EP2176322A1 - Degradable polymeric films - Google Patents

Abstract

A method of controlling the degradation of a polymeric film to cause the film to degrade after an intended useful life time includes providing a polymeric film comprising a polymer and prodegradant for the polymer adapted to be activated on irradiation with a controlled dosage of electromagnetic radiation, activating one or more sources of artificial radiation adapted to emit electromagnetic radiation and irradiating at least part of the polymeric film with the artificial radiation. The electromagnetic radiation comprises wavelengths less than about 400 nm. A system for predisposing a polymeric film containing a prodegradant to degrade after an intended service life includes one or more sources of artificial radiation and an irradiation controller, together with a film dispenser dispensing film into the irradiation zone.

Description

Degradable Polymeric Films

Field

The present invention relates to a method of controlling the degradation of a polymeric film to cause the film to degrade after an intended useful life time. The invention further relates to use of a prodegradant such as nano-scaled

TiO2 and/or a metal carboxylate and artificial UV to cause the film to degrade after an intended useful life time, and an apparatus for performing the same.

The invention also relates to a system for controlling degradation of a polymeric film containing a prodegradant which system involves an artificial source of electromagnetic radiation.

Background

Plastic articles find widespread applications in everyday life because of their durability in use and cost effectiveness. With proper stabilization, most commercial plastics are made to last for years.

In recent years, however, environmental concern has led to the development of so-called biodegradable materials, of diverse origin and nature, which will maintain their function and integrity during service life, but disintegrate after use into carbon dioxide and water, either triggered by chemical means or by microorganisms. One problem, however, is establishing a suitable equilibrium between biodegradability and integrity during service life.

Compostable thermoplastic compositions are described in e.g. US-A- 5,258,422.

Degradable synthetic polymeric compounds are disclosed in e.g. US-A- 5,352,716.

Polyolefin compositions and degradable films made therefrom are disclosed in e.g. US-A-3,454,510. Degradable/compostable concentrates, process for making degradable/compostable packaging materials and the products thereof are described in e.g. US-A-5,854,304.

Chemically degradable polyolefin films are disclosed in e.g. US-A-5,565,503.

On the other hand photodegradable polyolefin compositions are described in e.g. JP-A-Sho 50-34,045.

The use of photosensitizing additives to enhance photo-degradability takes advantage of the natural tendency of most organic polymers to undergo gradual reaction with atmospheric oxygen, particularly in the presence of light. The photosensitizing additive absorbs ultraviolet light (e.g., from sunlight); the additive, in the resulting photo-excited state, undergoes a chemical reaction that leads to the generation of free radicals, which initiate an autoxidation process thereby leading to the eventual disintegration of the plastic material.

However, there are some difficulties with the use of degradable plastic films of the aforementioned kind in that the time to embrittlement is governed by the loading of the photosensitizing additive, making it necessary to produce multiple films of different formulations in order to obtain a balance between the desired life time and the time until complete breakdown of the plastic film occurs. Further, these films are essentially non-degradable in the dark.

Summary

One objective of the present invention is to provide a polymer film, which will degrade when desired, and at desired rates, depending on the end application- both in the light and in the dark. Such a film is useful, for example, in packaging applications and for temporary covers such as ground covers for agricultural applications. For example, under such films crops or other plants may grow. 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 degradation of the film. It may be 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 positioned over the crops and plants or buried in soil. This radiation treatment may be the only treatment after manufacture, or may follow an earlier pretreatment at the time of manufacture. The radiation dosage is used to control the rate of degradation of the film.

The current invention provides a method and system for providing control over the start of degradation, the extent and timing of degradation and moreover, the areas where degradation is to occur, including those sections of film placed in the dark, for example under the soil or in landfill. The invention is particularly useful for very thin (between 3 and 10 micron), polyolefin films, particularly pre- stretched polyolefin films. The use of such films provides significant cost benefits through material savings, while the physical properties of the films are such that they are sufficiently tough to withstand the demands of the envisaged applications.

It is the combination of prodegradants and a controlled source artificial radiation delivering doses of radiation as required during use to initiate more rapid degradation in these thin films that provides the key advantage of this technique.

A further advantage is the use of synergistic additive combinations, which can lead to an increased rate of thermal aging and control of whitening under sunlight exposure. For example, by the addition of hydrocarbon additives, films containing prodegradants that typically cause whitening on aging in the sun remain transparent for an extended period of time. This may be sufficient to enable practical use in, for example, horticultural applications wherein plants require good light transmittance. However, it should be noted that in some - A -

circumstances, whitening may be a beneficial effect that would be of particular value, such as for weed suppression and/or light reflection/heat reduction as the plant ages when the film is used as a mulch film, so that a particular advantage is that whitening control is optional. Further combinations of prodegradants that operate by different mechanisms (e.g. metal stearates in combination with, for example, titania or metal-doped transition metal oxides, for example, iron-doped titania) often demonstrate a greatly enhanced rate of carbonyl formation upon thermal aging in the dark, as compared to films containing the prodegradant system alone. Amphiphilic additives may also potentially accelerate the rate of thermal oxidation.

The invention provides a method of controlling the degradation of a polymeric film to cause the film to degrade after an intended useful life time, including the steps of: providing a polymeric film comprising a polymer and prodegradant for the polymer adapted to be activated on irradiation with a controlled dosage of electromagnetic radiation; and activating one or more sources of artificial radiation adapted to emit electromagnetic radiation comprising wavelengths less than about 400 nm; and irradiating at least part of the polymeric film with the artificial radiation.

The one or more sources of artificial radiation may irradiate one or both sides of the polymeric film. Preferably, the electromagnetic radiation comprises UV light in the range 250 nm to 385 nm.

In a preferred embodiment the invention provides a method of controlling the degradation of a polymeric film used to package or cover a material and the method further comprises the step of wrapping or covering the material with the irradiated film.

There is further provided a system for predisposing a polymeric film containing a prodegradant to degrade after an intended service life, the system including: one or more sources of artificial radiation adapted to emit electromagnetic radiation comprising wavelengths less than about 400 nm; an irradiation zone configured to receive at least part of the polymeric film for exposure to radiation; an irradiation controller configured to provide a control signal for controlling operation of the one or more sources of artificial radiation to emit a radiation dosage to predispose the polymeric film to degrade after the intended service life; and a film dispenser dispensing polymeric film into the irradiation zone.

Preferably, the radiation dosage is determined automatically by the controller, based on inputs provided by a user of the system.

Brief Description of the Drawings

Embodiments of the invention will now be described with reference to the accompanying drawings. It is to be understood that the description which follows is provided for the purpose of explaining the features and operation of particular embodiments of the invention. It is not to be taken as limiting the scope of the invention as defined in the claims appended hereto.

Fig 1 is a flow diagram representing steps of a method according to an embodiment of the invention.

Fig 2 is a flow diagram representing steps of a method according to another embodiment of the invention. Fig 3 is a block diagram representing aspects of an irradiation controller according to an embodiment of the invention.

Fig 4a is a schematic drawing showing features of irradiation apparatus for use with an embodiment of the invention. Fig 4b shows examples of masks for use with embodiments of the invention. Fig 5 is a schematic drawing of irradiation apparatus adapted for irradiating a length of polymeric film on a spool.

Fig 6a is a side schematic representation of irradiation apparatus according to another embodiment of the invention. Fig 6b is a top schematic representation of the irradiation apparatus of Fig 6a in which the radiation sources are positioned to deliver radiation to edge strips of the film.

Fig 7 is a side schematic representation of alternate irradiation apparatus.

Fig 8 is a side schematic representation of alternate irradiation apparatus for irradiating polymeric film prior to use for wrapping rolled newspaper.

Figs 9a and 9b show the effect of exposure to UV-C radiation on mechanical properties of two films. In Fig 9a the effect is shown for film containing Degussa Aeroxide P25; in Fig 9b the effect is shown for film containing no prodegradant. Fig 10 is a graph showing the effect of 254 nm pre-irradiation followed by thermal aging (50 ⁰C) on carbonyl index of oleic acid-coated titania nanorod- containing films (Example 2).

Fig 11 is a graph showing the effect of 254 nm pre-irradiation followed by thermal aging (50 ⁰C) on carbonyl index of nanotitania-containing films (sample D).

Fig 12 is a graph showing the effect of UV-A (340 nm) pre-irradiation followed by thermal aging (50 ⁰C) on carbonyl index of nanotitania-containing films (sample D).

Fig 13 is a graph showing the effect of 254 nm pre-irradiation on carbonyl index during thermal aging of sample E from Example 4.

Fig 14 is a graph showing the effect of 254 nm pre-irradiation followed by thermal aging on carbonyl index growth of sample F (Example 5).

Fig 15 is a graph showing the effect of 254 nm pre-irradiation followed by thermal aging on carbonyl index of sample G (Example 6). Fig 16 is a graph showing the effect of 254 nm pre-irradiation followed by thermal aging (50 ⁰C) on carbonyl index growth of sample H (Example 7).

Fig 17 is a graph showing the effect of 254 nm pre-irradiation on carbonyl index of sample I during thermal aging at 50 ⁰C (Example 8).

Fig 18 is a graph showing the effect of 254 nm pre-irradiation on carbonyl index during Suntest aging of sample J (Example 9). Fig 19 is a graph showing the effect of 254 nm pre-irradiation on carbonyl index during thermal aging (60 ⁰C) of sample K (where values presented are the average of duplicate experiments). (Example 10).

Fig 20 is a graph showing the effect of 254 nm pre-irradiation on carbonyl index during Suntest aging of sample N and reference sample O (Example 12).

Fig 21 is a graph showing the effect of 254 nm pre-irradiation on carbonyl index during oven aging (60 ⁰C) of sample P (data presented are the average of duplicate experiments). (Example 13). Fig 22 is a graph showing the effect of 254 nm pre-irradiation on rate of carbonyl growth during Suntest aging of sample Q (Example 14).

Detailed Description

In a preferred embodiment the polymeric film is a polyolefin film. 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, 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 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 different, and especially by the following, methods:

a) radical polymerisation (normally under high pressure and at elevated temperature). 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 either π- or σ-coordinated. These metal complexes may be in the free form or fixed on substrates, typically on activated magnesium chloride, titanium(lll) chloride, alumina or silicon oxide. These catalysts may be soluble or insoluble in the polymerisation medium. The catalysts can be used by 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 Ia, Ma and/or Ilia of the Periodic Table. The activators may be modified conveniently with further ester, ether, amine or silyl ether groups. These catalyst systems are usually 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 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 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, 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, ethyl en e/a Iky I methacrylate copolymers, ethylene/vinyl acetate copolymers or 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 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 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.

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 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.

In a particularly preferred embodiment of the invention the prodegradant comprises TiO2 TiO2 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. 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.

Photoactive metal oxide particles may be prepared via a process selected from the group selected from the sol-gel process, hydrothermal methods, solvo- thermal methods, emulsion process and chemical precipitation. In the preferred embodiment, the sol-gel process is utilized and involves hydrolysis and polycondensation of metal alkoxides or salts and can be carried out either in aqueous or non-aqueous media to produce metal oxides with desired particle size, structure and morphology.

The photoactive metal oxide may also be produced by modification of metal alkoxides to produce clusters. For example, the modification of titanium alkoxide by reaction with acetic acid results in the formation of a molecular titanium oxo-alkoxide cluster of the following formula - Ti₆(μ₃-O)₂(μ₂- O)₂(CH₃COO)₈^-OiPr)₂(OiPr)₆ (abbreviated as [Ti₆O₄]). These hexanuclear compounds of titanium are small-size clusters (the number of atoms is approximately 150 and the diameter approx 30 A). Their structure determines to some degree the morphology of the end product.

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 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 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.

As a further option, photoactive titania in the form of nanostructured silica/titania composites, or other inert carrier-semiconductor particulate systems with controlled morphology, may offer advantages. One specific preferred embodiment concerns the size and distribution of the titania domains in or on a silica (inert carrier) matrix, such that by reducing the size of the titania domains to the level of so-called quantum dots, the absorption band edge will occur at wavelengths shorter than is provided by terrestrial solar radiation, thus increasing the stability on exposure to normal sunlight. Furthermore, by maintaining separation between the titania nanoparticles through fixation on the silica plate, thus confining the particles and preventing agglomeration, the quantum efficiency may be increased while also maintaining transparency to visible radiation.

The terms titanium dioxide and titania are used as synonyms in the context of the 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 titanium dioxide also may have been surface modified, for example to improve the contact between the metal oxide and the polymer matrix. These additives may be covalently bound to the titania surface, or they may be associated with the prodegradant by a mechanism other than direct covalent linkage. These materials may be bound to the prodegradant prior to masterbatch preparation and/or film extrusion; alternatively, they may be added during processing in such a way that mixing in the melt provides sufficient contact between the prodegradant and the additive to allow for an interaction between the two. Additives such as hydrophobic materials containing binding sites, or others that enable the titania surface to be altered in such a way as to modify the interface between the prodegradant and the polymeric matrix. In particular this modification could consist of chemical coupling of the surface functional groups of titania to compounds having end- groups that are able to react with these functional groups: for example, alkoxysilanes like Y-glycidoxypropyltrimethoxysilane, n-hexylthmethoxysilane, isobutyltrimethoxysilane, Y-methacryloxypropylthmethoxysilane, n- octadecyltrimethoxysilane, and n-propylthmethoxysilane dicyclohexyldimethoxysilane, diethyldiethoxysilane, dimethyldichlorosilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, diphenyldimethoxysilane, di-n-hexyldichlorosilane, n- hexylmethyldichlorosilane, methyldodecyldiethoxysilane, neophylmethyldimethoxysilane, and n-octylmethyldimethoxysilane; and n- octadecyldimethylmethoxysilane, triethylsilanol, thmethylethoxysilane, and thmethylmethoxysilane; or halosilanes, such as Sigmacote (a commercially available chlorinated organopolysiloxane solution in heptane, available from Sigma-Aldhch); or fatty acids, such as oleic acid, stearic acid, linoleic acid, linolenic acid; or phosphine derivatives such as trioctyl phosphine and or surfactant materials, such as sodium dodecylbenzenesulfonate (DBS); and more particular oleic acid, octadecyltrimethoxysilane, Sigmacote, trioctyl phosphine and sodium dodecylbenzenesulfonate.

Amphiphilic materials including block copolymers and other surfactants, either with functional end groups or as components of the composition, may also be envisaged as additives to modify the interaction between titania and the polymeric matrix. Examples would include lrgasurf HL 560 (a commercial product from Ciba), Efka-4300 (a commercial high molecular-weight dispersing agent from Ciba), Efka 5207 (a commercial wetting and dispersing agent from Ciba), and organic acids, in particular oleic acid, polyethylene-co-acrylic acid and Efka 5207.

In a preferred embodiment the titanium dioxide is surface modified as described above.

Suitable examples of metal carboxylate prodegradant include metal salts of a fatty acids with a carbon number ranging from C2 to C36, in particular from C12 to C₃₆ is preferred. Particularly preferred examples are metal carboxylates of palmitic acid (Ci₆), stearic acid (Ci₈), oleic acid (Ci₈), linoleic acid (Ci₈), linolenic acid (Ci₈) and naphthenic acid. As C₂-C₃6carboxylate, in particular stearate, palmitate or naphthenate, of Fe, Ce, Co, Mn or Ni are of particular interest. Particularly preferred is Fe-stearate. It is, however, also possible to use mixtures of the afore-mentioned metal carboxylates.

The nano-scaled titanium dioxide and the metal carboxylates are items of commerce and may be used in their various commercial grades.

The nano-scaled TiO₂ is typically present in an amount of from 0.1 to 20% by weight, preferably 0.2 to 10% percent by weight and most preferably from 0.5 to 3% by weight based on the weight of the polyolefin.

The metal carboxylate is typically present in an amount of from 0.1 to 20% by weight, preferably 0.2 to 10% percent by weight and most preferably from 0.5 to 3% by weight based on the weight of the polyolefin.

For example the weight ratio between the nano-scaled TiO₂ and the metal carboxylate is from 20:1 to 1 :20.

The titanium dioxide useful in accordance with the present invention has a particle size such that the largest dimension of the particle is less than 200 nm, preferably from 1 nm to 100 nm, most preferably from 1 nm to 30 nm.

In a preferred embodiment the prodegradant is activated by UV-radiation. Other possibilities may be by corona treatment or 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 production facility, or immediately before its end use, for example as an agricultural cover film such as a 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 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 in use are uncontrolled and occur either upon solar 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 when neutralized allows degradation to occur by the usual mechanisms.

The total radiation necessary to produce the desired effect depends on the concentration of prodegradant(s), the intensity of the radiation, the exposure time (i.e. total dose delivered) and the wavelengths of the incident radiation that may be absorbed by the film and prodegradant(s). This may be determined empirically on a case-by-case basis.

The wavelength range of terrestrial UV radiation is accepted to be -295 to 385 nm. Further, the maximum UV dose rate in areas receiving high intensity sunlight, such as Spain (at noon in June), is typically 45 VWm². In contrast, the present invention delivers radiation at dose rates which are greater than that which can be practically achieved with direct exposure to sunlight, e.g. an artificially high dose rate of up to approximately 15,000 WIm². Preferably the radiation is UV-light between 200 nm and 400 nm and more preferably between 200 nm and 385 nm.

In one embodiment of this invention, the wavelength of 90% of the emitted energy of the artificial sources of radiation is approximately 254 nm (i.e. a non- terrestrial wavelength) and the preferred dose rate is at least 50 VWm². In a preferred embodiment of the invention at least 80% of the irradiation dosage energy is emitted in the range 200 nm to 400 nm and the preferred dose rate is at least 100 VWm², such as at least 500 VWm², at least 1000 VWm² and at least 7,500 VWm².

The duration of irradiation is sufficient to induce the desired degradation rate and is preferably short, in the order of seconds or minutes. Prolonged exposure to UV radiation can be detrimental to the polymer. For example, Figure 9 shows the effects of prolonged exposure to UV-C pre-irradiation on the mechanical properties (tensile strain at break) on two sample polyolefin films, one containing TiO2 and one without. Figure 1 clearly shows that exposure to UV-C radiation for >1 hour (to a total dose of 0.17 MJ/m²) results in a significant drop in tensile strength.

Figs 9a and 9b show the effect of exposure to UV-C radiation on mechanical properties of two films. In Fig 9a the effect is shown for film containing Degussa Aeroxide P25; In Fig 9b the effect is shown for film containing no prodegradant. TD refers to the transverse direction and MD the machine direction with respect to blowing and/or orienting the film by post-fabrication stretching. There may be further additives added, which are selected from the group consisting of antioxidants, light stabilizers, processing stabilizers, clarifiers, antistatic and antifogging agents.

In a specific embodiment of the invention oils or waxes are added additionally, having a refractive index matching that of the polymer.

Examples for suitable additional additives are given below.

1. Antioxidants

1.1. Alkylated monophenols, for example 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl- 4,6-dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di-tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-isobutylphenol, 2,6-dicyclopentyl-4-methylphenol, 2-(α- methylcyclohexyl)-4,6-dimethylphenol, 2,6-dioctadecyl-4-methylphenol, 2,4,6- tricyclohexylphenol, 2,6-di-tert-butyl-4-methoxymethylphenol, nonylphenols which are linear or branched in the side chains, for example, 2,6-di-nonyl-4-methylphenol, 2,4- dimethyl-6-(1 '-methylundec-1 '-yl)phenol, 2,4-dimethyl-6-(1 '-methylheptadec-1 '- yl)phenol, 2,4-dimethyl-6-(1 '-methyltridec-1 '-yl)phenol and mixtures thereof.

1.2. Alkylthiomethylphenols, for example 2,4-dioctylthiomethyl-6-tert-butylphenol, 2,4- dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-di- dodecylthiomethyl-4-nonylphenol.

1.3. Hvdroquinones and alkylated hydroquinones, for example 2, 6-d i-tert-butyl-4- methoxyphenol, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, 2,6- diphenyl-4-octadecyloxyphenol, 2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4- hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenyl stearate, bis(3,5-di-tert-butyl-4-hydroxyphenyl) adipate.

1.4. Tocopherols, for example α-tocopherol, β-tocopherol, γ-tocopherol, δ-tocopherol and mixtures thereof (vitamin E).

1.5. Hydroxylated thiodiphenyl ethers, for example 2,2'-thiobis(6-tert-butyl-4- methylphenol), 2,2'-thiobis(4-octylphenol), 4,4'-thiobis(6-tert-butyl-3-methylphenol), 4,4'-thiobis(6-tert-butyl-2-methylphenol), 4,4'-thiobis(3,6-di-sec-amylphenol), 4,4'- bis(2,6-dimethyl-4-hydroxyphenyl)disulfide.

1.6. Alkylidenebisphenols, for example 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), 2,2'-methylenebis[4-methyl-6-(α- methylcyclohexyl)phenol], 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'- methylenebis(6-nonyl-4-methylphenol), 2,2'-methylenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(4,6-di-tert-butylphenol), 2,2'-ethylidenebis(6-tert-butyl-4- isobutylphenol), 2,2'-methylenebis[6-(α-methylbenzyl)-4-nonylphenol], 2,2'- methylenebis[6-(α,α-dimethylbenzyl)-4-nonylphenol], 4,4'-methylenebis(2,6-di-tert- butylphenol), 4,4'-methylenebis(6-tert-butyl-2-methylphenol), 1 , 1 -bis(5-tert-butyl-4- hydroxy-2-methylphenyl)butane, 2,6-bis(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4- methylphenol, 1 ,1 ,3-tris(5-tert-butyl-4-hydroxy-2-methylphenyl)butane, 1 ,1-bis(5-tert- butyl-4-hydroxy-2-methyl-phenyl)-3-n-dodecylmercaptobutane, ethylene glycol bis[3,3- bis(3'-tert-butyl-4'-hydroxyphenyl)butyrate], bis(3-tert-butyl-4-hydroxy-5-methyl- phenyl)dicyclopentadiene, bis[2-(3'-tert-butyl-2'-hydroxy-5'-methylbenzyl)-6-tert-butyl- 4-methylphenyl]terephthalate, 1 ,1-bis-(3,5-dimethyl-2-hydroxyphenyl)butane, 2,2- bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane, 2,2-bis(5-tert-butyl-4-hydroxy2- methylphenyl)-4-n-dodecylmercaptobutane, 1 , 1 ,5,5-tetra-(5-tert-butyl-4-hydroxy-2- methylphenyl)pentane.

1.7. Q-, N- and S-benzyl compounds, for example 3,5,3',5'-tetra-tert-butyl-4,4'- dihydroxydibenzyl ether, octadecyl-4-hydroxy-3,5-dimethylbenzylmercaptoacetate, tridecyl-4-hydroxy-3,5-di-tert-butylbenzylmercaptoacetate, tris(3,5-di-tert-butyl-4- hydroxybenzyl)amine, bis(4-tert-butyl-3-hydroxy-2,6- dimethylbenzyl)dithioterephthalate, bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide, isooctyl-S^-di-tert-butyM-hydroxybenzylmercaptoacetate.

1.8. Hydroxybenzylated malonates, for example dioctadecyl-2,2-bis(3,5-di-tert-butyl-2- hydroxybenzyl)malonate, di-octadecyl-2-(3-tert-butyl-4-hydroxy-5- methylbenzyl)malonate, di-dodecylmercaptoethyl-2,2-bis (3,5-di-tert-butyl-4- hydroxybenzyl)malonate, bis[4-(1 , 1 ,3,3-tetramethylbutyl)phenyl]-2,2-bis(3,5-di-tert- butyl-4-hydroxybenzyl)malonate.

1.9. Aromatic hydroxybenzyl compounds, for example 1 ,3,5-tris(3,5-di-tert-butyl-4- hydroxybenzyl)-2,4,6-trimethylbenzene, 1 ,4-bis(3,5-di-tert-butyl-4-hydroxybenzyl)- 2,3,5,6-tetramethylbenzene, 2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)phenol.

1.10. Triazine compounds, for example 2,4-bis(octylmercapto)-6-(3,5-di-tert-butyl-4- hydroxyanilino)-1 ,3,5-triazine, 2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4- hydroxyanilino)-1 ,3,5-triazine, 2-octylmercapto-4,6-bis(3,5-di-tert-butyl-4- hydroxyphenoxy)-1 ,3,5-triazine, 2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenoxy)-1 ,2,3- triazine, 1 ,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 1 ,3,5-tris(4-tert- butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, 2,4,6-tris(3,5-di-tert-butyl-4- hydroxyphenylethyl)-1 ,3,5-triazine, 1 ,3,5-tris(3,5-di-tert-butyl-4-hydroxy- phenylpropionyl)-hexahydro-1 ,3,5-triazine, 1 ,3,5-tris(3,5-dicyclohexyl-4- hydroxybenzyl)isocyanurate. 1.1 1. Benzylphosphonates, for example dimethyl-2,5-di-tert-butyl-4- hydroxybenzylphosphonate, diethyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate, dioctadecyl3,5-di-tert-butyl-4-hydroxybenzylphosphonate, dioctadecyl-5-tert-butyl-4- hydroxy-3-methylbenzylphosphonate, the calcium salt of the monoethyl ester of 3,5- di-tert-butyl-4-hydroxybenzylphosphonic acid.

1.12. Acylaminophenols, for example 4-hydroxylauranilide, 4-hydroxystearanilide, octyl N-(3,5-di-tert-butyl-4-hydroxyphenyl)carbamate.

1.13. Esters of β-(3,5-di-tert-butyl-4-hvdroxyphenyl)propionic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, n-octanol, i-octanol, octadecanol, 1 ,6-hexanediol, 1 ,9-nonanediol, ethylene glycol, 1 ,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N'-bis(hydroxyethyl)oxamide, 3-thiaundecanol, 3- thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1- phospha-2,6,7-trioxabicyclo[2.2.2]octane.

1.14. Esters of β-(5-tert-butyl-4-hvdroxy-3-methylphenyl)propionic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, n-octanol, i-octanol, octadecanol, 1 ,6-hexanediol, 1 ,9-nonanediol, ethylene glycol, 1 ,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N'-bis(hydroxyethyl)oxamide, 3-thiaundecanol, 3- thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1- phospha-2,6,7-trioxabicyclo[2.2.2]octane; 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5- methylphenyl)propionyloxy}-1 ,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

1.15. Esters of β-(3,5-dicvclohexyl-4-hvdroxyphenyl)propionic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, octanol, octadecanol, 1 ,6-hexanediol, 1 ,9-nonanediol, ethylene glycol, 1 ,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N'-bis(hydroxyethyl)oxamide, 3-thiaundecanol, 3- thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1- phospha-2,6,7-trioxabicyclo[2.2.2]octane. 1.16. Esters of 3,5-di-tert-butyl-4-hvdroxyphenyl acetic acid with mono- or polyhydric alcohols, e.g. with methanol, ethanol, octanol, octadecanol, 1 ,6-hexanediol, 1 ,9- nonanediol, ethylene glycol, 1 ,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris(hydroxyethyl)isocyanurate, N,N'-bis(hydroxyethyl)oxamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-1 -phospha-2,6,7- trioxabicyclo[2.2.2]octane.

1.17. Amides of β-(3,5-di-tert-butyl-4-hvdroxyphenyl)propionic acid e.g. N,N'-bis(3,5- di-tert-butyl-4-hydroxyphenylpropionyl)hexamethylenediamide, N,N'-bis(3,5-di-tert- butyl-4-hydroxyphenylpropionyl)trimethylenediamide, N,N'-bis(3,5-di-tert-butyl-4- hydroxyphenylpropionyl)hydrazide, N,N'-bis[2-(3-[3,5-di-tert-butyl-4- hydroxyphenyl]propionyloxy)ethyl]oxamide (Naugard^®XL-1 , supplied by Uniroyal).

1.18. Ascorbic acid (vitamin C)

1.19. Aminic antioxidants, for example N,N'-di-isopropyl-p-phenylenediamine, N,N'-di- sec-butyl-p-phenylenediamine, N,N'-bis(1 ,4-dimethylpentyl)-p-phenylenediamine,

N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p- phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine, N,N'-diphenyl-p- phenylenediamine, N,N'-bis(2-naphthyl)-p-phenylenediamine, N-isopropyl-N'-phenyl- p-phenylenediamine, N-(1 ,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-(1- methylheptyl)-N'-phenyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p- phenylenediamine, 4-(p-toluenesulfamoyl)diphenylamine, N,N'-dimethyl-N,N'-di-sec- butyl-p-phenylenediamine, diphenylamine, N-allyldiphenylamine, 4- isopropoxydiphenylamine, N-phenyl-1-naphthylamine, N-(4-tert-octylphenyl)-1- naphthylamine, N-phenyl-2-naphthylamine, octylated diphenylamine, for example p,p'- di-tert-octyldiphenylamine, 4-n-butylaminophenol, 4-butyrylaminophenol, 4- nonanoylaminophenol, 4-dodecanoylaminophenol, 4-octadecanoylaminophenol, bis(4-methoxyphenyl)amine, 2,6-di-tert-butyl-4-dimethylaminomethylphenol, 2,4'- diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, N,N,N',N'-tetramethyl-4,4'- diaminodiphenylmethane, 1 ,2-bis[(2-methylphenyl)amino]ethane, 1 ,2-bis(phenyl- amino)propane, (o-tolyl)biguanide, bis[4-(1',3'-dimethylbutyl)phenyl]amine, tert- octylated N-phenyl-1-naphthylamine, a mixture of mono- and dialkylated tert-butyl/tert- octyldiphenylamines, a mixture of mono- and dialkylated nonyldiphenylamines, a mixture of mono- and dialkylated dodecyldiphenylamines, a mixture of mono- and dialkylated isopropyl/isohexyldiphenylamines, a mixture of mono- and dialkylated tert- butyldiphenylamines, 2,3-dihydro-3,3-dimethyl-4H-1 ,4-benzothiazine, phenothiazine, a mixture of mono- and dialkylated tert-butyl/tert-octylphenothiazines, a mixture of mono- and dialkylated tert-octyl-phenothiazines, N-allylphenothiazine, N, N₁N', N'- tetraphenyl-1 ,4-diaminobut-2-ene.

2. UV absorbers and light stabilizers

2.1. 2-(2'-Hvdroxyphenyl)benzotriazoles, for example 2-(2'-hydroxy-5'-methylphenyl)- benzotriazole, 2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(5'-tert-butyl-2'- hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-(1 ,1 ,3,3- tetramethylbutyl)phenyl)benzotriazole, 2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)-5-chloro- benzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-methylphenyl)-5-chloro-benzotriazole, 2- (3'-sec-butyl-5'-tert-butyl-2'-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-4'- octyloxyphenyl)benzotriazole, 2-(3',5'-di-tert-amyl-2'-hydroxyphenyl)benzotriazole, 2- (3',5'-bis-(α,α-dimethylbenzyl)-2'-hydroxyphenyl)benzotriazole, 2-(3'-tert-butyl-2'- hydroxy-5'-(2-octyloxycarbonylethyl)phenyl)-5-chloro-benzotriazole, 2-(3'-tert-butyl-5'- [2-(2-ethylhexyloxy)-carbonylethyl]-2'-hydroxyphenyl)-5-chloro-benzotriazole, 2-(3'- tert-butyl-2'-hydroxy-5'-(2-methoxycarbonylethyl)phenyl)-5-chloro-benzotriazole, 2-(3'- tert-butyl-2'-hydroxy-5'-(2-methoxycarbonylethyl)phenyl)benzotriazole, 2-(3'-tert-butyl- 2'-hydroxy-5'-(2-octyloxycarbonylethyl)phenyl)benzotriazole, 2-(3'-tert-butyl-5'-[2-(2- ethylhexyloxy)carbonylethyl]-2'-hydroxyphenyl)benzotriazole, 2-(3'-dodecyl-2'- hydroxy-5'-methylphenyl)benzotriazole, 2-(3'-tert-butyl-2'-hydroxy-5'-(2- isooctyloxycarbonylethyl)phenylbenzotriazole, 2,2'-methylene-bis[4-(1 , 1 ,3,3- tetramethylbutyl)-6-benzotriazole-2-ylphenol]; the transesterification product of 2-[3'- tert-butyl-5'-(2-methoxycarbonylethyl)-2'-hydroxyphenyl]-2H-benzotriazole with

polyethylene glycol 300; ^l h , where R = 3'-tert-butyl-4'- hydroxy-5'-2H-benzotriazol-2-ylphenyl, 2-[2'-hydroxy-3'-(α,α-dimethylbenzyl)-5'-

(1 ,1 ,3,3-tetramethylbutyl)-phenyl]benzotriazole; 2-[2'-hydroxy-3'-(1 , 1 ,3,3- tetramethylbutyl)-5'-(α,α-dimethylbenzyl)-phenyl]benzotriazole.

2.2. 2-Hvdroxybenzophenones, for example the 4-hydroxy, 4-methoxy, 4-octyloxy, 4- decyloxy, 4-dodecyloxy, 4-benzyloxy, 4,2',4'-trihydroxy and 2'-hydroxy-4,4'-dimethoxy derivatives. 2.3. Esters of substituted and unsubstituted benzoic acids, for example 4-tert-butyl- phenyl salicylate, phenyl salicylate, octylphenyl salicylate, dibenzoyl resorcinol, bis(4- tert-butylbenzoyl)resorcinol, benzoyl resorcinol, 2,4-di-tert-butylphenyl 3,5-di-tert- butyl-4-hydroxybenzoate, hexadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, octadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, 2-methyl-4,6-di-tert-butylphenyl 3,5-di-tert-butyl- 4-hydroxybenzoate.

2.4. Acrylates, for example ethyl α-cyano-β,β-diphenylacrylate, isooctyl α-cyano-β,β- diphenylacrylate, methyl α-carbomethoxycinnamate, methyl α-cyano-β-methyl-p- methoxycinnamate, butyl α-cyano-β-methyl-p-methoxy-cinnamate, methyl α- carbomethoxy-p-methoxycinnamate, N-(β-carbomethoxy-β-cyanovinyl)-2- methylindoline, neopentyl tetra(α-cyano-β,β-diphenylacrylate.

2.5. Nickel compounds, for example nickel complexes of 2,2'-thio-bis[4-(1 ,1 ,3,3- tetramethylbutyl)phenol], such as the 1 :1 or 1 :2 complex, with or without additional ligands such as n-butylamine, triethanolamine or N-cyclohexyldiethanolamine, nickel dibutyldithiocarbamate, nickel salts of the monoalkyl esters, e.g. the methyl or ethyl ester, of 4-hydroxy-3,5-di-tert-butylbenzylphosphonic acid, nickel complexes of ketoximes, e.g. of 2-hydroxy-4-methylphenylundecylketoxime, nickel complexes of 1- phenyl-4-lauroyl-5-hydroxypyrazole, with or without additional ligands.

2.6. Stericallv hindered amines, for example bis(2,2,6,6-tetramethyl-4- piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)succinate, bis(1 ,2,2,6,6- pentamethyl-4-piperidyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethyl-4- piperidyl)sebacate, bis(1 ,2,2,6,6-pentamethyl-4-piperidyl) n-butyl-3,5-di-tert-butyl-4- hydroxybenzylmalonate, the condensate of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4- hydroxypiperidine and succinic acid, linear or cyclic condensates of N,N'-bis(2,2,6,6- tetramethyl-4-piperidyl)hexamethylenediamine and 4-tert-octylamino-2,6-dichloro- 1 ,3,5-triazine, tris(2,2,6,6-tetramethyl-4-piperidyl)nitrilotriacetate, tetrakis(2,2,6,6-tetra- methyl-4-piperidyl)-1 ,2,3,4-butanetetracarboxylate, 1 , 1 '-(1 ,2-ethanediyl)-bis(3, 3,5,5- tetramethylpiperazinone), 4-benzoyl-2,2,6,6-tetramethylpiperidine, 4-stearyloxy- 2,2,6,6-tetramethylpiperidine, bis(1 , 2,2,6, 6-pentamethylpiperidyl)-2-n-butyl-2-(2- hydroxy-3,5-di-tert-butylbenzyl)malonate, 3-n-octyl-7,7,9,9-tetramethyl-1 ,3,8- triazaspiro[4.5]decane-2,4-dione, bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)sebacate, bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl)succinate, linear or cyclic condensates of N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and 4-morpholino-2,6- dichloro-1 ,3,5-triazine, the condensate of 2-chloro-4,6-bis(4-n-butylamino-2,2,6,6- tetramethylpiperidyl)-1 ,3,5-triazine and 1 ,2-bis(3-aminopropylamino)ethane, the condensate of 2-chloro-4,6-di-(4-n-butylamino-1 ,2,2,6,6-pentamethylpiperidyl)-1 ,3,5- triazine and 1 ,2-bis(3-aminopropylamino)ethane, 8-acetyl-3-dodecyl-7,7,9,9-tetrame- thyl-1 ,3,8-triazaspiro[4.5]decane-2,4-dione, 3-dodecyl-1 -(2,2,6,6-tetramethyl-4- piperidyl)pyrrolidine-2,5-dione, 3-dodecyl-1 -(1 , 2,2,6, 6-pentamethyl-4- piperidyl)pyrrolidine-2,5-dione, a mixture of 4-hexadecyloxy- and 4-stearyloxy-2, 2,6,6- tetramethylpiperidine, a condensate of N,N'-bis(2,2,6,6-tetramethyl-4- piperidyl)hexamethylenediamine and 4-cyclohexylamino-2,6-dichloro-1 ,3,5-triazine, a condensate of 1 ,2-bis(3-aminopropylamino)ethane and 2,4,6-trichloro-1 ,3,5-triazine as well as 4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No. [136504-96-6]); a condensate of 1 ,6-hexanediamine and 2,4,6-trichloro-1 ,3,5-triazine as well as N, N- dibutylamine and 4-butylamino-2,2,6,6-tetramethylpiperidine (CAS Reg. No. [192268- 64-7]); N-(2,2,6,6-tetramethyl-4-piperidyl)-n-dodecylsuccinimide, N-(1 , 2,2,6,6- pentamethyl-4-piperidyl)-n-dodecylsuccinimide, 2-undecyl-7,7,9,9-tetramethyl-1-oxa- 3,8-diaza-4-oxo-spiro[4,5]decane, a reaction product of 7,7,9,9-tetramethyl-2- cycloundecyl-1-oxa-3,8-diaza-4-oxospiro-[4,5]decane and epichlorohydrin, 1 ,1- bis(1 ,2,2,6,6-pentamethyl-4-piperidyloxycarbonyl)-2-(4-methoxyphenyl)ethene, N, N'- bis-formyl-N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine, a diester of 4-methoxymethylenemalonic acid with 1 ,2,2,6,6-pentamethyl-4-hydroxypiperidine, poly[methylpropyl-3-oxy-4-(2,2,6,6-tetramethyl-4-piperidyl)]siloxane, a reaction product of maleic acid anhydride-α-olefin copolymer with 2,2,6,6-tetramethyl-4-ami- nopiperidine or 1 ,2,2,6,6-pentamethyl-4-aminopiperidine, 2,4-bis[N-(1-cyclohexyloxy- 2,2,6,6-tetramethylpiperidine-4-yl)-N-butylamino]-6-(2-hydroxyethyl)amino-1 ,3,5- triazine, 1-(2-hydroxy-2-methylpropoxy)-4-octadecanoyloxy-2, 2,6,6- tetramethylpiperidine, 5-(2-ethylhexanoyl)oxymethyl-3,3,5-trimethyl-2-morpholinone, Sanduvor (Clariant; CAS Reg. No. 106917-31-1], 5-(2-ethylhexanoyl)oxymethyl-3,3,5- trimethyl-2-morpholinone, the reaction product of 2,4-bis[(1-cyclohexyloxy-2,2,6,6- piperidine-4-yl)butylamino]-6-chloro-s-triazine with N,N'-bis(3-ami- nopropyl)ethylenediamine), 1 ,3,5-tris(N-cyclohexyl-N-(2,2,6,6-tetramethylpiperazine-3- one-4-yl)amino)-s-triazine, 1 ,3,5-tris(N-cyclohexyl-N-(1 ,2,2,6,6- pentamethylpiperazine-3-one-4-yl)amino)-s-triazine.

2.7. Oxamides, for example 4,4'-dioctyloxyoxanilide, 2,2'-diethoxyoxanilide, 2,2'- dioctyloxy-5,5'-di-tert-butoxanilide, 2,2'-didodecyloxy-5,5'-di-tert-butoxanilide, 2- ethoxy-2'-ethyloxanilide, N,N'-bis(3-dimethylaminopropyl)oxamide, 2-ethoxy-5-tert- butyl-2'-ethoxanilide and its mixture with 2-ethoxy-2'-ethyl-5,4'-di-tert-butoxanilide, mixtures of o- and p-methoxy-disubstituted oxanilides and mixtures of o- and p- ethoxy-disubstituted oxanilides.

2.8. 2-(2-Hvdroxyphenyl)-1 ,3,5-triazines, for example 2,4,6-tris(2-hydroxy-4- octyloxyphenyl)-1 ,3,5-triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(2,4- dimethylphenyl)-1 ,3,5-triazine, 2-(2,4-dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)- 1 ,3,5-triazine, 2,4-bis(2-hydroxy-4-propyloxyphenyl)-6-(2,4-dimethylphenyl)-1 ,3,5- triazine, 2-(2-hydroxy-4-octyloxyphenyl)-4,6-bis(4-methylphenyl)-1 ,3,5-triazine, 2-(2- hydroxy-4-dodecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1 ,3,5-triazine, 2-(2-hydroxy- 4-tridecyloxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1 ,3,5-triazine, 2-[2-hydroxy-4-(2- hydroxy-3-butyloxypropoxy)phenyl]-4,6-bis(2,4-dimethyl)-1 ,3,5-triazine, 2-[2-hydroxy- 4-(2-hydroxy-3-octyloxypropyloxy)phenyl]-4,6-bis(2,4-dimethyl)-1 ,3,5-triazine, 2-[4- (dodecyloxy/tridecyloxy-2-hydroxypropoxy)-2-hydroxyphenyl]-4,6-bis(2,4- dimethylphenyl)-1 ,3,5-triazine, 2-[2-hydroxy-4-(2-hydroxy-3- dodecyloxypropoxy)phenyl]-4,6-bis(2,4-dimethylphenyl)-1 ,3,5-triazine, 2-(2-hydroxy-4- hexyloxy)phenyl-4,6-diphenyl-1 ,3,5-triazine, 2-(2-hydroxy-4-methoxyphenyl)-4,6- diphenyl-1 ,3,5-triazine, 2,4,6-tris[2-hydroxy-4-(3-butoxy-2-hydroxypropoxy)phenyl]- 1 ,3,5-triazine, 2-(2-hydroxyphenyl)-4-(4-methoxyphenyl)-6-phenyl-1 ,3,5-triazine, 2-{2- hydroxy-4-[3-(2-ethylhexyl-1-oxy)-2-hydroxypropyloxy]phenyl}-4,6-bis(2,4-di- methylphenyl)-1 ,3,5-triazine, 2,4-bis(4-[2-ethylhexyloxy]-2-hydroxyphenyl)-6-(4- methoxyphenyl)-1 ,3,5-triazine.

3. Metal deactivators, for example N,N'-diphenyloxamide, N-salicylal-N'-salicyloyl hydrazine, N,N'-bis(salicyloyl)hydrazine, N,N'-bis(3,5-di-tert-butyl-4- hydroxyphenylpropionyl)hydrazine, 3-salicyloylamino-1 ,2,4-triazole, bis(benzylidene)oxalyl dihydrazide, oxanilide, isophthaloyl dihydrazide, sebacoyl bisphenylhydrazide, N,N'-diacetyladipoyl dihydrazide, N,N'-bis(salicyloyl)oxalyl dihydrazide, N,N'-bis(salicyloyl)thiopropionyl dihydrazide.

4. Phosphites and phosphonites, for example triphenyl phosphite, diphenylalkyl phosphites, phenyldialkyl phosphites, tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearylpentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert- butylphenyl)pentaerythritol diphosphite, bis(2,4-di-cumylphenyl)pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, diisodecyloxypentaerythritol diphosphite, bis(2,4-di-tert-butyl-6-methylphenyl)- pentaerythritol diphosphite, bis(2,4,6-tris(tert-butylphenyl)pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4'-biphenylene diphosphonite, 6-isooctyloxy-2, 4,8,10-tetra-tert-butyl-12H-dibenz[d,g]-1 , 3,2- dioxaphosphocin, bis(2,4-di-tert-butyl-6-methylphenyl)methyl phosphite, bis(2,4-di- tert-butyl-6-methylphenyl)ethyl phosphite, 6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyl- dibenz[d,g]-1 ,3,2-dioxaphosphocin, 2,2',2"-nitrilo[triethyltris(3,3',5,5'-tetra-tert-butyl- 1 ,1 '-biphenyl-2,2'-diyl)phosphite], 2-ethylhexyl(3,3',5,5'-tetra-tert-butyl-1 ,1 '-biphenyl- 2,2'-diyl)phosphite, 5-butyl-5-ethyl-2-(2,4,6-tri-tert-butylphenoxy)-1 ,3,2- dioxaphosphirane.

The following phosphites are especially preferred:

Tris(2,4-di-tert-butylphenyl) phosphite (lrgafos^®168, Ciba Specialty Chemicals Inc.), tris(nonylphenyl) phosphite,

5. Hydroxylamines, for example N,N-dibenzylhydroxylamine, N₁N- diethylhydroxylamine, N,N-dioctylhydroxylamine, N,N-dilaurylhydroxylamine, N₁N- ditetradecylhydroxylamine, N,N-dihexadecylhydroxylamine, N₁N- dioctadecylhydroxylamine, N-hexadecyl-N-octadecylhydroxylamine, N-heptadecyl-N- octadecylhydroxylamine, N,N-dialkylhydroxylamine derived from hydrogenated tallow amine. 6. Nitrones, for example, N-benzyl-alpha-phenylnitrone, N-ethyl-alpha-methylnitrone, N-octyl-alpha-heptylnitrone, N-lauryl-alpha-undecylnitrone, N-tetradecyl-alpha- tridecylnnitrone, N-hexadecyl-alpha-pentadecylnitrone, N-octadecyl-alpha- heptadecylnitrone, N-hexadecyl-alpha-heptadecylnitrone, N-ocatadecyl-alpha- pentadecylnitrone, N-heptadecyl-alpha-heptadecylnitrone, N-octadecyl-alpha- hexadecylnitrone, nitrone derived from N,N-dialkylhydroxylamine derived from hydrogenated tallow amine.

7. Thiosynergists, for example dilauryl thiodipropionate, dimistryl thiodipropionate, distearyl thiodipropionate or distearyl disulfide.

8. Peroxide scavengers, for example esters of β-thiodipropionic acid, for example the lauryl, stearyl, myristyl or tridecyl esters, mercaptobenzimidazole or the zinc salt of 2- mercaptobenzimidazole, zinc dibutyldithiocarbamate, dioctadecyl disulfide, pentaerythritol tetrakis(β-dodecylmercapto)propionate.

9. Polvamide stabilizers, for example copper salts in combination with iodides and/or phosphorus compounds and salts of divalent manganese.

10. Basic co-stabilizers, for example melamine, polyvinylpyrrolidone, dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamides, polyurethanes, alkali metal salts and alkaline earth metal salts of higher fatty acids, for example calcium stearate, zinc stearate, magnesium behenate, magnesium stearate, sodium ricinoleate and potassium palmitate, antimony pyrocatecholate or zinc pyrocatecholate.

11. Nucleating agents, for example inorganic substances, such as talcum, metal oxides, such as titanium dioxide or magnesium oxide, phosphates, carbonates or sulfates of, preferably, alkaline earth metals; organic compounds, such as mono- or polycarboxylic acids and the salts thereof, e.g. 4-tert-butylbenzoic acid, adipic acid, diphenylacetic acid, sodium succinate or sodium benzoate; polymeric compounds, such as ionic copolymers (ionomers). Especially preferred are 1 ,3:2,4-bis(3',4'- dimethylbenzylidene)sorbitol, 1 ,3:2,4-di(paramethyldibenzylidene)sorbitol, and 1 ,3:2,4-di(benzylidene)sorbitol. 12. Fillers and reinforcing agents, for example calcium carbonate, silicates, glass fibres, glass beads, asbestos, talc, kaolin, mica, barium sulfate, metal oxides and hydroxides, carbon black, graphite, wood flour and flours or fibers of other natural products, synthetic fibers.

13. Other additives, for example plasticisers, lubricants, emulsifiers, pigments, rheology additives, catalysts, flow-control agents, optical brighteners, flameproofing agents, antistatic agents and blowing agents.

14. Benzofuranones and indolinones, for example those disclosed in U.S. 4,325,863; U.S. 4,338,244; U.S. 5,175,312; U.S. 5,216,052; U.S. 5,252,643; DE-A-4316611 ; DE-A-4316622; DE-A-4316876; EP-A-0589839, EP-A-0591 102; EP-A-1291384 or 3- [4-(2-acetoxyethoxy)phenyl]-5,7-di-tert-butylbenzofuran-2-one, 5,7-di-tert-butyl-3-[4- (2-stearoyloxyethoxy)phenyl]benzofuran-2-one, 3,3'-bis[5,7-di-tert-butyl-3-(4-[2- hydroxyethoxy]phenyl)benzofuran-2-one], 5,7-di-tert-butyl-3-(4- ethoxyphenyl)benzofuran-2-one, 3-(4-acetoxy-3,5-dimethylphenyl)-5,7-di-tert- butylbenzofuran-2-one, 3-(3,5-dimethyl-4-pivaloyloxyphenyl)-5,7-di-tert- butylbenzofuran-2-one, 3-(3,4-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one, 3- (2,3-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2-one, 3-(2-acetyl-5-isooctylphenyl)- 5-isooctylbenzofuran-2-one.

Materials that reduce or eliminate whitening of the film following aging, are for example materials having a refractive index approximately matching that of the bulk material. 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. 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 polyoles are preferred. Hydrocarbon oils, especially mineral oils (paraffinum liquidum), are especially preferred, in particular Mobil DTE Heavy oil.

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). The additives of the invention and optional further components may be added to the polymer material individually or mixed with one another. If desired, the individual components can be mixed with one another before incorporation into the polymer for example by dry blending, compaction or in the melt.

The incorporation of the additives of the invention and optional further components into the polymer is carried out by known methods such as 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 by addition of the additive in the form of a spray or solution to the polymeric material following formation of the article. The additives of the invention and optional further additives may be incorporated, for example, before or after molding or also by applying the dissolved or dispersed additive or additive mixture to the polymer material, with or without subsequent evaporation of the solvent or the suspension/dispersion agent. They may be added directly into the processing apparatus (e.g. extruders, internal mixers, etc), e.g. as a dry mixture or powder or as solution or dispersion or suspension or melt.

The incorporation can be carried out in any heatable container equipped with a stirrer, e.g. in a closed apparatus such as a kneader, mixer or stirred vessel. The incorporation is preferably carried out in an extruder or in a kneader. It is immaterial whether processing takes place in an inert atmosphere or in the presence of oxygen.

The addition of the additive or additive blend to the polymer can be carried out in all customary mixing machines in which the polymer is melted and mixed with the additives. Suitable machines are known to those skilled in the art. They are predominantly mixers, kneaders and extruders.

The process is preferably carried out in an extruder by introducing the additive during processing.

Particularly preferred processing machines are single-screw extruders, contrarotating and corotating twin-screw extruders, planetary-gear extruders, ring extruders or cokneaders. It is also possible to use processing machines provided with at least one gas removal compartment to which a vacuum can be applied. Suitable extruders and kneaders are described, for example, in Handbuch der Kunststoff extrusion, 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).

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 - 400 rpm.

The maximum throughput is dependent on the screw diameter, the rotational speed 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.

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 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.

Incorporation can take place prior to or during the shaping operation, or by applying the dissolved or dispersed compound to the polymer, with or without subsequent evaporation of the solvent.

Preferably the film is initially translucent or transparent to visible light. Translucent or transparent in the context of the invention means, that at least 90 % of the incident visible light are transmitted. Visible light means light of the wave length from about 400 nm to 750 nm. The thickness of the films can range, for example, between 5 to 100 microns. Films from 10 to 60 microns are preferred. Films of up to about 180 microns thickness may be used although thicker films tend to attenuate or absorb shorter wavelength radiation which may limit the extent to which the film may be pre-disposed to degrade using the invention. Blown films are particularly preferred.

In a specific embodiment of the invention the film has been stretched after production to increase its length and decrease its thickness, producing a cold drawn thin film. The film may be of a single or double layer, or be a multilayer construction which has been manufactured, for example, by co-extrusion with up to 20 layers, and in which prodegradant is present in one or more layers.

The films can be coextruded by film extrusion such as blown film extrusion or by cast film extrusion or they can be laminated and they can include layers based on polymers such as polyethylene (low density, linear low density, high density and copolymers), poly-4-methylpent-1-ene, polyamide (PA 6 or 6,6 or 11 or 12 or 6/6,6 copolymer including OPA), polyethylene terephthalate (PET including OPET), polyethylene naphthalate (PEN), ethylene vinyl alcohol (EvOH), polypropylene (including OPP), ethylene acrylic acid copolymers and their salts, ethylene methacrylic acid copolymers and their salts or polyvinylidenchloride (PVDC).

A brief description of some exemplary articles made in accordance with the invention follows.

Typically, the articles are required to have a relatively long shelf or service life followed by a relatively short period during which embrittlement and fragmentation occurs, either in situ or in a landfill. The articles may be film or film products.

Such films may, for example, be used for agricultural applications, packaging, wrapping pallets and plastic bags.

Typical agricultural applications are greenhouse, mulch, silage or bale wrap films.

Specifically in the field of crop production, films of plastic material laid on the ground, usually at sowing or planting, readily provide a desirable micro-environment that enhances crop yield through the control of soil temperature, retention of moisture, and control of weed growth. They have also proved to be effective in reducing soil crusting, thus improving seed germination and seedling emergence. It is also important that the films be sufficiently strong and flexible such that they can be laid out over large surface areas by use of a machine without rupture or tearing. Normally, however, a film that has these mechanical properties and that will not degrade provides a problem for growth of seedlings after the initial germination phase. To make holes in the film by mechanical means at a suitable time may not be economically feasible. The properties of the film and system and method for its degradation that, according to the present invention, enable the mechanical properties of the laid film to be controlled so that the film weakens such that plants may easily break through the film at a required period of time following germination, solves this issue. The film may be retained in place by partial burial and degradation of the exposed and the buried film may occur within the same growing season, the degradation extending to a stage where the film becomes a friable material that does not impede further use of the soil, or leave portions of film that are still large enough to foul cultivating implements, particularly under the soil.

Referring now to Fig 1 , a method of controlling degradation of a polymeric film to cause the film to degrade (e.g. embrittle) after an intended useful life time includes, in a step 102, providing a polymeric film comprising a polymer and a prodegradant for the polymer. Examples of formulations for the polymeric film and prodegradant and methods for their production are provided in the preceding paragraphs and the examples which follow. The method of controlling degradation further includes activating one or more sources of artificial radiation which are adapted to emit a controlled electromagnetic (EM) radiation dosage (step 104) at a high dose rate. The dosage comprises EM wavelengths less than about 400 nm. In a step 106, the polymeric film or at least part thereof is exposed to the radiation dosage emitted by the artificial radiation sources. Activation of the artificial radiation sources may be continuous or intermittent. Similarly, the dosage received by the film may be received in a single exposure event, or over a series of sequential exposures.

Preferably, the EM radiation comprises UV wavelengths in the range 250 nm to 385 nm. In one preferred embodiment, the majority of the radiation dosage energy (e.g. >80%) is emitted in the range 250 to 260 nm, and more preferably still, greater than 90% of the radiation dosage energy is emitted at a wavelength near 254 nm although other wavelengths in the UV-C, UV-B and UV-A ranges are suitable.

It is desirable to treat polymeric film using the method and system of the present invention to pre-dispose the polymeric film to degrade after an intended service life substantially without adversely affecting its physical properties during service. In order to achieve the desired level of irradiation the dosage is preferably greater than about 25 kJ/m². In some embodiments the preferred radiation dose rate is greater than about 1 ,000 W/m² and in others, the dosage comprises wavelengths in the range 200 nm to 385 nm at a rate of 7,500 W/m² or higher. It is to be understood that a desired dosage may be obtained by altering parameters of the artificial radiation source(s) such as duration and intensity of EM radiation emitted.

Fig 2 is a variation of Fig 1 showing steps in a method which provides spatially heterogeneous distribution of the radiation dosage over the area of the polymeric film.

This is achieved by, in a step 103, placing a filter or mask device between the polymeric film and one or more (or all) of the sources of artificial radiation. The filter or mask has transmission characteristics which control the distribution of EM radiation over the polymeric film. The filter may have an opaque centre region which substantially precludes transmission of EM radiation while the side strips of the mask permit substantially all of the emitted EM radiation to pass therethrough. This results in a spatially heterogeneous treatment of the polymeric film in which the area beneath the centre region has substantially no exposure to radiation. Meanwhile, side bands of the polymeric film beneath the side strips of the mask are exposed to the entire EM radiation dosage.

It will be noted that the method represented in Fig 2 further includes the step 105 of cooling the film to maintain a desirable temperature e.g. within the range 15 deg C to 45 deg C. This prevents thermal shrinkage which can affect the physical properties of the polymer. Fig 2 also provides, in a step 108, conveying the film through an irradiation zone. This has special utility when irradiating continuous lengths of the film, rather than film which is in smaller sheets. Motorised rollers may be used to convey the film on a roll through the irradiation zone for immediate deployment (step 112) e.g. in agriculture, pallet wrapping, newspaper wrapping or the like. Alternatively the irradiated film may be collected on a roll or collection spool (step 1 10) for storage or transportation prior to deployment. Where irradiated film is stored on a roll, it is desirable for the roll to be contained or wrapped in a light-impermeable container or wrapping to minimize further and uncontrolled photodegradation of the prodegradant prior to deployment of the film into service.

In one embodiment, the one or more radiation sources are positioned to deliver radiation to both sides of the polymeric film although in many applications this is not necessary as the film is sufficiently thin that the radiation dosage incident on one side of the film is sufficient to activate the prodegradant additive throughout the film's thickness.

In one embodiment, the method includes use of an irradiation controller device 300 (Fig 3). Preferably, the irradiation controller device includes a programmable logic device (PLD) 302 which determines the required radiation dosage automatically, based on inputs provided by a user. The PLD receives via input bus 306 inputs from a user which indicate e.g. the intended service use of the polymeric film, or service life after which it is desirable for the polymeric film to degrade. For film to be deployed as a mulch film, the user may enter the crop type (e.g. potatoes) and information about the prevailing environmental conditions (e.g. latitude) as inputs together with the film type. The PLD then determines automatically the radiation dosage (e.g. intensity and exposure duration, and wavelength selection where applicable) required to achieve the desired level of controlled degradation necessary to cause the film to degrade after the intended useful lifetime.

The PLD may be pre-programmed to utilize data in one or more look-up tables stored on memory 304 which relate e.g. crop data, environmental/location data and prodegradant data to radiation dosages suitable for pre-treatment using the invention. Alternatively/additionally, the PLD may execute algorithms stored in memory 304 to calculate the required dosage. The irradiation controller may output the radiation dosage parameters on a display using output bus 306, for manual implementation by an operator. Alternatively the controller is adapted to use dosage parameters (either determined automatically by the PLD or entered by a user) to derive control signals which are conveyed to various aspects of apparatus causing them to operate in such a way that the required radiation dosage is delivered to the film.

Thus, the irradiation controller may generate signals activating the radiation sources so that they emit radiation for a required duration of exposure, at a required intensity. Where the radiation sources have variable spectral outputs (e.g. depending on bulb selection), the irradiation controller may also control the radiation sources to emit a particular wavelength or narrow band emission (e.g. by automating bulb selection). The desired intensity may be achieved by controlling the position of the artificial radiation sources, relative to the polymeric film or providing more power to the radiation sources. Reflective surfaces may also be employed. Thus, the irradiation controller may also control operation of motors adapted to alter the distance of one or more radiation sources and/or reflectors from the polymeric film. Additionally/alternatively, the irradiation controller may also control a conveyor or spools and the rate at which polymeric film is conveyed through the irradiation zone to achieve delivery of the designed dosage to the film.

Referring now to Fig 4a there is shown a schematic drawing of irradiation apparatus 400 according to an embodiment of the invention. The apparatus includes at least one source of radiation 402 adapted to emit a controlled dosage of EM radiation comprising wavelengths less than about 400 nm, preferably in the range 250 nm to 385 nm and more preferably in the range 250 nm to 280 nm at a high dose rate (e.g. at least 50 VWm², or preferably at least 100 VWm² or more preferably at least 7,500 VWm²). Irradiation zone 404 receives at least part of the polymeric film 406 for exposure to the radiation dosage. Use of the apparatus 400 to perform controlled irradiation of the polymeric film predisposes at least part of the polymeric film to degrade after an intended useful service life. In one embodiment, the film may be drawn from a spool 404 in the direction shown by arrow A although it is contemplated that discrete sheets of film may be irradiated by placement in the irradiation zone.

In one embodiment, the irradiation apparatus is adapted to deliver a radiation dosage to the polymeric film which is spatially heterogeneous. That is, the radiation dosage is not evenly distributed over the polymeric film area. Rather, it is distributed with particular areas of the film receiving a higher dosage of radiation than other areas. This may be achieved by positioning the one or more sources of radiation in such a way that the irradiation zone covers only a portion of the polymeric film. In an alternative arrangement, spatially heterogeneous treatment is achieved by positioning a mask or filter 408 between the one or more sources of artificial radiation 402 and irradiation zone 404. The mask/filter has EM radiation transmission characteristics which determine the spatial distribution of the radiation dosage which is incident on the polymeric film. The mask/filter 408 may take a number of different forms, some of which are illustrated schematically in Fig 4b, and achieve any desired radiation pattern. In one form, the mask/filter may include opaque regions which substantially preclude transmission of EM radiation therethrough. The opaque regions may be patterned (e.g. 408a) and/or may include regions of graduated density (e.g. 408b). Alternatively, the opaque regions may be differential such as the mask exemplified at 408c which has a substantially opaque central region, O, and substantially transparent lateral bands, T. Use of mask 408c, is useful for controlling spatial distribution of radiation for a polymeric film which is intended for use in agriculture as a mulch film, where the edge portions of the film are buried in soil and, under the normal prevailing conditions would not normally degrade prior to the next crop being sown. Pre-irradiation of the film edges using mask 408a pre-disposes side regions of the film to degrade earlier than would otherwise be the case where only mild thermal oxidation is naturally occurring beneath the soil surface. Thus, despite being buried in soil and deprived of terrestrial light, the submerged film degrades after the intended purpose has expired (i.e. the crop has been harvested) and before the soil is prepared for the next crop to be sown.

Preferably the mask/filter is interchangeable with a mask/filter having different transmission characteristics. This enables the spatial distribution of radiation to be altered quickly and easily. As well as providing for spatially heterogeneous distribution of radiation over the polymeric film (or as an alternative), an interchangeable filter may be used to determine e.g. the intensity and/or wavelength of EM radiation which is incident on the polymeric film with out necessarily affecting the spatial distribution of radiation. Thus, for radiation sources emitting broader spectrum EM radiation, a narrower band of EM radiation can be achieved by selecting a suitable mask/filter. Further, a mask/filter may be used to achieve the required intensity level without e.g. changing the distance of the artificial radiation sources from the polymeric film.

Referring now to Fig 5, irradiation apparatus 500 is adapted for irradiating a length of polymeric film 502 from a roll 504. In this embodiment, EM radiation is emitted from artificial source 506 to irradiation zone 508 in which roll of film 504 is positioned. The height of the radiation source 506 may be adjusted manually or more preferably using a motor driven actuator 514 which adjusts the height according to a signal received from irradiation controller 510. Tension rollers 516a, 516b maintain the integrity (i.e. tension) of the film as it is drawn from roll 504 through the irradiation zone and collected on collection spool 512. Collection spool 512 is rotated at a rate which delivers the desired radiation dosage to the polymeric film in the irradiation zone. Thus, it is preferred that the collection spool is driven by motor 518 also controlled by irradiation controller 510. In the embodiment shown, corona discharge lamp 520 treats the underside of the film to maintain transparency and aid with water runoff (e.g. for use in agriculture) although this may not affect the rate or time of commencement of degradation of the prodegradant.

Fig 6a and Fig 6b show side and top schematic representations respectively of another embodiment of the irradiation apparatus which is adapted for delivering radiation dosages focused on the lateral edges of the polymeric film. Fig 6a shows an advantage of irradiating film 602 while it is still on roll 604; the radiation dosage incident in irradiation zone 608 penetrates the layers of the transparent film roll to a depth d. This results in cyclic exposure of the film length as it is drawn through the irradiation zone by operation of take up roll 612. This increases the overall exposure time and hence the efficiency of the irradiation technique. This advantage is achieved by the embodiment illustrated in Fig 5 also.

Fig 6b shows the arrangement of Fig 6a in plan view. A pair of artificial radiation sources 606a, b positioned over film roll 604 toward its edges, deliver a spatially heterogeneous radiation dosage to film 602. Radiation sources 606a, b are positioned to achieve radiation of edge strips 630a, b resulting in a polymeric film having edge portions pre-disposed to degrade after an intended useful service when used as a mulch film. However, radiation emitted from sources 606a, b may also treat regions of the film between the edge strips 630a, b albeit to a lesser extent. Alternatively/additionally, a further radiation source may be provided and adapted to deliver a lower dosage of radiation to the centre of the film.

Fig 7 shows yet another embodiment of irradiation apparatus 700. Film 702 is conveyed from roll 704 though irradiation zone 708 where it is exposed to a radiation dosage delivered by a bank of artificial radiation sources 706. To improve the efficiency of the exposure, a reflector 740 is provided to reflect radiation which has passed though the transparent film, so that it is incident on the film undersurface. Tension spools 716 ensure the physical integrity of the film as it is conveyed through the apparatus. Irradiated film may then be wound onto a collection spool (not shown). Alternatively, the film may be deployed for immediate use, e.g. in agriculture, as pallet wrap, newspaper wrap or the like. Where the irradiated film is deployed immediately in agriculture, the irradiation apparatus may be mounted on a vehicle driven over the crop area to pre-irradiate the film (or regions of it) immediately before it is deployed as a mulch film, greenhouse tube or the like. A filter/mask may be used with apparatus 700 to control the irradiation dosage and distribution, and may be selected according to e.g. crop type and prevailing environmental conditions into which the crop is to be sown.

Fig 8 is yet another example of irradiation apparatus which has been configured for irradiating a continuous length of polymeric film containing a prodegradant prior to use as a newspaper wrapping. Polymeric film 802 is drawn from roll 804 through an irradiation zone in which the film receives a radiation dosage emitted by artificial radiation sources provided in the form of UV light banks 806a, b. The light banks and rollers 818 are arranged so that both sides of the film are exposed to emitted radiation, reducing the time required to deliver the dosage. Rollers 818 guide the film though the apparatus, maintaining its physical integrity.

One or more motorized rollers convey the film through the irradiation zone at a rate which achieves the total required dosage of EM radiation to which the film is exposed. Cooling vents 840 provided to cool the film which would otherwise undergo heating as a result of thermal energy radiating from the light banks. Film which has been irradiated is then deployed as a wrap for newspaper 850 which, once wrapped, is then ready for delivery. The radiation dosage may be determined so that the film in which the newspaper is wrapped is predisposed to commence degradation within e.g. 2 to 4 weeks of irradiation, irrespective of the thermal or photoactive oxidation which is triggered by environmental conditions into which the film is disposed. A typical dose may be 30 kJ/m².

Suitable polymer articles include plastic films, sheets, bags, blister packages, boxes, package wrappings, plastic fibers, tapes, agricultural articles such as twine agricultural films, mulch films, small tunnel films, banana bags, direct covers, geotextiles, landfill covers, industrial covers, waste covers, temporary scaffolding sheets, building films, silt fences, poultry curtains, films for building temporary shelter constructions, and the like. In all of the foregoing examples, the article, made in accordance with the invention, will keep its properties during use and will degrade after its service life.

Mulch films represent a particular preferred embodiment of the present invention.

Mulch films are used to protect crops in the early stages of their development. Mulch films, depending on the type of crop and on the purpose, can be laid after the seeding or at the same time as the seeding. They protect the crop until the crop has reached a certain development stage. When the harvest is finished, the field is again prepared for cultivation.

Standard plastic films have to be collected and disposed of in order to allow the new cultivation. The additive system of the present invention, when added to the standard plastic mulch films, allows the film to keep its properties until the crop has reached the required development, then degradation accelerates after exposure to sunlight and the film is completely embrittled when the new cultivation has to be started.

The length of the service period and of the time to degradation and time to complete disappearance depends on the type of crop and on the environmental conditions. Depending on the specific time requirements, the amount of additive and pre- irradiation dose is tailored such that the film will embrittle at the desired time for that particular application.

By appropriately dosing the amount of the present additive system, the required service periods and time to degradation and disappearance can be obtained. Examples of typical life times of mulch films are 10 to 180 days. Periods of use up to 24 months can also be required and achieved.

Preferably the films are used in an agricultural application which is selected from the group consisting of mulch films, small tunnel films, shading nets and direct covers.

In another embodiment the films are used in packaging, wrapping pallets and plastic bags. In one embodiment of the invention the article has been subjected to radiation directly after production, to trigger polymer degradation.

In another embodiment the article has been subjected to radiation immediately before, during or following its use, to trigger polymer degradation.

It is, however, also possible to combine both embodiments.

For example, the film is treated with different radiation doses over its area, resulting in a selective predetermined rate of degradation.

A further aspect of the invention is the use of a) a nano-scaled TiO₂ with a particle size of less than 200 nm in the largest dimension; and b) a metal carboxylate; for increasing or starting the degradation of a polyolefin article when incorporated therein and subjected to UV-radiation.

The definitions and preferences described for the method apply equally for the other aspects of the invention.

The following examples illustrate the invention. 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 and that they are in no way limiting to the scope of the invention.

EXAMPLE 1

Four identical samples of commercial X-Tend™ photodegradable film, manufactured by Integrated Packaging, Australia, were placed in plastic slide holders. X-Tend is a 6 micron blown polyethylene film containing 5% by weight of a commercial masterbatch - Ampacet™ 30091 -K, containing an iron-based prodegradant. The samples were irradiated in a Q-UV aging cabinet, incorporating a battery of eight 40 W Q-UV-A lamps, at a distance of 0.5 cm from the samples (dose rate -1 ,200 VWm²). The peak emission is at 340 nm with a cut-off at 295 nm. All pre-irradiation and aging was conducted at ambient humidity. The samples were irradiated for 1.5, 5, 15 and 60 seconds, respectively, to a total dose of 1.8, 6, 18 and 72 kJ/m². Following pre-irradiation, the samples were aged in a Contherm digital series fan- forced oven, thermostatted at 50 ⁰C. Periodically, the samples were withdrawn and the carbonyl index obtained by taking the ratio of the height of the carbonyl peak at 1714 cm^"1 to that of the reference peak at 1460 cm^"1, as measured using transmission infrared spectroscopy (Perkin Elmer FT-IR Spectrometer - Spectrum 1000, 4000- 500 cm^"1, 4 cm^"1 resolution). The period in days that had transpired before each sample reached embrittlement is given in Table 1.

Table 1 : Effect of pre-irradiation under UV-A followed by thermal aging on time to embrittlement of iron stearate-containing films

At 270 days, the carbonyl indices also demonstrate the effect of longer irradiation times, with the sample pre-irradiated for 5 seconds having a carbonyl index of 0.084, in comparison with the sample pre-irradiated for 60 seconds, with a carbonyl index of 0.173.

EXAMPLE 2

Oleic acid-coated nanoscale titania (anatase) nanorods (approximately 4 x 25 nm in dimension) were prepared by means of a sol-gel process. A mixture of 160 ml. of oleic acid (technical grade - 90 % - from Sigma-Aldrich), 8 ml. of titanium (IV) isopropoxide (97 % from Sigma-Aldrich) and 2 ml. triethylamine (≥ 98 % pure from Fluka) was heated to 1 10 ⁰C in a 500 ml_, three-necked round-bottomed flask fitted with a magnetic stirrer bar, nitrogen inlet and outlet, and condenser, and held under nitrogen for 1 h with stirring, then cooled to 80 ⁰C. Distilled water (10 ml.) was then added and the mixture stirred at 80 ⁰C for 24 h. Ethanol was then added to precipitate the resulting titania nanocrystals from solution. The precipitate was centrifuged and washed with methanol before centrifuging again. The resulting solid was dried in a vacuum oven for 2 h giving a white powder. 2.5 g of the above powder was suspended in toluene and then added to 47.5 g of LLDPE resin A (a linear low density polyethylene, with a density of 0.920 g/cc and melt flow index of 1.0 g / 10 min) pellets, obtained from Dow Plastics. The solvent was then slowly removed from the resulting mixture under reduced pressure. The resulting coated pellets were removed from the round-bottomed flask, extra LLDPE resin A pellets added to make up a formulation equivalent to 0.5 % by weight as titania, and the mixture then extruded and blown by means of an Axion cut flight single-screw extruder at a screw speed of 20 rpm, with the temperature profile of the five-zone extruder set at 165, 185, 210, 220 and 220 ⁰C to give sample B. A reference film sample (sample C) containing LLDPE resin A alone was prepared under identical film extrusion and blowing conditions.

Five identical samples of the resulting film were clamped into plastic slide holders before being pre-irradiated, using a low-pressure mercury vapour lamp system, purchased from Heraeus, with single wavelength 254 nm emission, 2 x 60 W lamps. The system is of high power (approx. 50 VWm² at the irradiation platform), with a large illumination area (~ 1 m arc length) and a parabolic reflector for collection of stray UV light. The spectral emission of a low-pressure mercury vapour lamp is a line spectrum with approximately 90 % of its output at 254 nm. The irradiation times for the samples were 10 s, 30 s, 60 s, and 1 h, respectively corresponding to a UV-C dose of 500, 1500, 3000 and 180,000 J/m², respectively. The samples were then aged in an oven at 50 ⁰C using the method of Example 1. Figure 10 shows that the effect of pre- irradiation treatment time on carbonyl index (as measured by FT-IR using the method described in Example 1 ) during thermal aging. The control (sample C) films did not embrittle within 395 days.

EXAMPLE 3

A film sample (sample D) was made using Degussa Aeroxide P25 titania (a commercially available titania). In this example, Degussa Aeroxide P25 titania powder was added directly to LLDPE resin A to make a masterbatch, using an Axion single- screw extruder at 20 rpm with the same temperature profile as in Example 2. 10.22 g Degussa P25 powder and 372.76 g LLDPE resin A were blended and extruded before being pelletized. This masterbatch was mixed with 18.85 g of Daelim PBMB-60, 49.40 g of LDPE resin B, and a further 370.56 g LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 20 rpm. The final formulation (sample D) was composed of 1.2 % percent titania by weight, 6 % of LDPE resin B, 2.3% Daelim PBMB-60 (a 60 % PIB masterbatch - PIB mol. wt. 1 ,800 g/mol) and 90.5 % of LLDPE resin A. The sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0, 1 , 5 and 60 minutes were used corresponding to dosages of 0, 3, 15 and 180 kJ/m² respectively. A second set of samples was pre-irradiated with UV-A (340 nm) radiation for periods of 0, 1 , 5 and 60 minutes corresponding to dosages of 0, 52, 260 and 3,100 kJ/m². The samples were then placed in an oven at 50 ⁰C for aging, as per Example 1. The effect of pre-irradiation on time for films to embrittle in an oven at 50 ⁰C is summarized in Table 2. Figures 11 and 12 show the effect of 254 nm and UV-A (at 340 nm) pre-irradiation, respectively, on carbonyl index (measured by the method given in Example 1 ).

Table 2: The number of days of thermal aging (50 ⁰C) transpired until sample D embrittles after pre-irradiation at 254 nm or 340 nm for 0 - 60 min.

EXAMPLE 4

Into a pomade jar (150 mL) was placed 35.5 g PIB (average M_v ~ 420,000 g/mol, average M_w ~ 500,000 g/mol, average M_n ~ 200,000 g/mol by GPC/MALLS, obtained from Sigma-Aldrich). To this was added 95.434 g hexane and the mixture dissolved by stirring overnight. A portion of this mixture (53.696 g) was removed from the jar, and 19.923 g Degussa Aeroxide P25 was added to this portion. The mixture was mixed together with a mortar and pestle to give a white rubbery solid. This solid was dried in a vacuum oven for 3 h at 50 ⁰C to give a final mass of 42.54 g. A subsample of this material (10.04 g) was chopped into small pieces before being mixed with 25.12 g of oxidized polyethylene (Sigma - Aldrich, acid number 17 mg KOH/g) and 46.81 g LLDPE resin A. A masterbatch was prepared by extruding and pelletizing as per Example 2, using extra LLDPE resin A in the process to give 159.88 g product. This masterbatch was then mixed with 9.02 g of Daelim PBMB-60, 24.92 g of LDPE resin B, and a further 306.1 g LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 20 rpm. The final formulation (sample E) is theoretically composed of 0.9 % percent Degussa P25 titania by weight, 5.0 % of LDPE resin B, 1.8 % Daelim PBMB-60 (an ~ 57-63 % masterbatch of Daelim polybutene obtained from Daelim Corporation, Korea), 0.7 % PIB (average M_n ~ 200,000 g/mol), 5.0 % oxidized polyethylene and 86.6 % LLDPE resin A. This sample was prepared and p re- irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0, 60 seconds, 10 minutes and 60 minutes (corresponding to UV-C dosages of 0, 300, 3000 and 180,000 J/m²) were used. The samples are then placed in an oven at 50 ⁰C for aging, as per Example 1. The effect of pre-irradiation on the time to embrittlement at 50 ⁰C is summarized in Table 3. The effect of pre-irradiation on the carbonyl index (measured by the method given in Example 1 ) is shown in Figure 13.

Table 3: Effect of pre-irradiation on LLDPE films containing Degussa P25 and oxidized polyethylene (sample E)

EXAMPLE 5: Compatibilisation by functionalisation with octadecyltrimethoxysilane 3.493 g Degussa Aeroxide P25 was placed in a watchglass and exposed to a saturated water atmosphere for 5 minutes. The sample was dried for 2 h at 120 ⁰C, then placed in a dried, stoppered 250 mL conical flask. To this was added to a freshly prepared solution of 0.395 g octadecyltrimethoxysilane (from Sigma-Aldrich) in 100 ml. AR grade methanol, and the mixture was flushed with nitrogen and the flask sealed. The mixture was placed in an ultrasound bath for 15 minutes before being left to stand overnight and the solvent was then evaporated under reduced pressure. A separate solution of 5.0 g PIB (average M_v ~ 420,000 g/mol, average M_w ~ 500,000 g/mol, average M_n ~ 200,000 g/mol by GPC/MALLS, obtained from Sigma-Aldrich) in hexane (30 ml.) was then mixed with the solid remaining after rotary evaporation. After evaporation of the bulk of the solvent on standing, the resulting rubbery solid was ground in a mortar and pestle as the residue of the solvent evaporated. The resulting product was then mixed with LLDPE resin A for extrusion and pelletizing to give 318.85 g of pelletised masterbatch. This was then mixed with 9.06 g Daelim PBMB-60 (a masterbatch containing - 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), 25.07 g LDPE resin B and an extra 147.83 g LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 20 rpm. The final formulation (sample F) is theoretically composed of 0.7 % percent of titania by weight, 5.0 % of LDPE resin B, 1.8 % Daelim PBMB-60, 1.0 % PIB (average M_n ~ 200,000 g/mol), and 91.5 % LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0, 1 and 10 minutes (corresponding to UV-

C doses of 0, 3000 and 30,000 J/m²) were used. The samples were then placed in an oven at 50 ⁰C for aging, as per Example 1. The effect of pre-irradiation on the time to embrittlement at 50 ⁰C is summarized in Table 4. Fig 14 shows the effect of 254 nm pre-irradiation on carbonyl index (measured according to method given in Example 1 ) during oven aging.

Table 4: Effect of pre-irradiation on LLDPE films containing Degussa P25 plus octadecyltrimethoxysilane (sample F)

EXAMPLE 6: Compatibilisation by blending with polyethylene-co-acrylic acid. Oleic acid-coated nanoscale titania (anatase) nanorods (4 x 25 nm in dimension) were prepared by a variation of the method in Example 2: 120 ml. of oleic acid (technical grade - 90 % - from Sigma-Aldrich), 60 ml. octadecene (technical grade - 90 % - from Sigma-Aldrich) and 20 ml. titanium(IV) isopropoxide (97 % from Sigma-Aldrich) were heated to 90 ⁰C in a 500 ml_, three-necked round-bottomed flask fitted with magnetic stirrer bar, nitrogen inlet and outlet, and condenser, and held at 90 ⁰C under nitrogen for 1 h with stirring. A solution of trimethylamine-Λ/-oxide dihydrate (Sigma-Aldrich) in 30 ml. of distilled water was then added and the mixture stirred at 90 ⁰C overnight. Methanol was then added to precipitate the resulting titania nanocrystals from solution. The precipitate was centrifuged, washed again with methanol, centrifuged and washed (x 2) then dried in a vacuum oven for 2 h, resulting in a beige/white solid.

6.50 g of the above solid was chopped into pieces and mixed with 6.50 g poly(ethylene-co-acrylic acid) (20 wt% acrylic acid, Sigma-Aldrich) and 65.02 g

LLDPE resin A. The resulting mixture was then extruded and pelletized, along with extra LLDPE resin A, to give 168.75 g of pelletized masterbatch. This was mixed with

10.9 g Daelim PBMB-60 (a masterbatch containing - 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), 33.1 g LDPE resin B and extra LLDPE resin A to bring the total weight to 650.0 g. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and screw speed of 20 rpm. The final formulation (sample G) is theoretically composed of 1.0 % percent oleic acid-coated titania (anatase) nanorods by weight, 1.0% poly(ethylene-co-acrylic acid),

5.1 % of LDPE resin B, 1.7 % Daelim PBMB-60 and 91.2% LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0, 60 s, 10 and 60 minutes (corresponding to UV-C dosages of 0, 300, 3000, and 180,000 J/m²) were used. The samples were then placed in an oven at 50 ⁰C for aging, as per Example 1. The effect of pre- irradiation on the time to embrittlement at 50 ⁰C is given in Table 5. Fig 15 shows the effect of 254 nm pre-irradiation followed by thermal aging on carbonyl index (measured according to method given in Example 1 ) of sample G.

Table 5: Effect of pre-irradiation on LLDPE films containing Degussa P25 plus poly(ethylene-co-acrylic acid) (sample G)

EXAMPLE 7: Compatibilisation by functionalisation with oleic acid 5.027 g Degussa Aeroxide P25 was placed in a 500 ml. round-bottomed flask, fitted with stirrer bar, reflux condenser and nitrogen inlet and outlet. To this was added 70 ml. oleic acid (technical grade - 90 % - from Sigma-Aldrich) and 50 ml. octadecene (technical grade - 90 % - from Sigma-Aldrich), and the mixture was heated to reflux overnight. Acetone was added to precipitate a beige material that after drying weighed 4.992 g, of which 0.234 g was removed for analysis. To the remaining solid was added 6.503 g PIB (average M_v ~ 420,000 g/mol, average M_w ~ 500,000 g/mol, average M_n ~ 200,000 g/mol by GPC/MALLS, obtained from Sigma-Aldrich) in 4.216 g hexane to give a final mass after evaporation of 12.15 g (indicating some solvent retention). 9.46 g of the product was chopped and then mixed with LLDPE resin A for extrusion and pelletizing to give 238.78 g of pelletized masterbatch. This was then mixed with 6.27 g Daelim PBMB-60 (a masterbatch containing - 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), 18.8 g LDPE resin B and an extra 178.74 g LLDPE resin A to give a final mass of 342.59 g. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 20 rpm. The final formulation (sample H) is theoretically composed of 0.7 % percent titania by weight, 5.0 % LDPE resin B, 1.8 % Daelim PBMB-60, 1.0 % PIB (average M_n ~ 200,000 g/mol), and 91.5 % LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0, 60 s, 10 and 60 minutes (corresponding to UV-C dosages of 0, 300, 3000, 180,000 J/m²) were used. The samples were then placed in an oven at 50 ⁰C for aging, as per Example 1. The effect of pre-irradiation on the time to embrittlement at 50 ⁰C is summarized in Table 6. Fig 16 shows the effect of 254 nm pre-irradiation on carbonyl index (measured according to the method given in Example 1 ) during aging. Table 6: Effect of pre-irradiation on LLDPE films containing Degussa P25 plus oleic acid (sample H)

EXAMPLE 8: Effect of pre-irradiation on oven aging of film containing 1 wt% P25 & 1 wt% Fe (II) Stearate

2.99 g of Degussa Aeroxide P25 and 3.00 g of Fe (II) stearate (obtained from Pfaltz and Bauer - F01280, lot 60086-5) was mixed with 29.03 g of LLDPE resin A in a Brabender Plastograph (160 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets. This was then mixed with Daelim PBMB-60 (a masterbatch containing - 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), LDPE resin B and extra LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 28 rpm. The final formulation (sample I) is theoretically composed of 1.0 % percent titania by weight, 1.0 % Fe (II) stearate by weight, 5.0 % LDPE resin B, 1.7 % Daelim PBMB- 60 and 91.3 % LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0, 1 and 10 minutes (corresponding to UV- C dosages of 0, 300 and 3000 J/m²) were used. The samples were then aged in an oven at 50 ⁰C using the method of Example 1. The period in days that transpired before each sample reached embrittlement is given in Table 7. Fig 17 shows the effect of pre-irradiation on the carbonyl index (measured by the method described in Example 1 ) during aging.

Table 7: Effect of pre-irradiation on thermal aging (50 ⁰C) LLDPE films containing Degussa P25 plus ferrous stearate (sample I)

EXAMPLE 9 Degussa Aeroxide P25 was mixed with Sigmacote® (obtained from Sigma-Aldrich) in a weight ratio of 3.0 : 2.4 and stirred in hexane. The solution was left to dry and then placed under vacuum to remove solvent. 3.0 g of this surface functionalized P25 powder and 3.0 g of calcium carbonate were mixed with 29.0 g of LLDPE resin A in a Brabender Plastograph (160 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets. 30.00 g of this material was then mixed with 4.29 g of Daelim PBMB-60 (a masterbatch containing - 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), 12.86 g of LDPE resin B and 210.00 g of LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 28 rpm. The final formulation (sample J) is theoretically composed of 1.0 % percent titania by weight, 1.0 % calcium carbonate by weight, 5.0 % LDPE resin B, 1.7 % Daelim PBMB-60 and 91.3 % LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0 and 10 minutes (corresponding to UV-C dosages of 0 and 3000 J/m²) were used. Weathering tests were then conducted by placing these samples in a Heraeus Suntest Xenon Arc Weatherometer (UV only; continuous light cycle, no moisture cycle), using a 1500 W xenon arc solar simulator lamp with an average integrated light intensity in the different UV regions of: UV-A: 880W/m²; UV-B: 240 VWm²: UV-C: 0 W/m². The lamps are fitted with a UV filter to remove wavelengths below 290 nm. The samples were maintained at a blackbody radiation temperature of 55 ⁰C over an extended period. The exposed samples were removed from the Suntest after certain periods of time and examined for embrittlement. The period in hours that transpired before each sample reached embrittlement is given in Table 8. Fig 18 shows the effect of pre-irradiation on carbonyl index (measured by method given in Example 1 ) during aging. Table 8: Effect of 254 nm pre-irradiation on time to embrittlement during Suntest aging of sample J

EXAMPLE 10

Degussa Aeroxide P25 was mixed with Sigmacote® (obtained from Sigma-Aldrich) in a weight ratio of 3.0 : 2.4 and stirred in hexane. The solution was left to dry and then place under vacuum to remove residual solvent. 3.0 g of the surface- modified Degussa Aeroxide P25 powder and 1.2 g of manganese stearate (Pfaltz & Bauer) were mixed with 29.0 g of LLDPE resin A in a Brabender Plastograph (160 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets. 28.00 g of this material was then mixed with 4.00 g of Daelim PBMB-60 (a masterbatch containing ~ 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), 12.00 g of LDPE resin B and 196.00 g of LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 28 rpm. The final formulation (sample K) is theoretically composed of 1.0 % percent titania by weight, 0.4 % manganese stearate by weight, 5.0 % LDPE resin B, 1.7 % Daelim PBMB-60 and 91.9 % LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0 and 10 minutes (corresponding to UV-C dosages of 0 and 3000 J/m²) were used. Thermal aging studies were conducted according to the method described in Example 1 with the exception that the oven temperature was 60 ⁰C. The time for these samples to embrittle at 60 ⁰C is given in Table 9 and the plot showing the effect of pre-irradiation on the carbonyl index (measured by method given in Example 1 ) during aging is given in Figure 19 (Note: values presented are the average of duplicate experiments). Table 9: Effect of 254 nm pre-irradiation on time to embrittlement during oven aging of sample K at 60 ⁰C

EXAMPLE 1 1

Degussa Aeroxide P25 was mixed with Sigmacote® (obtained from Sigma-Aldrich) in a weight ratio of 3.0 : 2.4 and stirred in hexane. The solution was left to dry and then place under vacuum to remove residual solvent. 0.35 g of the surface-modified Degussa Aeroxide P25 powder was mixed with 34.65 g of poly(4-methyl-1-pentene) (Sigma-Aldrich cat no. 190993, melt index 26 g / 10 min) in a Brabender Plastograph (240 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets and melt-pressed between Teflon sheets at 240 ⁰C to produce ca. 100 μm plaques (sample L). Reference plaques (sample M) were also made from as received poly(4- methyl-1-pentene).

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation time of 10 minutes (UV-C dosage of 3000 J/m²) was used. Weathering tests were then conducted according to the method described in Example 9 with the exception that FT-IR-ATR was used instead of transmission FT- IR. The period in hours that transpired before each sample reached embrittlement is given in Table 10.

Table 10: Effect of 254 nm pre-irradiation on time to embrittlement during Suntest aging of samples L and M

EXAMPLE 12

Degussa Aeroxide P25 was mixed with Sigmacote® (obtained from Sigma-Aldrich) in a weight ratio of 3.0 : 2.4 and stirred in hexane. The solution was left to dry and then place under vacuum to remove solvent. 0.35 g of the surface-modified Degussa Aeroxide P25 powder was mixed with 34.65 g of polypropylene (Sigma-Aldrich cat no. 1452149, syndiotactic, melt index 2.2) in a Brabender Plastograph (160 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets and melt-pressed between Teflon sheets at 160 ⁰C to produce ca. 190 μm plaques (sample N). Reference plaques (sample O) were also made from as received polypropylene.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0 and 10 minutes were used. Weathering tests were then conducted according to the method described in Example 9 with the exception that FT-IR-ATR was used instead of transmission FT-IR. Figure 20 shows the effect of pre-irradiation on carbonyl index (measured by the method given in Example 1 with the exception that ATR-FT-IR was used) during aging.

EXAMPLE 13 Degussa Aeroxide P25 was mixed with Sigmacote® (obtained from Sigma-Aldrich) in a weight ratio of 3.0 : 2.4 and stirred in hexane. The solution was left to dry and then place under vacuum to remove solvent. 3.0 g of the surface- modified Degussa Aeroxide P25 powder and 3.0 g of manganese stearate (Pfaltz & Bauer) were mixed with 29.0 g of LLDPE resin A in a Brabender Plastograph (160 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets. 30.00 g of this material was then mixed with 4.29 g of Daelim PBMB-60 (a masterbatch containing - 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), 12.86 g of LDPE resin B and 210.0 g of LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 28 rpm. The final formulation (sample P) is theoretically composed of 1.0 % percent titania by weight, 1.0 % manganese stearate by weight, 5.0 % LDPE resin B, 1.7 % Daelim PBMB-60 and 91.3 % LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0, 3 and 10 minutes (corresponding to a

UV-C dosage of 0 900 and 3000 J/m²) were used. Thermal aging studies were conducted according to the method described on Example 1 , with the exception that the oven temperature was 60 ⁰C. The plot showing the effect of pre-irradiation on the carbonyl index (measured according to the method given in Example 1 ) during aging is given in Fig 21. Note: data presented are the average of duplicate experiments.

EXAMPLE 14

5.54 g of cobalt naphthenate ((in mineral oil) 6% Cobalt Content, Pfaltz & Bauer) was added to a solution of 3.018 g of PIB (average M_v ~ 420,000 g/mol, average M_w ~ 500,000 g/mol, average M_n ~ 200,000 g/mol by GPC/MALLS, obtained from Sigma- Aldrich) in n-hexane (100 ml.) and stirred. The solvent was allowed to evaporate whilst stirring to obtain a homogeneously colored tacky solid. This material was dried in a vacuum oven to remove residual solvent. Degussa Aeroxide P25 was mixed with Sigmacote® (obtained from Sigma-Aldrich) in a weight ratio of 3.0 : 2.4 and stirred in hexane. The solution was left to dry and then place under vacuum to remove solvent.

3.0 g of the surface- modified Degussa Aeroxide P25 powder and 6.0 g of cobalt naphthenate/PIB/mineral oil material were mixed with 26.0 g of LLDPE resin A in a Brabender Plastograph (160 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets. 25.00 g of this material was then mixed with 3.66 g of Daelim PBMB-60 (a masterbatch containing - 57 - 63 % PIB of mol. wt. 1 ,800 g/mol), 10.98 g of LDPE resin B and 179.86 g of LLDPE resin A. The constituents were physically mixed by hand before being extruded and blown, using the same temperature profile as in Example 2 and a screw speed of 28 rpm. The final formulation (sample Q) is theoretically composed of 1.0 % percent titania by weight, 0.6 % cobalt naphthenate by weight, 0.5 % mineral oil, 0.6 % PIB (average M_n ~ 200,000 g/mol, Sigma-Aldrich), 5.0 % LDPE resin B, 1.7 % Daelim PBMB-60 and 90.6 % LLDPE resin A.

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0 and 10 minutes (corresponding to dosages of 0 and 3000 J/m²) were used. Weathering tests were then conducted according to the method described in Example 9. Fig 22 shows the effect of pre- irradiated on carbonyl index (measured according to the method given in Example 1 ) during Suntest aging. EXAMPLE 15

Degussa Aeroxide P25 was mixed with Sigmacote® (obtained from Sigma-Aldrich) in a weight ratio of 3.0 : 2.4 and stirred in hexane. The solution was left to dry and then place under vacuum to remove solvent. 0.35 g of the surface-modified Degussa Aeroxide P25 powder was mixed with 34.65 g of high density polyethylene (HDPE) (Qenos HD5148) in a Brabender Plastograph (160 ⁰C, 60 rpm) for 5 minutes. The resulting product was chopped into pellets and melt-pressed between Teflon sheets at 160 ⁰C to produce ca. 200 μm plaques (sample R). Reference films were also melt- pressed from as-received HDPE (sample S).

This sample was prepared and pre-irradiated at 254 nm as described in Example 2, with the exception that irradiation times of 0 and 10 minutes (corresponding to UV-C dosages of 0 and 3000 J/m²) were used. Weathering tests were then conducted according to the method described in Example 9. The carbonyl index, measured according by ATR-FT-IR (as described in Example 1 1 ) after 288 hours of aging in the Suntest chamber is given in Table 11.

Table 1 1 : Carbonyl indices after 288 hours aging in Suntest chamber for samples R and S.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method of controlling the degradation of a polymeric film to cause the film to degrade after an intended useful life time, including the steps of: providing a polymeric film comprising a polymer and prodegradant for the polymer adapted to be activated on irradiation with a controlled dosage of electromagnetic radiation; and activating one or more sources of artificial radiation adapted to emit electromagnetic radiation comprising wavelengths less than about 400 nm; and irradiating at least part of the polymeric film with the artificial radiation.

2. A method according to claim 1 wherein at least part of the film is exposed to light in the range 200 nm to 385 nm at a radiation dose rate of least about 50 Watts per m² of film, preferably at least 1 ,000 W/m² and more preferably at least about 7,500 W/m².

3. A method according to claim 1 or claim 2 wherein at least 80 % of the radiation energy is emitted in the range 250 nm to 260 nm.

4. A method according to any one of the preceding claims wherein at least part of the film is exposed to a radiation dosage of at least 9 kJ/m², preferably at least 15 kJ/m², more preferably at least 20 kJ/m² and more preferably still at least 25 kJ/m².

5. A method according to any one of the preceding claims further including the step of positioning a filter/mask between the polymeric film and one or more sources of artificial radiation, the filter/mask having transmission characteristics which control the spatial distribution of the radiation dosage over the polymeric film.

6. A method according to any one of the preceding claims wherein the one or more sources of radiation define an irradiation zone for the film, the film is passed through the irradiation zone and the rate of passage of the film and the intensity of the radiation provide a dose rate of at least 50 W/m²

7. A method according to any one of the preceding claims wherein the one or more sources of artificial radiation deliver radiation to both sides of the polymeric film.

8. A method according to any one of the preceding claims further comprising wrapping or covering material with the irradiated film.

9. A method according to any one of the preceding claims including the step of cooling the polymeric film during exposure to the radiation dosage.

10. A method according to any one of the previous claims wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polyethylene copolymers polypropylene copolymers, and blends of any of the aforementioned.

1 1. A method according to any one of the previous claims wherein the prodegradant is selected from the group consisting of particulate metal oxide peodegradants, metal carboxylate prodegradants and mixtures of two or more thereof;

12. A method according to any one of the previous claims wherein the prodegradant comprises TiO₂ with a particle size of less than 200 nm in the largest dimension and a metal carboxylate selected from at least one of the C2-C₃₆carboxylates of a metal selected from the group consisting of Fe, Ce, Co, Mn and Ni.

13. A method according to claim 10 or claim 1 1 wherein the metal oxide prodegradant is present in an amount of from 0.1 to 20 % by weight, based on the weight of the polyolefin.

14. A method according to any one of claims 11 to 13 wherein the metal carboxylate prodegradant is present in an amount of from 0.1 to 20 % by weight, based on the weight of the polyolefin.

15. A method according to any one of the previous claims wherein the prodegradant comprises TiO₂ with a particle size of less than 200nm in the largest dimension and a metal carboxylate and the weight ratio between the TiO₂ and the metal carboxylate is from 20:1 to 1 :20.

16. A method according to any one of the preceding claims wherein activation of the one or more sources of artificial radiation is controlled by an irradiation controller device, and wherein the irradiation controller device is configured to receive one or more inputs pertaining to intended service use of the polymeric film and determine automatically, a radiation dosage required to achieve a desired level of controlled degradation to cause the film to degrade after the intended useful life time.

17. A system for predisposing a polymeric film containing a prodegradant to degrade after an intended service life, the system including: one or more sources of artificial radiation adapted to emit electromagnetic radiation comprising wavelengths less than about 400 nm; an irradiation zone configured to receive at least part of the polymeric film for exposure to radiation; an irradiation controller configured to provide a control signal for controlling operation of the one or more sources of artificial radiation to emit a radiation dosage to predispose the polymeric film to degrade after the intended service life; and a film dispenser dispensing polymeric film into the irradiation zone.

18. A system according to claim 17 wherein the film is passed through the irradiation zone and the irradiation controller regulates at least one of the rate of passage of the film and the radiation intensity to provide a radiation dosage of at least 9 kJ/m², preferably at least 15 kJ/m², more preferably at least 20 kJ/m² and more preferably still at least 25 kJ/m².

19. A system according to claim 17 or claim 18 wherein one or more sources of artificial radiation emit at least 80 % of the radiation dosage in the range 250 to 260 nm.

20. A system according to any one of claims 17 to 19 further including a filter/mask positionable between one or more sources of artificial radiation and the irradiation zone and adapted to control spatial distribution of the radiation dosage over the polymeric film.

21.A system according to any one of claims 17 to 20 wherein the irradiation controller is adapted to: receive one or more inputs pertaining to an intended service use of the polymeric film; determine automatically, the radiation dosage required to achieve the desired level of controlled degradation, based on the one or more inputs; and control the one or more sources of artificial radiation to deliver the determined radiation dosage.