Classifications

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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M141/00—Lubricating compositions characterised by the additive being a mixture of two or more compounds covered by more than one of the main groups C10M125/00 - C10M139/00, each of these compounds being essential
  • C10M141/08—Lubricating compositions characterised by the additive being a mixture of two or more compounds covered by more than one of the main groups C10M125/00 - C10M139/00, each of these compounds being essential at least one of them being an organic sulfur-, selenium- or tellurium-containing compound
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M141/00—Lubricating compositions characterised by the additive being a mixture of two or more compounds covered by more than one of the main groups C10M125/00 - C10M139/00, each of these compounds being essential
  • C10M141/10—Lubricating compositions characterised by the additive being a mixture of two or more compounds covered by more than one of the main groups C10M125/00 - C10M139/00, each of these compounds being essential at least one of them being an organic phosphorus-containing compound
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2203/00—Organic non-macromolecular hydrocarbon compounds and hydrocarbon fractions as ingredients in lubricant compositions
  • C10M2203/10—Petroleum or coal fractions, e.g. tars, solvents, bitumen
  • C10M2203/102—Aliphatic fractions
  • C10M2203/1025—Aliphatic fractions used as base material
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2203/00—Organic non-macromolecular hydrocarbon compounds and hydrocarbon fractions as ingredients in lubricant compositions
  • C10M2203/10—Petroleum or coal fractions, e.g. tars, solvents, bitumen
  • C10M2203/106—Naphthenic fractions
  • C10M2203/1065—Naphthenic fractions used as base material
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2205/00—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions
  • C10M2205/17—Fisher Tropsch reaction products
  • C10M2205/173—Fisher Tropsch reaction products used as base material
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/02—Hydroxy compounds
  • C10M2207/023—Hydroxy compounds having hydroxy groups bound to carbon atoms of six-membered aromatic rings
  • C10M2207/026—Hydroxy compounds having hydroxy groups bound to carbon atoms of six-membered aromatic rings with tertiary alkyl groups
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/28—Esters
  • C10M2207/287—Partial esters
  • C10M2207/289—Partial esters containing free hydroxy groups
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2215/02—Amines, e.g. polyalkylene polyamines; Quaternary amines
  • C10M2215/06—Amines, e.g. polyalkylene polyamines; Quaternary amines having amino groups bound to carbon atoms of six-membered aromatic rings
  • C10M2215/064—Di- and triaryl amines
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2215/22—Heterocyclic nitrogen compounds
  • C10M2215/223—Five-membered rings containing nitrogen and carbon only
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/08—Thiols; Sulfides; Polysulfides; Mercaptals
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/08—Thiols; Sulfides; Polysulfides; Mercaptals
  • C10M2219/082—Thiols; Sulfides; Polysulfides; Mercaptals containing sulfur atoms bound to acyclic or cycloaliphatic carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/08—Thiols; Sulfides; Polysulfides; Mercaptals
  • C10M2219/082—Thiols; Sulfides; Polysulfides; Mercaptals containing sulfur atoms bound to acyclic or cycloaliphatic carbon atoms
  • C10M2219/083—Dibenzyl sulfide
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10M—LUBRICATING COMPOSITIONS; USE OF CHEMICAL SUBSTANCES EITHER ALONE OR AS LUBRICATING INGREDIENTS IN A LUBRICATING COMPOSITION
  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/08—Thiols; Sulfides; Polysulfides; Mercaptals
  • C10M2219/082—Thiols; Sulfides; Polysulfides; Mercaptals containing sulfur atoms bound to acyclic or cycloaliphatic carbon atoms
  • C10M2219/086—Thiols; Sulfides; Polysulfides; Mercaptals containing sulfur atoms bound to acyclic or cycloaliphatic carbon atoms containing sulfur atoms bound to carbon atoms of six-membered aromatic rings
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2020/00—Specified physical or chemical properties or characteristics, i.e. function, of component of lubricating compositions
  • C10N2020/01—Physico-chemical properties
  • C10N2020/02—Viscosity; Viscosity index
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/40—Low content or no content compositions
  • C10N2030/43—Sulfur free or low sulfur content compositions
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/64—Environmental friendly compositions
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
  • C10N2040/16—Dielectric; Insulating oil or insulators
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2040/00—Specified use or application for which the lubricating composition is intended
  • C10N2040/14—Electric or magnetic purposes
  • C10N2040/17—Electric or magnetic purposes for electric contacts
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10N—INDEXING SCHEME ASSOCIATED WITH SUBCLASS C10M RELATING TO LUBRICATING COMPOSITIONS
  • C10N2070/00—Specific manufacturing methods for lubricant compositions

Definitions

• the invention is related to an oxidation stable oil formulation comprising a base oil composition and additives .
• Background of the invention is related to an oxidation stable oil formulation comprising a base oil composition and additives .
• US-A-6790386 describes a dielectric fluid comprising an iso-paraffin base oil and additives.
• the iso-paraffin base oil is prepared by hydrotreating, hydroisomerisation and hydrogenation of a paraffinic vacuum feedstock.
• US-A-6214776 describes a formulation comprising a paraffinic base oil and an additive package containing a hindered phenol antioxidant and a metal deactivator, for use as load tap changer or transformer oil .
• base oils having a kinematic viscosity at 40 0 C of between 5 and 20 cSt can be used as base oil in formulations such as electrical oils or transformer oils .
• US-A-5241003 discloses a combination of a sulfur- containing antiwear additive and a carboxylic derivative dispersant for use as additive package for lubricants.
• US-A-5773391 describes a composition comprising a polyol ester base oil, an aliphatic monocarboxylic acid mixture, and an additive package comprising an antioxidant and a metal deactivator.
• the document further discloses phosphorodithionates as antiwear additives.
• WO-A-02070629 describes a process to make iso- paraffinic base oils from a wax as made in a Fischer- Tropsch process.
• base oils having a kinematic viscosity at 100 0 C of between 2 and 9 cSt can be used as base oil in formulations such as electrical oils or transformer oils.
• US-A-5912212 describes oxidative stable oil lubricating formulations consisting of a hydrocracked paraffinic mineral base oil and 0.1 to 5 wt% of a sulphur or phosphorus containing compound.
• a formulation consisting of a base oil and 3-methyl-5-tert- butyl-4 -hydroxy propionic acid ester, dioctylamino- methyltolyltriazole and 0.4 wt% of dilaurylthio- dipropionate .
• the oil had a high oxidative stability.
• Oxidation stable oil formulation comprising a base oil composition comprising a mineral-derived naphthenic base oil, a mineral-derived paraffinic base oil, and/or a Fischer-Tropsch derived base oil, a copper passivator and of from 0.001 to less than 0.1 wt% of an organic sulphur or phosphorus based compound.
• Figure 1 and 2 represent the carbon distribution of two Fischer-Tropsch derived base oils as used in the examples .
• a mineral-derived base oil of the so-called paraffinic type or naphthenic type, and/or a Fischer-Tropsch derived base oil is combined with at least one copper passivator and a low content of an anti-wear additive, an oil product is obtained which has properties highly suitable for use as an electrical oil. It was not to be expected that the combination of the copper passivator and a small amount of an anti-wear additive would result in such an improvement in oxidative stability.
• a mineral-derived base oil has the meaning within the context of this specification that the base oil was obtained from a mineral oil source, while a Fischer-Tropsch derived base oil was derived from Fischer-Tropsch synthesis products.
• Organic sulphur or phosphorus based compounds preferably are sulphur and phosphorus containing compounds such as sulfides, phosphides, dithiophopsphates and dithiocarbamates . More preferably, sulphur and phosphorus containing compounds are used which are known to be used as an anti-wear additive in lubricating oil formulations . Yet more preferably an organic polysulphide compound is used. With polysulfide is here meant that the organic compound comprises at least one group where two sulphur atoms are directly linked. A preferred polysulfide compound is a disulfide compound. Preferred polysulfide compounds are represented by the formula (I)
• R 1 and R 2 may be the same or different and each may be straight or branched alkyl group of 1 to 22 carbon atoms, aryl groups of 6-20 carbon atoms, alkylaryl groups of 7-20 carbon atoms or arylalkyl groups of 7-20 carbon atoms. Preferred are arylalkyl groups, more preferred are optionally substituted benzyl groups. More preferably R 1 and R 2 are independently selected from a benzyl group or a straight or branched dodecyl group. Examples of possible sulphur and phosphorus containing compounds and the preferred compounds mentioned here are described in the aforementioned US-A-5912212 as its component (b) , which publication is incorporated by reference.
• Suitable disulfide compounds are dibenzyldi- sulfide,ditertdodecyldisulfide and didodecyldisulfide.
• the content of the organic sulphur or phosphorus anti- wear additive in the oil formulation is preferably less than formulation 800 mg/kg and even more preferably less than 400 mg/kg.
• the lower limit is preferably 1 mg/kg more preferably 10 mg/kg, most preferably 50 mg/kg.
• the copper passivator or electrostatic discharge depressant may be the typical copper passivator of which N-salicylideneethylamine, N,N'-di salicylideneethyl- diamine, triethylenediamine, ethylenediamminetetraacetic acid, phosphoric acid, citric acid and gluconic acid. More preferred are lecithin, thiadiazole, imidazole and pyrazole and derivates thereof. Even more preferred are zinc dialkyldithiophosphates, dialkyldithiocarbamates and benzotriazoles and their tetrahydroderivates . Most preferred are the compounds according to formula (II) or even more preferred the optionally substituted benzotriazole compound represented by the formula (III)
• R 4 may be hydrogen or a group represented by the formula (IV)
• R 3 is a straight or branched C]__4 alkyl group.
• R 3 is methyl or ethyl and C is 1 or 2.
• R 5 is a methylene or ethylene group;
• R 6 and R 7 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;
• R 8 and R 9 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-lH-benzotriazole .
• copper passivator additives as described above are described in US-A-5912212 , EP-A-1054052 and in US-A-2002/0109127, which publications are hereby incorporated by reference. These benzotriazoles compounds are preferred because they also act as an electrostatic discharge depressant, which is beneficial when the oil formulation is used as an electrical oil. Copper passivator additives as those described above are commercially available under the product names BTA, TTA, IRGAMET 39, IRGAMET30 and IRGAMET 38S from CIBA Ltd Basel Switzerland, also traded under the trade name Reomet by CIBA. The content of the above copper passivator in the oil formulation 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 oil formulation. For example, when desiring improved dielectric discharge tendencies of the oil for use as electrical oil it may be desired to add a high concentration of the copper passivator additive. This concentration may be up to 3 wt%, preferably however in the range of from 0.001 to 1 wt%. Applicants found that the advantages of the invention can be achieved at concentrations below 1000 mg/kg and more preferably below 300 mg/kg, even more preferably below 50 mg/kg.
• the oil formulation preferably also comprises an anti-oxidant additive.
• the base oil is a mineral paraffinic base oil or a Fischer-Tropsch derived base oil
• the sludge formed and total acidity both measured after the IEC 61125 C oxidation test which properties are indicators for good oxidation stable oils, are considerably reduced when also an anti-oxidant is present.
• the anti-oxidant may be a so-called hindered phenolic or amine antioxidant, 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.
• hindered phenolic or amine antioxidant 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 antioxidants of particular interest are selected from the group consisting of 2 , 6-di-tert-butylphenol (IRGANOX TM L 140, CIBA) , di tert-butylated hydroxotoluene (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) (IRGANOX TM LlO9, CIBA) ,
• CIBA 3, 5-di-tert-butyl-4-hydroxyhydrocinnamic acid, C7- Cgalkyl esters
• IRGANOX TM L135, CIBA 3, 5-di-tert-butyl-4-hydroxyhydrocinnamic acid, C7- Cgalkyl esters
• IRGANOX TM 1010, CIBA 3, 5-di-tert-butyl-4-hydroxyphenyl) -propionyloxymethyl) methane
• IRGANOX TM 1010, CIBA thiodiethylene bis (3 , 5-di-tert- butyl-4 -hydroxyhydrocinnamate
• IRGANOX TM 1035, CIBA octadecyl 3 , 5 -di-tert-butyl-4 -hydroxyhydrocinnamate
• IRGANOX TM 1076, CIBA 2,5-di-tert- butylhydroquinone
• amine antioxidants are aromatic amine anti-oxidants for example N, N 1 -Di-isopropyl-p- phenylenediamine, N, N 1 -di-sec-butyl-p-phenylenediamine, N, N 1 -bis (1, 4-dimethyl-pentyl) -p-phenylenediamine, N, N 1 - bis (l-ethyl-3-methyl-pentyl) -p-phenylene-diamine, N, N'- bis (1-methyl-heptyl) -p-phenylenediamine, N, N 1 - dicyclohexyl-p-phenylene-diamine, N, N 1 -diphenyl-p- phenylenediamine,
• amine antioxidants are those according to formula VIII and IX of EP-A-1054052, which compounds are also described in US-A-4, 824, 601, which publications are hereby- incorporated by reference.
• the content of the anti oxidant additive is preferably less than 2 wt% and more preferably less than 1 wt%.
• the content is preferably less than 0,6 wt% in certain applications, such as when the oil formulation is used as an electrical oil.
• the content of antioxidant is preferably greater than 10 mg/kg.
• the oil formulation preferably has a sulphur content of below 0,5 wt% and even more preferably below 0,15 wt%.
• the source of the majority of the sulphur in the oil formulation will be the sulphur as contained in the base oil component of the oil formulation according the invention.
• the base oil composition preferably has a kinematic viscosity at 100 °C of less than 50 mm 2 /sec, more preferably between 2 and 25 mm 2 /sec, most preferably between 2 and 15 mm 2 /sec.
• the base oil composition preferably has a kinematic viscosity at 40 0 C of between
• the viscosity of the base oil composition will also depend on the particular use of the oil formulation. If the oil formulation is used as an electrical oil its kinematic viscosity at 40 °Cis preferably between 1 and 50 mm 2 /sec. More preferably, if this electrical oil formulation is a transformer oil, the base oil will preferably have a kinematic viscosity at 40 0 C of between 5 and 15 mm 2 /sec. If the electrical oil is a low temperature switch gear oil the base oil viscosity at 40 0 C is preferably between
• the flash point of the base oil composition as measured by ASTM D92 may be greater than 90 0 C, preferably greater than 120 0 C, yet more preferably greater than 140 0 C, and even more preferably greater than 170 0 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.
• the base oil composition may comprise one or more base oils selected from mineral-derived naphthenic base oils, mineral-derived paraffic base oils, or Fischer- Tropsch derived base oils.
• the base oil composition may this 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 naphthenic base oils for the purpose of this invention are defined as having a pour point of below -20 0 C and a viscosity index of below 70.
• Mineral-derived paraffin base oils are defined by a viscosity index of greater than 70, preferably greater than 90.
• the base oil composition preferably comprises a base oil comprising a series of iso-paraffins having n, n+1, n+2 , n+3 and n+4 carbon atoms and wherein n is a number between 20 and 35.
• the paraffin content in the base oil composition is greater than 80 wt%, more preferably greater than 90 wt%, yet more preferably greater than 95%, and again more preferably greater than 98%.
• the base oil composition furthermore may preferably have a content of naphthenic compounds of between 1 and 20 wt%. It has been found that these base oils have a good additive response to the additives listed above when aiming to improve oxidation stability.
• the content of naphthenic compounds and the presence of such a continuous series of iso-paraffins may be measured by Field desorption/Field Ionisation (FD/FI) technique. In this technique the oil sample is first separated into a polar (aromatic) phase and a non-polar (saturates) phase by making use of a high performance liquid chromatography (HPLC) method IP368/01, wherein as mobile phase pentane is used instead of hexane as the method states.
• HPLC high performance liquid chromatography
• the saturates and aromatic fractions are then analyzed using a Finnigan MAT90 mass spectrometer equipped with a Field desorption/Field Ionisation (FD/FI) interface, wherein FI (a "soft” ionisation technique) is used for the determination of hydrocarbon types in terms of carbon number and hydrogen deficiency.
• FI Field desorption/Field Ionisation
• the type classification of compounds in mass spectrometry is determined by the characteristic ions formed and is normally classified by "z number". This is given by the general formula for all hydrocarbon species: C n H2 n+z - Because the saturates phase is analysed separately from the aromatic phase it is possible to determine the content of the different iso- paraffins having the same stoichiometry or n-number.
• the results of the mass spectrometer are processed using commercial software (poly 32; available from Sierra Analytics LLC, 3453 Dragoo Park Drive, Modesto, California GA95350 USA) to determine the relative proportions of each hydrocarbon type.
• the base oil composition having the continuous iso- paraffinic series as described above are preferably obtained by hydroisomerisation of a paraffinic wax, yet more preferably followed by some type of dewaxing, such as solvent or catalytic dewaxing.
• the above described base oil composition may preferably be obtained by hydroisomerisation of a paraffinic wax, preferably followed by a dewaxing treatment, such as a solvent or catalytic dewaxing treatment.
• the paraffinic wax may be a highly paraffinic slack wax. More preferably the paraffinic wax is a Fischer-Tropsch derived wax, because of its purity and even higher paraffinic content.
• Fischer-Tropsch derived base oils The base oils as derived from a Fischer-Tropsch wax as here described will be referred to in this description as Fischer-Tropsch derived base oils.
• Fischer-Tropsch processes which for example can be used to prepare the above-described Fischer-Tropsch derived base oil are the so-called commercial Slurry Phase Distillate technology of Sasol, the Shell Middle Distillate Synthesis Process and the "AGC-21" Exxon Mobil process. These and other processes are for example described in more detail in EP-A-776959, EP-A-668342, US-A-4943672 , US-A-5059299 , WO-A-9934917 and WO-A-9920720.
• these Fischer-Tropsch synthesis products will comprise hydrocarbons having 1 to 100 and even more than 100 carbon atoms.
• This hydrocarbon product will comprise normal paraffins, iso-paraffins, oxygenated products and unsaturated products. If base oils are one of the desired iso-paraffinic products it may be advantageous to use a relatively heavy Fischer-Tropsch derived feed.
• the relatively heavy Fischer-Tropsch derived feed has at least 30 wt%, preferably at least 50 wt%, and more preferably at least 55 wt% of compounds having at least 30 carbon atoms.
• the weight ratio of compounds having at least 60 or more carbon atoms and compounds having at least 30 carbon atoms of the Fischer-Tropsch derived feed is preferably at least 0.2, more preferably at least 0.4 and most preferably at least 0.55.
• the Fischer-Tropsch derived feed comprises a C20 "1" fraction having an ASF-alpha value (Anderson-Schulz-Flory chain growth factor) of at least 0.925, preferably at least 0.935, more preferably at least 0.945, even more preferably at least 0.955.
• ASF-alpha value Anderson-Schulz-Flory chain growth factor
• Such a Fischer-Tropsch derived feed can be obtained by any process, which yields a relatively heavy Fischer-Tropsch product as described above. Not all Fischer-Tropsch processes yield such a heavy product.
• An example of a suitable Fischer-Tropsch process is described in WO-A-9934917.
• the Fischer-Tropsch derived product will contain no or very little sulphur and nitrogen containing compounds. This is typical for a product derived from a Fischer- Tropsch reaction, which uses synthesis gas containing almost no impurities. Sulphur and nitrogen levels will generally be below the detection limits, which are currently 5 mg/kg for sulphur and 1 mg/kg for nitrogen respectively.
• the process will generally comprise a Fischer-Tropsch synthesis, a hydroisomerisation step and an optional pour point reducing step, wherein said hydroisomerisation step and optional pour point reducing step are performed as : (a) hydrocracking/hydroisomerisating a Fischer-Tropsch product,
• step (b) separating the product of step (a) into at least one or more distillate fuel fractions and a base oil or base oil intermediate fraction. If the viscosity and pour point of the base oil as obtained in step (b) is as desired no further processing is necessary and the oil can be used as the base oil according the invention. If required, the pour point of the base oil intermediate fraction is suitably further reduced in a step (c) by means of solvent or preferably catalytic dewaxing of the oil obtained in step (b) to obtain oil having the preferred low pour point.
• the desired viscosity of the base oil may be obtained by isolating by means of distillation from the intermediate base oil fraction or from the dewaxed oil the a suitable boiling range product corresponding with the desired viscosity. Distillation may be suitably a vacuum distillation step.
• the hydroconversion/hydroisomerisation reaction of step (a) is preferably performed in the presence of hydrogen and a catalyst, which catalyst can be chosen from those known to one skilled in the art as being suitable for this reaction of which some will be described in more detail below.
• the catalyst may in principle be any catalyst known in the art to be suitable for isomerising paraffinic molecules.
• suitable hydroconversion/hydroisomerisation catalysts are those comprising a hydrogenation component supported on a refractory oxide carrier, such as amorphous silica- alumina (ASA) , alumina, fluorided alumina, molecular sieves (zeolites) or mixtures of two or more of these.
• ASA amorphous silica- alumina
• zeolites molecular sieves
• hydroconversion/ hydroisomerisation catalysts comprising platinum and/or palladium as the hydrogenation component.
• a very much preferred hydroconversion/hydroisomerisation catalyst comprises platinum and palladium supported on an amorphous silica-alumina (ASA) carrier.
• ASA amorphous silica-alumina
• the platinum and/or palladium is suitably present in an amount of from 0.1 to 5.0% by weight, more suitably from 0.2 to 2.0% by weight, calculated as element and based on total weight of carrier. If both present, the weight ratio of platinum to palladium may vary within wide limits, but suitably is in the range of from 0.05 to 10, more suitably 0.1 to 5.
• Suitable noble metal on ASA catalysts are, for instance, disclosed in WO-A-9410264 and EP-A-0582347.
• Other suitable noble metal-based catalysts, such as platinum on a fluorided alumina carrier, are disclosed in e.g. US-A-5059299 and WO-A-9220759.
• a second type of suitable hydroconversion/ hydroisomerisation catalysts are those comprising at least one Group VIB metal, preferably tungsten and/or molybdenum, and at least one non-noble Group VIII metal, preferably nickel and/or cobalt, as the hydrogenation component. Both metals may be present as oxides, sulphides or a combination thereof .
• the Group VIB metal is suitably present in an amount of from 1 to 35% by weight, more suitably from 5 to 30% by weight, calculated as element and based on total weight of the carrier.
• the non-noble Group VIII metal is suitably present in an amount of from 1 to 25 wt%, preferably 2 to 15 wt%, calculated as element and based on total weight of carrier.
• a hydroconversion catalyst of this type which has been found particularly suitable, is a catalyst comprising nickel and tungsten supported on fluorided alumina .
• the above non-noble metal-based catalysts are preferably used in their sulphided form.
• some sulphur needs to be present in the feed.
• a preferred catalyst which can be used in a non- sulphided form, comprises a non-noble Group VIII metal, e.g., iron, nickel, in conjunction with a Group IB metal, e.g., copper, supported on an acidic support. Copper is preferably present to suppress hydrogenolysis of paraffins to methane.
• the catalyst has a pore volume preferably in the range of 0.35 to 1.10 ml/g as determined by water absorption, a surface area of preferably between 200-500 m ⁇ /g as determined by BET nitrogen adsorption, and a bulk density of between 0.4-1.0 g/ml .
• the catalyst support is preferably made of an amorphous silica-alumina wherein the alumina may be present within wide range of between 5 and 96 wt%, preferably between 20 and 85 wt%.
• the silica content as SiC>2 is preferably between 15 and 80 wt%.
• the support may contain small amounts, e.g., 20-30 wt%, of a binder, e.g., alumina, silica, Group IVA metal oxides, and various types of clays, magnesia, etc., preferably alumina or silica.
• the catalyst is prepared by co-impregnating the metals from solutions onto the support, drying at
• the Group VIII metal is present in amounts of about 15 wt% or less, preferably 1-12 wt%, while the Group IB metal is usually present in lesser amounts, e.g., 1:2 to about 1:20 weight ratio respecting the Group VIII metal.
• a typical catalyst is shown below:
• Suitable hydroconversion/ hydroisomerisation catalysts are those based on zeolitic materials, suitably comprising at least one Group VIII metal component, preferably Pt and/or Pd, as the hydrogenation component.
• Suitable zeolitic and other aluminosilicate materials include Zeolite beta, Zeolite Y, Ultra Stable Y, ZSM-5, ZSM-12, ZSM-22, ZSM-23, ZSM-48, MCM-68, ZSM-35, SSZ-32, ferrierite, mordenite and silica-aluminophosphates, such as SAPO-Il and SAPO-31.
• hydroisomerisation/ hydroisomerisation catalysts examples include, for instance, described in WO-A-9201657. Combinations of these catalysts are also possible.
• Very suitable hydroconversion/ hydroisoraerisation processes are those involving a first step wherein a zeolite beta or ZSM-48 based catalyst is used and a second step wherein a ZSM-5, ZSM- 12, ZSM-22, ZSM-23, ZSM-48, MCM-68, ZSM-35, SSZ-32, ferrierite, mordenite based catalyst is used. Of the latter group
• ZSM-23, ZSM-22 and ZSM-48 are preferred. Examples of such processes are described in US-A-20040065581, which disclose a process comprising a first step catalyst comprising platinum and zeolite beta and a second step catalyst comprising platinum and ZSM-48.
• Combinations wherein the Fischer-Tropsch product is first subjected to a first hydroisomerisation step using the amorphous catalyst comprising a silica-alumina carrier as described above followed by a second hydroisomerisation step using the catalyst comprising the molecular sieve has also been identified as a preferred process to prepare the base oil to be used in the present invention. More preferred the first and second hydroisomerisation steps are performed in series flow. Most preferred these two steps are performed in a single reactor comprising beds of the above amorphous and/or crystalline catalysts.
• step (a) the feed is contacted with hydrogen in the presence of the catalyst at elevated temperature and pressure.
• the temperatures typically will be in the range of from 175 to 380 0 C, preferably higher than 250 0 C and more preferably from 300 to 370 0 C.
• the pressure will typically be in the range of from 10 to 250 bar and preferably between 20 and 80 bar.
• Hydrogen may be supplied at a gas hourly space velocity of from 100 to 10000 Nl/l/hr, preferably from 500 to 5000 Nl/l/hr.
• the hydrocarbon feed may be provided at a weight hourly space velocity of from 0.1 to 5 kg/l/hr, preferably higher than 0.5 kg/l/hr and more preferably lower than 2 kg/l/hr.
• the ratio of hydrogen to hydrocarbon feed may range from 100 to 5000 Nl/kg and is preferably from 250 to 2500 Nl/kg.
• the conversion in step (a) as defined as the weight percentage of the feed boiling above 370 0 C which reacts per pass to a fraction boiling below 370 0 C, is at least 20 wt%, preferably at least 25 wt%, but preferably not more than 80 wt%, more preferably not more than 65 wt%.
• the feed as used above in the definition is the total hydrocarbon feed fed to step (a) , thus also any optional recycle of a high boiling fraction which may be obtained in step (b) .
• step (b) the product of step (a) is preferably separated into one or more distillate fuels fractions and a base oil or base oil precursor fraction having the desired viscosity properties. If the pour point is not in the desired range the pour point of the base oil is further reduced by means of a dewaxing step (c) , preferably by catalytic dewaxing. In such an embodiment it may be a further advantage to dewax a wider boiling fraction of the product of step (a) . From the resulting dewaxed product the base oil and oils having a desired viscosity can then be advantageously isolated by means of distillation. Dewaxing is preferably performed by catalytic dewaxing as for example described in
• the final boiling point of the feed to the dewaxing step (c) may be the final boiling point of the product of step (a) or lower if desired.
• the oil formulation may comprise a single type of base oil or blends of the above-described base oils as base oil composition.
• the present invention further relates to formulations wherein the base oil composition comprises at least 80% by weight of the total formulation of a mineral-derived naphthenic base oil; to formulations wherein the base oil comprises at least 80% by weight of a mineral-derived paraffinic base oil; and to formulations wherein the base oil composition comprises at least 80% by weight of a Fischer-Tropsch derived base oil.
• base oils and other synthetic base oil components may be present in the oil formulation, such as for example esters, poly alpha olefins, as preferably obtained by oligomerisation of an olefinic compound, poly alkylene glycols and the like.
• Possible base oil compositions preferably include mineral-derived paraffinic base oils and Fischer-Tropsch derived base oils, mineral-derived naphthenic base oils and Fischer- Tropsch derived base oils, and mixtures of the three base oil components .
• a Fischer-Tropsch derived base oil as the substantially the sole base oil component.
• substantially here meant that more than 80 wt%, more preferably more than 90 wt% and most preferably 100 wt% of the base oil component in the oil formulation is a Fischer-Tropsch derived base oil as described in detail above .
• additives next to the ones described above may also be present in the formulation.
• the type of additives will depend on the specific application. Without intending to be limiting, examples of possible additives are dispersants, detergents, viscosity modifying polymers, hydrocarbon or oxygenated hydrocarbon type pour point depressants, emulsifiers, demulsifiers, antistaining additives and friction modifiers. Specific examples of such additives are described in for example Kirk-Othmer Encyclopedia of Chemical Technology, third edition, volume 14, pages 477-526.
• the dispersant is an ashless dispersant, for example polybutylene succinimide polyamines or Mannic base type dispersants .
• the detergent is an over-based metallic detergent, for example the phosphonate, sulfonate, phenolate or salicylate types as described in the above referred to General Textbook.
• the viscosity modifier is a viscosity modifying polymer, for example polyisobutylenes, olefin copolymers, poly- methacrylates and polyalkylstyrenes and hydrogenated polyisoprene star polymer (Shellvis) .
• suitable antifoaming agents are polydimethylsiloxanes and polyethylene glycol ethers and esters.
• the oil formulation may find use as turbine oil, gasoline engine oil, diesel engine oil, automotive and industrial gear oils, for example automatic and manual transmission and differential oils, hydraulic machine oil, refrigerator oil, plastic processing oil for rolling, press, forging, sqeezing, draw, punch and the like operations, thermal treating oil, discharge processing oil, slide guide oil, rust proofing oil and heat medium.
• a preferred use of the oil formulation is as electrical oil. It has further been found that when the base oil component of the oil formulation comprises substantially of the Fischer-Tropsch derived base oil an electrical oil formulation is obtained which has good oxidative stability, as expressed by low acid formation and/or low sludge formation and also excellent low temperature viscosity values .
• Examples of applications are switch gears, transformers, regulators, circuit breakers, power plant reactors, cables and other electrical equipment.
• a problem often encountered when using an electrical oil based on a naphthenic base oil is that the kinematic viscosity at -30 0 C is too high. When such an oil would be used in application which have to start up at low temperatures, especially at temperatures below 0 0 C, the higher viscosity will have a negative effect on the required heat dissipation of the electrical oil. Overheating of the equipment can result.
• 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 Kunststoff GmbH.
• Another preferred mixture of aromatic compounds is comprised in a mixture of 2 , 6-di-t-butyl phenol and 2, 6-di-t-butyl cresol.
• 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 oil formulation preferably comprising the anti- wear additive, is preferably subjected to an additional clay treatment.
• Clay treatment is a well know treatment to remove polar compounds from the oil formulation. It is performed in order to further improve the color, chemical and thermal stability of the oil formulation. It may be performed prior to adding the additives mentioned in this description on a, partly, formulated oil formulation. 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-
• the copper passivator and optional anti-oxidant are added after the clay treatment .
• the oil formulations comprising a Fischer-Tropsch derived base oil as described above show a very low dielectric dissipation factor, even after prolonged testing at elevated temperature.
• the low dissipation factor is indicative for a low loss of electric power in the application wherein the electrical oil is used. Because the dissipation factor does not significantly increase over time, especially when compared to the naphthenic based electrical oil formulations, a very efficient application of the oil results.
• the electrical oil as described above may find use in applications which have to start up regularly, especially more than 10 times per year at a temperature of below 0 0 C, more preferably below -5 0 C, wherein the temperature of the oil when the application is running is above 0 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 invention will be illustrated with the following non-limiting examples.
• One Fischer-Tropsch derived base oil referred to as GTL BO
• two naphthenic type of base oils referred to as naphthenic-1 and naphthenic-2
• a mineral paraffinic base oil The properties of these base oils are listed in Table 1.
• Example 1 two formulations A and B were prepared of which the base oil component consisted of 95 wt% of the naphthenic-2 base oil and for 5 wt% of the paraffinic-1 base oil. To these mixtures 10 mg/kg of
• oil mixtures were prepared according to the scheme as presented in Table 4. Two oil mixtures were subjected to a clay treatment using Tonsil 411 clay as obtainable from Sued Chemie, Muenchen (D) . The anti-oxidant and copper passivator additives were added after the clay treatment. The properties of the oil mixtures were measured and the oil mixtures were subjected to the IEC OXIDATION TEST at 50Oh/120 0 C.
• Table 4 shows that the oil formulation based on the Fischer-Tropsch derived base oil has a low viscosity at -30 0 C in combination with excellent oxidative stability properties.
• the gassing tendency of the Mixture Z of Table 4 can be improved by adding an aromatic solvent as illustrated in Table 5.
• Three oil formulations A-C were made using the GTL Base Oils 1, 2 and 3 of Table 1 according to the formulation as listed in Table 6.
• the oil formulations A-C were subjected to a clay treatment using Tonsil 411 clay as obtainable from Sued Chemie, M ⁇ nchen (D) .
• Tonsil 411 clay as obtainable from Sued Chemie, M ⁇ nchen (D) .
• the anti-oxidant and copper passivator additive were added after the clay treatment.
• the oils were tested with the test methods listed in Table 6. The results show that excellent oils for use as electrical oils.

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