FULLY RECYCLABLE POLYETHYLENE PACKAGING

Abstract

A multilayer polymer film for use in packaging, particularly food packaging, and packaging made from the multilayer film, are disclosed, along with methods of manufacture of the multilayer film and the packaging. In preferred embodiments, the polymer film comprises an outer layer comprising machine direction oriented high-density polyethylene, an intermediate layer comprising adhesive and optionally ink, and an inner layer comprising high-density polyethylene, metallocene linear low-density polyethylene, and a plastomer. The inner or outer layer can be coated to lower the water vapor and oxygen transmission rates. In preferred embodiments, the layers are laminated to form the multilayer film. The multilayer film can be used to produce food packaging such as heat-sealable bags or pouches. Packaging made from the film is suitable for hot filling, and in contrast to packaging materials known in the art for hot filling, is fully recyclable.

Claims

1. Packaging comprising a multilayer film, said multilayer film comprising: an outer layer comprising high-density polyethylene (HDPE); an inner layer comprising HDPE, metallocene linear low-density polyethylene (mLLDPE), and a plastomer; and an intermediate layer disposed between said outer layer and said inner layer, said intermediate layer comprising at least one component selected from the group consisting of adhesives, colorants, pigments, and dyes.

2. The packaging according to claim 1, wherein said packaging is characterized by at least one characteristic selected from the group consisting of: said outer layer comprises machine-direction oriented HDPE (MDO-HDPE); and, said inner layer comprises blown HDPE.

3. The packaging according to claim 1, wherein said packaging is characterized by at least one characteristic selected from the group consisting of: said inner layer is characterized by a thickness of between 40 m and 100 m; and said outer layer is characterized by a thickness of between 20 m and 40 m.

4. The packaging according to claim 1, wherein said inner layer comprises HDPE, mLLDPE, and plastomer layers characterized by thicknesses in a ratio of about 1:2:1.

5. The packaging according to claim 1, wherein said inner layer comprises plastomer comprising at least one polymer selected from the group consisting of polyethylene and poly--olefin.

6. The packaging according to claim 1, wherein said intermediate layer comprises adhesive and ink approved for use in food packaging.

7. The packaging according to claim 1, wherein at least one of said outer layer and said inner layer is coated by a coating.

8. The packaging according to claim 7, wherein at least one of the following is true: said outer layer is coated with a coating comprising aluminum oxide; and said inner layer is coated by a coating comprising poly-(ethylene vinyl alcohol) (EVOH).

9. The packaging according to claim 7, wherein said packaging is characterized by at least one characteristic selected from the group consisting of: a water vapor transmission rate of 1.5-2.0 g/m.sup.2/day as determined by ASTM method F1249-06; and, an oxygen transmission rate of 2.5-4.5 cm.sup.3/m.sup.2/day as determined by ASTM method D3985.

10. A multilayer film suitable for use in food packaging, said multilayer film comprising: an outer layer comprising high-density polyethylene (HDPE); an inner layer comprising HDPE, mLLDPE, and a plastomer; and an intermediate layer disposed between said outer layer and said inner layer, said intermediate layer comprising at least one component selected from the group consisting of adhesives, colorants, pigments, and dyes.

11. The multilayer film according to claim 10, wherein said multilayer film is characterized by at least one characteristic selected from the group consisting of: said outer layer comprises machine-direction oriented HDPE (MDO-HDPE); and, said inner layer comprises blown HDPE.

12. The multilayer film according to claim 10, wherein said packaging is characterized by at least one characteristic selected from the group consisting of: said inner layer is characterized by a thickness of between 40 m and 100 m; and said outer layer is characterized by a thickness of between 20 m and 40 m.

13. The multilayer film according to claim 10, wherein said inner layer comprises HDPE, mLLDPE, and plastomer layers characterized by thicknesses in a ratio of about 1:2:1.

14. The multilayer film according to claim 10, wherein said inner layer comprises plastomer comprising at least one polymer selected from the group consisting of polyethylene and poly--olefin.

15. The multilayer film according to claim 10, wherein at least one of said outer layer and said inner layer is coated by a coating.

16. The multilayer film according to claim 15, wherein at least one of the following is true: said outer layer is coated with a coating comprising aluminum oxide; said inner layer is coated by a coating comprising poly-(ethylene vinyl alcohol) (EVOH); and said inner layer is coated by a coating that is co-extruded with said mLLDPE.

17. A method of producing packaging suitable for use with food, said method comprising: preparing an outer layer comprising an HDPE film characterized by a first thickness; preparing an inner layer comprising a film HDPE, mLLDPE, and a plastomer, said inner layer characterized by a second thickness; applying at least one substance selected from the group consisting of adhesives, colorants, pigments, and dyes to a surface of at least one of said outer layer and said inner layer, thereby forming an intermediate layer; optionally, coating said outer layer with at least one outer layer coating material; optionally, coating said inner layer with at least one inner layer coating material; laminating said outer layer, inner layer and said intermediate layer such that said intermediate layer is disposed between said outer layer and said inner layer, thereby producing a multilayer film; producing packaging characterized by an exterior and an interior and is open on at least one side, by a method selected from the group consisting of: obtaining two pieces of said multilayer film and sealing together said two pieces of multilayer film such that said inner layers are facing each other in said interior and such that at least one side remains unsealed; and, folding a piece of said multilayer film such that said inner layers face one another and sealing said folded piece of multilayer film such that at least one side remains unsealed.

18. The method according to claim 17, wherein at least one of the following is true: said first thickness is 20 m-40 m; and said second thickness is 40 m-100 m.

19. The method according to claim 17, wherein at least one of the following is true: said step of preparing an outer layer comprises preparing an outer layer comprising MDO-HDPE; said step of preparing an inner layer comprises preparing an inner layer comprising blown HDPE, mLLDPE, and at least one plastomer selected from the group consisting of polyethylene and poly--olefin; said step of preparing an inner layer comprises co-extruding said blown HDPE, mLLDPE, and at least one plastomer; and said step of preparing an inner layer comprises preparing an inner layer in which said HDPE, said mLLDPE, and said plastomer are characterized by thicknesses having a ratio of about 1:2:1.

20. The method according to claim 17, wherein at least one of the following is true: said method comprises coating said outer layer with at least one outer layer coating material, said outer layer coating material comprising aluminum oxide; said method comprises coating said outer layer with at least one outer layer coating material so as to produce a coating characterized by a thickness of 0.001 m-0.005 m; said method comprises coating said outer layer with at least one outer layer coating material, said step of coating said outer layer comprising coating said outer layer with said outer layer coating material by vacuum deposition; said method comprises coating said inner layer with at least one inner layer coating material, said inner layer coating material comprising EVOH; said method comprises coating said inner layer with at least one inner layer coating material so as to produce a coating characterized by a thickness of 3 m-5 m; and said method comprises coating said inner layer with at least one inner layer coating material, and said step of coating said inner layer comprises co-extruding said inner layer coating material and said mLLDPE.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0075] In the following description, various aspects of the invention will be described. For the purposes of explanation, specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent to one skilled in the art that there are other embodiments of the invention that differ in details without affecting the essential nature thereof. Therefore the invention is not limited by that which is illustrated in the FIGURE and described in the specification, but only as indicated in the accompanying claims, with the proper scope determined only by the broadest interpretation of said claims. In some cases, for clarity or conciseness, individual elements of the invention are discussed separately. Nonetheless, any combination of individual elements of the invention that is not self-contradictory is considered by the inventors to be within the scope of the invention.

[0076] Unless explicitly stated otherwise, in cases in which the term comprising is used to describe an embodiment of the invention, embodiments in which the invention includes only those specific elements that are described explicitly in the description (i.e. embodiments in which the invention consists of rather than comprises the listed element or elements) are considered by the inventor to be within the scope of the invention.

[0077] As used herein, the abbreviation MDO stands for Machine-Direction Oriented.

[0078] As used herein, the abbreviation PE stands for polyethylene.

[0079] As used herein, the abbreviation HDPE stands for high-density polyethylene.

[0080] As used herein, the abbreviation LLDPE stands for linear low-density polyethylene.

[0081] As used herein, the abbreviations mLLDPE and mLL stand for metallocene linear low-density polyethylene, i.e. LLDPE that has been produced using a metallocene polymerization catalyst.

[0082] As used herein, the abbreviation EVOH stands for poly-(ethylene vinyl alcohol).

[0083] As used herein, the abbreviation ALOX stands for aluminum oxide.

[0084] As used herein, the abbreviation WVTR stands for water vapor transmission rate. Unless otherwise stated, all values of WVTR given herein are WVTR values as determined by the procedure of ASTM standard method F1249-06.

[0085] As used herein, the abbreviation OTR stands for oxygen transmission rate. Unless otherwise stated, all values of OTR given herein are OTR values as determined by the procedure of ASTM standard method D3985.

[0086] As used herein, the abbreviation LB stands for low barrier, and the abbreviation HB for high barrier.

[0087] As used herein, with reference to numerical quantities, the term about is used to define a range of 25% about the nominal value.

[0088] The instant invention discloses a laminated multilayer film comprising or consisting of at least one inner layer and at least one outer layer, the use of the multilayer film in the production of packaging materials and packaging, the use of the multiplayer film in packaging materials, packaging materials comprising the laminated multilayer film, and packaging comprising the laminated multilayer film.

[0089] In preferred embodiments, the multilayer film additionally comprises an intermediate layer disposed between the inner layer and the outer layer. The film may be produced by any method known in the literature for producing multi-layer polymer films for use in the food industry. Non-limiting examples of methods that may be used to produce the film include adhesive and extrusion lamination processes. In preferred embodiments of the invention, solvent-based adhesive lamination is used to produce the multilayer film.

[0090] In preferred embodiments, the outer layer comprises HDPE; in especially preferred embodiments, the HDPE comprises MDO-HDPE. The outer MDO-HDPE layer provides stiffness and puncture resistance as well as esthetically pleasing optical qualities to the packaging. The MDO-HDPE outer layer is typically made from HDPE having a peak melting point of 105-115 C. In typical embodiments, the layer is between 20 and 40 m thick. In preferred embodiments, it is about 25 m thick. It is typically produced at a draw ratio of between 3 and 7, and preferably at a draw ratio of 5. In some non-limiting embodiments of the invention, the outer layer is translucent or transparent. In some other non-limiting embodiments, an additive such as calcium carbonate is added to the outer layer during its production in order to give the outer layer a matte finish.

[0091] In some embodiments of the invention, a design is printed on the outer layer. Non-limiting examples of designs that may be printed on the outer layer include logos and text (e.g. information regarding the content of a package made from the multilayer film). Any means known in the art for printing on polymer sheets may be used. In preferred embodiments of the invention, gravure or flexo printing is used.

[0092] In preferred embodiments, the inner layer comprises HDPE, mLLDPE, and a plastomer. The HDPE is preferably blown HDPE. Any mLLDPE known in the art that is suitable for use in hot-fill food packaging may be used. ELITE (Dow Chemical) and MARLEX (Chevron Phillips) are non-limiting examples of mLLDPE types that may be used in the instant invention. The plastomer may be any type known in the art that is approved for food use and that has a melting point appropriate for use in sealable hot-fill packaging. In preferred embodiments, the plastomer comprises polyethylene and/or poly--olefin.

[0093] The inner layer may be produced by any method known in the art. In preferred embodiments, the three components are co-extruded to form the inner layer material. In preferred embodiments of the invention, the inner layer is produced by blown film extrusion of the three components. In typical embodiments, the inner layer as a total thickness of between 40 m and 100 m. In preferred embodiments, it is about 60 m thick. In typical embodiments of the invention, the thicknesses of the HDPE/mLL/Plastomer components of the inner layer are in a ratio of about 1:2:1. In typical embodiments of the invention, the inner layer comprises blown HDPE produced at a blow-up ratio (BUR) of 1:2.

[0094] In typical embodiments of the invention, the HDPE used in the outer and inner layers is characterized by a density of 0.955 g/cm.sup.3, and of about 0.4.

[0095] In embodiments of the invention in which the multilayer film comprises an intermediate (adhesive) layer, the intermediate layer comprises an adhesive, an ink, or both. Any appropriate adhesive and ink known in the art may be used. In typical (non-limiting) embodiments, the intermediate layer is 2-3.5 m thick. In preferred embodiments, the adhesive is water-based. In some non-limiting embodiments of the invention in which the adhesive layer comprises ink, the ink is water-based. In some non-limiting embodiments of the invention in which the adhesive layer comprises ink, the ink is solvent-based. In the most preferred embodiments of the invention, adhesive and, if present, ink approved for use in food packaging are used. In some non-limiting embodiments of the invention in which the adhesive layer comprises ink, the ink may be printed on either of the inner or outer layers according to any method known in the art prior to the lamination of the layers to form the final product.

[0096] In some non-limiting embodiments of the invention, the multilayer film comprises one or more coatings or additives. These coatings or additives are especially useful for controlling the physical properties of the final product.

[0097] In some preferred embodiments of the invention, at least one layer of the multilayer film is coated in order to reduce the WVTR and OTR. In preferred embodiments of the invention in which the multilayer film is coated, the outer surface (i.e. the surface not facing the intermediate layer) is coated. As a non-limiting example, a three-layer film with no additional additives or coatings (LB film) typically has a WVTR of 25-30 g/m.sup.2/24 h, and an OTR of 25-30 cm.sup.3/m.sup.2/24 h. For applications in which lower water vapor and oxygen transmission rates are desired, it is possible to coat one or more of the layers to produce a high-barrier (HB) film. As a non-limiting example, in some embodiments, the outer layer is coated with ALOX, typically by vacuum deposition. The ALOX layer is typically 0.001-0.005 m thick, and preferably about 0.002 m thick. As a second non-limiting example, in some embodiments, a layer of EVOH, typically about 3-5 m thick, is co-extruded with the inner layer (preferably with the mLLDPE). In typical embodiments, HB films have a WVTR of 1.5-2.0 g/m.sup.2/24 h and an OTR of 2.5-4.5 cm.sup.3/m.sup.2/24 h.

[0098] In preferred embodiments of the invention, the heat seal strength of the laminated film, as measured according to ASTM standard method F2029, is typically 25 N/25 mm. In preferred embodiments of the invention, the peel strength, as measured according to ASTM standard method D1876, is 300 g/25 mm. In preferred embodiments of the invention, the outer layer of the laminated film (i.e. the surface comprising MDO-HDPE) has a coefficient of friction, as measured according to ASTM standard method D1894-90, of 0.25-0.45. The multilayer film typically has a peak melting point of 130-180 C., preferably 150-160 C.

[0099] It is also within the scope of the invention to disclose packaging made from the multilayered film described above. In some non-limiting embodiments of the invention, the packaging is in the form of a bag or pouch. In some preferred embodiments of the invention, the packaging is in the form of a stand-up pouch, the multilayer film being sufficiently stiff to produce a usable stand-up pouch. The bag or pouch is generally made from two pieces of laminated multilayer film that are sealed together by any appropriate means known in the art (e.g. heat sealing) to form a bag that is open on one side. The bag can be heat-sealed after filling. In some embodiments of the invention, the bag has a notch or perforation on at least one side to make breaking the seal easier. The bag may be made resealable, e.g. by inclusion of a zipper-type closure.

[0100] In preferred embodiments of the packaging, it is made from a multilayer film comprising an intermediate layer. In particularly preferred embodiments of the invention, the intermediate layer includes ink or dye that forms a pattern such as a design, a logo, or text that relates to the content of the packaging.

[0101] In typical embodiments, the packaging is characterized by a WVTR of 10 g/m.sup.2/day. In preferred embodiments in which the packaging is made from HB film, the WVTR is between 1.5 and 2.0 g/m.sup.2/day, while in preferred embodiments in which the packaging is made from LB film, the WVTR is between 25 and 30 g/m.sup.2/day. In typical embodiments, the packaging is characterized by an OTR, a of 1000 cm.sup.3/m.sup.2/day. In some preferred embodiments in which the packaging is made from LB film, the OTR is between 25 and 30 cm.sup.2/m.sup.2/day, while in preferred embodiments in which it is made from HB film, the OTR is between 2.5 and 4.5 cm.sup.2/m.sup.2/day.

[0102] Packaging produced from the multilayer film disclosed herein is suitable for packaging of foods. In particular, it is suitable for hot filling. In preferred embodiments of the invention, the packaging may be heated at a temperature of >85 C. without damage. The packaging is also suitable for use with modified-atmosphere and modified-atmosphere/modified-humidity packaging. In contrast to polyethylene-based packages known in the art that are not suitable for heating above 120 C., packaging made from the multilayer film of the invention disclosed herein can withstand temperatures of up to 150 C., i.e. temperatures more typical of non-recyclable packaging material such as polyester-polyethylene blends. The inner layer, on the other hand, can seal at relatively low temperatures, typically between 120 C. and 150 C., preferably about 140 C.

[0103] Because the packaging material disclosed herein is made essentially entirely from PE, the packaging is not only strong and heat-resistant, but fully recyclable as well. Packaging made from the multilayer laminated film of the present invention thus combines the desirable physical properties of packaging made from non-recyclable plastics with the complete recyclability of polyethylene.