GB2506975A

GB2506975A - Lubricant compositions

Info

Publication number: GB2506975A
Application number: GB1314570.1A
Authority: GB
Inventors: Manfred Jungk; Andreas Stammer; Herbert Stoegbauer
Original assignee: Dow Corning Corp
Current assignee: Dow Silicones Corp
Priority date: 2012-08-14
Filing date: 2013-08-14
Publication date: 2014-04-16
Also published as: GB201214473D0; GB201314570D0

Abstract

A lubricant composition comprising (A) a polyalphaolefin, and (B) a polymethylalkylsiloxane in which each alkyl group contains at least 2 carbon atoms (especially 8 carbon atoms as an octyl group). (B) is present in an amount of from 1 to 85% by weight of the total weight of (A) + (B). The composition is intended for use as an automatic transmission fluid, a manual transmission fluid, an axle lubricant, a transaxle lubricant, an industrial gear lubricant, a circulating lubricant, an open gear lubricant, an enclosed gear lubricant, an hydraulic fluid a compressor fluid, a gear box lubricant of a wind turbine or a grease.

Description

LUBRICANT COMPOSITIONS

[0001] Disclosed herein are lubricant compositions comprising a polyalphaolefin and a silicone oil.

[0002] 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 (API) in five Groups, namely Groups I, II, Ill, IV and V. Lubricant base stocks include natural lubricating oils, synthetic lubricating oils, and mixtures thereof.

Groups Ito Ill include base stocks derived from petroleum based oils, while Groups IV and V include synthetic base stocks including silicones.

[0003] Viscosity Index (VI) is an empirical, unit less number which indicates the rate of change in the viscosity of an oil within 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 little change of viscosity with temperature.

In a variety of applications, a high or very high Viscosity Index is preferred.

[0004] The chemical composition of the base stocks from Group I, Group II and Group Ill 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 stock generally determine this composition. Lubricant base stock from Group I, Group II and Group Ill 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 D445-1 2) have a Viscosity Index ranging of from 80 to 120, or 140 for high performance grades (ASTM D2270-lOel).

[0005] Group IV is composed of polyalphaolefins (PAO) which are hydrogenated oligomers obtained from the oligomerization of alphaolefin monomers and Group V base stocks include base stocks not included in Groups l-IV.

[0006] Silicones 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 behaviour. They show chemical resistance, lubricity and thermal and oxidative stability.

[0007] GB1224885 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.

[0008] EP0177825 discloses lubricating composition based on organopolysiloxane miscible with mineral oil, which have a pour point (measured according to DIN 51583) below-15°C.

[0009] US3634246 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 volume percent of a 50-50 copolymer of dimethylsiloxane units and phenylmethylsiloxane units.

[0010] US4190546 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.

[0011] EP0283922 discloses a homogeneous blend of a dimethylsiloxanet 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.

[0012] US4449415 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.

[0013] US7553429 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.

[0014] 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.

[0015] There is also a need for lubricant compositions with improved load carrying ability in metal-metal lubrication applications, because more stable lubricant films will ultimately reduce the wear in such applications. The load carrying ability of a lubricant film can for example be assessed by determining the Load Carrying Capacity (LCC) in accordance with the test method defined in ASTM D 5706-05.

[0016] There is also a need for lubricant compositions having high levels of Viscosity Index improvement combined with good lubrication.

[0017] Disclosed herein is a lubricant composition comprising (A) a polyalphaolefin, (B) a polymethylalkylsiloxane in which each alkyl group contains at least 2 carbon atoms; alternatively at least 4 carbon atoms wherein (B) is present in an amount of from ito 85% by weight of the total weight of(A) + (B).

[0018] Also disclosed is a method to lubricate metal-to-metal surfaces with the composition hereinbefore described.

[0019] Further disclosed is the use of the lubricant composition as hereinbefore described as hydraulic fluid, transmission fluid, gear fluid and/or compressor fluid.

[0020] The polyalphaolefin base stock oil (Component (A)) is any Group IV base stocks as classified by the American Petroleum Institute. In accordance with such definition polyalphaolefins (PAO) 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, and hexamers of the alphaolefin monomer.

[0021] When the PAO is based on alphaolefin monomers of 6 to 16 carbon atoms, its viscosity may rangefrom 1.7 to 100 mPa.s, at 100°C ora viscosity in the range of from ito 10000 mPa.s at 40°C (ASTM D445-i2), and its viscosity index (VI) may range of from 120 to 150. Typically, the PAO may have a viscosity of from about 2 to about 15 or from about 3 to about 12 or from about 4 to about 8 mPa.s, at 100° C (ASTM D445-i2). Examples of PAOs include poly-alpha-olefins 4 mPa.s, at 100°C, poly-alpha-olefins 6 mPa.s at 100°C [0022] Polymethylalkylsiloxanes (Component (B)) are polymers in which silicon-oxygen atom bonds form the backbone of the polymer. Polymethylalkylsiloxanes include, but are not limited to, silicone fluids, liquid silicone resins, silicone waxes.

[0023] Linear polymethylalkylsiloxanes generally conform to the general formula: Ri R4 R2si 0 Si 0 SL\R Me t In which Me is a methyl group and each R1, each R2, each R3 and each R4is an organic group having at least 2 carbon atoms selected from hydrocarbon groups having from 1 to carbon atoms, such as alkyl groups having at least 2 alkyl groups (ethyl, propyl, isopiopyl, butyl, octyl, nonyl, tetiadecyl, octadecy; alkenyl gioups (vinyl, hexenyl); aryl gioups (phenyl, diphenyl, naphthyl); alkaiyl groups (tolyl, xylyl, ethylphenyl); aialkyl gioups (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 anothei substituent, also ieferied to as oiganyl 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, pertluorobutyl, trifluoioethyl, 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 nitiile, 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. Typically the linear polymethylalkylsiloxanes described above are the only siloxanes present in the composition.

[0024] Alternatively, each R1, each R2, and each R3 may be independently selected from alkyl groups, of ito 45, alternatively of ito 30 and further alteinatively ito 16 carbon atoms or phenyl groups containing 6 to 16 caibon atoms and each R4 is independently an alkyl group having from 2 to 16 carbon atoms.

[0025] In a further alternative the polymethylalkylsiloxanes may be in the form of random copolymers, such as ABA or ABn type block copolymers in which each R1, each R2, each R3 and each R4 are independently as hereinbefore described.

[0026] The polymethylalkylsiloxane (B) may have a viscosity at 4000 of from 0.5 to 100,000 mPa.s, alternatively of from ito 10,000 mPa.s, alternatively 20 to 1,000 mPa.s (using a cone/disk viscometer (Physica® MCR 301) at constant shear rate of 0 = 8.7sj.

[0027] The polymethylalkylsiloxane (B) is present of from lwt% to 85wt%, alternatively lwt% to 5Owt%, alternatively lwt% to 4Owt%. alternatively 5wt% to 2Owt%, alternatively 5% to lOwt% based on the total weight of (A) ÷ (B), which is lOOwt%. Hence, when (B) is the above (A) is present in an amount of 100% -the wt% of (B).

[0028] 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.

[0029] Further additives include deposit control additives, film forming additives, tackifiers, antimicrobials, additives for biodegradable lubricants, haze inhibitors, chromophores, and limited slip additives.

[0030] 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 fafty acid amides, aliphatic carboxylic acids, aliphatic carboxylic esters, polyol esters, aliphatic carboxylic ester-amides, imidazolines, aliphatic phosphonates, aliphatic phosphates, aliphatic thiophosphonates, aliphatic thiophosphates.

[0031] 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.

[0032] 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.

[0033] 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-diniercapto-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.

(0034] Examples of thickeners include metallic soaps such as lithium soaps, silica, expanded graphite, polyurea, clays such as hectorite or bentonite.

(0035] In some instances, when thickened, the lubricant composition may become a grease composition.

[0036] 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.

[0037] Examples of pour point depressants include wax-alkylated naphthalenes and phenols, polymethacrylates, styrene-ester copolymers.

(0038] 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-ter t-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.

[0039] Examples of free-radical scavengers include zinc dialkyl dithiophosphates, hindered phenols, and alkylated arylamines.

(0040] Examples of hydroperoxide decomposers include organo-sulfur compounds and organo-phosphorus compounds.

(0041] Examples of metal passivators include poly-functional (polydentate) compounds, such as ethylenediaminetetraacetic acid (EDIA) and salicylaldoxime.

(0042] 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 sultonate, 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 alcohol derived polyisobutylene derivatives.

[0043] Examples of defoamants include polysiloxanes, polyacrylates and styrene ester polymers.

[0044] 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.

[0045] 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.

[0046] 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 orfunctionalized 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.

[0047] An additive may be used alone or in combination with other additives.

[0048] When present in the lubricant composition of the invention, the sole or multiple additive(s) may be used at a level of from Oto lOwt%, alternatively 0.1 to Swt%, 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.

[0049] 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.

[0050] The lubricant composition is homogeneous. Homogeneity of the composition is considered at 25°C, after mixing, and the optional heating, is (are) interrupted.

[0051] 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 D71 55-11: Standard Practice for Evaluating Compatibility of Mixtures of Turbine Lubricating Oils.

[0052] 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.

[0053] Examples of homogeneous compositions include polymethyloctylsiloxane with polyalphaolefin.

[0054] Lubricating compositions may be used in a variety of applications where friction occurs between rubbing surfaces. The surfaces may be plastic or metal.

[0055] Types of friction include sliding, rolling, static, kinetic, stick-slip, solid (dry), boundary, mixed, wear, erosion, elasto-hydrodynamic frictions.

[0056] The present invention includes a method to lubricate metal-metal surfaces comprising i. obtaining a lubricant composition as hereinbefore described; U. lubricating the metal-metal surface with said lubricant composition.

[0057] 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. [0058] 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. The lubricant composition may alternatively be used as a gear oil for wind turbines.

[0059] Further systems also include traction and torque systems.

[0060] 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, an open gear lubricant, an enclosed gear lubricant, an hydraulic fluid, a compressor fluid, or a grease.

[0061] 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.

Examples

Test Methods Viscosity Index (VI) [0062] Viscosity Index is measured/calculated using ASTM D 2270-bE: Standard Practice for Calculating Viscosity Index from Kinematic Viscosity at 40 and 100°C.

Kinematic viscosity (mm2/s) = dynamic viscosity (mPa.s) material density [0063] The dynamic viscosity is determined by a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D = 8.7s1 and at the two different required temperatures: 40°C and 100°C.

[0064] 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: Vl= [((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.

[0065] The Load Carrying Capability ([CC) 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.

[0066] 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 50Hz. The measurements were carried out at 40°C using 1mm stroke. The load was increased in increments of SON every two minutes up to a maximum load of 2000N.

[0067] Wearing properties or lubrication performance may be evaluated by standard test method DIN 51 350-3 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 bearing being pressed onto three similar but immobile balls while applying a load of lOON, 400N and BOON for 1 hour test duration. Wear is determined by optically measuring the formed calotte (the worn depression area).

[0068] 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.

[0069] 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.

[0070] The lubricant composition of the present invention is characterized by a Viscosity Index »= 180, alternatively »= 200, alternatively »= 250.

[0071] The lubricant composition of the present invention is characterized by a load carrying capability according to the procedure described above. SRV-load »= BOON, SRV-load bOON, alternatively 1200N, alternatively 1500N (ASTM D 5706-05). All percentages are in wt. %.

Materials [0072] PAO: polyalphaolefin (PAO SpectrasynTM 6 from ExxonMobil Chemicals) having a typical viscosity of 30.3 mm2/s at 40°C (Producers datasheet dated 27 February 2012) -Mineral oil: Nynas® NS-100 (severely hydrotreated base oil obtained from Nynas AB) having a typical viscosity of 96 mm2fs at 40°C (Producers datasheet, dated 3 March 2008) -PMOS 1: polymethyloctylsiloxane, prepared by reacting a trimethylsilyl terminated methylhydrogen siloxanes (having a viscosity of approx 3OmPa.s at 20°C) with an excess of 1-octene using a platinum (Pt) catalyst at 120°C. The reaction was monitored by IR spectroscopy until the SiH stretch peak (at about 218OcH) had disappeared. The excess of 1-octene was then removed by vacuum distillation and a clear oil having a viscosity of 1130 mPa.s at 20°C was obtained (using a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D = 8.7sj; -PMOS 2: polymethyloctylsiloxane, prepared by reacting a trimethylsilyl terminated methylhydrogen siloxanes (having a viscosity of approx 6 mFa.s at 20°C) with an excess of 1-octene using a Pt catalyst at 120°C. The reaction was monitored by IR spectroscopy until the SiH peak had disappeared. The excess of 1-octene was then removed by vacuum distillation and a clear oil having a viscosity of 170 mPa.s at 20°C was obtained (using a cone/disk viscometer(Physica® MCR 301) at constant shear rate of D = 8.7s1); -VI type FiB: Polyisobutylene Viscosity Improver: commercial material Hitec® 7389, from Afton Chemical Corporation, with a typical viscosity of 176 mm2/s at 100°C (Producers datasheet); -VI type OCP: Olefin Copolymer Viscosity Improver: commercial material Hitec® 5704, from Afton Chemical Corp., with a typical viscosity of 1100 mm2/s at 100°C.

[0073] The density of the materials was measured using a glass pycnometer according to DIN 51757 (Procedure V2). The following parameters for the densities p in g/ml (for a given temperature p a-(b x Temperature (°C)) were obtained using linear regression which were then used to calculate the densities at 40°C and 100°C. a B

PAO 0.8343 0.0006 PMOS 1 0.9216 0.0006 PMOS 2 0.9161 0.0007 [0074] For the blends ideal mixing was assumed meaning that the density of the blend can be calculated from the respective values of the ingredients.

[0075] The viscosity, viscosity index and the wear properties i.e. Load Carrying Capability (LCC) were measured for different compositions. The results are shown in the following tables; values for the individual components are given as a reference Example 1: PMOS I + PAO PMOS 1 PAO LCC(N) (Wt%) (Wt%) 0 100 450 90 2000 60 1800 10 1200 0 1300 [0076] Example 1 shows that compositions as hereinbefore described containing PMOS1 have an LCC much higher than the 100% PAC. The effect can clearly identified with a 10% addition level of PMOS1 into the PAO.

Example 2: PMOS I + PAO PMOS PAO Four ball (Wt%) (Wt%) wearscarat 800N load (mm) 0 100 nm 80 3.346 40 1.475 20 1.432 [0077] Example 2 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 and above) than the pure PAO (nm stands for non measurable, i.e. where the load is too high to run the test).

Example 3: PMOS I + PAO PMOS 1 PAO Viscosity at Viscosity at Viscosity (Wt%) (Wt%) 4000 100°C Index (mPa.s) (mPa.s) 0 100 --143* 90 38.15 8.02 216 80 55.62 11.77 234 60 106.1 22.44 259 40 183.6 39.02 278 20 310.0 69.92 310 10 402.0 95.95 332 5 458.0 111.0 341 0 497.3 131.0 364 [0078] Example 3 shows that mixtures according to the invention containing PMOS1 have VI much higher than the 100% PAO (*: Viscosity Index 143 as provided by the supplier).

Example 4: PMOS 2 + PAO PMOS2 PAO LOG (Wt%) (Wt%) (N) 0 100 450 90 1750 60 2000 10 1550 0 1450 [0079] Example 4 shows that mixtures according to the invention containing PMOS2 have an LCC much higher than 100% FAO. The effect is clearly evident at 10% addition level of PMOS1 into the PAO.

Example 5: PMOS 2 + PAO PMOS 2 PAO Viscosity at Viscosity at Viscosity (Wt%) (Wt%) 40°C 100°C Index (mPa.s) (mPa.s) 0 100 143* 95 27.8 6.09 211 80 33.59 7.24 218 60 42.55 9.81 248 40 52.45 12.49 265 20 66.25 16.59 287 10 75.51 19.59 301 5 76.46 20.18 306 0 82.77 22.34 314 [0080] The Example 5 shows that mixtures according to the invention containing PMOS2 have much higher Viscosity Index values than 100% PAO (*: Viscosity Index 143 as provided by the supplier).

Comparative examples 1-6 [0081] PAO Blends with organic VI Improvers were prepared using the commercial Hitec 5704 and Hitec® 7389 Comparative VI improver Viscosity at Viscosity at 100°C Viscosity example 40°C (mPa.s) (mPa.s) Index 1 5% Hitec® 5704 40.4 7.1 168 2 10% Hitec® 5704 60.1 9.6 167 3 20% Hitec® 5704 113.8 18.2 199 4 55% Hitec® 7389 30.7 6.1 186 10% Hitec® 7389 37.6 7.1 184 6 20% Hitec® 7389 57.4 10.4 196 [0082] 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).

Comparative example 7 a and b. Example 6 a and b: 7 VI improver Viscosity at -35°C (mPa.s) Comparative 10% Hitec® 5704 9520

example 7a

Comparative 10% Hitec® 7389 6175

example 7b

Example 6a 10% PMOS1 4520 Example 6b 10% PMOS2 3331 [0083] The comparative example 7 a and b show that a PMOS used at 10% in PAO has a low temperature-viscosity significantly lower than commercial VI improvers at the same addition level.

Claims

CLAIMSA lubricant composition comprising (A) a polyalphaolefin, (B) a polymethylalkylsiloxane in which each alkyl group contains at least 2 carbon atoms; wherein (B) is present in an amount of from ito 85% by weight of the total weight of (A)+(B).
2. A lubricant composition according to claim 1 where (A) has a viscosity in the range of from ito 10000 mPa.s at 40°C (ASTM D445-12).
3. A lubricant composition according to any preceding claim where (B) has a viscosity in the range of from Sto 1000 mPa.s at 40°C (ASTM D445-12).
4. A lubricant composition in accordance with any preceding claim characterised in that polymethylalkylsiloxane (component B) is generally of the general formula: Si 0 Si 0 SiN Mewherein Me is a methyl group and each R1, each R2, and each R3 may be independently selected from alkyl groups, of 1 to 45, carbon atoms or alkylaryl groups containing 6 to 16 carbon atoms and each S4 is independently an alkyl group having from 2 to 16 carbon atoms and t is an integer.
5. A lubricant composition in accordance with any preceding claim characterised in that polymethylalkylsiloxane (component B) is generally of the general formula: Si 0 Si 0 SiN Metwherein Me is a methyl group and each 1, each 2, and each p3 may be independently selected from methyl or phenyl each R4is independently an alkyl group having from 2 to 16 carbon atoms and t is an integer.
6. A lubricant composition according to any preceding claim where (A) is present of from 4Owt% to 99wt%, based on the total weight of (A) + (B).
7. A lubricant composition according to any preceding claim where (B) is present of from 6Owt% to iwt%, based on the total weight of (A) + (B).
8. A lubricant composition according to any preceding claim further comprising an optional additive (C) selected from the group consisting of 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, deposit control additives, film forming additives, tackifiers, antimicrobials, additives for biodegradable lubricants, haze inhibitors, chromophores, limited slip additives, and mixtures thereof.
9. A lubricant composition according to any preceding claim wherein the optional additive (C) is present at a level of from 0 to lOwt%, alternatively 0.1 to 5wt%, based on the total weight of the lubricant composition.
10. A lubricant grease comprising the composition of any preceding claim.
11. A lubricant composition according to any preceding claim wherein the LCC is above 1000N when determined in accordance with ASIM D 5706-05.
12. A lubricant composition according to any of the preceding claim wherein the Viscosity Index is above 180 when determined in accordance with ASTM D 2270-1OE.
13. A lubricant composition according to any preceding claim wherein viscosity at -35°C is below S000mPas when determined by a cone/disk viscometer (Physica® MCR 301) at constant shear rate of D = 8.7s-1.
14. A lubricant composition according to any preceding claim wherein the 4 ball wear at 800N is below 2mm when determined in accordance with DIN 51350-3.
15. A method to lubricate metal-metal surfaces comprising obtaining a lubricant composition in accordance with any one of claims 1 to 14, and ii lubricating the metal-metal surface with said lubricant composition.
16. The use of a lubricant composition in accordance with any one of claims 1 to 14 as an automatic transmission fluid, a manual transmission fluid, an axle lubricant, a transaxle lubricant, an industrial gear lubricant, a circulating lubricant, an open gear lubricant, an enclosed gear lubricant, an hydraulic fluid a compressor fluid, a gear box lubricant of a wind turbine or a grease.