A continuous process for producing high pressure polyethylene is described. The process includes contacting first amounts of ethylene, an optional polar comonomer, and a first C2 to C12 modifier in the presence of a first amount of initiator in a reaction system under polymerization conditions to form a reaction system effluent comprising a first polyethylene resin having a first concentration of unreacted monomer therein; and directing an ethylene stream and the reaction system effluent to a pressure separation unit operated at separation conditions thereby removing at least a portion of the unreacted monomer from the reaction system effluent.