News update: UV stabilizers.

Improved thermal stability and compatibility with other additives and polymer systems, reduced volatility and color development, and low dust in handling are the basic themes of uv stabilizer development in the past year. Particularly notable are new and improved forms of hindered-amine light stabilizers (HALS). These include high-molecular-weight (HMW) monomeric and oligomeric HALS, as well as versions that are chemically linked to a monomer backbone or have reactive functionality that binds them to certain polymer systems. New versions of traditional uv absorbers--benzotriazoles, benzophenones and two brand-new chemistries--also appeared. There's also a growing trend toward multicomponent systems combining HALS and uv absorbers to achieve optimal cost performance. Finally, several new players in the uv-stabilizer market have emerged in recent months.

HALS DEVELOPMENTS

A new HMW monomeric HALS from Ciba Additives, Ciba-Geigy Corp., Hawthorne, N.Y., is geared to LDPE, LLDPE and EVA/LLDPE agricultural films. Free-flowing, granular Chimassorb 119 is also suited to color-critical polyolefins, particularly PP fibers. Typical use levels in films are in the 0.25-0.5% range. The product is priced at a small premium over Ciba's Chimassorb 944 FL another recently introduced HALS for fibers and PE film.

Ciba has also launched Chimassorb 944 FD to replace the FL version. The FD grade is in pastille form--a tiny pellet with very few fines. In the same vein, Ciba's Tinuvin 770 DF is a new version of workhorse Tinuvin 770 HALS. This free-flowing granular-type product reportedly has much lower dusting tendency than Tmuvin 770 powder.

Another new HALS from Ciba is Tinufin 765 liquid for polyurethanes, styrenics and polyolefins. It's designed for easy addition to PUR polyols and other liquid precursors prior to polymerization. It reportedly gives light-stabilization performance similar to Tinuvin 770.

Ciba also has new Tinuvin 123, with the lowest alkalinity of the company's HALS. It's recommended for polyolefins and PVC and reportedly does not interact with pigments, thioester antioxidants, or flame retardants.

One new name in uv stabilizers is Mayzo Inc., Norcross, Ga. Through its joint venture with Ever Springs, a div. of the Taiwanese Sunko conglomerate, Mayzo began importing light stabilizers in the past year. Among them is a HALS product, BLS 1770, reportedly identical to Ciba's Tinuvin 770. It's priced $1-2/lb lower.

With the acquisition of two European companies in the past year, Great Lakes Chemical Corp., West Lafayette, Ind., has become a player in HALS and other uv stabilizers. Most recently, Great Lakes bought Chemische Werke Lowi GmbH of Germany, which produces two HALS. Before the purchase, Lowi had started to introduce them here through the now defunct Lowi Chemical Corp. in Akron, Ohio. One HALS is Lowilite 77, designed to compete with Ciba's Tinuvin 770 and offered in both powder and 2-mm micropellet. The other is Lowilite 62, a solid that can compete with Ciba's Tinuvin 622 in general polyolefin uses and with Tinuvin 944 in PP fibers and PE film.

Also relative newcomers among HALS suppliers are Hoechst Celanese Corp., Specialty Chemicals in Charlotte, N.C., and BASF Corp., Plastics Materials in Parsippany, N.J. Hoechst has been importing from its German parent a monomeric, low-molecular weight HALS based on tetramethyl piperidine. Hostavin N20 competes with Ciba's Tinuvin 770 and reportedly exhibits excellent extraction resistance, low volatility and excellent compatibility with thioester antioxidants. Marketing manager Helmut Ricke says the product has superior long-term thermal stability. It is targeted for PP and HDPE films and thick-section extrusion and molding applications including outdoor furniture and auto bumpers.

Hoechst also offers Hostavin N30, a HMW oligomeric HALS designed to compete with Ciba's Tinuvin 944 in LDPE, HDPE and PP films, tapes, fibers and thin-section molded parts. Long-term heat stability, low volatility, low migration, and good dispersion with pigments are said to be key features. Also, it has chemical resistance to sulfur-containing compounds--both thioester antioxidants and pesticides that may be applied to agricultural films.

BASF Corp. recently made its entry into the HALS business with the commercial introduction of Uvinul 4049H, produced by its German parent company. This monomeric HALS is aimed particularly at HDPE colored with either organic or inorganic pigments. Commercial quantities are also available of another monomeric HALS, Uvinul 4050H, for use in polyolefins, ABS, nylon and acrylic. BASF, which already offers benzophenones and diphenyl acrylates, is stepping up its efforts in polymer uv stabilization, according to marketing manager Mike Corcoran. Additional HALS products and new uv-absorber chemistry are in development, he says.

Cytec Industries, West Paterson, N.J., the chemical business of American Cyanamid Co. (which will be spun off as an independent company by year's end), is launching a new non-polymeric HALS, Cyasorb 3853. Somewhere between a monomeric and an oligomeric HALS in molecular weight, it has relatively low volatility and both good surface stabilization and good solubility/migration balance. It's offered as a workhorse light stabilizer with excellent cost/performance in ABS and other styrenics, filled PP, nylon, and olefinic elastomers. For ease of handling, it comes in a 50% LDPE concentrate with a 6-8 M.I.

POLYMERIC & REACTIVE HALS

With growing frequency, suppliers are developing HALS that are or can be molecularly linked to a polymer chain in order to provide higher, compatibility with resins and other additives and greater resistance to volatilization, leaching or weathering.

As reported recently, the first of a new generation of reactive stabilizers were introduced commercially by the Fine Chemicals Group of Elf Atochem North America, Philadelphia. These products have reactive functionality that allows them to permanently bind to polymers. Besides permanence, such polymer-bound stabilizers are said to show unusual efficiency in reduced quantities. This reactive stabilization technology is expected to have its most significant impact in coatings but it is also suited for use with certain plastics via reactive extrusion.

The first of the uv products is Luchem HA-R100, a HALS modified with reactire hydrazide functionality. The hydrazide group will react with maleated PE and PP, styrene maleic anhydride and other anhydride-functional copolymers, some nylons and epoxy resins. HA-R100 is a white odorless solid that melts at 315-318 F. It also contains an oxamide metal-deactivating functionality. Though premium priced at $26/lb, lower use levels make it competitive in cost/performance with standard HALS.

Three other Luchem HALS are to be launched in 1994. First will be Luchem HA-B-AO, a nonreactive combination of HA-R100 and a hindered phenolic antioxidant, aimed at polyolefins, nylon, ABS, and other styrenics.

Lupersol HA-505 is a peroxide-functional reactive HALS, in which the HALS portion is similar to that of HA-R100. It has potential for grafting to polyolefins and styrenics.

For polymer systems that do not have reactive sites, Luchem HA-B18 is a patented developmental product made by reacting HA-R100 with a maleated polyolefin resin. Unlike other HALS products, it can be used together with thioester antioxidants for maximum stabilization of PP. It is suitable for unmodified polyolefins, HIPS, SAN, ABS and high temperature thermoplastics. Though in most cases it is nonreactive, this product does react with nylons that contain residual amine groups.

Gerry Gimbarski, manager of Elf Atochem's stabilizer systems program, stresses that these stabilizers are not geared to replacing workhorse HALS products. Instead, they are being targeted to high-performance niche applications where current stabilization technology is not doing an adequate job.

Over a year ago, EniChem America, N.Y.C. introduced Uvasil 299, a HMW oligomeric HALS consisting of tetramethyl piperidine side chains on a silicone polymer backbone. It is geared to thin-section PP parts and fibers, styrenic polymers, and irradiated polymers in medical applications. This viscous liquid has also become available as Uvasil 125 dust-free powder containing 30% ultrafine silica, and as Uvasil 2000 pellet concentrate in PP. EniChem can tailor the molecular weight of the silicone polymer backbone for optimum migration rate in thin or thick sections. The company can also produce reactive silane-bound stabilizers that can be grafted directly onto the polymer to be stabilized.

Another "sililated" HMW oligomeric HALS is now being produced by EniChem in pilot-plant quantities. Uvasil 8 is similar in basic composition to Uvasil 299 but has a different structure that is said to make it highly compatible with LDPE. Typical loading levels for both Uvasil 299 and Uvasil 8 are in the 0.1-0.5% range.

The Bedford Chemical Div. of Ferro Corp., Bedford, Ohio, is making its entry into the HALS business with UV-Check AM 806. The patented product is a complex oligomeric ester containing basic secondary amine groups attached to an acrylic copolymer backbone. Product manager Jody Tusick says this product takes advantage of the well-known compatibility of acrylic copolymers with polyolefins. AM 806 reportedly shows superior compatibility and performance compared with other HALS in all polyolefins--including LDPE, which generally poses the most difficulty in uv stabilization, she says. UV-Check AM 806 is also effective in ABS, TPOs and nylon. It has no effect on initial color of polymeric substrates, has low volatility, low extractability and exhibits good thermal and processing stability, she adds. Sample quantities are available now, with full production expected by second-quarter 1994. The product will be available in micro-pastille form.

AM 806 is synergistic with antioxidants and other stabilizers, especially hydroxybenzoate esters such as the company's UV-Chek AM-340. Tusick says Ferro has found UV-Chek AM-340 to be an excellent synergist for HALS in general. "Some HALS products have problems in certain pigment systems. AM-340 has a tendency to stabilize both the polymer and the pigment, so you get a dual-stabilization action." This HALS synergy has contributed to considerable growth in use of this benzoate, Tusick notes, particularly in PP carpet fiber and PP or TPO auto exterior parts.

Tusick notes that Ferro's next HALS product is likely to be a stabilizer combining UV-Chek-806 and UV-Chek-340.

NEWS IN UV ABSORBERS

Cytec Industries reports that it has introduced two products based on brand-new uv-absorber chemistries. Cyasorb 1164 is a triazine developed for use in nylon. Cyasorb UV-3638 is a benzoxazinone geared for PET and PBT. Both are said to perform similarly to benzophenones and benzotriazoles but can be processed at higher temperatures. They can be processed at up to 572 F, vs. a max. of 392 F for conventional uv absorbers. Prices are around $20/lb, or about double those of benzophenones.

Fairmount Chemical Co., Newark, N.J., has developed two dimer uv stabilizers, which combine two benzotriazole molecules into a larger molecule, resulting in good uv stability and reduced volatility. Mixxim BB/200, explains product manager Chester Swayze, combines two molecules of Ciba-Geigy's Tinuvin P into one large molecule. It can be processed at temperatures as high as 518 F, explains Swayze, while its very low volatility reduces worker exposure levels--an issue gaining increasing attention with benzophenones. Good results have been obtained in resins processed at high temperatures, such as PBT, poly-carbonate and nylon.

Mixxim BB/100, the other new dimer stabilizer, is produced by coupling two molecules of Cytec's Cyazole 5411. It's heat stable to 572 F and is geared for use in color-critical applications where clarity is required, such as polycarbonate glazing.

Ciba Additives has launched a new liquid benzotriazole, Tinuvin 213, which is said to be particularly effective in combination with a HALS, and convenient for use in liquid systems. Suggested applications are in urethanes and poly-olefins where liquid-color dispersions are added. It is also easily incorporated into flexible PVC systems, and has potential in styrenics.

Mayzo has introduced the Taiwanese import BLS 531, a benzophenone chemically identical to Cytec's Cyasorb UV 531. This light-yellow powder, lists for around $6.50/lb, vs. $8.50/lb list price of the competitive product. Early next year, Mayzo plans to launch BLS P, which is said to be identical to Ciba's Tinuvin P hydroxyphenyl benzotriazole.

EniChem plans to broaden its product line by starting production of benzotriazoles, including Uvazol P 236, P 237 and P 311, in 1994, with commercial availability by early 1995.

As noted above, Great Lakes Chemical recently became a factor in uv stabilizers. Last year, the company purchased a line of benzophenones from Rhone-Poulenc of France, now trade-named Cyntase.

And now in the advanced development stage is a reactive benzotriazole from a new supplier to the plastics market, Noramco Corp., a Johnson & Johnson Co., New Brunswick, NJ. Business development manager Daniel Aultz says Norbloc 7966 contains a substituted phenol with side chains of methacrylic ester that can copolymerize efficiently with a variety of vinyl monomers. The product was developed primarily for coatings but has considerable potential in plastics Aultz says, particularly acrylics, but also styrenics and PVC. Chemical bonding to the polymer backbone is said to eliminate volatility, migration, and blooming. Samples are currently available and commercial quantities can be produced on request. Commercial pricing will probably be in the $30-40/lb range.