US20140072674A1

US20140072674A1 - Leak-proof containers, made from expandable thermoplastic resin beads

Info

Publication number: US20140072674A1
Application number: US14/020,140
Authority: US
Inventors: George Holinda, JR.; Todd M. Link; Justin Rubb
Original assignee: Nova Chemicals Inc
Current assignee: Nova Chemicals Inc
Priority date: 2012-09-10
Filing date: 2013-09-06
Publication date: 2014-03-13
Also published as: MX2015002981A; PE20150715A1; CO7220319A2; BR112015004808A2; CA2881023A1; WO2014039948A1

Abstract

This invention discloses a leak proof disposable container, comprising of a bottom portion composed of expandable thermoplastic resin beads and a lidding film, for containing non-carbonated drinks or food products that do not require heating prior to consumption. The inventive container eliminates the use of polypropylene and polystyrene snap-on lids currently used for cups and containers. The snap-on lid is replaced with a thermoplastic lidding film, a leak proof seal is formed between the lidding film and upper flange of the bottom portion. Replacement of the snap-on lid with lidding film, reduces the weight of the disposable lidding material by 74 percent. Through the appropriate selection of materials, one can produce a leak proof container that is 100 percent recyclable under the #6 PS (polystyrene) symbol.

Description

REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. Provisional Application Ser. No. 61/698,811, filed Sep. 10, 2012 entitled Leak-Proof Containers, Made From Expandable Thermoplastic Resin Beads, which is herein incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention is directed to a leak proof disposable container; comprised of a bottom portion composed of expandable thermoplastic beads and a lidding film. The bottom portion of the container is formed using a conventional shape molding process, food or drink is deposited into the bottom portion and a lidding film is attached, producing a leak proof container.
The container can be used for hot or cold liquids, such as noncarbonated beverages, or hot or cold foods such as instant noodles, soups, fried chicken, yogurt, ice cream and the like.
One object of the invention is to provide a disposable container that reduces waste; more specifically, replacing the conventional disposable snap-on lid, with a thermoplastic lidding film, reduces the weight of the lidding material by 74%.
Another object of the invention is to provide a disposable container that is 100 percent recyclable under the #6 PS (polystyrene) symbol.
Another object of the invention is to provide a leak proof disposable container that eliminates leaking, dripping, splashing and spilling of food and/or drink; particularly while transporting food or drink in the container, e.g., walking, bicycling and driving in a vehicle, etc.
Another object of the invention is to provide a container with excellent heat insulating properties, such that hot drink and/or food remains hot, and the consumer does not experience discomfort while holding the container due to excessive heat. The excellent heat insulating properties of the container are also advantageous in keeping cold, semi-frozen and frozen food and drink cold.
In one embodiment of the invention, the leak proof containers are produced continuously. In another embodiment of the invention, the leak proof containers are produced individually, as needed or as purchased in a retail setting.
Another embodiment of the invention includes a hypodermic needle-like piercing straw. More specifically, when the consumer wishes to consume the liquid stored within the leak proof disposable container, the thermoplastic lidding film is punctured with the piercing straw and the liquid is consumed through the straw.

SUMMARY OF INVENTION

The present invention provides a leak proof container for packaging food or drink comprising: a bottom portion having an upper flange circumferentially extending around at least one compartment for supporting a food or drink, wherein said bottom portion comprises expanded thermoplastic beads; and a lidding film attached to said upper flange, forming a leak proof seal, enclosing said food or drink.
A further embodiment of the present invention provides a leak proof container wherein said bottom portion is comprised of expandable polystyrene beads.
In a further embodiment, the present invention provides a leak proof container wherein said bottom portion has a density from 0.5 pounds per cubic foot (8 g/L) to 12 pounds per cubic foot (192 g/L).
In a further embodiment, the present invention provides a leak proof container wherein said lidding film is a monolayer film.
In a further embodiment, the present invention provides a leak proof container wherein said monolayer lidding film comprises a styrene butadiene copolymer.
In a further embodiment, the present invention provides a leak proof container comprising a monolayer lidding film, wherein the monolayer lidding film comprises a styrene butadiene copolymer and the Average Plateau Peeling Force required to peel the lidding film from the leak proof container is greater than 0.32 pounds-force, or 1.4 Newton; wherein said Average Plateau Peeling Force is calculated from an Instron load-displacement curve (extension-mode) as the lidding film is peeled from 1 inch to 3 inches of travel on said upper flange.
In a further embodiment, the present invention provides a leak proof container comprising a monolayer lidding film, wherein the monolayer lidding film comprises a styrene butadiene copolymer and the Average Puncture Force at Straw Breakthrough is greater than 2.9 pounds-force, or 13 Newton; wherein said Average Puncture Force at Straw Breakthrough is calculated from an Instron load-displacement curve (compression-mode).
An advantage of the monolayer styrene butadiene copolymer lidding film is a leak proof container that reduces waste, i.e. replacing the conventional disposable snap-on lid with a lighter weight thermoplastic film; thus, reducing the weight of the lidding material by 74%.
An additional advantage of the monolayer styrene butadiene copolymer lidding film is a leak proof container that is 100% recyclable under the #6 PS symbol (polystyrene).
In a further embodiment, the present invention provides a leak proof container comprising a monolayer lidding film, wherein the lidding film comprises an ethylene vinyl acetate copolymer containing from 3 wt % to 16 wt % vinyl acetate and has a melt index from 0.2 dg/min to 20 dg/min; wherein melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.
In a further embodiment the present invention provides a leak proof container comprising a monolayer lidding film, wherein the lidding film comprises a polyolefin with a DSC melting point from 90° C. to 125° C. and has a melt index from 0.2 dg/min to 20 dg/min.
Further embodiments of the present invention include leak proof containers wherein the lidding film is a multilayer film.
In a further embodiment, leak proof containers are lidded with a multilayer film, wherein the inner most layer of the multilayer film comprises an ethylene vinyl acetate copolymer containing 3 wt % to 16 wt % vinyl acetate and has a melt index from 0.2 dg/min to 20 dg/min.
In a further embodiment, the leak proof container comprises a multilayer film, wherein the inner most layer of the multilayer film comprises an ethylene vinyl acetate copolymer containing 3 wt % to 16 wt % vinyl acetate and has a melt index from 0.2 dg/min to 20 dg/min; and the Average Plateau Peeling Force required to peel this multilayer lidding film from said leak proof container is greater than 0.24 pounds-force, or 1.1 Newton.
The present invention provides a leak proof container comprising a multilayer lidding film, wherein the inner most layer of the multilayer film comprises a polyolefin with a DSC melting point from 90° C. to 125° C. and a melt index from 0.2 dg/min to 20 dg/min.
The present invention further provides a process for producing a leak proof container for food or drink comprising the following steps: (A) shape molding a bottom portion having an upper flange circumferentially extending around at least one compartment for supporting a food or drink, wherein said bottom portion comprises expanded thermoplastic beads; (B) transporting said bottom portion to a filling station; (C) filling said compartment(s) with said food or drink, forming a filled container; (D) transporting said filled container to a lidding station; (E) attaching a lidding film to said upper flange on said filled container, forming a leak proof container; (F) manually transporting said leak proof container to a point of purchase (single serving retail counter), or optionally mechanically transporting said leak proof container to a fully integrated bulk packaging line.
The present invention further provides a process wherein the bottom portion comprises expanded polystyrene beads.
The present invention provides a process wherein said bottom portion has a density from 0.5 pounds per cubic foot (8 g/L) to 12 pounds per cubic foot (190 g/L).
The present invention provides a process wherein said lidding film is a monolayer film.
The present invention provides a process wherein said monolayer lidding film comprises a styrene butadiene copolymer.
The present invention provides a process that produces a leak proof container comprising a monolayer lidding film, wherein the monolayer film is comprised of a styrene butadiene copolymer; and the Average Plateau Peeling Force required to peel this lidding film from said leak proof container is greater than 0.32 pounds-force, or 1.4 Newton.
The present invention provides a process that produces a leak proof container comprising a monolayer lidding film, wherein the monolayer film is comprised of a styrene butadiene copolymer; and the Average Puncture Force at Straw Breakthrough is greater than 2.9 pounds-force, or 13 Newton.
The present invention provides a process that produces a leak proof container comprising a monolayer lidding film, wherein the monolayer film comprises an ethylene vinyl acetate copolymer containing from 3 wt % to 16 wt % vinyl acetate and has a melt index from 0.2 dg/min to 20 dg/min.
The present invention provides a process that produces a leak proof container comprising a monolayer lidding film, wherein the monolayer film comprises a polyolefin with a DSC melting point from 90° C. to 125° C. and a melt index from 0.2 dg/min to 20 dg/min.
Further embodiments of the present invention provide a process that produces leak proof containers comprising a multilayer lidding film.
The present invention provides a process that produces a leak proof container comprising a multilayer lidding film, wherein the inner most layer of the multilayer film comprises an ethylene vinyl acetate copolymer containing 3 wt % to 16 wt % vinyl acetate and has a melt index from 0.2 dg/min to 20 dg/min.
The present invention provides a process that produces a leak proof container comprising a multilayer film, wherein the inner most layer of the multilayer film comprises an ethylene vinyl acetate copolymer containing 3 wt % to 16 wt % vinyl acetate and has a melt index from 0.2 dg/min to 20 dg/min; and the Average Plateau Peeling Force required to peel this multilayer lidding film from said leak proof container is greater than 0.24 pounds-force, or 1.1 Newton.
The present invention provides a process that produces a leak proof container comprising a multilayer lidding film, wherein the inner most layer of the multilayer film comprises a polyolefin with a DSC melting point from 90° C. to 125° C. and a melt index from 0.2 dg/min to 20 dg/min.

DEFINITION OF TERMS

Other than in the operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, etc., used in the specification and claims are to be understood as modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties, which the present invention desires to obtain. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10; that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. Because the disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless expressly indicated otherwise, the various numerical ranges specified in this application are approximations.
In order to form a more complete understanding of the invention the following terms are defined and should be used with the accompanying figures and the description of the various embodiments throughout.
As used herein, the term “monomer” refers to a small molecule that may chemically react and become chemically bonded with itself; other monomers to form a polymer.
As used herein, the term “polymer” refers to macromolecules composed of one or more monomers connected together by covalent chemical bonds. The term polymer is meant to encompass, without limitation, homopolymers, copolymers, terpolymers, quatropolymers, block polymers, graft copolymers, and blends and combinations thereof.
The term “homopolymer” refers to a polymer that contains one type of monomer.
The term “copolymer” refers to a polymer that contains two monomer molecules that differ in chemical structure randomly bonded together. The term “terpolymer” refers to a polymer that contains three monomer molecules that differ in chemical structure randomly bonded together. The term “quatropolymer” refers to a polymer that contains four monomer molecules that differ in chemical structure randomly bonded together.
As used herein the term “expandable polystyrene beads”, or EPS, refers to spherical polystyrene beads generally prepared by an aqueous suspension polymerization process. EPS beads are expandable because they contain a physical blowing agent, e.g. pentane.
As used herein, the term “styrenic polymer” refers to a polymer derived from the homopolymerization of styrene or copolymerizing styrene with one or more monomers, wherein the monomers are covalently linked in a random fashion and the resulting polymer contains at least 50 weight percent of one or more monomers selected from styrene, p-methyl styrene, a-methyl styrene, tertiary butyl styrene, dimethyl styrene, nuclear brominated or chlorinated derivatives thereof and combinations thereof. Non-limiting examples of comonomers include butadiene, alkyl acrylates (for example, butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate), alkyl methacrylates (for example, methyl methacrylate, ethyl methacrylate, butyl methacrylate and 2-ethylhexyl methacrylate) acrylonitrile, vinyl acetate, alpha-methylethylene, divinyl benzene, dimethyl maleate and diethyl maleate.
The term “styrene butadiene copolymer” refers to high impact polystyrenes (HIPS) and styrene butadiene block copolymers.
The synthesis and morphology of high impact polystyrene is well described by A. Echte et al. in “Half a Century of Polystyrene—A Survey of the Chemistry and Physics of a Pioneering Material”, Agnew. Chem. Int. Ed. Engl. 20, 344-361 (1981). Typically, HIPS is produced by dissolving a rubber, such as polybutadiene, in styrene and polymerizing the styrene as well as grafting (covalently linking) a portion of the polystyrene macromolecules to the polybutadiene macromolecules. The original homogeneous solution of polybutadiene in styrene phase separates at relatively low styrene conversion. In general, the final morphology of HIPS consists of a continuous rigid polystyrene matrix with embedded polybutadiene particles; importantly, grafted macromolecules nit the two incompatible phase (polystyrene and butadiene) together and significantly influence final properties. Several morphological and structural features play an important role in determining the end-use performance of HIPS, e.g. rubber content, phase volume ratio, rubber particle size, rubber particle size distribution, degree of grafting and the degree of cross linking within the rubber. As a specific example, it is generally accepted that HIPS impact strength goes through a maximum when the rubber particle size is approximately 0.039 mil (1 μm) to 0.079 mil (2 μm). Typically, commercial HIPS contains approximately 75 wt % polystyrene.
The term “styrene butadiene copolymer” also refers to styrene butadiene block copolymers. The term “block copolymer” refers to a polymer that contains at least two monomer molecules that upon polymerization form at least two chemically distinct regions, segments or blocks. The term block copolymer includes linear block copolymers, multi-block copolymers and star shaped block copolymers. A block copolymer can be prepared using a living or anionic polymerization process. More specifically, a styrene butadiene block copolymer may be produced using the following steps: butadiene monomer is added to a reactor and completely converted to living polybutadiene anions using a butyllithium initiator; styrene monomer is then added to the reactor and completely polymerized to form poly(butadiene-block-styrene) anions, and; the living polymerization system is terminated producing a linear styrene butadiene block copolymer. Such living polymerization systems allow one to precisely control the weight fraction or length of each block. In addition, prior to termination a third monomer could be added to form a tri-block copolymer, or multi-block copolymer, such as -A_x-B_y-C_Z, wherein A, B and C represent monomers and x, y, z are integers that represent the length of the homopolymer sequence. The term tri-block, or multi-block, may also refer to a block copolymer with the following structure:—A_x-B_y-A_z-, wherein the two A blocks differ in length. Through the use of a coupling agent one can use anionic polymerization to produce star shaped block copolymers such as -(A_xB_y)_n—X; wherein X is the coupling agent and n is an integer that represents the number of macromolecular arms attached to X, n can be 3, 4, 5 or higher. Silicon tetrachloride (SiCl₄) is a non-limiting example of a coupling agent which could be used to produce a star shaped block copolymer with four arms. It is also possible to produce asymmetric star shaped block copolymers wherein the arm lengths differ in length, i.e. three short polystyrene arms and one long polystyrene arm attached to a polybutadiene core. In general, block copolymers covalently link two (or more) polymer segments that are immiscible, as a result the homopolymer-like blocks within a block copolymer phase separate. For example, in the case of styrene butadiene block copolymers, the polystyrene and polybutadiene segments microscopically phase separate, producing unique morphologies that may be spherical, rod-like or lamellar in nature, wherein the phases have dimensions from hundreds to thousands of angstroms. Such morphological dimensions results in glass-clear transparency, in addition the rubbery polybutadiene phases (low T_g) dramatically improve the impact resistance of the block copolymer, relative to pure polystyrene.
As used herein, the term “thermoplastic” refers to a broad class of polymers that soften or become liquid when heated, will flow under pressure and harden when cooled. In many cases, thermoplastics are high-molecular-weight polymers that can be repeatedly heated and remolded.
As used herein, the term “polyolefin” refers to a broad class of polymers that includes polyethylene and polypropylene.
As used herein, the term “polyethylene” includes ethylene homopolymers, ethylene copolymers containing one comonomer, ethylene terpolymers containing two comonomers and ethylene quatropolymers containing three comonomers, etc. Polyethylenes are typically produced using Ziegler/Natta catalysts, chrome catalysts, metallocene catalysts or free radical catalysts. Suitable comonomers include propylene, C₄to C₈α-olefins, vinyl acetate, methyl acrylate, methyl methacrylate, acrylic acid and methacrylic acid.
As used herein, the term “polypropylene” includes isotactic, syndiotactic and atactic polypropylene homopolymers, random propylene copolymers containing one comonomer, random propylene terpolymers containing two comonomers, random propylene quatropolymers containing three comonomers, etc., and impact or heterophasic polypropylenes. Random polypropylenes typically contain less than 20 wt % of comonomer, based on the weight of the random polypropylene; typical comonomers include ethylene and C₄to C₈α-olefins. Impact or heterophasic polypropylenes, typically contain up to 40 wt % of an ethylene/propylene rubber finely dispersed in a propylene homopolymer. The ethylene/propylene rubber may also include one or more of the following monomers; 1,2-propadiene, isoprene, 1,3-butadiene, 1-5-cyclooctadiene, norbornadiene or dicyclopentadiene.
As used herein, the term “intercalated” refers to the insertion of one or more polymer molecules within the domain of one or more other polymer molecules having a different composition. In the embodiments of this invention, the term “intercalated polymer” refers to a styrenic polymer intercalated within polyolefin particles, produced by polymerizing a styrenics monomer mixture within a polyolefin particle. U.S. Pat. No. 7,411,024, U.S. Pat. No. 7,906,589, U.S. Pat. No. 8,101,686 and U.S. Pat. No. 8,168,722, herein incorporated by reference in their entirety, describe intercalated polymers comprised of 20 percent to 60 percent by weight of a polyolefin and from 40 percent to 80 percent by weight of a styrenic polymer, based on the weight to the interpolymer resin particles.
As used herein, the term “bottom portion” refers to a container such as a cup, a bowl or a tray produced in a shape molding process from expandable thermoplastic resin beads. A shape molded bottom portion may contain one or more “compartments”, wherein food or drink can be placed.
As used herein, the term “lidding film” refers to a monolayer or a multilayer film that is capable of being attached to said bottom portion, forming a leak-proof seal. Sealing may be accomplished by any know method such as heat sealing, ultrasonic sealing, pressure sensitive adhesives or hot melt adhesives, etc.
As used herein the term “monolayer film” contains a single layer of one thermoplastic, or blends of more than one thermoplastic.
As used herein, a “multilayer film” is comprised of more than one thermoplastic layer, or optionally non-thermoplastic layers such as metals or paper products. A single layer within a multilayer film may contain a blend of more than one thermoplastic. Multilayer lidding films are common in food and drink packaging because one may incorporate additional functionality into the lidding film; for example, moisture barrier, oxygen barrier, adhesive layers, toughness, abuse resistance, scratch resistance, decorations (print or graphics) and sealability layers.
As used herein, the term “sealant layer” refers to a layer of thermoplastic film that is capable of being attached to said bottom portion, forming a leak proof seal. In the case of monolayer films, the terms sealant layer and lidding film are equivalent.
The term “inner most layer” refers to a multilayer film; the inner most layer of a multilayer film is the sealant layer that is capable of being attached to said bottom portion, forming a leak proof seal. The inner most layer is also in contact with the internal environment within the container, the inner most layer may also be in physical contact with the food or drink contained within the compartment of the bottom portion.
The term “outer most layer” refers to a multilayer film. The outer most layer of a multilayer film is in contact with the external environment, forming the outer surface of the multilayer film.
Herein, the term “barrier layer” refers to a functional layer within a multilayer film that protects food or drink from the deleterious effects of moisture and/or oxygen. Polyethylene films containing a high density polyethylene (HDPE) barrier layer provide reasonable moisture barrier. However, when high moisture and high oxygen barrier is required, a wide variety of barrier resins are available. Typical thermoplastic barrier resins include, polyvinylalcohol (PVOH), ethylene vinyl alcohol (EVOH), polyamides (Nylon), polyesters, polyvinylidene chloride (PVDC), polyacrylonitrile and acrylonitrile copolymers and polyvinylchloride (PVC). Barrier layers may also include a layer of thermoplastic film upon which a metal oxide has been applied by vapor deposition; for example a thin silicon oxide (SiOx) or aluminum oxide (AlOx) layer vapor deposited on polypropylene, polyamide or polyethylene terephthalate.
Herein, the term “tie layer” refers to a layer within a multilayer film that promotes adhesion between adjacent film layers that are dissimilar in chemical composition. Common tie resins or adhesive resins are functionalized polyethylenes containing monomer units derived from C₄to C₈unsaturated anhydrides, or monoesters of C₄to C₈unsaturated acids having at least two carboxylic acid groups, or diesters of C₄to C₈unsaturated acids having at least two carboxylic acid groups, or mixtures thereof. Tie layers in multilayer films typically contain less than 20 wt % of a tie resin blended with a polyolefin, e.g., plastomer, ULDPE, VLDPE, LLDPE, MDPE, HDPE or polypropylenes, etc. Depending the multilayer film structure, in some cases the following resins may also be effective as tie resins; ethylene/vinyl acetate copolymers, ethylene/methyl acrylate copolymers, ethylene/butyl acrylate copolymers, very low density polyethylene (VLDPE), ultralow density polyethylene (ULDPE), as well as metallocene catalyzed ethylene/α-olefin copolymers.
Herein, polymer density was determined using American Society for Testing and Materials (ASTM) methods ASTM D1505 or D792.
Herein, polymer melt index was determined using ASTM D1238, Condition I was measured at 190° C., using a 2.16 kg weight and Condition G was measured at 230° C., using a 2.16 kg weight.
Herein, the VICAT softening temperatures of polymers was measured using ASTM D1525.
Herein, polymer melting temperature was measured using ASTM D3418.
Herein, the gel content of intercalated polymers was measured using ASTM D2765 using toluene as solvent.
Herein, water vapor transmission rate (WVTR) of lidding film, expressed as grams of water vapor transmitted per 100 square inches of film per day at a specified film thickness (mils), or g/100 in²/day, was determined using ASTM F 1249-06 at 100° F. (37.8° C.) and 100% relative humidity using a MOCON permatron developed by Modern Controls Inc.
Herein, oxygen gas transmission rate of lidding film was determined using ASTM F2622-08.
Herein, lidding film dart impact strength was determined using ASTM D-1709B.
Herein, lidding film machine direction and transverse direction Elmendorf tear strength and tensile strength was determined using ASTM D-1922 and ASTM D882, respectively.
Herein, lidding film machine direction and transverse direction tensile properties (2% secant modulus, tensile strength at yield, tensile elongation at yield, tensile strength at break, tensile elongation at break) were determined using ASTM D882.
Herein, the optical properties of lidding film were measured as follows: Haze, ASTM D1003; Clarity ASTM D1746 and; Gloss(20°) ASTM D2457.

DESCRIPTION OF THE FIGURES

In the accompanying Figures:

FIG. 1 illustrates a typical container molded from expandable thermoplastic beads, which includes a bottom portion 101, an upper flange 102 and a food or drink compartment 103. The dimensions r₁and r₂represent the outer and inner radius of the upper flange; the difference (r₁-r₂) defines the width of the upper flange.

FIG. 2 illustrates another embodiment, a tray molded from expandable thermoplastic beads.

FIG. 3 illustrates another embodiment, an assembly of four cup-like bottom portions and four compartments of equal volume molded from expandable thermoplastic beads.

FIG. 4 illustrates another embodiment, an assembly of three tray-like bottom portions and three compartments that differ in volume molded from expandable thermoplastic beads.

FIG. 5 illustrates various lidding film embodiments; monolayer lidding film 5 a, three layer lidding film 5 b, four layer lidding film 5 c, five layer lidding film 5 d and seven layer lidding film 5 e.

FIG. 6 illustrates an atomic force micrograph (AFM) showing the heterophasic morphology of an intercalated polymer; styrenic polymer (bright regions) intercalated within a polyolefin (dark regions) particle.

FIG. 7 illustrates a process to produce a leak proof container made from expandable thermoplastic resin beads.

FIG. 8 illustrates one embodiment of a sealing station, with a sealing device 61, a heat sealing disk 63, a cutting disk 64, a continuous roll of lidding film 62, a lower platform 66 and a bottom portion 60.

FIG. 9 illustrates a top view of a leak proof container, wherein a leak proof seal 71, attaches the bottom portion 70 to the lidding film 72. The dimensions r₁₁and r₁₂represent the outer and inner radius of the upper flange; the dimension r₁₃is the lidding film radius, the difference (r₁₃-r₁₁) defines the lidding film overhang.

FIG. 10 illustrates the DSC melting points of EVA copolymers as a function of vinyl acetate content (wt %).

FIG. 11 illustrates the DSC of a poly(ethylene-co-ethylene vinyl acetate) copolymer, Elvax 3135X, 13% VA, 0.35 I₂(190° C.), 0.93 g/cc, available from DuPont. Peak melting point of 94.78° C.

FIG. 12 illustrates the DSC thermogram of a poly(ethylene-co-1-octene) plastomer, Affinity PL1881G, 0.904 g/cc, 1.0 melt index (190° C.), available from Dow Chemical. Peak melting point of 97.48° C.

FIG. 13 illustrates the DSC thermogram of a poly(propylene-co-ethylene) copolymer, Adsyl 5C 37 F, available from LyondellBasell, 0.90 g/cc and 5.512 (230° C.). DSC melting peaks at 104.69° C., 134.80° C. and 145.65° C.

FIG. 14 plots the compressive load (Ib-f), or the lidding film puncture strength, of lidding film Example 3 (five specimens) as a function of compressive extension (inches).

FIG. 15 plots the extensional load (Ib-f), or the lidding film peel strength, of lidding film Example 3 (five specimens) as a function of extension (inches).

DESCRIPTION OF EMBODIMENTS

The manufacture of molded articles, such as cups, bowls and the like from expanded thermoplastic beads is known. Any suitable expandable resin beads can be used in a shape molding process to form a cup or bowl as shown in FIG. 1, comprising a bottom portion 101, an upper flange 102 and a compartment 103 for holding food or drink. Herein, the term “bottom portion” refers to any molded shape, a cup, a bowl, a tray, etc. Suitable expandable resin beads include those with dimensions that allow the expandable and/or pre-expanded beads to be fed to a two-part mold without clogging or obstructing the feed channels in the mold and are able to expand and fuse together to form the molded bottom portion 101 shown in FIG. 1. Suitable expandable resin beads, include but are not limited to, those that contain homopolymers of vinyl aromatic monomers. Suitable vinyl aromatic monomers include, but are not limited to, styrene, isopropylstyrene, alpha-methylstyrene, nuclear methylstyrenes, chlorostyrene, tert-butylstyrene. In an embodiment of the invention, the vinyl aromatic monomers can be copolymerized with one or more other monomers, non-limiting examples being divinylbenzene, conjugated dienes (non-limiting examples being butadiene, isoprene, 1,3- and 2,4-hexadiene), alkyl methacrylates, alkyl acrylates, acrylonitrile, and maleic anhydride, where the vinyl aromatic monomer is present in at least 50% by weight of the copolymer. In many embodiments of the invention, styrenic polymers are used, particularly polystyrene, however, other suitable polymers can be used, such as polyolefins (e.g. polyethylene, polypropylene), polycarbonates, polyphenylene oxides, and mixtures thereof.
In one embodiment of the invention, the resin beads comprise expandable polystyrene (EPS) beads. EPS is generally prepared by an aqueous suspension polymerization process, which produces spherical polystyrene beads, which become expandable after impregnation with a blowing agent. When heated the impregnated polystyrene beads soften, the blowing agent vaporizes and the beads expand. Expandable polystyrene beads can be screened to relatively precise bead sizes. Typically, bead diameters are within the range of from 0.008 inch to 0.02 inch (0.2 mm to 0.5 mm). Occasionally, molded articles (cups and bowls) are made from beads having bead diameters as high as 0.03 inches (about 0.8 mm).
In the present invention, the resin beads are formed via polymerization in a suspension process, from which essentially spherical resin beads are produced. These beads are useful for making the bottom portion shown in FIG. 1. However, polymers derived any polymerization process can be pelletized to from cylindrical or spherical resin beads of appropriate dimensions, impregnated with a blowing agent and shape molded to produce a bottom portion; non-limiting examples of polymerization processes include bulk, solution or gas phase processes.
In an embodiment of the invention, resin beads containing any of the above-mentioned polymers have a minimum average particle size of at least 0.4 mil (10 μm), in some situations at least 1 mil (25 μm), in some cases at least 2 mil (50 μm), in other cases at least 3 mil (75 μm), in some instances at least 4 mil (100 μm) and in other instances at least 6 mil (150 μm). Also, the resin beads can have a maximum average particle size of up to 24 mil (600 μm), in some instances up to 22 mil (550 μm), in other instances up to 20 mil (500 μm), in some cases up to 18 mil (450 μm), in other cases up to 16 mil (400 μm), and in some situations up to 14 mil (350 μm). The maximum average size of the resin beads will be limited by the dimensions of the two-part mold to allow for feeding of the expandable and/or pre-expanded resin beads into the mold that forms the bottom portion. The size of resin beads used in this embodiment can be any value or can range between any of the values recited above.
The number average particle size and size distribution of the resin beads can be determined using low angle light scattering, which can provide a weight average value. A non-limiting example of such a device is Model LA-910 Laser Diffraction Particle Size Analyzer available from Horiba Ltd., Kyoto, Japan.
In an embodiment of the invention, the polymers in the resin bead have a weight average molecular weight (Mw) of at least 25,000, in some cases at least 50,000, and in other cases at least 75,000 and the Mw can be up to 1,000,000, in some cases up to 750,000 and in other cases up to 500,000. The weight average molecular weight of the polymers in the resin bead can be any value or can range between any of the values recited above. Unless stated otherwise, all molecular weight values are determined using gel permeation chromatography (GPC) using appropriate polystyrene standards. Unless otherwise indicated, the molecular weight values indicated herein are weight average molecular weights (Mw).
In an embodiment of the invention, after polymerization, the resin beads are isolated and dried and then suspended in an aqueous system. As used herein, “aqueous system” means a solution or mixture containing at least 50 weight % water as the solution medium and/or continuous phase. Dispersing aids, nonionic surfactants and/or waxes can also be added to the aqueous system. When the resin beads are dispersed in the aqueous system, one or more blowing agents can be added.
The expandable thermoplastic beads or resin beads can optionally be impregnated using any conventional method with a suitable blowing agent. As a non-limiting example, the impregnation can be achieved by adding the blowing agent to the aqueous suspension during the polymerization of the polymer, or alternatively by re-suspending the beads or resin beads in an aqueous medium and then incorporating the blowing agent as taught in U.S. Pat. No. 2,983,692. Any gaseous material or material which will produce gases on heating can be used as the blowing agent. Conventional blowing agents include aliphatic hydrocarbons containing 4 to 6 carbon atoms in the molecule, such as butanes, pentanes, hexanes, and the halogenated hydrocarbons, e.g. CFC's and HCFC's, which boil at a temperature below the softening point of the polymer chosen. Mixtures of these aliphatic hydrocarbon blowing agents can also be used.
Alternatively, water can be blended with these aliphatic hydrocarbons blowing agents or water can be used as the sole blowing agent as taught in U.S. Pat. Nos. 6,127,439; 6,160,027; and 6,242,540 in these patents, water-retaining agents are used. The weight percentage of water for use as the blowing agent can range from 1 wt % to 20 wt %. The texts of U.S. Pat. No. 6,127,439, U.S. Pat. No. 6,160,027 and U.S. Pat. No. 6,242,540 are incorporated herein by reference.
In an embodiment of the invention, the blowing agent can include one or more selected from nitrogen, sulfur hexafluoride (SF₆), argon, carbon dioxide, 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane, difluoromethane (HFC-32), 1,1-difluoroethane (HFC-152a), pentafluoroethane (HFC-125), fluoroethane (HFC-161) and 1,1,1-trifluoroethane (HFC-143a), methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, cyclopentane, neopentane, hexane, azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonylhydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonyl semi-carbazide, barium azodicarboxylate, N,N′-dimethyl-N,N′-dinitrosoterephthalamide, trihydrazino triazine, mixtures of citric acid and sodium bicarbonate, and combinations thereof.
In an embodiment of the invention, the blowing agent can be present in the resin beads at a level of less than 14 wt %, in some situations less than 6 wt %, in some cases ranging from about 2 wt % to about 5 wt %, and in other cases ranging from about 2.5 wt % to about 3.5 wt % based on the weight of the resin bead.
Any suitable dispersing aid can be used in the present invention. Suitable dispersing aids prevent the resin beads from sticking together when dispersed in the aqueous system. Examples of suitable dispersing aids include, but are not limited to finely divided water-insoluble inorganic substances such as tricalcium phosphate, zinc oxide, bentonite, talc, kaolin, magnesium carbonate, aluminum oxide and the like as well as water-soluble polymers such as polyvinyl alcohol, alkyl aryl sulfonates, hydroxyethyl cellulose, polyacrylic acid, methyl cellulose, polyvinyl pyrrolidone, and the like, sodium linear alkyl benzene sulfonates, such as sodium dodecylbenzene-sulfonate, and combinations thereof. In an embodiment of the invention, the dispersing aid includes tricalcium phosphate together with a sodium linear alkylbenzene sulfonate. The amount of the dispersing aid necessary will vary depending on a number of factors but will generally be at least about 0.01 parts, in some cases at least about 0.05 parts, and in other cases at least about 0.1 parts and can be up to about 2 parts, in some cases up to about 1 parts, and in other cases up to about 0.75 parts by weight per 100 parts by weight of resin beads. The amount of the dispersing aid can be any value or can range between any of the values recited above.
One or more non-ionic surfactants can be included such as polyoxyalkylene derivatives of sorbitan fatty acid esters, such as C₈to C₃₂linear or branched with up to five units of unsaturation, non-limiting examples being oleates, stearates, monolaurates and monostearates, an ethylene oxide/propylene oxide block copolymer, or other non-ionic or anionic surface active agent can be added to the aqueous suspension if desired. In an embodiment of the invention, the amount of surfactant is at least 0.01 parts, in some cases at least 0.05 parts, and in other cases at least 0.1 parts and can be up to 2 parts, in some cases up to 1 parts, and in other cases up to 0.75 parts by weight per 100 parts by weight of resin beads. The amount of surfactant can be any value or can range between any of the values recited above. In an embodiment of the invention, the HLB (Hydrophilic/Lipophilic/-Balance) of the above-mentioned polyoxyalkylene containing surfactants is at least 8, in some cases at least 10 and in other cases at least 12 and can be up to 22, in some cases up to 20 and in other cases at least 18. HLB is applicable to non-ionic surfactants and it predicts water solubility, the higher the HLB the more hydrophilic or water soluble the non-ionic surfactant. The HLB of the polyoxyalkylene containing surfactants can be any value or can range between any of the values recited above. The non-ionic surfactants can aid in the formation of fine cell structure in the expanded resin beads.
The waxes are used in the present invention were selected to promote the formation of fine cell structure in the expanded resin beads. At atmospheric pressure, waxes are typically solid at 20° C. and below, in some cases 25° C. and below, and in other cases 30° C. and below, and are liquid at 125° C. and above, in some cases 150° C. and above, and in other cases 200° C. and above.
In an embodiment of the invention, the waxes are selected from natural and/or synthetic waxes. As such, the waxes used in the present invention can be one or more materials selected from C₁₀to C₃₂, in some instances C₁₂to C₃₂, in some cases C₁₄to C₃₂, and in other cases C₁₆to C₃₂linear, branched or cyclic alkyl, alkenyl, aryl, alkaryl, or aralkyl alcohols; C₁₀to C₃₂, in some instances C₁₂to C₃₂, in some cases C₁₄to C₃₂, and in other cases C₁₆to C₃₂linear, branched or cyclic alkyl, alkenyl, aryl, alkaryl, or aralkyl carboxylic acids and/or their corresponding ammonium and metal salts or C₁to C₃₂, in some instances C₁₂to C₃₂, in some cases C₁₄to C₃₂, and in other cases C₁₆to C₃₂linear, branched or cyclic alkyl, alkenyl, aryl, alkaryl, or aralkyl esters; C₁₀to C₃₂, in some instances C₁₂to C₃₂, in some cases C₁₄to C₃₂, and in other cases C₁₆to C₃₂linear, branched or cyclic alkyl, alkenyl, aryl, alkaryl, or aralkyl hydrocarbons; polyethylene; polypropylene; polyester; polyether; and combinations thereof, so long as they meet a combination of liquid and solid temperatures as defined above. The polyethylene, polypropylene, polyester, and polyether waxes can have a molecular weight (Mw) of from about 1,000 to about 100,000 so long as they meet a combination of liquid and solid temperatures as defined above
In an embodiment of the invention, the amount of wax is at least 0.01 parts, in some cases at least 0.05 parts, and in other cases at least 0.1 parts and can be up to 2 parts, in some cases up to 1 parts, and in other cases up to 0.75 parts by weight per 100 parts by weight of resin beads. The amount of wax can be any value or can range between any of the values recited above.
The resin beads used in the invention are advantageously solid particles in the form of thermoplastic resin beads produced from suspension polymerization as indicated above. The polymer is formed as a slurry of finely divided beads in the aqueous suspension. The beads are recovered by washing and drying.
In an embodiment of the invention, the resulting resin beads can be screened to remove any resin beads with particle sizes that are too large. In many cases, resin beads having a particle size greater than 24 mil (600 μm), in some cases greater than 20 mil (500 μm) and in other cases greater than 16 mil (400 μm) are removed by screening.
The production of shape molded articles from impregnated polystyrene beads is generally done in two steps. First, the blowing agent impregnated polystyrene beads are pre-expanded to a density from about 0.5 to 12 pounds per cubic foot, hereafter pcf, (8 to 192 g/L); an example of this first step shown Table 2. Second, the pre-expanded beads are heated in a closed mold to further expand the pre-expanded beads to form a fused or molded article having the shape of the mold, i.e., a cup or bowl. An example of this second step is shown in Table 3. Such EPS cups and bowls are lightweight, have adequate structural properties and have excellent insulating properties.
For a better understanding of the present invention, FIGS. 1 through 5 are presented; however, these figures are intended purely as examples and are not to be construed as limiting.
FIG. 1, shows EPS beads molded into a cup or bowl shape, with a bottom portion 101 and an upper flange 102. The bottom portion forms a hollow compartment 103 within which food or drink is placed. The bottom portion can be any number of shapes, e.g. the tray shapes shown in FIG. 2. FIG. 2 shows an upper flange 202, a tray-like bottom portion 201 and a tray-like compartment 203. FIG. 3 shows an upper flange 302 with four cup-like bottom portions, bottom portion 301 a, 301 c and 301 d can be seen in FIG. 3, while bottom portion 301 b is obscured. FIG. 3 shows four cup- like compartments 303 a, 303 b, 303 c and 303 d of equal volume. FIG. 4 shows an upper flange 402 and three tray-like bottom portions; bottom potion 401 a and 401 c can be seen in FIG. 4, while bottom portion 401 b is obscured. FIG. 4 shows three tray-like compartments 403 a, 403 b and 403 c that differ in volume. The dimensions of the bottom portions and the dimensions of the multiple compartments are not critical; rather, these dimensions are governed by practical requirements such as the standard sizes for food and drink containers; for example, cups from 8 ounces to 32 ounces are common (from about 237 mL to about 947 mL) and food compartments typically vary from 1 ounce to 40 ounces (from about 30 mL to about 1183 mL).
In FIG. 1, the width of the upper flange (w_f) is the difference between the upper flange's outer radius, r₁, and the upper flange's inner radius, r₂; w_f=r₁−r₂. The width of the upper flange, w_f, must be large enough such that a leak proof seal is formed between the upper flange and the lidding film. In some instances, w_fis from 0.039 inches to 0.39 inches (1 mm to 10 mm), in some cases from 0.079 inches to 0.31 inches (2 mm to 8 mm) and in other cases 0.1 inch to 0.2 inch (2.5 mm to 5 mm). In the case of a bottom portion containing multiple compartments, perforation lines, or easy-failure lines may be incorporated into the bottom portion by a variety of methods know to those skilled in the art, such as cutting, punching, nicking with blades, heat treatment, laser radiation, electron beam radiation, electrostatic erosion, dissolving with solvents or etching by chemical reaction. Perforation lines or easy-failure lines facilitate the separation of one multiple compartment from the remaining multiple compartments, while maintaining a leak proof seal on all compartments.
FIG. 5 shows several non-limiting examples of lidding film. At the top of FIG. 5, film 5 a illustrates a monolayer 10 of lidding film comprised of at least one thermoplastic. In the case of monolayer film 5 a, such a film must be capable of sealing to the bottom portion forming a leak proof seal; thus one could also call film 5 a the sealant film and/or the lidding film. Non-limiting examples of a thermoplastic monolayer include: styrene butadiene copolymers, blends of styrene butadiene copolymer with other styrenic polymers, blends of styrene butadiene copolymers with intercalated polymers, a polyolefin, polyolefin blends and polyolefins blended with intercalated polymers. Particularly suitable polyolefins and/or polyolefin blend components include metallocene catalyzed ethylene copolymers commonly referred to as elastomers, metallocene catalyzed ethylene copolymers commonly referred to as plastomers, ultralow density polyethylene (ULDPE), very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), low density polyethylene (LDPE), ethylene vinyl acetate copolymers (EVA), ethylene alkyl acrylate copolymers, ethylene acrylic acid copolymers, metal salts of ethylene acrylic acid (commonly referred to as ionomers), random propylene copolymers and impact or heterophasic propylene copolymers. An example of a 4.09 mil thick (104 μm) monolayer styrene butadiene copolymer film is shown in Table 11. Typical densities of film grade styrene butadiene copolymers range from 1.00 g/cm to 1.05 g/cm, as determined by ASTM D792. The melt indexes of film grade styrene butadiene copolymers range from 3 to 20 g/10 min, as determined by ASTM D1238 measured at 200° C. using a 5 kg load.
Embodiments of this invention also include multilayer lidding films, i.e. films containing more than one chemically distinct layer of thermoplastic, or optionally layers of non-thermoplastic materials such as aluminum foil or paper products, etc.
Film 5 b, shown in FIG. 5, illustrates a three layer lidding film with three chemically distinct layers: layer 20 is an outer most layer; layer 21 is a core layer; and layer 22 is an inner most layer. In film 5 b the core layer is thicker than the outer most and inner most layers. In this non-limiting example, the core layer could be a lower cost thermoplastic, i.e. lower cost relative to monolayer film 5 a because the 3-layer film 5 b uses less of a higher cost sealant thermoplastic. Not wishing to be bound to any particular three layer lidding film composition, an example of a three layer lidding film is LLDPE/LDPE/EVA where the EVA (poly(ethylene-co-vinyl acetate)) is the inner most layer, or sealant layer. Three layer film embodiments also include thermoplastic blends; more specifically, any one of the three layers in film 5 b, any two of the three layers in film 5 b, or all three layers in film 5 b may be comprised of blends of more than one thermoplastic.
Film 5 c, shown in FIG. 5, illustrates a four layer lidding film with four chemically distinct layer: layer 30 is an outer most layer; layer 31 is an outer-most-intermediate layer; layer 32 is an inner-most-intermediate layer and; layer 33 is an inner most layer. As shown, the outer most intermediate layer of film 5 c is the thickest. A non-limiting examples of four layer lidding films are polyamide/adhesive/LLDPE/plastomer or PET/adhesive/LLDPE/plastomer where the polyolefin plastomer is the inner most layer, or sealant layer; in these 4-layer structures it would be desirable that the adhesive layer is relatively thin, for example about 1 to 5 percent of the total film thickness. In the case of lidding film 5 c, shown in FIG. 5, embodiments also include thermoplastic blends; more specifically, any one of the four layers in film 5 c, any two of the four layers in film 5 c, any three of the four layers in film 5 c or all four of the layers in film 5 c may be comprised of blends of more than one thermoplastic. Examples of four layer films are shown in: Table 5, film Example 1 is a 3.071 mil (77.9 μm) thick film with PET/adhesive/LDPE/EVA (3.2% VA) layers, and; Table 9, film Example 2 is a 2.043 mil (51.9 μm) thick film with PET/adhesive/polypropylene/poly(propylene-co-ethylene) layers.
Film 5 d, shown in FIG. 5, illustrates a five layer lidding film with five chemically distinct layers of approximately equal thickness: layer 40 is an outer most layer; layer 41 is a outer-most-intermediate layer; layer 42 is a core layer; layer 43 is an inner-most-intermediate layer; and layer 44 is an inner most layer, or sealant layer. Not wishing to be bound to any particular five layer lidding film composition, an example of a five layer lidding film is LLDPE/tie-layer/EVOH/tie-layer/plastomer, where the polyolefin plastomer is the inner most, or sealant layer. The core layer in this five layer example is EVOH (ethylene vinyl alcohol) which is a barrier resin (oxygen barrier). The intermediate layers of tie resin layers are required to prevent delamination between the EVOH and polyolefin layers. Five layer embodiments also include thermoplastic blends, e.g. any one, any two, any three, any four or all five of the layers of film 5 d shown in FIG. 5, may be comprised of blends of more than one thermoplastic. In multilayer food packaging films the number of individual layers typically increases when moisture barrier layers and/or oxygen barrier layers are introduced; which generally requires additional tie resin layers. Barrier layers containing EVOH or polyamides are frequently sandwiched between polyolefin layers, where the polyolefin layers provide functionality such as sealability, toughness, puncture resistance and abuse and/or scratch resistance.
Film 5 e, shown in FIG. 5, illustrates a seven layer lidding film with seven chemically distinct layers: layer 50 is an outer most layer; layer 51 is an outer-most-intermediate layer; layer 52 is an outer-most-core intermediate layer; layer 53 is the core layer; layer 54 is an inner-most-core intermediate layer; layer 55 is an inner-most-intermediate layer, and; layer 56 is the inner most layer, or sealant layer. Not wishing to be bound to any particular seven layer lidding film composition, an example of a seven layer lidding film is LLDPE/tie layer/polyamide/EVOH/polyamide/tie layerNLDPE, where the VLPE is the inner most layer, or sealant layer. Such a seven layer structure is a high barrier film, will excellent barrier properties with respect to both oxygen and moisture. Seven layer embodiments also include thermoplastic blends; wherein any one, any two, any three, any four, any five, any six or all seven layers of film 5 e shown in FIG. 5 may be comprised of blends of more than one thermoplastic.
Not wishing to be bound by any particular lidding film thickness, the total thickness of the monolayer or multilayer lidding films shown in FIG. 5 may vary from 0.5 mil to 16 mil (13 μm to 406 μm), in some instances from 1.0 mil to 8 mil (25 μm to 203 μm) and in other cases from 2.0 mil to 4 mil (51 μm to 102 μm). It will be appreciated by those skilled in the art that one can optimize lidding film performance through: the selection of thermoplastic(s); the blending of thermoplastics; adjusting the thickness of individual layers (layer ratios) and; adjusting the overall, or total, thickness. A non-limiting example of layer ratios for a three layer LLDPE/LDPE/EVA film is 20/60/20. By adjusting layer ratios, an experienced artisan can optimize lidding film performance attributes; non-limiting examples of performance attributes lidding film sealability, peelability, puncture resistance, toughness and optical properties, etc.
A non-limiting example of layer ratios for a four layer film PET/adhesive/LDPE/EVA are 20/2/43/35, as shown in Table 5 for film Example 1.
A non-limiting example of layer ratios for a five layer LLDPE/tie layer/EVOH/tie-layer/plastomer film are 60/10/10/10/10.
A non-limiting example of layer ratios for a seven layer LLDPE/tie layer/polyamide/EVOH/polyamide/tie layer/VLDPE film is 25/10/10/10/10/10/25.
Additional embodiments of this invention includes films containing more than 7 layers; such embodiments also include so call “microlayered” films containing greater than 100 layers.
Another embodiment includes multilayer films containing non-thermoplastic materials such as paper products or metals such as aluminum, or a thermoplastic layer having a vapor deposited metal on its surface, for example a thin silicon oxide (SiO_x) or aluminum oxide (AlO_x) layer vapor deposited on polypropylene.
Another lidding film embodiment includes at least one layer of intercalated polymer, or intercalated polymer blended with other thermoplastics. As used herein, the term “intercalated” refers to the insertion of one or more polymer molecules within the domain of one or more other polymer molecules having a different composition. More specifically, styrenic polymers are inserted into polyolefin particles by polymerizing a styrenic monomer mixture within the polyolefin particles, as described in U.S. Pat. No. 7,411,024; the disclosure of which is incorporated herein by reference in its entirety. The intercalated polymer typically contains 20% to 60% by weight of an uncross-linked polyolefin, e.g. polyethylene, polypropylene, and from 40% to 80% by weight of a vinyl aromatic monomer, e.g., styrene; based on the weight of the intercalated polymer.
Not wishing to be bound by any particular monolayer lidding film composition, but one or more intercalated polymers may comprise 100% of the lidding film or 100% of one or more layers of the lidding film. In addition, intercalated polymers may be blended with one or more thermoplastics, such as polyolefins or styrene butadiene copolymers. The amount of intercalated polymer in any layer may range from 0.5 wt % to 100 wt %, based on the total weight of the intercalated polymer plus the other thermoplastics, in some cases from 5 wt % to 80 wt % and in other cases from 10 wt % to 50 wt % of intercalated polymer. Suitable thermoplastics for blending include styrene butadiene copolymers, styrenic polymers or polyolefins.
Not wishing to be bound by any particular theory, the heterophasic morphology of intercalated polymers in the sealant layer of the lidding film is advantageous when sealing to a bottom portion composed of expandable polystyrene. The heterophasic morphology of intercalated polymers is shown in FIG. 6, the brighter regions correspond to styrenic polymer and the darker regions correspond to poly(ethylene-co-vinyl acetate) containing 4 wt % vinyl acetate. In a multilayer lidding film, the presence of intercalated polymer in intermediate layers, or the outer layers, is advantageous, for example, in producing a lidding film that is easy to puncture with a piercing straw. The amount and types of intercalated polymer in the lidding film is determined based on the desired end use and physical properties, particularly the strength of the seal between the lidding film and the bottom portion, and puncture strength of the lidding film.
Monolayer thermoplastic lidding films are typically produced using a blown film or cast film process. In the blown film process, thermoplastic pellets are melted in an extruder and passed through an annular or tubular die. A molten thermoplastic tube is extruded, inflated with air, solidified, collapsed into a sheet and the sheet collected on a product roll. In the cast film process, thermoplastic pellets are melted in an extruder, passed through a slot die, solidified on a chill roll and collected on a product roll.
Similarly, multilayer thermoplastic films can be produced using blown or cast film processes by adding additional extruders and using multilayer extrusion dies. Monolayer or multilayer lidding film may also be printed or decorated. Lidding film may also be produced by extrusion coating or extrusion lamination, these processes allow one to adhesively bond incompatible thermoplastic polymer layers and/or combine dissimilar materials such as aluminum foil or paper products with thermoplastics, as well as protect a high quality print or decoration layer with a protective thermoplastic layer.
The lidding film can optionally include, depending on its intended use, additives and adjuvants, which can include, without limitation, anti-blocking agents, antioxidants, anti-static additives, colorants, dyes, filler materials, heat stabilizers, impact modifiers, light stabilizers, light absorbers, lubricants, pigments, plasticizers, slip agents, softening agents, and combinations thereof.
Suitable anti-blocking agents, slip agents and lubricants include without limitation silicone oils, liquid paraffin, synthetic paraffin, mineral oils, petrolatum, petroleum wax, polyethylene wax, hydrogenated polybutene, higher fatty acids and the metal salts thereof, linear fatty alcohols, glycerine, sorbitol, propylene glycol, fatty acid esters of monohydroxy or polyhydroxy alcohols, phthalates, hydrogenated castor oil, beeswax, acetylated monoglyceride, hydrogenated sperm oil, ethylenebis fatty acid esters, and higher fatty amides. Suitable lubricants include, but are not limited to, ester waxes such as the glycerol types, the polymeric complex esters, the oxidized polyethylene type ester waxes and the like, metallic stearates such as barium, calcium, magnesium, zinc and aluminum stearate, salts of 12-hydroxystearic acid, amides of 12-hydroxystearic acid, stearic acid esters of polyethylene glycols, castor oil, ethylene-bis-stearamide, ethylene-bis-cocamide, ethylene-bis-lauramide, pentaerythritol adipate stearate and combinations thereof in an amount of from 0.1 wt % to 2 wt % of the lidding film composition.
Suitable antioxidants include without limitation Vitamin E, citric acid, ascorbic acid, ascorbyl palmitrate, butylated phenolic antioxidants, tert-butylhydroquinone (TBHQ) and propyl gallate (PG), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and hindered phenolics such as IRGANOX® 1010 and IRGANOX 1076 available from Ciba Specialty Chemicals Corp., Tarrytown, N.Y.
Suitable heat stabilizers include, without limitation, phosphite or phosphonite stabilizers and hindered phenols, non-limiting examples being the IRGANOX® stabilizers and antioxidants available from Ciba Specialty Chemicals. When used, the heat stabilizers are included in an amount of 0.1 wt % to 2 wt % of the lidding film compositions.
Suitable anti-static agents include, without limitation, glycerine fatty acid, esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, stearyl citrate, pentaerythritol fatty acid esters, polyglycerine fatty acid esters, and polyoxethylene glycerine fatty acid esters in an amount of from 0.01 wt % to 2 wt % of the lidding film compositions.
Suitable colorants, dyes and pigments are those that do not adversely impact the desirable physical properties of the lidding film include, without limitation, white or any colored pigment. In embodiments of the invention, suitable white pigments contain titanium oxide, zinc oxide, magnesium oxide, cadmium oxide, zinc chloride, calcium carbonate, magnesium carbonate, kaolin clay and combinations thereof in an amount of 0.1 wt % to 20 wt % of the lidding film. In embodiments of the invention, the colored pigment can include carbon black, phthalocyanine blue, Congo red, titanium yellow or any other colored pigment typically used in the printing industry in an amount of 0.1 wt % to 20 wt % of the lidding film. In embodiments of the invention, the colorants, dyes and pigments include inorganic pigments including, without limitation, titanium dioxide, iron oxide, zinc chromate, cadmium sulfides, chromium oxides and sodium aluminum silicate complexes. In embodiments of the invention, the colorants, dyes and pigments include organic type pigments, which include without limitation, azo and diazo pigments, carbon black, phthalocyanines, quinacridone pigments, perylene pigments, isoindolinone, anthraquinones, thioindigo and solvent dyes.
Suitable fillers are those that do not adversely impact, and in some cases enhance, the desirable physical properties of the lidding film. Suitable fillers, include, without limitation, talc, silica, alumina, calcium carbonate in ground and precipitated form, barium sulfate, talc, metallic powder, glass spheres, barium stearate, calcium stearate, aluminum oxide, aluminum hydroxide, glass, clays such as kaolin and montmorolites, mica, silica, alumina, metallic powder, glass spheres, titanium dioxide, diatomaceous earth, calcium stearate, aluminum oxide, aluminum hydroxide, and fiberglass, and combinations thereof can be incorporated into the polymer composition in order to reduce cost or to add desired properties to the lidding film. The amount of filler is desirably less than 20% of the total weight of the lidding film as long as this amount does not alter the properties of the lidding film.
Suitable impact modifiers include, without limitation, styrene butadiene copolymers (e.g. HIPS or styrene butadiene block copolymers), acrylonitrile butadiene styrene terpolymers (ABS), copolymers of C₁-C₁₂linear, branched or cyclic olefins, copolymers of C₁-C₁₂linear, branched or cyclic alkyl esters of (meth)acrylic acid and styrenic monomers, ethylene propylene diene monomer (EPDM) rubbers and styrene/ethylene copolymers. The amount of impact modifier used is typically in the range of 0.5 wt % to 25 wt % of the lidding film.
Suitable softening agents and plasticizers include, without limitation, cumarone-indene resin, terpene resins, and oils in an amount of about 2 parts by weight or less based on 100 parts by weight of the lidding film.
FIG. 7 is a sketch of a process to make a leak proof container comprising a bottom portion composed of expanded thermoplastic beads, a compartment containing food or drink and a lidding film. The first process step in FIG. 7 is referred to as “shape molding”. Typically shape molding is a two-step process. First, blowing agent impregnated expandable beads are pre-expanded to a density from 2 pcf to 12 pcf (32 g/L to 192 g/L) forming a “pre-puff. This first step, which is typically called the pre-expansion step, can be accomplished by heating the blowing agent impregnated beads using any conventional heating medium such as steam, hot air, hot water, or radiant heat. In the second step, typically referred to as shape molding, the bottom portion is formed. Expandable and/or pre-expanded resin beads are injected into the mold cavity. When the mold cavity is full, steam is applied thereby heating the mold and further expanding the pre-puff to form the bottom portion. At the end of the heating cycle, the mold is water cooled, the male portion and female portion of the mold are separated and compressed air is supplied in order to facilitate the ejection of the bottom portion from the mold. Typically, molded EPS bottom portions have a density from about 2 pcf to 8 pcf (32 g/L to 128 g/L). As shown in FIG. 1 through 4, the bottom portion, or portions, may be a cup, bowl or tray; comprising one or more compartments. Table 1 summarizes the EPS that was used to produce the bottom portions, i.e. DYLITE® F271T, expandable polystyrene beads, available from NOVA Chemicals Inc.
It will be appreciated by those skilled in the art that processes and equipment are available for forming, heating, cooling, holding and delivering foods or liquids into containers, or bottom portions. In addition, a non-limiting embodiment, includes filling the bottom portion manually, and then manually transporting the filled bottom portion to the sealing station; such an embodiment would be common in a retail or convenience store setting. The filling station step shown in FIG. 7 is intended to include all processes that are used to deliver liquids and/or solid foods to a container, including manual processes.
Referring to FIG. 7, after the food or drink has been deposited into the compartment (or compartments), the bottom portion (or bottom portions) is transported to the lidding station. FIG. 8 illustrates one embodiment of a lidding station, where the lidding station consists of a sealing device 61 device adapted to move in the vertical direction between an open position and a closed position, as shown by position a (top of FIG. 8) and position b (middle of FIG. 8), respectively. A continuous roll of lidding film 62 is shown in FIG. 8. The bottom portion, 60, rests on a lower platform 66. In transitioning from the opened position a, to the closed position b, the sealing device 61 moves downward. In the closed position b, the sealing device produces intimate contacts between: i) a heat sealing disk 63 and the outer most layer of the lidding film, and ii) the inner most layer of the lidding film and the bottom portion 60. Heat from the sealing disk 63, is transferred to the interface between the inner most layer and the bottom portion 60, whereupon the inner most layer and the bottom portion fuse together and upon cooling a leak proof seal is formed. In the case of a continuous roll of lidding film the sealing device also includes a cutting disk 64. More specifically, when in closed position b, the sealing disk 63 forms the leak proof heat seal and simultaneously the cutting disk 64 cuts the lidding film from the continuous roll. As shown in the lower portion of FIG. 8, after sealing and cutting are complete, the sealing device 61 returns to the open position and the leak proof disposable container 65 can be transferred manually or mechanically from the lower platform 66.
The cutting disk and heat sealing disk are non-overlapping and concentric, with the cutting disk having the larger diameter. Referring to FIG. 9, when the lidding film is simultaneously sealed and cut, a disk of lidding film with radius r₁₃is produced. Radius r₁₃is larger than the outer radius of the upper flange, r₁₁, producing a lidding film overhang with a radius (r₁₃-r₁₁). The length of the lidding film overhang is not critical. In some cases (r₁₃-r₁₁) was from 0 mm to 1 mm, in some situations from 1 mm to 5 mm, in other cases from 5 mm to 10 mm and in still other cases from 10 mm to 20 mm. The width of the upper flange, w_f=(r₁₃-r₁₂), must be wide enough such that a leak proof heat seal is formed between the upper flange and the inner most layer of the lidding film. In some cases w_fis at least 0.039 inches (1 mm), in some instances from 0.039 inches to 0.39 inches (1 mm to 10 mm), in other cases from 0.079 inches to 0.31 inches (2 mm to 8 mm) and in still other cases 0.1 inch to 0.2 inch (2.5 mm to 5 mm).
In the embodiment shown in FIG. 8 the continuous web of lidding film may move in an intermittent fashion. More specifically, the lidding film 62 advances horizontally, then stops while the sealing device 61 closes to lid the bottom portion 60 and then opens to release the leak proof container 65 and accept the next bottom portion 60. In another embodiment, the continuous web of lidding film advances horizontally with constant velocity, and the sealing device is adapted to move back and forth horizontally. Table 6 summarizes the operating conditions of the sealing device used in this work, the sealing device used was an intermittent Automatic Sealing Machine (Model ET-999S), available from Boba Tea Direct.
In an alternative embodiment, the lidding film sealing device 61 is stationary and the lower platform 66 is adapted to move in the vertical direction between an opened position and a closed position. In transitioning from the opened position to the closed position, the lower platform moves upward. In the closed position the bottom portion 60 produces intimate contacts between: i) the bottom portion and the inner most layer of the lidding film, and ii) the outer most layer of the lidding film and the heat sealing disk 63. When the bottom portion and the inner most lidding film layer are in intimate contact, heat from the sealing disk is transferred to the interface between the inner most layer and the bottom portion whereupon the inner most layer and the bottom portion fuse together and upon cooling a leak proof seal is formed. In the case of a continuous roll of lidding film the sealing device 64 simultaneously cuts the lidding film as the leak proof seal is formed. In the open position, the leak proof container is not in contact with the lidding film, and the lidding film is not in contact with sealing device, such that the leak proof container can be transferred manually or mechanically from the sealing station.
In the case of heat sealing, the optimal temperature and time required to form a leak proof seal depends on the thermal properties of both the lidding film and the bottom portion. In the case of 2 mil thick (51 micron) monolayer films comprised of polyethylene sealants, sealing disk temperatures between 90° C. and 150° C. are typical, with sealing disk dwell times between 0.25 seconds and 1.5 seconds. In the case of styrene butadiene copolymers and sealant grade polypropylenes, higher sealing disk temperature between 130° C. and 190° C. are more typical. Given a specific lidding film thickness and lidding film structure, one skilled in the art can optimize sealing conditions to produce a leak proof seal. Relevant data to the skill artisan is shown in Tables 7, 8, 10, 13 and 14 and FIGS. 10, 11, 12 and 13. More specifically: the physical properties of a polyethylene-co-vinyl acetate) sealant, or EVA, Elvax 3135X are summarized in Table 7 and melting point information is shown in FIGS. 10 and 11; the physical properties of a polyolefin plastomer sealant Affinity PL 188G are summarized in Table 8 and a DSC melting curve is shown in FIG. 12; the physical properties of a poly(propylene-co-ethylene sealant Adsyl 5C37F are summarized in Table 10 and the DSC melting curve is shown in FIG. 13; the physical properties of a high impact polystyrene (HIPS), Innova RC600, are summarized in Table 13, and; the physical properties of a styrene butadiene block copolymer are summarized in Table 14. Styrene butadiene copolymers with melt indexes that range from 3 to 20 g/10 min are suitable for lidding film applications, wherein the melt index is determined using ASTM D1238 and measured at 200° C. using a 5 kg load. Film grade styrene butadiene copolymers typically have densities that range from 1.00 to 1.04 g/cc, as measured by ASTM D792.
Not wishing to be bound by any theory, it is believed that to achieve a leak-proof seal by heat sealing the most critical material parameters are the softening/melting behavior of the sealant layer, the softening/glass transition behavior of the EPS bottom portion (cup or bowl) and the settings or parameters on the heat sealing device, i.e., the heat sealing parameters shown in Table 6. As demonstrated by lidding film Example 1, a leak proof seal was produced when the inner most layer was composed of an EVA containing 3.2 wt % of vinyl acetate. FIG. 10 suggests that a leak proof seals can be obtained with EVA copolymers up to about 12 wt % vinyl acetate. More specifically, the DSC melting point of an EVA containing 12 wt % vinyl acetate is similar to the 95° C. glass transition of EPS (relative to pure polystyrene, the glass transition of EPS is depressed due to the presence of the pentane blowing agent which acts as a plasticizer). The DSC thermogram of a 12 wt % vinyl acetate EVA copolymer is shown in FIG. 11, specifically, Elvax 3135X (available from DuPont Packaging & Industrial Polymers). As shown in FIG. 11, the peak DSC melting point of Elvax 3135X is 94.78° C., which is close to the glass transition temperature of EPS.
Additional physical properties of Elvax 3135X are summarized in Table 7. Suitable lidding films, where the inner most layer contains an EVA, with a DSC melting point between about 90° C. and about 125° C., are suitable to form a leak proof seal with an EPS bottom portion (cup, bowl, tray, etc.). In addition, one would expect lidding films, wherein the inner most layer contains a blend of more than one thermoplastic, wherein at least 30 wt % is an EVA copolymer with a DSC melting point between about 90° C. and about 125° C., to form a leak proof seal with an EPS bottom portion.
Similar to EVA's, poly(ethylene-co-α-olefin) plastomers also have well defined melting points. FIG. 12 shows the DSC thermogram of a poly(ethylene-co-1-octene) plastomer, Affinity PL1881G, 0.904 g/cm³and 1.0 melt index (available from Dow Chemical). The peak DSC melting point of Affinity PL1881G is 97.48° C., which is close to the glass transition temperature of EPS. Additional physical properties of Affinity PL1881G are summarized in Table 8. Suitable lidding films, where the inner most layer contains a polyolefin plastomer, with a DSC melting point between about 90° C. and about 125° C., should form a leak proof seal with an EPS bottom portion (cup, bowl, tray, etc.). In addition, lidding films, wherein the inner most layer contains a blend of more than one thermoplastic, wherein at least 30 wt % is a polyolefin plastomer with a DSC melting point between about 90° C. and about 125° C., should form a leak proof seal with an EPS bottom portion.
Specific polypropylene sealants are also suitable sealants. For example, Adsyl 5C37F, commercially available from LyondellBasell Industries, has a seal initiation temperature of 105° C., as shown in Table 10. This seal initiation temperature is supported by the DSC thermogram of Adsyl 5C37F, as indicated by the broad melting peak at 104.69° C. shown in FIG. 13. Portions of Adsyl 5C37F also melt at 134.80° C. and 145.65° C. Additional physical properties of Adsyl 5C37F are summarized in Table 10.
The lidding film need not be supplied to the sealing station from a continuous roll. Rather, pre-cut pieces of lidding film of circular, ellipsoid, square, rectangle or polygon shapes may fed to the sealing station mechanically or manually. In the case of bottom portions with multiple compartments the sealing and cutting device may be adapted to individually seal each compartment, such that each compartment is isolated from all other compartments. In another embodiment, sealing device may be adapted to include a perforation template, such that peroration lines, or easy-failure lines may be incorporated into the assembly of leak proof containers. Easy-failure lines facilitate the separation of one compartment from the multiple compartment assembly, while maintaining a leak proof seal on all compartments. A variety of methods know to those skilled in the art, can be used to incorporate easy-failure lines; such as cutting, punching, nicking with blades, heat treatment, laser radiation, electron beam radiation, electrostatic erosion, dissolving with solvents or etching by chemical reaction.
Recall FIG. 7 illustrating a process to produce a leak proof container made from expandable thermoplastic resin beads. After lidding is complete, the process bifurcates into: i) a bulk packaging station, or; ii) a retail station. These two processes differ significantly in the degree of automation and output rates, i.e., leak proof containers produced per unit time.
High throughput, fully integrated bulk packaging lines are well known per se and will not be described in detail. In brief, integrated food packaging plants may include: shape molding equipment and filling machines followed by at least one downstream packaging train which may including food package accumulators, stacking, cardboard box packers, pallet systems and stretch film wrappers. Such high throughput lines are typically computer controlled and monitored with the aim of optimizing the interaction between the filling machines and downstream packaging operations to maximize packaging line output.
In contrast with bulk packaging stations, the Retail Station (single serving) shown in FIG. 7 represents embodiments such as retail stores, convenience stores or take-out restaurants. In such settings, manual filling, manual lidding and manually transportation from station to station may be more cost effective than high speed automated packaging equipment.
An additional embodiment of the present invention includes an optional disposable drinking straw. The drinking straw may be composed of any suitable material. For example, a straw produced from one or more thermoplastics by an extrusion process where a straw-like tube is extruded and cut to length. Optionally, one end of the straw is cut in a hypodermic needle-like fashion, hereafter referred to as a “piercing straw”. The consumer can use the piercing straw to puncture the lidding film of the leak proof container, inserting the piercing straw into a liquid and consume the liquid through the piercing straw. Although not leak proof, an adequate seal remains between the piercing straw and the pierced lidding film, due to the elastic nature of the lidding film. The leak proof seal remains intact between the lidding film and upper flange of the bottom portion. As a result, once pierced with the piercing straw, the leak proof container prevents splashing or loss of the liquid during transport, for example walking, riding a bicycle or sudden stops in a motor vehicle. Optionally, one could completely remove the lidding film from the bottom portion; insert a straw or piercing straw into the liquid and drink.
In a retail store, convenience store or take-out restaurant setting, a straw or piercing straw could be a separate item where the consumer selects the straw or piercing straw from a dispenser. Optionally, one could produce a leak proof container and straw or piercing straw that is 100 percent recyclable under the #6 PS symbol.
In a high throughput, fully integrated bulk packaging line the optional straw or piercing straw could be added in an automated straw attachment step and packaged along with the leak proof container. Optionally, one could produce a leak proof container and straw or piercing straw combination that is 100% recyclable under the #6 PS symbol.
The puncture performance and peel performance of the leak proof containers were evaluated by developing the following the in-house tests.

Lidding Film Puncture Test

An Instron Model 4400R equipped with Instron Bluehill 2 software and a 100 pound load cell was used to generate a displacement-load curve in compression mode to measure the puncture strength of the lidding film attached to the EPS bottom portion. The bottom portions tested were 16 ounce (0.47 liters) noodle bowls fabricated from the expandable polystyrene beads (EPS) described in Table 1. The EPS beads were expanded and the noodle bowls were molded (forming the bottom portion) as described in

Example 1

Noodle bowl r₁and r₂dimensions were 1.860 inches (4.724 cm) and 1.716 inches (4.359 cm), respectively, thus the upper flange dimension was 0.144 inch (0.365 cm); see FIG. 1.
To prepare the noodle bowls for puncture testing a galvanized steel washer weighing 0.2 pounds (91 grams) and with dimensions of 0.18 inch (0.46 cm) thick, 2.5 inch (6.4 cm) diameter with a 1 inch (2.5 cm) hole in the center was placed in the bottom of each noodle bowl. The noodle bowl containing the washer was lidded with lidding film (Example 1 and Example 3) using the Automatic Sealing Machine (Model ET-999S) as described in Example 1 above. The washer containing leak proof container was mounted into the Instron as described in the following paragraph.
Four clear Plexiglass acrylic sheets, 4 inches (10 cm) square and 0.177 mil (0.45 cm) thick, were glued together using GE Silicone II glue forming a testing platform. A puck-shaped rare earth magnet, 1.57 cm diameter (4 cm) and 0.47 inch thick (1.2 cm), was glued (GE Silicone II) to the bottom of the testing platform, wherein the magnet was placed precisely in the center of the testing platform, forming a magnetic fixture. The bottom of the magnetic fixture (magnet side) was centered over and magnetically attached to an Instron compression platen, thus securely attaching the magnetic fixture to the Instron. The Instron compression platen was a stainless steel plate mounted into a tool steel support column that was pinned directly into the Instron base. A circular rubber spacer, 2.33 inch (5.92 cm) in diameter and 0.1 inch (0.25 cm) thick was centered on the top of the magnetic fixture and the washer containing leak proof container was placed on top of the rubber spacer, forming a puncture test specimen. The rubber spacer fit snuggly into the empty space defined by the bottom rim on the noodle bowl and the top of the magnetic fixture. If the rubber spacer was not employed a cylindrical air gap of about 0.1 inch (0.25 cm) in height and 2.35 inches (5.97 cm) in radius would exist between the bottom of the noodle bowl and the magnetic fixture; given such an air gap, magnetic forces would distort the shape of the washer containing leak proof container, or alternatively pull the washer completely through the bottom of the noodle bowl. The rubber spacer was reusable and was used for all puncture and peel tests. The acrylic sheets used to fabricate the magnetic fixture provide a flat and rigid testing platform as well as allow one to control (strengthen or weaken) the magnetic force on the washer in the leak proof container, i.e. four acrylic sheets were used in puncture testing and two acrylic sheets were used in peel testing.
In the puncture test the Instron's upper test fixture was adapted to hold a piercing straw. The piercing straw as fabricated as described in the rest of this paragraph. Drinking straws were purchased from a convenience store with the following dimensions: length 7 inch (18 cm), outside diameter 0.45 inch (1.1 cm) and wall thickness 0.014 inch (0.036 cm). With the long dimension of the straw oriented in a vertical fashion, the lower end of the straw was cut at a 45° angle from horizontal (forming a hypodermic needle-like lower end) and 4 inches of straw was cut (horizontally) from the top end of the straw and discarded. These two cuts produced a hypodermic needle like piercing straw that was about 3 inches (7.6 cm) in length. The reduced straw length increased the effective stiffness of the straw and made it easier to mount the straw in the Instron such that the straw was oriented perpendicular to the lidding film surface.
In the puncture test, the downward movement of the Instron's upper test fixture, travelling at a crosshead speed of 20 inches per minute (50.8 cm/min), generated a displacement-load curve in compressive mode as the straw descended, contacted and pierced the lidding film. A typical displacement-load curve is shown in FIG. 14. In FIG. 14, five leak proof containers (specimen 1 to 5) were tested, wherein the lidding film was the same, i.e. lidding film Example 3 which was the monolayer styrene butadiene film described in Table 11. In FIG. 14, each successive displacement-load curve was arbitrarily shifted to the right, this shift made it easier for the viewer to inspect the shape of each curve. The average puncture test results (average of five specimens) are summarized in Table 15. The “Average Puncture Force at Straw Breakthrough” was the average compressive force in pounds force (Ib-f) required to pierce the lidding film.

Lidding Film Peel Test

An Instron Model 4400R equipped with Instron Bluehill 2 Software and a 100 pound load cell was used to generate a displacement-load curve in extension mode to measure the peel strength of the lidding film attached to the EPS bottom portion. The washer containing leak proof containers tested were fabricated as described above in the Lidding Film Puncture Test, hereafter the puncture test. A peel test magnetic fixture was fabricated as described in the puncture test, with the exception that two acrylic sheets were used rather than four. In peel testing a higher magnetic force was required to hold the washer containing leak proof container in place, thus the number of acrylic sheets were reduced from four to two. The peel test magnetic fixture was attached to the Instron as described in the puncture test above. A peel test specimen was formed by centering the rubber spacer on the top of the magnetic fixture and the washer containing leak proof container was placed on top of the rubber spacer.
In the peel test, the Instron's upper test fixture was adapted to hold a stainless steel fishing leader (wire). The top loop on the leader was directly attached to the Instron load cell by sliding the load cell pin through the loop in the leader. The bottom loop on the leader was attached to a strong metal clip and the jaws of the metal clip were attached to the lidding film overhang. FIG. 9 defines a lidding film overhang of length (r₁₃-r₁₁).
With the washer containing leak proof container securely attached to the magnetic fixture and the strong metal clip attached to the lidding film overhang, the upward movement of the Instron's upper text fixture, travelling at a crosshead speed of 20 inches per minute (50.8 cm/min), generated a displacement-load curve, or a peeling force curve. A typical peeling force curve is shown in FIG. 15. In FIG. 15 five leak proof containers (specimen 1 to 5) were tested, wherein the lidding film was the same, i.e. lidding film Example 3, the monolayer styrene butadiene film described in Table 11. In FIG. 15, each successive displacement-load curve was arbitrarily shifted to the right, this shift made it easier for the viewer to inspect the shape of each curve.
As shown in FIG. 15 there was an initial spike (the left-most peak in FIG. 15) in the peeling force at the point where the leak proof seal was broken; this initial spike was called the “Average Peel Force at Start of Lidding Film Peel Off (Ib-f)” in Table 16. As shown in FIG. 15, a plateau in the peeling force was observed starting at an extension of about 1 inch (2.54 cm) and ending at an extension of about 3 inches (7.6 cm). This plateau in peeling force was called the “Average Plateau Peeling Force” in Table 16. The Average Plateau Peeling Force is the average of five specimens, and it is the peeling force measure as the lidding film is peeled from the upper flange between 1 inch and 3 inches of travel on the upper flange. As shown in FIG. 15 at the end of the peel test, at the moment the lidding film was completely detached from the upper flange, there was a second spike in peeling force (the right-most peak in FIG. 15); this second spike was called the “Average Peel Force at End of Lidding Film Peel Off (Ib-f)” in Table 16. The average peel test results (average of five specimens) are summarized in Table 16.
The present invention will further be described by reference to the following examples. The following examples are merely illustrative of the invention and are not intended to limit the scope of the invention.

EXAMPLES

Example 1

The specifications of expandable polystyrene beads, DYLITE® F271T available from NOVA Chemicals are summarized in Table 1. F271T beads were pre-expanded to produce pre-puff using the continuous pre-expansion conditions shown in Table 2. Pre-expansion was carried out in a Thermoware VA-40 continuous type pre-expander, available from Thermoware EPS Machinery by in Barneveld, The Netherlands. Pre-expansion conditions were adjusted to produce two samples of pre-puff, a high density pre-puff or pre-foam from 3.95 pcf to 4.15 pcf (63.3 g/L to 66.5 g/L) and a low density pre-puff or pre-foam from 2.70 pcf to 2.85 pcf (43.2 g/L to 45.7 g/L).
After pre-expansion, the pre-puff was air dried for 5 minutes to remove moisture and aged from 2 hours to 4 hours prior to molding. Expandable polystyrene containers, cups or bowls, can be fabricated by any conventional molding machine that has an inner shell and an outer shell, for example, Cup Production Model 6-VLC-125 machine made by Autonational B.V., or Model M10 cup machine made by Master Machine and Tool, LLC. 12 ounce (0.35 L) and 16 ounce (0.47 L) cups, and a 16 ounce (0.47 L) noodle bowls were molded using the conditions shown in Table 3, using the Model 6-VLC-125 machine made by Autonational B.V. Once molded, the containers were aged at least 24 hours prior to attaching the lidding film. The width of the upper flange, w_f, of the containers, cups and bowl, are shown in Table 4, w_fis an important parameter; the wider the upper flange the greater the contact area between the bottom portion (EPS cup or bowl) and the lidding film.
Lidding film Example 1 was purchased from Boba Tea Direct, 9674 E. Arapahoe Road #155, Greenwood Village, Colorado 80112. Table 5 shows the structure and composition of lidding film Example 1. The data in Table 5 was generated by FTIR-microscopy; films samples were cut using a Leitz 1400 Microtome and the chemical composition of each layer of the multilayer film, or monolayer film, was determined using a Nicolet Avatar 360 FT-IR spectrometer. As shown in Table 5, lidding film Example 1 had to a total thickness of 3.071 mil (77.9 μm) and consisted of four chemically distinct layers. The inner most layer, or sealant layer, of film Example 1 was composed of poly(ethylene-co-vinyl acetate) or EVA. The EVA in film Example 1 contained 3.2 wt % vinyl acetate. An EVA containing 3.2 wt % of vinyl acetate has a DSC melting point of 108.5° C., based on the linear regression line shown in FIG. 10. As shown in Table 5, the outer most layer of Example 1 was composed of polyethylene terephthalate (PET). The PET layer was adhesively laminated to an intermediate layer of high pressure low density polyethylene (LDPE), as shown in Table 5.
Lidding film Example 1 was sealed to the bottom portion (EPS cups and bowls) using Y-Fang Sealing Machine LTD, Automatic Sealing Machine (Model ET-999S), available from Boba Tea Direct. The Model ET-999S was equipped with a 3.74 inch (95 mm) diameter heat sealing ring and a universal cutter base that fits 3.62 inch (92 mm), 3.74 inch (95 mm) and 3.86 inch (98 mm) diameter cups. The experimental conditions used to attach lidding film Example 1 to EPS cups and bowls are shown in Table 6. The successful attachment of lidding film Example 1 to EPS cups and bowls was a surprising result. The manufacturer, Boba Tea Direct, stated that they do not have a sealing machine that will attached lidding film to EPS cups and their machines can only attach lidding film to polypropylene or polyethylene terephthalate cups.

Example 2

Expandable polystyrene beads, DYLITE® F271T available from NOVA Chemicals, was pre-expanded and molded into cups and bowls, as described in Example 1.
In Example 2, lidding film Example 2 was used. Film Example 2 was a 2.043 mil thick (51.9 μm) four layer film, as shown in Table 9. The data in Table 9 was generated by FTIR-microscopy, as described in Example 1. The inner most layer, or sealant layer, was composed of a random poly(propylene-co-ethylene) sealant. As shown in Table 9, the outer most layer of Example 2 was composed of polyethylene terephthalate (PET). The PET layer was adhesively laminated to an intermediate layer of polypropylene. Lidding film Example 2 was purchased from Boba Tea Direct, 9674E. Arapahoe Road #155, Greenwood Village, Colorado 80112.
Regardless of the setting used on the Automatic Sealing Machine (Model ET-999S), lidding film Example 2 could not be attached to the EPS cups or bowl.
Not wishing to be bound by any theory, it is believed that in the case of lidding film Sample #2, the DSC melting point of the poly(propylene-co-ethylene) inner most layer was too high. In other words, a leak-proof seal between the inner most layer of the lidding film and EPS bottom portion could not be achieved due to a mismatch in thermal properties. However, lower temperature poly(propylene-co-ethylene) sealants are available. For example, Adsyl 5C37F, commercially available from LyondellBasell Industries, has a seal initiation temperature of 105° C., as shown in Table 10. This seal initiation temperature is supported by the DSC thermogram of Adsyl 5C37F, as indicated by the broad melting peak at 104.69° C. shown in FIG. 13. Portions of Adsyl 5C37F also melt at 134.80° C. and 145.65° C. Additional physical properties of Adsyl 5C37F are summarized in Table 10.

Example 3

Expandable polystyrene beads, DYLITE® F271T available from NOVA Chemicals, was pre-expanded and molded into cups and bowls, as described in Example 1.
In Example 3, lidding film Example 3 was used. As shown in Table 11, film Example 3 was a 4.09 mil thick (104 μm) monolayer film containing a styrene butadiene copolymer. The data in Table 11 was generated by FTIR-microscopy, as described in Example 1. Film Example 3 was manufactured by Multiplastics, Inc. 7770 North Central Drive, Lewis Center, Ohio 43035, USA. Table 12 summarizes additional Multiplastic Inc. technical data on film Example 3, referred to as “370W White Lidding Film”. Styrene butadiene copolymers are available from a variety of suppliers. For example, Table 13 summarizes a suitable high impact polystyrene Innova RC600 available from Innova S A, Higienopolis, Porto Alegre, R S Brazil; and Table 14 summarizes a suitable styrene butadiene block copolymer, K-Resin SBC KR01BR, available from Chevron Phillips Chemical Company LLC, The Woodlands, Tex. USA.
Lidding film Example 3 was attached to the bottom portion (EPS cups and bowls) using Y-Fang Sealing Machine LTD, Automatic Sealing Machine (Model ET-999S), available from Boba Tea Direct. The attachment and operation of the Automatic Sealing Machine is described in Example 1. The successful attachment of lidding film Example 3 to EPS cups and bowls produces a leak proof container. Such a leak proof container has the advantage of being 100 percent recyclable under the #6 PS symbol (polystyrene); in addition, the use of a thermoplastic lidding film reduces the mass of lidding material by 74% relative to the commonly used snap-on polystyrene lid.

Lidding Film Puncture Test Results

The average puncture test results (average of five specimens) are summarized in Table 15, as well as the standard deviations, for the two lidding films tested, i.e. film Examples 1 and 3. Film Example 2 was not tested because this film could not be attached to the EPS noodle bowl, or bottom portion. The “average puncture force at straw breakthrough” was the average compressive force in pounds force (Ib-f) required to pierce the lidding film and the “average extension at straw breakthrough” was distance the straw travelled from the point of contacting the lidding film to the point of piercing the lidding film.

Lidding Film Peel Test Results

The average peel test results (average of five specimens) are summarized in Table 16, as well as the standard deviations, for the two lidding films tested, i.e. film Examples 1 and 3. Film Example 2 was not tested because this film could not be attached to the EPS noodle bowl, or bottom portion.

TABLE 1

Specification of DYLITE ® F271T, expandable polystyrene beads,
available from NOVA Chemicals Inc.

	Typical Values	Typical Values
Parameter	(English Units)	(S.I. Units)

Bead Size	0.012 to 0.02	0.3 to 0.5 mm
	inches

	Pentane Content	5.3 to 5.9%
		based on the weight of the EPS beads

Bulk Density	38-40 lbs/ft³	608-640 g/L
Thermal Resistance	4.2 per inch	—
(R-value)
Thermal	0.235	33.9
Conductivity	Btu in/(hr ft²° F.)	milliWatts/(m ° K)
(K-factor, Lambda)
Coefficient of	3.5 × 10⁵in/in/° F.	6.3 cm/cm/° C.
Linear Expansion
Maximum	175° F.	80° C.
Continuous Service
Temperature

TABLE 2

Pre-expansion experimental conditions to
produced EPS pre-puff at two densities.

Container Density (Target)	2.75 pcf (44 g/l)	4.05 pcf (65 g/l)
Feeder Screw Speed	6 rpm	6 rpm
Inlet Steam Temperature	94.0 to 95.5° C.	91.0 to 93.0° C.
Steam Pressure	0.50 to 0.60 bar	0.50 to 0.60 bar
	(0.05 to 0.06 MPa)	(0.05 to 0.06 MPa)
Air Pressure	0.40 to 0.60 bar	0.75 to 1.00 bar
	(0.04 to 0.06 MPa)	(0.075 to 0.1 MPa)
Fluidized Bed Dryer Air	175 to 185° F.	175 to 185° F.
Temperature	(79.4 to 85° C.)	(79.4 to 85° C.)
Pre-puff Density Range	2.70 to 2.85 pcf	3.95 to 4.15 pcf
	(43.2 to 45.7 g/L)	(63.3 to 66.5 g/L)

TABLE 3

Container molding conditions using the M-10 cup
molding machine made by Master Machine and Tool,
LLC. Containers were produced at two densities.

Container Density (Target)	2.75 pcf (44 g/L)	4.05 pcf (65 g/L)
Mold Used	12 or 16 ounce cup	16 ounce noodle bowl
	(0.35 L or 0.47 L)	(0.47 L)
Pre-puff Aging Time	2 to 4 hours	2 to 4 hours
(after Pre-Expansion)
Steam Pressure	22 to 28 psig	22 to 28 psig
	(0.15 to 0.19 MPa)	(0.15 to 0.19 MPa)
Air Pressure	90 to 100 psig	90 to 100 psig
	(0.62 to 0.69 MPa)	(0.62 to 0.69 MPa)
Cooling Water Temperature	100 to 115° F.	100 to 115° F.
	(38 to 46° C.)	(38 to 46° C.)
Fill Time	1.0 to 1.5 seconds	2.0 to 3.0 seconds
Pre-heat Time	1.5 to 2.5 seconds	2.0 to 3.0 seconds
Cook Time	2.5 to 3.5 seconds	4.0 to 6.0 seconds
Cool Time	3.0 to 4.0 seconds	4.5 to 6.0 seconds
Total Cycle Time	12.0 to 13.5 seconds	18.5 to 20.0 seconds

TABLE 4

Upper Flange dimensions of 12, 16 and
32 ounce cups and 16 ounce noodle bowl.

Cups

			32 ounce	16 ounce
	12 ounce	16 ounce	step cup	noodle
Dimension	(0.35 L)	(0.47 L)	(0.94 L)	bowl (0.47 L)

Upper Flange	0.126 inch	0.116 inch	0.122 inch	0.144 inch
Width	(3.21 mm)	(2.96 mm)	(3.09 mm)	(3.77 mm)
w_f= (r₁− r₂)

TABLE 5

Multilayer structure of lidding film Example 1 (12-10952).

	Film Layer	Film Layer
	Thickness	Thickness
Film Layer	(mils)	(micron)	Material

1	1.08	27.4	EVA (3.2% VA)
			Inner most, or Sealant Layer
2	1.33	33.7	LDPE
3	0.051	1.3	Adhesive
4	0.61	15.5	Polyethylene terephthalate
	Total: 3.071	Total: 77.9

TABLE 6

Lidding film attachment (sealing) conditions used: Automatic Sealing
Machine (Model ET-999S), available from Boba Tea Direct.

Sealing Conditions

Container	12 or 16 ounce cup	16 ounce noodle
	(0.35 L or 0.47 L)	bowl (0.47 L)
Sealing Temperature Setting	120-140° C.	120-140° C.
Sealing Time	1.5-2.5 seconds	1.5-2.5 seconds
Settling/Rest Time	1.5-2.5 seconds	1.5-2.5 seconds

TABLE 7

Poly(ethylene-co-ethylene vinyl acetate), Elvax 3135X
Ethylene Vinyl Acetate Copolymer, available from
DuPont Packaging and Industrial Polymers. Data extracted
from Elvax 3135X Technical Datasheet.

	Nominal Value
Property	Unit	Test Method

Specific Gravity

0.930

g/cm³

ASTM D792, ISO 1183

Melt Mass-Flow Rate	0.35 g/10 min	ASTM D1238, ISO 1133
(MFR) (190° C./2.16 kg)

Vinyl Acetate Content	12.0	wt %
Vicat Softening	82.0°	C.	ASTM D1525, ISO 306
Temperature
Melting Temperature (DSC)	95°	C.	ASTM D3418, ISO 3146
Freezing Point (DSC)	78°	C.	ASTM D3418, ISO 3146
Extrusion Melt	<230°	C.
Temperature

Fabrication Conditions for blown film: screw size 2.5 in. (63.5 mm); extruder barrel 24:1 L/D; screw type DSB II; die gap 70 mil (1.8 mm); melt temperature 430° F. (221° C.); output 6 lb/hr/in of die circumference; die diameter 6 inch; blow-up ratio 2.5:1; screw speed 40 rpm.

TABLE 8

Poly(ethylene-co-1-octene) plastomer, Affinity
PL 1881G, available from Dow Chemical. Data
extracted from PL 1881G Technical Datasheet.

	Nominal Value
Property	Unit	Test Method

Specific Gravity

0.904

g/cm³

ASTM D792

Melt Mass-Flow Rate (MFR)	1.0 g/10 min	ASTM D1238
(190° C./2.16 kg)

Seal initiation Temperature	85°	C.	Dow Internal
			Method
Melting Temperature (DSC)	100°	C.	Dow Internal
			Method
Vicat Softening Temperature	86.0°	C.	ASTM D1525

Coefficient of Friction	0.15	ASTM D1894
(vs Itself-Dynamic)

Film Thickness - Tested	51	μm
Film Puncture Energy	8.09	J	Dow Internal
			Method
Film Puncture Force	52.3	N	Dow Internal
			Method
Film Puncture Resistance	21.9	J/cm³	Dow Internal
			Method
Secant Modulus
2% Secant, MD	97.4	MPa	ASTM D882
Secant Modulus
2% Secant, TD	96.9	MPa	ASTM D882
Tensile Strength MD Yield	8.07	MPa	ASTM D882
Tensile Strength TD Yield	7.17	MPa	ASTM D882
Tensile Strength MD Break	45.4	MPa	ASTM D882
Tensile Strength TD Break	42.5	MPa	ASTM D882

Tensile Elongation, MD Break	590%	ASTM D882
Tensile Elongation, TD Break	630%	ASTM D882

Dart Drop Impact	>830	g	ASTM D1709B
Elmendorf Tear Strength, MD	560	g	ASTM D1922
Elmendorf Tear Strength, TD	730	g	ASTM D1922
Block Force	70	g	ASTM D3354-89

Gloss (20°)	112	ASTM D2457
Clarity	83.0	ASTM D1746
Haze	3.2%	ASTM D1003

Extrusion Melt Temperature	221°	C.

Fabrication Conditions for blown film: screw size 2.5 in. (63.5 mm); extruder barrel 24:1 L/D; screw type DSB II; die gap 70 mil (1.8 mm); melt temperature 430° F. (221° C.); output 6 lb/hr/in of die circumference; die diameter 6 inch; blow-up ratio 2.5:1; screw speed 40 rpm.

TABLE 9

Multilayer structure of lidding film Example 2 (12-10953).

	Film Layer	Film Layer
	Thickness	Thickness
Film Layer	(mils)	(micron)	Material

1	0.25	6.3	Poly(propylene-co-ethylene)
			Inner most, or Sealant Layer
2	1.23	31.3	Polypropylene
3	0.067	1.7	Adhesive
4	0.496	12.6	Polyethylene terephthalate
	Total: 2.043	Total: 51.9

TABLE 10

Poly(propylene-co-ethylene) sealant Adsyl 5 C 37 F,
available from LyondellBasell Industries. Data extracted
from Adsyl 5 C 37 F Technical Datasheet.

	Nominal
Property	Value Unit	Test Method

Specific Gravity	0.900	g/cm³	ASTM D792, ISO
			1183/A

Melt Mass-Flow Rate (MFR)	5.5 g/10 min	ASTM D1238,
(230° C./2.16 kg)		ISO 1133

Seal initiation Temperature	105°	C.
Melting Temperature	132°	C.	ISO 11357-3
Vicat Softening Temperature	107°	C.	ISO 306/A50
Tensile Strength (Yield)	21.4	MPa	ASTM D638

Tensile Elongation (Yield)

13%

ASTM D638

Flexural Modulus 1% Secant	648	MPa	ASTM D790A
Film Thickness - Tested	50	μm
Tensile Modulus MD, Cast Film	280	MPa	ISO 527-3/25
Secant Modulus TD, Cast Film	280	MPa	ISO 527-3/25
Tensile Stress MD Yield, Cast Film	14.0	MPa	ISO 527-3/500
Tensile Stress TD Yield, Cast Film	14.0	MPa	ISO 527-3/500
Tensile Stress MD Break, Cast Film	45.0	MPa	ISO 527-3/500
Tensile Stress TD Break, Cast Film	35.0	MPa	ISO 527-3/500

Tensile Elongation MD Yield, Cast	17%	ISO 527-3/500
Film
Tensile Elongation TD Yield, Cast	15%	ISO 527-3/500
Film
Tensile Elongation MD Break, Cast	900%	ISO 527-3/500
Film
Tensile Elongation TD Break, Cast	800%	ISO 527-3/500
Film

Notched Izod Impact (23° C.)	85	J/m	ASTM D256A
Deflection Temperature Under Load,	62.8°	C.	ASTM D648
0.45 MPa unannealed
Deflection Temperature Under Load,	62.0°	C.	ISO 75-2/B
0.45 MPa unannealed

Gloss (45°, 50 μm, Cast Film)	87	ASTM D2457
Haze	1.0%	ASTM D1003

TABLE 11

Monolayer structure of lidding film Example 3 (13-09907).

	Film Layer	Film Layer
	Thickness	Thickness
Film Layer	(mils)	(micron)	Material

1	4.09	104	Styrene Butadiene
			Copolymer
	Total: 4.09	Total: 104

TABLE 12

Example 3, data extracted from Multiplastics, Inc.
product data sheet on 370W White Lidding Film.

Property	Units	Typical Values

Vicat Softening	° F. (° C.)	194 (90)
Point
Tensile Strength	psi (MD (Machine Direction))	4,500
	psi (TD (Transverse	4,700
	Direction))
Elongation at Break	% (MD)	55
	% (TD)	45
COF		0.44 to 0.55
Gloss (45°)		16 to 25
Treatment Level	Dynes (treated side)	≧45
	Dynes (untreated side)	38
WVTR (water vapor	g/100 in²/24 hr	1.14
transmission rate)
OTR (oxygen	cm³/100 in²/24 hr	93.6
transmission rate)
CO₂transmission	cm³/100 in²/24 hr	645
rate

TABLE 13

High Impact Polystyrene (HIPS), Innova RC600, data
extracted from Innova SA technical datasheet.

	Nominal Value
Property	Unit	Test Method

Specific Gravity	1.04	g/cm³	ASTM D792, ISO
			1183

Melt Mass Flow Rate (MFR)	6.0 g/10 min	ASTM D1238, ISO
(200° C./5 kg)		1133
Vicat Softening Point	196° F. (91° C.)	ASTM D1525, ISO
		306/A50
Tensile Strength	3,916 psi (27 MPa)	ASTM D638
(Break,, 23° C.)
Tensile Elongation	40%	ATM D638, ISO
(Break, 23° C.)		527-2
Rockwell Hardness	80	ASTM D785, ISO
(L-scale)		2039-2

Notched Izod Impact	70	J/m	ASTM D256
(23° C., 3.2 mm)

TABLE 14

Styrene butadiene block copolymer (K-Resin SBC
KR01BR); data extracted from Chevron Phillip
Chemical Company LLC technical datasheet..

	Nominal Value
Property	Unit	Test Method

Specific Gravity

1.01

g/cm³

ASTM D792

Melt Mass-Flow Rate (MFR)	8.0 g/10 min	ASTM D1238
(230° C./2.16 kg)
Vicat Softening Point	194° F. (90° C.)	ASTM D1525

Tensile Strength (Yield)

4,844

psi

ASTM D638

Tensile Elongation (Break)	30%	ASTM D638
Durometer Hardness (Shore D)	69	ASTM D2240

TABLE 15

Leak proof container lidding film puncture test
results (average of five puncture tests).

Film	Film	Film
Example 1	Example 2	Example 3

Average puncture force	4.68 ± 0.73	film failed	5.31 ± 0.76
at straw breakthrough		to seal
(lb-f)
Average extension at	0.348 ± 0.049	film failed	0.269 ± 0.020
straw breakthough		to seal
(inches)

TABLE 16

Leak proof container lidding film peel test
results (average of five peel tests).

	Film	Film	Film
Measurement	Example 1	Example 2	Example 3

Average Peel Force at	1.69 ± 0.13	film failed	1.26 ± 0.092
Start of Lidding Film Peel		to seal
Off (lb-f)
Average Peel Extension	0.196 ± 0.013	film failed	0.197 ± 0.020
at Start of Lidding Film		to seal
Peel Off (inches)
“Average Plateau	0.480 ± 0.078	film failed	0.384 ± 0.019
Peeling Force (lb-f)”		to seal
peeling force between 1
inch and 3 inch of travel
on the upper flange
Average Peel Force at	2.02 ± 0.17	film failed	1.28 ± 0.22
End of Lidding Film Peel		to seal
Off (lb-f)
Average Peel Extension	3.65 ± 0.02	film failed	3.56 ± 0.019
at End of Lidding Film		to seal
Peel Off (inches)

While the present invention has been particularly set forth in terms of specific embodiments thereof, it will be understood in view of the instant disclosure that numerous variations upon the invention are now enabled yet reside within the scope of the invention. Accordingly, the invention is to be broadly construed and limited only by the scope and spirit of the claims now appended hereto.

Claims

What is claimed is:

1. A leak proof container for packaging food or drink comprising: a bottom portion having an upper flange circumferentially extending around at least one compartment for supporting a food or drink, wherein said bottom portion comprises expanded thermoplastic beads; and a lidding film attached to said upper flange, forming a leak proof seal, enclosing said food or drink.

2. A leak proof container according to claim 1, wherein said bottom portion comprises expanded polystyrene beads.

3. A leak proof container according to claim 2, wherein said bottom portion has a density from 0.5 pounds per cubic foot (8 g/L) to 12 pounds per cubic foot (192 g/L).

4. A leak proof container according to claim 3, wherein said lidding film is a monolayer film.

5. A leak proof container according to claim 4, wherein said monolayer lidding film comprises a styrene butadiene copolymer.

6. A leak proof container according to claim 5, wherein an Average Plateau Peeling Force required to peel said monolayer lidding film from said leak proof container is greater than 0.32 pounds-force, or 1.4 Newton; wherein said Average Plateau Peeling Force is calculated from an Instron load-displacement curve (extension-mode) as said monolayer lidding film is peeled from 1 inch to 3 inches of travel on said upper flange.

7. A leak proof container according to claim 5, wherein said monolayer lidding film attached to said leak proof container has an Average Puncture Force at Straw Breakthrough that is greater than 2.9 pounds-force, or 13 Newton; wherein said Average Puncture Force at Straw Breakthrough is calculated from an Instron load-displacement curve (compression-mode).

8. A leak proof container according to claim 4, wherein said monolayer lidding film comprises an ethylene vinyl acetate copolymer containing from 3 wt % to 16 wt % vinyl acetate and a melt index from 0.2 dg/min to 20 dg/min; wherein melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.

9. A leak proof container according to claim 4, wherein said monolayer lidding film comprises a polyolefin with a DSC melting point from 90° C. to 125° C. and a melt index from 0.2 dg/min to 20 dg/min; wherein melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.

10. A leak proof container according to claim 3, wherein said lidding film is a multilayer film.

11. A leak proof container according to claim 10, wherein said multilayer lidding film comprises an inner most layer comprising a styrene butadiene copolymer.

12. A leak proof container according to claim 11, wherein an Average Plateau Peeling Force required to peel said multilayer lidding film from said leak proof container is greater than 0.32 pounds-force, or 1.4 Newton; wherein said Average Plateau Peeling Force is calculated from an Instron load-displacement curve (extension-mode) as said monolayer lidding film is peeled from 1 inch to 3 inches of travel on said upper flange.

13. A leak proof container according to claim 10, wherein said multilayer lidding film comprises an inner most layer comprising an ethylene vinyl acetate copolymer containing 3 wt % to 16 wt % vinyl acetate and a melt index from 0.2 dg/min to 20 dg/min; wherein the melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.

14. A leak proof container according to claim 13, wherein an Average Plateau Peeling Force required to peel said multilayer lidding film from said leak proof container is greater than 0.24 pounds-force, or 1.1 Newton; wherein said Average Plateau Peeling Force is calculated from an Instron load-displacement curve (extension-mode) as said multilayer lidding film is peeled from 1 inch to 3 inches of travel on said upper flange.

15. A leak proof container according to claim 10, wherein the multilayer lidding film comprises an inner most layer comprising a polyolefin with a DSC melting point from 90° C. to 125° C. and a melt index from 0.2 dg/min to 20 dg/min; wherein the melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.

16. A process for producing a leak proof container for food or drink comprising: (A) shape molding a bottom portion having an upper flange circumferentially extending around at least one compartment for supporting a food or drink, wherein said bottom portion comprises expanded thermoplastic beads; (B) transporting said bottom portion to a filling station; (C) filling said compartment(s) with said food or drink, forming a filled container; (D) transporting said filled container to a lidding station; (E) attaching a lidding film to said upper flange on said filled container, forming a leak proof container; (F) manually transporting said leak proof container to a point of purchase (single serving retail counter), or optionally mechanically transporting said leak proof container to a fully integrated bulk packaging line.

17. A process according to claim 16, wherein said bottom portion comprises expanded polystyrene beads.

18. A process according to claim 17, wherein said bottom portion has a density from 0.5 pounds per cubic foot (8 g/L) to 12 pounds per cubic foot (192 g/L).

19. A process according to claim 18, wherein said lidding film is a monolayer film.

20. A process according to claim 19, wherein said monolayer lidding film comprises a styrene butadiene copolymer.

21. A process according to claim 20, wherein an Average Plateau Peeling Force required to peel said monolayer lidding film from said leak proof container is greater than 0.32 pounds-force, or 1.4 Newton; wherein said Average Plateau Peeling Force is calculated from an Instron load-displacement curve (extension-mode) as said monolayer lidding film is peeled from 1 inch to 3 inches of travel on said upper flange.

22. A process according to claim 20, wherein said monolayer lidding film attached to said leak proof container has an Average Puncture Force at Straw Breakthrough that is greater than 2.9 pounds-force, or 13 Newton; wherein said Average Puncture Force at Straw Breakthrough is calculated from an Instron load-displacement curve (compression-mode).

23. A process according to claim 19, wherein said monolayer lidding film comprises an ethylene vinyl acetate copolymer containing from 3 wt % to 16 wt % vinyl acetate and a melt index from 0.2 dg/min to 20 dg/min; wherein melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.

24. A process according to claim 19, wherein said monolayer lidding film comprises a polyolefin with a DSC melting point from 90° C. to 125° C. and a melt index from 0.2 dg/min to 20 dg/min; wherein melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.

25. A process according to claim 18, wherein said lidding film is a multilayer film.

26. A process according to claim 25, wherein said multilayer lidding film comprises an inner most layer comprising styrene butadiene copolymer.

27. A process according to claim 26, wherein an Average Plateau Peeling Force required to peel said multilayer lidding film from said leak proof container is greater than 0.32 pounds-force, or 1.4 Newton; wherein said Average Plateau Peeling Force is calculated from an Instron load-displacement curve (extension-mode) as said monolayer lidding film is peeled from 1 inch to 3 inches of travel on said upper flange.

28. A process according to claim 25, wherein said multilayer lidding film comprises an inner most layer comprising an ethylene vinyl acetate copolymer containing 3 wt % to 16 wt % vinyl acetate and a melt index from 0.2 dg/min to 20 dg/min; wherein the melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.

29. A process according to claim 28, wherein an Average Plateau Peeling Force required to peel said multilayer lidding film from said leak proof container is greater than 0.24 pounds-force, or 1.1 Newton; wherein said Average Plateau Peeling Force is calculated from an Instron load-displacement curve (extension-mode) as said multilayer lidding film is peeled from 1 inch to 3 inches of travel on said upper flange.

30. A process according to claim 25, wherein the multilayer lidding film comprises an inner most layer comprising a polyolefin with a DSC melting point from 90° C. to 125° C. and a melt index from 0.2 dg/min to 20 dg/min; wherein the melt index is determined by ASTM D-1238 at 190° C. and a 2.16 kg load.