| In many papermaking mills, corrugated paper was made from OCC (old corrugatedcontainer) recycled fiber due to the shortage of plant fibrous material and the demand of costreduction in recent years. Corrugated paper is the major part in corrugated paperboard, itshould possess the quality of good strength and water-resistance properties for its applicationof packing. Generally speaking, sizing agent is added in papermaking process to improve thewater-resistance of corrugated paper.However, OCC recycled fiber has experienced the process of pulp and papermaking,contains more fines, fillers, auxiliary chemicals and other impurities compared to originalwood pulp, which will affect the effect of sizing.The sizing ability of OCC pulp, softwood pulp as control sample, and the performance of AKDwere studied, It was found that there are many fines in OCC, most fiber are shooter than1.0mm and fibersbetween100and200mesh sizes shows better sizing ability。Comparing with softwood pulp,OCC pulparrived isoelectric point slowly when added same dosage amount of retention aid,the cationic demand ofOCC pulp was higher than that of softwood sulp, and fillers in waste paper stock also give a certainnegative effects on sizing. AKD agent used in this paper shows even particle size distribution, the Zetapotential was about30mv,the active wax content was11%, the hydrolytic ratio was15.2%and themelting point was47°C。Moreover, the influence factors of sizing on OCC pulp were also studied, When the usage of AKDwas0.3%, the cobb value of paper was about30g/m2. Both talc powder and PCC will produce negativeeffects on sizing, and the latter give greater effect. The sequence of sizing will also affects sizing, thesequence of CS+AKD+PCC achieved best water resistance. Another significant factor is drying condition,the action between AKD and fiber completed in10min under the temperature of100°C, so the paper hasgood water resistance. The addition of CS and CPAM increased the retention of AKD, and obviouslychanged the physical properties of paper. For CS and CPAM, the effects of them on physical propertieswere similar, there was a critical value in the trend of physical, the paper strength properties, permeabilityand evenness got better before achieving the critical value, but once beyond this critical point, theperformance of the paper will be reduced. Fillers reduced the strength properties of paper, however, the airpermeability of paper was increased by the addition of fillers. When the addition of PCC was10%, therewas no obvious strength properties damage of paper. However, when the addition of PCC was increased to20%, the strength properties of paper were decreased sharply. With the increasing of drying temperatureand time, the sizing effect of paper improved gradually. When the drying temperature increased from70°Cto130°C and the drying time increased from5min to30min, the water resistance of paper increased49.3%and48%respectively. With the increasing of drying temperature and time, bounds between fibersgot more tightly, and the strength properties of paper were improved. The optimal drying temperature was 100°C for15min. Too higher drying temperature and too long drying time will caused fiber hornificationand induced the damage of paper strength properties.In this thesis, the influence factors of Alkyl ketene dimer (AKD) sizing agent used inOCC recycled fibers were studied, and it expected to provide theoretical foundation for sizingtechnics optimization of recycled fiber. Furthermore, the reaction mechanism between AKDand fibers was studied form the standpoint of surface chemistry, and the influence of sizing onrecycled fiber properties was analysised from the view of microscopic. The main innovativepoint of this paper is that the relation between AKD sizing and micro properties of fiber wasestablished from the angle of surface chemistry. The water-resistance of paper obtained for thereaction of AKD and fiber and the coverage of AKD on the surface of fiber. It was confirmedthat paper with lower Cobb shows better stability of water-resistance by surface contactingangle test, the porosity and WRV(water retention value) of fiber were also decreased aftersizing. The reasons of the decline of WRV can be explained as following: the decrease ofcumulative pore volume and average pore diameter of fiber after sizing lead to the decrease ofmoisture entered to lumen through holes in fiber, and the movement of permeability of watermolecules in paper was obstructed or stopped by internal sizing, so the swelling ability offiber was decreased. |
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