Packages having readily peelable seals

Claim 2

In the process of sealing and opening packages constructed from thermoplastic film and having large flange areas, the improvement which comprises forming a readily peelable seal between the surfaces of two unoriented films whose sealed together surfaces comprise polyolefin material, by performing the steps of: a. irradiating each polyolefin film with ionizing radiation to a minimum dosage level of about 3 MR to cross-link same; b. forming a package by heat sealing a portion of the surfaces of said cross-linked polyolefin films together with a product enclosed therebetween to cause said films to bond together in a hermetic seal in the flange area around the perimeter of the product; and, thereafter, c. opening said package by peeling said films apart in the sealed area without rupturing either of the films.

Claim 3

The process of claim 1 wherein at least one of said polyolefin films is an outer layer in a multi-layer film and the package can be opened by using a force not greater than 1000 gms/linear inch.

Claim 4

The process of claim 1 wherein said polyolefin films are selected from the group consisting of ethylene-vinyl acetate copolymers, polyethylene, and isomers.

Claim 5

The process of claim 3 including prior to step (b) the steps of: (i) thermoforming a product receiving cavity in one of said films; (ii) filling said cavity with a product; and (iii) covering said filled cavity with the other film.

Claim 6

A package having a peelable seal comprising: a. two unoriented multi-layer, thermoplastic sheets with a product disposed therebetween; b. each of said sheets comprising material which is cross-linked to the equivalent of a minimum dosage of 3 MR, the bonding surface layer of each sheet comprising polymeric material selected from the group consisting of homopolymers, copolymers, and ionomers of ethylene; c. a portion of the surface of each sheet being bonded to the other sheet by a relatively wide, continuous, peripheral, heat seal to enclose said product; and, d. said sealed together films being separable by a force of not more than 1000 gms./linear inch.

Claim 7

A package having a peelable seal comprising: a. two unoriented multi-layer, thermoplastic sheets with a product disposed therebetween; b. each of said sheets comprising material which is cross-linked to the equivalent of a minimum dosage of 3 MR, the bonding surface layer of each sheet comprising polymeric material selected from the group consisting of homopolymers, copolymers, and ionomers of ethylene; c. a portion of the surface of each sheet being bonded to the other sheet by a relatively wide, continuous, peripheral, heat seal to enclose said product; and, d. said sealed together films being separable by a force of not more than 1000 gms./linear inch.

Claim 8

The package of claim 5 wherein at least a portion of one of said sheets conforms to the shape of said products.

Claim 9

A package having a peelable seal comprising: a. a first thermoplastic sheet having a cavity formed therein, said sheet having a peripheral sealing surface encircling said cavity, the material forming said sealing surface comprising a material selected from the group consisting of homopolymers, copolymers, and ionomers of ethylene which have been cross-linked to the equivalent of a minimum dosage of 9.0 MR; b. a product disposed within said cavity; c. a second thermoplastic sheet closing the opening to said cavity and enclosing the product between said first and second sheets, said second sheet having a sealing surface, the material forming said sealing surface comprising a material selected from the group consisting of homopolymers, copolymers, and ionomers of ethylene which have been cross-linked to the equivalent of a minimum dosage of 9.0 MR; d. a continuous heat seal between the sealing surfaces of said first and second films which hermetically seals said product between said films, said seal being separable by a force of not more than 600 gms./linear inch.

Claim 10

A package having a peelable seal comprising: a. a first thermoplastic sheet having a cavity formed therein, said sheet having a peripheral sealing surface encircling said cavity, the material forming said sealing surface comprising a material selected from the group consisting of homopolymers, copolymers, and ionomers of ethylene which have been cross-linked to the equivalent of a minimum dosage of 9.0 MR; b. a product disposed within said cavity; c. a second thermoplastic sheet closing the opening to said cavity and enclosing the product between said first and second sheets, said second sheet having a sealing surface, the material forming said sealing surface comprising a material selected from the group consisting of homopolymers, copolymers, and ionomers of ethylene which have been cross-linked to the equivalent of a minimum dosage of 9.0 MR; d. a continuous heat seal between the sealing surfaces of said first and second films which hermetically seals said product between said films, said seal being separable by a force of not more than 600 gms./linear inch.

Claim 11

The package of claim 7 wherein at least one of the thermoplastic sheets is a multi-layer film.