Synthetic resin liquid container

A collapsible synthetic resin liquid container comprising:

• a collapsible container body having a bottom and a side wall made of flexible and relatively hard plastic synthetic resin, and a form that resists oscillation and vertical stress during transport with liquid therein and facilitates reducing the volume of the container body by applying a vertical and/or twisting force which collapses a portion of the container body from an extended state to a collapsed state when the container body is empty;
• the side wall includes a collapsible upper body portion and a collapsible lower body portion, the collapsible upper body portion having a resilient threaded neck portion and a taper portion, when the collapsible upper body portion is in an extended state the resilient threaded neck portion includes a cap opening at the upper edge of the resilient threaded neck portion and the taper portion extends below the resilient threaded neck portion, and an upper end rim of the collapsible lower body portion formed so that the resilient threaded neck portion and the taper portion are collapsed inside-out with formerly inside surfaces of the neck portion and the taper portion facing outwardly thereby disposing the cap opening below the neck portion and the taper portion;
• a cap covering the cap opening from the bottom and releasably and threadably engaged to the resilient threaded necked potion when the collapsible upper body portion is collapsed with inside surfaces of the neck portion and the taper portion facing outwardly, the cap is adapted to cover the cap opening from the top and releasably and threadably engage the resilient threaded necked potion when the collapsible upper body portion is extended.