Note: Descriptions are shown in the official language in which they were submitted.
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3-16536/+
Stabilised diesel engine oil
The present invention relates to a diesel engine oil which is
stabilised with an ester of a sterically hindered 3-~4-hydroxy-
phenyl) compound and to the use of said ester of 3-(3-hydroxy-
phenyl~ compound for stabilising diesel engine oils.
Owing to the substantially greater load as compared with Otto
engines and to the sulfur content of the diesel fuel, resistance to
wear, oxidation and corrosion stability, low residue formation and
nonsludging capacity are especially important for lubricant oils
for diesel engines.
The life of diesel engines depends substantially on piston
cleanliness as well as on the wear of the cylinder bore and on the
wear of piston rings and bearings caused by mechanical abrasion and
chemical corrosion. Abrasion is increased by engine soiling.
Corrosive wear is mainly caused by the sulfur content of the fuel,
which results in the formation of highly corrosive sulfur-containing
acids. The higher thermal stresses in the piston area necessitate
the use of detergent additives for effectively preventing increased
coking and lacquering on the piston under these conditions. As
diesel engines discharge more solid combustion products into the
engine oil than do gasoline engines, dispersant additives are added
to the lubricating oil to prevent sludge formation. In addition, the
trend towards longer oil-change intervals requires an adequate
stability to ageing of the lubricating oils for diesel engines.
These oils must not thicken appreciably over the entire running time
and must prevent the formation of residues. Good thermal and
oxidative stability is therefore essential.
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Ash-free antioxidants of the alkylated diphenylamine or sterically
hindered phenol type are not markedly effective in lubricant oils
for diesel engines.
Esters of 3-( 3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid are
disclosed as antioxidants for polymers, industrial oils and for
diesel fuel in US patent specifications 3 285 855, 3 330 859,
3 345 327 and 4 652 272.
Surprisingly, it has now been found that esters of a sterically
hindered 3-(4-hydroxyphenyl) compound are very effective anti-
oxidants for diesel engine lubricating oils.
The present invention relates to a lubricant oil composition
comprising a diesel engine oil and, as antioxidant, a compound of
formula I
Rl~
HC) ~ X
R2/
wherein Rl and R2 are each independently of the other C1-C12alkyl
and X is -CH2-CH2-C-OR, -CH~-S-CH~-~-OR or
-CH2-S-R and R is a straight chain or branched alkyl radical of the
formula -C H2 +1' wherein n is an integer from 9 to 30.
Rl and R2 as C1-C12alkyl are straight chain or branched, preferably
branched, alkyl radicals and, most preferably, those in which the
(Y-carbon atom is a tertiary carbon atom, for example methyl, ethyl,
n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl,
straight chain or branched pentyl, hexyl, heptyl, octyl, nonyl,
decyl, undecyl or dodecyl.
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The C H2 +1 radical denotes preferably straight chain Cg-C30alkyl
radicals. Most preferably the C H2 +1 radical denotes a straight
chain C1s-C30alkyl radical.
R as Cg-C30alkyl is for example nonyl, decyl, undecyl, dodecyl,
tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,
eicosyl, heneicosyl, docosyl and others up to triacontyl. Preferred
are C1s-C30alkyl radicals as defined above.
A preferred lubricant oil composition is one in which the diesel
engine oil is an engine oil of API classes CC, CD or class CD~ ).
The API classes CC and CD are classifications of the American
Petroleum Institute for engine oils. The C classes relate to diesel
engine oils which, in accordance with their degree of doping and
thus performance rating, are given a further letter in their
classification.
Engine oils of the CC class conform to the requirements for diesel
aspirating engines since 1961. They contain additives for the
prevention of high- and low-temperature deposits and of corrosion
(requirement according to MIL-L-2104 B).
Class CD engine oils conform to the requirements of supercharged
diesel engines, also those powered by fuels of higher sulfur
content. They contain additives for the prevention of
high-temperature deposits, wear and corrosion.
The CD( ) class comprises engine oils for higher supercharged
vehicle diesel engines which do not yet have an API classification.
These oils are required above all in Europe, where engine oils are
subjected to very high thermal stress on account of the high
performance/weight ratio of the diesel engines.
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The basis oil used for the preparation of engine oils of the
aforementioned classes is normally a mineral oil. However, it can
also consist of hydrogenated mineral oil distillates such as
severely hydrotreated oil (refining hydrogenation, Ullmann's
Encyclopedia of Industrial Chemistry, Vol. 10, pp. 6gO-699, Verlag
Chemie, Weinheim, 1977) or hydrocracked oil (cleaving hydrogenation,
Ullmann's Encyclopedia of Industrial Chemistry, Vol. 10,
pp. 690-706, Verlag Chemie, Weinheim 1977) or synthetic components
or mixtures thereof.
The synthetic oils comprise e.g. oils based on diesters, complex
esters or poly-~-olefins.
A further preferred lubricant oil composition is one in which the
diesel engine oil is a lubricant oil based on mineral oil, a
synthetic oil or a mixture thereof, of SAE viscosity classes 15 W 40
or 30, and comprising 2.5 to 7.5 % by weight of a detergent, 3.5 to
6.0 % by weight of a dispersant and 1.2 to 1.8 % by weight of a
zinc dialkyldithiophosphate.
Yet a further preferred lubricant oil composition is one in which
the diesel engine oil contains 0.5 to 2.0 % by weight, preferably
0.75 to 1.5 % by weight, of an antiwear additive in addition to the
detergent, dispersant and zinc dialkyldithiophosphate.
Examples of detergents which are added to diesel engine oils are
basic alkali metal sulfonates or alkaline earth metal sulfonates
such as sodium, calcium and magnesium salts of long-chain
alkylarylsulfonic acids or basic alkali metal or alkaline earth
metal phenolates and salicylates.
The dispersants for diesel engine oils are for example polyiso-
butenylsuccinimides, polybutenylphosphonic acid derivatives or
copolymers of vinyl acetate and fumaric acid esters.
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The zinc dialkyldithiophosphates are preferably compounds of the
general formula
RO-P-S Zn
R'O
wherein R and R' are each independently of the other C2-CI2alkyl
preferably C2-Cgalkyl, and the total number of carbon atoms of R and
R' is at least 5.
The antiwear additives are for example polar, oil-soluble substances
such as fatty alcohols, fatty acids, fatty acid esters or fatty acid
amides whose acti~ity increases with increasing molecular weight and
in the sequence alcohol ~ ester < unsaturated acid < saturated acid.
A useful lubricant oil composition is also one comprising a diesel
engine oil, an antioxidant of formula I and also, as additional
antioxidant, a triarylphosphite, a trialkylphosphite, a mixed
alkylarylphosphite andtor a thio compound of formula II
(ÇH2) -~-oR3
II
(CH2) ~ -oR3
wherein R3 is C6-C24alkyl, preferably Clz-Clgalkyl, and m is an
integer from 1 to 6.
Examples of triarylphosphites, trialkylphosphites and mixed alkyl-
arylphosphites are triphenylphosphite, diphenylalkylphosphites,
phenyldialkylphosphites, tris(nonylphenyl)phosphite, trilauryl-
phosphite, trioctyldecylphosphite, distearylpentaerythritol
6 1 3 3 3 7 9 9
diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecyl-
pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)penta-
erythritol diphosphite, tristearyl sorbitol triphosphite.
Examples of compounds of formula II are dilaurylthiodipropionate
and distearylthiopropionate.
A particularly preferred lubricant oil composition is one which
contains a compound of formula I, wherein Rl and R2 are each
independently of the other Cl-C4alkyl.
A further especially preferred lubricant oil composition is one
which contains a compound of formula I, wherein Rl and R2 are
identical and are a tert-butyl radical.
Likewise very preferred is a lubricant oil composition which
contains a compound of formula I, wherein Rl is methyl and R2 is
tert-butyl.
A further interesting lubricant oil composition is one which
contains a compound of formula I, wherein n is an integer from 12
to 24 and is preferably 1~.
A particularly interesting lubricant oil composition is one in which
the compound of formula I is n-octadecyl-3-(3,5-di-tert-butyl-
4-hydroxyphenyl)propionate.
Examples of compounds of formula I are:
n-nonyl-3-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionate,
2-butyl-octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,
n-eicosyl-3-(3,5-diisopropyl-4-hydroxyphenyl)propionate,
2-hexyldecyl-3-(5-tert-octyl-4-hydroxy-3-methylphenyl)propionate,
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7 21~89-7425
n-triacontyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,
n-octadecyl-3-(3~5-di-Lert-butyl-4-llydroxyphenyl)propionate~
n-dodecyl-3-(3,5-di-n-dodecyl-4-hydroxyphenyljpropionate.
The compounds ot tormu1a I are known and can be prepared in a mallner
known per se, for example by the methods described in US patent
specifications 3 247 240, 4 085 13~ and 4 228 297. Any compounds
which are novel can be prepared in analogous manner.
Preferred compositions of the present invention contain a compound
ol lormu1a
\ / CH~-S-CH2-~-0-C i~2 +1 (Ia)
X
wherein n is an integer from 9 to 30, preterably trom 12 to 24 and,
most preferab1y, is 18.
A1so preterred are compositlons containillg a compound ot tormula
H0--~ ~--CH~-S-C H2 +1 (Ib)
. _ --
wherein n is an integer from 9 to 30, preferably from 12 to 24 and,
mu~L pre1er~b1y, 1~
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The compounds of formula I are excellent antioxidants for diesel
engine oils. They are added thereto preferably in an amount of 0.2
to 2.0 % by weight, most preferably 0.5 to 1.5 % by weight, based on
the total weight of the lubricant oil composition.
Hence the present invention also relates to the use of compounds of
formula I for stabilising diesel engine oil against oxidative
degradation.
The diesel engine oils stabilised with the compounds of formula I
may preferably be used in the following types of diesel engines:
- high-speed vehicle diesel engines which are naturally aspirated or
supercharged (automobiles, locomotives),
- marine diesel engines such as 4-cycle trunk-type piston engines,
or 2-cycle crosshead diesel engines,
- gas diesel engines.
The lubricant oil compositions of this invention can contain still
further additives which are added to the diesel engine oil to
improve its basic properties further, for example viscosity
modifiers.
Examples of viscosity modifiers are polymethacrylates,
vinylpyrrolidone/methacrylate copolymers, polybutenes, olefin
copolymers or styrene/acrylate copolymers.
In the following Examples parts and percentages are by weight,
unless otherwise stated.
1 33379~
g
Example 1: Engine test in a MWM test diesel engine in accordance
with DIN 51 361 or CECL 12-A-76
The field of application of this test relates to engine oils. The
purpose of the test is to assess the cleansing action of engine
oils. This is done by testing principally the snug fit of the piston
rings and the coke-like deposits in the piston ring grooves of
diesel engines.
Piston cleanliness in the context of this standard denotes the
ability of engine lubricating oils to keep the engine clean
internally and to keep in check the unavoidable impurities stemming
from combustion [extraneous oil contamination and by ageing
substances which form in the engine lubricating oil (inherent oil
contamination)].
a) Test procedure and test engine:
A new test piston is run in with the engine lubricating oil for
testing in the test engine. There follows a 50 hour test run with a
fresh oil supply under exactly defined and constantly maintained
operating conditions of the test engine.
The test engine is a single cylinder four-cycle diesel engine, type
MWM KD 12E. This engine is a rotochamber aspirating engine with an
engine capacity of 0.85 1 (cylinder bore 95 mm, piston stroke
120 mm) and a highest useful compression ratio of 22.
Operating conditions of the engine during the test run
Test duration: 50 hours without interruption.
Gradual increase of engine speed and torque from start of operation
so that the following engine speed and useful performance is reached
after ca. 30 minutes:
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engine speed: 2200 min 1 + 25 min 1
fuel consumption: 3100 g/h + 40 g/h
coolant inlet temperature: at least 100C
coolant outlet temperature: (110 + 2)C.
Amount of oil: 3.2 1; the weight must be determined and entered in
the test report. The engine lubricating oil must not be replenished
or drawn off during the test run.
Lubricating oil consumption: at most 1400 g for the 50 hour duration
of the test run.
oil temperature in the crankcase: (110+ 2)C
oil pressure: 1.3 to 1.8 bar overpressure
exhaust gas counterpressure: 25 to 45 mbar
air suction temperature: 25 to 35C
density of exhaust smoke: density value according to Bosch:
at most 4.
After the 50 hour test run, the piston cleanliness is evaluated by
visual observation in accordance with DIN 51 361, Part 2.
The values corresponding to a specific piston cleanliness are
reported in Table 1
Table 1
Piston cleanliness Evaluation factor
clean 100
discoloured 65
black 30
coke - 30
The 1st, 2nd and 3rd groove beds, the 2nd piston land, the piston
head and piston skirt are evaluated.
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At each site the product of the respective piston cleanliness and
the area thereof is formed.
A mean value is computed for the measuring sites at the 1st, 2nd and
3rd groove bed and at the 1st and 2nd land of the piston.
b) Test procedure
The base oil is a formulated mineral oil of SAE viscosity class
15 ~-40 with a TBN (total basic number) of 8.8 mg of KOH/g of
mineral oil and having a Zn content of 0.11 % by weight, a P content
of 0.095 % by weight, a Ca content of 0.25 % by weight, a Mg content
of 0.045 % by weight and a sulfate ash content of 1.21 ~O by weight.
This corresponds to a zinc dialkyldithiophosphate content of 1.2 %
by weight, a detergent content (magnesium sulfonate, calcium
phenate) content of 3.5 % by weight and a dispersant content of
3.5 % by weight.
The oil additionally contains 8 % by weight of a viscosity modifier
(olefin copolymer). The oil is thus a diesel engine oil of API
class CD.
The antioxidant of formula I of this invention is added to this base
oil and the measurement is made as described in a).
The results are reported in Table 2.
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Table 2
~easuring Base Base oil Base oil
site oil + 0.6 % of AO + 1.2 % of AO
1st groove bed 18 40 27
2nd groove bed 84 93 8~
3rd groove bed 100 100 100
1st land 62 63 67
Znd land 100 98 98
Mean value 73 79 7~
AO = n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate
Example 2: Following the procedure described in Example 1, the
improvement in the cleansing action of a base oil of the following
composition is tested hy the addition of an antioxidant of
formula I of this invention to said base oil.
Base oil: formulated mineral oil of SAE viscosity class l0 W-30 with
a TBN (total basic number) of 5.5 mg of ~OH/g of mineral oil and
having a Zn content ol 0 07 C~O by weight, a P content of 0.07 ~/O by
weight, a calcium content of 0.2 % by weight and a sulfate ash
content of 0.74 % by weight. This corresponds to a zinc
dialkyldithiophosphate content of O.Y ~/O by weight, a detergent
content (calci~m sulfonate, calcium phenate) of 3.0 % by weight, and
a dispersant content of 3.5 % by weight.
The oil additionally contains 6 ~O by weight of a viscosity modifier
~olefin copolymer). The oil is thus a diesel engine oil of API
class CC.
The antioxidant is n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxy-
phenyl)propionate.
The results are reported in Table 3
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Table 3
Measuring site Base oil Base oil + 0.6 ~/0 of AO
1st groove bed O O
2nd groove bed 22 71
3rd groove bed ~1 98
1st land 44 53
2nd land 86 93
Mean value 49 63
