SUSPENSION POLYMERISATION METHOD Russian patent published in 2013 - IPC C08F10/02 C08F2/00 C08L23/06 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing multimodal polyethylene. The method is carried out in at least two reactors connected in series in the presence of an olefin polymerisation catalyst, where 20-80 wt % of a high-molecular weight polymer is obtained in a suspension in the first reactor and 20-80 wt % of a low-molecular weight polymer is obtained in a suspension in the second reactor in the presence of the high-molecular weight polymer. Concentration of solid particles in the second reactor of the low-molecular weight product, which is defined as weight of the polymer divided by total weight of the suspension is at least 35 wt %, more preferably lies in the range of 45-60 wt %, and/or the ratio of the concentration of solid particles in the first reactor to that ratio in the second reactor is maintained at a level below 1.0, preferably in the range of 0.6-0.8. Volume of the second reactor is at least 10%, preferably at least 30%, and even more preferably at least 50%, greater than the volume of the first reactor. The ratio of the average effective concentration of substance in the reactor the low-molecular weight product to the average effective concentration of substance in the reactor of the high-molecular weight product is 0.25-1.5, where the average effective concentration of substance in each reactor is defined as output of polyethylene obtained in the reactor (kg PE/h)/[concentration of ethylene in the reactor (mol %) x residence time in the reactor (h) x rate of feeding catalyst into the reactor (g/h)]. Residence time is defined as the mass of the polymer in the reactor (kg)/rate of removal of the polymer from the reactor (kg/h). The ratio of concentration of ethylene in the liquid phase (mol %) in the second reactor to that ratio in the first reactor is 5 or less, concentration of ethylene in the second reactor is less than 8 mol % and average volume output (defined as polymer output in kg/h per unit volume of the reactor) in all combined reactors is greater than 100 kg/m³/h.

EFFECT: method of producing multimodal polyethylene in two reactors with optimum ratio of dimensions.

13 cl, 1 tbl, 1 ex