February 1949
devend uvon individual stocks and local conditions.
TABLE V. DISULFIDE FORMATION IN ACIDTREATMENT” Run 40 41
399
INDUSTRIAL AND ENGINEERING CHEMISTRY
Material Pressure distillate Pressure distillate
Initial HnB Mg. Liter 8/
Lb./Bbl. Acid.
0 0
Initial Final Mercaptan, Mercaptan,
yge7/
ygc,”/
yg1
Disulfide Increase, MLiter 4.W
102
63
57
135
63
37
6% caprylene in 6 841 0 21 Skellysolve 45 5% ea rylene in 5 650 0 22 BkelPysolve 50 15’7 oaprylene in 5 648 0 29 sfcellysolve 49 16’7 caprylene in 6 1175 0 77 Stellysolve a All treatments conducted a t initial temperature of 77’ F., with 97.4% acid.
0
120
10
5
222 220
Initial Disulfide,
46
centration the acid would cease to be effective in promoting mercaptan formation. Because of hydrocarbon diluents in the alkylation acid, its acid strength on basis of aqueous dilution was probably considerably higher than the value of 81.75% indicated by analysis. CONCLUSIONS
On the basis of the above data and discussion, i t is concluded that mercaptans may be formed in the acid treatment of pressure distillate by combination of hydrogen sulfide with olefins. Similar behavior is probable for other materials containing appreciable amounts of olefinic compounds. At short acid-oil contact times, such as are encountered in continuous acid treatment operations, conditions are favorable for a net increase in mercaptan content. At longer contact times, such as are used in agitator operations, it is probable that the mercaptans initially formed will be converted, all or in part, to sulfides or polysulfides. The mercaptan sulfur increases observed, nearly 1000 mg. per liter in some experiments, are of sufficient magnitude to justify removal of hydrogen sulfide prior to acid treatment in many cases of industrial practice, particularly if the material is to be used for production of motor fuel. The economic significance will, of course,
0
58
0
24
0
64
ACKNOWLEDGMENT
The authors wish to express their appreciation to the Union Oil Company of California for providing the pressure distillate and alkylation-acid used in the experiments, and for assistance with analytical methods. LITERATURE CITED
(1) Andersen, J. W., Beyer, G. H.,
and Watson, K. M., Natl. Petroleum News, Technical Data Section (July 5, 1944). (2) Barr, F. T.,and News, D. B., IND. ENG.CHElf., 26,1111 (1934). (3) Birch, 5. F., and Norris, W. S., Ibid., 21,1087 (1929). (4) Duffy, H. R., Snow, R. D., and Keyes, D. B., Ibid., 26,91 (1934). (5) Ipatieff, v. N., and Friedman, B. s.,J. Am. Chem. sot., 61,71 (1939). (6) Ipatieff, V. N.,Pines, H., and Friedman, B. S., Ibid., 60,2731 (1938). (7) Jones, S. O., and Reid, E. E., Ibid., 60,2452(1938). ( 8 ) Kalichevsky, V. A., and Stagner, B. A., “Chemical Refining of Petroleum,” New York, Reinhold Publishing Corp., 1942. (9) Kiemstedt, H., OeZ u. Kohle, 39,833-6 (1943). (10) Mayo, F.R., and Walling, C., Chem. Revs., 27,387 (1940). (11),Nelson, W. L.. “Petroleum Refinery Engineering,” 2nd ed., New York, McGraw-Hill Book Co., 1941. (12) Tamele, M. W., and Ryland, L. B., IND.ENG.CHEM.,ANAL. ED.,8,16 (1936). (13) Thomas, C. L., Bloch, H. S., and Hoekstra, J., Ibid., 10, 153 (1938). (14) U.S.Bur. Mines, Rept. Invest. 3591,38(December 1941). (15)Ibid., p. 45. (16) Wood, A. E.,Lowy, A., and Faragher, W. F., IND. ENG.CHEW, 16,1116 (1924). RECEWEDJuly 30, 1947. Presented before the Division of Petroleum at the 112th Meeting of the CHEMICAL SOCIETY, New York, N. y.
Action of Organic Accelerators in Vulcanization of Rubber EFFECT OF BASICITY G. D. KRATZ’, H. H. YOUNG, JR,*, AND ISADORE KATZa Norwalk Tire and Rubber Company, Norwalk, Conn. w i t h a closely related series of accelerators, the sulfur combined in a given time at a given temperature is a linear function of the logarithm of the basic dissociation constant of the accelerator employed. Series of this type include the isomeric toluidines and phenylenediamines, and the phenylguanidines. The accelerating activity of strongly basic materials, such as guanidine and sodium hydroxide, is of a different order from that of the preceding 1
Present address, General Latex and Chemical Corporation, New York
18, N. 2
a
Y.
Present address, Thompson Chemical Laboratory, Williamstown, MESS. Present address, Norwich University, Northfield, Vt.
type of accelerators. In the accelerators examined, structures permitting greater resonance in the molecule resulted in a decrease of accelerating activity.
WHEN
organic compounds were first found to function as accelerators for the vulcanization of rubber, Peachey (8) and others attributed their activity, a t least in part, t o the basicity of the substances employed. Patents, t o mention but one ( g ) , were issued stating that there was a specific order of basic strength beneath which accelerating activity would not occur. We have already shown (6) that this is not necessarily true since acceleration was observed with a weaker base than the
Vol. 41, No. 2
INDUSTRIAL AND ENGINEERING CHEMISTRY
400
I n order to obtain conveniently measurable results with several series of accelerators of widely different activities a t the same temperature of vulcanization (298' F.),it was necessary to employ them in different molar quantities. Thus the combined sulfur values (Table I ) for the diamines were obtained a t 60 minutes with 0.04 mole of accelerator, guanidines a t 30 minutes with 0.02 mole, the methylanilines and toluidines a t 90 minutes with 0.01 mole, and the phenylamines at 90 minutes with 0.04 mole. This procedure precludes a direct comparison of the accelerating activity of the five series. Since only two of the substances employed for examination are of commercial importance, such a comparison would he of little practical intereiit. EXPERIMENTAL
LOG KB X 10-l4 Figure 1
patent (2) would have permitted. However, the whole subject has been dormant for many years. The results reported here indicate that there is a real correlation between accelerating power and basic strength: In a closely related series of compounds-e. g., aniline, methylaniline, dimethylaniline-the accelerating power, as rneasured by combined sulfur, is a linear function of the logarithm of the basic dissociation constant, Kb. This relationship has been observed most strikingly with 0-, m-,and p-phenylenediamines, and with 0-,nz-, and p-toluidines. It has been observed also with aniline, diphenylamine, and triphenylamine, and with mono-, di-, and triphenylguanidines. Guanidine itself does not fall into line, but exhibits a behavior comparable with that of sodium hydroxide, which it approaches in basicity (approximately 108 to lo4times the phenyl-substituted compounds). Resonance in thc accelerator molecule exerts an important influence, but steric factors may be quite important also, and the effect of either of these is chiefly in contributing to the basicity of the molecule. For each series of substances examined as accelerators, the introduction of resonant groups, or the rearrangement of groups to permit of greater resonance in the molecule, resulted in a decrease of its accelerating activity. Speculation as to the mechanism of acceleration and the role of the base therein lies beyond the scope of this paper.
About 100 pounds of good quality No. 1 smoked sheet were blended on a 60-inch mill with minimum mixing to effect the blend. Laboratory batches for each series consisted of 400 grams rubber, 30 grams sulfur, and molecularly equivalent quantities of the accelerators. A mixing time of 11 minutes mas employed for each batch, the sulfur and accelerator being thoroughly mixed together and added as such to the rubber when banded on the mill. Vulcanization was effected in the usual type of platen press, test slabs being approximately 0.10 inch thick, and the temperature held a t 298" * 1 " F. Physical tests were made on a L-6 Scott tester after one-week aging a t room temperature. Combined sulfurs were obtained by a method previously described (4, after acetone ext'raction for 16 hours in an A.S.T.M. extraction apparatus (1). The accelerators used, Tyhen necessary, were purified by redistillation or crystallizat,ion, and had the following melting or boiling points (in degree centigrade) : MELTINGPOINTS.o-Phenylenediamine, 99.0; m-phenylenediamine, 63.5; p-phenylenediamine, 139.7; monophenylguanidine, 69.0; diphenylguanidine, 147; triphenylguanidine, 143.7; p-toluidine, 44.5. ROILINGPOINTS.Aniline, 184.0; methylaniline 192.0; dimethylaniline, 192.5; diphenylamine, 53.0; triphenylamine, 125.2; o-toluidine, 200.0; rn-toluidine, 202.5.
Table I lists combined sulfurs found with the logarithms of the dissociation constants, Ka, of the accelerators employed. In Figure 1,values for the combined sulfurs found are plotted against such logarithms, the latter having all been reduced to Ka X 10-14. The results are linear for all five series, particularly good agreement being found for the methylamines, toluidines, and phenylenediamines. The low combined sulfurs found for guanidine arid sodium TABLEI. COMBINED SULFURAND DISSOCIATIOX CONSTAXT hydroxide and t,heir extremely high Kb value8 preclude them from DATA Corntabular or graphic comparison a i t h t,he other series. bined Log Temp., s, 70 Kb ~a x 10-14 o c , Phen lamine Series" Anline Diphenylamine Triphenylamine Methylaniline series b Aniline Methylaniline Dimethylaniline Toluidine seriesc o-Toluidine in-Toluidine p-Toluidine Phenylenediamine seriesd o-Phenylenediamine m-Phenylenediamine p-Phenylenediamine Guanidine seriesc NaOH Guanidine Monophenylguanidine Diphenylguanidine Triphenylguanidine
4.78 3.53 3.44
38,000 X 10-14 7 . 1 X 10-14 5.0 X 10-14
4.t7978 0.85126 0.69897
25 25 25
4.98 3.10 2.83
S . 5 0 X 10-10 2 . 5 5 x 10-10 2.42 X 1O-'D
4.54407 4.40654 4.38382
15-18 15-18 15-18
3.25 4.22 5.07
2.45 X 10-10 4 . 9 1 X 10-10 11.80 X 10-10
4.38112 4.69028 5 071138
25 25 25
2.20 3.37 5.70
2.3 X 10-10 6 . 0 X 10-'0 Q 5 . 0 X lo-"
4.36173 4.77815 5.97772
21 21 18
2.52 2.26 4.71 4.34 1.73
. . . . , .. . . .
....
..
58.9 X 10-6 13.2 X 10-6 1 . 3 X 10-6
10:77012
25
... . .. ....
oaloulated from p K h of Hall ( 5 ) from Kraez et aZ.-(G). Kb calculated from p K h of Ilali and Sprinkle d Kb from Landolt-Bornstein (7). 0
The authors take this opportunity t o thank the Norwalk Tire and Rubber Company f o r permission to publish thwe results. LITERATURE
a Kb
b Kb
ACKXOWLEDGMENT
(4)
10,12077 9.11394
25 25
crrm
(1) Am. Soo. Testing Materials, Standards of Ilubher Products. 1944. 12) Bayer and Co., Ger. Patent 280,198 (1914). (3) Hall, N. F.. J. Am. Chem. Soc., 52, 6115 (1930). (4) Hall, N. F., and Sprinkle,M. R., Ibid., 54, 34G9 (1932). ( 5 ) Krats, G. D., Flower, h. H., and Coolidge, C., India fluhber World, 61, 356 (1920). (6) Krats, G. D., Flower, A. E ,and Bhapiro, B. J., ,J. INU. Enio. CHEM.,13, 67 (1921). (7) Landolt-Bornstein,Physik.-chem. Tabellen (1932). (8) Peschey, S. J.,J.Soc. Chem.I.nd., 36,331,424,950 (1917). RECEIVED June 10, 1947. Presented before the meeting of the Di\.isiun of Rubber Chemistry, B?dimxchN CHEMICAL SOCIETY, Cleveland Ohio, M a y 1947. Previous papers in this series appeared in J. TND EXQ.CEEhl., 12, 317 (1920): 13, 67 (1921); 13. 128 (1921).
