121:2; :21" Good 'Seal Range For' Uncoated Tyvek®, Evidence of Seal
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USOO5830547A Ulllted States Patent [19] [11] Patent Number: 5,830,547 MacKenZie et al. [45] Date of Patent: Nov. 3, 1998 [54] PEEL-OPEN PACKAGE 0 785 066 7/1997 European Pat. Off. 7144391 6/1995 Japan . [75] Inventors: Fiona MacKenzie, Bloomington, 07205562 3/1997 Japan - Minn; Roy Christopherson, SWindon; 96/04861 2/1996 WIPO - Kingdom European Patent Of?ce, International Search Report for [73] Assignee: ReXam Medical Packaging, Inc-, PCT/IB 97/00862, completed Oct. 27, 1997 by P. Olle. Vernon H1115, 111- “Coated Vs. Uncoated Webs In Thermoform/Fill/Seal”; Randall D. Brinkman; Paper Film Foil Conv. 1984, 58, No. [21] Appl. No.: 678,984 10, Oct. 19, 1984; pp. 78—82. [22] Filed? Jul- 12, 1996 Primary Examiner—Christopher Raimund 6 Attorne , A em, or Firm—Bell Seltzer Intellectual Pro ert [51] Int. Cl. ................................................... .. B29D 22/00 Law GryoupgofAlston & Bird LLP P Y [52] US. Cl. ...................... .. 428/361; 428/365; 206/363; 206/439 [57] ABSTRACT [58] Field of Search ................................ .. 428/358, 36.5, _ _ _ 428/357, 361; 206/363, 439 A peel-open package includes a polymeric ?lm, a lid adhered to the polymeric ?lm along a continuous portion [56] References Cited thereof and a product encapsulated between the polymeric ?lm and lid material. The polymeric ?lm is typically a US PATENT DOCUMENTS coeXtruded multiple layer ?lm having a scalable layer and at 3 891 089 6/1975 Goodwin et a1‘ ' least one base layer. The sealable layer comprises an ethyl 4j194:622 3/1980 Lewis _ ene copolymer derived from at least one monomer selected 473617237 11/1982 Heiremans et a1_ _ from the group consisting of vinyl acetate and 4,367,312 1/1983 Bontinck et a1. alkylacrylates, a talc additive, and an additive Which pro 4,859,514 8/1989 Friedrich et al. vides peelability to the heat seal layer. The lid material is 4,956,212 9/1990 Bekele- preferably a microporous layer to alloW sterilization and 57033252 7/1991 Cane/L prevent subsequent contamination by bacteria and other 573247555 6/1994 Hughart et a1" microbial organisms. The peel-open package provides a 121:2; :21" good ‘seal range for‘ uncoated Tyvek®, evidence of seal 576267929 5/1997 Stevenson ......................... .. 428/358 mtegnm reduced Tmnng> and a Seal Strength Whlch 1S ’ ’ suf?ciently loW to prevent the delaminating or branching of FOREIGN PATENT DOCUMENTS the lid material When it is removed. The present invention 2191764 2/1996 Canada ' also includes methods of making peel-open packages. O 024 270 2/1981 European Pat. Off. O 042 831 12/1981 European Pat. Off. 20 Claims, 1 Drawing Sheet U.S. Patent Nov. 3, 1998 5,830,547 5,830,547 1 2 PEEL-OPEN PACKAGE Tyvek® to a blister pack material Which alloWs the package contents to be steam steriliZed Without adversely affecting FIELD OF THE INVENTION the package seal. Nevertheless, Carter does not address heat seal compositions for sealing uncoated Tyvek® to a ther The present invention relates to primary packaging, moplastic ?lm and therefore fails to address the seal ranges particularly, form, ?ll and seal packaging. More particularly, and the problems associated With heat sealing uncoated the present invention relates to peel-open, sterile packaging. Tyvek®. BACKGROUND OF THE INVENTION In addition to providing an easily openable seal, heat seals preferably should provide evidence of seal integrity to alloW Medical, food and other packaging manufacturers offer a the user to be con?dent that the seal remained intact prior to variety of products in peel-open packages. Often these opening of the peel-open package. This evidence is particu packages are of the type referred to as form, ?ll and seal larly helpful in the medical industry Where the product user (FFS) packages. With FFS packages, a bloWn or cast ther must be con?dent that the packaged product is sterile. US. moplastic ?lm or sheet is typically formed into a desired Pat. No. 5,324,555 to Hughart et al. describes a heat seal package shape. The thermoplastic ?lm is then ?lled With the 15 containing coextruded layers of high density polyethylene packaged product, after Which a lid material is sealed to the (HDPE), EVA, and polyionomer blended With loW density plastic ?lm to envelop the packaged product. polyethylene (LDPE) Which exhibits a frosty appearance in One common method of sealing the thermoplastic ?lm to the sealed area When opened to alloW the user to be con?dent the lid is to apply heat and pressure to a continuous portion of the integrity of the package seal. Nevertheless, Hughart et of the ?lm thereby causing a heat sealable composition in the al. is not directed to heat seal compositions for uncoated thermoplastic ?lm to form an adhesive bond betWeen the lid Tyvek®. and the thermoplastic ?lm. One traditional heat sealable composition used With thermoplastic ?lms is ethylene vinyl OBJECT and SUMMARY OF THE INVENTION acetate copolymer (EVA). For example, US. Pat. No. 3,891, Therefore, it is an object of the present invention to 089 to GoodWin et al. and US. Pat. No. 4,956,212 to Bekele 25 provide a peel-open package Which can be steriliZed Without describe heat seal layers consisting essentially of EVA. adversely affecting the package seal. Although EVAprovides an adhesive, heat-sealable layer, the It is a further object of the present invention to provide a seal strength of the EVA may be greater than the strength of peel-open package in Which the lid material may be removed the lid material thus possibly causing the lid material to from the ?lm Without delaminating or linting of the lid delaminate in an undesired fashion When the package is material or stringing of the polymeric ?lm material. being peeled open. In addition, branching may occur such It is a further object of the present invention to provide that ?bers continue to extend across the polymeric ?lm after evidence of the integrity of the heat seal to insure the the lid has been removed thus providing an obstacle to the steriliZation of the packaged product. removal of the product packaged therein. 35 It is a further object of the present invention to provide a Another problem Which occurs With high seal strength polymeric ?lm for a peel-open package Which Will adhere to packages is that the sealed area may exhibit linting, i.e., an uncoated spunbonded nonWoven polyole?n Web over a exhibit the release of small particles of lid material, When the broad range of temperatures. package is opened. Linting can especially be a problem in a The present invention meets these objects by providing a sterile environment such as an operating room Where the peel-open package comprising a polymeric ?lm comprising ?bers can come into contact With a patient. an ethylene copolymer derived from at least one monomer In addition to the problems described above, the heat seal selected from the group consisting of vinyl acetate and composition used may result in other problems When the alkylacrylates, a talc additive for providing uniform sepa package is peeled open. Speci?cally, the ?lm material may ration betWeen the lid and the polymeric ?lm and evidence be subject to stringing, i.e., the formation of polymeric 45 of the integrity of the heat seal, and a peelability additive for ?laments on the surface of the ?lm. interrupting the sealability of the ethylene copolymer to the These problems are further compounded by the lid mate lid to provide peelability to the polymeric ?lm, and a lid rials used in the area of medical packaging. In medical adhered to the polymeric ?lm along at least a portion thereof packaging, the lid material is often a microporous Web for encapsulating a product therebetWeen. Typically, the Which alloWs the products being packaged to be steriliZed. polymeric ?lm is a coextruded multiple layer ?lm having a For example, a microporous non-Woven spunbonded poly sealable layer and at least one base layer and the sealable ole?n substrate such as Tyvek® or a medical grade kraft layer comprises the ethylene copolymer, talc additive and paper may be used as the lid material. Preferably, When peelability additive described above. Tyvek® is used, the Tyvek® is uncoated because it is a less In the preferred embodiment of the present invention, the expensive alternative than using adhesive coated Tyvek®. 55 lid material is microporous thus alloWing the package con Nevertheless, the seal range, i.e., the range of heat seal tents to be steriliZed. Preferably, the lid material is an temperatures yielding a desired heat seal strength, is small uncoated spunbonded nonWoven polyole?n material such as for heat seals betWeen uncoated Tyvek® and thermoplastic Tyvek®. The uncoated spunbonded nonWoven polyole?n ?lms, thus limiting the temperature range at Which the lid Web is adhered to a sealable layer of a multilayer coextruded material can be heat bonded to form a peel-open package. In polymeric ?lm by a heat and pressure activated seal Which addition, Tyvek® is highly susceptible to delaminating or is generally adjacent to a peripheral edge of the polymeric linting When the heat seal strength betWeen the Tyvek® and ?lm. The sealable layer comprises betWeen about 45 and 95 the lid material is too strong. percent by Weight of an ethylene copolymer, greater than 0 Therefore, there is a de?nite need to provide a heat seal to about 30 percent by Weight of a talc additive, and betWeen composition Which can be used With uncoated Tyvek® 65 about 5 and 40 percent by Weight of a peelability additive. Without experiencing the problems discussed above. US. The present invention also includes methods of making Pat.