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Coating is paperboard's key to functionality and printability.

STRONG, BRIGHT, AND value-added is the composition of many a woman's dream man. It's also what consumer product companies (CPCs) are looking for in their paperboard packaging. And for the most part, that's what they're getting—a resilient substrate that's brighter and more functional than ever.

Improved paperboard materials continue to hit the marketplace, spurring and supporting a slow but steady growth of the substrate. While it's still rebounding from a low base in 2002, the growth is expected to climb steadily at 2.8 percent per year to more than $35 billion in 2007, according to Corrugated & Paperboard Boxes, a study published last year by The Freedonia Group Inc.

Already, developments have made paperboard brighter, whiter, stronger, smoother, and more printable. Most of these advances have come by way of better coatings and raw materials. The styling and printability of paperboard are the two areas where coatings have contributed the most.

Styling: Getting the look

Styling refers to the combination of color, whiteness, and brightness of paperboard, according to Bryan Ortman, segment manager of MeadWestvaco Packaging Resources Group. Styling is one of the biggest differentiators to paperboard and is influenced by coatings and coating ingredients.

"Coating is a key driver in achieving brightness," Ortman said. "Three factors impact the styling and brightness of the coated surface: the type of pigments used in the coating, the amount of dyes added to the coating, and the amount of fluorescent whitening agents added."

In the last five-to-seven years, paperboard producers have revamped their coating recipes to achieve maximum brightness. Mills now use more calcium carbonate (CaCO3) pigments, the main ingredient to obtaining higher brightness, said Quintin Parker, senior technical service advisor at BASF.

Advances in latex, a binder, also has helped increase brightness. Latex, of which there are several kinds, holds the white pigment to the paper, said John Kelly, Dow Chemical Co. technical service and development engineer.

"Typically, we see each of the different latex chemistries having key performance criteria that recommend them for various applications," Kelly said. "For instance, S/B (styrene butadiene) latex is a great choice for high strength, especially in a beverage carrier where water resistance is important. S/B/AN (styrene butadiene acrylonitrile) latexes typically improve offset printing quality compared to S/B latexes, but may not be as strong in pick performance. S/A (styrene acrylate) latexes are great for high brightness, resistance to fading, and good offset printing performance. As you would expect, there is a price/performance balance when choosing a latex for your coating."

Printability: A smooth surface

Uncoated paperboard has a rough, absorptive surface that impacts the quality of printing results. Of coatings' many purposes, making the paperboard surface smooth and printable is one of the most important.

"Coatings are applied to paper to correct imperfections in the surface to provide a smoother sheet and improve ink holdout, which results in better dot reproduction and higher gloss," Ortman said. "The more coat weight and the more coating layers that are applied, the smoother and more uniform the surface. This translates to printed results. Surface smoothness can be seen with the naked eye, but ink on paper enhances any surface defects.

"Also, a smoother surface contributes to uniformity and improves paper quality. This allows the printer to run the job through equipment with increased throughput and less downtime," Ortman added.

Another benefit from increasing paperboard's printability is process improvement. As coatings make paperboard smoother with a more consistent surface, print quality increases because the substrate is easier to print and handle in process.

"Coatings can reduce or increase surface friction to modify the handling of board packaging in various machine configurations," said André DiMino, president of ADM Tronics Inc.

In addition, Parker explained, "In many cases, printers and converters can run at faster speeds with less concerns on paperboard quality."

However, while coatings already make a significant contribution to paperboard, they will have to improve even more as printing equipment advances.

"As printing technology improves, the coated surface must improve to support the expectation of higher print quality and functional properties," said Dave Smith, technical service and development engineer at Dow Chemical Co. "Since there are several possible methods of printing coated paperboard, future coatings must be capable of bringing out the best in all of the printing processes."

Other benefits

Besides styling and printability, coatings also give paperboard capabilities that open its range of application, including:

• Barrier—According to Corrugated & Paperboard Boxes, food and beverages comprise the largest single end use for boxes, accounting for more than 40 percent of aggregate demand in 2002. Paperboard has only been able to make inroads into the food and beverage markets, as well as other select markets, because of coatings.

"Coatings can make paperboard more resistant to water, grease, oil, and other chemicals that contact the board either in their environment or from the actual product contained therein," DiMino said.

This includes boxes for juice, detergents, and freezer and refrigerated foods.

• Durability—If a package can withstand the taxing trials of filling, shipping, and retail without scuffs and other markings or dents, it's more likely to catch the eye of a consumer and be purchased.

"Protective coatings used to prolong print life quality of paperboard surfaces can reduce damage caused by abrasion to the product in storage and transit," explained David Newell, president of Newchem Corp. "This will reduce returns and promote re-orders."

• Environmentally friendly—While paperboard is innately kind to the environment due to its biodegradable make-up, many of the coatings used to give the substrate its functionality and value aren't. There is a growing concentration, however, on environmentally-friendly coatings, including coatings made with low VOC binders.

"There will be a push for producers to use more environmentally friendly raw materials," Parker said. "The use of low VOC binder products, replacing the use of NH4OH and going to raw materials that are formaldehyde- and APO-free will be some of the requirements placed on the vendor to supply to the industry."

Rising costs

Coatings are an important part of paperboard packaging, but they're getting expensive. Nearly all coating suppliers and their raw materials vendors have had to raise their prices in the last few months and years due to increased insurance premiums, and the rising cost of fuel (both oil and natural gas), freight, and raw material ingredients.

"Although we try to absorb as much of our increased costs as possible to remain competitive, increased energy and related costs have caused the necessity to increase our prices by a modest 3-5 percent," DiMino said. "We anticipate that we will be stable for the near future as we don't see a continued upward pressure in these areas."

However, not everyone is as confident as DiMino. "Raw materials currently have had the largest impact, with dramatic increases in costs for natural gas and benzene," said Donna Babcock, North American marketing manager of Dow Latex for Dow Chemical Co. "The pricing of natural gas has hit three times the traditional pricing from $2/MMBTU to $6/MMBTU. These increases resulted from inadequacy of supply and rising demand. … As natural gas has started to level out at high prices, we have now seen benzene continue to skyrocket. In the last three months, pricing is now at record levels with contract price trading at $3.07/gallon and will likely continue to increase. Dow has announced $.09 in increases this year. If this cost trend continues, we will require more price increases."

By Kate Sharon

Associate Editor