Strengthened Alkaline Peroxide Mechanical Pulping Of Poplar

Three ways to strengthen poplar APMP and improve the physical properties were studied. The poplar was taken as the raw material and the conventional APMP process was taken as the basis. To achieve the purpose of high brightness, high strength and high yield by three pulping strengthen ways: increasing the amount of chemical charge in the impregnation stage, alkali peroxide supplementary bleaching and enzyme treatment.Firstly, pulping process was strengthened by increasing the amount of chemical charge in the impregnation stage. For wood chips, the optimal treatment temperature was 75℃. Under high chemical charge, it was different between the treatment of high temperature and short time and the treatment of low temperature and long time in chemical impregnation stage for wood chips. The former treatment promoted hydrogen peroxide invalid decomposition and alkali darkening, resulting in brightness declined. However, the latter treatment couldn't ensure the growth efficiency of breaking length. The ratio of NaOH and H2O2 should be taken with 1:1 for the aim of obtaining the relatively high brightness and high strength properties at the same time. In addition, bark and knot were not easy to soften in the impregnation stage. They were broken into fiber bundles during refining. Thus not only reduced the pulp yield, but also decreased the brightness and strength properties. Most importantly, the increasing amount of H₂O₂ had played a positive role in the breaking length growth when NaOH was 18%.Secondly, poplar APMP was treated by alkaline peroxide bleaching. Two chemical impregnation stage APMP followed by peroxide bleaching achieved good results. Compared with the unbleached pulp, the bleached pulp had high brightness and high strength properties. The beating energy consumptions of the bleached pulp reduced. On this basis, one chemical impregnation stage APMP followed by peroxide bleaching improved pulp qualities by different distribution of chemical charge between the chemical impregnation stage and the peroxide bleaching stage. Through the analysis from SEM, XRD and FT-IR, peroxide bleaching rised the cristallinity of cellulose, softened and swelled the fibers, improving the pulp properties. The brightness of APMP pulp after peroxide bleaching could achieve above 80.00% ISO at one time. Compared with the conventional APMP, except the light absorption coefficient declined, the opacity, the brightness and the light scattering coefficient of APMP pulp after peroxide bleaching were all improved. So did the strength properties: the breaking length, the tearing index and the bursting index. Through the peroxide bleaching, the physical properties of the APMP pulp were improved. Meanwhile, the beating energy consumptions reduced after peroxide bleaching. The reduction of yield was in the range of 5%.Finally, APMP process was taken as followed: the screwed wood chips were treated by pectinase, before the chemical impregnation stage and refining. The pulp was treated by the xylanase after latency. By FQA analyzed, the fiber aspect ratio was promoted, the contents of fiber bundle and fines decreased remarkable. Furthermore, compared with the untreated pulp, the optical and strength properties of the APMP pulp treated by pectinase and xylanase were all improved.The three methods mentioned above, the methods of peroxide bleaching and enzyme treatment showed small impact on pulp yield, but the pulp yield of APMP produced by high chemical charge in impregnation stage reduced remarkable.