BACKGROUND TO THE INVENTIONS A wide variety of foods, beverages and other materials are susceptible to loss in quality if they are exposed to significant amounts of oxygen during storage. The damage can arise from, for example, chemical oxidation of the product and/or microbial growth In me field of packaging, such damage has been traditionally addressed by generating relatively low- oxygen atmospheres by vacuum packing and/or inert gas flushing. However, these methods are not generally applicable for various reasons. For example, the fast filling speeds commonly used in the food and beverage industries often prevent effective evacuation of, or thorough inert gas flushing of, food and beverage packages, and neither evacuation or inert gas flushing provides any residual capacity for removal of oxygen which may have desorbcd from the package contents or entered the package by leakage or permeation. As a consequence, there has been much interest in the identification and development of chemical techniques for generating low-oxygen atmospheres. ln. Australian Patent No. 672661 (the entire disclosure of which is incorporated herein by reference), the present applicants describe novel oxygen scavenging compositions comprising a source of labile hydrogen or electrons and a reducible organic compound, which may be readily activated or"triggered" (ic brought to. its oxygen scavenging form) as required by exposure to, for example, ultraviolet (UV) light. The oxygen scavenging compositions, once activated, are capable of scavenging oxygen from an oxygenated atmosphere or liquid in substantial darkness for periods ranging from up to a few minutes or hours to over 100 days.

Most of the exemplified oxygen scavenging compositions described in Australian Patent No. 672661, are based on substituted anthraquinones as the reducible organic compound.

Further examples of substituted anthraquinones suitable for use as the reducible organic compound in such oxygen scavenging compositions are disclosed in International Patent Application No-PCT/AU02/00341 (WO 02/076916) (the entire disclosure of which is hereby incorporated by reference).

Substituted anthraquinones tend to be coloured in both the oxidised and reduced states.

Compositions and packaging which contain such anthraquinones also tend to be coloured, for instance, films made using anthraquinone-based compositions are often a light yellow colour which turns deep yellow when the film is reduced to activate the oxygen scavenging capacity.

The coloured nature of the anthraquinone-based compositions is undesirable in many forms of packaging, particularly in the packaging of foodstuffs.

The present applicants have now identified a certain class of reducible organic compounds, namely benzophenones, that has the characteristic of having substantially less visible colour in at least the reduced state than other classes of reducible organic compounds that arc also useful for scavenging oxygen, such as anthraquinones.

DISCLOSURE OF THE INVENTION : Thus, the present invention provides a method of scavenging oxygen (particularly ground state oxygen) in an atmosphere or liquid comprising the steps of : (i) treating benzophenone or a benzophenone derivative (or a salt thereof), or a composition including said benzophenone or benzophenone derivative (or salt thereof), with predetermined conditions so as to reduce the benzophenone or benzophenone derivative (or salt thereof) to a reduced state oxidisable by oxygen ; and (ii) exposing the atmosphere or liquid to said composition ; such that at least a portion of the oxygen in the atmosphere or liquid is removed through oxidation of the reduced state of the benzophenone or a'benzophenone derivative (or salt thereof).

Preferably the benzophenone derivative is a substituted benzophenone of formula I:

wherein ; X1, X2, X3, X4, X5, X6, X7, X8, X9 and X10 are each independently selected from H and L-R1 provided that at least one of X1, X2, X3, X4, X5, X6, X7, X8, X9 and X10 is L-R1 wherein L is selected from 0 and CH (It2) wherein W is H or C1-C20 alkyl, CO2, CO, CONH, SO3, SO2, or SO2NH, and R'is selected from H, C1-C20 alkyl, Cl-C20 alkoxy, C1-C20 alkanoyl, C1-C20 alkanol, C1-C20 alkylamido, C1-C20 alkylcarboxy, C1-C20 alkylsulfonyl, C1-C20 alkylsulfonamido, sulfonate substituents, carboxylate substituents, C1-C20 alkylamino, C1-C20 alkylmorpholino, C1-C20 alkylpiperazinyl, and the radicals represented by, wherein n is any integer between 1 and 20, Z1 and Z2 are selected from H, Ci-C, 2n alkyl, C1-C20 alkancl, C1-C20 aminoalkyl and and the radical represented by, -CH2-CH2-(OCH2CH2)n-OH wherein n is as defined above, and Z3 is selected from C1-C20 alkanol, C1-C20 aminoalkyl, Cl-Czomorpholinoalkyl, C1-C20 piperazinylalkyl, and the radical represented by, -CH2-CH2-(OCH2CH2)n-OH wherein n is as defined above ; or a compound of formula Il :

(II) wherein ; Xl, X2, X3, X4, X7, X8, X9 and X10 are as defined above and wherein Y is not a carbonyl group and is preferably selected from S, O, NX11 and CX11X12 wherein X11 and X12 are selected from H and C1-C20 alkyl. More preferably, Y is selected from NX11 and CX11X12.

The benzophenone and benzophenone derivatives for use in the method of the present invention arc substantially colourless or show reduced colour in at least the reduced state, but more preferably in both the reduced and oxidised states, relative to anmraqumones (particularly 2-ethylanthraquinone). Preferably, when the method of the present invention uses a benzophenone derivative, the benzophenone derivative is selected such that in the reduced state it has a maximum absorbance in the visible spectrum (400nm-7fl0nm) that is no more than half tha t of 2-ethylanthraquinone under the same conditions.

The steps (i) and (ii) may be carried out in either order.

Step (i) may involve treatment of the benzophenone or benzophenone derivative (or salt thereof) with, for example, light of a certain intensity or wavelength (eg UV light) or, altematively, the application of heat, y-irradiation, corona discharge or an electron beam.

The reduced benzophenone or benzophenone derivative (or salt thereof) is reactive towards molecular oxygen to produce activated species such as hydrogen peroxide, hydroperoxy radical or a superoxide ion.

Where the benzophenone or benzophenone derivative (or salt thereof) or, alternatively, a composition including said benzophenone orbcnzophcnone derivative (or salt thereof), forms or is incorporated in a packaging material, the exposure of step (ii) may be effected by a step of packing a product (eg a food or beverage) within said packaging material. In the case, where the packaging material is provided in the form of a container, the packing step may generate said atmosphere (eg generation of a"headspace").

Alternatively, or additionally, the benzophenone or benzophenone derivative itself may be in a polymerised form either as homopolymers or copolymers. Oligomer forms may also be suitable. Benzophenone-based monomers can be made by covalently bonding an ethylenically unsaturated group to one of the benzophenone phenyl rings. The benzophenone derivative may also carry groups, such as carboxylic add, ester, anhydride, epoxy, hydroxy, and amine groups, capable of reaction with othcr polymerisable molecules and preformed-polymers.

When the method according to the present invention employs a composition including said benzophenone or benzophenone derivative (or salt thereof), the composition preferably further comprises an activated oxygen scavenging agent (ie an agent which reacts with activated oxygen species such as peroxide). S-attable activated oxygen scavenging agents include organic antioxidants, organic phosphites, organic phosphines, organic phosphates, hydroquinone and substituted hydroquinone ; inorganic compounds including sulphates, sulphites, phosphites and nitrites of metals ; sulphur-containing compounds including thiodipropionic acid and its esters and salts, thio-bis (ethylene glycol beta-aminocrotonate), cysteine, cystine and methionine ; and nitrogen-containing compounds including primary, secondary and tertiary amines and their derivatives.

Compositions used in the method of the present invention may be in a solid, serni-solid (eg a gel) or liquid form. They may therefore be applied as, or incorporated in, for example, bottle dosure liners, inks, coatings, adhesives (eg polyurethanes), films, sheets or layers in containers such a-i trays or bottles either alone or as laminations or co-extrusions. When used in films or layers, they may be blended with typical polymers or copolymers used for construction of films or layers such as those approved for food contact. Such films or layers may be produced by extrusion at temperatures between S0 °C and 350 °C depending upon chemical composition and molecular weight distribution.

The benzophenone or benzophenone derivatives and compositions of the present invention can be used in any suitable application in which oxygen scavenging is required.

Numerous specific applications, for instance, are disclosed in Australian Patent No. 672661 as well as in Australian Patent No. 758893 (the entire disclosure of which is incorporated herein by reference).

The terms"comprise","comprises"and"comprising"as used throughout the specification are intended to refer to the inclusion of a stated step, component or feature or group of steps, components or features with or without the inclusion of a further step, component or feature or group of steps, components or features.

In the specification, unless stated otherwise, where a document, act or item of knowledge is referred to or discussed, that reference or discussion is not an admission that the document, act or item of knowledge, or any combination thereof at the priority date, was part of the common general knowledge in the art in Australia or elsewhere.

The invention will now be described with reference to the following, non-limiting examples and accompanying figure (s).

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES : Figure l (a) provides absorption spectra of a film prepared according to the present invention before and after exposure to W radiation.

Figure l (b) provides comparative absorption spectra of a film prepared according to prior art methods before and after exposure to W radiation.

EXAMPLES : The compositions referred to in Examples 1 to 4 and 6 were prepared by blending benzophenone or the specified benzephenone derivative at a level of 2%w/w into saponifie EVA. The saponifie EVA compositions used in Examples 1 to 4 and 6 were prepared by saponification of EvataneQ ! S55, The compositions were then compression molded to form a film having a thickness of about 50 pun. This film was placed between two layers of polypropylene film and vacuum-scaled to form a flat package containing essentially no headspace. The package was placed on a conveyor belt. moving at 10 m/min and then exposed to light from a commercial UV-curing lamp (model F-300 fitted with a

'D'bulb (Pusion. Systems Corp. , Maryland, USA)). After exposure to the lamp, the package was opened and the film was then quickly transferred into a foil multilayer bag, and this bag was then vacuum-sealed to form a flat package containing essentially no headspace.

This foil-lined pouch allows essentially no ingress of oxygen from the atmosphere into the inside of the pouch. Air was then injected into the foil-lined pouch and the pouch stored at constant temperature. The oxygen content inside the pouch was measured by gas chromatography.

Example 1 : Oxygen scavenging by a composition comprising benzophenone in saponified EVA The change in oxygen concentration in three pouches prepared in the manner described above, and stored at 40 °C, is shown in Table 1. The films were substantially colourless and remained that way after exposure to oxygen Table 1. Storage Time Oxygen content inside pouch (%) (hours) Pouch 1 Pouch 2 Pouch 3 0 20. 9 20. 9 20. 9 1. 8 17. 7 17. 7 1. 7. 9 22 17. 7 17.7 17.8 J17 17.5 t7. 4 17.6 Example 2: Oxygen scavenging by a composition comprising 2-isopropylbenzophenone ester in saponified EVA The change in oxygen concentration in three pouches prepared in tl-te manner described above, and stored at 25"C, is shown m Table 2. The films were substantially colourless auzd remained that way after exposure to oxygen.

Table 2. Storage Time Oxygen content inside pouch (%) (hours) Pouch 1 Pouch 2 Pouch 3 0 20. 9 20. 9 20-9 1 19. 5 19.4 19.6 2 19.4 19. 2 19.4 4. 7 19. 3 19.1 19. 3 24 19. 2 19. 1 19.2

Example 3: Oxygen scavenging by a composition comprising 3-methylbenzophenone in saponifie EVA The change in oxygen concentration in three pouches prepared in the manner described above, and stored at Z ; °C, is shown in Table 3. The films were substantially colourless and remained that way after exposure to oxygen.

Table 3. Storage Time Oxygen content inside pouch (%) (hours) Pouch 1 Pouch 2 Pouch 3 0 20.9 20. 9 20.9 1 18.3 17. 8 18.2 2 18.0 17. 7 18. 0 4. 7 18. 0 17. 6 17. 9 24 18. 0 17. 6 17.9

Example 4: Oxygen scavenging by a composition composing 4-methoxybenzophenone in saponifie EVA The change in oxygen concentration in three pouches prepared in the manner described above, and stored at 25 °C, is shown in Table 4. The films were substantially colourless and remained that way after exposure to oxygen.

Table 4- Storage Time Oxygen content inside pouch (%) (hours) Pouch 1 Pouch 2 Pouch 3 U 20.9 20. 9 20. 9 1 19. 1 19. 2 19.3 2 19.0 19. 1 19. 1 4.7 18.9 19.0 19. 0 24 18.8 18.9 18. 9

Example 5 : Oxygen scavenging by a composition comprising benzophenone in commercial EVOR A composition was prepared by blending benzophenone into a commercially available EVOH (SoarnolX C32 at a level of 1.7%w/w. The composition was then compression molded to form a film having a thickness of about 50 wu. This film was placed between two layers of polypropylene film and vacuum-sealed to form a flat package containing essentially no headspace. The package was placed on a conveyor belt moving at 10 mImi n and then exposed to light from a commercial UV-curing lamp (model F-300 fitted with a 'D'bulb (Fusion Systems Corp., Maryland, USA) ). After exposure to the lamp, the package was opened and the film was then quickly transferred into a foil multilayer bag together

with 1ml of water to increase the rate of permeation of oxygen into the EVOH, and this bag was then vacuum-sealed to form a flat package containing essentially no headspace. This foil-lined pouch allows essentially no ingress of oxygen from the atmosphere into the inside of the pouch. Air was then injected into the foil-lined pouch and the pouch stored at 40 °C. The films were substantially colourless and remained that way after exposure to oxygen. The oxygen content inside the pouch was measured by gas chromatography. The change in oxygen concentration in two pouches prepared in the manner described is shown in Table 5.

Table 5. Storage Time Oxygen content inside pouch (%) (days) Pouch 1 Pouch 2 0 20. 9 20.9 1 19. 1 19.1 2 18.8 18.8 7 18.0 18.0 14 17.5 17. 6 21 17.1 17.2

Example 6: Substantial colour reduction A composition was prepared by blending benzophenone at a level of 2%w/w into saponifie EVA. The composition was then compression molded to form a film having a thickness of about 50 jim. The absorption spectrum of this film before and after exposure to light from a commercial Ut-curing lamp (bulb (Fusion Systems Corp., Maryland, USA; model F-300 fitted with a'D') is shown in Figure l (a).

A composition was prepared by blending 9-ethylanttara@ìnone at a level of 2% w/w into saponified EVA. The composition was then compression molded to form a film having a thickness of about 30 u. m. The absorption spectrum of this film before and after exposure to light from a commercial LTV-curing lamp (bulb (Fusion Systems Corp., Maryland, USA ; model F-300 fitted with a'D') is shown in Figure 1 (b).

The maximum absorbance in the visible spectrum (400-700run) for the film containing the reduced benzophenone is less than half that of the film containing the reduced 2- ethylanthraquinone.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications maybe made to the invention as shown in the specific embodiments Without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.