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INDUSTRIAL AND ENGINEERING CHEMISTRY'
are made, the prints are put into a third container where they remain in water. Upon returning to t.he laboratory, they may be taken from the water, allon-ed to dry, and kept as permanent records. With the portable device, round surfaces as well as flat surFaces may be tested. For this, a strong rubber band is applied in the test procedure. Figure 8 shows diagrammatically two forms of application of the portable device. I n one form the surface to be tested is small and the C-clamp can be used for the applicat'ion of pressure. In another form, the surface to be tested is large and the tourniquet method of applying pressure is used. Figure 9 shows a photograph of t'he arrangement of the portable test box.
Vol. 42, No. 8
Shaw and E. T. Moore of the KationaI Lead Company gave a t the start of this work, and the work of L. J. Rogers, now with the Valspar Corporation, in developing the portable ele~t~rographic printing out'fit. The work reported herein is in partial fulfillment of a research and development contract sponsored by the U. S. Signal Corps Engineering Laboratories, Fort Monmouth, K. J., and carried out in the Paint Research Laboratories of the College of Engineering, S e w York University. LITERATURE CITED Glazunov, A., Chem. Zentr., 101,11, 1104 (1930). Ibid., 103,I, 1398 (1932).
Glaaunov, A., and Jenicek. L., Korrosion u. Metullschutt, 16,341
SUMMARY
Rapidly made t'ests enable the research worker to check constantly on the progress and the necessary modifications of his development work. They have been used over many months of development work in these laboratories during which time they have shown consistent, reproducible results. ACKNOWLEDGMENT
T h e authors wish to acknowledge the assistance which \Ti. E.
(1940). Hermance,
H. IT.,Bell Lab. Record. 18,269 (1940). Kronstein, M., C. S. P a t e n t 2,476,879 (July 19, 1949). Shaw, W. E., a n d Moore, E. T., Anal. Chem.. 19,777 (1947). RECEIVED July 26, 1948. This paper was presented in two parts. The first part was presented by Max Kronstein and Marion >I. Ward before the Division of Paint, Varnish, and Plastics Chemistry a t the 114th Meeting of the AXIERICAN C H m f I c A L SOCIETY, Washington. D. C.; the secon? part was presented by Max Kronstein, Marion M. Ward, and Robert Roper before the s a m e division at the 116th Alecting of the .%hmRIcAx CHEMLCAL SOCIETY, Atlantic City, S . 6.
Effect of Oxygen on Polymerization Systems at 41"F. J
R. W. HOBSON AND J. D. D'IANNI Research Department, The Goodyear Tire & Rubber Company, Akron, Ohio T h e presence of oxygen in the GR-S poljmerization system is considered undesirable since i t inhibits polymerization. Recent work with low temperature (41" F.) redox polymerization systems indicated they were even more sensitive to the presence of oxygen, in view of the poor reproducibility of the polymerization rate. A systematic study was made of four different polymerization systems a t 41" F. to which various amounts of oxygen were : podermic syringe just before polymerization added b j h w-as started. Two systems w-ere of the sugar-ferrous iron redox t j pe, another was of the polyamine-cumene hydroperoxide type, and the fourth was of the mercaptan-ferricyanide type. The mutual system was run as the control. Only the systems containing ferrous iron were markedly affected by the addition of small amounts of oxygen. No evidence was obtained that a small amount of
oxygen TI as necessary for optimum polymerization rate. Since oxygen was shown to have a major effect in the ferrous iron redox systems (undoubtedly due to oxidation to the ferric state) 5-gallon reactor polymerizations were carried out in which a chemical "scavenger," sodium dithionite, w-as added to destroy oxygen in the soap solution and monomers prior to the addition of the activator system. Improved rates of polymerization were obtained by the addition of 0.05 part, whereas smaller amounts had little effect and larger amounts caused polymerization to cease a t lower conversions (probably due to destruction of the hydroperoxide). Since small amounts of oxygen have a deleterious effect on the ferrous redox systems in current use for production of cold rubber, great care should be exercised a t all times to eliminate the presence of oxygen from the sS-stem.
X Y G E S is known to exert two directly opposite effects on the polymerization reaction of vinyl and diene monomers. As early as 1910 Stobbe and Posjnak ( I S ) observed t h a t samples of styrene stored several days a t room temperature in the presence of air polymerized in bulk more rapidly a t 200" C. than freshly distilled samples. More recently, Talmud et al. ( 1 4 ) found that oxygen was an initiator for the polymerization of butadiene in aqueous emulsions, particularly when the monomer was previously stored in air. In these cases, polymerization catalysts such as peroxy compounds were not deliberately added, a n d the results can be interpreted to mean t h a t oxygen reacted with the monomers to form peroxides which initiated the polymerization reaction. On the other hand, Heuck ( 6 ) stated that Logemann, a t least
as early as 1939, observed the inhibitory action of atmospheric oxygen in emulsion polymerizations of styrene initiated by per compounds, such as potassium persulfate and hydrogen peroxide. He recognized that quite generally molecular oxygen retards the emulsion p o l y n ~ r i z a t ~ oof n styrene, acrylates, and other unsaturated compounds, and that the inhibition is prevented by exclusion of oxygen with the aid of inert gases. The next logical step was the use of reducing agents, such as sulfites and dithionites, to destroy the molecular oxygen present so that the peroxy compound could function without interference as the initiator of the polymerization. Use of this technique gave much faster polymerization rates than expected and inadvertently led to the so-called redox catalysis. According to Kern ( 7 ) , Logemann, and contemporaneously and independently
August 1950
INDUSTRIAL AND ENGINEERING CHRMISTRY
hlonheim and Sonke, recognized the true role-i.e., reaction with the oxidant to form free radicals which catalyzed polymerization-played by these reducing agents; the last two workers were the first to use the terms redox acceleration and redox catalysis. A recent study was made by Kolthoff and Dale (8) on the effects of oxygen in the emulsion polymerization of styrene. Induction periods were shown to be due to oxygen acting as an inhibitor and the length of the period of inhibition was a function of the catalyst (persulfate) concentration. Bovey and Kolthoff (8)showed t h a t oxygen actually copolymerized with styrene. The effects of oxygen on the emulsion polymerization of butadiene (9) and of butadiene-styrene (10) were also studied by Kolthoff and co-workers. Kern (6) recently surveyed the literature on the influence of molecular oxygen on the polymerization of unsaturated compounds. A timely review of inhibition and retardation of vinyl polymerization in general was recently completed by Bovey and Kolthoff ( 1 ) The present investigation was prompted by the occurrence of slow, irreproducible rates of polymerization in the authors' pilot plant runs a t 41 F. with a typical redox recipe containing sugar, ferrous sulfate, potassium pyrophosphate, and cumene hydroperoxide. I n that work it was discovered that rigid exclusion from the system of air, both dissolved and in the vapor state, allowed polymerization to occur a t a fast,er, more reproducible rate. I t was then decided to conduct a bottle polymerization program to study the effect of adding measured quantities of oxygen by hypodermic syringe to several different redox polymerization systems a t 41 ' F , using essentially the GR-S system a s the control GEVERAL PROCEDURE
Polymerization data from 20-gram monomer charges with butadiene and styrene in the recipes shown in Table I are tabulated in Table 11. Three distinct redox systems were employed i n the 41" F. recipes because it was realized that the type of ,catalyst might influence the effect of oxygen on the polymerization system. The control runs represent polymerization systems which are not oxygen-free, but which contain only the small .amounts of oxygen normally included-i.e., the dissolved oxygen .in the monomers and distilled water, the oxygen incorporated .in the preparation and transfer of solutions, and the oxygen left .in the vapor phase over the charges after venting the excess butadiene. Polymerization charges which contain sodium dithionite represent those in which the oxygen in the soap solution, monomers, and vapor phase has been removed by reaction with the qdithionite. The required amount of sodium dithionite (0.01 part on 90% basis) was determined by titration in separate experiments using Azocarmine G as indicator; the results are shown in Table 111. Thus the data in Table I1 allow comparisons in polymerization rates between essentially oxygen-free systems (dithionite-treated), systems containing oxygen in amounts normally included (controls), and systems which contain, in addition to the same amounts of oxygen as in the controls, various amounts which have been added just before polymerization. It should be emphasized that because oxygen was added to these syskms shortly before polymerization, equilibrium conditions (with respect to oxygen in liquid and vapor phases) may not have been established immediately. The average conversion a t 2 , 4 , 6, and 16 hours has been calculated from the individual values (in parentheses). The individual values are included not only to show the range, but also, for some of the 2-, 4-, and 6-hour conversions, to show how sampling fromseparate charges compares with sampling from thesame charge. Conversion values obtained from separate charges are indicated by asterigks. The values in parentheses are also arranged in order of correspondence for samples taken from the same charge-e.@;., in Table 11, recipe I, the 2-, 4-, and 6-hour .conversion values for
