Patent ID: 8291674

Claim:
A method of forming a window frame, the method comprising: a) reacting an isocyanate component with an isocyanate-reactive component in a mold, the mold having an interior cavity complementary to a stepped frame section including four sides and having a lower step surface and an upper step surface, the lower step surface being adapted to receive a first light-panel having a first length and a first width and the upper step surface being adapted to receive a second light-panel having a second length and a second width, the first length being less than the second length and the first width being less than the second width, wherein: the isocyanate component comprises: an isophorone diisocyanate (IPDI) trimer/monomer mixture having an NCO content of from 24.5 to 34% by weight; and the isocyanate-reactive component comprises: a polyetherpolyol having terminal OH groups, an average nominal functionality of 2 to 4, and an average equivalent weight of from 800 to 4000; at least one chain extender component having as functional groups only aliphatic or alicyclic OH groups; and at least one amine-initiator component; and wherein step a) is performed in the presence of: at least one catalyst component selected from the group consisting of organolead (II), organobismuth (III), and organotin (IV) catalysts; at least one pigment component; and at least one antioxidant/UV absorber component.