In the gas phase process, ethylene with the comonomer and hydrogen are fed to the base of a fluid bed reactor into which the catalyst is injected. Polymerisation takes place at 60-100oC and 22 bar pressure. The polymer particles formed are kept in a fluidised state by the gas stream. The polymer leaves the reactor as a white powder and is sent to a degasser where unreacted olefins are removed. Advantages claimed for the gas phase route include low temperature operation and lower operating costs.