繊維学会誌

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The effects of EDTA and ascorbic acid on the oxidative dyeing behavior of wool fibers dyed with the couple systems of p-phenilenediamine/p-amino-o-cresol (pPDA/pAOC) and p-aminophenol/p-amino-o-cresol (pAP/pAOC) were investigated by means of analyzing dyeing rate curve which was expressed in relation to the surface dye concentration (K/S) and the dyeing time. The effects of these additives on the dye uptake behavior were dependent on the reactivity of the oxidative dye intermediate, hydrogen peroxide concentration, and the additive concentration. In pAP/pAOC dyeing system, the amount of dye uptake in dying system with EDTA was reduced compared with that of non-additive dyeing system. This is due to the fact that oxidative coupling reaction is inhibited by chelating metal ions present on the fiber surface. However, the amount of dye uptake increased with increasing of the added amount of EDTA. This finding implies that there is another effect of EDTA. This effect was believed to arise from that the oxidative decomposition of the oxidation dye generated in the fiber-liquid interface is suppressed by the reduction in the perhydroxyl anion concentration. On the other hand, ascorbic acid exerted the effect in both dyeing system and brought on the action similar to EDTA; the inhibiting action of oxidative coupling reaction and the suppressing action of the oxidative decomposition of the generated dye. These actions are due to the fact that ascorbic acid preferentially reacts with the active oxygen species. The former is primarily caused by the decrease in the amount of hydroxyl radical, and the latter is due to the decrease in the perhydroxyl anion. In addition, ascorbic acid acted as a pro-oxidant and resulted in decomposition of the dye that adsorbed into the fiber.

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We investigated the relationship between superstructure, especially crystallinity determined by the X-ray diffraction intensity of 2θ=9°, and dyeing of wool treated by mechano-chemical method, and the effects of water on the structural change of the wool. The cuticles of wool surface seemed to be completely destroyed by ball-milling. The X-ray diffraction patterns indicated that the crystallinity (2θ=9°)originating from α-helix structures of keratin in the wool markedly decreased by the ball-milling when water content of the wool was low. The wool samples with water content of over 25% tended to keep their crystallinity even after the ball-milling treatment. The degree of dyeing of wool samples increased with decrease of the crystallinity of the wool, probably due to increasing accessibility of dyes to inner structure. On the other hand, the superstructure including the crystallinity of the wool seemed to be recovered with addition of water after ball-milling treatment, resulting in low dyeing ability.

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The precise identification of bast fibers such as ramie and hemp found at several archaeological sites is a very difficult problem because organic materials are usually heavily degraded during the long term preservation at under-ground or mound. Both excavated ramie and hemp usually show very similar degraded FT-IR spectra (glober light source). The authors are continuing to study the identification of several kinds of archaeological silk and vast fibers using BL43IR beam line (FT-IR micro-spectroscopy) at SPring-8. It has already known that excavated ramie and hemp show the possibility of distinguish ramie from hemp under polarized light source. In this report, various modern ramie fibers are analyzed by detailed IR polarization measurement. As a result of the measurement, the absorption band of 1160 cm^-1 disappeared at 45°(angle of polarizer) irrespective of sample history. In the next measurement, the disappearance angle of specific peak of modern hemp (several origins) will be confirmed. The determination of specific disappearance of certain peak for ramie or hemp will be effective for the identification of each fiber.

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A safer dyestuff for hair colouring, catechinone, was prepared from (+)-catechin introducing O₂ into basic water / ethanol mixed solution substituting for aqueous solution in order to increase the production efficiency. The solubility of (+)-catechin in water / ethanol solution is much higher than that in water, and 34 times higher concentration of (+)-catechin was adopted for the preparation in the mixed solution. The results show that the amount and rate of catechinone production in the mixed solution are much increased as compared with those in aqueous solution. The amount of catechinone produced for the water / ethanol system is 27 times larger than that for the aqueous system. The amount and rate of the production increase with the basicity of the solution, as increasing with added triethanol amine, diethanol amine or monoethanol amine in this order.

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