Study On The Application And Retention Mechanism Of New AKD Emulsion In Closed White Water System

The modern papermaking industry is developing forward to neutral-alkalescence and closed white water system. At the same time, the anionic trash accumulated in circular white water which make the effect of all kinds of wet-end additives (particularly cationic additives) worsen, the wastage and also the cost of papermaking become larger constantly. Now there is a better non-ion retention aid system which composed of poly ethylene oxide (PEO) and bentonite and could resist the interfere of anionic trash preferably. In this paper, the sizing effect of traditional cationic AKD in CPAM/bentonite and PEO/bentonite systems and the sizing effect in condition of the presence of anionic trash were studied. The method of appending some additives to improve the sizing degree was also studied. And the method of changing the component of the emulsifier and ameliorating the technics of emulsification to prepare a new AKD emulsion which can resist the interferer of anionic trash and the applying effect and the retention mechanism of the new AKD emulsion were discussed in this paper. Main results have been obtained as follows:1. The traditional cationic AKD could gain good sizing degree in PEO/bentonite system and CPAM/bentonite system; the sizing degree of cationic AKD emulsion could be strongly interfered by anionic trash in these two retention systems. The average decreasing extent is 30%. The decreasing extent of sizing degree could be advanced by adding water soluble phelonic resin(PFR) to PEO/bentonite system and the increasing extent was about 10%.2. Anionic composite emulsifier composed of 6-8-9, HLB15, dosage20% has a suitable emulsion capacity for AKD, and anionic AKD emulsion made by this way has a good sizing effect. But its stability was not very good and it could be applied as emulsion emulsifing on the spot. This should be improved in the future.3. The sizing degree of new AKD emulsion are higher than that of cationic AKD emulsion when dosage was larger than 0.15% in PEO/bentonite system. The sizing effect of new emulsion is better than cationic emulsion and the decreasing extent interfered by anionic trash is 50% of that of cationic emulsion. When adding fillers to the system, the sizing degree of new emulsion is better than cationic emulsion and the sizing degree of adding talc was higherlhan adding GCC. The new AKD emulsion is adaptive in neutral pH. And the physical properties of paper sized by new emulsion are as well as that of by cationic emulsion except tensile strength which was worse than cationic emulsion. In a word, the physical properties of the paper sized by new AKD emulsion could satisfy the request of fine paper.4. It can be concluded that the retention of new AKD emulsion particles is finished by flocculated with PEO. The best adding orders of additives is AKD-PEO-bentonite when used in fine paper. The sizing degree is increasing with alum. But the sizing degree decreased after the dosage of alum reached to 1%.5. The sizing effect of new AKD emulsion is better than cationic AKD emulsion. It's show that the dynamic retention ratio of new emulsion is higher than cationic emulsion in PEO/bentonite system.6. The adsorbance of AKD emulsion particles on pulp is very little, while the absorbance become larger after adding PEO/bentonite retention system to it. It also shows that the retention of AKD emulsion particles are performed by PEO. The experiment of absorbance on long fibers and on short fibers shows that the capability of adsorbing AKD particles of long fibers is stronger than short fibers in this specifically papermaking system.