HIGH-PRESSURE FREE-RADICAL COPOLYMERIZATION OF ETHENE AND METHYL ACRYLATE

The free-radical copolymerization of ethene (E) and methyl acrylate (M A) is studied between 220 and 290 degrees C at 2000 bar. The reactions which have been induced thermally are carried out in a continuously o perated device at total monomer conversions mostly below 1%. Monomer c oncentrations are obtained from measured mass fluxes. Copolymer compos ition 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 2 20 degrees 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 significan tly, differ from corresponding data for ethene-butyl acrylate (BA) and ethene-2-ethylhexyl acrylate (EHA) copolymerizations. Toward higher t emperature r(E) increases and the acrylate (MA, BA, EHA) reactivity ra tio r,decreases. The temperature dependences of r(E) and r(A) can not be distinguished for the three ethene-acrylate systems. From an experi ment 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 compos ition behavior of free-radical ethene-acrylate copolymerizations at te chnically relevant temperatures and pressures.