OXYGEN SCAVENGER COMPOSITIONS

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application Ser. No. 60/819,922 filed on July 11, 2006.

FIELD OF THE INVENTION

[0002] The invention refers to oxygen-scavenging materials used in active packaging for products which are susceptible for degradation due to the presence of oxygen. It concerns particularly oxygen-scavenging compositions for the food industry.

BACKGROUND OF THE INVENTION

[0003] There are many products which have to be kept in a closed volume with little or almost no oxygen. These products include pharmaceutical and food which are susceptible for degradation due to the presence of oxygen.

[0004] The removal of oxygen from the packed foods and building barriers against oxygen penetration during storage represents an important objective for the food-packaging technologist. Oxygen is present even within packaging that is practically gas tight, since foods contain occluded and dissolved oxygen. Furthermore, gas tight packaging such as bottles and jars may present a certain level of gas permeability at the body-closure contact whereas plastic packaging may have significant wall oxygen ingress.

[0005] Spoilage of food occurs due to biochemical reactions, microbiological growth, and survival of insect larvae. Biochemical reactions can be triggered by very small amounts of oxygen. The result may be loss of nutrient value, change of food color and rancidity processes.

[0006] Oxygen scavenging packaging may be built of polymers that contain oxygen absorbers. Oxygen absorbing materials in food packaging eliminate the oxygen dissolved and occluded in foods, the oxygen present in headspace packaging, and avoid oxygen ingress. These materials retard the spoilage and extend the shelf life of the product.

Oxygen scavenging packaging is very effective when combined with gas flushing or vacuum packaging techniques.

[0007] The use of iron-based oxygen scavengers for food packaging is known in the prior art. Conventional oxygen scavengers based on the corrosion of metals comprise at least a metal and a salt. The metal, usually an iron powder, is the oxidizable component and the salt is the corrosion enhancer. The most common corrosion enhancers are sodium chloride, calcium chloride and magnesium chloride. Oxygen scavenging compositions have been incorporated in polymers to build packaging structures.

[0008] U.S. Patent No. 4,769,175 discloses a sheet-like oxygen scavenger which can be fixed to the inner wall of a packaging. The oxygen scavenger is composed of a mixture of fibrous material, iron powder, water and electrolytic material. The fibrous material is used as carrier of the scavenger composition and is intended to enhance the permeability of oxygen and to increase the air-iron contact area. Natural or synthetic fibers were used. The preferred electrolytic materials are NaCl, CaCl ₂ , MgCl ₂ , FeCl ₂ and FeCl ₃ .

[0009] U.S. Patent No. 5,089,323 is directed to an oxygen absorbing sheet which was obtained by using a resin composition comprising 30 to 85% by weight of an oxygen absorbent. The oxygen absorbent comprises from 90 to 99.9% by weight iron and from 0.1 to 10% by weight of a salt where the salt is adhered on the surface of iron to increase corrosion efficiency. The salts used were calcium chloride, sodium chloride or magnesium chloride. To further increase the efficiency of the system the sheet was stretched to produce micro-voids and thus facilitate the penetration of oxygen and water vapors to the active material.

[0010] U.S. Patent No. 5,721,187 discloses an oxygen scavenging system comprising an active carbon material layer and an oxygen absorbing layer. The active carbon layer may contain powdered or fibrous active carbon.

[0011] U.S. Patent No. 5,153,038 discloses a plastic multilayer vessel which under heat sterilization conditions and after the heat sterilization the resistance against the penetration of oxygen is very high. The multilayer structure of the plastic vessel contains an oxygen scavenger. The oxygen scavenger, and optionally a water absorbing agent are incorporated in a gas barrier resin. The oxygen scavenger comprises iron powder, zinc powder, tin

powder and low-valence metal oxides. The oxygen scavenger can be used in combination with an assistant such as a hydroxide, carbonate, sulfite, thiosulfite, tertiary phosphate, secondary phosphate, organic acid salt or halide of an alkali metal or alkaline earth metal, or active carbon, active alumina or activated clay according to need. A deliquescent inorganic salt, a deliquescent organic compound or a highly water-absorbing resin is used as the water-absorbing agent. The oxygen scavenger is used at a concentration of 1 to 1000% by weight, especially 5 to 200% by weight based on the gas barrier resin. The optionally water-absorbing agent is incorporated at a concentration of 1 to 300% by weight, especially 5 to 100% by weight based on the gas barrier resin.

[0012] Another packaging structure containing an oxygen scavenger is disclosed in U.S. Patent No. 5,143,763. The sheet has, from the inner surface of a container, the following structure: an oxygen permeable non-porous layer; an asymmetric porous membrane consisting of a dense skin layer and a porous layer; a support layer consisting of a woven or non-woven fabric; an oxygen absorbent composition layer containing an oxygen absorbent in a resin; and a back side laminate. A variety of oxygen absorbers can be used with this invention including iron-based oxygen absorbers.

[0013] U.S. Patent No. 5,744,056 discloses oxygen-scavenging compositions comprising an oxidizable metal component, an electrolyte component, a solid non-electrolytic acidifying component and optionally a water-absorbing binder. The binder can serve to provide additional moisture which enhances oxidation of the metal in the presence of the promoter compounds. The water-absorbing binders include diatomaceous earth, boehmite, molecular sieves, talc, activated carbon, graphite and carbon black. The electrolyte component can be sodium chloride, potassium bromide, calcium carbonate magnesium sulfate and cupric nitrate. The solid, non-electrolytic acidifying component is a material which dissociates into positive and negative ions in aqueous solutions only slightly and produces an acidic pH. The preferred non-electrolytic acidifying component is sodium acid pyrophosphate. The compositions can be used as an oxygen absorbent in packets or in combination with thermoplastic resins.

[0014] U.S. Patent No. 6,899,822 to McKedy discloses an oxygen-absorbing composition for combining a resin as a component thereof to effect oxygen-absorption consisting essentially of in relatively sufficient proportions by weight iron, preferably sponge-grade

iron, an acidifier selected from the group consisting of sodium and potassium bisulfate and an electrolyte, preferably sodium chloride.

[0015] U.S. Patent Appl. Publication No. 2006/0192176 to Rollick et al., discloses a composition for use in film forming polymers, wherein a oxygen-scavenging composition comprises: an oxidizable metal particle, such as elemental iron; at least one water- hydrolysable Lewis acid, such as aluminum chloride; and an acidifying electrolyte such as sodium or potassium bisulfate.

[0016] U.S. Patent Appl. Publication No. 2006/0208218 to Al Ghatta discloses a composition for walls of containers and preforms, wherein an oxygen-scavenging composition comprises: a protic solvent hydrolysable halogen compound (i.e., water- hydrolysable Lewis acid), such as aluminum chloride, which is deposited upon oxidizable metal particles, such as elemental iron. The metal is contacted with an essentially moisture free liquid (i.e., an organic solvent) containing the protic solvent hydrolysable halogen compound and then any remaining solvent is evaporated from the solid.

[0017] U.S. Patent No. 6,248,690 to McKedy discloses an oxygen-absorbing composition containing particulate annealed electrolytically reduced iron of between about 100 mesh and 325 mesh in an amount of about up to 63% by weight, a salt such as sodium chloride in an amount by weight of about up to 3.5%, and a water-supplying component comprising activated carbon with liquid water therein of a mesh size of between about 20 mesh and 50 mesh in an amount by weight of up to about 85%.

[0018] U.S. Patent No. 7,147,799 to DelDuca et al., discloses an oxygen scavenging packet containing an iron-based oxygen scavenger and an electrolyte in which the rate of uptake of oxygen is increased by virtue of the introduction into the packet of an oxygen uptake accelerator containing water. Methods of increasing the rate of oxygen absorption by use of the iron-based oxygen scavenging packet are also set forth.

[0019] International Patent Publication No. WO99/28411 to Mehlmann et al., discloses oxygen-scavenging compositions including a powdered metal in wet-corrosion compositions using strong corrosion agents, and specifically materials (such as strong acids and strong alkalis) that will reduce the pH to well below 4 or increase it to well above 9. More particularly, it is proposed that the metal and a large-surface-area, reaction-site

material be utilized in a very finely powdered form, and especially one in which a significant proportion of the particles are deformed, possibly with fracturing. The compositions can be dispersed within a water and oxygen-permeable sheet that can be disposed in actual, direct contact with the oxygen-sensitive substance to be protected.

[0020] Accordingly, there is a need for an oxygen-scavenger composition providing efficiency in terms of absorption capacity and rate of oxygen removal to preserve freshness and extend the shelf life of a variety of foods and medicines.

SUMMARY OF THE INVENTION

[0021] One embodiment of the present invention relates to an oxygen scavenging composition including a metal component that is itself capable of corroding (i.e., oxidizing) in the presence of moisture, at least one acidic large surface area material and at least one salt.

[0022] In another embodiment, the acidic large surface area material may be an acid- treated large surface area ceramic material, an acid-treated large surface area carbonaceous material or an acidic zeolite. Acid-treated large surface area materials have the acid adsorbed on their surface. Acidic zeolites contain acidic sites throughout their crystalline structure.

[0023] In another embodiment, the disclosed composition may be incorporated in polymeric materials and used to fabricate packaging and packaging components or used as a powder in sachets or labels.

[0024] These compositions can be incorporated into oxygen-scavenging compositions for the use in active packaging multilayer structures such as sealing films and foils, closure liners, trays, cups and other packaging structures.

[0025] In a further embodiment, the oxygen-scavenging compositions are useful in a sachet.

DETAILED DESCRIPTION OF THE INVENTION [0026] 1. The Oxygen Scavenging Powder

[0027] The present oxygen scavenger is a finely-particulate composition of metal together with various materials. The oxygen-scavenging powders of the invention include:

i) an oxidizable metallic powder, preferably an iron powder, ii) an acidic large surface area material, and iii) a salt.

[0028] The metal utilized in the compositions of the invention is most preferably one that is itself capable of corroding in the presence of moisture. Suitable examples of such a metal are zinc, copper, tin and, especially iron. The metal is in form of powder. Preferably the powder has a particle size up to about 200 microns, more preferably up to about 20 microns, most preferably not greater than about 10 microns in diameter. The smaller the particle size, the higher the corrosion rate, consequently the more efficient the oxygen uptake rate of the oxygen-scavenging composition. The metal is preferably pure, that is without any alloying ingredients except the normal impurities present after its production.

[0029] The purpose of the acidic large surface area porous material is to create an acidic environment throughout the oxygen scavenger composition. Acidic large surface area materials can be acid-treated ceramic materials, acid-treated carbonaceous materials, acidic zeolites and a mixture thereof. The term "acidic" means a pH less than about 7.0, more particularly less than about 6.0 and still more particularly about 3.0 to about 6.0.

[0030] Particularly suitable for adsorption of acids are the materials such as activated aluminum oxide, silica gel, zeolites and activated carbon. The adsorbed acids may be organic or inorganic. Most preferable are strong corrosive acids such as: hydrochloric acid, sulfuric acid and acetic acid (Herbert H. Uhlig and R. Winston Revie, Corrosion and Corrosion Control, 1985; Robert J. McKay and Robert Worthington, Corrosion Resistance of Metals and Alloys, 1937). A weaker acid such as phosphoric acid may be also used.

[0031] The term "large surface area" is used herein to refer to a class of high surface area materials known, as such, in the art such as the aforementioned zeolites, aluminum oxide, and carbons. In one embodiment, the term large surface area refers to materials having a surface area of at least about 50 m ² /g and more particularly greater than about 150 m ² /g as found in certain aluminum oxide. In another embodiment, the term refers to surface area of

at least about 400 m ² /g as found in certain carbons and more particularly greater than about 800 m ² /g. In one embodiment, large surface area materials may be characterized by their porosity, for example, materials having a pore volume of at least about 0.25 m ² /g as in the case of aluminum oxide may be used.

[0032] The salts used in this invention may have in an aqueous solution acidic, neutral or basic pH values. Salts which can be used are: sodium chloride, calcium chloride, magnesium chloride, calcium chloride dihydrate, sodium bisulfate, ferric chloride, ferrous chloride ferrous sulfate, zinc sulfate, sodium acetate and a mixture thereof.

[0033] The ratio of the salt to the acidic large surface area material is established according to the needs and the nature of the components. The weight ratio of the salt to the acidic large surface area porous material can range from about 1 : 100 to about 100:1, preferably from about 5:100 to about 100:5.

[0034] At least about 5 parts salt plus acidic large surface area material per 100 parts by weight oxidizable metal is used in one embodiment. More particularly, about 5 parts to about 200 parts by weight salt plus acidic large surface area porous material per 100 parts by weight oxidizable metal may be used.

[0035] The compositions may also include abrasive materials such as but not limited to titanium dioxide, silicon dioxide, aluminum oxide, silicon carbide and the like. Abrasives can be used in an amount of about 20 parts by weight to about 300 parts by weight abrasive materials per 100 parts by weight oxidizable metal.

[0036] The compositions described hereinbefore can be used as loose powders in the preparation of sachets and labels for food as well as non food packaging applications.

[0037] 2. The oxygen-scavenging compositions and the polymer matrix

[0038] One embodiment provides an oxygen-scavenging polymer composition containing an oxygen-scavenging powder mixture described hereinbefore dispersed within a film-forming polymer.

[0039] The mixture of metal, acidic large surface area material and salt represents the oxygen-scavenging powder. The oxygen-scavenging powder can be incorporated into the

polymer matrix by a compounding process. The composition may range quite widely between about 5 parts to about 150 parts of oxygen-absorbing powder per 100 parts polymer, typically from about 5 parts to about 100 parts.

[0040] Suitable polymers are, but not limited to: low density polyethylene (LDPE), high density polyethylene (HDPE), very low-density polyethylene (VLDPE), linear low density polyethylene (LLDPE), polypropylene (PP) and polyethylene terephthalate (PET). Furthermore, the polymers may be blended with water absorbing resins such as, but not limited to, polyvinyl alcohol, polyethylene oxide and acrylic acid/vinyl alcohol copolymer. In one embodiment, suitable polymers may be characterized by an oxygen transmission rate of at least about 77 cc/m ² day for a film thickness of 25 μm at standard temperature and pressure..

[0041] The oxygen-scavenging materials incorporated into a polymer matrix maybe used in removing headspace oxygen as well as the oxygen dissolved and/or occluded in foodstuff. The obtained oxygen-absorbing polymers may be used in making oxygen- absorbing packaging and packaging components such as heat-sealable foils, films and closure liners. In addition, it is possible to build oxygen-scavenging devices in the form of labels, strips, disks, cards for the use with foodstuff, preferably inside high-barrier packaging as a supplement to vacuum and modified atmosphere packaging (MAP) environment.

[0042] Various compositions of the invention are illustrated in the following non-limiting examples.

EXAMPLES [0043] 1. Preparation of acidified large surface area material

a) Adsorption of hydrochloric acid on activated aluminum oxide

[0044] Activated aluminum oxide is obtained by mild calcination of aluminum hydroxide. This process yields basic aluminum oxide due to its trace amounts of Al-O-Na groups on the surface of the material. The amount of material on the surface of the activated aluminum oxide having basic pH values can be neutralized or over-neutralized by

adding precise amounts of HCl gas in a fluidized bed. This technique is used to obtain the commercial neutral and acidic activated aluminum oxide.

[0045] The activated aluminum oxide types utilized in our experiments were: acidic activated aluminum oxide (pH 4.5, Aldrich product number 199966) neutral activated aluminum oxide (pH 7, Aldrich product number 199974) and basic activated aluminum oxide (pH 9.5, Aldrich product number 199443).

[0046] The pH of acidic, neutral and basic activated aluminum oxide was measured by the manufacturer (CAMAG in Switzerland) in a 5% aqueous suspension (stirred).

b) Adsorption of hydrochloric acid on activated carbon

[0047] The adsorption of hydrochloric acid on the surface of the activated carbon was performed as follows. The activated carbon (Riedel-de Haen, product number 18003) having a pH value of 9 to 10 in aqueous slurry was introduced in beakers of 250 ml. Each beaker was loaded with 10 grams of material. Subsequently 10 ml of HCl 37% (Riedel-de Haen, product no 30721) was added in each beaker. The vessels were covered and stored at room temperature for 1 hour. Finally, the beakers were kept in a furnace at 200 ⁰ C for about 1 hour. The resulted activated charcoal had a pH value of 4 to 5 in aqueous slurry. The pH of acidic and basic activated carbon was measured by mixing 1 gram of activated carbon with 5 ml of water and testing using pH paper test strips.

[0048] 2. Preparation of Powder Mixtures

[0049] The oxygen scavenging powder compositions were prepared using Fritch Pulverisette 7 (Examples 1 to 6) and Pulverisette 5 (Examples 7 and 8) planetary milling machines. The grinding/mixing operation was performed in two stages. In the first stage the iron powder together with the large surface area material were mixed. In the second stage a salt was added and the milling was continued to homogenize the powder mixture.

[0050] 3. Preparation of Compounds and Polymer Films

[0051] The oxygen-scavenging materials were compounded into low density polyethylene (LDPE 320 manufactured by Carmel Olefins, Israel). The compounded material was cooled under an air stream and cut in pellets. The compounded material was

then formed into cast films of about 160 μm thickness using a Randcastle 5L COEX cast extrusion machine. The heating zones of the extruder were set at 140, 160, 190, 200 and 200 ⁰ C.

[0052] 4. Experimental Setup for Analysis of Oxygen Uptake by Oxygen Scavenger Powders

[0053] The experiments were performed in 500 ml headspace glass containers with hermetically sealed metal lids. The gas samples were collected through the lid of the containers fitted with gas sampling septa. Each container held 20 ml of distilled water. The oxygen scavenger powder was spread in a glass dish (60 mm diameter and 10 mm height) placed at the bottom of the container keeping the powder out of direct contact with the water. The containers were incubated at 20 ⁰ C and the oxygen concentration was measured using a gas chromatograph.

[0054] 5. Experimental Setup for Analysis of Oxygen Uptake by Oxygen Scavenger Films

[0055] The experiments were performed in 500 ml glass containers with hermetically sealed lids. The gas samples were collected through the lid of the containers fitted with gas sampling septa. Each container held a 100 square centimeters film. Each container held 20 ml of distilled water. The containers were incubated at 20 ⁰ C and the oxygen concentration was measured using a gas chromatograph.

Example 1

[0056] Three different compositions were prepared using a Pulverisette 7 milling machine as detailed hereinabove.

[0057] Composition Alb contains 100 parts iron powder of 1-5 μm (Atlantic Equipment Engineers cat. no. Fe-101), 133 parts basic activated aluminum oxide (pH 9.5, Aldrich product number 199443) and 3.33 parts calcium chloride (Scharlau cat. no. CA 0192).

[0058] Composition AIn contains 100 parts iron powder of 1-5 μm (Atlantic Equipment Engineers cat. no. Fe-101), 133 parts neutral activated aluminum oxide (pH 7, Aldrich product number 199974) and 3.33 parts calcium chloride (Scharlau cat. no. CA 0192).

[0059] Composition Ala contains 100 parts iron powder of 1-5 μm (Atlantic Equipment Engineers cat. no. Fe-IOl), 133 parts acidic activated aluminum oxide (pH 4.5, Aldrich product number 199966) and 3.33 parts calcium chloride (Scharlau cat. no. CA 0192). In an aqueous solution calcium chloride has a pH value of about 8. The compositions of tested samples are summarized in Table 1.

Table 1

[0060] A quantity of 0.697 grams of oxygen scavenger powder was used for each sample tested. The results of the oxygen uptake kinetics for samples containing acidic, neutral and basic activated aluminum oxide are given in Table 2.

Table 2

[0061] As shown in Table 2, the composition prepared using acidic activated aluminum oxide absorbs oxygen faster and has a higher oxygen absorption capacity than samples prepared with neutral and basic activated aluminum oxide.

Example 2

[0062] For the preparation of the oxygen scavenging compositions detailed hereinafter NaCl (Riedel-de Haen, product number 31434) was used as salt. NaCl is neutral in aqueous solutions. Composition A2b contained 100 parts iron powder, 133 parts basic activated aluminum oxide and 3.33 parts sodium chloride. Composition A2n contained

100 parts iron powder, 133 parts neutral activated aluminum oxide and 3.33 parts sodium chloride. Composition A2a contained 100 parts iron powder, 133 parts acidic activated aluminum oxide and 3.33 parts sodium chloride. The compositions of tested samples are summarized in Table 3.

Table 3

[0063] A quantity of 0.697 grams of oxygen scavenger powder was used for each sample tested. The results of the oxygen uptake kinetics for samples containing acidic, neutral and basic activated aluminum oxide are given in Table 4.

Table 4

Example 3

[0064] For the preparation of the oxygen scavenging compositions in the following example FeCl ₃ (Riedel-de Haen, product number 12321) was used as salt. FeCl ₃ is strongly acidic in aqueous solutions. Composition A3b contained 100 parts iron powder, 133 parts basic activated aluminum oxide and 3.33 parts ferric chloride. Composition A3n contained 100 parts iron powder, 133 parts neutral activated aluminum oxide and 3.33 parts ferric chloride. Composition A3a contained 100 parts iron powder, 133 parts acidic activated aluminum oxide and 3.33 parts ferric chloride. The compositions of tested samples are summarized in Table 5.

Table 5

[0065] A quantity of 0.697 grams of oxygen scavenger powder was used for each sample tested. The kinetics of oxygen uptake is summarized in Table 6.

Table 6

[0066] The results in Table 6 emphasize that even when using a salt which in aqueous solutions is strongly acidic, such as ferric chloride, the oxygen uptake rate and the oxygen absorption capacity are typically higher in the composition containing the acidic aluminum oxide (A3a) in comparison with the composition containing the basic aluminum oxide (A3b) and the composition containing neutral aluminum oxide (A3n).

Example 4

[0067] Three calcium chloride concentrations were used with compositions containing acidic activated aluminum oxide and compositions containing basic activated aluminum oxide. Compositions Alb, A4b and A5b each contained 133 parts basic activated aluminum oxide and compositions Ala, A4a and A5a each contained 133 parts acidic activated aluminum oxide. Compositions Alb and Ala contained 3.33 parts CaCl ₂ each, compositions A4b and A4a contained 6.66 parts CaCl ₂ each, and compositions A5b and A5a contained 10 parts CaCl ₂ each. All compositions had 100 parts iron. The compositions of the oxygen scavenging powders and the oxygen uptake volumes after 168 hours are detailed in Table 7.

Table 7

[0068] Table 7 shows that over the entire range of calcium chloride concentrations the oxygen absorbed by the samples containing activated aluminum oxide with a pH value of 4.5 is typically higher than the oxygen absorbed by the samples containing activated aluminum oxide with a pH value of 9.5.

Example 5

[0069] Three sodium chloride concentrations were used with compositions containing acidic activated aluminum oxide and compositions containing basic activated aluminum oxide. NaCl is neutral in aqueous solutions. Compositions A2b, A6b and A7b each contained 133 parts basic activated aluminum oxide and compositions A2a, A6a and A7a each contained 133 parts acidic activated aluminum oxide. Compositions A2b and A2a contained 3.33 parts NaCl each, compositions A6b and A6a contained 6.66 parts NaCl each, and compositions A7b and A7a contained 10 parts NaCl each. All samples had 100 parts iron. The compositions of the oxygen scavenging powders and the oxygen uptake volumes after 168 hours are detailed in Table 8.

Table 8

[0070] Table 8 shows that over the entire range of sodium chloride concentrations the oxygen absorbed by the samples containing activated aluminum oxide with a pH value of

4.5 is typically higher than the oxygen absorbed by the samples containing activated aluminum oxide with a pH value of 9.5.

Example 6

[0071] Ferric chloride was used for preparing the oxygen scavenging compositions detailed herein below. FeCl ₃ is strongly acidic in aqueous solutions. Compositions A3b, A8b, A9b and AlOb each contained 133 parts basic activated aluminum oxide and compositions A3 a, A8a, A9a and AlOa each contained 133 parts acidic activated aluminum oxide. Compositions A3b and A3a contained 1.66 parts FeC13 each, compositions A8b and A8a contained 3.33 parts FeCl ₃ each, compositions A9b and A9a contained 5 parts FeCl ₃ each, and compositions AlOb and AlOa contained 6.66 parts FeCl ₃ each. All samples contained 100 parts iron. The compositions of the oxygen scavenging powders and the oxygen uptake levels after 168 hours are detailed in Table 9.

Table 9

[0072] Table 9 shows that over the entire range of ferric chloride concentrations the oxygen absorbed by the samples containing activated aluminum oxide with a pH value of 4.5 is typically higher than the oxygen absorbed by the samples containing activated aluminum oxide with a pH value of 9.5.

Example 7

[0073] Powder compositions containing iron, activated aluminum oxide and calcium chloride were prepared in a Pulverisette 5 milling machine. Each of the compositions contained 100 parts iron and 20 parts calcium chloride. The composition used for sample FAb contained 150 parts basic activated aluminum oxide and the composition used for sample FAa contained 150 parts acidic activated aluminum oxide. Each of the two

compositions was compounded into LDPE (low density polyethylene, as detailed herein above) and films of 160 μm thickness were subsequently cast extruded as described in the "Preparation of Compounds and Polymer Films" section detailed herein above. The oxygen absorption activity was measured as described in the "Experimental Setup for Analysis of Oxygen Uptake by Oxygen Scavenger Films" section detailed herein above. The films were kept sealed in glass containers for 336 hours (two weeks). The film compositions (in weight percent) and the volume of oxygen absorbed are detailed in Table 10 below.

Table 10

[0074] The difference between the oxygen uptake kinetics of the films containing acidic aluminum oxide and the oxygen uptake kinetics of the films containing basic aluminum oxide is given in Table 1 1.

Table 11

[0075] The data presented in Table 10 and Table 11 demonstrate that the film containing acidic activated aluminum oxide is typically more effective in removing the oxygen from the headspace than the film containing basic activated aluminum oxide. The absorption capacity expressed as milliliters of oxygen per gram of iron of the film containing activated

aluminum oxide which adsorbed hydrochloric acid is about 46% higher than the uptake capacity of the film which contains activated aluminum oxide with basic pH value.

Example 8

[0076] Two powder compositions containing iron, activated charcoal and sodium chloride (as detailed herein above) were prepared using a Pulverisette 5 milling machine. The powder composition used for film FCb contained 100 parts iron, 40 parts basic activated charcoal and 40 parts sodium chloride. The commercially available activated charcoal (Riedel-de Haen, product no. 18003) had a pH value of 9 in aqueous slurry. The powder composition used for film FCa contained 100 parts iron, 40 parts acidic activated charcoal and 40 parts sodium chloride. The acidic activated charcoal was prepared as described herein above in the "Adsorption of hydrochloric acid on activated carbon" section. Each composition was compounded into LDPE and films of 160 μm thickness were subsequently cast extruded, as described in the "Preparation of Compounds and Polymer Films" section, detailed herein above. The oxygen absorption activity was measured, as described in the "Experimental Setup for Analysis of Oxygen Uptake by Oxygen Scavenger Films" section, detailed herein above. The films were kept sealed in glass containers for 336 hours (i.e., two weeks). The film compositions (i.e., in weight percent) and the oxygen absorption capacity (i.e., expressed as milliliters of oxygen absorbed per gram of iron) are detailed in Table 12 herein below.

Table 12

[0077] The comparison between the oxygen uptake of films FCb and FCa is presented in Table 13.

Table 13

I Time (days) Oxygen uptake (ml) |

[0078] The data presented in Table 12 and Table 13 demonstrate that the film containing charcoal which adsorbed hydrochloric acid is typically more effective in removing the oxygen from the headspace than the film containing charcoal with basic pH value. The absorption capacity expressed as milliliters of oxygen per gram of iron of the film containing charcoal which adsorbed hydrochloric acid is about 31% higher than the uptake capacity of the film which contains charcoal with basic pH value.

[0079] Having described the invention in detail and by reference to the preferred embodiments, it will be apparent that modifications and variations thereof are possible without departing from the scope of this disclosure.

[0080] What is claimed is: