PAPER
CHEMISTRY LABORATORY, INC.
September 2009 Newsletter
Cost-Efficient Papermaking
John Penniman
| Viewpoints
Everyone active in the paper industry may view it from a different perspective. …..some believe that philosophically, papermaking comprises the complementary application of physics and chemistry, perhaps with insufficient emphasis on the latter. …..and a small number of scientists, including the author, consider the principal rationale lies in nanotechnology: the molecular and inter-particulate relationships of the stock. Papermaking Nanotechnology There are several compelling arguments which favor papermaking nanotechnology. In the author's studies, nanotechnology has simultaneously maximized both process and physical property parameters. The principles are straightforward: use the most effective chemistry; disperse the stock to homogeneity; and eliminate the repulsive negative charge by neutralizing the zeta potential. On the other hand, conventional wet end chemistry is routinely obliged to make major compromises in both process and quality, such as sacrificing formation for retention. Dispersing chemicals to molecular dimensions is also beneficial because it increases chemistry efficiency, resulting in a chemical cost reduction of 90-99%. Operating at zero zeta potential neutralizes the repulsive negative surface charge and thereby enhances inter-particle attraction, or van der Waals force. This enables the counter-intuitive result of increased filler loading at a higher level of strength. In its purest form, papermaking nanotechnology will inevitably produce a print surface so smooth and ink receptive, it will rival the best of current generation coated sheets. Stock homogeneity is easily quantified. An automatic zeta potential instrument measures zeta potential, drainage, specific conductance and temperature in cycles less than 90 seconds. This includes calculation and output of the trailing average zeta potential standard deviation, a highly precise homogeneity measure. The Process Control Alternative The other side of the coin is the method currently used globally for process control, called “charge titration.” It purports to measure the ions adsorbed on a Teflon tube immersed in white water, with the objective of leaving a final residual negative charge. This is a problematic technology. The objective is not appropriate, because the desired final repulsive charge decisively conflicts with inter-particle attraction, and mitigates the beneficial value of van der Waals attractive force. Secondly, the most extensive of many charge titration studies conducted by the author showed a poor correlation coefficient of 0.17 with zeta potential. In simple terms, the cationic demand measurement is neither appropriate for wet end process control, nor is it sufficiently repeatable. Nanotechnology on the Machine Variable speed pilot plant studies have shown that water re-wetting in the press section can be substantially inhibited by reducing the surface tension and controlling the hydrodynamics. This results in a significant consistency increase, exiting the press. When combined with azeotrope usage in the dryer section, to minimize the energy requirement for vaporizing water, the total paper machine energy reduction can approximate 50%. The catalyst used to create cost-effective azeotropic volatilization is completely re-cycled; there is no residual in the product. Effective application of nanotechnology principles increases press and dryer section efficiency so much that both sections can be greatly reduced in size and cost. The typical white water system is much too large. Common white water systems are counter-productive because they complicate the task of obtaining stock homogeneity. Nanotechnology mixing is highly focused and confined to a small locus, resulting in an enormous decrease in size and cost of the white water system. Conclusion Papermaking nanotechnology simultaneously maximizes physical property and process parameters, attaining impeccable quality and runnability, reduces chemical usage and cost by at least 90%, and reduces energy usage on the machine about 50%, while achieving a payback measurable in months. It will cut the size and cost of a new machine, or rebuild, by about half.
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