GAS PHASE FLUIDIZED BED METHOD AND ETHYLENE HOMO- AND COPOLYMERS OBTAINED USING SAID METHOD

摘要

The invention relates to a continuous gas phase fluidization method for producing ethylene homopolymerisates and copolymerisates with a density (d) of 0.87 to 0.97 g/cm3. According to said method, ethylene or mixtures of ethylene and C3- to C8-.alpha.-monoolefins are (co)polymerised in the polymerisation zone of a gas phase fluidized bed reactor at pressures of 1 to 100 bar and at temperatures of 30 to 125 ~C in the gas phase in an intermixed bed of fine particulate polymerisate in the presence of a supported chromium catalyst. The polymerisation heat produced is evacuated by cooling the reactor gas, said reactor gas being guided in a closed circuit, and the resulting (co)polymerisate is transferred out of the gas phase fluidized bed reactor. In order to produce a (co)polymerisate of a pre-selected density (d), the (co)polymerisation is carried out at a temperature within a range limited by an upper envelope of equation (I) and a lower envelope of equation (II), the variables in said equations having the following meanings: TH = the highest reaction temperature in ~C; TN = the lowest reaction temperature in ~C; and d'= the numerical value of the density (d) of the (co)polymerisate to be produced.