FIELD OF THE INVENTION
[0001] The present invention relates to SAE 0W and SAE 5W multigrade crankcase lubricants
for heavy duty diesel (HDD) engines that have less than 50 mass % of Group IV and
Group V base stock, containing phosphorus-based antiwear agents in an amount introducing
no greater than 1200 ppm of phosphorus into the lubricant, which lubricants meet the
wear performance requirements of API CJ-4, API CI-4 and/or ACEA E7 specifications.
BACKGROUND OF THE INVENTION
[0002] Crankcase lubricants comprise base stock and additives that delay degradation of
the base stock and improve its performance. Such additives typically include dispersant,
overbased and neutral salts of organic acids, corrosion inhibitors, antiwear agents,
antioxidants, friction modifiers, antifoamants, and demulsifiers. These additives
may be combined in a package, sometimes referred to as a detergent inhibitor (or DI)
package. The additives in such a package may include functionalized polymers, but
these have relatively short chains, typically having a number average molecular weight
M
n of not more than 7000.
[0003] Multigrade lubricants perform over wide temperature ranges. Typically, they are identified
by two numbers such as 10W-30 or 5W-30. The first number in the multigrade designation
is associated with a safe cranking temperature (e.g., -20° C) viscosity requirement
for that multigrade oil as measured by a cold cranking simulator (CCS) under high
shear rates (ASTM D5293). In general, lubricants that have low CCS viscosities allow
the engine to crank more easily at lower temperatures and thus improve engine startability
at those ambient temperatures.
[0004] The second number in the multigrade designation is associated with a lubricant's
viscosity under normal operating temperatures and is measured in terms of the kinematic
viscosity (kV) at 100°C (ASTM D445). The high temperature viscosity requirement brackets
minimum and maximum kinematic viscosity at 100°C. Viscosity at high temperatures is
desirable to prevent engine wear that would result if the lubricant thinned out too
much during engine operation. However the lubricant should not be too viscous because
excessive viscosity may cause unnecessary viscous drag and work to pump the lubricant
which in turn can increase fuel consumption. In general, the lower a lubricants' kV
100°C, the better the scores that lubricant achieves in fuel economy tests.
[0005] Thus, in order to qualify for a given multigrade oil designation a particular multigrade
oil must simultaneously meet both strict low and high temperature viscosity requirements
that are set by SAE specifications such as SAE J300. The current viscosity limits
set in SAE J300 are as follows:
SAE VISCOSITY GRADES |
SAE viscosity grade |
Maximum CCS Viscosity (10-3Pa.s @ (°C)) |
kV100°C (mm2/s) minimum |
kV100°C (mm2/s) maximum |
0W |
3250 (-30) |
3.8 |
|
5W |
3500 (-25) |
3.8 |
- |
10W |
3500 (-20) |
4.1 |
- |
15W |
3500 (-15) |
5.6 |
- |
20W |
4500 (-10) |
5.6 |
- |
25W |
6000 (-5) |
9.3 |
- |
20 |
- |
5.6 |
<9.3 |
30 |
- |
9.3 |
<12.5 |
40 |
- |
12.5 |
<16.3 |
50 |
- |
16.3 |
<21.9 |
60 |
- |
21.9 |
<26.1 |
[0006] In the SAE J300 scheme multigrade oils meet the requirements of both low temperature
and high temperature performance. For example, an SAE 5W-30 multigrade oil has viscosity
characteristics that satisfy both the 5W and the 30 viscosity grade requirements --
i.e., a maximum CCS viscosity of 3500×10
-3 Pa.s at - 25°C, a minimum kV
100°C of 9.3 mm
2/s and a maximum kV
100°C of < 12.5 mm
2/s.
[0007] The viscosity characteristics of a lubricant depend primarily on the viscosity characteristics
of the base stock and on the viscosity characteristics of the viscosity modifier.
Of the other additives often found in lubricants only high molecular weight dispersants
have been thought to influence viscometrics, and their influence has been deemed small
in comparison to base stock and viscosity modifier.
[0008] The viscosity characteristic of a base stock on which a lubricating oil is based
is typically expressed by the neutral number of the oil (e.g., S150N) with a higher
neutral number being associated with a higher viscosity at a given temperature. This
number is defined as the viscosity of the base stock at 40°C measured in Saybolt Universal
Seconds. Blending base stocks is one way of modifying the viscosity properties of
the resulting lubricating oil. For example a lubricant formulated entirely with S100N
will have both a lower kV 100 and a lower CCS than a lubricant formulated entirely
with a S 150N base stock. A base stock comprised of a blend of S100N and S150N will
have a CCS in between those of the straight cuts. The average base stock neutral number
(ave. BSNN) of a blend of straight cuts may be determined according to the following
formula:
where
BSRn = base stock ratio for base stock n
= (wt. % base stock n/ wt. % total base stock in oil) x 100%
BSNNn= base stock neutral number for base stock n
[0009] Merely blending base stocks of different viscosity characteristics may not enable
the formulator to meet the low and high temperature viscosity requirements of some
multigrade oils. The formulator's primary tool for achieving this goal is an additive
conventionally referred to as a viscosity modifier or viscosity index (V.I.) improver.
Usually, to reach the minimum high temperature viscosity required, it is necessary
to add significant amounts of viscosity modifier. However, the use of an increased
amount of viscosity modifier results in increased low temperature lubricant viscosity.
The ever increasing need to formulate crankcase lubricants that deliver improved performance
in fuel economy tests is driving the industry to HDD engine lubricants in the lower
viscosity grades, such as 0W20, 0W30, 5W20 and 5W30.
[0010] Concurrent with the demand for lower viscosity, high fuel economy lubricants, there
has been a continued effort to reduce the content of sulfated ash, phosphorus and
sulfur in the crankcase lubricant due to both environmental concerns and to insure
compatibility with pollution control devices used in combination with modem engines
(e.g., three-way catalytic converters and particulate traps). A particularly effective
class of antioxidant-antiwear additives available to lubricant formulators is metal
salts of dialkyldithiophosphates, particularly zinc salts thereof, commonly referred
to as ZDDP. While such additives provide excellent performance, ZDDP contributes each
of sulfated ash, phosphorus and sulfur to lubricants.
[0011] The most recent specifications for heavy duty diesel (HDD) engine crankcase lubricants
in each of Europe (ACEA E7) and the United States (API CJ-4) require reductions in
allowable levels of sulfated ash, phosphorus and sulfur relative to the prior standard,
thus limiting the amount of ZDDP that can be used. At the same time, modem lubricants
are required to provide improved wear protection. Where reduced amounts of ZDDP are
employed, alternative means of providing engine wear protection must be identified,
preferably means that do not cause introduction of additional sulfated ash, phosphorus
and/or sulfur into the lubricant. Alternative means of providing wear protection are
particularly critical in low viscosity lubricants formulated with lower viscosity
base stocks which, as noted above, are less capable of contributing to antiwear performance
at high temperature.
[0012] To provide low viscosity, low phosphorus lubricating oil compositions capable of
meeting API CJ-4; API CI-4 and/or ACEA E7 performance standards, lubricant manufacturers
have formulated fully synthetic, lubricants and lubricants containing significant
proportions of synthetic base stocks defined as Group IV base stocks (polyalphaolefin
or PAO base stocks) and/ or Group V base stocks, such as ester base stocks. Compared
to Group I, Group II and Group III base stocks, Group IV and Group V base stocks have
a high viscosity index (VI), which means that the kinematic viscosity of the base
stock varies less with temperature. Thus, by using a low viscosity, high VI PAO, for
example, a lubricant can be provided having a low CCS viscosity and high kV100. However,
Group IV and Group V base stocks are expensive relative to Group I, Group II and Group
III mineral oil base stocks.
[0013] Therefore, it would be advantageous to provide a means for blending low viscosity
SAE 0W and SAE 5W multigrade crankcase lubricants for heavy duty diesel (HDD) engines
having reduced amounts, such as less than 30 mass %, of Group IV and/or Group V base
stock, and phosphorus-based antiwear agents in amounts introducing no greater than
1200 ppm of phosphorus into the lubricant, which lubricants meet the wear performance
requirements of API CJ-4; API CI-4; and/or ACEA E7 specifications.
[0014] Surprisingly, it has been found that SAE 0W and SAE 5W multigrade crankcase lubricants
for heavy duty diesel (HDD) engines having less than 30 mass %, of Group IV and/or
Group V base stock, and phosphorus-based antiwear agents in amounts introducing no
greater than 1200 ppm of phosphorus into the lubricant, can meet the performance requirements,
including the wear performance requirements of the API CJ-4; API CI-4; and/or ACEA
E7 specifications when formulated with a minor amount of a non-hydrogenated olefin
polymer and at least 40 ppm of boron.
SUMMARY OF THE INVENTION
[0015] In accordance with a first aspect of the invention, there is provided a SAE 0W and
SAE 5W multigrade crankcase lubricating oil composition for heavy duty diesel (HDD)
engines meeting the performance requirements of at least one of the API CJ-4; API
CI-4; and/or ACEA E7 specifications, having a sulfated ash content of no greater than
1.0 mass %, such as from about 0.7 to 1.0 mass %, a sulfur content of no greater than
0.4 mass %, and a phosphorus content of no greater than 0.12 mass % (1200 ppm), such
as from about 0.08 to 0.12 mass %; which lubricating oil composition comprises a major
amount of oil of lubricating viscosity including less than about 30 mass %, preferably
less than 10 mass %, based on the total mass of oil of lubricating viscosity, of Group
IV and/or Group V base stock, at least 0.3 mass %, such as 0.3 to 5 mass %, of a non-hydrogenated
olefin polymer; and greater than about 40 ppm, such as 40 to 600 ppm, of boron.
[0016] In accordance with a second aspect of the invention, there is provided a lubricating
oil composition, as described in the first aspect, having a TBN of from about 7 to
about 15,
[0017] In accordance with a third aspect of the invention, there is provided a lubricating
oil composition, as described in the first or second aspect, comprising a magnesium
detergent in an amount providing said composition with at least 0.09 mass % (900 ppm),
preferably at least 0.10 mass % (1000 ppm), more preferably at least 0.115 mass %
(1150 ppm) of magnesium.
[0018] In accordance with a fourth aspect of the invention, there is provided a lubricating
oil composition, as described in the first, second or third aspect, further comprising
a nitrogen-containing dispersant in an amount providing the lubricating oil composition
with at least 0.08 mass% of nitrogen.
[0019] In accordance with a fifth aspect of the invention, there is provided a lubricating
oil composition, as described in the first through fourth aspects, comprising at least
0.5 mass %, such as at least 0.6 mass %, preferably at least 0.8 mass%, more preferably
at least 1.0 mass % of at least one ashless antioxidant selected from sulfur-free
hindered phenol antioxidants, aminic antioxidants, and combinations thereof.
[0020] In accordance with a sixth aspect of the invention, there is provided a heavy duty
diesel (HDD) engine, lubricated with a lubricating oil composition as described in
any of the first through fifth aspects.
[0021] In accordance with a seventh aspect of the invention, there is provided a method
for improving the fuel economy and wear performance of a heavy duty diesel (HDD) engine,
which method comprises the steps of lubricating the engine with a lubricating oil
composition as described in any of the first through fifth aspects, and operating
the lubricated engine.
[0022] In accordance with a eighth aspect of the invention, there is provided the use of
a lubricating oil composition as described in any of the first through fifth aspects
to improve the fuel economy and wear performance of a heavy duty diesel (HDD) engine.
[0023] Other and further objects, advantages and features of the present invention will
be understood by reference to the following specification.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The oil of lubricating viscosity useful in the practice of the invention may range
in viscosity from about 2 mm
2/sec (centistokes) to about 40 mm
2/sec, especially from about 3 mm
2/sec to about 20 mm
2/sec, most preferably from about 9 mm
2/sec to about 17 mm
2/sec, measured at 100°C.
[0025] Natural oils include animal oils and vegetable oils (e.g., castor oil, lard oil);
liquid petroleum oils and hydrorefined, solvent-treated or acid-treated mineral oils
of the paraffinic, naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating
viscosity derived from coal or shale also serve as useful base oils.
[0026] Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon
oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes,
propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes),
poly(1-decenes)); alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,
di(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols);
and alkylated diphenyl ethers and alkylated diphenyl sulfides and derivative, analogs
and homologs thereof.
[0027] Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal
hydroxyl groups have been modified by esterification, etherification, etc., constitute
another class of known synthetic lubricating oils. These are exemplified by polyoxyalkylene
polymers prepared by polymerization of ethylene oxide or propylene oxide, and the
alkyl and aryl ethers of polyoxyalkylene polymers (e.g., methyl-polyiso-propylene
glycol ether having a molecular weight of 1000 or diphenyl ether of poly-ethylene
glycol having a molecular weight of 1000 to 1500); and mono- and polycarboxylic esters
thereof, for example, the acetic acid esters, mixed C
3-C
8 fatty acid esters and C
13 Oxo acid diester of tetraethylene glycol.
[0028] Another suitable class of synthetic lubricating oils comprises the esters of dicarboxylic
acids (e.g., phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic
acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic
acid, linoleic acid dimer, malonic acid, alkylmalonic acids, alkenyl malonic acids)
with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol). Specific
examples of such esters includes dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl
fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate,
didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer,
and the complex ester formed by reacting one mole of sebacic acid with two moles of
tetraethylene glycol and two moles of 2-ethylhexanoic acid.
[0029] Esters useful as synthetic oils also include those made from C
5 to C
12 monocarboxylic acids and polyols and polyol esters such as neopentyl glycol, trimethylolpropane,
pentaerythritol, dipentaerythritol and tripentaerythritol.
[0030] Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy- or polyaryloxysilicone
oils and silicate oils comprise another useful class of synthetic lubricants; such
oils include tetraethyl silicate, tetraisopropyl silicate, tetra-(2-ethylhexyl)silicate,
tetra-(4-methyl-2-ethylhexyl)silicate, tetra-(p-tert-butyl-phenyl) silicate, hexa-(4-methyl-2-ethylhexyl)disiloxane,
poly(methyl)siloxanes and poly(methylphenyl)siloxanes. Other synthetic lubricating
oils include liquid esters of phosphorous-containing acids (e.g., tricresyl phosphate,
trioctyl phosphate, diethyl ester of decylphosphonic acid) and polymeric tetrahydrofurans.
[0031] Other examples of base oil are gas-to-liquid ("GTL") base oils, i.e. the base oil
may be oil derived from Fischer-Tropsch-synthesized hydrocarbons made from synthesis
gas containing hydrogen and carbon monoxide using a Fischer-Tropsch catalyst. These
hydrocarbons typically require further processing in order to be useful as base oil.
For example, they may, by methods known in the art, be hydroisomerized; hydrocracked
and hydroisomerized; dewaxed; or hydroisomerized and dewaxed.
[0032] Definitions for the base stocks and base oils in this invention are the same as those
found in the American Petroleum Institute (API) publication "Engine Oil Licensing
and Certification System", Industry Services Department, Fourteenth Edition, December
1996, Addendum 1, December 1998. Said publication categorizes base stocks as follows:
- a) Group I base stocks contain less than 90 percent saturates and/or greater than
0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less
than 120 using the test methods specified in Table 1.
- b) Group II base stocks contain greater than or equal to 90 percent saturates and
less than or equal to 0.03 percent sulfur and have a viscosity index greater than
or equal to 80 and less than 120 using the test methods specified in Table 1.
- c) Group III base stocks contain greater than or equal to 90 percent saturates and
less than or equal to 0.03 percent sulfur and have a viscosity index greater than
or equal to 120 using the test methods specified in Table 1.
- d) Group IV base stocks are polyalphaolefins (PAO).
- e) Group V base stocks include all other base stocks not included in Group I, II,
III, or IV.
Table 1 - Analytical Methods for Base Stock
Property |
Test Method |
Saturates |
ASTM D 2007 |
Viscosity Index |
ASTM D 2270 |
Sulfur |
ASTM D 2622; ASTM D 4294; ASTM D 4927; ASTM D 3120 |
[0033] Oil of lubricating viscosity useful in the practice of the present invention may
comprise a Group I, Group II, Group III, base stocks or base oil blends of the aforementioned
base stocks. The oil of lubricating viscosity may also comprise a base oil blend of
one or more Group I, Group II, and/or Group III, base stocks and less than 30 mass
%, based on the total mass of oil of lubricating viscosity, of one or more Group IV
and/or Group V base stocks. Preferably, the oil of lubricating viscosity is mixture
of one or more Group II and/or Group III base stock and an amount of less than 30
mass %, preferably less than 10 mass %, based on the total mass % of oil of lubricating
viscosity, of one or more Group IV or Group V base stocks. Particularly preferred
are Group III base stocks and base stock blends, and blends of one or more Group III
base stocks and 0 to 10 mass %, based on the total mass of oil of lubricating viscosity,
of one or more Group IV base stocks. The base stock, or base stock blend preferably
has a saturate content of at least 65%, more preferably at least 75%, such as at least
85%.
[0034] Most preferably, the base stock, or base stock blend, has a saturate content of greater
than 90%. Preferably, the oil or oil blend will have a sulfur content of less than
1 mass %, preferably less than 0.6 mass %, most preferably less than 0.4 mass %, such
as less than 0.3 mass %.
[0035] Preferably the volatility of the base stock or base stock blend, as measured by the
Noack test (ASTM D5800), is less than or equal to 30 mass %, such as less than about
25 mass%, preferably less than or equal to 20 mass %, more preferably less than or
equal to 15 mass %, most preferably less than or equal 13 mass %. Preferably, the
viscosity index (VI) of the base stock or base stock blend is at least 85, preferably
at least 100, most preferably from about 105 to 140.
[0036] A certain amount of oil of lubricating viscosity may be introduced into the lubricating
oil composition as a diluent for the various additives and are commonly Group I base
stocks. The preferred mass percentages, saturates contents, Noack and VI described
above are for the base stock or base stock blends used to formulate the lubricating
oil composition, excluding any oil that may be introduced as an additive diluent.
[0037] The non-hydrogenated olefin (co)polymer useful in the practice of the present invention
is preferably a polymer or copolymer of one or more acyclic olefin monomers. Generally,
the non-hydrogenated olefin (co)polymers useful in the invention have, or have on
average, about one double bond per polymer chain.
[0038] The (co)polymer may be prepared by polymerizing alpha-olefin monomer, or mixtures
of alpha-olefin monomers, or mixtures comprising ethylene and at least one C
3 to C
28 alpha-olefin monomer, in the presence of a catalyst system comprising at least one
metallocene (e.g., a cyclopentadienyl-transition metal compound) and an alumoxane
compound. Using this process, a polymer in which 95 % or more of the polymer chains
possess terminal ethenylidene-type unsaturation can be provided. The percentage of
polymer chains exhibiting terminal ethenylidene unsaturation may be determined by
FTIR spectroscopic analysis, titration, or C
13 NMR. Interpolymers of this latter type may be characterized by the formula POLY-C(R
1)=CH
2 wherein R
1 is C
1 to C
26 alkyl, preferably C
1 to C
18 alkyl, more preferably C
1 to C
8 alkyl, and most preferably C
1 to C
2 alkyl, (
e.
g., methyl or ethyl) and wherein POLY represents the polymer chain. The chain length
of the R
1 alkyl group will vary depending on the comonomer(s) selected for use in the polymerization.
A minor amount of the polymer chains can contain terminal ethenyl,
i.
e. vinyl, unsaturation,
i.
e. POLY-CH=CH
2, and a portion of the polymers can contain internal monounsaturation,
e.
g., POLY-CH=CH(R
1), wherein R
1 is as defined above. These terminally unsaturated interpolymers may be prepared by
known metallocene chemistry and may also be prepared as described in
U.S. Patent Nos. 5,498,809;
5,663,130;
5,705,577;
5,814,715;
6,022,929 and
6,030,930.
[0039] Another useful class of (co)polymers is (co)polymers prepared by cationic polymerization
of isobutene, styrene, and the like. Common (co)polymers from this class include polyisobutenes
obtained by polymerization of a C
4 refinery stream having a butene content of about 35 to about 75 mass %., and an isobutene
content of about 30 to about 60% by wt., in the presence of a Lewis acid catalyst,
such as aluminum trichloride or boron trifluoride, with aluminium trichloride preferred.
A preferred source of monomer for making poly-n-butenes is petroleum feedstreams such
as Raffinate II. These feedstocks are disclosed in the art such as in
U.S. Patent No. 4,952,739. Polyisobutylene is a most preferred polymer of the present invention because it
is readily available by cationic polymerization from butene streams (
e.
g., using AlCl
3 or BF
3 catalysts). Such polyisobutylenes generally contain residual unsaturation in amounts
of about one ethylenic double bond per polymer chain, positioned along the chain.
A preferred embodiment utilizes polyisobutylene prepared from a pure isobutylene stream
or a Raffinate I stream to prepare reactive isobutylene polymers with terminal vinylidene
olefins. Preferably, these polymers, referred to as highly reactive polyisobutylene
(HR-PIB), have a terminal vinylidene content of at least 65%,
e.
g., 70%, more preferably at least 80%, most preferably, at least 85%. The preparation
of such polymers is described, for example, in
U.S. Patent No. 4,152,499. HR-PIB is known and is commercially available, for example, under the tradenames
Glissopal
™ (from BASF) and Ultravis
™ (from BP-Amoco).
[0040] In another embodiment, the non-hydrogenated olefin (co)polymer, for example, polyisobutylene,
has at most 10, such as 5 to 10, %, of the polymer chains possessing a terminal double
bond (or terminal ethenylidene-type or terminal vinylidene unsaturation). Such a polymer
is considered not highly reactive; an example of a commercially available polymer
is under tradename Napvis
™ (from BP-Amoco), and usually obtained by polymerization with aluminium trichloride
as catalyst.
[0041] Preferably the (co)polymer is derived from polymerisation of one or more olefins
having 2 to 10, such as 3 to 8, carbon atoms. An especially preferred olefin is butene,
advantageously isobutene.
[0042] The number average molecular weight of the non-hydrogenated olefin (co)polymer useful
in the present invention is preferably in the range of from about 450 to about 2300,
such as from about 450 to about 1300, preferably from about 450 to about 950. The
molecular weight can be determined by several known techniques. A convenient method
for such determination is by gel permeation chromatography (GPC), which additionally
provides molecular weight distribution information (see
W.W. Yau, J.J Kirkland and D.D Bly, "Modern Size Exclusion Liquid Chromatography",
John Wiley and Sons, New York, 1979). Further, it is preferred that the kinematic viscosity of the non-hydrogenated olefin
polymer at 100°C, as measured according to ASTM D445, is at least 9 or 15, such as
100 or 150 to 3000, advantageously 200 to 2500 or 2700 mm
2s
-1. In one embodiment of the present invention, a polyisobutylene polymer having a number
average molecular weight of 450 to 2300, and a kinematic viscosity at 100°C of from
about 200 to 2400 mm
2s
-1 was found to provide particularly beneficial properties. Lubricating oil compositions
of the present invention can contain the non-hydrogenated olefin polymer in an amount
of at least 0.3 mass %, such as from about 0.3 to about 5.0 mass %, particularly from
about 0.5 to about 3.0 mass %, preferably from about 1.0 to about 2.5 mass %. Preferably,
lubricating oil compositions of the present invention contain less than about 35 mass
%, preferably less than about 15 mass %, based on the combined total mass of oil of
lubricating viscosity and non-hydrogenated olefin polymer, of a combination of Group
IV and/or Group V base stock and non-hydrogenated olefin polymer.
[0043] Lubricating oil compositions of the present invention contain greater than about
40 ppm, such as 40 to 600 ppm, preferably from about 50 to 200 ppm, more preferably
from about 50 to 100 ppm of boron. The boron can be introduced into the lubricating
oil composition by a borated dispersant, a borated detergent, or other boron-containing
additive, or a mixture thereof, or by addition of elemental boron or other boron compound.
[0044] Metal-containing or ash-forming detergents function as both detergents to reduce
or remove deposits and as acid neutralizers or rust inhibitors, thereby reducing wear
and corrosion and extending engine life. Detergents generally comprise a polar head
with a long hydrophobic tail. The polar head comprises a metal salt of an acidic organic
compound. The salts may contain a substantially stoichiometric amount of the metal
in which case they are usually described as normal or neutral salts, and have a total
base number or TBN (as can be measured by ASTM D2896) of from 0 to less than 150,
such as 0 to about 80 or 100. A large amount of a metal base may be incorporated by
reacting excess metal compound (e.g., an oxide or hydroxide) with an acidic gas (e.g.,
carbon dioxide). The resulting overbased detergent comprises neutralized detergent
as the outer layer of a metal base (e.g. carbonate) micelle. Such overbased detergents
have a TBN of 150 or greater, and typically will have a TBN of from 250 to 450 or
more.
[0045] Detergents that may be used include oil-soluble neutral and overbased sulfonates,
phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates and
other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth
metals, e.g., barium, sodium, potassium, lithium, calcium, and magnesium. The most
commonly used metals are calcium and magnesium, which may both be present in detergents
used in a lubricant, and mixtures of calcium and/or magnesium with sodium. Combinations
of detergents, whether overbased or neutral or both, may be used.
[0046] Sulfonates may be prepared from sulfonic acids which are typically obtained by the
sulfonation of alkyl substituted aromatic hydrocarbons such as those obtained from
the fractionation of petroleum or by the alkylation of aromatic hydrocarbons. Examples
included those obtained by alkylating benzene, toluene, xylene, naphthalene, diphenyl
or their halogen derivatives such as chlorobenzene, chlorotoluene and chloronaphthalene.
The alkylation may be carried out in the presence of a catalyst with alkylating agents
having from about 3 to more than 70 carbon atoms. The alkaryl sulfonates usually contain
from about 9 to about 80 or more carbon atoms, preferably from about 16 to about 60
carbon atoms per alkyl substituted aromatic moiety.
[0047] The oil soluble sulfonates or alkaryl sulfonic acids may be neutralized with oxides,
hydroxides, alkoxides, carbonates, carboxylate, sulfides, hydrosulfides, nitrates,
borates and ethers of the metal. The amount of metal compound is chosen having regard
to the desired TBN of the final product but typically ranges from about 100 to 220
mass % (preferably at least 125 mass %) of that stoichiometrically required.
[0048] Metal salts of phenols and sulfurized phenols are prepared by reaction with an appropriate
metal compound such as an oxide or hydroxide and neutral or overbased products may
be obtained by methods well known in the art. Sulfurized phenols may be prepared by
reacting a phenol with sulfur or a sulfur containing compound such as hydrogen sulfide,
sulfur monohalide or sulfur dihalide, to form products which are generally mixtures
of compounds in which 2 or more phenols are bridged by sulfur containing bridges.
[0049] Carboxylate detergents, e.g., salicylates, can be prepared by reacting an aromatic
carboxylic acid with an appropriate metal compound such as an oxide or hydroxide and
neutral or overbased products may be obtained by methods well known in the art. The
aromatic moiety of the aromatic carboxylic acid can contain hetero atoms, such as
nitrogen and oxygen. Preferably, the moiety contains only carbon atoms; more preferably
the moiety contains six or more carbon atoms; for example benzene is a preferred moiety.
The aromatic carboxylic acid may contain one or more aromatic moieties, such as one
or more benzene rings, either fused or connected via alkylene bridges. The carboxylic
moiety may be attached directly or indirectly to the aromatic moiety. Preferably the
carboxylic acid group is attached directly to a carbon atom on the aromatic moiety,
such as a carbon atom on the benzene ring. More preferably, the aromatic moiety also
contains a second functional group, such as a hydroxy group or a sulfonate group,
which can be attached directly or indirectly to a carbon atom on the aromatic moiety.
[0050] Preferred examples of aromatic carboxylic acids are salicylic acids and sulfurized
derivatives thereof, such as hydrocarbyl substituted salicylic acid and derivatives
thereof. Processes for sulfurizing, for example a hydrocarbyl - substituted salicylic
acid, are known to those skilled in the art. Salicylic acids are typically prepared
by carboxylation, for example, by the Kolbe - Schmitt process, of phenoxides, and
in that case, will generally be obtained, normally in a diluent, in admixture with
uncarboxylated phenol.
[0051] Preferred substituents in oil - soluble salicylic acids are alkyl substituents. In
alkyl - substituted salicylic acids, the alkyl groups advantageously contain 5 to
100, preferably 9 to 30, especially 14 to 20, carbon atoms. Where there is more than
one alkyl group, the average number of carbon atoms in all of the alkyl groups is
preferably at least 9 to ensure adequate oil solubility.
[0052] Detergents generally useful in the formulation of lubricating oil compositions also
include "hybrid" detergents formed with mixed surfactant systems, e.g., phenate/salicylates,
sulfonate/phenates, sulfonate/salicylates, sulfonates/phenates/salicylates, as described,
for example, in
U.S. Patent Nos. 6,153,565;
6,281,179;
6,429,178; and
6,429,178.
[0053] Borated detergents and methods for borating detergents are well known and described,
for example, in
U.S. Patent Nos. 3,929,650;
3,480,548; and
4,792,410. Borated detergents can be used to provide the lubricating oil compositions of the
present invention with all, or a portion, of the requisite amount of boron.
[0054] Lubricating oil compositions of the present invention preferably contain a magnesium
detergent, more preferably an overbased magnesium detergent, in an amount providing
the lubricating oil composition with at least 0.09 mass % (900 ppm), preferably at
least 0.10 mass % (1000 ppm), more preferably at least 0.115 mass % (1150 ppm) of
elemental magnesium. Preferably, the overbased magnesium detergent will have, or have
on average, a TBN of at least about 200, such as from about 200 to about 500; preferably
at least about 250, such as from about 250 to about 500; more preferably at least
about 300, such as from about 300 to about 450.
[0055] Overbased ash-containing detergents based on metals other than magnesium are preferably
present in amounts contributing no greater than 40 % of the TBN of the lubricating
oil composition contributed by overbased detergent. More preferably, lubricating oil
compositions of the present invention contain overbased ash-containing detergents
based on metals other than magnesium in amounts providing no greater than about 20%
of the total TBN contributed to the lubricating oil composition by overbased detergent.
[0056] Lubricating oil compositions of the present invention may also contain ashless (metal-free)
detergents such as oil-soluble hydrocarbyl phenol aldehyde condensates described,
for example, in
US-2005-0277559-A1.
[0057] Preferably, detergent in total is used in an amount providing the lubricating oil
composition with from about 0.35 to about 1.0 mass %, such as from about 0.5 to about
0.9 mass %, more preferably from about 0.6 to about 0.8 mass % of sulfated ash (SASH).
Preferably, the lubricating oil composition has a TBN of from about 7 to about 15,
such as from about 8 to about 13, more preferably from about 9 to about 11. TBN may
be contributed to the lubricating oil composition by additives other than detergents.
Dispersants, antioxidants and antiwear agents may in some cases contribute 40 % or
more of the total amount of lubricant TBN.
[0058] Conventionally, lubricating oil compositions formulated for use in a heavy duty diesel
engine comprise from about 0.5 to about 10 mass %, preferably from about 1.5 to about
5 mass %, most preferably from about 2 to about 3 mass % of detergent, based on the
total mass of the formulated lubricating oil composition. Detergents are conventionally
formed in diluent oil. Conventionally, detergents are referred to by the TBN, which
is the TBN of the active detergent in the diluent. Therefore, while other additives
are often referred to in terms of the amount of active ingredient (A.I.), stated amounts
of detergent refer to the total mass of detergent including diluent.
[0059] Dihydrocarbyl dithiophosphate metal salts are frequently used as antiwear and antioxidant
agents. The metal may be an alkali or alkaline earth metal, or aluminum, lead, tin,
molybdenum, manganese, nickel or copper. The zinc salts are most commonly used in
lubricating oil in amounts of 0.1 to 10, preferably 0.2 to 2 mass %, based upon the
total weight of the lubricating oil composition. They may be prepared in accordance
with known techniques by first forming a dihydrocarbyl dithiophosphoric acid (DDPA),
usually by reaction of one or more alcohol or a phenol with P
2S
5 and then neutralizing the formed DDPA with a zinc compound. For example, a dithiophosphoric
acid may be made by reacting mixtures of primary and secondary alcohols. Alternatively,
multiple dithiophosphoric acids can be prepared where the hydrocarbyl groups on one
are entirely secondary in character and the hydrocarbyl groups on the others are entirely
primary in character. To make the zinc salt, any basic or neutral zinc compound could
be used but the oxides, hydroxides and carbonates are most generally employed. Commercial
additives frequently contain an excess of zinc due to the use of an excess of the
basic zinc compound in the neutralization reaction.
[0060] The preferred zinc dihydrocarbyl dithiophosphates are oil soluble salts of dihydrocarbyl
dithiophosphoric acids and may be represented by the following formula:
wherein R and R' may be the same or different hydrocarbyl radicals containing from
1 to 18, preferably 2 to 12, carbon atoms and including radicals such as alkyl, alkenyl,
aryl, arylalkyl, alkaryl and cycloaliphatic radicals. Particularly preferred as R
and R' groups are alkyl groups of 2 to 8 carbon atoms. Thus, the radicals may, for
example, be ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, amyl, n-hexyl,
i-hexyl, n-octyl, decyl, dodecyl, octadecyl, 2-ethylhexyl, phenyl, butylphenyl, cyclohexyl,
methylcyclopentyl, propenyl, butenyl. In order to obtain oil solubility, the total
number of carbon atoms (i.e. R and R') in the dithiophosphoric acid will generally
be about 5 or greater. The zinc dihydrocarbyl dithiophosphate (ZDDP) can therefore
comprise zinc dialkyl dithiophosphates. Lubricating oil compositions of the present
invention have a phosphorous content of no greater than about 0.12 mass % (1200 ppm).
Conventionally, ZDDP is used in an amount close or equal to the maximum amount allowed.
Thus, lubricating oil compositions in accordance with the present invention, formulated
for use in heavy duty diesel engines, will preferably contain ZDDP or other metal
salt of a dihydrocarbyl dithiophosphate, in an amount introducing from about 0.08
to about 0.12 mass % of phosphorus, based on the total mass of the lubricating oil
composition. Preferably, ZDDP is the sole phosphorus- containing additive present.
[0061] Oxidation inhibitors or antioxidants reduce the tendency of mineral oils to deteriorate
in service. Oxidative deterioration can be evidenced by sludge in the lubricant, varnish-like
deposits on the metal surfaces, and by viscosity growth. Such oxidation inhibitors
include hindered phenols, alkaline earth metal salts of alkylphenolthioesters having
preferably C
5 to C
12 alkyl side chains, calcium nonylphenol sulfide, oil soluble phenates and sulfurized
phenates, phosphosulfurized or sulfurized hydrocarbons or esters, phosphorous esters,
metal thiocarbamates, oil soluble copper compounds as described in
U.S. Patent No. 4,867,890, and molybdenum-containing compounds.
[0062] Aromatic amines having at least two aromatic groups attached directly to the nitrogen
constitute another class of compounds that is frequently used for antioxidancy. Typical
oil soluble aromatic amines having at least two aromatic groups attached directly
to one amine nitrogen contain from 6 to 16 carbon atoms. The amines may contain more
than two aromatic groups. Compounds having a total of at least three aromatic groups
in which two aromatic groups are linked by a covalent bond or by an atom or group
(e.g., an oxygen or sulfur atom, or a -CO-, - SO
2- or alkylene group) and two are directly attached to one amine nitrogen also considered
aromatic amines having at least two aromatic groups attached directly to the nitrogen.
The aromatic rings are typically substituted by one or more substituents selected
from alkyl, cycloalkyl, alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro groups.
The amount of any such oil soluble aromatic amines having at least two aromatic groups
attached directly to one amine nitrogen should preferably not exceed 0.4 mass %.
[0063] The antiwear agent ZDDP provides a strong antioxidant credit to lubricants. When
less ZDDP is used in order to meet phosphorus and SASH limits, lubricant formulators
must compensate for the resulting reduction in oxidation inhibition, preferably by
use of highly effective, ashless, sulfur-free antioxidants. Lubricating oil compositions
in accordance with the present invention therefore preferably contain at least about
0.5 mass%, preferably at least about 0.6 mass %, such as at least 0.8 mass%, more
preferably, at least 1.0 mass % of an ashless antioxidant selected from the group
consisting of sulfur-free phenolic antioxidant, aminic antioxidant, or a combination
thereof. Preferably, lubricating oil compositions in accordance with the present invention
contain a combination of sulfur-free phenolic antioxidant and aminic antioxidant.
[0064] Dispersants maintain in suspension materials resulting from oxidation during use
that are insoluble in oil, thus preventing sludge flocculation and precipitation,
or deposition on metal parts. The lubricating oil composition of the present invention
comprises at least one dispersant, and may comprise a plurality of dispersants. The
dispersant or dispersants are preferably nitrogen-containing dispersants and preferably
contribute, in total, from about 0.08 to about 0.19 mass %, such as from about 0.09
to about 0.18 mass %, most preferably from about 0.09 to about 0.16 mass % of nitrogen
to the lubricating oil composition.
[0065] Dispersants useful in the context of the present invention include the range of nitrogen-containing,
ashless (metal-free) dispersants known to be effective to reduce formation of deposits
upon use in gasoline and diesel engines, when added to lubricating oils and comprise
an oil soluble polymeric long chain backbone having functional groups capable of associating
with particles to be dispersed. Typically, such dispersants have amine, amine-alcohol
or amide polar moieties attached to the polymer backbone, often via a bridging group.
The ashless dispersant may be, for example, selected from oil soluble salts, esters,
amino-esters, amides, imides and oxazolines of long chain hydrocarbon-substituted
mono- and polycarboxylic acids or anhydrides thereof; thiocarboxylate derivatives
of long chain hydrocarbons; long chain aliphatic hydrocarbons having polyamine moieties
attached directly thereto; and Mannich condensation products formed by condensing
a long chain substituted phenol with formaldehyde and polyalkylene polyamine.
[0066] Generally, each mono- or dicarboxylic acid-producing moiety will react with a nucleophilic
group (amine or amide) and the number of functional groups in the polyalkenyl-substituted
carboxylic acylating agent will determine the number of nucleophilic groups in the
finished dispersant.
[0067] The polyalkenyl moiety of the dispersant of the present invention has a number average
molecular weight of from about 700 to about 3000, preferably between 950 and 3000,
such as between 950 and 2800, more preferably from about 950 to 2500, and most preferably
from about 950 to about 2400. In one embodiment of the invention, the dispersant comprises
a combination of a lower molecular weight dispersant (e.g., having a number average
molecular weight of from about 700 to 1100) and a high molecular weight dispersant
having a number average molecular weight of from about at least about 1500, preferably
between 1800 and 3000, such as between 2000 and 2800, more preferably from about 2100
to 2500, and most preferably from about 2150 to about 2400. The molecular weight of
a dispersant is generally expressed in terms of the molecular weight of the polyalkenyl
moiety as the precise molecular weight range of the dispersant depends on numerous
parameters including the type of polymer used to derive the dispersant, the number
of functional groups, and the type of nucleophilic group employed.
[0068] The polyalkenyl moiety from which the high molecular weight dispersants are derived
preferably have a narrow molecular weight distribution (MWD), also referred to as
polydispersity, as determined by the ratio of weight average molecular weight (M
w) to number average molecular weight (M
n). Specifically, polymers from which the dispersants of the present invention are
derived have a M
w/M
n of from about 1.5 to about 2.0, preferably from about 1.5 to about 1.9, most preferably
from about 1.6 to about 1.8.
[0069] Suitable hydrocarbons or polymers employed in the formation of the dispersants of
the present invention include homopolymers, interpolymers or lower molecular weight
hydrocarbons. One family of such polymers comprise polymers of ethylene and/or at
least one C
3 to C
28 alpha-olefin having the formula H
2C=CHR
1 wherein R
1 is straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and wherein
the polymer contains carbon-to-carbon unsaturation, preferably a high degree of terminal
ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of ethylene
and at least one alpha-olefin of the above formula, wherein R
1 is alkyl of from 1 to 18 carbon atoms, and more preferably is alkyl of from 1 to
8 carbon atoms, and more preferably still of from 1 to 2 carbon atoms. Therefore,
useful alpha-olefin monomers and comonomers include, for example, propylene, butene-1,
hexene-1, octene-1, 4-methylpentene-1, decene-1, dodecene-1, tridecene-1, tetradecene-1,
pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1,
nonadecene-1, and mixtures thereof (e.g., mixtures of propylene and butene-1, and
the like). Exemplary of such polymers are propylene homopolymers, butene-1 homopolymers,
ethylene-propylene copolymers, ethylene-butene-1 copolymers, propylene-butene copolymers
and the like, wherein the polymer contains at least some terminal and/or internal
unsaturation. Preferred polymers are unsaturated copolymers of ethylene and propylene
and ethylene and butene-1. The interpolymers of this invention may contain a minor
amount, e.g. 0.5 to 5 mole % of a C
4 to C
18 nonconjugated diolefin comonomer. However, it is preferred that the polymers of this
invention comprise only alpha-olefin homopolymers, interpolymers of alpha-olefin comonomers
and interpolymers of ethylene and alpha-olefin comonomers. The molar ethylene content
of the polymers employed in this invention is preferably in the range of 0 to 80 %,
and more preferably 0 to 60 %. When propylene and/or butene-1 are employed as comonomer(s)
with ethylene, the ethylene content of such copolymers is most preferably between
15 and 50 %, although higher or lower ethylene contents may be present.
[0070] These polymers may be prepared by polymerizing alpha-olefin monomer, or mixtures
of alpha-olefin monomers, or mixtures comprising ethylene and at least one C
3 to C
28 alpha-olefin monomer, in the presence of a catalyst system comprising at least one
metallocene (e.g., a cyclopentadienyl-transition metal compound) and an alumoxane
compound. Using this process, a polymer in which 95 % or more of the polymer chains
possess terminal ethenylidene-type unsaturation can be provided. The percentage of
polymer chains exhibiting terminal ethenylidene unsaturation may be determined by
FTIR spectroscopic analysis, titration, or C
13 NMR. Interpolymers of this latter type may be characterized by the formula POLY-C(R
1)=CH
2 wherein R
1 is C
1 to C
26 alkyl, preferably C
1 to C
18 alkyl, more preferably C
1 to C
8 alkyl, and most preferably C
1 to C
2 alkyl, (e.g., methyl or ethyl) and wherein POLY represents the polymer chain. The
chain length of the R
1 alkyl group will vary depending on the comonomer(s) selected for use in the polymerization.
A minor amount of the polymer chains can contain terminal ethenyl, i.e., vinyl, unsaturation,
i.e. POLY-CH=CH
2, and a portion of the polymers can contain internal monounsaturation, e.g. POLY-CH=CH(R
1), wherein R
1 is as defined above. These terminally unsaturated interpolymers may be prepared by
known metallocene chemistry and may also be prepared as described in
U.S. Patent Nos. 5,498,809;
5,663,130;
5,705,577;
5,814,715;
6,022,929 and
6,030,930.
[0071] Another useful class of polymers is polymers prepared by cationic polymerization
of isobutene, styrene, and the like. Common polymers from this class include polyisobutenes
obtained by polymerization of a C
4 refinery stream having a butene content of about 35 to about 75 mass %, and an isobutene
content of about 30 to about 60 mass %, in the presence of a Lewis acid catalyst,
such as aluminum trichloride or boron trifluoride. A preferred source of monomer for
making poly-n-butenes is petroleum feedstreams such as Raffinate II. These feedstocks
are disclosed in the art such as in
U.S. Patent No. 4,952,739. Polyisobutylene is a most preferred backbone of the present invention because it
is readily available by cationic polymerization from butene streams (e.g., using AlCl
3 or BF
3 catalysts). Such polyisobutylenes generally contain residual unsaturation in amounts
of about one ethylenic double bond per polymer chain, positioned along the chain.
A preferred embodiment utilizes polyisobutylene prepared from a pure isobutylene stream
or a Raffinate I stream to prepare reactive isobutylene polymers with terminal vinylidene
olefins. Preferably, these polymers, referred to as highly reactive polyisobutylene
(HR-PIB), have a terminal vinylidene content of at least 65%, e.g., 70%, more preferably
at least 80%, most preferably, at least 85%. The preparation of such polymers is described,
for example, in
U.S. Patent No. 4,152,499. HR-PIB is known and HR-PIB is commercially available, for example, under the tradenames
Glissopal
™ (from BASF) and Ultravis
™ (from BP-Amoco).
[0072] Polyisobutylene polymers that may be employed are generally based on a hydrocarbon
chain of from about 700 to 3000. Methods for making polyisobutylene are known. Polyisobutylene
can be functionalized by halogenation (e.g. chlorination), the thermal "ene" reaction,
or by free radical grafting using a catalyst (e.g. peroxide), as described below.
[0073] The hydrocarbon or polymer backbone can be functionalized, e.g., with carboxylic
acid producing moieties (preferably acid or anhydride moieties) selectively at sites
of carbon-to-carbon unsaturation on the polymer or hydrocarbon chains, or randomly
along chains using any of the three processes mentioned above or combinations thereof,
in any sequence.
[0074] Processes for reacting polymeric hydrocarbons with unsaturated carboxylic acids,
anhydrides or esters and the preparation of derivatives from such compounds are disclosed
in
U.S. Patent Nos. 3,087,936;
3,172,892;
3,215,707;
3,231,587;
3,272,746;
3,275,554;
3,381,022;
3,442,808;
3,565,804;
3,912,764;
4,110,349;
4,234,435;
5,777,025;
5,891,953; as well as
EP 0 382 450 B1;
CA-1,335,895 and
GB-A-1,440,219. The polymer or hydrocarbon may be functionalized, for example, with carboxylic acid
producing moieties (preferably acid or anhydride) by reacting the polymer or hydrocarbon
under conditions that result in the addition of functional moieties or agents, i.e.,
acid, anhydride, ester moieties, etc., onto the polymer or hydrocarbon chains primarily
at sites of carbon-to-carbon unsaturation (also referred to as ethylenic or olefinic
unsaturation) using the halogen assisted functionalization (e.g. chlorination) process
or the thermal "ene" reaction.
[0075] Selective functionalization can be accomplished by halogenating, e.g., chlorinating
or brominating the unsaturated α-olefin polymer to about 1 to 8 mass %, preferably
3 to 7 mass % chlorine, or bromine, based on the weight of polymer or hydrocarbon,
by passing the chlorine or bromine through the polymer at a temperature of 60 to 250°C,
preferably 110 to 160°C, e.g., 120 to 140°C, for about 0.5 to 10, preferably 1 to
7 hours. The halogenated polymer or hydrocarbon (hereinafter backbone) is then reacted
with sufficient monounsaturated reactant capable of adding the required number of
functional moieties to the backbone, e.g., monounsaturated carboxylic reactant, at
100 to 250°C, usually about 180°C to 235°C, for about 0.5 to 10, e.g., 3 to 8 hours,
such that the product obtained will contain the desired number of moles of the monounsaturated
carboxylic reactant per mole of the halogenated backbones. Alternatively, the backbone
and the monounsaturated carboxylic reactant are mixed and heated while adding chlorine
to the hot material.
[0076] While chlorination normally helps increase the reactivity of starting olefin polymers
with monounsaturated functionalizing reactant, it is not necessary with some of the
polymers or hydrocarbons contemplated for use in the present invention, particularly
those preferred polymers or hydrocarbons which possess a high terminal bond content
and reactivity. Preferably, therefore, the backbone and the monounsaturated functionality
reactant, e.g., carboxylic reactant, are contacted at elevated temperature to cause
an initial thermal "ene" reaction to take place. Ene reactions are known.
[0077] The hydrocarbon or polymer backbone can be functionalized by random attachment of
functional moieties along the polymer chains by a variety of methods. For example,
the polymer, in solution or in solid form, may be grafted with the monounsaturated
carboxylic reactant, as described above, in the presence of a free-radical initiator.
When performed in solution, the grafting takes place at an elevated temperature in
the range of about 100 to 260°C, preferably 120 to 240°C. Preferably, free-radical
initiated grafting would be accomplished in a mineral lubricating oil solution containing,
e.g., 1 to 50 mass %, preferably 5 to 30 mass % polymer based on the initial total
oil solution.
[0078] The free-radical initiators that may be used are peroxides, hydroperoxides, and azo
compounds, preferably those that have a boiling point greater than about 100°C and
decompose thermally within the grafting temperature range to provide free-radicals.
Representative of these free-radical initiators are azobutyronitrile, 2,5-dimethylhex-3-ene-2,
5-bis-tertiary-butyl peroxide and dicumene peroxide. The initiator, when used, typically
is used in an amount of between 0.005% and 1% by weight based on the weight of the
reaction mixture solution. Typically, the aforesaid monounsaturated carboxylic reactant
material and free-radical initiator are used in a weight ratio range of from about
1.0:1 to 30:1, preferably 3:1 to 6:1. The grafting is preferably carried out in an
inert atmosphere, such as under nitrogen blanketing. The resulting grafted polymer
is characterized by having carboxylic acid (or ester or anhydride) moieties randomly
attached along the polymer chains: it being understood, of course, that some of the
polymer chains remain ungrafted. The free radical grafting described above can be
used for the other polymers and hydrocarbons of the present invention.
[0079] The preferred monounsaturated reactants that are used to functionalize the backbone
comprise mono- and dicarboxylic acid material, i.e., acid, anhydride, or acid ester
material, including (i) monounsaturated C
4 to C
10 dicarboxylic acid wherein
- (a) the carboxyl groups are vicinyl, (i.e., located on adjacent carbon atoms) and
(b) at least one, preferably both, of said adjacent carbon atoms are part of said
mono unsaturation; (ii) derivatives of (i) such as anhydrides or C1 to C5 alcohol derived mono- or diesters of (i); (iii) monounsaturated C3 to C10 monocarboxylic acid wherein the carbon-carbon double bond is conjugated with the
carboxy group, i.e., of the structure -C=C-CO-; and (iv) derivatives of (iii) such
as C1 to C5 alcohol derived mono- or diesters of (iii). Mixtures of monounsaturated carboxylic
materials (i) - (iv) also may be used. Upon reaction with the backbone, the monounsaturation
of the monounsaturated carboxylic reactant becomes saturated. Thus, for example, maleic
anhydride becomes backbone-substituted succinic anhydride, and acrylic acid becomes
backbone-substituted propionic acid. Exemplary of such monounsaturated carboxylic
reactants are fumaric acid, itaconic acid, maleic acid, maleic anhydride, chloromaleic
acid, chloromaleic anhydride, acrylic acid, methacrylic acid, crotonic acid, cinnamic
acid, and lower alkyl (e.g., C1 to C4 alkyl) acid esters of the foregoing, e.g., methyl maleate, ethyl fumarate, and methyl
fumarate.
[0080] To provide the required functionality, the monounsaturated carboxylic reactant, preferably
maleic anhydride, typically will be used in an amount ranging from about equimolar
amount to about 100 mass % excess, preferably 5 to 50 mass % excess, based on the
moles of polymer or hydrocarbon. Unreacted excess monounsaturated carboxylic reactant
can be removed from the final dispersant product by, for example, stripping, usually
under vacuum, if required.
[0081] The functionalized oil-soluble polymeric hydrocarbon backbone is then derivatized
with a nitrogen-containing nucleophilic reactant, such as an amine, aminoalcohol,
amide, or mixture thereof, to form a corresponding derivative. Amine compounds are
preferred. Useful amine compounds for derivatizing functionalized polymers comprise
at least one amine and can comprise one or more additional amine or other reactive
or polar groups. These amines may be hydrocarbyl amines or may be predominantly hydrocarbyl
amines in which the hydrocarbyl group includes other groups, e.g., hydroxy groups,
alkoxy groups, amide groups, nitriles, imidazoline groups, and the like. Particularly
useful amine compounds include mono- and polyamines, e.g., polyalkene and polyoxyalkylene
polyamines of about 2 to 60, such as 2 to 40 (e.g., 3 to 20) total carbon atoms having
about 1 to 12, such as 3 to 12, preferably 3 to 9, most preferably form about 6 to
about 7 nitrogen atoms per molecule. Mixtures of amine compounds may advantageously
be used, such as those prepared by reaction of alkylene dihalide with ammonia. Preferred
amines are aliphatic saturated amines, including, for example, 1,2-diaminoethane;
1,3-diaminopropane; 1,4-diaminobutane; 1,6-diaminohexane; polyethylene amines such
as diethylene triamine; triethylene tetramine; tetraethylene pentamine; and polypropyleneamines
such as 1,2-propylene diamine; and di-(1,2-propylene)triamine. Such polyamine mixtures,
known as PAM, are commercially available. Particularly preferred polyamine mixtures
are mixtures derived by distilling the light ends from PAM products. The resulting
mixtures, known as "heavy" PAM, or HPAM, are also commercially available. The properties
and attributes of both PAM and/or HPAM are described, for example, in
U.S. Patent Nos. 4,938,881;
4,927,551;
5,230,714;
5,241,003;
5,565,128;
5,756,431;
5,792,730; and
5,854,186.
[0082] Other useful amine compounds include: alicyclic diamines such as 1,4-di(aminomethyl)
cyclohexane and heterocyclic nitrogen compounds such as imidazolines. Another useful
class of amines is the polyamido and related amido-amines as disclosed in
U.S. Patent Nos. 4,857,217;
4,956,107;
4,963,275; and
5,229,022. Also usable is tris(hydroxymethyl)amino methane (TAM) as described in
U.S. Patent Nos. 4,102,798;
4,113,639;
4,116,876; and
UK 989,409. Dendrimers, star-like amines, and comb-structured amines may also be used. Similarly,
one may use condensed amines, as described in
U.S. Patent No. 5,053,152. The functionalized polymer is reacted with the amine compound using conventional
techniques as described, for example, in
U.S. Patent Nos. 4,234,435 and
5,229,022, as well as in
EP-A-208,560.
[0083] A preferred dispersant composition is one comprising at least one polyalkenyl succinimide,
which is the reaction product of a polyalkenyl substituted succinic anhydride (e.g.,
PIBSA) and a polyamine (PAM) that has a coupling ratio of from about 0.65 to about
1.25, preferably from about 0.8 to about 1.1, most preferably from about 0.9 to about
1. In the context of this disclosure, "coupling ratio" may be defined as a ratio of
the number of succinyl groups in the PIBSA to the number of primary amine groups in
the polyamine reactant.
[0084] Another class of high molecular weight ashless dispersants comprises Mannich base
condensation products. Generally, these products are prepared by condensing about
one mole of a long chain alkyl-substituted mono- or polyhydroxy benzene with about
1 to 2.5 moles of carbonyl compound(s) (e.g., formaldehyde and paraformaldehyde) and
about 0.5 to 2 moles of polyalkylene polyamine, as disclosed, for example, in
U.S. Patent No. 3,442,808. Such Mannich base condensation products may include a polymer product of a metallocene
catalyzed polymerization as a substituent on the benzene group, or may be reacted
with a compound containing such a polymer substituted on a succinic anhydride in a
manner similar to that described in
U.S. Patent No. 3,442,808. Examples of functionalized and/or derivatized olefin polymers synthesized using
metallocene catalyst systems are described in the publications identified
supra.
[0085] The dispersant(s) of the present invention are preferably non-polymeric (e.g., are
mono- or bis-succinimides).
[0086] Dispersant(s), particularly the lower molecular weight dispersants, may optionally
be borated. Such dispersants can be borated by conventional means, as generally taught
in
U.S. Patent Nos. 3,087,936,
3,254,025 and
5,430,105. Boration of the dispersant is readily accomplished by treating an acyl nitrogen-containing
dispersant with a boron compound such as boron oxide, boron halide boron acids, and
esters of boron acids, in an amount sufficient to provide from about 0.1 to about
20 atomic proportions of boron for each mole of acylated nitrogen composition. Borated
dispersants can be used to provide the lubricating oil compositions of the present
invention with all, or a portion, of the requisite amount of boron.
[0087] Dispersants derived from highly reactive polyisobutylene have been found to provide
lubricating oil compositions with a wear credit relative to a corresponding dispersant
derived from conventional polyisobutylene. This wear credit is of particular importance
in lubricants containing reduced levels of ash-containing antiwear agents, such as
ZDDP. Thus, in one preferred embodiment, at least one dispersant used in the lubricating
oil compositions of the present invention is derived from highly reactive polyisobutylene.
[0088] Non-dispersant/detergent boron sources are prepared by reacting a boron compound
with an oil-soluble or oil-dispersible additive or compound. Boron compounds include
boron oxide, boron oxide hydrate, boron trioxide, boron trifluoride, boron tribromide,
boron trichloride, boron acid such as boronic acid, boric acid, tetraboric acid and
metaboric acid, boron hydrides, boron amides and various esters of boron acids. Suitable
"non-dispersant boron sources" may comprise any oil-soluble, boron-containing compound,
but preferably comprise one or more boron-containing additives known to impart enhanced
properties to lubricating oil compositions. Such boron-containing additives include,
for example, borated dispersant VI improver; alkali metal, mixed alkali metal or alkaline
earth metal borate; borated overbased metal detergent; borated epoxide; borate ester;
and borate amide.
[0089] Alkali metal and alkaline earth metal borates are generally hydrated particulate
metal borates, which are known in the art. Alkali metal borates include mixed alkali
and alkaline earth metal borates. These metal borates are available commercially.
Representative patents describing suitable alkali metal and alkaline earth metal borates
and their methods of manufacture include
U.S. Patent Nos. 3,997,454;
3,819,521;
3,853.772;
3,907,601;
3,997,454; and
4,089,790.
[0090] The borated amines maybe prepared by reacting one or more of the above boron compounds
with one or more of fatty amines, e.g., an amine having from four to eighteen carbon
atoms. Borated amines may be prepared by reacting the amine with the boron compound
at a temperature of from 50 to 300, preferably from 100 to 250 °C and at a ratio from
3:1 to 1:3 equivalents of amine to equivalents of boron compound.
[0091] Borated fatty epoxides are generally the reaction product of one or more of the above
boron compounds with at least one epoxide. The epoxide is generally an aliphatic epoxide
having from 8 to 30, preferably from 10 to 24, more preferably from 12 to 20, carbon
atoms. Examples of useful aliphatic epoxides include heptyl epoxide and octyl epoxide.
Mixtures of epoxides may also be used, for instance commercial mixtures of epoxides
having from 14 to 16 carbon atoms and from 14 to 18 carbon atoms. The borated fatty
epoxides are generally known and are described in
U.S. Patent 4,584,115.
[0092] Borate esters may be prepared by reacting one or more of the above boron compounds
with one or more alcohol of suitable oleophilicity. Typically, the alcohol contains
from 6 to 30, or from 8 to 24, carbon atoms. Methods of making such borate esters
are known in the art.
[0093] The borate esters can be borated phospholipids. Such compounds, and processes for
making such compounds, are described in
EP-A-0 684 298. Borated overbased metal detergents are known in the art where the borate substitutes
the carbonate in the core either in part or in full.
[0094] Additional additives may be incorporated into the compositions of the invention to
enable particular performance requirements to be met. Examples of additives which
may be included in the lubricating oil compositions of the present invention are metal
rust inhibitors, viscosity index improvers, corrosion inhibitors, oxidation inhibitors,
friction modifiers, anti-foaming agents, anti-wear agents and pour point depressants.
Some are discussed in further detail below.
[0095] In addition to the dispersants described above, lubricating oil compositions, particularly
lubricating oil compositions for HDD engines, preferably include additives effective
in the dispersion of soot.
U.S. Published Patent Application 2006/0189492 A1 to Bera et al. discloses certain reaction products of acylating agents and oligomers having the
following structure:
where each Ar independently represents an aromatic moiety having 0 to 3 substituents
selected from alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, acyloxy, acyloxyalkyl,
aryloxy, aryloxy alkyl, halo and combinations thereof; each L is independently a linking
moiety comprising a carbon-carbon single bond or a linking group; each Y' is independently
a moiety of the formula Z(O(CR
2)
n)
yX-, where X is selected from (CR'
2)
z, O and S; R and R' are each independently selected from H, C
1 to C
6 alkyl and aryl; z is 1 to 10; n is 0 to 10 when X is (CR'
2)
z, and 2 to 10 when X is O or S; y is 1 to 30; Z is H, an acyl group, an alkyl group
or an aryl group; each a is independently 0 to 3, at least one Ar moiety bears at
least one group Y in which Z is not H; and m is 1 to 100. Such compounds are described
as useful soot dispersants (see also
U.S. Patent Nos. 6,495,496 and
6,750,183 and
U.S. Patent Application Serial No. 11/672,660).
[0096] Friction modifiers and fuel economy agents that are compatible with the other ingredients
of the final oil may also be included. Examples of such materials include glyceryl
monoesters of higher fatty acids, for example, glyceryl mono-oleate; esters of long
chain polycarboxylic acids with diols, for example, the butane diol ester of a dimerized
unsaturated fatty acid; oxazoline compounds; and alkoxylated alkyl-substituted mono-amines,
diamines and alkyl ether amines, for example, ethoxylated tallow amine and ethoxylated
tallow ether amine.
[0097] Other known friction modifiers comprise oil-soluble organo-molybdenum compounds.
Such organo-molybdenum friction modifiers also provide antioxidant and antiwear credits
to a lubricating oil composition. Examples of such oil soluble organo-molybdenum compounds
include dithiocarbamates, dithiophosphates, dithiophosphinates, xanthates, thioxanthates,
sulfides, and the like, and mixtures thereof. Particularly preferred are molybdenum
dithiocarbamates, dialkyldithiophosphates, alkyl xanthates and alkylthioxanthates.
[0098] Additionally, the molybdenum compound may be an acidic molybdenum compound. These
compounds will react with a basic nitrogen compound as measured by ASTM test D-664
or D-2896 titration procedure and are typically hexavalent. Included are molybdic
acid, ammonium molybdate, sodium molybdate, potassium molybdate, and other alkaline
metal molybdates and other molybdenum salts, e.g., hydrogen sodium molybdate, MoOCl
4, MoO
2Br
2, Mo
2O
3Cl
6, molybdenum trioxide or similar acidic molybdenum compounds.
[0099] Among the molybdenum compounds useful in the compositions of this invention are organo-molybdenum
compounds of the formula
Mo(ROCS
2)
4
and
Mo(RSCS
2)
4
wherein R is an organo group selected from the group consisting of alkyl, aryl, aralkyl
and alkoxyalkyl, generally of from 1 to 30 carbon atoms, and preferably 2 to 12 carbon
atoms and most preferably alkyl of 2 to 12 carbon atoms. Especially preferred are
the dialkyldithiocarbamates of molybdenum.
[0100] The molybdenum compounds described above, in addition to providing friction-reducing
properties, also provide antiwear credits and, therefore, molybdenum compounds have
been used in lubricating oil compositions formulated with reduced amounts of ZDDP.
When used in such reduced phosphorus lubricating oil compositions, molybdenum compounds
have been used in amounts introducing from about 10 to about 1000 ppm, such as 10
to about 350 ppm, or 10 to about 100 ppm of molybdenum (measured as atoms of molybdenum).
[0101] The viscosity index of the base stock is increased, or improved, by incorporating
therein certain polymeric materials that function as viscosity modifiers (VM) or viscosity
index improvers (VII). Generally, polymeric materials useful as viscosity modifiers
are those having number average molecular weights (Mn) of from about 5,000 to about
250,000, preferably from about 15,000 to about 200,000, more preferably from about
20,000 to about 150,000. These viscosity modifiers can be grafted with grafting materials
such as, for example, maleic anhydride, and the grafted material can be reacted with,
for example, amines, amides, nitrogen-containing heterocyclic compounds or alcohol,
to form multifunctional viscosity modifiers (dispersant-viscosity modifiers). Polymer
molecular weight, specifically M
n , can be determined by various known techniques. One convenient method is gel permeation
chromatography (GPC), which additionally provides molecular weight distribution information
(see
W. W. Yau, J. J. Kirkland and D. D. Bly, "Modern Size Exclusion Liquid Chromatography",
John Wiley and Sons, New York, 1979). Another useful method for determining molecular weight, particularly for lower
molecular weight polymers, is vapor pressure osmometry (see, e.g., ASTM D3592).
[0102] One class of diblock copolymers useful as viscosity modifiers has been found to provide
a wear credit relative to, for example, olefin copolymer viscosity modifiers. This
wear credit is of particular importance in lubricants containing reduced levels of
ash-containing antiwear agents, such as ZDDP. Thus, in one preferred embodiment, at
least one viscosity modifier used in the lubricating oil compositions of the present
invention is a linear diblock copolymer comprising one block derived primarily, preferably
predominantly, from vinyl aromatic hydrocarbon monomer, and one block derived primarily,
preferably predominantly, from diene monomer. Useful vinyl aromatic hydrocarbon monomers
include those containing from 8 to about 16 carbon atoms such as aryl-substituted
styrenes, alkoxy-substituted styrenes, vinyl naphthalene, alkyl-substituted vinyl
naphthalenes and the like. Dienes, or diolefins, contain two double bonds, commonly
located in conjugation in a 1,3 relationship. Olefins containing more than two double
bonds, sometimes referred to as polyenes, are also considered within the definition
of "diene" as used herein. Useful dienes include those containing from 4 to about
12 carbon atoms, preferably from 8 to about 16 carbon atoms, such as 1,3-butadiene,
isoprene, piperylene, methylpentadiene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene,
4,5-diethyl-1,3-octadiene, with 1,3-butadiene and isoprene being preferred.
[0103] As used herein in connection with polymer block composition, "predominantly" means
that the specified monomer or monomer type that is the principle component in that
polymer block is present in an amount of at least 85% by weight of the block.
[0104] Polymers prepared with diolefins will contain ethylenic unsaturation, and such polymers
are preferably hydrogenated. When the polymer is hydrogenated, the hydrogenation may
be accomplished using any of the techniques known in the prior art. For example, the
hydrogenation may be accomplished such that both ethylenic and aromatic unsaturation
is converted (saturated) using methods such as those taught, for example, in
U.S. Pat. Nos. 3,113,986 and
3,700,633 or the hydrogenation may be accomplished selectively such that a significant portion
of the ethylenic unsaturation is converted while little or no aromatic unsaturation
is converted as taught, for example, in
U.S. Pat. Nos. 3,634,595;
3,670,054;
3,700,633 and
Re 27,145. Any of these methods can also be used to hydrogenate polymers containing only ethylenic
unsaturation and which are free of aromatic unsaturation.
[0105] The block copolymers may include mixtures of linear diblock polymers as disclosed
above, having different molecular weights and/or different vinyl aromatic contents
as well as mixtures of linear block copolymers having different molecular weights
and/or different vinyl aromatic contents. The use of two or more different polymers
may be preferred to a single polymer depending on the rheological properties the product
is intended to impart when used to produce formulated engine oil. Examples of commercially
available styrene/hydrogenated isoprene linear diblock copolymers include Infineum
SV140™, Infineum SV150™ and Infineum SV160™, available from Infineum USA L.P. and
Infineum UK Ltd.; Lubrizol® 7318, available from The Lubrizol Corporation; and Septon
1001™ and Septon 1020™, available from Septon Company of America (Kuraray Group).
Suitable styrene/1, 3-butadiene hydrogenated block copolymers are sold under the tradename
Glissoviscal™ by BASF.
[0106] Pour point depressants (PPD), otherwise known as lube oil flow improvers (LOFIs)
lower the temperature. Compared to VM, LOFIs generally have a lower number average
molecular weight. Like VM, LOFIs can be grafted with grafting materials such as, for
example, maleic anhydride, and the grafted material can be reacted with, for example,
amines, amides, nitrogen-containing heterocyclic compounds or alcohol, to form multifunctional
additives.
[0107] In the present invention it may be necessary to include an additive which maintains
the stability of the viscosity of the blend. Thus, although polar group- containing
additives achieve a suitably low viscosity in the pre-blending stage it has been observed
that some compositions increase in viscosity when stored for prolonged periods. Additives
which are effective in controlling this viscosity increase include the long chain
hydrocarbons functionalized by reaction with mono- or dicarboxylic acids or anhydrides
which are used in the preparation of the ashless dispersants as hereinbefore disclosed.
In another preferred embodiment, the lubricating oil compositions of the present invention
contain an effective amount of a long chain hydrocarbons functionalized by reaction
with mono- or dicarboxylic acids or anhydrides.
[0108] When lubricating compositions contain one or more of the above-mentioned additives,
each additive is typically blended into the base oil in an amount that enables the
additive to provide its desired function. Representative effective amounts of such
additives, when used in crankcase lubricants, are listed below. All the values listed,
except for those referring to metal detergents, are stated as mass percent active
ingredient (A.I.).
ADDITIVE |
MASS % (Broad) |
MASS % (Preferred) |
Dispersant |
0.1 - 20 |
1-8 |
Metal Detergents |
0.1 - 15 |
0.2 - 9 |
Corrosion Inhibitor |
0 - 5 |
0 - 1.5 |
Metal Dihydrocarbyl Dithiophosphate |
0.1 - 6 |
0.1 - 4 |
Antioxidant |
0 - 5 |
0.01 - 2.5 |
Pour Point Depressant |
0.01 - 5 |
0.01 - 1.5 |
Antifoaming Agent |
0 - 5 |
0.001 - 0.15 |
Supplemental Antiwear Agents |
0 - 1.0 |
0 - 0.5 |
Friction Modifier |
0 - 5 |
0 - 1.5 |
Viscosity Modifier |
0.01 - 10 |
0.25 - 3 |
Base stock |
Balance |
Balance |
[0109] Preferably, the Noack volatility of the fully formulated lubricating oil composition
(oil of lubricating viscosity plus all additives) will be no greater than 20 mass
%, such as no greater than 15 mass %, preferably no greater than 13 mass %.
[0110] It may be desirable, although not essential to prepare one or more additive concentrates
comprising additives (concentrates sometimes being referred to as additive packages)
whereby several additives can be added simultaneously to the oil to form the lubricating
oil composition.
[0111] The final composition may employ from 5 to 25 mass %, preferably 5 to 22 mass %,
typically 10 to 20 mass % of the concentrate, the remainder being oil of lubricating
viscosity.
[0112] As used herein, the terms phosphorus content, boron content, molybdenum content,
magnesium content, calcium content, etc. refer to the content as measured by ASTM
D5185; and sulfated ash content refers to the content as measured by ASTM D874.
[0113] This invention will be further understood by reference to the following examples,
wherein all parts are parts by mass, unless otherwise noted and which include preferred
embodiments of the invention.
EXAMPLES
[0114] A SAE SW40 grade lubricants containing base stock, dispersant (combination of borated
dispersant and non-borated dispersant), detergent (a combination of calcium phenate,
calcium sulfonate and magnesium sulfonate detergents), ZDDP, soot dispersant, a combination
of ashless, sulfur-free phenolic and aminic antioxidants (0.7 mass % total), a molybdenum
dithiocarbamate compound, viscosity modifier, pour point depressant and 1 mass % of
950 Mn polybutene (PIB) was formulated consistent with API CJ-4 and CI-4 specifications
(1.0 mass % SASH; 0.4 mass % sulfur and 0.12 mass % phosphorus) in a blend of 4 and
6 cSt. Group III base stocks. The resulting oil had a boron content of 65 ppm, a magnesium
content of 1156 ppm, a molybdenum content of 44 ppm and a TBN of 9.9; 79 % of the
TBN contributed by overbased detergent (52% of the TBN of the composition), was provided
by the overbased magnesium detergents.
[0115] Valve train wear resulting from the use of the above lubricant was measured in a
Cummins ISB engine test; one of the engine tests for the API CJ-4/CI-4
specifications for HDD lubricants. The ISB engine test includes two stages. Stage
1 runs for 100 hours to produce soot in the oil. Stage 2 is a 250 hour cyclic portion,
intended to produce heavy load on the engine in short bursts. At the end of the test,
the valve train parts are measured for wear, reported as tappet weight loss, in milligrams,
and camshaft lobe wear, in microns.
[0116] The results achieved with the exemplified oil are shown in Table 2.
Table 2
Oil |
Oil 1 |
Passing Limit |
Grade |
5W40 |
|
Tappet Weight Loss (mg.) |
85 |
100 max |
Cam Shaft Lobe Wear, Snap Gauge (µm) |
43 |
55 max |
[0117] As shown, Oil 1, a 5W40 grade lubricant formulated with all Group III base stock
and having a phosphorus content of less than 1200 ppm, was able to meet the wear performance
requirements of the API CJ-4/CI-4 specifications.
[0118] The disclosures of all patents, articles and other materials described herein are
hereby incorporated, in their entirety, into this specification by reference.
Compositions described as "comprising" a plurality of defined components are to be
construed as including compositions formed by admixing the defined plurality of defined
components. The principles, preferred embodiments and modes of operation of the present
invention have been described in the foregoing specification. What applicants submit
is their invention, however, is not to be construed as limited to the particular embodiments
disclosed, since the disclosed embodiments are regarded as illustrative rather than
limiting. Changes may be made by those skilled in the art without departing from the
spirit of the invention.