Compositions: coating or plastic – Coating or plastic compositions – Contains fireproofing or biocidal agent
Reexamination Certificate
2002-08-01
2003-07-01
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Contains fireproofing or biocidal agent
C106S015050, C106S281100, C106S284020, C052S518000, C424S630000, C424S650000, C424S660000, C428S144000, C428S403000, C428S489000
Reexamination Certificate
active
06585813
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to surface covering building materials for roofs, sidewalls and other exterior surfaces exposed to the weather such as, but not limited to, asphaltic roofing materials, non-asphaltic roofing materials and other exterior cladding building materials wherein said surface covering building materials exhibit resistance to microbial growth-induced staining thereon. The present invention further relates to methods of making these surface covering building materials.
BACKGROUND OF INVENTION
Since the conversion of roofing shingles from felt based substrates to fiberglass substrates, asphalt shingles have been increasingly vulnerable to staining from biological growth. Although biological growth-induced staining problems are more acute in warm, humid climates such as the Gulf Coast area of the Unites States, the problem exists in all moist climates. Roofing materials, such as shingles, frequently comprise a fiberglass substrate with a filled asphalt coating. The filler in the asphalt coating acts to make the roofing materials more fire resistant; but it has also been partly responsible for the increase in microbial growth-induced staining because the filler is often a flour-like substance (typically calcium carbonate—CaCo
3
) which is conducive to microbial growth. Other filler materials besides calcium carbonate also support microbial growth.
Studies have shown that the organism responsible for the microbial growth-induced staining of roofing materials is primarily a cyanobacterium, formerly known as blue-green algae. See “Study of Algal Discoloration of Asphalt Roofing Shingles” 3M Industrial Mineral Products Division, St. Paul, Minn., December 1987. While the species of cyanobacterium may be different depending on the geographical location and environmental conditions, all of these organisms secrete a mucilaginous biofilm around their cells. This biofilm provides protection and a moisture reservoir for the cells of the organism and also contributes to the staining of roofing materials. Cyanobacteria need only indirect sun light, air, moisture and minute amounts of minerals to grow. Many asphaltic and non-asphaltic roofing materials provide sufficient nutrients and a habitable environment to support the growth of cyanobacteria.
Roofing materials generally must weather before the conditions become suitable for the establishment of microbial growth. Weathering occurs from UV degradation and washing from rain which causes the exposure of the filler and the deterioration (e.g. pitting, cracking) of the filled asphalt coating portion of the roofing material. The roughening of the filled asphalt coating, coupled with moisture from the dew or rain and the exposure of the filler, creates an environment for the attachment and growth of microbes, such as cyanobacterium.
The cement tile roofing industry has addressed the problem of microbial growth-induced staining by deferring the treatment to the after market roof cleaning industry which provides high pressure water cleaning systems incorporating chlorine bleach. In warm, humid climates, such cleaning may be required annually.
The Asphalt Roofing Manufacturers Association, on the other hand, suggests a cleaning procedure which comprises a gentle application of dilute chlorine bleach and trisodium phosphate to avoid roof damage, and cautions against high pressure water cleaning because this process can remove surface granules from asphaltic roofing-products and shorten roof life. See U.S. Pat. No. 5,599,586.
Roof material cleaning by gentle application of chlorine bleach and trisodium phosphate or by high pressure water cleaning is only temporarily effective however, and that effectiveness is minimal. To further address the problem, roofing material manufacturers have offered several types of microbial resistant products, but they have achieved limited success.
For instance, antimicrobial agents have been mixed with the granules which surface certain asphaltic roofing materials. U.S. Pat. No. 5,573,810 and U.S. Pat. No. 5,356,664 describe copper containing algae resistant granules which may be applied to the surface of an asphalt roofing material together with non-algae resistant granules. Similarly, U.S. Pat. No. 3,484,267 describes the application of zinc alloyed with another metal (e.g. copper, tin, lead, mercury, titanium, cadmium, boron, arsenic, selenium) to the surface of a roofing material either as an antimicrobial granule or as a weather corrodible strip. In U.S. Pat. No. 3,484,267, the roofing material to which the antimicrobial granule or weather corrodible strip is applied also comprises non-antimicrobial mineral granules substantially embedded in its surface. In addition, U.S. Pat. No. 5,382,475 describes three-layer ceramic-coated, algae-resistant roofing granules comprising a copper compound in the first two layers. The granules of U.S. Pat. No. 5,382,475 may be colored by adding a pigment to the third ceramic layer. Algicidal roofing granules are also described in U.S. Pat. No. 5,427,793 which discloses a roofing granule having an algicidal coating comprising an organic oil and a tin-acrylate polymer. The coating of the 5,427,793 patent may be applied to colored or non-colored granules. Similarly, U.S. Pat. No. 3,888,682, U.S. Pat. No. 3,888,683, U.S. Pat. No. 3,894,877 and U.S. Pat. No. 3,888,176 describe adding a metallic algicide to the heavy processing oils which are used in the post-treatment of color coated roofing materials. Furthermore, U.S. Pat. No. 3,884,706 discloses an algicidal roofing granule wherein copper and zinc are added to the color coating of a granule.
In addition, U.S. Pat. No.5,599,586 describes the application of antimicrobial agents in the form of a polymer film, with improved weatherability, to the surface of roofing materials. However, surface application of antimicrobial metals is susceptible to the environment, and certain weather conditions such as rain can considerably shorten the residence time of such metals and limit the effectiveness of such methods.
Other methods to reduce the microbial growth-induced staining of asphaltic-based roofing materials have sought to address the problem by using a filler, which itself has antimicrobial properties. U.S. Pat. No. 5,391,417 describes a roofing material which includes a class F fly ash filler which has antimicrobial characteristics due to its acidity. While such fillers may address to some extent the problem of microbial growth induced staining of asphaltic-based roofing materials, they are limited to roofing materials comprising such fillers and thus cannot address the roofing material staining problem generally. In addition, class F fly ash filler is not fully effective on all the types of organisms that stain roofs (e.g. Florida filamentous-type cyanobacteria).
Methods to inhibit microbial growth-induced staining of non-asphaltic roofing materials have also been described. U.S. Pat. No. 3,197,313 describes adding an antimicrobial agent, barium metaborate monohydrate, throughout an asbestos-cement composite roofing material or to an asbestos-cement veneer which surfaces an asbestos cement composite roofing material. However, this method is also limited in that it only relates to asbestos-cement composite roofing materials which are no longer marketable due to the adverse medical conditions associated with asbestos. This method also requires significant amounts of the antimicrobial agent (e.g. at least 5% and preferably 10-15% by weight of the asbestos-cement product) which can be expensive.
Another method for inhibiting microbial growth-induced staining of non-asphaltic roofing materials has been described in U.S. Pat. No. 4,193,898. The patent discloses a protective covering for use such as in shingles and siding which comprises a resin, a plasticizer and vermiculite. The protective covering can further be made resistant to microbial growth by the addition of copper sulphate during the process of making the protective covering. The method of the patent is limited to only a particular type of ro
Bryson Michael L.
Kiik Matti
Pine Robert Eugene
Weaver Casimir Paul
Baker & Botts L.L.P.
Elk Premium Building Products, Inc.
Green Anthony J.
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