932
Vol. 40, No. 5
INDUSTRIAL AND ENGINEERING CHEMISTRY
retardation-namely, by the use of mixtures of normal and tertiary mercaptans and by a n increase in the sodium hydroxide content of the syst,em. The role of mercaptan in a recipe, such as given in Table I, is a dual one. It acts both as a chain initiator and as a chain transfer agent. The data i n Table VI suggest that a DDhl content. of from 0.075 to 0.2 part should be sufficient to function as a n initiator and that a tertiary mercaptan could then be used as modifier. This was verified in pilot plant experiments and found to be a practical method of overcoming retardation by ammonia. hleasurements of Mooney viscosity of rubbers produced with ammoniaretarded recipes indicated that ammonia has litt’leif any effect on the modifier activity of tertiary mercaptans. Thus, it appears that retardation affects initiation and not chain transfer. The effect of increasing the sodium hydroxide content of the recipe above that required to give a pH of 10 is interesting. Without ammonia (part A, Table VIII), the conversion is quit’e constant up to a sodium hydroxide cont’ent of 0.50 part. Some precoagulum appeared in the reaction vessel a t higher conversions with the highest alkali concentrat’ion. I n the presence of 200 p.p.m. ammonia, however, the increase in rate of conversion was very marked, At 16 hours, with 0.512 part sodium hydroxide, a conversion of 90.0% was obtained (Figure 4). This is about 15% higher than was expected without ammonia. The results indicate that, under these conditions, ammonia is a polymerization
accelerator rather than a retarder. To verify this rather surprising observation the experiments report,ed in part C of Table VI11 were conducted. The ammonia content was varied in two series of experiments, one with, and the other without., sodium hydroxide. The now familiar ret,ardation was observed in the absence of sodium hydroxide but an increase in rate wit,h increase of ammonia up, to 200 p.p.m., followed by an extremely pronounced retardation, was obtained in t,he presence of sodium hydroxide. The data are plotted in Figure 5. LITERATURE CITED ( 1 ) Baker, W , O., Hell Laboratories, to Office of Rubber Reserve, private communication, 1942. (2) Cragg, L. H., Rubber Chem. Technol., 19, 1092 (1946). (3) Cuthbertson, G. R., Coe, W. S., and Brady, J. L., ISD. ENQ. CHEM.,38, 975 (1946). (4) Fryling, C. F., Ibid., 3 9 , 8 8 2 (1947). (5) Fryling, C. F., U. S. Patent, 2 , 3 7 8 , 6 9 5 (June 19, 1945). (6) Houston, R. J., Anal. Chem., 20, 49 (1948). (7) India Rubber World. 1 1 0 . 4 1 8 11944). (8) Kolthoff, I. M., and Harris, 6‘.E., IXD. ENG.CHEX.,AXAL.Ed., 18, 161 (1946). (9) McCleary, C. D., U. S.Rubber Co., to Office of Rubber Reserve, private communication, 1944. RECEIVED January 27, 1947. Presented in the High Polymer F o r u m before the Division of Rubber Chemistry a t the 110th Meeting of the ~ M E R I C A N CHEMICAL SOCIETY, Chicago, Ill.
Curnene Hydroperoxide in Redox Emulsion Polvmerization J E. J. VANDENBERG
AND
G. E. HULSE
Hercules Powder Company, Wilmington 99, Del.
a
redox system consisting of cumene hydroperoxide
(a,a-dimethylbenzyl hydroperoxide), a reducing sugar and
iron pyrophosphate has been found to be remarkably effective for initiating emulsion polymerization with disproportionated rosin soap emulsifier. It gave ten- to twenty fold faster polymerization rates for a variety of vinyl compounds-styrene, methyl methacrylate, butadiene, butadiene-styrene, butadiene-acrylonitrile, and vinyl chloride-than did the conventional potassium persulfate initiator. In addition, it was superior to
I
N R E C E N T years, efforts have been made t o increase the
reaction rate of peroxide-initiated polymerizations t o increase plant capacity or, in certain cases, t o obtain improved products by lower temperature polymerization. The obvious use of more peroxide or peroxides of lower thermal stability to accomplish this is generally unsatisfactory for economical, quality, or handling considerations. On the other hand, emulsion polymerization has been a significant improvement (10, 11, 20) because i t usually gives rates of polymerization as much as tenfold faster than a similar bulk or homogeneous system. The most important recent development i n this field consisted of combining reducing agents with peroxides. This method, which was first disclosed in the patent literature (4, 6, 7 , 8 2 , 23,86,87), has been the subject of recent publications (8, 3, 11, IS, 14, 81) including some German work on synthetic rubber (86). Many workers (11, 28, 86) have used the term “redox,” borrowed from the similar oxidation-reduction biological systems
similar redox systems based on the common peroxides and per salts. The polymerization rate curves were linear and free from induction periods. The copolymerization of butadiene and styrene (GR-S) with this system gave 72Yo conversion in 2 hours at 40” C. or in 23 hours at 15’ C. The mercaptan (thiol) modifier was not required for the initiation process, but i t was necessary to obtain a soluble and processable rubber. Laboratory tests indicated that the physical properties of the synthetic rubber prepared at either 40” or 15” C. were similar to commercial GR-S-10.
of Tarburg, to characterize this combination of reducing and oxidizing agents for initiating polymerization. Bacon ( 2 ) , on the other hand, coined the term “reduction activation.” Baxendale, Evans, and Park (3) elucidated the mechanism for the relatively simple ferrous iron-hydrogen peroxide system for water solution polymerization. I n this case, free radicals are generated for initiating polymerization by a simple electron transfer reaction: H20z F e f f . . . . HO . OHFei The mechanism of the more complex redox systems may be similar but a detailed analysis of the factors involved has not been presented. The advant,age of redox systems is that fast rates can be obtained with peroxides of high thermal stabilitg Various peroxidea and per salts which are widely used in polymerization work (hydrogen peroxide, benzoyl peroxide, and potassium persulfate) have been successfully used in redox systems.
+
+
+
.
+ +
INDUSTRIAL AND ENGINEERING CHEMISTRY
Map 1948
It has now been found that a,a-dimethylbenzyl hydroperoxide, usually designated as cumene hydroperoxide, provides a superior redox system for initiating emulsion polymerization with a disproportionated rosin soap ( I , 9) Dresinate 731 (registered, U. S. Patent Office by Hercules Powder Company). This system consists of cumene hydroperoxide plus a reducing sugar and a soluble iron salt such as ferric pyrophosphate. Most of the authors' studies have been on the preparation of GR-S type synthetic rubber a t 40" C. by the copolymerization of 75 parts of butadiene with 25 parts of styrene. A polymerization formula which gave good results and which is the basis for the subsequent discussion is as follows:
933
T I M E , HOURS
Figure 1.
Initiators for GR-S Polymerization
REDOXFORMULA Ingredient Butadiene Stvrens Water Dresinete 731 (soap solids) Sodium hydroxide MercaptanQ Cumene hydroperoxide (initiator) Fructose (reducin agent) Ferric iron, as sulfate (activator) NadPnOr. lOHnO
}
a
Parts 75 25
180
5 0.061 0.5 0.17 0.5 0.017 1.5
Tertiary mercaptan unless otherwise noted
EXPERIMENTAL
Each polymerization was carried out GENERALPROCEDURE. with 50 grams of monomers in a n 8-ouGce beverage bottle whose cap had one or two holes (approximately 0.125 inch) and a selfsealing, Buna N rubber liner of the type desi ned by Kluchesky (16). During the polymerization the bottye was rotated a t 15 r.p.m. in a 40.0' * 0.05" C. (unless otherwise notedywater bath on a cylindrical rack. The bottle was tangentially located 10.6inches from and a t right angles t o the axis of rotation. The per cent conversion of the monomers t o polymer for a given reaction time was calculated from the solids found on drying an aliquot (approximately 4 grams plus 20 mg. of hydroquinone) of the latex which was obtained by the hypodermic syringe sampling technique of Houston (13). Numerous precautions were taken t o eliminate all extraneous material from the polymerization system. The bottles were cleaned by soaking them in the usual dichromate-sulfuric acid mixture followed by a n extensive washing procedure with distilled water and finally with double-distilled water. The Buna N rubber cap liners were extracted in a Soxhlet extractor for 3 days with benzene and then dried. REAGENTS-SOURCEAND TREATMENT. Butadiene. Phillips Petroleum Company, pure grade (99 i. mole yo),freed of inhibitor by distillation at atmospheric pressure. Styrene. Dow Chemical Company, N-99, washed with 10% aqueous sodium hydroxide until color-free, then with water until alkali-free; dried with Drierite and filtered. Water. Double distilled. Dresinate 731. Hercules Powder Company sodium soap of disproportionated rosin (64 * 1% solids in aqueous medium and acid number of 11 * l), neutralized with the equivalent amount of sodium hydroxide and dissolved in most of the water used. The resin acids in this product are mainly dehydroabietic acid and hydroabietic-type acids. Mercaptans. The primary mercaptan was the Office of Rubber Reserve's standard dodecyl mercaptan which is approximately 5% Cl0, 58% Clz, and 25% (&,with 12% impurities (19). The tertiary mercaptan was the Phillips Petroleum Company's Blend No. 7, which consists of 3 parts C1?,1 part C14, and 1 part
monomers. The p H at this point, with the proportions given in the redox formula, was 10.0 * 0.2. I n the case of GR-S, the butadiene, styrene, and mercaptan were added together. Any air present in the free space within the bottle was swept out by permittin a slight excess (approximately 0.5 gram) of butadiene With monomers whose boiling points were above t o boil room temperature, such as styrene and methyl methacrylate, this was 'accomplished by a nitrogen sweep before capping. For convenience of operation, the bottle was then stored in a dry ice chest not longer than 16 hours. Before placing in the polymerization bath, i t was left at room temperature for 1 hour. RUBBERISOLATION PROCEDURE. The rubber prepared for the determination of physical properties contained 1.5% phenyl0-naphthylamine antioxidant which was added as a n aqueous suspension t o the latex prior t o its precipitation. The latex, after steaming t o remove unreacted styrene, was creamed by the addition of a 12% sodium chloride solution and then coagulated with a 1% sulfuric acid solution. After water washing, it was dried t o constant weight a t 80' C. in vacuum.
08.
e R - s POLYMERIZATION
The cumene hydroperoxide redox system copolymerized butadiene and styrene (GR-S) t o a 72% conversion in 2 hours a t 40' C. (Figure 1). This was sixteen times faster than with a n equivalent amount (0.3 part) of the conventional potassium persulfate initiator. I n addition, the slow initial rate which has been characteristic i n the past of Dresinate 731 (9) or even the purest resin acid soaps (1) was eliminated. The effect of a number of variables on this cumene hydroperoxide redox system haa been studied for GR-S polymerization at 40" C.
HYDROPEROXIDE CONCENTRATION. The initial rate of polymerization was not very dependent on the cumene hydroperoxide concentration (Figure 2). Thus, i t increased only about 30% as t,he hydroperoxide was increased from 0.04 t o 0.4 part and then fell off a n equal amount as the hydroperoxide was further increased t o 1.4 parts. However, with less than about 0.1 part
-1
..t
I
I
I
I 2 TIME-
I
I
I 3
d
cl6.
Cumene Hydroperoxide. A sample prepared in this laboratory, dissolved in the soap solution on the basis of its hydroperoxide content (47%); the main impurity was cumene. Fructose. Pfanstiehl Chemical Company's C.P. special dlevulose added 8s a n aqueous solution. Iron Activator. A stock solution of ferric sulfate, c.P., and sodium pyrophosphate, c.P., in water such t h a t 10 cc., were equivalent to the amounts given by the pol merization formula. LOADINQTECHNIQUE. The fructose andriron activator were mixed in the beverage bottle with the Dresinate 731, water, and cumene hydroperoxide combination just prior t o adding the
zot OA
Figure 2.
I
HOURS
Effect of Cumene Hydroperoxide
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
934
T I M E , HOURS
F i g u r e 3.
Stepwise A d d i t i o n of C u m e n e Hydroperoxide
T I M E , HOURS
F i g u r e 4.
Effect of Fructose
of hydroperoxide the polymerization either stopped or slowed down before a high conversion was reached. This was due t o hydroperoxide exhaustion, as the addition of more hydroperoxide after the polymerization reaction had ceased, caused it to proceed a t the original rate (Figure 3 ) . FRUCTOSE CONCENTRATIOX. The polymerization rate could be controlled and a wide range of useful rates obtained by simply adjusting the amount of fructose in the redox formula (Figure 4). Thus, decreasing the fructose from the usual 0.5 part t o 0.02 part decreased the rate of polymerization approximately fourfold without deviating from a linear rate curve. On the other hand, increasing the fructose above 0.5 part to 4.0 parts increased the initial polymerization rate only slightly. The major effect, in this case, was to slow down the polymerization before a high conversion was reached. The decrease in rate occurred a t a lower conversion for the higher amount of fructose and was apparently due to the depletion of the hydroperoxide. This indicated that the rate of hydroperoxide decomposition increases progressively with the fructose concentration. It appears that the optimum amount of hydroperoxide varies directly with the fructose: i t is greater or less than 0.17 part depending on whether the fructose is greater or less than 0.5 part. ROLE OF IRoK A k C ~ ~ ~ The ~ 4 ~major o ~ . effect of the iron activator (ferric sulfate-sodium pyrophosphate combination) was t o eliminate initial periods of very slow polymerization. Above a concentration of about 10 p.p.m. iron (based on monomers), it had little effect on the final polymeiization rate (curves 1, 2 , and 5 , Figure 5 ) . Without any iron acbivator in the cumene hydroperoxide redox system (curve 5, Figure 5), a fast rate was obtained only after 6 hours of slow polymerization. The final rate was about one third of that obtainable with the iron activator present. Omitting either the ferric sulfate or the sodium pyrophosphate constituent of the iron activator from the redox formula aIso gave inferior results (curves 3 and 4, Figure 5). In addition to the beneficial effect of thc sodium pyrophosphate on the efficiency of the iron, presumably by providing a watersoluble iron complex a t p H 10, i t was required to obtain a low viscosity emulsion. It has also been found that ferric and ferrous iron give equivalent results i n the cumene hydroperoxide redox sysbem.
Vol. 40, No. 5
It is emphasized that the amount of iron required t o overcome the initial period of slow polymerization varies considerahly with the type and amount of reducing agent and peroxide (Figures 2, 4, 9, and 10). For example, the less effective reducing agents, such as glucose, require more iron. Further evidence that the iron activator does not exeri a controlling influence on the polymerization rate was shown by some experiments in which the reducing sugar was completely omitted from the redox formula. The polymerization rate was considerably slower than when a reducing sugar was present. Under these conditions replacement of the ferric iron Kith ferrous iron until it was equivalent t o the hydroperoxide still did not give a fast polymerization. This latter result would not be expected on the basis of a mechanism for cumene hydroperoxide decomposition similar to t h a t which Baxendale, Evans, and Park (3) show for the ferrous iron-hydrogen peroxide system. Soap CONCENTRATIOK. The effect of soap concentration o n the cumene hydroperoxide redox sjstem (Figure 6) was similar t o t h a t observed by others for emulsion polymerization systems (1, 8, 16, 24). The rate of polymerization wah approximateliproportional to the soap concentration. ROLEOF MERCAPTAN.As has been shomi by Kolthoff and Harris ( 1 7 ) , the mercaptan used in the regular GR-Spolymerization with potassium persulfate initiator serves a dual purpose. I n the first place, it plays a role in the initiation process; without mrrcaptan, the rate of polymerization is very 1o~v. Secondly, it controls the molecular weight of the copolLmcr by a chain transfer process. I n the cumene hydroperoxide redox system, as in the German redox systems (26),mercaptan was unnecessary for the initiation process because the same rate of polymcrization was obtained with or without mercaptan. The mercaptan did, however, tend to minimize the retardation period obtained with systems containing a n insufficient amount of iron (Figure 8). It was necessary t o use a mercaptan t o obtain a soluble and pioressable rubber. At 40" C., the tertiary mercaptan was a n
Figure 5.
Effect of A m o u n t and C o m p o s i t i o n of Iron Activator
F i g u r e 6 . Effect of D r e s i n a t e 731
-
May 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
935
TABLE I. 40" C. REDOXCOPOLYMER COMPARED WITH GR-S-10 IN TREAD FORMULA (Tread formula, parts: polymer, 100; stearic acid, 1.0; Santocure, 1.8; zinc oxide, 5.0; channel black, 50.0; sulfur, 2.0) 40° C. Cure Time Redox GR-S-10 a t 280° F., Copolymer ' Property Minutes from Plant Tertiary mercaptan, parts 0.40 Conversion, % 72.3 Reaction time. hours .. 2.0 56 Mooney viscosity-uncompounded ' ,, 58 Mooney viscosity-compounded .. 85 86 Tensile strength, Ib./sq. in. 30 1330 1880 en 2xxn ---2730 2620 90 2400 2230 120 2240 Elongation a t break, yo 30 655 715 60 485 440 385 90 390 120 335 345 Modulus a t 200% elongation 30 250 350 lb./sq. in. 60 750 825 875 90 825 950 . 120 1000 Bashore rebound, % 30 33 36 38 60 31 90 32 38 37 120 32 Tear strength, lb./sq. in. 30 235 310 60 310 265 90 230 280 120 250 225
. --
20
02
0.4
06
08 MERCAPTAN,
Figure 7.
12
IO
TABLE11. 15" C. REDOXCOPOLYMER COMPARED WITH GR-S-10 IW TREADFORMULA^ (Tread formula parts: polymer 100. softener 5.0. mercaptobenscthiazole, 1.5; dinc oxide, 5.0; channei black, 50:O; s h f u r , 2.0; D P G masterbatch, 1.0;stearic acid, 1.5) Cure Time 15" C. a t 292' F.. GR-S-10 Redox Property Minutes Plant Laboratory Copolymer Primary mercaptan, parts . . .. . 0.55 0.3b Conversion, % .. ..... 72.6 71.5 Reaction time, hours .. . . . 15.2 a t 23.0 a t 50° C. 15O C. Intrinsic viscosity, 171, in benzene ,. 2.12 2.02 2.12 Mooney viscosity-uncompounded 0 57 58 68 Mooney viscosity-compounded 0 60.5 63 74.5 Tensile strength, lb./sq. in. 25 2720 2940 3340 50 2925 3090 3170 90 2740 2990 2850 Elongation at break, % 25 710 680 635 50 755 560 540 90 420 500 465 Modulus a t 300% elongation, 25 650 750 1000 Ib./sq. in. 50 1175 1200 1200 90 1500 1300 1500 Bashore rebound, % 25 25 30 31 50 26.5 32 33 90 26.5 29 33 Tear strength, lb./sq. in. , 25 420 455 460 50 355 425 430 90 290 380 400 Heat build-up, AT = O F. 50 73 67 62 (at 212O F.) 90 60 51 50 Hot flex cut-growth, inohes 50 38 ..... 32 per 100 kilocycles of flexing 90 38 ,.... 30 a t 185O F. Rubber Reserve tread formula, ingredients, and procedure used.
-
. .
excellent modifier, whereas an equal amount of the primary mercaptan gave very little modification (Fi re 7). This large difference is probably due t o the greater d i g s i v i t y and/or the slower rate of oxidation of tertiary mercaptans as compared with primary mercaptans of the same molecular weight (18). EFFECTOF TEMPERATURE. The effect of temperature on the cumene hydroperoxide redox system (Figure 8) was similar to that found for other vinyl polymerization reactions (a, 6, 84). Thus, increasing the temperature from 40" to 50' C. doubled the initial polymerization rate. However, after 50% conversion, the rate fell off very markedly. This was probably due to the exhaustion of the hydroperoxide and indicated that the decomposition of the hydroperoxide was accelerated more by increasing temperature than was the over-all polymerization reaction. This could be due to the limitation of the polymerization reaction by the diffusion rate of the monomers. On the other hand, lowering the temperature from 40" to 15'
C. indicated a somewhat greater change of the polymerization rate with temperature. Thus, 23 hours were required a t 15" C. to obtain a 7201, conversion as compared t o 2 hours for the same conversion a t 40' C. This corresponds to about a 2.5-fold decrease in reaction time for each 10' C.
@
80
I
I
,
I
0 @, /@
RUBBER PROPERTIES O F REDOX COPOLYMERS
The physical properties of the GR-S type synthetic rubber prepared with the redox sgstem a t either 40" or 15' C. (Tables I and 11) were similar to those of plant GR-S-10 (butadiene-styrene copolymer prepared with Dresinate 731 emulsifier and potassium persulfate initiator). The higher rebound and lower heat buildup of the redox copolymers as compared with plant
16
Effect of Mercaptans
..
However, the redox proportions which gave good results a t 40' C. may not necessarily be the best for a very low temperature polymerization. I n view of the complexities of the system, the variables would have t o be investigated to determine if other proportions or ingredients would be more desirable. It might be necessary to use more iron because the rate curve obtained at 15' C., without mercaptan (dotted curve, Figure S ) , showed the retardation period characteristic of systems containing insufficient iron. It was also found thac, contrary to the results a t 40' C., the primary mercaptan was just as effective as the tertiary mercaptan a t 15' C., 0.35 part being required for a 55 Mooney viscosity a t 72y0conversion.
14
PARTS
/%bS:ERCAPTAN
/' @ '
20
/
10
Figure 8.
/'
T I M E , HOURS
I5
Effect of Temperature
20
25
'
936
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 40, No. 5
loo1
Figure 9.
Effect of Fructose and Other Sugars TIME, HOURS
Figure 11.
GR-S and Other Monomers
hydrogen peroxide were duplicated when it was compared with cumene hydroperoxide on a weight basis. OTHER R.~ONO,MERSCOMPARED WITH GR-S
Figure 10.
Effect of Various Initiators in Redox Formula
GR-S-10 must be discounted as the laboratory GR-S-10 also showed a similar improvement (Table 11). Although all the copolymers were almost completely soluble in benzene (5% concentration), the low temperature copolymer formed a much smoother and more nearly gel-free solution. This indicates that the low cemperature copolymer is somewhat different than the higher temperature copolymers. However, the intrinsic viscosity of the low temperature copolviner m-as found t o be substantially the same as the plant or laboratory GR-S-10 copolymer of similar hlooney viscosity (Table 11). Further studies a t low temperatures are necessary t o determine the best combination of redox ingredients and to ascertain if such low temperature polymerization gives a superior rubber as has been indicated by numerous investigators (11).
The cumene hydroperoxide redox system gave very fast rates at 40" C. for the polymerization of styrene, methyl methacrylate, butadiene, and 75 butadiene-25 acrylonitrile (Figure 11). The rates with styrene, methyl methacrylate, and 75 butadiene25 acrylonitrile were so fast that they may have been limited by the diffusion rate of the monomers. I n addition, vinyl chloride, which polymerizes a t a very low rate in a persulfate-initiated Dresinate 731 emulsion svstem, gave a fair rate with the redox system. The initial retardation period shown by the rate curves of Figure 1I indicates the need for more iron. SUEIh'IARY
A redox system consisting of cumene hydroperoxide, fructose, and ferric pyrophosphate is remarkably effective for initiating the emulsion polymerization of a variety of vinyl compounds with Dresinate 731 emulsifier. It gives linear rate curves and is superior t o similar redox systems based on the common initiators such as benzoyl peroxide, tert-butyl hydroperoxide, h? drogen peroxide, and potassium persulfate. The optimum proportions for this redox system varied with the temperature and with the ingredients of the polymerization svstem. Studies of the important variables for GR-S polymerization at 40" C. showed that: (1) the concentration of fructose was the most important factor in obtaining fast polymerizations; by decreasing the fructose from the usual 0.5 part per 100 parts of monomer to 0.02 part, the rate of polymerization could be de-
OTHER REDUCING AGENTS COMPARED WITH FRUCTOSE
The keto monosaccharides, sorbose and fructose, gave the best results i n the cumene hydroperoxide redox system for GR-S polymerization (Figure 9). Other reducing sugars as glucose, invert sugar, and lactose, and, in general, other enolizable hydroxycarbonyl compounds functioned (Table 111). Thus acetylacetone, benzoin, and ascorbic acid were effective, whereas sucrose, sorbitol, methyl glucoside, the lactone of gluconic acid, acetone, diacetone alcohol, acetaldehyde, formaldehyde, glyoxal, benzaldehyde, dincetly, and sodium hydrosulfite were not. OTHER INITIATORS COMPARED WITH CUMENE HYDROPEROXIDE
Cumene hydroperoxide was remarkably superior in the redox system for GR-S polymerization to equivalent amounts of the common initiators (Figure 10). Thus, benzoyl peroxide and tert-butyl hydroperoxide were only one third or less as effective aa cumene hydroperoxide, whereas potassium persulfate and hydrogen peroxide were completely ineffective. The results on
-
G IN REDOX TABLE111. EFFECTOF VARIOUSR E D U C I NAGENTS FORMULA
Reaction 'Time, Conversion, Reducing Agent Part8 Hours % Redox formula except t h a t 0.0017 part irou and primary mercaptan used 3.0 74 Fructose 0.5 5.5 Acetylacetone 0.25 59 Benzoin 0.5 5.5 77 5.6 54 Ascorbic acid 0.2 10.3 27 Sucrose 0.5 Sorbitol 0.5 9.5 27 13 9.0 Methyl glucoside 0.5 9.2 7 Gluconic acid laatose 0.5 Diacetone alcohol 0.25 9.5 25 11.0 29 Benzaldehyde 0.25 9.0 8 Sodium hydrosulfite 0.20 Redox formula Fructose' 2 .O 69 0.5 Acetaldehyde 0.5 7.0 41 Formaldehyde 3 0.5 7.0 Glyoxal 5 0.5 7.0 Acetone 8 0.5 7.0 Diacetyl 24. 0.4 0.5
‘IN D U
May 1948
sT R I AL
creased fourfold without deviating from a linear rate curve; (2) the major effect of the iron component was t o eliminate initial periods of very slow polymerization; above fi concentration of about 10 p.p.m., it had little effect on the final polymerization rate; and (3) the variation of the hydroperoxide concentration from 0.04 to 1.4 parts had only a small effect on the initial polymerization rate but with 0.04 t o 0.1 part the polymerization was incomplete due t o peroxide exhaustion. The GR-Stype synthetic rubber prepared with this redox system in 2 hours a t 40’ C., or in 23 hours at 15” C., had physical properties equal t o commercial GR-S-10. ACKNOWLEDGMENT
Adsorption, A Tool in the Preparation of High-Purity Saturated HydrocarbonsCorrection I n the paper, “Adsorption, a Tool in the Preparation of HighPurity Saturated Hydrocarbons” [IND. ENG. CHEM.,39, 1585 (1947)l: Table I, for the system n-hexane-2,2,5-trimethylhexane on carbon at 9.2% equilibrium concentration of n-hexane, “Ml. Adsorbed per 100 G. Adsorbent” should be >4.2. Table 11,the heading of column 6 should be, “Ml. Adsorbed per 100 G. of Adsorbent.” Also, the system n-decane-cyclohexane should include a n “S” in column 3.
The authors are indebted to E. J. Lorand, of this laboratory, for the cumene hydroperoxide used in this study; t o A. E. Drake, of the company’s Papermakers Chemical Department, for help on the experimental procedures; t o L. 0. Amberg, of this laboratory, for the work on physical properties of the G R S type copolymers; and to Victoria Gage, of this laboratory, for assistance in carrving out the experimental work. (1) A&or10sa,J. L., “Use of Pure Resin Acid Soaps in GR-S Poly-
merization,” presented before the High Polymer Forum at CHEMICAL SOCIETY, the 112th Meeting of the AMERICAN New York, N. Y . (2) Bacon, R.G. R., Trans. Faraday SOC.,42, 140-55 (1946). (3) Baxendale, J. H., Evans, M. G., and Park, G. S., Ibid., pp. 155-69.
z a X
w I
P a a V
sW
f!
0 V J
2.
I w I-
5.
0
0 \
(4) Britton, E. C., and LeFevre, W. J., U. S. Patent 2,333,633
(Aug. 3, 1940). (6) Cohen, S.G., J . Am. Chem. SOC.,67,17 i1945). (6) E. I. du Pont de Nemours and Company, French Patent 812,267(Aug. 4, 1937). (7) Fryling, C. F., U. S. Patent 2,379,431(June 27, 1941). (8) Harkins, W .D.,J. Am. Chem. SOC.,69,1428 (1947). (9) Hays, J. T., Drake, A. E., and Pratt, Y. T., IND.ENG.CHBM., 39, 1129 (1947). (10) Hohenstein, W. P.,and Mark, H., J. Polymer Sci., 1, 128 (1946). (11) Ibid., pp. 549-80. (12) Houston, B. F. (B. F. Goodrich Co.), private communication, Jan. 11. 1945. (13) Josefowitz. D., and Mark, H., Polymer Bull., 1, 140 (1945). (14) Kamenskava. S., and Medvedev, S., Acta Physicochim. U.R. S.S., 13,565 @Q40). (15) Kluchesky, E. F. (Firestone Tire and Rubber Company), private communication, June 15, 1945. (16) Kolthoff, I. M.,and Harris, W. E., J . Am. Chem. Soc., 69, 441-6 (1947). (17) Kolthoff, I. M., and Harris, W. E., J . Polymer Sci., 2, 41-8 (1947). (18) Ibid., p. 68. (19) McCleary, C. D., Messer, W. E., and Howland, L. H., private communication, March 17, 1943. (20) Mark, H., and Raff, R., “High Polymeric Reactions-Their Theory and Practice,” p. 270, New York, Interscience Publishers, 1941. (21) Morgan, L. B., Trans. Faradau SOC.,52, 16g (1946). (22) Stewart, W.D.(to B. F. Goodrich Company), U. S. Patents 2,380,474-7 especially 2,380,476 (Feb. 19, 1941): U. S. Patent 2,388,373(Apr. 15, 1942). (23) Stewart, W. D., and Zwicker, B. M. G. (to B. F. Goodrich Company), U. S. Patent 2,380,617(Oct. 13,1941). (24) Vinograd, J. R.,and Ronay, G. S.; Vinograd, J. R., and
Sawyer, W. M., presented before the Division of Colloid Chemistry at the 108th Meeting of the AMERICAN CHEMICAL SOCIETY, New York, N. Y. (25) Voss, Eisfeld, and Freudenberger (to I. G. Farbenindustrie A . G.) Ger. Patent 664,337(May 13,1933). (26) Weidlein, E.R., Jr., Chem. Eng. News, 24,774 (1946). (27) Youker, M. A.,U. S. Patent 2,365,035(Jan. 26, 1939).
0 W
m
a
0
W
z
a
m
I-
U
I
a
n w I
5
z
VOL. %
York,
METHYLCYCLOHEXANE
Table 111, for the system cyclohexane-ethylcyolohexane on silica gel, the composition of point of zero selectivity should be 90% B. Also, for the system methylcyclohexane-ethylcyclohexane on silica gel, the component adsorbed should be “B.” The lower part of Figure 5 is plotted in terms of volume yo nheptane instead of volume yo methylcyclohexane as stated. The corrected figure is shown. ALFREDE. HIRSCHLER SENTAAMON
SUNOIL COMPANY NORWOOD, PA.
.
P-V-T-x Relations of the System Propane- T sopentane-Correc tion I n the paper “P-V-T-z Relations of the System Propane-Isopentane” [ IND. ENG.CHEM.,34,885 (1942)l the second and third columns of Table I11 are in error. The correct figures are: Weight %, CI 0 15.53 29.80 53.41 71.85 93.57
Presented before the High Polymer Forum
at the 112th Meeting of the AMERICAN CHEVICAL SOCIETY, New
N. Y
w
2
LITERATURE CITED
RECEIVED September 23, 1947.
937
A N D E N G I N E E R IN G CHEMIST R Y
SHELLDEVELOPMENT COMPANY EMERYVILLE, CALIF.
hloleoular Weight 44.09 46.92 4’2.87 55.65 61.12 69.31
WILLIAM R.VAUGHAN FRANK C. COLLINS.
