STUDIES ON THE MECHANISM OF THE PHOTOYELLOWING OF BLEACHED MECHANICAL AND CHEMIMECHANICAL PULPS .1. THE ROLE OF SINGLET OXYGEN

Light-shielded sheets of peroxide-bleachedTMP were exposed to singlet oxygen generated in the thermal decomposition of 1,4-dimethylnaphthalene endoperoxide and by the Rose Bengal-photosensitized activation of triplet oxygen. In both instances, singlet oxygen treatment had little or no effect on the brightness of the bleachedTMP. A lignin model compound, apocynol, was coated on the surface ofWhatman filter paper and exposed to singlet oxygen generated by the photosensitization method. In this case, a small (1—2 point) decrease in brightness was observed. Attempts to identify photooxidation products in the methanol extract of the exposed filter paper were unsuccessful. © 1990, Walter de Gruyter. All rights reserved.