I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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VOl. 34, NO. ’I
Literature Cited (1) Beattie, Kay, and Kaminsky, J . Am. Chem. Soc., 59, 1509 (1937). (2) Beattie, Poffenberger, and Hadlock, J . Chem. Phys., 3, 96 (1935). (3) Budenholzer, Sage, and Lacey, IND. EN@. CHEM., 31, 369 (1939). (4)Ibid., 31, 1288 (1939). (5)Ibid., 32,384 (1940). (6) Edmister, Ibid., 30,352 (1938). (7) Kay, Ibid., 28, 1014 (1936). (8) Lewis, J . A n . Chem. SOC., 30, 668 (1908). (9) Lewis, PTOC.A m . Acad. Sci., 43, 273 (1907). (10) Nellis, Calif. Inst. of Tech., master’s thesis, 1938. (11) Roozeboom, “Die heterogenen Gleichgewichte”, Vol. 11, part 1, p. 288 (1904); Lewis and Randall, “Thermodynamics”, p. 38. New York, McGraw-Hill Book Co., 1923. (12) Sage, Budenholzer, and Lacey, IND. I I 1 ENG.CHEM.,32, 1262 (1940). 250 500 150 I000 1250 1500 (13) Sage, Kennedy, and Lacey, Ibid., 28, 601 (1936). P R E S S U R E LE. PER Sa. IN. (14) Sage and Lacey, Ibid., 31, 1497 (1939). FIQURE5. ISOTHERMAL ENTHALPY-PRESSURE COEFFICIEKT FOR A MIXTURE (15) Ibid., 34, 730 (1942). (16) Sage, Lacey, and Schaafsma, Ibid., 26, CONTAINING 0.7552 WEIGHT FRACTION METHANE 214 (1934). . , (17) Sage, Webster, and Lacey, Ibid., 29, 1309 (1937). (18) Vold, J . Am. Chem. SOC., 57,1192(1935). acknowledged in connection with the calculation of the heat . , 388 (1940). (19) York and Weber, IND.ENG.C H ~ M32, capacities and of the partial enthalpies.
I
Viscositv of Naphtha-Resin Solutions J
E. H. MCARDLE AND E. L. BALDESCWIELER Esso Laboratories, Standard Oil Development Company, Elizabeth, N. J.
A variation of only a few degrees in the average boiling point of a given thinner produces critically large changes i n resin solution viscosity. The average boiling point-viscosity slope of a resin solution in a hydrocarbon thinner becomes steeper with increasing homogeneity, with respect to hydrocarbon type.
I
N A PREVIOUS paper (3)attention was called to the surprisingly large increment in resin solution viscosity resulting from slight changes in the average boiling point, or average molecular weight, of a 99 per cent isoparaffinic naphtha solvent. A rise of only 9’ F. (5” C.) in average boiling point produced an increase in viscosity of 55.6 per cent, in the case of the particular alkyd resin solution studied. It was therefore decided t o extend this survey to other types of
hydrocarbons and also to include resins of a variety of molecular weights. A series of resins was accordingly obtained ranging in average molecular weight from that of ester gum (a monomer-dimer mixture) to that of an alkyd with high glycerol phthalate content; and two groups of naphthas were assembled as base stocks. One group included a series of three blends, respectively, of paraffins, naphthenes, and aromatics of high purity; the other was chosen from representative commercial thinners. Each pure hydrocarbon blende. g., normal paraffins-and each commercial thinner was then fractionated into a series of five naphthas whose average boiling points differed by only a degree or two. Except for the pure naphthenes and pure aromatics, all naphtha fractions lie in the mineral-spirits boiling range.
Naphthas The normal paraffinic naphtha stock was a blend of two volumes of nonane, two volumes of decane, and one volume of undecane. These materials were obtained through the courtesy of the Petroleum Refining Laboratory of Pennsyl-
883
INDUSTRIAL AND ENGINEERING CHEMISTRY
July, 1942
HYDROCARBON NAPHTHA FRACTIONS NAPHTHA PROPERTIES
-
- NAPHTHA PROPERTIES-
$ U
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341
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340
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339
c a $330
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FIGURE 3. VISCOSITIES OF 50% SOLUTIONS OF SYNTHETIC RESINS IN PURE NAPHTHENIC HYDROCARBON FRACTIONS
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$ 331 a $330 .2
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vania State College, which designated purities, respectively, as 90+, 90+, and 85-90 per cent. Impurities were indicated to be mainly naphthenic although the undecane probably contained a trace of aromatics. Cottrell boiling points, from initial to 50 per cent off, ranged, respectively, from 150.8' to 150.85' C., 174.1' to 174.2', and 195.95' to 195.95'. Refractive indices were 1.4070, 1.4146, and 1.4245. Five hundred milliliters of the mixture of normal paraffins were then fractionated, a t "refinery fractionation", and the following overhead cuts were collected: 0-75 per cent, 75-80, 80-85, 85-90, and 90-95. Four blends were then made from the 0-80 per cent, 0-75 80-85, 0-75 85-90, and the 075 90-95 per cent fractions; the original normal paraffin mixture constituted the fifth member of the series. A. S. T. M. distillations were run on each member of the series, and the average boiling point of each was taken as the arithmetic average of the 10,20,30, 70,80, and 90 per cent distillation points ( 3 , 4 ) . It was felt that this procedure represented the simplest means of obtaining naphthas of practically identical solvencies and closely similar physical properties, while differing in small gradients of average molecular weight. Distribution of the average boiling points of the n-paraffin fractions (Figure 1) over the range plotted is the least uniform of the several series of naphtha blends. Nevertheless, this system of fractionation and blending has produced well-spaced average boiling points in the other six series. Kauri-butanol solvent powers (1, 8) were determined with 5 grams, instead of the usual 20, of standardized kauri-butanol solution. Since, however, they were taken in a room maintained a t 77' * 0.5' F. (25' * 0.28' C.) and run consecutively for each group of naphtha fractions, both accuracy and precision were undoubtedly equal to solvent powers normally run with 20 grams. The pure naphthenic base stock was blended 50/50 from isomeric dimethylcyclohexanes and 1,2,4-trimethylcyclohexane. These materials were left over from cooperative work done in 1939 by the Philadelphia Paint and Varnish Production Club (4), and had been made for the Philadelphia club from highly purified c. P. xylene and pseudo-cumene, respectively, by catalytic hydrogenation, through the courtesy of Charles Lennig & Company, Inc. Inspections of these naphthenes (4) indicated a purity of more than 95 per cent. The pure aromatic base stock was blended 50/50 from c. P. 3' C. xylene and Barrett's Cumene Fraction. The 87 per cent paraffinic hydrocarbon base stock is a commercial mineral spirits derived from Michigan crude, and the 70 per cent
+
VISCOSITY IN STOKES AT 77.F.
,
(GARDNER --HOLDS
+
+
a84
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 34, No. 7
naphthenic stock a commercial mineral spirits made from coastal crudes. The 93 per cent aromatic commercial stock was blended from 56 volumes of an aromatic commercial naphtha boiling from 275-350" F. (135-177" C.) and 44 volumes of a companion product boiling from 345-410" F. (174-210" C.). The 70 per cent aromatic stock is a commercial mineral spirits boiling from 312-405" F. (156-207" C.). (Boiling points noted above are A. S. T. &I. initial and A. S. T. RI. final, while those plotted are initial and A. S. T. M. dry points. Dry points were selected since they showed a better concordance with the average boiling points plotted.)
FIGURE 5. VISCOSITIES OF 40% SOLUTIONS OF SYNTHETIC RESINS IN PURE AROMATIC HYDROCARBON NAPHTHA FRACTIONS
Synthetic Resins I n selecting synthetic resins for this study, it was hoped to obtain products which would differ in average molecular weight in a regularly increasing gradient. That the selection has been fortuitous is shown in the charts. The materials were all obtained from a single manufacturer. The ester gum, Synthe Copal Ester No. 1202, has an acid number of G and a capillary-tube melting point of 68" C., and is nitrocellulose-compatible. The lowest molecular weight alkyd, Beckosol KO. 18 Solids, contains approximately 30 per cent of phthalic constituent, the balance linseed oil. Beckosol No. 19 Solids is an alkyd-type resin of somewhat higher molecular weight. Beckosol KO. 31 Solids has a phthalic constituent of approximately 50 per cent, the balance being largely soybean oil. The resins used for the aromatic naphtha solutions (Beckacite No. 1120, Beckosol No. 1 Solids, and Beckosol No. 13 Solids) are, respectively, a glycerol-maleate modified ester gum with approximately 16 per cent maleic content, a phenolmodified and oil-extended alkyd, and a high-molecular-weight alkyd with some 50 per cent phthalic constituent, the balance chiefly linseed oil.
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IGARDNER-HOLDT VIS. GlMk IN L E T T E k ) .2 .3 .4 .5 .6 .6 I I 2 5 15 VISCOSITY IN STOKES A T 77.F.
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FIGURE 6. VISCOSITIES OF 40% SOLUTIONS SYNTHETIC RESINS IN 93 % AROMATIC HYDROCARBON NAPHTHA FRACTIONS NAPHTHA PROPERTIES
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FIGURE 7. VISCOSITIES OF 40 % SOLUTIONS OF SYNTHETIC RESINS IN 70% AROMATIC HYDROCARBON NAPHTHA FRACTIONS
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Figures 1 to 7 reveal two important trends. First, the average boiling point-viscosity slopes are greater in the case of the purer hydrocarbons. With the normal paraffinic naphthas (Figure 1) the increase ranges from 28.5 to only 34 per cent with a rise in average boiling point of 7" F., while the corresponding increment in the less pure paraffinic commercial fractions (Figure 2) ranges from 21 to 58 per cent. A similar divergence is apparent in the three aromatic series (Figures 5 to 7 ) , where the lowest aromaticity exhibits the greatest increments. It might be interesting to carry this farther, to the naphthas of the mixed, or blended, types, t o ascertain whether thc divergence mould be still greater. An apparently anomalous confluence occurs between plots for the naphthenic solutions of the two highest molecular weight resins (Figures 3 and 4). It may be noted that Beckosol N o . 19 Solids contains an appreciable proportion of a terpene derivative, and thus molecular similarity with the naphthenic solvent makes for better conformity to the general average slope than is obtained in the case of the relatively high phthalic No. 31 Solids, a mutually dissimilar molecular combination. Secondly, and most important, is the fact that a variation of only a few degrees in the average boiling point of a given thinner causes changes in resin solution viscosity of as much as 50 per cent-enough t o eliminate a thinner from formulations where its competitor, or "match", is ideally suited. Since plotted viscosities were determined in Ubbelohde tubes a t 77" * 0.05" F., and occasionally compared with Gardner-Holdt viscosities, it is felt that the results are suf-
July, 1942
INDUSTRIAL AND ENGINEERING CHEMISTRY
ficiently precise to permit of a superimposition of charts, with abscissas in alignment, to aid in Selecting the correct hydrocarbon type for use with a given resin. It is thus hoped that comparative thinning efficiencies, estimated directly from such superimpositions, may prove helpful to formuIators.
Acknowledgment
885
Literature Cited (1) Baldeschwieler, E. L., Morgan, M. D., and Troeller, W. J., IND. ENQ.CHEM.,ANAL.ED..9.540 (1937). (2) Baldeachwieler, E. L., Troeller,'W. J., and hiorgan, M. D., Ibid., 7, 374 (1935). (3) McArdle, E.H., and Baldeschwieler, E. L., Ibid.. 13,301 (1941). (4) Philadelphia Paint and Varnish Production Club, Federation of Paint and Varnish Production Clubs, Tech. Proc., 1939, 115.
w.
the Division of Paint, Varnish, and Plastics Chemistry Thanks are due L, Rossin of Reichold chemicals, I ~ ~ . PRESENTED , the 102ndbefore Meeting of the AMERICAN CHEMICAL EOCIETY, Atlantic City, at who assisted in the selection of resins and supplied the samples. N. J.
P-V-T-x Relations of the System Propane-Isopentane J
WILLIAM E. VAUGHAN AND FRANK C. COLLINS Shell Development Company, Emeryville, Calif.
An experimental study has been made of the P-Y-T-x relations of five mixtures of propane and isopentane in the temperature range 0' to 300' C. and in the pressure range 2 to 80 atmospheres. The two-phase and the critical regions have been carefully defined. The data, which are presented in tabular and in graphical form, have been used to calculate the phase equilibrium constants.
T
HE study of the phase behavior of pure hydrocarbons and their mixtures has been greatly extended in the recent past, as a result of the increasing importance of such data to both the field production and refinery engineers. The following report presents in detail data obtained from measurement of the FV-T relations of five different mixtures of propane and isopentane. The primary data consist of pressure-volume relations measured isothermally a t 25" intervals from 0" to 300" C. in a pressure range from about 2 to 80 atmospheres. Supplementing these are other data obtained to define clearly the critical region. It is hoped that the present data will eventually lend themselves to development of a generalized system for predicting volumetric and phase behaviors. P-Y-T Apparatus The apparatus described in an earlier publication (9) was employed with a few modifications. It is essentially the type used by Young (11) as modified by Kay ( 4) ; it consists of a steel compressor unit, with mercury as the liquid, on which are mounted glass capillary tubes containing the hydrocarbon samples. The pressures are measured by closed-end nitrogen manometers, also mounted on the compressor block. The attainment of equilibrium conditions was expedited by magnetic stirrers, composed of Alnico alloy, which were manually raised and lowered in the capillaries by directcurrent-actuated solenoids. The volumes of weighed stirrers were calculated from the density determined from a larger sample of the material.
Accurate regulation of temperature was necessary, especially in the critical region. Considerable difficulty was a t first experienced due to the presence of impurities in the refluxing vapor baths and to decomposition of the liquids employed. The higher boiling liquids were later refluxed under nitrogen to minimize decomposition. The following liquids were selected for the various isotherms since they were found to be relatively stable and fairly easy to obtain in a high degree of purity: 0" C., methyl chloride; 25", diethyl ether; 50", acetone; 75", trichloroethylene; loo", methylcyclohexane; 125", chlorobenzene; 150°, bromobenzene; 175", phenol; 200°, tetrahydronaphthalene; 225", quinoline; 250-275 ", a-bromonaphthalene ; 300 ", benzophenone. Special precautions were taken to avoid contamination of the hygroscopic substances with moisture from the atmosphere.
Filling Apparatus and Procedure This apparatus and method were described in some detail (9), and accordingly only the modifications will be discussed. Because of the tendency of isopentane t o dissolve rapidly in stopcock grease, the filling apparatus was so designed as to eliminate stopcocks from the isopentane lines. All-metal packless valves (9) and mercury cutoffs were used to control the flow of isopentane. The compositions of the various mixtures were determined by measuring out calculated amounts of the pure substances from the calibrated gas buret which was accurately thermostated a t 30" C. The densities of propane and isopentane a t atmospheric pressure and 30" C. had been carefully determined, so that accurate calculation of the molal composition and weight of the sample condensed into the capillary was made possible. After filling, mercury was flowed into the inverted capillary over the condensed sample. Then atmospheric pressure was restored in the system, and the tube removed and mounted on the compressor block. Considerable difficulty had been experienced as a result of vaporization of the hydrocarbon upon contact with the warmer mercury. This was overcome by chilling the capillary immediately above the condensed sample with liquid nitrogen so as to freeze the mercury before it flowed into contact with the hydrocarbon sample. The
