Verfahren zur Herstellung von Ethylenhomo- und Ethylencopolymerisaten niederer Dichte

摘要

The invention relates to a method for producing ethylene homopolymerizates and ethylene copolymerizates exhibiting a lower mass density of up to 0.930 g/cm<3> and a melt index ranging from 0.15 to 25 g/10 min (2,16 kg; 463 K). Said polymerizates exhibit an improved processing stability and improved availability in the installation at pressures greater than 1000 bar and at temperatures of up to 603 K. The polymerizates are produced in tubular reactors in the presence of radical-forming initiators, oxygen thereunder and chain transfer agents, of which at least one comprises an aldehydic structure. According to the inventive method, chemokinetic characteristics of the reactive feed materials (thermal half-life periods, concentrations, dosing quantities) are coupled with the fluidically relevant characteristics of the tubular reactor (flow rate) while taking the target product quality (melt index, flow figure) into consideration. This coupling is carried out such that the interfering secondary reactions, especially polar-inductive substitution effects, which can lead to the formation and the enrichment of organic hydroperoxides are reduced to a minimum and, as a result, extraordinarily stable processing conditions can be obtained.