| Recently, domestic low density printing paper was made with inward commercial Softwood BTCMP or commercial Hardwood BCTMP and APMP as the main material, adding bleached softwood chemical pulp in a ratio. The effect of HYP assure the high bulk and opacity, the effect of Softwood enhance the bonding strength. Compared with international level, our nation low density printing paper had some gaps at technology, equipment and addition agent. On this condition, as the reason of ratio of raw materials, there was being high cost in different degrees due to the high price of inward commercial Softwood BTCMP. Or there was poor product quality in due to the short fiber length of domestic Hardwood BCTMP and APMP.The questions were brought by the product materials, on the basis of some advantages of domestic aspen BECMP(bleached extrude chemical pulp), such as high pulp strength, low power consumption and etc. The study tried to discuss the feasibility of making low density printing paper on basis of adding bleached chemical pulp as little as possible. And then, optimize the ratio, beating degree, the dosage of fillings and the adding mode, sizing mode and so on. The study laid a theoretical foundation in order to popularize the industrialization of making low density printing paper by using aspen BECMP.The result indicated, the study used orthogonal tableL9(33) to do experimental analysis (three variables were ratio of SW pulp and HW pulp, beating degree of SW pulp, beating degree of HW pulp respectively). Combining intuitive analysis, range analysis, variance analysis and trend curve analysis, obtained the optimum combination which was benefit for tensile index. The data of this optimum combination was that the ratio of SW pulp and HW pulp was3:1, the beating degree of SW pulp was55～57°SR, the beating degree of HW pulp was32～35°SR.The sheet which was using aspen BECMP with SW pulp and HW pulp respectively was needed to do performance test. The result of performance test indicated, when the dosage of aspen BECMP was below or equal to84%, the tensile index was steady and ideal. Through the further optimum experimental analysis, have ensured the feasibility of making low density printing paper with aspen BECMP under the lab in the pure fiber system. Moreover, the optimal condition was84%aspen BECMP:12%commercial bleached SW chemi-pulp:4%commercial bleached HW chemi-pulp.According to characteristic and requirement of low density printing paper, these conditions as premise, the study took neutral sizing mode. Due to neutral sizing agent AKD had some advantages, such as simple operation, easy control, low scaling etc. So the study had chose AKD as sizing agent for making low density printing paper with aspen BECMP. According to pre-experiment result, sizing process affected slightly bulk of low density printing paper, and, light sizing didn’t produce harmful effect for tensile strength, only when the dosage of sizing agent exceeded0.25%, tensile index declined obviously. Therefore, the result of optimum experiment indicated, when the dosage of AKD was0.18%～0.22%, sizing degree was excellent and tensile index increased, at the same time, bulk didn’t decline obviously.Consider with neutral-alkaline sizing agent(AKD), filler was chosen PCC(Precipitated Calcium Carbonate). According to low density and particle size, high refractive index and light scattering coefficient, high brightness and opacity of PCC, using PCC to make low density printing paper could meet the requirements of bulk and opacity and could enhance printability. Experiment obtained, when the dosage of PCC was15%～20%, the bulk, strength and sizing degree of sheet hadn’t a great change, and could raise a certain bulk meanwhile preserved strength.In order to solve filler retention rate of the system which was affected by high content of fines and adding PCC, this study used CS/CPAM dual retention aid system to improve filler retention rate of fiber in order to enhance sizing efficiency, the amount was1.0%/200ppm. Reliability of this process was well by verification test, mean physical indexes of handsheet were as followed:bulk was2.44cm3/g, tensile index was41.60Nm/g, opacity was90.6%, sizing degree was161.68s.Completion of this article would save cost of producing low density printing paper effectively, improve the physical index of low density printing paper, provide a new thought for high-grade low density printing paper’production, promote the level of low density printing paper industry in china. At the same time, expand application range of aspen BECMP and also lay a theoretical foundation for popularizing extrusion pulping technology. |
