Polypropylene-polybutylene heat sealable laminated packaging film with improved optics

Abstract

A packaging film comprising a core layer of polypropylene and a surface layer comprising a propylene ethylene random copolymer wherein at least one of said core or said surface layers contains a minor amount of a high melt index butylene homopolymer.

What is claimed is: 
     
       1. A multiple-layer, heat-sealable laminated film comprising: (I) a core layer comprising propylene homopolymer and copolymers of propylene with from 1% to about 30% by weight of an α-olefin having 2 or 4 to 8 carbon atoms,   (II) on at least one side of said core, an outer layer comprising a propylene-ethylene random copolymer having an ethylene content of 7% by weight or less,   wherein at least one of said core or said outer layer contains from about 0.2% to about 10% by weight of a high melt index butene-1 homopolymer having a melt index of from about 20 to about 1000 g/10 minutes at 190° C.   
     
     
       2. The film of claim 1 wherein the high melt index butylene homopolymer has a melt index of from 30 to 650 g/10 minutes at 190° C. 
     
     
       3. The film of claim 1 wherein the high melt index butylene homopolymer has a melt index of from 50 to 300 g/10 minutes at 190° C. 
     
     
       4. The film of claim 1 wherein the high melt index butylene homopolymer has a melt index of from 100 to 200 g/10 minutes at 190° C. 
     
     
       5. The film of claim 1 wherein the high melt index butylene homopolymer has a melt viscosity of from 10,000 to about 200,000 centipoise at 200° C. 
     
     
       6. The film of claim 1 wherein the high melt index butylene homopolymer has a melt viscosity of from 40,000 to 100,000 centipoise at 200° C. 
     
     
       7. The laminated film of claim 1 wherein said outer layer is from about 0.02 mils to about 0.6 mils thick and the total film thickness is between 0.5 and 2.0 mils. 
     
     
       8. The laminated film of claim 1 wherein the film is formed by coextrusion. 
     
     
       9. A multiple-layer, heat-sealable laminated film comprising: (I) a core layer comprising propylene homopolymers and copolymers of propylene with from 1% to about 30% by weight of an α-olefin having 2, or 4 to 8 carbon atoms,   (II) on at least one side of said core, an outer layer comprising a blend of:   (a) from 40% to 80% by weight of a propylene-ethylene random copolymer having an ethylene content of 7% by weight or less,   (b) from 20% to 60% by weight of a low melt index butene-1 polymer having a melt index of between 1.0 and 15 g/10 minutes at 190° C.,   and wherein at least one of said core or said outer layer contains from about 0.2% to about 10% by weight of a high melt index butene-1 homopolymer having a melt index of from about 20 to about 1000 g/10 minutes at 190° C.   
     
     
       10. The film of claim 9 wherein the outer layer comprises from 50 to 70% by weight of said propylene ethylene random copolymer, 30 to 50% by weight of said low melt index polybutylene and from 0.5 to about 5.0% by weight of said high melt index butylene homopolymer. 
     
     
       11. The film of claim 10 wherein the outer layer comprises from 55 to 65% by weight of said propylene ethylene random copolymer, 35 to 45% by weight of said low melt index polybutylene and from 2.0 to about 4.0% by weight of said high melt index butylene homopolymer. 
     
     
       12. A multiple-layer, heat-sealable laminated film comprising: (I) a core layer comprising propylene homopolymers and copolymers of propylene with from 1% to about 30% by weight of an α-olefin having 2, or 4 to 8 carbon atoms,   (II) on at least one side of said core, an outer layer comprising a blend of:   (a) from 55% to 65% by weight of a propylene-ethylene random copolymer having an ethylene content of 7% by weight or less, and a melt index of from 6 to 10 g/10 minutes at 230° C.,   (b) from 35% to 45% by weight of a low melt index butene-1 ethylene random copolymer having an ethylene content of from 0.3 to 20.0 mole % and a melt index of between 1.0 and 15 g/10 min. at 190° C.,   wherein at least one of said core or said outer layer contains from about 2% to about 4% by weight of a high melt index butene-1 homopolymer having a melt index of from 100 to about 300 g/10 minutes at 190° C., and a melt viscosity of between 40,000 and 100,000 centipoise at 200° C.