Stringent demands of automotive industry drive 21st-century advances in carbon black pigments.



A legendary figure in the automotive world once told an automobile hungry American public that it could have any color car made by his company "as long as it's black."

Nearly a century later, automakers are offering an expansive array of color choices, but continue to find that many customers remain intrigued by the sleek, sexy aura that black can project.

This isn't your great-grandfather's Model T or Henry Ford's idea of black, though. This is very likely a "high color" black, one of many different versions of black as measured by "jetness" - a gauge of just how dark the black is - and undertone tint, with a bluer tint providing a more appealing black color.

Makers of carbon black, the dominant pigment used in the manufacture of black and many other deep coatings shades, can attest to the stringent demands of automakers when it comes to formulating finishes that offer far more than just black-as-night darkness. This isn't any color as long as it's black - it's any version of black the automotive industry fancies.

Just ask Vipul Joshi, Global Marketing manager, Coatings, for Cabot Corp., the world's biggest supplier of carbon black. Carbon black is used in many types of coatings, but it is the automotive sector that puts pigment suppliers to the test when it comes to developing new technologies and grades designed to meet appearance, performance and environmental demands, Joshi says. On the average, an estimated 10% of automobiles are black in color, with the percentage going even higher in luxury cars.

In the case of carbon black, Joshi says a key focus of R&D activity is the development of high-color pigment grades for waterborne basecoats, where optimum dispersion and color development are crucial to allowing coatings formulators to match the richness of colors produced in solventborne finishes.

Joshi says German automakers have taken the lead in pushing environmentally friendly automotive coatings technologies. The Japanese coatings manufacturers are also moving towards waterbornes to meet requests from the automakers. "In the next five years they want to convert basecoats to waterborne technology," he says. This trend towards waterbornes will find its way to the other major automotive markets, in Europe and the Americas.

Such technologies are particularly important in the market for "premium" black finishes for the luxury car segment - such as BMW, Volvo, Porsche, Audi and others. The coating systems utilized include high performance acrylic and polyester resins. In this market, the coatings supplier doesn't enjoy the option of delivering just performance or an environmentally friendly product profile - the market is demanding both.

"Automakers are not willing to sacrifice appearance as coating systems shift to environmentally friendly technology," Joshi says.

In response to the demand for carbon black pigments designed for high-end black automotive finishes, Cabot in 2001 introduced Emperor 2000, a grade in which the pigment surface is chemically treated to allow greater compatibility in waterborne coatings. The result is a high level of "jetness," the coveted blue undertone tint with improved weatherability and stability, the company says. The proprietary treatment is designed to produce a specific uniform chemistry on the pigment surface, which provides greater compatibility with dispersing agents and resins used in waterborne coatings, Cabot says.

The patented technology modifies the carbon black surface chemistry and provides stabilizing groups that are attached to the surface for compatibility and stability, Cabot says. The appropriate chemical treatment technology not only allows for higher color development, but also improves dispersion quality and weatherability of the coating. The treatment also is said to result in a pigment with neutral pH, reducing pigment flocculation.

The Emperor 2000 technology allows the automotive coatings manufacturer to formulate waterborne basecoats with the high color and outstanding appearance and performance properties found in solventborne systems, the company says.

In addition to Emperor 2000, Cabot also offers high-color black Monarch pigments for conventional high-solids automotive coatings applications. Cabot's R&D efforts in high-color blacks will continue to push the envelope of carbon black pigments for high-performance applications, Joshi says.

Carbon Black Properties: More Than Just Dark Color

In terms of performance, key considerations for carbon black include particle morphology (particle size, aggregate size and aggregate shape distribution) and chemical composition (surface chemistry).

Joshi says Cabot's proprietary surface treatment used in producing new pigment grades designed for waterborne coatings addresses common formulating challenges, particularly in terms of color development, dispersion and stability. Surface treatment also provides other benefits, including lower viscosity, better wetting of the pigment and reduced dispersion time.

Pigment particle size is a factor in a number of formulating issues, with smaller sizes offering benefits such as darker masstone jetness and tint strength. The smaller particle size, however, will be more difficult to disperse. Large particle size generates a bluer undertone tint and is easier to disperse.

Pigment "structure," or the geometry and complexity of aggregate shape, also affects coating performance. A high level of structure tends to produce a bluer undertone tint, and the pigment is easier to disperse.

The morphology of carbon black must be taken into account in order to optimize the desired performance properties, Joshi says. In addition, the pigment form - pellet or fluffy - is an important consideration. Advantages of the pellet version include better handling and ease of incorporation, but pellets are more difficult to disperse. The fluffy form requires more housekeeping and is slow to incorporate, even though the pigment is easier to disperse. Joshi says the carbon black user must weigh these factors in determining which pigment form to employ. Grind and dispersion capabilities are important if the user prefers the pellet version.

Due to the processing and equipment challenges presented by the pigment, dispersion suppliers also represent a key link in the supply chain for carbon black pigments used in coatings. Major suppliers of dispersions include Penn Color, Clariant, Bayer, and Plasticolors.

Technology Advances Hold Key to Market Growth

In recent years, carbon black suppliers have expanded capacities in response to increased tire and rubber demand. Growth in demand is expected to return following volume erosion in 2001 due to slowdowns in industrialized economies.

"During the fourth quarter of last year and first quarter of 2002, there was a decline in carbon black demand, and we attribute that to a slowdown in the economy and inventory reductions in the supply chain," Joshi says. "We saw an upturn this past summer, with things starting to come back to normal levels."

Demand for carbon black, as is the case with the coatings industry and its other key raw materials markets, is greatly affected by economic growth trends in general and the automotive and housing sectors in particular. Both sectors have remained relatively robust, with sales of new and existing homes hitting record levels during several months of this year, and with strong automotive sales continuing in the United States.

Advances in specialty black applications such as coatings, inks and plastics are seen as crucial for growth of carbon black sales and profitability. Tire applications account for the overwhelming majority of carbon black volume - around 70% - but specialty black applications offer greater profit potential as a result of product performance, industry sources say. Thus, specialty black applications will continue to be a focus of R&D activity.

The carbon black industry also is feeling the effects of technical developments in the tire segment, where new carbon black grades and incorporation of precipitated silica and silanes are designed to improve wet traction and reduce rolling resistance for increased safety. A so-called "green tire" is said to provide increased fuel economy due to lower friction on the road surface.

Worldwide, Cabot commands the leadership position in terms of carbon black market share, with approximately 30% of the total. Other key suppliers are Columbian Chemicals and Degussa/ECI, with estimated positions of 10% and 20%, respectively.

Depending on growth trends in key industrialized economies, carbon black consumption is projected to expand by a modest 3% per year in the near term. Thus, producers such as Cabot are focusing considerable R&D attention on high-value, high-growth specialty blacks and manufacturing efficiencies to maintain growth and boost margins.

Clearly, suppliers such as Cabot - unlike Mr. Ford - know they must do more than offer just any pigment "as long as it's black."