Solar reflective composite granules and method of making solar reflective composite granules

• US 10,730,799 B2
• Filed: 12/27/2017
• Issued: 08/04/2020
• Est. Priority Date: 12/31/2016
• Status: Active Grant

• Current Assignee: CertainTeed Corp. (Compagnie De Saint-Gobain)
• Original Assignee: CertainTeed Corp. (Compagnie De Saint-Gobain)
• Inventors: Panzarella, Tracy H., Koseski, Ryan, Dinoia, Todd P., Lante, Bojana
• Primary Examiner(s): Van Sell, Nathan L
• Application Number:
  US15/855,095
• Publication Number:
  US 20180194684A1
• Time in Patent Office: 951 Days
• CPC Class Codes: C04B 2111/00586 Roofing materials
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3218 Aluminium (oxy)hydroxides, e.g. boehmite, gibbsite, alumina sol
• CPC Class Codes: C04B 2235/3232 Titanium oxides or titanates, e.g. rutile or anatase
• CPC Class Codes: C04B 2235/3284 Zinc oxides, zincates, cadmium oxides, cadmiates, mercury oxides, mercurates or oxide forming salts thereof
• CPC Class Codes: C04B 2235/3463 Alumino-silicates other than clay, e.g. mullite
• CPC Class Codes: C04B 2235/402 Aluminium
• CPC Class Codes: C04B 2235/5427 millimeter or submillimeter sized, i.e. larger than 0,1 mm
• CPC Class Codes: C04B 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/5472 Bimodal, multi-modal or multi-fraction
• CPC Class Codes: C04B 2235/608 Green bodies or pre-forms with well-defined density
• CPC Class Codes: C04B 2235/61 Mechanical properties, e.g. fracture toughness, hardness, Young's modulus or strength
• CPC Class Codes: C04B 2235/6562 Heating rate
• CPC Class Codes: C04B 2235/6565 Cooling rate
• CPC Class Codes: C04B 2235/9646 Optical properties
• CPC Class Codes: C04B 35/18 rich in aluminium oxide
• CPC Class Codes: C04B 35/62695 Granulation or pelletising devices for shaping artificial aggregates from ceramic mixtures B28B1/004
• CPC Class Codes: C04B 35/62805 Oxide ceramics
• CPC Class Codes: C04B 35/6303 Inorganic additives
• CPC Class Codes: C04B 35/636 Polysaccharides or derivatives thereof
• CPC Class Codes: C04B 41/0081 : characterised by the subsequent cooling step
• CPC Class Codes: E04D 7/005 : characterised by loose or embedded gravel or granules as an outer protection of the roof covering

Abstract

A method of making a plurality of composite granules can include: forming green body granules comprising an aluminosilicate; heating the green body granules to form sintered granules; cooling the sintered granules according to a cooling regime, wherein the cooling regime comprises a temperature hold between 700° C. and 900° C. for at least one hour. In a particular embodiment, the aluminosilicate for making the composite granules can have a particle size less than 150 μm. The composite granules are particularly suitable as roofing granules and can have a desired combination of high solar reflectance SR and low lightness L*, a low bulk density, good weather resistance and strength.

Claims

1. A method of making a plurality of composite granules, comprising:

forming green body granules comprising an aluminosilicate;

heating the green body granules to form sintered granules;

cooling the sintered granules according to a cooling regime, wherein the cooling regime comprises a temperature hold between 700°

C. and 900°

C. for at least one hour,

wherein a difference in solar reflectance Δ

SR of composite granules subjected to the temperature hold (SR_TH) in comparison to composite granules not subjected the temperature hold (SR_F) is at least 3%, with Δ

SR=SR_TH−

SR_F.

2. The method of claim 1, wherein the temperature hold is at least two hours.

3. The method of claim 1, wherein the solar reflectance of the composite granules is at least 25%.

4. The method of claim 1, wherein the L* value of the composite granules is not greater than 50.

5. The method of claim 1, wherein forming of the green body granules includes adding of a solvent and a binder.

6. The method of claim 5, wherein the binder is modified starch and the solvent is water.

7. The method of claim 1, wherein forming of the green body granules includes adding of ATH in an amount of at least 2 wt % based on the total dry weight of the green body granules.

8. The method of claim 7, wherein the ATH has a median particles size not greater than 30 μ

m.

9. The method of claim 1, further including sizing the green body granules to a size of at least 0.3 mm and not greater than 3.0 mm.

10. The method of claim 1, wherein heating is conducted up to a maximum sintering temperature of at least 1000°

C.

11. The method of claim 1, wherein heating is conducted up to a maximum sintering temperature of not greater than 1300°

C.

12. The method of claim 1, wherein the aluminosilicate is a natural rock including rhyolite, andesite, basalt, meta-basalt, or any combination thereof.

13. The method of claim 1, wherein an amount of the aluminosilicate in the green body granules is at least 50 wt % based on the total weight of the green body granules.

14. The method of claim 1, wherein the aluminosilicate of the green body granules has an average particle size not greater than 150 μ

m.

15. The method of claim 1, wherein a bulk density of the composite granules is not greater than 1.0 g/cm³.

16. The method of claim 1, wherein the composite granules have an average crush strength of at least 45 N.

17. The method of claim 1, wherein the green body granules are essentially free of TiO₂, ZnO₂, and Mg(OH)₂.

18. A plurality of composite granules, comprising:

a bulk density not greater then 1.0 g/cm³;

an amount of aluminosilicate of at least 50 wt % based on a total weight of the composite granules;

an amount of aluminum trihydrate of at least 2 wt % based on the total weight of the composite granules;

a solar reflectance of at least 25%;

an L* value of not greater than 50; and

an average crush strength of at least 45 N.

19. The plurality of composite granules of claim 18, wherein the composite granules are free of a coating.