Oil additive having reduced lacquer forming tendencies

An oil additive, particularly useful for railroad engines having reduced lacquer forming tendencies characterized by a novel alkaline earth phenate in which the normal tendency to form lacquers is reduced by the substitution of electron-donating groups; such as sulfur or tertiary amines for the secondary amine in the structural formula.

FIELD OF THE INVENTION 
This invention relates to novel alkaline earth metal phenates that are oil 
soluble and employed in a lubricant to give improved oxidation resistance, 
detergency, antiwear characteristics and basicity. The improved phenates 
of this invention have reduced tendency to form lacquer and varnish 
deposits in the engine in which lubricants containing these additives are 
employed. 
DESCRIPTION OF THE PRIOR ART 
The prior art is replete with a wide variety of approaches to improve the 
oxidation and corrosion resistance, detergency, dispersancy, lubricity, 
basicity and other properties of engine oils and other lubricants. One 
type of additive which has been widely used to improve these properties 
for diesel engine oils, especially for railroad diesel engine oils, are 
the alkaline earth metal phenates. 
There are three general types of alkaline earth phenates which are known in 
the prior art and used commercially in railroad and other diesel engine 
oils. They are differentiated by the bridging atoms between the aromatic 
nuclei of the phenols. 
The first type is the sulfur-bridged phenates. They have one or more sulfur 
atoms between the aromatic nuclei and are prepared by treating 
alkylphenols with suitable sulfur compound, followed by treating with 
alkaline earth metal hydroxide. Examples of prior art patents using this 
approach include the follows: 
U.S. Pat. Nos. 2,398,253, 2,406,041, 2,425,824, 2,449,026, 2,785,131, 
3,320,163, 3,336,224, 3,367,867, Re. 29661. 
British Pat. Nos. 1,094,609, 1,121,437, 1,164,417, 1,153,269. 
The second type is the so-called carbon-bridged, or methylene-bridged, 
phenates. They have a CH.sub.2 group between the aromatic nuclei and are 
prepared by treating alkylphenols with formaldehyde and alkaline earth 
metal hydroxide. Examples of prior art patents include: 
U.S. Pat. Nos. 2,361,804, 2,375,222, 2,410,652, 2,453,850, 2,632,696, 
2,736,701, 2,760,852, 2,833,719, 2,862,883, 2,913,412, 3,014,868. 
The third type is the so-called nitrogen-bridged, or Mannich base type, 
phenates. They have CH.sub.2 NHCH.sub.2 CH.sub.2 or other alkylene amine 
groups between the aromatic nuclei and are prepared by treating 
alkylphenols with formaldehyde and an alkylene polyamine, followd by 
treating with an alkaline earth metal hydroxide. Examples of prior art 
patents employing this approach include the follows: 
U.S. Pat. Nos. 3,036,003, 3,057,800, 3,340,190, 3,368,972, 3,429,812. 
Of the three types of alkaline earth phenates listed hereinbefore, the 
Mannich base type phenates are the most effective in providing oxidation 
and corrosion resistance to the engine oil. For this reason, the following 
abstracts are given of the patents cited in that section: 
U.S. Pat. No. 3,036,003 describes a lubricating oil composition containing 
the reaction product of alkylphenol, formaldehyde and an alkylene 
polyamine such as diethylenetriamine, and lime. It showed the superior 
oxidation resistance over a sulfur-bridged phenate. U.S. Pat. No. 
3,057,800 used monoethanolamine in place of diethylenetriamine. 
U.S. Pat. No. 3,340,190 describes a lubricant composition containing a 
succinimide type dispersant and a calcium phenate prepared from 
nonylphenol, formaldehyde and ethylendiamine. 
U.S. Pat. No. 3,368,972 describes a lubricating oil containing the calcium 
phenate from high molecular weight alkylphenol (molecular weight 
600-3000), formaldehyde and polyalkyl polyamines. Instead of mono-phenols, 
sulfur-bridged phenols are also used. 
U.S. Pat. No. 3,429,812 describes the overbasing of the third type of 
phenates. 
From the foregoing, it can be seen that the prior art does not provide or 
make obvious an oil additive that will have the advantages of this 
invention including the reduced tendency to form lacquer and varnish 
deposits in the engine in which the lubricants containing the additives 
are employed and that has the superior antioxidant use of this invention. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide an oil additive 
that has the hereinbefore delineated advantages, including superior 
oxidation resistance and which is not obvious in view of the prior art. 
Specifically, it is an object of this invention to provide an oil additive 
having reduced lacquer forming tendency, providing superior oxidation 
resistance to the oil as well as providing detergency and antiwear 
characteristics and basicity recognized as important in lubricants. 
These and other objects will become apparent from the descriptive matter 
hereinafter. 
In accordance with this invention, there is provided an additive for 
lubricating oils having a superior antioxidant performance with reduced 
tendency to form varnish and lacquer characterized by the alkaline earth 
metal salts of the reaction products formed by treating an alkylphenol and 
formaldehyde with a sulfur-containing polyalkylene amine, the products of 
which contain primarily a compound having the following generic formula: 
##STR1## 
where: X is selected from the group consisting of sulfur moiety and 
tertiary amine moiety; 
G is an alkylene group containing 1 to 8 carbon atoms; and 
R is an alkyl group containing 7 to 24 carbon atoms, and 
M is an alkaline earth metal. 
It is theorized that the compound represented by structural formula (I) is 
the compound responsible for the improved performance. There is improved 
performance by these reaction products formed by treating an alkylphenol 
and formaldehyde with a sulfur containing polyalkylene amine regardless of 
whether other by products are necessary for this or not and this invention 
is not to be limited to the consequences of any theory that the above 
compound represents. The reason for the improved performance of the 
lubricating oil having the additive in it is not totally clear but is 
believed to be due to the improved compound represented by structural 
formula (I).

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS 
As indicated hereinbefore, the Mannich base type alkaline earth phenates 
are most effective in providing the improved oxidation and corrosion 
resistance demonstrated by the railroad diesel engine oils having the oil 
additive in it. This has been supported by many bench oxidation tests such 
as the Oxygen Absorption Test, the Sinclair Railroad Oxidation Test, the 
ARCO Railroad Oxidation Test and engine tests such as EMD 2-567 Engine 
Test. Oils containing this type of phenates invariably show lower uptake 
of oxygen, lower increases of acid number, viscosity and insolubles, lower 
loss of metals by corrosion, slower consumption of reserve basicity than 
oils containing other types of phenates. This superior oxidation 
resistance has been substantiated by actual performance in railroad diesel 
engines in prolonging drain periods, in saving the costs of oil and 
maintenance, and in prolonging the life of engines. 
The superior performance is believed to have resulted at least in part, 
from the antioxidant and metal-deactivating capability of this type of 
phenates. They contain, in their molecules a number of atoms which can 
donate pairs of electrons to metals such as iron, copper and lead and form 
a chelate compound or complex; and, in so doing, they effectively 
eliminate or reduce the catalytic effects of these metals on oil 
oxidation. 
One drawback of this type of additive is the stronger lacquer forming 
tendency of compounds containing the amine groups. Upon oxidation, nitro- 
and nitroso-compounds and sometimes nitrates are formed. These compounds 
can be converted to lacquer or varnish under severe engine conditions. The 
lacquer and varnishes can also serve as binders for carbonaceous deposits. 
The result is increases in both lacquer and carbon deposits on engine 
parts. For diesel engines these compounds can increase piston ring groove 
and land deposits and then cause ring sticking and engine failure. The 
problem becomes increasingly more severe as new engine designs raise 
temperatures and pressures of the piston ring belt area and reduce oil 
flow thereto. 
The invention described hereinbefore is accomplished by replacing the 
polyalkylene polyamines used in preparing the normal Mannich-base type 
phenates with sulfur-containing polyalkylene amines. One example of these 
compounds is di(2-mercaptoethyl) amine, (HSCH.sub.2 CH.sub.2).sub.2 NH. 
When three moles of tertiary octylphenol, three moles of formaldehyde, and 
one mole of di(2-mercaptoethyl) amine are reacted in a solvent or carrier 
oil and then treated with lime, or calcium hydroxide, the following 
compound (II) is formed among the reaction products and is believed to 
contribute significantly to the efficacy of this oil additive. 
##STR2## 
This compound contains only one-third of the nitrogen content of a similar 
compound prepared from the same reactants except that diethylene triamine 
is used instead of di(2-mercaptoethyl) amine. This can be seen clearly 
from the following equation resulting in compound (III). 
##STR3## 
As can be seen there are three amine groups in (III) and only one tertiary 
amine group in (II). By eliminating two out of three amine groups, which 
can be oxidized to nitro-, nitroso-, and nitrate compounds, the 
lacquer-forming tendency and amount of lacquer and carbon deposits on 
engine parts can be substantially reduced. On the other hand, since the 
sulfur atoms in (II) can donate pairs of electrons to catalytic metals and 
form chelates, their effectiveness as metal deactivators is retained. 
Their effectiveness as anti-oxidants should be improved, since the phenate 
groups remain the same and the two --S-- groups should provide additional 
anti-oxidant capability. 
Compounds suitable for the replacement of diethylenetriamine and other 
polyalkylene polyamines include secondary amines of the following formula: 
(HSG).sub.2 NH 
wherein: 
G equals --CH.sub.2 CH.sub.2 --, --CH.sub.2 --CH--CH.sub.3, --CH.sub.2 
CH.sub.2 CH.sub.2 -- or a C.sub.4 -C.sub.8 alkylene group and 2 G's can be 
the same or different. 
Also in another embodiment of this invention, the two primary amine groups 
in diethylene triamine are replaced with secondary amine groups, 
(YNHCH.sub.2 CH.sub.2).sub.2 NH, 
where: 
Y is methyl, ethyl, isopropyl, n-propyl or a C.sub.4 to C.sub.8 alkyl 
group. 
by this approach, the secondary amine groups which are believed to be more 
susceptible to lacquer and varnish formation are replaced with tertiary 
amine groups to yield phenates represented by formula (IV): 
##STR4## 
The following examples illustrate how the improved lubricating oil 
additives can be prepared and used to provide lubricating oils having 
superior oxidation and corrosion resistance, as well as good anti-wear 
characteristics and engine cleanliness and durability. 
EXAMPLE 1 
A 5-liter, 3-necked flask is equipped with a heating mantle, a mechanical 
stirrer, a dropping funnel and a water separating trap. 1236 grams (6 
moles) of p-tert-octylphenol is placed in the flask and heated to 
85.degree. C. In the dropping funnel is placed 274 grams (2 moles) of 
di(2-mercaptoethyl) amine. With mechanical stirring the amine is added 
dropwise over a period of thirty minutes. In the dropping funnel is then 
placed 487 grams (6 moles, 37%) of formalin, which is added slowly into 
the flask over a period of two hours in which the temperature of the 
reaction mixture is raised to 160.degree. C. Water is removed periodically 
from the trap. The mixture is heated at 160.degree. C. until no more water 
distils into the trap. Upon cooling to about 100.degree. C., 2,000 grams 
of a paraffinic base oil having a viscosity of about 150 SUS at 
100.degree. F. and a viscosity index of 95 is added. This is followed with 
4 moles of hydrated lime and 200 ml of water. The mixture is then heated 
at 150.degree. C. with stirring for a period of three hours or until the 
water removal is completed. To the reaction mixture is added 1% of Hyflo 
Super-Cel and the mixture is filtered through a Buchrer funnel using a 
vacuum. The product is a mineral oil solution of a mixture containing the 
calcium phenate having the structural formula (II), believed to be the 
effective ingredient in the superior performance of this engine oil 
additive in accordance with this invention. 
EXAMPLE II 
The same preparation as in Example I is carried out except that the 
di(2-mercaptoethyl) amine is replaced by N,N'-dimethyl diethylene-triamine 
and the amount of each reactant is reduced by half. The reaction can be 
completed in a shorter period of time. The product is a mineral oil 
solution of a reaction product that includes the calcium phenate having 
structural formula (IV), believed to be responsible for superior 
performance of one embodiment of this invention. 
The calcium phenates as illustrated in the above examples contain mineral 
oils and can be used directly in engine oil formulations. The 
concentrations to be used is dependent upon severity requirements of the 
engine oil and can vary from about 1% by weight to as much as 5% by weight 
on an active ingredients basis. The base oil to be used includes both 
paraffinic and napthenic oils and is dependent upon the service required. 
For railroad diesel engine oils a mixture of paraffinic and napthenic oils 
is often required and a range of viscosity is specified by the engine 
builder. The phenates of this invention can also be advantageously used in 
synthetic and highly hydrogenated base oils. In diesel engine and other 
severe services, it is also advantageous to have the presence of other 
additives, including other calcium phenates (sulfur-or CH.sub.2 -bridged), 
calcium phenates which have been overbased by passing carbon dioxide in 
the presence of lime and promoter, other alkaline earth metals (magnesium, 
barium and the like) phenates, neutral and overbased alkaline earth metal 
sulfonates, ashless dispersants (succinimide or Mannich base type), or 
other anti-wear additives and friction modifiers. 
Having thus described the invention, it will be understood that such 
description has been given by way of illustration example and not by way 
of limitation, reference to the latter purpose being had to the appended 
claims.