Several Roofing Manufacturers have introduced Algae resistant roofing shingles based on patents like these.
BACKGROUND OF THE INVENTION
1. field of the Invention
This invention relates to roofing granules having algicidal properties. More particularly, it relates to an economical method for producing novel color coated roofing granules possessing algicidal properties for effectively retarding the biological growth of algae and/or fungi on roofing surfaces.
2. Description of the Prior Art
Roofing granules, both natural and artificially color-coated granules, are extensively used in roll roofing and asphalt shingle compositions. The roofing granules are generally embedded in the asphalt coating on the surface of an asphalt-impregnated felt base material, the granules thus forming a coating that provides an adherent, weatherresistant exterior roofing surface. As this outer granule coating also provides the esthetic effect observable with respect to the roofing composition, the appearance of the granules is of major maketing interest. For this reason, therefore, a pigmented color coat is ordinarily applied to the base mineral granules to enhance their visual, decorative effect.
As white or light-colored roofs are particularly favored in warmer climates, TiO 2 pigment is commonly used in the production of light color-coated roofing granules. In such warmer climates, as in the southern part of the United States, discoloration of asphalt roofing compositions by the growth of algae and/or fungi is of particular concern. Such discoloration, of course, is particularly noticeable on the white or light-colored roofs otherwise so desired to popular in such regions. Upon discoloration, the roof becomes unsightly in appearance and is found to cause a greater heat absorbence as, for example, when a white roof is turned dark brown or black in a period of a few years in use.
Nor is this problem so widespread in areas such as the southern United States, particularly the gulf state area, confined necessarily to such regions. Thus, discoloration of roofing surfaces by the growth of algae and/or fungi has also been found in the northern part of the United states, particularly so in areas along rivers and lakes and along the northern coastal regions. While home owners and others have been aware of this discoloration problem for many years, effective, practical solutions thereto have not been forthcoming at a reasonable cost. The problem of roofing granule discoloration, therefore, has remained a major marketing problem for the roofing industry.
For many years, this problem of roofing granule discoloration was believed to be caused only by fungi, as is the case with respect to some outdoor paint surfaces. Many different types of fungi have, in fact, been isolated from discolored roofing surfaces. More recently, however, it has been learned that other organisms contribute principally to this discoloration and have been identified as terrestrial blue-green algae of the Cyanophyta division. Such algae are transferred through the air as spores and/or vegetative matter and deposited on roofing surfaces where they thrive and grow. Natural pigments produced by the algae add to the dark discoloration of the roof, which is generally first noticeable in spots that develop into dark vertical streaks that gradually darken until the entire roof becomes a totally discolored black within 5 to 15 years. Predominant algae thus identified from infested roofing shingles include Gloeocapsa Magma, Tolypothrix Byssoidea, Nostoc sp. and Scytonema sp. In general, metallic algicides that are effective in retarding the biological growth of such algae are likewise effective in similarly retarding the growth of fungi. The incorporation of a metallic algicide in the color coat of roofing granules, therefore, has heretofore been proposed in order to inhibit or prevent the discoloration of roofing surfaces containing such granules as a result of algae and/or fungi growth.
The incorporation of a metallic copper algicide in the color coat of roofing granules was disclosed in the Skadulis patent, U.S. Pat. No. 3,528,842. Skadulis particularly proposes the incorporation of copper algicides that are substantially waterinsoluble but that have limited solubility in acidic solutions, e.g., Cu 2 O. Highly water-soluble copper algicides, such as CuSO 4 , were indicated as being ineffective for this application since it was suggested that such algicides would be leached out of the color coat very rapidly, i.e., within a few months, so that the resistance to algae growth and roofing discoloration would not be effective over any reasonable length of time. Skadulis also indicated that virtually water-insoluble compounds, such as CuO, would not be effective because, it was suggested, of insufficient solubility thereof in rainwater and dew (Column 2, lines 24-44). Similarly, slightly soluble zinc algicides were disclosed for incorporation in the color coat of roofing granules in the McMahon patent, U.S. Pat. No. 3,507,676. As was pointed out in the McMahon patent in Column 2, lines 58-65, such zinc algicides are effective when employed in an amount constituting at least about 1% by weight of the base mineral granules, i.e., about 20 lbs. of the zinc algicide compound or metal per ton of granules.
The incorporation of particular copper or zinc algicides in the color coat of roofing granules, in the manner and in the quantities taught by the Skadulis and McMahon patents, imparts a desirable resistance of roofing surfaces containing such granules to discoloration upon exposure to atmospheric weathering. The teachings of these patents, however, have not led to the development, commercial availability and use of algicidal roofing granules providing the desired degree of algae and/or fungi resistance over an extended period of time at economically competitive cost. In part, of course, this unavailability of a totally satisfactory algicidal roofing granule reflects the continual desire in the roofing industry for a more effective algicidal effect from a roofing granule of ever diminishing incremental cost to achieve such an algicidal effect. Any incorporation of metallic algicides in an otherwise conventional roofing granule coating in order to achieve the necessary or desirable algicidal effect necessarily adds an incremental cost to the roofing granule and to the roofing material incorporating such an algicidal granule. While the desired toxic effect is a necessary or highly desirable feature of the algicidal roofing granule, the providing of this property or function is an expense item that, from a marketing viewpoint, must be minimized to the fullest possible extent. The use of minimum quantities of metallic algicides to produce a desired level of effectiveness over an extended period of time is, therefore, highly desirable. While the prior techniques have imparted an algicidal effect to roofing granules, an enhanced effect would provide further assurance of the desired toxic effect, thereby enhancing the quality of such granules. In this regard, it should be noted that the algicidal granules of McMahon require the incorporation of a relatively large amount of zinc for effective algicidal action as noted above. As the amount of metallic algicide required for effective action increases, the cost of the resulting algicidal granule is directly increased thereby. In addition, the use of relatively large amounts of metallic algicides frequently requires the incorporation of pigment in the granule coating in amounts in excess of that otherwise required to achieve a desired roofing granule color. As the amount of Cu 2 O employed is increased, for example, the amount of TiO 2 pigment that must be employed in the granule coating composition to produce a white roofing granule is also generally increased. Such an additional requirement necessarily adds to the overall cost of the algicidal roofing granule product and of roofing materials made therefrom.
The requirements flowing from the assumptions and teachings of the prior art tend to limit or restrict the metallic algicidal materials to be employed in a manner not necessarily consistent with the economic availability and feasibility of such materials in any particular application. Optimum flexibility, as to the metallic algicides employed is, in other words, another desirable aspect for the providing of an economically attractive algicidal roofing granule to the roofing industry. One further troublesome aspect of previous efforts to impart algicidal properties to roofing granules has been the practical necessity for producing such algicidal roofing granules as a sepearate production operation apart from the production of conventional, non-algicidal, color-coated roofing granules because of the variation in the color coating formulation necessarily required to incorporate the algicidal compound into the color coating. As the vast preponderance of roofing granules presently manufactured are of conventional, non-algicidal character, the interruption of such conventional roofing granule production and the scheduling and inventory problems associated therewith all tend to create a further economic disadvantage associated with the production and marketing of algicidal roofing granules. As hereinabove indicated, the commercial acceptance and use of algicidal roofing granules depend upon the providing of an economically acceptable balance between algicidal effectiveness and the incremental cost required to achieve such algicidal properties as compared with the cost of conventional roofing granules, all taken in light of the degree of algicidal effectiveness achieved. In light of these factors, the requirements for the production of algicidal roofing granules in accordance with the teachings of the prior art constitute a further detrimental element serving to diminish the prospects for employing algicidal roofing granules despite the genuine need for algicidal control and an improved resistance of roofing surfaces to discoloration during extended periods of exposure to atmospheric weathering
We clean roofs using these algae resistant shingles under warranty for several shingle manufactures such as GAF, Tamko, Certainteed, and Owens Corning. These shingles do help keep roofs here in tampa free from Algae and black streaks, for awhile. They are better then nothing. However, the copper and zinc granules eventually fall off the roof, and you are left with little or no protection from returning Algae.
We offer a yearly roof treatment option, and guarantee your roof in tampa will stay free of algae growth and black streaks.
APPLE ROOF CLEANING 7401 Patrician Place Tampa FL 33619 (813)655 8777
711 Westbrook Ave
Brandon, Florida 33511