WO2005002849A2

WO2005002849A2 - Contamination infiltration barrier and method

Info

Publication number: WO2005002849A2
Application number: PCT/US2004/010131
Authority: WO
Inventors: John D. Langley; Todd R. Carroll
Original assignee: Kappler, Inc.
Priority date: 2003-04-02
Filing date: 2004-04-01
Publication date: 2005-01-13
Also published as: WO2005002849A3

Abstract

A flexible, high chemical barrier film with modified surface characteristics is used to form an effective contamination infiltration barrier that offers a significant and drastic improvement as compared to the polyethylene-based sheeting materials presently used for this purpose. The flexible multi-layered barrier film has two opposing surfaces, at least one of which has a surface energy of 35 dynes/cm or greater. The barrier film also has a permeation efficiency greater than 50% when exposed to the chemicals included on ASTM 1001 and offers resistance to military chemical agents, toxic industrial chemicals, and biological hazards.

Description

CONTAMINATION INFILTRATION BARRIER AND METHOD

FIELD OF THE INVENTION This invention relates generally to the field of flexible films, and more specifically to plastic sheeting that can be used over windows, doors, vents, passageways, and other openings to prevent the infiltration of hazardous substances into various permanent and temporary dwellings and enclosures.

BACKGROUND OF THE INVENTION The expanding threat of world terrorism and chemical/biological weaponization by third world and developing nations has heightened international awareness for the need for highly specialized protective devices and equipment. While significant effort has been placed on developing chemically resistant clothing, respiratory protection, protective covers and shelters, air monitoring devices, and release plume modeling, little effort has been placed on general civilian safety, and more specifically equipment that is currently being recommended for "shelter-in-place" (SIP) scenarios. The general civilian population must be prepared for the threat of accidental and deliberate releases of hazardous substances. While recent events associated with global terrorism has heighten awareness of these threats, the potential for such events has been present for many years. While major cities are only recently preparing for chemical attacks by aggressors, communities located in high chemical production areas (i.e., the gulf coast region of the U.S.) live with the daily threat of accidental chemical releases. Additionally, foreign states such as Israel have operated in a perpetual state of preparedness with respect to chemical attack. The two primary civilian responses to potential large scale chemical exposure events whether deliberate or accidental are 1) evacuation and 2) shelter- in-place (SIP). The extent and severity of the event will ultimately determine which response model is employed; however it should be evident that large scale evacuation is difficult to accomplish effectively and efficiently. Plume modeling has demonstrated that for many potential events the shelter-in-place response is the most rapid and effective mode of protection for those in direct path of a release since normal environmental conditions (i.e., wind, natural dilution in air, and unrestricted volatilization, etc.) tend to drastically and rapidly reduce and dilute airborne threats. SIP is a common protective strategy that has been employed by the North Atlantic Treaty Organization (NATO) and the Israeli Civil Defense since the mid- 1980s. One of the largest domestic uses of the SLP practice began as a result of the Chemical Stockpile Emergency Preparedness Program (CSEPP). CSEPP is a program resulting from the U.S. Congress directing the U.S. Army to destroy certain kinds of chemical weapons stockpiles. With the help of the Federal Emergency Management Agency (FEMA), CSEPP has readied eight major communities located in close proximity to the Army facilities responsible for destroying the weapons for the unlikely event of a chemical accident. Chemical stockpiles are located in Anniston Army Depot (Alabama), Blue Grass Army Depot (Kentucky), Aberdeen Proving Grounds (Maryland), Newport Chemical Activity (Indiana & Illinois), Pine Bluff Arsenal (Arkansas), Pueblo Chemical Depot (Colorado), Tooele Army Depot (Utah), and Umatilla Chemical Activity (Oregon & Washington). General SIP practice comprises the following steps: closing off all nonessential rooms such as garages, storage areas, interior doors, fireplaces, dampers, exhaust and dryer vents, windows, extra rooms and the like; turning off all ventilation equipment; entering a predesignated "safe room"; closing and locking all doors, windows and vents; sealing all gaps around doors, windows, vents, and other openings with duct-tape and plastic sheeting; and placing wet towels under all doors. While the SIP principle can be an effective contamination avoidance practice, the equipment and materials currently recommended and used have several shortcomings that are obviated by the present invention. It has been widely accepted that traditional HNAC duct tape and generic plastic sheeting are acceptable for SIP preparedness kits. The practice of using generic HNAC duct tape for chemical applications has been debated for years within the hazardous materials emergency response community and responded to by Carroll, U.S. Pat. No. 6,183,861. Carroll describes a conformable, hand-tearable, high chemical barrier closure and attacliment tape made up of a film composite or multi-layered fihn containing at least one stratum selected from polyvinylidene chloride, ethylene vinyl acetate, ethylene vinyl alcohol, nylon, polyvinyl alcohol, polyester, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene chloride copolymer, acrylonitrile, ionomer, high density polypropylene, linear-low density polypropylene, metallized polyester and the like. The film composite providing the chemical barrier is coated with an appropriate pressure sensitive adhesive which is further adhered to a woven base cloth. The cloth is further coated with additional pressure sensitive adhesive. In addition, a conformable composite chemical barrier closure and attachment tape is presented which is comprised of a film composition containing a layer of at least one of polyester with a layer of polyethylene or ethylene vinyl alcohol which can be disposed between additional layers of polyethylene. The conformable, composite chemical barrier closure and attachment tape also provides the multi-layered film with coating on the exterior of the film to promote release, unwinding characteristics from a roll so that the conformable, composite chemical barrier and attachment tape can be manufactured and stored in rolled form and yet provide immediate release upon demand from the roll. The multi-layered film can have an exposed surface of polyethylene, the film having a thickness in the range from about 0.5 mils to about 6.0 mils. The multi-layered film can have a lacquer or similar coating on the exterior of the film to promote release from unwinding from a roll. While Carroll has addressed the need for an improved adhesive tape for use in SIP scenarios, little has been done to evaluate or develop improved products to replace the thin polyethylene sheeting currently being recommended literally throughout the world. One of the few references on the subject was published in August of 2001 by Oak Ridge National Laboratory (Oak Ridge Tennessee). John Sorensen and Barbara Vogt reported on the performance of both HVAC duct tape and polyethylene sheeting in a report entitled "Will Duct Tape and Plastic Really Work? Issues Related to Expedient Shelter-In-Place" (Report No. ORLN/TM-2001/154). The performance of duct tape and sheeting were evaluated on a material basis and on the basis of infiltration or air exchange. While the "practice" of using tape and sheeting appears to significantly decrease the air exchange in a "safe room" the effectiveness of the standard polyethylene sheeting was found to be questionable especially the thin (i.e., below 2 mil) sheeting that is most readily accessible to the civilian population. The authors extrapolated a general correlation between sheeting thickness and chemical resistance which is a commonly accepted principle in the chemical barrier industry as derived from Fick's Law of Diffusion. Polyethylene sheeting below 2.5 mils was shown to have poor resistance to distilled Mustard (H) and only marginal resistance to Nerve Agent (Vx). Polyethylene (PE), as will be shown later, is known within the chemical protective clothing industry to offer very low resistance, especially to a broad range of chemicals. With the ever expanding list of chemical, biological, and radiological challenges available to the modern terrorist, polyethylene film is actually of little value in an effective SL? preparedness kit. While generic thin polyethylene offers marginal to poor resistance to a broad range of chemicals including military warfare agents and toxic industrial chemicals and materials (TICs and TLMs), it also exhibits a low surface energy which limits its overall effectiveness as a SL? component. Surface energy is an inherent polymer characteristic that dictates how well a polymer surface will wet out and thus adhere to a liquid (i.e. the adhesive on duct tape). The lower the film surface energy, the lower the bond strength of the tape to the film. It should be evident that low bond strengths could lead to problems during installation and use when "taping-up" a safe room during an actual chemical emergency. Adhesion is the molecular force of attraction between dissimilar materials. Materials exhibiting high surface energies or surface tensions, as measured in dynes/cm, will allow improved wetting and thus will exhibit superior bond strengths when compared to materials with lower surface tensions. This inherent property becomes critical when combining thin film sheeting with pressure sensitive adhesives (PSA), which are the generic class of adhesives used on common HVAC duct tape. The primary mode of bonding a pressure sensitive adhesive is not chemical or mechanical, but rather a polar attraction to the substrate surface. Application pressure is required to achieve sufficient wet-out onto the surface of the substrate to provide maximum bond, however pressure alone will not allow a user to achieve a sufficient bond if the film exhibits a low surface energy. To obtain good wetability, the surface energy of the fihn must be greater than that of a liquid according to Owens and Wendt (D.K. Owens, R.C. Wendt, J. Applied Polymer Science, 13, 1741 (1969)). The interactions between every solid and liquid consists of both dispersive (i.e., polar and non-polar Van- der-Waal forces) and electrostatic interactions and hydrogen bonding. Common surface tension measurement methods include the hanging or pending drop, or tensiometer method for liquids and contact angle for solids. Effective bond strength is required when considering SIP components. Since the purpose of "taping-up" a room is to minimize air infiltration, the bond made between the tape and the sheeting must be sufficient to hold the sheeting in place as well as to resist pressure build-up and release resulting from air gaps around the window, vent, or other opening that is being covered. Maximum bond strength can only be achieved when the surface energy of the polyethylene is sufficiently high to allow adequate "wet-out" of the adhesive. Table 1 includes typical material surface energies for a variety of polymers. It is evident from this listing that polyethylene, the most commonly used SIP film, exhibits one of the lowest surface energies of the common flexible films. TABLE 1. Typical Surface Energies of Polymers

A secondary and still significant limitation of polyethylene sheeting as an effective SIP preparedness component is its limited chemical resistance. A truly effective film barrier/composite for use as a contamination infiltration barrier (CIB) should offer resistance to a wide variety of potential threats including TICs, TLMs, military chemical agents, and various other biological and radiological hazards. Other desirable characteristics are described below that make the present invention a novel improvement over the polyethylene based films currently being recommended and used for SIP preparedness kits. Given the limited chemical resistance of polyethylene, one might consider one of the many high chemical barrier films already in use within the chemical protective clothing industry, such as those described by Langley U.S. Pat. No. 4,833,010 or Blackburn U.S. Pat. No. 5,035,941. Unfortunately, a critical characteristic of chemical barrier fabrics is heat sealabilty which is most successfully accomplished through the use of polyolefin, and most preferably, linear low density polyethylene which exhibits a low surface energy. Numerous attempts have been made to develop chemical protective fabrics that offer a wide range of chemical resistance, as described for example in Bartasis U.S. Pat. No. 4,920,575, Blackburn U.S. Pat. No. 5,035,941, Hauer et al. U.S. Pat. No. 5,626,947, Hendriksen U.S. Pat. No. 5,059,477, Langley U.S. Pat. Nos. 4,833,010 and 4,855,178, Sahatjian et al. U.S. Pat. No. 4,943,472, Shah U.S. Pat. No. 4,755,419, and van Gompel U.S. Pat. No. 4,753,840. Other attempts have been made to develop high chemical barriers for specialty packaging applications such as those described by Perlman U.S. Pat. No. 5,302,344 and Shacklett U.S. Pat. No. 6,265,103. It should be apparent from the discussion above that an immediate need exists for an improved flexible contamination infiltration barrier that offers resistance to a wide range of chemical, biological, and radiological threats as well as full compatibility with existing pressure sensitive adhesives as are found as a component of common duct-tape. It should be further noted that other characteristics are desirable that make an efficient and novel component in an effective SIP preparedness kit.

SUMMARY OF THE INVENTION The present invention provides for a novel combination of flexible, high chemical barrier films with modified surface characteristics and properties to result in an effective contamination infiltration barrier that offers a significant and drastic improvement as compared to existing polyethylene-based sheeting material. Each of the earlier noted approaches for developing chemical protective fabrics incorporates various types of continuous chemical barriers, and strength enhancing substrates, scrims, and reinforcing base fabrics to achieve the desired level of chemical resistance and physical durability. These and other "barrier" approaches today make up what is termed the limited-use chemical protective clotlήng market. These lightweight, cost effective garments offer a variety of advantages including ease of hermetic heat-sealability. The performance objective of these composites is to minimize or prevent the infiltration of chemicals from the outside environment and onto the wearer (i.e., outside in). The primary obj ective of the exterior surface is that of a heat sealable layer to promote and facilitate a highly resistive hermetic seal. The most common and effective heat seal layer has been found to be polyethylene (PE). While one may suggest that an effective CLB might simply be the same material used in traditional limited used chemical protective clothing, the low surface energy characteristics of most chemical composites is similar to that of the existing inferior thin polyethylene sheeting currently in use with SIP kits. A novel improvement comes when one considers modifying the surface of a variety of high chemical barrier composites to facilitate strong adhesion to pressure sensitive adhesives as well as considering other desirable characteristics as discussed below. Surface modification of plastic films is common within the flexible film packaging industry. Film surfaces are modified with the distinct purpose of increasing surface energy to promote adhesion of the film to various coatings, print layers or other film layers. In the majority of cases the "energized" surface of the film is ultimately buried or covered by the coating, print layer or other film layer . The present invention is based upon the use of films having an accessible and durable high energy surface to ensure adequate adhesion between the fihn and the pressure sensitive adhesive on the duct tape that is used to secure the film in I place in a shelter-in-place (SIP) application. The process of surface modification is common within the industry and essentially includes both physical and chemical treatments. Physical treatment techniques include oxidizing the surface to render it more receptive to wetting and adhesion by creating excited sites consisting of various functional groups such as hydroxyl (HO-), hydroperoxide (HOO-), carboxylic (HOOC), carbonyl (C=O) all of which heighten the surface energy of the film. Common physical techniques used to raise film surface energy include, corona treatment, UN irradiation, flame treatment, plasma treatment, fluorine gas treatment, RF cold gas plasma, and others. Chemical treatments include priming and top coating with materials such as polyurethanes, acrylics, copolyesters, and other materials. Chemical treatment techniques tend to be more durable and have longer shelf-lives than the above- noted physical techniques which make them more desirable in a SL? product which will typically sit on the shelf for extended periods of time. Films used in accordance with the present invention have at least one exterior film surface with a surface energy of 35 dynes/cm or greater to assure good adhesion to the traditional rubber-based pressure sensitive adhesives commonly used on duct tape. Surface energies of 40 dynes/cm or greater, and more preferably 45 dynes/cm or greater are desired to maximize adhesion. Table 2 shows the drastic increase in bond strength of a pressure sensitive adhesive to high and low energy surfaces. A two inch wide piece of ChemTape® (manufactured by Kappler Inc. of Guntersville AL) was applied by hand to the surface of the listed film and tested using a constant rate of extension machine according to ASTM D751 (peel) at a crosshead speed of 12 in/min, averaging the five (5) highest values recorded during the 3 -inch peel distance.

TABLE 2. Peel Strength vs. Surface Energy Film Surface Energy Peel Strength

A about 30 dynes/cm 5.0 lbf

B about 40 dynes/cm 6.81bf

In addition to having at least one exterior surface with high surface energy, films used in accordance with the present invention have chemical barrier properties, offering resistance to military chemical agents, toxic industrial chemicals and biological hazards. Films suitable for use in the present invention preferably have a permeation efficiency greater than 50% when exposed to the 15 liquid chemicals included on ASTM 1001, and more preferably closer to 100%. Barriers showing higher PEFs demonstrate improved chemical resistance to a wider range of potential threats than barriers exhibiting lower PEFs. As described in Carroll U.S. Patent 6,183,861, a value called "permeation efficiency" has been commonly used in connection with chemical protective fabrics as a way to easily compare the.relative chemical resistances of chemical barrier fabric materials. Permeation efficiency is determined by testing the material in accordance with ASTM F739 - Standard Test Method for Resistance of Protective Clothing Materials to Permeation by Liquids and Gases to determine the breakthrough time for each of the 15 liquid chemicals specified in ASTM F1001. These chemicals are listed in Table 3. The "permeation efficiency" is calculated by adding the breakthrough times for the chemicals tested and dividing by the total number of chemicals tested multiplied times 480 minutes (i.e. 8 hours). Eight hours represents the duration of the permeation test and has become the defacto target level of performance (i.e., breakthrough time) desired by end- users when considering chemical resistance data. Thus, a barrier fabric that had a breakthrough time of at least 8 hours for each of the chemicals tested would have a permeation efficiency of 100%. The broad range of desired chemical resistance for an effective CLB can only come from using a multi-layered film with a combination of polymers. The multi-layered film can be a coextrusion and/or an adhesive or extrusion laminate. Since CLBs will typically be stored for extended periods of times, extrusion laminates of multiple film barriers is preferred over adhesive laminates as these composites typically exhibit shortened shelf-lives. Barrier layers can include one or more of the following base polymers; polyvinyl chloride, chlorinated polyethylene, chlorinated butyl, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polyurethane, PTFE, combinations thereof, or multiple-layered co extruded films which include one or more layers of ethylene- vinyl acetate, ethylene vinyl alcohol, polyvinyl alcohol, nylon, ionomers, polyester, PET, liquid crystal polymers, metallized films, fluorochemical based films, and/or blends thereof. Additionally, since the primary purpose of the CLB is to conform around various openings such as door, windows, vents, etc. it is desired that the barrier film be flexible. Reinforcing scrims and substrates can be used, but are not required. From the foregoing discussion, it should be understood that one significant aspect of the present invention involves providing and using a film having the characteristics described above for protecting against the infiltration of contamination. More particularly, the present invention provides a method for protecting against the infiltration of contamination comprising the steps of defining a predetermined space to be protected, and forming a sealed enclosure around this predetermined space with the use of a flexible multi-layered barrier film having two opposing surfaces, at least one of which has a surface energy of 35 dynes/cm or greater. The barrier film has a permeation efficiency greater than 50 when exposed to the chemicals included on ASTM 1001 and offers resistance to military chemical agents, toxic industrial chemicals, and biological hazards. When used in a shelter-in-place (SIP ) application, the aforementioned step of defining a predetermined space to be protected comprises locating a room or building with ceiling, floor and wall surfaces that define the predetermined space and with at least one surface opening. The step of forming a sealed enclosure around this predetermined space with the use of a flexible multi-layered barrier comprises mounting the flexible multi-layered barrier film across the surface opening and sealing the opening with the barrier film. Preferably, the flexible multi-layered barrier film is mounted across the opening with high energy surface of the barrier film oriented away from the ceiling, floor or wall surface, and with the barrier film positioned across the surface opening and into overlapping relation with portions of the adjacent ceiling, floor or wall surface. Then, an adhesive tape is applied to the ceiling, floor or wall surface and to the exposed high energy barrier film surface to thereby seal the opening. When used for protecting equipment from contamination, the step of defining a predetermined space comprises identifying an article of a predetermined size which is to be protected from contamination, and the step of forming a sealed enclosure around said predetermined space with the use of a flexible multi-layered barrier comprises enclosing the article in a wrapper formed of the flexible multi-layered barrier film. Preferably, the barrier film is oriented with the high surface energy surface thereof (the surface having a surface energy of 35 dynes/cm or greater) facing outwardly away from the article, and an adhesive tape is applied to the exposed surface of the barrier film wrapper to thereby seal the wrapper. The wrapper may, for example, be in the form of a bag or cover formed of the flexible multi-layered barrier film, with the bag or cover having an opening which is subsequently sealed by applying an adhesive tape to the exposed surface of the barrier film. The flexible multi-layered barrier fihn used in accordance with the present invention preferably includes at least one chemical barrier layer selected from the group consisting of polyvinyl chloride, chlorinated polyethylene, chlorinated butyl rubber, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polyurethane, polytetrafluoroethylene (PTFE), and combinations thereof. A number of chemical barrier films are commercially available that can be suitably used in practicing the method for protecting against the infiltration of contamination in accordance with the present invention, after appropriate physical or chemical surface modification to the film surface impart the requisite high surface energy. The present invention also provides several unique and novel multi-layer films and film features that are especially well suited for use as a CL? film. For example, in order to facilitate proper installation of the barrier film, the film may be initially fabricating with the two opposing surfaces thereof differentiated either visually or by texture or both, h this way, the person installing the film will be able to easily differentiate the high energy surface (i.e., the surface to which the tape should be applied) from the other surface. This differentiation can be in the form of different colors, a logo or imprint, other type of printing (e.g. a photoilluminenscent ink), embossing or other surface modification techniques. The opaqueness of the CIB film can be controlled by using colored films and/or extrudate tie-layers and printing depending on the desired level of light transmission. For certain applications, the CLB film may also exhibit resistance to other hazards including radiological and biological threats by way of radio-opaque treatments or additives such as barium sulfate as described by DeMeo U.S. Patent Application Publication US 2003/0010939 Al, and anti-microbial treatments or additives such as reactive and/or detoxification enzymes. A desirable characteristic for wrapping complex shapes is heat-activated shrinkability. This can be engineered into the CIB composite film by using one or more layers of shrinkable films as described by Hanada U.S. Pat. No. 6,352,785, Garland U.S. Pat. No. 5,079,051, Walton U.S. Pat. No. 5,562,958, and Schirmer U.S. Pat. No. 4,853,287. CLB composite films used in outdoor environments would benefit from common additives such as thermal and UN stabilizers as are commonly known in the industry. The CIB barrier film can be embodied in a variety of configurations including film for SLP kits, field deployable chemical hardening applications, temporary flexible packaging, tentage, covers, bags, and overwraps. The film may also be used as a housewrap or construction membrane to prevent and reduce the ill effects of exposure to radon gas or other environmental contaminants. One particularly advantageous multi-layer film construction in accordance with the present invention includes a transparent exterior film having an exterior surface exhibiting a surface energy of 35 dynes/cm or greater and an interior surface to which is adhered a reverse-printing layer that provides a visual indication to differentiate the high energy surface of the multi-layer film. An inner high barrier chemical film is extrusion laminated to the reverse printed surface of the exterior film and includes outer coextruded layers of low density polyethylene and a core layer of ethylene vinyl alcohol copolymer (ENOH).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: Figure 1 illustrates how the window of a room is "taped up" in accordance with the general shelter-in-place (SIP) practice using a contamination infiltration barrier film according to the present invention. Figure 2 illustrates how a piece of equipment may be protected from contamination by forming a sealed enclosure in the form of a wrapper made of the contamination infiltration barrier film. Figure 3 is a cross-sectional view of a contamination barrier film in accordance with one embodiment of the present invention. Figure 4 is a cross-sectional view showing a more complex contamination barrier film in accordance with another embodiment of the present invention. DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. Figure 1 illustrates how the window of a room is "taped up" in accordance with the shelter-in-place (SIP) practice using a contamination infiltration barrier film in accordance with the present invention. As shown in Figure 1, the contamination barrier film 10 is unrolled from a supply roll and placed across a window opening 11 of the room. The contamination barrier film 10 has an outer surface that has been treated physically and/or chemically to impart a high surface energy for enhanced adhesion. The film 10 is oriented so that the high energy surface is facing into the room and away from the wall surface. A piece of the film 10, cut from the roll, and of a size larger than the window opening is then secured in place to the room wall with conventional duct tape 12. As shown, . portions of the film 10 overlie the wall surface adjacent to the window opening. Strips of the duct tape 12 are applied to the exposed high energy surface of film 10 and to the wall surface to secure the film to the wall and to thereby seal the window opening. In a similar manner, all other window, door and ventilation openings into the room will be sealed. Figure 2 illustrates how an object, such as a piece of equipment 14 can be protected from contamination by surrounding it in a sealed enclosure formed from a contamination infiltration barrier film. In this illustration, the contamination infiltration barrier film is fabricated into a large bag or cover 15 having an opening and a flap 17. The contamination barrier film 10 has an outer surface that has been treated physically and/or chemically to impart a high surface energy for enhanced adhesion and this high energy surface is oriented facing outwardly. Once the equipment 14 is placed within the bag 15, the flap 17 is folded over to close the opening, and then duct tape is used to fasten the high energy surface of the flap to the outwardly facing high energy surface of the bag, forming a sealed closure. Other ways of protecting the equipment include wrapping the equipment like a package with the contamination barrier film and sealing all seams with duct tape. Alternatively, the bag 15 can be provided with a self-sealing resealable closure, such as is used with household food storage bags. Figure 3 illustrates a three-layer contamination barrier film 30 in accordance with one illustrative embodiment of the invention. The fihn 30 is a coextrusion having opposite outer surfaces 31, 32 formed of low density polyethylene and a core 33 of a copolymer of ethylene vinyl alcohol (EVOH) and polyethylene. The exterior surface 31 has been corona discharge treated to raise the surface energy to greater than 40 dynes/cm. hi order to assist the installer in identifying which surface of the contamination barrier film is intended to receive the duct tape during installation, the two opposing surfaces of the barrier film can be differentiated either visually or by texture or both visually and by texture. The visual differentiation can readily be achieved in any of several ways, with printing being especially convenient. It is beneficial to incorporate the printing layer within the multi-layer contamination barrier film, such as by reverse printing a legend or other visual indicia onto an interior surface of one of the film layers. Figure 4 illustrates a multi-layer contamination barrier film 40 constructed in this manner. The film 40 includes a transparent exterior film layer 41 having an exterior surface 42 that has been treated by corona discharge such that it exhibits a surface energy of 35 dynes/cm or greater, preferably about 50 dynes/cm. The interior surface 43 of the film has been reverse printed with a printing layer 44 adhered to inner surface 43 and visible through the exterior surface 42. The printing layer 44 provides a visual indication to differentiate the high energy surface of the multi-layer film 40. A high chemical barrier film layer 45 is extrusion laminated to the reverse printed surface of the exterior film layer 41 by a polyethylene extrudate layer 46. The barrier film layer 45 is a 5-layer coextruded film including outer coextruded layers 47 of low density polyethylene, a core layer 48 of ethylene vinyl alcohol copolymer, and intermediate tie layers 49 of a blend of polyethylene and ethylene methyl acrylate (EMA) copolymer. Table 3 compares the chemical barrier properties of conventional polyethylene sheeting to two CLB films suitable for use in the present invention. The list of chemicals in Table 3 has been taken from the ASTM standard battery of chemicals (liquids only) set forth in ASTM FI 001. Shown are the breakthrough times (BTT) for each chemical material combination as tested and reported in accordance with ASTM F739 - Standard Test Method for Permeation Resistance - Liquid. F739 is the commonly accepted method for evaluating the chemical resistance for films and composites in the chemical protective clothing industry.

TABLE 3. PERMEATION RESISTANCE - BTT

The following examples are provided to illustrate several film constructions that may be used in the present invention. Example 1 : LDPE/EVOH/LDPE, one exterior surface of which has been corona discharge treated to raise the surface energy to >40 dynes/cm. Example 2: PP/LCP (liquid crystal polymer)/PP, one exterior surface of which has been chemically or physically treated to raise the surface energy to >40 dynes/cm. Example 3: LLDPE/Nylon/ENOH/Nylon/Nylon, one exterior surface of which has been chemically or physically treated to raise the surface energy to >40 dynes/cm. Example 4: Polyester/LLDPE/Nylon/EVOH/Nylon/Nylon, one exterior surface of which has been chemically or physically treated to raise the surface energy to >40 dynes/cm. Example 5: PP/PNOH/LDPE/PVDC/LDPE, one exterior surface of which has been chemically or physically treated to raise the surface energy to >40 dynes/cm. Example 6: PNDC/PET/PNDC/print/Νylon/Νylon/ENOH/Νylon/LLDPE, one exterior surface of which has been chemically or physically treated to raise the surface energy to >40 dynes/cm. Example 7: LLDPE/ENOH/LLDPE/print, one exterior surface of which has been chemically or physically treated to raise the surface energy to >40 dynes/cm. Example 8: A transparent, clear 1.0 mil polyamide nylon 6 film produced by Honeywell Inc. under the designation Capran® 100K was obtained. This film had a polyvinylidene chloride (PNDC) coating on one surface, with the opposite nylon 6 surface being uncoated. The uncoated nylon 6 surface was corona treated to impart a surface energy of greater than 50 dynes/cm. A graphic design was reverse printed onto the polyvinylidene chloride coated surface of the film using standard Gravure printing equipment. The reverse printed surface was corona treated and subsequently primed with a chemical primer coating. A 1.5 mil five layer cast coextruded film (Cadillac Plastics) was obtained having low density polyethylene (LDPE) outer layers, an interior core layer of ethylene vinyl alcohol copolymer (EvOH) 15%, and with tie layers of LDPE and EvOH copolymer positioned between these layers. One surface of the coextruded film was extrusion laminated to the primed printed surface of the nylon 6 film using about 12 pounds/ream of low density polyethylene extrudate. Line speed was 300 feet per minute at a take-up tension of about 30 pounds. The film tension of the coextruded film was set at about 20-25 pounds, while the nylon exterior film tension was set at about 15 pounds. Film to film bond strengths ranged from 300-2000 gm/in at the extrudate/ink interface and WNS (would not separate) at the extrudate to backside film interface. Subjective clarity was determined to be good and the products exhibited minimal curling. Example 9: Example 8 was repeated substituting a .48 mil aluminum oxide coated polyester fihn exhibiting a surface energy of 52 dynes/cm on the aluminum oxide surface and 43 dynes/cm on the polyester surface, which is commercially available under the designation GL-AS film from Toppan Printing Co. Ltd. of Japan for the nylon 6 film of Example 8. The following comparative physical data are provided comparing the two films used in producing this composite to a standard 3.5 mil clear polyethylene which is commonly recommended as a generic SIP barrier. Clear PE (3.5 mil) Ex. 8 Ex. 9 grab tensile md 19.91bs 32.31bs 34.71bs xd 17.31bs 31.81bs 38.01bs

trap tear md 5.91bs 3.31bs 0.51bs xd 9.61bs 9.01bs 0.61bs

Other films that can be used as an alternative to the polyamide nylon 6 outer film layer include the following: DuPont's Sclairfihn® DARTEK® B-602 barrier film, which is also a PVDC coated nylon 6 film; Nectran N300P (Ticona) which is a co-extruded liquid crystal polymer (LCP); Bicor AOH (Mobil) which is a two-side coated (acrylic coating one side and PvOH coating the opposite side) oriented polypropylene film; Bicor ASB-X (Mobil) which is a two-side coated (acrylic coating one side, PNDC coating the opposite side) oriented polypropylene film; Bicor AXT (Mobil) which is similar to the ASB-X except that the PNDC is sealable. Other alternatives include the Skyrol series of polyester films from SKC, including SP81 (1-side acrylic coated PET), SP91 (1-side copolyester treated PET), SP95 (1-side acrylic coated 1-side corona treated PET), and SP93 (1-side urethane treated PET).

Claims

CLAIMS:

1. A method for protecting against the infiltration of contamination comprising defining a predetermined space to be protected, and forming a sealed enclosure around said predetermined space with the use of a flexible multi-layered barrier film having two opposing surfaces, at least one of which has a surface energy of 35 dynes/cm or greater, the barrier film having a permeation efficiency greater than 50% when exposed to the chemicals included on ASTM 1001 and offering resistance to military chemical agents, toxic industrial chemicals, and biological hazards.

2. The method of claim 1 , wherein the step of forming a sealed enclosure is carried out using a flexible multi-layered barrier fihn including at least one chemical barrier layer selected from the group consisting of polyvinyl chloride, chlorinated polyethylene, chlorinated butyl rubber, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polyurethane, polytefrafluoroethylene (PTFE), and combinations thereof.

3. The method of claim 1 , wherein the step of forming a sealed enclosure is carried out using a flexible multi-layered coextruded barrier film which includes one or more layers of ethylene- vinyl acetate, ethylene vinyl alcohol, polyvinyl alcohol, nylon, ionomers, polyester, polyethylene terephthalate (PET), liquid crystal polymers, or a vacuum metallized layer.

4. The method of claim 2, wherein the permeation efficiency is greater than 75% when exposed to the 15 liquid chemicals included on ASTM 1001.

5. The method of claim 1, wherein said at least one surface having a surface energy greater than or equal to 35 dynes/cm is modified by a surface treatment selected from the group consisting of corona treatment, UN irradiation, flame treatment, plasma treatment, fluorine gas treatment and RF cold gas plasma treatment.

6. The method of claim 1, wherein said at least one surface having a surface energy greater than or equal to 35 dynes/cm is treated by a chemical treatment.

7. The method of claim 6, wherein the chemical treatment comprises coating the surface with a compound selected from the group consisting of acrylic compounds, polyurethane compounds, copolyester compounds, and polyvinylidene chloride.

8. The method of claim 1, wherein the barrier fihn includes an organophosphate hydrolase enzyme and/or an oxidizing polymer, thus rendering the barrier film reactive to phosphorous-based and oxidizable chemicals such as military chemical warfare agents.

9. The method of claim 1, wherein the barrier film includes a radio- opaque additive selected from the group consisting of barium, barium compounds, bismuth, bismuth compounds, tungsten, and tungsten compounds.

10. The method of claim 1 , wherein the step of defining a predetermined space comprises locating a room or building with ceiling, floor and wall surfaces that define the predetermined space and with at least one surface opening, and wherein the step of forming a sealed enclosure around said predetermined space with the use of a flexible multi-layered barrier comprises mounting the flexible multi-layered barrier film across said at least one surface opening and sealing the opening with the barrier film.

11. The method of claim 10, wherein the step of mounting the flexible multi-layered barrier film across said at least one opening and sealing the opening with the barrier film comprises orienting the barrier film with its surface having a surface energy greater than or equal to 35 dynes/cm oriented away from the ceiling, floor or wall surface, positioning the barrier film across the surface opening and into overlapping relation with portions of the adjacent ceiling, floor or wall surface, and applying an adhesive tape to the ceiling, floor or wall surface and to the exposed barrier film surface to thereby seal the opening.

12. The method of claim 11 , including the further step of also covering the walls of the room or building with a housewrap formed of the flexible multi- layered barrier film.

13. The method of claim 1 , wherein the step of defining a predetermined space comprises identifying an article of a predetermined size which is to be protected from contamination, and wherein the step of forming a sealed enclosure around said predetermined space with the use of a flexible multi- layered barrier comprises enclosing the article in a wrapper formed of the flexible multi-layered barrier film.

14. The method of claim 13, wherein the step of enclosing the article in a wrapper comprises orienting the barrier film with said at least surface with a surface energy greater than or equal to 35 dynes/cm oriented outwardly away from the article, and applying an adhesive tape to the exposed surface of the barrier film wrapper to thereby seal the wrapper.

15. The method of claim 14, wherein the step of enclosing the article in a wrapper includes positioning the article within a bag or cover formed of the flexible multi-layered barrier film, the bag or cover having an opening which is subsequently sealed by said step of applying an adhesive tape to the exposed surface of the barrier film.

16. The method of claim 1 , including the step of initially fabricating the flexible multi-layered barrier film with the two opposing surfaces thereof differentiated either visually or by texture or both.

17. The method of claim 16 wherein the visual differentiation comprises printing and the texture differentiation comprises embossing.

18. The method of claim 1 , including the step of initially fabricating the flexible multi-layered barrier film as a multiple layered coextruded fihn which includes one or more layers selected from the group consisting of ethylene-vinyl acetate, ethylene vinyl alcohol, polyvinyl alcohol, nylon, ionomers, polyester, liquid crystal polymers, metallized films, and fluorochemical based films.

19. The method of claim 18, wherein the step of initially fabricating the flexible multi-layered barrier film includes providing a transparent exterior film layer having an exterior surface exhibiting a surface energy of 35 dynes/cm or greater and an interior surface, reverse printing an indicia onto said inner surface that is visible through the exterior surface to provide a visual indication to differentiate the high energy surface of the multi-layer film, and extrusion laminating the printed surface of said transparent outer film to one surface of said flexible multi-layered barrier film.

20. A flexible multi-layer composite barrier film comprising a transparent exterior film layer having an exterior surface exhibiting a surface energy of 35 dynes/cm or greater and an interior surface, a reverse printing layer adhered to said inner surface and visible through the exterior surface to provide a visual indication to differentiate the high energy surface of the multi-layer film, an inner high chemical barrier film extrusion laminated to the reverse printed surface of the exterior film and including outer coextruded layers of low density polyethylene and a core layer of ethylene vinyl alcohol copolymer.

21. The film of claim 20, wherein the exterior film comprises a nylon 6 film having a corona treated exterior surface with a surface energy of 50 dynes/cm. or greater.

22. The film of claim 21 wherein the interior surface of exterior film includes a polyvinylidene chloride coating layer overlying the nylon 6 film.

23. The film of claim 20, wherein the exterior film comprises a polyester film having an aluminum oxide coating on the exterior surface exhibiting a surface energy of 50 dynes/cm.

24. The film of claim 20, wherein said inner high chemical barrier film is a five-layer coextruded film including said outer coextruded layers of low density polyethylene, said core layer of ethylene vinyl alcohol copolymer, and intermediate polymer tie layers therebetween.

25. The film of claim 20, wherein said at least one of the film layers is heat shrinkable.