WO2012037180A1

WO2012037180A1 - Coextruded multilayer film structure

Info

Publication number: WO2012037180A1
Application number: PCT/US2011/051483
Authority: WO
Inventors: Jeffrey E. Bonekamp; Stephen J. Skapik
Original assignee: Dow Global Technologies Llc
Priority date: 2010-09-16
Filing date: 2011-09-14
Publication date: 2012-03-22

Abstract

Disclosed is a multilayer film structure. More particularly the present invention relates to a formable, high vapor barrier multilayer film structure comprising at least four layers, a core layer comprising a polyvinylidene chloride resin, a first tie layer, a second tie layer, and a first outer layer, wherein the copolyester outer layer has an intrinsic viscosity of 0.4 dl/g to 0.7 dl/g. Optionally, the multilayer film structure comprises a second outer layer comprising one or more copolyester resin. The multilayer film structure may optionally have one or more inner layer and/or one or more additional tie layer between each of the outer/inner layers and the first and second tie layers. The multilayered films of the present invention are particularly well suited for use in food and medical packaging applications, particularly in medicine packaging applications such as blister packs.

Description

COEXTRUDED MULTILAYER FILM STRUCTURE

CROSS REFERENCE STATEMENT

This application claims the benefit of U.S. Provisional Application No. 61/383,534, filed September 16, 2010, which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to a coextruded multilayer film structure. More particularly the present invention relates to a formable, high vapor barrier multilayer film structure comprising at least four layers: a core layer comprising a polyvinylidene chloride resin, a first tie layer, a second tie layer, and a first outer layer comprising one or more amorphous copolyester resin wherein the amorphous copolyester resin has an intrinsic viscosity of from 0.4 dl/g to 0.7 dl/g.

BACKGROUND OF THE INVENTION

A wide variety of thermoplastic resins are presently known, and films formed from such thermoplastic resins feature chemical and physical characteristics which are related to the thermoplastic resin from which they are formed. Important physical characteristics of films which are of significant interest to the art include the barrier properties, including gas and/or vapor such as water vapor, of the film as well as the physical characteristics, such as toughness, wear and weathering resistances, and light-transmittance. Processing capability of such films, for example thermoformability, is also often advantageous for many packaging applications. Such properties are especially important in the film applications wherein such properties are critical; one example of which includes the use of films as a packaging material for foodstuffs or medicinal drugs. However, rarely can a single thermoplastic resin provide all the physical characteristics and barrier properties required in such packaging applications.

A suitable means of achieving the balance of barrier, thermoformability and physical characteristics needed in a packaging material is to form a multilayer structure in which one polymer film is laminated with one or more different polymer film(s). In such a laminate structure, the different polymer films providing different attributes, in other words one provides physical characteristics while another provides barrier properties. For example, USP 4,677,017; 4,659,625; and 5,139,878 discloses multilayered films comprising an inner layer of a fluoropolymer, for barrier properties, and outer layers of a polyester resin, for the required physical characteristics, specifically, toughness, and thermoformability. Typically, fluoropolymers and polyesters are compatible as both require relatively high processing temperatures. However, this approach has several drawbacks, fluoropolymers are expensive and they require specialized adhesive layers to bond to the polyester layers as fluoropolymers are known for their non-stick characteristics.

Alternatively, copolymers of vinylidene chloride (PVDC) with vinyl chloride or methyl acrylate are known to provide excellent barrier characteristics. Extruded and coextruded films containing a barrier layer of PVDC copolymer having from 75 to 98 percent vinylidene chloride provide excellent barrier with respect to transportation of oxygen, water, carbon dioxide and flavoring for food, medical and other high barrier packaging. Vinylidene chloride copolymers and their uses are described in numerous references, such as R. A. Wessling, Polyvinylidene Chloride (Gordon & Breach Sci. Pub. 1977) and 23 Ency. Chem. Tech., Vinylidene Chloride and Poly(Vinylidene Chloride), 764 (J. Wiley & Sons 1983).

It would be desirable to have a formable, tough and clear PVDC barrier film produced by the coextrusion process. PVDC resins are a cost effective barrier resin alternative. However, PVDC resins alone can not provide the required physical

characteristics for many packaging applications. Moreover, they are generally susceptible to thermal degradation during extrusion which has limited their use in multilayered films with traditional outer layers, such as the polyesters discloses in USP 5,139,878. PVDC resins process considerably cooler than temperatures recommended for, and commonly run for, coextrusion of amorphous copolyester resins. These copolyester process temperatures are commonly targeted within a range of 246°C to 274°C, with key target temperature of 260°C as per the literature (e.g., Eastman processing guide for EASTAR™ PETG copolyester 6763, Publication DDS-1B, Mayl994)). Processing temperature required for such polyesters may cause PVDC degradation resulting in holes in the barrier film from HC1 gas generated during processing, resulting in significant yellowing or browning of the PVDC layer and coextruded film or resulting in specks of carbonaceous material to appear in the coextruded product. The level of degradation ordinarily increases at higher extrusion rates, which produce higher temperatures in the polymer. Holes are untenable in barrier film, and color generation and carbonaceous material is unsightly and may cause the customer of the extruded product to reject the product.

There remains a continuing need in the art for further improvements in formable multilayered film structures for food stuff and medicinal drug packaging applications, particularly those which provide a film structure featuring low water vapor and gas transmission, and good physical characteristics.

SUMMARY OF THE INVENTION

The present invention is such a coextruded multilayer film structure comprising at least four layers, a core layer (B), a first tie layer (X , a second tie layer (X₂), and a first outer layer (A) wherein:

i) the core layer is disposed between the first and second tie layers and

comprises a copolymer of polyvinylidene chloride resin (PVDC), ii) the first tie layer comprises a first polymer and the second tie layer

comprises a second polymer wherein the first polymer may be the same or different than the second polymer and the polymer(s) is an alkyl ester copolymer, a grafted alkyl ester copolymer, a modified polyolefin, or blends thereof, and

iii) the first outer layer comprises a first amorphous copolyester having an

intrinsic viscosity (IV) of from 0.40 dl/g to 0.70 dl/g,

wherein the core layer is sandwiched between the first and second tie layers and the first outer layer is adjacent to the first tie layer represented by the structure: AXiBX₂.

In one embodiment, the present invention is the coextruded multilayer film structure disclosed herein above further comprising a second outer layer (C) wherein the second outer layer comprises a second amorphous copolyester having an intrinsic viscosity of from 0.40 dl/g to 0.70 dl/g, said second amorphous copolyester may be the same or different than the first copolyester, wherein the second tie layer is adjacent to the second outer layer represented by the structure AXiBX₂C.

In a preferred embodiment, the present invention is the coextruded multilayer film structure disclosed herein above wherein the first outer layer and the second outer layer comprise the same copolyester and the first tie layer and the second tie layer comprise the same polymer having the structure AXBXA.

In another embodiment, the present invention is the coextruded multilayer film structure disclosed herein above wherein the first amorphous copolyester and/or second amorphous copolyester independently have an intrinsic viscosity (IV) of from 0.45 dl/g to 0. 65 dl/g.

In one embodiment, the present invention is the coextruded multilayer film structure disclosed herein above wherein the polyvinylidene chloride resin comprises a copolymer of vinylidene chloride and methyl methacrylate, wherein the methyl methacrylate is present in an amount of 4.8 to 8.5 weight percent based on the weight of the copolymer.

In another embodiment, the present invention is the coextruded multilayer film structure disclosed herein above wherein the first and second tie layers independently comprise a maleic anhydride grafted polyethylene (gMAH-PE), a maleic anhydride grafted ethylene/ethyl acetate copolymer (gMAH- EEA), a maleic anhydride grafted

ethylene/maleic anhydride copolymer (gMAH- EMA), a maleic anhydride grafted ethylene/vinyl acetate copolymer (gMAH- EVA), a maleic anhydride grafted ethylene/n- butyl acetate copolymer (gMAH-EnBA), or mixtures thereof.

In one embodiment, the present invention is the coextruded multilayer film structure disclosed herein above further comprising a second outer layer (C) wherein the second outer layer comprises one or more of the following resins: homopolymer polypropylene, random polypropylene, substantially isotactic propylene, polyethylene, copolymer of ethylene and vinyl acetate, copolymer of ethylene and methyl acrylate, copolymer of ethylene and ethyl acrylate, copolymer of ethylene and carbon monoxide, copolymer of ethylene and n-butyl acrylate, terpolymer of ethylene, acrylic acid and carbon monoxide, terpolymer of ethylene, n-butyl acrylate and carbon monoxide, terpolymer of ethylene, methacrylic acid and carbon monoxide, terpolymer of ethylene, vinyl acetate and carbon monoxide, ionomers, thermoplastic urethane, polyamide, K-resin, substantially linear ethylene polymer, linear ethylene polymer, linear low density polyethylene, very low density polyethylene, ultra low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, or mixtures thereof, wherein the second tie layer is adjacent to the second outer layer represented by the structure AXiBXiC.

In another embodiment, the present invention is the coextruded multilayer film structure disclosed herein above wherein the second outer layer (C) forms a peelable or permanent seal, wherein the second tie layer is adjacent to the second outer layer

represented by the structure AXiBXiC.

In yet another embodiment of the present invention, the coextruded multilayer film structure disclosed herein above is in the form of a packaging application requiring horizontal forming with lidding, preferably the packaging application is in the form of a blister pack.

Another embodiment of the present invention is a process to make a packaging application requiring horizontal forming with lidding by thermoforming the multilayer film structure disclosed herein above.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, the multilayer film structure of the present invention comprises at least one polyvinylidene chloride resin (PVDC) core layer sandwiched by a first tie layer and a second tie layer, and at least one outer layer comprising an amorphous copolyester resin. Optionally, one or more adhesive layer or tie layer is interposed between the core layer and one or both outer layer. The multilayer film structure is thermoformable and provides excellent gas and moisture barrier properties.

The polyvinylidene chloride resin core layer of the present invention preferably comprises a formulated vinylidene copolymer composition comprising a vinylidene chloride copolymer, an inorganic stabilizer, and one or more of a high density polyethylene (HDPE), an epoxidized vegetable oil, acrylic process aids, additional organic acid

scavengers or stabilizers, plasticizers, an oxidized polyolefin and/or a paraffin or

polyethylene wax. The major component is vinylidene chloride copolymer. The minor components are in an amount suitable to provide a composition which demonstrates improved thermal stability during extrusion and has high barrier with respect to water vapor, oxygen and other permeants.

Vinylidene chloride copolymers suitable for use in the present invention are known, for example see USP 5,002,989, incorporated herein by reference in its entirety. Vinylidene chloride copolymers are those vinylidene chloride copolymers formed from a monomer mixture of vinylidene chloride monomer and a comonomer which is vinyl chloride and/or an alkyl acrylate. The alkyl acrylates are generally selected to have from about 1 to about 8 carbon atoms per alkyl group. Preferably, alkyl acrylates are selected to have from about 1 to about 4 carbon atoms per alkyl group, for example methyl meth acrylate or butyl acrylate. The alkyl acrylate is more preferably ethyl or methyl acrylate. The comonomer is most preferably methyl acrylate. Of course, vinylidene chloride copolymers useful in formulated vinylidene copolymer compositions may also contain small amounts (usually less than about 1 to 2 percent) of other ethylenically-unsaturated monomers which do not substantially reduce the extrudability or increase the permeability of the copolymer.

The amount of vinyl chloride or alkyl acrylate comonomer in the copolymer is low enough to preserve the semicrystalline character of the copolymer and high enough to provide a commercially extrudable polymer. By "semicrystalline character" it is meant that the copolymer has between about 5 percent and about 95 percent crystallinity. Crystallinity values depend upon the measuring technique, and as used herein crystallinity is defined by the commonly used density method. See, for example, the discussion by R. Wessling, in Chapter 6 of Polyvinylidene Chloride. Vol. 5, Gordon and Breach Science Publishers, New York, 1977, the teachings of which are incorporated herein by reference. Vinyl chloride comonomer is preferably equal to or greater than about 8 percent, more preferably equal to or greater than about 10 percent, and even more preferably equal to or greater than about 12 percent of the copolymer: it is preferably equal to or less than about 25 percent, more preferably equal to or less than about 20 percent, and even more preferably equal to or less than about 17 percent of the copolymer. The acrylate comonomer, preferably methyl acrylate, is preferably equal to or greater than about 3 percent, more preferably equal to or greater than about 4 percent, more preferably equal to or greater than about 4.8 percent, and even more preferably equal to or greater than about 5 percent of the resulting copolymer; it is preferably equal to or less than about 10 percent, more preferably equal to or less than about 9 percent, more preferably equal to or less than about 8.5 percent, and even more preferably equal to or less than about 8 percent of the resulting copolymer.

The vinylidene chloride copolymer useful in the present invention preferably has a melting point of from 130°C to 185°C and more preferably of from 140°C to 175°C.

The vinylidene chloride copolymer useful in the present invention preferably has a weight average molecular weight equal to or greater than 60,000, more preferably equal to or greater than 70,000, more preferably equal to or greater than 75,000, more preferably equal to or greater than 80,000, and more preferably equal to or greater than 85,000. The vinylidene chloride copolymer useful in the present invention preferably has a weight average molecular weight equal to or less than 150,000, more preferably equal to or less than 140,000, more preferably equal to or less than 130,000, more preferably equal to or less than 120,000, and more preferably equal to or greater than 110,000.

Vinylidene chloride copolymers are known and are commercially available.

Methods to synthesize them, such as by an emulsion or suspension polymerization process, are also familiar to persons of ordinary skill in the art. The copolymers and processes to synthesize them are described in USP 2,558,728: 3,007,903; 3,642,743; and 3,879,359; all of which are incorporated herein by reference, in R. A. Wessling, Polyvinylidene Chloride, supra, at 21-33 and 44-53; in 23 Encyclopedia of Polymer Science, supra, at 783-87; and in Yen et al., Barrier Resins, Report No. 179 of SRI International Process Economics Program 55-106 (February 1986).

Typically, the monomeric materials, for example vinylidene chloride and methyl acrylate, are emulsified or suspended in an aqueous phase. In a typical suspension polymerization, the aqueous phase contains a surface active agent capable of suspending the monomer phase in the aqueous phase. The monomer phase will contain vinylidene chloride, comonomer, initiator and optionally other additives. The polymerization of the monomeric materials is usually carried out with heating and agitation. After polymerization, the resulting suspension of vinylidene chloride copolymer is vacuum stripped, cooled, dewatered and dried. The resultant polymer appears as a powder or bead of approximately 200 to 350 micron diameter.

The additives used in formulated vinylidene copolymer compositions useful in the present invention may be added during polymerization of the vinylidene chloride copolymer or to the polymerized vinylidene chloride copolymer, for example in powder form. The additives may be blended individually with the vinylidene chloride copolymer

monomers/powder (e.g., one at a time); or they may be blended concurrently (e.g., all at the same time) with the vinylidene chloride copolymer, such as by physically blending the vinylidene chloride copolymer with an additive composition which has been separately prepared. Such additive compositions make up one embodiment of the present invention. They comprise the same additives as the polymer compositions described herein. The additives will ordinarily be in about the same weight ratios with respect to each other as are found in the formulated vinylidene copolymer composition. However, the inorganic stabilizer and/or the epoxidized vegetable oil may be in a lesser proportion to make up for quantities of those additives already found in the base resin. Unless otherwise stated, amounts of additive compounds are in parts per hundred parts of the formulate vinylidene copolymer composition (herein after 'parts per hundred resin').

Additives should be blended with the vinylidene chloride copolymer to form a formulated vinylidene copolymer composition useful in the present invention before extrusion or melt-phase processing of the vinylidene chloride copolymer. The additives are blended with the vinylidene chloride copolymer by any method which is effective to achieve substantially homogeneous dispersion of the additives without unduly heating the resin. Blending of the vinylidene chloride copolymer and the formulation package can be accomplished by conventional dry blending techniques. It preferably uses medium or high intensity blending. Suitable dry blending equipment include, medium intensity plow blenders from Littleford and/or Lodige, or high intensity blenders such as Hobart mixers, Welex mixers, Henschel High Intensity mixers, and the like.

Formulated vinylidene copolymer compositions useful in the present invention contain one or more inorganic stabilizer. The inorganic stabilizer is preferably tetrasodium pyrophosphate (TSPP), magnesium hydroxide (Mg(OH)2), a complex (A) of a metal silicate and a metal hydroxide, or mixtures thereof. Examples of other suitable inorganic stabilizers may include magnesium oxide, calcium oxide, calcium hydroxide, potassium pyrophosphate, and other inorganic stabilizers disclosed in Johnson, Process for Imparting Stability to Particulate Vinylidene Chloride Polymer Resins, USP 4,418,168, which is incorporated herein by reference. Inorganic stabilizers are known compounds which are, or have been, commercially available. Both TSPP and Mg(OH)₂ can be synthesized by known processes, such as those described in The Merck Index, 10th Edition, (1983), which is hereby incorporated by reference. The PVDC compositions of the present invention preferably comprise TSPP, Mg(OH)₂, a complex (A) of a metal silicate and a metal hydroxide, or mixtures thereof.

The one or more inorganic stabilizer preferably has an average particle diameter no larger than the average particle diameter of the vinylidene chloride copolymer. Persons skilled in the art will recognize that the effectiveness of the inorganic stabilizer is generally related to the surface area of the stabilizer employed. For purposes of this invention, the inorganic stabilizer (e.g., TSPP or Mg(OH)₂) beneficially has an average particle diameter of from about 1 to about 50 microns. One skilled in the art, without undue experimentation, will be able to determine the optimum particle size for specific additives. It is most preferable to have any inorganic additive particle size be sufficiently small to prevent optical light scattering and haze in films made with such additives.

Alternatively, a suitable inorganic stabilizer for use in the present invention is a thermal stabilizer component comprising a complex (A) of a metal silicate and a metal hydroxide, preferably calcium hydroxide compound represented by the formula 1 :

C_ai__x__y M ²⁺ _x Al_y (OH)₂ 1 wherein M²⁺ represents at least one bivalent metal selected from the group consisting of Mg, Zn, or Cu, preferably Mg and/or Zn, x is in the range of 0 < x < 1, preferably 0 < x < 0.9, and more preferably 0 < x < 0.4 and y is in the range of 0 < y < 0.5, preferably 0 < y < 0.3, and more preferably 0 < y < 0.1. In formula 1, when x = 1, there is no detectable calcium present in the metal silicate metal hydroxide stabilizer, however, even in this embodiment the stabilizer may still be referred to as a metal silicate calcium hydroxide compound.

In the complex (A) used in the present invention, a metal silicate has chemical interaction with a calcium hydroxide compound and as a result thereof the primary crystallite size of the calcium hydroxide compound becomes extremely small so that the reaction activity as a thermal stabilizer is improved. The complex (A) has a BET specific surface area of at least 20 m²/g, preferably at least 30 m²/g. The BET specific surface area of calcium hydroxide is about 5 to 10 m /g. The difference in BET specific surface area is obvious. The complex (A) can be produced by thermally hydrating a metal silicate represented by the formula 2,

2

(Al₂0₃)_a(M²⁺ 0)_bSi0₂(H₂0)_m wherein M²⁺ is at least one bivalent metal selected from the group consisting of Zn, Mg, Ca and etc., preferably Zn and/or Mg, a is in the range of 0.1 < a < 0.5, b is in the range of 0.1 < b < 1, provided that a+b is in the range of 0 < a+b < 1, and m is in the range of 0.1 < m < 2, with calcium oxide or a solid solution comprised of calcium oxide and M²⁺ and/or Al in an aqueous medium. In this case, the hydration reaction is carried out at preferably 60°C or higher, particularly preferably 80°C or higher, for preferably 10 to 30 minutes with stirring. As a production process other than the above process, it is possible to add an aqueous solution of a water-soluble salt of M²⁺ and/or Al such as a chloride or a nitrate after the above hydration reaction and allow the resultant mixture to react. Thereafter, the complex (A) is preferably surface-treated with a higher fatty acid or an alkali metal salt of a higher fatty acid, a phosphoric acid ester, a silane coupling agent, a titanium coupling agent or an aluminum coupling agent in an amount of 0.1 to 10 percent by weight based on the weight of the complex (A).

Examples of the metal silicate include crystalline activated white clay, acid white clay, amorphous aluminum silicate, zinc silicate and zinc aluminum silicate. The complexing amount of the metal silicate based on the calcium hydroxide compound is 0.5 to 40 percent by weight, preferably 1 to 10 percent by weight, particularly preferably 2 to 8 percent by weight.

A preferred a metal silicate and a calcium hydroxide compound is SEASTAB™ 510 available from Mitsui Plastics, Inc. SEASTAB 510 comprises (Ca, Mg)(OH)₂, Si0₂ and may have, for example, about 67.2 weight percent CaO, 1.09 weight percent MgO, and 3.26 weight percent Si0₂. SEASTAB 510 is a white powder with an average particle size of about 2.858 microns, a specific gravity of about 2.2, a refractive index of about 1.54 to 1.57, a hardness (Mohs') of about 12.3 to 12.4, a beginning temperature of dehydration of about 340°C, a moisture content of about 1 percent at 120°C, 1H and a BET surface area of about 39 m /g.

A preferred a metal silicate and a calcium hydroxide compound is SEASTAB 705 available from Mitsui Plastics, Inc. SEASTAB 705 comprises (Ca, Mg, Al)(OH)₂, Si0₂ and may have, for example, 40.06 weight percent CaO, 14.05 weight percent MgO, 8.54 weight percent A1₂0₃, and 2.35 weight percent Si0₂. SEASTAB 705 is a white powder with an average particle size of about 2.77 microns, a specific gravity of about 2.2, a refractive index of about 1.54 to 1.57, a hardness (Mohs') of about 12.3 to 12.4, a beginning temperature of dehydration of about 200°C, a moisture content of about 1 percent at 120°C, 1H and a BET surface area of about 23 m /g.

The concentration of any one inorganic stabilizer individually is preferably no more than about 3 parts per hundred (resin), and preferably no less than about 0.05 part per hundred (resin). (For the purposes of this Application, the term "parts per hundred (resin)" shall mean parts of additive per 100 parts of vinylidene chloride copolymer, by weight.) The specific weight ratios for optimum performance vary with different stabilizers. The concentration of TSPP and/or Mg(OH)₂ in the formulated barrier composition is more preferably between 0.1 and 1.1 part per hundred (resin). Its concentration is most preferably between 0.5 and 1 part per hundred (resin). When present, the concentration of the thermal stabilizer component comprising a complex (A) of a metal silicate and a metal hydroxide is preferably between 0.05 and 3 parts per hundred (resin), more preferably between 0.1 and 2 parts per hundred (resin), more preferably between 0.3 and 1 parts per hundred (resin), and most preferably between 0.5 and 1 parts per hundred (resin).

Formulated vinylidene copolymer compositions useful in the present invention comprise one or more additive commonly used in such compositions such as epoxidized vegetable oil, such as soybean and/or linseed oil; one or more lubricant, such as high density polyethylene, a paraffin or polyethylene wax, oxidized polyolefin, amide waxes, stearate waxes, stearic acid or similar fatty acid derivatives, acrylic process aides, silicon process aides, fluorocarbon process aides, and the like; a plasticizer such as dibutyl sebacate and/or acetyl tributyl citrate, additional acid scavengers such as calcium stearyl lactylate, calcium hydroxide, magnesium hydroxide, magnesium oxide, and/or tetrasodium pyrophosphate; an antioxidant; an anti-block agent; an anti-stat; a slip aid; colorants; and the like.

When used, the high density polyethylene may contain a minor amount of oxygen. These oxygen-containing polyolefins are formed by copolymerization of ethylene with some other comonomer, which may contain oxygen. For the purpose of this invention, a "minor amount" of oxygen means that the polyolefin may contain oxygen below an amount that will significantly change the properties from that of the homopolymer. High density polyethylenes are ordinarily substantially linear and preferably have a weight-average molecular weight of at least about 40,000. High density polyethylene, its properties and its synthesis are described in 16 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed., Linear (High Density) Polyethylene and Olefin Polymers (Ziegler Polyethylene), at 421-51 (J. Wiley & Sons 1980).

If present, the concentration of high density polyethylene in the formulated vinylidene copolymer composition is equal to or greater than about 0.45 parts per hundred resin, preferably equal to or greater than about 0.5 parts per hundred resin and more preferably equal to or greater than about 0.9 parts per hundred resin. If present, the high density polyethylene in the formulated vinylidene copolymer composition is equal to or less than about 1.05 parts per hundred resin and preferably equal to or less than about 1.0 parts per hundred resin. The formulated vinylidene copolymer compositions useful in the present invention may also contain epoxidized vegetable oils, such as epoxidized soybean oil and epoxidized linseed oil. The epoxidized oil should be of a type suitable to act as a plasticizer for the copolymer. The epoxidized oil is most preferably epoxidized soybean oil. Epoxidized vegetable oils are known and are commercially available compounds. They and processes to synthesize them are described in 9 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed.,

Epoxidation, at 251-63 (J. Wiley & Sons 1980). If present, the concentration of epoxidized vegetable oil in the formulated vinylidene copolymer composition is equal to or greater than about 0.1 parts per hundred (resin), preferably equal to or greater than about 0.2 parts per hundred (resin), preferably equal to or greater than about 0.5 parts per hundred (resin), and even more preferably equal to or greater than about 0.8 parts per hundred (resin). If present, the concentration of epoxidized vegetable oil in the formulated vinylidene copolymer composition is equal to or less than about 7 parts per hundred (resin), more preferably equal to or less than about 5 parts per hundred (resin), more preferably equal to or less than about 3 parts per hundred (resin), and even more preferably equal to or less than about 1 part per hundred (resin).

The formulated vinylidene copolymer compositions useful in the present invention may also contain oxidized polyolefins, which are low molecular weight polymers which have a number average molecular weight of less than about 5,000, as determined by vapor phase osmometry. Preferably the number average molecular weight is about 1,000 to about 4,000, and most preferably between about 1,500 and about 2,500. The polyolefins have preferably been oxidized to an acid number of about 10 to 35, more preferably 13 to 17. These oxidized polyolefins preferably have a softening point, as determined by ASTM E-28 of about 85°C to 145°C, more preferably 95°C to 140°C, and most preferably 98°C to 115°C. Generally, such oxidized polyolefins have a Brookfield viscosity at 140°C of about 120 to 300 centipoise (cps), and preferably 170 to 250 cps. Exemplary oxidized polyolefins including oxidized polyethylene, oxidized polypropylene, or mixtures thereof are employed. Oxidized polyethylene is preferred.

Oxidized polyethylene and oxidized polypropylene are known polymers which are commercially available, for instance under the trademark Allied 629A from Allied-Signal Corp. They can be prepared by reacting an ethylene homopolymer or copolymer with oxygen or an organic peroxide or hydroperoxide. The processes for synthesizing them are described in 16 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed. Olefin Polymers (High Pressure Polyethylene), at 412 (J. Wiley & Sons 1980) and 24 Kirk-Othmer Ency. Chem. Tech. - 3rd Ed. Waxes, at 477 (J. Wiley & Sons 1980).

When present, the concentration of oxidized polyolefin in the formulated vinylidene copolymer compositions useful in the present invention is at least about 0.05 parts per hundred (resin), preferably at least about 0.1 parts per hundred (resin), and more preferably at least about 0.2 parts per hundred (resin). When present, the concentration of oxidized polyolefin in the formulated vinylidene copolymer compositions useful in the present invention is at most about 0.4 parts per hundred (resin) and preferably at most about 0.3 parts per hundred (resin).

Formulated vinylidene copolymer compositions useful in the present invention may also contain a paraffin or polyethylene wax. They most preferably comprise a polyethylene wax. Paraffin waxes are defined herein as having a Brookfield viscosity in the range of about 50 to about 300 cps at 140°C, a melting point in the range of about 40°C to about

80°C, and a density in the range of about 0.85 g/cm 3 to about 0.95 g/cm 3. Exemplary paraffin waxes include waxes commercially available from Degussa Corporation such as VESTOWAX™ SH-105 or Hoechst AG, such as Hoechst XL-165FR, Hoechst XL-165SB, Hoechst XL- 165: and the like. Polyethylene waxes are defined herein as having Brookfield viscosity in the range of about 130 to about 450 cps at 140°C: a melting point in the range of about 80°C to about 100°C; and a density in the range of about 0.85 H g/cm to about 0.95 g/cm . Exemplary polyethylene waxes include waxes commercially available from Allied Chemical Co. such as Allied 617A and 6A; and the like.

Paraffin and polyethylene waxes suitable for food contact purposes are known and commercially available, as previously described. Their properties and synthesis are described in 24 Kirk-Othmer Ency. Chem. 35 Tech. - 3rd Ed., Waxes, at 473-77 (J. Wiley & Sons 1980).

When present, the concentration of paraffin and/or polyethylene wax in the formulated vinylidene copolymer compositions useful in the present invention is at least about 0.1 parts per hundred (resin), preferably at least about 0.2 parts per hundred (resin), and more preferably at least about 0.25 parts per hundred (resin). When present, the concentration of paraffin and/or polyethylene wax in the formulated vinylidene copolymer compositions useful in the present invention is at most about 0.75 parts per hundred (resin) and preferably at most about 0.55 parts per hundred (resin). The formulated vinylidene copolymer composition may contain additional additives well-known to those skilled in the art. Exemplary of additives which may be incorporated in the formulation are light stabilizers, metal chelators and antioxidants such as hindered phenol derivatives, pigments such as titanium dioxide and the like. Each of these additives is known and several types of each are commercially available.

The barrier provided by the PVDC core layer of the present invention varies depending upon the particular ratio of ingredients, the proportion of vinylidene chloride in the vinylidene chloride copolymer, and the structure (rigid container or flexible film, etc.) into which the formulated barrier product is fabricated. For coextrusion applications, the rate of transmission for oxygen is on average preferably equal to or less than about

0.20 Dow Units (D.U.), more preferably equal to or less than about 0.10 D.U., and even more preferably equal to or less than about 0.05 D.U. The rate of transmission is measured on an OXTRAN™ 10/50 oxygen permeability instrument produced by Modern Controls Inc. One D.U. equals:

(1 cm³ of 0₂ at S.T.P.)(1 mil thickness PVDC) (100 in² area)(l atmosphere Pressure)(24 hours) and D.U. are reported as: cm 3 -mil/100 in 2 -atm-day.

Suitable copolyester resins useful for the first outer layer and optionally second outer layer are known in the art and may be formed from aromatic dicarboxylic acids, esters of dicarboxylic acids, anhydrides of dicarboxylic esters, glycols, and mixtures thereof. As used herein the term 'copolyester' refers to a polyester with two different polyester groups in the repeating units. (See R.B. Seymour, Engineering Polymer Sourcebook (1990 McGraw Hill Publishing Company). Suitable partially aromatic copolyesters are formed from repeat units comprising terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, dimethyl-2,6 naphthalenedicarboxylate, 2,6-naphthalenedicarboxylic acid, 1,2-, 1,3- and l,4phenylene dioxydoacetic acid, ethylene glycol, diethylene glycol, 1,4-cyclohexane-dimethanol, 1,4-butanediol, and neopentyl glycol mixtures thereof.

Preferably, the copolyester(s) used in the present invention are amorphous. As defined herein, amorphous means having a low amount of crystallinity, for example equal to or less than 20 weight percent, preferably equal to or less than 10 weight percent, more preferably equal to or less than 5 weight percent, even more preferably equal to or less than 2 weight percent, and most preferably equal to or less than 1 weight percent.

Preferably, the structural polyesters comprise repeat units comprising terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, and/or dimethyl-2,6- naphthalenedicarboxylate. The dicarboxylic acid component of the polyester may optionally be modified with one or more different dicarboxylic acids (preferably up to about 20 mole percent). Such additional dicarboxylic acids comprise aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbon atoms, or cycloaliphatic dicarboxylic acids preferably having 8 to 12 carbon atoms. Examples of dicarboxylic acids to be comprised with terephthalic acid are: phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diphenyl-4,4'-dicarboxylic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, mixtures thereof and the like.

In addition, the glycol component may optionally be modified with one or more different diols other than ethylene glycol (preferably up to about 20 mole percent). Such additional diols comprise cycloaliphatic diols preferably having 6 to 20 carbon atoms or aliphatic diols preferably having 25 to 20 carbon atoms. Examples of such diols comprise: diethylene glycol, triethylene glycol, glycerol, mannitol, pentaerythritol, 1,4-cyclo- hexanedimethanol, propane- 1 ,3-diol, butane- 1 ,4-diol, pentane- 1 ,5-diol, hexane- 1 ,6-diol, 3-methylpentanediol-(2,4), 2-methylpentanediol-( 1 ,4), 2,2,4-trimethylpentane-diol-( 1 ,3), 2-ethylhexanediol-(l,3), 2,2-diethylpropane-diol-(l,3), hexanediol-(l,3), l,4-di-(hydroxy- ethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy- 1 , 1 ,3,3-tetra- methyl-cyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)-propane, 2-bis-(4-hydroxy- propoxyphenyl)-propane, hydroxyethyl resorcinol, mixtures thereof and the like. Polyesters may be prepared from two or more of the above diols.

In one embodiment, the copolyester useful in the present invention is a

copolymerized polyester which has greater than 20 percent, preferably greater than 30 percent, more preferably greater than 40 percent, and even more preferably greater than 50 percent by mole of glycol polymerization units. The remainder of the copolymer comprises acid polymerization units, preferably terephthalic acid polymerization units and, optionally, diol polymerization units other than glycol polymerization units. One example of a copolymer which is a glycol-modified PET in accordance with the present invention is one comprised of polymerization units derived from terephthalic acid, cyclohexanedimethanol, and ethylene glycol, wherein the copolymer comprises greater than 50 percent by mole of glycol polymerization units. Another example of a suitable copolymer is a glycol-modified PET in accordance with the present invention is one comprised of polymerization units derived from terephthalic acid, diethylene glycol, and ethylene glycol, wherein the copolymer comprises greater than 50 percent by mole of glycol polymerization units.

Another example of a suitable copolymer comprises terephthalic acid, spiro glycol, and ethylene glycol known as SPG-PET available from Mitsubishi.

The resin may also contain small amounts of trifunctional or tetrafunctional comonomers such as trimellitic anhydride, trimethylolpropane, pyromellitic dianhydride, pentaerythritol, and other polyester forming polyacids or polyols generally known in the art.

A preferred copolyester is a low viscosity amorphous copolyester of ethylene 1,2 cyclohexylenedimethylene terephthalate.

Preferably the copolyester(s) of the present invention has an intrinsic viscosity (IV) of equal to or greater than 0.4 deca-liters per gram (dl/g), preferably equal to or greater than 0.45 dl/g, more preferable equal to or greater than 0.48 dl/g, and even more preferably equal to or greater than 0.5 dl/g. Preferably the copolyester of the present invention has an intrinsic viscosity of equal to or less than 0.7 dl/g, preferably equal to or less than 0.68 dl/g, more preferable equal to or less than 0.65 dl/g, even more preferable equal to or less than 0.60 dl/g, and most preferably equal to or less than 0.58 dl/g. Unless otherwise noted, copolyester IV is determined in 60/40 phenol/tetrachloroethane at 25°C as taught in

US Patent Publication 20030141625, which is incorporated herein in its entirety.

Surprisingly, it has been found that by using a low intrinsic viscosity copolyester, typically considered insufficiently tough to be useful for packaging, hitherto unknown coextruded multilayer films may be made with PVDC and copolyester having sufficient formability and physical properties useful for a variety of packaging.

Preferably the copolyester used in the present invention has a haze (determined according to ASTM D1003) of less than 50, more preferably of less than 40 and most preferably of less than 30.

Preferably the copolyester used in the present invention has an Elmendorf tear

(determined according to ASTM D1922) of greater than 50 g at 10 mil, more preferably of greater than 80 g at 10 mil and most preferably of greater than 100 g at 10 mil. Preferably the copolyester used in the present invention has a 1 percent Secant Modulus (determined according to ASTM D882) of greater than 50 kpsi, more preferable of greater than 100 kpsi, and most preferably of greater than 150kpsi.

Preferably the copolyester used in the present invention is formable, more preferably thermoformable.

The second and/or additional outer skins may be the same copolyester as used for the first outer skin, a different copolyester, or may comprise one or more of the following resins: isotactic polypropylene (homopolymer), random polypropylenes, substantially isotactic propylene, very low density polyethylene, ultra low density polyethylene, low density polyethylene, medium density polyethylene or high density polyethylene, linear low density polyethylene, substantially linear ethylene polymer, linear ethylene polymer, copolymers of ethylene and vinyl acetate, copolymers of ethylene and methyl acrylate, copolymers of ethylene and ethyl acrylate, copolymers of ethylene and carbon monoxide, copolymers of ethylene and n-butyl acrylate, terpolymers of ethylene, acrylic acid and carbon monoxide, terpolymers of ethylene, n-butyl acrylate and carbon monoxide, terpolymers of ethylene, methacrylic acid and carbon monoxide, terpolymers of ethylene, vinyl acetate and carbon monoxide, acid copolymers or terpolymers of polyethylene neutralized or partially neutralized by cations of sodium, potassium, zinc, or quaternary ammonium (e.g., and a preferred cation is didecyl dimethyl ammonium cation), sometimes referred to as ionomers (for example see US Patent Publication US 2007/0207332(Al) incorporated herein by reference in its entirety), thermoplastic urethane, polyamides, and K-resin. It is most preferred that the second outer skin resin be comprised of copolyester resin. It is also preferable that the second outer skin layer be a seal layer capable of heat sealing, such as by hot bar or impulse sealing, to itself or to the adhesive seal layer from a dissimilar but mating film or foil. Such a seal so formed to be a peelable seal or a permanent seal.

The preferred substantially isotactic propylene polymer may be described as follows and is a propylene/alpha-olefin copolymer. The propylene/alpha- olefin copolymer is characterized as having substantially isotactic propylene sequences. "Substantially isotactic propylene sequences" means that the sequences have an isotactic triad (mm) measured by

13 C NMR of greater than about 0.85; in the alternative, greater than about 0.90; in another alternative, greater than about 0.92; and in another alternative, greater than about 0.93. Isotactic triads are well-known in the art and are described in, for example, U.S. Patent No. 5,504,172 and International Publication No. WO 00/01745, which refer to the isotactic sequence in terms of a triad unit in the copolymer molecular chain determined by 13 C NMR spectra. 13 C NMR spectroscopy is one of a number of techniques known in the art for measuring comonomer incorporation into a polymer. An example of this technique is described for the determination of comonomer content for ethylene/cc- olefin copolymers in Randall (Journal of Macromolecular Science, Reviews in Macromolecular Chemistry and Physics, C29 (2 & 3), 201 - 317 (1989)). Due to the novel molecular architecture, substantially isotactic propylene copolymers are significantly different than homopolymer or random copolymer polypropylene.

The substantially isotactic propylene/alpha-olefin copolymer may have a melt flow rate in the range of from about 0.1 to about 25 grams per 10 minutes (g/10 min), measured in accordance with ASTM D-1238 (determined at 230°C under a load of 2.16 kilograms (kg)). All individual values and subranges from about 0.1 to about 25 g/10 min are included herein and disclosed herein; for example, the melt flow rate can be from a lower limit of about 0.1 g/10 min, about 0.2 g/10 min, or about 0.5 g/10 min to an upper limit of about 25 g/10 min, about 15 g/10 min, about 10 g/10 min, about 8 g/10 min, or about 5 g/10 min. For example, the propylene/alpha-olefin copolymer may have a melt flow rate in the range of from about 0.1 to about 10 g/10 min; or in the alternative, the propylene/alpha-olefin copolymer may have a melt flow rate in the range of from about 0.2 to about 10 g/10 min.

The substantially isotactic propylene/alpha-olefin copolymer has a crystallinity in the range of from at least about 1 percent by weight (a heat of fusion of at least

2 Joules/gram) to about 30 percent by weight (a heat of fusion of less than 50 Joules/gram). All individual values and subranges from about 1 percent by weight (a heat of fusion of at least 2 Joules/gram) to about 30 percent by weight (a heat of fusion of less than

50 Joules/gram) are included herein and disclosed herein; for example, the crystallinity can be from a lower limit of about 1 percent by weight (a heat of fusion of at least

2 Joules/gram), about 2.5 percent (a heat of fusion of at least 4 Joules/gram), or about

3 percent (a heat of fusion of at least 5 Joules/gram) to an upper limit of about 30 percent by weight (a heat of fusion of less than 50 Joules/gram), about 24 percent by weight (a heat of fusion of less than 40 Joules/gram), about 15 percent by weight (a heat of fusion of less than 24.8 Joules/gram) or about 7 percent by weight (a heat of fusion of less than 11

Joules/gram). For example, the propylene/alpha-olefin copolymer may have a crystallinity in the range of from at least about 1 percent by weight (a heat of fusion of at least 2 Joules/gram) to about 24 percent by weight (a heat of fusion of less than 40 Joules/gram); or in the alternative, the propylene/alpha- olefin copolymer may have a crystallinity in the range of from at least about 1 percent by weight (a heat of fusion of at least 2 Joules/gram) to about 15 percent by weight (a heat of fusion of less than 24.8 Joules/gram); or in the alternative, the propylene/alpha-olefin copolymer may have a crystallinity in the range of from at least about 1 percent by weight (a heat of fusion of at least 2 Joules/gram) to about 7 percent by weight (a heat of fusion of less than 11 Joules/gram); or in the alternative, the propylene/alpha-olefin copolymer may have a crystallinity in the range of from at least about 1 percent by weight (a heat of fusion of at least 2 Joules/gram) to about 5 percent by weight (a heat of fusion of less than 8.3 Joules/gram). The crystallinity is measured via DSC method, as described above. The substantially isotactic propylene/alpha-olefin copolymer comprises units derived from propylene and polymeric units derived from one or more alpha-olefin comonomers. Exemplary comonomers utilized to manufacture the substantially isotactic propylene/alpha-olefin copolymer are C₂, and C₄ to C₁₀ alpha-olefins; for example, C₂, C₄, C₆ and alpha-olefins.

The substantially isotactic propylene/alpha-olefin copolymer comprises from 1 to 40 percent by weight of the units derived from one or more alpha-olefin comonomers. All individual values and subranges from 1 to 40 weight percent are included herein and disclosed herein; for example, the comonomer content can be from a lower limit of 1 weight percent, 3 weight percent, 4 weight percent, 5 weight percent, 7 weight percent, or 9 weight percent to an upper limit of 40 weight percent, 35 weight percent, 30 weight percent, 27 weight percent, 20 weight percent, 15 weight percent, 12 weight percent, or 9 weight percent. For example, the substantially isotactic propylene/alpha-olefin copolymer comprises from 1 to 35 percent by weight of units derived from one or more alpha-olefin comonomers; or in the alternative, the propylene/alpha-olefin copolymer comprises from

1 to 30 percent by weight of units derived from one or more alpha-olefin comonomers; or in the alternative, the propylene/alpha-olefin copolymer comprises from 3 to 27 percent by weight of units derived from one or more alpha-olefin comonomers; or in the alternative, the propylene/alpha-olefin copolymer comprises from 3 to 20 percent by weight of units derived from one or more alpha-olefin comonomers; or in the alternative, the

propylene/alpha-olefin copolymer comprises from 3 to 15 percent by weight of units derived from one or more alpha-olefin comonomers. The substantially isotactic propylene/alpha-olefin copolymer has a molecular weight distribution (MWD), defined as weight average molecular weight divided by number average molecular weight (M_w/M_n) of 3.5 or less; in the alternative 3.0 or less; or in another alternative from 1.8 to 3.0.

Such substantially isotactic propylene/alpha-olefin copolymers are further described in details in the USP 6,960,635 and 6,525,157, incorporated herein by reference. Such substantially isotactic propylene/alpha-olefin copolymers are commercially available from The Dow Chemical Company, under the tradename VERSIFY™, or from ExxonMobil Chemical Company, under the tradename VISTAMAXX™.

In one embodiment, the substantially isotactic propylene/alpha-olefin copolymers are further characterized as comprising (A) between 60 and less than 100, preferably between 80 and 99 and more preferably between 85 and 99, weight percent units derived from propylene, and (B) between greater than zero and 40, preferably between 1 and 20, more preferably between 4 and 16 and even more preferably between 4 and 15, weight percent units derived from at least one of ethylene and/or a C₄_₁o cc-olefin; and containing an average of at least 0.001, preferably an average of at least 0.005 and more preferably an average of at least 0.01, long chain branches/1000 total carbons, wherein the term long chain branch refers to a chain length of at least one (1) carbon more than a short chain branch, and wherein short chain branch refers to a chain length of two (2) carbons less than the number of carbons in the comonomer. For example, a propylene/ 1-octene interpolymer has backbones with long chain branches of at least seven (7) carbons in length, but these backbones also have short chain branches of only six (6) carbons in length. The maximum number of long chain branches in the propylene interpolymer is not critical to the definition of this embodiment of the instant invention, but typically it does not exceed 3 long chain branches/ 1000 total carbons. Such propylene/alpha-olefin copolymers are further described in details in the US Provisional Patent Application No. 60/988,999 and International Patent Application No. PCT/US08/082599, each of which is incorporated in its entirety herein by reference.

In another embodiment, the substantially isotactic polypropylene composition comprises units derived from propylene and polymeric units derived from one or more alpha-olefin comonomers. The propylene/alpha-olefin copolymer may be VERSIFY™ (The Dow Chemical Company) 3000 Plastomer. In another embodiment, the propylene/alpha-olefin copolymer may be VERSIFY (The Dow Chemical Company) 3200 Plastomer.

Preferred substantially linear ethylene polymers and linear ethylene polymers (S/LEP) can be described as follows. Both substantially linear ethylene polymers and linear ethylene polymers are known. Substantially linear ethylene polymers and their method of preparation are fully described in USP 5,272,236 and USP 5,278,272. Linear ethylene polymers and their method of preparation are fully disclosed in USP 3,645,992; USP 4,937,299; USP 4,701,432; USP 4,937,301; USP 4,935,397; USP 5,055,438; EP 129,368; EP 260,999; and WO 90/07526.

Suitable S/LEP comprises one or more C₂ to C₂o alpha-olefins in polymerized form, having a T_g less than 25°C, preferably less than 0°C, most preferably less than

-25 °C. Examples of the types of polymers from which the present S/LEP are selected include copolymers of alpha-olefins, such as ethylene and propylene, ethylene and 1-butene, ethylene and 1-hexene or ethylene and 1-octene copolymers, and terpolymers of ethylene, propylene and a diene comonomer such as hexadiene or ethylidene norbornene.

As used here, "a linear ethylene polymer" means a homopolymer of ethylene or a copolymer of ethylene and one or more alpha-olefin comonomers having a linear backbone (i.e. no cross linking), no long-chain branching, a narrow molecular weight distribution and, for alpha-olefin copolymers, a narrow composition distribution. Further, as used here, "a substantially linear ethylene polymer" means a homopolymer of ethylene or a copolymer of ethylene and of one or more alpha-olefin comonomers having a linear backbone, a specific and limited amount of long-chain branching, a narrow molecular weight distribution and, for alpha-olefin copolymers, a narrow composition distribution.

Short-chain branches in a linear copolymer arise from the pendent alkyl group resulting upon polymerization of intentionally added C₃ to C₂o alpha-olefin comonomers. Narrow composition distribution is also sometimes referred to as homogeneous short-chain branching. Narrow composition distribution and homogeneous short-chain branching refer to the fact that the alpha-olefin comonomer is randomly distributed within a given copolymer of ethylene and an alpha-olefin comonomer and virtually all of the copolymer molecules have the same ethylene to comonomer ratio. The narrowness of the composition distribution is indicated by the value of the Composition Distribution Branch Index (CDBI) or sometimes referred to as Short Chain Branch Distribution Index. CDBI is defined as the weight percent of the polymer molecules having a comonomer content within 50 percent of the median molar comonomer content. The CDBI is readily calculated, for example, by employing temperature rising elution fractionation, as described in Wild, Journal of

Polymer Science, Polymer Physics Edition, Volume 20, page 441 (1982), or USP 4,798,081. The CDBI for the substantially linear ethylene copolymers and the linear ethylene copolymers in the present invention is greater than about 30 percent, preferably greater than about 50 percent, and more preferably greater than about 90 percent.

Long-chain branches in substantially linear ethylene polymers are polymer branches other than short chain branches. Typically, long chain branches are formed by insitu generation of an oligomeric alpha-olefin via beta-hydride elimination in a growing polymer chain. The resulting species is a relatively high molecular weight vinyl terminated hydrocarbon which upon polymerization yields a large pendent alkyl group. Long-chain branching may be further defined as hydrocarbon branches to a polymer backbone having a chain length greater than n minus 2 ("n-2") carbons, where n is the number of carbons of the largest alpha-olefin comonomer intentionally added to the reactor. Preferred long-chain branches in homopolymers of ethylene or copolymers of ethylene and one or more C₃ to C₂o alpha-olefin comonomers have at least from 20 carbons up to more preferably the number of carbons in the polymer backbone from which the branch is pendant. Long-chain branching may be distinguished using 13 C nuclear magnetic resonance spectroscopy alone, or with gel permeation chromatography-laser light scattering (GPC-LALS) or a similar analytical technique. Substantially linear ethylene polymers contain at least 0.01 long-chain branches/1000 carbons and preferably 0.05 long-chain branches/1000 carbons. In general, substantially linear ethylene polymers contain less than or equal to 3 long-chain

branches/1000 carbons and preferably less than or equal to 1 long-chain branch/1000 carbons.

Preferred substantially linear ethylene polymers are prepared by using metallocene based catalysts capable of readily polymerizing high molecular weight alpha-olefin copolymers under the process conditions. As used here, copolymer means a polymer of two or more intentionally added comonomers, for example, such as might be prepared by polymerizing ethylene with at least one other C₃ to C₂o comonomer. Preferred linear ethylene polymers may be prepared in a similar manner using, for instance, metallocene or vanadium based catalyst under conditions that do not permit polymerization of monomers other than those intentionally added to the reactor. Other basic characteristics of

substantially linear ethylene polymers or linear ethylene polymers include a low residuals content (i.e. a low concentration therein of the catalyst used to prepare the polymer, unreacted comonomers and low molecular weight oligomers made during the course of the polymerization), and a controlled molecular architecture which provides good processability even though the molecular weight distribution is narrow relative to conventional olefin polymers.

While the substantially linear ethylene polymers or the linear ethylene polymers used in the practice of this invention include substantially linear ethylene homopolymers or linear ethylene homopolymers, preferably the substantially linear ethylene polymers or the linear ethylene polymers comprise between about 50 to about 95 weight percent ethylene and about 5 to about 50, and preferably about 10 to about 25 weight percent of at least one alpha-olefin comonomer. The comonomer content in the substantially linear ethylene polymers or the linear ethylene polymers is generally calculated based on the amount added to the reactor and as can be measured using infrared spectroscopy according to ASTM D-2238, Method B. Typically, the substantially linear ethylene polymers or the linear ethylene polymers are copolymers of ethylene and one or more C₃ to C₂o alpha-olefins, preferably copolymers of ethylene and one or more C₃ to C₁₀, alpha-olefin comonomers and more preferably copolymers of ethylene and one or more comonomers selected from the group consisting of propylene, 1-butene, 1-hexene, 4-methyl-l-pentane, and 1-octene. Most preferably the copolymers are ethylene and 1-octene copolymers.

The density of these substantially linear ethylene polymers or linear ethylene polymers is equal to or greater than 0.850 grams per cubic centimeter (g/cm ) and preferably equal to or greater than 0.860 g/cm . Generally, the density of these substantially linear ethylene polymers or linear ethylene polymers is less than or equal to about 0.93 g/cm 3 and preferably less than or equal to about 0.900 g/cm 3. The melt flow ratio for substantially linear ethylene polymers, measured as I₁₀/I₂, is greater than or equal to about 5.63, is preferably from about 6.5 to about 15, and is more preferably from about 7 to about 10. I₂ is measured according to ASTM Designation D 1238 using conditions of 190°C and 2.16 kilogram (kg) mass. Iio is measured according to ASTM Designation D 1238 using conditions of 190°C and 10.0 kg mass.

The M_w/M_n for substantially linear ethylene polymers is the weight average molecular weight (M_w) divided by number average molecular weight (M_n). M_w and M_n are measured by gel permeation chromatography (GPC). For substantially linear ethylene polymers, the I₁₀/I₂ ratio indicates the degree of long-chain branching, i.e. the larger the I₁₀/I₂ ratio, the more long-chain branching exists in the polymer. In preferred substantially linear ethylene polymers M_w/M_n is related to Iw/ by the equation: M_w/M_n < (I₁₀/I₂) - 4.63. Generally, M_w/M_n for substantially linear ethylene polymers is at least about 1.5 and preferably at least about 2.0 and is less than or equal to about 3.5, more preferably less than or equal to about 3.0. In a most preferred embodiment, substantially linear ethylene polymers are also characterized by a single DSC melting peak.

The preferred I₂ melt index for these substantially linear ethylene polymers or linear ethylene polymers is from about 0.01 g/10 min to about 100 g/ 10 min, and more preferably about 0.1 g/10 min to about 10 g/10 min.

The preferred M_w for these substantially linear ethylene polymers or linear ethylene polymers is equal to or less than about 180,000, preferably equal to or less than about 160,000, more preferably equal to or less than about 140,000 and most preferably equal to or less than about 120,000. The preferred M_w for these substantially linear ethylene polymers or linear ethylene polymers is equal to or greater than about 40,000, preferably equal to or greater than about 50,000, more preferably equal to or greater than about 60,000, even more preferably equal to or greater than about 70,000, and most preferably equal to or greater than about 80,000.

In one embodiment of the present invention, when a second outer layer is present, the second outer layer is a seal layer. For example, the seal may be between lidding stock, such as foil, or it can be a seal with the same second outer layer, for example folded back on itself. In one embodiment, the seal is permanent. In another embodiment, the seal is peelable. The difference between permanent and peelable is based on the seal strength between the two mating films.

One method of making a seal between film surfaces comprises applying heat energy to a sealing area of a multilayer film, such that the applied energy is sufficient to heat the sealing area to a sealing temperature; and contacting and sealing the sealing area to another sealing area on a surface of the same film or a different film so as to provide a seal between the contacted sealing areas of the film surfaces.

"Seal strength" is defined herein as the force required to pull a seal apart, which can be measured in accordance with ASTM F88. A seal having a seal strength equal to or less than about 0.46 pounds per inch (lb/in) is considered here to be an ineffective seal for use in intended commercial and industrial applications. Preferably, the seals obtainable and provided according to the present invention have a seal strength of equal to or greater than about 0.46 lb/in, more preferably equal to or greater than about 0.57 lb/in, more preferably equal to or greater than about 1.1 lb/in, and more preferably equal to or greater than about 2.9 lb/in. As defined herein, a peelable seal has a seal strength equal to or greater than 0.46 lb/in but equal to or less than about 3.5 lb/in, preferably equal to or less than about 2.9 lb/in. As defined herein, a permanent seal has a seal strength of greater than 3.5 lb/in, more preferably equal to or greater than about 5 lb/in, and even more preferably equal to or greater than 10 lb/in.

Optionally the multilayer film structure of the present invention may comprise one or more tie layer between the core layer and the first outer layer and/or the second outer layer. As used here in, the term tie layer refers to any inner layer having the primary purpose of adhering two layers to one another. The first tie layer comprises a first polymer, the second tie layer comprises a second polymer, a third tie layer comprises a third polymer, etc. In a preferred embodiment, the first polymer is the same as the second polymer. In another embodiment of the present invention the first polymer is different than the second polymer.

Suitable polymers for use as a tie layer are alkyl ester copolymers, grafted alkyl ester copolymers, modified polyolefins, and blends thereof and are well known, see USP 5,139,878 which is incorporated herein in by reference in its entirety. Preferably, polymers for use as a tie layer comprise polar functional groups. Preferably, tie layers are compatible and extrude well with both adjacent layers.

Such tie layers can include one or more polymers that contain mer units derived from at least one of C₂-C₁₂ alpha-olefin, styrene, amide, ester, and urethane, preferably one or more of anhydride-grafted ethylene/alkyl ester copolymer, anhydride-grafted

ethylene/alkyl ester copolymer, and anhydride-grafted ethylene/ethylenically unsaturated acid copolymer. The term copolymer is used herein to represent a polymer comprising two or more monomers.

Alkyl ester copolymers are particularly useful for use as a tie layer in the present invention. They can be produced in accordance with the processes well known to the art forming random, block and graft copolymers. Those production processes include, but are not limited to, the ones described in USP 2,953,551; 3,350,372; and 3,350,372, the alkyl ester copolymers of the present invention can be prepared by a continuous polymerization of an olefin of about 2 to about 8 carbon atoms and an alkyl ester of an alpha, beta- ethylenically unsaturated carboxylic acid in the presence of a free radical polymerization initiator such as lauroyl peroxide or capryl peroxide. The olefins which may be used to form the alkyl ester copolymers include olefins having between 2 and 8 carbon atoms. Non-limiting examples of suitable olefins include ethylene, propylene, butylene, pentene- 1,3-methylbutene-l, 4-methylpentene-l, and hexene. Of these, preferred olefins are ethylene, propylene, and butylene; most preferred is ethylene.

The alkyl esters of an alpha, beta-ethylenically unsaturated carboxylic acid which may be used to form the alkyl ester copolymers include, but are not limited to, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, octadecyl acrylate, methyl methacrylate, ethyl metacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, and octadecyl methacrylate. Of these, preferred are methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate; more preferred are methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate.

Non-limiting examples of the alkyl ester copolymers suitable for use in the present invention include ethylene/methyl acrylate, ethylene/ethyl acrylate, ethylene/butyl acrylate, ethylene/2-ethylhexyl acrylate, ethylene/decyl acrylate, ethylene/octadecyl acrylate, ethylene/methyl methacrylate, ethylene/ethyl methacrylate, ethylene/butyl methacrylate, ethylene/2-ethylhexyl methacrylate, ethylene/decyl methacrylate, ethylene/octadecyl methacrylate, and copolymers and blends thereof. Of these, preferred are ethylene/methyl acrylate, ethylene/ethyl acrylate, ethylene/butyl acrylate, ethylene/methyl methacrylate, ethylene/ethyl methacrylate, ethylene/butyl methacrylate, and copolymers and blends thereof including ethylene/methyl acrylate-ethylene/butyl acrylate copolymer; more preferred are ethylene/methyl acrylate, ethylene/methyl methacrylate, ethylene/butyl acrylate, ethylene/butyl methacrylate, and copolymers and blends thereof. The preferred alkyl ester copolymer suitable for the present invention comprises between about 5 and about 50 weight percent of the alkyl ester, based on the total weight of the alkyl ester copolymer.

Most preferred tie layers comprise ethylene/vinyl acetate copolymer (EVA), ethylene/maleic anhydride copolymer (EMA), ethylene/ethyl acetate copolymer (EEA), and ethylene/n-butyl acetate copolymer (EnBA).

In a preferred embodiment, the tie layer preferably comprises an ethylene/alkyl ester copolymer wherein the alpha olefin is present in the ethylene/alkyl ester copolymer in an amount of from 5 percent to 40 weight percent based on the weight of the thermoplastic resin, preferably of from 10 weight percent to 35 weight percent, preferably of from 15 weight percent to 30 weight percent, more preferably of from 18 weight percent to

28 weight percent based on the weight of the thermoplastic resin.

In a preferred embodiment, the tie layer comprises a grafted ethylene/alkyl ester copolymer. Preferably the graft is a maleic anhydride graft and is present in an amount of from 0.03 weight percent to 1.3 weight percent by weight of the grafted ethylene/alkyl ester copolymer (e.g., total weight of graft and ethylene/alkyl ester copolymer combined), preferably 0.04 weight percent to 0.5 weight percent, more preferably from 0.05 weight percent to 0.3 weight percent, and more preferably from 0.07 weight percent to 0.2 weight percent based on the total weight of the grafted ethylene/alkyl ester copolymer.

Most preferred graft-modified tie layers comprise maleic anhydride grafted polyethylene (gMAH-PE), a maleic anhydride grafted ethylene/ethyl acetate copolymer (gMAH- EE A), a maleic anhydride grafted ethylene/maleic anhydride copolymer (gMAH- EMA), a maleic anhydride grafted ethylene/vinyl acetate copolymer (gMAH- EVA), a maleic anhydride grafted ethylene/n-butyl acetate copolymer (gMAH-EnBA), or mixtures thereof.

Preferably, a tie layer has a thickness of from about 0.01 mil to about 2 mil, more preferably from about 0.05 mil to about 1.5 mil, most preferably from about 0.05 mil to about 1 mil. The thickness of a tie layer is preferably from about 1 to about 50 percent, more preferably from about 5 to about 30 percent, most preferably from about 5 to about 20 percent of the total thickness of the multilayer film.

Another group of suitable polymers for use in the tie layer includes modified polyolefin compositions having at least one functional moiety selected from the group consisting of unsaturated polycarboxylic acids and acid anhydrides. The polyolefins which may be used to form the modified reaction product of the modified polyolefin compositions suitable for the present invention include polyolefins and their copolymers, wherein the olefin monomers have between about 2 and about 8 carbon atoms. Non-limiting examples of suitable polyolefins include low, medium or high density polyethylene, linear low density polyethylene, polypropylene, polybutylene, polypentene-1, poly-3-methylbutene-l, poly-4- methylpentene-1, polyhexene-1, and copolymers and blends thereof. Of these, preferred polyolefins are polyethylenes, polypropylene, polybutylene, and copolymers and blends thereof.

The modified polyolefin compositions suitable for use in conjunction with the present invention include copolymers and graft copolymers of a polyolefin and a constituent having a functional moiety selected from the group consisting of unsaturated polycarboxylic acids and acid anhydrides thereof. The unsaturated polycarboxylic acids and anhydrides include maleic acid, maleic anhydride, fumaric acid, crotonic acid, citraconic anhydride, itaconic anhydride and the like. Preferred of these are anhydrides, of which most preferred is maleic anhydride.

The preferred modified polyolefin composition comprises between about 0.001 and about 10 weight percent of the functional moiety, based on the total weight of the modified polyolefin. More preferably, the functional moiety comprises between about 0.005 and about 5 weight percent; most preferably, between about 0.01 and about 2 weight percent.

The modified polyolefin composition useful in the present invention preferably further comprises up to about 40 weight percent, based on the total weight of the modified polyolefin, of vinyl acetate. More preferably, the modified polyolefin comprises between about 4 and about 30 weight percent of vinyl acetate; most preferably, between about 5 and about 25 weight percent.

In one embodiment, the tie layer compositions of the present invention are blends of an alkyl ester copolymer and a modified polyolefin. The preferred adhesive layer compositions may vary between a weight ratio of alkyl ester copolymer to modified polyolefin of about 90 percent to about 10 percent to a weight ratio of alkyl ester copolymer to modified polyolefin of about 10 percent to about 90 percent. More preferably, the ratio of alkyl ester copolymer to modified polyolefin is within the range of about 80 percent to 20 percent alkyl ester copolymer to about 20 percent to 80 percent modified polyolefin; most preferably the ratio of alkyl ester copolymer to modified polyolefin is within the range of about 70 percent to 30 percent alkyl ester copolymer to about 30 percent to 70 percent modified polyolefin.

Although each layer (i.e., core layer, first tie layer, second tie layer, first outer layer, optionally the second outer layer, one or more additional layers, etc.) of the multilayer film structure can be a different thickness, the thickness of each of the layers of the films in the multilayer film structure is independently equal to or greater than 0.05 mils, preferably equal to or greater than 0.1 mils, more preferably equal to or greater than 0.5 mil, more preferably equal to or greater than 1 mil, more preferably equal to or greater than 3 mils, and more preferably equal to or greater than 5 mils. Although each layer of the multilayer film structure can be a different thickness, the thickness of each of the layers of the film in the multilayer film structure is independently equal to or less than 100 mils, preferably equal to or less than 75 mils, more preferably equal to or less than 50mils, more preferably equal to or less than 35 mils, more preferably equal to or less than 25 mils, more preferably equal to or less than 20 mils, more preferably equal to or less than 17 mils, and more preferably equal to or less than 15 mils.

The thickness of the one or more tie layer may vary, but is generally equal to or greater than 0.01 mils, preferably equal to or greater than 0.05 mils, more preferably equal to or greater than 0.1 mils, more preferably equal to or greater than 0.25 mils, and more preferably equal to or greater than 0.5 mils. The thickness of the tie layer may vary, but is generally equal to or less than 15 mils, preferably equal to or less than 10 mils, more preferably equal to or less than 5 mils, more preferably equal to or less than 2.5 mils, more preferably equal to or less than 1 mils, more preferably equal to or less than 0.75 mil, and more preferably equal to or less than 0.6 mils.

The multilayer film structure of the present invention can have a variety of structures so long as there is a minimum of four layers, a core layer (B) sandwiched by a first tie layer (X0 and a second tie layer (X₂), and a first outer layer (A), wherein the first tie layer is sandwiched, or is adjacent to, the first outer layer and the core layer, such a structure may be represented as: AXiBX₂. In one embodiment, the multilayer film structure of the present invention is a five layer film having a first tie layer (X0 between the core layer (B) a first outer layer (A) and a second tie layer (X₂) between the core and the second outer layer (C) and is represented by the structure AX₁BX₂C. In one embodiment, the first tie layer (X0 comprises the same resin as the second tie layer (X₂) such that Xi = X₂, sometimes both tie layers represented simply as X, and the first outer layer (A) comprises the same resin as the second outer layer (C) such that A = C, sometimes both outer layers simply referred to as both A or both C, this structure may be represented as AXBXA or CXBXC. In another embodiment, both tie layers are the same, but, the first outer layer (A) comprises a different resin than the second outer layer (C), wherein that structure may be represented as AXBXC. In yet further embodiments, both tie layers comprise different resins from each other and both outer layers comprise different resins from each other and the different five layer films may have structures such as AXiBX₂A, AXiBX₂C, and the like. Further embodiments may comprise one or more inner layers ((D), (E), (F), (G), (H), etc.) between the outer layers and the tie layers, such a structure may be represented as ADX₁BX₂DC, AEXBXEA, AEX₁BX₂FC, and the like. These structure examples are not inclusive; rather, they demonstrate just a few possible structures of the multilayered film of the present invention. The multilayer films of the present invention may have more than 5 layers, for example 6, 7, 8, 9, 10, or more. These are only a few of the many possible combinations of multilayer film structures, and any variation of the order and thickness of the layers of the core layer, first outer layer, second outer layer, and optional one or more tie layer can be made.

As defined herein, the core layer is sandwiched between the first tie layer and the second tie layer, the first tie layer is sandwiched between the core layer and the first outer layer and, when a second outer layer is present, the second tie layer is sandwiched between the core layer and the second outer layer. As used herein sandwiched between means disposed between, or having adjacent surfaces, for example, a core layer has a first and a second surface, a first tie layer has a first and a second surface, and a second tie layer has a first and a second surface wherein the first surface of the core layer is adjacent to the first surface of the first tie layer and the second surface of the core layer is adjacent to the first surface of the second tie layer, in other words the core layer is sandwiched between or disposed between the first and second tie layers.

The multilayer films of this invention are produced by conventional methods useful in producing multilayer films such as by coextrusion techniques. Coextrusion techniques include methods which include the use of a feed block with a standard die, a multimanifold die such as a circular die for blown bubble film, as well as a multimanifold die such as used in forming multilayer films for forming flat cast films and cast sheets. One particular advantage of coextruded films is in the formation of a multilayer film in one process step by combining molten layers of each of the film layers of PVDC formulation, tie layer composition, and copolyester layers, as well as optionally more film layers, into a unitary film structure.

In order to produce a multilayer film by a coextrusion process, it is necessary that the constituents used to form each of the individual films be compatible in the film extrusion process. What is to be understood by the term "compatible" in this respect is that the film-forming compositions used to form the films have melt properties which are sufficiently similar so to allow coextrusion; melt properties of interest include melting points, melt flow indices, apparent viscosity, as well as melt stability. It is important that such compatibility be present so to assure the production of a multilayer film having good adhesion and relatively uniform thickness across the width of the film being produced. As is known in the art, film-forming compositions which are not sufficiently compatible to be useful in a coextrusion process frequently produce films having poor interfacial lamination, poor physical properties as well as poor appearance. In the practice of the present invention, the above-noted factors which are useful in determining compatibility may be determined, and once polymers having desirable physical properties are selected, experimental trials may be conducted in order to determine the optimal combination of relative properties in adjacent layers.

If a coextrusion process is used, it is important that the constituents used to form a multilayer film be compatible within a relatively close temperature range so they may be extruded through a common die. In using conventional processing equipment for thermally sensitive polymers, three conditions should be met. Two conditions, which are interrelated, are processing time and processing temperature. In melt processing polymers, it is generally recognized that as processing temperatures increase, processing times must decrease in order to avoid undesirable results such as polymer degradation. Melt processing must be accomplished at a temperature below that at which decomposition of the vinylidene chloride copolymer becomes significant. A third condition is that sufficient mixing must be generated during melt processing to provide a visually homogeneous blend, i.e., no visible solids, within a reasonable mixing time. The most appropriate residence time and temperature conditions vary with different equipment. Persons of ordinary skill in the art can ascertain the optimum conditions for their own equipment without undue

experimentation. PVDC is a resin that requires both melt temperature and time at high temperatures to be sufficiently low as to not undergo significant degradation during the coextrusion process. Preferably, the co-extrusion processing temperature for the outer layer(s) is equal to or less than 230 °C, preferably equal to or less than 225 °C, more preferably equal to or less than 220 °C and more preferably equal to or less than 215 °C.

Alternatively, the coextruded multilayer films of the present invention can be used to produce multilayer laminates. Lamination techniques are well known in the art. Such lamination techniques involve forming a multilayer film structure from pre-fabricated film plies. The basic methods used in film laminating techniques are fusion, wet combining, and heat reactivation. Fusion is a method of laminating two or more film plies using heat and pressure without the use of adhesives. This method can only be used where the films being laminated are comprised of polymers that readily form interfacial adhesion. Wet combining and heat reactivation are utilized in laminating incompatible films using adhesive materials. Further details of lamination techniques are disclosed, for example, in the Modern Plastics Encyclopedia, Vol. 57, No. 10A, pp 345-348, McGraw Hill, October 1980.

The multilayer films structures of the present invention may be subjected to orientation resulting from a stamping or molding process wherein the film is heated and formed into a three dimensional structure; the regions of the film which are formed undergo orientation. One particularly useful type of article is packaging materials associated with medicinal drugs and pharmaceutical compositions which are provided in either pill, caplet or capsule form. Such a packaging structure is known to the art as a "blister" pack. Blister packs conventionally comprise at least two elements, a first sheet of a thermoformed multi- layer film which has been stamped, thermoformed, vacuum pressure formed, or the like with at least one, but more generally a plurality of indentations which form receptacles. Such indentations extend out of the plane of the film (which may be generally be considered to be two-dimensional) to form a three-dimensional shape. Such shapes form individual receptacles are suited for the retention of the medicinal drugs. A further, second sealant sheet is generally layered in registry with the film sheet which seals the individual receptacles formed within the first sheet and containing the pharmaceutical composition. Typically, the second sealant sheet is a metallic sheet such as aluminum foil or metallized film which provides good strength and low water vapor transmission and/or odor permeability. Further, the use of a metal or metallized sheet as the sealant sheet may be desirable as such materials being substantially opaque provide a backing with the first sheet containing the indentations and a rapid means of visual inspection by which it may be readily determined which of the contents of the receptacles have been removed from the packaging structure. Alternatively, such a second sealant sheet may be a sheet comprised of a fibrous material such as a paper product, or of a polymeric film or sheet which may or may not be colored or which alternately may or may not be opaque.

The multilayered film structure of the present invention may be imparted with a conventional coloring agent or a dye or pigment so to impart a color to the laminated film structures, or alternately to render the film structures substantially opaque. Any

conventional coloring agent or a dye or pigment which is appropriate for use in the films may be used.

In addition to packaging and retaining medicinal drugs and pharmaceuticals, blister pack sheets formed from the multilayer film structures may be used to contain other materials, such as foodstuffs (including liquids or gelatinous materials). Further it should be recognized that the multilayer film may be thermoformed into a container suitable for foodstuffs, pharmaceutical compositions and other articles of manufacture, such as paints, liquid slurries, and gelatinous compositions.

For example, one common method of packaging would be horizontal form fill seal (HFFS) packaging which consists of heating and pressure forming a web of film (here multilayer), filling the cavity, lidding the cavity and cutting the package from the web. Such equipment is available from Multivac Inc., Kansas City Missouri, for example.

Liquids, solid foods, medical devices, hardware, pharmaceuticals, beauty aids, etc. may be packaged in this manner. The HFFS method is advantageous as many cavities can be made and filled simultaneously rather than sequentially.

The invention is more easily understood by reference to specific embodiments which are representative examples according to the teachings of the instant invention. It must be understood however, that the specific embodiments discussed herein are provided only for the purpose of illustration, and not by way of limitation, and it is to be further understood that the invention may be practiced otherwise than specifically described and yet be within the inventive scope.

EXAMPLES Examples 1 to 5 and Comparative Example A are five-layer AXBXA symmetrical multilayer films produced using a cast co-extrusion film process as generally shown or described in USP 5,685,128, incorporated herein in its entirety. The copolyester resins (CoPET) are desiccant dried at 65 °C overnight prior to extruding. The compositions for each of the layers are listed in Table 1. The amount of each layer is given as volume percent based on the total volume of the multilayer film structure and the amount of each component making up an individual layer is given in parts based on 100 parts for the total layer composition. In Table 1:

"CoPET- 1" is an amorphous copolyester of ethylene 1, 2 cyclohexylenedimethylene terephthalate having an IV of about 0.75 dl/g, DMS viscosity at 10 rad/sec of 4,472 Pa-sec and a Notched Izod impact of about 3 Joules per centimeter (J/cm) available as X-29319- 109-1 from Eastman Chemical Company;

"CoPET- 2" is an amorphous copolyester of ethylene 1, 2 cyclohexylenedimethylene terephthalate having an IV of about 0.52 dl/g, DMS viscosity at 10 rad/sec of 1,407 Pa-sec and a Notched Izod impact of about 1 J/cm available as X-29319- 109-2 from Eastman Chemical Company;

In the following PVDC compositions:

"Epoxidized soy bean oil" is available as PARAPLEX™ G60 from Hallstar;

"TSPP" is micronized tetrasodium pyrophosphate;

"Calcium stearyl lactylate" is available as PANTIONIC™ 930 from Patco

Additives;

"Polyethylene wax" is available as A-C 629A from Honeywell;

"Paraffin wax" is available as VESTOWAX™ SH-105 from Evonik Degussa;

"Magnesium hydroxide" is available as MAGSHIELD™ UF from Marten

Marrietta; and

"Ultramarine Blue RB30" is available from Ferro Corporation.

"PVDC-1" is a vinylidene chloride copolymer formulation comprising a vinylidene chloride copolymer formed through a suspension process comprising 4.8 percent methyl acrylate and having a weight average molecular weight of about 96,000, 2 weight percent epoxidized soy bean oil, 0.25 weight percent calcium stearyl lactylate, 0.25 weight percent polyethylene wax, 0.1 weight percent paraffin wax, 1 weight percent magnesium hydroxide, and 125 parts per million (PPM) of Ultramarine Blue RB30;

"PVDC-2" is a vinylidene chloride copolymer formulation comprising a vinylidene chloride copolymer formed through a suspension process comprising 4.8 percent methyl acrylate and having a weight average molecular weight of about 96,000, 2 weight percent epoxidized soy bean oil, 0.25 weight percent calcium stearyl lactylate, 0.25 weight percent polyethylene wax, 0.1 weight percent paraffin wax, 1 weight percent magnesium hydroxide, and 500 parts per million (PPM) of Ultramarine Blue RB30;

"PVDC-3" is a vinylidene chloride copolymer formulation comprising a vinylidene chloride copolymer formed through a suspension process comprising 4.8 percent methyl acrylate and having a weight average molecular weight of about 96,000, 1 weight percent epoxidized soy bean oil, 0.25 weight percent calcium stearyl lactylate, 0.25 weight percent polyethylene wax, 0.1 weight percent paraffin wax, 0.5 weight percent magnesium hydroxide, 1 weight percent tetrasodium pyrophosphate, and 500 parts per million (PPM) of Ultramarine Blue RB30;

"PVDC-4" is a vinylidene chloride copolymer formulation comprising a vinylidene chloride copolymer formed through a suspension process comprising 20 percent vinyl chloride 2 weight percent epoxidized soy bean oil, 0.25 weight percent calcium stearoyl lactylate, 0.25 weight percent polyethylene wax, 0.1 weight percent paraffin wax, and 1 weight percent magnesium hydroxide;

"EVA-gMA" is a tie layer of an ethylene copolymer comprising 25.4 weight percent vinyl acetate with an 0.11 weight percent maleic anhydride graft having a melt index of 8 g/10 min as determined by ASTM 1238-86 at 190 °C under a load of 2.16 kg; and

"S/AB" is a slip anti/block concentrate available as EASTAR™ Copolyester 6763 C0030 Slip/AB from Eastman Chemical Company.

Intrinsic viscosity of the copolyesters is determined according to Eastman method (EMN-A-AC-G-V-1-10,). Polymer samples are dissolved in a solvent (60 percent phenol and 40 percent 1,1,2,2-tetrachloroethane, percents are by weight) at a concentration of 0.50 grams per 100 milliliters (g/100 ml). The viscosity of the polymer solutions is determined using a Viscotek Relative Viscometer. The relative viscosity is determined by measuring the pressure difference between two capillaries, PI and P2. PI acts as a reference or blank capillary and has pure solvent running through it; P2 is the sample capillary. The pressure in each capillary is measured by means of independent transducers. The data produced is then analyzed by a computer and/or manual controller and converted to inherent viscosity. The IV calculated for the sample is compared to that for a reference polymer having an "accepted" IV, usually determined by a different primary method, such as ASTM D 4603, "Test Method for Determining Inherent Viscosity of Poly(ethylene terephthalate) (works for PET)." Values obtained by this method should correlate with those obtained by ASTM D 4603 but may not match them at all IV levels.

Table 1

When the outer layer is 99 percent CoPET-1 (Comparative Example A) the pressure capability and/or torque of the extruder is exceeded at a temperature required to coextrude with PVDC and a multilayer film could not be made.

Examples 1 to 5 are vacuum pressure formed with plug assist capability using a Pentapack CT 1200L Blister Packaging Line operating with a 110 millimeter sample width. Each formed multilayer film having 10 blisters. Examples 1, 2, 4 and 5 are formed with a heated top and bottom plate at 118 °C, Example 4 is formed with a heated top and bottom plate at 113 °C. A draw ratio of 4: 1 is achieved. Acceptable line speeds are achieved between 40 cycles per minute up to 80 cycles per minute.

The resulting formed multilayer film structures from Examples 1 to 5 are filled with

350 grams to 500 grams silica desiccant, sealed with foil, and tested. Foil lidding is applied using a 1 mil aluminum foil with a 0.6 mil EVA seal. The foil is a 7 mil Klockner

Pentaplast Alfoil P 200/40 (200 micron PVC/40 micron PVDC). The lidding is sealed with knurled plates with 140 °C heat on the top plate only.

The following properties are determined on the blister packs made from Examples 1 to 5 and the results are reported in Table 2:

"Gauge" is the thickness of the multilayer film as determined according to ASTM D374 and is reported in mils;

"Haze" is run according to ASTM D1003 and is reported in percent;

"Core Layer Thickness" is reported in mils;

"WVTR" is Water Vapor Transmission Rate and is determined according to ASTM F1249 at 38 °C and 100 percent relative humidity and is reported in grams per 100 square inches per day (g/lOOin 2 /day) and grams per square meter per day (g/m 2 /day);

"OTR" is Oxygen Transmission Rate and is determined according to ASTM D3985 at 23 °C and at 50 percent relative humidity and is reported in cubic centimeters per 100 square inches per day per atmosphere (cc/lOOin /day/atm) and cubic centimeters per square meters per day per atmosphere (cc/m /day/atm);

"MVTR" is Moisture Vapor Transmission Rate and is determined gravimetrically on sealed blisters with 350 to 500 grams of silica desiccant sealed into the blisters with foil lidding. Initial weights for five samples (each having 10 blisters) are determined, and then the samples are aged, up to 45 days, at 40 °C and 75 percent relative humidity. Weights are obtained versus time and reported in milligrams moisture per day per blister

(mg/day/blister); "Shrink" is shrink as determined according to ASTM D1204 at 120 °C for 10 minutes and reported in percent ( );

"Tear" is Elmendorf tear as determined according to ASTM D1922 and reported in grams (g);

"Modulus" is 1 % sec modulus as determined according to ASTM D882 and reported in 10 pounds per square inch (kpsi); and

"YI" is yellowness index as determined according to ASTM D1925.

Table 2

Example 6 is a five layer symmetrical AXBXA film of the present invention produced on production scale equipment.

In the PVDC composition of Example 6:

"SEASTAB™ 705" is a (Ca, Mg, Al)(OH)₂,Si0₂ thermal stabilizer with a BET of about 26 m /g available as SEASTAB 705 in the form of a white powder having an average particle size of 2.77 microns from Mitsui Plastics, Inc.

In Table 3:

"CoPET-3" is an amorphous copolyester of ethylene 1, 2 cyclohexylenedimethylene terephthalate having an IV of about 0.73 dl/g and a Notched Izod impact of about 3 J/cm available as X-29319- 109-3 from Eastman Chemical Company and "PVDC-5" is a vinylidene chloride copolymer formulation comprising a vinylidene chloride copolymer formed through a suspension process comprising 4.8 percent methyl acrylate and having a weight average molecular weight of about 86,000, 2 weight percent epoxidized soy bean oil, 0.25 weight percent calcium stearyl lactylate, 0.5 weight percent polyethylene wax, 0.25 weight percent paraffin wax, 1 weight percent SEASTAB 705, 0.5 weight percent magnesium hydroxide, and 500 parts per million (PPM) of Ultramarine Blue RB30.

Table 3 summarizes the composition and processing parameters for Example 6.

Table 3

The multilayer film of Example 6 demonstrates good barrier and formability properties. Blister packs from the multilayer film of Example 6 are made by the same method as described herein above for Examples 1 to 5. The film forms good blisters at commercial cycle times. Samples are collected for stability/barrier testing as described herein above:

Table 4

Claims

CLAIMS:

1. A coextruded multilayer film structure comprising at least four layers, a core layer

(B) , a first tie layer (Xi), a second tie layer (X₂), and a first outer layer (A) wherein:

i) the core layer is disposed between the first and second tie layers and

comprises a copolymer of polyvinylidene chloride resin,

ii) the first tie layer comprises a first polymer and the second tie layer

iii) the first outer layer comprises a first amorphous copolyester having an

intrinsic viscosity of from 0.40 dl/g to 0.70 dl/g,

2. The coextruded multilayer film of Claim 1 further comprising a second outer layer

(C) wherein the second outer layer comprises a second amorphous copolyester having an intrinsic viscosity of from 0.40 dl/g to 0.70 dl/g, said second amorphous copolyester may be the same or different than the first copolyester, wherein the second tie layer is adjacent to the second outer layer represented by the structure AXiBXiC.

3. The coextruded multilayer film of Claim 2 wherein the first outer layer and the second outer layer comprise the same copolyester and the first tie layer and the second tie layer comprise the same polymer having the structure AXBXA.

4. The coextruded multilayer film of Claims 1 or 2 wherein the first amorphous copolyester and/or second amorphous copolyester independently have an intrinsic viscosity of from 0.45 dl/g to 0.65 dl/g.

5. The coextruded multilayer film of Claim 1 wherein the polyvinylidene chloride resin comprises a copolymer of vinylidene chloride and methyl methacrylate, wherein the methyl methacrylate is present in an amount of 4.8 to 8.5 weight percent based on the weight of the copolymer.

6. The coextruded multilayer film structure of Claim 1 wherein the first and second tie layers independently comprise a maleic anhydride grafted polyethylene (gMAH-PE), a maleic anhydride grafted ethylene/ethyl acetate copolymer (gMAH- EEA), a maleic anhydride grafted ethylene/maleic anhydride copolymer (gMAH- EM A), a maleic anhydride grafted ethylene/vinyl acetate copolymer (gMAH- EVA), a maleic anhydride grafted ethylene/n-butyl acetate copolymer (gMAH-EnBA), or mixtures thereof.

7. The coextruded multilayer film of Claim 1 further comprising a second outer layer (C) wherein the second outer layer comprises one or more of the following resins:

homopolymer polypropylene, random polypropylene, substantially isotactic propylene, polyethylene, copolymer of ethylene and vinyl acetate, copolymer of ethylene and methyl acrylate, copolymer of ethylene and ethyl acrylate, copolymer of ethylene and carbon monoxide, copolymer of ethylene and n-butyl acrylate, terpolymer of ethylene, acrylic acid and carbon monoxide, terpolymer of ethylene, n-butyl acrylate and carbon monoxide, terpolymer of ethylene, methacrylic acid and carbon monoxide, terpolymer of ethylene, vinyl acetate and carbon monoxide, an ionomer, thermoplastic urethane, polyamide, K-resin, or mixtures thereof wherein the second tie layer is adjacent to the second outer layer represented by the structure AXiBXiC.

8. The coextruded multilayer film of Claim 1 further comprising a second outer layer

(C) wherein the second outer layer comprises one or more of the following resins:

homopolymer polypropylene, random polypropylene, substantially isotactic propylene, substantially linear ethylene polymer, linear ethylene polymer, linear low density

polyethylene, very low or ultra low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, or mixtures thereof, wherein the second tie layer is adjacent to the second outer layer represented by the structure AXiBXiC.

9. The coextruded multilayer film of Claim 1 further comprising a second outer layer (C) wherein the second outer layer forms a permanent or a peelable seal, wherein the second tie layer is adjacent to the second outer layer represented by the structure AXiBXiC.

10. The coextruded multilayer film structure of Claim 1 in the form of a packaging application requiring horizontal forming with lidding.

11. The coextruded multilayer film structure of Claim 1 in the form of a blister pack.

12. A process to make a packaging application requiring horizontal forming with lidding by thermoforming the coextruded multilayer film structure of Claim 1.