Free-radical polymerization under high pressure (Dedicated to professor Heinz geory wagner on the occasion of his 70th birthday

摘要

Ethene homo-and copolymerizations are important technical processes. At pressures up to about 3000 bar and temperatures up to 300 deg C , approximately 16 million tons LDPE (low density polyethylene) have been produced worldwide in 1997. The continued interest in the LDPE process is primarily due to the enrormous flexibility of this reaction which is carried out under supercritical (sc) conditions. A particular advantage of free-radical polymerization in sc fluid phase relates to the potential of widely tuning polymer properties just by continuously varying polymerization conditions. Further advantages consist in the tunability of solvent properties (which allows for choosing P and T conditions such that either homogeneity, e.g., for reaction, or inhomogeneity, e.g., for the subsequent separation step, are achieved) and in heat and mass transfer processes being very efficient under sc conditions. It is occasionally overlooked that the high-pressure ethene polymerization is the archetype of an extremely useful and successful sc fluid phase process. The situation met with the high-pressure ethene polymerization is referred to as reactive sc fluid phase. Ethene acts as both reactant and tunable supercritical fluid medium.