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
  • 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
  • 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
  • C10M169/06—Mixtures of thickeners and additives
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
  • F16C33/00—Parts of bearings; Special methods for making bearings or parts thereof
  • F16C33/30—Parts of ball or roller bearings
  • F16C33/66—Special parts or details in view of lubrication
  • F16C33/6603—Special parts or details in view of lubrication with grease as lubricant
  • F16C33/6633—Grease properties or compositions, e.g. rheological properties
• • 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
  • C10M105/00—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound
  • C10M105/08—Lubricating compositions characterised by the base-material being a non-macromolecular organic compound containing oxygen
  • C10M105/32—Esters
  • C10M105/38—Esters of polyhydroxy compounds
• • 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
  • C10M129/00—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing oxygen
  • C10M129/02—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing oxygen having a carbon chain of less than 30 atoms
  • C10M129/04—Hydroxy compounds
  • C10M129/10—Hydroxy compounds having hydroxy groups bound to a carbon atom of a six-membered aromatic ring
• • 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
  • C10M133/00—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing nitrogen
  • C10M133/02—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing nitrogen having a carbon chain of less than 30 atoms
  • C10M133/26—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing nitrogen having a carbon chain of less than 30 atoms containing a nitrogen-to-nitrogen double bond
• • 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
  • C10M135/00—Lubricating compositions characterised by the additive being an organic non-macromolecular compound containing sulfur, selenium or tellurium
  • C10M135/12—Thio-acids; Thiocyanates; Derivatives thereof
  • C10M135/14—Thio-acids; Thiocyanates; Derivatives thereof having a carbon-to-sulfur double bond
  • C10M135/18—Thio-acids; Thiocyanates; Derivatives thereof having a carbon-to-sulfur double bond thiocarbamic type, e.g. containing the 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
  • C10M2207/02—Hydroxy compounds
  • C10M2207/023—Hydroxy compounds having hydroxy groups bound to carbon atoms of six-membered aromatic rings
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • 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
  • C10M2207/04—Ethers; Acetals; Ortho-esters; Ortho-carbonates
  • C10M2207/0406—Ethers; Acetals; Ortho-esters; Ortho-carbonates 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
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/121—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms
  • C10M2207/123—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms polycarboxylic
• • 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
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/121—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms
  • C10M2207/123—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms polycarboxylic
  • C10M2207/1236—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of seven or less carbon atoms polycarboxylic used as thickening agent
• • 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
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/125—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids
  • C10M2207/1256—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids used as thickening agent
• • 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
  • C10M2207/10—Carboxylix acids; Neutral salts thereof
  • C10M2207/12—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms
  • C10M2207/125—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids
  • C10M2207/128—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids containing hydroxy groups; Ethers thereof
  • C10M2207/1285—Carboxylix acids; Neutral salts thereof having carboxyl groups bound to acyclic or cycloaliphatic carbon atoms having hydrocarbon chains of eight up to twenty-nine carbon atoms, i.e. fatty acids containing hydroxy groups; Ethers thereof used as thickening agents
• • 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
  • C10M2207/283—Esters of polyhydroxy compounds
  • C10M2207/2835—Esters of polyhydroxy compounds 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
  • C10M2215/00—Organic non-macromolecular compounds containing nitrogen as ingredients in lubricant compositions
  • C10M2215/18—Containing nitrogen-to-nitrogen bonds, e.g. hydrazine
• • 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
• • 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
  • C10N2010/02—Groups 1 or 11
• • 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
  • C10N2030/10—Inhibition of oxidation, e.g. anti-oxidants
• • 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
  • C10N2040/02—Bearings
• • 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
  • C10N2050/00—Form in which the lubricant is applied to the material being lubricated
  • C10N2050/10—Semi-solids; greasy

Definitions

• the present invention relates to a grease composition
• a grease composition comprising a base oil, a thickener, a particular antioxidant and a metal deactivator.
• the invention relates to a grease composition with improved lubrication life, suitable for use in rolling bearings operated under high temperatures, and bearings where the above-mentioned grease composition is enclosed.
• the motors used in railway vehicles, automobiles, electrical machines, various kinds of industrial machines and the like are being reduced in size and weight, improved toward higher-speed rotation, higher efficiency and longer life.
• the tendency of motors toward smaller size and lighter weight as mentioned above decreases the amount of lubricant to be used, and the higher-speed rotation of motors tends to increase the operating temperature, which has made the operating environments of lubricant severer.
• totally-enclosed motors are being used to solve the problem of noise development and meet the demand for extension of the maintenance interval.
• the totally-enclosed motors require more heat-resistant and longer life greases because the cooling efficiency is decreased in the totally-enclosed motors.
• a lubricant with improved fatigue life where a compound having an alkylthiocarbamoyl group and a molybdenum compound are added to the lubricant base, and an ester compound is optionally further added thereto to improve the fatigue life (e.g., in JP 03-31760 B).
• an improved abrasive-resistant extreme-pressure composition having resistance to oxidation, containing (a) methylenebis(di-n-butyldithiocarbamate) and (b) a diphenylamine derivative of tolutriazole or benzotriazole at a ratio by mass of about 4:1 to about 50:1, and a lubricant containing the above-mentioned extreme pressure composition (e.g., in JP 2005-509732 A).
• a lithium grease composition comprising (a) a lubricating oil, (b) at least one compound selected from the group consisting of lithium salts of aliphatic monocarboxylic acid having at least one hydroxyl group and 12 to 24 carbon atoms, dilithium salts of aliphatic dicarboxylic acid having 2 to 12 carbon atoms, and lithium salts of aliphatic monocarboxylic acid having 12 to 24 carbon atoms, and (c) at least one compound selected from the group consisting of 3-(N-salicyloyl)amino-1,2,4-triazole and decamethylene-dicarboxylic acid-disalicyloyl hydrazide (e.g., in JP 2936084).
• Grease compositions comprising a urea compound that contains no metal in the molecule thereof as the thickener and a synthetic oil as the base oil are commonly used for automotive auxiliaries mainly employing deep-groove radial bearings because those grease compositions are considered to be excellent in thermo-oxidative stability.
• those grease compositions are applied to the main motor of railway vehicles where cylindrical roller bearings are indispensable, sufficient lubrication life cannot be obtained.
• An object of the invention is to provide a grease composition suitable for rolling bearings under elevated temperatures and capable of exhibiting stable lubricating properties for an extended period of time. Namely, it is an object to provide a grease composition excellent in the thermo-oxidative stability and the lubrication life.
• Another object of the invention is to provide a bearing where the above-mentioned grease composition is enclosed.
• the inventors of the invention have completed a grease composition which has improved thermo-oxidative stability and lubrication life, and is suitable for rolling bearings operated under high temperatures, and exhibits stable lubricating properties for an extended period of time by using a base oil, a thickener, particular antioxidants and a metal deactivator in combination.
• the invention provides a grease composition and a bearing shown below:
• a grease composition comprising (a) a base oil, (b) a thickener, (c) a compound having an alkylthiocarbamoyl group, represented by the formula (1), (d) a hindered phenol antioxidant, and (e) a metal deactivator;
• R 1 , R 2 , R 3 and R 4 are each independently an alkyl group having 1 to 20 carbon groups, and X represents S, S—S, S—CH 2 —S, S—CH 2 CH 2 —S or S—CH 2 CH 2 CH 2 —S.
• the base oil (a) is contained in an amount of 50 mass % or more; the thickener (b), in an amount of 1 to 30 mass %; the compound (c) having the alkylthiocarbamoyl group represented by the formula (1), in an amount of 0.1 to 10 mass %; the hindered phenol antioxidant (d), in an amount of 0.1 to 10 mass %; and the metal deactivator (e
• the grease composition of the present invention is remarkably advantageous because the grease composition has improved thermo-oxidative stability and lubrication life, and is suitable for use in the rolling bearings under high temperatures, and in addition, exhibits stable lubricating properties for an extended period of time.
• the grease composition of the invention can maintain a constant consistency and does not extremely harden or soften for an extended period of time even when used under high temperatures.
• mineral oils such as diesters and polyol esters
• synthetic oils such as diesters and polyol esters
• synthetic hydrocarbon oils such as poly ⁇ -olefins and polybutene
• ether type synthetic oils such as alkyl diphenyl ethers and polypropylene glycols
• silicone type synthetic oils fluorinated synthetic oils, and the like.
• a mixed oil may be preferably used.
• a mixed oil of two or more kinds of synthetic oils, in particular, two or more ester type synthetic oils is more preferable.
• a mixed oil of remarkably heat-resistant polyol ester type synthetic oil and alkyldiphenyl ether type synthetic oil is most preferable.
• the base oil may have a kinematic viscosity at 40° C. of 30 to 300mm 2 /s.
• the kinematic viscosity at 40° C. is less than 30mm 2 /s, the increase of evaporation loss and the decrease in oil film thickness will lower the lubricating properties and therefore the long life cannot be expected.
• the kinematic viscosity at 40° C. exceeds 300mm 2 /s, the viscous resistance will increase and therefore the torque will unfavorably be increased.
• the grease composition of the invention may preferably contain the base oil (a) in an amount of 50 mass % or more, and more preferably 60 mass % or more, with respect to the total mass of the grease composition.
• any thickeners are usable for the grease composition of the invention.
• Specific examples include soap-type thickeners such as lithium soaps and lithium complex soaps, urea type thickeners such as diurea compounds, inorganic thickeners such as organoclay and silica, organic thickeners such as PTFE, and the like.
• the lithium complex soaps that can be used in the invention may preferably be lithium salts of hydroxy fatty acids (C12-24) having one or more hydroxyl groups and aliphatic dicarboxylic acids (C2-12).
• hydroxy fatty acids C12-24
• aliphatic dicarboxylic acids C2-12
• Examples of the above-mentioned hydroxy fatty acid include 12-hydroxystearic acid, 12-hydroxylauric acid, 16-hydroxypalmitic acid and the like. In particular, 12-hydroxystearic acid is preferred.
• aliphatic dicarboxylic acid examples include azelaic acid, sebacic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, undecanedioic acid, and dodecanedioic acid.
• azelaic acid is preferred.
• soap type thickeners are preferable, and lithium soaps and lithium complex soaps are more preferable because of the excellent heat resistance.
• the lithium complex soaps a lithium salt of 12-hydroxystearic acid and azelaic acid is most preferable.
• the lithium soaps and the lithium complex soaps are more advantageous over urea compounds in the invention because longer lubrication life can be ensured when applied to the main motors where the cylindrical roller bearing is indispensable.
• the grease composition of the invention may preferably contain the thickener (b) in an amount of 1 to 30 mass %, and more preferably 5 to 20 mass %, with respect to the total mass of the grease composition. Too much thickener makes the resultant grease hard, which may unfavorably increase the stirring resistance. On the other hand, when the content of thickener is too small, the resultant grease becomes soft and may cause the problem of leakage.
• the grease composition of the invention comprises as the antioxidants, (c) the compound having an alkylthiocarbamoyl group represented by the formula (1) (ATC), and (d) the hindered phenol antioxidant.
• the grease composition of the invention further comprises (e) the metal deactivator.
• the compound (c) having an alkylthiocarbamoyl group used in the invention is represented by the formula (1).
• R 1 , R 2 , R 3 and R 4 are each independently a straight-chain or branched alkyl group having 1 to 20 carbon atoms, preferably a straight-chain or branched alkyl group having 1 to 8 carbon atoms.
• R 1 to R 4 may be the same.
• X represents S, S—S, S—CH 2 —S, S—CH 2 CH 2 —S or S—CH 2 CH 2 CH 2 —S.
• S—CH 2 —S is preferable.
• Examples of the compound represented by the formula (1) include bis(dimethylthiocarbamoyl)monosulfide, bis(dimethylcarbamoyl)disulfide, methylenebis(dimethyldithiocarbamate), methylenebis(di-n-butyldithiocarbamate), and the like. In particular, methylenebis(di-n-butyldithiocarbamate) is preferred.
• the grease composition of the invention may preferably comprise the compound (c) having the alkylthiocarbamoyl group represented by the formula (1) in an amount of 0.1 to 10 mass %, and more preferably in an amount of 0.5 to 5 mass %, with respect to the total mass of the grease composition.
• the content of the compound (c) exceeds 10 mass %, the oxidative deterioration inhibiting effect will be saturated.
• the content of the compound (c) is less than 0.1 mass %, there is no significant effect even though the compound (c) is added.
• the hindered phenol antioxidant (d) at least one can be selected from the group consisting of 2,6-di-tert-butyl-4-methylphenol, pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C 7-9 alkyl ester (side chain), and octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.
• 2,6-di-tert-butyl-4-methylphenol is preferred.
• the grease composition of the invention may preferably comprise the hindered phenol antioxidant (d) in an amount of 0.1 to 10 mass %, more preferably 0.5 to 5 mass %, with respect to the total mass of the grease.
• the content of the component (d) exceeds 10 mass %, the effect of inhibiting oxidative deterioration will be saturated.
• the content of the component (d) is less than 0.1 mass %, there is no significant effect even though the hindered phenol antioxidant (d) is added.
• Examples of the metal deactivator (e) include oxalic acid derivatives, salicylic acid derivatives, hydrazine derivatives and the like.
• the grease composition of the invention may preferably comprise the metal deactivator (e) in an amount of 0.1 to 10 mass %, more preferably 0.1 to 5 mass %, with respect to the total mass of the grease composition.
• the metal deactivator (e) exceeds 10 mass %, the metal deactivating effect will be saturated.
• the content of the component (e) is less than 0.1 mass %, there is no significant effect even though the metal deactivator (e) is added.
• antioxidants may be used when necessary.
• other antioxidants for example, quinoline antioxidants, amine antioxidants, rust preventive, metal corrosion inhibitor, oilness improver, antiwear agent, extreme pressure agent, solid lubricant and the like can be used.
• the grease composition of the invention may preferably comprise the base oil (a) in an amount of 50 mass % or more, more preferably 60 mass % or more; the thickener (b), in an amount of 1 to 30 mass %, more preferably 5 to 20 mass %; the compound (c) having the alkylthiocarbamoyl group represented by the formula (1), in an amount of 0.1 to 10 mass %, more preferably 0.5 to 5 mass %; the hindered phenol antioxidant (d), in an amount of 0.1 to 10 mass %, more preferably 0.5 to 5 mass %; and the metal deactivator (e), in an amount of 0.1 to 10 mass %, more preferably 0.1 to 5 mass %, with respect to the total mass of the grease composition.
• the base oil (a) in an amount of 50 mass % or more, more preferably 60 mass % or more
• the thickener (b) in an amount of 1 to 30 mass %, more preferably 5 to 20 mass %
• the worked penetration of the grease composition according to the invention is preferably 200 to 400, more preferably 250 to 350.
• the worked penetration exceeds 400, the leakage may tend to easily occur.
• the stirring resistance will unfavorably increase.
• the suitable bearings to be charged with the grease composition of the invention are rolling bearings, especially roller bearings, in particular, cylindrical roller bearings.
• the bearings used for the totally-enclosed motors, in particular the totally-enclosed main motors for railway vehicles are desirable.
• the material for bearings is not particularly limited, but preferably copper.
• grease compositions of Examples 1 to 7 and Comparative Examples 1 to 6 were prepared.
• the amount of each component means mass % based on the total mass of the grease composition.
• 12-hydroxystearic acid (82.5 g) was added to each base oil (467.5 g). The resultant mixture was heated to a temperature (80 to 90° C.) where the mixture assumed a completely transparent liquid state.
• a solution prepared in advance by dissolving 11.9 g of lithium hydroxide monohydrate into 60 g of water under application of heat was added, followed by vigorous stirring to subject 12-hydroxystearic acid to a saponification reaction.
• a lithium salt of 12-hydroxystearic acid was formed.
• azelaic acid 26 g
• the base oil (with a kinematic viscosity of 101 mm 2 /s at 40° C.) was a mixture of an ether oil (alkyldiphenyl ether with kinematic viscosities of 100 mm 2 /s at 40° C. and 12.5 mm 2 /s at 100° C.) and an ester oil (pentaerythritol ester with kinematic viscosities of 102 mm 2 /s at 40° C. and 12.9 mm 2 /s at 100° C.) at a ratio by mass of 1:1.
• ether oil alkyldiphenyl ether with kinematic viscosities of 100 mm 2 /s at 40° C. and 12.5 mm 2 /s at 100° C.
• an ester oil penentaerythritol ester with kinematic viscosities of 102 mm 2 /s at 40° C. and 12.9 mm 2 /s at 100° C.
• Each grease was applied to the surface of an SPCC stainless steel sheet (60 mm ⁇ 80 mm ⁇ 1 mm) in a thickness of 2 mm.
• the total acid number was determined before and after the test.
• the total acid number was determined after test, i.e., after leaving the stainless sheet at a prescribed temperature (160° C.) for a prescribed duration (500 hours). The total acid number was determined in accordance with JIS K2501 5.
• a bearing charged with each test grease (5.6 g) was set in a tester. With the application of a radial load (100 kgf), the bearing was rotated at 8000 rpm while the outer ring temperature of the bearing was constantly controlled at 120° C. by use of a heater. The time duration taken for the outer ring temperature of bearing to reach 130° C. was regarded as the life time.
• cylindrical roller bearing (model: NU214, with an inner diameter of 70 mm and an outer diameter of 125 mm)
• the mixture has a kinematic viscosity of 101 mm 2 /s at 40° C.
• the mixture has a kinematic viscosity of 101 mm 2 /s at 40° C.

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• 2012
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