Abstract:
An improved waterproofing membrane comprising a preformed waterproofing adhesive layer, releasable sheet liner, and a string or plurality of strings operative to cut the release sheet liner into smaller portions for selective removal to expose portions of the adhesive layer for installation onto a building surface or civil engineering surface.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a preformed, sheet-like waterproofing membrane laminate having a release sheet liner that can be cut using one or more strings contained and/or embedded within the membrane laminate structure. 
     BACKGROUND OF THE INVENTION 
     It is known in the waterproofing art to combine a pre-formed waterproofing membrane, such as a rubberized bitumen layer, with a carrier support layer. The carrier support layer may comprise a variety of materials, such as rubber, plastic, and/or metal. It has also been desirable to employ cross-laminated plastic films, such as high density polyethylene, or felts or non-woven sheets as carrier supports for improved stability of the membrane. Such preformed waterproofing membrane laminates are considered “sheet-like” because they are sufficiently flexible that they can be rolled up and transported after manufacture to the job site where they are unrolled and installed on the building surface. 
     Although such waterproofing membranes provide a considerable improvement in handling and installation when compared to the hot-applied waterproofing of decades ago, the membranes do provide some challenges in that they are often sold in three-foot widths which sometimes makes application difficult. This difficulty is due, in large part, to the tenacity of the waterproofing adhesive. 
     The preformed adhesive layer of waterproofing membranes are typically protected by a release sheet liner, made of waxed paper or plastic, which may be peeled from the adhesive at the time of application. The use of split, or perforated, release sheets are known in the waterproofing arts. For example, U.S. Pat. No. 4,172,830 of Rosenberg and Gaidis disclosed waterproofing membranes in which release sheets were perforated so that strips could be removed from the adhesive layer, and exposed portions of the adhesive could be overlaid onto the back of an adjacent, installed membrane. This was believed to increase the handling and installation ease of the membranes. 
     The use of a split release sheet is particularly useful for membrane application in detail areas, such as roof valleys. It is also useful when the membrane is applied as a flashing material around windows and doors, because a portion of the membrane can be affixed into position, while the remaining portion of the membrane is covered by the release sheet and is not capable of fouling (sticking to itself) or prematurely adhering to surfaces. 
     However, it is quite possible that in some detail areas the use of split release liner sheets can hinder application, since the applicator would have to deal with two portions of the release sheet if he or she wishes to expose at once the entire face of the adhesive layer for attaching the waterproofing membrane to a surface. Pre-split release sheets require that the applicator remove both split portions at once during application on flat (non-detail) areas, and this can make control and accurate placement difficult. 
     In view of the disadvantages of the prior art, the present inventors believe that a novel waterproofing membrane release sheet liner system is needed. 
     SUMMARY OF THE INVENTION 
     In surmounting the disadvantages of the prior art, the present invention provides an improved waterproofing membrane having at least one string for cutting a portion of the release sheet liner at the application site. 
     One of the objectives of the invention is to provide a waterproofing membrane that avoids the disadvantage of pre-split release sheet liners that make it difficult to install an entirely exposed adhesive layer at once. 
     Another objective of the invention is to provide the ability for the applicator to cut a portion of the release sheet liner at the application site, to facilitate the application of the membrane. In preferred embodiments, more than one string can be used so that the area of the waterproofing adhesive face to be exposed can be controlled. 
     Another objective of the invention is to provide convenience and flexibility in applying waterproofing membranes to detail areas (e.g., non-flat surfaces) and also to areas around doors, windows, and other discontinuities in the building surface or other civil engineering surface. 
     Accordingly, an exemplary improved waterproofing membrane of the present invention comprises a pre-formed, sheet-like waterproofing adhesive layer which is releasable attached to a release sheet liner, and at least one string operative, when pulled away from said adhesive layer, to cut said release sheet liner, whereby a portion of said cut release sheet liner may be removed from said adhesive layer. Preferably, the waterproofing adhesive layer further comprises a carrier support layer, such as a continuous polymeric film. Where a continuous film is used as the carrier support, the string or strings will be positioned within the membrane laminate between the carrier support layer and the release sheet liner, usually entirely or partially embedded within the waterproofing adhesive layer. 
     The present invention also provides a method for installing sheet-like waterproofing membranes and for manufacturing such membranes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a cross-sectional view of an exemplary waterproofing membrane of the present invention. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     As shown in FIG. 1, an exemplary improved waterproofing membrane  10  of the present invention comprises a pre-formed, sheet-like waterproofing adhesive layer  12  having a first major face adjacent to, or directly attached to, a release sheet liner  14  that is releasably attached to the membrane  10 . At least one string  16 , or more a plurality of strings, positioned beneath the release sheet liner  14 , are operative, when pulled away from the adhesive layer  12 , to cut the release sheet liner into smaller portions for selective partial removal if and when desired. The string  16  is preferably oriented along the length of the membrane  10 , in the so-called “machine” direction, because this will facilitate both the manufacture and application of the membrane  10 . Where a number of strings  16  are employed, they should be spaced at intervals across the width of the membrane  10  so that variously-sized portions of the release sheet liner  14  may be cut by pulling on the appropriate string. 
     The term “string” as used herein is not intended to be limiting but means and refers to thin cords, monofilaments, strands (including single or multi-strands), or lines or even wires which are operative to cut or tear the release sheet liner when pulled in a direction away from the waterproofing adhesive layer. Preferably, the string has a thickness which is a fraction of the waterproofing adhesive layer thickness (total), but the string may have a similar or identical thickness so long as it can still cut or tear through the release sheet liner when pulled by hand. Presumably, thin line will work best because it will tear/cut the release sheet most effectively and cleanly. 
     An exemplary waterproofing membrane  10 , as shown in FIG. 1, preferably comprises a carrier support sheet  18 , which can be attached to a major face of the adhesive layer  12  opposite the other major face to which the release sheet liner  14  is attached. The carrier support sheet  18  can also be embedded (e.g., as a scrim) within the adhesive layer  12 . 
     The carrier support sheet  18 , waterproofing adhesive layer  12 , and release sheet liner  14  may be comprised of materials such as are conventionally known in the waterproofing art. Thus, the carrier  18  may be a continuous film made of paper, polymer, metal, glass, fabric (e.g., non-woven), felt, or mixture thereof, attached to the adhesive layer  12  and/or embedded therein. Preferably, the carrier support  18  comprises a polyolefin polymer (e.g., cross-laminated or oriented polyethylene or polypropylene). Exemplary waterproofing adhesive layers  12  may comprise bituminous materials (e.g., rubber-modified bitumen) or non-bituminous synthetic adhesive materials (e.g., SIS, SEBS, butyl rubber, etc.) as known in the art. Exemplary release sheet liners  16  may comprise waxed or siliconized paper or plastic film or other known materials. 
     Examples of waterproofing membranes, and methods of using and making them, are disclosed in U.S. Pat. No. 3,741,856 of Hurst; U.S. Pat. No. 3,900,102 of Hurst; 
     U.S. Pat. Nos. 4,172,830 and 4,421,623 of Rosenberg and Gaidis; U.S. Pat. No. 4,751,122 of Basil J. May; and Canadian Pat. No. 861467 of Geoffrey Davis, all of which are fully incorporated by reference herein. Pre-formed, sheet-like waterproofing membranes are commercially available for use in sub-grade installations from W. R. Grace &amp; Co.-Conn., Cambridge, Mass., under the trade name BITUTHENE®. Roofing membranes are also available from Grace under the trade names ICE &amp; WATER SHIELD® and VYCOR®. 
     Again, it is preferred that the string  16  be relatively thinner gauge than the waterproofing adhesive layer. The string should be of sufficient strength and tenacity to pull through and tear the release liner  14  without breaking. Examples of suitable string are fishing line, such as 10-25 pound line, or dental floss string, which may optionally be coated with wax, silicone, or other friction-reducing material, to facilitate removal or peeling from the waterproofing adhesive  12 . The string could comprise nylon, metal, cotton, hemp, glass, or other tough material, depending on the nature of the release sheet liner material used. 
     An exemplary method of the invention for installation of a waterproofing membrane  10  comprises providing a membrane, as above described, and cutting a portion of the release sheet liner  14  with a string  16 . A portion of the release sheet is removed, such that an uncut portion of the release sheet  14  can be removed at a subsequent time. 
     In further exemplary membranes  10  of the invention, a very large number of parallel strings (preferably not in contact with each other) can be employed, for example located between the adhesive layer  12  and release sheet liner  14 , to decrease the surface area of the adhesive layer  12  when it is exposed. 
     One method of the invention for making an exemplary waterproofing membrane  10  is to melt-coat waterproofing adhesive onto the waxed or siliconized surface of the release sheet liner  14  on which the string or strings  16  are positioned (or releasably attached such as by wax droplets, adhesive, and/or tape). Another exemplary manufacturing method involves forming the waterproofing adhesive layer  12 , and thereafter embedding at least one string in the formed adhesive layer  12  and/or disposing at least one string against the surface of the adhesive layer. 
     In further exemplary membranes, a plurality of strings are positioned between the adhesive layer  12  and release liner  14 , while another plurality of strings are embedded within the adhesive layer  12 . As a practical matter, since the waterproofing adhesive is extremely viscous, strings initially placed “between” the adhesive layer and release liner may become partially or totally embedded in the waterproofing adhesive in any event, since the adhesive will tend to flow around the string. String which is taped against the release sheet liner may have less of a tendency to become entirely embedded within the adhesive layer. However, it is believed that the invention will work even if the strings are located away from the release sheet liner, such as being initially positioned or located between the carrier support sheet (if attached to a major face of the waterproofing adhesive layer) and the waterproofing adhesive layer. 
     In other exemplary embodiments, a portion of string length can extend beyond an edge of the waterproofing membrane to facilitate grabbing the string and pulling it so as to cut the release sheet liner into portions. The string may have a color that is different than the color of the waterproofing adhesive or release sheet liner to facilitate visual detection of the string by the applicator. In further exemplary embodiments, the outer face of a releasably-attached release sheet liner may contain markings or indicia to suggest to the applicator the location of the cutting string within the membrane laminate. 
     The foregoing exemplary embodiments are provided for illustrative purposes only, and are not intended to limit the scope of the invention.