Color concentrates: a new palette emerges.

Heavy metals and diarylides are "out." Special effects, micropellets, and superconcentrates are "in."

Colorant makers and users are learning to live without heavy-metal and diarylide workhorses of the past. Alternatives include new low-toxicity pigment chemistries and a trendy palette of "special-effects" colorants. Meanwhile, micropellets and superconcentrates are improving the economics of coloring plastics.

Replacing lead and cadmium pigments remains the biggest story - however the question is no longer "when?" but "what next?" Driven by customer demands and their own plant environmental and worker-safety costs, many concentrate suppliers have all but eliminated heavy metals from their repertoire.

Color formulators keep getting better at achieving bright red, orange, and yellow colors with non-heavy-metal pigments, and pigment suppliers are coming out with promising new alternatives. But colorant buyers may still have to accept some compromises.

Or they could try something completely different - fluorescents, pearlescents, marbles, granites, speckles, "edge-glow," and even "holographic" special effects seem to be all the rage.

While replacing economical work-horse pigments has tended to increase coloring costs, concentrate makers have responded with more highly loaded masterbatches and micropellets that offer savings for many users.

GOOD-BYE HEAVY METALS

The toughest challenge faced is still finding pigments on heavy metals - mainly cadmium and lead. Few available alternatives can match these old standbys for their combination of color strength, opacity, light and heat fastness, chemical resistance, dispersibility, and cost-effectiveness. Diehard defenders of heavy-metal pigments, like Robert Swain, president of Chroma Corp., steadfastly maintain that these inorganic complexes are biologically inert and thus present no hazard to consumers, workers, or the environment (see PT, May '95, p. 7).

However, most concentrate makers consider any defense of heavy metals to be moot. Many potential applications have effectively been ruled off-limits by the steady spread of CONEG-type state legislation limiting heavy metals in packaging. What's more, concentrate makers are not about to argue with customers that simply do not want any heavy metals in their products.

PLASTICS TECHNOLOGY'S poll of color-concentrate producers reveals that nearly half still offer color formulations that contain cadmium or lead. But the vast majority report that their usage of these pigments has declined sharply. They cite both customer resistance and their own reluctance to incur added costs for waste disposal. Scrutiny by environmental and occupational-health authorities is an added disincentive.

* Quantum Chemical Corp. eliminated both cadmium and lead pigments from its Spectratech color concentrates in 1991, switching primarily to organics.

* Ampacet Corp., according to R&D director Victor Mimeault, still makes some lead-containing colors for weatherable applications - but only at its offshore facilities. "We don't make them here - not because customers don't want them, but because EPA requires you to dispose of any lead-containing product in a registered toxic-waste landfill, which is very expensive."

* Jim Cafferty, product manager at Teknor Color Co., estimates that 80-90% of his customers have eliminated heavy-metal-pigment use in the last year or so.

* Says Wayne Prescott, director of sales and marketing at ReedSpectrum, "Since early 1993, we have stopped using cadmium." He estimates that about 75% of all U.S. color-concentrate users have dropped cadmium pigments. ReedSpectrum still has some customers using lead chromates, especially for weatherable applications. Prescott says leads have been harder to replace than cadmiums because there are fewer available substitutes.

* Jack Bateman, director of marketing and sales for Ferro Corp.'s Plastics Colorants and Dispersions Div., says at least 90% of his customers have made the transition to non-heavy-metal substitutes. His firm is trying to avoid use of any toxic heavy-metal pigments and has turned instead to nickel titanates.

* Dwight Morgan, exec. v.p. of marketing and technology at Allied Color Industries (part of M.A. Hanna), says Allied has gone heavy-metal-free, despite losing some business as a result. "We expect to see more stringent regulations and we feel that handling heavy-metal pigments is inappropriate for us." Two sister firms within M.A. Hanna - PMS Consolidated and Wilson Color - still use some heavy-metal pigments, but have seen a sharp decline in demand for them.

TACKLING TRADEOFFS

Concentrate makers and users have to accept tradeoffs when formulating "environmentally correct" colors in the red-yellow-orange range covered by lead and cadmium pigments. Processability is one compromise cited by Chris McCormick, technical manager at Ciba-Geigy Corp.'s Pigments Div.: "It has been easier to process inorganics than their organic alternatives. Loading capability and dispersibility have been the major issues."

Another tradeoff with organic pigments is their lower heat stability. That factor becomes more important in resins with the higher processing temperatures or when processors hike up the barrel temperatures in order to run faster. Few conventional organic pigments are stable at temperatures above 400-475 F. Some higher-performance organic pigments can be processed at up to about 600 F. But even when organics are heat-stable, they may be vulnerable to chemical instability in chemically aggressive resins like nylon. And the high-performance organics' cost typically exceeds that of medium-performance organics by an order of magnitude.

As a result, McCormick says organics are most successful as heavy-metal replacements in polyolefins and PVC. "PS and ABS are a bit more difficult, but not as difficult as engineering resins such as nylon 6 and 66 and specialty alloys."

For higher heat stability, the main nontoxic alternatives have been calcined complex inorganic color pigments (sometimes called mixed-metal oxides). "These inorganics are very heat-stable and have excellent lightfastness and uv stability, excellent chemical resistance, and good opacity," says Vahe Karayan, technical marketing manager at Engelhard Corp., one producer of mixed-metal oxides. "Because they are manufactured at 2000 F and are almost entirely inert, these pigments can be used in virtually any plastic. Also, they are typically less expensive than organics."

Their shortfall, however, is in color strength - they are not intense colors, but rather more earthy, muted browns and yellows. Pigment suppliers have now broadened the mixed-metal color range to include blues and greens. But there are still no bright reds in this group. Organics can offer the brightness of shade and color strength needed but typically come up short in opacity. Mixing organics and inorganics utilize the strengths of each. "Typically you can use a lot higher loading of inorganics and lower loadings of one or two organics to achieve desired color," says Karayan.

Pigment suppliers are developing new chemistries to give more alternatives to cadmium and lead (see box). Teknor's Cafferty reports, "We are starting to see new organic pigments - primarily oranges and yellows - that are more economical, more heat-stable, stronger, brighter, and light-stable."

But there may not always be effective substitutes for heavy metals. Reed-Spectrum's Prescott says bright red, orange, and yellow tones for outdoor applications such as rotomolded toys and swing sets are much more difficult to formulate without lead or cadmium. Even if higher cost were not an issue, long-term lightfastness is hard to achieve unless customers are willing to switch to pastels or blue/greens. Instead of trying to imitate the shades of cadmium and lead, Prescott says granite or speckle effects are becoming increasingly popular alternatives.

DIARYLIDES UNDER FIRE

Organic pigments are not immune to environmental or health concerns. Diarylide yellows have come under suspicion because they decompose at temperatures over 392 F, releasing potentially harmful amines.

"We have no assurances that our customers won't process above those temperatures," says Prescott of ReedSpectrum, explaining why his company eliminated diarylide use four years ago.

Diarylide yellows continue to be used in plastics that are processed at under 300 F. But Teknor's Cafferty would not be surprised to see them phased out in this area as well. "When something gets a bad name, it tends to stick."

Most concentrate houses polled by PLASTICS TECHNOLOGY are looking for substitutes. Candidates include combinations of inorganics such as iron oxides or nickel titanates with various standard or high-performance organics. Color formulators caution that the organics are generally weaker in tint strength and opacity and cost about 10-30% more than diarylide pigments.

PIGMENT LOADINGS UP

With resin prices sky high, concentrate buyers don't want to pay for any more carrier resin than necessary. Consequently, more and more suppliers are offering black concentrates with up to 50% pigment, while whites and colors are loaded as high as 70-80%. Letdown ratios have gone from 25:1 to 50:1 to as high as 100:1 to 200:1. Thermocolor Corp., for example, offers E-Z Color Superpellets containing as much as 90% pigment.

These highly loaded color concentrates lower coloring costs, says Ferro's Bateman, because customers use less concentrate. Prescott of ReedSpectrum notes that a concentrate containing twice as much pigment won't cost the user twice as much.

Bateman cautions that not all color shades can be loaded up to the maximum extent - it depends on the pigments used. High loadings with good dispersion are harder to achieve with organics than inorganics. Marc Potemans, masterbatch sales and marketing manager at Hoechst Celanese, agrees. "We have the technology to overcome limitations of organics when it comes to dispersion."

Teknor Color claims to have led the recent trend toward what Cafferty calls "superconcentrates" in bead form. "At first, the highly loaded concentrates were available only in flake. We moved away from flake to nice flowing beads because flakes are inconsistent shapes, so they are more difficult to meter accurately. Our beads are in a proprietary vehicle and are very uniform. Others are now coming out with bead forms, typically in a PE carrier."

Cliff Bloom, president of Peacock Colors, points out that an extruder or molding machine must do a better job of mixing than is required with standard masterbatches. "You may not be able to use superconcentrates, depending on your shot size in relation to your barrel capacity. For example a 16-oz shot in a 16-oz barrel will simply not give you enough residence time [to achieve proper mixing]," he says.

Josef Feldman, president of FM Group, which offers superconcentrates, says, "Most customers can't use them unless they are willing to make equipment changes. In many cases the barrel must be longer, giving you more time to mix." He adds that processors must have accurate feeders to proportion the smaller mounts of superconcentrates. Without proper equipment and know-how, he says, the result will be greater color variation than with a standard concentrate.

MICROPELLETS FIT A NICHE

Of the color-concentrate suppliers contacted, more than a dozen supply so-called "micropellets" measuring 0.02-to 0.05-in. diameter, as compared with standard 1/8-in. pellets. Yet suppliers concede that use of micropellets is quite small, and that they may be best suited to niche markets.

Micropellets reportedly disperse more quickly and easily and give greater color uniformity than conventional pellets. The downside is that the smaller die holes raise backpressures and reduce extrusion rates for concentrate producers (see p. 55). In response, suppliers have raised the pigment loadings. Suppliers caution users that micropellets may require a change of metering screws in additive feeders. They also note that the smaller particles raise the potential for stratification or segregation in hoppers.

Says Prescott of ReedSpectrum, which offers micropellets: "They are best for when you need quick dispersion. One example is for high-speed molding of PS microfloppy diskettes. Another is PVC bottles and possibly some film applications." On the other hand, he notes that micropellets cost about 10-15% more than typical pellets.

HIGHLY LOADED CONCENTRATES

A SAMPLE OF WHAT'S AVAILABLE(a)

                                  MAXIMUM PIGMENT LOADINGS
Supplier                         White     Black     Colors

Akrochem Corp.                   75%       60%       50%
Allied Color Industries          80%       50%       70%
Ampacet Corp.                    70-80%    50%        -
Color Formulators, Inc.           -         -        40%
Colortech, Inc.                  70%       52%        -
Hoechst Celanese                 70%       40%       40% (Organic)
                                                     60% (Inorganic)
Holland Colors Americas          70%       35%       60-75%
Korlin Concentrates              80%        -        75%
Liochem, Inc.                    70%       50%       50%
Peacock Colors                   80%        -        70+%
Penn Color, Inc.                 80%       40%       65%
PMS Consolidated                 80%       50%       65-70%
Progressive Polymers             75%        -        75%
Quantum Chemical Corp.           70-80%     -        65-70%
ReedSpectrum                     80%       50%        -
Spartech Compounding             80%        -         -
Standridge Color Corp.           80%       50%        -
Teknor Color Co.                 80%       50%       75%

a Information from suppliers interviewed and those who responded to
PLASTICS TECHNOLOGY's mailed survey.

Cafferty from Teknor Color (another micropellet producer) sees growth potential for these products in PVC dryblends for both flexible and rigid applications like profiles and calendered film.

The key advantage of micropellets, according to lab technician Kathy Lamb of Progressive Polymers, is higher letdown ratios of 100:1 to 200:1, which serve to reduce coloring costs. Progressive Polymers has made micropellet concentrates with pigment loadings of 75%. The company has seen steady growth of these products in injection molding of polyolefins and some styrenics.

Allied Color is finding its Unispheres micropellet color concentrates best suited to large injection molded parts where processors may have trouble dispersing regular concentrates. Another application, says Morgan, is for liquid-color users who want to go to a cost-competitive alternative that can still be metered by their liquid pumps. Allied offers white micropellets with up to 80% pigment and colors with up to 70% pigment.

Feldman of FM Group argues against very high pigment concentrations in micropellets. He says the added effort required to disperse highly loaded micropellets negates the inherent benefit of improved color uniformity imparted by the smaller particles. Feldman sees a prime market for micropellets among processors who have not yet made the transition from precolored resins to concentrates. For them, micropellets can offer the superior color uniformity they require - but may not do so if the pellets are too highly loaded. FM Group is finding greatest success with micropellet pigment loadings of 40-50%.

Peacock Colors offers micropellets with pigment loadings of 40-70%. Cliff Bloom sees PVC dryblends and HDPE rotomolding as the most promising applications.

Hoechst Celanese currently offers micropellets only in Europe, but Potemans hints they would be an excellent fit in certain North American markets. Hoechst is working on a new technology for micropellets, which is still in early stages of development.

Others that offer micropellets include Penn Color, Liochem, Standridge Color, HiTech Polymers, and Holland Colors. But leading polyolefin concentrate suppliers like Ampacet and Quantum do not offer micropellets nor do they plan to. Ampacet president David Weil questions whether they melt faster than conventional concentrates. "In polyethylene, for example, I think the difference would be minute when compared to an average color concentrate."

Although Ferro is evaluating micropellets, Bateman says, "We think a good highly loaded concentrate may be better than micropellets. The micropellets on the market use carriers that are acceptable in several resin families. But if you go over a 2% use level, you may end up with screw slippage."

SPECIAL EFFECTS ARE 'IN'

In the past decade, what may be termed "special-effects" colorants have found favor in applications such as novelties, toys, and eye-catching packaging for cosmetics and other household products. PLASTICS TECHNOLOGY'S informal poll indicates that most concentrate suppliers offer a variety of these colorants, including granite or speckle types, sparkle or glitter pigments, pearlescents, fluorescents, marbles, and "neon" or "edge-glow" types.

Pearlescents are back in fashion for polyolefin caps and closures for personal-care products like shampoos, according to Teknor Color's Cafferty. The company's new TekPearlite series consists of four FDA-sanctioned colors and four less-costly versions for non-FDA applications. Another recently introduced series is ReedSpectrum's ReedLite line of 13 pearlescents for polyolefins.

Much in vogue over the last two years are granite and speckled colorants. Unlike marble effects, these do not require special equipment, says Teknor's Cafferty, adding that the granite effect hides surface scratches or marring. Uses include patio furniture, rotomolded playground equipment, cosmetics packaging, and office products.

Several new lines of granite and "stone-effect" concentrates were introduced last year at NPE in Chicago. These include entries from FM Group, Ferro, ReedSpectrum, and Safas Corp. More recently, Ferro supplemented its gray granite colorants with pastel, chromate, and dark colors. Colorco has added a new line of granite-effect concentrates in a range of pastel shades. And a new supplier, United Granules, offers Ultragran TP concentrates in formulations for most thermoplastics.

A year ago, Calsak Corp. introduced Play Color concentrates from O.K. Kasei Co. Ltd. of Japan. These products are said to produce marble effects without any changes in equipment Or processing conditions.

In the area of speckle effects, Teknor has a new "Holographic" series of glitter concentrates for flexible PVC applications such as bike seats, ornaments, and footwear.

Texturizing colorants are an emerging special-effect market, according to Feldman of FM Group. The company's Sprincol products visually simulate surface textures normally associated with textiles. "Instead of embossing the plastic, which attracts dirt, we can give a visual texture yet still have a smooth surface," Feldman says. Applications can include wall panels, appliances, housewares, computer keyboards, and air-conditioner bezels.

Another relatively new fashion is so-called edge-glow fluorescent effects for transparent resins. ReedSpectrum launched some of these in its Reedlite special-effects series last year. Also new is Teknor's Tekneonlite series of four transparent orange, red, yellow, and blue shades designed for 50:1 or 100:1 letdowns, depending on the part thickness. PMS Consolidated recently brought out Edgeglo concentrates, along with PPROtint high-chroma transparent colorants for clarified PP.

Hoechst Celanese is coming out this month with its first standard line of special-effects concentrates, including pearlescents, marbles, granites, metallics, fluorescents, and glow-in-the-dark colorants.

Allied Colors is finding some success with photochromic (uv-activated) and thermochromic (heat-activated) color concentrates in toys and functional applications (i.e., detectors). These products are based on novel dyes from 2nd Story Concepts that change color when exposed to sunlight, heat, or water (see PT, Dec. '94, p. 10). These high-tech colorants cost up to 25-30 times as much as standard colorants.

Other suppliers that offer a range of special-effects concentrates include Korlin Concentrates, Peacock, Progressive Polymers, Penn Color, Liochem, Standridge Color, HiTech Polymers, Holland Colors, ViChem, Colorit, A. Schulman, J. Meyer & Sons, Riverdale Color, Action Color, and Dunlop Plastics.

FOR MORE DETAILS ON ITEMS IN THIS ARTICLE, USE READERS' SERVICE CARD

Action Color, Inc., Huntley, Ill.

Akrochem Corp., Akron, Ohio

Allied Color Industries, Inc., Broadview Heights, Ohio

Ampacet Corp., Tarrytown, N.Y.

Calsak Corp., Schaumburg, Ill.

Ciba-Geigy Corp., Pigments Div., Newport, Del.

Chroma Corp., McHenry, Ill.

Colorco, Inc., Linden, N.J.

Color Formulators, Inc., Fairfield, N.J.

Colorit, Inc., Parsippany, N.J.

Colortech, Inc., Brampton, Ont.

Dunlop Plastics, Ltd., Ajax, Ont.

Engelhard Corp., Iselin, N.J.

Ferro Corp., Color Div., Cleveland

Ferro Corp., Plastics Colorants & Dispersions Div., Stryker, Ohio

FM Group, Inc., Sloatsburg, N.Y.

HiTech Polymers, Cincinnati

Hoechst Celanese Corp., Masterbatch Business Unit, Coventry, R.I.

Holland Colors Americas, Richmond, Ind.

Korlin Concentrates, Stratford, Ont.

Liochem, Inc., Conyers, Ga.

J. Meyer & Sons, Inc., West Point, Pa.

Peacock Colors, Inc., Addison, Ill.

Penn Color, Inc., Doylestown, Pa.

PMS Consolidated, Inc., Suwannee, Ga.

Progressive Polymers, Jacksonville, Texas

Quantum Chemical Corp., Cincinnati

ReedSpectrum, Holden, Mass.

Rhone-Poulenc Inc., Monmouth Junction, N.J.

Riverdale Color Mfg., Brooklyn, N.Y.

2nd Story Concepts, Canton, Ohio

Safas Corp., Clifton, N.J.

A. Schulman, Inc., Akron, Ohio

Spartech Compounding, Color Concentrates Div., Goddard, Kans.

Standridge Color Corp., Social Circle, Ga.

Teknor Color Co., Pawtucket, R.I.

Thermocolor Corp., Sandusky, Ohio

United Granules, Mt. Bethel, Pa.

ViChem Color, Inc., Grand Rapids, Mich.

Wilson Color Inc., Neshanic Station, N.J.

RELATED ARTICLE: Two New Pigment Chemistries

Ciba-Geigy recently launched the first of a family of organic pigments based on a new color chemistry called diketo-pyrrolo-pyrrol (DPP). Chromophtal DPP Red BP products, which range from a very yellow-shade red to a mid-shade red, are claimed to be the brightest, cleanest, and most opaque organic pigments on the markets. "They have become a major portion of the red market in toys and automotive applications," says Ciba Pigments technical manager Chris McCormick.

DPP pigments are heat-stable to 525-550 F, so they can be used in polyolefins, PVC, PS, and ABS. They can be mixed with other pigments because they are inherently nonreactive. They sell for around $45/lb, whereas other high-performance organics cost about $60/lb.

Ciba is now launching Chromophtal Orange TRP transparent pigments based on DPP chemistry. Ciba is building a facility to make the new family of pigments; it will come on-stream at Newport, Del., in early 1997.

Last year, Ferro Corp. and Rhone-Poulenc Chimie of France announced they would cooperate in technical and market evaluation of new rare-earth sulfide pigments as a replacement for cadmium types in engineering thermoplastics (PT, Aug. '94, p. 13). Rare-earth sulfides are inorganic pigments said to be generally low in toxicity. Joe Golowski, market manager for these products at Rhone-Poulenc's U.S. office, says the company will have a pilot plant up and running this month in France, producing about 33,000 lb/yr for global sampling.

First to be introduced next year will be two cerium sulfide pigments, a mid-shade red and a fairly bright orange that can compete with lead molybdate. "Physical properties and color values compare favorably with those of cadmium pigments," says Harry Sarvis, marketing manager at Ferro's Color Div. 'They show very good lightfastness in interior applications and uv stability in exterior applications that surpasses that of cadmium." Their opacity is equal to cadmium pigments and they disperse well and do not promote warping, adds Sarvis.

Most important, these pigments are heat-stable up to at least 600 F, matching cadmium in heat stability, says Sarvis. Adds Golowski, "We have created a new color space that is better in terms of brightness than iron oxide, yet not quite as pure in color as a cadmium." Prices will be in the range of $15-30/lb. Rhone-Poulenc is developing a darker red and a yellow may follow.