NZ331862A - Compositions and methods for selectively cross-linking films and improved film articles resulting therefrom - Google Patents

Abstract

The application relates to polymeric compositions capable of providing enhanced cross-linking efficiency, to single and multilayer films having the subject composition contained within at least one layer of film. To a method of treating film to provide enhanced cross-link within at least one layer of the film; and to the resultant cross-linked film product. Also included are articles made from the cross-linked film product.

Description

COMPOSITIONS AND METHODS FOR SELECTIVELY CROSSLINKING FILMS AND IMPROVED FILM ARTICLES RESULTING THEREFROM This application claims the benefit of 35 USC 119(c) with respect to U S Provisional Application 60/014,476 filed March 29,1996, U S Provisional Application 60/016,289, filed Apnl 26,1996, U S Provisional Application 60/016,800, filed April 26, 1996, and claims the benefit of 35 USC 120 as a continuation-in-part of U S Application Serial Number 08/708,517, filed 10 September 5, 1996 The teachings of each referenced application is incorporated herein by reference The present invention generally relates to polymeric compositions capable of providing enhanced crosslinkmg efficiency to multilayer films having the subject composition contained within at least one layer of said film, to a method of 15 treating said film to provide enhanced crosslink within said at least one layer of the film and to the resultant cross-linked film product as weli as articles made from said cross-linkcd film product The present invention is particularly useful for the manufacture of flexible packaging films including those used to package food items 20 It has long been known that the physical properties of polymers can be altered by crosslinkmg Control of crosslinkmg can induce a ni mber of desirable changes in the physical properties of a polymer, depending on the application For example, for polyolefins, the softening temperature increases, as does the toughness, impact strength, and resistance to attack by solvents and grease 25 Further, if a cross! inked polymer is stretched to induce orientation, the material will have a greater degree of heat-shrink characteristics than an uncrosslmkcd counterpart sample However, these same physical properties"can present difficulties for manufacture of a product if an attempt is made to merely substitute the crosshnked material for an uncrosslinked raw material This is particularly Printed from Mimosa true in manufacturing processes that rely on extrusion, coating, or spraying to produce a thin layer of material An increase in softening temperature or viscosity, for instance, may take a polymer completely out of the useable range for a given type of equipment A 5 higher softening temperature would require higher manufactunng temperatures, w hich may cause other useful components of a film or coating to degrade A higher viscosity may mean that the material is difficult to spray or extrude, or that the resulting thickness of a coaung is undesirably high Some of the changes in physical properties obtained by crosslinkmg polymers are discussed in 10 Photoimtiated Cross-Linking of Polyethylenes andDiene Copolymers, B Ranby, ACS Symposium Series. 1990. Vol 417, pp 140-150, and Photouiitiated Crosslinkmg of Low Density Polyethylene I Reaction and Kinetics, Y Qmg, X Wenying, andB Ranby. Polymer and Eng Sci. Nov 1991, Vol 31,No 22 Various processes are known for the industrial manufacture of crosslinked 15 polyolefin materials These include the use of high energy ionizing irradiation, such as gamma- and accelerated electron beam irradiation (e-beam), as well as chemical crosslinkmg agents, such as peroxides, silanes and difunctional compounds, monomers and oligomers which can combine with the target polymer One of the problems generally associated with chemically cross-linked 20 polymers is that the agents capable of causing the cross-link are normally introduced into the composition prior to its being formed into a packaging article (e g , film) Thus, cross-linking may occur under the elevated temperature and/or pressure conditions normally encountered while forming the initial film, such as by extrusion By having the polymeric material cross-linked prior to or during its 25 being processed into a film or the like, the processing step requires much higher energy, may produce a product having unacceptable properties, or, in certain instances, is not practical at all Various parties have disclosed the use of high energy irradiation as a means of cross-linking polymeric compositions For example, German patent 2- Prxnted from Mimosa publication P 16 29 772 6 by Rosenthal discloses that a relatively thick (500 micron) polyethylene film can be irradiated with an electron beam at a dose of 5 Mcgarads at a penetration depth of 250 microns and then stretched to a thickness of 20 microns to produce a film with sides (material adjacent to a major surface of 5 the film) having different properties In that case, the treated side was said to have a melting point of about 160°C, while the untreated side was said to have a melting point of 115°C Rosenthal teaches that crosslinkmg can also be accomplished using UV, gamma-rays or x-rays using a photoinitiator such as a chlorinated aromatic or aliphatic compound Examples cited include 10 tetrachloroethylene, 1,2,4,5-tetrachlorobenzene, and 1,2,4 tnchlorobenzene Such chlorinated aromatic materials are not desirable from a toxicity standpoint, especially for food packaging European Application 0 549 372 A1 discloses a method of crosslinkmg the surface of a molded article made of a copolymer of an alkenylsilane and an olefin 15 having at least two unsaturated double bonds, by dipping the article into a solution of a catalyst m hydrocarbon solvent, and then heating the article for two hours at 80°C European Patent Application 0 490 854 A2 teaches a continuous process for crosslinkmg polyethylene with UV light Crosslinkmg occurs during extrusion 20 of the polyethylene while it is in the melt state and under a nitrogen atmosphere The method employs a photoinitiator such as benzophenone or a benzophenone derivative, and tnallylcyanurate (TAC) or triallylwocyanurate (TAIC) While crosslinkmg aids such as TAC and TAIC are well known in the prior art, they are also highly toxic and unsuitable for food package applications and are taught to 25 require the use of an inert atmosphere, which is costly and inconvenient United States Patent No 4,737,559, issued to Kellen et al April 12, 1988 relates to pressure-sensitive adhesives for bandages The application discloses that such adhesives tend to build adhesion strength over time, but that the addition of a crosslinkmg monomer with p-acryloxybenzophenone and subsequent exposure to Printed from Mimosa UV radiation yields an adhesive which has a good ability to conform to the skin surface, adequate initial adhesion, and limited adhesion build-up, while providing low residue upon removal In Polymer, 1993, 34( 12), 2585-91, Gedde et al, describe the thermal 5 crosslinkmg of polyethylene using low molecular weight. 1,2-poIybutadiene and peroxides Thermal crosslinkmg has limited applicability because of inherent instability during the extrusion and/or molding steps Such processes always suffer from some degree of trade off between processability and amount of premature crosslinkmg 10 In Polymer Science, Ser A, 1994, 36(5), 608-14, Zamotaev et al, describe the UV crosslinkmg of polypropylene and low density polyethylene using benzophenone and difunctional acrylates In Reza Kenkyu, 1993,21(9), 974-80, Ueda et al, describe the crosslinkmg of polyethylene with an excimei laser using benzophenone or 4-chlorobenzo-15 phenone as photomitiators The excimer laser is an impractical radiation source because it requires focusing to a small area (10x20 mm) and is quite expensive Furthermore, in this case, long irradiation times and high radiation doses were required While each of the above referenced teachings and others disclose means of 20 cross-linking polymeric films using irradiation, a number of problems are associated with the resultant cross-linked product, especially when the film is contemplated for use as a packaging article Packaging matenals formed of one or more polymer layers, such as films having two major surfaces and thickness of up to about 50 mils, have been used to form closed packages For example, the 25 packaging material may be a film which has at least one layer (normally a surface layer) which is suitable to provide heat sealing The ability to be heat sealed relies on the ability of the material to flow when heated near its softening or melting temperature Inner or core layers, on the other hand, may be present to provide strength, toughness, shrink characteristics and the like Y Printed from Mimosa During manufacture, such films are sometimes exposed to radiation, such as electron-beam radiation or other radiation to crosslink the polymeric material forming the film packaging material Such techniques do not distinguish the different layers forming a film Thus, when the irradiation is applied, it may 5 adversely affect one or more layers while providing the desired beneficial effect to other layers of the film For example, it is desirable to have certain surface characteristics which provide desired sealabihty of the outer layer of a polyolefin film when subjected to highspeed packaging equipment However, when irradiation is applied to such films to enhance the core layers characteristics, the 10 radiation indiscriminately adversely effects the sealabihty of the film In addition, the performance of the sealart layer for its intended purpose is generally lowered when crosslinkmg is induced This is because the higher the degree of crosslinkmg of the sealant material, the less is its ability to flow at a given processing temperature Thus, the resultant packaging material exhibits weaker 15 and sometimes defective seals If one lowers the dosage of irradiation to which the overall film is exposed (if irradiation is the method of crosslinkmg) one may be able to lessen the adverse effect on the sealant material However, when this is done, other layers which benefit from crosslinkmg (e g to provide toughness, improved optics, or greater 20 processabihty during manufacture) may not perform as well Thus, the processor is faced with the trade-off between compromising sealing properties and other desired properties of films, such as toughness and processabihty Furthermore, it is well known that certain resins, such as poly(vinylidene dichlonde) (PVDC) and poly(propylene) (PP), and other polymers having tertiary 25 carbons within their structure, degrade upon exposure to ionizing radiation Thus, improvements in physical properties associated with crosslinkmg by such method cannot always be realized in films containing such matenals In addition to balancing the concerns associated with irradiation crosslinkmg to achieve good seal properties as well as processabihty and ff" Printed from Mimosa toughness properties, there are two technical parameters which further complicate this matter The first is that materials typically used in sealant layers (e g , ethylene/vinyl acetate copolymers ("EVA") and the like) tend to crosslink to a higher degree at a given irradiation dosage than those matenals typically used as 5 part of the internal layers of a film (e g , ethylene/alpha-olefm copolymers, such as linear low density polyethylene (LLDPE) and the like) Stated another way, a polymenc layer for which crosslinkmg is desired may be inherently less susceptible to crosslinkmg than a layer of the film for which crosslinkmg is not required A second factor is that in irradiation processes where a tubular film is exposed to irradiation from one side of the tube, then the other in a "multipass" setup, the geomeuy of the tubular film and the physics of irradiation are such that the surface layers (e g , sealant matenal) will absorb more radiation than the internal or core layers Thus, although the preferred approach is to minimize 15 crosslinkmg of the sealant layers, the tendency of many typical irradiation processes, is to cause more, not less, crosslinkmg of the sealant matenal In order to overcome the indiscriminate crosshnking caused by high voltage irradiation, U S Patent 4,863,768 (Ishio et al) teaches low voltage irradiation of films to provide for attenuation of the radiation across the films 20 cross-section (thickness) However, this method has certain defects including the significant financial investment in equipment needed to use this technology on a commercial scale, the inherent unpredictability as to the degree of crosslinkmg achieved at each layer as well as the inapplicability of this technique for films having a sealant/core/sealant configuration 25 Still another proposed solution is the use of crosslinkmg enhancers typically in the form of liquids or powders Examples include low molecular weight (LMW) compounds such as peroxides, and unsaturated esters such as diallylmaleate, tnmethylolpropanetnmethylacrylate, and 1,6-hexanediol diacrylate These materials pose several practical problems, including difficulty of handling Printed from Mimosa o5 1 862 PCT™6 liquids and powders during extrusion, regulatory status (lack of food law compliance for many of these matenals), organoleptic concerns, and poor compatibility with typical extrusion-grade polymers Peroxides, m particular, are inherently thermally unstable When used, they can inmate crosslinkmg of polymers in the extruder The reaction kinetics involved makes the extrusion process difficult to control Extrusion rates and overall process conditions must be rigorously controlled to avoid fluctuations m final film properties It is highly desired to have a means to selectively enhance the crosslinkmg efficiency (l e , degree of crosslinkmg at a unit dosage of radiation) of a specific layer or layers of a film m an effective and commercially acceptable manner, preferably m a continuous process. It is further highly desired to provide a means to crosslink one or more layers of a film composed of a polymer (e g , polypropylene, PVDC and the like) generally deemed degraded by certain ionizing irradiation, especially electron beam radiation It is still further desired to be able to crosslink a polymer film by irradiation to provide a clear, transparent film product suitable for use in packaging applications Summary of the Invention The present invention provides a means to selectively enhance the crosslinkmg efficiency of a polymeric film and, more particularly, to achieve enhanced crosslinkmg with respect-to certain layer or layers of a multilayer film A preferred embodiment of the present invention further provides a means of achieving selective crosslinkmg of at least one layer of a polymeric film using actinic irradiation (e g , ultraviolet radiation or electron beam radiation) and, still further, to permit the desired crosslinkmg to occur on films containing polypropylene, PVDC and other polymers, without having the resultant film exhibit the degradative effects normally associated with such treatment Specifically, a first aspect of the present invention is directed to a multi-layer film having at least one layer for which crosslinkmg is desired wherein said layer contains a polymeric crosslink enhancer (PCE) composition composing (i) a copolymer having ?- intcllcctijal pr"\rtv dhicn OF HZ ! 1 1 JAN 2000 WO 97/36741 PCT/US97/04796 331862 polymenc units derived from (a) at least one polyene monomer, (b) at least one C2-C20 olefmic monomer and, optionally, (c) one or more additional copolymenzable monomers different from (a) and (b) above or, alternatively, (n) polymer mixture composed of at least one polymer having uruts derived from (a) at least one polyene monomer, and at least one polymer having units derived from (b) at least one C2-C20 olefinic monomer and, optionally, at least one additional copolymenzable monomer different from (a) and (b) above for this mixture, each ^ of the at least one layer formed with polymenc crosslink enhancer composition being crosslmked to a greater degree than at least one other layer of the film, wherein at least one layer forming a major surface of the film is sealable The composition, preferably, further contains a photomitiator agent, especially when the radiation to be applied is ultra-violet radiation The layer(s) having the PCE composition results in a crosslmked layer of the film having a higher degree of crosslink than other layers The subject PCE composition can be ]0 used alone to form a layer of a film or can be blended with one or more polymers to provide a layer of film for which crosslinkmg is desired According to a second aspect of the present invention there is provided a polymenc composition composing a copolymer having polymeric units denved from (a) at least one polyene, (b) at least one C2-C20 olefinic monomer and, optionally, (c) at least one copolymenzable monomer other than (a) or (b), wherein the copolymer is an advanced unsaturated poly(olefin) copolymer, and a photomitiator, wherein the composition further compnses at least one diluent C2-C20 olefinic homopolymer, copolymer thereof and mixtures thereof According to a third aspect of the present invention there is provided a process of forming a film having a plurality of layers and at least one of said layers is selected to have an elevated degree of crosslink with respect to at least one other layer comprising A extruding a film having a plurality of layers wherein at least one of said layers contains a polymenc crosslink enhancer composition comprising (i) copolymer having polymenc units derived from (a) at least one polyene monomer, - (b) at least one C2-C20 olefinic monomer and, optionally, (c) at least one copolymenzable monomer other than (a) or (bj, or (11) mixture composed of at least one polymer having polymenc units derived from (a) at least one polyene monomer and at least one polymer compnsmg polymenc units 25 derived from (b) at least one Ci-C,„ olefinic monomer and, optionally, at least one copolymenzable monomer other than (a) or (b), and B subjecting the film to actinic radiation Preferably the film is subjected to electron beam or ultra-violet irradiation 9 (followed by page 8a) 331862 Preferably there may be provided a multi-layer film product having at least one first layer of the film's thickness which comprises a crosslmked polymenc composition and at least one second layer of the film's thickness composing a polymenc composition which is crosslmked to a lesser degree than that of the first layer The film product is preferably formed according to the process descnbed hereinabove According to a fourth aspect of the present invention there is provided a package formed of a packaging matenal and having a cavity capable of containing or actually containing an article, wherein the packaging matenal is composed of the multi-layer film outlined in the first aspect above which has the subject polymenc crosslink enhancer composition in at least one layer thereof Preferably the package matenal has been subjected to irradiation to cause 8a 1 1 JAN 2000 WO 97/56741 T *| \4 PCT/US97/04796 i O* crosslinkmg of the polymenc material of said at lexsf one layer The above invention is fully described herein below Bnef Descnption of the Drawings Figure 1 is a schematic diagram of a meu- "tate irradiation cross process In this process, a conical twin screw extruder (1) is attached to a flat sheet die (2) with a die lip gap (3) A source of irradiation, such as a Fusion Systems UV lamp (4) (equipped with a H-bulb) is positioned at or near the die hp gap (3) 10 in such a way as to insure that the extruded film (5) passes through the focal point of the lamp (4) The irradiated film (6) is drawn over a chill roll (7) and cooled The resulting film is drawn through pinch rolls (8) and wound up on a take-up reel (9), Figure 2 is a schematic cross-section of a film suitable for use as part of a 15 multilayer film of the present invention, Figures 3 through 8 are schematic cross-sections of alternative embodiments of films of the present invention, and Figures 9 through 12 are bar graphs comparing films of the present invention to other films Descnption of the Invention The present invention is directed to a new and novel composition and process of using same to provide an unproved multi-layer film suitable for packaging foodstuffs and other products and the like At least one layer of the film formed according to at least a preferred embodiment of the present invention compnses a polymenc crosslink enhancer (PCE) composition which provides that said at least one layer can be crosslmked to a higher degree than would occur in the absence of enhancer composition without adversely affecting the desirably charactenstics of other layers present in the film tnfToFFic?j 2000 J IVED ! 331862 WO 97/36741 SI I v "™ PCT/US97/04796 An aspect of the present invention provides for a polymeric crosslink enhancing composition comprising (1) a copolymer comprising units derived from (a) polyene monomer, (b) at least one C2-C20 olefinic monomer, and optionally (c) at least one additional copolymenzable monomer which is different from (a) and (b) 5 above or, alternatively, (11) a mixture of a polymer formed from monomers compnsmg polyene monomer (a) and a polymer formed from monomers compnsing at least one C2-C20 olefin monomer (b) and, optionally at least one additional copolymenzable monomer different from (a) and (b) above of composition (11) In addition, the PCE composition preferably 10 further contains a photomitiator compound, especially when the contemplated irradiation of the film is to be by ultra-violet radiation The following terms are defined herein below to aid m describing and defining the subject invention herein and in the claims appended hereto: "Film" shall mean a sheet, laminate, non-woven or woven web or the like 15 or combinations thereof, having length and breadth dimensions and having two major surfaces with a thickness therebetween The film can be composed of more than one layer (laminate, plies) composed of at least two different compositions, extending substantially the length and breadth dimensions of the film The thickness of the film can be any suitable thickness of up to about 50 mils to form a 20 package and is normally up to about 20 mils, preferably up to about 15 mils, more preferably up to about 10 mils and most preferably from 0 1 to 8 mils "Layer" or "ply" means herein a member forming all or a fraction of the thickness of a film wherein the member extends the length and breadth of the film and is composed of a distinct composition 25 "Crosslmked" or "crosslink" means herein the formation of chemical bonds directly or indirectly (via some chemical structural entity) between two or more of the molecular chains of polymers within a layer of the film The degree of crosslinkmg is typically shown by a change in the melt flow index, as measured according to ASTM D-1238 with respect to uncrosslmked comi /2 (^ItiSffiOfAthErC1" tRTV OFFICII OF NZ 1 1 JAN RECEIVED j same type Higher degrees of crosslinkmg are typically reported gel fraction as measured according to ASTM-D-2765 with values of greater than one percent (1 %) gel indicating some degree of crosslink "Polyene" means herein a monomer, as defined in Hawley's Condensed 5 Chemical Dictionary, 12th Edition, page 932, comprising any unsaturated aliphatic or alicyclic compound containing at least four carbon atoms in a chain and having at least two double bonds The term "at least two double bonds" refers to carbon-carbon double bonds One or more bonds or double bonds of carbon and an element other than carbon can, optionally, also be present in the polyene, 10 such as carbonyl "Substituted" means herein the result of a chemical reaction in which one atom or group of atoms replaces another atom or group of atoms tn the structure of a molecule It especially refers to the substitution of a hydrogen atom, of a hydrogen-carbon moiety, with an alkyl aiyl, hydroxy, halogen, or other chemical 15 substituent "Polymer" means herein a molecule that has been formed by the union of a considerable number of simple molecules with one another The simple molecules that will unite to provide a polymer are known as monomers and their union is called polymerization The polymer may comprise a union of monomer; which 20 are all alike to provide a homopolymer, or of two or more varieties of monomers to provide copolymers which are sometimes specifically called copolymers, terpolymers, tetrapolymers, etc "Flowabihty" means herein the ability of a film or layer to flow under the influence of heat and/or pressure This term is especially used with respect to 25 films or layers capable of sealing to itself or some other matenal Flowabihty is typically reported as melt flow index (MFI) conventionally measured according to the procedure of ASTM D-1238 Flowabihty is an alternative way to indicate the level of crosslinkmg as the higher the degree of crosslink a material, the lower is its MFI K Printed from Mimosa "Ultra-violet" or "UV" means radiation at a wavelength or a plurality of wavelengths m the range of from 170 to 400 nm "Ionizing radiation" means high energy radiation capable of generating ions and includes electron beam radiation, gamma rays and x-rays 5 "E-Beam" means ionizing radiation of an electron beam generated by Van de Graaff generator, electron-accelerator or x-ray "PCE" means a polymenc crosslink enhancer and refers to composition of the subject invention and to the components thereof "AUPO" means herein a PCE copolymer of an advanced unsaturated 10 polyolefin type formed by catalytic polymerization using at least one single-site catalyst, preferably at least one catalyst known as metallocene catalyst, to have high random distribution of comonomenc units therein The present PCE composition can be composed of composition (i) comprising a copolymer formed with monomeric units derived from (a) at least 15 one polyene monomer, (b) at least one Ci-C2o olefinic monomer, and, optionally, (c) at least one or more copolymenzable monomers other than (a) and (b) above Further, the present PCE composition may contain a compound suitable to act as a photomitiator wherein said compound is blended with the PCE copolymer The monomer (a) of the PCE copolymer is selected from a polyene 20 Examples of such polyenes are exemplified by but not limited to the following 5-ethylidene-2- norbornene ("ENB"), 5- mcthylidene-2- norbomenc, 5-vinyl-2-norbornene ("VNB"), 5-methylene-2-norbornene, 2,5-norbornadiene, butadiene, isoprene, 1,4 - hexadiene ("HD"), 4-methyl-l ,4-hexadiene, 5-methyl-l ,4-hexadiene, 4-ethyl-l,4-hexadiene, 1,5-hexadiene, 1,6-heptadiene, 1,4-heptadiene, 25 1,5-heptadiene, 5-methyl-l,4-heptadiene, 1,4-octadiene, 1,5-octadiene, 1,6- octadtene, 5-ethyl-l,6-octadiene, 6-methyl-l,6-octadiene, 7-methyl-l,6-octadiene, 6-ethyl-l,6-octadiene, 6-propy!-l,6-octadiene, 6-butyl-l,6-octadiene, 1,7-octadiene, 6-methyl-l,6-nonadiene, 7-methyl-1,6-nonadiene, 6-ethyl-l,6-nonadiene, 7-ethyl-1,6-nonadiene, 6-methy 1-1,6-decadiene, 1,9-decadiene, 6- t~L- Printed from Mimosa PCT/US97/0479fi methyl-1,6-undccadiene, 1,8-nonadiene, 1,13-tetradecadiene, 1,4-dodccadiene, 1,5-cyclooctadiene, 1,4-divinylcyclohexanc, 1,3-divinylcyclohexenc, l-allyl-4-vinylcyclohexane, 1,4-divinylcyclohexane, 1,3-di viny lcyclopentane, l-allyl-3-vmylcyclopentane, 1,5-divmylcyclooctane, l-allyI-5-vinylcyclooctane, 1,5-5 diallylcyclooctane, l-ally]-4-isopropenyIcyclooctane, l-allyl-4- isopropenylcyclohexane, 1 -isopropenyl-3-vinyIcyclopentane, 1 -alIyI-4-isopropenylcyclohexane, 4-vmylcyclohexcne("VCH"), dicyclopentadiene ("DCPD"), divmylbenzene and vmylisopropenylbenzenc They can be used singly or in combination with one another as the polyene component of the polymeric 10 crosslink enhancer The preferred polyenes axe butadiene, ENB, VNB, HD, DCPD and VCH and particularly preferred as part of AUPOs are ENB and VNB and most preferred arc VNB The monomer (a) should be capable of forming units of the PCE copolymer wherein at least some of the units retain ethylenic unsaturation 15 The monomer(s) (b) of the PCE copolymer is at least one C2-C20 olefinic monomer such as an olefin of 2 to 20 carbon atoms Such monomers (b) are exemplified by, but are not limited to ethylene, propylene, 1-butene, l-hexene, 3-methyl-l-butene, 3-melhyl-l-pentene, 3-ethyl-l -pentene, 4-methyl-l-pentene, 4,4-dimcthyl-l-pentene, 4-methyl-l-hexene, 4,4-dimethyI-l-hexene, 4-ethyl-l-hexene, 20 3-ethyl-l-hexene, 3,5,5-trimethylhexcne, 1-octene, 1-decene, 1-dodecene, I- tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene Typically the monomer (b) is a C2-C8 -olefin and most typically either ethylene or propylene The PCE copolymer may, optionally, contain at least one third monomer (c) selected from monomers which are other than (a) or (b) monomers described 25 above Such monomer (c) are exemplified by but not limited to vinyl aromatics, such as styrene or styrene derivatives and the like, cycloolefin monomers, such as cyclopentene, norbornene, tetracyclododecene and the like, unsaturated esters, such as vinyl acetate, methyl aciylate, ethyl acrylate, and butyl acrylatc and the Printed from Mimosa ljke, and unsaturated acids, such as acrylic acid or methacryhc acid or their acid salts and the like as well as polyvinyl halide such as polyvinyl chloride PCE copolymers of the present invention have a density at 25°C of preferably between 0 8 and 1 0 g/cc 5 The PCE copolymer, as used in PCE composition (i), will generally have a polyene content of 0 01 to 40 mole %, preferably from 0 1 to 10 mole % The remainder of the PCE copolymer (the at least one C2 to C2o olefinic monomer(s) (b) as well as any third or additional monomer(s) (c) will form 99 99 to 60 mole %, such as 99 9 to 90 mole %, of the polymcnc crosslinkmg enhancer The 10 weight average molecular weight (My/) of the copolymer should be at least about ,000 daltons, preferably from at least about 10,000 to 1,000,000 daltons A variety of factors will determine the optimal composition for a particular end-use which include compatibility with any diluent polymer, degree of reactivity with respect to the radiation to be utilized and the like The optimal composition for a 15 particular PCE copolymer can be readily determined by minor experimentation PCE copolymers of the present invention are exemplified by but not limited to ethylene-propylene-diene monomer terpolymers (EPDM's) where the diene monomer is most commonly selected from ENB, HD, DCPD or VCH The PCE composition may further include a photomitiator compound 20 Such compounds are blended with the PCE copolymer to provide a substantially uniform composition When ultra-violet radiation is contemplated as the form of irradiation, the PCE composition preferably should contain the photomitiator in order to increase the crosslink efficiency, i e , degree of crosslink per unit dose of radiation When E-Beam radiauon is contemplated as the form of irradiation, the 25 PCE composition may, optionally, include a photoinititator Although E-Beam radiation is not normally associated with photoinitiators as crosslmking readily occurs in the absence of such compounds, it has been unexpectedly found that when the present PCE composition is employed which contains such photomitiator compounds, crosslink efficiency increases and, therefore, the ?Y Printed from Mimosa PCMJS97/04796 operator can use less PCE composition, attain higher degree of crosslink, utili t& lower dosage of electron beam radiation or a combination thereof Suitable photoinitators include, but are not limited to, benzophenone, ortho- and para-methoxybenzophenone, dimethylbenzophenone, dimethoxy-benzophenone, diphenoxybenzophenone, acetophenone, o-methoxy-acetophenone, acenaphthenequinone. methyl ethyl ketone, vaierophenone, hexanophenone, a-phcnyl-butyrophenone, g-morpholinopropiophenone, dibenzosuberone, 4-morpholmobenzophenone, benzoin, benzoin methyl ether, 3-o-morphohnodeoxybcnzoin, g-diacetylbenzene, 4-aminobenzophenone, 4'-methoxyacetophenone, a-tetralone, 9-acetylphenanthrene, 2-acetyl-phenanthrene, 10-thioxanthenone, 3-acetyl-phenanthrene, 3-acetylindole, 9-fluorenone, 1-mdanone, 1,3,5-tnacetylbenzene, thioxanthen-9-one, xanthene-9-one, 7-H-benz[de]anthracen-7-one, benzoin tetrahydrophyranyl ether, 4,4'-bis(dimethylammo)-benzophenone, l'-acetonaphthone, 2'acctonaphthone, acetonaphthone and 2,3-butanedione, benz[a]anthracene-7,12-dione, 2,2-dimethoxy-2-phcnylacetophenone, ct,a-diethoxy-acetophenone, a,a-dibutoxyacetophenone, anthraquinone, isopropylthioxanthone and the like Polymenc initiators include poly(ethylene/carbon monoxide), oligo[2-hydroxy-2-mcthyl-l-[4-(l-methylvinyl)phenyl]propanone], polymethylvinyl ketone, and polyvinylaryl ketones Use of a photomitiator is preferable m combination with UV irradiation because it generally provides faster and more efficient crosslmking Preferred photoinitiators that are commercially available include benzophenone, anthrone, xanthone, and others, the Irgacure™ series of photoinitiators from Ciba-Geigy Corp, including 2,2-dimethoxy-2-phenylacetophenone (Irgacure™ 651), 1-hydroxycyclohexylphenyl ketone (Irgacure™ 184) and 2-mcthyl-l-[4-(methylthio)phenyl]-2-morophohno propan-1-one (Irgacure™ 907) The most preferred photoinitiators will have low migration from the formulated resin, as well as a low vapor pressure at extrusion temperatures and sufficient solubility in the polymer or polymer blends to yield Printed from Mimosa good crosslmking efficiency The yapor pressure and solubility, or polymer compatibility, of many familiar photoinitiators can be easily improved if the photomitiator is denvatized The derivatizcd photoinitiators include, for example, higher molecular weight derivatives of benzophenone, such as 4-5 phenylbenzophenone, 4-alIyloxybenzophenone, 4-dodecyloxybenzophenone and the like The photomitiator can be covalently bonded to the PCE copolymer or to a polymer diluent, as described herein below The most preferred photoinitiators will, therefore, be substantially non-migratory from the packaging structure The photomitiator is added in a concentration of about 0 1 to 3 weight 10 percent, preferably 1 to 2 weight percent of the layer containing the PCE composition In the case where the photomitiator is bound to a polymer, the polymer will typically be added at such a level as to provide 0 1 to 3 percent of photomitiator by weight of the layer containing the PCE composition In another embodiment of the present invention, the PCE composition may 15 be composed of a mixture of at least one polymer having units derived from a polyene (a), and at least one polymer having units derived from C2-C20 olefinic monomer(s) (b) alone or with monomer(s) (c), each described hereinabove For example, 1,2-polybutadiene, styrene/butadiene copolymers and the like having a molecular weight (Mw) of 1,000 to 1,000,000, preferably 1,000 to 200,000 can be 20 used in combination with a second polymer formed of at least one monomer (b) and, optionally, at least one monomer (c) For purposes of this description and the defined invention of the claims appended hereto the term "PCE copolymer" shall also refer to the mixture of polymers as herein described unless specifically stated otherwise In view of the fact that same such polymers arc substantially 25 compatible with polyolefins in up to about 5 weight percent, good distribution can be easily obtained which results in more uniform distribution of crosslinks in the resultant layer of the film When the PCE copolymer comprises a polymer mixture (u) as described above, the mixture will generally be of a polymer comprising a polyene in from Printed from Mimosa 0 01 to 40 weight percent, preferably from about 0 1 to 10 weight percent based on the mixture (n) and the polymer of monomers) (b) and, optionally (c) will comprise the remainder of the polymer mixture (n) The preferred polyene of the mixture is polybutadiene, styrene-butadiene copolymers and styrene-isoprene 5 copolymers The PCE copolymer may be formed by known polymerization processes employing Ziegler-Natta transition metal catalysts as, for example, those based on vanadium However, it is preferred that the resultant copolymer have the unsaturation uniformly distributed throughout the PCE polymer molecule That is 10 to state, it is preferred that the copolymers contain unsaturated sites which are essentially isolated from each other Conventional polymerization processes tend to incorporate multiple identical units adjacent to one another (in blocks) resulting in polymers with less random distribution of unsaturation within the polymer molecule A preferred set of PCE copolymers are PCE copolymers (i) and, of these the most preferred are those which are produced by at least one single-site catalyst, preferably at least one metallocene catalyst, to provide polymenc materials with a super-random distnbution of comonomers A single-site catalyst is defined as a catalyst which contains a single type of activc center The resulting 20 polymer from a single-site catalyst exhibits a narrow molecular weight distribution frequently has a polydispersity (Mw/Mn) of less than 3, and narrow compositional distnbution A metallocene catalyst is defined as an organometalhc compound with at least one pi-bound cyclopentadienyl-moiety (or substituted cyclopentadienyl moiety) and most frequently two pi-bound cyclopentadienyl-25 moieties or substituted moieties This includes other C5 pi bound moieties such as mdenyls or fluorenyls or derivatives thereof These matenals often display higher regio-regulanty and, in certain cases, higher stereoregulanty than conventionally prepared copolymers, such as conventionally prepared PCE copolymers For the /?- Pnnted from Mimosa purposes of this disclosure such PCE copolymers are referred to as advanced unsaturated poly(olefin)s (hereinafter "AUPO") AUPO's are produced in more chemically homogeneous form, with a molecular weight distnbution that is narrow, with less catalyst residue than 5 conventionally prepared PCE copolymers They are thus beneficial in forming films for packaging applications according to the present invention, especially food packaging They also offer physical properties superior in utility and scope to current copolymer technology AUPO's can be described as copolymers identical in composition to that 10 described above for PCE copolymers (l) They differ however in the process by which they are manufactured which involves the use of at least one single-site catatlyst and preferably a metallocene catalyst Typical polyenes which traditionally have been used are limited to highly substituted polyenes such as 5-ethylidene-2-norbornene, dicyclopcntadicne or 1,4-hexadiene More reactive 15 polyenes often cannot be employed using vanadium-based catalytic systems (used in conventional EPDM technology, for example) as they tend to crosslink prematurely leading to gelled, difficult to process materials It is highly desirable to be able to prepare AUPO's which contain more reactive polyenes to facilitate crosslmking and other polymer modification/grafting reactions Such materials 20 can be crosslmked by chemical (such as peroxide, silane or sulfur), or by ionizing or nonionizing radiation processes A first improvement obtained by the use of these AUPO materials is that they require less energy to be crosslmked to a given level of crosslinkmg, and provide more versatility in crosslmking, than conventional PCE copolymers of the 25 same type AUPO's crosslink to a substantially higher degree than saturated resins at a given energy level This improvement is largely based on improved distnbution of the polyene component along the polymer backbone leading to improved crosslink efficiency (V Printed from Mimosa A second improvement wilh AUPO resins involves improved regioselectivity over vanadium-based catalysts giving less chain scission, which competes with crosslinkmg A third improvement of AUPO's over conventional PCE copolymers of 5 the same type involves the oxidative and light stability of the resin This leads to unsaturated resins with a lower yellowness index A fourth improvement of AUPO's over conventional PCE copolymers is there greater ease of processing to form films and layers AUPO's, by virtue of their higher crosslmking efficiency, offer enhanced 10 onentabihty, toughness, puncture resistance, tear resistance, impact, tensile strength, and/or elongation, and thus are suitable as for aiding in the formation of a core and/or abuse layer in multilayer films, bags and laminates They can be selectively crosslmked at a lower radiation (e g , electron-beam) dosage than currently used materials so that ionizing radiation-sensitive resins such as 15 vinylidene dichlondc copolymers and polypropylene can be used without substantial degradation, and with improved organoleptic quality AUPO's also offer comparably better blends with improved physical properties compared with blends using conventional PCE copolymers (including amorphous EPDM resins) due to improved grafting reactions and reduced chain 20 mobility For example, melt crosslinkmg a blend of two or more polymers which exhibit appreciable solubility at elevated temperatures but phase separate on cooling could be improved if one of the components crosslinks and/or grafts thus reducing the tendency to phase segregate and, thus, improve the aging characteristics This can result in improve 1 optics in the final film made from 25 these materials Improvements in blend properties can also be realized since there can be closer matching of resin densities and refractive indices, and also provides for reduced yellowness Multicomponent blends containing AUPO's with improved optics and physical properties can be thereby produced /? Printed from Mimosa AUPO's can be chosen with regard to their molecular weight and crystallmity in order to tailor blends of these materials with other resins in order to optimize physical properties of a film made from the blend, e g optical properties such as gloss, haze, and clarity This degree of tailoring is not possible with more 5 conventionally produced PCE copolymers AUPO's also offer outstanding shrink characteristics, i e higher free shrink, lower shrinking temperatures, and improved orientability compared with conventional ethylene/alpha-olefin copolymers Methods of making these matenals using metallocene catalysts are 10 disclosed in International Application WO 88/04674 by Welborn, et al , which teaching is incorporated herein by reference as if set forth m full Typical examples of AUPO'S are those copolymers described above except that they are prepared using a single-site catalytic process, such as mctallocenes These include, but are not limited to, terpolymers of ethylene-propylene-polyene 15 monomer, ethylene-butene-polyene monomer, ethylene-hexcnc-polyene monomer, ethylene-heptene-polyene monomer, ethylene-octene-polyene monomer, ethylene-4-methyl-l-pentene-polyene monomer, ethylene-norbomene-polyene monomer , and ethylene-styrene-polyene monomer, where the diene is selected from ENB, VNB, HD, DCPD, VCH, 1,7-octadiene, 1,9-decadiene or DVB 20 Preferred AUPO resins contain highly reactive vinyl groups without premature crosslmking or gelation such as reaction extruder or reactor or the like The preferred dienes include 5-vinyl-2-norbornene Unsaturated PCE copolymers of olefins and 5-vinyl-2-norbornene can be prepared using simple metallocene catalysts such as Cp2ZrCl2 without premature crosslinkmg In this case, the 25 cychc-olefmic group is polymenzed leaving the pendant vinyl group available for subsequent crosslinkmg or modification/grafting reactions Alpha,omega-dienes, such as 1,7-octadienc and 1,9-decadienc, and other acyclic dienes containing an alkyl substituent alpha to one of the vinyl groups are also preferred Examples of such acyclic dienes are 3-methyl-l,5-hexadiene, and 3-methyl-l,7-octadiene Printed from Mimosa WO 97/36741 PCT/US97/04796 Vinyl-unsaturated matenals exhibit outstanding crosslmking characteristics which lead to films, bags or laminates with improved physical properties Preferred AUPO resins comprise single-site catalyzed polymenc materials with a density of between 0 8 and 1 0 g/cc, such as between 0 84 and 0 96 g/cc, 5 between 0 86 and 0 94 g/cc, between 0 88 and 0 92 g/cc, and between 0 89 and 0 91 g/cc All density values falling within any of these stated ranges are also included herein The PCE composition of the present invention can be used alone to provide at least one layer of a film or can be used m conjunction with one or more 10 diluent polymers suitable for forming the at least one layer for which enhanced crosslmking is desired The amount of PCE composition (either as PCE copolymer alone or further with photomitiator, as desenbed above) to be combined with diluent polymer(s) may be from about 0 1 to 99 9 weight percent of the composition forming the target layer The exact amount will depend on the 15 degree of crosslinkmg desired, the compatibility of the subject PCE compsition and the diluent polymers used in a particular instance and, therefore, all values of weight percentages and ranges between 0 I and 99 9 weight percent are made pan of the present teaching The diluent polymers are exemplified by, but not limited to 20 homopolymers and copolymers of olefins, such as polyethylene, including high density polyethylene, low density polyethylene, ultra-low density polyethylene, linear low density polyethylene, polypropylene, as well as ethylene/propylene copolymers, polystyrene copolymers, ethylene/acrylate or alkacrylate copolymers, ethylene/acrylic acid or alkacryhc acid copolymers and lonomers, ethylene/vmyl 25 acetate and the like and mixtures thereof The crosslink may occur between and/or among molecules of PCE copolymer Further, the PCE copolymer may crosslink or react with molecules or fragments of molecules of the diluent polymer For example, a crosslink may be formed between a first and a second PCE copolymer molecule or crosslinks may ef Printed from Mimosa WO 97/36741 PCT/US97/04796 occur among a first PCE copolymer molecule, a second PCE copolymer molecule and a third PCE copolymer Crosslink may also occur between at least one PCE copolymer and diluent polymer molecule or a fragment of such molecules Diluent polymer molecules may have residual cthylenic unsaturation suitable as a 5 site for entering into a crosslmking with another moleculc In the case of polymers having tertiary carbon-hydrogen bonds, such as polypropylene and the like, which may undergo scission of the polymer molecule upon ionizing irradiation, it has been found that the presence of the subject PCE coplymer inhibits scission to occur and/or provides a means of recombming the polymer 10 fragments formed with thermselves or as part of the PCE copolymer Thus, the degradative effect of scission commonly associated with ionizing inadiation of certain polymers is substantially reduced The PCE composition is preferably a solid at ambient temperatures which is usually between 20 and 25°C When the PCE copolymer is used in a 15 composition which will be used in conjunction with diluent polymer, the melt flow index (MFI) is chosen to be compatible with the rheology of the PCE copolymer with the polymer diluent or with the materials of the other layers of the film, if present PCE copolymers of low weight average molecular weight (LMW) of about 5,000 grams/mole or less, are less preferred because they present 20 difficulties in handling, because of the extra step which may be required to compound such low molecular weight compounds with the diluent polymer forming the layer's matnx, and because of the tendency of these low molecular weight matenals to bloom or migrate through the film after extrusion if crosslmking is delayed It is preferred to provide the PCE composition as solid 25 pellets so that they are easily blended with the other polymenc raw matenals (such as ethylenic polymers), which are also typically provided in pellet form Thus, these matenals can be preblended pnor to being fed to an extruder or other apparatus used to form the film structures The polymenc crosslmking enhancer composition will preferably have a low yellowness index pnor to, and following, ZZ- Printed from Mimosa WO 97/36741 PCT/US97/04796 irradiation and should possess good organoleptic properties (1 e not impart off-odors or flavors to foods) The melt flow index (MFI) of the solid PCE copolymer should be between 0 01 and 100 dg/mm under ASTM D-1238 at 2 16 kg/190°C, although higher MFI 5 materials may be used The preferred MFI is between 0 1 and 20 dg/min, and more preferably between 0 1 and 10 dg/min, as such MFI polymers are typically used in packaging applications (ASTM D-1238, Condition E) The number average molecular weight (Mn) of the PCE copolymer of the invention is preferably at least 10,000 daltons, and more preferably at least 15,000, 10 20,000,40,000, or 60,000 daltons The M„ ss normally between 10,000 and 1,000,000, preferably between 10,000 and 200,000 daltons, such as between 20,000 and 100,000, between 30,000 and 80,000, between 40,000 and 70,000, and between 50,000 and 60,000 daltons (grams/mole) The weight average molecular weight (Mw) of the PCE copolymer should 15 be at least about 10 000 daltons and preferably at least 20,000 daltons The preferred Mw can be between 20,000 and 1,000,000 daltons, such as between 30,000 and 350,000, between 50,000 and 250,000, between 70,000 and 170,000, more preferably between 90,000 and 130,000 daltons The viscosity average molecular weight (Mv)of the PCE copolymer can be 20 between 20,000 and 1,000,000, preferably between 30,000 and 350,000, such as between 50,000 and 250,000, between 75,000 and 150,000, more preferably between 90,000 and 125,000 daltons For example, when the subject film has a food contact end-uses, a Mv of at least 120,000 daltons is preferred for purposes of compliance with current U S food law (FDA) regulations 25 Although the PCE copolymer may be amorphous, il is preferred that the copolymer be semi-crystalline Thus, AUPO's used as PCE copolymers in the present invention can have crystallinity ranging from 0 to about 70% or greater, such as ranges of from 0 001% to 45% for materials with propylene as the predominant monomer (b), and from 0 001 % to 70% for matenals with ethylene 2-3 Printed from Mimosa as the predominant monomer (b) For the purposes of this disclosure, crystallinity is defined as the fraction of crystals formed as determined by conventional X-ray diffraction methods Conventional polyolefins typically have a certain number of double bonds 5 within their molecular structure The PCE copolymers of the present invention contributes additional unsaturation to this "background" or baseline unsaturation primarily due to the polyene present Too low a polyene content (taking into account the percent of the polyene in the copolymer, the percentage unsaturation of the polyene monomer itself, the amount of antioxidant present and the 10 percentage of the PCE copolymer in a blend of PCE composition and diluent polymer, where present* can result in insufficient crosslmking enhancement It is preferred that the PCE copolymer contain al least 10 carbon-carbon ethy'ienic double bonds (C-C) per 100,000 carbon atoms of the copolymer molecule The number of ethylemc double bonds may range from 10 to 33,333 double bonds per 15 100,000 carbon atoms with from about 20 to about 1000 being preferred It is understood that all numerical values and ranges within the specific ranges disclosed are incorporated herein by reference Thus, the PCE copolymer will provide more double bonds to the layer's composition because of the presence of the polyene, than a similar polymer without the polyene The most desirable 20 unsaturation is vinyl unsaturation (also called terminal or pendent unsaturation), but internal double bonds can also be used Such polymers will contain unsaturation at a level significantly higher than that represented by the polymer end groups, and are also characterized by a uniform distribution of unsaturation within the matrix (i e, random copolymers) The unsaturation of such polymers is 25 most readily characterized by infra-red (IR) spectroscopy Too high a polyene content (again taking into account the percent of the polyene in the copolymer, the percentage unsaturation of the polyene monomer itself, the percentage of the PCE composition and diluent polymer, where present) can result in extrusion gels or inclusions which can, if severe enough, affect Printed from Mimosa orientation stability (if an oriented film is being made) and can even result m bubble breaks Even if not severe enough to cause the film to break, the optics (gloss, clarity, haze) of the final film can be adversely affected by such inclusions For packaging applications where optics are important, this can mean film which 5 is not commercially acceptable Thus, it is preferred to have the polyene content of the PCE copolymer within a range to provide from 10 to about 10,000 and preferably from 20 to 1,000 ethylenic double bonds per 100,000 carbon atoms present in the layer composition For example, the calculated levels of unsaturation (number of C=C bonds 10 per 100 000 carbon atoms) for a representative group of polyenes useful as PCE copolymers are as shown in Table 1 herein below TABLE 1 Weieht % oolvene in PCE Copolymer C=C/100.000 C ENB 1.4-HD 0 0 0 1 116 171 2 233 3<» 1 3 349 512 4 465 682 581 852 6 697 1022 7 8H 1192 The values of unsaturation given in Table 1 assume that (1) ethylene and propylene are the two other monomers in the PCE copolymer, and (2) the ratio by weight of ethylene to propylene is 3 1 The present invention provides a means of providing a desired degree of crosslmking of polymeric matenal of a particular layer or layers of a film while 20 not adversely effecting any other layers of the film It is useful in providing the desired crosslmking of the target layer(s) of a multi-layer film having resins, which are normally adversely effected by ionizing irradiation, especially that of E- Printed from Mimosa Beam irradiation as, for example, polypropylene, vinyhdene dichlonde copolymers and the like Such polymers tend to undergo chain scission and resultant degradation when exposed to E-Beam radiation at dosages of 10 to 100 kiloGrays It has been found that the PCE compositions of the present invention 5 when used as a layer or a blend component of a layer, unexpectedly imparts the desired level of crosslink and its associated properties while minimizing or substantially eliminating the degradation products and results normally encountered The film of the invention can be made by any conventional means, 10 including coextrusion, lamination, extrusion coating, or corona bonding, irradiated and optionally oriented The above steps can be earned out in various order and/or repeated as known to those skilled in tne art The materials to be used m forming the subject layer of the film may be formed, for example, by initially mixing the PCE composition with diluent polymer (if desired) during the film-15 forming extnision step by using a single or twin screw extruder in any of various mixing sections m manners well known in the art In some instances, it may be preferable to pre-compound the materials prior to the film-forming extrusion step Irradiation can be done by any conventional means In the mediation process, the film is subjected to an actinic radiation treatment, such as ultra-violet, corona 20 discharge, plasma, X-ray, gamma ray, beta ray, or high energy electron treatment, such as electron-beam radiation, which induccs cross-linking between molecules of the irradiated material The ionizing irradiation of polymenc films is disclosed in U S Patent No 4,064,296, to Bomstein, et al, which teaching is hereby incorporated in .ts 25 entirety by reference Ionizing radiation dosages are commonly referred to in terms of the radiation unit "RAD", with one million RADS, also known as a megarad, being designated as "MR", or, in terms of the radiation unit kiloGray (kGy), with 10 kiloGray representing 1 MR, as is known to those skilled in the art A suitable radiation dosage of high energy electrons is in the range of between Z^p Printed from Mimosa and 200 kGy, preferably between 20 and 150 kGy, and more preferably between 30 and 120 kGy such as between 40 and 90 kGy Preferably, irradiation is carried out by an electron accelerator and the dosage level is determined by standard dosimetry methods Other accelerators such as a Van de Graaff or resonating 5 transformer may be used The radiation is not limited to electrons from an accelerator since any ionizing radiation may be used As can be seen from the descriptions of preferred films for use in the present invention, the most preferred amount of radiation is dependent upon the film and its end use and the exact dosage can be readily determined by one skilled in the art 10 The film may, alternately, be irradiated with ultra-violet radiation In this embodiment the PCE composition may, preferably, contain at least one photomitiator agent described herein above The radiation should be emitted from a source capable of emitting radiation of the wavelength of from 170 to 400 nanometers (nm) The radiation dosage should be at least 0 I Joule per cm2 and 15 preferably from 0 5 to 10 Joules per cm2 and most preferably from 0 5 to about 5 Joules per cm2 The dosage required on a particular application will depend on the configuration of the layer in the film, the composition of the layer, the temperature of the film being irradiated and the particular wavelength used The dosage required to cause crosslinkmg to occur for any particular set of conditions can be 20 determined by the artisan Any UV source capable of being positioned at or near the die lip so that the film passes through the focal point of a lamp while the layer to be crosslmked is still in the melt state can be used In another embodiment of the invention, the layer need not be crosslmked 25 upon extrusion, but may be crosslmked at some later time, at the convenience of the processor, and typically m conjunction with other processing steps In this embodiment, the crosslinkmg may take place at room temperature or at an elevated temperature which is below the melting point of the film as a whole For example, a film having layers with different melting points can be heated to a Printed from Mimosa temperature between the two melting points and then irradiated The crosslmking effect would be greatly enhanced in the layer with the lower melting point, yielding some of the benefits of melt-phase crosslmking without tying the crosslinkmg step to the time and location of the extrusion step 5 The present invention as desenbed herein relates to improved methods and matenals for making multilayer thermoplastic films, however, one of ordinary skill in the art will readily recognize that it is applicable to thermoplastic objects in a vanety of forms such as cups, bottles and trays In addition, a film or coating made according to the present invention may be applied to a variety of substrates, 10 including other polymeric matenals, paper, glass, silica, and metal, as well as fabrics made from natural and synthetic fibers A common measure of the amount of crosslmking m an irradiated film is gel content or percent (%) gel The weight fraction of polymer insoluble in a suitable solvent, such as boiling toluene or boiling xylenes, is referred to as the % gel and 15 this is an indication of degree of crosslinkmg It is determined by placing a 0 4 to 0 5 gram sample weighed to + 0 1 mg into a cellulosic or Teflon extraction thimble About 100 ml solvent is poured into a 400 ml Erlenmeyer flask having a block-tin condenser with copper cover, and borosilicate glass siphon cup Three to six boiling stones (carborundum or equivalent) are added to the flask The flask is then set on a 20 hot plate, the thimble is placed in the siphon cup, and the siphon cup and condenser are positioned into the flask The toluene is brought to a boil, and the heat is adjusted to yield a reflux rate of between two and four drops per second The material is refluxed for twenty one hours The thimble is then removed with forceps The sample is air dned under a hood for at least two hours The sample 25 is transferred to a vacuum oven heated at 50°C under 25 to 30 inches of mercury vacuum, and the sample is dned in the oven for 24 hours The gel is weighed on an analytical balance Gel % is calculated by the formula Gel weight, g X 100 = % gel Sample weight, g 2# Printed from Mimosa The sample is extracted a second 21 hours to assure complete dissolution of all soluble portions If the gel of the second extraction is more than 3% (absolute) less than the gel of the first extraction, subsequent extractions are run An alternate measure of the amount of crosslmking in an irradiated film is 5 "flowabihty" A lower flowabilility value indicates a greater degree of crosslinkmg The following is a detailed descnpUon of the drawings Figure 1 is a schematic diagram of a melt-state irradiation crosslinkmg process In this process, a conical twin screw extruder (1) is attached to a flat sheet 10 die (2) with a die hp gap (3) A source of irradiation, such as a Fusion Systems UV lamp (4) (equipped with a H-bulb) is positioned at or near the die hp gap (3) m such a way as to insure that the extruded film (5) passes through the focal point of the lamp (4) The irradiated film (6) is drawn over a chill roll (7) and cooled The resulting film is drawn through pinch rolls (8) and wound up on a take-up reel 15 (9), Figure 2 illustrates a layer 11 which contains a PCE composition of the present invention to provide enhanced crosslink at a given irradiation dosage Such a layer can be combined with other layers to provide a multilayer film Figure 3 shows a multilayer film having layers 11 and 12 Layer 12 is a 20 heat sealable layer which can be formed of any polymcric matenal, such as a polyolcfin, more preferably ethylenic polymers, such as ethylene/alpha-olefin or ethylene/unsaturated ester copolymers, such as ethylene/vmyl acctate copolymer, and ethylene/alkyl acryiate copolymer, as well as polyamides, or polyesters Layer 11 is as desenbed above 25 Figure 4 shows a multilayer film with layers 11, 12, and 13 Layer 13 is an abuse-resistant layer useful as an outermost layer of a film for packaging applications This layer can be formed by any polymenc matenal such as a polyolefin, more preferably ethylenic polymers, such as ethylene/alpha-olefin or Z-f Printed from Mimosa ethylene/unsaturated ester copolymers, polypropylene, polyamide, polyester, and the like The layers 11 and 12 are as described above Figure 5 shows a multilayer film with layers 11, 12, 13 and 14 Layer 14 is an adhesive layer m films where such a matenal beneficially ensure or enhance 5 inlerlaminar bond strength between any or all of layers 11, 12, and 13 The specific placement of layer 14 in a film of the invention, as shown in Figure 4, is by way of example only Such adhesives may be polymeric, such as an acid or an acid anhydnde-grafted polyolefins Alternatively, layer 13 can represent a convemional adhesive or glue of any suitable kind, e g polyurethane adhesive 10 where a laminate of the multilayer film 10 with another is contemplated The remaining layers are as described above Figure 6 shows a multilayer film with layers 11, 12, 13,14, and 15 Layer 15 compnses an oxygen bamer material, such as ethylene-vinyl alcohol copolymer (EVOH), vinylidene dichlorideMnyl chloride copolymer, vmylidene 15 dichlonde/methyl acrylate copolymer, polyester, or polyamide, etc The remaining layers are as described above Figure 7 shows a multilayer film with layers 11, 12, 13,14, 15, and 16 Layer 16 comprises a core or internal layer which contributes bulk, shnnkability, toughness, or some other function or property to the overall film Layer 16 can 20 comprise any of the polymers disclosed for the other layers The remaining layers are as described above Figure 8 shows a multilayer film with layers 11, 12, 13,14,15,16, and 17 Layer 17 comprises an adhesive layer in cases where such a material can be beneficial in ensunng or enhancing mterlaminar bond strength Such adhesives 25 have already been described with respect to Figure 4 The remaining layers are as described above The present invention can be used to crosslink to the polymenc composition of different layers at different levels For example, an abuse-resistant layer (13) and/or an internal layer (16) can be crosslmked to a greater extent than a 3$ Printed from Mimosa sealant layer (12) This may be accomplished by varying the amount of PCE composition contained in each target layer Figures 9 through 12 are bar graphs comparing monolayer films of the present invention to other, control films that do not have a crosslmking enhancer 5 These graphs are described in detail below with respect to the examples The present invention can be used to enhance the crosslink content of one or more layers of a film The film has two major surfaces and a thickness which extends from one major surface to the other The film thickness is composed of n layers where n is a positive integer of from 1 to an upper value Z which can be any 10 positive integer of two or greater and usually is a value of from 2 to 14, preferably 2 to 12 The film will have x layers for which enhanced crosslink is desired (target layers) where x is an integer of from 1 to an upper value of (Z-1) The target layers may be any layer or combination of layers of the film including layer(s) providing one or both of the film's major surfaces or any of the layers 15 spaced away from the major surfaces (core layers) or a combination thereof The choice of layers will be dictated by the configuration of the film and the layer(s) for which crosslink is desired without causing deterioration of the other layers and, thereby, provide an improved film product The invention may be further understood by reference to the examples 20 shown below These examples are given for illustrative purposes only and are not meant to be a limitation on the invention described herein or defined by the claims appended hereto All parts and percentages are by weight unless otherwise stated Tables 2,2A, and 2B identify the materials used in the examples The Tables thereafter desenbe the films made with these materials / Printed from Mimosa FCT/US97/04796 TABLE2 MATERIAL* TRADENAME SOURCE PE1 Dowlex™ 2045 03 Dow PE2 DPF 1150 02 Dow PE3 Affinity™ PL 1270 Dow PE4 Affinity™ PF 1140 Dow PE5 XU59001 00 Dow PE6 XU59202 01 Dow PE7 DPF1150 01 Dow PE8 Affinity™ XU 59220 04 Dow PE9 Dowlex™ 2045 14 Dow PE10 Dowlex™ 2037 Dow EV1 XV 65 93 Exxon EV2 LD-318 92 Exxon EV3 Escorene™ LD-761 36 Exxon EV4 PE 1335 Rexene OBI XU 32034 06 Dow OB2 E-151 Evalca PA1 Grilon™CF6S EMS EMI EM AC™ SP 1305 Chevron AB1 ,075 ACP concentrate Teknor Color AB2 80,274 ACP concentrate Telenor Color AD1 Admer™ SF 700 A Mitsui *PE1 = LLDPE, an ethylene/ 1-octene copolymer with a density of 0 920 gm/cc and a 1-octene content of about 6 5 wt% PE2 = a single site, branched, ethylene/ 1-octene copolymer with a density of 0 901 gm/cc and a 1-octene content of about 12 5 wt% PE3 = a single site, branched, ethylene/ 1 -octene copolymer with a density of 0 898 gm/cc and a 1 -octene content of about 13 wt% PE4 = a single site, branched, ethylene/ 1-octene copolymer with a density of 10 0 8965 gm/cc and a 1-octene content of about 14 wt% PE5 = a single site, branched, ethylene/ 1-octene copolymer with a density of 0 91 gm/cc and a 1-octene content ol about 10 wt% PE6 = a single site, branched, ethylene/ 1 -octene copolymer with a density of 0 900 gm/cc and a 1 -octene content of about 13 wt% 32- Printed from Mimosa PE7 = a single site, blanched, ethylene/ 1-octene copolymer with a density of 0 901 gm/cc and a 1-octene content of about 12 5 wt% PE8 = a single site, branched, ethylene/ 1-octene copolymer with a density of 0 896 gm/cc and a 1-octene content of about 14 wt% PE9 = LLDPE, an ethylene/ 1-octene copolymer with a density of 0 920 gm/cc and a 1-octene content of about 6 5 wt% PE10 = LMDPE, an ethylene/ 1-octene copolymer with a density of 0 935 gm/cc and a 1-octene content of 2 5 wt% EV1 = ethylene vinyl acetate copolymer with 15 wt% vinyl acetate comonomes 10 EV2= ethylene vinyl acelate copolymer with 9 wt% vinyl acetate comonomcr EV3= ethylene vinyl acetate copolymer with 28 wt% vinyl acetate comonomer EV4 = ethylene vinyl acetate copolymer with 3 3 wt% vinvl acetate monomer OBI = 96 wt % vinyhdene dichlonde/methyl aery late copolymer with 8 5 wt % methyl acrylate comonomer, 2 wt % epoxidized soybean oil, and 2 wt % butyl 15 acrylate/methyl methacrylale/butyl methacrylate terpolymer OB2 = ethylene/vmyl alcohol copolymer (44 mole % ethylene ) PA1 = nylon 6,12 copolymer EM 1 = ethylene/methyl acrylate copolymer with 20 wt % methyl acrylate comonomer AB1 = 89 8 wt% low density polyethylene (Exxon LD 203 48) + 10 wt% synthetic amorphous silica (Syloid™ 74X6500 from Davison Chemical) + 02 wt% calcium stearate AB2= about 82 wt% low density polyethylene (Exxon LD 203 48) + 10 wt% synthetic amorphous silica (Syloid™ 74X6500 from Davison Cnemical) + 02 25 wt% calcium stearate + small amount of pigments AD1 = anhydride-grafted polyolefin blend 33 Printed from Mimosa TABLE 2A CE1 Keltan™ 2308 DSM CE2 Polysar™ 227P Bayer CE3 Vistalon™ 8731 Exxon CE4 Dutral™ 4033 Enichem CE5 Vistalon™ 3708 Exxon CE6 Polysar 847XP Bayer CE7 Nordel™ 2722-elec DuPont CE8 Keltan™ 5509 DSM CE9 Rovalene™ IM 7200 Umroyal CE10 Tafmer™ TP 3180 Mitsui CE1I Royalene™ IM 7100 Umroyal CE12 EP 181SP JSR CEI3 Keltan™ 5808 DSM CE14 Nordel™ 5892 (2760) DuPont CE15 Nordel™ 3681 (2744) DuPont CE16 EP57P JSR CE17 Dutral™ 4028 Enichem CEI8 Dutral™ 4038 Enichem CE19 Keltan™ E801 DSM CE 20 Nordel™ 2722-P DuPont The crosslmking enhancers copolymer (CE1 through CE 20 ) were EPDM resin type PCE copolymers having the composition and properties listed in Table ?B below Printed from Mimosa PCT/XJS97/04796 TABLE 2B PCE c2 (wt%) 3 DENE (wt%)a DIENE TYPE MOONEY VISCOSITY MFI (dg/min) ML 1 + 8 @100°C ML 1 +4 @125°C CE1 73 ENB* CE2 75 ENB 24 2 14 3 CE3 74 ENB 3 21 0 CE4 76 ENB 26 9 3 CE5 65 3 5 ENB 79 2 47 0 CE6 74 40 ENB 85 0 57 0 CE7 72 60 HD** 31 I 23 2 CE8 73 45 ENB CE9 76 45 ENB 65 8 46 4 CE10 75 47 ENB 12 6 66 CE11 74 50 ENB 6 0 b CE12 75 59 ENB CE13 67 60 ENB CE14 71 60 HD 804 58 9 CE15 71 60 HD 61 9 46 1 CE16 72 7 1 ENB CE17 76 3-5 ENB CE18 73 3-5 ENB CE19 - — ENB 3 0^ CE20 HD 31 9 24 1 a Monomer content determined by ASTM D-3900 5 b MR determined by ASTM D-1238 at 230°C/21 6 kg C MR determined by ASTM D-1238 at 230°C/10 0 kg * ENB = 5-ethylidene-2- norbomenc ** HD = 1,4 - hcxadiene Mooney Viscosity was measured in accordance with ASTM 1646 In this procedure a Mooney viscometer is used to measure the effects of time of sheanng ZT Printed from Mimosa WO 97/36741 PCT/US97/047W and temperature on the comparative viscosities of rubber compounds Rotor torque in "Mooney units" (1 MU = 0 833 N m) is recorded over a 4 or 8 minute period, typically passing through a broad minimum, and the minimum is reported as the Mooney viscosity 5 Certain matenals were blended together to form some of the film structures, and these blends are identified as follows PEB1 = 90 parts PEI + 10 parts AB1 PEB2 = 92 5 parts EV2+ 7 5 parts PEI PEB3 = 90 parts PE6 + 10 parts PEI 10 PEB4 = 85 parts PE7 + 15 parts PEI PEB5 = 75 parts PE6 + 25 parts PEI PEB6 = 75 parts PE7 + 25 parts PEI CEB1 = 90 parts PE2 + 10 parts CE3 CEB2 = 90 parts PE2 + 10 parts CE2 15 CEB3 = 70 parts PE2 + 20 parts PEI+10 parts CE2 CEB4 = 60 parts PE2 + 30 parts PE1+10 parts CE2 CEB5 = 60 parts PE2 + 30 parts PE1+10 parts CE3 Some of the PCE copolymers were further analyzed to determine molecular weight and molecular weight distribution The results of the analysis 20 appear in Table 3 3 Printed from Mimosa "WO 97/36741 TABLE 3 PCE type Mn (xlOOO g/raol) Mw (xlOOO g/mol) Mr (xlOOO g/mol) M„, (xlOOO g/mol) My (xlOOO g/mol) Dispersity Mw/M„ Intrinsic Viscosity fdL/g) CE2 56 121 270 549 109 2 15 1 41 CE3 39 162 574 1,058 117 418 1 26 CE4 47 115 203 B02 105 245 1 31 CE5 62 200 489 873 173 3 22 I 97 CE6 188 217 49! 876 188 247 2 10 CE7 31 153 505 894 110 4 87 1 15 CE9 71 192 435 [766 165 12 73 1 84 CEIO 48 (90 152 235 84 9 1 86 1 11 CE14 63 248 664 1,096 192 396 1 88 CE15 159 206 526 881 163 1347 1 70 CE20 131 168 611 1,094 116 541 1 19 Some of the polymenc crosslinkmg enhancers were also analyzed to 5 determine melt flow index at different ASTM D-1238 conditions, and also to determine density (at room temperature) using heptane displacement in a Toyoseiki densimeter The results of these analysis appears in Table 4 below TABLE 4 PCE type Melt Flow Index (dg/min) Density (g/cc) 2 16 kg/190°C I00kg/190oC 2 16 kg/230°C CE2 1 33 11 30 2 69 0 878 CE3 0 29 35 0 80 0 877 CE4 1 43 33 2 98 0 873 CE5 0 14 1 66 0 28 0 839 CE6 008 0 99 015 0 879 CE7 023 05 056 0 874 CE9 0 10 2 98 0 22 0 879 CEIO 4 06 27 40 748 0 879 CE14 001 041 0O3 0 870 CE15 0 02 0 72 005 0 868 CE20 0 16 3 78 046 0 873 3^ Printed from Mimosa Example 1-16 Sixteen monolayer films in accordance with the invention were extrusion cast Each film was then exposed to electron beam irradiation, at a given power 5 setting (beam current), in an E-beam irradiation unit By adjusting the power settings one can directly change the dosage received Thus, the beam current is substantially directly proportional to received dosage The process was repeated twice with additional samples of each film, but at different power settings (different radiation dosage) The composition of these films, and two comparative 10 films (COMP A and B) produced in the same manner, are given in Tables 5 and 6 below Each film had a thickness of about 12 mils TABLE 5 Example Film Structure COMP A 100% PEI 1 90% PEI + 10% CE7 2 90% PEI + 10% CE3 3 90% PEI + 10% CE4 4 90% PEI + 10% CE2 90% PEI + 10% CE5 6 90% PEI + 10% CE6 7 90% PEI + 10% CE9 8 90% PEI + 10% CE10 3P Printed from Mimosa TABLE 6 Example Film Structure COMP B 100% PE2 9 90% PE2 + 10% CE7 90% PE2 + 10% CE3 11 90% PE2 + 10% CE4 12 90% PE2 + 10% CE2 13 90% PE2 + 10% CE5 14 90% PE2 + 10% CE6 90% PE2 + 10% CE9 16 90% PE2+ 10% CE10 Figures 9 and 10 provide bar graphs depicting the received dosage, in KGy, versus the gel % determined for each film sample Numerals in the drawing 5 correspond to the respective samples It can be seen that very substantial improvements in crosslinkmg efficiency (values shown at the top of each bar), as measured by % gel, are obtained by films of the present invention when compared to a control film of LLDPE Example 17-28 Seven three-layer films, and one control film (COMP BB) were cast coextruded to producc a substrate In each case, the substrate was exposed to electron beam irradiation, at a dosage of about 50 kGy, in an irradiation unit After irradiation of the substrate, four additional layers were added to the substrate 15 by simultaneous extrusion coating process The resulting seven-layer films was then oriented by conventional trapped bubble method to produce crosslmked heat shrinkable films The composiuon of these films is given in Table 7 below The thickness (in mils) of each layer of the film of Example 17 was measured , before orientation, and was determined to be Printed from Mimosa layer 1 layer 2 layer 3 layer 4 layer 5 layer 6 layer 7 49 132 . — , 1 0 1 8 1 0 29 1 7 After orientation, the final thickness of the film of Example 17 was 2 7 mils In a similar manner, the thickness (in mils) of each layer of the films of 5 Examples 18 to 23 and COMP.BB was measured, before orientation and was determined to be layer 1 layer 2 layer 3 layer 4 layer 5 layer 6 layer 7 54 98 1 0 1 9 1 0 26 1 8 After orientation, the final thickness of the film of each of Example 18 to 10 23 was 2 2 mils In each film, layer 1 would preferably form the food or product contact layer, and sealant layer, for a typical packaging application The composition of each layer of the films is given m Table 7 below The double slash (//) indicates where a substrate is adhered to an extrusion coated layer Printed from Mimosa TABLE 7 EXAMPLE STRUCTURE COMP.BB PEB3/PE2/ EV1//OBI/EM1/PE7/PEB2 17 PE5/CEB1/EV1 //OB 1 /EM 1/PE7/PEB2 18 PEB3/CEB2/ EV1//OB1/EM1/PE7/PEB2 19 PEB3/CEB1/ EV1//OB1/EM1/PE7/PEB2 PEB3/CEB3/ EV1//OB1/EM1/PE7/PEB2 21 PEB3/CEB4/ EV 1//OB 1/EM 1/PE7/PEB4 22 PEB3/CEB 51E V1 //OB 1 /EM 1 /PE7/PEB4 23 PEB5/CEB4/ EV1//OB I/EM 1/PEB6/PEB6 Some of the film formulations, and COMP BB, were rerun at four different dosage levels of E-Beam irradiation in an irradiation unit to evaluate the gel % as 5 a function of level of irradiation Table 7A shows the dosage received, in KGy, versus the gel % determined for these selected films The % gel was in each example determined for the substrate (layers 1 to 3) TABLE 7A EX Gel % @30kGy @44 kGy @57 kGy @71 kGy COMP BB 0 0 3 18 0 8 21 19 0 7 13 21 0 6 14 21 ¥i Printed from Mimosa Examples 24-29 Six monolayer films were extrusion cast, and then exposed to electron beam irradiation, at a given power setting (beam current), m an E-beam irradiation unit The process was repeated with additional samples of each film, but at two 5 different power settings The composition of these films, and the three comparative films (COMP A, B, and C) produced in the same manner, are given in Tables 8 and 9 Figure 11, with respect to the samples of Table 8, and Figure 12, with respect to the samples of Table 9, graphically show the received dosage, in kGy, versus the gel % determined for each film example TABLE 8 Example Film Structure COMP A 100% PEI 24 95% PEI + 5% CE3 90% PEI + 10% CE3 26 95% PEI + 5% CE5 27 90% PEI + 10% CE5 TABLE 9 Example Film Structure COMPB 100% PE2 28 90% PE2 + 10% CE5 COMP C 100% PE8 29 90% PE8 + 10% CE5 The bar graphs of Figures 11 and 12 clearly show that one achieves higher crosslink efficiency with the films of the present invention than the comparative films of examples Comp A, B and C Printed from Mimosa Preparation and Characterization of Representative Advanced Unsaturated Polvfolefins) fAUPO's) Example 30 Polymerizations listed in Tables 10 and 11 herein below were each conducted in a 2L stainless steel autoclave reactor equipped with an overhead helical impeller at either 50 °C and 50 psig ethylene or 75 °C and 60 psig ethylene using bis(cyclopentadienyl)zirconium(IV)dichloride (CP2Z1CI2) and methylaluminoxane (MAO) in dry, degassed toluene The reactor was charged 10 with toluene (300 to 1300g), l-hexene (50 to 200 g) or norbornene (10-100 g), diene (0 1 to 20 g), and MAO (2 to 20 g of MAO/toluene solution containing 10 v/X.% Al), and saturated with ethylene at either 50 °C and 50 psig or 75 °C and 60 psig The polymerization was commenced by addition of the metalloccne catalyst (0 1 to 3 mg CpjZrCb m 10 mL toluene) to the reactor and the polymerizations 15 were allowed to proceed for 0 5 to 2 hours The reactor was quickly vented and the contents discharged into methanol, filtered and dried Tables 10 and 11 show the amount and type of starting matenals, and the amount and type of polymers, made by this procedure "E" herein means ethylene, "H" herein means 1-hcxene, and "NB" herein means norbornene A-1 through A-8 represent polymers 20 produced in each of eight polymerization reactions in accordancc with the above-desenbed procedure V3 Printed from Mimosa TABLE 10 Ethvlene/l-Hexene/Polvene Copolymer A-r A-2" A-3a A-4n A-5a A-6" toluene (grams) 300 300 500 506 746 754 1-hexenc (gram';) 64 67 108 112 178 4 175 diene (type) ENB ENB -VNB -VNB -VNB ENB diene (grams) 33 96 1 1 83 87 MAO (grams) 75 75 catalyst (mg) 0 25 0 38 0 25 1 0 0 38 05 reaction time (hours) 05 1 7 1 7 1 5 1 7 polymer (type) E-H-ENB E-H-ENB E-H- VNB E-H-VNB E-H-VNB E-H-ENB polymer (grams) 46 52 65 50 4 104 109 a) 50 psig ethylene and 50 °C Printed from Mimosa Table 11 Ethvlene/Norbornene/Polvene Copolymer A-7b A-8 b toluene (grams) 1285 1235 NB (grams) 76 65 diene (type) VNB VNB diene (grams) 43 165 MAO (grams) 12 catalyst (mg) 28 1 4 reaction time (hours) 1 2 polymer(type) E-NB-VNB E-NB-VNB polymer (grams) 103 76 b) 60 psig ethylene and 75 °C The AUPO's described above were found to be compositionally pure as indicated by a single melting endotherm by differential scanning calonmeiry (DSC) at 10°C per minute and with narrow polydispersities by gel permeation chromatography (GPC) Table 12 summarizes the characterization of the terpolymeis Printed from Mimosa TABLE 12 AUPO A-l A-2 A-3 A-4 A-5 A-6 Density (g/cc) 0913 0919 0 906 0915 0 908 0 909 Mol% H 1 37 55 45 54 1 Mol% diene 1 2 22 08 1 9 09 1 1 (ENB) (ENB) (VNB) (VNB) (VNB) (ENB) Tm(°C) 90 91 91 96 93 93 AHf(J/g) 60 40 50 60 70 70 h (dg/min) 28 63 06 46 45 5 Mw x 10* 81 68 124 70 nd nd (grams/mole) Mw/Mn 1 9 1 9 1 9 1 9 nd nd To further illustrate the breadth of the invention, copolymers of ethylene and norbornene, as well as unsaturated terpolymers based on these monomers with 5 VNB (at two different levels) were also prepared An ethylene-norbomene copolymer was prepared in a 20 gallon jacketed stainless steel autoclave equipped with baffles and an overhead turbine-style stirrer The reactor was charged with 48 1 kg of toluene containing 0 2 wt% MAO, 4 2 kg of norbornene solution (65wt% in toluene) and heated to 75 °C and pressurized to 60 psig ethylene 10 After the system equilibrated, the polymerization was initiated by addition of a total of 38 mg of Cp^ZrClz and ethylene was fed in on demand The polymerization was allowed to proceed for 4 25 hours. It was then terminated by addition of 100 mL of methanol The reactor was vented, the contents discharged and precipitated into methanol and the polymer filtered and dried in a vacuum 15 oven 7 1 Ifg of polymer was isolated The polymer (A9 ) had an MFI (190 °C and 2 16 kg) of 1 7 dg/imn with a Tm of 75 °C The polymer was found, by carbon-13 NMR, to contain 10 mol% NB and the microstruclure was consistent with an Printed from Mimosa addition polymerization with NB monomer inserted without ring-opening The reaction conditions for the unsaturated E-NB terpolymers A-7 and A-8 .s listed zn Table 11 and the characterization of these matenals A-7, A-8 and A-9 arc listed in Table 13 Table 13 AUPO A-7 A-8 A-9 Density (g/cc) 0 958 0 952 0 958 Mol% NB 140 112 100 Mol% diene 02 (VNB) 09 (VNB) 0 Tm(°C) 65 68 75 I2 (dg/min) 13 5 39 1 7 Mw x 1G3 (grams/mole) 103 63 112 Mw/M„ 23 1 8 24 The resins listed above were found to contain 0% gel pnor to exposure to electron -beam radiation To further explore the utility of AUPO's as crosslinkmg enhancers, blends containing said matenals (10 % unsaturated resin) were prepared on a Brabender mixing chamber with a LLDPE (Dowlex 2045 14 of Dow Chemical Co ), 6 5 wt% octene, (0 920 g/cc, 1 0 dg/min) These blends 15 were PEB7 = 90% PE9 + 10% CE5 PEB8 = 90% PE9 + 10% A5 PEB9 = 90% PE9 + 10% A6 PEB10 = 90% A10 + 10% CE5 Printed from Mimosa The effect of electron -beam irradiation on the AUPO resins and their blends is shown in Table 14 The data clearly shows that VNB is a more efficient diene at promoting crosslinkmg than ENB, and that high levels of crosslmking could be 5 achieved using these AUPO's either alone or as a crosslmking enhancer to improve the crosslinkmg in other resins It also clearly shows that the AUPO resins, as a component of a blend, enhanced the crosslmking of LLDPE giving higher gel contents at lower doses than the base resin Table 14 Gel Content of AUPO Crosslink Enhancers and Their Blends Resin Dose (kGray) 37 70 Al (E-H-ENB) 46 9 ± 1 9 74 4 ± 6 3 A2 (E-H-ENB) 45 0 ± 8 3 66 9 ± 4 3 A3 (E-H-5VNB) 66 3 ± 3 5 83 0 ± 4 0 A4(E-H-5VNB) 60 7 ± 3 7 78 1 ± 0 9 A5(E-H-5VNB) 37 2 ± 12 1 nd A6 (E-H-ENB) nd nd PE9 (LLDPE) 0 PEB7 (EPDM) 24 0 ±4 1 7 ± 7 3 PEB8 (E-H-5VNB) 21414 1 37 2 ± 12 1 PEB9 (E-H-ENB) 45 6 ± 3 5 Table 14 demonstrates that AUPO type PCE copolymers (A1-A5) can be employed on their own to generate highly crosslmked films, and to enhance 15 crosslmking (PEB8 and PEB9) in other resins Printed from Mimosa WO 97/36741 PCT/US97/04796 Table 15 %Gel Content of E-NB Co-CTerlpolvmers as a Function of Pose Dose (kGray) 70 100 A9 0 3 PEB10 19 37 A7 3 43 50 A8 51 73 80 Table 15 clearly shows that enhanced crosslmking of E-NB copolymers can be achieved by blending in a PCE copolymer of the presnt invention or by copolymenzation with a diene monomer The level of diene determines the extent to which the crosslinkmg can be enhanced Films formed with at least one layer containing the subject PCE 10 composition and subjected to irradiation, as descnbed herein above and illustrated by Examples 1-30 above, are particularly useful in the production of bags for packaging fresh red meat, smoked and processed meat, pork, chcese, poultry, and the like, as descnbed in e g US Patent Nos 3,741,253 (Brax et al), 3 891,008 (D'Entremont), 4,048,428 (Baird), and 4,284 458 (Schirmer), all incorporated by 15 reference herein in their entirety However, the film can also be used m other applications For example, the film can be used as a shrink film in packaging applications for packaging food and non-food items Films in which the present invention can be beneficially used are descnbed in e g US Patent Nos 4,551,380 and 4,643,943, both to Schoenberg, and both incorporated by reference herein in 20 their entirety In addition, the present invention can also be used with films having oxygen, moisture, or odor barner functionality, as descnbed in e g 4,064,296 (Bomstem et al), 4,724,185 (Shah), 4,839,235 (Shah), and 5,004,647 (Shah), all incorporated by reference herein in their entirety Printed from Mimosa Example 31-34 Four oxygen bamer films were formed with layers of PCE copolymer of the present invention (Examples 31 and 34) as well as a comparative control film (COMP D) Each had the layer structure A/B/C/D/C/B/A These films were made by a coextnision of the layers, and each film was irradiated and oriented. A small amount of anhydrous aluminum silicate (an 10 antiblock) and mono- and diglycende/propylene glycol (an antifog) were compounded into the resin blend of the two outside layers, such that, after compounding, the additives comprised about 6% of the total compounded blend The film of COMP D was compositionally and structurally as shown below 50% PE9 90% OB2 % PE10 PE10 AD1 AD1 PE10 % EV4 %PA1 50% PE9 25% PE10 25% EV4 The films of Examples 31 and 32 had the same general formulation as shown above for COM D except that the second and sixth layers (the "B" layers) comprised 90% PE10+ 10% CE3 The film of Examples 33 and 34 had the same general formulation as shown above for COMP D except that the third and fifth layers (the "C" layers) comprised 90% AD1 + 10% CE3 Data comparing the power settings of the E-Beam irradiauon unit and MFI of these examples is given in Table 16 herein below Printed from Mimosa WO 97/36741 PCT/US97/04796 TABLE 16 Example Beam Current (mA) Melt Flow Index (dg/min) COMP D 0 63 31 12 2 64 32 0 37 33 90 14 4 34 120 59 A review of the data of Table 16 shows two benefits of the present invention First, the data shows that two films with identical composition and structure ( COMP D and Example 32), except for the presence of 10% of a crosslmking enhanccr in the B layers of Ex 32, were irradiated at the same dosage, yet had very different MFI values The lower MFI value of Ex 32 reflects the increased crosslinkmg of the film of Ex 32 as the result of the presence of the 10 crosslmking enhancer As pointed out in the description of the invention, crosslinkmg improves processabihty in making oriented ri!ms Secondly, the data shows that two films with identical composition and structure (COMP D and Example 31), except for the presence of 10% of a crosslmking enhancer in the B layers of Ex 31, had nearly the same MFI (6 3 vs 15 f 4) even though the film of Ex 31 had been irradiated at a power setting of only 12 2 mA, compared with the higher power setting of 15 0 for COMP D Again, as pointed out in the description section of this specification, higher levels of crosslinkmg generally degrade the performance of sealing layers By lowering the power setting of irradiation to which the extruded tape is exposed, the flowabihty 20 of the sealant is less severely affected, and the sealant will perform better <r/ Printed from Mimosa Example 35 Films formed according to the present invention were prepared for use as or in connection with a patch as descnbed in e g US Patent No 4,755,403 (Ferguson) the teachings incorporated by reference herein m its entirety An exemplary patch structure was made having the formulation 87% PEI 10% CE2 3% EV1 EV3 EV3 87% PEI 10% CE2 3% EV1 This patch matenal was a tubular patch self-welded to itself at the // interface It was coextruded, and irradiated at a dosage of 98 kGy The patch 10 thickness after orientation was 4 5 mils The patch film was oriented and rendered heat shnnkable This matenal can be used alone, or as a patch for a bag or other film For comparative purposes, a tubular patch film was formed by coextrusion in the same manner as the above exemplary patch of the present invention The 15 film was also irradiated with E-Beam at a dosage of 98 kGy and oriented by stretching to a thickness of 4 5 mils In the case of this control film the layer structure was 90% PEI 10% EV2 ev! EV3 90% PEI 10% EV2 The two patch materials were measured for gel % and it was determined that the exemplary film had a gel % of 55 0% while the comparative film had a gel % of only 46 5% reprinted from Mimosa Example 36 Films were formed m which the outer layer was crosslmked by UV irradiation The films contained unsaturated block copolymers in combination with a second polymer The polymers were compounded in a Brabender mixing 5 chamber, pressed to make pressed-film samples, or plaques, and exposed to a low intensity UV source (Amergraph lamp, pnmanly UVA output) for ten minutes at room temperature in the solid state At ten minutes the Amergraph radiometer measurement was 1600 mJ/sq cm at 365 nm Unsaturated polymer additive The blends were 69% by weight of an ethylene/vinyl acetate resin having 9% by weight vinyl acetate (EVA 9) and 29% by weight of an unsaturated polymer and 2% by weight of benzophenone The unsaturated polymers were Kraton® D1107, a linear styrene-isoprene-styrene tnblock copolymer available from Shell (Sample A), Kraton D1102, a linear styrene-butadiene-styrene tnblock copolymer available from Shell (Sample B), and Stereon® 840, a styrene-butadiene block polymer available from Firestone, Akron, Ohio (Sample C) Gel content was analyzed as above Table 17 Gel Content Data Sample A % Sample B 6% Sample C 3% The only unsaturated block copolymer to yield significant gel levels was Sample A, the styrene-isoprene-styrene block copolymer However, the styrene-25 butadiene-styrene block copolymer did not yield significant gel content under these conditions O Printed from Mimosa WO 97/36741 PCT/US97/04796 Comparative Example For comparative purposes, a chemically crosslink polymer composition wai formed and exposed to UV radiation in the same manner as Sample A above 5 EVA9 resin was compounded with 2 weight percent of tnallyicyanuratc (TAC) and 2 weight percent of benzophenone as initiator The matenal formed was labeled "Sample G" The gel content of this Sample G was 26% and, therefore, similar in crosslink as that of Sample A Samples A and G were selected for extrusion in multilayer test films 10 Sample G was found to be difficult to extrude due to blooming and bleeding (separation of one component so that it selectively appears on the surface of the extrudate) of the TAC To obtain a sample, 50 weight percent of ethylene/vinyl acetate with 9% vinyl acetate was added In comparison. Sample A did not exhibit blooming Further, films were formed having multiple layers as follows EVA-9 resin and an ethylene/vmyl acetate resin with 15% vinyl acetate (EVA15) were coextruded as a bilayer annular tape, electronically crosslmked, and cooled The tape was then coated by coextrudmg three more layers, a Saran/PVDC barrier layer blend, and ethylene/vinyl acetate with 28% vinyl acetate layer, and a layer of 20 the resin of Samples A or G The Saran/PVDC layer was in contact with the EVA 15 layer, and the Sample resins were located on the outside The tapes were UV irradiated using lamps from Fusion Systems, Inc , Rockville, MD The doses v-ere 450 and 900 mJ/sq cm The tape was then biaxiall/ oriented (stretched) at a racking ratio of about 3x in the transverse direction and about 4x in the 25 longitudinal direction Gel content of the outside layer was then determined and is reported below The gel content from Sample A was higher than from Sample G The film from Sample A was tested and showed no tendency for film "pick-off' during the sealing process, had excellent grease resistance and good optics rY Printed from Mimosa WO 97/36741 PCT/US97/04796 Table 18 Irradiated Film Samples Crosslmked Layer Dose, mJ/sq cm at 360 nm % Gel Sample A 450 Sample A 900 66 Sample G 450 0 Sample G 900 0 These examples demonstrate a UV system that produces a crosslmked 5 network The resulting film dose can eliminate applied seal delammation, increase grease resistance, and still maintain good optics These results also show that the films having the present PCE composition performed significantly better than Films which were chemically crosslmked Example 37 Benzophenone was dissolved in low molecular weight 1,2-polybutadiene (1,2-PBD) with gentle warming The liquid was poured onto pellets of LLDPE and was evenly distnbuted by tumble mixing to provide a PCE composition The final composition was 5% by weight 1,2-PBD and 1% by weight benzophenone The apparatus in Figure 3 was used to extrude and irradiate the mixture The lamp was positioned directly above the die lip Linear extrusion rate was varied by varying a combination of extruder rpm and take-up speed Gel content of the resulting film was determined as descnbed above The results are reported in Table 19 below Printed from Mimosa PCT/U597/04796 Table 19 Gel Contcnt Data - Linear Low Density Polyethylene Linear Extrusion Rate (ft /mm ) Gel Content (% by wt) Film Thickness (mil) 2 66 50 114 2 83 45 8 1 8.50 22 66 These data demonstrate thai useful gel contents can be achieved m 5 polyethylene by this process These data also show that 1,2-polybutadiene is as effective as TAC as a crosslmking aid in addition, high gel contents can be achieved in relatively thick films These films gave 0% gel content in the absence of UV Example 38 This example was earned out exactly like that in Example 37, except that LLDPE polymer was substituted with an ethylene-propylene copolymer (having 3 1% ethylene) The following data were obtained Table 20 Gel Content for EP Copolymer Linear Extrusion Rate (ft /min ) Gel Content (% by wt) Film Thickness (mil) 28 37 7 1 57 19 74 90 7 92 These data show that useful crosslinkmg can be obtained by this method in propylene copolymers Printed from Mimosa PCIVUS97/04796 Example 39 The same equipment and method descnbed in Example 37 was also used in this example except that the 1,2 PBD polymer was substituted with a 5 developmental LLDPE copolymer composed of ethylene/octene/polyene having 430 C=C per 100,000 carbon atoms, in the form of terminal vinyl unsaturation by IR analysis With the addition of 1 % benzophenone, this PCE composition gave a gel content of 90% when extruded at a linear rate between 2 and 3 ft /min and irradiated with UV irradation Again there was no gel content in the absence of 10 UV irradiation Example 40 In this example, two formulations were prepared in a Brabender mixing chamber by melt blending the components to compare chemically crosslmked 15 matenal to that of the present invention The first formulation was commercially available LLDPE (Attanc 4201) with 1% tnallylcyanurate (TAC) and 1% benzophenone The second was the developmental unsaturated LLDPE copolymer descnbed in Example 39 above, with 1 % benzophenone A 10 inch Fusion Systems lamp (H-buIb) mounted on a conveyor belt was used to irradiate 20 pressed films of the above formulations (15-20 mil thick) at room temperatuie (UV doses measured at 365 nm) The following results were obtained Printed from Mimosa Table 21 Gel Content at Various UV Doses in the Solid State Formulation UVDose (J/cm2 @ 365 nm) Gel Content (% by wt) Attane 4201, 1%TAC, \% benzophenone 02 00 same as above 04 1 4 same as above 06 1 7 unsaturated LLDPE, 1% benzophenone 02 196 same as above 04 same as above 08 41 These data show that a high degree of crosslmking was not obtained for 5 chemical system with TAC in the solid state, however, the PCE copolymer (developmental unsaturated LLDPE), a high degree of crosslmking was obtained sn the solid state at relatively low doses of UV radiation These data when combined with the previous examples, further demonstrate that even higher gel contents for a given system can be obtained when irradiation occurs in the melt 10 state Example 41 In this example, a PCE copolymer was prepared by grafting In a Brabender mixing chamber, an ethylene-alkyl acrylate-maleic anhydride 15 terpolymer (Lotadcr 3200, AtoChem Inc ) was melt compounded and reacted with 5% by weight hydroxyl terminated 1,2-PBD (Nisso-PB®, G-3000, Nippon Soda Co , Ltd ) To ihe formed graft copolymer, \% benzophenone was further incorporated by melt blending A pressed film was irradiated at room temperature as descnbed above to a UV dose of 0 8 J/cm2 (measured at 365 nm), which S f Printed from Mimosa resulted in a gel content of 23% by weight In contrast, the unirradiated film had a gel content of 0 8% by weight, as a result of the difunctional nature of the 1,2-PBD Example 42 In this example, two formulations were prepared in a Brabender mixing chamber by melt blending the components. The first formulation was PCE copolymer of developmental unsaturated LLDPE combined with 1% 4-allyloxybcnzophenone The second was the same developmental unsaturated 10 LLDPE with 1%, 4,4'-diallyloxybenzophenone A 10 inch Fusion Systems lamp (H-buIb) mounted on a conveyor belt was used to irradiate pressed films of the above formulations (15-20 mil thick) at room temperature (UV doses measured at 365 nm) The following results were obtained Table 22 Gel Content at Various UV Doses m the Solid State Formulation UV Dose (J/cm2 @ 365 nm) Gel Content (% by wt) UnsaL LLDPE, 1% 4-al lyloxybenzophenone 02 18 5 same as above 04 195 same as above 08 185 UnsaL LLDPE, 1% 4,4'-diallyloxybenzophenone 02 110 same as above 04 22 0 same as above 08 34 7 ^7 Printed from Mimosa WO 97/36741 PCMJS97/04796 These data show tdat usefui crosslinkmg can be obtained even in the solid state for polyethylene-polyene copolymer and that useful crosslinkmg can be obtained from substituted benzophenone Example 43 Pellets of EVA-9 were coated with a mixture of low molecular weight 1,2-polybutadiene (1,2-PBD) and benzophenone to form a PCE composition Benzophenone was dissolved in the 1,2-PBD with gentle warming pnor to coating The final composition was 5% by weight 1,2-PBD and 1 % by weight 10 benzophenone The twin screw extruder in Figure 1 was used to extrude and pel letize the mixture The resulting pellets were fed into a Randcastle micro-extruder, which had the UV lamp in Figure 1 mounted at the hp of the 6" flat sheet die The linear extrusion rate was varied by varying a combination of extruder rpm and take-up speed Gel content of the resulung film v/as determined as 15 descnbed above The following results were obtained Table 23 Gel Content Data for EVA-9a Linear Extrusion Rate (ft /min) Gel Content (% by wt) Film Thickness (mil) 80 28 21 U 42 1 5 * EVA-9 (polyethylene/vinyl acetate resin with 9% vinyl acetate comonomer LD 318 92 available from Exxon Corp , Houston, TX) compounded with 5% by weight 1,2-PBD and 1 % by weight benzophenone and extruded using a Brabcnder twin-screw extruder These data clearly show that PCE compositions containing EVA-9 can be UV crosslmked to high gel contents (rd Printed from Mimosa WO 97736741 Example 44 The Randcastle micro-extruder descnbed above was used to make a three layer film that was irradiated in a similar fashion The skin layers of the structure 5 were a PCE composition composed of a blend of LLDPE, with 5% by weight 1,2-polybutadiene (1,2-PBD) and 1% by weight benzophenone The skin layer blend was compounded pnor to coextrusion as descnbed above The core layer of the structure was LLDPE (Dowlex 3010) The approximate ratio of the layer gauges was 1 1 1 based on the extruder rpm Table 24 LLDPE'/LLDPEb/LLDPE* Linear Extrusion Rate (ft /msn) Total Gel Content (%±2ct) Skin Gel Content' (%±2a Film Thickness (total, mil) 45 21±7 32±11 67 80 24±4 36±6 3 7 11 ±2 ±3 29 a Skin layer LLDPE is Dowlex 2045 03 with 5% 1,2-PBD and 1 % Benzophenone, 15 twin screw compounded prior to coextrusion b Middle layer LLDPE is Dowlex 3010 c Approximate gel content of skin layers calculated assuming 2/3 of structure These data clearly indicate that the skin layers of a multilayer film can be substantially crosslmked by UV irradiation Example 45 The Randcastle micro-extruder descnbed in Example 43 was used to make a three layer film that was irradiated as in Example 8 The skin layers of this Printed from Mimosa structure were LLDPE (Dowlex 3010, Dow Chcmical) The core layer of the structure was a PCE composition comprosed of a blend of LLDPE (Dowlex 2045 03, Dow Chemical) with 5% 1,2-PBD (Nisso PB®, B-1000, Nippon Soda Co, Ltd ) and 1 % acrylated benzophenone derivative (Ebecryl® P-36, UCB 5 Radcure Inc ), that was compounded prior to coextrusion as descnbed in Example 7 Tht. approximate ratio of the layer gauges was 1 1 1 based on the extruder rpm Table 25 lldpe'/lldpeYlldpe" Linear Extrusion Rate (ft /min ) Total Gel Content (%±2 a) Core Gel Content0 (%±2a) Film Thickness (total, mil) 80 17±4 51±12 55 14 27±5 81+15 38 a Skin layer LLDPE is Dowlex 3010 b Core layer LLDPE is Dowlex 2045 03 with 5% 1,2-PBD and 1 % acrylated benzophenone, twin screw compounded prior to coextrusion c Approximate gel content of core layer calculated assuming 1/3 of structure These data clearly indicate that an internal layer of a multilayer film can be substantially crosslmked by UV with these additives and apparatus Printed from Mimosa 331862 WO 97/36741 PCT/US97/04796

Claims (8)

1. WHAT WE CLAIM IS

   1 A multilayer Film having at least one layer of said film containing a polymenc crosslink enhancer composition comprising 5 (0 copolymer having polymenc units derived from (a) at least one polyene monomer, (b) at least one C2-C20 olefinic monomer and, optionally, (c) at least one copolymenzable monomer other than (a) or (b); or (11) polymer mixture composed of at least one polymer having polymenc units denved from (a) at least one polyene monomer, and at least one polymer 10 having polymenc units denved from (b) at least one C2-C20 olefinic monomer and, optionally, at least one copolymenzable monomer other than (a) or (b),

   each of said at least one layer formed with polymenc crosslink enhancer composition being crosslmked to a greater degree that at least one other layer of said film wherein at least one layer forming a major surface of the film is sealable

   15

   20

   25
2. 2 The film of Claim 1 wherem the polymenc crosslink enhancer composition is polymenc crosslink enhancer composition (1)
3. 3 The film of Claim 1 wherein the polymeric crosslink enhancer composition is polymeric crosslink enhancer composition (11)
4. 4 The film of Claim 1 wherein the polymeric crosslink enhancer composition further compnses a diluent polymer
5. 5 The film of Claim 1 wherem the polyene of the polymenc crosslink enhancer composition is present in sufficient amount to provide 10 to 25,000 carbon to carbon double bonds per 100,000 carbon atoms contained in the layer having said polymenc crosslink enhancer composition

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6. 6 The film of Claim 2 wherein the polymenc crosslink enhancei copolymer (l) has a weight average molecular weight (Mw) of at least about 10,000 daltons
7. 7 The film of Claim 3 wherein the polymenc crosslink enhancer copolymer (11)

   has a weight average molecular weight (Mw) of at least 1,000 daltons
8. 8 The film of Claim 1 wherein the polymenc crosslink enhancer composition compnses copolymer (1) and said copolymer is an advanced unsaturated poly(olefin) copolymer

   10 9 The film of Claim 2 wherem the copolymer is an ethylene/propylene/polyene copolymer

   10 The film of Claim 4 wherein the copolymer is an ethylene/propylene/polyene copolymer

   15

   11 The film of Claim 8 wherein the copolymer is an ethylene/propylene/polyene copolymer

   12 The film of Claim 2 wherein the polymenc crosslink enhancer composition 20 further compnses a photomitiator compound

   13 The film of Claim 3 wherein the polymenc crosslink enhancer composition further compnses a photomitiator compound

   25

   14 The film of Claim 4 wherein the polymenc crosslink enhancer composition further compnses a photomitiator compound

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   15 The film of Claim 12 wherein the photomitiator compound is present in from about 0 1 to 3 weight percent of the layer having the polymenc crosslink enhancer composition

   16 The film of Claim 13 wherein the photomitiator compound is present m from about 0 1 to 3 weight percent of the layer having the polymenc crosslink enhancer composition

   17 The film of Claim 14 wherein the photomitiator compound is present in from about 0 1 to 3 weight percent of the layer having the polymenc crosslink enhancer composition

   18 The film of Claim 1 wherem the at least one of said layers containing the polymenc crosslink enhancer composition is an internal layer of the film

   19 The film of Claim 8 wherein the at least one of said layers containing the polymenc crosslink enhancer composition is an internal layer of the film

   20 The film of Claim 10 wherem the at least one of said layers containing the polymenc crosslink enhancer composition is an internal layer of the film

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   21 The film of Claim 1 wherein the polyene monomer compnses a non-conjugated polyene

   22 The film of Claim 1 wherein the polyene monomer compnses a substituted polyene

   23 The film of Claim 1 wherein the polyene monomer compnses a polyene with vinyl unsaturation

   24 The film of Claim 1 wherein the polyene monomer compnses a diene

   25 The film of Claim 8 wherein the polymenc crosslink enhancer copolymer compnses a single-site catalysed unsaturated polymenc material and the polyene monomer compnses a polyene with vinyl unsaturation

   26 The film of Claim 1 wherem the polymenc crosslink enhancer copolymer compnses semi-crystalline material

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   27 The film of Claim 1 wherem the polyene monomer is selected from the group consisting of 5-ethylidene-2- norbornene ("ENB"), 5- methylidene-2-norbornene, 5-vinyl-2-norbomene ("VNB"), 5-methylene-2-norbomene, 2,5-norbomadiene, butadiene, isoprene, 1,4 - hexadiene ("HD"), 4-methy 1-1,4-hexadiene, 5-methyl-l ,4-hexadiene, 4-ethy 1-1,4-hexadiene, 1,5-hexadiene, 1,6-heptadiene, 1,4-heptadiene, 1,5-heptadiene, 5-methyl-l,4-heptadiene, 1,4-octadiene, 1,5-octadiene, 1,6-octadiene, 5-ethyl-l,6-octadiene, 6-methyl-l,6-octadiene, 7-methyl-l,6-octadiene, 6-ethyl- 1,6-octadiene, 6-propyl-l,6-octadiene, 6-butyl-l,6-octadiene, 1,7-octadiene, 6-methyl-l,6-nonadiene, 7-methy 1-1,6-nonadiene, 6-ethyl-1,6-nonadiene, 7-ethyl-l,6-nonadiene, 6-methyl-l,6-decadiene, 1,9-decadiene, 6-methyl-l,6-undecadiene, 1,8-nonadiene, 1,13-tetradecadiene, 1,4-dodecadiene, cyclooctadiene, 4-vinylcyclohexene, 1,4-divmylcyclohexane, 1,3-divmylcyclohexene, 1-ally 1-4-vinylcyclohexane, 1,4-divmylcyclohexane, 1,3-divmylcyclopentane, l-allyl-3-vmylcyclopentane, 1,5-divmylcyclooctane, 1-allyl-5-vinylcyclooctane, 1,5-dialiylcyclooctane, l-allyl-4-isopropenylcyclooctane, 1-allyI-4-isopropenylcyclohexane, 1 -isopropenyl-3-vmylcyclopentane, 1 •allyl-4-lsopropenylcyclohexane, 4-vmylcyclohexene("VCH"), dicyclopentadiene ("DCPD"), divmylbenzene, and vinyhsopropenylbenzene

   28 The film of Claim 1 wherem the C2 to C20 olefinic monomer is selected from the group consisting of ethylene, propylene, 1-butene, l-hexene, 3-methyl-l-butene, 3-methyl-l-pentene, 3-ethyI-l-pentene, 4-methyl-l-pentene, 4,4-dimethyl-l-pentene, 4-methyl-l-hexene, 4,4-dimethyl-l-hexene, 4-ethy 1-l-hexene, 3-ethyl-l-hexene, 3,5,5-tnmethylhexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene

   29 The film of Claim 1 wherein the additional monomer (c) is selected from the group consisting of vinyl aromatics, cycloolefin monomers, unsaturated esters, unsaturated acids, and salts of unsaturated acids —-—

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   30 The film of Claim 6 wherein the polyene crosslink enhancer copolymer (l) has a weight average molecular weight (Mw) of at least 20,000 daltons

   31 The film of Claim 1 wherein the copolymer of polymenc crosslink enhancer copolymer has a density at 25 °C of between 0 8 and 1 Og/cc

   32 The film of Claim 3 wherein the second polymer of the polymenc crosslink enhancer composition (11) is selected from the group consisting of polyethylene, ethylene/olefin copolymer, propylene/olefin copolymer, polypropylene, polyvinyl chlonde, polyvmyhdene dichlonde, polybutene, ethylene/acid copolymer, and ethylene/ester copolymer

   33 A polymenc composition comprising a copolymer having polymenc units denved from (a) at least one polyene, (b) at least one C2-C20 olefinic monomer and, optionally, (c) at least one copolymenzable monomer other than (a) or (b), wherein the copolymer is an advanced unsaturated poly(olefin) copolymer, and a photomitiator, wherein the composition further compnses at least one diluent C2-C;o olefinic homopolymer, copolymer thereof and mixtures thereof

   20

   25

   34 The polymenc composition of Claim 33 wherein the copolymer contains at least 10 to 25,000 carbon to carbon double bonds per 100,000 carbon atoms of the copolymer molecule

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   35 The polymenc composition of Claim 33 wherein the copolymer has a weight average molecular weight of at least about 10,000 daltons

   36 The po ymenc composition of Claim 33 wherem at least one diluent polymer is present and said diluent polymer compnses a polymer or copolymer having tertiary carbon atoms m the polymer molecule

   37 The polymenc composition of Claim 33 wherein at least one diluent polymer is present and said diluent polymer compnses a polymer or copolymer having tertiary carbon atoms in the polymer molecule

   38 The polymenc composition of Claim 33 wherein at least one diluent polymer is present and said diluent polymer compnses a polymer or copolymer having tertiary carbon atoms in the polymer molecule

   39 The polymeric composition of Claim 53 wherem the diluent polymer is selected from polypropylene, polyvinyl chlonde, polybutcne, and copolymers and mixtures thereof

   40 The polymenc composition of Claim 33 wherein the diluent polymer is selected from polypropylene, polyvinyl chlonde, polybutene, and copolymers and mixtures thereof.

   INTELLECTUAL PROPtHTY 5f-FICr OF NZ

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   PCT/DS97/04796

   4 j A process of forming a film having a plurality of layers and at least one of said layers is selected to have an elevated degree of crosslink with respect to at least one other layer comprising

   A. extruding a film having a plurality of layeis wherein at least one of said layers 5 contains a polymenc crosslink enhancer composition comprising

   (I) copolymer having polymenc units denved from (a) at least one polyene monomer, (b) at least one C2-C20 olefinic monomer and, optionally, (c) at least one copolymenzable monomer other than (a) or (b), or

   (II) mixture composed of at least one polymer having polymenc units denved 10 from (a) at least one polyene monomer, and at least one polymer compnsmg polymeric unts denved from (b) at least one C2-C20 olefinic monomer and, optionally, at least one copolymenzable monomer other than (a) or fb),

   and

   15 B subjecting the film to actinic radiation

   42 The process of Claim 41 wherem the radiation is selected from ionizing radiation or ultra-violet radiation

   >

   20 43 The process of Claim 41 wherein the film formed is according to Claim 1, 2,

   3,4, 5,6, 7,8,9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20

   44 The piocess of Claim 43 wherein the film is at a temperature higher than ambient temperature during irradiation.

   25

   45 The process of Claim 43 wherein the layer having the polymenc crosslink enhancer composition is in a molten state j "ACTUAL Prlc/trifFOFFICE I /u [ OF NZ

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   46 The process of Claim 43 wherein the film is subjected to ultra-violet radiation and the polymenc crosslink enhancer composition further compnses a photomitiator compound

   47 The process of Claim 43 wherein the film is subjected to electron beam ^ radiation or ionizing irradiation

   48 A package comprising a film surrounding a cavity suitable for containing or containing an article, the film being selected from the film of Claim 1

   10

   49 A multilayer film substantially as hereinbefore described with reference to the accompanying figures

   50 A multilayer film as claimed in Claim 1 substantially as hereinbefore descnbed with reference to any one of the examples contained herein

   51 A polymenc composition as claimed in Claim 33 substantially as hereinbefore descnbed with reference to the accompanying figures or any of the examples contained herein

   52 A process of forming a film as claimed in Claim 41 substantially as hereinbefore descnbed with reference to the accompanying figures or any of the examples contained herein

   53 A package comprising a film as claimed in Claim 48 substantially as hereinbefore described with refeience to the accompanying figures or any of the examples contained herein

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