[0001] Internal combustion engines operate under a wide range of temperatures including
low temperature stop-and-go service, as well as high temperature conditions produced
by continuous high speed driving. Sludges or insolubles are produced under some operating
conditions and dispersants are added to the lubricating oil so that potentially insoluble
materials remain dispersed in the oil.
[0002] It is known to employ nitrogen containing dispersants and/or detergents in the formulation
of crankcase lubricating oil compositions. Many of the known dispersant/detergent
compounds are based on the reaction of an alkenylsuccinic acid or anhydride with an
amine or polyamine to produce an alkylsuccinimide or an alkenylsuccinamic acid as
determined by selected conditions of reaction.
[0003] It is also known to chlorinate alkenylsuccinic acid or anhydride prior to the reaction
with an amine or polyamine in order to produce a reaction product in which a portion
of the amine or polyamine is attached directly to the alkenyl radical of the alkenyl
succinic acid or anhydride. The thrust of many of these processes is to produce a
product having a relatively high level of nitrogen in order to provide improved dispersancy
in a crankcase lubricating oil composition.
[0004] A serious problem facing the lubricant manufacturer is that of seal deterioration
in the engine. All internal combustion engines use elastomer seals, such as nitrile-rubber
or fluorocarbon-rubber seals, in their assembly. Over time, these seals are susceptible
to serious deterioration caused by the lubricating oil composition. A lubricating
oil composition that degrades the elastomer seals in an engine is unacceptable to
engine manufacturers and has limited value.
[0005] It is an object of this invention to provide a lubricating oil composition which
does not degrade nitrile elastomer seals in internal combustion engines.
[0006] U S Patent No. 4,304,678 discloses a lubricating oil composition containing a friction
modifier from the class of glycerol esters. The use of esters of glycerol and a fatty
acid as an additive in lubricating oil compositions is also described in, e.g. EP-A-0,305,538
and US-A-4,304,678.
[0007] The present invention relates to the use of an ester of glycerol and an unsaturated
fatty acid having from 8 to 45 carbon atoms in an oil of lubricating viscosity in
order to provide nitrile elastomer seal compatibility properties.
[0008] The ester which imparts the seal compatibility properties may be a mono-, di- or
triester of glycerol and may be prepared from a simple unsaturated fatty acid or a
mixture of unsaturated fatty acids. In general, the fatty acid will contain from about
8 to 45 carbon atoms, preferably 12 to 30 carbon atoms. These fatty acids may be represented
by the formula R-COOH in which R is an unsaturated aliphatic radical having from 7
to 44 carbon atoms.
[0009] The preferred unsaturated fatty acids have from 12 to 30 carbon atoms. Typical unsaturated
fatty acids which are suitable include the following: oleic, linoleic, hexadecenoic
and linolenic.
[0010] The ester additive of the invention is made by either reacting glycerol with one
or more of the prescribed fatty acids or by reacting natural triglyceride oils with
water or glycerol according to known methods. The ester additive may be a monoester,
diester or triester or a mixture of mono-, di- and triesters. In general, it is preferable
to have a high proportion of monoesters in the ester additive.
[0011] Typical glycerol esters of unsaturated fatty acids which are suitable are illustrated
by the following: glyceryl monooleate; glyceryl dioleate; glyceryl trioleate; glyceryl
monolinoleate; glyceryl dilinoleate and glyceryl trilinoleate and glyceryl ricinoleate.
[0012] The lubricating oils contemplated for use with the esters herein disclosed include
both mineral and synthetic hydrocarbon oils of lubricating viscosity and mixtures
thereof with other synthetic oils. The synthetic hydrocarbon oils include long chain
alkanes, such as cetanes, and olefin polymers, such as trimers and tetramers of octene
and decene. The synthetic oils, which can be used as the sole lubricating oil, or
which can be mixed with the mineral or synthetic hydrocarbon oil include (1) fully
esterified ester oils, with no free hydroxyls, such as pentaerythritol esters of monocarboxylic
acids having 2 to 20 carbon atoms, (2) polyacetals and (3) siloxane fluids. Especially
useful among the synthetic esters are those made from polycarboxylic acids and monohydric
alcohols. More preferred are the ester fluids made from pentaerythritol, or mixtures
thereof with di- and tripentaerythritol, and an aliphatic monocarboxylic acid containing
from 1 to 20 carbon atoms, or mixtures of such acids.
[0013] An effective amount of ester in the lubricant for nitrile seal compatibility is an
amount ranging from about 0.01 to 3.0 weight percent based on the weight of the oil
composition. A preferred concentration is from 0.1 to 0.75 weight percent.
Seal Compatibility Tests
[0014] An important property of a lubricating oil additive and blended lubricating oil compositions
containing the additive is the compatibility of the oil composition with the rubber
seals employed in the engine. Some of the nitrogen containing succinimide dispersants
and other additives such as active sulfur compounds employed in crankcase lubricating
oil compositions may have the effect of seriously degrading the elastomer seals in
internal combustion engines. In particular, such additives are known to attack rubber
seals, such as nitrile rubber and fluorocarbon rubber seals which are commonly employed
in internal combustion engines. This deterioration exhibits itself by sharply degrading
the flexibility of the seals and in increasing their hardness. This is such a critical
problem that a number of automotive engine builders require that all crankcase lubricating
oils pass a seal compatibility test before the oil composition will be rated acceptable
for engine crankcase service. The seal compatibility tests used for nitrile rubbers
are described below and are designed to determine the seal compatibility properties
of a crankcase lubricating oil composition.
[0015] The test method for the Mercedes-Benz Seal Compatibility Test is based on the VDA
521-01 test procedure.
[0016] The seal compatibility test is conducted by soaking samples of the elastomer-rubber
in the oil under investigation at an elevated temperature and then measuring the effect
of the oil composition on the rubber sample for volume change, elongation change,
hardness change and tensile strength change.
[0017] The specimens are weighed in air and in water to the nearest mg. After weighing in
water, each specimen is dried on clean filter paper. The elongation and tensile strength
of three of the specimens are measured.
[0018] The hardness of the specimens is determined with a durometer. The specimens conform
to the standard S2 definition.
[0019] Six specimens are suspended in a beaker by inserting a piece of nichrome wire through
the small hole in the end of each specimen. The specimens are arranged so that they
do not touch each other or the beaker. The test oil is added in a ratio of 1:80 of
elastomer to oil in the beaker. The elastomer specimens in the beaker are aged for
168 hours in an oven maintained at 100°C.
[0020] At the end of the test period, the beakers are removed from the oven and the specimens
are removed from the beaker and cleaned with absorbent paper. Elongation and tensile
strength measurements are made on each aged specimen. Each specimen is weighed in
air and in water and measured for hardness.
[0022] The following examples illustrate the practice of this invention.
EXAMPLE I
[0023] The base oil employed in this example was a refined oil (NMP SN 100/200) which was
fully formulated with a conventional detergent-inhibitor package. The fully formulated
oil (Oil 1) and a modification containing 0.55 weight percent glyceryl monooleate
(Oil 2) were tested for their effect on a nitrile rubber (NBR-34 formulated from an
acrylonitrile-butadiene copolymer containing about 34 percent of acrylonitrile) in
the Mercedes-Benz Seal Compatibility Test. The percent change in tensile strength
(TS) and in elongation (E) were reported.
[0024] Oil 2 containing the glyceryl monooleate exhibited excellent nitrile seal compatibility
properties.
EXAMPLE II
[0025] A fully formulated lubricating oil composition designated as Oil 1 was employed in
the CCMC Seal Test, the Mercedes-Benz Seal Test and the MAN Seal Test. Modifications
of this oil, designated as Oil 2 containing 0.20 weight percent glyceryl monooleate
and Oil 3 containing 0.55 weight percent glyceryl monooleate, which was supplied by
C. P. Hall, were also employed in the CCMC Seal Test. The elastomer tested was a nitrile
rubber. The test results are indicated in Table 2 below.
[0026] The additive oils of the invention containing glyceryl monooleate exhibited excellent
improved nitrile seal compatibility properties.
EXAMPLE III
[0027] The lubricating oil employed in this example was a fully formulated gasoline engine
oil and is designated as Oil 1. Oil 2 contains 0.20 weight percent of glyceryl monooleate,
Oil 3 contains 0.55 weight percent of glyceryl monooleate and oil 4 contains 0.20
weight percent of Radiasurf 7150, another brand of glyceryl monooleate. These oils
were tested in the Mercedes Benz Seal Test and the results are set forth in Table
3 below.
[0028] All of the oils containing the glyceryl monooleate exhibited excellent nitrile seal
compatibility properties.
EXAMPLE IV
[0029] A commercial Ford Factory Fill lubricating oil composition was tested in the CCMC
Seal Compatibility Test. A modified oil or variant was prepared containing 0.20 weight
percent of glyceryl monooleate. A nitrile rubber was used in the test. The results
are reported in Table 4 below.
[0030] The foregoing results demonstrate that the modified oil containing 0.20 percent of
glyceryl monooleate gave excellent results in the CCMC Seal compatibility Test for
the nitrile rubber.
EXAMPLE V
[0031] A variety of glycerol esters were tested in the same lubricating oil employed in
Example II. In all cases, the glycerol ester was employed in a concentration of 0.20
weight percent. The following table lists the oils tested and the particular glycerol
ester.
- Oil No.
- 1 Radiasurf 7150 Glyceryl Monooleate
2 Radiasurf 7140 Glyceryl Monostearate,
approx. 35% monoglycerides
3 Radiasurf 7600 Glyceryl Monostearate,
approx. 52% monoglycerides
4 Radiasurf 7153 Glyceryl Monoricinoleate
5 None (Ref. oil)
[0032] These oils were tested in a Mercedes-Benz Seal Compatibility Test and the results
are set forth in Table 5 below.
[0033] The test results show that there is criticality in the nature of the glycerol ester.
The esters formed from glycerol and a saturated fatty acid, namely glyceryl monostearate,
fail to pass the test limits for the Mercedes-Benz Seal Compatibility Test while the
oils containing a glycerol ester of an unsaturated fatty acid gave excellent nitrile
seal compatibility properties.
1. The use of an ester of glycerol and an unsaturated fatty acid having from 8 to 45
carbon atoms in an oil of lubricating viscosity in order to provide nitrile elastomer
seal compatibility properties.
2. The use as claimed in Claim 1 in which said ester is a mono-, di- or triester of glycerol
or a mixture thereof.
3. The use as claimed in Claim 1 or Claim 2 in which said ester is predominantly a monoester
of glycerol.
4. The use as claimed in Claim 1 in which said ester is glyceryl monooleate, glyceryl
ricinoleate or glyceryl linoleate.
5. The use as claimed in any one of the preceding Claims in which from 0.01 to 3 weight
percent of said glycerol ester is present in said oil of lubricating viscosity.
1. Die Verwendung eines Esters aus Glycerin und einer ungesättigten Fettsäure mit von
8 bis 45 Kohlenstoffatomen in einem Öl mit Schmierviskosität, um Nitrilelastomerdichtungskompatibilitätseigenschaften
bereitzustellen.
2. Die Verwendung, wie beansprucht in Anspruch 1, wobei besagter Ester ein Mono-, Di-
oder Triester von Glycerin oder eine Mischung derselben ist.
3. Die Verwendung, wie beansprucht in Anspruch 1 oder Anspruch 2, wobei besagter Ester
überwiegend ein Glycerin-Monoester ist.
4. Die Verwendung, wie beansprucht in Anspruch 1, wobei besagter Ester Glycerylmonooleat,
Glycerylricinoleat oder Glyceryllinolsäureester ist.
5. Die Verwendung, wie beansprucht in irgendeinem der vorangehenden Ansprüche, wobei
von 0,01 bis 3 Gew.-% von besagtem Glycerinester in besagtem Öl mit Schmierviskosität
vorhanden sind.
1. Utilisation d'un ester du glycérol et d'un acide gras insaturé ayant de 8 à 45 atomes
de carbone dans une huile d'une viscosité lubrifiante afin de conférer des propriétés
de compatibilité avec les joints en élastomère nitrile.
2. Utilisation selon la revendication 1, dans laquelle ledit ester est un mono-, di-
ou triester du glycérol ou un mélange de ceux-ci.
3. Utilisation selon la revendication 1 ou 2, dans laquelle ledit ester est de façon
prédominante un monoester du glycérol.
4. Utilisation selon la revendication 1, dans laquelle ledit ester est le mono-oléate
de glycéryle, le ricinoléate de glycéryle ou le linoléate de glycéryle.
5. Utilisation selon l'une quelconque des revendications précédentes, dans laquelle de
0,01 à 3 pour cent en poids dudit ester du glycérol est présent dans ladite huile
de viscosité lubrifiante.