Decontamination of Radioactivelv J

Contaminated Water by Slurrying with Clay

J

WILLIAM J. LACY Engineering Research and Development Laboratories, Fort Belvoir, Va.

X T H E event of an atomic disaster, water supplies may I become contaminated with radioactive materials. The level of radioactivity to be expected is dependent upon many condi- tions, including the type of bomb (atomic, radiological, or hydrogen), the type of burst (air, surface, underground, under- water), the kind of water (ai. pertaining to induced activity), and atmospheric conditions. The air burst is the most likely use of the bomb for which the contamination of water would be a t a low level (probably less than 10-2 microcurie per ml.). However, even with an air burst, extenuating circumstances such as atmoe- pheric precipitation (rain or snow) could give rise to considerable contamination. Therefore, all nuclear weapons must be regarded as potentially capable of contaminating water supplies.

The dissolved or suspended radioactive material in water could be a source of alpha, beta, and/or gamma radiation. In- gestion of large amounts of radioactive material could cause physio- logical damage. Morgan and Straub ( 7 ) have presented a for- nul la for estimating the emergency maximum permissible con- centration (MPC) values of radioactive contamination in air and water following a nuclear explosion. They estimated that the emergency value of maximum permissible concentration for the radioactive fission products in microcuries per milliliter is given approximately by the equation

MPC = Kt-1.2

foi 30 minutes to 3 years following the explosion. If time is given in days, K = for drinking water contaminated with any material emitting alpha, beta, or gamma radiation.

Many adsorbents have been used for decontaminating water, with varying degrees of efficiency. One such adsorbent of interest because of its effectiveness and low cost is clay. The removal of radioactive contaminants from water by clay has been reported by Straub, Morton, and Placak (8). This report pre- sents jar test data pertaining to the decontamination of radio- actively contaminated water by the use of clay indigenous to the Oak Ridge, Tenn., area, as well as the effect on removal of radio- active material of varying the concentration of clay, hydrogen ions, radioactive contaminants, and calcium ions. Also studied was the ease of removal of different nuclides and mixtures of various fission products.

TABLE I. CHEMICAL ~ v A L Y S I ? O F G R a B SAMPLE OF O A K RIDGE TAP WATER

Concen- tration.

Chemical Constituent P .P .M.a

Methyl orange alkalinity (as CaCOd 98 Phenolphthalein alkalinity (as CaCOd 2 Soap hardness (as CaCOa) 94 Dissolved solids 110 Nonvolatile solids 75 Calcium 25 Magnesium 5 Sodium Silicon dioxide P H

6 7 7.9

The clay in the Oak Ridge area is composed principally of montmorillonite [(AI or hfg)(8i80,0)(OH)41 XH,O)] and kaolinite [A14(Si4010)(OH)3 and Akl(SirO~)(OH)l~j. The clay used in this test was analyzed by the Geochemistry and Petrology Branch, Geological Survey, U. S, Department of Interior, and found to be the montmorillonite type. The base exchange capacity of this clay was 29 meq. of exchangeable cations per 100 grams dry weight of clay (105’ (2.).

RADIOISOTOPES

Oak Ridge tap water was used in all tests. A chemical analysis of a “grab” sample of this water is given in Tahle I.

The following radioactive materials were used as contaminants: ruthenium-106-rhodium-106; strontium-90-yttrium-90; zir- conium-95-niobium-95; cerium-141, -144-praseodymium-144; iodine-131; barium-140-lanthanum-140; and four fission prod- uct mixtures known as NFP-1) MFP-2, MFP-3, and MFP-4. The ruthenium-106-rhodium-106, strontium-90-yttrium-90, ce- rium-141, -144-praseodymium-144, and barium-140-lanthanum- 140 were obtained as the chlorides in hydrochloric acid solution with a radiochemical purity greater than 95%. Zirconium-95- niobium-95 was obtained as the oxalate complex in oxalic acid solution. Radioiodine131 was obtained as the iodide in rreak basic sodium sulfite solution having a radiochemical purity greater than 99%.

MFP-1 mas a mixed fission product contaminant consisting of 44y0 trivalent rare earths, 27% cerium, 17y0 strontium, 5y0 barium, 3% ruthenium, 1% cesium, and 3% traces of a large number of other radioisotopes. MFP-2 was a mixed fission product contaminant consisting of 50% cesium, 16% ruthenium, 10% trivalent rare earths, 10% strontium, 5% cerium, 5% barium, and 4% traces of a large number of other radioisotopes. RIFP-3 was a fission product mixture composed of 20% rare earths, 20% niobium, 15% zirconium, 13% yttrium, 12% ruthen- ium-rhodium, 12% strontium, and 8% traces of a large number of other radioactive fission fragments. RIFP-4 was a fission product mixture consisting of 30% cerium-144-praseodymium- 144, 22% promethium-147, 22% strontium-90-yttrium-90, 18% cesium-137-barium-137, 6% ruthenium-106-rhodium-106, and 2% traces of a large number of other radioisotopes. The fission product mixtures were nitrates in strong nitric acid solution. All the radioactive contaminants were obtained from the Opera- tions Division of the Oak Ridge National Laboratory (1) .

A stock solution was made by dissolving the radioactive mate- rial to be used in tap water. After mixing, the p H of this “spiked” solution was taken using a Beckman Model G glass electrode pH meter. Then 1-ml. initial samples of the solution were taken, placed in a stainless steel counting dish, dried under infrared lamps, and counted using a Geiger-Muller (G-RI) mica end-window tube (1.8 mg. per sq. em. thick), filled -n-ith helium plus alcohol vapor. This tube was connected to a 64 scaler. The counting results were corrected for background and coinci- dence loss. Difference between the initial and final count rate represented the removal. The initial concentration of radio- activity in the spiked solution was in the range of 5 X 10-3 to 5 x 10-2 pc. per ml. (assuming 10% counting efficiency).

CONCENTRATION OF CLAY

Five hundred milliliters of this stock solution were then added to each of four 1-liter beakers containing quantities of the clay to give concentrations of 1000, 2000, 3000, and 4000 p.p.m. of clay

Except pH

1061

1062 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 46, No. 5

Figure 1. Jar Test Equipment for Decontamination of Radioactively Contaminated Water by Slurrying with Clay

(Figure 1). The slurry was stirred a t a constant, speed of approximately 250 r.p.m. for 90 minutes. Samples were taken from each beaker every 15 minutes and filtered through filter paper. An aliquot portion of the filtrate vias placed in a counting dish. dried, and counted, using t,he same Geiger-LIuller tube and scaler used for counting the stock solution. By this procedure, i t was possible to evaluate the efficiency of the clay at variable concentrations and for different contact times. In order to ascertain what, if any, portion of the radioactive material was removed by adsorption on the filt,er paper alone, a duplicate sample mas taken a t 90 minutes for each of the tests using 1000 p.p.m. clay. This sample was centrifuged and an aliquot part of the supernatant liquid placed in a counting dish, dried. and counted using the procedure described.

pN EFFECT

In an iiivest'igation of the eflect of hydrogen ion ooiiceiitration, MFP-3 was selected as the radioactive coiitamiriaiit. ii stock solution of the contaminant, in tap water \\-as prepared in the nianner described. Then 500 mi. of this solution were adtled to each glass 1-liter beaker. The pH was adjusted t o the desired hydrogen ion concentration upiiig a solution of either hydro- chloric acid or sodium hydroxide. Enough clay was added to give a concentration of 1000 p.p.m. and the test procedure of stirring, sampling, and counting folloived.

COYCENTRATION OF ACTIVITY

In order to detect any effect the initial concentration of radio- activity may have on removal, experiments Tvere made a t t,hree levels of activity: (1) Ion (487 counts per minute per ml.), (2) moderate (4820 counts per minute per ml.)> and (3) high (45,000 counts per minute per ml.). These three concentrations of radio- act,ive contaminants cover the expected range of Contamination immediately aft,er a bomb blast near a large wat,er supply ( 8 , 3). The best estimated concentration of radioactivity that can be expected in a large water supply due to induced activity, fall-out, and other factors is about pc. per ml. or 2220 counts per minute per ml. (assuming 10% counting efficiency).

The tap Lvater, a t the activity level to be investigated, waE added to each beaker, the pH was t'aken, and the various concen- trations of clay material were added. In this particular investi- gation, t,he concentrations of clay used were 430, 900, 1800, and 2250 p.p.m. The radioactive contaminant used in this series of te& was fission product mixture hIFP-4. I n order to obtain comparable results, the foregoing t,est procedure was followed.

CONCENTRATION O F CALCIUM IOXS

T o note t'he effect of calcium ion concentration on removal The test pro- efficiency, an additional investigation was made.

cedure varied only slight,ly from that used previously.

A% stock solution was made by dis- solving the radioactive material to be used (MFP-3) in distilled water. After mixing, 500 ml. of this spiked solution xas added to each 1-liter beaker con- taining enough calcium hydroxide or calcium chloride t o give the desired con- centration of calcium ions. After the calcium hydroxide or calcium chloride had been dissolved, the pH of t,he solu- tion was adjusted t o the range 7.0 to 7.9) using either hydrochloric acid 01' sodium hydroxide. Initial samples were then taken for counting and 0.5 gramof clay was adtled to each beaker. The mist>ure xas slurried for 90 minutes at R, constant speed (250 r.p.m.). Samples xere taken every 15 minutes and fil- tered, and an aliquot portion was placed in a counting dieh, dried, and counted. By this procedure i t %-as pofisible to evaluate the effect of calcium ion con- centration on removal of mixed fission products. In order to ascertain tho effects of various chemical forms of cal- cium, both calcium hydroxide and cal- cium chloride u-ere used.

RESULTS

Summarized data for the test' are given in Table 11. Detailed data for two tests on two of the more important contaminantP, zirconium-95-niobium-95 and MFP-1, are given in Table 111.

The data on effect of pH on removal of mixed fisilion product,r; by clay slurry are given on Table IV.

Table V reports the results of the investigation on the effect of calcium ion concentration on per cent removal of LIFP-3, whrvi 1000 p.p.m. of clay ivas used as the slurry agent.

The pH values given in Tahle I1 are riot necessarily optimum for the particular radioact,ive materials reported. However, test results reported indicated that variations of 1 or 2 pH units on either side of the neutral point did not, afi'ect the efficiency of removal.

The results obtained a t 90 minutes' cont,act time are plotted in Figure 2. The plot s h o w per cent removal versus clay dosage for the various radioactive contaminants.

TABLE 11. D E c o x r A n m . I T I o y OF RADIOACTIVELY COSTAMIXATED m A T E R BY SLURRYING WITII CLAY

Clay Concentration, P.P.31. 1 O O O b 1000 2000 3000 4000

Initial i i c t i ~ i t y , ~

Con- C./Min./ taminant 311. pH Per Cent Removal

Ru13B-R11106 1 , 3 8 0 5 . 2 50.9 50 .5 59 .3 61.5

gr50.1-90 3,G70 7 . 7 8 3 . 3 83 .4 89.1 9 2 . 9 9 5 . 0 3,360 7 . 5 3 . 9 4 . 9 5 .0 3 . 4 3 . 4 4,150 8 . 0 9 9 , 6 99 .7 99 .8 9 9 . 9 9 % 9 ce141,u4-pr144

Bal40-Lal40 3 ,340 7 . 8 8 7 . 8 8 8 . 8 92 .0 9 4 . 3 97 .1 M F P- 1 10,900 8 . 8 82 .2 8 2 . 0 82 .9 8 8 . 3 9 0 . 3 MFP-2 2,110 9 . 0 68.7 70.0 70.9 72 .8 7 3 . 3 MFP-3 3 ,290 7 . 7 7 9 . 2 79 .0 82.1 8 3 . 6 8 4 . 9

12,100 7 . 5 9 7 . 9 98 .0 99.1 99.4 5 i . O Zr05.Nb55

I131

a Uncorrected for counting efficiency (approximately 10%). All per cent removal figures based upon SO-minute filtered samples,

except this column, which is for centrifuged samples.

~~- Initial Slurry Time, Winutee Clay Activity." Con- Concn., in./ 15 Per 30 Cent 45 Removal 60 90

taminant P.P.M. hll. ZrQS-NbBb 1000 12,100 9 3 . 5 94.6 95 .8 9 7 . 0 9 7 . 9

2000 12 ,000 9 6 . 7 97.9 98 .0 98.8 90.1 3000 12,100 97.1 9 8 . 4 9 8 . 7 99 .1 99 .4 4000 12,000 98 .5 9 8 . 8 99 .2 99 .4 99 .6

MFP-1 1000 10,700 61 .3 7 0 . 6 76.6 79.9 8 2 . 0 2000 10,900 64.7 73 .7 78 .5 81 .4 82 .9 3000 10,700 67.4 79 .4 82.6 85 .0 8 6 . 3 4000 11,300 7 1 . 6 7 0 . 9 87 .4 8 9 . 1 90 .3

a Uncorrected for counting efficiency (approximately 10%)

May 1954 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 1063

Figure 2. Decontamination of Radioactively Con- taminated Water by Slurrying with Clay

90-minute contact time

It is seen from Table I1 and Figure 2 that clay slurried with con- taminated water was very effective for removing certain radio- active materials, particularly cerium-141,-144-praseodyrnium- 144, zirconium-95-niobium, barium-140-lanthanum-140, stron- tium-90-yttrium-90, MFP-1, and MFP 3. Clay was leas effec- tive for MFP-2 and ruthenium-106-rhodium-106, and very poor for iodine-131.

Increased concentrations of clay increased the per cent re- movals, but not to an appreciable degree. It appears that 1000 p.p.m. is an adequate dose for batch treatment and that higher quantities are wasteful of clay.

Increased contact times proved to be of value for difficult-to- remove r a d i o a c t i v e m a t e r i a1 s . For easy-to-remove materials, such as zirconium-95-niobium-95, 15 minutes’ contact time was almost as effective as 90 minutes’ contact time.

The results of the hydrogen ion concentration study are plotted in Figure 3, which shows per cent removal versus pH for the partic- u l a r c l a y c o n c e n t r a t i o n a n d MFP-3 solution. It can be seen from Table I V and Figure 3 that at pH values lower than 5 the efficiency of the clay decreases rapidly until pH 4, where the

removal decreases more slowly. I n the range of pH 5 to 11, the removal is essentially constant.

Figure 4 is a plot of the per cent removal of MFP-4 obtained a t 90 minutes’ contact time and for three levels of radioactivity versus concentration of clay in parts per million. The results shown indicate that the initial concentration of a fission product mixture does affect the per cent removal, under test conditions, to some extent. The moderate concentration of activity yielded the highest per cent removal, while the highest concentration gave the lowest per cent removal.

Figure 5 shows the effect of calcium concentration on the re- moval of fission product mixture MFP-3. The removals are

TABLE Iv. EFFECT OF pH ON REMOVAL O F hfIXED FISHOV PRODUCTS BY CLAY SLURRY

(Radioactive contaminant MFP-3; concentration of clay 1000 p p In )

Slurry Time, Minutes 15 30 45 60 75 90 BOa

P H Per Cent Removal

I . Initial activity 2730 e./min./ml. 3 49.2 50.9 50.1 51 .6 51.4 52.9 55.3 5 64.6 66.6 72.6 74.0 75.2 76.2 75.9 7 64.0 66.7 72.9 74.9 78.2 78.7 78.6 9 64.2 67.5 73.5 76 .3 79 .5 80 .4 80 .5

I1 80.3 80 .1 81.1 81 .7 82.2 82.6 83.4

11. Initial activity 3400 c./min./ml. * ,1 49.8 51.3 52.3 52.9 54.9 55.2 j 4 . 0 8 06.4 68.5 74.3 76.1 75.9 76.0 76.2 7 65.5 69.0 75.7 76 .7 78.7 7 8 . 8 78 .5 8 70.6 74.1 79.1 79.2 79.5 8 0 . 8 81.0 10 76.6 77.1 79.4 79 .1 78.8 79.2 78.9

a All per cent removal figures based upon filtered samples, except this

b Uncorrected for counting efficiency (approximately 10%). column which is for centrifuged samples.

TABLE v. EFFECT OF CALCIUM 10s CONCENTRATIOS O S R m f o V A L OF MIXED FISSION PRODKCTS BY CLAY SLURRY

(Radioactive contaminant MFP-3; concentration of clay 1000 p.p.m.)

- Slurry Time, Minutes 15 30 45 60 75 90 90“

Per Cent Removal Ca,

P.P.hl. pH

I. Initial activity 3590 c./min./ml.* Ca added as Ca(0H)Z 20 7.20 71.9 72.8 74.9 75.5 76.0 77.2 7 6 . 6 40 7.35 72.8 73.9 28 .0 78.2 78 .8 79.9 79.2 60 7.45 7 2 . 6 75 .2 ( 7 . 7 78.0 78.6 78.9 7 8 5

100 7.70 72.2 74 .3 78.2 78 .3 78.9 79.2 79.3 200 7.90 72.9 75.0 78 .1 78 .5 78.4 78 .8 79.1

11. Initial activity 2680 o./min./inl. Ca added a8 CaClz 40 7.05 71 .3 71.9 75.0 24.1 74.7 75 .2 7 5 . 3 80 7.15 71.0 73.1 7 5 . 3 13.7 75.3 75.8 7 5 6

120 7.00 70.0 71.2 72 .9 7 3 . 2 74.7 75.2 76 .4 150 7 . 2 0 69.7 72.4 73 .5 73.7 7 4 . 4 75 .0 75.0 a All per cent removal figures based upon filtered samples, except this

column which is for centrifuved samples. Uncorrected for counting efficiency (approximately 10%).

PH Figure 3. Effect of pH on Removal of MFP-3 by Clay Slurry

1000 p.p.m.

1064 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol. 46, No. 5

CONCENTRATION OF CLAY I N Pp.m.

Figure 4. Effect of Initial Concentration of Radioactbit? on Removal of hlixed Fission Products by Clay Slurrj

90-minute contact time

similar when eithei calcium hydioxide or calcium chloride is used as the source of calcium ions. The plot of the calciuni chloride additive was slightly lower than the cuive obtained with calcium hydroxide. T h k may be due to the slightly Ion-er pH values and the necessary addition of other ions to adjust the pH. Hoviever, as the resulte indicate, calcium ions do not appieciably influence the removal of MFP-3 within the test range studied.

DISCUSSION

Clays are colloidal silicates of closely packed oxygen atoms and silicon tetroxide tetrahedra linked together by sharing corners, edges, and faces in such a fashion that large, complex units result. The structural differences betxyeen clays detelmine the degree of preferential adsorption or ionic dissociation which gives rise to the exchange capacities.

According to Kaufman (C), the ion exchange capacities of typical clays are, in terms of milliequivalents of cations per 100 grams of clay:

~Iontmori l loni te Attapulgite-montmorillonite group Illite Kaolinite

60-100 25-30 20-40

3-16

The exchange affinities for most' ionic systems, in aqueous media, folloir- the lyotropic series:

Li < S a < I< < Rb < Cs

9 1 < Sc < Y < Eu < Sm < S c i < Pr < Ce < La 1Ig < Ca < Sr < Ra

3Iattson ( 6 ) states that the phosphate ion is more stronglj- adsorbed than the sulfate ion and the sulfate ion more strongly than the chloride ion.

The explanation of the individual behavior of the catioiis in the eschange process is based on Coulomb'a law, which expresses the magnitude of attradion existing between negative oxygen ionc of the carystal lattice and adsorbed cations.

The haiie exchange capacity of clay and Gmple surface adsorp- tion capacity may be used to explain the mechanism of t,he re- nioval of radioactive contaminants from n-ater solution. How- ever, the inechanism of adsorption is obscure, alt'hough it has been suggested that the adsorbent Filters into a loose combina.tion n-iih the material adsorbed by means of latent valences of atoms in the surface layers. The adsorbed material may be released (eluted from the surface of t,he clay particles) by changing the acidity of the soil solution. It can be seen from the results that the rate of adsorption or exchange (of the radioactive material) commences with a very high velocity for the f i s t few minutes, ])ut rapidly falls off with time; t,hus i t ir-odd require many hours to increase the amount removed.

The radioisotopes used in this series of teats were selectecl be- cause they are all high-yield fission products having significantly long half lives and therelore ~vould be present after a nuclear detonation. The various mixtures of fission products were used in order to indicate the range of removal values that could be expected when the contaminating radioactive material resulted from a nuclear weapon.

The clay was very effective in the renioval of certain radioiso- topes and less effective on ot'liers, as seen in Figure 2. Tlie pro- cedure reported herein was least eflective in the removal of radioiodine-131. Ot,liers also have reported no measurable re- moval of iodine-131. Straub, Morton: and Placak (8) reported caoagulation, settling, and filtration ineffective on iodine-131. Pordered metals were repoyted by the author ( 5 ) to remove onl\- 45% of radioiodine from a tap n-ater solution. However, Friend (2) reported that, Amherlite IRA-100 ion rxchange resin, when used on t,he hydroxide cycle, effected a rem.ova1 of 98+% of iodine-131 in tap water a t an initial dosage of 3310 counts per minute per ml.

-is most surface waters contain some clay in suspension, it is probable that a certain aniount of self-decontaminat,ion n-oultl

80

70 _I

z 0 z w 1x160 6e

a

50

eo 4 0 60 eo 100 120 140 I60 I 8 0 200

Effect of Calcium Ion Concentration on Removal of 3Iixed Fission Products by

p,p.m. C A L C I U M

Figure 5. Clay Slurry

90-minutc contact time 0. Ca as calcium hydroxide X. Ca as calcium chloride

May 1954 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 1065

take place if the waters were contaminated with radioactive materials. In addition, the water would come in contact with clay and soil particles in the bed or bottom of the stream or lake. Treatment of the water by coagulation would remove much of the radioactivity by removing the contaminated clay particles and also by coagulation per se. The effectiveness of a coagulation process in regard to radioactivity removal could undoubtedly be increased by either a preliminary slurrying with clay or the addition of rlay directly to the water during the coagulation step along with the coagulating chemicals.

The removal of radioactive materials by clay slurrying is in the preliminary stage of investigation and there is definite need for more information, in order that the technique may be exploited to its best advantage and its limitations recognized.

LITERATURE CITED

(1) Atomic Energy Commission, “Isotopes,” catalog and price list No. 3, July 1949.

(2) Friend, 9. G., “Report on Investigation of the Removal of 1’8’ and SrE9 from T$7ater by Ion Exchange Resins,” master’s thesis

submitted to Faculty of Virginia Polytechnic Institute, June S, 1952.

(3) Glasstone, Samuel Ed., “Effects of Atomic Weapons,” U. S. Government Printing Office, 1950.

(4) Kaufman, W. J., Nesbitt, J. B., Goldman, M. I., and Eliassen, R., “Removal of Radioactive Anions by Water Treatment,” Atomic Energy Commission, NYO-1571 (Sept. 20, 1951).

(5) Lacy, W. J., J . Am. Wafw Works Assoc., 44, 824 (September 1952).

(6) AIattson, Sante, Soil Sci., 30, 459-96 (1930). (7) Morgan, K. Z., and Straub, C. P., “External and Internal Ex-

posure to Ionizing Radiation and MPC of Radioactive Con- tamination in Air and Water Following an Atomic Explosion.” talk before Southeastern Section, American Physical Society, April 10, 11, and 12, 1952.

(8) Straub, C. P., Morton, R. J., and Placak, 0. R., J . Am. Water Works Assoc., 43, 773 (October 1951).

(9) Sullivan, W. H., “Problem of Radioactive Water Contamination in Warfare,” U. 8. Atomic Energy Commission, Technical Information Division, ORO, Oak Ridge, Tenn., ADZ-83, N.S.

RECEIVED for review Blrtroh 14, 1953. .&CCEPTED February 3, 1954.

Superfast GR-S Polymerization at 41” F. J. R. MILLER AND H. E. DIEM

Akron Experimental Station, B. F . Goodrich Chemical Co., Akron, Ohio

RESErlRCH and development goal of reducing the cold A rubber reaction cycle at 41” F. to 30 minutes or less was instituted a t the B. F. Goodrich Chemical Co. early in 1951. Only by achieving this aim could the economic feasibility of making cold GR-S in a pipeline reactor ( 7 ) of practical length be properly studied. Production of cold synthetic rubber in poten- tially inexpensivc pipe reactors, rather than in thc present large pressure kettles, is now considered possible.

The term “superfast” was adopted to describe the polymeriza- tion recipes developed for use in the pipeline reactor, because reaction rates are 50 times as rapid as those for conventional commercial cold rubber recipes which have already been termed “fast” recipes. The superfast recipes were made possible by the availability of very active organic hydroperoxides, increased acti- vator and initiator concentrations in the interest of reaction speed, and further refinements of the redox polymerization discoveries which date back to 1940 (8). The rubber produced by this new process promises to be equal in quality to standard cold rubber.

Pertinent studies of rapid recipes have been made on emulsion butadiene-styrene systems a t 122” and 158” F. in both Germany ( I O ) and the United States (I), while 41’ F. and colder rapid recipes have been reported by several groups, including Fryling and Follett (d), Howland et al. (6), and Stewart and Paxton (9).

MATERIALS AND METHODS

The following materials mere used throughout this develop- ment program.

MONOMERS. Butadiene. Carbide and Carbon Chemicals

Styrene. Dow Chemical Co., assumed 100% pure, used as

MODIFIER. tert-Dodecyl mercaptan. Hooker Electrochemi-

Corp., 98.5% pure, used as received.

received.

cal Co., 100%.

Powder Co., 79% total solids. EMULSIFIERS AND ELECTROLYTES. Dresinate 214. Hercules

A disproportionated rosin acid . _ ~- potassium soap.

Dresinate 731. Hercules Powder Co., 70% total solids. A disproportionated rosin acid sodium soap, containing same acid as Dresinate 214.

Potassium laurate. Armour and Co.’s Neofat 12 neutralized

Potassium myristate. Armour and Co.’s Neofat 14 neutral-

Potassium soap, Office of Synthetic Rubber. Procter and

Potassium chloride. General Chemical Co. Tamol N. Rohm and Haas, dispersing agent. Sodium salt

Water. ACTIVATOR COMPONENTS. Ferrous gluconate. Charles Pfizer

Ferrous sulfate heptahydrate. Sodium pyrophosphate. General Chemical Co. Sodium silicate. Harshaw Chemical Co., 40” €34. NaeO-

Si02 ratio ca. 1 to 3. Versene Fe-3. Bersworth Chemical Co., 89%. Tetrasodium

salt of ethylenediaminetetraacetic acid. INITIATORS. tert-Butylisopropylbenzene hydroperoxide (Diox

7). Phillips Petroleum Co., 40%. Chlorocumene hydroperoxide. Cumene hydroperoxide (CHP). Hercules Powder Co., 68%. Diisopropylbenzene hydroperoxide (DIP). Hercules Powder

with reagent potassium hydroxide.

ized with reagent potassium hydroxide.

Gamble Co., 97.6%.

of polymerized alkyl naphthalene sulfonate.

& co .

Fat ty acid type (KOSR).

Distilled water was used throughout.

General Chemical Co.

Hercules Powder Co., 34%.

Co., 50%. Phenylcyclohexane hydroperoxide (PCH). Hercules Powder

co., 20 to 25%. SHORTSTOP AND ANTIOXIDANT. Good-rite Shortstop 3955.

B. F. Goodrich Chemical Co. A 41% total solids aqueous solu- tion of a 50/50 mixture of sodium oolvsulfide and sodium di- ~. methyldithiocarbamate.

phenylamine. Good-rite Stalite. B. F. Goodrich Chemical Co., alkyldi-

The polymerization reactions were conducted a t 41” F. in crown-capped 32-ounce beverage bottles. The quart-bottle charges contained only 50 grams of monomers plus proportionate amounts of other recipe ingredients in order to minimize heat build-up within the bottles during polymerization. The usual order of charging consisted of adding the hot emulsifier solution first and, after cooling, the styrene-hydroperoxide solution and the butadiene. The bottles were capped with self-sealing caps, pressured with nitrogen, and rotated in the polymerization bath a t 41” F. for a t least 30 minutes prior to initiating the reaction by injecting the activator suspension. Increasing the time of tum-