WO2008104023A1

WO2008104023A1 - Packaging films

Info

Publication number: WO2008104023A1
Application number: PCT/AU2008/000253
Authority: WO
Inventors: David Carew
Original assignee: Amcor Pty Ltd
Current assignee: Amcor Pty Ltd
Priority date: 2007-02-27
Filing date: 2008-02-27
Publication date: 2008-09-04
Anticipated expiration: 2009-08-27

Abstract

The present invention relates to a water dispersible flexible film and packages such as bags made with the dispersible flexile film. The dispersible film includes a water dispersible biodegradable film substrate and a coating on one or both sides of the film that provides differential water resistance on the opposite sides of the film. When in use, the side of the film that has the higher water resistance contacts the material being packaged by the film, and the other side of the film that has the lower water resistance forms the outside of the package. The material in the package is released by contacting the outside of the package with water, whereupon the film disperses and fails.

Description

-_vl - PACKAGING FILMS

FIELD OF THE INVENTION

The present invention relates to flexible water dispersible films having different water dispersion rates on the two sides of the films .

The term "dispersion" in this context is understood to cover both breakdown of a film into smaller sections, or particulates, on contact with water and also dissolution of a film on contact with water. It should be further understood in this context that when a dispersable film is broken down in water then it is possible for it to breakdown into either particulates that, while invisible to the eye, will eventually settle out giiren the opportunity, or fully. soluble molecules that will not settle out.

BACKGROUND OF THE INVENTION Water dispersible flexible filmέ may be used, for example, for wrapping materials when the materials need to be wrapped securely for an extended period and then released automatically and where flexible 1 film residues would be disadvantageous .

Water soluble flexible films of -many types are known in the art. Polymeric resins such 4s poly vinyl alcohol, polyacrylates , polymethacrylates j and others are disclosed in patent literature for use as {water soluble films.

Applications of such films include, for example, wrapping dry products, as disclosed in US ,7, 005,168, and wrapping low water activity liquids such as detergents or fabric conditioning compositions. Significant development work has been performed on the use of modifiers to change the rate of dissolution of films and the water activity of dissolution, and to modify films to be insoluble in the presence of certain materials in water, such as selected surfactants.

Another application of water soluble flexible films is as carriers for ingestible pharmaceutical preparations. Polymers for making such films include, for example, poly vinyl alcohol, as disclosed, in US 5,948,430, and Pullulan (Trade Mark), as disclosed in US 7,025,983, as carriers for portable mouthwash compositions.

Λ common feature of the art, and a limitation in certain potential applications, is the limited range of solubility properties of the films of the art.

Films of the known art are either slowly soluble, or rapidly soluble, or are only soluble in specific chemical environments.

It is possible to wrap hazardous materials having a high water activity (the ratio of the vapor pressure of the material divided by the vapor pressure of pure water at the same temperature — a high ratio indicates a high level of available water molecules in the _jmaterial) with water insoluble films, such as common commodity polyethylene films, before disposal. This has traditionally been acceptable, for example, in medical waste applications, which are disposed by landfill or incineration .

For more benign waste materials; such as human excreta, the usual final disposal is into, a sewer for biological processing. An alternative to direct sewer disposal for benign waste materials is portable toilets.

A known issue with most toilets: is the need to carry significant amounts of water for flushing. This is most critical, for example, in aircraft, where a significant weight of water is carried fo± the sole purpose of flushing lavatories, and this weight increases the energy consumption of aircraft.

In the modern world of rising energy pricing, and consciousness of pollution, the use of water for lavatory flushing in aircraft is wasteful. However, no viable alternate system has yet been developed.

The need for water for rinsing can also be an issue in other applications where water mdy be scarce or costly.

Another potential solution for disposal of benign waste materials is to wrap the waste in biodegradable t polymer films that can later be treated by biodegradation with the waste in a conventional water based treatment facility. For example, a lavatory could ba designed to wrap human waste in this way. There would be other applications for this waste disposal system. A desirable film for such application must be highly resistant to warm water contact prior to wrapping waste and!readily dispersible after use.

SUMMARY OF THE INVENTION

The applicant has developed a w^ter dispersible flexible film that includes a water dispersible biodegradable film substrate and a coating on one or both sides of the film that provides differential water resistance on the opposite sides of the film. In the following disclosure, "water resistance" is understood to mean the elapsed time of contact of pure water at 23⁰C on the surface of a film, substrate or coated film required to reduce the tensile strength of the film, coated film or substrate to less than 10% of its original uncoated tensile strength.

The tensile strength may be determined by any means known in the art .

According to the present invention there is provided a water dispersible flexible film that includes a water dispersible substrate and a coating on one side or a first side of the substrate that provides water resistance that slows water degradation of the film when the first side of the film is contacted by wet substances compared to water degradation of the film that occurs when the other side or second side of the substrate is contacted by wet substances .

The second side of the substrate may be uncoated.

Alternatively, the second side of the substrate has a coating that provides a lower water resistance than the coating on the first side of the substrate. In other words, the rate of degradation when water contacts the second side is less than rate of degradation when water contacts the first side.

According to the present invention there is also provided a package made from the above-described water dispersible flexible film that is designed to retain wet contents within the package for a required period of time and which readily degrades when the film is contacted by wet substances on the outside of the package. In the above-described package, the first side of the film that has higher water resistance; forms the inside of the package .

According to the present invention there is also provided a method of handling liquid containing materials that includes packaging the materials in packages made from the above-described water dispersiblø flexible film, whereby the film releases the contents of; the packages through wetting the outside of the packages, wherein the packages fail through external and not internal wetting of the packages .

In the simplest form, the water 'dispersible flexible film of the present invention includes a water dispersible substrate that has a water resistance of less than one hour, preferably less than 10 minutes, and most preferably less than 2 minutes , and a hydrophobic coating on one side of the substrate.

The hydrophobic coating may be e^f any composition .

Suitable hydrophobic coatings comprise waxes, polymeric resins, fats and oils, proteins ,or other biologically sourced materials .

The hydrophobic coating is selected to modify the water resistance of the water dispersible Jflexible film on that side of the substrate.

Desirably, the substrate is a flexible biodegradable film according to European Standard EN13432- 2000.

An example of a suitable substrate is a flexible starch based film ("Plantic^® film") as described in US patents 5,316,578 and 5,346,936, International applications PCT/AU2005/000794, PCT/AU2005/001507 and PCT/AU2005/001605, US patent application 10/474907 and others in the name of Plantic Limited.

Desirably, the substrate, in the absence of water, has comparable flexibility and tenacity to low density polyethylene (LDPE) . The term "tenacity" in this context is used generically to summarize the resistance of the substrate to tear, puncture or fracture.

It will be understood by those skilled in the art that any biodegradable polymeric film having the required mechanical strength and desirably low water resistance may be used in place of Plantic® film.

Also desirably, the coating is a biodegradable coating. Example coating materials are aliphatic polyesters, although other materials may be suitable.

More preferably, the coating material is degradable according to European Standard EN13432-2000.

Most preferably, the coating material is degradable under aquatic or other environmental conditions, and does not display significant ecotoxicity.

As an example, a preferred watei dispersible flexible film is based on a Plantic® film isubstrate. The Plantic® film is marketed by Plantic® as ^Rl" and comprises chemically modified high amylase starch, native starch, water soluble polymer, a stearatθ, and water, and has a water resistance of less than one minute.

As an example, the film includes a polyester coating on one side of the above-described Plantic® film substrate that provides a water resistance on the coated side of greater than 6 hours .

A preferred coating is sold as ^Rapidly Biodegradable Hydrophobic Material" (RBHM) by Polymate Ltd of Israel . A coating such as RBHM is preferred due to the certified biodegradation of the coating. Other polyester coatings, or coatings of other chemical nature, either specifically developed for the application or already available in the market are within the scφpe of the present invention .

The applicant found through experiments that a normally rapidly dispersible film such as ' Plantic® Rl film has a water resistance of greater than 6 hours when coated with 3 grams per square metre of the RBHM' coating as described above.

The applicant found through experiments that a coating weight between 1 and 10 grams per j square metre dry weight is suitable where the coating is RBHM.

The applicant found in early experiments that a nominal coating of 3 grains per square metre works well , but other applications may require different coating weights and are within the scope of the present invention.

The selection of preferred coating weights will be understood by those skilled in the art :to be a process of determining the relative performance of proposed coatings at a range of weights to optimize cost and performance .

The coating can be applied by any convenient means . Should the coating material be thermoplastic, extrusion coating, or even coextrusion with the substrate may be preferred.

If the coating is not thermoplastic, solution coating methods are preferred.

Suitable solution coating methods are roller coating, rod coating, gravure coating, flexographic coating, spray coating, and bath coating.

The choice of coating method is not important to the practice of the present invention, except that an essentially continuous coating is particularly preferred for the practice of the invention

It can be readily appreciated that if the coating is only applied to the inside of a sealed package formed from the water dispersible film of the present invention, the package will have sufficient water resistance not to "disperse" (i.e. break down due to solubilization or mechanical failure of the material in the! liquid - breaking down may lead to total disappearance of the film) within an extended period of contact by a waste having a high water activity that is contained in the package, but wetting the outside of the package, say daring waste management or treatment, will rapidly disperse the packaging film. The coating will not be strong enough to hold the package together once the substrate has been dispersed.

It will be understood by those skilled in the art of material science, which is the relevant technology field for the present invention, that even an intrinsically strong coating material, at a sufficiently thin gauge, will be fragile enough to disperse once the film substrate begins to disperse. fl ¬

it will also be appreciated by those persons that it should be possible to apply a coating on the other side of the film, with similar or differing water resistance depending the needs of a user .

A film coated on one side with the above coating can be mechanically applied to a solid receptacle, such as a toilet in an aircraft, and accept wastes including liquid of water activity up to 1.0, and remain stable for an extended period. ' i In one embodiment, the water dispersible film of the present invention is indexed through a disposal hatch, sealed if desired, and then severed.

In preparation for later disposal, contact with liquid water on the opposite side of the film weakens and pre-disperses the film, so the waste material can be pumped.

Simple rinsing with water is sufficient to break down any residual film sections to a pumpable consistency.

The use of the water dispersible film of the present invention, as exemplified above, permits the reduction of the cartage of water in aircraft, and allows the final waste product to be treated as a. normal sewer discharge, thus requiring no infrastructure other than the modified lavatory .

The above-described water dispedsible film of the present invention is not intended to be limited by the above description thereof.

For example, other starch polymer blends comprising film modifiers , sugar alcohols ,; polyols , and ester plasticizers are suitable. Films shpwing acceptable tenacity and flexibility, and having acceptably low native water resistance, are also within the scope of the present invention .

Other water dispersible polymers, based for example on cellulose rather than starch, may also be used.

There may also be other applications which will benefit from a controllable rate of dissolution apart from those as disclosed in the above description of the present invention .

One example is wrapping fresh food by a delicatessen in an edible version of the film, where the food is cooked, heated or otherwise prepared by placing the unopened packaging into cold or hot wφter.

Another example is sterile packaging of small volumes of medical or pharmaceutical products, which are swallowed by the patient.

A further application is the us^ of the film of the present invention in disposable medical applications . Example applications include flushable colostomy bags and vomit collection bags that are currently Constructed from non-dispersible polymers .

The use of coating materials with very long water resistances makes it possible to prepare film-based packaging for carrying liquids of high water activities that are easily disposed by rinsing down & sink once the contents have been removed.

Many modifications may be made tio the embodiments of the present invention described above Without departing from the spirit and scope of the invention.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS

1. A water dispersible flexible film including a water dispersible substrate and a coating on a first side of the substrate that provides water resistance that slows water degradation of the film when the first side of the film is contacted by wet substances compared to the water degradation of the film that occurs when a second side of the substrate is contacted by wet substances .

2. Tha water dispersible film according to claim 1 , wherein the second side of the substrate is uncoated.

3. The water dispersible film according to claim 1, wherein the second side of the substrate has a coating that provides a lower water resistance than the coating on the first side of the substrate.

4. The water dispersible film according to any one of claims 1 to 3, wherein the water dispersible substrate has a water resistance of less than one hour.

5. The water dispersible film according to any one of claims 1 to 3, wherein the water dispersible substrate has a water resistance of less than 10 minutes.

6. The water dispersible film according to any one of claims 1 to 3, wherein the water dispersible substrate has a water resistance of less than 2 minutes.

7. The water dispersible film according to any one of the proceeding claims, wherein the substrate is a flexible biodegradable film according to European Standard EN13432-2000.

8. The water dispersible film according to any one of the proceeding claims , wherein the substrate comprises starch based polymer.

9. The water dispersible film according to any one of claims 1 to 7 , wherein the substrate is a starched based polymer blend comprising any one or; a combination of film modifiers, sugar alcohols, polyols, and ester plasticizers . '

10. The water dispersible film according to any one of claims 1 to 7 , wherein the substrate comprises a cellulose based polymer .

11. The water dispersible film according to any one of claims 1 to 6, wherein the substrate is a Plantic® film substrate and has a water resistance of less than one minute.

12. The water dispersible film according to any one of claims 1 to 6, wherein the substrate wien dry has comparable flexibility and tenacity to low density polyethylene (LDPE) .

13. The water dispersible film according to any one of claims 1 to 12, wherein the coating on] the first side of the substrate is in the form of a hydrophobic coating, and if present, the coating on the second .side is less hydrophobic .

14. The water dispersible film according to claim 13, wherein the hydrophobic coating comprises Iany one or a combination of waxes, polymeric resins, fdts and oils, proteins or other biologically sourced materials .

15. The water dispersiblθ film according to any one of claims 1 to 14, wherein the coating is a biodegradable coating.

16. The water dispersible film according to any one of claims 1 to 14, wherein the coating material is degradable according to European Standard: EN13432-2000.

17. The water dispersible film according to any one of claims 1 to 13, wherein the coating material is a polyester coating.

18. The water dispersible film according to claim 11, wherein a polyester coating material is applied to the first side of the Plantic® film substrate i and provides a water resistance on the coated side of greater than 6 hours .

19. The water dispersible film according to any one of claims 1 to 13, wherein the coating material is Rapidly Biodegradable Hydrophobic Material (BBHM) .

20. The water dispersible film according to any one of claims 1 to 13, wherein dry weight of -the coating on the first side is between 1 and 10 grams per square metre.

21. The water dispersible film according to claim 19 when dependant on claim 11 , wherein the substrate is Flantic® Rl film having a water resistance of greater than 6 hours when coated with 3 grams per square metre of the

RBHM coating.

22. The water dispersible film according to any one of claims 1 to 13, wherein the coating material is a thermoplastic and is applied by way of extrusion coating, or coextrusion with the substrate.

23. The water dispersible film according to any one of claims 1 to 13, wherein the coating material is applied by way of solution coating comprising any; one or a combination of roller coating, rod coating, gravure coating, flexographic coating, spray coating, and bath coating.

24. The water dispβrsible film according to any one of claims 13 to 23, wherein the coating is an essentially continuous coating on the substrate.

25. Use of the water dispersible film according to any one of claims 1 to 24 , wherein the film is dispensed in a receptacle such that the first side film receives waste material and is in contact with liquid of water activity up to 1.0. ,

26. Use of the water dispersible film according to claim 25, wherein the waste received by the film is sealed by film and then severed to form a disposable package.

27. Use of the water dispersible film according to claim 25 or 26, wherein the other side of, the film is contacted with liquid water when it is desired to pre- disperse the film and allow the waste to be pumped.

28. Use of the water dispersible film according to any one of claims 25 to 27, wherein the receptacle is a toilet bowl .

29. Use of the water dispersible film according to any one of claims 1 to 24, wherein the film is an edible version in which food is packaged and the food is prepared by placing unopened packaging into cold or hot water .

30. Use of the water dispersible film according to any one of claims 1 to 24, wherein medical or pharmaceutical products are packaged in the film and are suitable for being administered orally.

31. Use of the water dispersible film according to any one of claims 1 to 24, wherein the film forms at least part of a disposable bag and is suitable for use as either a flushable colostomy bag or vomit collection bags.

32. Use of the water dispersible film according to any one of claims 1 to 24, wherein the film forms at least part of packaging for carrying liquids of: high water activities and the packaging is disposable by rinsing down a sink .

33. A package made with the water dispersible flexible film according to any one of claims 1 to 24, wherein the first side of the film havingi the coating forms the inside of the package and retains wet contents within the package for a required period of time and the second side of the substrate forms at least part of the outside of the package which readily disperses when contacted by wet substances.

34. A method of handling liquid containing materials that includes packaging the materials in packages made from the water dispersible flexible film according to any one of claims 1 to 24, whereby the film releases the contents of the packages as a result of wetting the outside of the packages.