BACKGROUND OF THE INVENTION

The present invention relates generally to primary packaging and more particularly, to multilayer high moisture harrier laminates for use as a chemically- resistant barrier film.

The food, beverage, and pharmaceutical industries have high demand for packages with characteristic high barrier to gases, water vapor and flavors, while maintaining durability. For this reason, flexible multilayer polymeric film is commonly used in a variety of packages and decorative applications. Regardless of the type of product stored in the package, it is necessary that the package be capable of containing the product without the film degrading due to the type of product, in some instances where metallic foil or metallized film is used as a barrier against air and moisture, it can be difficult to maintain the packaging film's integrity when solvents, halogens or strong acids and bases are present in the product. For example, commonly used topical antiseptic products contain isopropyi or ethyl alcohol, povidone iodine, poloxamer iodine, benzalkonium chloride, benzethonium chloride, or chiorhexidine gluconate as a single agent or in combination with alcohol. Food condiments such as mustard, ketchup, and horseradish typically include acetic, citric and/or formic acid as an ingredient. Those skilled in the art recognize that halogens, acids and bases can slowly destroy the barrier properties of a film by attacking the metal layer directly or by affecting the adhesion of the metal layer to other film layers. As a result, there is a need to develop packaging materials having a layer of metallic foil or metallized film which provides high oxygen and/or moisture barrier properties and which can withstand the corrosive effects of products containing solvents, halogens or acids and bases. Those skilled in the art will recognize that conventional film laminate commonly used in the healthcare packaging industry require multiple layers of biaxiaSSy oriented polyethylene terephthalate (OPET) which act as a chemical barrier to aggressive solvents and other chemicals. The metal foil iayer and its adjacent layers of such laminates need to be protected against the ingress of these aggressive chemicals which could minimize or destroy the adhesion between these layers and ultimately affect the barrier properties of the laminate. Consequently, the method of making these conventional laminates is complex and costly because the foil Iayer and each of the OPET layers require a separate lamination operation in order to fabricate the final laminate structure. Therefore, it would be highly desirable to provide high oxygen and/or high moisture barrier film laminates which can withstand the aggressive chemical effects of solvents, halogens or acids and bases without the need for multipl layers of biaxially oriented polyethylene terephthalate (OPET).

SUMMARY OF THE INVENTION

The present invention is directed to flexible chemically-resistant barrier laminates for packaging a product. The product may be a foodstuff, a personal health care product, a pharmaceutical product an industrial product or an agricultural product. The laminate includes a first exterior layer comprising a thermoplastic film or paper, a second exterior layer comprising a heat seatable material, a first interior layer comprising metallic foil or metallized polymer material, and a second inferior Iayer positioned between the first interior Iayer and the second exterior Iayer; wherein the second interior layer comprises a cyclic olefin copoiymer. An important aspect of the present invention is relative positioning of the cyclic olefin copolymer Iayer with respect to other film layers of the laminate. The inventors have discovered that the layer of cyclic olefin copoiymer can act as a chemical barmr to some substances that may migrate from the product through the film to the metallic foil or metallized film layer and cause undesirable degradation of the barrier properties of the metalfic foil or metallized film and/or undesirable delamination to adjacent layers. This in turn means that the cyclic olefin copolymer layer must be positioned between the sealant layer which is exposed fo the product and the layer of metallic foil or metallized film. The cyclic olefin copolymer (COC) may be any copolymer having at least one norbornene structural moiety within the repeating backbone of the potymer. Typical cyclic olefin copolymers include both norbornene and olefin structural moieties. Preferably, the COC is a copolymer of ethylene and 2-norbornene. Suitable COCs for use in the present invention may have a heat deflection temperature under load (0.45 SVIPa) of about 75° C, or 130° C, or 150° C, or 170° C. Exemplary of commercially available cyclic olefin copolymers include, but are not limited to, the TOPAS ^® family of resins which is supplied by TOPAS Advanced Polymers, Inc. (Florence, KY, USA),

[05] Another important aspect of the present invention is that the laminates have sufficient flexibilit to permit the fabrication of flexible pouches, bags and the like on conventional packaging equipment such as for example, but not limited to vertical form-f ill-seal or horizontal form-fili-seal manufacturing equipment. A precondition for such flexibility is that the laminates should exhibit a bending resistance (or stiffness) of between 51.4 and 177 Gurley Units (0.50 and 1.74 mNewion) in either the machine and/or transverse direction. Industry standards for measuring the bending resistance (or stiffness) adopted by the Technical Association of the Pulp and Paper Industry (TAPPI) can be used to characterize the bending resistance of the laminates of the present invention. Bending resistance can be measured in accordance with T 543 TAPPI test method. For example, the Gurley Stiffness value can be measured via a Gurley Stiffness Tester, manufactured by Gurley Precision Instruments of Troy, .Y. The Gurley Stiffness Tester measures the externally applied moment required to produce a given deflection of a strip of materia! of specific dimensions fixed at one end and having a concentrated load applied to the other end. The results are obtained as "Guriey Stiffness Units", which can be readily converted into force units, mNewton (mN) by multiplying the "Gurley Stiffness Units" by 9.807 x 10 ^"3 .

Still another important aspect of the present invention is that the laminates provide a barrier to the outside environment for products packaged within these laminates. The term "barrier" refers to laminates having an oxygen gas transmission rate of between 0 to 10.0 cm ³ /100 tn ² /24 hours (0 to 155 cm ³ /m ² 124 hours) at 73° F (23* C) and 0% relative humidity and/or a water vapor transmission rate of between 0 to 0.1 g/100 in /24 hours (0 to 1.55 g/m ² /24 hours) at 100° F (38° C) and 90% relative humidity.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 illustrates a schematic view of one preferred embodiment of a laminate according to the present invention.

FIG. 2 illustrates a schematic view of another preferred embodiment of a laminate according to the present invention.

FIG. 3 illustrates a schematic view of another embodiment of a laminate according to the present invention.

FIG. 4 illustrates a schematic view of still another embodiment of a laminate according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now more particularly to FIG. 1 of the drawings, a preferred embodiment of laminate 10 embodying the present invention is shown having at least four layers. The laminate 10 has a first extenor surface 10a and a second exterior surface 10b, and comprises a first layer 11 comprising a heat sealabie material, a second layer 12 comprising a cyclic olefin copolymer, a third layer 13 comprising metallic foil or metallized polymer material, and a fourth iayer 14 comprising a thermoplastic film or paper. As can be seen, the first Iayer 11 forms the first exterior surface 10a and the fourth layer 14 forms the second exterior surface 10b of laminate 10. Second iayer 1 is positioned between first iayer 1 and third Iayer 13. In this embodiment, laminate 10 may include more layers than depicted and may include any number of film layers and film Iayer composittons depending upon both functional and aesthetic requirements of the laminate. For example, the thermoplastic film of fourth iayer 14 may itself be a multilayer film having 2, 3, 4, 5, 8, 7 or more layers. Alternatively, the first Iayer 11 may include a multilayer film with the proviso that there is a second layer 12 containing a cyciic olefin copoiymer disposed between it and the metallic foil or metallized polymer film of third layer 13.

[13] First Iayer 11 comprising a heat sealabie material may be any thermoplastic materia! which forms a fusion or peetabie fusion seal to itself or a similar material under pressure and heat. Such material may include, but is not limited to, homopofymers and copolymers of polyethylene such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ver low density polyethylene (VLDPE), ultra-low density polyethylene (ULDPE), ionomers and blends thereof. First Iayer 11 may also include copolymers of ethylene with one or more comonomers selected from C ₃ to C< ₀ aSpha-o!efins such as propene, butene-1 , hexene-1 , octene-1 , etc. in which the molecules of the copolymers comprise long polymer chains with relatively few side chain branches arising from the alpha- olefin which was reacted with ethylene. Heat sealabie materials may also include ethylene vinyl acetate copolymers, ethylene acrylic acid copolymers, ethylene methacrylic acid, ethylene methacrylate copolymers and blends thereof. Heat sealabie materials may even further include certain grades of cyclic olefin copolymers. So one preferred embodiment, first layer 11 has a total thickness of at least 25.4 pm (1 mil). In anothe preferred embodiment, first layer 11 has a total thickness of about 50.8 pm (2 mil).

The second layer 12 comprises a cyclic olefin copolymer. Ethylene norbornene copolymers are known commercially as cyclic o!efm copolymers, "COC," with one or more different cyclic olefin units randomly or alternately attached to the ethylene polymer backbone. In general, COCs exhibit a high glass transition temperature (greater than 50° C), optica! clarity, low heat shrinkage, low moisture absorption and low birefringence. These materials have been produced by a number of polymerization techniques which include chain polymerization of cyclic monomers such as 6, 9, 10-trinorborn-2-ene (norbomene) of 1 , 2, 3, 4, 4a, 5, 8, 8a-octa-hydro-1 , 4:5, 8-dimethanonaphthalene (tetracyclododecene) with ethane; or ring-opening metathesis of various cyclic monomers followed by hydrogenation. It is also contemplated that second layer 12 may comprise a blend of COC and another thermoplastic material such as, but not limited to homopolymers and copolymers of polyethylene.

Third layer 13 may comprise any metallic foil such as, but not limited to, aluminum, tin, copper and the like. These materials are well known in the art. Alternatively, third iayer 13 may include a metallized polymer layer. Any conventional metallization technique known to those skilled in the art can be used to form a metallized polymer layer. An especially preferred metallization technique is vacuum deposition wherein the metal is vacuum evaporated and then deposited onto the polymer Iayer. (See, William Goldie in Metallic Coating of Plastics.. Vol. 1 , Electrochemical Publications Limited, Chap. 12 (1968), the disclosure of which is incorporated herein by reference in its entirety.) A metal may be preferably deposited onto a polymer layer b vapor deposition techniques, typically by applying the molten metal under vacuum by such techniques as electron beam evaporation, sputtering, induction heating, or thermal evaporation. A particularly specific technique for metallization is by electron beam vacuum evaporation deposition methods. Preferred values for the average thickness of the metal are within the range of about 1.0 to 100 nanometers, with the preferred average thickness being within the range of about 3 to 25 nanometers. (1 micron equals 10 ^"7 meters, and 1 nanometer equals 10 ^"8 meters.) Regardless, the metal coating preferably has a thickness less than the polymer substrate on which it is deposited, preferably substantially less than said substrate. It is contemplated that the metallized polymer layer can also include a metal oxide such as but not limited to aluminum oxide.

[16] The thermoplastic film of fourth layer 14 may include, but is not limited to, aromatic polyesters such as, but not limited to, polyethylene terephtha!ate (PET), oriented polyethylene terephtha!ate (OPET), amorphous polyethylene terephthalate (APET), glyco!-modified polyethylene terephthalate (PETG), aliphatic polyesters such as, but not limited to, poiylactic acid (PLA); poiyhydroxyalkonates including but not limited to polyhydroxypropiona!e, poSy(3~ hydroxybutyrate) (PH3B), poly(3~hydroxyvaSerate) (PH3V), po!y{4~ hydroxybutyrate) (PH4B), poly(4-hydroxyvalerate) (PH4V), poly(5- hydroxyvaferate) (PH5V), poly(6-hydroxydodecanoate) (PH6D); or poiyamides such as, but not limited to, oriented and unonented nylon 6, nylon 66, nylon 6/66 and blends thereof, polystyrenes such as, but not limited to, high impact polystyrene (HIPS), general purpose polystyrene (GPPS), and styrene block copolymer (SBC). HIPS is sometimes called rubber-modified polystyrene and is normally produced by copoSymerization of styrene and a synthetic rubber. (See Wagner, et al., "Polystyrene," The Wiley Encyclopedia of Packaging Technology, Second Edition, 1997, pp. 768-771 (John Wiley & Sons, Inc., New York, New York), which is incorporated in its entirety in this application by this reference.) Examples of HIPS include but are not limited to Impact Polystyrene 825E and Impact Polystyrene 945E, both of which are available from Total Petrochemicals USA, Inc.; EB6025 Rubber Modified High Impact Polystyrene, which is available from Chevron Phiilips Company (The Woodlands, Texas); and 6210 High impact Polystyrene, which is available from Sneos Nova LLC (Channahon, Illinois). Alternatively, the thermoplastic film may comprise a polyoleftn such as poiyethyiene including, but not limited to, high density poiyethyiene (HOPE), medium density polyethylene (MOPE), low density polyethylene (LDPE), linear low density poiyethyiene (LLDPE), very low density polyethylene (VLDPE), ultra- low density polyethylene (ULDPE) and blends thereof, or polypropylene and biends thereof. A non-limiting example of high density polyethylene includes Aiathon* M6020 from Equistar Chemicals LP (Houston, Tex.). Other specific non-limiting examples of HOPE include Aiathon ^® M8Q2Q available from Equistar Chemicals LP (Houston, Tex,); Alathon^ L5885 available from Equistar Chemicals LP (Houston, Tex.); ExxonMobil™ HDPE HD 7926.30 available from ExxonMobil Chemical Company (Houston, Tex,); and ExxonMobil™ HDPE HD 7845,30 available from ExxonMobil Chemical Company (Houston, Tex,). In one preferred embodiment, the thermoplastic film is uniaxially oriented, in another preferred embodiment, the thermoplastic film is biaxialSy oriented.

In contrast to a thermoplastic film, fourth layer 14 may alternatively comprise paper. Those skilled in the art can differentiate paper from paperboard based on a variety of different characteristics. For example, generally paper is composed of a single layer and has an area weight of less than 224 g/m ² , preferably less than 224 g/m ² , more preferably, less than 100 g/m ² , and most preferably, less than 50 g/m ² . In contrast to paper, paperboard usually consists of two or three layers and has an area weight of 224 g/m ² or more. Typically, most papers have a thickness of between 2.54 and 254 pm (0.1 and 10 mil), while paperboard is generally thicker than paper having a thickness of at least 305 pm (12 mil). Suitable papers for use in the present invention include, but are not limited to Kraft paper, medical grade paper, bleached paper, vegetable parchment, water, grease and oil-resistant paper, waxed paper, specialty-treated paper, wet- strength paper, absorbent paper, tissue paper and coated paper. (See Brody, et al., "Paper" and "Paperboard", The Wiley Encyclopedia of Packaging Technology, Second Edition, 1997, pp. 714-723 (John Wiley & Sons, Inc., New York, New York), which is incorporated in its entirety in this application by this reference.) Specific non-limiting examples of commercially available papers for use in the present invention include Duncote II HG high gloss calendared family of paper manufactured by Dunn Corporation (Port Huron, Ml).

Referring now to FIG. 2, there is shown a preferred embodiment of a six-layer laminate 20 which has the same layer compositions described above for laminate 10 and illustrated in FIG. 1 , but also includes a fifth layer 15 a sixth layer 16. Layers 15 and 16 are positioned on either side of the third layer 13 and adheres the foil or metallized polymer layer within the laminate structure. Accordingly, each of layers 15 and 16 may comprise an adhesive material or an extrusion lamination material such as, but not limited to ethylene acrylic acid copolymer, a polyurethane adhesive, and polyethylene including low density polyethylene and linear low density polyethylene or blends thereof.

As shown in FIG. 3, there is illustrated a seven-layer preferred embodiment of a laminate 30 of the present invention. Laminate 30 includes the same layer compositions described above for laminate 20 and illustrated in FIG. 2, but further includes a seventh layer 17. As depicted, seventh layer 17 is disposed between fourth layer 14 and sixth layer 16. Layer 17 may include a polyethylene such as, but not limited to as low density polyethylene (LDPE), linear Sow density poiyethylene (LLDPE), very low density poiyethylene (VLDPE), ultra-low density polyethylene (ULDPE) and blends thereof.

Alternatively, the laminate of the present invention may inciude an eight-layer structure 40 as illustrated in FIG. 4. This embodiment includes the same layer sequence having the same layer compositions as described above for laminate 30. but further includes an eighth layer 18 positsoned between the sixth layer 16 and fourth layer 14. Layer 18 may comprise a homopo!ymer or copolymer of polyethylene, an ethylene acrylic acid copolymer or blends thereof.

WORKING EXAMPLE

In the following example, laminate structure 30 was produced using tandem extrusion lamination apparatuses, and methods which are well know to those skilled in the art. Prior to lamination, a unitary film composed of layers 11 and 12 was fabricated by blown film co-extrusion film apparatus and methods which are also well known in the art. The unitary film and the remaining layers were fabricated into a laminate using a tandem laminator.

Example 1 is one embodiment of laminate 30 of the present invention having a layer sequence (in the order as shown below) and layer compositions as described below and as illustrated in FIG. 3. Reported below is the layer composition relative to the total weight of the layer.

Layer 11 (Sealant): 82.3 wt-% of a linear low density polyethylene (LLDPE)- DOWLEX™ 2045G (The Dow Chemical Company, Midland, Ml, USA), 15 wt-% of a low density polyethylene (LDPE)- Petrothene* NA952QGG (Equistar Chemicals, LP, Houston, IX, USA) and 2.7 wt.-% of a polyethylene masterbatch comprising processing additives.

Layer 12: 100 wt-% of a cyclic olefin copolymer (COC)-TOPAS ^® 8007F-400

(TOPAS Advanced Polymers, Inc., Florence, KY, USA).

Layer 15: 100 wt-% of a polyurethane adhesive-Liofo 3849/ Liofo 6255

(Liofo! Company, Gary, NC, USA),

Layer 13: 100 wt.-% of a 35 gauge aluminum foil-{Jiangsu Zhongji Lamination

Materials Co., Ltd., Jiangyin City, jiangsu Province, P.R.C.). Layer 16: 100 wt.-% of an ethylene acrylic acid copolymer (EAAJ-Pri acor ^® 3440 (The Dow Chemical Company, Midland, Ml, USA),

Layer 17; 100 wt.~% of a low density polyethylene (LDPE)~Petrathene ^®

MA216000 (Equistar Chemicals, LP, Houston, TX, USA).

Layer 14: 100 wt,-% of a 48 gauge btaxia!!y oriented polyethylene terephthalate (OPET)-Skyrof SP65 (SKC, Inc., Covington, GA, USA).

In the following example, laminate structure 40 illustrated In F!G. 4 was produced using tandem extrusion lamination apparatuses, and methods which are well known to those skilled in the art. Prior to lamination, a unitar film composed of layer 11 was fabricated by blown film co-exfrusion film apparatus and methods which are also well known in the art The unitary film and the remaining layers were fabricated into a laminate by a tandem laminator.

Example 2

Example 2 is one embodiment of laminate 40 of the present invention which was produced using tandem extrusion lamination apparatuses, and methods which are well known to those skilled in the art. Prior to lamination, a unitary film composed of layer 11 was fabricated by blown fifm co-extrusion film apparatus and methods which are also well known in the art. The unitary film and the remaining layers were fabricated into a laminate using a tandem laminator.

Layer 1 1 (Sealant); 82.3 wt-% of a linear low density polyethylene (LLDPE)- DOWLEX™ 2045G (The Dow Chemical Company, Midland, MS, USA), 15 wt.-% of a low density polyethylene (LDPE)- Petrofhene^ A952Q00 (Equistar Chemicals, LP, Houston, TX, USA) and 2.7 wt.-% of a polyethylene masferbatch comprising processing additives. Layer 18: 100 wt.-% of a low density polyethylene (LDPE)-DOW™ LOPE 4012 (The Dow Chemical Company, Midland, Mi, USA),

Layer 12: 100 wt.~% of a cyclic olefin copolymer (CGC)-TOPAS ^® 8007F-40G

(TOPAS Advanced Polymers, inc., Florence, KY, USA).

Layer 15: 100 wt.-% of an ethylene acrylic acid copolymer (EAA)-Prirnacor ^®

3440 (The Dow Chemical Company, Midland, Mi, USA).

Layer 13: 100 wt-% of a 35 gauge aluminum foil-{Jiangsu Zhongji Lamination

Materials Co., Ltd., Jiangyin City, Jiangsu Province, P.R.C.).

Layer 16: 100 w -% of an ethylene acrylic acid copolymer (EAAJ-Primaco^

3440 (The Dow Chemical Company, Midland, Mi, USA),

Layer 17: 100 wt~% of a low density polyethylene (LDPE)-Petrothene*

NA218000 (Equistar Chemicals, LP, Houston, TX, USA).

Layer 14: 100 wt..-% of a 48 gauge biaxialiy oriented polyethylene iemphthalate (OPET)~Skyro SP85 (S C, Inc., Covington, GA, USA).

In the following comparative example, a laminate was produced using tandem extaiston lamination apparatuses, and methods which are well known to those skilled in the art. Prior to lamination, a primary unitary film composed of layer 11 was fabricated by blown film co-extrusion film apparatus and methods which are also well known in the art. Then this primary unitary l!m was laminated together with layers 18 and 12 to form a three-layer secondary unitary film. Subsequently, this secondary unitary film and the remaining layers were fabricated into a iaminate using a tandem Saminator,

Comparative Example 1 Comparative Exampie 1 is a iami ^' nate having the layer sequence (in the order as shown beiow) as illustrated in FIG. 4, but with different layer compositions as described above for laminate 40. Those skilled in the art will recognize that Comparative Exampie 1 is a conventional film laminate commonly used in the health and food packaging industry. Reported below is the layer composition relative to the total weight of the layer.

Layer 1 1 {Sealant); 100 wt.-% of a linear Sow density polyethylene (LLDPE)- DOWLEX™ 2045G (The Dow Chemical Company, Midland, MS, USA).

Layer 18: 100 wt.-% of a polyurethane adhesive-LiofoS ^® 3649/ Lsofoi ^® 6255

(Liofol Company, Gary, NC, USA).

Layer 12: 100 wt~% of a 36-48 gauge hiaxiail oriented polyethylene terephthalate (OPET)-SkyroS ^® SP65 (SKC, Inc., Covington, GA, USA).

Layer 15: 100 wt-% of a polyurethane adhesive-LiofoS ^® 3649/ Liofol ^® 6255

(Liofol Company, Cary, NC, USA).

Layer 13; 100 wt-% of a 35 gauge aluminum foil-(jiangsu Zhongji Lamination

Materials Co., Ltd., Jiangyin City, jiangsu Province, P.R.G.).

Layer 16: 100 wt.-% of an ethylene acrylic acid copolymer {EAA)-Primacor ^®

3440 (The Do Chemical Company, Midland, Ml, USA).

Layer 17: 100 wt-% of a low density polyethylene (LDPE)-DOW™ LDPE

4012 (The Dow Chemical Company, Midland, Mi, USA).

Layer 14: 100 wt-% of a 48 gauge biaxiaSly oriented polyethylene terephthalate (OPET)-Skyroi ^® SP65 (SKC, Inc., Covington, GA, USA). The bending resistance of Example 2 was measured on a Gurley-fype tester. This measurement substantially followed the test procedure in accordance with TAPPI Test Method T 543 "Bending Resistance of Paper (Gurley-Type Tester)". The results are reported below in TABLE 1.

The chemical resistance of Exampie 2 and Comparative Example 1 to various liquid substances was determined by folding a film specimen in half to form a 3 inch x 3 inch area pouch having two 0.375 in. side heat seals. Into each pouch there was placed a 10 mL aliquot of a liquid substance, the pouch was sealed with a third 0.375 in. side heat seal and then was laid flat for a number of days under accelerated aging conditions in an aging chamber (50° C and 10% relative humidity). After 1 , 5, 12, 22 and 32 days in the aging chamber, the pouch was opened, the liquid removed and the pouch was dried. A positive test result was indicated ( ^" +"} when no dtscernable de!amination of the foil layer to its adjacent layers or corrosion of the foil was observed. A negative test result was indicated ("-") when delamination between the foil layer and its adjacent layers and/or corrosion of the foil was observed. The results for Example 2 and Comparative Example 1 are reported below in TABLES 2 and 3, respectively.

TABLE 2-Example 1

Chemical Resistance

Acetic Acid + _

^♦ -

Isopropanol + + +

Water

*

These accelerated aging test results indicate that the tamsnaies of the present invention having a single layer of cyclic olefin copolymer (COC) between the sealant layer and the metal foil layer performed as well as or better than a conventional laminate structure having multiple layers of biaxiaily oriented polyethylene terephthalate (ΌΡΕΤ).

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