Polypropylene films with improved printability

Abstract

The patent application discloses a polypropylene-plastomer-blend comprising ethylene-based plastomer, which—after conversion into final articles and exposing to surface modification like corona treatment, shows improved dyne retention behavior and improved dyne retention ratio over time. Further disclosed are final articles and a process how to provide compositions and final articles having improved dyne retention behavior.

The invention claimed is: 
     
       1. A polypropylene-plastomer-blend comprising 80-93 wt. % of a polypropylene random copolymer and 7-20 wt. % of an ethylene-based plastomer, based on the sum of the amount of the polypropylene random copolymer and the ethylene-based plastomer, wherein
 the polypropylene random copolymer comprises at least 1.5 wt % ethylene as a comonomer, and 
 the ethylene based plastomer has a density ISO 1183D of 0.915 g/cm 3  or below. 
 
     
     
       2. The polypropylene-plastomer-blend according to  claim 1 , wherein the MFR(230/2.16) of the polypropylene-plastomer-blend according to ISO 1133 is 15 g/10 min or below. 
     
     
       3. An article made out of the polypropylene-plastomer blend according to  claim 1 . 
     
     
       4. The article according to  claim 3 , wherein the article is produced via blown film or cast film production. 
     
     
       5. A film comprising the polypropylene-plastomer blend according to  claim 1 , wherein the film comprises a blown film or a cast film and has a dyne retention of >38 dyne/cm measured according to ASTM D2578-09 14 days or more after surface treatment. 
     
     
       6. The article according to  claim 3 , wherein in the article has a dyne retention ratio (DDR x ) after surface treatment of at least 70% or more, wherein x is defined to be 14 days or more. 
     
     
       7. A process for the production of articles having increased dyne retention, the process comprising the steps of:
 a. providing a polypropylene-plastomer-blend by blending 80 93 wt. % of a polypropylene random copolymer and 7-20 wt. % of an ethylene-based plastomer, based on the sum of the amount of the polypropylene random copolymer and the ethylene based plastomer, wherein
 the polypropylene random copolymer comprises at least 1.5 wt % ethylene as a comonomer, and 
 the ethylene based plastomer has a density ISO 1183D of 0.915 g/cm 3  or below, 
 
 b. forming an article out of the polypropylene-plastomer-blend, 
 c. exposing one or more surface(s) of said article to a treatment that increases the surface energy, and optionally 
 d. further modifying the surface having increased surface energy by printing, coating or metallization. 
 
     
     
       8. A method of use of ethylene based plastomers having a density less than 0.915 g/cm 3  to improve the dyne retention or the dyne retention ratio DRRx of articles comprising polypropylene, wherein x is defined to be 14 days or more. 
     
     
       9. The film according to  claim 5 , wherein in the film has a dyne retention ratio (DDR x ) after surface treatment of at least 70% or more, wherein x is defined to be 14 days or more.