US2337868A - Inhibitor and process of making same - Google Patents

Description

1943- A. w. BURWELL ETAL Q 2,337,868.

INHIBITOR AND PROCESS OF MAKING SAME Filed Dec. 2, 1940 Patented Dec.-

INHIBITOR AND PROCESS OF MAKING SAME Arthur W. Bur-well and James Allan Camelford,

Niagara Falls, N. Y., assignors to Alox Corporation, New York, N. Y., a corporation of New York Application December 2, 1940, Serial No. 368,288

6 Claims.

This invention relates to the lubricating compositions art, and is particularly concerned with the provisions of lubricating compositions consisting essentially of lubricating oil and relatively small amounts of thio-alkyl derivatives of oxygenated saturated aliphatic compounds (alcohols, alcohol-ketones, ketones, hydroxy carboxylic acids, and alkyl esters of such acids, of relatively high molecular weights) derived from mineral hydrocarbonaceous mixtures (e. g., petroleum oils and/or waxes) by the controlled partial oxidation of the latter in liquid phase. The invention is concerned with processes for the production of such thio-alkyls, with the thio-alkyls per se, and with lubricating compositions containing such thio-alkyls.

It is known that some highly refined lubricating oils, more particularly paraflinic oils refined by selective solvent methods of refining, tend in use to form sludge and/or to acquire corrosive properties toward, for example, bearing metals with which they are in contact. Thus, it is known that some crankcase oils, initially free from corrosive constituents, in course of use develop corrosive properties towards copper-lead, cadmiumsilver, and other bearing alloys, and form objectionable sludge in the presence of some metals. In the case of relatively high-speed Diesel engines it heretofore has been considered necessary to use only babbitt as the bearing alloy, because babbitt is less sensitive-than, say, copper-lead hearing alloyto the corrosive action of the low molecular weight acids formed in the oil by oxidation of the latter in the crankcase, and from other decomposition products.

It is an object of the present invention to provide a thio-alkyl additive which, when added in small amount to a highly refined lubricating oil, prevents or delays sludge-formation and corrosive-formation therein during use. Another object of invention is the provision of lubricating oil compositions which can be used in the crankcases of internal combustion engines employing bearing alloys sensitive to corrosion.

U. S..Patent No. 1,863,004 to Arthur W. Burwelldiscloses improving the oiliness of crankcase oils by the incorporation therein of an oilsoluble addition material consisting essentially of a mixture of high-molecular weight aliphatic oxygen-containing compounds including free saturated aliphatic carboxylic acids, said mixture being obtainable by the controlled, liquid-phase, partial oxidation of a mixture of hydrocarbons of mineral origin (e. g., petroleum wax and/or oil). Said patent discloses that the described oxidation procedureyields oxygen-containing compounds classifiable as "saponifiables (typified by free saturated aliphatic carboxylic acids, and lactones and esters thereof) and unsaponlfiables (typified by alcohols,a1cohol-ketones and ketones), and that the "addition material" may consist exclusively of the saponifiables" portion or may be composed of saponifiables in admixture with unsaponifiables. U. S. Patent No. 2,128,523 to Arthur W. Burwell discloses the prevention of corrosion of metal surfaces by filming them with a composition containing the aforesaid unsaponifiables, and his Patent No. 2,110,- 078 discloses as an "oiliness agent for lubricating Diesel engines a mixture of non-acidic, partially oxidized saturated aliphatic chainhydrocarbons of more than 5 carbon atoms each, including alcohols, alcohol-ketones, ketones, lactones and esters, produced by theBurwell oxidation process.

We have found that thio-allryl products-compatible with refined mineral lubricating oilshaving both sludge-inhibiting and corrosion-inhibiting properties, may be produced by treat- 0 ing with phosphorus hepta sulphide (P481) at an elevated temperature of the order of 250 to 300 F., the oxygenated hydrocarbons mixtures produced by the process described in the aforesaid Burwell Patents Nos. 1,863,004. 2,110,078 and 2,128,523. That is to say, we have found that these oxygenated hydrocarbonswhlch heretofore had been known to inhibit corrosion and/or to enhance oilinessmay have sludging-inhib iting properties conferred upon them by reacting them with phosphorus hepta sulphide under conditions to form thio-alkyls of the same-and that the resulting reaction products, when freed from components soluble in water, are trebly valuable additives for refined lubricating oils. The said additive are, in general, mixtures of a plurality of sulphur-containing aliphatic compounds each of relatively high molecular weight (i. e., containing 6 or more carbon atoms to the molecule); these compounds may be broadly designated as thio-alkyls, which term is here employed to embrace thio-ethers, thlo-esters, thin-ketones and polymers thereof, and similar sulphidized oxidation products of mineral hydrocarbons. The type reactions involved are believed to'be representable as follows, the R or R being in each instance an alkyl radical containing from 6 to 24 carbon atoms, and n or m being whole numbers greater than 1:

R- S R (thin-ether) (I) (alcohol) v P431 (2) 2CHi.(CHr) -CH.(CH|) -.C O OH H (bydroxy-carboxylic acid) CHMOH!) a-CE.(CH!) .00 OH The product of Type 2 reaction may, we believe, be called a dicarboxylic acid of an aliphatic thin-ether or a compound comprising two sulphur-linked aliphatic radicals each containing a carboxylic acid group," as well as "thio-ether of an aliphatic carboxylic-acid as indicated above.

Further exemplifying the above, the same treatment with P431, practiced upon normal hexanol, CH3.(CH2)5.0H, results in a 55% yield of di-n-hexyl sulphide, CH3.(CH2) 5-S (CH2) 5.CH3, which is a neutral liquid of distinctly ethereal odor.

We have found, also, that substitution of other phosphorus sulphides for the hepta sulphide of the present process effects an essentially different result: little or no thio-alkyl production is effected, and the reaction products are largely thio-phosphoric acid esters (found to be relatively unstable and readily hydrolizable) and other non-analogous compounds. The phosphorus compounds have the peculiar (and disadvantageous) property of causing a considerable rise in friction, in oils into which they have been introduced, particularly after the oils have undergone some oxidation in the crankcase, and hence are undesirable additives for this further reason. a

The aliphatic thio-alkyl additives of the present invention-which are, as a group, soluble in mineral lubricating oilsare added to the oils in relatively small amount, e. g., in amounts corresponding to from about 0.5% to about 2% by weight of the oils per se. Working within this preferred range, we have found that incorporation of the additive into a refined lubricating oil oi mineral origin serves to inhibit corrosion of metal parts (specifically, of sensitive bearing metals) in contact with the oil in use. to enhance the oiliness of the oil, and to inhibit sludge formation in the oil in use, without imparting disadvantageous friction properties to the oily composition containing it.

The invention will be described in greater detail in the following:

Exaurnr: I

A mixture of non-acidic, unsaponiflable oxidation products of alcoholic, alcohol-ketonic and ketonic constitutions, derived from a 36-49 petroleum distillate by controlled liquid-phase partial oxidation according to the Burwell oxidation process and separation of saponifiables, was reacted with an excess of P487 for three hours at a temperature of 300 F. The resulting dark (reddish) liquid was filtered, treated with sodium carbonate, in dilute aqueous solution, and then washed with hot water until the wash water was neutral. The washed product was an acid-free liquid, of dark wine color, which contained no phosphorus and reacted positively to a test for alkyl thio-ethers and thin-ketones.

EXAMPLE II The procedure of Example I was followed in reacting with excess P481 a mixture of alcohols, alcohol-ketones and ketones from the oxidation of a 45 petroleum distillate by the Burwell process, except that the reaction mixture was maintained at 250 F. (because of the greater volatility of the components).

EXAMPLE III A mixture of the non-acidic unsaponifiables derived from crude scale wax by oxidation according to the Burwell process was extracted with ethyl alcohol to obtain the alcohols, alcohol-ketones and ketones of relat vely lower molecular weight. The extractives w e reacted, as in Example I, with excess P4S'z for three hours at 300 F., the reaction product was filtered warm, and the filtrate was treated and washed, as in Example I, to a neutral product. This latter, upon cooling, solidified to the consistency of the extracted mixture from which it was derived: it was slightly darker in color than the starting material.

The procedure just described was duplicated with the unsaponifiable portion of an oxidized mass obtained from amorphous wax (i. e., Sharples wax) by the Burwell process.

Indiana oxidation tests on the additive materials from Example III abo'ue Two samples of lubricating oil were subjected to the standardized Indiana oxidation procedure (Journal of the Society of Automotive Engineers,

' vol. 34, 1934, page 167, article by Barnard, Rogers,

- the test were of a copper-lead alloy used as bearing metal.

At the end of hours, microscopic'examination of the test pieces was made. Inspection showed that the test piece in sample #1 had corroded slightly: the lead had receded slightly from the surface of the metal. The test piece in sample #2 showed no demonstrable loss of surface lead.

Sample #1 5.05 mg. KOH/gr. Sample #2 3.93 mg. KOH/gr.

Determination of sludge formation at completion of the Indiana test showed the following:

Sample #1 199.8 mg. per gr. oil Sample #2 111.9 mg. per 10 gr. oil

The above test demonstrated that the thioalkyl mixture of Example III inhibited bearing corrosion in a bearing metal known to be very sensitive to corrosion and also materially retarded the rate of sludge formation. The neutralization value of sample #2 at the end of the test was materially lower than that of the oil not containing the additive.

It should be noted. inconnection with the foregoing, that the thio-ketones prepared from ketones containing from about 6 to about 24 carbon atoms per molecule have a relatively high sulphur content: in general, they show very desirable stability from the standpoints of temperature and further oxidation. By further oxidation we refer to the normal oxidation of hydrocarbon oils in use in the crankcase, the progress of which oxidation is retarded by presence of the thioalkyl compounds of the present invention. Also, it is noted that the thio-ester products of the Type 4 reaction above given have a relatively high sulphur content. Our researches tend to indicate that a direct relationship may exist between the relative sulphur contents of the thio-alkyls and their anti-oxidant effects.

As was indicated in Reactions 3 above, the thio-ketone is susceptible, under mild oxidation conditions. to

condensation or polymerization to a cyclic trimer EXAMPLE IV The starting material was a product produced by oxidizing sharples wax, by the Burwell process, to a saponification equivalent of between 100 and 130, subjecting a portion of the, resulting oxidation mass, including both saponifiable and unsaponifiable oxygen-containing compounds, to esterification treatment with methyl alcohol whereby to convert all the esterifiable components of the mass to methyl esters, and removing all water-absorbing materials from the treated mass.

100 parts by weight of the starting material just described was intimately mixed with 10 parts by weight of phosphorus hepta sulphide. These proportions were selected because experience had shown that an excess of unreacted P4S'1 would remain at the end of the reaction, and hence that the concentration was suitable for completion of substitution of sulphur in the starting material. The mixture was maintained at a temperature of 300 F. for 2 hours, with constant stirring. By

the end of the heating and stirring period all visible evidence of reaction had disappeared. The reaction mixture was strained through a very fine sieve, the strained material was washed with l successive amounts of hot water, until no free phosphoric acid remained in the material and the wash water was neutral to alkacid indicator paper, and the washed product was dried.

Exmru: V

The procedure of Example IV was duplicated using, instead of the starting material described therein, the esterified product of the following:

A portion of the oxidation mass described in. Example IV was treated with aqueous sodium hydroxide solution under conditions to insure saponification of the saponifiable constituents thereof. The resulting soaps were separated from th unsaponifiable constituents, the so-separated soaps were decomposed by treatment with a mineral acid whereby the organic acids of the soaps were freed, and the free organic acids were recovered. The recovered free organic acids were esterified, in known manner, with methyl alcohol, and the resulting esters were salted out in order to free them from any residual free acid.

By the end of the two-hour treatment of the above mixture of esters with P487 all visible evidence of reaction had disappeared. The reaction mixture was then strained, neutralized by washing with dilute sodium carbonate solution,

greater inhibiting action (-both as to corrosion and as to sludge formation) than did the product of Example V. Moreover, friction tests demonstrated that the sulphidized products of Examples IV and V enhanced th oiliness of the oils to which they were added in small amounts.

' EXAMPLE VI An oil containing the sulphidized product of Example IV was further tested, for tangent drag, coemcient of friction, and breakdown, as described below and with reference to the accompanying drawing, in which Fig. 1 is a graph representing breakdown characteristics .of two oils; Fig. 2 is a graph representing changes of Breakdown tests on Samples A and B The samples were tested in a lubarometer equipped with brone bearing elements; the journal speed was 500 ft./min. and the pressure was maintained constant at 1000 lbs/sq. in. During the continuance of the test the temperature and power requirements were observed at regular intervals. In each case the test was continued until the lubricating oil film between the rotating shaftand the bearings ruptured. From the beginning of the test to incipient breakdown of sample A at about 290 F. the power requirements of the two were closely similar. Sample A showed complete breakdown at 300 I.- However, sample B did not show incipient breakdown until a temperature of about 420 F. had

been reached, with complete breakdown at 430 F.: between 290 F. and 420 F. the power requirements in the case of sample B did not rise (with increasing temperature) but remained between 26 and 20 watts net.

The breakdown test readings are represented in curves A and B of Fig. 1 of the accompanying drawing.

Coemcz'ent of friction, and tangent drag, tests on samples A and B Figs. 2 and 3 represent the determination of coefficient of friction, and tangent drag, respectively, of tests of samples A and B. For these tests, the lubarometer was run at a journal speed of 500 ft./min. and the temperature was maintained constant at 212 F., while the bearing pressure was progressively increased through the range between 100 and 1000 lbs/sq. in. The observed coefficients of friction, by 100 pound in- The tangent drag values in pounds per square inch, through the same range, were as follows:

Pressure A B It is to be understood that instead of the esterification agent (methyl alcohol) described in Examples IV and V above there may be employed ethyl alcohol, propyl alcohol or other similar estrification agent for converting the esterifiable acidic bodies to alkyl esters. Instead of sodium carbonate solution, described in Example V, we may reduce the acidity of the product (e. g., remove the phosphoric acid, which is one of the reaction products) by Washing the Piss-treated material with an aqueous solution of another mild alkali.

It is to be understood, also, that thio-ether products, equivalent to that described in Example V, may be produced by treating a mixture of the free acids with P487 and thereafter esterifying the acidic groups of the resulting thio-ether compounds with a suitable esterifying agent (e. g., with methyl or ethyl alcohol).

We have found, also, that the aforesaid free acids may be treated with P481 as above described and salts, e. calcium salts, produced from the resulting acidic thio-ethers (or, that salts, e. g., calcium salts, of the free acids may be produced and the salts treated with P481) whereby to produce anti-corrosive lubricity-increasing additives for lubricating oils and anti-corrosive ingredients or greases. Thus, calcium soaps of the Esq-treated free acids are valuable additives for lubricating oils used in high-speed Diesel engines: their presence in such oils inhibits the sticking of the piston rings'and the development of varnish" on cylinder and piston walls, and retards or limits formation of sludge in the oils.

vThe production of calcium salts of the carboxylic acid thio-ethers above described is illustrated below:

Exmrns VII The starting material was a product obtained by the oxidation of crude scale wax by the Burwell process. The total reaction product from the oxidation was utilized and consists of a mixture of carboxylic acids, alcohols. alcoholketones, ketones, lactones, esters and the like.

100 parts by weight of the starting material just described was intimately mixed with 10 parts by weight of phosphorus heptasulphide. Th mixture was heated to a temperature of 300 F. and maintained at that temperature with constant mechanical agitation for a period of 2 hours. At the end of this time all vlsual'evidence of reaction had ceased. The reaction product was then strained through a very fine mesh screen to remove solid aggregates, and the strained materiaI was washed with successive amounts of hot water until the wash water was neutral to a sensitive indicator paper. The product was then dried.

The saponification value of the starting material was 107 mg. per g1. KOH and the saponification value of the dried reaction product was 92 mg. per gr. KOH.

100 parts by weight of this reaction product was then mixed with 412 parts of petroleum lubricating oil. To this was added 8 parts by weight of calcium hydroxide which had previously been dispersed in 15 parts of water. The

. mixture was heated to about 205 F. and maintained at that temperature for about 3 hours, with constant stirring. At the end of this period the temperature was gradually increased until a temperature of about 270 F. was attained; at this point all the water had been expelled. The mass was then cooled. When a small portionof this final product was thoroughly mixed with previously neutralized ethyl alcohol a very definite alkaline reaction was observed. Analysis of the product showed an equivalent of 1.79% CaSOs in the mass.

The resulting calcium soap concentrate, which was roughly equivalent to a 20% concentrate of the calcium soap of the sulphidized reaction product, was readily soluble in several types of hydrocarbon lubricating oils in amounts equivalent to 10% of the starting oxygenated hydrocarbon material.

A lubricating oil composition particularly desirable for use as a Diesel engine lubricant consists essentially of a solution of the aforesaid calcium soap concentrate in a petroleum hydrocarbon lubricating oil (e. g., a high viscosity index petroleum hydrocarbon lubricating oil), the calcium soap content of which composition amounts to from about 0.5 to about 3.0% by weight.

It is to be observed fromthe foregoing that.

The mineral lubricating fraction employed in preparing such a composition may vary from a low viscosity naphthalene-base oil to an extremely viscous paraflinic base oil which has been subjected to drastic selective solvent refining treatment. In a plurality of cases involving use of oils within this range, it has been demonstrated that the addition of a calcium salt of the type above described effected substantial decreases in sludge formation and corrosion of bearing alloys.

It is to be noted, relative to the above example descriptive of a normal calcium soap of the dicarboxylic salt of an aliphatic thio-ether, which calcium soap is believed to have the formula 'di-carboxylic acid compound so to react as to form an acid salt of the type the reaction with P481 may be carried out either (a) with the total oxidation mass which includes acids, alcohols, .alcohol-ketones, ketones, esters and lactones or'(b) with any desired fraction of the total oxidation mass which may, by suitable known manipulation, be separated therefrom.

. It has been found that the hereindescribed thio-alkyl compounds as a group are to a high degree polar compounds which find utility as surface active agents in solutions in media which per se do not possess the property of wetting, or spreading on, surfaces (solid, or liquid). Moreover, it has been found that when a thio-alkyl compound of the present invention is added to a two-component emulsion one of whose components is a solvent for the same, complete and sharp separation of the two phases of the emulsion occurs within a very short period of time.

This application contains subject matter in common with, and is a continuation-in-part of, our application Serial No. 334,036, filed May 8, 1940.

CHa.(OHa)n.J3H.(CHa) .0 OOH HO O C.(CH:) WJJHJCHDmCHa While in the foregoing the use of purely aliphatic compounds has been'referred to in describing and illustrating the present invention, and while it is a fact that the crux of this invention is the concept of conferring additional properties (to wit, sludge-inhibiting and corrosion-inhibiting properties) upon the "oiliness compounds described and/or claimed in the Burwell patents hereinbefore recited by the conversion thereof to thio-alkyl compounds, we note that the invention embraces the possibility of producing from said oiliness compounds" mixed thio-alkyl-aryl compounds, as follows: It is possible to modify the Reaction 1 hereinbefore given by substituting a phenolic, or naphtholic, compound for part of the high molecular weight aliphatic alcohol (R.0H) employed, whereby to form a thio-ether product wherein a high molecular weight alkyl radical and an aryl radical are linked together thus:- R-S-aryl. The conditions for such reaction are essentially the same as those relating to Reaction 1 above. Again, the reaction product in "4" abovelikewise may be modified by substituting an aryl alcohol (e. g., a phenol, or a naphthol) for R, whereby to provide a thio-ester of the following type:

S--aryl R'O/ wherein R' is an alkyl radical containing from 6 to 24 carbon atoms, and aryl means phenyl or naphthyl (substituted or unsubstituted). Such compounds may be produced by reacting the mercaptan corresponding to the aryl alcohol with the carboxylic acid, or by first converting the carboxylic acid to the corresponding thioether and thereafter esterifying with the aryl alcohol, as follows from the description hereinbefore given relative to the all-alkyl thio-ester type products. Such mixed alkyl-aryl thio compounds largely retain the properties of the parent compounds including the property of enhancing the oiliness of a lubricating oil with which they may be associated, and are also useful in inhibiting corrosion and sludging of the lubricating oils.

We claim: 1. Process of producing a thio-alkyl compound,

' which comprises reacting phosphorus hepta sulture, with a mixture of a plurality of different.

relatively high molecular weight, saturated, aliphatic compounds selected from the group consisting of carboxylic acids, hydroxy carboxylic acids, carboxylic acid esters, hydroxy carboxylic acid esters, and lactones of such acids, containing from 6 to 24 carbon atoms.

3. Process of producing acomposition rich in thio-alkyl compounds from a mixture oi oxygenated saturated aliphatic compounds resulting from liquid-phase partial oxidation of a fraction of petroleum, which comprises reacting parts by weight of the latter with about 10 parts by weight of phosphorus hepta sulphide at an elevated temperature of the order of 300 F. until visible, evidence of reaction has disappeared, removing free acid from the reaction mixture, and drying the so-treated reaction mixture.

4. A compound of the formula cnzromnomcm)..coo.x

cmromyhcnrom)...ooo.x wherein .n and m are whole numbers greater than unity, the sum of the 12's and ms being not less than 12 nor more than 48, and X stands for a substituent of the group consisting of hydrogen, an alkyl, radical and a metallic saltforming group.

5. A compound of the formula omrcnonm vnrcnnacoo wherein n and m are whole numbers greater wherein n and m are whole numbers greater than unity, the sum of the ns and m's being not than unity, the sum of the ns and m; being less than 12 nor more than 48. not less than 12 nor more than 48.

6. A compound of the general formula cm(cno..cn.(cm)..coo m1 5 ARTHUR w. BURWELL'.

JAMES ALLAN CAMELFORD. emwnnhemwmacoo um

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