Abstract:
A method for preparing a roofing membrane, and a membrane, having significantly less adhesive while retaining the same sealing properties. The reduction in the amount of adhesive significantly decreases the cost of raw materials needed for manufacturing the membrane and thus reduces the overall cost of the membrane itself.

Description:
FIELD OF THE INVENTION 
     The present invention relates to roofing products. More specifically, the invention relates to roofing products having waterproofing functionality and which are provided with a compound and/or adhesive thereon but which uses less compound or adhesive while remaining waterproof. 
     BACKGROUND 
     Adhesive or compound cost is a significant portion of total raw materials cost of most roofing products. Roofing products such as single-ply membranes are most often coated with one or more compounds and/or adhesives before being applied upon a roof surface. It is essential as well that the roofing products and the adhesives which bind the products to the roof surface provide a waterproof covering to prevent the seepage of rain or precipitation through the roof surfaces. 
     In order to create the most effective water-tight seal, roofing products such as single-ply membranes are generally completely coated on their undersurface for complete adherence to the roof deck substrate. Currently, most asphaltic or non-asphaltic peel-and-stick products used in the roofing industry are fully coated over the surface area that is intended to be adhered to a given surface. One exception includes membranes provided with straight or curvy stripes formed in the coating. However, this stripe coat leaves continuous channels which permits water to flow through and thus compromising the water sealing properties of the membrane. 
     SUMMARY OF THE INVENTION 
     The invention provides a method for preparing a roofing membrane which utilizes significantly less adhesive while retaining the same waterproofing or sealing properties as in the traditionally fully coated products. Also provided is a roofing membrane having significantly less adhesive thereon. The reduction in the amount of adhesive significantly decreases the cost of raw materials needed for manufacturing the membrane and thus reduces the overall cost of the membrane itself. 
     The above and other features of the invention, including various novel details of construction and composition, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular device embodying the invention is shown by way of illustration only and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
         FIG. 1  is perspective view of a starve coated membrane in accordance with the present invention; 
         FIG. 2  is a perspective view of an alternative embodiment of a starve coated membrane in accordance with the present invention; 
         FIG. 3  is a perspective view of an alternative embodiment of a starve coated membrane in accordance with the present invention; and 
         FIG. 4  perspective view of an alternative embodiment of a starve coated membrane in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The puddle or starve coated peel-and-stick membrane  10  in accordance with the present invention is shown in a first embodiment in  FIG. 1 . Membrane  10  includes an upper or exposed adhesive surface  12  and a lower or substrate surface  14 . An adhesive coating  16  which can include a chemical composition such as a sealant, primer, adhesive or the like, or a mixture thereof, is coated, sprayed or spread upon lower or substrate surface  14 . In  FIG. 1 , numerous puddles  18  are randomly dispersed in adhesive coating  16  on substrate surface  14  of membrane  10 . The puddles  18  in adhesive coating  16  allow for the use of less adhesive coating  16  thus resulting in a cost saving to the manufacturer and purchaser. In spite of the puddles  18 , the membrane still completely adheres to the roofing surface and creates a watertight seal thereto such that membrane  10  provides for a substantially waterproof layer on the roof. After lower or substrate surface  14  of membrane  10  is coated, a release liner  20  is positioned on coating  16  to facilitate transit and storage of the membranes. To apply membrane  10  to a roof surface (not shown), release liner  20  is peeled away and the exposed coating  16  on upper surface  12  will adhere to the roof surface. 
     In alternative embodiments illustrated in  FIGS. 2 ,  3  and  4 , puddles  18  are shown as diamonds  22  ( FIG. 2 ) and as wavy or zig-zag patterns  24  ( FIG. 3  and  FIG. 4 ) in adhesive coating  16  on upper or adhesive surface  12  of membrane  10 . As with the puddles  18  in  FIG. 1 , the diamonds  22  and waves  24  in  FIGS. 2 and 3  respectively also allow membrane  10  to be adhered to a roof surface while providing for the use of significantly less coating  16 . Other embodiments contemplated by the present invention included a variety of patterns formed in coating  16  such as checker board, criss-crossed, cross-hatched, overlapping zig-zag path and overlapping spiral puddles in both machine and cross-machine directions. The present invention is not limited to the configuration of the puddles discussed as an example here, but contemplates any and all patterns that result in discontinuous paths for rain water or precipitation and is directed to significantly reducing the amount of adhesive needed to coat membrane. The patterns in coating  16  may be random or non-random (periodic) or a combination of the patterns. 
     Patterns such as puddles  18 , diamonds  22  and waves  24 , as well as all other patterns in coating  16  that are contemplated by the present invention are generally formed by starving the feed of coating  16  as it is layered, cast, extruded, sprayed or dispersed upon lower or substrate surface  14 . 
     Patterns such as puddles  18 , diamonds  22  and wavy channels  24  in coating  16  may be formed in a variety of ways and this invention is not limited with respect to the manner of creating the patterns in coating  16 . The patterns may be formed in coating  16  such as by roll coating, knife over roll coating, reverse roll coating, slot die coating, fiberizing the adhesive, rotating patterned-cylinder over slot die or extrusion device, or a combination of these methods. 
     Depending upon the type of pattern formed in coating  16  on membrane  10 , the method in accordance with the present invention, as well as the peel-and-stick final product formed from the method is contemplated to utilize approximately 5-80% less adhesive on membrane  10  for comparable thickness relative to a fully coated membrane product, depending upon the adhesive quality and patterns  2  formed on membrane  10 . 
     Exemplary adhesives for coating on membrane  10  include, but are not limited to asphaltic and modified bituminous compounds commonly used in roofing products, polyisobutenes (PIB), polybutenes, polyisoprene, butyl rubber, styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), styrene-ethylene-butadiene-styrene (SEBS), acrylics, polyurethanes, atactic polypropylene (APP) or suitable mixtures and blends thereof. 
     While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.