Postwar Developments in Synthetics J. E D M U N D G O O D Vice President, Woburn Chemical Corp., of New Jersey, Harrison, N . J. T H E manufacture of paints and varnishes is largely a matter of science today, though until comparatively recently the preparation of protective coatings was almost entirely an art. Today the complex and varied specific requirements for paints and varnishes compel the manufacturers to use many more raw materials and to produce many more products with much finer lines of demarcation than any known before. The old-time manufacturers did not have to meet conditions where actinic rays, infrared rays, alkali and acid resistance, salt spray, heat, cold, and other factors were of vital consideration. With our present complex industrial needs it is necessary to prepare products to such rigid specifications and within such narrow limitations, that each paint and varnish is almost a separate industry in itself. Nature's raw materials vary from season to season and according t o the locality from which they are obtained. W e know that the iodine value of linseed oil varies from possibly 165 t o 195, depending on the soil in which the flaxseed is grown, the fertilizer used, the selection of seed, climatic conditions, and other factors. Similar variations occur in natural gums and resins. Today synthetic resins can be made uniform within a narrow range of limits, they can be modified t o meet particular needs, and new ones can be produced as other needs develop· T h e field of the paint and varnish manufacturers has been very much widened b y the development of synthetic resins, and this tendency will no doubt continue after the war. The manufacture of synthetic resins in turn was given increased impetus by fatty acids that were iron-free, waterclear, and of uniform specifications within narrow limits. These high-grade fatty acids were put on the market about ten years ago. Special equipment had to be designed to make them. The next step was further to refine these fatty acids, so that they would not darken in color when subjected t o heat while being made into resins. I t is possible by chemical means t o bleach the acids, but heat will destroy the bleaching effect. The small percentage of ingredients that caused the discoloration had to be removed· 94
T w o developments I believe will come about in the postwar period. One is the fractionation of fatty acids. By removing the nondrying constituents, the iodine value of the remaining portions will be raised, and thus a quicker drying resin will be obtained. Linseed fatty acids consist of approximately 10 per cent palmitic and stearic acids, 10 per cent oleic, 41 per cent linoleic, and 39 per cent linolenic acid. It is comparatively simple to remove the palm^ic and stearic acids, but to separate the oleic, linoleic, and linolenic acids from each other is much more difficult. We have made pure lin-
olenic acid in our laboratories, but it is a. very costly operation. I t may develop that separation by the solvent process will prove the best method. T h e oleic acid, being nondrying, retards the drying time of the linoleic and linolenic. Linoleic acid has a theoretical iodine value» of 180, has good drying properties, almost absolute color retention, and imparts some» flexibility to the films. Linolenic acid with a theoretical iodine value of 270 ha.** great drying properties, but makes a veryhard brittle film with a strong tendency to» yellow. We doubt if either of these> acids alone would make good films, but.
Lighting one of the preheat·» at Wobam Chemical Corp.*» plant at Harrison, N . J., is ome of the first staps in creating dehydrated castor oil and preparing it for further processing.
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b y varying ihe proportions of the various constituents it is possible to obtain practically anything we want in a film. The true measure of the drying properties of an oil is not the iodine value but the position of the double bonds in the molecule. In linoleic acid these bonds are in doublets and in linolenic acid they are in triplets. The other postwar development involving fatty acids in resins is the use of conjugated fatty acids—in fact, some firms have already begun to use them. With the double bonds in the conjugated position these fatty acids take on properties somewhat similar to those of tung oil fatty acids. Because of their increased polymerizing speed, alkyds can be prepared in less time and this property is imparted to the finished alkyd as well. Such alkyds have greater thermosetting speed than alkyds made from natural fatty acids and tests have shown that this difference of baking speeds is the greater the higher the temperature of baking. Even at ordinary temperatures (on air-drying), the conjugated alkyds are somewhat faster than those made from the natural acids, but not in proportion to their increased bodying and thermosetting tendencies. There are at present three synthetic conjugated fatty acids in commercial production: Isoline fatty acid made from dehydrated castor oil, Conjulin fatty acid made from linseed oil, and Conjusoy fatty acid made from soybean oil. Isoline fatty acid contains about 40 t o 45 per cent each of linoleic and 9,11-octadecadienic acid (the conjugated form of linoleic acid) with only about 7 to 8 per cent of oleic and no linolenic acid. It has color retention t o the highest degree. Tung oil fatty acid contains 70 t o 75 per cent of eleostearic acid (the conjugated form of linolenic acid), about 10 per cent of linolenic acid not conjugated, and about 10 t o 15 per cent of oleic. Its color retention is poor. Conjusoy fatty acid contains about 50 t o 55 per cent of linoleic acid, only about 7 to 10 per cent of linolenic acid, both largely converted to the conjugated position, and about 25 per cent of oleic. Its color retention is very good, but not equivalent t o that of Isoline fatty acid. Conjulin has greater polymerizing speed than the other two acids, but with about 39 per cent of linolenic acid has poor color retention. Conjulin fatty acid more nearly duplicates tung oil fatty acid than a n y other product. Linolenic acid seems to be the chief troublemaker so far as after-yellowing is concerned. A fatty acid or an oil with a smaller linolenic acid content has better color retention. One with no linolenic acid approaches absolute color retention. Incidentally, Heiioiine-D, with no linolenic content, is a fractionated highly refined portion of cottonseed oil which gives results practically identical t o those of sunflower oil fatty acid. Sunflower oil has very good color retention and contains n o linolenic acid, but is n o t available now. Necessity has compelled the industry t o
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After the castor oil has bean put through the preheating process, it is pumped into vacuum chambers where the molecular structure of the oil is changed. This is ac· compllshed by the use of extreme vacuum in conjunction with the presence of certain catalysts. Hourly readings of pressure gages on the vacuum tanks ensure uniformity.
turn to synthetic drying oils during the war. We believe that after the war it will continue t o use these synthetic drying oils, and wiD never be so dependent on tung oil as in the past. Tung oil is the best all-round natural drying ou, but does not run uniformly and manufacturers are obliged to test each lot in order to make compensations for the lack of uniformity. The synthetic drying oils have this uniformity. Numerous synthetic oils have already been developed. We are familiar with the segregated fish oils, segregated linseed oils, pentaerythritol esters, oils fortified with maleic anhydride and other dibasic acids. A majority of these oils give satisfaction when properly handled and for specific purposes, but like any other products have their limitations. So does tung ou or any other oE whether natural or synthetic·
Replacements for Tuns O i l Replacements for tung oil must have substantially the same properties as tung; ©iL It has been necessary to study not only behavior, but aiso molecular structure in order to find out what the peculiar properties responsible for Its behavior are. It is generally accepted) that the conjugated position of the double bonds in the tung oil molecules is largely responsible for its valuable properties. I n making: synthetic drying oils with, similar properties it was necessary therefore to produce oifo in which the double bond* were similarly in a conjugated! posknois m the molecule.
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The first serious attempt to duplicate this molecular structure of tung oil was made with castor oil. The process of dehydrating castor oil (which in its natural state is a nondrying oil) and converting it into a drying oil with characteristics somewhat similar to those of tung oil, consists of removing two atome of hydrogen and one atom of oxygen from the molecule. These three atoms combine t o form water vapor and pass off in that condition. This conversion is made from the whole oil without first converting the oil into a fatty acid and then esterifying the fatty acid. I t thus differs from the Scheiber process. B y this time the industry is thoroughly familiar with dehydrated castor oil, and is well satisfied with the product. W e believe that dehydrated castor oil will continue in use after the war because o>f its inherent properties. Even before the United States was officially in the war a shortage began t o develop in castor oil, because our normal sources of supply for castor beans were Brazil and India, and a shortage in shipping space developed. Although additional shipping space was allotted for the transportation of castor beans as a result of pressure brought to bear b y the National Paint, Varnish and Lacquer Association, the situation became tighter and tighter and b y October 1,1942, i t was necessary to freeze all stocks of castor oil and of dehydrated castor oil. The authorities in Washington decided t h a t as a measure of safety i t was necessary t o accumulate a stockpile of approximately
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After the molecular structure of the castor oil has been changed so that the prodvet is now dehydrated; quite a different substance, the product is piped to huge cooler kettles, where it is cooled off, filtered, and shipped to the many war industries that are in vital need of it. The flow of chill water used in the condensing apparatus is being checked. Quantities of water can be seen at top of tank. 50,000,000 pounds of castor oil, and while accumulating this stockpile very small quantities of dehydrated castor oil were allotted. By this time the stockpile of oil is close to the goal; and with further easing of the situation in the near future more castor oil may be allocated for dehydrating. There were two possible methods for increasing the supply of castor beans: to grow them in this country and to procure increased shipping facilities to get the beans from Brazil. In 1941 the Department of Agriculture planted an experimental crop, which was used as seed to plant more in the year 1942. A year ago the Department of Agriculture expected to arrange to plant about 125,000 to 150,000 acres of castor beans in 1943, from which approximately 125,000,000 pounds of castor oil would be obtained. However, that program was changed by February 1943 to one of growing about 3,000,000 pounds of seed beans to be held in reserve. In the meantime more beans were brought from Brazil and arrangements were made to import 70,000 to
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75,000 tons from Mexico and about double that amount in 1944. If we continue to get large supplie? of castor beans from Mexico we will not have the same transportation problem as if w e depended entirely on Brazil, and the situation therefore may become increasingly easier. Investigation was being conducted at the same time t o see if the tung oil characteristics could be imparted to domestic oil such as linseed and soybean. Out of that work came Conjulin and Conjusoy drying oils. The method of conversion for these oils is different from that of castor oil. In the case of linseed and soybean oils the conjugation is brought about after the glycerol has been removed from the oil molecule. The conjugated fatty acid is then processed and esterified. In isomerizing soybean oil we approach tung oil to about the same degree as i n dehydrated castor oil. The product is color-retentive to a high degree and retains the flexibility of dehydrated castor oil. Progress in connection with the use of Conjusoy has been retarded by the fact that soybean oil for
some time has been allocated only for edible and a few special industrial purposes. Isomerized linseed oil is a much nearer approach to tung oil than is dehydrated castor oil of isomerized soybean oil. The gel time is only a little longer than that of tung oil and its water resistance is at least equivalent to that of tung ' oil. In numerous tests it has shown greater water resistance than tung oil. Its film is tough and hard rather than brittle and it retains flexibility. This oil is a satisfactory substitute for tung oil in the manufacture of insulating varnishes, wrinkle finishes, and baked finishes of all kinds. When used in baked finishes its rate of drying increases much more rapidly than the increase in the baking temperatures, and these finishes can be baked either in the oven or with the infrared ray. Every product has its own peculiarities, and this is true of the conjugated -oils. The cooking procedure, cooking temperature, and use of the proper resins are all a part of successful handling. In general, the resins which react favorably with dehydrated castor oil also react satisfactorily with the isomerized linseed or soybean oils. As the use of these oils becomes more widely extended, new resins no doubt will be developed. Considerable progress has been made in esterifying various fatty acids with different types of the higher alcohols. It is likely that some good oils of this nature will soon be on the market. The increased tempo of scientific advance is some compensation for the terrible destruction of life and property that inevitably comes with war. By the time this war is over many new products wU> have been developed, new raw materials will have come into use, and additional outlets will have been provided for these new materials. The paint and varnish industry will atëb benefit by this progress and will be better prepared than ever to cope with new living conditions. This paper was written before Washington removed the restriction on castor oil. We have been at liberty to use all the dehydrated castor oil we wanted for civilian as well as military uses during the fourth quarter of 1943. It is likely that the arrangement will be continued into the year 1944. According to information supplied to me, the CCC arranged t o buy approximately 200,000 metric tons of castor beans from Brazil and approximately 75,000 metric tons from Mexico during 1943, a total of about 275,000 metric tone, which would produce about 275,000.000 pounds of castor oil. For 1944 it has been announced that the CCC will buy 250.000 metric tons of castor beans from Brazil and 150,000 metric tons from Mexico, making a total of 400,000 metric tons of beans. If all these beans are pressed into oil, we will have in 1944 about 400,000,000 pounds of castor oil, or about ten times what-the country consumed only five years ago. PBB8BMTBD before the fall technical symposium of the Federation of Paint and Varoieh Production Clubs. Cleveland, Ohio, October 23. 1943.
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