Sprue gated injection molding apparatus for molding preforms or other products having two layers of a barrier material such as EVOH or nylon alternating between three layers of another thermal plastic material such as PET. The PET is injected by one injection cylinder into first and third melt passages...http://www.google.co.uk/patents/US6350401?utm_source=gb-gplus-sharePatent US6350401 - Method of multi-layer injection molding
