TAPPI Coating Conference raises the curtain on coating.

Curtain coating was clearly in the spotlight at the TAPPI Coating and Graphic Arts Conference, held in Baltimore this past May. It was the hottest topic area on the technical program--even though this technology is still in the early stages of development without commercial installations for regular coated printing paper grades. There are several commercial installations of curtain coaters making carbonless and thermal papers, and the method is used in coating photo film and paper and in wax coating corrugated. All sessions dealing with curtain coating were "standing room only".

Uwe Froelich and Martin Tietz of Voith Paper GmbH & Co. KG reported on the results of surfactant addition to curtain coating formulations. Their pilot coating trails showed that the types and amounts of surfactants used could have significant effects on curtain coater runnability and final print quality.

Michael Voss of Polymer Latex GmbH & Co. KG, and Sascha Tadjbach of Bayer Products, discussed extensional rheology of curtain coating colors. The use of conventional offset coating formulations causes curtain coater runnability problems due to insufficient stretchability of the coating color. Conventional rheological measurement techniques do not measure the needed property. Extensional rheology--a totally new technique--shows excellent correlation between laboratory measurements and curtain coater runnability. Choice of cobinder and rheology modifier are critical. In particular, research found the use of a special high molecular weight water-soluble thickener to be a key to achieving problem-free runnability and excellent curtain coating at high speed.

"The Impact of Coating Non-Impact Panel Discussion" also focused on curtain coating. Peeyush Tripathi, Western Michigan University graduate student, discussed operating experiences with a pilot scale curtain coater and the effect of steam substitution of stabilization of dynamic wetting behavior. This report was based on his experience as an intern at Mitsubishi Heavy Industries Ltd. in Japan. Martin Kustermann of Voith Paper GmbH & Co. KG discussed the challenges in transferring curtain coating technology from specialty grades to pigment coated printing papers. Peter Schweizer of Polytype SA discussed degassing requirements for curtain coating.

The New Technology Tutorial Session on Curtain Coating included presentations on:

* Die Design and Curtain Stability by Peter Schweizer

* Heel Stability Dynamics by Peeyush Tripathi

* Fundamental Considerations of Leveling and the Relevance to Contactless Coating Methods by James L. Vaughn of OMNOVA Solutions Inc.

There is also interest in spray coating, which has one current commercial installation. Anthony Hiorns of IMERYS Minerals Ltd. And Robert Fogelholm of Metso Paper presented a paper on kaolin use in spray coating.

INNOVATION MANAGEMENT

Peter A. Koen of Steven Institute of Technology made an abstract generic presentation Innovation in Product Development: From Chaos to Clarity in the Front End of Innovation. He was particularly critical of the Stage Gate[TM] methods widely used by paper companies and suppliers, saying that they are inappropriate for developing platform and breakthrough products.

Valerie Lejeune of Arjo Wiggins made a presentation focused on innovation in the paper industry. She outlined the responsibilities of R & D to include:

* Importing technologies from other industries

* Imagining new concepts for paper

* Finding new applications for existing products

* Producing rough prototypes.

She defined marketing responsibilities as:

* Analyzing market and customer needs

* Arranging R & D contact with "trend agencies."

Joint responsibilities of R & D and marketing include:

* Defining innovation niches

* Establishing prototype specifications

* Organizing brainstorming sessions

* Setting up action plans

* Transferring prototype developments to commercial development groups.

Frank Perkowski of Business Development Advisory discussed North American coated paper trends and implications. He pointed out that both coated free sheet and coated groundwood demand growth has slowed since the 1990s. Prices have fallen, investment has slowed, and high cost equipment has been shut down. Nevertheless, the North American coated paper asset base remains globally uncompetitive and profit margins are low. This has led to industry consolidation and acquisition of North american assets by foreign-owned producers.

Perkowski discussed "on demand" drivers--especially the growth of digital printing and electronic communications. This will lead to demand for different types of coated papers. Globalization, consolidation, rationalization and declining capacity growth will have implications for product design, paper performance properties, paper cost and price structures, industry structure, and capital investment levels. These factors will have both positive and negative impacts on the the supply chain for coated papers.

Robin McCann of RohmNova reported on magazine trends, advertising, and innovations required to change this dynamic market. About 3.6 million tons--1/3 of total coated paper--is used to print 8000 consumer and 5000 business magazines in the United States. In spite of electronic communications, magazines will continue to consume large coated paper tonnage in the future.

UNIVERSITY RESEARCH UPDATE

The University Update session included nine research report papers by students:

* Influence of Mechanical Properties on the Cutting of Coated Papers, Robert A. Rioux, William N. Unerti, and Douglas W. Bousfield, University of Maine 

* Optimum Level of Internal and External ESA for LWC Paper, Deepak Kumar, Western Michigan University

* Pigment Ratio Effect on Printability of Glossy Inkjet Paper Coatings, Hyun-Kook Lee, Western Michigan University

* Increased MD/CMD Strength Ratio Through Impregnation, Melissa S. Rivard, Western Michigan University

* The Effect of Paper Substrate on Color Gamut and the Trend Towards Reference Printing Conditions, Mohammed Ali Salahuddin and Abhay Sharma, Western Michigan University; and Fay Summer, Flint Ink Corporation

* Gravure Printability Comparison of Laser and Electromechanically Engraved Cylinder, Xiaoying Rong, Western Michigan University

* A Liquid-Bridge Probe to Characterize Coated Surface Uniformities, Yingfeng Shen, Adriaan Van Heiningen, and Douglas W. Bousfield, University of Maine

* Evaluation of New ICC profiles: ECI Process Standards for Gravure, Adam Rasmusson, Western Michigan Univ.

* Particle Size vs. Color Stability of Roto-Gravure Inks During Long Runs, Veronika Chovancova, Western Michigan Univ.

COATING MATERIALS

Several papers reported on advances in coating materials. Roger Carlsson, Dow Chemical Europe GmbH, Charles Kan, Dow Chemical USA and Magnus L. Wikstrom, Korsnas AB presented results of a study on the effects of coating process temperature/times and latex viscoelasticity on binding. The results showed that high calendering temperatures, high drying intensity and elevated storage temperatures--for example, in a jumbo reel--can improve binding strength. Latex with better deformability at actual process conditions, seen as a low storage modulus, gives the improvement more easily.

Z. Richard Zhang, Mississippi Lime Co., Margaret Joyce, Oznur Ogden and Vidit Kumar--all of Western Michigan University--presented results of a study comparing fine aragonite PCC to GCC in LWC and CFS coating applications. In both coating applications, fine aragonite PCC provided high sheet gloss. In coated free sheet, fine aragonite PCC gave better opacity and brightness compared to fine GCC and engineered GCC. In LWC both rhombic and fine aragonite PCC gave better brightness than fine GCC. The high shear stability of fine aragonite PCC was found to be better than the engineered GCC.

It is generally believed that a decrease in coating solids leads to a decline in optical performance. Amy Dimmick, Michael Kroeber, George Alderfer, and Esko Aarni--all of Specialty Minerals Inc.--reported on a study of solids performance relationships for a variety of PCC and GCC pigments. The results of this study indicated that reducing coating color solids had no appreciable effect on optical properties, provided that other key coating properties such as viscosity and water holding were properly controlled.

WHAT YOU WILL LEARN:

* Why curtain coating was the center of attention at the Coating Conference.

* How coated paper producers and suppliers can manage innovation.

* Recent advances in coating materials.

ADDITIONAL RESOURCES:

* To purchase the CD-ROM from the 2004 TAPPI Coating and Graphic Arts Conference, go to www.tappi.org and type COATING-04 in the search engine: Member price: US$ 55.00, non-member price: US$ 80.00.

CHARLES KLASS, SOLUTIONS! EDITORIAL BOARD

ABOUT THE AUTHOR

Charles P. (Chuck) Klass heads a consulting firm, Klass Associates, Radnor, Pennsylvania, USA. He has been active in TAPPI for many years and is a member of the Solutions! Editorial Board. Contact him at [e-mail]

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