Polymer film having linear tear properties

Abstract

Certain blends or mixtures of polyethylene and ionomer resins are blow extruded to make a film having excellent linear tear properties in the direction of extrusion, which property is not found in films of either of the resins alone.

What is claimed is: 
     
       1. A method of imparting linear tear properties in the direction of extrusion to a polymer film comprising the steps of preparing a blend of resins consisting essentially of from about 12% to about 95% ionomer resin and from about 5% to about 88% low density polyethylene resin, and extruding said blend of resins .Iadd.at a stretch ratio of approximately 1.5 to 1 .Iaddend.into a film.[.,.]. whereby said film exhibits linear tear properties in a direction parallel to the direction of extrusion .Iadd.and an Elmendorf tear strength of from 30 to 125 g. .Iaddend. 
     
     
       2. The method of claim 1 wherein said polyethylene resin contains up to about 7.5% of ethylene-vinyl acetate copolymer. 
     
     
       3. The method of claim 1 wherein said blend of resins is blow extruded in the form of a tube. 
     
     
       4. The method of claim 1 wherein the density of said polyethylene resin is in the range of from about 0.910 to about 0.960. 
     
     
       5. The method of claim 1 wherein .Iadd.a polymer .Iaddend.lacking linear tear properties selected from the group consisting of polyethylene, polyethylene modified with vinyl acetate, polyethylene modified with isobutylene, ionomer and an ionomerpolyethylene blend, is coextruded with said blend of resins to provide a coextruded film having linear tear properties in the direction of extrusion. 
     
     
       6. An extruded polymer film consisting essentially of from about 12% to about 95% of ionomer and the remainder as polyethylene having a density of from about 0.910 to about 0.960, said film being .Iadd.extruded at a stretch ratio of approximately 1.5 to 1 and being .Iaddend.capable of being torn in substantially a straight line in the direction of extrusion at a deviation of less than 20° from said straight line, .Iadd.said film having an Elmendorf tear strength of from 30 to 125 g. .Iaddend. .[. 
     
     
       7.  The film of claim 6 wherein the Elmendorf tear strength of said film is less than 125 g..]. 
     
     
       8. The film of claim .[.7.]. .Iadd.6 .Iaddend.wherein the Elmendorf tear strength of said film is from about 30 to about 125 g. 
     
     
       9. The film of claim 6 wherein said polyethylene contains up to about 7.5% vinyl acetate. 
     
     
       10. The film of claim 6 wherein said film is blow extruded. 
     
     
       11. The film of claim 6 wherein said film is coextruded with a second polymer film selected from the group consisting of polyethylene, polyethylene modified with vinyl acetate, polyethylene modified with isobutylene, ionomer and an ionomer-polyethylene blend. 
     
     
       12. A pouch composed of an extruded polymer film, said pouch having a top edge, bottom edge and side edges, said top and bottom edges being substantially parallel with the direction of extrusion of said film, the film of said pouch consisting essentially of from about 12% to about 95% ionomer with the remainder as polyethylene having a density of 0.910 to about 0.960 and containing from about zero to 7.5% vinyl acetate, .Iadd.the film of said pouch being extruded at a stretch ratio of approximately 1.5 to 1 and having an Elmendorf tear strength of from 30 to 125 g, .Iaddend.said pouch being capable of being torn from side to side in substantially a straight line parallel with the direction of extrusion. 
     
     
       13. The pouch of claim 12 wherein said film is coextruded with a second polymer, said second polymer being selected from the group consisting of polyethylene, polyethylene modified with vinyl acetate, polyethylene modified with isobutylene, ionomer, and an ionomer-polyethylene blend. 
     
     
       14. A pouch comprising a blow extruded polymer tube section having open ends, said tube being heat sealed adjacent each open end to form an enclosure, said tube consisting essentially of from about 12% to about 95% ionomer with the remainder as polyethylene and zero to about 71/2% vinyl acetate, the heat sealed edges of said tube being perpendicular to the direction of extrusion, .Iadd.said tube being extruded at a stretch ratio of approximately 1.5 to 1 and having an Elmendorf tear strength of from 30 to 125 g, .Iaddend.said pouch being capable of being torn in substantially a straight line between the sealed edges thereof. 
     
     
       15. The pouch of claim 14 comprising a notch in one of the sealed edges thereof.