Thermal and fluorescent properties of optical brighteners and their whitening effect for pelletization of cycloolefin copolymers

The thermal and fluorescent properties of 4,4-bis(5-methyl-2-beazoxoazol)ethylene (Hostalux KS-N), 1,4-bis(benzoxazolyl-2-yl)naphthalene (Hostalux KCB), 2,5-bis-(5-tertbutylbenzoxazole-2-yl) thiophene (Uvitex OB), 2,2′-(4,4′-diphenolvinyl)dibenzoxazol (Uvitex OB-1), and 1,1′-biphenyl-4,4′-bis(2-(methoxyphenyl)ethenyl) (Uvitex 127) have been investigated. All of them exhibit good thermal stability (> 300 °C) and high fluorescent quantum yields (> 0.8). Furthermore, we also have successfully blended these optical brighteners into cycloolefin copolymers with the antioxidant (Irganox HP2921) to improve the discoloration after pelletization based on their whitening effect.