Note: Descriptions are shown in the official language in which they were submitted.
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MARINE ENGINE LUBRICATION
FIELD OF THE INVENTION
This invention relates to a trunk piston marine engine lubricating composition
for a
medium-speed four-stroke compression-ignited (diesel) marine engine and
lubrication of such
an engine.
BACKGROUND OF THE INVENTION
Marine trunk piston engines generally use Heavy Fuel Oil ('HF0') for offshore
running. Heavy Fuel Oil is the heaviest fraction of petroleum distillate and
comprises a
complex mixture of molecules including up to 15% of asphaltenes, defined as
the fraction of
petroleum distillate that is insoluble in an excess of aliphatic hydrocarbon
(e.g. heptane) but
which is soluble in aromatic solvents (e.g. toluene). Asphaltenes can enter
the engine
lubricant as contaminants either via the cylinder or the fuel pumps and
injectors, and
asphaltene precipitation can then occur, manifested in 'black paint' or 'black
sludge' in the
engine. The presence of such carbonaceous deposits on a piston surface can act
as an
insulating layer which can result in the formation of cracks that then
propagate through the
piston. If a crack travels through the piston, hot combustion gases can enter
the crankcase,
possibly resulting in a crankcase explosion.
It is therefore highly desirable that trunk piston engine oils ('TPEO's)
prevent or
inhibit asphaltene precipitation. The prior art describes ways of doing this.
WO 96/26995 discloses the use of a hydrocarbyl-substituted phenol to reduce
'black
paint' in a diesel engine. WO 96/26996 discloses the use of a denquisifier for
water-in-oil
emulsions, for example, a polyoxyalkylene polyol, to reduce 'black paint' in
diesel engines.
US-B2-7,053,027 describes use of one or more overbased metal carboxylate
detergents in
combination with an antiwear additive in a dispersant-free TPEO.
The problem of asphaltene precipitation is more acute at higher basestock
saturate
levels. WO 2008/128656 describes a solution by use of an overbased metal
hydrocarbyl-
substituted hydroxybenzoate detergent having a basicity index of less than 2
and a degree of
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carbonation of 80% or greater in a marine trunk piston engine lubricant to
reduce asphaltene
precipitation in the lubricant. Mentioned, but not exemplified, are lubricants
comprising
Group III and Group IV basestocks, and exemplified are lubricants comprising a
Group II
basestock, all of which basestocks have high saturates levels.
The above-described solution is however restricted to a specific class of
detergents. It
is now found, in the present invention, that the problem in WO 2008/128656 is
solved for a
different range of overbased metal carboxylate detergents by employing, in
combination
therewith, a hydrocarbyl-substituted carboxylic acid, anhydride, ester or
amide in high
saturates basestocks.
WO-A-2008/021737 describes lubricating an internal combustion engine with a
composition that includes at least 0.5 wt % of a carboxylic acid or an
anhydride thereof. It
exemplifies such compositions that include an overbased phenate and an
overbased sulfonate
and provides panel coker test data thereof. It does not however address the
presence of heavy
fuel oil in the composition.
SUMMARY OF THE INVENTION
A first aspect of the invention is a trunk piston marine engine lubricating
oil
composition for improving asphaltene handling in use thereof, in operation of
the engine
when fuelled by a heavy fuel oil, which composition comprises or is made by
admixing an oil
of lubricating viscosity, in a major amount, containing 50 mass % or more of a
basestock
containing greater than or equal to 90% saturates and less than or equal to
0.03% sulphur or a
mixture thereof, and, in respective minor amounts:
(A) an overbased metal hydrocarbyl-substituted hydroxybenzoate
detergent other
than such a detergent having a basicity index of less than two and a degree of
carbonation of 80% or greater, where degree of carbonation is the percentage
of carbonate present in the overbased metal hydrocarbyl-substituted
hydroxybenzoate detergent expressed as a mole percentage relative to the total
excess base in the detergent; and
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(B) a hydrocarbyl-substituted carboxylic acid, anhydride, ester or
amide thereof,
wherein the or at least one hydrocarbyl group contains at least eight carbon
atoms, the acid, anhydride, ester or amide constituting at least 1 mass % of
the
lubricating oil composition.
A second aspect of the invention is the use of a detergent (A) in combination
with a
carboxylic acid, anhydride, ester or amide (B) as defined in, and in the
amounts stated in, the
first aspect of the invention in a trunk piston marine lubricating oil
composition for a medium-
speed compression-ignited marine engine, which composition comprises an oil of
lubricating
viscosity in a major amount and contains 50 mass % or more of a basestock
containing greater
than or equal to 90% saturates and less than or equal to 0.03% sulphur or a
mixture thereof, to
improve asphaltene handling during operation of the engine, fueled by a heavy
fuel oil, and its
lubrication by the composition, in comparison with analogous operation when
the same
amount of detergent (A) is used in the absence of (B).
A third aspect of the invention is a method of operating a trunk piston medium-
speed
compression-ignited marine engine comprising
(i) fueling the engine with a heavy fuel oil; and
(ii) lubricating the crankcase of the engine with a composition as defined
in the
first aspect of the invention.
A fourth aspect of the invention is a method of dispersing asphaltenes in a
trunk piston
marine lubricating oil composition during its lubrication of surfaces of the
combustion
chamber of a medium-speed compression-ignited marine engine and operation of
the engine,
which method comprises
(i) providing a composition as defined in the first aspect of the
invention;
(ii) providing the composition in the combustion chamber;
(iii) providing heavy fuel oil in the combustion chamber; and
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(iv) combusting the heavy fuel oil in the combustion chamber.
In this specification, the following words and expressions, if and when used,
have the
meanings ascribed below:
"active ingredients" or "(a.i.)" refers to additive material that is not
diluent or solvent;
"comprising" or any cognate word specifies the presence of stated features,
steps, or
integers or components, but does not preclude the presence or addition of one
or more
other features, steps, integers, components or groups thereof; the expressions
"consists of' or "consists essentially of' or cognates may be embraced within
"comprises" or cognates, wherein "consists essentially of' permits inclusion
of
substances not materially affecting the characteristics of the composition to
which it
applies;
"major amount" means in excess of 50 mass % of a composition;
"minor amount" means less than 50 mass % of a composition;
"TBN" means total base number as measured by ASTM D2896.
Furthermore in this specification:
"calcium content" is as measured by ASTM 4951;
"phosphorus content" is as measured by ASTM D5185;
"sulphated ash content" is as measured by ASTM D874;
"sulphur content" is as measured by ASTM D2622;
"KV100" means kinematic viscosity at 100 C as measured by ASTM D445.
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Also, it will be understood that various components used, essential as well as
optimal
and customary, may react under conditions of formulation, storage or use and
that the
invention also provides the product obtainable or obtained as a result of any
such reaction.
Further, it is understood that any upper and lower quantity, range and ratio
limits set
forth herein may be independently combined.
DETAILED DESCRIPTION OF THE INVENTION
The features of the invention will now be discussed in more detail below.
OIL OF LUBRICATING VISCOSITY
The lubricating oils may range in viscosity from light distillate mineral oils
to heavy
lubricating oils. Generally, the viscosity of the oil ranges from 2 to 40
mm2/sec, as measured
at 100 C.
Natural oils include animal oils and vegetable oils (e.g., caster 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.
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)); alkybenzenes (e.g., dodecylbenzenes,
tetradecylbenzenes,
dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls,
terphenyls,
alkylated polyphenols); and alkylated diphenyl ethers and alkylated diphenyl
sulphides and
derivative, analogs and homologs thereof.
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
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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 C3-C8 fatty acid esters and C13 Oxo acid diester of
tetraethylene glycol.
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.
Esters useful as synthetic oils also include those made from C5 to C12
monocarboxylic
acids and polyols and polyol esters such as neopentyl glycol,
trimethylolpropane,
pentaerythritol, dipentaerythritol and tripentaerythritol.
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-eth yl hex yl)si licate, 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.
Unrefined, refined and re-refined oils can be used in 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; petroleum oil obtained directly from distillation; or
ester oil obtained
directly from an esterification and used without further treatment would be an
unrefined oil.
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Refined oils are similar to unrefined oils except that the oil is further
treated in one or more
purification steps to improve one or more properties. Many such purification
techniques, such
as distillation, solvent extraction, acid or base extraction, filtration and
percolation are known
to those skilled in the art. Re-refined oils are obtained by processes similar
to those used to
provide refined oils but begin with oil that has already been used in service.
Such re-refined
oils are also known as reclaimed or reprocessed oils and are often subjected
to additional
processing using techniques for removing spent additives and oil breakdown
products.
The American Petroleum Institute (API) publication "Engine Oil Licensing and
Certification System", Industry Services Department, Fourteenth Edition,
December 1996,
Addendum 1, December 1998 categorizes base stocks as follows:
a) Group I base stocks contain less than 90 percent saturates and/or greater
than 0.03
percent sulphur and have a viscosity index greater than or equal to 80 and
less than 120
using the test methods specified in Table E-1.
b) Group II base stocks contain greater than or equal to 90 percent saturates
and less
than or equal to 0.03 percent sulphur and have a viscosity index greater than
or equal to
80 and less than 120 using the test methods specified in Table E-1.
c) Group III base stocks contain greater than or equal to 90 percent saturates
and less
than or equal to 0.03 percent sulphur and have a viscosity index greater than
or equal to
120 using the test methods specified in Table E-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, TIT, or
IV.
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Analytical Methods for Base Stock are tabulated below:
PROPERTY TEST METHOD
Saturates ASTM D 2007
Viscosity Index ASTM D 2270
Sulphur ASTM D 2622
ASTM D 4294
ASTM D 4927
ASTM D 3120
By way of example, the present invention embraces Group II, Group III and
Group IV
basestocks and also basestocks derived from hydrocarbons synthesised by the
Fischer-
Tropsch process. In the Fischer-Tropsch process, synthesis gas containing
carbon monoxide
and hydrogen (or `syngas') is first generated and then converted to
hydrocarbons using a
Fischer-Tropsch catalyst. These hydrocarbons typically require further
processing in order to
be useful as a base oil. For example, they may, by methods known in the art,
be
hydroisomerized; hydrocracked and hydroisomerized; dewaxed; or hydroisomerized
and
dewaxed. The syngas may, for example, be made from gas such as natural gas or
other
gaseous hydrocarbons by steam reforming, when the basestock may be referred to
as gas-to-
liquid ("GTL") base oil; or from gasification of biomass, when the basestock
may be referred
to as biomass-to-liquid ("BTL" or "BMTL") base oil; or from gasification of
coal, when the
basestock may be referred to as coal-to-liquid ("CTL") base oil.
As stated, the oil of lubricating viscosity in this invention contains 50 mass
% or more
of the defined basestock or a mixture thereof. Preferably, it contains 60,
such as 70, 80 or 90,
mass % or more of the defined basestock or a mixture thereof. The oil of
lubricating viscosity
may be substantially all the defined basestock or a mixture thereof.
OVERBASED METAL DETERGENT (A)
A metal detergent is an additive based on so-called metal "soaps", that is
metal salts of
acidic organic compounds, sometimes referred to as surfactants. They generally
comprise a
polar head with a long hydrophobic tail. Overbased metal detergents, which
comprise
neutralized metal detergents as the outer layer of a metal base (e.g.
carbonate) micelle, may be
,
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provided by including large amounts of metal base by reacting an excess of a
metal base, such
as an oxide or hydroxide, with an acidic gas such as carbon dioxide.
In the present invention, overbased metal detergents (A) are overbased metal
hydrocarbyl-substituted hydroxybenzoate, preferably hydrocarbyl-substituted
salicylate,
detergents.
"Hydrocarbyl" means a group or radical that contains carbon and hydrogen atoms
and
that is bonded to the remainder of the molecule via a carbon atom. It may
contain hetero
atoms, i.e. atoms other than carbon and hydrogen, provided they do not alter
the essentially
hydrocarbon nature and characteristics of the group. As examples of
hydrocarbyl, there may
be mentioned alkyl and alkenyl. The overbased metal hydrocarbyl-substituted
hydroxybenzoate typically has the structure shown:
OH
OM
wherein R is a linear or branched aliphatic hydrocarbyl group, and more
preferably an alkyl
group, including straight- or branched-chain alkyl groups. There may be more
than one R
group attached to the benzene ring. M is an alkali metal (e.g. lithium, sodium
or potassium) or
alkaline earth metal (e.g. calcium, magnesium barium or strontium). Calcium or
magnesium
is preferred; calcium is especially preferred. The COOM group can be in the
ortho, meta or
para position with respect to the hydroxyl group; the ortho position is
preferred. The R group
can be in the ortho, meta or para position with respect to the hydroxyl group.
Hydroxybenzoic acids are typically prepared by the carboxylation, by the Kolbe-
Schmitt process, of phenoxides, and in that case, will generally be obtained
(normally in a
diluent) in admixture with uncarboxylated phenol. Hydroxybenzoic acids may be
non-
sulphurized or sulphurized, and may be chemically modified and/or contain
additional
substituents. Processes for sulphurizing a hydrocarbyl-substituted
hydroxybenzoic acid are
well known to those skilled in the art, and are described, for example, in US
2007/0027057.
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In hydrocarbyl-substituted hydroxybenzoic acids, the hydrocarbyl group is
preferably
alkyl (including straight- or branched-chain alkyl groups), and the
alkyl groups
advantageously contain 5 to 100, preferably 9 to 30, especially 14 to 24,
carbon atoms.
The term "overbased" is generally used to describe metal detergents in which
the ratio
of the number of equivalents of the metal moiety to the number of equivalents
of the acid
moiety is greater than one. The term low-based' is used to describe metal
detergents in
which the equivalent ratio of metal moiety to acid moiety is greater than 1,
and up to about 2.
By an "overbased calcium salt of surfactants" is meant an overbased detergent
in
which the metal cations of the oil-insoluble metal salt are essentially
calcium cations. Small
amounts of other cations may be present in the oil-insoluble metal salt, but
typically at least
80, more typically at least 90, for example at least 95, mole %, of the
cations in the oil-
insoluble metal salt, are calcium ions. Cations other than calcium may be
derived, for
example, from the use in the manufacture of the overbased detergent of a
surfactant salt in
which the cation is a metal other than calcium. Preferably, the metal salt of
the surfactant is
also calcium.
Carbonated overbased metal detergents typically comprise amorphous
nanoparticles.
Additionally, there are disclosures of nanoparticulate materials comprising
carbonate in the
crystalline calcite and vaterite forms.
The basicity of the detergents may be expressed as a total base number (TBN).
A total
base number is the amount of acid needed to neutralize all of the basicity of
the overbased
material. The TBN may be measured using ASTM standard D2896 or an equivalent
procedure. The detergent may have a low TBN (i.e. a TBN of less than 50), a
medium TBN
(i.e. a TBN of 50 to 150) or a high TBN (i.e. a TBN of greater than 150, such
as 150-500). In
this invention, Basicity Index and Degree of Carbonation may be used. Basicity
Index is the
molar ratio of total base to total soap in the overbased detergent. Degree of
Carbonation is the
percentage of carbonate present in the overbased detergent expressed as a mole
percentage
relative to the total excess base in the detergent.
Overbased metal hydrocarbyl-substituted hydroxybenzoates can be prepared by
any of
the techniques employed in the art. A general method is as follows:
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1. Neutralisation of hydrocarbyl-substituted hydroxybenzoic acid with a
molar excess of
metallic base to produce a slightly overbased metal hydrocarbyl-substituted
hydroxybenzoate complex, in a solvent mixture consisting of a volatile
hydrocarbon, an
alcohol and water;
2. Carbonation to produce colloidally-dispersed metal carbonate followed by
a post-
reaction period;
3. Removal of residual solids that are not colloidally dispersed; and
4. Stripping to remove process solvents.
Overbased metal hydrocarbyl-substituted hydroxybenzoates can be made by either
a
batch or a continuous overbasing process.
Metal base (e.g. metal hydroxide, metal oxide or metal alkoxide), preferably
lime
(calcium hydroxide), may be charged in one or more stages. The charges may be
equal or
may differ, as may the carbon dioxide charges which follow them. When adding a
further
calcium hydroxide charge, the carbon dioxide treatment of the previous stage
need not be
complete. As carbonation proceeds, dissolved hydroxide is converted into
colloidal carbonate
particles dispersed in the mixture of volatile hydrocarbon solvent and non-
volatile
hydrocarbon oil.
Carbonation may by effected in one or more stages over a range of temperatures
up to
the reflux temperature of the alcohol promoters. Addition temperatures may be
similar, or
different, or may vary during each addition stage. Phases in which
temperatures are raised,
and optionally then reduced, may precede further carbonation steps.
The volatile hydrocarbon solvent of the reaction mixture is preferably a
normally
liquid aromatic hydrocarbon having a hniling point not greater than about 150
C. Aromatic
hydrocarbons have been found to offer certain benefits, e.g. improved
filtration rates, and
examples of suitable solvents are toluene, xylene, and ethyl benzene.
The alkanol is preferably methanol although other alcohols such as ethanol can
be
used. Correct choice of the ratio of alkanol to hydrocarbon solvents, and the
water content of
the initial reaction mixture, are important to obtain the desired product.
=
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Oil may be added to the reaction mixture; if so, suitable oils include
hydrocarbon oils,
particularly those of mineral origin. Oils which have viscosities of 15 to 30
mm2/sec at 38 C
are very suitable.
After the final treatment with carbon dioxide, the reaction mixture is
typically heated
to an elevated temperature, e.g. above 130 C, to remove volatile materials
(water and any
remaining alkanol and hydrocarbon solvent). When the synthesis is complete,
the raw
product is hazy as a result of the presence of suspended sediments. It is
clarified by, for
example, filtration or centrifugation. These measures may be used before, or
at an
intermediate point, or after solvent removal.
The products are generally used as an oil solution. If the reaction mixture
contains
insufficient oil to retain an oil solution after removal of the volatiles,
further oil should be
added. This may occur before, or at an intermediate point, or after solvent
removal.
In this invention, (A) may have:
(Al) a basicity index of two or greater and a degree of carbonation of 80% or
greater; or
(A2) a basicity index of two or greater and a degree of carbonation of less
than 80%; or
(A3) a basicity index of less than two and a degree of carbonation of less
than 80%.
CARBOXYLIC ACID, ANHYDRIDE, ESTER OR AMIDE THEREOF (B)
As stated, the acid, anhydride, ester or amide thereof constitutes at least 1
mass % of
the lubricating oil composition. Preferably it constitutes from 1.5 such as up
to 10, such as 2
to 10, for example 3 to 6, mass %. (13) may be a mixture.
The acid may be mono or polycarboxylic, preferably dicarboxylic, acid. The
hydrocarbyl group preferably has from 8 to 400, such as 12 to 100, such as 8
to 100, such as 16
to 64, carbon atoms.
As (B), an anhydride of a dicarboxylic acid is preferred.
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Esters may be half or diesters when the acid is a dicarboxylic acid. Ester
groups may
include alkyl, aryl, or aralkyl, and amide groups may be unsubstituted or
carry one or more
alkyl, aryl or aralkyl groups.
General formulae of exemplary monocarboxylic and dicarboxylic acids and
anhydrides, esters or amides thereof may be depicted as
R1
HC¨COX
H2C¨COY (I)
where RI represents a C8 to C100 branched or linear hydrocarbyl such as a
polyalkenyl,
alkyl or alkaryl group;
X and Y each independently represents OR2 and OR3, where each R2 and R3
independently represents a hydrogen atom, or an alkyl, aryl or aralkyl group,
or X and Y
together represent -0-; and/or depicted as
R I CH2COR4 (II)
where R4 represents OR5 or NR6R7, where each R5, R6 and R7 independently
represents a hydrogen atom or an alkyl group.
Preferably, the hydrocarbyl group is a polyalkenyl group. Such polyalkenyl
moiety
may have a number average molecular weight of from 200 to 3000, preferably
from 350 to
950.
Suitable hydrocarbons or polymers employed in the formation of the
acid/derivative 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 C3 to C28 alpha-olefin having the formula H2C=CHRI wherein RI 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.
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Preferably, such polymers comprise interpolymers of ethylene and at least one
alpha-olefin of
the above formula, wherein R1 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-meth ylpentene-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 C4
to C18 non-conjugated 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.
These polymers may be prepared by polymerizing alpha-olefin monomer, or
mixtures
of alpha-olefin monomers, or mixtures comprising ethylene and at least one C3
to C28 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 he determined by FTIR spectroscopic
analysis,
titration, or C13 NMR. Interpolymers of this latter type may be characterized
by the formula
POLY-C(R1)=CH2 wherein R1 is CI to C26 alkyl, preferably CI to C18 alkyl, more
preferably
CI to C8 alkyl, and most preferably C1 to C2 alkyl, (e.g., methyl or ethyl)
and wherein POLY
represents the polymer chain. The chain length of the R1 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=CH2, and a
portion of the polymers can contain internal monounsaturation, e.g. POLY-
CH=CH(R1),
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wherein RI 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.
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 C4 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 AlC13 or BF3 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. RR-
PIB is known and HR-PIB is commercially available under the tradenames
GlissopalTM (from
BASF) and UltravisTM (from BP-Amoco).
Polyisobutylene polymers that may be employed are generally based on a
hydrocarbon
chain of from 400 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.
To produce (B) the hydrocarbon or polymer backbone may be functionalized, with
carboxylic acid producing moieties (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.
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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 BI; CA-1,335,895 and GB-A-1,440,219. The polymer or
hydrocarbon
may be functionalized, with carboxylic acid producing moieties (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.
Selective functionalization can be accomplished by halogenating, e.g.,
chlorinating or
brominating the unsaturated a-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
I60 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.
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.
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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
to 30 mass % polymer based on the initial total oil solution.
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 derivative) 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.
The preferred monounsaturated reactants that are used to functionalize the
backbone
comprise mono- and dicarboxylic acid material, i.e., acid, or acid derivative
material,
including (i) monounsaturated C4 to C10 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-00-; 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
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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.
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.
The treat rate of additives (A) and (B) contained in the lubricating oil
composition
may for example be in the range of 1 to 2.5, preferably 2 to 20, more
preferably 5 to 18, mass
%.
CO-ADDITIVES
The lubricating oil composition of the invention may comprise further
additives,
different from and additional to (A) and (B). Such additional additives may,
for example
include ashless dispersants, other metal detergents, anti-wear agents such as
zinc
dihydrocarbyl dithiophosphates, anti-oxidants and demulsifiers.
It may be desirable, although not essential, to prepare one or more additive
packages
or concentrates comprising the additives, whereby additives (A) and (B) can be
added
simultaneously to the base oil to form the lubricating oil composition.
Dissolution of the
additive package(s) into the lubricating oil may be facilitated by solvents
and by mixing
accompanied with mild heating, but this is not essential. The additive
package(s) will
typically be formulated to contain the additive(s) in proper amounts to
provide the desired
concentration, and/or to carry out the intended function in the final
formulation when the
additive package(s) is/are combined with a predetermined amount of base
lubricant. Thus,
additives (A) and (B), in accordance with the present invention, may be
admixed with small
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amounts of base oil or other compatible solvents together with other desirable
additives to
form additive packages containing active ingredients in an amount, based on
the additive
package, of, for example, from 2.5 to 90, preferably from 5 to 75, most
preferably from 8 to
60, mass % of additives in the appropriate proportions, the remainder being
base oil.
The final formulations as a trunk piston engine oil may typically contain 30,
preferably 10 to 28, more preferably 12 to 24, mass % of the additive
package(s), the
remainder being base oil. Preferably, the trunk piston engine oil has a
compositional TBN
(using ASTM D2896) of 20 to 60, such as 25 to 55.
EXAMPLES
The present invention is illustrated by but in no way limited to the following
examples.
COMPONENTS
The following components were used:
Component (A):
(Al) a calcium salicylate detergent having a TBN of 350 (basicity index of two
or
greater; a degree of carbonation of 80% or greater)
(A2) a calcium salicylate detergent having a TBN of 225 (basicity index of two
or
greater; a degree of carbonation of less than 80%)
(A3) a calcium salicylate detergent having a TBN of 65 (basicity index of less
than
two; a degree of carbonation of less than 80%)
Component (B):
a polyisobutene succinic anhydride ("PIBSA") derived from a polyisobutene of
number average molecular weight 950 (72% ai)
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Base oil II: an API Group II 600R basestock from Chevron
Base oil III: an API Group IQ base oil known as XHV 182
TM
Base oil IV (1): an API Group IV base oil known as DURASYN82
Base oil IV (2): an API Group IV base oil known as SPECTRAP AO100TM
HFO: a heavy fuel oil, ISO-F-RMK 380
LUBRICANTS
Selections of the above components were blended to give a range of trunk
piston
marine engine lubricants. Some of the lubricants are examples of the
invention; others are
reference examples for comparison purposes. The compositions of the lubricants
tested when
each contained HFO are shown in the tables below under the "Results" heading.
TESTING
Panel Coker Test
The Panel Coker test was used to evaluate the performance of test lubricants.
The test
method involved splashing the oil under test onto a heated metal plate by
spinning a metal
comb-like device within a sump containing the oil. At the end of the test
period, deposits
formed may be assessed by weight and by visual inspection of the plate's
appearance.
The testing was performed using a panel coker tester, model PK-S, supplied by
the
Yoshida Kagaku ICikai Co., of Osaka, Japan. Test panels were thoroughly
cleaned and
weighed before inserting them into the apparatus. The test oil was mixed with
2.5% HFO and
225g of the resulting mixture added to the sump of the apparatus. When the
temperature of
the oil was at 100 C and the test plate at 320 C, a metal comb device was
automatically
rotated causing the oil to be splashed onto the test plate.
The test sequence lasted for 120 cycles, each cycle consisting of 15 seconds
in which
the oil was splashed onto the plate and 45 seconds without splashing.
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At the end of test, the plate was washed with n-heptane, dried, reweighed and
visually
examined. The deposit weight was reported.
Light Scattering
Test lubricants were also evaluated for asphaltene dispersancy using light
scattering
according to the Focused Beam Reflectance Method ("FBRM"), which predicts
asphaltene
agglomeration and hence 'black sludge' formation.
The FBRM test method was disclosed at the 7th International Symposium on
Marine
Engineering, Tokyo, 24th - 28th October 2005, and was published in 'The
Benefits of
Salicylate Detergents in TPEO Applications with a Variety of Base Stocks', in
the Conference
Proceedings. Further details were disclosed at the CIMAC Congress, Vienna,
21St -24th May
2007 and published in "Meeting the Challenge of New Base Fluids for the
Lubrication of
Medium Speed Marine Engines ¨ An Additive Approach" in the Congress
Proceedings. In
the latter paper it is disclosed that by using the FBRM method it is possible
to obtain
quantitative results for asphaltene dispersancy that predict performance for
lubricant systems
based on base stocks containing greater than or less than 90% saturates, and
greater than or
less than 0.03% sulphur. The predictions of relative performance obtained from
FBRM were
confirmed by engine tests in marine diesel engines.
The FBRM probe contains fibre optic cables through which laser light travels
to reach
the probe tip. At the tip, an optic focuses the laser light to a small spot.
The optic is rotated
so that the focussed beam scans a circular path between the window of the
probe and the
sample. As particles flow past the window they intersect the scanning path,
giving
backscattered light from the individual particles.
The scanning laser beam travels much faster than the particles; this means
that the
particles are effectively stationary. As the focussed beam reaches one edge of
the particle
there is an increase in the amount of backscattered light; the amount will
decrease when the
focussed beam reaches the other edge of the particle.
The instrument measures the time of the increased backscatter. The time period
of
backscatter from one particle is multiplied by the scan speed and the result
is a distance or
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22
chord length. A chord length is a straight line between any two points on the
edge of a
particle. This is represented as a chord length distribution, a graph of
numbers of chord
lengths (particles) measured as a function of the chord length dimensions in
microns. As the
measurements are performed in real time the statistics of a distribution can
be calculated and
tracked. FBRM typically measures tens of thousands of chords per second,
resulting in a
robust number-by-chord length distribution. The method gives an absolute
measure of the
particle size distribution of the asphaltene particles.
TM
The Focused beam Reflectance Probe (FBRM), model Lasentec D600L, was supplied
by Mettler Toledo, Leicester, UK. The instrument was used in a configuration
to give a
particle size resolution of 1 pm to lmm. Data from FBRM can be presented in
several ways.
Studies have suggested that the average counts per second can be used as a
quantitative
determination of asphaltene dispersancy. This value is a function of both the
average size and
level of agglomerate. In this application, the average count rate (over the
entire size range)
was monitored using a measurement time of 1 second per sample.
The test lubricant formulations were heated to 60 C and stirred at 400rpm;
when the
temperature reached 60 C the FBRM probe was inserted into the sample and
measurements
made for 15 minutes. An aliquot of heavy fuel oil (10% w/w) was introduced
into the
lubricant formulation under stirring using a four blade stirrer (at 400 rpm).
A value for the
average counts per second was taken when the count rate had reached an
equilibrium value
(typically overnight).
RESULTS
Panel Coker Test
The results of the Panel Coker tests are summarized in the table below where
figures
are mass % unless otherwise stated
TABLE 1
Ex Ca salicylate PIBSA Base oil Base oil Base oil
Deposits (g)
(A 1 ) (B) III IV (1) IV(2)
1 5.71 6.1 72.21 15.98 0.0484
X 5.71 77.59 16.71 0.0916
2 5.71 6.1 70.96 17.23 0.0738
5.71 75.43 18.56 0.1062
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Each lubricant contained 44.6 mM of soap and had a TBN of 30. Also, each
lubricant
contained 0.5 mass % HFO.
The results show that the examples of the invention (Ex 1 and 2) gave rise to
much
lower deposits, i.e. improved asphaltene dispersency, than corresponding
examples lacking
PI-BSA (Ex X and Y respectively), and also than an example in a Group IV base
oil lacking
PIBSA (Ex Y).
Light Scattering
Results of the FBRM tests are summarized in the tables below (TABLES 2-4).
TABLE 2 (Base oil II)
Ex Ca Salicylate (A) Component (B) Particle count/s
(mass % a.i.) (mass % a.i.)
Ref 2.6 13,710
Al (2.6) 15,888
Al (2.6) 2.6 4,355
Ref 2.1 15,191
A2 (2.1) 8,782
A2 (2.1) 2.1 6,149
A2 (2.1) 2.6 3,438
Ref 1.8 15,564
A3 (1.8) 10,748
A3 (1.8) 1.8 5,803
A3 (1.8)
2.6
3,629
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TABLE 3 (Base oil III)
Ex Ca Salicylate (A) Component (B) Particle count/s
(mass % a.i.) (mass % a.i.)
Ref 6.1 19,478
Al (5.2) 24,647
Al (5.2) 6.1 11,889
Ref A2 (4.2) 22,953
A2(4.2) 6.1 13,168
Ref A3(3.6) 20,170
A3 (3.6) 6.1 13,724
TABLE 4 (Base oil IV(I))
Ex Ca Salicylate (A) Component (B) Particle count/s
(mass % a.i.) (mass %
Ref 6.1 15,386
Al (5.2) 20,585
Al (5.2) 6.1 10,094
Ref A2 (4.2) 22,366
A2 (4.2) 6.1 9,385
Ref A3 (3.6) 16,440
A3 (3.6) 6.1 7,528
The results show that, in each of the base oils, II, III and IV(I), (A),
represented by
each of Al, A2 and A3, in combination with (B) is better than (A) alone and
better than (B)
alone.
