JPH0917235A - Electrical insulating material and electronic power cable employing the electric insulating material - Google Patents

Abstract

PURPOSE: To make volume resistivity high, and temperature dependability low by letting the electrical insulating material be made out of ethylene (co)polymer the density, a melt flow rate and electrical activation energy of which is in a specified range, and of resin containing other polyolefin. CONSTITUTION: This invention is concerned with electrical insulating material which is made out of 2 to 100% ethylene (co)polymer by weight where its density is 0.86 to 0.97g/cm<3> , its melt flow rate(MFR) is 0.01 to 200g/10min and its electrical activation energy is less than 0.4 (eV), and of resin containing 0 to 98% other polyolefin by weight. Ethylene (co)polymer the density of which is less than or equal to or more than the aforesaid rang, is practically hard to manufacture. When a MFR is less than the aforesaid range, its forming processability is inferior, and when the MFR exceeds the specified range, its mechanical strength such as impact resistance and the like are inferior. And the ethylene (co)polymer the electrical activation energy of which exceeds the aforesaid range, is high in temperature dependability for volume resistivity.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a novel ethylene (co)
The present invention relates to an electrical insulating material having a high volume resistance and excellent electrical characteristics, which is composed of a polymer and a composition of the polyolefin and another polyolefin, and a high voltage power cable using the same.

[0002]

2. Description of the Related Art Conventionally, high-voltage polyethylene and cross-linked polyethylene have been widely used as insulators for high-voltage power cables because of their excellent electrical characteristics. One of the problems of high voltage power cables is power loss during high voltage power transmission, and reducing it is an important issue. One means of reducing this power loss can be achieved by increasing the high voltage characteristics of the insulating material, especially the volume resistance. However, in the insulator for a power cable, the temperature is high (about 90 ° C.) near the inner conductor due to Joule heat due to current, but the temperature is the outside air (about 20 ° C.) near the outer conductor. With conventional polyethylene, the volume resistance decreases significantly with increasing temperature, so the volume resistance near the inner conductor where current is flowing decreases significantly, and the electric field concentrates near the outer conductor-insulator interface, causing a breakdown value. Is reduced. This phenomenon becomes a serious problem especially in DC power cables. For this reason, a material whose volume resistance has a small temperature dependence is desired. The use of high-voltage polyethylene as a high-voltage cable insulator has a drawback that it has a low melting point and poor electrical characteristics at high temperatures. On the other hand, the conventional low-pressure polyethylene having a high melting point also has the drawback that it does not have excellent electrical characteristics due to the influence of catalyst residues and is inferior in flexibility. A method of grafting and improving maleic anhydride in order to improve the electrical properties of low-pressure polyethylene has been proposed (for example, Japanese Patent Application Laid-Open No. 2-10610), but it is not always satisfactory including the problem of flexibility. Not going. Furthermore, as a material having excellent heat resistance and flexibility and high volume resistance, low density polyethylene having a density of 0.92 g / cm ³ and density of 0.
An insulator (Japanese Patent Laid-Open No. 5-266723) obtained by blending 0.5 parts by weight or more and 20 parts by weight or less of linear low-density polyethylene of 91 to less than 0.94 g / cm ³ is disclosed. However, the above composition is still not sufficiently satisfactory because the volume resistance near the inner conductor has a large temperature dependency.

[0003]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an insulating resin which comprises an ethylene (co) polymer alone or a composition of the same with another polyolefin and which has a high volume resistance and a small volume resistance with temperature dependence. To provide the material.

[0004]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in view of the above objects, an ethylene (co) polymer having a specific electric activation energy and a composition of the ethylene (co) polymer and another polyolefin The above object was achieved by using

That is, the first aspect of the present invention is that (I) (A) has a density of 0.86 to 0.97 g / cm ³ ,
(B) Melt flow rate (MFR) is 0.01 to 20
Ethylene (co) polymers 100 to 2 having an electric activation energy of 0.4 (eV) or less at 0 g / 10 min.
An electrical insulating material comprising a resin containing 0 to 98% by weight of (II) another polyolefin.

A second aspect of the present invention is that the ethylene (co) polymer has an (A) density of 0.86 to 0.96 g / cm ³ , (B).
Melt flow rate 0.01-200g / 10min,
(C) Molecular weight distribution (Mw / Mn) 1.8-4.5,
(D) Composition distribution parameter Cb 1.08 to 2.00,
(E) Ortho-dichlorobenzene (ODC at 25 ° C
B) When the amount X (% by weight) of the soluble component and the density d and MFR are (1) d-0.008 × logMFR ≧ 0.93, X <2.0, (2) d-0.008 × logMFR
<0.93, X <9.8 × 10 ³ × (0.930
It is 0-d + 0.008xlogMFR) ² + 2.0, and is an ethylene / alpha-olefin copolymer whose electric activation energy is 0.4 (eV) or less, It is characterized by the above-mentioned. It is an electrical insulating material.

A third aspect of the present invention is a power cable using the above-mentioned electric insulating material as an insulator.
The electrical insulating material referred to in the present invention includes those obtained by crosslinking the above resin.

The present invention will be described in more detail below. The (I) ethylene (co) polymer of the present invention includes an ethylene homopolymer or a copolymer of ethylene and one or more kinds selected from α-olefins having 3 to 20 carbon atoms. Particularly in the ethylene / α-olefin copolymer, an ethylene / α-olefin copolymer satisfying specific parameters is preferable. The α-olefin having 3 to 20 carbon atoms is preferably 3 to 12 and specifically includes propylene, 1-butene, 4-methyl-1-pentene,
1-hexene, 1-octene, 1-decene, 1-dodecene and the like can be mentioned. The total content of these α-olefins is usually 30 mol% or less, preferably 2 mol% or less.
It is desirable to select in the range of 0 mol% or less.

The (A) density of the ethylene (co) polymer (I) of the present invention is 0.86 to 0.97 g / cm ³ , preferably 0.88 to 0.96 g / cm ³ , and particularly used alone. In that case, 0.90 to 0.93 g / cm ³ is a preferable range. Density less than 0.86 g / cm ³ or 0.
Those exceeding 97 g / cm ³ are difficult to practically manufacture.

The (B) MFR of the (I) ethylene (co) polymer of the present invention is 0.01 to 200 g / 10 min, preferably 0.1 to 100 g / 10 min, more preferably 0.2 to 50 g / 10 min. It is desirable to be in the range. If the MFR is less than 0.01 g / 10 min, the moldability will be poor, and if it exceeds 200 g / 10 min, the mechanical strength such as impact resistance will be poor.

When the (I) ethylene (co) polymer is an ethylene / α-olefin copolymer, (C) the molecular weight distribution Mw / Mn is 1.8 to 4.5, more preferably 2.0 to
3.5. When used alone, Mw / Mn is 1.
If it is less than 8, the moldability may be poor. In addition, Mw / M
The method of calculating n is to determine the weight average molecular weight (Mw) and the number average molecular weight (Mn) by gel permeation chromatography (GPC), and then determine the ratio Mw / Mn.

When the (I) ethylene (co) polymer of the present invention is an ethylene / α-olefin copolymer, the (D) composition distribution parameter Cb is 1.08 to 2.00, more preferably 1.10 to 10. 1.70, more preferably 1.12
It is desirable to use one in the range of 1.50.

The method for measuring the composition distribution parameter Cb of the ethylene / α-olefin copolymer of the present invention is as follows.

A heat resistance stabilizer is added to the sample, and the sample is heated and dissolved in orthodichlorobenzene (ODCB) at 135 ° C. so that the sample concentration becomes 0.2% by weight. This heated solution is transferred to a column packed with diatomaceous earth (Celite 545), filled and cooled to 25 ° C at 0.1 ° C / min to deposit and deposit a sample on the surface of Celite. Next, while flowing ODCB through the column at a constant flow rate, the column temperature was increased by 12 ° C. every 5 ° C.
While gradually increasing the temperature to 0 ° C., a solution in which the sample is dissolved is collected at each temperature. After cooling the solution, the sample is reprecipitated with methanol, filtered and dried to obtain samples at each elution temperature. The weight fraction and the degree of branching (the number of branches per 1000 carbon atoms) of the separated sample are measured. The degree of branching is measured by 13C-NMR.

For each fraction collected from 30 ° C. to 90 ° C. by such a method, the degree of branching is corrected as follows. That is, the degree of branching measured against the elution temperature is plotted, and the correlation is approximated to a straight line by the least square method,
Create a calibration curve. The correlation coefficient of this approximation is large enough.
The value obtained from this calibration curve is defined as the degree of branching of each fraction. Note that, for a fraction collected at an elution temperature of 95 ° C. or higher, this correction is not performed because a linear relationship is not always established between the elution temperature and the degree of branching.

Next, the weight fraction wi of each fraction is determined by the change amount (b) of the branching degree bi per elution temperature of 5 ° C.
_i- b _i-1 ) to obtain the relative concentration ci, and plot the relative concentration against the branching degree to obtain a composition distribution curve. This composition distribution curve is divided by a certain width, and the composition distribution parameter Cb is calculated from the following equation.

[0017]

(Equation 1)

Here, C _j and b _j are the relative density and branching degree of the j-th section, respectively. Composition distribution parameter Cb
Is 1.0 when the composition of the sample is uniform, and the value increases as the composition distribution spreads.

Many methods have been proposed for describing the composition distribution of ethylene / α-olefin copolymers. For example, in Japanese Patent Application Laid-Open No. 60-88016, numerical processing is performed on the assumption that the cumulative weight fraction has a specific distribution (log normal distribution) with respect to the number of branches of each separated sample obtained by solvent separation of the sample. The ratio between the weight average branching degree (Cw) and the number average branching degree (Cn) is determined. The accuracy of this approximation calculation decreases when the number of branches of the sample and the cumulative weight fraction deviate from the lognormal distribution, and when the measurement is performed on commercially available linear low density polyethylene, the correlation coefficient R ₂ is considerably low, and the accuracy of the value is Not enough. This Cw / Cn and Cb of the present invention have different definitions and measurement methods.

When the (I) ethylene (co) polymer of the present invention is an ethylene / α-olefin copolymer, (E) 25 ° C.
The relationship between the amount X (% by weight) of the ODCB soluble component and the densities d and MFR in (3) is (1) d-0.008 × logMF.
When R ≧ 0.93, X <2.0, (2) d−0.00
If 8 × log MFR <0.93, X <9.8 × 10
³ x (0.9300-d + 0.008 x logMFR)
^It is desirable to use the one that is ² +2.0.

The amount of the ODCB-soluble component at 25 ° C. indicates the proportion of the highly branched component and the low molecular weight component contained in the ethylene / α-olefin copolymer.
The amount of the B-soluble component is influenced by the content of the α-olefin and the average molecular weight of the entire copolymer, that is, the density and the MFR. (F) When the amount X of the ODCB-soluble component at 25 ° C exceeds the above range, the proportion of the highly branched component and the low molecular weight component is high. In the case of the conventional Ziegler-catalyzed ethylene / α-olefin copolymer, this value exceeds the above range.

The ODCB-soluble component X at 25 ° C. is measured by the following method. That is, sample 0.
5 g is added to 20 ml of ODCB and heated at 135 ° C. for 2 hours to completely dissolve the sample, and then cooled to 25 ° C. After leaving this solution at 25 ° C. overnight, the filtrate is collected by filtering through a Teflon filter. Infrared spectroscopic analysis was performed on the filtrate, which is a sample solution, by the wavenumber 2925c of asymmetric stretching vibration of methylene.
The absorption peak intensity around m ⁻¹ is measured, and the sample concentration in the filtrate is calculated from the calibration curve prepared in advance. From this value, the ODCB-soluble matter at 25 ° C. is determined.

In the case where the (I) ethylene (co) polymer of the present invention is an ethylene / α-olefin copolymer, (F) the elution temperature-elution amount curve determined by the continuous temperature rising elution fractionation method (TREF) It is desirable that there are a plurality of peaks (F), and that the peak on the higher temperature side be present between 85 ° C and 100 ° C. FIG. 1 shows the elution temperature-elution amount curve of the copolymer of the present invention. FIG. 2 is an elution temperature-elution amount curve of a copolymer with a typical metallocene catalyst, and the two are clearly different.

The TREF measuring method according to the present invention is as follows. A heat-resistant stabilizer is added to the sample, and the sample is heated and dissolved at 135 ° C. in ODCB so that the sample concentration becomes 0.05% by weight. After pouring 5 ml of this heated solution into a column filled with glass beads, it is cooled to 25 ° C. at a cooling rate of 0.1 ° C./min to deposit a sample on the surface of the glass beads. Next, while flowing ODCB at a constant flow rate through this column, the column temperature is raised at a constant rate of 50 ° C./hr to sequentially elute the sample soluble in the solution at each temperature.
At this time, as for the sample concentration in the solvent, the absorption of the asymmetric stretching vibration of methylene at a wave number of 2925 cm ⁻¹ is continuously detected by an infrared detector. From this concentration, an elution temperature-elution amount curve can be obtained. In the TREF analysis, a change in the elution rate with respect to a temperature change can be continuously analyzed with a very small amount of sample, so that relatively fine peaks that cannot be detected by the fractionation method can be detected.

The electrical activation energy of the (I) ethylene (co) polymer of the present invention must be 0.4 (eV) or less, preferably 0.3 (eV) or less. 0.4 (e
Those exceeding V) have large temperature dependence of volume resistance.

The activation energy is one of the constants included in the Arrhenius equation expressing the temperature change of the rate constant in the process of transport phenomenon, and transitions in the process from the original system to the transition system to the production system. It corresponds to the energy difference between the state and the state of the original system. In particular, electrical activation energy is used in the Arrhenius equation that shows the temperature dependence of current. Here, the small activation energy indicates that the temperature dependence of the current is small. The method of measuring activation energy according to the present invention is as follows. The activation energy can be obtained from the following equation (Arrhenius equation). I ∝ exp (-U / kT) (I: current, U: activation energy, k: Boltzmann constant, T: absolute temperature) Using the above equation, volume resistance measurement at room temperature (20 ° C) and 90 ° C Calculate using current value at time. The method for measuring the volume resistance will be described later.

The ethylene (co) polymer (I) of the present invention may be produced by a known Ziegler catalyst, Phillips catalyst, metallocene catalyst or the like, but the above-mentioned (A) is particularly preferable.
The most preferable one satisfying all of (F) to
It is desirable to polymerize with a catalyst composed of 1 to H5. That is, H1: general formula Me ¹ R ¹ _p (OR ² ) _q X ¹
A compound represented by _4-pq (wherein Me ¹ represents zirconium, titanium, and hafnium, R ¹ and R ² each represent a hydrocarbon group having 1 to 24 carbon atoms, X ¹ represents a halogen atom, and p 1 , Q are integers that satisfy the ranges of 0 ≦ p <4 and 0 ≦ p + q ≦ 4, respectively, and H2: general formula Me ² R ³ _m (O
R ⁴ ) _n X ² _z-m-n A compound (in the formula, Me ²
Is a Group I to III element of the periodic table, R ³ and R ⁴ are each a hydrocarbon group having 1 to 24 carbon atoms, X ² is a halogen atom or a hydrogen atom (provided that when X ² is a hydrogen atom, Me ² is (Only in the case of a Group III element of the periodic table), and z is M
represents the valence of e ² , and m and n are 0 ≦ m ≦ z and 0 ≦, respectively.
An integer satisfying the range of n ≦ z, and 0 ≦ m + n ≦
z), H3: an organic cyclic compound having a conjugated double bond, and H4: a modified organoaluminum compound containing an Al-0-Al bond obtained by the reaction of an organoaluminum compound and water, H5: an inorganic carrier and / or Alternatively, it is a catalyst obtained by bringing the particulate polymer carriers into contact with each other.

The above catalyst component (H1) has the general formula Me ¹ R ¹
wherein Me ¹ of _{^{p (OR 2) q X 1}} 4-p-q compounds represented by represents zirconium, titanium, Hauniumu. The type of these transition metals is not limited, and a plurality of transition metals can be used. However, it is particularly preferable that zirconium having excellent weather resistance of the copolymer is contained. R ¹ and R ² are each a hydrocarbon group having 1 to 24 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and specifically, methyl group, ethyl group, propyl group, isopropyl group. , Alkyl groups such as butyl group; alkenyl groups such as vinyl group and allyl group; aryl groups such as phenyl group, tolyl group, xylyl group, mesityl group, indenyl group, naphthyl group; benzyl group, trityl group, phenethyl group, styryl group Group, benzhydryl group, phenylbutyl group, aralkyl group such as neophyl group, and the like. These may have branches. X ¹ represents a halogen atom such as fluorine, iodine, chlorine and bromine, and p and q satisfy the ranges of 0 ≦ p <4, 0 ≦ q <4, 0 ≦ p + q ≦ 4, and preferably 0 ≦ p + q ≦ The range is 4.

Examples of the compound represented by the above general formula of the catalyst component (H1) include tetramethylzirconium, tetraethylzirconium, tetrabenzylzirconium, tetrapropoxyzirconium, tripropoxymonochlorozirconium, dipropoxydichlorozirconium,
Examples thereof include tetrabutoxyzirconium, tributoxymonochlorozirconium, dibutoxydichlorozirconium, tetrabutoxytitanium, and tetrabutoxyhafnium. These may be used as a mixture of two or more.

The above catalyst component (H2) has the general formula Me ² R ³
_m ^(OR ₄₎ wherein Me ² in n ^X compounds represented by _{2 z-m-n} represents the periodic table I~III group element, lithium, sodium, potassium, magnesium, calcium, zinc, boron, Such as aluminum. R ³ and R ⁴ are each a hydrocarbon group having 1 to 24 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms. Specifically, methyl group, ethyl group, propyl group, isopropyl group, Alkyl groups such as butyl group; alkenyl groups such as vinyl group, allyl group; aryl groups such as phenyl group, tolyl group, xylyl group, mesityl group, indenyl group, naphthyl group; benzyl group, trityl group, phenethyl group, styryl group , And aralkyl groups such as benzhydryl group, phenylbutyl group, and neofuryl group. These may have branches. X ² represents a halogen atom such as fluorine, iodine, chlorine and bromine, or a hydrogen atom. However, when X ² is a hydrogen atom, Me ² is limited to a group III element of the periodic table exemplified by boron, aluminum and the like. Further, z represents the valence of Me ² , m and n are integers satisfying the ranges of 0 ≦ m ≦ z and 0 ≦ n ≦ z, and 0 ≦ m + n ≦ z.

Examples of the compound represented by the above general formula of the catalyst component (H2) include organic lithium compounds such as methyllithium and ethyllithium; dimethylmagnesium, diethylmagnesium, methylmagnesium chloride,
Organomagnesium compounds such as ethylmagnesium chloride; Organozinc compounds such as dimethylzinc and diethylzinc; Organoboron compounds such as trimethylboron and triethylboron; Trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, tridecylaluminum, diethyl Examples thereof include derivatives of organic aluminum compounds such as aluminum chloride, ethyl aluminum dichloride, ethyl aluminum sesquichlorite, diethyl aluminum ethoxide, and diethyl aluminum hydride.

The organic cyclic compound having a conjugated double bond of the catalyst component (H3) is a cyclic ring having two or more conjugated double bonds, preferably 2 to 4 and more preferably 2 to 3. It has 1 or 2 or more, and the total carbon number is 4 to 2.
4, preferably 4 to 12 cyclic hydrocarbon compounds; wherein the cyclic hydrocarbon compounds are partially 1 to 6 hydrocarbon residues (typically, alkyl groups or aralkyl groups having 1 to 12 carbon atoms) A cyclic hydrocarbon compound substituted by; a compound having 2 or more, preferably 2 to 4, more preferably 2 to 3 rings having a conjugated double bond and having a total carbon number of 4 to 24 An organosilicon compound having a cyclic hydrocarbon group which is preferably 4 to 12; said cyclic hydrocarbon group being partly substituted with 1 to 6 hydrocarbon residues or an alkali metal salt (sodium or lithium salt) Includes organosilicon compounds. Particularly preferably, those having a cyclopentadiene structure in any of the molecules are desirable.

Examples of the above-mentioned suitable compounds include cyclopentadiene, indene, azulene or their alkyl, aryl, aralkyl, alkoxy or aryloxy derivatives. Moreover, the compound which these compounds couple | bonded (bridge | crosslink) through the alkylene group (The carbon number is 2-8 normally, Preferably 2-3) is also used suitably.

The organosilicon compound having a cyclic hydrocarbon group can be represented by the following general formula. ALSiR4-L Here, A represents the cyclohydrogen group exemplified by a cyclopentadienyl group, a substituted cyclopentadienyl group, an indenyl group, and a substituted indenyl group, and R is a methyl group, an ethyl group, a propyl group, an isopropyl group. Groups, alkyl groups such as butyl groups; alkoxy groups such as methoxy groups, ethoxy groups, propoxy groups, butoxy groups; aryl groups such as phenyl groups; aryloxy groups such as phenoxy groups; aralkyl groups such as benzyl groups, Represents a hydrocarbon residue or hydrogen having 1 to 24 carbon atoms, preferably 1 to 12, wherein L is 1
≦ L ≦ 4, preferably 1 ≦ L ≦ 3.

Specific examples of the organic cyclic hydrocarbon compound of the above component (H3) include cyclopentadiene, methylcyclopentadiene, ethylcyclopentadiene, 1,3-dimethylcyclopentadiene, indene, 4-methyl-1-indene, 4, 7-Dimethylindene, cycloheptatriene, methylcycloheptatriene, cyclooctatetraene, azulene, fluorene, methylfluorene-containing cyclopolyene or substituted cyclopolyene, monocyclopentadienylsilane, biscyclo Examples thereof include pentadienylsilane, triscyclopentadienylsilane, monoindenylsilane, bisindenylsilane, and trisindenylsilane.

The modified organoaluminum compound containing an Al--O--Al bond obtained by the reaction of the catalyst component (H4) organoaluminum compound with water is usually referred to as an aluminoxane by reacting an alkylaluminum compound with water. The modified organoaluminum obtained is obtained, and usually 1 to 100, preferably 1 to 50 Al in the molecule.
Contains an -O-A1 bond. The modified organoaluminum compound may be linear or cyclic.

The reaction of organoaluminum with water is usually carried out in an inert hydrocarbon. As the inert hydrocarbon,
Aliphatic, alicyclic and aromatic hydrocarbons such as pentane, hexane, heptane, cyclohexane, benzene, toluene and xylene are preferable. The reaction ratio between water and the organoaluminum compound (water / Al molar ratio) is usually 0.25 / 1 to 1.2.
/ 1, preferably 0.5 / 1 to 1/1.

The catalyst component (H5) inorganic carrier and / or particulate polymer carrier means a carbonaceous material, a metal, a metal oxide, a metal chloride, a metal carbonate or a mixture thereof, or a thermoplastic resin, a thermosetting resin or the like. Is mentioned. Suitable metals that can be used for the inorganic carrier include:
Examples include iron, aluminum, and nickel. Specifically, SiO2, Al2O3, MgO, ZrO2, TiO
2, B2O3, CaO, ZnO, BaO, ThO2, etc. or a mixture thereof can be mentioned. SiO2-Al2O
3, SiO2-V2O5, SiO2-TiO2, SiO
2-V2O5, SiO2-MgO, SiO2-Cr2O
3 and the like. Among these, SiO2 and Al
It is preferable that the main component is at least one component selected from the group consisting of 2O3. As the particulate polymer carrier, either a thermoplastic resin or a thermosetting resin can be used, and specifically, particulate polyolefin, polyester, polyamide, polyvinyl chloride, poly (meth)
Methyl acrylate, polystyrene, polynorbornene,
Examples include various natural polymers and mixtures thereof.

The above-mentioned inorganic carrier and / or particulate polymer carrier can be used as they are, but preferably, as a pretreatment, these carriers are treated with an organoaluminum compound or a modified organoaluminum compound containing an Al-O-A1 bond. It can also be used as the component (H5) after the contact treatment.

The above-mentioned (I) ethylene (co) polymer is produced by a gas phase method, a slurry method, a solution method or the like.
The method is not particularly limited, such as a one-stage polymerization method and a multi-stage polymerization method. Among these, the one manufactured by the vapor phase method is the most preferable in consideration of the electrical characteristics and economical efficiency.

The (II) other polyolefin in the present invention means a homo- or copolymer of a hydrocarbon represented by the general formula C _n H _2n and other than (I). Specific examples of the hydrocarbon include ethylene, propylene, 1-butene, 2-butene, isobutylene, 1-pentene, 2-
Penten, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 2,3-dimethyl-2
-Butene, 4-methyl-1-pentene, 1-heptene,
1-octene, 1-nonene, 1-decene and the like.

Specific examples of the other polyolefins (II) include high / medium density polyethylene, linear low density polyethylene, ultra low density polyethylene, polypropylene, polybutene, poly-4-methyl-1-pentene, and ethylene / α.
-Olefin copolymer rubber, ethylene-propylene copolymer rubber (EPR), high pressure radical method low density polyethylene,
A high-pressure radical method ethylene copolymer and the like can be mentioned. Among the above-mentioned polyolefins, when high-pressure radical method low-density polyethylene is particularly used as an electric insulating material, it is most preferably used because it has excellent electric characteristics, processability and flexibility.

The high-pressure radical method low-density polyethylene is a branched low-density polyethylene (LDPE), which is generally used in a tank reactor or a tubular reactor in the presence of a radical initiator at a normal pressure of 500 to 3000 kg. /
It is obtained by polymerizing ethylene at cm ² and a temperature of 150 to 330 ° C. Its MFR is 0.1
100g / 10min, preferably 0.2-50g / 1
It is 0 min. Those in this range have high melt tension and are easy to mold.

The above (II) other polyolefin (I)
The blending amount with respect to the ethylene (co) polymer is 0 to 98% by weight
It is. When it is desired to maintain the excellent electrical properties of the (I) ethylene / α-olefin copolymer, (I) is 100 to 7
0% by weight. Further, when it is desired to utilize the processability and economy of the (II) polyolefin, it is desirable to add (I) 70 to 2% by weight.

When used after crosslinking as described below,
(I) Ethylene (co) polymer 30 to 10% by weight, (I
I) It is desirable that 70 to 90% by weight of other polyolefin is blended.

The first aspect of the present invention is the above-mentioned (I) ethylene (co).
When the polymer satisfies the above (a) and (b) and has an electric activation energy of 0.4 (ev) or less, it is suitable as an electric insulating material. Further, in particular, the use of the ethylene / α-olefin copolymer according to the second aspect of the present invention provides an even more preferable electrical insulating material.

In the present invention, when it is used as a power cable, it may be used as it is, but it is preferable to crosslink it in order to improve heat resistance.
The method of cross-linking is not particularly limited, and examples thereof include a method using a radical generator such as an organic peroxide, electron beam cross-linking, a method of performing silane cross-linking, etc., but it is economically inexpensive. Therefore, a method using a radical generator such as an organic peroxide is preferable.

Radical generators used include benzoyl peroxide, lauryl peroxide, dicumyl peroxide, t-butyl hydroperoxide,
α-α-bis (t-butylperoxydiisopropyl)
Benzene, di-t-butylperoxide, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di- (t-butylperoxy) Hexine, peroxides such as azobisisobutyronitrile, 2,3-dimethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-diphenylbutane,
2,3-diethyl-2,3-di (p-methylphenyl)
Examples include butane and 2,3-diethyl-2,3-di (bromophenyl) butane.

As the radical generator, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexane and 2,5-dimethyl-2,5-di- (t-butylperoxy) are used. Xin, dicumyl peroxide and the like are preferably used. The amount is 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the resin composition.

The electric insulating material of the present invention means an insulating material for capacitors, insulation of high voltage parts such as an X-ray generator, various measuring equipment, insulation of containers for dry and wet batteries, various printed boards, various connectors, They are power distribution cords, high-voltage current work gloves, and insulation materials for jigs and tools.

The power cable of the present invention preferably comprises a cross-linked insulating layer using the above-mentioned electric insulating material. As a specific example of the power cable, there is at least a power cable in which a conductor is coated with the crosslinked electrically insulating material of the present invention to form an insulating layer, and if necessary, the conductor portion is formed into an assembly line or insulated from the conductor. Providing a semi-conductive layer between layers,
A flame-retardant resin layer can be formed outside the insulating layer. The electrically insulating material of the present invention is particularly effective for high-voltage electricity.

In the power cable of the present invention, it is preferable to crosslink during coating. At this time, a radical generator may be blended in advance and crosslinked by heating, or it may be crosslinked by using radiation.

Cooling after molding is optional such as natural cooling and cooling in a water tank, but it is desirable to cool comparatively gently for the reason that no defective portion (void) is generated inside.

Since the crosslinked electrical insulating material of the present invention is excellent in insulation and also has elasticity, it is most suitable for coating electric wires, and can be widely used without being limited to DC / AC power supplies. Since the volume resistance has a small temperature dependence and excellent electrical characteristics, it can be suitably used as a power cable particularly for high-voltage DC.

[0055]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

(Procedure for measuring volume resistance) 1. Preparation of sample for measuring volume resistance The blended product of the ethylene / α-olefin copolymer and the polyolefin to be measured is a plastomill at 160 ° C. for 5
After kneading for a minute, the thickness is 0.3mm by hot pressing.
Into a sheet. The conditions for hot pressing were as follows: ・ The uncrosslinked sample was molded under the following conditions by sandwiching the sample between aluminum sheets. 1) Preheat the sample at 140 ° C for 5 minutes 2) Press at 140 ° C and 100 kg / cm ² for 5 minutes 3) Cool under pressure from 140 ° C to 30 ° C for 5 minutes A sample prepared by kneading 2 parts by weight of oxide was sandwiched between Teflon sheets and molded under the following conditions. 1) Preheat the sample at 120 ° C for 5 minutes 2) Pressurize at 120 ° C and 100 kg / cm ² for 5 minutes 3) Cool under pressure from 120 ° C to 30 ° C for 5 minutes, excluding the sample containing voids at this time 4) Preheat again at 120 ° C for 5 minutes 5) Pressurize at 120 ° C for 5 minutes at 100 kg / cm ² 6) Increase temperature from 120 ° C to 160 ° C under pressure 7) Crosslink at 160 ° C for 30 minutes under pressure 8) Cool under pressure from 120 ℃ to 30 ℃ in 5 minutes

2. Measurement of volume resistance The electrode system shown in FIGS. 3 (a) and 3 (b) was used. FIG.
FIG. 3A is a plan view and FIG. 3B is a side view thereof, in which reference numeral 11 is a main electrode (50 mmφ), 12
Is a guard electrode (inner diameter 75 mmφ, outer diameter 80 mmφ), 1
3 is a sample, 14 is a high voltage electrode (80 mmφ), the main electrode is connected to an oscillating capacitance type ammeter, and the high voltage electrode is connected to a high voltage source by a cable. The electrode material was a stainless steel plate, and the surface in contact with the sample was polished to a mirror surface state with a buffing machine. In addition, the measurement is performed on the sample as shown in FIGS.
The sample was placed in the electrode system as shown in FIG. 3, and the upper and lower electrodes were short-circuited for 5 minutes to remove the charges charged on the surface of the sample. The value measured at 90 ° C should be adjusted so that the temperature in the sample is 90 ° C.
Shorted for a minute. Applied voltage is DC 3300V by battery
It is. A vibrating capacitance type ammeter (TR8411 manufactured by Advantest) was used as a measuring instrument. The cable connecting the measuring instrument and the electrodes was a pipe cable to remove extraneous noise. In this measurement system, at room temperature 3 × ^{10 17} Ω, it can be measured stably to 90 ° C. In 3 × ^{10 16} Ω. The thickness of each sample was about 0.3 mm, and each sample was used by measuring up to two decimal places. The effective electrode area is 19.6 cm ² .
From the examination of the current-time characteristics, after applying voltage, there is no decrease in the current due to the absorption current, and the stable current measurement is 1
0 minutes later. Therefore, the current value after 10 minutes of voltage application is taken as the measured value, but if the current is not stable even after 10 minutes, measurement is waited for about 2 minutes until it stabilizes. Excluded from measurement. The volume resistance was determined based on the current value obtained from the measurement. Each measurement was performed 10 times, and the average value was used as data.

Samples A1 to A3 used in Examples 1 to 3 were polymerized by the following method.

(Polymerization of Sample A1) (1) Preparation of Catalyst 150 ml of purified toluene was added to a 500 ml eggplant type flask equipped with an electromagnetic induction stirrer under nitrogen, and then tetraprocoxyzirconium (Zr (On-Pr) ₄ ) 0. 60 g
And 1.0 g of indene were added, and the mixture was stirred at room temperature for 30 minutes, then at 0 ° C.
The system is kept in triisobutylaluminum (Al (i
3.2 g of -Bu) ₃ ) was added dropwise over 30 minutes, and after the addition was completed, the system was brought to room temperature and stirred for 24 hours. Next, a toluene solution of methylaluminoxane (concentration: 1 mmo
(1 / ml) 200 ml was added, and the mixture was reacted at room temperature for 1 hour.
Separately, 50 g of silica (manufactured by Fuji Devison Co., Ltd., grade # 952, surface area 300 m ² / g), which was previously baked at 600 ° C. for 5 hours in a 1.51 three-necked flask equipped with a stirrer under nitrogen.
Was added, the whole amount of the solution was added, and the mixture was stirred at room temperature for 2 hours. Then, the solvent was removed by nitrogen blowing to obtain a powder having good fluidity.

(2) Polymerization Using a continuous fluidized bed gas phase polymerization apparatus, a polymerization temperature of 70
Copolymerization of ethylene and 1-butene was carried out at a temperature of 20 ° C. and a total pressure of 20 kgf / cm ² G. The gas composition in the system was 1-butene / ethylene molar ratio 0.08 and ethylene concentration 60 mol%. Polymerization was performed while continuously supplying each gas in order to continuously supply the catalyst and keep the gas composition in the system constant. The MFR was adjusted by adjusting the hydrogen concentration in the system. The physical properties of the produced copolymer are shown in Table 1.

(Polymerization of Sample A2) Polymerization was carried out in the same manner as Al using 1-hexene as a comonomer. The physical properties of the produced copolymer are shown in Table 1.

(Polymerization of Sample A3) (1) Preparation of Catalyst Under a nitrogen atmosphere, 150 ml of purified toluene was added to a catalyst controller equipped with an electromagnetic induction stirrer, and then 0.50 g of dipropoxydichlorozirconium (Zr (OPr) ₂ Cl ₂ ). And 1.0 g of methylcyclopentadiene were added, and 9.0 g of tridecylaluminum was added dropwise while maintaining the system at 0 ° C. After completion of the addition, the reaction system was maintained at 50 ° C. and stirred for 16 hours. Next, 200 ml of a toluene solution of methylaluminoxane (concentration 1 mmol / ml) was added to this solution, and the mixture was reacted at room temperature for 1 hour. Separately, purified toluene was added to a catalyst adjuster equipped with a stirrer under nitrogen, and then the silica was preliminarily calcined at 400 ° C. for a predetermined time (Fuji Davison, grade #
952, 50 m of the physical volume of 300 m ² / g), and then the whole amount of the solution was added and stirred at room temperature. Then, the solvent was removed by nitrogen blowing to obtain a solid catalyst powder having good fluidity.

(2) Polymerization Polymerization was carried out under the same conditions as in A1. The physical properties of the produced copolymer are shown in Table 1.

(B1) Linear Low Density Polyethylene with Ziegler Catalyst Titanium tetrachloride and triethylaluminium catalyst were used to obtain ethylene and 1-butene by copolymerization. Density 0.923
g / cm ³ , MFR 3.0 g / 10 min (B2) Low-density polyethylene by high-pressure radical polymerization method Product name: Nisseki Lexron W2000, manufactured by Nippon Petrochemical,
Density 0.919 g / cm ³ , MFR 1.0 g / 10 mi
n. Other physical properties of the above sample are shown in Table 1.

Examples 1 to 3 Table 2 compares the volume resistance and activation energy of uncrosslinked samples. Examples 1 to 3 are samples (A1 to A3)
Is the measured value.

Comparative Example 1 The measured values of linear low density polyethylene (B1) using Ziegler catalyst are shown in Table 2. The activation energy is high, the temperature dependence is large, and the volume resistance is particularly low at 90 ° C.

Comparative Example 2 Low Density Polyethylene (B2) by High Pressure Radical Polymerization
The measured values are shown in Table 2. It has low volume resistance, high activation energy, and high temperature dependence.

Examples 4 to 11 Table 3 shows the results of mixing the sample (A1) with the sample (B2) and measuring the volume resistance without crosslinking. The results were also compared with Example 1 and Comparative Example 2.

Examples 12 and 13 Examples 12 and 13 in Table 4 are samples (A2) or (A
3) The volume resistance was measured for a mixture of 10% by weight and 90% by weight of (B2).

Comparative Example 3 10% by weight of (B1) and 90% by weight of (B2) were mixed and shown in Table 4. Low volume resistance.

Example 14 Table 5 shows measured values of crosslinked samples. Example 1
A mixture of 10% by weight of sample (A1) of 0 and 90% by weight of (B2) was crosslinked by the above method.

Comparative Example 4 The value of the volume resistance of the crosslinked product of Comparative Example 2 is shown. As shown in Table 5, the volume resistance value is low.

FIG. 4 is a graph showing the examples and comparative examples shown in Table 3 among the above experimental examples.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

[0077]

[Table 4]

[0078]

[Table 5]

[0079]

EFFECT OF THE INVENTION The electrical insulating material containing an ethylene (co) polymer as a main component of the present invention has a large volume resistance and a small temperature dependence, and is excellent in flexibility and workability, and after cross-linking. Is also a material having the above-mentioned excellent electrical characteristics and is suitable as an electrical insulating material. Further, when used as an insulating layer of a power cable, it is possible to reduce power loss during high voltage power transmission without thickening the insulating layer.

[Brief description of the drawings]

FIG. 1 is an elution temperature-elution amount curve of the copolymer of the present invention determined by TREF.

FIG. 2 Elution temperature-elution amount curve obtained by TREF of a copolymer with a metallocene catalyst

FIG. 3 Volume resistance measuring device

FIG. 4 is a graph showing the results of Examples and Comparative Examples shown in Table 3.

Claims (6)

[Claims] 1. The density of (I) (A) 0.86 to 0.97 g /
cm ³ , (B) Melt flow rate (MFR) 0.01
~ 200g / 10min, the electrical activation energy is 0.4 (eV) or less ethylene (co) polymer 100
An electric insulating material comprising a resin containing 2 to 2% by weight, and (II) 0 to 98% by weight of another polyolefin. 2. The ethylene (co) polymer has a (A) density of 0.86 to 0.96 g / cm ³ (B) a melt flow rate of 0.01 to 200 g / 10 m.
in (C) molecular weight distribution (Mw / Mn) 1.8 to 4.5 (D) composition distribution parameter Cb 1.08 to 2.00 (E) ortho-dichlorobenzene (ODC) at 25 ° C.
B) The amount X (% by weight) of the soluble component and the densities d and MFR have the following relationship (1) In the case of d-0.008 × log MFR ≧ 0.93 X <2.0 (2) d-0 When 0.008 × log MFR <0.93, X <9.8 × 10 ³ × (0.9300−d + 0.008)
XlogMFR) ² +2.0, and the electrical activation energy is an ethylene / α-olefin copolymer having an electric activation energy of 0.4 (eV) or less, The electrical insulating material according to claim 1. 3. The ethylene (co) polymer has a (A) density of 0.86 to 0.96 g / cm ³ (B) a melt flow rate of 0.01 to 200 g / 10 m.
in (C) molecular weight distribution (Mw / Mn) 1.8 to 4.5 (D) composition distribution parameter Cb 1.08 to 2.00 (E) ortho-dichlorobenzene (ODC) at 25 ° C.
B) The amount X (% by weight) of the soluble component and the densities d and MFR have the following relationship (1) In the case of d-0.008 × log MFR ≧ 0.93 X <2.0 (2) d-0 When 0.008 × log MFR <0.93, X <9.8 × 10 ³ × (0.9300−d + 0.008)
XlogMFR) ² +2.0 (F) There is a plurality of peaks in the elution temperature-elution amount curve by the continuous temperature rising elution fractionation method (TREF), and the electric activation energy is 0.4 (eV). The electrical insulating material according to claim 1 or 2, which is the following ethylene / α-olefin copolymer. 4. The electrical insulating material according to claim 1, wherein the other polyolefin (II) is polyethylene by a high pressure radical polymerization method. 5. A power cable using the electrical insulating material according to any one of claims 1 to 4 as an insulator. 6. The power cable according to claim 5, wherein the power cable is a DC power cable.