Cascaded polyolefin slurry polymerization employing disengagement vessel between reactors

Abstract

A disengagement vessel employing a lock hopper effectively reduces concentration of non-polymer-associated components in the polymer product slurry of a first olefin slurry polymerization reactor, allowing cascading of a second slurry polymerization reactor operating at lesser concentration of comonomers, hydrogen, and other components to produce multicompositional polyolefin polymers and/or polymers having a multimodal monomer distribution, e.g. diblock polymers having substantially non-overlapping comonomer contents between the blocks.

1 - 18 . (canceled)  
     
     
         19 . A polyethylene copolymer of multimodal molecular weight distribution, comprising an interstitially mixed blend of a polyethylene polymer of a first molecular weight and a polyethylene polymer of a second molecular weight higher than said first molecular weight, comprising: 
 a) a first polyethylene polymer prepared by continuously polymerizing ethylene and one or more copolymerizable comonomers in light solvent at a first hydrogen concentration in a first slurry reactor; and    b) a second polyethylene polymer prepared by continually polymerizing ethylene and optionally one or more copolymerizable comonomers in the presence of said first polyethylene polymer, in the absence of additional olefin polymerization catalysts and at a hydrogen concentration lower than said first hydrogen concentration, wherein said olefin polymerization catalyst is not a rapidly hydrogen-consuming catalyst.    
     
     
         20 . The polyethylene copolymer of  claim 19 , wherein at least one comonomer selected from the group consisting of propene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-norbornene, and 1,3-butadiene is employed preparing said first polyethylene polymer, and the same or different comonomer is employed preparing said second polyethylene polymer.  
     
     
         21 . A polyethylene polymer prepared by 
 a) first polymerizing ethylene and at least one comonomer in a first slurry reactor optionally containing hydrogen to form a first polymer slurry;    b) substantially removing said at least one first comonomer from said first polymer slurry and optionally substantially removing hydrogen, if present in said first slurry reactor, to form a comonomer-depleted slurry;    c) introducing said comonomer depleted slurry into a second slurry reactor, introducing a comonomer different from said first comonomer; and    d) recovering an interstitially mixed polymer having blocks of different comonomer content.    
     
     
         22 . The copolymer of  claim 19 , prepared by the process of 
 polymerizing ethylene and at least one copolymerizable monomer in a first slurry reactor;    introducing a non-polymer-associated component-containing polymer slurry from a first slurry reactor into a disengagement vessel, said disengagement vessel terminating at a lower end thereof with a lock hopper having a cavity therein which is selectively communicatable between an interior of said disengagement vessel and a supply of slurry solvent;    filling said cavity with slurry solvent when said cavity is not in fluid communication with said disengagement vessel;    causing said cavity to be in fluid communication with said interior of said disengagement vessel, and allowing polymer particles contained in a polymer particle slurry in said disengagement vessel to enter said cavity, displacing slurry solvent into said disengagement vessel from said cavity;    ceasing communication of said cavity with said interior of said disengagement vessel, establishing fluid communication of said cavity with said supply of slurry solvent, and flushing polymer particles from said cavity with slurry solvent as a solvent flush polymer slurry, at least one non-polymer-associated component concentration in said solvent flush polymer slurry being less than the concentration of said at least one non-polymer-associated component in said disengagement vessel;    introducing said solvent flush polymer slurry into a second slurry polymerization reactor and polymerizing ethylene, optionally with one or more copolymerizable olefins, in said second slurry polymerization reactor; and    recovering a multimodal polymer from said second slurry polymerization reactor.    
     
     
         23 . The copolymer of  claim 22 , wherein the interior of the disengagement vessel is maintained at a pressure and at a temperature such that said slurry solvent is at its bubble point.  
     
     
         24 . The copolymer of  claim 22 , wherein a liquid phase in said disengagement vessel is maintained at a pressure lower than the pressure of said first slurry reactor and at a temperature higher than the temperature of said first slurry reactor.  
     
     
         25 . The polymer of  claim 21 , wherein a single olefin polymerization catalyst is employed, and no additional catalyst is added to said second slurry reactor.  
     
     
         26 . The polyethylene polymer of  claim 21 , wherein at least one comonomer selected from the group consisting of propene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-norbornene, and 1,3-butadiene is employed preparing said first polyethylene polymer, and the same or a different comonomer is employed preparing said second polyethylene polymer.  
     
     
         27 . The process of  claim 21 , wherein said first comonomer is butene.