GB2435394A

GB2435394A - Oxygen scavenger

Info

Publication number: GB2435394A
Application number: GB0603655A
Authority: GB
Inventors: Cam Nguyen Tat
Original assignee: Sun Chemical Ltd
Current assignee: Sun Chemical Ltd
Priority date: 2006-02-23
Filing date: 2006-02-23
Publication date: 2007-08-29
Also published as: GB0603655D0

Abstract

An oxygen scavenging composition comprises a hydrogen donor (e.g. polyvinylpyrrolidone or a dioxane), ascorbic acid or an oxygen-scavenging derivative thereof, a radical-generating photoinitiator, and optionally Vitamin E or a derivative thereof or a transition metal compound or complex, the composition including a polymer or oligomer.

Description

I

OXYGEN SCAVENGER

The present invention relates to a novel oxygen scavenging composition, to its preparation and to its use, especially in the packaging of foodstuffs, medicines and other materials likely to be harmed by prolonged storage in the presence of oxygen.

Market conditions, competitive challenges and environmental regulations require the food industry to find ways of improving profitability and reducing costs, while ensuring safety and compliance with environmental legislation. As the global trend towards more stringent food packaging regulations increases, the need for product safety, shelf-life extension, cost-efficiency, environmental issues, and consumer convenience has become of increasing importance. In order to improve the performance of packaging in meeting these varied demands, innovative modified-and controlled-atmosphere packaging, and active and intelligent packaging systems are being developed, tested and optimised in laboratories around the world. Amongst these systems are oxygen scavenging systems, designed to reduce the level of oxygen in contact with the packaged material, e.g. food and other perishable material, and so reducing or slowing down the rate at which the material perishes. The majority of presently available oxygen scavengers are based on the principle of iron oxidation, in which oxygen is absorbed by the iron to form rust. To prevent the iron powder from imparting colour to the food, the iron is contained in a sachet. However, iron-based oxygen scavengers have several disadvantages. They cannot pass the metal detectors usually installed on packaging lines to detect alien objects. It is also possible that the oxygen scavenger sachets in the food package could accidentally be ingested by the consumer. Another concern is that contents of the sachet could leak out and contaminate the product. When sachets are used, there also needs to be a free flow of air surrounding the sachet in order to scavenge headspace oxygen.

To eliminate these problems, oxygen removing agents can be incorporated into such packaging material as polymer films, labels, crown corks, liners in closures etc. These oxygen scavenging materials have the additional advantage that they can be used for all products, including liquid products. The oxygen consuming substrate can be either the polymer itself or some easily oxidisable compound dispersed or dissolved in the packaging material. A problem related to the use of 02 scavenging films is that the films should not react with atmospheric oxygen prior to use. This problem has been solved by inclusion of an activation system triggering the 02 consuming capabilities of the film in the packaging system. Activation by illumination or catalysts or reagents, supplied at the time of filling, may be required to start the reaction. Thus, it is not surprising that the future trend in active packaging is to use absorbing or releasing compounds incorporated in the packaging film or in an adhesive label to get rid of separate objects in packaging and thus to avoid consumer resistance towards new packaging techniques.

However, the selection of oxygen scavenging materials which may be incorporated into packaging is not simple. Apart from the inherent requirements that they must be capable of forming the desired physical conformation (e.g. a plastics film) and that they must be capable of scavenging oxygen, where they are to be used in packaging for foodstuffs, medicines or similar sensitive materials, it is important that they should not impart unwanted colour or odour to the package, especially as such colour or odour may migrate into the contents of the package. It is also desirable that the oxygen scavenger should be inert or substantially inert until activated so that its scavenging activity is not wasted.

US Patent 6, 254,803 discloses an oxygen scavenging composition comprising a polymer or oligomer having at least one cyclohexene group and a transition metal salt, compound or complex. However, this has a number of disadvantages. A major disadvantage is that it cannot be brought into direct contact with substances to be consumed, because of the presence of metal ions (the specification proposes the use of cobalt compounds as the source of the transition metal, and cobalt is currently suspected of being carcinogenic). Moreover, the material is noticeably malodorous.

In accordance with the present invention, there is provided an oxygen scavenging composition comprising: (a) a hydrogen donor; (b) ascorbic acid or an oxygen-scavenging derivative thereof; and (c) a radical-generating photoinitiator, the composition including a polymer or oligomer.

The invention also provides a packaged material enclosed in packaging, wherein the packaging comprises an oxygen scavenging material of the present invention.

The invention still further provides a packaged material enclosed in packaging, having a composition of the present invention disposed within the packaging.

The hydrogen donor may be chosen from a wide range of compounds capable of donating a hydrogen radical to an ascorbate free radical. Examples of such compounds include: tertiary amines, for example NmethyldiethaflOlafflifle, isopentyl 4- dimethylaminobeflZOate, N-methylsuccinimide, Ncyc1ohexyIsucciflimide, N-(2-cyanoethyl)succinimide, 3-succinimidopropiOflic acid, 1 -methyl-2-pyrrolidone, 1-ethyl2-pyrrolidone, I,5dimethyl-2-pyrrOlidOne, 1 -butyl-2-pyrrolidone, 1 -octyl-2- pyrrolidone, I dodecyl-2-pyrrolidOfle, 1 -(1 adamantyl)-2-PYrrOlid0fle, 1- hydroxymethyl2pyrr0tid0ne, 1 (2hydroxyethy1)-2-pYIT0lid0fle, N-(3-aminopropyl)-2- pyrrolidone, 2-oxo-I pyrrolindinecarboxamide, 2-oxo-I -pyrrolindinebutyramide, 2-(2-oxopyrrolindin-1 -yl)acetamide, 2-(2-oxopyrrolindin-1 -yl)butanamide, 2-oxo-1-pyrrolidinepropionitrile, 2-(2,5-dioxo-1 pyrrolidinyl)-N-mCthY1acetamide, oxotremorine and its salts such as the sesquiftimarate, 1 -vinyl-2-pyrrolidone, 1 -cyclohexyl-2- pyrrolidone, 1 phenyl-2-pyrro1idofle, 1 benzy1-2-pyrrolidOne, I -benzylpyrrolidine-2,S-dione, I phenylethy1succinimide, 1 (2cyanoethyl)5OxOpYrr01idifle2 arboxyhc acid, thioacetic acid 3-(1,3dioxooctahydro-iSOind0l-2YlPr0PYl ester, 2-morpholinomethylhexahYdr0i50110l 1,3 -dione, N-methyl-N' -[2-(2-oxo-1-pyrrolidinyl)ethyllurea, 2-(4-hydroxy-2-OxO-I pyrro1idinyl)acetamide, N-(2-amino-2- oxoethyl)-2-(2-oxo-1 pyrrolidinyl)acetamide, methyl 2-oxo-1 -pyrrolidineacetate, 6- (1,3 acid, 1,1 -ethylenebis(5-oXo-3-pyrrolidinecarboxylic acid), ethyl 2-oxo-I -pyrrolidinecarboxylic acid, ethyl 1,3dirnethyl2_oxo3pyrrOlidinecarb0xyte, or 3-benzyl-3 -azabicyclo[3.i.0]hexane-2,4-dione; polyethylene glycols, e.g. PEG 400; polyhydroxy compounds, such as glucose; allyl ethers, such as diallyl ether or allyl butyl ether; dioxane derivatives, such as 5-hydroxymethyl5 -methyl-1,3 -dioxane, 2[2(benzyloxy)ethyl] -5,5-dimethyl-1,3-dioxane, 1,3-dioxane-5,5-dimethanol, 2(3-bromopropyl)-S,5-dimethyl-1,3 -dioxane, 3,6-dimethyl-1,4-dioxane-2,5-diofle, 4-methyl-i,3-dioxane, 4-phenyl-1,3 -dioxane, 5,5- dimethyl-I,3-dioxane-2-ethanOl, 1,3 -dioxane- 2-ethanol diacrylate, diglycolic anhydride, and 1,4-dioxane-2,3-diol; chitosan; morpholine derivatives; polyvinyl butyral, such as those sold under the trade names Butvar, Denka Butyral, Eslec B, Mowital 3OHH, Pioloform BS, and S-Lec B; polyvinyl butyral copolymers, such as poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate); or a polymer or oligomer having pendant hydrogen donor groups, such as the pyrrolidone group, the morpholine group, the succinimide group or an allyl ether group.

The preferred hydrogen donors are polymers or oligomers having pendant pyrrolidone or morpholine groups, or dioxane derivatives, especially 5-hydroxymethyl- 5-methyl-i,3-dioxane.

The polymer or oligomer having pendant pyrrolidone groups is preferably a polyvinylpyrrolidone (PVP), a copolymer of vinylpyrrolidone with one or more copolymerisable monomers, or a PVP-iodine complex. The polyvinyl pyrrolidone preferably has a molecular weight in the range of from 5,000 to 360,000, more preferably from 5,000 to 120,000. Commercially available polyvinylpyrrolidones include PVP 10, PVP4O, PVP4OT, PVP36O, Agrimer 90, Albigen A, Divergan RS, Kollidon I 7PF, Luviskol K, Plasdone C, Polyclar L, Povidone K 2932, and Sokolan HP 60. PolyvinylpyrrolidOfle (PVP1O) with a molecular weight of about 10,000, is preferred.

It is necessary that the scavenging composition of the present invention should contain a binder, preferably a polymer. Where the hydrogen donor is a PVP or another polymer containing pendant pyrrolidone groups, the binder polymer may be provided by this. However, where such a polymer is not present, another compound must be present as a binder. Since the composition of the present invention is preferably used as a film, forming a layer on, or on part of, a packaging film, the binder is preferably a film-forming polymer. Examples of such film-forming polymers include: polyvinyl alcohol or polyvinyl butyral.

Ascorbic acid, otherwise known as Vitamin C, is well known for use as an antioxidant, especially in foodstuffs. However, although we do not wish to be limited by any theory, in this case, it is thought merely to play a part in the sequence of reactions by which the pyrrolidone groups abstract oxygen from the environment. As well as ascorbic acid itself, other well known derivatives of ascorbic acid having the same antioxidant properties may be used, for example 5,6-isopropylidene-L-ascorbic acid or L-ascorbic acid 6-palmitate.

The function of the photoinitiator is to initiate the oxygen scavenging reaction when it is activated by suitable energy, e.g. ultraviolet or electron beam. Any compound known, for example, for the free radical photoinitiation of polymerisable compounds may be used, although, when the compositions of the present invention are to be used for packaging substances to be ingested, the photoinitiator should be so chosen that neither it nor its breakdown products is toxic at the levels present, and preferably that neither it nor its breakdown products imparts any adverse colour, odour or taste to the packaged substance.

Various types of photoinitiator may be used, for example the cleavage type and the hydrogen abstraction type. Examples of suitable cleavage type photoinitiators include: benzoin ethers, such as those of formula (I): (I) (where R represents an alkyl group, such as a methyl, ethyl, isopropyl or isobutyl group, and the phenyl groups may be substituted or unsubstituted); phosphine oxides, such as those of formula (II): () (where the groups represented by R1 may be the same as or different from each other and are various organic groups, especially substituted or unsubstituted aryl, e.g. phenyl, groups), for example benzoyldiphenylphosphine oxide (Lucerine TPO), (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (Lucern TPO) or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Irgacure 819); benzil ketals, such as those of formula (III): iiii:: (where R represents an alkyl group, such as a methyl, ethyl, isopropyl or isobutyl group, especially a methyl group, and the two groups R may be the same as or different from each other, and the phenyl groups may be substituted or unsubstituted), for example benzil dimethyl ketal (Irgacure 651); hydroxy(cyclo)alkylphenones, such as those of formula (IV): Q___11___R2 (IV) (where R2 represents an alkyl or cycloalkyl group having a hydroxy substituent, and the phenyl group may be substituted or unsubstituted), for example 2-hydroxy-2-methyl-1-phenyl-1-propanone (Darocure 1173) or 1-hydroxycyclohexyl phenyl ketone (Irgacure 184); oligomeric materials, such as the Esacure KIP series from Lamberti; a-aminoalkylphenones, such as those of formula (V): KIIIi1Tf' (V) (where R3 represents an alkyl, aralkyl or aryl group, and the two groups represented by R3 may be the same as or different from each other, R4 represents an alkyl group and the two groups represented by R4 may be the same as or different from each other, or the two groups R4, together with the nitrogen atom to which they are attached, may represent a nitrogen-containing heterocyclic group such as a morpholino, piperidino or 1 -pyrrolidinyl group, and the phenyl group may be substituted or unsubstituted), for example 2-benzyl-2-dimethylamino-I -(4-morpholinophenyl)-butan-1-one (Irgacure 369) or 2-methyl-i-[4-(methylthio)phenyl] -2-morpholinopropan-1-one (Irgacure 907); dialkoxy acetophenones, such as those of formula (VI): (VI) (where R represents an alkyl group and the two groups R may be the same as or different from each other, and the phenyl group may be substituted or unsubstituted) for example diethoxyacetophenone; and O-acyl-a-oximinoketones, such as those of formula (VII): OR (VII) (where R represents an alkyl group and the two groups R may be the same as or different from each other, and the phenyl group may be substituted or unsubstituted) for example 1-phenyl-1,2-propanedione 2-(O-ethoxycarbonyl)oxime (Quantacure PDO).

Examples of suitable hydrogen abstraction type photoinitiators include: benzophenone and its derivatives, such as 4-phenylbenzophenone, 4-methylbenzophenone, 2-hydroxybenzophenone, 2-methoxybenzophenone, 4-benzoylbiphenyl, the 2-methyl ester of benzophenone, 4-benzoyl-4'-methyldiphenyl suiphide (BMS), acrylated benzophenone (Ebecryl P38), 4,4'-diphenoxybenzophenone, 4,4'-bis(N,N-diethylamino)benzophenone (EMK), polymeric and multifunctional esters of 2-benzoylbenzoic acid, or polymeric and multifunctional esters of 4-carboxymethoxybenzophenone, such as Omnipol BP or Omnipol TX; thioxanthones, such as 2-isopropylthioxanthone (ITX), 2,4-diethyithioxanthone (DETX), 2- chlorothioxanthone (CTX), polymeric and multifunctional esters of 2-carboxymethoxythioxanthone (Omnipol TX), polymeric and multifunctional derivatives of 1 -hydroxythioxanthone or 2-hydroxythioxanthone; anthraquinone derivatives and polymers thereof such as 2-ethylanthraquinone; aromatic 1,2-diketones, such as benzil; phenyiglyoxylates, such as phenyiglyoxic acid ethyl ester, and polymeric and multifunctional esters of phenylglyoxic acid; -ketosulphones, such as 4-(4-benzoylphenylthio)phenyl 1-methyl-i -(4-methylphenylsulphonyl)ethyl ketone (Esacure 1001); camphorquinone derivatives, such as ( )-camphorquinone, (1R,E)-(+)-camphorquinone 3-oxime, camphorquinone-1 0-sulphonic acid; polymers of camphorquinone compounds; and 1,1'-azobis(cyclohexanecarbonitrile), which has the formula (VIII): (VIII) Where a synergist is required or desirable for use with the photoinitiator, this may be any, preferably amine, synergist commonly used in the art. Examples include: N,N-dimethylaminobenzoic acid derivatives, such as the ethyl ester (EPD), the 2-ethyihexyl ester (EHA), the 2-butoxyethyl ester (BEDB), the isopentyl ester (Quantacure MCA), polymeric esters (Speedcure 2000) and multifunctional esters (Genocure AB-l); aminoacrylates, such as the diethylamine Michael adduct of tripropylene glycol diacrylate (Ebecryl P115), and the diethylamine Michael adduct of ethoxylated trimethylolpropane triacrylate (Actilane 715); other primary or secondary amine Michael adducts of common acrylate monomers, for example where the amine is morpholine, piperazine, dibutylamine, ethanolamine or piperazinoacetophenone; and other compounds, such as ethoxylated trimethyloipropane triacrylate or tripropylene glycol diacrylate.

The amounts of the ingredients of the scavenging composition of the present invention may vary over a wide range. However, we prefer that these amounts should be from 2 to 30%, more preferably from 15 to 25%, of the hydrogen donor, from 10 to 40%, more preferably from 15 to 30%, of ascorbic acid or active derivative thereof, and from 1 to 10%, more preferably from 1 to 5%, of the photoinitiator, based on the weight of the whole of the scavenging composition.

We have surprisingly found that certain other materials may have a synergistic effect when employed with the ascorbic acid (or derivative thereof) and hydrogen donor of the present invention. Examples of such materials include compounds and complexes of transition metals and Vitamin E and active derivatives thereof Where such a transition metal compound or complex is employed, the transition metal may be selected from the first, second or third transition series of the Periodic Table. Examples of such metals include rhodium, ruthenium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or zinc. The metals are employed in a form in which their ions are readily available, i.e. as a compound or complex, preferably as a salt. Suitable salts include the acetate, chloride, sulphate, oleate, stearate, palmitate, 2-ethylhexanoate, decanoate and naphthenate, of which copper (II) acetate is preferred.

However, for the reasons given above in relation to iron, it is generally undesirable to include metals or metal compounds in compositions of the present type.

Accordingly, in place of the transition metal, we prefer to use Vitamin E or an active derivative thereof, i.e. a compound containing the hydroxychroman group characteristic of the Vitamin E derivatives. The term "Vitamin E" is used to cover a group of closely related compounds, and any of these may be used, the preferred one being a-tocopherol, which has the formula

CH

CH3 CH3 CH3 CH3 H3 I CH3 Examples of suitable derivatives include salts, such as the succinate or acetate of Vitamin E, 6-hydroxyflavanone and 6-hydroxy-2,5,7,8-tetramethyl-2-chromanecarboxylic acid, which have the following formulae: HO::0 0H CH3 and salts and esters of the acid.

Where a transition metal compound or complex is used, the amount employed is preferably from 0.01 to 5%, more preferably from 0.01 to 1.2%. Where Vitamin E or a derivative thereof is used, the amount employed is preferably from 0.01 to 5%, more preferably from 0.01 to 2%. The percentages are by weight based on the whole oxygen scavenging composition.

The polymer (c) may be provided by one or more of the components (a) and (b) of the composition of the present invention, or it may be an additional component.

Where an additional polymer is employed in the composition of the present invention, and where the polymer if film-forming, this may itself be used as the packaging material. However, it is more preferred that the composition of the present invention should form a layer forming part of the packaging material. Preferably, the composition of the present invention is coated with a layer of a composition inert to the material, e.g. foodstuff, being packaged. The composition is preferably in the form of a flexible film, which may be used as such or which may be formed into, for example, a pouch.

However, the composition may also be used as a coating on rigid or semi-rigid packaging materials, such as plastics, paper or cardboard cartons, bottles, trays or cups.

The composition of the present invention, where it contains a polymer, may be used as the sole polymeric material, forming a packaging film comprises one or more layers, or it may form one or more films of a multi-layer film. In the case of a multi-layer film, the other layer or layers can comprise any one or more of: an inert layer, a gas barrier layer, an adhesive layer, or a sealant layer.

There is no real limitation on the nature of the polymers used to form these other layers, and examples of suitable such polymers include: polyethylenes, such as low density polyethylene, very low density polyethylene, high density polyethylene, and linear low density polyethylene; polyesters, such as polyethylene terephthalate, polyvinyl chloride and polyvinylidene chloride; and copolymers of ethylene with other copolymerisable monomers, such as ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate or methacrylate copolymers, and ethylene-acrylic or methacrylic acid copolymers. Mixtures of any two or more of these polymers may also be used, if desired.

Although not most preferred, the compositions of the present invention may also be used as pellets of particles in a sachet, in the same way as iron is currently used.

The compositions of the present invention may also contain other conventional additives, including, but not limited to, pigments, dyes, stabilisers, plasticisers, waxes, slip aids, levelling aids, adhesion promoters, surfactants, fillers, processing aids and anti-blocking agents.

The composition may be formed into a film by conventional processes well known in the art, for example by extrusion. Alternatively, it may be formulated as a coating and may be printed onto a substrate, using any conventional printing technology.

The composition of the present invention is inert until it is exposed to ionising radiation, which activates the photoinitiator. Although we do not wish to be limited by any theory, it is thought that this then converts the ascorbic acid to a radical form, and the radical form of the ascorbic acid converts a pyrrolidone group or other hydrogen donor group to an active form in which it is capable of abstracting oxygen from the atmosphere.

The invention also comprises a process for preventing oxygen-induced degradation of a material, in which a packaged material including a composition of the present invention is exposed to energy to activate the photoinitiator in the composition.

The energy employed should be such that the photoinitiator is sensitive to it, and may be, for example, ultraviolet or electron beam, preferably ultraviolet.

The package is preferably substantially air-tight and sealed.

The present invention is further illustrated by the following non-limiting

Examples.

EXAMPLES 1 & 2

The components shown in Table 1 were mixed to form a coating composition.

The Vitamin C was dissolved in water, and the PVP was dissolved in ethanol prior to mixing. These solutions and the other components were then mixed, adding enough additional ethanol to dissolve all the components. The composition was then coated on 0.06m2 A4 paper using a No 3 K Bar, applying approximately 1 Ogsm of active components. After the coated paper had been allowed to dry, it was subjected to a Primarc Maxicure UV rig fitted with a single 300W/inch medium pressure mercury lamp, operating at full power. The coated paper was passed through the rig three times at a speed of 50m/minute. The radiated paper was then inserted into a polypropylene bag, which is permeable to oxygen but impermeable to volatile solvents. The sealed polypropylene bag was then introduced into an aluminium/polyethylene laminate bag (2000 cm3) and sealed using a heat press (170 C). Subsequently, the aluminium/polyethylene laminate bag was filled with atmosphere containing 20.9% oxygen. The oxygen level was measured at the time intervals shown in Table 1, using a Dansensor gas analyser. The gas inlet of the gas analyser was attached to a needle which was then inserted into the aluminium/polyethylene laminate bag through a septum. The septum was attached to the bag using double sided tape and held firmly with super glue. After each reading, a piece of double sided tape was used to cover the septum. The results are shown in Table 1, as the percentage of oxygen in the atmosphere as measured above after each time interval.

Table 1

Coating Composition, wt % Percentage of oxygen present after time Capacity Example non volatiles mug/rn2! No. *Vit 24h 48h 72h 144h 192h 216h 312h 360h *Bzp PVP *Cu2 O.Oh 15h 20h day C id 2d 3d 6d 8d 9d 13d 15d 1 19.5 1.6 22.5 0 20.9 20.4 20.4 20.4 19.9 19.2 18.0 17.9 17.9 17.0 17.0 161 2 17.9 1.4 20.7 0.7 20.9 20.0 19.4 19.4 17.8 16.0 13.1 12.5 12.5 11.1 11.1 426 * Abbreviations: Vit C = Vitamin C, PVP = polyvinylpyrrolidone, Bzp = benzophenone, Cu2 = copper acetate hydrate It can be seen from the results above that the compositions of the present invention are effective oxygen scavengers, although the composition containing the copper ions is by far the more effective.

EXAMPLES 3-9

The procedure described in Examples 1 and 2 was repeated, except that the amount of oxygen in the atmosphere in the aluminium/polyethylene laminate bag was 2%, the balance, 98%, being nitrogen. In this case, after introducing the sealed polypropylene bag into the aluminium/polyethylene laminate bag, the air in the aluminium/polyethylene laminate bag was evacuated using a vacuum pump. A 2%oxygenl98% nitrogen mixture was then introduced into the bag until it assumed a pillow shape. The results are shown in Table 2.

Table 2

Example Coating Composition, wt % Percentage of oxygen remaining after time No. Non volatiles Capacity Vit Bzp PVP Cu2 96h 144h 168h 192h 240h 264h 336h 384h 696h ml/gIm2/day O.Oh 16h C 4d 6d 7d 8d lOd lid 14d 16d 29d 3 42.7 0 0 0 2.45 2.75 2.81 2.84 2.84 2.87 2.91 3.78 ---0 4 0 6.3 12.7 3.2 2.54 2.65 2.39 2.34 2.32 2.32 2.26 3.60 ---29 35.7 0 0 1.4 2.50 2.46 2.47 2.58 2.67 2.79 3.01 3.17 ---2 6 31.3 2.5 0 1.3 2.36 1.93 1.80 1.77 1.73 1.56 1.53 1.47 ---48 7 36.5 2.9 0 0 2.56 1.87 1.59 1.56 1.93 2.52 2.80 3.09 ---12 8 17.9 1.4 20.7 0.7 2.44 2.04 0.462 0.205 0.157 0. 135 0.031 0.025 0.016 0.022 0.423 124 9 19.5 1.6 22.5 0 2.48 1.65 0.006 0.000 0.000 0.000 0.000 0.000 --0.769 190 abbreviations as in Table 1 In Table 2, Examples 3-7 are comparative Examples, in which one or more of the components of the oxygen scavenging composition of the present invention is omitted, whilst Examples 8 & 9 are examples of the present invention, it can be seen that the comparative examples show little or no oxygen scavenging ability, whilst the compositions of the present invention reduce the oxygen to very low levels. It is thought that the slight increase in oxygen shown towards the end of the experiment in Example 9 is a result of atmospheric air entering the aluminium bag through the septum.

EXAMPLES 10-12

The experiments described in Examples I & 2 were repeated, but using Vitamin E in place of the copper salt. Examples 10 and 11 are comparative. PVA (polyvinyl alcohol) was included as a binder. The composition is shown in Table 3, and the results are shown in Table 4.

Table 3

Ex No. Composition, wt % Vit C Bzp PVA PVP Vit E 22.2 1.6 8.5 0 3.1 11 0 3.2 12.6 0 15.6 12 19.8 1.35 3.8 11.6 3.1

Table 4

Ex No. Percentage of oxygen remaining after time Capacity ml/g/m2/day 72h 120h 144h 168h 216h 240h 264h 288h 312h 360h 720h O.Oh 3d 5d 6d 7d 9d lOd lid 12d 13d 15d 30d 2.49 2.68 2.64 2.69 2.80 2.97 2.96 2.96 3.00 3.06 3.25 -0 11 2.44 2.89 2.91 2.93 2.95 2.99 3.01 3.01 3.02 3.05 3.10 -0 12 2.43 1.73 1.44 1.36 1.26 0.913 0.839 0.782 0.720 0.664 0.487 0.356 82

EXAMPLES 13-18

The components shown in Table 5 were mixed to form a coating composition.

The Vitamin C was dissolved in water, and the PVP was dissolved in ethanol prior to mixing. These solutions and the other components were then mixed, adding enough additional ethanol to dissolve all the components. The composition was then coated on O.06m2 A4 paper using a No 3 K Bar, applying approximately l0gsm of active components. After the coated paper had been allowed to dry, it was subjected to a Primarc Maxicure UV rig fitted with a single 300W/inch medium pressure mercury lamp, operating at full power. The coated paper was passed through the rig three times at a speed of 50m/minute. The radiated paper was then inserted into 500ml round bottom glass flask and sealed with Aldrich septum. Subsequently, the flask was evacuated using a vacuum pump and filled with 2% oxygen and 98% nitrogen. The oxygen level was measured at the time intervals shown in Table 5, using an O2xySense 200T gas analyser.

O2xySense200T gas analyser is an optical system that can measure oxygen non-invasively within packages or vessels that are transparent. The results are shown in Table 5, as the percentage of oxygen in the atmosphere as measured above after each time interval.

Table 5 Composition wt% Percentage of oxygen remaining after time Capacity

Example Omni-2

ml/g/m I No. PVP VitC VitE' VitE Bzp Cu2 cat 0.Oh 2h 4h 16h 24h 96h day 13 19.5 16.8 0 0 1.3 0.7 0 3.1 -1.4 0.012 0.016 0.014 126.06 14 19.3 17.6 10.2 0 0 0 1.3 4.2 4.4 -3.8 3.3 1.6 21.72 19.6 17.4 0 0 1.4 0 0 5.5 4.9 -4.2 3.5 2.7 94.09 16 20.1 0 14.9 0 1.3 0 1.4 3.7 4.1 -3.8 3.8 3. 2 4.60 17 20.4 20.1 0 13.9 1.5 0 0 4.5 4.4 -4.0 3.0 2.2 55.72 18 21.1 18.2 0 0 1.35 0.7 0 4.0 1.6 ---0.008 140.96 Footnote: PVP = Polyvinyl pyrrolidone; VitC = Ascorbic acid; VitE = vitamin E acetate; VitE = Vitamin E; Bzp = Benzophenone; Cu2 = copper (II) acetate As mentioned earlier, Table 5 shows the results obtained from an O2xySense200T gas analyser. These are in agreement with results obtained from the Dansensor gas analyser used in the previous Examples. For example, using a Dansensor gas analyser in Example 9 shows a capacity of 190 ml/gIm2/day as compared to Example 13 where a capacity of 126.06 mI/g/m2/day was obtained using the O2xySense200T gas analyser.

Example 14 shows that using Omnicat 550 as a photoinitiator is not as effective as using benzophenone. This is because Omnicat 550 is not as good a radical generator as benzophenone and hence a lower concentration of radicals is formed. However, Example 14 shows that a cationic photoinitiator, such as Omnicat 550, can be used in the present invention.

EXAMPLES 19-23

The procedure described in Examples 13 -18 was repeated, except that the acetal compound, 5-ethyl-I,3-dioxane-5-methanol (DM), was used as the oxidisable compound.

In Table 6, Examples 19 -23 are comparative Examples, in which DM and one or more of the components of the oxygen scavenging composition is omitted. It can be seen that, although the comparative examples show oxygen scavenging ability, the compositions containing DM, Vitamin C, Vitamin E, benzophenone and copper show the ability to reduce oxygen to a very low level (Example 20). Example 21 shows a similar oxygen scavenging capacity when using DM as the oxidisable compound instead of PVP. It is thought that the low oxygen scavenging capacity in Example 17, as compared to Example 22, is a result of the high concentration of vitamin E which, in combination with Vitamin C, may act as an antioxidant.

Table 6

Composition Percentage of oxygen remaining after time Capacity Example _____ _____ _____ ________ ______ _____ _____ ________ ________ ________ Omni-mug/rn2! No. DM VitC VitE VitE Bzp Cu2 0.Oh 2h 4h 16h 24h 96h cat 550 day 19 34.2 0 0 0 0 0 3.62 5.0 5.4 -4.5 4.3 3.0 13.73 6.5 17. 7 0 0.8 1.41 0.7 0 3.7 0.8 --0.010 0.010 495.97 21 6.5 17.8 0 0 1.42 0.66 0 4.1 2.1 -0.004 0.004 0.008 146.56 22 6.6 18.1 0 0.8 1.38 0 0 4.6 4.0 -3.3 2.9 1.2 122.13 23 6.9 0 18.3 0 0 0 18.2 4.0 3.9 -3.7 3.6 2.5 62.50 Footnote: DM = S-ethyl-1,3-dioxane-5-methanol; PVP = Polyvinyl pyrrolidone; VitC = Ascorbic acid; VitE vitamin E acetate; VitE = Vitamin E; Bzp = Benzophenone; Cu2 = copper (II) acetate

EXAMPLES 24 & 25

The procedure described in Examples 1 and 2 was repeated, except that 5-ethyl-I,3-dioxane-5-methanol was used in place of polyvinyl pyrrolidone. The results, obtained using a Dansensor gas analyser, are shown in Table 7.

Table 7

Example Composition, wt % Percentage of oxygen remaining after time ____ ____ _____ _____ _____ ____ ______ ______ ______ ______ ______ ______ ______________ Capacity No. ____ ____ ___ ____ ____ ___ _________ Vit Bzp DM Cu2 24h 48h 72h 96h 144h 360h 504h 960h O.Oh 16h ml/g/m2/day C id 2d 3d 4d 6d 15d 21d 40d 24 18.1 0.9 1.8 0 2.42 2.37 2.35 2.19 2.05 1. 90 1.42 0.856 0.548. 0.177 31.3 18.2 1.5 2.1 0.5 2.35 2.19 2.16 2.03 1.91 1.77 1.40 0.862 0.614 0.341 53.8

Claims

CLAIMS: 1. An oxygen scavenging composition comprising: (a) a hydrogen

donor; (b) ascorbic acid or an oxygen-scavenging derivative thereof and (c) a radical-generating photoinitiator, the composition including a polymer or oligomer.

2. A composition according to Claim 1, in which said hydrogen donor is a tertiary amine, a polyethylene glycol, a dioxane derivative, chitosan, a morpholine derivative, polyvinyl butyral, a polyvinyl butyral copolymer, or a polymer or oligomer having pendant hydrogen donor groups.

3. A composition according to Claim 2, in which said hydrogen donor is a polymer or oligomer having pendant pyrrolidone or morpholine groups.

4. A composition according to Claim 3, in which said polymer or oligomer is polyvinylpyrrolidone.

5. A composition according to Claim 4, in which said polyvinylpyrrolidone has a molecular weight in the range of from 5,000 to 360,000.

6. A composition according to Claim 5, in which said polyvinylpyrrolidone has a molecular weight in the range of from 5,000 to 120,000.

7. A composition according to Claim 2, in which said hydrogen donor is a dioxane derivative.

8. A composition according to Claim 7, in which said dioxane derivative is 5-hydroxymethyl-5-methyl-1,3-dioxane.

9. A composition according to any one of the preceding Claims, in which said photoinitiator is a benzoin ether, a phosphine oxide, a benzil ketal, a hydroxy(cyclo)alkylphenone, a dialkoxy acetophenone, an O-acyl-a-oximinoketone, benzophenone or a derivative thereof, a polymeric or multifunctional ester of 2- benzoylbenzoic acid, a polymeric or multifunctional ester of 4-carboxymethoxybenzophenone, a thioxanthone, a polymeric or multifunctional ester of 2-carboxymethoxythioxanthone, a polymeric or multifunctional derivative of 1-hydroxythioxanthone or 2-hydroxythioxanthone, an anthraquinone derivative or a polymer thereof, an aromatic I,2-diketone, a phenyiglyoxylate, a polymeric or multifunctional ester of phenyiglyoxic acid, a 3-ketosulphone, a camphorquinone derivative, a polymer of a camphorquinone compound or 1,1'-azobis(cyclohexanecarbonitrile).

10. A composition according to any one of the preceding Claims, in which the polymer is one of said hydrogen donor, said oxygen- scavenging derivative of ascorbic acid, and said radical-generating photoinitiator.

11. A composition according to any one of Claims 1 to 9, in which said polymer is an additional compound.

12. A composition according to Claim 11, in which said polymer is a polyethylene, a polyester, or a copolymer of ethylene with another copolymerisable monomer.

13. A composition according to any one of the preceding Claims, comprising a polyvinylpyrrolidone, ascorbic acid and a radical-generating photoinitiator, the composition including a polymer or oligomer.

14. A composition according to any one of Claims 1 to 12, comprising a dioxane, ascorbic acid and a radical-generating photoinitiator, the composition including a polymer or oligomer.

15. A composition according to any one of the preceding Claims, additionally comprising a compound or complex of a transition metal.

16. A composition according to Claim 15, in which the compound of the transition metal is an acetate, chloride, sulphate, oleate, stearate, palmitate, 2-ethylhexanoate, decanoate and naphthenate of rhodium, ruthenium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, or zinc.

17. A composition according to Claim 16, in which the metal is copper.

18. A composition according to Claim 17, in which the compound is copper (II) acetate.

19. A composition according to any one of the preceding Claims, additionally comprising a Vitamin E or an active derivative thereof.

20. A composition according to Claim 19, in which the Vitamin E is a-tocopherol.

21. A packaged material enclosed in packaging, wherein the packaging comprises an oxygen scavenging composition according to any one of the preceding Claims.

22. A packaged material enclosed in packaging, having an oxygen scavenging composition according to any one of Claims 1 to 20 disposed within the packaging.

23. A material according to Claim 21 or Claim 22, which is a foodstuff or medicine.

24. A process for preventing oxygen-induced degradation of a material, in which a packaged material including a composition according to any one of Claims 1 to 20 is exposed to energy to activate the photoinitiator in the composition.