Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
2002-03-26
2003-07-08
Carr, Deborah D. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
active
06590113
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for treating oils containing antioxidant compounds containing free hydroxyl groups to form esters of the antioxidant compounds. This invention also relates to a process for treating triglyceride based oils to reduce yellowing of the oils, and oil-based coatings or inks. This invention further relates to a process for treating triglyceride based oils to improve the drying time of the oils, and oil-based coatings or inks. This invention further relates to a process for recovering esters of antioxidant compounds from treated oils.
For as long as triglyceride oils have been used either as triglycerides or modified for coatings such as alkyd based paints, yellowing has been a significant problem and has hindered their effective use or limited their applications. Due to cost and availability, linseed oil in particular has been an oil of choice for coatings, but significantly suffers from this problem. Additionally, the dry time has been a problem due to the presence of tocopherols, which are antioxidants and act as a brake to slow drying. Processing steps to improve dry times generally include blowing or heat bodying the oils or, more recently, conjugation of oils. Tung oil generally dries in a reasonable time and yellows to a lesser extent, but is costly. It is well known that a major contribution to the browning of oils results from the tocopherols present, which, when oxidized, impart a significant brown color. One such oxidization reaction product is known as toco red.
Frying fats are generally stripped by high temperature deodorization to reduce the amount of tocopherols to a minimum in order to improve fry life (U.S. Pat. No. 4,789,554, Scavone et al., “High Temperature Vacuum Steam Distillation Process to Purify and Increase the Fry Life of Edible Oils”). Fry life is determined by the increased browning of the oil until it reaches a quality control maximum, at which point the frying oil is discarded. After tocopherol stripping this browning is significantly reduced and apparent fry life can thus be increased. The paper “Effect of physical refining on selected minor components in vegetable oils”, by Wim F. De Greyt, Marc J. Kellens and Andre D. Huyghebaert, Fett/Lipid 101 (1999), Nr. 11, pp. 428-432 (“De Greyt, et al.”), discloses that deodorization can be used to reduce the level of tocopherols in refined soybean oil from approximately 900-1400 ppm to approximately 500 ppm while maintaining the optimum oxidative stability of the soybean oil. Tocopherols slow the dry time as discussed above. In the book, “Handbook of Coatings Additives” edited by Leonard J. Calbo, Marcell Dekker, Inc., New York, Publisher, 1987, page 490 it is disclosed that “[t]he drying of unsaturated oil films is the result of autoxidation. Drying by autoxidation is a very interesting and useful process. Once a film has been cast, all that is required for the drying to occur is the absorption of oxygen from the air. Like oils, alkyds containing unsaturated side chains dry as a result of the autoxidation process. The stages of drying include an initial quiescent period where the film appears dormant. This is generally attributed to the presence of antioxidants in the oil. The next steps are oxygen absorption, peroxide formation, and peroxide decomposition resulting in the generation of free radicals . . . ”. The free radicals generate and propagate chain reactions, which accelerate drying. The quiescent period referred to above, which is due to antioxidants in the oil, is a direct result of the tocopherols, since these are the major antioxidants present.
The antioxidant activity of tocopherols in oils has been known for a long time. In “The Effects of Various Concentrations of Tocopherols and Tocopherol Mixtures on the Oxidative Stability of a Sample of Lard”, by R. M. Parkhurst, W. A. Skinner and Priscilla Sturm, Journal of the American Oil Chemists Society 45, 641-642 (1968) and “Fat Oxidation at Low Oxygen Pressure: II Kinetic Studies on Linoleic Acid Oxidation in Emulsions in the Presence of Antioxidants”, by R. Marcuse and P. O. Fredriksson, Journal of the American Oil Chemists Society 46, 262-268 (1969) disclose that significant increase in induction time (the period of quiescence) occurs when tocopherols are added to oils, which have been totally stripped. Tocopherols inhibit oxidation by terminating free radical propagation. The induction time, then, is the period when the tocopherols are being oxidized, while terminating this free radical oxidation.
It is currently known in the art to reduce the level of tocopherols in oils by utilizing: (1) removal by high vacuum steam stripping at elevated temperature, commonly referred to as deodorization (a process known as physical refining utilizes similar techniques, namely vacuum stripping of free fatty acids), (2) molecular distillation (also, now utilizing short path high vacuum distillation technology), and (3) adsorption with the use of powdered or granular carbon, which can selectively adsorb a portion of the tocopherols present. A reference with conditions for the use of molecular distillation to recover tocopherols from oils is given by Max Stern, C. D. Robeson, L. Weisler and J. C. Baxter in Journal of the American Chemical Society 69, 869-874 (1947), “gamma-tocopherol I, Isolations from Soybean Oil and Properties”. The conditions used were a centrifugal type molecular still at 240□C and 0.004 mm Hg. Carbon adsorption of tocopherols is known generally in the art but is not widely used because it is too costly and inefficient, and companies that employ such techniques hold their procedures proprietary.
Most triglyceride oils, including linseed oil, contain trace amounts of free fatty acids. Two primary means of removing these free fatty acids are caustic refining and physical refining. Most oils, including linseed oil, are generally caustic refined to remove these trace amounts of free fatty acids. This process is described in “Bailey's Industrial Oil and Fat Products, Vol. 2, Fourth Ed., edited by Daniel Swern, John Wiley and Sons publishers, 1982, pp. 268-288. It should be noted that prior to refining, oils are generally subjected to removal of phosphatides by employing the process known as degumming. The crude oil is mixed with hot water. Often phosphoric acid is added to acidify non-hydratable phosphatides. After a period of contact the phosphatide gums are separated by centrifugation. Following degumming, the caustic refining process involves the addition of an alkali solution of water to the oil with heat to form soaps of free fatty acids by allowing a short residence time to insure complete soap formation. The soaps are then subsequently removed by centrifuges followed by washing steps. Caustic refining is optimally used when the free fatty acid content is low.
Physical refining of oils is used primarily for triglyceride oils, such as palm oil, which contain large quantities of free fatty acids and low levels of phosphatides. For palm oils and other oils having high amounts of free fatty acids, caustic refining results in large losses of neutral oil. Thus physical, or vacuum/steam, refining is preferred. A review of the effect of physical refining is given in De Greyt, et al. De Greyt, et al. described conditions with steam rate, vacuum, temperature and time. De Greyt, et al. focused on tocopherols content and discussed their retention and effect in the physically refined oil products. The vacuum, steam and temperature involved generally do not remove a significant amount of the tocopherols from the oil.
It is desirable to provide an improved process for treating oils that reduce yellowing and drying time of the oils but which does not require the removal of antioxidant compounds containing free hydroxyl groups, e.g. tocopherols. It is also desirable to provide an improved process that permits the facile stripping of esters of antioxidant compounds containing free hydroxyl groups, e.g. tocopherols, from treated oils when needed.
SUMMARY OF THE INVENTION
Accor
Carr Deborah D.
Lathrop & Gage LC
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