US2311931A - Lubricant - Google Patents

Description

lead, silver-cadmium,

Patented Feb. 23, 1943 Elmer William Cook, New York, N. Y and William David Thomas, Jr., Stamford, Conn, assignors to American Cyanamid Company, New York. N. Y., a corporation of Maine No Drawing.

Application December 27, 1941,

a Serial No. 424,600 7 Claims. (CL 25248) This invention relates to lubricants of improved characteristics containing new organic compounds which possess detergent, anti-corrosion; filmformina and other valuable properties when dispersed therein. I

The new compounds of our invention to be described herein may be designated as metal salts of alkyl or cycloalkyl salicylate sulfides having the general formula which R1 and Rs are alkyl or cycloalkyi radicals having 4 or more carbon atoms, n is a positive integer not more than 2,M is a metal radical and X is the valence of M.

These compounds are particularly valuable as additives to lubricating oils used in heavy duty service and under extreme pressure conditions because of the unique detergent. anti-corrosion, film-forming and other properties which they possess. When conventional hydrocarbon lubricating oils are subjected to high operating temperatures for long periods of time, as in heavy duty service, they tend to decompose with the formation of complex oxidation and decomposition products. These acidic oxidation products formation.

perse the sludge or prevent the formation of the varnish deposits mentioned above.

A number of oil-soluble detergents of the type of metal soaps, phenolates and alcoholates have been proposed and used in crankcase oils to dissolve or disperse the sludge and prevent varnish deposits and piston ring sticking. Unfortunately, however, the greater majority of these substances increase the rate of oxidation in a manner somewhat analogous to the accelerating action of the various metallic soaps or driers" on the oxidation of varnish films, and their presence results in an increased concentration of acidic oxidation products in the oil. When individual detergents and anticorrosion agents are used together in the oil the two separate chemicals do not cooperate to reduce corrosion and sludge and varnish The lack of cooperative effect is believed to be due to the action of the detergent in removing from the metal surfaces the passlvating film of anti-corrosion agent which is supposed to cover the metal surface and thereby prevent corrosion. A

The compounds of the present invention show both excellent detergent and excellent anti-corrosive action when dispersed in lubricating oils and thereby enable us to provide a lubricating oil having a single additive effective to inhibit corrosion, sludge and varnish formation, ring corrode certain alloy bearings such ascoppernickel-cadmium, etc.

which are commonly employed in internal combustion engines. These decomposition products also tend to polymerize under the high temperature conditions obtaining in the engine to form sludge which precipitates when the engine is cooled or when fresh oil is added. The precipitated sludge. clogs the oil filter and becomes caked on heated metal surfaces to form lacquer-like deposits which may cause the piston rings or even the piston itself to stick.

Attempts have been made to overcome these deficiencies of the lubricating oil by the addition of detergents or anti-corrosion agents, or both.

.Certain anti-corrosion agents, such as triphenyl phosphite and sulfurized sperm oil, counteract the corrosive effect of the oxidation products formed in the oil. These anti-corrosion agents have no detergent properties, however, and while they cover the bearing surfaces and other corrodable parts of the engine with a passivating' film that prevents corrosion of the metal by the organic acids of the oil, they do not act to dissticking and other difllculties experienced in lubricating oils serving in a heavy-duty capacity.

The addition of our compounds .to lubricating oils also imparts to the oil a high film strength thus enabling the oil to be used under extreme pressure conditions under which the film formed by' conventional oils would break and result in seizing of the bearing surfaces.

mThe extremely high solubility. of these compounds in hydrocarbon oils leads to another important advantage, namely, the ease with which ."they are blended with lubricating oils. This step is further simplified by our practice of dissolving them in ordinary types of lubricatingv oils to the extent of 50% or more for storage and shipping purposes. For this reason it will be understood that the appended claims are intended to cover lubricating compositions contaming such high concentrations of our.new

compounds. p

Another advantage to be obtained by the use oi our alkyl and cyclo-alkyl salicylate sulfides is their solubilizing action on certain materials which are known to be good detergents, anti-oxijdents, etc. or have good corrosion inhibiting properties but which cannot normally be used in high concentrations on account of their oil insolubility. Certain dithiophosphates, such as di(para-tertiary amyl phenyl) dithiophosphate;

- calcium, barium, aluminum, zinc, and magnesium stearates, palmitates, naphthenates; etc. are difficultly soluble in lubricating oils, but because of their solubi ity in the compounds described herein, it is possible to add them to oils in this way in amounts suil'lciently large for them to be effective.

The compounds of the present invention may be prepared by reacting an aliphatie'or cycloaliphatic ester of salicylic acid with sulfur chloride (SaClz), sulfur di-chloride (SCla), or thionyl chloride (8001:) in the presence of Cu, depending upon whether a mono-sulfide or di-sulflde is desired as the reaction product. We prefer the mono-sulfide compounds because 01 their greater chemical stability. The monosulfldes are prepared by reacting approximately 2 mols of an aliphatic or cyclo-aliphatic ester of salicylic acid with 1 mol of sulfur-dichloride in the presence of a small amount, for example 0.2 mol, of anhydrous AlCla as catalyst. catalysts, such "as SbCls, FeCla,- TeClz, SnCh, TiClt, TeCh, BiCh and ZnCl: may also be employed as catalysts in our reaction, but with decreasingly effective results. The disulfides are prepared in the same manner by substituting sul-. fur chloride-in place of sulfur dichloride. The

reaction may be illustrated as follows:

11 C-OB The product illustrated a then treated with a metal oxide or hydroxide to prepare salts having the general formula:

in which R1, R2, M and X are as indicated in the general formula described above.

The metal radicals which we introduce into our alkyl or cycloalkyl salicylate sulfides to form salts thereof, include metal radicals such as aluminum,

lead, magnesium, zinc, calcium, barium, stronreaction should be an ester of an' aliphatic or cyclo-aliphatic alcohol having at least 4 carbon atoms so that R1 and R2 in the general formula may be alkyl or cycloalkyl radicals of at least 4 carbon atoms. The size of the alkyl or cycloalkyl radical is important in that the higher molecular weight radicals promote'the solubility of our compounds in lubricating oils and the radicals should be of at least the size indicated in order that our compounds may be dissolved in Other Friedel -Crafts o o i R0(": 8- -o a i v +2nci no on e t if f Rio-"C B 0-0 R:

O O M the lubricant without undue difllculty. R1 and R2 may therefore be alkyl radicals such as butyl, normal amyl, tertiary amyl, ethyl hexyl, normal octyl, decyl, dodecyl, hexadecyl, octadecyl, etc. or cyclo-aliphatic radicals such as cyclopentyl; cyclo hexyl, methyl, ethyl, propyl, butyl, and amyl, monodi-, and tri-substituted cyclo hexyl radicals, etc. Ordinarily we carry out th reaction with the reactants dissolved in a suitable solvent such as carbon disuliide, ethylene chloride, petroleum naphtha, nitrobenzene, etc. The reaction mixture with a catalyst present is then heated until the evolution of Hcl has substantially stopped.

The mixture is then treated with cool dilute hydrochloric acid or other acids such as sulphuric acetic, etc. and the product recovered by extraction with toluene or other solvents. The product can be further purified by washing with water in which it is insoluble and the solvents remov by evaporation. I

It will be understood, of course, that the prep aration of the disulflde with sulphur chloride proceeds in the'same way under the same reaction conditions. cyclo-aliphatic esters of salicylic acid may b employed in place of the aliphatic esters of salicylic acid illustrated in the above illustration in the same manner and using the same molecular proportions.

The preparation of barium dodecyl salicylate monosulflde will now be described in detail in the following example in which particular parts of the reactants, catalysts, solvents, etc. are indicated merely for purposes of illustration. It will also be understood that our invention is not to be limited to the particular compound described since as stated above the invention is of broader scope and is to be limited only by the scope-of the appended claims. The parts indicated are by weight.

Example 150 parts by weight of dodecyl (lauryl) sallcylate was condensed with 24 parts of sulfur dichloride in 30 parts of A. S. T. M. naphtha in the presence of!) parts of AlCl: as catalyst. Condensation was carried out by warming the reaction mixture on a steam bath between'60-70 C.

with stirring for 30 minutes. The reaction mixture was then cooled and diluted with cold dilute hydrochloric acid, extracted with toluene, washed and the solvent evaporated. Dodecyl salicylate monosulflde was removed as a brownish-yellow liquid.

The barium salt of dodecyl salicylate monosulfide was prepared by neutralizing 40 parts of dodecyl salicylate monosulflde with 18 parts of barium hydrate in a solution of 20 arts of ethyl alcohol and 16 parts of toluene with stirring at 70 C. As the solvent evaporated fresh toluene was added from time to time and the heating increased to a temperature of C. The solution was then filtered from traces of inorganic salts and then evaporated, the last of the solvent being evaporated under reduced pressure. 55 parts of barium dodecyl salicylate monosulflde was obtained which was dissolved in an equal amount of lubricating oil for storage and blending purposes.

The compounds as described above are heat stable and not easily decomposed in the lubricant because of high operating temperatures which may be encountered. They are also practically water-insoluble and are not extracted from the It will also be understood that the iiiericent by contact with water nor do they appreciebly promote the formation oi emulsions with in the oil.

The metal salts of alkyl and cyclo-alkyl selics-"late sulfides are so very effective as detergents and as corrosion inhibitors that it is possible to hnprcve lubricating oils, particularly those of the crankcase type, to a great extent by the use of very small amounts of the compound. In lubricating oils intended for ordinary purposes where high temperatures occur only occasional- 1y, from ill to 9.8% of the metal salt of the alkyl or cycioaikyl salicylate monosuliide is sufidcient. in extreme pressure lubricants and in oils intended ior heavy duty service, it is generally scivisable to use a little more, as for example 0.5 to 3.0% of the oil.

The efiectiveness of our compounds in lubrieating oils as corrosion inhibitors, detergents and anti-oxidants was demonstrated by the results obtained upon subjecting aNo. fill-W grade Mid-Continent solventrefined oil to the Catalytic Indiana Test. This test was conducted in an apparatus consisting of a number of large glass test tubes immersed in a constant temper ature bath maintained at 341 F. 300 cc. samples oi the oil containing dispersed therein 0.4% of barium dodecyl salicylate monosulflde were poured into the tubes and air passed through the oil at the rate of 10 liters per hour. In order to simulate the conditions prevailing in the craniacase or" an engine, weighed strips of copper-leaci alloy were suspended in the oil. A test tube containing a sample of the same oil without benefit the barium dociecyl salicylate monosuliide additive was used as a control. After subjecting the oil to the test for 70 hours, the copper-lead alloy strips were removed, washed and weighed. The copper 'lead strips immersed in the lubricat- .lrsg oil containing no additive, showed a hearing loss of 275 mg. per sq. inch. The copper-lead strips immersed in the lubricating oil containing 9.4% oi barium lauryl salicylate monosulfide showed, at the end of the '70 hour test, no corrosicn loss whatever. After pouring out the oii and rinsing once with kerosene, the two test tubes in which R1 and R2 are members of the group consisting of allryi and cycloalkyl radicals having or more carbon atoms, 11. is a positive integer and not more than 2, M is a metal radical and X is the valence of M.

i 2. A lubricating composition comprising a major proportion oi? a lubricant having dispersed therein a minor proportion of a compound havinu.

the general formula in which R1 and R2 are members of the group consisting of alkyl and cycloalkyl radicals having 4 or more carbon atoms, and M is an alkaline earth metal radical.

3. A lubricating oil having dispersed therein 0.1-3% of barium dcidecyl salicyiate monosulfide. 4. A lubricating oil having dispersed therein iii-3% of barium octyl 'sallcylate monosulflde.

5. A lubricating oil having dispersed therein 0.1 of barium deeyl salicylate monosulflde.

ELMER "*WLLIIAM COOK. WELLIAM navm THOMAS, JR.-