Copper complexes of oxazolines and lactone oxazolines as lubricating oil additives

There are disclosed lubricating oil compositions containing an oil soluble hydrocarbon substituted mono-oxazoline, bis-oxazoline or lactone oxazoline dispersant containing 0.2 to 2.0 wt % of complexed copper, the dispersant exhibiting improved varnish inhibition properties as well as providing anti-oxidation properties to the lubricating oil.

This invention relates to copper complexes of oxazoline or lactone 
oxazoline lubricating oil dispersants which offer improved performance as 
varnish inhibiting additives for lubricating oil compositions. 
Oxazolines and lactone oxazoline lubricating oil additives are known in the 
art and are disclosed for example in U.S. Pat. Nos. 4,116,876; 4,169,836 
and 4,062,786. 
The use of a metal salt promoter in preparing oxazoline compounds is 
disclosed in U.S. Pat. No. 4,035,309 issued to Brois, the metals useful 
therein being zinc, cobalt, manganese, nickel and iron. Borated 
derivatives of oxazolines and lactone oxazolines useful as sludge 
dispersants in lubricating oils are disclosed in U.S. Pat. No. 4,116,876, 
and molybdenum complexes of oxazoline dispersants useful as friction 
reducing antiwear additives are disclosed in U.S. Pat. No. 4,177,074. 
The use of oil soluble organic copper compounds in lubricating oil 
compositions is a relatively recent development of oil additive technology 
and the disclosure of these compounds as highly effective antioxidants is 
found in European publication No. 80302627.7 published on Feb. 25, 1981, 
which discloses the use of 5 to 500 ppm copper in the form of an oil 
soluble organic compound such as a copper salt of a C.sub.10 -C.sub.22 
fatty acid. 
The present invention is based upon the discovery that copper may be 
successfully incorporated into mono-oxazoline, bis-oxazoline or lactone 
oxazoline dispersants to yield products exhibiting greatly improved 
varnish inhibition properties when formulated into lubricating oil 
compositions. 
In accordance with the present invention there have been discovered 
lubricating oil compositions comprising a major amount of lubricating oil 
and a minor but varnish and oxidation inhibiting amount of an oil-soluble 
copper complex of an oil-soluble hydrocarbon substituted mono- or 
bis-oxazoline or a hydrocarbon substituted lactone oxazoline dispersant, 
the copper being present in said dispersant in an amount of about 0.2 wt% 
to 2 wt% of the dispersant. 
The copper-containing oxazoline and lactone oxazoline dispersants of the 
present invention provide a number of significant advantages to 
lubricating oil compositions. The oils, due to the presence of the copper, 
will exhibit the desirable anti-oxidant properties as disclosed in said 
European Application No. 8030.2627.7 and also exhibit improved dispersancy 
as indicated by the substantial improvements in the inhibition of varnish 
deposits when compared with the same oxazoline and lactone oxazoline 
dispersants prior to being complexed with copper. 
A further advantage resides in improved storage stability of lubricating 
oil compositions in that the copper complexed dispersants of this 
invention exhibit improved compatibility with other metal-containing 
additives customarily used in lubricating oil composition, especially the 
metal and overbased metal oil soluble sulfonate, phenate and sulfurized 
phenate detergent additives. This improved compatibility is evidenced by 
viscosity stability when the copper-complexed oxazoline and lactone 
oxazoline dispersants of this invention are blended in lubricating oil 
compositions with the metal detergent additives. 
Dispersants are normally provided in the form of a 50% by weight 
concentrated solution in mineral oil of lubricating viscosity and said 
dispersant concentrates are incorporated into a finished lubricating oil 
in amounts of from about 0.5 to 7 wt% of solution concentrate based on the 
total weight of the lubricating oil compositions. In the compositions of 
the present invention it is preferred that the finished lubricating oil 
composition contain about 50 to 300 ppm (parts per million) of copper in 
the form of the copper complexed oxazoline or lactone oxazoline dispersant 
to provide the optimum performance in terms of both oxidation inhibition 
and inhibition of varnish deposits forming on engine parts. 
The mono-oxazoline, bix-oxazoline and lactone oxazoline dispersants that 
may be complexed with certain copper compounds in accordance with the 
present invention are described hereinbelow and are the same materials 
referred to in the patents listed above. 
Mono- and bis-oxazoline dispersants are prepared by reaction of a C.sub.4 
-C.sub.8 amino alcohol of the formula NH.sub.2 --C(X).sub.2 --CH.sub.2 OH 
wherein X is alkyl or hydroxyalkyl, at least one X being the hydroxyalkyl 
of the formula --(CH.sub.2).sub.m OH, m being 1 to 3, with an oil-soluble 
hydrocarbon substituted C.sub.4 -C.sub.10 dicarboxylic acid material 
(acid, anhydride, or ester), the hydrocarbon substituent having an 
average, based upon the Mn, of at least about 50 carbon atoms and 
preferably being a polymeric alkenyl group derived from a C.sub.2 -C.sub.5 
monoolefin, e.g., ethylene, propylene, butylene, isobutylene, and pentene 
with polyisobutenyl being preferred herein. Examples of suitable 
amino-alkanols are 2-amino-2-methyl-1,3 propanediol, tris-(hydroxymethyl) 
aminomethane, a preferred amino-alcohol, also referred to as THAM, 
2-amino-2-ethyl,1-3 propanediol and similar disubstituted amino alcohols 
capable of forming oxazoline ring in reaction with the oil-soluble 
hydrocarbon substituted dicarboxylic acid material. 
The mono-oxazoline is formed by reaction of equivalent proportions of 
amino-alkanol and dicarboxylic acid material. The bis-oxazoline is formed 
by reaction of 2 moles of aminoalkanol per mole of dicarboxylic acid 
material at about 140.degree.-240.degree. C. for about 0.5 to 24 hours 
with or without an inert diluent. 
Preferred dicarboxylic acid materials are polymers of C.sub.3 -C.sub.4 
olefins, such as polyisobutenyl succinic anhydrides wherein the 
polyolefinic or polyisobutenyl group has an Mn of 900 to 5,600 and 
especially polyisobutenyl of Mn=900-2,000. 
Other suitable but less preferred dicarboxylic acid materials are those 
derived from C.sub.4 -C.sub.10 dicarboxylic acid materials such as, 
fumaric acid, itaconic acid, chloromaleic acid, dimethyl fumarate and the 
like. 
An oxazoline product is considered represented by the following structure 
showing a bis oxazoline: 
##STR1## 
wherein R is hydrocarbyl group, such as a polyisobutenyl group, and X 
would be, for example, a --CH.sub.2 OH if THAM were the aminoalkanol used. 
Lactone oxazoline co-dispersants useful in the present invention are 
described in the U.S. Pat. No. 4,062,786 issued Dec. 13, 1977 to Brois et 
al. and are the reaction products of hydrocarbyl substituted lactone 
carboxylic acids which the above described 
2,2-disubstituted-2-amino-1-alkanols. 
The preferred lactone oxazoline co-dispersant is the reaction product of 
polyisobutenyl lactone carboxylic acid with tris-(hydroxymethyl) 
amino-methane at a temperature of from about 100.degree.-240.degree. C., 
preferably 150.degree.-180.degree. C., until two moles of H.sub.2 O per 
mole of reactant is removed from the reaction. 
Generally, the lactone oxazoline co-dispersant is formed by lactonization, 
an intramolecular cyclization, in the presence of an acid catalyst, such 
as a mineral acid, a Lewis acid, or an alkanesulfonic acid, of a 
hydrocarbyl substituted dicarboxylic acid material (acid, anhydride, or 
ester), such as an alkenyl succinic acid analog obtained via the Ene 
reaction of an olefin with an alpha-beta unsaturated C.sub.4 -C.sub.10 
dicarboxylic acid, anhydride or ester such as fumaric acid, itaconic acid, 
maleic acid, maleic anhydride, dimethyl fumarate, and the like. The olefin 
source for the hydrocarbyl substituted comprises the same materials 
described hereinabove for the mono- and bis-oxazoline co-dispersants used 
in the present invention, i.e., C.sub.2 -C.sub.5 monoolefin polymers, 
especially polyisobutenyl polymers. 
The lactone oxazoline co-dispersant is formed by heating together the 
hydrocarbon substituted lactone dicarboxylic acid material noted above 
with the 2,2-disubstituted-2-amino-1-alkanol, preferably THAM, in at least 
equivalent amounts. 
An example of a lactone oxazoline co-dispersant produced thereby is 
considered to have the following structure where the dicarboxylic acid 
material is a lactonized polyisobutenyl succinic anhydride and THAM is the 
aminoalkanol used, R represents the polyisobutenyl moiety: 
##STR2## 
The foregoing mono-oxazolines, bis-oxazolines or lactone oxazolines are 
reacted with a complex-forming copper compound. Copper carboxylates of 
C.sub.1 -C.sub.5 carboxylic acids, copper oxides, and thiocyanates of 
copper have been found especially useful in preparing the compositions of 
this invention. 
The copper complexes of the present invention are formed by reacting the 
copper salts with the oxazoline or lactone oxazoline dispersant utilizing 
a molar ratio of about 1 mole of oxazoline or lactone oxazoline per mole 
of copper at elevated temperatures of about 50.degree. C.-200.degree. C. 
for about 2 to 10 hours in an inert hydrocarbon solvent such as mineral 
oil of lubricating viscosity, kerosene, neutral mineral oils, xylene, 
halogenated hydrocarbons, such as carbon tetrachloride and 
dichlorobenzene. Mineral oil is preferred as a reaction solvent to 
facilitate the use of the products as lubricating oil and additives. 
It is believed that the final product is a coordination complex wherein the 
nitrogen contained in the oxazoline moiety is the ligand which complexes 
with copper. 
Lubricating oil compositions of this invention will typically contain a 
number of conventional additives in amounts as required to provide their 
normal attendant functions and these include the metal detergent 
additives, viscosity index improvers, other anti-oxidant products, 
anti-wear additives and the like. 
The metal detergent additives suitable in the oil formulations of the 
present invention are known in the art and include one or more members 
selected from the group consisting of overbased oil-soluble calcium, 
magnesium and barium phenates, sulfurized phenates, and sulfonates 
especially the sulfonates of C.sub.16 -C.sub.50 alkyl substituted benzene 
or toluene sulfonic acids which have a total base number of about 80 to 
300. These overbased materials may be used as the sole metal detergent 
additive or in combination with the same additives in the neutral form but 
the overall metal detergent additive combination should have a basicity as 
represented by the foregoing total base number. Preferably they are 
present in amounts of from about 3 to 6 wt% with a mixture of overbased 
magnesium sulfurized phenate and neutral calcium sulfurized phenate, 
obtained from C.sub.9 or C.sub.12 alkyl phenols being especially useful. 
The anti-wear additives useful are the oil-soluble zinc 
dihydrocarbyldithiophosphates having a total of at least 5 carbon atoms, 
the alkyl group being preferably C.sub.5 -C.sub.8, typically used in 
amounts of about 1-6% by weight. 
Suitable conventional viscosity index improvers, or viscosity modifiers, 
are the olefin polymers such as polybutene, ethylene-propylene copolymers, 
hydrogenated polymers and copolymers and terpolymers of styrene with 
isoprene and/or butadiene, polymers of alkyl acrylates or alkyl 
methacrylates, copolymers of alkyl methacrylates with N-vinyl pyrollidone 
or dimethylaminoalkyl methacrylates, post-grafted polymers of 
ethylene-propylene with an active monomer such as maleic anhydride which 
may be further reacted with alcohol or an alkylene polyamine, 
styrene-maleic anhydride polymers post-reacted with alcohols and amines 
and the like. These are used as required to provide the viscosity range 
desired in the finished oil, in accordance with known formulating 
techniques. 
Examples of suitable oxidation inhibitors are hindered phenols, such as 
2,6-di-t-butyl-para-cresol, amines, sulfurized phenols and alkyl 
phenothiazones; usually a lubricating oil will contain about 0.01 to 3 
weight percent of oxidation inhibitor depending on its effectiveness. 
Rust inhibitors are employed in very small proportions such as about 0.1 to 
1 weight percent with suitable rust inhibitors being exemplified by 
C.sub.9 -C.sub.30 aliphatic succinic acids or anhydrides such as dodecenyl 
succinic anhydride. 
Antifoam agents are typically the polysiloxane silicone polymers present in 
amounts of about 0.01 to 1 weight percent. 
While a wide variety of lubricating oil base stocks may be used in 
preparing the composition of this invention, most typically mineral oils 
having a viscosity of about 2-40 centistokes (ASTM-D-445) at 99.degree. C. 
are employed.

The invention is further illustrated by the following examples which are 
not to be considered as limitative of its scope. 
EXAMPLE I--VIB RESULTS 
A lactone oxazoline and a bis-oxazoline dispersant were prepared and 
complexed with either copper thiocyanate or copper acetate by reacting the 
mixture at about 55.degree. C. for 2 hours in mineral oil. The products 
were evaluated in the Varnish Inhibition Test and compared with the same 
oxazoline and lactone oxazoline dispersants prior to their complexing with 
copper. 
The lactone oxazoline dispersant was prepared by first lactonizing a 
polyisobutenyl succinic anhydride of molecular weight of 1300 and a 
Saponification No. of 49 with H.sub.2 SO.sub.4 for three hours and 
thereafter reacting with an equimolar quantity of THAM at 180.degree. C. 
for about four hours; the procedure being fully disclosed in U.S. Pat. No. 
4,062,786. 
The bis-oxazoline was prepared from a polyisobutenyl succinic anhydride of 
molecular weight 1300 and saponification No. 103 by heating about 1 mole 
of the polyisobutenyl succinic anhydride with about two moles of THAM as a 
40% aqueous solution and 3.4 grams of zinc acetate over a period of two 
hours to form the bis-oxazoline dispersant. The results are tabulated 
below followed by a description of the Varnish Inhibition test. 
TABLE I 
______________________________________ 
VIB TEST RESULTS 
Dispersant % N % Cu VIB Rating 
______________________________________ 
(A) Lactone 0.52 None 7 
(B) CuSCN Complex of (A) 
0.52 2.27 5 
(C) Bis-oxazoline 0.88 None 61/2 
(D) Cu SCN Complex of (C) 
0.88 1.55 4 
(E) Cu SCN Complex of (C) 
0.88 1.64 41/2 
(F) Cu Acetate Complex of (C) 
0.88 1.20 5 
______________________________________ 
In the VIB Test, a test sample consisting of ten grams of lubricating oil 
containing the additive being evaluated is used. The test oil is a 
commercial lubricating oil obtained from a taxi after two thousand miles 
of driving with said lubricating oil. Each sample is heat soaked overnight 
at about 140.degree. C. and thereafter centrifuged to remove the sludge. 
The supernatant fluid of each sample is subjected to heat cycling from 
about 150.degree. C. to room temperature over a period of 3.5 hours at a 
frequency of about two cycles pr minute. During the heating phase, a gas 
containing a mixture of 0.7 volume percent SO.sub.2, 1.4 volume percent 
NO, and the balance air, was bubbled through the test samples, and during 
the cooling phase, water vapor was bubbled through the test samples. At 
the end of the test period, which testing cycle can be repeated as 
necessary to determine the inhibiting effect of any additive, the wall 
surfaces of the test flasks in which the samples were contained are 
visually evaluated as to the extent of varnish inhibition. The amount of 
varnish imposed on the walls is rated at values of from one to seven with 
the higher number being the greater amount of varnish. It has been found 
that this test correlates with the varnish results obtained as a 
consequence of carrying out engine tests. 
EXAMPLE II--OXIDATION RESULTS 
The anti-oxidant benefits of the dispersants of this invention were 
evaluated in the LMOT (Laboratory Multiple Oxidation Test) in which 50 ml 
of test fluid with 2.0 g of iron filings and 0.5 g of a 1% solution of 
copper naphthenate is heated to 150.degree. C. and 25 ml air per minutes 
is passed through the sample. Daily samples are taken and the number of 
days for visible sludge to appear on blotter paper is recorded. For 
mineral oils containing 2% of dispersant (A) of Example I, the LMOT value 
was less than 2 days but the same oil having 2% of dispersant (B) showed 
an improvement to 4 days. In base oils containing 0.3 wt% of a 
conventional P.sub.2 S.sub.5 -pinene antioxidant, dispersant (A) at 2% 
gave a value of 7 days but a sample of the same oil with dispersant (B) at 
2% showed an improvement to 9 days.