Process for preparing double-wall blow-molded articles having a high stretching ratio and products so obtained

A process for preparing double-wall blow-molded articles having a high stretching ratio, which comprises: a) extruding a tubular body (1) made of a thermoplastic polymer through an essentially annular extruder; b) positioning the tubular body (1) into an open blow-molding mold composed of a first concave half-mold (2), which partially reproduces the shape of the article to be produced, and of a second half-mold (3), which comprises a movable piston (4) supporting a template (5) capable of conforming to the concavities of the first half-mold (2); and c) closing the mold, molding by means of the blow-molding technique the tubular body (1) while it is still in a softened state, and simultaneously, or almost simultaneously introducing the movable piston (4) of the second half-mold (3) into the concavities of the first half-mold (2).