Process for producing bimodal polyethylene resins

Abstract

A process for producing bimodal polyethylene resins in two reactors in series, the process comprising producing a first polyethylene resin fraction in a first slurry loop reactor in a diluent in the presence of a catalyst and producing a second polyethylene resin fraction in a second slurry loop reactor, serially connected to the first reactor, in the diluent in the presence of the catalyst, the first polyethylene resin fraction being passed from the first reactor to the second reactor together with the catalyst, one of the first and second reactors producing a resin fraction of higher molecular than the resin fraction produced by the other of the first and second reactors, characterised in that the first reactor is fed with a feed of ethylene and diluent having an ethylene content of at least 70 wt % based on the weight of the diluent and in that in the first reactor the slurry of polyethylene in the diluent has a solids content of at least 30 wt % based on the weight of the dilent.

1 - 13 . (canceled)  
     
     
         14 . A process for producing a bimodal polyethylene resin in first and second slurry loop reactors connected in a series comprising: 
 supplying a feed comprising a diluent, ethylene, hydrogen and a polymerization catalyst to said first reactor;    polymerizing said ethylene in said first reactor to produce a relatively low molecular weight polyethylene resin fraction in a slurry in the diluent in said first reactor;    transferring said polyethylene resin fraction, diluent and catalyst from said first slurry loop reactor to said second slurry loop reactor;    supplying a feed stream comprising ethylene and a C 3 -C 12  alpha olefin comonomer to said second reactor;    copolymerizing said ethylene and said C 3 -C 12  alpha olefin comonomer in said second reactor to produce a second copolymer resin fraction in said second reactor by the copolymerization of ethylene and said C 3 -C 12  alpha olefin, said second copolymer resin fraction having a higher molecular weight than the resin fraction produced in said first reactor; recovering a bimodal polyethylene resin comprising said copolymer and said homopolymer from said second reactor; and    supplying said bimodal polyethylene resin for further processing in an extruder without additional polymerization.    
     
     
         15 . The process of  claim 14  wherein said catalyst is a Ziegler-Natta catalyst and the slurry in the first reactor has a solids content within the range of 30-60 wt. % based on the weight of the diluent.  
     
     
         16 . The process of  claim 14  wherein said alpha-olefin comonomer is present in the feed stream to said second reactor in a concentration within the range of 2-15 wt. % based upon the weight of the diluent.  
     
     
         17 . The process of  claim 14  wherein said polyethylene resin fraction, diluent and catalyst is continuously transferred from said first reactor to said second reactor.