The Dispersion Market.

Use of dispersions can provide added value, while saving time and money

When a person looks at the color of a printing ink, they are really looking at the pigment, the key ingredient that supplies the color. Pigments are also the most expensive component in an ink system.

It is necessary to break down pigment particles before they can be used to manufacture an ink. One such means is to create a dispersion, a suspended system, which then can be made into the final ink. The ink is prepared by adding a vehicle to the dispersion using low shear mixing.

What is a Dispersion?

One of the most common ways to introduce pigments into a final blend is through the use of a dispersion, which is complex colloidal system.

A dispersion is the suspension of a pigment in a vehicle, and usually is a color concentrate," said Lisa Hahn, president of Flexo Tech. "The ultimate goal is to make a fine suspension of pigment particles and maintain that suspension. If the dispersion is stable, the particles will remain separated."

"Dispersions, in their simplest form, are combinations of pigments, resins, and solvents (or water)," said Merril Garret, vice president of CDI Dispersions. "Of course, there are several additives that are generally used to obtain the properties desired of the final compound that is targeted for a specific application."

"A good dispersion is one that has been developed with broad compatibility for a wide variety of end applications," said Chris Allen, sales and marketing manager, Dispersions Division for Sun Chemical. "It has evolved from extensive research/development efforts aimed at maximizing the pigment strength, and color requirements, gloss and transparency. A good dispersion must also incorporate ease of use, and good storage stability as well."

"Dispersions are stable colloids of inert materials suspended in a continuous phase," said Chuck Rybny, vice president of research and development for Penn Color Inc. "Generally, there is some polymeric component. In paste inks, a dispersion can be based upon hydro-treated oils, for instance. In a UV system, it could be in acrylic functional polymers. For a water-based ink, for instance, one polymer might be an alkali-soluble styrene acrylic copolymer; for solvent-based systems, the polymer might be nitrocellulose or polyamide."

"A good dispersion is a product in which the pigment is reduced pretty close to its primary particle size," said Mr. Rybny. "It would demonstrate maximum color strength, gloss, transparency and stability, all of which are important for process printing."

"Generally speaking, the finer you grind a dispersion, the more color development, transparency and tint strength you'll achieve, to a point," said Kirk Deysher, technical sales representative for Reitech Corp., which manufactures water-based dispersions.

Providing Value

A good dispersion can do more than offer an easier way to introduce pigment to a final compound. With the right information, a better dispersion can be created. Among the advantages of buying a dispersion are saving manufacturing time, saving the cost of dispersing and grinding equipment, and saving the time in quality control required to achieve consistent quality, said Mr. Deysher.

"The more information you have from your customer, the better you can serve them," noted Mr. Deysher. "You must be able to recommend another dispersion. For example, a customer might be using a pigment yellow 14 dispersion with a touch of pigment red 22 for a silver foil application to achieve a gold color. A pigment yellow 83 dispersion would be a better selection because of shade and transparency."

Mr. Rybny spoke of the value that a dispersion can provide, and offered an example using a violet pigment. "If you were to consider a high performance violet such as carbazole violet, the value of such a pigment would be $35 to $40 per pound," Mr. Rybny said. "If we were able to obtain 15 percent more color strength by getting a better dispersion, we would be getting $6 more value per pound of dispersed pigment."

Mr. Garret said that companies generally buy dispersions that consist of anywhere from 25 to 70 percent of pigment, then cut them back to the final composition. For printing inks, the final pigment concentration may contain as little as 10 percent, or as much as 40 to 50 percent, depending upon the specific pigment involved.

Flocculation

If a dispersion is stable, it will keep the pigment particles separate. If it is unstable, there are many things that can go wrong, all of which bode poorly for an ink manufacturer.

"If a dispersion is unstable, the particles will flocculate," Ms. Hahn said. "If there is inadequate adsorption of the resin or surfactant, the particle is will be subject to flocculation. The reason for that is that the pigment particles have an attraction for one another, and the adsorption of the resin or surfactant acts as a barrier.

"The consequences of flocculation are that color strength will decrease; gloss will also decrease, as bigger particles are more disruptive to the ink film surface; transparency will decrease; and shear-thinning behavior will increase, which changes how well the ink transfers," Ms. Hahn added.

Changes and the Future

Like all other aspects of industry, many dispersions have changed over the years.

"There have been changes," Ms. Hahn said. "Most have been centered around the formulations themselves, such as the pigment-binder ratio, total pigment loading, and the types of surfactants that are added to the formulation. There's also been a reduction of VOC content for water-based formulations."

"The printing ink industry, unlike some others, is very dynamic, due to the types of substrates, processes and many other variations in printing ink requirements. As such, printing ink is a very interesting industry, " said Mr. Garret. "It is constantly evolving over the years and has been very good for CDI, because we are a specialty house. We make lots of small batches and create custom dispersions, specifically tailored to our customers' needs."

"The dispersion business is not just stock items off the shelf; there are more custom-made items and custom systems," said Tom Ashe, vice president of sales and marketing at CDR Pigments & Dispersions. "The systems have improved, and this is making a difference in the end applications."

Even though there have been changes, some older systems have remained the same. "We continue to sell a great deal of Flexiverse, which has been the primary product line for the Dispersion Division over the years," Mr. Allen said. "However, we continue to develop next generation products that fit with today's changing marketplace. These innovations will assure our success going forward, and are a critical part of our strategic planning as a company."

Business remains strong for dispersion, partially because they can be used outside of ink. "It's a very competitive market," Mr. Ashe said, adding that dispersions are used in other specialty markets, ranging in diversity from coatings and paper tissue to balloons.

"Our business is very steady throughout the year with normal seasonality for the printing industry coming in during the early third quarter, and running strong through early to mid November," Mr. Allen said. "Because we service other industries besides the ink market, we do see some peaks in these other industry cycles at various times during the year."

Pigment dispersions remain a critical component of many ink systems. As the needs of ink manufacturers evolve, dispersions will undoubtedly continue to keep pace.