AU2012297566B2

AU2012297566B2 - Degradable polyolefin

Info

Publication number: AU2012297566B2
Application number: AU2012297566A
Authority: AU
Inventors: Gregory Anthony Cash; Ian John Dagley; Emilie GAUTHIER; Peter Halley; Bronwyn Glenice Laycock; Melissa Anna Louise Nikolic
Original assignee: Integrated Packaging Group Pty Ltd
Current assignee: Integrated Packaging Group Pty Ltd
Priority date: 2011-08-16
Filing date: 2012-08-16
Publication date: 2016-05-05
Anticipated expiration: 2032-08-16
Also published as: NZ621361A; AU2012297566A1; WO2013023247A1

Abstract

A degradable polyolefin composition comprising a metal containing prodegradant selected from the group consisting of transition metal salts, photoactive metal oxide prodegradants and mixtures thereof and alkoxylated ethylenically saturated non-ionic surfactant.

Description

WO 2013/023247 PCT/AU2012/000961 Degradable Polyolefin Field The invention relates to a degradable polyolefin composition comprising a metal 5 containing prodegradant including a metal salt, a metal oxide or mixture thereof and a non-ionic surfactant and products formed therefrom including polyolefin film, such as polyolefin film used in agriculture, for example that's used in providing plant mulch or in plant propagation, or as packaging and processes for preparing such a composition and film or as packaging film. 10 Background Products made from polyolefins are widely used for disposable items such as packaging film and agricultural film. While polyolefins slowly degrade they can remain in the environment for many years, which has led to the use of prodegradants in 15 polyolefins for many disposable products. The most widely used prodegradants are metal containing compounds. One group of metal containing prodegradants is the transition metal salts. US Patent 3454510, 5854304 and International patent publication W02008/0208752 describe 20 polyolefin compositions with various transition metal salts including fatty acid salts such as cobalt and manganese salts. Another group of metal containing prodegradants is the photoactive metal oxides such as nanoparticulate titanium oxide which are described in International 25 Publication W02009/021270. There are several reasons to improve the efficiency of metal containing prodegradants in promoting degradation of polyolefin films. They are comparatively expensive and their high reactivity creates problems in consistently producing films 30 with the desired rate of degradation and adequate shelf life. This is because the extent of degradation of the film is affected by many variables that include: the conditions during thermal processing to produce the composition, the time between 1 WO 2013/023247 PCT/AU2012/000961 producing the composition and production of the film, the processing conditions used to produce the polymer film and the time between production of the film and its use. The metal oxide containing prodegradants include nanoparticulate titanium oxide. 5 They are potentially very useful for controlling light induced degradation, however, they are particularly problematic to cost-effectively use. They agglomerate when added to polyolefins and generally they must first be chemically modified to improve dispersion, e.g. by reacting the surface of the particles with organosilanes. A particular feature of films containing well-dispersed nanoparticulate titanium oxide 10 alone is that these films display uniform whitening that is a precursor to embrittlement. Furthermore, because transition metal salts and metal oxides have different modes of action, greater control of the degradation of polyolefin films under different conditions could be achieved if their effects on degradation were complementary. However, we 15 have found that this frequently is not the case. For example, when we combined titania nanoparticles, added to accelerate light induced degradation, with cobalt stearate, added to accelerate below ground degradation, there was antagonism which resulted in light induced degradation rates that took more than double the time to embrittle compared to films containing titania nanoparticles or cobalt stearate alone. 20 Without wishing to be bound by theory, it is believed that the photo-antagonism effect can be explained by the transition metal salt switching off the photo-initiation of polyethylene degradation by hydroxyl radicals that are generated at the surface of the metal oxide nanoparticle, by the scavenging of electrons and holes by redox reactions of the transition metal salt. This also reduces the effectiveness of the transition metal 25 salt in catalysing hydroperoxide decomposition. Further details of the photo antagonism mechanism are described in Nikolic et al. (Antagonism between transition metal pro-oxidants in polyethylene films. Polymer Degradation and Stability. 2012;97:1178-88). 30 It is also desirable to provide a more uniform rate of degradation of polyolefin under a range of conditions, whether buried or exposed to the sun. While metal containing prodegradants can be used to produce films that degrade to particles on exposure to the sun within a period of several months, the best metal containing prodegradants for 2 WO 2013/023247 PCT/AU2012/000961 buried films typically cannot achieve similar rates of degradation to those of nanotitania-containing films. The rate of degradation is a particular issue for degradable films used for agricultural 5 applications. Crop propagation film formed from polyolefins is used to produce a microclimate conducive to plant growth. Polyolefin crop propagation film is used to cover seed or planted seedlings to increase soil and air temperatures, water conservation and rate of plant germination and growth, whilst protecting the crop during early development. The film will generally allow the plants to break through the 10 film as they mature and the film degrades. Polyolefin films are also used as a mulch, in which case the mulch surrounds each plant on top of the ground and controls soil temperature, weed growth, pest infestation and carbon dioxide retention. Polyolefin film for use as mulch may contain pigment to reduce light transmission and resultant weed growth. The onset of whitening early in the degradation process may also 15 enhance the mulching properties of the film. Polyolefin film used in agriculture is often buried at its perimeter to retain it against wind and rain. This is especially the case for films used in propagation and as mulch. Burying of film produces a significant difference in the rates of degradation between 20 sun exposed and portions buried in the soil. As a result buried film can persist in the environment for a period much longer than that required for the growing season and can disrupt subsequent plant maintenance or later growing seasons. It may also cause problems with harvesting should the plastic retain sufficient strength under the ground as to entangle in the moving parts of the harvesting machinery. 25 For packaging materials as well, it is important that the lifetime of polyethylene films disposed of in landfill or by soil burial be reduced so as to minimize the volume that such materials occupy. 30 The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to 3 WO 2013/023247 PCT/AU2012/000961 the present invention as it existed before the priority date of each claim of this application. Summary 5 There is provided a polyolefin composition comprising a metal containing prodegradant selected from the group consisting of transition metal salts, photoactive metal oxide prodegradants and mixtures thereof and an alkoxylated ethylenically saturated non-ionic surfactant. 10 It is well known that photoactive metal oxides require compatibilisation in order to be well-dispersed within a polyolefin matrix. We have found that in the absence of such compatibilising treatment, a material is produced that has a rough texture, and evidences uneven whitening and embrittlement. We have further found that photoactive metal oxides can be readily and efficiently incorporated into polyolefins 15 using saturated alkoxylated ethylenically saturated non-ionic surfactants, and this combination of compounds can provide rates of embrittlement in a UVA aging test that are at least equivalent to those observed for chlorosiloxane coated titania nanoparticles in LLDPE film. Without wishing to be bound by theory, it is believed that the alkoxylated ethylenically saturated non-ionic surfactant compound may act 20 not only as dispersants but also by providing an oxidisable interface with the metal oxide photo-initiator. Accordingly there is provided a polyolefin composition comprising a photoactive metal oxide prodegradant and an alkoxylated ethylenically saturated non-ionic surfactant 25 compound. We have also observed polyolefin degradation synergies between transition metal salts and the non-ionic surfactants. Films containing the combination of a transition metal salt and an alkoxylated ethylenically saturated non-ionic surfactant compound 30 degrade faster than films that contain just the transition metal salt or surfactant. The use of a pre-treatment with UV-C irradiation (as described in EP2176322 (Al)) has also been shown to be effective in further promoting dark thermal aging for films containing this composition. 4 WO 2013/023247 PCT/AU2012/000961 Accordingly there is also provided a polyolefin composition comprising a transition metal salt prodegradant and an alkoxylated ethylenically saturated non-ionic surfactant compound. 5 We have also prepared compositions using a combination of metal salt and metal oxide prodegradants such as photoactive titanium oxide and cobalt stearate and found that the combination of the two types of prodegradant produced antagonism under a UVA degradation test. In the presence of the alkoxylated ethylenically 10 saturated non-ionic surfactant compound, however, the combination of metal oxide and metal salt prodegradants provide significantly enhanced degradation and uniformity of degradation. Without wishing to be bound by theory, we believe the select group of surfactants may reduce the interaction of the two prodegradants, which would otherwise lead to antagonism, as well as accelerating degradation. The 15 use of a pre-treatment with UV-C irradiation (as described in EP2176322 (Al)) has also been shown to be effective in further accelerating below-ground embrittlement for films containing this composition. Accordingly there is further provided a polyolefin composition comprising a transition 20 metal salt prodegradant, a photoactive metal oxide prodegradant and an alkoxylated ethylenically saturated non-ionic surfactant compound. In one set of embodiments there is provided a film formed of the polyolefin composition, which is most preferably used in agriculture such as a propagation film, 25 mulch film or silage wrap etc. In another set of embodiments there is provided a film formed of the polyolefin composition, which is most preferably used in packaging applications, such as newspaper overwrap. 30 In a further set of embodiments there is provided a method of improving the regulation of plant growth comprising providing an area of the polyolefin film as described above as ground cover about plants which film is buried in soil at the periphery. The film 5 WO 2013/023247 PCT/AU2012/000961 may cover plants, as in the case of propagation film, or plants may be located in holes in the film as in the case of mulch film. Throughout the description and the claims of this specification the word "comprise" 5 and variations of the word, such as "comprising" and "comprises" is not intended to exclude other additives, components, integers or steps. Detailed Description The polyolefin composition comprises of an alkoxylated ethylenically saturated non 10 ionic surfactant. The term saturated with reference to the surfactant means that the compound has no double, triple bonds or aromatic moieties. The presence of unsaturation in the carbon-carbon system is not desirable as this makes the system highly susceptible to 15 oxidation during and after processing, significantly reducing the shelf-life of the film. The non-ionic surfactant comprises carbon, oxygen and hydrogen and generally will not comprise other heteroatoms such as nitrogen, sulfur, phosphorus, silicon or the like. The incorporation of surfactants or other additives that are unhindered amines, into the polyolefin film are not desirable as they cause film discolouration, are 20 unstable during processing and produce a strong odour. Additional surfactant may be present if desired but are generally not required to obtain the advantage of the invention. In one set of embodiments the polyolefin is free of such surfactants. The alkoxylated ethylenically saturated non-ionic surfactant is a surfactant that 25 contains at least one alkylene glycol unit and at least one saturated hydrocarbon chain that contains at least eight carbon atoms. The hydrophillic-lipophillic balance (HLB) of the surfactant is less than 12, preferably no more than 10, more preferably no more than 8 and most preferably no more than 7. Generally the HLB will be at least 2 and preferably at least 3. Accordingly, a particularly preferred HLB range is 30 from 3 to 7. The HLB of a surfactant is a measure of the balance between the size and strength of hydrophilic portion of the surfactant which comprises the alkylene glycol groups and 6 WO 2013/023247 PCT/AU2012/000961 the lipophilic groups which includes the saturated hydrocarbon chain. Generally speaking, surfactants which are more lipophilic in character have a lower HLB than surfactants which are hydrophilic. HLB may be calculated using the method of Griffin referred to in "Schick Non-Ionic Surfactants", Suf. Sci. Series Vol 1. Chapter 18. The 5 HLB is frequently reported by manufacturers such as reported in McCutcheon's Emulsifiers and Detergents 2010. In the absence of information of a definitive structure or information from the manufacturer, HLB may be experimentally determined as described in "The HLB System a time-saving guide to emulsifier selection" ICI Americas Inc. March 1980, Chapter 7. 10 The surfactant contains at least one carbon chain which can be linear or branched. The surfactant will generally comprise a saturated carbon chain of at least 8 carbons, preferably at least 12 carbons and more preferably at least 16 carbons. Generally the 15 carbon chain length will be no more than 40 carbons such as no more than 36 carbons, no more than 30 carbons, no more than 26 carbons or no more than 22 carbons. Accordingly useful ranges include C8-C40, such as C8 to C26, preferably C12 C30, more preferably C12 to C26, and most preferably C16-C18. 20 The surfactant contains at least one alkoxylate (alkylene glycol) unit which can be derived from ethylene oxide, propylene oxide or butylene oxide, most preferably it is derived from ethylene oxide. The surfactant may contain more than one alkoxylate unit which may be an alkylene glycol dimer or polyalkyleneglycol. 25 The surfactant contains at least one carbon chain and at least one alkoxylate unit which may be linked by either an ether or ester linkage. Thus the surfactant may be the product of condensing preformed alkyleneglycol, alkylene glycol dimer or polyalkyleneglycol with one or more saturated alcohols or saturated carboxylic acids. Alternatively the surfactant can be the product of alkoxylation of a saturated alcohol or 30 saturated carboxylic acid. The non-ionic surfactant can be a diblock or multiblock structure, including an ABA structure (for example a copolymer formed by the condensation reaction of a polyethylene glycol with two or more mole equivalents of 7 WO 2013/023247 PCT/AU2012/000961 12-hydroxystearic acid). The non-ionic surfactant may also be terminally blocked, for example by alkylation of a terminal hydroxyl group. Examples of the classes of non-ionic surfactants include those selected from the 5 group consisting of alkoxylated ethylenically saturated alcohols, including alkoxylated saturated fatty alcohols; alkoxylated, ethylenically saturated natural oils including alkoxylated hydrogenated natural oils such as alkoxylated hydrogenated castor oil; saturated fatty acid esters of alkoxylated glycerol, hexitan, hexitol and isohexide such 10 as saturated fatty acid esters of alkoxylated glycerol, saturated fatty acid esters of alkoxylated sorbitan and saturated fatty acid esters of alkoxylated sorbitol; and saturated-polyester polyalkylene glycol copolymers including polyester-polyalkylene glycol-polyester block copolymers such as polyhydroxystearic (PHS) acid polyethylene PEG glycol block copolymers which may be PHS-PEG-PHS ABA-type 15 block copolymers. The alkoxylated ethylenically saturated compound may be of the formula: R-CO-O-(AO)o-H or RO-(AO)o-H where R is a saturated hydrocarbon of from 8 to 40 carbon atoms, preferably 8 to 26 20 carbon atoms, more preferably 12 to 26 carbon atoms and most preferably 16 to 18 carbon atoms; A is a C2 to C4 alkylene, and A is more preferably selected from ethylene and propylene and mixtures thereof such as in the case of one or more blocks of ethylene glycol and one or more blocks of propylene glycol, most preferably A is ethylene; n is an integer, more preferably from 1 to 9; and more preferably 1-5, 25 where n is selected so that HLB is less than 12. In one set of embodiments the alkoxylated saturated compound is of formula: RO-(AO)o-H wherein R is C8 to C26 alkyl; preferably C12 to C26 alkyl; A is C2 to C4 alkylene (preferably ethylene); and n is from 1 to 5. Such alkoxylated fatty acids 30 generally have an HLB less than 12. The alcohol may be straight chain or branched. The alcohol may be a fatty alcohol. Alkoxylated saturated alcohols comprise a saturated hydrophobic alcohol linked to an 8 WO 2013/023247 PCT/AU2012/000961 alkoxylate which may be derived from one or more alkylene oxide units. The unifying feature of this group of surfactants is (i) the use of alcohols drawn from alkyl chains between 8 and 40 carbons in length preferably 12 to 30, more preferably from 16 to 18) (In one embodiment the alcohol is a saturated fatty alcohol comprising in the 5 range of from 8 to 26 or from 12 to 26 carbon atoms) and (ii) the chemical addition to these alcohols of alkylene oxide in molar ratios ranging from 1 to 9. Preferably the alkylene oxide is selected from ethylene oxide and propylene oxide. Most preferably the alkylene oxide is ethylene oxide. Preferred examples of non-ionic surfactants include saturated alcohols alkoxylated with from one to 5 moles of alkylene oxide per 10 mole of saturated alcohol. Specific examples of non-ionic surfactants for use in the polyolefin composition may include at least an alcohol portion selected from the group consisting of: capryl alcohol (1-octanol) 8 carbon atoms 2-ethyl hexanol 8 carbon atoms branched pelargonic alcohol (1-nonanol) 9 carbon atoms capric alcohol (1-decanol, decyl alcohol) 10 carbon atoms undecyl alcohol (1-undecanol, undecanol, Hendecanol) 11 carbon atoms lauryl alcohol (Dodecanol, 1-dodecanol) 12 carbon atoms tridecyl alcohol (1-tridecanol, tridecanol, isotridecanol) 13 carbon atoms myristyl alcohol (1-tetradecanol) 14 carbon atoms pentadecyl alcohol (1-pentadecanol, pentadecanol) 15 carbon atoms cetyl alcohol (1-hexadecanol) 16 carbon atoms heptadecyl alcohol (1-n-heptadecanol, heptadecanol) 17 carbon atoms stearyl alcohol (1-octadecanol) 18 carbon atoms isostearyl alcohol (16-methylheptadecan-1-ol) 18 carbon atoms branched nonadecyl alcohol (1-nonadecanol) 19 carbon atoms arachidyl alcohol (1-eicosanol) 20 carbon atoms heneicosyl alcohol (1-heneicosanol) 21 carbon atoms behenyl alcohol (1-docosanol) 22 carbon atoms lignoceryl alcohol (1-tetracosanol) 24 carbon atoms ceryl alcohol (1-hexacosanol) 26 carbon atoms montanyl alcohol, cluytyl alcohol (1-octacosanol) 28 carbon atoms myricyl alcohol, melissyl alcohol (1-triacontanol) 30 carbon atoms geddyl alcohol (1-tetratriacontanol) 34 carbon atoms cetearyl alcohol 9 WO 2013/023247 PCT/AU2012/000961 Non-ionic alkoxylated alcohols can be made by controlled synthesis to give the adduct of alcohols having alkyl chains between 8 and 40 carbons in length (preferably 8 to 26 and more preferably from 16 to 18), with a defined length ethylene glycol 5 consisting of 1 to 9 units (more preferably one to five units), or mixtures of these compounds. It will be understood by those skilled in the art that the HLB may be determined by the choice of appropriate lengths of the ethylenically saturated chain and alkylene glycol 10 chain. For example, generally a non-ionic surfactant comprising an ethylenically saturated alcohol of at least eight carbon atoms and from 1 to 5 alkylene glycol units will have an HLB of less than 12. Increasing the number of carbon atoms in the saturated alcohol will reduce the HLB and increasing alkoxylation will increase HLB. 15 Surprisingly, we discovered that the combination of the transition metal salt and an alkoxylated ethylenically saturated non-ionic surfactant in a polyolefin film is synergistic, resulting in rates of photo- and thermo-oxidation greater than the transition metal salt and non-ionic surfactant alone in a polyolefin matrix. Without wishing to be bound by theory, it is believed that the surfactant interacts with the 20 transition metal salt in a way to accelerate the overall rate of polyolefin oxidation. We have discovered that the photo-antagonism between the metal oxide and transition salt can be mitigated by effectively coating the titania nanoparticles with an alkoxylated ethylenically saturated non-ionic surfactant compound. Without wishing 25 to be bound by theory, it is believed that the glycol moiety of the surfactant effectively coats the metal oxide nanoparticle and the alkyl chain of the surfactant aids the dispersion of the titania nanoparticles in the polyethylene matrix. It is also believed that the surfactant acts as a highly oxidisable interface between the metal oxide and transition metal salt. The hydroxyl radicals produced by the metal oxide oxidise the 30 surfactant to form hydroperoxides, which are then decomposed by the transition metal salt, avoiding photo-antagonistic reactions between the metal oxide and transition metal salt. 10 WO 2013/023247 PCT/AU2012/000961 Without wishing to be bound by theory, it is believed that alkoxylated ethylenically saturated non-ionic surfactants within the HLB range of 3 up to 12, effectively coat the surface of the titania nanoparticle, whilst still enabling good dispersion of the titania in the hydrophobic polyolefin matrix and processability into a film. Alkoxylated 5 ethylenically saturated non-ionic surfactants with a HLB index of 12 or greater have been shown to be difficult to blow and produce a poor quality film. Alkoxylated ethylenicially saturated non-ionic surfactant compounds of low HLB (3 - 7) are most preferred. We have found that the non-ionic surfactants of HLB less than 12 (preferably less than 10 and most preferably from 3 to 7) are more compatible with 10 the degradable polyolefin matrix whilst still sufficiently coating the hydrophilic surface of the titania nanoparticles to aid dispersion of the prodegradant in the polyolefin matrix. We have found that non-ionic surfactants of HLB greater than 12 cause significantly more processing difficulties than the lower HLB surfactants when incorporated into a hydrophobic polyolefin matrix, such as: less stable bubble 15 formation during film blowing and a greater propensity to leach out of the film. Non ionic surfactants within the HLB range of 3 up to 12, have been successfully blown into a polyolefin film, increase the rate of photo- and thermo-oxidation of polyolefin film and provide the best reduction in antagonism between titania and the transition metal salt prodegradants, compared to titania and the transition metal salt alone in 20 polyethylene. In many cases, commercially available non-ionic surfactants suitable for use in the polyolefin composition will be in the form of mixtures of compounds comprising mixtures of alcohols of a range of chain length and additionally or alternatively a 25 mixture of numbers of moles of alkylene oxide per mole of saturated alcohol. The alkylene oxide derived component of the non-ionic surfactant will typically include at least one of ethylene oxide, propylene oxide and butylene oxide and more preferably at least one of ethylene oxide and propylene oxide or combinations thereof. Saturated alcohols ethoxylated with from 1 to 9 moles of ethylene oxide per mole of 30 alcohol, particularly 1 to 5 moles of ethylene oxide, are preferred. 11 WO 2013/023247 PCT/AU2012/000961 The non-ionic surfactant is typically present in an amount of from 0.05% to 5% by weight, preferably 0.1% to 3% percent by weight and most preferably from 0.2% to 2% by weight based on the weight of the polyolefin. 5 The polyolefin composition comprises a metal containing prodegradant selected from the group consisting of metal salt prodegradants, metal oxide prodegradants and a combination of photoactive metal oxide and metal salt prodegradants. The photo active metal oxide prodegradant is preferably photoactive nano particulate 10 titanium oxide. TiO 2 may be in the form of Rutile or Anatase, preferred is Anatase. Mixtures of Anatase and Rutile may also be used; preferably such mixtures contain 50% to 90% by weight of Anatase, based on the weight of the mixture. A commercially available form of TiO 2 that fits this description is supplied by Evonik Industries as "Aeroxide" TiO 2 P 25 ("Aeroxide" is a trademark). 15 The titanium oxide may also be doped, wherein at least a portion of the titanium dioxide particles comprise, in their crystal lattice, metal ions selected from the group consisting of copper, manganese, nickel, cobalt, iron, and zinc. 20 Alternatively, the photoactive titanium dioxide is produced by combustion or thermal decomposition via spray or aerosol, atomizing from a starting colloidal solution or precursor to prepare particles in the required size range. The photoactive titanium dioxide may also be produced via spray pyrolysis of a 25 solution or precursor or by thermal decomposition of precursors from a solution or by thermal deposition in vacuum such as chemical vapour deposition and plasma processing methods. As another alternative, the photoactive titanium dioxide may be produced by melting 30 or rapid quenching, by microwave processing, by ultrasonic processing, by electrochemical and mechanochemical methods or by cryochemical (freeze-drying) methods so that the particle size of the metal oxides is within the range required. 12 WO 2013/023247 PCT/AU2012/000961 The titanium dioxide useful in accordance with the present invention preferably has a particle size such that the largest dimension of the particle is less than 200 nm, more preferably from 1 nm to 100 nm, most preferably from 1 nm to 30 nm. The terms titanium dioxide and titania are used as synonyms in the context of the 5 present invention. In the context of the present invention both terms comprise the doped titania and the titania which is fixed on a carrier, such as silica. The metal oxide prodegradant, such as nano-scaled TiO 2 , is typically present in an amount of from 0.05% to 10% by weight, preferably 0.2% to 10% percent by weight 10 and most preferably from 0.5 to 3% by weight based on the weight of the polyolefin. The metal salt may be a transition metal salt of a carboxylic acid, amide or dithiocarbamate and is preferably a metal salt of a fatty acid. The preferred transition metal salts comprise transition metal ions selected from the group consisting of 15 manganese, cobalt, nickel, cerium, copper and iron. Preferred metals are selected from the group consisting of cobalt, iron, manganese, copper, nickel and cerium and iron or mixtures thereof. Suitable examples include metal salts of a fatty acids with a carbon number ranging 20 from C4 to C36, in particular from C8 to C36 is preferred. Metal salts formed with saturated fatty acids are preferred. Particularly preferred examples are metal carboxylates of palmitic acid (C16), stearic acid (C18), 12-hydroxy stearic acid (C18) and naphthenic acid. As C4-C36 carboxylate salts, in particular stearate, palmitate or naphthenate salts of Fe, Ce, Co, Mn, Ni or mixtures thereof are of particular interest. 25 In one embodiment the salts are saturated fatty acid salts. Particularly preferred are Fe-stearate, Mn-stearate and Co-stearate. It is, however, also possible to use mixtures of the afore-mentioned metal carboxylates. The metal salt prodegradant, such as metal carboxylate, is typically present in an amount of from 0.05% to 20% by 30 weight, such as 0.05% to 10% percent by weight, 0.2% to 3% by weight or from 0.5% to 3% by weight, based on the weight of the polyolefin. 13 WO 2013/023247 PCT/AU2012/000961 The metal oxide prodegradant, such as nano-scaled titanium dioxide, and the metal salt prodegradants, such as metal carboxylates, are items of commerce and may be used in their various commercial grades. 5 In a preferred set of embodiments the prodegradant comprises both metal oxide and metal salt type prodegradants. In this set of embodiments, the weight ratio between the nano-scaled TiO 2 and the metal carboxylate is preferably from 20:1 to 1:20 and more preferably from 10:1 to 1:10 10 The composition comprises a polyolefin. Examples of suitable polyolefins are given below: 1. Polymers of monoolefins and diolefins, for example polypropylene, polyisobutylene, polybut-1 -ene, poly-4-methylpent-1 -ene, 15 polyvinylcyclohexane, polyisoprene or polybutadiene, as well as polymers of cycloolefins, for instance of cyclopentene or norbornene, polyethylene (which optionally can be crosslinked), for example high density polyethylene (HDPE), high density and high molecular weight polyethylene (HDPE-HMW), high density and ultrahigh molecular weight polyethylene (HDPE-UHMW), medium 20 density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), (VLDPE) and (ULDPE). Polyolefins, i.e. the polymers of monoolefins exemplified in the preceding paragraph, preferably polyethylene and polypropylene, can be prepared by 25 different, and especially by the following, methods: a) Radical polymerisation (normally under high pressure and at elevated temperature). 30 b) Catalytic polymerisation using a catalyst that normally contains one or more than one metal of groups IVb, Vb, Vib or VIII of the Periodic Table. These metals usually have one or more than one ligand, typically oxides, halides, alcoholates, esters, ethers, amines, alkyls, alkenyls and/or aryls that may be 14 WO 2013/023247 PCT/AU2012/000961 either 7r- or a-coordinated. These metal complexes may be in the free form or fixed on substrates, typically on activated magnesium chloride, titanium(III) chloride, alumina or silicon oxide. These catalysts may be soluble or insoluble in the polymerisation medium. The catalysts can be used by 5 themselves in the polymerisation or further activators may be used, typically metal alkyls, metal hydrides, metal alkyl halides, metal alkyl oxides or metal alkyloxanes, said metals being elements of groups la, Ila and/or Illa of the Periodic Table. The activators may be modified conveniently with further ester, ether, amine or silyl ether groups. These catalyst systems are usually 10 termed Phillips, Standard Oil Indiana, Ziegler (-Natta), TNZ (DuPont), metallocene or single site catalysts (SSC). 2. Mixtures of the polymers mentioned under 1), for example mixtures of polypropylene with polyisobutylene, polypropylene with polyethylene (for 15 example PP/HDPE, PP/LDPE) and mixtures of different types of polyethylene (for example LDPE/HDPE). 3. Copolymers of monoolefins and diolefins with each other or with other vinyl monomers, for example ethylene/propylene copolymers, linear low density 20 polyethylene (LLDPE) and mixtures thereof with low density polyethylene (LDPE), propylene/but-1-ene copolymers, propylene/isobutylene copolymers, ethylene/but-1 -ene copolymers, ethylene/hexene copolymers, ethylene/methylpentene copolymers, ethylene/heptene copolymers, ethylene/octene copolymers, ethylene/vinylcyclohexane copolymers, 25 ethylene/cycloolefin copolymers (e.g. ethylene/norbornene like COC), ethylene/1-olefins copolymers, where the 1-olefin is generated in-situ; propylene/butadiene copolymers, isobutylene/isoprene copolymers, ethylene/vinylcyclohexene copolymers, ethylene/alkyl acrylate copolymers, ethylene/alkyl methacrylate copolymers, ethylene/vinyl acetate copolymers or 30 ethylene/acrylic acid copolymers and their salts (ionomers) as well as terpolymers of ethylene with propylene and a diene such as hexadiene, dicyclopentadiene or ethylidene-norbornene; and mixtures of such copolymers with one another and with polymers mentioned in 1) above, for example 15 WO 2013/023247 PCT/AU2012/000961 polypropylene/ethylene-propylene copolymers, LDPE/ethylene-vinyl acetate copolymers (EVA), LDPE/ethylene-acrylic acid copolymers (EAA), LLDPE/EVA, LLDPE/EAA and alternating or random polyalkylene/carbon monoxide copolymers and mixtures thereof with other polymers, for example 5 polyamides. Homopolymers and copolymers from 1) - 3) may have any stereostructure including syndiotactic, isotactic, hemi-isotactic or atactic; where atactic polymers are preferred. Stereoblock polymers are also included. 10 For example in one embodiment the film is a polyolefin film comprising at least one selected from the group consisting of polyethylene, polypropylene, polyethylene copolymers polypropylene copolymers and blends of any of the aforementioned. Blends of the aforementioned may be blends of one or more of the aforementioned 15 with other polymer where preferably at least 50% by weight is a polyolefin or blends of two or more of the polymers. It will be understood by those skilled in the art that the polyolefin composition may contain the types of processing aids and additives used in the art. 20 The polyolefin composition and articles made therefrom such as fibre or film may comprise additional additives. Examples for suitable additional additives include: 1. Antioxidants such as alkylated monophenols, alkylthiomethylphenols, hydroquinones and alkylated hydroquinones, tocopherols hydroxylated thiodiphenyl 25 ethers, alkylidenebisphenols, 0-, N- and S-benzyl compounds, hydroxybenzylated malonates, aromatic hydroxybenzyl compounds, triazine compounds, benzylphosphonates, acylaminophenols, esters of P-(3,5-di-tert-butyl-4 hydroxyphenyl)propionic acid with mono- or polyhydric alcohols, esters of P-(5-tert butyl-4-hydroxy-3-methylphenyl)propionic acid with mono- or polyhydric alcohols, 30 esters of p-(3,5-dicyclohexyl-4-hydroxyphenyl)propionic acid with mono- or polyhydric alcohols, esters of 3,5-di-tert-butyl-4-hydroxypheny acetic acid, amides of p-(3,5-di 16 WO 2013/023247 PCT/AU2012/000961 tert-butyl-4-hydroxyphenyl)propionic acid, ascorbic acid (vitamin C) and minic antioxidants; 2. UV absorbers and light stabilizers such as 2-(2'-Hydroxyphenyl)benzotriazoles, 5 2.2. 2-Hydroxybenzophenones, esters of substituted and unsubstituted benzoic acids, acrylates, nickel compounds, sterically hindered amines, oxamides and 2-(2 hydroxyphenyl)-1,3,5-triazines; 3. Metal deactivators; 10 4. Phosphites and phosphonites; 5. Hydroxylamines; 15 6. Nitrones; 7. Thiosynergists; 8. Peroxide scavengers; 20 9. The Polyamide class of stabilizers; 10. Basic co-stabilizers; 25 11. Nucleating agents; 12. Fillers and reinforcing agents; 13. Other additives, for example plasticisers, lubricants, emulsifiers, pigments, 30 rheology additives, catalysts, flow-control agents, optical brighteners, flameproofing agents, antistatic agents and blowing agents; 14. Benzofuranones and indolinones; and 17 WO 2013/023247 PCT/AU2012/000961 15. Some of the films produced with these compositions whiten as they degrade, for example films that contain titania or titania in combination with iron stearate. Materials that reduce or eliminate whitening of the film following aging, such as 5 materials having a refractive index approximately matching that of the bulk material, can be added. Such materials could include, but are not limited to, oils and waxes. Waxes can include animal, vegetable, mineral and synthetic waxes, for example petrolatum (Vaseline.RTM.), polyolefin waxes, such as polybutene and polyethylene waxes, wool wax and its derivatives, such as wool wax alcohols, and silicone waxes. 10 Oils can include vegetable oils, animal oils, mineral oils, silicone oils or their mixtures. In particular, hydrocarbon oils, such as paraffin oils, isoparaffin oils, squalane, oils from fatty acids and polyols are preferred. Hydrocarbon oils, especially mineral oils (paraffinum liquidum), are especially preferred, in particular Mobil DTE Heavy oil. Further examples of such additives are provided in International Patent Publication 15 W02009/021270. The additional additives are, for example, present in the composition in an amount of 0.001 to 10% by weight, preferably 0.001 to 5% by weight, relative to the weight of the polymer (component a). 20 The incorporation of the prodegradants and non-ionic surfactant components and optional further components into the polymer is carried out by known methods such as melt blending, dry blending in the form of a powder, or wet mixing in the form of solutions, dispersions or suspensions for example in an inert solvent, water or oil, or 25 by addition of the additive in the form of a spray or solution to the polymeric material following formation of the article. The melt blended or dried metal oxide/surfactant mixture may be added directly into the processing apparatus equipped with a mixing mechanism (e.g. extruders, internal mixers, etc.), e.g. as a dry mixture or powder, e.g. in a closed apparatus such as a kneader, mixer or stirred vessel. It is immaterial 30 whether processing takes place in an inert atmosphere or in the presence of oxygen. Particularly preferred processing machines are single-screw extruders, contra-rotating and co-rotating twin-screw extruders, planetary-gear extruders, ring extruders or 18 WO 2013/023247 PCT/AU2012/000961 cokneaders. It is also possible to use processing machines. In some cases it may be beneficial to have at least one gas removal compartment to which a vacuum can be applied. 5 Suitable extruders and kneaders are described, for example, in Handbuch der Kunststoffextrusion, Vol. 1 Grundlagen, Editors F. Hensen, W. Knappe, H. Potente, 1989, pp. 3-7, ISBN:3-446-14339-4 (Vol. 2 Extrusionsanlagen 1986, ISBN 3-446 14329-7). 10 For example, the screw length is 1 - 60 screw diameters, preferably 20-48 screw diameters. The rotational speed of the screw is preferably 1 - 800 rotations per minute (rpm), very particularly preferably 25 - 400rpm. The maximum throughput is dependent on the screw diameter, the rotational speed 15 and the driving force. Film preparation can also be carried out at a level lower than maximum throughput by varying the parameters mentioned or employing weighing machines delivering dosage amounts. If a plurality of components is added, these can be premixed or added individually. 20 The additives of the invention and optional further additives can also be added to the polymer in the form of a masterbatch ("concentrate") which contains the components in a concentration of, for example, about 1 % to about 40% and preferably 2% to about 20% by weight incorporated in a polymer. The polymer must not be necessarily of 25 identical structure as the polymer where the additives are added finally. In such operations, the polymer can be used in the form of powder, granules, solutions, suspensions or in the form of lattices. In one embodiment a number of batches each containing one or more prodegradants and at least one comprising the non-ionic surfactant are blended. Alternatively the additives of the invention can be added to 30 the polymer directly at the levels required for film produced from that polymer. It may be advantageous to blend the prodegradants in the presence of the non-ionic surfactant. 19 WO 2013/023247 PCT/AU2012/000961 The rate of degradation of the film may be controlled by the level of prodegradants used and any accelerating treatment such as radiation exposure described herein. The properties of the prodegradant polyolefin composition are particularly suited to agricultural use and enable a film produced from the polyolefin to perform its function 5 in propagation of plants or seeds or as a mulch film and to degrade in the soil after the film has served its purpose. For instance, when used in propagation of plants from seed or seedlings the film may be adapted to become sufficiently embrittled for the plants to rupture the film during growth. The film will then subsequently degrade in the soil so that little or no film remains at the commencement of the next growing 10 season. Accordingly, in one embodiment, the polyolefin is in the form of a film used for covering seed, soil, seedlings or in covering soil in which seed or seedlings are to be planted. 15 In another embodiment, the polyolefin is in the form of a film for temporary packaging such as packaging for the purpose of retaining or protecting articles temporarily before degrading of the film. One example of such packaging the protection of material such as mail, commercial products or correspondence during delivery to 20 customers. One specific example of such packaging is in newspaper wrap adapted to allow newspapers to be protected from the weather for the short period between delivery and being unwrapped by the consumer. Another example is in shopping bags required to merely maintain strength for a period sufficient to allow them to be dispensed to customers in shops at the point of sale of goods and to transport the 25 goods to the point of use. The films, processed by cast or blowing methods, are particularly suited to agricultural use such as plant propagation or mulch. For example existing machinery may be used to cultivate the soil and plant seed or seedlings and apply the plastic film 30 simultaneously. Such techniques allow the earlier germination of seeds and provide protection for the seedlings from late season frosts, but do not impede growth of the seedlings beyond the initial germination stages. 20 WO 2013/023247 PCT/AU2012/000961 In forming the polyolefin composition into suitable film for propagation it may be preferred to use the procedures described in US 6168840 the contents of which are herein incorporated by reference. Accordingly, such plastic film for covering seeded soil or soil destined to contain seeds for propagation may be stretched in at least 5 localised regions along a length of said film to beyond the yield point of the film to achieve a reduced thickness in the stretched region or regions whereby in use the film will deteriorate to allow passage of a germinated seedling through the film. Indeed the film may be completely stretched beyond its yield point. In one embodiment the film is completely stretched biaxially. The film is preferably stretched at its point of 10 extrusion, that is, in line stretching of the film during the extrusion process. The film may be stretched at a secondary out of line stretching process. Alternatively the film may be stretched at the point of application of the film to the soil. Stretching at the point of extrusion (in-line stretching) and/or stretching during a secondary 15 process before working in the field will be the preferred option to reduce the likelihood of damage to the film at the point of laying the film onto a crop bed. In a further aspect of the invention, there is provided a film for use in the covering of soil containing plant seeds or destined to contain plant seeds to be germinated in 20 which a non-ultraviolet resistant (photodegradable) degradable film web has undergone stretching beyond its yield point whereby the thickness of the film is reduced to a thickness such that at least part of the web will more quickly deteriorate through weathering and or biological activity and thereby allow passage of a germinated seedling from beneath the protective cover of the film which has acted to 25 facilitate heating of the soil and protection from frosts during the seed germination process and/or preceding period. The film formed from the polyolefin composition may be used as a mulch film and may be adapted to undergo whitening and/or may contain pigment such as carbon 30 black to improve heat retention. The film formed from the polyolefin composition may be of thickness of for example from 1 to 500 microns and preferably from 2 to 200 microns. In the case of film for 21 WO 2013/023247 PCT/AU2012/000961 plant propagation the stretching of the film may provide areas of thickness of less than 10 microns or the thickness of the whole film may be reduced to less than 10 microns. 5 Film formed of the polyolefin composition may be subject to a pre-treatment with UV C irradiation as described in EP2176322 (also published as WO 2009/021270). Degradation can be started by appropriate exposure to radiation. The radiation may be supplied at the time of the production of the film, or immediately before, during or following use of the film to commence or accelerate degradation of the film. It may be 10 applied in one or more predetermined zones of the film, or across the full surface area. Once degradation is initiated it continues, including while the film is in use such as positioned over the crops and plants. This radiation treatment may be the only treatment after manufacture, or may follow an earlier pre-treatment at the time of manufacture. 15 In one set of embodiments there is thus provided a method of controlling the rate of degradation of a polyolefin film used to package or cover a material to cause embrittlement of the film after an intended useful lifetime, including the steps of: providing a polyolefin film comprising a polyolefin, and 20 exposing at least part of the polyolefin film to artificial radiation of wavelength less than about 400 nm. The exposure time may be up to one hour. The method may comprise covering the material or forming a package for the material 25 with the exposed film. The rate of degradation of the polyolefin film is accelerated by the exposure to cause embrittlement of the film following the intended useful lifetime of the film. In this embodiment, it is generally preferred that at least 80% of the radiation energy 30 is emitted in the range 250 nm to 260 nm. 22 WO 2013/023247 PCT/AU2012/000961 Preferably at least part of the film is exposed to light in the range 200 nm to 385 nm at a radiation dose rate of at least about 50 Watts per m 2 of film, more preferably at least 1,000 W/m 2 and more preferably at least about 7,500 W/m 2 . 5 In one set of embodiments at least part of the film is exposed to a radiation dosage of at least 9 kJ/m 2 , preferably at least 15 kJ/m 2 , more preferably at least 20 kJ/m 2 and more preferably still at least 25 kJ/m 2 . In a further embodiment the polyolefin composition, preferably in the form of a film is 10 subject to radiation treatment to activate the prodegradant prior to disposal of the polyolefin. The prodegradant is activated, for example by corona treatment or by irradiating the film with UV radiation, near-IR radiation, or any other suitable radiation including heat to commence a controlled degradation of the film from the point in time that the film is so treated. The activating treatment process may occur at the film 15 production facility, or immediately before its end use, for example as an agricultural cover film or mulch film, or at some stage during its end use, for example by treatment of shopping bags at point of sale, or post-treatment of agricultural or non-agricultural films at time of disposal into a waste treatment facility, or a combination of treatments may be used. Post-irradiation could be of particular benefit for those films that most 20 desirably have as long a service life as possible e.g. greenhouse covers or long-term mulches, but that then need to be made degradable following use. The activation process may be spatially controlled so the film may degrade at different rates in different regions of the film or as a result of differing levels of exposure to the treatment regime. Subsequent degradations are designed to occur either upon solar 25 exposure or under mild thermal oxidation (as may occur on soil burial). In alternative embodiments, the aim may be to neutralize the stabilizing effect of a film formulation that normally inhibits degradation but then neutralized allows degradation to occur by the usual mechanisms. 30 Preferably the radiation is UV-light between 250 nm and 380 nm. A specifically preferred embodiment of the invention is a composition comprising 23 WO 2013/023247 PCT/AU2012/000961 a) a polyethylene, a polypropylene, a polyethylene copolymer or a polypropylene copolymer; b) at least one of (i) titanium dioxide and (ii) iron stearate or cobalt stearate; and 5 c) a non-ionic surfactant as described above; and further characterised in that the composition has been subjected to radiation. The invention will now be described with reference to the following examples. It is to be understood that the examples are provided by way of illustration of the invention 10 and that they are in no way limiting to the scope of the invention. Examples Experimental Materials 15 The polyethylene resin matrix used to prepare materials described herein was based on a mixture of the following resins: * Resin R-1, a Linear Low Density Polyethylene with a density of 0.920 g CM-3, melt flow index 1.00g 1 Omins- 1 . * Resin R-2, a Linear Low Density Polyethylene with a density of 0.916 g CM-3, 20 melt flow index 1.00g 1 Omins- 1 . * Resin R-3, a Low Density Polyethylene with a density of 0.922g cm- 3 , melt flow index 1.0 g 1Omins- 1 . * Resin R-4, a Linear Low Density Polyethylene with a density of 0.920 g CM-3, melt flow index 0.85g 1 Omins- 1 . 25 e Resin R-5, a Low Density Polyethylene with a density of 0.922g cm- 3 , melt flow index of 0.45 g 1 Omins-1 * Resin R-6, a High Density Polyethylene with a density of 0.949 g cm-3, melt flow index of 0.1 g 1 Omins-1 * Resin R-7, a Linear Low Density Polyethylene with a density of 0.935 g CM-3, 30 melt index 0.50 g 10mins- 1 . 24 WO 2013/023247 PCT/AU2012/000961 A small amount of Mobil DTE Heavy Oil (referred to as oil in the text) was used to improve dispersion of prodegradants in the polyethylene matrix. A polyisobutylene masterbatch containing 57 - 63% polyisobutylene of molecular weight of 1800 Da), was added to the mix as a tackifying agent and is referred to as PIB in the text. 5 Cobalt (II) Stearate (9.5% Co) (CoSt) was obtained from both the OM Group Incorporated and Alfa Aesar. The iron (Ill) stearate (FeSt) was sourced from SunAce, Melbourne. The manganese (II) stearate (MnSt) was sourced from Pfaltz and Bauer. The "Aeroxide" Degussa P25 Titania (TiO 2 ) was supplied by Evonik Industries 10 Australia. "Aeroxide" TiO 2 P25 is a fumed titanium dioxide having photocatalytic properties, has an approximate surface area of 50 m 2 /g and an average primary particle size of approx. 21 nm (CAS-No 13463-67-7). ("Aeroxide" is a trademark). The alkoxylated ethylenically saturated non-ionic surfactant compounds were supplied commercially or, in the case of the pure compounds, prepared by synthesis 15 and are described in Table 1 (Surfactants A to K & M to P). An ionic surfactant, dodecylbenzenesulphonate (DBS) supplied by Aldrich, was also trialled and has been denoted as Surfactant L in the examples. Surfactant Q is Atlox 4912 supplied by Croda and has a molecular weight of = 5000 Da. 20 Table 1 A list and description of the alkoxylated ethylenically saturated non-ionic surfactants used. Surfactant Surfactant Description Hydrophilic-Lipophililc Stearyl (C18) alcohol ethoxylate (Mixture A prepared by reacting the alcohol and ethylene 3 oxide in a 1:1 mole ratio) Stearyl (C18) alcohol ethoxylate (Mixture B prepared by reacting the alcohol and ethylene 5 oxide in a 1:2 mole ratio) Behenyl (C22) alcohol ethoxylate (Mixture C prepared by reacting the alcohol and ethylene 4 oxide in a 1:2 mole ratio) Behenyl (C22) alcohol ethoxylate (Mixture D prepared by reacting the alcohol and ethylene 6 oxide in a 1:5 mole ratio) E C30 alcohol triethoxylate, C30E3 5 25 WO 2013/023247 PCT/AU2012/000961 Surfactant Surfactant Description Hydrophilic-Lipophililc F Stearyl alcohol monoethoxylate, C18E1, 4 prepared as a pure compound G Stearyl alcohol diethoxylate, C18E2, prepared 6 as a pure compound H Stearyl alcohol triethoxylate, C18E3, prepared 7 as a pure compound Behenyl alcohol monoethoxylate, C22E1, 3 prepared as a pure compound Behenyl alcohol diethoxylate, C22E2, 5 prepared as a pure compound K Behenyl alcohol triethoxylate, C22E3, 7 prepared as a pure compound L Dodecylbenzene sulfonate ionic surfactant N/At M Polyethylene glycol sorbitan monolaurate 15 N C12 - C15 alcohol polyethylene glycol ether 12-13 with 7 ethoxylates units, C12-15E7 Stearyl alcohol with 10 ethoxylate units, C18E10 (Mixture prepared by reacting the 13 alcohol and ethylene oxide in a 1:10 mole ratio) Stearyl alcohol with 20 ethoxylate units, C18E20 (Mixture prepared by reacting the 16 alcohol and ethylene oxide in a 1:20 mole ratio) ABA block copolymer of poly-hydroxy-stearic 6* acid copolymerized with polyethylene glycol ABA block copolymer of polypropylene oxide R polyethylene oxide-polypropylene oxide (70% 14 ethylene oxide) ABA block copolymer of polypropylene oxide S polyethylene oxide-polypropylene oxide (80% 16 ethylene oxide) 1 HLB index was calculated using the Griffin method for non-ionic surfactants; HLB = 20 x Mh/M; where Mh is the molecular mass of the hydrophilic portion of the molecule; M is the molecular mass of the whole molecule. 5 tA calculated HLB index does not apply to ionic surfactants as the hydrophilic moiety of the surfactant ionizes and adds extra emphasis, therefore making the ionic surfactant more hydrophilic. Dodecylbenzene sulfonate is soluble in water. The HLB value was provided by Croda. 26 WO 2013/023247 PCT/AU2012/000961 Degussa P25 TiO 2 - Alkoxylated Ethylenically Saturated Non-ionic Surfactant Concentrate Preparation TiO 2 and non-ionic surfactant concentrates were prepared for most surfactants using a solvent dissolution method prior to film blowing. 10 g of the non-ionic surfactant was 5 placed in a beaker of 50 mL of diethyl ether at room temperature whilst being stirred with a magnetic stirrer. After 20 - 30 minutes, 5 g of TiO 2 was added to the resulting solution and an additional 20 mL of diethyl ether was added to ensure the P25 was well dispersed into the alkoxylated ethylenically saturated non-ionic surfactant matrix. The mixture was left to stir for another 20 - 30 minutes until the slurry was of a 10 homogeneous viscous consistency, without clumps of surfactant/TiO 2 . The slurry was cast into petri dishes and left to dry for 48 hours in a fume hood. Titan ia/surfactant M and titania/surfactant N concentrates were prepared using the same procedure described above except using isopropanol as the solvent and titania/surfactant 0 & titania/surfactant 0 concentrates using acetone. Cyclohexane was used in place of 15 diethyl ether to dissolve Surfactant E as well as the addition of heat to 700C using a paraffin oil bath and mixing using an overhead stirrer. Surfactant E was also prepared by a melt blending method without the use of solvent by adding the Degussa P25 into the melted surfactant matrix in a 1:2 weight ratio (P25:surfactant), followed by mixing for 10 minutes. Once the mixture was cooled it was ready to be used for film blowing. 20 The details of the surfactant type used to prepare each concentrate (C) are described in Table 2. Degussa P25 TiO 2 - Ionic Surfactant Concentrate Preparation Dodecylbenzene sulphonate (DBS) (Surfactant L) coated TiO 2 nanoparticles (denoted 25 as C-13 in Table 2) were prepared based on the method described by Ramakrishna et al. (Ramakrishna G, Ghosh HN. Optical and Photochemical Properties of Sodium Dodecylbenzenesulfonate (DBS)-Capped TiO 2 Nanoparticles Dispersed in Non aqueous Solvents. Langmuir. 2003;19:505-8). The method involved dispersing 4g of Degussa P25 in 500 mL of water which was then added to 250 mL toluene in a round 30 bottom flask, followed by stirring for 15 - 20 minutes. To the mixture was added 100 mL of 0.23 M (sodium dodecylbenzenesulphonate), followed by stirring at a low speed for 3 h. The positively charged TiO 2 particles bind through the sulfonic group (S03-) of the DBS which can then be dissolved in an organic solvent. In this case, DBS 27 WO 2013/023247 PCT/AU2012/000961 coated TiO 2 nanoparticles migrated from the aqueous layer to the organic phase (toluene). The organic phase was dried with CaCl 2 , refluxed for 2 hours, followed by rotary evaporation to remove the toluene. The dried DBS capped TiO 2 nanoparticles were then ready to be processed into the polyethylene matrix. 5 Table 2 A description of surfactant type used to prepare each TiO 2 -surfactant concentrate prior to extrusion in a polyethylene film. Concentrate # Surfactant # C-1 A C-2 B C-3 C C-4 D C-5 G C-6 H C-7 I C-8 J C-9 K C-10* E C-11 F C-12* E C-13 L C-14** M C-15** N C-16t 0 C-1 7 1 P 10 * Cyclohexane was used in place of diethyl ether to dissolve Surfactant E as well as the addition of heat to 700C using a paraffin oil bath and mixing using an overhead stirrer. 'TiO 2 /Surfactant E concentrate was prepared using a melt method without solvent. ** Isopropanol was used to dissolve the surfactant. I Acetone was used to dissolve the surfactant. 15 28 WO 2013/023247 PCT/AU2012/000961 Extrusion Masterbatching An Entek extruder of 27 mm diameter co-rotating twin screw (40 L/D) was used to 5 prepare masterbatches of metal oxides and transition metal salts in the polyethylene resin as described herein. It was operated at 50-70 rpm (residence time approximately 3.5 minutes). Some surfactant/titania mixes with resins were also passed through this extruder at 60rpm and a maximum temperature of 1330C. For pre-mixing the material to be blown, screw speed was 40-60 rpm (residence time 3.5 10 4.5 minutes) and a feed rate of 4 kg/h. The maximum temperature was between 195 205 OC with the die face at 126 -127 OC. The extrudate from both masterbatching and pre-mixing materials (prior to film blowing) was passed through a hot, die-faced, 4 blade pellitiser running at 200 rpm producing air-cooled pellets averaging 6 mm in diameter. Each masterbatch type used herein to manufacture prototype films are 15 described in Table 3 and details of the various film mixes are shown in Table 4. The iron (III) stearate/surfactant A masterbatch (MB-5) was prepared by a specialist masterbatching company on a Leistritz ZSE Maxx 27 mm extruder with an L/D ratio of 36. The surfactant was placed in an appropriately sized mixer which was heated to 20 melt the surfactant. The iron (III) stearate was mixed with 0.75kg of an untreated fumed silica filler (Cabosil M5) and then added to the melted surfactant and mixed. The ratio of the mix was iron (III) stearate: surfactant 1:1 by weight. This mixture was then added to a polyethylene carrier resin, extruded, then pelletised. The maximum temperature was between 170 - 175 0C with the die face temperature of at 170 OC. 25 The composition of MB-5 is described in Table 3. Table 3 A description of the materials and extruder conditions used to manufacture polyethylene carrier resin masterbatches (MB). The final concentration of cobalt (II) stearate was 10.6 wt.% (MB-1 & MB-1A) and 10 wt.% iron (111) 30 stearate (MB-5), unless stated otherwise in the table footnote. 29 WO 2013/023247 PCT/AU2012/000961 Wt.% Surfactant Surfactant Wt.% Resin Resin Resin Resin Cabosi Screw Max B FeSt CoSt TiO2 TiO 2 Type Amount Surfactant R-1 R-2 R-3 R-7 M5 PIB Speed Temp. Code (g) (g) (g) (%) (g) (g) (%) (g) (g) (g) (g) (kg) (g) (rpm) C MB-1 106.0 - - - - - 384 450 50 ~ ~ 10 60 190 MB- 106 - - - - - 378 450 50 16 75 200 1A MB- - 18 - - - - - 491 491 - - 40 207 1 B* MB-2 - 50.2 25.1 K 50.4 25.2 44 48.2 - ~ ~ 7.2 60 133 MB-3 - - 32.1 15.9 F 30.4 15.1 64 68.2 - - - 7.2 60 133 MB-4 ~ - 60.3 30.1 A 60 30.0 34 38.8 - ~ ~ 7.2 60 133 MB-5 - - - A k 10.0 - - - 39.25 0.75 - 550 200 *The concentration of cobalt (II) stearate in the final masterbatch was 1.8 wt.% Film Blowing Extrusion 5 Either the titania/surfactant concentrate as received, the prodegradant pellets or surfactant as received or the prepared masterbatch pellets were then used to manufacture prototype films on an Axon BX25 extruder. For the majority of films made, the mix of prodegradants and resins was first pre-mixed by passing a total of 400 g of material was passed through the Entek extruder and pelletising the extrudate 10 as described above. 300g of these pellets were then blown by means of a 25 L/D Axon extruder with a 25mm cut flight single-screw, with a blowing die (215 0 C) of 40 mm diameter and associated tower. The blow up ratio was a maximum of 3. Table 4 describes the composition and further extrusion details used to manufacture prototype films evaluated herein. In the examples (unless specified otherwise in the table 15 footers) the concentration of titania, cobalt (II) sterate, manganese (II) stearate, iron (IlI) stearate and surfactant were lwt.%, 1.06wt.%, 1.13wt.%, 0.6 wt.% and 2wt.% respectively in the final film formulation. Prior to extrusion of films containing TiO 2 **, the TiO 2 was mixed with Sigmacote* (chlorinated organopolysiloxane solution in heptane, available from Sigma Aldrich) in a weight ratio of 1.0:0.8 and stirred in 20 hexane to improve its compatibility with the polyethylene matrix. The solution was left to dry and then placed under vacuum to remove solvent. Note: for films using P25 (Sigmacote@), this material was added last to the mix as is. Mineral oil (0.5%) was added to assist the P25 to bind to the resins. For films using the surfactant and P25, they were combined using the solvent, melt mixing or masterbatch extrusion method 30 WO 2013/023247 PCT/AU2012/000961 (as described above) and then the correct amount of this mix was added during extrusion. A specialist packaging film company processed films CE-2 and example 16 described 5 in Table 4. 2 wt.% of MB-5 was mixed with the resin composition given in Table 4 to produce the film described as example 17. Film was produced at approximately 350 kg per hour with a 350 mm film blowing die with a single screw extruder using temperatures between 150 and 1800C. The blow up ratio was less than 3 and the residence time in the extruder was estimated to be approximately 1 minute. 10 31 WO 2013/023247 PCT/AU2012/000961 r- Go 0) 0o t0) f- CO C ) 0 co O C C C COi eq C40) 0 0 .0 0 ) 0 - 'n CD -n 'n t)C O .) CO C. C O C C O C C." C4'Z U0) ) C 4 cm (0 C4 . .~ .D I0 ( D C 0 D C D ucoi U t -- EO W ~ o u d) ZEEt .00 (D a)C ~ ix OCO C w %N6 " dU) w m c J w v0 C 0)Z .

0O O~ .u 2 .5 a) ~zo i- i : < h L xm z 0 0 CU-4 EN E In ~.~ - 000 mO c O) - - - - - - - EI- Ca E r 0 .6 a~~ 0 ) - - - - - - - - - - - - ): E lU -j k ) S, , * E 460) oP 2 lb 0 2- - - - - - - - - LL < N U) LL CP L0N C O C D JC LL) 32 WO 2013/023247 PCT/AU2012/000961 co N o co N N N NN N N C'4 C4 OC C C 4 C. CIA N N Nv N C0 (rZ~~ 6)6)j -c4 Rc 4R2 -S~~ R 2 R D 9 a U) 2 22 ~~~c 2R 2CR 2 2292

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C~~~4 CV 00Cq C ci)" 4--4 It. It LL L99 4), lb~- - - -- - - IL N2 N N NN N Z5LL W LJ> C caO O O N -. . ' -vN N 33 WO 2013/023247 PCT/AU2012/000961 E C 2wt ) Cq U)U U ) ) CON C4(N( co co- " .. .

0- 00 C0 C0 *4 (N CN .a R N (N - R t (D 0 ----- -- -- --- - --- 0 - - - - - - - - - - - - - 0 0 , 022. 0) .0 0~ coo .. 0 2~ :N. -r U kn c C D0 CD C) cl .) J 34 WO 2013/023247 PCT/AU2012/000961 Accelerated Laboratory Weathering After film blowing, duplicate samples of each film formulation were aged under 'dark thermo-oxidative' conditions in a Contherm digital series fan-forced oven, thermostatted at 60 0 C, under conditions of 100% humidity by being enclosed in a desiccator, where the 5 base was filled with 20 mL of MilliQ water. Another series of dark thermo-oxidative experiments were performed which involved duplicate samples of each film formulation being pre-treated at 254 nm with a UVC dosage of 3000 J/m 2 prior to evaluation under dark thermo-oxidative conditions. Further details of this pre-treatment treatment are described in EP2176322 (Al). Once the pre-treatment on duplicate samples of each film 10 formulation was performed, thermo-oxidative experiments were then conducted at 60 0 C and 100% humidity as described previously herein. The results from the accelerated dark thermal experiments are used to screen for key formulations to be trialed under outdoor weathering conditions. Periodically, samples were withdrawn and evaluated for film embrittlement. An elongation at break less than 5% defines the embrittlement point. At 15 this point the film fractures and fragments under light load or by a gentle finger tap on the film. When used as agricultural film, the embrittled material cannot be removed and fragments in place. This process is distinguished from film splitting in which there is a loss of properties only in one direction and the split agricultural film may remain intact on the soil without fragmenting. 20 Duplicate samples of the film formulations were aged in a UVA aging cabinet, which incorporates a battery of eight 40W UVA-340 lamps, at a distance of 1 cm from the samples. The peak average emission at 340 nm was 0.56 W/m 2 , with a short wavelength profile that mimics solar radiation with a cut-off at 295 nm. Periodically, samples were 25 withdrawn and evaluated for film embrittlement. Outdoor Weathering Outdoor weathering trials were performed on film formulations at a trial site at Pinjarra Hills in Queensland, Australia. A weather station was installed at the trial site where the 30 rainfall, temperature, solar radiation and air humidity were monitored during the trials. 35 WO 2013/023247 PCT/AU2012/000961 Film degradation was investigated above- and below-ground. For the above-ground film degradation studies, 2 - 6 samples of each film formulation were laid on a commercial garden soil, with the edges of the film buried in the soil to keep the films in place during the trial. The films were monitored every 2 days to evaluate for film whitening and 5 embrittlement. For below-ground film degradation studies, each formulation was buried under-the-ground for a total duration of 6 months. Monthly, film was removed from below-ground, washed with distilled water, pat-dried, followed by measurement of the change in tensile properties, characterized using an Instron. UVC pre-treated (UVC dosage of 3000 J/m 2 as described previously herein) and non-treated film formulations 10 were investigated below-ground. The change in the elongation at break at each sampling point was averaged over 10 sample repeats and the standard deviation was the spread in the data across the samples tested. In the examples section below (unless specified otherwise in the table footers) the 15 concentration of titania, cobalt (II) stearate, manganese (II) stearate, iron (III) stearate and surfactant (when present in a given formulation) were lwt.%, 1.06wt.%, 1.13 wt.%, 0.6 wt.% and 2wt.% respectively in the final film formulation. Examples 1 to 13 and Comparative Examples (CE) 1, 3 to 8 20 Table 5 demonstrates that photoactive metal oxide nanoparticles dispersed using alkoxylated ethylenically saturated non-ionic surfactants in polyolefin films can provide rates of embrittlement in a UVA aging test that are at least equivalent to those observed for chlorosiloxane coated titania nanoparticles. Titania nanoparticles coated with an ionic surfactant (Surfactant L) resulted in times to embrittlement double those of titania/non 25 ionic surfactant containing polyolefin films. Table 5 The days to embrittlement for a polyolefin containing titanium dioxide in the absence and presence of an alkoxylated ethylenically saturated non-ionic surfactant or ionic surfactant in a UVA test. 30 36 WO 2013/023247 PCT/AU2012/000961 UVA Example Metal Surfactant (Days to oxide Emb.) CE-1 - - 29± 3 CE-3 - A* 11± 1 CE-4 - A 20± 2 CE-5 - K 25± 1 CE-6 - F 27± 1 CE-7 - H 25± 1 CE-8 TiO 2 ** - 7± 1 1 TiO 2 A 5± 1 2 TiO 2 K 5± 1 3 TiO 2 G 5± 1 4 TiO 2 J 5± 1 5 TiO 2 E 4± 2 6 TiO 2 H 7± 1 7 TiO 2 I 7± 1 8 TiO 2 B 7± 1 9 TiO 2 C 7± 1 10 TiO 2 D 7± 1 11 TiO 2 KA 7± 1 12 TiO 2 FA 7± 1 13 TiO 2 LA 13± 1 * Concentration 0.6wt%. ** The TiO 2 has been surface reacted with a chlorosiloxane prior to incorporation into the final film formulation. 5 A Concentration 1.0 wt.% ~ A titania/surfactant masterbatch was prepared prior to film blowing extrusion. Examples 1 to 10, 14, 40 and Comparative Examples (CE) 16 - 21 Table 6 illustrates a comparison of the film blowing capabilities of alkoxylated 10 ethylenically saturated non-ionic surfactant compounds into a polyolefin matrix of varied HLB index. The film blowing characteristics of examples 1 - 11 & 14 where a non-ionic surfactant of HLB index between the range of 3 - 7 was incorporated into the polyolefin matrix, resulted in optimal film quality; whereas CE-16 to CE-21 show a decline in film 37 WO 2013/023247 PCT/AU2012/000961 properties as the HLB index of the surfactant is increased above 12 to 16 and are not practically useful. Table 6 A comparison HLB index and processing details alkoxylated ethylenically 5 saturated non-ionic surfactant compounds of high and low HLB incorporated into a polyolefin film. The concentration of the TiO 2 and non-ionic surfactant in the final film formulation was 1 & 2wt.% respectively. Metal Non-Ionic , Film Blowing Example Oxide Surfactant HLB Characteristics 1 - T10, Surfactant 3 -7 OK 14,36 A - K, Q CE-16 TiO 2 M 15 Holes formed in films CE-1 7 TiO2 N 12-13 Some holes in film, usable film obtained CE-1 8 TiO2 O 13 Some holes, usable film obtained CE-19 TiO 2 P 16 Holes formed in film Leaks in film blowing CE-20 TiO 2 R 14 bubble, highly unstable, unusable film produced Leaks in film blowing CE-21 TiO 2 S 16 bubble, highly unstable, unusable film produced Example 15 to 20 and Comparative Examples (CE) 1 to 3, 9 to 11 10 Table 7 shows that polyolefin films containing the combination of the transition metal salt and the alkoxylated ethylenically saturated non-ionic surfactant degrade faster than polyolefin films that contain only the transition metal salt or alkoxylated ethylenically saturated non-ionic surfactant. An acceleration in the time to embrittlement was observed for films containing cobalt (II) stearate with surfactant under dark thermal 15 conditions (with and without UVC), manganese (II) stearate (MnSt) examples containing surfactant under photo-oxidative conditions and iron (III) stearate (FeSt) examples containing the surfactant under both photo-oxidative and thermo-oxidative conditions (with and without UVC). Note the acceleration in the oxidation of a typical polyolefin packaging wrap formulation containing FeSt and surfactant A (example 16), compared to 38 WO 2013/023247 PCT/AU2012/000961 a packaging wrap formulation containing no prodegradant (CE-2), in an accelerated UV and dark thermal test after UVC pre-treatment. Table 7. The days to embrittlement for polyethylene film containing a transition metal 5 salt, an alkoxylated ethylenically saturated non-ionic surfactants and a combination of both in a dark thermal aging test (with and without UVC pre treatment) and in a UVA test. UVA (Days Dark Thermal Aging to (Days to Emb.) Emb.) Example Transition Non-ionic No UVC 3000 J/m 2 metal salt surfactant UVC CE-1 - 29 ±3 111 ±1 83± 1 CE-2 - 29 ±1 > 108 > 108 CE-3 A* 11 ±1 81 ±1 11 1 CE-9 CoSt - 7 1 13 ±1 3 1 CE-10 FeSt - 27 7 99 ±6 24 4 CE-11 MnSt - 19 1 > 54 3 1 15 CoSt A* 7 1 7 1 1 1 16 FeSt A* 18 2 31 3 9 1 17 FeSt* A$ 9 1 > 108 67 1 18 MnSt AA 11 5 > 80 3 1 19 MnSt A 15 1 > 54 3 1 20 MnSt KA 13 3 >80 3 1 * Concentration 0.6wt.% t Concentration 0.5wt.% 10 A Concentration 1.0 wt.% Comparative Examples (CE) 1, 8, 9, 11 to 15 Table 8 demonstrates the UV antagonism effect between the metal oxide (TiO 2 ) and transition metal salt (cobalt (II) stearate or manganese (II) stearate). These results 15 indicate that the antagonism effect occurs in the presence of UV (and heat) and results in longer times to embrittlement, compared to the metal oxide or transition metal salt in the polyolefin alone. The dark thermo-oxidation (no UV, only heat 60 0 C and 100 % humidity) results show that there is no increase in the time to embrittlement for the combination 39 WO 2013/023247 PCT/AU2012/000961 formulation of TiO 2 and cobalt (II) stearate compared to the cobalt (II) stearate only control. TiO 2 is not considered to be an effective dark thermal aging catalyst, however is very photoactive. Cobalt (II) stearate is active under both photo- and dark thermo oxidative conditions, however it is not as efficient a photo-catalyst compared to TiO 2 , but 5 is far more responsive to heat compared with TiO 2 . Table 8 Laboratory aging results demonstrating the antagonism effect between TiO 2 and CoSt prodegradants in the presence of UV compared to dark thermo oxidative conditions. Dark Thermal Aging (Days to Emb.) Comparative Transition Metal UVA No 3000 J/m 2 Example metal salt oxide (Days to UVC Emb.) CE-1 - - 29 3 111 1 83± 1 CE-8 - TiO 2 ** 7 1 95 1 37± 1 CE-9 CoSt - 7 1 13 1 3± 1 CE-11 MnSt - 19 1 > 54 3± 1 CE-12 CoSt TiO 2 17 1 13 ±1 2± 2 CE-13 CoSt TiO 2 ** 11 1 13 ±4 2± 2 CE-14 MnSt TiO 2 11 3 > 92 5± 1 CE-15 MnSt TiO 2 ** 15 1 > 92 5 ± 1 10 ** This metal oxide has been surface reacted with a chlorosiloxane prior to incorporation into the final film formulation. Examples 21 to 35 and Comparative Examples (CE) 12 to 15, 22 to 25 Table 9 demonstrates for a film containing both TiO 2 and CoSt or MnSt, that the 15 antagonism effect in the UVA test is overcome by the incorporation of alkoxylated ethylenically saturated non-ionic surfactants between the HLB index range of 3 - 7, which provide rates of degradation equal to or greater than observed for the metal oxide &/or transition metal salt alone (see Table 5 & Table 7). UVA results demonstrate that non ionic surfactants within the HLB range of 12 - 15 (CE-22 to 25) were not as effective as 20 non-ionic surfactants within the HLB range of 3 - 7 (Examples 21 - 33) in reducing photo antagonism between titania and cobalt (II) stearate prodegradants. The time to 40 WO 2013/023247 PCT/AU2012/000961 embrittlement is also reduced in the dark thermal aging test for a film containing both TiO 2 and cobalt (II) stearate by the incorporation of various alkoxylated ethylenically saturated non-ionic surfactants, and is less than with cobalt stearate alone and no surfactant (see Table 8). 5 Table 9 further demonstrates the significant acceleration in the time to embrittlement under dark thermo-oxidation conditions for these same films following UVC pre treatment. 10 Table 9 The antagonism effect between CoSt and TiO 2 has been overcome by the incorporation of alkoxylated ethylenically saturated non-ionic surfactant. UVA Dark Thermal Example Transition Metal Non-Ionic (Days Aging (Days to metal salt oxide Surfactant to Emb.) Emb.) 3000 Nil J/m 2 UVC CE-12 CoSt TiO 2 - 17 ± 1 13 ±1 2± 2 CE-13 CoSt TiO 2 ** - 11 ± 1 13 ±4 2± 2 CE-14 MnSt TiO 2 - 11 ± 3 > 92 5± 1 CE-15 MnSt TiO 2 ** - 15 ±1 > 92 5± 1 21 CoSt TiO 2 A 3 ±1 4 ±2 1± 1 22 CoSt TiO 2 H 5 ±1 1 ±1 1± 1 23 CoSt TiO 2 1 5 ±1 3 ±3 1± 1 24 CoSt TiO 2 K 5 ±1 1 ±1 1± 1 25 CoSt TiO 2 C 5 ±1 4 ±2 1± 1 26 CoSt TiO 2 D 5 ±1 3 ±1 1± 1 27 CoSt TiO 2 G 5 ±1 5 ±1 1± 1 28 CoSt TiO 2 J 5 ±1 4 ±2 1± 1 29 CoSt TiO 2 B 5 ±1 6 ±2 1± 1 30 CoSt TiO 2 E 3 ±1 3 ±1 1± 1 31 CoSt TiO 2 E 5 ±1 3 ±1 1± 1 32 CoSt TiO 2 F 3 ±1 5 ±1 1± 1 33 CoSt TiO 2 Q 3 ±1 7 ±1 1± 1 CE-22 CoSt TiO 2 M > 12 N/A N/A CE-23 CoSt TiO 2 N > 12 N/A N/A CE-24 CoSt TiO 2 0 > 12 N/A N/A CE-25 CoSt TiO 2 P > 12 N/A N/A 34 MnSt TiO 2 KA 7 ±1 > 92 3± 1 35 MnSt TiO 2 AA 5 ±1 > 92 3± 1 41 WO 2013/023247 PCT/AU2012/000961 ** This TiO 2 has been surface reacted with a chlorosiloxane prior to incorporation into the final film formulation. 'TiO 2 /Surfactant E concentrate was prepared using a melt method without solvent. A Concentration 1.0 wt.% 5 Examples 1, 2, 6 to 8, 10, 18, 21 to 24, 26, 29, 32, 33, 36, 37 and Comparative Examples (CE) 1, 8, 9, 11, 13 Table 10 illustrates outdoor weathering data for films aged above-ground under photo oxidative conditions at Pinjarra Hills, Queensland. A significant acceleration in the time 10 to embrittlement was observed for films containing titania nanoparticles coated with a non-ionic surfactant compared with polyethylene containing TiO 2 compatibilised with Sigmacote*. A reduction in the photo-antagonism was observed between the metal oxide and transition metal salt in the presence of an alkoxylated ethylenically saturated non-ionic surfactant within the HLB range of 3 - 7, as well as a further acceleration in the 15 rate of embrittlement compared to the metal oxide or transition metal salt alone. Additionally, an acceleration in the rate of above-ground embrittlement was obtained for polyolefin films containing a combination of transition metal salt and an alkoxylated ethylenically saturated non-ionic surfactant, compared to transition metal salt alone. 20 Table 10. A demonstration of the significant acceleration in time to embrittlement above ground for formulations containing a metal oxide and/or transition metal salt and non-ionic surfactant under outdoor conditions at Pinjarra Hills, Queensland. 42 WO 2013/023247 PCT/AU2012/000961 Above Transition Metal Non-Ionic Ground Average Example Metal Salt Oxide Surfactant Total Solar Air T Radiation to (00) Emb. (W/m 2 ) CE-1 - - - 1772 22 CE-8 - TiO 2 ** - 346 19 1 - TiO 2 A 194 24 2 - TiO 2 K 194 24 6 - TiO 2 H 239 24 7 - TiO 2 1 239 24 8 - TiO 2 B 194 24 10 - TiO 2 D 285 24 36 - TiO 2 F 303 24 CE-9 CoSt - - 521 22 37 CoSt - A 407 18 CE-11 MnSt - - > 1260 16 18 MnSt - AA 638 17 CE-13 CoSt TiO 2 ** - 706 27 21 CoSt TiO 2 A 194 21-24 22 CoSt TiO 2 H 194 24 23 CoSt TiO 2 1 285 24 24 CoSt TiO 2 K 285 24 26 CoSt TiO 2 D 332 24 29 CoSt TiO 2 B 194 24 32 CoSt TiO 2 F 285 24 33 CoSt TiO 2 Q 363 16 ** This TiO 2 has been surface reacted with a chlorosiloxane prior to incorporation into the final film formulation. 5 A Concentration 1.0 wt.% Examples 21 to 22 and Comparative Examples (CE) 13 - Effect of UVC Pre treatment Table 11 demonstrates the significant acceleration in the below-ground degradation of 10 polyethylene film containing TiO 2 , CoSt and an alkoxylated ethylenically saturated non ionic surfactant pre-treated with 3000 J/m 2 UVC under outdoor weathering conditions at Pinjarra Hills, Queensland. 43 WO 2013/023247 PCT/AU2012/000961 Table 11 A demonstration of the significant acceleration in time to embrittlement below-ground for formulations containing cobalt (II) stearate, TiO 2 and alkoxylated ethylenically saturated non-ionic surfactant, pre-treated with UVC, followed by weathering under real outdoor conditions at Pinjarra Hills, 5 Queensland. 3000 No j/M2 UVC UVC Below- Below Transition Metal Non-Ionic Ground Ground Average Example Metal Salt Oxide Surfactant (Months (Months Air T to to (0C) Emb.) Emb.) CE-13 CoSt TiO 2 ** - > 6 < 4 27 21 CoSt TiO 2 A > 3 < 2 21-24 22 CoSt TiO 2 H > 3 < 1 21-24 ** This TiO 2 has been surface reacted with a chlorosiloxane prior to incorporation into the final film formulation. 10 44

Claims

1. A polyolefin composition comprising a metal-containing prodegradant selected from the group consisting of transition metal salts, photoactive metal oxide prodegradants and mixtures thereof and a non-ionic surfactant selected from alkoxylated ethylenically saturated compounds of HLB less than 12.

2. A polyolefin composition according to claim 1 where in the surfactant has an HLB of no more than 10.

3. A polyolefin composition according to claim 1 wherein the surfactant has an HLB of no more than 8.

4. A polyolefin composition according to claim 1 wherein the surfactant has an HLB in the range of from 3 to 7.

5. A polyolefin composition according to any of the previous claims where the surfactant contains at least one alkoxylate unit and at least one hydrocarbon chain with at least eight carbon atoms.

6. A polyolefin according to any one of the previous claims wherein the surfactant is selected from the group consisting of: alkoxylated ethylenically saturated alcohols; alkoxylated ethylenically saturated natural oils; saturated fatty acid esters of alkoxylated glycerol, hexitan, hexitol and isohexide; and saturated-polyester polyalkylene glycol copolymers.

7. A polyolefin composition according to any of the previous claims wherein the surfactant contains an ethylenically saturated carbon chain of from 8 to 40 carbon atoms.

8. A polyolefin composition according to claims 1-4 wherein the alkoxylated ethylenically saturated compound is of formula: R-CO-O-(AO)n-H or RO-(AO)n-H 45 WO 2013/023247 PCT/AU2012/000961 where R is saturated hydrocarbon of from 8 to 40 carbon atoms; A is a C2 to C4 alkylene, and n is from 1 to 9; and where n is selected so that HLB is less than 12.

9. A polyolefin composition according to any one of the previous claims wherein the non-ionic surfactant is of formula RO(AO)n-H wherein R is C8 to C26 alkyl, A is C2 to C4 alkylene and n is from 1 to 5.

10. A polyolefin composition according to any of the above claims where the alkoxylated compound comprises one or more alkoxylates selected from, propylene glycol, ethylene glycol and combinations thereof.

11. A polyolefin composition according to any of the above claims where the alkoxylated compound is an ethoxylated compound.

12. A polyolefin composition according to any one of the previous claims wherein the surfactant is an ethoxylated hydrogenated castor oil.

13. A polyolefin composition according to any one of the previous claims wherein the photoactive metal oxide is selected from the group consisting of photoactive nanoparticulate titanium oxide; transition metal salts selected from fatty acid salts of transition metals selected from the group consisting of iron, manganese, copper, cobalt, nickel, cerium and mixtures thereof; and mixtures of said photoactive nanoparticulate titanium oxide and transition metal salt.

14. A polyolefin composition according to any one of the previous claims wherein the non-ionic surfactant is present in an amount in the range of from 0.05% to 5% by weight based on the weight of the polyolefin.

15. A polyolefin composition according to any one of the previous claims wherein the photoactive metal oxide is nano-scaled TiO 2 present in an amount of from 0.05% to 10% by weight based on the weight of the polyolefin. 46 WO 2013/023247 PCT/AU2012/000961

16. A polyolefin composition according to any one of the previous claims the transition metal salt is present in an amount of from 0.05% to 5% percent by weight based on the weight of the polyolefin.

17. A polyolefin composition according to any one of the previous claims wherein the weight ratio between the photoactive metal oxide and the transition metal salt is from 10:1 to 1:10.

18. A polyolefin composition according to any one of the previous claims in the form of a film of thickness in the range of from 2 to 200 microns.

19. A polyolefin composition according to claim 18 wherein the film is stretched in one or more regions of the film to beyond the yield point of the film to achieve a reduced thickness in at least said stretched regions.

20. A polyolefin composition of claim 18 or claim 19 wherein the film is for use in agricultural film or in packaging.

21. A polyolefin composition according to any one of the previous claims wherein the composition is free of unhindered amines.

22. A method of controlling the rate of degradation of a polyolefin film used to cover or package a material comprising providing an area of polyolefin film according to any one of claims 18 or claim 19, subjecting at least portions of the film to irradiation from an artificial source of ultraviolet light in the UVC region of the spectrum and covering or packaging the material with the film. 47