Food package, retort lidding, and coextruded film therefor

Claim 2

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock comprising: a first skin layer comprised of a majority of polyolefin and a minority of elastomer; and a second, core layer comprised of a majority of elastomer and a minority of polyolefin, said polyolefin characterized as having a semi-crystalline or crystalline melting point of at least 110° C., and the elastomer present in said skin layer being selected from the group consisting of polyisobutylene, butyl rubber, halogenated butyl rubber, ethylene-propylene rubber, ethylene-propylenediene rubber, polyisoprene polychloroprene, styrene-butadiene rubber, polybutene copolymers, nitrile rubber and chlorosulfonated polyethylene.

Claim 3

The multilayer film of claim 1 wherein said core layer comprises 55-70 weight percent of said elastomer.

Claim 4

The multilayer film of claim 1 further comprising a third, outer layer, said skin layer and said outer layer on opposite sides of said core layer and identical in composition.

Claim 5

The multilayer film of claim 1 wherein said polyolefin present in said skin layer is polypropylene.

Claim 6

The multilayer film of claim 4 wherein said elastomer is polyisobutylene.

Claim 7

The multilayer film of claim 4 wherein said elastomer is ethylene-propylenediene rubber.

Claim 8

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock, said multilayer heat seal film comprising: a skin layer comprised of a majority of polyolefin and of a minority of elastomer, and a core layer comprised of a majority of elastomer and of a minority of polyolefin, wherein said elastomer in said skin layer and said core layer is polyisobutylene.

Claim 9

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock, said multilayer heat seal film comprising: a skin layer comprised of a majority of polyolefin and of a minority of elastomer, and a core layer comprised of a majority of elastomer and of a minority of polyolefin, wherein said elastomer in said skin layer and said core layer is polyisobutylene.

Claim 10

The multilayer heat seal film of claim 7 wherein said polyolefin in said skin layer is a blend of polyolefins.

Claim 11

The multilayer heat seal film of claim 7 wherein said polyolefin in said core layer is a reactor copolymer of propylene.

Claim 12

The multilayer heat seal film of claim 7 wherein said polyolefin has a semi-crystalline or crystalline melting point of at least 110° C.

Claim 13

The multilayer heat seal film of claim 7 wherein said elastomer has a glass transition temperature (Tg) of less tan 0° C.

Claim 14

A lidding stock comprising an outer layer laminated to a barrier layer, said barrier layer laminated to a multilayer heat seal film, said multilayer heat seal film comprising, in combination: a skin layer comprised of a majority of polyolefin and of a minority of elastomer, and a core layer comprised of a majority of elastomer and of a minority of polyolefin, wherein said elastomer in said skin layer and said core layer is polyisobutylene.

Claim 15

A lidding stock comprising an outer layer laminated to a barrier layer, said barrier layer laminated to a multilayer heat seal film, said multilayer heat seal film comprising, in combination: a skin layer comprised of a majority of polyolefin and of a minority of elastomer, and a core layer comprised of a majority of elastomer and of a minority of polyolefin, wherein said elastomer in said skin layer and said core layer is polyisobutylene.

Claim 16

The multilayer heat seal film of claim 12 wherein said polyolefin in said skin layer is a blend of polyolefins.

Claim 17

The multilayer heat seal film of claim 12 wherein said polyolefin in said core layer is a reactor copolymer of propylene.

Claim 18

The multilayer heat seal film of claim 12 wherein said polyolefin has a semi-crystalline or crystalline melting point of at least 110° C.

Claim 19

The multilayer heat seal film of claim 12 wherein said elastomer has a glass transition temperature (Tg) of less than 0° C.

Claim 20

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock comprising: a first skin layer comprised of a majority of polyolefin and a minority of elastomer; and a second, core layer comprised of a majority of elastomer and of a minority of polyolefin, said polyolefin characterized as having a semi-crystalline or crystalline melting point of at least 110° C. and the polyolefin present in said skin layer being selected from the group consisting of polypropylene, copolymers of ethylene and 3-15% of an olefin having 4 to 12 carbon atoms, polybutylene, and mixtures thereof and the elastomer present in said skin layer being selected from the group consisting of polyisobutylene, butyl rubber, halogenated butyl rubber, ethylene-propylene rubber, ethylene-propylenediene rubber, polyisoprene polychloroprene, styrene-butadiene rubber, polybutene copolymers, nitrile rubber and chlorosulfonated polyethylene.

Claim 21

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock comprising: a first skin layer comprised of a majority of polyolefin and a minority of elastomer; and a second, core layer comprised of a majority of elastomer and of a minority of polyolefin, said polyolefin characterized as having a semi-crystalline or crystalline melting point of at least 110° C. and the polyolefin present in said skin layer being selected from the group consisting of polypropylene, copolymers of ethylene and 3-15% of an olefin having 4 to 12 carbon atoms, polybutylene, and mixtures thereof and the elastomer present in said skin layer being selected from the group consisting of polyisobutylene, butyl rubber, halogenated butyl rubber, ethylene-propylene rubber, ethylene-propylenediene rubber, polyisoprene polychloroprene, styrene-butadiene rubber, polybutene copolymers, nitrile rubber and chlorosulfonated polyethylene.

Claim 22

The multilayer film of claim 17 wherein said polyolefin present in said skin layer is polypropylene.

Claim 23

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock comprising: a first skin layer comprised of a majority of polyolefin and a minority of elastomer; and a second, core layer comprised of a majority of elastomer and of a minority of polyolefin, wherein said elastomer in said skin layer and said core layer is polyisobutylene and wherein said polyolefin in said skin layer is a blend of polyolefins and said polyolefin in said core layer is a reactor copolymer of propylene.

Claim 24

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock comprising: a first skin layer comprised of a majority of polyolefin and a minority of elastomer; and a second, core layer comprised of a majority of elastomer and of a minority of polyolefin, wherein said elastomer in said skin layer and said core layer is polyisobutylene and wherein said polyolefin in said skin layer is a blend of polyolefins and said polyolefin in said core layer is a reactor copolymer of propylene.

Claim 25

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock comprising; a first skin layer comprised of a majority of polyolefin and a minority of elastomer; and a second, core layer comprised of a majority of elastomer and of a minority of polyolefin, said polyolefin characterized as having a semi-crystalline or crystalline melting point of at least 110° C. and said elastomer characterized as having a glass transition temperature (Tg) of less than 0° C.

Claim 26

A multilayer heat seal film having at least two layers for use in a multilayer laminate lidding stock comprising; a first skin layer comprised of a majority of polyolefin and a minority of elastomer; and a second, core layer comprised of a majority of elastomer and of a minority of polyolefin, said polyolefin characterized as having a semi-crystalline or crystalline melting point of at least 110° C. and said elastomer characterized as having a glass transition temperature (Tg) of less than 0° C.