This may be the pulp connection to the Polyurethane filter.

Filtering face-piece respirator having a face seal comprising a water-vapor-breathable layer Patent Assignee 3M INNOVATIVE PROPERTIES COMPANY (St. Paul, MN, US)

http://www.freepatentsonline.com/9408424.html

In discussing a way to take water vapour from exhaled breath away from the filter surface. If this is the case while the polyurethane is the primary material the pulp fibre is applied to it as a layer which may not appear in a spec sheet.

"In some embodiments, a face seal may consist only of a water-vapor-breathable layer and a wicking layer (that is located on the rearward side of at least a portion of the water-vapor-breathable layer), with no other layers being present. In other embodiments, other layers may be present in the face seal.

There are several general approaches to providing such a wicking layer, which approaches will be described herein in a non-limiting manner. In one approach, a fibrous wicking layer (e.g., a non-woven web, a woven or knitted fabric, and so on) can be comprised (e.g., generally, substantially, or completely) of fibers with “moderate” hydrophilicity. Materials that might be suitable for such fibers include e.g. certain nylons, polyesters, cellulose acetates, and so on. In another approach, a fibrous wicking layer can be comprised of relatively hydrophobic fibers (e.g., polyethylene, polypropylene, natural rubber, and so on), but with the web incorporating some portion of relatively hydrophilic fibers (e.g., cellulosic fibers, acrylic fibers comprising a significant amount of hydrophilic co-monomer, and so on). That is, any suitable blend of hydrophobic fibers and hydrophilic fibers can be used to arrive at the optimum balance of properties. In a variation of such approaches, a fibrous wicking layer can be comprised of relatively hydrophobic fibers but may further comprise hydrophilic particles of any suitable composition (e.g. hydrocolloids, WOOD PULP, starch particles, and so on). Conversely, a fibrous wicking layer can be comprised of relatively hydrophilic fibers but may further comprise hydrophobic particles of any suitable composition."

and further

Enhancement of barrier fabrics with breathable films and of face masks and filters with novel fluorochemical electret reinforcing treatment

http://www.freepatentsonline.com/y2005/0079379.html

“In the late 1970s this lead inventor, as an R&D scientist with Johnson & Johnson Surgikos Company led a successful program to replace the glass fiber filter media with melt blown (MB) polypropylene (PP). To achieve 95% In vitro BFE, it was necessary to electrostatically charge the MB filter media (Wadsworth, Larry C. and Solomon P. Hersh, Raleigh, N.C., “Method of Making Fibrous Electrets,” U.S. Pat. No. 4,375,718, assigned to Surgikos, Inc., issued Mar. 8, 1983). Latex-bonded dry-laid and wet-laid nonwovens with fiber contents viscose rayon, PULP or blends of cellulosic and synthetic fibers were utilized for the outer and inner facings, with the filter media in the center. By the late 1980s, virtually all surgical FMs consisted of an electrostatically charged MB PP filter media core (Wadsworth, Larry C. and Solomon P. Hersh, Raleigh, N.C., “Method of Making Fibrous Electrets,” U.S. Pat. No. 4,375,718, assigned to Surgikos, Inc., issued Mar. 8, 1983; Kubik, Donald A. and Charles I. Davis, “Melt-Blown Fibrous Electrets,” U.S. Pat. No. 4,215,682, assigned to Minnesota Mining and Manufacturing Company, issued Aug. 5, 1980; Klasse, P. T. A. and Jan van Tumhout, “Method for Manufacturing an Electret Filter Media,” U.S. Pat. No. 4,588,537, issued May 13, 1986) with pigmented SB PP on the outside and un-pigmented (white) SB PP on the body side. In 1995 and 1997, Wadsworth and Tsai obtained patents, for much improved cold electrostatic charging (Tantret™) technology (Tsai, P. P. and L. C. Wadsworth, “Method and Apparatus for the Electrostatic Charging of a Web or Film,” U.S. Pat. No. 5,401,446, assigned to The University of Tennessee Research Corporation (UTRC), issued Mar. 28, 1995; Wadsworth, L. C. and P. P. Tsai, “Method and Apparatus for the Electrostatic Charging of a Web or Film,” U.S. Pat. No. 5,686,050, assigned to UTRC, issued Nov. 11, 1997) assigned to The University of Tennessee Research Foundation (UTRF), which enabled the charged MB PP filter media in FMs and respirators to filter greater than 95% of particles with a diameter of 0.1 μm, which has been licensed to more than 20 companies world-wide. Such small particles are produced in laser surgery and concerns about the transmission of Aids and Hepatitis during surgery prompted the demand for high filtration efficiency to particles which could contain viruses.

Construction of Face Masks and Respirators
Today, face masks (FMs) are typically composed of three layers, as illustrated in FIG. 2, with an outer layer (OL) of 12-25 g/m2 spunbond (SB) PP, a center of 15-30 g/m2 of electrostatically charged MB PP, and a body-side (BS) layer of 12-25 g/m2 SB PP. Generally, face masks (e.g. surgical face masks and dust masks) are not bonded together and are only bonded on the edges of the face mask (FM) being fabricated by either sewing (FIG. 3, FIG. 3a, FIG. 3b, and FIG. 6), or preferably by ultrasonic bonding. Nevertheless, the FM laminates may be thermally or ultrasonically bonded (FIG. 4 and FIG. 11) together by a “spot welding” technique which does not fuse enough of the laminate together to excessively increase the pressure drop across the filter and make it difficult for one to breathe easily through the fabric, or to cause pin holes to form in the laminate and thereby increase the risk of harmful particles penetrating through the FM. However, FM laminate layers may be thermally fused together to produce a pre-formed cup-shaped mask or respirator, which may be held firmly, yet comfortably against the mouth to ensure that no or minimal leakage occurs where the edges of the cup-shaped mask contacts the human face. In fact a non-air-leaking rubbery or spongy layer may be attached around the edges of the cup mask to assure both a comfortable fit and non-leakage. An example with this innovation is the Willson 5000 Series respirator (Dalloz Safety Ltd., Hampshire RG27 9HX, United Kingdom, Willson 5000 Series Brochure). Respirators may also be fitted with exhalation valves which open when exhaling but which close for a tight seal when inhaling (FIG. 4b). European standards for respirators, EN 149:2001/Standard AS/NZS 1716:1994 require that the laminate construction must be able to be welded ultrasonically, as illustrated in FIG. 1, FIG. 2 and in the FIG. 11 process schematic, and that the thickness of the filter media must be as small as possible in order to obtain good welding of the mask with the media (FFP1 Media [Standard EN 149: 2001/Standard AS/NZS 1716: 1994], summary document and specifications by Bacou-Dalloz France; FFP2 Media [EN 149: 2001 Standard/AS/NZS 1716: 1994 Standard], summary document and specifications by Bacou-Dalloz France; FFP3 Media [EN 149: 2001 Standard], summary document and specifications by Bacou-Dalloz France). Typically to produce a cup mask with the required filtration efficiency (FE) and not too much pressure drop (ΔP), coarser and lower bulk density components, including MB media with larger fiber diameters and pores, may be used for spot thermal bonding or spot ultrasonic bonding of three-dimensionally shaped mask to meet the required end-use specifications in terms of FE, Δp and proper fitting to the face. Examples of cup-type face masks and respirators are readily found on the internet (NIOSH/NPPTL/Concept for SBRN Full Facepiece APR Standard, Sep. 16, 2002, Website: httD://www.cdc.gov/niosh/npptl/npptlrespfact.html; Respirators/NIOSH Topic Page, Website: http://www.cdc.gov/niosh/topics/respirators/;"