Abstract
The free‐radical copolymerization of ethene (E) and methyl acrylate (MA) is studied between 220 and 290°C at 2000 bar. The reactions which have been induced thermally are carried out in a continuously operated device at total monomer conversions mostly below 1%. Monomer concentrations are obtained from measured mass fluxes. Copolymer composition is determined via elemental analysis. Reactivity ratio data, r~E~ and r~MA~, are derived from non‐linear least squares fitting of the monomer mixture and copolymer compositions. r~E~ and r~MA~, e.g., at 220°C and 2000 bar, are found to be 0,045 ± 0,002 and 5,3 ± 0,2, respectively. The r~E~ and r~MA~ values slightly, but significantly, differ from corresponding data for ethene‐butyl acrylate (BA) and ethene‐2‐ethylhexyl acrylate (EHA) copolymerizations. Toward higher temperature r~E~ increases and the acrylate (MA, BA, EHA) reactivity ratio r~A~ decreases. The temperature dependences of r~E~ and r~A~ can not be distinguished for the three ethene‐acrylate systems. From an experiment at two levels of polymerization pressure, 1500 and 2000 bar, the pressure dependence of r~E~ has been estimated. The available data for r~E~ and r~A~ allow to model monomer concentration vs. polymer composition behavior of free‐radical ethene‐acrylate copolymerizations at technically relevant temperatures and pressures.