U.S. patent application number 11/066644 was filed with the patent office on 2006-08-31 for algae resistant shingle.
Invention is credited to Yihsien H. Teng.
Application Number | 20060194023 11/066644 |
Document ID | / |
Family ID | 36932243 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060194023 |
Kind Code |
A1 |
Teng; Yihsien H. |
August 31, 2006 |
Algae resistant shingle
Abstract
An algae resistant asphalt-based roofing material including a
portion that is normally exposed when the roofing material is
installed on a roof. The roofing material comprises a substrate
coated with an asphalt coating. The asphalt coating includes an
upper surface that is positioned above the substrate when the
roofing material is installed on the roof. A surface layer of
granules adheres to the asphalt coating. An application of metallic
particles is applied to the upper surface of the asphalt coating.
The metallic particles contain a component that inhibits the growth
of algae. The metallic particles are applied such that greater than
fifty percent of the metallic particles are covered by the asphalt
coating, or by the granules, or by both the asphalt coating and the
granules. The covering of the metallic particles provides sustained
algae resistance at a low cost and prevents premature loss of the
metallic particles.
Inventors: |
Teng; Yihsien H.;
(Westerville, OH) |
Correspondence
Address: |
OWENS CORNING
2790 COLUMBUS ROAD
GRANVILLE
OH
43023
US
|
Family ID: |
36932243 |
Appl. No.: |
11/066644 |
Filed: |
February 25, 2005 |
Current U.S.
Class: |
428/143 |
Current CPC
Class: |
E04D 2001/005 20130101;
E04D 1/26 20130101; Y10T 428/24372 20150115; E04D 13/002
20130101 |
Class at
Publication: |
428/143 |
International
Class: |
E01F 9/04 20060101
E01F009/04 |
Claims
1. An algae resistant asphalt-based roofing material including a
portion that is normally exposed when the roofing material is
installed on a roof, the exposed portion of the roofing material
comprising: a substrate coated with an asphalt coating, the asphalt
coating including an upper surface that is positioned above the
substrate when the roofing material is installed on the roof, a
surface layer of granules adhered to the asphalt coating; and an
application of metallic particles applied to the upper surface of
the asphalt coating, the metallic particles having a component that
inhibits the growth of algae, the metallic particles being applied
such that greater than fifty percent of the metallic particles are
covered by the asphalt coating or the granules, or both.
2. The roofing material of claim 1 wherein the metallic particles
are applied such that greater than seventy percent of the metallic
particles are covered by the asphalt coating or the granules, or
both.
3. The roofing material of claim 1 wherein the metallic particles
are applied such that greater than ninety percent of the metallic
particles are covered by the asphalt coating or the granules, or
both.
4. The roofing material of claim 1 wherein the metallic particles
are pre-applied to the asphalt coating prior to the application of
the granules.
5. The roofing material of claim 1 wherein greater than ninety
percent of the metallic particles have an aspect ratio of less than
or equal to 1.5.
6. The roofing material of claim 1 wherein greater than ninety
percent of the metallic particles have an aspect ratio of less than
or equal to 1.3.
7. The roofing material of claim 1 wherein the size of the largest
dimension of the individual metallic particles is within the range
of from about 0.05 mm to about 1.0 mm.
8. The roofing material of claim 1 wherein the size of the largest
dimension of the individual metallic particles is within the range
of from about 0.1 mm to about 0.5 mm.
9. The roofing material of claim 7 wherein greater than ninety
percent of the metallic particles have an aspect ratio of less than
or equal to 1.5.
10. The roofing material of claim 1 wherein the metallic particles
are applied to the roofing material at a rate that provides the
algae inhibiting component of the metallic particles in an amount
within the range of from about 0.05 pounds per square to about 0.29
pounds per square.
11. The roofing material of claim 10 wherein the leach rate of the
algae inhibiting component of the metallic particles is within the
range of from about 0.3 parts per million to about 1.0 parts per
million in dew runoff from the roofing material.
12. The roofing material of claim 1 wherein algae inhibiting
component of the metallic particles consists essentially of
copper.
13. The roofing material of claim 1 wherein the algae inhibiting
component of the metallic particles consists essentially of a
copper alloy.
14. An algae resistant asphalt-based roofing material including a
portion that is normally exposed when the roofing material is
installed on a roof, exposed portion of the roofing material
comprising: a substrate coated with an asphalt coating, the asphalt
coating including an upper surface that is positioned above the
substrate when the roofing material is installed on the roof; an
application of metallic particles applied to the upper surface of
the asphalt coating, the metallic particles having a component that
inhibits the growth of algae, wherein greater than ninety percent
of the metallic particles have an aspect ratio of less than or
equal to 1.5; and a surface layer of granules adhered to the
asphalt coating.
15. The roofing material of claim 14 wherein the metallic particles
are pre-applied to the asphalt coating prior to the application of
the granules.
16. The roofing material of claim 14 wherein greater than ninety
percent of the metallic particles have an aspect ratio of less than
or equal to 1.3.
17. The roofing material of claim 14 wherein the size of the
largest dimension of the individual metallic particles is within
the range of from about 0.05 mm to about 1.0 mm.
18. The roofing material of claim 14 wherein the size of the
largest dimension of the individual metallic particles is within
the range of from about 0.1 mm to about 0.5 mm.
19. The roofing material of claim 14 wherein the metallic particles
are applied to the roofing material at a rate that provides the
algae inhibiting component of the metallic particles in an amount
within the range of from about 0.05 pounds per square to about 0.29
pounds per square.
20. The roofing material of claim 19 wherein the leach rate of the
algae inhibiting component of the metallic particles is within the
range of from about 0.3 parts per million to about 1.0 parts per
million in dew runoff from the roofing material.
21. A microorganism resistant asphalt-based roofing material
including a portion that is normally exposed when the roofing
material is installed on a roof, the exposed portion of the roofing
material comprising: a substrate coated with an asphalt coating,
the asphalt coating including an upper surface that is positioned
above the substrate when the roofing material is installed on the
roof; an application of metallic particles applied to the upper
surface of the asphalt coating, the metallic particles having a
component that inhibits the growth of algae, wherein the metallic
particles are applied to the roofing material at a rate that
provides the algae inhibiting component of the metallic particles
in an amount within the range of from about 0.05 pounds per square
to about 0.29 pounds per square. a surface layer of granules
adhered to the asphalt coating.
22. The roofing material of claim 21 wherein the leach rate of the
algae inhibiting component of the metallic particles is within the
range of from about 0.3 parts per million to about 1.0 parts per
million in dew runoff from the roofing material.
23. The roofing material of claim 21 wherein the metallic particles
are pre-applied to the asphalt coating prior to the application of
the granules.
24. The roofing material of claim 21 wherein the metallic particles
are applied to the roofing material at a rate that provides the
algae inhibiting component of the metallic particles in an amount
within the range of from about 0.10 pounds per square to about 0.20
pounds per square.
25. The roofing material of claim 21 wherein the metallic particles
are applied such that greater than fifty percent of the metallic
particles are covered by the asphalt coating or the granules, or
both.
26. The roofing material of claim 25 wherein greater than ninety
percent of the metallic particles have an aspect ratio of less than
or equal to 1.5.
27. The roofing material of claim 25 wherein the size of the
largest dimension of the individual metallic particles is within
the range of from about 0.05 mm to about 1.0 mm.
28. The roofing material of claim 27 wherein greater than ninety
percent of the metallic particles have an aspect ratio of less than
or equal to 1.5.
29. An algae resistant asphalt-based roofing material including a
portion that is normally exposed when the roofing material is
installed on a roof, the exposed portion of the roofing material
comprising: a substrate coated with an asphalt coating, the asphalt
coating including an upper surface that is positioned above the
substrate when the roofing material is installed on the roof; an
application of metallic particles applied to the upper surface of
the asphalt coating, the metallic particles having a component that
inhibits the growth of algae, the metallic particles comprising
elongated copper-containing particles having an aspect ratio within
the range of from about 1.5 to about 200; and a surface layer of
granules adhered to the asphalt coating.
30. The roofing material of claim 29 wherein the elongated
copper-containing particles have a substantially circular
cross-section.
31. The roofing material of claim 29 wherein the elongated
copper-containing particles have a substantially circular
cross-section, the diameter of the cross-section being within the
range of from about 0.050 mm to about 1.5 mm.
32. The roofing material of claim 29 wherein the elongated
copper-containing particles are pre-applied to the asphalt coating
prior to the application of the granules.
33. The roofing material of claim 29 wherein the elongated
copper-containing particles are applied to the roofing material at
a rate that provides the algae inhibiting component of the
elongated copper-containing particles in an amount within the range
of from about 0.05 pounds per square to about 0.29 pounds per
square.
34. The roofing material of claim 29 wherein the leach rate of the
algae inhibiting component of the elongated copper-containing
particles is within the range of from about 0.3 parts per million
to about 1.0 parts per million in dew runoff from the roofing
material.
35. The roofing material of claim 29 wherein the elongated
copper-containing particles are applied such that greater than
fifty percent of the metallic particles are covered by the asphalt
coating or the granules, or both.
Description
TECHNICAL FIELD
[0001] This invention relates to roofing materials. More
particularly, the invention pertains to asphalt roofing shingles
having an application of metallic particles applied to the asphalt
base material to provide algae resistance to the roofing
shingle.
BACKGROUND OF THE INVENTION
[0002] Asphalt-based roofing materials, such as roofing shingles,
are installed on the roofs of buildings to provide protection from
the elements. Typically, the roofing material is constructed of a
substrate, an asphalt coating on the substrate, and a surface layer
of granules embedded in the asphalt coating.
[0003] In certain climates, particularly warm climates with high
humidity, algae, fungus, and other types of microorganisms often
grow on the exposed surfaces of the roofing material. This algae
and fungus growth is particularly prevalent in the southeastern
Gulf Coast area of the United States, and has recently become
increasingly prevalent in the northern and midwest regions of the
United States. This algae and/or fungal growth leads to a
discoloring of the exposed roofing material surfaces. The
discoloration begins as dark spots of algae/fungus that develop
into dark streaks and eventually cover a majority of the roof. The
discoloration generally occurs over a period of years. For example,
in southeastern regions of the United States, the discoloration
generally becomes visible during the second or third year after the
roofing shingles have been applied. This discoloring is
particularly noticeable and unsightly on white or light-colored
roofing materials, which are often used in warm and humid climates
because of their aesthetic and sun reflectivity properties.
[0004] To combat algae and/or fungus growth, it is generally known
to include metallic granules on the surface of the roofing
material. The metallic granules are generally either composed
primarily of or coated with a coating containing copper and/or
other metals such as zinc. When wetted by rain or otherwise, the
copper and zinc compounds leach out from the roofing material and
act as algaecides and/or fungicides to inhibit the growth of the
algae and/or fungus.
[0005] The metallic materials and compounds used to provide the
algae and/or fungal resistance are generally very expensive and can
often undesirably increase the cost of the roofing material.
Additionally, the metallic granules on the roofing material are
often not aesthetically pleasing because they are highly reflective
and appear shiny on the surface of the roofing material. Hence,
there is a need for an improved, less expensive algae resistant
roofing material.
SUMMARY OF THE INVENTION
[0006] The above objects as well as other objects not specifically
enumerated are achieved by asphalt roofing shingles having an
application of metallic particles applied to the asphalt base
material to provide algae resistance to the roofing shingle. The
algae resistant asphalt-based roofing material includes at least a
portion that is normally exposed when the roofing material is
installed on a roof. The exposed portion of the roofing material is
comprised of a substrate coated with an asphalt coating. The
asphalt coating includes an upper surface that is positioned above
the substrate when the roofing material is installed on the roof. A
surface layer of granules is adhered to the asphalt coating. An
application of metallic particles having a component that inhibits
the growth of algae is applied to the upper surface of the asphalt
coating. The metallic particles are applied such that greater than
fifty percent of the metallic particles are covered by the asphalt
coating or by the granules, or by both the asphalt coating and the
granules. The metallic particles are preferably applied to the
roofing material at a rate that provides the algae inhibiting
component of the metallic particles in an amount within the range
of from about 0.05 pounds per square to about 0.29 pounds per
square of roofing material. In a preferred embodiment, the algae
inhibiting component of the metallic particles is copper or a
copper alloy. Preferably, greater than ninety percent of the
metallic particles applied to the asphalt coating have a particle
geometry having an aspect ratio of less than or equal to 1.5.
[0007] In another embodiment of the invention, elongated
copper-containing particles are applied to the upper surface of the
asphalt coating. The copper-containing particles preferably have an
aspect ratio within the range of from about 1.5 to about 200. A
surface layer of granules is also adhered to the asphalt
coating.
[0008] Various objects and advantages of this invention will become
apparent to those skilled in the art from the following detailed
description of the preferred embodiments, when read in light of the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of the roofing shingle of the
present invention.
[0010] FIG. 2 is a cross-sectional view of the shingle portion of
the roofing shingle taken along Line 2-2 in FIG. 1.
[0011] FIG. 3 is an enlarged cross-sectional view of a portion of
the roofing shingle cross-section shown in FIG. 2.
[0012] FIG. 4 is a schematic view of an alternate embodiment of the
present invention using chopped copper wire.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring now to the drawings, FIG. 1 shows an algae
resistant roofing shingle according to the present invention. The
illustrated roofing shingle, indicated generally at 10, is in large
measure conventional in the art and is intended merely to
illustrate one environment in which this invention may be used.
Thus, the scope of this invention is not intended to be limited for
use with the specific structure for the roofing shingle 10
illustrated in FIG. 1 or with roofing shingles in general. On the
contrary, as will become apparent below, this invention may be used
in any desired environment for the purposes described below. For
example, it will be appreciated that any other roofing material,
such as roll roofing and commercial roofing, may also be formed
according to the present invention.
[0014] The roofing shingle 10 includes a headlap region 12 and a
prime region 14. The headlap region 12 of the shingle 10 is the
portion of the shingle 10 that is covered by adjacent shingles when
the shingle 10 is installed upon a roof. The prime region 14 of the
shingle 10 is the portion of the shingle 10 that remains exposed
when the shingle 10 is installed upon a roof. The prime region 14
is the portion of the shingle 10 where growth of fungus, algae, or
other such microorganisms may occur. The shingle 10 may have any
suitable dimensions. The shingle 10 may also be divided between the
headlap region 12 and the prime region 14 in any suitable
proportion. For example, a typical residential roofing shingle 10
is approximately three feet wide by one foot high, with the height
dimension being equally divided between the headlap region 12 (six
inches) and the prime region 14 (six inches).
[0015] FIGS. 2 and 3 illustrate the composition of the shingle 10
of the present invention. Generally, the shingle 10 consists of a
substrate material 20 that is coated with a coating material,
indicated generally at 22. An application of metallic particles 30
is applied to the coating material 22. A surface layer of granules
32 is preferably applied over the metallic particles 30 and the
coating material 22.
[0016] The substrate 20 can be any suitable material for receiving
the asphalt coating 22, such as fiberglass mat or organic felt
material. The substrate material 20 is preferably coated with an
asphalt coating, indicated generally at 22. It will be appreciated
that any suitable coating material other than asphalt may be used
as well. The asphalt coating 22 includes an upper region 24 and a
lower region 26. The upper region 24 includes an upper surface 28.
The upper region 24 and upper surface 28 are positioned above the
substrate 20 when the roofing material is installed on a roof. The
lower region 26 is positioned below the substrate 20 when the
roofing material is installed on a roof.
[0017] An application of metallic particles 30 is applied to the
upper surface 28 of the asphalt coating 22. The metallic particles
30 are applied to provide the algae and/or fungal resistance to the
shingle 10. The metallic particles 30 may be formed from any
suitable metal or metal alloy that provides an algae/fungus
inhibiting component. The algae/fungus inhibiting component of the
metallic particles 30 provides the appropriate algaecidal and/or
fungicidal properties desired for the algae resistant shingle 10.
Preferably, the algae inhibiting component of the metallic
particles 30 consists essentially of copper or a copper alloy. The
metallic particles 30 can be applied by any suitable mechanism,
such as a vibratory feeder.
[0018] A surface layer of granules 32 is applied to the top surface
28 of the asphalt coating 22. The granules 32 can be any suitable
material typically used in roofing material construction, such as
limestone, ceramic coated limestone, or other stone or ceramic
coated stone material. The granules 32 can be applied in any
suitable manner to the top surface 28 of the asphalt coating 22.
For example, the granules 32 may be applied in a single
application. The granules may also be applied in a series of
applications, such as blend drops and background granules, as is
common practice when multiple colors of granules 32 are applied to
the roofing shingle 10.
[0019] The metallic particles 30 are preferably pre-applied to the
upper surface 28 of the asphalt coating 22. The term "pre-applied",
as used herein, refers to the application of the metallic particles
30 to the asphalt coating 22 prior to the final application of the
surface layer of granules 32. It is preferable that the metallic
particles 30 be applied directly to the upper surface 28 of the
asphalt coating 22 prior to the application of any granules 32. It
will be appreciated, however, that it is also possible to apply the
metallic particles 30 in conjunction with one or more of a series
of granule 32 applications, provided that the metallic particles 30
are applied prior to the final application of the surface granules
32.
[0020] The roofing shingle 10 must contain a suitable amount of
metallic particles 30 to provide algae resistance as the shingle 10
erodes over time when it is installed on a roof. Roofing shingles
10 may be manufactured to different specifications regarding the
duration of protection desired. The desired duration of the algae
resistance of the roofing shingle 10 of the present invention is
preferably at least ten years, and preferably longer. It will be
appreciated, however, that the roofing shingle 10 may have any
suitable desired wear duration. Accordingly, it will also be
appreciated that the composition of the shingle 10 may be adapted
accordingly to obtain the desired duration of algae resistance.
[0021] The amount of metallic particles 30 contained on the roofing
shingle 10 contributes significantly to the overall cost of the
roofing shingle 10. A particular advantage of the present invention
is that the amount of metallic particles 30 required on the roofing
shingle 10 is minimized while still achieving the desired duration
of algae resistance for the roofing shingle 10.
[0022] The metallic particles 30 provide algae/fungus protection
because metallic ions from the algae inhibiting component of the
metallic particles 30 are leached, or drawn out, from the roofing
shingle 10 over time. The leach rate of the algae inhibiting
component from the metallic particles 30 can be measured by the
parts per million (ppm) of the algae inhibiting component present
in a sample of moisture taken from a roofing shingle 10 installed
on a roof. For purposes of this patent, this leach rate measurement
is determined using a "dew test". The dew test can be carried out
in either a natural weathering environment or a simulated
weathering environment. In a natural weathering environment, the
dew test analyzes the concentration of the algae-inhibiting
component of the metallic particles 30 dissolved in dew formed on
the roofing shingles 10 during natural weathering. To collect dew
samples for the analysis, a trough is typically installed below the
lower edge of a north-facing deck covered with the roofing
material, which has a minimum runoff path of 4 feet and a pitch
angle of 22 degrees. When weather permits, dew forms on the roofing
material and runs off into the trough. The dew samples are
collected in the morning hours (i.e. generally between 7:00 a.m.
and 8:00 a.m.) before the dew evaporates from the roofing shingles
10. The dew samples are collected from roofing shingles 10 that
have been naturally weathered for a minimum of 6 months, and at
least 10 collections of dew samples are collected and analyzed to
determine the average algae inhibiting component concentration in
the dew runoff. The dew runoff is preferably analyzed by
inductively-coupled plasma analysis.
[0023] The dew test used for purposes of this patent may also be
carried out in a laboratory under simulated environmental
conditions. Where simulated conditions are used, a sample is cut
from a roofing shingle 10. The dimensions of the roofing shingle
sample are preferably approximately two inches by six inches. The
shingle sample is placed face-up on a Plexiglas.RTM. plate. Thin
strips of butyl tape sealant are placed around the edges of the
sample, and six 3.2 millimeter spacers are placed at the corners
and in the middle of each long dimension. A second Plexiglas.RTM.
sheet fitted with flow ports located 1.375 inches from the opposite
narrow edges of the sample is placed on top of the sample. The
second Plexiglass sheet is pressed to the spacers and the two
plates are then clamped together. The sample is thus enclosed in a
watertight compartment which permits fluid to enter at one end,
then allows a thin sheet-like flow of the fluid across the surface
of the sample, and directs the fluid out the other end. This fluid
flow simulates the natural weathering environment described above.
These sample holders are hung vertically at room temperature and
flow lines are connected to the inlet and outlet ports of the
prepared sample. Fluid is pumped through the holders at a target
rate of 19.4 milliliter per day, which corresponds to 0.30
milliliter per square centimeter per day. The fluid used is
preferably a 0.1 N sodium acetate acetic acid pH 6.0 buffer
solution. This fluid simulates the dew runoff that is collected by
the natural environment dew test described above. The simulated dew
runoff is collected periodically and analyzed for its concentration
of the algae inhibiting component of the roofing shingles 10. The
simulated dew runoff is also preferably analyzed by
inductively-coupled plasma analysis.
[0024] The leach rate of the algae inhibiting component from the
metallic particles 30 on the roofing shingle 10, as determined by
the above dew test method, must be sufficient to provide the
shingle 10 with algae resistant characteristics without prematurely
depleting the metallic particles 30 from the shingle 10. The leach
rate of the algae inhibiting component of the metallic particles 30
for the ten year algae-resistant roofing shingle 10 of the present
invention is preferably within the range of from about 0.3 parts
per million to about 1.0 parts per million as measured in dew
runoff collected from the natural weathering environment. One
skilled in the art appreciates that the leach rate measured from
the simulated test may differ from the natural runoff due to the
relative moisture content and environmental conditions, such as
acidity, etc. It will also be appreciated that the leach rate can
be any other suitable rate or range of rates as well. It will also
be appreciated that the leach rate may be proportionally adjusted
depending upon the desired duration of the algae resistance of the
roofing shingle 10.
[0025] The leach rate of the metallic particles 30 can be affected
by a number of design features of the roofing shingle 10. One such
factor is the percent of metallic particles 30 covered by the
asphalt coating 22 and/or surface granules 32. The metallic
particles 30 are preferably applied such that a portion of the
metallic particles 30 are covered by the asphalt coating 22 or by
the granules 32, and a portion is left exposed. The covering of the
metallic particles 30 by the asphalt coating 22 and/or the granules
32 maximizes the useful life of the metallic particles 30. The
covering of the metallic particles 30 also prevents loss of the
metallic particles 30 that may be caused by exposure to the
elements, such as rain or hail. Additionally, the covering of the
metallic particles 30 helps lessen the undesirable effects of the
metallic particles 30 on the aesthetics of the roofing shingle 10.
The term "covered by the asphalt coating", as used herein, refers
to any particle that is positioned below the top surface 28 of the
asphalt coating 22 and encapsulated within the asphalt coating 22.
The term "covered by the asphalt coating" may also refer to
metallic particles 30 that are covered partially by the asphalt
coating 22 and partially by a granule or granules 32 applied over
the metallic particles 30. Finally, the term "covered by the
Applicants coating" may also refer generally to metallic particles
30 that are not visible on the top surface 28 of the asphalt
coating 22. In the preferred embodiment, greater than fifty percent
of the metallic particles 30 are covered by the asphalt coating 22,
the granules 32, or by both the asphalt coating 22 and the granules
32. In another embodiment, it is preferable that greater than
seventy percent of the metallic particles 30 are covered by the
asphalt coating 22, the granules 32, or by both the asphalt coating
22 and the granules 32. In yet another embodiment, it is preferable
that greater than ninety percent of the metallic particles 30 are
covered by the asphalt coating 22, the granules 32, or by both the
asphalt coating 22 and the granules 32.
[0026] The percentage of metallic particles 30 covered by the
asphalt coating 22 or the granules 32 affects the leach rate of the
metallic particles 30 from the roofing shingle 10. As discussed
above, the leach rate affects the overall algae resistance of the
roofing shingle 10. The covered metallic particles 30 are preserved
within the asphalt coating 22 and/or under the granules 32 until
micro-cracks form in the asphalt coating 22 as the asphalt coating
22 degrades over time or until the granules 32 erode from the
surface of the shingle 10. As the asphalt coating 22 degrades
and/or the surface granules 32 erode, the metallic particles 30 are
exposed and the metal is leached from the roofing shingle 10. By
covering at least a certain percentage of the metallic particles
30, the invention provides a particular advantage in that the
asphalt coating 22 and/or granules 32 protects the metallic
particles 30 from premature leaching. Subsequently, this reduces
the amount of metallic particles 30 required to achieve the desired
algae resistance of the roofing shingle 10 over a long period of
time.
[0027] Another factor affecting the leach rate and the amount of
metallic particles 30 required is the particle geometry of the
metallic particles 30. A common measure of particle geometry is
aspect ratio. The aspect ratio of a metallic particle 30 is the
ratio of the length of the longest dimension of the metallic
particle 30 to the shortest dimension of the metallic particle 30.
Where the aspect ratio of a specified percentage of the individual
metallic particles 30 is low, the surface area of the individual
metallic particles 30 is minimized, and the corresponding leach
rate of the metallic particles 30 is low. This slows down the leach
rate, thereby extending the effective life of the metallic particle
30 with respect to leaching of the metal. Also, this allows for a
reduced amount (by weight) of the metallic particles 30 to be used
on the roofing shingle 10. In the preferred embodiment, greater
than ninety percent of the metallic particles 30 have an aspect
ratio of less than or equal to about 1.5, and more preferably
greater than ninety percent of the metallic particles 30 have an
aspect ratio of less than or equal to 1.3. An example of a metallic
particle 30 having the preferred aspect ratio is copper shot, which
is a small, bead-like copper particle that is nearly spherical in
shape, i.e. having an aspect ratio of approximately one. It will be
appreciated, however, that the metallic particles 30 may have any
suitable particle geometry that provides a sufficient leach rate to
support the reduced application of the metallic particles 30 to the
roofing shingle 10.
[0028] The particle size of the metallic particles 30 may also
contribute to the reduced amount (by weight) of metallic particles
30 required on the roofing shingle 10. To maintain a sufficient
leach rate to control algae growth while minimizing the amount of
metallic particles 30 applied, it is desirable to increase the
surface area of the metallic particles 30. A smaller particle size
increases the overall surface area of the metallic particles 30,
which subsequently increases the metal leach rate of the metallic
particles 30. Preferably, the size of the largest dimension of the
individual metallic particles 30 is within the range of from about
0.05 mm to about 1.0 mm, and is more preferably within the range of
from about 0.1 mm to about 0.5 mm. It will be appreciated, however,
that the particle size may be proportionally adjusted to any other
suitable size or range of sizes depending upon the desired duration
of algae resistance for the roofing shingle 10. It will also be
appreciated that particle size may be proportionally adjusted to
any other suitable size or range of sizes depending upon the metal
consumption rate through leaching or corrosion in the natural
environment of the algae inhibiting component of the metallic
particles 30.
[0029] The reduced size of the metallic particles 30 provides a
number of advantages. The reduced size of the metallic particles
30, relative to conventional metal-leaching particles, allows the
metallic particles 30 to be easily covered by the asphalt coating
22, which is usually heated or otherwise softened during the
manufacturing process. Additionally, those metallic particles 30
that are not covered by the asphalt coating 22 may also be more
easily embedded between the asphalt coating 22 and the surface
granules 32 or covered by the surface granules 32 applied over the
metallic particles 30. The covering of the metallic particles 30
impacts the leach rate of the roofing shingle 10, as discussed
above. The reduced size of the metallic particles 30 also provides
an aesthetic advantage in that the particles 30 that are not
covered by the asphalt coating 30 are less visible when the roofing
shingle 10 is applied on a roof. In fact, particles of a size in
these ranges are substantially visually undetectable from the
ground when the shingles are applied to a roof.
[0030] As discussed above, the improvements of the present
invention permit a reduced amount of metallic particles 30 to be
applied to the roofing shingle 10 while achieving superior algae
resistance on the roofing shingle 10. For the ten year algae
resistant shingle 10 discussed above, the metallic particles 30 are
preferably applied to the roofing material at a rate that provides
the algae inhibiting component of the metallic particles 30 in an
amount within the range of from about 0.05 pounds per square to
about 0.29 pounds per square of roofing shingles 10, and is more
preferably within the range of from about 0.10 to about 0.20 pounds
per square. The term "square" is well recognized in the art and
refers to the amount of roofing shingles 10 necessary to cover one
hundred square feet of roof surface. It will be appreciated that
the amount of metallic particles 30 required per square may be
proportionally adjusted to any other suitable amount depending upon
the algae inhibiting component used and/or the desired duration of
algae resistance for the roofing shingle 10.
[0031] The reduced amount of metallic particles 30 required per
square provides a particular advantage in that it results in a
significant manufacturing cost savings. For example, whereas the
manufacturing costs attributable to conventional metal-leaching
particles, such as metallic chips, flakes, or coated granules, are
approximately $1.00 to $1.50 per square, the cost per square of the
metallic particles 30 of the roofing shingles 10 of the present
invention is approximately $0.50 or less.
[0032] In an alternate embodiment of the invention, as shown in
FIG. 4, the metallic particles are in the form of elongated
copper-containing particles 40, such as recycled copper wire. The
copper functions as the algae inhibiting component of the elongated
particles 40. It will be appreciated that other elongated metallic
particles having any other suitable algae inhibiting component may
also be used, such as elongated particles formed from a copper
alloy or any other suitable metal. The elongated copper-containing
particles 40 function in substantially the same manner as the
metallic particles 30 described above, and are also preferably
pre-applied to the asphalt coating 22 of the roofing shingle 10.
The elongated copper-containing particles may also be applied
within a series of granule 32 applications, as discussed above.
[0033] The elongated copper-containing particles 40 are preferably
applied such that greater than fifty percent of the elongated
copper-containing particles are covered by the asphalt coating 22
or the granules 32, or by both the asphalt coating 22 and the
granules 32 of the roofing shingle 10. As such, the leach rate of
the elongated copper-containing particles is preferably the same as
discussed above, i.e. preferably within the range of from about 0.3
parts per million to about 1.0 parts per million of copper (the
algae inhibiting component). Similarly, the preferred amount of
elongated copper-containing particles 40 applied per square of
roofing material provides within the range of from about 0.05 to
about 0.29 pounds of copper per square, and is more preferably
within the range of from about 0.10 to about 0.20 pounds of copper
per square of roofing material.
[0034] The elongated copper-containing particles 40 may have any
suitable aspect ratio. Preferably, the aspect ratio of the
copper-containing particles is within the range of from about 1.5
to about 200, and more preferably within the range of from about 10
to about 50. The elongated copper-containing particles preferably
have a substantially circular cross-section, although it will be
appreciated that the copper-containing particles may have any other
suitable cross-sectional shape as well. The diameter of the
cross-section of the elongated copper-containing particles is
preferably within the range of from about 0.050 mm to about 1.5
mm.
[0035] A particular advantage of using the elongated
copper-containing particles is the availability of the material and
the subsequent cost savings associated therewith. As mentioned
above, copper wire, which is readily available in scrap or recycled
form, may be used to form the elongated copper-containing particles
40. Subsequently, the use of the recycled copper wire may even
further reduce the manufacturing costs of the algae resistant
roofing shingle 10 discussed above.
[0036] The principle and mode of operation of this invention have
been described in its preferred embodiments. However, it should be
noted that this invention can be practiced otherwise than as
specifically illustrated and described without departing from its
scope.
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