New technology for new markets.
According to Charles Klass of Klass Associates, Radnor, Pennsylvania, USA and a member of the Solutions! Editorial Board, the use of engineered pigments is likely to continue to increase over the next decade as papermakers and coaters develop more understanding of the potential applications and overall value of using them.
"Although engineered pigments cost more than conventional pigments, they can favorably impact overall system cost," he said. "For example, use of an engineered kaolin precoat pigment-which provides more uniform coverage and better hiding of a dark base sheet-can reduce the amount of expensive titanium dioxide pigment required in the topcoat. Use of engineered pigments in surface sizing can facilitate making a base stock that either requires lower coat weight to achieve the same optical properties, or offers improved properties at the same coat weight. The keys to getting the value from engineered pigments are non-conventional approaches to the overall paper product and process design."
According to Tony Lyons, director of research, Imerys, "The high value potential of engineered pigments warrants changes in formulations and the way that coaters are run. When you consider the advances in coater head technologies like the metered-size press, jet applicator, spray and curtain technologies, runnability is no longer a concern."
Added Leslie McLain, technical manager, uncoated papers, Imerys, "As paper companies struggle to balance profitability and productivity, building functionality into the sheet through the use of engineered pigments creates differentiation needed in a tight market. Papermakers are beginning to realize that engineered pigments, though more costly than most commodity pigments from a raw material standpoint, allow savings through more efficient light scatter. Additionally, engineered pigments are beginning to gain momentum in niche markets such as barrier grades."
Rajan Iyer, technical manager for coated papers, Imerys, pointed to the trend in pursuing new grades to provide "touch and feel," as art designers look at using paper as a fabric in their designs. He suggested that "this trend will require pigment and other suppliers to provide innovative materials to provide functionality. Producers are also looking to see how nanoengineered materials can give them a step up in performance and possibly a whole new way of making coated paper for the graphics market."
Prakash B. Malla, Ph.D., manager of research and development, Thiele Kaolin Co., Sandersville, Georgia, said the discussion should start with a definition of "engineered pigments."
"An engineered pigment may mean different things to different people," said Malla. "Many people think of an engineered pigment as the one with a low level of fine particles and narrow particle size distribution. To be more representative, the meaning of an engineered pigment--in a sense of processing/manufacturing and performance--should be as follows: A pigment whose particle size, shape, and surface properties have been deliberately and uniquely modified by mechanical, chemical, mechanochemical, thermal or other means to enhance single- or multiple-performance attributes."
VALUE AND COST
The cost of an engineered pigment is normally higher than that of a conventional pigment for one-to-one replacement, according to Malla. However, the cost difference is much less if compared on a "total cost" system basis. "An engineered pigment, depending on the type, has the potential to replace (partially or totally) other expensive pigments and additives such as Ti[O.sub.2], plastic pigment or optical brightening agents (OBA)," he said. "The additional benefits from an engineered pigment include improved blister resistance and print quality."
The use of engineered pigments will continue to grow-not by choice but by necessity. "This will allow paper manufacturers to design coating structure to meet specific end use performance goals," said Malla. "Consequently, the concept of 'one size fits all' will be obsolete and will be replaced by the tailored/dial-in pigment concept. This would also help paper manufacturers to differentiate their products from their competitors."
Malla noted that the major drawbacks of engineered clays to date have primarily been poor rheology and coater runnability. "This area requires further understanding of flow characteristics of narrow particle size distribution and structured pigments in a highly crowded suspension," he said. "We must also search for ways to enhance the mechanical properties of paper such as strength and stiffness through modified pigment systems. As the pressure for improved productivity at lower cost intensifies, there will be a vigorous search for synergy between pigments. The opportunity for synergy exists not only between pigments of different type (e.g., clays and carbonate or clays and Ti[O.sub.2]), but also within a family of pigments (e.g., clays)."
According to Shripal Sharma, senior industry manager, paper for Luzenac America, Centennial, Colorado, engineered pigments offer greater value to the end-users than has been recognized. "Pigment suppliers have not done a good job in developing believable value propositions for their engineered products," he said. "Pigment suppliers can help themselves and their customers by developing a strong working relationship with their key customers, which will enable the suppliers to better understand the value provided by their engineered products. While the majority of the engineered products cost more than the standard products, if used properly they can actually reduce the overall cost of the paper products while improving productivity and machine efficiency. Pigment suppliers should consider a total system approach as part of their market strategy instead of a single component approach."
[FIGURE 1 OMITTED]
Sharma noted that the current state of the global paper industry is forcing paper companies to change their business model. The old model--selling high volume commodity paper grades--is moving to the new model of low volume, high value grades that are profitable and can justify additional capital investment. Paper companies are also resegmenting their customer base to better understand and satisfy customer needs. This will enable them to manage inventory and their production schedules while providing better control on supply chain management. "Visionary companies that understand and act on this new reality, in part by using tools like engineered pigments, will be the market winners. The role of functional and engineered pigments will only grow in the next decade," concluded Sharma.
Papermakers are still evaluating engineered products as a way to reduce costs by replacing more expensive pigments like titanium dioxide or other extenders, according to Mike Strutz, manager of technical services, Omya. "Their use is growing and this growth will continue as long as there are pressures to reduce costs or develop lighter weight grades and the opacity and brightness requirements that they demand."
INKJET AND LASER PRINTING
How has the use of pigments and fillers been affected by the growth of inkjet and laser printing in office and home office environments? According to Klass, the growth of inkjet and laser printing in these environments has resulted in increased use of pigment in general-especially brighter and specialty pigments. "This trend has been facilitated by alkaline papermaking, which allows higher filler levels. There is a growing demand among users for higher brightness office papers. Calcium carbonate pigments are well matched to this need, providing high brightness, desired shade, and compatibility with optical brighteners."
Klass noted that demand for ink jet and digital-printing papers is growing rapidly as color ink jet printers become the dominant printers in both homes and offices. Digital printing is the fastest growing area of the printing industry, according to Klass. Users of ink jet printers and desktop publishers are looking for higher quality papers (see Figure 1).
"Most ink jet papers sold today are uncoated, multipurpose papers for use on copiers, laser and ink jet printers," he said. "These papers are produced on large-scale commodity paper machines using on-machine synthetic surface sizing with metering size presses. Typical costs for these products range from US$ 0.01 to US $0.02 per sheet. However, while they are suitable for routine correspondence, uncoated grades do not allow high-end print and image appearance. At the other end of the quality spectrum are photo-quality ink jet papers and papers coated with silica pigment using polyvinyl alcohol binder. These papers are coated off-machine on low speed coating lines, and typically cost $0.30-$1.50 per sheet."
According to Klass, the market is seeking papers that give improved performance over basic uncoated grades at affordable cost. These "mid-grade" papers would approach the quality of silica-coated papers but be produced at costs allowing them to be sold at US$0.03-US$0.10 per sheet. Availability of these types of papers would fill the "gap" between expensive silica-coated papers and low quality, synthetic surfaced sized uncoated papers. Market research has shown that the volume potential for ink jet and digital printing papers filling the gap would be at least an order of magnitude bigger than the current market, according to Klass. "Papermakers, printer manufacturers and commercial printers recognize this huge potential. It has been the subject of intensive research over the past half decade with no breakthrough," he said.
The critical elements in making these "gap" grades are:
* Pigment that costs less than silica
* Capability to coat on-machine at high speed
* Capability to use lower cost starch as a cobinder with polyvinyl alcohol would further reduce the cost of manufacture and cost of the coated paper.
At present, commercial coated ink jet papers are coated with amorphous silica pigments, Klass explained. Precipitated silica is most common for this application, but fumed and gel silicas are also used. These pigments sell for US$2.00 to US$4.00 per pound; however, the high price of silica pigments is only part of the problem. Silica pigments pose production problems because they must be applied at very low coating solids. Silica slurries alone do not flow well at solids levels above 15% to 20%. Silica has great affinity for water due to its pore volume, so it forms a paste as water is added until the voids are filled; only then does it become fluid enough for coating formulation. Coatings must be formulated and applied at low solids concentration-usually less than 20%. The absorbed water in the pores also demands extra energy during drying of the coating. The combination of these factors has limited production of silica-coated papers to low-speed, off machine coaters that have much higher variable cost than on-machine coating at high speed.
"The major pigment suppliers have developed specialty engineered and chemically modified kaolin and precipitated calcium carbonate pigments claimed to meet the need." stated Klass. "These products have been available for several years, but none has gained widespread commercial acceptance. A recently developed modified natural zeolite pigment shows promise of filling the gap. It can be applied on machine via metered size press to achieve inkjet print results close to those of silica. The new zeolite pigment is much lower in cost than silica."
Balancing several demands in this area is critical, according to lyer of Imerys. "Producers are looking to make multi-functional papers that would work with traditional office copiers and also give the inkjet printers an improved surface to achieve quality graphics for the home and office. The key is to provide materials that can be easily applied to the paper at low coat weights to function in these very different applications."
McLain of Imerys said that the interaction of pigment and ink has been widely studied, and it is clear that surface functionality on pigments can enhance the printed image dramatically by minimizing the ink spread in ink jet printing.
She summed it up this way: "As the home office environment has grown, and as more consumers have demanded high print fidelity for digital images, pressure has been applied to the papermaker to produce higher quality paper. Engineered pigments are, and will continue to be, an integral component in that matrix."
According to Thiele's Malla, there has been no proportional increase in the use of pigments in coating due to the explosive growth of ink jet printers for the office and home. "Ink jet printing requires a special paper surface and coating for achieving high quality images due to the nature of the inks used and the design of the print head," he said. "Some of the important quality requirements for ink jet papers are vibrant color, image accuity, and quick ink absorption. Ink jet papers and coatings can be grouped in several ways: uncoated or surface treated versus coated, matte versus glossy, photographic versus non-photographic or pigmented (so called micro-porous) coating versus resin coating."
Currently, high surface area silica and alumina are the pigments of choice for ink jet coating in high quality ink jet papers, according to Malla. "Most of the conventional kaolin or carbonate based pigments do not have sufficient surface area or porosity for rapid ink (water based) absorption; therefore, they are not suitable for ink jet coating," he said. "However, a few kaolin and carbonate based pigments have been 'radically' modified and are slowly making inroads in the ink jet coating market. Most of the growth in ink jet paper has been in the high quality grades, and there is an obvious grade gap in the middle quality range."
Clay and carbonate pigments have not made a major contribution to the growth of ink jet printing in the office and home environments. However, this situation could change rapidly if paper manufacturers commercialize intermediate quality grades between a copier paper and a high quality photographic paper, Malla concluded.
Omya's Strutz noted that these applications have demanded higher surface products and controlled pore structures for proper ink setting and image development. "Modified surface structures and charges on the pigments for these applications will continue to be an area of development with these fast developing printing technologies," he said.
WHAT YOU WILL LEARN:
* Why the use of engineered pigments and fillers is growing.
* How the use of inkjet and laser printing his affecting the use of pigments and fillers.
* "Coated paper and board: Grades in transition," by Charles P. Klass, Solutions!, May 2004, pp. 36-40. Product Code: 04MAYS036.
EDITED BY ALAN ROOKS, EDITORIAL DIRECTOR
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|Title Annotation:||Pigments and Fillers|
|Publication:||Solutions - for People, Processes and Paper|
|Date:||Jul 1, 2004|
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