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
  • C10M161/00—Lubricating compositions characterised by the additive being a mixture of a macromolecular compound 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
  • 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
• • 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
  • 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
  • C10M141/12—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 compound containing atoms of elements not provided for in groups C10M141/02 - C10M141/10
• • 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
  • 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
• • 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
  • C10M2205/02—Organic macromolecular hydrocarbon compounds or fractions, whether or not modified by oxidation as ingredients in lubricant compositions containing acyclic monomers
  • C10M2205/022—Ethene
• • 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
  • C10M2207/00—Organic non-macromolecular hydrocarbon compounds containing hydrogen, carbon and oxygen as ingredients in lubricant compositions
  • C10M2207/28—Esters
  • C10M2207/34—Esters having a hydrocarbon substituent of thirty or more carbon atoms, e.g. substituted succinic acid 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
  • 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
  • C10M2215/086—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
  • C10M2219/04—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
• • 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
  • 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
  • C10N2030/04—Detergent property or dispersant property
• • 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
  • C10N2030/40—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
  • C10N2030/52—Base number [TBN]
• • 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

Definitions

• the present invention relates to a lubricating oil composition favorably employable for lubricating internal combustion engines such as diesel engines and gasoline engines.
• the invention relates to a lubricating oil composition having a low sulfur content of about 0.5 wt.% or less, particularly about 0.2 wt.% or less, which reduces friction occurring in the internal combustion engines mounted to land-travelling automotives using low sulfur hydrocarbon fuel and shows good high temperature detergency.
• the sulfur contained in fuels such as gasolines or diesel fuels employed for operating internal combustion engines is oxidized when it bums in the engine to give sulfur oxide such as sulfuric acid.
• a portion of the sulfur oxide enter the lubricating oil employed for lubricating the engine, and the remaining portion is exhausted with other exhaust gases.
• the sulfur oxide exhausted with other exhaust gases causes environmental pollution.
• the sulfur content in the fuel has been heretofore under severe regulation.
• the regulation on the sulfur content was initially applied to gasolines (fuels for gasoline engines). However, the regulation on the sulfur content has been also applied recently to diesel fuels having a higher sulfur content.
• the sulfur content in the diesel fuels has been recently regulated to be not higher than 0.0010 wt.%.
• the lubricating oil is less contaminated with sulfur oxide such as sulfuric acid which is produced when the fuel bums. This means that the amount of the overbasic metal-containing detergent in the lubricating oil can be reduced.
• the basic metal-containing detergent serves for neutralizing the sulfur oxide in the lubricating oil.
• the recently employed lubricating oils for internal combustion engines comprise a base oil (hydrocarbon oil having lubricating viscosity) and a variety of additives (i.e., lubricating oil additives) such as a basic metal-containing detergent for neutralizing the emigrated sulfur oxide, an oxidation inhibitor for keeping the base oil functioning at elevated temperature from deteriorating, a dispersant for dispersing soots produced by burning of fuels and residues produced by deterioration of the base oil and metal-containing detergent in the base oil, an extreme pressure agent for preventing of seizure of the piston and cylinder, a friction-reducing agent (friction modifier) for reducing friction occurring between the piston and cylinder.
• a basic metal-containing detergent for neutralizing the emigrated sulfur oxide
• an oxidation inhibitor for keeping the base oil functioning at elevated temperature from deteriorating
• a dispersant for dispersing soots produced by burning of fuels and residues produced by deterioration of the base oil and metal-containing detergent in the
• the phosphorus component and metal component contained in the additive placed in the lubricating oil composition are decomposed when the lubricating oil composition bums and enter the exhaust gas in the form of phosphorus oxides and metal oxides.
• the phosphorus oxides and metal oxides contained in the exhaust gas are brought into contact with oxidative catalyst or reductive catalyst placed in the exhaust gas-cleaning apparatus and inactivate the catalyst.
• Patent publication 1 JP 2002-53888 A discloses a lubricating oil composition favorably employable for lubricating internal combustion engines operated using a fuel having a low sulfur content, particularly, diesel engines.
• the disclosed lubricating oil composition comprises a base oil having a sulfur content of 0.1 wt.% or less (preferably 0.03 wt.% or less) and the following additives:
• Patent Publication 1 further discloses in the working examples that the disclosed lubricating oil compositions show good high temperature detergency in the internal combustion engines.
• Patent Publication 1 furthermore discloses that the lubricating oil composition may contain a molybdenum-containing compound which can serve as a friction modifier, an oxidation inhibitor as well as an anti-wear agent.
• the molybdenum-containing compound can be one of known molybdenum-containing compounds such as sulfoxymolybdenum dithiocarbamate, sulfoxymolybdenum dithiophosphate and molybdenum complexes of succinimide possibly containing sulfur.
• Patent Publication 2 JP 2004-149802 A discloses a lubricating oil composition having a low sulfated ash content, a low phosphorus content and a low sulfur content, preferably employable for lubricating internal combustion engines (that is, engine oil), which comprises a base oil, an ethylene carbonate post-treated ashless dispersant, a borated ashless dispersant, an overbased metal-containing detergent and a phosphorus compound.
• Patent Publication 2 further discloses that the disclosed lubricating oil composition may contain a molybdenum-succinimide complex. In the working examples of Patent Publication 2, it is shown by experimental data that the lubricating oil composition shows good oxidation stability as well as good anti-wear performance.
• Patent Publication 3 discloses a low sulfated ash, low phosphorus, low sulfur engine oil (engine oil composition) comprising a low sulfur base oil, a boron-containing ashless dispersant, a molybdenum-containing friction modifier, a metal-containing detergent such as sulfonate, phenate or salicylate, and a zinc dithiophosphate.
• the molybdenum-containing friction modifier can be molybdenum diorgano-dithiocarbamate, molybdenum diorgano-dithiophosphate, molybdenum carboxylate, and a trinuclear molybdenum compound such as Mo 3 S 7 (dtc) 4 or Mo 3 S 4 (dtc) 4.
• the lubricating oil composition employing the above-mentioned trinuclear molybdenum compound has particularly good high temperature oxidation stability and a good friction reductive performance.
• the molybdenum-containing compound is particularly effective as a friction modifier to be incorporated into lubricating oil compositions.
• molybdenum diorgano dithiocarbamate and molybdenum diorgano dithiophosphate are most generally employed.
• both compounds have disadvantage problems, in that the former contains sulfur (S) in its molecular structure and the latter contains phosphorous (P) in its molecular structure, and hence both produce poisonous gases such as sulfur oxide gas and phosphorus oxide gas when the lubricating oil burns in the internal combustion engine, resulting in inactivation of the catalysts of the exhaust gas-clearing apparatus.
• Patent Publication 3 describes that a trinuclear molybdenum compound such as Mo 3 S 7 (dtc) 4 or Mo 3 S 4 (dtc) 4 shows a good friction-modifying function (friction-reducing function).
• these trinuclear molybdenum compounds contains sulfur atoms in the molecular structure of its ligand moiety, i.e., dithiocarbamate, dtc, and further contains other sulfur atoms directly attached to the molybdenum atom, and hence, the trinuclear molybdenum compounds contains a relatively large amount of sulfur in the compound per se. Therefore, the trinuclear molybdenum compound is not favorably employed for incorporation into the lubricating oil composition if reduction of the sulfur content in the oil composition is intended.
• a molybdenum-containing friction-reducing agent having no or a relatively less amount of sulfur and phosphorus which is favorably employable in place of the conventionally employed friction-reducing agents containing sulfur and phosphorus in relatively large amounts, such as molybdenum diorgano-dithiocarbamate, molybdenum diorgano-dithiophosphate, molybdenum carboxylate, and a trinuclear molybdenum compound such as Mo 3 S 7 (dtc) 4 or Mo 3 S 4 (dtc) 4 .
• the present inventors have found that the friction-reducing function of the known molybdenum complex of a basic nitrogen-containing compound such as a molybdenum-succinimide complex is prominently enhanced if the molybdenum complex is incorporated into lubricating oil compositions in combination with specifically selected amounts of an alkenyl- or alkyl-succinimide or its derivative (which is known as an ashless dispersant) and an alkenyl- or alkyl-succinic acid ester (succinate) or its derivative (which is also known as an ashless dispersant).
• an alkenyl- or alkyl-succinimide or its derivative which is known as an ashless dispersant
• succinate alkenyl- or alkyl-succinic acid ester
• the present invention has been made on the above-mentioned inventors' new finding. It has been further found out that the lubricating oil compositions containing the above-mentioned molybdenum complex of a basic nitrogen-containing compound but not containing the succinimide or its derivative (and further not containing the succinate or its derivative) show improved resistance to oxidation at high temperatures but the oil compositions show little reduction of the friction coefficient.
• the present invention provides a lubricating oil composition for lubricating internal combustion engines which has a sulfur content of 0.5 wt.% or less and which comprises a base oil having a lubricating viscosity and at least the following additive components a) to e):
• the present invention further provides a method for operating internal engines mounted to land-travelling vehicles using a fuel having a sulfur content of 0.001 wt.% or less under lubrication with the above-mentioned lubricating oil composition according to the invention.
• the lubricating oil composition of the invention contains a molybdenum complex of a basic nitrogen-containing compound (serving as a friction-modifier) in combination of a mixture of known dispersants, that is, an alkenyl- or alkyl-succinimide or a derivative thereof and an alkenyl- or alkyl-succinic acid ester (succinate) or a derivative thereof both in specific amounts. Therefore, the lubricating oil composition can be prepared to contain sulfur at a low level. Nevertheless, the lubricating oil composition of the invention shows a prominently good friction-reducing function.
• the base oil 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 100 to 150, 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 having a viscosity index of 140-160 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 comprises at least two different ashless dispersants, that is, an alkenyl- or alkyl-succinimide or a derivative thereof (component a) and an alkenyl- or alkyl-succinic ester or a derivative thereof (component b), in an amount of 0.5-5.0 wt.%, preferably 1.0-4.0 wt.%, for each (the amount is based on the total amount of the lubricating oil composition).
• the component a) and component b) are preferably contained in a weight ratio of 1:4 to 4:1, more preferably 1:2 to 2:1.
• the component a namely, the alkenyl- or alkyl-succinimide or a derivative thereof, may be a known alkenyl- or alkyl-succinimide or a derivative thereof.
• the alkenyl- or alkyl-succinimide derived from a polyolefin or its derivative may be employed.
• 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 a polybutene (particularly a high reactivity polybutene having a vinylidene terminal) 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.
• the chlorination process is advantageous in its reaction yield.
• the reaction product obtained by the chlorination process contains a large amount (for instance, approx. 2,000-3,000 wt.ppm) of chlorine.
• the reaction product contains only an extremely small chlorine (for instance, 0-30 ppm).
• the succinimide be prepared from a polybutenyl succinic anhydride which is produced by the thermal reaction, whereby the chlorine content of the resulting succinimide is in the range of 0 to 30 wt.ppm.
• the succinimide can be reacted with boric acid, alcohol, aldehyde, ketone, alkylphenol, cyclic carbonate, organic acid or the like, to give a modified succinimide.
• a borated alkenyl(or alkyl)-succinimide which is obtained by the reaction with boric acid or a boron compound is advantageous from the viewpoints of thermal and oxidation stability.
• the component b), namely, the alkenyl- or alkyl-succinic ester or a derivative thereof, may be a known alkenyl- or alkyl-succinic ester or a derivative thereof.
• the alkenyl- or alkyl-succinic ester derived from a polyolefin or its derivative may be employed.
• a representative succinic ester can be prepared by the reaction between succinic anhydride substituted with a high molecular weight alkenyl or alkyl and an alcohol containing average 1 to 6 hydroxyl groups in one molecule.
• the high molecular weight alkenyl or alkyl is preferably derived from a polybutene (particularly a high reactivity polybutene having a vinylidene terminal) having a number average molecular weight of about 900 to 3,000.
• the lubricating oil composition of the invention may contain other ashless dispersants such as an alkenylbenzylamine ashless dispersant in addition to the ashless dispersant a) (i.e., component a)) and ashless dispersant b) (i.e., component b)).
• ashless dispersants such as an alkenylbenzylamine ashless dispersant in addition to the ashless dispersant a) (i.e., component a)) and ashless dispersant b) (i.e., component b)).
• the lubricating oil composition of the invention further comprises a molybdenum complex of a basic nitrogen-containing compound in an amount of 50-1,200 wt.ppm in terms of a molybdenum content thereof.
• This molybdenum complex is already known as a multifunctional addi-tive.
• the molybdenum complex of a basic nitrogen-containing compound may contain a small amount of sulfur.
• the molybdenum complex of basic nitrogen-containing compound functions mainly as an oxidation inhibitor, an anti-wear agent or a friction modifier in the lubricating oil composition.
• a preferred molybdenum complex of a basic nitrogen-containing compound is an oxymolybdenum complex produced by reaction of an acidic molybdenum compound and a basic nitrogen-containing compound.
• the acidic molybdenum compounds include molybdic acid, ammonium molybdate, and alkali metal salts of molybdate.
• the basic nitrogen-containing compounds include succinimide, carboxylic amide, hydrocarbylamine and a Mannich basic compound.
• Examples of the molybdenum complex of basic nitrogen-containing compounds include a molybdenum complex of succinimide and a molybdenum complex of a secondary aliphatic amine.
• the molybdenum complex of a basic nitrogen-containing compound can be employed after reaction with a small amount of sulfur or a sulfur-containing compound.
• the reaction product preferably contains sulfur in a relatively small amount such as 10 wt.% or less.
• the sulfoxymolybdenum complex can be prepared in the manner described in Examples C to H of United States Patent 6,562,765 B.
• the lubricating oil composition of the invention can further contain other molybdenum-containing compounds such as sulfoxymolybdenum dithiocarbamate, sulfoxymolybdenum dithiophosphate, and oxymolybdenum monoglyceride.
• molybdenum-containing compounds such as sulfoxymolybdenum dithiocarbamate, sulfoxymolybdenum dithiophosphate, and oxymolybdenum monoglyceride.
• the lubricating oil composition of the invention further comprises an alkaline earth metal-containing detergent having a TBN in the range of 10 to 400 mg•KOH/g in an amount of 0.05-1.0 wt.% in terms of an alkaline earth metal content thereof.
• the known alkaline earth metal-containing detergent having a TBN in the range of 10 to 400 mg•KOH/g is employable.
• Preferred is a calcium alkylsalicylate detergent.
• the calcium alkylsalicylate detergent preferably contains an organic acid salt in an amount of 0.2-7 wt.%, more preferably 0.5-5 wt.%, most preferably 1.0-3 wt.%.
• the calcium alkylsalicylate detergent preferably comprises an unsulfurized calcium alkylsalicylate detergent having an alkyl group containing 14-18 carbon atoms.
• the unsulfurized calcium alkylsalicylate detergent having an alkyl group containing 14-18 carbon atoms can be employed in combination with an unsulfurized calcium alkylsalicylate detergent having an alkyl group containing 20-28 carbon atoms.
• the unsulfurized calcium alkylsalicylate detergent having an alkyl group containing 14-18 carbon atoms means an unsulfurized calcium alkylsalicylate detergent having an alkyl group in which 90 mole % or more of the alkyl groups contain 14-18 carbon atoms.
• the unsulfurized calcium alkylsalicylate detergent having an alkyl group containing 20-28 carbon atoms has the same meaning, that is, the unsulfurized calcium alkylsalicylate detergent having an alkyl group containing 20-28 carbon atoms means an unsulfurized calcium alkylsalicylate detergent having an alkyl group in which 90 mole % or more of the alkyl groups contain 20-28 carbon atoms.
• the unsulfurized calcium alkylsalicylate preferably is a calcium salt of an alkylsalicylic acid which can be prepared from an alkylphenol (which is produced by the reaction of ⁇ -olefin having the desired number of carbon atoms and phenol) by the Kolbe-Schmidt reaction.
• the calcium salt of an alkylsalicylic acid can be overbased by the use of lime and carbon dioxide, to give an overbased calcium salicylate.
• the calcium salt of an alkylsalicylate can be prepared by the steps of neutralizing phenol to give its calcium salt and subsequent carbonation.
• the calcium alkylsalicylate detergent is preferably incorporated into the lubricating oil composition under such conditions that the amount of the organic acid salt (contained in the calcium alkylsalicylate detergent) is in the range of 0.2 to 7 wt.%, preferably 0.5 to 5 wt.%, more preferably 1.0 to 3 wt.%, based on the total amount of the lubricating oil composition.
• the calcium alkylsalicylate detergent is an oily dispersion which comprises an organic acid metal salt (generally called a soap component) and basic inorganic salt micro-particles (e.g., calcium carbonate particles) aggregated around the organic acid metal salt in an oily medium.
• the dispersion contains the oily medium in an amount of 30 to 50 wt.%. Even if the amount of the calcium alkylsalicylate detergent is reduced, the high temperature detergency (i.e., power for keeping the inside space of an engine operated at high temperatures) of the lubricating oil composition does not substantially lower provided that the amount of the organic acid metal salt is kept at or above a certain level.
• the alkaline earth metal-containing detergent can be an alkaline earth metal salt of an organic acid having a carbon-nitrogen bonding or a phenol derivative.
• This detergent can have a high TBN regardless of a sulfated ash content, if it is treated with an amine compound.
• the amine compound brings a base number originating from the basic nitrogen atoms.
• a metal salt of an aminocarboxylic acid can be employed.
• an unsulfurized alkylphenate i.e., alkaline earth metal salt
• This compound can be obtained by Mannich reaction using an alkylphenol, formaldehyde, and an amine or an amine compound to give an aminomethylated phenol, and subsequent neutralization of the reaction product by a base such as calcium hydroxide.
• the alkaline earth metal-containing detergent can be an alkaline earth metal salt of a sulfonic acid (i.e., sulfonate) obtained from a petroleum sulfonic acid, an alkylbenzenesulfonic acid, or an alkyltoluenesulfonic acid.
• a sulfonic acid i.e., sulfonate
• the alkaline earth metal-containing detergent can be a sulfurized phenate, namely, an alkaline earth metal salt of a sulfurized alkyl phenol
• the lubricating oil composition of the invention further comprises an anti-wear agent (component e)) in an amount of 0.05-5.0 wt.%.
• an anti-wear agent component e
• the anti-wear agent there are no specific limitation on the anti-wear agent, and the known sulfur-containing anti-wear agent as well as the known phosphorus-containing anti-wear agent can be employed.
• the sulfur-containing anti-wear agents include sulfurized olefin, polysulfide compound, sulfurized ester, sulfurized alcohol, sulfurized amide, sulfurized oil/fat, ashless dithiocarbamate, metal (other than molybdenum) dithiocarbamate, mercapto thiadiazole, mercapto benzothiadiazole, and mercapto thiazoline.
• Examples of the phosphorus-containing anti-wear agents include phosphoric acid ester, phosphorous acid ester, thiophosphoric acid ester, their amine salts, and their metal salts such as zinc dialkyldithiophosphate, zinc dialkyldithiophosphate, and zinc dialkylphosphate.
• the anti-wear agent i.e., component e
• the anti-wear agent preferably is zinc dialkyldithiophosphate or zinc dihydrocarbylphosphate.
• These zinc phosphate anti-wear agents are well known and easily produced by the known procedures.
• the zinc phosphate anti-wear agent can be employed in an amount of 0.01-0.12 wt.%, but preferably in an amount of 0.01-0.06 wt.%, in consideration of the desired low phosphorus content and sulfur content.
• 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 oxidation inhibitor in an amount of 0.01-5 wt.%, preferably 0.1-3 wt.%.
• the oxidation inhibitor can be the phenolic oxidation inhibitor and the amine oxidation inhibitor.
• a lubricating oil composition having a low sulfated ash content, a low phosphorus content and a low sulfur content is apt to show a relatively low high-temperature detergency, oxidation-inhibiting performance and anti-wear performance due to decrease of the amounts of the metal-containing detergent and zinc dithiophosphate. Therefore, the lubricating oil composition of the invention preferably contains an oxidation inhibitor so as to keep these performances high.
• Preferred oxidation inhibitors are a diarylamine oxidation inhibitor and a hindered phenol oxidation inhibitor. These oxidation inhibitors also function for improving high-temperature detergency.
• 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-di-t-butyl-4-hydoxyphenyl)propionate], octyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, octadecyl 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionat
• 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 alkali metal borate hydrate for increasing stability at high temperatures and a base number.
• 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. From the viewpoint of resistance to hydrolysis, potassium is preferably replaced with sodium.
• 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.
• auxiliary additives are described below. benzotriazol compounds and thiadiazol compounds functioning as metal deactivating agent; nonionic polyoxyalkylene surface active agents such as polyoxyethylenealkylphenyl ether and copolymers of ethylene oxide and propylene oxide functioning as an anti-rust agent and an anti-emulsifying agent.
• various compounds functioning as an anti-foaming agent and a pour point depressant can be incorporated.
• 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 having a low sulfur content (0.5 wt.% or less) for evaluation on the oil performance were prepared in the below-described manner using the below-mentioned base oil and additives.
• the lubricating oil compositions were formulated to show a viscosity grade (SAE viscosity grade) of 5W30 by addition of a viscosity index improver.
• Base oil (mixture of the below-mentioned base stock A and base stock B in the weight ratio of 46:54)
• Ashless dispersant A Ethylene carbonate post-treated succinimide dispersant (nitrogen content: 0.85 wt.%) prepared by the steps of thermally reacting polybutene (number average molecular weight: about 2,200) and maleic anhydride to give polyisobutenylsuccinic anhydride, reacting about 2 moles of the polyisobutenylsuccinic anhydride and polyalkylene polyamine containing 6.5 nitrogen atoms (average) in one molecule to give a bis-type succinimide, and finally treating the bis-type succinimide with ethylene carbonate under reaction.
• Ashless dispersant B Alkenylsuccinic ester (TAN: 5 mg•KOH/g) prepared by the steps of thermally reacting polybutene (number average molecular weight: about 1,000) and maleic anhydride to give polyisobutenylsuccinic anhydride, reacting about 1.14 moles of the polyisobutenylsuccinic anhydride and one mole of pentaerythritol.
• Mo complex of succinimide A product (Mo content: 4.5 wt.%, N content: 2.1 wt.%, S content: 0.16 wt.%) obtained by the steps of reacting a mono-type alkenylsuccinimide derived from polyisobutene having a number average molecular weight of about 1,000 and molybdic acid to give a molybdenum complex and reacting the molybdenum complex with a small amount of sulfur.
• the friction coefficient was determined by means of High Frequency Reciprocating Rig (HFRR) under the below-described conditions:
• Oil temperature 105°C
• Load 400 g
• Friction length 1,000 ⁇ m
• Reciprocating frequency 20 Hz
• Test Period one hour.
• a glass tube In a heater block was placed vertically a glass tube (inner diameter: 2 mm). The test oil and air were supplied into the tube from its bottom at supply rates of 0.31 cc/h and 10 cc/min., respectively. These procedures were performed under keeping the temperature of the heater element at 280°C for 16 hours. Thereafter, the glass tube was taken out from the heater block, washed with petroleum ether, and dried. The deposit attached to the inner surface of the glass tube was observed and marked according to the merit rating.
• the merit rating was done in the known manner on the basis of 10 points. The higher point means that the power of inhibiting production of deposit is high.
• Table 1 Base oil/ Additives Example 1 Com. Ex. 1 Com. Ex. 2 Ashless dispersant A (wt.%) 3.0 5.5 3.0 Ashless dispersant B (wt.%) 2.5 - 2.5 Succinimide Mocomplex (Mo wt.
• the lubricating oil composition of the invention comprising succinimide-Mo complex, succinimide dispersant (Ashless dispersant A) and succinic ester dispersant (Ashless dispersant B) in combination (Test oil of Example 1) shows the same high-temperature deposit production-inhibiting power but markedly low friction coefficient as compared with the lubricating oil composition (Test oil of Comparison Example 1) comprising the succinimide-Mo complex and succinimide dispersant (Ashless dispersant A) in combination but containing no succinic ester dispersant (Ashless dispersant B).
• Test oil of Comparison Example 2 prepared by replacing the succinimide-Mo complex with the same amount of MoDTC (sulfoxy molybdenum dialkyldithiocarbamate) shows the same friction coefficient but poor power of inhibiting production of high-temperature deposit.

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