News update: antioxidants.

Environmental and workplace health concerns are among the key forces driving new developments in antioxidants. Suppliers are looking to address these issues with alternative packaging that reduces disposal costs and with nondusting forms of their products.

Among the principal performance issues is the search for reduced volatility, as evidenced by the proliferation of higher-molecular-weight (HMW) primary antioxidants, which increasingly are replacing the old workhorse BHT. Lower extractability is also being sought through polymer-bound phenolic antioxidants of high molecular weight. Other trends are toward greater hydrolytic stability in phosphite secondary antioxidants and wider ranges of preblended stabilizers.

'ENVIRONMENTAL' FORMS

Traditional fiber bags and drums are being replaced by antioxidant packaging that is more "environmentally friendly" and lowers the cost of waste disposal. Approaches include "consumable" or soluble packaging, which becomes part of the final resin product, as well as reusable packaging and lower-bulk containers--forms of solid-waste "source reduction." Development of low-dusting or nondusting forms aimed at reducing workers' exposure to chemicals is also well under way.

For example, Ciba Additives, div. of Ciba-Geigy Corp., Hawthorne, N.Y., is developing products in free-flowing, low-dust forms (e.g., granular) and placing them in packages that are safer as well as mechanically easier to handle and dispose of, says Patrick Kiernan, director of marketing for basic polymers. Ciba's new packaging includes 1200-lb semi-bulk PP bags that hold as much as eleven 110-lb fiber drums, thereby reducing waste by 90%, according to Kiernan. Also offered are 44-lb LLDPE bags and process-consumable 25-lb bags made of rubber-modified PS for use in styrenics.

Bill Jenkins, marketing manager for GE Specialty Chemicals, Parkersburg, W.Va., expects the trend in packaging to be more toward the "reusable" option. For higher-volume applications, GE is providing its liquid phosphites in reusable 325-gal metal totes. For its solid phosphites, GE is evaluating new 55-lb multilayer foil-lined bags intended to replace 50-lb metal drums. Jenkins says GE has also evaluated the option of "consumable" packaging for its products used in PVC compounding. However, customers were concerned that the bag constituted a contaminant to their formulations and also cost more than standard bags.

As another sign of the trend, Ethyl Corp.'s Chemicals Group in Baton Rouge, La., is looking to develop consumable PE-based packaging for the company's solid antioxidants used in PE processing.

LOWER DUSTING & VOLATILITY

"Look at BHT," says product manager Chester Swasey of Fairmount Chemical Co., Newark, N.J. "It used to be the antioxidant, but has lost ground due to its volatility, especially as processing temperatures and demand for higher throughputs have increased."

One application in which higher processing temperatures make BHT volatility an issue is in flexible PUR foam systems. Douglas Reed, product manager of Rhone-Poulenc's Fine Organics Group, Cranbury, N.J. (a major producer of BHT), concedes that flexible foamers' conversion to non-CFC blowing agents has resulted in considerably elevated processing temperatures, making BHT's performance marginal. Rhone-Poulenc has begun to explore various "mechanical modifications" to the foaming process that may retain BHT in the polyol solution at higher processing temperatures.

The other two key BHT producers also addressing its deficiencies. Uniroyal Chemical Co., Inc., Middlebury, Conn., has an alternative liquid phenolic for flexible urethane foams that is said to minimize both volatility and susceptibility to yellowing. And PMC Specialties Group, Cincinnati, is now offering a variant of BHT that reportedly eliminates yellowing.

R.T. Vanderbilt Co., Norwalk, Conn., is introducing a patented, low-volatility, liquid HMW antioxidant system for flexible PUR slabstock. Vanox 927 consists of a diphenylamine in combination with a hindered phenolic.

Another trend is toward nondusting antioxidants, whether pellets or liquids. Although not everyone has equipment in place to handle liquid systems, marketing manager John Gillette of Mayzo, Inc. in Norcross, Ga., sees growing interest in them. "It is easier to meter them and they blend more easily and quickly into dispersions. In addition, they are cleaner and safer for people to use," he says.

Ciba's Kiernan agrees that some users are looking to liquids as a solution to dusting. But for most, he says, that would entail some conversion of their operations. Also, he warns, it is harder to design a multicomponent additive system with liquids: "You have to go either all-solids or all-liquids if you don't want severe solubility constraints."

NEW PRIMARY ANTIOXIDANTS

Next year, EniChem America, Inc., N.Y.C., expects to commercially launch Silanox, a HMW liquid hindered phenolic based on the same polymer-bound technology as the company's Uvasil HALS (see PT, Oct. '93, p. 12). Silanox consists of hindered phenolic side chains on a silicone polymer backbone. Products made with this technology have much lower extractability than conventional hindered phenolics, says Vic Jackson, business manager for plastics additives. The first product now being sampled is very compatible with HDPE and may also work in LLDPE and LDPE. A major application is expected to be telecommunications wire and cable.

As reported previously (PT, Nov. '93, p. 36; July '93, p. 44), Elf Atochem North America, Inc., Philadelphia, has launched a new generation of reactive stabilizers that can permanently bind to polymers. Primarily aimed at coatings, they are also said to be suitable for modifying certain polyolefins, styrenics and possibly nylon via reactive extrusion. Among them is Luchem AO-R300, a hindered phenolic with reactive hydrazide functionality. A white, odorless solid that melts at 302 F, it is priced at $14/lb--more than other hindered phenolics, but it reportedly can be used at much lower levels. A companion product expected to be launched next year is Luchem HA-B-AO, a nonreactive combination of AO-R300 and a HALS.

Sandoz Chemicals Corp., Charlotte, N.C., has a product in fairly advanced developmental stages that could "revolutionize" nylon stabilization, says technical services manager Joseph Webster. It can serve as a combination uv stabilizer, antioxidant, processing aid, and color suppressant, he explains. Webster will only say that the product is based on a new chemistry that reacts with the amino groups in nylon 6 and nylon 66, which are responsible for poor stability of nylon. "It ties the amino groups up so they can't react with anything else," he says. "It will thus allow use of pigments that could not be previously used with nylon."

Both Zeneca Inc., Wilmington, Del. (formerly part of ICI Americas), and Great Lakes Chemical Corp., West Lafayette, Ind. (which recently acquired Chemische Werke Lowi in Germany), have developed solvent-free versions of HMW hindered phenolics. Topanol CASF is new from Zeneca; Lowinox 22 is from Great Lakes.

Within the last year, Dover Chemical Corp., Dover, Ohio, became a supplier of hindered phenolics with the introduction of Dovernox 3114, 10 and 76. The latter two are equivalents to Ciba's Irganox 1010 and 1076, says market manager Tom Slam.

Another new player in polymer stabilization is Hoffman-LaRoche Inc., Industrial & Agricultural Products, Nutley, N.J., which recently commercialized proprietary formulations of alpha-tocopherol (vitamin E). Besides having lower volatility than BHT, these are said to dramatically enhance color stability without use of secondary antioxidants. They also reportedly can replace BHT or hindered phenolics of the Irganox 1010/1076 sort (PT, July '92, p. 52). Ronotec 202 (100% alpha-tocopherol) and 201 (92%) are now used commercially in PP fibers and HDPE water and milk bottles, as well as HDPE film, says Peter Zambetti, manager of industrial products. He notes that polymers stabilized with vitamin E impart less taste and odor than those stabilized with conventional antioxidants. Although nearly three times the cost/lb of workhorse hindered phenolics, vitamin E products are said to be more cost-effective as they can be used at 80% lower dosages. Recommended concentrations are 100 ppm in PE and 250 ppm in PP.

The company's newest addition is Ronotec CF-120. Zambetti says the single-phase liquid formulation contains about 20% alpha-tocopherol and 20% of another functional additive, with no phosphites. It reportedly can replace phenolic/phosphite combinations in polyolefins and possibly BHT in urethanes. It is said to have excellent hydrolytic stability and "unmatched" color stability.

Other new compounds based on vitamin E are in development. The first to be launched will be products that could supplement or potentially replace thioesters in ABS and nylon for high-temperature applications such as under the hood.

IMPROVED SECONDARY ANTIOXIDANTS

A clearly emerging trend is toward high-performance phosphites and phosphonites with enhanced hydrolytic stability. Dover Chemical, for one, has developed a new solid phosphite said to have better hydrolytic stability than other phosphites on the market. Doverphos S-9228, now being produced in pilot quantities, is based on pentaerythritol diphosphite chemistry (as is GE's Ultranox 626). "It has the excellent color stability of 626, but is more hydrolytically stable so that it can be used in higher-temperature processing," says Dover's Tom Slam.

Also newly available from Dover in sample quantities is a solid form of trisnonylphenyl phosphite (TNNP), which is normally a liquid. The powdered product is about 70% TNNP and is aimed at polyolefins, PVC, polyesters, and ABS. It's reportedly less costly to use than other phosphites.

Dover has also launched Doverphos S-480, a chemical equivalent to Ciba's Irgafos 168 low-volatility, hydrolytically stable phosphite.

A developmental product now being field tested by Ciba is CGA 12 high-performance phosphite processing stabilizer. It offers "extremely high hydrolytic stability--better than Irgafos 168," according to Ciba's Kiernan. It's aimed at all polyolefins.

R.T. Vanderbilt has a new auxiliary antioxidant for flexible PUR slabstock foams. Vanox 1887 is a liquid, low-color diphenylamine that acts as an anti-scorch stabilizer when added to a polyol that already contains an inhibitor.

FINDING NEW USES

Some established secondary antioxidants are finding new uses. For example, Ethyl Corp. sees increased interest in improved performance and higher line speeds in slit-film PP carpet backing. Ethyl says throughputs can be increased by 20% or more with combinations of its Ethanox 330 high-performance phenolic and Ethanox 398 fluorophosphonite, which is nonhygroscopic and both hydrolytically and thermally stable.

Sandoz reports that its broadly FDA-approved HMW phosphonite, Sandostab P-EPQ, initially sold as an adjunct to primary phenolic antioxidants, has growing potential as a sole antioxidant in polyolefins. Sandoz's Webster notes that most phenolics tend to contribute to color formation. With the trend toward light pastel colors in fibers, he says, many processors are electing to replace phenolics with a phosphite or a phosphonite. P-EPQ, which is heat stable to 662 F, has been chosen as a direct phenolic replacement due to its ability to provide processing stability alone without dripping and smoking at the die, Webster says.

P-EPQ has also been shown to synergize with both sulfur and phenolic antioxidants, and in highly filled systems, it's not deactivated by fillers. It is especially well suited to low-water-carry-over applications and to clarified polyolefins requiring long-term retention of clarity and low haze. Due to its unique solubility in PE, Sandostab P-EPQ reportedly shows extremely low migration compared with alternative phosphorus chemistries. In addition, it eliminates the black specks or charring that occur with competitive products, Webster says.

Jenkins of GE Specialty Chemicals expects an increased trend toward use of phosphites in PVC. "As PVC producers move away from heavy-metal stabilizers |e.g., cadmium and lead~, they have found that alternative mixed metals--zinc or barium--are not efficient in flexible PVC. So they are looking to use more phosphites in these mixed-metal systems."

TRENDS IN BLENDS

GE Specialty Chemicals has focused lately on developing value-added blends of its solid phosphite antioxidants with other additives, including hindered phenolics and even HALS. Says GE's Jenkins, "The value this brings to customers is that we have the responsibility for the quality control and analytical work to provide the correct ratios needed. Some customers tell us they have experienced variations of as much as 30-50% because of the inaccuracy of their blending systems." GE has introduced a series of blends (such as Ultranox 627A) based on its Ultranox 626 phosphite combined with hindered phenolics and a proprietary neutralizer into a compacted, lowdusting powder.

EniChem has done a lot of work in blends lately. Earlier this year, the company introduced patented NDB (No Dust Blend) granules (PT, Oct. '93, p. 88). These use various phenolics as thermoplastic matrices to incorporate phosphites, uv stabilizers, and stearates into one free-flowing pellet. Thus far, EniChem has come up with 60 customer-specified formulations, primarily for use in HDPE, LLDPE and PP.

Another family of products is EniChem's PAM (phosphite/amorphous) blends, made by microencapsulating GE's Ultranox 626 phosphite with Anox 20AM phenolic (equivalent to Irganox 1010), resulting in a free-flowing pellet that is hydrolytically stable and disperses efficiently. The product is said to be particularly effective in PP extrusion and other high-throughput, low-residence-time polyolefin processes. Commercially produced in Italy, PAM blends are now being sampled here.

Also new from EniChem are patented Anox-TB blends of a phenolic, a phosphite, and a thioester. They are chemically similar to Ciba's Irganox B blends; however, EniChem's blends use a very small amount of thioester, which provides reduced yellowing in polyolefins without a negative effect on melt flow, Jackson says.

Witco Corp.'s Polymer Additives Group, Styrenics and Olefins dept., N.Y.C., has also been developing nondusting blends, says group leader Dr. David Peveler. A product currently being sampled is Mark 5004, a thioester/phenolic blend that comes in the form of a compressed pellet. Still in development is a phenolic/zinc stearate blend in pastille form. Both products are geared for use in PP, although they have potential in other polyolefins. Yet another nondusting product is a new paste-like stable dispersion of Witco's Mark 2112 tert-butylphenyl phosphite in mineral oil.

Looking to broaden its position in antioxidants, Mayzo (which imports Taiwanese equivalents of Irganox 1010 and 1076) has launched BNX 1000, a synergistic liquid blend of a hindered phenolic and four other antioxidants. Mayzo is producing the proprietary product in the U.S. under license and has applied for a patent. The product has been gaining acceptance in adhesives and rubber and reportedly has good potential in plastics, particularly polyolefins. "It acts like Bennox 1010, but costs about 20% less," says John Gillette, v.p. of Mayzo's additives group.