Static structures (e.g. – buildings) – Processes – Adhering preformed sheet-form member
Reexamination Certificate
2000-11-10
2003-04-08
Horton, Yvonne M. (Department: 3635)
Static structures (e.g., buildings)
Processes
Adhering preformed sheet-form member
C052S746100, C052S408000, C052S411000, C156S308200, C156S351000, C156S353000, C156S512000, C156S517000, C428S215000, C428S516000, C428S517000, C428S519000, C428S521000, C428S522000
Reexamination Certificate
active
06543199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to a method for covering a roof. More specifically, this invention is directed to a method for covering a roof using a sheeting material comprising a copolymer of ethylene, propylene, and at least two nonconjugated dienes.
2. Description of Related Art
Industrial roofs in the past were traditionally treated with bitumen compositions to provide weather proofing. This practice in recent years has been replaced to a significant degree by applying rubber sheet materials to industrial roofs. In one common form of roofing system, a single-ply waterproof membrane or sheet, composed of ethylene propylene diene rubber (EPDM), is placed on top of a flat roof structure. The single-ply roof membrane is supplied in rolls having widths varying from ten to forty feet. In use, the membrane is unrolled on the roof and positioned in place. Appropriate splices are made at the edges of adjacent sheets, and suitable flashing is provided at curbs, skylights, vent pipes, and the like, all in a manner well known in the art.
To secure the membrane to the roof structure, three fundamentally different approaches have been taken. In one approach, known as the “adhered” roofing system, adhesive is applied to the entire roof and used to fasten the lower surface of the membrane and the upper surface of the roof structure. In a second approach, known as the “ballasted” system, the membrane is placed on the roof structure without adhesive there between, that is “loosely laid,” and the membrane is held in position by a layer of smooth stone placed on top of it. In a third approach, known as a “mechanically attached” roofing system, elongated metal or plastic nailing strips having adhesive applied to the bottoms thereof are placed on top of the membrane at periodic spaced intervals, much like a grid, and secured in place by driving fasteners through the nailing strip and membrane into the underlying roof structure.
Originally, the roofing material was available only in rolls of relatively narrow width, for example, four feet wide. For a roof of large dimensions, the time required to apply the roofing material strips of narrow width was found to be excessive and, owing to high labor costs, intolerable from a commercial standpoint. Accordingly, to reduce the application time, and hence the cost, of roofing with synthetic rubber sheet stock, it was found desirable to provide sheet stock in rolls of very large width, such as forty feet wide. With sheet stock of such width, the time required to roof a building in this manner was a mere fraction of that necessary with sheet stock of narrow width. A method and apparatus for providing indefinite length stock of very large width from indefinite length stock of relatively narrow width are described in U.S. Pat. No. 4,337,112.
The use of elastomeric ethylene-propylene-nonconjugated diene terpolymer and isobutylene-conjugated diene copolymer compositions as the material in the construction of roof sheeting is well known in the art. Such sheeting in the cured, or cross-linked, state provides excellent roofing material in those applications where flat material is acceptable for disposition on equally flat or moderately contoured structures. Additionally, it is possible, as disclosed in U.S. Pat. No. 4,461,875, to modify such materials in order to render them suitable as flashing, for use on those portions of a roof characterized by irregular shape.
Owing to outstanding weathering resistance and flexibility, cured EPDM based roof sheeting has been rapidly gaining acceptance. This material is normally prepared by vulcanizing the composition in the presence of sulfur or sulfur-containing to compounds such as mercaptans. U.S. Pat. No. 4,803,020 also discloses the use of radiation cross-linking promoters in an EPDM sheeting composition that can be cured by ionizing radiation. A disadvantage of utilizing these elastomers is the lack of adhesion of EPDM, especially cured EPDM, to itself. In applying EPDM sheets to a roof, it is usually necessary to splice the cured EPDM sheets together. The splice or seam area is subjected to both short-term and long-term stresses such as those caused by roof movement, heavy winds, freeze-thaw cycling, and thermal cycling. Such stresses may manifest themselves in shear forces or peel forces (i.e., the seam peels back under severe stress conditions or results in a partially open seam under less severe conditions).
In view of the foregoing problem, adhesives have been used to bond the cured EPDM sheets together. Alternatively, special EPDM formulations have been devised that permit heating the overlapped edges and seaming them using heat and pressure in the absence of an adhesive.
A variety of methods for adhering or seaming the roofing membranes together has developed over the years. For example, solvent-based adhesives, which typically employ neoprene or butyl-based compounds, have been used to bond roof sheeting materials together by applying with a brush or other similar means the liquid or pastelike adhesives directly to the edge areas of the roofing membranes to be joined.
Alternatively, polymeric tapes have been developed, as adhesive compositions that are unvulcanized but which contain curatives so as to be vulcanizable or vulcanized. These are typically used in the form of a preformed tape to bond sheet membranes together.
U.S. Pat. No. 4,000,140 discloses a waterproof sheet material suitable for use as a waterproof roofing layer, the sheet being composed of a mixture comprising (a) a bituminous material, (b) a synthetic polymeric material, and (c) particulate filler, said synthetic material comprising at least one uncured copolymer selected from ethylene-propylene copolymers and ethylene-propylene-diene copolymers and at least one synthetic polar elastomer.
U.S. Pat. No. 4,129,542 discloses a thermoplastic, elastomeric material that is obtained by curing under shear conditions (e.g., in a high shear internal mixer) a blend of vulcanizable rubber (e.g., SBR, EPDM) and a bituminous material in the presence of a rubber vulcanizing agent (e.g., sulfur or peroxide).
U.S. Pat. No. 4,337,112 discloses an apparatus and method for making a composite sheet of indefinite length and very large predetermined width from indefinite length sheet stock of relatively small width.
U.S. Pat. No. 4,424,253 discloses blends of chlorinated hydrocarbon rubber selected from chlorosulfonated polyethylene having about 22 to 28 weight percent Cl and 0.4-1.2 weight percent sulfur and chlorinated polyethylene having about 22 to 28 weight percent Cl with EPM or EPDM elastomers (which may be terpolymers or tetra polymers) in a proportion of 75 to 93 percent of the former and 6 to 25 percent of the latter that can be compounded with usual fillers, pigments, stabilizers, and processing aids and formed into sheets that form hot bonded laminate structures with linear ethylene polymer sheets.
U.S. Pat. No. 4,445,306 discloses a system for mechanically attaching a flexible waterproof membrane to an underlying structure including an elongated fastening bar that is placed above the membrane and fastened to the roof structure with fasteners that are driven through the bar from the tops thereof through the underlying membrane and into the roof structure, and an elongated waterproof strip having (a) a central region sandwiched beneath the bottom of the bar and the membrane, and through which the fasteners also pass, and (b) marginal regions that wrap upward around the bar and overlap each other above the bar and the heads of the fasteners, providing a waterproof seal for the bar with a double thickness layer of strip material above the fastener heads.
U.S. Pat. No. 4,461,875 discloses a composition for application as roof sheeting or flashing comprising 100 parts of an elastomer selected from the group consisting of EPDM, butyl rubber, and an EPDM-butyl rubber mixture; 0.1 to 3.0 parts of a compound having the structural formula {(CH
2
)
n
NCS}
2
S
6
, where n is 4 or 5; and 0 to 5.0 parts of
Jablonowski Thomas L.
Tomlinson Richard W.
Horton Yvonne M.
Uniroyal Chemical Company, Inc.
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