Note: Descriptions are shown in the official language in which they were submitted.
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3759-01
TITLE
Lubricating Composition Containing an Ester
FIELD OF INVENTION
[0001] The invention relates to a method of lubricating a limited slip
differential comprising supplying to the limited slip differential a
lubricating
composition containing (a) an oil of lubricating viscosity, and (b) a C4_30-
diester of a dicarboxylic acid. The invention further provides for the use of
the
C4_30-diester of a dicarboxylic acid as a friction modifier, typically in a
limited
slip differential.
BACKGROUND OF THE INVENTION
[0002] A limited slip differential in a vehicle typically employs a wet multi-
plate clutch, i.e., clutch plates are immersed in a lubricant. The limited
slip
differential typically has bevel gear or spur gear planetary systems which
distribute the drive torque evenly to the two driving wheels irrespective of
their
rotational speed. This makes it possible for the driven wheels to roll during
cornering without slip between the wheel and road surface in spite of their
different rotational speed. In order for the slip to be controlled lubricants
containing compounds capable of improving friction performance, dispersants
and sulphur- and/or phosphorus- containing extreme pressure agents may be
used. Examples of lubricants of this type are disclosed in US Patents
4,308,154; 5,547,586; 4,180,466; 3,825,495; and European Patent Application
0 399 764 Al.
[0003] EP 0 767 236 Al discloses a gear lubricant composition having a
kinematic viscosity at 100 C in the range of 4 to 32 mm2/s. The composition
contains more than 20 % by volume a hydrogenated poly-a-olefin, and less than
80 % by volume of mineral oil or synthetic ester oil or a combination thereof.
The examples contain 10 % by volume bis(tridecyl)-adipate. The gear is
described is especially a transmission for use in large vehicles equipped with
manual transmissions of the synchronizer type.
[0004] International Publication WO 98/04658 Al discloses base stocks for
synthetic gear oils for use in automotive heavy and medium duty axle gear
lubricants and transmission fluid application. The lubricant disclosed therein
contains 1 % to 20 % by weight of an ester. The ester includes diesters of
C8_13
adipates, in particular di-isodecyl adipate.
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[0005] US Patent 4,370,247 discloses a gear or axle lubricant containing 25
to 60 mass % of at least one di-Cs_12 alkyl ester of a dicarboxylic acid. The
whole lubricant disclosed therein is reported to decrease power loss due to
friction, therefore conserving fuel consumption.
[0006] Canadian Publication CA 2 637 401 discloses the use as a lubricant a
variety of diesters derived from a dicarboxylic acid having 2 to 36 carbon
atoms and a branched alcohol having 4 to 40 carbon atoms. The lubricants can
contain 0.1 to 100 % by weight, or 5 to 99 % by weight of the diesters.
SUMMARY OF THE INVENTION
[0007] The inventors of this invention have discovered that a lubricating
composition and method as disclosed herein is capable of providing an
acceptable level of at least one of (i) lubricant thermal stability, (ii)
lubricant
oxidative stability, (iii) high static coefficient of friction, (iv) fuel
economy, (v)
deposit control, (vi) seal compatibility, (vii) cleanliness and (viii) low
tendency
towards noise, vibration and harshness (NVH) often manifested as chatter (i.e.
an abnormal noise typically referred to as a low-frequency "growl" and
"groan", particularly during higher-speed cornering manoeuvres). The
inventors have also discovered that unexpectedly the lubricant composition and
method disclosed herein may also be suitable for limited slip systems having
one or more distinct plate materials. For example the plate materials may be
steel, paper, ceramic, carbon fibers and systems employing a mixture of plate
types such as steel on ceramic, carbon fibers in paper, or steel on paper. In
one
embodiment the plate material may be paper.
[0008] In one embodiment, the invention provides a method of lubricating a
limited slip differential comprising supplying to the limited slip
differential a
lubricating composition comprising (a) an oil of lubricating viscosity, and
(b) a
C4_30-diester of a dicarboxylic acid, or mixtures thereof, wherein the
dicarboxylic acid has formula HO(O)C-RI-C(O)OH, and R1 may be an aliphatic
group having 2 to 38, or 2 to 28 carbon atoms.
[0009] The number of carbon atoms present on an ester group of the C4-30-
diester may contain 4 to 30 carbon atoms. As used herein, an "ester group"
means the alcohol-derived portion of the ester, that is, R' in an ester
RCOOR',
in the case of a carboxylic acid RCOOH, where R' may be a hydrocarbyl group
of the indicated number of carbon atoms.
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[0010] In one embodiment the carboxylic acid may be have formula
HO(O)C-RI-C(O)OH, and R1 may be an aliphatic group having 5 to 8 carbon
atoms (typically R1 may be an alkylene group). The carboxylic acid may be
saturated or unsaturated.
[0011] In different embodiments the alcohol-derived portion of the ester
groups of the C4_30-diester of the carboxylic acid disclosed herein may be
C8_20,
or C1o_15, or C13. The ester groups of the diester may be linear or branched,
typically branched.
[0012] In one embodiment, the invention provides a method of lubricating a
limited slip differential comprising supplying to the limited slip
differential a
lubricating composition comprising (a) an oil of lubricating viscosity, and
(b) a
C4_30-diester of adipic acid.
[0013] In one embodiment, the invention provides a method of lubricating a
limited slip differential comprising supplying to the limited slip
differential a
lubricating composition comprising (a) an oil of lubricating viscosity, (b)
C4_30-diester of a dicarboxylic acid, wherein the dicarboxylic acid has
formula
HO(O)C-RI-C(O)OH, and R1 may be an aliphatic group having 2 to 38, or 2 to
28 carbon atoms (typically a C4_30-diester of adipic acid), and (c) a
phosphorus
containing compound.
[0014] In one embodiment, the invention provides a method of lubricating a
limited slip differential comprising supplying to the limited slip
differential a
lubricating composition comprising (a) an oil of lubricating viscosity, and a
friction modifier package consisting of, or, alternatively, comprising, a
C4_30-diester of a dicarboxylic acid, wherein the dicarboxylic acid has
formula
HO(O)C-RI-C(O)OH, and R1 may be an aliphatic group having 2 to 38, or 2 to
28 carbon atoms (typically a C4_30-diester of adipic acid), and a phosphorus
containing compound.
[0015] In one embodiment the lubricating composition comprises (a) an oil
of lubricating viscosity, and a friction modifier package consisting of, or,
alternatively, comprising, a C4_30-diester of adipic acid, and 0.05 wt % to
4.5 wt
% of a phosphorus containing compound.
[0016] In one embodiment, the invention provides a method of lubricating a
limited slip differential comprising supplying to the limited slip
differential a
lubricating composition comprising (a) an oil of lubricating viscosity,
wherein
the oil of lubricating viscosity is an API Group III or API Group IV base oil,
or
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mixtures thereof, (b) a C4_30-diester of a dicarboxylic acid, wherein the
dicarboxylic acid has formula HO(O)C-R'-C(O)OH, and R1 may be an aliphatic
group having 2 to 38 carbon atoms (typically a C4_30-diester of adipic acid),
and
(c) a phosphorus containing compound.
[0017] The lubricating compositions disclosed herein may contain 0.01 wt
% to less than 1 wt %, or 0.02 wt % to 0.9 wt %, or 0.05 wt % to 0.5 wt %, or
0.1 wt % to 0.3 wt % of the C4_30-diester of a dicarboxylic acid, wherein the
dicarboxylic acid has formula HO(O)C-R1-C(O)OH, and R1 may be an aliphatic
group having 2 to 38 carbon atoms (typically C4_30-diester of adipic acid).
[0018] The limited slip differential in one embodiment may have plate
contact surfaces of steel on paper (or cellulose).
[0019] In one embodiment, the invention provides for the use of a
lubricating composition comprising (a) a C4_30-diester of a dicarboxylic acid
wherein the dicarboxylic acid has formula HO(O)C-R1-C(O)OH, and R1 may be
an aliphatic group having 2 to 38 carbon atoms (typically a C4_30-diester of
adipic acid), and (b) an oil of lubricating viscosity in a limited slip
differential
to provide an acceptable level of at least one of (i) lubricant thermal
stability,
(ii) lubricant oxidative stability, (iii) friction, (iv) fuel economy, (v)
deposit
control, (vi) seal compatibility, and (vii) chattering (abnormal noise). In
one
embodiment the use provides an acceptable level of friction.
[0020] In one embodiment the invention provides for the use of a
lubricating composition comprising (a) an oil of lubricating viscosity, (b) a
C4_30-diester of a dicarboxylic acid wherein the dicarboxylic acid has formula
HO(O)C-R1-C(O)OH, and R1 may be an aliphatic group having 2 to 38 carbon
atoms (typically a C4_30-diester of adipic acid), and (c) a phosphorus
containing
compound in a limited slip differential to provide friction modification.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present invention provides a lubricating composition and method
as disclosed herein above.
C4.3o-Diester of a dicarboxylic acid
[0022] The C4_30-diester of a dicarboxylic acid disclosed herein may include
C4_30-diesters of glutaric acid, adipic acid, pimelic acid, suberic acid,
azelaic
acid, brassylic acid, dodecanedioic acid, thapsic acid, or mixtures thereof.
In
one embodiment the C4_30-diester of a dicarboxylic acid disclosed herein may
be a C4_30-diester of adipic acid.
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[0023] Ester groups of the C4_30-diester of the dicarboxylic acid disclosed
herein may be CS-20, or Cio_15, or C13. Examples of ester groups include
butyl,
2-methylpentyl, 2-propylheptyl, 2-butyloctyl, 2-ethylhexyl, octyl, neooctyl,
neoheptyl, nonyl, isooctyl, isononyl, neononyl (may also be called
3,5,5-trimethyl-l-hexyl), decyl, neodecyl, undecyl, 5-methylundecyl, dodecyl,
2-methyldodecyl, tridecyl, 5-methyltridecyl, tetradecyl, pentadecyl,
hexadecyl,
2-methylhexadecyl, heptadecyl, 5-isopropylheptadecyl, 3-isopropyloctadecyl,
octadecyl, nonadecyl, eicosyl, cetyleicosyl, stearyleicosyl, docosyl,
eicosyltetratriacontyl, or mixtures thereof.
[0024] In one embodiment the ester group may be a C8_20-, or Clo_15-, or C13-
branched alkyl group, typically iso-tridecyl, or mixtures thereof.
[0025] The C4_30-diester of a dicarboxylic acid disclosed herein may be
derived from an esterification reaction of (i) a carboxylic acid having
formula
HO(O)C-RI-C(O)OH, wherein R1 may be an aliphatic group having 2 to 38
carbon atoms, and (ii) an alcohol having 4 to 30 carbon atoms. Reactions of
this type are known to a person skilled in the art.
Amine Salt of a Phosphoric Acid Ester
[0026] In one embodiment the lubricating composition further includes a
phosphorus containing compound. The phosphorus containing compound may
be an amine salt of a phosphoric acid ester. The phosphoric acid utilised to
prepare the phosphoric acid ester amine salt may be either a phosphoric acid,
or
a thiophosphoric acid.
[0027] The amine salt of a phosphorus acid ester may be present at 0 wt % to
5wt%,or0.0lwt%to5wt%,or0.05wt%to4.5wt%,or0.lwt%to2wt%,or
0.25 wt % to 1 wt % of the lubricating composition.
[0028] The amine salt of a phosphoric acid ester may contain ester groups
each having 1 to 30, 6 to 30, 8 to 30, 10 to 24 or 12 to 20, or 16 to 20
carbon
atoms, with the proviso that the amine salt of a phosphoric acid ester is
soluble
in an oil of lubricating viscosity or a formulated lubricant. Typically ester
groups containing 4 or more carbon atoms are particularly useful.
[0029] Examples of suitable ester groups include isopropyl, methyl-amyl
(may also be referred to as 1,3-dimethyl butyl), 2-ethylhexyl, heptyl, octyl,
nonyl, decyl, dodecyl, butadecyl, pentadecyl, hexadecyl, heptadecyl,
octadecyl,
nonadecyl, eicosyl, or mixtures thereof.
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[0030] In one embodiment the ester groups is selected from the group
consisting of isopropyl, methyl-amyl (may also be referred to as 1,3-dimethyl
butyl), 2-ethylhexyl, heptyl, octyl, nonyl, decyl, and mixtures thereof.
[0031] The amines which may be suitable for use as the amine salt include
primary amines, secondary amines, tertiary amines, and mixtures thereof. The
amines include those with at least one hydrocarbyl group, or, in certain
embodiments, two or three hydrocarbyl groups. The hydrocarbyl groups may
contain 2 to 30 carbon atoms, or in other embodiments 8 to 26, or 10 to 20, or
13 to 19 carbon atoms.
[0032] Primary amines include ethylamine, propylamine, butylamine,
2-ethylhexylamine, octylamine, and dodecylamine, n-octylamine, n-
decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-
octadecylamine and oleyamine. Other useful fatty amines include
commercially available fatty amines such as "Armeen " amines (products
available from Akzo Chemicals, Chicago, Illinois), such as Armeen C, Armeen
0, Armeen OL, Armeen T, Armeen HT, Armeen S and Armeen SD, wherein
the letter designation relates to the fatty group, such as coco, oleyl,
tallow, soy,
or stearyl groups.
[0033] Examples of suitable secondary amines include dimethylamine,
diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine,
diheptylamine, methylethylamine, ethylbutylamine, ethylamylamine,
dicocoamine and di-2-ethylhexylamine. The secondary amines may be cyclic
amines such as piperidine, piperazine and morpholine.
[0034] The amine may also be a tertiary-aliphatic primary amine. The
aliphatic group in this case may be an alkyl group containing 2 to 30, or 6 to
26, or 8 to 24 carbon atoms. Tertiary alkyl amines include monoamines such as
tert-butylamine, tert-hexylamine, 1-methyl-l-amino -cyclohexane, tert-octyl-
amine, tert-decylamine, tertdodecylamine, tert-tetradecylamine, tert-hexadecyl-
amine, tert-octadecylamine, tert-tetracosanylamine, and tert-octacosanylamine.
[0035] The amine may be represented by the formula:
R2(R3)bN-(R4-C(=O)-X-(R5)c)a, wherein R2 is a hydrocarbyl group of 12 to 20
carbon atoms, or R2 is an aminoalkyl group of up to 3 carbon atoms substituted
on the nitrogen atom thereof by a hydrocarbyl group of 12 to 22 carbon atoms;
R3 is hydrogen or a hydrocarbyl group; a is 1 or 2, and b is 2-a. That is,
there
may be 1 or 2 -R4-C(=O)X(R5), groups on the amine nitrogen. If there are
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multiple amine nitrogen atoms in the molecule and if there are multiple
-R4-C(=O)X(R5), groups, such groups may be attached to the same or to
different nitrogens.
[0036] R4 may be a linking group which is attached to the amine nitrogen.
If there are multiple R4 groups, they may be the same or different from each
other. They may be an alkylene group of 1 to 4 carbon atoms such as
methylene, ethylene, ethylidene, propylene (in the 1,2 configuration, that is,
methylethylene, or in the 1,3 configuration, that is, trimethylene), or
butylene
(in the 1,2 configuration or any other configurations such as 1,4, that is,
tetramethylene). They may also comprise a chain of 2 to 8 carbon atoms
interrupted by one or two nitrogen or oxygen atoms within the chain. Examples
of these may include -CH2CH2CH2NHCH2CH2- or
-CH2CH2CH2NHCH2CH2CH2NHCH2CH2- or -CH2CH2CH2OCH2CH2- or
-CH2CH2OCH2CH2- .
[0037] X may represent either oxygen or nitrogen. In the case of oxygen,
the resulting group will be a carboxylic acid or an ester. In the case of
nitrogen, the resulting group will be an amide. One or two R5 groups will be
attached to the X to satisfy its valence: one such group for oxygen and two
such groups for nitrogen. That is, c will be 1 or 2, as the case may be. If a
mixture of materials is present such that some of the X are nitrogen and some
are oxygen, then c may have a fractional value between 1 and 2, but it will be
either 1 or 2 for any given molecule. The R5 group or groups may
independently be hydrogen, or a hydrocarbyl group of 1 to 20 carbon atoms,
such as 12 to 20 carbon atoms (as described above) or a nitrogen-containing
group represented by the formula -R4-NHR6, where R4 is as defined above and
R6 is a hydrocarbyl group of 12 to 20 carbon atoms. (The R4 contained within
the R4 group need not be identical to any of the R4 linking groups as used
above, as is implicit from the statement that each R4 is independently one of
the
groups listed.) Specific examples of -C(=O)X(R5), groups include -COOH,
-CONH2, -COOCH3, -CONHCH3, -CON(CH3)2, -CONH-coco, -CONH-tallow,
and -CONH-CH2CH2NH-tallow, where "coco" and "tallow" are the
hydrocarbyl residues of cocoamine and tallowamine, as described above.
[0038] Certain of the amines of the present invention (that is, containing the
carbonyl functionality) may be obtained by reaction of an amine with an
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equivalent amount of an unsaturated ester such as methyl acrylate. A
generalized reaction scheme would be as follows:
O O
NH + ~ N
R2/ O-CH3 R2~ O-CH3
and the resulting ester may be converted to an amide or other functionality by
known methods. The starting amine, designated here as R2R3NH may have
suitable R groups provided that at least one of them is selected so as to meet
the
requirements of the present invention, e.g., containing a hydrocarbyl group of
12 to 22 carbon atoms. In certain embodiments the precursor amine itself
R2R3NH may be a polyamine in the "Duomeen" series, available from Akzo,
having a general structure such as:
R2
jN NH2
R3
[0039] The amine salt of a phosphorus acid ester may be a reaction product
of a C12-20 alkyl phosphoric acid with a tertiary C 11-22 alkyl primary amine.
[0040] In one embodiment the amine salt of a phosphorus acid ester
includes an amine which is a C I I to C14 tertiary alkyl primary amine or
mixtures thereof. In one embodiment the amine salt of a phosphorus compound
includes an amine which is a C14 to C18 tertiary alkyl primary amine or
mixtures thereof. In one embodiment the amine salt of a phosphorus compound
includes an amine which is a C18 to C22 tertiary alkyl primary amine or
mixtures thereof.
[0041] In one embodiment the amine salt of a phosphorus acid ester includes
the reaction product of octadecenyl phosphoric acid with Primene 81RTM
[0042] Mixtures of amines may also be used in the invention. In one
embodiment a useful mixture of amines is "PrimeneTM 81R" and "PrimeneTM
JMT." PrimeneTM 81R and PrimeneTM JMT (both produced and sold by Rohm
& Haas) are mixtures of C l 1 to C 14 tertiary alkyl primary amines and C 18
to
C22 tertiary alkyl primary amines respectively.
[0043] In one embodiment the amine salt of a phosphorus acid ester is the
reaction product of a C14 to C18 alkyl phosphoric acid with Primene 81 RTM
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(produced and sold by Rohm & Haas) which is a mixture of Cl1 to C14 tertiary
alkyl primary amines.
[0044] The amine salt of a phosphate hydrocarbon ester may be prepared as
is described in US Patent 6,468,946, wherein column 10, lines 15 to 63
describes phosphoric acid esters formed by reaction of phosphorus compounds,
followed by reaction with an amine to form an amine salt of a phosphate
hydrocarbon ester. Column 10, line 64, to column 12, line 23, describes
preparative examples of reactions between phosphorus pentoxide with an
alcohol (having 4 to 13 carbon atoms), followed by a reaction with an amine
(typically Primene 81-R) to form an amine salt of a phosphate hydrocarbon
ester. In one somewhat oversimplified schematic representation using P205 for
illustrative purposes, the reaction of a phosphating agent with alcohol(s) may
be represented as follows:
3 ROH + P205 - (RO)2P(=O)OH + RO-P(=O)(OH)2
where ROH represent an alcohol (such as monools or polyols or hydroxy-
containing carboxylic compounds or mixtures thereof). As is described herein,
the residual phosphoric acidic functionality may be reacted at least in part
with
an amine.
[0045] Examples of the amine salt of a phosphorus acid ester include the
reaction product(s) of isopropyl, methyl-amyl (1,3-dimethylbutyl or mixtures
thereof), 2-ethylhexyl, heptyl, octyl, nonyl or decyl dithiophosphoric acids
with
ethylene diamine, morpholine, or Primene 81RTM, and mixtures thereof.
[0046] Examples of the amine salt of a phosphorus acid ester include the
reaction product(s) of tetradecyl, pentadecyl, hexadecyl, heptadecyl,
octadecyl,
nonadecyl or eicosyl dithiophosphoric acids with ethylenediamine, morpholine,
or Primene 81RTM, and mixtures thereof. In one embodiment the amine salt of
a phosphorus acid ester includes the reaction product of octadecenyl
dithiophosphoric acid with Primene 81 RTM.
[0047] In one embodiment the amine salt of a phosphorus compound may be
an amine salt of (i) a hydroxy-substituted di- ester of phosphoric acid, (ii)
a
phosphorylated hydroxy-substituted di- or tri- ester of phosphoric acid, or
(iii) or
mixtures thereof. A more detailed description of this type of compound is
described
in International Publication WO 2008/094759.
[0048] In one embodiment the amine salt of a phosphoric acid is a
compound described in US Patent 3,197,405. In one embodiment the amine
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salt of a phosphorus compound other than those disclosed above, may be
prepared by any one of examples 1 to 25 of US Patent 3,197,405.
[0049] In one embodiment the amine salt of a phosphorus compound other
than those disclosed above, is a reaction product prepared from a
dithiophosphoric acid is reacting with an epoxide or a glycol. This reaction
product is further reacted with a phosphorus acid, anhydride, or lower ester
(where "lower" signifies 1 to 8, or 1 to 6, or 1 to 4, or 1 to 2 carbon atoms
in
the alcohol-derived portion of the ester). The epoxide includes an aliphatic
epoxide or a styrene oxide. Examples of useful epoxides include ethylene
oxide, propylene oxide, butene oxide, octene oxide, dodecene oxide, styrene
oxide and the like. In one embodiment the epoxide is propylene oxide. The
glycols include aliphatic glycols having 1 to 12, or 2 to 6, or 2 to 3 carbon
atoms. The dithiophosphoric acids, glycols, epoxides, inorganic phosphorus
reagents and methods of reacting the same are described in U.S. Patent numbers
3,197,405 and 3,544,465. The resulting acids are then salted with amines.
[0050] An example of suitable dithiophosphoric acid based product is
prepared by adding phosphorus pentoxide (about 64 grams) at 58 C over a
period of 45 minutes to 514 grams of hydroxypropyl O,O-di(1,3-
dimethylbutyl)phosphorodithio ate (prepared by reacting di(1,3-dimethylbutyl)-
phosphorodithioic acid with 1.3 moles of propylene oxide at 25 C). The
mixture is heated at 75 C for 2.5 hours, mixed with a diatomaceous earth and
filtered at 70 C. The filtrate contains 11.8% by weight phosphorus, 15.2% by
weight sulphur, and an acid number of 87 (bromophenol blue).
Oils of Lubricating Viscosity
[0051] The lubricating composition comprises an oil of lubricating viscosity.
Such oils include natural and synthetic oils, oil derived from hydrocracking,
hydrogenation, and hydrofinishing, unrefined, refined, re-refined oils or
mixtures
thereof. A more detailed description of unrefined, refined and re-refined oils
is
provided in International Publication W02008/147704, paragraphs [0054] to
[0056]. A more detailed description of natural and synthetic lubricating oils
is
described in paragraphs [0058] to [0059] respectively of W02008/147704.
Synthetic oils may also be produced by Fischer-Tropsch reactions and typically
may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one
embodiment oils may be prepared by a Fischer-Tropsch gas-to-liquid synthetic
procedure as well as other gas-to-liquid oils.
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[0052] Oils of lubricating viscosity may also be defined as specified in
April 2008 version of "Appendix E - API Base Oil Interchangeability
Guidelines for Passenger Car Motor Oils and Diesel Engine Oils", section 1.3
Sub-heading 1.3. "Base Stock Categories". In one embodiment the oil of
lubricating viscosity may be an API Group II, Group III or Group IV base oil.
In one embodiment the oil of lubricating viscosity may be an API Group III
(typically including hydrocracked/hydroisomerized base oil), or API Group IV
base oil or mixtures thereof.
[0053] The amount of the oil of lubricating viscosity present is typically the
balance remaining after subtracting from 100 wt % the sum of the amount of
the compound of the invention and the other performance additives.
[0054] The lubricating composition may be in the form of a concentrate
and/or a fully formulated lubricant. If the lubricating composition of the
invention (comprising the additives disclosed herein) is in the form of a
concentrate which may be combined with additional oil to form, in whole or in
part, a finished lubricant), the ratio of the of these additives to the oil of
lubricating viscosity and/or to diluent oil include the ranges of 1:99 to 99:1
by
weight, or 10:90 to 80:20 by weight.
Other Performance Additives
[0055] The composition of the invention optionally further includes at least
one other performance additive. The other performance additives include
dispersants, metal deactivators, detergents, viscosity modifiers, extreme
pressure agents (typically boron- and/or sulphur- and/or phosphorus-
containing), antiwear agents, antioxidants (such as hindered phenols, aminic
antioxidants or molybdenum compounds), corrosion inhibitors, foam inhibitors,
demulsifiers, pour point depressants, seal swelling agents, friction modifiers
and mixtures thereof.
[0056] The total combined amount of the other performance additives
(excluding the viscosity modifiers) present on an oil free basis may include
ranges of 0 wt % to 25 wt %, or 0.01 wt % to 20 wt %, or 0.1 wt % to 15 wt %
or
0.5 wt % to 10 wt %, or 1 to 5 wt % of the composition. Although one or more
of the other performance additives may be present, it is common for the other
performance additives to be present in different amounts relative to each
other.
[0057] In one embodiment the lubricating composition is free of molybdenum-
containing additives.
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Viscosity Modifiers
[0058] In one embodiment the lubricating composition further includes one or
more viscosity modifiers.
[0059] When present the viscosity modifier may be present in an amount of 0.5
wt % to 70 wt %, l wt % to 60 wt %, or 5 wt % to 50 wt %, or lO wt % to 50 wt
%
of the lubricating composition.
[0060] Viscosity modifiers include (a) polymethacrylates, (b) esterified
copolymers of (i) a vinyl aromatic monomer and (ii) an unsaturated carboxylic
acid, anhydride, or derivatives thereof, (c) esterified interpolymers of (i)
an
alpha-olefin; and (ii) an unsaturated carboxylic acid, anhydride, or
derivatives
thereof, or (d) hydrogenated copolymers of styrene-butadiene, (e) ethylene-
propylene copolymers, (f) polyisobutenes, (g) hydrogenated styrene-isoprene
polymers, (h) hydrogenated isoprene polymers, or (i) mixtures thereof.
[0061] In one embodiment the viscosity modifier includes (a) a
polymethacrylate, (b) an esterified copolymer of (i) a vinyl aromatic monomer;
and (ii) an unsaturated carboxylic acid, anhydride, or derivatives thereof,
(c) an
esterified interpolymer of (i) an alpha-olefin; and (ii) an unsaturated
carboxylic
acid, anhydride, or derivatives thereof, or (d) mixtures thereof.
Extreme Pressure Agents
[0062] Extreme pressure agents include compounds containing boron and/or
sulphur and/or phosphorus.
[0063] The extreme pressure agent may be present in the lubricating
composition at 0 wt % to 20 wt %, or 0.05 wt % to 10 wt %, or 0.1 wt % to 8 wt
% of the lubricating composition.
[0064] In one embodiment the extreme pressure agent is a sulphur-
containing compound. In one embodiment the sulphur-containing compound
may be a sulphurised olefin, a polysulphide, or mixtures thereof.
[0065] Examples of the sulphurised olefin include a sulphurised olefin
derived from propylene, isobutylene, pentene; an organic sulphide and/or
polysulphide including benzyldisulphide; bis-(chlorobenzyl) disulphide;
dibutyl tetrasulphide; di-tertiary butyl polysulphide; and sulphurised methyl
ester of oleic acid, a sulphurised alkylphenol, a sulphurised dipentene, a
sulphurised terpene, a sulphurised Diels-Alder adduct, an alkyl sulphenyl N'N-
dialkyl dithiocarbamates; or mixtures thereof. In one embodiment the
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sulphurised olefin includes a sulphurised olefin derived from propylene,
isobutylene, pentene or mixtures thereof.
[0066] In one embodiment the extreme pressure agent sulphur-containing
compound includes a dimercaptothiadiazole or derivative, or mixtures thereof.
Examples of the dimercaptothiadiazole include compounds such as
2,5-dimercapto-1,3,4-thiadiazole or a hydrocarbyl-substituted 2,5-dimercapto-
1,3,4-thiadiazole, or oligomers thereof. The oligomers of hydrocarbyl-
substituted
2,5-dimercapto-1,3,4-thiadiazole typically form by forming a sulphur-sulphur
bond
between 2,5-dimercapto-1,3,4-thiadiazole units to form derivatives or
oligomers of
two or more of said thiadiazole units. Suitable 2,5-dimercapto-1,3,4-
thiadiazole
derived compounds include for example 2,5-bis(tert-nonyldithio)-1,3,4-
thiadiazole
or 2-tert-nonyldithio-5-mercapto-1,3,4-thiadiazole.
[0067] The number of carbon atoms on the hydrocarbyl substituents of the
hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole typically include 1
to
30, or 2 to 20, or 3 to 16.
[0068] In one embodiment the dimercaptothiadiazole may be a thiadiazole-
functionalised dispersant. A detailed description of the thiadiazole-
functionalised dispersant is described is paragraphs [0028] to [0052] of
International Publication WO 2008/014315.
[0069] The thiadiazole-functionalised dispersant may be prepared by a method
including heating, reacting or complexing a thiadiazole compound with a
dispersant
substrate. The thiadiazole compound may be covalently bonded, salted,
complexed
or otherwise solubilised with a dispersant, or mixtures thereof.
[0070] The relative amounts of the dispersant substrate and the thiadiazole
used
to prepare the thiadiazole-functionalised dispersant may vary. In one
embodiment
the thiadiazole compound is present at 0.1 to 10 parts by weight relative to
100 parts
by weight of the dispersant substrate. In different embodiments the
thiadiazole
compound is present at greater than 0.1 to 9, or greater than 0.1 to less than
5, or 0.2
to less than 5: to 100 parts by weight of the dispersant substrate. The
relative
amounts of the thiadiazole compound to the dispersant substrate may also be
expressed as (0.1-10):100, or (>0.1-9):100, (such as (>0.5-9):100), or (0.1 to
less
than 5): 100, or (0.2 to less than 5): 100.
[0071] In one embodiment the dispersant substrate is present at 0.1 to 10
parts
by weight relative to 1 part by weight of the thiadiazole compound. In
different
embodiments the dispersant substrate is present at greater than 0.1 to 9, or
greater
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than 0.1 to less than 5, or about 0.2 to less than 5: to 1 part by weight of
the
thiadiazole compound. The relative amounts of the dispersant substrate to the
thiadiazole compound may also be expressed as (0.1-10):1, or (>0.1-9):1, (such
as
(>0.5-9):1), or (0.1 to less than 5): 1, or (0.2 to less than 5): 1.
[0072] The thiadiazole-functionalised dispersant may be derived from a
substrate that includes a succinimide dispersant (for example, N-substituted
long chain alkenyl succinimides, typically a polyisobutylene succinimide), a
Mannich dispersant, an ester-containing dispersant, a condensation product of
a
fatty hydrocarbyl monocarboxylic acylating agent with an amine or ammonia,
an alkyl amino phenol dispersant, a hydrocarbyl-amine dispersant, a polyether
dispersant, a polyetheramine dispersant, a viscosity modifier containing
dispersant functionality (for example polymeric viscosity index modifiers
(VMs) containing dispersant functionality), or mixtures thereof. In one
embodiment the dispersant substrate includes a succinimide dispersant, an
ester-containing dispersant or a Mannich dispersant.
[0073] In one embodiment the extreme pressure agent includes a boron-
containing compound. The boron-containing compound includes a borate ester
(which in some embodiments may also be referred to as a borated epoxide), a
borated alcohol, a borated dispersant, a borated phospholipid or mixtures
thereof. In one embodiment the boron-containing compound may be a borate ester
or a borated alcohol.
[0074] The borate ester may be prepared by the reaction of a boron compound
and at least one compound selected from epoxy compounds, halohydrin compounds,
epihalohydrin compounds, alcohols and mixtures thereof. The alcohols include
dihydric alcohols, trihydric alcohols or higher alcohols, with the proviso for
one
embodiment that hydroxyl groups are on adjacent carbon atoms, i.e., vicinal.
[0075] Boron compounds suitable for preparing the borate ester include the
various forms selected from the group consisting of boric acid (including
metaboric acid, HBO2, orthoboric acid, H3B03, and tetraboric acid, H2B407),
boric oxide, boron trioxide and alkyl borates. The borate ester may also be
prepared from boron halides.
[0076] In one embodiment suitable borate ester compounds include tripropyl
borate, tributyl borate, tripentyl borate, trihexyl borate, triheptyl borate,
trioctyl
borate, trinonyl borate and tridecyl borate. In one embodiment the borate
ester
compounds include tributyl borate, tri-2-ethylhexyl borate or mixtures
thereof.
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[0077] In one embodiment, the boron-containing compound is a borated
dispersant, typically derived from an N-substituted long chain alkenyl
succinimide. In one embodiment the borated dispersant includes a
polyisobutylene succinimide. Borated dispersants are described in more detail
in US Patents 3,087,936; and Patent 3,254,025.
[0078] In one embodiment the borated dispersant may be used in
combination with a sulphur-containing compound or a borate ester.
[0079] In one embodiment the extreme pressure agent is other than a
borated dispersant.
[0080] The number average molecular weight of the hydrocarbon from
which the long chain alkenyl group was derived includes ranges of 350 to 5000,
or 500 to 3000, or 550 to 1500. The long chain alkenyl group may have a
number average molecular weight of 550, or 750, or 950 to 1000.
[0081] The N-substituted long chain alkenyl succinimides are borated using
a variety of agents including boric acid (for example, metaboric acid, HBO2,
orthoboric acid, H3B03, and tetraboric acid, H2B407), boric oxide, boron
trioxide, and alkyl borates. In one embodiment the borating agent is boric
acid
which may be used alone or in combination with other borating agents.
[0082] The borated dispersant may be prepared by blending the boron
compound and the N-substituted long chain alkenyl succinimides and heating
them at a suitable temperature, such as, 80 C to 250 C, or 90 C to 230 C,
or
100 C to 210 C, until the desired reaction has occurred. The molar ratio of
the boron compounds to the N-substituted long chain alkenyl succinimides may
have ranges including 10:1 to 1:4, or 4:1 to 1:3; or the molar ratio of the
boron
compounds to the N-substituted long chain alkenyl succinimides may be 1:2.
Alternatively, the ratio of moles B : moles N (that is, atoms of B : atoms of
N)
in the borated dispersant may be 0.25:1 to 10:1 or 0.33:1 to 4:1 or 0.2:1 to
1.5:1, or 0.25:1 to 1.3:1 or 0.8:1 to 1.2:1 or about 0.5:1 An inert liquid may
be
used in performing the reaction. The liquid may include toluene, xylene,
chlorobenzene, dimethylformamide or mixtures thereof.
[0083] In one embodiment the lubricating composition further includes a
borated phospholipid. The borated phospholipid may be derived from
boronation of a phospholipid (for example boronation may be carried out with
boric acid). Phospholipids and lecithins are described in detail in
Encyclopedia
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of Chemcial Technology, Kirk and Othmer, 3rd Edition, in "Fats and Fatty
Oils", Volume 9, pages 795-831 and in "Lecithins", Volume 14, pages 250-269.
[0084] The phospholipid may be any lipid containing a phosphoric acid, such
as lecithin or cephalin, or derivatives thereof. Examples of phospholipids
include phosphatidylcholine, phosphatidylserine, phosphatidylinositol,
phosphatidylethanolamine, phosphotidic acid and mixtures thereof. The
phospholipids may be glycerophospholipids, glycero derivatives of the above
list of phospholipids. Typically, the glycerophospholipids have one or two
acyl, alkyl or alkenyl groups on a glycerol residue. The alkyl or alkenyl
groups
may contain 8 to 30, or 8 to 25, or 12 to 24 carbon atoms. Examples of
suitable
alkyl or alkenyl groups include octyl, dodecyl, hexadecyl, octadecyl,
docosanyl, octenyl, dodecenyl, hexadecenyl and octadecenyl. In one
embodiment the phospholipid is lecithin, or derivatives thereof.
[0085] Phospholipids may be prepared synthetically or derived from natural
sources. Synthetic phospholipids may be prepared by methods known to those
in the art. Naturally derived phospholipids are often extracted by procedures
known to those in the art. Phospholipids may be derived from animal or
vegetable sources. A useful phospholipid is derived from sunflower seeds.
The phospholipid typically contains 35 % to 60 % phosphatidylcholine, 20 % to
35 % phosphatidylinositol, 1 % to 25 % phosphatidic acid, and 10 % to 25 %
phosphatidylethanolamine, wherein the percentages are by weight based on the
total phospholipids. The fatty acid content may be 20 wt % to 30 wt % by
weight palmitic acid, 2 wt % to 10 wt % stearic acid, 15 wt % to 25 wt % oleic
acid, and 40 wt % to 55 wt % linoleic acid.
[0086] A more detailed description and methods of preparation of borated
phospholipids is described in US Patent 5,487,838. Examples 1 to 7 as
disclosed in column 20 line 64 to column 22 line 51 of US Patent 5,487,838
exemplify the preparation borated phospholipids. Borated phospholipids are
also disclosed in International Publication WO 2009/073390, in particular
paragraphs [0014] to [0024].
[0087] Friction modifiers (other than those described above) may include
fatty amines, esters such as borated glycerol esters, fatty phosphites, fatty
acid
amides, fatty epoxides, borated fatty epoxides, alkoxylated fatty amines,
borated
alkoxylated fatty amines, metal salts of fatty acids, or fatty imidazolines,
condensation products of carboxylic acids and polyalkylene-polyamines.
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[0088] In one embodiment the lubricating composition may contain
phosphorus- or sulphur- containing antiwear agents other than compounds
described as an extreme pressure agent of the amine salt of a phosphoric acid
ester described above. Examples of the antiwear agent may include a non-ionic
phosphorus compound (typically compounds having phosphorus atoms with an
oxidation state of +3 or +5), a metal dialkyldithiophosphate (typically zinc
dialkyldithiophosphates), a metal mono- or di- alkylphosphate (typically zinc
phosphates), or mixtures thereof.
[0089] The non-ionic phosphorus compound includes a phosphite ester, a
phosphate ester, or mixtures thereof. A more detailed description of the non-
ionic phosphorus compound include column 9, line 48 to column 11, line 8 of
US 6,103,673.
[0090] In one embodiment the lubricating composition of the invention
further includes a dispersant. The dispersant may be a succinimide dispersant
(for example N-substituted long chain alkenyl succinimides), a Mannich
dispersant, an ester-containing dispersant, a condensation product of a fatty
hydrocarbyl monocarboxylic acylating agent with an amine or ammonia, an
alkyl amino phenol dispersant, a hydrocarbyl-amine dispersant, a polyether
dispersant or a polyetheramine dispersant.
[0091] In one embodiment the succinimide dispersant includes a
po lyisobutylene- substituted succinimide, wherein the polyisobutylene from
which the dispersant is derived may have a number average molecular weight
of 400 to 5000, or 950 to 1600.
[0092] Succinimide dispersants and their methods of preparation are more
fully described in U.S. Patents 4,234,435 and 3,172,892.
[0093] Suitable ester-containing dispersants are typically high molecular
weight esters. These materials are described in more detail in U.S. Patent
3,381,022.
[0094] In one embodiment the dispersant includes a borated dispersant.
Typically the borated dispersant includes a succinimide dispersant including a
polyisobutylene succinimide, wherein the polyisobutylene from which the
dispersant is derived may have a number average molecular weight of 400 to
5000. Borated dispersants are described in more detail above within the
extreme pressure agent description.
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[0095] Dispersant viscosity modifiers (often referred to as DVM5) include
functionalised polyolefins, for example, ethylene-propylene copolymers that
have been functionalized with the reaction product of maleic anhydride and an
amine, a polymethacrylate functionalised with an amine, or esterified styrene-
maleic anhydride copolymers reacted with an amine may also be used in the
composition of the invention.
[0096] Corrosion inhibitors include 1-amino-2-propanol, octylamine
octanoate, condensation products of dodecenyl succinic acid or anhydride
and/or a fatty acid such as oleic acid with a polyamine.
[0097] Metal deactivators include derivatives of benzotriazoles (typically
tolyltriazole), 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles
or
2-alkyldithiobenzothiazoles. The metal deactivators may also be described as
corrosion inhibitors.
[0098] Foam inhibitors include copolymers of ethyl acrylate and 2-
ethylhexyl acrylate and optionally vinyl acetate.
[0099] Demulsifiers include trialkyl phosphates, and various polymers and
copolymers of ethylene glycol, ethylene oxide, propylene oxide, or mixtures
thereof.
[0100] Pour point depressants including esters of maleic anhydride-styrene,
polymethacrylates, polyacrylates or polyacrylamides.
[0101] Seal swell agents including Exxon Necton-37TM (FN 1380) and
Exxon Mineral Seal Oi1TM (FN 3200).
Industrial Application
[0102] The limited slip differential typically incorporates a self-contained
lubricant supply isolated from the lubricant disposed in the differential
housing
or carrier. The self-contained lubricant of the limited slip differential is
generally different from the lubricant supplied to a manual transmission or an
automatic transmission fluid. In both the manual and automatic transmission
systems not comprising a limited slip differential one lubricant is sufficient
to
lubricate all of the transmission constituents.
[0103] An axle gear may have any one of a number of different types of
differential. A differential typically has three major functions. The first
function is to transmit engine power to the wheels. The second function is act
as the final gear reduction in the vehicle, slowing the rotational speed from
the
transmission to the wheels. The third function is to transmit the power to the
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wheels while allowing them to rotate at different speeds. A number of
differentials are known and include an open differential, a clutch-type
limited
slip differential, a viscous coupling differential, a torque sensing
differential
(such as those sold under the trademark Torsen by JTEKT Torsen North
America Inc) and a locking differential. All of these differentials may be
generically referred to as axle gears.
[0104] Axle gears typically require a lubricant. The lubricant formulation is
dependent on the type of axle gear, and the operating conditions of the axle
gear. For example an open differential axle gear is believed to require
antiwear
and/or extreme pressure additives. In contrast, a limited slip differential
typically requires a friction modifier because in addition to an open
differential
(known from many axle fluids), a spring pack and a clutch pack are typically
present. The clutch pack may contain one or more reaction plates (often made
from steel) and one or more friction plates. The friction plates are known,
and
may be made from a number of materials including paper (or cellulose), carbon,
graphite, steel and a composite.
[0105] The lubricating composition suitable for the limited slip differential
may have a sulphur content in the range of 0.3 wt % to 5 wt %, or 0.5 wt % to
5
wt%,or0.5wt%to3wt%or0.8wt%to2.5wt%,orlwt%to2wt%.
[0106] In one embodiment the lubricating composition suitable for the limited
slip differential may be a fully formulated fluid.
[0107] In one embodiment the lubricating composition suitable for the limited
slip differential may be a top treat concentrate (that is, a concentrate
suitable to
be added to an existing lubricant formulation as a top treat).
[0108] When the lubricating composition is in the form of a top treat
concentrate, the concentrate may be added at 0.2 wt % to 10 wt %, or 0.5 wt %
to 7
wt % relative to the amount of lubricant in a limited slip differential.
[0109] It is known that some of the materials described above may interact
in the final formulation, so that the components of the final formulation may
be
different from those that are initially added. The products formed thereby,
including the products formed upon employing lubricant composition of the
present invention in its intended use, may not be susceptible of easy
description. Nevertheless, all such modifications and reaction products are
included within the scope of the present invention; the present invention
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encompasses lubricant composition prepared by admixing the components
described above.
[0110] Each of the documents referred to above is incorporated herein by
reference. Except in the Examples, or where otherwise explicitly indicated,
all
numerical quantities in this description specifying amounts of materials, reac-
tion conditions, molecular weights, number of carbon atoms, and the like, are
to
be understood as modified by the word "about." Unless otherwise indicated,
each chemical or composition referred to herein should be interpreted as being
a commercial grade material which may contain the isomers, by-products,
derivatives, and other such materials which are normally understood to be
present in the commercial grade. However, the amount of each chemical
component is presented exclusive of any solvent or diluent oil, which may be
customarily present in the commercial material, unless otherwise indicated. It
is to be understood that the upper and lower amount, range, and ratio limits
set
forth herein may be independently combined. Similarly, the ranges and
amounts for each element of the invention may be used together with ranges or
amounts for any of the other elements.
[0111] As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl
group" is used in its ordinary sense, which is well-known to those skilled in
the
art. Specifically, it refers to a group having a carbon atom directly attached
to
the remainder of the molecule and having predominantly hydrocarbon
character. Examples of hydrocarbyl groups include: hydrocarbon substituents,
including aliphatic, alicyclic, and aromatic substituents; substituted
hydrocarbon substituents, that is, substituents containing non-hydrocarbon
groups which, in the context of this invention, do not alter the predominantly
hydrocarbon nature of the substituent; and hetero substituents, that is,
substituents which similarly have a predominantly hydrocarbon character but
contain other than carbon in a ring or chain. A more detailed definition of
the
term "hydrocarbyl substituent" or "hydrocarbyl group" is described in
paragraphs [0118] to [0119] of International Publication W02008147704.
[0112] While the invention has been explained in relation to its preferred
embodiments, it is to be understood that various modifications thereof will
become apparent to those skilled in the art upon reading the specification.
Therefore, it is to be understood that the invention disclosed herein is
intended
to cover such modifications as fall within the scope of the appended claims.
