Patent Description:
The inventor is aware of the use of flexible films for packaging foodstuffs such as wine and fruit juice. Such packaging of liquid foodstuffs are often also packaged and supported in a box and known as "Bag-in-Box" packaging. Typically, the main oxygen barrier will be an aluminium film layer however, this layer is prone to damage during transport and is not recyclable and not transparent which prevents the food-stuffs being visible through the film. The main objective of the films is to extend the shelf life of the foodstuffs for as long as possible by limiting exposure of the food-stuffs to oxygen, light and microorganisms.

It is an objective of the invention to provide films for packaging foodstuffs with improved shelf life.

<CIT>discloses a laminate structure having improved resistance to the migration of essential oils, aromas and flavors and improved oxygen barrier characteristics for beverage packaging comprising an exterior coating of polyethylene applied onto the outer surface of paperboard substrate, a barrier layer of aluminum foil, EVOH, polyamide or PET applied directly or indirectly onto the paperboard and tie and other sublayers which may or may not contain inorganic filler applied intermediate the barrier layer and the innermost food contact layer which may or may not contain filler. The containers or cartons prepared from the laminate structures are characterized by minimized scalping and preserved product quality.

<CIT> teaches a compound permitting the economic production of packaging containers, which when activated produces concentrated amounts of CO2 gas for extended periods for preservation of perishable products therein, comprises a mixture including a CO2 generating portion incorporated within a polymer matrix. Preferably, the mixture includes citric acid; calcium carbonate, and polyethylene resin. More preferably, the mixture includes a mixture of a carboxylic acid (<NUM>-<NUM>%); a hydrogen carbonate (<NUM>-<NUM>%) and any polyolefin resin. Even more preferably, the mixture includes a mixture including (<NUM>-<NUM>%) Citric Acid; (<NUM>-<NUM>%); and <NUM>-<NUM>% polyethylene resin. Most preferably, the mixture includes by weight <NUM>% citric acid; <NUM>% calcium carbonate; and <NUM>% low density polyethylene resin with a melt index of <NUM> and a density of <NUM>/cc. Alternatively, the carboxylic acid and hydrogen carbonate components are compounded into separate polymer matrixes, and later combined. The compound may be packaged in containers that are formed of flexible or rigid material.

<CIT> shows a heat sealable barrier layer for food and beverage cartons is provided, the barrier layer including an additive material which reduces the amount of essential oil scalping from citrus products. Additionally, a carton coating layer and process is provided for reducing a coefficient of friction of stacked carton blanks. An additional embodiment of the invention provides for a paperboard substrate having reduced water vapor transmission rates, the reduction in water vapor transmission rates being attributed to one or multiple extruded layers containing an effective amount of an inorganic additive.

<CIT> discloses a flexible packaging material with an oxygen adsorption function based on natural gallic acid, a preparation method for the packaging material and an application of the packaging material, and belongs to the technical field of packaging materials. The flexible packaging material comprises at least four functional structure layers. The outmost layer is an oxygen blocking layer. An oxygen adsorption layer, which comprises the gallic acid and a polyurethane binder, is below the oxygen blocking layer. An activation layer (catalyst layer), which comprises sodium carbonate and EVA resin, is below the oxygen adsorption layer. The innermost layer, below the activation layer, is a food contacting layer and also an oxygen permeating layer. On contacting water vapor, oxygen adsorption film prepared by the method starts the oxygen adsorption function and slowly generates an inert gas carbon dioxide at the same time. The packaging material is particularly suitable for storage and fresh-keeping of beer, fruit juice and sodas, and is capable of avoiding oxidization of nutritional ingredients of oxygen sensitive food and beverage, improving food quality and prolonging the shelf life.

Peter Maul "BARRIER ENHANCEMENT USING ADDITIVES" overviews general approaches to enhancing plastic package barrier and provides details about the use of additives to accomplish the goal. Particular emphasis is given to the role of nanotechnology in barrier packaging.

"Nanoclays in Food and Beverage Packaging" by Nattinee Bumbud-sanpharoke and Seonghyuk Ko discusses the technical benefits of using nanoclays as a promising property enhancer in organic polymers for food and beverage packaging. The incorporation of nanoclays can improve the thermal, mechanical and barrier properties of a host polymer.

According to the invention there is provided a composite active flexible polymeric film for containers for containing acidic material, which film generates carbon dioxide gas when in contact with the acidic material to settle in the headspace of the container.

The acidic material is acidic foodstuffs which are beverages containing fruity acids material, such as wine and fruit juice. Typically, the container can be selected from the bag in a box type of container.

The film includes more than one layer and the inner layer which is in contact with the acidic material will be active and generate carbon dioxide gas.

At least one layer is a barrier layer. A barrier layer provides a barrier against fluids.

The active film or layer includes a polyethylene calcium carbonate (PE/CaCO<NUM>) composite.

The CaCO<NUM> particles may be up to a few micron-size range and incorporated into the polymer. Preferably, the CaCO<NUM> particles may be between <NUM> and <NUM> micron, and more preferably about <NUM> micron.

The concentration of the CaCO<NUM> may be selected to complement the intended product to be packaged by releasing the optimum amount of carbon dioxide.

A blend of Linear Low Density Polyethylene (LLDPE) and Low Density Polyethylene (LDPE) and CaCO<NUM> may be produced by melt extrusion before a film blowing process. The ratio of LLDPE to LDPE may be between <NUM>:<NUM> and <NUM>:<NUM>. Apart from the feeding zone (set at <NUM>), the temperatures of the rest of the extrusion process zones including the die can be <NUM> - <NUM>; in this particular instance it is <NUM>. The feed rate and screw speed are maintained at <NUM>/h and <NUM> rpm, respectively. It is to be appreciated that PE has a good resistance to tartaric, malic citric and lactic acids.

The inner layer, which may be blended from Linear Low Density Polyethylene (LLDPE) and Low Density Polyethylene (LDPE), may be produced by melt extrusion before a film blowing process. The ratio of LLDPE to LDPE may be between <NUM>:<NUM> and <NUM>:<NUM>, preferably <NUM>:<NUM>.

The batch of polyethylene or polyethylene blend may be mixed with a selected weight of MCO<NUM> particles to give a certain weight percentage of CaCO<NUM> in a range of between <NUM> and <NUM> weight percent, preferably selected from <NUM>, <NUM> and <NUM> weight percent.

The inner active layer of the film is separate from an outer layer to form an active layer container or bag inside the outer layer.

An outer layer is a composite passive barrier layer, which includes nanoclay particles.

The composite passive barrier is polyamide (PA) based. The nanoclay particles may be mixed with the PA and extruded to form the nano composite (PA PNC). The nanoclay can be a bentonite and preferably a Montmorillonite. The nanoclays particle size may be between <NUM> and <NUM> micron in width and length and preferably below <NUM>. The nanoclays may be between one silicate layer of about <NUM> thickness or may constitute a stack of up to <NUM> layers of <NUM> thickness but preferably between <NUM> and <NUM> layers.

The film may include a PA layer on its operatively outer side and functions as a physical barrier to gas permeation and is not in contact with the foodstuffs.

The film includes a polyacrylic acid (PAA) tie layer between the active barrier layer and the composite passive barrier layer.

In one embodiment, PA PNC is prepared via a masterbatch dilution technique. The processing temperatures for different extrusion zones are selected at <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (die) °C. The feed rate and the screw speed were <NUM>/h and <NUM> rpm, respectively. According to thermogravimetric analysis (TGA) the inorganic / silicate content of masterbatch is <NUM> wt%. PA PNC with desired amount of nanoclay can then be prepared by diluting this masterbatch in neat PA. The inorganic content of PA PNC (determined by TGA) is <NUM> wt%. Before processing, PA and nanoclay were dried at <NUM> overnight and the processed samples were also dried at the same conditions.

The invention also extends to a container constructed from a film as described above.

The invention also extends to the use of an inner active layer in a composite film as described above as a source of carbon dioxide gas when in contact with the acidic material.

The traditional function of a packaging is to encase or contain food products to limit the ingress from elements outside the package, which may cause degradation and spoilage. <CIT> discloses multilayer film structures comprising polyethylene (PE)-CaCO<NUM> as a core and outer layer. [<NUM>] The CaCO<NUM> in that patent is either steric or palmitic acid coated. Moreover, a salt of polyacrylic acid and/or a salt of copolymer of acrylic acid have been used as a grinding aid during wet-grinding of CaCO<NUM> after surface modification. One or more layers of ethyl vinyl acetate (EVA), ethylene ethyl acetate (EEA), ethylene acrylic acid (EAA) have been used as an inner layer to promote sealing. The authors have claimed that the moisture vapour transmission rate reduces in the presence of CaCO<NUM>. Not only that, but also, the surface roughening effect enhances the printability and print register. Addition of CaCO<NUM> has been shown to lower the coefficient of friction too.

<CIT> relates to bi-oriented multi-layered PE films having high water-vapour transmission rate [<NUM>]. The base layer (central layer) comprises of PE with CaCO<NUM> as a captivating agent. This layer has been sandwiched between a copolymer (ethylene-propylene co-polymer or ethylene-propylene-butylene ter-polymer) or hydrocarbon resin (e.g. terpene, styrene and cyclopentadiene). The authors claimed that may have unidirectional tear properties in the machine direction and may be useful for packaging food products like candy.

Preparation of breathable micro-porous film by stretching a casting of a composition of a LLDPE (linear low density PE) and CaCO<NUM> and calcium stearate in two directions has been disclosed in <CIT>[<NUM>]. Such microporous film is desired for disposable items e.g. diapers, bed-sheets, and hospital gowns. LDPE (low density PE) - CaCO<NUM> has also been used to prepare cross-tearable decorative sheet material as disclosed in <CIT>[<NUM>]. In <CIT> it has been demonstrated that inorganic filler (e.g. CaCO<NUM>) containing ethylene polymers (can be homo and copolymers) exhibit improved mechanical strengths (impact and tear) in presence of steric and palmitic acid mixtures (<NUM>:<NUM>), zinc stearate and <NUM>,<NUM>-di-ter-butyl-p-cerol [<NUM>]. None of these disclosures reports the use of polymer/CaCO<NUM> composite as an inner functional layer for suppression of oxygen through generation of CO<NUM> into the headspace and in the packaged acidic liquid.

One report is available on the PA PNC/tie/PE; where Cloisite30B and Dellite 43B nanoclays were used to prepare PA PNC. LDPE-g-MA was used as a tie layer [<NUM>]. This report can be found at: <NPL>.

The current invention is a novel film construction that comprises the innovatively utilized PE/CaCO<NUM> composite inner layer and passive barrier layer based on South African nanoclays (Betsopa™).

The invention is now described by way of example with reference to the accompanying images.

A blend of Linear Low Density Polyethylene (LLDPE) and Low Density Polyethylene (LDPE) is produced by melt extrusion before a film blowing process. The ratio of LLDPE to LDPE is <NUM>:<NUM>.

The CaCO<NUM> particles are in the micron to nano sized range, preferably about <NUM> micron. The PE Active composite is prepared by mixing the blend of LLDPE and LDPE before extrusion with <NUM>, <NUM> and <NUM> weight percent of CaCO<NUM> to obtain different CaCO<NUM> loaded films.

Apart from the feeding zone (set at <NUM>), the temperatures of the rest of the extrusion process zones including the die can be <NUM> - <NUM>; in this particular instance it is <NUM>. The feed rate and screw speed are maintained at <NUM>/h and <NUM> rpm, respectively. It is to be appreciated that PE has a good resistance to tartaric, malic citric and lactic acids.

The nanoclay particles of the composite passive barrier is mixed with the PA and extruded to form the nanocomposite (PA PNC).

The PA PNC can be prepared via a masterbatch dilution technique and by direct incorporation of nanoclay with specific loading.

In one instance, PA PNC is prepared via a masterbatch dilution technique. The processing temperatures for different extrusion zones are selected at <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> (die) °C. The feed rate and the screw speed were <NUM>/h and <NUM> rpm, respectively. According to thermogravimetric analysis (TGA) the inorganic / silicate content of masterbatch is <NUM> wt%. PA PNC with desired amount of nanoclay can then be prepared by diluting this masterbatch in neat PA. The inorganic content of PA PNC (determined by TGA) is <NUM> wt%. Before processing, PA and nanoclay were dried at <NUM> overnight and the processed samples were also dried at the same conditions.

A co-rotating twin-screw extruder, with L/D of <NUM> and a die diameter of <NUM>) is used for processing and extruded samples are collected via a water bath and then pelletized.

The respective films are either single- (not according to the invention) or multi-layered co-extruded blown films.

The main objective and advantage of the invention is the controlled release of CO<NUM> from the PE active film, to enhance the shelf life of beverages containing fruity acids by displacing dissolved oxygen from the liquid and creating a positive pressure.

Single-layer PE Active (not according to the invention) with varied concentration of CaCO<NUM> and neat PE films demonstrate that PE Active can release CO<NUM> when in contact with fruity acid such as tartaric acid.

PE Active layer is also integrated in a multi-layered film by addition to PA PNC which provides passive oxygen barrier.

Single-layer PE Active with <NUM>% CaCO<NUM> (Example <NUM>). The composition of the film and the key film processing parameters are tabulated in Table <NUM>. The scanning electron microscope (SEM) image captured on the freeze-fractured cross-sections of the film is presented in <FIG>. The circular patterns represent the dispersed Ca-CO<NUM> particles. The CaCO<NUM> embedded active films generates CO<NUM> while in contact with acidic fluid over a period of time and eventually create a positive pressure inside the pouch / container and block the permeation of oxygen from the atmosphere. It is important to note that the inventors found that incorporation of CaCO<NUM> does not affect the inherent sealing properties of PE.

Quantification of release of CO<NUM> gas is determined by bottle-tube displacement experiments (refer to APPENDIX-A) from the reaction of the tartaric acid solution with the experimental film. The graphical representation of CO<NUM> (volume) released over time is presented in <FIG>. It is evident that over time, tartaric acid penetrates the film, reacts with CaCO<NUM> in the film, and releases CO<NUM>. The neat PE film containing <NUM>% LLDPE and <NUM>% LDPE does not exhibit such CO<NUM> release capability. In most cases, the visible change is noticeable approximately after <NUM> days.

Single-layer PE Active with <NUM>% CaCO<NUM> (Example <NUM>) shows the effect of Ca-CO<NUM> concentration of the particles on the CO<NUM> release. The composition of the film and the key film processing parameters are tabulated in Table <NUM>. The SEM image captured on the freeze-fractured cross-sections of the film is presented in <FIG>. It is evident from the figure that reactive sites increase with the loading of CaCO<NUM>. As a result, the release of CO<NUM> increases (refer to <FIG>). Therefore, it is to be expected that as the concentration of CaCO<NUM> increases, more CaCO<NUM> particles will be available for the reaction with acid in the contained foodstuffs.

Further concentration of CaCO<NUM> is increase to <NUM>% in the single-layer PE Active film (Example <NUM>). The composition of the film and the key film processing parameters are tabulated in Table <NUM>. The SEM image captured on the freeze-fractured cross-sections of the film is presented in <FIG>. It is evident from the figure that the surface roughness increases with the loading of CaCO<NUM> and more sites are available for the targeted reaction. Subsequently, the release of CO<NUM> increases as observed in <FIG>. The contact area can be manipulated by optimum loading of Ca-CO<NUM> and/or by process induced porous structure formation.

PE active (similar as EXAMPLE2) composite is integrated in a multi-layered active-passive barrier film where the dispersed nanoclays in PA PNC retards the ingress of oxygen by creating tortuosity (Example <NUM>). The composition of the film and the key film processing parameters are tabulated in Table <NUM>. The SEM image captured on the freeze-fractured cross-sections of the film is presented in <FIG>. Presence of multiple layers are clearly visible in <FIG> and the thickness of PE active layer is approximately <NUM>. The volume of CO<NUM> released from the film is presented in <FIG>. The multi-layered structure is the less reactive than the single layered films containing different concentration of CaCO<NUM> (EXAMPLES <NUM> - <NUM>). However, it exhibits slow release of CO<NUM> over time. The amount of CO<NUM> that will be released over <NUM>, <NUM> and <NUM>-month period is estimated using a curve fitting of polynomial of order <NUM>. The estimated CO<NUM> release from the film after <NUM>, <NUM>, <NUM>-month are <NUM>, <NUM> and <NUM> ppm, respectively. Such concentration of CO<NUM> falls within the prescribed limit. For the safety reason, in case of BIB package the amount of CO<NUM> specified is <<NUM>-<NUM> ppm. Above <NUM>-<NUM> ppm the bag may swell when the temperature rises as the CO<NUM> comes out of solution.

CO<NUM> becomes perceptible to the human palate at around <NUM>/l, which creates a slight spritz on the tongue. The recommended concentrations of CO<NUM> (at <NUM>) in still, semi-sparkling and the sparkling wines are < <NUM>/l, <NUM> to <NUM>/l and > <NUM>/l, respectively. According to wine makers, CO<NUM> limit in sauvignon blanc and aromatic whites, Chardonnay and red wines are respectively <NUM> - <NUM>, <NUM> and < <NUM> ppm in and less than <NUM> ppm. Generally, the accepted concentrations of CO<NUM> in the red and white wines are different; specifications are about a maximum of <NUM> ppm for reds and <NUM>-<NUM> ppm for white wines.

Higher concentration of CO<NUM> gives crisper wine with lower dissolved oxygen, but less flavor intensity. However, a bit of CO<NUM> helps preserving the wine. Addition of Sulfur dioxide (SO<NUM>) to the wine during fermentation is a common practice to extend the shelf-life. SO<NUM> itself is a gas, but readily reacts with water and forms bisulfite / sulfite. The formation of sulfite depends on the pH of water. It increases logistically with increase in pH. This sulfite binds to the anthocyanins, a phenolic molecule that gives red color to the wine. As a result, the SO<NUM> containing red wines have less intense color. This reaction reduces the chance of reaction between the anthocyanin and the dissolved oxygen. The reaction between anthocyanin and the dissolved oxygen produces acetaldehyde and gives wine a brownish hue. The level of free SO<NUM> upon filling is often <NUM>-<NUM> ppm. However, it falls over time; the free left after <NUM> months can be <NUM> ppm. SO<NUM> can prevent wine oxidation, but it can have adverse allergic effects. Since CO<NUM> as a blanket over the surface of wine can help prevent oxidation and the growth of spoilage organisms, a slow release of CO<NUM> over time can compensate the loss of SO<NUM> and prolong the shelf life of wine. Not only that, it might allow reduction of the initial SO<NUM> concentration to reduce the health risk.

Typical properties of the multi-layered active-passive barrier film is summarised in Table <NUM>. The typical oxygen permeation for the film is <NUM> cc-mm/m<NUM>. day at <NUM>% RH. In comparison to the Comparative example, where neat PA is used as a passive barrier instead of PAPNC, there is approximately <NUM>% reduction in oxygen permeation. The transparency of the film is measured using UV-Vis spectrometer and the transmittance before and after exposure to humidity (<NUM>% RH, <NUM> for <NUM>) are respectively <NUM>% and <NUM>%. As depicted in Table <NUM>, replacing PA by PA PNC does not have any effect the transparency of the film. Overall, tensile properties of the multi-layered active passive barrier film is also better than the comparative example.

Safety and migration of nanoparticles from the packaging film is of utmost importance in any application. Migration of nanoclay constituents from the co-extruded multi-layered films (Example <NUM> and Comparative example) are presented in Tables <NUM> and <NUM>. Inductively coupled plasma mass spectroscopy (ICP-MS) and graphite furnace atomic spectroscopy (GFAAS) have been used to quantify the amount of inorganic contents (Mg, Al, and Si are used as main markers) migrated into Type C simulant (Following EU10/<NUM> regulatory procedure) recommended for high alcohol containing food and beverages. Whereas High performance liquid chromatography (HPLC) coupled with MS has been employed to quantify the organic content migrated from the representative films. The effect of storage time of the film prior to the exposure to the simulant is investigated. The concentration of Mg, Al and Si migrated from the films to the simulant are tabulated in Table <NUM>. The point to be noted is that according to Swiss Ordinance from the Federal Department of Home Affairs FDHA Federal Food Safety and Veterinary Office FSVO Annex <NUM> of the Ordinance of the FDHA on materials and articles intended to come into contact with food-stuffs, List of permitted substances for the production of packaging inks, and related requirements, <NUM>, nanoclay is recognised as a class-A material and safe. For class-B material, the default specific migration limit is <NUM> ppm [<NUM>]. Some results indicate that no nanoclay compositions are below detection limit (BDL) or in the range of ppb concentration. In addition, presence of porous active inner layer does not induce migration of clay constituents into food simulant.

HPLC-MS results are summarized in Table <NUM>. Migration concentration trend of precursor ions from the surfactant used to modify the nanoclay with storage time is quite stable and is not expected to give rise to safety concerns of estimated <NUM>µg. kg-<NUM> or <NUM> ppm of dimethylalkyl (C16-C18) amines migration according to a Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) panel, see <NPL> [<NUM>].

<FIG> shows diagrammatically different configurations and embodiments of the bag in a box application of the invention.

Multi-layered film comprises of PE Active and PA as a passive gas barrier layer (Comparative example). The composition of the film and the key film processing parameters are tabulated in Table <NUM>. The typical oxygen permeation for the film is <NUM> cc-mm/m<NUM>. day at <NUM>% RH. The transparency of the film is measured using UV-Vis spectrometer and the transmittance before and after exposure to humidity (<NUM>% RH, <NUM> for <NUM>) are respectively <NUM>% and <NUM>%. The tensile properties of the film is also reported in Table <NUM> and the film exhibits similar properties in both machine and transverse direction.

The film in comparative example is used as a control to quantify the migration of nanoclay constituents from the film presented in EXAMPLE <NUM>. Though the comparative example does not contain nanoclay, there are some traces of Mg, Al, and Si detected in GFAAS. Such result may originate from instrument error and/or sampled deionised water.

Claim 1:
A composite active flexible polymeric film for containers for containing acidic foodstuffs which are beverages containing fruity acids material, which film includes an inner active layer of a polyethylene calcium carbonate composite, which layer generates carbon dioxide gas when in contact with the acidic material to settle in the headspace of the container,
characterized in that
an outer layer is provided which is a composite passive barrier layer is polyamide based and includes nano clay particles, and
a polyacrylic acid (PAA) is provided as a tie layer to tie the two layers together, which layers are coextruded and blown films.