Patent ID: 6156289
Filing Date: 2000-12-05
Classification: C01P,C09C,E04D,Y10T

Abstract:
A method of preparing colored roofing granules from granulated mineral-containing matter comprising slag having an iron content of about 15% to about 70% by weight and being sized so that approximately 100% of said granulated matter will pass through a number 8 U.S. Standard Sieve and no more than approximately 2% will pass through a number 40 U.S. Standard Sieve, said method comprising the steps of:heating said granules to a temperature of from about 450.degree. C. to about 1000.degree. C.; andmaintaining said temperature for a period of time sufficient to cause oxidation of said iron to effect a color change in said granules and thereby form said colored roofing granules.