Photo-antioxidant abilities of 2-hydroxybenzoyl compounds

Plastics are indispensable for our comfortable life. But, they are easily degraded by autoxidation, especially under the action of UV light, due to their organic character. Therefore, additives preventing the photo-oxidation are needed. 2-Hydroxybenzophenones are widely used as ultraviolet absorbers (UVA), and their effect is discussed in many papers. However, there are few papers, in which the effect of substituents on the benzene nucleus and/or the 2-hydroxybenzoyl group on the photo-antioxidant ability is directly examined. This study focuses on clarifying such substituent effect. As a result, it has been made clear that the photo-antioxidant ability is better improved by introducing a substituent into p-position than m-position of the 2-hydroxyl group. In addition, it was found that the photo-antioxidant ability is enhanced by enlarging the conjugation system of the group bonded to the 2-hydroxybenzoyl carbonyl group. The substituent effect activity of (2-hydroxybenzoyl)-benzene is also discussed. (c) 2005 Elsevier Ltd. All rights reserved.