No abstract

3-Vinylphenylazo)-methylmalonodinitrile (2) was copolymerized with styrene up to high conversion giving no remarkable change in the monomer composition. The reactions were carried out in emulsion at 5"C, in bulk at 50°C, and in solution at 60°C. The azo compound displays not only the properties of an initiator (thermolysis) and monomer (vinyl group), but also the behaviour of a retardation reagent (azo-function) explaining the decrease of polymerization rates and of molecular weights with increasing amounts of azo compound.

Phenyl(3-vinylphenylazo) sulfide (2)-displaying not only the properties of an initiator (thermolysis) and a monomer (vinyl group) but also of a chain transfer agent (sulfenyl group) -was copolymerized with styrene in emulsion at 40 "C and in bulk at SO "C. Terpolymerization with styrene and butadiene at 5 "C in emulsion led to azo-containing unsaturated polymers, which could be used for self crosslinking.

In this study, the terpolymerisation, under high pressure, has been examined for the ethylene-methyl acrylate-vinyl acetate system. The polymerisations were carried out in a high pressure polymerisation facility designed for continuous operation. To assess the effect of pressure and temperature on the reaction, polymerisation was carried out at two different pressures of 1900 and 1 100 bar and at temperatures of 180 and 230 "C. By varying the concentration of the ethylene, methyl acrylate and vinyl acetate monomers in the feed, polymers of different composition were obtained. The ratio of the monomer concentrations in the reactor was calculated from the amount of polymer weighed out and its comonomer content as well as the composition of the feed, using the mass balance for the ideal stirred tank reactor. The result was used to determine the reactivity ratios of the three possible binary copolymerisation systems ethylene/ methyl acrylate, ethylene/vinyl acetate and methyl acrylate/vinyl acetate. This made it possible to predetermine, by calculation, the composition of a product obtained by continuous polymerisation in a stirred autoclave.

The present study was carried out to examine the effectiveness of an addition of triethylaluminium to tert-butyl perpivalate which is frequently used in industrial applications for initiating the copolymerisation of ethylene with vinyl acetate. For this purpose, polymerisation tests were carried out in the laboratory on a continuous basis at 1900 bar and 150°C. Vinyl acetate was added in concentrations of up to 36 wt.-% in the feed to the reactor. The organic peroxide concentration was 50 mole ppm; the concentration of organoaluminium alkyl was varied within the range of 0-75 mole ppm.The effects observed, namely an increase in the conversion and a decrease in the peroxide consumption were more marked than with the homopolymerisation of ethylene. This is attributable to the increased rate of chain growth in addition to the increased amount of radicals available.The properties of the copolymers obtained are changed only moderately by aluminium alkyl. Apart from a decrease in density and an increase in the melting point, a decrease in the polydispersity was observed. CCC 0003-3146/96/$07.00 87 G. Luft, M. Jabbari, M. Dorn len. Dies wird auf die zusatzliche Steigerung der Reaktionsgeschwindigkeit des Kettenwachstums neben dem erhohten Radikalangebot zuriickgefuhrt.Die Eigenschaften der erhaltenen Copolymeren werden durch das Triethylaluminium nur moderat verandert. Neben einer Abnahme der Dichte und einer Zunahme des Schmelzpunkts wurde eine Vemngerung der Polydispersitat beobachtet.