Study On The Structural Properties Of MWL Isolated Form Bleaching And Yellowing Of Bamboo SCMP Pulp

In the thesis,the brightness stability of hydrogen peroxide bleaching of SCMP pulp was researched.And then it showed the effect of bleaching process to the brightness stability and the mechanism of yellowing,and got the MWL from bamboo,bleaching pulp and yellowing pulp.the modern spectrum analytical technologies of UV/VIS,FTIR,GPC,¹H-NMR were applied to study the the Structural Properties and the chromophore groups of MWL isolated from yellowing of Bamboo SCMP pulp.It has important meaning for Solving the poor brightness stability of high yield bamboo pulp.1.During the H₂O₂ bleaching,it can increase the brightness about 3%for adopting the two stage of H₂O₂ bleaching.It was easy to yellow of H₂O₂ bleaching pulp,and the more bight,the more aggravate.For example,when the brightness increased from 50.08%to 55.80%,the PC increased from 11.00 to 13.51.During the H₂O₂ bleaching,it could bring down the brightness stability for increasing NaOH or H₂O₂ and prolonging the bleaching time,and the Difference of PC can reach to 7.2.The mechanism of yellowing was different in the different irradiated,and the potential chromophore groups of MWL isolated from paper was unlike.It was main dye-mediated photo-oxidation for phenol-type and Carbonyl Compounds in the Initial Stages of yellowing,, decreased yellowing rates for the Consumption of phenol-type and Carbonyl Compounds,but increased yellowing rates for the additon ofβ-O-4 aryl-ether bonds.It was the main function to decrease the brightness for the chromophore groups of phenol-type.3.It was a large amount of guaiacyl and ester bond linkages in bamboo,exposured under the long time UV irradiation,while creating a mount of chromophoric groups,and the lignin structures were destroied and oxidative degradated which ester bond was oxidative scised.It was a mount of ortho-phenol structures and o-quinone in the bamboo MWL,which about 0.64%～1.49%,but low contents of carbonyl compounds that coundn't reach to 0.0019%.During the yellowing,the contents of o-quinone was geater ortho-phenol,which differences exceed to 0.82%.After SCMP bleaching,the Molecular Weight declined from 7253 to 5069,and the polydispersity declined from 1.47 to 1.22.The ¹H-NMR show that the lignin of bamboo is a GSH style lignin.