JPS6155203B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrical insulating material, and particularly to an electrical insulating material made from a composition containing a specific ethylene/α-olefin copolymer rubber as a rubber component. Electrical insulators, such as cylindrical insulating layers covering current-carrying parts such as power transmission wires, marine wires, and automobile ignition cables, and those around automobile engines such as plug caps, ignition caps, and distributor caps. Ethylene-propylene random copolymer rubber or ethylene-propylene random copolymer rubber, which has excellent weather resistance, heat resistance, and electrical insulation, is used for general insulating electrical parts such as electrical insulation caps, condenser caps, and cable joint covers.
It is well known that vulcanized rubber compounds containing propylene/polyene random copolymer rubber as a rubber component are widely used. However, these rubbers (hereinafter abbreviated as EP rubber) still have many unsatisfactory points. For example, when using an EP rubber vulcanizate as an insulating layer for electric wires, especially high-voltage power transmission wires, the vulcanizate must have high electrical properties and mechanical strength. In practical terms, the transmission voltage of a power transmission cable with a vulcanized material as an insulating layer remains at about 20,000 volts. The reason for this is that in the process of manufacturing electric wires using EP rubber vulcanizate as an insulating layer, the processability of EP rubber unvulcanized compound rubber and the strength of EP rubber vulcanizate cannot be balanced, and high-level electrical properties and mechanical This is caused by not being able to satisfy the following characteristics. i.e.
Electric wires with an insulating layer made of EP rubber vulcanizate are usually produced by feeding an unvulcanized rubber compound containing EP rubber, a vulcanizing agent, a softening agent, and a filler to an extruder.
It is produced by covering a conductive wire, which becomes the current-carrying part of the electric wire separately introduced into the extruder, in a cylindrical shape with compounded rubber in the extruder, and then heating it in a vulcanization system, but the electric wire has an even higher voltage. In order to be used as an insulating layer, the insulating layer must have a low dielectric loss tangent.
This is achieved by using a compounded rubber with a small amount of filler, etc. However, in this case, due to the small amount of softener blended, the so-called extrusion processability deteriorates, in which the outer surface of the cylinder loses its smoothness in the extrusion process in which the compound rubber is coated in a cylindrical shape around the current-carrying part in the manufacturing process of the electric wire. However, due to the loss of smoothness, the withstand AC breakdown voltage of the insulating part decreases, and it cannot be used as a high-voltage power transmission wire. As a method to solve this extrusion processability, methods have been attempted to lower the molecular weight of EP rubber or use EP rubber with a wide molecular weight distribution, but the present inventors have found that this method does indeed improve extrusion processability. It was learned that as the molecular weight of the vulcanizate decreases or the molecular weight distribution expands, the strength of the vulcanizate, especially the stress at break, decreases, making it unusable as an insulating layer for high-voltage power transmission lines. Therefore,
In any case, as long as common EP rubber is used, the practical voltage limit for power transmission wires using the vulcanizate as an insulating layer is about 20,000 volts. In addition, when used for applications such as plug caps, ignition caps, distributor caps, ignition cable insulating layers, and cable joint covers, inexpensive softeners are not required because they do not require such high levels of electrical properties. It is desirable to mix a large amount of inorganic fillers and the like to manufacture the product as inexpensively as possible, but in view of the strength of the EP rubber vulcanizate, the softener should be about 80 parts by weight and the inorganic filler should be added to 100 parts by weight of EP rubber. The upper limit of the blending amount is about 200 parts by weight, and there is a limit to lowering manufacturing costs from the current situation. However, the present inventors have investigated the factors that affect the mechanical properties of vulcanizates of ethylene/α-olefin copolymer rubber, particularly the type of α-olefin in the copolymer rubber, the composition ratio of ethylene and α-olefin, etc. As a result, when the molar ratio of ethylene units to α-olefin units is 80/20 to 95/5, α-olefins are α-olefins having 4 to 10 carbon atoms.
We have discovered the surprising fact that when olefin is used, the strength of a copolymer rubber vulcanizate is significantly higher than in the case of EP rubber where propylene is used as α-olefin, and this has led to the present invention. That is, the present invention has an ethylene unit and a carbon number of 4.
−10 α-olefin unit molar ratio (ethylene/
α-olefin) is 80/20−95/5, preferably 85/
15-95/5, and the intrinsic viscosity [η] is 0.6-6.0
dl/g, preferably 0.8-4.0 dl/g, contains a polyene component with an iodine value of 4-50, and has a molecular weight distribution index Q value (M _W /M _N ) of 4-12. - An object of the present invention is to provide an electrical insulation material comprising a composition of olefin copolymer rubber. The advantages of the invention will become clearer from the description that follows. In other words, even if a large amount of inexpensive softeners and inorganic fillers are blended, the ethylene/α-olefin copolymer rubber vulcanizate of the present invention has sufficient strength for practical use, so it has a high level of dielectric constant, dielectric loss tangent, etc. Electrical insulation materials that do not require the same electrical properties can be produced at a lower cost than EP rubber. In the rubber composition for covering electric wires, the blending amount of the softener and inorganic filler is limited so that the dielectric loss tangent (%) of the vulcanizate is 0.3 or less. However, the molecular weight distribution index Q value of the present invention is 4
If an ethylene/α-olefin copolymer rubber having 1 to 12 is used, the extrusion processability is good even in the case of wire coating, so the surface smoothness of the insulating layer can be maintained sufficiently, and the vulcanizate can be coated with ethylene/α-olefin copolymer rubber. The strength at break of
It is possible to set it to 100Kg/cm ³ or more. As a result, the vulcanized product of the ethylene/α-olefin copolymer rubber of the present invention functions satisfactorily as an insulating layer for high-voltage power transmission wires of about 60,000 volts. As described above, since the vulcanized product of the ethylene/α-olefin copolymer rubber of the present invention has high strength, it further guarantees its function as an insulating layer for power transmission wires or marine wires that are not very high voltage. The configuration of the present invention will be explained in detail below. α-olefin, which is a component of the ethylene/α-olefin copolymer rubber used in the present invention, has 4 carbon atoms.
to 10 α-olefins. Specifically 1
Examples include -butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, and mixtures thereof, with 1-butene being particularly preferred. The molar ratio of ethylene units to α-olefin units (ethylene/α-olefin) is 80/20 to 95/5, preferably 85/15 to 95/5.
Examples include 95/5, more preferably 85/15 to 93/7. When the molar ratio is 95/5 or more and the ethylene unit content is large, the vulcanizate loses its rubber elasticity, becomes hard and loses flexibility. If it is 80/20 or less, the strength of the vulcanizate is the same as that of EP rubber. The ethylene/α-olefin copolymer rubber of the present invention preferably contains a polyene component. The amount is preferably 4 to 50, more preferably 8 to 40, expressed in terms of iodine value. In particular, when a sulfur compound is used as a vulcanizing agent, it is essential to contain the polyene component within the above range. Specifically, the polyene component is 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5
- linear non-conjugated dienes such as hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene −
2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2
- cyclic nonconjugated dienes such as norbornene, 2,
3-diisopropylidene-5-norbornene, 2
-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene, 1,4,
Trienes such as 9-decatriene can be exemplified as a representative example. Suitable polyenes are cyclic non-conjugated dienes and 1,4-hexadiene, especially dicyclopentadiene or 5-ethylidene-2
- Norbornene. The intrinsic viscosity [η] of the ethylene/α-olefin copolymer rubber of the present invention is 0.6 to 6.0 dl/g, preferably 0.8 to 4.0 dl/g, as measured in decalin at 135°C. If it is less than 0.6 dl/g, the strength of the vulcanizate will be low, and if it is more than 6.0 dl/g, it will be difficult to prepare an unvulcanized compounded rubber. When the vulcanized product of the composition of the present invention is used as an insulating layer for electric wires, the amount is preferably 0.8 to 2.5 dl/g, particularly preferably 0.8 to 1.8 dl/g. When the vulcanizate of the copolymer rubber of the present invention is used as an insulating layer of an electric wire, especially when the electric wire is a high-voltage power transmission wire, the molecular weight distribution index Q value of the ethylene/α-olefin copolymer rubber of the present invention is 4-4. When the number is 12, extrusion processability is excellent in the process described later for producing an electric wire having an insulating layer made of vulcanized rubber. Here, the molecular weight distribution index Q value is the ratio of the weight average molecular weight M _W to the number average molecular weight M _N (M
_W /M _N ). The measurement is carried out according to the following method according to "Gel Permeation Chromatography" (Maruzen). (1) Using standard polystyrene with a known molecular weight (monodisperse polystyrene manufactured by Toyo Soda Kogyo), calculate the molecular weight M and its GPC (Gel Permeation
Chromatograph) count and create a correlation diagram (calibration curve) between molecular weight M and EV (Elution Volume). The concentration at this time is 0.02% by weight. (2) Obtain a GPC pattern of the sample using the GPC measurement method, and find M using the above (1). The sample preparation conditions and GPC measurement conditions at that time are as follows. <Sample Preparation> (a) Aliquot the sample into an Erlenmeyer flask together with o-dichlorobenzene solvent to a concentration of 0.04% by weight. (b) Add 2,6-di-tert-butyl-p-cresol, an anti-aging agent, to the Erlenmeyer flask containing the sample in an amount of 0.1% by weight based on the polymer solution. (c) Heat the Erlenmeyer flask to 140°C and stir for about 30 minutes to dissolve. (d) Then pass through a 1 μm Millipore filter at 135°C to 140°C. (e) Apply the liquid to GPC. <GPC measurement conditions> Perform under the following conditions. (b) Apparatus 200 type (b) manufactured by Waters Column S-type (Mix type) manufactured by Toyo Soda Kogyo (c) Sample amount 2 ml To produce such an ethylene/α-olefin copolymer of the present invention can be produced using a known catalyst. That is, in a medium, using a Ziegler catalyst such as a soluble vanadium compound and an organoaluminium compound, ethylene, carbon number 4 or
It is produced by supplying α-olefin of No. 10, polyene if necessary, hydrogen gas as a molecular weight regulator, etc. Examples of media include aliphatic hydrocarbons such as pentane, hexane, heptane, octane, and kerosene, alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, chlorobenzene, and tetrachloride. Carbon, halogenated hydrocarbons such as tetrachlorethylene, trichlorethylene, ethyl chloride, methylene chloride, and dichloroethane can be used alone or in combination. Examples of soluble vanadium compounds include vanadium tetrachloride, vanadyl trichloride, vanadium triacetylacetonate, vanadyl diacetylacetonate, vanadyl trialkoxide VO(OR) ₃ (where R represents an aliphatic hydrocarbon group), Halogenated vanadyl alkoxide VO(OR)nX _3-o (where R is an aliphatic hydrocarbon group, X is a halogen atom, and O
<n<3. ) can be used alone or in combination. On the other hand, as an organoaluminum compound, the general formula
Compounds represented by RmAlX _3-n (where R is an aliphatic hydrocarbon group, X is a halogen, and 1≦m≦3), such as triethylaluminum,
Diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, and the like can be used alone or in combination. In particular, ethylene with a molecular weight distribution index Q value of 3 or more
When producing α-olefin copolymer rubber, for example, vanadyl trichloride and ethylaluminum sesquichloride are mixed at an Al/V (molar ratio) of 2 to 2.
An example is a method in which copolymerization is carried out at a temperature of 20 to 100°C using a catalyst system in the range of 50°C. When manufacturing an electric wire having an insulating layer made of the vulcanizate obtained from the copolymer rubber of the present invention, for example, a mixer such as a Banbury mixer is used to
After kneading the copolymer rubber of the present invention, filler, softener, etc. at 150°C for about 4 to 10 minutes, the temperature of the rolls is increased using rolls such as open rolls.
A sheet or ribbon-shaped unvulcanized rubber compound prepared by additionally mixing a vulcanizing agent and, if necessary, a vulcanization accelerator or vulcanization aid at a temperature of 70 to 100°C, or the method described below. The unvulcanized compounded rubber pelletized with is fed to an extruder heated to 90 to 110°C, and a conducting wire separately introduced into the extruder is covered in a cylindrical shape with the compounded rubber in the extruder,
Next, the coated conductor wire is heated to 180% by steam etc.
By continuously introducing the copolymer rubber into a vulcanization tank heated to 220° C. to 220° C. and heating for 0.5 to 10 minutes, an electric wire having an insulating layer made of the vulcanizate of the copolymer rubber of the present invention can be produced. In addition, when manufacturing electrical insulating materials such as caps and cable joint covers, the unvulcanized compounded rubber is molded into the shape of electrical insulating materials using an extrusion molding machine, and either simultaneously with molding or vulcanization. 1 at 130 to 220℃ in a sulfur tank
It can be produced by heating for 60 minutes to 60 minutes, or by vulcanizing an unvulcanized compounded rubber by heating it at the temperature and for the time at the same time as molding using a hot press. The proportion of the ethylene/α-olefin copolymer contained in the insulating material of the present invention is 25 to 90% by weight, preferably 40 to 88% by weight, and can be used as an insulating layer for high-voltage power transmission wires of about 30,000 volts or more. If used, 55 to 90% by weight, preferably 65 to 90% by weight
It is 88% by weight. Examples of the inorganic filler that can be used in the copolymer rubber of the present invention include finely divided silicic acid, calcium carbonate, talc, clay, and carbon black. The volume resistivity of electrical insulators is 1×10 ¹⁴ Ω・cm
Since the above is preferable, it is preferable to use a non-conductive filler. For applications that do not require such high levels of electrical properties, practical strength can be maintained even when such inorganic fillers are blended in a large amount of about 250 parts by weight per 100 parts by weight of copolymer rubber, making it cheaper. Manufacturability is one advantage of the present invention. When used as an insulating layer for high-voltage power transmission wires of approximately 30,000 volts or more, the amount is 50 parts by weight or less, preferably 30 parts by weight or less, per 100 parts by weight of copolymer rubber. In addition, when carbon black is used, it is preferable to limit it to 15 parts by weight or less based on 100 parts by weight of the copolymer rubber. Softeners that can be blended into the copolymer rubber of the present invention include softeners commonly used for rubber, such as process oils, lubricating oils, paraffin, liquid paraffin,
Petroleum-based softeners such as petroleum asphalt and vaseline, coal tar-based softeners such as coal tar and coal tar pitch, fatty oil-based softeners such as coconut oil, linseed oil, rapeseed oil, and coconut oil.Tall oil; sub; beeswax; waxes such as , carnauba wax, and lanolin; fatty acids and fatty acids such as ricinoleic acid, palmitic acid, barium stearate, calcium stearate, and zinc laurate; synthetic polymeric substances such as petroleum resin, atactic polypropylene, and coumaron indene resin. be able to.
Among these, petroleum-based softeners are preferably used, and process oils are particularly preferred. For applications that do not require such high levels of electrical properties, practical strength can be maintained even when an inexpensive softener is blended in large amounts (approximately 100 parts by weight to 100 parts by weight of copolymer rubber). can be manufactured. When used as an insulating layer for high-voltage power transmission wires of about 30,000 volts or more, the amount is 7 parts by weight or less, preferably 5 parts by weight or less, based on 100 parts by weight of the copolymer rubber. As a vulcanizing agent, sulfur-based compounds such as sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, selenium dimethyldithiocarbamate; dicumyl peroxide,
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-
Di(benzoylperoxy)hexane, 2,5-
Dimethyl-2,5-di(tert-butylperoxy)
Organic peroxides such as hexene-3, di-tert-butyl peroxide, di-tert-butyl peroxy-3,3,5-trimethylcyclohexane, and tert-butyl hydroperoxide can be mentioned. Among them, sulfur and organic peroxides are preferably used, especially sulfur, dicumyl peroxide, di-tert-butyl peroxide, di-tert-butyl peroxide-3,3,5
-trimethylcyclohexane is preferred. When producing an electric wire having an insulating layer made of the electrical insulating material of the present invention, it is preferable to use the above-mentioned peroxide as a vulcanizing agent, except in the case of ignition cables. The sulfur compound is 0.1 to 100 parts by weight of copolymer rubber.
It is used in amounts of 10 parts by weight, preferably 0.5 to 5 parts by weight. The organic peroxide is used in an amount of 0.1 to 15 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the copolymer rubber. Further, a vulcanization accelerator is used in combination with a vulcanizing agent, if necessary. As the vulcanization accelerator, N-cyclohexyl-2-benzothiazole-sulfenamide, N-oxydiethylene-2-benzothiazole-sulfenamide, N,N-diisopropyl-2-benzothiazole-sulfenamide,
2-mercaptobenzothiazole, 2-(2,4
-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, dibenzothiazyl-disulfide, and other thiazoles; diphenylguanidine, triphenylguanidine, diorthotolylguanidine, orthotolyl・Guanide,
Guanidine type such as diphenylguanidine phthalate; aldehyde amine or aldehyde-ammonia type such as acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde ammonia; imidazoline type such as 2-mercaptoimidazoline; thiocarbanilide, Thiourea series such as diethylthiourea, dibutylthiourea, trimethylthiourea, diorthotolylthiourea; tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, Thiuram series such as pentamethylene thiuram tetrasulfide; zinc dimethyldithiocarbamate, zinc diethylthiocarbamate, di-
Dithioate salts such as zinc n-butylthiocarbamate, zinc ethyl phenyl dithiocarbamate, zinc butylphenyl dithiocarbamate, sodium dimethyl dithiocarbamate, selenium dimethyl dithiocarbamate, tellurium diethyl thiocarbamate; zinc dibutyl xanthate, etc. Examples include metal oxides such as xanthate, zinc oxide, magnesium oxide, and red lead. These vulcanization accelerators are used per 100 parts by weight of copolymer rubber.
It is used in a proportion of 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight. In addition, when crosslinking with peroxides, metal oxides such as zinc oxide, magnesium oxide, red lead, etc.
Quinone dioxime systems such as sulfur and P-quinone dioxime; methacrylate systems such as polyethylene glycol dimethacrylate; allyl systems such as diallyl phthalate and triallyl cyanurate; other maleimide systems; and crosslinking aids such as divinylbenzene. Good too. When manufacturing electric wires having the electrical insulating material of the present invention as an insulating layer, using pelletized compounded rubber brings about the advantage of labor saving in manufacturing the electric wires. Pelletization is possible by using the copolymer rubber of the present invention. In order to make pellets using the copolymer rubber of the present invention, it is possible to make pellets without adding a softener or an inorganic filler to the copolymer rubber, or when a softener or an inorganic filler is added to the copolymer rubber. If x≦80, then x+y≦400, and if x>80, then y>5(x-80). Pelletization is possible by satisfying x+y≦400. In order to produce such pelletized compounded rubber, the unvulcanized compounded rubber containing softeners, inorganic fillers, vulcanizing agents, etc. is prepared by the method described above.
It is fed into a pelletizer heated to 90 to 110°C and turned into pellets. Incidentally, substances that define the vulcanization system, such as a vulcanizing agent, a vulcanizing aid, or a vulcanizing accelerator, may be mixed in the step of pelletizing with a pelletizer. The following will specifically explain examples and comparative examples. Example 1 The molar ratio of ethylene unit and 1-butene unit content (ethylene/1-butene) was 85/15, the iodine value was 10,
Ethylene with [η] of 1.35 and Q value of 4.5,
Using 800 g of a copolymer rubber consisting of 1-butene and 5-ethylidene-2-norbornene, it was rolled at a roll temperature of 75°C/80°C (front roll/ The mixture was kneaded for 20 minutes using a back roll to obtain an unvulcanized compounded rubber. This compounded rubber was heated under a pressure of 150 kg/cm ² for 30 minutes using a press heated to 160°C to form a 14 cm x 12
A vulcanized sheet with a thickness of 2 mm and a thickness of 2 mm was prepared. JIS No. 3 dumbbells were punched out from this sheet according to the method specified in JIS K6301 at a tensile speed of 500 in an atmosphere of 25℃.
The stress at break TB (Kg/cm ² ) and elongation at break EB (%) were measured using mm/min. In addition, the hardness HS (JIS A) was measured according to the same JIS regulations. In addition, a sample was taken from the vulcanized sheet and the AC breakdown voltage and dielectric loss tangent at 25°C and 500V were measured using the Schering-Brissige method at a voltage increase rate of 1KV/sec. Separately, the unvulcanized compounded rubber is processed using a 50mmφ extruder (L/
D=10, compression ratio=6, Garvey dye),
The appearance of the surface of the strands obtained by extrusion at an extrusion temperature of 105° C. and a rotational speed of 40 rpm was observed, and the extrusion texture was evaluated in five grades as an index of extrusion processability. 5... No surface unevenness at all, good gloss 4... Almost no surface unevenness, no gloss 3... Slight surface unevenness, no gloss 2... Surface unevenness, no gloss 1... Surface There were large irregularities and no gloss at all. The above results are shown in Table 2.

[Table] Examples 2, 3, 4, Comparative Examples 1, 2 Ethylene, 1-butene, and 5-ethylidene listed in Table 2 as the copolymer rubber in Example 1
The same operation as in Example 1 was performed except that 2-norbornene copolymer rubber was used. The results are shown in Table 2. Comparative Examples 3 and 4 Ethylene, propylene, and 5-ethylidene listed in Table 2 as the copolymer rubber in Example 1
The same operation as in Example 1 was performed except that a copolymer rubber consisting of 2-norbornene was used. The results are shown in Table 2. Comparative Example 5 The same operations as in Comparative Example 3 were performed except that the formulation was changed as shown in column B of Table 1 to improve extrusion processability. The results are shown in Table 2.

[Table] Example 5, Comparative Example 6 Ethylene-1-
Butene/dicyclopentadiene copolymer rubber (Example 5) and ethylene/propylene/dicyclopentadiene copolymer rubber (Comparative Example 6) were used, the proportions were as shown in column A of Table 3, and vulcanization was performed. The same operation as in Example 1 was performed except that the temperature was 180° C. for 5 minutes. The results are shown in Table 4.

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Claims (1)

[Scope of Claims] 1. A copolymer in which the molar ratio of ethylene units to α-olefin units having 4 to 10 carbon atoms (ethylene/α-olefin) is in the range of 80/20 to 95/5; , its intrinsic viscosity [η] is 0.6 to 6.0 dl/g
The polyene unit content is 4-50 in terms of iodine value and the molecular weight distribution index Q value (M _W /M
An electrical insulating material mainly composed of ethylene/α-olefin copolymer rubber having _N ) of 4 to 12. 2. The electrical insulating material according to claim 1, which is an insulating layer of an electric wire.