	US 11,851,552 B2
	Biaxially oriented polypropylene film with improved breakdown strength
Dietrich Gloger, Linz (AT); Hermann Braun, Linz (AT); Antonios Gitsas, Linz (AT); Davide Tranchida, Linz (AT); Franciscus Jacobs, Evergem (BE); and Wolfram Stadlbauer, Linz (AT)
Assigned to Borealis AG, Vienna (AT)
Appl. No. 17/413,612
Filed by BOREALIS AG, Vienna (AT)
PCT Filed Dec. 20, 2019, PCT No. PCT/EP2019/086504 § 371(c)(1), (2) Date Jun. 14, 2021, PCT Pub. No. WO2020/127861, PCT Pub. Date Jun. 25, 2020.
Claims priority of application No. 18214673 (EP), filed on Dec. 20, 2018.
Prior Publication US 2022/0033631 A1, Feb. 3, 2022
Int. Cl. C08L 23/12 (2006.01); B29C 48/00 (2019.01); B29C 55/16 (2006.01); C08J 5/18 (2006.01); C08L 23/14 (2006.01); C08L 23/20 (2006.01); H01G 4/18 (2006.01); B29K 23/00 (2006.01); B29L 9/00 (2006.01)

CPC C08L 23/12 (2013.01) [B29C 48/022 (2019.02); B29C 55/16 (2013.01); C08J 5/18 (2013.01); C08L 23/142 (2013.01); C08L 23/20 (2013.01); H01G 4/18 (2013.01); B29K 2023/12 (2013.01); B29K 2023/14 (2013.01); B29K 2023/18 (2013.01); B29L 2009/003 (2013.01); C08L 2203/16 (2013.01); C08L 2205/025 (2013.01); C08L 2205/03 (2013.01)]

15 Claims

1. 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 MFR₂of 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 cm²utilizing 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.