with better performance is desired.

Further, in the crosslinking treatment for improving heat resistance, the crosslinkability of polyethylene is insufficient, and an insulating layer with high heat resistance cannot be obtained. Furthermore, since the crosslinking rate is slow, it is difficult to increase the production rate.

Therefore, an insulating material with excellent crosslinking properties is desired.

[Object of the Invention] In view of the above points, the present invention aims to provide an electrical insulating material having excellent dielectric strength and crosslinking properties compared to conventional insulating materials.

[Means for Solving the Problems] The object of the present invention is to combine ethylene or ethylene in the presence of a 1- to 3-ring aromatic compound having one carbon-carbon double bond in one molecule width and a non-conjugated diene. Polymerization pressure of 500 to 4000 kg/
ci 1 polymerization In li An ethylene copolymer obtained by high-pressure radical polymerization under conditions of 50 to 400°C, or a composition obtained by blending the copolymer with another ethylene photopolymer, The copolymer or composition contains 0.005 to 1 mol% of units derived from an aromatic compound, and the copolymer or composition has an iodine value of 0.2 to 20. This is achieved by providing an electrically insulating material that

Various types of 1- to 3-ring aromatic compounds having one carbon-carbon double bond per molecule width can be preferably used in the present invention. Particularly preferred are aromatic hydrocarbon compounds.

Representative compounds are illustrated below, but the present invention is not limited thereto.

First, styrenic monomers are representative of monocyclic aromatic compounds having one carbon-carbon double bond and one benzene ring in one molecule width.

For example, styrene, nuclear substituted styrenes (e.g. methylstyrene, dimethylstyrene, ethylstyrene, methoxystyrene, ethoxystyrene, vinylbenzoic acid, methyl vinylbenzoate, vinylbenzyl acetate, hydroxystyrene, divinylbenzene), α-substituted styrenes (
For example, α-methylstyrene, α-ethylstyrene, α
-chlorostyrene), β-substituted styrene (e.g. β-
methylstyrene, β-ethylstyrene, β-chlorostyrene), etc.

Other examples include those represented by the following general formulas (I) and (II).

General formula [wherein R4 represents an alkylene group having 1 or 2 carbon atoms, R2 is a hydrogen atom, a chlorine atom, or a carbon number 1 to 4]
does not represent a straight chain or branched alkyl group. Also, n is O
It is an integer of ~3. ] Specific compounds of the above formula (I) include furylbenzene, 4-phenyl-1-butene, allyltoluene, 4-tolylbutene-1, allyl-3eC
-butylbenzene, chloroallylbenzene and the like.

General formula [wherein R1 represents a hydrogen atom or a methyl group, R2
represents a hydrogen atom, a chlorine atom, or a straight or branched alkyl group having 1 to 4 carbon atoms. ] Specific compounds of the above formula (II) include benzyl methacrylate, methylbenzyl methacrylate, chlorobenzyl methacrylate, benzyl acrylate, methylbenzyl acrylate, and chlorobenzyl acrylate.

Typical examples include indenes such as indene and its derivatives, alkenylbenzenes and their derivatives, phenylcyclohexene, arylcycloalkenes and their derivatives.

In addition, these and styrene monomers, halogen substituted by halogen such as chlorine, methoxy group, carboxyl group, ether bond, ester bond, phenolic hydroxyl group, alcoholic Examples include oxygen-containing derivatives having a hydroxyl group, etc., derivatives having a sulfur atom, a nitrogen atom, and the like. Specific examples include methoxy-β-methylstyrene, chlorophenylcyclohexene, and phenyl vinyl ether.

Examples of the two-ring aromatic compound having one carbon-carbon double bond in one molecule width include olefins having a fused or non-fused two-ring aromatic ring.

These olefins include cyclic olefin derivatives such as cyclopentene and cyclohexene, and chain olefin derivatives. For example, such olenoins include compounds represented by the following general formulas (III) to IV). .

[In the formula, R1 is an alkenylene group or a cycloalkenylene group having one unsaturated double bond.

In addition, m and nGio are integers of ~3, m R's and n R3's are the same or different, and are hydrogen atoms or alkyl groups] General formula [wherein R4 is an alkenyl group or a cycloalkenyl group] group, and R5 is an alkylene group or a cycloalkylene group. In addition, m and n are integers of 0 to 3, and m R2 and n R3 are each the same or different, and are a hydrogen atom or an alkyl group] [In the formula, R4 is an alkenyl group or a cycloalkenyl group] It is the basis. Further, m and n are integers from 0 to 3, and m R's and n R3's are each the same or different,
They are hydrogen atoms or alkyl groups] General formula [wherein R4 is an alkenyl group or a cycloalkenyl group]. In addition, m and n are integers from O to 3, and m R's and n R3's are each the same or different,
They are hydrogen atoms or alkyl groups] The alkenylene group or cycloalkenylene group of R1 in the above formula (I [I) is ethylene, propylene, butene, isobutyne, pentene, methylpentene, hexene, cyclopentene, cyclohexene, alkylcyclohexene, etc. is a divalent substituent from which two hydrogen atoms have been removed, and the alkyl groups R2 and R3 are methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, 5ec-butyl, tert-butyl and amyl groups. etc.

Specific compounds of formula (III) include 1.1-diphenylethylene, 1,1-ditolylethylene, 1.1-dicumylethylene, 1.1-di(butylphenyl)ethylene, and 1.1-ditolylethylene. (Chlorophenyl)ethylene, 1-phenyl-1-tolylethylene, 1-phenyl-1-xylylethylene, stilbene, 4-methylstilbene, 1.
2-diphenylpropene, 1,3-diphenylpropene, 1,4-diphenylbutene-1,1,4-diphenylbutene-2,1,1-diphenylpropene-1,2,3
-diphenylpropene, 1,2-diphenylbutene-2
, 1,3-diphenylbutene-1,2,4-diphenyl-4-methylpentene-1.2.4-diphenylbutene-1,2,4-diphenylpentene-1,2,4-ditolylbutene-1, 2,4-ditolylpentene-1,2
, 4-ditolyl-4-methylpentene-1,1,2-diphenylsic, lohexene, phenylbenzylcyclohexene, and the like.

These can be produced by bilayering or bilayering of styrene or styrenes such as α-methylstyrene and vinyltoluene using a 1m solvent.

In addition, stilbene etc. can be obtained by reacting penzalde7de with benzylmagnesium bromide and dehydrating it.
-Diphenylpropene is also similar to □. Further 1,1-
Diphenylethylene can be produced by reacting diphenylketone with a Grignard reagent such as methylmagnesium iodide and dehydrating it.

R4 in the compound of formula (IV) is an alkenyl group or cycloalkenyl group such as vinyl, propenyl, isopropenyl, furyl, butenyl, cyclopentenyl, cyclohexenyl, etc., and R5 is a linear saturated aliphatic hydrocarbon or cycloalkenyl group. It is a divalent substituent obtained by removing two hydrogen atoms from a saturated alicyclic hydrocarbon such as pentane, cyclohexane, and cycloheptane. Further, R2 and R3, which are alkyl groups, are the same as R2 and R3 in formula (II).

Specific compounds of formula (IV) include 1-phenyl-1
-Styrylethane, 1-phenyl-1-styrylpropane, 1-xylyl-1-styrylethane, 1-3ec-
Butylphenyl-1-styrylethane, 1-chlorophenyl-1-styrylethane, 1-phenyl-1-(4-
vinylphenyl)ethane, 1-(4-methylphenyl)
-1-(4-vinylphenyl)ethane, 1-phenyl-
1-(4-isopropenylphenyl)ethane, phenyl-(4-vinylphenyl)methane, phenyl-(Schiff D
hexenylphenyl)methane, etc.

These can be synthesized by various synthetic chemical methods, for example,
Phenyl-(vinylphenyl)ethane etc. are produced by reacting diphenylethane with acetyl chloride using a Friedel-Krach catalyst.
It is obtained by obtaining ethane, which is then reduced with sodium borohydride or the like, and then dehydrated. Phenyl-(isopropenylphenyl)ethane and the like can be obtained by reacting phenyl-(formylphenyl)ethane with a Grignard reagent such as methylmagnesium iodide, followed by dehydration.

Furthermore, R4, which is an alkenyl group or a cycloalkenyl group in formula ('/), is the same as R4 in formula (IV), and R2 and R3 as alkyl groups are also the same as R2 and R3 in formula (IV). It is.

Specific compounds of this formula (V) include allyl biphenyl, vinyl biphenyl, 2-isopropenylbiphenyl, 4-isobrobenyl biphenyl, 2-isopropenyl-4'-isopropylbiphenyl, and cyclohexenyl biphenyl. , cyclopentenyl biphenyl, etc. Among these, for example, isopropenyl biphenyl,
It can be obtained by dehydrogenating isopropylbiphenyl.

Furthermore, R4 as an alkenyl group or a cycloalkenyl group in Formula 11 (Vl) is also R4 in Formula (IV).
4, and R2 and R3 as alkyl groups are also the same as R2 and R3 in formula (IV).

Specific compounds of this formula (Vl) include α-vinylnaphthalene, isoprobenylnaphthalene, allylnaphthalene, 1-cyclopent-2-enylnaphthalene, and the like. Among these, for example, vinylnaphthalene can be obtained by reacting formylnaphthalene with a Grignard reagent such as methylmagnesium fluoride, followed by dehydration.

Examples of other two-ring aromatic olefins include phenylbenzyl methacrylate, phenylbenzyl acrylate, arylindenes, alkylindenes, and acenaphthylenes.

Examples of three-ring aromatic olefins include the following general formulas (■) to (
Examples include those shown in XI).

[In the formula, R, R2 and R3 are hydrogen atoms or carbon atoms with 1
It is an aliphatic hydrocarbon residue that may have an ethylenic double viscosity of 1 to 4. m is an integer from 0 to 3,
n is an integer from 0 to 2. However, 1 R, m R2
And the total number of ethylenic double bonds possessed by n R3s is 1. ] Specific examples of compounds represented by the general formula (Vl) include 1-vinylanthracene, 2-vinylanthracene, 9-vinylanthracene, 2-isopropenylanthracene 1,9-propenyl- 10- [wherein R, R and R3 are hydrogen atoms or ethylenic dihydrogen atoms having 1 to 4 carbon atoms]
is an aliphatic hydrocarbon residue that may have a bond,
1. m is an integer of 0 to 3, and n is an integer of 0 to 2. However, the total number of ethylenic double bonds of one R, m R2, and nl1 R3 is 1. ] Specific examples of compounds represented by the general formula (■) include:
Examples include 2-vinylphenanthrene, 3-isoprobenylphenanthrene, 3-vinylphenanthrene, and 9-vinylphenanthrene.

(R2), (R3).

[In the formula, R1 is an aliphatic hydrocarbon residue having 1 to 4 carbon atoms and may have an ethylenic double bond, and R2-R4
is an aliphatic hydrocarbon residue that may contain a hydrogen atom or an ethylenic double bond having 1 to 4 carbon atoms. kG,
t O or 1, and 1, m, and n are each integers of O to 3. However, R1m R3 and n of R,1@
The combination of R4 ethylenic double bonds J1 is 1] Specific examples of compounds represented by the general formula <IX) include 1-phenyl-2-(1-naphthyl)ethylene, 1- Phenyl-2-(2-naphthyl)ethylene, 1-phenyl-1-(1-naphthyl)ethylene, 1-phenyl-1-
(2-naphthyl)ethylene, 1-phenyl-1-(1-
Examples include naphthyl)propene, 1-phenyl-1-(2-naphthyl)propene, 1-phenyl-2-(2-naphthyl)propene, and 1-(1-naphthyl)-2-0-tolylethylene.

General formula [wherein R and R2 are aliphatic hydrocarbon residues having 1 to 4 carbon atoms that may have an ethylene double bond, and R
3-R5 is a hydrogen atom or an aliphatic hydrocarbon residue having 1 to 4 carbon atoms and which may have an ethylenic double bond.

j and k are 0 or 1; 1. m and n are O~
It is an integer of 3. However, the total of the ethylenic double bonds of R, R2, 1 R3, m R4 and n R5 is 1
] Specific examples of compounds represented by the above general formula (X) include 2-phenylstilbene, 4-phenylstilbene, 1-phenyl-1-biphenylethylene, 4-benzylstilbene, 1-biphenyl- 4-yl-1-p-tolylethylene, 1-biphenyl-4-yl-2-phenylpropene, 1-phenyl-2-(4-benzylphenyl)propene, 1-phenyl-1-(benzylphenyl)ethylene, Examples include 1-tolyl-1-(benzylphenyl)ethylene and 1-phenyl-1-(phenylnibru-phenyl)ethylene.

[In the formula, R1 is an aliphatic hydrocarbon residue having 1 to 4 carbon atoms that may bind an ethylenic double bond, and 1(
~R4 is a hydrogen atom or an aliphatic hydrocarbon residue having 1 to 4 carbon atoms and which may have an ethylenic double bond. Also, 1. m and n are integers from O to 3. However, R
The total number of ethylenic double bonds of 11 R1m R and n R4 is 1] Specific examples of compounds represented by the above general formula (XI) include 1,1.2- Triphenylethylene, 1.1.2
-triphenylpropene, 1.1.3-triphenylbutene, 1.1-diphenyl-2-0-tolylethylene,
1.1-diphenyl-2-p-tolylethylene and 3
．． 3.3-triphenylpropene-1 and the like.

The above-mentioned compounds are exemplified as those that can be applied to the production of the electrically insulating material of the present invention, and the present invention is not limited only to these.

These aromatic olefins can be synthesized by various synthetic chemical methods,
For example, it can be obtained by producing alcohol using the Grignard reaction and dehydrating it.

For example, 1-phenyl-1-naphthylethylene is obtained by reacting the Grignard reagent from bromonaphthalene with 7cetophenone and dehydrating the resulting 1-phenyl-1-naphthylethanol. Moreover, vinyl anthracene can be obtained by reacting Grignard 1tlFi from bromo anthracene with acetaldehyde and dehydrating the obtained hydroxyethyl anthracene.

Furthermore, the above-mentioned aromatic olefin can also be produced by dehydrating an aromatic hydrocarbon that is saturated, that is, does not have an ethylenic bicity bond.

That is, as a method using a dehydrogenation reaction, it is possible to produce a saturated aromatic hydrocarbon having three or more integrated or non-fused aromatic rings by dehydrogenating it using an appropriate dehydrogenation catalyst. can.

Note that diolefins can also be produced from monoolefins. During dehydrogenation, side reactions such as polymerization are suppressed, but if an aromatic hydrocarbon having three fused or non-fused aromatic rings is produced, side reactions such as decomposition reactions may occur. .

The dehydrogenation catalyst is not particularly limited and any catalyst can be used. For example, Cr, Fe, Cu, K, MI
J.

Examples include one or a mixture of two or more gold BM compounds such as Ca, noble metals such as Pt and Pd, and dehydrogenation catalysts in which these metal oxides and noble metals are supported on a carrier such as alumina.

The temperature of the dehydrogenation reaction is 350 to 650°C, preferably 4
00-600°C. L HS V Ha, 0.2~1
0, preferably 0.5 to 3.0. Further, during dehydrogenation, a gas such as water vapor, nitrogen, or hydrogen may be present in order to lower the partial pressure or to prevent carbon precipitation. Moreover, an appropriate diluent can also be used if necessary. However, it is usually advantageous if the dehydrogenation rate is not so high because the raw material I itself can serve as a diluent.

Through the above dehydrogenation, ethyl anthracene is produced from ethyl anthracene, phenylnaphthyl ethylene is produced from phenylnaphthylethane, and phenylstilbene is produced from phenyl biphenylylethane.

In addition to the above examples, examples of the three-ring aromatic olefin include diarylindenes, dialkylindenes, and terphenyls.

Derivatives of the above-mentioned 2- to 3-ring aromatic olefins include halogen substituted products such as chlorine and bromine, oxygen-containing derivatives having methoxy groups, carboxyl bonds, ester bonds, phenolic hydroxyl groups, alcoholic hydroxyl groups, etc., sulfur atoms, and nitrogen atoms. Examples include derivatives having

In addition to the aromatic olefins of formulas (I) to (X) and their derivatives, double bonds such as unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and fumaric acid, or vinyl esters, etc. Biphenyl, naphthalene, diarylalkanarylsiakanthrene, arylnaphthalene, 7ralkylnaphthalene,
Aromatic compounds to which a 2- to 3-ring aromatic FA ring t\i position such as terphenyl or a derivative thereof is bonded can also be used.

All of the above-mentioned aromatic compounds have structural characteristics that can be included as polymer components in the polymer chain produced by high-pressure radical polymerization of ethylene or a mixture with other monomers containing ethylene as the main component. have.

Among these various aromatic compounds, monocyclic aromatic compounds are preferred. Among these monocyclic aromatic compounds, styrene compounds are most preferred.

The non-conjugated diene used in the present invention is one having 5 to 15 carbon atoms, and specifically includes alkenyl norbornene such as cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinyl-2-norbornene, 5-vinyl-2-norbornene, etc. -ethylidene-2-norbornene, 5-methylene-
alkylidene norbornene such as 2-norbornene, 5-isopropylidene-2-norbornene, cyclic non-conjugated dienes such as alkenylcyclohexene such as 6-chloromethyl-5-isobenyl-2-norbornene, norbornadiene, 4-vinylcyclohexene, etc.;
．． 4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-hebutadiene, 7-methyl-1,6-octadiene, 1.5
- Chain nonconjugated dienes such as hexadiene and the like can be exemplified.

Among the above-mentioned non-conjugated dienes, cyclic non-conjugated dienes are preferred, and 5-vinyl-2-norbornene and 5-1 thylidene-2-norbornene are particularly preferred.

Further, the ethylenically unsaturated monomers of the present invention include propylene, butene-1, hexene-1,4-methylpentene-1
, olefins having 3 to 10 carbon atoms such as octene-1 and decene-1, styrene, vinyl esters of C2 to C3 alkane carboxylic acids, ar-glyric acid or methyl methacrylate, acrylic acid or methacrylic acid ethyl,
Acrylic acid or methacrylic acid esters such as propyl acrylic acid or methacrylate, glycidyl acrylate or glycidyl methacrylate; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and maleic anhydride; At least one selected from the group of anhydrides thereof, ethylenically unsaturated carboxylic acid amides such as acrylamide, methacrylic acid amide, maleic acid amide and fumaric acid amide, etc.
It is a seed.

The content of the above ethylenically unsaturated monomer is 0 to 10 mol%
, preferably in the range of 0 to 7 mol%, more preferably 0 to 5 mol%.

The ethylene copolymer of the present invention is produced by a radical polymerization method under high pressure. In other words, the radical polymerization method under high pressure is a polymerization pressure of 500 to 4000 kg/
CD, preferably 1000-3500! F/cj
, reaction temperature 50~400℃, preferably G, 1100~
Ethylene and the aromatic compound, and if desired other monomers, are reacted simultaneously or at 350° C. in a seed or tube reactor in the presence of a free radical catalyst and a chain transfer agent, if necessary auxiliaries. A method of contacting and polymerizing in stages. When the aromatic compound is solid, it is dissolved in a solvent and supplied.

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

In addition, as a chain transfer agent, hydrogen, propylene, butene-1
, c -C2° or higher saturated aliphatic hydrocarbons and halogen-substituted hydrocarbons, such as methane, ethane, butane, butane, isobutane, n-hexane, n-
Hebutane, cycloparaffins, chloroform and carbon tetrachloride, saturated aliphatic alcohols of 01 to 20 or more, such as methanol, ethanol, propatool and isopropanol, C-C2o or more saturated aliphatic Included are carbonyl compounds such as acetone and methyl ethyl ketone.

The mt content of the aromatic compound in the ethylene copolymer of the present invention is suitably 0□005 to 1 mol, preferably 0.01 to 0.7 mol, per 100 mol of ethylene.
- When the amount of the aromatic compound is less than 0,005 mol, almost no effect of improving dielectric strength is seen, and when it exceeds 1.0 mol, the dielectric strength not only decreases compared to when no aromatic compound is contained, but also It is uneconomical due to the large consumption of initiators for high-pressure radical polymerization and the use of large amounts of expensive aromatic compounds, and the chain transfer reaction becomes intense, resulting in a significant decrease in the molecular weight of the ethylene copolymer. This makes the polymer unsuitable as an insulating material.

Further, the iodine value of the ethylene copolymer in the present invention is 0.
2 to 20 is appropriate. When the iodine number is less than 0.2, no improvement in crosslinking properties is observed, and therefore no improvement in heat resistance is observed. If it exceeds 20, the crosslinking efficiency will reach saturation and the heat resistance will not be improved any further. The density of the ethylene copolymer in the present invention is 0.890 to
A range of 0.950g/as3 is desirable. In addition, the melt index (hereinafter abbreviated as Ml) is 0.05 to 50g/
10 minutes, preferably 0.1 to 20 g/10 minutes, more preferably 0.2 to 109/10 minutes.

The ethylene copolymer of the present invention can be used in combination with an ethylene polymer that does not contain other aromatic units or non-conjugated dienes. Compositions containing other ethylene polymers are also preferred embodiments of the present invention, and by having the aromatic unit content and iodine value in the composition within the above range, the dielectric strength and heat resistance of the composition are improved. Improved.

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

[Action and Effect of the Invention] The ethylene copolymer produced by Wg as described above or the composition containing the ethylene copolymer has excellent dielectric strength as an electrical insulating material, has a high crosslinking rate, and has excellent heat resistance. Therefore, it is very useful as an insulating material for ultra-high voltage electrical cables.

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

In the present invention, olefin polymers (including copolymers) other than the other ethylene polymers, polyacrylonitrile, polyamide, etc. , thermoplastic resins such as polycarbonate, ABS resin, polystyrene, 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.

It can be used in combination with at least one synthetic rubber or natural rubber such as butadiene rubber, IIR, chloroprene rubber, isoprene rubber, and styrene-butadiene-styrene block copolymer.

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 polymer composition of the present invention may be used as is without crosslinking, or may be subjected to crosslinking treatment if necessary. A normal crosslinking method is applied to the crosslinking method.

[Examples] Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these Examples unless it departs from the gist of the present invention. It should be noted that throughout this specification, all references are to degrees Celsius, and parts and percentages are by weight unless otherwise specified.

Examples 1 to 15 Into a stirrer-equipped gold Jiil J autoclave reactor with an internal volume of 3°8j, which was sufficiently purged with nitrogen and ethylene, about 1,7009 ml of ethylene, the aromatic compounds and nonconjugated dienes shown in Table 1, and A predetermined amount of n-hexane was charged, di-tert-butyl peroxide as a polymerization initiator was added, and the polymerization temperature was 170°C and the polymerization pressure was 16°C.
000/cd and gA during polymerization for 60 minutes to prepare various ethylene polymers as shown in Table 1.

A part of the produced polymer was dissolved in heated carbon tetrachloride and reprecipitated by pouring it into a large amount of acetone. This operation was repeated several times to produce a polymer, which was then vacuum dried.

The purified polymer was molded into a sheet with a thickness of 500 μm by heat compression, and the origin of aromatic compounds in each produced polymer was determined by infrared spectroscopy using a compensation method using a sheet of ethylene homopolymer of the same thickness as a control. The unit was 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 aromatic ring around 1600cII-'. In addition, the measurement of the melt index of each produced polymer is based on JIS-67.
The test was carried out in accordance with 60.

In addition, the impulse breaking strength was measured by the following method. The sample was made into a sheet with a thickness of 50 μm by heat compression molding. A fixed electrode, a so-called Matskeon electrode (Fig. 1), was used as the electrode system. The electrode system substrate 4 is made of polymethyl methacrylate and has a hole with a diameter of 1/2 inch in its center. A 1×2 inch stainless steel bulb 1 was used as the electrode. Sample 2 was cut into a square of approximately 8 to 10 JW and sandwiched between the electrodes. A degassed epoxy resin 3 was filled between the sample 2 and the electrode and cured. The Matsukeon electrode was immersed in a container filled with silicone oil, and then placed in constant temperature baths at 20° C. and 80° C. for measurement.

The voltage waveform used for destruction was a negative 1X 40JIs 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.

The gel fraction was determined by adding 1.5 parts by weight of dicumyl peroxide to 100 parts by weight of ethylene copolymer, forming a sheet with a thickness of 1 JIII, cross-linking at 165°C for 30 minutes, then crushing into 20 mesh passes, heating at 120°C with xylene, 10:00 11Il
The remaining hb release rate was determined.

The heat deformation rate was calculated using a cylindrical sample with a diameter of 10a*φ and a thickness of 6M, which was cross-linked in the same manner as when determining the gel fraction.
It was pressurized with a load of 2.64 psi in an oil bath at ℃, and the deformation rate after 30 minutes was determined.

The above results are shown in Table 1.

Comparative Example 1 Low density polyethylene was produced under the same conditions as in Example 1, and the physical properties of the polymer were measured in the same manner as in Example 1. The results are shown in Table 1.

Friend 11 Once the ethylene-styrene-5-vinyl-2-norbornene copolymer was prepared under the same conditions as in Example 1, and 5 parts by weight of the ethylene copolymer and 95 parts by weight of the low-density polyethylene used in Comparative Example 1 were added. Part a was kneaded using a blastograph to obtain an ethylene copolymer composition containing styrene, ii1G, 09 mol %, and an iodine value of 0.7. Table 1 shows the results of physical property measurements.

1 direct N 17 Containing benzyl methacrylate ff in the same manner as in Example 16
An ethylene copolymer composition having an iodine value of 0.9 and an iodine value of 0.9 was obtained. Table 1 shows the results of physical property measurements.

Kandan M2el Ethylene copolymers shown in Table 1 were prepared under the same polymerization conditions as in Example 1, and their physical properties were measured.

[Evaluation Results] As is clear from Table 1, in Examples 1 to 17, the copolymers of the present invention had superior impulse rupture strength, especially in the high temperature range, compared to the conventional low-density polyethylene produced by low-density process (Comparative Example 1), and had a higher gel content. This shows that it is also superior in terms of heat deformation rate and thermal deformation rate.

On the other hand, in Comparative Examples 2 to 7, when the aromatic compound content and iodine value were outside the range of the present invention, no improvement effect was observed.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing a Matsukeon electrode for impulse breakdown testing according to the present invention. 1... Stainless steel ball 2... Sample 3...
Epoxy resin

Claims (5)

[Claims] (1) 1~ having one carbon-carbon double bond in one molecule width
In the presence of a 3-ring aromatic compound and a non-conjugated diene, ethylene or a mixture of ethylene and an ethylenically unsaturated monomer is subjected to high pressure at a polymerization pressure of 500 to 4000 kg/cm^2 and a polymerization temperature of 50 to 400°C. An ethylene copolymer obtained by radical polymerization or a composition obtained by blending the copolymer with another ethylene polymer, wherein the copolymer or composition contains units derived from an aromatic compound. An electrically insulating material characterized in that the copolymer or composition contains 0.005 to 1 mol% of iodine, and the iodine value of the copolymer or composition is in the range of 0.2 to 20. (2) The electrical insulating material according to claim 1, wherein the aromatic compound is a monocyclic aromatic compound. (3) The electrical insulating material according to claim 2, wherein the monocyclic aromatic compound is a styrene compound. (4) The electrically insulating material according to any one of claims 1 to 3, wherein the nonconjugated diene is a cyclic nonconjugated diene. (5) The electrically insulating material according to claim 4, wherein the cyclic nonconjugated diene is 5-vinyl-2-norbornene or 5-ethylidene-2-norbornene.