News update: PVC heat stabilizers.

The most evident trend in PVC heat stabilizers is the quickening phase-out of heavy metals, principally cadmium and lead. Barium, a key component of many of the cadmium-replacement stabilizer systems for flexible PVC may be the next metal to come under scrutiny in the future for toxicity. Consequently, suppliers are working to come up with barium-free systems, especially improved calcium/zinc formulations.

The new replacements are quickly evolving to provide performance at least equal to that of their heavy-metal counterparts, while at the same time the cost differential appears to be narrowing. Another trend is toward making products with lower levels of VOCs (volatile organic compounds) by reducing or eliminating solvent carriers in liquid heat stabilizers and boosting the concentration of active stabilizer.

For rigid PVC, new developments include reduced tin content and cost, lower odor, and improved weatherability for siding and window profiles, particularly in dark colors.

FLEXIBLES GO 'HEAVY-METAL-FREE'

Suppliers of mixed-metal stabilizers indicate that the move away from cadmium in the U.S. is speeding up, while work on lead replacements is starting to come to fruition. One major player, Witco Corp.'s Polymer Additives Group, N.Y.C., has already announced that it will discontinue the sale of all cadmium-containing heat stabilizers by year's end (see PT, Jan. '94. p. 63). In the market at large, the transition away from solid cadmium products is occurring rapidly, as users may run afoul of new stricter OSHA airborne exposure limits. Liquids (the most common form) will probably continue in use for a while longer, though some suppliers estimate that complete cadmium stabilizer elimination will come within the next five years.

A good portion of the barium/cadmium replacements are barium/zinc products. "So far, they have been the workhorse cadmium replacements," says Victor Struber, Witco's manager of new business development for vinyl additives. Witco has a new liquid Ba/Zn, Mark 4794, which contains no volatile solvents. It's aimed at general-purpose flexibles where VOC requirements are critical.

Jim Keenan, industry sales manager for Cookson America's Synpron Stabilizers unit in Philadelphia, says that while barium/zincs are still higher priced than cadmium types, they are now more like 20-30|cents~/lb higher vs. 50-60|cents~/lb in the past, and their performance has been improved, particularly in high-shear applications.

Two lower-cost Ba/Zn liquids are new from Cookson. Synpron AE76 is for extrusion and calendering. Used at 2.5-3.0 phr, it reportedly has performance similar to that of the company's Synpron 1904--including low plateout--but costs about 10% less. New Synpron AE66, also used at 2.5-3.0 phr, offers improved clarity over 1904 and is aimed at high-clarity applications; it also costs about 10% less. Also new from Cookson are Ba/Zn stabilizers for auto interiors. Among them is Synpron AE 71, a liquid that boasts excellent antifogging properties, sells for about $2/lb, and is used at 2-3 phr.

Elf Atochem North America, Philadelphia, has launched its first Ba/Zn product. Stephen Hulme, market manager for plastics additives, says Stavinor ATA 1056 is a very low-toxicity liquid for such flexible applications as children's toys. Ferro Corp.'s Bedford Chemical Div., Bedford, Ohio, has two new barium/zincs. Therm-Chek 6258 powder booster is used at up to 0.5 phr with 2.5-3 phr of Ferro's Therm-Chek 139 Ba/Ca/Zn in filled or pigmented extrusion and calendering. It costs $2.70/lb. Therm-Chek F694, a liquid for clear and filled plastisols, reportedly has a good balance of early color and processing stability. It sells for $1.64/lb and is used at 2-3 phr.

A new Ba/Zn liquid comes from Ciba-Geigy Corp.'s Additives Div., Hawthorne, N.Y. Irgastab BZ 505, designed to work with the company's uv stabilizers, is for calendered sheet such as flooring. It costs about $3/lb and is used at 1.5 phr. The newest entrant in the flexible PVC stabilizer business is The OM Group, Inc., Cleveland (formerly Mooney Chemicals), which was spun off by Finnish corporation Outokompu last October. A leader in metal carboxylates, OMG is producing a new line of PlastiStab Ba/Zn and Ca/Zn powders and liquids that use plasticizer instead of solvent vehicles.

Another new name in flexible stabilizers is Akcros Chemicals, New Brunswick, N.J., the new joint venture of Dutch Akzo NV (parent of Akzo Chemicals) and England's Harcros Chemical. Akcros offers liquid Ba/Zn-phosphites and Ca/Zn-phosphites customized for specific customers as alternatives to its Ba/Ca/Zn products, says Donald Hampson, general manager of thermoplastic additives. With Harcros technology, Akcros is working on non-cadmium mixed-metal stabilizers that have greater inherent lubrication.

A third relatively new player, Baerlocher USA in Dover, Ohio, is now producing a broad line of heavy-metal-free mixed-metal heat stabilizers in the U.S. According to general manager Ed Jirousek, liquid mixed-metal stabilizers--including barium-zincs and calcium-zincs--are being developed that provide better printability with water-based inks used on film and sheet. BARIUM-FREE OPTIONS

Baerlocher USA, Ferro and Ciba Additives all have active Ca/Zn development programs for barium replacement. Several other firms have recently introduced new products. For example, Witco has introduced a calcium/potassium/zinc liquid, Mark 4796, as an alternative to both cadmium- and barium-containing stabilizers for general-purpose flexible vinyls.

Elf Atochem has three new liquid calcium/zincs. Stavinor XL-CZ 009A is a substitute for Ba/Zn in flexible filled calendering. XL-CZ 011B imparts transparency and color hold for clear, flexible extrusion or calendering. And XL-CZ002 is for plastisols.

Synpron NP 9300, a Ca/Zn powder with improved heat stability for use in FDA applications, is new from Cookson.

Meanwhile, Cardinal Stabilizers, Inc., Columbia, S.C., is looking to challenge mixed metals with its organotins in some flexible applications, according to president Tim Ross. One example is CC120, a sulfur-free butyltin carboxylate for calendered sheet and film, said to have excellent clarity and mildly lubricating properties. It costs $3/lb and is used at 1.5-2.5 phr.

Huber Chemicals, Havre De Grace, Md., is offering a new synthetic hydrotalcite (magnesium/aluminum hydroxy carbonate) as the first domestic alternative to Japanese imports. Huber says it used be used as an acid-scavenging secondary stabilizer or costabilizer with mixed-metal types. It's aimed primarily at boosting performance of Ca/Zn in bottles and of the new non-lead types for wire. LEAD REPLACEMENTS FOR WIRE

There has been continued development in the past six months of non-lead stabilizers for wire and cable (see PT, July '93, p. 35 for our last report). Eliminating lead is not yet required by any law, and lead stabilizers reportedly maintain superiority in cost and performance. But there's enough customer interest in alternatives that even lead-stabilizer suppliers like Baerlocher, Cookson, and Halstab Div. of Hammond Lead Products, Inc., Hammond, Ind., have active development programs for lead replacements.

As reported previously, Baerlocher has come up with Ba/Zn liquids and Ca/Zn solids for jacketing, where electrical properties are less demanding. One is Baeropan MC-KA 4 Ca/Zn, which costs under $2/lb and is used at 2-4 phr. For insulation, Baerlocher is in the final development stage with a number of solid mixed-metal products that are expected to match the performance of lead stabilizers both in heat stability and electrical performance.

Cookson, which recently introduced its 350 Series of calcium/zincs for jacketing and lower-temperature primary insulation (under 105 C), now has three newer mixed-metal products for which a patent is pending. They're geared to primary insulation for 105 C wire. Sample quantities are available.

Witco recently added a Ba/Zn liquid to the three new Ba/Zn powders previously reported. Mark 4716 liquid is for jacketing that does not require premium electrical properties. It's used at 2-3 phr and costs $1.90/lb. Among the solids, Mark 6736 is for primary insulation. It costs $2.57/lb and is used at 3-5 phr. TS-153 is a less lubricating version of 6736, which gives it processing characteristics more closely resembling lead types. Introductory price is $2.88/lb, and use levels are 3-5 phr. Mark 6735 for jacketing reportedly offers improved color control under processing and long-term heat aging. It costs about $2.25/lb and is used at 2-3 phr.

Ferro also has new lead-replacement technology for which a patent is pending. Two of these proprietary products, trade-named EZN-Chek, are being field tested. Grades 788I and PH 601 are for primary insulation of 105 C wire in dry applications. Both are said to give excellent dynamic thermal stability and electrical properties and are priced in the $2.25-2.60/lb range.

Akcros, Elf Atochem, and R.T. Vanderbilt Co., Norwalk, Conn., are also actively developing lead replacements, including barium/zincs, solid calcium/zincs, and other non-heavy-metal complexes.

TRENDS IN RIGIDS

In stabilizers for pipe and injection molding, cost reduction is still a major issue, and lowering the content of tin metal is the major lever available to suppliers. In pipe stabilizers, for example, tin content has been pushed down to the 3-6% level. Elf Atochem's new Thermolite PA 1121 is an example of a low-cost, low-tin, butyltin mercaptide liquid stabilizer for colored PVC pipe, used typically at 0.35-0.45 phr in pipe and 0.40-0.60 phr in conduit.

In food packaging, however, low-odor organotins appear to be the major goal. Cardinal is testing new butyl and octyl tins, aiming to reduce odor while maintaining high performance.

Morton International, Industrial Chemicals & Additives, Danvers, Mass., claims to have achieved acceptably low odor in its TM 2080 food-grade methyltin. Newer still is TM 404, a low-odor food-grade methyltin for water bottles and other food packaging, used at 1-1.5 phr.

Baerlocher has a new, high-efficiency butyltin, Baerostab M25S, with much lower odor for calendered sheet and film.

Akcros now offers a full line of octyltins for food-grade bottles, containers and sheet. By varying mono- and di-octyltin ratios, some products are optimized for early color/clarity and others for long-term stability.

NEWS IN SIDING & WINDOWS

There's lots of activity in developing heat stabilizers for improved weatherability in siding and window profiles. Elf Atochem has a developmental product that's said to significantly improve weatherability of dark-colored siding and windows. PV 1003 is a butyltin-based product also containing a tin synergist. "While the cost may be up to three times higher than a heat stabilizer used in a white window profile, you can use the same process equipment at the same output rates as for whites," says Atochem's Hulme.

Akcros has developed new organotins for dark-colored siding and profiles. These are mixtures of tin mercaptides and carboxylates (an approach also used in Witco's Mark 1975). Near commercialization are T-5507 and T-5507-A. Weathering data reportedly are very promising, and the products are said to show good dynamic thermal stability and color hold. Typical recommended usage is 1.5 phr and price is around $5/lb.

Also new from Akcros is T-4940 for white and light-pastel siding and profiles. A 10%-butyltin product based on patented technology that allows reduced tin levels, it reportedly offers excellent uv stability and low odor. It sells for $3.95/lb and is used at 1.5 phr.

A new liquid butyltin carboxylate from Ciba Additives, Irgastab T 634, reportedly features a good combination of thermal stability and weatherability for use in dark-brown window profiles. Designed to work with the company's uv stabilizers, it costs about $5/lb and is used at 1.5-2.0 phr.

Lubricant/stabilizer combinations ("one-packs"), while a small factor in the U.S. market, are attracting interest for use in substrate layers of coextruded siding. Morton is offering a new family of customized products, called Advapak LS-S1000, for siding and window profiles. All contain a methyltin mercaptide stabilizer plus external and internal lubricants and are used at 3-4 phr.

Availability is still limited of Morton's new family of WLWS (weatherable lubricant/weatherable stabilizer) systems. Advastab WS-499 is geared for dark-brown siding and profiles, costs about $5/lb, and is used at 3.0-3.5 phr. WS-379 is for light-colored siding and translucent sheet and reportedly allows 30-40% reduction in Ti|O.sub.2~ content while still offering good weatherability. It costs about $4/lb and used at 2.5-3 phr.

Elf Atochem has a new family of multifunctional systems (MFS), which include stabilizer, impact modifier, processing aid, and calcium stearate. They are aimed at siding and higher-performance pipe.

Cardinal is field testing new stabilizer/lubricant one-packs for pipe, siding, and windows. Some use liquid and others use solid organotins, and some contain sulfur while others do not. They also contain calcium stearate, paraffin wax, oxidized PE, and ester lubricant.