Polypropylene composition

Abstract

New polypropylene composition which combines low sealing initiation temperature (SIT), high hot-tack, good optical properties, like low haze and its use, and improved stiffness/impact balance.

1 . A polypropylene composition comprising
 (A) a blend of
 (a) 60.0 to 96.0 wt %, based on the blend, of a propylene terpolymer comprising
 (i) ethylene-derived comonomer units in an amount of from 0.3 to 4.0 wt % and 
 (ii) comonomer units derived from a C 4  to C 10  α-olefin in an amount of from 4.0 to 16.0 wt %, 
 
 whereby the terpolymer has an MFR 2  (230° C., 2.16 kg, ISO1133) in a range of 0.5 to 20.0 g/10 min and 
 (b) 4.0 to 40.0 wt %, based on the blend, of an ethylene based plastomer having a density according to ISO 1183 of from 0.850 g/cm 3  to 0.900 g/cm 3  and an MFR 2  according to ISO 1133 (190° C.; 2.16 kg) in the range of 0.1 to below 5.0 g/10 min, and 
   (B) optional one or more additives in a total amount of from 0.0 up to 5.0 wt %, based on the polypropylene composition, selected from the group consisting of slip agents, anti-block agents, UV stabilizers, alpha and/or beta nucleating agents, antistatic agents, and antioxidants.   
     
     
         2 . The polypropylene composition according to  claim 1 , wherein the propylene terpolymer has a melting temperature Tm measured via DSC according to ISO 11357 of equal or higher than 130° C. 
     
     
         3 . The polypropylene composition according to  claim 1 , wherein the propylene terpolymer has a xylene cold soluble (XCS) amount in the range of 3.0 to below 20.0 wt % (measured according to ISO 16152, 2005, at 25° C.). 
     
     
         4 . The polypropylene composition according to  claim 1 , wherein the ethylene based plastomer has an MFR 2  according to ISO 1133 (190° C.; 2.16 kg) in the range of 0.3 to 2.0 g/10 min. 
     
     
         5 . The polypropylene composition according to  claim 1 , wherein the polypropylene composition has a xylene cold soluble (XCS) amount below 35.0 wt % (measured according to ISO 16152, 2005, at 25° C.). 
     
     
         6 . A process for the preparation of the polypropylene composition according to  claim 1 , the process comprising the steps of
 (i) preparing the propylene terpolymer by polymerizing propylene, ethylene and a C 4  to C 10  α-olefin in the presence of a Ziegler-Natta catalyst,   (ii) mixing said propylene terpolymer with the ethylene based plastomer, optionally in the presence of one or more additives, to obtain a mixture of the propylene terpolymer and the ethylene based plastomer, and   (iii) extruding said mixture, to obtain the polypropylene composition comprising the blend (A) of the propylene terpolymer and the ethylene based plastomer.   
     
     
         7 . A method comprising producing articles with the polypropylene composition according to  claim 1 . 
     
     
         8 . The method according to  claim 7 , wherein the articles are sterilizable articles. 
     
     
         9 . An article comprising the polypropylene composition according to  claim 1 . 
     
     
         10 . The article according to  claim 9 , wherein the article is an unoriented film comprising more than 90% of the polypropylene composition according to  claim 1 , wherein the unoriented film is a cast film or a blown film. 
     
     
         11 . The article according to  claim 10 , wherein the unoriented film has a sealing initiation temperature in the range of from 95° C. to 110° C. 
     
     
         12 . The article according to  claim 10 , wherein the unoriented film has a haze according to ASTM D1003-00 determined on 50 μm blown film of below 25.0%. 
     
     
         13 . The article according to  claim 10 , wherein the unoriented film has a hot-tack force determined on 50 μm blown film in the range of from 2.8 to 7.0 N. 
     
     
         14 . The article according to  claim 10 , wherein the unoriented film has a Dart Drop Impact according to ASTM D1709, method A of at least 100 g. 
     
     
         15 . A sealing layer in a multi-layer film, the sealing layer comprising an unoriented film comprising more than 90% of the polypropylene composition according to  claim 1 , wherein the unoriented film is a cast film or a blown film.