New additives and polyols surface at urethane conference.

Getting along without CFCs still takes a lot of work, and R&D currently appears to be focusing on catalysts, surfactants and other additives tailored to remedy the shortcomings of water- and HCFC-blown flexible and rigid foams. That, and the drive to develop new polyols for improving foam performance and manufacturing economics, were the dominant themes at April's Utech '92 conference and exhibit in the Hague, Netherlands.

CATALYSTS FOR NEW FOAMS

Urethane processors are trying out new catalysts to accommodate non-CFC formulations. This is especially true for flexible foams, which for the most part have shifted to water-blown systems that often result in foams with flowability problems, decreased softness and high closed-cell content. Primary amines released during the water/isocyanate reaction are also believed to lead to automotive windshield fogging.

To counter this, Condea Chemie, GmbH of Hamburg, Germany, has developed two fully incorporable amine catalysts for these water-blown systems. Thancat AN 20 and Thancat DA 401 also are said to overcome other disadvantages of water-blown foams, such as higher ILD. Because they improve flow (in an all-MDI foam system they were found to create a condition where the string/gel time and rise time are about the same), Condea is promoting these catalysts for any molded foam application. (CIRCLE 102)

Another method to overcome the increased firmness of water-blown foams is the use of a plasticizer. Monsanto Europe S.A. (U.S. offices in St. Louis) has found that the firm's benzyl phthalate and phosphate ester plasticizers can improve softness while maintaining aged compression-set and other mechanical properties. (CIRCLE 103)

Also making catalyst news was Tosoh Corp. of Japan (U.S. office in Atlanta), which introduced two new reactive tertiary amine blends--Toyocat-HX and HX70--both said to improve mold-ability and aging properties and to increase resistance to vinyl staining in low-density, semi-rigid foams for auto interiors. (CIRCLE 104)

Union Carbide Chemicals and Plastics S.A. of Geneva (Danbury, Conn.) unveiled Niax EPB-26, a delayed-action amine blowing catalyst developed to optimize MDI or MDI/TDI formulations for difficult-to-mold parts. It reportedly can be used in flexible, semi-rigid and rigid systems that incorporate polymeric MDI. Union Carbide says it provides a density reduction in all applications. EPB-26 also performs well in water-blown rigid refrigeration foams, Carbide reports, and helps minimize staining problems in automotive applications. (CIRCLE 105)

SURFACTANTS & ADDITIVES

Among the other news at the exhibition were a variety of unique surfactants, flame retardants and other urethane chemicals.

As with catalysts, the elimination of CFCs has led to extensive foam system reformulation. In an effort to meet this need in hot-cure molded systems, Air Products and Chemicals PURA GmbH & Co. in Germany (U.S. headquarters in Allentown, Pa.) tested new silicone surfactants in more than 300 foams, resulting in the introduction of two experimental products, XF-G25-19 and XF-G25-18 that reportedly provide substantial increases in air-flow values over many other surfactants and produce split-free foams with heights and recession values similar to CFC-blown systems. Currently, Air Products says, about 0.8 phr surfactant are used in a system blown with 3.5 to 4.5 phr of water. The company says it will continue to evaluate these experimental surfactants in formulations with higher water levels and will examine their compatibility with some experimental softening agents. (CIRCLE 106)

A non-hydrolyzable silicone surfactant designed for rigid foams blown with HCFCs 123 and 141b was introduced by Union Carbide. The surfactant, Y-10733, gives these foams good thermal insulation and physical properties, Carbide says. In an HCFC-123 free-rise foam system, the surfactant provided compressive strength of about 30 psi, while in a HCFC-141b system, compressive strength was about 27.5 psi. (CIRCLE 107)

Two new premium-priced flame retardants for rigid and flexible foams based on reactive phosphorus were introduced by Pelron, Corp., Lyons, Ill. Grade 9730 is a proprietary halogen-containing polymer blend containing 2% phosphorus, 7.4% chlorine and 36% bromine. At 77 F, its viscosity is between 5500 and 7500 cps. Grade 9729 has 1.6% phosphorus, 6.4% chlorine and 36% bromine, with viscosity of 7000-9000 cps. Pelron says the new products are highly efficient and require about 20% lower dosages than many standard flame retardants. (CIRCLE 108)

Experiments with an aromatic secondary diamine that was originally developed as a chain extender for urethane elastomers are said to show a number of property enhancements in rigid foams, including reduced flammability. Unilink 4200 from UOP Inc., Des Plaines, Ill., reportedly gives foams higher compressive strengths, finer cell structure, slower diffusion of C|O.sub.2~ in water-blown foams, and higher closed-cell content. Dimensional stability of water-blown foams increase dramatically, researchers say. (CIRCLE 109)

Microfine-celled rigid foam insulation using an HCFC-22/HCFC-142b blend was the topic of a paper from ICI Polyurethanes (West Deptford, N.J.). ICI says the foams, developed for appliance insulation, show equivalent or better thermal conductivity, compared with reduced-CFC-ll systems. Other benefits of the HCFC blend, ICI says, include nonflammability, high affinity for both polyol and isocyanate, and ozone depletion levels as much as 20 times lower than the lowest CFC systems.

Despite these advantages, ICI says the HCFCs have low boiling points that could lead to processing problems; and the HCFCs have higher gaseous thermal conductivity than CFCs, leading to poorer insulation values than conventional CFC-blown foams, but still better than current reduced-CFC foams. (CIRCLE 110)

POLYOLS ENHANCE PERFORMANCE

As the need for better polyurethane properties becomes increasingly urgent, European suppliers are developing what they say are polyols that can produce superior quality foams. Du Pont International, Geneva, Switzerland, (Du Pont Chemicals, Wilmington, Del.) rolled out four new polyols and announced one still in development. Two of the new polyols are part of Du Pont's Terathane N series of PTMEGs. The newest version in this line is a 1400 M.W. polyol that Du Pont says eliminates the need for 1000/2000 PTMEG blends. It reportedly imparts improved low-temperature flexibility, higher resilience, lower prepolymer viscosities, and better abrasion resistance.

The other new Terathane is a polyether polyol that is a 50/50 blend of PTMEG and PCLG. It exhibits low crystallinity and low viscosity compared with PTMEG. The 3000 M.W. copolymer is targeted at formulating polyurethanes with high water-vapor transmission, improved oil resistance, and good low-temperature properties.

Du Pont's third new commercial offering is a paraphenylene diisocyanate for producing higher performance PUR elastomers. Hylene PPDI is said to greatly improve the phase separation and crystallinity of elastomers while also improving dynamic properties, oil stability and abrasion resistance. Du Pont says PPDI elastomers give almost nine times better abrasion resistance than nitrile rubber. The company also said it is developing a cyclohexane diisocyanate that will produce uv-stable urethanes; and, when combined with the Terathane products, it reportedly will improve hydrolytic stability. It's expected to be commercially available in early 1993. (CIRCLE 111)

Olin Corp., Stamford, Conn., unveiled one commercial polyol and six developmental polyols, all designed to compete with PTMEG. These polyether-based, low-saturation products boast higher functionalities than most competitive products and are said to provide foams with better mechanical properties. Olin says foam properties approach those of PTMEG, but at a lower cost.

The one commercial product in Olin's new Poly-L line is 220-28, a 4000 M.W. propylene oxide diol. Olin also has three developmental diols--225-28, a 4000 M.W. polyol that is ethylene oxide endcapped for increased reactivity; plus 220-14 (8000 M.W.) and 220-10 (11,000 M.W.), both based on propylene oxide. Three developmental triols include 385-29 (6000 M.W.) and 385-17 (10,000 M.W.) grades with ethylene oxide endcaps. Initially, these polyols are aimed at elastomers where they can produce softer products with less than 70 Shore A hardness. (CIRCLE 112)

One of the more unique polyols discussed at the conference is a low-viscosity, highly fire-retardant material based on lactose or milk sugar. Lactose-based polyols are made from whey, the byproduct of cheese manufacturing. The nitrogen in the whey acts as a flame retardant, while the lactose serves as the polyurethane initiator. In a paper from Polylactane Inc., div. of Horton International, Cambridge, Mass., researchers compared foams made with a lactose-based polyol blend and a sucrose-based polyol. They found the two had very similar smoke indexes of 307 and 290, while the foams made with lactose polyol were less friable and had higher compressive strength than foams made with sucrose polyol. What's more, cream time for the lactose-based foams was 12 sec, or 40%, shorter; rise time was 55 sec, or 54%, lower; string time dropped 66 sec, or 55%; and tack-free time was decreased 100 sec, or almost 60%. Density of the lactose-based foams was 1.92 pcf, vs. 2.07 pcf for the sucrose-based foams. (CIRCLE 113)

Although not yet available in North America, polymeric polyester polyols that can improve hardness and cell structure over conventional polyester products were introduced at Utech by Hoocker S.A. of Barcelona, Spain. Called Hoopol PM, the polyols are vinyl monomers with saturated polyesters. For now, they are aimed at shoe soles, but tests are being run to determine their suitability for flexible foams. These polyols reportedly offer processors a cost savings because they require lower isocyanate consumption and produce comparable foams at lower density than conventional polyesters. (CIRCLE 114)