USE OF GLYCERIDES OF HYDROXY POLYCARBOXYLIC ACIDS AS
ANTI-CAMSHAFT-WEAR ADDITIVES IN LUBRICANTS AND FUELS
This invention relates to anti-camshaft-wear additives and their use in lubricant
compositions and fuel compositions.
It is known to use anti-wear additives and/or friction modifiers in lubricant
compositions. It is also known to use anti-wear additives and/or friction modifiers in fuel
compositions for internal combustion engines.
The ingress of fuel and fuel additives into the crankcase lubricant of an internal
combustion engine is known, for example from paragraph 2 of the abstract of SAE paper
2001-01-1962 by C. Y. Thiel et al. "The Fuel Additive/lubricant Interactions:..."
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 composition engines, they give rise to ash which contributes to
particulate matter in the exhaust emissions from the internal combustion engines. It is
therefore desirable to reduce the amount of ash-forming additives used for lubricating
internal combustion engines. It is also desirable to reduce the amount of zinc and/or
phosphorus and/or sulphur in the exhaust emissions from internal combustion engines. A
range of anti-wear additives and/or friction modifiers which contain neither zinc nor
phosphorus, or at least contain them in reduced amounts, have therefore been produced.
Various methods have been developed for testing the effectiveness of wear reducing
additives, including both ash-forming and ashless additives. A particularly widely used
test is the Sequence IVA test, and a number of organic, ashless anti-wear components are
known to improve performance in these tests. However, whilst the Sequence IVA test is
the key wear test in the API test sequences, it is not applicable for European ACEA
specifications. The key engine wear test for ACEA specifications is the diesel OM646LA
test. Generally, organic, ashless anti-wear additives, for example oleamide, that are known
to improve performance in the Sequence IVA test do not give similar benefits in the
OM646LA test. The OM646LA test particularly measures camshaft wear, and it would
therefore be useful to identify ashless, anti-wear additives that function as anti-camshaftwear
additives in lubricant compositions, or in fuel compositions when the fuels are used
to lubricate internal combustion engines and at least a portion of the additives ingress into
the lubricating composition during operation of said engine; for example additives which
enable compositions containing the additives to pass the OM646LA engine test.
International patent application publication WO 2008/124191 relates to the use of
one or more oil-soluble fatty acid esters of a polyol in a lubricating oil composition having
a base oil comprising a major amount of a gas-to-liquid (GTL) derived base oil. Polyols
are said to include diols, triols and the like. It is stated therein that the esters of the polyols
are those of carboxylic acids having 12 to 24 carbon atoms According to WO
2008/124191, preferably the fatty acid ester is a fatty acid ester of glycerol, more
preferably, a monoester of glycerol and most preferably, the ester is glycerol
monooctadecanoate. WO 2008/124191 does not describe the use of glycerides of hydroxy
polycarboxylic acids.
International patent application publication WO 201 1/161406 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 WO 201 1/161406,
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. WO 201 1/161406 does not describe the use of oilsoluble
mono-, di-, or tri-glycerides of at least one hydroxy polycarboxylic acid, or
derivatives thereof, as anti-camshaft-wear additives.
There remains a need for alternative compositions exhibiting anti-camshaft-wear
properties, for example for use in non-aqueous lubricant compositions and/or for use in
internal combustion engine fuel compositions.
Thus, according to the present invention there is provided 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-camshaft-wear additive in a non-aqueous lubricant composition and/or
in a fuel composition.
Also according to another aspect of the present invention there is provided a method
of improving the anti-camshaft-wear properties of an oil of lubricating viscosity, which
method comprises admixing said oil with an effective amount of at least one additive
which is an oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic
acid, or a derivative thereof.
The present invention solves the technical problem defined above by the use as an
anti-camshaft-wear additive of an oil-soluble mono-, di-, or tri-glyceride of at least one
hydroxy polycarboxylic acid, or a derivative thereof.
In at least some examples, 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-camshaft-wear
additive in a non-aqueous lubricant composition and/or in a fuel composition reduces
camshaft wear as measured in the OM646LA engine test.
Uses of the non-aqueous lubricant composition incorporating an oil-soluble mono-,
di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, as
an anti-camshaft-wear additive include all conventional lubricant purposes, for example to
lubricate internal combustion engines. In at least some examples, the lubricating oil
composition may initially be free of oil-soluble mono-, di-, or tri-glycerides of hydroxy
polycarboxylic acids, or derivatives thereof, or contain only very low amounts thereof, the
oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a
derivative thereof, instead being provided in liquid fuel composition used to operate an
internal combustion engine, and at least a portion of said glyceride ingressing into the
lubricating oil composition to act as an anti-camshaft-wear additive during the operation of
said engine.
The amount of oil-soluble mono-, di- or tri-glyceride of at least one hydroxy
polycarboxylic acid, or a derivative thereof, used as an anti-camshaft-wear additive in a
non-aqueous lubricant composition in accordance with the present invention includes any
amount suitable to reduce camshaft wear, for example an amount sufficient for the
composition to pass the OM646LA engine test, for example from 0.1 to 5% by weight,
from 0.2 to 2.5% by weight or from 0.5 to 1% by weight.
In at least some examples, the numerical percentages referenced in this application
may be preceded by the word "about."
The amount of oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy
polycarboxylic acid, or a derivative thereof, used as an anti-camshaft-wear additive in a
fuel composition in accordance with the present invention includes any amount suitable to
cause a lubricating oil composition used to provide lubrication to an internal combustion
engine fuelled by the liquid fuel composition to have anti-camshaft-wear properties
following the ingress of the oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy
polycarboxylic acid, or a derivative thereof, into lubricating oil composition during
operation of said engine, for example sufficient to provide amounts as discussed above.
In at least some examples, the hydroxy polycarboxylic acid of the oil-soluble mono-,
di-, or tri-glyceride of at least one hydroxy carboxylic acid, or a derivative thereof, used as
an anti-camshaft-wear additive 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
4 to 22 carbon atoms, for example 4 to 15 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 16 to 80 carbon atoms. The number of carbon atoms in the
glyceride may affect its solubility in oil of lubricating viscosity and/or in liquid fuel.
By oil-soluble is meant that the glyceride is soluble in an oil of lubricating viscosity
and/or a liquid fuel, suitably in an anti-camshaft-wear improving amount, for example in
an amount by weight of at least 200 ppm in an oil of lubricating viscosity and/or in an
amount by weight of at least 10 ppm in a liquid fuel. In at least some examples, the
solubility is determined at ambient temperature, for example at 20 °C. Methods of
determining the solubility include those for determining solubility at atmospheric pressure.
Suitable hydroxy polycarboxylic acids include:
o citric acid (also sometimes called 3-carboxy-3-hydroxy pentanedioic acid; 2-
hydroxypropane- 1,2,3- tricarboxylic acid; or 3-hydroxypentanedioic acid-3-
carboxylic acid);
o tartaric acid (also sometimes called 2,3-dihydroxybutanedioic acid; or 2,3-
dihydroxysuccinic acid);
o malic acid (also sometimes called hydroxybutanedioic acid);
o monohydroxy trimesic acid; and
o hydrogenated monohydroxy trimesic acid (sometimes also called 1,3,5 tricarboxy, 2-
hydroxy cyclohexane).
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 having 4 to 22 carbon atoms, or a derivative
thereof.
In at least some examples, the second carboxylic acid is saturated, mono-unsaturated
or poly-unsaturated. Suitably, 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-13-
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):
OR'
RO - CH2 - C
I
- CH2 - OR" (I)
wherein RO, OR' and OR" independently represent:
-OH;
a saturated, mono-unsaturated or poly-unsaturated, branched or linear,
monocarboxylic or polycarboxylic group having from 4 to 22 carbon atoms or an ether or
an ester thereof; or
a hydroxy polycarboxylic acid moiety or an ether and/or ester thereof, 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 having from 4 to 22 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 4 to 22 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 at least some examples, in formula (I), when present, each saturated, branched or
linear, monocarboxylic or polycarboxylic group having from 4 to 22 carbon atoms or an
ester thereof, 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 having from 4 to 22 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 C4 to C 2 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 C4 to C22 polycarboxylic acid, or a derivative thereof.
Suitable polycarboxylic acids include branched or linear acids. In at least some examples,
the glyceride is a glyceride of at least one hydroxy polycarboxylic acid and a saturated C4
to C22 monocarboxylic acid, or a derivative thereof. Suitable monocarboxylic acids
include branched and linear acids. Suitable saturated C1 monocarboxylic acids include
palmitic acid. Suitable saturated C1 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 C4 to C monocarboxylic acid, or a derivative
thereof. Suitable unsaturated monocarboxylic acids include branched and linear acids. In
at least some examples, the glyceride is a glyceride of at least one hydroxy polycarboxylic
acid and an unsaturated C1 monocarboxylic acid, or a derivative thereof. Suitable
monocarboxylic acids include branched or linear acid. Suitable hydroxy polycarboxylic
acids include citric acid. The glyceride additive may be a glyceride of citric acid and an
unsaturated C18 monocarboxylic acid, or a derivative thereof. Suitable unsaturated C1
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 C4 to C22 carboxylic acid, for example a C1 or C1 carboxylic acid, for
example palmitic acid, stearic acid, oleic acid or linoleic acid. Suitable glycerides include
citric acid esters of mono-glyceride made from vegetable oil, for example sunflower and/or
palm oil. Suitable glycerides include citric acid esters 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):
O OH O COOH
CH3-Y-C-O-CH 2-CH-CH 2-O-C-CH 2- C-CH2-COOH (II)
OH
wherein -Y- represents a C1 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 having 18 carbon atoms, which
may be derivable from oleic acid and/or linoleic acid, (ii) OR' represents a hydroxy
moiety, and (iii) OR' ' represents a hydroxy polycarboxylic acid moiety, which may be
derivable from citric acid.
GRINSTED® CITREM N 1 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 2-IN-l from Danisco as a carboxylic acid anionic
surfactant is described in paragraphs [0167] to [0171] of US patent application publication
US 2008/0176778. US 2008/0176778 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 2
or more of the hydroxy groups each being coupled to a carboxylic acid as an ester group
(paragraph [0033]). In the example at paragraphs [0167] to [0171], two triglyceride
lubricant compositions were tested. Lubricant A was said to contain an emulsion of 10
wt% of a caprylate, caprate, cocoate triglyceride in water to which was added the anionic
surfactant 1.5 wt% lecithin (sold under the trade name Terradrill V408, Cognis) and the
emulsifier 1.5 wt% 20 mol ethoxysorbitan monostearate (sold under the trade name Tween
60V, ICI). Lubricant B was said to contain 1.5 wt% citrate ester, said to be a carboxylic
acid anionic surfactant sold under the name GRTNSTED CITREM 2-GN - 1, Danisco in
place of the Terradrill V408. According to paragraph [0171], Triglyceride lubricants
including anionic surfactant worked well as dry conveyor lubricants and effectively
lubricated after water was applied to the conveyor. According to paragraph [0061] of US
2008/0176778, 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 [0065] to [0075] of ten classes of
anionic surfactant.
According to paragraph [0029] of US patent application publication US
2009/0152502, 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, 6 to 24 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 hydroxy 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). Thus, suitable glycerides include a citric acid ester of the
monoglyceride of hydrogenated tallow fatty acid, for example Lamegin® ZE 309, or an
ester of diacetyl tartaric acid with monoglyceride of hydrogenated tallow fatty acid, for
example Lamegin® DW 8000, or citric acid ester based on sunflower oil fatty acid
monoglyceride, for example Lamegin® ZE 609 FL. Such esters are described, for
example, in US 5770185 and US 2010/0087319.
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 hydroxy polycarboxylic acid is independently derivatisable as an ester.
Suitable ester derivatives include hydrocarbyl esters, in which the hydrocarbyl moiety has,
for example, from 4 to 22 carbon atoms. In at least some examples, the hydrocarbyl
moieties include alkyl moieties which have, for example, from 4 to 22 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
hydroxy 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 hydroxy 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 1 to 22
carbon atoms, for example, from 1 to 18 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 1 to 22 carbon atoms,
for example, from 1 to 18 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 4 to 22 carbon atoms. Suitable hydrocarbyl moieties of each ester independently
include alkyl moieties. In at least some examples, the alkyl moiety of each ester may
independently have from 4 to 22 carbon atoms. 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 having 4 to 22 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 4 to 22 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 4 to 22 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 4 to 22 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.
GRINSTED CITREM SP70 (Trade Mark) has low volatility and has low toxicity.
Lubricant Compositions
In at least some examples, the oil-soluble mono-, di-, or tri-glycerides of at least one
hydroxy polycarboxylic acid, or derivatives thereof, are used as anti-camshaft-wear
additives in any suitable lubricant compositions. Similarly, in at least some examples, the
oil-soluble mono-, di-, or tri-glycerides of at least one hydroxy polycarboxylic acid, or
derivatives thereof, are used to improve the camshaft wear properties of any conventional
lubricant composition. 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 additive. Major amount means
greater than 50% and minor amount means less than 50 % by weight.
In at least some examples, the lubricant composition and the oil of lubricating
viscosity may comprise base oil. Base oil comprises at least one base stock. In at least
some examples, the lubricant composition comprises one or more additives other than the
mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid. 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 50 % to about 99.5 % by weight, for example from
about 85% to about 95% by weight.
The base stocks may be defined as Group I, II, III, IV and V base stocks according to
API standard 1509, "ENGINE OIL LICENSING AND CERTIFICATION SYSTEM",
April 2007 version 16th edition Appendix E, as set out in Table 1.
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 150, for example, available from ExxonMobil. Suitable
Group II basestocks include EHC 50 and EHC 110, for example, available from
ExxonMobil. Suitable group III base stocks include Yubase 4 and Yubase 6 available, for
example, from SK Lubricants. Suitable Group V base stocks include ester base stocks, for
example Priolube 3970, available from Croda International pic. Suitable Group IV base
stocks include hydrogenated oligomers of alpha olefins. Suitably, the oligomers may be
made by free radical processes, Zeigler catalysis or by cationic Friedel-Crafts catalysis.
Polyalpha olefin base stocks may be derived from C8, CIO, C12, C14 olefins and mixtures
of one or more thereof.
Table 1
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 paraffmic oils, naphthenic oils and paraffinic-naphthenic oils.
Mineral oils may also include oils derived from coal or shale.
Suitable base oils and base stocks may be 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 may be derived from gas-to-liquids materials, coalto-
liquids materials, biomass-to-liquids materials and combinations thereof.
Suitable gas-to-liquids (sometimes also referred to as GTL materials) include these
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, WO 2008/124191).
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,
WO-2007-068799-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 100 °C in the range of 2 to 100 cSt, for example in the range of 3 to
50 cSt or in the range 3.5 to 25 cSt.
In at least some examples, the lubricant composition is a multi-grade lubricating oil
composition according to the API classification xW-y where x is 0, 5, 10, 15 or 20 and y is
20, 30, 40, 50 or 60 as defined by SAE J300 2004, for example 5W-20, 5W-30, or OW-20.
In at least some examples, the lubricant composition has a High Temperature High Shear
rate (HTHS) viscosity at 150 °C of at least 2.6 cP, for example as measured according to
ASTM D4683, CEC L-36-A-90 or ASTM D5481.
In at least some examples, the lubricant composition has an HTHS viscosity at
150 °C according to ASTM D4683 of from 1 to < 2.6 cP, for example about 1.8 cP.
Methods of preparing the lubricant compositions include admixing an oil of
lubricating viscosity with an effective amount of at least one additive which is an oilsoluble
mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a
derivative thereof, optionally together with one or more other lubricant additive.
Uses and methods of improving the anti-camshaft-wear properties of an oil of
lubricating viscosity according to the present invention, include admixing an oil of
lubricating viscosity with an effective amount of at least one additive which is an oilsoluble
mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a
derivative thereof.
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.
Other Anti-wear Additives
In at least some examples, the lubricant composition further comprises at least one
anti-wear additive other than the additive which is an oil-soluble mono-, di-, or tri¬
glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof. 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 phosphoruscontaining
anti-wear additives. Examples of suitable ashless phosphorus-containing antiwear
additives include trilauryl phosphite and triphenylphosphorothionate and those
disclosed in paragraph [0036] of US 2005/0198894. 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 having 1 to 18 carbon atoms, for example 2 to 13
carbon atoms or 3 to 18 carbon atoms, or for example 2 to 12 carbon atoms or 3 to 13
carbon atoms, for example 3 to 8 carbon atoms. Examples of suitable hydrocarbyl groups
include alkyl, cycloalkyl and alkaryl groups, examples of which include those 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 3 to 8 carbon atoms. Suitable ZDDP's include those comprising hydrocarbyl groups
which are a mixture of secondary alkyl groups and primary alkyl groups, for example 90
mol. % secondary alkyl groups and 10 mol. % primary alkyl groups.
The oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic
acid, or a derivative thereof, additive may reduce the amount of phosphorus- and/or zinccontaining
anti-wear additive which might be required to achieve a desired amount of antiwear
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 10 to 6000 ppm by weight of
phosphorus, for example 10 to 1000 ppm by weight of phosphorus, or 200 to 1400 ppm by
weight of phosphorus, or 200 to 800 ppm by weight of phosphorus or 200 to 600 ppm by
weight of phosphorus.
It has been found that the presence in the lubricant composition of at least one oilsoluble
mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a
derivative thereof, 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 exhauster
emissions when the lubricant is used to lubricant an internal combustion engine. The
reduction in the amount of sulphur in exhauster emissions may have benefits for any
exhaust after treatment system.
Other Friction Modifiers.
In at least some examples, the lubricant composition comprises at least one friction
modifier other than the additive which is an oil-soluble mono-, di-, or tri-glyceride of at
least one hydroxy polycarboxylic acid, or a derivative thereof. 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 ester friction modifiers include
esters of glycerol, for example mono-, di-, and tri-oleates, mono-palmitates and monomyristates,
for example glycerol monooleate. 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 EP-1533362-A1, for example, in paragraphs [0101] to [01 17].
Examples of friction modifiers other than the additive which is an oil-soluble mono-,
di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof,
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 WO 93/21288.
In at least some examples, the oil-soluble mono-, di-, or tri-glyceride of at least one
hydroxy polycarboxylic acid, or a derivative thereof, 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 an oilsoluble
mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a
derivative thereof, which are fatty acid derivative friction modifiers are present in the
lubricating oil composition at a concentration of 0.01 to 5 % by weight actives, for
example in the range of 0.01 to 1.5 % by weight actives.
In at least some examples, molybdenum containing friction modifiers are present in
the lubricating oil composition at a concentration of 10 to 1000 ppm by weight
molybdenum, for example in the range of 400 to 600 ppm by weight.
Other Additives.
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, pour point depressants, 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, nonphosphorus
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
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 having one or more functional groups which are capable of associating
with particles to be dispersed. The functional groups may be amine, alcohol, aminealcohol,
amide or 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, aminoesters,
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 having 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 20000, for example 300 to 20000, 500 to
10000, 700 to 5000 or less than 15000. 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 222.
Dispersant Viscosity Modifiers.
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 15000, for example in the range 20000 to 600000 (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 WO99/21902, WO2003/099890 and WO2006/099250. In at least some
examples, more than one dispersant viscosity modifier is present in the lubricant
composition.
Detergents
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 acidneutralising
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 2 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 hydroxy 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 is
present.
In at least some examples, additionally or alternatively, non-metallic detergents are
present. Suitable non-metallic detergents are described for example in US762243 1.
In at least some examples, more than one detergent is present in the lubricant
composition and/or additive concentrate.
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 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-olefms); polyesters (for example, polymethacrylates); hydrogenated poly(styrene-cobutadiene
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 methods.
Viscosity modifiers may have additional functions as multifunction viscosity
modifiers. In at least some examples, more than one viscosity index improver is present.
Pour Point Depressants
Pour point depressants (also called lube oil improvers or lube oil flow improvers),
lower the minimum temperature at which the lubricant will flow and can be poured.
Examples of suitable pour point depressants include C8 to C18 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, wax naphthalene and the
like.
In at least some examples, more than one pour point depressant is present.
Rust inhibitors
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
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, nonionic
polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, thiadiazoles,
triazoles and anionic alkyl sulphonic acids. Examples of suitable epoxidised ester
corrosion inhibitors are described in US2006/0090393.
In at least some examples, more than one corrosion inhibitor is present.
Antioxidants
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-a-naphthylamine, alkylated
phenyl-a-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, 1,3,4-dimercaptothiadiazole and derivatives, oil soluble copper
compounds (for example, copper dihydrocarbyl thio- or fhio-phosphate, copper salts of a
synthetic or natural carboxylic acid, for example a C to C fatty acid, an unsaturated acid
or a branched carboxylic acid, for example basic, neutral or acidic Cu1 and/or Cu1 salts
derived from alkenyl succinic acids or anhydrides), alkaline earth metal salts of
alkylphenolthioesters, for example containing C5 to C 2 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 anti-oxidant is present. In at least some
examples, more than one type of anti-oxidant is present.
Antifoams
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
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.
Other Additives
In at least some examples, other additives are present in the lubricant composition
and these include, for example, extreme pressure additives (including metallic, nonmetallic,
phosphorus containing, non-phosphorus containing, sulphur containing and nonsulphur
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.
Solvent
The additive concentrate for a lubricant composition may comprise solvent.
Examples of suitable solvents include highly aromatic, low viscosity base stocks, for
example 100N, 60N and 100SP base stocks.
The representative suitable and more suitable independent amounts of additives (if
present) in the lubricant composition are given in Table 2. The concentrations expressed in
Table 2 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 solvents or diluents.
Table 2
Lubricant Composition
Suitable amount More suitable amount
ADDITIVE TYPE (actives), if present (actives), if present
(by weight) (by weight)
Oil-soluble mono-, di-, or tri-glyceride of at
least one hydroxy polycarboxylic acid, or a 0.02 to 5% 0.1 to 2.5%
derivative thereof
corresponding to 10 corresponding to 10
Phosphorus-containing anti-wear additives
to 6000 ppm P to 1000 ppm P
corresponding to 10 corresponding to 40
Molybdenum-containing anti-wear additives
to 1000 ppm Mo to 600 ppm Mo
corresponding to 10 corresponding to 50
Boron-containing anti-wear additives
to 250 ppm B to 100 ppm B
Friction modifiers other than the mono-, di-,
or tri-glyceride of at least one hydroxy 0.01 to 5 % 0.01 to 1.5 %
polycarboxylic acid, or a derivative thereof
corresponding to 10 corresponding to 400
Molybdenum-containing friction modifiers
to 1000 ppm Mo to 600 ppm Mo
Dispersants 0.1 to 20 % 0.1 to 8 %
Detergents 0.01 to 6 % 0.01 to 4 %
Viscosity index improvers 0.01 to 20% 0.01 to 15%
Pour point depressants 0.01 to 5 % 0.01 to 1.5 %
Corrosion and/or rust inhibitors 0.01 to 5 % 0.01 to 1.5%
Anti-oxidants 0.1 to 10 % 0.5 to 5 %
corresponding to 1 corresponding to 1 to
Antifoams containing silicon
to 20 ppm Si 10 ppm Si
Lubricant Applications.
In at least some examples, the mono-, di-, or tri-glyceride of at least one hydroxy
polycarboxylic acid, or a derivative thereof, is used as an anti-camshaft-wear additive in a
non-aqueous lubricant composition and/or in a fuel composition.
In at least some examples, the oil-soluble mono-, di-, or tri-glyceride of at least one
hydroxy polycarboxylic acid, or a derivative thereof, is used as an anti-camshaft- wear
additive 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 mono-, di-, or tri-glyceride of at least one hydroxy
polycarboxylic acid, or a derivative thereof, is used as an anti-camshaft-wear additive in a
non-aqueous lubricant composition and/or in a fuel 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 nonmetallic
materials coated with metallic materials; surfaces of diamond-like carbon coated
materials and SUMEBore™ materials for example, as described in Sulzer technical review
4/2009 pages 11-13.
In at least some examples, the oil-soluble, mono-, di-, or tri-glyceride of at least one
hydroxy polycarboxylic acid, or a derivative thereof, is used in a non-aqueous lubricant
composition and/or in a fuel 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 250°C, e.g. 90 to 120°C. Typical ambient temperature is 20°C,
but in at least some examples, is less than 20°C, for example 0°C or lower.
Internal Combustion Engine Lubrication.
In at least some examples, the oil-soluble mono-, di-, or tri-glyceride of at least one
hydroxy polycarboxylic acid, or a derivative thereof, is used as an anti-camshaft-wear
additive in a lubricant composition which is used to lubricate an internal combustion
engine, for example as a crankcase lubricant. Examples of suitable engines include sparkignition,
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 the
examples, the oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy
polycarboxylic acid, or a derivative thereof, is used as an anti-camshaft-wear additive 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.
In at least some examples, additionally, or alternatively the mono-, di- or tri-glyceride
of at least one hydroxy polycarboxylic acid, or a derivative thereof, is present in the fuel
for an internal combustion engine. In use, the oil-soluble, mono-, di- or tri-glyceride of at
least one hydroxy polycarboxylic acid, or a derivative thereof, passes with or without fuel
into a lubricant composition used to lubricate the engine, for example as a crankcase
lubricant, and thereby provides anti-camshaft-wear benefits to the engine.
Typically, the rate of ingress of fuel into crankcase lubricant is higher for sparkignition
internal combustion engines than for compression-ignition engines. However, the
rate at which fuel ingresses into the crankcase lubricant for compression-ignition engines
may depend and may increase depending upon the use of post-injection strategies for
operation of the engine.
Fuels
In at least some examples, the oil-soluble mono-, di- or tri-glyceride of at least one
hydroxy polycarboxylic acid, or a derivative thereof, is used as anti-camshaft-wear
additives in any suitable fuel compositions.
Suitable liquid fuels, particularly for internal combustion engines, include
hydrocarbon fuels, oxygenate fuels and combinations thereof. Hydrocarbon fuels may be
derived from mineral sources and/or from renewable sources such as biomass (e.g.
biomass-to-liquid sources) and/or from gas-to-liquid sources and/or from coal-to-liquid
sources. Suitable sources of biomass include sugar (e.g. sugar to diesel fuel) and algae.
Suitable oxygenate fuels include alcohols, for example straight and/or branched chain alkyl
alcohols having from 1 to 6 carbon atoms, esters, for example fatty acid alkyl esters and
ethers, for example methyl tert butyl ether. Suitable fuels may also include LPG-diesel
fuels (LPG being liquefied petroleum gas). In at least some examples, the fuel
composition is an emulsion. In at least some examples, the fuel composition is not an
emulsion.
Suitable fatty acid alkyl esters include methyl, ethyl, propyl, butyl and hexyl esters.
In at least some examples, the fatty acid alkyl ester is a fatty acid methyl ester. In at least
some examples, the fatty acid alkyl ester has 8 to 25 carbon atoms, for example 12 to 25
carbon atoms, for example 16 to 18 carbon atoms. In at least some examples, the fatty acid
is saturated. In at least some examples, the fatty acid is unsaturated. In at least some
examples, the fatty acid alkyl ester is acyclic. Methods of preparing such fatty acid alkyl
esters include esterification of one or more fatty acids and/or by transesterification of one
or more triglycerides of fatty acids. In at least some examples, the triglycerides is obtained
from vegetable oils, for example castor oil, soyabean oil, cottonseed oil, sunflower oil,
rapeseed oil (which is sometimes called canola oil), Jatropha oil or palm oil, or obtained
from tallow (for example, sheep and/or beef tallow), fish oil or used cooking oil. Suitable
fatty acid alkyl esters include rapeseed oil methyl ester (RJVIE), soya methyl ester or
combinations thereof.
In at least some examples, the fuel compositions are prepared by admixing in one or
more steps a hydrocarbon fuel, an oxygenate fuel, or a combination thereof, with an
effective amount of at least one additive which is a mono-, di- or tri-glyceride of at least
one hydroxy polycarboxylic acid, or a derivative thereof, and optionally at least one other
fuel additive.
In at least some examples, the use and the method of improving the anti-camshaftwear
properties of a liquid fuel of the present invention comprises admixing in one or more
steps said liquid fuel (which may be, for example, a hydrocarbon fuel, an oxygenate fuel or
a combination thereof) with an effective amount of at least one additive which is a mono-,
di- or tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, and
optionally at least one other fuel additive.
In at least some examples, the fuel 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 hydrocarbon fuel,
oxygenate fuel or combination thereof is prepared by admixing in one or more steps by
methods known in the art, one or more base fuels and components therefor, 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 is
admixed with the fuel or components therefor in one or more steps by methods known in
the art.
Fuels For Compression-ignition Engines.
In at least some examples, the fuel composition comprising an oil-soluble, mono-, dior
tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, as an
anti-camshaft-wear additive is suitable for use in an internal combustion engine which is a
compression-ignition internal combustion engine, suitably a direct injection diesel engine,
for example of the rotary pump, in-line pump, unit pump, electronic unit injector or
common rail type, or in an indirect injection diesel engine. In at least some examples, the
fuel composition is suitable for use in heavy and/or light duty diesel engines.
In at least some examples, the fuel composition for compression-ignition internal
combustion engines has a sulphur content of up to 500 ppm by weight, for example up to
15 ppm by weight or up to 10 ppm by weight. In at least some examples, the fuel
composition for compression-ignition internal combustion engines meets the requirements
of the EN590 standard, for example as set out in BS EN 590:2009.
In at least some examples, oxygenate components in the fuel composition for
compression-ignition internal combustion engines include fatty acid alkyl esters, for
example fatty acid methyl esters. In at least some examples, the fuel comprises one or
more fatty acid methyl esters complying with EN 14214 at a concentration of up to 7 % by
volume. In at least some examples, oxidation stability enhancers are present in the fuel
composition, comprising one or more fatty acid alkyl or methyl esters, for example at a
concentration providing an action similar to that obtained with 1000 mg/kg of 3,5-di-tertbutyl-
4-hydroxy-toluol (also called butylated hydroxy-toluene or BHT). In at least some
examples, dyes and/or markers are present in the fuel composition for compressionignition
internal combustion engines.
In at least some examples, the fuel composition for compression-ignition internal
combustion engines have one or more of the following, for example, as defined according
to BS EN 590:2009 :- a minimum cetane number of 51.0, a minimum cetane index of 46.0,
a density at 15 °C of 820.0 to 845.0 kg/m3, a maximum polycyclic aromatic content of
8.0% by weight, a flash point above 55°C, a maximum carbon residue (on 10% distillation)
of 0.30 % by weight, a maximum water content of 200 mg/kg, a maximum contamination
of 24 mg/kg, a class1 copper strip corrosion (3 h at 50 °C), a minimum oxidation stability
limit of 20 h according to EN 1575 1 and a maximum oxidation stability limit of 25 g/m
according to EN ISO 12205, a maximum limit for lubricity corrected wear scar diameter at
60 °C of 460m , a minimum viscosity at 40°C of 2.00 mm /s and a maximum viscosity at
40°C of 4.50 mm /s, < 65% by volume distillation recovery at 250°C, a minimum
distillation recovery at 350°C of 85% by volume and a maximum of 95 % by volume
recovery at 360°C.
In at least some examples, the fuel composition suitable for use in a compressionignition
internal combustion engine further comprises at least one friction modifier other
than the additive which is a mono-, di- or tri-glyceride of at least one hydroxy
polycarboxylic acid, or a derivative thereof. Such other friction modifiers include
compounds described herein as friction modifiers for lubricant compositions and additive
concentrates for lubricant compositions.
In at least some examples, the fuel composition suitable for use with a compressionignition
internal combustion engine further comprises at least one lubricity additive.
Suitable lubricity additives include tall oil fatty acids, mono- and di-basic acids and esters.
In at least some examples, the fuel composition suitable for use in a compressionignition
internal combustion engine further comprises independently one or more cetane
improver, one or more detergent, one or more anti-oxidant, one or more anti-foam, one or
more demulsifier, one or more cold flow improver, one or more pour point depressant, one
or more biocide, one or more odorant, one or more colorant (sometimes called dyes), one
or more marker, one or more spark aiders and/or combinations of one or more thereof. In
at least some examples, other suitable additives are present, including one or more thermal
stabilizers, metal deactivators, corrosion inhibitors, antistatic additives, drag reducing
agents, emulsifiers, dehazers, anti-icing additives, antiknock additives, anti-valve-seat
recession additives, surfactants and combustion improvers, for example as described in
EP-2107102-A.
In at least some examples, the additive concentrate for a fuel composition for a
compression-ignition internal combustion engine comprises one or more solvents, for
example carrier oils (for example mineral oils), polyethers (which may be capped or
uncapped), non-polar solvents (for example toluene, xylene, white spirits and those sold
by Shell companies under the trade mark "SHELLSOL"), and polar solvents (for example
esters and alcohols e.g. hexanol, 2-ethylhexanol, decanol, isotridecanol and alcohol
mixtures, for example those sold by Shell companies under the trade mark "LINEVOL",
e.g. LINEVOL 79 alcohol which is a mixture of C7 - 9 primary alcohols, or a C12-14 alcohol
mixture which is commercially available.
Suitable cetane improvers include 2-ethyl hexyl nitrate, cyclohexyl nitrate and dife
rt-butyl peroxide. Suitable antifoams include siloxanes. Suitable detergents include
polyolefin substituted succinimides and succinimides of polyamines, for example
polyisobutylene succinimides, polyisobutylene amine succinimides, aliphatic amines,
Mannich bases and amines and polyolefin (e.g. polyisobutylene) maleic anhydride.
Suitable antioxidants include phenolic antioxidants (for example 2,6-di-tert-butylphenol)
and aminic antioxidants (for example N,N'-di-sec-butyl-p-phenylenediamine). Suitable
anti-foaming agents include polyether-modified polysiloxanes.
The representative suitable and more suitable independent amounts of additives (if
present) in the fuel composition suitable for a compression-ignition engine are given in
Table 3. The concentrations expressed in Table 3 are by weight of active additive
compounds that is, independent of any solvent or diluent.
In at least some examples, the additives in the fuel composition suitable for use in
compression-ignition internal combustion engines are suitably present in a total amount in
the range of 100 to 1500 ppm by weight.
Table 3
Fuels For Spark-ignition Engines.
In at least some examples, the fuel composition comprising an oil-soluble, mono-, dior
tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, as an
anti-camshaft- wear additive is suitable for use in an internal combustion engine which is a
spark-ignition internal combustion engine.
In at least some examples, the fuel composition for spark-ignition internal
combustion engines has a sulphur content of up to 50.0 ppm by weight, for example up to
10.0 ppm by weight.
In at least some examples, the fuel composition for spark-ignition internal
combustion engines is leaded or unleaded.
In at least some examples, the fuel composition for spark-ignition internal
combustion engines meets the requirements of EN 228, for example as set out in BS EN
228:2008. In at least some examples, the fuel composition for spark-ignition internal
combustion engines meets the requirements of ASTM D 4814-09b.
In at least some examples, the fuel composition for spark-ignition internal
combustion engines has one or more of the following, for example, as defined according to
BS EN 228:2008 :- a minimum research octane number of 95.0, a minimum motor octane
number of 85.0 a maximum lead content of 5.0 mg/1, a density of 720.0 to 775.0 kg/m , an
oxidation stability of at least 360 minutes, a maximum existent gum content (solvent
washed) of 5 mg/1 00 ml, a class 1 copper strip corrosion (3 h at 50 °C), clear and bright
appearance, a maximum olefin content of 18.0 % by weight, a maximum aromatics content
of 35.0 % by weight, and a maximum benzene content of 1.00 % by volume.
In at least some examples, oxygenate components in the fuel composition for sparkignition
internal combustion engines include straight and/or branched chain alkyl alcohols
having from 1 to 6 carbon atoms, for example methanol, ethanol, n-propanol, n-butanol,
isobutanol, tert-butanol. In at least some examples, oxygenate components in the fuel
composition for spark-ignition internal combustion engines include ethers, for example
having 5 or more carbon atoms. In at least some examples, the fuel composition has a
maximum oxygen content of 2.7% by mass. In at least some examples, the fuel
composition has maximum amounts of oxygenates, as specified in EN 228, for example
methanol: 3.0% by volume, ethanol: 5.0% by volume, iso-propanol: 10.0 % by volume,
iso-butyl alcohol: 10.0%> by volume, tert-butanol: 7.0% by volume, ethers (C5 or higher):
10% by volume and other oxygenates (subject to suitable final boiling point): 10 .0% by
volume. In at least some examples, the fuel composition comprises ethanol complying
with EN 15376 at a concentration of up to 5.0%> by volume.
In at least some examples, the fuel composition suitable for use in a spark-ignition
internal combustion engine further comprises at least one friction modifier other than the
additive which is a mono-, di- or tri-glyceride of at least one hydroxy polycarboxylic acid,
or a derivative thereof. In at least some examples, such other friction modifiers include
compounds described herein as friction modifiers for lubricant compositions and additive
concentrates for lubricant compositions.
In at least some examples, the fuel composition suitable for use in a spark-ignition
internal combustion engine further comprises independently one or more detergent, one or
more octane improver, one or more friction modifier, one or more anti-oxidant, one or
more valve seat recession additive, one or more corrosion inhibitor, one or more anti-static
agent, one or more odorant, one or more colorant, one or more marker and/or combinations
of one or more thereof.
In at least some examples, the additive concentrate for a fuel composition for a sparkignition
internal combustion engine comprises one or more solvents, for example
polyethers and aromatic and/or aliphatic hydrocarbons, for example heavy naphtha e.g.
Solvesso (Trade mark), xylenes and kerosine.
Suitable detergents include poly isobutylene amines (PIB amines) and polyether
amines.
Suitable octane improvers include N-methyl aniline, methyl cyclopentadienyl
manganese tricarbonyl (MMT) (for example present at a concentration of up to 120 ppm
by weight), ferrocene (for example present at a concentration of up to 16 ppm by weight)
and tetra ethyl lead (for example present at a concentration of up to 0.7 g/1, e.g. up to 0.15
)
Suitable anti-oxidants include phenolic anti-oxidants (for example 2,4-di-tertbutylphenol
and 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid) and aminic anti
oxidants (for example para-phenylenediamine, dicyclohexylamine and derivatives thereof).
Suitable corrosion inhibitors include ammonium salts of organic carboxylic acids,
amines and heterocyclic aromatics, for example alkylamines, imidazolines and
tolyltriazoles.
In at least some examples, valve seat recession additives are present at a
concentration of up to 15000 ppm by weight, for example up to 7500 ppm by weight.
The representative suitable and more suitable independent amounts of additives (if
present) in the fuel composition suitable for a spark-ignition engine are given in Table 4.
The concentrations expressed in Table 4 are by weight of active additive compounds that
is, independent of any solvent or diluent.
In at least some examples, the additives in the fuel composition suitable for use in
spark-ignition internal combustion engines are present in a total amount in the range of 20
to 25000 ppm by weight.
Table 4
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 labeled numerically as Example 1, Example 2, etc. and experiments not according to
the present invention are labeled alphabetically as Experiment A, Experiment B, etc.
Preparation of Lubricant Compositions.
A lubricant composition (Lubricant A) was prepared to model a typical lubricant
composition suitable for passenger cars with either compression-ignition or spark-ignition
internal combustion engines. The lubricant composition was made by admixing additives
as in a commercially available additive package containing dispersant, calcium sulphonate
and calcium phenate detergents, antioxidant, antifoam and ZDDP with Group III base oil, a
pour point depressant and a viscosity modifier.
A lubricant composition (Lubricant B) was prepared in the same way as Lubricant A,
but with the addition of 0.2% by weight of oleamide.
A lubricant composition (Lubricant 1) according to the invention was prepared in the
same way as Lubricant A, but with the addition of 0.5 % Citrem SP 70 (Trade Mark) (a
diglyceride of citric acid and oleic/linoleic acid).
A lubricant composition (Lubricant C) was prepared to model a typical lubricant
composition suitable for passenger cars with either compression-ignition or spark-ignition
internal combustion engines. The lubricant composition was made by admixing additives
as in a commercially available additive package containing dispersant, calcium sulphonate
and calcium phenate detergents, antioxidant, antifoam and ZDDP with Group I and III base
oils, a pour point depressant and a viscosity modifier.
A lubricant composition (Lubricant D) was prepared in the same way as Lubricant C,
but with the addition of 0.2% by weight of oleamide.
A lubricant composition (Lubricant 2) according to the invention was prepared in the
same way as Lubricant C, but with the addition of 0.5 % Citrem SP 70 (Trade Mark) (a
diglyceride of citric acid and oleic/linoleic acid).
Lubricants A to D are not according to the present invention because the lubricant
compositions do not contain an oil-soluble mono-, di-, or tri-glyceride of at least one
hydroxy polycarboxylic acid, or a derivative thereof, in particular a diglyceride of citric
acid and an unsaturated C18 carboxylic acid (e.g. oleic and/or linoleic acid), for example
Citrem SP70 (Trade Mark). Lubricants 1 and 2 are according to the present invention.
Anti-Wear Testing of Lubricant Compositions.
1. Sequence IVA Engine Test
Sequence IVA engine tests according to ASTM test method ASTM D6891 were
undertaken for Lubricants A and B, as well as for Lubricant 1. The Sequence IVA test is
an industry standard test used to evaluate the camshaft wear protection of internal
combustion engine lubricant compositions. This test method is designed to simulate
extended engine idling vehicle operation. The primary result is camshaft lobe wear
(measured at seven locations around each of the twelve lobes) and the pass/fail criteria for
the test include a maximum average seven-location cam lobe wear of 90 microns (mh ) .
The results for the tests are shown in Table 5. Experiments A and B are not
according to the present invention because the lubricant compositions do not contain an
oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a
derivative thereof, in particular a diglyceride of citric acid and an unsaturated C18
carboxylic acid (e.g. oleic and/or linoleic acid), for example Citrem SP70 (Trade Mark).
Example 1 is according to the present invention.
The results in Table 5 show that both oleamide and an oil-soluble mono-, di-, or tr i
glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, in particular
a diglyceride of citric acid and an unsaturated C18 carboxylic acid (e.g. oleic and/or linoleic
acid), for example Citrem SP70 (Trade Mark), significantly reduce cam lobe wear and are
thus effective as anti-camshaft-wear additives in the Sequence IVA test.
Table 5
2. OM646LA Engine Test
OM646LA (CEC L-99-08) engine tests were undertaken for Lubricants C and D, as
well as for Lubricant 2. This 300 hour cyclic test uses a 4 cylinder 2.2L diesel OM646 DE
22 LA engine to evaluate engine lubricant performance with respect to engine wear and
overall cleanliness, as well as piston cleanliness and ring sticking, under severe operating
conditions. The primary result is cam wear, although bore polish, cylinder wear and tappet
wear may also be measured.
The results for the tests are shown in Table 6. Experiments C and D are not
according to the present invention because the lubricant compositions do not contain an
oil-soluble mono-, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid, or a
derivative thereof, in particular a diglyceride of citric acid and an unsaturated C18
carboxylic acid (e.g. oleic and/or linoleic acid), for example Citrem SP70 (Trade Mark).
Example 2 is according to the present invention.
The results in Table 6 show that there is moderately high camshaft wear in the
OM646LA test in respect of Lubricant C, which contains no anti-camshaft- wear additive
(Experiment C). No appreciable reduction in camshaft wear is observed as a result of the
presence of oleamide additive in Lubricant D (Experiment D). In contrast, a significant
reduction in camshaft wear is observed for Lubricant 2, containing Citrem SP70 (trade
mark) (Example 2). Thus, the results demonstrate that an oil-soluble mono-, di-, or triglyceride
of at least one hydroxy polycarboxylic acid, or a derivative thereof, in particular
a diglyceride of citric acid and an unsaturated C18 carboxylic acid (e.g. oleic and/or linoleic
acid), for example Citrem SP70 (Trade Mark), is effective as an anti-camshaft-wear
additive in the OM646LA test.
Table 6
In contrast to known anti-wear additives, such as oleamide, an oil-soluble mono-, di-, or
tri-glyceride of at least one hydroxy polycarboxylic acid, or a derivative thereof, in
particular a diglyceride of citric acid and an unsaturated C1 carboxylic acid (e.g. oleic
and/or linoleic acid), for example Citrem SP70 (Trade Mark), is surprisingly effective as
an anti-camshaft-wear additive in both Sequence IVA and OM646LA wear tests.

Claims
1. 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-camshaft-wear additive in a nonaqueous
lubricant composition and/or in a fuel composition.
2. The use as claimed in claim 1, wherein the oil-soluble mono-, di-, or tri-glyceride of
at least one hydroxy polycarboxylic acid, or a derivative thereof, reduces camshaft wear as
measured in the OM646LA engine test.
3. The use as claimed in claim 1 or claim 2, wherein the lubricant composition is used
to lubricate an internal combustion engine.
4. The use as claimed in claim 3, wherein the oil-soluble mono-, di-, or tri-glyceride of
at least one hydroxy polycarboxylic acid, or a derivative thereof, is provided in a liquid
fuel composition used to operate the internal combustion engine, and a portion at least, of
said glyceride ingresses into the lubricating oil composition during operation of said
engine.
5. The use as claimed in any one of the preceding claims, wherein the hydroxy
polycarboxylic acid has at least one hydroxy group which is in an alpha position with
respect to a carboxylic moiety.
6. The use as claimed in claim 5, wherein the hydroxy polycarboxylic acid is citric acid.
7. The use as claimed in any one of claims 1 to 6, wherein 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 having 4 to 22 carbon atoms, or a derivative thereof.
8. The use as claimed in any one of claims 1 to 6, wherein the glyceride is a glyceride of
at least one hydroxy polycarboxylic acid and a mono-unsaturated C4 to C22
monocarboxylic acid, or a derivative thereof.
9. The use as claimed in any one of claims 1 to 6, wherein the glyceride is a glyceride of
at least one hydroxy polycarboxylic acid and a polyunsaturated C4 to C 2 monocarboxylic
acid, or a derivative thereof.
10. The use as claimed in claim 8 or claim 9, wherein the glyceride is a glyceride of at
least one hydroxy polycarboxylic acid and a mono-unsaturated or polyunsaturated C18
monocarboxylic acid, or a derivative thereof.
11. The use as claimed in claim 10, wherein the glyceride is a glyceride of citric acid and
a mono-unsaturated or polyunsaturated C\ monocarboxylic acid, or a derivative thereof.
12. The use as claimed in any one of claims 8 to 11, wherein the mono-unsaturated or
polyunsaturated C4 to C22 carboxylic acid is linear.
13. The use as claimed in any one of claims 1 to 6, wherein the glyceride is a glyceride of
citric acid and oleic acid, a glyceride of citric acid and linoleic acid or a mixture thereof.
14. The use as claimed in claim 7, wherein the carboxylic acid having 4 to 22 carbon
atoms is a polycarboxylic acid and the derivative is an ester of a carboxylic acid moiety of
said polycarboxylic acid.
15. The use as claimed in any one of the preceding claims, wherein the derivative of the
glyceride is an ether of the hydroxy moiety of the hydroxy polycarboxylic acid.
16. The use as claimed in any one of claims 1 to 14, wherein the derivative of the
glyceride is an ester of the hydroxy moiety of the hydroxy polycarboxylic acid.
17. The use as claimed in any one of the preceding claims, wherein the derivative of the
glyceride is an ester of a carboxylic acid moiety of the hydroxy polycarboxylic acid.