Study On Papermakiug Characteristics Sties Of The Bleached Magnesium Bisulilte Rice Straw Pulp

Bleached magnesium bisulfite rice straw pulp was studied in this paper withserials of experiments, such as beating, retention and drainage, sizing, blending, etc.Then, the performances of the obtained sheets were evaluated and met the demands ofcultural paper.The medium (12%) and high (20%) consistency beating were carried outrespectively to observe the influence of beating on fiber morphology, optical andphysical properties of paper sheets. Compared with high consistency beating,medium consistency beating led to less fiber cutting and less fines with smaller fiberwidth and coarseness in terms of fiber morphology; The optical performancesincluding whiteness, opacity and light scattering coefficient, decreased with a certaindegree as beating continued, while no obvious difference on optical performances wasobserved between medium and high consistency beating; Tensile and tear index of theobtained sheets for medium consistency beating were much higher than that of highconsistency beating with respect to the physical performances.The poor retention and drainage performance of bleached magnesium bisulfiterice straw pulp were primarily caused by the high content of fiber fines. The retentionand drainage properties were investigated with three retention systems, single elementsystem, double element system and microparticle retention system. These indicatedthat the retention and drainage effect of microparticle system was most obvious.Compared with blank samples (with rate of filler retention49.61%, packing filterwater time26.8s). Filler retention increased to67.91%and the drainage timedecreased to22.7s with microparticle retention system, which probably due to themore uniform network-type flocculation formed in microparticle retention system.Chemicals were strongly adsorbed on fiber fine because of its high specificsurface area and high charge density, therefore most of AKD particles were absorbedby fines and ran off with the white water. At the same time, the effective adsorption ofAKD onto fiber surface could be interrupted by the high content of amorphous SiO2in bleached magnesium bisulfite rice straw pulp, leading to poor internal sizingefficiency. The problem of AKD loss did not exist in surface sizing, AKD can be usedin combination with oxidation starch, which can result in not only good sizingefficiency, but also good tensile strength and surface printing strength of paper sheetsas well as cost saving.Adding wood pulp to the rice straw pulp mentioned above can improve thequality of cultural paper, such as surface strength, flex deformation and printingadaptability. When10%commercial soft wood pulp was added with the bleachedmagnesium bisulfite rice straw pulp, the performance indexes of surface-sized culturepaper were as follows: white degree77.87%, opacity94.54%, fracture length3096m,folding strength8times, surface strength2.02m/s, sizing degrees35s, All parametershad been improved obviously.