Patent attributes
A resource-saving neck of a synthetic resin bottle having high resistance to pressure and heat and a high, stable sealing property is provided. The part is aimed at equalizing an effect of thread-formed portions on the crystallization of a molten resin material along the circumferential direction of the part. These objectives are achieved by (1) forming screw threads of a multi-threaded screw structure on the outer surface of the neck wall, each screw thread comprising a main thread, with a starting and ending extension, with a width and height thereof being reduced gradually; (2) disposing the starting extension of a screw thread vertically above the ending extension of another thread; and (3) whitening the entire part by thermal crystallization. Sinks are prevented in the neck wall, and the height can be restricted despite increase in the diameter.
