U.S. patent application number 13/932983 was filed with the patent office on 2013-11-07 for controlled time-release algae resistant roofing system.
The applicant listed for this patent is Keith C. Hong, Husnu M. Kalkanoglu, Joong Youn Kim, Ming Liang Shiao. Invention is credited to Keith C. Hong, Husnu M. Kalkanoglu, Joong Youn Kim, Ming Liang Shiao.
Application Number | 20130295155 13/932983 |
Document ID | / |
Family ID | 38175510 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130295155 |
Kind Code |
A1 |
Kalkanoglu; Husnu M. ; et
al. |
November 7, 2013 |
CONTROLLED TIME-RELEASE ALGAE RESISTANT ROOFING SYSTEM
Abstract
Time-release algae-resistant roofing granules have a base
particle including an algaecide and an outer coating layer
including another algaecide. The at least two algaecides are
released over different predetermined periods. The outer layer
protects the base particle from exposure to the environment for a
predetermined period, then fails catastrophically so that the
interior algaecide can be released.
Inventors: |
Kalkanoglu; Husnu M.;
(Swarthmore, PA) ; Hong; Keith C.; (Lititz,
PA) ; Kim; Joong Youn; (Newtown Square, PA) ;
Shiao; Ming Liang; (Collegeville, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kalkanoglu; Husnu M.
Hong; Keith C.
Kim; Joong Youn
Shiao; Ming Liang |
Swarthmore
Lititz
Newtown Square
Collegeville |
PA
PA
PA
PA |
US
US
US
US |
|
|
Family ID: |
38175510 |
Appl. No.: |
13/932983 |
Filed: |
July 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11610405 |
Dec 13, 2006 |
|
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13932983 |
|
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|
|
60597903 |
Dec 23, 2005 |
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Current U.S.
Class: |
424/419 ;
424/417; 424/630; 424/635; 424/641; 427/214 |
Current CPC
Class: |
A01N 59/16 20130101;
Y10T 428/2998 20150115; A01N 59/20 20130101; Y10T 428/31815
20150401; Y10T 428/2993 20150115; E04D 2001/005 20130101; A01N
59/16 20130101; A01N 25/12 20130101; Y10T 428/2991 20150115; E04D
13/002 20130101; E04D 1/00 20130101; E04D 5/12 20130101; A01N 59/20
20130101; A01N 25/12 20130101; Y10T 428/24372 20150115; A01N 59/16
20130101; A01N 25/26 20130101; C09D 5/14 20130101; A01N 59/20
20130101; A01N 59/16 20130101; C09C 1/00 20130101; A01N 25/26
20130101; A01N 2300/00 20130101; A01N 2300/00 20130101; A01N 25/26
20130101; A01N 25/12 20130101 |
Class at
Publication: |
424/419 ;
427/214; 424/417; 424/630; 424/641; 424/635 |
International
Class: |
E04D 1/00 20060101
E04D001/00 |
Claims
1. A process for producing time-release algae-resistant roofing
granules, the process comprising: (a) providing base particles
comprising at least one first algaecidal material; (b) providing an
interlayer on the base particles, the interlayer enhancing the
release of the at least one first algaecidal material under
predetermined conditions, and (c) encapsulating the
interlayer-covered base particles with an outer coating composition
including at least one second algaecidal material to form an outer
layer, the at least one second algaecidal material differing from
the at least one first algaecidal material, the encapsulating outer
layer protecting the base particles from exposure to the
environment, the at least one second algaecidal material being
releasable from the outer layer during a predetermined period.
2. A process according to claim 1 further comprising; (a) providing
inert core particles; and (b) forming the base particles by coating
the inert core particles with an inner coating composition to form
an inner layer on the inert core particles, the inner coating
composition including the at least one first algaecidal
material.
3. A process according to claim 2 wherein the inner coating
composition includes a binder comprising an aluminosilicate
material and an alkali metal silicate.
4. A process according to claim 1 wherein the at least one first
algaecidal material is selected from the group consisting of copper
compounds, zinc compounds, and mixtures thereof.
5. A process according to claim 1 wherein the outer coating
composition includes a binder comprising a material selected from
the group consisting of an organic polymeric material or/and an
inorganic material.
6. A process according to claim 1 further comprising providing base
particles comprising metallic granules.
7. A process according to claim 1 wherein the interlayer includes a
UV degradable material selected from the group consisting of virgin
and recycled natural or synthetic polymers and copolymers and
combinations thereof.
8. A process according to claim 1 wherein the interlayer includes a
photocatalytic material.
9. Time-release algae-resistant roofing granules, each granule
comprising: (a) a base particle comprising at least one first
algaecidal material; and (b) an interlayer formed on the base
particles, the interlayer enhancing the release of the at least one
first algaecidal material under predetermined conditions, and (c)
at least one outer coating layer formed from an outer coating
composition including at least one second algaecidal material and
encapsulating the base particle, the at least one second algaecidal
material differing from the at least one first algaecidal material,
the encapsulating at least one outer layer protecting the base
particle from exposure to the environment, the at least one second
algaecidal material being releasable from the outer layer during a
predetermined period.
10. Time-release algae-resistant roofing granules according to
claim 9 wherein the base particles comprise inert core particles
coated with an inner coating composition to form an inner layer on
the inert core particles, the inner coating composition including
the at least one first algaecidal material.
11. Time-release algae-resistant roofing granules according to
claim 9 wherein the at least one first algaecidal material is
releasable from the granule during a second predetermined
period.
12. Time-release algae-resistant roofing granules according to
claim 9 wherein the inner coating composition includes a binder
comprising an aluminosilicate material and an alkali metal
silicate.
13. Time-release algae-resistant roofing granules according to
claim 9 wherein the at least one first algaecidal material is
selected from the group consisting of copper compounds, zinc
compounds, and mixtures thereof.
14. Time-release algae-resistant roofing granules according to
claim 13 wherein the at least one first algaecidal material is
cuprous oxide.
15. Time-release algae-resistant roofing granules according to
claim 9 wherein the outer coating composition includes a binder
comprising a material selected from the group consisting of an
organic polymeric material and an inorganic material.
16. Time-release algae-resistant roofing granules according to
claim 15 wherein the at least one second algaecidal material is
initially uniformly dispersed in the binder, and subsequently
diffuses to the exterior surface of the outer layer.
17. Time-release algae-resistant roofing granules according to
claim 9 wherein the at least one second algaecidal material is an
organic biocide.
18. Time-release algae-resistant roofing granules according to
claim 17 wherein the binder is selected from the group consisting
of poly(meth)acrylate, polyurethanes and polyureas and the
inorganic materials include aluminosilicate, silica and phosphate
binders.
19. Time-release algae-resistant roofing granules according to
claim 9 wherein the outer layer has a thickness of from about 5
micrometers to about 200 micrometers.
20. Time-release algae-resistant roofing granules according to
claim 9 wherein the base particles comprise metallic granules.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of pending U.S.
patent application Ser. No. 11/610,405 filed Dec. 13, 2006, and
claims the priority of U.S. Provisional Patent Application
60/597,903 filed Dec. 23, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to asphalt roofing shingles,
protective granules for such shingles, and processes for making
such granules and shingles.
[0004] 2. Brief Description of the Prior Art.
[0005] Pigment-coated mineral rocks are commonly used as color
granules in roofing applications to provide aesthetic as well as
protective functions to the asphalt shingles. Dark blotches or
streaks sometimes appear on the surfaces of asphalt shingles,
especially in warmer humid climates, because of the growth of algae
and other microorganisms. The predominant species responsible is
Gloeocapsa sp, a blue-green algae. Other microbial growth,
including fungi, moss and lichen, can also occur under proper
conditions, for example, in a shady and/or persistently damp
environment. In addition to being aesthetically unpleasant, the
discoloration can lead to heat buildup and accelerate premature
roofing failure. Eventually, severe discoloration of the entire
roof can occur.
[0006] Various methods have been used in an attempt to remedy the
roofing discoloration. Washing the roof surfaces with dilute
cleaning solutions containing a strong oxidizer such as bleach can
remove the algae from roofs. However, frequent washing and cleaning
with cleaning solutions is required, since the effective duration
of such treatments is rather short. In addition, topical treatments
with organic algaecides have been used. However, such topical
treatments are also usually effective only for short term,
typically one to two years.
[0007] If the freshly cleaned surfaces are treated with a coating
containing some form of biocides, the antimicrobial properties
could remain for a long period of time, between five to seven
years. To prevent algal growth, various types of biocides have been
used. The most commonly used biocides are metals and inorganic
metal oxides, such as, for example zinc metal granules and copper
oxide-coated granules. However, these biocides typically persist
for around ten years, and in some limited cases, for periods
approaching fifteen years. One drawback is these compounds are
effective against only one microbe, Gloeocapsa sp. At the same
time, the service life of roofing products can extend considerably
longer than ten to fifteen years, depending on the composition and
structure of the roofing materials employed to construct the
roof.
[0008] Companies, including Minnesota Mining and Manufacturing (3M)
and ISP Mineral Products Inc., have commercialized several
algaecide granules that are effective in inhibiting algae
growth.
[0009] A common method used to prepare algae-resistant (AR) roofing
granules generally involves two major steps. In the first step,
metal oxides such as cuprous oxide and/or zinc oxide are added to a
clay and alkali metal silicate mixture. The mixture in turn is used
to coat crushed mineral rocks. The mixture is rendered insoluble on
the rock surfaces by firing at high temperatures, such as about
500.degree. C., to provide a ceramic coating. In the second step,
the oxides covered rocks are coated with various color pigments to
form colored algae-resistant roofing granules. The algae-resistant
granules, alone, or in a mixture with conventional granules, are
then used in the manufacture of asphalt shingles using conventional
techniques. The presence of the algae-resistant granules confers
algae-resistance on the shingles.
[0010] Roofing granules typically comprise crushed and screened
mineral materials, which are subsequently coated with a binder
containing one or more coloring pigments, such as suitable metal
oxides. The binder can be a soluble alkaline silicate that is
subsequently insolubilized by heat or by chemical reaction, such as
by reaction between an acidic material and the alkaline silicate,
resulting in an insoluble colored coating on the mineral
particles.
[0011] U.S. Pat. No. 3,507,676 discloses roofing granules
containing zinc, zinc oxide, or zinc sulfide, as an algaecide and
fungicide.
[0012] Algae resistant shingles are disclosed, for example, in U.S.
Pat. No. 5,356,664 assigned to Minnesota Mining and Manufacturing
Co., which discloses the use of a blend of algae-resistant granules
and non-algae-resistant granules. The algae-resistant granules have
an inner ceramic coating comprising cuprous oxide and an outer seal
coating initially devoid of copper.
[0013] There is a continuing need for algae-resistant roofing
products having algaecide leaching rates that can be controlled so
that the roofing products can be tailored for specific local
conditions. In addition, there is a continuing need for
algae-resistant roofing products that can provide sustained
algae-resistance over extended periods of time.
SUMMARY OF THE INVENTION
[0014] The present invention provides algae-resistant roofing
granules, algae-resistant sheet roofing products such as asphalt
shingles and roofing membranes, and processes for make such
products. Algae-resistance is provided by a plurality of
antimicrobial agents, which exhibit different release rates over
time. In one presently preferred embodiment, degradable boundary or
containment layers are used to control the release of biocides.
[0015] However, in general, the present invention provides at least
a first anti-microbial agent and a second anti-microbial agent, the
first anti-microbial agent and the second anti-microbial agent each
having characteristic and differing release rates from the
algae-resistant roofing granules, such that the different release
behavior results in effective algae resistance over a longer period
than if only the first anti-microbial agent or the second
anti-microbial agent were employed in the absence of the other. The
differing release rates can be the result of the physical and/or
chemical characteristics of the anti-microbial agents themselves.
For example, the first anti-microbial agent may differ in aqueous
solubility from the second anti-microbial agent. In addition, or
alternatively, the difference in release rates may be related to
the physical structure of the algae-resistant granules. For
example, the algae-resistant granule may include at least two
coating layers. In this case, the first anti-microbial agent may be
dispersed in an inner coating layer, with the second anti-microbial
agent being dispersed in an outer coating layer, such that the
outer coating layer(s) inhibits the diffusion of the first
anti-microbial agent from the algae-resistant granules. The outer
coating layer(s) can include, for example, a layer of a degradable
material, that fails catastrophically after a predetermined period.
Such a structure, or interlayer, can provide for an induction
period before the first algae-resistant agent is effectively
released from the algae-resistant granules. During the induction
period for release of the first anti-microbial agent, the second
anti-microbial agent can be diffusing out from an outer layer of
the granule, thus providing interim algae resistance.
[0016] In one presently preferred embodiment of the present
invention, the algae-resistant sheet roofing products include
algae-resistant roofing granules.
[0017] The present invention provides a process for producing
time-release algae-resistant roofing granules. This process
comprises providing base particles comprising at least one first
algaecidal material. As disclosed below, the base particles can be
prepared in a number of different ways. The base particles are in
turn encapsulated with an outer coating composition including at
least one second algaecidal material to form an outer layer. The at
least one second algaecidal material preferably differs from the at
least one first algaecidal material. The encapsulating outer layer
protects the base particles from exposure to the environment. The
outer coating composition is preferably selected such that the
outer layer fails catastrophically after a predetermined period
thereby exposing the base particles to the environment. In the
interim, during the predetermined period, the at least one second
algaecidal material is releasable from the outer layer, thereby
providing algae resistance. After the outer layer fails, the base
particle is exposed to the environment, and the at least one first
algaecidal material thereafter provides algae resistance.
[0018] In one presently preferred embodiment, the base particles
are prepared by providing inert core particles, and subsequently
forming the base particles by coating the inert core particles with
an inner coating composition to form an inner layer on the inert
core particles. In this case, the inner coating composition
preferably includes the at least one first algaecidal material.
[0019] Preferably, the inner coating composition includes a binder,
which preferably comprises an aluminosilicate material, such as
clay, and an alkali metal silicate. The inner coating composition
can also include colorants, or solar reflective additives, such as
metal oxide pigments.
[0020] In the present process, the at least one first algaecidal
material of the inner coating composition is preferably selected
from the group consisting of compounds and/or zinc compounds, and
mixtures thereof, with cuprous oxide and zinc oxide being
especially preferred. When cuprous oxide is employed as the at
least one first algaecidal material, the cuprous oxide preferably
comprises at least 0.5 percent of the algae-resistant granules.
When zinc oxide is employed as the at least one first algaecidal
material, the zinc oxide preferably comprises at least 0.05 percent
by weight of the algae-resistant granules.
[0021] In another presently preferred embodiment of the present
process, the base particles are prepared by providing a metallic or
metal oxide granule core, such as zinc granules or copper oxide
granules. In this case, the at least one first algaecidal material
is preferably selected from the group consisting of zinc, copper
and copper oxide.
[0022] In another presently preferred embodiment of the present
process, the base particles are prepared by providing the at least
one first algaecidal material, and forming the base particles by
encapsulating the at least one first algaecidal material in
microshells. Each microshell has a wall enclosing an interior
cavity, and the interior cavity contains the at least one first
algaecidal material. Preferably, the microshell wall is at least
partially permeable to the at least one first algaecidal
material.
[0023] In a presently preferred embodiment of the process of the
present invention, the process further comprises providing an
interlayer on the base particles. The interlayer preferably
enhances the release of the at least one second algaecidal material
under predetermined conditions. In one aspect of the process of the
present invention, the interlayer preferably includes a
water-swellable resin. Preferably, the water-swellable resin is
selected from the group consisting of natural or synthetic
water-swellable resins, starch, cellulose, and gums. In another
aspect of the process of the present invention, the interlayer
preferably includes a UV degradable material. Optionally, a
photocatalytic material, such as, for example, the anatase form of
titanium oxide, can also be added to modify material degradation.
Preferably, the UV degradable polymeric material is selected from
the group consisting of virgin and recycled polyolefins and
polyolefin copolymers, and combinations thereof. In a further
aspect of the process of the present invention, the at least one
first algaecidal material releases algaecidal metal ions, and the
interlayer includes at least one metal oxidizable by the algaecidal
metal ions. Preferably, in this case the at least one first
algaecidal material releases copper ions, and the interlayer
includes zinc.
[0024] Preferably, in the present process, the outer coating
composition includes a binder. Preferably, the composition and/or
morphology of the encapsulating outer layer are selected such that
the encapsulating outer layer fails after a predetermined time to
expose the first layer to the environment. Thus, the second
algaecide is released from the outer layer during the initial
predetermined period.
[0025] In one presently preferred embodiment, the binder of the
outer coating composition comprises an organic polymeric material.
The organic polymeric material is preferably selected from the
group consisting of poly(meth)acrylates, polyurethanes and
polyureas; and the inorganic material is an aluminosilicate or
phosphate material. In the process of the present invention, the at
least one second algaecidal material is preferably initially
uniformly dispersed in the organic polymeric material. The second
algaecidal material subsequently diffuses to the exterior surface
of the outer layer and is released into the environment.
[0026] In another presently preferred embodiment, the binder of the
outer coating composition comprises an inorganic material. The
inorganic polymeric material is preferably selected from the group
consisting of aluminosilicate, silica and phosphate materials.
Silica materials may be derived, for example, from sol-gel
chemistries or colloidal silica dispersions or suspensions, or the
like. In the process of the present invention, the at least one
second algaecidal material is preferably initially uniformly
dispersed in the inorganic material. The second algaecidal material
subsequently diffuses to the exterior surface of the outer layer
and is released into the environment.
[0027] In a presently preferred embodiment, the at least one second
algaecidal material is a quaternary ammonium compound. Preferably,
the quaternary ammonium compound is selected from the group
consisting of n-alkyl dimethyl benzyl ammonium chloride, dimethyl
didecyl ammonium chloride, and
poly(oxy-1,2-ethanediyl(dimethylimino)-1,2-ethanediyl(dimethylimino)-1,2--
ethanediyl dichloride). In some instances it may be desirable to
employ a quaternary ammonium functionality bound to an organic
polymer structure. In a preferred such material, the organic
polymeric material is a poly(meth)acrylate including at least one
quaternary ammonium salt functional group. Other polymer backbone
structures could also be employed.
[0028] In a presently preferred embodiment, the at least one second
algaecidal material is an organic biocide compound. Preferably, the
organic biocide can include one or more compounds that are halogen
based, nitrogen based, sulfur based, or phenolics. An exemplary
halogen based organic biocide is 3-iodo-2-propynylbutyl carbamate
(IPBC). Oxazolidine compounds are representative of nitrogen based
biocides. An exemplary sulfur based organic biocide is
2-n-octyl-4-isothiazolin-3-one (OIT). An example of a phenolic
organic biocide is trichlorophenoxy phenol (TCPP).
[0029] Preferably, the outer layer has a thickness of from about 5
micrometers to about 200 micrometers, and more preferably the outer
layer has a thickness of from about 12.5 micrometers to about 40
micrometers.
[0030] The present invention also provides time-release
algae-resistant roofing granules. Each such granule comprises a
base particle that includes at least one first algaecidal material.
The base particles are encapsulated with an outer coating
composition that forms an outer layer and which includes at least
one second algaecidal material. Preferably, the at least one second
algaecidal material differs from the at least one first algaecidal
material. The at least one second algaecidal material provides
algae-resistance during an initial predetermined period. During
this initial predetermined period, the outer layer encapsulating
the base particles preferably protects the base particles from
substantial exposure to the environment. The composition and/or the
morphology of the outer coating layer is preferably selected so
that the outer layer fails catastrophically after the initial
predetermined period, thereby exposing the base particle to the
environment. After the failure of the outer layer, the base
particle is exposed to the environment, and the at least one first
algaecidal material thereafter provides algae resistance.
[0031] In one presently preferred embodiment, the base particles
are prepared by providing inert core particles, and subsequently
forming the base particles by coating the inert core particles with
an inner coating composition to form an inner layer on the inert
core particles. In this case, the inner coating composition
preferably includes the at least one first algaecidal material.
[0032] Preferably, the inner coating composition includes a binder,
with the binder preferably comprising an aluminosilicate material,
preferably clay, and an alkali metal silicate. The inner coating
composition can also include colorants, such as metal oxide
pigments.
[0033] Preferably, the at least one first algaecidal material of
the inner coating composition is selected from the group consisting
of copper compounds, zinc compounds, and mixtures thereof. In one
presently, preferred embodiment, the at least one first algaecidal
material is cuprous oxide. In this embodiment, the cuprous oxide
comprises at least about 0.5 percent of the algae-resistant
granules. In another presently preferred embodiment, the at least
one first algaecidal material is zinc oxide. In this embodiment,
the zinc oxide comprises at least about 0.05 percent by weight of
the algae-resistant granules.
[0034] In another presently preferred embodiment of the
algae-resistant roofing granules of the present invention, the base
particles include a metallic or metal oxide granule core, such as
zinc granules or copper oxide granules. In this case, the at least
one first algaecidal material is preferably selected from the group
consisting of zinc, copper and copper oxide.
[0035] In yet another presently preferred embodiment, the base
particles comprise microshells encapsulating the at least one first
algaecidal material. Each microshell has a wall enclosing an
interior cavity, and the interior cavity contains the at least one
first algaecidal material. Preferably, the microshell wall is at
least partially permeable to the at least one first algaecidal
material.
[0036] In a presently preferred embodiment of the algae-resistant
roofing granules of the present invention, the granules further
comprise an interlayer between the base particle and the outer
layer. The interlayer preferably enhances the release of the at
least one second algaecidal material under predetermined
conditions. In one aspect of the present invention, the interlayer
preferably includes a water-swellable resin. Preferably, the
water-swellable resin is selected from the group consisting of
natural or synthetic water-swellable resins, starch, cellulose, and
gums. In another aspect of the process of the present invention,
the interlayer preferably includes a UV degradable material, and
may optionally include a photocatalytic material. Preferably, the
UV degradable polymeric material is selected from the group
consisting of virgin and recycled polyolefins and polyolefin
copolymers, and combinations thereof.
[0037] In a further aspect of the present invention, the at least
one first algaecidal material releases algaecidal metal ions, and
the interlayer includes at least one metal oxidizable by the
algaecidal metal ions. Preferably, in this case the at least one
first algaecidal material releases copper ions, and the interlayer
includes zinc.
[0038] In a presently preferred embodiment, the at least one second
algaecidal material is a quaternary ammonium compound. Preferably,
the quaternary ammonium compound is selected from the group
consisting of n-alkyl dimethyl benzyl ammonium chloride, dimethyl
didecyl ammonium chloride, and
poly(oxy-1,2-ethanediyl(dimethylimino)-1,2-ethanediyl(dimethylimino)-1,2--
ethanediyl dichloride). Preferably, the organic polymeric material
comprises a poly(meth)acrylate including at least one quaternary
ammonium salt functional group.
[0039] In another presently preferred embodiment, the at least one
second algaecidal material is an organic biocide compound.
Preferably, the organic biocide can include one or more compounds
that are halogen based, nitrogen based, sulfur based, or phenolics.
An exemplary halogen based organic biocide is
3-iodo-2-propynylbutyl carbamate (IPBC). Oxazolidine compounds are
representative of nitrogen based biocides. An exemplary sulfur
based organic biocide is 2-n-octyl-4-isothiazolin-3-one (OIT). An
example of a phenolic organic biocide is trichlorophenoxy phenol
(TCPP).
[0040] In general, it is preferable that the outer layer have a
thickness of from about 5 micrometers to about 200 micrometers; and
more preferably, the outer layer has a thickness of from about 12.5
micrometers to about 40 micrometers.
[0041] The present invention also provides a sheet-roofing product,
such as asphalt roof shingles or roofing membranes. In one
embodiment, a sheet-roofing product according to the present
invention includes a bituminous base and algae-resistant roofing
granules according to the present invention.
[0042] The algae-resistant granules prepared according to the
process of the present invention can be employed in the manufacture
of algae-resistant roofing products, such as algae-resistant
asphalt shingles or roofing membranes. The algae-resistant granules
of the present invention can be mixed with conventional roofing
granules, and the granule mixture can be embedded in the surface of
bituminous roofing products using conventional methods.
Alternatively, the algae-resistant granules of the present
invention can be substituted for conventional roofing granules in
manufacture of bituminous roofing products, such as asphalt roofing
shingles, to provide those roofing products with
algae-resistance.
[0043] It is an object of the present invention to provide a
process for preparing roofing shingles to have algae-resistance
that can be customized to the specific geographic region in which
the shingles are intended to be used.
[0044] It is a further object of the present invention to provide
algae-resistant roofing granules having controllable levels of
algaecide release.
[0045] It is a further object of the present invention to provide
asphalt roofing shingles resistant to algae over extended
periods.
[0046] These and other objects of the invention will become
apparent through the following description and claims.
BRIEF DESCRIPTION OF THE FIGURES
[0047] FIG. 1 is a schematic representation of a first type of an
algae-resistant granule of the present invention.
[0048] FIG. 2 is a schematic representation of a second type of an
algae-resistant granule of the present invention.
[0049] FIG. 3 is a schematic representation of a third type of an
algae-resistant granule of the present invention.
[0050] FIG. 4 is a schematic representation of a fourth type of an
algae-resistant granule of the present invention.
[0051] FIG. 5 is a schematic representation graphing the release of
algaecide from algae-resistant granules of the present invention as
a function of time.
[0052] FIG. 6 is a graph showing the release of copper ions as a
function of time from algae-resistant granules according to the
present invention prepared according to Example 1.
[0053] FIG. 7 is a graph showing the release of copper ions as a
function of time from algae-resistant granules according to the
present invention prepared according to Example 2.
[0054] FIG. 8 is a graph showing the release of copper ions as a
function of time from algae-resistant granules according to the
present invention prepared according to Example 3.
DETAILED DESCRIPTION
[0055] The present invention provides algae-resistant roofing
granules, algae-resistant sheet roofing products such as asphalt
shingles or roofing membranes, and processes for make such
products. In the present invention algae-resistance is provided by
a plurality of antimicrobial agents, each of which exhibits
different release rates over time. In one presently preferred
embodiment, degradable boundary or containment layers are used to
control the release of one or more of the biocides.
[0056] In one presently preferred embodiment, the present invention
provides a process for producing time-release algae-resistant
roofing granules. In this embodiment the process comprises
providing base particles comprising at least one first algaecidal
material, and encapsulating the base particles with an outer
coating composition including at least one second algaecidal
material to form an outer layer, the at least one second algaecidal
material differing from the at least one first algaecidal material,
the encapsulating outer layer protecting the base particles from
exposure to the environment, the outer coating composition being
selected such that the at least one second algaecidal material is
releasable from the outer layer during a first predetermined
period. Preferably, this process further comprises providing inert
core particles, and forming the base particles by coating the inert
core particles with an inner coating composition to form an inner
layer on the inert core particles, the inner coating composition
including the at least one first algaecidal material. Preferably,
in this embodiment of the process of the present invention the at
least one first algaecidal material is releasable from the granule
during a second predetermined period. Preferably, in this
embodiment, the at least one first algaecidal material is selected
from the group consisting of copper compounds, zinc compounds and
mixtures thereof. Preferably, in this embodiment, the outer coating
composition is selected such that the outer layer fails
catastrophically after a predetermined period thereby exposing the
base particles to the environment.
[0057] In another presently preferred embodiment, the present
invention provides time-release algae-resistant roofing granules,
each granule comprising (a) a base particle comprising at least one
first algaecidal material, and (b) at least one outer coating layer
formed from an outer coating composition including at least one
second algaecidal material and encapsulating the base particle,
with the at least one second algaecidal material differing from the
at least one first algaecidal material, the at least one outer
layer protecting the base particle from exposure to the
environment, and the outer coating composition being selected such
that the at least one second algaecidal material is releasable from
the outer layer during a first predetermined period. In this
embodiment, it is preferred that the base particles comprise inert
core particles coated with an inner coating composition to form an
inner layer on the inert core particles, with the inner coating
composition including the at least one first algaecidal material.
Preferably, the at least one first algaecidal material is
releasable from the granule during a second predetermined period.
Preferably, the at least one first algaecidal material is selected
from the group consisting of copper compounds, zinc compounds, and
mixtures thereof. Preferably, the at least one first algaecidal
material is cuprous oxide. Preferably, the outer coating
composition is selected such that the outer layer fails
catastrophically after a predetermined period thereby exposing the
base particles to the environment.
[0058] In yet another presently preferred embodiment, the present
invention provides a sheet roofing product including a bituminous
base and time-release algae-resistant roofing granules. In this
product, each granule comprises (a) a base particle comprising at
least one first algaecidal material, and (b) at least one outer
coating layer formed from an outer coating composition including at
least one second algaecidal material and encapsulating the base
particle, with the at least one second algaecidal material
differing from the at least one first algaecidal material, the at
least one outer layer protecting the base particle from exposure to
the environment, and the outer coating composition being selected
such that the at least one second algaecidal material is releasable
from the outer layer during a first predetermined period, the at
least one first algaecidal material being releasable from the
granule during a second predetermined period.
[0059] Some of the presently preferred embodiments of the
algae-resistant roofing granules of the present invention can be
prepared through traditional granule preparation methods, such as
those disclosed in U.S. Pat. No. 2,981,636, incorporated herein by
reference. Other embodiments employ coating compositions including
synthetic or natural organic polymeric binders.
[0060] In the algae-resistant roofing granules of the present
invention, base particles are encapsulated in an outer coating that
preferably fails catastrophically after an initial predetermined
period. The base particles include at least one first algaecidal
material, and the outer coating layer includes at least one second
algaecidal material. During the initial predetermined period,
algae-resistance is provided by the at least one second algaecidal
material in the outer coating layer. After the initial
predetermined period and the failure of the outer coating layer,
algae resistance is provided by the at least one first algaecidal
material of the base particles.
[0061] The base particles employed in the process of preparing the
algae-resistant granules of the present invention can take several
forms.
[0062] In one presently preferred embodiment, the base particles
are prepared using inert core particles, which are subsequently
coated with a first or inner coating composition including at least
one first algaecidal material to form a first or inner layer on the
core particles.
[0063] In this embodiment, the core particles are preferably
chemically inert materials, such as inert mineral particles, solid
or hollow glass or ceramic spheres, or foamed glass or ceramic
particles. Suitable mineral particles can be produced by a series
of quarrying, crushing, and screening operations, are generally
intermediate between sand and gravel in size (that is, between
about #8 US mesh and #70 US mesh). Preferably, the core particles
have an average particle size of from about 0.2 mm to about 3 mm,
and more preferably from about 0.4 mm to about 2.4 mm.
[0064] In particular, suitably sized particles of naturally
occurring materials such as talc, slag, granite, silica sand,
greenstone, andesite, porphyry, marble, syenite, rhyolite, diabase,
greystone, quartz, slate, trap rock, basalt, and marine shells can
be used, as well as recycled manufactured materials such as crushed
bricks, concrete, porcelain, fire clay, and the like.
[0065] Solid and hollow glass spheres are available, for example,
from Potters Industries Inc., P.O. Box 840, Valley Forge, Pa.
19482-0840, such as SPHERIGLASS.RTM. solid "A" glass spheres
product grade 1922 having a mean size of 0.203 mm, product code
602578 having a mean size of 0.59 mm, BALLOTTINI impact beads
product grade A with a size range of 600 to 850 micrometers (U.S.
Seive size 20-30), and QCEL hollow spheres, product code 300 with a
mean particle size of 0.090 mm. Glass spheres can be coated with a
suitable coupling agent if desired for better adhesion to the
binder of the inner coating composition.
[0066] In preparing algae-resistant roofing granules according to
this embodiment of the process of the present invention,
intermediate or base particles are formed by coating the inert core
particles with a first or inner coating composition including at
least one first algaecidal material to form at least one first or
inner layer on the inert core particles, and thus to encapsulate
the inert core particles. The inner coating composition includes at
least one first algaecidal material, and preferably includes a
suitable coating binder. The coating binder can be an inorganic or
organic material, and is preferably formed from a polymeric organic
material or a silicaceous material, such as a metal-silicate
binder, for example an alkali metal silicate, such as sodium
silicate.
[0067] When a metal-silicate binder is employed in the preparation
of algae-resistant granules of the present invention, the binder
preferably includes a heat-reactive aluminosilicate material, such
as clay, preferably, kaolin. Alternatively, the metal silicate
binder can be insolubilized chemically by reaction with an acidic
material, for example, ammonium chloride, aluminum chloride,
hydrochloric acid, calcium chloride, aluminum sulfate, and
magnesium chloride, such as disclosed in U.S. Pat. Nos. 2,591,149,
2,614,051, 2,898,232 and 2,981,636, each incorporated herein by
reference, or other acidic material such as aluminum fluoride. In
another alternative, the binder can be a controlled release
sparingly water-soluble glass such as a phosphorous pentoxide glass
modified with calcium fluoride, such as disclosed in U.S. Pat. No.
6,143,318, incorporated herein by reference.
[0068] Suitable inert core particles, for example, mineral
particles with size passing #8 mesh and retaining on #70 mesh, can
be coated with a combination of the at least one first algaecidal
material, a metal-silicate binder, kaolin clay, and, optionally,
color pigments such as metal oxide pigments to reach desirable
colors, followed by a heat treatment to obtain a durable inner
layer or coating.
[0069] When a metal silicate binder is used, the at least one first
algaecidal material is preferably selected to resist heat-induced
degradation such as that encountered during elevated temperature
cure of the metal silicate binder. Thus, in this case, the at least
one first algaecidal material is preferably an inorganic algaecidal
material, such as cuprous oxide, zinc oxide, or the like.
Conversely, when, for example, a polymeric organic material is
employed as a binder for the inner layer coating composition, such
as a polymeric (meth)acrylate, an epoxide, or the like, which does
not require an elevated temperature cure, the at least one first
algaecidal material can be an organic algaecidal material.
[0070] When the coated core particles are fired at an elevated
temperature, such as at least about 400 degrees C., and preferably
at about 500 to about 650 degrees C., the clay binder densifies to
form strong particles.
[0071] Examples of clays that can be employed in the process of the
present invention include kaolin, other aluminosilicate clays,
Dover clay, bentonite clay, etc.
[0072] In the alternative, a suitable silicaceous binder can be
formed from sodium silicate, modified by the addition of at least
one of sodium fluorosilicate, aluminum fluoride, or Portland
cement.
[0073] Preferably, the at least one first algaecidal material of
the inner coating composition is selected from the group consisting
of copper compounds, zinc compounds, and mixtures thereof. In one
presently preferred embodiment, the at least one first algaecidal
material is cuprous oxide. In this embodiment, the cuprous oxide
comprises at least 0.5 percent of the algae-resistant granules. In
another presently preferred embodiment, the at least one first
algaecidal material is zinc oxide. In this embodiment, the zinc
oxide comprises at least 0.05 percent by weight of the
algae-resistant granules.
[0074] In another presently preferred embodiment of the
algae-resistant roofing granules of the present invention, the base
particles include a metallic or metal oxide granule core, such as
zinc granules or copper oxide granules. In this case, the at least
one first algaecidal material is preferably selected from the group
consisting of zinc, copper and copper oxide.
[0075] In yet another presently preferred embodiment, the base
particles comprise microshells encapsulating the at least one first
algaecidal material. Each microshell has a wall enclosing an
interior cavity, and the interior cavity contains the at least one
first algaecidal material. Preferably, the microshell wall is at
least partially permeable to the at least one first algaecidal
material.
[0076] Microshells for use in the present invention can be prepared
from inorganic materials such as glass and ceramic materials such
as silica-alumina ceramics, or from synthetic polymeric materials
such as poly(meth)acrylates, epoxy resins, polyurethanes,
polypropylene, polyimides, acrylonitrile copolymers, vinylidene
halide copolymers, and the like. The production of large (up to 6
mm), porous hollow glass microshells is disclosed, for example, in
U.S. Pat. Nos. 5,225,123 and 5,397,759, each incorporated herein by
reference.
[0077] The at least one first algaecidal material can be
encapsulated in microshells using conventional techniques for
forming microcapsules or microshells, including such techniques as
interfacial polymerization, phase separation/coacervation, spray
drying, spray coating, fluid bed coating, supercritical
anti-solvent precipitation, and the like. Techniques for
microencapsulating solid biocidal particles and other solid
particles are disclosed, for example, in G. Beestman,
"Microencapsulation of Solid Particles," Controlled-Release
Delivery Systems for Pesticides, (H. B. Scher, Ed., Marcel Dekker,
Inc. New York 1999) pp. 31-54, Kirk-Othmer Encyclopedia of Chemical
Technology, 4th Edition; as well in U.S. Pat. Nos. 6,156,245,
6,797,277, and 6,861,145. Preferably, the microshells formed have
an average size of from about 200 micrometers to about 5
millimeters, and more preferably of from about 250 micrometers to
about 3.2 millimeters, and even more preferably of from about 400
to about 2.5 millimeters. Preferably, when a synthetic polymeric
material is employed to form microshell walls, a material with good
exterior durability such as a poly(meth)acrylate is selected.
[0078] Preferably, the microshells are formulated to provide
controlled release of the at least one first algaecidal material
from the microshells over an extended period. A mixture of
microshells having differing time-release characteristics can be
employed, so that there is a continuous release of the at least one
algaecidal material over an extended period of time.
[0079] The microshell wall is formed such that the at least one
first algaecidal material encapsulated within the microshell can
diffuse through the wall when the exterior of the wall is exposed
to the environment. The rate of release of the at least one first
algaecidal material depends on a number of factors, including the
nature of the at least one algaecidal material, the nature of the
material from which the microshell wall is formed, the thickness of
the microshell wall, the geometry and size of the microshell,
specific morphological features of the microshell wall such as the
existence, distribution, and characteristics of pores in the wall,
etc.
[0080] Preferably, the microcapsules are formed from a material
that provides capsule walls that are environmentally degradable in
a controlled manner. Such controlled release microcapsules are well
known in the pharmaceutical and agrochemical arts. A variety of
mechanisms can be employed to provide such capsules. For example,
the capsule wall can include additive to increase their sensitivity
to environmental degradation, such as disclosed in U.S. Pat. No.
6,936,644 (IR sensitivity).
[0081] The outer coating composition includes the at least one
second algaecidal material that provides algae resistance during
the initial predetermined period. In the various embodiments of the
present invention, the outer coating composition forms an outer
layer that encapsulates, directly or indirectly, the base particles
as prepared according to each of the various alternative
embodiments described above. Preferably, the outer coating
composition includes a binder. Preferably, the composition and/or
morphology of the encapsulating outer layer are selected such that
the encapsulating outer layer fails after a predetermined time to
expose the first layer to the environment. For example, the outer
coating composition can comprise a mixture of compatible polymeric
materials with differing proportions of hydrophilic functional
groups such that one of the polymeric materials is water sensitive
and the other or second polymeric material has substantially less
water sensitivity than the first polymeric material. The
proportions of hydrophilic residues in the two polymeric materials
and the weight ratio of the two polymeric materials are preferably
selected such that during the predetermined period, environmental
water gradually diffuses into and through the outer coating layer
to swell the first polymeric material, eventually causing the layer
to fail catastrophically.
[0082] For example, the two polymeric materials can each be a
copolymer of (meth)acrylate monomers, including hydrophobic monomer
such as n-butyl acrylate, ethyl acrylate and methyl methacrylate,
and hydrophilic monomers such as hydroxyethyl methacrylate,
methacrylic acid and acrylic acid, with the molar ratio of
hydrophobic monomer to hydrophilic monomer in the first polymeric
material from that of the second polymeric material.
[0083] In another, alternative embodiment, the outer coating
composition includes an incompatible mixture of polymeric materials
with differing proportions of hydrophilic functional groups such
that one of the polymeric materials is water sensitive and the
other or second polymeric material has substantially less water
sensitivity than the first polymeric material, and the two
polymeric material tend to form separate phases. The weight ratio
of the two polymeric materials is preferably selected such that
during the predetermined period, environmental water gradually
diffuses into and through the outer coating layer to swell the
first polymeric material in one of the two phases, eventually
causing the entire layer to fail catastrophically. In yet another
alternative embodiment, the outer coating composition includes an
incompatible mixture of polymeric materials with differing
proportions of hydrophilic functional groups such that one of the
polymeric materials is water sensitive and the other or second
polymeric material has substantially less water sensitivity than
the first polymeric material, and the two polymeric material tend
to form separate phases, but the two polymeric material are
crosslinked together to form an interpenetrating polymer network.
Again, the proportions of hydrophilic functional groups and the
weight ratio of the two polymeric materials are preferably selected
such that during the predetermined period, environmental water
gradually diffuses into and through the outer coating layer to
swell the first polymeric material eventually causing the outer
layer to fail catastrophically.
[0084] Thus, in one presently preferred embodiment, the binder of
the outer coating composition comprises an organic polymeric
material, and the organic polymeric material is preferably selected
from the group consisting of poly(meth)acrylates. The at least one
second algaecidal material is preferably initially uniformly
dispersed in the organic polymeric material. The second algaecidal
material subsequently diffuses to the exterior surface of the outer
layer and is released into the environment to provide algae
resistance.
[0085] In another presently preferred embodiment of the present
invention, an interlayer is provided between the core particle and
the outer layer. The interlayer preferably enhances the release of
the at least one first algaecidal material by failing
catastrophically after a predetermined period. For example, the
interlayer can be formed by a hydrophilic, water-swellable
polymeric material. During the predetermined period, water can
diffuse through the outer layer, which preferably has a composition
such that the outer layer is substantially hydrophobic and only
slightly water permeable. Eventually, however, enough water
diffuses through the outer layer to cause the interlayer to swell
significantly, disrupting the outer layer and causing the outer
layer to fail catastrophically. Preferably, interlayer comprises at
least one water-swellable resin selected from the group consisting
of natural or synthetic water-swellable resins, starch, cellulose,
and gums.
[0086] In another presently preferred embodiment of the present
invention, an interlayer is provided between the core particle and
the outer layer including a UV degradable material. The interlayer
preferably enhances the release of the at least one first
algaecidal material by failing catastrophically after a
predetermined period. For example, the interlayer can be formed by
UV degradable polymeric material, and may optionally include a
photocatalytic material, as needed. During the predetermined
period, UV light transmission through the outer layer can cause
photochemical degradation of the interlayer. Eventually, however,
enough degradation takes place in the interlayer leading to
disrupting of the outer layer and causing the outer layer to fail
catastrophically. Preferably, interlayer comprises at least one UV
degradable material selected from the group of virgin and recycled
polyolefins and polyolefin copolymers, and combinations thereof.
Exemplary photocatalytic materials include oxides of titanium and
zinc.
[0087] In other aspect of the process of the present invention, the
at least one first algaecidal material releases algaecidal metal
ions, and the interlayer includes at least one metal oxidizable or
corrodible by the algaecidal metal ions. In this case, the
interlayer gradually becomes more hydrophilic and swellable over
time as the metal oxidizable by the at least one first algaecidal
material becomes oxidized, eventually failing catastrophically to
disrupt the outer layer and expose the base particles to the
environment. Preferably, in this case the at least one first
algaecidal material releases copper ions, and the interlayer
includes zinc.
[0088] The at least one first algaecidal material and the at least
one second algaecidal material can be identical, or they can differ
from one another. The at least one first algaecidal material and
the at least one second algaecidal material can be selected from
inorganic biocidal materials, such as copper, cuprous oxide, cupric
acetate, cupric chloride, cupric nitrate, cupric oxide, cupric
sulfate, cupric sulfide, cupric stearate, cupric cyanide, cuprous
cyanide, cuprous stannate, cuprous thiocyanate, cupric silicate,
cuprous chloride, cupric iodide, cupric bromide, cupric carbonate,
cupric fluoroborate, zinc oxide, such as French process zinc oxide,
zinc sulfide, zinc borate, zinc sulfate, zinc pyrithione, zinc
ricinoleate, zinc stearate, zinc chromate, zinc carbonate, titanium
oxide (such as the photocatalytic anatase), metallic silver, silver
oxide, silver chloride, silver bromide, silver iodide and mixtures
thereof. Metal alloys, such as alloys of copper and silver, alloys
of copper and zinc, and alloys of silver and zinc, can also be
employed.
[0089] The proportion of algaecidal materials in the
algae-resistant roofing granules can be adjusted depending on a
number of factors, such as the intended use of the roofing products
manufactured using the algae-resistant granules, the expected
environmental conditions at the site where the roofing products
including the algae-resistant granules are to be installed, the
proportion of algaecidal materials in the algae-resistant granules,
the proportion of algae-resistant roofing granules to conventional
non-algae-resistant roofing granules employed in the roofing
product, et al. In general, however, the proportion of algaecidal
materials is preferably selected to provide algae-resistant roofing
granules in which the algaecidal material comprises from about
0.005 to about 10 percent by weight of the granules. Preferably,
the proportion of algaecidal material in the exterior coating
composition is selected to provide algae-resistant roofing granules
in which the biocidal particles have a surface area of from about
0.05 to about 5 square meter per gram of algae-resistant roofing
granules.
[0090] The algae resistance properties of the algae-resistant
roofing granules of the present invention are determined by a
number of factors, including the porosity of the surface coating of
the roofing granules, the nature and amount(s) of the algaecidal
materials employed, and the spatial distribution of the algaecidal
materials in the granules.
[0091] The algae-resistant roofing granules of the present
invention can be colored using conventional coatings pigments. The
coatings pigments can be included in the outer layer, in the inner
layer (in those embodiments of the present invention that employ an
inner coating layer), or both the inner layer and the outer layer.
Examples of coatings pigments that can be used include those
provided by the Color Division of Ferro Corporation, 4150 East 56th
St., Cleveland, Ohio 44101, and produced using high temperature
calcinations, including PC-9415 Yellow, PC-9416 Yellow, PC-9158
Autumn Gold, PC-9189 Bright Golden Yellow, V-9186 Iron-Free
Chestnut Brown, V-780 Black, V0797 IR Black, V-9248 Blue, PC-9250
Bright Blue, PC-5686 Turquoise, V-13810 Red, V-12600 Camouflage
Green, V12560 IR Green, V-778 IR Black, and V-799 Black. The said
roofing granules can also contain color pigments or additives that
reflect solar radiation. Preferably, the color pigments or
additives can reflect the near infrared radiations of solar
spectrum, such that the solar heat absorption can be reduced
without affecting the color.
[0092] The process of the present invention advantageously permits
the algae resistance of the shingles employing the algae-resistant
granules to be tailored to specific local conditions. For example,
in geographic areas encumbered with excessive moisture favoring
rapid algae growth, the granules can be structured to release the
relatively high levels of algaecide required to effectively inhibit
algae growth under these conditions. Conversely, where algae growth
is less favored by local conditions, the granules can be structured
to release the lower levels of algaecide effective under these
conditions.
[0093] Referring now to the drawings, in which like reference
numerals refer to like elements in each of the several views, there
are shown schematically in FIGS. 1, 2, 3 and 4 examples of
algae-resistant granules prepared according to the process of the
present invention.
[0094] FIG. 1 is a schematic representation of a first type of an
algae-resistant granule of the present invention. FIG. 1
schematically illustrates an algae-resistant granule 10 formed from
a base particle 12 comprising an inert mineral core particle 14
covered with an inner layer 16 composed of an inner coating
composition 18 including a first algaecidal material 20. The base
particle 12 is in turn covered with an outer coating layer 30
comprising an outer coating composition 32 including a second
algaecidal material 34.
[0095] FIG. 2 is a schematic representation of a second type of an
algae-resistant granule of the present invention. FIG. 2
schematically illustrates an algae-resistant granule 40 formed from
a base particle 42 comprising a metallic granule core 44 of a first
algaecidal material. The base particle 42 is covered with an outer
coating layer 50 comprising an outer coating composition 52
including a second algaecidal material 54.
[0096] FIG. 3 is a schematic representation of a third type of an
algae-resistant granule of the present invention. FIG. 3
schematically illustrates an algae-resistant granule 60 formed from
a base particle 62 comprising a microshell 64 having an exterior
wall 66 encapsulating a first algaecidal material 68. The base
particle 62 is in turn covered with an outer coating layer 70
comprising an outer coating composition 72 including a second
algaecidal material 74.
[0097] FIG. 4 is a schematic representation of a fourth type of an
algae-resistant granule of the present invention. FIG. 4
schematically illustrates an algae-resistant granule 80 formed from
a base particle 82 comprising an inert mineral core particle 84
covered with an inner layer 86 composed of a inner coating
composition 88 including a first algaecidal material 90. The base
particle 82 is in turn covered with an interlayer 92 formed from a
material that is selected to fail catastrophically after a
predetermined period. The interlayer 92 is in turn covered with an
outer coating layer 94 comprising an outer coating composition 96
including a second algaecidal material 98.
[0098] FIG. 5 is a schematic graphical representation showing the
release of algaecidal material over time from an algae-resistant
granule according to the present invention. In this example,
conventional cuprous oxide-loaded algae resistant granules are
encapsulated with an acrylic coating including an algaecidal
quaternary ammonium salt. Initially, algae resistance is provided
by the release of the second algaecidal material, such as a
quaternary ammonium salt, from the outer layer of the granule. The
acrylic coating is formulated to last for five years. During this
time, the ammonium salt functions as the sole biocide to prevent
algae growth. After the predetermined period, the outer layer fails
catastrophically, so that portions of the surface of the base
particle are exposed to the environment. At the end of five years,
numerous cracks start forming on the coating surface due to
weathering. Soon afterward, the film peels off from the algae
resistant granules, or otherwise loses film integrity. The granules
are now exposed to the environment, and cuprous oxide embedded on
the granule surfaces starts leaching out and becomes the sole
biocide, which is effective for an additional ten years. From the
time the outer coating is lost, algae resistance is provided by the
first algaecidal material, namely, the cuprous oxide. The result is
an algae-resistant system that is effective against algae for
fifteen years.
[0099] The present invention also provides a process for the
manufacture of algae-resistant roofing granules. The process
comprises providing base particles comprising at least one first
algaecidal material. The base particles can be prepared in a number
of different ways. The base particles are in turn encapsulated with
an outer coating composition including at least one second
algaecidal material to form an outer layer. The at least one second
algaecidal material preferably differs from the at least one first
algaecidal material. The encapsulating outer layer protects the
base particles from exposure to the environment. The outer coating
composition is preferably selected such that the outer layer fails
catastrophically after a predetermined period thereby exposing the
base particles to the environment.
[0100] In one presently preferred embodiment, the base particles
are prepared by providing inert core particles, and subsequently
forming the base particles by coating the inert core particles with
an inner coating composition to form an inner layer on the inert
core particles. In this case, the inner coating composition
preferably includes the at least one first algaecidal material.
[0101] Preferably, the inner coating composition includes a binder,
which preferably comprises an aluminosilicate material, such as
clay, and an alkali metal silicate. The inner coating composition
can also include colorants, such as metal oxide pigments, and other
components, such as solar heat-reflective pigments.
[0102] In the present process, the at least one first algaecidal
material of the inner coating composition is preferably selected
from the group consisting of copper compounds, zinc compounds, and
mixtures thereof, with cuprous oxide and zinc oxide being
especially preferred. When cuprous oxide is employed as the at
least one first algaecidal material, the cuprous oxide preferably
comprises at least 0.5 percent of the algae-resistant granules.
When zinc oxide is employed as the at least one first algaecidal
material, the zinc oxide preferably comprises at least 0.05 percent
by weight of the algae-resistant granules.
[0103] In another presently preferred embodiment of the present
process, the base particles are prepared by providing a metallic or
metal oxide granule core, such as zinc granules or copper oxide
granules. In this case, the at least one first algaecidal material
is preferably selected from the group consisting of zinc, copper
and copper oxide.
[0104] In another presently preferred embodiment of the present
process, the base particles are prepared by providing the at least
one first algaecidal material, and forming the base particles by
encapsulating the at least one first algaecidal material in
microshells. Each microshell has a wall enclosing an interior
cavity, and the interior cavity contains the at least one first
algaecidal material. Preferably, the microshell wall is at least
partially permeable to the at least one first algaecidal
material.
[0105] In a presently preferred embodiment of the process of the
present invention, the process further comprises providing an
interlayer on the base particles. The interlayer preferably
enhances the release of the at least one second algaecidal material
under predetermined conditions. In one aspect of the process of the
present invention, the interlayer preferably includes a
water-swellable resin or a UV degradable material. Preferably, the
water-swellable resin is selected from the group consisting of
natural or synthetic water-swellable resins, starch, cellulose, and
gums. Preferred UV degradable materials include virgin or recycled
polyolefins, virgin or recycled olefin copolymers, and mixtures or
combinations thereof. In other aspect of the process of the present
invention, the at least one first algaecidal material releases
algaecidal metal ions, and the interlayer includes at least one
metal oxidizable by the algaecidal metal ions. Preferably, in this
case the at least one first algaecidal material releases copper
ions, and the interlayer includes zinc.
[0106] Preferably, in the present process, the outer coating
composition includes a binder. Preferably, the composition and/or
morphology of the encapsulating outer layer are selected such that
the encapsulating outer layer fails after a predetermined time to
expose the first layer to the environment. Thus, the second
algaecide is released from the outer layer during the initial
predetermined period.
[0107] In one presently preferred embodiment, the binder of the
outer coating composition comprises an organic polymeric material
or an inorganic material. The organic polymeric material is
preferably selected from the group consisting of
poly(meth)acrylates, polyurethanes and polyureas. When an inorganic
material is used as the binder, the inorganic material is
preferably selected from the group consisting of an
aluminosilicate, silica and phosphate materials. In the process of
the present invention, the at least one second algaecidal material
is preferably initially uniformly dispersed in the binder. The
second algaecidal material subsequently diffuses to the exterior
surface of the outer layer and is released into the
environment.
[0108] In a presently preferred embodiment, the at least one second
algaecidal material is a quaternary ammonium compound. Preferably,
the organic biocides include compounds that are halogenated based
(such as IPBC [3-iodo-2-propynylbutyl carbamate]), nitrogen based
(such as oxazolidines), sulfur based (such as OIT
[2-n-octyl-4-isothiazolin-3-one]), or phenolics (such as TCPP
[trichlorophenoxy phenol]). Preferably, the quaternary ammonium
compound is selected from the group consisting of n-alkyl dimethyl
benzyl ammonium chloride, dimethyl didecyl ammonium chloride, and
poly(oxy-1,2-ethanediyl(dimethylimino)-1,2-ethanediyl(dimethylimino)-1,2--
ethanediyl dichloride). Preferably, the binder is an organic
polymeric material including at least one quaternary ammonium salt
functional group. More preferably, the organic polymeric material
is a poly(meth)acrylate.
[0109] In another presently preferred embodiment, the at least one
second algaecidal material is an organic biocide. Preferably, the
organic biocide includes one or more compounds that are
halogenated, such as 3-iodo-2-propynylbutyl carbamate (IPBC),
nitrogen based, such as oxazolidines, sulfur based, such as
2-n-octyl-4-isothiazolin-3-one (OIT), or phenolic in nature, such
as trichlorophenoxy phenol (TCPP).
[0110] The coating compositions used in preparing the
algae-resistant granules can include other components, such as
conventional metal oxide colorants of the type employed in the
manufacture of roofing granules, solar heat-reflective pigments
such as titanium dioxide, other biocidal materials, and the
like.
[0111] The algae-resistant granules prepared according to the
process of the present invention can be employed in the manufacture
of algae-resistant roofing products, such as algae-resistant
asphalt shingles, using conventional roofing production processes.
Typically, bituminous roofing products are sheet goods that include
a non-woven base or scrim formed of a fibrous material, such as a
glass fiber mat. The base is coated with one or more layers of a
bituminous material such as asphalt to provide water and weather
resistance to the roofing product. One side of the roofing product
is typically coated with mineral granules to provide durability,
reflect heat and solar radiation, and to protect the bituminous
binder from environmental degradation. The algae-resistant granules
of the present invention can be mixed with conventional roofing
granules, and the granule mixture can be embedded in the surface of
such bituminous roofing products using conventional methods.
Alternatively, the algae-resistant granules of the present
invention can be substituted for conventional roofing granules in
the manufacture of bituminous roofing products to provide those
roofing products with algae-resistance.
[0112] Bituminous roofing products are typically manufactured in
continuous processes in which a continuous substrate sheet of a
fibrous material such as a continuous felt sheet or glass fiber mat
is immersed in a bath of hot, fluid bituminous coating material so
that the bituminous material saturates the substrate sheet and
coats at least one side of the substrate. The reverse side of the
substrate sheet can be coated with an anti-stick material such as a
suitable mineral powder or a fine sand. Roofing granules are then
distributed over selected portions of the top of the sheet, and the
bituminous material serves as an adhesive to bind the roofing
granules to the sheet when the bituminous material has cooled. The
sheet can then be cut into conventional shingle sizes and shapes
(such as one foot by three feet rectangles), slots can be cut in
the shingles to provide a plurality of "tabs" for ease of
installation, additional bituminous adhesive can be applied in
strategic locations and covered with release paper to provide for
securing successive courses of shingles during roof installation,
and the finished shingles can be packaged. More complex methods of
shingle construction can also be employed, such as building up
multiple layers of sheet in selected portions of the shingle to
provide an enhanced visual appearance, or to simulate other types
of roofing products.
[0113] The bituminous material used in manufacturing roofing
products according to the present invention is derived from a
petroleum processing by-product such as pitch, "straight-run"
bitumen, or "blown" bitumen. The bituminous material can be
modified with extender materials such as oils, petroleum extracts,
and/or petroleum residues. The bituminous material can include
various modifying ingredients such as polymeric materials, such as
SBS (styrene-butadiene-styrene) block copolymers, resins, oils,
flame-retardant materials, oils, stabilizing materials, anti-static
compounds, and the like. Preferably, the total amount by weight of
such modifying ingredients is not more than about 15 percent of the
total weight of the bituminous material. The bituminous material
can also include amorphous polyolefins, up to about 25 percent by
weight. Examples of suitable amorphous polyolefins include atactic
polypropylene, ethylene-propylene rubber, etc. Preferably, the
amorphous polyolefins employed have a softening point of from about
130 degrees C. to about 160 degrees C. The bituminous composition
can also include a suitable filler, such as calcium carbonate,
talc, carbon black, stone dust, or fly ash, preferably in an amount
from about 10 percent to 70 percent by weight of the bituminous
composite material.
[0114] The following examples are provided to better disclose and
teach processes and compositions of the present invention. They are
for illustrative purposes only, and it must be acknowledged that
minor variations and changes can be made without materially
affecting the spirit and scope of the invention as recited in the
claims that follow.
EXAMPLE 1
Preparation of Encapsulated AR Granules
[0115] 1,000 g of conventional cuprous oxide-loaded algae-resistant
(AR) roofing granules (Product Code GH 71 AR) manufactured at
CertainTeed's Gads Hill roofing granule plant located at Piedmont,
Mo. were used as the base particles. In this case, cuprous oxide
acted as the first algaecidal material. These granules were in turn
encapsulated with an outer coating. Composition of this outer
coating consisted of 125 g of sodium silicate (40% solids, with
Na.sub.2O:SiO.sub.2 ratio of 1:3.2; Occidental Chemical
Corporation, Dallas, Tex.), 100 g of clay slurry (70% solids,
Unimin Corporation, New Canaan, Conn.), 20 g of titanium oxide
(TiPure Product Number R-101, DuPont, Wilmington, Del.) and 120 g
of water. The outer coating was applied onto the roofing granules
using a fluidized bed coater Model 2 supplied by Fluid Air, Inc.
(Aurora, Ill.). The operating conditions were set at 24 scfm of
inlet air flow rate, 70.degree. C. of inlet temperature, 10 psi of
spraying pressure, 65 psi of filter blow back pressure, 5.3 g/min
of binder solution pump rate, and total processing time of 40
minutes. The coated granules were then fired in a gas-fired kiln at
a temperature of 500.degree. C. for 20 minutes to form a composite
roofing granule having cuprous oxide in the interior fully
encapsulated by an exterior layer of sodium silicate binder.
EXAMPLE 2
Preparation of Encapsulated AR Granules
[0116] The process of Example 1 was repeated, except the outer
coating composition was modified. The composition consisted of 188
g of sodium silicate (40% solids, with Na.sub.2O:SiO.sub.2 ratio of
1:3.2; Occidental Chemical Corporation, Dallas, Tex), 100 g of clay
slurry (70% solids, Unimin Corporation, New Canaan, Conn.), 20 g of
titanium oxide (TiPure Product Number R-101, DuPont, Wilmington,
Del.), 12 g of zinc oxide (Zinc Corporation of America, Monaca,
Pa.) and 150 g of water. The coated granules were fired in a
gas-fired kiln at a temperature of 500.degree. C. for 20 minutes to
form a composite roofing granule having cuprous oxide in the
interior fully encapsulated by an exterior layer of zinc
oxide-loaded sodium silicate binder. In this case, the resultant
composite granules have dual algaecides: cuprous oxide in the
interior and zinc oxide on the outer layer.
EXAMPLE 3
Preparation of Encapsulated AR Granules
[0117] The process of Example 1 was repeated, except the outer
coating composition was modified further. The composition consisted
of 60 g of colloidal silica Ludox CL-X (45% solids, pH 9.1,
Sigma-Aldrich Corporation, St. Louis, Mo.), 30 g of clay slurry
(70% solids, Unimin Corporation, New Canaan, Conn.), 12 g of
aluminum phosphate (Sigma-Aldrich Corporation, St. Louis, Mo.), 20
g of titanium oxide (TiPure R-101, DuPont, Wilmington, Del.), 18 g
of zinc oxide (Zinc Corporation of America, Monaca, Pa.) and 135 g
of water. The coated granules were fired in a gas-fired kiln at a
temperature of 500.degree. C. for 20 minutes to form a composite
roofing granule having cuprous oxide on the interior fully
encapsulated by an exterior layer of zinc oxide-loaded phosphate
binder. In this case, the resultant composite granules have dual
algaecides: cuprous oxide in the interior and zinc oxide on the
outer layer.
[0118] Leaching Procedure of Metal Ions from Roofing Granules
[0119] Leaching study was conducted on roofing granules which were
immersed in warm water at pH 5 and 45.degree. C. The reported
leached concentration of metal ions, in ppm, is the amount of ions
leached out to the environment. The leaching procedure was as
follows:
[0120] 10 g of the test granules were placed in a clean 40 ml glass
vial filled with 10 ml of pH 5.0 buffer (potassium
biphthalate-sodium hydroxide buffer, 0.05M, Fisher Scientific). The
vial was placed in a water bath (Fisher Scientific ISOTEMP Model
220) and maintained at a constant temperature of 45.degree. C.
After one day, the solution was decanted into a cuvette, and a
pre-measured packet of powder pillow containing a coloring reagent
was added to the solution. Selection of the coloring agent depended
on the metal ions to be measured. For the detection of copper ions,
CuVer 1 copper reagent of dipotassium 2,2' bicinchoninate (Product
number 21058-69, Hach Company, Loveland, Colo.) was used. The
concentration of copper ions, in ppm, leached out from the granules
into the surrounding water was determined by measuring the color
intensity of the resulted complex at 560 nm using a laboratory
spectrophotometer (Model DR/2010 by Hach Company).
[0121] For the detection of zinc ions, Zinc Ver5 reagent containing
potassium borate, boron oxide, sodium ascorbate and potassium
cyanide (Product number 21066-69, Hach Company) was used. The
concentration of zinc ions, in ppm, leached out from the granules
into the surrounding water was determined by measuring the color
intensity of the resulted complex at 620 nm using a laboratory
spectrophotometer (Model DR/2010 by Hach Company). The composite
granules prepared following the procedure described in Example 1
consist of cuprous oxide, from the conventional AR roofing
granules, in the interior. Using the fluidized bed coating process,
these AR granules were in turn coated with an outer layer of sodium
silicate binder. The AR granules were well encapsulated by the
sodium silicate binder so that only very minimal amount of copper
ions was able to escape through the outer layer and leach out to
the surrounding. FIG. 6 shows that the leaching of copper ions
started at very low level (below 0.5 ppm), and reached around 5 ppm
after one month.
[0122] The composite granules prepared following the procedure
described in Example 1 consist of cuprous oxide, from the
conventional AR roofing granules, in the interior. Using the
fluidized bed coating process, these AR granules were in turn
coated with an outer layer of sodium silicate binder. The AR
granules were well encapsulated by the sodium silicate binder so
that only very minimal amount of copper ions was able to escape
through the outer layer and leach out to the surrounding. FIG. 6
shows that the leaching of copper ions started at very low level
(below 0.5 ppm), and reached around 5 ppm after one month.
[0123] For the composite granules prepared following the procedure
described in Example 2, the outer layer of sodium silicate binder
encapsulating the AR granules was not able to prevent copper ions
from leaching out to the surroundings. The leached copper
concentration was 57 ppm on the first day, and increased to 167 ppm
after one month. In addition, the outer layer contained zinc oxide
as the second algaecide, which was leached out rapidly and reduced
to less than 20% of its initial concentration after one month. The
leaching curves of copper and zinc ions from granules of Example 2
are depicted FIG. 7, in comparison to the leaching of copper ions
from the granules of Example 1.
[0124] Composite granules prepared per Example 3 had a different
material composition for the outer layer. A metal phosphate binder
was used in place of the silicate binder as in Example 2. The
initial leached copper level was even higher at 232 ppm, then
increased rapidly to 513 ppm after one month. While the leaching of
copper ions from these granules was more accelerated than that of
the granules from Example 2, the leaching of zinc ions as the
second algaecide from both cases was rather similar, as can be seen
in FIG. 8.
[0125] These results demonstrate that by proper design and
selection of the material and composition of the outer layer, and
of the base particle, the leaching rate and concentration of the
algaecide from the interior can be controlled at will. Furthermore,
a second algaecide can be added to the outer layer, if desired, for
specific functionalities, and the leaching of the second algaecide
can also be modified accordingly.
[0126] Various modifications can be made in the details of the
various embodiments of the processes, compositions and articles of
the present invention, all within the scope and spirit of the
invention and defined by the appended claims.
* * * * *