Suspension process for preparing ethylene polymers comprising workup of the suspension medium

A process for preparing an ethylene polymer in a suspension polymerization in a polymerization reactor or a series of polymerization reactors comprising the steps of:

• polymerizing ethylene or copolymerizing ethylene and one or more C3-C12-1-alkenes at temperatures of from 40 to 150° C. and pressures of from 0.1 to 20 MPa in the presence of a polymerization catalyst and forming a suspension of ethylene polymer particles in a suspension medium comprising a hydrocarbon diluent,
• transferring the suspension of ethylene polymer particles into a solid-liquid separator, wherein the suspension is separated into ethylene polymer particles and mother liquor,
• transferring a first part of the mother liquor into a work-up section comprising an evaporation unit for producing a wax-depleted portion of the mother liquor, wherein a protic agent is added to the part of the mother liquor which is transferred into the work-up section, and
• recycling a first part of the wax-depleted portion of the mother liquor to the polymerization reactor or the series of polymerization reactors.