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United States Department of Agriculture

Agricultural Research Service

Title: Synthesis of Triglyceride Estolides from Lesquerella and Castor Oils

Authors
item Isbell, Terry
item Cermak, Steven

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 23, 2002
Publication Date: N/A

Interpretive Summary: Lesquerella is a winter annual seed oil crop native to the desert southwestern United States and is currently undergoing an intensive research effort for its successful introduction into agriculture. Lesquerella produces a small seed that has 25 - 30% oil which contains 55 - 64% hydroxy fatty acids. Hydroxy fatty acids are useful for the production of a large number of useful products in today's market. One such product where hydroxy oils can be useful is environmentally friendly lubricants. However, the hydroxy oil will require chemical modification to meet the needs of the equipment they will lubricate. This manuscript describes the process for making compounds called triglyceride-estolides. These triglyceride-estolides have properties that make the lubricant work better in cold temperature environments. This new process is very safe and requires no solvents or catalysts (most of which are toxic to the earth) to produce these new materials. Lastly, the chemistry is very simple for making triglyceride-estolides and will add very little cost to the price of the vegetable oil. This efficient method will allow industry to use more oil from farm production.

Technical Abstract: Triglyceride-estolides were synthesized from the hydroxy moieties of lesquerella and castor oils with oleic acid. Complete esterification of the hydroxy oils was possible when a slight excess of oleic acid was employed (1 to 1.5 mole equivalents). The estolides could be formed in the absence of catalyst at 175 C to 250 C under vacuum or a nitrogen atmosphere. The optimum conditions were found to be a reaction that was run under vacuum at 200 C for 12 h for lesquerella and 24 h for castor oil. The lesquerella esterification reaction was completed in half the time as castor and with lower equivalents of oleic acid due to the difunctional hydroxy nature of lesquerella compared to the trifunctional nature of castor. Interesterification or dehydration of the resulting estolides to conjugated fatty acids were not significant side products of the reaction with only a slight amount of dehydration occurring at the highest temperature studied, 250 C. Use of a mineral or Lewis acid catalyst increased the rate of triglyceride-estolide formation at 75 C but formed a dark oil and the reaction did not go to completion in 24 h. Estolide numbers for the reaction and characterization of the products were made by H NMR and 13C NMR. The decrease in the hydroxy methine signal at 3.55 ppm was used to quantitate the degree of esterification by comparing this integral to the integral of the alpha methylene protons on the glycerine at 4.28 and 4.13 ppm.

Last Modified: 7/25/2014
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