Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
1999-07-28
2001-04-10
Green, Anthony (Department: 1755)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C106S015050, C106S018360, C427S214000, C427S215000, C427S219000, C428S403000, C428S489000
Reexamination Certificate
active
06214466
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to algae-resistant roofing granules. More particularly, it relates to algae-resistant roofing granules of the type which are artificially colored and contain a slow-release bimetallic algicide as a component of the color coating.
2. Reported Development
Roofing granules, both natural and artificially colored granules, are extensively used in roll roofing and asphalt shingle compositions. The roofing granules are embedded in the asphalt coating on the surface of the asphalt-impregnated felt base material, the granules thus forming a coating that provides an adherent, weather-resistant exterior roofing surface.
In warm and humid climates discoloration of asphalt roofing compositions by the growth of algae is of particular concern. To prevent such discoloration the prior art proposed the use of metallic algicides incorporated into roofing granules that are effective in retarding the biological growth of algae. Illustrative examples of prior art compositions are as follows.
U.S. Pat. No. 3,494,727 discloses a microbe resistant roof wherein the roofing material contains embedded therein visually observable metallic chips, such as copper, lead, zinc and iron.
U.S. Pat. No. 3,507,676 discloses zinc-containing coating for roofing granules in the form of zinc, ZnO or ZnS.
U.S. Pat. No. 3,528,842 discloses copper compound-containing algicidal surfacing, the copper compound being cuprous oxide or cuprous bromide.
U.S. Pat. No. 3,598,627 discloses fungus-resistant shingles the outside surface of which are asphalt coated and are covered by a hard, granular weathering material and granular zinc.
U.S. Pat. No. 3,884,706 discloses algicidal roofing granules coated with a substantially water insoluble silicate-clay coating into which small amounts of algicides, e.g. 0.05% to 0.5% zinc algicide and 0.05% to 0.5% copper algicide, are incorporated based on the total weight of the roofing granules.
U.S. Pat. No. 4,092,441 discloses roofing granule treatment by coating the granules with a metallic algicide, such as zinc, copper, nickel and mixtures thereof. The metals are sprayed onto the granules in the form of molten droplets.
U.S. Pat. No. 5,382,475 discloses algicidal granules having a ceramic coating thereon comprising three layers, the first two of which have a copper compound, and the third layer has a pigment, a borate compound and zinc oxide.
While the teaching of the above-mentioned references greatly advanced the state of the art and provided impetus for the building materials industry in creating algicidal roofing granules, the need for creating enhanced, long-term and slow-release algicide-containing granules still exists. The object of the present invention is to provide for that need.
The present invention provides bimetallic algicide-coated granules in which the two metals act synergistically in preventing/retarding the growth of algae.
SUMMARY OF THE INVENTION
The present invention provides algae-retardant, artificially colored roofing granules comprising:
a) a base of crushed mineral aggregates coated with
b) a first or inner layer of semi-ceramic composition consisting of a fired silicate-clay matrix containing: of from about 80 pounds to about 180 pounds, and preferably 90 pounds to 115 pounds, cuprous oxide (Cu
2
O) per ton of the base material; and of from about 6 pounds to about 60 pounds, and preferably 12 pounds to 25 pounds, of zinc sulfide (ZnS) per ton of the base material;
c) a second or outer layer of semi-ceramic composition, coated on the first or inner layer of the semi-ceramic composition, consisting of a fired silicate-clay matrix containing coloring pigments that determine the overall appearance of the granules.
The combination of cuprous oxide and zinc sulfide is a concentrated source of slow-release bimetallic ions, i.e. copper and zinc, that provides a synergistic combination of toxic metal ions for more effective long-term algicidal performance. Unlike cuprous oxide and zinc oxide bimetallic combinations suggested by the prior art wherein the zinc oxide retards the rate of copper ion release, the cuprous oxide and zinc sulfide combination provides a higher rate of copper and zinc ion release. The rate of copper ion release from the cuprous oxide/zinc sulfide combination is proportional to, and can be regulated by, the amount of zinc sulfide present.
Optionally the second or outer layer may contain zinc sulfide, which can function as both a light-colored pigment and a source of slow release zinc algicide. If used in the second or outer layer, the zinc sulfide should be present in an amount of from about 5 pounds to about 30 pounds, and preferably 10 pounds to 20 pounds, per ton of the base material.
The algae-retardant granules of the present invention may be mixed with standard, non-algicidal roofing granules in a ratio of from about 5% w/w to about 60% w/w or higher and preferably from 10% to 20%. The ratio of algae-resistant and non-algae resistant granules can be tailor-made to the geographic area where algae infestation is influenced by the environment. In addition, the desire or requirement of providing a light-colored appearance of the roofing granules will influence the ratio of algicidal and non-algicidal granules in the mixture providing the final product.
The present invention is also directed to the manufacturing of the algae-retardant, artificially colored roofing granules comprising the steps of:
a) crushing and sizing the base aggregate to the desired size, typically to No. 11 grading;
b) pre-heating the sized/graded granules to about 210° F.-230° F.;
c) coating the pre-heated granules with a first or inner coat of ceramic composition being in the from of an aqueous slurry comprising:
Sodium silicate,
Kaolin clay,
Pigment,
Cuprous oxide, and
Zinc sulfide;
d) pre-drying the first or inner coat granules to adjust their moisture content to from about 0.2% to about 0.5% w/w;
e) kiln-firing the granules at a temperature of from about 740° F. to about 760° F. to form an insolubilized silicate-clay matrix coating in which the cuprous oxide, zinc sulfide and pigment are uniformly distributed;
f) cooling the kiln-fired, first-coated granules to a temperature of from about 210° F. to about 230° F.;
g) coating the first or inner coated granules with a second or outer coat of a semi-ceramic aqueous composition comprising:
Sodium silicate,
Kaolin clay and
Pigment;
h) pre-drying the second-coated granules to adjust the moisture content to about 0.2% to 0.5% w/w;
i) kiln-firing the granules at a temperature of from about 890° F. to about 960° F. to form an insolubilized silicate-clay matrix coating in which the pigment is uniformly distributed;
j) reducing the temperature of the granules to about 200° F.-220° F.; and
k) treating the granules with a mixture of process oil and an organosilicone compound to impart dust control and adhesion to a substrate, such as asphalt.
REFERENCES:
patent: 3494727 (1970-02-01), Rapaport
patent: 3507676 (1970-04-01), McMahon
patent: 3528842 (1970-09-01), Skadulis
patent: 3560196 (1971-02-01), Horai et al.
patent: 3598627 (1971-08-01), Klimboff
patent: 3884706 (1975-05-01), Little
patent: 3888176 (1975-06-01), Horai et al.
patent: 3888682 (1975-06-01), Nelson
patent: 3888683 (1975-06-01), Horai et al.
patent: 3888684 (1975-06-01), Little
patent: 3894877 (1975-07-01), Nelson
patent: 3998644 (1976-12-01), Lodge
patent: 4092441 (1978-05-01), Meyer et al.
patent: 5356664 (1994-10-01), Narayan et al.
patent: 5382475 (1995-01-01), Kayser
patent: 5411803 (1995-05-01), George et al.
patent: 5573782 (1996-11-01), Bigham et al.
Balogh Imre
Davis William J.
Green Anthony
ISP Investments Inc.
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