US2138771A - Lubricating oil - Google Patents

Description

Patented Nov. 29, E938 UNKE'E sra'res mam 2,1383? 1 LUBBICATDNG (DEL Ernest -F. revere,

Texas Company, .tion of Delaware No Drawing.

Beacon, N. Y., assignmto The New York, N. Y., a corpora- Application June 23, 1934,

Eerial No. 732,092

7' Claims.

This invention relates to the manufacture of lubricating oil characterized by a low pour test and/or an increased viscosity index.

The invention contemplates the preparation of mineral lubricating oil having a reduced pour test and other desired qualities from lubricating 011 stock, such as those derived from mixed base and paraflin base crudes and the like, by the addition to the lubricating oil of a pour'point depressant material or wax crystal inhibitor. The invention particularly contemplates the addition higher fatty acid ester of a higher aliphatic alcohol having 6 or more carbon atoms to the molecule, such as mannitan tetrastearate.

The invention also contemplates the preparation of mineral lubricating oil having an in creased viscosity index from naphthene base crudes as well as mixed base and parafin base orudes, by the addition to the a minor proportion of the same fatty acid esters of higher aliphatic alcohols.

Lubricating oil stocks derived from parafiln and mixed base crudes contain appreciable amounts of wax and, therefore, have a relatively high pour test unless a substantial amount of this wax is removed. The removal of this wax is usually accomplished by cold settling, filtration or centrifuging. However, lubricating oil stocks, after dewaxing by these processes, may still retain some wax, and may have a pour test above 15 F. and up to about 40 F. The removal of further quantities of wax further reduce the pour test necessitates expensive further processing.

On the other hand, the presence of a certain amount of wax in a lubricating oil may be beneficial from the standpoint of providing a comparatively flat temperature-viscosity curve. That is, there is a relatively small change in the viscosity of the oil between temperatures of say 100 F. and 210 F. Consequently, it is of advantage to add to the oil a material which will have the effect of reducing the pour test or cold test to the desired extent without the necessity of entirely removing the remaining wax.

I have discovered that a higher fatty acid ester of a higher aliphatic alcohol having 6 or more carbon atoms to the molecule constitutes an efiective material for addition to a partially dewaxed mineral lubricating oil of this character to' lower the pour point thereof. Fatty acid esters, particularly from the saturated higher fatty acids including stearic and palmitic acids, with the nicer aliphatic monohydric alcohols, including lubricating oil of from these stocks in order to.

hexyl, heptyl, octyl and cetyl, and the hexahydric alcohols such as mannltol and sorbitol, are representative of this class of compounds.

In the production of high grade lubricating oils, it is well known that a relatively small change in the viscosity ohthe oil between temperatures of say 100 F. and 210 F., is desirable. In other words, it is advantageous for the oil to have a relatively fiat viscosity-temperature curve, which means that the oil has a high viscosity index as defined by Dean and Davis in their article in Chemical and Metallurgical Engineering, vol. 36, page 618. Improvement in lubricating oils has heretofore been accomplished by refining, as by the use of selective solvents which are effective in extracting or separating naphihenic constituproportions to a naphthene base or parafiin base lubricating oil. is also found to materially increase the viscosity index thereof, without objectionably affecting other desirable properties. When the esters are added to improve the viscosity index of a lubricating oil, a proportion of about 5-15% by weight is generally employed. On the other hand, where reduction in pour point of a partially dewaxed paraffin base lubricating oil is desired, a smaller proportion of such an ester may be employed with resulting economy. For example, as little as of 1% by weight of the ester will effect substantial reduction in pour point, and a proportion range of about to il is generally employed.

By way of example, mannitan tetrastearate was prepared by heating 1 mol of mannitol and 4 mols of commercial stearic acid together under sub-atmospheric pressure at temperatures of 200-250 C. The reaction product was then purified by crystallization from ethyl alcohol, thereby removing free fatty acid. The purified product was then added to a partially dewaxed parafiin base lubricating oil having a pour point A portion of the mannitan tetrastearate prepared as outlined above was added to a naphthene base lubricating oil in the proportion of 5% by weight with the following results:

% naphthene gg ggg base lube oil,

on 5% mannitan totrastearate Saybolt vis. at F 530 499 Saybolt vis. at 210 F 52 54 Viscosity index 2 29 lization from ethyl alcohol, and was dried over calcium chloride. The cetyl palmitate was added to a naphthene base oil in the proportion of 5% by weight with the following results:

' 95% naphthene ggg ggg base lube oil,

on 5% cetyl palmitate Saybolt vis. at 100 F 630 400 Saybolt vis. at 210 F.. 52 51 Viscosity index 2 32. 5

Where the expression paraii'in base lubricating oil is 'used in the accompanying description and claims, it is to be understood that this refers to an oil of the mixed base or Mid-Continent type as Well as an oil of the paraifin base or Pennsylvania type, .unless the contrary appears from the text. 7'

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A lubricating oil comprising a mixture of a petroleum lubricating oil with a minor proportion of a higher saturated fatty acid ester. of mannitol. I

2. Alubricating oil comprising a mixture of a petroleum lubricating oil with a minor proportion of mannitan tetra'stearate.

3. A lubricating oil having avpour point of approximately 5 F. or below comprising a mixture of a partially dewaxed parafiln base lubricating oil normally having a pour point above 15 F. with mannitan tetrastearate in the proportion of about 4. A lubricating oil having a relatively higher viscosity index comprising a petroleum lubricating oil having a relatively lower viscosity index admixed with about 5-15% by weight of a higher saturated fatty acid ester of manni'tol.

5. A lubricating oil having a relatively higher viscosity index comprising a petroleum lubricating oil having a relatively lower viscosity index admixed with about 545% by weight of mannitan tetrastearate. o

6. A lubricating oil comprising a mixture of a petroleum lubricating oil with a minor proportion of a higher fatty acid ester of a hexahydric alcohol selected from the group consisting of mannitol and sorbitol.

7. A lubricating oil as defined in claim 6, in which the ester is substantially devoid of free fatty acid.

ERNEST F. PEVERE.