Patent ID: 8669334

Claim:
A process for the gas phase polymerisation, comprising: polymerizing an olefin monomer in a fluidised bed reactor in a dry mode or in a condensed mode with a gas stream comprising an inert gas, wherein the inert gas comprises a mixture of inert components: (1) 5-60% by mole of nitrogen (2) 10-90% by mole of a gas heat capacity increasing agent which regulates the dew point and at the same time improves the vapor stream heat capacity (3) 1-50% by mole of a sorption promoting agent which acts as promoting agent of the ethylene and alpha olefins local concentrations at the growing polymer micro-particle level where sorption of such components into the polyethylene increases the local concentration of ethylene and/or alpha-olefins in terms of micro-conditions surrounding the catalyst active sites and (4) 0.1-10% by mole a polymer swelling agent which acts as a polymer physical and viscoelastic properties modifying agent, developed instantaneously during polymer growth, by swelling and plasticizing the polymer formed during growth and which agent influences the characteristics of the crystalline phase wherein the total amount of the inert components (1), (2), (3) and (4) is 100%.