Pigment additive for improving solar reflectance
View Patent ↗A pigment additive and resulting pigment are described that when incorporated in paints for example, significantly increases total solar reflectance. Also described are compositions utilizing the noted pigments, and related methods. The pigments are formed from iron oxide and/or chromium oxide and utilize as an additive, one or more phosphate compounds.
1. A black colored pigment exhibiting improved solar reflectance, the pigment comprising:
a material formed in the presence of an effective amount of a phosphate and in the form of a solid solution having a formula (Cr x Fe y Me z ) 2 O n wherein x+y+z=1, n is the number of oxygens required for electroneutrality, Me is at least one metal, and z is less than 0.3, wherein x and y cannot be zero;
wherein the material when in a pressed cup form, exhibits an average reflection of less than p20% for light having a wavelength between 400 and 600 nm;
wherein the material when in a pressed cup form, exhibits an average reflection of greater than 40% for light having a wavelength between 1300 and 1600 nm; and
wherein the material includes phosphate ions.
2. The pigment of claim 1 wherein z is less than 0.2.
3. The pigment of claim 1 wherein the material exhibits an average reflection of less than 15% for light having a wavelength between 400 and 600 nm.
4. The pigment of claim 1 wherein the material exhibits an average reflection of less than 10% for light having a wavelength between 400 and 600 nm.
5. The pigment of claim 4 wherein the material exhibits an average reflection of less than 5% for light having a wavelength between 400 nm and 600 nm.
6. The pigment of claim 1 wherein the material exhibits an average reflection of greater than 45% for light having a wavelength between 1300 and 1600 nm.
7. The pigment of claim 1 wherein the material exhibits an average reflection of greater than 50% for light having a wavelength between 1300 and 1600 nm.
8. A brown or green pigment exhibiting improved solar reflectance, the pigment comprising:
a material formed in the presence of an effective amount of a phosphate and in the form of a solid solution having a formula (Cr x Fe y Me z ) 2 O n wherein x +y+z=1, n is the number of oxygens required for electroneutrality, Me is at least one metal, and z is less than 0.3 wherein x and y cannot be zero;
wherein the material when in a pressed cup form, exhibits an average reflection of less than 25% for light having a wavelength between 400 and 600 nm;
wherein the material when in a pressed cup form, exhibits an average reflection of greater than 50% for light having a wavelength between 1300 and 1600 nm; and
wherein the material includes phosphate ions.
9. The pigment of claim 8 wherein the material exhibits an average reflection of less than 20% for light having a wavelength between 400 and 600 nm.
10. The pigment of claim 8 wherein the material exhibits an average reflection of less than 15% for light having a wavelength between 400 and 600 nm.
11. The pigment of claim 8 wherein the material exhibits an average reflection of greater than 55% for light having a wavelength between 1300 and 1600 nm.
12. A method for forming a pigment exhibiting improved solar reflectance, the method comprising:
providing a pigment precursor composition including at least one of iron oxide and chromium oxide;
adding an effective amount of a phosphate compound to the precursor composition;
heating the precursor composition and phosphate compound to a temperature of at least 1500° F. to form a secondary composition;
cooling the secondary composition to thereby form a pigment, the pigment including a material in the form of a solid solution having either (i) a formula (Cr x Fe y Me z ) 2 O n wherein x+y+z=1, n is the number of oxygens required for electroneutrality, Me is at least one metal, and z is less than 0.3 wherein x and y cannot be zero; and wherein the material when in a pressed cup form, exhibits an average reflection of less than 20% for light having a wavelength between 400 and 600 nm; wherein the material when in a pressed cup form, exhibits an average reflection of greater than 40% for light having a wavelength between 1300 and 1600 nm; wherein the material includes phosphate ions.
13. The method of claim 12 wherein heating is performed at a temperature of from about 1750° F. to about 2250° F. for about 0.5 to about 48 hours.