Membrane composite structure and method of production

#This invention relates to a composite structure, and more particularly, to an improved composite structure that utilizes a thermoplastic material that is thermally melted to a porous membrane and a method of production.

#A membrane, such as an expanded polytetrafluoroethylene (ePTFE) membrane, provides a significant advantage of being porous. This allows perspiration and moisture vapor to pass directly through the membrane while remaining waterproof. A significant drawback to the tremendous potential of this material is that body oils, sweat, suntan lotion, and makeup can contact and “foul” portions of the membrane and create areas that no longer prevent water passage through the membrane and thereby negate the waterproof nature of such a membrane.

#The present invention is directed to overcoming the drawback set forth above.

#For a better understanding of the present invention, reference may be made to the accompanying drawings in which:

#FIG. 1 is a schematic sectional side view of a laminated fabric that includes a composite structure embodying the present invention;

#FIG. 2 is an enlarged schematic plan view of a portion of the composite structure illustrated in FIG. 1 with a view that is approximately located along Line 2-2 in FIG. 1;

#Referring now to FIG. 1, a composite structure, according to the present invention, is generally indicated by numeral 12. This composite structure 12 has a two layer construction and is resistant to wind and moisture while remaining moisture vapor transmissive. Typically, but not necessarily, this composite structure 12 can be combined with a textile material 14 to form a laminated fabric 10 for use in performance apparel, sleeping bags, footwear, industrial fabric applications, and the like. Performance apparel can include, but is not limited to, consumer apparel, workwear, fire service, medical and military applications. This textile material 14 can include virtually any textile fabric base or shell fabric material such as woven textile fabric, knit textile fabric and nonwoven textile fabric so long as the textile material 14 meets the performance and other criteria established for the desired application for the laminated fabric 10. The textile material 14 can be laminated to the composite structure 12 by any suitable process forming an additional third layer to the present invention.

#“Moisture vapor transmissive” is defined as being able to readily permit passage of water vapor through the composite structure 12 as well as the entire laminated fabric 10. The composite structure 12 is preferably “oleophobic”, which means that the composite structure 12 is resistant to contamination by absorbing oils, greases or body fluids, such as perspiration and certain contaminating agents. The term “resistant to moisture” is used to described how the composite structure 12 will not “wet” or “wet-out” by a challenge liquid, such as water, and prevents the penetration of liquid through the composite structure 12 under varying ambient conditions of relatively low pressure.

#A first layer of the composite structure 12 embodying the present invention includes a membrane and is generally indicated by numeral 16. The membrane 16 is preferably expanded polytetrafluoroethylene (hereinafter also known as “ePTFE”), available under the part number “QM011” from BHA Technologies, Inc., having a place of business at 8800 East 63rd Street, Kansas City, Mo. 64133. However, the membrane 16 may also be made from other suitable materials such as polyolefin, polyamide, polyester, polysufone, polyether, acrylic polymers, methacrylic polymers, polystyrene, polyurethane, polypropylene, polyethylene, cellulosic polymers and combinations thereof. The membrane 16 includes structural elements defining voids, openings, pores or holes, and the like. For example, as shown in FIG. 2, if PTFE is utilized for the membrane 16. The preferred ePTFE material of the membrane 16 is made from a mixture of PTFE fine powder resin and lubricant that is extruded and calendered. These PTFE particles are available under the trademark “TEFLON®” from E. I. du Pont de Nemours and Company, having a place of business at 1007 Market Street, Wilmington, Del. 19898.