Reflective granules having sustained solar reflectance

Abstract

The present disclosure is directed to reflective granules including a granules including a granulated mixture of a powdered reflective mineral and a binder, the granules having: a sphericity of at least 0.9, as determined by dynamic image analysis; and / or a symmetry of at least 0.9, as determined by dynamic image analysis. The reflective granules may have a round and / or spherical shape.

Description

REFLECTIVE GRANULES HAVING SUSTAINED SOLAR REFLECTANCECROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 734,893, filed on December 17, 2024, and U.S. Provisional Application No. 63 / 651 ,446, filed on May 24, 2024, the disclosures of which are hereby incorporated by reference in their entireties.BACKGROUNDField

[0002] The present disclosure relates to reflective granules having sustained solar reflectance, architectural materials comprising the reflective granules, and methods for making the same.Technical Considerations

[0003] Commercial and residential roofs are continuously exposed to the outside elements, which are often harsh or extreme. Even under moderate external conditions, these roofs are exposed to environmental or weather conditions that affect the ability of the roofs to insulate the building or residence interiors from the effects of the environmental or weather conditions. In many parts of the world, during the summer months, roofs are continuously exposed to high heat and sunny conditions under which the roofing materials absorb solar energy and retain high levels of heat. As the roofs absorb the solar energy and retain heat, the conditions inside the underlying buildings or residences suffer adversely, which often causes the interiors to heat up to uncomfortable conditions.

[0004] In order to remedy these conditions, the buildings or residences often resort to increased amounts of internal insulation, or increased use of artificial cooling systems (e.g., HVAC equipment). However, increasing the amount of insulation has a limited ability to reduce heat transfer, and increasing energy costs make the increased use of artificial cooling systems undesirable or even cost prohibitive.SUMMARY

[0005] The present disclosure relates to reflective granules including granules comprising a granulated mixture of a powdered reflective mineral and a binder, thegranules having: a sphericity of at least 0.9, as determined by dynamic image analysis; and / or a symmetry of at least 0.9, as determined by dynamic image analysis.

[0006] The present disclosure relates to a granulated mixture of a powdered reflective mineral and a binder, the granules having a particle size distribution including: at least 90% of the granules having an average particle size of from greater than or equal to 0.841 mm to less than 2.38 mm, such as at least 95% or at least 98%, or at least 90% of the granules having an average particle size of from greater than or equal to 0.297 mm to less than 0.555 mm, such as at least 95%, at least 97%, or at least 98%.

[0007] The present disclosure relates to reflective granules including a granulated mixture of a powdered reflective mineral and a binder, the granules having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.5, such as having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.9.

[0008] The present disclosure relates to reflective granules including a granulated mixture of a powdered reflective mineral and a binder, the granules having a greater roundness and / or sphericity and / or symmetry (compared to crushed granules), as determined by dynamic image analysis.

[0009] The present disclosure relates to reflective granules including a granulated mixture of a powdered reflective mineral and a binder, the granules having a more spherical width :length ratio (compared to crushed granules), as determined by dynamic image analysis. The width:length ratio may range from 0.7-1 .0, such as 0.8- 1.0.

[0010] The present disclosure relates to reflective granules including a granulated mixture of a powdered reflective mineral and a binder, the granules not crushed following granulating of the mixture of the powdered reflective mineral and the binder.

[0011] In some non-limiting embodiments or aspects, the powdered reflective mineral may include kaolin clay, a sand-based material that converts into cristobalite upon kilning, or any combination thereof. The reflective granules may further include a coating applied to a surface of the granules. The granules may not be crushed following granulating of the mixture of the powdered reflective mineral and the binder.

[0012] The present disclosure also relates to an architectural material including the reflective granules as described herein.

[0013] In some non-limiting embodiments or aspects, the architectural material may include a roofing material. The architectural material may include an asphalt substrateto which the reflective granules are adhered. The architectural material may include further reflective granules applied over the reflective granules, the further reflective granules having a smaller average particle size compared to the reflective granules.

[0014] The present disclosure also relates to a method for making reflective granules including: mixing a powdered reflective mineral and a binder to form a mixture; and granulating the mixture to form reflective granules, the granules having: a sphericity of at least 0.9, as determined by dynamic image analysis; and / or a symmetry of at least 0.9, as determined by dynamic image analysis.

[0015] The method may further include: sieving the reflective granules to obtain reflective granules having a particle size distribution by removing undersized particulate below the particle size distribution and / or removing oversized particulate above the particle size distribution, the reflective granules having the particle size distribution not crushed following the granulating.

[0016] In some non-limiting embodiments or aspects, the method may further include milling the oversized particulate to form milled particulate; and mixing the milled particulate with the reflective granules. The undersized particulate may be used in the granulating to form the reflective granules. The particle size distribution may include: at least 90% of the reflective granules having an average particle size of from greater than or equal to 0.841 mm to less than 2.38 mm, such as at least 95% or at least 98%, or at least 90% of the granules having an average particle size of from greater than or equal to 0.297 mm to less than 0.555 mm, such as at least 95%, at least 97%, or at least 98%. The reflective granules may have a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.5, such as having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.9. The reflective granules may include a granulated mixture of a powdered reflective mineral and a binder, the granules having a greater roundness and / or sphericity and / or symmetry (compared to crushed granules), as determined by dynamic image analysis. The reflective granules may include a granulated mixture of a powdered reflective mineral and a binder, the granules having a more spherical width :length ratio (compared to crushed granules), as determined by dynamic image analysis. The width:length ratio may range from 0.7-1 .0, such as 0.8-1 .0. The powdered reflective mineral may include kaolin clay, a sand-based material that converts into cristobalite upon kilning, or any combination thereof. The method may further include applying a coating to the reflective granules having the particle size distribution.

[0017] The present disclosure also relates to reflective granules prepared using the method described herein.

[0018] The present disclosure also includes the following clauses.

[0019] Clause 1 : Reflective granules, comprising: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having: a sphericity of at least 0.9, as determined by dynamic image analysis; and / or a symmetry of at least 0.9, as determined by dynamic image analysis.

[0020] Clause 2: The reflective granules of clause 1 , the granules having an aspect ratio of at least 0.8, as determined by dynamic image analysis.

[0021] Clause 3: The reflective granules of clause 1 or 2, the granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a particle size distribution comprising: at least 90% of the granules having an average particle size of from greater than or equal to 0.841 mm to less than 2.38 mm, such as at least 95% or at least 98%, or at least 90% of the granules having an average particle size of from greater than or equal to 0.297 mm to less than 0.555 mm, such as at least 95%, at least 97%, or at least 98%.

[0022] Clause 4: The reflective granules of any of clause 1 -3, the granules having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.5, such as having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.9.

[0023] Clause 5: The reflective granules of any of clause 1 -4, the granules having a greater roundness and / or sphericity and / or symmetry (compared to crushed granules), as determined by dynamic image analysis.

[0024] Clause 6: The reflective granules of any of clause 1 -5, the granules having a more spherical width :length ratio (compared to crushed granules), as determined by dynamic image analysis.

[0025] Clause 7: The reflective granules of any of clause 1 -6, the granules not crushed following granulating of the mixture of the powdered reflective mineral and the binder.

[0026] Clause 8: The reflective granules of any of clauses 1 -7, wherein the powdered reflective mineral comprises kaolin clay, a sand-based material that converts into cristobalite upon kilning, or any combination thereof.

[0027] Clause 9: The reflective granules of any of clauses 1 -8, further comprising: a coating applied to a surface of the granules.

[0028] Clause 10: The reflective granules of any of clauses 1 -9, wherein the granules are not crushed following granulating of the mixture of the powdered reflective mineral and the binder.

[0029] Clause 11 : An architectural material comprising the reflective granules of any of clauses 1 -10.

[0030] Clause 12: The architectural material of clause 1 1 , wherein the architectural material comprises a roofing material.

[0031] Clause 13: The architectural material of clause 11 or 12, comprising an asphalt substrate to which the reflective granules are adhered.

[0032] Clause 14: The architectural material of any of clauses 1 1 -13, further comprising further reflective granules applied over the reflective granules, the further reflective granules having a smaller average particle size compared to the reflective granules.

[0033] Clause 15: A method for making reflective granules, comprising: mixing a powdered reflective mineral and a binder to form a mixture; and granulating the mixture to form reflective granules; the granules having: a sphericity of at least 0.9, as determined by dynamic image analysis; and / or a symmetry of at least 0.9, as determined by dynamic image analysis.

[0034] Clause 16: The method of clause 15, the granules having an aspect ratio of at least 0.8, as determined by dynamic image analysis.

[0035] Clause 17: The method of clause 15 or 16, further comprising sieving the reflective granules to obtain reflective granules having a particle size distribution by removing undersized particulate below the particle size distribution and / or removing oversized particulate above the particle size distribution.

[0036] Clause 18: The method of any of clauses 15-17, further comprising: milling the oversized particulate to form milled particulate; and mixing the milled particulate with the reflective granules.

[0037] Clause 19: The method of any of clauses 15-18, wherein the undersized particulate is used in the granulating to form the reflective granules.

[0038] Clause 20: The method of any of clauses 15-19, wherein the particle size distribution comprises: at least 90% of the reflective granules having an average particle size of from greater than or equal to 0.841 mm to less than 2.38 mm, such as at least 95% or at least 98%, or at least 90% of the granules having an average particlesize of from greater than or equal to 0.297 mm to less than 0.555 mm, such as at least 95%, at least 97%, or at least 98%.

[0039] Clause 21 : The method of any of clauses 15-20, the reflective granules having the particle size distribution not crushed following the granulating.

[0040] Clause 22: The method of any of clauses 15-21 , the reflective granules having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.5, such as having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.9.

[0041] Clause 23: The method of any of clauses 15-22, the reflective granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a greater roundness and / or sphericity and / or symmetry (compared to crushed granules), as determined by dynamic image analysis.

[0042] Clause 24: The method of any of clauses 15-23, the reflective granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a more spherical width:length ratio (compared to crushed granules), as determined by dynamic image analysis.

[0043] Clause 25: The method of any of clauses 15-24, wherein the powdered reflective mineral comprises kaolin clay, a sand-based material that converts into cristobalite upon kilning, or any combination thereof.

[0044] Clause 26: The method of any of clauses 15-25, further comprising: applying a coating to the reflective granules having the particle size distribution.

[0045] Clause 27: Reflective granules prepared using the method of any of clauses 15-26.

[0046] Clause 28: An architectural material comprising the reflective granules of clause 27.

[0047] Clause 29: The architectural material of clause 28, wherein the architectural material comprises a roofing material.

[0048] Clause 30: The architectural material of clause 28 or 29, comprising an asphalt substrate to which the reflective granules are adhered.

[0049] Clause 31 : The architectural material of any of clauses 28-30, further comprising further reflective granules applied over the reflective granules, the further reflective granules having a smaller average particle size compared to the reflective granules.BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Additional advantages and details are explained in greater detail below with reference to the non-limiting, exemplary embodiments that are illustrated in the accompanying schematic figures, in which:

[0051] FIG. 1 shows a photograph of uncrushed granules according to non-limiting embodiments or aspects of the present disclosure.

[0052] FIG. 2 shows a photograph of crushed granules according to a comparative example.

[0053] FIGS. 3A-3B show graphs of the particle size distributions for the reflective granules of Examples 1 -2.

[0054] FIG. 4 shows a graph of total solar reflectance (TSR) for architectural materials prepared using reflective granules of Examples 1 -2.

[0055] FIG. 5 shows a process flow diagram of a process for preparing reflective granules according to non-limiting embodiments or aspects of the present disclosure.DETAILED DESCRIPTION

[0056] For purposes of the following detailed description, it is understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0057] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in its respective testing measurement.

[0058] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

[0059] In this application, the use of the singular includes the plural and plural encompasses singular, unless specifically stated otherwise. In addition, in this application, the use of “or” means “and / or” unless specifically stated otherwise, even though “and / or” may be explicitly used in certain instances. Further, in this application, the use of “a” or “an” means “at least one” unless specifically stated otherwise.

[0060] As used herein, the transitional term “comprising” (and other comparable terms, e.g., “containing” and “including”) is “open-ended” and open to the inclusion of unspecified matter. Although described in terms of “comprising”, the terms “consisting essentially of” and “consisting of” are also within the scope of the disclosure.

[0061] As used herein, the term “granular roofing material,” “particulate roofing material,” and like terms, refer to solar reflective particulates or granules that are useful in so-called “cool roof” applications, and these terms are used interchangeably with the terms “solar reflective particulates,” “solar reflective granules,” “reflective particulates,” “reflective granules,” and like terms. Additionally, while the particulates and granules described herein are described in terms of their efficacy in “cool roof” applications, it is understood that the described particulates and granules may have other uses and applications, and that the described embodiments are not limited to use in “cool roof” applications. For example, in some non-limiting embodiments, the particulate roofing materials described herein may be useful on any exterior surface, for example, as a filler in an exterior paint, or like application.

[0062] Reflective granules may include: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a particle size distribution comprising: at least 90% of the granules having an average particle size of from greater than or equal to 0.841 mm to less than 2.38 mm, such as at least 95% or at least 98%, at least 90% of the granules having an average particle size of from greater than or equal to 0.297 mm to less than 0.555 mm, such as at least 95%, at least 97%, or at least 98%.

[0063] Reflective granules may include: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a Krumbeinroundness of at least 0.5 and a Krumbein sphericity of at least 0.5, such as having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.9.

[0064] Reflective granules may include: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a greater roundness and / or sphericity and / or symmetry (compared to crushed granules) as determined by dynamic image analysis.

[0065] In some non-limiting embodiments or aspects, the reflective granules may have a sphericity (as defined by Mean value SPHT as determined by dynamic image analysis) of at least 0.9. In some non-limiting embodiments or aspects, the reflective granules may have a symmetry (as defined by Symm as determined by dynamic image analysis) of at least 0.9. In some non-limiting embodiments or aspects, the reflective granules may have an aspect ratio (as defined by b / l as determined by dynamic image analysis) of at least 0.8. In some non-limiting embodiments or aspects, the reflective granules may have a non-uniformity factor (as defined by U as determined by dynamic image analysis) of at least 1.4. In some non-limiting embodiments or aspects, the reflective granules may have a SPAN value (as determined by dynamic image analysis) of at least 0.54.

[0066] Reflective granules may include: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a more spherical width :length ratio (compared to crushed granules), as determined by dynamic image analysis. The width:length ratio may range from 0.7-1 .0.

[0067] Reflective granules may include: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having a more uniform roundness and / or sphericity and / or symmetry (compared to crushed granules), as determined by dynamic image analysis.

[0068] Reflective granules may include: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules not crushed following granulating of the mixture of the powdered reflective mineral and the binder.

[0069] A method for making reflective granules, comprising: mixing a powdered reflective mineral and a binder to form a mixture; granulating the mixture to form reflective granules; and sieving the reflective granules to obtain reflective granules having a particle size distribution by removing undersized particulate below the particle size distribution and / or removing oversized particulate above the particle sizedistribution, the reflective granules having the particle size distribution not crushed following the granulating.

[0070] In some non-limiting embodiments or aspects, the reflective granules may comprise a granulated mixture of a powdered reflective mineral and a binder.

[0071] The powdered reflective mineral may include kaolin clay, a sand-based material that converts into cristobalite upon kilning, and / or any combination thereof.

[0072] The powdered reflective mineral may include kaolin clay. The type or source of the kaolin clay used in the powdered reflective mineral is not particularly limited in the present disclosure. Non-limiting examples of kaolin clay materials include EPK kaolin (e.g., having an Fe content of about 0.93 wt%, where the reported Fe content is adjusted to exclude loss-on-ignition (LOI) and normalized to a total oxide content of 100%) available from Edgar Minerals (Edgar, FL), MCNAMEE kaolin (e.g., having an Fe content of about 0.38 wt%, where the reported Fe content is adjusted to exclude LOI and normalized to a total oxide content of 100%) available from Vanderbilt Minerals, LLC (Norwalk, CT), Kingsley kaolin (e.g., having an Fe content of about 0.45 wt%, where the reported Fe content is adjusted to exclude LOI and normalized to a total oxide content of 100%) available from Kentucky-Tennessee Clay Company (Roswell, GA), 6 TILE kaolin (e.g., having an Fe content of about 0.4 wt%, where the reported Fe content is adjusted to exclude LOI and normalized to a total oxide content of 100%) available from Kentucky-Tennessee Clay Company (Roswell, GA), optiKasT kaolin (e.g., having an Fe content of about 0.58 wt%, where the reported Fe content is adjusted to exclude LOI and normalized to a total oxide content of 100%) available from Kentucky-Tennessee Clay Company (Roswell, GA), lone Airfloated Kaolin (e.g., having an Fe content of about 0.7 wt%, where the reported Fe content is adjusted to exclude LOI and normalized to a total oxide content of 100%) available from lone Minerals, Inc. (lone, CA), kaolin-containing products available from Thiele Kaolin Company (Sandersville, GA), kaolin-containing products available from Imerys S.A. (Paris, France), and kaolin-containing products available from KaMin (Macon, GA). The kaolin clay may comprise calcined kaolin clay. In response to the granules undergoing the kilning process, the kaolin may undergo a transformation to form a mixture of mullite and amorphous silica.

[0073] The powdered reflective mineral may include a sand-based material. In response to the granules undergoing the kilning process, the sand-based material mayundergo a transformation to cristobalite. As used herein, “cristobalite” refers to a crystalline polymorph of silica.

[0074] The powdered reflective mineral may include aluminum trihydrate (ATH).

[0075] The powdered reflective mineral, after kilning, may comprise at least 80% by weight, such as at least 85%, at least 90%, at least 95%, at least 99%, or 100% of the reflective granules, based on total solids thereof. The binder may be substantially (e.g., present by less than 1 % by weight and / or non-detectable) burned off by the kilning, such that the powdered reflective mineral (and any additives) may adhere together to form the granules via a sintering process.

[0076] The powdered reflective mineral in the reflective granules may function as a reflective pigment which is highly reflective at certain wavelengths of solar radiation which reach the Earth’s surface. When the reflective granules are arranged over a surface of an object positioned in outdoor conditions, the powdered reflective mineral may reflect at least a portion of the solar radiation incident to the object to reduce the rise in temperature of the object caused by the incident solar radiation (by the object absorbing less and reflecting more solar radiation compared to the same object coated with the same granules not containing the powdered reflective mineral).

[0077] The reflective granules may be prepared from a slurry. The slurry may include a liquid media (e.g., water) in addition to a binder. The slurry may form a substantially homogeneous mixture. As used herein, the term “substantially” is used as a term of approximation, and not as term of degree, and is intended to account for the inherent deviations and variations in measured, observed, or calculated properties or values. Accordingly, the term “substantially homogeneous” denotes that while the mixture may not be perfectly homogeneous, the mixture would be considered homogeneous by those of ordinary skill in the art.

[0078] In non-limiting embodiments, a method of forming the slurry may include adding a liquid media (e.g., water) to the powdered reflective mineral and binder until a desired consistency is achieved. The desired consistency at this stage of the process may vary depending on a variety of factors, e.g., whether the composition is desired to be ultimately moldable or flowable. In some non-limiting embodiments, however, the liquid media may be added in an amount of from 20 to 50% by weight, such as from 30 to 40% by weight, based on total weight of the slurry. For example, in some non-limiting embodiments in which the material is desired to be moldable, the liquid media may be added in an amount of from 20 to 40% by weight, such as from 25 to35% by weight or from 25 to 30% by weight, based on total weight of the slurry. In some non-limiting embodiments in which the material is desired to be flowable, the liquid media may be added in an amount of from 30 to 50% by weight, such as from 35 to 45% by weight or 35 to 40% by weight, based on total weight of the slurry.

[0079] Moreover, in order to improve the consistency and adhesion of the particles (e.g., granulation) within the slurry, a binder may be added. Suitable binders may include the class of water-soluble polymers, such as water-soluble synthetic polymers. Water-soluble synthetic polymers may contain hydrophilic functional groups, such as ethers, alcohols, amides, and pyrrolidones. In some non-limiting embodiments or aspects, the binder may comprise polyvinyl alcohol.

[0080] The binder may be added to the slurry mixture in an amount of from 1 to 10% by weight, such as from 3 to 8% by weight, based on the dry weight of the powdered reflective mineral. The binder material may be added to the slurry mixture in an amount of from 1 to 8% by weight, from 1 to 5% by weight, from 3 to 10% by weight, or from 5 to 10% by weight, based on dry weight of the powdered reflective mineral. The binder material may be added to the slurry mixture in an amount of from 1 to 3% by weight, from 3 to 5% by weight, from 5 to 8% by weight, or from 8 to 10% by weight, based on dry weight of the powdered reflective mineral. The slurry may be processed into granule form.

[0081] The granules may be dried. In some non-limiting embodiments, a method may further include extruding the slurry, or spray granulating the slurry, and drying the extruded or sprayed product. The drying may be performed at any suitable temperature to substantially drive off the liquid media. As discussed above, as used herein, the term “substantially” is a term of approximation, and not a term of degree, and the phrase “substantially drive off the liquid media” is intended to account for inherent deviations in the measurement, calculation or observation of the amount of the liquid media remaining in the mixture after drying. For example, the liquid media would be considered substantially driven off if the amount of liquid media remaining in the mixture is either not detectable or is otherwise negligible, as would be understood by those of ordinary skill in the art.

[0082] The temperature for drying the slurry is not particularly limited, and it may vary depending on the liquid media selected. However, the temperature should be high enough to substantially drive off the liquid media, but not high enough to constitute a heat treatment or kilning procedure. For example, drying may be performed at atemperature of from 100 °C to 800 °C, such as from 100 °C to 700 °C, from 120 °C to 160 °C, or from 130 °C to 150QC. Additionally, the time needed to dry the wet mixture is not particularly limited, and it may vary depending on the consistency of the wet mixture, the liquid media used in the wet mixture, the temperature used to perform the drying, and the amount of the liquid media in the wet mixture. In some non-limiting embodiments, drying is performed for from 10 minutes to 90 minutes, such as from 20 minutes to 70 minutes, or from 30 minutes to 60 minutes.

[0083] The reflective granules may comprise an effective amount of the powdered reflective mineral so as to exhibit a bulk total solar reflectance (also referred to herein as “total solar reflectance” (TSR) or simply “solar reflectance”) of at least 50%, such as at least 65%, or at least 70% or at least 80% or at least 85%, as measured using a reflectometer from Surface Optics Corporation (San Diego, CA). The reflective granules may exhibit a TSR of from 50-90%, from 70-90%, from 80-90%, from 50- 95%, from 70-95%, or from 80-95%. For example, the 410-Solar visible / NIR Portable Reflectometer from Surface Optics Corporation (San Diego, CA) may be used, which measures reflectance over 7 wavelength bands and uses an algorithm to calculate the TSR.

[0084] The reflective granules may sustain a high TSR for an extended time. For example, the reflective granules may not have a reduced TSR after 2 weeks of more than 25%.

[0085] In some non-limiting embodiments or aspects, the dried granules may be kilned. The kilning process may be performed at any suitable temperature and for any suitable length of time. For example, in some non-limiting embodiments, the dried mixture may be kilned (or fired) at a temperature of from 900 °C to 1500 °C, such as from 1000 <C to 1300 °C, from 1025 <C to 1275 °C, or from 1050 <C to 1250QC.

[0086] In some non-limiting embodiments or aspects, a coating and / or surface treatment that does not significantly decrease the reflectance of the granules may be applied to the granules. For example, many suitable coatings and / or surface treatments may be sealants or otherwise clear coatings that do not adversely affect the overall solar reflectance of the granules. In some non-limiting embodiment, the granules may be treated with an emulsion of silicones, silanes, and siloxanes without added solvents. The coating may decrease staining of the granules (e.g., by the asphalt of the substrate).

[0087] The surface treatments and / or coatings can be applied to the granules using a variety of methods and processes known to those of skill in the art. For example, in one exemplary embodiment, after the raw material has been sized according to the preferred screen size and packaged, the particles can be treated by adding the particles to an aqueous solution, fully saturating the particles with the treatment, and then immediately drying the particles to drive off excess moisture at a temperature not exceeding 600 °F (316°C). In another exemplary embodiment, after the raw material has been sized according to the preferred screen size and packaged, the particles can be post-treated by spraying the particles with an aqueous solution and then immediately drying the particles to drive off excess moisture at a temperature not to exceed 600 °F (316 °C). In yet another exemplary embodiment, after the raw material has been sized according to the preferred screen size, the particles can be treated by spraying the particles with an aqueous solution and then immediately kiln drying the particles to drive off excess moisture at a temperature not to exceed 600 °F (316°C) after which time they can be packaged. In still yet another embodiment of coating and / or treating the surface of granules, after the raw material has been sized according to the preferred screen size, the particles are treated by spraying with an aqueous solution followed by immediately aerating the particles to drive off excess moisture after which time the particles can be packaged. The coatings and / or surface treatments may be applied as delivered (e.g., off the shelf) or from aqueous dilutions. The dilution ratio may range from 1 :5 to 1 :200. The dilutions may be prepared from demineralized water.

[0088] In some non-limiting embodiments or aspects, the granules may have a particle size distribution comprising at least 90% of the granules having an average particle size of from greater than or equal to 0.841 mm (not passing through 20 Mesh) to less than 2.38 mm (passing through 8 Mesh but not 12 Mesh), such as at least 95% or at least 98%. The particle size distribution may be determined by running the granules through a series of sieves that get progressively smaller. For example, the granules may be sequentially passed through the following series of sieves: 6 Mesh (3.36 mm), 8 Mesh (2.38 mm), 12 Mesh (1.68 mm), 16 Mesh (1.19 mm), 20 Mesh (0.841 mm), 30 Mesh (0.555 mm), 40 Mesh (0.4 mm), 50 Mesh (0.297 mm), 70 Mesh (0.21 mm), 100 Mesh (0.149 mm), with the material passing through the 100 mesh settling in a pan.

[0089] In some non-limiting embodiments or aspects, the granules may have a particle size distribution comprising at least 90% of the granules having an average particle size of from greater than or equal to 0.297 mm (not passing through 50 Mesh) to less than 0.555 mm (passing through 30 Mesh but not 40 Mesh), such as at least 95% or at least 97%. The particle size distribution may be determined by running the granules through a series of sieves that get progressively smaller. For example, the granules may be sequentially passed through the following series of sieves: 6 Mesh (3.36 mm), 8 Mesh (2.38 mm), 12 Mesh (1.68 mm), 16 Mesh (1.19 mm), 20 Mesh (0.841 mm), 30 Mesh (0.555 mm), 40 Mesh (0.4 mm), 50 Mesh (0.297 mm), 70 Mesh (0.21 mm), 100 Mesh (0.149 mm), with the material passing through the 100 mesh settling in a pan.

[0090] Without being bound by a particular theory, it is believed that the granules having a narrow particle size distribution as described herein result in a more sustained high TSR due to better coverage of the substrate from the narrow particle size distribution (and shape described herein).

[0091] In some non-limiting embodiments or aspects, the granules may have a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.5, such as having a Krumbein roundness of at least 0.7 and a Krumbein sphericity of at least 0.7, such as having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.9, such as having a Krumbein roundness of at least 0.7 and a Krumbein sphericity of at least 0.9, such as having a Krumbein roundness of at least 0.9 and a Krumbein sphericity of at least 0.9, determined using the Krumbein Roundness and Sphericity chart.

[0092] In some non-limiting embodiments or aspects, the granules may have a greater roundness and / or sphericity and / or symmetry (compared to crushed granules), as determined by a dynamic image analysis system, such as a CAMSIZER particle size and shape analyzer (available from Microtrac (York, PA)).

[0093] In some non-limiting embodiments or aspects, the granules may have a more spherical width:length ratio (compared to crushed granules), as determined by a dynamic image analysis system, such as the CAMSIZER particle size and shape analyzer.

[0094] Without being bound by a particular theory, it is believed that the granules having a shape as described herein result in a more sustained high TSR due to thegranules having fewer crevices that would be difficult to coat by the coating applied to the granules as described herein.

[0095] In some non-limiting embodiments or aspects, the granules are not crushed following granulating of the mixture of the powdered reflective mineral and the binder. Without being bound by a particular theory, it is believed that not crushing the granules after the granulating step as described herein result in a more sustained high TSR due to the crushing of the granules resulting in granules having more crevices (compared to uncrushed granules, which crevices make it difficult to coat by the coating applied to the granules as described herein. Further, crushing of the granules result in particles having more jagged edges that are more easily broken during downstream processes in which the granules are applied to architectural materials, thus exposing a larger surface area of uncoated granule, resulting in a decrease in TSR over time. Not crushing the granules is also believed to make them less susceptible to fracture, which potentially avoids many of the above issues associated with crushed granules and / or granules having crevices and / or jagged edges.

[0096] The foregoing characteristics of the granules may enable better coverage of the granules by a coating as described herein. The coating may prevent staining of the granules (e.g., by the asphalt). Thus, granules having the size, shape, and / or particle size distribution more conducive to full and / or uniform coating and less susceptible to fractures that would expose uncoated granules may be more stain resistant.

[0097] The reflective granules may be used to form an architectural material. The architectural material may comprise a roofing material or other building material. The architectural material may be positioned in an outdoor environment.

[0098] The roofing material may be formed by applying the reflective granules to an asphalt layer to adhere the granules thereto. The asphalt layer may comprise bitumen or modified bitumen, modified with at least one reinforcing material, such as polyester or fiberglass. Such roofing material having the reflective granules applied to an asphalt layer may constitute a cool roof system.

[0099] In some non-limiting embodiments or aspects, the reflective granules may be applied to the asphalt layer to adhere the reflective granules thereto. Subsequently, further reflective granules may be applied to the asphalt layer to adhere the further reflective granules thereto. The further reflective granules may have a smaller average particle size compared to the reflective granules. The application of thefurther reflective granules having a smaller average particle size (being finer in particle size) over the reflective granules (being coarser in particle size) may result in better coverage over the asphalt layer by reflective granules, due to the smaller further reflective granules filling in the gaps over the asphalt layer left by the initial application of the larger reflective granules. Thus, the roofing material as a whole may have a higher TSR compared to a roofing material using only a single layer of the coarser solar reflective granules.

[0100] The present disclosure is also directed to a method for making reflective granules. The method may include mixing the powdered reflective mineral and the binder to form a mixture. The mixture may be granulated to form the granules by building up the powdered reflective mineral into granules within or having approximately the desired particle size distribution.

[0101] The granules may be sieved to obtain granules within the desired particle size distribution. The granules may be sieved to remove undersized particulate below the particle size distribution and / or removing oversized particulate above the particle size distribution. For example, the granules may be sieved through a series of sieves that get progressively smaller as described herein. The reflective granules within the desired particle size distribution may not be crushed after the granulating step.

[0102] In some non-limiting embodiments or aspects, the oversized (relative to the desired particle sized distribution) particulate removed through the sieving may be milled to a smaller particle size to form milled particulate. The milled particulate may be mixed (e.g., recycled and / or recirculated) back into the mixture with the powdered reflective mineral and the binder and / or in with the reflective granules. Milling the oversized particulate may avoid wasting oversized granules and form granules having a particle size within the desired particle size distribution.

[0103] In some non-limiting embodiments or aspects, the undersized (smaller relative to the desired particle sized distribution) particulate removed through the sieving may be mixed (e.g., recycled and / or recirculated) back into the mixture with the powdered reflective mineral and the binder so as to be used in the granulating to form the reflective granules. This recycling of the undersized particulate may avoid wasting undersized granules and form (e.g., build up) those undersized granules into granules having a particle size within the desired particle size distribution. When recycling the undersized particulate into the mixture, the amount of the liquid media needed to reach the desired consistency of the wet mixture may be increased. In somenon-limiting embodiments, the recycled undersized particles may be added to the production feed in an amount of from 25 wt% of the feed or less.

[0104] Referring to FIG. 5, a process is shown for preparing reflective granules according to non-limiting embodiments or aspects of the present disclosure. The process shown in FIG. 5 prepares reflective granules from a kaolin powered reflective mineral, but it will be appreciated that other types of powered reflective mineral may be used.

[0105] According to the non-limiting process in FIG. 5, a kaolin slurry may be mixed with the binder and other additives (e.g., hardeners, pigments, and the like) to form a reflective formulation. The reflective formulation may undergo a granulating step in which spherical and / or nodular granules having the shape described herein are formed. The formed granules may be sieved through a series of sieves (as described herein) to achieve the desired particle size distribution of the granules. Undersized granules below the desired particle size distribution may be recycled to the granulating step to build up to granules at or above the desired particle size distribution. Oversized granules above the desired particle size distribution may be recycled by further milling the oversized granules and recycling them to the mixing step.

[0106] The sieved granules within the desired particle size distribution may be kilned to form granules having a high crush strength, having the desired spherical and / or nodular shape, and having a high solar reflectance. The granules may not be crushed during the process, particularly following the granulating step.EXAMPLES

[0107] The following examples are presented to demonstrate the general principles of the disclosure. The disclosure should not be considered to be limited to the specific examples presented.Examples 1-3 Reflective Granules

[0108] For Examples 1 and 3, an aqueous slurry including a powdered kaolin clay was mixed with a polyvinyl alcohol binder. The aqueous slurry was dried to drive off the water and form reflective granules. The reflective granules were kilned. In Examples 1 and 3, the reflective granules were not crushed after granulation and were sieved to have the particle size distribution shown in Tables 1 A-1 B below.

[0109] For Comparative Example 2, the aqueous slurry including the same powdered kaolin clay was mixed with the same polyvinyl alcohol binder to form. The aqueous slurry was dried to drive off the water and form reflective granules. The reflective granules were kilned. In Example 2, the reflective granules were crushed after granulation and were sieved to have the particle size distribution shown in Table 1 A below.Table 1ATable 1 B

[0110] It can be seen from Table 1 A-1 B that the reflective granules of Example 1 had a narrower particle size distribution than the reflective granules of Comparative Example 2. The reflective granules of Example 3 also had a narrow particle size distribution.FIGS. 3A-3B show graphs of the particle size distributions to visually show the narrower particle size distribution of Example 1 compared to Comparative Example 2.

[0111] Table 1 C shows the average particle sizes (D10, D50, D90) of Example 1 and Comparative Example 2 and data defining the shape of the granules in each:Table 1Cd10) / d50} . A higher SPAN corresponds to a wider size distribution.U: Non-uniformity factor is defined as the symmetry of the size distribution (typically U= d60 / d10). A higher U corresponds to a wider range of particle size & greater variation in size.SPHT: Sphericity is defined as the roundness. Perfect circles or spheres have a SPHT equal to 1 . For all other shapes, SPHT <1 .Symm: Symmetry- a perfectly symmetrical shape has a symmetry equal to 1 . For all other shapes, symmetry <1 . b / l: Aspect ratio “width / length”.

[0112] The properties measured in Table 1 C were determined by a CAMSIZER particle size and shape analyzer (dynamic image analysis). As the data indicates, the uncrushed granules are more spherical and symmetric than the crushed granules.

[0113] FIG. 1 shows a photograph of the reflective granules of Example 1 , while FIG. 2 shows a photograph of the reflective granules of Comparative Example 2. As can be seen from the photographs, the reflective granules of Example 1 had a rounder, more spherical shape compared to the reflective granules of Comparative Example 2.

[0114] The reflective granules of Example 1 and Comparative Example 2 were tested for their strength according to a crush test method based on a modified version of ISO 13503-2, Section 11 . The testing showed that the reflective granules of Example 1 generated approximately one-third of the amount of fines compared to the reflectivegranules of Comparative Example 2, indicating that the reflective granules of Example 1 were stronger, which translates to a lower chance of the reflective granules breaking to expose uncoated surface, which could lower the TSR.

[0115] An architectural material was formed by coating the granules and applying each of the coated reflective granules of Example 1 and Comparative Example 2 over an asphalt substrate.

[0116] Further architectural material was formed by applying each of the reflective granules of Example 1 and Comparative Example 2 over an asphalt substrate, and over each of the asphalt substrates coated in the reflective granules, further granules were applied, the further granules made from the same materials (i.e., kaolin clay and polyvinyl alcohol binder). The further granules were not crushed after granulation. The further granules were finer (i.e., had smaller average particle size) compared to the reflective granules of Example 1 and Comparative Example 2. Thus, for each of the further architectural materials prepared, a first layer of reflective granules (of Example 1 or Comparative Example 2) was coated with the further (finer) granules.

[0117] The architectural materials were tested for initial and sustained TSR values, the results of which are shown in Table 2.Table 2

[0118] As can be seen from the results in Table 2, the architectural material prepared with the reflective granules of Example 1 had a higher TSR after 2 weeks and less reduction compared to initial TSR after 2 weeks compared to the architectural material prepared with the reflective granules of Comparative Example 2. Thus, the reflective granules of Example 1 have an enhanced sustained TSR. FIG. 4 shows agraph of the TSR of the tested architectural material to visually show the enhanced sustained TSR of Example 1 compared to Comparative Example 2.

[0119] It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.

Claims

WHAT IS CLAIMED IS1 . Reflective granules, comprising: granules comprising a granulated mixture of a powdered reflective mineral and a binder, the granules having: a sphericity of at least 0.9, as determined by dynamic image analysis; and / or a symmetry of at least 0.9, as determined by dynamic image analysis.

2. The reflective granules of claim 1 , the granules having an aspect ratio of at least 0.8, as determined by dynamic image analysis.

3. The reflective granules of claim 1 , the granules having a particle size distribution comprising: at least 90% of the granules having an average particle size of from greater than or equal to 0.841 mm to less than 2.38 mm, or at least 90% of the granules having an average particle size of from greater than or equal to 0.297 mm to less than 0.555 mm.

4. The reflective granules of claim 1 , the granules having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.5.

5. The reflective granules of any of claim 1 , wherein the granules not crushed following granulating of the mixture of the powdered reflective mineral and the binder.

6. The reflective granules of claim 1 , wherein the powdered reflective mineral comprises kaolin clay, a sand-based material that converts into cristobalite upon kilning, or any combination thereof.

7. The reflective granules of claim 1 , further comprising: a coating applied to a surface of the granules.

8. An architectural material comprising the reflective granules of claim 1 .

9. The architectural material of claim 8, wherein the architectural material comprises a roofing material.

10. The architectural material of claim 8, comprising an asphalt substrate to which the reflective granules are adhered.1 1 . The architectural material of claim 8, further comprising further reflective granules applied over the reflective granules, the further reflective granules having a smaller average particle size compared to the reflective granules.

12. A method for making reflective granules, comprising: mixing a powdered reflective mineral and a binder to form a mixture; and granulating the mixture to form granules, the granules having: a sphericity of at least 0.9, as determined by dynamic image analysis; and / or a symmetry of at least 0.9, as determined by dynamic image analysis.

13. The method of claim 12, the granules having an aspect ratio of at least 0.8, as determined by dynamic image analysis.

14. The method of claim 12, further comprising sieving the reflective granules to obtain reflective granules having a particle size distribution by removing undersized particulate below the particle size distribution and / or removing oversized particulate above the particle size distribution.

15. The method of claim 14, further comprising: milling the oversized particulate to form milled particulate; and mixing the milled particulate with the reflective granules.

16. The method of claim 14, wherein the undersized particulate is used in the granulating to form the reflective granules.

17. The method of claim 14, wherein the particle size distribution comprises: at least 90% of the reflective granules having an average particle size of from greater than or equal to 0.841 mm to less than 2.38 mm or at least 90% of the granules having an average particle size of from greater than or equal to 0.297 mm to less than 0.555 mm.

18. The method of claim 12, wherein the reflective granules are not crushed following the granulating.

19. The method of claim 12, the reflective granules having a Krumbein roundness of at least 0.5 and a Krumbein sphericity of at least 0.5.

20. The method of claim 12, wherein the powdered reflective mineral comprises kaolin clay, a sand-based material that converts into cristobalite upon kilning, or any combination thereof.

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