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  Method of improving the acrylic rubber sealant compatibility in an internal combustion engineUSPTO Application #: 20070184992Title: Method of improving the acrylic rubber sealant compatibility in an internal combustion engine Abstract: It has been discovered that a lubricating oil composition containing a certain combination of a nitrogen-containing dispersant and a metal-containing detergent of an alkali metal salt of alkylphenol derivative having a Mannich base structure, together with a phosphorus-containing organic compound, can be effectively employed in a method for improving the acrylic rubber sealant compatibility in an internal combustion engine, if the ratio of the nitrogen-containing dispersant and a metal-containing detergent of an alkali metal salt of alkylphenol derivative having a Mannich base structure is adjusted to a specific range, i.e., in the range of from 1:0.005 to 1:2 in terms of the nitrogen contents. (end of abstract)
Agent: Chevron Corporation - San Ramon, CA, US Inventors: Yoshitaka Takeuchi, Yoshito Yamashita, Morikuni Nakazato USPTO Applicaton #: 20070184992 - Class: 508287000 (USPTO) Related Patent Categories: Solid Anti-friction Devices, Materials Therefor, Lubricant Or Separant Compositions For Moving Solid Surfaces, And Miscellaneous Mineral Oil Compositions, Lubricants Or Separants For Moving Solid Surfaces And Miscellaneous Mineral Oil Compositions (e.g., Water Containing, Etc.), Heterocyclic Ring Compound; A Heterocyclic Ring Is One Having As Ring Members Only Carbon And At Least One Hetero Atom Selected From Nitrogen And Chalcogen (i.e., Oxygen, Sulfur, Selenium, Or Tellurium), The Hetero Ring Contains Five Members Including Nitrogen And Carbon (e.g., Polyvinylpyrrolidone, Etc.), Plural Oxygens Double Bonded Directly To Ring Carbons Of The Hetero Ring Which Are Adjacent To The Ring Nitrogen The Patent Description & Claims data below is from USPTO Patent Application 20070184992. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present invention relates to a method of improving the acrylic rubber sealant compatibility in an internal combustion engine. More specifically, the present invention relates to a method comprising contacting acrylic rubber sealants in an internal combustion engine and operating the internal combustion engine with a lubricating oil composition having improved acrylic rubber sealant compatibility. BACKGROUND OF THE INVENTION [0002] In mechanical devices such as internal-combustion engine vehicles and various other industrial machines, it is necessary to supply a lubricating oil to mechanisms involving rubbing movement. Lubrication systems for supplying a lubricating oil are generally equipped with various sealing materials (sealants). Examples of the sealing materials include resin or rubber sealants such as silicone rubber sealant, acrylic rubber sealant, fluorocarbon resin sealant, nitrile rubber sealant, hydrogenated nitrile rubber sealant and ethylene-propylene rubber sealant. According to their physical and chemical characteristics, those sealants are optionally selected to be installed in proper parts of the lubrication systems. Among the above-mentioned materials, acrylic rubber sealant is particularly used as packing parts for fixation because it is not only excellent in heat resistance and oil resistance but also inexpensive, [0003] At the present time, it is required to improve lubricating oils for the purpose of meeting certain performance requirements. Most lubricating oils contacting rubbing mechanisms in various machines are nowaday high-performance lubricating oil compositions comprising a lubricating base oil and various additives added thereto. [0004] However, lubricating oil compositions containing various additives often deteriorate resin or rubber sealants despite satisfying lubricating performance requirements. Most of the additives contained in the compositions are so chemically active that they are liable to shrink the sealants and/or to impair their strength and elasticity. [0005] Accordingly, it is desirable to have a lubricating oil composition which satisfies the severe performance requirements concerning lubricating oil compositions and, at the same time, which hardly impairs sealing performance of the sealants themselves. [0006] U.S. Pat. No. 6,124,247 describes a lubricating oil composition containing a borated glycerol ester and a mono-succinimide or bis-succinimide type dispersant subjected or not subjected to post-treatment with, for example, ethylene carbonate. It is stated that this oil composition has excellent compatibility with fluorocarbon elastomer, which is used as a sealant in a lubrication system of an internal-combustion engine. [0007] JP-A-11-181461 describes that a lubricating oil composition containing an aliphatic amine has excellent compatibility with rubber sealants. [0008] U.S. Pat. No. 6,569,818 describes a lubricating oil composition containing an ashless dispersant of an alkenyl- or alkyl-succinic imide or a derivative thereof, an alkali metal or alkaline earth metal alkylsalicylate of non-sulfide or otherwise an alkali metal salt of alkylphenol derivative having a Mannich base structures a zinc dialkyldithiophosphate, and an oxidation inhibiting phenol or amine compound. It is stated that all of the ash content, the phosphorus content and the sulfur content of the disclosed lubricating oil composition are low levels and that the lubricating oil composition gives high detergency at a high temperature. U.S. Pat. No. 6,569,818, however, is silent about a lubricating oil composition of the present invention described hereinbelow. Further, this reference neither describes nor suggests any effect that the lubricating oil composition has on sealants. SUMMARY OF THE INVENTION [0009] The present invention relates to a method of improving acrylic rubber sealant compatibility in an internal combustion engine. The method involves contacting the acrylic rubber sealant in the internal combustion engine and operating the internal combustion engine with a lubricating oil composition comprising: [0010] a) a major amount of a base oil of lubricating viscosity, [0011] b) a nitrogen-containing ashless dispersant in an amount of 0.01 to 0.3 wt. %, preferably 0.01 to 0.1 wt. %, in terms of the nitrogen content based on the total amount of the lubricating oil composition, [0012] c) a metal-containing detergent of an alkali metal or alkaline earth metal salt of alkylphenol derivative having a Mannich base structure in an amount of 0.001 to 0.4 wt. % in terms of the metal content or 0.002 to 0.1 wt. % in terms of the nitrogen content, based on the total amount of the lubricating oil composition, and [0013] d) a phosphorus-containing organic compound in an amount of 0.001 to 0.5 wt. %, preferably 0.01 to 0.2 wt. %, in terms of the phosphorus content, based on the total amount of the lubricating oil compositions [0014] wherein the ratio of components b) to c) is in the range of from 1:0.005 to 1:2, preferably 1:0.01 to 1:0.3, in terms of the nitrogen content. [0015] The nitrogen-containing ashless dispersant in the lubricating oil composition employed in the method of the present invention is an alkenyl- or alkyl-succinic imide or a derivative thereof. [0016] The metal-containing detergent of an alkali metal or alkaline earth metal salt of alkylphenol derivative in the lubricating oil composition employed in the method of the present invention has a Mannich base structure represented by the following formula: wherein R is an alkyl group having 8 to 30 carbon atoms, and n is 0 or a positive integer. [0017] The lubricating oil composition employed in the method of the present invention may further comprise a phosphorus-containing organic compound selected from the group consisting of zinc dihydrocarbyldithiophosphates, zinc dihydrocarbylphosphates, phosphoric acid esters, phosphorous acid esters, and thiophosphoric acid esters. [0018] The lubricating oil composition employed in the method of the present invention may further comprise a metal-containing detergent selected from the group consisting of alkali metal or alkaline earth metal salicylates, carboxylates, phenates and sulfonates in an amount of 1.0 wt. % or less in terms of the metal content. [0019] The amount of metal-containing detergent selected from the group consisting of alkali metal or alkaline earth metal salicylates, carboxylates, phenates and sulfonates to the amount of metal-containing detergent of an alkali metal or alkaline earth metal salt of alkylphenol derivative having a Mannich base structure is in a ratio of 1:0.003 to 1:1 in terms of the metal content. [0020] The lubricating oil composition employed in the method of the present inventions may further comprise a molybdenum compound selected from the group consisting of an oxymolybdenum complex prepared by the reaction between an acidic molybdenum compound and a basic nitrogen compounds sulfurized oxymolybdenum dithiocarbamate, and sulfurized oxymolybdenum dithiophosphate, in amount of 0.25 wt. % or less in terms of the molybdenum content. [0021] The lubricating oil composition employed in the method of the present invention may further comprise an alkali metal borate in an amount of 2 wt. % or less and an oxidation inhibitor selected from the group consisting of hindered phenol compounds and diarylamine compounds in an amount of 5 wt. % or less. [0022] The base oil of lubricating viscosity contains 10 wt. % or more of a mineral oil showing the following characteristics: [0023] 17 wt. % or less evaporation loss according to ASTM: D-5800, [0024] 90 wt. % or more saturated content, [0025] 10 wt. % or less, aromatic component, [0026] 0.01 wt. % or less, sulfur content, and [0027] 120 or more viscosity index. [0028] The lubricating oil composition employed in the method of the present invention is a SAE viscosity grade selected from the group consisting of 0W20, 0W30, 5W20, 5w30 and 10W30. Preferably, the lubricating oil composition meets the SAE 10W-30 viscosity grade. [0029] Among other aspects, it has been discovered that a lubricating oil composition containing a certain combination of a nitrogen-containing dispersant and a metal-containing detergent of an alkali metal salt of alkylphenol derivative having a Mannich base structure, together with a phosphorus-containing organic compound, can be effectively employed in a method for improving the acrylic rubber sealant compatibility in an internal combustion engine, if the ratio of the nitrogen-containing dispersant and a metal-containing detergent of an alkali metal salt of alkylphenol derivative having a Mannich base structure is adjusted to a specific range, i.e., in the range of from 1:0.005 to 1:2 in terms of the nitrogen content. The lubricating oil composition hardly impairs the sealing performance of the acrylic rubber sealant. DETAILED DESCRIPTION OF THE INVENTION [0030] The present invention resides in a method of employing a certain lubricating oil composition to improve the acrylic rubber sealant compatibility in an internal combustion engine. The lubricating oil composition, while meeting the lubricating performance requirements of internal combustion engines, at the same time is less detrimental to the sealing performance of acrylic rubber sealants found in internal combustion engines as compared to conventionally used lubricating oil compositions. Thus, the method of the present invention advantageously improves the acrylic rubber sealant compatibility in internal combustion engines. [0031] The preferred embodiments of the present invention will be described in further detail below. It should be noted that when weight percent is used. herein, it is based on the total weight percent of the lubricating oil composition unless otherwise specified. Continue reading... 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