Mechanism and type of polymerization of chloroethene
You got it wrong - monomer is chloroethene (vinyl chloride) and nothing is eliminated in addition polymerization in contrary to polycondensation. This monomer is made via addition of chlorine molecule to ethene and elimination of hydrogen chloride. Alternative methods are addition of hydrogen chloride to acetylene or oxychlorination - in this reaction $\ce{HCl}$ and $\ce{O2}$ react with ethylene to form the monomer and water.