Multifunctional additives for lubricants and fuels

A lubricant or fuel composition contains a multifunctional antioxidant and antiwear amount of an O,O-diorgano-S-(2-hydroxyalkyl) phosphorodithioate derived hydrogen phosphonate which can be made by reacting a diorganophosphorodithioic acid with an epoxide and a dialkyl phosphite, such as dimethyl phosphite.

FIELD OF THE INVENTION 
This invention relates to automotive and industrial fluid compositions. 
Specifically, lubricants or fuels containing the reaction products of 
O'O-diorganophosphorodithioic acids, alkylene oxides and secondary 
phosphite esters. 
BACKGROUND OF THE INVENTION 
During the normal storage and usage of automotive and industrial 
lubricants, the lubricants are subject to high temperatures and oxygen 
which can lead to oxidation of the lubricants. Oxidized lubricants can 
cause the build up of oil-soluble acids, lacquers and sludge which can 
promote premature deterioration of engines and other lubricated systems. 
Another problem associated with mechanical systems relates to the 
frictional forces created between relatively moving metal parts which can 
cause the wearing away of metal surfaces. An ability to reduce the 
coefficient of friction between these metal surfaces is not an inherent 
property of all lubricants. 
Additionally, it is often found that lubricants are corrosive to certain 
metals, typically iron, copper, aluminum and lead, which are found in 
engines. 
Additives are often blended with lubricants to inhibit oxidation of the 
lubricant as well as to prevent the wear and corrosion of metal parts. 
Phosphorodithioate compositions, i.e., the metal salts of 
phosphorodithioates, such as zinc dialkylphosphorodithioates, have been 
widely reported as multifunctional antiwear, peroxide decomposing and 
bearing corrosion inhibiting additives for industrial fluids. Further, 
organic phosphonates such as dibutyl hydrogen phosphonates and dioleyl 
hydrogen phosphonates have been described as antiwear and extreme pressure 
additives for lubricants. 
SUMMARY OF THE INVENTION 
It has now been found that products made by reacting an 
O'O-diorganophosphorodithioic acid with an alkylene oxide to form an 
intermediate which is then reacted with a secondary phosphite ester, i.e., 
dihydrocarbyl hydrogen phosphonate, are effective multifunctional 
antioxidant and antiwear additives with potential high temperature 
stabilizing and metal passivating properties as well as possible 
antifatigue, antiscuffing, metal deactivating, bearing corrosion 
inhibiting and cleanliness properties. 
The invention is directed to a product having the formula 
##STR1## 
where R.sub.1 and R.sub.2 are hydrocarbyl radicals having 1 to 30 carbon 
atoms, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are, independently, hydrogen 
atoms or hydrocarbyl radicals containing 1 to 60 carbon atoms or which 
contain at least 1 heteroatom which is oxygen, sulfur or nitrogen, R.sub.7 
and R.sub.8 are hydrocarbyl radicals containing 1 to 20 carbon atoms, n is 
an integer ranging from 1 to 2 and m is an integer ranging from 0 to 1 the 
sum of n and m being 2, automotive or industrial fluid compositions 
containing the product and methods of making the same. The invention is 
also directed to automotive or industrial fluid compositions containing a 
reaction product having multifunctional antioxidant and antiwear 
properties which is the reaction product of an 
O'O-diorganophosphorodithioic acid, an alkylene oxide and a phosphite 
ester. 
The dithiophosphate substituted diorgano phosphite products of the present 
invention are formed in a transesterification reaction between an 
O'O-diorgano phosphorodithioate intermediate and a diorgano phosphite. The 
intermediate products, the O'O-diorgano phosphorodithioates, are formed in 
a reaction between a diorganophosphorodithioic acid and an alkylene oxide. 
The diorganophosphorodithioic acid is prepared in a known reaction between 
a hydroxy compound and phosphorus pentasulfide. It is believed that the 
following equation is illustrative of the reaction mechanism: 
##STR2## 
where R.sub.1 and R.sub.2 are hydrocarbyl radicals, typically aliphatic, 
aromatic or naphthenic or combinations thereof containing 1 to 30 carbon 
atoms, preferably from 2 to 20 carbon atoms. Representative examples of 
suitable hydroxy compounds are alcohols which include ethyl alcohol, 
propyl alcohol, n-butyl alcohol, isobutyl and sec-butyl alcohols, the 
isomeric primary and secondary amyl alcohols and mixtures thereof, the 
primary and secondary isomers of hexyl alcohol, cyclohexyl alcohol, the 
isomers of octyl alcohol, decyl alcohol, lauryl alcohol, benzyl alcohol, 
phenol, cresol, xylenol, naphthol, ethylphenol, butylphenol, nonylphenol 
and mixtures of the foregoing. The preferred alcohols are 
4-methyl-2-pentanol and 2-ethyl-1-hexyl alcohol. 
The alkylene oxide most suitable for preparing the intermediate product has 
the structural formula 
##STR3## 
wherein R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are hydrogen or hydrocarbyl 
containing from 1 to 60 carbon atoms and can additionally contain sulfur, 
oxygen and/or nitrogen. The contemplated hydrocarbyl can be either 
aliphatic, aromatic or naphthenic. Suitable oxides include ethylene oxide, 
propylene oxide, butylene oxide, cyclohexene oxide and styrene oxide. 
The intermediate can be made in the presence of an inert organic solvent 
such as benzene, toluene or xylenes. The reaction mixture can be 
maintained between a temperature range of 0.degree. C. to 100.degree. C., 
from 30.degree. C. to 80.degree. C. is preferred. Preferably, the 
intermediates are contacted in equimolar amounts of acid to alkylene oxide 
and; thereafter, refluxed to insure complete reaction. The solvent and any 
unreacted components can be removed by distillation under reduced 
pressure. In the preferred procedure the product is further refined by 
filtration. 
It is believed that the reaction intermediates have the structural formula 
##STR4## 
where R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are herein 
defined above. For the reaction to proceed most efficiently, it is 
preferred that the intermediate be a primary or a secondary alcohol. 
The intermediate is then reacted with the secondary phosphite ester, in a 
transesterification reaction in which there is an interchange of acyl or 
alkoxyl groups resulting in the formation of a different ester. The 
secondary phosphite ester, a diorgano phosphite, always has a hydrogen 
atom attached directly to the phosphorus atom and can be characterized by 
the structural formula 
##STR5## 
where R.sub.7 and R.sub.8 are hydrocarbyl radicals, usually aliphatic, 
containing 1 to 20 carbon atoms and more preferably 1 to 6 carbon atoms, 
and can additionally contain sulfur, oxygen and nitrogen. An example of a 
phosphite ester is dimethyl phosphite. It is believed that the phosphite 
products of the invention, also known as hydrogen phosphonates, have the 
following structure 
##STR6## 
where R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7 and 
R.sub.8 are described above, n is 1 to 2 and m is 0 to 1. Other structures 
which may be formed are: 
##STR7## 
when n=1 and m=1 or 
##STR8## 
when n=2 and m=0. 
The reaction, typically, takes place in the liquid phase with one of the 
reactants being introduced gradually. An excess of one reactant is usually 
used in order to enable the reaction to proceed to completion. Thus, the 
reactants can be contacted in proportion expressed in a molar ratio of 
intermediate to phosphite of 1:5 to 5:1, preferably 2:1. The reaction 
temperature can range from 0.degree. to 300.degree. C., preferably from 
50.degree. to 175.degree. C. A catalyst, such as that of the alkali metal 
alkoxide type, can be employed, the preferred catalyst is titanium 
isopropoxide. The reactants are contacted for three to ten hours, 
preferably six hours. 
It is believed that the effectiveness of the additives of the present 
invention when blended with industrial fluids is due to the synergistic 
activity between the phosphorodithioate group and the phosphonate group. 
The reaction products are useful in low concentrations and do not contain 
any potentially undesirable metals or corrosion promoting materials. 
The contemplated automotive or industrial fluids are lubricants such as 
liquid oils in the form of either a mineral oil or synthetic oils or 
mixtures thereof and greases in which any of the foregoing oils are 
employed as a base. Still further materials which it is believed would 
benefit from the reaction products of the present invention are fuels. 
In general, the additives can be blended with the lubricant in a 
concentration of from 0.05% to 10% by weight of the total composition. The 
preferred amount ranges from 0.1% to 5%. The lubricating oils contemplated 
are mineral oils, both paraffinic and naphthenic and mixtures thereof, and 
synthetic oils. The lubricant can be of any suitable lubricating viscosity 
range, for example, from about 45 SSU at 100.degree. F. to about 6000 SSU 
at 100.degree. F., and preferably from about 50 to 250 SSU at 210.degree. 
F. The oils may have viscosity indexes ranging from up to 100 or higher. 
Viscosity indexes from about 70 to 95 being preferred. The average 
molecular weights of these oils can range from about 250 to about 800. 
Where the lubricant is employed as a grease, the lubricant is generally 
used in an amount sufficient to balance the total grease composition, 
after accounting for the desired quantity of the thickening agent, and 
other additive components included in the grease formulation. A wide 
variety of materials can be employed as thickening or gelling agents. 
These can include any of the conventional metal salts or soaps, such as 
calcium, or lithium stearates or hydroxystearates, which are dispersed in 
the lubricating vehicle in grease-forming quantities in an amount 
sufficient to impart to the resulting grease composition the desired 
consistency. Other thickening agents that can be employed in the grease 
formulation comprise the non-soap thickeners, such as surface-modified 
clays and silicas, aryl ureas, calcium complexes and similar materials. In 
general, grease thickeners can be employed which do not melt or dissolve 
when used at the required temperature within a particular environment; 
however, in all other respects, any material which is normally employed 
for thickening or gelling hydrocarbon fluids for forming greases can be 
used in the present invention. 
The additives are effective when used in industrial lubrication 
applications, such as in circulation oils and steam turbine oils where 
large charges of oil are expected to last the lifetime of the machinery 
without being replaced. Gas turbines, both heavy-duty gas turbines and 
aircraft gas turbines would also benefit from the lubricant additives of 
the present invention. The additives are believed useful in diesel engine 
oils, i.e., those used in marine diesel engines, locomotives, power plants 
and high speed automotive diesel engines. Gasoline burning engines would 
also benefit from the present additives. Automatic transmission fluids are 
another class of lubricants for which these additives are suited. These 
fluids represent a careful balance of properties needed to meet the unique 
requirements of automatic transmissions. Gear oils are another class of 
fluids which would benefit from the additives of the present invention. 
Typical of such oils are automotive spiral-bevel and worm gear axle oils 
which operate under extreme pressures, load and temperature conditions and 
hypoid gear oils which operate under both high speed, low torque and 
low-speed, high torque conditions. It is also desirable to employ the 
additive in greases. Greases containing the additive are particularly 
useful in automobile chassis lubrication. 
The lubricating oils and greases contemplated for blending with the 
additive of the invention can also contain other additive materials such 
as corrosion inhibitors, detergents, extreme pressure agents, viscosity 
index improvers, friction reducers, antiwear agents and the like. 
Representative of these additives include, but are not limited to, 
phenates, sulfonates, imides, heterocyclic compounds, polymeric acrylates, 
amines, amides, esters, sulfurized olefins, succinimides, succinate 
esters, metallic detergents containing calcium or magnesium, arylamines, 
hindered phenols and the like. 
It is also contemplated that the additives may be useful in fuels. The 
additives can be blended in a concentration from about 0.01% to about 10 
wt. % based on the total weight of the composition. Preferably, the 
concentration is from 0.1 to about 5 wt. %. 
When the additives are utilized in fuels, the fuels contemplated are liquid 
hydrocarbon and liquid oxygenated fuels such as alcohols and ethers. 
Liquid hydrocarbon fuels include gasoline, fuel oils, diesel oils and 
alcohol fuels include methyl and ethyl alcohols and ethers such as methyl 
tert butyl ether and tert amyl methyl ether. 
Specifically, the fuel compositions contemplated include gasoline base 
stocks such as a mixture of hydrocarbons boiling in the gasoline boiling 
range which is from about 90.degree. F. to about 450.degree. F. This base 
fuel may consist of straight chain or branched chain aliphatic 
hydrocarbons or paraffinic hydrocarbons, cycloparaffins, olefins, aromatic 
hydrocarbons, or mixtures thereof. The base fuel can be derived from among 
others, straight run naphtha, polymer gasoline, natural gasoline or from 
catalytically cracked, alkylate or thermally cracked hydrocarbons and 
catalytically cracked reformed stock. The composition and octane level of 
the base fuel is not critical, and any conventional motor fuel base can be 
employed in the practice of this invention. Further examples of fuels of 
this type are petroleum distillate fuels having an initial boiling point 
from about 75.degree. F. to about 135.degree. F. and an end boiling point 
from about 250.degree. F. to about 750.degree. F. It should be noted in 
this respect that the term distillate fuels is not intended to be 
restricted to straight-run distillate fractions. These distillate fuel 
oils can be straight-run distillate fuel oils catalytically or thermally 
cracked (including hydrocracked) distillate fuel oils, etc. Moreover, such 
fuel oils can be treated in accordance with well-known commercial methods, 
such as acid or caustic treatment, dehydrogenation, solvent refining, clay 
treatment and the like. 
Particularly contemplated among the fuel oils are Nos. 1, 2 and 3 fuel oils 
used in heating and as diesel fuel oils, gasoline, turbine fuels and jet 
combustion fuels. 
The fuels may contain alcohols and/or gasoline in amounts of 0 to 50 
volumes per volume of alcohol. The fuel may be an alcohol-type fuel 
containing over 50 volumes to little or no hydrocarbon. Typical of such 
fuels are methanol, ethanol and mixtures of methanol and ethanol. The 
fuels which may be treated with the additive include gasohols which may be 
formed by mixing 90 to 95 volumes of gasoline with 5 to 10 volumes of 
ethanol or methanol. A typical gasohol may contain 90 volumes of gasoline 
and 10 volumes of absolute ethanol. 
The fuel compositions of the instant invention may additionally comprise 
any of the additives generally employed in fuel compositions. Thus, 
additive packages of the instant invention may additionally contain 
solvents, conventional carburetor detergents, anti-knock compounds such as 
tetraethyl lead, anti-icing additives, upper cylinder and fuel pump 
lubricity additives and the like.

EXAMPLE 1 
Propoxylated Di-(2-Ethylhexyl) Phosohorodithioic Acid 
Approximately 708.6 gm of di-(2-ethylhexyl)phosphorodithioic acid 
(commercially available from Stauffer Chemical Company) is charged into a 
1 liter stirred reactor equipped with a condenser and a thermometer. 
Approximately 116.2 gm of propylene oxide (equal molar) is slowly added 
over a course of 2 hours. The reaction temperature is controlled at or 
below 40.degree. C. by using an ice-water bath for cooling. At the end of 
the addition, the reaction mixture changed its color from dark greenish to 
light yellowish. It weighed approximately 825 gm. 
EXAMPLE 2 
Propoxvlated Di-(4-Methyl-2-Pentyl) Phosohorodithioic Acid 
Into a four-necked flask equipped with a stirrer, condenser, dropping 
funnel and thermometer are added 838 g (8.2 moles) of 4-methyl-2-pentanol 
and the contents are heated to 60.degree. C. At that temperature, 444.5 g 
(2.0 moles) of phosphorus pentasulfide are added portionwise over a 
three-hour period with agitation. After all of the sulfide reactant is 
introduced, the temperature is raised to 65.degree. C. and held for three 
hours. The evolution of hydrogen sulfide gas indicates a substantially 
complete reaction and the hydrogen sulfide gas is trapped by a caustic 
scrubber. The reaction is then allowed to cool to ambient temperature 
under a nitrogen blanket and the solution is filtered through diatomaceous 
earth to produce a greenish fluid (1158.5 g) which is the desired 
phosphorodithioic acid. 
The phosphorodithioic acid is further reacted with an equimolar amount of 
propylene oxide (232.4 g) following the exact procedure as described in 
Example 1. At the end of the reaction, the mixture changes its color to 
light yellowish, and excess unreacted 4-methyl-2-pentanol is removed by 
distillation. 
EXAMPLE 3 
Reaction Product of S-2-Hydroxypropyl-O,O-Di-(2-Ethylhexyl) 
Phosphorodithioate and Dimethyl Phosphite 
Approximately 206 g (0.5 mole) of the above product of Example 1 and 1.0 g 
of titanium isopropoxide catalyst were charged in a reaction flask, slowly 
27.5 g (0.25 mole) of dimethyl phosphite is added dropwise over a period 
of one hour at 65.degree. C. This mixture is then heated at 100.degree. C. 
for three hours, at 120.degree. C. for five hours, and finally at 
145.degree. C. for one hour, during which time volatiles are collected in 
a Dean-Stark condenser. The final solution is filtered through 
diatomaceous earth to produce 215 g light yellowish liquid as desired 
product. This product shows a distinct P-H peak at 2430 cm.sup.-1 on its 
infrared spectrum. 
EXAMPLE 4 
Reaction Product of S-2-Hydroxypropyl O,O-Di-(4-Methyl-2-Pentyl) 
Phosphorodithioate and Dimethyl Phosphite 
Approximately 178 g (0.5 mole) of the product of Example 2 and 1.0 g of 
titanium isopropoxide catalyst is charged in a reaction flask slowly, 27.5 
g (0.25 mole) of dimethyl phosphite is added at 65.degree. C., and the 
reaction is followed according to the same procedure as described in 
Example 3. Finally, all volatiles are removed by vacuum distillation to 
leave about 185 g of a yellow fluid which is the desired product. This 
product shows a distinct infrared peak of P-H at 2440 cm.sup.-1. 
EVALUATION OF THE PRODUCT 
The organic phosphite products of the present invention were blended in a 
concentration of 1 wt % in a mineral oil and evaluated for antioxidant 
performance in the Catalytic Oxidation Test at 325.degree. F. for 40 hours 
(Table 1) and in the Catalytic Oxidation Test at 325.degree. F. for 72 
hours (Table 2). 
The test procedure consisted of subjecting a volume of the test lubricant 
to a stream of air which was bubbled through the composition at a rate of 
about 5 liters per hour for the specified number of hours and at the 
specified temperature. Present in the test composition were metals 
frequently found in engines, namely: 
1) 15.5 square inches of a sand-blasted iron wire; 
2) 0.78 square inches of a polished copper wire; 
3) 0.87 square inches of a polished aluminum wire; and 
4) 0.107 square inches of a polished lead surface. 
The results of the test were presented in terms of changes in kinematic 
viscosity (KV), change in neutralization number (TAN) and lead loss. 
Essentially, the small change in KV meant that the lubricant maintained 
its internal resistance to oxidation under high temperatures, the small 
change in lead loss indicated that the lubricant was not corrosive to lead 
under corrosive conditions, such as high temperatures and oxidizing 
conditions. 
It will be noted that the lubricant blended with the additive compositions 
of the present invention attained small delta values. Thus, the 
compositions are effective multifunctional antioxidant additives. 
The ability of the oil, containing the products of the present invention, 
to prevent the wearing down of metal parts under severe operating 
conditions was tested in the 4-Ball Wear Test. Three stationary stainless 
steel balls of 1/2 inch in diameter were placed in a container. The 
mineral oil lubricant containing the additive was added to the container 
and a fourth stainless steel ball was placed in a chuck mounted on a 
device which spinned the ball at 2000 RPM under 60 kg load for 30 minutes 
at 200.degree. F. From the reported data (Table 3), it will be noted that 
the additives of the present invention exhibit good antiwear performance. 
TABLE 1 
______________________________________ 
Catalytic Oxidation Test 
40 Hours at 325.degree. F. 
Addi- Change Percent 
tive In Acid Change In 
Conc. Number Viscosity 
Item (wt %) Delta TAN % Delta KV 
Sludge 
______________________________________ 
Base Oil (200 
-- 4.78 57.9 Heavy 
second, solvent 
refined, paraffinic 
neutral, mineral oil) 
Example 4 1.0 2.60 22.0 Heavy 
in above base oil 
______________________________________ 
TABLE 2 
______________________________________ 
Catalytic Oxidation Test 
72 Hours at 325.degree. F. 
Addi- Change Percent 
tive In Acid Change In 
Conc. Number Viscosity 
Item (wt %) Delta TAN % Delta KV 
Sludge 
______________________________________ 
Base Oil (200 
-- 9.60 118.9 Heavy 
second, solvent 
refined, paraffinic 
neutral, mineral oil) 
Example 3 1.0 4.41 38.9 Heavy 
(in above 
base oil) 
Example 4 1.0 8.55 65.2 Heavy 
(in above 
base oil) 
______________________________________ 
TABLE 3 
______________________________________ 
Four-Ball Test 
(60 kg load, 2000 rpm, 30 min., 200.degree. F.) 
Item Wear Scar Diameter (mm) 
______________________________________ 
Base Oil (80% solvent paraffinic 
4.15 
bright, 20% solvent paraffinic 
neutral mineral oil) 
1% Example 3 in above base oil 
0.43 
1% Example 4 in above base oil 
0.57 
______________________________________