Patent ID: 9393725
Filing Date: 2016-07-19
CPC Classification: B29B,B29C,B29K,B29L,B65D,Y10T

Claim Text:
1. A synthetic resin preform in the shape of a test tube, which is molded by injecting molten resins into a mold through a multiple nozzle section and a gate disposed at a position opposed to a center of a bottom of the preform, and is used in biaxial drawing and blow molding, comprising: an intermediate layer (1) made of a colored resin, (2) formed having substantially a same thickness throughout a height range starting from a tower portion of the preform, (3) embedded in a main resin layer comprising a main resin and (4) having a thickness-related color-gradated portion caused by a change in layer thickness when a thickness of the intermediate layer is gradually reduced, the thickness having a shape of a wedge, in an upward direction at an upper end of the intermediate layer, wherein a side wall of the preform has a three layer structure, the three layer structure being a first portion of the main resin layer, followed by the intermediate layer, followed by a second portion of the main resin layer, wherein the preform is molded by a simultaneous injection molding method in which the main resin for the preform is supplied at a time span, and optionally at a pressure and/or velocity and the colored resin is supplied at a pressure and/or velocity during a time within the time span, and wherein the supplied pressure and/or velocity of the colored resin is gradually increased when the supply of the colored resin is started, so that the change in the layer thickness in the color-gradated portion is shown by a condition of L/t