PAPER CHEMISTRY LABORATORY, INC.
NEWSLETTER SUMMER 2001
A FLEXIBLE NEW WET END PARADIGM
How to Maximize Productivity and Quality at Minimum Raw Material Cost
One of the enduring papermaking problems is that of insufficient water removal, leading to excessive web moisture, low wet web strength and wet end breaks. The potential causes center around the quality and consistency of feedstock, its freeness, and variability in broke, filler, fines, refining, etc.
The conventional treatment is to add a "drainage aid" which improves water removal at the expense of degraded formation and physical properties. We have developed a better way. Machine management can now adjust water removal to fully accommodate feed stock variation, with minimum adverse effect on quality and productivity.
In principle, we simply take advantage of the inherent flexibility of the microparticulate process: the more micro-flocs, the better the water removal. The principle has led to the development of many new microparticles with greater surface area. We can obtain a controllably greater surface area, and commensurately increased water removal, by simply increasing the flow rate of microparticle and cationic polymer in tandem, while maintaining the optimum zeta potential.
The benefits are described in more detail in a web site paper, entitled "Maximizing van der Waals Force in Papermaking" in the technical paper section. There is a big difference between the results obtained from a stable process, and one that is flexibly and precisely controlled to maintain optimum conditions. It turns out that optimizing a process parameter such as drainage also results in maximizing retention, and importantly also maximizes physical property parameters such as sizing and strength.
This procedure also helps to address one of the important unresolved problems in papermaking: that of runnability, quality and process control during transient periods of upset, such as start-up, grade change and re-start after a break.
The paper industry is generally reluctant to innovate, and usually waits for somebody else to take the first risky step. It may be significant that Muetek (now part of BTG), arguably the international leader in supplying cationic demand instrumentation, and a supplier of an off-line zeta potential instrument, is now promoting an on-line zeta potential measurement, even though they are not offering a product for sale in North America.
We consider that this step by Muetek represents a belated vote of confidence in our fielding a first generation On-Line Zeta Data in July, 1989. The On-Line Zeta Data has been perfected over a more than a decade of field experience. It is now in its 6th generation, and fully described on the web site, together with the Lab Zeta Data, and many examples of their use.
John G. Penniman
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