High-pressure free-radical copolymerization of ethene and 2-ethylhexyl acrylate

The free-radical copolymerization of ethene (E) and 2-ethylhexyl acrylate (EHA) is studied between 150 and 250 degrees C and at pressures from 1500 to 2500 bar. The reactions which were induced either thermally or laser-photochemically are carried out in two types of continuously operated devices and also within a batch reactor. The precision in the determination of reactivity ratios is considered in detail for the continuous experiments taking the error structure of the copolymer composition measurement into account. The reactivity ratios r(E) and r(EHA) at 220 degrees C and 2000 bar are found to be 0,050 +/- 0,002 and 3,9 +/- 0,9, respectively. From the ethene rich reaction mixtures r(E) is available with higher precision than is r(EHA). The E/EHA reactivity ratios are found to be very close to literature data for the E/butyl acrylate (BA) copolymerization. Fitting of the combined data set, for E/EHA and E/BA, yields for the activation energy and activation volume of the ethene reactivity ratio E(A)(r(E)) = (11,9(-1,4)(+1,5) kJ . mol(-1) and Delta V-not equal(r(E)) = -(8,2 +/- 3,5) cm(3) . mol(-1), respectively.