US 2544376 A
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Patented Mar. 6, 1951 LUBRICATING OIL CONTAINING A POLYMER OF OLEYL METHACRYLATE John Mann Butler, Dayton, Ohio, assignor to Monsanto Chemical Company, St. Louis, M0,, a corporation of Delaware No Drawing. Application August 21, 1948,
Serial No. 45,582
This invention relates to the improvement of lubricating oils, and more particularly to the reduction of pour points of wax containing mineral oils. More specifically the invention relates to a method of altering the crystallization characteristics of the paraifin wax dissolved in lubricating oils, and avoiding the solidification of the lubricant upon cooling.
Many of the commerciall available petroleum stocks contain high molecular weight hydrocarbon waxes, and the lubricating oil fractions separated by various refining procedures, contain a substantial proportion dissolved therein. Upon cooling these lubricants, the dissolved waxes crystallize in such form that the mass is solidified. It is known that some substances affect the crystallization of the wax and permit the lubricants to retain their fluidity after cooling to temperatures below the normal pour points of the oils.
The purpose of this invention is to provide a convenient and readily available agent for depressing the pour points of lubricating oils. .A further purpose of this invention is to enable the selection of an effective pour point depressant for a wide variety of wax containing lubricating oils.
The pour points of lubricating oils are measured by a standard A. S. T. M. procedure by whicha sample of oil is heated and then gradually cooled while observing thefiuid characteristics of the sample at every 5 F. interval; the temperature being multiples of 5 F. The pour point is the lowest recorded temperature at which the sample is fiuid. The details of the method of determining pour points are set forth in the American Society for Testing Materials Bulletin on petroleum products and lubricants D-9'739.
It has been found that there is a critical rela tionship between the structure of a methacrylic acid ester and the pour point of a wax containing petroleum fraction if effective depression of pour point is to be achieved. In accordance with this invention, a polymer of oleyl methacrylate is used as a pour point depressant for wax containing mineral oils having pour points between 10 F. and +5 F., inclusive. Comparable polymers of saturated esters are not effective and the polymer of oleyl methacrylate will not depress the pour point of oils having pour points higher than +5 F. and lower than 10 F.
In the practice of this invention, the polymerized oleyl methacrylate is prepared by the polymerization of oleyl methacrylate, preferably by the well known thermal polymerization at temperatures between 50 and 150 C., in the pres- 2 ence of --a peroxide catalyst such as benzoyl peroxide, acetyl peroxide, or hydrogen peroxide, if desired. The effectiveness of the polymer as a pour point depressant is not materially affected b the molecular weight of the polymer; the wide range of molecular weight achieved by conventional polymerization operations all appear to have the same or very similar pour point depression. The polymerized oleyl methacrylate may be used in an amount varying from 0.01 to 5 percent by weight, but preferred practice involves the use of 0.05 to 2 percent. The polymer is dissolved in the oil by adding it directly and stirring the mixture until a homogeneous mixture is effected. It is frequently desirable to prepare master batches by dispersing or dissolv ing large amounts of the polymerized oleyl methacrylate in a lubricating stock and thereafter mixing the concentrate with a suitable larger quantity of untreated oil, the proportions being chosen so as to achieve a small but effective proportion of the polymerized oleyl methacrylate in the final lubricant. I
This invention may be practiced by using mixtures of polymeric methacrylates containing predominantly polymeric oleyl methacrylate, or copolymers of mixed methacrylic esters containing predominantly oleyl methacrylate, and substantial proportions of polymers of near homologues, for example, octadecyl methacrylate and linoleyl methacrylate. These copolymers are generally derived by the esterification of methacrylic acid with a mixed alcohol derived from animal or vegetable sources.
The pour depressants may be used in combination with other known depressants and with other modifying agents, such as antioxidants and detergents.
The critical characteristics of the pour point depression of lubricating oils with polymerized oleyl methacrylate are demonstrated by the following examples.
Ezample I These data demonstrate that no pour point depression efiect is achieved in 20 F. pour oil and that an unusually desirable depression is achieved in F. pour oil. A depression efiect is also noticed for pour points below zero, but these are of little commercial value except in special low temperature oils.
Example I! Pour Depres- Polymerized Agent Point, sion,
Oieyl methacrylate -25 25 Octadccyl mcthacrylatc l0 These data demonstrate that a very desirable eifect is achieved by using oleyl methacrylate, but
when the saturated homologue, octadecyl methacrylate, is used, an increase in pour point is produced instead of a. decided depression.
The invention is defined by the following claim:
A lubricating composition which comprises a wax containing mineral lubricating oil of an A. S. T. M. pour point between 10 F. and +5 F., containing dissolved therein from 0.05 to 2 percent by weight of a polymer of oleyl methacrylate, said lubricating oil containing mineral oil as its major increment.
JOHN MANN BUTLER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,091,627 Bruson Aug. 31, 1937 2,129,665 Barrett Sept. 13, 1938 2,407,954 Fenske Sept. 17, 1946