US3317426A - Phospho-substituted urethane lubricating oil additives - Google Patents

Description

United States Patent fiice 3,317,426 Patented May 2, 1967 This invention concerns novel polyfunctional compounds finding use as lubricating oil additives. More particularly, this invention concerns. phosphoro-substituted diurethanes and their use as lubricating oil additives.

Numerous additives are incorporated in oils and greases to enhance their lubricating properties. A wide variety of materials have been employed to reduce friction and increase the load-carrying capacity of lubricants employed under boundary or extreme pressure (EP) conditions. When moving surfaces are separated by oil, as the load is increased and the clearance is reduced between the surfaces, the condition of boundary, or thin film, lubrication is reached. Metal-to-rnetal contact occurs, and wear or seizure results. Under these conditions, the effectiveness of lubricants in reducing wear or friction varies widely. At still higher loads, the condition commonly known as extreme pressure lubrication is reached. Scuffing, galling, and rapid wear or seizure may occur. The term extreme pressure is a misnomer since the damage results from the high temperature reached. Welding of asperities of two contacting surfaces occurs followed by metal transfer (galling) or cleavage in production of wear fragments.

In order to avoid the undesirable effects described above, EP agents are added. One class of EP agents contains heteroatoms such as chlorine, sulfur or phosphorus or combinations thereof which react with the metal surface. Included in this class are dithiophosphates and particularly popular are the zinc dithiophosphates. However, it has become increasingly more desirable to remove metal salts from lubricating media. The use of metal free EP agents is particularly desirable when one is using an ashless detergent, e.g., alkenyl succinirnide of polyalkylene polyamine, in order to avoid the presence of metals in the oil. Metals are undesirable since on decomposition of the solubilizing portion of the molecule the metals may form deposits in the engine, interfering with the engines eificient operation.

It has now been found that extreme pressure properties can be introduced into an oil or lubricating viscosity by combining with the oil a phosphorodithioate-substituted urethane having from 1 to 2 phosphorodithioatesubstituted urethane groups per molecule and of from 16 to 50 carbon atoms per phosphorodithioate-substituted urethane group.

For the most part, diurethan'es will be used of the following formula:

wherein R is hydrocarbylene of from 2 to 12 carbon atoms, more usually of from 6 to 10 carbon atoms, R is hydrocarbylene of from 2 to 14 carbon atoms, more usually of from 2 to 6 carbon atoms and desirably of from 2 to 4 carbon atoms, having from 2 to 3 saturated aliphatic carbon atoms as a bridge between the oxygen and the sulfur and R is hydrocarbyl of from 1 to 30 carbon atoms, more usually of from 4 to 25 carbon atoms and desirably of from 4 to 18 carbon atoms. (Hydrocarbylene is a divalent organic radical composed solely of carbon and hydrogen having its free valences n different carbon atoms and may be aliphatic, alicyclic, aromatic or combinations thereof, e.g., aralkyl and alkaryl, and may have aliphatic unsaturation, e.g., olefinic; hydrocarbyl is a monovalent organic radical composed solely of carbon and hydrogen which may be aliphatic, alicyclic, aromatic or combinations thereof, e.g., alkaryl and aralkyl and may have aliphatic unsaturation, e.g., olefinic.)

A preferred group of compounds has the following formula:

1 i (R onPsR ooNH 5.

wherein Ar is arylene of from 6 to 10 carbon atoms, R is alkylene of from 2 to 6 carbon atoms, preferably of from 2 to 4 carbon atoms, and R is hydrocarbyl of from 1 to 30 carbon atoms, desirably of from 4 to 25 carbon atoms and more desirably of from 4 to 18 carbon atoms.

A further preferred aspect of this invention is compounds of the following formula:

1 if [(R OMP S-alk-OCNH]:

wherein the benzene ring is tri-substituted, two substit uents being the phosphoroalkyl urethanyl radical (alternatively described as S- phosphinothioylthioalkoxycarbonyl amino) which are preferably separated by at least 3 carbons on the benzene ring, i.e., meta or para, alk is alkylene of from 2 to 6 carbon atoms, preferably of from 2 to 4 carbon atoms, R is hydorcarbyl of from 1 to 30 carbon atoms, more usually of from 4 to 25 carbon atoms, and desirably of from 4 to 18 carbon atoms, and R is either hydrogen or lower alkyl of from 1 to 4 carbon atoms, preferably methyl. I

As indicated, the hydrocarbylene bridging the two nitrogens of the carbamic acids is preferably aromatic, while the bridge between the carbamic acid and the phosphoro derivative may be aliphatic, cycloaliphatic or aralkyl, but is preferably aliphatic and free of aliphatic unsaturation. The hydrocarbyloxy groups indicated as R R and R may be the same or different and are preferably aliphatic.

Illustrative of compounds which come within the scope of the above formulae are the following: ethane-1,2-dicarbamic acid di[2-(dibutoxyphosphinothioylthio)ethyl] diester; toluene-2,4-dicarbamic acid di[3-(dihexoxyphosphinothioylthio)propyl]diester; toluene-2,6 dicarbamic acid di[2 (di[tetrapropenylphenoxy]phosphinothioylthio) l butyl] diester; cyclohexane 1,4 dicarbamic acid di[2 (butoxy(hexoxy)phosphinothiolythio) lphenylethyl] diester; benzene 1,3 dicarbamic acid di[2 (diethoxyphosphinothioylthi0) l hexyl] diester; cumene 2,4 dicarbamic acid di[2 (dicumyloxyphosphinothiolythio) l propyl]diester; hexane 1,6 dicarbamic acid di[2 (didodecyloxyphosphinothiolythio) ethyl] diester; naphthalene 1,4 dicarbamic acid di- [2 (butoxyhexoxyphosphinothiolythio)ethyl] diester; toluene 2,4 dicarbamic acid di[2 (di[pe ntapropenylphenoxy]phosphinothiolythio)ethyl] diester; etc. The nomenclature is based on the Handbook for Chemical Society Authors, The Chemical Society, London, 1961 (pages 157-158).

The compounds used in this invention are readily prepared by reacting an alkylene oxide with 0,0-dihydro.- carbyl phosphorothiolothionic acid. The resulting alcohol is then reacted with the desired isocyanate compound. With diisocyanate, two molecules of the alcohol are used per diisocyanate.

The reaction between the phosphorothionothiolic acid and the oxide is readily carried out by slowly adding the oxide to the phosphorothionothiolic acid either neat or in a solvent while maintaining the temperature between about 100 to 200 F. Conveniently, the reaction can be carried out in the range of from about 100 to 175 F. Generally, about stoichiometric amounts of the-reactants are used.

To the resulting alcohol is then added the desired isocyanate, either neat or in the presence of an inert solvent and the mixture heated from about 200 to 300 F. Approximately equivalent amounts of the materials are used.

Illustrative of 0,0-dihydrocarbyl phosphorothionothiolic acids which find use are 0,0-dibutyl phosphoro-. thionothiolic acid, 0,0-dihexyl phosphorothionothiolic acid, 0,0-dioctyl phosphorothionothiolic acid, O-butyl, O-hexyl phosphorothionothiolic acid, O-pentyl, O-hexyl phosphorothionothiolic acid, 0,0 ditolyl phosphorothionothiolic acid, 0,0-ditetrapropenylphenyl phosphorothionothiolic acid, 0,0-dihexadecyl phosphorothionothiolic acid, 0,0 pentapropenylphenyl phosphorothionothiolic acid, etc. The preferred phosphorothionothiolic acid Will have a total number of carbon atoms of from 8 to 40, more usually of from 8 to 16.

The alkylene oxides which find use are ethylene oxide, 1,2-propylene oxide, 1,3-propylene oxide, 1,2-butylene oxide, styrene oxide, 1,2-hexylene oxide, 2,3-butylene oxide, decene-1,2-oxide, etc.

The isocyanates which find use are phenyl isocyanate, toluene isocyanate, tolylene diisocyanate, phenylene diisocyanate, bis-phenyl isocyanate, hexane diisocyanate, etc.

The oils used with the compounds of this invention may be derived from natural or synthetic sources. Fluids of lubricating viscosity generally have viscosities of from about 35 to 50,000 Saybolt Universal seconds (SUS) at 100 F. Among natural hydrocarbonaceous oils are paraflin base, naphthenic base, asphaltic base and mixed base oils. Illustrative of synthetic oils are hydrocarbon oils, such as polymers of various olefins, generally of from 2 to 6 carbon atoms, and alkylated aromatic hydrocarbons; and non-hydrocarbon oils, such as polyalkylene oxides, aromatic ethers, and silicones. The preferred media are the hydrocarbonaceous media, both natural and synthetic.

Usually included in the oils besides extreme pressure agents are various other additives. These additives include rust inhibitors, antioxidants, oiliness agents, detergents, foam inhibitors, viscosity index improvers, pour point depressants, etc. Usually, these will be present in the range of from about 0.1 to 10 weight percent, more usually from about 0.5 to 5 weight percent of the composition and generally each of the additives will be in the range from about 0.01 to 5 Weight percent of the composition. It is of particular importance that the compounds of this invention are compatible with the various additives and do not interfere with their efficacy.

The amount added of the compounds of this invention will generally be in the range of about 1 to 5 weight percent of the oil composition. However, the compositions may be prepared as oil concentrates and the compounds of this invention may be present in amounts as high as 50 weight percent or even as high as 80 weight percent of the total composition.

The following example is offered by way of illustration and not by way of limitation.

Example 1 Into a reaction flask was introduced 1,581 g. of O- isobutyl, O-hexyl phosphorothionothiolic acid and 399 g. of butylene oxide added drop-wise using a water bath to maintain the temperature under 150 F. At the end of the addition, the mixture was stirred at 140 F. for 4 hours and then stripped in vacuo while heating the solution to 275 F.

To a 148.8 g. aliquot of the above mixture was added 34.8 g. of tolyl diisocyanate (an 80:20 mixture of the 2,4- and 2,6-isomers) and the mixture stirred and heated 4 at 250-260 F. for 8 hours. The mixture was then stripped in vacuo at 250 F. leaving a residue of 183 g.

Analysis.Percent P=6.9.

In order to demonstrate the effectiveness of the compounds of this invention as extreme pressure agents, the exemplary compound of Example 1 was tested under the Falex El Wear and Shear Test. The test is described in Journal of the Institute of Petroleum, volume 32, April 19, 1946. The figures reported are the loads under which the particular lubricating oil composition failed, that is, seizure occurred. Also reported is the wear on the rod when applying a load of 850 pounds for a period of 30 minutes. The value reported is the lost weight in milligrams resulting from Wear on the rod.

The oil used was a 480 neutral oil having 5 weight percent of polyisobutenyl succinimide of tetraethylene pentamine (approximately 1,000 molecular weight). To this oil was added 40 mM./kg. based on phosphorus of the exemplary compound of Example 1. The results with and without the additives of this invention in the oil are reported in the following table.

TABLE I Wear TestRod Weight Loss, mg.

Shear TestLoad to Failure, lbs.

OilWithout Additive Oil With Additive An oxidation test was carried out to determine the effectiveness of the compounds of this invention as inhibitors. Oil samples were prepared using 480 neutral oil containing 5 weight percent of a commercial ashless detergent (polyisobutenyl alkenyl succinimide of tetraethylene pentamine) and 0.1 Weight percent of terephthalic acid (corrosion inhibitor). Into one of the samples was added the exemplary composition of Example 1 in an amount providing a concentration of 40 mM./ kg. of phosphorous. To 25 g. aliquots of each of the above samples were added 0.2 cc. of a solution having 3,160 p.p.m. of copper, 2,670 p.p.m. of iron, p.p.m. of manganese, 36,700 p.p.m. of lead and 1,631 p.p.m. of tin as their napthenates, providing a distribution of metals which would be expected to be found in used crankcase oils after an L-4 Chevrolet Engine Test. The oil sample to be tested is then maintained at 340 F. and the time required to absorb 1000 ml. 0 observed. Without the additive, the oxygen was absorbed in 0.42 hour, while the sample with the additive required 10.5 hours.

The results demonstrate the excellent protection from wear and the great enhancement in lubrication resulting by the addition of the compounds of this invention to a compounded oil. Also, significant oxidation inhibition is also observed. It is evident that the compounds of this invention afford excellent protection under extreme lubrieating conditions. Moreover, the compounds of this invention are compatible with a wide variety of additives which are included in compounded oils as demonstrated by its activity with a common commercial ashless detergent, e.g., alkenyl succinimides.

As will be evident to those skilled in the art, various modifications on this invention can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the following claims.

I claim:

1. A lubricating oil composition comprising in a major amount an oil of lubricating viscosity and in an amount sufficient to impart extreme pressure properties to said lubricating oil, a composition of the formula:

wherein R is hydrocarbylene of from 2 to 12 carbon atoms, 4. A lubricating oil composition according to claim 3, R is hydrocarbylene of from 2 to 14 carbon atoms and wherein said composition which imparts extreme pressure has from 2 to 3 saturated alphatic carbon atoms as a properties is of the formula:

bridge between the oxygen and the sulfur, and R is S OH CH3 3 I hydrocarbyl of from 1 to 30 carbon atoms. 1 1

2. A composition according to claim 1, wherein R is of C4HQOPS*CHZ I GNH from 6 to carbon atoms, R is of from 2 to 4 carbon O6H13- CH3 2 atoms and R is of from 4 to 18 carbon atoms.

3. A lubricating oil composition comprising in a major amount an oil of lubricating viscosity and in an amount 5. A lubricating oil composition according to claim 3, wherein said composition which imparts extreme pressure 10 properties is of the formula:

sufiicient to impart extreme pressure properties to said CH3 lubricating oil, a composition of the formula: CH3 I C4H OPSCHz]OCNH Q C0H13-O CH3 2 S 0 References Cited by the Examiner [(n onismoiiNnlAr UNITED STATES PATENTS 1 2,494,126 1/1950 Hoegberg 252-46] 2,494,283 1/ 1950 Cassaday et a1. 257-49.9 2,901,481 8/1959 Fusco et a1. 260-928 3,094,550 6/1963 Schlor 2609 2'8 wherein Ar is arylene of from 6 to 10 carbon atoms, R is alkylene of from 2 to 6 carbon atoms and R is hydro- DANIEL WYMAN Prlmary Emmmer carbyl of from 4 to carbon atoms L. G. XIARHOS, Assistant Examiner.

Claims (1)

1. A LUBRICATING OIL COMPOSITION COMPRISING IN A MAJOR AMOUNT OF OIL OF LUBRICATING VISCOSITY AND IN AN AMOUNT SUFFICIENT TO IMPART EXTREME PRESSURE PROPERTIES TO SAID LUBRICATING OIL, A COMPOSITION OF THE FORMULA: