Polymer-bound stabilizers stay put.

Now they're commercial: The first two products of a 10-year effort to develop antioxidants stabilizers with reactive functionality that enables them to permanently bind to the backbone of polymers they're intended to protect. Not only does this make the stabilizers immune to gradual loss through volatilization, weathering or leaching, but their intimate binding to the host polymer reportedly also makes them unusually efficient in reduced quantities.

The former Lucidol Div. of Pennwalt Corp. began presenting technical papers on its patented reactive-functional stabilizer technology in 1988 and 89, when still in the developmental stage (see PT, Aug. 89, p. 13). Now called the Fine Chemicals Group of Elf Atochem North America, Inc., the Philadelphia-based company has introduced two commercial products and has several more ready to announce later this year and in 1994.

Gerry Gimbarski, manager of the Stabilizer Systems program at Elf Atochem, says the new-technology stabilizers will initially be aimed at "high-performance niche applications where current stabilization technology is not doing an adequate job. These will not be drop-in substitutes for use in current applications."

HYDRAZIDE FUNCTIONALITY

The two commercial entries are both specially modified with reactive hydrazide functionality. One is a hindered-amine light stabilizer (HALS), Luchem HA-R100, and the other is a hindered-phenolic antioxidant, Luchem AO-R300. The hydrazide group reacts quickly at relatively low temperatures (140 F and above) with anhydrides, isocyanates, and epoxy groups. Although Elf Atochem sees much of the new stabilizers' market potential in coatings, they would also be suitable for modifying certain polyolefins, styrenics and possibly nylons via reactive extrusion. According to Gimbarski, the new stabilizers' hydrazide group will react with maleated PE and PP, styrene maleic anhydride (SMA) and other anhydride-functional copolymers, some nylons, and epoxy resins.

Luchem HA-R100 modified HALS is a white odorless solid that melts at 315-318 F. It contains an oxamide functionality that gives it metaldeactivating properties, according to Gimbarski, who adds that this characteristic is unusual in a HALS. He believes this property could be valuable in neutralizing catalyst residues in polyolefins.

Luchem HA-R100 costs $26/lb. Despite its relatively high unit price, Gimbarski expects it to be competitive in cost-performance with standard HALS because it can be used at lower levels."Tying a HALS to the polymer backbone makes it more efficient than any comparable stabilizer," he claims. He says this advantage has been confirmed by customers who have had these products in testing over the last two years. "Significant opportunities in polyolefins are expected later this year," Gimbarski says.

Gimbarski further notes that functionalized additives are uniquely suited to polymer recycling, since polymerbound stabilizers will remain with the polymer through multiple uses and reprocessing. HA-R100 also boasts good thermal stability, withstanding extended exposure to 536 F.

Luchem AO-R300 functionalized phenolic antioxidant is a white, odorless solid that melts at 302 F. It costs 14/lb, more than other hindered phenolics, but it can be used at much lower levels.

MORE TO COME

By the end of this year, Elf Atochem plans to commercialize Luchem HA-B-AO, a novel combination of HALS and hindered phenolic antioxidant. It consists of Luchem HA-R100 and AO-R300 joined together with the main functional groups at either end of a dumbbell-shaped molecule. HA-B-AO has the metal-deactivating oxamide group of HA-R100 as an additional stabilizing functionality in the middle of the structure. This highly efficient molecule with no extra baggage" has potential uses in PE and PP, Gimbarski says.

Elf Atochem also has a peroxidefunctional reactive HALS, Lupersol HA-505, in which the HALS portion is a piperidine moiety similar to that of HA-R100. This developmental product, which may be commercialized next year, can be incorporated during reactor polymerization. Although as yet unproven, it may be possible to graft this product onto PP, ABS, HIPS, or SAN by reactive extrusion.

Farther back in the development stages is Luchem UV-R200, a reactive hydrazide-functional benzotriazole. "We know the market wants it," says Gimbarski, but Elf Atochem must first iron out the manufacturing economics.

The company has carried its technology a logical step forward with Luchem HA-B18, made by pre-reacting HA-R100 with a polyolefin resin--in this case an octadecene-maleic anhydride copolymer, similar to a maleated PP. This patented developmental product, planned for commercial release next year, is said to be compatible with both PP and PE. Unlike other HALS products, HA-B18 can be used together with thioester antioxidants for maximum stabilization of PP. Though it is in most cases a nonreactive additive, this product does react with nylons that contain residual amine groups.

As an alternative to HA-B18, Elf Atochem has Luchem HA-B-HMPA, a nonpolymeric reaction product of HA-R100 and an anhydride. This nonreactive stabilizer is planned for introduction in 1994. It was developed specifically for EVA greenhouse film. Since EVA has no reactive "handles" for the hydrazide functionality, Elf Atochem reacted HA-R100 with an anhydride to raise the molecular weight, thus preventing migration and providing a resin-compatible "carrier." Other potential uses are in PP fiber and film. Use levels will be around 0.2-0.5%, less than with conventional uv stabilizers.

(CIRCLE 7)