Volume 1, Number 1
Jun 1994

Highlights of TAPPI Papermakers

TAPPI (Technical Association of the Pulp and Paper Industry) held its Papermakers Conference April 24-27 in San Francisco, and it must have set some kind of a record for the number of presentations on alkaline papermaking and related topics. Seven or eight of the papers dealt with alkaline papermaking directly, and many others dealt with related additives and operations. One of the posters described a promising new alkyl ketene dimer (AKD) size. Alkaline papermaking (and marketing) issues were covered in a "Meet the Experts" session and a Papermakers Roundtable. Many of the participants were familiar with the topic and made good contributions to both formal and informal discussions. For instance, a Japanese papermaker volunteered, at one of the coffee breaks, that almost all mills are alkaline in Japan now; all copy paper is alkaline. (In 1979, Vasant Chapnerkar gave the first TAPPI session on alkaline sizing. Only 30 or 40 people came, he says. This 1994 conference was quite a change from those days.)

The poster was "New Generation of AKD Size for the Sizing of PCC Containing Fine Paper," by W. Todd Walters of Raisio Inc. of Harrisburg, Pennsylvania. The new size it describes was developed to address three persistent problems that arise when AKD is used with high PCC (precipitated calcium carbonate) filler levels: slipperiness, size migration and size reversion.

Some of the papers were:

"Improving the Converting and End-Use Performance of Alkaline Fine Paper," by C.L. Brungardt and J.C. Gast. The authors, both from Hercules, Inc., describe three modified sizing agents designed to address the problems sometimes encountered with alkaline paper: reduced operating speed, double feeds or jams in high speed copiers, paper welding, and registration errors on envelope folding and high speed printing equipment. Two of the sizing agents gave improved performance on the IBM 3800. The results held even up to filler levels of 30%. AKD and ASA sized papers were used for controls. In order to tell whether a paper will feed and handle properly, it is necessary to run it about 30 minutes, because this is how long it takes for things to start going wrong, if they are going to; however, it only takes about 15 seconds for good performance to return after good paper is substituted for the problem paper.

"Practical Applications of Neutral Papermaking with Rosin Size," by M.C. Peck and M.A. Markillie. The authors give some general information about neutral papermaking in their introduction, saying that it is generally practiced over a pH range of 6.0 to 7.5, and is distinguished from alkaline papermaking by the degree of calcium carbonate usage, rather than pH. Neutral papers (usually unbleached kraft or recycled white paper) are "essentially non-buffered." This paper describes how Neutral Sizing Agent (NSA), a rosin dispersion sizing agent from Georgia-Pacific Paper & Pulp Chemicals, can be used. The preferred pH range is 6.5 to 7.5, to avoid soluble calcium and deposit problems.

"AKD Sizing with Blended PCC Morphologies at High Filler Loading," by J.L. Ozment and A.R. Colasurdo, of Eka Nobel. This paper addresses the problem of achieving a PCC filler level higher than the usual 12-18%, without adverse effects on the sizing.

"Alkyl Ketene Dimer Sizing Reversion and Efficiency in Papers Filled with Calcium Carbonate," by W.J. Bartz, F.L. Kurrie, and M.E. Darroch, all of Westvaco. Size reversion is the loss of water repellency, weeks or months after the paper is manufactured. It is aggravated by high drying temperature and small filler particles (below about 1.9 microns).

"Analysis of Alkyl Ketene Dimer (AKD) by Potentiometric Titration," by S. Nyarku and B.B. Sitholé. This method was developed to determine non-reacted AKD, and to monitor the stability of AKD formulations.

"A Converting and End-Use Approach to Alkaline Fine Paper Size Development," by M.A. Meixner and S. Ramaswamy, both of Hercules. The converters and end-users of alkaline printing and writing, book, cover, offset and coated papers are happy with the products they get, but printers and converters have been struggling with alkaline forms bond, envelope, adding machine tape and some cut-size uses like photocopy paper, because they cannot control them precisely during high-speed handling. Control can be improved by increasing porosity, reducing triboelectric charge (a kind of static charge caused by passing materials of dissimilar surfaces across each other) with salt in the size press, and adjusting any of six or more other variables. Hercules integrated converters and end-users into the feedback loop for development of new sizes to address these problems.

"Carboxylic Acids (Including Hydrolyzed ASA) in Neutral/Alkaline Papermaking and the Potential for Deposits," by J.M. Gess. The deposits investigated here are called "pitch balls," the product of reaction between calcium carbonate particles and carboxylic acids. They can form in the kraft pulp mill and be passed along to the paper mill on the fiber; or in the paper mill, where it is hypothesized that the PCC filler sorbs hydrolyzed ASA; or in the size press system, where the calcium carbonate attracts and sorbs residual fatty acids in corn starch. Deposits that form on surfaces of the wet end or dry end of the paper machine do not always stay put, but often break off and become incorporated in the paper as dirt or faults. The author gives several suggestions for avoiding pitch ball formation.