Use of Alternative Activators in 41° F. Polymerization Recipes

Kinetic studies of a redox-initiated polymerization have indicated activation energies of 9.7 kcal. per mole for the decomposition of the initiating system, approximately 6 kcal. per mole for the propagation reaction, and 9.0 kcal. per mole for the consumption of MTM-4 in the emulsion system. Lower polymerization temperatures raised the gel point without shortening the polymer chains, apparently by decreasing the proportion of cross-linking to propagation reactions. Two types of nonmercaptan termination have been found to occur to appreciable extents: mutual termination of free radicals and a termination process involving the emulsifier.

Section: Methodsmentioning

confidence: 99%

Kinetic Studies of a Redox Polymerization

Brown¹,

Winkler²

1953

“…by the amount of ferrous sulphate used, the other ingredients remaining in equimolar ratio. Greater detail will be found in two earlier papers (41,42) and others from this laboratory (4,39,48 For personal use only.…”

Section: Caivadian Journal Of C H E X I S T R Y 10lmentioning

confidence: 99%

“…The use of three parts of dextrose has been meniionecl in many papers (32,39,47,58,59,61) and the use of about one part in many others (4,11,20,29,33,39,46,47,48,5S,61). , Sorbose (10,13,14,19,20,62,63), dihydroxyacetone (20,26,27,30,33), ascorbic acid (31,33) invert sugar (GO), lactose (60), fructose (25,60), and scylloinosose (30) have also been me~ztionecl.…”

Section: Caivadian Journal Of C H E X I S T R Y 10lmentioning

confidence: 99%

The Role of Alpha-Ketols in the Low-Sugar Redox Recipe for Low Temperature Emulsion Copolymerization

Orr¹,

Williams²

1951

Self Cite

I t was found.that the induced deconlposition of peroxy co~llpounds c o~~l d lead to faster rates of polymerization or practical rates of polymerization a t lower tcmperat~tres. In Germany polymerization recipes were developed containing a pefosy conlpound in the oil phase, a reducer in the aqueous phase and a metal carrler. 'This idea was transferred to America after the war and became the basis of the present recipes used i n the production of cold rubbers. As reducers the most comn~only used appear to be digested d-glucose or a n excess of ferrous iron but recently the polyamines and other amine conipounds have been found to be quite effective. 'The mixture of anline and sugar was better than either alone. I t has been shown that this mixture will function in the presence of reactive monomers such a s acrylonitrile. The role of such reducers is of considerable interest so t h a t further studies were undertaken. The results obtained may be illustrated by acetoin. .4s the amount of acetoin is increased in the recipe the arnount of ferrous iron required for maximal conversion in a given time 1s decreased. This is because a t higher than the optimal amounts, although the reaction rate is still increasing, the catalyst system is rapidly exhausted so that the reaction dies a t a lower conversion. T h e data can be explained by assuming formation of free radicals by the induced decomposition of the peroxide either by the acetoin, the ferrous iron, or a co~nplex between the iron and acetoin. This free radical then initiates polymerization. T h e acetoin free radical residue can induce the further decon~position of the peroside or possibly can reduce ferric iron to ferrous. Other con~pounds yield similar results. IntroductionSome of the earliest studies of activated polymerization reactions are those of Stewart (49,50,51,52,53) in which redox catalysts con~posed of a polymerization initiator, a heavy metal, and a phosphate or polyphosphate such as pyrophosphate or fructose diphosphate, an organic acid, or a polyhydroxy conlpound such as dextrose. E. I. du Pant de Nemours and Co. patented similar systems (44).The German work developed the desirable combination of an oil soluble peroxy conlpound and a water soluble reducer in combination with a heavy metal carrier to a high degree. These results were summarized by Weidlein (63) who mentioned the system benzoyl peroxide -ferrous fatty acids -sorbosesodium pyrophosphate. Later several publications appeared in Germany (17, 18,19,20,21,31,33) describing their earlier work and several in the United States describing the studies there which were stimulated by the earlier report (63).Wall and Swoboda (62) attempted to formulate the reactions of such a system. Some credence to their postulate could be given when such highly

“…\\'hen interest became centered around low temperature polymerizatioi~s to yield better and Illore uniform butadiene-styrene copolymers, the activated recipes (see (12,22)) were applied successfully t o the butadiene-acrylonitrile system.…”

Section: C4nadzalv J O U R N a L Of Chebiistry 1'ol 29mentioning

confidence: 99%

Compositional Heterogeneity of Butadiene–acrylonitrile Copolymers Prepared in Emulsion at 5°c

Embree¹,

Mitchell²,

Williams³

1951

Self Cite

The copolymerization of b~rtadiene and acrylonitrile is very similar to the copolymerization of butadiene and styrene. Polymers predominantly butadiene may be studied by conventional solution techniques but the study of polymers rich in acrylonitrile requires improved solvents for these materials. Polymerization rates are greatest for monomer ratios approximating equal proportions. The mercaptan modilier disappears much more slowly than in the b~~tadiene-styrene system, the regulating index approximating unity. The n~unber average molecular weights calculated from the mercaptan disappearance curves indicate uniform polymer molecular weights to relatively high conversions after which there is a decrease. T h e viscosity data indicate a rise in viscosity \vith conversion, which elfect is overcome for charges rich in acrylonitrile by the lessening of branching, the more rapid disappearance of mcrcaptan a t high conversion, and the tendency of polymers containing over 50% acrylonitrile to show very low dilute s o l~~t i o n viscosities in the solvents tested. Viscosity molecular weights have been calculated and estimates of the molecular weight tlistributjon made. These distributions appear to be quite narrow and the ~~s u a l broaden~ng a t higher conversions is prevented by tlre increased nrodiher consun~ption and increased vinyl content of the poly~ner prepared with 50 parts acrylonitrile in the charge. The bountl acrylonitrile has been determined a t various conversions and the reactivity ratios have been found to be r, = 0 . 2 s and r2 = 0.02 for emulsions and rl = 0. 18 and r? = 0.03 for oil phase portion only. Q is 0.74 and e is 1.17 as calculated by the Alfrey-Price equations.