Abstract Method for molding plastic articles by forming a parison on a core within an injection mold, cooling the internal and external walls of the parison thus formed by heat transfer through the core and the injection mold, transferring said core to a delay position for permitting redistribution of heat from the interior of the parison to the exposed walls to obtain a more uniform temperature just above the material's glass transition temperature, and subsequently transferring said core to an expansion mold for expanding same, the cooling and heat redistribution permitting a greater degree of orientation of the polymer chains of the formed articles. Preferably, the apparatus for practicing the process includes injection and expansion molds supported in such a relation as to permit a substantial time interval between injection and expansion of the parison.
A process for making a hollow article of thermoplastic material which comprises a. injecting a thermoplastic material having a nitrile monomer content of at least 60% into an injection mold about a core to form a parison; b. cooling the interior wall of the parison to a temperature just above its glass transition temperature and the exterior wall to a temperature below the glass transition temperature; c. permitting the exterior wall to reheat to a temperature above the glass transition temperature by heat transfer from the interior of the parison; and
Claim 2
Dependent Claim
91 words
A process for making a hollow article of thermoplastic material which comprises a. injecting a thermoplastic material having a nitrile monomer content of at least 60% into an injection mold about a core to form a parison; b. cooling the interior wall of the parison to a temperature just above its glass transition temperature and the exterior wall to a temperature below the glass transition temperature; c. permitting the exterior wall to reheat to a temperature above the glass transition temperature by heat transfer from the interior of the parison; and
Claim 3
Dependent Claim
18 words
A process as recited in claim 1 in which the expanding step includes cooling of the hollow article.