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  Lubricating oil compositionUSPTO Application #: 20070197411Title: Lubricating oil composition Abstract: wherein the lubricating oil composition has a kinematic viscosity at 40° C. in the range of from 22 to 95 mm2/s; a kinematic viscosity at 100° C. in the range of from 10 to 30 mm2/s; a pour point of −10° C. or less; a CCS viscosity at −20 ° C. of 2500 mPas or less; and a flash point of 140° C. or more. A lubricating oil composition is provided containing a base oil having a kinematic viscosity at 40° C. in the range of from 2 to 20 mm2/s and a viscosity index of 50 or more and a polymethacrylate, (end of abstract) Agent: Shell Oil Company - Houston, TX, US Inventors: Hiroshi Kaneko, Hirohiko Otsu, Tetsuo Wakizono USPTO Applicaton #: 20070197411 - Class: 508469000 (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.), Organic -c(=o)o- Compound, Specified Compound Wherein The Single Bonded Oxygen Is Bonded Oxygen Is Bonded Directly To An Additional Carbon, Which Carbon May Be Single Bonded To Any Atom But May Be Multiple Bonded Only To Carbon (i.e., Specified Carboxylic Acid Ester), Plural -c(=o)o- Groups Attached Directly Or Indirectly To Each Other By Nonionic Bonding (e.g., Estolides Of Hydroxy Carboxylic Acids, Etc.), Polymer Of Alpha, Beta-olefinically Unsaturated Carboxylate Monomer (e.g., Polymethylmethacrylate, Etc.) The Patent Description & Claims data below is from USPTO Patent Application 20070197411. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates lubricating oil compositions, in particular to hydraulic oil compositions. More specifically, the present invention relates to a hydraulic oil composition for use in a door closer or a floor hinge employed for opening/closing various types of doors. BACKGROUND OF THE INVENTION [0002] Door closers using hydraulic oil compositions are widely employed for door opening/closing. Such door closers slowly close a door which has been manually opened, and when the door is caused by a wind or the like to move abruptly, the door closer is required to have the function of slowing down the motion of the door lest it should close on a hand. SUMMARY OF THE INVENTION [0003] A lubricating oil composition is provided comprising a base oil having a kinematic viscosity at 40.degree. C. in the range of from 2 to 20 mm.sup.2/s and a viscosity index of 50 or more and a polymethacrylate, wherein the lubricating oil composition has a kinematic viscosity at 40.degree. C. in the range of from 22 to 95 mm.sup.2/s; a kinematic viscosity at 100.degree. C. in the range of from 10 to 30 mm.sup.2/s; [0004] a pour point of -10.degree. C. or less; [0005] a CCS viscosity at -20.degree. C. of 2500 mPas or less; and [0006] a flash point of 140.degree. C. or more. [0007] A method of lubricating a door closer or a floor hinge using such lubricating oil composition is also provided. DETAILED DESCRIPTION OF THE INVENTION [0008] The door closer fundamentally comprises a cylinder, a piston and an orifice, and prevents the door from being abruptly closed due to the resistance generated by the passage of a hydraulic oil composition through the orifice. [0009] Since the door closer uses a hydraulic oil composition, sometimes opening and closing of the door becomes difficult due to temperature fluctuations. For example, during high temperature in summer, the viscosity of a hydraulic oil composition is decreased and thus the hydraulic oil composition passes through the orifice in a shorter period of time, leading to abrupt closing of the door. In contrast, during low temperature in the cold season, the viscosity of a hydraulic oil composition is increased and it takes a longer period of time to pass through the orifice, thereby causing the problem that an unduly long period of time is required for closing the door, and also that an unduly large force is required for opening the door. [0010] Ordinarily, for lubricating oil compositions in general, when viscosity is to be increased for the purpose of viscosity adjustment, a polymer having a large molecular weight is added to a mineral oil or a synthetic oil. However, if such a polymer having large molecular weight is added to the oil, although the viscosity of the oil at high temperature is increased, the viscosity under low temperature is also increased. Therefore, when the oil is used in machinery, problems sometimes occur, particularly when the machinery is operated at low temperature. [0011] Further, mineral oil contains a wax component which is crystallized at low temperature, and such wax crystals grow with time and thereby lower flowability of the oil. As a result, the oil comes to have an increased viscosity or sometimes may even become solidified. In order to prevent such a wax component from being crystallized, a pour-point depressant which is adsorbed on the wax crystals and suppresses the growth of the crystals is generally used; however, there are cases where because of the pour-point depressant the viscosity of the oil does not increase at high temperatures. [0012] Still further, after a door closer is fixed to a building, it is used for a long period of time, and during such period, there is a tendency for the hydraulic oil composition to deteriorate. The thus-deteriorated oil hardens the oil seal so that the hydraulic oil composition leaks and becomes reduced in quantity. As a result, there are cases in which the door closer does not function satisfactorily. In particular, in order to perform the opening and/or closing of a door smoothly, a typical hydraulic oil composition is a mineral oil or synthetic oil having a low viscosity, which also causes a problem of compatibility with the oil seal. [0013] In addition, as per Japanese Laid-open Patent Application No. H. 5-747488 it has been pointed out that when a mineral oil having low viscosity is used, a large amount of viscosity index improving agent needs to be added to the oil in order to increase the viscosity, and a problem arises regarding flowability of the oil at low temperatures. [0014] It is highly desirable to obtain hydraulic oil compositions which show little fluctuation of viscosity over low temperatures and high temperatures and which can operate in the same condition at any time. [0015] The present invention provides lubricating oil composition, in particular a hydraulic oil composition, comprising a base oil having a kinematic viscosity at 40.degree. C. in the range of from 2 to 20 mm.sup.2/s and a viscosity index of 50 or more and a polymethacrylate, wherein the lubricating oil composition has a kinematic viscosity at 40.degree. C. in the range of from 22 to 95 mm.sup.2/s; a kinematic viscosity at 100.degree. C. in the range of from 10 to 30 mm.sup.2/s; a pour point of -10.degree. C. or less; a CCS (cold cranking shear) viscosity at -20.degree. C. of 2500 mPas or less; and a flash point of 140.degree. C. or more. [0016] The polymethacrylate used in the lubricating oil composition of the present invention preferably has a weight average molecular weight in the range of from 150,000 to 700,000. [0017] In the present invention, the lubricating oil composition, in particular the hydraulic oil composition, is uninfluenced by hot or cold and shows practically the same degree of viscosity whether at low temperature or high temperature and stays in the same condition at all times, thereby making it possible to achieve smooth operation in, for example, a door closer. Also, since the lubricating oil composition, in particular the hydraulic oil composition is compatible with oil seals, problems of oil leakage seldom occur even over long periods. In addition, apart from in door closers or floor hinges as referred to above, the lubricating oil composition of the present invention may be widely employed as hydraulic oil composition of various types. [0018] In a preferred embodiment of the present invention, the lubricating oil composition, in particular the hydraulic oil composition, has a viscosity index of at least 260. [0019] The base oil in the lubricating oil composition of the present invention may be conveniently chosen from mineral oils, synthetic oils and mixtures thereof. [0020] Mineral oils that may be conveniently used include base oils manufactured by conducting one or more treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, or hydrorefining on the lubricating oil fraction obtained from the reduced pressure distillation of reduced crude obtained by atmospheric distillation of crude oil. [0021] Various types of synthetic oil may be conveniently used as the synthetic oil. Examples of synthetic oils include so-called GTL (gas-to-liquid) base oils obtained by solvent dewaxing or contact dewaxing after synthesis using the Fischer-Tropsch process. Other examples of synthetic oils that may be conveniently used include poly-.alpha.-olefins (for example ethylene-propylene copolymers, polybutylenes, 1-octene oligomers, 1-decene oligomers, and hydrides thereof), alkyl benzenes, alkyl naphthalenes, monoesters (for example, butyl stearate or octyl stearate), diesters (for example, ditridecyl glutarate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, dioctyl sebacate, or dioctyl azelate), polyesters (for example, trimellitate esters), polyol esters (for example, trimethylol propane caprylate, trimethylol propane pelargonate, pentaerythritol-2-ethyl hexanoate, or pentaerythritol pelargonate), polyphenyl ethers and dialkyl diphenyl ethers. Continue reading... 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