US2423789A - Pour point depressants for lubricating oils - Google Patents

Description

Patented July 8, 1947 POUR POINT DEPRESSAN TS FOR LUBRICATING' OILS Thomas G. Murphy, Franklin, Pa., and Jacob Faust, Belleville, N. J assignors to L. Sonneborn Sons, Inc., a corporation of Delaware No Drawing. Application June 1, 194:4, Serial No. 538,332

This inventicnrelates to new and useful improvements in pour point depressants for lubrieating oils.

Aluminum stearate has inthe past been used as a pour point depressant for waxy petroleum hydrocarbon oils having normally a relatively high pour point due to the wax contained therein.

,The use of aluminum stearate as a depressant, .however, is attended by the disadvantage that the pour point obtained is substantially fugitive and reverts upon storage or in service progressively towards the pour point of the original undepressed oil.

Pour point depression and/or reversion has been conventionally determined in the past by the Well known ASTM test designated as D97-39. This test involves storing the oil at 32 F. and observing the temperature at which the oil loses.

fluidity after predetermined time intervals.

Measured against the ASTM D97-39 method, relatively successful attempts were made to improve the pour depressant and/or reversioncharacteristics of aluminum stearate and similar depressants. This is, for instance, described in U. S. Patent No. 2,308,116 issued to ,I. Silverman, in which the compounding of aluminum stearate depressant with small amounts of sodium mahogany sulfonate results in a depressant which is relatively non-reverting within the test conditions of the aforementioned ASTM method.

Todays'ever increasingly rigid conditions of use to which lubricating oils are subjected and particularly the increasingly more rigid requirements for stability against relatively extreme temperature fluctuations have necessitated the establishment of more exacting test conditions to meet present day requirements of lubricating oil uses. Such testing method is, for instance, the Goodloe and Brown ASTM test (Jan. 1944). In accordance with this test, the oil is heated to --115 F. and cooled to minus 40 F. and the pour point of the oil is recorded as that point on the downward cooling .curve at which the oil loses fluidity. After the oil has reached the temperature of minus 40 F., it is immediately transferred to a bath maintained at plus 30 F. and allowed to rise in temperature until it reaches plus 20 F.

' Then the oil' is again transferred to a bath maintained atminus 30 F. and the pour point recorded as that point on the second downward cooling curve atwhich it loses fluidity. This latter point. called the Stable pour point; The oil is in this manner alternately subjected to relatively high and low temperatures, thus exposing it to *re- "peated drastic temperature jolts in simulation of 2 Claims. (01. 25232.7)

actual service conditions encountered, for example, in aviation and wintry climates.

When tested against this Goodloe and Brown method, it was found that the aluminum stearate metal mahogany sulfonate depressant of the aforementioned Silverman patent is not as stable as was originally assumed. In fact, as shown in the following Table I, reversion of the pour point obtained by this product will occur to a marked degree.

Table I Depressed Pour Point Degrees 1st chilling 2d chilhng from from Reversion +115 F. F. to 40 F. to 30 F.

SAE 10 lfertm aged; oil orig.

our om 20 10 Aluminum stearate+sodium mahogany sulfonate. SAE 40 Ifelln+ggadle oil orig. our om v 1 p p 10 10 Aluminum stearate+sodium mahogany sulfonate.

The pour point measurements of the oil were carried out in accordance with the'Goodloe and Brown method aforedescribed, the oil being first heated to a temperature of 115 F. and chilled to minus 40 F. with a pour point reading at the point of cessation of free flow, the oil thereafter being permitted to rise in temperature to plus 20 F., being again thereafter chilled to minus 30 F. with a second pour point reading at the point of cessation of free flow. In each case, the oil tested comprised 1% of the depressant containing the aluminum stearate and mahogany sulfonate. As shown in Table I, the oils when so tested showed reversion of pour points in each case of 10 degrees.

We have discovered that a substantially permanent lowering of the pour point and a substantlally non-fugitive non-reverting pour point as tested against rigid conditions of drastic temperature fluctuation may be obtained by compounding the aluminum stearate depressant with a hydrocarbon vehicle and phosphorous pentasulfide reacted alkali metal petroleum mahogany sulfonate.

The phosphorous pentasulfid reacted alkali metal petroleum mahogany sulfonate useful in accordance with the invention may be, for example, obtained by reacting a potassium orsodium mahogany petroleumsulfonate in solution of an aromatic solvent of the benzol series with phosphorous pentasulfid until completion of the reaction and removing the solvent. A convenient method for obtaining the mahogany sulfonate pentasulfid reaction product is, for instance, furnished in the following Example I.

Example I water containing sufiicient caustic soda (10% aqueous alkaline solution) to make the entire mixture slightly alkaline to phenolphthalein; the mixture is allowed to settle, the aqueous layer removed and the xylol solution washed With water to remove inorganic impurities and then distilled to remove the solvent; the solvent free product is then dried by heating at about 240 F. The time necessary for completion of the reaction may vary somewhat with circumstances and conditions.

The reaction product, obtained, as for instance described in Example I, may be then incorporated in a suitable hydrocarbon carrier together with aluminum stearate. The order of addition to the hydrocarbon carrier is, as such, not critical.

In accordance with the preferred practice of obtaining the phosphorous pentasulfid mahogany sulfonate reaction product, it is of advantage to procure the same in a form already dissolved in hydrocarbon carrier material. For this purpose, the phosphorous pentasulfid reaction may be carried out with a suitable petroleum mahogany sulfonate product as such dissolved in a hydrocarbon vehicle. This is, foriinstance, exemplified in the following Example II.

Example II 30 parts by weight of sodium mahogany petroleum sulfonate are dissolved in 70 parts by weight of a SAE 40 Penn lubricating oil and 12 parts by weight of phosphorous "pentasulfid are mitted to settle out and the reaction product is then heated after removal of the caustic layer to a temperature of 240 F. to drive out retained moisture. If desired the .reaction product may be further purified for removal of inorganic salts resulting from the reaction by, for .instance, dissolution in benzol, countercurrent washing with water followed by removal of the benzol. a

In making the-depressant in accordance with the invention, a ratioofaluminum stearate to phosphorous pentasulfid reacted ;alkali metal petroleum mahogany sulfonate 'of from 1011' to 4 2/1 is preferred, the latter ratiobeing the most satisfactory.

When preparing the phosphorous pentasulfid reacted mahogany petroleum sulfonate product in the form of its hydrocarbon solution, it is of advantage to useas a starting material a mahogany petroleum sulfonate in solution in what is termed retained oil as such solution is the conventional product normally obtained in the manufacture of these substances.

For the purpose of depressing the pour point of a paraffin base oil such as a Pennsylvania grade oil, so much of the depressant prepared in accordance with the invention is added thereto as is equivalent to an amount of aluminum stearate sufficient to appreciably reduce the pour point, of the oil and preferably reduce the same at least 10 below its normal pour point induced by the wax contained therein. Depending on the viscosity of the oil, an amount equivalent to yield in the depressed oil at least .01 to 25% aluminum stearatewill usually suffice. It is generally preferred, however, to procure maximum depression of pour point for a given oil and in most cases, dependingon the viscosity of the oil, approximately .1 to .5% aluminum stearate will produce such result.

In the following Table II reversion tests are tabulated for a series of oils, each containing about 1% of depressant comprising aluminum stearate and phosphorus pentasulfid reacted alkali metal petroleum mahogany sulfonate.

Table II Depressed Four Points Original SAE Designa- Degrees tion Oil $55 2 1st gag 2d gag Reversion +ll5 F. +20 F.

to 40 F. to, -30 F,

. F. Degrees Degrees 25. 20 -20 5:0 25- --20 -20 i0 25 -15 15 i0 25 l5 l5 i0 30 v -15 -15 i0 30 i0 :i:0 .:i:() 30 +5 +5 $0 The pour point measurements vrepresentedrin Table II were carried out in accordance with the Goodloeand Brown test hereinabove described. Whereas, in the case of aluminum stearate and sodium mahogany petroleum sulfonate depressant, illustrated in accordance with Table I, pour point reversions of 10 took place, :the reversion of the product depressed with aluminum stearate and phosphorous pentasulfid reacted sodium mahogany petroleum sulfonate is, zero, i. e., in the latter case the stability is absolute.

Although it ispossible within the scope of our invention to add phosphorous pentasulfid reacted petroleum mahogany sulfonate and aluminum stearate, each as such to the oil, the pour point of which isto'be depressed, it is preferred in normal practiceto add the depressant in the form of a base containing both the aluminum stearate and the phosphorous pentasulfidreacted petroleum mahogany sulfonate in a suitable vehicle or carrier preferably of the petroleum hydrocarbon type. .When usingthedepressantin accordance withthe inventionin the form'of suchbase, it is desirable that the volume of, the hydrocarbon ,oil

carrier is such that it is atl'east sufficient to wet the. entire amount, (of aluminum Lst'earat'e sand dissolve the phosphorous .peritasulfidirea'cted sulfonateproduct. fAjpr'eferre'dTbase, however, should comprise a sufilcient amount of hydrocarbon oil carrier so that the aluminum stearate is substantially dissolved therein. Approximately 30% of the oil carrier will sufiice in the majority of cases for this purpose. In many instances, it is of advantage to use as the carrier that petroleum hydrocarbon oil to which the base or concentrate containing the depressant is to be added for the purpose of reducing its pour point.

When using as the phosphorous pentasulfid reacted petroleum sulfonate component of the base, a mixture of sulfonates as those, for example obtained from the acid treatment of a lubricating oil distillate under sulfonating conditions and containing retained oil as aforedescribed, the latter may serve as the carrier, thus eliminating the necessity for further hydrocarbon oil addition to the base. In most cases, it is preferred to use in excess of 30% and preferably between 45 and 94% petroleum hydrocarbon oil carrier (by weight) for the base.

The aluminum stearate should be present in the hydrocarbon oil carrier to an appreciable extent and preferably at least in or in excess of normally gel forming amounts, i. e., at least or in excess of 4% stearate. The concentration of stearate in the hydrocarbon oil carrier may, however, range from as low as 1% to as high as 48%. In most cases, depending upon the amount of aluminum stearate in the base, amounts of between 2 and 15% of the phosphorous pentasulfid reacted petroleum mahogany sulfonate are recommended for incorporation into the base.

The foregoing description is for the purpose of illustration and not of limitation, and it is therefore our intention that the invention be limited only by the appended claims or their equivalents wherein we have endeavored to claim broadly all inherent novelty.

We claim:

1. A pour point depressant composition for addition to a wax containing petroleum hydrocarbon oil having normally a relatively high pour point due to the wax contained therein comprising in excess of 30% petroleum hydrocarbon oil carrier, and substantially dissolved therein approximately 4 to 48% aluminum stearate and approximately 2 to 15% phosphorous pentasulfid reacted alkali metal petroleum mahogany sulfonate.

2. A pour point depressant composition in accordance with claim 1 in which at least the major portion of said hydrocarbon oil carrier is oil entrained by the alkali metal petroleum mahogany sulfonate in the course of its production by sulfonation of petroleum hydrocarbon stock.

THOMAS G. MURPHY. JACOB FAUST.

REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,308,116 Silverman Jan, 12, 1943 2,350,959 Cook June 6, 1944 2,349,785 Faust May 23, 1944