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(4) Ibid., 796,797 (April 15, 1936). (5) Adams, B. A., and Holmes, E. L., J . SOC.Chem. Ind., 54, 1-6T (1935). (6) Adams, B. A,, and Holmes, E. L.,U. S.Patent 2,104,501 (Jan. 4. 1938). (7) Ibid., 2,161,883 (March 28, 1939). (8) Akeroyd, E. I., and Broughton, G., J . Phus. Chem., 42, 343-52 (1938). (9) Austerweil, G., BUZZ. soc. chim., 6 , 55-70 (1939). (10) Austerweil, G., Rev. g i n . mat. color., 42, 201-5, 241-6 (1938). (11) Austerweil, G., and Fiedler, A., Compt. rend., 205, 1235-7 (1937). (12) l’duxiliaire des chemins de fer et de l’industrie, and Austerweil G., Brit. Patent 497,928 (Dec. 23, 1938). (13) 1’Auxiliaire des chemins de fer et de I’industrie, and Austerweil, G., French Patent 832,866 (Oct. 4, 1938). (14) Bhatnagar, S. S.,Kapur, A. N., and Bhatnagar, hf. S., J . I n d i a n Chem. Soc., 16, 249-57 (1939). (15) Ibid., 16, 261-8 (1939). (16) Bird, P. G., Proc. Am. SOC. Testing Materials, Preprint 101 (1938). (17) Bird, P. G., Kirkpatrick, W. H., and Melof, E., J . Am. Water Works Assoc.. 29, 1526-32 (1937). (18) Broughton. G., and Lee, Y. N., J . Phys. Chem., 43, 737-41 (1939). (19) Burrell, H., IND.ENG.CHEM.,30, 358-63 (1938). (20) fitahlissernents Phillips & Pain, French Plttent 819,433 (Oct. 19, 1937). (21) Ibid., 826,408 (March 31, 1938). (22) Goudey, R. F., J . Am. Water Wmks Assoc., 32, 435-55 (1940). (23) Griesshach, R., Beiheft 2.V u . deut. Chem. No. 31,Angew. Chem., 52, 215- 19 (1939). (24) Griesshach, R., Alelliand TeztiZber., 20, 577-9 (1939). (25) Highberger, J. H., IND.ENO.CHEM.,Anal. Ed., 8, 227 (1936).
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(26) Holmes, E. L., Brit. Patent 474,361 (Oct. 25, 1937). (27) I. G. Farbenindustrie A.-G., Brit. Patent 489,173 (July 20, 1938). (28) Ibid., 489,251 (Jan. 2, 1939). (29) Ibid., 489,437 (July 26, 1938). (30) Ibid., 495,032 (Nov.4, 1938). (31) Ibid., 505,186 (May 5, 1939). (32) I. G. Farbenindustrie A.-G., French Patent 814,808 (June 30. 1937). (33) Ibid., 816,448 (Aug. 7, 1937). (34) Ibid., 820,969 ( N o v . 24, 1937). (35) Ibid., 823,808 (Jan. 27, 1938). (36) Ibid., 828,691 (May 25, 1938). (37) Ibid., 830,227 (July 25, 1938). (38) Ibid., 832,725 (Oct. 3, 1938). (39) Ibid., 832,726. (Oct. 3, 1938). (40) Ibid., 838,332 (March 2. 1939). (41) Ibid., 839,999 (April 17, 1939). (42) Kirkpatrick, W. H., (to National Aluminate Gorp.), U. S. Patent 2,106,486 (Jan. 25, 1938). (43) Perniutit Co. Ltd., Brit. Patent 490,799 (Aug. 22, 1938). (44) Perrnutit Co. Ltd.. Hvlrnea, E. L., Holmes, L. E., and Prescott, W. G., Ibid., 506,291 (May 25, 1939). (45) Richter, A., Angew. Chem., 52, 679-81 (1939). (46) Richter, A., Melliand Taztilber., 20, 579-82 (1939). (47) Sheen, R. T., and Kahler, H. L., IND. ENG.CHEM.,Anal. Ed., 8, 127-30 (1936). (48) Urbain, 0. M., and Steman, W. R. (to Charles H. Lewis), U. S. Patent 2,148,970 (Feb. 28, 1938). PRESENTED before t h e Division of Water, Sewage, and Sanitation Chemistry at t h e 99th Meeting of t h e American Chemical Society. Cincinnati, Ohio. This paper desrribes a portion of t h e experimental work submitted b y Grace Boudreaux in partial fulfillment of the requirements for t h e degree of doctor of philosophy.
DEHYDRATED CASTOR OIL An Economic Study D. H. KILLEFFER 60 E. 42nd Street, New York, N. Y.
NE learns about castor oil early in life and what one learns is nnne too pleasant. Actually, that is a small fraction of the story-at most a twelfth-and even that fraction is diminishing as other uscs of this oil increase. For castor oil is valuable for many things and in quantities far
0
larger than a tablespoon measures. Newest, and possibly most important, of these applications is in the field of drying oils, where dehydrated castor oil is proving of great value. The story of this development is fascinating and a splendid illustration of the value of research. Before going into it in detail, it will be well to survey the position of castor oil and its applications before the drying oil phase became important. This will permit us to sketch the background against which the new phase developed and to judge somewhat of the effect it may have in the future.
Uses Castor oil’s uses in the United States before 1938 can be roughly allocated as follows: Medicinal Sulfonatrd oil Artificial leather Lacquc.rs Luhrication hliscellaneous
a yo
25 20
10 17
100 20
These figures represent informed guesses and are not to be given the dignity of statistics. They apply to an annual
average over the past twenty years of some 44 million pounde of oil. Sulfonated castor oils are principally used in textile finishing. In lacquers and artificial leather coatings castor oil isuseful as a plasticizer of nitrocellulose and certain resins. I n lubrication, blown castor oil is mixed with petroleum lubricants and the mixture, among other applications, is used in aviation engines. Included in miscellaneous uses are hydraulic brake fluids (door closers and automotive applications are large), sticky flypapers, synthesis of sebacic acid, and a number of minor uses. All of these applications depend t o an extent on the fact that castor oil does not dry or polymerize. T o form permanent mixtures with petroleum lubricants, i t is necessary to treat castor oil to increase its solubility. Formerly this treatment consisted of blowing air through the heated oil. Among the products of this blowing operation is water. The oil becomes thick in the process, and its solubility in petroleum products increases.
Chemical Nature Ricinoleic acid, the principal acid of castor oil, is peculiar in possessing a hydroxyl group attached to its hydrocarbon chain, which also contains a double bond. The structure of this acid is represented as:
CH,(CH*),CH-CH-CH=.CH(CHt)7COOH I OH
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Several changes occur in the blowing of this oil, one of which is the splitting out from part of the oil of the hydroxyl group along with a hydrogen atom from a neighboring methylene group. If air is used for blowing, some oxidation apparently occurs to destroy the effect of the additional double bond this dehydration produces. I n any case the treated oil is more soluble in mineral oils. To promote this increase of solubility, Ufer (8‘)suggested a small proportion of nonoxidizing mineral acid (containing oxygen) as a catalyst. This accelerates the solubilizing process and avoids thickening by replacing the blowing operation. However, i t does something more. Apparently, the removal of the hydroxyl group is essential to make castor oil soluble, and if it is accomplished by Ufer’s catalytic process, oxidation is prevented and the treated oil has two double bonds in each acid radical. As may be seen from the structural formula, the splitting out of water may occur with hydrogen from either of two neighboring methylene groups, in one case yielding a double bond in the position conjugate to the one already present. This produces a profound change in the nature of the oil. Instead of being a permanent, nonpolymerized oil, its properties approach those of tung oil in drying, film-forming, and polymerizing ability. The acid of tung oil is characterized by three conjugated double bonds. I n the castor oil molecule two conjugated double bonds may be produced by the dehydrating process. About 25 per cent of the double bonds in dehydrated castor oil are apparently in the conjugated position. There may be some difference in this proportion a s produced by different catalyst and treatments, and efforts are being made to increase it. If sulfuric or phosphoric acid will promote this dehydration obviously other catalysts are worth investigating. The patents of Scheiber (6), for instance, describe a treatment consisting of heating and distilling the fatty acids of castor oil i n vacuo and subsequently recombining the product with glycerol. Schwarcman ( 7 ) heats castor oil in the presence of sodium acid sulfate on an inert carrier. Pelikan ( 5 ) forms a sulfuric acid ester through the hydroxyl group and heats to 130-150° C. after partial neutralization. Patents of the Sherwin-Williams Company on the subject have not yet issued, but indications are that an earthy or oxide catalyst is used in the reaction. Forbes and Xeville (1) describe the reactions of a large number of catalysts, including clays and various metallic oxides. On the whole, the reaction appears relatively simple and many substances seem to promote it. There are indications that i t has often been accidentally accomplished, particularly in the use of castor oil as a softening agent in alkyd resins. The presence of acid in the resinifying mixture may be sufficient to produce the change. Meanwhile, patent battles loom to determine priority and validity, and at, least four manufacturers are producing and selling dehydrated castor oil for paint uses. Trade names are “Isoline”, “Dehydrol”, “Synthenol”, and “Castolene”.
Economic Considerations The striking similarity of dehydrated castor oil to tung has been mentioned. Actually it is more like a mixture of tung and perilla oils, for i t dries quickly but to a relatively soft flexible film instead of the hard product of tung oil. But because tung oil is several times more important in the American paint industry than perilla, similarity to the former is of more consequence. By successive chlorination and dechlorination (with hypochlorous acid), i t is possible to produce from castor oil an oil whose acid radical contains three double bonds and which resembles tung oil in all of its properties ( 2 ) . The method of
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hlunzel (4) for accomplishing this result is considered too costly for present application in the United States, although it is said to have been used abroad. The whole development has been given extraordinary impetus by the scarcity and high price of oriental oils caused by the war in China. The price of tung oil has soared from a customary average of 12 to 14 cents per pound to double or treble that figure. At present (August, 1940), tungoilis quoted a t 24.75 cents per pound. Similarly, from like causes, perilla oil went up from an average of 9 to 10 cents per pound to a recent figure (April, 1940) of 21 cents per pound and was down to 17 cents in August, 1940.
Lo
A
I n this situation dehydrated castor oil has quickly assumed a place of importance in the drying oil field. Characteristic of drying oils is their interchangeability through variations in formulation to meet fluctuations in markets (3). Thus, castor oil, whose price over the past decade has averaged about 10 cents per pound and which can be converted to a superior drying oil for 4 cents per pound, or less, was easily fitted to the need. I n August, 1940, dehydrated castor oil sold for 13 cents per pound. It is too early to place its economic position accurately in view of the swift changes still in progress. Several points about dehydrated castor are, however, apparent: ( a ) it can be used to replace either tung or perilla oil in usual formulas appropriately modified ; ( b ) its film is approximately equivalent to that of a mixture of tung and perilla; (c) its speed of drying is close to that of tung oil; ( d ) in admixture with treated soybean oil, i t produces useful paint vehicles; and (e) its film is permanently light in color. Thus it is apparent that the new oil has values which will justify its continued use by the coatings industry even after the causes of the present disturbances in tung and perilla oils have righted themselves. Just how great a part it will form of our future drying oil supply will naturally depend upon many factors which cannot now be evaluated. Probably there will always have to be a differential between the prices of tung and dehydrated castor in favor of the latter to enable it to hold a substantial market. Estimates based on present indications place the probable permanent market for dehydrated castor oil in paints and varnishes a t 25 to 40 million pounds annually, assuming it can be sold for as much as 2 cents per pound less than tung oil. Some believe these estimates high. Others suggest that they are too conservative, and would double or treble them. When such a potential increase in the permanent demand for castor oil is set alongside the fact that production of castor
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oil during the past twenty years has averaged about 44 million pounds, the probable economic effect of this development is striking. A possible increase in demand of 60 to 100 per cent may well require a complete reorientation of the entire castor oil industry and cause a major readjustment in drying oil. Certainly i t justifies a careful examination of the entire situation and thoughtful planning of its future course. As nearly as they can be gotten, the facts of the matter are these: The United States is accustomed to import its drying oils or the seeds from which they are pressed here. I n the first category belong tung, perilla, and oiticica. Tung and perilla oils are imported from the Orient, and efforts to grow them here are interesting but so far have supplied only minor amounts of oil. Oiticica oil comes from Brazil and, in the five years since its first introduction here, is assuming a position of some consequence. Linseed oil is pressed in this country from seed imported largely from the Argentine and Canada in addition to some domestically grown seed.
Sources Castor oil, like linseed, is pressed from imported seeds grown principally in India, Manchuria, and Brazil. Because i t is a useful lubricant in aviation engines, the war in Europe has greatly enlarged demand and has placed a burden on producers of beans. Britain has taken India’s entire production, and Brazil has consequently had to supply the rest of the world. Some demand from Italy and an increased demand from the United States, based largely, if not entirely, on need for the oil for dehydration, have created a stringency in the market for Brazilian castor beans. The average price of castor beans delivered in the United States varied between $34 and $48 per short ton from 1931 to 1937, inclusive (general average, $42). This figure has reached $110 and stands now a t about $48 per ton (August, 1940). Such fluctuations are serious in the new development, and naturally thoughts have turned to growing castor beans in this country: Several important questions arise in this connection which are not easily answered. They are centered primarily around economic questions of yield of beans, harvesting of the crop, and possible by-products which may assist in making the crop profitable. I n the period of the first World War, the demand for castor oil as a lubricant for airplane engines prompted widespread efforts to grow the beans in this country. Although the plants grow well in most locdities in the United States, the crop is not profitable except in regions where the growing season is long. Competition from tropical areas requires that castor farms be practically confined to warm parts of the country where as many as three crops of beans can be harvested each year. I n Florida and the southern part of Texas, the castor plant is a perennial and produces a triple crop as i t does in India and Brazil. Yields of 1000 pounds of beans per acre per annum are reported to be reasonable for these sections. The beans contain 45 to 50 per cent or more of oil. I n selected areas particularly adapted to the plant, there has been substantial advance from an agronomic point of view from the failures of 1917-19. However, the harvesting of the crop presents difficulties which have not yet been surmounted. Castor beans grow in large fruiting heads which when ripe shatter and drop their beans. I n India and Brazil, where human labor is cheap, the beans can be cheaply gathered from the ground. I n the United States this labor item is likely to be high. Common strains do not retain the ripe beans in the pods, and no satisfactory method of harvesting them has been devised. The facts that the plants grow to considerable heights (as much as 30 feet) and that the fruiting heads are generally located in the crown add to the difficulty. New
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dwarf hybrids are reported which hold ripe seeds a week or more and which grow to a height of only 6 or 8 feet.
By-products Obviously a partial, if not a complete, solution of the agronomical problem may be found in profitable by-products from the crop. Three possibilities have so far been discovered, and each is being explored. The rapid growth of the woody plant suggests i t as a source of cellulose. The bast fibers of the bark are particularly attractive, since they are long and strong, in addition to possible use of the wood itself for pulping. The known high toxicity of the ricin present in the beans prevents the use of the press cake from the oil mills as a feed but suggests that it may have a special value, in addition to the fertilizing value of its nitrogen content, as a means of controlling insects which winter in the ground. Among these are two of our worst insect pests, cotton boll weevil and Japanese beetle. If a top dressing of castor promace, put on the ground in early spring before the larvae of these insects mature, can kill them, a substantial value will have been realized. Tests are so far inconclusive. Insects have long been observed to avoid growing castor plants. This observation suggested the use of the leaves of the plant as a source of an insecticide and insect repellent. Attempts to extract the active constituent from the leaves proved unsuccessful, and the method of using them finally adopted consists of grinding the leaves themselves to a stable aqueous emulsion, to which preservatives are added. This insecticide is reported to be highly successful against the insect pests of the citrus groves of Florida and already enjoys an active demand. It possesses the advantage over inorganic poisons that it leaves no toxic residue on the harvested fruits. These and other developments promise to put castor beans among American staple crops and castor oil into the permanent picture of the paint and varnish industry. Especially significant is the potential replacement of a substantial share of the drying oils now imported from a war-torn area by one that can be grown and processed within our own borders.
Acknowledgment Many persons contributed information to this article, especially George W. Priest, H. A. Gardner, R. A. Nagle, E. E. Ware, and H. A. Neville. T o them all the author extends his thanks for kind cooperation.
Literature Cited (1) Forbes, W. C.,and Neville, H. A., IND.ENQ.CHEM.,32, 555 (1940). (2)Gardner, H. A,, Natl. Paint, Varnish Lacquer Assoc., Nov. 2, 1939. (3) Killeffer, D. H.,IND.ENCI. CEEM.,29,1365 (1937). Munzel, F.,Swiss Patent 193,931 (Nov., 1937); French Patent (4) 830.494 (May, 1938). (5) Pelikan, K., et al., U. S. Patent, 2,198,884(April 30,1940). (6) Scheiber, J.,Ibid., 1,942,778(Jan., 1934); 1,979,495(Nov., 1934). (7) Schwarcman, A., Ibid., 2,140,271(Dec., 1938). (8) Ufer, H., Ibid., 1,892,258(Dec. 27, 1932).
Correction-Dilatometer Studies of PigmentRubber Systems Figures 6 and 7 of the article by H. C. Jones and H. A. Yiengst [IND.ENQ.CHEM.,32, 1364-9 (1940)l were inadvertently reversed in publication. The cut which now appears in the second column of page 1356 is really Figure 7 (0.40 micron particle size zinc oxide), and the one now appearing in the first column of page 1357 should be labeled Figure 6 (0.22 micron particle size zinc oxide).
