Pressure sensitive tape for forming water-tight field joints in rubber membranes

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG.
1 of the drawings, roof sheeting 8 is shown generally (not to scale) having roofing membranes or sheets 10 and 12 with regions 14 and 16 overlapped to form lap-joint 18.
As will be appreciated by those skilled in the art, a number of materials are used in the industry to form roofing sheets 10 and 12 such as EPDM which provides a barrier against water and provides good durability.
In order to form a water-impervious seal at lap-joint 18, adhesive roofing tape 20 is interposed between sheets 14 and 16.
Roofing tape 20 is preferably placed on surface 22 of membrane 10 whereupon region 16 of sheet 12 is placed on top of roofing tape 20.
Pressure may then be applied to lap joint 18 to enhance the surface contact between tape 20 and sheets 10 and 12.
As will be explained more fully hereinafter, tape 20 has a surface tack which contributes to the superior adhesive properties of the tape.
In the most preferred embodiment, tape 20 includes a polymeric material which is based on a combination of brominated butyl rubber and ethylene propylene diene terpolymer to produce a cross-linked polymer network.
Interspersed within this matrix, styrene ethylene-butylene block terpolymer synergistically enhances the thermoplastic properties for improved processing without affecting the brominated butyl rubber/ethylene propylene diene terpolymer cross-linked network structure.
Tape 20 also includes a significant portion of a high molecular weight plasticizer which provides added resiliency to the composition without producing bleeding of tape 20 into roofing sheets 10 and 12 which is common in formulations that rely on low molecular weight tackifiers.
Surface tack in the present invention is provided through the use of a thermoplastic phenolic resin tackifier and a thermoplastic non-phenolic resin tackifier.
Due to the presence of the high-molecular weight plasticizer, relatively small amounts of these tackifiers can be used which reduces bleed of the tackifiers onto sheets 10 and 12