US 2022/0033631 A1 · BIAXIALLY ORIENTED POLYPROPYLENE FILM WITH IMPROVED BREAKDOWN STRENGTH

Abstract

The present invention is directed to a biaxially oriented polypropylene (BOPP) film with improved breakdown strength and to a capacitor comprising an insulation film comprising a layer of the biaxially oriented polypropylene film of the present invention. The present invention is further directed to a process for producing a biaxially oriented polypropylene film. Finally, the present invention is further directed to the use of a biaxially oriented polypropylene film of the present invention as layer of an insulation film of a capacitor. The BOPP film comprises a polypropylene composition, wherein the polypropylene composition comprises a high isotactic homopolymer of propylene and a polymeric α-nucleating agent. The BOPP film has a dielectric breakdown field strength Eb63.2 of at least 595 kV/mm. The process for producing a biaxially oriented polypropylene film comprises the steps of extruding a polypropylene composition to a flat film and orienting the flat film simultaneously in the machine direction and in the transverse direction.

Claims15

Dependent claims

A biaxially oriented polypropylene film, comprising a polypropylene composition, wherein the polypropylene composition comprises:

(i) from 90 to 99.99 wt %, based on the total weight of the polypropylene composition, of a homopolymer of propylene having a content of isotactic pentad fraction of from 93 to 98% and a melt flow rate MFR2 of from 0.4 to 10 g/10 min, and
(ii) from 0.0000001 to 1 wt %, based on the total weight of the polypropylene composition, of a polymeric α-nucleating agent,
wherein the biaxially oriented polypropylene film has
a dielectric breakdown field strength Eb63.2 of at least 595 kV/mm, which is obtained as the Scale parameter α of a fitted two-parameter Weibull distribution based on 50 results, measured with active electrode area of 2.84 cm2 utilizing 250 V/s DC voltage ramp rate on films with a thickness of 3.8-4.2 μm, and
a thickness of 2 to 5 μm, wherein further the film is stretched simultaneously in machine direction and transverse direction.

2 more elements

Dependencies are inferred from the claim text.

Biaxially oriented polypropylene film with improved breakdown strength

Life of this patent

Biaxially oriented polypropylene film with improved breakdown strength

Life of this patent

Abstract

Claims15