Patent Description:
It is known to use anti-wear additives and/or friction modifiers in lubricant compositions. It is also known to use pour point depressant additives in lubricant compositions.

The pour point of a liquid is the lowest temperature at which it becomes semi-solid and loses its flow characteristics. In general, pour point depressants prevent wax crystals in lubricants from agglomerating or fusing together at reduced ambient temperatures, and they therefore lower the minimum temperature at which the lubricant will flow and can be poured. Thus, if lubricants are not adequately protected with pour point depressants, their flow characteristics can be adversely affected, which may have a negative impact, for example, on engine performance and protection where the lubricant is used to provide lubrication to an internal combustion engine at low ambient temperatures.

Many materials are known to be suitable for use as pour point depressants in non-aqueous lubricant compositions, and these include Cs to C<NUM> dialkyl fumarate/vinyl acetate copolymers, methacrylates, polyacrylates, polyacrylamides, polymethacrylates, polyalkyl methacrylates, vinyl fumarates, styrene esters, condensation products of halo paraffin waxes and aromatic compounds, vinyl carboxylate polymers, terpolymers of dialkyfumarates, vinyl esters of fatty acids and allyl vinyl ethers, and wax naphthalene.

However, these materials are generally all relatively expensive, and their incorporation in non-aqueous lubricant compositions can significantly increase the price of such compositions. Additionally, these materials may adversely affect one or more other properties of the lubricant compositions in which they are incorporated. In general therefore, it would be beneficial if such materials could be replaced by lower cost materials and/or materials that provide additional beneficial properties to the lubricant compositions in which they are incorporated, such as anti-wear and/or friction reduction properties.

A range of materials are known to be useful as anti-wear additives and/or friction modifiers in lubricant compositions; for example, zinc dihydrocarbyl dithiophosphates (ZDDP) have been used as anti-wear additives in lubricant compositions for many years. A disadvantage of these additives is that, when used to lubricate internal combustion engines, they give rise to ash which contributes to particulate matter in exhaust emissions from the internal combustion engines. Thus, in order to reduce the amount of ash-forming additives used for lubricating internal combustion engines, and also to reduce the amount of zinc and/or phosphorus and/or sulphur in the exhaust emissions from internal combustion engines, a variety of ashless, organic ester, anti-wear additives and/or friction modifiers have been developed for use in non-aqueous lubricant compositions.

<CIT> relates to a lubricating composition comprising a major amount of a GTL lubricating base oil and a friction modifier consisting essentially of oil soluble fatty acid esters of a polyol. According to <CIT>, the friction modifier is one or more fatty acid esters of a polyol, and it is stated that suitable polyols include diols, triols and the like, such as ethylene glycol, propylene glycol, glycerol and sorbitol. It is also stated that the esters of these polyols are those of carboxylic acids containing <NUM> to <NUM> carbon atoms, and that examples of such carboxylic acids include octadecanoic acid, dodecanoic acid, stearic acid, lauric acid and oleic acid. <CIT> does not describe the use of ashless, organic ester, anti-wear additives and/or friction modifiers as pour point depressants.

<CIT> relates to the use of an oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, as an anti-wear additive and/or friction modifier in a non-aqueous lubricant composition and/or in a fuel composition. According to <CIT>, lubricant compositions comprising the oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, may be used to lubricate internal combustion engines. It is stated that in one embodiment, the hydroxy polycarboxylic acid has at least one hydroxy group which is in an alpha position with respect to a carboxylic moiety. Particularly desirable results are said to have been obtained with additives in which the glyceride is a glyceride of citric acid and oleic acid, a glyceride of citric acid and linoleic acid, or a mixture thereof. <CIT> does not describe the use of ashless, organic ester, anti-wear additives and/or friction modifiers as pour point depressants in non-aqueous lubricant compositions.

<CIT> relates to the use as an anti-wear additive and/or friction modifier in a non-aqueous lubricant composition and/or in a fuel composition of least one long chain fatty acid ester of a hydroxy carboxylic acid in which the long chain fatty acid has at least <NUM> carbon atoms and the ester is an oil-soluble ester of a mono- or poly- hydroxy carboxylic acid containing <NUM> to <NUM> groups which are independently carboxylic acid groups or lower hydrocarbyl esters thereof and in which, when the hydroxy carboxylic acid is a mono-hydroxy carboxylic acid, the ester has a long chain fatty acid ester moiety of the hydroxy group of the hydroxy carboxylic acid and, when the hydroxy carboxylic acid is a poly-hydroxy carboxylic acid, the ester has independently long chain fatty acid ester moieties of one or two of the hydroxy groups of the poly-hydroxy carboxylic acid. According to <CIT>, lubricant compositions comprising the specified long chain fatty acid esters of hydroxyl carboxylic acids may be used to lubricate internal combustion engines. <CIT> does not describe the use of ashless, organic ester, anti-wear additives and/or friction modifiers as pour point depressant additives in non-aqueous lubricant compositions.

<CIT>, <CIT> and <CIT> relate to lubricating compositions that are intended to have a low pour point. There remains a need for alternative materials that may be used as pour point depressant additives in non-aqueous lubricant compositions, including materials that have additional properties, for example being effective anti-wear additives and/or friction modifiers in such compositions.

According to the present invention there is provided the use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive in a non-aqueous lubricant composition.

The present invention solves the technical problem defined above by the use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive in a non-aqueous lubricant composition.

In at least some examples, the use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive in a non-aqueous lubricant composition depresses the pour point of the non-aqueous lubricant composition by at least <NUM>, as compared to a non-aqueous lubricant composition having the same composition other than for the incorporation of the ashless, organic ester, anti-wear additive and/or friction modifier. For example, in at least some examples, the pour point is depressed by between <NUM> and <NUM>, for example by <NUM>, <NUM> or <NUM>. Pour point depression is measured by any suitable method, for example using the standard method set out in ASTM D97.

Uses of the non-aqueous lubricant compositions incorporating ashless, organic ester, anti-wear additives and/or friction modifiers as pour point depressant additives include all conventional lubrication purposes, for example to lubricate an internal combustion engine. In at least some examples, the use of ashless, organic ester, anti-wear additive and/or friction modifiers as pour point depressant additives in non-aqueous lubricant compositions permits the compositions to be used to provide effective lubrication at lower temperatures than equivalent compositions not comprising any pour point depressant additive. In at least some examples, the use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive in a non-aqueous lubricant composition permits the non-aqueous lubricant composition to provide effective lubrication at a temperature of -<NUM> or less, for example to provide effective lubrication at a temperature as low as -<NUM>, or to provide effective lubrication at a temperature of -<NUM> or less, for example to provide effective lubrication at a temperature as low as -<NUM> or -<NUM>.

Thus, in at least some examples, the use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive provides non-aqueous lubricant compositions exhibiting pour points of -<NUM> or less, for example of -<NUM> to - <NUM>, or -<NUM> or less, for example of -<NUM> or -<NUM>.

The use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant in a non-aqueous lubricant composition effectively reduces the viscosity of the non-aqueous lubricant composition at lower temperatures, for example when compared to compositions that are otherwise the same other than for the absence of a pour point depressant additive. Methods for measuring reduced viscosity at low temperatures include standard methods, for example using the Mini Rotary Viscosity test as set out in ASTM D4684. In at least some examples, the use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive in a non-aqueous lubricant composition provides non-aqueous lubricant compositions exhibiting viscosities of <NUM>,<NUM> cP or less, for example <NUM>,<NUM> cP or less, for example when measured in the Mini Rotary Viscosity test at -<NUM>.

In at least one embodiment of the invention, an ashless, organic ester, anti-wear additive and/or friction modifier is used as a pour point depressant additive in a non-aqueous lubricant composition which is essentially free of any conventional pour point depressants. The term "essentially free" in this context means that the compositions are either entirely free of conventional pour point depressants, or comprise only negligible amounts thereof that are insufficient to provide significant pour point depressant effect, for example, less than <NUM>% by weight, less than <NUM>% by weight, or less than <NUM>% by weight. Conventional pour point depressants include C<NUM> to C<NUM> dialkyl fumarate/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 dialkyfumarates, vinyl esters of fatty acids and allyl vinyl ethers, and wax naphthalene or the like.

The amount of ashless, organic ester, anti-wear additive and/or friction modifier used as a pour point depressant additive in a non-aqueous lubricant composition in accordance with the present invention includes any amount suitable to act as a pour point depressant, for example use at a concentration at which it provides both effective pour point depressant additive effects and effective anti-wear and/or friction modification properties, for example from <NUM> to <NUM>% by weight, or <NUM> to <NUM>% by weight, for example <NUM>% by weight.

In at least some examples, the numerical percentages referenced in this application may be preceded by the word "about.

According to the present invention, the ashless, organic ester, anti-wear additive and/or friction modifier used as a pour point depressant additive in a non-aqueous lubricant composition in accordance with the present invention, is at least one oil-soluble mono, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or at least one oil-soluble mono, di-, or tri-glyceride of an ether or ester derivative of the hydroxyl moiety of the hydroxy polycarboxylic acid, or at least one oil-soluble mono, di-, or tri-glyceride of an ester derivative of a carboxylic acid moiety of the hydroxy polycarboxylic acid.

Also disclosed herein is an ashless, organic ester, anti-wear additive and/or friction modifier which is:.

for use as a pour point depressant additive in a non-aqueous lubricant composition. Unlike the oil-soluble mono, di-, or tri-glycerides or derivatives thereof mentioned above, the use of one or more of components (a)-(c) is not required by the appended claims.

Where the ashless, organic ester, anti-wear additive and/or friction modifier used as a pour point depressant additive in a non-aqueous lubricant composition comprises at least one fatty acid ester of a polyol, suitable polyols include diols, triols and the like, such as ethylene glycol, propylene glycol, glycerol and sorbitol. Examples of the esters of these polyols are those of carboxylic acids containing <NUM> to <NUM> carbon atoms. Examples of such carboxylic acids include octadecanoic acid, dodecanoate acid, stearic acid, lauric acid and oleic acid. In at least some examples, the fatty acid ester is a glycerol ester, for example a glycerol mono-ester, including for example glycerol mono-oleate, glycerol monostearate, glycerol monolaurate, glycerol dodecanoate and glycerol octadodecanoate.

As mentioned above, the use of fatty acid esters is not required by the appended claims.

According to the present invention, the ashless, organic ester, anti-wear additive and/or friction modifier used as a pour point depressant additive in a non-aqueous lubricant composition in accordance with the present invention is at least one oil-soluble mono, di-, or tri- glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, in at least some examples, the hydroxy polycarboxylic acid has at least one hydroxy group or derivative (for example ether or ester) thereof, which is in an alpha position with respect to a carboxylic moiety.

In at least some examples, each hydroxy polycarboxylic acid independently has from <NUM> to <NUM> carbon atoms, for example <NUM> to <NUM> carbon atoms. In at least some examples, the oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid or derivative thereof has from <NUM> to <NUM> carbon atoms. The number of carbon atoms in the glyceride may affect its solubility in oil of lubricating viscosity.

By oil-soluble is meant that the glyceride is soluble in an oil of lubricating viscosity for example in a pour point depressant and friction modifying and/or anti-wear improving amount, for example in an amount by weight of at least <NUM> ppm in an oil of lubricating viscosity. In at least some examples, the solubility is determined at ambient temperature, for example at <NUM>. Methods of determining the solubility include those for determining solubility at atmospheric pressure.

Suitable hydroxy polycarboxylic acids include:.

Examples of the oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof include a di-, or tri-glyceride which is a glyceride of at least one hydroxy polycarboxylic acid and at least one second carboxylic acid which is a saturated, mono-unsaturated or poly-unsaturated, branched or linear, monocarboxylic or polycarboxylic acid containing <NUM> to <NUM> carbon atoms, or a derivative thereof.

In at least some examples, the second carboxylic acid is saturated, mono-unsaturated or poly-unsaturated. In at least some examples, the second carboxylic acid is unsaturated. In at least some examples, the second carboxylic acid is branched or linear. In at least some examples, the second carboxylic acid is a monocarboxylic or polycarboxylic acid. If the second carboxylic acid is a polycarboxylic acid, the derivative of the glyceride includes those in which the glyceride is an ester of the second carboxylic acid group.

Suitable saturated second carboxylic acids include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid. Suitable unsaturated second carboxylic acids include oleic acid, linoleic acid, linolenic acid, myristoleic acid, palmitoleic acid, sapienic acid, erucic acid (also known as cis-<NUM>-docosenoic acid) and brassidic acid.

In at least some examples, the glyceride is a glyceride of citric acid and oleic acid, a glyceride of citric acid and linoleic acid or a mixture thereof.

In at least some examples, the mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid or derivative thereof is represented by the general formula (I):
<CHM>
wherein RO, OR' and OR" independently represent:.

provided that at least one of RO, OR' and OR" is a hydroxy polycarboxylic acid moiety or an ether and/or ester thereof.

In at least some examples, in formula (I) at least one of RO, OR' and OR" is a hydroxy polycarboxylic acid moiety or an ether and/or ester thereof and at least one of RO, OR' and OR" is a saturated, mono-unsaturated or poly-unsaturated, branched or linear, monocarboxylic or polycarboxylic group containing from <NUM> to <NUM> carbon atoms or an ester thereof.

In at least some examples, in formula (I), the hydroxy polycarboxylic moiety acid has at least one hydroxy group or derivative (for example ether or ester) thereof which is in an alpha position with respect to a carboxylic moiety.

In at least some examples, in formula (I), each hydroxy polycarboxylic moiety independently has from <NUM> to <NUM> carbon atoms. In formula (I), the hydroxy polycarboxylic moiety, in at least some examples, is derivable from acids including, for example, citric acid, tartaric acid, malic acid, monohydroxy trimesic acid and hydrogenated monohydroxy trimesic acid.

In formula (I) when present, each saturated, branched or linear, monocarboxylic or polycarboxylic group containing from <NUM> to <NUM> carbon atoms or an ester thereof, in at least some examples, is derivable 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 (I) when present, each mono-unsaturated or poly-unsaturated, branched or linear, monocarboxylic or polycarboxylic group containing from <NUM> to <NUM> carbon atoms or an ester thereof may be derivable from unsaturated carboxylic acids or their halide equivalents. Suitable mono-unsaturated acids include for example, oleic acid, myristoleic acid, palmitoleic acid, sapienic acid, erucic acid and brassidic acid. Suitable polyunsaturated acids include for example, linoleic acid and linolenic acid.

In at least some examples, the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a saturated C<NUM> to C<NUM> polycarboxylic acid, or a derivative thereof. Suitable polycarboxylic acids include branched and linear acids. In at least some examples, the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a mono-unsaturated or polyunsaturated C<NUM> to C<NUM> polycarboxylic acid, or a derivative thereof. Suitable polycarboxylic acids include branched and linear acids. In at least some examples glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a saturated C<NUM> to C<NUM> monocarboxylic acid, or a derivative thereof. Suitable monocarboxylic acids include branched and linear acids. Suitable saturated C<NUM> monocarboxylic acids include palmitic acid. Suitable saturated C<NUM> monocarboxylic acids include stearic acid. In at least some examples, the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a mono-unsaturated or polyunsaturated C<NUM> to C<NUM> monocarboxylic acid, or a derivative thereof. Suitable unsaturated monocarboxylic acids include branched and linear acid. In at least some examples, the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and an unsaturated C<NUM> monocarboxylic acid, or a derivative thereof. Suitable monocarboxylic acid include branched and linear acids. Suitable hydroxy polycarboxylic acids include citric acid. The glyceride additive may be a glyceride of citric acid and an unsaturated C<NUM> monocarboxylic acid, or a derivative thereof. Suitable unsaturated C<NUM> monocarboxylic acids include oleic acid and linoleic acid.

In at least some examples, the glyceride is a citric acid ester of a mono-glyceride of a saturated, mono-unsaturated or polyunsaturated, branched or linear, monocarboxylic or polycarboxylic C<NUM> to C<NUM> carboxylic acid, for example, a C<NUM> or C<NUM> carboxylic acid, for example palmitic acid, stearic acid, oleic acid or linoleic acid. Suitable glycerides include citric acid ester of mono-glyceride made from vegetable oil, for example sunflower and/or palm oil. Suitable glycerides include citric acid ester of mono-glyceride made from edible, refined sunflower and palm based oil. Suitably, 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 glycerides of citric acid with oleic acid and/or linoleic acid is GRINSTED CITREM SP70 (Trade Mark) which is available from Danisco. GRINSTED CITREM SP70 is believed to be a citric acid ester of mono-glyceride made from edible, refined sunflower and palm based oil. GRINSTED CITREM SP70 is also believed to comprise at least one diglyceride having the structural formula (II):
<CHM>
wherein -Y- represents a C<NUM> hydrocarbyl moiety which is mono- or di-unsaturated.

Thus, diglycerides having structural formula (II) 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 (I) in which (i) RO represents a carboxyl group containing <NUM> carbon atoms, which may be derivable from oleic acid and/or linoleic acid, (ii) OR' represents a hydroxyl moiety, and (iii) OR" represents a hydroxy polycarboxylic acid moiety, which may be derivable from citric acid.

GRINSTED® CITREM N <NUM> VEG from Danisco is believed to be a neutralised citric acid ester of mono-glyceride made from edible, fully hydrogenated palm based oil. It was found to be unsuitable because it was not oil soluble.

The use of GRINSTED® CITREM <NUM>-IN-<NUM> from Danisco as a carboxylic acid anionic surfactant is described in paragraphs [<NUM>] to [<NUM>] of US patent application publication <CIT>. <CIT> relates to conveyor lubricants including emulsion of a lipophilic compound and an emulsifier and/or an anionic surfactant (title). The lipophilic compound is said to include water insoluble organic compounds including two or more ester linkages and in one embodiment is said to be a water insoluble organic compound including three or more oxygen atoms. It is stated that in one embodiment, the lipophilic compound is an ester including a di-, tri-, or poly-hydric alcohol, such as glycerol, with <NUM> or more of the hydroxyl groups each being coupled to a carboxylic acid as an ester group (paragraph [<NUM>]). In the example at paragraphs [<NUM>] to [<NUM>] two triglyceride lubricant compositions were tested. Lubricant A was said to contain an emulsion of <NUM> wt% of a caprylate, caprate, cocoate triglyceride in water to which was added the anionic surfactant <NUM> wt% lecithin (sold under the trade name Terradrill V408, Cognis) and the emulsifier <NUM> wt% <NUM> mol ethoxysorbitan monostearate (sold under the trade name Tween 60V, ICI). Lubricant B was said to contain <NUM> wt% citrate ester, said to be a carboxylic acid anionic surfactant sold under the name GRINSTED® CITREM <NUM>-IN-<NUM>, Danisco in place of the Terradrill V408. According to paragraph [<NUM>], Triglyceride lubricants including anionic surfactant worked well as dry conveyor lubricants and effectively lubricated after water was applied to the conveyor. According to paragraph [<NUM>] of <CIT>, the composition therein can include any variety of anionic surfactants that are effective to increase the ability of the lipophilic emulsion to withstand application of water to the conveyor. Examples are given in paragraphs [<NUM>] to [<NUM>] often classes of anionic surfactant.

According to paragraph [<NUM>] of US patent application publication <CIT>, hydrophilic emulsifier CITREM is a composition of matter containing citric esters of mono- and diglycerides of edible fatty acids. It is also stated therein that edible fatty acids have, in particular, <NUM> to <NUM> carbon atoms.

The glyceride may be an ester of citric acid with a partial glyceride, for example mono- or di- glyceride or mixtures thereof, which have free hydroxyl groups. Suitable partial glycerides include those derived from fatty acids with <NUM> to <NUM> carbon atoms, including, for example, those derived from coconut oil fatty acids and palm oil fatty acids. Examples include Lamegin® ZE <NUM>, Lamegin® ZE <NUM> and Lamegin® ZE <NUM> (Cognis Deutschland GmbH & Co. Thus suitable glycerides include a citric acid ester of the monoglyceride of hydrogenated tallow fatty acid, for example Lamegin® ZE <NUM>, or an ester of diacetyl tartaric acid with monoglyceride of hydrogenated tallow fatty acid, for example Lamegin® DW <NUM>, or citric acid ester based on sunflower oil fatty acid monoglyceride, for example Lamegin® ZE <NUM> FL. Such esters are described, for example, in <CIT> and <CIT>.

In at least some examples, the derivative of the glyceride is an ester of the at least one hydroxy polycarboxylic acid moiety. Suitable esters include esters of a carboxylic acid moiety of the hydroxy polycarboxylic acid. In at least some examples each carboxylic acid moiety of the hydroxyl polycarboxylic acid is independently derivatisable as an ester. Suitable ester derivatives include hydrocarbyl esters, in which the hydrocarbyl moiety has, for example, from <NUM> to <NUM> carbon atoms. Suitable hydrocarbyl moieties include alkyl moieties which have, for example, from <NUM> to <NUM> carbon atoms. In at least some examples, the hydrocarbyl moiety comprises one or more hetero atoms for example nitrogen and/or oxygen.

In at least some examples, the derivative of the glyceride is an ether or an ester of the hydroxyl moiety of the hydroxy polycarboxylic acid. In at least some examples, if more than one hydroxy moiety is present in the mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, each hydroxyl moiety is, for example, independently derivatisable as an ether or an ester. Suitable ethers include hydrocarbyl ethers. In at least some examples, the hydrocarbyl moiety of each ether independently has from <NUM> to <NUM> carbon atoms, for example from <NUM> to <NUM> carbon atoms. In at least some examples, the hydrocarbyl moiety of each ether is independently an alkyl moiety. Suitable alkyl moieties of each ether independently include alkyl moieties containing from <NUM> to <NUM> carbon atoms, for example from <NUM> to <NUM> carbon atoms. In at least some examples, the hydrocarbyl moiety of each ether independently comprises one or more hetero atoms, for example nitrogen and/or oxygen. In at least some examples, each ester is independently a hydrocarbyl ester. In at least some examples, the hydrocarbyl moiety of each ester has from <NUM> to <NUM> carbon atoms. Suitable hydrocarbyl moieties of each ester independently include alkyl moieties. In at least some examples, the alkyl moiety of each ester independently has from <NUM> to <NUM> carbon atoms. In at least some examples, the hydrocarbyl moiety of each ester independently comprises one or more hetero atoms, for example nitrogen and/or oxygen.

If the saturated, mono-unsaturated or polyunsaturated, branched or linear carboxylic acid containing <NUM> to <NUM> carbon atoms is a polycarboxylic acid, the derivative of the glyceride in at least some examples, is an ester of a carboxylic acid moiety of one or more of the at least one saturated, mono-unsaturated or poly-unsaturated, branched or linear, polycarboxylic acid containing from <NUM> to <NUM> carbon atoms, if present. In at least some examples, each ester independently is a hydrocarbyl ester. Suitable hydrocarbyl moieties of each ester independently include those containing from <NUM> to <NUM> carbon atoms. In at least some examples, the hydrocarbyl moiety is an alkyl moiety. Suitable alkyl moieties of each ester independently include those containing from <NUM> to <NUM> carbon atoms. In at least some examples, the hydrocarbyl moiety of each ester independently comprises one or more hetero atoms for example nitrogen and/or oxygen.

The oil-soluble mono-, di-, or tri-glycerides of at least one hydroxy polycarboxylic acid and derivatives thereof may be made by methods known in the art. Suitable methods for the preparation of the di- and tri-glycerides include the partial hydrolysis of a fat to produce a mono-glyceride followed by esterification with a hydroxy polycarboxylic acid. Suitable methods for the preparation of the mono-glycerides include esterification of glycerol with a hydroxy polycarboxylic acid. In at least some examples, the hydrocarbyl ether derivatives are made from corresponding hydrocarbyl halides.

The oil-soluble mono-, di-, or tri-glycerides of at least one hydroxy polycarboxylic acid and derivatives thereof do not contain zinc or molybdenum, that is, they are molybdenum-free and zinc-free. They also are sulphur-free and phosphorus-free.

Where the ashless, organic ester, anti-wear additive and/or friction modifier used as a pour point depressant additive in a non-aqueous lubricant composition comprises at least one long chain fatty acid ester of a hydroxy carboxylic acid in which the long chain fatty acid has at least <NUM> carbon atoms and the ester is an oil-soluble ester of a mono- or poly-hydroxy carboxylic acid containing <NUM> to <NUM> groups, as defined herein, in at least some examples, the oil-soluble ester has at least one long chain fatty acid ester moiety in an alpha position with respect to a carboxylic acid group or lower hydrocarbyl ester thereof.

In at least some examples, the oil-soluble ester defined contains from <NUM> to <NUM> carbon atoms. The number of carbon atoms in the ester may affect its solubility in oil of lubricating viscosity.

By oil-soluble is meant that the ester is soluble in an oil of lubricating viscosity for example, in a pour point depressant and friction modifying and/or antiwear improving amount, for example in an amount by weight of at least <NUM> ppm in an oil of lubricating viscosity. In at least some examples, the solubility is determined at ambient temperature, for example at <NUM>. In at least some examples, the solubility is determined at atmospheric pressure.

Suitable mono-hydroxy carboxylic acids include:.

In at least some examples, the mono-hydroxy carboxylic acid is citric acid.

Suitable poly-hydroxy carboxylic acids include:.

In at least some examples, the poly-hydroxy carboxylic acid is tartaric acid.

The long chain fatty acid of the ester contains at least <NUM> carbon atoms. Examples of long chain fatty acids include saturated, mono-unsaturated or poly-unsaturated long chain fatty acids. Examples of long chain fatty acids that are saturated carboxylic acids include, for example, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid. Examples of long chain fatty acids that are mono-unsaturated or polyunsaturated acids include, for example, oleic acid, linoleic acid, linolenic acid, myristoleic acid, palmitoleic acid, sapienic acid, erucic acid and brassidic acid. The long chain fatty acid may be branched or linear. Examples of long chain fatty acids include monocarboxylic acids and polycarboxylic acids. In at least some examples, the long chain fatty acid contains <NUM> to <NUM> carbon atoms, for example <NUM> to <NUM> carbon atoms, or <NUM> to <NUM> carbon atoms, or <NUM> to <NUM> carbon atoms or <NUM> to <NUM> carbon atoms, for example <NUM>, <NUM>, <NUM> or <NUM> carbon atoms, for example <NUM>, <NUM> or <NUM> carbons atoms, or for example <NUM> carbon atoms. Suitable saturated C<NUM> monocarboxylic acids include octanoic acid. Suitable saturated C<NUM> monocarboxylic acids include myristic acid. Suitable saturated C<NUM> monocarboxylic acids include palmitic acid. Suitable saturated C<NUM> monocarboxylic acids include stearic acid. Suitable unsaturated C<NUM> monocarboxylic acids include oleic acid and linoleic acid.

In at least some examples, each carboxylic acid group of the mono- or poly-hydroxyl carboxylic acid is independently derivatisable or derivatized as a lower hydrocarbyl ester. The lower hydrocarbyl esters have hydrocarbyl moieties which independently include for example those containing <NUM> to <NUM> carbon atoms. In at least some examples, the lower hydrocarbyl moieties are independently straight chain or branched chain alkyl moieties. Suitable lower hydrocarbyl moieties of the lower hydrocarbyl esters include those for example that are independently C<NUM> to C<NUM> alkyl moieties, for example C<NUM> to C<NUM> alkyl moieties, for example, ethyl moieties.

In at least some examples, the ester is triethyl citrate oleate (sometimes also called oleyl triethyl citrate). In at least some examples, the ester is triethyl citrate butyrate, triethyl citrate octanoate or triethyl citrate myristate, for example triethyl citrate myristate.

In at least some examples, the ester is diethyl tartrate dioleate (sometimes also called diethyl dioleate tartrate or diethyl dioleyl tartrate). In at least some examples, the ester is diethyl tartrate dibutyrate.

The long chain fatty acid esters do not contain zinc or molybdenum, that is, they are molybdenum-free and zinc-free. They also are sulphur-free and phosphorus-free. Generally, the esters as herein defined will have low volatility.

Methods for making the long chain fatty acid esters are known in the art, for example by reaction of the corresponding long chain fatty acid with the corresponding mono- or poly-hydroxy carboxylic acid or its corresponding lower hydrocarbyl esters. Another suitable method involves reaction of an acyl halide of the corresponding long chain fatty acid with the corresponding mono- or poly-hydroxy carboxylic acid or its corresponding lower hydrocarbyl esters. For example, triethyl citrate oleate may be made by reaction of triethyl citrate with oleyl chloride, for example in the presence of sodium hydride and tetrahydrofuran solvent. The esters may be made by the Yamaguchi reaction.

The esters may also be made by using enzymes as biological esterification catalysts.

As mentioned above, the use of long chain fatty acid esters of hydroxy carboxylic acids is not required by the appended claims.

However, in at least some examples, the at least one fatty acid ester of a polyol, at least one oil-soluble glyceride of at least one hydroxy polycarboxylic acid, or at least one oil-soluble mono, di, or tri-glyceride of an ether or ester derivative of the hydroxyl moiety of the hydroxy polycarboxylic acid, or at least one oil-soluble mono, di-, or tri-glyceride of an ester derivative of a carboxylic acid moiety of the hydroxy polycarboxylic acid, and the at least one long chain fatty acid ester of a hydroxy carboxylic acid, as defined herein, is used as pour point depressant additives in non-aqueous lubricant compositions in any suitable combination, provided that at least one oil-soluble glyceride of at least one hydroxy polycarboxylic acid, or at least one oil-soluble mono, di, or tri-glyceride of an ether or ester derivative of the hydroxyl moiety of the hydroxy polycarboxylic acid, or at least one oil-soluble mono, di-, or tri-glyceride of an ester derivative of a carboxylic acid moiety of the hydroxy polycarboxylic acid is used.

In at least some examples, the ashless, organic ester, anti-wear additives and/or friction modifiers are used as pour point depressant additives in any suitable lubricant compositions. Similarly, in at least some examples, the ashless, organic ester, anti-wear additives and/or friction modifiers are used to improve the low temperature properties of any conventional lubricant compositions. Further details of suitable lubricant compositions are set out herein.

In at least some examples, the lubricant composition comprises a major amount of oil of lubricating viscosity and a minor amount of at least one ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant. Major amount means greater than <NUM>% and minor amount means less than <NUM>% by weight.

In at least some examples, the lubricant composition and the oil of lubricating viscosity comprise base oil. Base oil comprises at least one base stock. In at least some examples, the oil of lubricating composition comprises one or more additives other than the ashless, organic ester, anti-wear additive and/or friction modifier; in at least some examples, the lubricant composition is essentially free of any conventional pour point depressant additives, as discussed herein. In at least some examples, the lubricant composition and/or the oil of lubricating viscosity comprises base oil in an amount of from greater than <NUM> % to about <NUM> % by weight, for example from about <NUM>% to about <NUM>% by weight.

The base stocks may be defined as Group I, II, III, IV and V base stocks according to API standard <NUM>, "<NPL> version <NUM>th edition Appendix E, as set out in Table <NUM>.

Group I, Group II and Group III base stocks may be derived from mineral oils Group I base stocks are typically manufactured by known processes comprising solvent extraction and solvent dewaxing, or solvent extraction and catalytic dewaxing. Group II and Group III base stocks are typically manufactured by known processes comprising catalytic hydrogenation and/or catalytic hydrocracking, and catalytic hydroisomerisation. A suitable Group I base stock is AP/E core <NUM>, for example, available from ExxonMobil. Suitable Group II basestocks include EHC <NUM> and EHC <NUM>, for example, available from ExxonMobil. Suitable group III base stocks include Yubase <NUM> and Yubase <NUM> available, for example, from SK Lubricants. Suitable Group V base stocks include ester base stocks, for example Priolube <NUM>, available from Croda International plc. Suitable Group IV base stocks include hydrogenated oligomers of alpha olefins. In at least some examples, the oligomers are made by free radical processes, Zeigler catalysis or by cationic Friedel-Crafts catalysis. Polyalpha olefin base stocks may be derived from C8, C10, C12, C14 olefins and mixtures of one or more thereof.

In at least some examples, the lubricant composition and the oil of lubricating viscosity comprise one or more base oil and/or base stock which is/are natural oil, mineral oil (sometimes called petroleum-derived oil or petroleum-derived mineral oil), non-mineral oil 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.

Suitable base oils and base stocks include those derived from processes such as chemical combination of simpler or smaller molecules into larger or more complex molecules (for example polymerisation, oligomerisation, condensation, alkylation, acylation).

Suitable base stocks and base oils include those derived from gas-to-liquids materials, coal-to-liquids materials, biomass-to-liquids materials and combinations thereof.

Suitable gas-to-liquids (sometimes also referred to as GTL) materials include those obtained by one or more process steps of synthesis, combination, transformation, rearrangement, degradation and combinations of two or more thereof applied to gaseous carbon-containing compounds. Suitable GTL derived base stocks and base oils include those obtained from the Fischer-Tropsch synthesis process in which synthesis gas comprising a mixture of hydrogen and carbon monoxide is catalytically converted to hydrocarbons, usually waxy hydrocarbons that are generally converted to lower-boiling materials hydroisomerisation and/or dewaxing (see for example, <CIT>).

Suitable biomass-to-liquids (sometimes also referred to as BTL) materials include those manufactured from compounds of plant origin, for example, by hydrogenation of carboxylic acids or triglycerides to produce linear paraffins, followed by hydroisomerisation to produced branched paraffins (see for example, <CIT>A).

Suitable coal-to-liquids materials include those made by gasifying coal to make synthesis gas which is then converted to hydrocarbons.

In at least some examples, the base oil and/or oil of lubricating viscosity have a kinematic viscosity at <NUM> in the range of <NUM> to <NUM> cSt, for example in the range of <NUM> to <NUM> cSt or in the range <NUM> to <NUM> cSt.

In the present invention, the lubricant composition is a multi-grade lubricating oil composition according to the API classification xW-y where x is <NUM>, <NUM>, <NUM>, <NUM> or <NUM> and y is <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, as defined by SAE J300 <NUM>, for example 5W-<NUM>, 5W-<NUM>, or 0W-<NUM>. In at least some examples, the lubricant composition has a High Temperature High Shear rate (HTHS) viscosity at <NUM> of at least <NUM> cP, for example as measured according to ASTM D4683, CEC L-<NUM>-A-<NUM> or ASTM D5481.

In at least some examples, the lubricant composition has an HTHS viscosity at <NUM> according to ASTM D4683 of from <NUM> to < <NUM> cP, for example about <NUM> cP.

Methods for preparing the lubricant composition include admixing an oil of lubricating viscosity with a pour point depressant effective amount of at least one additive which is an ashless, organic ester, anti-wear additive and/or friction modifier together with, optionally, at least one other lubricant additive.

Uses and methods of improving the low temperature properties of an oil of lubricating viscosity according to the present invention, include admixing an oil of lubricating viscosity with a pour point depressant effective amount of at least one additive which is an ashless, organic ester, anti-wear additive and/or friction modifier.

In at least some examples, the oil of lubricating viscosity is admixed with at least one additive in one or more steps by methods known in the art. In at least some examples, the additives are admixed as one or more additive concentrates or part additive package concentrates, optionally comprising solvent or diluent. In at least some examples, the oil of lubricating viscosity is prepared by admixing in one or more steps by methods known in the art, one or more base oils and/or base stocks, optionally with one or more additives and/or part additive package concentrates. In at least some examples, the additives, additive concentrates and/or part additive package concentrates are admixed with oil of lubricating viscosity or components thereof in one or more steps by methods known in the art.

In at least some examples, the lubricant composition further comprises at least one anti-wear additive other than the additive which is an ashless, organic ester, anti-wear additive and/or friction modifier. Such other anti-wear additives include ash-producing additives and ashless additives. Examples of such other anti-wear additives include non-phosphorus containing additives for example, sulphurised olefins. Examples of such other anti-wear additives also include phosphorus-containing antiwear additives. Examples of suitable ashless phosphorus-containing anti-wear additives include trilauryl phosphite and triphenylphosphorothionate and those disclosed in paragraph [<NUM>] of <CIT>. Examples of suitable ash-forming, phosphorus-containing anti-wear additives include dihydrocarbyl dithiophosphate metal salts. Examples of suitable metals of the dihydrocarbyl dithiophosphate metal salts include alkali and alkaline earth metals, aluminium, lead, tin, molybdenum, manganese, nickel, copper and zinc. Suitable dihydrocarbyl dithiophosphate metal salts include zinc dihydrocarbyl dithiophosphates (ZDDP). Suitable ZDDP's include those comprising hydrocarbyl groups independently containing <NUM> to <NUM> carbon atoms, for example <NUM> to <NUM> carbon atoms or <NUM> to <NUM> carbon atoms, or for example <NUM> to <NUM> carbon atoms or <NUM> to <NUM> carbon atoms, for example <NUM> to <NUM> carbon atoms. Examples of suitable hydrocarbyl groups include alkyl, cycloalkyl and alkaryl groups examples of which include that comprising ether or ester linkages and also those that comprise substituent groups for example, halogen or nitro groups. Suitable hydrocarbyl groups include alkyl groups including for example, linear and/or branched alkyl groups including for example those containing from <NUM> to <NUM> carbon atoms. Suitable ZDDP's include those comprising hydrocarbyl groups which are a mixture of secondary alkyl groups and primary alkyl groups for example, <NUM> mol. % secondary alkyl groups and <NUM> mol. % primary alkyl groups.

The ashless, organic ester, anti-wear additive and/or friction modifier may reduce the amount of phosphorus- and/or zinc- containing anti-wear additive which might be required to achieve a desired amount of anti-wear properties for the lubricant composition.

In at least some examples phosphorus-containing anti-wear additives are present in the lubricating oil composition at a concentration of <NUM> to <NUM> ppm by weight of phosphorus, for example <NUM> to <NUM> ppm by weight of phosphorus, or <NUM> to <NUM> ppm by weight of phosphorus, or <NUM> to <NUM> ppm by weight of phosphorus or <NUM> to <NUM> ppm by weight of phosphorus.

It has been found that the presence in the lubricant composition of at least one ashless, organic ester, anti-wear additive and/or friction modifier may assist in the performance of anti-wear additives, such as, for example, zinc dihydrocarbyl dithiophosphate additives. This may reduce the amount of metals, for example zinc, present in the lubricant composition.

This may also reduce the amount of phosphorus-containing anti-wear additives in the lubricant composition, which in turn may reduce the amount of phosphorus in the exhaust emissions when the lubricant is used to lubricate an internal combustion engine. The reduction in the amount of phosphorus in the exhaust emissions may have benefits for any exhaust after treatment system.

This may also reduce the amount of sulphur-containing anti-wear additives in the lubricant composition, which in turn may reduce the amount of sulphur in exhaust emissions when the lubricant is used to lubricate an internal combustion engine. The reduction in the amount of sulphur in the exhaust emissions may have benefits for any exhaust after treatment system.

In at least some examples, the lubricant composition comprises at least one friction modifier other than the additive which is an ashless, organic ester, anti-wear additive and/or friction modifier. Such other friction modifiers may be ash-producing additives or ashless additives. Examples of such other friction modifiers include fatty acid derivatives including, for example, fatty acid esters, amides, amines, and ethoxylated amines. Examples of such other friction modifiers also include molybdenum compounds, for example, organo molybdenum compounds, molybdenum dialkyldithiocarbamates, molybdenum dialkylthiophosphates, molybdenum disulphide, tri-molybdenum cluster dialkyldithiocarbamates, non-sulphur molybdenum compounds and the like. Suitable molybdenum-containing compounds are described, for example, in <CIT>, for example, in paragraphs [<NUM>] to [<NUM>].

Examples of friction modifiers other than the additive which is an ashless, organic ester, anti-wear additive and/or friction modifier also include a combination of an alkoxylated hydrocarbyl amine and a polyol partial ester of a saturated or unsaturated fatty acid or a mixture of such esters, for example as described in <CIT>.

In at least some examples, the ashless, organic ester, anti-wear additive and/or friction modifier is used as an alternative to other friction modifiers and/or to reduce the amount of such other friction modifiers that might be required to achieve a desired friction property for the lubricant composition. This may reduce the amount of metals, for example molybdenum, present in the lubricant composition.

In at least some examples, friction modifiers other than the additive which is ashless, organic ester, anti-wear additive and/or friction modifier, which are fatty acid derivative friction modifiers are present in the lubricating oil composition at a concentration of <NUM> to <NUM> % by weight actives, for example in the range of <NUM> to <NUM> % by weight actives.

In at least some examples, the molybdenum containing friction modifiers may be present in the lubricating oil composition at a concentration of <NUM> to <NUM> ppm by weight molybdenum, for example in the range of <NUM> to <NUM> ppm by weight.

In at least some examples, the lubricant composition also comprises other additives. Examples of such other additives include dispersants (metallic and non-metallic), dispersant viscosity modifiers, detergents (metallic and non-metallic), viscosity index improvers, viscosity modifiers, rust inhibitors, corrosion inhibitors, antioxidants (sometimes also called oxidation inhibitors), anti-foams (sometimes also called anti-foaming agents), seal swell agents (sometimes also called seal compatibility agents), extreme pressure additives (metallic, non-metallic, phosphorus containing, non-phosphorus containing, sulphur containing and non-sulphur containing), surfactants, demulsifiers, anti-seizure agents, wax modifiers, lubricity agents, anti-staining agents, chromophoric agents and metal deactivators.

Dispersants (also called dispersant additives) help hold solid and liquid contaminants, for example resulting from oxidation of the lubricant composition during use, in suspension and thus reduce sludge flocculation, precipitation and/or deposition, for example on lubricated surfaces. They generally comprise long-chain hydrocarbons, to promote oil-solubility, and a polar head capable of associating with material to be dispersed. Examples of suitable dispersants include oil soluble polymeric hydrocarbyl backbones each containing one or more functional groups which are capable of associating with particles to be dispersed. Suitable functional groups include amine, alcohol, amine-alcohol, amide and ester groups. In at least some examples, the functional groups are attached to the hydrocarbyl backbone through bridging groups. In at least some examples, more than one dispersant is present in the lubricant composition.

Examples of suitable ashless dispersants include oil soluble salts, esters, amino-esters, amides, imides and oxazolines of long chain hydrocarbon-substituted mono- and polycarboxylic acids or anhydrides thereof; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons containing polyamine moieties attached directly thereto; Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylene polyamine; Koch reaction products and the like. Examples of suitable dispersants include derivatives of long chain hydrocarbyl-substituted carboxylic acids, for example in which the hydrocarbyl group has a number average molecular weight of up to <NUM>, for example <NUM> to <NUM>, <NUM> to <NUM>, <NUM> to <NUM> or less than <NUM>. 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. Suitable dispersants include those that are borated or non-borated. A suitable non-borated dispersant is ADX <NUM>.

Additionally or alternatively, in at least some examples, dispersancy is provided by polymeric compounds capable of providing viscosity index improving properties and dispersancy. Such compounds are generally known as dispersant viscosity improver additives or multifunctional viscosity improvers. Methods of preparing such suitable dispersant viscosity modifiers include chemically attaching functional moieties (for example, amines, alcohols and amides) to polymers which tend to have number average molecular weights of at least <NUM>, for example in the range <NUM> to <NUM> (for example, as determined by gel permeation chromatography or light scattering methods). Examples of suitable dispersant viscosity modifiers and methods of making them are described in <CIT>, <CIT> and <CIT>. In at least some examples, more than one dispersant viscosity modifier is present in the lubricant composition.

Detergents (also called detergent additives) may help reduce high temperature deposit formation, for example, on pistons in internal combustion engines, including, for example, high-temperature varnish and lacquer deposits, by helping to keep finely divided solids in suspension in the lubricant composition. Detergents may also have acid-neutralising properties. In at least some examples, ashless (that is non-metal containing detergents) are present. 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 in relation to the stoichiometric amount required to neutralise the organic acid. The excess metal is usually in the form of a colloidal dispersion of metal carbonate and/or hydroxide. Examples of suitable metals include Group I and Group <NUM> metals, for example calcium, magnesium and combinations thereof. In at least some examples, more than one metal is present.

Examples of suitable organic acids include sulphonic acids, phenols (sulphurised or sulphurised and including, for example, phenols with more than one hydroxyl group, phenols with fused aromatic rings, phenols which have been modified, for example alkylene bridged phenols, and Mannich base-condensed phenols and saligenin-type phenols, produced, for example, by reaction of phenol and an aldehyde under basic conditions) and sulphurised derivatives thereof, and carboxylic acids including, for example, aromatic carboxylic acids (for example, hydrocarbyl-substituted salicylic acids and sulphurised derivatives thereof, for example hydrocarbyl substituted salicylic acid and derivatives thereof). In at least some examples more than one type of organic acid may be present.

In at least some examples, additionally or alternatively, non-metallic detergents are be present. Suitable non-metallic detergents are described for example in <CIT>.

In at least some examples, more than one detergent is present in the lubricant composition.

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 remaining shear stable at elevated temperatures whilst also exhibiting acceptable viscosity and fluidity at low temperatures.

Examples of suitable viscosity modifiers include high molecular weight hydrocarbon polymers (for example polyisobutylene, copolymers of ethylene and propylene 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 <NUM>,<NUM> to <NUM>,<NUM>,<NUM>, preferably <NUM>,<NUM> to <NUM>,<NUM> as determined by gel permeation chromatography or light scattering methods.

Viscosity modifiers may have additional functions as multifunction viscosity modifiers. In at least some examples more than one viscosity index improver is present.

Rust inhibitors generally protect lubricated metal surfaces against chemical attack by water or other contaminants. Examples of suitable rust inhibitors include non-ionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, polyoxyalkylene polyols, anionic alkyl sulphonic acids, zinc dithiophosphates, metal phenolates, basic metal sulphonates, fatty acids and amines.

In at least some examples, more than one rust inhibitor is present.

Corrosion inhibitors (also called anti-corrosive agents) reduce the degradation of metallic parts contacted with the lubricant composition. Examples of corrosion inhibitors include phosphosulphurised hydrocarbons and the products obtained by the reaction of phosphosulphurised hydrocarbon with an alkaline earth metal oxide or hydroxide, non-ionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, thiadiazoles, triazoles and anionic alkyl sulphonic acids. Examples of suitable epoxidised ester corrosion inhibitors are described in <CIT>.

In at least some examples, more than one corrosion inhibitor is present.

Antioxidants (sometimes also called oxidation inhibitors) reduce the tendency of oils to deteriorate in use. Evidence of such deterioration might include for example the production of varnish-like deposits on metal surfaces, the formation of sludge and viscosity increase. ZDDP's exhibit some antioxidant properties.

Examples of suitable antioxidants other than ZDDP's include alkylated diphenylamines, N-alkylated phenylenediamines, phenyl-α-naphthylamine, alkylated phenyl-α-naphthylamines, dimethylquinolines, trimethyldihydroquinolines and oligomeric compositions derived therefrom, hindered phenolics (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), sulphurised alkyl phenols and alkali and alkaline earth metal salts thereof, alkylated hydroquinones, hydroxylated thiodiphenyl ethers, alkylidenebisphenols, thiopropionates, metallic dithiocarbamates, <NUM>,<NUM>,<NUM>-dimercaptothiadiazole and derivatives, oil soluble copper compounds (for example, copper dihydrocarbyl thio- or thio-phosphate, copper salts of a synthetic or natural carboxylic acid, for example a C<NUM> to C<NUM> fatty acid, an unsaturated acid or a branched carboxylic acid, for example basic, neutral or acidic CuI and/or CuII salts derived from alkenyl succinic acids or anhydrides), alkaline earth metal salts of alkylphenolthioesters, for example, containing C<NUM> to C<NUM> alkyl side chains, calcium nonylphenol sulphide, barium t-octylphenyl sulphide, dioctylphenylamine, phosphosulphised or sulphurised hydrocarbons, oil soluble phenates, oil soluble sulphurised phenates, calcium dodecylphenol sulphide, phosphosulphurised hydrocarbons, sulphurised hydrocarbons, phosphorus esters, low sulphur peroxide decomposers and the like.

In at least some examples, more than one antioxidant is present. In at least some examples, more than one type of antioxidant is present.

Anti-foams (sometimes also called anti-foaming agents) retard the formation of stable foams. Examples of suitable anti-foam agents include silicones, organic polymers, siloxanes (including poly siloxanes and (poly) dimethyl siloxanes, phenyl methyl siloxanes), acrylates and the like.

In at least some examples, more than one anti-foam is present.

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

In at least some examples , more than one seal swell agent is present.

In at least some examples other additives are present in the lubricant composition and these include for example, extreme pressure additives (including metallic, non-metallic, phosphorus containing, non-phosphorus containing, sulphur containing and non-sulphur containing extreme pressure additives), surfactants, demulsifiers, anti-seizure agents, wax modifiers, lubricity agents, anti-staining agents, chromophoric agents and metal deactivators.

Some additives may exhibit more than one function.

The amount of demulsifier, if present, might be higher than in conventional lubricants to off-set any emulsifying effect of the mono-, di-, or tri-glyceride additive.

The representative suitable and more suitable independent amounts of additives (if present) in the lubricant composition are given in Table <NUM>. The concentrations expressed in Table <NUM> are by weight of active additive compounds, that is, independent of any solvent or diluent.

In at least some examples, more than one of each type of additive is present. Within each type of additive, in at least some examples, more than one class of that type of additive is present. In at least some examples, more than one additive of each class of additive is present. In at least some examples additives are supplied by manufacturers and suppliers in solvent or diluents.

In at least some examples, the ashless, organic ester, anti-wear additive and/or friction modifier is used as a pour point depressant in any suitable non-aqueous lubricant composition.

In at least some examples , the ashless, organic ester, anti-wear additive and/or friction modifier is used as a pour point depressant in a lubricant composition which is a functional fluid, for example a metalworking fluid. In at least some examples, this metalworking fluid is to lubricate metals during machining, rolling and the like.

In at least some examples, the ashless, organic ester, anti-wear additive and/or friction modifier is used as a pour point depressant in a lubricant composition which is a power transmission fluid, for example as an automatic transmission fluid, a fluid in a clutch (for example a dual clutch), a gear lubricant, or in other automotive applications and the like. In at least some examples, the additive and lubricant composition are used in aviation lubricant applications.

In at least some examples, the ashless, organic ester, anti-wear additive and/or friction modifier is used as a pour point depressant in a non-aqueous lubricant composition used to lubricate a solid surface, including, for example, metallic surfaces and non-metallic surfaces. Suitable metallic surfaces include surfaces of ferrous based materials, for example cast iron and steels; surfaces of aluminium-based solids, for example aluminium-silicon alloys; surfaces of metal matrix compositions; surfaces of copper and copper alloys; surfaces of lead and lead alloys; surfaces of zinc and zinc alloys; and surfaces of chromium-plated materials. Suitable non-metallic surfaces include surfaces of ceramic materials; surfaces of polymer materials; surfaces of carbon-based materials; and surfaces of glass. Other surfaces which may be lubricated include surfaces of coated materials, for example surfaces of hybrid materials, for example metallic materials coated with non-metallic materials and non-metallic materials coated with metallic materials; surfaces of diamond-like carbon coated materials and SUMEBore™ materials, for example as described in Sulzer technical review <NUM>/<NUM> pages <NUM>-<NUM>.

In at least some examples, the ashless, organic ester, anti-wear additive and/or friction modifier is used in a non-aqueous lubricant composition to lubricate a surface at any typical temperature which might be encountered in a lubricating environment, for example at a temperature such as may be encountered in an internal combustion engine, for example a temperature in the range of ambient to <NUM>, e.g. <NUM> to <NUM>. Typical ambient temperature is <NUM>, but in at least some examples is less than <NUM>, for example <NUM> or lower.

In at least some examples, the ashless, organic ester, anti-wear additive and/or friction modifier is used as a pour point depressant in a lubricant composition which is used to lubricate an internal combustion engine, for example as a crankcase lubricant. Examples of suitable engines include spark-ignition, internal combustion engines, and compression-ignition, internal combustion engines. In at least some examples, the internal combustion engine is a spark-ignition internal combustion engine used in automotive or aviation applications. Suitable internal combustion engines include two-stroke compression-ignition engines and in at least some examples, the ashless, organic ester, anti-wear additive and/or friction modifier is used as a pour point depressant in a system oil lubricant composition and/or a cylinder oil lubricant composition used to lubricate the engine. In at least some examples, the two-stroke compression-ignition engine is used in marine applications.

The present invention is defined in the appended claims and relates to the use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive in a non-aqueous lubricant composition. Also disclosed herein, though not specifically claimed, are the following methods.

A first method of improving the low temperature properties of an oil of lubricating viscosity, which method comprises admixing said oil with at least one additive which is an ashless, organic ester, anti-wear additive and/or friction modifier.

A second method is as described in the first method but with the further feature that the ashless, organic ester, anti-wear additive and/or friction modifier depresses the pour point of the non-aqueous lubricant composition by at least <NUM>.

A third method is as described in the first method but with the further feature that the non-aqueous lubricant composition is used to lubricate an internal combustion engine.

A fourth method is as described in the third method but with the further feature that the non-aqueous lubricant composition provides effective lubrication at a temperature of - <NUM> or less, preferably at a temperature of -<NUM> or less.

A fifth method is as described in the first method but with the further feature that the non-aqueous lubricant composition has a pour point of -<NUM> or less, preferably -<NUM> or less.

A sixth method is as described in the first method but with the further feature that the non-aqueous lubricant composition has a viscosity of <NUM>,<NUM> cP or less, preferably <NUM>,<NUM> cP or less, when measured in the Mini Rotary Viscosity test at -<NUM>.

A seventh method is as described in the first method but with the further feature that the non-aqueous lubricant composition is essentially free of any conventional pour point depressants selected from C<NUM> to C<NUM> dialkyl fumarate/vinyl acetate copolymers, methacrylates, polyacrylates, polyarylamides, polymethacrylates, polyalkyl methacrylates, vinyl fumarates, styrene esters, condensation products of halo paraffin waxes and aromatic compounds, vinyl carboxylate polymers, terpolymers of dialkyfumarates, vinyl esters of fatty acids and allyl vinyl ethers, and wax naphthalene.

An eighth method is as described in the first method but with the further feature that the ashless, organic ester, anti-wear additive and/or friction modifier is:.

A ninth method is as described in the eighth method but with the further feature that the at least one fatty acid ester of a polyol is an ester of a fatty acid containing <NUM> to <NUM> carbon atoms, preferably wherein the at least one fatty acid ester of a polyol is glycerol mono-oleate, glycerol monostearate, glycerol monolaurate, glycerol dodecanoate or glycerol octadodecanoate.

A tenth method is as described in the eighth method but with the further feature that the hydroxy polycarboxylic acid has at least one hydroxy group which is in an alpha position with respect to a carboxylic moiety.

An eleventh method is as described in the tenth method but with the further feature that the hydroxy polycarboxylic acid is citric acid.

A twelfth method is as described in the eighth method but with the further feature that the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and at least one second carboxylic acid which is a saturated, mono-unsaturated or poly-unsaturated, branched or linear, monocarboxylic or polycarboxylic acid containing <NUM> to <NUM> carbon atoms, or a derivative thereof.

A thirteenth method is as described in the eighth method but with the further feature that the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a mono-unsaturated C<NUM> to C<NUM> monocarboxylic acid, or a derivative thereof.

A fourteenth method is as described in the eighth method but with the further feature that the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a polyunsaturated C<NUM> to C<NUM> monocarboxylic acid, or a derivative thereof.

A fifteenth method is as described in the thirteenth method but with the further feature that the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a mono-unsaturated or polyunsaturated C<NUM> monocarboxylic acid, or a derivative thereof.

A sixteenth method is as described in the fifteenth method but with the further feature that the glyceride is a glyceride of citric acid and a mono-unsaturated or polyunsaturated C<NUM> monocarboxylic acid, or a derivative thereof.

A seventeenth method is as described in the thirteenth method but with the further feature that the mono-unsaturated or polyunsaturated C<NUM> to C<NUM> carboxylic acid is linear.

An eighteenth method is as described in the eighth method but with the further feature that the glyceride is a glyceride of citric acid and oleic acid, a glyceride of citric acid and linoleic acid or a mixture thereof.

A nineteenth method is as described in the twelfth method but with the further feature that the carboxylic acid containing <NUM> to <NUM> carbon atoms is a polycarboxylic acid and the derivative is an ester of a carboxylic acid moiety of said polycarboxylic acid.

A twentieth method is as described in the eighth method but with the further feature that the derivative of the glyceride is an ether of the hydroxyl moiety of the hydroxy polycarboxylic acid.

A twenty-first method is as described in the eighth method but with the further feature that the derivative of the glyceride is an ester of the hydroxyl moiety of the hydroxy polycarboxylic acid.

A twenty-second method is as described in the eighth method but with the further feature that the derivative of the glyceride is an ester of a carboxylic acid moiety of the hydroxy polycarboxylic acid.

A twenty-third method is as described in the eighth method but with the further feature that the oil-soluble ester has at least one long chain fatty acid ester moiety in an alpha position with respect to a carboxylic acid group or lower hydrocarbyl ester thereof.

A twenty-fourth method is as described in the eighth method but with the further feature that the mono- or poly- hydroxy carboxylic acid is selected from the group consisting of glycolic acid, lactic acid, citric acid, malic acid, monohydroxy trimesic acid, hydrogenated monohydroxy trimesic acid and tartaric acid.

A twenty-fifth method is as described in the eighth method but with the further feature that the mono- or poly- hydroxy carboxylic acid is citric acid or tartaric acid.

A twenty-sixth method is as described in the eighth method but with the further feature that the long chain fatty acid has <NUM> to <NUM> carbon atoms. A twenty-seventh method is as described in the twenty-sixth method but with the further feature that the long chain fatty acid has <NUM> to <NUM> carbon atoms, <NUM> to <NUM> carbon atoms, <NUM> to <NUM> carbon atoms, or <NUM>, <NUM> or <NUM> carbon atoms.

A twenty-eighth method is as described in the twenty-seventh method but with the further feature that the long chain fatty acid is oleic acid or myristic acid.

A twenty-ninth method is as described in any one of the eighth or twenty-third to twenty-eighth methods but with the further feature that the lower hydrocarbyl esters have hydrocarbyl moieties which independently have <NUM> to <NUM> carbon atoms.

A thirtieth method is as described in the twenty-ninth method but with the further feature that the lower hydrocarbyl moieties of the lower hydrocarbyl esters are independently ethyl.

A thirty-first method is as described in the eighth method but with the further feature that the oil-soluble ester is triethyl citrate butyrate, triethyl citrate oleate, triethyl citrate octanoate, triethyl citrate myristate, diethyl tartrate dibutyrate or diethyl tartrate dioleate.

A thirty-second method is as described in the first method but with the further feature that the method is of depressing the pour point of the oil of lubricating viscosity.

The invention will now be described by way of example only with reference to the following experiments and examples in which examples according to the present invention are labelled numerically as Example <NUM>, Example <NUM>, etc. (unless otherwise indicated) and experiments not according to the present invention are labelled alphabetically as Experiment A, Experiment B, etc..

A 0W-<NUM> lubricant composition (Lubricant A) was prepared to model a typical multi-grade lubricant oil composition, but containing no conventional pour point depressant. The lubricant composition was made by admixing additives as in a commercially available additive package containing dispersants, detergents, anti-oxidants and antifoam with a Group III base oil, ZDDP and viscosity modifier.

A lubricant composition (Lubricant <NUM>) according to the present invention was prepared by admixing <NUM>% by weight of Lubricant A with <NUM>% by weight Citrem SP70 (Trade Mark) (a diglyceride of citric acid and oleic/linoleic acid).

Several other lubricant compositions (Lubricants <NUM> to <NUM>) were prepared as Lubricant <NUM> but with increasing proportions of Citrem SP70, as indicated below. Thus, Lubricant <NUM> comprised <NUM> wt% Citrem SP70, Lubricant <NUM> comprised <NUM> wt% Citrem SP70 and Lubricant <NUM> comprised <NUM> wt% Citrem SP70.

A further lubricant composition (Lubricant <NUM>) was prepared in the same way as Lubricant <NUM>, but the Citrem SP70 was replaced by <NUM> wt% Infineum C <NUM> (a glycerol mono-oleate organic ester friction modifier).

Several other lubricant compositions (Lubricants <NUM> to <NUM>) were prepared as Lubricant <NUM> but with increasing proportions of Infineum C <NUM>, as indicated below. Thus, Lubricant <NUM> comprised <NUM> wt% Infineum C <NUM>, Lubricant <NUM> comprised <NUM> wt% Infineum C <NUM> and Lubricant <NUM> comprised <NUM> wt% Infineum C <NUM>.

Two further lubricant compositions (Lubricants <NUM> and <NUM>) according to the present invention were prepared in an identical manner to Lubricant <NUM> but using different batches of Citrem SP70.

Several other lubricant compositions (Lubricants B to E) were prepared as Lubricants <NUM> to <NUM> respectively but using a conventional pour point depressant, Viscoplex <NUM>-<NUM> (Evonik), rather than Citrem SP70 as the pour point depressant.

Lubricants A to E are not according to the present invention because the lubricant compositions do not contain any ashless, organic ester, anti-wear additive and/or friction modifiers as pour point depressants. Lubricants <NUM> to <NUM> are not according to the present invention because the lubricant compositions do not contain at least one oil-soluble mono, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof.

Pour point evaluations were undertaken for Lubricants <NUM> to <NUM> and Lubricants A to E.

Pour point evaluation was carried out according to ASTM D97. Samples of lubricants were heated to erase any thermal memory and were then cooled in cylindrical test jars at a specified rate and examined at <NUM> intervals for flow characteristics. The test was continued until no movement was observed when the test jar was held horizontally for <NUM> seconds. The lowest temperature at which movement of each lubricant was observed was recorded as the pour point for the lubricant. The results of the pour point tests are shown in Table <NUM>. Experiments A to E are not according to the present invention because the lubricant compositions do not contain any ashless, organic ester, anti-wear additive and/or friction modifier. Lubricants <NUM> to <NUM> are not according to the present invention because the lubricant compositions do not contain at least one oil-soluble mono, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof. Examples <NUM> to <NUM> and <NUM> to <NUM> are according to the present invention.

The results in Table <NUM> show that the ashless, organic ester, anti-wear additive and/or friction modifiers, such as glycerol mono-oleate and, in particular, a diglyceride of citric acid and an unsaturated C<NUM> carboxylic acid (e.g. oleic and/or linoleic acid), for example Citrem SP70 (Trade Mark), exhibit good pour point depressant properties in a lubricant composition. In particular, the diglyceride of citric acid and an unsaturated C<NUM> carboxylic acid significantly decreases the pour point of the lubricant composition, i.e. to -<NUM>, when used at its typical treat rate for use as an anti-wear additive (<NUM> wt%). Furthermore, at treat rates of <NUM> to <NUM> wt%, the pour point depressant effect of the diglyceride of citric acid and an unsaturated C<NUM> carboxylic acid is comparable to the pour point depressant effect of a commercial pour point depressant, Viscoplex <NUM>-<NUM>, when this is used at its typical treat rate of from <NUM> to <NUM> wt%.

As also shown in Table <NUM>, the pour point depressant effect of the diglyceride of citric acid and unsaturated C<NUM> carboxylic acid is consistent across three different batches of material (when used at a treat rate of <NUM> wt%).

Mini Rotary Viscometer (MRV) tests according to ASTM D4684, but modified to test viscosity at -<NUM>, were undertaken for lubricants with the same compositions as those used in the previously described tests.

The apparatus used was a Mini-Rotary Viscometer, consisting of viscometric cells each containing a calibrated rotor-stator assembly, in a temperature-controlled aluminium block. The lubricant samples were cooled from <NUM> to -<NUM> at a non-linear programmed cooling rate over a period exceeding <NUM> hours. Standard torques were then applied to the rotor shafts. Firstly, a small torque was applied to determine whether yield stress was present, then a larger one was used to determine the apparent viscosity.

The results for the tests performed at -<NUM> are shown in Table <NUM>. Experiments F to J are not according to the present invention because the lubricant compositions do not contain any ashless, organic ester, anti-wear additives and/or friction modifiers as pour point depressants. Examples <NUM> to <NUM> are not according to the present invention because the lubricant compositions do not contain at least one oil-soluble mono, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof. Examples <NUM> to <NUM> and <NUM> to <NUM> are according to the present invention.

The results in Table <NUM> show that the ashless, organic ester, anti-wear additive and/or friction modifiers, and in particular glycerol mono-oleate, for example Infineum C <NUM>, and a diglyceride of citric acid and an unsaturated C<NUM> carboxylic acid (e.g. oleic and/or linoleic acid), for example Citrem SP70 (Trade Mark), exhibit good pour point depressant properties in lubricant compositions when evaluated in an MRV test at -<NUM>. In particular, when used at a typical treat rate for use at an anti-wear additive (e.g. <NUM> wt%) both glycerol mono-oleate and a diglyceride of citric acid and an unsaturated C<NUM> carboxylic acid are as effective as pour point depressants in the MRV test as a commercial pour point depressant, Viscoplex <NUM>-<NUM> (when used at its typical treat rate of <NUM> to <NUM> wt%). Furthermore, at treat rates of <NUM> wt%, both glycerol mono-oleate and the diglyceride of citric acid and an unsaturated C<NUM> carboxylic acid have improved performances as pour point depressants in the MRV test at -<NUM> when compared to all treat rates of the commercial pour point depressant Viscoplex <NUM>-<NUM> (from <NUM> wt% to <NUM> wt%).

As also shown in Table <NUM>, the performance of the diglyceride of citric acid and an unsaturated C<NUM> carboxylic acid as a pour point depressant at a treat rate of <NUM>% is consistent across three different batches of material when measured in the MRV test at -<NUM>.

The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention.

Claim 1:
The use of an ashless, organic ester, anti-wear additive and/or friction modifier as a pour point depressant additive in a non-aqueous lubricant composition being a multi-grade lubricating oil composition according to the API classification xW-y where x is <NUM>, <NUM>, <NUM>, <NUM> or <NUM> and y is <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, as defined by SAE J300 <NUM>, wherein the ashless, organic ester, anti-wear additive and/or friction modifier is:
i) at least one oil-soluble mono, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or at least one oil-soluble mono, di-, or tri-glyceride of an ether or ester derivative of the hydroxyl moiety of the hydroxy polycarboxylic acid, or at least one oil-soluble mono, di-, or tri-glyceride of an ester derivative of a carboxylic acid moiety of the hydroxy polycarboxylic acid.