Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coating or impregnation specified as porous or permeable to...
Reexamination Certificate
1999-09-08
2003-01-28
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coating or impregnation specified as porous or permeable to...
C442S076000, C442S086000, C442S394000, C442S079000
Reexamination Certificate
active
06511927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to a breathable, waterproof textile laminate. More specifically, the invention relates to textile laminates useful in the production of apparel, industrial, military, and medical products, and the like, which are resistant to contamination, thereby retaining breathability and waterproofness throughout use and numerous cleaning, laundering, or restoration cycles. The invention also relates to a method of producing such a laminate.
2. Description of the Prior Art
Breathable waterproof textile laminates are beneficial in a myriad of applications. For example, breathable waterproof textile laminates are useful in a range of apparel, industrial, medical, and military applications. More particularly, breathable waterproof textile laminates are useful in articles of apparel such as uniforms, workwear, outerwear, active wear, and protective clothing. Beneficial industrial applications include uses such as filtration. Medical applications for breathable waterproof laminates include uses such as surgical drapes and cast linings. Military applications include use in tents, tarps, and such. Other applications for such laminates include but are not limited to use in mattress pads and animal protective wear.
Breathable waterproof laminates are particularly advantageous in traditional textile fabric applications, such as apparel. Conventional textile fabric which is designed to be waterproof often tends to be uncomfortable to the user, because moisture given off by the body is generally retained within the interior space defined by the textile fabric and thus remains adjacent the user's body. This represents a particular problem to those users who are active while in a moist or wet environment and in those environments which are warm as well as wet, since the incidence of user perspiration therefore is increased.
Retained moisture is particularly problematic in textile fabrics worn as garments. For example, military personnel, sportsmen and athletes often find the discomfort due to perspiration trapped within their garments to be particularly acute. Therefore, garments are often provided with vents in locations on the garment where it is perceived to be less critical that full waterproofness be provided. For example, vents are often provided underneath the arms of garments (i.e. in the armpit region) or beneath flaps provided in the garment. As will be readily recognized, however, such vents only enable moisture to escape from localized areas within the garment, and the passage is still often inadequate to insure complete wearer dryness and comfort. Furthermore, the provision of such vents requires specially-configured garments which can be more expensive to produce, and the integrity of the waterproofness of the garment can be diminished due to the vent openings.
It is now recognized that, rather than utilizing air vents, merely transporting the water vapor contained in perspiration away from the user provides adequate comfort. A textile fabric's ability to transport water vapor through its thickness is commonly referred to as its “breathability.” Although generally more comfortable, breathable materials often provide unacceptable levels of waterproofness, as the ability of a textile fabric to prevent the passage through of liquid water generally tends to be inversely proportional to the high moisture vapor transmission rate characteristic of breathable fabrics.
However, textile fabric constructions have been developed which attempt this difficult balance between breathability and waterproof properties. In general, these constructions are laminates incorporating a polymeric film, also referred to as a membrane. The primary purpose of the film layer is to repel liquid water without sacrifice to breathability. Two types of waterproof breathable films are currently available: solution-diffusion films and porous diffusion films.
Solution-diffusion films are extremely hydrophilic films which “solubilize” water vapor within their molecular chains. These films transport individual water molecules through their thickness by molecular diffusion. Solution-diffusion films are nonporous, thus providing the additional benefit of air-impermeability, or “windproofness.” Although breathable and waterproof, the hydrophilic nature of solution-diffusion films cause them to swell and weaken significantly when in prolonged contact with liquid water. Therefore, solution-diffusion films usually exhibit poor durability. The problems encountered in the use of solution-diffusion films are discussed extensively in U.S. Pat. No. 5,660,198.
In contrast, porous diffusion films, commonly referred to as microporous films, are hydrophobic in nature. Porous diffusion films are generally characterized by a network of interconnecting pores which span the thickness of the film. These pores are too small to allow liquid water to pass, but are large enough to permit water vapor to readily flow through. Expanded polytetraflouroethylene film (“e-PTFE”) is a particularly widely known example of such a microporous film. Unfortunately, although microporous films do retain their physical integrity over time, they too lack durability for another reason. Porous diffusion films are adversely affected by exposure to surface active agents present during wear or laundering. For example, surface active agents present in perspiration, such as body oils, salts, and the like, penetrate the microporous membrane over time, coating its pores and causing it to lose its waterproof characteristics.
Coatings have been used to protect the pores of microporous films, in particular e-PTFE films. These coatings are applied to the microporous membrane as either a continuous layer of a liquid solution or a molten application. Although providing protection, coatings penetrate the surface of the microporous film and stiffen the resulting laminate. Several coated microporous membranes are marketed by W. L. Gore and Associates, Inc., under the tradename GORETEX. Examples of coated e-PTFE fabrics are described in U.S. Pat. Nos. 4,194,041 to Gore et al. and 5,026,591 to Henn et al, the disclosures of which are incorporated herein by reference. It is also generally known to bond e-PTFE membranes to a thick, protective film using an adhesive; however, the use of thick protective films likewise increases the stiffness of the resulting laminate. Increasing the stiffness adversely affects the drape, i.e., the feel and flexibility in all directions, of the resulting fabric.
Further, the manner in which the layers comprising the waterproof breathable laminate are joined also affects the performance of the resulting fabric structure. In particular, the layers within the laminate must be cohesive, i.e. move in unison upon flexing. This unitary flexing is especially important in fabrics subjected to pressure testing, such as fabrics for use in military applications. In particular, it is important that the laminate layers act in unison in fabrics subjected to hydrostatic testing.
To provide a cohesive laminate, it is known to use adhesives, in particular nonbreathable adhesives, to bond the layers together. However, by definition, nonbreathable adhesives, although highly durable, detract from the overall performance of the product by lowering the moisture vapor transmission rate of the resulting laminate. The use of such nonbreathable adhesives in conjunction with hydrophilic films is taught in U.S. Pat. Nos. 5,660,918 and 4,761,324.
Breathable adhesives are available for use in waterproof fabric laminates. However, caution must be taken in their use, as well. Breathable adhesives are hydrophilic in nature. Similar to solution-diffusion films, breathable adhesives lack durability due to their tendency to swell with water and subsequently weaken over time. This issue is especially problematic when bonding stretch resistant materials, which do not yield, or give, when the adhesive swells. The use of breathable adhesives presents particular difficulties in those applications involv
Ellis Laurence Fitch
Montie Frank Christopher
Alston & Bird LLP
Brookwood Companies, Inc.
Juska Cheryl A.
Pratt Christopher L.
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