Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1998-11-20
2001-09-18
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S150000, C522S157000, C522S161000, C428S141000, C428S147000, C264S494000
Reexamination Certificate
active
06291542
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and apparatus for selectively curing a sheet of ethylene-propylene diene termonomer (EPDM) material and the product formed thereby. More particularly, this invention relates to a method and apparatus for selectively curing at least the field portion of a sheet of EPDM material for use as a roofing, membrane and to a method of joining the roofing membranes and the product formed thereby.
BACKGROUND OF THE INVENTION
EPDM membranes are used as a single ply roofing material for industrial and commercial flat roofs. Such membranes are generally applied to the roof surface in a vulcanized or cured state. Because of outstanding weather resistance and flexibility, cured EPDM roofing membrane material has rapidly gained acceptance. The material is typically prepared by vulcanizing the composition in the presence of sulfur or sulfur containing compounds such as mercaptans or by using radiation cross linking promoters in the EPDM material which can be cured by ionizing radiation, for example, see U.S. Pat. No. 4,803,020, incorporated herein by reference.
Notwithstanding the usefulness of radiation curing and sulfur curing of a sheet of EPDM, a disadvantage of utilizing EPDM material is the lack of adhesion of cured EPDM to itself. Accordingly, it is usually necessary to splice the cured EPDM roofing membranes together with an adhesive to bond the cured EPDM membranes together to form a continuous EPDM membrane to cover the roof. It will be appreciated that the use of an adhesive for splicing cured EPDM membranes together requires that the adhesive and the resulting bond must meet a number of requirements which are extremely difficult to satisfy. The adhesive must provide sufficient seam peel and shear strength to permit the splice formed by bonding the cured EPDM membranes together to resist both the short-term and long-term stresses experienced by the spliced EPDM roofing membrane.
In view of the foregoing, it is an object of the present invention to provide a method and apparatus for selectively curing only the field of a sheet of EPDM. It is another object of the present invention to provide a method and apparatus for selectively curing only the field of a sheet of EPDM with radiation, preferably infrared radiation, and to a method of joining at least two selectively cured EPDM membranes to form a larger membrane. Yet another object of the present invention is to provide a method of splicing selectively cured EPDM membranes having a cured field and uncured longitudinal edge area which eliminates the need for a solvent based or non-solvent based splicing adhesive along the overlapping edge area and the related labor and hardware necessary for mixing and application thereof. It is another object of the present invention to provide a method and apparatus for curing only the field of a sheet of EPDM that is simple and economical.
SUMMARY OF THE INVENTION
Briefly, according to the present invention there is provided a method and apparatus for selectively curing a sheet of EPDM to form a roofing membrane for installation on a roof deck. The method includes the steps of providing a sheet formed of ethylene-propylene diene termonomer, the sheet having a field and longitudinal edge portions bordering the field. The field is defined by a planar surface portion exclusive of the longitudinal edge portions. The longitudinal edge portions are defined by the extent of overlap of adjacent roofing membranes when installed on a roof deck. The sheet is then selectively cured such that at least only the field is cured thereby leaving at least one longitudinal edge portion of the sheet uncured.
The apparatus for selectively curing a sheet of ethylene-propylene diene termonomer (EPDM) defined by a field and longitudinal edge areas bordering the field includes a curing oven, a radiation source and at least one screen. The curing oven has a roof and a floor interconnected by sidewalls, a front end and a back end. The front end includes an entrance and the back end includes an exit. A conveyor is positioned between the front end and the back end of the curing oven for continuously conveying the sheet of EPDM through the curing oven. The radiation source is located above the conveyor within the curing oven. At least one screen operatively projects from each sidewall of the curing oven and extends the longitudinal length of the curing oven to cover at least one edge area of the sheet and shield the edge area of the sheet of EPDM as the sheet passes through the curing oven under the radiation source.
The resulting roofing membrane from the process of the present invention is a sheet formed of ethylene-propylene diene termonomer. The sheet has a field defined by a cured planar surface portion and at least one noncured longitudinal edge area bordering the field and defined by the extent of overlap of adjacent roofing membranes when installed on a roof deck.
The selectively cured sheets of EPDM membrane may be joined by providing at least two sheets formed of ethylene-propylene diene termonomer, the sheets having a field defined by a cured planar surface portion and at least one noncured longitudinal edge area bordering the field defined by the extent of overlap of adjacent roofing membranes when installed on a roof deck. The noncured edge areas of two EPDM roofing membranes are then overlapped and pressed together and then the edge areas are vulcanized to splice the edge areas together.
REFERENCES:
patent: 4458128 (1984-07-01), Chabinsky
patent: 4680071 (1987-07-01), Candle
patent: 4803020 (1989-02-01), Valaitis et al.
Hubbard Michael J.
Kelly Walter J.
Verrocchi Anthony
Weinert Raymond J.
McClendon Sanza
Meenan Larry R.
OMNOVA Solutions Inc.
Rywalski Robert F.
Seidleck James J.
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