パルプ・紙化へのガンマ線照射の影響 (第3報)

パルプへのガンマ線照射

抄録

The dissolving pulp (DP) involving no lignin and the cold soda pulp involving much amounts of lignin were used in order to study the influence of gamma irradiation.
The experimentals were carried out in the presence of air (dryed state), in the water, methanol, acetic anhydride, acetic anhydride+methanol, dioxane, dimethyl sulfoxide and 1% NaOH solution as deaerated as possible from each solutions. The irradiation was for 100 hours at the temperature of 2021°C. Total irradiation dose was 1.47 × 10⁷ R.
The yields, lignin content, 1 % NaOH solubility, and then brightness were determined. In the case of acetic anhydride and the mixing solution of acetic anhydride and methanol the degree of acetylation also was determined.
The following results were obtained from the above-mentioned experiments.
1) Yield and analytical value
In the case of dimethyl sulfoxide which is a good solubilizer for pulp as well as especially in the case of 1% NaOH solution, the yield decreased by the irradiation.
It was found that this phenomenon was denoted remarkably for the cold soda pulp.
2) For the pulp immersed in the water the brightness of pulp was not pratically improved by the irradiation, but relatively remarkably improved for immersing in methanol. Thus phenomenon was observed in both DP and the cold soda pulp. The improvement of the degree of brightness is not the change in quality of lignin, but it may be considered reasonably to take place by the action of oxidizing bleach with a smaller amount of oxygen of air remaining in the material. And also by comparison with immersing in water, it is considered for immersing in methanol that the action of bleaching arises from the presence of an extremely small amount of oxygen. Additionally, 1% NaOH solubility gets a small value in the both systems. Therefore, it may be considered that the degree of brightness is improved by the oxidation reaction, but the degradation degree of pulp gives a small value.
3) From the scope of results obtained by the infrared analysis. it seems most reasonable to conclude that methanol does not react with lignin in the cold soda pulp even on irradiating.
4) In practice, it was found that the acetylation was accelerated by the gamma-rays irradiation.