HAROLD M. CODY Executive Editor
Pulp & Paper

Pigments evolve as customer's demand improved grades

The major trend effecting all businesses, whether they make paper or sell shirts over the Internet, is increased competition. Increased competition is driving paper mill customers—whether a box buyer, printer or direct marketer—to demand higher quality products to provide a competitive advantage to differentiate their products. In addition, they expect these new improved products to cost no more, and hopefully even less, than the old product. The paper industry is responding by continuing to produce new products that offer better value and provide higher quality. These factors continue to have a major impact on new product development and demand for paper chemicals.

The explosion in the use of the Internet is having an impact on the use of paper and board. For example, consider a merchant selling products (clothing, electronics, etc.) over the Internet. As competition intensifies, a number of e-retailers are looking to gain a competitive edge by establishing an image of quality, or in some cases branding their products, as a strategy. An integral component of this is the appearance or perceived quality of a product when it arrives at the customer’s doorstep.

MOVE TO HIGHER BRIGHTNESS. Improving the quality of the primary packaging (the product box) and well as the secondary packaging, (the corrugated shipping container) can aid its perception as a quality product. These and other market factors are driving high quality graphics paperboard grade (white top linerboard and SBS paperboard) producers to raise quality. One result is that some SBS mills have turned to the use of precipitated calcium carbonate filler pigment, driven by a move to higher brightness and a bluer shade in North America. In the case of white-top grades, several producers have also switched to PCC filler for the top ply (whether it’s composed of bleached kraft or mixed-office waste). PCC use can lower costs by reducing the amount of bleached fiber used and by replacing more expensive pigments such as titanium dioxide. A gain of two or more points of brightness is also possible.

Users also continue to demand higher quality printing and writing grades. For example, newer generation SCA-plus uncoated groundwood grades are pushing brightness levels up to 77-78 ISO and print quality compares to coated paper. These sheets are practically a “composite,” as they are essentially coated on the inside. New wet end technology allows the filler pigment (35-40% ash in these grades) to be concentrated near the surface of the sheet. Similarly, the application of on-machine calendering (plus coating in some cases) in conjunction with pigment use has spawned a whole new array of high quality printing papers.

TAILORING THE SHEET. In order to meet these needs paper mills are raising brightness, improving opacity and modifying other sheet properties. In turn, pigment suppliers have responded by introducing a wide array of new products, many of which are “engineered” to produce a specified attribute. One of the major developments is a wide array of new products with a narrow particle size distribution (NPSD). These include new 90 brightness kaolin pigments that can reduce the use of more expensive pigments such titanium dioxide or plastic pigment, while retaining optical performance. Others include modified delaminated clays to provide improved gloss and ink holdout in LWC. Producers of ground calcium carbonate have introduced similar NPSD products. PCC producers have modified the morphology of their products as well in order to provide similar enhancements. NPSD products are also be-ing developed that target the ink jet paper market.

NPSD pigments work by controlling porosity and sheet structure to build pore structure, thus enhancing light reflection and refraction, which in turn influence sheet optical and print properties. However, there can be a trade off when using NPSD products. For example, runability can suffer if rheology becomes more challenging.

In terms of overall usage trends, the drive to higher brightness (and often in conjunction with a lower cost) continues to propel the use of carbonate higher. In addition to growing use in paperboard, as noted above, carbonate continues to find wide spread use as a coating pigment. By one estimate (by a producer), ground calcium carbonate (GCC) use will account for 20% of the 4 million tons of coating pigments used in North America this year. Clay comprises the majority of use, accounting for about 70%. In contrast, GCC use in Europe will account for nearly 60% of coating pigment demand this year.

As mills fine-tune their products, by employing products such as NPSD pigments a couple of other trends are occurring. One view embraced by many is that use of a combination of different minerals (e.g. clay and carbonate) produces the best sheet properties by optimizing particle. An increase in sources of supply, such as clays from Brazilian, is another trend. This provides papermills more options than ever to select pigments with a specific particle size distribution, brightness, scattering coefficient, etc.