Polypropylene-based article having an increased surface tension retention

A process for the production of a polypropylene based article having improved surface tension retention, the process comprises:

• A) providing a metallocene-catalysed propylene-ethylene random copolymer (RACO) having
• (a) an ethylene content in a range of from 1.0 to 10.0 wt % based on a total weight of the metallocene-catalysed propylene-ethylene random copolymer (RACO);
• (b) a melt flow rate MFR2 (230° C./2.16 kg) measured according to ISO 1133 in a range of from 1.0 to 20.0 g/10 min;
• (c) a melting temperature Tm as determined by DSC according to ISO 11357 of from 115 to 150° C.;
• (d) a xylene cold soluble (XCS;
• ISO 16152, 2005;
• 25° C.) fraction of from 0.1 wt % to 5.0 wt % and
• (e) a content of 2,1 regio-defects in a range from 0.05 to 1.5 mol % as determined by 13C-NMR spectroscopy
• B) forming a polypropylene based article out of the metallocene-catalysed propylene-ethylene random copolymer (RACO) with a thickness in a range of from 1.0 to 1000 μm and
• C) subjecting one or more surface(s) of the polypropylene based article to a treatment that increases the surface tension, to yield a polypropylene based article having improved surface tension retention,
• wherein the polypropylene based article having improved surface tension retention has a dyne retention ratio (DRR7) of at least 76% or more, wherein dyne retention ratio (DRR7) indicates the dyne retention of the polypropylene based article having improved surface tension retention after 7 days of storage, in relation to an original dyne retention value of the polypropylene based article having improved surface tension retention, determined 6 hours after the treatment that increases the surface tension, multiplied by 100, and
• wherein the metallocene-catalysed propylene-ethylene random copolymer (RACO) is the sole polymer used for forming the polypropylene based article.