Toughened propylene polymers having little tendency to white fracture

Abstract

Propylene polymers contain a) from 50 to 95 parts by weight of a propylene homopolymer having a melt flow index of from 0.1 to 100 g/10 min., at 230° C. and under a weight of 2.16 kg, according to ISO standard 1133, and an isotacticity index of at least 98%, b) from 5 to 50 parts by weight of an ethylene copolymer containing from 4 to 40% by weight of polymerized C 4 -C 20 -alk-1-ene and having a density of from 0.865 to 0.920 g/cm 3 and c) from 0 to 1.5 parts by weight of a nucleating agent, the sum of the parts by weight of the propylene homopolymer a) and of the ethylene copolymer b) always being 100 parts by weight. The propylene polymers are distinguished in particular by high rigidity and little tendency to white fracture.

We claim:  
     
         1 . A propylene polymer containing 
 a) from 50 to 95 parts by weight of a propylene homopolymer having a melt flow index of from 0.1 to 100 g/10 min., at 230° C. and under a weight of 2.16 kg, according to ISO standard 1133, and an isotacticity index of at least 98%,    b) from 5 to 50 parts by weight of an ethylene copolymer containing from 4 to 40% by weight of polymerized C 4 -C 20 -alk-1-ene and having a density of from 0.865 to 0.920 g/cm 3  and    c) from 0 to 1.5 parts by weight of a nucleating agent, the sum of the parts by weight of the propylene homopolymer a) and of the ethylene copolymer b) always being 100 parts by weight.    
     
     
         2 . A propylene polymer as claimed in  claim 1 , containing 
 a) from 75 to 90 parts by weight of the propylene homopolymer a),    b) from 10 to 25 parts by weight of the ethylene copolymer b) and    c) from 0.05 to 1.5 parts by weight of a nucleating agent, the sum of the parts by weight of the propylene homopolymer a) and of the ethylene copolymer b) always being 100 parts by weight.    
     
     
         3 . A propylene polymer as claimed in  claim 1 , wherein the propylene homopolymer a) has a melt flow index of from 0.2 to 50 g/10 min. at 230° C. and under a weight of 2.16 kg, according to ISO standard 1133.  
     
     
         4 . A propylene polymer as claimed in  claim 1 , wherein the propylene homopolymer a) has an isotacticity index of from 98.0 to 99.5%.  
     
     
         5 . A propylene polymer as claimed in  claim 1 , wherein the ethylene copolymer b) has a density of from 0.868 to 0.91 g/cm 3 .  
     
     
         6 . A propylene polymer as claimed in  claim 1 , wherein the ethylene copolymer b) contains but-1-ene, hex-1-ene or oct-1-ene as the C 4 -C 20 -alk-1-ene.  
     
     
         7 . A propylene polymer as claimed in  claim 1 , wherein the ethylene copolymer b) contains from 7 to 30% by weight of polymerized C 4 -C 20 -alk-1-ene.  
     
     
         8 . A propylene polymer as claimed in  claim 1 , wherein the nucleating agent c) used is finely divided talc.  
     
     
         9 . A process for the preparation of a propylene polymer as claimed in  claim 1 , wherein the propylene homopolymer a) and the ethylene copolymer b) and, if required, the nucleating agent c) are combined with one another in a mixing apparatus at from 200 to 250° C.  
     
     
         10 . A process as claimed in  claim 9 , wherein the mixing apparatus used is an extruder.