Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
1998-05-06
2003-10-14
Szekely, Peter (Department: 1714)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C524S412000, C524S445000, C524S451000, C524S464000
Reexamination Certificate
active
06632509
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to fire retardant sheeting materials and, more particularly, to fire retardant EPDM-based roofing membranes exhibiting such an improved burn resistivity that they are suitable for use on roofs having high slopes. Specifically, these preferably scrim-reinforced, fire retardant EPDM roofing membranes have relatively low process oil loadings, relatively high levels of non-combustible mineral fillers, and a fire retardant package containing at least decabromodiphenyl oxide (DBDPO) or similar bromine-containing additives and antimony trioxide (Sb
2
O
3
) such that the roofing membranes have a limiting oxygen index (LOI) of at least 40 percent oxygen when tested in accordance with ASTM D2863-91.
BACKGROUND OF THE INVENTION
Ethylene-propylene-diene terpolymer (EPDM) is extensively utilized in a variety of applications. For example, it is particularly useful as a polymeric rubber sheeting material which, because of its excellent physical properties, flexibility, weathering resistance and heat aging resistance, has gained acceptance as a single-ply roofing membrane for covering industrial and commercial flat roofs. Such roofing membranes are typically applied to the roof surface in a vulcanized or cured state and serve as an effective barrier to prevent the penetration of moisture through the roof being covered.
These EPDM roofing membranes typically are prepared by compounding the EPDM or mixtures of EPDM and other polymers, such as ethylene-propylene copolymers (EPM) or ethylene-butene copolymers, with the appropriate reinforcing and non-reinforcing fillers, processing oils, and other desired ingredients, such as plasticizers, antidegradants, crystallinity-enhancing promoters, adhesive-enhancing promoters, etc., in a suitable internal mixer, and calendering the resulting compound into the desired rubber sheet. The roofing membranes may then be cured, if desired, by vulcanizing the resultant composite sheet in the presence of one or more vulcanizing agents and/or compatible vulcanizing accelerators. Vulcanizing agents such as sulfur or sulfur containing compounds such as mercaptans are normally used today, although vulcanization and curing can be done using other agents or in the presence of other compounds. For example, ethylene-butene copolymers may be cured in the presence of a triazine or organic peroxide. As another alternative, curing by ionizing radiation through the use of radiation crosslinking promoters has also been suggested.
One major drawback of EPDM-based sheeting materials, and roofing membranes in particular, are that they lack flame resistance or burn resistivity. In other words, EPDMs, like other olefinic elastomers, are combustible, and the roofing membranes are not fire-proof. At least one test has been set forth as an American Standard Testing Method (ASTM) in order to compare the flame resistance or burn resistivity of various compositions. In particular, ASTM D2863-91 provides for a determination of the limiting oxygen index (LOI) which, generally speaking, correlates to the burn resistivity of a composition. That is generally, the higher the LOI is, the greater the burn resistivity of the composition.
The LOI is determined by measuring the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen that will just support flaming combustion of either rubber or plastic materials.
In the past, typical EPDM-based roofing membranes exhibited relatively low LOI values, typically on the order of about 18 to 22 percent oxygen, while molded plaques of the raw polymer itself had LOI values of between about 18 and 19 percent oxygen. These roofing membranes contained several combustible materials and were readily flammable when ignited.
In order to improve the flame resistance or burn resistivity of products employing olefinic elastomers, e.g., EPDM roofing membranes, flame retardant fillers such as antimony trioxide, decabromodiphenyl oxide (DBDPO), dechlorane (chlorinated alicyclic hydrocarbon), alumina trihydrate, and chlorinated or brominated paraffins, have been introduced and incorporated into the composition of the product, as shown in U.S. Pat. Nos. 4,839,412 and 4,851,463. However, it will be appreciated that the capacity of some of those products, and particularly olefinic roofing membranes that exhibit thermoplastic characteristics, to accept these flame retardant fillers is somewhat limited. Excessive amounts of the fillers will often result in a loss of physical properties, flexibility and/or even processibility.
Thus, while flame retardant fillers have often been used in polymeric sheeting and roofing membranes to increase flame resistance and burn resistivity, the amount of flame retardant fillers that can be added is necessarily limited, and therefore, the burn resistivity of a product containing these flame retardant fillers is also limited. In essence, while attempts have been made to improve the flame resistance or burn resistivity of EPDM-based roofing membranes, the art has not, heretofore, found a way to increase the flame resistance such that the roof sheeting membranes have a limiting oxygen index (LOI) of at least 40 percent when tested in accordance with ASTM D2863-91. It has been found that in order to provide a roofing membrane that meets or exceeds national flammability testing standards for roof covering materials such as Underwriter Laboratory's UL-790 Test for Fire Resistance of Roof Covering Materials for all roofs, including those having high slopes, and particularly, for use on sloped roofs having an incline of 1 inch or more per linear foot, an LOI of at least 40 percent oxygen when tested in accordance with ASTM D2863-91 is necessary.
Prior art roofing membranes have not met such standards when applied to such high sloped roofs. For example, U.S. Pat. No. 4,810,565 discloses a fire retardant elastomeric EPDM roof sheeting composite comprising an upper layer of a fire retardant EPDM material and a lower layer of a non-fire retardant EPDM material. Among its advantages, this patent notes the elimination of the use of subsequently-applied coatings as a necessary means of enabling standard EPDM materials to pass testing standard UL-790 in some roofing assemblies. While this is true for roofing membranes developed for essentially flat roofs, i.e., those roofs having inclines of less than 1 inch per linear foot, it is believed that the composite sheet does not pass testing standard UL-790 on high-sloped roofs, i.e., those roofs having inclines of 1 inch per linear foot or greater. In fact, as set forth hereinbelow, even the preferred fire retardant EPDM material employed as the upper layer of the composite alone (without its lower layer) does not have an LOI of 40 percent oxygen when tested in accordance with ASTM D2863-91.
Therefore, while the use of flame retardant additives offer effective means of increasing flame or burn resistivity, these additives cannot be provided in great enough quantity to effectively render all EPDM roofing membranes unflammable, particularly on high sloped roofs. Thus, the need exists for an EPDM roofing membrane composition with a limiting oxygen index (LOI) of at least 40 when tested in accordance with ASTM D2863-91, such that the EPDM roofing membrane composition meets or exceeds testing standard UL-790 for roofs having slopes of 1 inch per linear foot or more. Moreover, physical properties of the roofing membrane should not change significantly.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide vulcanizable elastomeric roof sheeting materials that possess improved burn resistivity.
It is another object of the present invention to provide vulcanizable elastomeric roof sheeting materials that possess improved burn resistivity in high slope uses.
It is yet another object of the present invention to provide vulcanizable elastomeric roof sheeting materials, as above, that have a limiting oxygen index of at least 40 percent oxygen when tested in accordance with ASTM D2863-91.
It is still another object of
Barham, Jr. William F.
Brandt Gregory A.
Davis James A.
BFS Diversified Products LLC
Skoglund Rodney L.
Szekely Peter
LandOfFree
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