THERMOFORMED PACKAGING ARTICLES WITH ALTERNATING INDIVIDUAL LAYERS OF GLASS AND PLASTIC

Abstract

The present invention is directed to thermoformed packaging articles comprising a coextruded film having alternating individual layers of glass and plastic. These thermoformed packaging articles may be used for packaging oxygen- and/or moisture sensitive foods and pharmaceutical/medical/dental products.

Claims

1. A thermoformed packaging article comprising: a draw depth within a range from 2.5 mm to 254 mm, a multilayer packaging film comprising a coextruded film comprising alternating layers of glass and plastic, wherein the number of glass layers is at least two and the number of plastic layers is at least one, wherein the multilayer packaging film has a total thickness within a range from 10 m to 250 m, and wherein the glass comprises on an elemental basis tin in a mole percentage within a range from 12.0 to 17.1, fluorine in a mole percentage within a range from 11.2 to 24.3, phosphorus in a mole percentage within a range from 12.1 to 19.6, and oxygen in a mole percentage within a range from 43.3 to 61.1.

2. A thermoformed packaging article of claim 1, wherein the multilayer packaging film has a water vapor transmission rate within a range from 0 to 1 g/m.sup.2/24 hour at 38 C. and 90% relative humidity.

3. A thermoformed packaging article of claim 1, wherein the multilayer packaging film has an oxygen transmission rate within a range from 0 to 1 cm.sup.3/m.sup.2/24 hour at 23 C. and 0% relative humidity.

4. A thermoformed packaging article of claim 1, wherein the plastic comprises aliphatic and aromatic polyamides, polyethers, polyimides, aliphatic and aromatic polyesters, cyclic olefin copolymers, polyolefin homopolymers and copolymers, high density polyethylenes, anhydride-modified polyethylenes, ethylene vinyl acetate copolymers, polypropylenes, polyamideimides, polycarbonates, polyetheretherketones, polyetherimides, polyethersulphones, polymethyl methacrylates, polyoxymethylenes, polyphenylene sulphides, polystyrenes, unplasticized polyvinyl chlorides, and blends thereof.

5. A thermoformed packaging article of claim 1, wherein the glass has a glass transition temperature, T.sub.g of less than 200 C.

6. A thermoformed packaging article of claim 1, wherein the glass has a glass transition temperature, To of less than 150 C.

7. A thermoformed packaging article of claim 1, wherein the glass comprises on an elemental basis tin in a mole percentage within a range from 15.4 to 17.1, fluorine in a mole percentage within a range from 19.6 to 24.3, phosphorus in a mole percentage within a range from 14.2 to 16.6, and oxygen in a mole percentage within a range from 43.3 to 56.

8. A thermoformed packaging article of claim 1, wherein the number of glass layers is at least ten and the number of plastic layers is at least ten.

9. A thermoformed packaging article of claim 1, further comprising a sealant layer.

10. A thermoformed packaging article of claim 1, further comprising an abuse layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] As used herein, the terms comprises, comprising and grammatical variations thereof are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0024] Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which:

[0025] FIG. 1 is a drawing illustrating the viscosity-shear rate curves of a tin fluorophosphate glass, SnF Glass and a glycol-modified polyethylene terephthalate copolymer, SKYGREEN PETG SK2008.

[0026] FIG. 2 is a conceptual drawing illustrating general embodiments of the thermoformed packaging articles comprising a coextruded film having alternating individual layers of glass and plastic.

[0027] FIG. 3 is a conceptual drawing illustrating a thermoformed packaging article having a hemispherical shape formed from a coextruded film having alternating individual layers of glass and plastic.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The thermoformed packaging articles now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0029] FIG. 2 is a conceptual drawing illustrating general embodiments of multilayer packaging film 10 comprising a coextruded film having alternating individual layers of glass and plastic. In this drawing, layers designated as A represent a heat sealing material, layers designated as B represent a polymer, and layers designated as C represent a glass. Reference n represents a multiplier of an eight-layer set of alternating individual layers of glass and plastic. This drawing represents different examples that were fabricated with the total number of alternating individual layers of glass and plastic of the coextruded film varying between 17, 65 and 257 when n=2, 8 and 32, respectively.

Examples

[0030] Examples 1-10 of multilayer packaging films were prepared having structures illustrated in FIG. 2. A batch material of tin fluorophosphate glass was prepared having a molar composition of 20% SnO+50% SnF.sub.2+30% NH.sub.4H.sub.2PO.sub.4 by melting in the carbon crucible at 500 C. in air in an electric furnace for 15 minutes, casting the molten composition onto aluminum and cooling to room temperature. The cooled sintered glass composition was ground to a particle size of approximately 3 mm. This glass composition is denoted by reference Layer C and had, on an elemental basis, tin in a mole percentage within a range from 15.4 to 17.1, fluorine in a mole percentage within a range from 19.6 to 24.3, phosphorus in a mole percentage within a range from 14.2 to 16.6, and oxygen in a mole percentage within a range from 43.3 to 56. A first plastic resin denoted as Layer B was introduced into a first extruder and heated to a temperature sufficient to plasticize the resin to produce a first plastic flow stream. Generally this temperature was above a melting point of the crystalline or semi-crystalline plastic resin, and/or at or above the glass transition temperature for an amorphous plastic resin. Next, the glass composition described above as Layer C was introduced into a second extruder and heated to above its glass transition temperature to produce a glass flow stream. The first plastic and glass flow streams were sent through a feed-block manifold to produce a vertically stacked flow stream of alternating layers of plastic and glass having a three-layer sequence of plastic/glass/plastic or Layer B/Layer C/Layer B. The feed-block manifold was manipulated to multiply this three-layer sequence to produce multiple three-layered vertically stacked flow streams. For example, doubling of a three-layer sequence can produce a five-layer flow stream having the sequence of plastic/glass/plastic/glass/plastic or Layer B/Layer C/Layer B/Layer C/Layer B while a doubling of the five-layer sequence can produce a nine-layer sequence of plastic/glass/plastic/glass/plastic/glass/plastic/glass/plastic or Layer B/Layer C/Layer B/Layer C/Layer B/Layer C/Layer B/Layer C/Layer B. While the feed-block manifold multiplied the three-layer plastic/glass/plastic flow stream, a second plastic resin denoted as Layer A was introduced into a third extruder. This second plastic resin was heated to a temperature sufficient to plasticize the resin to produce a second plastic flow stream which entered the feed-block manifold. The flow streams of the multiplied three-layered sequence of plastic and glass (Layer B/Layer C/Layer B), and that for Layer A then exited simultaneously through an extrusion slot die head to produce the embodiments depicted in FIG. 2. The construction of some embodiments of the packaging films are reported below in TABLE 1. The oxygen and moisture permeability for some of these packaging films were measured and also reported below in TABLE 1.

TABLE-US-00001 TABLE 1 Total Oxygen Moisture Vapor Total # Thickness Transmission Transmission Layer Layer Layer of Glass/ Film Rate Rate Ex. A B C n Plastic (micron) (cm.sup.3/m.sup.2/24 h) (grams/m.sup.2/24 h) 1 A B1 C 2 17 50 0.90 0.32 2 A B1 C 2 17 25 3 A B1 C 8 65 50 0.12 0.70 4 A B1 C 8 65 25 0.05 0.22 5 A B1 C 32 257 50 6 A B2 C 2 17 25 7 A B2 C 8 65 50 0.15 0.09 8 A B2 C 8 65 25 9 A B3 C 32 257 50 10 A B4 C 32 257 50 A = a low density polyethylene, DOW LDPE 640I (The Dow Chemical Company, Midland MI) having a density of 0.922 g/cm.sup.3, and a melt flow rate of 2.0 g/10 min. B1 = a glycol-modified polyethylene terephthalate copolymer, SKYGREEN PETG SK2008 (SK Chemicals, Pangyo, Korea) having a glass transition temperature of 80 C. B2 = a polyamide, nylon 6, BASF Ultramid B36 (BASF Corporation, Wyandotte, MI) having a density of 1.13 g/cm.sup.3 and a melting temperature of 220 C. B3 = a thermoplastic polyurethane, Elastollan WY1158 (BASF Corporation, Wyandotte, MI). B4 = an ethylene acrylic acid copolymer, PRIMACOR 1430 (The Dow Chemical Company, Midland MI) having a density of 0.930 g/cm.sup.3, and a melt flow rate of 5.0 g/10 min (190 C./2.16 kg).

[0031] Turning now to FIG. 3, there is shown a thermoformed packaging article 20. Film 21 was a multilayer packaging film having a structure and composition identical to Example 8 (Ex. 8) as described above. Article 20 was made by heating the top side of film 21 using a conventional tabletop thermoforming machine set to a temperature of 140 C. for 2 seconds. The softened film was then drawn down into the mold by application of vacuum (507 mm Hg) until the film conformed to the shape of the mold. The mold had a radius, r, of 25 mm and a draw depth, d, of 25 mm. After thermoforming, the packaging article 20 had no visible signs of breaking or cracking.

[0032] The above description and examples illustrate certain embodiments of the present invention and are not to be interpreted as limiting. Selection of particular embodiments, combinations thereof, modifications, and adaptations of the various embodiments, conditions and parameters normally encountered in the art will be apparent to those skilled in the art and are deemed to be within the spirit and scope of the present invention.