Meet the new firestoppers.

New flame-retardant additives do more than squelch combustion. They also offer improved heat and uv stability, easier processing, and better mechanical properties in end products. Bromine and chlorine compounds still dominate the news, but there are also some improved non-halogen options.

Despite a decade of advances in non-halogen flame-retardant systems, halogenated additives remain the dominant tool of plastics formulators today. The vast majority of new FR developments in the past 18 months has been of the halogen-containing sort. The crop of new products is ample, even though the move from development to commercial fruition for flame retardants can be slow and arduous.

Several factors are driving strong growth of FR consumption, estimated by suppliers at 6-8%/yr. Chief among those factors, according to marketing manager Harold James of Great Lakes Chemical Corp., are increasing demand for a variety of consumer electronic products requiring ignition protection and the expanding scope of product fire-safety regulations.

For example, recent media publicity about small-appliance fires is leading the U.S. Consumer Product Safety Commission to consider tightening fire standards on these products. In addition, the CPSC is due to act this month on a petition by the State Fire Marshals Association asking that California Technical Bulletin 117 flammability standards be applied nationwide. All urethane foams used in upholstered furniture currently sold in the State of California must be flame retardant. The petition seeks to extend the Cal 117 standard to all furniture sold in the U.S.

HALOGEN SHUNNED ABROAD

Safety and environmental concerns about halogenated flame retardants have always been primarily European phenomena. And though no new scientific evidence of dangers from these products has emerged, the pressure to find substitutes in Europe has not abated - and is in fact finding new targets, according to John Kardos, marketing manager of Dover Chemical Corp, Although it was polybrominated biphenyls that came under fire in the late 1980s, Kardos notes that there is now pressure in Europe to reduce usage of chlorinated flame retardants. He says Dover Chemical. whose mainstay is chlorinated paraffins. takes this trend seriously enough to begin focusing R&D on non-halogenated alternatives.

Even if European market preferences have forced most U.S. FR additive suppliers to work on developing non-halogenated products, all concede that there is still nothing commercially available that can match the cost/performance of halogen-containing chemicals. Additive suppliers say they know of no existing nor pending regulation in the U.S. nor elsewhere that would restrict use of halogenated flame retardants. Says Great Lakes' James, "Attempts to restrict the use of certain brominated flame retardants in Europe a few years ago were abandoned. After much review of toxicological test results and the recognition that these products have been used for many years without any significant human health or environmental issues, the European regulators declined to enact any restrictions."

Meanwhile, suppliers say "eco-labels," such as Germany's Blue Angel and Sweden's Nordic White Swan, are causing much confusion in the marketplace. To secure one of these eco-labels, a manufacturer must certify that a product meets certain requirements, which may include not using halogenated materials (as is true for PCs that obtain the Blue Angel label). Explains James, "While they are entirely voluntary and not required in order to sell products, some consumer electronic manufacturers have mistakenly interpreted these labels as requirements for European commerce." He says that misinterpretation could lead to material selections that sacrifice cost or performance or both unnecessarily. As a result, the Chemical Manufacturers Association's Brominated Fire Retardant Industry Panel and its European counterpart are aiming to educate the industry about eco-labels to ensure that appropriate material choices are made.

PLENTY OF NEWS IN HALOGENS

The newest halogenated flame retardants are designed for improved thermal and uv stability, minimal color development, improved flow characteristics, and optimal compatibility with specific polymers.

One trend is toward thermally stable, melt-blendable brominated flame retardants, which tend to optimize impact and tear strengths and enhance flow as compared with higher-melting additives that act as inert fillers. For example, one product soon to be launched by AmeriBrom is SR-245 (tris-tribromophenoxy triazine). Permanence or bloom resistance is a key attribute here.

Also, the latest addition to AmeriBrom's family of brominated epoxies is the F-3000 Series of end-capped brominated epoxy that show good FR efficiency and mold-release properties, according to product manager Tom Harrington. The tri-bromophenol end cap adds 6-7% of bromine to the molecule, he says.

The first commercial product in this series, F-3020, is a low-molecular-weight grade for use in ABS. Other grades with varying molecular weights for use with other plastics will soon be launched, according to Harrington. F-3020 can also provide UL 94V-0 in PP with the addition of a polymeric grade of magnesium hydroxide now offered by AmeriBrom.

Another recent commercial offering from AmeriBrom is FR-1808, a brominated phenyl indan that's said to be particularly effective in styrenics, although it may have broad-spectrum utility in most thermoplastics, according to Harrington. It reportedly has excellent resistance to thermal aging, high melt flow, and excellent polymer compatibility, allowing for good impact strength. It can also be used to formulated 94V-0 PP in combination with the company's magnesium hydroxide.

Soon to be launched commercially is FR-1025M pentabromobenzyl monoacrylate (71.8% bromine). It can be copolymerized with a resin matrix via reactive extrusion or conventionally compounded with engineering resins such as PBT, PET, polycarbonate, and nylon 6 and 66 to provide 94V-0 ratings while maintaining the host resin's mechanical and physical properties. Graft copolymers of 1025M with PP produced by reactive extrusion can be used as adhesion promoters, dyeability enhancers, or compatibilizers in blends of PP with nylon, PBT, or PET.

Since last year's completion of a commercial plant to produce PDBS-80 dibromostyrene homopolymer, Great Lakes says the product is experiencing strong growth in electrical/electronic applications. Its high flow, good processing stability, and excellent color hold are reportedly gaining it acceptance in thin-section nylon applications, according to James. A series of PDBS-80 derivatives with improved compatibility in nylon and other engineering resins is now in the works.

Great Lakes is also preparing to commercialize a new imide additive containing 67-70% bromine. CN-1753 (N,N,-bis-tetrabromophthalimide) is aimed at polyolefin films, crosslinked PE, HIPS, and PBT. It is said to offer high thermal stability, white color, cost-effective flame protection, good impact strength, uv stability, and non-blooming characteristics. Its thermal stability is indicated by a TGA 5% weight loss at 554 F. Plant construction has begun for expected start-up in early 1998. Pilot-plant samples are now available.

Also new from Great Lakes is a low-viscosity (500 cp at room temperature) liquid additive with 55% bromine for flexible polyurethane foams in automotive and furniture upholstery or packaging. CN-2065 is not based on diphenyl oxide and is said to offer excellent resistance to discoloration during processing, superior hydrolytic stability, and low volatility in automotive fogging tests. It is also said to promote low IFD spread in high-resilience (HR) foams and to improve the adhesive properties of laminable foam.

MORE BROMINATED FR NEWS

There has also been a flurry of new brominated FR developments from Albemarle Corp., which has a total of four new products slated for introduction before year's end. Already launched are two proprietary compositions, Saytex BC56-HS and HP-7010.

BC56-HS (56% Br) is designed to withstand high-temperature processing without discoloration. Marketing manager John McChesney says its development has been driven by growing use of recycled polystyrene and the need for products that withstand higher temperatures without darkening the resin. This additive has a TGA of 493 F at 50% weight loss and over 1100 F at 90% weight loss. BC56-HS competes with HBCD (hexabromocyclododecane), traditionally used to flame retard PS resins, which has TGA of 435 F at 5% weight loss but only 487 F at 90% weight loss. BC56-HS can be used in EPS for small electronic enclosures, HIPS, and PS foams such as insulation board.

Saytex HP-7010 (69% Br) is geared to engineering thermoplastics used in high-temperature applications such as "cool-body" toasters, PC diskette drives, and electronic connectors. This polymeric additive is said to be non-blooming in all applications and to resist breakdown at high processing temperatures, suiting it to PET, PBT, and nylons. Exceptional purity reportedly also results in superior color and electrical properties.

Albemarle also has two developmental proprietary brominated products, one of which is slated for introduction this month. This flame retardant is designed for PP and will be targeted to end-use applications such as consumer electronics and Christmas tree lights. The second product is for use with styrenics and engineering resins in applications such as molded speaker modules for large tv sets.

McChesney also hints that Albemarle is focusing development efforts on FR additives for new metallocene-based polymers that are expected to find use in automotive applications.

REDUCED ADDITIVE LOADING IN FR NYLON 66 (15% GLASS)(a)

                              Standard               New
                             Formulation         Formulation

Brominated
Polystyrene                      21%                   -

Antimony Oxide                    7%                   -

Dechlorane Plus                    -                 16%

Firebrake ZB(b)                    -                  6%

Kemgard 981(c)                     -                  3%

Total FR Additive                28%                 25%

UL 94 @ 1/16 in.                 V-O                 V-O

TGA (12 min @ 608 F)

Weight Loss, %                     8                   8
Onset Temp., F                   649                 649

Relative FR Cost                 100                  92

a Source: Laurel Industries. b Zinc borate from U.S. Borax and
Chemical Corp. C Zinc phosphate from Sherwin-Williams Chemicals.

Meanwhile, Pyronil 45, an FR liquid plasticizer with 45% Br from Elf Atochem North America, has recently gained commercial applications as a combination flame retardant and flow additive in injection molded PBT and nylon electrical components that also contain antimony oxide. (Up to now, the product's main use was in PVC wire and cable.) Engineering-resin uses are made possible by the additive's high heat stability (TGA weight loss is 5% at 554 F and 10% at 582 F). Its plasticizer effects are said to restore some of the toughness, flow, and resiliency of engineering polymers, particularly mineral- or glass-filled formulations, that may be lost with the addition of solid flame retardant.

AmeriBrom has introduced a new version of an old, cost-effective standby - hexabromocyclododecane or HBCD - used in EPS foam. New FR-1206 (66.5% Br) utilizes novel heat-stabilizer technology that allows it to be used in HIPS and PP. Powdered FR-1206 is said to be thermally stable to 456 F, unlike standard HBCD grades, which start to decompose at 392 F [ILLUSTRATION FOR FIGURE 2 OMITTED]. It reportedly can achieve UL 94V-2 ratings in HIPS and PP with use levels as low as 2.1%, versus 3-4% for more costly brominated alternatives.

LATEST IN CHLORINATED FRs

Dover Chemical has introduced a new chlorinated paraffin produced by a new process that's said to impart better thermal stability than previous products [ILLUSTRATION FOR FIGURE 3 OMITTED]. Chlorez 700-SSNP in combination with antimony oxide outperforms decabromodiphenyl oxide in uv stability of HIPS compounds, according to Kardos, who says the product will not yellow. In PS and HIPS, Chlorez 700 SSNP with antimony reportedly provides 94V-0 at 1/16 in. and 94-5VA at 1/8 in. The company also sees potential for it to replace bromine-based FRs in polyolefins, where it achieves a UL 94V-0 rating at 1/16 in. Chlorez 700-SSNP is also recommended for unsaturated polyesters.

Through its acquisition last year of Laurel Industries, Occidental Chemical Corp. has become a broader-based FR supplier. Its Laurel industries subsidiary now offers OxyChem's Dechlorane Plus chlorinated organic FR additive plus Laurel's Fireshield and Ultrafine II antimony oxides.

The company's latest development is a new Dechlorane Plus formulation for nylon 66 that involves a lower total FR additive loading than conventional brominated systems and completely eliminates use of antimony oxide. As shown in the table on p. 40, the new Dechlorane Plus formulation employs two synergists - zinc borate and zinc phosphate. Business manager Gery Maneth says the new formulation costs less, has a lower density, is non-bloom-ing, has good uv stability, and offers thermal stability equal to or slightly better than brominated PS.

UPDATE ON PHOSPHORUS

FMC Corp.'s Process Additives Div. offers developmental quantities of two new phosphorus/bromine FR additives. Director of technology Fred Scholer says the new additives are well suited to PP applications because of their melt-blendability. PB-370 is for general-purpose use and FG-372 is geared to fibers. Their key attributes reportedly include excellent uv stability and processability. Typical use levels are 3-5% in PP fibers and 4% in 94V-2 PP.

A reactive phosphorous-containing polyol for flexible polyurethane foam was introduced a few months ago by Hoechst Celanese Corp.'s Additives Business Unit. (As of July 1, that business was merged into the specialty chemicals business of Clariant Corp.) Key properties of Hostaflam OP 550 polyol are low fogging (a key requirement for automotive seating) and heat-aging resistance.

According to technical/marketing manager Dan Scharf, Clariant will continue to emphasize the "halogen free" theme in its FR developments. One example is an improved version of Hostaflam AP 750, an intumescent ammonium polyphosphate launched last year that reportedly achieves 94V-0 and 5V ratings in polyolefins. The product is now said to be heat stable to 500 F and to have less tendency to bloom and pick up water. It also reportedly offers excellent processability and a good balance of compound properties in sheet extrusion, injection molding, and wire/cable applications.

Soon to come, Scharf adds, are stabilized and "desensitized" grades of red phosphorus for use in nylons and polyolefins.

Albright & Wilson Americas has introduced a new flame retardant that offers better cost performance in flexible PUR foam, according to senior marketing manager Dale Lyman. Antiblaze 140 is a chlorinated phosphate ester that is said to be 15% more efficient than conventionally used products such as tris-dichloropropyl phosphates. Typical use levels are 10-12 pph vs. 12-15 pph for TDCPP. The product is aimed primarily at automotive seating and headliners.

A modified version of the company's Amgard NP alkyl amine phosphate has an optimized particle-size distribution (8-10 micron average) that is showing benefits in PP, Lyman reports. The product has the advantage of being non-hygroscopic, unlike competing ammonium polyphosphates.

Akzo Nobel, Inc. plans to expand its Fyrolflex RDP (resorcinol diphenyl phosphate) product line in the next year with new non-halogenated biphosphates and other phosphorus compounds for commodity and engineering resins. Over the last few years, Fyrolflex RDP has gained commercial application at typical use levels of 10% in PC/ABS, PPO, and injection molded PET. The product has also been shown to offer improved flow in engineering resins when used as a processing aid at low levels (around 2%) without significantly affecting heat-distortion temperatures, according to marketing manager Ted Halchak.

Changes in vinyl heat stabilizers have stimulated increased use of FMC's Reofos triaryl phosphate esters in PVC wire and safety flooring, according to Sholer. Particular success has been seen in replacing FR systems containing antimony oxide in heavy-metal-free vinyls.