Disclosed is a method for reducing fouling in an apparatus and process for separating polyolefin from a slurry in a slurry polymerization reactor system comprising contacting in a reactor at a pressure of at least 2000 kPa a catalyst composition and .alpha.-olefin monomers to form a polyolefin reaction mixture; transferring the polyolefin reaction mixture to a high pressure separator, wherein the pressure in the high pressure separator is within the range of from 200 to 2500 kPa; and contacting the polyolefin reaction mixture with an organic amine prior to its entering the high pressure separator.