INDUSTRIAL AND ENGINEERING CHEMISTRY
896
Vol. 19, No. 8
SYMPOSIUM: EFFECT OF HEAT, LIGHT, AND OXIDIZING CONDITIONS O N DRYING OILS Papers presented before the Section of Paint and Varnish Chemistry a t the 73rd Meeting of the American Chemical Society, Richmond, Va., April 11 t o 16, 1927
Effect of Foreign Oleaginous Seeds, when Crushed with Flaxseed, on the Drying and Bodying Properties of Linseed Oil By W. H. Eastman and W. L. Taylor WILLIAM 0. GOODRICH COMPANY, MILWAUKEE, \TIS.
D
URING the past decade the industries consuming linseed oil have made great advances, through researches in the fields of physics and chemistry, in more accurately defining the specifications of the oils that would meet their particular requirements. I n consequence the manufacturers of linseed oil have devised methods and processes for refining the raw linseed oil of commerce into a great variety of so-called special oils, each one designed for a specific use. The various refining methods thus developed now permit the removal of the foots, moisture, fats, waxes, and coloring matter natural to raw linseed oil. I n addition, it is possible to lower or raise the free fatty acid content and, by oxidation and heat treatment, to vary the viscosity, the drying time, and the bodying time of the oil. A review of these process improvements of the linseed oil manufacturer, however, would show that heretofore the emphasis has been placed upon the treatment the oil receives after it leaves the presses. That the quality and purity of the flaxseed which is fed to the presses are limiting factors of decided importance, and that many of the qualities of the raw and special oils are determined before any refining is started, have received little attention from the crusher or from those who write specifications. The ordinary raw oil of commerce has been customarily crushed from flaxseed which, after screening, contains from 3 to 6 per cent of dockage-a dockage which on account of the screening methods employed is rich in small oleaginous seeds. Naturally, raw linseed oil has contained varying amounts and kinds of foreign oils. It is obvious that the constants of a pure linseed oil will differ from one containing 3 to 6 per cent of other seed oils. Regular factory tests have shown this. The effects of these foreign oils have received little consideration because it has never been possible to produce on a commercial scale flaxseed that would be free from other oil-bearing seeds. Within the past year, however, cleaning machinery has been adapted to the flaxseed-crushers' requirements which permits the separation of weed seeds from flaxseed according to length and which, when combined with the older methods of separation by sieving and air draft, nom permits the production of oil from flaxseed absolutely free from other oleaginous material. With the production of pure linseed oil on a commercial scale it became a matter of importance to gather data showing how much past variations were due to differences in different lots of flaxseed and how much was due to the presence of impurities. It was, therefore, decided to make a pure linseed oil and a dockage linseed oil under conditions which mould be as closely comparable as possible and run tests on them and on the special oils made from them.
Tests on Raw Oils
Ten thousand bushels of S o r t h American flaxseed were run through a split spout to obtain two 5000-bushel lots of the same quality. Six per cent of dockage-consisting of foxtail, red and black mustard, wild oats, millet, wild buckwheat, pigweed, cow cockle, smartweed, corn cockle, rag weed, sweet clover, vetch, and broken straw-were allowed to remain in the first lot. The second lot was cleaned thoroughly by screening and air draft and then sent through a Carter disc machine and a Carter disc recleaner until tests showed no oleaginous seeds. Old-process oils made with hydraulic presses from these two lots gave the constants shown in Table I. Table I-Constants Iodine number Specific gravity Acid number Saponification number Foots, A. S. T. 31 Refractive index
of Raw L i n s e e d O i l s CLEAXSEED DOCKAGE SEED 185 6 189 5 0 9341 0 9343 1 38 1 96 189 4 188 6 1 1 0 75 1 48 (051) 1 48 (028)
The Wijs iodine tests, the foots, saponification, and acid tests were made according to the methods proposed by the A. S. T. 31. and the Federal Specifications Board. The refractive indices were taken a t 25' C. and the figures in the last three places put in parenthesis for ease of contrast. The drying tests mere made in a glass case shielded from direct sunlight in which mas circulated a current of air maintained at a temperature of 30 * 2" C . and a humidity of 32 * 4 per cent. Color readings are according to the Lovibond scale. The sharpest contrast is in the iodine number and justifies the important place given to this constant in the examination of drying oils. The refractive indices, taken in conjunction with the specific gravities, tell the same story. Slight differences in the other constants would mean little in ordinary control tests, but where careful examination eqtablishes such differences they will appear in later control work. Saponification values of seed oils do not differ widely enough to make clear distinctions possible unless larger percentages of foreign oil are present, in spite of the fact that some oils from weed seeds have saponification values lower than that found in linseed oil. Ordinarily no significance would attach to the differences shown in this respect in Table I, but repeated tests on oils made from these two raw oils showed that these differences persisted. Tests on Boiled Oils
One part of each of the two types of raw oil was made up as two lots of ordinary boiled oil, the analyses of which are shown in Table 11.
I S D U S T R I A L AND ENGINEERING CHEMISTRY
August, 1927
T a b l e 11-Constants of Boiled Oils CLEANSEED DOCKAGE SEED Lot 119 Lot 121 179 8 175 7 Iodine number 0 9416 0 943 Specific gravity 4 12 4 95 Acid number 1 48 (182) 1 48 (17s) Refractive index Drying time, hours 9 9 5 Lot 120 Lot 123 Iodine number 181.4 l 7 i .4 Specific gravity 0.9394 0 9412 Acid number 3.6 4.37 1 . 4 8 (145) Refractive index 11 Drying time, hours 10
As would be expected. the iodine number, acid number, and refractive index vary with the specific gravity of the boiled oil, but a higher iodine number persists with the oils made from clean seed and the difference in drying time is very noticeable. Tests on Blown Oils Further portions of the oil were made u p as oils aged by blowing a t temperatures ranging from 300" to 240" F. (149" to 116" C.), but to as nearly the same final specific gravity as factory conditions allow. The differences given in Table 1x1 show the effects of heat and air upon the refractive index and acid number. The refractive index is much more sensitive t o heat than to oxidation and oil with a high original index will show a high final index. T a b l e 111-Constants BLOWISG EKTEMP ATURE o -r.
O .F .
149
300
138
280
127
260
116
240
LOT
SEED
33 41 34 42 35 43 36 44
Clean Dockage Clean Dockage Clean Dockage Clean Dockage
of Blown Raw Oils
REBRAC-IODINE ACID SAPONIFISPECIFIC TIVE NUM- NUXCATIOK GRAVITY INDEX BER EER NUMBER 0,9509 0.9516 0.9516 0.9504 0.9504 0.951 1 0.9511 0.9606
169.4 167.2 169.1 168.3 170.7 168.1 1.48(264) 1 7 0 . 4 1.48(247) 1 6 9 . 3
1.48(330) 1.48(289) 1.48(291) 1.48(271) 1.48(263) 1.48(260)
2.37 2.75 2.73 2.89 2.70 3.32 2.65 3.12
19.5.9 193.8 194.9 193.2 195.7 195.3 195.4 195.3
I n general, further heating intensifies differences in the blown raw oils, as shown in Table IV. Tubes of oil from the eight batches were heated a t the same time in an oil bath with a double bottom and tubes kept a t the same distance from the sides of the bath. of B l o w n R a w Oils H e a t e d for 90 M i n u t e s at 560-600O F. (293-316' C . ) CLEANSEED DOCKAGE SEED Refractive Refractive BLOWING TEMPERATURE Index Viscosity Index Viscosity C. F. Poises Poises 1.49(239) 57 1.49(20!2) 52 149 300 1,49(2201 46 1.49(111) 28 138 280 1.49(224) 65 1.49(082) 20 127 260 1 49(265) 76 1.49(150) 31 116 240
Table I\-Constants
897
Tests on Varnish Oils
In order to make a further study of bodying qualities the remainder of the original raw oils was made into a neutral varnish oil, thoroughly bleached to produce an oil of the mater-white class, and refrigerated so that it would stand in melting ice for 12 hours without showing any cloudiness. Some data concerning these varnish oils are given in Table T', and the results of varnish tests made on them in Table VI. Table V-Constants CONSTANT Varnish Oil: Iodine number Refractive index Color Supreme (water-white class) : Iodine number Refractive index Color Arctic supreme: Iodine number Refractive index Color
of V a r n i s h O i l s C L E A N S E E D DOCKAGESEED 189.8 1.48(033) 7.7 R
185.6 1.48(023) 7.3 R
189, i 1.48(041) 3 3 R
185.7 1 , 48(026) 3.4 R
191,6 1.48(046) 3.2 R
186.7 1.48(034) 3.3R
T a b l e VI-Varnish T e s t s CLEAN SEED A-LIGHT
VARNISH.
TIME, 90 MINUTES, H E A T , 560-600'
DOCKAGE SEED F
(293-316'
C )
Varnish 1.49(141) 1 49(098) Supreme 1.49(122) 1 49(030) Arctic supreme 1 49(067) 1 49(026) B-HEAVY VARNISH. T I M E , 160 M I N U T E S , HEAT, 66C-6Oo0 F. (293-316' C ) 1 49(398) 1 49(362) Varnish 1 49(379) 1 49(280) Supreme 1 49(294) 1 49(274) Arctic supreme
Table V I suggests an interesting relationship between the viscosity of a heat-treated oil as shown by the refractive index and the higher melting point fats and the iodine number of the original oil. It indicates that of two oils with the same proportion of high melting point fats the one with the higher iodine number will body faster. Conclusion
The investigation shows the variations which may be expected in oils made from the same crop from the same district, if greater or less amounts of dockage seeds are allowed to remain mixed with the flaxseed a t the time of crushing, and further, that these variations cause differences which will affect the processes of the linseed-oil consumer. Thus far all the writers' work with pure linseed oils and linseed oils containing a proportion of dockage oil demonstrates that there is an appreciable difference in their constants, that these differences are maintained in the refined oils made from them and are often magnified in later blowing and heat treatments.
Absorption of Ultra-Violet Light b y Paint Vehicles By George F. A. Stutz NEWJERSEYZINCCOMPANY, PALMERTON, PA.
I
N X recent paper' the results are given of an investigation of the action of ultra-violet radiations on wet paint vehicles. Included is a determination of the degree to which various paint vehicles absorb the ultra-violet light. In the present paper this absorption determination is extended to the case of the dry films of a number of vehicles. The nature and amount of this absorption is of particular importance, because of the action of the ultra-violet portion of sunlight in "weathering," or decomposing, vehicle films; and also because of the growing use of strong sources of ultraviolet light in accelerated weathering apparatus. To further aid in this study, the change in the absorption caused by StUtZ, THIS JOCRN.AI., 18, 1235 (1926).
exposure of the films to sunlight and the mercury arc is also determined. Method
Because of the relatively high opacity of all vehicles to ultra-violet light, it is necessary to examine them in very thin films. A film thickness of 0.02 mm. or less is required in most cases in order that sufficient light will be transmitted to make accurate measurements possible. Most satisfactory results were obtained by flowing out thin films of the vehicles on transparent plates. For this purpose plates of fused quartz and Corning glass G 980 A were used. The vehicles were allowed to dry in diffused daylight, in the laboratory,
