Reduction of residual monomer in polycaprolactam melts - by addn. of materials which evolve gas during vacuum treatment

Production of polycaprolactam metals with reduced monomer content is by adding materials which splitt off gases to the melt before evacuation. Monomer content is reduced without the need for higher temps. or longer times, which increase formation of monomer, or for higher vacuum which increases dimer concn. in the condensate with detrimental effect on continuous processes. The gases evolved and residues left have no harmful effects on the polymer. The additives pref. evolve reducing gases, examples claimed being Na, K or Li formates, or NH4 acetate or oxalate. Specifically claimed, is the addn. of 0.01-10 wt. % Na formate to the melt.