as the well-known rule of thumb states. This was also confirmed by cycling tests at 140”F yielding seeded paints in approximately half the time as those “cycled“ at 1 1 7 F. Storage temperatures play a critical role in the seeding process. The addition of water again is extremely detrimental, with the addition of 0.2LjL; being about as deleterious as additions of 0.5‘;. The (negative) slopes of the curves increase slightly for higher water contents. Studies on conditions in the pigment dispersion step did not yield a clear picture and were limited in variability by the need to achieve a suitable dispersion. Dispersion operations reaching higher temperatures for shorter periods of time apparently gave less tendency toward seeding in the final product. Conclusion ,
3.2
I/TX I O - ’
3,4 \
,
(OK)“
Figure 4. Pseudoactivation energy plot for zinc oxide-free fatty acid reaction in oil base paint media mO.O%
water
AO.25Yo water 0 0 . 5 % water
Product seeding tendencies in paints can be affected by formulation, processing techniques, and storage conditions. Examination of each step is advised where premature seeding is encountered. Formulation changes should be examined to determine the effect on the vehicle since certain additives give apparent improvement in some respects while imparting undesirable side effects a t the same time. Acknowledgment
indicating the surfactant plays a role in the process, although the mechanism is not clear. More extensive studies of this type on zinc oxides having well-defined properties and prior histories would be reasonable. Our current data are insufficient in these respects to determine whether this type measurement would be a suitable control test. However, slight variations in water content appear to far outweigh other factors. The exotherms on finished paints were too small to be detected. The gel time test w x used to study the effect of temperature and water content on the reaction rate. The plot of (gel time) vs. (absolute temperature) ‘ in Figure 4 yields straight lines for these data. This pseudoactivation energy plot shows that a t temperatures corresponding to those of storage in warmer climates, a 10°C (18°F) rise in temperature approximately doubles the reaction rate
The authors acknowledge the analytical assistance of James B. Lear, the dta measurements by Charles E. Cowan, and the customary group effort a t the Springdale Research Center leading to this report. Literature Cited
+
Bult, R., Furbe Luck, 72 (9), 842 (1966). Dittrich, H., Dreher, B., Oberflaeche-Surfuce, 9 (6), 146 (1968). Elm, A. C., Digest Fed SOC. Puint Technol., 387, 351 (1957). Haug, R., Deut. Furben-2, 23 ( l o ) , 467 (1969). Liehr, W., Furbe Lack, 74 (l), 31 (1968).
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RECEIVED for review August 7, 1970
CORRECTION
I n the March issue [ I n d .Eng. Chem. Prod. Res. Develop., 10, 2 (1971)], the title of the paper as published is incorrect; the word “Clear” should read “CHAR.” The correct title is “Characteristics of Bone Char Carbon.”
192
Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No. 2, 1971
ACCEPTED February 8, 1971
