A method for manufacturing a resin container includes: a first injection-molding step of injection-molding a bottomed cylindrical resin intermediate molded body; a second injection-molding step of injection-molding a resin material on an outer side of the intermediate molded body to manufacture a multilayered preform having a resin layer laminated on an outer peripheral side of the intermediate molded body; and a blow-molding step of blow-molding the preform to manufacture a resin container having a thick portion.

A preform for molding a dual container, in which an inner preform is inserted into an outer preform in a state in which a mouth portion of the inner preform is fitted into a mouth portion of an outer preform, the inner preform is formed of a crystalline resin, a crystallized region is provided in at least a portion of the inner preform, the crystallized region having a degree of crystallization greater than that of the other portion, the portion of the inner preform adjacent to the mouth portion from below the mouth portion and located below the outside air introduction hole, a step portion facing upward and a rib extending upward from the step portion are formed on an inner circumferential surface of the inner preform, and at least a part of the rib is adjacent to the crystallized region from above the crystallized region.

A method for producing a multiple preform, including a primary injection for injection molding a preform main body using a primary mold, and a secondary injection for injection molding, using a secondary mold, a covering layer that covers the preform main body such that the terminal end side of the covering layer covers the lower surface of the neck ring and reaches the peripheral edge of the neck ring. A projection strip portion is formed when the preform main body is inserted into the secondary mold to be clamped, that projects in a gap in which the covering layer is molded to be in contact with or adjacent to a lower surface of the neck ring, and that extends with a given length along an axis direction, is formed on an inner peripheral surface of the secondary molding mold, thereby forming an easy tear portion in the covering layer.

A manufacturing method of a resin container includes: a first injection molding process for injection-molding a first layer of a preform by using a first resin material, the preform having a bottomed cylindrical shape and including a groove that extends in an axis direction; a second injection molding process for injecting a second resin material into the groove of the first layer, the second resin material having a color that is different from a color of the first resin material, and laminating a second layer on an outer peripheral side or an inner peripheral side of the first layer; and a blow-molding process for blow-molding a preform that includes multiple layers and has been obtained in the second injection molding process in a state where residual heat at a time of injection molding is contained, and manufacturing the resin container having a vertical-striped color pattern formed by using the second layer.

A preform, a synthetic resin container, and a method for manufacturing a synthetic resin container in which an air passage leading from an ambient air introduction hole to a trunk can be easily preserved. In the mouth, the inner body includes a large-diameter portion provided at an upper end thereof, and a small-diameter portion continuously extending below the large-diameter portion via a connecting portion. In the mouth, the outer body is provided with an ambient air introduction hole passing through the outer body, and a neck ring positioned within a height range of the small-diameter portion. The inner body is made of a crystalline resin, and a crystallized region is formed in part of the inner body, the crystallized region having a higher degree of crystallization than other regions.

A preform assembly includes: an outer preform that includes an outer mouth portion and a stretch portion connected to the outer mouth portion and in which a recess extending in a vertical direction is provided on an inner surface of the stretch portion; and an inner preform that includes an inner mouth portion and a stretch portion connected to the inner mouth portion, wherein an outside air introduction port communicating with a part between the outer preform and the inner preform is provided in a mouth portion composed of the outer mouth portion and the inner mouth portion located on an inner side of the outer mouth portion.

A method for manufacturing a resin container, the method including: injection-molding a bottomed preform made of resin; and blow-molding the preform to manufacture a resin container, in which the injection molding includes filling a cavity formed by at least an injection core mold and an injection cavity mold with a molten resin to form the preform, and a first groove that extends from a bottom portion defining portion to a neck portion defining portion is formed in a surface of the body portion defining portion of the injection core mold.

A preform for molding a dual container, in which an inner preform is inserted into an outer preform in a state in which a mouth portion of the inner preform is fitted into a mouth portion of an outer preform, the inner preform is formed of a crystalline resin, a crystallized region is provided in at least a portion of the inner preform, the crystallized region having a degree of crystallization greater than that of the other portion, the portion of the inner preform adjacent to the mouth portion from below the mouth portion and located below the outside air introduction hole, a step portion facing upward and a rib extending upward from the step portion are formed on an inner circumferential surface of the inner preform, and at least a part of the rib is adjacent to the crystallized region from above the crystallized region.

A method for manufacturing a resin container, the method including: injection-molding a bottomed preform made of resin; and blow-molding the preform to manufacture a resin container, in which the injection molding includes filling a cavity formed by at least an injection core mold and an injection cavity mold with a molten resin to form the preform, and a first groove that extends from a bottom portion defining portion to a neck portion defining portion is formed in a surface of the body portion defining portion of the injection core mold.

A preform assembly includes: an outer preform that includes an outer mouth portion and a stretch portion connected to the outer mouth portion and in which a recess extending in a vertical direction is provided on an inner surface of the stretch portion; and an inner preform that includes an inner mouth portion and a stretch portion connected to the inner mouth portion, wherein an outside air introduction port communicating with a part between the outer preform and the inner preform is provided in a mouth portion composed of the outer mouth portion and the inner mouth portion located on an inner side of the outer mouth portion.