Abstract:
The invention pertains to a novel method for flashing a door, window, ductwork or other rough opening in a building surface. The method involves the use of a tape strip having a continuous, non-perforated, machine-direction-splittable plastic release sheet liner which is selectively removed in controlled portions without the need for cutting strings. Anisotropic tear-resistance properties of the release liner facilitate a careful, controlled, and progressive installation of the tape strip while avoiding unwanted transverse tearing that could block or foul the adhesive.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to waterproofing sealants which are in the form of a pre-formed sheet-like structure, and more particularly to a method for flashing detail areas, such as door and window openings, using tape strips having a continuous, non-perforated, machine-direction-splittable plastic release liner having anisotropic tear-resistance properties which facilitate tearing while minimizing fouling or blocking of the adhesive.  
       BACKGROUND OF THE INVENTION  
       [0002]     It is known that substructural surfaces can be sealed in a waterproof manner by application of pre-formed, flexible membranes of waterproofing pressure-sensitive adhesives. The membranes are protected by a release sheet liner made of waxed paper or plastic that can be peeled from the adhesive at the time of application.  
         [0003]     The use of split or perforated release sheets is known in the waterproofing industry. In U.S. Pat. No. 4,172,830, for example, waterproofing membranes were disclosed having, release sheets that were perforated, so that strips could be progressively removed from the adhesive layer, and exposed portions of the adhesive could be overlaid onto the back of adjacent, installed membranes.  
         [0004]     Another waterproofing membrane having a pre-split or perforated release liner was disclosed in U.S. Pat. No. 5,916,654 of Phillips et al. It was explained that one of the problems with typical one-piece release sheets is that an applicator may have difficulty removing a large liner without tearing the release liner. Tearing of the release liner made it difficult to remove the remaining liner material, and portions of the release liner that remained on the adhesive layer reduced the area of adhesion.  
         [0005]     Phillips et al. therefore disclosed the use of a strip of material placed on the adhesive surface below and between each abutting edge of pre-split release liners to allow sections of the release liners to be removed without the (unwaxed) edges of the liners from sticking. If the release liner was perforated instead of pre-split, the strip material was to be located underneath the perforations. Thus, the strip was useful for preventing edge adhesion of release liners, which otherwise would be difficult to remove, and preventing tearing of the liner material which would leave liner material remaining on the adhesive surface. The strip disclosed by Phillips et al. could also served to prevent adhesive from flowing through perforations in the liner material.  
         [0006]     In U.S. Pat. No. 6,235,365, Schaughency et al. explained that split release sheets were useful for installing membranes in detail areas such as roof valleys. Split release sheets were also considered useful for when the membrane is applied as a flashing material around windows and doors because a portion of the membrane could be affixed into position, while the remaining portion of the membrane could be covered by the release sheet, and thus not stick to itself or prematurely adhere to the installation surfaces. It was further remarked that split release liner sheets could hinder application in some detail areas, because the applicator would have to deal with two portions of the release sheet liner if she wished to expose at once the entire face of the adhesive layer for attaching the waterproofing membrane. Pre-split release sheets required that the applicator remove both split portions at once during application on flat (non-detail) areas, rendering control and accurate placement difficult.  
         [0007]     Schaughency et al. therefore disclosed cutting string located between the adhesive and release liner, for cutting the release sheet liner into smaller portions for selective removal of release liner portions from the waterproofing membrane. Cutting strings were also disclosed in World Patent Application WO2004/070108 by Hamdar et al. for selective removal of release liner.  
         [0008]     The objective of the present invention relates to the flashing of the building surfaces, particularly complex or small detail areas, such as door openings, window openings, ductwork passages, and other building surfaces and openings. Methods of the invention involve the use of a flexible membrane flashing tape strip having a release sheet liner that is neither pre-split or perforated and that does not rely upon the use of cutting strings for selective removal of portions thereof. For example, the method can be used for large and flat installations, such as for roofing underlayment applications, as well as very small detail areas, such as around openings or across multi-level surfaces. In particular, methods of the invention are well-suited for installation on multi-planar surfaces, such as building surfaces which form corners and edges.  
       SUMMARY OF THE INVENTION  
       [0009]     In avoiding pre-split release sheets and cutting strings of the prior art, the present invention provides a convenient method for protecting surfaces, particularl very detail areas, such as door, window, ductwork, and other openings.  
         [0010]     An exemplary method comprises providing a tape strip having a preformed pressure-sensitive adhesive layer (e.g., 5-100 mils thickness), a backing layer attached to one side of the adhesive layer, and, attached to the opposite side of the adhesive, a continuous, non-perforated plastic release sheet having a cross-direction (CD) tear resistance and machine direction (MD) tear resistance, whereby the ratio of tear resistances CD:MD is at least 2:1 and the MD tear resistance is no greater than 1 pound (the tear resistance values being determined in accordance with ASTM D1938). The method involves removing portions of the release sheet by peeling portions thereof along the machine direction, during progressive attachment of the tape strip to surfaces of the building structure opening. A first portion of the plastic release sheet is removed along the machine direction, without using a cutting string thereby exposing a first portion of the adhesive layer; and the first exposed adhesive layer portion is attached to the target substrate, thereby affixing a first portion of the tape strip into installation position; then a second portion of the plastic release sheet is removed from the adhesive layer to expose a second portion of the adhesive layer; and the exposed second adhesive layer portion is then attached to the substrate.  
         [0011]     The plastic release sheet is notched (e.g., using box cutter, or knife point) at the point that defines the desired width of the first portion of the release sheet liner to be removed, and the first portion is then torn in the machine direction, without further use of cutting tools, to expose a longitudinally extending portion of the adhesive layer. The machine-direction-tearable release sheet liner allows an applicator the freedom of selecting the desired width to be removed initially, in contrast to pre-split or perforated release sheets which having a fixed first-removable width portion.  
         [0012]     Anisotropic tear-resistance properties of the release liner facilitates a controlled, progressive installation of the tape strip in highly detailed areas, and yet minimizes transverse tearing (cross-direction) which could induce blocking of the adhesive (due to release sheet pieces remaining on the adhesive) or fouling of the adhesive (due to premature exposure of adhesive portions). Further advantages and features of the invention are described in detail hereinafter.  
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0013]      FIG. 1  is a perspective illustration of an exemplary method of the invention wherein a first portion of a plastic release sheet liner is removed in the machine direction (shown by the arrow);  
         [0014]      FIG. 2  is another perspective illustration of the tape strip of  FIG. 2  shown in an inverted position ready for installation onto a building surface opening;  
         [0015]      FIG. 3  is a perspective partial illustration of a door opening or window opening (shown on the left side of the drawing) wherein the tape strip of  FIG. 2  is progressively installed (shown on the right side of the drawing) during removal of the remainder of the first portion of the release liner; and  
         [0016]      FIG. 4  is a perspective partial illustration of the tape strip of  FIG. 3  wherein a second portion of the tape strip is attached during removal of a second portion of the release liner. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0017]     Exemplary tape strips of the present invention are particularly suitable for providing a waterproofing seal within and around openings in building structures such as window, openings, doorway openings, ductwork passages, and other types of openings that can be found in houses and other building structures. The tape strips operate in the manner of conventional waterproofing membranes in that they are flexible, sheet-like articles that provide water- and moisture-sealing properties to porous substrates such as concrete, wood, gypsum board, and other building materials. The tape strips can be applied within and around the rough openings of doors and windows, for example, before the door frame or window frames are installed.  
         [0018]     As shown in  FIG. 1 , an exemplary tape strip  10  of the invention comprises a preformed, pressure-sensitive adhesive layer  12 , a backing layer  14  attached on a first major face of the adhesive layer, and a plastic release sheet liner  16  that has anisotropic tear-resistant properties in that they are more easily torn, simply by notching at one of the ends of the release sheet liner  16  and peeling away (in the machine direction designated by the arrow) a substantially rectangular first portion of the release sheet liner  16 , to expose a first portion of the adhesive layer  12 A. The applicator should pull the release liner portion substantially in a direction that is parallel to the machine direction of the tape strip to ensure that the tearing will align in the desired direction. While the initial notching is preferably done by hand using a box cutter or other blade device, the tearing of the plastic release sheet is preferably done by hand (e.g., pulling on the plastic sheet liner at  16 A) by hand without using a string, blade, or other cutting tool.  
         [0019]     It is contemplated that adhesive layers  12  can comprise materials as conventionally used in the waterproofing art, such as rubber-modified asphaltic adhesive or butyl adhesive. The average thickness of the adhesive layer  12  may be 5-100 mils, or more preferably 10-60 mils. The backing layer may comprise a continuous polymer film sheet (e.g., polyolefin such as polyethylene, polypropylene), a woven or nonwoven fabric, or layer of granular material (e.g., sand, carbonate, talc, etc.), and it may have an average thickness of 1-25 mils or more.  
         [0020]     An exemplary release sheet  16  of the inventions is non-perforated and continuous in nature. It is removably attached to the adhesive layer  12  and is peeled from the tape strip  10  when pulled along the length of the tape strip (machine direction). The plastic release sheets  16  have a cross-direction (CD) tear resistance and machine direction (MD) tear resistance, whereby the ratio of tear resistances CD:MD is at least 2:1 and the MD tear resistance is no greater than 1 pound, the tear resistance values being determined in accordance with ASTM D1938. More preferably the CD:MD ratio is at least 3:1; and, more preferably, the CD:MD ratio is at least 4:1 or more. More preferably, the MD tear resistance resistance is no greater than 0.75 pound (ASTM D1938).  
         [0021]     Thus, it can be said that the plastic release sheets  16  have an anisotropic tear resistance characteristic in that it is easier to tear them in the machine direction, or in a straight direction along the length of the tape strip, such that substantially rectangular portions of the release sheet can be removed.  
         [0022]     As shown in  FIG. 1 , a first portion  16 A of the release sheet liner  16  is removed to expose a first portion  12 A of the adhesive layer  12 ; and then the tape strip  10  is inverted, as shown in  FIG. 2 , such that the first exposed adhesive layer portion can be adhered onto the substrate and anchor the tape strip  10  into place.  
         [0023]     As shown in  FIG. 3  (left side), the preferred substrate will be an opening  20  in a building wall  30  or foundation, such as a rough door opening, window opening, ductwork opening, etc., which will usually have a number of non-coplanar surfaces, usually in vertical  24  and horizontal  22  directions. The tape strip  10  of  FIG. 2  is then anchored into the opening by attaching the first exposed adhesive portion ( 12 A of  FIG. 1 ) onto one of the surfaces (in this case left-most vertical surface  24 ), once the tape strip is suitably positioned within the opening  20 , with backing layer  14  facing outwards. The remainder of the first portion  16 A of the release sheet liner  16  can then be removed, by pulling along the machine direction shown by the arrow in  FIG. 3 , so that a longitudinally extending portion of the waterproofing membrane strip  10  can be progressively exposed and affixed carefully by the applicator into installation position. By employing a release sheet liner  16  having an anisotropic tear-resistance characteristic, the applicator can be sure that a constant width of adhesive layer  12 A is being exposed to anchor the tape-strip  10  into the target position. As shown in  FIG. 3 , at least two intersecting surfaces surfaces  20  and  24 , and the corners defined between these surfaces, can conveniently be protected by the tape strip  10 .  
         [0024]     As shown in  FIG. 4  the remaining unattached portion of the tape strip  10  can be fitted into place, against the substrate  30  (e.g., roof, wall, or foundation surrounding the opening  20 ). This is done by cutting the backing layer  14  and adhesive layer ( 12 ) to size, and then carefully removing a second portion  16 B of the plastic release sheet liner  16  in the machine direction shown by the arrow. Accordingly, a second portion of the tape strip  10  is affixed into installation position.  
         [0025]     The procedure shown in  FIGS. 1 through 4  can then be repeated for covering each of the sides  24 / 30  of the opening, as well as for the top of the opening (not shown).  
         [0026]     The partial release liner method discussed hereinabove may be used to apply the tape strip in other situations. For example, the tape strip may be used to attach a tape to a substantially flat surface, such as would occur in sealing a window frame to exterior building surface.  
         [0027]     For example, the tape strip can be applied as a flashing to a rough window or door opening (e.g., sill), and a window or door frame can be installed over this flashing in a similarly progressive manner wherein a first longitudinal portion of the adhesive is exposed so that the tape strip can be initially edge-attached to the substrate as a first portion of the release sheet is being peeled off. Then, once the long tape strip is anchored into position, a second portion of the release sheet is peeled off to attach a further portion of the adhesive to the substrate.  
         [0028]     Given the anisotropic tear-resistant characteristic of the plastic release sheet liner  16 , it will then be evident from the drawing and explanations provided herein the that method of the invention can also involve more than two stages of selective removal of the release liner  16 , so as to facilitate progressive installation of the tape strip  16  to openings. For example, the various multi-planar surfaces of the openings  22 / 24 / 30  may be stepped, so that the process of selective removal of portions of the plastic release sheet  16  can be repeated a number of times.  
         [0029]     The foregoing exemplary embodiments are provided for illustrative purposes only and are not intended to limit the scope of the invention.