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 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 method of producing containers with at least one enhanced property, such as high strength, sturdy, durable, and recyclable are described herein. The container so formed have ribs/patterns at the inner surface, leaving the entire outer surface for decorative or marketing purposes. The ribs/pattern is selected from linear lines, curved lines, honeycombs, hexagons, square, rectangular, circular and combination thereof. The containers so formed may have reduced amount of materials used.

Hollow injection molded article made of plastic material, esp. preform for blow molding a container, with a wall (17) extending along axis (I), which is composed of a layer of variable thickness (), being remarkable in that longitudinal ribs are provided in said axis direction, wherein the wall has a tooth profile of periodic nature varying periodically between a minimum and a maximum threshold value (m, resp. M) which is determined by a typical injection molding length (Ls) for said plastic material and/or characteristic ratio (max/min). A method of manufacturing thereof (10) by injection molding comprising forming inner and outer preforms (11, 12) with formation of an integrated composite preform (10), and apparatus for this purpose.

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.