Study On The Inhibiting Yellowing Technique And Mechanism Of Bambusa Chungii APMP Pulp

In this thesis, Bambusa Chungii APMP pulp was deoxidization, acidification or treated with additive, then the effect of the anti-photoinduction yellowing and anti-thermal induction yellowing of these pulp were studied. The mechanism of yellowing inhibition of Bambusa Chungii APMP pulp were also discussed.Firstly, on the basis of the primary study, the grinding process and H₂O₂ supplement bleaching of Bambusa Chungii APMP pulp were researched in order to understand the yellowing mechanism better. The results showed that Bambusa Chungii APMP pulp was fit for the grinding method of gap narrowing stepwisely, and the three sector grinding process was adopted. The best results of H₂O₂ supplement bleaching of Bambusa Chungii APMP pulp could be achieved under the conditions as follows: H₂O₂ 5.0%, NaOH 5.0%, EDTA 0.1%, Na₂SiO₃ 4.0%, and other conditions should not be changed.The effect of the anti-photoinduction and anti-thermal induction yellowing of Bambusa Chungii APMP pulp was studied systemly, the results showed that the pulp was treated by H₂O₂ in the first step and then reduced by the compound of sodium borohydride and odium bisulfite in the second step, could preferably improve the anti-photoinduction and anti-thermal induction yellowing performance and the stability of the brightness of the pulp. Bambusa Chungii APMP pulp was acidificated by Hydrochloric acid, Oxalic acid, Sulfuric acid, Formic acid, Sulfurous acid and Acetic acid respectively, The results showed that oxalic acid could get better anti-photoinduction and anti-thermal induction yellowing performance than other acids. And ultraviolet radiation absorbent UV-P could get better anti-yollewing performance in the four assistants used. Finally, IR and Solid ultraviolet—visible light diffuse reflection spectrum were used to analyze the change of the lignin structure in the process and the anti-yellowing mechanism of the Bambusa Chungii APMP pulp. The study showed that one of the most important mothods to improve the the stability of the brightness of the the Bambusa Chungii APMP pulp was to decrease the content of conjugate carbonyl in the UV light induced process. IR results showed that the content of hydroxyl and conjugate carbonyl was decreased by deoxidizing treatment, which worked in a certain extent to the yellowing inhibition. Conjugate carbonyl of the pulp was obviously decreased by oxalic acid treatmeant, the relative absorption strength decreased from 0.592 to 0.637. Solid ultraviolet—visible light diffuse reflection spectrum showed, the increasing range of light absorption strength in 400～600nm of the the pulp acidificated by oxalic acid was on the small side in the photoinduction process, when compared with blank sample, which indicated that coloring structure of the acidificated pulp was less than blank sample, and the stability of the brightness of the acidificated pulp was also better. The Ultraviolet Spectrogram of water extractive from Bambusa Chungii APMP pulp showed that, the light absorption strength of the yellowing pulp which was illuminated after oxalic acid acidificating in the range of 250～350nm was abvously decreased, which proved that quinoid structure in the process was less than the untreated pulp.