Note: Descriptions are shown in the official language in which they were submitted.
CA 02627866 2008-04-01
=
I LUBRICATING OIL COMPOSITION CONTAINING
2 ALKALI METAL BORATES WITH
3 IMPROVED FRICTIONAL PROPERTIES
4
FIELD OF THE INVENTION
6
7 The present invention relates to lubricants generally and, more
specifically, to
8 lubricants for automotive gears.
9
BACKGROUND OF THE INVENTION
11
12 The use of dispersed alkali metal borates in lubricant formulations is well
13 known. The patent literature has taught the combination of an alkali metal
14 borate with sulfur compounds and particular phosphorus compounds. See for
example, U.S. Patent Nos. 4,717,490; 4,472,288; and patents cited therein.
16 These prior art formulations suffered from shortened shelf life compared to
17 other commercially available lubricants which do not use solid dispersions
of
18 borate. Published U.S. Patent Application No. US20060252656, filed May 4,
19 2005, teaches how to overcome this shortcoming by the judicious use of non-
acidic phosphorus compounds. Patent Application No. US20060252656 also
21 teaches how to maintain and improve load carrying ability by carefully
22 balancing the ratio of tetrasulfide : trisulfide : disulfide in the
lubricating
23 composition.
24
SUMMARY OF THE INVENTION
26
27 The present invention provides a lubricating composition comprising an oil
of
28 lubricating viscosity having dispersed therein a minor amount of a mixture
of:
29 (a) a hydrated alkali metal borate component; (b) a dihydrocarbyl
polysulfide
component comprising a mixture including less than 64.5 wt.% dihydrocarbyl
31 trisulfide, greater than 5.5 wt.% dihydrocarbyl disulfide, and at least 30
wt.%
32 dihydrocarbyl tetrasulfide or higher polysulfides; (c) a non-acidic
phosphorus
33 component comprising a trihydrocarbyl phosphite component, at least 90
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CA 02627866 2008-04-01
1 wt.% of which has the formula (RO)3 P, where R is a hydrocarbyl of 4 to 24
2 carbon atoms and (d) a dihydrocarbyl dithiophosphate derivative. Optionally,
3 a dihydrocarbyl hydrogen phosphite component, at least 90 wt.% of which has
4 the formula (RO)2 POH, where R is a hydrocarbyl of 4 to 24 carbon atoms,
may also be used in the lubricant composition.
6
7 BRIEF DESCRIPTION OF THE DRAWINGS
8
9 Figures 1-5 are graphs of breakaway torque vs. gear shifting cylces of the
composition of the present invention and of comparative lubricating oil
11 compositions. Figure 1 is a graph depicting a flat slope and an acceptable
12 break-away torque. Figure 2 is a graph depicting a negative slope with the
13 breakaway torque gradually moving away from an acceptable range. Figure 3
14 is a graph depicting a flat slope but a break-away torque which is too low.
Figure 4 is a graph depicting an undesirable negative slope in which the
16 breakaway torque never quite reaches the desired torque of 2.0 Nm. Figure 5
17 is a graph depicting a typical commercial oil which also has a negative
slope.
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1 DETAILED DESCRIPTION OF THE INVENTION
2
3 The present invention is directed to a gear oil additive package, a
lubricating
4 oil composition, a method of making the gear oil additive package, and a
method of making the lubricating oil composition.
6
7 The Additive Package
8
9 The gear oil additive package of the present invention is an oil-soluble
additive composition. The gear oil additive package may be used in a gear
11 lubricating oil. The additive package of the present invention comprises
(1) at
12 least one hydrated alkali metal borate component; (2) at least one
13 dihydrocarbyl polysulfide component comprising a mixture including less
than
14 about 64.5 wt% dihydrocarbyl trisulfide, greater than about 5.5 wt%
dihydrocarbyl disulfide, and at least about 30.0 wt% dihydrocarbyl
tetrasulfide
16 or higher polysulfides; (3) at least one non-acidic phosphorus component
17 comprising a trihydrocarbyl phosphite component, at least 90 wt% of which
18 has the formula (RO)3 P, wherein R is hydrocarbyl group having 4 to 24
19 carbon atoms; and (4) at least one dihydrocarbyl dithiophosphate. The term
"non-acidic" refers to the phosphorus contained in the component and is not
21 meant to limit the acidic or non-acidic hydrocarbyl groups attached to
22 phosphorus. This base mix may be combined with base oil a dialkyl
23 phosphite, foam inhibitors, viscosity modifiers, metal deactivators, and
24 optional detergents, dispersants, and oxidation inhibitors to form a
complete
lubricant formulation.
26
27 Hydrated Alkali-Metal Borates
28
29 The first additive component employed in the lubricating oil composition of
the
present invention is a hydrated particulate alkali metal borate. Hydrated
31 particulate alkali metal borates are well known in the art and are
available
32 commercially. Representative patents disclosing suitable borates and
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1 methods of manufacture include: U.S. Patent Nos. 3,313,727; 3,819,521;
2 3,853,772; 3,907,601; 3,997,454; 4,089,790; and 6,534,450.
3
4 The hydrated alkali metal borates can be represented by the following
formula:
6
7 M20.mB2O3.nH2O
8
9 where M is an alkali metal of atomic number in the range 11 to 19,
e.g., sodium or potassium; m is a number from 2.5 to 4.5 (both whole and
11 fractional); and n is a number from 1.0 to 4.8. Preferred are the hydrated
12 potassium borates, particularly the hydrated potassium triborate
13 microparticies having a potassium-to-boron ratio of about 1:2.75 to 1:3.25.
14 The hydrated borate particles generally have a mean particle size of less
than
1 micron.
16
17 Dihydrocarbyl Polysulfides
18
19 The dihydrocarbyl polysulfide component employed in the present invention
comprises a mixture which contains less than about 64.5 wt.%, and preferably
21 no more than about 60.0 wt.% dihydrocarbyl trisulfide, greater than about
5.5
22 wt.% dihydrocarbyl disulfide, and preferably greater than about 6.0 wt% and
23 at least about 30.0 wt.% and preferably at least 40 wt.% dihydrocarbyl
24 tetrasulfide or higher polysulfides. Preferably, the dihydrocarbyl
polysulfide
mixture contains predominantly dihydrocarbyl tetrasulfide and higher
26 polysulfides. The term "polysulfide" as used herein may also include minor
27 amounts of dihydrocarbyl monosulfides, also referred to as monosulfide or
28 sulfide. Generally, the monosulfide is present in relatively small amounts
of
29 less than about 1 wt.% of the total sulfur-containing compounds present.
Typically, monosulfides may be present in amounts ranging from about
31 0.3 wt.% to about 0.4 wt.%. The monosulfides are preferably less than about
32 0.4 wt.% and more preferably less than about 0.3 wt.%.
33
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1 The term "hydrocarbyl" includes hydrocarbon, as well as substantially
2 hydrocarbon groups. "Substantially hydrocarbon" describes groups which
3 contain heteroatom substituents that do not substantially alter the
4 predominantly hydrocarbon nature of the substituent. Non-limiting examples
of hydrocarbyl groups include the following: (1) hydrocarbon substituents,
6 i.e., aliphatic (e.g., alkyl or alkenyl) and alicyclic (e.g., cycloalkyl,
7 cycloalkenyl, etc.) substituents, aromatic-, aliphatic-, and alicyclic-
substituted
8 aromatic substituents and also includes cyclic substituents wherein the ring
is
9 completed through another portion of the molecule (that is, for example, any
two indicated substituents may together form an alicyclic radical);
11 (2) substituted hydrocarbon substituents, i.e., those substituents
containing
12 non-hydrocarbon groups which do not substantially alter the predominantly
13 hydrocarbon nature of the substituent and which includes groups such as,
14 e.g., halo (especially chloro and fluoro), hydroxy, mercapto, nitro,
nitroso, and
sulfoxy; (3) heteroatom substituents, i.e., substituents which will contain an
16 atom other than carbon in a ring or chain otherwise composed of carbon
17 atoms (e.g., alkoxy or alkylthio). Suitable heteroatoms include, for
example,
18 sulfur, oxygen, nitrogen, and such substituents containing one or more
19 heteroatoms exemplified by pyridyl, furyl, thienyl, and imidazolyi.
21 In general, no more than about 2, preferably no more than 1, heteroatom
22 substituent will be present for every 10 carbon atoms in the hydrocarbyl
23 group. Typically, there will be no heteroatom substituents in the
hydrocarbyl
24 group in which case the hydrocarbyl group is a hydrocarbon. Preferred is an
alkyl group; more preferred, the hydrocarbyl group is tertiary butyl.
26
27 The organic polysulfides may be prepared as described in U.S. Patent
28 Nos. 6,489,721; 6,642,187; and 6,689,723, which are incorporated by
29 reference herein.
31
32
33
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1 Non-Acidic Phosphorous Components
2
3 The lubricating oil composition of the present invention also employs a at
least
4 two non-acidic phosphorous component. The at least two non-acidic
phosphorus components, according to the present invention, are non-acidic
6 as defined herein and, more preferably, comprise two phosphorus
7 compounds, a trihydrocarbyl phosphite and a phosphoric acid derivative,
i.e.,
8 a dihyrocarbyl dithiophosphate.
9
Acidic phosphorus compounds as used herein mean compounds that contain
11 a hydrogen atom bonded directly to a phosphorus atom or a hydrogen atom
12 bonded to a hetero atom which is in turn bonded to a phosphorus atom.
13 Non-acidic phosphorus compounds as used herein means that the
14 trihydrocarbyl phosphite or the dithiophosphate derivative may contain an
acid
group, such as a carboxylic acid group, but do not contain a hydrogen atom
16 bonded directtyto a phosphorus atom or a hydrogen atom bonded to a hetero
17 atom which is in turn bonded to a phosphorus atom. Thus compounds having
18 -P-H, -P-O-H and -P-S-H would be considered to be acidic, whereas the
19 dithiophosphoric acid ester as described in U.S. Patent No. 5,922,657 would
be considered non-acidic as used herein even though it has a carboxylic acid
21 functionality.
22
23 Acidic phosphoric acid compounds may be based on a phosphorus
24 compound as described in Salentine, U.S. Patent No. 4,575,431, the
disclosure of which is incorporated by reference herein. Preferably, if an
26 amino phosphorus compound is employed, then the amino phosphorus
27 compound is an amine dithiophosphate (that is, an amine dithiophosphate
28 salt). Typical dithiophosphates useful in the lubricant of the present
invention
29 are well known in the art. These dithiophosphates are those containing two
hydrocarbyl groups and one hydrogen functionality, and are therefore acidic
31 and must be neutralized for use in the present composition. The hydrocarbyl
32 groups useful herein are preferably aliphatic alkyl groups of 3 to 8 carbon
33 atoms.
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1 Representative dihydrocarbyt dithiophosphates include di-2-ethyl-l-hexyl
2 hydrogen dithiophosphate, diisoctyl hydrogen dithiophosphate, dipropyl
3 hydrogen dithiophosphate, and di-4-methyl-2-pentyl hydrogen
4 dithiophosphate.
6 Preferred dithiophosphates are dihexyl hydrogen dithiophosphate, dibutyl
7 hydrogen dithiophosphate, and di-n-hexyl hydrogen dithiophosphate.
8
9 For use in the present invention, acidic phosphates are completely
neutralized
by reaction with alkylamines, as disclosed in Salentine, U.S. Patent No. 4,
11 575,431. Neutralization must be at least least 80% complete. For best
12 results, neutralization should be in the range of 85% to 100%, wherein 100%
13 neutralization refers to the reaction of one alkylamine with each acid
hydrogen
14 atom.
16 The amine moiety is typically derived from an alkylamine. The amine alkyl
17 group is from 10 to 30 carbon atoms, preferably 12 to 18 carbon atoms in
18 length. Typical amines include pentadecylamine, octadecylamine, cetylamine,
19 and the like. Most preferred is oleylamine. When using a mixture of
dithiophosphates and sulfur-free phosphates, the mole ratio of the
21 dithiophosphates to the sulfur-free phosphates should be in the range of
22 70:30 to 30:70, preferably 55:45 to 45:55, and most preferably 1:1. The
mole
23 ratio of the substituted dihydrogen phosphates to the disubstituted
hydrogen
24 phosphates should be in the range 30:70 to 55:45, preferably 35:65 to
50:50,
and most preferably 45:55.
26
27 The preferred non-acidic phosphoric acid derivative is a dithiophosphoric
acid
28 ester as described in Camenzind, et al., U.S. Patent No. 5,992,657.
29 Preferably the dihydrocarbyl ester groups are alkyl as exemplified by
Irgalube
353 from Ciba Specialty Chemicals.
31
32 The phosphorus component of the present invention also includes a
33 trihydrocarbyl phosphite, which is non-acidic. Trihydrocarbyl phosphites
useful
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1 in the present invention include (RO)3 P wherein R is a hydrocarbyl group of
2 about 4 to 24 carbon atoms, more preferably about 8 to 18 carbon atoms, and
3 most preferably about 10 to 14 carbon atoms. The hydrocarbyl may
4 be saturated or unsaturated. Preferably, the hydrocarbyl group is alkyl.
More
preferably, the trialkyl phosphite contains at least 90 wt.% of the structure
6 (RO)3 P wherein R is as defined above. Representative trialkyl phosphites
7 include, but are not limited to, tributyl phosphite, trihexyl phosphite,
trioctyl
8 phosphite, tridecyl phosphite, trilauryl phosphite and trioleyl phosphite. A
9 particularly preferred trialkyl phosphite is trilauryl phosphite, such as
commercially available Duraphos TLP by Rhodia Incorporated Phosphorus
11 and Performance Derivatives or Doverphos 53 by Dover Chemical
12 Corporation. Such trialkyl phosphites may contain small amounts of dialkyl
13 phosphites as impurities, in some cases as much as 5 wt.%. Preferred are
14 mixtures of phosphites containing hydrocarbyl groups having about 10 to 20
carbon atoms. These mixtures are usually derived from animal or natural
16 vegetable sources. Representative hydrocarbyl mixtures are commonly
17 known as coco, tallow, tall oil, and soya.
18
19 Optionally, a dihydrocarbyl phosphite may be added to the present invention
in addition to the trihydrocarbyl phosphite. Dihydrocarbyl phosphites useful
in
21 the present invention include (RO)2POH where R is as described as above. A
22 particularly preferred dihydrocarbyl phosphite is dialkyl phosphite. More
23 preferred, dialkyl phosphite is dioleyl hydrogen phosphite, such as
24 commercially available Duraphos AP-240L by Rhodia Incorporated
Phosphorus and Performance Derivatives. Such dialkyl phosphites may
26 contain small amounts of impurities, in some cases as much as 6 wt.%.
27 Preferred are mixtures of phosphites containing hydrocarbyl groups having
28 about 10 to 20 carbon atoms.
29
Polyalkylene Co-oligomer
31
32 Optionally, a polyalkylene co-oligomer may be employed in the present
33 invention. Preferred polyalkylene co-oligomers are co-oligomers of ethylene
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1 and an olefin which have no polar groups. Particularly preferred
2 polyalkylenes are the Lucant series of synthetic oils which may be
3 purchased from Mitsui Chemicals (U.S.A.) Incorporated, New York, New York,
4 or the SpectraSyn Ultra series of synthetic oils which may be purchased
from ExxonMobil Chemical Company. Typical oils in these series have
6 kinematic viscosities (ASTM D445, @ 100 C) of 10 to 2000 cSt. Preferred
7 oils are those having viscosities between 100 and 2000 cSt.
8
9 The Lubricating Oil Composition
11 The hydrated alkali metal borate, dihydrocarbyl polysulfide and non-acidic
12 phosphorus components are generally added to a base oil that is sufficient
to
13 lubricate gears and other components which are present in automotive axles
14 and transmissions, and in stationary industrial gear drives. Typically, the
lubricating oil composition of the present invention comprises a major amount
16 of oil of lubricating viscosity and a minor amount of the gear oil additive
17 package.
18
19 One embodiment of the present invention comprises the combination of: (1)
sodium triborate; (2) tertiary butyl polysulfide; (3) trilauryl phosphite and
(4)
21 dialkyl dithiophosphate ester in a major amount of oil of a lubricating
viscosity.
22 Optionally a polyalkylene co-oligomer is added to the lubricating oil
23 composition.
24
The base oil employed may be any of a wide variety of oils of lubricating
26 viscosity. The base oil of lubricating viscosity used in such compositions
may
27 be mineral oils or synthetic oils. A base oil having a viscosity of at
least
28 2.5 cSt at 40 C and a pour point below 20 C, preferably at or below 0 C, is
29 desirable. The base oils may be derived from synthetic or natural sources.
Mineral oils for use as the base oil in this invention include, for example,
31 paraffinic, naphthenic and other oils that are ordinarily used in
lubricating oil
32 compositions. Synthetic oils include, for example, both hydrocarbon
synthetic
33 oils and synthetic esters and mixtures thereof having the desired
viscosity.
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1 Hydrocarbon synthetic oils may include, for example, oils prepared from the
2 polymerization of ethylene, polyalphaolefin or PAO oils, or oils (i.e.,
Fischer-
3 Tropsch oils) prepared from hydrocarbon synthesis procedures using carbon
4 monoxide and hydrogen gases such as in a Fisher-Tropsch process.
Examples of Fischer-Tropsch oils used in the present invention include, but
6 are not limited to, those described in U.S. Patent Publication Nos.
7 US20060289337, US20060276355, US20040079078, and U.S. Patent Nos.
8 6080301, 6090989, 6165949, which are herein incorporated by reference.
9 Other Fischer-Tropsch oils that may be employed in the present process
include those oils described in pending U.S. patent applications 11/613,883
11 and 11/400,570, which are herein incorporated by reference. Useful
synthetic
12 hydrocarbon oils include liquid polymers of alpha olefins having the proper
13 viscosity. Especially useful are the hydrogenated liquid oligomers of C6 to
C12
14 alpha olefins such as 1-decene trimer. Likewise, alkyl benzenes of proper
viscosity, such as didodecyl benzene, can be used. Useful synthetic esters
16 include the esters of monocarboxylic acids and polycarboxylic acids, as
well
17 as mono-hydroxy alkanols and polyols. Typical examples are didodecyl
18 adipate, pentaerythritol tetracaproate, di-2-ethylhexyl adipate,
19 dilaurylsebacate, and the like. Complex esters prepared from mixtures of
mono and dicarboxylic acids and mono and dihydroxy alkanols can also be
21 used. Blends of mineral oils with synthetic oils are also useful.
22
23 Thus, the base oil can be a refined paraffin type base oil, a refined
naphthenic
24 base oil, or a synthetic hydrocarbon or non-hydrocarbon oil of lubricating
viscosity. The base oil can also be a mixture of mineral and synthetic oils.
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1 Additionally, other additives well known in lubricating oil compositions may
be
2 added to the additive composition of the present invention to complete a
3 finished oil.
4
The hydrated alkali-metal borate component will generally comprise 0.1 to
6 20.0 wt.% of the lubricant composition, preferably 0.5 to 15.0 wt.%, and
more
7 preferably 1.0 to 9.0 wt.%. The dihydrocarbyl polysulfide component will
8 comprise 0.1 to 10.0 wt.% of the lubricant composition, preferably 0.2 to
4.0
9 wt.%, and more preferably 0.25 to 3.0 wt.%. The trihydrocarbyl phosphite
component will comprise 0.01 to 15.0 wt.% of the Iubricant composition,
11 preferably 0.05 to 5.0 wt.%, and more preferably 0.20 to 1.5 wt.%. The
12 dihydrocarbyl dithiophosphate component will comprise 0.03 to 3.0 wt.% of
13 the lubricant composition, preferably 0.07 to 1.5 wt.%, and more preferably
14 0.15 to 0.9 wt.%. If a dihydrocarbyl phosphite is optionally added to the
lubricating oil composition, it will generally comprise 0.01 to 10.0 wt% of
the
16 lubricant composition, preferably 0.05 to 5.0 wt%, and more preferably 0.1
to
17 1.0 wt%.
18
19 Optionally, a polyalkylene co-oligomer may be employed in the lubricating
oil
composition. Preferably, the lubricating oil composition comprises from about
21 0.1 to 10 wt% of the polyalkene derivative. More preferred, the lubricating
oil
22 composition comprises from about I to 7 wt% of the polyalkylene derivative.
23 Most preferred, the lubricating oil composition comprises from about 2 to 5
24 wt% of the polyalkylene derivative.
26 The lubricating composition described above can be made by addition of an
27 additive package to a lubricating base oil. Generally, the lubricating oil
28 composition will contain 1.0 to 50.0 wt.% of the additive package;
preferably,
29 the lubricating oil composition will contain 1 to 10.0 wt% of the additive
package; and more preferably, the lubricating oil composition will contain 3.0
31 to 8.0 wt.% of the additive package.
32
33
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1 Other Additives
2
3 A variety of other additives can be present in lubricating oils of the
present
4 invention. These additives include antioxidants, viscosity index improvers,
dispersants, rust inhibitors, foam inhibitors, corrosion inhibitors, other
antiwear
6 agents, demulsifiers, friction modifiers, pour point depressants and a
variety of
7 other well-known additives. Preferred dispersants include the well known
8 succinimide and ethoxylated alkylphenois and alcohols. Particularly
preferred
9 additional additives are the oil-soluble succinimides, oil-soluble alkali or
alkaline earth metal sulfonates, and dihydrocarbyl hydrogen phosphites.
11
12 The following additive components are examples of some of the components
13 that can be favorably employed in the present invention. These examples of
14 additives are provided to illustrate the present invention, but they are
not
intended to limit it:
16 1. Metal Detergents
17 Sulfurized or unsulfurized alkyl or alkenyl phenates, alkyl or alkenyl
18 aromatic sulfonates, borated sulfonates, sulfurized or unsulfurized
19 metal salts of multi-hydroxy alkyl or alkenyl aromatic compounds, alkyl
or alkenyl hydroxy aromatic sulfonates, sulfurized or unsulfurized alkyl
21 or alkenyl naphthenates, metal salts of alkanoic acids, metal salts of an
22 alkyl or alkenyl multiacid, and chemical and physical mixtures thereof.
23
24 2. Anti-Oxidants
Anti-oxidants reduce the tendency of mineral oils to deteriorate in
26 service which deterioration is evidenced by the products of oxidation
27 such as sludge and varnish-like deposits on the metal surfaces and by
28 an increase in viscosity. Examples of anti-oxidants useful in the
29 present invention include, but are not limited to, phenol type (phenolic)
oxidation inhibitors, such as 4,4'-methylene-bis(2,6-di-tert-butylphenol),
31 4,4'-bis(2,6-di-tert-butylphenol), 4'-bis(2-methyl-6-tert-butylphenol),
32 2,2'-methylene-bis(4-methyl-6-tert-butylphenol),
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1 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol),
2 4,4'-isopropylidene-bis(2,6-di-tert-butylphenol), 2,2'-methylene-bis(4-
3 methyl-6-nonylphenol), 2,2'-isobutylidene-bis(4,6-dimethylphenol),
4 2,2'-5-methylene-bis(4-methyl-6-cyclohexylphenol), 2,6-di-tert-butyl-4-
methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butyl-
6 phenol, 2,6-di-tert-l-dimethylamino-p-cresol, 2,6-di-tert-4-(N,N'-
7 dimethylaminomethylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol),
8 2,2'-thiobis(4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-
9 10-butylbenzyl)-sulfide, and bis(3,5-di-tert-butyl-4-hydroxybenzyl).
Diphenylamine-type oxidation inhibitors include, but are not limited to,
11 alkylated diphenylamine, phenyl-.alpha.-naphthylamine, and
12 alkylated-.alpha.-naphthylamine. Other types of oxidation inhibitors
13 include metal dithiocarbamate (e.g., zinc dithiocarbamate), and
14 1 5-methyl enebis(d i butyid ith ioca rba mate).
16 3. Anti-Wear Agents
17 As their name implies, these agents reduce wear of moving metallic
18 parts. Examples of such agents include, but are not limited to,
19 phosphates, carbamates, esters, and molybdenum complexes.
21 4. Rust Inhibitors (Anti-Rust Agents)
22 a) Nonionic polyoxyethylene surface active agents: polyoxyethylene
23 lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene
24 nonyl phenyl ether, polyoxyethylene octyl phenyl ether,
polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether,
26 polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol
27 mono-oleate, and polyethylene glycol mono-oleate.
28 b) Other compounds: stearic acid and other fatty acids, dicarboxylic
29 acids, metal soaps, fatty acid amine salts, metal salts of heavy
sulfonic acid, partial carboxylic acid ester of polyhydric alcohol, and
31 phosphoric ester.
32
33
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1 5. Demulsifiers
2 Addition product of alkylphenol and ethylene oxide, polyoxyethylene
3 alkyl ether, and polyoxyethylene sorbitan ester.
4 6. Extreme Pressure Anti-Wear Agents (EP/AW Agents)
Zinc diaiky-l-dithiophosphate (primary alkyl, secondary alkyl, and aryl
6 type), diphenyl sulfide, methyl trich lorostea rate, chlorinated
7 naphthalene, fluoroalkylpolysiloxane, lead naphthenate, neutralized
8 phosphates, dithiophosphates, and sulfur-free phosphates.
9
7. Friction Modifiers
11 Fatty alcohol, fatty acid, amine, borated ester, other esters,
12 phosphates, phosphites and phosphonates.
13
14 8. Multifunctional Additives
Sulfurized oxymolybdenum dithiocarbamate, sulfurized
16 oxymolybdenum organo phosphorodithioate, oxymolybdenum
17 monoglyceride, oxymolybdenum diethylate amide, amine-molybdenum
18 complex compound, and sulfur-containing molybdenum complex
19 compound.
21 9. Viscosity Index Improvers
22 Polymethacrylate type polymers, ethylene-propylene copolymers,
23 styrene-isoprene copolymers, hydrated styrene-isoprene copolymers,
24 polyisobutylene, and dispersant type viscosity index improvers.
26 10. Pour Point Depressants
27 Polymethyl methacrylate.
28
29 11. Foam Inhibitors
Alkyl methacrylate polymers and dimethyl silicone polymers.
31
32
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1 12. Metal Deactivators
2 Disalicylidene propylenediamine, triazole derivatives,
3 mercaptobenzothiazoles, and mercaptobenzimidazoles.
4 13. Dispersants
Alkenyl succinimides, alkenyl succinimides modified with other organic
6 compounds, alkenyl succinimides modified by post-treatment with
7 ethylene carbonate or boric acid, pentaerythritols, phenate-salicylates
8 and their post-treated analogs, alkali metal or mixed alkali metal,
9 alkaline earth metal borates, dispersions of hydrated alkali metal
borates, dispersions of alkaline-earth metal borates, polyamide ashiess
11 dispersants and the like or mixtures of such dispersants.
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1 EXAMPLES
2
3 The following Examples are illustrative of the present invention, but are
not
4 intended to limit the invention in any way beyond what is contained in the
claims which follow.
6
7 Automotive Gear Oil Examples
8
9 The additive concentrate package shown in Table 1 may be blended by any
conventional method. An automotive gear lubricant of typical viscosity (8.0 -
11 18.0 cSt @ 100 C) grade may be blended by any conventional method with at
12 least one base stock as shown in Table 2 to achieve the desired viscosity
13 range. Specific mixtures of polysulfides were chosen according to the
present
14 invention to achieve desired ratios of di-, tri-, tetra- and higher
polysulfides.
Using mixtures of commercially available polysulfides (such as TBPS 344,
16 TBPS 34, TBPS 454, and dialkyl disulfides available from ChevronPhittips
17 Chemical Company), the ratios of polysulfides (that is, the relative
18 concentrations) can be adjusted according to the present invention to
achieve
19 optimum frictional performance while maintaining improved anti-wear
performance.
21
Table 1- Typical Additive Packages
com onents in weight %)
Example I Example 2 Example 3 Example 4
Components
Potassium triborate dispersion 55 62 56 40
Dialkyl polysulfides 5' 18 322
Dialkyl dithio hos hate 6.5 8 4
Trialkyl phosphite 13 15 5
Corrosion inhibitors 1.9 1.9 1.9 1.9
Succinate ester dispersant 8 8 9 8
Calcium sulfonate detergent 5 5 5 4
Foam Inhibitor 0.1 0.1 0.1 0.1
Diluent oil 5.5 5 5 5
Total weight % 100.00 100.00
' The dialkylpolysulfide employed in Example 1 contained 7.3 wt% disulfide,
44.4 wt%
trisulfide, and 48.3 wt% tetrasulfide or higher.
2 The dialkylpolysulfide employed in Example 4 contained 2.8 wt% disulfide,
92.4 wt%
trisulfide and 4.8 wt% tetrasulfide or higher.
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CA 02627866 2008-04-01
100.00 100.00
1
2
3
Table 2 - Typical Gear Lubricant Blend
Component Weight %
Mineral or Synthetic Base Stocks 80 - 77
Viscosity index improver 9
Package in Table 1 6-9
Friction modifier 4
Pour Point Depressant I
Total weight % 100.00
4
Although frictional properties of the lubricating oil can be improved by the
6 addition of friction modifiers, the extent of the improvement is limited.
Addition
7 of too much friction modifier can lead to detrimental side effects such as
loss
8 of oxidation stability. Table 3 shows the effect on oxidation performance of
9 adding too much friction modifier. Oxidation performance is measured by
standard method CEC L-48-A-95 which measures the per cent increase in
11 viscosity after heating the lubricant for a specified length of time. Lower
per
12 cent viscosity increase is better.
13 Table 3
14
Lube Oil using Example 1
No FM 0.5% FM
Limit
Oxidation Test, CEC L-48-A-95
160 C / 192 hr
50%
% increase in viscosity @ 100 C max 45 95
16
17 Frictional performance is very important to gear shifting in both manual
and
18 automatic transmissions. If the friction is too low, too much pressure must
be
19 exerted on the friction plates to achieve synchronization of the gears
prior to
shifting. If the friction is too high, the friction plates do not release
smoothly
21 after the shift is complete, leading to a jerky feel in the transmission.
22
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CA 02627866 2008-04-01
1 Friction can be measured by measuring the amount of torque required to
2 cause the friction plates in a transmission to separate after the gear shift
is
3 complete. Specifically, this type of torque is called the breakaway torque
and
4 is measured in Newton meters of force.
6 Specifically, breakaway torque is measured by employing a gear cone that is
7 driven at a low rotating speed by an electric engine and gear reduction. A
8 pneumatic cylinder with controlled compressed air pushes the synchronizing
9 collar against the gear cone with a given axial force. Meanwhile the torque
is
measured. This method enables the determination of the static and dynamic
11 friction coefficients. After release of the applied force, the torque to
release
12 the blocked synchronizing collar is determined, which is also known as the
13 breakaway torque.
14
With any new gear set, there is usually an initial break-in period of about 25
16 gear shifting cycles before smooth shifting occurs and an average break-
away
17 torque can be measured. An ideal break-away torque after 25 cycles (new) is
18 below 10 Nm. In addition to the desired average break-away torque value
19 over 100 shifting cycles being close to 2.0 Nm, it is also important that
the
break-away torque remain relatively constant after the break-in period. This
21 can be evaluated by looking at the slope of the break-away torque curve
over
22 time. It is desired that the curve be flat with a slope close to zero. If
the slope
23 is negative, it will lead to lower and lower break-away torque. If the
slope is
24 positive, it will lead to higher break-away torque. Neither situation is
acceptable because of the changing feel of the automotive transmission to the
26 driver.
27
28 The examples of the present invention show how a lubricating oil
composition
29 can be achieved, which meets the required frictional criteria mentioned
above
and produces optimum anti-wear performance, by appropriate balance of
31 components in the lubricating oil additive package. Table 4 shows the
32 average break-away torque after run-in for lubricating oils made as shown
in
33 Table 2 using lubricating oil additive packages shown in Table 1.
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1
2
3 Table 4
Target Oil1 Oil 2 Oil 3 Oil 4 Commercial
Comp. Comp. Comp. Ex. Oil
Ex. Ex.
Average Break- 2.0 2.070 1.445 0.712 2.496 1.354
Away Torque,
Nm
Slope of Curve flat flat negative flat negative negative
4
Oil 1, prepared using the additive package of Example 1, contains an alkali
6 metal borate, a polysulfide with the specified ratio of tetra-, tri-, and di-
sulfides,
7 a dialkyl dithiophosphate ester and a trialkyl phosphite. This particular
8 combination of components meets all frictional requirements and requires
only
9 minimal amount of extra friction modifiers to achieve the final desired
frictional
properties. Oil 2, prepared using the additive package of Example 2, is a
11 similar blend but lacks trialkyl phosphite and dialkyl dithiophosphate
ester
12 components. The resultant oil has an unacceptably low break-away torque.
13 Oil 3, prepared using the additive package of Example 3, lacks the
14 polysulfides which are an essential component of the present invention. Not
only is the break-away torque extremely low, but the torque keeps changing
16 leading to a negative slope which is also unacceptable. Oil 4, prepared
using
17 the additive package of Example 4, has all the basic components of Oil 1
18 except that the polysulfides in Oil 4 are not of the desired ratio of tetra-
, tri-,
19 and di-sulfides as specified in the claims. This leads to an unacceptably
high
break-away torque.
21
22 The effects described above can be seen more explicitly in Figures 1 - 5
23 which show the actual break-away torque measured at each cycle for Oils 1-
24 5. The changes in break-away torque leading to an undesirable negative
slope can be readily seen. Figure 1 is a graph depicting a flat slope and an
26 acceptable break-away torque. Figure 2 is a graph depicting a negative
slope
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CA 02627866 2008-04-01
I with the breakaway torque gradually moving away from the acceptable range.
2 Figure 3 is a graph depicting a flat slope but a break-away torque which is
too
3 low. Figure 4 is a graph depicting an undesirable negative slope in which
the
4 breakaway torque never quite reaches the desired torque of 2.0 Nm. Figure 5
is a graph depicting a typical commercial oil which also has a negative slope.
6
7 While frictional performance is important for smooth shifting in a
transmission,
8 a lubricating oil must also have acceptable anti-wear performance to protect
9 gears. The preferred lubricating oils described in the present invention
also
show improved anti-wear performance. This is shown in Table 5. Anti-wear
11 performance can be evaluated using the FZG narrow gear stage test
12 A10/16,6R/120 which measures changes in gear tooth appearance as greater
13 loads (stages) are placed on the gears. Thus a higher load stage result
14 reflects better performance. In Table 5, Oil 1 prepared from additive
package
1 which uses trialkyl phosphite and polysulfides with an optimum ratio of
tetra-
16 , tri-, and disulfides shows improved anti-wear performance over the other
oils
17 which lack the key components of the present invention.
18
19 Table 5
Oil 1 Oil 2 Oil 3 Oil 4 Commercial
Oil
FZG Pass Stage 10 9 9 8 9
21 Although used to prepare an automotive gear oil in the present example, the
22 additive concentrate described in Table 1 may also by used to prepare
23 industrial oils and greases as well.
24
Industrial Oil Example
26
27 Using the lubricating additive concentrates described in Examples 1- 4,
Table
28 1, industrial gear oils may be blended as shown in Table 6 by any
29 conventional method to achieve any desired ISO viscosity range.
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1
2
Table 6- Industrial Gear Lubricant Blend
Component Weight %
Mineral or Synthetic Base Stocks 97
Packages in Table 1 2.75
Demulsifier 0.25
3
4
There are numerous variations on the present invention which are possible in
6 light of the teachings and supporting examples described herein. It is
7 therefore understood that within the scope of the following claims, the
8 invention may be practiced otherwise than as specifically described or
9 exemplified herein.
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