WO1996024543A1

WO1996024543A1 - Collapsible, microwavable container

Info

Publication number: WO1996024543A1
Application number: PCT/US1996/000301
Authority: WO
Inventors: Charles L. Mott; Michael D. Read
Original assignee: Dowbrands Inc.
Priority date: 1995-02-10
Filing date: 1996-01-16
Publication date: 1996-08-15
Also published as: AU4750996A

Abstract

A collapsible, microwavable container (10) for storing food and non-food items is provided. The container is substantially clear in appearance and includes an upper open end (12), a lower end (14) closed by a bottom wall (16), and a peripheral side wall (18) extending between the upper and lower ends which is movable between extended and collapsed positions upon the exertion of a force. The peripheral side wall of the container includes upper, lower and intermediate portions with the container walls being comprised of outer (28, 32) and inner (30) layers of a thermoplastic polymer such as polypropylene having a first flex modulus and a second layer having a lower flex modulus than the outer and inner layers. The source of polypropylene in the second polymer layer is preferably obtained from recycled scrap from the container manufacturing process, which allows the container to be economically produced.

Description

COLLAPSIBLE, MICROWAVABLE CONTAINER

The present invention relates to a collapsible container for storing items, and more particularly to a collapsible, microwavable container for storing and heating foods comprising multiple layers of thermoplastic polymers which permit the container to move between collapsed and extended positions.

A need exists in this art for a thermoplastic container which is flexible enough to be collapsed for compact storage of food or non-food items, rigid enough to withstand microwave heating, and which maintains optical clarity.

The present invention meets that need by providing a reusable, thermoplastic container which is microwavable for cooking and reheating food, which is collapsible to provide compact storage for both food and non-food items, and which maintains excellent optical clarity. The container may be produced by coextrusion or coinjection followed by blow molding techniques.

The peripheral side wall of the container is movable between extended and collapsed positions upon the exertion of a force. Preferably, the container may be moved from an extended position to a collapsed position by exerting a closing force of about 5 pounds (2.3 kg). The opening force required to move the container from a collapsed position to an extended position is preferably from 2 to 10 pounds (0.91 to 4.5 kg).

The walls of the container are formed from layers of polymers having different properties which provide flexibility for permitting collapse of the container while maintaining rigidity and stain resistance for microwave heating. In a preferred embodiment of the invention, the container walls comprise an inner layer of a thermoplastic polymer having a first flex modulus and a second layer of a thermoplastic polymer having a lower flex modulus than the inner polymer layer. Preferably, the inner polymer layer has a flex modulus of about 150,000 pounds per square inch (psi) (10,546 kg/sq.cm).

Of the total wall thickness, the inner polymer layer preferably comprises about 15-45% of the total thickness, the second polymer layer comprises 30-70% of the total thickness, and the outer polymer layer comprises 10-40% of the total thickness.

When the container is in its extended position, the peripheral side wall includes an upper portion, an intermediate portion, and a lower portion. In a preferred embodiment of the invention, the intermediate portion has a wall thickness which is less than the wall thicknesses of the upper and lower portions so as to permit collapse of the container by the folding of the intermediate portion. In this embodiment, the upper and lower portions of the peripheral sidewall preferably have substantially equal thicknesses of between 0.030 - 0.060 inches (0.08 to 0.15 cm), and the intermediate portion has a thickness of between 0.008 and 0.040 inches (0.02 to 0.10 cm). However, it should be appreciated that thicknesses of the upper, intermediate and lower portions of the peripheral sidewall may be varied as desired to facilitate collapse of the container. In various embodiments of the invention, in the extended position of the peripheral side wall, the upper portion, the intermediate portion, and the lower portion may be vertical, or angled. When the container is in the collapsed position, the upper and lower portions of the peripheral sidewall are telescoped within one another and the intermediate portion is folded therebetween.

The container is substantially clear in appearance and has a haze value of no more than 50%. By substantially clear, it is meant that the container walls are sufficiently transparent such that one can see the contents of the container. The container is capable of holding either solid foods or liquids, and is resistant to leakage and deformation which may occur as a result of microwave heating. The container is also resistant to staining by foods. The container may be repeatedly extended and collapsed during use, and may be repeatedly refrigerated and reheated.

The present invention also includes a process of making a microwavable multi- layer container which comprises the steps of coextruding an inner layer of a thermoplastic polymer having a first flex modulus and a second layer of a thermoplastic polymer having a lower flex modulus than the inner polymer layer. Preferably, an outer layer of a thermoplastic polymer is coextruded with the inner and second polymer layers.

The extruded layers are then molded such that a container is formed which includes an upper open end, a lower end closed by a bottom wall, and a peripheral side wall as described above.

Preferably, the inner and outer polymer layers comprise polypropylene. The second polymer layer comprises a blend of a substantially linear ethylene copolymer and polypropylene, where the polypropylene preferably comprises recycled scrap from the container manufacturing process.

Accordingly, it is a feature of the present invention to provide a collapsible, adjustable, microwavable container which is reusable and is suitable for heating and storing food. It is a further feature of the invention to provide a container which is substantially clear and resistant to staining, and is economical to produce. These, and other features and advantages of the present invention, will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

Fig. 1 is a perspective view of the collapsible container of the present invention;

Fig. 2 is a side view of the container shown in Fig. 1;

Fig. 3A is a cross-sectional view of the container wall showing inner, second and outer layers taken along line 3-3 in Fig. 2;

Fig. 3B is a cross-sectional view of an alternative embodiment of the container wall comprising inner and second layers;

Fig. 4 is a side view of the container of Fig. 2 shown in a collapsed position; Fig. 5 is a side view of an alternative embodiment of the container;

Fig. 6 is a side view of the container of Fig. 5 shown in a collapsed position;

Fig. 7 is a side view of another alternative embodiment of the container;

Fig.8 is a side view of the container of Fig. 7 shown in collapsed position; Fig.9 is a side view of another alternative embodiment of the container;

Fig. 10 isa side view of the container of Fig. 9 shown in collapsed position;

Fig. 11 is a side view of another alternative embodiment of the container;

Fig. 12 is a side view of the container of Fig. 11 shown in collapsed position;

Fig. 13 is a side view of another alternative embodiment of the container; Fig. 14 is a side viewofthe container of Fig. 13 shown in collapsed position;

Fig. 15 is a side view of another alternative embodiment of the container;

Fig. 16 is a side view of the container of Fig. 15 shown in collapsed position;

Fig. 17 is a side view of another alternative embodiment of the container; and

Fig. 18 is a side view of the container of Fig. 17 shown in collapsed position. The container of the present invention provides a combination of properties which has not been achieved with the use of prior art thermoplastic containers which utilize only a single layer of polymer or blends of polymers. The container structure of the present invention uses dual or multiple layers of polymers having different properties. In the multi¬ layer structure, outer and inner layers of a polymer having a flex modulus of about 150,000 psi (10,546 kg/sq.cm) (as measured by ASTM method D790 B) are used to provide sufficient stiffness and heat deflection under load. The second layer positioned between the outer and inner layers comprises a softer polymer of a lower flex modulus (that is, between about 15,000- 80,000 psi) (1,054-5,625 kg/sq.cm) which provides flexibility to the container wall during collapsing. Thus, by utilizing polymers with different properties in a multi-layer construction, the container of the present invention provides both the flexibility needed for collapsing and the rigidity required for microwavability. The containers may also be used in the freezer or refrigerator. In addition, the containers have very good drop impact resistance at room temperature.

With reference to Figs. 1 and 2, a collapsible, microwavable multi-layer container 10 is illustrated. The container 10 includes an upper open end 12, a lower end 14 closed by a bottom wall 16, and a peripheral side wall 18 extending between the upper and lower ends. The peripheral sidewall is shown in the extended position in Fig. 1, and includes an upper portion 22, an intermediate portion 24, and a lower portion 26. In this embodiment, the upper portion of the peripheral sidewall generally has a thickness of about 0.050 inches (0.13 cm), and the lower portion has a thickness of about 0.040 inches (0.10 cm). The intermediate portion of the sidewall is much thinner, having a thickness of from about 0.008 inches (0.020 cm), which permits collapse of the container by the folding of the intermediate portion. While illustrated in a preferred form with upper, intermediate, and lower sidewall portions, it will be apparent to those skilled in the art that the container may be made with as few as one sidewall portion or as many as several portions, each using a combination of high and lower flex modulus polymer layers. Further, the container may be configured to collapse at different portions of the sidewall by varying the wall thickness at selected seαions or portions. However, the sidewall portions should be configured so that when the container is collapsed, minimal spacing exists between the collapsed walls which could entrap the contents of the container.

As shown in Fig. 2, the upper and lower sidewall portions 22 and 26 are vertical o while the thinner intermediate portion 24 is angled outward to facilitate collapsing and extension of the container. The container 10 may be collapsed to the position shown in Fig. 4 by exerting a closing force of from 2 to 10 pounds at the upper portion of the container. This causes the intermediate portion of the sidewall to fold back on itself such that the upper portion of the sidewall 22 is telescoped within the lower portion 26. As can be seen in Fig. 4, 5 the container is approximately one-half of its original height in the collapsed position. To revert the container to its fully extended position, a user may grip the container at opposite ends and pull the container in opposite directions, which requires an opening force of from 2- 10 pounds (0.91 to 4.5 kg). As illustrated, a roughened surface 27 is provided around the periphery of the lower portion of the container to provide a gripping surface. 0 Fi - 3A illustrates a cross section of one embodiment of the container wall in which the wall comprises an inner polymer layer 28, a second polymer layer 30 and an outer layer 32. Preferably, the inner and outer polymer layers comprise polypropylene. Preferred high flex modulus polypropylenes for use in the present invention are Pro Fax SV256M (a homopolymer of propylene) or SR256M (trademark) (a clarified random copolymer of 5 propylene), commercially available from Himont Incorporated. Other suitable grades of polypropylene include PD199 and Pro Fax 7624 (trademark), available from Himont.

A preferred layer structure includes 25% by weight of the inner polymer layer which may consist of 100% polypropylene or clarified polypropylene random copolymer. The second layer preferably comprises 50% by weight of the layer structure and may consist of 30% 0 high flex modulus polypropylene or polypropylene scrap from the manufacturing process, and 70% of a substantially linear copolymer of ethylene and an α-olef in. The outer layer preferably comprises 25% by weight of the total layer structure and comprises a clarified polypropylene random copolymer.

It should be appreciated that the number of layers, the range of thickness of the 5 layers, and the amount of polyethylene or polypropylene is not limited to the above described structure. Various other combinations may be used depending on the particular polymers selected. However, it is preferred that the inner layer comprise from at least 50-100% polypropylene in order to obtain the best stain resistance. The melt index of polypropylene Profax SR-256M is preferably 2.0 as measured by ASTM method 01238 at 230°F (110° , 2.16 dg/min and may range from 0.5 to 4.0. The preferred density of polypropylene is about 0.90 as measured by ASTM 0792A, and may range from 0.8 to 1.5. The deflection temperature under load of 187°F (72°C) at 66 psi (4.64 kg/sq.cm) is about 187 and may range from 170-230. The melting point is preferably 248°F (120°C) and may range from 225°F (108°C) to 260°F (127^βQ.

The second layer 30 has a lower flex modulus than the outer and inner layers and comprises a blend of polypropylene and a substantially linear ethylene copolymer. Suitable low flex modulus polypropylenes include KS-050 (flex modulus 18,500 psi) (1,300 kg/sq.cm), commercially available from Himont. The source of polypropylene used in the second polymer layer is preferably scrap obtained from the manufacturing process, which will be explained in greater detail below.

The substantially linear ethylene copolymers used in the second layer of the present invention are polymer resins made using Insite™ constrained geometry catalyst technology (CGCT) such as Affinity™ resins, available from The Dow Chemical Company. Such resins are taught in commonly-assigned U.S. Patent Nos. 5,272,236 and 5,278,272, the disclosures of which are hereby incorporated by reference. As used herein, "substantially linear" means that the polymer backbone is substituted with from about 0.01 to 3 long-chain branches/1000 carbon atoms. While the substantially linear ethylene polymers used in the practice of this invention include homopolymers of ethylene, preferably the substantially linear ethylene polymers include from 5 to 50% by weight of at least one α-olef in comonomer as taught in the above-referenced patents.

Such substantially linear copolymers have the strength and toughness of linear low density polyethylene (LLDPE) but with processability similar to highly branched low density polyethylene (LDPE). Thus, the polymers have processing indices (Pi's) less than or equal to 70% of those of a comparable linear olefin polymer and a critical shear rate at onset of surface melt fracture of at least 50% greater than the critical shear rate at onset of surface melt fracture of a traditional linear ethylene polymer at about the same l and Mw M_n (by "about the same", it is meant that the values do not differ from one another by more than 10 percent), where l₂ is the melt index measured according to ASTM D-1238, Condition 190°C/2.16 kg (formerly known as "Condition E"), M_w is the weight average molecular weight, and M_n is the number average molecular weight of the polymer.

Suitable ethylene copolymer resins which can be used in the present invention include, but are not limited to, resins having the following properties: an ethylene α-olefin copolymer resin having a melt index of 1.0 gm/10 min, an lιo/l₂ ratio of 1.0, a density of 0.909, and a Dow Rheology Index of 4.6 (commercially available from The Dow Chemical Company under the designation AFFINITY™ PL 1840); an ethylene α-olefin copolymer resin having a melt index of 1.6 gm/10 min, an I₁0 I2 ratio of 10.2, a density of 0.895, and a Dow Rheology Index of 4.4 (commercially available f om The Dow Chemical Company under the designation AFFINITY™ PF 1140); and an ethylene copolymer having a melt index of 1.0 gm/10 min, an I10/I2 ratio of 9.5, a density of 0.885, and a Dow Rheology Index of 4.0. The properties of the resins chosen may vary depending on the exact layer structure chosen, and the amount of scrap i ncorporated i nto the contai ner.

It may be desirable to use more or less scrap in the container, depending on the exact modulus of the chosen polymers as long as the container exhibits the desired collapsibility and microwavability.

It is possible to achieve the desired collapsibility using as little as 10% polypropylene for the inner layer with the other layer(s) comprising a balance of 90% consisting of Dow Affinity resin and/or polypropylenes having lower flex modulus. The use of polypropylene in the second layer provides an unexpected improvement in the processing of the substantially linear ethylene copolymer. For example, in the blow molding process, the melt strength of the substantially linear ethylene copolymer is improved by the inclusion of polypropylene. In addition, strong adhesion between the polymer layers is achieved. Further, depending on the particular ethylene copolymer resin selected for use, the resulting container has a higher heat distortion resistance.

Alternatively, the second polymer layer may comprise a blend of a substantially linear ethylene copolymer and an ethylene vinyl acetate copolymer. Suitable copolymers of ethylene and vinyl acetate include Elvax 3135SB, commercially available from duPont. Fig. 3B illustrates an alternative embodiment of the invention in which the container wall comprises inner layer 28 and second layer 30 where the inner layer (that is, the layer in contact with the contents of the container) comprises polypropylene and the second layer comprises a blend of polypropylene and a substantially linear ethylene copolymer. Typically, the inner layer will comprise from about 10-50% of the total wall thickness, while the second layer will comprise from 90-50% of the total wall thickness.

Where the container wall comprises inner, second and outer polymers layers, the inner layer comprises from 15-45%, and preferably about 30% ofthe total thickness, the second layer comprises from 30-70%, and preferably 50% of the total thickness, and the outer layer comprises from about 10-40%, and preferably about 20% of the total thickness. While the actual thicknesses of the upper, lower, and intermediate portions of the container wall will vary, as described previously, the percentages of polymers making up the layers in those wall portions will be in the above-described ranges.

Fig. 5 illustrates an alternative embodiment ofthe container in which the upper sidewall portion 22 is vertical, the intermediate portion 24 is angled outward, and the lower portion 26 is angled downwardly inward. In this embodiment, the upper portion has a thickness of about 0.050 inches (0.13 cm), the intermediate portion has a thickness of about 0.040 inches (0.10 cm), and the lower portion has a thickness of about 0.050 inches (0.13 cm). The container 10 may be collapsed to the position shown in Fig.6 where the intermediate portion 24 folds down and the upper portion ofthe sidewall 22 is telescoped within the lower portion 26.

Fig. 7 illustrates another alternative embodiment ofthe container in which the upper portion 22 includes a vertical section 22a and a section 22b which angles inward. The intermediate portion 24 is vertical, and the lower portion 26 is angled outward. In this embodiment, the vertical section 22a has a thickness of about 0.050 inches (0.13 cm), section 22b has a thickness of about 0.010 inches (0.03 cm), intermediate portion 24 has a thickness of about 0.040 inches (0.10 cm), and lower portion 26 has a thickness of about 0.050 inches (0.13 o cm). Fig. 8 illustrates the container in a collapsed position where the thinner, angled section 22b of the upper portion is folded down over the intermediate portion 24.

Fig. 9 illustrates another embodiment ofthe container which includes upper portion 22 which is vertical, intermediate portion 24 which angles inward, and lower portion 26 which is vertical. In this embodiment, the vertical upper portion 22 has a thickness of about 5 0.050 inches (0.13 cm), the angled intermediate portion 24 has a thickness of about 0.010 inches (0.03 cm), and the lower portion 26 has a thickness of about 0.040 inches (0.10 cm). In the collapsed position of this container shown in Fig. 10, the intermediate portion 24 is folded down over the lower portion 26.

Fig. 11 illustrates yet another embodiment of the container in which the upper 0 portion 22 is vertical, the intermediate portion 24 is angled inward, and the lower portion 26 comprises a vertical section 26a and a section 26b which is angled outward. The upper portion has a thickness of about 0.050 inches (0.13 cm), the intermediate portion has a thickness of about 0.010 inches (0.03 cm), and the lower portion has a thickness of about 0.050 inches (0.13 cm). When the container is collapsed as shown in Fig. 12, the intermediate portion 24 is folded down such that the lower portion is telescoped within the upper portion.

Fig. 13 illustrates yet another embodiment of the invention in which the upper portion 22 is vertical, the intermediate portion 24 is angled inward, and the lower portion 26 is angled outward. The upper portion has a thickness of about 0.050 inches (0.13 cm), the intermediate portion has a thickness of about 0.010 inches (0.03 cm), and the lower portion has a thickness of about 0.050 inches (0.13 cm). In the collapsed position shown in Fig. 14, the intermediate portion 24 is folded down such that the lower portion 26 is telescoped within the upper portion 22.

Fig. 15 illustrates yet another embodiment of the invention in which the upper portion 22 comprises a vertical section 22a and a section 22b which angles inward. The intermediate portion 24 includes a section 24a which angles outward and a section 24b which angles inward. In this embodiment, sections 22b and 24b have a thickness of about 0.010 inches (0.03 cm) while sections 22a and 24a have a thickness of about 0.050 inches (0.13 cm). The lower portion 26 angles outward and has a thickness of about 0.050 inches (0.13 cm). When the container is collapsed as illustrated in Fig. 16, the thinner sections 22b and 24b are folded down over the intermediate and lower portion in an accordion style.

Fig. 17 illustrates yet another embodiment of the invention in which the upper portion 22 and the intermediate portion 24 are vertical. As is shown, the upper portion 22 includes extended sides 22' such that the upper portion is wider than the intermediate portion. In this embodiment, the upper portion has a thickness of 0.050 inches (0.13 cm), the extended sides have a thickness of 0.010 inches (0.03 cm), the intermediate portion has a thickness of about 0.040 inches (0.10 cm), and the lower portion has a thickness of about 0.050 inches (0.13 cm). When the container is collapsed as shown in Fig. 18, the extended sides 22' ofthe upper portion fold down over the intermediate portion 24. In this case, the extended sides 22' are comprised of an elastomeric material, allowing "stretching" of the sides when the container is collapsed or extended.

The multilayer container ofthe present invention is preferably produced by coextruding the polymers layers followed by a conventional blow-molding process, although other processes such as injection molding may be employed. The preferred process for making the container includes the step of extruding the inner, second, and outer layers as a tubular parison between a pair of separated mold halves which form the desired container shape. The mold halves are then closed and the parison is blown into engagement with the interior surfaces of the mold. Preferably, the polypropylene included in the second polymer layer is comprised of recycled scrap from the container manufacturing process. By utilizing scrap as the source of polypropylene, the cost of producing the container is substantially decreased. In addition, the scrap polypropylene functions as a processing aid when the substantially linear ethylene copolymers are included as a part of the second polymer layer. The parison extrudate stability and quality is improved dramatically with the presence of polypropylene, either in virgin or reground trim scrap form. The preferred method of incorporating polypropylene in scrap form is in pelletized form for ease of handling and uniform feeding in the extruder. The addition of polypropylene in this form has been found to improve parison melt strength, which allows acceptable processing of the difficult shape ofthe container, that is, the thick bottom, thin center, and thick top section.

The container is preferably formed so as to provide a generally cylindrical shape from top to bottom, with a round closed bottom and an open upper end as shown in Fig. 1. The open end should be wide enough to allow access to and cleaning of the interior of the container. Also as shown in Fig. 1, the container preferably includes a threaded portion 20 for receiving a screw-on closure 21. However, it should be appreciated that other conventional caps or lids may be employed in the present invention. It should also be appreciated that the shape and size of the container may vary. For example, the container may be designed as a 2, 3, 6, 8, or 9 cup container and may have a cylindrical, oval, square or other shape as desired. Further, the ratio ofthe opening diameter of the container to the container width is preferably equal to or greater than about 0.7 to provide easy access to the interior of the container for food removal and/or cleaning. Other variations ofthe container structure are within the scope ofthe invention.

For example, as shown in Fig. 2, the lower sidewall 26 of the container may be textured or roughened as shown at 27 to enable a user to grip the container during collapse and extension of the container.

To aid in the collapsing and opening ofthe container, the polymers may contain from 0.2 to 3.0%, and more preferably, about 1% by total weight of the polymer of a slip additive and/or antiblocking agent.

In order to maintain a suitable optical clarity, the container should have a haze value of no more than 50%. The haze value may be measured by the Digital Photometric Method (ASTM D-1003) using a Gardner Model TG5500. The optical clarity of the container is maintained even after microwaving food due to the inner polypropylene layer of the container wall which is resistant to staining.

In order that the invention may be more readily understood, reference is made to the following examples, which are intended to be illustrative of the invention, but are not intended to be limiting in scope. Example 1

A collapsible, multi-layer container was produced in accordance with the present invention using Bekum blow molding equipment. The resulting 3.5 cup container structure comprised inner and outer layers of HIMONT SR256M polypropylene, and an intermediate layer comprising a blend of 55% AFFINITY™ PL 1840, an ethylene/1 -octene copolymer available from The Dow Chemical Company having a density of about 0.909 g/cc, a melt index of about 1 g/10 minutes, an I10/I2 ratio of about 1.0 and a Dow Rheology Index of about 4.6, and 45% HIMONT SR256M polypropylene. The average measured haze value of the container was 48.7%.

The container was tested to determine acceptable resistance to microwave cooking processes by placing approximately 12 oz. (355.2 cubic centimeters) of a commercially prepared can of chili into the container. The container was then heated, uncovered, in a microwave oven under full power (750 watts) for about 3 minutes. After each minute of heating, the food was stirred thoroughly and the container was inspected for deformation and staining. The container was found to have minimal staining and was resistant to deformation. No leaks were noted. Example 2

A multi-layer container was made as in Example 1 except that polypropylene scrap from the manufacturing process containing about 35% AFFINITY™ PL1840 resin and 65% of reground scrap containing 66% HIMONT SR256M polypropylene and 33% AFFINITY™

PL1840 resin was utilized as the source of polypropylene in the intermediate layer. The average measured haze value ofthe container was 44.6% .

The container was tested for microwavability by placing approximately 12 oz. (355.2 cubic centimeters) of a commercially prepared can of chili into the container and heating the container, uncovered, in a microwave oven under full power (750 watts) for about 3 minutes. The container was found to have acceptable resistance to staining and deformation.

Example 3

A blow-molded multi-layer container was produced in which the inner layer o comprised 25% of the total layer thickness, the second layer comprised 50% of the layer thickness, and the outer layer comprised 25% ofthe layer thickness. The inner and outer layers consisted of 100% polypropylene S 256M. The center layer consisted of 70% Dow Affinity™

1140 and 30% polypropylene. The average measured haze value of the container was less than

50%. 5 The container easily collapsed to its low-volume position, and easily extended to its open position.

Example 4

A blow-molded multi-layer container was produced consisting of inner, second and outer layers comprising 20%, 60% and 20% of the total layer structure, respectively. The 0 inner and outer layers consists of polypropylene S 256M. The center layer of the structure consisted of 55% Dow Affinity 1140 and 45% polypropylene SV256M. The average measured haze value of the resulting container was less than 50%, and the container was found to extend and collapse in an acceptable manner.

5

Claims

What is claimed is:

1. A collapsible, microwavable multi-layer container which includes an upper open end, a lower end closed by a bottom wall, and a peripheral side wall extending between said upper and lower ends which is movable between extended and collapsed positions upon the exertion of a force, said peripheral side wall including an upper portion, an intermediate portion, and a lower portion, said container walls comprising an inner layer of a thermoplastic polymer having a first flex modulus, and a second layer of a thermoplastic polymer having a lower flex modulus than said inner polymer layer.

2. The container of claim 1 further including an outer layer of a thermoplastic polymer having said first flex modulus.

3. The container of claim 1 wherein said inner polymer layer has a flex modulus of about 150,000 psi (10,546 kg/sq.cm).

4. The container of claim 1 wherein said second polymer layer includes recycled, scrap from the container manufacturing process.

5. The container of claim 2 wherein said inner layer comprises 15-45% of the total container wall thickness, said second layer of thermoplastic polymer comprises 30-70% of the total thickness, and said outer layer comprises 10-40% of the total thickness.

6. The container of claim 1 wherein in the extended position of said peripheral side wall, said upper portion is vertical and said intermediate portion is angled outward.

7. The container of claim 6 wherein said lower portion is vertical.

8. The container of claim 6 wherein said lower portion is angled inward.

9. The container of claim 1 wherein in said extended position of said peripheral side wall, said upper portion includes a vertical section and a section which angles inward, said intermediate portion is vertical, and said lower portion is angled outward.

10. The container of claim 1 wherein in the extended position of said peripheral side wall, said upper portion is vertical and said intermediate portion is angled inward.

11. The container of claim 10wherein said lower portion is vertical.

12. The container of claim 10 wherein said lower portion includes a vertical section and a section which angles outward.

13. The container of claim 10 wherein said lower portion is angled outward.

14. The container of claim 1 wherein in the extended position of said peripheral sidewall, said upper portion includes a vertical section and a section which angles inward, said intermediate portion comprises a section which angles outward and a section which angles inward, and said lower portion angles outward.

15. The container of claim 1 wherein in the extended position of said peripheral side wall, said upper portion and intermediate portion are vertical, and are interconnected by a generally outwardly extending sidewall portion, and said lower portion is angled outward.

16. The container of claim 15 wherein said extending sidewall portion comprises an elastomeric material which allows said sidewall portion to stretch when said container is collapsed or extended.

17. The container of claim 1 wherein the wall thicknesses of said upper and lower portions are from 0.030 to 0.060 (0.08 to 0.15cm) inches.

18. The container of claim 1 wherein the wall thickness of said intermediate portion is from 0.008 to 0.040 inches (0.02 to 0.10 cm).

19. The container of claim 1 having a haze value of no greater than 50%.

20. The container of claim 1 having an opening force from said collapsed position to said extended position of from 2 to 10 pounds (0.91 to 4.5kg).

21. The container of claim 1 having a closing force from said extended position to said collapsed position of about 5 pounds (2.3kg).

22. A process for making a microwavable multi-layer container comprising the steps of: a) coextruding an inner layer of a thermoplastic polymer having a first flex modulus and a second layer of a thermoplastic polymer having a lower flex modulus than said inner polymer layer; b) molding said extruded layers such that a container is formed which includes an upper open end, a lower end closed by a bottom wall, and a peripheral side wall extending between said upper and lower ends which is movable between extended and collapsed positions upon the exertion of a force.

23. The process of claim 22 wherein said coextruding step includes coextruding an outer layer of a thermoplastic polymer having said first flex modulus.