INDUSTRIAL A N D ENGINEERING CHEiWISTRY
1252
Vol. 18, No. 12
Rate of Molecular Weight Increase in the Boiling of Linseed Oil’s’ By J. S. Long a n d W. J. Arner Wu. H. CHANDLER CREMICAL LABORATORY, LEHIGHUNIVERSITY, BETHLEHBM, PA.
T
HIS paper is an extension of previous work on rate of molecular weight increase of linseed 0i1.3
weight of the product from which they were made and on other factors, films were made from sets of samples from a number of the runs as follows: Materials Weighed quantities of oil were brushed onto measured LINSEEDOIL-TWO shipments of raw linseed oil were used, areas of plates of amalgamated tinned iron. The plates were both derived from northwest seed. They showed the following selected so as to be as free as possible from imperfections. constants at the time when used : The films were dried in water-jacketed ovens at 65.5” C. * 1” I I1 for 32 hours under a relative humidity of 50 per cent, obSpecific gravity a t 15.5°/15.50 C. 0.9335 0.9330 tained by blowing air into the ovens through three 5-pint Iodine number 189 187 Acid value 2.05 2.34 bottles of sulfuric acid (sp. gr. 1.330)5 connected in series. Neither oil showed any break when heated to 300” C . in a test The films were then removed from the plates and three to tube over a Bunsen flame with interposed asbestos gauze. I five test specimens, 10 mm. wide a t the narrow portion, and was used in runs 100 to 107, 127 mm. long,6cut with an inclusive; I1 was used in runs arbor press and die. Films 108 to 111. inclusive. of approximately 0.1 mm. BENZENE -Thiophene-free The effect of driers o n t h e boiling of linseed oil can were used and the actual benzene was further purified be conveniently studied by the rate of molecular weight by the method suggested by thickness in each case was increase. Richards4 T h e freezing determined with a platform The elongation, ultimate tensile strength, a n d repoint constant, K , of this gage graduated in 0.01-mm. benzene as determined using lated physical characteristics of films made from boiled divisions and which could purified carbon tetrachloride, linseed oil are bound t o be dependent o n t h e molecular carbon disulfide, and nitrobe read to fractions of a weight of t h e oil from which they were made. benzene gave a value of 5065 division. as compared with the value The test specimens were 5067, calculated by Raoult’s stored in 23-cm. desiccators formula. The so-called “iron salts of the fatty acids” used in run 51 over sulfuric acid (sp. gr. 1.330), thus giving a constant relative were prepared by treating the sodium soaps of the mixed free humidity of approximately 50 per cent. After varying periods fatty acids from linseed oil (I) with a hot solution of ferrous of time the specimens were broken in a film testing machine sulfate. The product was a dark reddish brown oil. LITHARGE-Three kinds of litharge were used. That labeled which is a duplicate of the one used and described by Nelson.6 L is a commercial product, pinkish yellow in color. E is also Effect of Lead a n d Iron Driers a commercial product having a deep orange color. The litharge marked “special” was made in this work by precipitation as lead The results are shown in Tables I to V. Comparison of hydroxide. The product was dried at 110-115” C. It had a tables for runs 100, 101, and 103 reveals the fact that even greenish yellow color. PRUSSIAN BLUE-A commercial band of Prussian blue was the 1-hour samples show the effect of the presence of lead used. It was in the form of lumps. For runs 106 and 107 this monoxide. Within the limits used increase in the proportion was ground in some of the No. 1 oil. The paste contained 40 per cent of Prussian blue by weight. For runs 109, 110, and 111 of lead monoxide leads to higher rate of molecular weight Prussian blue was ground in oil No. 11, in a “colloidal mill.” increase. The lead monoxide made by precipitation and The resultant paste contained 40 per cent of Prussian blue by drying at a low temperature acted more rapidly than either weight. FERRICOXIDE-The ferric oxide used in run 107 was prepared of the commercial samples. Substitution of iron oxide for Prussian blue as a drier in by the action of sodium carbonate on ferrous sulfate. The resulting precipitate after washing was dried a t 110’ C. and certain enamels, such as those used in the manufacture of ground-to a paste with the oil used in this work. patent leather, has been suggested by Toch’ and by Enna. Results obtained by the use of ferric oxide are given in run Method 107. Comparison of these with run 106 reveals the fact that Essentially the same methods of heating the oil and ob- free ferric oxide acts more rapidly than the stoichiometric taining molecular weights of the samples were followed as weight of Prussian blue. I n the latter three-sevenths of the have been previously described.3 Five hundred grams of oil, iron is in the ferrous condition a t the start. The rapid inalone or with driers as noted in Table I, were heated in open crease in weight for run 107 has been noticed in other runs 13-cm. porcelain casseroles and mechanically stirred a t the in which the iron drier used was in a readily available form. rate of 200 r. p. m. Samples were withdrawn a t regular No comparable effect has been noticed with lead monoxide. intervals, up to heat, after 0.5 hour, 1, 1.5, 2, 2.5, and 3 hours, It was thought that if the Prussian blue was finely ground, and the molecular weights of these determined by the freezing the rate of molecular weight change would be increased. point method using benzene as solvent. Prussian blue was accordingly ground (1) in an ordinary mill I n order to study the extent of dependence of physical and (2) in a colloidal mill in the linseed oil No. 11. Weights characteristics of the resultant oil films on the molecular of these pastes, which contained 16.1 grams of Prussian blue in each case, were introduced into enough oil to make 500 1 Presented before the Midwest Regional Meeting and the Meeting of the Section of Paint and Varnish Chemistry of the American Chemical grams and boiled as before. The results obtained, however, Society, Madison, Wis., May 27 to 29, 1926. do not show any greater rate of molecular weight increase. 2 This work was carried out under the Pfister & Vogel Leather Company Fellowship at Lehigh University, acknowledgment of which is gratefully made. 3 Long and Wentz, THIS JOURNAL, 17, 905 (1925). 4 J . Am. Chem. SOC., 47, 2285 (1925).
6
Wilson, THISJOURNAL. 13, 329 (1921).
e Nelson, A m SOC.Tesfing Malerials, 21, 1111 (1925). 7 “Chemistry and Technology of Paints,” 3rd ed., p. 169.
I9DUSTRIAL AND ENGINEERING CHEMISTRY
December, 1926
I n fact, comparison of runs 109 and 111 seems to indicate that the proportions of driers used, which are in line with practice in making certain commercial enamels, are in excess of the quantity required for the reactions which take place. The excess Prussian blue does, however, impart a color to the oil, which may be desirable for certain enamels such as those used in making patent leather. Table I-Rate
Run 100 101 103 104 105 106 107 108 109 110 111
tensile strength on molecular weight and indicates that for these films the optimum elongation and ultimate tensile strength (U. T. S.) for either 30 or 60 days are obtained from oil heated until the molecular weight is in the neighborhood of 1100. Table I11 gives data for series which also show maxima for elongation or U. T. S., the two being in general not coincident.
of M o l e c u l a r W e i g h t I n c r e a s e of Linseed Oil w i t h and wit- h o u t Driers .___MOLEC 'ULAR WEIGHT
Nature of run 16.1 g. Prussian blue 500 g. linseed oil in an open 1.3-cm. casserole 16.1 g. Prussjan blue 0.25 g. PbO (L) in open 13-cm. casserole 500 g. linseed oil 500 g. linseed oil 16.1 g. Prussian blue 1.0 g. PbO (L) in open 13-cm. casserole 16.1 g. Prussian blue 1.0 g. PhO (E) in open 13-cm. casserole 500 g. linseed oil 500 g. linseed oil 16.1 g. Prussian blue 1.0 g. PbO (special) in open 13-cm. casserole 500 4. linseed oil 16.1 g. Prussian blue [ground in oil (lab.)] 1.0 g. P b O (special) in open 13-cm. casserole 500 g. linseed oil 12.2 g. Fez02 [ground in oil (lab.:)] 1.0 g. PbO (special) in open 13-cm. casserole 500 g. linseed oil in open 13-cm. casserole 500 g. linseed oil 16.1 g. Prussian blue [ground in oil (special)] 1.0 g. PbO (I,) in open 13-cm.casserole 500 g. linseed oil 16.1 g. Prussian blue [ground in cil (special)] 1.0 g. PhO (L) in open 13-cm. casserole 600 g. linseed oil 12 g. Prussian blue [ground in oil (special)] 0.0 g. PbO in open 13-cm. casserole
+ + + ++ + + + + +
++ ++
+
+
+ + +
Relation of Molecular Weights and Other Factors to Some Physical Characteristics of Oil Films
Thickened oils made as described, using driers but no pigments or gums, yielded smooth, dry, uniform films which could be handled without injury. It was believed that the physical characteristics of oil films must be to some extent dependent on the molecules from which they were derived. Since the molecular weight of the samples taken out a t various intervals during the boil increased regularly from 720 up to nearly 3000, it was thought that this regular increase in the size and weight of the molecule up to four times the original molecular weight must have a measurable effect in the films. That this is true is evidenced by inspection of the tables. Since, however, inany factors enter into the properties of oil films, these data are presented as suggestive of met,hod and of this point as a factor. Conclusions drawn are only general and in some sense preliminary. T a b l e 11-Effect of E l o n g a t i o n and T e n s i l e S t r e n g t h ( R u n 100) 500 grams linseed oil. 16.1 grams Prussian blue, no litharge Films dried 32 hours' a t 65.5' C.; in desiccator a t 50 per cent relative humidity II m n u. 1.3. Elongation G./sq. cm. Mol. wt. 4 days
36 25
11,000 10,100
1068 1216
30 .. davs -~
41 47 32 30 45 45 52 37 37 57
11,300 12,800 12,700 12,500 15,500 63 days 10,100 17,100 23,800 22,600 92 days 30,500
9E7 1068 1163 1200 1216 957 1068 1163 1216 1163
T a b I e 111-Effect of M a x i m a E l o n g a t i o n or T e n s i l e S t r e n g t h C-I: 4 grams umber; 1 g. P b O in 500 grams of oil at 293' C. 101:16.1 grams Prussian blue; 0.25 g. litharge (I,) in 500 grams oil a t 277.5' C. 105:16.1 grams Prussian blue; 1 gram litharge (S) in 500 grams oil a t 277.5O C. SET C-1,DRIED3 0 DAYS SET 101, DRIED90 DAYSSET105, DRIED5 DAYS Mol. ElonMol. ElonMol. Elonwt. gation U.T.S. wt. gation U.T.S. wt. gation U.T.S. 1678 32 5500 1114 39 12,500 1143 30 9,600 1738 37 5600 1203 44 22,900 1266 31 10,200 1841 42 8100 1336 46 19,300 1418 33 12,600 1997 31 6400 1594 35 12,400
TebL I1 gives data representative of a number of film It shows dependence of elongation and ultimate
Temp.
c.
277.5 277.5 277.5 277.5 277.5
After u p to 0.5 After heat hour 1 hour 884 987 1041 1021 1041 1040
After After 2 1.5 hours hours 1068 1163 1114 1203 1165 1258 1115 1233 1143 1266
After After 2.5 3 hours hours 1200 1216 1336 1417 1341 1458 1367 1507 1418 1594
277.5
996
1178
1303
1380
1470
277.5 277.5
995 886
1198 1031
1515 1132
1607 1293
1671 1401 1548
759
277,s
947
1010
1131
1287
277.5
930
1133
1206
1367
926
1159
1222
1405
277,5
787
i48
1545
Pronounced gain in U. T. S. is often accompanied by loss in elongation. I n set 101 there is no evidence that the maximum elongation has been reached a t a molecular weight of 1336, although the U. T. S. has decreased. T a b l e IV-Effect of V a r y i n g P r o p o r t i o n s of L i t h a r g e All sets contain 16.1 grams Prussian blue in 500 grams of linseed oil Films dried 32 hours a t 65.5O C.; in desiccator at 50 per cent relative humidity DAYS-60 DAYS-- 7 - 9 0 DAYS-PbOMol. -30 wt. Elong. U. T. S. Elong. U.T. S. Elong. U. T.S. G./500 g. Oz./gal. 57 0.00 1163 12,700 36,500 0.25 1114 12,500 8,100 39 44 1203 22,900 11,100 1142 0.050 9 800 1232 8:lOo 1.00 1165 8,100 40 4,350 1115 8,400 0.00 1068 12,800 0.25 1041 5,200 1.00 1021 6 400 1041 1.00 7hOO
I n Table I V comparison is made between films from oils having molecular weights near 1050 and near 1150 but with varying proportions of litharge. The general conclusion reached is that films containing no litharge have greater elongation and greater U. T. S. for lengths of time up to 90 days. The films made from oils having molecular weights in the neighborhood of 1050 showed the greater elongation. Those made from oils having molecular weights in the neighborhood of 1150 showed the greater U. T. S.
Mol. wt.
,. 1203 1458 1341 1380
series.
1253
T a b l e V-Effect of E x t e n d e d -10 DAYS4 0 DAYS-70 ElonElonElongation U. T.S. gation U.T.S. gation 28 8200 29 9,400 33 25 8000 17 11,100 33 38 32 22 15
15,300 8,100 18,400
42 36 27
Drvina -
I
DAYS-
-
-
100 DAYS
Elon-
U.T.S. gation U.T.S. 6,700 12,400 8,600
4 45
22,900 7,300
20,500 12.400
43 42
16,200 13.600
28,800
150
40
days
25,520
Despite general opinion to the contrary, some oil films show increase in elongation and U. T. S. over a period of 5 months, as can be seen from Table V which gives results for a number of film sets having molecular weights of 1200 to 1460. The data secured so far are suggestive of more fundamental studies. It seems possible that the various maxima of physical properties such as elongation or ultimate tensile strength, which are dependent on the physical state, density, and granule size, can be related to the molecular weight of the oil from which they were derived. More work on this is in progress in this laboratory.
