Heat-Resistant Easy-Open Package

Abstract

The present invention is directed to manually openable heat-resistant packages for containing a product that include a thermoformed tray having a product receiving area and a sealing flange endowed with sufficient heat resistance to withstand the cooking and/or pasteurization/sterilization conditions required to produce a ready-to-eat packaged meal. The tray comprises a bulk layer, and a heat sealing layer in direct contact with the bulk layer. The inventive packages also include a flexible transparent lidding film covering the thermoformed product receiving area comprising a heat sealing layer. The package includes a hermetic seal comprising a perimeter heat seal which circumvents the thermoformed tray formed by heat sealing a portion of the heat sealing layer of the lidding film to the sealing flange of the tray. Only the heat sealing layer of the tray is readily frangible and renders the heat seal manually peelable.

Claims

1. A manually openable heat-resistant package for containing a product comprising: a thermoformed tray having a product receiving area and a sealing flange, wherein the tray comprises: a bulk layer; a heat sealing layer in direct contact with the bulk layer and comprising a blend of substantially amorphous aromatic polyester and a polyester-immiscible contaminant; a flexible transparent lidding film covering the thermoformed product receiving area comprising a heat sealing layer comprising a substantially amorphous aromatic polyester; a hermetic seal comprising a perimeter heat seal circumventing the thermoformed tray formed by heat sealing a portion of the heat sealing layer of the lidding film to the sealing flange of the tray; wherein the hermetic seal comprises a seal strength of between 500 g/in and 3000 g/in at 93 C. (200 F.); and wherein only the heat sealing layer of the tray is readily frangible and renders the heat seal manually peelable.

2. A package according to claim 1, wherein the substantially amorphous aromatic polyester copolymer is selected from the group consisting of polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate; polyethylene-2,6-naphthalate, polytrimethylene-2,6-naphthalate, polybutylene-2,6-naphthalate, polyhexamethylene-2,6-natphthalate, polyethylene isophthalate, polytrimethylene isophthalate, polybutylene isophthalate, polyhexamethylene isophthalate, poly-1,4-cyclohexane-dimethanol terephthalate, and polybutylene adipate terephthalate and derivatives thereof.

3. A package according to claim 1, wherein the heat sealing layer of the tray comprises a substantially amorphous aromatic polyester comprising a copolymer comprising a terephthalatic acid repeating component and a diethylene glycol diol repeating component.

4. A package according to claim 3, wherein the diethylene glycol dial repeating component which is present in an amount of greater than 2 mole % of the total copolymer composition.

5. A package according to claim 3, wherein the diethylene glycol dial repeating component is present in an amount of at least 37 mole % of the total copolymer composition.

6. A package according to claim 1, wherein the heat sealing layer of the tray comprises a substantially amorphous aromatic polyester comprising a terephthalatic acid repeating component and an isophthalatic acid repeating component.

7. A package according to claim 1, wherein the bulk layer of the tray comprises a polyethylene terephthalate.

8. A package according to claim 7, wherein the polyethylene terephthalate is crystalline polyethylene terephthalate.

9. A package according to claim 1, wherein the polyester-immiscible contaminant is a polyolefin.

10. A package according to claim 9, wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutene and blends thereof.

11. A package according to claim 10, wherein the polyethylene is a high density polyethylene.

12. A package according to claim 10, wherein the polyolefin is polypropylene.

13. A package according to claim 1, wherein the heat sealing layer of the tray comprises between 40% and 85% by weight of polyethylene terephthalate or polyethylene terephthalate/isophthalate copolymer relative to the total weight of the heat sealing layer.

14. A package according to claim 1, wherein the heat sealing layer of the tray comprises between 15% and 80% by weight of a polyester-immiscible contaminant relative to the total weight of the heat sealing layer.

15. A package according to claim 1, wherein the hermetic seal has a seal strength of between 1000 g/in and 3,000 g/in at 93 C. (200 F.).

16. A package according to claim 1, wherein the hermetic seal has a peel strength of between 2000 g/in and 3,000 g/in at 93 C. (200 F.).

17. A package according to claim 1, wherein the hermetic seal remains sealed while subjected to a temperature of 100 C. for between 1-10 minutes and under an internal pressure of between 3-4 psi.

18. A package according to claim 1, wherein the flexible lidding film has a haze value of 10% or less.

19. A package according to claim 1, wherein the package comprises an integrally formed tamper-evident feature.

20. A package according to claim 1 wherein the tamper-evident feature comprises visible whitened area of the lidding film produced when the hermetic seal has been breached.

21.-23. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0018] FIG. 1 illustrates a schematic view of one embodiment of a package in the closed state according to the present invention,

[0019] FIG. 2 illustrates a schematic view of one embodiment of a package in a partially opened state according to the present invention.

[0020] FIG. 3 illustrates a cross-sectional view of one embodiment of a tray according to the present invention.

[0021] FIG. 4 illustrates a cross-sectional view of one embodiment of a lidding film according to the present invention.

[0022] FIG. 5 illustrates an enlarged cross-sectional view of one embodiment of the lidding film peeling away from the tray taken along line A-A of FIG. 2 according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0024] Referring now more particularly to FIGS. 1 and 2 of the drawings, a preferred embodiment of package 10 embodying the present invention is shown in its closed and partially opened state, respectively. In one preferred embodiment, package 10 comprises a rigid or semi-rigid thermoformed tray 20 having a product receiving area 30 and a sealing flange 40 circumscribing the product receiving area 30. It will be noted that tray 20 may be of any shape desired, such as, for example, rectangular, square, circular or polygon depending on both functional and aesthetic requirements. It will be also appreciated that tray 20 may have any depth as desired depending upon type and amount of food product container therein. It will be further appreciated that tray 20 may be configured to include two or more recessed areas depending again on both functional and aesthetic requirements. Tray 20 also includes a bulk layer 22 (shown in FIG. 3) and a heat sealing layer 21 (shown in FIG. 3) which is in direct contact with bulk layer 22. A more detailed description of sealing layer 21 and bulk layer 22 is provided herein below,

[0025] Further included with package 10 is a flexible lidding film 50 which covers the product receiving area 30. Package 10 also includes a hermetic seal 60 comprising a perimeter heat seal 70 circumventing the thermoformed tray formed by heat sealing a portion of the heat sealing layer 51 (shown in FIG. 4) of lidding film 50 to sealing flange 40 of the tray. As used herein, the term heat seal refers to welding or melting of two polymeric surfaces together by the application of heat and pressure. It will be appreciated by those skilled in the art that heat seals are hermetic seals meaning that they prevent the ingress of air and/or moisture through the seal. In accordance with an important aspect of the present invention, the removal of lidding film 50 as depicted in FIG. 4 from the tray 20 as depicted in FIG. 3 is achieved by peelably tearing lidding film 50 away from tray 20 whereby the heat sealing layer 21 of tray 20 ruptures cohesively within this layer as illustrated in FIG. 5. It should be appreciated that only the heat sealing layer 21 of the tray is readily frangible and renders heat seal 70 manually peelable without the addition of score-lines, cuts or perforations to lidding film 50.

[0026] An advantageous optional feature of the present invention is that it may include an integrally formed tamper-evident feature. In one preferred embodiment, the tamper-evident feature comprises a visible whitened area of the sealing flange of the tray produced when the hermetic seal has been breached which occurs when the lidding film is peeled from the tray. In another preferred embodiment, the tamper-evident feature comprises a visible whitened area of the lidding film produced when the hermetic seal has been breached which occurs when the lidding film is peeled from the tray. In still another embodiment, the tamper-evident feature comprises both a visible whitened area of the sealing flange of the tray and a visible whitened area of the lidding film produced when the hermetic seal has been breached which occurs when the lidding film is peeled from the tray.

[0027] In a preferred embodiment of the package of the present invention, lidding film may be a mono-layer film comprising heat sealing layer formed from a substantially amorphous aromatic polyester. Specific examples of substantially amorphous aromatic polyester copolymers may include, but are not limited to: polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate; polyethylene-2,6-naphthalate, polytrimethylene-2,6-naphthalate, polybutylene-2,6-naphthalate, polyhexamethylene-2,6-natphthalate, polyethylene isophthalate, polytrimethylene isophthalate, polybutylene isophthalate, polyhexamethylene isophthalate, poly-1,4-cyclohexane-dimethanol terephthalate, and polybutylene adipate terephthalate. Among these, amorphous polyethylene terephthalate is preferably used. In another preferred, lidding film may comprises a multilayer film which includes heat sealing layer formed from an aromatic polyester, especially an amorphous polyethylene terephthalate copolymer and bulk layers, abuse layers, tie layers and/or barrier layers. It should be understood that lidding film may include any number of layers with the condition that it includes at least a heat sealing layer formed from an aromatic polyester. For example, as depicted in FIG. 4, lidding film 50 comprises four distinct layers including a heat sealing layer 51 comprising 1.75 mil thick amorphous polyethylene terephthalate, in direct contact with a bulk layer 52 comprising a 48 gauge thick biaxially oriented polyethylene terephthalate film (OPET), in direct contact with a tie (adhesive) layer 53 comprising a two-part polyurethane adhesive, in direct contact with an abuse layer 54 comprising a 60 gauge thick biaxially oriented nylon film (BOPA). In one preferred embodiment, lidding film 50 was produced by coating bulk layer 52 with an amorphous polyethylene terephthalate layer 51 using conventional cast extrusion methods generally known to those skilled in the art. This two-ply substrate was then adhesively laminated to abuse layer 54 using conventional adhesive lamination methods and equipment also generally known to those skilled in the art. This four-layer film had a haze value of between 5-6%.

[0028] Referring back now to FIG. 3, a preferred embodiment of the tray 20 is illustrated comprising a heat sealing layer 21 and a bulk layer 22. Bulk layer 22 may include any material such as, but limited to plastics, aluminum or coated cardboard. If bulk layer 22 is formed from such materials as aluminum or coated cardboard, tray 20 may include additional layer such as a tie layer (not shown) or an adhesive layer (not shown) between bulk layer 22 and heat sealing layer 21. In one preferred embodiment, bulk layer 22 comprises a polyethylene terephthalate. In another preferred embodiment, bulk layer 22 comprises a crystalline polyethylene terephthalate. Various specific examples of heat sealing layer 21 are described herein below.

WORKING EXAMPLES

Trays

[0029] In the following Examples 1-8, there is described various preferred embodiments of a tray 20 having a two-layer structure as illustrated in FIG. 3. In all these Examples 1-7, a blend was produced by dry mixing the substantially amorphous aromatic polyester copolymer (dried at 180 F. for 12 hours) with the polyester-immiscible contaminant. The blend forming layer 21 was then coextruded with bulk layer 22 of crystalline polyethylene terephthalate using a single screw extruder to form a two-ply film having a sealing layer 21 thickness of approximately 25.4 micron (1 mil) and a bulk layer 22 thickness of approximately 737 micron (29 mil). A tray was thermoformed using conventional methods and equipment well known in the art.

Example 1

[0030] Example 1 is one preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. Reported below is the layer composition relative to the total weight of the layer. [0031] Layer 21: 100 wt.-% of a blend of 6.8 kg (15 lb) of an amorphous polyethylene terephthalate copolymer (APET)-EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc., Kingsport, Tenn., USA)+6.8 kg (15 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0032] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Example 2

[0033] Example 2 is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. In this embodiment, layers 21 and 22 were prepared in a manner similar to that described above for Example 1 except for the composition of sealing layer 21. Reported below is the layer composition relative to the total weight of the layer. [0034] Layer 21: 100 wt.-% of a blend of 8.16 kg (18 lb) of an amorphous polyethylene terephthalate copolymer (APET)-EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc. Kingsport, Tenn., USA)+5.44 kg (12 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0035] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Example 3

[0036] Example 3 is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. In this embodiment, layers 21 and 22 were prepared in a manner similar to that described above for Example 1 except for the composition of sealing layer 21. Reported below is the layer composition relative to the total weight of the layer. [0037] Layer 21: 100 wt.-% of a blend of 8.85 kg (19.5 lb) of an amorphous polyethylene terephthalate copolymer (APET)-EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc., Kingsport, Tenn., USA)+4.76 kg (10.5 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0038] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Example 4a

[0039] Example 4 is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. In this embodiment, layers 21 and 22 were prepared in a manner similar to that described above for Example 1 except for the composition of sealing layer 21. Reported below is the layer composition relative to the total weight of the layer. [0040] Layer 21: 100 wt.-% of a blend of 9.53 kg (21 lb) of an amorphous polyethylene terephthalate copolymer (APET)-EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc., Kingsport, Tenn., USA)+4.1 kg (9 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0041] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Example 4b

[0042] Example 4b is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. In this embodiment, layers 21 and 22 were prepared in a manner similar to that described above for Example 1 except for the composition of sealing layer 21. Reported below is the layer composition relative to the total weight of the layer. [0043] Layer 21: 100 wt.-% of a blend of 9.53 kg (21 lb) of an amorphous polyethylene terephthalate/isophthalate copolymer (APET)-Type 7391 (Indorama Ventures Auriga Polymers, Inc., Charlotte, N.C., USA)+4.1 kg (9 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0044] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Example 5

[0045] Example 5 is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. In this embodiment, layers 21 and 22 were prepared in a manner similar to that described above for Example 1 except for the composition of sealing layer 21. Reported below is the layer composition relative to the total weight of the layer. [0046] Layer 21: 100 wt.-% of a blend of 10.21 kg (22.5 lb) of an amorphous polyethylene terephthalate copolymer (APET)-EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc., Kingsport, Tenn., USA)+3.4 kg (7.5 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0047] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Example 6

[0048] Example 6 is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. In this embodiment, layers 21 and 22 were prepared in a manner similar to that described above for Example 1 except for the composition of sealing layer 21. Reported below is the layer composition relative to the total weight of the layer. [0049] Layer 21: 100 wt.-% of a blend of 10.89 kg (24 lb) of an amorphous polyethylene terephthalate copolymer (APET)-EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc., Kingsport, Tenn., USA)+2.72 kg (6 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0050] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Example 7

[0051] Example 7 is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below. In this embodiment, layers 21 and 22 were prepared in a manner similar to that described above far Example 1 except for the composition of sealing layer 21. Reported below is the layer composition relative to the total weight of the layer. [0052] Layer 21: 100 wt.-% of a blend of 11.57 kg (25.5 lb) of an amorphous polyethylene terephthalate copolymer (APET)-EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc., Kingsport, Tenn., USA)+2.0 kg (4.5 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0053] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Comparative Example 1

[0054] Comparative Example 1 is an embodiment of the heat sealing layer 21 of tray 20 having a structure and layer compositions as described below and as illustrated in FIG. 3. Reported below is the layer composition relative to the total weight of the layer. [0055] Layer 21: 100 wt.-% of an amorphous polyethylene terephthalate (APET)-Laser+ C 9921 (F65A) (DAK Americas LLC, Chadds Ford, Pa., USA). [0056] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Comparative Example 2

[0057] Comparative Example 1 is an embodiment of the heat sealing layer 21 of tray 20 having a structure and layer compositions as described below and as illustrated in FIG. 3. Reported below is the layer composition relative to the total weight of the layer. [0058] Layer 21: 100 wt.-% of a blend of 8.85 kg (19.5 lb) of an amorphous polyethylene terephthalate (APET)-Laser+ C 9921 (F65A) (DAK Americas LLC, Chadds Ford, Pa., USA)+4.76 kg (10.5 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA), [0059] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

[0060] In the following Example 8, there is described another preferred embodiment of a tray 20 having a two-layer structure as illustrated in FIG. 3. In Example 8, a blend was produced by first dry blending the substantially amorphous aromatic polyester copolymer (dried at 180 F. for 12 hours) with the polyester-immiscible contaminant, then melt blending the dry mixture and pelletized using a Baker Perkins Twin Screw Extruder Model MP2050 (Baker Perkins Limited, Peterborough, U.K.) with a 50 mm screw diameter approximate 25:1 L/D ratio, and a co-rotating screw design. The blend forming layer 21 was then coextruded with bulk layer 22 of crystalline polyethylene terephthalate using a single screw extruded to form a two-ply film having a sealing layer 21 thickness of approximately 25.4 micron (1 mil) and a bulk layer 22 thickness of approximately 737 micron (29 mil).

Example 8

[0061] Example 8 is another preferred embodiment of the heat sealing layer 21 of tray 20 of the present invention having a structure and layer compositions as described below and. Reported below is the layer composition relative to the total weight of the layer. [0062] Layer 21: 100 wt.-% of a blend of 4.54 kg (10 lb) of an amorphous polyethylene terephthalate copolymer (APET)-Eastman Eastobond Copolyester 19212 (Eastman Chemical Company, Inc., Kingsport, Tenn., USA)+6.8 kg (15 lb) of a high density polyethylene (HDPE)-Alathon L5885 (having a density of 0.958 g/cc and a melt index of 0.85 g/10 min) (Lyondell Chemical Company, Houston, Tex., USA). [0063] Layer 22: 100 wt.-% of a crystalline polyethylene terephthalate film (CPET)-Preformance PET 1708 (StarPET, Inc., Asheboro, N.C., USA).

Seal Strengths

[0064] The seal strengths for the different heat sealing layers of Examples 1-8 and Comparative Examples 1-2 were determined by cutting a one-inch wide strip from the formed trays. Each strip was heat sealed to a one-inch wide strip of lidding film 50 as described above (see FIG. 4) using a Sencorp model 12ASL/1 tabletop heat sealer at 350 F. and 40 psi with a dwell time of 3 seconds. The laminated specimens were allowed to cool to room temperature and placed into an Instron tensile tester with an unsealed portion of the tray secured to the bottom jaw and an unsealed portion of the lidding film secured to the top jaw. Each laminated specimen was pulled apart at a 180 angle with at a speed of 12 in/min while the average force to separate the specimen was measured. The seal strength of each laminated specimen was measured at room temperature (23 C.) and in a heated chamber at 93 C. (200 F.). The results are reported in TABLE 1 below.

Burst Strengths

[0065] The burst strengths for the different heat sealing layers of Examples 1-8 and Comparative Example 1 were determined by filling each tray (maximum volume is 600 mL) with approximately 100 mL of water and sealing a lidding film 50 as described above (see FIG. 4) to the flange of each tray. Each filled and sealed tray was placed inside a microwave oven. An optical probe connected to a MWS microwave work station (FISO Technologies, Inc., Quebec, CA) recorded the maximum pressure (psi) inside the sealed tray to rupture the heat seal. The results are reported in TABLE 1 below

TABLE-US-00001 TABLE 1 SEAL SEAL Wt.-% STRENGTH STRENGTH BURST HDPE/Wt.-% @ 23 C. @ 93 C. STRENGTH SAMPLE APET (g/in) (g/in) (psi) Example 1 50/50.sup.a 3185 861 0.11 Example 2 40/60.sup.a 3078 1191 1.81 Example 3 35/65.sup.a 5059 1655 3.03 Example 4a 30/70.sup.a 5365 2324 2.35 Example 4b 30/70.sup.b 4890 1690 Example 5 25/75.sup.a 4551 1707 3.16 Example 6 20/80.sup.a No peel.sup.d 3455 3.05 Example 7 15/85.sup.a No peel.sup.d 3339 3.38 Example 8 60/40.sup.a 2671 879 Comparative (100% APET) 3169 No peel.sup.d 3.11 Example 1 Comparative 35/65.sup.c No seal No seal Example 1 .sup.a = APET is EASTOBOND Copolyester 19412 (Eastman Chemical Company, Inc., Kingsport, TN, USA); .sup.b = APET is Type 7391 (Indorama Ventures Auriga Polymers, Inc., Charlotte, NC, USA); .sup.c = APET is Laser+ C 9921 (F65A) (DAK Americas LLC, Chadds Ford, PA, USA); .sup.d = no peel refers to delamination occurring at or above 4000 g/in.

[0066] It will be learned from the above results that a preferred embodiment of a heat sealing layer of a tray according to the present invention includes, but is not limited to, a substantially amorphous aromatic polyester having only a terephthalatic acid repeating component and greater than 2 mole % or at least 37 mole % of a diethylene glycol diol repeating component or both a terephthalatic acid repeating component and an isophthalatic acid repeating component combined with between 15% and 80% by weight of a polyester-immiscible contaminant, especially high density polyethylene which provides a manually openable heat-resistant package having a seal strength of between 500 g/in and 3,000 g/in at 93 C. (200 F.).

[0067] The above description and examples illustrate certain embodiments of the present invention and are not to be interpreted as limiting. Selection of particular embodiments, combinations thereof, modifications, and adaptations of the various embodiments, conditions and parameters normally encountered in the art will be apparent to those skilled in the art and are deemed to be within the spirit and scope of the present invention.