Oxidation inhibitor and compositions containing the same

A method for stabilizing organic materials against autoxidation, a composition useful therefor and organic compositions containing the autoxidation stabilizers. The method comprises the steps of adding a compound capable of reducing the peroxide content and a transition metal containing compound to an organic material and thereafter recovering a stabilized composition. The components of the inhibitor may be added separately or simultaneously and the same may be added directly to the organic material or first combined in a concentrated solution and then added to the organic material. The basic and neutral primary, secondary and tertiary amines have been found particularly effective in reducing the peroxide content. Also, the transition metal salts containing cations which easily change valence by a single electron are the most effective transition metal salts. The inhibitor combination is effective in both liquid and solid compositions. The inhibitor combination is particularly effective in both natural and synthetic lubricating oil compositions, grease compositions, polymers and the like. When used at the most effective relative and actual concentrations, the inhibitor combination will yield stability comparable to that exhibited by conventional oxidation inhibitors even though one component is a known oxidation catalyst.

BACKGROUND OF THE INVENTION 
This invention relates to an additive combination and to various 
compositions comprising the same. More particularly, this invention 
relates to a combination oxidation inhibitor and to various organic 
compositions comprising the same. 
As is well known, most organic compounds, especially those comprising 
relatively long hydrocarbon segments, are subject to autoxidation when the 
same are contacted with oxygen. This oxidation, in turn, results in a 
deterioration of the base material leading, generally, to increases in 
acid number and in sludge formation. In this regard, it is generally 
believed that the autoxidation first results in the formation of 
hydroperoxides which, in turn, decay, decompose or dissociate to yield 
corresponding acid, aldehydes, water and other undesirable 
oxygen-containing products and free radicals, which, in turn, may react to 
yield more hydroperoxides or higher molecular weight materials, which may 
or may not contain oxygen in some form. It will, of course, be appreciated 
that the acids thus formed will increase the total acid number while the 
higher molecular weight products will lead to increased viscosities and, 
indeed, if the same are insoluble in the initial media could result in 
sludge formation. 
Heretofore, several materials have been proposed for use designed to 
prevent autoxidation. Generally, these materials will fall into one of 
three categories; viz., selective reducing agents, peroxide removers or 
decomposers and free radical scavengers. The first of these will, of 
course, be selectively oxidized, when oxygen is present, thereby 
preventing the formation of the undesirable hydroperoxide in the first 
place. The second of these, on the other hand, will complex with or 
decompose the peroxide immediately upon formation, generally, to a product 
which will not produce additional free radicals. Finally, the latter group 
simply converts the free radicals to an inert product. Of these, the 
materials generally classified as peroxide removers or decomposers and 
those classified as scavengers are most commonly used. 
As is also well known, several materials qualify as peroxide removers or 
decomposers and these materials may be acidic, basic or neutral. Moreover, 
peroxide removers or decomposers from each of these classes have been used 
as oxidation inhibitors in various organic compositions such as 
lubricants, fuels and the like. The basic and neutral materials are, 
however, most generally used, especially in lubricant type compositions, 
since increased acid content is generally undesirable. Of the basic and 
neutral materials, the amines and particularly the naphthenic and 
aliphatic amines, are commonly used and such use is well known in the 
prior art. Moreover, amines as well as other possible peroxide complexing 
agents or decomposers are used for other purposes in organic compositions 
such as lubricating and specialty oils and fuels. 
Similarly, several materials are well-known free radical scavengers and the 
use of a large number of such scavengers in organic compositions has, 
heretofore, been proposed. These materials function by interrupting the 
chain reaction by which oxidation takes place. This chain reaction 
proceeds by a two-step process. In the first reaction, a peroxy radical or 
an alkyoxy radical formed from peroxide decomposition attacks the material 
being oxidized to abstract a hydrogen atom by breaking a carbon hydrogen 
bond. This results in the formation of a peroxide or an alcohol and an 
alkyl type radical from the substrate. In the second reaction the alkyl 
type radical combines with oxygen to form a peroxy radical which can react 
to start off the chain again. The second reaction is extremely rapid 
compared to the first. As a result, the concentration of peroxy radicals 
in normally several magnitudes greater than that of the hydrocarbon 
radicals. The free radical scavengers normally employed for inhibition are 
compounds which can react very rapidly with the peroxy radicals to destroy 
the chain. 
Transition metals are well known catalysts for autoxidation. It is well 
established in the prior art that when organic materials such as 
lubricating oils, polymers or -plastics must be used in contact with iron, 
copper or other transition metals it is much more difficult to stabilize 
them against oxidative degradation. Many laboratory tests for oxidation 
stability incorporate transition metals, either in their metallic form or 
as low concentrations of soluble compounds, to accelerate the test and to 
provide results which are more representative of degradation under 
conditions of expected use. As the concentration of a transition metal 
increases, the catalytic activity increases until, at a concentration 
often referred to as the critical concentration, the catalytic activity 
drops sharply to zero and at concentrations above this level the 
transition metal salts function as inhibitors. This phenomenon too is 
known in the prior art and has been discussed extensively, either directly 
or indirectly, in a large number of papers published throughout the world 
but the reasons for this abrupt change have never been completely 
explained. 
Notwithstanding the general knowledge with respect to the ability of the 
transition metal salts to function as inhibitors, the use of such 
materials as inhibitors in organic compositions subject to autoxidation 
has been limited. Reasons for this are that the transition from catalysts 
to inhibitor has usually been observed to occur at relatively high 
concentrations; second, that the reasons why an abrupt change from 
catalyst to inhibitor takes place has not been understood and third, it 
has been impossible to predict the critical concentration level. Prior 
attempts to use transition metals as inhibitors have, therefore, produced 
inconsistent results. This limited use has continued notwithstanding that 
the cost of the transition metal salts is often less than the cost of the 
more conventional oxidation inhibitors and notwithstanding evidence that 
the same will often function as oxidation inhibitors yielding results 
superior to those often obtained with the more conventional inhibitors. 
SUMMARY OF THE INVENTION 
It has now surprisingly been discovered that various transition metal 
containing componds can be effectively used as oxidation inhibitors and 
that the same may be used with consistent results when used in accordance 
with the present invention. Accordingly, it is an object of one embodiment 
of this invention to provide a method whereby certain transition metal 
containing compounds can be used as oxidation inhibitors in organic 
compositions subject to autoxidation. It is another object of this 
embodiment of the invention to provide such a method whereby the 
transition metal containing compound can be used with good and consistent 
results. It is an object of another embodiment of this invention to 
provide an oxidation inhibitor composition which can be added to an 
organic composition subject to autoxidation in accordance with the method 
of the first embodiment. It is another object of this second embodiment of 
the present invention to provide such a composition which can be added to 
organic compositions subject to autoxidation in such a manner as to yield 
effective and consistent performance. It is an object of a third 
embodiment of this invention to provide various organic compositions 
comprising the inhibitor of the second embodiment and added thereto in 
accordance with the method of the first embodiment such that the same will 
exhibit improved oxidation stability. 
In accordance with the present invention, the foregoing and other objects 
and advantages are accomplished by adding one or more transition metal 
containing compounds in combination with one or more compounds capable of 
reducing the concentration of hydroperoxide to an organic composition 
otherwise subject to autoxidation. As indicated more fully hereinafter, it 
is essential that the concentration of the transition metal containing 
compound be maintained above a minimum, critical concentration and that 
the ratio of the transition metal containing compound to the compound 
capable of complexing with a hydroperoxide be carefully controlled. As 
also more fully pointed out hereinafter, it is possible through a proper 
selection of transition metal containing compound combinations to further 
improve the oxidation stability of the various organic compositions 
contemplated by the present invention. 
DETAILED DESCRIPTION OF THE INVENTION 
As previously indicated, the present invention relates to an oxidation 
inhibitor, a method of using the same and organic compositions comprising 
the oxidation inhibitor. As also previously indicated, the oxidation 
inhibitor comprises at least one transition metal containing compound, and 
a compound capable of reducing the concentration of hydroperoxide in the 
medium to which the same is ultimately added. 
In general, any compound, including the organic and inorganic salts of any 
transition metal can, under proper circumstances, be effectively used in 
the oxidation inhibitor of the present invention. As is well known, the 
transition metals include elements 21 through 29 (scandium through 
copper), 39 through 47 (yterium through silver), 57 through 79 (lanthanum 
through gold) and the metals from 89, i.e., the metals of actinide series. 
A characteristic of these metals is, of course, their ability to exhibit 
more than one oxidation state and this ability is essential to the 
performance of the salts used in the oxidation inhibitor of the present 
invention. In this regard, it should be noted that many of these metals 
are known to exhibit more than 2 oxidation states and these oxidation 
states may correspond to a change of from 1 to 5 electrons in the outer 
orbitals. For purposes of this invention, however, those metals in which 
the oxidation state differs by only one electron are most preferred, since 
the transition from one state to the other is most readily achieved. 
From the foregoing, it should be clear that salts of scandium, titanium, 
vanadium, chromium, manganese, iron, cobalt, nickel and copper could be 
operative in the oxidation inhibitor of the present invention. Similarly, 
salts of itrium, zirconium, niobium, molybdenum, tellurium, ruthenium, 
rhodium, palladium and silver could be effective. Also, salts of 
lanthanum, the rare earth metals, hafnium, tantalum, tungsten, rhenium, 
osmium, irridium, platinum, gold and the metals of the actenide series 
could be effectively used. Notwithstanding the general characteristics of 
these metals, however, some, such as scandium, yttrium, lanthanum and the 
like exhibit only one known valence state and others, such as nickel, 
silver, gold and the like do not change valence state easily and as a 
result, while these metals would, theoretically be useful, they are not, 
generally, effective in the oxidation inhibitor compositions of the 
present invention. Also, and as suggested previously, the more stable 
oxidation states of several of these metals will differ by an even number 
of electrons and salts of these metals are not, generally, as effective in 
the inhibitor compositions of the present invention as are the salts of 
those metals which exhibit stable valence states differing by a single 
electron. Metals having more stable valence states differing by two or 
more electrons include titanium, zirconium, vanadium and the like. 
With respect to the effectiveness of the various valence states, it should 
be noted that, while the inventor does not wish to be bound by any 
particular theory, it is believed that the several metal ions function as 
inhibitors when they are in a valence state which has an unshared electron 
in the outer orbital. The same metals, on the other hand, function as 
catalyst in all other valence states. It is, therefore, believed essential 
to the present invention that the metal or metals actually employed be 
capable of an oxidation reduction reaction involving an exchange of 
electrons which leaves one free electron in the outer shell in one valence 
state and either no electrons or an even number of electrons in the outer 
shell in the other state. 
Again, and while the inventor does not wish to be bound by any particular 
theory, it is believed that the following equations are pertinent when the 
inhibitor compositions of the present invention are used in organic 
compositions containing one or more materials subject to autoxidation: 
EQU M.sup.n+ + ROOH .fwdarw. (ROOHM).sup.n+ ( 1) 
EQU (ROOHM).sup.n+ .fwdarw. M.sup.n+ + ROOH (2) 
EQU (roohm).sup.n+ .fwdarw. RO. + M.sup.(n+1)+ + OH.sup.- ( 3) 
EQU m.sup.(n+1)+ + ROOH .fwdarw. (ROOHM).sup.(n+1)+ ( 4) 
EQU (ROOHM).sup.(n+1)+ .fwdarw. M.sup.(n+1)+ + ROOH (5) 
EQU (roohm).sup.(n+1)+ .fwdarw. RO.sub.2 + M.sup.n+ + H.sup.+ ( 6) 
EQU ro + rh .fwdarw. roh + r tm (7) 
EQU r + o.sub.2 .fwdarw. ro.sub.2 ( 8) 
EQU ro.sub.2 + rh .fwdarw. rooh + r (9) 
EQU ro.sub.2 + ro.sub.2 .fwdarw. products (10) 
EQU RO.sub.2 + M.sup.n+ .fwdarw. M.sup.(n+1)+ + Products (11) 
EQU R + M.sup.(n+1)+ .fwdarw. M.sup.n+ + Products (12) 
In these equations, M is the transition metal or metals actually used in 
the oxidation inhibitor and n is a whole number generally from 1 to 8 
reflecting the valence in one of the two oxidation states involved and 
n+1, reflecting another oxidation state (generally, however, the other 
oxidation state could be represented by n.+-.1, 2, 3, 4, 5, 6 or 7). For 
purposes of the present illustration, R may be any organic radical either 
substituted or unsubstituted, saturated or unsaturated, straight or 
branched chain, cyclic or noncyclic, aromatic or naphthenic, etc., and 
represents that portion of the original organic material remaining after 
the peroxide has been formed as the result of autoxidation. R, RO and 
RO.sub.2 represent corresponding free radicals. The remaining symbols all 
have conventional meanings. 
As will be apparent from the equations as presented, if the metal ion has 
an unpaired electron in its lower valence state, it functions as a free 
radical scavenger in accordance with equation 11, while if the metal has 
an unpaired electron in its higher state (n+1 as illustrated) it will 
function as a free radical scavenger in accordance with equation 12. 
Depending, then, as to which of the valence states corresponds to the 
oxidation state with an unshared electron in the outer shell, termination 
of the autoxidation reaction will occur in accordance with one of these 
two equations. 
Although the individual equations (1) through (12) have been postulated to 
be involved in metal catalyzed autoxidation, it has not been recognized 
that, combined in this manner, they furnish the first satisfactory 
explanation of why transition metals suddenly change from catalysts to 
inhibitors as their concentration is increased and what determines the 
concentration at which this change takes place. This new understanding 
arises from the recognition that before a transition metal can become a 
strong inhibitor by terminating autoxidation through either reaction (11) 
or (12), it is essential that the metal be present in the system at a 
concentration in excess of the concentration of peroxide present in the 
system. This requirement arises from the fact that the metal in either the 
higher or the lower valence state forms a strong complex with peroxide 
according to equations 1 and 4. Therefore, if the metal is present at a 
concentration lower than that of the peroxide, almost all of the metal 
will be converted to the metal peroxide complex which functions as a 
powerful catalysts for autoxidation through reactions 3 or 6. Inhibition 
by the free, uncomplexed transition metal ions is unimportant because 
under existing equilibrium conditions their concentration is restricted to 
a very low level. As the total concentration of the metal increases, 
however, to the point at which the total metal concentration exceeds that 
of the hydroperoxide in the system, the situation suddenly reverses. The 
transition metal is bound tightly into a complex with the peroxide as 
before, but there is no longer enough peroxide to sequester all of the 
transition metal. Therefore, as the total metal concentration approaches 
and exceeds that of the peroxide in the system, the concentration of free 
metal ion suddenly changes from a greatly repressed value to a magnitude 
similar to that of the total metal so that the effect of the transition 
metal as a powerful inhibitor can suddenly become dominant. This explains 
why the transition from catalysis to inhibition with transition metals is 
so sudden and predicts the concentration at which this transition should 
take place. 
In general, the anion portion of the transition metal containing compound 
may be in essentially any form including both organic and inorganic. It 
is, however, essential to the present invention that the anion portion be 
compatible with the remaining portion of the system and particularly the 
organic composition in which the same will be used. In this regard, it 
should be noted that the transition metal salts otherwise useful in the 
present invention would not be useful if either the anion or the cation of 
the salt reacted with a constituent of the composition in which the same 
is used so as to prevent the redox reaction leading to the presence of the 
cation in at least two oxidation states. Moreover, when the inhibitor 
composition of this invention is used in a liquid composition, it is most 
desirable that the same be soluble therein and when used in a solid or 
semi-solid composition that the same be in a form which may be uniformly 
distributed therethrough. 
With the foregoing in mind, then, it should be clear that, depending upon 
the particular composition in which the inhibitor will be used, the same 
might be derived from any one or a mixture of the organic and inorganic 
acids. In this regard, and when an organic acid is used the same may be 
aromatic, naphthenic, aliphatic, cyclic, branched or a combination of any 
one or all of these. Moreover, the same may comprise essentially any 
number of carboxylic acid groups, especially from about 1 to about 6, but 
acids having only one carboxylic acid group are most preferred. When an 
inorganic acid, on the other hand, is used, the same may be derived from 
either a weak or strong acid and, again, compatibility in the system in 
which the same will be used will be the principal controlling criteria. In 
this regard, however, it should be noted that the use of weak acids is, 
generally, preferred since salts derived from strong acids could lead to 
an increase in total acid number in the organic composition in which the 
same is used. Also, care should be used in selecting a particular anion 
moiety so as to ensure that materials which might emit pollutants to the 
atmosphere are not used. 
Notwithstanding that a broad range of anion sources could be used in the 
salt portion of the inhibitor composition of this invention, the same 
will, generally, be derived from a carboxylic acid comprising from about 1 
to about 50 and preferably from about 8 to about 18 carbon atoms. 
Moreover, the organic moiety would, generally, be aromatic, naphthenic, 
aliphatic, cycloaliphatic, or a combination of one or more of these. In a 
most preferred embodiment, the anion portion of the salt will be derived 
from a monocarboxylic fatty acid having from about 8 to about 18 carbon 
atoms. 
In general, any compound which will complex with the hydroperoxide more 
strongly than the cation of the transition metal containing compound could 
be used in combination with the transition metal containing compound used 
in the inhibitor composition of this invention. These include both the 
basic and neutral complexing agents, peroxide decomposers and the like as 
well as the acidic materials. The use of basic and/or neutral peroxide 
decomposers does, however, offer the advantage of not increasing the total 
acid number of the composition in which the same is used and therefore the 
use of these materials is particularly preferred. 
As in the case of the transition metal containing component, essentially 
any basic or neutral complexing agent, peroxide decomposer or the like 
could be used in the inhibitor composition of the present invention. It 
is, however, important that the complexing compound actually used be 
compatible with the system and that the same not react or in some other 
way be tied up with another material such that it would not function as a 
complexing agent, peroxide decomposer or the like, or such that the same 
would form a noxious material. Moreover, when the inhibitor composition is 
used in a liquid medium, it is most desirable that the same be soluble 
therein and when used in a solid or semi-solid material the same must be 
in a form which can be uniformly distributed throughout the organic 
composition in which it is used. Operable materials which will complex 
with the hydroperoxide more strongly than the transition metal ions 
include the primary, secondary and tertiary amines, the alkyl selenides, 
particularly the dialkylselenides and the alkyl phosphines and alkyl 
phosphites, particularly the trialkyl phosphines and trialkyl phosphites 
wherein the organic portion of the compound may be aliphatic, aromatic, 
naphthenic or essentially any other structure including mixtures of the 
type specified. Again, the organic portions may each contain from about 1 
to about 50 carbon atoms and preferably from about 8 to 18 carbon atoms. 
Generally, the length of the organic moiety will be determined on the 
basis of solubility and in a most preferred embodiment the complexing 
agent or peroxide decomposer will be a primary amine having from about 8 
to about 18 carbon atoms. 
Again, and while the inventor still does not wish to be bound by any 
particular theory, it is believed that the use of a compound which will 
complex more strongly with hydroperoxides than can the transition metal 
ion reduces the concentration of uncomplexed peroxide in the organic 
composition in which the same is used and thereby reduces the amount of 
transition metal ion in an inhibiting valence state which must be added to 
produce inhibition, rather than catalysis, of oxidation. Stated somewhat 
differently, then, it is believed that the presence of a peroxide 
complexing agent, a peroxide decomposer or the like, changes the critical 
concentration of the catalyst-inhibitor system, generally, reducing the 
same in an amount proportionate to the log of the concentration of the 
complexing agent, the peroxide decomposer or the like. It follows, then, 
that the use of such a compound will reduce the concentration at which the 
metal will effect inhibition rather than catalysis and as the amount of 
such compound is increased the amount of metal required is further 
decreased. This conclusion is, of course, consistent with experimental 
observations made in connection with the present invention. 
Consistent with these observations, it has been found that effective 
inhibition can be achieved with total transition metal concentrations as 
low as about 100 parts per million by weight when the concentration of 
complexing agent, peroxide decomposer or the like, is sufficient to 
maintain the peroxide concentration at a substantial minimum. Better, more 
consistent results are, however, obtained at transition metal 
concentrations of about 600parts per million and above and best results 
are, generally obtained when the transition metal concentration is above 
about 1000 parts per million. It will, of course, be appreciated that the 
amount of complexing agent peroxide decomposer or the like required 
becomes less as the concentration of metal is increased and that minimum 
concentrations of the complexing compound are required when the metal 
concentration is above about 1000 parts per million. From an operating 
standpoint, there does not appear to be an upper limit on the 
concentration of transition metal or metal ion, as the case may be, in 
solution or in the composition being inhibited. As a practical matter, 
however, there is little benefit associated with the use of higher 
concentrations once a level consistent with best or optimum performance 
has been achieved. On the other hand, peroxide decomposer, complexing 
agent or the like concentrations of about 100 parts per million, by 
weight, and above have been found essential to consistent and optimum 
results and concentrations of about 20,000 parts per million, by weight, 
result in maximum reduction in peroxide concentrations. Accordingly, metal 
or metal ion concentrations within the range from about 100 parts per 
million, by weight, to about 5000 parts per million, by weight, will be 
used in the oxidation inhibitor composition of the present invention in 
combination with peroxide decomposer concentrations within the range from 
about 20,000 parts per million, by weight, to about 100 parts per million, 
by weight. It will be understood, however, that peroxide decomposer or 
complex agent concentrations in the lower portion of this range and 
particularly within the range from about 1000 parts per million, by 
weight, to about 10,000 parts per million, by weight, will, generally, 
ensure maximum consistency at any metal concentration. 
At this point, it should be noted that the foregoing ranges of effective 
concentrations have been found to be applicable to the use of one or more 
transition metal containing compounds of the same transition metal as well 
as many combinations which function additively. In another embodiment of 
the present invention, however, it has been discovered that certain metal 
combinations function synergistically and when such combinations are used 
the total metal concentration required for effective as well as consistent 
oxidation inhibition is reduced as is the amount of peroxide decomposer, 
complexing agent or the like, required to insure optimum, consistent 
results. In this regard, it has been found that those metal combinations 
which will exhibit synergism can be predicted from a consideration of the 
electromotive force. Particularly, the electromotive force which is 
important to such prediction is, in effect, the voltage created when the 
transition metal goes from a catalytic to an inhibitor form. Such voltages 
can, of course, be either positive or negative. When a combination of 
metals is used, then, the same will exhibit synergism if the sum of these 
voltages favors the presence of the stronger inhibitor and/or the weaker 
catalyst and is, generally, positive. 
The electromotive force associated with the conversion of various preferred 
transition metal ions from a catalytic state to an inhibitor state and 
useful in the present invention are illustrated in the following table: 
______________________________________ 
Transition 
Metal Catalytic Form 
Inhibitor Form 
EMS, Volts 
______________________________________ 
Cr Cr.sup.++ Cr.sup.+++ 0.41 
M.sub.n M.sub.n.sup.+++ 
M.sub.n.sup.++ 
1.51 
Fe Fe.sup.++ Fe.sup.+++ -0.77 
Co Co.sup.+++ Co.sup.++ 1.84 
Cu Cu.sup.+ Cu.sup.++ -0.16 
______________________________________ 
From this, it can be predicted that combinations such as chromium and 
manganese, chromium and cobalt, manganese and iron, manganese and copper, 
iron and cobalt, and cobalt and copper would exhibit synergism when used 
in combination as the oxidation inhibitors of the present invention since 
the electromotive potential would favor reaction between the respective 
metals in their catalytic form to maintain both of them in the inhibiting 
form. For this type of synergistic interaction to occur, the transition 
from catalytic to inhibitor form must represent an oxidation for one metal 
versus a reduction for the other and the sum of the voltages for these two 
simultaneous reactions must be positive. Another type of synergistic 
interaction is possible when the valence change going from the catalytic 
to the inhibitor form is in the same direction for both metals providing 
the electromotive force values favor the metal which is the stronger 
inhibitor when in the inhibiting state. An example of this type of 
synergism is the mixture of copper, which is a very strong inhibitor as 
cupric ion, with iron which does not inhibit nearly as strongly. In such a 
mixture, any cuprous ion present can be oxidized to cupric ion, a strong 
inhibitor, with the simultaneous reduction of ferric ion which is a weak 
inhibitor. The copper will therefore be maintained entirely in the 
inhibiting valence state and will inhibit more effectively than if it were 
utilized alone. 
The electromotive potentials used in making these predictions are measured 
in aqueous solution and, therefore, must be used cautiously to predict 
effects in non-polar systems where different solvation characteristics can 
affect the outcome. However, these predictions have been useful as a guide 
to discovering synergistic interactions between some metal ions as 
reported in subsequent examples. 
When a synergistic combination of metals is used in the oxidation 
inhibitors of the present invention, the combinations will, generally, be 
effective at concentrations of about 100 ppm, by weight, or less, when the 
amount of peroxide decomposer complexing agents or the like approaches 
20,000 ppm, by weight. More consistent and effective results are, however, 
achieved when the total metal concentration in the composition being 
treated is at least about 500 ppm, by weight, and when the metal 
concentration is increased to this amount, the amount of peroxide 
decomposer, complexing agent or the like can be reduced. Generally, then, 
the amount of peroxide decomposer complexing agent or the like required at 
these higher metal concentrations is from about 1000 ppm, to about 10,000 
ppm, by weight. Finally, optimum results will, generally, be achieved when 
the total metal content from a synergistic combination is above about 1000 
ppm, by weight and, in this case, peroxide decomposer, complexing agent or 
the like, concentrations within the range from about 100 ppm, by weight, 
to about 1000 ppm, by weight, will be effective. Accordingly, when 
synergistic metal combinations are used the same will be effective at 
concentrations within the range from about 100 ppm, by weight, to about 
5000 ppm, by weight, and the same will be used as peroxide decomposer, 
complexing agent or the like concentrations within the range from about 
20,000 ppm, by weight, to about 100 ppm, by weight. Maximum consistency 
will, however, be achieved when the synergistic combination is used at a 
concentration within the range of from about 500 to about 1000 ppm, by 
weight with corresponding peroxide decomposer, complexing agent or the 
like concentrations within the range from about 10,000 to 1000 ppm, by 
weight. 
In general, and as suggested previously, the oxidation inhibitors of the 
present invention may be used to stabilize any organic composition which 
is subject to autoxidation in the presence of oxygen. In this regard, it 
should be noted that "compositions", as used herein in connection with an 
organic composition, is intended to encompass pure compounds as well as 
naturally occurring and synthetic mixtures. 
Broadly, then, the inhibitor compositions of the present invention will be 
effective as oxidation stabilizers in pure hydrocarbons such as the 
alkanes, alkenes, alkynes, cyclic hydrocarbons, aromatics, naphthenes and 
the like. The inhibitors of the present invention are also effective 
stabilizers for substituted derivatives of the various hydrocarbon 
compounds and for mixtures of such hydrocarbon compounds, mixtures of the 
substituted derivatives and mixtures of the hydrocarbon and substituted 
derivatives. The inhibitors of this invention are also effective in the 
various oxygen containing hydrocarbon derivatives such as the esters, 
ethers, alcohols and the like, nitrogen containing derivatives such as the 
amines, and various sulfur and phosphorous containing derivatives such as 
sulfides and phosphides. The inhibitors of this invention are also 
effective as stabilizers for polymers of the various hydrocarbons and 
substituted hydrocarbons, particularly polyethylene, polypropylene, 
polyvinylchloride, and the like. The inhibitors of this invention are 
particularly effective when used as stabilizers for various hydrocarbon 
distillate fractions such as the various naphthas, kerosene, lubricating 
and specialty oils, fuel oils, and the like. The inhibitors are also 
effective as stabilizers for the various synthetic oils such as those 
derived from polyolefins, esters and the like and the same are 
particularly effective in modified petroleum products such as greases, 
waxes and the like. 
In general, any suitable method could be used to add the inhibitor 
compositions of this invention to the organic material which is to be 
stabilized therewith. Such methods include separate and simultaneous 
addition of the additive components to the organic material and the 
components may be added directly or with a carrier material. After 
addition, it will, of course, be necessary to subject the blend to a 
mixing action so as to insure uniform distribution of the additive 
combination throughout the organic material. 
Notwithstanding that essentially any method could be used to effect the 
addition, it has been found most advantageous, from the standpoint of 
consistency and predictability of performance, to either add the peroxide 
decomposer, the complexing agent or similar compound to the organic 
material prior to adding the transition metal containing compound or 
compounds or to effect the addition simultaneously. 
When simultaneous addition is used, this is most effectively accomplished 
with a concentrated solution of the additive combination which, when 
prepared in an organic solvent, will, preferably be prepared by first 
dissolving the peroxide decomposer, the complexing agent or the like in 
the solvent and thereafter dissolving the transition metal compound or 
compounds. When a concentrated solution of the additive combination is 
used, the same will, generally, contain the peroxide decomposer, the 
complexing agent or the like or a mixture of such compounds at a 
concentration within the range from about 2 to about 20 wt. % and the 
transition metal compound or compounds also at a concentration within the 
range from about 2 to about 20 wt. %. Moreover, when a concentrated 
solution of the additive combination is used, the same will, generally, be 
prepared in the same organic material to which it will ultimately be added 
as an inhibitor or at least in a solvent which is itself soluble therein. 
It will, of course, be appreciated that the preparation of a concentrated 
solution or the addition of an additive combination to an organic medium 
can, often, be facilitated, particularly where one or more of the 
additives is a solid, by heating either the solvent or the organic medium 
into which the same is added and the use of such a technique is 
contemplated by the present invention. Also, many solid or semi-solid 
organic materials can be converted to liquid by heating and, where this 
can be done, it is preferred, in the method of the present invention, to 
convert such materials to liquids prior to adding the inhibitor 
combination of this invention. Similarly, and where conversion to a liquid 
form is not practical, addition of the additive combination to a solution 
of the solid or semisolid organic media can be used. Where neither 
liquefaction nor the preparation of a solution is practical, however, 
addition can be effected by milling or other suitable solid mixing 
techniques. In this case, though, the selection and use of solid peroxide 
decomposers complexing agents or the like and solid transition metal 
compounds is most preferred. 
Having thus broadly described the present invention, it is believed that 
the same will become even more apparent and more readily understood from 
the description of the preferred embodiment which follows. It should be 
noted, however, that due to the nature of the present invention the 
preference actually described is for particularly preferred combinations 
of transition metal salts and peroxide decomposers and the same could be 
used in essentially any of the organic compositions heretofore described 
and, while particularly good results have been achieved with fully 
formulated lubricating oil and greases, improved stability will be 
realized when inhibitor compositions of this invention are used in 
essentially any organic material. 
PREFERRED EMBODIMENTS 
In a preferred embodiment of the present invention, salts of chromium, 
cobalt, copper and manganese will be used, either alone or in combination, 
with an aliphatic amine as a lubricating oil stabilizer. The preferred 
salts will be those derived or obtained with an organic acid having from 
about 10 to about 18 carbon atoms and particularly those derived from 
naphthenic acids and the aliphatic amine will be a primary amine and the 
same will contain between about 10 and about 18 carbon atoms in the 
organic moiety thereof. In the preferred embodiment, the preferred salts 
or mixtures will be present at a concentration of at least 600 parts per 
million, by weight, in the fully formulated lubricating composition when 
the same are used individually and when two or more salts are combined the 
same will be present at a concentration of at least 500 parts per million, 
by weight. Also, the aliphatic amine peroxide decomposer will be present 
at a concentration within the range from about 1000 to about 10,000 ppm, 
by weight. Also, when the salts of two metals are used, the same will be 
used in relative molar concentrations ranging from about 1:3 to about 3:1. 
In the preferred embodiment, the base oil may be any natural or synthetic 
lubricant base stock. Such oils include naphthenic or paraffinic 
hydrocarbon base stocks. Such oils also include diester oils such as 
di(2-ethylhexyl) sebacate; complex oils such as those formed from 
dicarboxylic acids, glycols and either monobasic acids or monohydric 
alcohols; silicone oils, sulfide esters; organic carbonates; and other 
synthetic oils known in the art. In a most preferred embodiment of the 
present invention, the additive combination of the invention will be used 
to stabilize the oils against oxidation in the presence of solid 
transition metal cataysts such as metallic copper or metallic iron.

The invention will be even more readily understood by reference to the 
following Examples which illustrate the several embodiments thereof. 
EXAMPLE 1 
In this example, several blends were prepared in a DEWTS solvent 150 
neutral base oil. In four of the blends, copper was added as copper 
naphthenate in concentrations ranging from 0.012% to 0.63%. A fifth blend 
consisted of the pure base oil alone. All blends were then subjected to 
oxidation by bubbling air through the blend at a rate of 40 cc/min. for 
168 hours while the blend was held at 110.degree. C. The air which had 
bubbled through the blend was then bubbled through a water trap held at 
room temperature. The amount of volatile acid formed during the oxidation 
was determined by titrating the water in the water trap at frequent 
intervals using a standardized KOH solution with phenolphthalein as the 
indicator. At the end of the test, the oxidized oil was filtered and the 
acid number of the filtrate determined by the ASTM D 974 procedure. The 
acid number of the oxidized oil and the acid number of water accumulated 
in the water trap during the test were added together to give the total 
increase in acid number which resulted from oxidation. This is expressed 
as mg KOH/gm of oil blend. The precipitate filtered from the oxidized oil 
was washed with normal heptane and its weight recorded as the sludge 
formed during the test. The composition of each blend and the results 
observed are summarized in the table below: 
EFFECT OF Cu ON THE OXIDATION OF DEWTS SOLVENT 150N BASE STOCK 
______________________________________ 
% Cu .DELTA. TAN (mg KOH/gm) 
Sludge (mg.) 
______________________________________ 
0.0 0.2 0.3 
0.013 9.5 195 
0.063 14.6 221 
0.126 18.1 335 
0.630 1.1 0.1 
1.26 2.1 0.1 
______________________________________ 
It can be seen that the amount of oxidation which occurs during the test 
becomes greater as the copper concentration is increased from 0.012% to 
0.126% but that above 0.12% the catalytic effect of the copper disappears 
and its inhibiting characteristics take over. 
EXAMPLE 2 
This example presents results obtained with n-trioctylamine, a known 
hydroperoxide decomposer, in DEWTS solvent 150N base stock. The effect of 
this additive at two different concentrations is compared to the results 
obtained with the pure base stock in the same oxidation test described in 
Example 1. The composition of each blend and the results obtained are 
summarized in the table below: 
______________________________________ 
% TOA.sup.(1) 
.DELTA. TAN (mg KOH/gm) 
Sludge (mg.) 
______________________________________ 
0.0 1.5 1.2 
0.8 32.3 1.3 
1.6 51.2 1.3 
______________________________________ 
.sup.(1) n-trioctylamine 
These data show that although the n-trioctylamine is a peroxide decomposer 
the decomposition products apparently can be active in initiating 
oxidation which produces acids (but not sludge). 
EXAMPLE 3 
In this example a series of blends were prepared in DEWTS solvent 150N base 
oil. Several of these samples contained Cu.sup.++, as copper naphthenate, 
and 0.8% of the peroxide decomposer, n-trioctylamine. One sample contained 
the trioctylamine alone and another sample consisted of the pure solvent 
150 Neutral base oil. The results obtained when all these samples were 
oxidized together under the conditions described in Example 1 are 
presented in the following table: 
Cu PLUS A PEROXIDE DECOMPOSER (n-TRIOCTYLAMINE) 
______________________________________ 
% Cu % TOA .DELTA. TAN (mg KOH/mg) 
Sludge (mg.) 
______________________________________ 
0.0 0.0 1.5 1.2 
0.0 0.8 32.3 1.3 
0.06 0.8 2.0 2.2 
0.12 0.8 2.6 1.2 
0.60 0.8 11.9 0.1 
1.20 0.8 19.1 0.5 
______________________________________ 
A comparison of these results with those presented in Example 1 shows that 
the presence of the peroxide decomposer substantially reduces the 
concentration at which the copper can act as an inhibitor rather than as 
an oxidation catalyst. Oil blends resistant to oxidation are obtained with 
either 0.06% or 0.12% copper combined with 0.8% n-trioctylamine, whereas 
with either of these copper concentrations alone or with the 
n-trioctylamine alone at 0.8% concentration severe oxidation was 
encountered. 
EXAMPLE 4 
In this example a series of blends containing various amounts of Cu.sup.++, 
as copper naphthenate, and various concentrations of n-trioctylamine were 
prepared in the DEWTS solvent 150N base oil and the blends were subjected 
to oxidation under the conditions described in Example 1. The results are 
presented in the following table: 
Cu PLUS A PEROXIDE DECOMPOSER (n-TRIOCTYLAMINE) 
______________________________________ 
% Cu % TOA .DELTA. TAN (mg KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.12 1.6 0.23 0.0 
0.12 0.8 0.35 0.0 
0.12 0.4 0.35 3.7 
0.06 0.8 0.20 1.0 
0.06 0.6 0.21 0.6 
0.06 0.4 0.20 1.1 
0.06 0.3 0.29 0.5 
0.06 0.2 0.24 0.5 
0.06 0.1 0.18 0.5 
0.012 0.8 0.11 5.4 
0.012 0.1 14.48 138.8 
______________________________________ 
The first three samples show that with the Cu.sup.++ concentration held at 
0.12% while the n-trioctylamine concentration is varied from 0.4 up to 
1.6%, substantially equivalent results are obtained. The molecular weight 
of n-trioctylamine is 5.25 times the atomic weight of copper. A 1:1 
complex of the amine with 0.12% copper would require 0.63% of the amine. 
Similarly, 1.26% of amine would be required to form a 2:1 complex of the 
amine with copper. The data in the first three lines of this example show 
that the ability of the amine to reduce the concentration at which copper 
can act as an inhibitor does not seem to be related to the ability of the 
amine to form a complex with the copper. 
This conclusion is further substantiated by the data on the samples which 
contained 0.06% Cu.sup.++ with n-trioctylamine concentrations varying from 
0.1% to 0.8%. 0.32% of the amine would be required to form a 1:1 complex 
with the Cu.sup.++ at 0.06% concentration. It can be seen here that the 
effectiveness of the amine is maintained down to a concentration which is 
about 0.3 that required for 1:1 complex formation and that there is no 
change in the effect when the concentration of the amine is increased 
stepwise up to 0.8%, which is 25% greater than that required for the 
formation of a 2:1 complex of the amine with copper. 
The last two lines of this table show that the catalyst to inhibitor 
transition can be produced with Cu.sup.++ at concentrations as low as 
0.012% using 0.8% peroxide decomposer. But with copper concentrations this 
low, effective results cannot be achieved when the n-trioctylamine 
concentration is reduced to 0.1%. 
EXAMPLE 5 
In this example a series of blends were prepared using Fe.sup.+++, as iron 
naphthenate, plus n-trioctylamine in DEWTS solvent 150N base stock. These 
blends were oxidized according to the procedure described in Example 1 and 
the results are presented in the following table: 
IRON PLUS A PEROXIDE DECOMPOSER (n-TRIOCTYLAMINE) 
______________________________________ 
% Fe % TOA .DELTA. TAN (mg KOH/gm) 
Sludge (mg.) 
______________________________________ 
0.06 0.0 30.56 286.0 
0.06 0.1 36.60 (1) 
0.06 0.4 36.15 629.0 
0.06 2.0 22.40 28.9 
0.06 4.0 21.30 41.7 
0.12 0.0 33.77 (1) 
0.12 0.1 31.04 35.3 
0.12 0.4 27.33 24.5 
0.12 0.8 27.85 18.5 
0.12 2.0 18.31 24.1 
0.12 4.0 15.27 26.7 
0.60 0.0 19.49 154.3 
0.60 0.1 12.63 7.0 
0.60 0.4 9.26 8.7 
0.60 0.8 7.49 1.6 
0.60 2.0 8.37 19.1 
0.60 4.0 0.69 140.0 
0.60 4.0 13.07 3.9 
______________________________________ 
(1) Too viscous to filter. 
These results show that with iron, the peroxide decomposer was not 
effective when the iron was present at a concentration of 0.60%. Optimum 
results were obtained with a 0.8% concentration of n-trioctylamine, which 
is only about 25% of that required to form a 1:1 complex. Additional 
n-trioctylamine was beneficial with respect to acid number formation but 
harmful with respect to the formation of sludge. The iron blends oxidized 
much more rapidly than those containing copper. This could be due to the 
fact that iron is a less effective inhibitor or to the fact that the iron 
naphthenate employed contained 50% diluent oil of unknown oxidation 
stability. 
EXAMPLE 6 
Due to the rapid oxidation experience in blends containing iron 
naphthenate, a series of blends similar to those discussed in Example 5 
were oxidized for 120 hours under conditions otherwise the same as those 
used in Example 1. The results are presented in the following table: 
120 Hr. TEST ON IRON PLUS n-TRIOCTYLAMINE 
______________________________________ 
% Fe % TOA .DELTA. TAN (mg KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.06 0.0 24.2 4.9 
0.12 0.0 24.0 6.7 
0.60 0.0 8.0 7.1 
1.20 0.0 2.5 1.8 
0.06 0.1 26.1 21.9 
0.06 0.4 27.1 20.3 
0.06 0.8 25.6 18.5 
0.12 0.1 19.7 9.6 
0.12 0.4 20.2 8.3 
0.12 0.8 18.0 8.7 
0.60 0.1 8.0 3.1 
0.60 0.4 3.6 4.0 
0.60 0.8 1.1 0.3 
______________________________________ 
These results are similar to those presented in Example 5 in that little 
benefit was produced from the use of n-trioctylamine at Fe.sup.+++ 
concentrations of 0.12% or less. Again, however, a synergistic interaction 
is observed to occur with blends containing 0.60% Fe.sup.+++. 
EXAMPLE 7 
In this Example, a series of blends containing Co.sup.++, as the 
naphthenate, with the peroxide decomposer n-trioctylamine were prepared in 
DEWTS solvent 150N base stock. These blends were all oxidized under the 
conditions described in Example 1. The results, presented in the following 
Table, show that concentrations of the amine of at least 0.8% are needed 
to produce synergism. 
COBALT PLUS A PEROXIDE DECOMPOSER 
______________________________________ 
% Co % TOA .DELTA. TAN (mg KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.06 0.0 39.0 40.8 
0.12 0.0 32.0 14.2 
0.60 0.0 17.1 8.7 
0.06 0.4 33.7 17.1 
0.12 0.4 34.1 14.2 
0.60 0.4 26.4 26.9 
0.06 0.8 37.9 26.4 
0.12 0.8 32.5 5.1 
0.60 0.8 9.0 2.3 
______________________________________ 
EXAMPLE 8 
In this Example, a series of blends containing Cu.sup.++, as the 
naphthenate, were prepared in the DEWTS solvent 150N base oil. These were 
tested under the oxidation conditions described in Example 1 except that 6 
cm. of No. 14 electrolytic copper wire, cut into 1 cm. lengths, were 
introduced into the oil and were present during the oxidation. The results 
are presented in the following table. 
Cu PLUS Cu WIRES IN DEWTS-SOLVENT 150N 
______________________________________ 
% Cu .DELTA. TAN (mg KOH/gm) 
Sludge (mg.) 
______________________________________ 
0.0 2.30 13.0 
0.012 13.10 155.0 
0.06 15.80 117.8 
0.12 0.26 0.9 
0.60 0.82 1.4 
1.20 0.89 1.7 
______________________________________ 
These data show that the presence of the copper wire resulted in an 
increase in the oxidation of the pure base stock as can be seen by 
comparing the first line of this table with the results presented in 
previous examples. In the presence of the copper wire, the transition from 
catalysis to inhibition occurred at a copper concentration of 0.12%. 
EXAMPLE 9 
In this Example, a series of blends were prepared using Cu.sup.++, as the 
naphthenate, and the peroxide decomposer n-trioctylamine in DEWTS solvent 
150N base stock and these samples were oxidized in the presence of copper 
wire as described in Example 8. The results are presented in the following 
table: 
Cu PLUS A PEROXIDE DECOMPOSER (TOA) WITH Cu WIRES 
______________________________________ 
% Cu % TOA .DELTA. TAN (mg KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.0 0.0 2.25 9.3 
0.0 0.4 7.88 25.5 
0.012 0.4 0.07 1.4 
0.06 0.4 0.41 1.5 
0.12 0.4 0.28 1.5 
0.60 0.4 1.41 1.2 
0.0 0.8 17.14 41.1 
0.012 0.8 0.39 3.7 
0.06 0.8 0.65 5.7 
0.12 0.8 0.50 1.9 
0.60 0.8 1.64 1.5 
______________________________________ 
These data show that in the presence of copper wire, the decomposition 
products resulting from the presence of the peroxide decomposer 
n-trioctylamine are capable of initiating both acid and sludge formation. 
The presence of either 0.4% or 0.8% of the peroxide decomposer, however, 
will permit the inhibition rather than the catalytic properties of 
Cu.sup.++ to be exhibited at concentrations as low as 0.012%. In other 
words, the catalytic effect of the copper wire in accelerating the 
oxidative degradation of the base oil can be overcome by adding a small 
concentration of soluble copper to the base oil as long as a peroxide 
decomposer is incorporated in the formulation. 
EXAMPLE 10 
In this Example, a series of blends containing Fe.sup.+++, as the 
naphthenate, and some also containing the peroxide decomposer 
n-trioctylamine were prepared in DEWTS solvent 150N base oil and oxidized 
in the presence of copper wires according to the procedure described in 
Example 8. The results are presented in the following table: 
Fe PLUS A PEROXIDE DECOMPOSER (TOA) PLUS Cu WIRES 
______________________________________ 
% Fe % TOA .DELTA. TAN (mg KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.0 0.0 2.54 13.0 
0.012 0.0 30.20 686.0 
0.06 0.0 32.45 1006.7 
0.12 0.0 36.73 72.6 
0.60 0.0 18.86 52.6 
1.20 0.0 1.64 1.0 
0.0 1.0 0.66 13.0 
0.012 1.0 0.34 17.6 
0.06 1.0 0.26 1.1 
0.12 1.0 0.31 2.6 
0.60 1.0 1.83 3.2 
1.20 1.0 2.85 5.0 
______________________________________ 
In the upper half of this table it can be seen that in the presence of 
copper wires, the transition from catalysis to inhibition occurs with 
Fe.sup.+++ solution at an iron concentration between 0.6% and 1.20% if no 
peroxide decomposer is present. In the presence of 1% n-trioctylamine, 
however, the transition from catalyst to inhibitor occurs at a 
concentration in the neighborhood of 0.012% Fe.sup.+++. 
EXAMPLE 11 
In this Example, a series of blends were prepared using varying 
concentrations of Cu.sup.++, as the naphthenate, in DEWTS solvent 150N 
base oil and some of the samples containing 0.012% Cu.sup.++ were blended 
with varying amounts of the peroxide decomposer n-trioctylamine. These 
samples were tested under the conditions described for Example 1 except 
that a coil of interwined copper and iron wire, of the type used in the 
ASTM D 943 test and of a length to give the same ratio of wire to oil as 
employed in that test, was inserted in the oil prior to the test and 
remained there as the test was conducted. The results are presented in the 
following table: 
Cu PLUS A PEROXIDE DECOMPOSER WITH Cu AND Fe WIRES 
______________________________________ 
% Cu % TOA .DELTA. TAN (mg.KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.0 0.0 2.72 10.3 
0.012 0.0 13.96 179+ 
0.060 0.0 3.47 4.8 
0.12 0.0 2.08 3.3 
0.60 0.0 1.19 1.5 
1.20 0.0 1.74 1.4 
0.012 0.80 0.03 17.9 
0.012 0.10 0.11 1.9 
0.012 0.05 0.35 1.2 
0.012 0.02 0.46 3.3 
0.0 0.80 0.10 9.7 
______________________________________ 
This table shows that in the presence of both copper and iron wire, the 
transistion from a catalyst to an inhibitor in the absence of a peroxide 
decomposer takes place at a soluble copper concentration between 0.012% 
and 0.060%. The sludge formation for the 0.012% copper sample in line 2 of 
this table represents a minimum value since some of the sludge was lost 
during the workup. The data in the last five lines of this table, however, 
show that the catalyst to inhibitor transition can be produced at 0.012% 
Cu.sup.++ if the n-trioctylamine is incorporated in the formulation. 
EXAMPLE 12 
In this Example, a series of blends of Fe.sup.+++, as the naphthenate, some 
of which contained the peroxide decomposer n-trioctylamine, were prepared 
in DEWTS solvent 150N base oil were oxidized under the conditions 
described in Example 11. The results are presented in the following table; 
Fe PLUS A PEROXIDE DECOMPOSER WITH Cu AND Fe WIRES 
______________________________________ 
% Fe % TOA .DELTA. TAN (mg KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.0 0.0 2.72 10.3 
0.012 0.0 26.29 513+ 
0.060 0.0 (1) (1) 
0.12 0.0 (1) (1) 
0.60 0.0 8.86 11.0 
1.20 0.0 1.84 1.2 
0.060 0.10 32.98 416.7 
0.12 0.10 24.30 36.9 
0.60 0.10 1.07 1.2 
0.060 0.40 0.03 1.2 
0.12 0.40 9.45 1.8 
0.60 0.40 1.05 2.4 
0.12 0.80 0.14 1.1 
0.60 0.80 0.69 2.4 
0.0 0.80 0.10 9.7 
______________________________________ 
(1) too viscous to filter. 
The data in the upper part of this table show that in the presence of 
copper and iron wires and in the absence of a peroxide decomposer, the 
transition from catalyst to inhibitor for Fe.sup.+++ occurs at a 
concentration greater than 0.60% iron and that massive oxidation occurs at 
Fe.sup.+++ concentrations below this value. In the presence of 0.10% 
n-trioctylamine, however, the transition to inhibitor occurs at an iron 
concentration below 0.60%. With an n-trioctylamine concentration of 0.40% 
or greater, however, inhibition is observed at all the Fe.sup.+++ 
concentrations which were measured. 
EXAMPLE 13 
In this Example, several blends containing differing concentrations of both 
Cu.sup.++ and Fe.sup.+++, as the naphthenate, were prepared in DEWTS 
solvent 150N base stock. Three of these blends also contained 1% of 
n-trioctylamine. They were oxidized under the conditions described in 
Example 1. The results are presented below: 
Cu + Fe IN DEWTS WITH TOA at 110.degree. C. FOR 7 DAYS WITH 40 cc AIR/MIN. 
______________________________________ 
Sludge 
% Cu % Fe % TOA .DELTA. TAN (Mg KOH/gm.) 
(mg.) 
______________________________________ 
0.6 0.6 -- 0.17 1.0 
0.6 0.12 -- 4.20 1.1 
0.6 0.06 -- 0.23 0.8 
0.12 0.6 -- 0.40 0.9 
0.12 0.12 -- 0.21 0.9 
0.12 0.06 -- 1.72 0.5 
0.06 0.6 -- 0.59 1.0 
0.06 0.12 -- 0.36 0.2 
0.06 0.06 -- 0.70 0.2 
0.6 0.6 1.0 5.37 4.5 
0.12 0.12 1.0 0.20 3.5 
0.06 0.06 1.0 0.55 23.5 
______________________________________ 
A comparison of these data with those presented in Example 1 and in Example 
5 shows the synergistic effect produced by having both Cu.sup.++ and 
Fe.sup.+++ present in the oil. Very satisfactory inhibition was produced 
by all combinations studied. In these circumstances addition of the TOA 
did not produce any additional benefit and in fact seemed detrimental to 
some extent. 
EXAMPLE 14 
In this Example, several blends were prepared by dissolving Cu.sup.++, as 
the naphthenate, and n-dodecylamine in a DEWTS solvent 150N base stock. 
These blends were oxidized under the conditions described in Example 1. 
The results are presented along with comparative data from Example 1 in 
the following table: 
SYNERGISM BETWEEN Cu AND DODECYLAMINE 
______________________________________ 
.DELTA. TAN 
Cu.sup.(1) % 
Dodecylamine % 
(mg KOH/gm) Sludge (mg.) 
______________________________________ 
-- -- 1.5 1.3 
0.06 -- 14.6 220.8 
0.12 -- 18.1 334.7 
-- 0.1 0.98 1.1 
0.06 0.1 0.23 0.0 
0.12 0.1 0.67 2.5 
-- 0.8 34.3 0.3 
0.06 0.8 0.50 0.2 
0.12 0.8 0.23 1.6 
______________________________________ 
.sup.(1) As copper naphthenate 
These data show that the concentration at which copper which act as an 
inhibitor rather than a catalyst was reduced from the level of 0.6% as 
shown in Example 1 down to a concentration of 0.06% or less by the 
presence of the perioxide decomposer, n-dodecylamine. 
EXAMPLE 15 
In this Example several blends were prepared using Cu.sup.++, as copper 
naphthenate, and diabietylthiodipropionate in a DEWTS solvent 150N base 
oil. These oils were oxidized under the conditions described in Example 1. 
The results are presented in the following table: 
DIABIETYLTHIODIPROPIONATE (DATDP) AS A PEROXIDE DECOMPOSER 
______________________________________ 
Cu% DATDP % .DELTA. TAN (mg KOH/gm.) 
Sludge (mg.) 
______________________________________ 
0.0 0.1 0.9 0.3 
0.06 0.1 10.4 191 
0.12 0.1 1.1 0.7 
0.0 0.8 0.04 0.4 
0.06 0.8 8.1 90 
0.12 0.8 0.4 1.5 
______________________________________ 
These results show that DATDP is quite effective even when used alone. But 
it is not acting simply as a conventional free radical inhibitor. If that 
were the case, it should be more effective in inhibiting oxidation in the 
presence of the lower copper concentration where the copper catalyzed 
oxidation is proceeding with less velocity. Instead, it is more effective 
at the higher copper concentration, showing that it lowers the 
concentration at which copper can be converted from a catalyst to an 
inhibitor and therefore is acting as a peroxide decomposer. 
EXAMPLE 16 
In this Example, copper, cobalt, iron, copper and cobalt and copper and 
iron were added to a DEWTS Solvent 150N base oil and the blend then 
thickened with 12-hydroxy substituted lithium stearate to form a grease. 
The "spindle life" of the resulting grease at 250.degree. F. was then 
determined by conventional methods. The results obtained are summarized 
and compared with a grease containing no additives in the following table: 
______________________________________ 
Cu, Wt. % 
Co, Wt. % Fe, Wt. % Spindle Life, Hrs. 
______________________________________ 
0 0 0 386,550 
0.1 0 0 770,900 
0 0.1 0 220,400 
0 0 0.1 260,660 
0.1 0.1 0 1350,1540 
0.1 0 0.1 1920,980 
Commercial Grease good at 250.degree. F. 
750 
______________________________________ 
These data show that greases of excellent stability at 250.degree. F. are 
produced by using combinations of either Cu + Co or Cu + Fe as the 
inhibitors. 
EXAMPLE 17 
In this Example, several blends were prepared in an ester oil base stock 
containing 66 mol % of ester obtained by esterifying trimethylol propane 
with a mixture of aliphatic monocarboxylic acids having from 7 to 10 
carbon atoms therein and 34 mol % of esters obtained by esterifying a 
technical grade pentaerythritol with a mixture of aliphatic monocarboxylic 
acids having from 5 to 10 carbon atoms. The acids used to esterify the 
trimethylolpropane contained 7.9 carbon atoms, on average, while those 
used to esterify the pentaerythritol contained 6.0 carbon atoms, on 
average. The sulfur content of this synthetic ester is less than 2 ppm. In 
two blends, only copper, as copper naphthenate, was added. In two other 
blends, only trioctylamine (TOA) was added. In the remaining two blends, 
copper as copper naphthenate, and trioctylamine were added. All blends 
were then subjected to oxidation in the FTMS (Federal Test Method 
Standard) 791-5308-6 test for synthetic aviation oil stability. The 
composition of each blend and the results are summarized in the table 
following: 
______________________________________ 
TOA 
Cu.sup.++, Wt.% 
Wt.% .DELTA. TAN mg.KOH/mg 
.DELTA.KV at 100.degree. F. 
______________________________________ 
0.012 0 49.6 67.9 
0.12 0 17.0 32.8 
0 0.2 47.3 85.5 
0 1.0 44.5 69.0 
0.12 0.2 15.2 18.3 
0.12 1.0 8.7 16.6 
______________________________________ 
From the foregoing examples, it is clear that transition metal salts which 
are useful in the present invention are effective oxidation inhibitors for 
a broad range of organic materials when the same are used, either alone or 
in combination, with a peroxide decomposer. These Examples, are, however, 
included solely for the purpose of illustration and are in no way intended 
to be limiting. The scope of the invention should, therefore, be 
determined solely from the appended claims.