Flame retardants seek uses in broader resin spectrum.

A modest number of new halogenated, phosphorus-based, and intumescent flame-retardant additives are moving out of the laboratory and into the marketplace. However, most of the supplier activity today is in development of new applications for products launched in the last few years.

In the halogenated additives, a key focus has been to reduce or eliminate reliance on antimony oxide, whose price has been highly unstable of late. While antimony prices this spring had dropped about 25% from the dizzying highs of 1994 (see PT, July '95, p. 27), the pressure is once again upwards. In June and July, antimony metal prices rose 60%. Industry observers do not expect antimony oxide prices - which climbed above $3/lb last year and then dropped to $2.60-2.90/lb in May - to return to their former level of under $1/lb any time soon.

Interest in the use of phosphorus-based compounds has been growing, as evidenced by both new products and expanded application of existing products. However, compounders have not made a major shift to non-halogenated flame retardants as some had projected a few years ago. Even in Europe, the regulatory climate for halogens is somewhat more relaxed. Says one global FR additives supplier, "There is no impetus to replace halogen flame retardants in the U.S., as they are not regulated. And even in Germany, demand for halogenated flame retardants continues strong."

Still, there are some market segments where non-halogenated alternatives are increasingly being sought. A good example is mass-transit applications. There are concerns about both acid corrosivity in smoke that can affect electrical systems and about the higher smoke density observed with halogens versus phosphorus compounds, which can obscure vision. Low-smoke intumescent additives are one of the most active areas of new-product development.

MORE HALOGENATED FR CAPACITY

FR suppliers' confidence in continued strong demand for halogenated flame retardants is demonstrated by numerous capacity expansions under way:

* Occidental Chemical Corp., Dallas, has begun a 30-40% incremental expansion at its Niagara Falls, N.Y., plant that produces its Dechlorane Plus additives.

* Dover Chemical, Dover, Ohio, will boost capacity for chlorinated paraffins by 50-75% this quarter at its Dover site. The addition will produce Chlorez grades for HIPS using a new process that results in a product with better thermal stability and uv stability, says technical director Don Stevenson.

* Albemarle Corp. (formerly Ethyl Corp.) in Baton Rouge, La., will nearly double capacity for Saytex BT-93 and BT-93W (bis-tetrabromo phthalamide) by next January at Magnolia, Ark. Also at Magnolia, Albemarle will add 20% more capacity for Saytex HBCD (hexabromocyclododecane) by year's end. Earlier this year, the company also completed a 50% expansion of capacity for Saytex RB-100 (tetrabromobisphenol-A).

* Another tetrabromobisphenol-A plant is being built as a joint venture between Great Lakes Chemical Corp., West Lafayette, Ind., and Israel's Dead Sea Bromine Group. The 55-million-lb/yr plant will start up in Israel by year's end.

* In late May, Great Lakes brought on stream a new plant at Eldorado, Ark., to produce commercial quantities of PDBS-80, a homopolymer of dibromostyrene (DBS) monomer. PDBS-80 is presently a semi-commercial product aimed at nylon and TP polyesters used in electrical/electronic components. This brominated thermoplastic resin comes in tan pellets and has excellent thermal stability, according to business manager Charles Yacomeni. It is used at 17-22% levels together with antimony trioxide.

NEW HALOGENATED PRODUCTS

AmeriBrom Inc., the N.Y.C. subsidiary of Dead Sea Bromine, will participate in the global launching of FR-1808, a new "environmentally friendly" brominated aromatic flame retardant, by the end of this year. The product is a proprietary material not based on diphenyl oxide and is considered an alternative to deca- and octabromodiphenyl oxide. An off-white, free-flowing powder containing 73% bromine, FR-1808 is designed for a wide spectrum of thermoplastics and possibly thermosets as well.

Product manager Tom Harrington says it works particularly well in HIPS and ABS, where it provides improved impact strength and noticeably higher melt flow. In lower-melting thermo-plastics like polyolefins and HIPS, it processes as a filler additive. Above its melting range of 460-482 F - more like the processing range of engineering thermoplastics - FR-1808 is totally melt blendable.

AmeriBrom is also exploring new uses for its brominated epoxies. Launched a couple of years ago (PT, Sept. '93, p. 45), this family of products was originally designed for use in ABS, TP polyesters, and nylons. Now these additives are also finding theirway into polyolefins, reports Harrington. The products are melt blendable and show outstanding uv stability, he says.

Campine America of Dover, Ohio (Dover Chemical's new joint venture with Belgium's Campine SA), introduced the Mastertek series of flame-retardant PP masterbatches for extrusion earlier this year (PT, May '95, p. 68). Marketing and technical manager Steve Landau says several developmental products are in the works. Among them is Mastertek PE-5503, a concentrate of a bromine compound and antimony oxide for LDPE extrusion coating. It can be used at up to 605-610 F, can provide a V-0 rating, and reportedly does not corrode extrusion equipment.

Albemarle is investigating new uses for Saytex 8010, a proprietary product containing 82% aromatic bromine. It was developed as an alternative to decabromodiphenyl oxide (DBDPO) for ABS and HIPS because it does not form diphenyl oxides and furans. It also has significantly greater uv stability and does not affect physical properties as much as DBDPO, allowing parts to have thinner walls, says marketing manager John McChesney. Albemarle is now investigating application of Saytex 8010 in nylon, polycarbonate, epoxies, and thermoset polyesters.

Ferro Corp.'s Bedford Chemical Div., Bedford, Ohio, is working on new products to complement its PyroChek 60PB and 68PB - two very heat-stable bromostyrene polymeric flame retardants for high-temperature engineering resins. Product manager Fran Quinn says these products are getting a lot of use in newly developed high-temperature resins for electronic components. Both withstand processing temperatures above 600 F, but Quinn says Ferro is looking to develop a polymeric FR with even higher thermal stability.

Pyronil 45, a plasticizer with 45% bromine from Elf Atochem North America, Inc., Philadelphia, has seen significantly increased use in PVC wire and cable. It has been used in wire that meets UL-1581 (105 C) and has allowed PVC to compete with fluoropolymers in certain plenum applications. Pyronil 45 is now also being evaluated as an additive for injection molded PET and PBT electrical components using a bromine/antimony-oxide system. Pyronil's plasticizer effect reportedly improves compound flow and restores some of the physical properties that are compromised with the addition of solid flame retardants.

Occidental Chemical has aimed recent R&D on Dechlorane Plus at reducing or eliminating the need for expensive antimony oxide. Commercial manager John Tramontana says Dechlorane can be used in nylon 66 and epoxy with other synergists such as zinc borate, zinc oxide, and iron oxide (red, yellow, or black). Using mixed synergists - e.g., antimony with a zinc compound or iron oxide with zinc borate - can permit lower total FR additive use.

Figure 1 shows that 20% Dechlorane Plus with either 10% antimony oxide, 10% zinc borate, or a mixture of 5% zinc borate plus 5% zinc oxide, produces a V-0 nylon 66 at 1/64 in. The same FR performance reportedly can be achieved at lower cost with only 16% Dechlorane Plus together with 2% antimony oxide and 4% zinc borate. Least costly are formulations using iron oxide as the synergist. Only 12-14% Dechlorane Plus is needed with 3-4% of iron oxide alone or in combination with zinc borate. The same effect has been seen in 25% glass-reinforced nylon 66.

Another new application for Dechlorane Plus is in combination with magnesium hydroxide in EVA and EPDM wire and cable. This system eliminates antimony oxide and lowers both smoke density and corrosivity.

OxyChem is also exploring synergistic effects with brominated epoxy and Dechlorane Plus in ABS and HIPS. The goal is to lower total halogen levels and increase uv stability. Tramontana says, "A 50:50 blend of brominated epoxy and Dechlorane Plus amounts to a 16% halogen content, versus a more typical 23% content."

HALOGEN/PHOSPHORUS SYNERGY

FMC Corp.'s Process Additives Div. in Philadelphia has been studying the unusual bromine/phosphorus synergy of a relatively new product in engineering thermoplastics. FMC research fellow Joe Green first showed that Reoflam PB-460 demonstrates true synergy in PC/PET blends. More recently, he demonstrated similar synergism in PC/ABS blends [ILLUSTRATION FOR FIGURE 2 OMITTED]. Explains Green, "The flame-retardant efficiency of PB-460 is significantly greater than all-bromine or all-phosphorus flame retardants. We have shown that 6% of the brominated phosphate is equivalent to 14% triphenyl phosphate in a 3:1 PC/ABS blend, giving UL 94V-0 and 5V." The lower concentration of flame retardant produces significantly higher impact and HDT, along with excellent process-ability, Green notes. Moreover, higher levels of ABS could be used in the blend, reducing cost.

It's also interesting that these compounds meet UL 94-5V rating without burn-through at only 0.70 in. thickness. And while PB-460 is not itself an intumescent FR, it enhances the natural intumescence of polycarbonate, Green adds.

Dover Chemical is now developing blends of bromine/chlorine products with phosphorus, which could be launched within the next two years.

PHOSPHORUS AND INTUMESCENTS

Hoechst Celanese Corp.'s Polymer Additives Div., Charlotte, N.C., is working on a modified version of Hostaflam AP 750 - an intumescent based on ammonium polyphosphate that was launched two years ago for use in polyolefins and epoxies. That product reportedly overcame most of the limitations of Hoechst's previous Exolit IFR line - i.e., improved heat stability of 480 F and much lower moisture sensitivity. The new version of AP 750 is even more heat-stable and shows less tendency toward blooming and water pick-up, says marketing manager Helmut Ricke. This product could be introduced commercially as early as the beginning of next year.

DSM Melamine Americas, Inc., Atlanta, reports that melamine cyanurate, which has long been used in unfilled nylon 6 and 66 in Europe and Japan, is gaining interest here as well. Business development manager Remko Goudappel says, "The product is increasingly being viewed as the most cost-effective alternative to bromine/antimony flame-retardant systems." Loadings required for V-0 in unfilled nylon are typically 10%, which is considerably less than those for halogen flame retardants. Cost savings of about 15% reportedly can be realized when replacing a bromine/antimony system with melamine cyanurate. DSM is now exploring the synergy of melamine with other flame retardants, including bromine compounds.

Chemie Linz North America Inc., part of the Austrian OMV Group, is also finding increased North American interest in melamine cyanurate, which reportedly can meet V-0 in unreinforced nylon and V-2 in glass-filled nylon. The company has improved its Melapur MC product by narrowing its particle-size distribution for use in nylon.

Sales representative David Doles also notes that two new nitrogen/phosphorus intumescents have been added to the Melapur line. Melapur PA90 is said to achieve V-0 at 1/16 in. with a 20-25% loading in glass-filled nylon. Melapur P46 reportedly provides V-0 at 1/16 in., plus good electrical and mechanical properties, with a 25% loading in filled and unfilled PP.

The Functional Chemicals Group of Montell Polyolefins, Wilmington, Del., says it has seen renewed interest in the company's Spinflam line of nitrogen-based compounds that use ammonium polyphosphate as a synergist, particularly in small appliance parts, electrical circuit boxes, and pipes in mines.

The company is also exploring the products' use in polyolefin wire and cable. And a new fine-ground version is said to be particularly suited to thin cross sections. "Versus the typical 2025 micron particle size, the new version is slightly less than 10 microns, so there is less adverse effect on physical and electrical properties," says marketing manager Michael Golden.

Antiblaze 1045, a bridged phosphonate ester from Albright and Wilson Americas, Richmond, Va., has seen growing use in PET and nylon fiber and monofilament. Product development manager Mark Huggard says the company is also investigating its use in PBT, where at 10% use level it provides V-0 at 1/16 in. "This amorphous liquid does not affect PBT's elongation and impact strength," he says.

Akzo Nobel, Inc., Dobbs Ferry, N.Y., is developing non-halogenated biphosphates and other phosphorous compounds to complement its Fyroflex RDP biphosphate, which is designed for PPE/PPO alloys, PET, polycarbonate, and PC/ABS. Marketing manager Ted Halchak says the company is aiming to expand its product line for both engineering resins and commodity polyolefins and styrenics.