Hydrogen Peroxide as Catalyst for Emulsion Polymerization of Butadiene and Styrene*

C . S. MARVEL, RUDOLPH DEANJN,+ C. J. CLAUS, MARY B. WYLD, and RACHEL L. SEITZ, William Albert Noyes Laboratory, University of Illinois, Urbana, Illinois

H Y D R O G E N peroxide has been recommended as a catalyst for the copolymerization of butadiene and styrene in several articles and It has also been shown by Baxendale, Evans, and Parks that hydrogen peroxide and ferrous sulfate make a good redox pair for the polymerization of acrylonitrile. It seemed likely therefore that hydrogen peroxide could be used as the oxidizing cata- lyst in a reduction-activation recipe for butadiene-styrene copolymerization.

In a preliminary study of the hydrogen peroxide-sodium ferripyrophosphate system recommended by Stewart,l it was found than an 80% conversion could be obtained in four hours a t 50" if the proportions indicated in Table I were used in the standard bottle polymerization technique for butadiene and styrene.6

TABLE r HYDROGEN PEROXIDE - SODIUM FERRIPYROPHOSPHATE RECIPE

Recipe Weight, g.

Hydrogen peroxidea.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.06 Ferric sulfate [Fez(S0&.8.3H20]. . . . . . . . . . . . . . . . . . . . . . . . . 0.02 Sodium pyrophosphate (NaaP207. 10H20). . . . . . . . . . . . . . . . . . 0.65 Soap flakes (Procter & Gamble S.F.) . . . . . . . . . . . . . . . . . . . . . . 1.00 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40.00 Styrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.00 Butadiene.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 .00

a This reagent was added as 0.2 cc. of a 30% solution.

* This investigation was carried out under the sponsorship of the Office of Rubber Reserve, Reconstruction Finance Corporation, in connection with the Government Synthetic Rubber Pro- gram.

t Present address : Allied Chemical and Dye Corporation, Morristown, New Jersey. 1 W. D. Stewart, U. S. Pat. 2,380,473 (1945).

3 W. L. Semon, India Rubber World, 115,364 (1946). 4 F. Marchionna, Butalastie Polymers. 6 J . H. Baxendale, M. G. Evans, and G. S. Park, Trans. Faraduy Soe., 42, 155 (1946). 6 C. S. Marvel, R. Deanin, C. G. Overberger, and Beryl M. Kuhn, J . Polymer Sci., 3, 128

W. D. Stewart and B. M. G. Zwicker, U. S. Pat. 2,380,617 (1945).

Reinhold, New York, 1946.

(1948).

350 Journal of Polymer Science

HYDROGEN PEROXIDE AS CATALYST FOR EMULSION POLYMERIZATION

0.06 40.00

1.00 0.02 0

Stewart' believed the hydrogen peroxide initiated polymerization by an at- tack on the vinyl monomer and the sodium ferripyrophosphate acted as a critalyst similar to those present in biological oxidation-reduction reactions. If this recipe is related to the reduction-activation ~ys t ems ,~ it seems to be deficient in a reducing agent. It seemed likely, therefore, that replacement of ferric iron by ferrous iron in the recipe of Table I might lead to a further improvement in polymerization time. In Table I1 are indicated experiments which show that this is not true, but that the two iron salts are apparently equivalent.

0.06 40.00

1.00 0 0.02

TABLE I1 EQUIVALENCE OF FEFIROUS AND FERRIC IRON IN HYDROGEN PEROXIDE RECIPE

HrOz, g .

0.06 0.06 0.06 0.06 0.06 0.06

- -

0.02 - -

0 .02 -

- 0.02 - -

0.02

0.65 0.65 0.65

Conversion, %

6 8

41 36 9

78 80

This equality of ferric and ferrous iron is not too surprising since Haber and Weiss7 have shown that hydrogen peroxide converts ferrous iron to ferric iron and ferric iron to ferrous iron.

Fez+ + HZ02 - Fe3+ + .OH + OH- Fe3+ + HzOz - Fez+ + .OOH + H +

Hence, in our system the two irons are to a certain extent interconvertible. More- over, Haber and Weiss have demonstrated that the free hydroxyl radical attacks hydrogen peroxide to give hydroperoxide radical and hydroperoxide radical can convert hydrogen peroxide to oxygen, water, and hydroxyl radical.

.OH + H202 H20 + *OOH .OOH + Hz02 - 0 2 + HzO + *OH

TABLE I11 HYDROGEN PEROXIDE DECOMPOSITION IN AQUEOUS SOAP SOLUTIONS

Composition (grams) for recipe number Iugredienb

Hydrogen peroxide Water Soap flakes Ferrous sulfate (FeSOa .'i'H~o) Ferric sulfate (Fe(So&.8.3HzO) Sodium pyrophosphate

(NaaP207 10HZO) Hydrogen peroxide remaining after a

hours at 50"

0.06 40.00

1.00 0 0

0

76 % 21% I 31%

7 Haber and Weiss, Proc. Roy. Soc. London, A147, 332 (1934).

40.00 40.00 .::~ i Volume 3, No. 3 (1948) 351

M A R V E L , D E A N I N , C L A U S , W Y L D , A N D S E J T Z

I I I

EN PEROXIDE -#--< .**

8'

P. O"oNVERSIoN - #'

,' I,,' 1

I00 peroxide could not be directly re- sponsible for initiating the polymeriza-

$- tion reaction. Still, it was essential V) in some way, since recipes charged

without the hydrogen peroxide com- 0 pletely failed to polymerize. The

analytical method8 used to determine

8o

-600

40 2 oz

-20

TABLE IV ACTIVE OXYGEN (PEROXIDE) IN THE HYDROGEN PEROXIDE~ODIUM FERRIPYRO-

PHOSPHATE RECIPE DURING POLYWERIZATION Active oxygen present, g.

Type of peroxide in which oxygen was present - At zero time I After 1 hr. at 50'

Hydrogen peroxide 0.0282 0,00000 Organic peroxide 0.0000000

These data suggest that an intermediate organic peroxide may be responsible for activation of the polymerization reaction. They do not account for the fate of all the hydrogen peroxide which was decomposed during the induction period. Because of the severity of this induction period, it is probable that some of the hy- drogen peroxide was decomposed to molecular oxygen, which then exerted its usual inhibiting effect upon the polymerization reaction.I0

The emulsifier seems to be important in this system since with the standard soap flakes an 80% conversion was attained in 4 hours at 50 O , while potassium oleate

Rev. ed., Macmillan, New York, 1943.

* I. M. Kolthoff and E. B. Sandell, Quantitative Inorganic Analysis.

V. R. Kokatnur and M. Jelling, J . Am. Chern. SOL, 63,1432 (1941). 10 I. M. Kolthoff and C. F. Fryling, privale communication, through the Office of Rubber

Reserve.

352 Journal of Polymer Science

HYDROGEN PEROXIDE AS CATALYST FOR EMULSION POLYMERIZATION

gave 67%, rosin soap (Hercules Resin 731) and a sodium alkylnaphthalene sulfon- ate (General Aniline & Film Corp. SA-178) gave no polymer, and a sodium alkane- sulfonate* gave only 6% conversion in the same time.

This suggests that soap peroxide which KolthofP1 has shown is capable of bringing about GR-S polymerization may be the active agent in these hydrogen peroxide recipes.

Using the same hydrogen peroxide-sodium ferripyrophosphate system with different monomers gives widely varying results as shown in Table V.

TABLE V POLYMERIZATION OF OTHER MONOMERS IN THE HYDROGEN PEROXIDE-SODIUM

FERRIPYROPHOSPHATE RECIPE Conversion, %

15 g. butadiene and 5 g. s tpene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 g. butadiene.. . . . . . . . . . . . . . . . .... . . . . . 69 20 g.styrene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 20 g. acrylonitrile.. . . . . . . . . . . . . . . . . . . . 5 20 g. vinyl acetate. . . . . . . . . . . . . . . . . . . . 0 20 g. methyl acrylat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

80

This can be construed to mean either that the monomer has played a role in the formation of the active peroxide or that soap peroxide is not effective as a poly- merization catalyst with certain monomers. Further work will be needed to clarify these points.

Synopsis

Evidence is presented to show that either sodium ferri- or ferropyrophosphate with hydrogen peroxide effectively initiates emulsion copolymerization of butadiene and styrene. The hydrogen peroxide appears to be destroyed as such before polymerization begins, thus indicating that i t con- verts some other constituent of the recipe into the effective catalyst for polymerization.

R6sumB L’Bvidence est prkentBe pour dBmontrer que ferri- ou ferropyrophosphate de sodium avec

le peroxyde d’hydrogbne initie effectivement la copolymBrisation du butadihe et du styrhne. Le peroxyde d‘hydroghne apparaft &re detruit avant le commencement de la polymbrisation, ainsi denotant qu’il convertit quelque autre constituant du recipe au catalyseur effectif de la poly- mbrisation.

Zusam menfassung

Es wird bewiesen, dass sowohl Natriumferri- als auch Natriumferropyrophosphat mit Wasserstoffsuperoxyd den Emulsions-copolymerisationsvorgang von Butadien und Styrol aus- losen. Dies deutet darauf hin, dass es einen andern Bestandteil der Mischung in den “wirksamen” Polymerisations- beschleuniger verwandelt.

Received October 20, 1947

Anscheinend wird das Peroxyd zerstiirt, bevor Polymerisation einsetzt.

* This emulsifier was prepared from a petroleum hydrocarbon fraction containing about 16 We are indebted to Dr. Stanley Detrick of Jackson Laboratory, E. I. carbon atoms per molecule.

du Pont de Nemours and Company for the material. 11 I. M. Kolthoff, private communication, through the Office of Rubber Reserve.

Volume 3, No. 3 (1948) 353