New horizons: there is a new forecast for coated paper manufacturers--but the weather looks good.

The industry has seen a lot of activity in the coated papers arena. As discussed in our previous article (see "Additional resources," left), overall demand has taken a bit from a decline in print advertising, and economic pressures have prompted some customers to shift their focus onto lower quality, less expensive grades. Coated paper manufacturers also have had to learn to adapt to the evolving tastes of an increasingly global market.

New coating technologies--including a few borrowed from other industries--promise further change for coated papermakers. In this second of two articles on coating, we asked industry experts to gaze into their crystal balls and see what lies ahead.

NON-CONTACT SPORT

New, non-contact coating methods such as curtain coating and spray coating are gaining favor with papermakers eager to improve efficiency and productivity while lowering manufacturing costs. According to Nick Triantafillopoulos, director of polymer innovations for OMNOVA Solutions, Akron, Ohio, USA, and a member of the TAPPI Editorial Board, both techniques have been borrowed from other industries. "Curtain coating has been used for the past 40 year in the photographic and other specialty media industries. The broad patents held by these industries, which blocked these processes from being used elsewhere, have now expired," he said. "As a pre-metered coating process, curtain coating improves substrate coverage by creating a bulky coating layer, while it provides opportunities to reduce web strength requirements and reduce web breaks. The applied thickness of the coated film depends on the ratio of volumetric flow rate/width to web speed and is a function of coating rheology. Therefore, there is precise control of the coating film thickness and ability to multi-layered coating. The latter gives an opportunity to apply multiple--even different coating formulations--for one-step coating and can eliminate the need for multiple coating heads for high-quality differentiating products. The disadvantage is that a curtain coater can coat only one side of the web at a time.

"The spray-coating method is based on a spray fan producing coating color droplets that level at the surface impact and produce a contour-type coverage," Triantafillopoulos continued. "The technique opens possibilities to improve coating process efficiency with fewer web breaks over conventional techniques that have direct mechanical contact for metering. The reduced strength requirement for the base paper can potentially allow reduction of the kraft content in LWC (light weight coated paper), which then contributes to lower furnish costs. It can also be used for coating substrates like rotonews basestock and newsprint. The spray application, however, puts new requirements on the color formulation strategies to achieve optimal atomization and on the base sheet properties to get optimal leveling of the droplets and smooth coverage."

According to Yun-Long Pan, product development manager at Smart Papers, Hamilton, Ohio, USA, both methods offer the greatest economic benefit in specialty niche applications, "where machine speeds and machine width are not the most important parameters to gauge profitability. This is because the new coating methods have their own limitations, despite their advantages. Those limitations--such as machine speed, width, air bubbles in the coating, vibrations in the coater head, nozzle plugging, and shot precision maintenance--prevent their use in a typical paper coating environment."

Commercially, these technologies will only be adopted when the industry can find the capital to invest in new equipment, and then develop the products and attendant marketing support that offer the best synergies for the new techniques. "Most likely, they will show up on new coated paper machines, or on upgrades from uncoated to coated paper lines," noted Dean Benjamin, product development manager for Stora Enso North America, Wisconsin Rapids, Wisconsin, USA.

GOING ONLINE

As its supporting technology has improved, more mills are using on-line coating for LWC grades. Experts expect this trend to carry over into other grades currently produced using off-line coating. "The significant advantages gained from the efficiencies of on-line coating makes this the optimal choice for new coating applications," said Sharad Agarwal, product manager-coated freesheet products, Coated and SC Papers, for International Paper Co.

"Improvements in base stock manufacture-including draw-free wet ends, single-felted dryer sections and computerized process controls--reduce break frequency," added consultant Charles P. (Chuck) Klass, a member of the TAPPI Editorial Board. "The growing use of metered size press precoaters also contributes to reducing the likelihood of coater breaks. Variable costs are lower for on-machine coating. On the other hand, it is likely that value-added specialty coated grades will continue to be developed using off-machine coaters, and produced t off-machine in the early stages of the product life cycle."

For large volume grades that require few changes, on-line coating offers a clear economic advantage. Specialty coated grades produced in smaller volumes with many grade changes require increased flexibility, however, and should probably stay with off-line coating.

THE DIGITAL AGE?

Efficiency and flexibility concerns have spurred the growth of another hot coating topic: digital printing. In coated grades, digital printing's most immediate implications lie in packaging. "Packaging is an ideal application for digital printing because of the amount of variable information involved," said Pan. "Digital printing needs, in general, are not well met with conventional coated paper or paperboard. To be compatible with digital printing applications, the coating formulation must be specifically designed."

Klass agrees that digital printing is likely to gain wide acceptance "especially in short run, just-in-time, high graphic quality corrugated box and flexible packaging applications." Time and cost efficiencies of pre-press and make-ready are major factors. "Implementing digital printing in packaging applications will require development of new grades of coated linerboard and packaging papers, but the market potential is very high."

Still, not all the experts we spoke to agree. "We do not view digital printing as a major implication for coated paper at this time, as digital breakthroughs affecting users of coated papers have primarily been in the pre-press area. Moreover, the vast majority of publications that use coated paper are run offset or rotogravure," said Rick Schneider, manager-catalog marketing, Coated & SC Papers, for International Paper.

COATED NEWSPRINT VS. SCA 

Will new "coated newsprint" grades take market share from SCA for heatset offset printing? According to Benjamin, declining demand for newsprint has already driven some producers to find new products for their machines. "When 'coated newsprint' grades become acceptable from a pressroom runnability standpoint, they will have a chance to start competing with SCA. Wider, faster machines will be in the best position to displace SCA," he said.

There are tradeoffs to consider when comparing the two, said Schneider. Unlike SCA, for coated newsprint grades the coating is applied, which aids printing; also, sheets tend to be bulkier. "However, these sheets are available in a very limited range of basis weights, and sheet aesthetics are typically a disadvantage," he added. "Given these tradeoffs, it is likely that some applications have potential to shift from SCA to coated newsprint."

That is already happening for heatset offset printing, noted Pan. "With the availability of pre-metered film press technology in combination with on-line soft nip calendering, coated newsprint can be made economically with relatively good print quality. The relatively open newsprint base with a low weight coating on the surface is especially suitable for heatset offset printing where blistering is a concern."

Yet printing SC grades on a heatset-offset press can be problematic, warned Klass. "There is no binder holding the pigment on the surface, and there can be problems with water sensitivity, dot gain, and milking. If a heatset offset printer sets the press up to run SC papers exclusively, these problems can be overcome with proper management of ink tacks, fountain solution, and press operating conditions. Yet, many big publication printers alternate running SC and coated papers. The new coated newsprint grades provide an economical alternative to blade-coated LWC papers."

IN THIS ARTICLE YOU WILL LEARN:

* Potential benefits and drawbacks of non-contact coating methods.

* The implications of digital printing on coated papers.

* Whether coated newsprint grades are likely to displace SCA papers.

ADDITIONAL RESOURCES:

* For books and CD-ROM materials about coating and coated papers visit www.tappi.org and click on TAPPI Press.

* "Coated papers: It's a brand new ballgame," Jan Bottiglieri, Solutions! magazine, May 2002, pp. 32-35. Also available online at www.tappi.org