Research On Quality Control And Mechanism Analysis Of High Tensile Strength And Bulk Of Chemi-mechanical Pulp

Due to the advantages of high yield and its paper of good bulk,chemi-mechanical pulp was concerned widely by paper workers at the earlystage of development. In recent years, improving the chemical mechanical pulpproduct performance and reduce production costs have become an importantresearch topic. However, as the difference between the major domestic andinternational products, improving the quality of domestic chemi-mechanical pulpbecomes an imminent task. This study aims to explore quality control process ofchemi-mechanical pulp’s high tensile strength and bulk pulp （HTB-CMP, namedHTBP for short） by mixing two different freeness（high freeness pulp and lowfreeness pulp, named HFP、LFP for short） for making an new pulp （named MP）.Then observing paper microstructure aims to optimize the HTBP process andclarify the relationship between chemical mechanical pulp quality and its paperperformance theory. This will promote the production and application ofchemical mechanical pulp in China, and expand the scope of application andusage of the machine pulp in paper industry.Firstly, the factors of the dry types, the additon amount （or ratio） ofappended pulp （LFP） and the properties of appended pulp and backbond pulp ofHTBP were studied. The results showed that, compared with oven dry, theair-dry was more conducive to reflect the variation tendency of bulk for MP. Theadditon amount （or ratio） of HTBP is an important factor affecting theperformance of the mixed pulp. The dosage of HTBP should not exceed60%.Fines fiber content and ratio of appended pulp and the fiber average length ofbackboned pulp are major factors affecting the performance of the mixed pulp.The beating types can affect fiber properties of appended pulp. When compring two kinds appended pulp in the mixed pulp, the PFI appended pulp has betterfiltration, high bulk and a certain degree of high paper strength than the valleyappended pulp.Then, the process of HTBP making by the air dry, PFI appended pulp andbackbond pulp was optimized. Considering the practical application of whitecardboard core, we select the dosage by20%. At this process, the bulk isincreased by3%, the tensile index increased4%; internal bond strengthdecreased by1%, compared with the paper properties of CP. The bulk of CP is3.5cm³Â·g-1, the tensile strength is14.39N·m/g-1and the bond strength is30J/m^-2.Thirdly, according to the optimum conditions of HTBP, we analysed thefundamental regularity of its quality control. The results showed comparing toCP, MP has higher content of R30、R50、P200and lower content of R100、R200.With the adding of appended pulp increased, when the rate of increase of MPbulk reduced; the strength has been greatly improved, therefore, high strengthand bulk are achieved. In other words, the contant of R50is reduced to a certainextent, but the contant of R100or R200is greatly improved, which may be acritical point. Coarse fiber, fines and other fiber components need coexistent infiber network with an appropriate proportion.Finally, the bulk of oven-dryed HTBP is better than the comparison pulp （CP）about3%. That indicated the HTBP can enforce at practice. Then the structure ofHTBP paper was studied. On one hand, the paper properties of scatteringcoefficient, air permeability and pore size distribution were researched. Theresults showed that:the appended pulp formed an highten network in the HTBPpaper, which resulted the difference of CPï¼›HTBP has loose sheet, and a largepore contrast to CP.On the other hand, many methods, such as the microscope, SEM, theaperture test （PMI）, were observed and test the HTBP and other mixed pulps.The results showed that the fiber morphologyof backbond pulp is stiff, headundevilicate of fiber and the fines of almost fragmentary while the fibermorphologyof appended pulp is short, soft, wide and cottony of coarse fiber, thefines with filamentous, andzonal and little fragmentary. Fines can fill in to thenetwork to form a bridging role on long fibers, so the sheets have both betterbulk and strength. The appended pulp and backbone pulp of MP sheets are a random uniform distribution. The coarse fibers in the backbone pulp and theappended pulp can form a network. The HTBP is similar to the structur of ABcrosslinked polymer.