Going Organic

New organic coatings are enabling the glass container industry to meet regulatory demands, as well as the need for high quality, vibrant colors.

For more than a decade, inorganic coatings and fritted systems have become an increasingly less attractive option for the glass industry. These systems, which require lead and cadmium and firing cycles of 560 to 620∞C (1040 to 1150∞F) to promote adhesion, were once the standard for decorating glass. They provided good color and quick adhesion at a low cost. For a range of reasons, however, including the low quality of many imported products that contain these heavy metals, lead and cadmium have been under increasing regulatory pressures since the 1970s.

This year, the Environmental Protection Agency began enforcing another demanding rule involving the use of lead. Beginning in 2002, lead users must produce an annual Toxic Release Inventory report on how much lead was used at their plants in the previous year. While this new rule doesn’t ban lead outright, it adds to the considerable regulatory burden surrounding the use of lead.

These regulations have made it imperative for the glass decorating industry to find alternative products. However, without the use of lead and cadmium, bright red, yellow and green colors are difficult to achieve. This problem is especially challenging in the cosmetics field, where young consumers, who are attracted to very bright colors, drive much of the demand. The earth tones and subtle hues easily achieved with lead- and cadmium-free products might work inside the bottle, but bright colors on the outside of the container are what sell the product. Clearly, new products are needed that can achieve bright colors while meeting the necessary environmental regulations.

During the last five years, organic coatings have been dramatically modified to meet the demand for lead- and cadmium-free coatings and colors for the cosmetic and container glass decorating industry. As a result of intensive research and testing, today’s organic products can be used to replace fritted systems without compromising color or quality.

The Development of Organic Coatings

Unlike inorganic systems, which contain glass frits and mixed metal oxides and must be fired at high temperatures, organic coatings are either epoxy- or polymer-based with a pigment, and can be dried or cured at low or even ambient temperatures. While organic coatings have always been able to achieve bright colors, early systems did not exhibit good adhesion or chemical resistance. Recently, however, these challenges have been overcome. Today’s organic coatings generally perform well even in harsh environments, such as filling and cleaning lines.

Several types of organic coating systems are currently on the market, ranging from air drying and infrared (IR) drying systems to ultraviolet (UV) and water-based systems. Water-based and air drying systems tend to be thinner and are therefore more favorable for spray applications, while IR and UV drying systems work best for direct printing on glass.

In general, organic coatings can be used with the same processes and equipment currently employed in today’s decorating plants. However, the use of heat drying organic printing inks can be a problem on multi-color, high-speed printing lines. With conventional fritted colors, thermoplastic (TP) color systems can be used in these applications. Researchers are investigating the development of organic TPs for high-speed printing, but it might be several years before such systems will be reliable enough to bring to the market. In the meantime, modern technologies such as UV systems are filling the gap in the organic product line to enable the printing of multiple colors at fast rates.

The Benefits of Organic Coatings

Currently, not all of the glass markets can switch over to the organic coatings. Table glassware, drinking glasses and plates, for example, require high durability to meet the harsh requirements of dishwashers, which are highly alkali environments and are not friendly to organic coatings. However, research currently under way on sodium silicates might lead to new coating technology that addresses this issue.

In the meantime, the cosmetic industry has begun taking advantage of the benefits and flexibility of organic coatings for decorating glassware. Besides their regulatory advantages, organic coatings also provide enhanced manufacturing efficiency and visual appeal. Spraying cosmetic bottles with an organic color is a far more efficient way to produce colors and effects than using oxides during the glass manufacturing process itself. Organic coatings also offer a greater selection of final colors compared to conventional lead- and cadmium-containing products, and the batch size can be changed easily because the organic systems are easier to remove through cleaning. Additionally, making changeovers in bottle sizes and product colors is less problematic compared to conventional lead- and cadmium-containing products. And since organic coatings are processed at lower temperatures than conventional systems, they provide energy savings and expand the substrate portfolio available to decorators and designers.

As environmental regulations become increasingly stringent, new products such as organic coatings will become an important option for glass decorators seeking to ensure their environmental compliance, increase their manufacturing efficiencies and meet consumer demand for high quality, vibrant decorations.

For More Information

For more information about organic coatings, contact Engelhard Corp., 101 Wood Ave., Iselin, NJ 08830; (973) 269-7800; fax (973) 268-7914; e-mail jim.nugent@engelhard.com; or visit http://www.engelhard.com.