Process for the production of polypropylene films

US5716570A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Herbert Peiffer · Mainz, DE
• Gunter Schlogl · Kelkheim, DE
• Karl-Heinz Kochem · Neunkirchen, DE
• Detlef Busch · Saarlouis, DE
• Robert Schmidt · Eltville am Rhein, DE

Key dates

• Filing date: May 2, 1996
• Grant date: Feb 10, 1998
• Expiry date: May 2, 2016

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B29C48/12
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

A process for the production of biaxially oriented polypropylene films which include at least one layer is described, in which a propylene polymer B is heated in an extruder and the melt of the propylene polymer B is extruded through a flat sheet die and the melt emerging from the flat sheet die is taken off on one or more rolls and is solidified to give a prefilm and this prefilm is stretched in the longitudinal and transverse direction. A propylene polymer or a propylene polymer mixture A is heated and melted in a second extruder and the melt of the propylene polymer or of the propylene polymer mixture A is fed to the two sides of the propylene polymer melt B so that both melts are extruded together and simultaneously through the flat sheet die. The propylene polymer or the propylene polymer mixture A forms the edge region of the film during the production process, and the edge regions including the propylene polymer or the propylene polymer mixture A are cut off after the longitudinal and transverse stretching of the film.