INDUSTRIAL AND ENGINEERING CHEMISTRY
1604
Then the number of ester groups formed a t any time in the system under discussion is
Assuming that esterification proceeds only intermolecularly, each ester group formed will result in the loss of one in the total number of molecules. Therefore, the total number of molecules a t this time is
N - [2(M
+ P ) + AI [1 - AN 2x1
By definition, then, the (number-average) maleic functionality is
Vol. 47, No. 8
and hold it there for some time with moderate reflux. Previous experience in polymerizations of this type had shown that the 6 peroxide additions provided for would yield a practical maximum of styrenation. Simple nonvolatile determinations (using a carefully controlled sample size and a uniformly thin distribution of sample) could provide a reasonably close check on yield of copolymer as deduced from a much more elaborate determination of residual styrene monomer by means of ultraviolet spectroscopy. Following a 2-hour holding period just under reflux and after the last peroxide addition, the styrenated alkyd was reduced with 145 grams of xylene to a practical solids content of 65% or a theoretical value of 67 % if the styrene polymerization had been 10070 complete. The properties found for this batch were Solids content. 7” (Styrene conversbn % Viscosity a t 25’ C os. Color Gardner 1935
The same equation can be shown to hold for the special case of an alkyd composition having an excess of carboxyl over hydroxyl. A similar equation can be derived for the case of an alkyd derived from a glyceride oil by an ester-interchange process; in this case
N
total number of molecules of oil, polyhydric alcohols, and dibasic acids A = zero ANo = calculated initial acidity derived only from dibasic acids =
65 0
94) 17,400 5
LITERATURE CITED
Armitage, F., Hewitt, D. H., and Sleightholme, J: J., J. Oil & Colour Chemists’ Assoc., 31, 437-54 (1948).
Hewitt, D. H., and Armitage, F., Ibid., 29, 109-28 (1946). Lewis, F. M., Walling, C., Cummings, W., Briggs, E. It., and Mayo, F. M., J. Am. Chem. SOC.,70, 1519.-23 (1948). McCullough, K. V., Wynstra, J., and Waters, R. R., Ogic. DiQ. , Federation Paint & Varnish Production Clubs, No. 329,39&-407 (1952). Meeske, C. J., and Laganis, D., U. S. Patent 2,647,092 (1953). Peterson, N. R., Oflc.Dig. Federation Paint & Varnish Production Clubs, NO,283, 596--600 (1948).
EXPERIMENTAL
Most of the alkyds described were prepared by the simultaneous esterification of soya acids and phthalic and maleic anhydrides with a polyhydric alcohol such as glycerol. Usually about a 10% excesb of hydroxyl was provided. The esterifications were carried out under carbon dioxide to provide an inert atmosphere and also under aeeotropic reflux in a solvent like xylene to remove water and to facilitate completion of the reaction. An esterification temperature of 200” C. was employed and acid value used as an end point. The following typical alkyd preparation was made in a 2-liter three-necked glass flask equipped with agitator, thermometer, inert gas inlet, Dean-Stark trap, and reflux condenser and was heated electrically: Soya acids 98% Glycerol Phthalic anhydride Maleic anhydride
Grams 840 300 422 14.7
Moles 3.00 3.20 2.85 0.15
This charge yields a phthalic-maleic ratio of 95.5 and 6.770 excess of hydroxyl over carboxyl. To hold a 200” C. reflux required 117 grams of xylene, or 8% of the expected alkyd yield. After a total of 11.5 hours of reflux, an acid value of 9.3 or 10.0 on a solids basis was reached. The calculated maleic functionality was 0.325. The copolymerization of this alkyd with an equal weight of styrene illustrates the technique used in the styrenation step. The following charge was placed in a 1-liter three-necked glass flask equipped with agitator, thermometer, and reflux condenser: Alkyd plus 8% solvent Styrene Xylene
Grams 324 300 126
It was heated to 125” C., and 6 hourly additions of 1.43 cc. each (1.50 grams) of cumene hydroperoxide (70% assay) were made. The addition of catalyst was made in this manner to increase the peroxide efficiency at a high temperature and also to provide some moderating effect on the exothermic character of the polymerization. Initially copolymerization was sufficiently exothermic to aise the reaction mass t o reflux temperature (145” to 150” C.)
RECEIVED for review September 24, 1954. ACCEPTED February 15, 1955. This paper was presented before the Division of Paint, Plastics, and Printing Ink Chemistry, 126th Meeting ACS, New York, September 1954.
Correlating Diffusion Coefficients in Liquids-Correction R. D. Bird, University of Wisconsin, has called attention to a typographic error in Equation 14 of the article on “Correlating Diffusion Coefficients in Liquids” [Othmer, D. F., and Thakar, M. S., IND.E m . CHEM.,45, 589 (1953)]. The quantity in parentheses in the denominator of the right side of the equation should actually be a power function rather than a multiplication factor. The equation therefore should read as follows, as is clear from the derivation and the context: 14 0
Ds x 106
= p#,
LS/LW)
V$6 p;
-2 similar mistake appeared in Figure 5, where i t is not clear that the equation of the line and the units of the X axis have t,his term as an exponent. In Figure 6, which was intended to be placed horizontally rather than vertically, the first line of the caption should read: “Use only three scales a t bottom when water is solvent.” DONALD F. OTHMER
..... Mechanical Electrostatic Charging of Fabrics for Air Filters-Correction In the article on “Mechanical Electrostatic Charging of Fabrics for Air Filters” [IsD.ENG.CHEM.,47,952 (1955)] the scale of the abscissa of Figure 11 is incorrect. On Figure 11 each abscissa value should be multiplied by the factor 0.465.
LESLIESILVERMAN D. M. ANDERSON
