The present invention relates to a method to prevent deactivation of the metal catalyst in a catalytic polymerisation process of polymeric binders whereby pyrithione biocides are present which method comprises the addition of a Zn, Cu or Na salt selected from Zn, Cu or Na salts of fatty acids such as e.g. Zn, Cu or Na octoate, Zn, Cu or Na acrylate, Zn, Cu or Na neodecanoate, or Zn, Cu or Na salts of beta diketones such as e.g. Zn, Cu or Na acetylacetonate.