[0001] The present invention relates to the use of a lubricating oil composition, in particular
of a lubricating oil composition which is suitable for lubricating internal combustion
engines.
[0002] Total Base Number (TBN) is a measure of how well a lubricating oil composition can
neutralise acidic by-products of combustion/oxidation and is defined as the quantity
of acid, expressed in terms of the equivalent number of milligrams of potassium hydroxide,
that is required to neutralize all basic constituents present in 1 gram of a sample
of the lubricating oil composition (test methods include, for example, ISO 3771, ASTM
D-2896 and ASTM D-4739).
[0003] A high TBN is desirable in lubricating oil compositions in order to control corrosive
engine wear from the acidic by-products of combustion/oxidation. Detergent additives
in a lubricating oil composition are the primary source of alkalinity (TBN) and help
to control, for example, top-ring deposits and bore polish.
[0004] Hence, metal-based detergents are the primary source of TBN in crankcase lubricating
oil compositions.
[0005] In view of the adverse affects that the sulphated ash, sulphur and phosphorus concentrations
of lubricating oil compositions may have on vehicle exhaust after-treatment devices,
there is a trend towards lubricating oil compositions having reduced sulphated ash,
sulphur and/or phosphorus concentrations therein (i.e. so-called low-SAPS lubricating
oil compositions).
[0006] Phosphorus concentrations may be generally seduced by reducing the amount of zinc
dithiophosphates which are present as anti-wear additives in lubricating oil compositions.
[0007] Sulphur levels in lubricating oil compositions may be reduced by employing low sulphur
level base oils and reducing the amount of sulphur-containing additives employed therein.
[0008] Sulphated ash is the total weight percent of residue remaining after a lubricating
oil composition has been carbonised, and the residue subsequently treated with sulphuric
acid and heated to constant weight. The sulphated ash content in a lubricating oil
composition is related to the total metal content therein. Sulphated ash may be conveniently
measured according to ASTM D874.
[0009] The major sources of sulphated ash in a lubricating oil composition are generally
any metal detergent additives and zinc dithiophosphate anti-wear additives that are
employed therein.
[0010] Hence, in current low-SAPS lubricating oil compositions, sulphated ash levels, and
consequently detergent levels, are low. As a result, the starting TBN (i.e. of fresh
un-used lubricating oil compositions) of low-SAPS lubricating oil compositions tends
to be lower than in lubricating oil compositions having higher sulphated ash, sulphur
and/or phosphorus concentrations therein.
[0011] Thus, TBN retention (i.e. the ability to maintain an advantageous TBN level throughout
the lifetime of a lubricating oil composition) is of increased importance for low-SAPS
lubricating oil compositions which have lower starting TBNs.
[0012] US 2004/0102335 A1 describes lubricating oil compositions containing an additive formulation including
at least one sulphonate, saligenin and salixarate detergent.
[0013] However, it is apparent from the Working Examples in
US 2004/0102335 A1 that said lubricating oil compositions employ high TBN detergents therein.
[0014] In this regard, it is of note that the Working Examples in
US 2004/0102335 A1 all employ a high TBN calcium sulphonate detergent therein as a TBN booster.
[0015] Furthermore,
US 2004/0102335 A1 is concerned with the development of lubricating oil compositions with improved wear
performance and is not directed to the problem of TBN retention for low-SAPs lubricating
oil compositions which have lower starting TBNs.
[0016] EP-A-1167497 discloses a lubricating oil composition having a sulphur content of 0.01 to 0.3 wt.
% and a phosphorus content of 0.01 to 0.1 wt. %, and giving a sulphated ash content
in the range of 0.1 to 1 wt. %, which is said to have good high temperature detergency,
and which comprises:
- a) a major amount of a mineral base oil having a sulphur content of at most 0.1 wt.
%;
- b) an ashless dispersant comprising an alkenyl- or alkyl-succinimide or a derivative
thereof in an amount of 0.01 to 0.3 wt. % in terms of a nitrogen atom content;
- c) a metal-containing detergent containing an organic acid metal salt which is selected
from the group consisting of a non-sulphurised alkali metal or alkaline earth metal
salt of an alkylsalicylic acid having a TBN of 10 to 350 mg.KOH/g and a non-sulphurised
alkali metal or alkaline earth metal salt of an alkylphenol derivative having a Mannich
base structure, in an amount of 0.1 to 1 wt. % in terms of a sulphated ash content;
- d) a zinc dialkyldithiophosphate in an amount of 0.01 to 0.1 wt. % in terms of a phosphorus
content; and
- e) an oxidation inhibitor selected from the group consisting of a phenol compound
and an amine compound in an amount of 0.01 to 5 wt. %.
[0017] The Examples in
EP-A-1167497 all use a mixture of 0.7 wt. % aminic antioxidant in combination with 0.7 wt. % phenolic
antioxidant.
[0018] However,
EP-A-1167497 is in no way concerned with the problem of achieving good TBN retention, in particular
with regard to the VW T4 test (PV 1449), for compositions having reduced sulphated
ash, sulphur and/or phosphorus concentrations therein. In this regard, there is no
teaching in
EP-A-1167497 to suggest how to achieve good TBN retention in particular with regard to the VW
T4 test (PV 1449).
[0019] EP-A-1104800 describes a lubricating oil composition for internal combustion engines which comprises
- a) a major amount of a base oil of lubricating viscosity,
- b) a metal-containing detergent in an amount of 0.1 to 1 wt% in terms of its sulfated
ash content,
- c) a boron-containing alkenyl- or alkylsuccinimide in an amount of 1.0 to 15 wt% in
terms of its active ingredient,
- d) a zinc dialkyldithiophosphate in an amount of 0.1 to 0.1 wt% in terms of its phosphorus
content,
- e) an oxidation inhibitor in an amount of 0.1 to 5 wt% in terms of its active ingredient,
and
- f) an ashless dithiocarbamate in an amount of 0.1 to 5 wt% in terms of its active
ingredient.
[0020] US 2003/0148900 A1 discloses a lubricating oil composition for use in natural gas engines which comprises
a minor amount of one or more specific hindered phenols and a major amount of at leats
one of Group II, III and IV base oils.
[0021] US 2003/0148900 A1 indicates that increased amounts of antioxidants may have a detrimental effect on
piston deposit control. Accordingly,
US 2003/0148900 A1 is directed to a method to increase the oxidation life of lubricating oil base oil
without increasing the amount of antioxidant therein.
[0022] However,
US 2003/0148900 A1 is not concerned with the problem of TBN retention for low-SAPS lubricating oil compositions
which have lower starting TBNs.
[0023] WO-A-03/083020 describes a method of operating an internal combustion engine that comprises introducing
a nitrogen-containing detergent composition into a combustion chamber during the operation
of the engine.
[0024] Said detergent composition comprises
- (A) a reaction product of a hydrocarbyl-substituted acylating agent and an amine;
- (B) a hydrocarbyol-substituted amine;
- (C) a Mannich reaction product of a hydrocarbyl-substituted hydroxy-containing aromatic
compound, an aldehyde, and an amine;
- (D) a high molecular weight polyetheramine prepared by reacting one unit of a hydroxy-containing
hydrocarbyl compound with two or more units of butylene oxide to form apolyether intermediate,
and aminating the polyether intermediate by reacting the polyether intermediate with
an amine or with acrylonitrile and hydrogenating the reaction product of the polyether
intermediate and acrylnitrile; or
- (E) a mixture thereof.
[0025] WO 03/099972 discloses a low ash, low phosphorus lubricant composition suitable for use in a stationary
gas engine, comprising: (a) an oil of lubricating viscosity; (b) 1.5 to 8 percent
by weight of a succinimide dispersant; (c) 0.8 to 4.0 percent by weight of a hindered,
ester- substituted phenol antioxidant; and (d) at least one metal-containing sulfonate
detergent or metal-containing phenate detergent, in an amount which provides 1.1 to
2.1 percent by weight of said sulfonate or phenate moieties exclusive of the weight
of the metal moieties; said lubricant containing up to 0.08 percent by weight phosphorus
and up to 1.25 percent sulphated ash.
[0026] US-A-5595964 describes a method of lubricating a natural gas-fuelled internal combustion engine,
comprising supplying thereto a lubricating oil composition comprising an oil of lubricating
viscosity, an antioxidant, an anti-nitration agent and preferably at least about 0.1
wt. % of a borated product of an epoxide, wherein the composition is substantially
free of metals and wherein the amount of the antioxidants and the anti-nitration agent
are sufficient to reduce the amount of varnish formation in a natural gas-fuelled
internal combustion engine.
[0027] The total amount of antioxidant used in said lubricating oil composition is said
to be at least 1.8 wt. %, preferably at least 2 wt. %.
[0028] The lubricating oil composition of
US-A-5595964 is said to contain less than 1 % sulphated ash, as determined by ASTM D874.
[0029] The phosphorus level of the lubricating oil composition of
US-A-5595964 is said to preferably be less than 0.03 % phosphorus, more preferably less than 0.005
% phosphorus.
[0030] It is of note that
US-A-5595964 is concerned with reducing varnish formation in a natural gas-fuelled internal combustion
engine by the presence of an anti-nitration agent in addition to antioxidant in a
lubricating oil composition.
[0031] US-A-5595964 neither identifies nor addresses the problem of poor TBN retention in lubricating
oil compositions having reduced sulphated ash, sulphur and/or phosphorus concentrations
therein, and in particular in low-SAPS lubricating oil compositions which have lower
starting TBNs. There is no disclosure in
US-A-5595964 to suggest how to achieve good TBN retention in such lubricating oil compositions,
particularly in order to pass the VW T4 test (PV 1449).
[0032] It is therefore desirable to develop lubricating oil compositions having reduced
sulphated ash, sulphur and/or phosphorus concentrations therein which have good TBN
retention, and in particular low SAPS lubricating oil compositions which have lower
starting TBNs and which have good TBN retention.
[0033] It is particularly desirable to develop such lubricating oil compositions which have
good TBN retention with regard to the VW T4 test (PV 1449), more particularly to develop
such lubricating oil compositions having an end of test (VW T4 Test (PV 1449)) TBN
value of at least 5.0 mg.KOH/g, as measured by ISO 3771.
[0034] There has now been surprisingly found in the present invention, a lubricating oil
composition having a low sulphated ash content which is suitable for lubricating internal
combustion engines and which exhibits advantageous TBN retention properties.
[0035] Accordingly, the present invention provides a use of a lubricating oil composition
to maintain a TBN level of at least 5.0 mg.KOH/g, as measured by ISO 3771, in an internal
combustion engine in the VW T4 Test (PV 1449), wherein said lubricating oil composition
has a sulphated ash content of not greater than 0.9 wt. % and a phosphorus content
in the range of from 0.04 to 0.1 wt. %, and said lubricating oil composition comprises
base oil,
- (A) one or more detergents selected from phenate detergents, salicylate detergents
and sulphonate detergents, wherein said one or more detergents each, independently,
have a TBN (total base number) value in the range of from 30 to 350 mg.KOH/g, as measured
by ISO 3771; and
- (B) at least 3.5 wt. % of one or more antioxidants, based on the total weight of the
lubricating oil composition,wherein the one or more antioxidants in said lubricating
oil composition comprise aminic antioxidants.
[0036] In a preferred embodiment, said one or more antioxidants are present in an amount
of at least 3.7 wt. %, more preferably in an amount of at least 3.9 wt. %, and most
preferably in an amount of at least 4.0 wt. %, based on the total weight of the lubricating
oil composition.
[0037] The lubricating oil composition used in the present invention comprises one or more
aminic antioxidants.
[0038] Examples of aminic antioxidants which may be conveniently used include alkylated
diphenylamines, phenyl-α-naphthylamines, phenyl-β-naphthylamines and alkylated α-naphthylamines.
[0039] Preferred aminic antioxidants include dialkyldiphenylamines such as p,p'-dioctyl-diphenylamine,
p,p'-di-α-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.
[0040] 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.).
[0041] The lubricating oil composition used in the present invention may comprise one or
more phenolic antioxidants.
[0042] 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-α-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(26-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-methylphenyl)propionyloxy]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"-hydroxyphenyl)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.
[0043] Preferred phenolic antioxidants include those available under the following trade
designations: "Irganox L-135" (ex. Ciba Specialty Chemicals Co.), "Anteeji DBH" (ex.
Kawaguchi Kagaku 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.), "Ionox 220AH" (ex. Shell Japan Co.), bisphenol A, produced
by the Shell Japan 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.),
"Ionox 330" (ex. Shell Japan Co.).
[0044] The lubricating oil composition herein may comprise mixtures of one or more phenolic
antioxidants with one or more aminic antioxidants.
[0045] Detergents that may be used in the lubricating oil herein include one or more detergents
selected from salicylate detergents, phenate detergents and sulphonate detergents.
[0046] Alkali metal and alkaline earth metal salicylate, phenate and sulphonate detergents
are preferred in the lubricating oil compositions herein. Calcium and magnesium salicylates,
phenates and sulphonates are particularly preferred detergents therein.
[0047] In one embodiment, the lubricating oil composition herein may comprise (i) one or
more salicylate detergents; and/or (ii) a mixture of one or more phenate detergents
and one or more sulphonate detergents.
[0048] However, as metal organic and inorganic base salts which are used as detergents can
contribute to the sulphated ash content of a lubricating composition, in a preferred
embodiment of the present invention, the amounts of such detergent additives are minimised.
[0049] In order to maintain a low sulphur level, salicylate detergents are particularly
preferred.
[0050] Thus, in a preferred embodiment, the lubricating oil composition herein may comprise
one or more salicylate detergents.
[0051] In order to maintain the total sulphated ash content of the lubricating oil composition
herein at a level of not greater than 0.9 wt. %, preferably at a level of not greater
than 0.8 wt. %, more preferably at a level of not greater than 0.75 wt. % and most
preferably at a level of not greater than 0.7 wt. %, based on the total weight of
the lubricating oil composition, said one or more detergents (A) are preferably used
in amounts in the range of 0.05 to 12.5 wt. %, more preferably from 1.0 to 9.0 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.
[0052] Furthermore, it is preferred that said one or more detergents (A), each, independently,
have a TBN (total base number) value in the range of from 30 to 350 mg.KOH/g, more
preferably in the range of from 50 to 300 mg.KOH/g, as measured by ISO 3771.
[0053] That is to say, when there is more than one detergent selected from phenate detergents,
salicylate detergents and sulphonate detergents present in the lubricating oil composition
herein, then each of such detergents will have a TBN (total base number) value in
the range of from 30 to 350 mg.KOH/g, more preferably in the range of from 50 to 300
mg.KOH/g, as measured by ISO 3771.
[0054] The amount of base oil incorporated in the lubricating oil composition herein 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.
[0055] There are no particular limitations regarding the base oil used in the present invention,
and various conventional known mineral oils and synthetic lubricating oils may be
conveniently used.
[0056] Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral
lubricating oil of the paraffinic, naphthenic, or mixed paraffinic/naphthenic type
which may be further refined by hydrofinishing processes and/or dewaxing.
[0057] 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.
[0058] 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.
[0059] Fischer-Tropsch derived base oils may be conveniently used as the base oil in the
lubricating oil composition herein, 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.
[0060] Synthetic processes enable molecules to be built from simpler substances or to have
their structures modified to give the precise properties required.
[0061] Synthetic lubricating 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.
[0062] Preferably, the base fluid constituted from mineral oils and/or synthetic base oils
which contain more than 80% wt of saturates, preferably more than 90 % wt., as measured
according to ASTM D2007.
[0063] 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 B3120.
[0064] Preferably, the viscosity index of base fluid is more than 80, more preferably more
than 120, as measured according to ASTM D2270.
[0065] Preferably, the lubricating oil has a kinematic viscosity in the range of from 2
to 80 mm
2/s at 100 °C, more preferably of from 3 to 70 mm
2/s, most preferably of from 4 to 50 mm
2/s.
[0066] 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.
[0067] Zinc dithiophosphate is a well known additive in the art and may be conveniently
represented by general formula II;
wherein R
2 to R
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.
[0068] Zinc dithiophosphate compounds in which R
2 to R
5 are all different from each other can be used alone or in admixture with zinc dithiophosphate
compound in which R
2 to R
5 are all the same.
[0069] Preferably, the or each zinc dithiophosphate used in the present invention is a zinc
dialkyl dithiophosphate.
[0070] 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. Ethyl under the trade designation "HITEC
7197"; zinc dithiophosphates such as 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. Ethyl 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".
[0071] The lubricating oil composition herein may generally comprise in the range of from
0.4 to 1.0 wt. % of zinc dithiophosphate, (if primary or secondary alkyl type), preferably
in the range of from 0.4 to 0.9 wt. % and most preferably in the range of from 0.45
to 0.8 wt. %, based on total weight of the lubricating oil composition.
[0072] The total amount of phosphorus in the lubricating oil composition herein is therefore
generally in the range of from 0.04 to 0.1 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.
[0073] At phosphorus levels of 0.04 wt. % and below, there may be insufficient anti-wear
performance. At phosphorus levels of 0.1 wt. % and above, the phosphorus may have
a detrimental effect on vehicle exhaust after-treatment devices.
[0074] The lubricating oil composition herein preferably has a sulphated ash content of
not greater than 0.8 wt. %, more preferably not greater than 0.75 wt. % and most preferably
not greater than 0.7 wt. %, based on the total weight of the lubricating oil composition.
[0075] The lubricating oil composition herein 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.
[0076] Preferred compositions herein have one or more of the following features:
- (i) greater than 0.04 wt. % of phosphorus;
- (ii) greater than 0.045 wt. % of phosphorus;
- (iii) at least 0.04 wt. % of phosphorus;
- (iv) less than 0.09 wt. % of phosphorus;
- (v) not greater than 0.10 wt. % of phosphorus;
- (vi) at most 0.08 wt. % of phosphorus;
- (vii) not greater than 0.9 wt. % of sulphated ash;
- (viii) not greater than 0.8 wt. % of sulphated ash;
- (ix) not greater than 0.7 wt. % of sulphated ash;
- (x) not greater than 1.2 wt. % of sulphur;
- (xi) not greater than 0.8 wt. % of sulphur; and
- (xii) not greater than 0.2 wt. % of sulphur, based on the total weight of the lubricating
oil composition.
[0077] Particularly preferred compositions herein are:-
- (A): those having features (i) and (iv); those having features (i) and (v); those
having features (i) and (vi); those having features (ii) and (iv); those having features
(ii) and (v); those having features (ii) and (vi); those having features (iii) and
(iv); those having features (iii) and (v); and those having features (iii) and (vi);
- (B): those having features (i), (iv) and (vii); those having features (i), (iv) and
(viii); those having features (i), (iv) and (ix); those having features (i), (v) and
(vii); those having features (i), (v) and (viii); those having features (i), (v) and
(ix); those having features (i), (vi) and (vii); those having features (i), (vi) and
(viii); those having features (i), (vi) and (ix); those having features (ii), (iv)
and (vii); those having features (ii), (iv) and (viii); those having features (ii),
(iv) and (ix); those having features (ii), (v) and (vii); those having features (ii),
(v) and (viii); those having features (ii), (v) and (ix); those having features (ii),
(vi) and (vii); those having features (ii), (vi) and (viii); those having features
(ii), (vi) and (ix); those having features (iii), (iv) and (vii); those having features
(iii), (iv) and (viii); those having features (iii), (iv) and (ix); those having features
(iii), (v) and (vii); those having features (iii), (v) and (viii); those having features
(iii), (v) and (ix); those having features (iii), (vi) and (vii); those having features
(iii), (vi) and (viii); and those having features (iii), (vi) and (ix);
- (C): those having features (i), (iv) and (x); those having features (i), (iv) and
(xi); those having features (i), (iv) and (xii); those having features (i), (v) and
(x); those having features (i), (v) and (xi); those having features (i), (v) and (xii);
those having features (i), (vi) and (x); those having features (i), (vi) and (xi);
those having features (i), (vi) and (xii); those having features (ii), (iv) and (x);
those having features (ii), (iv) and (xi); those having features (ii), (iv) and (xii);
those having features (ii), (v) and (x); those having features (ii), (v) and (xi);
those having features (ii), (v) and (xii); those having features (ii), (vi) and (x);
those having features (ii), (vi) and (xi); those having features (ii), (vi) and (xii);
those having features (iii), (iv) and (x); those having features (iii), (iv) and (xi);
those having features (iii), (iv) and (xii); those having features (iii), (v) and
(x); those having features (iii), (v) and (xi); those having features (iii), (v) and
(xii); those having features (iii), (vi) and (x); those having features (iii), (vi)
and (xi); and those having features (iii), (vi) and (xii); and
- (D): those having features (i), (iv), (vii) and (x); those having features (i), (iv),
(viii) and (x); those having features (i), (iv), (ix) and (x); those having features
(i), (v), (vii) and (x); those having features (i), (v), (viii) and (x); those having
features (i), (v), (ix) and (x); those having features (i), (vi), (vii) and (x); those
having features (i), (vi), (viii) and (x); those having features (i), (vi), (ix) and
(x); those having features (ii), (iv), (vii) and (x); those having features (ii),
(iv), (viii) and (x): those having features (ii), (iv), (ix) and (x); those having
features (ii), (v), (vii) and (x); those having features (ii), (v), (viii) and (x);
those having features (ii), (v), (ix) and (x); those having features (ii), (vi), (vii)
and (x); those having features (ii), (vi), (viii) and (x); those having features (ii),
(vi), (ix) and (x); those having features (iii), (iv), (vii) and (x); those having
features (iii), (iv), (viii) and (x); those having features (iii), (iv), (ix) and
(x); those having features (iii), (v), (vii) and (x); those having features (iii),
(v), (viii) and (x); those having features (iii), (v), (ix) and (x); those having
features (iii), (vi), (vii) and (x); those having features (iii), (vi), (viii) and
(x); those having features (iii), (vi), (ix) and (x); those having features (i), (iv),
(vii) and (xi); those having features (i), (iv), (viii) and (xi); those having features
(i), (iv), (ix) and (xi); those having features (i), (v); (vii) and (xi); those having
features (i), (v), (viii) and (xi); those having features (i), (v), (ix) and (xi);
those having features (i), (vi), (vii) and (xi); those having features (i), (vi),
(viii) and (xi); those having features (i), (vi), (ix) and (xi); those having features
(ii), (iv), (vii) and (xi); those having features (ii), (iv), (viii) and (xi); those
having features (ii), (iv), (ix) and (xi); those having features (ii), (v), (vii)
and (xi); those having features (ii), (v), (viii) and (xi); those having features
(ii), (v), (ix) and (xi); those having features (ii), (vi), (vii) and (xi); those
having features (ii), (vi), (viii) and (xi); those having features (ii), (vi), (ix)
and (xi); those having features (iii), (iv), (vii) and (xi); those having features
(iii), (iv), (viii) and (xi); those having features (iii), (iv), (ix) and (xi); those
having features (iii), (v), (vii) and (xi); those having features (iii), (v), (viii)
and (xi); those having features (iii), (v), (ix) and (xi); those having features (iii),
(vi), (vii) and (xi); those having features (iii), (vi), (viii) and (xi); those having
features (iii), (vi), (ix) and (xi); those having features (i), (iv), (vii) and (xii);
those having features (i), (iv), (viii) and (xii); those having features (i), (iv),
(ix) and (xii); those having features (i), (v), (vii) and (xii); those having features
(i), (v), (viii) and (xii); those having features (i), (v), (ix) and (xii); those
having features (i), (vi), (vii) and (xii); those having features (i), (vi), (viii)
and (xii); those having features (i), (vi), (ix) and (xii); those having features
(ii), (iv), (vii) and (xii); those having features (ii), (iv), (viii) and (xii); those
having features (ii), (iv), (ix) and (xii); those having features (ii), (v), (vii)
and (xii); those having features (ii), (v), (viii) and (xii); those having features
(ii), (v), (ix) and (xii); those having features (ii), (vi), (vii) and (xii); those
having features (ii), (vi), (viii) and (xii); those having features (ii), (vi), (ix)
and (xii); those having features (iii), (iv), (vii) and (xii); those having features
(iii), (iv), (viii) and (xii); those having features (iii), (iv), (ix) and (xii);
those having features (iii), (v), (vii) and (xii); those having features (iii), (v),
(viii) and (xii); those having features (iii), (v), (ix) and (xii); those having features
(iii), (vi), (vii) and (xii); those having features (iii), (vi), (viii) and (xii);
and those having features (iii), (vi), (ix) and (xii).
[0078] The lubricating oil composition herein may further comprise additional additives
such as supplementary anti-wear additives, supplementary detergents, dispersants,
friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors,
defoaming agents and seal fix or seal compatibility agents.
[0079] Supplementary anti-wear additives that may be conveniently used include molybdenum-containing
compounds and boron-containing compounds.
[0080] Examples of such molybdenum-containing compounds may conveniently include molybdenum
dithiocarbamates, trinuclear molybdenum compounds, for example as described in
WO-A-98/26030, sulphides of molybdenum and molybdenum dithiophosphate.
[0081] Said molybdenum-containing anti-wear additives may be conveniently added to the lubricating
oil composition herein in an amount in the range of from 0.1 to 3.0 wt. %, based on
the total weight of lubricating oil composition.
[0082] Boron-containing compounds that may be conveniently used include borate esters, borated
fatty amines, borated epoxides, alkali metal (or mixed alkali metal or alkaline earth
metal) borates and borated overbased metal salts.
[0083] Said boron-containing anti-wear additives may be conveniently added to the lubricating
oil composition herein in an amount in the range of from 0.1 to 3.0 wt. %, based on
the total weight of lubricating oil composition.
[0084] The TBN value of fresh unused samples of the lubricating oil composition herein is
preferably in the range of from 5.0 to 12.0 mg.KOH/g, more preferably in the range
of from 6.0 to 11.0 mg.KOH/g, even more preferably in the range of from 6.0 to 10.0
mg.KOH/g and most preferably in the range of 6.0 to 9.0 mg.KOH/g, as measured by ISO
3771.
[0085] The lubricating oil compositions herein may additionally contain an ash-free dispersant
which is preferably admixed in an amount in the range of from 5 to 15 wt. %, based
on the total weight of the lubricating oil composition.
[0086] Examples of dispersants which may be used include the polyalkenyl succinimides and
polyalkenyl succininic acid esters disclosed in Japanese Patent Nos.
1367796,
1667140,
1302811 and
1743435. Preferred dispersants include borated succinimides.
[0087] Preferred friction modifiers that may be conveniently used include fatty acid amides,
more preferably unsaturated fatty acid amides.
[0088] The total amount of friction modifiers added to the lubricating oil composition herein
is conveniently in the range of from 0.05 to 1.2 wt. %, based on the total weight
of the lubricating oil composition.
[0089] Examples of viscosity index improvers which may conveniently be used in the lubricating
oil composition herein include the styrene-butadiene copolymers, styreneisoprene stellate
copolymers and the polymethacrylate-based and ethylene-propylene copolymers and the
like disclosed in Japanese Patent Nos.
954077,
1031507,
1468752,
1764494 and
1751082. 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.
Similarly, dispersing-type viscosity index improvers comprising copolymerized polar
monomer containing nitrogen atoms and oxygen atoms in the molecule may also be used
therein.
[0090] Polymethacrylates such as those as disclosed in Japanese Patent Nos.
1195542 and
1264056 may be conveniently employed in the lubricating oil compositions herein as effective
pour point depressants.
[0091] 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 herein as corrosion inhibitors.
[0092] Compounds such as polysiloxanes, dimethyl polycyclohexane and polyacrylates may be
conveniently used in the lubricating oil composition herein as defoaming agents.
[0093] Compounds which may be conveniently used in the lubricating oil composition herein
as seal fix or seal compatibility agents include, for example, commercially available
aromatic esters.
[0094] The lubricating oil compositions herein may be conveniently prepared by admixing
the one or more detergents (A), the one or more antioxidants (B) selected from phenolic
and/or aminic antioxidants, and, optionally, one or more further additives that are
usually present in lubricating oils, for example as herein before described, with
a mineral and/or synthetic base oil.
[0095] Lubricating oil compositions herein display advantageous TBN retention, in particular
with regard to the VW T4 test (PV 1449).
[0096] In a preferred embodiment of the present invention, the end of test (VW T4 Test (PV
1449)) TBN value is at least 5.0 mg.KOH/g, as measured by ISO 3771.
[0097] In a preferred embodiment of the present invention, the TBN value of a fresh unused
sample of the lubricating oil composition herein is in the range of from 5.0 to 12.0
mg.KOH/g and the end of test (VW T4 Test (PV 1449)) TBN value of the same lubricating
oil composition is at least 5.0 mg.KOH/g, as measured by ISO 3771.
[0098] In another preferred embodiment of the present invention, the TBN value of a fresh
unused sample of the lubricating oil composition herein is in the range of from 6.0
to 11.0 mg.KOH/g and the end of test (VW T4 Test (PV 1449)) TBN value of the same
lubricating oil composition is at least 6.0 mg.KOH/g, as measured by ISO 3771.
[0099] In yet another preferred embodiment of the present invention, the TBN value of a
fresh unused sample of the lubricating oil composition herein is in the range of from
6.0 to 10.0 mg.KOH/g and the end of test (VW T4 Test (PV 1449)) TBN value of the same
lubricating oil composition is at least 6.0 mg.KOH/g, as measured by ISO 3771.
[0100] In the present invention, it is preferred that the change in TBN between the TBN
of a fresh unused sample of the lubricating oil composition herein and the end of
test (VW T4 Test (PV 1449)) TBN value of the same lubricating oil composition (i.e.
wherein ΔTBN is the TBN of fresh oil - End of test TBN) is less than 2.5 mg.KOH/g,
more preferably less than 2.0 mg KOH/g and most preferably less than 1.8 mg.KOH/g.
[0101] In a preferred embodiment of the present invention, the end of test (VW T4 Test (PV
1449)) Vk40 value (i.e. kinematic viscosity at 40 °C) is less than 200 mm
2/s (cSt).
[0102] Accordingly, there is provided the use of a lubricating oil composition as hereinbefore
described to maintain a TBN level of at least 5.0 mg.KOH/g, as measured by ISO 3771,
in an internal combustion engine, in particular with regard to the VW T4 test (PV
1449).
[0103] The present invention is described below with reference to the following Examples,
which are not intended to limit the scope of the invention in any way.
EXAMPLES
Formulations
[0104] Table 1 indicates the formulations that were tested.
[0105] The formulations in Table 1 comprised conventional detergents, antifoam, dispersants,
pour point depressants, viscosity index modifiers and zinc dithiophosphate additives,
which were present as additive packages in diluent oil.
[0106] The phenolic antioxidant used was that available under the trade designation "Irganox
L-135" ex. Ciba Specialty Chemicals Co. (C7-C9 branched alkyl esters of 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-benzenepropanoic
acid).
[0107] The aminic antioxidant used was that available under the trade designation "Irganox
L-57" ex. Ciba Speciality Chemicals Co.
[0108] The base oils used in said formulations were mixtures of Group III base oils available
from "The Royal Dutch/Shell Group of Companies" under the trade designations "XHVI-5.2"
and "XHVI-8.2".
[0109] All formulations described in Table 1 were SAE 5W30 viscosity grade oils.
[0110] Table 2 indicates the physical characteristics of the formulations that were tested.
TABLE 1
Additive (wt. %) |
Ex. 1* |
Ex. 2* |
Ex. 3* |
Ex. 4* |
Ex. 5* |
Ex. 6 |
Comp. Ex. 1* |
Anti-foam |
30ppm |
30ppm |
30ppm |
30ppm |
30ppm |
30 ppm |
30ppm |
Additive package A1 |
14.0 |
- |
- |
- |
- |
14.0 |
14.0 |
Additive Package B2 |
- |
10.9 |
- |
- |
- |
- |
- |
Additive Package C3 |
- |
- |
10.1 |
- |
- |
- |
- |
Additive Package D4 |
- |
- |
- |
10.7 |
- |
- |
- |
Additive Package E5 |
- |
- |
- |
- |
11.5 |
- |
- |
Phenolic Antioxidant |
4.0 |
4.0 |
4.0 |
4.0 |
4.0 |
- |
- |
Aminic Antioxidant |
- |
- |
- |
- |
- |
4.0 |
- |
Viscosity modifier6 |
9.60 |
12.0 |
12.0 |
12.0 |
12.0 |
9.60 |
9.60 |
Pour point depressant |
0.3 |
- |
- |
- |
- |
0.3 |
0.3 |
Base oil7 |
72.10 |
73.10 |
73.90 |
73.80 |
72.50 |
72.10 |
76.10 |
TOTAL |
100 |
100 |
100 |
100 |
100 |
100 |
100 |
*Comparative Examples
1 Commercial additive package available ex. Lubrizol under the trade designation "LZ
OS183698", containing sulphonate and phenate detergents each having TBNs in the range
of from 30 to 350 mg.KOH/g, dispersant, zinc dithiophosphate and diluent oil.
2 Conventional additive package containing calcium salicylate detergents having TBNs
of 165 mg.KOH/g and 280 mg.KOH/g, dispersant, zinc dithiophosphate and diluent oil.
3 Conventional additive package containing magnesium salicylate detergent having a
TBN of 345 mg.KOH/g, dispersant, zinc dithiophosphate and diluent oil.
4 Conventional additive package containing magnesium salicylate detergent having a
TBN of 345 mg.KOH/g, dispersant, zinc dithiophosphate and diluent oil.
5 Conventional additive package containing calcium salicylate detergents having TBNs
of 64 mg.KOH/g and 165 mg.KOH/g, dispersant, zinc dithiophosphate and diluent oil.
6 Mixture of two different viscosity index modifiers.
7 Group III base oil mixtures of XHVI-5.2 and XHVI-8.2 |
TABLE 2
Analytical Measurements |
Total Sulphated ash |
Total Sulphur |
Total Phosphorus |
Ca |
Mg |
|
(wt. %) (ASTM D874) |
(wt. %) (ASTM D2622) |
(wt. %) (ICP-OES method) |
(wt. %) (ICP-OES method) |
(wt.%) (ICP-OES method) |
Ex. 1* |
0.77 |
0.188 |
0.068 |
0.163 |
0 |
Ex. 2* |
0.85 |
0.186 |
0.047 |
0.207 |
0 |
Ex. 3* |
0.64 |
0.125 |
0.050 |
0 |
0.118 |
Ex. 4* |
0.85 |
0.131 |
0.049 |
0 |
0.163 |
Ex. 5* |
0.63 |
0.135 |
0.050 |
0.150 |
0 |
Ex. 6 |
0.82 |
0.183 |
0.072 |
0.166 |
0 |
Comp. Ex. 1* |
0.76 |
0.131 |
0.074 |
0.167 |
0 |
VW T4 test (PV 1449)
[0111] The experimental methodology used for the Examples above was in accordance with the
publicly available test specification for the VW T4 test (PV 1449) and as described
in the standard test methods referred to in said test specification.
Results and Discussion
[0112] The formulations described in Tables 1 and 2 were tested using the afore-mentioned
test and the results obtained thereon are included in Table 3.
TABLE 3
Test Results |
Ex. 11 |
Ex. 21 |
Ex. 31 |
Ex. 41 |
Ex. 51 |
Ex. 6 |
Comp. Ex. 11 |
Vk40* increase (%) |
125.5 |
73.9 |
69 |
74.4 |
77.2 |
114.1 |
98 |
Vk40 at end of test** (mm2/s) |
144.6 |
121 |
117.8 |
121.2 |
122.8 |
141.7 |
135.4 |
(1) TBN of fresh oil (mg.KOH/g) (ISO 3771) |
7.8 |
8.0 |
7.6 |
9.4 |
5.9 |
5.28 |
6.9 |
(2) End of test TBN*** (mg.KOH/g) (ISO 3771) |
6.1 |
7.3 |
6.2 |
8.1 |
5.1 |
5.12 |
3.6 |
Δ TBN**** (mg.KOH/g) |
1.7 |
0.7 |
1.4 |
1.3 |
0.8 |
0.16 |
3.3 |
% change in TBN |
-21.7 |
-8.8 |
-18.4 |
-13.8 |
-13.6 |
-3.0 |
-47.3 |
* Kinematic viscosity at 40 °C.
** End of Test Limit (VW T4 test (PV 1449)) is <200 (mm2/s).
*** End of Test Limit (VW T4 test (PV 1449)) is 5.0 mg.KOH/g.
**** TBN of fresh oil - End of test TBN.
1 Comparative Examples |
[0113] It is evident from the above results that the formulation of Example 1 which comprises
a phenolic antioxidant, displays increased TBN retention according to the VW T4 test
(PV 1449), as compared with the formulation of Comparative Example 1 which fails to
meet the required minimum end of test TBN result of 5.0 mg.KOH/g.
[0114] Furthermore, the formulations or Examples 2 to 5 which also contain large amounts
of phenolic antioxidant, also surprisingly pass the VW T4 test (PV 1449) end of test
TBN limit of 5.0 mg.KOH/g.
[0115] It is further evident that the formulation of Example 6 which comprises an aminic
antioxidants, also displays increased TBN retention according to the VW T4 test (PV
1449), as compared with the formulation of Comparative Example 1.