US2526497A - Mineral lubricating oil containing polysulfides of thiophosphorous and thiophosphoric acid esters - Google Patents

Description

Patented Oct. 17, 1950 MINERAL LUBRICATIN POLYSULFIDES OF AND THIOPHOSPHORIC ACID ESTERS Louis A. Mikeska, Westfield, N. J., assignor to Standard Oil Development Company, a corporation of Delaware G OIL CONTAINING THIOPHO SPHOROUS No Drawing. Original application September 19,

1946, Serial No. 697,919. Divided and this application October 1, 1948, Serial No. 52,419

7 Claims. (01. 252-461)) This invention relates to a mineral lubricating oil and more particularly to a new type of additive which imparts pour stabilizing properties to such oil and improves other properties of the same.

This application is a division of application Serial No. 697,919, filed September 19, 1946, now issued as Patent No. 2,471,115, which is in turn a continuation-in-part of application Serial No. 653,152, filed March 8, 1946, now issued as Patent No. 2,443,264, granted June 15, 1948, which is a division of application Serial No. 523,091, filed February 19, 1944, now abandoned.

In accordance with the present invention a new class of organic compositions are described which are useful as additives for mineral lubricating oils, particularly those which are used in internal combustion engines, in which they act as pour depressing and pour stabilizing agents, also as inhibitors of oxidation. 4

The new class of additives have been found not only to be effective in substantially reducing the ASTM pour point of a lubricating oil, but in stabilizing the pour point, thus providing a stable lubricating oil which will not solidify under conditions of fluctuating temperature involved in normal outdoor conditions. The new additives of the present invention have been submitted to tests which simulate the normal varying temperature conditions encountered in winter field service, and satisfactory results were obtained from their use, as will be explained more particularly hereinafter.

In serving as inhibitors of oil deterioration, the new additives aid in the prevention of ring sticking, piston skirt varnish formation, deposition of sludge, and the like. They are particularly useful in inhibiting the normal corrosiveness of the oil when in contact with copper-lead, cadmiumsilver and other similar bearings, now widely used in automotive engines,

The'new class of compounds which are employed as additives in accordance with the present invention are organic compounds containing both phosphorus and sulfur and may beconsidered as polysulfide derivatives of thiophosphoric and thiophosphorous acids, the latter being obtained by reacting a sulfide of phosphorus with a mixture of a wax-phenol and an aliphatic alcohol. It has been found that the reaction product derived from a mixture of a wax-phenol and an alcohol is superior to similar products derived from wax-phenol or other alkylated phenols alonein possessing superior oil solubility. It is believed that the presence of the alcohol prevents the formation of products of too high molecular weight.

When the mixture of wax-phenol and alcohol is reacted with phosphorus pentasulfide, it is believed that the reaction proceeds according to the following equation:

In the above equation R represents the, waxphenol radical and/or, the aliphatic radical from the alcohol, the equation representing a statistical average of reactions among the various molecules. Undoubtedly in many cases the thiophosphoric acid molecule will contain boththe waxphenol and the aliphatic radicals. In forming the poly'sulfide derivatives of such thiophosphoric acid or thiophosphorous acid, the acid is treated with an oxidizing'agent, e. g., iodine, potassium triiodide, ferric chloride, sodium hypochlorite, or oxygen itself, or with sulfur dichloride or sulfur monochloride, to form a disulfide, trisulfide or tetrasulfide, respectively, according to the following equations: 4(RO)2PSH 02 2 R0)lP-s-s 1 0R)l +2Hz0 2(RO)1PSH sol, (R0)zP-SS-S-P(OR)2 21101 2(RO 2PSH s,o12-- aonr-s-fi-s-monn 21101 The wax-phenols employed in accordance with the present invention may be derived in the usual manner by first chlorinating paraffin wax and then reacting the latter with phenol. The aliphatic alcohols which are employed in conjunction with such phenols may be any aliphatic alcohols, particularly suitable examples being methyl alcohol, ethyl alcohol, isopropyl alcohol, octyl alcohol, decyl alcohol, stearyl alcohol, oleyl alcohol,

and the like. The mixture of wax-phenol and alcohol may be reacted with any of the sulfides of phosphorus, such as P283, P285, P483, P467, and the like.

The ratio of alcohol to phenol may be varied within wide limits. The higher the molecular weight of the wax phenol, the higher the ratio has to be in order to obtain satisfactor oil solubility. Generally, a preferred ratio is one to two waxphenol hydroXyl groups to one molecule of alco hol.

In employing the additives of the present invention for use either as pour depressants or as corrosion inhibitors it has been found desirable-to use the same in the proportions of about 0.02% to 3%, preferably about 0.1% to 2%, based on the lubricating oil base stock.

In the following examples are present invention, and tests of the same illustratillustrated methods for the preparation of typical products of the ing their usefulness when compounded with mineral lubricating oils. It is to be understood that these examples are illustrative only and are not to be considered as limiting the scope of the invention in any way.

Example 1.-Preparation of substituted thiophosphoric acid A three-way flask equipped with a stirrer and return condenser was charged with 51 g. of waxphenol (prepared by heating 450 g. of chloroparai'lin containing 14% 01 with 90 g. phenol in the presence of AIC13), 15.8 g. decanol (decyl alcohol), 22.2 g. Pass, and 150 cc. dioxane. (The amounts of wax-phenol and decanol were calculated to provide 2 wax-phenol hydroxyl groups for each molecule of decanol.) The mixture was refluxed until no more H28 was given of? (about 2 /2 hours). The reaction product was then dissolved in ether and transferred into a large beaker containing a volume ofwater approximately equal to the volume of the ether solution. Then while the mixture was rapidly stirred, a slight excess of hydrated lime was added. The mixture was stirred until the aqueous solution remained permanently alkaline to litmus. The ether layer was then separated from the aqueous layer and the extract was dried over calcium chloride. The ether was removed on a steam bath and the residue was taken up with acetone. The small amount of undissolved material was filtered oif and the acetone was removed at 100 C. under 2 mm. pressure. The product was obtained as a soft resin readily soluble in lubricating oils.

Example 2.Preparation of the disulfide derivatire sulfate. On removal of the ether, a viscous reddish brown residue was obtained which was found to be readily soluble in lubricating oils.

Example 3.-Preparation of the trz'sulfide derivatz'oe A portion of the substituted thiophosphoric acid obtained in the preparation of Example 1 was dissolved in an equal volume Of dioxane and was treated with SClz in the ratio of one mol of SC12 to 2 mols of the acid. The mixture was then heated at 80 C. for about 2 hours, whereupon it was poured into water and extracted with ether. The ether extract was then dried over sodium sulfate. On removal of the ether the reaction product was obtained as a viscous brown oil, readily soluble in mineral oils.

Example 4Pour point and pour stability tests of Examples 2 and 3 in a waxy base mineral lubricating oil consisting of an acid-treated Mid-Continent neutral oil with the addition of ti Of Pennsylvania bright stock, this oil having a viscosity of SAE grade and a cloud point of +34 F.

The pour stability of the various oil blends containing the new additives was determined by a test in which the temperature was varied to simulate rather severe winter temperature conditions. More specifically, the samples were first gradually reduced in temperature from room temperature to F. during the first day of the test, then warmed gradually to 45-50 F. during the second day, then held at about 35 F. for two days, these temperatures being close to the cloud points of the oil samples, and finall the temperature was gradually lowered to to F. during the last 24 hours. The temperature at which the oil samples became solid under these conditions was taken as the solid point. The results obtained with the tests applied to the unblended base oil and to the same when blended with various concentrations of the original wax-phenols and with the products of Examples 2 and 3 are shown in the following table:

Additive Concentration Pour Stability (Solid Point), F..

ASTM Pour Oil Blend Point, O

Base Oil Base Oil-l-Wax-phenoL.

Base Oil-l-Product of Base Oil+Product of Example 5.Bearz'ng corrosion test A test was made of the effect of the disulfide product of Example 2 in reducing the corrosiveness of a lubricating oil toward a copper-lead bearing, using a blend containing 1% of the additive in a solvent extracted Mid-Continent parafiinic lubricating oil of SAE viscosity grade. A similar test was made of the unblended base. The test was conducted as follows: 500 cc. of the oil was placed in a glass oxidation tube (13 inches long and 2 inches in diameter) fitted at the bottom with a 4 inch air inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. Two quarter sections of automotive bearings of copper-lead alloy of known weight having a total area of 25 sq. cm. were attached to opposite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. M., thus providing suificient agitation of the sample during the test. Air was then blown through the oil at the rate of 2 cu. ft. per hour. At the end of each 4-hour period the bearings were removed, washed. with naphtha and weighed to determine the amount of loss by corrosion. The bearings were then repolished. (to increase the severity of the test), reweighed, and then subjected to the test for additional 4- hour periods in like manner. The results are given in the following table as corrosion life,-

Bearing Cor- Oil rosion Life,

Hours Base Oil Q. 4 Base Oil +1% Product of Ex. 2 20 The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils but also in the heavy duty type of lubricating oils which have been compounded with such detergent type additive as metal soaps, metal petroleum sulfonates, metal phenates, metal alcoholates, metal alkyl phenol sulfides, metal organo phosphates, thiophosphates, phos- -phites and thiophosphites, metal salicylates,

metal xanthates and thioxanthates, metal thiocarbamates, amines and amine derivatives, reaction products of metal phenates and sulfur, reaction products of metal phenates and phosphorus sulfides, metal phenol sulfonates, and the like. Thus, the polysulfide derivatives of the organo-substituted thio acids of phosphorus may be used in lubricating oils containing such addition agents as barium tert.-octyl phenol sulfide, calcium tert.-amy1 phenol sulfide, nickel oleate, barium octadecylate, calcium phenyl stearate, zinc diisopropyl salicylate, aluminum naphthenate, calcium cetyl phosphate, barium di-tert.- amyl phenol sulfide, calcium petroleum sulfonate, zinc methyl cyclohexyl thiophosphate, calcium dichlorostearate, etc.

The lubricating oil base stocks used inthe compositions of this invention may be straight mineral lubricating oils or distillates derived from paraffinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. The oils may be refined by conventional methods using acid, alkali and/or clay or other agents such as aluminum chloride, or they may be extracted oils produced, for eX- ample, by solvent extraction with Solvents of the The lubricating oils, however they may have been produced, may vary considerably in viscosity and other properties depending upon the particular use for which they are desired, but they usually range from about 40 to 150 seconds Saybolt viscosity at 210 F. For the lubricating of certain low and medium speed Diesel engines the general practice has often been to use a lubricating oil base stock prepared from naphthenic or aromatic crudes and having a Saybolt viscosity at 210 F. of to 90 seconds and a viscosity index of 0 to 50. However, in certain typesof Diesel service, particularly with high speed Diesel engines, and in aviation engine and other gasoline engine service, oils of higher viscosity index are often preferred, for example, up to '75 to 100, or even higher, viscosity index. I

In addition to the materials to be addedaccording to the present invention, other agents may'also be used such as dyes, pour depressors, heat thickened fatty oils, sulfurized fatty oils, organo metallic compounds, metallic or other soaps, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, voltolized fats, voltolized mineral oils, and/ or voltolizedwaxes and colloidal solids such as graphite or zinc oxide, etc. Solvents and assisting agents, such as esters, ketones, alcohols, aldehydes, halogenated or nitrated compounds, and the like may also be employed.

Assisting agents which are particularly desirable are the higher alcohols having eight or more carbon atoms and preferably'12 to 20 carbon atoms. The alcohols may besaturated straight and 1 branched chain aliphatic alcohols such as octyl alcohol (CcHrzOI-I), lauryl alcohol (CmI-IzsOl-I), cetyl alcohol (CrcHasOI-I), stearyl alcohol, sometimes referred to as octadecyl alcohol (CISOS'lH), heptadecyl alcohol (CnHssO-H) and the like; the corresponding olefim'c alcohols such as oleyl alcohol; cyclic alcohols, such as naphthenic alcohols; and aryl substituted alkyl type of phenol, sulfur dioxide, furfural, dichlorodiethyl ether, nitrobenzene, crotonaldehyde, etc.

Hydrogenated oils or white oils may be employed as Well as synthetic oils prepared,'for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products. In certain instances cracking coil tar fractions and coal tar or shale oil distillates may also be used. Also, for special application, animal, vegetable or fish oils or their hydrogenated or voltolized products may be employed, either alone or in admixture with mineral oils.

For the best results the base stock chosen should normally be that oil which Without the new additives present gives the optimum performance in the service contemplated. However, since one advantage of the additives is that their use also makes feasible the employment of less satisfactory mineral oils or other oils, no strict rule can be laid down for the choice of the base stock. Certain essentials must of course be observed. The oil must possess the viscosity and volatility characteristics known to be required for the service contemplated. The oil must be a satisfactory solvent for the additive, although in some cases auxiliary solvent agents may be used.

alcohols, for instance, phenyl octyl alcohol, or octadecyl benzyl alcohol or mixtures of these various alcohols, which may be pure or substantially pure synthetic alcohols. One may also use mixed naturally occurring alcohols such as those found in wool fat (which is known to contain a substantial percentage of alcohols having about 16 to 18 carbon atoms) and in sperm oil (which contains a high percentage of cetyl alcohol) and although it is preferable to isolate the alcohols from those materials, for some purposes, the wool.

fat, sperm oil or other natural products rich in alcohols may be used per se. Products prepared synthetically by chemical processes may also be used, such as alcohols prepared by the oxidation of petroleum hydrocarbons, e. g., para-11in wax, petrolatum, etc. p

In addition to being employed in crankcase lubricants the additives of the present invention may also be used in extreme pressure lubricants, engine flushing oils, industrial oils, general machinery oils,process oils, rust preventive compositions, and greases.

What is claimed is:

1. A mineral lubricating oil containing 0.02% to 3% of a compound of the formula where R and R each represents a member of the group consisting of wax-phenyl and aliphatic hydrocarbon radicals, and in any given 'portion'of the compound represents substantial proportions of both such radicals; and where n represents 0 or 1, and :1: represents an integer from 2 to 4.

2. A composition according to claim 1 in which n of the formula represents 1.

3. A composition according to claim 1 in which n of the formula represents 1 and ac represents 3. 4. A mineral lubricating oil containing 0.02% to 3% of a compound of the formula RO\IS| fi/OR P-s,-P RO/ OR where R and R each represents a member of the group consisting of wax-phenyl and decyl radicals, and in any given portion of the compound represents substantially equal numbers of REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,343,831 Osborne Mar. 7, 1944 2,443,264 Mikeska June 15, 1948

Claims (1)

1. A MINERAL LUBRICATING OIL CONTAINING 0.02% TO 3% OF A COMPOUND OF THE FORMULA