January 2005 Newsletter Nanotechnology Depends on Intermolecular Contact

John Penniman

Consider the first step of the nanoparticle papermaking process. A charge-neutralizing cationic chemical is added to the wet end. Its purpose is to neutralize the negative charge on the stock, become adsorbed on individual stock particles, and make them all highly positive in charge. The final step of the process involves addition of the highly negative nanoparticle. It inter-acts with the cationic particles and forms a nanoflocculation structure that contributes a superb balance of formation and retention, and a structure that maximizes drainage/water removal. Should we fail to mix the cationic chemical to homogeneity, that which is not adsorbed will later react uselessly with the anionic nanoparticle. Should we fail to mix the anionic nanoparticle to homogeneity, the unmixed portion cannot nanoflocculate; or contribute to formation, retention or drainage. Thorough mixing of chemicals with stock is essential to maximizing nanotechnology efficiency. Process chemistry efficiency depends on it. For example the introduction of chemicals by preferential wetting, instead of simple mixing, enables a new level of intermolecular interaction. The amount of size required can be reduced by two orders of magnitude. It is also necessary to add precisely the proper balance of cationic component and nanoparticle, so that the repulsive surface charge is fully neutralized prior to web formation. This step alone can, for example, enable a 5-10% higher sheet ash level, with increased strength and performance. The 8th Generation On-Line Zeta Data System enables quantitative assessment of homogeneity at the two critical junctures on the machine. It also measures the headbox zeta potential, and enables a proper balance of chemical feed rates to continuously achieve zero zeta potential prior to web formation. Finally, it enables an increased but perfectly balanced level of total chemical flow; machine productivity is continuously maximized. John G. Penniman   Copyright Papermaking-Chemistry.Com ©2004 Click Here To Return to HOME PAGE