A preform for biaxial stretching blow molding. The preform being formed into a closed-end cylinder by direct blow molding and which is to be shaped into a container using a pressurizing liquid medium. The preform has either a single-layer or a multilayer structure constituted of one of a polyethylene resin having an MFR of 1.0-1.5 g/10 min. or a polypropylene resin having an MFR of 0.8 to 2.3 g/10 min.

A preform is biaxially stretch blow molded into a container by using a liquid as a pressurizing medium. The preform is formed in a bottomed tubular shape including a mouth, a trunk, and a bottom by extrusion blow molding. The preform includes bottom parting lines, which are formed in the bottom due to the extrusion blow molding, and the bottom parting lines are configured to extend to the outer side from the axis of the bottom to divide the bottom into at least three parts in the circumferential direction. Further, a container is formed by biaxially stretch blow molding the preform by using the liquid as the pressurizing medium.

A method for manufacturing a composite preform is provided, including preparing a preform that is formed from a plastic material, preparing a tubular heat shrinkable plastic member that is longer than the preform and has a margin for thermocompression bonding at one end, inserting the preform into the plastic member having the plastic member undergo thermal shrinkage by heating the preform and the plastic member, and bonding the margin of the plastic member by thermocompression.

A preform for biaxial stretching blow molding. The preform being formed into a closed-end cylinder by direct blow molding and which is to be shaped into a container using a pressurizing liquid medium. The preform has either a single-layer or a multilayer structure constituted of one of a polyethylene resin having an MFR of 1.0-1.5 g/10 min. or a polypropylene resin having an MFR of 0.8 to 2.3 g/10 min.

This method for manufacturing a composite preform (70) includes: preparing a preform (10a) that is formed from a plastic material; preparing a tubular heat shrinkable plastic member (40a) that is longer than the preform (10a) and has a margin (80a) for thermocompression bonding at one end; inserting the preform (10a) into the plastic member (40a); having the plastic member (40a) undergo thermal shrinkage by heating the preform (10a) and the plastic member (40a); and bonding the margin (80a) of the plastic member by thermocompression.