US2218618A - Lubricant - Google Patents

Description

I Patented Oct. 22, 1940 UNITED STATES PATENT OFFICE LUBRICANT John G. McNab, Roselle, and Walter T. Watkins, In, Elizabeth, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application February 25, 1939, Serial No. 258,456

9 Claims. (01. 252-32) The present invention relates to lubricants and 10 culty has been met in obtaining suitable acids for the purpose. The common saturated acids of commerce, such as stear ic, margaric, and palmitic, form heavy metal soaps which are not very soluble, especially in paraffinic oils and for this id reason they cannot be used. Naphthenic acids have not proven wholly satisfactory. It has been found that suitable acids can be obtained quite cheaply as a by-product of the oxidation of hydrocarbons, especially waxy hydrocarbons. Materials such as paraflin wax, petrolatum, especially deoiled petrolatum, and highly purified hydrocarbon oils may be oxidized with air or oxygen at relatively low temperatures, that is from about 100 to 150 (3., especially with the use of catalysts such as barium or magnesium soaps, manganese salts and the like, so as to produce large yields of readily distillable acids 0! the molecularweight range, comparable to the acids used in soap manufacture. In addition to this main product, there is a minor amount of an acidic product of uncertain constitution, probably polymerized to a considerable extent, which is substantially undistillable even under vacuum or with steam. This material contains a large percentage of free acids of high molecular weight which can be used for the present purposes, as well as combined acids which may also be used if desired.

The undistillable product referred tov above may be separated from the lower acids and the unoxidized hydrocarbon in a number of diflerent ways, but it has been found preferable to saponify the crude product of oxidation with aqueous caustic under pressure. The mixture obtained is fluid and its tendency to emulsify can be counteracted by the addition of alcohol. The aqueous fluid is then preferably extracted with'kerosene and naphtha so as to remove the unoxidized hydrocarbon and the alcohol may be distilled and recovered. The organic acids are regenerated by reacidification and form a layer which is decanted from the aqueous solution. 7

This organic layer may be purified further and it is then distilled under vacuum or with steam. The distillate is largely composed of acids of 12 to is or 20 carbon atoms and distillation is continued until substantially all of the material that can be vaporized without decomposition is removed, so as to leave as a residue the acidic substantially non-distillable by-product which is the 5' subject of the present invention. The chemical nature of this residue is not fully understood, but

a partial analysis shows the following:

Percent 10 Free acid"; about 30 Esters and lactones Unsaponifiable 5 The total residue as obtained above has a neutralization value of 46 mg. KOH/gr., and a saponification value, which is obtained by refluxing with KOH, of 1'75 mg. KOH/gr. When the refluxing is conducted under pressure, a higher value of 200 mg. KOH/gr. for the saponification number is obtained. From the above, it will be 20 seen that this material is quite different from ordinary fats and waxes. It is substantially free of aldehydes and aldehyde-like bodies and due to polymerization is of considerably higher molecular weight than the wax or other hydrocar- 25 bon from which it is produced, and likewise high- ,water soluble salts of the particular polyvalent metal or metals which are desired. If desired, the total oxidation product may be used and in this case it may be desirable to produce the soda salts by saponification under pressure so as to convert 40 at least a portion of the combined acids into soda soaps as well as the free acids. These soaps may then be purified and converted into heavy metal soaps as disclosed above.

If the total undistillable residue is employed 5 in produring soda soaps, the mixture then contains a considerable amount of unsaponiflable materials and, indeed, even if the roughly purified acids are used there is a certain amount of unsaponiflable material in the heavy metal soapjo mixture, and it has been found desirable to remove at least the larger portion of such impurities. This can be accomplished in several different ways, but the best method is by extrac-- tion or the heavy metal soap with low molecular weight oxygen-containing solvents such as ethyl or methyl alcohol, propyl or butyl alcohols or, if desired, ketones of the same general molecular weights may be employed. In this manner, the nonsaponaceous materials are removed from the heavy metal soaps or, at least, their proportion is so reduced as to make little or no det'riment.

Various polyvalent metal soaps can be made by the above described methods, but the ones which are of the. most importance for the present invention are the alkaline earth metal soaps, principally those of calcium and magnesium and also the soaps of aluminum, lead, zinc, and chromium, as well as the soaps of the 8th Group metals, particularly nickel and cobalt. Among the various advantages obtained by the use of these soaps of the high molecular Weight acids is the greatly increased solubility in various oils, not only of the naphthenic type but likewise of the paraflinic.

Soaps of the different polyvalent metals have somewhat different properties, but all may be added to oils in proportions ranging from about .10 to 3% or even 5% for specific purposes. These soaps dissolve readily and do not tend to separate out or gel on standing as is the case with similar soaps of the commercial fatty acids of the type of stearic acid.

The soaps of the acids as prepared above are also found to have a marked solubilizing effect on soaps of the saturated acids, such as stearic, so that it is quite advantageous in many i11- stances to use mixtures of soaps of stearic or margaric or other acids of the same class together with those of the higher molecular weight, such as described above, without danger of separation on standing. The proportion of the heavy molecular weight soaps necessary to effect the solubilizing depends on various factors, principally on the particular metal soaps employed, the oil in which they are used and also the amount or proportion of the total soap to be put into the oil. In general, equal amounts of the higher and the lower molecular weight soaps, such as thosenof stearic acid, will be sufficient to insure solubility, although less may be employed in many instances and a greater proportion of the heavier molecular weight soap is found to be unobjectionable. In any particu-. lar instance, the most desirable amount can be readily found by experiment.

The soaps disclosed above are especially useful in oils for the lubrication of Diesel engines and are found to reduce wear and generally to improve performance, but especially to maintain a clean enginecondition particularly in the. pisaluminum soaps or of calcium and nickel, or even mixtures of the three or more soaps.

These soaps may comprise the only addition agents which are employed, or they also may be used with other materials. It is found, for example, that small amounts of free stearic acid are quite desirable in the oils for certain purposes; also that heavier compounds, especially corrosive sulfur compounds, are used together with the lead and/ or zinc soaps for extreme pressure purposes. The soaps may be employed along with thickening agents, pour point depressants, sludge dispersing agents or various other materials which have some special use for particular service.

EXAMPLE 1 Calcium soaps were prepared from stearic acid and distilled acids obtained from the oxidation of sweater oil (oil sweated from wax). of these calcium soaps could be dissolved in oil. A calcium soap was then prepared fromthe substantially undistillable bottoms obtainedin the distillation of oxidized wax acids and it was found readily soluble in mineral oils. The aluminum soap of the bottoms was then prepared and found very freely oil-soluble. Aluminum stearate, although initially oil-soluble, causes gel formation on cooling.

EXAMPLE 2 soaps mentioned above were blended in separate samplesof naphthenic oils and a blend of each soap tested in a CFR engine test (375 F. jacket.

temperature, 14-hour test). All soaps produced an improvement in engine performance as will be seen from the data below. After each test the engine was taken down and the pistons carefully examined and rated on the basis of their condition and cleanliness. the separate parts of the piston assemblies, an overall rating was recorded. It should be noted that these ratings are demerits and the smaller numbers indicate superior performance.

CFR Engine tests: 375 F. iacket temperature N either From the rating of v Carbon Overall Rings Ring Ring Varnish 5 Samples demerit stuck slits grooves "3: 2" s Essolubo 30 (Ref) 4. 36 3 8. 33 6. 5 4 5 Oil-H.072, calcium soap of 50/50 (distilled sweater oil acids+undistillable acids) 1. 39 0 1. 00 4. 5 l. 6 0. 5 Oil+l.0% calcium soap 50/50 (stearic acid+undistillable acids) 2. 22 0 l. 33 6. 0 3 2 Oil-[4.0% aluminum soap stearic acid+l0% undistillable acids) 0 00 5 5 3 4 ton assemblies, rings, slits, grooves, and the like, and to reduce gummy or varnish-like'deposits. For use in Diesel engines, the single soaps, particularly those of calcium, aluminum, chromium,

nickel, and cobalt, are quite satisfactory but even EXAMPLEB A 1% blend of the calcium soap prepared from distilled sweater oil acids and undistillable acids in a naphthenic base stock was tested for a long period (almost 500 hours) in 9. Caterpillar Diesel engine. In this testmarked reduction in cylinder wear and improvement in overall engine perrormance were obtained as evident from the attached data.

carbon oxidation product, reacidiflcation and distillation of the volatile acids so as to leave a substantially non-distillable acid as a residue.

Caterpillar single cylinder engine tests Demerits Line. wear per Eng. Run Oman 1000 hrs. 011 Hours dgigggt Ring zone cleanliness C ff varnish on bon an fllte Slits Grooves SGLS Max 01 1 gaphgltignic stocki. i- 100 2. 13 2. 8 1. 69 4. 8 4. 00 4 0 0063 3D Bull 389 S 00 01 16 0 calcium 7 g g g 5 1 i 2 ed 191 2' 2' 4' a 2' 96- o 9 2' 00 2 2 '0016 and undistillable acids).

Cleanliness of ring slits, grooves, lands, and sides.

The. present invention is not to be limited by any specific examples which have been presented herein solely for the purpose of illustration, but only by the following claims in which it is desired to claim all novelty inherent in the invention.

We claim:

1. An improved lubricant comprising a, mineral lubricating oil and a polyvalent metal soap of substantially non-distillable organic acids obtained as a lay-product o! the oxidation or petroleum hydrocarbons.

2. An improved lubricant comprising a mineral lubricating oil and a polyvalent metal soap of substantially non-dlstillable high molecular weight acid obtained as aby-product of wax oxidation.

3. An improved lubricant comprising a mineral lubricating oil and .1 to 5% 01 a. polyvalent metal soap of a substantially non-distillable organic acid obtained by neutralization of a crude hydro- 4. Product according to claim 3 in which the soap is an alkaline earth metal soap.

5. Product according to claim 3 in which the soap is a calcium soap.

6. Product according to claim 3 in which the soap is a cobalt soap.

'7. Product according to claim 3 in which the soap'is a soap of the 8th Group metals.

8. Product according to claim 3 in which the soap is a nickel soap.

9. An improved lubricant for Diesel engines consisting of a mineral lubricating oil and a small amount of a polyvalent metal soap, of the substantially non-distillable high molecular weight acids'obtained as a by-product in the oxidation of waxy hydrocarbons.

JOHN G. MCNAB. ,WAL'IER T. WATKINS, JR.