Getting rid of cadmium. What's holding it up?

It's an issue that refuses to go away. For more than a decade, debate has raged over the use of pigments and PVC heat stabilizers based on cadmium, a heavy metal suspected of causing cancer and liver disease. Today, the argument over cadmium's use has reached a point where the metal's future in plastics looks bleak. With a growing number of states enacting legislation that would greatly reduce the allowable amounts of cadmium in packaging-and pigment, colorant and stabilizer suppliers developing more cadmium-free products-there may soon be little reason for processors to continue using cadmium-based additives. However, both suppliers and users say the increased cost and processing problems plaguing non-cadmium alternatives are still obstacles to replacing cadmium in cases where it is not prohibited.

"I'm absolutely sure the day will come when no one is using cadmium any longer," predicts Lawrence R. Brecker, v.p. of research and development for the Argus Div. of Witco Corp., N.Y.C. "But while I believe these changes are imminent, some people feel they're not breaking any laws, they're not polluting the air or water, so why should they want to change?" These people, industry insiders say, are simply not going to switch until the government bans cadmium.

While a total ban will probably never occur, limited prohibition of the heavy metal seems inevitable. Already eight states have enacted legislation curtailing the use of cadmium and three other heavy metals in packaging; and at least a dozen more are poised to follow suit. That's enough of a reason, many say, to get cadmium out Of the production process. "I don't think it will be legislated out entirely," says Ray Millard, v.p. of corporate development for Avecor Inc., Vonore, Tenn., an independent operating company of M.A Hanna Inc., Cleveland. "I think it will be gradually phased out by more and more users and may finally die from atrophy."

THE PROBLEM

The major argument against cadmium in plastics centers around burning waste containing additives made with the heavy metal. Opponents claim incinerator ash buried in landfills contains toxic cadmium oxide deposits left behind when the plastic compounds are burned. These deposits, they say, could leach into water tables supplying drinking water to surrounding areas.

To counter this, backers of cadmium pigments have compiled data showing that although exposure to high heat alters an insoluble cadmium pigment's chemical structure, it doesn't change it so drastically as to allow the cadmium contained in the compound to become soluble and therefore biologically available.

The organic cadmium salts used as vinyl stabilizers, however, are another matter. These are more soluble, and the question of potential toxicity cannot be dismissed as easily. It's probably for this reason more than any other that stabilizer manufacturers are scrambling to develop cadmium-free alternatives.

PVC HEAT STABILIZERS

Alternatives to cadmium-based stabilizers are not new. Barium/zinc, calcium/zinc and tin-based stabilizers have been around for years, and suppliers admit that very few technological secrets remain among them. Limited in their applications and usually less cost-efficient than their cadmium-containing counterparts, cadmium-free stabilizers have mostly been restricted to use in certain flexible applications such as food packaging films where the processing conditions and cost differences are not as severe as in rigid film and sheet. Nevertheless, recent advances in stabilizer technology are lessening processors'reliance on cadmium products by broadening the range of applications the alternatives can cover. "I think there are a few novel things that have come out in the past two years that have really helped," says Kenneth Bergman, marketing director for Synthetic Products, Cleveland.

"We have been very successful in economically replacing cadmium in the low- and medium-durometer applications," says Mitch Silkotch, market development manager for thermoplastic additives Akzo Chemicals Inc., Dobbs Ferry N.Y. "However, when you move toward the high-durometer compounds it becomes more difficult to provide cost-effective alternatives."

The problem, stabilizer producers say, comes from the high shear and extreme heat involved in calendering the more rigid sheet. Many of the alternatives to cadmium-based products simply cannot stand up to the high speed and shear that results from injection molding rigid PVC unless a larger amount of stabilizer is used in the production of the vinyl compounds-up to 50% more. A number of attempts have been made to solve this problem by improving noncadmium stabilizers to a point where less product has to be used. Akzo, for example, is developing multi-metal systems that Silkotch says perform well in high-shear situations, but "they contain additional metals and unfortunately are much higher in cost." Akzo and others are making the high-end alternatives more processable by adding small traces of metallic stearates to help the stabilizers handle the high heat and shear.

Still, suppliers and compounders agree that if cost is not a concern, there is no application for which a cadmium alternative cannot be used. Mere's really no reason to continue using cadmium stabilizers," says Jay Kotak, technical director of Synergistics Industries, Inc. (formerly Cary Chemicals Inc.), Farmingdale, NJ. "I have compared dozens of cadmium compounds and alternatives and have found the non-cadmium stabilizers work just as well as the cadmium stabilizers." Kotak admits the alternatives offered by suppliers frequently cost more than stabilizers made with cadmium, but he says he's beaten the cost factor by mixing many of his own noncadmium stabilizers from scratch.

Synergistics'case is probably unique since not a lot of compounders have the expertise or time to make their own stabilizers. Most suppliers now offer full lines of "drop-in" liquid and powder non-cadmium substitutes with the same compatibility, odor, clarity and aging resistance characteristics as cadmium versions. Most say their alternatives can be used in the exact same ratios as cadmium-containing products for most applications. If, for example, a processor were using 3 phr of a liquid barium/cadmium stabilizer to process semi-rigid vinyl, 3 phr of liquid barium/zinc stabilizer could be substituted without making other changes to the formula. In most cases then, the increased expense of producing a cadmium-free compound is proportionate to the increased cost of the alternative stabilizer. Some alternatives cost only a few cents more per pound. Others, like the barium/zinc phosphites used for compounding material with high pigment and low filler levels, can run as little as 5% to as much as 25%-30% more per pound.

Cadmium stabilizer substitutes tend to be very formula-specific and less suitable for use in a wide variety of applications unless other components are added to the formula. For example, if many of the alternative stabilizers are used in an unfilled system containing 12-15 phr of [TiO.sub.2] pigment, it becomes more difficult to maintain the bright white color in these systems, says Akzo's Silkotch. In an effort to preserve the brightness provided by the [TiO.sub.2], some stabilizer suppliers have recommended incorporating small amounts of calcium-containing stabilizers and other calcium-containing ingredients into the PVC formulation.

We think we can pretty much duplicate the performance of cadmium in just about any application," says Edward Freshman, director of sales and marketing for the Bedford Chemical Div. of Ferro Corp., Cleveland. However, he concedes that cost is still a key factor behind processors' reluctance to switch. Most suppliers say they think it is the dominant reason. "Let's face it," argues Witco's Brecker, "someone's not going to pay more if they don't have to."

MARKET WILL LEAD THE WAY

Suppliers suggest the end to cadmium use is more likely to be market driven. As processors (and some additives manufacturers as well) see their competition publicly announcing their intentions to get away from cadmium, they may feel pressured to follow the lead or risk falling into disfavor for not becoming environmentally responsible.

The first step in that direction may have been taken last year when Vista Chemical Co., Houston, announced its intention to make all of its flexible PVC compounds cadmium-free by the end of this year. Vista has tested dozens of commercially available non-cadmium stabilizers, says Rick Flammer, v.p. of the new Performance Polymers unit and is incorporating them into its compounds. "They perform equally well," Flammer says. "Reformulation is not simple. You have to do a lot of work to match the right material with a particular application, but it can be done." The resulting compounds, Flammer says, have the same performance and processing properties as PVC containing cadmium stabilizers and are reportedly not sold at premium prices because of a manufacturing process that enables Vista to produce the new material for just about the same cost as cadmium-stabilized compounds.

Now BF Goodrich Co., Cleveland, is following suit, trying to develop compounds manufactured without cadmium stabilizers. A few hitches still exist, a company spokesman says, such as developing alternative semi-rigid compounds with extreme weatherability.

Like alternatives to cadmium stabilizers, there are heavy-metal-free options to almost all colorants. And just like stabilizers, the better a processor wants those alternatives to perform, the more he will have to pay for them. Just about any color can be replicated if cost is not a factor, most pigment and colorant suppliers say. Yet, there are still some suppliers and users who argue that while cadmium-free alternatives can come close, there's just no substitute for cadmium colorants in certain applications and in certain resin systems. And besides, they ask, why mess with a proven technology that has been so beneficial for such a long time just because some environmentalists have suggested cadmium-containing plastics might pose a health risk? Environmental affects of the replacements being tried have not been studied in detail, cadmium's defenders say, leading some to wonder if replacing cadmium with organic compounds will be the equivalent of substituting one undesirable for another.

"There's no denying the fact that we're eliminating one problem and possibly creating another," says Kenneth Auer, business manager of colors and compounding for the USI div. of Quantum Chemical Corp., Cincinnati, which successfully has removed cadmium pigments from its concentrates. Industry insiders readily admit that the reactive properties of organics could lead to some problems not encountered with the inorganic cadmium pigments. For instance, they say, organics can react with other components of a formulation, leading to premature degradation.

Those who are not convinced of cadmium's alleged evils argue that the possibility of cadmium-containing plastic leaching contaminants into groundwater may also apply to organics. Me organic pigments have varying degrees of solubility and extractability," warns Robert Swain, president and CEO of Chroma Corp., McHenry, Ill. "They can migrate from plastic. You put enough plastic that's been colored with an organic in a landfill and you run the risk of discoloring the water table. They may tell you the plastic was colored with an FDA-approved additive, but who wants to drink yellow water?"

Possible substitutes for cadmium in pigments include not only organic compounds but inorganics such as iron oxide and nickel-antimony titanates. These pigments are generally less expensive than cadmiums and can actually drive down the cost of a formulation, suppliers say. The latter group provides heat stability comparable to that of cadmium. But the knock against both of these substitutes is their inability to provide the same color shades that can be achieved with cadmium. Use of iron oxide results in a muted reddish-brown color, while the nickel-antimony titanates give poorer color dispersion, compounders say.

"You can match the colors but to match them for performance is the key," says Allen Carlson, technical director for PDI/ICI Polymer Additives, Edison, NJ. Many of these formulations are even more polymer-specific than for cadmium-containing colorants and require different formulations for each type of resin or for each application. For example, inorganic/dye combinations provide opacity an bright colors in resin systems such as nylon, polycarbonate, ABS, polystyrene and acrylics but do not supply adequate light stability.

There has been some difficulty in developing dyes for polyolefins because the range of the polymers' chemical resistance limits their solubility for the basic dyestuff, resulting in migration problems. A combination of organic and inorganic pigments may fill this void, some say, providing colors that are both bright and opaque. Some suppliers have also said they have bad difficulty developing colorants for thermoplastics because of the wide array of processing temperatures and significant solubility effects between dyes, organic pigments and resins.

Most of the yellow, red organic pigments used as alternatives to the cadmiums have heat stabilities between 482 F and 572 F. A few-mostly the yellows and some of the reds-can achieve a level of lightfastness almost as good as cadmium, coming in at between 6 and 8 on the international blue wool scale. Others, though, are limited in the amount of lightfastness they can provide and are restricted to uses where the end product receives little or no sunlight.

In some cases, organic pigments are believed to adversely affect the cooling characteristics of resins in a mold-providing poorer heat-transfer than cadmium, resulting in warpage and shrinkage. Stress marks on molded parts are not uncommon when organics are used to color resin. The result of all this could be some molders being forced to modify their tooling.

And then there's the cost. Where a cadmium pigment might cost about 10/lb, an organic substitute for that pigment could range from $16-$30/lb. This increase is just the beginning, experts say. In many cases, a hidden cost factor is involved that could drive up the end price of non-cadmium formulations. Organic pigments have lighter bulk densities than cadmiums, giving them greater surface area and requiring more carrier polymer to wet out and disperse the organic pigment For instance, an inorganic concentrate that had been formulated at 33:1 letdown ratio would have to be changed to a less economical 25:1 or 20:1 ratio.

But in most instances, less pigment is needed because of the alternatives'increased color strength, reducing the price gap but still resulting in a slightly more expensive production process. "In many cases you can replace cadmium with an organic and it will cost more," says Joseph Cameron, Color Technical Support Manager for GE Plastics'total Quality Technology Center, Washington, W.Va. "But there are just as many cases where the cost is lower because you use less pigment since the color strength of the organics is so much higher." And even if the use of cadmium pigments can save a few cents in production costs, other factors have to be taken into consideration. Waste-disposal costs, for instance, are reduced with the use of cadmium alternatives since in-plant waste no longer has to be taken to toxic waste dumps.

SECOND THOUGHTS

Because of doubts about what they may be getting into as well as the price factor, many processors are reluctant to switch and are opting to stick with cadmium colorants.

Cadmium-pigmented concentrates have been so popular because they provide exceptional heat stability, lightfastness and color stability at a relatively low cost. They are considered easy to disperse, have a very attractive cost/performance ratio and are in great supply. But as the price of cadmium soared to more than $8/lb a few years ago at about the same time the metal came under attack from environmentalists, pigment and concentrate suppliers rushed to explore alternatives.

"There's a lot of stuff out there being touted as replacements and they're really not," warns Rick Matthew, v.p. of research and development for Americhem Inc., Cuyahoga Falls, Ohio. Matthew and most others involved in the color business agree there really is no replacement for cadmium. Rather, they say, there are alternatives. Few can provide exact replication of cadmium's overall color and performance profile, and the processor is usually forced to make a sacrifice if he opts to go to a non-cadmium product-either give up some color quality in exchange for better performance or have the same color as before at a higher cost. Usually, most colors can be duplicated through alternative chemistry. Concentrate makers say reformulating yellows has been relatively easy. Reds have proven a bit more difficult and the bright oranges, in which cadmium works so well, have caused the most problems. As for the alternatives' deficient dispersibility, compounders may have to resort to little tricks like tightening the screws on their extruders or increasing residence times in mixers.

Opacity, one of cadmium's strongest selling points, is another problem many cite as their reason for not switching. Organic substitutes simply cannot achieve the level of opacity cadmium colorants can, users and suppliers say. While this may not be that important in items such as containers and packaging materials, ifs vital to the automotive industry where the use of plastics is booming. Exterior car panels, expected to last at least 10 years, need the opaque colors to screen harmful radiation from reaching and prematurely degrading the polymer. Organic pigment suppliers such as HoechstCelanese, Coventry, R.I., the Coatings and Colorants div. of BASF Corp., Hot land, Mich., and the Pigments Div. of Ciba-Geigy Corp., Hawthome, N.Y., have incorporated micro-fine particles Of [TiO.sub.2] into their formulations to overcome this problem. BASF has developed a new line of cadmium-free powdered pigments using nickel-chromium titanates to boost opacity. These are a single product that can be plugged into a formula with just a slight change in the process," says Mike Corcoran, BASF's sales manager for pigments and dyes for plastics. These pigments, called Sicoplast, make reformulation easier, he says, because they allow a single pigment to be used where three or four different pigments were needed previously.

Still, after the color has been matched and the most obvious processing problems are overcome, there can still be unforeseen troubles. "The biggest problem for a compounder using organics is clean-down time," says Avecor's Millard. For some reason organic pigments seem to have an affinity for hot metal." Millard estimates that cleaning organic pigments from an extruder can take almost twice as long as cleaning out heavy-metal pigments. "So now, not only is the formula more costly, it costs you more to make the stuff."

MOVEMENT GROWING

Yet, these potential problems have not stopped almost every colorant and pigment supplier from developing at least a few of these options in case customers ask for them. And ifs probably those customers, color industry insiders say, that will dictate the future of cadmium. As an increasing number of large users begin to swear off cadmium, suppliers will be forced to adjust their product fines to include more alternatives. Last year, Procter & Gamble and Kraft General Foods began insisting their packaging suppliers certify that their products are free of heavy metals including cadmium. Perhaps an even bigger announcement is Ford Motor Co.'s recent declaration that it wants its suppliers to eliminate cadmium-based stabilizers and colorants by 1995. Other major auto makers have yet to issue similar policies.

"I think Ford's decision will have a significant impact on the industry," says GE's Cameron. "The industry itself is moving to replace the use of cadmium wherever it can. I think it's really just a matter of time before it's no longer used." Cameron is among a group of industry experts who interpret Ford's move as a signal to manufacturers that the metal's time may be about up. Further evidence of this can be found in Quantum's decision to stop producing cadmium-containing concentrates as of May 1; and announcements by Ampacet Corp., Tarrytown, N.Y., and Polycom Huntsman, Washington, Pa., that they too will soon stop using cadmium. Avecor, which manufactures colorants at four plants across the country and in Canada, will pull all heavy-metal pigments out of its North Kansas City, Mo., facility on Nov.1, switching the factory over to producing just non-heavy-metal alternatives. And Reed Plastics, Holden, Mass., plans to eliminate use of heavymetal colorants, even those aimed at durable goods, by the end of 1993. Wayne Prescott, Reed's director of sales and marketing, says most of the company's research in the past three years has been devoted to getting rid of heavy metals.

Processors, too, are switching. Carlingswitch Inc., a West Hartford, Conn. injection molder of nylon toggle, rocker and paddle switches for appliances, business machines, marine and automotive applications, recently changed from cadmium and lead concentrates to Reed's non-heavy-metal alternatives. "We don't want to scramble to get the new formulations in the future if stricter regulations are passed," explains Andy Rastallis, Carlingswitch's manufacturing process coordinator. The color intensity of the non-heavy-metal concentrates has been excellent and the color matches right on target Rastallis says. Performance considerations such as cycle times, letdown ratios and processing temperatures have not been compromised, he says. So far, Carlingswitch has tried the new colorants only on switches for coffee makers and has not had to deal with some of the troubles processors say they've encountered when using cadmium alternatives under more rigorous conditions-problems such as bleeding, bleaching or fading when the colored parts are exposed to direct sunlight

WHAT IF CADMIUM GOES?

The cutback on heavy metals and the increased reliance on organic compounds is bound to have some adverse affects on the industry. One of those affects, say manufacturers of pigments and colorants, could be a shortage of replacements. "There's not enough organic capacity in the world to cover the loss of cadmium," says Robert Dobecki, manager of technical services at the PMS Corporate Technical Center in Coral Springs, Fla. "What we may see if cadmium is banned is a lot of [compounders] going out of business. "that fear has led many pigment suppliers and colorant manufacturers to begin developing organic alternatives to their cadmium-containing products in an effort to establish an early foothold in the organics market when and if cadmium is eliminated as an option. Some suggest other technologies, such as dye/inorganic combinations, could help fill the void created in the high-performance end of the colorant business since these products can sustain processing temperatures in excess of 600 F.

Suppliers, like Engelhard Corp., Edison, NJ., and SCM Chemicals Inc., Baltimore, don't seem worried about cadmium's possible demise. These suppliers have chosen to continue making cadmium pigments, devising methods to reduce soluble or extractable cadmium levels to almost nothing. Engelhard has surface treated its Mindust pigments so they are both low dusting and have low solubility. SCM, on the other hand, has developed a manufacturing process that lowers the acid-soluble portion of cadmium in its pigments to a level below the EPA toxicity limit allowing the company to classify leftover cadmium as nonhazardous waste.