INDUSTRIAL AND ENGINEERING CHEMISTRY
218
TABLE 11. DIFFERENCES IN CONDUCTIVITY AND SPECIFICHEAT FOR GR-S AND NATURAL RUBBER STOCK Rubber
Conductivity C.G.8. X 1026
Crude GR-8 Pure umGR-8 Treat stock GR-S Tread atook natural
58 68
63 59
Temp. Range,
' F.
99-131 82-129 59-97 58-123
Sp. Heat, Cal./Gram 0.458 0.464
0.383 0.378
Temp. Range, F. 99-27 99-27 99-34 99-27
surface (Table I). Figure 5 shows the results of free sulfur determinations made at the center section of the slabs. From these and similar curves for modulus, hardness, and hysteresis the additional time required for reaching an equivalent state of cure was scaled. This additional time is that required for the thicker sheets to give a state of cure comparable to that of l/le-inch sheet. These additional times for compound H are shown in.Figure 6 as compared with those calculated for a natural rubber tread stock having a diffusivity of 0.014 square inch per minute, and those calculated for compound H, using a diffusivity of 0.0118 square inch, from the values found for specific heat and thermal conductivity as given in Table 11. The difference between these curves and that for compound H is appreciable and indicates that the allowances in use for natural rubber products for increased thicknesses do not apply to GR-S.
Vol. 36, No. 3
It was thought that the difference may be due to differences in thermal conductivity or specific heat. Determinations were made of both properties (Table 11). These differences between GR-S and natural rubber are insufficient to account for the more rapid rate of cure observed in thick specimens. CONCLUSIONS
1. Flat-curing accelerators are thought to function by combining sulfur a t a more rapid rate than the persistent accelerators; thus less sulfur is left t o cause additional stiffening by continued cure. 2. Oven aging of GR-S tread stocks increases modulus and decreases elongation. Tensile strength may be either increased or decreased. The rate of increase of modulus and decrease of elongation is approximately doubled for an 18' F. increase in oven temperature. 3. Less added time is required for GR-S than for natural rubber compounds to cure thick specimens. The difference cannot be explained by differences in specific heat or thermal conductivity values. It may be due to an exothermal reaction. ACKNOWLEDGMENT
The authors wish to thank C. W. Harris of The B. F. Goodrich Company for measurements of thermal conductivities, and 0. R. Fouts of Akron University for specific heat measurements. PRESE~NTEJD before the fall meeting of the Division of Rubber Chemistry, AMERICAN CEEMICAL SOCIETY, in New York. N. Y., 1943.
FANWEED SEED OIL Potential Substitute for Rapeseed Oil J. R. CLOPTONl AND H. 0. TRIEBOLD The Pennsylvania State College, State College, Pa.
Fanweed (Thlaspi arvense) seeds contain 33 to 35% oil. The composition and properties are similar to those of rapeseed oil. Glycerides of both oils are characterized by a high content of erucic acid. Fanweed seed oil glycerides are somewhat higher in linoIeic acid than those of rapeseed oil. Viscosities of the two oils at ordinary temperatures are similar, and their changes in viscosity with temperature are comparable. This property suggests that fanweed seed oil could be used in place of rapeseed oil as a lubricant constituent and for other industrial purposes.
URING 1940 the United States imported 12,919,000 pounds of rapeseed oil (8). Of that quantity 11,595,000 pounds or nearly 90% came from Japan and the Japanese-held territory of Kwantung. Argentina supplied the remaining 10%. Since importations from the East are now impossible, i t would be highly desirable if an oil could be produced in the United States for the same uses as rapeseed. Such a possibility appeared to exist in fanweed seed oil; a study was therefore made of the composition and properties of this oil in comparison with those of rapeseed oil. Fanweed grows abundantly in most of the northwestern and north central states, as well as in southwestern Canada. I n the western United States it is commonly called fanweed, but is known also as Frenchweed or pennycress. Its botanical name is Thluspi arvense, and i t is a member of the Cruciferae, to which rape and members of the mustard family belong. Therefore, i t was to be expected that fanweed seed oil would be similar in properties to rape and mustard oils. Fanweed seeds contain 33 to 35% oil by weight. Test plantings a t the Montana State College show that on irrigated land 1500 pounds of seed per acre can be obtained. The plant is hardy and grows well without irrigation, except on very dry land. 1
Present address, Armour Research Foundation, Chicago, 111.
It matures early (around July 1) making two crops in one season possible. The fanweed attains a height of 12 to 18 inches and can be harvested easily with the usual farm equipment. A yield of 500 to 1000 pounds of oil per acre in one season would compare favorably with other oil-producing crops. PHYSICAL AND CHEMICAL CHARACTERISTICS
The seeds, freed from foreign matter, were ground to pass a 20-mesh sieve. The oil was extracted with petroleum ether (boiling at 30-60' C.) in a modified Soxhlet extractor. Nearly all of the solvent was removed from the oil by distillation. The last traces were removed in vacuo while passing a small stream of nitrogen gas through the oil. The extracted oil was light green and had a mild, pleasant odor and flavor. During storage the color, due to chlorophyll, gradually disappeared, and the oil assumed a golden yellow color. The physical and chemical characteristics of freshly extracted fanweed seed oil are reported in Table I. The values obtained were determined by the commonly accepted methods for fat analysis (1, 7 ) . For comparison, the corresponding characteristics for rapeseed oil, taken from the literature (2,4,5), are given in Table I. The data show that in most instances the values obtained on fanweed seed oil compare favorably with the cor-
1
INDUSTRIAL AND ENGINEERING CHEMISTRY
March, 1944
responding values for rapeseed hat higher index of refraction, iodine number, and the lower solidification point for fanweed seed oil it is more unsaturated than rapeseed oil. These characteristics suggest that fanweed seed oil is more closely related to a semidrying oil than is rapeseed oil. COMPONENT FATTY ACIDS
2B
To compare the compositions of fanweed seed and rapeseed oils, it was necessary to identify and determine the percentage of individual acids comprising the glycerides af the two oils. The oil was saponified with alcoholic potassium hydroxide, and the soaps were washed with ether to remove unsaponifiable matter. The soaps were acidified with sulfuric acid to liberate the fatty acids which were then extracted with ether. The ether extracts were combined and washed with water until free of mineral acid and then dried with anhydrous sodium sulfate. The ether was removed from the mixed fatty acids by distillation under reduced pressure. Methyl esters were prepared by refluxing the mixed fatty acids 3 hours with four times their weight of absolute methanol and a little concentrated sulfuric acid. The ester layer was removed; the alcohol layer was diluted with three times its volume of water and extracted with several portions of ether to remove any dissolved esters. The ether extracts were combined with the ester layer and dried over anhydrous sodium sulfate. The dry methyl esters were then obtained by removal of the ether under reduced pressure. The mixed methyl esters of the fatty acids were then subjected to fractional distillation a t 1 mm. pressure with a fractionating column of the type described by Whitmore and Lux (9),equipped with a total-reflux partial-takeoff distilling head and packed with single-turn glass helices. The bath and jacket were electrically heated, and the temperature was controlled by water-cooled rheostats. The course of distillation was followed by determining the weight and refractive index of each fraction as it was obtained and by plotting a curve showing the refractive indices us. total grams distilled.
TABLE I.
PHYSICAL AND
Specific gravity, d:! Refractive index, n4,S Viscositv Saybolt seconds 20.00 c. 37.8’C. 98.9’C. Kinematic centistokes 20.00 c.
37.8’ C. 98.9’C. Viscosity index Iodine value Saponificstion v ~ 1 1 1 ~ Free f % t t vi c i d value
E s t.e. r.v d ,-, e -.
Unsaponifiable matter, % ’ Soluble tatty acids, yo Insoluble fatty acida, % Reichert Meissl value Polenske value Hydroxyl number Acetyl value Insoluble fatty acids Iodine value Acid ~-value Mean molecular weight Melting point O C. Solidification boint, C. ~~
CHEMICAL CHARACTDRISTICS O F
FANWEED SEEDAND RAPESEED OILS Fanweed Seed Oil
Rapeseed Oil
0.9168 1.4652
0.913-0.917 1.4629-1.4639
426.7 210.2 58.0
432.0 213.5 64.0
92.56 45.40 9.64 157 117.3 177.8 0.8
177.0
1.34
0.15 95.7 0.25 0.00 8.8 8.3 119.3 ism -B 301.3 16-18 10-12
... ... ... @:lo6 168-180 0.36-1.0 0 :8.:1.5
94.’dL96. i 3 0.0-0.79
...
ii17
...
100-106 18 .‘&-io. 0 11.7-13.6
Iodine values and neutral equivalents were determined on each of the fractions obtained during distillation. Using these values together with the fraction weight, it was possible to estimate the esters present in each fraction qualitatively and
219
,
the fatty acid composition
It is significant that the percentage of erucic acid is very high in the glycerides of both fanweed seed and rapeseed oils. This high erucic acid content is responsible for the peculiar characteristics of these oils and also their industrial importance. Fanweed seed oil glycerides have a higher linoleic acid and a lower oleic acid content than those of rapeseed oil. The effect of the increased linoleic acid is more pronounced than the decrease in oleic acid content, as evidenced by the higher iodine number and lower solidification point of fanweed seed oil. TABLE 11. COMPONENT FATTY ACIDSOF FANWEED SEEDAND RAPESEED OILS, IN PERCENT Fatty Acid Myristic Palmitic Oleic Linoleic
Fanweed Oil Trace 1.5 12.5 33.0
Rapeseed Oil Trace 5.0 17.0 24.0
Fatty Acid Linolenic Erucic Lignoceric
Fanweed Oil 0.5 49.0 3.5
Rapeseed Oil 1.0 52.0 1.0
Except for the differences exhibited in the percentages of linoleic and oleic acid, the component fatty acids contents of fanweed seed and rapeseed oils are similar. This suggests that the two oils should show comparable physical and chemical characteristics. POSSIBLE INDUSTRIAL IMPORTANCE
The relatively high viscosity of rapeseed oil, especially after it is blown, has led to its use as a lubricant constituent. The viscosity of fanweed seed oil is almost the same as that of rapeseed oil; if anything, it maintains a slightly higher viscosity a t elevated temperatures than does rapeseed oil. I n view of this fact and of the similarity in composition of the two oils, it appears that fanweed seed oil could be substituted for rapeseed oil as a lubricant constituent. There is good reason to believe that fanweed seed oil could serve as a substitute for rapeseed oil in many other industrial processes such as the manufacture of artgum, rubber substitutes, and materials used in compounding rubber. By proper treatment and blending of fanweed seed oil with drying oils, it might well be used in paints and varnishes and in other products involving drying oils. I n Russia (3, 6) an edible oil has been prepared from fanweed seed grown in Siberia. It seems likely that fanweed seed oil could, with proper purification, be used as a shortening or salad oil along with corn, cottonseed, peanut, and other vegetable oils. I n view of the present shortage of oils in this country the possibilities of mass production and processing of fanweed seed should be investigated. Further work is in progress to determine possible industrial uses of fanweed seed oil. LITERATURE CITED
(1) Assoc. of OfficialAgr. Chem., Official and Tentative Methods of
Analysis, 1940. (2) Hilditch, T. P.,“Industrial Chemistry of Fats and Waxes”, New York, D. Van Nostrand Co., 1941. (3) Ivanov, S., and Troitzkii, N., MasEobolno Zhirovoe Delo, 1, 30-1 (1928). (4) Jamieson, G. S., “Vegetable Fats and Oils”, A. C. S. Monograph Series 58, New York, Chemical Catalog Go., 1932. (5) Lewkowitsch, J., “Chemical Technology and Analysis of Oils, Fats and Waxes”, 6th ed., London, MacMillan Co., 1921. (6) Milashevskii, V., Maslobolno Zhirovoe Delo, 10,46-7 (1932). (7) Schuette, H. A., and Roberts, W. L., IND.ENQ.CHEM.,ANAL. ED., 4,257-9 (1932). (8) U. 5. Tariff Comm., “Fats, Oils, and Oil-Bearing Materials in the United States”, 1941. (9) Whitmore, F. C., and Lux, A. R., J. Am. Chem. SOC.,54, 344854 (1932). JOURNAL Seriea Paper 1187, Pennsylvania Agricultural Experiment Station.
