Study On The Chemical Agglomeration Deinking Of Laser Printed Waste Paper

"Laser Printed Waste Paper" plays an important role as recycling fiber for high qualityprinting and writing grade papers, because it has high brightness and a large enough proportionof long fiber. However, one main problem with using mixed office waste is that it containsthermoplastic-based inks that are printed and fused on the paper. Most toner for this type of paperis difficult to handle with conventional deinking methods of washing, and flotation. Besides, a lotof ink particles are absorbed onto fibers. The principle of liquid agglomeration is utilized to studythe type toner of deinking methods. Laboratory-scale agglomeration experiments followed byimage analysis were used to evaluate the effectiveness of agglomeration reagent and differentcationic surfactants, which were the co-agglomeration reagents on the agglomeration of lasertoner, by scanning the number of ink particles, the area of ink particles and the average area ofink particle. What's more, the morphology of ink was observed by optical microscope and SEM.Other methods such as contact angle and charge were also utilized to investigate the ink underdifferent conditions. The results were as follows:1．It was found that this toner became agglomerate under neutral pulping conditions, Theoptimum dosage of M₀was2.0%,when2.0%was added under neutral conditions, the number ofink particles per square meter (NPM) was27,600, reduced by93%and the average ink particlesize increased by three times, from0.055mm²to0.180mm²; the agglomeration effect of M₀forthe toner was influenced by NaOH. but it did not agglomerate under alkaline conditions atall,when0.5%NaOH was added with2.0%M₀, The NPM increased to224,000, and the averageink particle size decreased to0.04mm². A small amount of the cationic surfactant compensatedfor the agglomeration disruption cause by the NaOH and made this toner agglomerate very well.2. The cationic surfactants played an important role in agglomeration. All their bestperformance happened on the addition of a narrow range of a similar total positive charge density,when each surfactant's concentration exceeded its optimal dosing value, the effectivenessdecreased or leveled off; the phenol group of equally charged cationic surfactant has a positivecontribution to the agglomeration efficiency, however, its effectiveness was much less than thatof the charge.3."The chemical agglomeration deinking" had some demands for the cationic surfactant asco-agglomeration reagents, and the higher charge density did not mean the better agglomerationefficiency. For the cationic surfactant with coupling structure and dual positive charge, theeffectiveness of agglomeration was lower than that of the surfactant with one positive charge. Itwas also found that this positive charge effect could not be applied to the chemical polymer materials with low molecular weight or high molecular weight.4. The laser toner was with negatively charge. More negative charge was generated and thecontact angle was converted from hydrophobic to hydrophilic on the surface of the toner, and ledto the negative effect on agglomeration of this toner. Meanwhile, by observing the photos ofSEM, the internal structure of laser toner became loose under alkaline conditions compared withneutral conditions.5. The contact angle of laser toner can be converted from hydrophilic to hydrophobic underalkaline conditions by the cationic surfactant as co-agglomeration reagent. The contact angle oftoner was higher after treating by the one positive charge surfactant than by dual positive chargesurfactant.6. Using Infra-red analysis on toner agglomeration, it was investigated that the toner had thestructure of aromatic acid ester. The structure could be hydrolyzed by sodium hydroxide and ledto the negatively effect during the toner agglomeration.