Abstract:
An additive for lubricating oil, especially motor oil for internal combustion engines, uses a mixture of overbased zinc alhyl-dithiophosphate, a chlorinated paraffin and a glycol ether. The additive preferable is used in a mineral oil base for reduced wear and lower oil operating temperatures.

Description:
[0001]    This invention claims benefit of U.S. Provisional Application 60/206084 filed May 19, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to lubricating oils and particularly to additives which reduce friction and extend the life of the oil.  
           [0004]    2. Background and Related Art  
           [0005]    Lubricating oils are essential to the operation of modern machinery and, in particularly, to transportation devices. The oils are adapted to particular conditions of use and are customized chemically for optimal performance under those conditions.  
           [0006]    Lubricating oils used in motor vehicles fall into three use classifications. Lubricating oil for internal combustion engines (hereinafter motor oil) is required to form a film between metal parts and to do so under varying temperature conditions. Lubricating oil for gears (hereinafter gear lube) is a slightly more viscous material than motor oil and is particularly adapted to reduce friction at wiped services such as bevel cut gears and hyphoid differentials. Automatic transmission fluid (ATF) is a thin oil specifically adapted for torque converters, wet clutches and valves.  
           [0007]    Motor oil is a complex mixture of chemicals which must provide hydrodynamic lubrication and boundary layer lubrication. Typical operating temperatures range from −20° C. to 125° C. Recent developments in engine technology require oils with lower viscosity which must operate over a broader range of engine speeds, at higher temperatures, and must be consistently effective lubricants for longer periods of use. Specifically, the oils are expected to reduce cracking, oxidation, and gum formation while preventing formation of deposits of solids on engine surfaces.  
           [0008]    Lubricating oils may have many sources. Castor oil has been used for both the bulk of the lubricant and as an additive. Whale oil is preferred as an additive in ATF. Most oil today is mineral oil derived from petroleum. There are three predominant types. Conventional motor oil was and is obtained from the vacuum distillation of the higher boiling components of crude oil. The product is dewaxed to lower the pour point, aromatics are removed to increase the viscosity index, the oil is deasphalted and, typically, hydrotreated.  
           [0009]    Synthetic oils are of two types. A synthetic hydrocarbon may be formed from the polymerization of isobutylene produced from conventional petroleum cracking and it may be polymerized with additional components such as alpha-olefins and ethylene. Alternatively, a synthetic oil may be formed from a mixture of organic esters, typically having six to ten carbon branch chains attached.  
           [0010]    Regardless of the source, a number of additives are routinely employed, as described in U.S. Pat. No. 5,728,656 to Yamaguchi et al. These additives include dispersants, detergents, oxidation inhibitors, viscosity index improvers, anti-wear agents, and pour point depressants.  
           [0011]    U.S. Pat. No. 5,925,600 to Atherton discloses the use of aminic antioxidants and phenolic antioxidants in various ratios.  
           [0012]    U.S. Pat. No. 5,912,212 to Igarashi et al. is directed to the use of nitrogen-containing compounds, in combination with fatty acid esters, sulphur, phosphorus or phenols, as an effective antioxidant.  
           [0013]    U.S. Pat. No. 5,902,776 to Dohner et al. is directed to the use of amines and thiocarbamates as anti-wear agents.  
           [0014]    U.S. Pat. No. 5,792,732 to Jao et al. is directed to the use of overbased detergents which are salts of linear alkaryl acids.  
           [0015]    U.S. Pat. No.5,744,430 to Inome et al. discloses friction modifiers based on molybdenum.  
           [0016]    U.S. Pat. No. 5,712,230 to Abraham et al. is directed to the use of bound sulphur-containing compounds in oils having good anti-wear characteristics while lowering the amount of phosphorus in the oil.  
           [0017]    U.S. Pat. No. 4,844,825 to Sloan discloses an extreme pressure lubricant additive comprising chlorinated parrafin and alkaline earth metal sulfonate in a vehicle consisting of mineral oil, mineral spirits and an aromatic solvent.  
           [0018]    There continues to be a need for additives in oil to improve the performance of the oil by reducing wear on moving parts and by increasing the number of hours over which a motor may be operated before deterioration of the oil occurs and/or before unacceptable solid deposits occur within the engine.  
         BRIEF SUMMARY OF THE INVENTION  
         [0019]    It is a first objective of this invention to provide an additive chemical composition for a lubricating oil, most particularly a motor oil, which reduces friction between metal surfaces.  
           [0020]    It is a second objective of this invention to provide an additive combination for a lubricating oil which has a higher detergency and, in particular, the ability to hold small ash particles in suspension.  
           [0021]    It is a third objective of this invention to provide an additive chemical composition for a lubricating oil which bonds strongly to metal, especially aluminum surfaces.  
           [0022]    It is a fourth objective of this invention to provide an additive chemical composition for a lubricating oil which has a high capacity for moisture and acids.  
           [0023]    These and other objectives may be met by providing an additive composition including a dithiophosphate anti-wear agent, a chloroparaffin and an hydroxy polyether in a mineral oil base. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0024]    [0024]FIG. 1 is a plot of temperature versus time for the concentrated (undiluted) additive tested using a Timken test apparatus.  
         [0025]    [0025]FIG. 2 is a plot of temperature versus time for the additive of this invention diluted with P100 motor oil with ratio of 40:60 and 60:40. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    Motor oil performs two functions in a typical internal combustion engine. Hydrodynamic lubrication occurs when a film of oil separates two services. This occurs in locations where a rotating element is surrounded by a bearing or bushing. Crankshaft journals and camshaft bearings are typical examples. The rotating component rides on a cushion of oil and the oil is typically supplied to the area under pressure. As long as the oil is present, its quality is of minimal concern so long as the viscosity is sufficient to retain enough film thickness to prevent contact between the journal and the bearing surface. Following the Reynolds hydrodynamic theory, friction is a direct function of viscosity.  
         [0027]    Boundary layer lubrication occurs in those locations where the wetted surface of the metal parts prevents metal-to-metal contact. This typically occurs at places where metal components are in a wiping relationship. Typical examples include camshaft lobes, cam followers and bevel cut gears. This is sometimes called extreme pressure lubrication. For boundary layer lubrication, it is necessary for the oil to adhere to the surfaces of the metal while the metal surfaces are being urged towards each other. Mineral oil is ordinarily sufficient for hydrodynamic lubrication but is not especially good for a boundary layer lubrication. For this reason antiwear or “film forming” additives are added to motor oils to improve their lubricity.  
         [0028]    There are several ways to measure improvements in lubricity. The Timken method ASTMD D2782 is commonly used and was used in the development of this invention.  
         [0029]    When the oil is used in an internal combustion engine, the temperature of the oil becomes a measure of the overall lubricity of the oil. Lower oil temperatures are beneficial because they reduce the thinning of the oil and allow lower viscosity oils to maintain oil pressure in journals, resulting in lower friction in the film. A cooler oil is also beneficial because the circulating oil serves to remove heat from the engine, especially under heavy load.  
         [0030]    Improved lubricity and lower drag can also be measured as a horsepower increase, using a dynamometer. In the field, they can be measured in decreased fuel consumption.  
         [0031]    A third measure of lubricity is measured wear after a specified number of hours of operation. This is usually done with a micrometer after disassembly. Wear may also be measured chemically by analyzing oil drained from the motor for the presence of metals, especially bearing and bushing materials such as copper, tin and lead, as well as metals from the components such as aluminum and iron.  
         [0032]    Detergents and surfactants are important for maintaining lubricity. Water and acids in the oil and solid particles reduce lubricity by roughening wiped surfaces and forming sludge between moving parts. Soot thickens the oil. The primary source of water is condensation. The primary source of acid is blow-by, i.e., SO 2 MO x  formed in combustion. Particulate matter also enters primarily through blow-by and is increased when the exhaust is “sooty.” Particulate blow-by is a characteristic problem with diesel engines because carbon particles are formed in the combustion process in certain modes of operation.  
         [0033]    We have discovered that a remarkably effective additive for motor oils consists of a metal alkyldithiophosphate, a lightly chlorinated paraffin (chlorinated alkane) and a glycol ether. This composition is present in a weight ratio of between 1:5:2 and 1:15:8, preferably 1:10:5. This additive may be added directly to any base oil or blended with P100 mineral oil for addition to any oil base.  
         [0034]    The metal alkyldithiophosphate is preferably a zinc alkyldithiophosphate (ZEDnDTP) which is overbased by a ratio of up to 1.20:1. Representative proprietary examples are LUBRIZOL™ 1095, 1097 and 1375. This overbased additive is a known antiwear agent and antioxidant, and when used in the overbased form, is useful to neutralize acids formed in the oil.  
         [0035]    The chlorinated paraffin used in this invention is a saturated paraffin having between 13 and 18 carbon atoms, and between 4 and 8 chlorine atoms. Too low a chlorine content reduces film forming strength. Too high chlorine content results in acid build-up. It should be in the form of a light oil and readily soluble in mineral oil. Products under the name “CERECLOR™ Nos. S45, S52, 51L, S-52HV, S56 and S58 sold by ICI Americas are suitable for this purpose.  
         [0036]    As a detergent and surfactant, glycol ethers such as trimethylene glycol monohexyl ether and homologous glyme-type compounds are suitable. Commercial examples include ECOSOFT™ solvents PE, PB, and PH. These glymes emulsify the sludge format by water and acids in the oil, cut ring wear and cut smoking in diesel engines.  
         [0037]    When mixed with mineral oil P100 at a ratio of three parts of the additive to one part mineral oil, the additive itself is an excellent lubricant. Using a Timken test device (of ASTMD D2782), the temperature of the undiluted additive in is as shown in FIG. 1 using a 5 psig load. FIG. 2 shows the same test for the additive diluted to 60% and 40% with P 100.  
       EXAMPLE I  
       [0038]    Twenty-one grams of P100 base mineral oil was heated in a beaker with mild strirring to a temperature of 75° C. Four grams of zinc alkyldithiophosphate (lubrizol) was added, followed by 40 grams of a chlorinated paraffin (C14-C17 chlorinated alkanes, molecular formula C 15 -H 26 -Cl 16 , CERECLOR™, ICI). Twenty grams of a mixed glycol monohexyl ether (ECOSOFT™ PB, Union Carbide) was run in and the mixture stirred at 75° C. for 30 minutes, then cooled with gentle stirring to room temperature.  
         [0039]    A portion of the product was placed in a Tinken test apparatus having a thermocouple in the oil reservoir. The load on the tester was set at 5 lbs./in 2  and the axle spun at 1325 rpm. for one hour. Temperature readings were taken at 5 second intervals. The result of two successive tests on the undiluted product are shown in FIG. 1.  
         [0040]    The product was diluted with P100 mineral oil to 60% product and 40% P100 and also to 40% product and 60% P100. The same test as described above was repeated. The results are shown in FIG. 2.  
       EXAMPLE II  
       [0041]    The metal treatment product of this invention was mixed with a commercial ISO/SAE 30 motor oil and used in a diesel truck engine for 30,000 hours (approximately 50,000 miles). The table below compares the drained oil with the original.  
                                                                         Test   Original (Control)   Used                                        Viscosity   10.84   16.74           SAE Equiv.   30   40           Fe   9   58           al   3   9           Cu   2   8           Su   0   1           Pb   8   69           Cr   0   3           Si   2   6           Ba   0   0           Ca   1470   3082           Mg   445   15           Zn   1097   1263           P   988   1036                      
 
         [0042]    Field tests in diesel trucks have documented 10% fuel consumption improvement in a KENWORTH™, 20% in a CUMMINS™ powered FREIGHTLINER™ and 8% in a DETROIT DIESEL™.  
         [0043]    Dynomometer tests using a modified Briggs and STRATTON™ racing go-cart motor showed 3% h.p. improvements at 4000 rpm.  
         [0044]    The above examples demonstrate the invention but do not constitute a limitation thereto. Changes within the disclosure as would be obvious to those skilled in the art are within the scope of this invention.