(12) Patent Application Publication (10) Pub. No.: US 2003/ A1

Transcription

1 US A1 (19) United State (12) Patent Application Publication (10) Pub. No.: US 2003/ A1 Chang (43) Pub. Date: (54) DURABLE HIGH BARRIER METALLIZED Related U.S. Application Data PLY PRPYLENE FILM (60) Proviional application No. 60/330,088, filed on ct. 19, (76) Inventor: Keunuk P. Chang, North Kingtown, RI (US) Publication Claification (51) Int. Cl.... B32B 15/04 Correpondence Addre: (52) U.S. Cl /.457; 428/461; 428/462 Raj S. Dave, Ph.D., J.D. Morrion & Foerter LLP (57) ABSTRACT Suite Tyon Boulevard A laminate film capable of providing an oxygen and water McLean, VA (US) Vapor barrier to a perihable product i dicloed. The laminate film comprie a polyolefin rein layer compriing a dicharge-treated Surface, a metal layer having an optical (21) Appl. No.: 10/270,734 denity of at leat 2.0 depoited directly on Said dicharge treated Surface of Said polyolefin rein layer and a crolinked acrylate coating of at leat 0.1 micron thickne (22) Filed: ct. 16, 2002 depoited on Said metal layer. 2TR Barrier Durability Comparion ea C N E D n1 H CN

2 Patent Application Publication Sheet 1 of 2 US 2003/ A1 2TR Barrier Durability Comparion Unlaminated Film -- Ex. 1 2TR - - Ex. 2 2TR A- - - CEX. 1 2TR... o. -- C.Ex 2 2 R Figure la 2TR Barrier Durability Comparion Unlaminated Film S N E U 9. Y H CN -o-ex. 1 2TR -E-Ex. 2 2TR o- - - C.Ex 2 2TR Figure lb

3 Patent Application Publication Sheet 2 of 2 US 2003/ A1 MVTR Barrier Durability Comparion Unaminated Film 6 Figure 2 2TR Barrier Durability Comparion 350. e A N E D 1. H GN Figure 3

4 DURABLE HIGH BARRIER METALLIZED PLY PRPYLENE FILM RELATED APPLICATINS Thi application claim priority from Proviional Application Serial No. 60/330,088, filed ct. 19, 2001, entitled the ame a above, the entire dicloure of which i hereby incorporated herein by reference. FIELD F INVENTIN 0002 Thi invention relate to a metallized polypropy lene film containing a polyolefin layer and a metal depoited layer, over-coated in the metallizing chamber with a crolinkable material and a method for producing Same. BACKGRUND F INVENTIN Biaxially oriented polypropylene metallized film are ued for many packaging application, particularly in food packaging, becaue they have important Sealing and protective qualitie. The film minimize the amount of light, moiture, and oxygen which can normally enter an ordinary, unprotected package. The film are often ued in food packaging in combination with ga-fluhing application to protect the content from moiture and oxidation. Alo, the film often provide a heat Sealable inner layer for bag forming and Sealing Metallized film ued in vertical-form-fill-eal (VFFS) packaging provide an excellent barrier in both unlaminated or laminated form. However, becaue of the wide variety of forming collar ued, bag Size, filling Speed, and machine tenion ued during the proce of bag-forming, the laminated packaging containing the met allized film can be tretched in the packaging machine from 5 to 10% beyond the dimenion of the original film pack aging. Thi tretching may caue fracture or crack to form in the metal layer of the film. A a reult, the packaging loe it protective propertie. For intance, xygen can readily pa through a damaged packaging film and caue unwanted oxidation of the content High barrier metallized PP film are typically metallized to an optical denity range of Thi ha been hown to be adequate to provide good flat heet (unelongated) barrier propertie. However, Such an optical denity level alone ha not been hown to provide good barrier durability during the bag forming process U.S. Pat. No. 5,698,317, the dicloure of which i incorporated herein by reference, dicloe the ue of a four layer packaging film having a polyolefin rein layer Sand wiched between a polyolefin mixed rein layer compriing a petroleum or terpene rein and a heat Sealable layer or non-sealable winding layer. A metal layer i then depoited on the urface of the polyolefin mixed rein layer. The metal layer i depoited following the dicharge treatment of the polyolefin mixed rein layer. The inventor cite improve ment in flat heet barrier and metal adheion to the Subtrate, but do not dicloe any improvement in formed bag or elongated durability barrier U.S. Pat. No. 5,223,307 dicloe a method to produce a vapor-depoited metallized packaging foil where an anti-friction coating i depoited upon the metal Surface to provide protection of the metal from any damage and thu, maintain the impermeability of the foil to gae. U.S. Pat. No. 5,223,307 doe not dicloe a packaging foil having a crolinked acrylate layer U.S. Pat. No. 4,842,893 dicloe a proce and material for depoiting acrylate coating upon a Subtrate inide a vacuum chamber which i then cured via electron beam to form a protective coating. U.S. Pat. No. 5,725,909 and 6, (the Shaw patent) dicloe a method to produce a ga barrier material. The Shaw patent dicloe a flexible Subtrate having a firt acrylate layer, a metal layer on the firt acrylate and a Second acrylate layer depoited upon the metal layer and cured. Thee patent, however, dicloe the need to place the firt acrylate layer directly on the thermoplatic heet and then depoit a metal layer on the firt acrylate layer The preent invention improve upon the moiture and ga barrier propertie a well a the durability of the metal layer. SUMMARY F THE INVENTIN 0010 Thi invention provide a method to improve the flat heet barrier and barrier durability of conventional metallized film reulting in a metallized high barrier pack aging film with good formed bag barrier propertie. The invention help Solve the problem of leaky bag aociated with conventional metallized film packaging and the bag forming process by providing a metal layer with an optical denity of at leat 2.0 and an acrylate coating depoited on top of the metal layer of at leat 0.1 um which i then cured or crolinked by electron beam. The metal layer i depo ited on a polymer laminate film having at leat two layer, a polyolefin rein layer and a heat Sealable or a non-heat Sealable, winding layer. The acrylate coating i then depo ited upon the metal layer and i cured. The invention improve upon the moiture and ga barrier durability prop ertie of laminate film The laminate film of the invention include at leat a 1, 2 or 3-layer coextruded film and a metal layer, prefer ably a vapor depoited aluminum layer, with at leat an optical denity of 1.8, preferably with an optical denity of about 2.0 to 4.0, and even more preferably between 2.2 and 3.2. The aluminum layer i vapor depoited upon a dicharge treated Surface, preferably a dicharge-treatment produced in a C and N environment. Such dicharge-treatment in a C2/N2 atmophere reult in a treated Surface containing at leat 0.3% nitrogen-containing functional group, and preferably at leat 0.5% nitrogen-containing functional group. In the cae of the 2-layer laminate, the laminate film comprie a polymer rein, preferably a homopolymer polypropylene rein which ha been dicharge treated in the preferred method. In the cae of a 3-layer laminate, the metal vapor i depoited upon a dicharge treated Surface (via the preferred method) containing a polyolefin mixed rein. Thi polyolefin mixed rein layer i dipoed on one Side of a homopolymer propylene core layer. A heat Sealable Surface or a winding Surface containing antiblock and/or lip addi tive for good machinability and low coefficient of friction (CF) i dipoed on the oppoite ide of the propylene core layer. Additionally, if the third layer i ued a a winding Surface, it Surface may alo be modified with a dicharge treatment to make it Suitable for laminating or converter applied adheive and inks. The acrylate monomer i vapor

5 ized and depoited on the metallized flexible ubtrate and i cured by electron beam or ultra-violet radiation to form a coating that i micron thick, preferably micron in thickne, and more preferably between micron in thickne A will be realized, thi invention i capable of other and different embodiment, and it detail are capable of modification in variou obviou repect, all without departing from thi invention. Accordingly, the decription i to be regarded a illutrative in nature and not a retric tive. BRIEF DESCRIPTIN F THE DRAWINGS 0013 FIGS. 1a and 1b illutrate 2TR durability data of Ex. 1, Ex. 2, CEX. 1, and CEX. 2 graphically. FIG. 1b i the ame data a FIG. 1a with the exception of Ex. 1 in order to illutrate the difference between EX. 1, Ex. 2 and CEX. 2 more clearly FIG. 2 illutrate MVTR durability data of Ex. 1, Ex. 2, CEX. 1, and CEX. 2 graphically FIG. 3 illutrate 2TR durability of Ex. 1, Ex. 2, CEX. 3, and CEX. 4. DETAILED DESCRIPTIN F THE INVENTIN In one embodiment of the invention the laminate film comprie: a polyolefin rein layer, preferably a rein containing polypropylene; a heat Sealable layer or a non-heat Sealable, winding layer, a metal layer; and a cured coating of acrylate. The polyolefin rein layer will have a thickne of about 6 to 40 micron thick. The polyolefin rein layer i dicharge treated, and the metal layer depoited on the treated rein layer. The dicharge treatment i preferably conducted in an atmophere of air, C, N, or a mixture thereof, more preferably in a mixture of C and N. Thi method of dicharge treatment reult in a treated Surface that comprie nitrogen-bearing functional group, prefer ably 0.3% or more nitrogen in atomic %, and more prefer ably 0.5% or more nitrogen in atomic % The metal layer i preferably a vapor depoited metal, more preferably vapor depoited aluminum. The metal layer hall have a thickne between 5 and 100 nm, preferably between 30 and 70 nm, and an optical denity between 2.0 and 4.0, preferably between 2.2 and The acrylate monomer i preferably a diacrylate or triacrylate monomer, of molecular weight between , preferably between The acrylate monomer i preferably vaporized and depoited on top of the vapor depoited metal after Said metal ha been formed on the Subtrate. The acrylate monomer coating i then cured in itu, preferably uing electron beam or ultra-violet radiation Sufficient to polymerize the monomer into a Solid and Stable coating. Thi coating thickne i between micron, preferably between micron thick. It ha been found that a coating of the above thickne ignificantly improve the flat heet barrier (prior to bag-forming) a well a ubtantially improving the barrier durability (barrier after bag-forming). Without being bound to any theory, it i propoed that the cured acrylate coating form a continuou Surface upon the metal layer which: 1) Help protect the metal Surface from incidental damage and metal pick-off, thu improving the flat heet barrier; and 2) Help prevent the metal layer from fracturing under the Stree of bag forming or elongation which the metal layer and Subtrate are Subjected to during the coure of bag-forming. It ha alo been found that when the coating thickness i le than 0.1 micron thick, the coating can become dicontinuou, thu loing the benefit of barrier durability; when the coating i greater than 1.0 micron, no barrier durability propertie are lot, however, no further improvement i found either, which thu wate acrylate monomer material. Thi, in turn, raie the cot of Such a product The heat calable layer may contain an anti-block ing agent and/or lip additive for good machinability and a low coefficient of friction in about % by weight of the heat-ealable layer. The heat ealable layer will prefer ably comprie a ternary ethylene-propylene-butene copoly mer. If the invention comprie a non-heat Sealable, winding layer, thi layer will comprie a crytalline polypropylene or a matte layer of a block copolymer blend of polypropylene and one or more other polymer whoe Surface i roughened during the film formation Step So a to produce a matte finih on the winding layer. Preferably, the urface of the winding layer i dicharge-treated to provide a functional Surface for lamination or coating with adheive and/or inks The polyolefin rein i coextruded with the heat ealable layer will have a thickne between 0.2 and 5 micron, preferably between 0.6 and 3 micron, and more preferably between 0.8 and 1.5 micron. The coextruion proce include a two-layered compoiting die. The two layer laminate heet i cat onto a cooling drum whoe urface temperature i controlled between 20 C. and 60 C. to Solidify the non-oriented laminate heet The non-oriented laminate heet i tretched in the longitudinal direction at about 135 to 165 C. at a tretching ratio of about 4 to about 5 time the original length and the reulting tretched heet i cooled to about 15 C. to 50 C. to obtain a uniaxially oriented laminate heet. The uniaxially oriented laminate heet i introduced into a tenter and preliminarily heated between 130 C. and 180 C., and Stretched in the tranvere direction at a tretching ratio of about 7 to about 12 time the original length and then heat et to give a biaxially oriented heet. The biaxially oriented film ha a total thickne between 6 and 40 micron, prefer ably between 10 and 20 micron, and mot preferably between 12 and 18 micron The urface of the polyolefin rein layer of the biaxially oriented laminate film i Subjected to a dicharge treatment, preferably a corona-dicharge treatment. The di charge treatment i preferably conducted in an atmophere of air, C, N, or a mixture thereof, and more preferably in a mixture of C and N. The treated laminate heet i then wounded in a roll. The roll i placed in a metallizing chamber and the metal wa vapor-depoited on the dicharge treated polyolefin rein layer Surface. The metal film may include titanium, Vanadium, chromium, maganee, iron, cobalt, nickel, copper, Zinc, aluminum, gold, or palladium, the preferred being aluminum. After formation of the metal layer, an acrylate monomer i vaporized and depoited upon Said metal layer and cured in itu. The acrylate monomer may be a di- or tri-acrylate functionality, preferably of molecular weight between The cured acrylate coated metallized film i then teted for xygen and moiture permeability and durability.

6 0023 Thi invention will be better undertood with ref erence to the following example, which are intended to illutrate Specific embodiment within the overall Scope of the invention. EXAMPLE ne hundred part by weight of a crytalline pro pylene homopolymer rein; part by weight of a Sodium calcium aluminoilicate powder or an amorphou Silica having a mean particle diameter of 3 micron, were blended together. Thi mixture wa coextruded with a heat Sealable ternary ethylene-propylene-butene copolymer con taining 4000 ppm of a crolinked Silicone polymer of mean particle diameter of 2 micron by weight of the heat Sealable layer, and biaxially oriented to produce a 2-layer film where the propylene homopolymer rein layer wa 16 micron thick and the accompanying coextruded ternary ethylene-propy lene-butene copolymer layer wa 1.5 micron thick. The total oriented film thickne wa 17.5 micron or 70 G or 0.7 mil thick. The film wa then dicharge-treated in a controlled atmophere of N2 and C, on the propylene homopolymer ide (the metallizing urface) and wound in roll form. The roll wa then metallized by vapor-depoition of aluminum onto the dicharge-treated Surface to an optical denity target of The roll wa then coated by vapor-depoition of acrylate monomer and cured by electron beam of thickness 0.33 micron. The acrylate-coated metallized laminate film wa then teted for oxygen and moiture permeability, optical denity, and barrier durability. EXAMPLE A proce imilar to Example 1 wa repeated except that the cured acrylate coating thickne wa 1.1 micron thick. Comparative Example A proce imilar to Example 1 wa repeated except that no acrylate monomer wa depoited and cured on the vapor-depoited aluminum layer. Comparative Example ) A proce imilar to Example 1 wa repeated except that the cured acrylate coating thickne wa 0.1 micron thick. Comparative Example A proce imilar to Example 1 wa repeated except that the coating wa left uncured. Comparative Example A proce imilar to Example 1 wa repeated except that the optical denity wa 1.5. Tet Method 0030 The variou propertie in the above example were meaured by the following method: xygen tranmiion rate of the film wa meaured by uing a Mocon xtran 2/20 unit ubtantially in accor dance with ASTM D3985. Moiture tranmiion rate of wa meaured by uing a Mocon Permatran 3/31 unit meaured ubtantially in accordance with ASTM F1249. Barrier durability of the film wa meaured by elongating tet pecimen in an Intron Tenile teter at 0, 3, 6, and 9% elongation. The elongated Sample wa then meaured for barrier propertie uing Mocon Xtran 2/20 or permatran 3/31 unit. In general, preferred value of TR would be equal or le than 46.5 cc/m /day up to 9% elongation and MVTR would be equal or le than 0.69 g/m /day up to 9% elongation ptical denity wa meaured uing a Tobia Ao ciate model TBX tranmiion denitometer. ptical den ity i defined a the amount of light reflected from the tet Specimen under Specific condition. ptical denity i reported in term of a logarithmic converion. For example, a denity of 0.00 indicate that 100% of the light falling on the ample i being reflected. A denity of 1.00 indicate that 10% of the light reflected; 2.00 i equivalent to 1%, etc The reult of the foregoing example ( Ex. ) and comparative example ( CEX. ) are hown in Table 1, and FIGS. 1a, 1b, 2, and ) Table 1 how the oxygen tranmiion rate (2TR) of the metallized film ample at variou elonga tion. The 2TR of the acrylate-coated metallized PP Sample (Ex. 1 and Ex. 2) how ignificantly improved 2TR barrier than the uncoated metallized PP ample (CEX. 1), epecially after elongation. Such ignificant improvement i due to the cured acrylate coating protecting the metal layer and thu can be of Significant value to formed bagga barrier in Snack food packaging. Table 1 alo how that if the acrylate coating i too thin (CEX. 2), the effec tivene of the maintenance of barrier propertie can be degraded, but i till better than an uncoated Sample (CEX. 1). In addition, if the coating i not crolinked, barrier durability i not improved (CEX. 3). If the optical denity i too low (CEX. 4), although there may be Some improvement in initial barrier propertie, there i no ignificant improve ment in barrier durability even with the crolinked coating. TABLE 1. 2TR Barrier Durability Comparion for Unlaminated Film Elongation (%) Ex. 1 Ex. 2 CEx. 1 CEx. 2 CEx. 3 CEx ptical Denity The above decription i preented to enable a person Skilled in the art to make and ue the invention, and i provided in the context of a particular application and it requirement. Variou modification to the preferred embodiment will be readily apparent to thoe killed in the art, and the generic principle defined herein may be applied to other embodiment and application without departing from the Spirit and Scope of the invention. Thu, thi invention i not intended to be limited to the embodiment hown, but i to be accorded the widet Scope conitent with the principle and feature dicloed herein. 0036) Thi application dicloe everal numerical range limitation. Peron killed in the art would recognize that

7 the numerical range dicloed inherently Support any range within the dicloed numerical range even though a precie range limitation i not Stated verbatim in the Specification becaue thi invention can be practiced throughout the dicloed numerical range. A holding to the contrary would let form triumph over Subtance and allow the written decription requirement to evicerate claim that might be narrowed during proecution imply becaue the applicant broadly dicloe in thi application but then might narrow their claim during proecution. Finally, the entire dicloure of the priority document, patent and publication referred in thi application are hereby incorporated herein by refer CCC. 1. A laminate film, compriing: a polyolefin rein layer compriing a dicharge-treated Surface; a metal layer having a high optical denity of at leat 2.0 depoited directly on Said dicharge-treated Surface of Said polyolefin rein layer, and a crolinked acrylate coating of at leat 0.1 micron thickne depoited on Said metal layer. 2. The laminate film of claim 1, wherein a Surface of the polyolefin rein layer oppoite Said dicharge-treated Surface comprie a heat Sealable layer or winding layer compriing an antiblock Selected from the group coniting of a non polymeric antiblock and a polymeric antiblock. 3. The laminate film of claim 1, wherein aid polyolefin rein layer ha a thickne of about 6 to 40 micron. 4. The laminate film of claim 1, wherein aid polyolefin rein layer comprie a polypropylene rein. 5. The laminate film of claim 2, wherein aid heat-ealable layer or winding layer ha a thickne of about 0.5 to 5.0 micron. 6. The laminate film of claim 2, wherein aid heat Sealable or winding layer comprie an anti-blocking agent of about 0.05 to 0.5 percent by weight of aid heat ealable or winding layer. 7. The laminate film of claim 2, wherein aid heat Sealable layer comprie a ternary ethylene-propylene-butene copolymer. 8. The laminate film of claim 2, wherein aid winding layer comprie a crytalline polypropylene or a matte layer of a block copolymer blend of polypropylene and one or more other polymer having a roughened Surface. 9. The laminate film of claim 2, wherein aid winding layer i treated to provide a Surface for lamination or coating with adheive or ink. 10. The laminate film of claim 1 or 2, wherein aid metal layer ha a thickne of about 5 to 100 nm. 11. The laminate film of claim 1 or 2, wherein aid metal layer ha an optical denity of 2.0 to The laminate film of claim 1 or 2, wherein aid metal layer comprie aluminum. 13. The laminate film of claim 1 or 2, wherein aid dicharge treatment of Said polyolefin rein layer or Second polyolefin rein layer i performed in an atmophere of C2 and N. 14. The laminate film of claim 2, wherein the non polymeric antiblock i Selected from the group coniting of an amorphou Silica, an aluminoilicate and a Sodium cal cium aluminum Silicate 15. The laminate film of claim 2, wherein the non polymeric antiblock i Selected from the group coniting of crolinked Silicone polymer and polymethylmethacrylate. 16. The laminate film of claim 1, wherein the crolinked acrylate coating i between 0.1 to 2 micron thick. 17. A laminate film, compriing: a polyolefin rein layer compriing a dicharge-treated Surface; a metal layer having an optical denity of at leat 2.0 depoited directly on Said dicharge-treated Surface of Said polyolefin rein layer, and a crolinked acrylate coating of at leat 0.1 micron thickne depoited upon Said metal layer and cured; wherein the laminate film ha a barrier durability at 9% elongation of le than or equal to 46.5 cc/m/day TR and le than or equal to 0.69 g/m/day MVTR. 18. A method of providing an oxygen and water vapor barrier to a perihable product that i capable of degrading on expoure to oxygen and/or water vapor, compriing: covering the perihable product with a laminate film and expoing the laminate film to oxygen and/or water vapor, wherein the laminate film comprie: a polyolefin rein layer compriing a dicharge-treated Surface; a metal layer having an optical denity of at leat 2.0 depoited directly on Said dicharge-treated Surface of Said polyolefin rein layer; and a crolinked acrylate coating of at leat 0.1 micron thickne depoited upon Said metal layer and cured; wherein the laminate film ha a barrier durability at 9% elongation of le than or equal to 46.5 cc/m/day TR and le than or equal to 0.69 g/m/day MVTR.