Patent Issued for Microporous Composite Sheet Material


By a News Reporter-Staff News Editor at Journal of Engineering — Fiberweb, Inc. (Old Hickory, TN) has been issued patent number 8328968, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent’s inventors are Anderson, Gary W. (Mt. Juliet, TN); Gelotte, Susannah D. (Mauldin, SC).

This patent was filed on April 16, 2012 and was cleared and issued on December 11, 2012.

From the background information supplied by the inventors, news correspondents obtained the following quote: “This invention relates to a microporous composite sheet material. More particularly, the invention relates to a composite sheet material which is permeable to moisture vapor but which forms a barrier to the passage of water. The composite sheet material has strength and barrier properties which make it suitable for use as a housewrap.

“Various types of sheet materials have been used in the construction of buildings as a barrier fabric to block water and air while allowing transmission of moisture vapor from the building interior. These so-called housewrap products are typically applied over the sheathing layer of the building and beneath the exterior surface layer of brick or siding. During the time that the building is under construction, the housewrap material is exposed to the elements for a considerable period of time. Therefore, the fabric must have good weatherability, relatively high tear strength and puncture resistance. The fabric must also maintain the strength and barrier properties while it is exposed to the elements, and subsequently during the lifetime of the building.

“Various types of fabrics have been produced and sold commercially for use as a barrier fabric in building construction. One such commercially available product is manufactured and sold by DuPont under the trademark Tyvek.RTM. Homewrap.RTM.. This product is formed from flash spun high-density polyethylene fibers which are bonded together to form a nonwoven sheet material.

“Other commercially available housewrap products have been developed which utilize preformed microporous films laminated to a reinforcing substrate, as described for example in Sheth U.S. Pat. No. 4,929,303 or Martz U.S. Pat. Nos. 5,656,167 and 6,071,834.

“Still other commercially available housewrap products have used a woven or nonwoven substrate with a perforated film coating. For example, in Dunaway et al, U.S. Pat. No. 4,898,761, a barrier fabric is disclosed in which a polymer film is laminated to a nonwoven fabric, and the resulting composite sheet material is then needle-punched to provide micropores through the film. The nonwoven fabric is a spunbonded web formed of poly-olefin filaments, and the polymer film can be applied to the nonwoven web by hot cast extrusion.

“The currently available house-wrap materials have various deficiencies. Many of the commercially available housewrap materials can be easily torn when installed during construction or punctured by ladders or scaffolding leaning against the building. These materials are also susceptible to being torn by the wind during construction while the housewrap material remains exposed. Housewrap materials formed from laminates of a microporous film with a supporting substrate require a two-step process which increases the expense, and the resultant products suffer from low puncture strength and generally low overall tear and tensile strength.

“The need exists for an economical barrier material with superior strength and tear resistance, as well as excellent water and air barrier properties.”

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors’ summary information for this patent: “The present invention provides a moisture vapor permeable, water impermeable composite sheet material having superior strength and barrier properties. The composite sheet material is suitable for use as a housewrap material, and is also useful for other applications such as tarpaulins, or as covers for automobile, boats, patio furniture or the like. The composite sheet material includes a nonwoven substrate and an extrusion-coated polyolefin film layer overlying one surface of the substrate. The nonwoven substrate is comprised of polymeric fibers randomly disposed and bonded to one another to form a high tenacity nonwoven web. The nonwoven substrate has a grab tensile strength of at least 178 N (40 pounds) in at least one of the machine direction (MD) or the cross-machine direction (CD). The extrusion coated polyolefin film layer is intimately bonded to the nonwoven substrate. The film layer has micropores formed therein to impart to the composite sheet material a moisture vapor transmission rate (MVTR) of at least 35 g/m.sup.2/24 hr. at 50% relative humidity (RH) and C. ( F.) and a hydrostatic head of at least 55 cm.

“In one embodiment, the nonwoven substrate comprises a spunbonded nonwoven fabric formed of randomly disposed substantially continuous polypropylene filaments. The spunbonded nonwoven fabric is an area bonded fabric in which the filaments are bonded to one another throughout the fabric at locations where the randomly disposed filaments overlie or cross one another.

“The film layer is intimately bonded to the substrate to preferably provide a peel adhesion of at least 59 g/cm (150 grams per inch). The film layer suitably comprises a polyolefin polymer and at least 40% by weight of an inorganic filler such as calcium carbonate. The film layer preferably has a basis weight of at least 25 grams per square meter. The composite sheet material has been stretched in at least one of the machine direction or the cross machine direction. This stretching operation renders the composite sheet material microporous. The composite sheet material has a moisture vapor transmission rate (MVTR) of at least 35 g/m.sup.2/24 hours at 50% relative humidity and C. ( F.). The composite sheet material also has a hydrostatic head of at least 55 cm, preferably at least 100 cm.”

For the URL and additional information on this patent, see: Anderson, Gary W.; Gelotte, Susannah D.. Microporous Composite Sheet Material. U.S. Patent Number 8328968, filed April 16, 2012, and issued December 11, 2012. Patent URL:

Keywords for this news article include: Fiberweb Inc.

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