Method for forming layered thermoplastic articles

A method of forming a hollow thermoplastic article comprising the steps of:

• continuously feeding a first thermoplastic material into a blow molding die while intermittently, simultaneously feeding a second thermoplastic material into the blow molding die, the second material being incompatible with the first material;
• extruding the first and second thermoplastic materials from the blow molding die to form a thermoplastic parison having a first section comprising a single layer of the first material and a second section comprising an inner layer of the first material and an overlying layer of the second material;
• closing off the second section of the parison within a mold cavity to form a closed end wall comprising the inner first material layer covered by an overwrap formed by the overlying layer of the second material which, due to its incompatibility, can be selectively peeled away when desired to expose the inner first material layer without otherwise opening the end wall;
• blow molding the closed off parison in the mold cavity to form the desired configuration of the hollow article comprising side walls formed from the first parison section and the closed end wall formed from the second parison section;
• and,
• forming in the closed end wall of the hollow article an access port which is normally covered by the peel-away overwrap and which, upon peeling away of the overwrap, is exposed for use.