Abstract:
A roofing underlayment that includes at least two layers that form a weather resistant barrier between the plywood sheeting and the top roofing layer. The roofing underlayment is fastened to the plywood sheeting and is covered with a roofing material such as shingles. The roofing underlayment is synthetic and includes a polymer is that is extruded or laminated to a woven or non-woven substrate. The use of an extruded polymer provides water proofing, strength, and energy efficiency. The roofing underlayment is embossed by use of an embossment process to allow for trapped water vapor escape and to enhance traction of the roofing surface.

Description:
[0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/029,794 that was filed on Feb. 19, 2008 and is incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to underlayments, and in particular, to roofing underlayments for use under shingles. More particularly, the present disclosure relates to multi-layer roofing underlayments. For many decades organic felt has been used as the underlayment in roof installations. Roof joists are typically covered in plywood sheeting, which, in turn, is covered with the organic felt. The underlayment provides for a secondary defense against the elements. The organic felt material is not durable, which can be the cause of leaks and wood rot in a roofing structure. 
       SUMMARY 
       [0003]    A roofing underlayment in accordance with the present disclosure is a polymer material that is used to cover the plywood sheeting of a roof surface. The roofing underlayment includes at least two layers that form a weather resistant barrier between the sheeting and the top roofing layer. The roofing underlayment is fastened to the sheeting and covered with a roofing material such as shingles. 
         [0004]    In illustrative embodiments, the roofing underlayment is synthetic and includes a polymer is that is extruded or laminated to a woven or non-woven substrate. The use of an extruded polymer provides water proofing, strength, and energy efficiency. The polymer material used for the extrusion can be both mono-layered or multi layered. Multi layered film can be used to provide multiple properties that otherwise may not be available in a mono-layered polymer. The polymer film layer may be formed to include either a smooth and embossed textured surface. The embossed texture allows for increased traction for roofers in wet conditions and allows water to run off the roof in the channels created by the embossment. 
         [0005]    Additional features of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The detailed description particularly refers to the accompanying figures in which: 
           [0007]      FIG. 1  is a side plan view of a process for forming an embossed film for use with the roofing underlayment; 
           [0008]      FIG. 2  is a side plan view of the process of  FIG. 1  adding a substrate backing that a molten film is extruded onto and showing the combination passing through an embossing roller and a backer roller; 
           [0009]      FIG. 3  is a side plan view of the roofing underlayment showing an embossed polymer material having ridges and open spaces to allow gases to escape; 
           [0010]      FIG. 4  is a side plan view of the roofing underlayment showing an embossed polymer film layer having a series of ridges and a substrate polymer backing that is extruded with the film layer; 
           [0011]      FIG. 5  is a top view of the roofing underlayment showing an embossed pattern having triangular shaped areas that are raised in relief; 
           [0012]      FIG. 6  is a side plan view of the roofing underlayment showing a polymer film having ridges and open spaces and an adhesive layer; 
           [0013]      FIG. 7  is a enlarged side plan view of the roofing underlayment showing an embossment; 
           [0014]      FIG. 8  is a perspective view of a roof showing the roofing underlayment attached to plywood sheeting beneath shingles; 
           [0015]      FIG. 9  is a perspective view of the roofing underlayment showing water passing through the channels formed by the embossment; 
           [0016]      FIG. 10  is a top view of the roofing underlayment showing another embossed pattern having diamond shaped areas that are raised in relief; 
           [0017]      FIG. 11  is a top view of the roofing underlayment showing another embossed pattern having triangular shaped areas that are raised in relief; 
           [0018]      FIG. 12  is a top view of the roofing underlayment showing another embossed pattern having square shaped areas that are raised in relief; and 
           [0019]      FIG. 13  is a top view of the roofing underlayment showing another embossed pattern having hexagonal shaped areas that are raised in relief. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    In an illustrative embodiment, a roofing underlayment  10  includes a polymer film layer  12  that is extruded or laminated onto a polyester based spun bond substrate  14 , as shown in  FIG. 5 , using the process shown in  FIG. 2 . The roofing underlayment  10  is adapted to be installed onto the plywood sheeting  15  of a roof  17  beneath the asphalt shingles  11 , as shown in  FIG. 8 . Roofing underlayment  10  is configured to permit condensation to pass through channels  16  formed in the roofing underlayment  10  as an embossment, as shown in  FIG. 9 . The polymer film layer  12  is preferably made from polyethylene or polypropylene. 
         [0021]    The embossed pattern  18 , which is created during the process shown in  FIGS. 1 and 2 , increases the coefficient of friction of roofing underlayment  10  to increase surface traction when applied to a roofing surface  21 , such as plywood  15  or wood planking. The higher coefficient of friction is designed to prevent roofers from loosing their footing when walking across a pitched roof. 
         [0022]    Embossed pattern  18  can be added to the surface  20  of polymer film layer  12  to create relief. The embossing, formed by the process shown in  FIG. 2 , creates a controlled geometry in the material. The embossed relief can be added either to the polymer film layer  12  alone or to a film/substrate composite  23 . 
         [0023]    One of the possible embossing designs or patterns used to create the desired relief in polymer film layer  12  is shown in  FIG. 5 . The emboss relief creates raised regions  22  that significantly increase the coefficient of friction in polymer film layer  12 . The higher the coefficient of friction of the roofing underlayment  10  the more slip resistant the material becomes, which makes it safer to walk on a roof having various pitches in a variety of weather conditions. 
         [0024]    The embossed pattern  18  shown in  FIG. 5  includes triangular raised regions  22  having edges  24  that form channels  16 . Channels  16  permit moisture that has collected between the shingles  11  and the roofing underlayment  10  to gather and flow through channels  16  to prevent moisture from becoming trapped. Use of triangular raised regions  22  creates a first set of parallel channels  28 , a second set of parallel channels  30 , and a third set of parallel channels  32 . The intersection of the channels  28 ,  30 , and  32  forms a series of acute angles. The benefit of the overlapping channel design is that condensation can flow through alternate pathways in the event that a roofing nail  33  is blocking a first pathway in the polymer film layer  12 . 
         [0025]    The pattern, size, and depth of the embossing formed in the polymer film layer allows moisture to easily run off of the film surface through the embossing channels  28 ,  30 , and  32 . The embossing also contributes greatly to improving slip resistance of the polymer film material. When the polymer film layer  12  is embossed, the polymer material is stretched creating areas on the film that have a wall thickness that is thinner than other areas, as shown, for example, in  FIG. 7 . The embossment includes thin wall sections  34  and, thick wall sections  36 . 
         [0026]    Thin wall sections  34  are formed by stretching polymer film layer  12  during the embossing process of  FIG. 2 . As the polymer film layer  12  becomes thinner, it allows for greater air permeability  37  through the polymer material. The areas of the polymer film which have been embossed and stretched, allow for an increase in air permeability allowing the roofing underlayment  10  to be more breathable. Having a permeable polymer film layer  12  permits moisture, trapped between the roofing underlayment  10  and the plywood sheeting, to pass through the polymer film layer  12 . 
         [0027]    The process used to manufacture of the roofing underlayment  10  is shown in  FIGS. 1 and 2 . First, the spunbond polyester substrate is unwound into the machine. Next, a polymer material is extruded through a heated die  40  to form a polymer film  12 . The polymer film  12  is next bonded to the spunbond polyester substrate  14  at the nip point  42 . The polymer film  12  and spunbond polyester substrate  14  next pass through an engraved metal roller  43  and a backer roller  44 . The engraved metal roller  43  is temperature controlled to cool the polymer film extrusion. Using this process, the pattern is cast into the film while being applied to a substrate backing. The embossed relief in the polymer film  12  can be created by pressing a relief pattern into a flat film and/or a flat film being applied to a backing substrate at the nip point. 
         [0028]    One method of manufacturing the roofing substrate  10  is to cast an embossed pattern into the molten polymer film as shown, for example, in  FIG. 1 . In this example, the embossed pattern is cast into the polymer film  12  alone. Using this method, the spunbond polyester substrate  14  is applied to the polymer film  12  using a binder material, such as an adhesive, in a later process step as shown in  FIG. 4 . One or more polymer layers can be co-extruded prior to embossing of the polymer material or the addition of the polyester spun bond substrate  14 .  FIG. 3  illustrates a magnified cross-sectional view of one embossed pattern applied to the polymer material. In this embodiment, the film  12  has a first set of wide channels  46  and a second set of narrow channels  48 . The narrow channels  44  on the top side of the polymer film  12  form open spaces to allow gases to escape. 
         [0029]      FIG. 4  shows a magnified cross-sectional view of another embossed pattern applied to the polymer film  12 . Using the manufacturing methods, no open spaces occur on the underside of the polymer film  12 , making the raised relief a solid structure. In this embodiment, channels  48  are formed on the upper side of the polymer film  12  only and the bottom side is relatively planar. 
         [0030]      FIG. 5  illustrates another embodiment of roofing underlayment  10  having multiple layers coupled to polymer layer  12  including spunbond layer  14 , tie layer  51  and membrane  53 . 
         [0031]      FIG. 5   a  is a perspective view of the roofing underlayment  10  showing triangular raised regions  22  and channels  16 . The channels  16  adapted to permit water  55  to flow through the channels  16  to permit drainage. Embossing of polymer material  12  creates thin wall portions to allow water vapor  37  to permeate through polymer layer  12 . Use of multiple channels permits the flow of water even when there is an obstruction blocking certain flow paths. 
         [0032]    The roofing underlayment  10  uses of a polyester spunbond substrate  14  coated with a polymer film  12  that can either be smooth or embossed. The embossed pattern increases the coefficient of friction of the material by creating raised areas in relief, which, in turn, increase slip resistance and traction. The emboss pattern creates channels to allow moistures to easily run off a roof to which the roofing underlayment is applied. The embossed pattern also creates pockets for gases from an applied adhesive to escape. The embossed pattern also creates areas with a thinner polymer thickness which increases air permeability of the polymer material  12 . 
         [0033]      FIGS. 10-13  show alternate embossed patterns that can be applied to the polymer material  12 .  FIG. 10  illustrates the use of a diamond shaped areas raised in relief.  FIG. 11  illustrates triangular areas that are raised in relief.  FIG. 12  illustrates the use of square areas of relief and  FIG. 13  illustrates the use of hexagonal raised areas of relief. These alternate embossed patterns enhance the traction of the roofing underlayment  10  and create channels for vapor permeation and for drainage runoff. 
         [0034]    In use, the roofing underlayment  10  is manufactured using the techniques of  FIGS. 1 and 2  and is stored on rolls. To use the roofing underlayment  10 , a roofer unrolls and covers the plywood sheeting  21  with the roofing underlayment  10  with the polymer layer  12  facing upwardly and the spunbond polyester substrate  14  contacting the plywood sheeting  21 . The roofing underlayment  10  is next stapled or nailed to the plywood sheeting. Once the roofing underlayment  10  is secured to the roof, the roofer will appreciate the enhanced traction created by the embossments in the material. 
         [0035]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.