Digital Printing Paper Optimization: Computer Control of the Wet End

Our task is to: disperse the chemicals to approach molecular dimensions, thereby reducing chemical usage by about 90%; and neutralize the repulsive negative particle charge to maximize process control, productivity and strength. The effort is initiated by review of drawings and key metrics.

We propose to provide advice on installation and use of sensors and equipment, and to provide continuing process supervision support for computer control of nanotechnology processes that produce optimal digital printing paper. Integration of nanochemistry optimizes performance, as opposed to merely applying a coating to the surface.

While we could have focused on any grade of tissue, towel, fine paper or board, we selected digital printing paper because the performance metrics are clearly defined and widely accepted; and because the short term market growth is expected to be explosive.

1. Conventional chemical supplier services are replaced by closed loop computer process control, resulting in a higher and far more consistent level of quality. Supply of all wet end chemicals will preferably be provided by Paper Chemistry Laboratory, Inc., (PCL) at competitive prices, to ensure maximum quality and cost-effectiveness.

2. Chemical cost efficiency will be increased in the range of 1 to 2 orders of magnitude, representing a cost reduction of 90-99%. This occurs because nanochemicals in a homogeneous matrix function as molecules, rather than aggregates, with
correspondingly greater mass action efficiency. The counter-intuitive result is that the paper substrate will consume significantly less functional chemical than does a coating, while attaining a much higher level of performance.

3. Product smoothness and print quality will be greatly increased by employing a nanoflocculation mechanism instead of conventional macroflocculation. Proprietary on-line zeta potential and Specific Filtration Resistance sensor and control technology, the Zeta Data On-Line System^®, will be utilized, which has been under continual refinement since 1985.

4. The coating process with all of its requirements, performance issues and accompanying costs, is eliminated.

Papermaking is on the verge of transformation from an art to a science. A world of flawless digital printing is just around the corner!

A nanometer, one billionth of a meter, is the size measure of nanotechnology. It is the most precise (and perhaps the least useful) characterization; not dissimilar from using billions and trillions of dollars to discuss economics with those whose purchases are principally at the food market and gas station.

The reason is that, as particles get smaller, their properties change. Nanoparticles are typically not described by size, but by surface area. For example, the colloidal silica used at the wet end has a surface area of about 600m²/gram. Additionally, the smaller they are, the more negative, and (for quite different reasons) the more attracted to each other.

Turning to the specifics of wet end papermaking, the process is presently uncontrolled, even though the dry end has been under computer control for decades. Since closed loop computer control is one of our objectives, let us review the semi-quantitative process parameters and physical properties in the context of computer control.

The stock is a bleached hardwood Kraft (BHK) with precipitated calcium carbonate (PCC) as filler. The cationic chemical component is added first, mixed to homogeneity, and followed by the negative nanoparticle which is also mixed to homogeneity.

The nanotechnology papermaking example depicted is represented by the red line furthest to the right: cationic starch and colloidal silica. The two chemicals inter-act electrostatically to form a lattice work which functions to simultaneously increase both retention and water removal, or “drainage.” PCL provides a sensor that measures Specific Filtration Resistance (SFR), a parameter fundamental to drainage.

To illustrate the significance of zero zeta potential, two additional lines are plotted. The orange line is polyethylenimine (PEI). It shows a sharp charge reversal at zero zeta potential, towards macroflocculation, which results from its polymeric nature, and illustrates the importance of maintaining zero zeta potential in order to maximize smoothness, strength and sustainability.

The blue line is a monomeric cationic starch which manifests a more gentle inclination change at charge reversal.

The red line represents an optimum nanotechnology papermaking system, exhibiting the best retention and drainage.

Maximum retention and drainage are simultaneously achieved by increasing both feed rates in balance, to maintain zero zeta potential, until the Specific Filtration Resistance is maximized. This action also maximizes productivity.

The original data was first published at the 1993 Papermakers’ in a microparticulate process seminar organized by the author, and presented by Christian Pierre of Centre Technique in Grenoble. The author worked with a Lab Zeta Data^® to produce stock of fully characterized physical chemistry, followed by making hand sheets with the Mk V Dynamic Hand Sheet Mold.^® After several years work, and thousands of experiments, we achieved the understandings explicit in the graphic example.

This was a task of considerable conceptual magnitude. Among its many benefits is the generation of real-time actual cost of each reel, to the penny.

Installation Outline and Pay-Back

Our first action at a candidate mill is a thorough review to determine its operating efficiency metrics, and the precise specifications for additional equipment and sensors to enable papermaking nanotechnology. Advisory time spent at the mill by during this phase by PCL is compensable by the client.

The described efficiencies and many others will result from additional equipment and sensors specified by PCL, which will be purchased by PCL on behalf of the paper mill at out-of-pocket cost plus a 10% fee. The single exception is the Zeta Data On-Line System^®, including computer and software, which will be leased from PCL. The annual lease is priced at $150K for the first System and $25K for all additional Systems in a single order from one mill, including a warrantee for software maintenance, parts replacement. Continuing guidance will be provided in process control refinement, with emphasis on the first System as the prime example.

The paper mill agrees to make the wet end process and performance data available for viewing remotely on the Internet, and to appoint two young, fast-track chemical engineers machine to manage the day-to-day optimization effort.

The technology primarily consists of a good half dozen nanotechnology concepts, together with the hardware and software for implementation. The essential task is to flawlessly implement and integrate all of them harmoniously, under closed loop computer control, so they operate together in an optimal, self-reinforcing manner.

In summary, we propose to effectively apply the broad knowledge embodied in our patents, patent applications, related proprietary know-how, and the education, training and experience of our staff of engineers and chemists. Successful realization will result in maximizing quality, performance, productivity and sustainability at the lowest feasible cost, under closed loop computer control.

John Penniman
www.papermaking-chemistry.com

DIGITAL PRINTING

PAPER OPTIMIZATION

Computer Control of the Wet End