Dry strength agent is an amphoteric polymer, with the appearance of colorless to slightly turbid viscose, greatly enhance the strength of the paper,and good retention performance, reduce Whitewater COD and raw material costs. Adaptability is very well in different pH papermaking system, broader application. Anionic and cationic degree of products are adjustable, can be used in all kinds of papermaking environment and to product various kinds paper.
Additions exceeding 0.5 % of a PVAbased cationic dry strength agent fail to give a further strength increase. For dosages above 0.5 %, this saturation is accompanied by a saturation of the polymer level adsorbed on recycled pulps. If dosages of less than 0.5 % are added, 100% of the polymer adsorbs at the recycled pulp which results in a largely linear rise in strength values. When the 0.5 % mark is exceeded, a steadily growing part of the polymers is no longer adsorbed at the fibers so that the strength increase comes to a stop. Functions of the Carrier System. The saturation of polymer adsorption is chiefly charge-driven – a phenomenon that has been confirmed in adsorption tests of polymers with different levels of cationicity. If the saturation point of polymer adsorption is reached owing to a charge reversal, thus preventing a further strength increase, a dry strength agent in the form of a polymer carrying an opposite – i.e. anionic –charge can quantitatively adsorb at the cationic fibers, thus contributing toward higher strength levels. This mechanism has been demonstrated in pertinent studies.
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