In particular situations people may encounter harmful concentrations of hazardous chemicals. In such situations, it is necessary to wear chemical protective garments of special composition and construction. These protective garments are necessary for providing an effective barrier between the wearer and the chemicals encountered. However, as pointed out in U.S. Pat. No. 4,855,178 (Langley), in addition to providing an effective chemical barrier, materials for chemical protective garments should meet practical requirements for amenability to fabrication by existing methods (e.g., heat bonding of seams) as well as for providing sufficient strength to prevent tearing and the resulting loss of protection.
General practice in the protective garment trade is to construct chemical protective garments by seaming together panels of chemical protective garment material. These seams may be formed in a number of ways. The seams may be formed by traditional methods of sewing and then covering the seam with a layer of heat sealing tape. Alternatively, the seams may be formed by heat or ultrasonic welding of the garment material. These seams may utilize adhesives.
Suitable chemical protective garment materials must be flexible to allow manipulation during seaming on standard seaming equipment, whether it be by sewing, adhesives or heat sealing. The chemical protective garment materials must also be of a composition that allows the formation of strong sealed seams, whether these seams are sewn and taped, adhesively joined or whether they are welded by heat or ultrasonic energy.
In addition, chemical protective garments must be durable in use. The garments must not develop structural failures during use which would expose the wearer to hazardous chemicals. Thus, the chemical protective garment materials and the seams created in constructing the garments must be strong and resistant to structural failure (e.g., the tearing, cracking or shrinking).
In many situations, it is not feasible to decontaminate chemical protective garments after exposure to hazardous chemicals. A chemical protective garment contaminated with a hazardous chemical is generally considered as hazardous waste. There is limited space for the storage and burial of hazardous wastes. Chemical protective garments intended for limited-use, should be light in weight to reduce the burden on storage and disposal.
Strong, lightweight chemical protective garment materials made from laminates of different materials are known. U.S. Pat. No. 4,272,851 (Goldstein) describes a film of polyethylene that may be laminated to nonwoven chemical protective apparel. U.S. Pat. No. 4,772,510 (McClure) describes a chemical barrier film laminated to a nonwoven substrate using an adhesive. Other laminates having multiple barrier layers are described in U.S. Pat. No. 4,855,178 (Langley); U.S. Pat. No. 4,833,010 (Langley) and U.S. Pat. No. 5,035,941 (Blackburn).
Often, each layer of a chemical protective garment material is chosen to impart a specific property to the composite fabric. Some layers provide strength while other layers may be chosen to provide permeation resistance against specific classes of chemicals. Additional layers add weight and stiffness. However, stiff garments are difficult to assemble and reduce the wearer's mobility.
There has been a general trend in the protective garment art to add additional layers to chemical protective garment materials to increase and broaden resistance to various classes of chemicals. This adds weight, stiffness and cost to these materials. For example, EP-0 434 572 (Boyer et al.) discloses a six (6) layered chemical protective garment material employing polyvinylidene chloride coated polyethylene terephthalate (PET) as the chemical barrier layer. The material comprises a nonwoven substrate, a layer of polyethylene, an adhesive layer, a layer of polyvinylidene chloride coated PET film, another layer of adhesive, and finally a layer of polyethylene. U.S. Pat. No. 4,920,575 (Bartasis) discloses a multi-layered structure that may contain one or two layers of a polyester film.
Other multi-layer films for protective use have been disclosed. For example, Tung, in U.S. Pat. No. 5,250,350, discloses a modified burn characteristic SARANEX® film in the form of a four or five layer film product. Additionally, Boye et al., in U.S. Pat. No. 5,162,148 describe a laminated material comprising a polyolefin nonwoven substrate and a five layer coextruded film with a polyolefin outer layer and an intermediate layer selected from a group comprising ethylene-hydrolyzed vinyl acetate copolymer and polyethylene terephtalate coated with polyvinylidene chloride for manufacturing protective equipment against NBC attacks. Similarly, Smith, in U.S. Pat. Nos. 4,970,105 and 5,082,721, describes a fabric used in the manufacture of protective garments, containers and covers comprising an inner layer of a tear resistant, high tensile strength substrate and film layer comprised of a fusible, meltable, polyhalogenated ethylene resin group bonded on at least one surface of said high modules fabric substrate.
Bartacis discloses multilayer structure in U.S. Pat. No. 4,924,525. This reference describes a multilayer film structure having an inner layer of substantially isotactic oriented polypropylene homopolymer sandwiched between a layer of ethylene-propylene random copolymer and a layer of ethylene-vinyl-acetate. The multilayer film structure is then bonded to a two layer polyester substrate using an elastomeric adhesive. In a preferred embodiment, a barrier material having a layer of ethylene-vinyl alcohol is combined with a multilayer film structure to form a composite, which is then combined with the substrate. Additionally, Adiletta, in U.S. Pat. No. 4,865,903 describes a flexible, impermeable, universally chemically resistant composite structure which may be fabricated into protective clothing. The composite structure comprises a fabric substrate and thermally-melt-bonded on both sides thereof, a coated film, which coated film comprises a PTFE film having a thermoplastic flouropolymer coating on both sides thereof.
Despite the foregoing disclosures, there is still a need for biological and chemical protective material that can be used in making protective garments, covers, tents and shelters for personnel, equipment and supplies.