US2369632A - Lubricating oils - Google Patents

Description

Patented Feb. 13, 1945' LUBRICATING OILS Elmer W. Cook, New York, N. Y., and William D. Thomas, Jr., Stamford, Conn., assignors to American Cyanamid Company, New York, N. Y.,- a corporation of Maine No Drawing. Application November 13, 1941, Serial No. 419,016

6 Claims.

This invention relates to lubricating oils, particularly'those of the type known as crankcase oils. Although the improved lubricating oils of the present invention are highly desirable for use in the crankcases of passenger automobiles, they are especially valuable for heavy duty service in truck, bus, aeroplane, marine and Diesel engines which operate for long periods of time at high temperatures. I

The principal objects of the invention are to provide an improved lubricating oil of the heavy duty type which is particularly resistant to sludge formation and oxidation, being non-corrosive to alloy bearings and other metal parts under conditions of extreme service, and which is free from varnish formation and ring sticking tendencies.

In our copending application Serial No. 401,960, filed July 11, 1941, and in our copending'application Serial No. 415,411 filed October 17, 1941, we have disclosed that hydrocarbon lubricating oils having greatly improved detergent, anti-corrosive and anti-sludge forming properties may be prepared by the incorporation therein of minor amounts of various dithiophosphates. While the lubricating oils containing these organic substituted dithiophosphates are extremely resistant to sludge formation under conditions of heavy duty service we have found that when preparing these improved lubricating oils from ordinary classes of lubricating oils not highly refined a small amount of sludge will form when the oil is subjected to high temperatures for long periods of time in the presence of air or oxygen. With the more highly refined oils such as those treated by the solvent refining process the amount of sludge formed under such conditions is very small. Since it is desirable, however, to use a lower cost oil in trucks, buse's, Diesel engines, etc. which operate almost continuously at high temperatures a further improvement in lubricating oils reflned by conventional methods is desirable.

We have found that lubricating oils refined by ordinary methods may be rendered almost entirely resistant to sludge formation in heavy duty service for long periods of time by the incorporation therein of minor amounts of organic substituted dithiophosphates such as will be presently described, together with minor amounts of an oilsoluble organic sulfonate. Another advantage to be obtained by the use of organic sulfonates with dithiophosphates is the solubilizing action which the organic sulfonates exert on the dithiophossolubilized to a sufficient degree for their effective use in lubricating oils with the help of small amounts of organic sulfonates.

Although some of the oil soluble organic sulfonates have previously been added to lubricating oils as anti-corrosion agents experience has shown that on long continued heating in the presence of air they oxidize and break down to form sludge. As a result they will not effectively prevent the formation of undesirably large amounts of sludge under conditions of extreme service. It is surprising therefore that the addition of oil-soluble 'organic sulfonates to a lubricating oil composition containing a dithiophosphate additive will further increase the resistance of the oil to sludge formation.

Among the various oil-soluble organic sulfonates which are effective to produce improved anti-sludging properties in the oils of the present invention are the so-called petroleum or mahogany sulfonates, well-known products of the oil industry. We prefer to employ the petroleum sulfonates on account of their availability and low cost. Other oil-soluble organic sulfonates may, however, be employed. We may use, for example, the dialkyl sulfosuccinates such as the diamyl, dioctyl, dicapryl, diundecyl and dilauryl sulfosuccinates; also the alkylaryl sulfonates such as diisobutyl naphthalene sulfonate, diisopropyl naphthalene sulfonate, lauryl phenyl sulfonate; the esters of sulfophthalic acid such as the diamyl and dioctyl esters; lauryl-,S-sulfobutyrate which is an ester of a sulfomonocarboxylic acid; esters of sulfosebacic acid; capryl phenyl ether sulfonate; terpenyl alkyl ether sulfonates; sulfonated esters of talloel fatty acids such as the capryl ester; and the various sulfotricarballylates phates. Some of the dithiophosphates, for example di-(tert. amyl phenyl) dithiophosphate, which are diflicultly soluble in oil alone may be such as triethylhexyl sodium sulfotricarballylate and others. We prefer to use these oil-soluble surface-active organic sulfonates in the form of their metal salts such as those of zinc, sodium, magnesium, potassium, etc., and, preferably, those of the alkaline earth metals, calcium, barium and strontium.

- The various dithiophosphates which we have found useful in improving lubricating oils and which may be employed to advantage with the oil-soluble organic sulfonates just described are those having the general formula in which R is a. member of the group consisting of aryl, alkyl, aralkyl, cycloalkyl, aryloxyalkyl,

acylaryl and alkoxyaryl radicals and M is hydrogen or a salt-forming radical and n is the .valence of M. More specifically, compounds of 'dithiophosphate, dilauryl dithiophcsphate, di-

octadecyl dithiophosphate, etc. We prefer to use those dialkyl dithiophosphates in which the alkyl group has from 5 to 30 carbon atoms since the longer alkyl chains tend to increase the solubility of the dithiophosphates in lubricating oils. The diaryl dithiophosphates and the diaryl dithiophosphates in which the aryl group bears an alkyl, alkoxy or cycloaliphatic group are also useful such as for example diphenyl dithiophosphate, di-(2,4-diamyl phenyl) dithiophosphate, dikeryl diphenyl dithiophosphate (a product obtained by treating chlorinated kerosene with a phenol in th presence of aluminum chloride and then reacting with P2S5) and the various di-(wax substituted diaryl) dithiophosphates as described in detail in our copending application Serial No. 415,411, filed October 17, 1941, to have the alky] group in the alkaryl radical to have 5 to 30 carbon atoms so that the compounds are more easily oil-soluble. We may also employ the dicycloaliphatic dithiophosphates such as those prepared by reacting cyclopentanol, cyclohexanol, cycloheptanol, and methyl, ethyl, propyl and amyl substituted cyclopentanol, cyclohexanol and cycloheptanol, etc. with Pass. Th diaryloxyalkyl dithiophosphates such as bi(2,4-diamyl phenoxyethyl) dithiophosphate, the diacylaryl dithiophosphates such as di-(lauroyl phenyl) dithiophosphate and the dialkoxyaryl dithiophosphates may also be added to lubricating oils with oil-soluble organic sulfonates to improve the sludging properties of the oil.

We prefer to employ these various organic substituted dithiophosphates in the form of their metal salts, preferably the alkaline earth metal salts. Among the various metal salts which may be employed are those of the salt-forming radicals nickel, aluminum, cadmium, tin, zinc, mag nesium, calcium, strontium, barium and others.

The various dithiophosphates described above are employed by u in our improved lubricating oils, preferably in amounts ranging from 0.1 to 3% by weight. Smaller amounts, 0.05 to 1.0%, of the oil-soluble organic sulfonates may be employed with the dithiophosphates to prevent sludge formation. The greater the tendency of the oil to form sludge the more organic sulionate should be employed. The amount of both of these substituents in the oil will also depend to some extent upon the purpose for which the oil is intended. For example, an oil intended for extremely heavy duty service should contain more of both the dithiophosphate and the organic sulfonate as compared with the amounts required by an oil intended for ordinary usage.

The resistance of our improved lubricating oils to sludge formation was demonstrated by the following test. cc. samples of the oil to be tested were heated at 330 F. in a 50 cc. open glass beaker for 24 hours. At the end of the heating period the oil samples were cooled and examined for deposits of sludge. Under the conditions of this test conventionally refined lubricating oils, when containing certain dithiophosphate additives, show formation of a heavy dark sediment. When testing solvent refined oils the sedimentis not as heavy which indicates that some constituent in the oil tends to decompose under prolonged We also prefer Oil A-Mid-Continent, conventionally refined,

SAE 20-W Additive Results 1.07 barium diiauryl dithiophosphate--- Dark sedime 1.0% barium dilauryl dithiophosphate N at 0.45 calcium petroleum sulionate 0 5e OiZ B--Pennsylvania, solvent refined, SAE 10-W Additive Results 1.0% barium diiauryl dithiophosphate--. Sediment. 1.0% barium dilauryl dithiophos hate C} 0.2% dlal kyi benzene sodium sul onate..- 1.0% bar um dilauryl dithiophosphatc. D 0.2% tri-(n-hexyl) sodium sulfotricar- 1 giuglate' d 1 1 a h arium i aury it iophosphate..- Dark sedim 1.5%; barium dllauryl dithio hospbate-.- C1 ent 0.35% calcium petroleum su fonate 1.3% barium dlifllllyl ditbiophosphategioctyl si tliium 1silirilsuccinaule1 sum 1 aury it iophos ate.-. gg ya b d l g g g g }Very slight precipitate.

o ar um capry it 10p osphate... Heav reel 1 t 1.3% barium dicapryl dithiophosphate--. v h p m e 0.2% dioctyl sodium suliosuccinate ery 5 lg t precipitate Oil C-Mid-Contiment, solvent-refined, SAE 10-W Additive Results 1.0% barium di-(2, 4-diam 1 hen 1 di- Sedim thiopbosphate. y p y ent 1.0% barium di-(2, i-diamyl phenyl) dithiophosphate. Clear. 0.45% calcium petroleum suli'onate 1.0% bar um dioctyl dithiophosphate. Sediment. 1.0% barium dioctyl dithiophosphate- Cl 0.45% calcium petroleum Suiionate 1.0% bar um d iauryl dithiophosphate. Sediment. 0.6% bar1um dilauryl dithiophosphate 0.1 didecyl calcium sulfosuccinate What we claim is;

1. A hydrocarbon lubricating oil containing as an antioxidant and anticorrosive agent having a tendency to form sludge in the oil upon continued heating thereof 0.1-3% by weight of a dithiophosphate of the formula 2. A hydrocarbon lubricating oil containing as an antioxidant and anticorrosive agent having a tendency to form sludge in the oil upon continued heating thereof 0.1-3% by weight of a dithiophosphate of the formula in which R is a member of the group consisting of alkyl, aryl, aralkyl, cycloalkyl, aryloxyalkyl, acylaryl and alkoxyaryl radicals, M is a.

".polyvalent metal and n .is the valence of M, said oil also containing as a sludge-inhibiting agent for said dithiophosphate 0.05-1% by weight of an oil-soluble petroleum sulfonate.

3. A hydrocarbon lubricating oil containing as an antioxidant and anticorrosive agent having a tendency to form sludge in the oil upon continued heating thereof 0.l-3% by weight of a dithiophosphate of the formula in which R is a hydrocarbon radical having 5-30 carbon atoms, M is a polyvalent metal and n is the valence of M,- said oil also containing as a sludge-inhibiting agent for said dithiophosphate 0.054% by weight of an oil-soluble petro-' leum sulfonate.

4. A hydrocarbon lubricating oil containing as an antioxidant and anticorrosive agent having a tendency to form sludge in the oil upon continued heating thereof 0.1-3% by weight of a dithiophosphate of the formula in which R is an alkaryl group, the alkyl groups of which contain 5-30 carbon atoms, M is a polyvalent metal and n is the valence of M, said oil also containing as a sludge-inhibiting agent for said dithiophosphate 0.05-1% by weight of an oilsoluble petroleum sulfonate.

5. A hydrocarbon lubricating oil containing as an antioxidant and anticorrosive agent having a tendency to form sludge in the oil upon continued 10 heating thereof 0.13% by weight of a polyvalent 20 also containing as a sludge-inhibiting agent for said dithiophosphate 0.05-1% by weight of an oilsoluble organic sulfonate.

ELMER W. COOK. WILLIAM D. THOMAS, J R.