A plural preform assembly having nested preforms with an inner preform and an outer preform. The preforms are sealably joined together, defining a volume between the preforms. Propellant is disposed in the volume between the preforms. The preforms are later blow molded to provide a bag in bottle, bottle in bottle or similar container. The propellant charge is already present when blow molded, preventing the need for a later propellant filling step.

A plural preform assembly having nested preforms. The preforms are held together by an interference fit. The interference fit is provided by the friction between the preforms which occurs when the inner preform is inserted into the outer preform. At least one preform may have ribs extending radially towards the other preform. The ribs provided concentricity and interference to hold the preforms together during subsequent operations. The preforms may later be blow molded to provide a bag in bottle or similar container.

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 method of manufacturing containers consisting of a substantially stiff outer container and a readily deformable inner bag of first and second thermoplastic plastic materials, where the inner bag is detached from the wall of the outer container, includes the step of the excess material is supplied again to the first screw conveyor, which mixes the excess material with the first thermoplastic plastic material and supplies it to the extruder nozzle, wherein the first thermoplastic plastic material has a lower viscosity in the molten state than the excess material so that the outer layer of the extruded tube consists only of the first thermoplastic plastic material.

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.