New dispersants are being developed to overcome the recent cost and supply challenges with conventional polyacrylate formulations.



Polyacrylate (PAA) dispersants have been widely used by clay suppliers and ceramic manufacturers to deflocculate clay suspensions and disperse pigments in glazes. These chemicals neutralize surface charges on colloidal particles and disperse the formulation so that a high-solids, low-viscosity slurry or glaze is achieved. Over time, PAAs have replaced more conventional chemistries like silicates and phosphates as deflocculating agents, as many ceramic manufacturers found that PAAs were easier to use and provided better stability.

However, several challenges have recently begun to threaten the availability of these valuable materials. The cost of acrylic acid, the key raw material in the manufacture of polyacrylates, has continued to increase and remains well above historic average price levels. Manufacturers of PAA dispersants also consume raw materials derived from petroleum, natural gas and other commodities that are increasing dramatically in cost, along with the costs of labor, energy and regulatory compliance. Additionally, operational issues have produced "feedstock shortages" for the acrylic monomer producers, which, in turn, have resulted in limited availability of these monomers to PAA manufacturers. And high global demand, driven primarily by China, as well as a lack of investment in additional new capacity, have contributed to the acrylic monomer supply problems. As a result, some ceramic manufacturers are now finding conventional PAA dispersants to be cost-prohibitive, and others are unable to buy PAA dispersants regardless of price.

Fortunately, PAA suppliers are stepping up to the plate and are developing alternatives. Two of the most recent innovations-a non-acrylic acid-based PAA and new blends to replace PAA-are showing particular promise for ceramic applications.

Cost and Performance Benefits

The non-acrylic acid-based PAA, COLLOID 148, was specifically developed to replace a standard PAA dispersant, COLLOID 211. The new dispersant is the same molecular weight and concentration as the previous material, and many ceramic manufacturers who have used the new material have found it to be a direct, equal-dose replacement. Because it does not contain acrylic acid, the new dispersant is readily available at a cost similar to previous acrylic acid-based dispersants.

Figure 1 compares the deflocculation curve in a high-solids, clay-based ceramic tile body using the standard PAA and the new non-acrylic acid based PAA. As can be seen from the data, both additives produce virtually equivalent viscosity at equal dose levels.

For manufacturers that require some PAA for stability, new chemical blends can be used to reduce the amount of PAA required to achieve the same effect. Suppliers have found that using combinations of PAA and other conventional dispersing agents in synergistic ratios can replace PAA at a cost that is equal to or lower than the original treatment. Like COLLOID 148, these proprietary new blends are successfully being used in tile and other clay slurry applications.

Figure 2 illustrates the performance of two of these blends compared to COLLOID 211. As can be seen in the figure, although an increased dosage of the blends is required, a similar deflocculation effect is achieved.

Continued Developments

Global production of ceramic products is on the rise, particularly in Asia, and the challenges of high labor, energy and regulatory costs are not likely to disappear any time soon. As a result, PAA dispersants that were once low-cost and readily available are now becoming increasingly expensive and difficult to obtain. Ceramic manufacturers are being forced to choose between buying less of these chemicals than desired at a higher price, or seeking replacements.

Fortunately, some alternatives are now available that offer comparable or even improved performance at a cost equal to or lower than conventional PAAs, and additional developments are under way. By working closely with chemical suppliers, ceramic manufacturers can avoid the PAA supply and pricing issues and find new solutions that give them a competitive edge.

Editor's note: All of the new dispersants and blends described in this article are supplied by Kemira Chemicals, Inc.

For more information about the new dispersants, contact Kemira Chemicals, Inc. at 245 Town Park Dr., Ste. 200, Kennesaw, GA 30144; (800) 347-1542; fax (770) 436-3432; e-mail front-desk@kemira.com ; or visit http://www.kemira.com .