Measurement Of The Microstickics In Process Waste Paper Recovery And Research On Their Stability

In waste paper recycling, stickies refer to the tacky contaminants. Often been viewed asthe stubborn illness of waste paper and was usually divided into two type, macrostickies(>100μm) and microstickies (<100μm), according to the particle size. Most of themacrostickies can be removed effectively by the processes of screening with0.1mm screenslots. However, it was hard to remove a large amount of microstickies in the units of pulpingsince they are too small and have complicated features. These microstickies would be retainedin pulp and introduced into papermaking system to cause serious deterioration of paperquality and paper machine runability. For microstickies problems, especially these adhesivecontaminants in whitewater, more and more attentions were paid to measurement and control.However, as for the microstickies measurement, a satisfactory method has not beenestablished yet. Furthermore, those microstickies in some sense were free particles oragglomerated with some other substances, therefore their colloid nature as well the sizedistribution need to observe but unfortunately there were nearly no previous works involvedin this areaFirst, Microstickies Tester which based on Fluorescent Counting Method was establishedin our laboratory. A kind of fluorescent dye was added in filtrate and microstickies particleswere selectively dyed while the other components of pulp won’t be. The sizes and numbers ofdyed particles of microstickies were detected one by one when they passed through atransparent tube illuminated by a focused laser light. The information of all of particles inwhitewater can be tested through recording the signals of the forward scatter (FSC) lights andside scatter (SSC) lights, at same time the adhesive contaminates were pick out by redfluorescence. Then the sizes and the numbers of microstickies can be obtained throughcomparing collected information.The physicochemical characteristics of microstickies in whitewater from three kinds ofwastepaper, old newspaper(ONP), old books paper(OBP) and mixed office wastepaper(MOW), were investigated and analyzed through conventional methods respectively, such asash, extraction, turbidity, CD, TGA, Py-GC-MS etc.. Then using Microstickies Tester,distinguish non-stickies with microstickies, get the number, particle size and volume of themicrostickies in whitewater. The result showed that: there are significant differences betweendifferent micro-stickies in physico-chemical properties, size distribution and othercharacteristics. ONP content the minimum of ash, and the most number of stickies, but its average diameter was the minimum about8.31μm, so the total volume was the fewest. TheOBP microstickies content the most ash, at same time the particle size, total number andvolume between two other stickies. OBP stickies come from hot melt adhesive (HMA), whichwere probable made of styrene butadiene rubber (SBR) and diacetyl copolymer. The MOWwhitewater have the least number but the largest average particle of microstickies, and themost total volume of microstickies. The MOW stickies come from pressure-sensitiveadhesives (PSA), which contain ethylene vinyl acetate (EVA), furfural resin and copolymersof styrene. The stickies of ONP may from HMA, PSAs, ink and coating.The model compounds which can be found in above section were detected by FTIR,TGA, and Py-GC-MS, arm to establish basic information database. Then through the analysisof stickies above information can simple to predict its main source.The pH is an important influence on the characteristics of microstickies. Microstickies inacidic condition have gathered tendency, correspondingly have the dispersion trend in alkalinecondition. When adjust the pH value to5, the H2SO4compressed the double-layer structure ofmicrostickies, led to an obvious reversible flocculation phenomenon. However, when the pHvalue was adjusted to2.5, all the microstickies and the colloidal substances (CS) coagulatedsharply, led to whitewater getting clear and this reaction was irreversible. It’s because of theH+had the reaction with anion of microstickies, caused the absolute value of zeta potentialreduce to zero mV, and easily to coagulate. When the pH at8-10the microstickies havesaponification reaction with alkali, led the microstickies to disperse progressively, the particlesize and total stickies volume reduce. Which all meet the theory of DLVO. ONP stickies haveobvious temperature-sensitive settlement at40and90℃, which is the stickies softening pointand liquefaction point. Stirring, inorganic salts added, and cationic polymers added areconducive to the ONP microstickies polymerization.MOW microstickies have larger average particle size and adsorb lot of the polymer onthe surface, follow the state space theory. The stickies sensitive to pH value have tendency ofdeposition under alkaline conditions, would aggregated at pH6. Since the state space theorythe microstickies still keeps stability, even the absolute value of the Zeta potential is verylow at pH11. At same time, found that high and low temperatures are all conducive to itsflocculation. When the particle size is larger showed some vacancies stable phenomenon.The lipase treatment can reduce the amount of the microstickies, but also to make thestickies activity enhanced apt instability. And the production of lipase treated could competed with AKD, affect its retention and spreadability. The other enzymes have some effect onstickies treatment, but many effects of enzyme treatment were not contributed by enzymes butby the additive or carrier.Finally, the guess of microstickies instability together at whole system was proposed.1.)The first two microstickies in the critical state aggregated, adsorbed charge from around,broke the balance of microstickies around, then the round microstickies aggregated, andextended to all directions, caused the whole system instability. Resulting in conductivitydecreased rapidly, and recovered slowly.2.) The first two microstickies in the critical state aggregated, released charge to around,broke the balance of microstickies around, then the round microstickies aggregated, andextended to all directions, caused the whole system instability. Resulting in conductivityincreased rapidly, and recovered slowly.