Aminoplast Resin Photochromic Coating From PPG
l Patent No. U.S. 6,506,488 B1
PPG Industries has obtained a patent for an article comprising, in combination, a substrate and a cured photochromic aminoplast resin coating on at least one surface of the substrate, the coating being prepared by combining components comprising molecules having at least 2 hydroxyl groups per molecule; aminoplast component comprising molecules having at least two reactive groups per molecule; and a photochromic amount of photochromic component.
This is provided that the components are combined without reacting the components before combining, the cured coating being substantially free of cosmetic defects, the components being used in such proportions to produce a photochromic aminoplast resin coating having a Fischer microhardness of at least 45 to 180 Newtons per mm2 as measured with a Fischerscope H-100 using a 100 milli Newton load, 30 load steps and 0.5 second pauses and exhibiting a ∆OD of at least 0.15 after 30 seconds and at least 0.47 after eight minutes, and a bleach rate of not more than 180 seconds—all as measured in the 85° F photochromic performance test.