Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ADDITIVE COMPOSITION FOR TRANSMISSION OIL
CONTAINING HYDRATED ALKALI METAL BORATE AND HEXAGONAL
BORON NITRIDE
Field of the Invention
This invention is directed to an additive composition for a transmission oil.
More particularly, this invention is directed to an additive composition
comprising an
oil dispersion of a hydrated alkali metal borate and an oil dispersion of
hexagonal
boron nitride, as well as lubricating oil compositions containing the same.
References
The following references are cited in this application as superscript
numbers:
1 Peeler, U.S. Patent No. 3,313,727, Alkali Metal Borate E.P. Lubricants,
issued April 11, 1967
2 Adams, U.S. Patent No. 3,912,643, Lubricant Containing Neutralized
Alkali Metal Borates, issued October 14, 1975
3 Sims, U.S. Patent No. 3,819,521, Lubricant Containing Dispersed Borate
and a Polyol, issued June 25, 1974
4 Adams, U.S. Patent No. 3,853,772, Lubricant Containing Alkali Metal
Borate Dispersed with a Mixture of Dispersants, issued December 10, 1974
5 Adams, U.S. Patent No. 3,997,454, Lubricant Containing Potassium
Borate, issued December 14, 1976
6 Adams, U.S. Patent No. 4,089,790, Synergistic Combinations of Hydrated
Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued
May
16, 1978
7 Adams, U.S. Patent No. 4,163,729, Synergistic Combinations of Hydrated
Potassium Borate, Antiwear Agents, and Organic Sulfide Antioxidants, issued
August 7, 1979
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B Frost, U.S. Patent No. 4,263,155, Lubricant Composition Containing an
Alkali Metal Borate and Stabilizing Oil-Soluble Acid, issued April 21, 1981
9 Frost, U.S. Patent No. 4,401,580, Lubricant Composition Containing an
Alkali Metal Borate and an Ester-Polyol Compound, issued August 30, 1983
10 Frost, U.S. Patent No. 4,472,288, Lubricant Composition Containing an
Alkali Metal Borate and an Oil-Soluble Amine Salt of a Phosphorus Compound
issued September 18, 1984
1' Clark, U.S. Patent No. 4,534,873, Automotive Friction Reducing
Composition, issued August 13, 1985
12 Brewster, U.S. Patent No. 3,489,619, Heat Transfer and
Quench Oil, issued January 13, 1970.
13 Salentine, U.S. Patent No. 4,717,490, Synergistic Combination
of Alkali Metal Borates, Su fur Compounds, Phosphites and Neutralized
Phosphate,
issued January 5, 1988
State of the Art
High load conditions often occur in gear sets such as those used in automobile
transmissions and differentials, pneumatic tools, gas compressors,
centrifuges, high-
pressure hydraulic systems, metal working and similar devices, as well as in
many
types of bearings. When employed in such environments, it is conventional to
add an
extreme-pressure (E.P.) agent to the lubricant composition and, in this
regard, alkali
metal borates are well known extreme-pressure agents for such compositions.'-
11' 13
E.P. agents are added to lubricants to prevent destructive metal-to-metal
contact in the
lubrication of moving surfaces. While under normal conditions termed
"hydrodynamic", a film of lubricant is maintained between the relatively
moving
surfaces governed by lubricant parameters, and principally viscosity. However,
when
load is increased, clearance between the surfaces is reduced, or when speeds
of
moving surfaces are such that the film of oil cannot be maintained, the
condition of
"boundary lubrication" is reached; governed largely by the parameters of the
contacting surfaces. At still more severe conditions, significant destructive
contact
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manifests itself in various forms such as wear and metal fatigue as measured
by
ridging and pitting. It is the role of E.P. additives to prevent this from
happening.
For the most part, E.P. agents have been oil soluble or easily dispersed as a
stable
dispersion in the oil, and largely have been organic compounds chemically
reacted to
contain sulfur, halogen (principally chlorine), phosphorous, carboxyl, or
carboxylate
salt groups which react with the metal surface under boundary lubrication
conditions.
Stable dispersions of hydrated alkali metal borates have also been found to be
effective as E.P. agents.
Moreover, because hydrated alkali metal borates are insoluble in lubricant oil
media, it is necessary to incorporate the borate as a dispersion in the oil
and
homogenous dispersions are particularly desirable. The degree of formation of
a
homogenous dispersion can be correlated to the turbidity of the oil after
addition of
the hydrated alkali metal borate with higher turbidity correlating to less
homogenous
dispersions. In order to facilitate formation of such a homogenous dispersion,
it is
conventional to include a dispersant in such compositions. Examples of
dispersants
include lipophilic surface-active agents such as alkenyl succinimides or other
nitrogen
containing dispersants as well as alkenyl succinates.1-4 12 It is also
conventional to
employ the alkali metal borate at particle sizes of less than 1 micron in
order to
facilitate the formation of the homogenous dispersion."
In addition, anti-sticking agents are often employed in automotive gear boxes
to provide smooth synchronization and good shiftability. Examples of such anti-
sticking agents include phosphates, phosphites, phosphionates, thiophosphates,
carbamates, molybdenum dithiocarbamates and dithiophosphates.
It is also known that boron nitride exhibits friction modifying properties in
lubricants. For example, U.S. Patent No. 4,787,993, issued November 29, 1988
to
Nagahiro, discloses a lubricant effective for the reduction of friction which
comprises
dispersing a finely powdered aromatic or polyamide resin into a fluid fat or
oil, which
may additionally contain molybdenum disulfide, organic molybdenum or boron
nitride.
Furthermore, U.S. Patent No. 4,715,972, issued December 29, 1987 to
Pacholke, discloses a solid lubricant additive for gear oils comprising solid
lubricant
particles combined with a stabilizing agent and a fluid carrier, wherein the
solid
lubricant particles are selected from the group consisting of molybdenum
disulfide,
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graphite, cerium fluoride, zinc oxide, tungsten disulfide, mica, boron
nitrate, boron
nitride, borax, silver sulfate, cadmium iodide, lead iodide, barium fluoride,
tin sulfide,
fluorinated carbon, PTFE, intercalated graphite, zinc phosphide, zinc
phosphate, and
mixtures thereof. This patent further discloses that such lubricant additive
provides
the gear oil with improved demulsibility, stability and compatibility
characteristics of
the gear oil when contaminated with water.
Accordingly, it is an object of an aspect of the present invention to provide
a
lubricant additive composition having good anti-sticking properties when used
in
transmission oils.
SUMMARY OF THE INVENTION
The present invention provides a novel additive composition for a
transmission oil comprising:
(a) an oil dispersion of a hydrated alkali metal borate; and
(b) an oil dispersion of hexagonal boron nitride;
wherein the weight ratio of the hydrated alkali metal borate to the hexagonal
boron
nitride is in the range of about 95:5 to about 5:95.
According to another aspect, there is provided a lubricating oil composition
comprising a transmission oil of lubricating viscosity and an additive
composition
comprising:
(a) an oil dispersion of a hydrated alkali metal borate; and
(b) an oil dispersion of hexagonal boron nitride;
wherein the weight ratio of the hydrated alkali metal borate to the hexagonal
boron
nitride is in the range of about 95:5 to about 5:95.
The additive composition of the present invention may be suitably employed
in both manual transmission gear oils and automatic transmission oils.
Preferably, the
additive composition will be employed in a manual transmission gear oil.
The present invention further provides a lubricating oil composition
comprising a major amount of a transmission oil of lubricating viscosity and
an
effective synchronizer sticking reducing amount of the additive composition
described above. Preferably, the transmission oil is a manual transmission
gear oil.
Among other factors, the present invention is based in part upon the
surprising
discovery that the unique combination of an oil dispersion of a hydrated
alkali metal
borate and an oil dispersion of hexagonal boron nitride provides a significant
and
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unexpected reduction in synchronizer sticking when used as an additive
composition
in a manual transmission gear oil.
DETAILED DESCRIPTION OF THE INVENTION
As noted above, the present invention is directed to a novel additive
composition for a transmission oil comprising (a) an oil dispersion of a
hydrated
alkali metal borate, and (b) an oil dispersion of hexagonal boron nitride,
wherein the
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weight ratio of the hydrated alkali metal borate to the hexagonal boron
nitride is in the
range of about 95:5 to about 5:95.
Typically, the oil dispersion of hydrated alkali metal borate will contain a
hydrated alkali metal borate, a dispersant, optionally a detergent, and an oil
of
lubricating viscosity. Preferably, the dispersant employed in the oil
dispersion of
hydrated alkali metal borate will be selected from the group consisting of a
polyalkylene succinimide, a polyalkylene succinic anhydride, a polyalkylene
succinic
acid, a mono- or di-salt of a polyalkylene succinic acid, and mixtures
thereof.
Optionally, the oil dispersion of hydrated alkali metal borate will also
contain a
detergent, such as a metal sulfonate, preferably an alkylaromatic calcium
sulfonate or
other Group II metal sulfonate that acts in the present compositions to help
provide
for a homogeneous dispersion.
The oil dispersion of hydrated alkali metal borate preferably includes those
compositions comprising from about 10 to 75 weight percent of the hydrated
alkali
metal borate; from about 2 to 40 weight percent of a dispersant; and from
about 30 to
70 weight percent of an oil of lubricating viscosity, all based on the total
weight of the
oil dispersion.
Each of the components in the additive composition of the present invention
will
be described in further detail below.
THE HYDRATED ALKALI METAL BORATE
Hydrated alkali metal borates are well known in the art. Representative
patents
disclosing suitable borates and methods of manufacture include: U.S. Patent
Nos.
3,313,727; 3,819,521; 3,853,772; 3,912,643; 3,997,454; and 4,089,790.1.6
The hydrated alkali metal borates suitable for use in the present invention
can
be represented by the following general formula:
M20=xB203=yH2O
wherein M is an alkali metal, preferably sodium or potassium; x is a number
from 2.5
to 4.5 (both whole and fractional); and y is a number from 1.0 to 4.8. More
preferred
are the hydrated potassium borates, particularly the hydrated potassium
triborates.
The hydrated borate particles will generally have a mean particle size of less
than 1
micron.
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In the alkali metal borates employed in this invention, the ratio of boron to
alkali metal will preferably range from about 2.5:1 to about 4.5:1.
Oil dispersions of hydrated alkali metal borates are generally prepared by
forming, in deionized water, a solution of alkali metal hydroxide and boric
acid,
optionally in the presence of a small amount of the corresponding alkali metal
carbonate. The solution is then added to a lubricant composition comprising an
oil of
lubricating viscosity, a dispersant and any optional additives to be included
therein
(e.g., a detergent, or other optional additives) to form an emulsion that is
then
dehydrated.
Because of their retention of hydroxyl groups on the borate complex, these
complexes are referred to as "hydrated alkali metal borates" and compositions
containing oil/water emulsions of these hydrated alkali metal borates are
referred to as
"oil dispersions of hydrated alkali metal borates".
Preferred oil dispersions of alkali metal borates will have a boron to alkali
metal ratio of about 2.5:1 to about 4.5:1. In another preferred embodiment,
the
hydrated alkali metal borate particles generally will have a mean particle
size of less
than 1 micron. In this regard, it has been found that the hydrated alkali
metal borates
employed in this invention preferably will have a particle size where 90% or
greater
of the particles are less than 0.6 microns.
In the oil dispersion of hydrated alkali metal borate, the hydrated alkali
metal
borate will generally comprise about 10 to 75 weight percent, preferably 25 to
50
weight percent, more preferably about 30 to 40 weight percent of the total
weight of
the oil dispersion of the hydrated borate. (Unless otherwise stated, all
percentages are
in weight percent.)
The additive compositions and lubricant compositions of this invention can
further employ surfactants, detergents, other dispersants and other conditions
as
described below and known to those skilled in the art. Optionally, the
additive
compositions contain an alkylaromatic or polyisobutenyl sulfonate.
The oil dispersions of hydrated alkali metal borates employed in this
invention
generally comprise a dispersant, an oil of lubricating viscosity, and
optionally a
detergent, that are further detailed below.
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THE DISPERSANT
The dispersant employed in the oil dispersion of hydrated alkali metal borate
used in this invention can be ashless dispersants such as an alkenyl
succinimide, an
alkenyl succinic anhydride, an alkenyl succinate ester, and the like, or
mixtures of
such dispersants.
Ashless dispersants are broadly divided into several groups. One such group is
directed to copolymers which contain a carboxylate ester with one or more
additional
polar function, including amine, amide, imine, imide, hydroxyl carboxyl, and
the like.
These products can be prepared by copolymerization of long chain alkyl
acrylates or
methacrylates with monomers of the above function. Such groups include alkyl
methacrylate-vinyl pyrrolidinone copolymers, alkyl methacrylate-
dialkylaminoethy
methacrylate copolymers and the like. Additionally, high molecular weight
amides
and polyamides or esters and polyesters such as tetraethylene pentamine,
polyvinyl
polysterarates and other polystearamides may be employed. Preferred
dispersants are
N-substituted long chain alkenyl succinimides.
Alkenyl succinimides are usually derived from the reaction of alkenyl succinic
acid or anhydride and alkylene polyamines. These compounds are generally
considered to have the formula
R1 O
N-AIk-(N-AIk)X NR3R4
R2
wherein R1 is a substantially hydrocarbon radical having a molecular weight
from
about 400 to 3000, that is, R1 is a hydrocarbyl radical, preferably an alkenyl
radical,
containing about 30 to about 200 carbon atoms; Alk is an alkylene radical of 2
to 10,
preferably 2 to 6, carbon atoms, R2, R3, and R4 are selected from a C1-C4
alkyl or
alkoxy or hydrogen, preferably hydrogen, and x is an integer from 0 to 10,
preferably
0 to 3. The actual reaction product of alkylene succinic acid or anhydride and
alkylene
polyamine will comprise the mixture of compounds including succinamic acids
and
succinimides. However, it is customary to designate this reaction product as a
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succinimide of the described formula, since this will be a principal component
of the
mixture. See, for example, U.S. Patent Nos. 3,202,678; 3,024,237; and
3,172,892.
These N-substituted alkenyl succinimides can be prepared by reacting maleic
anhydride with an olefinic hydrocarbon followed by reacting the resulting
alkenyl
succinic anhydride with the alkylene polyamine. The Ri radical of the above
formula,
that is, the alkenyl radical, is preferably derived from a polymer prepared
from an
olefin monomer containing from 2 to 5 carbon atoms. Thus, the alkenyl radical
is
obtained by polymerizing an olefin containing from 2 to 5 carbon atoms to form
a
hydrocarbon having a molecular weight ranging from about 400 to 3000. Such
olefin
monomers are exemplified by ethylene, propylene, 1-butene, 2-butene,
isobutene, and
mixtures thereof.
The preferred polyalkylene amines used to prepare the succinimides are of the
formula:
H2N-AIk--- N -AIk--j-N R3R4
I z
R2
wherein z is an integer of from 0 to 10 and Alk, R2, R3, and R4 are as defined
above.
The alkylene amines include principally methylene amines, ethylene amines,
butylene amines, propylene amines, pentylene amines, hexylene amines,
heptylene
amines, octylene amines, other polymethylene amines and also the cyclic and
the
higher homologs of such amines as piperazine and
amino alkyl-substituted piperazines. They are exemplified specifically by
ethylene
diamine, triethylene tetraamine, propylene diamine, decamethyl diainine,
octamethylene diamine, diheptamethylene triamine, tripropylene tetraamine,
tetraethylene pentamine, trimethylene diamine, pentaethylene hexainine,
ditrimethylene triamine, 2-heptyl-3-(2-aminopropyl)-imidazoline,
4-methyl imidazoline, N,N-dimethyl- 1,3 -propane diamine, 1,3-bis(2-
aminoethyl)imidazoline, 1-(2-aminopropyl)-piperazine,
1,4-bis(2-aminoethyl)piperazine and 2-methyl-l-(2-aminobutyl)piperazine.
Higher
homologs such as are obtained by condensing two or more of the above-
illustrated
alkylene amines likewise are useful.
The ethylene amines are especially useful. They are described in some detail
under the heading "Ethylene Amines" in Encyclopedia of Chemical Technology,
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Kirk-Othmer, Vol. 5, pp. 898-905 (Interscience Publishers, New York, 1950).
The term "ethylene amine" is used in a generic sense to denote a class of
polyamines conforming for the most part to the structure
H2N(CH2CH2NH)aH
wherein a is an integer from 1 to 10.
Thus, it includes, for example, ethylene diamine, diethylene triamine,
triethylene tetraamine, tetraethylene pentamine, pentaethylene hexamine, and
the like.
Also included within the tern "alkenyl succinimides" are post-treated
succinimides such as post-treatment processes involving ethylene carbonate
disclosed
by Wollenberg, et al., U.S. Patent No. 4,612,132; Wollenberg, et al., U.S.
Patent No.
4,746,446; and the like as well as other post-treatment processes each of
which are
incorporated herein by reference in its entirety.
Preferably, the dispersant component, such as a polyalkylene succinimide,
comprises from 2 to 40 weight percent, more preferably 5 to 20 weight percent,
and
even more preferably 5 to 15 weight percent, of the weight of the oil
dispersion of,
hydrated alkali metal borate.
Polyalkylene succinic anhydrides or a non-nitrogen containing derivative of
the
polyalkylene succinic anhydride (such as succinic acids, Group I and/or Group
II
mono- or di-metal salts of succinic acids, succininate esters formed by the
reaction of
a polyalkylene succinic anhydride, acid chloride or other derivative with an
alcohol,
and the like) are also suitable dispersants for use in the compositions of
this invention.
The polyalkylene succinic anhydride is preferably a polyisobutenyl succinic
anhydride. In one preferred embodiment, the polyalkylene succinic anhydride is
a
polyisobutenyl succinic anhydride having a number average molecular weight of
at
least 500, more preferably at least 900 to about 3000 and still more
preferably from at
least about 900 to about 2300.
In another preferred embodiment, a mixture of polyalkylene succinic anhydrides
is employed. In this embodiment, the mixture preferably comprises a low
molecular
weight polyalkylene succinic anhydride component and a high molecular weight
polyalkylene succinic anhydride component. More preferably, the low molecular
weight component has a number average molecular weight of from about 500 to
below 1000 and the high molecular weight component has a number average
molecular weight of from 1000 to about 3000. Still more preferably, both the
low and
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high molecular weight components are polyisobutenyl succinic anhydrides.
Alternatively, various molecular weights polyalkylene succinic anhydride
components
can be combined as a dispersant as well as a mixture of the other above
referenced
dispersants as identified above.
As noted above, the polyalkylene succinic anhydride is the reaction product of
a
polyalkylene (preferably polyisobutene) with maleic anhydride. One can use
conventional polyisobutene, or high methylvinylidene polyisobutene in the
preparation of such polyalkylene succinic anhydrides. One can use thermal,
chlorination, free radical, acid catalyzed, or any other process in this
preparation.
Examples of suitable polyalkylene succinic anhydrides are thermal PIBSA
(polyisobutenyl succinic anhydride) described in U.S. Patent No. 3,361,673;
chlorination PIBSA described in U.S. Patent No. 3,172,892; a mixture of
thermal and
chlorination PIBSA described in U.S. Patent No. 3,912,764; high succinic ratio
PIBSA described in U.S. Patent No. 4,234,435; PolyPIBSA described in U.S.
Patent
Nos. 5,112,507 and 5,175,225; high succinic ratio Po1yPIBSA described in U.S.
Patent Nos. 5,565,528 and 5,616,668; free radical PIBSA described in U.S.
Patent
Nos. 5,286,799, 5,319,030, and 5,625,004; PIBSA made from high
methylvinylidene
polybutene described in U.S. Patent Nos. 4,152,499, 5,137,978, and 5,137,980;
high
succinic ratio PIBSA made from high methylvinylidene polybutene described in
European Patent Application Publication No. EP 355 895; terpolymer PIBSA
described in U.S. Patent No. 5,792,729; sulfonic acid PIBSA described in U.S.
Patent
No. 5,777,025 and European Patent Application Publication No. EP 542 380; and
purified PIBSA described in U.S. Patent No. 5,523,417 and European Patent
Application Publication No. EP 602 863.
Preferably, the polyalkylene succinic anhydride or other dispersant component
comprises from 2 to 40 weight percent, more preferably 5 to 20 weight percent,
and
even more preferably 5 to 15 weight percent, of the weight of the oil
dispersion of
hydrated alkali metal borate.
Typically, in the oil dispersion of hydrated alkali metal borate, the hydrated
alkali metal borate is in a ratio of at least 2:1 relative to the polyalkylene
succinic
anhydride or other dispersant, while preferably being in the range of 2:1 to
10:1. Ina
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more preferred embodiment the ratio is at least 5:1. In another preferred
embodiment,
mixtures as defined above of the polyalkylene succinic anhydrides are
employed.
THE DETERGENT
The oil dispersion of hydrated alkali metal borate employed in the additive
compositions of the present invention may optionally contain a detergent.
There are a
number of materials that are suitable as detergents for the purpose of this
invention.
These materials include phenates (high overbased or low overbased), high
overbased
phenate stearates, phenolates, salicylates, phosphonates, thiophosphonates and
sulfonates and mixtures thereof. Preferably, sulfonates are used, such as high
overbased sulfonates, low overbased sulfonates, or phenoxy sulfonates. In
addition
the sulfonic acids themselves can also be used.
The sulfonate detergent is preferably an alkali or alkaline earth metal salt
of a
hydrocarbyl sulfonic acid having from 15 to 200 carbons. Preferably the term
"sulfonate" encompasses the salts of sulfonic acid derived from petroleum
products.
Such acids are well known in the art. They can be obtained by treating
petroleum
products with sulfuric acid or sulfur trioxide. The acids thus obtained are
known as
petroleum sulfonic acids and the salts as petroleum sulfonates. Most of the
petroleum
products which become sulfonated contain an oil-solubilizing hydrocarbon
group.
Also included within the meaning of "sulfonate" are the salts of sulfonic
acids of
synthetic alkyl aryl compounds. These acids also are prepared by treating an
alkyl aryl
compound with sulfuric acid or sulfur trioxide. At least one alkyl substituent
of the
aryl ring is an oil-solubilizing group, as discussed above. The acids thus
obtained are
known as alkyl aryl sulfonic acids and the salts as alkyl aryl sulfonates. The
sulfonates where the alkyl is straight-chain are the well-known linear
alkylaryl
sulfonates.
The acids obtained by sulfonation are converted to the metal salts by
neutralizing with a basic reacting alkali or alkaline earth metal compound to
yield the
Group I or Group II metal sulfonates. Generally, the acids are neutralized
with an
alkali metal base. Alkaline earth metal salts are obtained from the alkali
metal salt by
metathesis. Alternatively, the sulfonic acids can be neutralized directly with
an
alkaline earth metal base. The sulfonates can then be overbased, although, for
purposes of this invention, overbasing is not necessary. Overbased materials
and
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methods of preparing such materials are well known to those skilled in the
art. See,
for example, LeSuer U.S. Pat. No. 3,496,105, issued Feb. 17, 1970,
particularly
columns 3 and 4.
The sulfonates are present in the oil dispersion in the form of alkali and/or
alkaline earth metal salts, or mixtures thereof. The alkali metals include
lithium,
sodium and potassium. The alkaline earth metals include magnesium, calcium and
barium, of which the latter two are preferred.
Particularly preferred, however, because of their wide availability, are salts
of
the petroleum sulfonic acids, particularly the petroleum sulfonic acids which
are
obtained by sulfonating various hydrocarbon fractions such as lubricating oil
fractions
and extracts rich in aromatics which are obtained by extracting a hydrocarbon
oil with
a selective solvent, which extracts may, if desired, be alkylated before
sulfonation by
reacting them with olefins or alkyl chlorides by means of an alkylation
catalyst;
organic polysulfonic acids such as benzene disulfonic acid which may or may
not be
alkylated; and the like.
The preferred salts for use in the present invention are those of alkylated
aromatic sulfonic acids in which the alkyl radical or radicals contain at
least about 8
carbon atoms, for example from about 8 to 22 carbon atoms. Another preferred
group
of sulfonate starting materials are the aliphatic-substituted cyclic sulfonic
acids in
which the aliphatic substituents or substituents contain a total of at least
12 carbon
atoms, such as the alkyl aryl sulfonic acids, alkyl cycloaliphatic sulfonic
acids, the
alkyl heterocyclic sulfonic acids and aliphatic sulfonic acids in which the
aliphatic
radical or radicals contain a total of at least 12 carbon atoms. Specific
examples of
these oil-soluble sulfonic acids include petroleum sulfonic acids, mono- and
poly-
wax-substituted naphthalene sulfonic acids, substituted sulfonic acids, such
as cetyl
benzene sulfonic acids, cetyl phenyl sulfonic acids, and the like, aliphatic
sulfonic
acid, such as paraffin wax sulfonic acids, hydroxy-substituted paraffin wax
sulfonic
acids, etc., cycloaliphatic sulfonic acids, petroleum naphthalene sulfonic
acids, cetyl
cyclopentyl sulfonic acid, mono- and poly-wax-substituted cyclohexyl sulfonic
acids,
and the like. The term "petroleum sulfonic acids" is intended to cover all
sulfonic
acids that are derived directly from petroleum products.
Typical Group II metal sulfonates suitable for use in the present invention
include the metal sulfonates exemplified as follows: calcium white oil benzene
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sulfonate, barium white oil benzene sulfonate, magnesium white oil benzene
sulfonate, calcium dipolypropene benzene sulfonate, barium dipolypropene
benzene
sulfonate, magnesium dipolypropene benzene sulfonate, calcium mahogany
petroleum sulfonate, barium mahogany petroleum sulfonate, magnesium mahogany
petroleum sulfonate, calcium triacontyl sulfonate, magnesium triacontyl
sulfonate,
calcium lauryl sulfonate, barium lauryl sulfonate, magnesium lauryl sulfonate,
etc.
The concentration of metal sulfonate that may be employed may vary over a wide
range, depending upon the concentration of alkali metal borate particles. When
present, however, the detergent concentration will generally range from about
0.2 to
about 10 weight percent and preferably from about 3 to about 7 weight percent,
based
on the total weight of the oil dispersion of the hydrated borate. In addition,
the
compositions of this invention may contain a mixture of both a metal sulfonate
and an
ashless dispersant, as described above, where the ratio is a factor of
achieving the
proper stability of the oil dispersion of the hydrated alkali metal borate.
THE OIL OF LUBRICATING VISCOSITY
The lubricating oil to which the hydrated alkali metal borate and the
dispersant
are added to form the oil dispersion of the hydrated alkali metal borate can
be any
hydrocarbon-based lubricating oil or a synthetic base oil stock. Likewise,
these
lubricating oils can be added to the oil dispersion of hydrated alkali metal
borate and
additive compositions containing them, as described herein, in additional
amounts, to
form finished oil compositions. The hydrocarbon-based lubricating oils may be
derived from synthetic or natural sources and may be paraffinic, naphthenic or
aromatic base, or mixtures thereof. The diluent oil can be natural or
synthetic, and
can be different viscosity grades.
In the oil dispersion of the hydrated alkali metal borate, the lubricating oil
typically comprises from about 30 to 70 weight percent, more preferably from
about
45 to 55 weight percent, based on the total weight of the oil dispersion of
the hydrated
alkali metal borate.
In general the oil dispersion of hydrated alkali metal borate is present in
the
additive composition of the invention in the range of about 10 to 90 weight
percent,
based on the total weight of the additive composition.
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THE OIL DISPERSION OF HEXAGONAL BORON NITRIDE
The additive composition of the present invention further contains an oil
dispersion of hexagonal boron nitride.
Hexagonal boron nitride, or h-BN, is a hexagonal, graphite-like form of boron
nitride, having a layered structure and planar 6-membered rings of alternating
boron
and nitrogen atoms. On alternate sheets, boron atoms are directly over
nitrogen
atoms. Hexagonal boron nitride can be prepared by heating boric oxide, boric
acid or
boric acid salts with ammonium chloride, alkali cyanides or calcium cyanamide
at
atmospheric pressure. Hexagonal boron nitride may also be prepared by the
reaction
of boron trichloride or boron trifluoride with ammonia. A discussion of
hexagonal
boron nitride can be found, for example, in Kirk-Othmer, Encyclopedia of
Chemical
Technology, Fourth Edition, Vol. 4, pp. 427-429, John Wiley and Sons, New
York,
1992.
Generally, the hexagonal boron nitride will have a mean particle size of less
than 1 micron. Preferably, the hexagonal boron nitride will have a particle
size
distribution wherein 90% or greater of the particles are less than about 0.5
microns
(500 nanometers, nm), with a preferred mean particle size of less than about
0.3
microns (300 nm).
Typically, the oil dispersion of the hexagonal boron nitride will contain
about 1
to about 50 weight percent of the hexagonal boron nitride, preferably about 1
to about
20 weight percent, and more preferably about 5 to about 15 weight percent,
based on
the total weight of the oil dispersion.
Preferably, the oil dispersion of the hexagonal boron nitride will contain a
surfactant as a stabilizer for the oil dispersion. Typical surfactants for use
as a
stabilizer include ethylene - propylene copolymers, or terpolymers of
ethylene,
propylene and an unconjugated dienes commonly known as ethylene-propylene-
diene
terpolymer, ethylene-propylene copolymers grafted with a nitrogen-containing
vinyl
functionality selected from the group consisting of N-vinyl pyrrollidone and N-
vinyl
pyridine, and the like. The ethylene-propylene copolymer generally has an
average
molecular weight in the range of about 22,000 to 200,000. A preferred
surfactant is
ethylene - propylene copolymer which has substantially equal proportions of
ethylene
and propylene monomers and an average molecular weight of from 22,000 to about
40,000. When present, the surfactant concentration in the oil dispersion of
hexagonal
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boron nitride will typically range from about 0.1 to about 25 weight percent,
preferably from about 2 to about 7 weight percent, and more preferably from
about
3.0 to about 5.0 weight percent, based on the total weight of the oil
dispersion of
hexagonal boron nitride.
The lubricant oil used to prepare the oil dispersion of the hexagonal boron
nitride may be selected from the same group of natural or synthetic
lubricating oils
described above for use in preparing the oil dispersion of the hydrated alkali
metal
borate, but other carrier fluids have been found to be satisfactory, including
vegetable
oils such as rapeseed oil; liquid hydrocarbons such as aliphatic and aromatic
naphthas
and mixtures thereof; synthetic lubricant fluids such as polyalphaolefins,
polyglycols,
diester fluids, and mixtures of these liquids. Moreover, the oil used in
forming the oil
dispersion of hexagonal boron nitride may be the same as, or different from,
the
lubricant oil employed in preparing the oil dispersion of hydrated alkali
metal borate.
Typical oils for preparing the oil dispersion of hexagonal boron nitride
include the
Group I and Group II base oils, such as 150 solvent neutral petroleum oil.
In general, the oil dispersion of hexagonal boron nitride is present in the
additive composition of the invention in the range of about 10 to 90 weight
percent,
based on the total amount of the additive composition.
FORMULATIONS
The additive compositions of the present invention containing oil dispersions
of
alkali metal borate and hexagonal boron nitride (as described hereinabove) may
be
blended further with additional additives to form additive packages containing
the
present additive compositions. These additive packages typically comprise from
about 10 to 80 weight percent of the additive composition of the present
invention
described above and from about 90 to 20 weight percent of one or more of
conventional additives selected from the group consisting of ashless
dispersants (0-
10%), detergents (0-5%), sulfurized hydrocarbons (0-40%), dialkyl hydrogen
phosphates (0-15%), zinc dithiophosphates (0-20%), alkyl ammonium phosphates
and/or thio- dithiophosphates (0-20%), phosphites (0 to 10%) fatty acid esters
of
polyalcohols (0-10%), 2,5-dimercaptothiadiazole (0-5%), benzotriazole (0-5%),
dispersed molybdenum disulfide (0-5%), foam inhibitors (0-2%), and
imidazolines (0-
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10%) and the like wherein each weight percent is based on the total weight of
the
composition.
Fully formulated finished oil compositions of this invention can be formulated
from these additive packages upon further blending with an oil of lubricating
viscosity. Preferably, the additive package described above is added to an oil
of
lubricating viscosity in an amount of from about 1 to 20 weight percent,
preferably
about 2 to 15 weight percent, to provide for the finished oil composition
wherein the
weight percent of the additive package is based on the total weight of the
composition.
A variety of other additives can be present in lubricating oils of the present
invention. These additives include antioxidants, rust inhibitors, corrosion
inhibitors,
extreme pressure agents, antifoam agents, other anti-wear agents, and a
variety of
other well-known additives in the art.
EXAMPLES
The invention will be further illustrated by the following examples, which set
forth particularly advantageous embodiments. While the examples are provided
to
illustrate the present invention, they are not intended to limit it.
EXAMPLE 1
The additive composition of the present invention was evaluated in a
lubricating oil for its anti-sticking properties following a test using an SAE
No. 2
bench, which evaluates transmission fluids during synchronization. The
friction pairs
used in this bench comprised a brass synchronizer ring and a steel gear cone.
During each cycle of the test, the cone is rotating, at a given speed, then
the
ring moves along the axis of the cone for its braking until it is blocked. At
the end of
each cycle, the ring is disengaged.
If sticking occurs, a sticking torque is measured when rotation of the cone is
resumed. During the test, the lubricating oil and the metal parts are heated
to a
temperature between about 60 C and 90 C. The contact pressure is about 20 MPa
and the initial sliding speed is 1.6 m/s.
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The anti-sticking coefficient for this test was calculated as follows:
Anti-sticking coefficient =1- (No. of cycles with sticking)
(Total No. of cycles in test)
Accordingly, an anti-sticking coefficient of 0 indicates the presence of cone
on
ring sticking during every cycle of the test. Conversely, an anti-sticking
coefficient of
1 indicates no sticking at all was observed over the entire duration of the
test. Thus,
the higher the anti-sticking coefficient, up to a maximum of 1, the better the
anti-
sticking performance of the lubricating oil.
The test lubricating oil compositions were formulated as follows:
Lubricant Composition 1
A lubricant composition was prepared containing the following:
(a) 7 weight percent of an oil dispersion of hydrated potassium triborate,
wherein the oil dispersion contained about 30 weight percent of the
hydrated potassium triborate, dispersed in a 150 N neutral oil;
(b) 10 weight percent of an oil dispersion of hexagonal boron nitride, wherein
the oil dispersion contained about 10 weight percent of the hexagon boron
nitride solids, dispersed in a 150 N neutral oil containing a stabilizing
agent; and
(c) 83 weight percent of a 50/50 mixture of neutral oil (150N plus 600N) and
a synthetic polyalphaolefin oil.
Lubricant Composition 2
The lubricant composition 2 was prepared containing the following:
(a) 7 weight percent of an oil dispersion of hydrated potassium triborate,
wherein
the oil dispersion contained about 30 weight percent of the hydrated potassium
triborate, dispersed in a 150 N neutral oil;
(b) 5 weight percent of an oil dispersion of hexagonal boron nitride, wherein
the
oil dispersion contained about 10 weight percent of the hexagon boron nitride
solids, dispersed in a 150 N neutral oil containing a stabilizing agent; and
(c) 88 weight percent of a 50150 mixture of neutral oil (150N plus 600N) and a
synthetic polyalphaolefin oil.
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Lubricant Composition 3
The lubricant composition 3 was prepared containing the following:
(a) 7 weight percent of an oil dispersion of hydrated potassium triborate,
wherein
the oil dispersion contained about 30 weight percent of the hydrated potassium
triborate, dispersed in a 150 N neutral oil;
(b) 2.5 weight percent of an oil dispersion of hexagonal boron nitride,
wherein the
oil dispersion contained about 10 weight percent of the hexagon boron nitride
solids, dispersed in a 150 N neutral oil containing a stabilizing agent; and
(c) 90.5 weight percent of a 50150 mixture of neutral oil (150N plus 600N) and
a
synthetic polyalphaolefin oil
Lubricant Composition A (comparative)
A lubricating composition was prepared containing the following:
(a) 7 weight percent of an oil dispersion of hydrated potassium triborate,
wherein the oil dispersion contained about 30 weight percent of the
hydrated potassium triborate, dispersed in a 150 N neutral oil; and
(b) 93 weight percent of a 50/50 mixture of neutral oil (150N plus 600N) and
a synthetic polyalphaolefin oil.
Lubricant Composition B (comparative)
A lubricating composition was prepared containing the following:
(a) 10 weight percent of an oil dispersion of hexagonal boron nitride, wherein
the oil dispersion contains about 10 weight percent of the hexagonal boron
nitride solids, dispersed in a 150 N neutral oil containing a stabilizing
agent; and
(b) 90 weight percent of a 50/50 mixture of neutral oil (150N plus 600N) and
a synthetic polyalphaolefin oil.
The above lubricant compositions were evaluated for anti-sticking performance
in
the synchronization test described above. A base oil containing a 50/50
mixture
of 150N and 600N neutral oil, with no additives, was also tested. The results
of
this evaluation are shown in Table 1.
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Table 1
Sample No. of Cycles with Total No. of Cycles Anti-sticking
Cone on Ring coefficient
Sticking
Base oil 5000 5000 0
Comparative
Composition A 8100 8100 0
Comparative
Composition B 6600 6600 0
Composition 1 1200 7500 0.84
Composition 2 1600 8710 0.82
Composition 3 300 10560 0.97
The above data demonstrates that the additive composition of the present
invention provides significant anti-sticking performance and shows a marked
improvement over the comparative compositions.
From the foregoing description, various modifications and changes in the
above-described invention will occur to those skilled in the art. All such
modifications coming within the scope of the appended claims are intended to
be
included therein.
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