Note: Descriptions are shown in the official language in which they were submitted.
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LUBRICATING OIL COMPOSITIONS COMPRISING 4-0X0BUTANOIC ACID
DERIVATIVES
FIELD OF THE INVENTION
This invention relates to automotive lubricating oil compositions, more
especially to
compositions suitable for use in piston engine, especially gasoline (spark-
ignited) and diesel
(compression-ignited), crankcase lubrication, such compositions being referred
to as
crankcase lubricants; and to use of additives in friction modification. The
invention concerns
use of friction modifiers in automotive lubrication.
BACKGROUND OF THE INVENTION
A crankcase lubricant is an oil used for general lubrication in an engine
where there is
an oil sump below the crankshaft of the engine and to which circulated oil
returns. It is well
known to include additives in crankcase lubricants for several purposes.
Friction modifiers,
also referred to as friction-reducing agents, may be boundary additives that
Operate by
lowering friction coefficient and hence improve fuel economy; the use of
glycerol monoesters
as friction modifiers has been described in the art, for example in US-A-
4,495,088; US-A-
4,683,069; EP-A.-0 092 946; and WO-A-01/72933. Glycerol monoester friction
modifiers
have been and are used commercially.
GB-A-2 106 106 describes reducing fuel consumption in an internal combustion
engine by lubricating the engine during operation with a lubricating
composition comprising a
minor amount of at least one ester having the formula RI (COOR4),õ wherein:
R1 is an aliphatic hydrocarbon-based radical free from acetylenic unsaturation
and
containing from about 10 to about 35 carbon atoms, in which at least 8 carbon
atoms are in a
straight-chain configuration;
each R4 is independently hydrogen or an alkyl or alkenyl radical containing up
to
about 18 carbon atoms, at least one R4 being alkyl or alkenyl; and
m is an integer from 2 to 5,
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Formulators of lubricants are always seeking further ways of reducing the
amount of
fuel consumed in operation of internal combustion engines.
SUMMARY OF THE INVENTION
This invention provides, surprisingly, as evidenced by the data in this
specification, an
improvement in friction modification over glycerol ester additives by
employing butanoic
acids or salts thereof.
In a first aspect, the invention comprises an automotive lubricating oil
composition
comprising or made by admixing:
(A) an oil of lubricating viscosity in a major amount; and
(B) as an oil-soluble or oil-dispersible additive component in a minor amount,
a 4-oxobutanoic acid, having the moiety
- CO (CH2)2COOH bonded to
(i) a group OR% where RI is hydrocarbyl group having from 10 to
30 carbon atoms, to provide a half-acid half-ester; or
(ii) a group X, where X an aromatic group substituted with at least
one hydrocarbyl group having from 10 to 30 carbon atoms to
provide a keto-acid; or
(iii) a group NR2R3 where one or both of R2 and R3 is hydrocarbyl
group having from 10 to 30 carbon atoms and one but not both
of R2 and R3 may be a hydrogen atom to provide a half acid-
half amide,
or a salt thereof.
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In a second aspect, this invention provides a method for lubricating an
internal
combustion engine comprising (a) supplying the crankcase thereof with a
composition
according to the first aspect of the invention, and (b) operating the engine.
In a third aspect, this invention provides the use of an oil-soluble or oil-
dispersible 4-
oxobutanoic acid or salt thereof as defined in the first aspect of the
invention as an additive
component in a lubricating oil composition to enhance, in the lubrication of
an internal
combustion engine, the friction-modifying properties of the lubricating oil
composition.
In this specification, the following words and expressions, if 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;
"hydrocarbyl" means a chemical group of a compound that contains hydrogen and
carbon atoms and that is bonded to the remainder of the compound directly via
a
carbon atom. The group may contain one or more atoms other than carbon and
hydrogen ("hetero atoms") provided they do not affect the essentially
hydrocarbyl
nature of the group;
"major amount" means in excess of 50 mass % of a composition;
"minor amount" means less than 50 mass % of a composition.
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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 to be 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 relating, where appropriate, to each and all
aspects of the
invention, will now be described in more detail as follows:
OIL OF LUBRICATING VISCOSITY (A)
The oil of lubricating viscosity (sometimes referred to as "base stock" or
"base oil") is
the primary liquid constituent of a lubricant, into which additives and
possible other oils are
blended, for example to produce a final lubricant (or lubricant composition).
A base oil is useful for making concentrates as well as for making lubricating
oil
compositions therefrom, and may be selected from natural (vegetable, animal or
mineral) and
synthetic lubricating oils and mixtures thereof. It may range in viscosity
from light distillate
mineral oils to heavy lubricating oils such as gas engine oil, mineral
lubricating oil, motor
vehicle oil and heavy duty diesel oil. Generally the viscosity of the oil
ranges from 2 to 30,
especially 5 to 20, mm2s-I at 100 C.
Natural oils include animal and vegetable oils (e.g. castor and lard oil),
liquid
petroleum oils and hydrorefined, solvent-treated mineral lubricating oils of
the paraffinic,
naphthenic and mixed paraffinic-naphthenic types. Oils of lubricating
viscosity derived from
coal or shale are also useful base oils.
Synthetic lubricating oils include hydrocarbon oils such as polymerized and
interpolymerized olefins (e.g. polybutylenes, polypropylenes, propylene-
isobutylene
copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes),
poly(1-decenes));
alkylbenzenes (e.g. dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes,
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di(2-ethylhexyl)benzenes); polyphenols (e.g. biphenyls, terphenyls, alkylated
polyphenols);
and alkylated diphenyl ethers and alkylated diphenyl sulfides and the
derivatives, analogues
and homologues thereof.
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 these esters include
dibutyl
adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate,
diisooctyl azelate,
diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate,
the 2-ethylhexyl
diester of linoleic acid dimer, and the complex ester formed by reacting one
mole of sebacic
acid with two moles of tetraethylene glycol and two moles of 2-ethylhexanoic
acid.
Esters useful as synthetic oils also include those made from C5 to C12
monocarboxylic
acids and polyols, and polyol ethers such as neopentyl glycol,
trimethylolpropane,
pentaerythritol, dipentaerythritol and tripentaerythritol.
Unrefined, refined and re-refined oils can be used in the compositions of the
present
invention. Unrefined oils are those obtained directly from a natural or
synthetic source
without further purification treatment. For example, a shale oil obtained
directly from
retorting operations, a petroleum oil obtained directly from distillation or
ester oil obtained
directly from an esterification process and used without further treatment
would be unrefined
oil. Refined oils are similar to the unrefined oils except they have been
further treated in one
or more purification steps to improve one or more properties. Many such
purification
techniques, 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 obtain refined oils applied to refined oils which
have been already
used in service. Such re-refined oils are also known as reclaimed or
reprocessed oils and
often are additional processed by techniques for approval of spent additive
and oil breakdown
products.
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Other examples of base oil are gas-to-liquid ("GTL") base oils, i.e. the base
oil may be
an oil derived from Fischer-Tropsch synthesised hydrocarbons made from
synthesis gas
containing H2 and CO 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.
Base oil may be categorised in Groups I to V according to the API EOLCS 1509
definition.
When the oil of lubricating viscosity is used to make a concentrate, it is
present in a
concentrate-forming amount (e.g., from 30 to 70, such as 40 to 60, mass %) to
give a
concentrate containing for example 1 to 90, such as 10 to 80, preferably 20 to
80, more
preferably 20 to 70, mass % active ingredient of an additive or additives,
being component
(B) above, or component (B) together with one or more co-additives. The oil of
lubricating
viscosity used in a concentrate is a suitable oleaginous, typically
hydrocarbon, carrier fluid,
e.g. mineral lubricating oil, or other suitable solvent. Oils of lubricating
viscosity such as
described herein, as well as aliphatic, naphthenic, and aromatic hydrocarbons,
are examples of
suitable carrier fluids for concentrates.
Concentrates constitute a convenient means of handling additives before their
use, as
well as facilitating solution or dispersion of additives in lubricating oil
compositions. When
preparing a lubricating oil composition that contains more than one type of
additive
(sometime referred to as "additive components"), each additive may be
incorporated
separately, each in the form of a concentrate. In many instances, however, it
is convenient to
provide a so-called additive "package" (also referred to as an "adpack")
comprising one or
more co-additives, such as described hereinafter, in a single concentrate.
In the present invention, the oil of lubricating viscosity, provided in a
major amount, is
in combination with a minor amount of at least one additive and, if necessary,
one or more co-
additives, such as described hereinafter, constituting a lubricating oil
composition. This
preparation may be accomplished by adding the additive directly to the oil or
by adding it in
the form of a concentrate thereof to disperse or dissolve the additive.
Additives may be added
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to the oil by any method known to those skilled in the art, either before, at
the same time as,
or after addition of other additives.
The terms "oil-soluble" or "oil-dispersible", or cognate terms, used herein do
not
necessarily indicate that the compounds or additives are soluble, dissolvable,
miscible, or are
capable of being suspended in the oil in all proportions. These do mean,
however, that they
are, for example, soluble or stably dispersible in oil to an extent sufficient
to exert their
intended effect in the environment in which the oil is employed. Moreover, the
additional
incorporation of other additives may also permit incorporation of higher
levels of a particular
additive, if desired.
The lubricating oil compositions of the invention may be used to lubricate
mechanical
engine components, particularly in internal combustion engines, e.g. spark-
ignited or
compression-ignited two- or four-stroke reciprocating engines, by adding the
composition
thereto. Preferably, they are crankcase lubricants.
The lubricating oil compositions of the invention (and also concentrates)
comprise
defined components that may or may not remain the same chemically before and
after mixing
with an oleaginous carrier. This invention encompasses compositions which
comprise the
defined components before mixing, or after mixing, or both before and after
mixing.
When concentrates are used to make the lubricating oil compositions, they may
for
example be diluted with 3 to 100, e.g. 5 to 40, parts by mass of oil of
lubricating viscosity per
part by mass of the concentrate.
ADDITIVE COMPONENT (B)
This, as stated, is a 4-oxobutanoic acid or salt thereof, carbon atoms number
2
and 3 thereof each being unsubstituted, i.e. they each carry two hydrogen
atoms and are part
of methylene groups so that the acid contains the ¨CO(CH2)2COOH moiety.
Without being
bound by any theory, it is believed that the methylene groups in the moiety
endow the three 0
atoms in the moiety with a greater ability to bond to iron on a surface
thereby enhancing the
friction modification properties of the molecule of which the moiety is a
part.
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Component (B) may be "ashless" in the sense of being a non-metallic organic
material
that forms substantially no ash on combustion in contrast to metal-containing
and hence ash-
forming materials. To confer oil-solubility or oil-dispersibility to the
additive component, it
carries an appropriate hydrocarbyl group, as in each of (i), (ii) and (iii) as
defined herein.
In (i), the 4-oxobutanoic acid (B) is a half acid¨half ester. The hydrocarbyl
group RI
confers oil-solubility and is straight chain or branched, preferably straight
chain, and
preferably has from 12 to 20 carbon atoms. It may be alkenyl or alkyl,
preferably alkenyl
when it preferably has one double bond only. As an example of (i), there may
be mentioned
RIO CO (CH2)2 COOH where the group RI is CH3 (CH2)7 CH = CH (CH2)8, i.e. the
group RI
is oleyl.
US-A-4 096 077 ('077) describes lubricating oil compositions that contain at
least one
half-acid half-ester of succinic acid and an alcohol. '077 describes their use
as wear inhibitors
but in combination with benzotriazoles, CI-Cm alkyl-substituted
benzotriazoles, and half-acid
half esters of maleic anhydride.
It is preferred that, when the additive component (B) is (i) or (iii), the
composition of
the invention does not contain either or both of: (a) a half-acid-half-ester
of maleic anhydride;
and (b) a benzotriazole or C1-C20 alkyl-substituted benzotriazole.
In (ii), (B) is a 4-keto carboxylic acid. The keto group is bonded to an
aromatic group
such as an aryl or phenyl group which, in turn, is hydrocarbyl-substituted,
such as with an
alkyl group having from 12 to 20 carbon atoms, in order to confer oil-
solubility or oil-
dispersibility. Such a keto-compound may conveniently be made by acylating an
alkyl-
substituted benzene with succinic anhydride.
In (iii), (B) is a half acid-half monoamide, such as obtained by reacting a
long chain
alkylamine, e.g. where the hydrocarbyl group is an alkyl group and has from 12
to 20 carbon
atoms, and succinic acid.
As examples of salts of 4-oxobutanoic acid, there may be mentioned salts
formed by
reacting the carboxylic acid group with a hydrocarbyl derivative of pyridine,
or salts formed
by reacting the carboxylic acid group with di-n-butylamine or with tri-n-
butylamine.
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CO-ADDITIVES
As co-additives in the compositions of the invention, there may be mentioned
other
organic friction modifiers, different from (B), such as those having a polar
head group that
contains an oxygen atom or a nitrogen atom or both. They may be referred to as
organic,
ashless (metal-free) friction modifiers and may be ester-based, such as
glycerol mono-oleate,
or amine-based (aminic). Also, there may be mentioned inorganic friction
modifiers, i.e.,
metal-containing friction modifiers. Organo-molybdenum compounds, such as
dinuclear or
trinuclear molybdenum compounds, are preferred where an inorganic friction
modifier is to
be provided, and may be present at a concentration in the range 0.1 to 2 mass
%, or providing
at least 10 such as 50 to 2,000 ppm by mass of molybdenum atoms.
Preferably, the molybdenum from the molybdenum compound is present in an
amount
of from 10 to 1500, such as 20 to 1000, more preferably 30 to 750, ppm based
on the total
weight of the lubricating oil composition. For some applications, the
molybdenum is present
in an amount of greater than 500 ppm.
Other co-additives, with representative effective amounts are listed below.
All the
values listed are stated as mass percent active ingredient.
Additive Mass % Mass %
(Broad) (Preferred)
Ashless Dispersant 0.1 ¨ 20 1 ¨ 8
Metal Detergents 0.1 ¨ 15 0.2 ¨9
Corrosion Inhibitor 0 ¨ 5 0 ¨ 1.5
Metal Dihydrocarbyl Dithiophosphate 0¨ 10 0 ¨ 4
Anti-Oxidants 0 ¨ 5 0.01 ¨3
Pour Point Depressant 0.01 ¨5 0.01 ¨ 1.5
Anti-Foaming Agent 0 ¨ 5 0.001 ¨0.15
Supplement Anti-Wear Agents 0 ¨5 0 ¨ 2
Viscosity Modifier (1) 0 ¨ 6 0.01 ¨4
Mineral or Synthetic Base Oil Balance Balance
(1) Viscosity modifiers are used only in multi-graded oils.
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The final lubricating oil composition, typically made by blending the or each
additive into the
base oil, may contain from 5 to 25, preferably 5 to 18, typically 7 to 15,
mass % of the
concentrate, the remainder being oil of lubricating viscosity.
The above mentioned co-additives are discussed in further detail as follows;
as is
known in the art, some additives can provide a multiplicity of effects, for
example, a single
additive may act as a dispersant and as an oxidation inhibitor.
A dispersant is an additive whose primary function is to hold solid and liquid
contaminations in suspension, thereby passivating them and reducing engine
deposits at the
same time as reducing sludge depositions. For example, a dispersant maintains
in suspension
oil-insoluble substances that result from oxidation during use of the
lubricant, thus preventing
sludge flocculation and precipitation or deposition on metal parts of the
engine.
Dispersants are usually "ashless", as mentioned above, being non-metallic
organic
materials that form substantially no ash on combustion, in contrast to metal-
containing, and
hence ash-forming materials. They comprise a long hydrocarbon chain with a
polar head, the
polarity being derived from inclusion of e.g. an 0, P. or N atom. The
hydrocarbon is an
oleophilic group that confers oil-solubility, having, for example 40 to 500
carbon atoms.
Thus, ashless dispersants may comprise an oil-soluble polymeric backbone.
A preferred class of olefin polymers is polybutenes, specifically
polyisobutenes (NB)
or poly-n-butenes, such as may be prepared by polymerization of a C4 refinery
stream.
Dispersants include, for example, derivatives of long chain hydrocarbon-
substituted
carboxylic acids, examples being derivatives of high molecular weight
hydrocarbyl-
substituted succinic acid. A noteworthy group of dispersants are hydrocarbon-
substituted
succinimides, made, for example, by reacting the above acids (or derivatives)
with a nitrogen-
containing compound, advantageously by a polyalkylene polyamine, such as a
polyethylene
polyamine. Particularly preferred are the reaction products of polyalkylene
polyamines with
alkenyl succinic anhydrides, such as described in US-A-3,202,678; -3,154,560; -
3,172,892; -
3,024,195; -3,024,237, -3,219,666; and -3,216,936; and BE-A-66,875 that may be
post-treated
to improve their properties, such as borated (as described in US-A-3,087,936
and -3,254,025)
fluorinated and oxylated. For example, boration may be accomplished by
treating an acyl
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nitrogen-containing dispersant with a boron compound selected from boron
oxide, boron
halides, boron acids and esters of boron acids.
A detergent is an additive that reduces formation of piston deposits, for
example high-
temperature varnish and lacquer deposits, in engines; it normally has acid-
neutralising
properties and is capable of keeping finely divided solids in suspension. Most
detergents are
based on metal "soaps", that is metal salts of acidic organic compounds.
Detergents generally comprise a polar head with a long hydrophobic tail, the
polar
head comprising a metal salt of an acidic organic compound. The salts may
contain a
substantially stoichiometric amount of the metal when they are usually
described as normal or
neutral salts and would typically have a total base number or TBN (as may be
measured by
ASTM D2896) of from 0 to 80. Large amounts of a metal base can be included by
reacting
an excess of a metal compound, such as an oxide or hydroxide, with an acidic
gas such as
carbon dioxide. The resulting overbased detergent comprises neutralised
detergent as an
outer layer of a metal base (e.g. carbonate) micelle. Such overbased
detergents may have a
TBN of 150 or greater, and typically of from 250 to 500 or more.
Detergents that may be used include oil-soluble neutral and overbased
sulfonates,
phenates, sulfurized phenates, thiophosphonates, salicylates, and naphthenates
and other oil-
soluble carboxylates of a metal, particularly the alkali or alkaline earth
metals, e.g. sodium,
potassium, lithium, calcium and magnesium. The most commonly used metals are
calcium
and magnesium, which may both be present in detergents used in a lubricant,
and mixtures of
calcium and/or magnesium with sodium. Particularly convenient metal detergents
are neutral
and overbased calcium sulfonates and sulfurized phenates having a TBN of from
50 to 450.
Anti-oxidants are sometimes referred to as oxidation inhibitors; they increase
the
resistance of the composition to oxidation and may work by combining with and
modifying
peroxides to render them harmless, by decomposing peroxides, or by rendering
an oxidation
catalyst inert. Oxidative deterioration can be evidenced by sludge in the
lubricant, varnish-
like deposits on the metal surfaces, and by viscosity growth.
They may be classified as radical scavengers (e.g. sterically hindered
phenols,
secondary aromatic amines, and organo-copper salts); hydroperoxide decomposers
(e.g.,
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organosulphur and organophosphorus additives); and multifimctionals (e.g. zinc
dihydrocarbyl dithiophosphates, which may also function as anti-wear
additives, and organo-
molybdenum compounds, which may also function as friction modifiers and anti-
wear
additives).
Examples of suitable antioxidants are selected from copper-containing
antioxidants,
sulphur-containing antioxidants, aromatic amine-containing antioxidants,
hindered phenolic
antioxidants, dithiophosphates derivatives, metal thiocarbamates, and
molybdenum-
containing compounds.
Dihydrocarbyl dithiophosphate metals salts are frequently used as antiwear and
antioxidant agents. The metal may be an alkali or alkaline earth metal, or
aluminium, lead, tin,
zinc molybdenum, manganese, nickel or copper. Zinc salts are most commonly
used in
lubricating oil such as in amounts of 0.1 to 10, preferably 0.2 to 2, mass %,
based upon the
total mass of the lubricating oil compositions. They may be prepared in
accordance with
known techniques by first forming a dihydrocarbyl dithiophosphoric acid
(DDPA), usually by
reaction of one or more alcohols or a phenol with P2S5, and then neutralising
the formed
DDPA with a zinc compound. For example, a dithiophosphoric acid may be made by
reaction with mixtures of primary and secondary alcohols. Alternatively,
multiple
dithiophosphoric acids can be prepared where the hydrocarbyl groups on one
acid are entirely
secondary in character and the hydrocarbyl groups on the other acids are
entirely primary in
character. To make the zinc salt, any basic or neutral zinc compound could be
used but the
oxides, hydroxides and carbonates are most generally employed. Commercial
additives
frequently contain an excess of zinc due to use of an excess of the basic zinc
compound in the
neutralisation reaction.
Anti-wear agents reduce friction and excessive wear and are usually based on
compounds containing sulphur or phosphorous or both, for example that are
capable of
depositing polysulfide films on the surfaces involved. Noteworthy are the
dihydrocarbyl
dithiophosphates, such as the zinc dialkyl dithiophosphates (ZDDP's) discussed
herein.
Examples of ashless anti-wear agents include 1,2,3-triazoles, benzotriazoles,
thiadiazoles, sulfurised fatty acid esters, and dithiocarbamate derivatives.
=
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Rust and corrosion inhibitors serve to protect surfaces against rust and/or
corrosion.
As rust inhibitors there may be mentioned non-ionic polyoxyalkylene polyols
and esters
thereof, polyoxyalkylene phenols, and anionic alkyl sulfonic acids.
Pour point depressants, otherwise known as lube oil flow improvers, lower the
minimum temperature at which the oil will flow or can be poured. Such
additives are well
known. Typical of these additive are C8 to C18 dialkyl fumerate/vinyl acetate
copolymers and
polyalkylmethacrylates.
Additives of the polysiloxane type, for example silicone oil or polydimethyl
siloxane,
can provide foam control.
A small amount of a demulsibring component may be used. A preferred
demulsifying
component is described in EP-A-330,522. It is obtained by reacting an alkylene
oxide with an
adduct obtained by reacting a bis-epoxide with a polyhydric alcohol. The
demulsifier should
be used at a level not exceeding 0.1 mass % active ingredient. A treat rate of
0.001 to 0.05
mass % active ingredient is convenient.
Viscosity modifiers (or viscosity index improvers) impart high and low
temperature
operability to a lubricating oil. Viscosity modifiers that also function as
dispersants are also
known and may be prepared as described above for ashless dispersants. In
general, these
dispersant viscosity modifiers are functionalised polymers (e.g. interpolymers
of ethylene-
propylene post grafted with an active monomer such as maleic anhydride) which
are then
derivatised with, for example, an alcohol or amine.
The lubricant may be formulated with or without a conventional viscosity
modifier
and with or without a dispersant viscosity modifier. Suitable compounds for
use as viscosity
modifiers are generally high molecular weight hydrocarbon polymers, including
polyesters.
Oil-soluble viscosity modifying polymers generally have weight average
molecular weights
of from 10,000 to 1,000,000, preferably 20,000 to 500,000, which may be
determined by gel
permeation chromatography or by light scattering.
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EXAMPLES
The invention will now be particularly described in the following examples
which are
not intended to limit the scope of the claims hereof.
In the examples, the following additive components were used in examples of
the
invention:
Bl: a 4-oxobutanoic acid in the form of 4-stearyl benzoyl propanoic acid
(SBP); and
B2: a 4-oxobutanoic acid in the form of mono-oleyl
succinate (MOS); and
a glycerol mono-oleate friction modifier (GMO), known in the art, used
in a reference example.
Component B1 was synthesised by acylation of stearylbenzene with succinic
anhydride according to a literature procedure (P. Nuhn et al; Pharmazie 53,
12, 825, 1998).
Thus, aluminium trichloride was added to a mixture of stearylbenzene and
succinic anhydride
in nitrobenzene at 5 C. After standing overnight the mixture was poured over
ice and washed
with water. Evaporation of the solvent from the organic layer gave the product
(SBP) in good
purity. A total of 230 grams of product was prepared in three batches.
Component B2 was prepared by reacting 0.5 moles of succinic anhydride with 0.5
moles of oleyl alcohol. The reactants were mixed under a nitrogen blanket with
an overhead
stirrer in a 500m1 flask fitted with a condenser for six hours at 120 C. The
resultant mono-
ley' succinate was used without further purification.
Using the same base oil, each of the above additive components was blended
into
compositions to provide examples of the invention and a reference example. The
contents of
the compositions are set forth below under the heading "Testing and Results".
CA 02612055 2007-11-22
. .
PF2006M012FF 15
TESTING AND RESULTS
A high frequency reciprocating rig (HFRR) was used to evaluate the coefficient
of
friction of each of the above compositions. Examples of the invention are
identified as
Examples 1 and 2, and corresponding reference examples as Examples l' and 2'.
Experiment 1
The HFRR test protocol employed was as follows:
Contact
6 mm ball on 10 mm disc
Load, N
4
Stroke Length, mm
1
Frequency, Hz
20
Temperature, C
100
Time of reciprocation, s
3600
The results obtained were as follows:
Example Additive Coefficient of
Friction
1 B1 (SBP) - 0.092
1' GMO 0.123
In this experiment, each oil composition contained 0.2 mass % of active
ingredient of
the additive in the above table. The compositions were identical other than in
respect of the
identity of the additive shown in the table above.
The coefficient of friction measurements were average values taken after 60
minutes
at 100 C.
Experiment 2
The HFRR test protocol employed was as follows:
CA 02612055 2007-11-22
PF2006M012FF 16
Contact 6
mm ball on 10 mm disc
Load, N 4
Stroke Length, mm 1
Frequency, Hz 20
Temperature range, C 40-
140
Temperature step, C 20
Time of reciprocation at each temperature, s 300
The results obtained were as follows:
Coefficient of Friction
Example Additive 40 C 60 C 80 C 100 C 120 C 140 C
2 B2 0.101 0.106 0.120 0.111 0.099 0.091
(MOS)
2' GMO 0.153 0.162 0.150 0.148 0.119 0.116
In this experiment, each oil composition contained 0.2 mass % of active
ingredient of
the additive in the table above. The compositions were identical other than in
respect of the
identity of the additive shown in the table above.
The coefficient of friction measurements were average values taken after 30
minutes
at each of the indicated temperatures.
The above results show that the compositions of the invention (Examples 1 and
2)
gave rise to better (i.e. smaller) coefficient of friction values in all cases
than the
corresponding reference compositions (Examples l' and 2').
