ES2954843T3 - Lubricating composition - Google Patents

Abstract

A lubricant composition is prepared having a base oil composition and an additive composition comprising a molybdenum dialkyldithiocarbamate and an organic friction modifier such as an oil-soluble mono, di or triglyceride of at least one hydroxypolycarboxylic acid, or a derivative of the same. can, especially when used in combination with a base oil composition of a functionally modified poly-alpha-olefin (e.g., alpha-olefin and ester copolymer), a poly-alpha-olefin and optionally an additive carrier such as a rented naphthalene. The lubricant composition of the present invention finds particular application as a lubricant composition for robotics and robotic gearboxes, industrial gears and wind turbine gears and especially for gearboxes having a rolling element (such as a spherical bearing or a cylindrical bearing ). Provides greater longevity, good compatibility with elastomers and good anti-wear properties. Embodiments of the invention also demonstrate excellent protection against leaks and sludge. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Lubricating composition

[0001] The present invention relates to a lubricating oil composition and a method of lubricating a gearbox or operating an apparatus having a gearbox, where the gearbox comprises a rolling element.

BACKGROUND

[0002] Industrial manufacturing facilities and procedures use apparatus and robots for manufacturing procedures, which have gearboxes that require lubrication. Depending on the manufacturer's design requirements, gearboxes can be lubricated with grease or lubricating oils. For oil-lubricated gearboxes, the demands for lubricants are particular and include sludge-free and leak-free performance over an extended period of time with a target of 20,000 hours, particularly in robotic gearboxes and especially in the automotive sector.

[0003] Commercial robotic gearbox oil offerings tend to suffer from a number of disadvantages, meaning that they tend to not be able to meet the industry requirement of 20,000 hours of uninterrupted operation.

[0004] Such disadvantages include poor elastomer compatibility resulting in degradation of the elastomer that forms seals in gearboxes, as well as characteristics that result in wear of metal gear components. This can result in gearbox oil leaks which, in many robotic applications, are problematic and in automotive manufacturing, especially when cleanliness is critical, can be considered catastrophic failures.

[0005] While mineral oil-based lubricant formulations are used, there is increasing demand for synthetic oil-based formulations to meet longevity requirements. Synthetic oils that have a poly-alpha-olefin base oil have the potential for greater longevity, but suffer from poorer solubility of additive components.

[0006] Gearboxes for manufacturing appliances such as robots, as well as for wind turbines, also have rolling elements within them that have a different set of wear and performance requirements than other gearboxes.

[0007] WO 2016/124293 A1 describes the use of an oil-soluble mono-, di- or tri-glyceride of at least one hydroxypolycarboxylic acid, or a derivative thereof, as a camshaft antiwear additive in a composition non-aqueous lubricant and/or in a fuel composition.

[0008] Therefore, there is a need for a synthetic gear oil formulation that provides stability and longevity, is compatible with sealing elastomers, has effective anti-wear properties, particularly in systems with rolling elements, is not prone to formation of sludge and have excellent performance characteristics. The present inventor has developed compositions that address one or more of the above problems.

SUMMARY OF THE INVENTION

[0009] According to a first aspect of the invention, there is provided a lubricant composition suitable for use as a gearbox lubricant comprising a rolling element, comprising: a base oil composition of lubricating viscosity; and an additive composition comprising a molybdenum dialkyldithiocarbamate and an organic friction modifier selected from an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof, composition lubricant having no more than 0.1% by weight of molybdenum dithiophosphate.

[0010] Also described in the present invention, but not encompassed within the present claims, is an additive composition for use in a lubricant composition defined above, the additive composition comprising a molybdenum dialkyldithiocarbamate and a friction modifier organic such as an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or a derivative thereof.

[0011] In a lubricant composition defined above, the base oil composition may comprise a functionally modified polyalpha-olefin, a polyalpha-olefin and optionally an additive carrier.

[0012] In a second aspect of the invention, there is provided a synthetic gear oil composition suitable for use as a gearbox lubricant comprising a rolling element, comprising: a base oil composition comprising a modified poly alpha olefin; and an additive composition comprising a molybdenum dialkyldithiocarbamate and an organic friction modifier selected from an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or ester derivative thereof.

[0013] In a third aspect of the invention, there is provided a use of a gear oil or lubricant composition as defined above as a lubricant for gearboxes comprising a rolling element.

[0014] The present invention describes, but is not included within the present claims, a kit for the manufacture of a lubricant, the kit comprises a base oil composition optionally as defined above, an additive package or concentrate of additives optionally having the additive composition as defined above.

[0015] In a fourth aspect of the invention, a method is provided for lubricating a gearbox comprising a rolling element, the method comprising supplying a gearbox comprising a rolling element with an oil of lubricating viscosity having the composition lubricant as defined above.

[0016] In a fifth aspect of the invention, a method is provided for operating an apparatus having a gearbox comprising a rolling element, the method comprising supplying the gearbox with a lubricating oil of lubricating viscosity having a composition as defined above.

DETAILED DESCRIPTION

[0017] The invention, according to a first aspect, relates to a lubricant composition suitable for use as a lubricant for gearboxes comprising a rolling element. The lubricant composition comprises a base oil composition and an additive composition. The base oil composition should be such that it provides a lubricating viscosity or the lubricating viscosity once the additive composition is added. The base oil composition constitutes the majority of the lubricant composition, by which is meant more than 50% by weight. The additive composition comprises a molybdenum dialkyldithiocarbamate and an organic friction modifier that is an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof.

[0018] The lubricant composition of the present invention finds particular application as a lubricant composition for robotic and robotic gearboxes, industrial gears and wind turbine gears and especially for gearboxes having a rolling element (such as a spherical bearing or a cylindrical bearing). The present invention addresses a particular problem related to lubricants in such applications, in particular the need for longevity, good elastomer compatibility and good anti-wear properties. Embodiments of the invention also demonstrate excellent protection against leaks and sludge.

[0019] Any suitable molybdenum dialkyldithiocarbamate (including dinuclear and trinuclear molybdenum species) can be used.

[0020] The molybdenum dialkyldithiocarbamate may be provided in an amount, in terms of molybdenum, of 100 to 5,000 ppm, preferably 500 to 3,000 ppm and more preferably 750 to 1,500 ppm. In one embodiment, the molybdenum dialkyldithiocarbamate is provided in the lubricant composition in an amount, in terms of molybdenum, of 800 to 1,300 ppm. In a particular embodiment, a molybdenum dialkyldithiocarbamate may be provided in an amount of 0.1 to 5% by weight of the lubricant composition, and preferably in an amount of 0.5 to 3% by weight of the lubricant compositions and more preferably, in certain compositions from 0.75 to 1.5% by weight of the lubricant composition.

[0021] The molybdenum dialkyldithiocarbamate may be provided in the lubricant composition in an amount, in terms of molybdenum, of 100 to 5,000 ppm, preferably 500 to 3,000 ppm and more preferably 750 to 1,500 ppm. In one embodiment, the molybdenum dialkyldithiocarbamate is provided in the lubricant composition in an amount, in terms of molybdenum, of 800 to 1,300 ppm. The organic friction modifier may be a metal-free organic friction modifier. Preferably, the organic friction modifier is free of sulfur and/or phosphorus. Suitable organic friction modifiers may include, but are not limited to, imidazolines, amides, amines, succinimides, alkoxylated amines, alkoxylated ether amines, amine oxides, amidoamines, nitriles, imines, amino guanidines, alkanolamides, glycerol esters and olefins, sunflower oil and other vegetable or animal oils of natural origin, dicarboxylic acid esters, esters or partial esters of a polyol and one or more aliphatic or aromatic carboxylic acids, and the like. The organic friction modifier used in the compositions of the present invention may comprise one or a combination of organic friction modifiers defined in this invention.

[0022] Suitable organic friction modifiers may contain hydrocarbyl groups which are selected from straight chain, branched chain or aromatic hydrocarbyl groups or mixtures thereof, and may be saturated or unsaturated. Hydrocarbyl groups may be composed of carbon and hydrogen or heteroatoms such as nitrogen or oxygen. Hydrocarbyl groups can range from about 12 to about 25 carbon atoms. In some embodiments, the organic friction modifier may be a long chain fatty acid ester. In one embodiment, the long chain fatty acid ester may be a monoester, or a diester, or a (tri)glyceride. The organic friction modifier may be a long chain fatty amide, a long chain fatty ester, a long chain fatty epoxide derivative, or a long chain imidazoline.

[0023] Other suitable organic friction modifiers may include organic, ashless (metal-free), nitrogen-free friction modifiers. Such organic friction modifiers may include esters formed by reacting carboxylic acids and anhydrides with alkanols and generally include a polar terminal group (e.g., carboxyl or hydroxyl) covalently linked to an oleophilic hydrocarbon chain. An example of a nitrogen-free and ashless organic friction modifier is generally known as glycerol monooleate (GMO) which may contain mono-, di-, and triesters of oleic acid. Other suitable friction modifiers are described in US 6,723,685.

[0024] Suitable organic friction modifiers may be amine organic friction modifiers including amines or polyamines. Such compounds may have hydrocarbyl groups that are linear, saturated or unsaturated, or a mixture thereof and may contain from about 12 to about 25 carbon atoms. Other examples of suitable organic friction modifiers include alkoxylated amines and alkoxylated ether amines. Such compounds may have hydrocarbyl groups that are linear, saturated, unsaturated or a mixture thereof. They can contain from about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ether ethoxylated amines. The amines and amides can be used as such or in the form of an adduct or reaction product with a boron compound such as a boric oxide, boron halide, metaborate, boric acid or a mono-, di- or tri-borate. I rent. Other suitable organic friction modifiers are described in US 6,300,291.

[0025] Preferably, the organic friction modifier may be present in an amount of up to about 10% by weight of the lubricant composition, preferably up to about 5% by weight.

Preferably, the organic friction modifier is present in an amount of about 0.1% by weight to about 4% by weight and more preferably up to about 1% by weight of the lubricant composition.

[0026] The organic friction modifier may comprise an ashless, nitrogen-free organic friction modifier and is preferably glycerol monooleate (GMO). According to this embodiment, the lubricant composition and the additive composition comprise molybdenum dialkyldithiocarbamate and GMO, preferably in the amounts mentioned above.

[0027] In another particular embodiment, the organic friction modifier may further comprise fatty acid amide having about 12 to about 25 carbon atoms and preferably is oleylamide. According to this embodiment, the lubricant composition and the additive composition comprise the molybdenum dialkyldithiocarbamate and the oleylamide, preferably in the amounts mentioned above.

[0028] According to the present invention, the organic friction modifier is and/or the lubricant composition and the additive composition comprise an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or a ether or an ester derivative thereof.

[0029] The lubricant composition of one aspect of the invention comprises a base oil composition of lubricating viscosity; and an additive composition comprising a molybdenum dialkyldithiocarbamate and an oil-soluble mono, di- or tri-glyceride of at least one hydroxyl polycarboxylic acid, or an ether or an ester derivative thereof.

[0030] The present invention describes an additive composition for use in a lubricant composition defined above, comprising a molybdenum dialkyldithiocarbamate and an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof.

[0031] The oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or ester derivative thereof may be provided in an amount of up to 5% by weight of the lubricant composition, preferably 0.1 to 2.5% by weight of the lubricant composition, more preferably 0.25 to 1% by weight of the lubricant composition.

[0032] In one embodiment, the oil-soluble mono-, di- or tri-glyceride of at least one acid hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof is provided in a weight percentage ratio with respect to molybdenum dialkyldithiocarbamate in the range of 1:3 to 3:1, more preferably 1:3 to 1:1, even more preferably in the range 1:2 to 2:3.

[0033] The additive composition makes it possible to produce a lubricant composition that has excellent longevity and provides a high performance oil. The present composition allows this longevity and performance to be achieved with very little or reduced content of molybdenum dialkyldithiophosphate or without molybdenum dialkyldithiophosphate. The composition comprises no more than 0.1% molybdenum dialkyldithiophosphate, even more preferably no more than 0.05% molybdenum dialkyldithiophosphate and most preferably the additive composition is absent of molybdenum dialkyldithiophosphate.

[0034] In a preferred embodiment, the lubricant composition and the additive composition further comprise, in addition to the oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof described above, a long chain fatty amide, and more preferably comprises oleylamide, which may optionally be in the amount of up to 1% by weight of the lubricant composition, preferably in the amount of up to 0.5% by weight of the composition lubricant and more preferably in the amount of 0.05 to 0.25% by weight of the lubricant composition. Optionally, the oleylamide may be provided in a weight percent ratio with respect to the oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof in the range of 1:10 to 1:1, more preferably 1:6 to 1:4 and most preferably about 1:5.

[0035] The lubricant composition and the additive composition may further comprise additional additive components, which may include other antiwear additives (but preferably not an organometallic dithiophosphate antiwear additive, especially not zinc- or molybdenum-based organometallic dithiophosphate antiwear additives), dispersants , viscosity modifiers, dispersants, detergents, corrosion inhibitors, antioxidants, antifoaming agents or other additives. Said additional additive components further constitute no more than 5% and more preferably no more than 3% by weight of the lubricant composition.

[0036] In a particular embodiment, no additional dispersing additives are used in the composition of the invention.

[0037] The additive composition may constitute a proportion of the lubricant composition of up to 20% by weight, more preferably up to 10% by weight and more preferably between 2.5 and 7.5% by weight, for For example, from 3% to 6% by weight.

[0038] As used in this invention, an additive concentrate comprises an additive composition and an additive carrier which may typically be a polar base oil and preferably comprises part of a base oil composition. Typically, an additive concentrate provides a stable concentrate that can be converted to a lubricant composition by the addition of appropriate base oils.

[0039] An additive composition, as used in this invention, comprises components other than a base oil composition.

[0040] A lubricant composition having an additive composition as defined above has improved properties useful in gear oils, especially for robotic gears and gears having a rolling element, such as low wear, reduced sludge formation. These properties reduce the risk of catastrophic failure and allow the lubricant composition to meet the longevity requirements of these applications. Therefore, one aspect of the invention relates to the use of a lubricant composition as defined above for gearboxes having a rolling element, especially robot gearboxes or wind turbine gears.

[0041] Described in the present invention, but not part of the present invention, is an additive package for subsequent mixing with a base oil composition or base material to produce the lubricant composition locally. Optionally, the additive package may be provided as a concentrate, which may comprise a portion of the base oil composition to be used, as defined above, or a base oil component base material, such as, for example , a rented naphthalene. An additive concentrate may comprise, for example, the composition of additives in a weight percentage ratio in the range of 1:5 to 5:1, preferably 1:2 to 3:1, more preferably 1:1 to 1:2 for subsequent dilution to the desired amount in a lubricant composition for use.

[0042] Molybdenum dialkyldithiocarbamate (MoDTC) may be any suitable MoDTC. For example, it may be a Formula 1 compound below:

where R1 to R4 indicate alkyl groups and X1 to X4 each indicate a sulfur atom or an oxygen atom.

[0043] Preferably, the MoDTC is a compound of Formula 2 below:

where R1 to R4 indicate alkyl groups.

[0044] The alkyl groups R1 to R4 in the molybdenum dialkyldithiocarbamates of Formula 1 and Formula 2 are preferably each independently lipophilic groups of 1 to 30 carbons, and it is preferable that at least one or two of these four lipophilic groups is a group secondary lipophilic. Preferably, the alkyl groups R1 to R4 are secondary branched lipophilic groups C8 to C13. The molybdenum dialkyldithiocarbamate may be provided in the lubricant composition in an amount, in terms of molybdenum, of 100 to 5,000 ppm, preferably 500 to 3,000 ppm and more preferably 750 to 1,500 ppm. In one embodiment, the molybdenum dialkyldithiocarbamate is provided in the lubricant composition in an amount, in terms of molybdenum, of 800 to 1,300 ppm.

[0045] A molybdenum dialkyldithiocarbamate used according to the present invention may preferably have an elemental analysis value for molybdenum of 9.5 to 10.5% by mass.

[0046] In an embodiment where the molybdenum dialkyldithiocarbamate has an elemental analysis value for molybdenum of 10% by mass, the molybdenum dialkyldithiocarbamate may be provided in an amount of 0.1 to 5% by weight of the lubricant composition, and preferably in an amount of 0.5 to 3% by weight of the lubricant compositions and more preferably, in certain compositions of 0.75 to 1.5% by weight of the lubricant composition.

[0047] The content of molybdenum dialkyldithiocarbamate in a lubricating oil composition can be determined by carrying out elemental analysis using an ICP (inductively coupled plasma atomic emission spectroscopy, hereinafter sometimes referred to as ICP) analysis apparatus. The amount of molybdenum can also be measured by the ICP procedure.

[0048] The weight % amounts of molybdenum dialkyldithiocarbamates and the weight ratios of other components to molybdenum dialkyldithiocarbamates as used in the present invention are based on molybdenum dialkyldithiocarbamate compounds (i.e., molybdenum dialkyldithiocarbamate compound compositions). molybdenum) that have a molybdenum content of 10% by weight. Therefore, when using molybdenum dialkyldithiocarbamate compositions having a different weight % content of molybdenum, said values are adapted accordingly.

[0049] As mentioned above, combinations of organic friction modifiers can be used.

[0050] The organic friction modifier is or comprises an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or ester derivative thereof.

[0051] Any suitable oil-soluble mono-, di- or tri-glyceride of at least one hydroxyl polycarboxylic acid, or an ether or ester derivative thereof, may be used.

[0052] Preferably, the hydroxypolycarboxylic acid has at least one hydroxy group or derivative (e.g., ether or ester) thereof, which is in an alpha position with respect to a carboxylic moiety.

Each hydroxypolycarboxylic acid can independently have from 4 to 22 carbon atoms, for example, from 4 to 15 carbon atoms. The oil-soluble mono-, di- or triglyceride of at least one hydroxypolycarboxylic acid or derivative thereof may suitably have from 16 to 80 carbon atoms. The number of carbon atoms in the glyceride can affect its solubility in lubricating viscosity oil and/or in liquid fuel.

[0053] By oil soluble it is meant that the glyceride is soluble in an oil of lubricating viscosity in a friction modifying and/or antiwear amount, for example, in an amount by weight of at least 200 ppm in an oil of viscosity lubricant. The solubility can be determined at room temperature, for example at 20 °C. Preferably, the oil-soluble glyceride is soluble at 0°C. Solubility can be determined at atmospheric pressure.

[0054] Suitable hydroxypolycarboxylic acids include: citric acid (also sometimes called 3-carboxy-3-hydroxypentanedioic acid; 2-hydroxypropane-1,2,3-tricarboxylic acid; or 3-hydroxypentanedioic-3-carboxylic acid); tartaric acid (also sometimes called 2,3-dihydroxybutanedioic acid; or 2,3-dihydroxysuccinic acid); malic acid (also sometimes called hydroxybutanedioic acid); monohydroxytrimesic acid; and hydrogenated monohydroxytrimesic acid (sometimes also called 1,3,5-tricarboxy, 2-hydroxycyclohexane).

[0055] The oil-soluble mono-, di- or tri-glyceride of at least one hydroxypolycarboxylic acid, or an ether or ester derivative thereof may be a di- or tri-glyceride which is a glyceride of at least one hydroxypolycarboxylic acid and at least one second carboxylic acid that is a saturated, monounsaturated or polyunsaturated, branched or linear monocarboxylic or polycarboxylic acid, having from 4 to 22 carbon atoms, or a derivative thereof.

[0056] The second carboxylic acid may be saturated, monounsaturated or polyunsaturated. Suitably, the second carboxylic acid is unsaturated. The second carboxylic acid can be branched or linear. The second carboxylic acid may be monocarboxylic acid or polycarboxylic acid. If the second carboxylic acid is a polycarboxylic acid, the glyceride derivative may be an ester of the second carboxylic acid group.

[0057] Suitable second saturated carboxylic acids include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid. Suitable second unsaturated carboxylic acids include oleic acid, linoleic acid, linolenic acid, myristoleic acid, palmitoleic acid, sapienic acid, eracic acid (also known as cis-13-docosenoic acid) and brasidic acid.

[0058] Preferably, the glyceride is a glyceride of citric acid and oleic acid, a glyceride of citric acid and linoleic acid or a mixture thereof.

[0059] The mono-, di- or tri-glyceride of at least one hydroxypolycarboxylic acid or derivative thereof may be represented by Formula 3:

where RO, OR' and OR" independently represent:- OH; a saturated, monounsaturated or polyunsaturated, branched or linear monocarboxylic or polycarboxylic group, having from 4 to 22 carbon atoms or an ether or an ester thereof; a residue of hydroxypolycarboxylic acid or an ether and/or ester thereof, provided that at least one of RO, OR' and OR" is a hydroxypolycarboxylic acid moiety or an ether and/or ester thereof.

[0060] Preferably, in Formula 3, at least one of RO, OR' and OR" is a hydroxypolycarboxylic acid moiety or an ether and/or ester thereof and at least one of RO, OR' and OR" is a saturated, monounsaturated or polyunsaturated, branched or linear, monocarboxylic or polycarboxylic group having from 4 to 22 carbon atoms or an ester thereof.

[0061] Preferably, in Formula 3, the acid of the hydroxypolycarboxylic moiety has at least one hydroxy group or derivative (e.g., ether or ester) thereof that is in an alpha position with respect to a carboxylic moiety.

[0062] In Formula 3, each hydroxypolycarboxylic moiety can independently have from 4 to 22 carbon atoms. In formula 3, the hydroxypolycarboxylic moiety may be derived from acids including, for example, citric acid, tartaric acid, malic acid, monohydroxytrimesic acid and hydrogenated monohydroxytrimesic acid.

[0063] In Formula 3, when present, each saturated, branched or linear, monocarboxylic or polycarboxylic group having 4 to 22 carbon atoms or an ester thereof may be derived from saturated carboxylic acids or their halide equivalents. Suitable saturated carboxylic acids include, for example, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid. In Formula 3, when present, each monounsaturated monocarboxylic or polycarboxylic group or polyunsaturated, branched or linear, having 4 to 22 carbon atoms or an ester thereof may be derived from unsaturated carboxylic acids or their halide equivalents. Suitable monounsaturated acids include, for example, oleic acid, myristoleic acid, palmitoleic acid, sapienic acid, erucic acid and brasidic acid. Suitable polyunsaturated acids include, for example, linoleic acid and linolenic acid.

[0064] The glyceride may be a glyceride of at least one hydroxypolycarboxylic acid and a saturated C4 to C22 polycarboxylic acid, or an ether or an ester derivative thereof. The polycarboxylic acid can be branched or linear. The glyceride may be a glyceride of at least one hydroxypolycarboxylic acid and a C4 to C22 monounsaturated or polyunsaturated polycarboxylic acid, or an ether or an ester derivative thereof. The polycarboxylic acid can be branched or linear. The glyceride may be a glyceride of at least one hydroxypolycarboxylic acid and a saturated C4 to C22 monocarboxylic acid, or an ether or an ester derivative thereof. The monocarboxylic acid can be branched or linear. Suitable saturated C16 monocarboxylic acids include palmitic acid. Suitable saturated C18 monocarboxylic acids include stearic acid. The glyceride may be a glyceride of at least one hydroxypolycarboxylic acid and a monounsaturated or polyunsaturated C4 to C22 monocarboxylic acid, or an ether or an ester derivative thereof. The unsaturated monocarboxylic acid can be branched or linear. The glyceride may be a glyceride of at least one hydroxypolycarboxylic acid and one C18 unsaturated monocarboxylic acid, or an ether or an ester derivative thereof. The monocarboxylic acid can be branched or linear. Suitable hydroxypolycarboxylic acids include citric acid. The glyceride additive may be a glyceride of citric acid and a C18 unsaturated monocarboxylic acid, or an ether or an ester derivative thereof. Suitable C18 unsaturated monocarboxylic acids include oleic acid and linoleic acid.

[0065] The glyceride may be a citric acid ester of a monoglyceride of a saturated, monounsaturated or polyunsaturated, branched or linear, monocarboxylic or polycarboxylic C4 to C22 carboxylic acid, suitably a C16 or C18 carboxylic acid, for example, palmitic acid, stearic acid, oleic acid or linoleic acid. The glyceride may be a citric acid ester of monoglyceride made from vegetable oil, for example, sunflower and/or palm oil. The glyceride may be a citric acid ester of monoglyceride made from edible and refined sunflower and palm-based oil. Preferably, the glyceride is a glyceride of citric acid and oleic acid, a glyceride of citric acid and linoleic acid or a mixture thereof. A suitable source of citric acid glycerides with oleic acid and/or linoleic acid is GRINSTED CITREM SP70 (Trade Mark) which is available from Danisco DuPont. GRINSTED CITREM SP70 is believed to be a monoglyceride citric acid ester made from refined edible sunflower and palm oil. GRINSTED CITREM SP70 is also believed to comprise at least one diglyceride having Formula 4:

where -Y- represents a C16 hydrocarbyl moiety that is mono- or diunsaturated.

[0066] Therefore, diglycerides having Formula 4 include a glyceride of citric acid and oleic acid and a glyceride of citric acid and linoleic acid. This corresponds to a structure of Formula 3 where (i) RO represents a carboxyl group having 18 carbon atoms, which can be derived from oleic acid and/or linoleic acid, (ii) OR' represents a hydroxyl moiety and (iii) OR " represents a hydroxypolycarboxylic acid moiety, which can be derived from citric acid.

[0067] The glyceride may be an ester of citric acid with a partial glyceride, for example, mono- or diglyceride or mixtures thereof, which have free hydroxyl groups. Suitable partial glycerides include those derived from fatty acids with 12 to 18 carbon atoms, including, for example, those derived from coconut oil fatty acids and palm oil fatty acids. Examples include Lamegin®ZE 306, Lamegin®ZE 609 and Lamegin® ZE 618 (Cognis Deutschland GmbH & Co. KG). Therefore, the glyceride may be a citric acid ester of hydrogenated tallow fatty acid monoglyceride, for example, Lamegin® ZE 309, or an ester of diacetyl tartaric acid with hydrogenated tallow fatty acid monoglyceride, for example, Lamegin ® DW 8000, or citric acid ester based on fatty acid monoglyceride of sunflower oil, for example, Lamegin® ZE 609 FL. Such esters are described, for example, in US 5,770,185 and US 2010/0087319.

[0068] The glyceride derivative may be an ester of at least one hydroxypolycarboxylic acid moiety. The ester may be an ester of a carboxylic acid moiety of hydroxypolycarboxylic acid. Each carboxylic acid moiety of the hydroxylpolycarboxylic acid can be independently derivatized as an ester. The ester derivative may be a hydrocarbyl ester, wherein the hydrocarbyl moiety may have from 4 to 22 carbon atoms. The hydrocarbyl moiety may be an alkyl moiety which may have from 4 to 22 carbon atoms. The hydrocarbyl moiety may comprise one or more heteroatoms, for example, nitrogen and/or oxygen.

[0069] The glyceride derivative may be an ether or an ester of the hydroxyl moiety of the hydroxypolycarboxylic acid.

If more than one hydroxy moiety is present in the mono-, di- or tri-glyceride of at least one hydroxypolycarboxylic acid, each hydroxyl moiety can be independently derivatized as an ether or an ester. Each ether may be a hydrocarbyl ether. The hydrocarbyl moiety of each ether may independently have from 1 to 22 carbon atoms, more suitably from 1 to 18 carbon atoms. The hydrocarbyl moiety of each ether may independently be an alkyl moiety. The alkyl moiety of each ether may independently have from 1 to 22 carbon atoms, more suitably from 1 to 18 carbon atoms. The hydrocarbyl moiety of each ether may independently comprise one or more heteroatoms, for example, nitrogen and/or oxygen. Each ester may independently be a hydrocarbyl ester. The hydrocarbyl moiety of each ester can have from 4 to 22 carbon atoms. The hydrocarbyl moiety of each ester may independently be an alkyl moiety. The alkyl moiety of each ester can independently have from 4 to 22 carbon atoms. The hydrocarbyl moiety of each ester may independently comprise one or more heteroatoms, for example, nitrogen and/or oxygen.

[0070] If the saturated, monounsaturated or polyunsaturated, branched or linear carboxylic acid having 4 to 22 carbon atoms is a polycarboxylic acid, the glyceride derivative may be an ester of a carboxylic acid moiety of one or more of the minus one saturated, monounsaturated or polyunsaturated, branched or linear polycarboxylic acid, having 4 to 22 carbon atoms, if present. Each ester may independently be a hydrocarbyl ester. The hydrocarbyl moiety of each ester can independently have from 4 to 22 carbon atoms. The hydrocarbyl moiety may be an alkyl moiety. The alkyl moiety of each ester can independently have from 4 to 22 carbon atoms. The hydrocarbyl moiety of each ester may independently comprise one or more heteroatoms, for example, nitrogen and/or oxygen.

[0071] Oil-soluble mono-, di- or tri-glycerides of at least one hydroxypolycarboxylic acid and derivatives thereof can be prepared by procedures known in the art. Diglycerides and triglycerides can be prepared by partial hydrolysis of a fat to produce a monoglyceride followed by esterification with a hydroxypolycarboxylic acid. Monoglycerides can be prepared by esterification of glycerol with a hydroxypolycarboxylic acid. Hydrocarbyl ether derivatives can be prepared from the corresponding hydrocarbyl halides.

[0072] As mentioned above, the lubricant composition and the additive composition may further comprise additional additive components.

[0073] Examples of additional additive components include dispersants (metallic and non-metallic), dispersant viscosity modifiers, detergents (metallic and non-metallic), viscosity index improvers, viscosity modifiers, pour point depressants, rust inhibitors, corrosion inhibitors, antioxidants, antifoaming agents, seal swelling agents, extreme pressure and/or antiwear additives (including non-metallic, phosphorus-containing, non-phosphorus-containing, sulfur-containing, extreme pressure non-sulfur additives and hydrocarbons containing phosphorus and sulfur), surfactants, demulsifiers, anti-capture agents, wax modifiers, lubricating agents, anti-staining agents, chromophore agents and metal deactivators.

[0074] Dispersants (also called dispersant additives) help keep solid and liquid contaminants, for example, resulting from oxidation of the lubricant composition during use, in suspension and, therefore, reduce flocculation, precipitation and/or sludge deposition, for example, on lubricated surfaces. They generally comprise long chain hydrocarbons, to promote solubility in oil, and a polar head capable of associating with the material to be dispersed. Examples of suitable dispersants include oil-soluble polymeric hydrocarbyl backbones, each with one or more functional groups that are capable of associating with particles to be dispersed. The functional groups may be amine, alcohol, amine-alcohol, amide or ester groups. Functional groups can be attached to the hydrocarbyl backbone through bridging groups. More than one dispersant may be present in the additive concentrate and/or lubricant composition. Optionally, the composition is absent of said dispersants.

[0075] Examples of suitable ashless dispersants include oil-soluble salts, esters, amino esters, amides, imides and oxazolines of mono- and polycarboxylic acids substituted with long chain hydrocarbons or anhydrides thereof; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons having polyamine moieties directly attached thereto; Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylenepolyamine; Koch reaction products and the like. Examples of suitable dispersants include derivatives of long chain hydrocarbyl substituted carboxylic acids, for example, wherein the hydrocarbyl group has a number average molecular weight of up to 20,000, for example, 300 to 20,000, 500 to 10,000, 700 to 5,000 or less than 15,000. Examples of suitable dispersants include hydrocarbyl substituted succinic acid compounds, for example, succinimide, succinate esters or succinate ester amides and, in particular, polyisobutenyl succinimide dispersants. Dispersants can be borated or non-borated.

[0076] Additionally or alternatively, dispersancy may be provided by polymeric compounds capable of providing viscosity index and dispersancy improving properties. These compounds are They are generally known as dispersant viscosity improving additives or multifunctional viscosity improvers. Examples of suitable dispersant viscosity modifiers can be prepared by chemically attaching functional moieties (e.g., amines, alcohols and amides) to polymers that tend to have number average molecular weights of at least 15,000, e.g., in the range of 20,000 to 600,000 (for example, as determined by gel permeation chromatography or light scattering procedures). Examples of suitable dispersant viscosity modifiers and procedures for preparing them are described in WO 99/21902, WO2003/099890 and WO2006/099250. More than one dispersant viscosity modifier may be present in the additive concentrate and/or lubricant composition.

[0077] Detergents (also called detergent additives) can help reduce the formation of high temperature deposits, for example, on metal surfaces within machinery, including, for example, high temperature varnish and lacquer deposits, by helping to keep the finely divided solids in suspension in the lubricant composition. Detergents may also have acid-neutralizing properties. There may be ashless detergents (which do not contain metals). The metal-containing detergent comprises at least one metal salt of at least one organic acid, which is called soap or surfactant. Detergents may be overbased in which the detergent comprises an excess of metal relative to the stoichiometric amount required to neutralize the organic acid. The excess metal is generally in the form of a colloidal dispersion of carbonate and/or metal hydroxide. Examples of suitable metals include Group I and Group 2 metals, more suitably calcium, magnesium and combinations thereof, especially calcium. There may be more than one metal present.

[0078] Examples of suitable organic acids include sulfonic acids, phenols (sulfurized or preferably sulfurized and including, for example, phenols with more than one hydroxyl group, phenols with fused aromatic rings, phenols that have been modified, for example, bridged phenols alkylene, and Mannich-based condensed phenols and saligenin-type phenols, produced, for example, by reaction of phenol and an aldehyde under basic conditions) and sulfur derivatives thereof, and carboxylic acids including, for example, carboxylic acids aromatics (for example, hydrocarbyl-substituted salicylic acids and sulfur derivatives thereof, for example, hydrocarbyl-substituted salicylic acid and derivatives thereof). There may be more than one type of organic acid.

[0079] Additionally or alternatively, non-metallic detergents may be present. Suitable non-metallic detergents are described, for example, in US Patent No. 7,622,431.

[0080] More than one detergent may be present in the lubricant composition and/or the additive concentrate.

[0081] Viscosity index improvers/viscosity modifiers. Viscosity index improvers (also called viscosity modifiers, viscosity improvers or VI improvers) impart high and low temperature operability to a lubricant composition and facilitate it to remain shear stable at elevated temperatures while also exhibiting acceptable viscosity and fluidity. at low temperatures.

[0082] Examples of suitable viscosity modifiers include high molecular weight hydrocarbon polymers (for example, polyisobutylene, ethylene-propylene copolymers and higher alpha-olefins); polyesters (for example, polymethacrylates); hydrogenated poly(styrene-co-butadiene or isoprene) polymers and modifications (for example, star polymers); and esterified poly(styrene-co-maleic anhydride) polymers. Oil-soluble viscosity-modifying polymers generally have number average molecular weights of at least 15,000 to 1,000,000, preferably 20,000 to 600,000, as determined by gel permeation chromatography or light scattering procedures.

[0083] Viscosity modifiers may have additional functions as multi-function viscosity modifiers. There may be more than one viscosity index improver.

[0084] Pour point depressants (also called lube oil improvers or lube oil flow improvers), reduce the minimum temperature at which the lubricant will flow and can be poured. Examples of suitable pour point depressants include dialkyl fumarate/C8 to C18 vinyl acetate copolymers, methacrylates, polyacrylates, polyarylamides, polymethacrylates, polyalkyl methacrylates, vinyl fumarates, styrene esters, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, terpolymers of dialkyl fumarates, vinyl esters of fatty acids and allyl vinyl ethers, wax naphthalene and the like.

[0085] There may be more than one pour point depressant.

[0086] Rust inhibitors generally protect lubricated metal surfaces against chemical attack by water or other contaminants. Examples of suitable rust inhibitors include nonionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, polyoxyalkylene polyols, anionic alkyl sulfonic acids, metal phenolates, basic metal sulfonates, fatty acids and amines.

Preferably, the rust inhibitor is not a zinc dithiophosphate.

[0087] There may be more than one rust inhibitor.

[0088] Corrosion inhibitors (also called anticorrosive agents) reduce the degradation of metal parts in contact with the lubricant composition. Examples of corrosion inhibitors include phosphosulfurized hydrocarbons and the products obtained by the reaction of phosphosulfurized hydrocarbons with an alkaline earth metal oxide or hydroxide, nonionic polyoxyalkylene polyols and esters thereof, polyoxyalkylenephenols, thiadiazoles, triazoles and anionic alkylsulfonic acids. Examples of suitable epoxidized ester corrosion inhibitors are described in US2006/0090393.

[0089] There may be more than one corrosion inhibitor.

[0090] Antioxidants (sometimes also called oxidation inhibitors) reduce the tendency of oils to deteriorate during use. Evidence of such deterioration could include, for example, the production of varnish-like deposits on metal surfaces, the formation of sludge, and increased viscosity. Examples of suitable antioxidants include alkylated diphenylamines, N-alkylated phenylenediamines, phenyl-a-naphthylamine, alkylated phenyl-anaphthylamines, dimethylquinolines, trimethyldihydroquinolines and oligomeric compositions derived therefrom, hindered phenolic compounds (including ashless (metal-free) phenolic compounds and neutral and basic metal salts of certain phenolic compounds), aromatic amines (including alkylated and non-alkylated aromatic amines), sulphured alkylphenols and alkali and alkaline earth metal salts thereof, alkylated hydroquinones, hydroxylated thiodiphenyl ethers, alkylidene bisphenols, thiopropionates, metal dithiocarbamates, 1 ,3,4-dimercaptothiadiazole and derivatives, oil-soluble copper compounds (for example, copper dihydrocarbylthio or thiophosphate, copper salts of a synthetic or natural carboxylic acid, for example, a C8 to C18 fatty acid, an unsaturated acid or a branched carboxylic acid, for example, basic, neutral or acidic Cu(I) and/or Cu(II) salts derived from alkenylsuccinic acids or anhydrides), alkaline earth metal salts of alkylphenolthioesters, suitably having C5 alkyl side chains to C12, calcium nonylphenol sulphide, barium t-octylphenyl sulphide, dioctylphenylamine, phosphorised or sulphurised hydrocarbons, oil soluble phenates, oil soluble sulphurised phenates, calcium dodecylphenol sulphide, phosphorised hydrocarbons, sulphurised hydrocarbons, phosphorus esters, low sulfur peroxide decomposers and the like.

[0091] There may be more than one antioxidant. There may be more than one type of antioxidant.

[0092] Antifoams (sometimes also called antifoaming agents) delay the formation of stable foams. Examples of suitable antifoam agents include silicones, organic polymers, siloxanes (including polysiloxanes and (poly)dimethylsiloxanes, phenylmethylsiloxanes), acrylates and the like.

[0093] There may be more than one defoamer.

[0094] Seal swelling agents (sometimes also called seal compatibility agents or elastomer compatibility aids) help swell elastomeric seals, for example, by causing a reaction in the fluid or a physical change in the elastomer. Examples of suitable seal swelling agents include long chain organic acids, organic phosphates, aromatic esters, aromatic hydrocarbons, esters (for example, butylbenzyl phthalate) and polybutenyl succinic anhydride.

[0095] There may be more than one seal swelling agent.

[0096] Examples of other additives that may be present in the lubricant composition and/or the additive concentrate include extreme pressure and/or antiwear additives (including non-metallic, phosphorus-containing, non-phosphorus-containing, extreme pressure additives). sulfur-containing, non-sulfur-containing and phosphorus- and sulfur-containing hydrocarbons), surfactants, demulsifiers, anti-capture agents, wax modifiers, lubricating agents, anti-staining agents, chromophore agents and metal deactivators.

[0097] The base oil composition used in the present aspect preferably constitutes at least 75% by weight of the lubricant composition, more preferably at least 80%, even more preferably at least 85%, even more preferably at least 90%. Even more preferably, the base oil composition constitutes 92 to 97% by weight, such as at least 94%.

[0098] The base oil composition may be any suitable base oil and may be selected from mineral oils, synthetic oils, vegetable and animal oils and mixtures thereof used in conventional lubricating oils, as appropriate. Specific examples thereof include base oils of groups I, II, III, IV or V in the API standard (American Petroleum Institute) in base oil categories according to API standard 1509, "SYSTEM OF MOTOR OIL LICENSE AND CERTIFICATION", April 2007 version,16. to Appendix E edition, as set out in Table 1.

___________________________________________ Table 1___________________________________________

YO

_______________________________________________ __________

[0099] Group I, Group II and Group III base materials can be derived from mineral oils. Group I base materials are typically manufactured by known procedures comprising solvent extraction and solvent dewaxing, or solvent extraction and catalytic dewaxing. Group II and Group III base materials are typically manufactured by known processes comprising catalytic hydrogenation and/or catalytic hydrocracking, and catalytic hydroisomerization. A suitable Group I base material is AP/E Core 150, available from ExxonMobil. Suitable Group II base materials are EHC 50 and EHC 110, available from ExxonMobil. Suitable Group III base materials include Yubase 4 and Yubase 6 available, for example, from SK Lubricants. Suitable Group V base materials are ester base materials, for example, Priolube 3970, available from Croda International μlc. Suitable Group IV base materials include hydrogenated alpha olefin oligomers. Suitably, the oligomers can be prepared by free radical processes, Zeigler catalysis or Friedel-Crafts cationic catalysis. Poly-alpha-olefin base materials can be derived from C8, C10, C12, C14 olefins and mixtures of one or more thereof. In one embodiment, the poly-alpha-olefin base material may be derived from C10 and C12 olefins.

[0100] The lubricating composition and the lubricating viscosity oil may comprise one or more base oils and/or base oils that are natural oils, mineral oils (sometimes referred to as petroleum oils or petroleum mineral oils), non-mineral oils. and mixtures thereof. Natural oils include animal oils, fish oils and vegetable oils. Mineral oils include paraffinic oils, naphthenic oils and paraffinic-naphthenic oils. Mineral oils may also include oils derived from coal or shale.

[0101] Suitable base oils and base materials can be derived from procedures such as the chemical combination of simpler or smaller molecules into larger or more complex molecules (for example, polymerization, oligomerization, condensation, alkylation, acylation).

[0102] Suitable base materials and base oils may be derived from gas-to-liquid materials, carbon-to-liquid materials, biomass-to-liquid materials, and combinations thereof.

[0103] Preferably, the base oil is a synthetic base oil comprising a poly-alphaolefin component.

[0104] A base oil comprising a modified poly-alpha-olefin is provided, in a preferred embodiment for use in the lubricant composition of the first aspect of the present invention. Any suitable amount of the modified poly-alpha-olefin may be used and may comprise from 5 to 95% by weight of the total composition, more preferably from 10 to 90% by weight and optionally from 30 to 88% by weight. Preferably, the base oil according to this embodiment is a synthetic base oil and more preferably comprises a conventional poly-alpha-olefin. Optionally, the base oil further comprises one or more additive carriers, which may typically be selected from other base materials such as Group V base materials, optionally polymeric or non-polymeric base materials and which optionally have a polar component. Preferably, the additive carrier does not shrink with the elastomer and more preferably swells with the elastomer.

[0105] A modified poly-alpha-olefin may preferably be a functionalized poly-alpha-olefin, preferably functionalized with a relatively polar functional group, such as an ester group. Preferably, the ratio of olefin to ester in the modified poly-alpha-olefin is in the range of 20:1 to 1:1. A modified poly-alpha-olefin, as used in this invention, can preferably be obtained and is preferably obtained by copolymerization of one or more alpha-olefin monomers with a monomer having a relatively polar functional group, for example, a monomer olefinic that has or is adapted to have a relatively polar functional group. The modified poly-alpha-olefin preferably comprises a copolymer of one or more alpha-olefin monomers with ester (for example, an alkyl ester of an acid, such as an alkyl ester of a dicarboxylic acid) and preferably an ester of olefinic alkyl. Other ester functional groups may include butanedioic and succinic anhydride. An example of the modified poly-alpha-olefin is a copolymer of a monomer of alpha-olefin (for example, with a chain length of dodecene) with an olefinic alkyl ester, for example, with an olefinic alkyl ester having an olefin chain length of decene and in a ratio of alpha-olefin monomer and functionalized monomer in the range of 3:2 to 5:1, preferably 2:1 to 3:1 and preferably in a randomized copolymer. Examples of commercially available modified poly-alpha-olefins include, but are not limited to, Aria™ WTP 40 or a grade of Ketjenlube™ such as Ketjenlube™ 240.

[0106] Preferably, the modified poly-alpha-olefin is selected from a kinematic viscosity at 100°C of 40 cSt or 100 cSt or about that. For use in robotic gears, it is preferred that the modified poly-alpha-olefin have a kinematic viscosity at 100°C of 40 cSt or about that. For use in wind turbines or industrial gears, it is preferred that the modified poly-alpha-olefin have a kinematic viscosity at 100°C of 100 cSt or about that.

[0107] Any suitable poly-alpha-olefin can be used, but preferably a relatively low viscosity poly-alpha-olefin (by which is meant low viscosity relative to the modified poly-alpha-olefin), such as a PAO 8. Optionally, the poly-alpha-olefin may be or may include or comprise a high viscosity poly-alpha-olefin, such as a conventional high-viscosity poly-alpha-olefin (e.g., conventional pAo 40 and/or 100 ) and/or a metallocene poly-alpha-olefin (e.g., PAO 50 and/or metallocene 135).

[0108] Particular base materials may be selected and particular base oils may be formulated to provide any suitable base oil viscosity grade, as required. The lubricant composition may have any suitable viscosity grade (defined by the kinematic viscosity at 40°C), such as from 60 to 700 cSt, more preferably from 68 to 680 cSt.

[0109] In a preferred embodiment, the base oil may comprise the modified poly-alpha-olefin and the polyalpha-olefin in a weight ratio of 25:75 to 85:15, more preferably 40:60 to 80:20, optionally 50:50 or a higher proportion of the modified poly-alpha-olefin, such as in the range of 60:40 to 75:25. A ratio of about 70:30 may be provided in one embodiment. Preferably, according to this embodiment, the modified poly-alpha olefin has a kinematic viscosity at 100 ° C of 40 cSt or about and is suitable for use in the formulation of a lubricant composition with a viscosity grade defined by a kinematic viscosity of 150 cSt at 40°C and is preferably for use in robotic gears. The poly-alpha-olefin and the modified polyalpha-olefin may constitute the majority of the base oil composition and preferably at least 60% by weight of the base oil composition, more preferably at least 75% by weight of the base oil composition. More preferably, it constitutes at least 85% of the base oil composition and, optionally, at least 90%.

[0110] A preferred base oil composition comprises one or more additive carriers. Additive carriers preferably serve to increase the polarity of the base oil and may preferably be used as the base material component of an additive concentrate. Said additive carrier may be a Group V base material. Preferably, the additive carrier is a relatively polar base material. Optionally, an additive carrier may have a kinematic viscosity at 40°C of 20 to 40 cSt, preferably 25-35 cSt. The additive carrier may be selected, for example, from alkylated naphthalene, alkylbenzene or low viscosity esters, preferably, alkylated naphthalene or low viscosity alkylbenzene is used. A low viscosity ester may be, for example, a diisodecyl adipate (DIDA) or a diisotridecyl adipate (DITA), which may be present in the base oil in an amount of up to 20% by weight, but more preferably up to 15% by weight and even more preferably up to 10% by weight and, in any case, at least 5% by weight. Preferably, the additive carrier comprises (and even more preferably is) an alkylated naphthalene and is provided in an amount of up to 25% by weight of the base oil composition, preferably up to 15%. The alkylated naphthalene is preferably provided in an amount of at least 5%, preferably at least 7.5% and preferably in an amount of up to 12%, more preferably 10% of the base oil composition.

[0111] The base oil compositions of the present embodiment are particularly advantageous in the lubricant compositions of the present invention because they provide a stable lubricant composition that can provide longevity, are less prone to sludge, and are capable of effectively solubilizing such an additive composition. as defined above. The base oil composition of the present embodiment also provides excellent elastomer compatibility properties.

[0112] The base oil according to a preferred embodiment may allow for the lubricant composition a viscosity of 130 to 170 cSt at 40 °C, more preferably 135 to 165 cSt at 40 °C.

[0113] In a preferred embodiment of the invention, a lubricant composition is provided as a synthetic gear oil composition suitable for use as a gearbox lubricant comprising a rolling element, comprising a base oil composition comprising a modified poly-alpha-olefin as defined above; and an additive composition comprising a molybdenum dialkyldithiocarbamate and an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof, having no more than 0.1 % by weight of molybdenum dithiophosphate.

EXAMPLES

[0114] Lubricating compositions were prepared for comparison with commercially available lubricating oils and subjected to a series of performance tests to compare performance as gear oils, particularly as robotic gear oils. In particular, wear tests were provided, including a gear wear test, a bearing gear performance test, and elastomer compatibility tests.

[0115] The performance or wear tests carried out are summarized below.

[0116] FZG Test: This test is a well-known test designed to test the wear performance of a lubricating oil at the interface of a gear set. For this test, the gears are loaded through a torsional coupling that is adjusted to known loading conditions or stages. The gears are turned by a variable speed electric motor. The temperature of the fluid is controlled by heating and/or cooling elements. The test evaluates gear tooth face wear resistance from fluids using A-profile gears. Equipment is operated at 1450 rpm through up to 12 stages of progressive loading at 15-minute intervals. Standard tests are performed at a fluid temperature of 90°C. The gear teeth are inspected after each loading stage for wear. The test was carried out in accordance with the test procedure defined in ISO14635-1. Load capacity before failure was identified by failure stage and determined as pass/fail. A failure was considered a failure to reach failure stage 12 or higher under the test conditions. The evaluation of the failure condition is when the cumulative scuff width on the gear exceeds 20 mm. This is indicative of scratch wear.

[0117] FE8 Test: The FE8 test is recognized within the industry and a good means of evaluating the performance of bearing gears. Both rolling and sliding lubrication conditions are present in the same test, making the test particularly suitable for testing the performance of a lubricant for use in gears that have rolling elements. Two stages of the FE8 test were carried out. In stage 1, wear and torque performance are measured and can be used to evaluate the performance of a lubricant composition. In stage 2, the long-term integrity of the product is examined. Test parts, including rollers and washers, were visually examined to evaluate surface finish.

[0118] FE8 tests were performed in accordance with DIN-51819-3. The test duration and weight loss of the bearing components are used to classify the suitability of the lubricant. The test bearings used are 81212 cylindrical roller thrust bearings with brass cage. A bearing consists of 15 cylindrical rolling elements, a brass cage, a housing washer and a shaft washer. The material of the washers and rolling elements is the usual 100Cr6 bearing steel and the material of the cage is CuZn40. The bearings are manufactured by FAG, Schweinfurt. An advantage of using a cylindrical bearing in an anti-wear test is that there is a high amount of slip (maximum 14.8%) and therefore the anti-wear requirements of the lubricant are high.

[0119] In test FE8, the test bench is equipped with two cylindrical roller thrust bearings. The test bearings are tensioned with a disc spring pack to provide the axial test force. A heat shield heats the test head by convection heating and a radial fan is used to reduce the temperature if necessary.

[0120] For stage 1 of FE8, a load of 80 kN is applied with a speed of 7.5 rpm at 80 ° C, for 80 hours. A 4 liter oil tank is used with a flow rate of 0.1 liters/minute per bearing. Bearing wear is measured in terms of weight loss of the roller, ring and cage assemblies. Less than 30 mg of roller assembly wear is considered acceptable under DIN-51819-3 methodology.

[0121] For stage 2 of FE8, a load of 80 kN is applied with a speed of 75 rpm at 70 ° C, for 800 hours. Again, a 4 liter oil tank is used with a flow rate of 0.1 liters/minute per bearing.

[0122] As an elastomer compatibility test, the condition of both elastomers and the oil was evaluated after the elastomer compatibility tests, in order to provide an evaluation of sludge formation as a component of elastomer compatibility. Two static elastomeric compatibility tests were carried out: the 72NBR902 elastomeric material was tested at 95 °C for 1008 hours (referred to as the NBR test) and a 75FKM585 elastomeric material was tested at 120 °C for 1008 hours (referred to as the FKM test). In each case, the change in mass, volume, Shore A hardness, tensile strength, and elongation at break were measured in percentage terms relative to a reference. The NBR and FKM tests were carried out in accordance with ISO 1817. The used oil from the NBR and FKM tests was evaluated visually for color change relative to fresh oil and sludge formation to further characterize the compatibility of the elastomer.

Example 1

[0123] The sample lubricating oil formulations were prepared by providing a base oil comprising a mixture of base materials and mixing therewith an additive composition comprising at least one antiwear agent and other additives in a diluent (the diluent being one of base materials). The formulations are summarized in Table 2.

T l 2: m i i n ^ l ri n m r n ni n n

Example 2

[0124] Samples S1 to S6 were then subjected to anti-wear performance and elastomer compatibility tests. In particular, the FZG and FE8 stage 1 and stage 2 tests for antiwear and the tests of NBR and FKM elastomers as described above. The post-test oil was checked visually for sludge and a surface finish examination was performed with a laser microscope. The test results on samples S1 to S6 are presented in Table 3 below.

Table 3: Anti-wear performance and elastomer compatibility testing

[0125] In subsequent tests performed (S5 and S6), FZG and other tests were not completed when the FE8 Stage 1 wear test demonstrated poor antiwear performance for use in long life robotic gear oils.

[0126] A significant improvement in antiwear can be demonstrated by the inclusion of the oil-soluble glyceride of hydroxylpolycarboxylic acid as illustrated by the significant improvement in the FE8 Stage 1 wear test results for samples S2, ^s 3 and S4 (which contained the oil-soluble glyceride of hydroxylpolycarboxylic acid) compared to S1, S5 and S6 (which did not).

[0127] As can be seen from the data in Table 3, the use of the modified PAO and PAO mixture together with an alkylated naphthalene generally provides adequate elastomer compatibility in all samples. All samples were free of sludge. Furthermore, for each of the samples (where the data were obtained), the measurements of mass change, volume change, and hardness change were within acceptable limits. Overall, very good elastomer compatibility was achieved in sample S3 and significantly better than other samples, such as S2 (differs in the proportions of MoDTC and alkylated naphthalene), in terms of change in breaking elongation for the elastomer compatibility test. NBR elastomers, as well as change in tensile strength. It is clear that formulations such as S2, S3 and S4 having a MoDTC in combination with an oil-soluble glyceride of hydroxylpolycarboxylic acid can provide oils of Long-life robotic gears with very good elastomer compatibility and excellent anti-wear properties, even for gears with a rolling element.

Claims (14)

1. A lubricant composition suitable for use as a gearbox lubricant comprising a rolling element, comprising: a base oil composition of lubricating viscosity; and an additive composition comprising a molybdenum dialkyldithiocarbamate and an oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or an ester derivative thereof, lubricant composition having no more than 0 .1% by weight of molybdenum dithiophosphate. 2. A lubricant composition according to claim 1, wherein the molybdenum dialkyldithiocarbamate is provided in an amount, in terms of molybdenum, of 500 to 3,000 ppm of the lubricant composition, preferably 750 to 1,500 ppm of the lubricant composition. 3. A lubricant composition according to claim 1 or 2, wherein the oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid, or an ether or ester derivative thereof is provided in an amount of 0. 1 to 2.5% by weight of the lubricant composition, preferably 0.25 to 1% by weight of the lubricant composition, and/or the oil-soluble mono-, di- or tri-glyceride of at least one hydroxylpolycarboxylic acid , or an ether or ester derivative thereof is provided in a weight percentage ratio with respect to molybdenum dialkyldithiocarbamate in the range of 1:3 to 1:1, more preferably in the range of 1:2 to 2:3 . 4. A lubricant composition according to any of the preceding claims, wherein molybdenum dithiophosphate is absent. 5. A lubricant composition according to any of the preceding claims, wherein the additive composition further comprises a fatty acid amide having 12 to 25 carbon atoms, such as oleylamide, in an amount of up to 1% by weight of the lubricant composition. . 6. A lubricant composition according to any of the preceding claims, wherein the additive composition constitutes a proportion of the lubricant composition of up to 10% by weight, preferably 2.5 and 7.5% by weight. 7. A lubricant composition according to any of claims 1 to 6, wherein the base oil composition comprises a functionally modified poly-alpha-olefin, a poly-alpha-olefin and optionally an additive carrier. 8. A lubricant composition according to claim 7, wherein the modified poly-alpha-olefin is a polyalpha-olefin functionalized with an ester group, preferably where the modified poly-alpha-olefin is a copolymer of an alpha-olefin monomer with a ester, preferably wherein the modified poly-alpha-olefin is a copolymer of an alpha-olefin monomer with an olefinic alkyl ester with an olefin chain length of decene and in a ratio of alpha-olefin monomer and functionalized monomer in the range from 3:2 to 5:1. 9. A lubricant composition according to claim 8, wherein the modified poly-alpha-olefin is a copolymer of an alpha-olefin monomer with an olefinic anhydride, preferably where the olefinic anhydride is a succinic or maleic olefinic anhydride. 10. A lubricant composition according to any of claims 7 to 9, wherein the poly-alpha-olefin and the modified polyalpha-olefin constitute the majority of the base oil composition, preferably at least 75% by weight of the base oil composition. base oil. 11. A lubricant composition as claimed in any of claims 7 to 10, wherein the base oil composition comprises one or more additive carriers. 12. A synthetic gear oil composition suitable for use as a gearbox lubricant comprising a rolling element, comprising: a base oil composition comprising a modified poly-alpha olefin; and an additive composition comprising a molybdenum dialkyldithiocarbamate and an oil-soluble mono-, di- or tri-glyceride of at least one hydroxyl polycarboxylic acid, or an ether or ester derivative thereof, having no more than 0.1% by weight of molybdenum dithiophosphate. 13. The use of a gear oil or lubricant composition as defined in any of claims 1 to 6 and 12 as a lubricant for gearboxes comprising a rolling element. 14. A method for lubricating a gearbox or operating an apparatus having the gearbox, wherein the gearbox comprises a rolling element, wherein the method comprises supplying a gearbox comprising a rolling element with an oil of viscosity lubricant having the lubricant composition as defined in any of claims 1 to 6 or 12.