The various bleaching methods of non-wovens which is yellowed by a fademeter were studied. Non-woven fabrics of polyester fiber (Tetron) and butadiene-styrene copolymer latex (Hycar 2570×5), were made and then we applied to the fademeter. The yellowed non-wovens were treated with some oxidizing and reducing agents and the bleaching activities of these agents were investigated.
These agents can be clasgified into two groups. Oxidizing agents such as water suspension of CaOCl2, acidic solution of K2Cr2O7, neutral solution of H2N2 and reducing agent such as neutral solution of Na2SO3, attack only _??_C=O which occurrs in the yellowed Hycar 2570×5.
On the other hand, acidic solution of KMnO4 and neutral solution of CH3COO2H seems to attack not only _??_C=O, but also other radicals. Therefore the bleaching activities of these oxidizing and reducing agents do not necessarily depend upon the oxidation-reduction potential of them. The recoloration properties of the bleached non-wovens are nearly in the inverse proportion to the weight-decrease in bleaching treatment.
H2O2-oxidation for bleaching may be recommended because of much weight-decrease and lessrecoloration.