US2676151A - Corrosion inhibitors for lubricating oils - Google Patents

Description

Patented Apr. 20, 1954 UNITED STATE ATENT OFFICE CORROSION'INHIBITORS FOR LUBRICATIN G IOILS corporation of Maine No Drawing.

Application April 9, 1952,

Serial No. 281,457

8 Claims.

This invention relates to additives for lubricants and more particularly to corrosion inhibitors of use in lubricating oils of the crankcase type. Although the additives of the present invention are highly desirable for use in the crankcases of passenger automobiles or similar vehicles, 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.

With the advent of greater horsepower output in internal combustion engines and their operation at higher speeds, it became necessary to gen erally strengthen or stiffen the engines to withstand the increased stresses which are cre" ated in the operating parts thereof, such as, for example, in the crankshaft or other rotating or moving parts. New hard-metal alloy bearings such as cadmium-silver, copper-lead, nickel-cadmium, and the like, have been introduced in the automotive industry to replace the softer babbit metal bearings in an effort to brace these operating parts against distortion due to the greater forces. These hard alloy bearings exhibit superior strength characteristics and are generally more satisfactory than their predecessor babbit metal bearings but have shown a greater susceptibility toward the corrosive action of the acidic materials developed in the lubricating oils due to oxidation or decomposition during use. As a consequence, efforts have been made to prevent this type of corrosion of the newer type of bearings by the use of corrosion inhibitors in the oil and such has become an important factor in the care and preservation of internal combustion engines.

How these corrosion inhibitors actually function in a composition as complex as the mixture of hydrocarbons found in lubricating oils and under the varying conditions which exist in an operating internal combustion engine is not precisely or positively known. However, it is believed that these inhibitors either prevent the corrosive substances from coming into contact with' the metal surfaces'of the engine parts by forming a protective coating thereon which is impervious to the corrosive materials and thus act as passi vators, or function, by converting the corrosive substances in the oil into harmless, non-corrosive materials by appropriate chemical action.

Various compounds have been utilized in such corrosion inhibiting functions and have normally comprised metallic salts of various phosphoric acids. Such have proved quite satisfactory in the industry but, being metallic, are subject to some disadvantages. For example, it has been noted that, upon the combustion of the lubrication oils containing these compounds, there is an objectionable ash or residue resulting from the decomposition of the lubricant. Consequently, there has been a growing demand in some groups in the lubricating oil industry for non-metallic additives which will not leave any ash or residue.

Furthermore, in some cases of these phosphorus-containing compounds, there has been some evidence of valve burning which has been attributed to the presence of th phosphorus.

It is therefore a principal object of the present invention to provide inhibitors for lubricating oil compositions capable of substantially reducing or inhibiting the corrosive effects of such lubricating oils and/or decomposition or oxidation products thereof on metallic elements.

It is another principal object of the present invention to provide an anti-corrosive'agent which will leave no ash or residue on decomposition and which will not result in any valve burning.

We have found that the corrosive effects of the acidic materials developed in lubricating oil compositions during use may be substantially reduced or inhibited by the addition to such compositions of a small amount of an oil-soluble ester of cyanuric acid wherein the oxygen has been replaced by sulfur, selenium, or tellurium.

These esters may be broadly defined by the following structural formula:

inwhich X is a member of the group consisting drogen,

It is to be observed that these compounds are non-metallic and, as a consequence, will leave no ash or residue when they are decomposed upon combustion of the lubricating oil compositions containing them. It is further to be noted that these compounds do not contain any phosphorus,

as is commonly found in most anti-corrosive agents, and thus are especially useful where phosphorus compounds have been found to cause valve burning.

The invention will be described in greater detail with particular reference to the sulfur-sub- 3 stituted esters of cyanuric acid, or thiocyanurates, but it is to be pointed out that this is not to be construed as limitative of the invention and that similar compounds containing selenium and tellurium can be substituted in order to accomplish the objects of the present invention.

The more specific aspects of the present invention are concerned with hydrocarbon sub stituted thiocyanurates (thiocyanidines) which have been rendered oil soluble by the attaching of hydrocarbon substituents to the sulfur atoms therein so as to be readily blendable with hydro carbon lubricating oils to form lubricating oil compositions having the requisite corrosion inhibiting properties.

As specific examples of particular compounds which have been found satisfactory within the principles of the present inventive concept, the following compounds are cited primarily for purposes of illustration: triallyltrithiocyanurate, triethyltrithiocyanurate, tribenzyltrithiocyanurate, tributyltrithiocyanurate, dioctyltrithiocyanurate, didecyltrithiecyanurate, mono-octadecyltrithiocyanurate, tricyclohexyltrithiocyanurate, etc.

It is tobe noted, however, that the radicals selected to be attached to the sulfur atom must be such that the resulting compound is sufficiently soluble in lubricating oil for the purposes of the present invention and in the concentrations hereinafter set forth.

For example, Where each of R1, R2 and R3 represents an organic radical, the number of carbon atoms in each radical may be small, such as typified by the triethyl ester, without reducing the oil solubility of the compound below that necessary for use. Where one of the characters R1, R2 and R3 represents hydrogen, the number of carbon atoms in the two remaining organic radicals should be correspondingly greater, such as exemplified by the dioctyl ester. In a similar fashion, where two of the characters R1, R2 and R3 represent hydrogen, the number of carbon atoms in the remaining organic radical should be correspondingly even greater, such as noted in the mono-octadecyl ester. The criterion in all cases is therefore seen to be the requirement of oil solubility and the term oil soluble or similar phrase, as used herein, limits the scope of the invention accordingly.

Easy blending of lubricating oil additives with hydrocarbon lubricating oils is of considerable importance from a practical and commercial viewpoint and, accordingly, while certain of the lower carbon atom radicals having decreased oil solubility characteristics can be blended with lubricating oils by the employment of special techniques, the difficulty and additional expense of doing so does not warrant their industrial use. It is also customary in the art to prepare, ship and store these additives in the form. of about 50% solutions in lubricating oil, for example, so that the blender need only pour the additive compound into the lubricating oil with suitable stirring. Additives of difficult solubility cannot be employed in such facile manner and consequently are not as desirable.

The amount of the inhibitor to be mixed with the hydrocarbon lubricating oil or other lubricant will depend to a large extent upon the nature and characteristics of the lubricating oil, itself; upon the particular ester used; upon factors of expense and intended use of the lubricating composition; upon the presence of other additives; etc. Oils having a marked tendency to oxidize or corrode metals will naturally require larger amounts of the additive and, conversely, oils having a lesser tendency to oxidize or corrode metals will not require so much of the additive. In general, we have found that an effective concentration range, which is hereinafter sometimes referred to as stabilizing amounts, may comprise from about 0.1 percent :by weight to about 5.0 percent by weight of the lubricating oil. For most oils we have found that concentrations of from about 0.5 percent !by weight to about 2.0 percent by weight of the lubricating oil have proved satisfactory.

If desired or necessary, the inhibitors of the present invention may be used in conjunction with other lubricating oil additives, for example, detergents or dispersants such as metal salts of organic acids, or pour point depressants such as wax naphthalene condensation products, or viscosity index improvers such as high molecular weight resins, or extreme pressure agents such as phosphorous or sulfur containing organic compounds, and the like.

The invention will be further illustrated in greater detail by the following specific examples and test results. It should be understood, however that although these examples may describe in particular detail some of the more specific features of the inventive concept, they are given primarily for purposes of illustration and the invention in its broader aspects is not to be construed as limited thereto.

Example 1 grams of allyl chloride was slowly added to 66 grams of trithiocyanuric acid and 74 grams of potassium hydroxide in a mixture of 300 grams of ethanol and 225 grams of water at room temperature. The reaction mixture was agitated vigorously and kept at a temperature of approximately 40-50 C. for 40 minutes and a yield of 89 grams of triallyltrithiocya-nurate was obtained. This was a clear, yellow, heavy oily product which was dissolved in lubricating oil and tested in an Underwood corrosion test machine. This test comprises heating approximately 1500 cc. of the oil composition for 10 hours at 325 F. in an open container providing for free circulation of air, while portions of the oil are sprayed continuously against freshly sanded bearings. The loss of weight in milligrams per Whole bearing is calculated and the maximum permissible corrosion loss is usually on the order of 250 mgms. The particular tests listed below employed a solventrefined, Midecontinent base oil, SAE 30:

49 grams of potassium hydroxide in 200 ml. ethyl valcohol was added at room temperature to a slurry of 44 grams of trithiocyanuric acid. cc. of water was then added to give a clear twophased liquid. Then, 77 grams of allyl chloride was added slowly from a dropping funnel with vigorous agitation. The reaction mixture was cooled in an ice water bath and the temperature kept at about 40 C. After the addition of the allyl chloride, the precipitated potassium chloride was filtered off. The product was stripped up to 170 C. bath temperature with the pressure reduced to 30 mm. The clear yellow residual liquid which was obtained weighed 58 grams, which corresponded to a yield of 78.4%. The product was very soluble in oil and, when added to a lubricating oil and used in the crankcase of an internal combusion engine, proved to be an excellent corrosion inhibitor.

An Underwood test was run at l additive and the bearing weight loss per whole bearing for cadmium-silver bearings was 7 mg., and for copper-lead bearings, it was 12 mg. (See Example 1.)

Example 3 108 grams of benzyl chloride was added slowly dropwise to a mixture of 44 grams of trithiocyanuric acid and 42 grams of potassium hydroxide in 600 cc. of alcohol at room temperature with vigorous agitation. After the addition of the benzyl chloride, the oil bath temperature was raised to 100 C. and held at that temperature for approximately 30 minutes. The potassium chloride which precipitated out was filtered off. The filtrate was a clear yellow solution when hot. On cooling, the tribenzyltrithiocyanurate crystallized out in long white needles. The yield was 109 grams and was calculated to be 78.4%. The melting point of the compound was 76-79 C.

Underwood test results at 1% additive on copper-lead bearings indicated 11 mgms. loss per whole bearing.

Example 4 A solution of 105 grams of cyanuric chloride in 250 grams of dioxane was treated with a solution of sodium ethyl mercaptide (from 62 grams of ethyl mercaptan and 41 grams of sodium hydroxide at a temperature of 35 C.) over a twohour period. The reaction mixture was agitated for an hour further and was then filtered. The dioxane was stripped off over a water bath at 45 C. with a reduced pressure of 35 mm. The residual liquid still contained some unreacted cyanuric chloride which was filtered off. The filtrate was heated at 100 C. for 1; hour until no more cyanuric chloride sublimed. The product was then distilled under vacuum. It was thiethyltrithiocyanurate and boiled at 150l52 C. at 0.7 to 0.8 mm. The freezing point was found to be22.5-23 C. The yield was 162 grams which indicated a percent yield of 61%.

Underwood test results with 0.5% of additive indicated 69 mg. bearing weight loss per whole bearing for cadmium-silver bearings and 22 mg. weight loss per whole bearing for copper-lead bearings. The product was oil soluble and was an excellent corrosion inhibitor when added to a crankcase lubricating oil.

Example 5 205 grams of cyanuric chloride was reacted with 124 grams of ethyl mercaptan and 81 grams of sodium hydroxide at a temperature of 40 C. for 60 minutes to yield 162 grams of triethyltrithiocyanurate. This corresponded to 62% yield. The heavy oily product was dissolved in a solvent refined Mid-Continent base stock lubricating oil SAE 30 and tested in an Underwood corrosion test following the procedures set forth in Ex- Although we have described but a few specific examples of our inventive concept, we consider the same not to be limited to the specific substances mentioned therein but to include various other compounds of equivalent constitution as set forth in the claims appended hereto. It is understood that any suitable changes, variations and modifications may be made without departing from the spirit and scope of the invention.

What We claim is:

1. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lubricating oil having dissolved therein a relatively small amount, sufilcient to reduce the corrosive effect of said composition on metallic elements of an oil-soluble compound having the following structural formula:

in which each of R1, R2 and R3 is a member of the group consisting of alkyl radicals having from 1 to 18 carbon atoms, allyl, aryl and cycloalkyl radicals and hydrogen.

2. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lubricating oil having dissolved therein from about 0.1% by weight to about 5.0% by weight of an oil-soluble corrosion inhibitor having the following structural formula:

in which each of R1, R2 and R3 is a member of the group consisting of alkyl radicals having from 1 to 18 carbon atoms, allyl, aryl and cycloalkyl radicals and hydrogen.

3. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lubricating oil having dissolved therein triallyltrithiocyanurate in an amount sufficient to reduce the corrosive effect of said composition on metallic elements.

4. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lubricating oil having dissolved therein from about 0.1% by weight to about 5.0% by weight of triallyltrithiocyanurate as a corrosion inhibitor.

5. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lubricating oil having dissolved therein triethyltrithiocyanurate in an amount suflicient to reduce the corrosive effect of said composition on metallic elements.

6. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lu- 7 bricatingoil having dissolved therein from about 0.1% by weight to about 5.0% by Weight of triethyltrithiooyanurate as a. corrosion inhibitor.

7. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lubricating oil having dissolved therein tribenzyltrithiocyanurate in an amount sufllcient to reduce the corrosive effective of said composition on metallic elements.

8. A hydrocarbon oil composition comprising a relatively large proportion of a hydrocarbon lubricating oil having dissolved therein from about 0.1% by Weight to about 5.0% by weight of tribenzyltrithiocyanurate as a corrosion inhibitor.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,160,293 Shoemaker May 30, 1939 2,375,733 Kaiser May 8, 1945

Claims (1)

1. A HYDROCARBON OIL COMPOSITION COMPRISING A RELATIVELY LARGE PROPORTION OF A HYDROCARBON LUBRICATING OIL HAVING DISSOLVED THEREIN A RELATIVELY SMALL AMOUNT, SUFFICIENT TO REDUCE THE CORROSIVE EFFECT OF SAID COMPOSITION ON METALLIC ELEMENTS OF AN OIL-SOLUBLE COMPOUND HAVING THE FOLLOWING STRUCTURAL FORMULA: