Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: HYDROXYCHROMAN DERIVATIVES AS ENGINE OIL
ANTIOXIDANTS
FIELD OF THE INVENTION
[0001] This invention relates to compositions suitable for use as
lubricants and
lubricant additive compositions which contain a hydroxychroman derived
antioxidant, where said antioxidants themselves may also be described
hydroxychroman compounds, and further optionally containing other additives
suitable for lubricants such as a detergent or a dispersant. The present
invention
provides an economical antioxidant which has good performance properties when
used in lubricant formulations especially for heavy duty diesel engines and
passenger car crankcase engines.
BACKGROUND OF THE INVENTION
[0002] Antioxidants are an important class of additives since they are
used to
provide and/or improve the anti-oxidation performance of organic compositions,
including lubricant compositions that contain organic components, by
preventing or
retarding oxidative and thermal decomposition. Antioxidants in some
applications
can result in an increase in volatility which can be undesirable due to
required
environmental regulations and/or performance standards.
[0003] It is known to use a hindered, ester-substituted phenol
antioxidant in an
oil of lubricating viscosity to reduce oxidation breakdown and improve
cleanliness.
[0004] U.S. Patent 5,523,007, Kristen et al., June 4, 1996, discloses a
lubricant
oil composition comprising a diesel engine lubricating oil and, as
antioxidant, a
compound of the formula
(H3C)3C
HO 0 X
(H3C)3C
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X can be ¨CH2¨CH2¨C(=0)¨OR and R is a straight chain or branched alkyl radical
of the formula ¨CnH2n+1 wherein n is an integer from 8 to 22.
[0005] U.S. Patent 3,285,855, Dexter et al., November 15, 1966, discloses
stabilization of organic material with esters containing an alkylhydroxyphenyl
group. The ester can have the structure
(lower)alkyl
(I?
HO (C),H2x)¨C¨ 0¨CyH2y)¨ H
(lower)alkyl
in which x has a value of from 0 to 6, inclusively, and y has a value of from
6 to 30,
inclusively. The "lower alkyl" groups can be t-butyl. Organic materials which
can
be stabilized include, among many others, lubricating oil of the aliphatic
ester type,
and mineral oil.
[0006] U.S. Patent 5,206,414, Evans et al., April 27, 1993, discloses a
process
for the preparation of compounds of the general formula
R1 R3
0
[HI 0 CrnHar,--C-]--A
R2
wherein R1 and R2 are identical or different and are hydrogen, C1-C18 alkyl,
phenyl, C1-C4 alkyl-substituted phenyl, C7-C9 phenylalkyl, C5-C12 cycloalkyl
or
C1-C4 alkyl-substituted C5-C12 cycloalkyl, R3 is hydrogen or methyl, m is
0,1,2, or
3 and n is a number from 1 to 4 or 6, and A can be ¨0R4 where R4 can be C2-C45
alkyl.
[0007] U.S. Patent No. 6,559,105 of Abraham et al. involves lubricant
compositions containing ester-substituted hindered phenol antioxidants.
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t-alkyl
0
HO
CH2CH2COR3
1-alkyl
wherein R3 is an alkyl group containing 2 to 6 carbon atoms, and a dispersant
or a
detergent, is a useful additive package for lubricant compositions.
[0008] U.S Patent 6,787,663, Adams et al., September 7, 2004 discloses a
process for the preparation of a hindered ester-substituted phenol and its use
in a
lubricant composition of the general formula
t-alkyl
HO
CH2CH2COR3
t-alkyl
wherein R3 is an alkyl group containing 2 to 6 carbon atoms.
[0009] While materials such as the hindered phenols described above can
provide good anti-oxidant performance in lubricating oils, their performance
generally suffers at elevated temperatures. Increasingly, current engine
technology
is leading to increasing operating temperatures for engines and the
lubricating oils
on which they rely. For example, modern EGR, turbochargers, and the increased
usage of smaller, more powerful and fuel efficient engines are leading to an
increase
in average engine operating temperatures. Therefore, there is a need for new
antioxidant technology that provides at least as good performance as known
antioxidant technology while also providing improved thermal stability and/or
performance at elevated temperatures.
SUMMARY OF THE INVENTION
100101 The present invention provides for a lubricating composition
containing
an oil of lubricating viscosity and an antioxidant having the formula:
3
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R1 R2 R2
R2
HO elII
R2
R2
R1 0
R2
R1 (I)
wherein each RI- is independently -0R2, -NH,, -
NR2R2, _sR2 or ¨R2;
each R2 is
independently a hydrogen, a hydrocarbyl group, or a ¨C(=0)-X-R3 group where X
is
0, NR3 or S and each R3 is independently a hydrogen or a hydrocarbyl group;
and n
is 0 or 1; and where the two adjacent RI- oups are hydrocarbyl groups, they
may be
linked to form a ring.
[0011] In some embodiments each RI- in the formula above is independently
a
hydrogen or hydrocarbyl group containing from 1 to 20 carbon atoms and each R2
is
independently a hydrogen or hydrocarbyl group containing from 1 to 15 carbon
atoms. In embodiments where one or more R3 groups is present the R3 group may
be a hydrocarbyl group containing from 3 to 22 carbon atoms, or from 8 to 18
carbon atoms, or may be a 2-ethyl or isotridecyl group.
[0012] The invention further provides for lubricant compositions
containing an
antioxidant with the following formula:
R2 R2
HO ill
R2
IR1 0
R2 (H)
wherein RI is hydrocarbyl group containing from 1 to 10 carbon atoms; and each
R2
is independently a hydrogen or hydrocarbyl group containing from 1 to 10
carbon
atoms. Each R2 in formula 11 may also be a ¨C(=0)-X-R3 group where X is 0, NR3
or S and each R3 is independently a hydrogen or a hydrocarbyl group.
[0013] The invention further provides for lubricant compositions as
described
above where the composition contains no more than 1200 ppm phosphorus, has a
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sulfur content of no more than 0.4 percent by weight, has a sulfated ash
content of
no more than 1.0 percent by weight, has a zinc dialkyldithiophosphatc at a
level of
no less than 300 ppm, or any combinations thereof. In some embodiments the
composition may have a phosphorus level of at least 300 ppm.
[0014] The invention further provides for methods of lubricating an
internal
combustion engine. Such methods include the step of supplying to the engine
any of
the lubricant compositions described herein.
[0015] The invention further provides a lubricant composition suitable
for
lubricating an internal combustion engine, comprising: (A) a major amount of
an oil
of lubricating viscosity; (B) a minor amount of at least one hydroxychroman
antioxidant, as described herein; and (C) a minor amount of at least one other
additive selected from the group consisting of viscosity modifiers, pour point
depressants, dispersants, detergents, antiwear agents, antioxidants are
different from
component (B), friction modifiers, corrosion inhibitors, seal swell agents,
metal
deactivators, foam inhibitors, and mixtures thereof.
[0016] The invention further provides for a lubricant concentrate
suitable for use
in preparing a lubricating composition suitable for lubricating an internal
combustion engine, comprising: (A) a concentrate-forming amount of an oil of
lubricating viscosity; (B) a minor amount of at least one hydroxychroman
antioxidant, as described herein; and (C) at least one other additive selected
from the
group consisting of viscosity modifiers, pour point depressants, dispersants,
detergents, antiwear agents, antioxidants that are different from component
(B),
friction modifiers, corrosion inhibitors, seal swell agents, metal
deactivators, foam
inhibitors, and mixtures thereof.
[0017] The present invention further provides a method for lubricating an
internal combustion engine, comprising: (A) supplying to said engine a
lubricant
comprising: (i) an oil of lubricating viscosity; (ii) a minor amount of at
least one
hydroxychroman antioxidant, as described herein; and (iii) a minor amount of
at
least one other additive selected from the group consisting of viscosity
modifiers,
pour point depressants, dispersants, detergents, antiwear agents, antioxidants
that are
different from component (ii), friction modifiers, corrosion inhibitors, seal
swell
agents, metal deactivators, foam inhibitors, and mixtures thereof
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DETAILED DESCRIPTION OF THE INVENTION
[0018] Various
preferred features and embodiments will be described below by
way of non-limiting illustration.
[0019] The present
invention provides various compositions that comprise one
or more hydroxychroman derived antioxidants, wherein said antioxidants may
themselves also be described as hydroxychroman compounds, and methods of
lubricating internal combustion engines utilizing such antioxidants. Such
antioxidants have been discovered to provide superior performance in the
harsher
operating conditions becoming more and more common in modern engine
technology. The drive to design smaller and more powerful engines along with
the
drive to increase fuel economy and reduce emissions, has led to higher demands
on
lubricants and lubricant additive technology. The antioxidants of the present
invention have been found to provide superior performance compared to
conventional antioxidants.
[0020] The compositions of the present invention comprise an oil of
lubricant
viscosity, one or more hydroxychroman derived antioxidants, and optionally one
or
more additional performance additives.
[0021] The lubricant
composition of this invention can find use in various
applications to include as a lubricant composition for an internal combustion
engine
to include a gasoline or spark-ignited engine such as a passenger car engine,
a diesel
or compression-ignited engine such as a heavy duty diesel truck engine, a
natural
gas fueled engine such as a stationary power engine, a two-cycle engine,
aviation
piston and turbine engines, marine and railroad diesel engines; for power
transmissions such as an automatic or transaxle or farm tractor transmission;
for
gears such as industrial or automotive gears; for metalworking; for hydraulic
systems; for special applications such as bearings which can require that the
lubricant composition be a grease; and for hydrocarbon fuels for an internal
combustion engine such as a gasoline or diesel fuel.
Oil of Lubricating Viscosity
[0022] The lubricant composition of the present invention can comprise (A)
a
major amount of an oil of lubricating viscosity. The oil of lubricating
viscosity can
function by providing lubrication and by serving as a medium to dissolve or
disperse
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the other components or additives of the lubricant composition. The oil of
lubricating viscosity can be a single oil or a mixture of two or more oils.
The
lubricating oil composition comprises of one or more base oils which are
generally
present in a major amount (i.e. an amount greater than 50 percent by weight).
Generally, the base oil is present in an amount greater than 60 percent, or
greater
than 70 percent, or greater than 80 percent by weight of the lubricating oil
composition. In one embodiment the base oil sulfur content can be 0.001 to 0.2
percent by weight, in another embodiment 0.0001 to 0.1 or 0.05 percent by
weight.
[0023] The lubricating oil composition may have a kinematic viscosity as
measured in ASTM D445, of up to about 16.3 mm2/s at 100 C, and in one
embodiment 5 to 16.3 mm2/s (cSt) at 100 C, and in one embodiment 6 to 13 mm2/s
(cSt) at 100 C. In one embodiment, the lubricating oil composition has an SAE
Viscosity Grade of OW, OW-20, OW-30, OW-40, 0W-50, OW-60, 5W, 5W-20, 5W-
30, 5W-40, 5W-50, 5W-60, 10W, 10W-20, 10W-30, 10W-40 or 10W-50.
[0024] The lubricating oil composition may have a high-temperature/high-
shear
viscosity at 150 C as measured by the procedure in ASTM D4683 of up to 4 mm2/s
(cSt), and in one embodiment up to 3.7 mm2/s (cSt), and in one embodiment 2 to
4
mm2/s (cSt), and in one embodiment 2.2 to 3.7 mm2/s (cSt), and in one
embodiment
2.7 to 3.5 mm2/s (cSt).
[0025] The base oil used in the lubricant composition may be a natural oil,
synthetic oil or mixture thereof, provided the sulfur content of such oil does
not
exceed the above-indicated sulfur concentration limit required for the
inventive low-
sulfur, low-phosphorus, low-ash lubricating oil composition. The natural oils
that
are useful include animal oils and vegetable oils (e.g., castor oil, lard oil)
as well as
mineral lubricating oils such as liquid petroleum oils and solvent treated or
acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed
par-
affinic-naphthenic types. Oils derived from coal or shale are also useful.
Synthetic
lubricating oils include hydrocarbon oils such as polymerized and
interpolymerized
olefins (e.g., polybutylenes, polypropylenes, and propylene isobutylene copoly-
mers); poly(1-hexenes), poly-(1-octenes), poly(1-decenes), etc. and mixtures
thereof; allcylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes,
dinonylbenzenes,
and di-(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls, terphenyls,
alkylated
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polyphenyls); alkylated diphenyl ethers and the derivatives, analogs and
homologs
thereof.
[0026] Alkylene oxide polymers and interpolymers and derivatives thereof
where the terminal hydroxyl groups have been modified by e.g., esterification,
etherification, constitute another class of known synthetic lubricating oils
that can be
used. These are exemplified by the oils prepared through polymerization of
ethylene
oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene
polymers (e.g., methyl-polypropylene glycol ether having an average molecular
weight of about 1000, diphenyl ether of polyethylene glycol having a molecular
weight of about 500-1000, diethyl ether of polypropylene glycol having a
molecular
weight of about 1000-1500, etc.) or mono- and polycarboxylic esters thereof,
for
example, the acetic acid esters, mixed C3-C8 fatty acid esters, or the
carboxylic acid
diester of tetraethylene glycol.
[0027] Another suitable class of synthetic lubricating oils that can be
used
comprises the esters of dicarboxylic acids (e.g., phthalic acid, succinic
acid, alkyl
succinic acids, alkenyl succinic acids, maleic acid, azelaic acid, suberic
acid, sebacic
acid, fumaric acid, adipic acid, linoleic acid dimer, dodecanedioic acid) with
a
variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-
ethylhexyl
alcohol, ethylene glycol, diethylene glycol monoether and propylene glycol)
Specific examples of these esters include 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.
[0028] Esters useful as synthetic oils also include those made from C5 to
C12
monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol,
trimethylol propane, pentaerythritol, dipentaerythritol and
tripentaerythritol.
[0029] The oil can be a poly-alpha-olefin (PAO). Typically, the PAOs are
derived from monomers having from 4 to 30, or from 4 to 20, or from 6 to 16
carbon
atoms. Examples of useful PAOs include those derived from octene, decene and
mixtures thereof. These PAOs may have a viscosity from 2 to 15, or from 3 to
12,
or from 4 to 8 mm2/s (cSt), at 100 C. Examples of useful PAOs include 4 mm2/s
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(cSt) at 100 C poly-alpha-olefins, 6 mm2/s (cSt) at 100 C poly-alpha-olefins,
and
mixtures thereof. Mixtures of mineral oil with one or more of the foregoing
PAOs
may be used.
[0030] Unrefined, refined and rerefined oils, either natural or synthetic
(as well
as mixtures of two or more of any of these) of the type disclosed hereinabove
can be
used in the lubricants of the present invention. Unrefined oils are those
obtained
directly from a natural or synthetic source without further purification
treatment.
For example, a shale oil obtained directly from retorting operations, a
petroleum oil
obtained directly from primary distillation or ester oil obtained directly
from an
esterification process and used without further treatment would be an
unrefined oil.
Refined oils are similar to the unrefined oils except they have been further
treated in
one or more purification steps to improve one or more properties. Many such
purification techniques are known to those skilled in the art such as solvent
extraction, secondary distillation, acid or base extraction, filtration,
percolation, etc.
Rerefined oils are obtained by processes similar to those used to obtain
refined oils
applied to refined oils which have been already used in service. Such
rerefined oils
are also known as reclaimed or reprocessed oils and often are additionally
processed
by techniques directed to removal of spent additives and oil breakdown
products.
[0031] Additionally, synthetic oils may be produced by Fischer-Tropsch
gas to
liquid synthetic procedure as well as other gas-to-liquid oils. In one
embodiment the
polymer composition of the present invention is useful when employed in a gas-
to-
liquid oil. Often Fischer-Tropsch hydrocarbons or waxes may be
hydroisomerised.
Hydroxychroman Derived Antioxidant
[0032] The antioxidant additives of the present invention are derived
from
hydroxychroman. As provided above, suitable antioxidants can be represented by
the formula:
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R1 R2 R2
R2
HO
R2
II
R2
R1 0
R2
R1 (I)
wherein each RI- is independently -0R2, -NH,, -
NR2R2, _sR2 or ¨R2;
each R2 is
independently a hydrogen, a hydrocarbyl group, or a ¨C(=0)-X-R3 group where X
is
0, NR3 or S and each R3 is independently a hydrogen or a hydrocarbyl group;
and n
is 0 or 1; and where the two adjacent RI- oups are hydrocarbyl groups, they
may be
linked to form a ring. In some embodiments each R1 is independently hydrogen
or a
hydrocarbyl group.
[0033] The antioxidant may be chromanol having a hydroxy group located on
the aromatic ring, i.e. as 6-chromanol. In such embodiments the antioxidant
may be
represented by the formula:
R1 R2 R2
HO
R2
R1 0
R2
R1 (Ia)
wherein each RI- is independently -0R2, -NH2, -NR2R2, _sR2 or ¨R2;
each R2 is
independently a hydrogen or hydrocarbyl group; and where the two adjacent R1
groups are hydrocarbyl groups, they may be linked to form a ring. In some
embodiments each Rl is independently hydrogen or a hydrocarbyl group. Any of
the R2 groups in formula Ia may also be a ¨C(=0)-X-R3 group where X is 0, NR3
or
S and each R3 is independently a hydrogen or a hydrocarbyl group.
[0034] Specific examples of suitable antioxidants include 2,3-
dihydrobenzofuranol having a hydroxy group located on the aromatic ring. In
such
embodiments the antioxidant may be represented by the formula:
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R1
R2
HO
R2
R2
R1 0
R2
R1 (Ib)
wherein each RI- is independently -0R2, -NH2, -NR2R2, _sR2 or ¨R2;
each R2 is
independently a hydrogen or hydrocarbyl group; and where the two adjacent RI-
groups are hydrocarbyl groups, they may be linked to form a ring. In some
embodiments each RI- is independently hydrogen or a hydrocarbyl group. Any of
the R2 groups in formula lb may also be a ¨C(=0)-X-R3 group where X is 0, NR3
or
S and each R3 is independently a hydrogen or a hydrocarbyl group.
[0035] In some embodiments, considering any of the formulas provided
above:
(i) at least one RI- group of the antioxidant is a hydrocarbyl group, (ii) at
least one R2
group of the antioxidant is a hydrocarbyl group, or (iii) combinations
thereof.
[0036] In still further embodiments, at least one of the Rl groups
adjacent to the
hydroxy group is a hydrocarbyl group.
[0037] In other embodiments, considering any of the formulas provided
above,
each Rl may be independently a hydrogen or hydrocarbyl group containing from 1
to 20 carbon atoms and each R2 may be independently a hydrogen or hydrocarbyl
group containing from 1 to 15 carbon atoms.
[0038] In some embodiments the antioxidant used in the compositions of
the
present invention may be represented by the following formula:
R2 R2
HO elR2
R1 0
R2 (To
wherein R1 is _0R2, _NH2, _NR2R2, _sR2 or --K2;
and each R2 is independently a
hydrogen or hydrocarbyl group. In some embodiments R1 is independently
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hydrogen or a hydrocarbyl group. In some embodiments, RI- is a hydrocarbyl
group
containing from 1 to 10 carbon atoms and each R2 is independently a hydrogen
or
hydrocarbyl group containing from 1 to 10 carbon atoms. Any of the R2 groups
in
formula Ic may also be a ¨C(=0)-X-R3 group where X is 0, NR3 or S and each R3
is
independently a hydrogen or a hydrocarbyl group.
[0039] In still other embodiments the antioxidant used in the
compositions of the
present invention may be represented by the following formula:
R1 R3
HO R2 ill
R4 0
R2
R1 (Id)
wherein Ri is _ow., _NR2R2; _sR2 or ¨R2;
each R2 is independently a
hydrogen or hydrocarbyl group; R3 is hydrogen or hydrocarbyl group; and R4 is
a
hydrogen or hydrocarbyl group. In some embodiments R1 is independently
hydrogen or a hydrocarbyl group. In some embodiments, RI- is a hydrocarbyl
group
containing from 1 to 10 carbon atoms and each R2 is independently a hydrogen
or
hydrocarbyl group containing from 1 to 10 carbon atoms. In some embodiments R3
is a linear alkyl group containing from 1 to 10 carbon atoms. In some
embodiments
R3 is a methyl group. In still other embodiments, where R3 is a methyl group,
both
R2 groups are methyl groups, all RI groups are hydrogen and R4 is a branched
alkyl
group containing from 1 to 10 carbon atoms, or even from 3 to 10 or 8 carbon
atoms.
In some embodiments R4 is a tert-butyl group. Any of the R2 groups in formula
Id
may also be a ¨C(=0)-X-R3 group where X is 0, NR3 or S and each R3 is
independently a hydrogen or a hydrocarbyl group.
[0040] The antioxidant (B) can be present on a weight basis in the
lubricant
composition of this invention at 0.1 to 10%, 0.3 to 8%, or 0.6 to 6%.
Additional Additives
100411 The lubricant composition of the invention can optionally comprise
(C) a
minor amount of at least one other additive. The other additive (C) can
comprise a
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member selected from the group consisting of a viscosity modifier, a pour
point
depressant, a dispersant, a detergent, an antiwear agent, an antioxidant that
is
different from component (B), a friction modifier, a corrosion inhibitor, a
seal swell
agent, a metal deactivator, a foam inhibitor, and a mixture thereof. The
mixture of
other additives can be 2 or more additives of the same type such as for
example a
sulfonate and phenate detergent, 2 or more additives of different types such
as for
example a detergent and dispersant and antiwear agent, or 2 or more additives
of the
same type as well as 2 or more additives of different types such as for
example a
sulfonate and phenate detergent and a dispersant and an antiwear agent.
[0042] The lubricant composition of the present invention may contain one
or
more dispersants. Carboxylic dispersants are reaction products of carboxylic
acylating agents (acids, anhydrides, esters, etc.) containing at least 34 and
preferably
at least 54 carbon atoms which are reacted with nitrogen containing compounds
(such as amines), organic hydroxy compounds (such as aliphatic compounds
including monohydric and polyhydric alcohols, or aromatic compounds including
phenols and naphthols), and/or basic inorganic materials. These reaction
products
include imide, amide, and ester reaction products of carboxylic ester
dispersants.
[0043] Succinimide dispersants are a species of carboxylic dispersants.
They are
the reaction product of a hydrocarbyl substituted succinic acylating agent
with an
organic hydroxy compound or, an amine containing at least one hydrogen
attached
to a nitrogen atom, or a mixture of said hydroxy compound and amine. The term
"succinic acylating agent" refers to a hydrocarbon-substituted succinic acid
or
succinic acid-producing compound (which term also encompasses the acid
itself).
Such materials typically include hydrocarbyl-substituted succinic acids,
anhydrides,
esters (including half esters) and halides.
[0044] Succinic based dispersants have a wide variety of chemical
structures
including typically structures such as
0
R1
N4R2-N-I-R2-N
0
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[0045] In the above structure, each RI is independently a hydrocarbyl
group,
such as a polyolefin-derived group having an Mr, of 500 or 700 to 10,000.
Typically the hydrocarbon based group is an alkyl group, frequently a
polyisobutylene group derived from polyisobutylene having a molecular weight
of
500 or 700 to 5000, or alternatively 1500 or 2000 to 5000. Alternatively
expressed,
the RI groups can contain 40 to 500 carbon atoms, for instance at least 50,
e.g., 50 to
300 carbon atoms, such as aliphatic carbon atoms. The R2 are alkylene groups,
commonly ethylene (C2F14) groups. X is an integer and is not overly limited.
In
some embodiments X has the value within the range of zero, 1 or even 2 up to
10, or
6 or 4. Such molecules are commonly derived from reaction of an alkenyl
acylating
agent with a polyamine, and a wide variety of linkages between the two
moieties is
possible beside the simple imide structure shown above, including a variety of
amides and quaternary ammonium salts. Succinimide dispersants are more fully
described in U.S. Patents 4,234,435, 3,172,892 and 6,165,235.
[0046] Additional details and examples of the procedures for preparing
the
succinimide dispersants of the present invention are included in, for example,
U.S.
Pat. Nos. 3,172,892, 3,219,666, 3,272,746, 4,234,435, 6,440,905 and 6,165,235.
[0047] "Amine dispersants" are reaction products of relatively high
molecular
weight aliphatic halides and amines, preferably polyalkylene polyamines.
Examples
thereof are described, for example, in the following U.S. Patents: 3,275,554,
3,438,757, 3,454,555, and 3,565,804.
[0048] "Mannich dispersants" are the reaction products of alkyl phenols
in
which the alkyl group contains at least 30 carbon atoms with aldehydes
(especially
formaldehyde) and amines (especially polyalkylene polyamines). The materials
described in the following U.S. Patents are illustrative: 3,036,003,
3,236,770,
3,414,347, 3,448,047, 3,461,172, 3,539,633, 3,586,629, 3,591,598, 3,634,515,
3,725,480, 3,726,882, and 3,980,569.
[0049] Post-treated dispersants are obtained by reacting carboxylic,
amine or
Mannich dispersants with reagents such as dimercaptothiadiazoles, urea,
thiourea,
carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-
substituted
succinic anhydrides, nitriles epoxides, boron compounds, phosphorus compounds
or
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the like. Exemplary materials of this kind are described in the following U.S.
Patents: 3,200,107, 3,282,955, 3,367,943, 3,513,093, 3,639,242, 3,649,659,
3,442,808, 3,455,832, 3,579,450, 3,600,372, 3,702,757, and 3,708,422.
[0050] Polymeric dispersants are interpolymers of oil-solubilizing
monomers
such as decyl methacrylate, vinyl decyl ether and high molecular weight
olefins with
monomers containing polar substituents, e.g., aminoalkyl acrylates or
acrylamides
and poly-(oxyethylene)-substituted acrylates. Examples of polymer dispersants
thereof are disclosed in the following U.S. Patents: 3,329,658, 3449,250,
3,519,656,
3,666,730, 3,687,849, and 3,702,300.
[0051] The composition can also contain one or more detergents, which are
normally salts, and specifically overbased salts. Such overbased materials are
well
known to those skilled in the art. Patents describing techniques for making
basic
salts of sulfonic acids, carboxylic acids, (hydrocarbyl-substituted) phenols,
phosphonic acids, and mixtures of any two or more of these include U.S.
Patents
2,501,731; 2,616,905; 2,616,911; 2,616,925; 2,777,874; 3,256,186; 3,384,585;
3,365,396; 3,320,162; 3,318,809; 3,488,284; and 3,629,109. Overbased
materials,
otherwise referred to as overbased or superbased salts, are generally single
phase,
homogeneous Newtonian systems characterized by an amount of excess metal that
which would be necessary for neutralization according to the stoichiometry of
the
metal and the particular acidic organic compound reacted with the metal. The
amount of excess metal is commonly expressed in terms of substrate to metal
ratio.
The term "substrate to metal ratio" is the ratio of the total equivalents of
the metal to
the equivalents of the substrate. A more detailed description of the term
metal ratio
is provided in "Chemistry and Technology of Lubricants", Second Edition,
Edited
by R. M. Mortier and S. T. Orszulik, pages 85 and 86, 1997. The overbased
alkali
or alkaline earth metal detergents suitable for use in the present invention
may have
a metal ratio of 0.8 to 10 or 3 to 9, or 4 to 8, or 5 to 7. The detergents may
be
overbased with calcium hydroxide. In different embodiments the alkali or
alkaline
earth metal detergents may have a total base number (TBN) of 30 or 50 to 400;
or
200 to 350; or 220 to 300, and in another embodiment 255. In other embodiments
the detergent has a TBN in the range of 30, 40 or 50 to 220, 205, or 190, and
in
another embodiment 150. In still other embodiments the detergent has a TBN of
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300 or more, 350 or more, or 400 or more, or from 300 or 350 to 400, and in
another
embodiment 395.
[0052] In one
embodiment the lubricant of the present invention can contain an
overbased sulfonate detergent. Suitable sulfonic acids include sulfonic and
thio-
sulfonic acids. Sulfonic acids include the mono- or polynuclear aromatic or
cyclo-
aliphatic compounds. Oil-soluble sulfonates can be represented for the most
part by
one of the following formulas: R2-T-(S01 )a. and R1-(S01 )b, where T is a
cyclic
nucleus such as typically benzene; R2 is an aliphatic group such as alkyl,
alkenyl,
alkoxy, or alkoxyalkyl; (R2)+T typically contains a total of at least about 15
carbon
atoms; and R3 is an aliphatic hydrocarbon based group typically containing at
least
carbon atoms. Examples of RI
are alkyl, alkenyl, alkoxyalkyl, and
carboalkoxyalkyl groups. The groups T, R2, and R3 in the above formulas can
also
contain other inorganic or organic substituents in addition to those
enumerated
above such as, for example, hydroxy, mercapto, halogen, nitro, amino, nitroso,
15 sulfide, or disulfide. In the above formulas, a and b are at least 1.
[0053] Another
overbased material which can be present is an overbased
phenate detergent. The phenols
useful in making phenate detergents can be
represented by the formula (R1)a-Ar-(OH)b, wherein R1 is defined above; Ar is
an
aromatic group (which can be a benzene group or another aromatic group such as
naphthalene); a and b are independently numbers of at least one, the sum of a
and b
being in the range of two up to the number of displaceable hydrogens on the
aro-
matic nucleus or nuclei of Ar. In one embodiment, a and b are independently
numbers in the range of 1 to 4, or 1 to 2. R1 and a are typically such that
there is an
average of at least 8 aliphatic carbon atoms provided by the R1 groups for
each
phenol compound. Phenate detergents are also sometimes provided as sulfur-
bridged species.
[0054] In one
embodiment, the overbased material is an overbased detergent
selected from the group consisting of overbased salixaratc detergents,
overbased
saligenin detergents, overbased salicylate detergents, and overbased
glyoxylate
detergents, and mixtures thereof. Overbased saligenin detergents are commonly
overbased magnesium salts which are based on saligenin derivatives. A general
example of such a saligenin derivative can be represented by the formula
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OM OM
________________________________________________ mX
Y\
Rip RI p
wherein X comprises -CHO or -CH2OH, Y comprises -CH2- or -CH2OCH2-, and
wherein such -CHO groups typically comprise at least 10 mole percent of the X
and
Y groups; M is hydrogen, ammonium, or a valence of a metal ion, RI is a
hydrocarbon based group containing 1 to 60 carbon atoms, m is 0 to typically
10,
and each p is independently 0, 1, 2, or 3, provided that at least one aromatic
ring
contains an RI- substituent and that the total number of carbon atoms in all
R1 groups
is at least 7. When m is 1 or greater, one of the X groups can be hydrogen. In
one
embodiment, M is an equivalent of a Mg ion or a mixture of Mg and hydrogen
(and
so in some embodiments can be less than a full Mg ion and/or include a partial
Mg
ion). Other metals include alkali metals such as lithium, sodium, or
potassium;
alkaline earth metals such as calcium or barium; and other metals such as
copper,
zinc, and tin.
[0055] As used herein, the expression "represented by the formula"
indicates
that the formula presented is generally representative of the structure of the
chemical
in question. However, it is well known that minor variations can occur,
including in
particular positional isomerization, that is, location of the X, Y, and R
groups at
different position on the aromatic ring from those shown in the structure. The
expression "represented by the formula" is expressly intended to encompass
such
variations.
[0056] Saligenin detergents are disclosed in greater detail in U.S.
Patent
6,310,009, with special reference to their methods of synthesis (Column 8 and
Example 1) and preferred amounts of the various species of X and Y (Column 6).
[0057] Salixarate detergents are overbased materials that can be
represented
by a substantially linear compound comprising at least one unit of formula (A)
or
formula (B):
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R4
(R2)i
I I
HO R7 R5
COOR3 R6
(A) (B)
and wherein each end of the compound has a terminal group of formula (C) or
formula (D):
R4
(R2)j=
R R5
COOR3 R6
(C) (D)
such groups being linked by divalent bridging groups A, which may be the same
or different for each linkage; wherein in formulas (A)-(D) le is hydrogen or a
hydrocarbyl group; R2 is hydroxyl or a hydrocarbon based group and j is 0, 1,
or
2; R6 is hydrogen, a hydrocarbyl group, or a hetero-substituted hydrocarbyl
group; either R4 is hydroxyl and R5 and R2 are independently either hydrogen,
a
hydrocarbyl group, or hetero-substituted hydrocarbyl group, or else R5 and R7
are
both hydroxyl and R4 is hydrogen, a hydrocarbyl group, or a hetero-substituted
hydrocarbyl group; provided that at least one of R4, R5, R6 and R7 is
hydrocarbyl
containing at least 8 carbon atoms; and wherein the molecules on average
contain
at least one of unit (A) or (C) and at least one of unit (B) or (D) and the
ratio of
the total number of units (A) and (C) to the total number of units of (B) and
(D)
in the composition is about 0.1:1 to about 2:1. The divalent bridging group
"A,"
which may be the same or different in each occurrence, includes -CF12-
(methylene bridge) and -CF2OCH2- (ether bridge), either of which may be
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derived from formaldehyde or a formaldehyde equivalent (e.g., paraform,
formalin).
[0058] Salixarate derivatives and methods of their preparation are
described
in greater detail in U.S. patent number 6,200,936 and PCT Publication WO
01/56968. It is believed that the salixarate derivatives have a predominantly
linear, rather than macrocyclic, structure, although both structures are
intended to
be encompassed by the term "salixarate."
[0059] Glyoxylate detergents are similar overbased materials which are
based
on an anionic group which, in one embodiment, may have the structure
C(0)0-
OH
CH OH
R-4())7 R
and more specifically,
C(0)0-
wherein each R is independently an alkyl group containing at least 4, and
preferably
at least 8 carbon atoms, provided that the total number of carbon atoms in all
such R
groups is at least 12, preferably at least 16 or 24. Alternatively, each R can
be an
olefin polymer substituent. The acidic material upon from which the overbased
glyoxylate detergent is prepared is the condensation product of a
hydroxyaromatic material such as a hydrocarbyl-substituted phenol with a
carboxylic reactant such as glyoxylic acid and other omega-oxoalkanoic acids.
Overbased glyoxylic detergents and their methods of preparation are disclosed
in
greater detail in U.S. Patent 6,310,011 and references cited therein.
[0060] Another detergent can be a salicylate detergent. The
alkylsalicylate
can be an alkali metal salt or an alkaline earth metal salt of an
alkylsalicylic acid
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which can in turn be prepared from an alkylphenol by Kolbe-Schmitt reaction.
The alkylphenol can be prepared by a reaction of a-olefin having 8 to 30
carbon
atoms (mean number) with phenol. Alternatively, calcium salicylate can be
produced by direct neutralization of alkylphenol and subsequent carbonation.
[0061] In another embodiment of the invention component (C) can comprise an
antioxidant comprising an aminic antioxidant that is different from component
(B).
In some embodiments this additional antioxidant comprises one or more of the
antioxidants described above. In other embodiments the additional antioxidant
is a
hindered phenol that is different from component (B), a diarylamine, a
sulfurized
olefinic compound, a molybdenum containing antioxidant, and a mixture thereof.
In
additional embodiments of the invention the antioxidant can comprise an alkyl
3-
(3,5-di-t-alkyl-4-hydroxyphenyl)propionate, such as an alkyl 3-(3,5-di-t-buty1-
4-
hydroxyphenyl)propionate where the alkyl group of the ester moiety has 1 or
more
carbon atoms, 2 or more carbon atoms, 2 to 30 carbon atoms, 2 to 20 carbon
atoms,
or 2 to 10 carbon atoms. In some embodiments this combination of antioxidants
leads to additional improvements in the performance of the composition.
[0062] Component (C) can comprise an antiwear agent. The antiwear agent
can
comprise a zinc dialkyldithiophosphate. In some embodiments the compositions
of
the present invention contain a zinc dialkyldithiophosphate, and in some of
these
embodiments, the zinc dialkyldithiophosphate is present at a level of no less
than
300 ppm (or in other embodiments the zinc dialkyldithiophosphate is present at
a
level such that the amount of phosphorus delivered to the composition from the
additive is no less than 300 ppm), such that, in combination with some of the
limits
below, essentially all of the phosphorus present in the composition is
delivered by
the zinc dialkyldithiophosphate.
[0063] In some embodiments the compositions of the present invention
further
comprises a friction modifier, such as a hydroxy acid derived friction
modifier, for
example olcyl tartrimidc, or amide-based friction modifier such as olcyl
amide.
[0064] The other additive or additives of component (C) can each be
present in
the lubricant composition on a weight basis at 0.001 to 14%, 0.001 to 11%, or
0.001
to 8%.
Sulfur, Phosphorus, Ash Content
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[0065] The present invention provides a composition as described above.
In
some embodiments the composition has total sulfur content of no more than 0.4
percent weight and in other embodiments of no more than 0.3, 0.2, or even 0.1
percent by weight. In some embodiments the sulfur content of the compositions
described herein is at least 0.01 or even 0.05 percent by weight. Often the
major
source of sulfur in the composition of the invention is derived from
conventional
diluent oil.
[0066] In some embodiments compositions described herein have a total
phosphorus content of no more than 1200 ppm, and in other embodiments no more
than 1000, 800, 500, 300, 200 or even 100 ppm. In some embodiments the
compositions described herein have a phosphorus content within a range that
includes a minimum value of 100 ppm.
[0067] In some embodiments the composition has a total sulfated ash
content as
determined by ASTM D-874 of no more than 1.0 percent by weight, and in other
embodiments of no more than 0.7, 0.4, 0.3, 0.05 percent by weight. In some
embodiments the sulfur content of the compositions described herein is at
least 0.01
or even 0.05 percent by weight.
Lubricant Composition
[0068] The lubricant composition can be a lubricant composition for an
application comprising those listed above. In one embodiment of the invention
the
lubricant composition can be a lubricant composition for an internal
combustion
engine. The internal combustion engine can comprise a spark-ignited engine or
a
compression-ignited engine.
Concentrate Composition
[0069] Components (B) and (C) of the invention can be combined in a
concentrated form as a concentrate composition for convenient and efficient
handling and shipping prior to being diluted in a base stock or oil of
lubricating
viscosity for use in a lubricant composition for an application. A concentrate
composition of the present invention can comprise a concentrate-forming amount
of
an oil of lubricating viscosity, at least one hindered-phenol-containing
diester
antioxidant as described above, and at least one other additive as described
above.
Each of the antioxidant and other additive or additives can be present in the
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concentrate composition on a weight basis at 1 to 99%, 5 to 85%, or 10 to 75%.
The
oil of lubricating viscosity can be present in the concentrate composition on
a weight
basis at 99 to 1%, 95 to 15%, or at 90 to 25%.
Preparation of Compositions
[0070] The lubricant and concentrate compositions of the invention can be
prepared by admixing or mixing, usually with a mixing device, the components
in
any suitable order from ambient to an elevated temperature of 60 C, 80 C, or
100 C
until the composition is homogeneous or the components are dispersed.
Method for Improving Lubricant Composition Performance
[0071] A method of the present invention for improving the performance of a
lubricant composition comprises incorporating into the lubricant composition a
performance-improving amount of a hydroxychroman derived antioxidant as
described above where the lubricant composition comprises an oil of
lubricating
viscosity and at least one other additive as described above. The improvement
in
performance can comprise a decrease in volatility, an increase in oxidation
inhibition, a reduction in deposits, or a combination thereof. The lubricant
composition can be a lubricant composition for an internal combustion engine.
The
internal combustion engine can comprise a spark-ignited engine or a
compression-
ignited engine. The spark-ignited or compression-ignited engine can have an
exhaust
gas recirculation system. The spark-ignited or compression-ignited engine can
have
at least one exhaust treatment device comprising a catalytic converter, a
catalyzed
diesel particulate trap, a noncatalyzed diesel particulate trap, a diesel
oxidation
catalyst, a selective catalytic reduction catalyst, a lean NO catalyst, or a
combination thereof. The lubricant composition can have normal or reduced
levels
of sulfated ash, phosphorus and sulfur as described above.
EXAMPLES
[0072] 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
[0073] A hydroxychroman derivative is prepared by adding to a 1-liter
round
bottom flask, equipped with a mechanical stirrer, thermowell, nitrogen inlet,
Dean-
22
Stark/Fredrich's condenser, 116.5 grams of 2-tert-butylbenzene-1,4-diol, 124.2
grams of 2-methylpentane-2,4-diol, 150 grams of heptane and 23.3 grams of
Amberlyst 15. The reaction mixture is heated to reflux temperature to
azeotrope
water for a total of about 14 hours. The resulting material is then filtered
using a frit
funnel in order to remove the catalyst and the solvent is removed via vacuum
stripping. The final material is a tan solid.
Example 2
[0074] A hydroxychroman derivative is prepared by adding to a 1-
liter round
bottom flask, equipped with a mechanical stirrer, thermowell, nitrogen inlet,
Dean-
Stark/Fredrich's condenser, 102.0 grams of 2-tert-butylbenzene-1,4-diol, 107.7
grams of 2,5-dimethy1-2,5-hexanediol, 150 gams of heptane and 22.0 grams of
Amberlysi'15. The reaction mixture is heated to reflux temperature to
azeotrope
water for a total of about 14 hours. The resulting material is then filtered
using a frit
funnel in order to remove the catalyst and the solvent is removed via vacuum
stripping. The final material is a tan solid.
Antioxidancy Performance Testing
[0075] The examples described above were prepared and then blended
into
samples for testing in antioxidancy performance screen tests.
[0076] Each sample is prepared by blending the antioxidant additive
being
evaluated, if any, at the specified level, into a fully formulated engine oil
composition. Each composition was blended into the same base oil, a mix of
commercially available 100N and 160N mineral oils. Also included in each
sample
is an additive package. The additive package contains a combination of various
lubricant additives including dispersants, detergents, antifoams, corrosion
inhibitors,
etc. The exact same additive package is present at the exact same treat level
in each
sample unless otherwise noted. The table below summarizes the samples prepared
for the testing:
Table 1 ¨ Sample Formulations in PBW
Ex A Ex B Ex C Ex D Ex E Ex F
(comp) (Invent) (Invent) (comp) (Invent)
(comp)
Base Oil' 100 100 100 100 100 100
Additive Pack2 8.80 8.80 8.80 8.80 8.35 , 8.35
Hindered Phenol AO 0.45 0.00 0.00 0.58 0.00 0.45
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Example 1 AO 0.00 0.45 0.00 0.00 0.35 0.00
Example 2 AO 0.00 0.00 0.45 0.00 0.00 0.00
I ¨ The base oil package used in all of the examples is a mixture of
commercially
available 100N and 160N mineral oils.
2 The additive package used in Examples A to D is identical. The
additive package
used in Examples E and F is identical to that used in the other examples
except that 0.45
phw of an alkaryl amine believed to possibly contribute to lubricant
antioxidancy
performance was removed.
[0077] Examples A, B and C compare the additives of the present invention
against a conventional hindered phenol antioxidant on an equal treat rate
basis, with
treat rate measured by percent by weight. Example D, when compared to Example
B, and Examples E and F, compare the additives of the present invention
against a
conventional hindered phenol antioxidant on an equal actives basis. In
addition,
Examples E and F were prepared using an additive package identical to that
used in
each of the other examples except that an alkaryl amine additive present in
the full
additive package, which is believed to possibly contribute to lubricant
antioxidancy,
was removed. Thus these examples ensure any improvement in antioxidancy
performance is the result of the inventive additive.
[0078] The tests used to evaluate the samples are commonly used in the
lubricant industry to evaluate the performance of antioxidant additives. The
testing
completed includes: (i) ASTM D7097, a bench-scale passenger car motor oil
qualification test for GF-4 and GF-5. The test measures the amount of deposit
generated on a steel rod heated at 285C. A lower result indicates a lower
amount of
deposit generation and so better performance. (ii) ASTM D6335, a bench-scale
passenger car motor oil qualification test for GF-2. The test measures the
amount of
deposit generated on a steel rod when cycling the rod temperature from 200C to
480C. A lower result indicates a lower amount of deposit generation and so
better
performance. (iii) An in-house PDSC test was also used. This test uses a
calorimetry method to determine the onset of oxidation activity in an oil
sample and
is used to rank the relative oxidative stabilities of a set of samples. Higher
onset
times indicate greater oxidative stability and so better performance.
[0079] The table below summarizers the results:
Table 2 ¨ Test Results
Ex A Ex B Ex C Ex D Ex E Ex F
(comp) (Invent) (Invent) (comp) (Invent)
(comp)
24
ASTIVI D7097
Total Deposits (mg) 54.6 42.3 47.3 47.2 77.3 82.4
ASTill D6335
Total Deposits (mg) 21.8 29.3
Oxidation Activity
Onset Time (min) 51.6 60.9 57.3 50.8 37.4 29.2
100801 The results show that, as seen in Examples A, B and C, the
hydroxychroman derivatives (see Examples B and C) give lower deposit levels
and
higher onset times than the conventional hindered phenolic antioxidants when
treated at equal weight, thus indicating better oxidation stability.
[0081] Furthermore, when the level of conventional hindered phenolic
antioxidant is increased to compare to the hydroxychroman antioxidants on an
equal
actives basis (see Example D compared to Inventive Examples B and C), we still
see
better oxidative stability for both hydroxychroman derivatives and at least
comparable, if not improved, deposit control.
[0082] When removing the additional amine antioxidant, as was done
in
Examples E and F while comparing the antioxidants at equal actives, we see
better
oxidation control and deposit control for the hydroxychroman derivatives
compared
to the conventional hindered phenolic antioxidants.
[0083] Except in the Examples, or where otherwise explicitly
indicated, all
numerical quantities in this description specifying amounts of materials,
reaction
conditions, molecular weights, number of carbon atoms, and the like, are to be
understood as modified by the word "about." Unless otherwise indicates all
percent
values and ppm values herein are weight percent values and/or calculated on a
weight basis and are relative to the overall composition to which the specific
material is added. Unless otherwise indicated, each chemical or composition
referred to herein should be interpreted as being a commercial grade material
which
may contain the isomers, by-products, derivatives, and other such materials
which
are normally understood to be present in the commercial grade. However, the
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amount of each chemical component is presented exclusive of any solvent or
diluent,
which may be customarily present in the commercial material, unless otherwise
indicated. It is to be understood that the upper and lower amount, range, and
ratio
limits set forth herein may be independently combined. Similarly, the ranges
and
amounts for each element of the invention can be used together with ranges or
amounts for any of the other elements. As used herein, the expression
"consisting
essentially of' permits the inclusion of substances that do not materially
affect the
basic and novel characteristics of the composition under consideration.
26
