A method of controlling the extrusion of a multilayer parison so that the injection pressure for an auxiliary resin and that for an adhesive do not act on the annular fluid passages while a main resin, an auxiliary resin and an adhesive are stored in a main resin accumulator, an auxiliary resin accumulator...http://www.google.co.uk/patents/US5252268?utm_source=gb-gplus-sharePatent US5252268 - Method of controlling extrusion of multilayer parison
