Table II. V.G.C. Class A
B C
D E F G
Carbon-Type Composition Corresponding to V.G.C. Classification of Rubber Processing Oils Same
Paraffinic (Pennsylvania) Relatively paraffinic (MidContinent) Naphthenic (Gulf Coast) Relatively aromatic (Gulf Coast) Aromatic Very aromatic Extremely aromatic
V,G.C. Range
% Carbon T y p e a %C N %CA
A p p r o x . Range for
%CP
0.790-0.819
75-60
20-35
0.820-0.849 0.850-0.899 0.900-0.949 0.95-0.99 1.00-1.05 Above 1.05
65-50 55-35 45-25 35-20 (25)-0 Below 25-0
25-40 30-45 20-45 20-40 (25)-0 Below 25-0
0-10 0-15 10-3 0 25-40 35-50 50-60
Above 60
Based on data in Figure 1. Ranges d o not necessarily apply for very narrow fractions or pure compounds. a
‘In the original publication ( 4 ) , the values obtained for yoCp and YOCN for samples having viscosiry-gravity constant values between 0.95 and 1.01 are not so reliable since the angle of crossing of the viscosity-gravity constant-refractivity intercept lines is not large. Since from experience no commercial oils have been found in the viscosity-gravity constant range 0.95 to 1.01 which have values of %C, or 7$, less than 20, it is assumed that these are minimum values in this region. Since the 7 0 C ~ in this viscosity-gravity constant region is usually 40 to joyc, there is a very limited area within nrhich the composition of the sample can fall [Figure 5 ( 4 )!. I n the last two columns of Table I, molecular-type composition data (obtained with silica gel) are also shown. Note that oil 14 appears to be very aromatic on the basis of rhe total per cent of material containing at least one aromatic ring. I t is much less aromatic on the basis of carbon-type composition, and this is correctly reflected in the viscosity-gravity constant and other physical properties. The data in Table I show that there is a limited range of naphthene carbon content (20 to 4570) whereas there can be a very wide range in per cent paraffinic carbon and per cent aromatic carbon. This is clearer when the data are plotted on a triangular diagram for per cent carbon-type composirion, as in Figure 1. This graph includes data for natural Pennsylvania, Mid-Continent, and Gulf Coast oils reported by Hill and Ferris (2) as well as commercial oils from Table I. It is particularly pertinent that nearly all the points for the commercial oils having 407, or less aromatic ring carbons fall in a band between 2070 and 45y0 naphthenic carbons. The viscosity-gravity constant lines cut across this band almost at right angles. Classifying oils by viscosity-gravity constant limits the oil to a composition represented by a portion of this band. This is the fundamental reason why the viscositygravity constant is so successful in classi-
2234
fying rubber processing oils according to composition in the viscosity-gravity constant range 0.79 to 0.95. Above 0.936, the viscosity-gravits constant is an extrapolated function ( 7 ) . In Figure 1, dotted lines indicate the probable course of the composition band above 0.950 viscosity-gravity constant. The curvature of the dotted lines (Figure 1) is supported by unpublished data for experimentally refined oils. These unpublished data indicate that when the aromatic carbon is above 60%, the naphthenic carbon is below 207,. Oils of this high degree of aromaticitv have not been widelv used in the rubber industry. Since the work of Weinstock, Storev. and Sweely (74) showed that minor differences in rubber processing oils were apparently not of major importance. classification by viscosity-gravity constant alone should be a useful way of defining the carbon-type composition. \$‘hen more detailed information on carbontype composition is needed, the viscositygravity constant-refractivity intercept graph can be used ( 4 ) . Table I1 shows the approximate range of carbon-type composition that can be associated with the viscosity-gravitv constant groupings used in Table I. In Table 11, the terms Pennsylvania and Mid-Continent correspond fairly \vel1 with paraffinic, and relatively paraffinic, respectively. Coastal or Gulf Coast includes naphthenic, and relatively aromatic groups.
The classification of rubber processing oils by viscosity-gravity constant brings together oils having similar carbontype composition irrespective of molecular weight. Since in practical compounding molecular weight is also important, the recommended classification system (72) defines oils by viscosity-gravity constant groups and viscosity. The viscosity, for any viscositygravity constant group, is an easy though indirect way of defining molecular weight. This very simple, fundamental system of classifying rubber processing oils should prove of value to working technologists in the rubber industry. It can be shown that many practical properties of oil-extended rubber are related to the viscosity-gravity constant and viscosity of the oil use‘d in extending the polymer (73). literature Cited ( 1 ) Hill, J. B., Coats, H. B., IND.ENG CHEM.20, 641 (1928). ( 2 ) Hill, J. B., Ferris, S. W., Ibid., 17, 1250 (1925). ( 3 ) Kurtz, ’S. S’.,Jr., “Chemistry of Petroleum Hydrocarbons,” vol. I, chap. 11, p. 327, Reinhold, New York, 1954. (4) Kurtz, S. S.,Jr., King, R. W., Stout, W. J., Partikian, D. G., Skrabek, E. A., Anal. Chem. 28, 1928 (1956). ( 5 ) Kurtz, S. S., Jr., Martin, C. C.: India Rubber M’orld 126, 495 (1952). (6) Kurtz, S. S., Jr., Sankin, A., IND. END.CHEM. 46, 2186 (1954). ( 7 ) Kurtz, S. S., Jr., Ward, A. L., J . Franklin Inst. 222, 563 (1 936). ( 8 ) Ibid., 224, 583, 697 (1937). (9) iVes, K. van, and Westen, H. A . van, “Aspects of the Constitution of Mineral Oil,” Elsevier, New York, 1951. (IO) Rostler, F. S., Sternberg, H. W., IND. ENG.CHEM. 41, 598 (1949). ( 1 1 ) Rostler, F. S., White, R. M., Rubber Age (N. Y . ) 70, 735 (1952). (12) Sun Oil Co., Marcus Hook, Pa., “A
Method for Classifying Oils Used in Oil-Extended Rubbers,” 1954. (13) Sweely, J. S.: Ferris, S.W., Peterkin, M. E., Kurtz, S. S., Jr., submitted to Rev. gen. caoutchouc. (14) Weinstock, K. V., Storey, E. B., Sweely, J. S., IND.ENG.CHEM.45, 1035 (1953).
RECEIVED for review hlay 31, 1956 ACCEPTED October 23, 1956 69th Meeting of Division of Rubber Chemistry, ACS, Cleveland, Ohio, May 1956.
Correction In the article entitled “4 Numerical Solution to Dimensional Analysis” [Octave Levenspiel, Norman J. Weinstein, and Jerome C. R. Li, ISD. ENG.CHEY.48, 324 (February 1956)], last portion of Equation 4 should read
INDUSTRIAL AND ENGINEERING CHEMISTRY
boZXk
-k
biZ(XiXk)
-k
hZ(xzxk)
+ ... +
bkZ(Xk2)
=
~ ( Y X B )
