Lubricant composition

Abstract

 The present invention describes a lubricant composition comprising a base oil component, at least one viscosity index improver, at least one metal salt of an organic acid and at least one metal salt of an inorganic acid and from 0.00005 wt% to 0.01 wt% abrasive particles, wherein the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfur.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a lubricant composition. More specifically, it relates to a lubricant composition comprising very low amounts of sulfur, phosphorus and/or sulfated ash. Furthermore, the present invention relates to a method for producing the lubricant composition and a motor or a gearbox comprising the lubricant composition.

BACKGROUND OF THE INVENTION

[0002] The improvement of wear and friction resistance of moving parts in motors and machines, such as engine pistons, is highly desirable in the modern automotive and transportation industry, as a major part of machine breakdowns are caused by mechanical wear of their moving parts. Typically, friction between moving parts in a system is reduced with different kinds of lubricants separating the moving parts, as lubricant-to-surface friction is much less detrimental than surface-to-surface friction.

[0003] Current market trends require cleaner fuels and lube oils. There is an emerging trend to substitute the undesirable components, such as sulphur S and phosphorus P. The driver is certainly the aim for reduced carbon dioxide and harmful exhaust gas emissions. One way to achieve the target is to further reduce the content of harmful components. The aim is to produce lubrication oils with as low content as possible of sulfated ash, phosphorus and sulphur, i.e. low SAPS oils.

[0004] The issue regarding low sulfur and low phosphorus content is also directed to the exhaust gas cleaning by using catalysts. The most of the catalysts used to clean exhaust gases of combustion engines are sensitive to sulfur and/or phosphorus. Therefore, motor oils containing high amounts of these compounds are responsible for the decrease of the catalyst capabilities to clean the exhaust gases.

[0005] A typical lubrication oils consists of base oil (appr. 80%) and an additive package. The additive packages comprise of dispersant packages (e.g. cleanliness agents, i.e. detergents, soot dispersants, anti-oxidants, anti-corrosion agents, anti-wear components) and viscosity modifiers (e.g. SBS, olefin copolymers). The base oils used for manufacturing of lubrication oils are divided into four categories: API 1, mineral oil base, API 2, modified mineral oil base, API 3, semi-synthetic oil base and API 4, synthetic (PAO) oil base.

[0006] At present, numerous types of lubricant compositions are known. One well-studied solution for improving the anti-frictional properties of lubricants is adding oil-soluble metal compositions to the base lubricant. United States patent US4431553 discloses a lubricant comprising a mixture of various greases, lubricating oil and from 0.1 to 10% by weight of copper, tin or lead in the form of copper oxyquinolinate, tin oxyquinolinate, lead oxyquinolinate or mixtures thereof. However, because of a low degree of solubility in oil of such metal oxyquinolinates, the lubricant is not effective in applications where high-pressure friction occurs.

[0007] Presently, basically all new engine lubrication oils introduced in Europe are based on API 3 base oil. Base oil is characterized by its sulphur content, paraffin content and viscosity index. The lower the sulphur contents the better. Other sources for sulphur and phosphorus compounds are originating from the anti-oxidants and anti-wear additives.

[0008] In the past fifty years metal-coating lubricants were developed especially for exploitation in harsh environments featuring high temperatures and pressures. Metal-coating lubricants are materials that form a non-oxidising thin metal film, such as a few micrometers thick copper film on the friction surfaces also on those surfaces not containing the film- forming metals. The protective thin metal film provides significant reduction of the friction coefficient even in marginal lubrication conditions and when friction surfaces are under high pressure.

[0009] Russian patent RU2277579 discloses a metal- containing oil-soluble composition for lubricant materials. Said composition comprises metal salt of inorganic acid, metal salt of organic acid, aliphatic alcohol, aromatic amine, epoxy resin, succinimide polymer and 2-imine-substituted derivative of indoline. A known disadvantage of said composition is ineffective formation of the protective thin metal film on friction surfaces, thus making such a lubricant useless in applications where it is crucial to achieve a maximum degree of protection as soon as possible.

PURPOSE OF THE INVENTION

[0010] The purpose of the present invention is to eliminate the drawbacks mentioned above. The purpose of the present invention is to prolong the lifespan of machines, engines and motors by reducing temperatures of friction surfaces and improving abrasive resistance, thus reducing wear of their moving parts. This is achieved by protecting friction surfaces with a novel lubricant composition providing a fast formation of the protective thin metal film on friction surfaces.

[0011] A further purpose of the lubricant composition according to the present invention is to provide an environmentally friendly lubricant comprising significantly less toxic and environmentally harmful chemicals or components than the lubricants and lubricant additives currently available on the market. Furthermore, it was thus an object of the present invention to provide a lubricant which leads to a reduction in the fuel consumption. Moreover, the lubricant composition should enable a high cleanliness and low sludge formation. Furthermore, the improvement of oils drain intervals is a further object of the present invention. These improvements should be achieved without environmental drawbacks.

SUMMARY OF THE INVENTION

[0012] These objects and further objects which are not stated explicitly but are immediately derivable or discernible from the connections discussed by way of introduction herein are achieved by the lubricant composition being characterized by what is disclosed in claim 1. Appropriate modifications to the inventive lubricants are protected in the subclaims which refer back to claim 1. The method for producing a lubricant composition according to the present invention is characterized by what is disclosed in claim 13. The motor according to the present invention is characterized by what is disclosed in claim 14. The gearbox according to the present invention is characterized by what is disclosed in claim 15.

[0013] The present invention provides a lubricant composition comprising a base oil component, at least one viscosity index improver and at least one metal salt, wherein the lubricant composition comprises at least one metal salt of an organic acid and at least one metal salt of an inorganic acid and from 0.00005 wt% to 0.01 wt%, preferably from 0.0001 wt% to 0.005wt%, most preferably from 0.0001 wt% to 0.003wt% abrasive particles, wherein the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfur.

[0014] Preferably, the lubricant composition comprises at most 0.05 wt%, especially at most 0.03 wt%, preferably at most 0.01 wt%, more preferably at most 0.003 wt%, more preferably at most 0.002 wt% and most preferably at most 0.001 wt% of phosphorus. According to a preferred aspect of the present invention the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfated ash.

[0015] Preferably, the average diameter size of abrasive particles ranges from 0.5µm to 20µm, preferably from 1µm to 10µm, most preferably from 1 µm to 3µm.

[0016] Preferably, the abrasive particles have a hardness of at least 7 on the Mohs scale.

[0017] Preferably, the abrasive particles comprise carbonates, nitrides, carbides and/ or oxides of elements of boron, carbon and/ or alkaline earth metal groups.

[0018] Preferably, the viscosity index improver is a polymer having a number average molecular weight ranging from 20000 to 500000 g/mol.

[0019] Preferably, the lubricant composition comprises a shear stability index of less than about 100, preferably less than about 65, more preferably less than about 25 measured according to DIN 51350-6 (20 h, tapered roller bearing). Moreover, the viscosity index improver may comprise a polymer on the basis of an olefin and/or a polyalkyl (meth)acrylate polymer. Preferably, the viscosity index improver may comprise dispersing groups. The viscosity index improver preferably comprises a shear stability index of less than about 40%.

[0020] Furthermore, the present invention provides a method for producing a lubricant in accordance with the definitions provided above and below comprising mixing a base oil with a viscosity index improver, at least one metal salt of an organic acid and at least one metal salt of an inorganic acid and from 0.00005 wt% to 0.01 wt%, preferably from 0.0001 wt% to 0.005wt%, most preferably from 0.0001 wt% to 0.003wt% abrasive particles, wherein the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfur.

[0021] In addition thereto, the present invention provides a motor comprising a lubricant in accordance with the definitions provided above and below. Moreover, the present invention provides a gearbox comprising a lubricant in accordance with the definitions provided above and below.

[0022] Furthermore, the present invention provides a lubricant which leads to a reduction in the fuel consumption. The lubricant composition according to the present invention does not comprise essential amounts of phosphorus- nor sulphur -based compounds.

[0023] Moreover, the lubricant composition enables a high cleanliness and low sludge formation. Furthermore, the improvement of oils drain intervals can be achieved. In addition thereto, the lubricant composition enables a prolonged catalyst lifetime.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The invention is based on research work, the aim of which was to show that a certain concentration of abrasive particles accelerate formation of the protective thin metal film. According to the studies, abrasive particles enhance diffusion of metal ions, which are present in lubricant in the form of metal salts, into the crystal lattice of friction surfaces.

[0025] The present invention is focused on a lubricant composition. Here, a lubricant means a substance introduced between moving surfaces to reduce the friction between them, i.e. a lubricant is any kind of a natural or a synthetic motor or transmission oil, or a plastic greasing substance. The compounds of the lubricant composition of the present invention react on frictions surfaces and form a non-oxidising thin metal film on said surfaces, thus reducing mechanical wear and tear of the surfaces the lubricant composition has been applied on. Therefore, the lubricant composition can be classified as a metal-coating composition.

[0026] Base oils that are useful in the practice of the present invention may be selected from natural oils, synthetic oils and mixtures thereof.

[0027] Natural oils include animal oils and vegetable oils (e.g., castor oil, lard oil); liquid petroleum oils and hydro-refined, solvent-treated or acid-treated mineral oils of the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating viscosity derived from coal or shale also serve as useful base oils.

[0028] Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes)); alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl sulfides and derivative, analogs and homologs thereof.

[0029] Preferred base oils include those obtained by producing heavy linear chain paraffins in the Fischer- Tropsch process where hydrogen and carbon monoxide obtained by the gasification process (partial oxidation) of natural gas (methane etc.) are used and then subjecting this material to a catalytic cracking and isomerisation process.

[0030] Such Fischer-Tropsch derived base oils may conveniently be any Fischer-Tropsch derived base oil as disclosed in for example EP-A-776959, EP-A-668342, WO-A-97/21788, WO-A-00/15736, WO-A-00/14188, WO-A-00/14187, WO-A-00/14183, WO-A-00/14179, WO-A-00/08115, WO-A- 99/41332, EP-A-1029029, WO-A-01 /18156 and WO-A-01 /57166.

[0031] Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc., constitute another class of known synthetic oils. These are exemplified by polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, and the alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyiso-propylene glycol ether having a molecular weight of 1000 or diphenyl ether of poly-ethylene glycol having a molecular weight of 1000 to 1500); and mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C₃-C₈ fatty acid esters and C₁₃ Oxo acid diester of tetraethylene glycol.

[0032] Another suitable class of synthetic oils comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic acids) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol). Examples of such esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic acid.

[0033] Esters useful as synthetic oils also include those made from C₅ to C₁₂ monocarboxylic acids and polyols and polyol esters such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.

[0034] Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- or polyaryloxysilicone oils and silicate oils comprise another useful class of synthetic lubricants; such oils include tetraethyl silicate, tetraisopropyl silicate, tetra-(2-ethylhexyl)silicate, tetra-(4-methyl-2-ethylhexyl)silicate, tetra-(p-tert-butyl-phenyl) silicate, hexa-(4-methyl-2-ethylhexyl)disiloxane, poly(methyl)siloxanes and poly(methylphenyl)siloxanes.

[0035] The oil of lubricating viscosity useful in the practice of the present invention may comprise one or more of a Group I Group II, Group III, Group IV or Group V oil or blends of the aforementioned oils. Definitions for the oils as used herein are the same as those found in the American Petroleum Institute (API) publication "Engine Oil Licensing and Certification System", Industry Services Department, Fourteenth Edition, December 1996 , Addendum 1, December 1998. Said publication categorizes oils as follows:

a) Group I oils contain less than 90 percent saturates and/or greater than 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table 1.

b) Group II oils contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table 1. Although not a separate Group recognized by the API, Group II oils having a viscosity index greater than about 110 are often referred to as "Group II+" oils.

c) Group III oils contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 120 using the test methods specified in Table 1.

d) Group IV oils are polyalphaolefins (PAO).

e) Group V oils are all other base stocks not included in Group I, II, III, or IV.

Table 1

Property	Test Method
Saturates	ASTM D2007
Viscosity Index	ASTM D2270
Sulfur	ASTM D4294

[0036] Preferably the volatility of the base oil, as measured by the Noack test (ASTM D5880), is less than or equal to about 40%, such as less than or equal to about 35%, preferably less than or equal to about 32%, such as less than or equal to about 28%, more preferably less than or equal to about 16%. Preferably, the viscosity index (VI) of the base oil is at least 100, preferably at least 110, more preferably greater than 120.

[0037] Base oils, also referred to as oils of lubricating viscosity useful in the context of the present invention may range in viscosity from light distillate mineral oils to heavy lubricating oils such as gasoline engine oils, mineral lubricating oils and heavy duty diesel oils. Generally, the viscosity of the oil ranges from about 2 mm²s^-1 (centistokes) to about 40 mm²s^-1, especially from about 4 mm²s^-1 to about 20 mm²s^-1 as measured at 100°C.

[0038] As well known for those skilled in the art, in order to form a metal film on the metal friction surfaces, the lubricant shall comprise metal ions. In addition, said ions must have higher ionization energy that that of the surface metal ions; i.e. if a friction surface is made of steel, the lubricant must comprise ions of metals having higher ionization energy than Fe. In that case, metal ions present in the lubricant fulfill the vacancies and diffuse inside the frictional surface removing dislocations caused by friction and forming crystals of protective thin metal film on the surface.

[0039] Addition of oil soluble metal salts of inorganic and organic acids to lubricants is crucial for formation of a protective thin metal film on friction surfaces where lubricant was applied. Said metal salts provide metal ions which fulfil the open vacancies and diffuse inside the frictional surface forming a thin metal film. This is a known practise in the art, with a composition disclosed in RU2277579 being an example. The document RU2277579 is expressly incorporated herein by reference for its disclosure regarding metal salts. Furthermore, an additive comprising metal salts useful for the present invention is commercially available under the trademark VALENA®. However, as an essential difference from the prior art, the lubricant composition according to the present invention comprises abrasive particles which enhance diffusion of metal ions, present in the composition in the form of metal salts, into friction surfaces and thus accelerate formation of protective metal film.

[0040] The lubricant composition according to the present invention comprises oil soluble metal salts of inorganic and organic acids and further comprises from 0.00005 wt% to 0.01 wt%, preferably from 0.0001 wt% to 0.005wt%, most preferably from 0.0001 wt% to 0.003wt% abrasive particles.

[0041] When added to friction surfaces, the lubricant composition according to the present invention forms a protective layer at the friction surfaces through physical bonding between the metal ions of the salt and the friction surfaces. The abrasive particles enhance diffusion of metal ions into friction surfaces and thus accelerate formation of protective metal film, as they remove oxide films from the friction surfaces. In other words abrasive particles, by removing oxidized films from the friction surface, they catalyse the build-up of the protective metal film through physical bonding between the metal ions of the salts and the friction surfaces. Oxide films, which typically form on metal surfaces due to air exposure, make the metal more resistant to chemical reactions. With no oxide films on the surfaces the protective metal film forms faster. In addition thereto, the prevention of oxide films improves the wear resistance and lowers the scuffing of the metal surface.

[0042] By abrasive particles it is meant here either naturally occurring or fabricated granular material composed of finely divided hard particles, such as mineral or metal particles. These particles are useful for removing oxide films from the friction surfaces and, hence should have an appropriate hardness. It shall be noted that the exact chemical composition of abrasive particles is of secondary importance; however, the crucial matter is the concentration of abrasive particles in an composition. According to the extensive studies, the optimal concentration of abrasive particles in the composition varies from about 0.00005wt% to about 0.01wt%, where wt% is mass percentage. The optimal concentration depends on factors such as the composition of the lubricant and the additives, the size of abrasive particles, etc. Studies show that when the composition comprises from about 0.0001 wt% to about 0.005wt% of abrasive particles, the protective metal film forms within about 30 seconds from the start of the friction between the lubricated surfaces (i.e. from the moment the lubricated engine or motor starts running). Measurements preformed for similar lubricant compositions without abrasive particles indicate that in these cases the protective metal film forms in about five minutes, which is a considerably longer period.

[0043] In another preferred embodiment of the present invention the average diameter size of abrasive particles ranges from 0.5µm to 20µm, preferably from 1µm to 10µm, most preferably from 1µm to 3µm. The exact chemical composition of abrasive particles may vary, however the average diameter size of the abrasive particles ranges approximately from 0.5µm to 20µm, preferably from 1µm to 10µm, most preferably from 1µm to 3µm. This means that statistically the majority of the abrasive particles has said diameter, however, variations around these values are possible. Therefore, in a lubricant composition one can find the majority of the abrasive particles having a diameter of about 1µm; however, the same lubricant composition may as well comprise abrasive particles having a diameter of about 5µm or 20µm. Similarly, the majority of abrasive particles found in another lubricant composition may have a diameter of about 10µm; however, the same lubricant composition may also comprise abrasive particles having a diameter of about 3µm. Studies show that abrasive particles having a diameter from 0.5µm to 20µm remove oxide films from the friction surfaces most efficiently and thus accelerate protective film formation.

[0044] In another preferred embodiment of the present invention abrasive particles have a hardness of at least 6, more preferably at least 6.5 and especially preferably of at least 7 on the Mohs scale. Therefore, abrasive particles comprise finely divided particles of ceramic materials, minerals, metals and/ or other compounds having a hardness of at least 6, more preferably at least 6.5 and especially preferably of at least 7 7 or more on the Mohs scale. Amongst others, the following minerals have a hardness of at least 7 on the Mohs scale, thus being suitable for use as abrasive particles: quartz, garner, beryl, chrysoberyl, topaz, emerald, spinel, corundum, boron and diamond. In addition, at least the following metals have a hardness of at least 6 on the Mohs scale, thus also being suitable for use as abrasive particles: osmium, steel, tungsten, chromium and titanium with osmium, tungsten, chromium and titanium having a hardness of at least 7 on the Mohs scale. Further, at least the following ceramic materials having a hardness of at least 7 on the Mohs scale can be used as abrasive particles: silicon carbide, tungsten carbide, titanium carbide, rhenium diboride and titanium diboride. According to the preferred embodiment of the present invention, abrasive particles comprise any of the above mentioned ceramic materials, minerals or metals, or mixtures thereof, in a form of a fine powder or a granular mixture.

[0045] In another preferred embodiment of the present invention abrasive particles comprise carbonates, nitrides, carbides and/ or oxides of elements of boron, carbon and/ or alkaline earth metal groups. Here, the boron group is a periodic table group consisting of boron (B), aluminium (Al), gallium (Ga), indium (In), thallium (Tl), and ununtrium (Uut); the carbon group is a periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and ununquadium (Uuq); and alkaline earth metals consist of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Examples of compounds fulfilling the above conditions are, amongst others, silicon dioxide, boron carbide, boron nitride and aluminium dioxide. According to the preferred embodiment of the present invention, abrasive particles comprise any of the above compounds separately, or a mixture thereof, in a form of a fine powder or a granular mixture.

[0046] According to the present invention the oil soluble metal salts of inorganic acid comprise oil soluble metal salts, i. e. chlorides, bromides and/ or iodides of at least one of the following metals: Cu, Co, Pb, Sn, Ni. More preferably, the oil soluble metal salts of inorganic acid comprise CuCl, CuBr, CuJ, CuCl₂, CuBr₂, CoCl₂, CoBr₂, CoJ₂, PbCl₂, PbBr₂, PbJ₂, SnCl₂, SnBr₂, SnJ₂, NiCl₂, NiBr₂ and/or NiJ₂. Copper salts are especially preferred.

[0047] Further, according to the present invention the oil soluble metal salts of organic acid comprises acids comprising carbon atoms and oxygen atoms. Regarding the organic acid salts, copper salts are especially preferred.

[0048] The organic metal salt, preferably the organic copper salt may be blended into the oil as any suitable oil soluble metal compound, preferably copper compound. By oil soluble we mean the compound is oil soluble under normal blending conditions in the oil or additive package. The copper compound may be in the cuprous or cupric form.

[0049] The organic metal salt, preferably the organic copper salt may be added as the metal salt, preferably copper salt of a synthetic or natural carboxylic acid. Examples include C₁₀ to C₁₈ fatty acids such as stearic or palmitic, but unsaturated acids such as oleic or branched carboxylic acids such as napthenic acids of molecular weight from 200 to 500 or synthetic carboxylic acids are preferred because of the improved handling and solubility properties of the resulting metal carboxylates, preferably copper carboxylates.

[0050] Exemplary of useful copper compounds are copper (Cu^I and/or Cu^II) salts of alkenyl succinic acids or anhydrides. The salts themselves may be basic, neutral or acidic.

[0051] Examples of the metal salts of this invention are Cu salts of polyisobutenyl succinic anhydride (hereinafter referred to as Cu-PIBSA), and Cu salts of polyisobutenyl succinic acid. Preferably, the selected metal employed is its divalent form, e.g., Cu²⁺. The preferred substrates are polyalkenyl succinic acids in which the alkenyl group has a number average molecular weight (Mn) greater than 700. The alkenyl group desirably has a Mn from 900 to 1400, and up to 2500, with a Mn of about 950 being most preferred. Especially preferred is polyisobutylene succinic acid (PIBSA). These materials may desirably be dissolved in a solvent, such as a mineral oil, and heated in the presence of a water solution (or slurry) of the metal bearing material. Heating may take place between 70°C and 200°C. Temperatures of 110°C to 140°C are entirely adequate. It may be necessary, depending upon the salt produced, not to allow the reaction to remain at a temperature above about 140°C for an extended period of time, e.g., longer than 5 hours, or decomposition of the salt may occur.

[0052] Preferred metal salts of organic acids comprising organic acids having from 15 to 18 carbon atoms in their molecular formula, such as metal salts of oleic acid CH₃(CH₂)₇CH=CH(CH₂)₇COOH. Preferred examples of a metal salt of organic acids are tin oleate C₃₆H₆₆O₄Sn, copper oleate C₃₆H₆₆O₄Cu, nickel oleate C₃₆H₆₆O₄Ni, lead oleate C₃₆H₆₆O₄Pb and cobalt oleate C₃₆H₆₆O₄Co with copper oleate C₃₆H₆₆O₄Cu being especially preferred. It shall be noted that said oil soluble metal salts of inorganic and organic acids are completely dissolved in the end product, i.e. in a lubricant composition according to the present invention.

[0053] In another preferred embodiment of the present invention the composition comprises, in addition to abrasive particles and oil soluble metal salts of inorganic and organic acids, at least one of the following: an aliphatic alcohol, a succinimide derivative, an aromatic amine, an epoxy resin and/ or a 2-iminosubstituted indoline.

[0054] In another preferred embodiment of the present invention the succinimide derivative comprises S-5A polyalkenyl succinimide, the aromatic amine comprises homotype diphenylamine and the epoxy resin comprises commercially available aliphatic epoxy resin

produced by condensation of epichlorohydrin with glycol.

[0055] The lubricating composition of the present invention comprises at least one viscosity index improver. Preferred viscosity index improvers for lubricating oil compositions advantageously increase the viscosity of the lubricating oil composition at higher temperatures when used in relatively small amounts (have a high thickening efficiency (TE)), provide reduced lubricating oil resistance to cold engine starting (as measured by "CCS" performance) and be resistant to mechanical degradation and reduction in molecular weight in use (have a low shear stability index (SSI)).

[0056] Viscosity index (VI) improvers include polymers based on olefins, such as polyisobutylene, copolymers of ethylene and propylene (OCP) and other hydrogenated isoprene/butadiene copolymers, as well as the partially hydrogenated homopolymers of butadiene and isoprene and star copolymers and hydrogenated isoprene star polymers, polyalkyl (meth)acrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, interpolymers of styrene and acrylic esters, and hydrogenated copolymers of styrene/isoprene and styrene/butadiene. The molecular weight of polymers useful as viscosity index improver in accordance with the present invention can vary over a wide range since polymers having number-average molecular weights (Mn) as low as about 2,000 can affect the viscosity properties of an oleaginous composition. The preferred minimum Mn is about 10,000; the most preferred minimum is about 20,000. The maximum Mn can be as high as about 12,000,000; the preferred maximum is about 1,000,000; the most preferred maximum is about 750,000. An especially preferred range of number-average molecular weight for polymer useful as viscosity index improver in the present invention is from about 15,000 to about 500,000; preferably from about 20,000 to about 250,000; more preferably from about 25,000 to about 150,000. The number average molecular weight for such polymers can be determined by several known techniques. A convenient method for such determination is by size exclusion chromatography (also known as gel permeation chromatography (GPC)) which additionally provides molecular weight distribution information, see W. W. Yau, J.J. Kirkland and D.D. Bly, "Modern Size Exclusion Liquid Chromatography", John Wiley and Sons, New York, 1979.

[0057] The polydispersity index (Mw/Mn)of preferred polymers useful as viscosity index improver in accordance with the present invention is less than about 10, preferably less than about 5, more preferably less than about 4 and most preferably less than about 3 e.g., from 1.05 to 3.5, most preferably from 1.1 to 3. Mw is the weight average molecular weight of the polymer as measured by Gel Permeation Chromatography ("GPC") with a polystyrene standard.

[0058] "Thickening Efficiency" ("TE") is representative of a polymers ability to thicken oil per unit mass and is defined as:


wherein c is polymer concentration (grams of polymer/1 00 grams solution), kν_oil+polymer is kinematic viscosity of the polymer in the reference oil, and kν_oil is kinematic viscosity of the reference oil. The TE is preferably measured at 100 °C.

[0059] The viscosity index improver useful for the present invention preferably has a TE of from about 1.5 to about 4.0, preferably from about 1.6 to about 3.3, more preferably from about 1.7 to about 3.0.

[0060] "Shear Stability Index" ("SSI") measures the ability of polymers used as V.I. improvers in crankcase lubricants to maintain thickening power during use and is indicative of the resistance of a polymer to degradation under service conditions. The higher the SSI, the less stable the polymer, i.e., the more susceptible it is to degradation. SSI is defined as the percentage of polymer-derived viscosity loss and is calculated as follows:


wherein kν_oil is the kinematic viscosity of the base oil, kν_fresh is the kinematic viscosity of the polymer-containing solution before degradation and kν_after is the kinematic viscosity of the polymer-containing solution after degradation. SSI is conventionally determined using ASTM D6278-98 (known as the Kurt-Orban (KO) or DIN bench test). The polymer under test is dissolved in suitable base oil (for example, solvent extracted 150 neutral) to a relative viscosity of 9 to 15 mm²s^-1 (centistokes) at 100 °C and the resulting fluid is pumped through the testing apparatus specified in the ASTM D6278-98 protocol for 30 cycles. As noted above, a 90 cycle shear stability test (ASTM D7109) was approved in 2004.

[0061] The shear stability index (SSI, 30 cycles) according to ASTM D6278-98 of preferred polymers useful as viscosity index improver in accordance with the present invention is preferably less than about 60 %, more preferably less than about 50 %, more preferably less than about 40 %. Preferred ranges are e.g. from about 1 % to about 60 %, preferably from about 2 % to about 50%, more preferably from about 5% to about 40%.

[0062] Polymers based on olefins include monomers consisting of carbon atoms and hydrogen atoms, such as ethylene, propylene, butylene and diene monomers, such as butadiene. Preferably, the polymers based on olefins comprise at least 30 wt%, more preferably at least 50 wt% and most preferably at least 80 wt% repeating units being derived from olefin monomers. Preferred olefin copolymers (or OCP) useful as viscosity index improvers conventionally comprise copolymers of ethylene, propylene and, optionally, a diene. Small polymeric side chains do not exert a substantial viscosity modifying effect in oil. Polymerized propylene has one methyl branch for every two backbone carbon atoms. Ethylene polymer is substantially straight chained. Therefore, at a constant amount of polymer in oil (treat rate), an OCP having a higher ethylene content will display an increased high temperature thickening effect (thickening efficiency, or TE). However, polymer chains having long ethylene sequences have a more crystalline polymer structure.

[0063] Due to their molecular architecture, star polymers are known to provide improved shear stability compared to OCPs. VI improvers that are star polymers made by hydrogenation of anionically polymerized isoprene are commercially available. Anionic polymerization results in a relatively low molecular weight distribution (Mw/Mn). Hydrogenation results in alternating ethylene/propylene units having a composition comparable to a polymer derived from 40 wt.% ethylene and 60 wt.% propylene. These VI improvers provide excellent shear stability, good solubility and excellent cold temperature properties.

[0064] Preferred polymers based on olefins are disclosed in EP0440506, EP1493800 and EP1925657. The documents EP0440506, EP1493800 and EP1925657 are expressly incorporated herein by reference for their disclosure regarding viscosity index improvers based on olefins.

[0065] Polyalkyl (meth)acrylates are based on alkyl (meth)acrylate monomers conventionally comprising 1 to 4000 carbon atoms in the alkyl group of the (meth)acrylates. Preferably, the polyalkyl (meth)acrylates are copolymers of alkyl (meth)acrylate monomers having 1 to 4 carbon atoms in the alkyl group, such as methyl methacrylate, ethyl methacrylate and propyl methacrylate and alkyl (meth)acrylate monomers having 8 to 4000 carbon atoms, preferably 10 to 400 carbon atoms and more preferably 12 to 30 carbon atoms in the alkyl group. Preferred polyalkyl (meth)acrylates are described in the patents US 5,130,359 and US 6,746,993. The documents US 5,130,359 and US 6,746,993 are expressly incorporated herein by reference for their disclosure regarding viscosity index improvers based on polyalkyl (meth)acrylates.

[0066] Preferably, the viscosity index improver may comprise dispersing groups. Dispersing groups including nitrogen-containing and/or oxygen-containing functional groups are well known in the art. Regarding functional groups nitrogen-containing groups are preferred. One trend in the industry has been to use such "multifunctional" VI improvers in lubricants to replace some or all of the dispersant. Nitrogen-containing functional groups can be added to a polymeric VI improver by grafting a nitrogen- or hydroxyl- containing moiety, preferably a nitrogen-containing moiety, onto the polymeric backbone of the VI improver (functionalizing). Processes for the grafting of a nitrogen-containing moiety onto a polymer are known in the art and include, for example, contacting the polymer and nitrogen-containing moiety in the presence of a free radical initiator, either neat, or in the presence of a solvent. The free radical initiator may be generated by shearing (as in an extruder) or heating a free radical initiator precursor, such as hydrogen peroxide. In the context of polyalkyl (meth)acrylate polymers, polymers having functional groups, preferably nitrogen-containing functional groups can be achieved by using comonomers comprising nitrogen-containing groups such as dimethylaminoethyl methacrylate (U.S. Pat. No. 2,737,496 to E. I. Dupont de Nemours and Co.), dimethylaminoethylmethacrylamide (U.S. Pat. No. 4,021,357 to Texaco Inc.) or hydroxyethyl methacrylate (U.S. Pat. No. 3,249,545 to Shell Oil. Co).

[0067] The documents US 2,737,496, US 4,021,357, US 3,249,545, US-B1-6331510, US-B1-6204224, US-B1-6372696 and WO 2008/055976 are expressly incorporated herein by reference for their disclosure regarding multifunctional viscosity index improvers.

[0068] The amount of nitrogen-containing monomer will depend, to some extent, on the nature of the substrate polymer and the level of dispersancy required of the polymer. To impart dispersancy characteristics to copolymers, the amount of nitrogen-containing and/or oxygen-containing monomer is suitably between about 0.4 and about 10 wt. %, preferably from about 0.5 to about 5 wt. %, most preferably from about 0.6 to about 2.2 wt. %, based on the total weight of polymer.

[0069] Methods for grafting nitrogen-containing monomer onto polymer backbones, and suitable nitrogen-containing grafting monomers are known and described, for example, in U.S. Patent No. 5,141,996, WO 98/13443, WO 99/21902, U.S. Patent No. 4,146,489 , U.S. Patent No. 4,292,414 , and U.S. Patent No. 4,506,056. (See also J Polymer Science, Part A: Polymer Chemistry, Vol. 26, 1189-1198 (1988) ; J. Polymer Science, Polymer Letters, Vol. 20, 481-486 (1982) and J. Polymer Science, Polymer Letters, Vol. 21, 23-30 (1983), all to Gaylord and Mehta and Degradation and Crosslinking of Ethylene-Propylene Copolymer Rubber on Reaction with Maleic Anhydride and/or Peroxides; J. Applied Polymer Science, Vol. 33, 2549-2558 (1987) to Gaylord, Mehta and Mehta. The documents US 5,141,996, US 4,146,489, US 4,292,414, US 4,506,056, WO 98/13443 and WO 99/21902 are expressly incorporated herein by reference for their disclosure regarding multifunctional viscosity index improvers.

[0070] The viscosity index improvers can be used as a single polymer or as a mixture of different polymers, for example, a combination of a polymer based on an olefin, such as polyisobutylene, copolymers of ethylene and propylene (OCP) and other hydrogenated isoprene/butadiene copolymers, as well as the partially hydrogenated homopolymers of butadiene and isoprene and/or star copolymers and hydrogenated isoprene star polymers, preferably a copolymer of ethylene and propylene (OCP) with an VI improver comprising polymethacrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, interpolymers of styrene and acrylic esters, and/or hydrogenated copolymers of styrene/isoprene and/or styrene/butadiene. Preferably a mixture of at least one polymer based on olefins, preferably copolymers of ethylene and propylene (OCP) and of at least one polyalkyl (meth)acrylate can be used.

[0071] The lubricating oil composition may preferably contain a VI improver useful for the invention in an amount of from about 0.1 wt. % to about 30 wt.%, preferably from about 0.3 wt. % to about 25 wt.%, more preferably from about 0.4 wt. % to about 15 wt.%, stated as mass percent active ingredient (Al) in the total lubricating oil composition.

[0072] The viscosity index improvers are widely generally sold in the market as commercial products. For example, there are commercial products of VISCOPLEX® (by Evonik Rohmax GmbH) and ACLUBE® (by Sanyo Chemical) as a poly(meth)acrylate reagent. Infineum® V534 and Infineum® V501 available from Infineum USA L.P. and Infineum UK Ltd. are examples of commercially available amorphous OCP. Other examples of commercially available amorphous OCP VI improvers include Lubrizol® 7065 and Lubrizol® 7075 , available from The Lubrizol Corporation; Jilin® 0010 , available from PetroChina Jilin Petrochemical Company; and NDR0135 , available from Dow Elastomers L.L.C. An example of a commercially available star polymer VI improver having an SSI equal to or less than 35 is Infineum® SV200 , available from Infineum USA L.P. and Infineum UK Ltd. Other examples of commercially available star polymer VI improver having an SSI equal to or less than 35 include Infineum® SV250, and Infineum® SV270 , also available from Infineum USA L.P. and Infineum UK Ltd.

[0073] Multifunctional viscosity index improvers are available from Evonik Rohmax GmbH under the trade designations "Acryloid 985", "Viscoplex 6-054", "Viscoplex 6-954" and "Viscoplex 6-565" and from The Lubrizol Corporation under the trade designation "LZ 7720C".

[0074] The present lubricant composition may comprise further additives with the provision that the content of sulfur or phosphorus should be as low as possible. These additives include friction modifiers, anti-foam agents, demulsifiers, dispersants and pour point depressants.

[0075] As anti-foam agents, silicone polymers and/or polymethacrylates are generally used. Demulsifiers which are generally applied are polyalkylene glycol ethers. Preferred friction modifiers are compounds based on poly(meth)acrylates as described in WO-A-2004/087850, WO 2006/105926, WO 2006/007934 and WO 2005/097956. The documents WO-A-2004/087850, WO 2006/105926, WO 2006/007934 and WO 2005/097956 are expressly incorporated herein by reference for their disclosure regarding poly(meth)acrylates useful as friction modifiers.

[0076] Dispersants maintain oil insolubles, resulting from oxidation during use, in suspension in the fluid thus preventing slide glocculation and precipitation or deposition on metal parts. Suitable dispersants include high molecular weight alkyl succinimides, the reaction product of oil-soluble polyisobutylene succinic anhydride with ethylene amines such as tetraethylene pentamine and borated salts thereof.

[0077] The ashless dispersants include the polyalkenyl or borated polyalkenyl succinimide where the alkenyl groups is derived from a C₃-C₄ olefin, especially polyisobutenyl having a number average molecular weight of 700 to 5,000. Other well-known dispersants include ethylene-propylene oligomers with N/O functionalities and oil soluble polyol esters of hydrocarbon substituted succinic anhydride, e.g., polyisobutenyl succinic anhydride, and the oil soluble oxazoline and lactone oxazoline dispersants derived from hydrocarbon substituted succinic anhydride and disubstituted amino alcohols. Lubricating oils preferably contain 0.5 to 5 wt. % of ashless dispersant.

[0078] The pour point improvers include especially polyalkyl (meth)acrylates (PAMA) having 1 to 30 carbon atoms in the alcohol group, C₈ to C₁₈ dialkyl fumarate/vinyl acetate copolymers and chlorinated paraffin-naphthalane condensation products. Lubricating oils preferably contain up to 5 wt. %, more preferably 0.01 to 1.5 wt of pour point improvers. These are widely generally sold in the market as commercial products. For example, there are commercial products of VISCOPLEX® (by Evonik Rohmax GmbH), ACLUBE® (by Sanyo Chemical) and PLEXOL® (by Nippon Acryl) as a poly(meth)acrylate reagent; and commercial products of LUBRAN® (by Toho Chemical) as a chlorinated paraffin-naphthalane condensation product. Preferred are poly(meth)acrylates.

[0079] Compilations of VI improvers and pour point improvers for lubricant oils are also detailed in T. Mang, W. Dresel (eds.): "Lubricants and Lubrication", Wiley-VCH, Weinheim 2001: R. M. Mortier, S. T. Orszulik (eds.): "Chemistry and Technology of Lubricants", Blackie Academic & Professional, London, 2nd ed. 1997; or J. Bartz: "Additive für Schmierstoffe", Expert-Verlag, Renningen-Malmsheim 1994.

[0080] Table 2 shows preferred compositions for lubricants according to the present invention.

Table 2.

	Amount in wt% preferred	Amount in wt% more preferred
base oil	50 to 98.0	60 to 95.0
viscosity index improver	0.1 to 30.0	1 to 20.0
ashless dispersant	0 to 7.0	0.5 to 5
pour point improver	0 to 5.0	0.01 to 1.5
abrasive particles	0.00005 to 0.01	0.00005 to 0.01
metal salt of organic acid	0.1 to 9.0	0.1 to 9.0
metal salt of inorganic acid	0.01 to 2.5	0.01 to 2.5
aliphatic alcohol	0.03 to 5.5	0.03 to 5.5
aromatic amine	0.01 to 2.0	0.01 to 2.0
epoxy resin	0.02 to 1.8	0.02 to 1.8
succinimide derivative	0.02 to 5.0	0.02 to 5.0
2-iminosubstituted indoline	0.005 to 6.0	0.005 to 6.0

[0081] The lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfur. The amount of sulfur in the lubricant composition should be as low as possible in order to improve the environmental acceptability. The amount of sulfur can be determined according to ASTM D4294.

[0082] Preferably, the sulfur content of the lubricant composition is identical or smaller than the sulfur content of the base oil. No sulfur containing additives are needed or added.

[0083] Preferably, the lubricant composition comprises at most 0.05 wt%, especially at most 0.03 wt%, preferably at most 0.01 wt%, more preferably at most 0.003 wt%, more preferably at most 0.002 wt% and most preferably at most 0.001 wt% of phosphorus. The amount of phosphorus in the lubricant composition should be as low as possible in order to improve the environmental acceptability. The amount of phosphorus can be determined according to ASTM D1091.

[0084] Preferably, the phosphorus content of the lubricant composition is identical or smaller than the phosphorus content of the base oil. No phosphorus containing additives are needed or added.

[0085] According to a preferred aspect of the present invention the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfated ash. The amount of sulfated ash in the lubricant composition should be as low as possible in order to improve the environmental acceptability. The amount of sulfated ash can be determined according to ASTM D874.

[0086] Preferably, the sulfated ash of the lubricant composition is identical or smaller than the sulfated ash of the base oil.

[0087] The low amount of sulfur, phosphorus and sulfated ash in the lubricant composition can be obtained by using base oils having low sulfur and low phosphorus content and by omitting sulfur and phosphorus containing additives. It should be noted that prolongation of the lifespan of machines, engines and motors by reducing temperatures of friction surfaces and improving abrasive resistance, thus reducing wear of their moving parts by using the present lubricant composition as mentioned above can surprisingly be improved by omitting conventional sulfur and/or phosphorus containing anti-wear and extreme pressure additives.

[0088] The compositions of this invention are used principally in the formulation of motor oils and in the formulation of crankcase lubricating oils for passenger car and heavy duty diesel engines, and comprise a major amount of an oil of lubricating viscosity, a VI improver, in an amount effective to modify the viscosity index of the lubricating oil, the metal salts and the abrasive particles as described above, and optionally other additives as needed to provide the lubricating oil composition with the required properties.

[0089] In general, the lubricant composition according to the present invention can be manufactured by any techniques known in the field, such as conventional mixing techniques, the different variations thereof being well known for those skilled in the art.

[0090] In a particular aspect of the present invention, preferred lubricant oil compositions have a viscosity index determined to ASTM D 2270 in the range of 100 to 400, more preferably in the range of 125 to 325 and most preferably in the range of 150 to 250.

[0091] Preferred lubricants have a PSSI to DIN 51350-6 (20 h, tapered roller bearing) less than or equal to 100. The PSSI is more preferably less than or equal to 65, especially preferably less than or equal to 25.

[0092] Lubricant oil compositions which are additionally of particular interest are those which preferably have a high-temperature high-shear viscosity HTHS measured at 150°C of at least 2.4 mPas, more preferably at least 2.6 mPas, more preferably at least 2.9 mPas and most preferably at least 3.5 mPas. The high-temperature high-shear viscosity HTHS measured at 100°C is preferably at most 10 mPas, more preferably at most 7 mPas and most preferably at most 5 mPas. The difference between the high-temperature high-shear viscosities HTHS measured at 100°C and 150°C HTHS₁₀₀-HTHS₁₅₀, is preferably at most 4 mPas, more preferably at most 3.3 mPas and most preferably at most 2.5 mPas. The ratio of high-temperature high-shear viscosity at 100°C HTHS₁₀₀ to high-temperature high-shear viscosity at 150°C HTHS₁₅₀, HTHS₁₀₀/ HTHS₁₅₀, is preferably at most 2.0, more preferably at most 1.9. The high-temperature high-shear viscosity HTHS can be measured at the particular temperature to ASTM D4683.

[0093] The lubricant composition of the present invention can be preferably designed to meet the requirements of the SAE classifications as specified in SAE J300. E.g. the requirements of the viscosity grades 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60 (single-grade) and 0W-40, 10W-30, 10W-60, 15W-40, 20W-20 and 20W-50 (multi-grade) could be adjusted. In addition thereto, also the specification for transmission oils can be achieved such as defined, e. g. in the SAE classifications 75W-90 or 80W-90.

[0094] According to a special aspect of the present invention, the lubricant composition stays in grade after a shear stability test according to CEC L-014-93 at 100°C after 30 cycles.

[0095] The lubricant composition of the present invention provides an excellent protection against wear and scuffing. Preferably, the tests according to CEC L-99-08 (OM646LA) are passed providing a cam wear outlet of at most 120 µm, a cam wear inlet of at most 100 µm and a cylinder wear of at most 5 µm.

[0096] Furthermore, the lubricant composition can be preferably designed to meet the requirements of the API classifications of the American Petroleum Institute. E.g. the requirements of the diesel engine service designations CJ-4, CI-4, CH-4, CG-4, CF-2, and CF can be achieved. Regarding the gasoline engines, the specifications API-SJ, API-SL und API-SM can be realized. Regarding gear oils, the specifications of API-GL1, API-GL2, API-GL3, API-GL4 and API-GL5 can be achieved.

[0097] In addition thereto, the lubricant composition can be designed to meet the requirements of the ACEA (Association des Constructeurs Européens d'Automobiles) regarding all oil types specified, e. g. ACEA Class A1/B1_-10, ACEA Class A3/B3_-10, ACEA Class A3/B4_-10, ACEA Class A5/B5_-10, ACEA Class C1_-10, ACEA Class C2_-10, ACEA Class C3_-10, ACEA Class C4_-10, ACEA Class E4_-08, ACEA Class E6_-08 and ACEA Class E7_-08 and ACEA Class E9_-08 according to the ACEA specifications 2010 as allowable from 22^nd December 2010.

[0098] The present lubricants can be used especially as a transmission oil, motor oil or hydraulic oil. Surprising advantages can be achieved especially when the present lubricants are used in manual, automated manual, double clutch or direct-shift gearboxes (DSG), automatic and continuous variable transmissions (CVCs). In addition, the present lubricants can be used especially in transfer cases and axle or differential gearings.

[0099] A motor comprising a lubricant of the present composition usually comprises a lubricant having a low amount of viscosity index improver. Preferably the lubricating oil composition useful as motor oil may contain the VI improver of the invention in an amount of from about 0.1 wt. % to about 2.5 wt.%, preferably from about 0.3 wt. % to about 1.5 wt.%, more preferably from about 0.4 wt. % to about 1.3 wt.%, stated as mass percent active ingredient (Al) in the total lubricating oil composition.

[0100] A preferred motor comprises a catalyst system for cleaning the exhaust gases. Preferably the motor fulfills the exhaust emission standard for modern diesel or gasoline motors such as Euro 4, Euro 5 and Euro 6 in the European Union and Tier 1 and Tier 2 in the United States of America.

[0101] The present invention further provides a method of lubricating an internal combustion engine, in particular a diesel engine, gasoline engine and a gas-fuelled engine, with a lubricating composition as hereinbefore described. This includes engines equipped with exhaust gas recirculation (EGR).

[0102] The lubricant composition of the present invention exhibits surprisingly good piston cleanliness, wear protection and anticorrosion performance in EGR engines.

[0103] In particular, lubricant composition according to the present invention surprisingly pass the API Cl-4 requirements (ASTM D4485-03a; Standard Specification for Performance of Engine Oils) despite having the afore-mentioned sulphur content, phosphorus content and sulfated ash content.

[0104] Furthermore, the lubricating oil composition of the present invention exhibits surprisingly good piston cleanliness, wear protection and anticorrosion performance in DaimlerChrysler and MAN engines. In particular, lubricant compositions according to the present invention can be preferably designed to pass the requirements of ACEA E4, DC 228.5 and MAN M3277 performance specifications.

[0105] A gearbox comprising a lubricant of the present composition usually comprises a lubricant having a high amount of viscosity index improver. Preferably the lubricating oil composition useful as gearbox oil may contain the VI improver of the invention in an amount of from about 1 wt. % to about 30 wt.%, preferably from about 2 wt. % to about 25 wt.%, more preferably from about 3 wt. % to about 15 wt.%, stated as mass percent active ingredient (AI) in the total lubricating oil composition.

Claims

1. A lubricant composition comprising a base oil component, at least one viscosity index improver and at least one metal salt, characterized in that the lubricant composition comprises at least one metal salt of an organic acid and at least one metal salt of an inorganic acid and from 0.00005 wt% to 0.01 wt%, preferably from 0.0001 wt% to 0.005wt%, most preferably from 0.0001 wt% to 0.003wt% abrasive particles, wherein the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfur.

2. Lubricant composition according to claim 1, characterized in that the lubricant composition comprises at most 0.05 wt%, especially at most 0.03 wt%, preferably at most 0.01 wt%, more preferably at most 0.003 wt%, more preferably at most 0.002 wt% and most preferably at most 0.001 wt% of phosphorus.

3. Lubricant composition according to any of claims 1 to 2, characterized in that the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfated ash.

4. Lubricant composition according to any of claims 1 to 3, characterized in that the average diameter size of abrasive particles ranges from 0.5µm to 20µm, preferably from 1µm to 10µm, most preferably from 1 µm to 3µm.

5. Lubricant composition according to any of claims 1 to 4, characterized in that abrasive particles have a hardness of at least 7 on the Mohs scale.

6. Lubricant composition according to any of claims 1 to 5, characterized in that abrasive particles comprise carbonates, nitrides, carbides and/ or oxides of elements of boron, carbon and/ or alkaline earth metal groups.

7. Lubricant composition according to any of claims 1 to 6, characterized in that the viscosity index improver is a polymer having a number average molecular weight ranging from 20000 to 500000 g/mol.

8. Lubricant composition according to any of claims 1 to 7, characterized in that the lubricant composition comprises a shear stability index of less than about 100, preferably less than about 65, more preferably less than about 25 measured according to DIN 51350-6 (20 h, tapered roller bearing).

9. Lubricant composition according to any of claims 1 to 8, characterized in that the viscosity index improver comprises a polymer on the basis of an olefin.

10. Lubricant composition according to any of claims 1 to 9, characterized in that the viscosity index improver comprises a polyalkyl (meth)acrylate polymer.

11. Lubricant composition according to any of claims 1 to 10, characterized in that the viscosity index improver comprises dispersing groups.

12. Lubricant composition according to any of claims 1 to 11, characterized in that the viscosity index improver comprises a shear stability index of less than about 40%.

13. A method for producing a lubricant composition according to any of claims 1 to 12 comprising mixing a base oil with a viscosity index improver, at least one metal salt of an organic acid and at least one metal salt of an inorganic acid and from 0.00005 wt% to 0.01 wt%, preferably from 0.0001 wt% to 0.005wt%, most preferably from 0.0001 wt% to 0.003wt% abrasive particles, wherein the lubricant composition comprises at most 0.2 wt%, especially at most 0.1 wt%, preferably at most 0.05 wt%, more preferably at most 0.03 wt%, more preferably at most 0.02 wt% and most preferably at most 0.01 wt% of sulfur.

14. A motor comprising a lubricant according to any of claims 1 to 12.

15. A gearbox comprising a lubricant according to any of claims 1 to 12.