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.

Polymerization tests were carried out in a stirred autoclave designed for continuous operation in order to determine the influence of the reaction pressure and temperature and of the acrylic acid methyl ester and vinyl acetate comonomers on the ethyleneacrylic acid methyl ester-vinyl acetate terpolymer formed. Pressures between 1 100 and I 900 bar and temperatures of 180 and 230 "C were used. The average residence time was 40 seconds. Tertiary butyl perpivalate and tertiary butyl perethyl hexanoate in concentrations of 50 to 180 mol-ppm in the ethylene feed were used as initiators. The characteristic properties of the polymers obtained were assessed by determining their composition, density, crystallinity, melting point, glass transition temperature, melt index, the average molecular weight, tensile strength and elongation at break. ZUSAMMMENFASSUNGUm den Einflulj der Reaktionsbedingungen Druck und Temperatur sowie der Comonomeren Acrylsauremethylester und Vinylacetat auf das entstandene Ethylen-Acrylsauremethylester-Vinylacetat-Terpolymerisat aufzuzeigen, wurden Polymerisationsversuche in einem kontinuierlich betriebenen Riihrautoklaven durchgefiihrt. Der Druck wurde zwischen 1 100 und 1900 bar variiert. Die Temperatur lag bei 180 bzw. 230 OC. Die mittlere Verweilzeit betrug 40 Sekunden. Als Initiator wurden t-Butylperpivalat und t-Butylperethylhexanoat in Konzentrationen von 50 bis 180 mol-ppm im Ethylenzulauf gewahlt. Die erhaltenen Polymeren wurden durch Bestimmung ihrer Zusammensetzung, ihrer Dichte, der Kristallinitat, des Schmelzpunktes, der Glasiibergangstemperatur, des Schmelzindexes, des mittleren Molekulargewichtes sowie der Zugfestigkeit und Reindehnung charakterisiert. 0 1993 Huthig & Wepf Verlag, Basel CCC O003-3146/93/$05.00