U.S. patent application number 13/394179 was filed with the patent office on 2012-07-12 for lubricating compositions.
Invention is credited to Cara Siobhan Tredget.
Application Number | 20120178658 13/394179 |
Document ID | / |
Family ID | 41664926 |
Filed Date | 2012-07-12 |
United States Patent
Application |
20120178658 |
Kind Code |
A1 |
Tredget; Cara Siobhan |
July 12, 2012 |
LUBRICATING COMPOSITIONS
Abstract
A lubricating composition comprising: (i) from 50% to 99% by
weight of base oil; (ii) from 0.01% to 5% by weight of ionic
liquid; and (iii) from 0.01% to 10% by weight of additive; wherein
the lubricating composition has a pour point of at most -54.degree.
C., a flashpoint of at least 246.degree. C. and a kinematic
viscosity at 100.degree. C. in the range of from 4.9 to 5.4
mm.sup.2/s. The lubricating compositions according to the present
invention are suitable for use in turbine engine oils and are
useful for reducing the build up of sludge and for reducing coking
in the lubricating composition.
Inventors: |
Tredget; Cara Siobhan; (Ince
Chester Cheshire, GB) |
Family ID: |
41664926 |
Appl. No.: |
13/394179 |
Filed: |
September 7, 2010 |
PCT Filed: |
September 7, 2010 |
PCT NO: |
PCT/EP2010/063082 |
371 Date: |
March 28, 2012 |
Current U.S.
Class: |
508/269 ;
508/524; 508/548 |
Current CPC
Class: |
C10M 2201/084 20130101;
C10M 171/02 20130101; C10N 2030/04 20130101; C10M 2227/00 20130101;
C10M 169/04 20130101; C10M 2215/223 20130101; C10M 2201/087
20130101; C10M 2215/16 20130101; C10M 2219/044 20130101; C10M
2215/226 20130101; C10M 2219/04 20130101; C10N 2030/08 20130101;
C10M 2223/06 20130101; C10M 2215/224 20130101; C10M 2215/02
20130101; C10M 2223/00 20130101; C10M 2215/221 20130101; C10M
2201/081 20130101; C10M 2219/104 20130101; C10N 2040/12 20130101;
C10M 2219/00 20130101; C10N 2020/077 20200501; C10M 2215/14
20130101; C10M 2227/063 20130101; C10M 2215/225 20130101; C10M
2207/2835 20130101; C10M 2201/082 20130101; C10N 2040/135 20200501;
C10M 2211/044 20130101; C10M 2201/085 20130101; C10M 2219/042
20130101; C10M 2223/043 20130101 |
Class at
Publication: |
508/269 ;
508/524; 508/548 |
International
Class: |
C10M 133/46 20060101
C10M133/46; C10M 135/10 20060101 C10M135/10; C10M 131/12 20060101
C10M131/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 7, 2009 |
EP |
09252138.4 |
Claims
1. A lubricating composition comprising: (i) from 50% to 99% by
weight of base oil; (ii) from 0.01% to 5% by weight of ionic
liquid; and (iii) from 0.01% to 10% by weight of additive; wherein
the lubricating composition has a pour point of less than
-54.degree. C., a flashpoint of greater than 246.degree. C. and a
kinematic viscosity at 100.degree. C. in the range of from 4.9 to
5.4 mm.sup.2/s.
2. A lubricating composition according to claim 1 comprising from
0.01% to 1% by weight of ionic liquid.
3. The lubricating composition according to claim 1 comprising from
0.05% to 0.5% by weight ionic liquid.
4. A lubricating composition wherein the ionic liquid is a salt of
general formula C.sup.+A.sup.- wherein the cation C.sup.+ is
selected from a quaternary ammonium cation, a phosphonium cation,
an imidazolium cation, a pyridinium cation, a pyrazolium cation, an
oxazolium cation, a pyrrolidinium cation, a piperidinium cation, a
trialkylsulfonium cation, a thiazolium cation, a guanidinium
cation, a morpholinium cation, a sulfonium cation and a triazolium
cation and wherein the anion A.sup.-is selected from
[PF.sub.6].sup.-, [CF.sub.3CO.sub.2].sup.-,
[CF.sub.3SO.sub.3].sup.-, as well as its higher homologues,
[C.sub.4F.sub.9SO.sub.3].sup.- or [C.sub.8F.sub.17SO.sub.3].sup.-
and higher perfluoroalkylsulfonates, [(CF.sub.3SO.sub.2).sub.2N],
[(CF.sub.3SO.sub.2)(CF.sub.3COO)N].sup.-, Cl.sup.-, Br.sup.-,
I.sup.-, [C(CN).sub.3].sup.-, SCN.sup.-,
[B(C.sub.2O.sub.4).sub.2].sup.-, [N(SO.sub.2CF.sub.3).sub.2].sup.-,
[R.sup.4SO.sub.3].sup.-, [R.sup.4OSO.sub.3].sup.-,
[R.sup.4COO].sup.-, [NO.sub.3].sup.-, [N(CN).sub.2].sup.-,
[HSO.sub.4].sup.-, PF.sub.6-xR.sup.6.sub.x or
[R.sup.4R.sup.5PO.sub.4].sup.-, wherein R.sup.4 and R.sup.5 are
independently selected from hydrogen, linear or branched, saturated
or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20
carbon atoms; heteroaryl, heteroaryl-C.sub.1-C.sub.6-alkyl groups
with 3 to 8 carbon atoms in the hetero aryl residue and at least
one heteroatom selected from N, O and S, which can be substituted
with at least one group selected from C.sub.1-C.sub.6 alkyl groups
and/or halogen atoms; aryl-aryl-C.sub.1-C.sub.6-alkyl groups with 5
to 12 carbon atoms in the aryl residue, which can be substituted
with at least one C.sub.1-C.sub.6-alkyl group, R.sup.6 can be a
perfluoroethyl or a higher perfluoroalkyl group, and x is an
integer of from 1 to 4.
5. The lubricating composition according to claim 4 wherein the
ionic liquid is selected from butyl
methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide,
methylpropylpyrrolidinium-bis(trifluoromethylsulfonyl)imide,
tris-hexylmethylimidazolium (perfluoroethylene)-trifluorophosphate,
hexylmethylimidazolium-bis(trifluoromethylsulfonyl)imide,
hexylmethylpyrrolidinium-bis(trifluoromethylsulfonyl)imide,
tris-tetrabutylphosphonium(perfluoroethylene)trifluorophosphate,
octylmethylimidazolium-hexafluorophosphate,
hexylpyridinium-bis(trifluoromethyl)sulfonylimide,
methyltrioctylammonium-trifluoroacetate, butylmethylpyrrolidinium
tris (pentafluoroethyl)trifluorophosphate, trihexyl
(tetradecyl)phosphonium-bis(trifluoromethylsulfonyl)imide,
hexylmethylimidazolium tetrafluoroborate, hexylmethylimidazolium
hexafluorophosphate, 1-ethyl-3-methylimidazolium diethylphosphate,
1-ethyl-3-methylimidazolium methyl sulphate,
1-ethyl-3-methylimidazolium bis[oxalate(2-)-O,O+]borate and
mixtures thereof.
6. The lubricating composition according to claim 4 wherein the
ionic liquid is selected from
methyltrioctylammonium-trifluoroacetate and trihexyl
(tetradecyl)phosphonium-bis(trifluoromethylsulfonyl)imide,
hexylmethylimidazolium tetrafluoroborate, hexylmethylimidazolium
hexafluorophosphate, 1-ethyl-3-methylimidazolium diethylphosphate,
1-ethyl-3-methylimidazolium methyl sulphate and mixtures
thereof.
7. The lubricating composition according to claim 4 wherein the
ionic liquid is selected from
trihexyl(tetradecyl)phosphonium-bi(trifluoromethylsulfonyl)imide,
hexylmethylimidazolium hexafluorophosphate, and mixtures
thereof.
8. The lubricating composition according to claim 4 wherein the
base oil is a synthetic ester formed by the reaction of a polyol
with a carboxylic acid of formula RCOOH wherein R is a straight or
branched chain hydrocarbyl group having from 5 to 10 carbon
atoms.
9. The use of a lubricating composition according to claim 4 for
lubricating a turbine engine.
10. The use of an ionic liquid according to claim 4 to reduce the
sludge content of a lubricating composition comprising (i) a base
oil, (ii) an ionic liquid and (iii) one or more additives.
11. The use of an ionic liquid to according to claim 4 reduce the
coking of a lubricating composition comprising (i) a base oil, (ii)
an ionic liquid and (iii) one or more additives.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to lubricating compositions,
particularly to lubricating compositions which are useful as
aviation turbine engine oils.
BACKGROUND OF THE INVENTION
[0002] Aviation turbine engine oils (TEOs) are required to exhibit
excellent performance over a wide temperature range in order to
meet military and civilian product specifications for these
products, namely MIL-PRF-23699 and SAE-AS-5780, respectively. In
particular, both specifications state that approved products must
meet certain viscosity, pour point and flash point
requirements.
[0003] As modern turbine engines evolve aviation turbine engines
oils are exposed to increasingly aggressive environments including
high thermal and oxidative stress. This can lead to undesirable
consequences for the turbine engine oil, in particular,
unacceptable build up of sludge and unacceptable levels of coking
in the oil system. Coke can generically be described as
carbonaceous deposits that form on the engine surface as the oil
ages. If these deposits form in an aircraft engine they have the
potential to block oil-ways and filters and cause heat transfer
reduction. The Hot Liquid Process Simulator (HLPS) test (SAE ARP
5996) has been developed by the aviation industry to assess the
propensity of aviation turbine engine oils to form coke and is a
key requirement in both the civil and military specifications. It
would therefore be desirable to formulate a turbine engine oil
wherein the build-up of sludge is reduced and wherein the level of
coking is reduced.
[0004] Ionic liquids are known for use in certain lubricating
compositions. WO2008/154998 discloses the use of ionic liquids for
improving the properties of lubricating compositions. However,
there is no mention in this document of the use of ionic liquids in
turbine engine oils. There is also no mention in this document of a
reduction in build-up of sludge or of a reduction in coking of the
lubricating composition.
[0005] WO2008/075016 discloses a non-aqueous lubricating oil
composition comprising a major amount of a base oil and a minor
amount of an additive which is present in solution in the base oil
and is a non-halide, non-aromatic ionic liquid which is a salt of
general formula C+A-, with the cation C+ being a quaternary
phosphonium or quaternary ammonium ion having four hydrocarbyl
groups, optionally containing heteroatoms, which hydrocarbyl groups
do not all have the same number of carbon atoms, there being at
least one long chain hydrocarbyl group having greater than 4 carbon
atoms and at least one short chain hydrocarbyl group having fewer
carbon atoms than each of the long chain hydrocarbyl groups, and
the anion A-, comprising at least one oxygen atom and having an
ionic head group attached to at least one alkyl or alicyclic
hydrocarbyl group which has at least four carbon atoms and
optionally one heteroatom. The ionic liquid may be used as an
anti-wear component and as a friction modifier in a lubricating oil
composition. The lubricating oil composition may be used in an
ignition engine. However, there is no mention in this document of
the use of ionic liquids in turbine engine oils. There is also no
mention in this document of a reduction in sludge build-up or of a
reduction of coking of the lubricating composition.
[0006] It has now surprisingly been found by the present inventors
that when ionic liquids are incorporated into turbine engine oils
there is a reduction in the build-up of sludge in the engine oil
and a reduction in coking. Advantageously, these benefits are
achieved while maintaining the physical properties of the
lubricating composition as required by military and civilian
specifications.
SUMMARY OF THE INVENTION
[0007] According to the present invention there is provided a
lubricating composition comprising:
(i) from 50% to 99% by weight of base oil; (ii) from 0.01% to 5% by
weight of ionic liquid; and (iii) from 0.01% to 10% by weight of
additive; wherein the lubricating composition has a pour point of
at most -54.degree. C., a flashpoint of at least 246.degree. C. and
a kinematic viscosity at 100.degree. C. in the range of from 4.9 to
5.4 mm.sup.2/s.
[0008] It has surprisingly been found that by substituting a
portion of the base oils used in a turbine engine oil with an ionic
liquid, the observed sludge content according to Test Method
FTD-STD-791-5308.7 is significantly reduced.
[0009] Hence according to the present invention there is further
provided the use of an ionic liquid to reduce the build-up of
sludge in a lubricating composition comprising (i) a base oil, (ii)
an ionic liquid and (iii) one or more additives.
[0010] It has also surprisingly been found that by substituting a
portion of the base oils used in a turbine engine oil with an ionic
liquid, the level of coking is significantly reduced.
[0011] Hence according to another aspect of the present invention
there is provided the use of an ionic liquid to reduce the coking
in a lubricating composition comprising (i) a base oil, (ii) an
ionic liquid and (iii) one or more additives.
[0012] It has also been found that the lubricating composition of
the present invention provides a reduction in viscosity increase, a
reduction in TAN increase and a reduction in evaporation loss
observed during the test method FTD-STD-791-5308.7.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The lubricating composition of the present invention has
particular use as a turbine engine oil. Turbine engine oils are
required to meet certain physical properties as set out in military
and civilian product specifications, MIL-PRF-23699 and SAE-AS-5780,
respectively.
[0014] The lubricating composition of the present invention has a
kinematic viscosity at 100.degree. C. (as measured by ASTM DIN455)
in the range of from 4.9 to 5.4 mm.sup.2/s, preferably in the range
of from 4.9 to 5.1 mm.sup.2/s.
[0015] The lubricating composition of the present invention has a
pour point (as measured by ASTM D97) of at most -54.degree. C.,
preferably at most -57.degree. C.
[0016] The lubricating composition of the present invention has a
flashpoint (as measured by ASTM D92) of at least 246.degree. C.,
preferably at least 250.degree. C.
[0017] The lubricating composition of the present invention
preferably has a kinematic viscosity at -40.degree. C. (as measured
by ASTM DIN455) of at most 13,000 mm.sup.2/s, more preferably at
most 11,500 mm.sup.2/s.
[0018] The lubricating composition of the present invention
preferably has a kinematic viscosity at 40.degree. C. (as measured
by ASTM DIN455) of at least 23 mm.sup.2/s, preferably at least 25
mm.sup.2/s.
[0019] The lubricating composition comprises, as an essential
component, a base oil.
[0020] The base oil is present at a level in the range of from 50%
to 99%, preferably in the range of from 70% to 99%, more preferably
in the range of from 80% to 97%, by weight of the lubricating
composition.
[0021] Any base oil suitable for use in a turbine engine oil may be
used herein.
[0022] Preferably, the base oil has a kinematic viscosity at
40.degree. C. in the range of from 20 to 30 mm.sup.2/s, more
preferably in the range of from 22 to 25 mm.sup.2/s, a kinematic
viscosity at 100.degree. C. in the range of from 4 to 6 mm.sup.2/s,
more preferably in the range of from 4.85 to 5.15 mm.sup.2/s, a
kinematic viscosity at -40.degree. C. in the range of from 7,000 to
13,000 mm.sup.2/s, more preferably in the range of from 8,000 to
10,000 mm.sup.2/s, a pour point in the range of -50 to -65.degree.
C., more preferably in the range of from -55 to -60.degree. C., and
a flash point in the range of 230 to 260.degree. C., more
preferably in the range of 250 to 260.degree. C.
[0023] Preferably the base oil comprises a synthetic ester based
base stock, in particular polyol ester-based base oils. Synthetic
ester based base oils are well known in the art and are for example
described in GB-A-2384245. Ester-based base oils (together with a
selected additive package) are functional over a wide temperature
range and exhibit good thermal and oxidative stability.
[0024] The preparation of esters from alcohols and carboxylic acids
can be accomplished using conventional methods and techniques known
and familiar to those skilled in the art, and form no part, per se,
of the present invention. In general, an alcohol, e.g. technical
pentaerythritol, is heated with the desired carboxylic acid
mixture, optionally in the presence of a catalyst. Generally, a
slight excess of acid is employed to force the reaction to
completion. Water is removed during the reaction and any excess
acid is then stripped from the reaction mixture. The esters, for
example of technical pentaerythritol, may be used without further
purification or may be further purified using conventional
techniques such as distillation.
[0025] For further information with respect to the synthetic ester
based base oil, reference is made to GB-A-2384245, EP-A-0695797,
EP-A-1323815, U.S. Pat. No. 4,826,633 and U.S. Pat. No. 5,503,761,
the teaching of which is hereby incorporated by reference.
[0026] Suitable synthetic polyol ester based base oils may be
formed by the esterification of an aliphatic polyol with carboxylic
acid. Preferably the aliphatic polyol contains from 4 to 15 carbon
atoms and has from 2 to 8 esterifiable hydroxyl groups. Preferred
examples are trimethylol propane, pentaerythritol,
dipentaerythritol, neopentyl glycol, tripentaerythritol and
mixtures thereof.
[0027] The carboxylic acid reactant used to produce the synthetic
polyol ester base oil may suitably be selected from aliphatic
monocarboxylic acid or a mixture of aliphatic monocarboxylic acid
and aliphatic dicarboxylic acid. The carboxylic acid may contain
from 2 to 20 carbon atoms, preferably from 4 to 12 carbon atoms,
more preferably from 5 to 10 carbon atoms and includes straight and
branched chain aliphatic acids. Mixtures of monocarboxylic acids
may also be used.
[0028] Suitable polyol esters are those commercially available
under the tradenames Hatcol 2954, Hatcol 1754, Hatcol 1764, Hatcol
1765 and Hatcol 1760 from Chemtura, Middlebury, Conn., USA,
Priolube 3939 from Croda, Snaith, UK and Synative ES 2939 and
Synative ES 2931 from Cognis, Monheim, Germany.
[0029] In addition, all base stocks described in EP-A-0518567 and
EP-A-0695797 are suitable for use in the lubricating compositions
of the present invention.
[0030] According to a preferred embodiment the polyol ester base
oil comprises at least 80 wt. % monopentaerythritol.
[0031] Suitably, the polyol ester base oil may be a mixture of
about 80 to 95 wt. % monopentaerythritol and 5 to 20 wt. %
dipentaerythritol. This mixture is typically known as `technical`
pentaerythritol and may also contain some tri and tetra
pentaerythritol, which are typically formed as by-products during
the production of technical pentaerythritol.
[0032] It is even more preferred that the polyol ester base oil
comprises more than 90 wt. % monopentaerythritol, more preferably
more than 95 wt. % monopentaerythritol. It is even more preferred
that the polyol ester base oil comprises about 100 wt. %
monopentaerythritol.
[0033] Another essential component of the lubricating composition
of the present invention is an ionic liquid.
[0034] The ionic liquid is present at a level in the range of from
0.01% to 5%, preferably in the range of from 0.01% to 2%, more
preferably in the range of from 0.05% to 0.5%, especially in the
range of from 0.1% to 0.3%, by weight of the lubricating
composition.
[0035] Ionic liquids are molten salts which are liquid at room
temperature or by definition have a melting point of less than
100.degree. C. They have virtually no vapour pressure and can
exhibit high thermal stability.
[0036] An ionic liquid can be presented by the formula
C.sup.+A.sup.- wherein C.sup.+ is a suitable cation and A.sup.- is
a suitable anion.
[0037] Suitable cations C.sup.+ are selected from a quaternary
ammonium cation, a phosphonium cation, an imidazolium cation, a
pyridinium cation, a pyrazolium cation, an oxazolium cation, a
pyrrolidinium cation, a piperidinium cation, a trialkylsulfonium
cation, a thiazolium cation, a guanidinium cation, a morpholinium
cation, a sulfonium cation and a triazolium cation. Preferred
cations are selected from quaternary ammonium cations and
phosphonium cations.
[0038] Suitable anions A.sup.- are selected from [PF.sub.6].sup.-,
[BF.sub.4].sup.-, [CF.sub.3CO.sub.2].sup.-,
[CF.sub.3SO.sub.3].sup.-, as well as its higher homologues,
[C.sub.4F.sub.9SO.sub.3].sup.- or [C.sub.8F.sub.17SO.sub.3].sup.-
and higher perfluoroalkylsulfonates,
[(CF.sub.3SO.sub.2).sub.2N].sup.-,
[(CF.sub.3SO.sub.2)(CF.sub.3COO)N].sup.-, Cl.sup.-, Br.sup.-,
I.sup.-, [C(CN).sub.3].sup.-, SCN.sup.-,
[B(C.sub.2O.sub.4).sub.2].sup.-, [N(SO.sub.2CF.sub.3).sub.2].sup.-,
[R.sup.4SO.sub.3].sup.-, [R.sup.4OSO.sub.3].sup.-,
[R.sup.4COO].sup.-, [NO.sub.3].sup.-, [N(CN).sub.2].sup.-,
[HSO.sub.4].sup.-, PF.sub.6-xR.sup.6.sub.x or
[R.sup.4R.sup.5PO.sub.4].sup.-, wherein R.sup.4 and R.sup.5 are
independently selected from hydrogen, linear or branched, saturated
or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20
carbon atoms; heteroaryl, heteroaryl-C.sub.1-C.sub.6-alkyl groups
with 3 to 8 carbon atoms in the hetero aryl residue and at least
one heteroatom selected from N, O and S, which can be substituted
with at least one group selected from C.sub.1-C.sub.6 alkyl groups
and/or halogen atoms; aryl-aryl-C.sub.1-C.sub.6-alkyl groups with 5
to 12 carbon atoms in the aryl residue, which can be substituted
with at least one C.sub.1-C.sub.6-alkyl group, R.sup.6 can be a
perfluoroethyl or a higher perfluoroalkyl group, and x is an
integer of from 1 to 4.
[0039] Particularly preferred are ionic liquids with highly
fluoridated anions, since these are generally highly thermally
stable. Also, the ability for water uptake by these anions can be
significantly reduced, for example, with
bis(trifluoromethylsulfonyl)imide anion. Another preferred anion is
trifluoroacetate.
[0040] Examples of suitable ionic liquids include, but are not
limited to, butyl
methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide (MBPimid),
methylpropylpyrollidinium-bis(trifluoromethylsulfonyl)imide
(MPPimid), tris-hexylmethylimidazolium
(perfluoroethylene)-trifluorophosphate (HMIMPFET),
hexylmethylimidazolium-bis(trifluoromethylsulfonyl)imide
(HMIMimid),
hexylmethylpyrrolidinium-bis(trifluoromethylsulfonyl)imide (HMP),
tris-tetrabutylphosphonium (perfluoroethylene)trifluorophosphate
(BuPPFET), octylmethylimidazolium-hexafluorophosphate (OMIM PF6),
hexylpyridinium-bis(trifluoromethyl)sulfonylimide (Hpyimid),
methyltrioctylammonium-trifluoroacetate (MOAac),
butylmethylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate
(MBPPFET),
trihexyl(tetradecyl)phosphonium-bis(trifluoromethylsulfonyl)imide
(HPDimid), hexylmethylimidazolium tetrafluoroborate (HMI BF4),
hexylmethylimidazolium hexafluorophosphate (HMI PF6),
1-ethyl-3-methylimidazolium diethylphosphate (EMIM DEP),
1-ethyl-3-methylimidazolium methyl sulphate (EMIM DSU),
1-ethyl-3-methylimidazolium bis[oxalate(2-)-O,O+]borate (EMIM BOB)
and mixtures thereof.
[0041] Ionic liquids such as those listed above are commercially
available from Merck, Darmstadt, Germany and Sigma Aldrich, St
Louis, Mo., USA. Ionic Liquids commercially available under the
tradename Basionics from BASF, Ludwigshafen, Germany, are also
suitable for use herein.
[0042] Preferred ionic liquids for use in the compositions of the
present invention are selected from
methyltrioctylammonium-trifluoroacetate (MOAac),
trihexyl(tetradecyl)phosphonium-bis (trifluoromethylsulfonyl)imide
(HDPimid), hexylmethylimidazolium tetrafluoroborate (HMI BF4),
hexylmethylimidazolium hexafluorophosphate (HMI PF6),
1-ethyl-3-methylimidazolium diethylphosphate (EMIM DEP),
1-ethyl-3-methylimidazolium methyl sulphate (EMIM DSU) and mixtures
thereof.
[0043] Especially preferred ionic liquids for use herein are
trihexyl(tetradecyl)phosphonium-bis(trifluoromethylsulfonyl)imide
(HDPimid), hexylmethylimidazolium hexafluorophosphate (HMI PF6),
and mixtures thereof.
[0044] The lubricating composition further comprises one or more
additives, in effective amounts, typically at a level of from 0.01%
to 10% by weight of the lubricating composition, such as for
example, but not limited to, metallic and ashless oxidation
inhibitors, metallic and ashless dispersants, metallic and ashless
detergents, corrosion and rust inhibitors, metal deactivators,
metallic and non-metallic, low-ash, phosphorus-containing and
non-phosphorus, sulphur-containing and non-sulphur-containing
anti-wear agents, metallic and non-metallic, phosphorus-containing
and non-phosphorus, sulphur-containing and non-sulphurous extreme
pressure additives, anti-seizure agents, pour point depressants,
wax modifiers, viscosity modifiers, seal compatibility agents,
friction modifiers, lubricity agents, anti-staining agents,
chromophoric agents, anti foaming agents, demulsifiers, and other
usually employed additive packages. For a review of many commonly
used additives, reference is made to D. Klamann in Lubricants and
Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN
0-89573-177-0, and to "Lubricant Additives" by M. W. Ranney,
published by Noyes Data Corporation of Parkridge, N.J. (1973).
[0045] Viscosity index improvers (also known as VI improvers,
viscosity modifiers, or viscosity improvers) provide lubricants
with high- and low-temperature operability. These additives impart
shear stability at elevated temperatures and acceptable viscosity
at low temperatures.
[0046] Preferable antiwear additives to be used with the
composition according to the invention include triaryl phosphates,
such as those available from Chemtura under the tradenames Reolube
OMTI, Durad 310M, Durad 110, Durad 125, Durad 150B, Reolube TXP,
Durad 220B, Durad 620B, Durad 110B, Fryquel 150 and Fryquel 220,
those available from Rhein Chemie under the tradenames Additin RC
3661, Additin RC 3760 and Additin RC 3680 and those commercially
available from Supresta under the tradenames SynOAd 8475, SynOAd
8484, SynOAd 8485, SynOAd 8478, SynOAd 8477, SynOAd 8499 and SynOAd
9578. Included within the term triaryl phosphates are tricresyl
phosphates, such as those approved to the specification
TT-T-656.
[0047] Other preferred antiwear additives include metal
alkylthiophosphates, more particularly zinc
dialkyldithiophosphates. Other preferred antiwear additives include
phosphorus-free antiwear additives such as sulphur-containing
aliphatic, arylaliphatic or alicyclic olefinic hydrocarbons. Other
preferred antiwear additives include polysulfides of thiophosphorus
acids and thiophosphorus acid esters, and phosphorothionyl
disulfides.
[0048] Esters of glycerol may be used as antiwear agents. For
example, mono-, di-, and tri-oleates, mono-palmitates and
mono-myristates may preferably be used. Generally, antiwear
additives may be used in an amount of about 0.01 to 6% by weight,
preferably about 0.01 to 4% by weight, based on the total weight of
the lubricating composition.
[0049] Suitable antioxidants retard the oxidative degradation of
the lubricating composition during service. Such degradation may
result in deposits on metal surfaces, the presence of sludge, or a
viscosity increase in the fluid. A wide variety of suitable
oxidation inhibitors are known, as for instance those described in
Klamann in Lubricants, and for example U.S. Pat. No. 4,798,684 and
U.S. Pat. No. 5,084,197.
[0050] Preferred antioxidants for the lubricating composition of
this invention include aminic antioxidants. These include alkylated
and non-alkylated aromatic amines such as aromatic monoamines with
aliphatic, aromatic or substituted aromatic group substituents at
the nitrogen atom. Typical aromatic amines antioxidants have alkyl
substituent groups of at least about 6 carbon atoms. Examples of
aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl.
Generally, the aliphatic groups will not contain more than about 14
carbon atoms. The general types of amine antioxidants useful in the
present compositions include diphenylamines, phenyl naphthylamines,
phenothiazines, imidodibenzyls and diphenyl phenylene diamines.
Mixtures of two or more aromatic amines may also be used, such as
for example a mixture of phenyl-alpha-naphthylamine (PANA)-type
antioxidant(s) and diphenylamine (DPA)-type antioxidant(s).
Polymeric amine antioxidants may also be used, such as Vanlube 9317
commercially available from RT Vanderbilt. Particular examples of
aromatic amine antioxidants useful in the present invention
include: p,p'-dioctyldiphenylamine;
t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and
p-octylphenyl-alpha-naphthylamine.
[0051] Commercially available phenyl-alpha-naphthylamine
(PANA)-type antioxidants include, for example, Irganox L06
commercially available from Ciba, Additin 7130 commercially
available from Rhein Chemie, Naugalube APAN and Naugard PAN
commercially available from Chemtura.
[0052] Commercially available diphenylamine (DPA)-type antioxidants
include, for example, Vanlube 81 commercially available from RT
Vanderbilt, Naugalube AMS, Naugalube 438, Naugalube 635, Naugalube
640, Naugalube 680 Commercially available from Chemtura, Germany,
Additin 7001, Addition 7005A, Additin 7135, Additin 10314A,
commercially available from Rhein Chemie, Hitec 4720, Hitec 4721,
Hitec 4777 commercially available from Afton, Irganox L57, Irganox
L67 commercially available from Ciba.
[0053] Other useful antioxidants include hindered phenols. Phenolic
antioxidants may be used either as such or in combination with
aminics. These phenolic antioxidants may be ashless (metal-free)
phenolic compounds or neutral or basic metal salts of certain
phenolic compounds. Typical phenolic antioxidant compounds are the
hindered phenolics which are the ones which contain a sterically
hindered hydroxyl group, and these include those derivatives of
dihydroxy aryl compounds in which the hydroxyl groups are in the o-
or p-position to each other. Examples of phenolic materials of this
type include 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol;
2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol;
2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl
phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful
hindered mono-phenolic antioxidants may include for example
hindered 2,6-di-alkyl-phenolic proprionic ester derivatives.
[0054] Bis-phenolic antioxidants may also be advantageously used in
the lubricating composition. Sulphurized alkyl phenols and alkali
or alkaline earth metal salts thereof also are useful antioxidants.
Low sulfur peroxide decomposers are useful as antioxidants. Another
class of suitable antioxidants is oil soluble copper compounds.
Examples of suitable copper antioxidants include copper
dihydrocarbyl-thio or dithio-phosphates and copper salts of
carboxylic acids. Other suitable copper salts include copper
dithiocarbamates, sulphonates, phenates, and acetylacetonates.
Basic, neutral, or acidic copper Cu(I) and or Cu(II) salts derived
from alkenyl succinic acids or anhydrides are known to be
particularly useful. These antioxidants may be used individually by
type or in combination with one another. Such additives may be used
in an amount of about 0.01 to 5% by weight, preferably about 0.01
to 2% by weight.
[0055] Detergents useful as additives may be simple detergents or
hybrid or complex detergents. Suitable detergents include anionic
compounds that contain a long chain oleophilic portion of the
molecule and a smaller anionic or oleophobic portion of the
molecule. The anionic portion of the detergent is typically derived
from an organic acid such as a sulphuric acid, carboxylic acid,
phosphorus acid, phenol, or mixtures thereof. The counter ion is
typically an alkaline earth or alkali metal. Preferred detergents
include the alkali or alkaline earth metal salts of sulfates,
sulfonates, phenates, carboxylates, phosphates, and salicylates.
Suitable alkaryl sulfonates typically contain about 9 to about 80
or more carbon atoms, more typically from about 16 to 60 carbon
atoms. Preferred are those disclosed in Klamann in Lubricants and
Related Products, and in "Lubricant Additives" cited above, and C.
V. Smallheer and R. K. Smith, published by the Lezius-Hiles Co. of
Cleveland, Ohio (1967). Alkaline earth phenolates represent another
useful class of detergents. These detergents are the products of
reacting alkaline earth metal hydroxides or oxides with an alkyl
phenol or sulphurized alkylphenol. Useful alkyl groups include
straight chain or branched C.sub.1-C.sub.30 alkyl groups,
preferably, C.sub.4-C.sub.20. Examples of suitable phenols include
isobutylphenol, 2-ethylhexylphenol, nonylphenol,
1-ethyldecylphenol, and the like. Metal salts of carboxylic acids
are also useful as detergents. Another preferred class of
detergents is alkaline earth metal salicylates, including monoalkyl
to tetraalkyl salicylates, wherein the alkyl groups have from 1 to
30 carbon atoms. Preferably, the alkaline earth metal is calcium,
magnesium, or barium; calcium being the most preferred. Another
useful class of detergents encompasses alkaline earth metal
phosphates. Typically, the total detergent concentration is about
0.01 to about 6% by weight, preferably, about 0.1 to 4% by weight,
calculated on the total lubricating composition. In addition,
non-ionic detergents may be preferably used in lubricating
compositions. Such non-ionic detergents may be ashless or low-ash
compounds, and may include discrete molecular compounds, as well as
oligomeric and/or polymeric compounds.
[0056] The additives may further comprise dispersants. Suitable
dispersants typically contain a polar group attached to a
relatively high molecular weight hydrocarbon chain. The polar group
typically contains at least one element of nitrogen, oxygen, or
phosphorous. Typical hydrocarbon chains contain about 50 to 400
carbon atoms. Suitable dispersants include phenolates, sulfonates,
sulphurized phenolates, salicylates, naphthenates, stearates,
carbamates and thiocarbamates. A particularly useful class of
dispersants is alkenylsuccinic derivatives, in which the alkenyl
chain constitutes the oleophilic portion of the molecule which
confers solubility in the oil. The alkenyl chain may be a
polyisobutylene group, such as those described in U.S. Pat. No.
3,172,892; U.S. Pat. No. 3,2145,707; U.S. Pat. No. 3,219,666; U.S.
Pat. No. 3,316,177; U.S. Pat. No. 3,341,542; U.S. Pat. No.
3,454,607; U.S. Pat. No. 3,541,012; U.S. Pat. No. 3,630,904; U.S.
Pat. No. 3,632,511; U.S. Pat. No. 3,787,374 and U.S. Pat. No.
4,234,435.
[0057] Other types of suitable dispersants are described in U.S.
Pat. No. 3,036,003; U.S. Pat. No. 3,200,107; U.S. Pat. No.
3,254,025; U.S. Pat. No. 3,275,554; U.S. Pat. No. 3,438,757; U.S.
Pat. No. 3,454,555; U.S. Pat. No. 3,565,804; U.S. Pat. No.
3,413,347; U.S. Pat. No. 3,697,574; U.S. Pat. No. 3,725,277; U.S.
Pat. No. 3,725,480; U.S. Pat. No. 3,726,882; U.S. Pat. No.
4,454,059; U.S. Pat. No. 3,329,658; U.S. Pat. No. 3,449,250; U.S.
Pat. No. 3,519,565; U.S. Pat. No. 3,666,730; U.S. Pat. No.
3,687,849; U.S. Pat. No. 3,702,300; U.S. Pat. No. 4,100,082; U.S.
Pat. No. 5,705,458; and EP-A-471071.
[0058] Other suitable dispersants include hydrocarbyl-substituted
succinic acid compounds, such as succinimides, succinate esters, or
succinate ester amides prepared by the reaction of
hydrocarbon-substituted succinic acid preferably having at least 50
carbon atoms in the hydrocarbon substituent, with at least one
equivalent of an alkylene amine, are particularly useful.
[0059] Friction modifiers i.e. a material or compound that can
alter the coefficient of friction of the fluid may be effectively
used in combination with the base oil components. Suitable friction
modifiers may include metal salts or metal-ligand complexes where
the metals may include alkali, alkaline earth, or transition group
metals, as those described in WO2004/053030.
[0060] Other useful additives include pour point depressants to
lower the minimum temperature at which the lubricating composition
will flow or can be poured. Examples of suitable pour point
depressants include polymethacrylates, polyacrylates,
polyarylamides, condensation products of haloparaffin waxes and
aromatic compounds, vinyl carboxylate polymers, and terpolymers of
dialkylfumarates, vinyl esters of fatty acids and allyl vinyl
ethers, such as those referred to in WO2004/053030.
[0061] Suitable seal compatibility agents include organic
phosphates, aromatic esters, aromatic hydrocarbons, esters
(butylbenzyl phthalate, for example), and polybutenyl succinic
anhydride.
[0062] Such additives may be used in an amount of about 0.01 to 3%
by weight.
[0063] Anti-foaming agents may advantageously be added to the
lubricating compositions. These agents retard the formation of
stable foams. Silicones and organic polymers are typical anti-foam
agents, such as for example polysiloxanes. Anti-foam agents are
commercially available, such as, for example, DCF 200/12500, DCF
200/500, DCF 200/30000, DCF 200/1000 from Dow Corning, and may be
used in conventional minor amounts along with other additives such
as demulsifiers; usually the amount of these additives combined is
less than 1% by weight.
[0064] Suitable corrosion inhibitors are those referred to in
Klamann, as cited above. Examples of suitable corrosion inhibitors
include thiadiazoles, benzotriazoles, tolutriazoles, zinc
dithiophosphates, metal phenolates, basic metal sulfonates, fatty
acids, carboxylic acids and amines. Such additives may be used in
an amount of from about 0.01 to 5% by weight, preferably from about
0.01 to 1.5% by weight, more preferably from about 0.01 to 1% by
weight. Examples of suitable corrosion inhibitors can be found in,
for example, U.S. Pat. No. 2,719,125; U.S. Pat. No. 2,719,126; and
U.S. Pat. No. 3,087,932. Examples of suitable corrosion inhibitors
are those commercially available under the tradenames Irgamet 39,
Irgamet TTA and Irgamet 42 from Ciba, and those commercially
available under the tradenames Vanlube 887 and Vanlube 887E from
Vanderbilt. A further example of suitable corrosion inhibitors are
dicarboxylic acids such as those commercially available from Cognis
under the tradenames Emerox 1144 and Emerox 1110.
[0065] Additional types of additives may be further incorporated
into the lubricating compositions of this invention may include one
or more additives such as, for example, demulsifiers, solubilizers,
fluidity agents, colouring agents, chromophoric agents, and the
like. Each additive may include individual additives or mixtures
thereof.
[0066] The present invention will now be described by reference to
the following Examples:
Examples 1-18 and Comparative Example A
[0067] The turbine engine oils of Examples 1-18 and Comparative
Example A were prepared by blending together the base oil and
additives shown in Tables 1 to 3 below.
[0068] The amounts in Tables 1 to 3 are in wt. %, based on the
total weight of the fully formulated formulations.
[0069] The base oil as used in the formulations of Tables 1 to 3
was a 5 cSt pentaerythritol ester further containing tricresyl
phosphate antiwear additive, tolutriazole corrosion inhibitor,
dicarboxylic acid corrosion inhibitor, dioctyldiphenyl amine
(DODPA) and diaryldiphenylamine as diphenylamine (DPA)-type
anti-oxidant components, p-tert.-octylphenyl-alpha-naphthylamine as
phenyl-alpha-naphthalene (PANA)-type anti-oxidant component, and a
polysiloxane anti-foam agent. The pentaerythritol ester had a
viscosity of 5 mm.sup.2/s at 100.degree. C. and a maximum viscosity
of 13,000 mm.sup.2/s at -40.degree. C. In addition, the
pentaerythritol ester has a maximum pour point of -54.degree. C.
and a minimum flash point of 246.degree. C.
TABLE-US-00001 TABLE 1 Comparative Ex. A Ex. 1 Ex. 2 Ex. 3 Ex. 4
Ex. 5 Ex. 6 Base Oil + 100 99.8 99.5 99.0 99.8 99.5 99.0 Additive
Package MOAac.sup.1 0 0.2 0.5 1.0 0 0 0 HDPimid.sup.2 0 0 0 0 0.2
0.5 1.0 .sup.1Methyltrioctylammonium Trifluoroacetate
.sup.2Trihexyl(tetradecyl)phosphonium
Bis(trifluoromethylsulfonyl)imide
TABLE-US-00002 TABLE 2 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Base
Oil + 99.8 99.5 99.0 99.8 99.5 99.0 Additive Package HMI BF4.sup.3
0.2 0.5 1.0 0 0 0 HMI PF6.sup.4 0 0 0 0.2 0.5 1.0
.sup.3Hexylmethylimidazolium tetrafluoroborate
.sup.4Hexylmethylimidazolium hexafluorophosphate
TABLE-US-00003 TABLE 3 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18
Base Oil + 99.8 99.5 99.0 99.8 99.5 99.0 Additive Package EMIM
DEP.sup.1 0.2 0.5 1.0 0 0 0 EMIM DSU.sup.2 0 0 0 0.2 0.5 1.0
.sup.51-Ethyl-3-methylimidazolium diethylphosphate
.sup.61-Ethyl-3-methylimidazolium methyl sulphate
Measurement of Physical Properties
[0070] Various physical properties of the lubricating compositions
of Examples 1 to 18 and Comparative Example A were determined by
subjecting the lubricating compositions to various standard test
methods (as indicated in Table 4). The measured properties are
shown in Table 4.
TABLE-US-00004 TABLE 4 Kinematic Kinematic Viscosity at Viscosity
at 40.degree. C. (mm.sup.2/s) 100.degree. C. TAN (mm.sup.2/s) (as
measured (mm.sup.2/s) (as Pour Point .degree. C. Flash Point
.degree. C. (as by Test measured by (as measured (as measured
measured by Method ASTM Test Method by Test Method by Test Method
Test Method Example D445) ASTM D445) ASTM D5950) ASTM D92) ARP5088)
A 25.47 5.02 -57 >246 0.3 1 (0.2% MOAac) 25.62 4.99 -57 >246
0.23 2 (0.5% MOAac) 25.71 5.02 -57 >246 0.25 3 (1% MOAac) 26.08
5.05 -57 >246 0.26 4 (0.2% HDPimid) 25.54 5.01 -57 >246 0.23
5 (0.5% HDPimid) 25.61 5.01 -57 >246 0.24 6 (1% HDPimid) 25.89
5.05 -57 >246 0.25 7 (0.2% HMI BF4) 25.44 4.99 -57 268 0.22 8
(0.5% HMI BF4) 25.45 4.99 -57 274 0.22 9 (1% HMI BF4) 25.46 4.99
-57 256 0.20 10 (0.2% HMI PF6) 25.5 5.00 -57 269 0.21 11 (0.5% HMI
PF6) 25.47 5.00 -57 273 0.23 12 (1% HMI PF6) 25.5 5.00 -57 264 0.23
13 (0.2% EMIM DEP) 25.62 5.005 -57 266 0.06 14 (0.5% EMIM DEP)
25.68 5.000 -57 262 0.04 15 (1% EMIM DEP) 25.69 5.013 -57 267 0.04
16 (0.2% EMIM MSU) 25.56 5.011 -57 263 0.19 17 (0.5% EMIM MSU)
25.62 5.010 -57 265 0.18 18 (1% EMIM MSU) 25.7 5.010 -57 263
0.17
Measurement of Viscosity Increase, TAN Increase and Evaporation
Loss
[0071] To demonstrate the various benefits of the turbine engine
oils of the present invention, Examples 1, 4 and 16 (containing
0.2% MOAac, 0.2% HDPimid and 0.2% EMIM MSU respectively) and
Comparative Example A were subjected to the test methods as set out
in FED-STD-791-5308.7 in order to measure viscosity increase, TAN
increase and evaporation loss during the test. The test was run at
218.degree. C. for 72 hours. The results are shown in Table 5
below.
TABLE-US-00005 TABLE 5 TAN Sludge Viscosity Change Evaporation
Content Example Change % mg KOH/l Loss % mg A.sup.# 60.44 9.71 4.56
1.0 1 (0.2% 39.10 5.61 3.72 0.1 MOAac).sup.## 4 (0.2% 46.85 6.62
3.72 <0.1 HDPimid).sup.## 16 (0.2% 48.87 7.53 3.91 0.4 EMIM MSU)
.sup.#results are the average of 8 measurements .sup.##results are
the average of 2 measurements
Measurement of Coking Behaviour
[0072] To measure the coking behaviour of the lubricating
compositions according to the present invention, Examples 1 and 4
(containing 0.2 wt % MOAac and 0.2 wt % HDPimid, respectively) and
Comparative Example A were subjected to the HPLS standard test
method SAE ARP 5996. The amount of coke formed on the stainless
steel tubes after 20 hours was weighed and the visual appearance of
the tubes was noted. The results are shown in Table 6.
TABLE-US-00006 TABLE 6 Visual appearance of Example Coke formed/mg
tube Comparative Example A 0.27 Significant levels of coke in
centre of tube Example 1 (0.2% 0.24 Reduced levels MOAac) of coke
along the length of the tube compared to Comparative Example A
Example 4 (0.2% 0.19 Significantly HDPimid) reduced levels of coke
in centre of tube compared to Comparative Example A
Measurement of Load Carrying Capability
[0073] To measure the load carrying capability & anti-wear
properties of the lubricating compositions according to the present
invention, Examples 7-12 and Comparative Example A were subjected
to the four-ball test (IP 239) and the maximum weld load of each
sample measured (10 second duration at each load stage). The
results are shown in Table 7 below.
TABLE-US-00007 TABLE 7 Wear Scar (60 min, Weld Load (10 secs
ambient, 1500 rpm, at each Example IP 239) (mm) load stage) (kg) A
0.41 140 7 (0.2% HMI BF4) 0.32 160 8 (0.5% HMI BF4) 0.31 170 9 (1%
HMI BF4) 0.33 210 10 (0.2% HMI PF6) 0.36 200 11 (0.5% HMI PF6) 0.32
230 12 (1% HMI PF6) 0.33 270
Discussion
[0074] The results shown in Table 4 demonstrate that the
introduction of low levels of ionic liquids into a turbine engine
oil do not detrimentally effect the physical properties of the
turbine engine oil (as required by military and civilian
specifications, namely MIL-PRF-23699 and SAE-AS-5780,
respectively).
[0075] As can be seen from Table 5, the lubricating compositions of
Example 1 (containing 0.2% of MOAac), Example 4 (containing 0.2%
HDPimid) and Example 16 (containing 0.2% EMIM MSU) exhibit a
reduction in the build-up of sludge compared to Comparative Example
A (containing no ionic liquid).
[0076] As can be seen from Table 6, the lubricating compositions of
Example 1 (containing 0.2% MOAac) and Example 4 (containing 0.2%
HDPimid) exhibit a reduction in coking compared to Comparative
Example A (containing no ionic liquid). Example 4 (containing 0.2%
HDPimid) exhibits a bigger reduction in coking than Example 1
(containing 0.2% MOAac).
[0077] As can be seen from Table 7, the lubricating compositions of
Examples 7-12 exhibit an increase in weld load and comparable wear
scar diameter compared to Comparative Example A.
* * * * *