a process for producing containers involves a tube and at least one separating partition , both formed from plasticized synthetic material . the partition extends within the tube . the tube and partition are extruded into an opened blow mold . the blow mold is then closed , and the tube is expanded by producing a pressure gradient that acts upon the tube . the pressure gradient is applied to expand the tube against the molding wall of the blow mold to form the container . the end of the tube that is the front end during the extrusion step and the front end of every separating partition are welded together by closing the opened blow mold , thereby closing the base of the container that is linked with every separating partition . the tube is expanded by adding blowing air from the end of the closed blow mold that is opposite to the container base and that is assigned to the container neck in such a manner that the blowing air has an expanding effect on both sides of the separating wall , thereby forming chambers in the container that are separate from one another .