CA1100304A

CA1100304A - Electrical insulating oil compositions

Info

Publication number: CA1100304A
Application number: CA277,393A
Authority: CA
Inventors: Shoji Kimura; Noboru Ishida; Midori Masunaga; Yoshiki Kohno
Original assignee: Nippon Oil Corp
Current assignee: Eneos Corp
Priority date: 1976-05-01
Filing date: 1977-04-28
Publication date: 1981-05-05
Also published as: JPS6051210B2; DE2719218C2; FR2349929B1; DE2719218A1; GB1569934A; JPS52133600A; FR2349929A1

Abstract

ELECTRICAL INSULATING OIL COMPOSITIONS

Abstract of the disclosure :
An electrical insulating oil composition consisting essentially of (I) 50 - 95 parts by weight of a mineral oil-derived electrical insulating oil, (II) 5 - 50 parts by weight of at least one oil selected from arylalkanes, diarylalkanes, polybutene, a highly aromatic oil having a specified refractive index and a hydrocarbon oil-derived hydrofined oil and an electrical insulating oil of naphthenic origin with the proviso that this insulating oil is omitted if the insulating oil (I) is of naphthenic origin, and (III) 0.001 - 1.0% by weight of a hydrocarbon-derived pour point depressant, based on the total weight of the oils (I) and (II).

Description

` 11003~4 This invention relates to a mineral oil-derived electrical insulating oll having improved pour point.
Electrical insulating oils of mineral oil origin have heretofore generally been produced from a naphthenic base crude oil as the starting oil. It has recently been expected to produce from a mixed or paraffinic base crude oil which is available at a relatively low cost in large quantities.
However, electrical insulating oils of mixed or paraffinic crude oil origin are disadvantageous in that they have a high pour point.
This invention is applicable to the improvement of all mineral oil-derived electrical insulating oils in pour point and is particularly valuable in improving in pour point electrical insulating oils produced from the mixed or paraffinic base crude oil as the starting oil.
The electrical insulating oil composition o~ this invention consists essentially of (I) 50 - 95 parts by weight of a mineral oil-derived electrical insulating oil, (II) 5 - 50 parts by weight of a member selected from the group consisting of (1) at least one arylalkane, (2) at least one diarylalkane, (3) polybutene~ (4) a highly aromatic oil having a refractive index of ( n d5) 1.56-1.60 obtained by hydrofining a distillate contained in a fraction having a boiling range of about 250 -about 400C at atmospheric pressure obtained by the pyrolysis f petroleum at a temperature of about 6000 - about 9000C (5) an oil obtained by hydrofining a distillate contained in a fraction having a boiling range of about 230 - about 450C
at atmospheric pressure produced as a by-product by reforming a hydrocarbon oil in the presence of a noble metal catalyst 0 and (6) an electrical insulating oil produced from a naphthenic

- 2 - ~

- 1~0~3g34 base crude oil as the starting oil, the insulating oil (6) being not used as the oil (II) if the mineral oil-derived electrical insulating oil (I) is of naphthenic origin and (III) 0.001 - 1.0% by weight of a hydrocarbon-derived pour point depressant, based on the total weight of the oils (I) and (II), the depressant being at least one compound selected from (i) a copolymer of ethylene and an ~-olefin having the general formula CH2=CH-R wherein R is an alkyl group having at least one carbon atom, (2) a poly-~-olefin, (3) a hydro-generated, styrene-butadiene copolymer, (4) a condensed alkyl-naphthalene, and (5) an alkylated polystyrene. Thus, this invention is based on the finding or discovery that the addi-tion of both the oil (II) and oil (III) to the oil (I) exhibits such an unexpectedly great pour point-depressing action on the oil (I) as may not be expected from the addition of the oil (II) alone or the oil (III) alone to the oil (I).
This invention will be detailed hereinbelow.
The mineral oil-derived electrical insulating oil (I) may be one which is produced from any of naphthenic, mixed and paraffinic base crude oils, or may be blends of the oils so produced.
The naphthenic base crude oil used herein is one con-taining naphthenic hydrocarbons in large proportions and more particularly the crude oil is such that its first key fraction (kerosene fraction) has an API specific gravity of not greater than 33 and its second key fraction (lubricating oil fraction boiling at 275 - 300C at a reduced pressure of 40 mm of mer-cury) has an API specific gravity of not greater than 20. As is described in "Sekiyu Binran (Handbook on Petroleum)" on page 19, 1972 edition published by Sekiyu Shunju Co., Ltd., Japan typical of the naphthenic base crude oils are a California crude oil, a Texas crude oil, a Mexico crude oil, a Venezuela crude oil and a Duri crude oil.
B - 3 _ `10~3~4 The paraffinic crude oil used herein is one contain-ing paraffinic hydrocarbons in large proportions and more par-ticularly the crude oil is such that its first key fraction has an API specific gravity of not smaller than 40 and its second key fraction ha~ an API specific gravity of not smaller than 30 as is described in said ~andbook on Petroleum: typical of the paraffinic base crude oils are a Pennsylvania crude oil, a Minas crude oil and the like.
The mixed base crude oil used herein is one which is qualitatively intermediate between the paraffinic and naphthenic base crude oils and more particularly the mixed base crude oil is such that its first key fraction has an API specific gravity of 33 - 40 and its second key fraction an API specific gravity of 20 - 30, typical of the mixed base crude oils are a Mid-continent crude, oil, an Arabia crude oil, a Khafji crude oil and the like.
This invention is applicable to an electrical insulat-ing oil, as a base oil, of naphthenic, mixed or paraffinic origin, as previously mentioned.
There have heretofore known many processes for the preparation of electrical insulating oils from naphthenic base crude oils, the processes including a process compri ing hydro-fining a mineral oil to effect a 65 - 96% desulfurization and then treating the thus-desulfurize~ mineral oil with a solid absorbent (Japanese Patent Gazette No. 18584/61) and a process comprising blending a mineral oil raffinate in hydrogenated form having an aromatic content of not higher than 23% by weight with not more than 15% by weight of a lubricating oil having a higher aromatic content than the hydrogenated raffinate (Japanese Patent Gazette No. 3589/66).
Processes for the preparation of electrical insulat-ing oils from paraffinic base crude oils include, for example, 10~4 ~ pr~cess comprising disti31ing a distillate obtained by dewax-ing a vacuum distilled gas oil fraction 5 - 95% of which boils at 288 - 399C (550 - 750F) and recovering a heart cut there-by obtaining an electrical insulating oil (Japanese Patent Gazette No. 46123/74).
The present inventors have already filed a patent application for a process for the preparation of an electrical insulating oil which comprises refining with furfural or other suitable solvents at 50 - 100C a distillate having a boiling range of 250 - 400C at atmospheric pressure obtained by the distillation of a paraffinic or mixed base crude oil at atmos-pheric pressure or by the distillation at a reduced pressure of a bottom oil obtained by the distillation of the crude oil at atmospheric pressure, to effect a 30 - 75 wt.% desulfurization thereby obtaining a raffinate, hydrofining the thus obtained oil to remove therefrom 40 - 90 wt.% of the sulfur contained therein, solvent d0waxing the desulfurized oil and, if desired, successively treating the dewaxed desulfurized oil with clay thereby to obtain the electrical insulating oi1 having a sul-fur content of 0.1 - 0.35 wt.%, satisfactory oxidation stabil-ity, electrical properties and resistance to copper corrosion (U. S. Patent No. 4,008,148), and they have also already filed a patent application for a process for the preparation of an electrical insulating oil having a total sulfur content of not more than 0.35 wt.%, excellent oxidation stability, thermal stability, corona resistance and corrosion resistance which consists essentially of (I) 80 - 99 parts by weight of a re-fined oil obtained by solvent refining a distillate contained in a fraction having a boiling range of 230 - 430C at atmospheric pressure, the fraction being obtained by the dis-tillation of a paraffinic or mixed base crude oil at atmospheric _ 5 _ B

- ` 110~ 4 pressure or by the distillation at a reduced pressure of a bottom oil obtained by the distillation of the crude oil at atmospheric pressure, to produce a raffinate, hydrofining the raffinate so produced, solvent dewaxing the thus-hydro-fined oil and, if desired, treating the dewaxed hydrofined oil with a solid adsorbent thereby to obtain the refined oil hav-ing a sulfur content of no higher than 0.25 wt.% and an aro-matic content of from more than 25 wt.% to 35 wt.% and (II) 1 - 20 parts by weight of a refined oil obtained by treating the lubricating fraction of a mineral oil with a solid adsor-ben~ (Japanese Pat. Appln. Laying-Open Gazette No. 93400/76).
There have been known various processes for the prep-aration of electrical insulating oils from any one of crude oils. Typical of them is a process for preparing an electrical insulating oil by either providing a lubricating oil fraction obtained by distilling at a reduced pressure a bottom oil obtained by the distillation of the crude oil at atmospheric pressure or providing a fraction having a boiling range of about 260 - 400C at atmospheric pressure obtained by deasph-alting the bottom oil to obtain a heavy oil, subjecting thethus-obtained heavy oil to hydrogenolysis at a temperature of not lower than 350C and a high hydrogen pressure of not lower than 150 kg/cm2G and distilling the thus-hydrogenolysed oil to obtain a fraction having a boiling range within the range of about 260 - 400C at atmospheric pressure, and, if necess-ary, successively dewaxing the ~raction with a suitable solvent thereby to prepare the electrical insulating oil. The sol-vent may be a benzene-toluene-methyl ethyl ketone Ivol. ratio, e.g. 25 : 25 : 50) mixture.

C1 3~4 This invention may of course be applicable not only to electrical insulating oils obtained by the said typical procesQ but also those of mineral oil origin obtained by any other processes, irrespective of the manner of the processes.
The second component oil (II) of the electrical in-sulating oil composition is at least one member selected from the group consisting of (1) at least one arylalkane. (2) at least one diarylalkane, (3) polybutene, (4~ a highly aromatic oil having a refractive index of (nl5) 1.56 - 1.60 obtained by thermocracking petroleum at about 600 - 900C to obtain a fraction having a boiling range within the range of about 250 - 400C at atmospheric pressure and hydrofining the fraction having a boiling range within the range of about 230 - 450C at atmospheric pressure, the fraction being obtained at the time of réforming a hydrocarbon oil in the presence of a noble metal catalyst and (6) an electrical in-sulating oil obtained from a naphthenic base crude oil as : the starting oil with the proviso that this in~ulating oil is omitted if the mineral oil-derived electrical insulating oil (I) is of naphthenic origin.
The axylalkane (1) used herein is an alkylbenzene represented by the following general formula ~ R2 wherein Rl and R2 are each hydrogen or a hydrocarbon residue having 1 - 20 carbon atoms with the proviso that the total -` 110~3~4 of the carbon atoms of Rl and R2 is not less than 9, prefer-ably 12 - 28.
The use of an arylalkane of said formula wherein the total of the carbon atoms of Rl and R2 is less than 9 will result in the production of an electrical insulating oil having an unsatisfactory flash point and exhibiting an unsatisfactory evaporation test result. The hydrocarbon residues Rl and R2 may be straight-chained or else branch-chained. The alkylbenzenes used herein may contain tetralin, indene, indane and their hydrocarbon derivatives in amounts of not more than about 50% by weight of the alkylbenzenes.
These alkylbenzenes may usually be obtained by conden-sing (alkylating) benzene with an olefin or with a halogenated paraffin in the presence of an acid catalyst such as a Friedel-Crafts type catalyst. The alkylbenzenes which may preferably be used in the industrial field, include mono-alkylbenzenes having about 9 - 16 carbon atoms obtained at the time of synthesis of straight-chained or branch-chained alkylbenzenes for use as cleansers or heavy alkylbenzenes obtained as a by-product at the time of synthesis of such monoalkylbenzenes, and a bottom oil (obtained after the distilling-off of the alkylbenzenes for use as cleansers).
It is preferable that these alkylbenzenes be used after their treatment with an adsorbent. Generally, it is also preferable that the arylalkanes be hydrofined prior to their use in view of the electrical properties of electrical insulating oil compositions to which the arylalkanes are to be added.
As catalysts for said hydrofining, there may preferably be used at least one member selected from the group consisting of metals of Groups VI, VII and VIII of the Periodic Table, ` llOQ3~4 and the oxides and sulfides of the metals ; the catalysts may preferably be supported on a solid carrier such as sillca, alumlna, diatomaceous earth or activated carbon.
More particularly, the catalysts which may be or may not be supported on the aforesaid carrier include palladium, platinum, nickel, copper-chromium, cobalt-molybdenum, nickel-molybdenum and nickel-tungsten. The hydrofining may be carried out at a pressure of usually 2 - 50 kg/cm2G and a temperature of 50 - 400C and at a liquid hourly space velocity (LHSV) of l - 15 vol./vol.
If the arylalkanes according to this invention are to be produced from straight-chained heavy alkylbenzenes, then it is particularly preferable that the heavy alkylbenzenes should be hydrofined under such conditions that only the alkyl polycyclic aromatic compounds contained as impurities in the heavy alkylbenzenes are select1vely hydrofined and should thus be used as a compound having an absorbancy of not higher than 0.4 x 10 3 g/l.cm at a wavelength of 400 m~
in the wavelength region of visible rays.
The diarylalkane (2) according to this invention is a compound represented by the following general formula R ~ ¦ ~ R4 ~6 wherein Rl , R2 ~ R3 and R4 are each hydrogen or an alkyl group having 1 - 15 carbon atoms with the proviso that the total of the carbon atoms of Rl - R4 is at least 2, and R5 and R6 _ g _ 110~3Q4 are hydrogen or a methyl group. The diarylalkanes may be produced easily at a low cost from aromatic compounds obtainable in the petrochemical industry, by the use of any one of various known processes. These knownprocesses include a process comprising reacting styrene, ~ -methylstyrene or their alkyl derivative with benzene or an alkylbenzene in the presence of an acid catalyst such as sulfuric acid or a cationic ion exchange re~in and a process comprising dehydrochlorination condensing an aryl chloride with benzene or an alkylbenzene in the presence o~ a Friedel-Crafts type catalyst.
Diarylalkanes produced by the use of other known processes may also be used in the practice of this invention. In addition, there may further be used diarylalkanes containing not more than 10,~ of a by-product produced at the time of reaction for producing the diarylalkanes. Typical of the diarylalkanes are ~ -methylbenzyltoluene, d, d' -dimethyl-benæyltoluene, ~-methylbenzylxylene, d, ~'-dimethylbenzylxylene and mixtures thereof.
The polybutene (3) used herein is a liquid polymer consisting mainly of isobutylene and is obtained by polymerizing a butane-butene fraction, obtained as a by-product when naphtha, for example, is thermocracked in attempts to produce ethylene, propylene or the like, at a temperature of about -30 to 30C in the presence of a Friedel-Crafts type catalyst such as aluminum chloride. The polybutene used herein should have an average molecular weight of about 200 - 400, prefcrably about 250 - 300.
The petroleum (4) according to this invention is thermocracked at about 600 - 900C to obtain a fraction boiling at about 250 - 400C at atmospheric pressure, a part or the whole ' llOQ3~}4 of which fraction is hydrofined thereby to obtain a highly aromatic oil having a refractive index of (nd5) 1.56 - 1.60.
The highly aromatic oil will be further detailed hereinbelow.
Hydrocarbons having at least 5 carbon atoms are obtained as a by-product when naphtha, kerosene, gas oil or other petroleum is subjected to steam cracking, thermo-cracking, catalytic cracking or the like at approximately 600 - 900C to produce therefrom ethylene, propylene and other lower olefins. Among these olefins, the olefins having 5 and 9 carbon atoms are partly used as a starting material for petroleum resins, those having 6 - 8 carbon atoms are used as a starting material for producing benzene, toluene and xylene and those having at least 9 carbon atoms excspt for those having 9 carbon atoms for the petroleum resins are used in the practice of this invention.
The residual cracked oil obtained by the aforesaid naphtha cracking is very highly aromatic substantially with-out paraffinic and naphthenic oils being contained. The residual cracked oil is distilled at a reduced pressure to separate therefrom a fraction having a boiling range within the range of about 250 - 400C. Or the cracked oil is dis-tilled at a reduced pressure to separate it into a liquid material boiling at not higher than about 400C and a heavy material boiling at not lower than this temperature. Then, said liquid material is heat treated at not higher than about 200C at atmospheric or superatmospheric pressure for longer than about one hour or else it is catalytically heat treated in the presence of a Friedel-Crafts type catalyst to polymer-ize alkylindenes and other unsaturated compounds contained therein thereby converting it to a heavy material which is then X

110~304 dlstilled to remove therefrom a polymerized material having a boiling range of higher than 400C while recovering a dlstlllate having a bolling range within the range of about 250 - 400C. The boiling range of the distillate used herein may include preferably at least about 80%, more preferably at least 90% of said range of about 250 - 400C.
The distillate so recovered is then hydrofined to obtain a desired highly aromatic hydrocarbon having a refractive index of ( n2d0 ) 1.56 - 1.60 and a specific dispersion of not lower than 200, preferably 225 - 300. The catalysts u~ed for said hydrofining may be conventional ~no~m ones such as, preferably, nickel, molybdcnum and cobalt oxides and sulfides supported on an alumina-containing carrier ; the most preferable ca-talyst is preliminarily sulfurized nickel oxide-molybdenum oxide supported on an alumina carrier.
In the hydrofining, the pressure used is usually in the range of 20 - 100 kg/cm2~, preferably 25 - 60 kg/cm2G ; the reaction temperature used is in the range of 2~0 - 400C, preferably 260 - 340C ; and the amount of hydrogen fed is in the range '0 of 100 - 10,000 Nm3, preferably 200 - 1,000 Nm3.
The hydrofined oil (5) according to this invention obtained by hydrofining a distillate contained in a fraction having a boiling range of about 230 - 450C at atmospheric pressure produced as a by-product at the time of reforming a hydrocarbon oil in the presence of a noble metal catalyst, will be detailed hereunder. A hydrocarbon oil, such as straight-ru~l naphtha or craoked gasoline, having a boiling range of about 40 - 200C, preferably about 60 - 180C , is reformed in the prescnce of a noble metal catalyst to ) produce a high octane number gasoline, benzene, toluene, 110~3~4 xylene and other aromatic hydrocarbons simultaneously with the production, as a by-product, of a fraction having a boiling range of about 230 - 450C at atmospheric pressure in which is contained a heavy oil distillate usable as material for the hydrofined oil (5) in the practice of this invention. The boiling range of the hydrofined oil (5) may include preferably at least ~30%, more preferably at least 90%, of that of the said fraction boiling at about 230 -4509C. The heavy oil distillate is usable as the hydrofined oil (5) without need of distillation thereof if it meets the requirements for the oil (5), however, it may be preferable to obtain such a usable distillate meeting the said require-ments by distillation of the original heavy oil distillate.
Almost all of the usable heavy oil distillate consists of polycyclic aromatic hydrocarbons having at least 10 carbon atoms. The noble metal catalysts used herein may be those which are known to be usable for such a reaction as above.
Particularly preferable catalysts include metals of the Platinum Group of the Periodic Table and mixtures thereof, each supported on a solid carrier. There may also prefer-ably be used catalysts comprising the Platinum Group metal and mixtures thereof in combination with at least one member selected from Ge, Sn, Re, Fe, Pb and halogens, the catalysts being supported on a solid carrier. The solid carriers which may preferably be used include alumina, silica, zeolite and silica-alumina~ The reforming reaction according to this invention may be carried out at a reaction pressure of 1 - 50 kg/cm2G, preferably 5 - 40 kg/cm G and a reaction temperature of 400 - 600C, preferably 470 - 530C, at a hydrogen feed rate of 100 - 1,500 Nm3, preferably 300 - 1,000 Nm , per Kl of oil and at a LHSV of --` 110~3~4 0.5 - 5 hr 1, preferably 1 - 3 hr 1 The aforesaid heavy oil distillate is usually subjected to hydrofining treatment thereby obtaining a desired hydrofined oil (5). The hydrofining catalysts used herein include the oxides, sulfides and mixtures thereof of metals of the Groups IB, IV and VIII
of the Periodic Table, the catalysts being supported on an inorganic carrier such as bauxite, activated carbon, diatomaceous earth, zeolite, silica, alumina or silica-alumina. The preferable metal~ of the Groups IB, IV and VIII include cobalt, nickel, molybdenum and tungsten. Particularly preferable catalysts are those comprising a mixture of at least two of molybdenum oxide, tungsten oxide and cobalt oxide, the mixture being supported on an alumina carrier. In the hydrofining treatment, the reaction temperature used is 230 - 400C, preferably 260 - ~60C ; the reaction pressure used is usually 20 - 150 kg/cm2G, preferably 25 - 80 kg/cm2G ; the hydrogen feed ra-te used i5 100 - 10,000 Nm3, preferably 200 - 1,000 Nm3, per kl of heavy oil distillate ; and LHSV used is 0.5 - 5 hr 1, preferably 1 - 4 hr 1 ~0 The hydrocarbon-derived pour point depressant which is the component (III) according to this invention, is ~' ~o~7o/~e~
at least one compound selected from (1) a coplymor of ethylene and an ~-olefin having the general formula CH2=CH-R wherein R i~
an alkyl group having at least one carbon atom , (2) poly- d-olefin ~5 ( ~-olefin polymer), (3) a hydrogenated, styrene-butadiene ~o~o/"~e ~^
copl~mor, (4) a condensed alkylnaphthalene and (5) an alkylated polystyrenc.
The copolymers (1) of ethylene and ~-olefin include ethylene-propylene copolymers, ethylene butene-l copolymers ~0 and ethylene hexene-l copolymers with ethylene-propylene -- 110~1t334 copolymers being particularly preferred. The ethylene~ a-olefin copolymers used herein are essentially amorphous oil-soluble ones having a number average molecular weight of usually 10,000 - 200,000, preferably 20,000 - 70,000, and an ethylene content of 30 - 90 mol%, preferably 40 - 80 mol%. The term "essentially amorphous" used herein means that the ethylene~ -olefin copolymers may have some degree of crystallization therein, the degree being usually 0 - 5%, preferably 0 - 2%. In addition, it is preferable that the copolymers have a relatively narrow distribution of molecular weight, the distribution being usually not higher than 8, particularly not higher than 4. The ethylene~ a-olefin copolymers may be produced by known processes. The co-polymerization may be effected by reacting ethylene with at least one a-olefin in an inert organic solvent containing an organic solvent-soluble specified homogeneous Ziegler type catalyst at atmospheric or somewhat superatmospheric pressure and at a temperature varying from a somewhat low temperature to a somewhat high temperature. The Ziegler type catalyst which may preferably be used is a coordination catalyst com-prising a vanadium compound and organoaluminum compound such as VOC13 - Al (C2H5) system.
The poly-a-olefin or polymer of a-olefin t2) usable as the component (III) of this invention is a homopolymer or copolymer of ~-olefin having the general formula CH2=CH - R
wherein R is any one of alkyl groups which have 7 - 18, preferably 8 - 16, carbon atoms and are identical with, or different from, each other at the same time. The polymer of a-olefin (2) may also be a mixture of said homopolymer and copoly~er.

-` 110~3~4 The polymer or copolymer contains ~ CH2 ~n in which n is at least 6. These polymers of a-olefin may be produced in the presence of the same homogeneous Ziegler type catalyst as the aforesaid ethylene~ a-olefin copolymer (1). The polymer of ~-olefin has a number average molecular weight of usually 10,000 - 200,000, preferably 20,000 - 70,000 and is essentially amorphous, in addition, it should preferably have a relatively narrow molecular weight distribution.
The hydrogenated styrene-butadiene copolymer (3) usable as the component (III) according to this invention may be produced by a known process such as a process com-prising copolymerizing styrene and butadiene in the presence of an alkyl-alkali metal compound, such as butyllithium, as a catalyst and hydrogenating the resulting styrene-butadiene copolymer using a known hydrogenating technique. It is desirable that at least 90%, preferably 100%, of the double bonds contained in the original styrene-butadiene copolymer be hydrogenated.
The hydrogenated styrene-butadiene copolymer (3) is preferably a random copolymer and has an average molecular weight of usually 10,000 - 200,000, preferably 20,000 -70,000. The ratio of content between the styrene units and the butadiene units in the copolymer is 15 - 50 : 85 - 50, preferably 25 - 40 : 75 - 60.
The condensed alkylnaphthalene (4) usable as the component (III) is a condensate of dichloroparaffin and naph-thalene and may be synthesized by a known process using a catalyst such as anhydrous AlC13. The dichloroparaffin usable herein is dichloride of a paraffin having about 15 - 60 car-bon atoms. The condensed alkylnaphthalene usable herein ~,.

11~103~4 has a molecular weight of several thousands to hundred thousands, usually about 2,000 - 70,000.
The alkylated polystyrene (5) usable as the component (III) according to this invention may be produced by a konwn process such as a process comprising subjecting styrene to radical polymerization in the presence of a peroxide, such as benzoyl peroxide, as an initiator. Starting polystyrene for the alkylated polystyrene (5) has a number avera~e rnolecular weight of 10,000 - 150,000 , preferably 20,000 - 70,000. The starting polystyrene is alkylated by contacting an alkyl halide therewith in the presence of a Friedel-Crafts type catalyst. The alkyl halide is represented by the general formula ~X wherein R is an alkyl group having 6 - 20, preferably 8 - 18, carbon atoms and X i5 a halogen atom.
This invention is based on the finding or discovery that a mineral oil-derivçd electrical insulating oil (I) may remarkably be depressed in pour point without impairing the electrical properties thereof by adding thereto a specified oil (II) and a specified hydrocarbon-derived pour point depressant each in a specified proportion.
According to this invention, the blending ratio by weight of the mineral oil-derived electrical insulating oil (I) as the 1st component to the oil (II) as the 2nd component may be in the range of 50 - 95 : 5 - 50, preferably 60 - 90 : 40 - 10, and more prefe~ably 70 - ~5 : 30 - 15.
The use of the oil (II) in a higher blending ratio than the oil (I) will not be effective in further improving the oil (I) in properties, particularly pour point, nor will it be economical. The use of the components (II) and (I) in a blending ratio of less than 5 : 95 will not be effective ~OQ3~4 in remarkably depressing the pour point of the component (I) although such remarkable depression is characteristic of this invention. In addition, the hydrocarbon-derived pour point depressant (III) as the third component of the insulating oil composition of this invention may be used in amounts of 0.001 - 1.0~, preferably 0.05 - 0.2Yo,Of the total weight of the components (I) and (II).
Furthermore, the electrical insulating oil composition of this invention may be incorporated with a known antioxidant such as DBPC (di-tert.-butyl-p-cresol), N-phenyl-~ -naphthylamine, nicotinic acid or hydroquinoline.
This invention will be illu6trated. by the following non-limitative Ex~mple9 wherein all percentages and parts are by weight unless otherwise specified.
Example 1 There was obtained a distillate having a boiling range of 260 - 380C at atmospheric pressure and a sulfur content of 2.2 wt.% by distilling an Arabia crude oil at atmospheric - pressure to obtain a bottom oil and distilling the thus-obtained bottom oil at a reduced pressure. The distillate so obtained was extracted with furfural in a solvent ratio (furfural/
distillate) of 1.3 at an extracting temperature of 75 - 90C
to obtain a raffinate having a sulfur content of 0.8 wt.%.
The thus-obtained raffinate was hydrofined at 310C under a hydrogen pressure of 40 kg/cm2G in the presence of an alumina-carried NiO-MoO3 catalyst (NiO : 3.0 wt.%, MoO3 : 14.0 wt./~) to obtain a hydrofined oil which was dewaxed with a benzene-toluene-methyl ethyl ketone mixed solvent in a solvent ratio (solvent/oil) of 1.6 at a cooling temperature of -30C and successively treated with clay at 70C for one hour thereby 110~3Q4 obtaining an electrical insulating oil (A).
Separately, there was obtained heavy alkylbenzenes having a boiling range of about 310 - 404C as a by-product at the time of synthesis of branched alkylbenzenes for use as cleansers from benzene and olefins composed ma~nly of propylene tetramer in the presence of boron trifluoride as a catalyst. The heavy alkylbenzenes so obtained was then treated with clay at 70C for one hour to obtain a clay-treated oil as the component (II) of the insulating oil composition of this invention. Thirty (30) parts of the clay-treated oil and 70 parts of the electrical insulating oil (A) were blended together thereby to obtain a blended oil (B).
Furthermore, an essentially amorphous ethylene-propylene copolymer having an average molecular weight of 36,000 and a propylene content of 30 mol% was added to the blended oil (B) in the amount of 0.05% of the oil (~) thereby obtaining an electrical insulating oil (C 3 according to this in~ention.
The properties of the electrical insulating oil (A), blended oil (B) and electrical insulating oil (C) are shown in Table 1.
For comparison, the said amorphous ethylene-propylene copolymer was added to two equal portions of the electrical insulating oil (A) in the amounts of 0.05,~ and 0.1% of the portions of the oil (A) to obtain blended oi7s ~D) and (E), respectively. The properties of these oils (D) and (E~ are also indicated in Table 1.
For further comparison, the blended oil (B) was incorporated with 0.2% of polymethacrylate which was a non-hydrocarbon derived pour point depressant, thereby to obtain a blended oil (F) the properties of which are also sno~m in Table 1.
As is apparent from Table 1, the addition of only the lll)Q3~4 clay-treated heavy alkylbenzenes to the electrical insulating oil (A) was hardly effective in depressing the pour point of the oil (A), the addition of only the amorphous ethylene-propylene copolymer to the electrical insulating oil (A) was somewhat effective in depressing the pour point of the oil (A) and the electrical insulating oil (C) obtained by the addition of both the clay-treated heavy alkylbenzenes and the amorphous ethylene-propylene copolymer to the insulating oil (A) exhibited a remarkably depressed pour point without imparing the other properties required in electrical insulating oils. Furthermore, an electrical insulating oil prepared by adding polymethacrylate to the blended oil (B) exhlbited remarkably unsatisfactory electrical properties, steam emulsion number and like properties and was therefore unsatisfactory as such.
In Table 1, corrosion test and evaluation of corrosiveness were carried out in accordance with ASTM D-1275 and ASTM D-130, respectively.

110~3~4 ~o 8 a) ~ ~ ~
-- ~ ~ O ~ ~ O
~) ~1 U ~1 + ~ N + ~, d' [` O ~ O
m o ~ o P~ R PO~ o o <`J ~;
, u~
-- .~ ~o a~ liil ~ 1 ~ 3 _1 ~
-- ~ ,1 _ + ~1 >,_I 1-') X O
S: ~ U ~ oQI OQ~-I ~ "~ o ,Q d' m o ~ o~3 ~,o ~ o __.__ _ I ~ s, . U~
~^ C)~ 3 1~ -1O
. _~ a~
~-- ~) ~ _ ~ 1 Lt) t` X O
~m o ~-~ o ~ ~ ~ ~ ~ o ~ ~
~ _, E~,1 ~ ~ ~ ~
o -,~ ~ n r~ ~ .~ ~
s~ ~ c) ~ L~l o _ ~ ~1 _ + ~ a) + _I ~ . ~ In U ::1 o ~S ~ N ~ 0<~1 X O
1 ~ 0~ h 0 d' ~1 O ~ O d' ~ O ~~1 0 ~ O ~ O ~ ~
~1 ~^ .~
a~ m s~ + ~ u~ o -- ~_ ~a~ . ~ ~r ~: ~ ~ t` ~ oo R
o ~: ~ -- -lo o R

. ~ ~q~ ~ ~ o C~ ~ O - ~ o O
o ~q ~ V ~_ ., ~ '~ V Vo ~ ~ ~ V 1` ~ ~ ~ O
~:: a~ . ~1 a) o ~ ~ 1 o ,~ ~,3 S~ >~1 ~ ~
o ~ ~ ~ ~1 x ~ ~ a) v v ~ ~v ~ 1 ~
v ~ ~ ~ O ~ R ~ ~ ~ ~
. o o o ~ c o ~1 a) ~ H ::~ 0 n _ _ u) c ~ X

~ 21 ~

` 110~3~4 ExamPle 2 The blended oil (B) obtained in Example 1 was incorporated with 0.1% of a styrene-butadiene copolymer having a number average molecular weight of about 40,000 and a styrene content of 32 mol%, in which copolymer 95~ of the doubles bonds of the butadiene has been hydrogenated, thereby to obtain an electrical insulating oil (G). In addition, the electrical insulating oil (A) obtained in Example 1 was incorporated with 0.1~ of said hydrogenated styrene-butadiene copolymer to obtain a blended oil (H). The propertiesof the oils (G) and (H) are shown in Table 2.

>o 110~3Q4 U D ~ 11 0 1~
0~ _ O S~
~ ~:: ~ ~1 ~ ~

c~ 0 a~ ~ ~ ~3E~

O S~ h :~ ~ CD ~ h h ~ U O O

'~

3 1(~Q3~i4 Example 3 Seventy-five (75) parts of the electrical insulating oil (A) were blended with 25 parts of polybutene having an average molecular ~reight of about 280 to obtain a blended oil (J). The blended oil so obtained was then incorporated with 0.07~ of of the a~orphous ethylene -propylene copolymer as used in Example 7 to obtain an electrical insulating oil (K) having the properties sho~m in Table 3. For comparison, Table 3 shows the properties of a blended oil (L) prepared by incorporating the electrical insulating oil (A) with 0.07% of the ethylene-propylene copolymer.

~0 110~3~4 n ,~"

l o ~
0~ Cc ~o o x o o _~
~0 ~

~ I', _ 0 ~o ~
o ~ ~ U~ X o I ~ I 1~
,~0 oo '~` o~ o ~ ~ ~
~ , o ~ o^ ~_ ~OEo O 0 E u o --~ x 0 ~ ~ , o :~ ~ O ~ o a) ~ H ~ ~ ~a -o ~ ._~ ~ ~ s~ æ ~

11003~4 Example 4 A distillate having a boiling range of about 280-380C obtained by distilling a Duri crude oil at atmospheric pressure, wa~ hydrofined at a reaction temperature of 330C, a hydrogen pressure of 35 kg/cm2G and a LHSV of 2.0 in the presence of the same alumina-carried NiO-MoO3 catalyst as used ~n Example 1 thereby to obtain a hydrofined distillate which was treated with clay at 70C for one hour to yield an electrical insulating oil (M). Seventy (70) parts of the insulating oil (M) were blended with 30 parts of the clay-treated heavy al~ylbenzenes as used in Example 1 to obtain a blended oil (N) which was then incorporated with 0.01%
of the ethylene-propylene copolymer as u~ed in Example 1 thereby obtaining an electrical insulating oil (0) according to this invention. The properties of these oils are shown in Table 4. For comparison, the base oil (M) was incorporated with 0.01% of the ethylene-propylene copolymer to obtain a blended oil (P) having the properties shown in Table 4.

3~4 _ W
_ `_ W
P. ,, ~ U~
_ .,, Q, ~ o ~o ,, .,1 -! ~ ~ o o ~ o X o .
.,,~ ~ ~ , , o .
~ ~ ~ ~1~ ~ .
~ ~ o~ .
m ~ 3 u ~A _ ,a W
U) ~rl ~ O
O O ~ ~I) O U~
w ~ h ~ X O
115 ~ + d N + I ~ ~
u ~ ~ a) o I u~ O
,~ ~ ~1 ~ h a~i h tlS h td ~) ,4a) ~ ~1 ~_I ~,1 1 ~ ~
U ~ W ~ ~
~ ~ _1 ~ ~ ~ O
~-~ ,~ u _ ~
o~ a~ o ~ ~ ~ ~ u~
,, ~ ~~ al . O
W O tl~1 N t` X O t`~
_I ~rl + aJ ~
R ~5 ,1~S~ O I 0 O
~ w S--I ~a ~
E~ ~ ~ ~I ,1 m ~
_ .,., c~ _ o ~o ~,c ~ ~
~rl ~ n X o a~
s~ ~ ~ .
1 0 o o ~ .
Q) ~
~ --.~ ~ ~
.,, ~ ~
o o O ~ ' ~ ~
~ a) .,, ~ ~
'~

~,~ oa3 o aJ ~J H
OO O ~rl 0 1 ~ ~ 0 a aD cq 0~

~ .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. An electrical insulating oil composition consisting essentially of (I) 50 - 95 parts by weight of a mineral oil-derived electrical insulating oil, (II) 5 - 50 parts by weight of at least one oil selected from the group consisting of (1) arylalkanes, (2) diacrylalkanes, (3) polybutene, (4) a highly aromatic oil having a refractive index of (nd15)1.56 - 1.60 ob-tained by hydrofining a distillate contained in a fraction hav-ing a boiling range of about 250° - 400°C at atmospheric pres-sure obtained by the thermocracking of petroleum at about 600° -900°C and (5) an oil obtained by hydrofining a distillate contained in a fraction having a boiling range of about 230° -450°C at atmospheric pressure obtained as a by-product at the time of reforming a hydrocarbon oil in the presence of a noble metal catalyst, and (6) an electrical insulating oil of naph-thenic origin with the proviso that this insulating oil (6) is omitted if the electrical insulating oil (I) is of naphthen-ic origin, and (III) 0.001 - 1.0% by weight of a hydrocarbon-derived pour point depressant, based on the total weight of the oils (I) and (II), the depressant being at least one compound selected from (1) a copolymer of ethylene and an ?-olefin hav-ing the general formula CH2=CH-R wherein R is an alkyl group having at least one carbon atom, (2) a poly-?-olefin, (3) a hydrogenated, styrene-butadiene copolymer, (4) a condensed alkylnaphthalene, and (5) an alkylated polystyrene.

2. An electrical insulating oil composition according to claim 1 wherein in the oil (II), the arylalkanes (1) are alkyl-benzenes represented by the general formula wherein R1 and R2 are each hydrogen or a hydrocarbon residue having 1 - 20 carbon atoms with the proviso that the total of carbon atoms of R1 and R2 , the diarylalkanes (2) are compounds represented by the general formula wherein R1 , R2 , R3 and R4 are each hydrogen or an alkyl group having 1 - 15 carbon atoms with the proviso that the total of carbon atoms of R1 - R4 is at least 2, and R5 and R6 are each hydrogen or a methyl group and the polybutene (3) is a liquid polymer mainly of isobutylene and has an average molecular weight of about 200 - 400, and the hydrocarbon-derived pour point depressant (III) is at least one member selected from the group consisting of (1) copolymers of ethylene and ?-olefin having the general formula CH2=CH-R wherein R is an alkyl group having at least one carbon atom, (2) polymers of ?-olefin having the general formula CH2=CH-R wherein R is any one of C7-18 alkyl groups which are identical with, or different from, each other, the polymers containing ? CH2 ?n wherein n is at least 6, (3) styrene-butadiene copolymers in hydrogenated form, (4) condensed alkylnaphthalenes obtained by the condensation of dichloroparaffin and naphthalene and (5) alkylated polystyrenes obtained by the reaction of a polystyrene having a number average molecular weight of 10,000 - 150,000 with an alkyl halide of the formula RX.
wherein R is an alkyl group having 6 - 20 carbon atoms and X
is a halogen atom.