Patent ID: 7935300

Claim:
A manufacturing method of a resin container, comprising: continuously supplying a base material resin forming a container body from a main extruder; discharging from a discharge portion provided in a die head a sub-material supplied from a sub-extruder through a supply path so that the sub-material joins the base material resin; extruding a parison from a slit portion opened on an end side of the die head; and blow-molding the parison, thereby forming a coating layer which covers a whole or a part of the container body by using the sub-material, wherein when joining the sub-material with the base material resin, a suck-back control which pulls back the sub-material from the discharge portion is performed while adjusting a resin pressure in the supply path so that a thickness reducing portion in which a thickness is continuously reduced in a reduction rate of 0.1 to 1.5 μm/mm in a height direction of the container is formed in the coating layer, and wherein the suck-back control is performed at least once before the resin pressure in the supply path of the sub-material is reduced to 70 to 15% of a maximum resin pressure when joining the sub-material with the base material resin.