U.S. patent application number 16/607927 was filed with the patent office on 2020-03-26 for lubricating composition.
The applicant listed for this patent is SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ BV, SHELL OIL COMPANY. Invention is credited to Artemis KONTOU, Neal Matthew MORGAN, Mark Clift SOUTHBY, Hugh Alexander SPIKES.
Application Number | 20200095516 16/607927 |
Document ID | / |
Family ID | 58638801 |
Filed Date | 2020-03-26 |
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United States Patent
Application |
20200095516 |
Kind Code |
A1 |
SOUTHBY; Mark Clift ; et
al. |
March 26, 2020 |
LUBRICATING COMPOSITION
Abstract
Use of a nitrogen-containing ashless dispersant in a lubricating
composition for the purpose of reducing wear in the presence of
ZDTP and soot wherein the nitrogen-containing ashless dispersant
has a Functionality (F) of greater than 1.4.
Inventors: |
SOUTHBY; Mark Clift;
(London, GB) ; MORGAN; Neal Matthew; (London,
GB) ; KONTOU; Artemis; (London, GB) ; SPIKES;
Hugh Alexander; (London, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ BV
SHELL OIL COMPANY |
THE HAGUE
HOUSTON |
TX |
NL
US |
|
|
Family ID: |
58638801 |
Appl. No.: |
16/607927 |
Filed: |
April 18, 2018 |
PCT Filed: |
April 18, 2018 |
PCT NO: |
PCT/EP2018/059960 |
371 Date: |
October 24, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 2217/028 20130101;
C10N 2030/45 20200501; C10M 2201/041 20130101; C10M 161/00
20130101; C10M 169/044 20130101; C10M 2203/003 20130101; C10M
149/10 20130101; C10N 2030/041 20200501; C10M 141/10 20130101; C10M
2205/173 20130101; C10N 2040/25 20130101; C10M 2215/28 20130101;
C10N 2030/06 20130101; C10M 137/10 20130101; C10M 2223/045
20130101; C10M 2223/045 20130101; C10N 2010/04 20130101 |
International
Class: |
C10M 161/00 20060101
C10M161/00; C10M 169/04 20060101 C10M169/04; C10M 137/10 20060101
C10M137/10; C10M 149/10 20060101 C10M149/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 27, 2017 |
EP |
17168538.1 |
Claims
1. A lubricating composition for the purpose of reducing wear in
the presence of a zinc dithiophosphate compound and soot, the
lubricating composition comprising a nitrogen-containing ashless
dispersant that has a Functionality (F) of greater than 1.4.
2. The lubricating composition of claim 1, wherein the
nitrogen-containing ashless dispersant has a Functionality (F) of
greater than 1.5.
3. The lubricating composition of claim 1, wherein the
nitrogen-containing ashless dispersant comprises a functionalized
oil-soluble polymeric hydrocarbon backbone which has been
derivatized with a nitrogen-containing nucleophilic reactant.
4. The lubricating composition of claim 3, wherein the
nitrogen-containing nucleophilic reactant is selected from an
amine, amino-alcohol, amide, or mixture thereof.
5. The lubricating composition of claim 3, wherein the
nitrogen-containing nucleophilic reactant is an amine.
6. The lubricating composition of claim 1, wherein the
nitrogen-containing ashless dispersant comprises at least one
polyalkenyl succinimide, which is the reaction product of a
polyalkenyl substituted succinic anhydride and a polyamine.
7. The lubricating composition of claim 1, wherein the
nitrogen-containing ashless dispersant comprises at least one
polyisobutylene succinimide.
8. The lubricating composition of claim 1, wherein the
nitrogen-containing dispersant is present in the lubricating
composition at a level such as to provide a level of nitrogen of
from 0.001 wt % to 15 wt %, by weight of the lubricating
composition.
9. The lubricating composition of claim 1, wherein the
nitrogen-containing dispersant is present in the lubricating
composition at a level such as to provide a level of nitrogen of
from 0.05 wt % to 0.1 wt %, by weight of the lubricating
composition.
10. The lubricating composition of claim 1, wherein the lubricating
composition comprises a base oil and one or more additives.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a lubricating oil
composition, in particular to a lubricating oil composition which
is suitable for lubricating internal combustion engines and which
has reduced wear properties.
BACKGROUND OF THE INVENTION
[0002] Increasingly severe automobile regulations in respect of
emissions and fuel efficiency are placing increasing demands on
both engine manufacturers and lubricant formulators to provide
effective solutions to improve fuel economy.
[0003] Optimising lubricants through the use of high performance
basestocks and novel additives represents a flexible solution to a
growing challenge.
[0004] Anti-wear additives are important to mitigate issues arising
from the desire to have low viscosity formulations in order to
reduce fuel consumption and various such additives are already
known in the art.
[0005] A common anti-wear additive which is well known for use in
lubricating compositions is a zinc dithiophosphate, such as, for
example, zinc dialkyl-, diaryl- or alkylaryl-dithiophosphates. Zinc
dithiophosphate may be conveniently represented by general formula
II:
##STR00001##
wherein R.sup.2 to R.sup.5 may be the same or different and are
each a primary alkyl group containing from 1 to 20 carbon atoms
preferably from 3 to 12 carbon atoms, a secondary alkyl group
containing from 3 to 20 carbon atoms, preferably from 3 to 12
carbon atoms, an aryl group or an aryl group substituted with an
alkyl group, said alkyl substituent containing from 1 to 20 carbon
atoms preferably 3 to 18 carbon atoms.
[0006] Examples of suitable zinc dithiophosphates which are
commercially available include those available ex. Lubrizol
Corporation under the trade designations "Lz 1097" and "Lz 1395",
those available ex. Chevron Oronite under the trade designations
"OLOA 267" and "OLOA 269R", and that available ex. Afton Chemical
under the trade designation "HITEC 7197"; C9417, zinc
dithiophosphates such as that available from Infineum under the
tradename Infineum C9417, those available from Lubrizol Corporation
under the trade designations "Lz 677A", "Lz 1095" and "Lz 1371",
that available ex. Chevron Oronite under the trade designation
"OLOA 262" and that available ex. Afton Chemical under the trade
designation "HITEC 7169"; and zinc dithiophosphates such as those
available ex. Lubrizol Corporation under the trade designations "Lz
1370" and "Lz 1373" and that available ex. Chevron Oronite under
the trade designation "OLOA 260".
[0007] While zinc dithiophosphate compounds are useful for reducing
wear in lubricating compositions, it has been recently found that
in the presence of soot, zinc dithiophosphates can lead to an
undesirable increase in wear via a newly identified wear mechanism.
The wear mechanism of corrosion/abrasion was identified and
published in 2010, see Olomolehin, Y., Kapadia, R. G., Spikes, H.
A., "Antagonistic interaction of antiwear additives and carbon
black." Trib Letters 37, 49-58, (2009). A more recent paper has
recently reaffirmed this mechanism, see Salehi, F. Motamen, D. N.
Khaemba, A. Morina, and A. Neville, "Corrosive-Abrasive Wear
Induced by Soot in Boundary Lubrication Regime." Trib Letters 63,
1-11, (2016).
[0008] It would therefore be desirable to find a way to reduce wear
of lubricating compositions containing zinc dithiophosphate
compounds in the presence of soot.
[0009] It has now surprisingly been found that by using certain
nitrogen-containing ashless dispersants, a lubricating oil
composition can be provided which exhibits reduced wear in the
presence of zinc dithiophosphate compounds and soot.
SUMMARY OF THE INVENTION
[0010] Accordingly, the present invention provides the use of a
nitrogen-containing ashless dispersant in a lubricating composition
for the purpose of reducing wear in the presence of zinc
dithiophosphate compounds and soot wherein the nitrogen-containing
ashless dispersant has a functionality (F) of greater than 1.4.
DETAILED DESCRIPTION OF THE INVENTION
[0011] As used herein the term "soot" means a deep black powdery or
flaky substance consisting largely of amorphous carbon. Gas-phase
soot contains polycyclic aromatic hydrocarbons (PAH). Soot is
produced by the incomplete burning of organic matter, such as
hydrocarbon based fuels. It consists of agglomerated nanoparticles
with diameters between 6 and 30 nm. The soot particles can be mixed
with metal oxides and with minerals and can be coated with sulfuric
acid. In the context of an internal combustion engine, soot can
travel from the combustion chamber into the lubricant and can
accumulate in the lubricant.
[0012] In the context of the present invention, the amount of soot
in the lubricating composition containing the zinc dithiophosphate
compound is typically at a level of from 0.1 wt % to 10 wt %. In
one embodiment, the level of soot is from 2 to 7 wt %, by weight of
the lubricating composition. In another embodiment, the level of
soot is from 3.5 to 7 wt %, by weight of the lubricating
composition. In another embodiment, the level of soot is from 5 to
6 wt %, by weight of the lubricating composition.
[0013] The nitrogen-containing ashless dispersant is present in the
lubricating composition herein at a level so as to provide a level
of nitrogen from 0.001 wt % to 0.15 wt %, preferably from 0.05 wt %
to 0.1 wt %, by weight of the lubricating composition.
[0014] The nitrogen-containing ashless dispersant is used herein to
reduce the wear exhibited by a lubricating composition in the
presence of zinc dithiophosphate compounds and soot. Hence the term
"reducing wear" as used herein means reducing the level of wear to
a level below that exhibited by a lubricating composition which
contains zinc dithiophosphate and soot but which does not contain
the nitrogen-containing ashless dispersant described herein.
[0015] In a preferred embodiment herein, the nitrogen-containing
ashless dispersant is used to reduce the wear by at least 5%, more
preferably by at least 10%, even more preferably by at least 50%,
and especially by at least 80%, even more especially by at least
90%, compared with that of an analogous lubricating composition
which contains zinc dithiophosphate and soot but which does not
contain the nitrogen-containing ashless dispersant described
herein.
[0016] Suitable dispersants for use herein comprise an oil soluble
polymeric long chain backbone having functional groups capable of
associating with particles to be dispersed. Typically, such
dispersants have amine, amine-alcohol or amide polar moieties
attached to the polymer backbone, often via a bridging group. The
dispersant may be, for example, selected from oil soluble salts,
esters, amino-esters, amides, imides and oxazolines of long chain
hydrocarbon-substituted mono- and polycarboxylic acids or
anhydrides thereof; thiocarboxylate derivatives of long chain
hydrocarbons;
[0017] long chain aliphatic hydrocarbons having polyamine moieties
attached directly thereto; and Mannich condensation products formed
by condensing a long chain substituted phenol with formaldehyde and
polyalkylene polyamine.
[0018] Generally, each mono- or dicarboxylic acid-producing moiety
will react with a nucleophilic group (amine or amide) and the
number of functional groups in the polyalkenyl-substituted
carboxylic acylating agent will determine the number of
nucleophilic groups in the finished dispersant.
PIB Description
[0019] The polyalkenyl moiety of the dispersant used in the present
invention has a number average molecular weight of from about 700
to about 3000, preferably between 950 and 3000, such as between 950
and 2800, more preferably from about 950 to 2500, and most
preferably from about 950 to about 2400. The molecular weight of a
dispersant is generally expressed in terms of the molecular weight
of the polyalkenyl moiety as the precise molecular weight range of
the dispersant depends on numerous parameters including the type of
polymer used to derive the dispersant, the number of functional
groups, and the type of nucleophilic group employed.
[0020] The polyalkenyl moiety from which the high molecular weight
dispersants are derived preferably have a narrow molecular weight
distribution (MWD), also referred to as polydispersity, as
determined by the ratio of weight average molecular weight
(M.sub.w) to number average molecular weight (Me). Specifically,
polymers from which the dispersants used in the present invention
are derived have a M.sub.w/M.sub.n of from about 1.5 to about 2.0,
preferably from about 1.5 to about 1.9, most preferably from about
1.6 to about 1.8.
[0021] Suitable hydrocarbons or polymers employed in the formation
of the dispersants used in the present invention include
homopolymers, interpolymers or lower molecular weight hydrocarbons.
One family of such polymers comprise polymers of ethylene and/or at
least one C.sub.3 to C.sub.28 alpha-olefin having the formula
H.sub.2C.dbd.CHR.sup.1 wherein R.sup.1 is straight or branched
chain alkyl radical comprising 1 to 26 carbon atoms and wherein the
polymer contains carbon-to-carbon unsaturation, preferably a high
degree of terminal ethenylidene unsaturation. Preferably, such
polymers comprise interpolymers of ethylene and at least one
alpha-olefin of the above formula, wherein R.sup.1 is alkyl of from
1 to 18 carbon atoms, and more preferably is alkyl of from 1 to 8
carbon atoms, and more preferably still of from 1 to 2 carbon
atoms. Therefore, useful alpha-olefin monomers and comonomers
include, for example, propylene, butene-1, hexene-1, octene-1,
4-methylpentene-1, decene-1, dodecene-1, tridecene-1,
tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1,
octadecene-1, nonadecene-1, and mixtures thereof (e.g., mixtures of
propylene and butene-1, and the like). Exemplary of such polymers
are propylene homopolymers, butene-1 homopolymers,
ethylene-propylene copolymers, ethylene-butene-1 copolymers,
propylene-butene copolymers and the like, wherein the polymer
contains at least some terminal and/or internal unsaturation.
Preferred polymers are unsaturated copolymers of ethylene and
propylene and ethylene and butene-1. The interpolymers used herein
may contain a minor amount, e.g. 0.5 to 5 mole % of a C.sub.4 to
C.sub.18 non-conjugated diolefin comonomer. However, it is
preferred that the polymers used in the present 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.
[0022] These polymers may be prepared by polymerizing alpha-olefin
monomer, or mixtures of alpha-olefin monomers, or mixtures
comprising ethylene and at least one C.sub.3 to C.sub.28
alpha-olefin monomer, in the presence of a catalyst system
comprising at least one metallocene (e.g., a
cyclopentadienyl-transition metal compound) and an alumoxane
compound. Using this process, a polymer in which 95% or more of the
polymer chains possess terminal ethenylidene-type unsaturation can
be provided. The percentage of polymer chains exhibiting terminal
ethenylidene unsaturation may be determined by FTIR spectroscopic
analysis, titration, or C.sup.13 NMR. Interpolymers of this latter
type may be characterized by the formula
POLY-C(R.sup.1).dbd.CH.sub.2 wherein R.sup.1 is C.sub.1 to C.sub.26
alkyl, preferably C.sub.1 to C.sub.28 alkyl, more preferably
C.sub.1 to C.sub.8 alkyl, and most preferably C.sub.1 to C.sub.2
alkyl, (e.g., methyl or ethyl) and wherein POLY represents the
polymer chain. The chain length of the R.sup.1 alkyl group will
vary depending on the comonomer(s) selected for use in the
polymerization. A minor amount of the polymer chains can contain
terminal ethenyl, i.e., vinyl, unsaturation, i.e.
POLY-CH.dbd.CH.sub.2, and a portion of the polymers can contain
internal monounsaturation, e.g. POLY-CH.dbd.CH(R.sup.1), wherein
R.sup.1 is as defined above. These terminally unsaturated
interpolymers may be prepared by known metallocene chemistry and
may also be prepared as described in U.S. Pat. Nos. 5,498,809;
5,663,130; 5,705,577; 5,814,715; 6,022,929 and 6,030,930.
[0023] Another useful class of polymers is polymers prepared by
cationic polymerization of isobutene, styrene, and the like. Common
polymers from this class include polyisobutenes obtained by
polymerization of a C.sub.4 refinery stream having a butene content
of about 35 to about 75 mass %, and an isobutene content of about
30 to about 60 mass %, in the presence of a Lewis acid catalyst,
such as aluminum trichloride or boron trifluoride. A preferred
source of monomer for making poly-n-butenes is petroleum
feedstreams such as Raffinate II. These feedstocks are disclosed in
the art such as in U.S. Pat. No. 4,952,739. Polyisobutylene is a
most preferred backbone herein because it is readily available by
cationic polymerization from butene streams (e.g., using AlCl.sub.3
or BF.sub.3 catalysts). Such polyisobutylenes generally contain
residual unsaturation in amounts of about one ethylenic double bond
per polymer chain, positioned along the chain. A preferred
embodiment utilizes polyisobutylene prepared from a pure
isobutylene stream or a Raffinate I stream to prepare reactive
isobutylene polymers with terminal vinylidene olefins. Preferably,
these polymers, referred to as highly reactive polyisobutylene
(HR-PIB), have a terminal vinylidene content of at least 65%, e.g.,
70%, more preferably at least 80%, most preferably, at least 85%.
The preparation of such polymers is described, for example, in U.S.
Pat. No. 4,152,499. HR-PIB is known and HR-PIB is commercially
available under the tradenames Glissopal.TM. (from BASF) and
Ultravis.TM. (from BP-Amoco).
[0024] Polyisobutylene polymers that may be employed are generally
based on a hydrocarbon chain of from about 700 to 3000. Methods for
making polyisobutylene are known. Polyisobutylene can be
functionalized by halogenation (e.g. chlorination), the thermal
"ene" reaction, or by free radical grafting using a catalyst (e.g.
peroxide), is described below.
[0025] The hydrocarbon or polymer backbone can be functionalized,
e.g., with carboxylic acid producing moieties (preferably acid or
anhydride moieties) selectively at sites of carbon-to-carbon
unsaturation on the polymer or hydrocarbon chains, or randomly
along chains using any of the three processes mentioned above or
combinations thereof, in any sequence.
[0026] 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. Pat. Nos. 3,087,936; 3,172,892; 3,215,707; 3,231,587;
3,272,746; 3,275,554; 3,381,022; 3,442,808; 3,565,804; 3,912,764;
4,110,349; 4,234,435; 5,777,025; 5,891,953; as well as EP 0 382 450
B1; CA-1,335,895 and GB-A-1,440,219.
[0027] The polymer or hydrocarbon may be functionalized, for
example, with carboxylic acid producing moieties (preferably acid
or anhydride) by reacting the polymer or hydrocarbon under
conditions that result in the addition of functional moieties or
agents, i.e., acid, anhydride, ester moieties, etc., onto the
polymer or hydrocarbon chains primarily at sites of
carbon-to-carbon unsaturation (also referred to as ethylenic or
olefinic unsaturation) using the halogen assisted functionalization
(e.g. chlorination) process or the thermal "ene" reaction.
Functionalisation
[0028] Selective functionalization can be accomplished by
halogenating, e.g., chlorinating or brominating the unsaturated
.alpha.-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.degree. C., preferably 110 to
160.degree. C., e.g., 120 to 140.degree. 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.degree. C., usually about
180.degree. C. to 235.degree. 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.
[0029] 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.
[0030] 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.degree.
C., preferably 120 to 240.degree. 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.
[0031] 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.degree. C. and decompose
thermally within the grafting temperature range to provide
free-radicals. Representative of these free-radical initiators are
azobutyronitrile, 2,5-dimethylhex-3-ene-2, 5-bis-tertiary-butyl
peroxide and dicumene peroxide. The initiator, when used, typically
is used in an amount of between 0.005% and 1% by weight based on
the weight of the reaction mixture solution. Typically, the
aforesaid monounsaturated carboxylic reactant material and
free-radical initiator are used in a weight ratio range of from
about 1.0:1 to 30:1, preferably 3:1 to 6:1. The grafting is
preferably carried out in an inert atmosphere, such as under
nitrogen blanketing. The resulting grafted polymer is characterized
by having carboxylic acid (or ester or anhydride) moieties randomly
attached along the polymer chains: it being understood, of course,
that some of the polymer chains remain ungrafted. The free radical
grafting described above can be used for the other polymers and
hydrocarbons used in the present invention.
[0032] The preferred monounsaturated reactants that are used to
functionalize the backbone comprise mono- and dicarboxylic acid
material, i.e., acid, anhydride, or acid ester material, including
(i) monounsaturated C.sub.4 to C.sub.10 dicarboxylic acid wherein
(a) the carboxyl groups are vicinyl, (i.e., located on adjacent
carbon atoms) and (b) at least one, preferably both, of said
adjacent carbon atoms are part of said mono unsaturation; (ii)
derivatives of (i) such as anhydrides or C.sub.1 to C.sub.5 alcohol
derived mono- or diesters of (i); (iii) monounsaturated C.sub.3 to
C.sub.10 monocarboxylic acid wherein the carbon-carbon double bond
is conjugated with the carboxy group, i.e., of the structure
--C.dbd.C--CO--; and (iv) derivatives of (iii) such as C.sub.1 to
C.sub.5 alcohol derived mono- or diesters of (iii). Mixtures of
monounsaturated carboxylic materials (i)-(iv) also may be used.
Upon reaction with the backbone, the monounsaturation of the
monounsaturated carboxylic reactant becomes saturated. Thus, for
example, maleic anhydride becomes backbone-substituted succinic
anhydride, and acrylic acid becomes backbone-substituted propionic
acid. Exemplary of such monounsaturated carboxylic reactants are
fumaric acid, itaconic acid, maleic acid, maleic anhydride,
chloromaleic acid, chloromaleic anhydride, acrylic acid,
methacrylic acid, crotonic acid, cinnamic acid, and lower alkyl
(e.g., C.sub.1 to C.sub.4 alkyl) acid esters of the foregoing,
e.g., methyl maleate, ethyl fumarate, and methyl fumarate.
[0033] 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.
Derivatisation
[0034] The functionalized oil-soluble polymeric hydrocarbon
backbone is then derivatized with a nitrogen-containing
nucleophilic reactant, such as an amine, amino-alcohol, amide, or
mixture thereof, to form a corresponding derivative. Amine
compounds are preferred. Useful amine compounds for derivatizing
functionalized polymers comprise at least one amine and can
comprise one or more additional amine or other reactive or polar
groups. These amines may be hydrocarbyl amines or may be
predominantly hydrocarbyl amines in which the hydrocarbyl group
includes other groups, e.g., hydroxy groups, alkoxy groups, amide
groups, nitriles, imidazoline groups, and the like. Particularly
useful amine compounds include mono- and polyamines, e.g.,
polyalkene and polyoxyalkylene polyamines of about 2 to 60, such as
2 to 40 (e.g., 3 to 20) total carbon atoms having about 1 to 12,
such as 3 to 12, preferably 3 to 9, most preferably form about 6 to
about 7 nitrogen atoms per molecule. Mixtures of amine compounds
may advantageously be used, such as those prepared by reaction of
alkylene dihalide with ammonia. Preferred amines are aliphatic
saturated amines, including, for example, 1,2-diaminoethane;
1,3-diaminopropane; 1,4-diaminobutane; 1,6-diaminohexane;
polyethylene amines such as diethylene triamine; triethylene
tetramine; tetraethylene pentamine; and polypropyleneamines such as
1,2-propylene diamine; and di-(1,2-propylene)triamine. Such
polyamine mixtures, known as PAM, are commercially available.
Particularly preferred polyamine mixtures are mixtures derived by
distilling the light ends from PAM products. The resulting
mixtures, known as "heavy" PAM, or HPAM, are also commercially
available. The properties and attributes of both PAM and/or HPAM
are described, for example, in U.S. Pat. Nos. 4,938,881; 4,927,551;
5,230,714; 5,241,003; 5,565,128; 5,756,431; 5,792,730; and
5,854,186.
[0035] Other useful amine compounds include: alicyclic diamines
such as 1,4-di(aminomethyl) cyclohexane and heterocyclic nitrogen
compounds such as imidazolines. Another useful class of amines is
the polyamido and related amido-amines as disclosed in U.S. Pat.
Nos. 4,857,217; 4,956,107; 4,963,275; and 5,229,022. Also usable is
tris(hydroxymethyl)amino methane (TAM) as described in U.S. Pat.
Nos. 4,102,798; 4,113,639; 4,116,876; and UK 989,409. Dendrimers,
star-like amines, and comb-structured amines may also be used.
Similarly, one may use condensed amines, as described in U.S. Pat.
No. 5,053,152. The functionalized polymer is reacted with the amine
compound using conventional techniques as described, for example,
in U.S. Pat. Nos. 4,234,435 and 5,229,022, as well as in
EP-A-208,560.
Preferred Dispersants
[0036] A preferred dispersant for use herein is one comprising at
least one polyalkenyl succinimide, which is the reaction product of
a polyalkenyl substituted succinic anhydride (e.g., PIBSA) and a
polyamine (PAM) that has a coupling ratio of from about 0.65 to
about 1.25, preferably from about 0.8 to about 1.1, most preferably
from about 0.9 to about 1. In the context of this disclosure,
"coupling ratio" may be defined as a ratio of the number of
succinyl groups in the PIBSA to the number of primary amine groups
in the polyamine reactant.
[0037] Another class of high molecular weight ashless dispersants
comprises Mannich base condensation products. Generally, these
products are prepared by condensing about one mole of a long chain
alkyl-substituted mono- or polyhydroxy benzene with about 1 to 2.5
moles of carbonyl compound(s) (e.g., formaldehyde and
paraformaldehyde) and about 0.5 to 2 moles of polyalkylene
polyamine, as disclosed, for example, in U.S. Pat. No. 3,442,808.
Such Mannich base condensation products may include a polymer
product of a metallocene catalyzed polymerization as a substituent
on the benzene group, or may be reacted with a compound containing
such a polymer substituted on a succinic anhydride in a manner
similar to that described in U.S. Pat. No. 3,442,808. Examples of
functionalized and/or derivatized olefin polymers synthesized using
metallocene catalyst systems are described in the publications
identified supra.
[0038] The preferred dispersants for use herein have a
Functionality (F) of greater than 1.4, more preferably greater than
1.5, such as from about 1.5 to about 2.2, more preferably from
about 1.5 to about 2.0 or from about 1.5 to about 1.9.
Functionality (F) can be determined according to the following
formula:
F=(SAP.times.M.sub.n)/((1122.times.A.I.)-(SAP.times.MW)) (1)
wherein SAP is the saponification number (i.e., the number of
milligrams of KOH consumed in the complete neutralization of the
acid groups in one gram of the succinic-containing reaction
product, as determined according to ASTM D94); M.sub.n is the
number average molecular weight of the starting olefin polymer
(polybutene); A.I. is the percent active ingredient of the
succinic-containing reaction product (the remainder being unreacted
polybutene and diluent); and MW is the molecular weight of the
dicarboxylic acid-producing moiety (98 for maleic anhydride).
Generally, each dicarboxylic acid-producing moiety (succinic group)
will react with a nucleophilic group (polyamine moiety) and the
number of succinic groups in the PIBSA will determine the number of
nucleophilic groups in the finished dispersant.
[0039] Polymer molecular weight, specifically M.sub.n, can be
determined by various known techniques. One convenient method is
gel permeation chromatography (GPC), which additionally provides
molecular weight distribution information (see W. W. Yau, J. J.
Kirkland and D. D. Bly, "Modern Size Exclusion Liquid
Chromatography", John Wiley and Sons, New York, 1979). Another
useful method for determining molecular weight, particularly for
lower molecular weight polymers, is vapor pressure osmometry (see,
e.g., ASTM D3592).
[0040] Suitable hydrocarbons or polymers employed in the formation
of the dispersants include polymers prepared by cationic
polymerization of isobutene. Common polymers from this class
include polyisobutenes obtained by polymerization of a C.sub.4
refinery stream having a butene content of about 35 to about 75% by
wt., and an isobutene content of about 30 to about 60% by wt., in
the presence of a Lewis acid catalyst, such boron trifluoride
(BF.sub.3). Preferably, the polyisobutylene is 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 60%, 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.
Pat. No. 4,152,499. Such polymers are conventionally referred to as
HR-PIB and HR-PIB is commercially available from Texas
Petrochemical Corporation (TPC), or from BASF (under the trade
names Glissopal.TM.). Processes for thermally reacting HR-PIB with
unsaturated carboxylic acids or anhydrides, and for further
reacting the resulting acylating agents (PIBSA) with amines are
well known and described, for example, in U.S. Pat. No. 4,152,499
and EP 0 355 895.
[0041] To provide the required functionality, the monounsaturated
carboxylic reactant, (maleic anhydride), typically will be used in
an amount ranging from about 5 to about 300% excess, preferably
from about 10 to 200%, such as 20 to 100% excess, based on the
moles of polymer. Unreacted excess monounsaturated carboxylic
reactant can be removed from the final dispersant product by, for
example, stripping, under vacuum, if required.
[0042] Polyamines useful in the formation of the dispersants
include polyamines having, or having on average, 3 to 8 nitrogen
atoms per molecule, preferably from about 5 to about 8 nitrogen
atoms per molecule. These amines may be hydrocarbyl amines or may
be predominantly hydrocarbyl amines in which the hydrocarbyl group
includes other groups, e.g., hydroxy groups, alkoxy groups, amide
groups, nitriles, imidazoline groups, and the like. Mixtures of
amine compounds may advantageously be used, such as those prepared
by reaction of alkylene dihalide with ammonia. Preferred amines are
aliphatic saturated amines, including, for example, polyethylene
amines such as diethylene triamine; triethylene tetramine;
tetraethylene pentamine; and polypropyleneamines such as
di-(1,2-propylene)triamine. Such polyamine mixtures, known as PAM,
are commercially available. Useful polyamine mixtures also include
mixtures derived by distilling the light ends from PAM products.
The resulting mixtures, known as "heavy" PAM, or HPAM, are also
commercially available. The properties and attributes of both PAM
and/or HPAM are described, for example, in U.S. Pat. Nos.
4,938,881; 4,927,551; 5,230,714; 5,241,003; 5,565,128; 5,756,431;
5,792,730; and 5,854,186.
[0043] The total amount of base oil incorporated in the lubricating
oil composition of the present invention is preferably present in
an amount in the range of from 60 to 92 wt. %, more preferably in
an amount in the range of from 75 to 90 wt. % and most preferably
in an amount in the range of from 75 to 88 wt. %, with respect to
the total weight of the lubricating oil composition.
[0044] There are no particular limitations regarding the base oil
used in the present invention, and various conventional known
mineral oils and synthetic oils may be conveniently used.
[0045] The base oil used in the present invention may conveniently
comprise mixtures of one or more mineral oils and/or one or more
synthetic oils.
[0046] Mineral oils include liquid petroleum oils and
solvent-treated or acid-treated mineral lubricating oils of the
paraffinic, naphthenic, or mixed paraffinic/naphthenic type which
may be further refined by hydrofinishing processes and/or
dewaxing.
[0047] Naphthenic base oils have low viscosity index (VI)
(generally 40-80) and a low pour point. Such base oils are produced
from feedstocks rich in naphthenes and low in wax content and are
used mainly for lubricants in which colour and colour stability are
important, and VI and oxidation stability are of secondary
importance.
[0048] Paraffinic base oils have higher VI (generally >95) and a
high pour point. Said base oils are produced from feedstocks rich
in paraffins, and are used for lubricants in which VI and oxidation
stability are important.
[0049] Fischer-Tropsch derived base oils may be conveniently used
as the base oil in the lubricating oil composition of the present
invention, for example, the Fischer-Tropsch derived base oils
disclosed in EP-A-776959, EP-A-668342, WO-A-97/21788, WO-00/15736,
WO-00/14188, WO-00/14187, WO-00/14183, WO-00/14179, WO-00/08115,
WO-99/41332, EP-1029029, WO-01/18156 and WO-01/57166.
[0050] Synthetic processes enable molecules to be built from
simpler substances or to have their structures modified to give the
precise properties required.
[0051] Synthetic oils include hydrocarbon oils such as olefin
oligomers (PAOs), dibasic acids esters, polyol esters, and dewaxed
waxy raffinate. Synthetic hydrocarbon base oils sold by the Royal
Dutch/Shell Group of Companies under the designation "XHVI" (trade
mark) may be conveniently used.
[0052] Preferably, the base oil comprises mineral oils and/or
synthetic oils which contain more than 80% wt of saturates,
preferably more than 90% wt., as measured according to ASTM
D2007.
[0053] It is further preferred that the base oil contains less than
1.0 wt. %, preferably less than 0.1 wt. % of sulphur, calculated as
elemental sulphur and measured according to ASTM D2622, ASTM D4294,
ASTM D4927 or ASTM D3120.
[0054] Preferably, the viscosity index of the base fluid is more
than 80, more preferably more than 120, as measured according to
ASTM D2270.
[0055] Preferably, the lubricating oil composition has a kinematic
viscosity in the range of from 2 to 80 mm.sup.2/s at 100.degree.
C., more preferably of from 3 to 70 mm.sup.2/s, most preferably of
from 4 to 50 mm.sup.2/s.
[0056] The total amount of phosphorus in the lubricating oil
composition of the present invention is preferably in the range of
from 0.04 to 0.12 wt. %, more preferably in the range of from 0.04
to 0.09 wt. % and most preferably in the range of from 0.045 to
0.08 wt. %, based on total weight of the lubricating oil
composition.
[0057] The lubricating oil composition of the present invention
preferably has a sulphated ash content of not greater than 2.0 wt.
%, more preferably not greater than 1.0 wt. % and most preferably
not greater than 0.8 wt. %, based on the total weight of the
lubricating oil composition.
[0058] The lubricating oil composition of the present invention
preferably has a sulphur content of not greater than 1.2 wt. %,
more preferably not greater than 0.8 wt. % and most preferably not
greater than 0.2 wt. %, based on the total weight of the
lubricating oil composition.
[0059] The lubricating oil composition of the present invention may
further comprise additional additives such as anti-oxidants,
anti-wear additives, detergents, dispersants, friction modifiers,
viscosity index improvers, pour point depressants, corrosion
inhibitors, defoaming agents and seal fix or seal compatibility
agents.
[0060] Antioxidants that may be conveniently used include those
selected from the group of aminic antioxidants and/or phenolic
antioxidants.
[0061] In a preferred embodiment, said antioxidants are present in
an amount in the range of from 0.1 to 5.0 wt. %, more preferably in
an amount in the range of from 0.3 to 3.0 wt. %, and most
preferably in an amount in the range of from 0.5 to 1.5 wt. %,
based on the total weight of the lubricating oil composition.
[0062] Examples of aminic antioxidants which may be conveniently
used include alkylated diphenylamines,
phenyl-.alpha.-naphthylamines, phenyl-.beta.-naphthylamines and
alkylated .alpha.-naphthylamines.
[0063] Preferred aminic antioxidants include dialkyldiphenylamines
such as p,p'-dioctyl-diphenylamine,
p,p'-di-.alpha.-methylbenzyl-diphenylamine and
N-p-butylphenyl-N-p'-octylphenylamine, monoalkyldiphenylamines such
as mono-t-butyldiphenylamine and mono-octyldiphenylamine,
bis(dialkylphenyl)amines such as di-(2,4-diethylphenyl) amine and
di(2-ethyl-4-nonylphenyl)amine, alkylphenyl-1-naphthylamines such
as octylphenyl-1-naphthylamine and
n-t-dodecylphenyl-1-naphthylamine, 1-naphthylamine,
arylnaphthylamines such as phenyl-1-naphthylamine,
phenyl-2-naphthylamine, N-hexylphenyl-2-naphthylamine and
N-octylphenyl-2-naphthylamine, phenylenediamines such as
N,N'-diisopropyl-p-phenylenediamine and
N,N'-diphenyl-p-phenylenediamine, and phenothiazines such as
phenothiazine and 3,7-dioctylphenothiazine.
[0064] Preferred aminic antioxidants include those available under
the following trade designations: "Sonoflex OD-3" (ex. Seiko Kagaku
Co.), "Irganox L-57" (ex. Ciba Specialty Chemicals Co.) and
phenothiazine (ex. Hodogaya Kagaku Co.).
[0065] Examples of phenolic antioxidants which may be conveniently
used include C7-C9 branched alkyl esters of
3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-benzenepropanoic acid,
2-t-butylphenol, 2-t-butyl-4-methylphenol,
2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol,
2,4-dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol,
3-t-butyl-4-methoxyphenol, 2,5-di-t-butylhydroquinone,
2,6-di-t-butyl-4-alkylphenols such as 2,6-di-t-butylphenol,
2,6-di-t-butyl-4-methylphenol and 2,6-di-t-butyl-4-ethylphenol,
2,6-di-t-butyl-4-alkoxyphenols such as
2,6-di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol,
3,5-di-t-butyl-4-hydroxybenzylmercaptooctylacetate,
alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionates such as
n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,
n-butyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate and
2'-ethylhexyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate,
2,6-d-t-butyl-.alpha.-dimethylamino-p-cresol,
2,2'-methylene-bis(4-alkyl-6-t-butylphenol) such as
2,2'-methylenebis(4-methyl-6-t-butylphenol, and
2,2-methylenebis(4-ethyl-6-t-butylphenol), bisphenols such as
4,4'-butylidenebis(3-methyl-6-t-butylphenol,
4,4'-methylenebis(2,6-di-t-butylphenol),
4,4'-bis(2,6-di-t-butylphenol), 2,2-(di-p-hydroxyphenyl)propane,
2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane,
4,4'-cyclohexylidenebis(2,6-t-butylphenol),
hexamethyleneglycol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)
propionate],
triethyleneglycolbis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate],
2,2'-thio-[diethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate],
3,9-bis{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methyl-phenyl)propionylo-
xy]ethyl}2,4,8,10-tetraoxaspiro[5,5]undecane,
4,4'-thiobis(3-methyl-6-t-butylphenol) and
2,2'-thiobis(4,6-di-t-butylresorcinol), polyphenols such as
tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane,
1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene,
bis-[3,3'-bis(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol
ester,
2-(3',5'-di-t-butyl-4-hydroxyphenyl)methyl-4-(2'',4''-di-t-butyl-3''-hydr-
oxyphenyl)methyl-6-t-butylphenol and
2,6-bis(2'-hydroxy-3'-t-butyl-5'-methylbenzyl)-4-methylphenol, and
p-t-butylphenol-formaldehyde condensates and
p-t-butylphenol-acetaldehyde condensates.
[0066] Preferred phenolic antioxidants include those available
under the following trade designations: "Irganox L-135" (ex. Ciba
Specialty Chemicals Co.), "Yoshinox SS" (ex. Yoshitomi Seiyaku
Co.), "Antage W-400" (ex. Kawaguchi Kagaku Co.), "Antage W-500"
(ex. Kawaguchi Kagaku Co.), "Antage W-300" (ex. Kawaguchi Kagaku
Co.), "Irganox L109" (ex. Ciba Speciality Chemicals Co.), "Tominox
917" (ex. Yoshitomi Seiyaku Co.), "Irganox L115" (ex. Ciba
Speciality Chemicals Co.), "Sumilizer GA80" (ex. Sumitomo Kagaku),
"Antage RC" (ex. Kawaguchi Kagaku Co.), "Irganox L101" (ex. Ciba
Speciality Chemicals Co.), "Yoshinox 930" (ex. Yoshitomi Seiyaku
Co.).
[0067] The lubricating oil composition of the present invention may
comprise mixtures of one or more phenolic antioxidants with one or
more aminic antioxidants.
[0068] In a preferred embodiment, the lubricating oil composition
may comprise a single zinc dithiophosphate or a combination of two
or more zinc dithiophosphates as anti-wear additives, the or each
zinc dithiophosphate being selected from zinc dialkyl-, diaryl- or
alkylaryl-dithiophosphates.
[0069] The zinc dithiophosphate compounds are present in the
lubricating composition in an amount so as to provide preferably
from 0.01 wt % to 0.16 wt %, more preferably from 0.06% to 0.12%,
by weight of the lubricating composition, of phosphorus.
[0070] Zinc dithiophosphate is a well known additive in the art and
may be conveniently represented by general formula II;
##STR00002##
wherein R.sup.2 to R.sup.5 may be the same or different and are
each a primary alkyl group containing from 1 to 20 carbon atoms
preferably from 3 to 12 carbon atoms, a secondary alkyl group
containing from 3 to 20 carbon atoms, preferably from 3 to 12
carbon atoms, an aryl group or an aryl group substituted with an
alkyl group, said alkyl substituent containing from 1 to 20 carbon
atoms preferably 3 to 18 carbon atoms.
[0071] Zinc dithiophosphate compounds in which R.sup.2 to R.sup.5
are all different from each other can be used alone or in admixture
with zinc dithiophosphate compounds in which R.sup.2 to R.sup.5 are
all the same.
[0072] Preferably, the or each zinc dithiophosphate used in the
present invention is a zinc dialkyl dithiophosphate. Examples of
suitable zinc dithiophosphates which are commercially available
include those available ex. Lubrizol Corporation under the trade
designations "Lz 1097" and "Lz 1395", those available ex. Chevron
Oronite under the trade designations "OLOA 267" and "OLOA 269R",
and that available ex. Afton Chemical under the trade designation
"HITEC 7197"; zinc dithiophosphates such as that available from
Infineum under the trade name Infineum C9417, those available ex.
Lubrizol Corporation under the trade designations "Lz 677A", "Lz
1095" and "Lz 1371", that available ex. Chevron Oronite under the
trade designation "OLOA 262" and that available ex. Afton Chemical
under the trade designation "HITEC 7169"; and zinc dithiophosphates
such as those available ex. Lubrizol Corporation under the trade
designations "Lz 1370" and "Lz 1373" and that available ex. Chevron
Oronite under the trade designation "OLOA 260".
[0073] The lubricating oil composition according to the present
invention may generally comprise in the range of from 0.4 to 1.2
wt. % of zinc dithiophosphate, based on total weight of the
lubricating oil composition.
[0074] Additional or alternative anti-wear additives may be
conveniently used in the composition of the present invention.
[0075] Typical detergents that may be used in the lubricating oil
of the present invention include one or more salicylate and/or
phenate and/or sulphonate detergents.
[0076] However, as metal organic and inorganic base salts which are
used as detergents can contribute to the sulphated ash content of a
lubricating oil composition, in a preferred embodiment of the
present invention, the amounts of such additives are minimised.
[0077] Furthermore, in order to maintain a low sulphur level,
salicylate detergents are preferred.
[0078] Thus, in a preferred embodiment, the lubricating oil
composition of the present invention may comprise one or more
salicylate detergents.
[0079] In order to maintain the total sulphated ash content of the
lubricating oil composition of the present invention at a level of
preferably not greater than 2.0 wt. %, more preferably at a level
of not greater than 1.0 wt. % and most preferably at a level of not
greater than 0.8 wt. %, based on the total weight of the
lubricating oil composition, said detergents are preferably used in
amounts in the range of 0.05 to 20.0 wt. %, more preferably from
1.0 to 10.0 wt. % and most preferably in the range of from 2.0 to
5.0 wt. %, based on the total weight of the lubricating oil
composition.
[0080] Furthermore, it is preferred that said detergents,
independently, have a TBN (total base number) value in the range of
from 10 to 500 mgKOH/g, more preferably in the range of from 30 to
350 mgKOH/g and most preferably in the range of from 50 to 300
mgKOH/g, as measured by ISO 3771.
[0081] Examples of viscosity index improvers which may be
conveniently used in the lubricating oil composition of the present
invention include the styrene-butadiene copolymers,
styrene-isoprene stellate copolymers and the polymethacrylate
copolymer and ethylene-propylene copolymers. Such viscosity index
improvers may be conveniently employed in an amount in the range of
from 1 to 20 wt. %, based on the total weight of the lubricating
oil composition.
[0082] Polymethacrylates may be conveniently employed in the
lubricating oil compositions of the present invention as effective
pour point depressants.
[0083] Furthermore, compounds such as alkenyl succinic acid or
ester moieties thereof, benzotriazole-based compounds and
thiodiazole-based compounds may be conveniently used in the
lubricating oil composition of the present invention as corrosion
inhibitors.
[0084] Compounds such as polysiloxanes, dimethyl polycyclohexane
and polyacrylates may be conveniently used in the lubricating oil
composition of the present invention as defoaming agents.
[0085] Compounds which may be conveniently used in the lubricating
oil composition of the present invention as seal fix or seal
compatibility agents include, for example, commercially available
aromatic esters.
[0086] The lubricating compositions herein may be conveniently
prepared using conventional formulation techniques by admixing base
oil with the liquid crystal compound and one or more additives at a
temperature of 60.degree. C.
[0087] The present invention is described below with reference to
the following Examples, which are not intended to limit the scope
of the present invention in any way.
EXAMPLES
[0088] Various lubricating compositions were prepared by combining
a base oil (GTL 4, a Fischer-Tropsch derived base oil having a
kinematic viscosity at 100.degree. C. of approximately 4 cSt,
available from Shell) with ZDTP. The ZDTP was added in an amount so
as to provide 0.08 wt % phosphorus in the final lubricating
composition. The formulations also contained a nitrogen-containing
ashless dispersant (designated as D1, D2, D3 or D4 in Table 1
below) in varying amounts to give lubricating compositions having
varying amounts of nitrogen (0.05 wt % N, 0.07 wt % N or 0.1 wt %
N, by weight of the final lubricating compositions). Carbon black
was also added to the lubricating compositions in an amount of 5 wt
%, by weight of the final lubricating compositions, in order to
simulate the effect of the presence of soot in the lubricant.
[0089] The nitrogen-containing ashless dispersants used in the
present examples were polyisobutylene succinimides having the
properties listed below in Table 1:
TABLE-US-00001 TABLE 1 Dispersant Functionality Maleation Number
PIB Mn (Fv) method Borated D1 2225 1.3 chloro No D2 2300 1.4
Thermal No D3 2225 1.5 Chloro No D4 2300 1.8 thermal No
HFRR Wear Test
[0090] The lubricant formulations were subjected to a HFRR wear
test. The HFRR (High-Friction Reciprocating Rig) is a controlled
reciprocating friction and wear testing device employed to assess
the performance of fuels and lubricants. The test uses a 6 mm
diameter steel ball loaded and reciprocated against the flat
surface of a stationary steel disc immersed in lubricant. At the
end of each test, the ball and disc were removed from the test rig,
rinsed with toluene and iso-propanol, and then treated with a 0.05
wt % solution of ethylenediaminetetraacetic acid (EDTA) for 60 s.
This was to remove any ZDTP anti-wear film on the surfaces since it
can interfere with optically-based wear measurement. Topography
images were then obtained and analysed to determine wear volumes of
the wear scars on the ball and the disc using the SWLI Veeco Wyko
model NT9100. The instrument was set in Vertical Scanning
Interferometry (VSI) mode, calibrated to measure rough surfaces
with a nanometre detection range.
[0091] The results of these wear tests are shown in Table 2
below.
TABLE-US-00002 TABLE 2 HFRR Wear Volume (.mu.m.sup.3) Dispersant
0.05% N 0.07% N 0.1% N D1 640818 367829 254700 D2 475946 402865
387829 D3 26865 28355 30466 D4 21960 20987 20412
DISCUSSION
[0092] From the results in Table 2 it can be seen that the
formulations containing the polyisobutylene succinimide dispersants
D3 and D4 (having functionality values of 1.5 and 1.8,
respectively), demonstrated reduced wear (low wear scar
measurements) compared with the formulations containing the
polyisobutylene succinimide dispersants D1 and D2 (having
Functionality Values Fv of 1.3 and 1.4, respectively).
* * * * *