MXPA99007619A - Oxygen scavenging metal-loaded high surface area particulate compositions - Google Patents

Abstract

An oxygen scavening composition composed of a carrier and a metal coated, inert, porous particulate material having the metal substantially in a zero valence state. The composition is contained within the interior cavity of a container to scavenge oxygen therein. The composition may form at least a part of the interior surface of the container or be present therein in the form of a film, mat, sachet or ceramic.

Description

PARTICULAR COMPOSITIONS. OF ELEVATED SUPERFICIAL AREA. CHARGED WITH METAL DEPURING OXYGEN BACKGROUND OF THE INVENTION The present invention relates to polymeric compositions that can be used to retain product quality and improve shelf life of oxygen sensitive materials, and to intermediate shaped structures, eg, films, coatings, three-dimensional solids, fibers , bands and the like, which contain the composition, as well as products configured within or on which the composition or structure is incorporated or applied to, are parts of or are attached to the structure of the container. The composition comprises a polymer composition, which contains porous particulate material containing a metal that cleanses oxygen. Specifically, the composition uses a microporous particulate material of large surface area, which has been coated with metal atoms selected from magnesium, calcium, tin or one of the transition metals from scandium to zinc, or their mixtures. The oxygen scavenging composition, which contains the metal-coated particulate material of the present invention, provides for effective absorption of oxygen from within a container, without adversely affecting the color, taste or odor of the packaged material contained therein. In addition, the resulting composition is thermally stable and does not emit volatile by-products that contaminate the packaged material. The present oxygen-purifying composition has the ability to chemically combine effectively with oxygen in contact with it, such as from inside a container, without undue migration of the metal-coated material that purifies oxygen outside of the container. matrix. The migration stability of the metal and its metal-coated material is of particular advantage in that it significantly reduces or eliminates the adverse effects on the color, taste or odor of the articles in contact with the matrix composition. In order to increase preservation, it is a normal practice to pack food and other materials into the laminated packer material, which generally includes a barrier layer, i.e., a layer having low oxygen permeability. The sheet material may be thin, and in this case it is wound around the material being packaged, or may be thick enough to form a shaped container body that is provided with a lid or other separate enclosure. The polymeric sheet material may constitute some or all of the exposed inner surface area of the container. It is known to include an oxygen scavenger in the sheet material. This oxygen scavenger reacts with the oxygen that is trapped in the package or that is introduced into the package. This is described in, for example, the patents of E. U. A., Nos. 4,536,409 and 4,702,966 and in the prior art discussed in these references. U.A. Patent No. 4,536,409, for example, describes cylindrical containers formed of such sheet material and provided with metal caps. When the container is formed of a glass or metal body and is provided with a hermetically sealed metal closure, the permeation of oxygen through the body and the closure is theoretically impossible, due to the impermeability of the materials forming the body and the closing. As a practical matter, metal cans can reliably prevent the ingress of oxygen. However, some oxygen intake can occur by diffusion through the package or the like, placed between a body of the container and its lid. It has long been recognized that when conventional containers of these types are used for the storage of oxygen sensitive materials, the shelf life of the stored materials is very limited. The quality of the packaged material tends to deteriorate over time, in part because dissolved oxygen is typically present in the package from the moment it is filled; and partly due to the entry of oxygen that occurs during storage. When the container is in the form of a can, the end of the can or other closure, in many cases, includes pushing components or pulling components, which they try, respectively, to push or pull in order to allow the removal of the container. fluid or other material in the container, without removing the entire closure of this container. These push or pull components are often defined by the discontinuities or lines of weakness in the closure panel. Problems that may arise in these lines of weakness or discontinuities include the risk of oxygen permeation in the container and the risk of corrosion of the metal, where the normal protective coating of lacquer is broken in lines of weakness or discontinuities. It would be very convenient to be able to significantly improve the shelf life while continuing to use conventional methods in forming the container body, closing the container and, where applicable, packing between the body and the closure.

Several types of oxygen scavengers have been proposed for this purpose. For example, it is well known to pack iron powder in a small sack for use with dry foods. See the literature of Mitsubishio Gas Chemical Company, Inc., entitled "Ageless® - A New Era in Food Preservation" (date unknown). However, these materials require the addition of water-soluble salts to increase the oxygen scavenging regime and, in the presence of moisture, salts and iron tend to migrate into liquids, producing unpleasant tastes. Similarly, U.S. Patent No. 4,536,409, issued to Farrell et al., Recommends potassium sulfite as a scavenger, with similar results. The patent of E. U. A., No. 5,211,875, issued to Speer et al., Discloses the use of hydrocarbons introduced for use as oxygen scavengers in packaging films. It is known in the art that ascorbate compounds (ascorbic acid, its salts, optical isomers and its derivatives) can be oxidized by molecular oxygen, and can thus serve as components of the oxygen scavenging formulation, for example, as a component of a compound for closure. For example, U.S. Patent No. 5,075,362, issued to Hofeldt et al., Discloses the use of ascorbates in container closures as oxygen scavengers. U.S. Patent No. 5,284,871, issued to Graf, refers to the use of an oxygen scavenger composition, made from a solution of a reducing agent and dissolved copper species, which are mixed with food, cosmetics and pharmaceuticals. The Cu2 + ascorbate is used in the examples. The reference indicates that relatively high levels of Cu + (|| 5 ppm) are required in the food for the purification to be effective, but it indicates that small amounts of Cu2 + can be combined with oxygen in the food, which cause deterioration. of these foods. In order to avoid this deterioration, it is required to reduce the amount of O2 from the upper space or partially flood the container with an inert gas (Col. 5, lines 32-39). A paper by E. Graf, "Copper Ascorbate (II): A Novel Food Preservation System", Journal of Agricultural Food Chemistry, Vol.42, pages 1616-1619 (1994), identifies copper gluconate as the material preferred premium. It is also well known in the scientific literature (See • Polymer Compositions Containing Oxygen Scavenging Compounds ", Teumae, FN et al, WO 91/17044, published on November 4, 1991, filed May 1, 1991), that the Oxidation rate of ascorbate compounds can be significantly increased by the use of catalysts Typical oxidation catalysts for ascorbic acid and its derivatives are the water soluble salts of transition metals When such catalysts are combined with a compound of ascorbate in a polymeric matrix, for example a formulation of for closures, of PVC, they are effective in catalyzing the oxidation of the ascorbate compound, and increasing the ascorbate regime in the oxygen purification In each of the above references, the active agents of systems that purify oxygen use organic materials, which will produce by-products (for example aldehydes, acids, ketones) of the oxidation process. These byproducts are known to adversely affect a large amount of the packaged material. Copper zeolite powders have been used in tubular rectors, under relatively high temperature conditions, such as 1402C or higher, to remove small amounts of the oxygen contained in the gas streams. See "Activation of Copper Dispersed on a Zeolite for Oxygen Absorption" by Sharma and Secham, Chem. Modif. Surf .. 3 (Chem Modif Oxide Surf), 65-80. Agents that perform at such elevated temperatures have not been considered appropriate for use in food or food container applications, since these foods are typically kept at relatively low temperatures and are not exposed to temperatures above 1202C for a long time. In addition, the US patent application, also pending, with No., US Serial No. 08 / 764,874, filed on December 3, 1996, teaches that certain zeolites, which have ion exchange capacity, they can be used as a medium of exchange, whereby copper and other metals that purify oxygen adhere to the zeolite by the ion exchange technique. The ability to purify the oxygen of the resulting product is substantially limited by the exchange capacity of the material. Thus, because the exchange capacity is normally low, the amount of the metal contained in the material is less than that desired by supplying a high capacity oxygen scavenger material, which can supply a prolonged shelf life to a product. It is highly convenient to provide an effective oxygen scavenger system, suitable for packaging applications, which have oxygen absorption capabilities and that by themselves or by their byproducts, do not supply material which adversely affects the color, taste or odor of the material packed.

It is also convenient to provide an effective oxygen scavenger system, which has an active purifying agent contained within a carrier and this agent still provides the effective purification capacity. It is also convenient to provide an effective oxygen scavenger system that is thermally stable and, thus, capable of allowing the packaged system to undergo pasteurization or sterilization.

SUMMARY OF THE INVENTION The present invention is directed to an oxygen scavenger composition, capable of providing good oxygen absorption capabilities, while not adversely affecting the color, taste or odor of the packaged material with a container having this composition as part of the composition. same. The present oxygen scavenging composition is formed of a polymer or similar carrier, containing a large surface area, porous particulate material having a transition metal coated on a major portion of the surface area of the particulate material and where the metal is substantially in the state of zero valence. The present invention is further directed to a shaped structure that contains or is derived from the present composition.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 through 5 are each graphic illustrations of the oxygen scavenging of particulate materials containing oxygen scavenging metals of Examples 1 to 7, respectively. Each figure shows the comparative values of the purifying activity under dry and humid environmental conditions. Figure 6 is a graphic illustration of the oxygen scavenging activity of a purifying composition, according to the present invention.

Detailed Description The present invention is directed to an oxygen scavenger composition, formed of a carrier having a large surface area, a microporous particulate material coated with a transition metal and where the metal is substantially in its zero-valent state. The carrier can be a polymer matrix in which the present microporous particulate material is distributed substantially uniformly, or a mat or mat (woven or non-woven) having the microporous particulate material distributed substantially uniformly or deposited thereon. , or a bag or bag permeable to moisture, which contains the present microporous particulate material coated with metal distributed therein. The present invention further provides an improved container for packaging materials, such as foods, beverages and the like, which are susceptible to oxidative degradation. The present improved container is capable of retaining the product quality and increased shelf life of the packaged material, without adversely affecting the color, taste or odor of the material packaged by the present oxygen scavenger composition. The oxygen scavenging composition of the present invention is composed of a porous particulate material, which has a metal coating across the surface of the material. The porous particulate material is either distributed through the matrix of the carrier or carried as a coating. This porous particulate material should generally be a particulate material of large surface area. This surface area can be from about 1 to 950 square meters per gram, with approximately 10 to 800 square meters per gram being preferred. The elevated surface area is provided by the porosity of the particulate material. The pore volume (BET) of the particulate material is preferably at least about 0.07 cc / g, with about 0.07 to 4 cc / g being more preferred.The particle size of the particulate material should be from about 0.007 to 100. microns in diameter, with 0.007 to 5 microns being preferred.This particulate material may be composed of a material which has a low degree of solubility in water or is substantially insoluble in water, to supply a material which is substantially insoluble and inert with respect to the packaged products of the intended application. The term "inert", as used herein and in the appended claims, refers to the feature of lacking reactivity with respect to the polymer matrix and the packaged material, with which the resulting composition is considered for use. For example, when the packaged product is organic, the material may have some degree of water solubility. However, if the packaged product has an aqueous component, the material chosen must be insoluble in water. When the packaged product does not contain organic or aqueous components (for example, electronic components), the solubility of the material will be immaterial with respect to the application. The particulate materials found useful here depend on the large surface area and the high porosity properties of the material. The materials must have these properties because they are useful here. These properties have unexpectedly been found to provide a means to provide high amounts of the active oxygen scavenger metal useful for the purposes described herein. It is preferred that the material does not substantially have the capacity for ion exchange with respect to the oxygen scavenging metal. However, it may have small amounts of ion exchange activity, when this activity does not provide a composition which exhibits a metal byproduct or salt lixibility in the packaged product. Representative of these particulate materials, which are insoluble in water and which can be used, in simple form or in combination, are the oxides of metal, sulfides and hydroxides, such as those of silicon, aluminum, calcium, magnesium, barium, titanium, iron, zinc and tin; metal carbonates such as those of calcium and magnesium; minerals such as montonorilonia, caolita, atapulguiita, sepiolita, diatomaceous earth, talc and vermiculite; synthetic hydrocalcite and natural zeolites; precipitated metal silicates, such as calcium silicate and aluminum polysilicate; alumina and silica gels; activated carbon; aluminum phosphate; and similar. These materials are preferred in most applications. Illustrative of water-soluble particulates, useful herein, are certain inorganic salts, such as, for example, sulfates, such as those of calcium or potassium; phosphates, like those of calcium; and carbonates, such as those of calcium; and similar. These materials are more useful in non-food applications. As noted above, the particulate carrier material must have a large surface area and, therefore, have high porosity. The pore volume of the particulate material should be at least 0.07 cc / g, with about 0.1 to 4 cc / g being preferred. The framework structure of the particulate material can be seen as enclosed cavities, which are linked by pore channels and both the cavities and the channels have a minimum pore diameter of at least 3 angstroms and thus allow the free passage of sufficient moisture as that molecules from oxygen to metal, to start the purification of oxygen. The present material either has, or can obtain by known methods, the required surface area, pore volume and pore diameter dimensions. The present particulate material has been found to provide a desired resource for supplying large quantities of the oxygen scavenging metal or the present composition and thus, providing an increased capacity and activity to purify oxygen, while not allowing the initial and resultant materials to adversely affect the color, taste or smell of the articles in contact with the present composition. The present particulate material must be impregnated with a metal compound that scavenges oxygen or salt, which can provide a metal coating, as described herein in the following. Any metal that can be substantially reduced to the state of zero valence, and where that state is capable of reacting with molecular oxygen, is suitable for this invention. In practice, metals are selected from those that do not react with oxygen too quickly, since it would make the scrubber too difficult to handle. Also, from the point of view of food safety, metals with low toxicity are preferred. In general, it is preferred to use a metal reduced to zero valence, selected from calcium, magnesium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc or tin. The preferred metals are the transition metals of the Periodic Table, which form the series from scandium to zinc (ie, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) with the iron and copper being more preferred. Copper is especially preferred for use with this invention. The porous metal-laden material can be formed by various known methods, such as the incipient wet impregnation, used in forming various catalyst materials. In general, the process uses a highly concentrated solution of the metal compound (for example, a metal al). Substantially saturated solutions are preferred. A volume of the solution is mixed with the porous material in a ratio of the volume of the solution to the total pore volume of the material from 0.5 to 1.2 and preferably from 0.8 to 1, to substantially allow complete impregnation and surface coating of the surface area of the porous material. Once the impregnation is complete, the solvent is removed by subjecting the porous material impregnated with metal at elevated temperatures, reduced pressure or both, to provide a substantially complete coating of the metal compound on the surface area of the porous material. The material is then calcined at elevated temperatures, such as from about 200 to 500 ° C, to cause the salt or metal compound to be converted into its oxide. The material is then chemically treated to reduce the metal to its zero valence state or to its lower valence state, or mixtures thereof. It is preferred to have the metal in its lower valence state (e.g., zero) to further increase oxygen scavenging capacity and system activity. Another method of achieving reduction is to subject the impregnated porous material to elevated temperatures in the presence of hydrogen gas. The hydrogen must be present in about 0.1 to 100% hydrogen (preferably 2 to 5%) of the atmosphere. The reduction can also be achieved by high pressure techniques using a reducing gas (for example carbon monoxide or hydrogen) and elevated temperatures (pressurized system.) This method provides the combined steps of metal reduction and removal of calcined counter ion. Another method of forming the particulate material containing the present metal is by the vapor deposition technique, in which the porous material is subjected to the metal scrubber in its vapor state.The resulting material has the metal coated through the area surface of the porous material This resulting material should have a major portion of its surface area coated with the metal and preferably at least 60 percent and more preferably at least 80 percent of the surface area is coated with metal. be acceptable, where it supplies enough metal for a particular application need. It can be in the form of a mono-atomic layer or it can be a thicker coating. Thus, the upper limit of the amount of metal contained within the carrier is limited only by its limitation of activity. The exact degree of coating can be easily determined by a person skilled in the art, who has knowledge of the surface area of the porous material and the amount of metal contained therein. The greater the surface area, the lower the degree of coating required to provide at least minimal oxygen purifying activity. However, the high surface area particulate materials, currently required, provide the ability to have a high capacity oxygen scavenger material. Such capacity makes it possible to achieve the prolonged storage capacity of the resulting packaged product. The amount of the coated metal on the surface area of the particulate material will depend on the anticipated application of the purifying composition. When large amounts of the composition are used to purify small volumes of oxygen (such as in can coating applications), the amount of the coated metal in the particulate material may be as low as about 0.5 weight percent of the particulate material. and preferably less than 1 weight percent of the particulate material. However, in other conventional applications, such as in cap liners and the like, where the charge of the particulate material in the polymer carrier is low and / or the amount of the composition is small, the amount of the metal must be at least 5 percent by weight, preferably 5 to 30 percent by weight, more preferably 10 to 30 percent by weight and especially preferred 15 to 30 percent by weight, based on the weight of the coated particulate material. The exact amount of metal required for a particular application can be easily determined by the artisan. The present invention provides a means to achieve a wide range of content of the metal scrubber, which includes high percentages by weight, which can not be easily obtained by other means. The metal-loaded porous material, described above, is a finely divided solid, which is particularly suitable for replacing part or all of the filler commonly found in sealant compositions, which is an application considered here. The present composition, as a whole, is preferably anhydrous. Thus, it is preferred that the carrier component of the composition is a polymer matrix which is also preferably anhydrous. In general, the polymer matrix substantially protects the moisture scrubber under normal atmospheric conditions and, therefore, the scrubber metal remains substantially inert to the scrubbing activity until high levels of moisture are present, as obtained in a packing environment. closed. The polymer matrix must be sufficiently porous to allow moisture and oxygen to pass into the porous, metal-laden particulate material. In one embodiment of the present invention, the carrier of the present composition comprises a polymeric matrix material, i.e. a polymeric material which will form a solid matrix having therein distributed the microporous particulate material, of large surface area, coated with metal. This polymeric matrix material will be selected with respect to the nature of the composition (dispersion, latex, plastisol, dry mixes, solution or metal) and its use as part of the container in a conventional manner. The polymeric matrix material is selected from at least one polymeric material that can form a solid or a semi-solid matrix. The polymeric matrix material can be derived from a variety of polymers, which are available in a variety of physical volumetric configurations, such as dispersions, latexes, plastisols, dry mixtures, solutions or melts (for example a thermoplastic melt polymer). The particular physical configuration of the selected polymer will depend on the final structure in which the present composition is ultimately formed or incorporated. The polymer matrix is derived from polymer types that can be thermoplastic or thermoset. The primary functions provided by the polymer matrix, for purposes of the present invention, are to provide a compatible carrier (a material which is stable under normal packing temperature conditions and does not deactivate the oxygen scavenging capability of the coated active material with metal) for the particulate material coated with the metal that cleans the oxygen, which was described here completely, and to allow the entry of both oxygen and water into the composition and by allowing it to come in contact with the metal that purifies oxygen. The scope of the polymer, in general, can be very broad. However, the polymer matrix can also be selected to perform additional functions that depend on the physical configuration in which it is provided in the final structure where it is configured or incorporated. Thus, the particular polymer or mixture of selected polymers will ultimately be determined by the end use in which their oxygen scavenging effect is exerted. Therefore, suitable polymers from which the polymer matrix can be derived include vinyl polymers, polyethers, polyesters, polyamides, phenol-formaldehyde condensation polymers, polysiloxanes, ionic polymers, polyurethanes, acrylics and naturally occurring polymers, such as cellulose, tannins, polysaccharides and starches. Materials suitable for use as the polymer matrix component of latex compositions, for example, for the ends of cans, are described in U.S. Patent Nos. 4,360,120, 4,368,828 and European Patent EP 0182674. Suitable polymeric materials for their use, when the compositions are organic solutions or aqueous dispersions, are described in U.S. Patent Nos. 4,360,120, 4,368,828 and British Patent GB 2,084,601. Suitable materials for use in thermoplastic compositions include the materials proposed in U.S. Patent Nos. 4,619,848, 4,529,740, 5,014,447, 4698,469; British patents GB 1,112,023, 1,112,024, 1,112,025 and European patent EP 129309. The teachings of each of the references cited herein are incorporated herein by reference in their entirety. In particular, the polymeric material can be selected generally from polyolefins such as, for example, from polyethylene, polypropylene, ethylene / propylene copolymers,. ethylene / propylene copolymers modified with acid, polybutadiene, butyl rubber, styrene / butadiene rubber, carboxylated styrene / butadiene, polyisoprene, styrene / isoprene / styrene block copolymers, styrene / butadiene / styrene block copolymers, copolymers of styrene / ethylene / butadiene / styrene block, ethylene / vinyl acetate copolymers, ethylene / acrylate / ethylene / (meth) acrylate copolymers (eg, ethylene / butyl acrylate or ethylene / butyl methacrylate copolymers), ethylene / vinyl alcohol copolymer, vinyl chloride homopolymers and copolymers, styrene / acrylic polymers, polyimides and vinyl acetate polymers, and mixtures of one or more of them. Polyethylenes found useful in forming the present composition include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE) and the like, as well as the like. that copolymers formed of ethylene with one or more other lower alkenes (for example octene) and the like. Particularly preferred compositions, according to the invention, use a polymeric matrix composed of the thermoplastic polymer such as, for example, polyethylene or polyethylene copolymers, such as ethylene / vinyl acetate and the like or mixtures of polyethylene, such as, HDPE blends and butyl rubber; polyethylene and ethylene / vinyl acetate copolymer; as well as polyethylene and the styrene / butadiene / styrene block polymer, and the like. The polyethylene, if used, is preferably a low density polyethylene, and may be a polyethylene of very low or ultra-low density, which may be branched or linear. The ethylene / vinyl acetate copolymer, if used, preferably has a melt index in the range of 3 to 15, preferably 5 to 10, and generally contains 5 to 40%, preferably 5 to 30%, of vinyl acetate. In addition, a plastisol or a dry blend of the polymer can be used in combination with a plasticizer, to form the polymer matrix. Suitable materials for use when the compositions are plstisols, include homopolymers and copolymers of vinyl chloride. Instead of preparing such compositions as true plastisols, they can be provided as dry mixtures of the polymer and plasticizer. The proportion of the plasticizer present in a vinyl resin plastisol can be any conventional proportion, typically from 30 to 150 parts by weight of plasticizer per hundred parts by weight of vinyl resin. The polymer carrier can be formed of various thermosetting resins, such as polyurethanes, phenolics, epoxy ester resins, epoxy resins, polyesters and alkyols. These resins are normally formed in solutions or suspensions with organic liquids and applied to the inner surface of a container, followed by the application of elevated temperature to remove the liquid and cause the solidification (for example by entanglement) of the resin coating on the substrate. . The polymer matrix of the composition may also contain conventional plasticizers, which include the phthalates, adipates, glycols, citrates and epoxidized oils and the like. Examples include, for example, dioctyl phthalate, diisooctyl phthalate or diisodecyl phthalate, which are readily available. Other plasticizers that can be used are buty-benzyl phthalate, acetyl tributyl citrate, ethyl-diphenyl phosphate and diisobutyl phthalate. A particularly useful combination of plasticizers for use with a vinyl chloride / vinyl acetate copolymer resin is a mixture of diisodecyl phthalate and diisooctyl phthalate in a weight ratio of about 7-8: 1. A preferred aspect of the invention is that the scrubber must remain substantially inert in the composition and in the package or other solid deposit formed with the present composition until the composition is on or in a sealed container. Exposure of the composition to high humidity, which normally exists within a sealed container, will therefore result in a sufficient permeation of the moisture in the composition and the present oxygen scavenger to initiate a satisfactory degree of the scrubber and result in the improved shelf life of the packaged material. In addition, the depuration reaction can be accelerated by heating the composition sufficiently, while in the closed container, to cause increased permeation of moisture. Thus, preferably, the scrubbing metal is a material that remains substantially inert in the carrier, until the scrubbing reaction has been accelerated by heating in the presence of moisture. Preferably, the depuration reaction of the present composition is accelerated by pasteurization (typically at 50-100 ° C) or sterilization (typically at 100-150 ° C), the container, after filling with an aqueous filler and sealing it. This activation appears to be a consequence of the present composition, when heated, allowing moisture to enter the composition and contact the present scrubbing particulate material. The moisture becomes trapped in the composition, thus bringing the scrubber in contact with enough water, to allow the reaction with oxygen. This oxygen can be introduced through the composition or from the oxygen trapped inside the container, when it is filled or subsequently enters the container from the surrounding atmosphere. The polymer matrix of the present compositions may further contain the inert filler, slip aids, process aids, pigments, stabilizers, antioxidants, tackifying resins, foaming agents and other conventional additives, in conventional amounts, depending on the nature of the composition. the composition and its final use. If the polymer matrix is part of a thermoplastic composition, the total amount of these additives is generally below 10%, more preferably below 3%, based on the total weight of the composition. However, when the composition is a plastisol, dispersion, organic solution or latex, the amounts of additives in the polymeric material may be greater. When an antioxidant is incorporated, it must be present in amounts capable of stabilizing the polymer composition against degradation, due to the free radicals formed during the process. However, the amount of the antioxidant must be sufficiently small to allow the oxygen scavenging component of the composition to react effectively with the molecular oxygen. The specific amount will depend on the antioxidant used and can be determined by minor experimentation. The composition of the invention can be formulated in any convenient manner, such as by melting, plastisol, organic solution, dry mix, latex or dispersion. The main ingredients of the composition, apart from the particulate material coated with the oxygen scavenging metal, are typically typical of those conventionally present for the intended purpose. It is preferred that the total composition be non-aqueous (ie, an anhydrous solution, plastisol or thermoplastic melt), so as to prevent the initiation of the reaction of the scavenger within the composition. Alternatively, the scrubber may be encapsulated in a carrier sufficient to prevent contact with the water until it is within the closed environment of the container. The polymer matrix carrier of the present composition can be selected from those used to form coatings on at least a portion of the inner surface of a package (e.g., a rigid container, such as a can, can lid, box or similar) . The polymer matrix can be selected from the kinds of polymer commonly referred to as epoxies, phenols (e.g., phenol-formaldehyde condensation polymer), lacquers (e.g., esters or cellulose esters, shellac, alkyl resins and similar), polyurethanes and the like. The carrier matrix can be blended with a metal-coated particulate material, to deliver an encapsulated particulate material which can be subsequently used in a second polymer matrix or applied to the surface (such as by solvent or melt application) of a second carrier material. The present composition is particularly suitable for use with the materials conventionally used to coat the inner surface of containers (eg, cans) in which the coating requires the application of heat to separate the solvent and / or cure the carrier material. For example, lacquers, epoxy resins and the like, can be coated on the inside of the metal can surfaces as a protective coating. To cure this coating, the treated can is subjected to elevated temperatures for short periods of time, to remove the solvent and cure the coating before filling and sealing the can. Conventional oxygen scavengers, composed of oxidizable organic products, are not suitable as part of the curable coating material, since it is known that they degrade and lose their purifying activity under the elevated temperatures normally required for each step of curing. The present composition is particularly suitable for such an application, because the scrubber is stable at high curing temperatures. For example, the carrier can be a polymer matrix formed of an organic lacquer, such as that composed of an ether or cellulose ester, alkyl resin or mixtures thereof, in a solvent such as, for example, an alcohol (e.g. , a C 1 -C 3 alkyl alcohol), a ketone (for example methyl ethyl ketone), an acetate (for example, butyl acetate) or an aromatic (for example, toluene or xylene) or mixtures thereof. The porous, metal-loaded carrier material of the present invention is stable (it does not degrade or lose the oxygen scavenging activity, when subjected to the elevated temperatures, considered for the curing process), it can be used as the scavenger component of oxygen in such applications. The present composition can also be used to form a film, which carries the porous carrier material of the oxygen scavenging metal present. This carrier can be formed of a polymeric material, such as those described herein above, capable of forming a film and on its surface the present oxygen scavenger is deposited. The surface of the film can be coated with the present carrier material loaded with the oxygen scavenging metal, by forming a suspension or dispersion of its powder in a polymer and depositing this suspension or dispersion by conventional means, such as by application of coatings by spraying or spatula, or the like, directly on the surface of the carrier film. The particular nature of the carrier film will depend on the considered application and the ability of the trained carrier to have the oxygen scavenger adhered to its surface and substantially retain its integrity during use. The carrier can, alternatively, be in the form of a fibrous mat (woven or non-woven). The present oxygen scavenging composition is contained in the interstices of the mat structure. The fibers forming the mat can be formed of any suitable material or synthetic fiber, such as cotton, glass, nylon, polyethylene and copolymers of ethylene with one or more ethylenically unsaturated monomers, polypropylene and copolymers of propylene with one or more ethylenically monomers unsaturated, and similar. The particular nature of the carrier mat will depend on the application of its use and the ability of the mat to retain the oxygen scavenging material within the interstices of the mat structure, during use.

The scrubber may be deposited on the mat structure by any means, such as by immersing the mat in a dispersion or suspension of the scrubber and then removing the liquid from the mat or first forming particulate material from the scrubber / polymer composition, which It is deposited in molten form on and within the structure of the mat. In another embodiment, the present oxygen scavenging composition can be retained within a carrier in the form of a bag or bag of a size suitable for being inserted into the container, which has an oxygen sensitive material. The bag or pouch should be sufficiently porous to allow moisture and oxygen to penetrate through the material that forms this bag or sac at ambient temperature conditions. The present oxygen scavenging composition thus composed of the bag or bag carrier, having the porous particulate carrier loaded with metal, per se, or additionally contained in a polymeric carrier and provided in the form of small particles of a sufficient size to allow that the bag structure retains the oxygen scavenger. The bag or bag can be formed of natural or synthetic materials, such as paper, cotton cloth, polymer films and the like, in forms well known in packaging technology.

A fourth embodiment is to use a carrier in the form of a porous inorganic material, such as a ceramic, having a porous particulate material, loaded with metal, that purifies oxygen thereon. The ceramic can be formed in any desired configuration (e.g., spheres, cubes, cylinders and the like) and with a size which is suitable for insertion into the container having the oxygen sensitive material. Useful porous inorganic materials include clay, cement pastes and the like. An essential feature of the invention is that the present composition contains the porous particulate material, which has a large surface area, which cleans the metal-loaded oxygen described above. in a suitable form to react with gaseous oxygen. The oxygen scavenger is a metal in its zero or low valence state, which reacts with gaseous oxygen in the presence of moisture. It has been found that the metal-coated high surface area materials, described above, having a metal with a zero valence state, as per the material configuration, while in a carrier, can be used as oxygen scavenging compositions. . The resulting composition can be used for the preservation of oxygen sensitive foods stored under environmental conditions. The present compositions have an advantage over those compositions containing organic oxygen scavengers (such as ascorbates and unsaturated hydrocarbons) because they do not produce byproducts of organic oxidation, which can contaminate the food material. Furthermore, water-soluble salts, normally used in conjunction with oxygen scavengers to increase the rate of purification, are not required. Also, the present compositions exhibit minimal migration of metal ions, metal by-products or metal salts in aqueous solutions. Therefore, the present invention unexpectedly provides a highly convenient oxygen scavenging composition which does not cause discoloration or impairs the taste of the packaged food product. The oxygen scavenging material of the present invention is a porous, high surface area particulate material having a major portion of its surface coated with a substantially zero valence metal. It has been found that the nature of the system is such that large amounts of the metal are supported by the porous material in a way that causes the metal to be highly reactive with molecular oxygen, even if it is caught in a manner that prevents migration of the metal or the oxidized product inside the packed material. It would be convenient to include a material in the composition, for example a surfactant, such as sodium dodecylbenzenesulfonate, which increases the permeability of the composition to water and a suitable amount of a surfactant such that it is between 0.1 and 1.0% by weight. The amount of the present particulate material containing the metal scrubber is dependent on the type of application. When the particulate material is incorporated into a package, the amount is usually at least 0.5 weight percent, based on the material of the polymer matrix, generally at least 1% and preferably at least 2%. It is usually not necessary for the amount to be greater than 20%, and from 4 to 10% is often a convenient maximum. In the case of a plastisol, lacquer or hot melt, applied to the central panel of a closure, where the matrix does not otherwise serve as a gasket, the particulate charges of the scrubber may be much greater. For example, charges of 20 to 60 percent or in some cases up to 90 percent, can work. When the composition is in the form of a film, mat, bag or sac, the oxygen scavenger must be present in an amount to effectively purify the oxygen during the storage period of the container for the appropriate contents. An amount in the range of 0.01 to 2 grams of the porous particulate material, which contains the metal, is normally sufficient to supply the desired oxygen scavenging capacity, in a normal-sized container (50 to 1000 ml). The present composition can be used as part of a packaging container that can provide storage stability to the material packaged therein, without impairing the flavor, odor or aroma of the material. The present composition must be exposed to the internal atmosphere of the resulting sealed container, in any form, such as a coating on all or part of the internal surface of the container body or the closure element (for example the lid or the end of the container). tin) or as an insert in the form of a film, mat, bag, sack or ceramic structure. The invention formed with a polymer matrix in the form of a film can be applied as a liner of the central panel on a container closure. This closure can be a lid, can end, lid or film material. The invention also includes container closures which carry a solid deposit formed on the closure of a polymer matrix or film composition and which is placed to seal around, or on a line of weakness in, the closure. The solid deposit may be a package deposited around the closure and formed of the composition. Instead of, or in addition to, the reservoir being such a packing, the composition can be deposited on the internal face of a closure in a position where there is a discontinuity or line of weakness around a pushing or pulling component, to open a sealed container for the closing. The closure occupies, as is conventional, only a minor part of the exposed surface area of the closed container, often less than 25% of the surface area. Thus, the area of the solid deposit can be very small in relation to the area of the container. Despite this, the invention can provide a greatly improved storage stability to the contents. The invention also includes filled containers sealed with such closures. The sealed container comprises a container body, with the closure thereon, and the packaged material is contained within the container body. The body of the container is preferably glass or metal. The closure is preferably made of metal. The packaged material can be any beverage, food product or other material that is stored inside the container, but the invention has a particular value when the filling is a material whose shelf life or the quality of the product is normally restricted due to the entry of oxygen or contamination during storage. The container body can be a can, generally metal, in this case the closure is one end of the can. In general, the entire closure is made of metal or polymeric material, but the closure panel may include a removable component of any metal or polymeric material. Instead of a can body, the body of the container can be a bottle or jar, in this case the closure is a lid. The bottle or jar is preferably made of glass, but can be made of a polymeric material with very low oxygen permeability. The lid can be a polymeric material, for example a polypropylene, which can include a barrier layer. In general, the lid is formed of metal and may include a push or pull component of metal or polymeric material. This cap may be of the crown type, such as a lever or twist-off crown, a screw-in, tongue-and-loop, pressure / separation by twist, or snap-in / lever-out, screw-cap, rolling metal lid, continuous screw cap, or any other conventional form of metal lid or polymer lid, suitable for closing the bottle or jar.

A package is normally provided between the container body and the closure. This package can be used to carry the composition of the invention (in particular, as a composition containing a polymer matrix) or as a mixture in the packaging composition or as a separate component applied on or near the package, but it is possible that the composition of the invention is otherwise used on the closure or elsewhere in the container. In that case the composition that forms the package can be a conventional composition not altered, suitable to form the package. When the closure is a lid, the present treatment composition can form a general package or a portion of a general package. This is true typically for small diameter caps, such as those less than 50 mm in diameter. For larger diameter lids, the package is ring type and can be deposited in a conventional manner from the composition that forms this package. For example, a ring-type package can be formed on a lid by applying a ring in liquid form and can be converted to the solid form by drying, heating to cure or cooling to harden the thermoplastic material, as appropriate. The oxygen scavenging composition can be mixed into the packing material, deposited on the packing material, or applied to an area of the lid not covered by the packing (the center panel). The composition forming the package can, for this purpose, be a dispersion, latex, plastisol, dry mix, suitable thermoplastic composition or organic solution. The lid, which bears the package, is then pressed onto an appropriate sealing face, around the open end of the container body filled and closed in a conventional manner. If the composition is formed of a thermoplastic polymer matrix, it can be applied as a low viscosity melt, while the lid rotates, so as to drive the composition in the shape of a ring, or it can be applied as a melt, the which is then molded into the desired configuration, often a disk, which has a thick ring-like portion. In addition, the package may be in the form of a preformed ring or disk, which is retained (eg by mechanical or adhesive means) within the lid. If the closure is a can end, the oxygen scavenging material is typically not used in the packaging composition because, under typical can sewing conditions, the package is not substantially exposed to oxygen in the package. Similarly, seams are not particularly vulnerable to oxygen ingress. The oxygen scavenger material is typically applied on a central panel or other interior surface in the can, and is thus applied as a coating of a can. It is particularly preferred that the package or coating on the closure of the container is formed by applying a fluid or melt composition of the present invention, formed with a polymer matrix and solidifying it on the closure. The method of application and solidification is generally conventional. It is particularly preferred that the container and the end of the can be both metal or the container body should be glass and the plastic metal closure, since the use of compositions defined to form the package, seems to provide particularly beneficial results. . In particular, excellent results can be achieved when the body of the container is a glass bottle and the closure is a metal lid. Instead of or otherwise using the fluid or meltable polymeric matrix composition according to the invention to form a package, it is possible to deposit the composition elsewhere on the internal face of the closure. It can be applied as a general coating of the internal face of the closure panel or it can be applied on only part of the inner face. In particularWhen the panel includes one or more push or pull components, defined in the panel by discontinuities or lines of weakness, the composition may be applied primarily to just cover the discontinuity or line of weakness. For example, a type of closure, usually a can end, includes at least one and often two, push components, which are defined by partial marking lines through the metal panel, so that the pressure of the finger can push a circular area of the panel in the container, in order to allow access to the contents of the container. This can be a small thrust component to allow the release of pressure and a larger thrust component to allow the liquid to be emptied from the container. Such a system is described, for example, in DE 3,639,426. In particular, the composition of the first embodiment of the present invention can be deposited as an annular area (or a disk) that covers the line of weakness. This line of weakness may merely be a weakened line in the metal panel, but it may be a total cut around the push component, for example as in the DE patent 3,639,426, in any case, the push component generally has a slight area greater than the opening in the panel that is defined by the cutting line and the composition of the invention can then form a seal between the pushing component and the rest of the closure panel. In all cases, when the push or pull components are to be formed within a metal panel, it is a serious risk that the formation of the push or pull components may damage the polymeric lacquer coating that is generally present in the inner surface of the metal panel. This can expose the metal to corrosion. The application of a composition of the present invention to a container, as described herein, can both inhibit the corrosion of the metal container as well as improve the storage stability of the contents of the container, especially the contents that carry water, such like beer. In addition to using metal, glass and plastic containers, the compositions can be used in a cardboard or laminate container, such as a juice box. Such a container is a cardboard box or tube with an inner liner. The composition can be placed in or as layers in the inner liner of the cardboard packaging, along a line of weakness in the closure of the package, or in any other convenient location in the package. Alternatively, the present composition can be placed inside the container as a film, mat or small sack. In addition, the composition of the present invention can be compounded and extruded in desired configurations, when the polymer matrix is a thermoplastic resin. For example, the present compositions can be formed into films per se or as a component of a film composition used to prepare flexible packaging, such as bags, or the films can be laminated onto the metal material, which can then be formed in cans and closures. Also, the compositions can be included in flexible packages, such as films or laminates of multiple layers, or as a girdle, patch, label or coating on a thermoplastic bag or cap material. When the present composition is part of a multilayer film, the layer formed of the present composition must be the surface layer that will be exposed to the inner surface of the resulting flexible package or must be an inner layer, which is covered by a layer surface having high porosity, to allow O2 and moisture to penetrate inside and make contact with the layer containing the present composition. Thus, the term "exposed to the interior", as used herein and in the appended claims, will mean direct or indirect exposure of the present composition to the internal atmosphere of a sealed container., that the packaged product has content. The compositions may also be used in conjunction with or as a portion of a membrane that exhibits evidence of violations, for pharmaceuticals and foods. The following examples are provided for illustrative purposes only and do not mean that they are a limitation or that they limit the appended claims. All parts and percentages are by weight, unless indicated otherwise. Example 1 TiO2 Impregnated with Cu A solution containing 45.4 parts of Cu (N03) 2 2.5 H2O and 54 parts of distilled water was prepared. The resulting solution was then added to 100 parts of IO2, which has a surface area of 108 m2 / g and a pore volume (Hg porosimetry) of 0.4 cs / cc (Kemir 908) and mixed until uniform to provide impregnation of the 2 2 • The ratio of the pore volume to the volume of the solution was approximately 1: 1. The material was then dried overnight at 100 ° C, followed by calcination at 400 ° C for 2 hours. Six parts of the calcined powder were placed in a cup of alumina in a controlled atmosphere oven and reduced for 26 hours in a flowing atmosphere of 4% by weight of H2 in N2 at 4002C. The resulting material had a copper metal coating over most of the surface area of the titania. The copper was 12 percent by weight of the resulting particulate.

Example 2 Cu Impregnation Silica A solution containing 45.4 parts of Cu (N03) 2 2.5H2O and 280 parts of distilled water was prepared. The resulting solution was then added to a mixture of 32.9 parts of silica, which has a surface area of 250 m2 / g (Cabosil MS-75) and 67.1 parts of silica having a surface area of 100 2 / g (Carboxil M- 5) and mixed until uniform to provide the incipient impregnation of the silica. The ratio of pore volume to volume of solution was approximately 1: 1. The material was dried overnight at 1102C followed by calcination at 400SC for 2 hours. Six parts of the calcined material were placed in a cup of alumina in a controlled atmosphere oven and reduced for 4 hours in the next atmosphere of 4% by weight of H2 in N2 at 4002C. The resulting silica coated with copper had a copper content of 9.8% by weight, which coated a major portion of the surface area of the silica.

Example 3 Kaolin Clay Impregnated with Cu A solution containing 45.4 parts of Cu (N? 3) 2 2.5 H2O and 19.0 parts of distilled water was prepared. The resulting solution was then added to 100 parts of kaolin clay, which has a surface area of 21 m2 / g and a pore volume of 0.01 sc / g (BET method of N2) (Nat) and mixed until uniform, to provide an incipient impregnation of the clay. The ratio of the pore volume to the volume of the solution was approximately 1: 1. The material was dried overnight at 1102C, followed by calcination at 4002C for 2 hours. The calcined material was ground with a mortar and pestle, to supply a fine powder product. Six parts of the powder were placed in a cup of alumina in a controlled atmosphere oven and reduced for 4 hours in a flowing atmosphere of 4% by weight of H2 in N2 at 4002C. The resulting clay material had a copper coating on the main portion of its surface and was 10.2% by weight of the product.

Example 4 USY Zeolite Impregnated with Cu A solution containing 90.8 parts of Cu (N03) 2 2.5 H2O and 33.6 parts of distilled water was prepared. The resulting solution was then added to 100.0 parts of USY-type zeolite, having a surface area of 750 m2 / g (Ultra-stable Y-zeolite) and mixed until uniform to provide an incipient impregnation of the zeolite. The ratio of the pore volume to the volume of the solution was approximately 1: 1. The material was dried overnight at 1102C, followed by calcination at 4002C for 2 hours. The calcined material was ground with a mortar and pestle to supply a fine powder product. Six parts were placed in a cup of alumina in a controlled atmosphere oven and reduced for 7 hours in a flowing atmosphere of 4% by weight of H2 in N2 at 4002C. The resulting zeolite had a copper coating on the major portion of its surface and 24.8 weight percent of the product. Although this zeolite has some ion exchange capacity, such capacity is small compared to the amount of copper coating contained therein.

Example 5 USY Zeolite extracted with acid in steam, impregnated with Cu Ninety parts of USY zeolite were placed on ceramic discs in a controlled atmosphere oven and treated with 95% steam for 1 hour at 8162C. The steam materials (65 parts) were then refluxed in 3M HCl for 3 hours. After cooling, the material was filtered, washed three times with 650 parts of distilled water and dried at 103 ° overnight. The vaporization and reflux of acid served to remove the aluminum from the USY zeolite, leaving behind a crystalline silica zeolite material with virtually no ion exchange capacity. A solution containing 7.16 parts of Cu (3 3) 2 2.5 H2O and 9.6 parts of ethylene glycol was prepared. The resulting solution was then added to 20 parts of USY zeolite extracted with acid in steam and mixed until uniform to provide the incipient impregnation of the USY zeolite (SAE). The ratio of the pore volume to the volume of the solution was approximately 1: 1. The material was then dried at 100 C for 10 hours, was calcined at 2002C for 30 minutes, followed by the temperature increase to 4502C in 1.25 hours and keeping at 450se for 4 hours. The calcined powder was placed in a cup of alumina in a controlled atmosphere oven and reduced for 24 hours in a flowing atmosphere of 4% by weight of H2 in N2 at 3502C. The resulting material had a copper coating on the main portion of its surface and 9.8 weight percent of the product.

EXAMPLE 6 The materials formed in Examples 1 to 5 above were tested in their oxygen scavenging properties by the following procedure: 0.5 part of a material was placed in a gas-impermeable container having 100 cs of ambient air ("conditions "dry") and a second 0.5 part material was placed in a gas-impermeable container with 100 ce of ambient air and 2 ce of water ("wet conditions"). Samples of 3 ml of gas were removed from each vessel at spaced time intervals and analyzed in oxygen. The results of each pair of samples (dry / wet) are shown in Figures 1 to 5, respectively. The results show that each material has good stability under environmental conditions, while providing the high purifying capacity of oxygen when initiation is activated by the presence of moisture.

Example 7 This experiment was conducted by composing 4.5 parts of a material, prepared according to Example 1 (except that the material was reduced for 7 hours at 400 ° C) with 40.5 parts of plasticized polyvinyl chloride, in a Brabender apparatus, for 5 minutes at 150-1602C. Five parts of the resulting mixture were hot-pressed into a film with a thickness of 127 to 254 microns, in a gas-impermeable container, containing 100 g of air and 2 g of water. Three millimeter gas samples were taken at various times in the vessel and analyzed for oxygen content using a Mocon gas analyzer (Model HS75). The results are given in Figure 6.

Claims (21)

1. An oxygen scavenging composition comprising a carrier of a polymeric matrix, having, in a substantially uniform manner, a porous, high surface area, inert, metal-coated particulate material, which substantially does not have an exchange capacity of ions, with respect to the metal, a surface area of about 1 to 950 square meters per gram and a pore volume of at least about 0.07 cc / g, and in that the metal is substantially in its zero valence state, forms a coating on a major portion of the surface area of the particulate material and is selected from the group consisting of calcium, magnesium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, tin or mixtures thereof.

2. The composition of claim 1, wherein the porous particulate material, coated with metal, is formed by the steps comprising the incipient impregnation of a solution of the metal compound, removal of the solvent and reduction of the metal compound, to provide a coating of metal, where the metal is substantially e? the valence state of zero.

3. The composition of claim 1, wherein the porous particulate material, coated with metal, is formed by the vapor deposition.

4. The composition of claim 1, wherein the porous particulate material is selected from the water insoluble material, the group consisting essentially of metal oxides, sulfides or hydroxides; metal carbonates; minerals; synthetic and natural zeolites; metal silicates, alumina and silica gels; carbon; aluminum phosphate; and its mixtures.

5. The composition of claim 2, wherein the porous particulate material is selected from a water insoluble material, the group consisting essentially of metal oxides, sulfides or hydroxides; metal carbonates; minerals; synthetic and natural zeolites; metal silicates; alumina and silica gels; carbon; aluminum phosphate; and its mixtures.

The composition of claim 4, wherein the porous particulate material is selected from oxides and hydroxides of silicon, aluminum, calcium, magnesium, barium, titanium, iron, zinc, tin and mixtures thereof.

7. The composition of claim 5, wherein the porous particulate material is selected from oxides and hydroxides of silicon, aluminum, calcium, magnesium, barium, titanium, iron, zinc, tin and mixtures thereof.

The composition of claim 4, wherein the porous particulate material is selected from montmorillonite minerals, kaolite, atapulguite, sepiolite, diatomaceous earth, talcum, vermiculite, and mixtures thereof.

9. The composition of claim 5, wherein the porous particulate material is selected from the minerals of montmorillonite, kaolite, atapulguite, sepiolite, diatomaceous earth, talcum, vermiculite, and mixtures thereof.

10. The composition of claim 4, wherein the porous particulate material is selected from synthetic and natural zeolites.

11. The composition of claim 5, wherein the porous particulate material is selected from synthetic and natural zeolites.

The composition of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein the coated metal is selected from the group consisting essentially of iron, copper, zinc, magnesium, tin, nickel or their mixtures.

The composition of claim 12, wherein the metal is copper.

14. The composition of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein the carrier comprises a polymer matrix having at least about 0.1 percent by weight of the particulate material porous, large surface area, inert, coated with metal, distributed there based on the weight of the polymer matrix.

15. The composition of claim 14, wherein the polymer matrix is a thermoplastic resin, having from about 0.1 to 20 parts by weight of the porous particulate material, based on the weight of the polymer matrix.

The composition of claim 15, wherein the thermoplastic resin is selected from the group consisting of polyethylene, ethylene / vinyl acetate copolymers, vinyl chloride homopolymers, vinyl chloride copolymers, and mixtures thereof.

17. The composition of claim 15, wherein the polymer matrix comprises polyethylene, selected from the group consisting of high density, low, very low, ultra low density and low density linear polyethylenes, their blends and blends of "polyethylene with other polymers.

18. The composition of claim 15, wherein the polymer matrix comprises a mixture of at least one polyethylene and at least one ethylene / vinyl acetate copolymer.

19. The composition of claim 15, wherein the polymer matrix comprises a polymer selected from the group consisting of polyolefin, ethylene / vinyl acetate copolymer, butyl rubber, styrene / butadiene rubber, styrene / butadiene block copolymers / styrene, styrene / isoprene / styrene block copolymers, styrene / ethylene / butylene / styrene block copolymers, and mixtures thereof.

The composition of claim 14, wherein the polymer matrix comprises one or more vinyl chloride resins.

21. The composition of claim 14, wherein the carrier comprises a film or mat, having a porous particulate material, coated with metal, on its surface.