Process for the production of a biaxially highly oriented polypropylene film

US5766532A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Herbert Peiffer · Mainz, DE
• Ursula Murschall · Nierstein, DE
• Detlef Busch · Saarlouis, DE
• Harald Lohmann · Neunkirchen, DE

Key dates

• Filing date: May 12, 1995
• Grant date: Jun 16, 1998
• Expiry date: May 12, 2015

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B29K2023/12
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

A process for the production of a biaxially oriented propylene polymer film contains, in its single ply (or, if it is a multi-ply film, in its base ply) a low molecular weight resin, and the film has improved stretchability and other desirable physical properties, even though the propylene polymer of the sole or base ply is preferably a homopolymer. The n-heptane-insoluble fraction of the film has a chain isotacticity index, measured by means of .sup.13 C-NMR spectroscopy, of at least 85 to 94%. The sole or base ply contains less than 10% by weight of resin. The film is stretched in such a way that the product of tensile strength in the longitudinal and transverse direction is greater than 50,000 (N/mm.sup.2).sup.2. The film is made by, among other steps, carrying out the orientation in the longitudinal and transverse directions such that the product of the longitudinal stretching ratio and the transverse stretching ratio is.gtoreq.60.