Patent ID: 8691140

Claim:
A process for the injection molding of a thin-walled preform comprising a neck, a transition zone and a body, the injection molding process comprising: injecting a molten material into a mold comprising a core, a countermold having a cavity for receiving the core, and a preform impression disposed between an internal surface of the countermold and the core, the core including main depression zones produced only in a zone corresponding to the transition zone of the preform, wherein the preform impression has an average thickness (w av ) in millimeter equal to or less than a+L/b (w av ≦+L/b), with 1.20<a<1.40 and 88<b<98, with L being a total length of the preform in millimeter, and where w av = 1 L ⁢ ∫ ϕ L ⁢ w u ⁢ u ⁢ ⁢ ⅆ u with u being a curvilinear abscissa at each point on the preform, and w u being a local thickness at each point on the preform in millimeter; arranging the mold to produce main variable-thickness zones extending inwardly only in the transition zone of the preform; cooling the preform down to a temperature at which the material no longer changes; demolding the preform, the preform having an average thickness (wav) defined by wav≦a+L/b, with 1.20<a<1.36 and 88<b<98.