Patent Application
20150232782
Disclosed herein are lubricant compositions comprising a non silicone lubricant base stock and a silicone oil.
Lubricant oils and compositions are used to reduce friction and wear between moving elements or surfaces. The main component of lubricant oils and compositions is commonly referred to as a base stock. Base stocks are classified by the American Petroleum Institute in five Groups, namely Groups I, II, III, IV and V. Lubricant base stocks include natural lubricating oils, synthetic lubricating oils, and mixtures thereof. Groups I to III include base stocks derived from petroleum based oils, while Groups IV and V include synthetic base stocks including silicones.
The viscosity of a lubricant changes with temperature. As temperature rises viscosity decreases and vice versa. Viscosity Index (VI) is an empirical, unit less number which indicates the rate of change in the viscosity of an oil in a given temperature range, usually between 40° C. and 100° C. The Viscosity Index is defined as the gradient of kinematic viscosities of a material, between 40° C. and 100° C. When the Viscosity Index is low (below 100) the fluid exhibits a relatively large change of viscosity with temperature. When the Viscosity Index is high (above 150), the fluid exhibits relatively less change of viscosity with temperature. In a variety of applications, a high or very high Viscosity Index is preferred.
The chemical composition of the base stocks from Group I, Group II and Group III can vary substantially, for example regarding the proportions of aromatics, paraffinics, and naphthenics. The degree of refining and the source materials used to produce the lubricant base stocks generally determine this composition. Lubricant base stock oils from Group I, Group II and Group III include paraffinic mineral oils and naphthenic mineral oils. Mineral oils of viscosities ranging of from 4.0 to 8.0 mPa.s, at 100° C., (ASTM D445-12) have a Viscosity Index ranging of from 80 to 120, or 140 for high performance grades (ASTM D2270-10e1).
The materials of Groups I, II and III are divided into groups based on sulphur content and Viscosity Index as follows:
Group IV base stocks are composed of polyalphaolefins (PAO) which are hydrogenated oligomers obtained from the oligomerization of alphaolefin monomers. These alphaolefin monomers may have from about 4 to about 30 or from about 4 to about 20 or from about 6 to about 12 carbon atoms, such as hexene, octene or decene. The oligomers may be dimers, trimers, tetramers, pentamers, hexamers of the alphaolefin monomer.
Group V base stocks include base stocks not included in Groups I-IV such as polyinternal olefins (PIO); polyalkylene glycols (PAG); alkylated aromatics such as alkylated benzenes, e.g. dodecylbenzene, tetradecylbenzene, di-nonylbenzene, and di-(2-ethylhexyl)benzene; polyphenyls e.g. biphenyls, terphenyl and alkylated polyphenyls; synthetic esters such as esters of dicarboxylic acids e.g. dibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate and dieicosyl sebacate, esters of carboxylic acids, polyol esters, e.g. neopentyl glycol, trimethylolethane, trimethylpropane, pentaerythritol, dipentaerythritol and tripentaerythritol; phosphate esters, e.g. tricresyl phosphate, trioctylphosphate, and diethyl ester of decylphosphonic acid; silicones; and further polyisobutylene (PIB) and halogenated hydrocarbons.
Other lubricant base stocks include those of vegetal and animal origin, such as rapeseed oil, castor oil and lard oil.
Silicones (Group V) may be used in lubricant compositions in both critical (metal-to-metal) applications and non critical (plastic-to-plastic) applications mainly due to their good low and high temperature behavior. They show chemical resistance, lubricity, thermal stability and oxidative stability.
However in respect of lubrication under high loads, silicones, with the exception of halogenated silicones, are generally both inferior to organic base oil as described above and are typically more costly than organic base stocks.
GB 1224885 claims a composition comprising a mineral oil and 0.1 to 15 per cent by weight thereof of an oil-miscible diorganopolysiloxane as a viscosity index improver in which a major proportion of the organo groups are methyl groups and the remainder of the organo groups are substituted or unsubstituted alkyl, alkaryl or aralkyl groups having at least 6 and not more than 30 carbon atoms in amount sufficient to render it miscible with mineral oil.
EP0177825 discloses lubricating compositions based on organopolysiloxane miscible with mineral oil, which have a pour point (measured according to DIN 51583) below −15° C.
U.S. Pat. No. 3,634,246 discloses lubricant compositions containing a major amount of triaryl phosphate and a minor amount of a silicone polymer containing at least 40 mole percent phenylsiloxane units. Exemplary is a blend of 60 volume percent tricresylphosphate and 40 volume percent of a 50-50 copolymer of dimethylsiloxane units and phenylmethylsiloxane units.
U.S. Pat. No. 4,190,546 discloses a traction fluid comprising from 50 to 90% wt of a naphthenic hydrocarbon or mixture of naphthenic hydrocarbons, from 8 to 40% wt of a silicone fluid and from 2 to 10% wt of a co-solvent which ensures complete miscibility between the naphthenic hydrocarbon and silicone fluid, the percentages being by weight of the three components. The silicone fluid improves the low temperature properties of the fluid without substantial damage to the good traction properties of the naphthenic hydrocarbons. Preferred co-solvents are aromatic hydrocarbons or aromatic ethers.
EP0283922 discloses a homogeneous blend of a dimethylsiloxane/alkylmethylsiloxane copolymer with a hydrogenated polyalphaolefin based on oligomers of decene-1. The blend serves as a base fluid which has a viscosity-temperature profile and flash point suitable for use in a −54° C. to 135° C. fire-resistant hydraulic fluid having particular utility in military aircraft hydraulic systems.
U.S. Pat. No. 4,449,415 discloses traction fluids containing certain siloxane components and, optionally, certain cycloaliphatic hydrocarbon components. These traction fluids possess high traction coefficients and good low temperature viscosity properties which make these fluids ideally suited for use in traction drive systems subjected to wide operating temperature conditions.
U.S. Pat. No. 7,553,429 discloses simple dimethylsilicone fluids of the proper viscosity/molecular weight distribution to modify the low temperature properties of cycloaliphatic hydrocarbon fluids. Addition of the dimethylsilicone fluid to cycloaliphatic fluids improves their low temperature performance without degrading the requisite elastohydrodynamic shear strength properties. Low viscosity dimethylsilicone lubricating fluids combined with cycloaliphatic hydrocarbon fluids are suitable for use in infinitely variable transmissions and other traction-drive transmission providing good low temperature flow properties and high elastohydrodynamic shear strength.
RU2194741 discloses lubricating oil intended for stable functioning of parts and mechanisms comprising steel-steel friction couples based on liquid polyethylsiloxanes (65-85%) with molecular weight 500-100 and viscosity 40-50 mm2/s and containing 14.25-33.25% poly-alpha-olefins with average degree of oligomerization 7-8 and molecular weight 900-1200 and 0.75-1.75% dioctyl sebacate, for lowered freezing temperature and improved lubrication property.
There is a need for lubricant compositions with a Viscosity Index (VI) of above 150, alternatively above 200, and good metal-to-metal lubrication, at acceptable cost. Currently Viscosity Index values of lubricant compositions are increased through the addition of additives typically referred to as viscosity index Improvers (VI Improvers). VI Improvers are currently typically high molecular weight organic polymers but their use does not always increase the Viscosity Index to the desired values for the purpose concerned and due to their high molecular weight said VI Improvers often lack shear stability. VI improvers are selected because they generally swell with increasing temperature which tends to counteract the decreasing viscosity of a base fluid as said temperature increases. This results in a lubricant that maintains sufficient oil thickness for lubrication at high temperatures. Conversely the VI improvers tend to shrink as temperatures decrease. In such situations the properties of the base oil dominate the viscosity of the fluid. However, VI Improvers are subject to shearing forces when present in lubricating situations and their stability as a result of these shearing forces (Shear Stability) may reduce their effectiveness. Excessive permanent shear effectively reduces lubricating temperature range of a lubricant and as such it is advantageous for lubricants to contain shear stable VI improvers in order to maintain or maximize the functional temperature range in which the fluid will lubricate.
The shear stability of lubricant compositions are usually measured with the KRL shear stability test according to DIN 51350-6 where a reduction in viscosity after the test of less than 10% is considered shear stable and values above 10% are considered shear unstable.
There is also a need for lubricant compositions having high levels of Viscosity Index improvement combined with good lubrication.
There is provided herein a lubricant composition comprising
There is also provided herein a lubricant composition comprising
Also disclosed is a method to lubricate metal-to-metal surfaces using the aforementioned lubricant compositions.
Further disclosed is the use of the lubricant composition as hydraulic fluid, transmission fluid, gear fluid and/or compressor fluid.
The non silicone base stock oil (Component (A)) is an oil that is mainly based on hydrocarbons and potentially nitrogen-, oxygen- and sulfur-containing hydrocarbon derivatives, from any of API Groups I to V discussed above and mixtures thereof, excluding silicone lubricant oils.
Component (A) may for example be:
Component (A) may additionally or alternatively consist of mixtures of the above. In one alternative Component (A) consists of mineral oil based lubricant base stock oils (i), polyalphaolefins (PAO) (ii) and polyinternal olefins (PIO) (iii) or mixtures thereof.
Component (A) has a viscosity in the range of from 1 to 10000 mPa.s at 40° C., alternatively 2 to 1000 mPa.s at 40° C. ASTM D445-12).
Alternatively Component (A (alone or in combination with component (B)) may be formulated into a grease after addition of a thickener to one of the non-silicone base stock oils described in API Groups I to V discussed above and mixtures thereof.
The processes to obtain the lubricant base stocks are known by the skilled in the art and will therefore not be described here any further.
Component (A) is present in the lubricant composition of from 50wt % to 99.5 wt %, alternatively 60wt % to 99wt %, alternatively 60wt % to 95wt %, alternatively 80wt % to 95wt %, alternatively 90wt % to 95wt % based on the total weight of (A)+(B), which is 100wt %.
The silicone oil (Component (B)) is to be understood as mainly based on silicon-oxygen atom bonds forming the backbone of the polymer. Silicone oils include, but are not limited to, silicone fluids, liquid silicone resins, silicone waxes. The terms silicone and siloxane may be used interchangeably to designate silicone oils such as trialkylsilyl terminated polydialkylsiloxane, trialkylsilyl terminated polyalkylalkylsiloxane and trialkylsilyl terminated polyalkylarylsiloxanes.
Siloxanes generally conform to a polymeric backbone consisting of units of the formula RmSiO4-m/2 in which m is zero, 1, 2 or 3 and where m has an average value of from 1.98 to 2.5 per molecule and has a degree of polymerisation ≧2. Each R may be the same or different and denotes, hydrogen or an organic group.
When R is an organic group R may be selected from hydrocarbon groups having from 1 to 45 carbon atoms, such as alkyl groups (methyl, ethyl, propyl, isopropyl, butyl, octyl, nonyl, tetradecyl, octadecyl); cycloalkyl groups (cyclohexyl, cycloheptyl); alkenyl groups (vinyl, hexenyl); aryl groups (phenyl, diphenyl, naphthyl); alkaryl groups (tolyl, xylyl, ethylphenyl); aralkyl groups (benzyl, phenylethyl).
Alternatively when R is an organic group R may be those hydrocarbon groups wherein one or more hydrogen atoms has been replaced with another substituent, also referred to as organyl groups. Examples of such substituents include, but are not limited to, halogen atom containing groups such as haloalkyl groups (chloromethyl, perfluorobutyl, trifluoroethyl, and nonafluorohexyl) and haloaryl groups (monochlorophenyl, dibromophenyl, tetrachlorophenyl, monofluorophenyl); oxygen atoms; oxygen atom containing groups such as carboxyl, carbinol, ester, ether, acrylic groups and polyoxyalkylene groups (polyoxyethylene, polyoxypropylene, polyoxybutylene); nitrogen atoms; nitrogen atom containing groups such as nitrile, amino, amido, cyano, cyanoalkyl and urethane groups; sulphur atoms; sulphur atom containing groups such as sulphide, sulphone, sulphate, sulphonate and mercapto groups; phosphorus atoms; phosphorus atom containing groups such as phosphate, phosphate and phosphonate groups.
Component B may be a cyclic, linear or branched silicone polymer.
Cyclic siloxanes have the general formula (R2SiO)x where R is as described above, and x is 3 to 20 and the total number of carbon atoms in the R groups is between 20 and 1000.
Examples of cyclic siloxanes include hexamethylcyclotrisiloxane (solid at 25° C.), octamethylcyclotetrasiloxane, tetraphenyltetramethylcyclotetrasiloxane, octaethylcyclotetrasiloxane, tetramethyltetraoctylcyclotetrasiloxane, pentamethylpentaoctylcyclopentasiloxane, pentamethylpentadodecylcyclopentasiloxane.
Linear siloxanes conform to the general formula R(SiR2O)rSiR3, where R is as described above and r is 1 to 5000 or higher. Linear siloxanes include polydimethylsiloxane when R is methyl and polydiethylsiloxane when R is ethyl. Such compounds may have a wide variety of terminal groups which typically include, for the sake of example methyl, ethyl phenyl groups. Polydimethylsiloxane and polydiethylsiloxane may have viscosities ranging of from 0.5 to 600 000 mPa.s at 25° C. (using a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D=8.7 s−1). The polydiethylsiloxane may be branched or contain other siloxanes units to depress the crystallization.
In one alternative component (B) may have the following formula:
in which Me is a methyl group and each R1, each R2 and each R3 is individually selected from hydrocarbon groups having from 1 to 45 carbon atoms, each R5 is individually selected from a hydrocarbon group containing from 1 to 18 carbon atoms e.g. linear or branched alkyl groups, phenyl groups and/or alkylaryl groups; and each R4 group is a hydrocarbon groups having from 2 to 45 carbon atoms, n is zero or an integer, v is zero or an integer and t is zero or an integer and wherein n+v+t>1; and that when v is >zero, n is zero and t is zero and that when t>zero, v is zero and n is zero or an integer.
The organic group of each R1, each R2, each R3 and each R4 may independently be alkyl groups having at least 2 alkyl groups, (ethyl, propyl, isopropyl, butyl, octyl, nonyl, tetradecyl, octadecyl); cycloalkyl groups (cyclohexyl, cycloheptyl); alkenyl groups (vinyl, hexenyl); aryl groups (phenyl, diphenyl, naphthyl); alkaryl groups (tolyl, xylyl, ethylphenyl); aralkyl groups (benzyl, phenylethyl).
Further organic groups include those hydrocarbon groups with at least 2 carbon atoms wherein one or more hydrogen atoms has been replaced with another substituent, also referred to as organyl groups. Examples of such substituents include, but are not limited to, halogen atoms (chlorine, fluorine, bromine, iodine); halogen atom containing groups such as haloalkyl groups (chloromethyl, perfluorobutyl, trifluoroethyl, and nonafluorohexyl) and haloaryl groups (monochlorophenyl, dibromophenyl, tetrachlorophenyl, monofluorophenyl); oxygen atoms; oxygen atom containing groups such as carboxyl, carbinol, ester, ether, acrylic groups and polyoxyalkylene groups (polyoxyethylene, polyoxypropylene, polyoxybutylene); nitrogen atoms; nitrogen atom containing groups such as nitrile, amino, amido, cyano, cyanoalkyl and urethane groups; sulphur atoms; sulphur atom containing groups such as sulphide, sulphone, sulphate, sulphonate and mercapto groups; phosphorus atoms; phosphorus atom containing groups such as phosphate, phosphate and phosphonate groups. In one alternative, each R1, each R2, and each R3 may be independently selected from alkyl groups, of 1 to 45, alternatively of 1 to 30 and further alternatively 1 to 16 carbon atoms or phenyl groups containing 6 to 16 carbon atoms and each R4 is independently an alkyl group having from 2 to 16 carbon atoms.
In one alternative all R5 groups may be ethyl groups in which case the formula given above may be re-written as follows:
With Et standing for an ethyl group.
Examples of linear siloxanes include polyalkylalkylsiloxane polymers such as polymethyloctylsiloxane, polymethylphenylsiloxane; polyalkylarylsiloxanes; having a viscosity at 40° C. of from 2 to 10.000 mPa.s, alternatively of from 10 to 1.000 mPa.s (using a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D=8.7 s−1).
Branched siloxanes which may be utilized as component (B) include, for the sake of example, silicone resins. Silicone resins generally contain two or more of the following groups (R13SiO1/2)a (R22SiO2/2))b (R3SiO3/2)c and (SiO4/2)d with R1, R2 and R3 independently represent an alkyl group containing from 1 to 8 carbon atoms, an aryl group, a carbinol group, an alkoxy group (preferably methoxy or ethoxy) or an amino group, 0.05≦a≦0.5; 0≦b≦0.3; c≧0; 0.05≦d≦0.6, and a+b+c+d=1 (with a, b, c and d being mole fractions), having a viscosity at 40° C. of from 2 to 10.000 mPa.s (using a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D=8.7 s−1), alternatively of from 20 to 1.000 mPa.s.
The silicone oil (B) may, for example, be selected from polydiethylsiloxane, polydimethylsiloxane, polydimethylmethylalkylsiloxane, polymethylalkylsiloxane.
In an alternative embodiment there is provided a lubricant composition as hereinbefore described comprising
wherein R1, R2 and R3 are independently selected from alkyl of 1 to 45, alternatively of 1 to 30 and further alternatively 1 to 16 of carbon atoms, v is an integer greater than zero, for the sake of example v may be from 3 to 10000, alternatively from 5 to 1000.
In a still further alternative embodiment there is provided a lubricant composition as hereinbefore described comprising
wherein R1, R2 and R3 are independently selected from alkyl groups of 1 to 45, alternatively of 1 to 30 and further alternatively 1 to 16 carbon atoms or phenyl groups containing 6 to 16 carbon atoms and each R4 is independently an alkyl group having from 2 to 16 carbon atoms, n is zero or an integer, and t is an integer. Hence, when n is zero, the polymer may be a random or block copolymer as previously discussed.
The silicone oil (B) may have a viscosity at 40° C. of from 0.5 to 100.000 mPa.s, alternatively of from 1 to 10.000 mPa.s, alternatively 20 to 1.000 mPa.s. (using a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D=8.7 s−1).
The silicone oil (B) can be a blend of multiple silicone oils described above.
The silicone oil (B) is present in an amount of from 0.5 wt % to 50 wt %, alternatively 1 wt % to 40 wt %, alternatively 5 wt % to 40 wt %, alternatively 5 wt % to 20 wt %, alternatively 5% to 10 wt % based on the total weight of (A)+(B), which is 100 wt %.
Lubricant additives may be used to impart or improve certain properties to the lubricating composition. Such additives include friction modifiers, anti-wear additives, extreme pressure additives, seal swelling agents, rust and corrosion inhibitors, thickeners, Viscosity Index improvers “other than (B)”, pour point depressants, anti-oxidants, free-radical scavengers, hydroperoxide decomposers, metal passivators, surface active agents such as detergents, emulsifiers, demulsifiers, defoamants, compatibilizers, dispersants, and mixtures thereof.
Further additives include deposit control additives, film forming additives, tackifiers, antimicrobials, additives for biodegradable lubricants, haze inhibitors, chromophores, and limited slip additives.
Examples of friction modifiers include long-chain fatty acids and their derivatives, molybdenum compounds, aliphatic amines or ethoxylated aliphatic amines, ether amines, alkoxylated ether amines, acylated amines, tertiary amines, aliphatic fatty acid amides, aliphatic carboxylic acids, aliphatic carboxylic esters, polyol esters, aliphatic carboxylic ester-amides, imidazolines, aliphatic phosphonates, aliphatic phosphates, aliphatic thiophosphonates, aliphatic thiophosphates.
Examples of anti-wear additives and extreme pressure additives include organosulfur and organo-phosphorus compounds, such as organic polysulfides among which alkylpolysulfides; phosphates among which trihydrocarbyl phosphate, dibutyl hydrogen phosphate, amine salt of sulfurized dibutyl hydrogen phosphate, dithiophosphates; dithiocarbamates dihydrocarbyl phosphate; sulfurized olefins, such as sulfurized isobutylene, and sulfurized fatty acid esters.
Examples of seal swell agents include esters, adipates, sebacates, azeealates, phthalates, sulfones such as 3-alkoxytetraalkylene sulfone, substituted sulfolanes, aliphatic alcohols of 8 to 13 carbon atoms such as tridecyl alcohol, alkylbenzenes, aromatics, naphthalene depleted aromatic compounds, mineral oils.
Examples of rust and corrosion inhibitors include monocarboxylic acids such as octanoic acid, decanoic acid and dodecanoic acid; polycarboxylic acids such as dimer and trimer acids from tall oil fatty acids, oleic acid, linoleic acid; thiazoles; triazoles such as benzotriazole, decyltriazole, 2-mercapto benzothiazole; thiadiazoles such as 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazole; metal dithiophosphates; ether amines; acid phosphates; amines; polyethoxylated compounds such as ethoxylated amines; ethoxylated phenols; ethoxylated alcohols; imidazolines; aminosuccinic acids.
Examples of thickeners include metallic soaps such as lithium soaps, silica, expanded graphite, polyurea, clays such as hectorite or bentonite.
In some instances, when thickened, the lubricant composition may become a grease composition.
Examples of Viscosity Index improvers “other than (B)” include polymethacrylates, olefin copolymers, polyisoalkylene such as polyisobutylene, styrene-diene copolymers, and styrene-ester copolymers such as styrenemaleic ester.
Examples of pour point depressants include wax-alkylated naphthalenes and phenols, polymethacrylates, styrene-ester copolymers.
Examples of anti-oxidants include phenolic antioxidants such as 2,6-di-tert-butylphenol, tertiary butylated phenols such as 2,6-di-tert-butyl-4-methylphenol, 4,4′-methylenebis(2,6-di-tert-butylphenol),2,2′-methylenebis(4-methyl6-tert-butylphenol), 4,4′-thiobis(2-methyl-6-tert-butylphenol); mixed methylene-bridged polyalkyl phenols; aromatic amine antioxidants; sulfurized phenolic antioxidants; organic phosphites; amine derivatives such as p-, p′-dioctyldiphenylamine, N,N′-di-sec-butylphenylenediamine, 4-isopropylaminodiphenylamine, phenyl-.alpha.-naphthyl amine, phenyl-.alpha.-naphthyl amine, ring-alkylated diphenylamines; bisphenols; cinnamic acid derivatives.
Examples of free-radical scavengers include zinc dialkyl dithiophosphates, hindered phenols, and alkylated arylamines.
Examples of hydroperoxide decomposers include organo-sulfur compounds and organo-phosphorus compounds.
Examples of metal passivators include poly-functional (polydentate) compounds, such as ethylenediaminetetraacetic acid (EDTA) and salicylaldoxime.
Examples of surface active agents such as detergents, dispersants, emulsifiers, demulsifiers include alkali metal or alkaline earth metal salts of organic acids such as magnesium sulfonate, zinc sulfonate, magnesium phenate, zinc phenate, lithium sulfonate, lithium carboxylate, lithium salicylate, lithium phenate, sulfurized lithium phenate, magnesium sulfonate, magnesium carboxylate, magnesium salicylate, magnesium phenate, sulfurized magnesium phenate, potassium sulfonate, potassium carboxylate, potassium salicylate, potassium phenate, sulfurized potassium phenate; common acids such as alkylbenzenesulfonic acids, alkylphenols, fatty carboxylic acids, polyamine, polyhydric alcoholderived polyisobutylene derivatives.
Examples of defoamants include polysiloxanes, polyacrylates and styrene ester polymers.
Examples of compatibilizers include aromatic hydrocarbons such as 1-methyl-naphthalene, aromatic ethers such as diphenyl ether or anisole (methyl phenyl ether), long chain alcohols such as nonyl phenol, octanol and decanol.
Examples of dispersants include alkenylsuccinimide such as polyisobutylene succinimide, N-substituted polyisobutenyl succinimides such as polyisobutenyl succinimide-polyethylenepolyamine, succinates, succinate esters, alkyl methacrylate-vinyl pyrrolidinone copolymers, alkyl methacrylate-dialkylaminoethyl methacrylate copolymers, alkylmethacrylate-polyethylene glycol methacrylate copolymers, polystearamides, high molecular weight amines, phosphoric acid derivatives such as bis-hydroxypropyl phosphorate.
Some additives may possess multiple properties and provide for a multiplicity of affects. For example, graphite and molybdenum disulfide may both be used as friction modifiers and extreme pressure additives or functionalized soaps may be used to thicken but also provide extreme pressure and antiwear performances to greases. This approach is well known by the person skilled in the art and need not be further elaborated herein.
An additive may be used alone or in combination with other additives.
When present in the lubricant composition of the invention, the sole or multiple additive(s) may be used at a level of from 0 to 10 wt %, alternatively 0.1 to 5 wt %, based on the total weight of the lubricant composition. Thickeners to produce greases may be used at a level of from 5 to 25% wt based on the total weight of the lubricant grease composition.
The lubricant composition is produced by mixing the lubricant base oil and the silicone oil and the optional additives, by conventional mixing means, optionally with heating.
The lubricant composition may be homogeneous, or non homogeneous. Homogeneity of the composition is considered at 25° C., after mixing, and the optional heating, is (are) disrupted.
A homogeneous composition is meant herein as a composition where the lubricant base oil and the silicone oil are compatible or miscible and form a monophasic system. A homogeneous composition may be hazy, clear or opaque. The intimate blend of the 2 oils is uniform and posses the same properties throughout. The compatibility of mixtures may be assessed using ASTM D7155-11: Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils.
A non homogeneous composition is meant herein as a composition where the lubricant base oil and the silicone oil form a biphasic system upon rest. A non homogeneous composition will be characterized by a varying composition of the blend throughout the container.
A non homogeneous system may be rendered homogenous by shaking, heating or addition of a compatibilizer, or a combination thereof. These non homogenous compositions will return to non homogeneous state upon disruption of the shaking or heating. When a compatibilizer is used, the duration of improved homogeneity will depend on the effectiveness of the compatibilizer—temporarily or over a longer period of time.
Compatibilizers may be surfactants or co-solvents. Homogeneity may be obtained through emulsification, dispersion or any other means known by the person skilled in the art. Emulsification techniques are known by the person skilled in the art and will not be further exemplified herein.
Examples of homogeneous compositions include polydiethylsiloxane with polyalphaolefin, polydiethylsiloxane with mineral oil, polymethyloctylsiloxane with polyalphaolefin.
Examples of non homogenous compositions include polytrifluoropropylmethylsiloxane with mineral oil, polydiethylsiloxane with polyol ester, polymethyloctylsiloxane with polyalkylene glycol, polymethyloctylsiloxane with polyol esters.
Compositions as hereinbefore described are shear stable in accordance with DIN 51350-6 (the KRL Tapered Roller Bearing Test in accord with DIN 51350-6) where a reduction in viscosity after the test of less than 10% is considered shear stable and values above 10% are considered shear unstable. It has been found that lubricant compositions as hereinbefore described result in much smaller rises in viscosity subsequent to testing according to DIN 51350-6 than that of conventional VI improvers,
Lubricating compositions may be used in a variety of applications where friction occurs between rubbing surfaces. The surfaces may be plastic or metal.
Types of friction include sliding, rolling, static, kinetic, stick-slip, solid (dry), boundary, mixed, wear, erosion, elasto-hydrodynamic frictions.
The present invention includes a method to lubricate metal-metal surfaces comprising:
The present lubricant composition may be used in any system that includes machine elements that contain gears of any kind and roller bearings. Examples of such systems include electricity generating systems, industrial manufacturing equipments such as paper, steel and cement mills hydraulic systems, automotive drive trains, aircraft propulsion systems, etc.
Further systems include crankcases, 2-stroke engines, 4-stroke engines, diesel engines, internal combustion engines, gears for manual or differential transmissions, industrial lubricants, hydraulic, compressor, turbine, metal working, metal forming, lubrication grease, solid.
Further systems also include traction and torque systems.
The lubricant composition may alternatively be used as an automatic transmission fluid, a manual transmission fluid, an axle lubricant, a transaxle lubricant, an industrial gear lubricant, a circulating lubricant, a gear oil for wind turbines, an open gear lubricant, an enclosed gear lubricant, an hydraulic fluid, a compressor fluid, or a grease.
Operating temperatures for the use of the lubricant composition, meaning the temperatures at which the lubricant composition may be used for prolonged time (also called service temperatures), range of from −55° C. to +200° C. Short term peak temperature may be higher.
Viscosity Index is measured/calculated using ASTM D 2270-10E: Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 and 100° C.
The dynamic viscosity is determined by a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D=8.7 s−1 and at the two different required temperatures: 40° C. and 100° C.
The density may be measured using glass pycnometer according to DIN 51757 (Procedure V2). Ideal mixing is assumed for blends of materials, meaning that the density of the blend can be calculated from the respective values of the ingredients. The values of dynamic viscosities were subsequently used to calculate kinematic viscosities using the material densities tabulated below. The calculated kinematic viscosities were then used to calculate Viscosity Index as per formula:
Viscosity Index=[((antilog N)−1)/0.00715+100]
where YN=H/U,
Y=kinematic viscosity at 100° C. of the oil whose viscosity index is to be calculated,
H=kinematic viscosity at 40° C. of a 100 Viscosity Index oil with the same viscosity at 100° C. as the unknown,
U=kinematic viscosity at 40° C. of the oil whose viscosity index is to be calculated.
The Load Carrying Capability (LCC) properties of the lubricant compositions being assessed were determined in accordance with ASTM D 5706-05 ‘Standard test method for determining extreme pressure properties of lubricating greases using a high-frequency, linear-oscillation (SRV) test machine’. The SRV test machine may be used to determine load carrying and wear properties and coefficient of friction of lubricating greases at selected temperatures and loads specified for use in applications where high-speed vibrational or start-stop motions are present for extended periods of time under initial high Hertzian point contact pressures. This method has found application in qualifying lubricating greases used in constant velocity joints of front-wheel-drive automobiles and for lubricating greases used in roller bearings. This method may also be used for determining a fluid lubricant's ability to protect against wear and its coefficient of friction under similar test conditions.
In the following examples a lubricating fluid was evaluated instead of lubrication greases; a steel cylinder was used instead of a steel ball; frequency was 10 Hz instead of 50 Hz. The measurements were carried out at 40° C. using 1 mm stroke. The load was increased in increments of 50N every two minutes up to a maximum load of 2000N.
Wearing properties or lubrication performance may be evaluated by standard test method DIN 51350-3 ‘Testing of lubricants in the Shell four-ball tester’. The Shell Four Ball Tester (FBT) is a testing device used to determine welding and metal loads as well as different friction and wear characteristics of lubricants. The standard test consists of a rotating ball of a ball bearing being pressed onto three similar but immobile balls while applying a load of 100N, 400N and 800N for 1 hour test duration. Wear is determined by optically measuring the formed calotte (the worn depression area).
This testing device is especially common in the lubricant industry where it is used for routine product development and quality control testing. The friction torque can be recorded continuously.
The testing was done according to DIN 51350-3 and the wear scar is reported as the average of the three steel balls in mm.
Shear stability of lubricant compositions was measured according to DIN 51350-6 using a tapered roller bearing to shear the lubricant composition for 4 hours (method A) and report the relative drop of viscosity after the test in percentage,
R
v=(v0−v1)/v0*100,
where v0 is the kinematic viscosity (mm2/s at 100° C.) before and v1 after the test.
The lubricant composition of the present invention is characterized by a Viscosity Index≧180, alternatively ≧200, alternatively ≧250.
The lubricant composition of the present invention is characterized by a load carrying capability according to the procedure described above. LCC≧800N, SRV-load ≧1000N, alternatively ≧1200N, alternatively ≧1500N (ASTM D 5706-05).
The lubricant composition of the present invention is characterized by a relative viscosity drop according to the procedure described above. In the case of the compositions as hereinbefore described, Rv<10%, alternatively Rv<7.5%, alternatively Rv<6%. Where Rv=(v0−v1)/v0*100, where v0 is the kinematic viscosity (mm2/s at 100° C.) before and v1 after the test when measured according to DIN 51350-6 (method A).
All percentages in the following examples are in wt. % unless otherwise indicated.
PDMS: polydimethylsiloxanes having a typical viscosity of 50 cst at 25° C., determined using a glass capillary viscosimeter
Viscosity Index Type PiB: Polyisobutylene Viscosity Improver: commercial material Hitec® 7389, from Afton Chemical Corporation, with a typical viscosity of 176 mm2/s at 100° C. (Producers datasheet)
The density of the materials was measured using a glass pycnometer according to DIN 51757 (Procedure V2). The following parameters for the densities ρ in g/ml (for a given temperature ρ=a−(b×Temperature (° C.)) were obtained using linear regression which were then used to calculate the densities at 40 and 100° C.
The values for PDMS are calculated using an equation from the Polymer Data Handbook (1999 Oxford University Press) to be 0.957 g/ml at 40° C. and 0.905 g/ml at 100° C.
For the blends ideal mixing was assumed meaning that the density of the blend can be calculated from the respective values of the ingredients.
Blending: The blends were prepared by adding a total of 50 g of materials to a glass bottle and shaking them until a homogenous mixture was obtained.
The viscosity, viscosity index, the wear properties i.e. Load Carrying Capability (LCC) and the relative viscosity drop were measured for different compositions. The results are shown in the following tables; values for the individual components are given as a reference. (Note the symbols (A) and (B) in the Tables below indicate the respective ingredients as identified in e.g. claim 1).
Example 1a shows that mixtures according to the invention containing PDES have an LCC much higher than the pure oils in the range of between 0.5 and 50% wt of component (B), namely the PDES. The effect can be already seen with a 5% wt % addition level of PDES into the PAO.
Example 1b shows that mixtures according to the invention containing PDES (i.e. component B) have much higher Viscosity Index values (at least 10% greater) than 100% PAO (*: Viscosity Index 143 from suppliers datasheet).
Example 2 a shows that compositions as hereinbefore described containing PDES and mineral oil have an LCC much higher than 100% mineral oil. The effect can be seen at 5% addition level of PDES into the mineral oil.
Example 2b shows that that compositions as hereinbefore described containing PDES and mineral oil have a lower wear scar in the four ball test than the pure mineral oil (nm stands for non measurable, load is too high to run the test).
Example 3a shows that compositions as hereinbefore described containing PMOS1 have an LCC much higher than the 100% PAO. The effect can clearly be identified with a 10% addition level of PMOS1 into the PAO.
Example 3b shows that that compositions as hereinbefore described containing PMOS1 and PAO have a lower wear scar in the four ball test at high loads (800N) than the pure PAO (nm stands for non measurable, load is too high to run the test).
Example 3c shows that mixtures according to the invention containing PMOS1 have Viscosity Index much higher (at least 10% greater) than for 100% PAO (*: Viscosity Index 143 as provided by the supplier).
Example 4a shows that mixtures according to the invention containing PMOS2 have an LCC much higher than value for 100% PAO, i.e. component (A) alone. The effect is clearly evident at 10% addition level of PMOS1 into the PAO.
The Example 4b shows that mixtures according to the invention containing PMOS2 have much higher VI values (greater than 10% higher) than 100% PAO. The Viscosity Index value for PAO provided by the supplier is 143 as previously indicated by *.
The Example 5a shows that mixtures according to the invention containing PDMS have an LCC much higher than 100% PAO. The effect can be clearly identified at 5% addition level of PDMS.
Example 5b shows that mixtures according to the invention containing PDMS have much higher Viscosity Index values (much greater than 10%) than the 100% value for PAO. The Viscosity Index value for PAO provided by the supplier is 143 as previously indicated by *.
Example 6a shows that mixtures according to the invention containing PDMS have an LCC much higher than 100% mineral oil. The effect can be already seen at 5% addition level of PDMS in the mineral oil.
Example 6b shows that that compositions as hereinbefore described containing PDMS and mineral oil have a lower wear scar in the four ball test than the pure mineral oil (nm stands for non measurable, load is too high to run the test).
Example 7 shows that mixtures according to the invention containing PDMS have LCC of above 1000N
Example 8 shows that mixtures according to the invention containing PMOS2 have an LCC of above 1000N.
Example 9 shows that mixtures according to the invention containing PDES have a load carrying (LCC) above 400N.
Example 10 shows that mixtures according to the invention containing PDES have an LCC higher than 650N.
PAO Blends with organic VI Improvers were prepared using the commercial Hitec® 5704 and Hitec® 7389
Comparative examples 1-6 indicate that the commercial viscosity improvers are less efficient than the disclosed siloxanes disclosed in Examples 1-10. Furthermore, the comparative viscosity improvers do not allow achieving viscosity indices above 200 when used with polyalphaolefin (density of the pure PAO was used to calculate the Viscosity Index values of the blends).
PAO blends with organic VI improver Hitec® 5704 and with PMOS 1 were tested for shear stability
Example 3 shows a composition according to the invention that is shear stable, while Comparative example 3 is shear instable.
The examples 3, 4, 1 show that compositions according to the invention at 10% siloxanes content in PAO have a “low temperature”-viscosity significantly lower than commercial VI improvers at the same addition level (Comparative 7a and b).
This application claims priority to and all the advantages of U.S. Provisional Patent Application No. 61/628,871, filed on Aug. 14, 2013, the content of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2013/054966 | 8/14/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61682871 | Aug 2012 | US |
