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 trunk piston marine engine lubrication for a medium-
speed four-
stroke compression-ignited (diesel) marine 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) as measured by ASTM D6560. 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, a problem which becomes more acute when the oil of
lubricating
viscosity has a higher saturates content. The prior art describes ways of
doing this by use of
metal carboxylate detergents in combination with a polyalkenyl-substituted
carboxylic acid
anhydride. WO 2010/115594 (`594) and WO 2010/115595 (`595) describe use, in
trunk piston
marine engine (TPEO) lubricating oil compositions that contain 50 mass % or
more of a Group II
basestock, of respective minor amounts of a calcium salicylate detergent and
of a polyalkenyl-
substituted carboxylic acid anhydride. The data therein shows that the
combination gives rise to
improved asphaltene dispersency. EP-A-2644687 ('687) describes use of a
combination of
defined calcium salicylates and defined polyalkenyl-substituted carboxylic
acid anhydrides in a
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TPEO lubricant comprising a major amount of an oil of lubricating viscosity
containing 50
mass % or more of a Group I basestock. This achieves good asphaltene
dispersency at lower and
hence more economical levels of soap.
The art does not, however, concern itself with the influence of the
succination ratio of the
anhydride in such combinations on the problem of asphaltene precipitation such
as at higher
saturate levels in the oil of lubricating viscosity in a TPEO. Component (B)
in the examples of
'594 is stated to be a PIBSA derived from a polyisobutene of number average
molecular weight
950; its succination ratio is not stated.
SUMMARY OF THE INVENTION
It is now surprisingly found that, when a polyalkenyl carboxylic acid
anhydride additive
of defined succination ratio, preferably made by a specifc process, is used in
a TPEO that
includes a hydroxybenzoate detergent additive, improved control of asphaltene
precipitation and
deposition on engine surfaces is achieved, particularly when the oil of
lubricating viscosity in the
TPEO is a high saturates content oil. The anhydride additive boosts the
performance of the
detergent additive.
Thus, 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
such engine when
fuelled by a heavy fuel oil, which composition comprises, or is made by
admixing, a major
amount of an oil of lubricating viscosity and, in respective minor amounts:
(A) an overbased metal hydrocarbyl-substituted hydroxybenzoate detergent
system,
and
(B) a hydrocarbyl-substituted succinic acid anhydride, preferably made
using
halogen- or radical-assisted functionalization processes, where the ratio of
succinic anhydride groups per substituted hydrocarbyl moiety is in the range
of
1.4 to 4.
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A second aspect of the invention is a method of preparing a trunk piston
marine engine
lubricating oil composition for a medium-speed compression-ignited marine
engine comprising
blending (A) and (B) with the oil of lubricating viscosity, each defined as in
the first aspect of
the invention.
A third aspect of the invention is a trunk piston marine engine lubricating
oil composition
for a medium-speed four-stroke compression-ignited marine engine obtainable by
the method of
the second aspect of the invention.
A fourth aspect of the invention is a method of operating a trunk piston
medium-speed
compression-ignited marine engine comprising:
(i) fuelling the engine with a heavy fuel oil; and
(ii) lubricating the engine with a composition as defined in the first
aspect of the
invention.
A fifth aspect of the invention is a method of dispersing asphaltenes in trunk
piston
marine lubricating oil composition during its lubrication of surfaces of a
medium-speed
compression-ignited marine engine and operation of the engine, which
comprises:
(i) providing a composition as defined in the first aspect of the
invention;
(ii) providing the composition to the engine;
(iii) providing heavy fuel oil to the engine; and
(iv) combusting the fuel oil.
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A sixth aspect of the invention is the use of detergent system (A) as defined
in, the first
aspect of the invention in combination with anhydride (B) as defined in the
first aspect of the
invention in a trunk piston marine lubricating oil composition for a medium-
speed compression-
ignited marine engine, to improve asphaltene handling during operation of the
engine which is
fueled by a heavy fuel oil.
A seventh aspect of the invention is the use of detergent system (A) as
defined in, the first
aspect of the invention in combination with anhydride (B) as defined in the
first aspect of the
invention in a trunk piston marine lubricating oil composition for a medium-
speed compression-
ignited marine engine, to improve asphaltene handling during operation of the
engine, fueled by
a heavy fuel oil, in comparison with analogous operation where anhydride (B)
has a ratio
different from that defined in the first aspect of the invention.
In this specification, the following words and expressions, if and when used,
have the
meanings ascribed below:
"Succination ratio" in relation to component (B) means the number of groups
derived
from succinic anhydride for each substituted hydrocarbyl moiety. The "succinic
ratio" or
"succination ratio" refers to the ratio calculated in accordance with the
procedure and
mathematical equation set forth in columns 5 and 6 of U.S. Pat. No. 5,334,321.
The calculation is
asserted to represent the average number of succinic groups in an alkenyl or
alkylsuccinic
anhydride per substituted alkenyl or alkyl chain.
"active ingredients" or "(a.i.)" refers to additive material that is not
diluent, solvent or
unreacted hydrocarbyl moeity;
"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
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"consists essentially of" permits inclusion of substances not materially
affecting the
characteristics of the composition to which it applies;
"major amount" means 50 or more, preferably 60 or more, more preferably 70 or
more,
and even more preferably 80 or more, mass % of a composition;
"minor amount" means less than 50, preferably less than 40, even more
preferably less
than 30 and most preferably less than 20, 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.
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.
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DETAILED DESCRIPTION OF THE INVENTION
The features of the invention in its various aspects, if and where applicable,
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);
alkylated naphthalenes; 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 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
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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-methy1-2-
ethylhexyl)silicate, tetra-(p-tert-butyl-phenyl) silicate, hexa-(4-methyl-2-
ethylhexyl)disiloxane,
poly(methyl)siloxanes and poly(methylphenyl)siloxanes. Other synthetic
lubricating oils include
liquid esters of phosphorous-containing acids (e.g., tricresyl phosphate,
trioctyl phosphate,
diethyl ester of decylphosphonic acid) and polymeric tetrahydrofurans.
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.
Refined oils are
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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, III, or IV.
Analytical Methods for Base Stock are tabulated below (Table E-1):
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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
The present invention particularly embraces those of the above oils containing
greater
than or equal to 90% saturates and less than or equal to 0.03% sulphur as the
oil of lubricating
viscosity, eg Group II, III, IV or V. They also include 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.
Preferably, the oil of lubricating viscosity in this invention contains 30,
such as 50,
mass % or more said basestocks. It may contain 60, such as 70, 80 or 90, mass
% or more of
said basestock or a mixture thereof. The oil of lubricating viscosity may be
substantially all of
said basestock or a mixture thereof.
It may be desirable, although not essential, to prepare one or more additive
packages or
concentrates comprising additives, whereby additives (A) and (B) can be added
simultaneously
to the oil of lubricating viscosity to form the TPEO.
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The final formulations as a trunk piston engine oil may typically contain up
to 30,
preferably 10 to 28, more preferably 12 to 24, mass % of the additive
package(s), the remainder
being the oil of lubricating viscosity. The trunk piston engine oil may have a
compositional
TBN (using ASTM D2896) of 20 to 60, preferably 30 to 55. Even more preferably,
it may be 40
to 55 or 35 to 50.
The combined treat rate of additives (A) and (B) contained in the lubricating
oil
composition may for example be in the range of 5 to 30, preferably 10 to 28,
more preferably 12
to 24, mass %.
OVERBASED METAL DETERGENT ADDITIVE (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
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
hydro carbyl-sub stituted hydroxybenzoate, preferably hydro c arbyl- sub
stituted 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:
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OH
C
%2
OM
R
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. When M is
polyvalent, it is
represented fractionally in the above formula.
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.
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
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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 is used. Basicity Index is the molar ratio of total base to
total soap in the
overbased detergent. The Basicity Index of the detergent (A) in the invention
is preferably in the
range of 1 to 8, more preferably 3 to 8, such as 3 to 7, such as 3 to 6. The
Basicity Index may for
example be greater than 3.
Overbased metal hydrocarbyl-substituted hydroxybenzoates can be prepared by
any of the
techniques employed in the art. A general method is as follows:
1.
Neutralisation of hydrocarbyl-substituted hydroxybenzoic acid with a molar
excess of
metallic base to produce a slightly overbased metal hydrocarbyl-substituted
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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 be 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 boiling 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 used as a diluent (or oil) dispersion. 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.
Preferably, the diluent used for (A) comprises a basestock containing greater
than or
equal to 90% saturates and less than or equal to 0.03% sulphur. (A) may
contain up to 20, 30, 40,
50, 60, 70, 80 or 90, mass% or more (such as all) of said basestock. An
example of said
basestock is a Group II basestock.
HYDROCARBYL-SUBSTITUTED SUCCINIC ACID ANHYDRIDE (B)
The anhydride may constitute at least 0.1 to 10, preferably 0.5 to 8.5, even
more
preferably 1 to 7, and most preferably 1.5 to 5, mass %, on an active
ingredient basis, of the
lubricating oil composition. Preferably it constitutes 2 to 5, more preferably
2.5 to 4, mass %.
The hydrocarbyl group is preferably a polyalkenyl group and preferably has
from 36 to
216, more preferably 56 to 108, carbon atoms. It may have a number average
molecular weight
in the range of 500 to 3,000; preferably 700 to 2,300, even more preferably
800 to 1,500.
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The succination ratio is, as stated, in the range of 1.4 to 4, preferably 1.4
to 3; more
preferably it is in the range of 1.50 to 2.20, even more preferably 1.50 to
2.00, and most
preferably 1.60 to 2.00.
Suitable hydrocarbons or polymers employed in the formation of the anhydrides
of the
present invention to generate the polyalkenyl moieties 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 R1 is
straight or branched chain alkyl radical comprising 1 to 26 carbon atoms and
wherein the
polymer contains carbon-to-carbon unsaturation, such as with a high degree of
terminal
ethenylidene unsaturation. Preferably, such polymers comprise interpolymers of
ethylene and at
least one alpha-olefin of the above formula, wherein RI is alkyl of from 1 to
18 carbon atoms,
and more preferably is alkyl of from 1 to 8 carbon atoms, and more preferably
still of from 1 to 2
carbon atoms. Therefore, useful alpha-olefin monomers and comonomers include,
for example,
propylene, butene-1, hexene-1, octene-1, 4-methylpentene-1, decene-1, dodecene-
1, tridecene-1,
tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1,
nonadecene-1, and
mixtures thereof (e.g., mixtures of propylene and butene-1, and the like).
Exemplary of such
polymers are propylene homopolymers, butene-1 homopolymers, ethylene-propylene
copolymers, ethylene-butene-1 copolymers, propylene-butene copolymers and the
like, wherein
the polymer contains at least some terminal and/or internal unsaturation.
Possible polymers are
unsaturated copolymers of ethylene and propylene and ethylene and butene-1.
The
interpolymers 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 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
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
CA 02913603 2015-11-30
monomer, in the presence of a catalyst system comprising at least one
metallocene (e.g., a
cyclopentadienyl-transition metal compound) and an alumoxane compound. Using
this process,
a polymer in which 95 % or more of the polymer chains possess terminal
ethenylidene-type
unsaturation can be provided. The percentage of polymer chains exhibiting
terminal ethenylidene
unsaturation may be determined by FTIR spectroscopic analysis, titration, or
C13 NMR.
Interpolymers of this latter type may be characterized by the formula POLY-
C(R1)=CH2
wherein RI is CI to C26 alkyl, preferably CI to C18 alkyl, more preferably CI
to C8 alkyl, and
most preferably Cl to C2 alkyl, (e.g., methyl or ethyl) and wherein POLY
represents the polymer
chain. The chain length of the RI 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), 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 polymer constitutes those 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. One embodiment utilizes
polyisobutylene prepared
from a pure isobutylene stream or a Raffinate I stream to prepare reactive
isobutylene polymers
with terminal vinylidene olefins. These polymers, referred to as highly
reactive polyisobutylene
(HR-PIB), may have a terminal vinylidene content of at least 65%. The
preparation of such
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polymers is described, for example, in U.S. Patent No. 4,152,499. HR-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 anhydride-producing moieties selectively at sites of carbon-to-
carbon unsaturation on
the polymer or hydrocarbon chains, or randomly along chains using one or more
of the three
processes mentioned above or combinations thereof, in any sequence.
Processes for reacting polymeric hydrocarbons with unsaturated carboxylic,
anhydrides
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 Bl;
CA-1,335,895 and GB-A-1,440,219. The polymer or hydrocarbon may be
functionalized, with
carboxylic acid anhydride moieties by reacting the polymer or hydrocarbon
under conditions that
result in the addition of functional moieties or agents, i.e., acid,
anhydride, 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- or radical-assisted
functionalization (e.g.
chlorination) processes, such as chloro or radical maleation.
Functionalization is preferably 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 130 to
220 C, e.g., 140
to 190 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
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adding the required number of functional moieties to the backbone, e.g.,
monounsaturated
carboxylic reactant, at 100 to 250 C, usually about 140 C to 220 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.
US 4,234,435 (above-mentioned) describes PIBSA's made by the chloro-route
(DieIs-
Alder process). Its abstract states "carboxylic acid acylating agents are
derived from polyalkenes
such as polybutenes, and a dibasic, carboxylic reactant such as maleic or
fumaric acid or certain
derivatives thereof These acylating agents are characterized in that the
polyalkenes from which
they are derived have a Mn value of about 1300 to about 5000 and a Mw/Mn value
of about 1.5
to about 4. The acylating agents are further characterized by the presence
within their structure of
at least 1.3 groups derived from the dibasic, carboxylic reactant for each
equivalent weight of the
groups derived from the polyalkene. The acylating agents can be reacted with a
further reactant
subject to being acylated such as polyethylene polyamines and polyols (e.g.,
pentaerythritol) to
produce derivatives useful per se as lubricant additives or as intermediates
to be subjected to
post-treatment with various other chemical compounds and compositions, such as
epoxides, to
produce still other derivatives useful as lubricant additives."
CA 2,471,534 describes PIBSA's made by the ene-reaction (falling outside the
present
invention). Its abstract relates to "a process for forming an ene reaction
product wherein an
enophile, such as maleic anhydride, is reacted with reactive polyalkene having
a terminal
vinylidene content of at least 30 mol%, at high temperature in the presence of
a free radical
inhibitor. The polyalkenyl acylating agents are useful per se as additives in
lubricating oils,
functional fluids, and fuels and also serve as intermediates in the
preparation of other products
(e.g., succinimides) useful as additives in lubricating oils, functional
fluids, and fuels. The
presence of the free radical inhibitor during the high temperature reaction
results in a reaction
product that is low, or substantially free from sediment."
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It is believed that the DieIs-Adler process produces a dicyclic two bond
attachment of the
succinic group to the polybutene. This is structurally rather rigid and keeps
the succinic group
limited to an imide structure when reacted with a functionalising agent such
as a polyamine. On
the other hand an ene-reaction (1,5 hydrogen shift reaction) PIBSA has a
single bond link
between the succinic group and polybutene, and as such will allow rotation and
opening of the
succinic group (to di-carboxylic acid) to allow di-amide formation in the
right energy conditions
(low temperature) and amine excess.
The hydrocarbon or polymer backbone can be functionalized by random attachment
of
functional moieties along the polymer chains by a variety of methods. For
example, the polymer,
in solution or in solid form, may be grafted with the monounsaturated
carboxylic reactant, as
described above, in the presence of a free-radical initiator. When performed
in solution, the
grafting takes place at an elevated temperature in the range of about 100 to
260 C, preferably
120 to 240 C. Preferably, free-radical initiated grafting would be
accomplished in a mineral
lubricating oil solution containing, e.g., 1 to 50 mass %, preferably 5 to 30
mass %, polymer
based on the initial total oil solution.
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 2% 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.
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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.
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.
The following examples illustrate but in no way limit the invention.
EXAMPLES
COMPONENTS
The following compounds were used:
Oil of lubricating viscosity
An API Group II 600R basestock from Chevron
(A) Detergents (1) a 225BN Ca alkyl salicylate (alkyl = C14-18)
(2) a 350BN Ca alkyl salicylate (alkyl = C14-18)
(B) A set of polyisobutene succinic anhydrides ("PIBSA") derived from a
polyisobutene and
made by a chloro-(Diels-Alder) process. The properties of each PIBSA are shown
in the
table in the RESULTS section below.
CA 02913603 2015-11-30
(C) A zinc dihydrocarbyl dithiophosphate at 0.5%.
Heavy Fuel Oil 1SO-F-RMG 380
LUBRICANTS
Selections of the above components were blended with the oil of lubricating
viscosity to
give a range of trunk piston marine engine lubricants. Some of the lubricants
were examples of
the invention; others were reference examples for comparison purposes. Each
lubricant
contained the same combination of detergents in (A) to give a lubricating oil
with a TBN of
40mgKOH/g and a different PIBSA at a treat rate of 2-6 mass %.
TESTING
Light Scattering
Test lubricants were 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.
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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 the
amount of backscattered light increases; 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 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.
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 i_tm to 1 mm. 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.
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The test lubricant formulations were heated to 60 C and stirred at 400 rpm. An
aliquot of
heavy fuel oil (16% w/w) was introduced into the lubricant formulation under
stirring using a
four-blade stirrer (at 400 rpm) and at 60 C. This mixture was stirred
overnight. With the
temperature at 60 C the FBRM probe was inserted into the sample- A value for
the average
counts per second was taken when the count rate had reached an equilibrium
value (typically
after 30 minutes equilibration time).
RESULTS
Response curves were generated showing the number of particle counts against
active
ingredient treat rate of the PIBSA. Results are presented as active ingredient
treat rate required
to deliver particle counts equivalent to a reference oil. Thus, lower active
ingredient treat rate
values indicate a better performance.
In the table below, the properties shown (Succination Ratio and MO are of the
PIBSA
used in each of the test lubricants.
Table 1
Active ingredient Treat
Maleation Succination PIB Mt, / rate required to reach
Examples
process Ratio g m01-1 normalised count=1 /
wt%
Comparative
Chloro 1.17 1331 4.50
example 1
Comparative
Chloro 1.19 950 4.93
Example 2
Comparative
Chloro 1.27 2225 4.10
Example 3
Comparative
Chloro 1.31 1600 4.70
Example 4
Example 1 Chloro 1.41 1331 2.58
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Example 2 Chloro 1.62 1331 3.10
Example 3 Chloro 1.64 950 1.60
Example 4 Chloro 1.88 950 1.70
Example 5 Chloro 1.91 1331 1.83
Example 6 Chloro 2.06 950 2.09
Example 7 Chloro 2.17 2225 2.67
Example 8 Chloro 2.20 2225 2.44
Example 9 Chloro 2.67 950 2.41
Example 10 Chloro 3.10 1331 2.01
Example 11 Chloro 3.94 950 2.35
The table shows that much better results are achieved at higher succination
ratios i.e. 1.41
to 3.94, as indicated below the bar. Although good results are achievable at
higher PIB
molecular weights, PIBSA's made therefrom have very high viscosities. They
therefore have to
be diluted much more than PIBSA's of lower PIB molecular weight. PIBSA's of
PIB Mõ 1,331
and 950 g mal are therefore preferred. Very high succination ratios or high
polymer molecular
weights leads to high viscosities; therefore a PIB Mr, range of 700-1500 g
moil and an SR range
1.50-2.00, preferably 1.70 or 1.65 ¨ 2.00, are preferred.
The anhydride additives of the invention have been shown to boost the
performance of
salicylates to improve their asphaltene dispersancy.
Conventionally, PIBSAPAM-type
dispersants are used to disperse contaminants in lubricating oils. Therefore,
a comparison was
made with two such PIBSAPAM-type dispersants (see table below). In combination
with
salicylates it can be seen that PIBSAPAM-type dispersants are not able to
reach equivalent
performance to the anhydride additives, which reach a normalised counts of ' 1
' (i.e. equivalent
performance) at much lower active ingredient treat rates.
Active ingredient Normalised
Example Description
Treat rate / wt% counts
Comparative Low molecular
3 9.0
Example 5 weight, low SR,
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chloro PIBSAPAM
type dispersant'
High molecular
Comparative weight chloro, low
3.3 4.17
Example 6 SR, PIBSAPAM type
dispersant'
1
As described in US-A-3,219,666 (low molecular weight PIBSAPAM) and US-A-
6,127,321 (high molecular
weight PIBSAPAM).
The materials of the invention do not work in the absence of salicylate
detergents to
affect asphaltene dispersancy. In the table below, the two PIBSAs were tested
in the absence of
salicylates and were unable to reach equivalent performance to any of the
PIBSA/salicylate
combinations of the invention. Even at significantly increased treat rates,
no further
improvements were observed.
CA 02913603 2015-11-30
Active ingredient Treat Normalised
Example Material SR
/ wt% counts
PIBSA
Comparative
from 1.18 3.58 6.4
Example 7
Example 4
Comparative
Example 2 1.62 3.78 7.16
Example 8
Furthermore, PIBSAs synthesised by a `thermal-ene' approach were ineffective
compared with the PIBSAs of the invention derived from a chloro or radical
maleation approach.
These were tested in combination with salicylates.
Active ingredient Treat rate
PIB Mi, / g
Example Process SR required to reach normalised
mo1-1
count=1 / wrio
Comparative
Thermal 1.18 450 4.72
Example 9
Comparative
Thermal 1.05 700 4.84
Example 10
Comparative
Thermal 1.05 950 4.8
Example 11
Comparative
Thermal 1.6 1300 6.8
Example 12
26
