Classifications

• • 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
  • C10M163/00—Lubricating compositions characterised by the additive being a mixture of a compound of unknown or incompletely defined constitution and a non-macromolecular compound, each of these compounds being essential
• • 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
  • C10M2205/00—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions
  • C10M2205/16—Paraffin waxes; Petrolatum, e.g. slack wax
  • C10M2205/163—Paraffin waxes; Petrolatum, e.g. slack wax 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
  • C10M2207/26—Overbased carboxylic acid salts
  • C10M2207/262—Overbased carboxylic acid salts derived from hydroxy substituted aromatic acids, e.g. salicylates
• • 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
  • 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
• • 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
  • C10M2215/28—Amides; Imides
• • 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
  • C10M2219/06—Thio-acids; Thiocyanates; Derivatives thereof
  • C10M2219/062—Thio-acids; Thiocyanates; Derivatives thereof having carbon-to-sulfur double bonds
  • C10M2219/066—Thiocarbamic type compounds
  • C10M2219/068—Thiocarbamate metal salts
• • 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
  • C10M2223/042—Metal salts thereof
• • 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
  • C10M2227/00—Organic non-macromolecular compounds containing atoms of elements not provided for in groups C10M2203/00, C10M2207/00, C10M2211/00, C10M2215/00, C10M2219/00 or C10M2223/00 as ingredients in lubricant compositions
  • C10M2227/06—Organic compounds derived from inorganic acids or metal salts
  • C10M2227/066—Organic compounds derived from inorganic acids or metal salts derived from Mo or W
• • 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
  • C10M2227/00—Organic non-macromolecular compounds containing atoms of elements not provided for in groups C10M2203/00, C10M2207/00, C10M2211/00, C10M2215/00, C10M2219/00 or C10M2223/00 as ingredients in lubricant compositions
  • C10M2227/09—Complexes with metals
• • 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
  • C10N2030/00—Specified physical or chemical properties which is improved by the additive characterising the lubricating composition, e.g. multifunctional additives
  • C10N2030/54—Fuel economy
• • 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
  • C10N2040/25—Internal-combustion engines
• • 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
  • C10N2040/25—Internal-combustion engines
  • C10N2040/255—Gasoline engines

Definitions

• the present invention relates to a lubricating oil composition which is favorably employable for lubricating internal combustion engines such as diesel engines, gasoline engines, and gas engines mounted on land-travelling vehicles, with high fuel economy.
• the improvement of fuel economy provided by the lubricating oil composition generally can be attained by reduction of torque of rotation of the engine parts which is caused by the use of a lubricating oil composition providing reduction of friction to the sliding parts of the engine.
• the extent of reduction of friction provided by the lubricating oil composition mainly depends on the viscosity of the lubricating oil composition and selection of additives, mainly the selection of the friction modifier. For instance, if the lubricating oil composition is formulated with a base oil of low viscosity, the friction-reducing effect provided by the lubricating oil composition increases. However, the use of the base oil of low viscosity likely results in unfavorable phenomenon such as increase of oil consumption occurring during operation of the engine.
• Patent publication 1 JP 5-163497 A discloses an engine oil composition showing low friction property, which comprises a base oil and an additive composition comprising a borated alkenylsuccinimide, an alkaline earth metal salicylate and molybdenum dithiophosphate and/or molybdenum dithiocarbamate.
• Patent publication 2 JP 6-336592 A ) describes that a lubricating oil composition comprising zinc dialkyldithiophosphate being mainly composed of a zinc dialkyldithiophosphate having a secondary alkyl group, a metal-containing detergent composition comprising calcium sulfonate (e.g., TBN 200-300) and calcium salicylate (e.g., TBN 10-100), and molybdenum dithiocarbamate having a C 8-23 hydrocarbyl group shows increased low wear-producing property and increased low friction property.
• a lubricating oil composition comprising zinc dialkyldithiophosphate being mainly composed of a zinc dialkyldithiophosphate having a secondary alkyl group, a metal-containing detergent composition comprising calcium sulfonate (e.g., TBN 200-300) and calcium salicylate (e.g., TBN 10-100), and molybdenum dithiocarbamate having a C 8-23 hydrocar
• Patent publication 3 JP 8-302378 A ) describes that an engine oil composition comprising a base oil having a specific kinematic viscosity and specific total aromatic content, an alkaline earth metal salicylate, zinc dialkyldithiophosphate, a succinimide ashless dispersant having a polybutenyl group having a molecular weight of 900-3500, a phenol type-ashless oxidation inhibitor, and molybdenum dithiocarbamate shows improved fuel economy.
• International publication WO94/28095 discloses lubricating oil compositions for internal combustion engines that reduce friction. The lubricating oil compositions contain molybdenum dithiocarbamate and a blend of a calcium salicylate and a calcium sulfonate detergent.
• the object of the invention to provide an improvement of a lubricating oil composition containing a molybdenum-containing friction modifier which is well known to give an excellent friction-reducing property as well as to improve the fuel economy.
• the improved lubricating oil composition of the invention shows further increased fuel economy.
• a lubricating oil composition containing a combination of the molybdenum-containing friction modifier and an overbased metal-containing detergent composition comprising calcium salicylate having an alkyl group having an average carbon atom number of 14-18 (at least 60 mol.% of the alkyl group has a carbon atom number of 14-18), and calcium sulfonate having an alkyl group having an average carbon atom number of 20-24 (at least 60 mol.% of the alkyl group has a carbon atom number of 20-24), and/or calcium salicylate having an alkyl group having an average carbon atom number of 20-28 (at least 60 mol.% of the alkyl group has a carbon atom number of 20-28) shows surprisingly improved fuel economy.
• the invention described herein has been made on this
• the present invention provides a lubricating oil composition for internal combustion engines which comprises a major amount of an oil of lubricating viscosity and a minor amount of an additive composition comprising an overbased metal-containing detergent composition and a molybdenum-containing friction modifier, wherein the overbased metal-containing detergent composition comprises calcium salicylate having an alkyl group having an average carbon atom number in the range of 14 to 18, at least 60 mol.% (preferably, at least 70 mol.%) of said alkyl group having a carbon atom number in the range of 14 to 18; and at least one of the following calcium-containing detergents:
• the lubricating oil composition of the invention contains the base oil (i.e., oil of lubricating viscosity) generally in the amount of 70 wt.% or more, preferably in the amount of 80 wt.% or more, of the lubricating oil composition.
• the base oil i.e., oil of lubricating viscosity
• the lubricating oil composition of the invention provides increased high fuel economy to internal combustion engines such as gasoline engines and diesel engines. Therefore, vehicles on which these internal combustion engines are mounted show improved fuel economy.
• the base oil (i.e., oil of lubricating viscosity) generally is a mineral oil or a synthetic oil showing a kinematic viscosity of 2 to 50 mm 2 /s at 100°C.
• the sulfur content of the base oil should be 0.1 wt.% or less.
• the sulfur content preferably is 0.03 wt.% or less, and more preferably is 0.005 wt.% or less.
• the mineral oil preferably is an oil which is obtained by processing a lubricating oil distillate of a mineral oil by solvent refining, hydrogenation, or their combination.
• a highly hydrogenated refined oil corresponding to a hydrocracked oil, typically has a viscosity index of 120 to 160, an aromatic component content of 5 wt.% or less, a nitrogen content of 50 wt.ppm or less, and a sulfur content of 50 wt. ppm or less).
• a high viscosity index base oil for instance, a base oil having a viscosity index of 140 to 160 which is obtained by hydroisomerization of slack wax or GTL wax (Gas-To-Liquid).
• synthetic oils examples include poly- ⁇ -olefin such as a polymerized compound of ⁇ -olefin having 3 to 12 carbon atoms; a dialkyl ester of a di-basic acid such as sebacic acid, azelaic acid or adipic acid and an alcohol having 4 to 18 carbon atoms, typically dioctyl sebacate; a polyol ester which is an ester of 1,1,1-trimethylolpropane or pentaerythritol and a mono-basic acid having 3 to 18 carbon atoms; and alkylbenzene having an alkyl group of 9 to 40 carbon atoms.
• poly- ⁇ -olefin such as a polymerized compound of ⁇ -olefin having 3 to 12 carbon atoms
• a dialkyl ester of a di-basic acid such as sebacic acid, azelaic acid or adipic acid and an alcohol having 4 to 18 carbon atoms, typically dioct
• the synthetic oil generally contains essentially no sulfur, shows good stability to oxidation and good heat resistance, and gives less residual carbon and soot when it is burned. Therefore, the synthetic oil is preferably employed for the lubricating oil composition of the invention. Particularly preferred is poly- ⁇ -olefin, from the viewpoint of the object of the invention.
• Each of the mineral oil and synthetic oil can be employed singly. If desired, however, two or more mineral oils can be employed in combination, and two or more synthetic oils can be employed in combination.
• the mineral oil and synthetic oil can be employed in combination at an optional ratio.
• the lubricating oil composition of the invention contains a molybdenum-containing friction modifier.
• the molybdenum-containing friction modifier can be any one of the known molybdenum-containing friction modifiers or the known molybdenum-containing friction modifier compositions. These friction modifiers and friction modifier compositions are described in the aforementioned Patent publications 1 to 3.
• Preferred molybdenum-containing friction modifier is, for example, sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum dithiophosphate, amine-molybdenum complex compound, oxymolybdenum diethylate amide, and oxymolybdenum monoglyceride. Most preferred is a molybdenum dithiocarbamate friction modifier.
• the lubricating oil composition of the invention generally contains the molybdenum-containing friction modifier in an amount of 0.01 to 0.15 wt.% in terms of the molybdenum content.
• the lubricating oil composition of the invention contains a combination of the following overbased metal-containing detergents:
• Each of the above-mentioned components (b), namely, calcium sulfonate having an alkyl group having an average carbon atom number in the range of 20 to 24, at least 60 mol.% of said alkyl group having a carbon atom number in the range of 20 to 24, and calcium salicylate having an alkyl group having an average carbon atom number in the range of 20 to 28, at least 60 mol.% of said alkyl group having a carbon atom number in the range of 20 to 28 can be employed singly or in combination.
• the above-mentioned component (a), namely, calcium salicylate having an alkyl group having an average carbon atom number in the range of 14 to 18, at least 60 mol.% of said alkyl group having a carbon atom number in the range of 14 to 18 preferably is a mixture comprising plural calcium salicylates having an alkyl group having an average carbon atom number in the range of 14 to 18 in an amount of 60 mol.% or more, particularly 70 mol.% or more.
• the lubricating oil composition contains each of the component (a) and component (b) generally in an amount of 0.01 to 0.4 wt.%, in terms of calcium content, based on the total amount of the lubricating oil composition.
• the calcium salicylate of the component (a) is calcium salicylate having an overbased degree of 1 to 4, particularly 1.5 to 3.
• the calcium salicylate can be sulfurized or unsulfurized.
• the calcium sulfonate and calcium salicylate of the component (b) are calcium sulfonate and calcium salicylate independently having an overbased degree of 6 to 24.
• the calcium sulfonate has an overbased degree of 14 to 20
• the calcium salicylate has an overbased degree of 6 to 12.
• the ratio of overbased degree for the component (b)/component (a) is preferably in the range of 2 to 12.
• the lubricating oil composition of the invention further contains calcium sulfonate having an alkyl group having an average carbon atom number in the range of 14 to 24, at least 60 mol.% (preferably, at least 70 mol.%) of said alkyl group having a carbon atom number in the range of 14 to 24 and having an overbased degree of 0.1 to 2.
• the lubricating oil composition of the invention can further contain relatively small amounts of other overbased or less overbased metal-containing detergents than the above-mentioned components (a) and (b).
• These metal-containing detergents may be salicylates, carboxylates, sulfonates and/or phenates.
• the lubricating oil composition of the invention can further contain other lubricating oil additives.
• the other lubricating oil additives include nitrogen-containing ashless dispersants, zinc phosphate oxidation inhibitors (or zinc phosphate anti-wear agent) such as zinc dihydrocarbyldithiophosphate, and organic oxidation inhibitors (e.g., phenolic oxidation inhibitors and amine oxidation inhibitors).
• the nitrogen-containing ashless dispersant preferably is an alkenyl- or alkyl-succinimide derived from polyolefin or a derivative thereof.
• the lubricating oil composition can contain the nitrogen-containing ashless dispersant in an amount of 0.01 to 0.3 wt.%, in terms of the nitrogen content, based on the amount of the lubricating oil composition.
• a representative succinimide can be prepared by the reaction between succinic anhydride substituted with a high molecular weight alkenyl or alkyl and a polyalkylene polyamine containing average 4 to 10 (preferably 5 to 7) nitrogen atoms in one molecule.
• the high molecular weight alkenyl or alkyl is preferably derived from polybutene having a number average molecular weight of about 900 to 3,000.
• the process for obtaining the polybutenyl-succinic anhydride by the reaction of polybutene and maleic anhydride is generally performed by the chlorination process using a chloride compound. Otherwise, a thermal reaction process using no chlorine compound can be employed. It is preferred to employ a polybutenylsuccinimide which is derived from a polybutenylsuccinic anhydride by the thermal reaction process.
• the succinimide can be a post-treated succinimide which is prepared by the reaction with boric acid, alcohol, aldehyde, ketone, alkylphenol, cyclic carbonate, organic acid or the like.
• a borated alkenyl(or alkyl)-succinimide which is obtained by the reaction with a boron-containing compound such as boric acid or a boron compound is advantageous from the viewpoints of thermal and oxidation stability.
• the lubricating oil composition may contain other ashless dispersants such as an alkenylbenzylamine ashless dispersant and/or an alkenylsuccinic acid ester ashless dispersant in addition to or in place of the above-mentioned alkenyl(or alkyl)-succinimide ashless dispersant.
• ashless dispersants such as an alkenylbenzylamine ashless dispersant and/or an alkenylsuccinic acid ester ashless dispersant in addition to or in place of the above-mentioned alkenyl(or alkyl)-succinimide ashless dispersant.
• the lubricating oil composition may contain a zinc phosphate oxidation inhibitor (or zinc phosphate anti-ware agent).
• the zinc phosphate oxidation inhibitor (or zinc phosphate anti-ware agent) may be selected from the group consisting of zinc dialkyldithiophosphate, zinc di-alkylmonothiophosphate and zinc dihydrocarbylphosphate).
• the zinc phosphate oxidation inhibitors/anti-wear agents are well known with respect to their preparation processes and natures.
• the zinc phosphate oxidation inhibitors/anti-wear agents are generally contained in an amount of 0.01 to 0.12 wt.%, in terms of the phosphorus content, based on the amount of the lubricating oil composition. However, the amount preferably is in the range of 0.01 to 0.06 wt.%, in consideration of the preparation of a low-phosphorus, low-sulfur lubricating oil composition.
• the zinc dialkyldithiophosphate preferably contains an alkyl group having 3-18 carbon atoms or an alkylaryl group having C 3-18 alkyl group. Most preferred is a zinc dialkyldithiophosphate containing an alkyl group derived from a secondary alcohol having 3-18 carbon atoms or a zinc dialkyldithiophosphate containing a mixture of alkyl groups derived from a mixture of a primary alcohol having 3-18 carbon atoms and a secondary alcohol having 3-18 carbon atoms. Both are particularly effective for reducing wear.
• a zinc dialkyldithiophosphate derived from a primary alcohol shows high thermal resistance.
• the lubricating oil composition of the invention preferably contains an organic oxidation inhibitor in an amount of 0.01-5 wt.%, preferably 0.1-3 wt.%.
• the oxidation inhibitor can be a hindered phenol oxidation inhibitor or a diarylamine oxidation inhibitor.
• the diarylamine oxidation inhibitor is advantageous in giving a base number originating from the nitrogen atoms.
• the hindered phenol oxidation inhibitor is advantageous in producing no NO x gas.
• hindered phenol oxidation inhibitors examples include 2,6-di-t-butyl-p-cresol, 4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-methylenebis(6-t-butyl-o-cresol), 4,4'-isopropylidenebis(2,6-di-t-butylphenol), 4,4'-bis(2,6-di-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,4'-thiobis(2-methyl-6-t-butylphenol), 2,2-thio-diethylenebis[3-(3,5-dit-butyl-4-hydoxyphenyl)propionate], octyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,
• diarylamine oxidation inhibitors examples include alkyldiphenylamine having a mixture of alkyl groups of 4 to 9 carbon atoms, p,p'-dioctyldiphenylamine, phenyl- ⁇ -naphthylamine, phenyl- ⁇ -naphthylamine, alkylated ⁇ -naphthylamine, and alkylated phenyl- ⁇ -naphthylamine.
• Each of the hindered phenol oxidation inhibitor and diarylamine oxidation inhibitor can be employed alone or in combination. If desired, other oil soluble oxidation inhibitors can be employed in combination with the above-mentioned oxidation inhibitor(s).
• the lubricating oil composition of the invention may further contain an oxymolybdenum complex of succinimide, particularly a sulfur-containing oxymolybdenum complex of succinimide.
• the sulfur-containing oxymolybdenum complex of succinimide can provide increased oxidation inhibition when it is employed in combination with the above-mentioned phenolic or amine oxidation inhibitors.
• the lubricating oil composition of the invention may further contain an alkali metal borate hydrate in an amount of 5 wt.% or less, particularly in an amount of 0.01 to 5 wt.%.
• a representative alkali metal borate hydrate can be prepared in the manner described in United States Patents 3,929,650 and 4,089,790 .
• the alkali metal borate hydrate can be in the form of a dispersion containing micro-particles of an alkali metal borate hydrate which is produced by carbonizing a neutral alkali metal or alkaline earth metal sulfonate in the presence of an alkali metal hydroxide to yield an overbased sulfonate and reacting the overbased sulfonate with boric acid.
• the alkali metal preferably is potassium or sodium.
• the alkali metal borate hydrate can be a dispersion of KB 3 O 5 ⁇ H 2 O particles having a particle size of about 0.3 ⁇ m or less which is dispersed in the presence of a neutral calcium sulfonate and succinimide.
• the lubricating oil composition of the invention preferably contains a viscosity index improver in an amount of 20 wt.% or less, preferably 1 to 20 wt.%.
• a viscosity index improver examples are polymers such as polyalkyl methacrylate, ethylene-propylene copolymer, styrene-butadiene copolymer, and polyisoprene.
• a dispersant viscosity index improver and a multi-functional viscosity index improver which are produced by providing dispersing properties to the above-mentioned polymer are preferably employed.
• the viscosity index improvers can be used alone or in combination.
• the lubricating oil composition of the invention may further contain a small amount of various auxiliary additives. Examples of the auxiliary additives are described below.
• Oxidation inhibitor or anti-wear agent such as zinc dithiocarbamate, methylenebis(dibutyldithiocarbamate), oil soluble copper compounds, sulfur-containing compounds (e.g., sulfurized olefins, sulfurized esters, and polysulfide), phosphoric acid esters, phosphorous acid esters, thiophosphoric acid esters, and organic amide compounds (e.g., oleylamide); benzotriazol compounds and thiadiazol compounds functioning as metal deactivating agent; and nonionic polyoxyalkylene surface active agents such as polyoxyethylenealkylphenyl ether and copolymers of ethylene oxide and propylene oxide functioning as an antirust agent and an anti-emulsifying agent.
• sulfur-containing compounds e.g., sulfurized olefins, sulfurized esters, and polysulfide
• phosphoric acid esters phosphorous acid esters
• thiophosphoric acid esters e.g., o
• auxiliary additives may be incorporated into the lubricating oil composition in an amount of 3 wt.% or less, particularly in an amount of 0.001-3 wt.%.
• Lubricating oil compositions were prepared by adding the below-mentioned additive components to the base oil to give the formulations set forth in Table 1.
• the lubricating oil compositions of Examples 1 to 3 are according to the invention, while the lubricating oil compositions of Comparative Examples 1 to 3 are for comparison.
• the lubricating oil compositions were formulated to show a viscosity grade (SAE viscosity grade) of 0W20 and a kinematic viscosity of 7.7-7.8 mm 2 /s at 100°C, by addition of a viscosity index improver.
• SAE viscosity grade SAE viscosity grade
• Mineral base oil (kinematic viscosity at 100°C: 4.1 mm 2 /s, viscosity index: 137) prepared from slack wax via hydrogenation, fractional distillation and dewaxing.
• Ethylene carbonate post-treated succinimide dispersant bis-type, nitrogen content: 1.0 wt.%) derived from polybutene (number average molecular weight: about 2,300).
• Zinc di(secondary alkyl)dithiophosphate Zinc di(secondary alkyl)dithiophosphate (ZnDTP-1, P: 7.8 wt.%, Zn: 7.8 wt.%, S: 14 wt.%)
• Zinc di(primary alkyl)dithiophosphate (ZnDTP-2, P: 7.3 wt.%, Zn: 8.4 wt.%, S: 14 wt.%)
• Amine oxidation inhibitor dialkyldiphenylamine
• Mo-containing complex Mo: 5.5 wt.%, S: 0.2 wt.%, N: 1.6 wt.%, TBN: 10 mg KOH/g
• crank shaft of a gasoline engine (in-line 4 cylinder engine, engine swept volume: 1.8 L, roller type-valve system) was rotated by means of an electric motor connected via a torque meter, and the running torque was monitored.
• the ignition plug was removed so as to minimize the effect caused by pumping loss of the pistons, and the test was carried out under open conditions.
• the oil temperature was kept to 100°C.
• the test was carried out at respective rotational rates for 150 seconds.
• the torques were continuously monitored during the period from the time at a lapse of 30 sec. from the beginning of the test to 120 sec. An average torque value was calculated from the monitored torque values.
• SAE viscosity grade 0W20, kinematic viscosity at 100°C: 8.9 mm 2 /s
• Table 1 Additives Ex.1 Ex.2 Ex.3 Com.1 Com.2 Com.3 Ashless Dispersant 0.03 0.03 0.03 0.03 0.03 0.03 Ca-sali-1 0.12 0.06 0.12 0.18 - - Ca-sul-1 0.06 0.12 - - 0.18 - Ca-sali-2 - - 0.06 - - 0.18 Ca-sul-2 0.02 0.02 0.02 0.02 0.02 0.02 Mo-DTC 0.07 0.07 0.07 0.07 0.07 0.07 ZnDTP-1 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 ZnDTP-2 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Ox.inhi. 1.2 1.2 1.2 1.2 1.2 Mo.comp. 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4
• Example 1 The test results set forth in Table 1 indicate that the lubricating oil composition according to the invention (Examples 1 to 3) show extremely high torque reduction as compared with the lubricating oil compositions (Comparison Examples 1 to 3) containing metal-containing detergents differing from those contained in the lubrication oil compositions of Examples 1 to 3.

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