US2325040A - Lubricating composition - Google Patents

Description

atented July 27, 1943 UNITED STATES LUBRICATING COMPOSITION PAT'ENT. OFFICE No Drawing. Application May 20, 1941, Serial No. 394,362

5 Claims.

This invention relates to lubricating compositions containing sulfurized esters of polymerized unsaturated acids having conjugated double bonds, and more particularly to lubricating com- .positions containing sulfurized alkyl esters of isomerized and polymerized unsaturated fatty acids having conjugated double bonds.

The compounds of the present invention may be prepared by heating monoalkyl esters of unsaturated fatty acids until they become isomerized and polymerized, substantially as described by one of us in Industrial and Engineering Chemistry 32, 802-808 .(1940) and 33, 86-89 (1941). The resulting isomerized and polymerized esters having conjugated double bonds are then heated with sulfur to produce the corresponding sulfurized esters.

We have found that the sulfurized esters of polymerized unsaturated fatty acids having conjugated double bonds, particularly those containing fro about of sulfur, impart excellent properties to lubricating compositions when incorporated therewith. Sulfurized oils and sulfurized esters have been used in the past in extreme pressure lubricants and as corrosion inhibitors in lubricating compositions generally, but these substances have never been entirely satisfactory due, in large measure, to their relative instability. The advantages of the improved lubricating properties obtained by the use of the sulfurized esters and oils of the prior art were often off-set by the formation of undesirable byproducts resulting from decomposition of the material added to the lubricant. The sulfurized esters of the present invention, however, have been found to produce lubricating compositions of excellent properties with substantially no decomposition of the esters and consequent formation of undesirable by-products.

It is an advantage of the present invention, therefore, that its products are very stable. Little or no sludge formation due to the production of resinous products takes place at the high temperatures prevailing in internal combustion engines, as is the case with the glycerides used in the prior art.

The products of the present invention possess a further advantage in that they are extremely effective corrosion inhibitors and anti-oxidants. The chief cause of corrosion of metal bearings and the like is the decomposition of hydrocarbon oils to form corrosive acids. This decomposition is catalyzed by the metal of the engine and therefore may be substantially reduced or completely eliminated by the presence of a relatively 7 We do not know whether the film formation involves merely a physical adhesion of polar groups to the metal or whether the film is a thin layer of a reaction product of the ester and the metal; the protection obtained may be due in part to both factors.

Addition of the new sulfurized esters of polymerized unsaturated fatty acids having conjugated double bonds to lubricating compositions leads to improved viscosity characteristics and increased oilin'ess properties of the lubricant. A lubricating oil must wet the metal bearing in or der to be effective and accordingly, the best lubricants are those having incorporated therewith a suitable polar compound since certain polar groups appear to have an afiinity for the metal. The esters of the present invention fall into this category of polar compounds. However, we have found that the esters produced from a short chain alcohol and a long chain acid are more desirable in lubricating compositions than those produced from a long chain alcohol and a long chain acid because of the closer packing and orientation of the molecules.

Only a small amount of the esters of the present invention is necessary to impart improved properties to a lubricating composition. We have found about /270, if added alone, or about 3%,

if added with soap, to be effective.

The invention will be described in greater detail in conjunction with the following specific example, it being understood that the invention is not intended to be limited to the details therein set forth.

Example The methyl esters of dehydrated castor oil fatty acids are isomer-Jed and polymerized by heat treatment at 250-300" C. The major porobtained.

Other unsaturated fatty acids than those of dehydrated castor oil may be used in the formation of the ester starting material. We have found the fatty acids of soya bean, linseed, cottonseed, corn, perilla, tung, oiticica, sunflower seed, samower seed, sardine and menhaden oils to be entirely satisfactory. Similarly, the invention is not limited to methyl esters, but other monoalkyi esters as ethyl, propyl, butyl and the like may be utilized.

We claim: i

1. A lubricating composition having incorporated therein a sulturized lower alkyl ester of a polymerized unsaturated higher fatty acid having conjugated double bonds.

-2. A lubricating composition having incorporated therein a suliurized lower alkyl ester of an isomerized and polymerized unsaturated higher fatty acid having conjugated double bonds.

it lubricating composition having incorporated therein a sulfurized lower alkyl ester of a dimerized unsaturated higher fatty acid having conjugated double bonds.

a. A lubricating composition having incorporated therein a small amount of a sulfurized lower alkyl ester of a dimerized unsaturated higher fatty acid having conjugated double bonds, said ester containing from about 1%-15% of sulfur.

5. A lubricating composition having incorporated therein a small amount of the sulfurized methyl ester of dimerized conjugated octadecadienoic acid.

ELMER WILLIAM COOK.

THEODORE FRANKLIN BRADLEY.