Granules

Patent metadata

Field	Value
Publication number	US-2020189986-A1
Application number	US-201816620087-A
Country	US
Kind code	A1
Filing date	Jun 13, 2018
Priority date	Jun 19, 2017
Publication date	Jun 18, 2020
Grant date	—

Abstract

Plurality of granules comprising a ceramic core having an outer surface and a shell on and surrounding the core, wherein the shell comprises ceramic particles bound together with an inorganic binder, the inorganic binder comprising reaction product of at least alkali silicate and hardener, wherein the ceramic particles are present as greater than 50 percent by weight of the shell of the respective granule, based on the total weight of the shell of the respective granule, wherein the shell of each granule has a total porosity in a range from greater than 0 to 60 percent by volume, based on the total volume of the shell of the respective granule, wherein the shell of each granule has a volume of at least 40 volume percent, based on the total volume of the respective granule, and wherein the granules have a minimum Total Solar Reflectance of at least 0.7. The granules are useful, for example, as roofing granules.

First claim

1 . A plurality of granules comprising a ceramic core having an outer surface and a shell on and surrounding the core, wherein the shell comprises ceramic particles bound together with an inorganic binder, the inorganic binder comprising reaction product of at least alkali silicate and hardener, wherein the ceramic particles are present as greater than 50 percent by weight of the shell of the respective granule, based on the total weight of the shell of the respective granule, wherein the shell of each granule has a total porosity in a range from greater than 0 to 60 percent by volume, based on the total volume of the shell of the respective granule, wherein the shell of each granule has a volume of at least 40 volume percent, based on the total volume of the respective granule, and wherein the granules have a minimum Total Solar Reflectance of at least 0.7.

2 . The plurality of granules of claim 1 , wherein the ceramic cores include solid ceramic cores.

3 . The plurality of granules of claim 1 , wherein the core has a diameter of at least 200 micrometers.

4 . The plurality of granules of claim 1 , wherein the shell has a thickness of at least 50 micrometers.

5 . The plurality of granules of claim 1 , wherein the ceramic particles of each granule comprise no more than 10 percent by weight pure TiO 2 , based on the total weight of either the core or granule for the respective core or granule.

6 . The plurality of granules of claim 1 , wherein the ceramic particles of each granule comprise no more than 10 percent by weight pure Al 2 O 3 , based on the total weight of the granule for either the core or granule for the respective core or granule.

7 . The plurality of granules of claim 1 , wherein the granules have a Tumble Toughness Value of least 70 after immersion in water at 20° C.±2° C. for two months.

8 . The plurality of granules of claim 1 , wherein the hardener is amorphous.

9 . The plurality of granules of claim 1 , wherein the hardener is at least one of an aluminum phosphate, an aluminosilicate, a cryolite, a calcium salt, or a calcium silicate.

10 . The plurality of granules of claim 1 , wherein the ceramic particles comprise at least one component with Total Solar Reflectance of at least 0.7.

11 . The plurality of granules of claim 1 , wherein the ceramic particles comprise mineral.

12 . The plurality of granules of claim 1 , wherein the shell comprises first and second concentric layers, with the first layer being closer to the core than the second layer.

13 . The plurality of granules of claim 12 , wherein the first shell layer has a first specific surface area, wherein the second shell layer has a second specific surface area, and wherein the first specific surface area is greater than the second specific surface area.

14 . A roofing material comprising a plurality of granules of claim 1 having a total solar reflectance of at least 70%.

15 . A method of making the plurality of granules of claim 1 , the method comprising:
providing a plurality of ceramic cores; coating each of the ceramic cores with a shell precursor, wherein the shell precursor comprises an aqueous dispersion comprising ceramic particles, alkali silicate precursor, and hardener precursor; and curing the coated aqueous dispersion to provide the plurality of granules.

16 . The method of claim 15 , wherein the coating the ceramic core with the shell comprises fluidized bed coating.

Assignees

• 3M Innovative Properties Co

Inventors

• Brown Robert P
• Skorina Taisiya
• Everman Rebecca L A
• Tangeman Jean A
• Budd Kenton D

Classifications

• C04B35/62897

  Coatings characterised by their thickness · CPC title

• B01J13/206 Primary

  Hardening; drying · CPC title

• C04B35/6316

  Binders based on silicon compounds · CPC title

• C04B41/87 Primary

  Ceramics · CPC title

• C04B35/62892

  with a coating layer consisting of particles · CPC title