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QUESTIONS ABOUT LIQUID COLOR? Visit short.ptonline.com/liquid; short.ptonline.com/hayward pelletized material and in some cases ofer critical advantages to the packaging and consumer goods sectors. "The personal- care market is growing rapidly and there is increasing interest in medical applications. We see the next big wave coming in the extrusion blow molding market as liquid color ofers exceptional processing and economic benefts." Liquid color has been integrated into Clariant's ColorWorks North America design and technology center in West Chicago, Ill., so that the technology can be considered along with other options early in the product-development process. Clariant's propri- etary dosing/handling equipment uses gravimetric (loss-in-weight) dosing of the color or additives, and training at the customer's site is provided. In the case of Riverdale, all colors are blended from pre-milled "single-pigment dispersions" (SPDs)—a process that takes more time, but report- edly ensures excellent repeatability. Such colors are said to be stronger and brighter and to be an easier route for companies that wish to develop in-house color blends. Riverdale's Maguire also emphasizes the importance of the cleanliness of its fully sealed delivery systems. Every container— drum or pail—has its own permanent, built-in pump. Called Pump-In-A-Drum and used by Riverdale for more than 10 years, these containers remain sealed and have built-in shutofs to prevent leakage even if a container is laid on its side. All connections are quick-disconnect style for rapid changeover to a new container. Delivery tubes are also sealed with shutofs at both ends to eliminate dripping, and throat adapter plates are now sealed to eliminate the dripping common with other designs. PROVEN ADVANTAGES & TRENDS Liquid color can be applied to most thermoplastics, but it has been most commonly used for PET packaging. One of the key reasons is that with these highly concentrated formulations, less colorant is required to achieve the tint and translucent efects common in PET packaging, explains PolyOne's Fielding. PCC's Hass says the PET industry is very educated in processing with liquid colorants. In fact, he sees the industry driven in that direction by cost and processing advantages, especially when incor- porating liquid colorant in very thin-walled, tinted packages. Some processors say that liquids are easier to disperse uniformly than solid colorants when used at low levels for tints. Other key advantages demonstrated for liquid vs. solid colo- rants: Liquids do not require predrying of the colorant; they leave less residue on screws and barrels, allowing for quicker changeover; and there are lower shear forces in processing, which protects both the equipment and sensitive pigments. Also, for intricate mold designs, the overall melt fow can be better with liquid colorants. In extrusion blow molding, liquid color has been used for some time, particularly for large parts, says PCC's Hass. But in the last few years, liquid-color suppliers have made signifcant dents in delivering carriers that are more compatible with a variety of plastics, including polyolefns, styrenics, and engineering resins. In injection molding, liquid colorants are playing an increasing part across the board. This is particularly true in pack- aging and housewares such as storage and totes. "Many of the bigger players have moved in this direction, and this is trickling down to smaller molders," says PCC's Hass. In extrusion, liquid colorants ofer faster color changes, as the colorant is introduced right above the screw. "You turn of the pump, run virgin resin though the machine instead of a purging agent, and then introduce the new color," says Hass. Liquid-color suppliers concede that how much time is saved depends on the color and also on the machine, but in "apples-to-apples" compari- sons, liquid-color changes generally achieve quicker changeovers than their solid counterparts. Moreover, there is less screw wear and easier machine cleanup. WHAT PROCESSORS REPORT Hayward Industries, Clemmons, N.C. (haywardindustries.com), manufactures a broad range of pool products blow molded in mul- tiple sizes and colors with fnished part weights from 7 to 100 lb. In 2010, it switched from pellet concentrates to liquid color on three "The ability to change colors quickly can help reduce waste and save time." Liquid color has traditionally made a splash with OEMs of housewares and toys. (Photo: PolyOne) 40 DECEMBER 2014 Plastics Technology PTonline.com ADDITIVE S