US2344395A - Lubricating oil - Google Patents

Description

Patented Mar. 14, 1944 LUBRICATING OIL Serial No. 447,273

No Drawing. Application June 16, 1942,

7 Claims. This invention relates to improved oils, particularly lubricating oil of the crankcase type.

Although lubricating oils of the present invention are highly desirable for use in crankcases of passenger automobiles they areespecially valuable for heavy duty use in truck, bus, airplane, marine and Diesel engines operating for long periods of time at high temperatures.

The principal objects of the invention are to provide a lubricating oil of the heavy duty type which is resistant to oxidation and sludge formation, being non-corrosive to alloy bearings and other metal parts, and free from varnish formation and ring sticking tendencies under the severe conditions of heavy duty service. These objects, and others which will appear hereinafter, are accomplished by us by providing a hydrocarbon lubricating oil containing a diaryloxyalkyl dithiophosphoric acid or a salt thereof. These compounds and their preparation will be described in greater detail hereinafter.

When conventional 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 and objectionable oxidation and decomposition products. Under the high temperature conditions prevailing in the engine these decomposition products polymerize to form lacquer-like deposits on or between the moving parts causing these parts to stick. Even larger quantities of polymerization products remain dispersed in the partly oxidized crankcase oil, and are readily precipitated to form sludge when the engine cools or when fresh oil is added to the engine. These precipitated sludges become caked on heated metal sufaces and out down the effective life of the engine.

employed in internal combustion engines. Alloys composed of copper-lead, silver-cadmium, nickel cadmium, etc. are widely used and are subject to attack by the acidic oxidation products formed in the oil.

Certain anti-corrosion agents which have no detergent properties, have been added to lubricating oils in order to counteract the corrosive effect of the oxidation products of the oil. Although many of the detergents and anti-corrosion agents which have been previously mentioned perform their individual function in lubricating oils the two separate additives do not cooperate to produce a satisfactory anti-corrosion and detergent action when used together. The function of a corrosion inhibitor is to 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 and other corrosive products of the oil. A detergent, as its name implies, operates to remove adhering solids in the metal parts of the engine and thus produce a clean metal surface. Consequently mixtures of detergent with a corrosion inhibitor have proven to be inefiective over any extensive period of time since the detergent action of the sludge inhibitor tends to remove the corrosion inhibitor.

The diaryloxyalkyl dithiophosphoric acids and salts thereof avoid the above described difficulties by possessing not only excellent corrosion-inhibiting properties, but also detergent characteristics, thus enabling us to provide a lubricating oil having a single additive effective to inhibit corrosion, sludge and varnish formation, ring sticking and other difficulties experienced with lubricating oil serving in a heavy duty capacity. These dithiophosphoric acid esters and their salts are surprisingly soluble in lubricating oils and are very stable at high temperatures. Being polar in character they have strong film-forming characteristics and may also be advantageously employed in hypoid greases and other high pressure lubricants. This film-forming tendency also akes these compounds of value in the preparation of slushing oils, their water insolubility further making them highly efficient in these preparations.

The various diaryloxyalkyl dithiophosphates which we have found useful in improving lubricating oils and which may be employed to adntage therein are new compounds having th general formula:

R: II-

dissolved and the evolution of H23 has subsided.

The crude bi(alkyl substituted phenoxyalkyl) dithiophosphoric acid resulting from the reaction may be employed as such in our new lubricating oils or may be first neutralized and added to the oil in the form of a salt.

As will appear from the general formula above we may react P285 with substituted aryloxyalkylol compounds having the general formula:

omou

in which R: is an alkylene group of 2-4 carbon atoms such as CH2CH2,

-CH2CH2CH2-, etc. may be hydrogen or alkyl radicals at least one of the Rs being an alkyl radical the total carbon atoms in both R1 and R2, or in one of the R's alone when the other R is hydrogen, being at least eight. More specifically, when R1 is a propyl radical R2 should be an alkyl radical at least as long as an amyl radical; Bi and R2 may be both butyl radicals or R2 may be a hexyl radicaland R1 an ethyl radical. When R1 is hydrogen then R2 should be a radical of at least eight carbon atoms such as octyl, dodecyl, tetradecyl, octaclecyl, or the like. When the alkyl chains are of shorter length the dithiophosphates become less oil soluble and dififlculty may be experienced in blending the compounds in mineral oil. Specific compounds of this group include 2,4-di-tertiary butyl phenoxyethanol, 4-octyl phenoxyethanol, 4-amyl-2-isopropyl phenoxyethanol, 4-octyl'phenoxypropanol, 2,4-diamyl phenoxyisopropanol, 2,4-diethyl hexyl phenoxyethanol, and others of similar character.

Metal salts of the alkyl substituted phenoxyalkyl dithiophosphoric acids may be prepared by simple neutralization of the bi(alkyl substituted phenoxyalkyl) dithiophosphoric acid with a suitable salt-forming base or by double decomposition. A wide variety of metal radicals including those such as nickel, aluminum, mercury, cadmium, tin, zinc, magnesium, lithium, strontium, calcium, and barium may be introduced by neutralizing the acids with a suitable hydroxide, carbon- As stated before R1 or R:

ate and in some cases sulfide or by double decom-' position of their Na salts with a desired metal salt. Salts of other metals may, of course, be prepared. The alkaline-earth salts of the bi(alkyl phenoxyalkyl) dithiophosphoric acids are preferred as lubricating oil additives.

Preparation of the bi alkyl substituted phenoxyalkyl) dithiophosphoric acids and their salts will now be described in detail by means of the following example in which the preparation of barium bi(2,4-diamyl phenoxyethyl) dithiophosphate is illustrated. Since other alkyl substituted phenoxyalkylols may be reacted with P255 in the same way using similar proportions of materials further description of the preparation of these prod-- ucts is not thought necessary.

parts by weight of 2,4-diamyl phenoxyethanol was stirred and heated for 3.5 hours at 95- C. with 22 parts by weight of finely ground Pass. At the end of this time practically all 01 the Pass had dissolved and the evolution of the H28 subsided. The product, crude bi(2,4-diamyl phenoxyethyl) dithiophosphoric acid, a light brown liquid, was recovered by decantation from the small amount of unreacted Pass.

The barium salt of the above product was prebarium salts the solvent was evaporated, the last of the solvent being removed under reduced pressure. A barium bi(2,4-diamyl phenoxyethyl) dithiophosphate remained as a yellow liquid that was practically insoluble in water but easily soluble in both gasoline and 10-W lubricating oil.

The products prepared as thus described may be added directly to lubricating oils in which they act as detergents, sludge dispersants and corrosion inhibitors. Since they are highly eifective it is necessary to employ only small amounts of the dithiophosphate in the lubricating oil. Ordinarily from 0.1-3.0% of the bi(alkyl substituted phenoxyalkyl) dithiophosphate is sufilcient for oils employed in heavy duty capacity. Although the compounds described are for the most part easily soluble in lubricating oils and may be easily blended therewith it is ordinarily more convenient to first dissolve the dithiophosphate in a lubricating oil in amounts of about 50%. Solutions of the dithiophosphate of this strength in lubricating oils are easily prepared by adding a suitable hydrocarbon lubricating oil to the preparation before all of the solvent has been removed by evaporation. This product may be stored, sold and shipped in this form and need onlyto be blended in mineral oils of suitable grade and in desired proportions to produce a lubricating oil of greatly improved properties.

The bi(alkyl substituted phenoxyalkyl) dithiophosphates may constitute the sole additive in our lubricating oil or it may be used in conjunction with other materials added for special purposes. For example, when blended with alkyl phenyl sulfides, such as barium 2,4-diamyl phen01 monosulfide, they tend to increase the detergency and heat stability of these products in lubricating oils. They also exert solubilizing efiects on the less soluble alkyl esters of dithiophosphoric acid such as barium diamyl dithiophosphate.

The eflectivness of the above described barium salt of bi(3,4-diamy1 phenoxyethyl) dithiophosphoric acid in lubricating oils as a detergent and anti-corrosive constituent may be demonstrated by the following results obtained by subjecting a 10-W grade solvent refined Pennsylvania oil containing 0.4% of the above named barium salt to the standard Underwood oxidation test. In this test 1500 cc. of the oil was heated for hours at 325 F. while continuously spraying portions of the oil against a 2 inch by inch freshly sanded copper strip and 2 freshly sanded alloy bearings while permitting free circulation 01' the air during the operation. Samples of the oxidized oil were then examined for A. P. I. gravity, neutralization number, naphtha insolubies and bearing loss due to the effects of cor- Unnnawoon OXIDATION TEST 5 hours at 325 F.

A. P. I Bearing New gmvny Nephtha tralizainsolubles tion sum End Cu-Pb Ag-Cd Oil-control, no

additive 31.1 21.4 71, 885 0.42 9.41 0ll+0.4% Ba bi(2,4-diamyl phenoxyethyi) ditiliophosphnte. 31.1 29.8 2 40 4 0.3 1.66

These results show the very great effectiveness of the bi(2, i-dialkyl phenoxyalkyl) dithiophosphates in reducing the oxidation of the oil, the formation of the sludge therein and the reduction in the corrosiveness of the oil to alloy bearings.

Another oil containing 0.4% of barium bi(2,4- diamyl phenoxyethyl) dithiophosphate was also tested by the Catalytic Indiana test. This test was conducted in an apparatus consisting of a constant temperature bath maintained at 341 F. in which a number of large glass test tubes were immersed. 300 00. samples of the oil under test were poured into test tubes and air was bubbled through the oll at the rate of 10 liters per hour. sanded strips of a copper-lead alloy were suspended in the oil and bearing corrosion determined by weighing the strips after 70 hours. The results of these tests were as follows:

Oi1control 215 Oil+0.% Ba bi(2,4-diamyl phenoxyethyl) dithiophosphate "+8 (gained) The walls of the test tube cont the all treated with the barium bi(2,4-diamyi wethyl) dithiophosphate were comparatively clean after the test thus showing the detergent action of the additive.

The results of this test not only confirm the results of the previously described Underwood test. but also emphasize the detergent quality of our improved lubricating oil compositions.

' We claim:

1. A lubricating oil composition containing a major portion of a lubricating oil and 0.1-3.0 per cent of a compound having the general formula:

in which R1 and Rz'are members of the group consisting of hydrogen and alkyl radicals at least one R being an alkyl radical the total carbon atoms in R1 and R2 being at least eight, R3 is an alkylene radical containing 2-4 carbon atoms inclusive, X is a member or the group consisting of hydrogen and metal salt forming radicals and n is the valence of X.

2. A lubricating oil composition containing a major portion of a lubricating oil and 0.1-3.0%

by weight of a compound having the general formula:

3. A lubricating oil composition containing a major portion of a lubricating oil and 0.1-3.0% by weight of a compound having the general formula:

in which R1 and R2 are alkyl radicals having a total number of carbon atoms of at least eight, R3 is an alkylene radical containing 2-4 carbon atoms inclusive, X is an alkaline earth metal.

4. A lubricating composition containing a major portion of a lubricating oil and 0.1-3.0% by weight of a compound having the general formula:

in which R1 and R2 are alkyl radicals having a. total number of carbon'atoms of ,at least eight and X is an alkaline earth metal.

5. A lubricating oil composition containing a major portion of hydrocarbon lubricating -oil and 0.1-3.0% of barium bi(2,4-diamyl phenoxyethyl) dithiophosphate.

6. A lubricating oil composition containing a major portion of hydrocarbon lubricating oil and 0.13.0% of barium bi(2,4-dibutyl phenoxyethyl) dithiophosphate.

7. A lubricating oil composition containing a major portion of lubricating oil and 0.1-3.0% by weight of a compound having the general formula:

R1 l RI in which R1 and R2 are alkyl radicals having a 10 total number of carbon atom of at least eight,

ELMER WILLIAM COOK. WILLIAM DAVID THOMAS, JR.