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Hyperbright white roofing granules with high solar reflectance

a technology of solar reflectance and roofing granules, applied in special ornamental structures, textiles and papermaking, spectral modifiers, etc., can solve the problems of low solar reflectance, low use value, and use of granular materials, and achieve the effect of high solar reflectan

Inactive Publication Date: 2015-07-09
SPECIALTY GRANULES
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a new type of refractory that is very white and reflective of solar energy. This refractory can be made from ceramic materials without any colored coatings. Additionally, this invention includes the use of hyperbright white granules made from this refractory, which can be used as a roofing material. These granules are bright white throughout their entire structure, not just having a white coating. The use of these hyperbright white granules in roofing materials can reduce heat absorption and provide a more energy efficient roof. The invention also includes methods for making the hyperbright white granules and a roofing system comprising them.

Problems solved by technology

Many of the granular materials used, such as artificially-colored crushed rock, are dark in color and also have low solar reflectance.
However, the manufacture of very white roofing granules having high solar reflectance (also referred to as “bright white” or “hyperbright white” granules) by using conventional silicate / clay coating processes on standard base rock is impractical and cost-prohibitive.
The coating cannot be cost-effectively pigmented or applied to completely shield the underlying base rock and provide a granular Total Solar Reflectance (TSR) requirement of at least 0.80.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0127]The following example demonstrates the performance parameters of hyperbright white roofing granules according to one embodiment of the present invention. This example does not limit the scope of the invention, and many variations and modifications of the exemplary embodiment are within the scope of the invention.

[0128]A homogeneous mixture of 75% KT Mercer Clay, 15% Unimin Silverbond 325 Silica, and 10% Calcium Hydroxide (Fisher Reagent) is dampened with sufficient water to produce a pliable mass in accordance with the process described above. After compaction at 2000 psi in a hydraulic press, oven firing at 1250° C., and crushing / screening to No. 11 grading, the resulting hyperbright white granules shows the following test results:

[0129]Hunter Color L=88.5

[0130]Hunter Color a=0.4

[0131]Hunter Color b=10.3

[0132]Solar Reflectance TSR=0.845

[0133]Translucency =0%

[0134]Barrett Hardness=84.4

[0135]Stain=2

[0136]EXAMPLE 2

[0137]A formulation of 75% KT Mercer Clay, 15% Unimin Silverbond ...

example 3

[0170]A formulation of 75% KT Mercer Clay, 15% Unimin Silverbond 325 Silica, and 10% Minspar 200 Feldspar is mixed, extruded, and kiln fired, and post-treated using the same equipment and procedure detailed in previous example #2. This finished refractory also exhibits similar characteristics:

[0171]Hunter Color L=89.7

[0172]Hunter Color a=−0.2

[0173]Hunter Color b=6.8

[0174]Solar Reflectance TSR=0.838

[0175]Thermal Emittance=0.90

[0176]Translucency=0

[0177]Barrett Hardness=87.0

[0178]Stain=3

[0179]Porosity=43.2%

[0180]XRF Analysis:[0181]Al2O3=34.3%[0182]SiO2=62.0%[0183]Fe2O3=0.4%[0184]Other=3.3%

[0185]Fibrous Minerals: None Detected

example 4

[0186]A rotary pelletizer is charged with a mixture consisting of 62.5% KT Mercer Clay, 15% Unimin Silverbond 325 Silica, 10% Minspar 200 Feldspar, 10% Minex 4 Nephaline Syenite, and 2.5% TATA Sodium Carbonate. As the pelletizer rotates, a water spray is directed at the tumbling dry refractory mixture which subsequently forms small aggregates when the water droplets are absorbed. Further spraying causes the aggregates to grow larger in size. The “green” refractory aggregates are then screened through an 8 mesh Tyler sieve onto a 35 mesh Tyler sieve to isolate material of roofing granule size (i.e. No. 11). Both the +8 mesh oversize (broken up) and the −35 mesh undersize materials are returned to the pelletizer for recycle. The −8+35 mesh granules are then fired in a muffle furnace at 1250° C. for 2 hours. After cooling to room temperature, the resulting hyperbright white granules have a glossy glazed surface and show the following test results:

[0187]Hunter Color L=88.4

[0188]Hunter C...

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Abstract

The invention provides a bright white refractory roofing granule, comprising a ceramic material formed from a substantially homogenous mixture of a ceramic-forming clay, sintering material, and optionally comprising silica particles, and other potential additives, said bright white refractory roofing granule having a total solar reflectance of at least 0.80 and a Hunter Color L-value of at least 85.0, together with processes for making and using the same.

Description

RELATED APPLICATIONS[0001]This application claims priority to U.S. Provisional Application 61 / 661,637, filed Jun. 19, 2012, as well as U.S. Provisional Application 61 / 764,301, filed Feb. 13, 2013, the entire contents of each of which are incorporated by reference herein.FIELD[0002]The present invention pertains to the fields of roofing materials and of ceramic materials, more particularly to high-reflectance ceramic materials containing clay, silica particles, sintering aids and roofing granules made therefrom.BACKGROUND OF THE INVENTION[0003]Due to increased interest in energy conservation, the USEPA has developed standards under its Energy Star® program for increased magnitude and retention of solar reflectance of roofing materials. A greater reflectance leads to less heat absorption by roofing materials and lowered temperature control costs for buildings. The most common roofing materials comprise substrates of asphalt and / or modified bitumen which themselves are black in color a...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G02B1/02B29C47/00B05D3/00E04D1/00B29C48/04
CPCG02B1/02E04D1/00E04D2001/005B05D3/002B29C47/0011D06N5/003C04B33/14C04B35/62695C04B35/62807C04B35/6316E04D7/005C04B2235/3201C04B2235/3206C04B2235/3208C04B2235/3215C04B2235/3217C04B2235/3232C04B2235/3272C04B2235/3284C04B2235/3418C04B2235/3427C04B2235/3463C04B2235/349C04B2235/6021C04B2235/6562C04B2235/6565C04B2235/72C04B2235/80C04B2235/96C04B2235/9607C04B38/009C04B2111/00586Y10T428/24413B29C48/04Y02A30/254Y02B80/00C04B38/0074C04B38/068
Inventor JOEDICKE, INGO B.SMALL, DEREK J.KEMP, III, WADE O.
Owner SPECIALTY GRANULES
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