Compositions of ethylene/vinyl acetate copolymers for heat-sealable easy opening packaging

1. A package comprising a multilayer structure having an easily peelable opening feature and a tight hermetic seal wherein the multilayer structure comprises at least one polychlorotrifluoroethylene fluoropolymer substrate layer, and wherein the multilayer structure is prepared by a method comprising the steps of:

A. providing a polychlorotrifluoroethylene fluoropolymer substrate layer;

B. providing a resin composition that, when tested substantially in accordance with ASTM F 904-98, peels cleanly away from a polychlorotrifluoroethylene fluoropolymer substrate layer, wherein said resin composition consists essentially of:

(1) from about 10 to about 90 weight %, based on the total weight of said resin composition, of at least one ethylene/vinyl acetate copolymer having a melt flow rate of 0.1 to 40 g/10 minutes, measured in accordance with ASTM D 1238, Condition E, at 190° C., using a 2.16 kg weight;

(2) from about 5 to about 35 weight %, based on the total weight of said resin composition, of at least one tackifying resin;

(3) from about 5 to about 45 weight %, based on the total weight of said resin composition, of at least one polyolefin selected from the group consisting of ethylene polymers; and

(4) from 0 to about 30 weight %, based on the total weight of said resin composition, of filler;

wherein the resin composition has a viscosity at 190° C. of from about 6 g/10 minutes to about 10.3 g/10 minutes as determined according to ASTM D 1238, Condition E, at 190° C., using a 2.16 kg weight, thereby providing a composition having a viscosity sufficiently high to form a sheet or tape when extruded at a temperature of 190° C.;

C. selecting an additional material selected from the group consisting of polyesters, polyamides, polyolefins, polyethylene vinyl alcohols, polyethylene vinyl acetates, ethylene/acrylic acid copolymers and ionomers thereof, ethylene/methacrylic acid copolymers and ionomers thereof, polyvinyl chloride, polyvinylidene chloride, anhydride-modified polyolefins and mixtures thereof that has a viscosity sufficiently high to form a sheet or tape when extruded at a temperature of 190° C.;

D. forming a multilayer coextrudate having at least two layers via coextrusion through a single die in the form of a film, a sheet or a tape, wherein i) a first layer of said extrudate comprises said resin composition of step B, ii) a second layer of said extrudate comprises said additional material of step C, and iii) said first layer is an outer layer of said multilayer coextrudate;

E. contacting said multilayer coextrudate with said polychlorotrifluoroethylene fluoropolymer substrate layer such that said first layer comprising said resin composition of step B is in contact with and adjacent to said polychlorotrifluoroethylene fluoropolymer substrate layer; and

F. applying sufficient heat and pressure for sufficient time to heat-seal said multilayer coextrudate to said polychlorotrifluoroethylene fluoropolymer substrate layer;

thereby forming a multilayer structure characterized by a tight hermetic seal and easy peelability wherein the coextrudate peels cleanly away from the polychlorotrifluoroethylene substrate leaving the substrate intact.

2. A package of claim 1 that is a blister package.

3. A package of claim 1 wherein the multilayer coextrudate having at least two layers is in the form of a film.

4. A package of claim 1 wherein the at least one ethylene/vinyl acetate copolymer has a melt flow rate of 3 to 8 g/10 minutes, measured in accordance with ASTM D 1238, Condition E, at 190° C., using a 2.16 kg weight.

5. A package of claim 1 wherein the multilayer structure additionally comprises at least one barrier layer.

6. A package of claim 5 wherein the at least one barrier layer comprises a material selected from the group consisting of metallized polypropylenes, polyethylene terephthalates, ethylene vinyl alcohol polymers, polyvinyl alcohols, polyvinylidene chlorides, polyolefins, aluminum foil, polyamides and mixtures thereof.

7. A package of claim 1 wherein the multilayer structure additionally comprises at least one bulking layer.

8. A package of claim 7 wherein the at least one bulking layer comprises a polymer selected from the group consisting of polyolefins, polyolefin polar copolymers, polyesters and mixtures thereof.

9. A package of claim 1 wherein the multilayer coextrudate additionally comprises at least one tie layer.

10. A package of claim 1 wherein the resin composition of step B consists essentially of:

(1) from about 35 to about 60 weight %, based on the total weight of said resin composition, of at least one ethylene/vinyl acetate copolymer having a melt flow rate of 0.1 to 40 g/10 minutes, measured in accordance with ASTM D 1238, Condition E, at 190° C., using a 2.16 kg weight;

(2) from about 5 to about 25 weight %, based on the total weight of said resin composition, of at least one tackifying resin; and

(3) from 25 to about 45 weight %, based on the total weight of said resin composition, of at least one polyolefin.

11. A package of claim 1 wherein component (1) of the resin composition is a mixture of two or more different ethylene/vinyl acetate copolymers, each of said ethylene/vinyl acetate copolymers having a melt flow rate of 0.1 to 40 g/10 minutes, measured in accordance with ASTM D1238, Condition E, at 190° C., using a 2.16 kg weight.

12. A package of claim 1 wherein the resin composition, when sealed at a temperature of between 250° F. to 400° F. to the polychlorotrifluoroethylene fluoropolymer substrate layer and tested substantially in accordance with ASTM F 904-98, peels cleanly away from the polychlorotrifluoroethylene fluoropolymer substrate layer and the average seal strength is between about 865 g/inch to about 1890 g/inch.

13. A package of claim 1 wherein the multilayer coextrudate is laminated to a layer made of a material selected from the group consisting of paper and foil.

14. A package of claim 1 wherein the polyolefin is an ethylene homopolymer.

15. A package of claim 1 wherein the polyolefin is a copolymer of ethylene and butene.

16. A package of claim 1 wherein the polyolefin is a copolymer of ethylene and octane.