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Making Nano
Paper in the Lab
Modern wet end chemistry can be dated to the mid-20th century, where it
was initiated with the flocculation chemistries used in the
pre-treatment of potable water. At the time, there was one key
lab instrument, the “Britt Jar”, developed by Ken Britt of SUNY
Syracuse, used mostly to measure fines.
In providing consulting services to the paper industry, the author
found it necessary to modify the Jar so that it could produce
hand-sheets which fully reflected both the process dynamics and
properties of the finished paper. Over time, it became known as
the Mk V Dynamic Hand-Sheet Mold, and produces 8” diameter hand-sheets,
of excellent formation, which fully reflect the wet end
chemistry.
Many of us in the industry recognized the importance of measuring and
controlling the electrostatic surface charge, or zeta potential.
Much later we realized that calculation of standard deviation is
necessary to quantify the quality of dispersion. This enables
maximizing the attractive benefit of small particles, down to molecular
dimensions.
It turns out that zero zeta potential is essential to maximum strength,
simply because that eliminates the repulsive electrostatic surface
charge (whether positive or negative.) This approach helps
enable, counter-intuitively, an increase in filler content while
simultaneously increasing sheet strength.
It led to a laboratory zeta potential instrument which measures zeta
potential, drainage, specific conductance and temperature in 90 second
cycles, printing out all the data as a permanent record. That
particular 1.5 liter batch of stock is transferred to a Mk V Jar,
hand-sheets made, pressed, dried and tested for ash level, sizing and
Scott Bond.
Over a period of years, with the execution of more than 5000 such
experiments, we learned how to definitively specify the optimum process
chemistry necessary to optimize papermaking nanotechnology.
In Pursuit of Anomalies
The other main thrust was the investigation of anomalies. When a
strange phenomenon was reported, any place on the machine, we pursued
it to a favorable conclusion.
For example, in consulting to a Pacific north-west newsprint mill the
author was informed of the occasion, soon after start-up, when the
automatic felt cleaning operation malfunctioned. Raw kerosene,
instead of a greatly diluted kerosene emulsion, was applied to the
felt. The first section dryer steam pressure fell by half!
On return to our home lab, we started doing a few experiments.
Much later, we started pilot plant trials. When we finally
employed a variable speed pilot plant, the mechanism became fully clear.
When executed in an effective manner, we can cause a particular
hydrocarbon to azeotrope with the residual water in the web, decreasing
dryer energy usage by about half.
Mixing to Homogeneity
Calculating the standard deviation of a commonly used physical
chemistry metric provides a quantitative measure of homogeneity.
In the lab, we routinely obtain the low zeta potential standard
deviation of 0.2mV.
A high speed tissue machine is imperfectly designed to operate at a
zeta potential standard deviation of 1.6mV and a modern alkaline fine
paper machine at 2.9mV, often accompanied by 6-10 wet end breaks/day.
Both physical and surface energy are required to disperse wet end
particles to a molecular scale, with a highly rewarding result: a
reduction in chemical usage of 90-99%.
Documentation
The key data from this vast experimental background has been documented
in two forms. Most resides in the Nano Recipe Book, in which
research reports have been typed, indexed and classified in a single
volume. The balance is in the form of a Compact Disc, which takes
about 30-minutes to play, and includes a video of our lab nano
procedure.
John Penniman
www.papermaking-chemistry.com
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PAPER
CHEMISTRY LABORATORY, INC.