Title:
Algae resistant shingle
Kind Code:
A1


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, US)
Application Number:
11/066644
Publication Date:
08/31/2006
Filing Date:
02/25/2005
Primary Class:
International Classes:
E01F9/04
View Patent Images:



Primary Examiner:
MOORE, WALTER A
Attorney, Agent or Firm:
OWENS CORNING (GRANVILLE, OH, US)
Claims:
What is claimed is:

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

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

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.

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.

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.

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

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.

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.

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

FIG. 1 is a perspective view of the roofing shingle of the present invention.

FIG. 2 is a cross-sectional view of the shingle portion of the roofing shingle taken along Line 2-2 in FIG. 1.

FIG. 3 is an enlarged cross-sectional view of a portion of the roofing shingle cross-section shown in FIG. 2.

FIG. 4 is a schematic view of an alternate embodiment of the present invention using chopped copper wire.

DETAILED DESCRIPTION OF THE INVENTION

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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® 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® 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.