ELECTRICAL OIL COMPOSITION
An electrical oil composition comprising: A) dc-asphalted cylinder oil (DACO) having a benzo [a] pyrene content of not more than 1 mg/kg and a total content of benz [a] anthracene, chrysene, benzo [b] fluoranthene, benzo [j] fluoranthene, benzo [k] fluoranthene, benzo [c] pyrene, benzo [a] pyrene and dibenz [a, h] anthracene of not more than 10 mg/kg; and B) one or more base oils each having a viscosity of not more than 4.0 mm2/s at 100° C.
The present invention relates to an electrical oil composition.
Many types of electrical equipment contain an electrical oil composition for dissipating the heat generated by energised components, for insulating the energised components from the equipment enclosure and from other internal parts and devices, and combinations thereof. Examples of electrical equipment include, but are not limited to, transformers, capacitors, switches, regulators, circuit breakers, cables, reclosers, rectifiers, reactors, x-ray equipment, and combinations thereof.
A transformer generally transfers electric power from one circuit to another electromagnetically. Transformers are generally used in the transmission of electrical power.
Large transformers generally require insulation of coils, conductors, and combinations thereof, in order to protect the transformer at normal operating voltages, during temperature overvoltages, during transient overvoltages, and combinations thereof. Transient overvoltages may result from lightning strikes, switching operations, and combinations thereof. When insulation fails, an internal fault or short circuit may occur. Such occurrences may cause the equipment to fail, typically leading to system outages and possibly endangering persons in the vicinity of the equipment.
In order to effectively transfer heat away from a transformer core and coil assembly and to maintain an acceptable operating temperature, conventional transformers use relatively large volumes of an electrical oil composition as insulation.
A demand is acknowledged for high oxidation resistant oil products for use as electrical oil compositions, in particular as a transformer oil or a switch gear oil, preferably without high additive treat rates due to adverse effects on other properties than oxidation stability.
Good oxidation stability may expressed by low acid formation and/or low sludge formation and low temperature viscosity values.
WO-A-01/54138 describes an electrical oil composition which is said to have improved oxidation and electrical resistance. Said electrical oil composition comprises a blend of (A) a substantially nitrogen and sulphur free, paraffinic or naphthenic base oil boiling in the electrical oil boiling range, and (B) a hydrofined light gas oil (LGO) boiling in the range of about 200° C. to about 400° C. and having a sulphur to basic nitrogen ratio (S/BN) greater than 100:1, the hydrofined LGO being present in an amount sufficient to provide a blend having greater than about 0.03 wt % sulphur.
However, many electrical oil compositions have been made from blends of naphthenic or paraffinic base oils with distillate aromatic extracts (DAE).
Distillate aromatic extracts have very high aromatic contents, typically at least 70 wt. %.
By the term “aromatic” it is meant a molecule composed primarily of carbon and hydrogen which comprises at least one ring which composed of conjugated unsaturated carbon bonds, such as compounds containing a benzene moiety, polynuclear aromatics or polyaromatic compounds, i.e. compounds comprising more than one aromatic ring fused together, such as anthracene based moieties, are also included in this definition of aromatic. Such molecules may comprise sulphur as a heteroatom.
Distillate aromatic extracts are obtained as a by-product of the process of solvent extraction of vacuum distillates used as a raw material for the manufacture of lubricant base oils. Such distillate aromatic extracts generally contain high concentrations of polynuclear aromatics, typically from 10 to 25 wt. %, as measured by IP 346 method.
Certain polynuclear aromatics (PNA), which are also known as higher aromatic rings, polycyclic aromatics (PCA) or polyaromatic hydrocarbons (PAH), are known carcinogens.
Distillate aromatic extracts are classified as “carcinogenic” according to the European legislation (EU Substance Directive 67/548/EEC) and must be labelled with the risk phrase “R45” (may cause cancer) and the label “T” (toxic, skull and crossbones) in Europe.
Accordingly, electrical oil compositions comprising 0.1 wt. % or more of distillate aromatic extracts must also be labelled with the risk phrase “R45” (may cause cancer) and the label “T” (toxic, skull and crossbones) in Europe due to the levels of polynuclear aromatics, and in particular polyaromatic hydrocarbons therein.
From the viewpoint of health, safety and environmental impact, it is highly desirable to use alternatives to distillate aromatic extracts as blending components in electrical oil compositions, which electrical oil compositions not only have low polynuclear aromatic content, and therefore also low carcinogenicity, but which also still have good oxidation stability, preferably without high additive treat rates due to adverse effects these can have on other properties than oxidation stability.
The present Application provides an electrical oil composition comprising (A) de-asphalted cylinder oil (DACO) having a benzo[a]pyrene content of not more than 1 mg/kg and a total content of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a, h]anthracene of not more than 10 mg/kg; and (B) one or more base oils each having a viscosity of not more than 4.0 mm2/s at 100° C.
In this respect it is noted that GB 716 979 (published in 1954), U.S. Pat. No. 2,725,345 (published in 1955) and GB 1 237 291 (published in 1971) disclose lubricating oil compositions comprising de-asphalted oils (optionally subjected to solvent extraction treatment) and a base oil. However, the lubricating oil composition as described in the above publications would need to be classified as “carcinogenic” and “toxic” as outlined above in view of the preparation methods as used at the time which resulted in relatively high polynuclear aromatics contents. This has also been the reason that in the last decades de-asphalted (cylinder) oils have not been used in lubricating oil compositions and the like.
Furthermore, the above 3 publications do not teach or suggest the low benzo[a]pyrene contents as required according to the present invention.
The de-asphalted cylinder oil (DACO) according to the present invention may be prepared by de-asphalting a mineral-derived vacuum residue to obtain a de-asphalted oil (DAO), solvent-extracting the de-asphalted oil and obtaining the de-asphalted cylinder oil (DACO) extract.
The de-asphalted oil (DAO) used is defined as the product of a de-asphalting process step wherein asphalt is removed from a reduced crude petroleum feed or from the residue, bottom fraction, of a vacuum distillation of a crude petroleum feed (hereinafter referred to as “mineral-derived vacuum residues”).
The de-asphalting process utilises a light hydrocarbon liquid solvent, for example propane, for asphalt compounds.
De-asphalting processes are well known and for example, are described in “Lubricant base oil and wax processing”, Avilino Sequeira, Jr., Marcel Dekker, Inc, New York, 1994, ISBN 0-8247-9256-4, pages 53-80.
The de-asphalted oil undergoes solvent extraction, wherein residual aromatic extract known as de-asphalted cylinder oil (DACO) is removed therefrom.
Examples of solvent extraction process that may be conveniently used include furfural or NMP solvent extraction processes or other solvent extraction processes, for example, as described in Chapter 5 of “Lubricant base oil and wax processing”, Avilino Sequeira, Jr., Marcel Dekker, Inc, New York, 1994, ISBN 0-8247-9256-4.
The benzo[a]pyrene content and 8 PAH content may be measured in the de-asphalted cylinder oil by GC/MS analysis. For example, this technique is commercially available at Biochemisches Institut fur Umweltcarcinogene (Prof. Dr. Gernot Grimmer-Stiftung), Lurup 4, D-22927 Grosshansdorf, Germany.
The amount of polyaromatic hydrocarbons subsequently present in the de-asphalted cylinder oil may be controlled during isolation of the mineral-derived vacuum residue by appropriate selection of the cut width of the highest boiling distillate fraction.
The de-asphalted cylinder oil preferably has a sulphur content in the range of from 0.5 to 5 wt. %, more preferably in the range of from 3 to 4.5 wt. %, as measured by ISO 14596, based on the total weight of the de-asphalted cylinder oil.
The kinematic viscosity at 100° C. of the de-asphalted cylinder oil is preferably less than 100 mm2/s, more preferably in the range of from 35 to 90 mm2/s.
Kinematic viscosity at 100° C. as mentioned herein may be conveniently measured in accordance with ISO 3104.
The flash point of the de-asphalted cylinder oil is preferably above 250° C., more preferably above 280° C. and most preferably above 290° C., as measured by the Cleveland Open Cap (COC) method, ISO 2592.
The de-asphalted cylinder oil (A) is preferably present in the electrical oil composition of the present invention in an amount in the range of from 0.05 to 5 wt. %, more preferably in an amount in the range of from 0.1 to 2 wt. % and most preferably in the range of from 0.1 to 0.8 wt. %, based on the total weight of the electrical oil composition.
In a preferred embodiment of the present invention, the one or more base oils (B) are base oils having a kinematic viscosity at 100° C. of not more than 3.5 mm2/s, more preferably in the range of from 0.8 to 3 mm2/s.
The one or more base oils (B) in the present invention preferably have a sulphur content of less than 2 wt. %, more preferably less than 0.5 wt. % and most preferably less than 0.1 wt. %, as measured by ISO 14596, based on the total weight of the one or more base oils (B).
The one or more base oils (B) as hereinbefore described may be conveniently prepared by vacuum distillation, followed by solvent extraction, hydrofining, hydrogenation and hydrocracking. Paraffinic oils may be de-waxed or hydroisomerised to improve the pour point.
Said one or more base oils (B) may also be conveniently prepared by Fischer-Tropsch synthesis.
In a preferred embodiment of the present invention, said one or more base oils (B) are selected from one or more mineral-derived paraffinic oils, one or more mineral-derived naphthenic oils, one or more Fischer-Tropsch derived base oils and mixtures thereof.
Particularly preferred paraffinic base oils (B) that may be used include Group I, Group II and Group III base oils.
By “Group I” base oils, “Group II” base oils and “Group III”, in the present invention are meant base oils according to the definitions of American Petroleum Institute (API) categories I and II. Such API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002.
Group I base oils contain less than 90% saturates (according to ASTM D2007) and/or greater than 0.03% sulphur (according to ASTM D2622, D4294, D4927 or D3120) and have a viscosity index of greater than or equal to 80 and less than 120 (according to ASTM D2270).
Group II base oils contain greater than or equal to 90% saturates and less than or equal to 0.03% sulphur and have a viscosity index of greater than or equal to 80 and less than 120, according to the aforementioned ASTM methods.
Group III base oils contain greater than or equal to 90% saturates and less than or equal to 0.03% sulphur and have a viscosity index of greater than 120, according to the afore-mentioned ASTM methods.
Naphthenic base oils are defined as Group V base oils according to API.
The base oil composition may thus comprise a mineral-derived base oil of the so-called paraffinic type or naphthenic type. Such base oils are obtained by refinery processes starting from paraffinic and naphthenic crude feeds.
Mineral-derived paraffin base oils are defined by a viscosity index of greater than 70, preferably greater than 90. Said base oils are produced from feedstocks rich in paraffins.
Mineral-derived naphthenic base oils for the purpose of the present invention are defined as having a pour point of below −20° C. and a viscosity index of below 70. Such base oils are produced from feedstocks rich in naphthenes and low in wax content and are used mainly for lubricants in which colour and colour stability are important, and VI and oxidation stability are of secondary importance.
Mineral-derived naphthenic and paraffin base oils are well known and described in more detail in “Lubricant base oil and wax processing”, Avilino Sequeira, Jr., Marcel Dekker, Inc, New York, 1994, ISBN 0-8247-9256-4, pages 28-35.
Fischer-Tropsch derived base oils may be conveniently used as the base oil in the lubricating oil composition of the present invention, for example, the Fischer-Tropsch derived base oils disclosed in EP-A-776959, EP-A-668342, WO-A-97/21788, WO-A-00/15736, WO-A-00/14188, WO-A-00/14187, WO-A-00/14183, WO-A-00/14179, WO-A-00/08115, WO-A-99/41332, EP-A-1029029, WO-A-01/18156 and WO-A-01/57166.
The one or more base oils (B) are preferably present in the electrical oil composition of the present invention in a total amount of at least 80 wt. %, more preferably in a total amount in the range of from 90 to 99.95 wt. %, based on the total weight of the electrical oil composition.
Further base oils and other synthetic base oil components may be present in the electrical oil formulation, including base oils having a kinematic viscosity at 100° C. which is greater than the kinematic viscosity at 100° C. of each of the one or more base oils (B). Such base oils may include, but are not limited to, esters, poly alpha olefins, as preferably obtained by oligomerisation of an olefinic compound and poly alkylene glycols.
The electrical oil composition of the present invention preferably has a sulphur content of below 0.3 wt. % and even more preferably below 0.15 wt. %, as measured by ISO 14596, with respect to the total weight of the electrical oil composition.
The source of the majority of the sulphur in the electrical oil formulation will be the sulphur as contained in the base oil components therein.
In a preferred embodiment of the present invention, the electrical oil composition is a non-corrosive electrical oil, as measured according to the CIGRE A2.32.01 Covered Conduct Deposition test (corrosive sulphur) and/or according to ASTM D 1275 B test. That is to say, in a preferred embodiment of the present invention, the electrical oil composition passes the CIGRE A2.32.01 Covered Conduct Deposition test for corrosive sulphur and/or the ASTM D 1275 B test for corrosive sulphur.
The electrical oil composition of the present invention preferably has a kinematic viscosity at 100° C. of less than 5 mm2/sec, more preferably less than 4 mm2/sec, most preferably less than 3 mm2/sec.
The flash point of the electrical oil composition as measured by ASTM D92 may be greater than 120° C., preferably greater than 135° C. The higher flash points are desirable for applications where peak temperatures can exceed the average oil temperature, for instance in applications under high temperature and/or with restricted heat transmission potential. Examples are electric transformers and electric engines.
In addition to base oils, the electrical oil composition of the present invention may comprise one or more additives.
For example, the electrical oil composition of the present invention may comprise one or more metal passivators, in particular one or more copper passivators.
Metal passivators or electrostatic discharge depressants, sometimes also referred as metal deactivators, that may be conveniently used include N-salicylideneethylamine, N,N′-disalicylideneethyldiamine, triethylenediamine, ethylenediamminetetraacetic acid, phosphoric acid, citric acid and gluconic acid. More preferred compounds are lecithin, thiadiazole, imidazole and pyrazole and derivatives thereof. Even more preferred compounds are benzotriazoles and their derivatives.
Most preferred are the compounds according to formula (I) or even more preferred the optionally substituted benzotriazole compound represented by the formula (II)
wherein R4 may be hydrogen or a group represented by the formula (III)
or by the formula (IV)
wherein:
- c is 0, 1, 2 or 3;
- R1 and R2 are hydrogen or the same or different straight or branched alkyl groups of 1-18 carbon atoms,
- preferably a branched alkyl group of 1-12 carbon atoms;
- R3 is a straight or branched C1-4 alkyl group,
- preferably R3 is methyl or ethyl and C is 1 or 2; R5 is a methylene or ethylene group; R6 and R7 are the same or different alkyl groups of 3-15 carbon atoms, preferably of 4-9 carbon atoms.
Preferred compounds are 1-[bis(2-ethylhexyl)-aminomethyl)benzotriazole, methylbenzotriazole, dimethylbenzotriazole, ethylbenzotriazole, ethylmethylbenzotriazole, diethylbenzotriazole and mixtures thereof. Other preferred compounds include (N-Bis(2-ethylhexyl)-aminomethyl-tolutriazole, non-substituted benzotriazole, and 5-methyl-1H-benzotriazole. Examples of copper passivator additives as described above are described in U.S. Pat. No. 5,912,212, EP-A-1054052 and in US-A-2002/0109127. These benzotriazole compounds are preferred because they also act as an electrostatic discharge depressant, which is beneficial when an oil formulation is used as an electrical oil.
Metal passivator additives such as those described above are commercially available under the trade designations “BTA”, “TTA”, “IRGAMET 39”, “IRGAMET 30” and “IRGAMET 38S” from CIBA Ltd Basel Switzerland, also traded under the trade name “Reomet” by CIBA.
The content of the above metal passivator in the electrical oil composition of the present invention is preferably above 1 mg/kg and more preferably above 5 mg/kg. A practical upper limit may vary depending on the specific application of the electrical oil composition. For example, when desiring improved dielectric discharge tendencies of the oil, it may be desired to add a high concentration of the metal passivator additive. This concentration may be up to 3 wt. %, preferably however in the range of from 0.001 to 1 wt. %. However, such compounds may be advantageously used at concentrations below 1000 mg/kg and more preferably below 300 mg/kg.
The electrical oil composition of the present invention may comprise one or more anti-oxidant additives.
Anti-oxidants that may be conveniently used are so-called hindered phenolic or amine anti-oxidants, for example naphthols, sterically hindered monohydric, dihydric and trihydric phenols, sterically hindered dinuclear, trinuclear and polynuclear phenols, alkylated or styrenated diphenylamines or ionol derived hindered phenols.
Sterically hindered phenolic anti-oxidants of particular interest may be selected from the group consisting of 2,6-di-tert-butylphenol (available under the trade designation “IRGANOX™ L 140” from CIBA), di tert-butylated hydroxytoluene (“BHT”), methylene-4,4′-bis-(2.6-tert-butylphenol), 2,2′-methylene bis-(4,6-di-tert-butylphenol), 1,6-hexamethylene-bis-(3,5-di-tert-butyl-hydroxyhydrocinnamate) (available under the trade designation “IRGANOX™ L109” from CIBA), ((3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)methyl)thio)acetic acid, C10-C14isoalkyl esters (available under the trade designation “IRGANOX™ L118” from CIBA), 3,5-di-tert-butyl-4-hydroxyhydrocinnamic acid, C7-C9alkyl esters (available under the trade designation “IRGANOX™ L135” from CIBA,) tetrakis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionyloxymethyl)methane (available under the trade designation “IRGANOX™ 1010” from CIBA), thiodiethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate (available under the trade designation “IRGANOX™ 1035” from CIBA), octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate (available under the trade designation “IRGANOX™ 1076” from CIBA) and 2,5-di-tert-butylhydroquinone.
Particularly preferred anti-oxidants are di-tert-butylated hydroxytoluene (“BHT”) and 3,5-di-tert-butyl-4-hydroxy-hydrocinnamic acid-C7-C9-alkyl ester.
Examples of amine anti-oxidants that may be conveniently used include aromatic amine anti-oxidants for example N,N′-Di-isopropyl-p-phenylenediamine, N,N′-di-sec-butyl-p-phenylenediamine, N,N′-bis(1,4-dimethyl-pentyl)-p-phenylenediamine, N,N′-bis(1-ethyl-3-methyl-pentyl)-p-phenylene-diamine, N,N′-bis(l-methyl-heptyl)-p-phenylenediamine, N,N′-dicyclohexyl-p-phenylene-diamine, N,N′-diphenyl-p-phenylenediamine, N,N′-di(naphthyl-2-)-p-phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, N-(1-methylheptyl)-N′-phenyl-p-phenylenediamine, N′-cyclohexyl-N′-phenyl-p-phenylenediamine, 4-(p-toluene-sulfoamido)diphenylamine, N,N′-dimethyl-N,N′-di-sec-butyl-p-phenylenediamine, diphenylamine, N-allyldiphenylamine, 4-isopropoxy-diphenylamine, N-phenyl-1-naphthylamine, N-phenyl-2-naphthylamine, octylated diphenylamine, e.g. p,p′-di-tert-octyldiphenylamine, 4-n-butylaminophenol, 4-butyrylaminophenol, 4-nonanoylaminophenol, 4-dodecanoylaminophenol, 4-octadecanoylaminophenol, di(4-methoxyphenyl)amine, 2,6-di-tert-butyl-4-dimethyl-aminomethylphenol, 2,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, N,N,N′,N′-tetramethyl-4,4′-diaminodiphenylmethane, 1,2-di(phenylamino)ethane, 1,2-di[(2-methylphenyl)amino]ethane, 1,3-di-(phenylamino)propane, (o-tolyl)biguanide, di[4-(1′,3′-dimethylbutyl)phenyl]amine, tert-octylated N-phenyl-1-naphthylamine, mixture of mono- and dialkylated tert-butyl-/tert-octyldiphenylamines, 2,3-dihydro-3,3-dimethyl-4H-1,4-benzothiazine, phenothiazine, N-, tert-octylated phenothiazine, 3,7-di-tert-octylphenothiazine. In addition, amine anti-oxidants according to formula VIII and IX of EP-A-1 054 052, which compounds are also described in U.S. Pat. No. 4,824,601 may also be conveniently used.
The content of the one or more anti-oxidant additives is preferably less than 2 wt. % and more preferably less than 1 wt. %, even more preferably less than 0.6 wt. % and most preferably less than 0.3 wt. %, with respect to the total weight of the electrical oil composition.
Further additives that may also be present in the electrical oil composition of the present invention are dependent upon the specific application of the electrical oil composition.
Examples of possible further additives are detergents and pour point depressants. Specific examples of such additives are described in for example Kirk-Othmer Encyclopedia of Chemical Technology, 3rd edition, volume 14, pages 477-526.
The detergent may conveniently be an over-based metallic detergent, for example the phosphonate, sulfonate, phenolate or salicylate types as described in the above referred to General Textbook.
Preferred pour point depressants are hydrocarbon or oxygenated hydrocarbon type pour point depressants.
As high additive treat rates can have adverse effects on other properties than oxidation stability in an electrical oil composition, in one embodiment of the present invention there is provided an electrical oil composition comprising (A) de-asphalted cylinder oil (DACO) having a benzo[a]pyrene content of not more than 1 mg/kg and a total content of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a, h]anthracene of not more than 10 mg/kg; and (B) one or more base oils each having a viscosity of not more than 4.0 mm2/s at 100° C., wherein said composition does not contain any anti-oxidant additives.
In a preferred embodiment of the present invention, there is provided an electrical oil composition comprising (A) de-asphalted cylinder oil (DACO) having a benzo[a]pyrene content of not more than 1 mg/kg and a total content of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a, h]anthracene of not more than 10 mg/kg; and (B) one or more base oils each having a viscosity of not more than 4.0 mm2/s at 100° C., wherein said composition does not contain any additives.
The electrical oil composition of the present invention may find particular application in switch gears, transformers, regulators, circuit breakers, power plant reactors, shunt reactors, cables and other electrical equipment.
In order to improve the gassing tendency of the electrical oil composition of the present invention, it is preferred to add between 0.05 and 10 wt %, preferably between 0.1 and 5 wt % of an aromatic compound. Preferred aromatic compounds are for example tertrahydronaphthalene, diethylbenzene, di-isopropylbenzene, a mixture of alkylbenzenes as commercially obtainable as “Shell Oil 4697” or “Shellsol A 150” both “Shell” products obtainable from Shell Deutschland GmbH.
A preferred electrical oil composition of the present invention comprises a mixture of 2,6-di-t-butyl phenol and 2,6-di-t-butyl cresol. Preferably the oil formulation comprises between 0.1 and 3 wt % of 2,6-di-t-butyl phenol and 0.1 to 2 wt % of 2,6-di-t-butyl cresol in a weight ratio of between 1:1 and 1:1.5.
The electrical oil composition according to the present invention is preferably subjected to a clay treatment.
Clay treatment is a well known treatment to remove polar compounds from electrical oil compositions. It is performed in order to further improve the colour, chemical and thermal stability of such compositions. It may be performed prior to adding the additives hereinbefore described on a partly formulated electrical oil composition.
Clay treatment processes are for example described in Lubricant base oil and wax processing, Avilino Sequeira, Jr., Marcel Dekker, Inc, New York, 1994, ISBN 0-8247-9256-4, pages 229-232.
Preferably, additive components such as copper passivators and anti-oxidants are added after the clay treatment.
The electrical oil composition of the present invention may find use in applications which have to start up regularly, especially more than 10 times per year at a temperature of below 0° C., more preferably below −5° C., wherein the temperature of the oil when the application is running is above 0° C. Examples of such applications are as low temperature switch gear oils, transformers, regulators, circuit breakers, power plant reactors, switch gear, cables, electrical equipment. Such applications are well known to the skilled person and described for example in Lubricants and related products, Dieter Klamann, Verlag Chemie GmbH, Weinhem, 1984, pages 330-339.
The electrical oil composition as herein before described may be conveniently prepared by admixing (A) de-asphalted cylinder oil (DACO) having a benzo[a]pyrene content of not more than 1 mg/kg and a total content of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a, h]anthracene of not more than 10 mg/kg with (B) one or more base oils each having a viscosity of not more than 4.0 mm2/s at 100° C., and, optionally, one or more additives as herein before described.
In the present invention, electrical oil compositions comprising (A) de-asphalted cylinder oil (DACO) having a benzo[a]pyrene content of not more than 1 mg/kg and a total content of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a, h]anthracene of not more than 10 mg/kg; and (B) one or more base oils each having a viscosity of not more than 4.0 mm2/s at 100° C. have been surprisingly found to have good oxidation stability, but also to avoid the need for R45 labelling.
In another embodiment of the present invention, there is provided a method of avoiding R 45 toxicological labelling for an electrical oil by utilising an electrical oil as hereinbefore described.
The present invention further provides the use of the composition as hereinbefore described as an electrical oil for application in one or more of transformers, regulators, circuit breakers, power plant reactors, shunt reactors, switch gears, cables and electrical equipment.
The invention will be described with reference to the following Examples which are not intended to limit the scope of the invention in any way.
EXAMPLESTable 1 indicates the formulations that were tested and the experimental results thereon. Table 2 indicates the properties of the base oils in Table 1.
Oxidation stability was assessed by the so-called Baader ageing test according to DIN 51554 and the IEC 61125 C Oxidation test 164H/120° C.
Comparative Example 1 represents a naphthenic base oil. Both the neutralisation number and saponification number after the Baader test are extremely high and indicate a severe oxidative degradation of said oil resulting in acids and ester structures. The total acidity in the IEC 61125C test is also unacceptably high.
Comparative Example 2 represents a typical electrical oil formulation comprising naphthenic base oil and distillate aromatic extract. Whilst said formulation has excellent ageing properties, in accordance with EU Substance Directive 67/548/EEC, it requires labelling with R 45 and “T” (skull and cross bones) due to the use of DAE (which is carcinogenic) as blend component.
Comparative Example 3 is a blend of a high sulphur and a low sulphur containing naphthenic base oil. Said formulation has a higher neutralisation number and a higher saponification number than Comparative Example 2 which represents the industry reference for a high quality un-inhibited electrical oil.
Example 1 represents an electrical oil composition according to the present invention, which composition comprise a blend of naphthenic base oil with DACO to match the sulphur content of Comparative Example 2. Not only are the neutralisation number and the saponification numbers for Example 1 good, but in addition, said composition also avoids the need for labelling according to EU Substance Directive 67/548/EEC.
Example 2 represents another electrical oil composition according to the present invention, which composition comprise a blend of naphthenic base oil with DACO. In addition to having good values for the neutralisation number and the saponification numbers after the Baader ageing test, said composition also avoids the need for labelling according to EU Substance Directive 67/548/EEC.
Example 3 represents an electrical oil composition according to the present invention, which composition comprises a blend of two naphthenic oils with DACO. This formulation shows an improved neutralisation value and saponification value when compared to Comparative Example 3. Furthermore, said composition also avoids the need for labelling according to EU Substance Directive 67/548/EEC.
Example 4 represents an electrical oil composition according to the present invention, which composition comprises a blend of two naphthenic oils with DACO and also contains a metal passivator. When compared with Comparative Example 2, it is apparent that this formulation has a lower total acidity in the IEC 61125 C oxidation test.
Not only are the neutralisation and saponification numbers after the Baader ageing test and the acidity value in the IEC 61125 C test for Example 4 greatly improved as compared to Comparative Example 1, but said composition also avoids the need for labelling according to EU Substance Directive 67/548/EEC.
Example 5 represents an electrical oil composition according to the present invention, which composition comprises a blend of a Fisher-Tropsch derived base oil with DACO.
Thus, unlike the Comparative Examples, the electrical oil compositions of Examples 1-5 not only avoid the need for labelling according to EU Substance Directive 67/548/EEC, but also have good oxidation stability.
Claims
1. An electrical oil composition comprising (A) de-asphalted cylinder oil (DACO) having a benzo[a]pyrene content of not more than 1 mg/kg and a total content of benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene and dibenz[a,h]anthracene of not more than 10 mg/kg; and (B) one or more base oils each having a viscosity of not more than 4.0 mm2/s at 100° C.
2. Electrical oil composition according to claim 1, wherein the one or more base oils (B) are selected from one or more mineral-derived paraffinic oils, one or more mineral-derived naphthenic oils, one or more Fischer-Tropsch derived base oils and mixtures thereof.
3. Electrical oil composition according to claim 1, wherein said composition has been subjected to a clay treatment.
4. Electrical oil composition according to claim 1, wherein said composition comprises one or more pour point depressant additives.
5. Electrical oil composition according to claim 1, wherein said composition comprises one or more metal passivator additives.
6. Electrical oil composition according to claim 5, wherein said one or more metal passivator additives are benzotriazole derivatives.
7. Electrical oil composition according to claim 1, wherein said composition comprises one or more anti-oxidants.
8. Electrical oil composition according to claim 7, wherein said composition comprises di tert-butylated hydroxytoluene (BHT) as an anti-oxidant.
9. Electrical oil composition according to claim 1, wherein said composition passes the CIGRE A2.32.01 Covered Conduct Deposition test for corrosive sulphur and/or the ASTM D 1275 B test for corrosive sulphur.
10. Use of the composition according to claim 1 as an electrical oil for application in one or more of transformers, regulators, circuit breakers, power plant reactors, shunt reactors, switch gears, cables and electrical equipment.
Type: Application
Filed: Oct 18, 2007
Publication Date: Jan 21, 2010
Inventors: Andree Hilker (Hamburg), Volker Klaus Null (Hamburg)
Application Number: 12/445,846
International Classification: C10M 133/44 (20060101); C10M 131/02 (20060101); C10M 129/10 (20060101);
