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
  • C10M169/00—Lubricating compositions characterised by containing as components a mixture of at least two types of ingredient selected from base-materials, thickeners or additives, covered by the preceding groups, each of these compounds being essential
  • C10M169/04—Mixtures of base-materials and additives
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  • C10M171/00—Lubricating compositions characterised by purely physical criteria, e.g. containing as base-material, thickener or additive, ingredients which are characterised exclusively by their numerically specified physical properties, i.e. containing ingredients which are physically well-defined but for which the chemical nature is either unspecified or only very vaguely indicated
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  • 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
  • C10M2203/1006—Petroleum or coal fractions, e.g. tars, solvents, bitumen used as base material
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  • 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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  • C10M2209/00—Organic macromolecular compounds containing oxygen as ingredients in lubricant compositions
  • C10M2209/02—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C10M2209/08—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing monomers having an unsaturated radical bound to a carboxyl radical, e.g. acrylate type
  • C10M2209/084—Acrylate; Methacrylate
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  • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2215/28—Amides; Imides
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  • 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
  • C10M2219/02—Sulfur-containing compounds obtained by sulfurisation with sulfur or sulfur-containing compounds
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  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
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  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/02—Sulfur-containing compounds obtained by sulfurisation with sulfur or sulfur-containing compounds
  • C10M2219/022—Sulfur-containing compounds obtained by sulfurisation with sulfur or sulfur-containing compounds of hydrocarbons, e.g. olefines
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  • 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
  • C10M2219/02—Sulfur-containing compounds obtained by sulfurisation with sulfur or sulfur-containing compounds
  • C10M2219/024—Sulfur-containing compounds obtained by sulfurisation with sulfur or sulfur-containing compounds of esters, e.g. fats
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  • 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
  • C10M2219/04—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions containing sulfur-to-oxygen bonds, i.e. sulfones, sulfoxides
  • C10M2219/046—Overbasedsulfonic acid salts
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  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/06—Thio-acids; Thiocyanates; Derivatives thereof
  • C10M2219/062—Thio-acids; Thiocyanates; Derivatives thereof having carbon-to-sulfur double bonds
  • C10M2219/066—Thiocarbamic type compounds
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  • 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
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  • C10M2219/00—Organic non-macromolecular compounds containing sulfur, selenium or tellurium as ingredients in lubricant compositions
  • C10M2219/10—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring
  • C10M2219/104—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring containing sulfur and carbon with nitrogen or oxygen in the ring
  • C10M2219/106—Thiadiazoles
• • C—CHEMISTRY; METALLURGY
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  • 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
  • C10M2219/10—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring
  • C10M2219/104—Heterocyclic compounds containing sulfur, selenium or tellurium compounds in the ring containing sulfur and carbon with nitrogen or oxygen in the ring
  • C10M2219/108—Phenothiazine
• • 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
  • C10M2223/00—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions
  • C10M2223/02—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions having no phosphorus-to-carbon bonds
• • 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
  • C10M2223/00—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions
  • C10M2223/02—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions having no phosphorus-to-carbon bonds
  • C10M2223/04—Phosphate esters
  • C10M2223/045—Metal containing thio derivatives
• • 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
  • C10M2223/00—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions
  • C10M2223/02—Organic non-macromolecular compounds containing phosphorus as ingredients in lubricant compositions having no phosphorus-to-carbon bonds
  • C10M2223/04—Phosphate esters
  • C10M2223/047—Thioderivatives not containing metallic elements
• • 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
  • C10N2010/00—Metal present as such or in compounds
  • C10N2010/04—Groups 2 or 12
• • 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
  • C10N2030/06—Oiliness; Film-strength; Anti-wear; Resistance to extreme pressure
• • 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
  • C10N2040/04—Oil-bath; Gear-boxes; Automatic transmissions; Traction drives
  • C10N2040/042—Oil-bath; Gear-boxes; Automatic transmissions; Traction drives for automatic transmissions
• • 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
  • C10N2040/04—Oil-bath; Gear-boxes; Automatic transmissions; Traction drives
  • C10N2040/045—Oil-bath; Gear-boxes; Automatic transmissions; Traction drives for continuous variable transmission [CVT]
• • 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
  • C10N2060/00—Chemical after-treatment of the constituents of the lubricating composition
  • C10N2060/14—Chemical after-treatment of the constituents of the lubricating composition by boron or a compound containing boron

Definitions

• the present invention relates to lubricating oil compositions for automatic transmissions and more particularly to those advantageously applicable to belt type continuously variable transmissions for automobiles, which compositions are capable of preventing the occurrence of scratch noise by making the friction material of such an automatic transmission exhibit the ⁇ -V characteristics of a positive gradient and of maintaining the positive gradient ⁇ -V characteristics for a longer period of time.
• a belt type CVT comprises a driving pulley, a driven pulley, and a belt for transmitting a power which belt is composed of a plurality of elements and a belt (steel belt) connecting the elements together.
• Automatic transmission fluids (ATF) conventionally used in stepped type automatic transmissions have also been used widely in such a belt type CVT because the ATFs have cooling, lubricating, and anti-abrasion properties and many common parts are used in stepped type automatic transmissions and CVTs.
• noises so-called “scratch phenomenon”.
• the object of the present invention is to provide a lubricating oil composition for automatic transmissions which composition is suitable for belt type CVTs and capable of preventing the occurrence of scratch noise by making friction materials exhibit the ⁇ -V characteristics of a positive gradient and of maintaining the positive gradient ⁇ -V characteristics for a longer period of time.
• the present invention was made based on the finding that the above object was able to be achieved with a composition wherein specific additives are blended so as to be at specific elemental ratios.
• a lubricating oil composition for automatic transmissions wherein the mass ratio of phosphorus calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 2):(0.06 to 2):(0.2 to 20), the concentration of phosphorus is from 0.01 to 0.06 percent by mass, the concentration of the sulfur derived from a base oil is from 0 to 0.1 percent by mass, and the concentration of the sulfur derived from sulfur-based additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition.
• the lubricating oil compositions according to the present invention are preferably those wherein the mass ratio of phosphorus:calcium:boron:sulfur determined by elemental analysis is 1:(0.1 to 1)(0.1 to 0.8):(0.4 to 5), the concentration of phosphorus is from 0.02 to 0.05 percent by mass, the concentration of the sulfur derived from a base oil is from 0 to 0.1 percent by mass, and the concentration of the sulfur derived from sulfur-based additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition.
• Sulfur-based additives contained in a lubricating oil composition according to the present invention are at least one compound selected from the group consisting of (A) thiadiazoles and/or benzothiazoles, (B) dithiocarbamates, (C) dithiophosphates, (D) trithiophosphites, (E) polysulfides, and derivatives of (A) though (E).
• the lubricating oil compositions of the present invention comprise, phosphorus, calcium, boron, and sulfur in addition to a lubricating base oil.
• sulfur is derived from the base oil or additives such as sulfur-based additives and/or calcium-based detergents such as calcium sulfonate and calcium phenate.
• Phosphorus is derived from phosphorus-based additives and a part of sulfur-based additives.
• Calcium is derived from calcium-based detergents.
• Boron is derived from various additives such as boric acid-modified succinimides and/or alkali metal borates or hydrates thereof.
• Lubricating base oils which may be used for the lubricating oil compositions of the present invention may be any mineral base oils and/or synthetic base oils which are conventionally used as base oils for a lubricating oil.
• Examples of such mineral base oil include paraffinic or naphthenic oils which can be obtained by subjecting a lubricating oil fraction produced by atmospheric- or vacuum-distilling a crude oil, to one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, washing with sulfuric acid, and clay treatment; and n-paraffines.
• Examples of synthetic base oils include poly- ⁇ -olefins such as 1-octene oligomer, 1-decene oligomer, and ethylene-propylene oligomer, and hydrides thereof; isobutene oligomer and hydrides thereof; isoparaffines; alkylbenzenes; alkylnaphthalenes; diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, and di-2-ethylhexyl cebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethyl hexanoate, and pentaerythritol pelargonate; polyoxyalkylene glycols; dialkyldiphenyl
• the kinematic viscosity of the lubricating base oil is preferably from 1 to 10 mm 2 /s, and more preferably from 2 to 8 mm 2 /s.
• the concentration of the sulfur derived from the base oil is 0.1 percent by mass or less, preferably 0.05 percent by mass or less, and more preferably 0.005 percent by mass or less.
• a sulfur concentration in excess of 0.1 percent by mass makes it difficult to maintain stable ⁇ -V characteristics over a long time.
• Sulfur-based additives which may be used in the present invention are any compounds (A) through (E) described below.
• thiadiazoles include compounds represented by the formula
• R 1 is a straight-chain or branched alkyl group having 1 to 30, preferably 6 to 24 carbon atoms
• R 2 is hydrogen or a straight-chain or branched alkyl group having 1 to 30 carbon atoms, preferably hydrogen or a straight-chain or branched alkyl group having 1 to 24 carbon atoms
• a and b are each independently 1, 2 or 3, preferably 1 or 2.
• benzothiazole include compounds represented by the formula
• R 3 is a straight-chain or branched alkyl group having 1 to 4 carbon atoms, preferably methyl and ethyl groups
• R 4 is a straight-chain or branched alkyl group having 1 to 30, preferably 6 to 24 carbon atoms
• c is an integer of 0 to 3, preferably 0 or 1
• d is an integer from 1 to 3, preferably 1 or 2.
• Component (A) When Component (A) is blended in a lubricating oil composition according to the present invention, one compound selected from those of formulas (1) and (2) may be used or alternatively two or more compounds having different structures selected from those of formulas (1) and (2) may be used.
• R 5 , R 6 , R 7 , R 8 , R 9 , and R 10 are each independently a hydrocarbon group having 1 to 30, preferably 1 to 20 carbon atoms, X is sulfur or methylene (-CH 2 -), and e is an integer of 0 to 6.
• Examples of hydrocarbon groups having 1 to 30 carbon atoms for R 5 through R 10 include alkyl, cycloalkyl, alkylcycloalkyl, alkenyl, aryl, alkylaryl, and arylalkyl groups.
• alkyl groups include straight-chain or branched alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups.
• cycloalkyl groups include those having 5 to 7 carbon atoms, such as cyclopentyl, cyclohexyl, and cycloheptyl groups.
• alkylcycloalkyl groups include those having 6 to 11 carbon groups, such as methylcyclopentyl, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl, methylethylcycloheptyl, and diethylcycloheptyl groups, of which the alkyl group may bond to any position of the cycloalkyl groups.
• alkenyl groups include butenyl, pentenyl, hexenyl, heptenyl, octenyl, noneyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, and octadecenyl groups, all of which may be straight-chain or branched and the position of which the double bond may vary.
• aryl groups include phenyl and naphtyl groups.
• alkylaryl groups include those having 7 to 18 carbon atoms, such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl groups, of which the alkyl group may be straight-chain or branched and may bond to any position of the aryl groups.
• arylalkyl groups include those having 7 to 12 carbon atoms, such as benzyl, phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl, and phenylhexyl groups, of which the alkyl groups may be straight-chain or branched.
• One or more Components (B) may be arbitrary blended.
• dithiophosphates include one dialkyldithiophosphate and mixtures of two or more dialkyldithiophosphates selected from compounds represented by the formula
• R 11 and R 12 are each independently a hydrocarbon group having 2 to 30, preferably 3 to 20 carbon atoms. Examples of hydrocarbon groups having 2 to 30 carbon atoms for R 11 and R 12 are the same as those as described with respect to R 5 through R 8 in formula (3).
• trithiophosphites include trithiophosphite compounds having a hydrocarbon group having 2 to 30, preferably 3 to 20 carbon atoms.
• hydrocarbon group having 2 to 30 carbon atoms are the same as those as described with respect to R 5 through R 8 in formula (3).
• Polysulfides are sulfur-based compounds generally referred to dihydrocarbylsulfides or olefin sulfides and represented by the formula
• R 13 and R 14 are each independently a straight-chain or branched alkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl group having 6 to 20 carbon atoms, or an arylalkyl group having 6 to 20 carbon atoms, and f is an integer of 2 to 6, preferably 2 to 5.
• alkyl groups for R 13 and R 14 include n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, straight-chain or branched pentyl, straight-chain or branched hexyl, straight-chain or branched heptyl, straight-chain or branched octyl, straight-chain or branched nonyl, straight-chain or branched decyl, straight-chain or branched undecyl, straight-chain or branched dodecyl, straight-chain or branched tridecyl, straight-chain or branched tetradecyl, straight-chain or branched pentadecyl, straight-chain or branched hexadecyl, straight-chain or branched heptadecyl, straight-chain or branched octadecyl, straight-chain or branched
• aryl groups for R 13 and R 14 include phenyl and naphthyl groups.
• alkylaryl groups for R 13 and R 14 include tolyl (inclusive all structural isomers), ethylphenyl (inclusive all structural isomers), straight-chain or branched propylphenyl (inclusive all structural isomers), straight-chain or branched butylphenyl (inclusive all structural isomers), straight-chain or branched pentylphenyl (inclusive all structural isomers), straight-chain or branched hexylphenyl (inclusive all structural isomers), straight-chain or branched heptylphenyl (inclusive all structural isomers), straight-chain or branched octylphenyl (inclusive all structural isomers), straight-chain or branched nonylphenyl (inclusive all structural isomers), straight-chain or branched decylphenyl (inclusive all structural isomers), straight-chain or branched undecylphenyl (inclusive all structural isomers),
• arylalkyl groups for R 13 and R 14 include benzyl, phenylethyl(inclusive all isomers), and phenylpropyl (inclusive all isomers).
• R 13 and R 14 each are preferably an alkyl group having 3 to 18 carbon atoms derived from propylene, 1-butene, or isobutylene, an aryl group having 6 to 8 carbon atoms, an alkylaryl group having 7 or 8 carbon atoms, or an arylalkyl group having 7 or 8 carbon atoms.
• alkyl group examples include isopropyl, branched hexyl derived from a propylene dimmer (inclusive all branched isomers), branched nonyl derived from a propylene trimer (inclusive all branched isomers), branched dodecyl derived from a propylene tetramer (inclusive all branched isomers), branched pentadecyl derived from a propylene pentamer (inclusive all branched isomers), branched octadecyl derived from a propylene hexamer (inclusive all branched isomers), sec-butyl, tert-butyl, branched octyl derived from a 1-butene dimmer (inclusive all branched isomers), branched octyl derived from an isobutylene dimmer (inclusive all branched isomers).
• aryl groups include phenyl group.
• alkylaryl groups are tolyl (inclusive all structural isomers), ethylphenyl (inclusive all structural isomers), and xylyl (inclusive all structural isomers).
• arylalkyl groups are benzyl and phenetyl (inclusive all structural isomers).
• One or more compounds selected from the above described sulfur-containing additive, i.e., Components (A) through (E) and derivatives thereof may be used in the lubricating oil composition of the present invention.
• the content of the sulfur-based additives is in such a range that the total sulfur concentration of the sulfur derived from Components (A) through (E) and derivatives thereof and the sulfur derived from other additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition and the total phosphorus concentration of the phosphorus derived from Components (A) through (E) and derivatives thereof and the phosphorus derived from the phosphorus-based additives is from 0.01 to 0.06 percent by mass, based on the total amount of the composition.
• sulfur-based additives When the sulfur-based additives are contained in an amount of less than 0.01 percent by mass in terms of sulfur or in an amount of less than 0.01 percent by mass in terms of phosphorus, they are less in effect to improve the ⁇ -V characteristics. When the sulfur-based additives are contained in an amount exceeding 0.15 percent by mass in terms of sulfur or in an amount exceeding 0.06 percent by mass in terms of phosphorus, they deteriorate the oxidation stability of the resulting lubricating oil composition.
• the content of the sulfur-based additives is preferably in such a range that the total sulfur concentration of the sulfur derived from Components (A) through (E) and derivatives thereof and the sulfur derived from the other additives is from 0.01 to 0.15 percent by mass, based on the total amount of the composition and the total phosphorus concentration of the phosphorus derived from Components (A) through. (E) and derivatives thereof and the phosphorus derived from the phosphorus-based additives is from 0.02 to 0.05 percent by mass, based on the total amount of the composition.
• Examples of phosphorus-based additives which may be used in the present invention are monophosphates, diphosphates, triphosphates, monophosphites, diphosphites, triphosphites, salts of phosphates and phosphites, phosphoric acid, phosphorous acid, zinc alkyldithiophosphates and mixtures thereof.
• Component (F) those other than phosphoric acid and phosphorus acid are compounds containing a hydrocarbon group having 2 to 30, preferably 3 to 20 carbon atoms.
• hydrocarbon groups having 2 to 30 carbon atoms include alkyl, cycloalkyl, alkylcycloalkyl, alkenyl, aryl, alkylaryl, and arylalkyl groups.
• alkyl groups include ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups, all of which may be straight-chain or branched.
• cycloalkyl groups include those having 5 to 7 carbon atoms, such as cyclopentyl, cyclohexyl, and cycloheptyl groups.
• alkylcycloalkyl groups include those having 6 to 11 carbon atoms, of which the cycloalkyl group may possess an alkyl substituent at any position, such as methylcyclopentyl, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl, methylethylcycloheptyl and diethylcycloheptyl groups.
• alkenyl groups include butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl and octadecenyl groups, all of which may be straight-chain or branched and the position of which the double bond may vary.
• aryl groups include those having 6 to 18 carbon atoms such as phenyl and naphthyl.
• alkylaryl groups include those having 7 to 18 carbon atoms, such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl groups, all of which the alkyl group may be straight-chain or branched and may bond to any position of the aryl group.
• arylalkyl groups include those having 7 to 12 carbon atoms, such as benzyl, phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl and phenylhexyl groups, all of which may be straight-chain or branched.
• Preferred compounds as Component (F) are phosphoric acid; phosphorus acid; zinc alkyldithiophosphates, of which the alkyl group may be straight-chain or branched, such as zinc dipropyldithiophosphate, zinc dibutyldithiophosphate, zinc dipentyldithiophosphate, zinc dihexyldithiophosphate, zinc diheptyldithiophosphate, and zinc dioctyldithiophosphate; monoalkyl phosphates, of which the alkyl group may be straight-chain or branched, such as monopropyl phosphate, monobutyl phosphate, monopentyl phosphate, monohexyl phosphate, monoheptyl phosphate and monooctyl phosphate; mono(alkyl)aryl phosphates such as monophenyl phosphate and monocresyl phosphate; dialkyl phosphates, of which the
• salts of phosphates and phosphites include those obtained by allowing monophosphate, diphosphate, monophosphite, or diphosphite to react with a nitrogen-containing compound such as ammonia or an amine compound having in its molecules only a hydrocarbon group or hydroxyl-containing hydrocarbon group having 1 to 8 carbon atoms so as to neutralize the whole or part of the remaining acid hydrogen.
• a nitrogen-containing compound such as ammonia or an amine compound having in its molecules only a hydrocarbon group or hydroxyl-containing hydrocarbon group having 1 to 8 carbon atoms
• nitrogen-containing compound examples include ammonia; alkylamines, of which the alkyl group may be straight-chain or branched, such as monomethylamine, monoethylamine, monopropylamine, monobutylamine, monopentylamine, monohexylamine, monoheptylamine, monooctylamine, dimethylamine, methylethylamine, diethylamine, methylpropylamine, ethylpropylamine, dipropylamine, methylbutylamine, ethylbutylamine, propylbutylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine and dioctylamine; alkanolamines, of which the alkanol group may be straight-chain or branched, such as monomethanolamine, monoethanolamine, monopropanolamine, monobutanolamine, monopentanolamine, monohexan
• the lubricating oil compositions of the present invention contain Component (F) in such an amount that the total phosphorus concentration of the phosphorus derived from Component (F) and the phosphorus derived from the other additives is from 0.01 to 0.06 percent by mass, based on the total amount of the composition.
• a phosphorus concentration of less than 0.01 percent by mass is not preferred because the resulting composition would be less effective in anti-abrasion properties, while a phosphorus concentration in excess of 0.06 percent by mass is not also preferred because the resulting composition would be deteriorated in oxidation stability.
• Component (F) is preferably contained in such an amount that the total phosphorus concentration of the phosphorus derived from Components (F) and the phosphorus derived from the other additives is from 0.02 to 0.05 percent by mass, based on the total amount of the composition.
• Examples of calcium-based detergents hereinafter referred to as Component (G) which may be used in the present invention include basic calcium-based detergents having a total base number of generally 20 to 450 mgKOH/g, preferably 50 to 400 mgKOH/g.
• total base number used herein denotes a total base number measured by the perchloric acid potentiometric titration method in accordance with section 7 of JIS K2501 (1992) “Petroleum products and lubricants-Determination of neutralization number”.
• Component (G) include one or more calcium-based detergents selected from the following compounds: (G-1) calcium sulfonate having a total base number of 20 to 450 mgKOH/g; (G-2) calcium phenate having a total base number of 20 to 450 mgKOH/g; and (G-3) calcium salicylate having a total base number of 20 to 450 mgKOH/g.
• Component (G-1), i.e., calcium sulfonate may be a calcium salt of an alkyl aromatic sulfonic acid obtained by sulfonating an alkyl aromatic compound having a molecular weight of 100 to 1,500 and preferably 200 to 700.
• alkyl aromatic sulfonic acids are petroleum sulfonic acids and synthetic sulfonic acids.
• Petroleum sulfonic acids may be those obtained by sulfonating the alkyl aromatic compound contained in the lubricant fraction of a mineral oil or mahogany acid by-produced upon production of white oil.
• Synthetic sulfonic acids may be those obtained by sulfonating an alkyl benzene having a straight-chain or branched alkyl group, which may be by-produced from a plant for producing an alkyl benzene used as materials of detergents or obtained by alkylating a polyolefin to benzene or sulfonating dinonylnaphthalene.
• fuming sulfuric acids and sulfuric acid as a sulfonating agent.
• Component (G-2), i.e., calcium phenate may be a calcium salt of an alkylphenol having at least one straight-chain or branched alkyl group having 4 to 30, preferably 6 to 18 carbon atoms; a calcium salt of an alkylphenolsulfide obtained by reacting such an alkylphenol with sulfur; or a calcium salt of a Mannich reaction product of an alkylphenol obtained by reacting an alkylphenol with formaldehyde.
• Component (G-3), i.e., calcium salicylate may be a calcium salt of an alkyl salicylic acid having at least one straight-chain or branched alkyl group having 4 to 30, preferably 6 to 18 carbon atoms.
• Component (G) i.e., the above described calcium sulfonate, calcium phenate, or calcium salicylate has a total base number within a range of 20 to 450 mgKOH/g, it may be a neutral (normal) salt obtained by reacting an alkylaromatic sulfonic acid, an alkylphenol, an alkylphenolsulfide, a Mannich reaction product of an alkylphenol or an alkyl salicylic acid directly with calcium oxide or calcium hydroxide or by substituting an alkylaromatic sulfonic acid, an alkylphenol, an alkylphenolsulfide, a Mannich reaction product of an alkylphenol or an alkyl salicylic acid which has been converted to an alkali metal salt such as a sodium salt or a potassium salt, with a calcium salt.
• an alkylaromatic sulfonic acid an alkylphenol, an alkylphenolsulfide, a Mannich reaction product of an alkylphenol or an al
• Component (G) may be a basic calcium salt obtained by heating a normal salt as described above with an excess amount of a calcium salt or calcium hydroxide in the presence of water.
• Component (G) may be an overbased calcium salt obtained by reacting a normal salt as described above with a basic calcium salt as described above in the presence of carbonic acid gas. These reactions are conducted in a solvent, for example, an aliphatic hydrocarbon solvent such as hexane, an aromatic hydrocarbon solvent such as xylene, or a light fraction lubricating base oil.
• Metallic detergents are commercially available in the form of being diluted with a light fraction lubricating base oil. It is preferred to use metallic detergents whose metal content is within the range of 1.0 to 20 percent by mass, preferably 2.0 to 16 percent by mass.
• Component (G) is contained in an amount of preferably 0.01 to 5.0 percent by mass, more preferably 0.05 to 4.0 percent by mass, based on the total amount of the composition. Component (G) of less than 0.01 percent by mass would be less effective in suppressing a wet clutch from being decreased in strength against repeating compression applied thereto, while Component (G) in excess of 5.0 percent by mass would decrease the oxidation stability of the resulting composition.
• Examples of boric acid-modified succinimides which may be used in the present invention include those obtained by modifying an alkenyl succinimide having in its molecules at least one alkyl or alkenyl group having 40 to 400 carbon atoms, with boric acid.
• One or more of such succinimides may be blended in the lubricating oil compositions of the present invention.
• the carbon number of the alkyl or alkenyl group is from 40 to 400, preferably from 60 to 350.
• An alkyl or alkenyl group having less than 40 carbon atoms would decrease the solubility of Component (H) in a lubricating base oil, while an alkyl or alkenyl group having more than 400 carbon atoms would deteriorate the low temperature fluidity.
• R 21 is an alkyl or alkenyl having 40 to 400, preferably 60 to 350 carbon atoms, and m is an integer from 1 to 5, preferably from 2 to 4; or
• R 22 and R 23 are each independently an alkyl or alkenyl group having 40 to 400, preferably 60 to 350 carbon atoms, and n is an integer of 0 to 4, preferably 1 to 3.
• the succinimides are classified into mono-type succinimides wherein a succinic anhydride is added to one end of a polyamine as represented by formula (7) and bis-type succinimides wherein a succinic anhydride is added to both ends of a polyamine as represented by formula (8).
• both types of the succinimides and mixtures thereof can be used as Component (H).
• the boric acid-modified succinimides used herein are boron-modified compounds obtained by bringing the above-described succinimide into the reaction with boric acid so as to neutralize or amidize the whole or part of the remaining amino and/or imino groups.
• the content thereof is generally from 0.01 to 10.0 percent by mass, preferably from 0.1 to 7.0 percent by mass, based on the total mass of the composition.
• Component (H) of less than 0.01 percent by mass would fail to obtain a sufficient detergency effect, while Component (H) in excess of 10.0 percent by mass would deteriorate extremely the low temperature fluidity of the resulting composition.
• Examples of Components (I), i.e., alkali metal borate and hydrides thereof include lithium borate hydride, sodium borate hydride, potassium borate hydride, rubidium borate hydride, and cesium borate hydride. Particularly preferred is potassium borate hydride.
• alkali metal borates may be obtained by dissolving potassium hydroxide or sodium hydroxide and boric acid in water such that the atomic ratio of boric acid to an alkali metal (potassium/sodium) falls within the range of 2.0 to 4.5 (boron/alkali metal); adding the solution in an oily solution containing a neutral alkaline earth metal sulfonate or a succinimide-based ashless dispersant, followed by vigorous stirring so as to produce a water in oil emulsion; and dehydrating the emulsion so as to obtain a dispersant of fine particles of a potassium borate hydride or a sodium borate hydride.
• the blend ratio of one or more Components (I) is arbitrarily selected but is preferably 0.002 percent by mass or more, preferably 0.005 percent by mass or more and 0.1 percent by mass or less, preferably 0.06 percent by mass or less, in terms of boron, based on the total amount of the composition.
• Component (I) of less than 0.002 percent by mass in terms of boron would make Component (A) less effective in providing the resulting composition with enhanced friction properties between metal parts, while Component (I) in excess of 0.1 percent by mass in terms of boron would decrease the storage stability of the resulting oil composition.
• the lubricating oil compositions of the present invention may be used in combination with various known additives in order to further enhance the scratch preventing properties and other properties as a lubricating oil.
• additives may be ashless dispersants, metal detergents other than Components (G), friction modifiers, oxidation inhibitors, viscosity index improvers, antifoamers, and abrasion inhibitors.
• Ashless dispersants which may be used in combination with the lubricating oil compositions of the present invention may be any compounds which are usually used as ashless dispersants in a lubricating oil.
• nitrogen-containing compounds having in the molecules at least one alkyl or alkenyl group having 40 to 400 carbon atoms, such as those having an amino or imino group or derivatives thereof, or the modified products of alkenyl succinimides.
• the alkyl or alkenyl group may be straight-chain or branched and is preferably a branched alkyl or alkenyl group derived from an oligomer of an olefin such as propylene, 1-butene, and isobutylene or a cooligomer of ethylene and propylene.
• the alkyl or alkenyl group has 40 to 400, preferably 60 to 350 carbon atoms.
• An alkyl or alkenyl group having less than 40 carbon atoms would adversely affect the solubility of the compound in a base oil, while an alkyl or alkenyl group having more than 400 carbon atoms would deteriorate the low-temperature fluidity of the resulting lubricating oil composition.
• the derivatives of nitrogen-containing compounds include oxygen-modified compounds obtained by bringing a nitrogen-containing compound into a reaction with a monocarboxylic acid having 2 to 30 carbon atoms, such as fatty acid or a polycarboxylic acid having 2 to 30 carbon atoms, such as oxalic acid, phthalic acid, trimellitic acid, and pyromellitic acid so as to neutralize or amidize the whole or part of the remaining amino and/or imino groups; sulfur-modified compounds obtained by bringing a nitrogen-containing compound into a reaction with a sulfuric compound; and modified products obtained by bringing the nitrogen-containing compound into a combination of two or more modifications selected from the oxygen modification and sulfur modification.
• a monocarboxylic acid having 2 to 30 carbon atoms such as fatty acid or a polycarboxylic acid having 2 to 30 carbon atoms, such as oxalic acid, phthalic acid, trimellitic acid, and pyromellitic acid so as to neutralize or amidize the whole
• one or more compounds selected from the above-described ashless dispersants may be blended in an arbitrary ratio, the content of the ashless dispersants is generally within the range of 0.1 to 10 percent by mass, based on the lubricating oil composition.
• Metal detergents, other than Component (G), which may be used in combination with the lubricating oil compositions of the present invention may be any compounds which are usually used as metal detergents in a lubricating oil.
• alkali metal or alkaline earth metal sulfonates there may be used alkali metal or alkaline earth metal sulfonates, alkali metal or alkaline earth metal pehnates, alkali metal or alkaline earth metal salicylates, and alkali metal or alkaline earth metal naphthenates.
• alkali metals are sodium and potassium, while example of alkaline earth metal is magnesium.
• Specific preferred examples of the metal detergents are magnesium sulfonate, magnesium phenate, and magnesium salicylate. The total base value and blend amount of these metal detergents are arbitrarily selected depending on the requisite performance characteristics of a lubricating oil.
• one or more compounds selected from the above-described metal detergents may be blended in an arbitrary ratio, the content of thereof is generally within the range of 0.01 to 5 percent by mass, based on the lubricating oil composition.
• Friction modifiers which may be used in combination with the lubricating oil compositions of the present invention may be any compounds which are usually used as friction modifiers in a lubricating oil.
• amine compounds for example, there may be used amine compounds, fatty acid esters, fatty acid amides, and fatty acid metal salts, all having in the molecules at least one alkyl or alkenyl group having 6 to 30 carbon atoms, preferably at least one straight-chain alkyl or alkenyl group having 6 to 30 carbon atoms.
• Examples of amine compounds include straight-chain or branched, preferably straight-chain aliphatic monoamines having 6 to 30 carbon atoms, straight-chain or branched, preferably straight-chain. aliphatic polyamines having 6 to 30 carbon atoms, and alkyleneoxide adducts of these aliphatic amines.
• Examples of fatty acid esters include esters of straight-chain or branched, preferably straight-chain fatty acids having 7 to 31 carbon atoms and aliphatic monohydric alcohols or aliphatic polyhydric alcohols.
• fatty acid amides include amides of straight-chain or branched, preferably straight-chain fatty acids having 7 to 31 carbon atoms and aliphatic monoamines or aliphatic polyamines.
• fatty acid metal salts include alkaline earth metal salts (magnesium salts and calcium salts) or zinc salts of straight-chain or branched, preferably straight-chain fatty acids having 7 to 31 carbon atoms.
• one or more compounds selected from the above-described friction modifiers may be blended in an arbitrary ratio, the content of thereof is generally within the range of 0.01 to 5.0 percent by mass, preferably 0.03 to 3.0 percent by mass, based on the total amount of the lubricating oil composition.
• Oxidation inhibitors which may be used in combination with the lubricating oil compositions of the present invention may be any conventional ones such as phenol-based compounds or amine-based compounds which are usually used as oxidation inhibitors in a lubricating oil.
• oxidation inhibitors are alkylphenols such as 2-6-di-tert-butyl-4-methylphenol, bisphenols such as methylene-4,4-bisphenol(2,6-di-tert-butyl-4-methylphenol), naphtylamines such as phenyl- ⁇ -naphtylamine, dialkyldiphenylamines, zinc dialkyldithiophosphates such as zinc di-2-ethylhexyldithiophosphate, and esters of (3, 5-di-tert-butyl-4-hydroxyphenyl) fatty acid such as propionic acid and monohydric or polyhydric alcohols such as methanol, octadecanol, 1,6-hexanediol, neopentyl glycol, thiodiethylene glycol, triethylene glycol, and pentaerythritol.
• alkylphenols such as 2-6-di-tert-buty
• one or more compounds selected from the above-described oxidation inhibitors may be blended in an arbitrary ratio, the content of thereof is generally within the range of 0.01 to 5.0 percent by mass, based on the total amount of the lubricating oil composition.
• Viscosity index improvers which may be used in combination with the lubricating oil compositions of the present invention may be non-dispersion type viscosity index improvers such as polymers or copolymers of one or more monomers selected from various methacrylates or hydrides thereof and dispersion type viscosity index improvers such as copolymers of various methacrylates further containing nitrogen compounds.
• viscosity index improvers are non-dispersion- or dispersion-type ethylene- ⁇ -olefin copolymers wherein the ⁇ -olefin may be propylene, 1-butene, or 1-pentene, or the hydrides thereof, polyisobutylenes or the hydrogenated products thereof, styrene-diene hydrogenated copolymers, styrene-maleate anhydride copolymers, and polyalkylstyrenes.
• ⁇ -olefin may be propylene, 1-butene, or 1-pentene, or the hydrides thereof, polyisobutylenes or the hydrogenated products thereof, styrene-diene hydrogenated copolymers, styrene-maleate anhydride copolymers, and polyalkylstyrenes.
• the number-average molecular weight of non-dispersion or dispersion type polymethacrylates is preferably from 5,000 to 150,000, and more preferably from 5,000 to 35,000.
• the number-average molecular weight of polyisobutylenes or hydrides thereof is from 800 to 5,000, preferably from 1,000 to 4,000.
• Ethylene- ⁇ -olefin copolymers and hydrides thereof have a number-average molecular weight of from 800 to 150,000, preferably from 3,000 to 12,000.
• one or more compounds selected from the above-described viscosity index improvers may be blended in an arbitrary ratio, the content of thereof is generally within the range of 0.1 to 40.0 percent by mass, based on the total amount of the lubricating oil composition.
• Anti-foamers which may be used in combination with the lubricating oil compositions of the present invention may be any conventional ones which are usually used as anti-foamers in a lubricating oil.
• Specific examples of anti-foamers include silicones such as dimethylsilicone and fluorosilicone.
• one or more compounds selected from the above-described anti-foamers may be blended in an arbitrary ratio, the content of thereof is generally within the range of 0.001 to 0.05 percent by mass, based on the total amount of the lubricating oil composition.
• Corrosion inhibitors which may be used in combination with the lubricating oil composition of the present invention may be any conventional ones which are usually used as corrosion inhibitors for a lubricating oil.
• corrosion inhibitors include benzotriazole-, tolyltriazole-, and imidazole-based compounds.
• one or more compounds selected from the above-described corrosion inhibitors may be blended in an arbitrary ratio, the content of thereof is generally within the range of 0.01 to 3.0 percent by mass, based on the total amount of the lubricating oil composition.
• the lubricating oil compositions of the present invention contain phosphorus, calcium, boron and sulfur in a mass ratio of 1:(0.1-2):(0.06-2):(0.2-20), determined by elemental analysis, based on the total amount of the composition.
• the mass ratio is preferably 1:(0.1-1.0):(0.1-0.8):(0.4-5.0).
• the lubricating oil compositions contain phosphorus at a concentration of from 0.01 to 0.06 percent by mass, preferably from 0.02 to 0.05 percent by mass, based on the total amount of the composition.
• the lubricating oil compositions contain the sulfur derived from the base oil at a concentration of from 0 to 0.1 percent by mass and the sulfur derived from the sulfur-based additives at a concentration of from 0.01 to 0.01 to 0.15.
• the resulting lubricating oil composition would be deteriorates in ⁇ -V characteristics and thus scratch phenomenon frequently occurs.
• the use of the lubricating oil compositions of the present invention can prevent the occurrence of scratch phenomenon by making the belt and elements in an automatic transmission exhibit the ⁇ -V characteristics of a positive gradient and can maintain the positive gradient ⁇ -V characteristics for a long period of time. Therefore, the lubricating oil compositions of the present invention are suitable for continuously variable transmissions such as belt type CVTs.
• the lubricating oil compositions can be also suitably used step type automatic transmission and final reduction drive gears equipped with a limited-slip differential.
• Lubricating oil compositions of Inventive Examples 1 to 8 and Comparative Examples 1 to 5 were prepared in accordance with the formulations set forth in Tables 1 to 3 below. Each of the compositions was subjected to the following ⁇ -V characteristics test. ( ⁇ -V characteristics test)
• ⁇ -V characteristics evaluation a friction coefficient at a slipping velocity of 0.020 m/s and a friction coefficient at a slipping velocity of 0.005 m/s are measured and the ratio (gradient) therebetween is calculated. There is a correlation between whether the gradient is positive or negative and whether scratch phenomenon occurs or not. When the gradient is positive, scratch phenomenon does not occur, while the gradient is negative, scratch phenomenon possibly occurs.
• Example 1 Example 2
• Example 3 Example 4 Base Oil Hydrocracking mass % Mineral Oil A 1) Hydrocracking mass % 100 100 100 100 100 Mineral Oil B 2) Solvent Refining mass % Mineral Oil A 3) Base Oil Viscosity (100° C.) mm 2 /s 4.1 4.1 4.1 4.1 Concentration of Sulfur mass % 0.000 0.000 0.000 0.000 0.000 derived from Base Oil Polyalkylmethacrylate A 4) mass % 6 6 6 6 Polyalkylmethacrylate B 5) mass % ATF Additive Package 6) 8 8 8 8 Ashless Dispersant A 7) 1.5 1.5 1.5 1.5 1.5 1.5 Calcium Sulfonate 8) mass % 0.09 0.09 0.09 Sulfur-based Thiadiazole 9) mass % 0.05 0.2 Additives Dithiocarbamate 10) mass % 0.2 Dithiophosphate 11) mass % 0.2 Trithiophosphite 12) mass % Polysulfide A 13) mass % Polysulfide B 14)
• Example 5 Example 6
• Example 7 Example 8 Base Oil Hydrocracking mass % 60 Mineral Oil A 1) Hydrocracking mass % 100 100 100 Mineral Oil B 2) Solvent Refining mass % 40 Mineral Oil A 3) Base Oil Viscosity (100° C.) mm 2 /s 4.1 4.1 4.1 2.8 Concentration of Sulfur mass % 0.000 0.000 0.000 0.027 derived from Base Oil Polyalkylmethacrylate A 4) mass % 6 6 6 Polyalkylmethacrylate B 5) mass % 10 ATF Additive Package 6) 8 8 8 8 8 Ashless Dispersant A 7) 1.5 1.5 1.5 1.5 1.5 1.5 Calcium Sulfonate 8) mass % 0.09 0.09 0.09 Sulfur-based Thiadiazole 9) mass % 0.05 Additives Dithiocarbamate 10) mass % Dithiophosphate 11) mass % Trithiophosphite 12) mass % 0.23 Polysulfide A 13) mass % 0.3 Polysulfide B 14
• lubricating oil compositions of Comparative Examples 6 and 7 were prepared in accordance with the formulations set forth in Table 4.
• the resulting compositions and the composition of Inventive Example 1 were evaluated in ⁇ -V characteristics prior to and after running for a certain period of time, i.e., prior to and after they were deteriorated by oxidation.
• Each of the compositions was deteriorated in accordance with ISOT under test conditions of an oil temperature of 165.5° C. and a test time of 150 hours to evaluate the oxidation stability in a manner prescribed by JIS K2514 (Test for Oxidation Stability of Lubricating Oil for Internal Combustion Engine). The results are also shown in Table 4.
• composition of Inventive Example 1 maintained positive gradient ⁇ -V characteristics even after it was deteriorated by oxidation.
• compositions of Comparative Examples 6 and 7 wherein the concentration of the sulfur derived from the base oil was high and wherein the same derived from the additives was high were deteriorated in ⁇ -V characteristics and exhibited negative gradient ⁇ -V characteristics.
• Example 6 Example 7 Base Oil Hydrocracking mass % 100 100 Mineral Oil B 1) Solvent Refining mass % Mineral Oil A 2) Solvent Refining mass % 100 Mineral Oil B 3) Base Oil Viscosity (100° C.) mm 2 /s 4.1 4.1 4.1 Concentration of Sulfur mass % 0.000 0.150 0.000 derived from Base Oil Polyalkylmethacrylate A 4) mass % 6 6 6 Polyalkylmethacrylate B 5) mass % ATF Additive Package 6) 8 8 8 Ashless Dispersant A 7) 1.5 1.5 1.5 1.5 Calcium Sulfonate 8) mass % 0.09 0.09 0.09 Sulfur-based Thiadiazole 9) mass % 0.05 0.05 0.4 Additives Dithiocarbamate 10) mass % Dithiophosphate 11) mass % Trithiophosphite 12) mass % Polysulfide A 13) mass % Polysulfide B 14) mass % Element Phosphorus mass

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