Patent ID: 9403927
Filing Date: 2016-08-02
CPC Classification: C08F

Claim Text:
1. Process for the continuous production of a medium and/or high density ethylene (co-)polymer in a gas phase fluidised bed reactor at an operating temperature (“Top”) higher than 90° C., under a selected ratio of the partial pressure of hydrogen to the partial pressure of ethylene (pH2/pC2=“RHop”), and under a selected ratio of the partial pressure of comonomer to the partial pressure of ethylene (pComo/pC2=“RCoop”), comprising non-steady-state operations made of at least two consecutive sequences wherein the first sequence takes place before catalyst introduction and consists in preparing the fluidised bed reactor comprising a charge powder at a reactor temperature “Tsu” lower than 90° C., under a ratio of the partial pressure of hydrogen to the partial pressure of ethylene (“RHsu”), and under a ratio of the partial pressure of comonomer to the partial pressure of ethylene (“RCsu”), wherein RHsu is higher than RHop, and RCsu is higher than RCoop, and, in a subsequent second sequence, the catalyst is introduced and the ratios of ethylene partial pressure to hydrogen partial pressure and the ratio of ethylene partial pressure to comonomer partial pressure are increased until steady-state conditions, i.e.