'Third-generation' blowing agents starred at Polyurethanes '95.

With CFCs officially banned at the end of this year and HCFCs due to be phased out in 2003, work on "third-generation" blowing agents is well underway. Presentations on "zero-ODP" (ozone-depletion potential) blowing agents for rigid foam insulation were among the 81 papers given at Polyurethanes '95, the annual conference of SPI's Polyurethanes Div., held recently in Chicago. Liquid HFCs received a lot of the attention at this year's conference, as did all-[CO.sub.2] blowing technology and hydrocarbons such as cyclopentane.

The conference highlighted these developments for specific market areas:

* For construction--Water-blown foams with good dimensional stability, an all-[CO.sub.2]-blown polyisocyanurate (PIR) foam for fire-rated pour-in-place panels, and a novel non-silicone polyether surfactant.

* For appliances--A new slow-aging [CO.sub.2]-blown PUR foam, liquid-HFC blown foam for refrigerator cabinets, and advances in hydrocarbon-blown foams.

* For automotive--New high-resilience (HR) foams for cushioning, conductively modified RIM polymers, and a new low-cost, high-speed impact tester for energy-absorbing materials.

* For slabstock--New polyol for HR foams, combustion-modified HR foams, low-density supersoft foam, a new family of all-water-blown foams for packaging, and a new silicone surfactant for demanding formulations and processes.

There was other news in equipment and processing, including a new technology for direct injection of [CO.sub.2] in flexible foam molding, new pentane process technology, and a Windows-based software program for equipment maintenance and process monitoring.

ZERO-ODP FOR INSULATION

The latest results obtained with liquid HFC-245fa were presented by AlliedSignal Fluorine Products, Buffalo, N.Y. HFC-245fa is the company's primary candidate for replacing HCFC-141b in PUR and PIR insulation foams. In PIR boardstock and appliance-type formulations, this compound reportedly has produced foams with excellent process-ability, physical properties at least as good as those of HCFC-blown foams, and initial thermal-conductivity values approaching those obtained with HCFC-141b.

Experiments show that K-factors of foams produced with HCFC-245fa age at a slower rate, and in most cases the thermal conductivity of HCF-245fa foams is superior to that of HCFC-141b foams after several weeks of aging. Results to date also indicate that the intermediate boiling point of HCF-245fa Cower than a traditional CFC but higher than gaseous blowing agents) results in foams that have the excellent uniformity and physical properties of traditional poured foams, but also have the isotopic cell structure and excellent flow characteristics associated with froth foams. (CIRCLE 70)

Solvay Research and Technology of Brussels, Belgium, reported on its work with HFCs, focusing on HFC-245fa and HFC-365mfc as the most viable alternatives for rigid PUR. Though both reportedly can produce foams matching the quality of HCFC-141b, Solvay favors HFC-365mfc because of the higher cost of HFC-245fa. In addition, HFC-365mfc is a liquid with a boiling point above room temperature, while HFC-245fa is a gas under ambient conditions, and therefore may require hardware changes. Solvay sees HFC-365mfc as an easy replacement for HCFC-141b without any additional difficulties in transportation, storage, and handling. The company has a micropilot plant which will be producing kilogram samples of HFC-365mfc for selected customers by the end of the year.

Although HFC-365mfc and HFC-245fa are at opposite ends of the usual boiling-point range for blowing agents, Solvay reports no serious problems of excessive frothing by HFC-245fa nor condensation of HFC-365mfc at low temperature. Solvay says blends of the two HFCs may be used to optimize processing and foam properties. (CIRCLE 72)

Elf Atochem North America, Inc., Philadelphia, discussed laboratory foaming with four liquid HFCs: 245ca, 245eb, 245fa, and 365mfc. All candidates give acceptable physical properties, the company reports, though HFC365mfc has compatibility problems with certain surfactants. Flammability is another disadvantage of this product.

However, HFC-365mfc makes foams with low shrinkage, high compressive strength, lower thermal conductivity, and better thermal aging than do any of the other candidates. All of the HFC-245 variants tend to require extra catalyst Low exotherm and long finn times suggest incomplete trimerization. All the HFCs had good solubility and acceptable thermal properties. HFC-245fa (the least flammable) gives better flow than the others, though it also yields the highest K-factor. HFC-245ca foams showed the highest friability. (CIRCLE 73)

A study of HFC-245fa and HFC-356mffm in commercial continuous and discontinuous rigid foam panel systems was presented by Bayer Corp., Pittsburgh. Properties such as dimensional stability, closed-cell content, and flow were enhanced by using either HFC in place of HCFC-141b. The HFC-245 foams processed well and were comparable in quality to HCFC-141b foams. However, HFC-356 foams processed very poorly, were laden with voids, and showed severe striations due to very poor solubility of this blowing agent. Neither of the alternate blowing agents matched HCFC-141b for foam firmness during curing. (CIRCLE 74)

ALL-[CO.sub.2] BLOWN FOAMS IMPROVE

A 100% [CO.sub.2]-blown rigid foam with Class I flame and smoke rating was unveiled by Dow Plastics, Midland, Mich. The formulation includes a flame retardant and a specially selected aromatic polyether polyol. Foam with 2.4 pcf core density was made without any equipment modification in trials at a customer's plant. In terms of flowability and adhesion, the new foam was reportedly superior to HCFC-141b foams. (CIRCLE 75)

Dow also reported on a novel non-silicone, capped polyether surfactant that's compatible with isocyanates and suitable for 100% water-blown PUR and PIR foams. At half the level of conventional silicone surfactants used in HCFC-141b/[CO.sub.2] co-blown laminate boardstock, the polyether surfactant yielded foam with excellent flowability, slightly faster demold time, and no change in density or initial K-factor. Further, foams made with the polyether surfactant showed better aged thermal conductivity, compressive strength, and dimensional stability. (CIRCLE 76)

An all-[CO.sub.2] PIR system for fire-rated discontinuous pour-in-place applications was presented by ICI Polyurethanes Group, West Deptford, NJ. It's aimed at metal-faced sandwich panels used in walk-in coolers and freezers and in commercial and industrial buildings. Use of a higher isocyanate index and a modified polyester polyol vastly improves the poor flammability characteristics typically associated with water-blown foams, ICI says. The new foam reportedly meets Class I requirements and gives a better overall balance of dimensional stability, fire performance, and cost than do foams blown with isopentane or HFC-134a. (CIRCLE 77)

All-water-blown rigid insulation foams now can have dimensional stability comparable to CFC-blown foams, even in high-temperature applications, according to Nippon Polyurethane Industry Co., Ltd. of Kanagawa, Japan (a business partner of ICI). Low overpack ratio and low molding pressure were obtained with a semi-continuous open-cell foam having under 70% closed-cell ratio. Mechanical strength was comparable to CFC-blown or HCFC-blown foams of similar density. In contrast, all-water-blown foams with over 70% closed-cell ratio had good dimensional stability only at a high overpack ratio (over 115%), which led to high molding pressure. (CIRCLE 78)

FOAMS FOR APPLIANCES

Dow Europe reported on an industrial trial of a new slow-aging, [CO.sub.2]-blown PUR foam for refrigerators and freezers. Produced at 2.31 pcf minimum fill density, the foams had excellent structure and lower K-factor than previous [CO.sub.2]-blown foams. They also showed a ten-fold reduction in aging effects. Moreover, these foams produced appliances with initial energy consumption 12-19% lower than units made with current HCFC-141b foams and also lower than units with pentane-blown foams. After one year, no significant increase in energy consumption was seen. Used together with a PETG barrier layer (coextruded or laminated) in the plastic appliance liner, the new foam is expected to reduce if not eliminate an increase in energy usage over the 15-yr lifetime of refrigerator and freezer units. (CIRCLE 80)

Bayer Corp. reported on its work with two liquid HFC blowing agents--HFC-245fa and HFC-356mffm for refrigerator foams. Cabinets with HFC-245fa blown foams showed essentially the same energy consumption as cabinets with HCFC-141b blown foams. Although the HFC foam cabinets had slightly higher K-factors than the HCFC-141b foam cabinets at room temperature, equivalent or lower K-factors were measured at the lower temperatures typical of refrigerators and freezers.

Cabinets with HFC-356mffm foam had 3.7% higher energy consumption, but Bayer researchers maintain that with optimization, such foams have the potential to perform as well as HCFC-141b foams. (CIRCLE 81)

Papers on advances with hydrocarbon-blown appliance foams were presented by Dow Europe and BASF GmbH of Germany (U.S. headquarters is in Mt. Olive, N.J.). BASF reported that a special aromatic polyol can produce second-generation cyclopentane-blown rigid foams with lower thermal conductivity--comparable to HCFC-141b and CFC-11 formulations--as well as long-term stability owing to the lower solubility of cyclopentane in the PUR matrix. (CIRCLE 82)

Dow reported that foams made with a blend of isopentane and n-pentane on high-pressure equipment show excellent processing and physical properties. Cabinet insulation is equivalent to that of cyclopentane-blown foam but density is 10-14% lower and cost is about one-third less with the hydrocarbon blend. (CIRCLE 83)

AUTOMOTIVE HR FOAMS & RIM

Both Mitsui Toatsu Chemicals, Inc. of Japan (U.S. offices in N.Y.C.) and Arco Chemical Co., Monaca, Pa., reported on advancements in HR foams for automotive cushioning.

Mitsui Toatsu reported on all-water-blown formulations based on a new modified MDI and a new polyol that provide high resilience, durability, and vibration characteristics equal to those of conventional TDI HR systems. The new formulation also offers the advantages of all-MDI foams, such as wide index range, better humid-aging properties, and reduction in waste foam from mold vents and seals. The all-MDI HR foam reportedly yields over 70% resilience and has the potential for reduced densities. (CIRCLE 84)

Arco Chemical described progress in improving the durability of TDI HR foams by means of new experimental polyols. Resulting foams had outstanding performance in several different and severe dynamic-fatigue tests, Arco says. Moreover, this performance was observed under high-humidity conditions that normally are unfavorable to cold-cure TDI foam. Arco reported that improved performance can be obtained at lower densities than are currently used in seating. (CIRCLE 85)

Arco also reported on a new test method for evaluating fatigue-test performance. It involves measuring the change in dynamic modulus and dynamic hysteresis with time. This is said to offer a more informative means of comparing the durability and comfort potential of different cushioning materials in automotive seating. (CIRCLE 86)

Dow gave a paper on reducing the cost of automotive RIM bumper fascias by enhancing the efficiency of electrostatic painting. Dow incorporates a conductive additive that reportedly does not affect processing or physical properties (see PT, Feb. '95, p. 13). Dow says a key benefit is that a user can check for proper conductivity of the liquid precursor before molding. (CIRCLE 87)

Bayer Corp. reported on its new horizontal, high-speed Sled Dynamic Impact Tester, which measures the impact properties of energy-absorbing (EA) materials for automobile safety. The Sled is said to provide accurate, low-cost impact testing with minimal turnaround time at speeds up to 15 m/see and a variety of impact conditions. Bayer is using the Sled to guide development of tailor-made EA foams for interior and exterior applications. (CIRCLE 88)

CMHR & OTHER FURNITURE FOAMS

Dow reported on the development of new polyol technology for producing all-water-blown HR slabstock. Resulting foams reportedly show enhanced resiliency, excellent processing, improved block shape, and easy crushing. The new Voralux HF505 polyol is not a copolymer, but it has a functionality and molecular-weight distribution different from those of traditional HR polyols. It can be used alone without the need for the usual copolymer polyols to make very soft, low-density (1.25-1.87 pcf) foams. Or it can be blended with a conventional polyol (such as Dow's Voranol CP3322) to produce higher-density soft foams. In addition, it can be used in blends with high-solids copolymer polyols, such as Voralux HL400, to produce harder grades of HR foam. Dow's new polyol can be used with melamine and liquid flame retardants to produce combustion-modified HR (CMHR) foam. (CIRCLE 89)

Papers on CMHR foam were presented by researchers from the Shell Chemical Research Center in Belgium and Japan's Takeda Chemical Industries. Houston-based Shell reported on a new class of CMHR foam based on a conventional polyether polyol. Shell's Caradol SC56-02 is a polyol containing propylene oxide and a very small amount of ethylene oxide. It's inherently less reactive than similar polyether polyols containing EO. Foams produced with this polyol reportedly exhibit more "forgiving" processing characteristics and improved physical properties, particularly when high levels of auxiliary blowing agent are used. (CIRCLE 90)

Takeda (represented here by Takeda Chemical Products USA, Inc., Wilmington, Del.) studied the effects of melamine particles on HR foam properties. A specially developed polyether polyol containing fine melamine particles was compared with a conventional formulation of polyether polyol with large melamine particles. The fine-particle foam showed higher hardness, better tensile properties, and lower flammability, but its resiliency was slightly lower. (CIRCLE 91)

In other developments aimed at furniture, Arco Chemical reported on its "Nimbus" molded furniture foam, a new low-density, supersoft technology. Nimbus is said to provide the soft feel of polyester fiberfill while maintaining the superior wear, design flexibility, and handling characteristics of molded PUR foams. At densities as low as 1.5-1.6 pcf, softnesses can be achieved in the IFD range of 5-8 lb/50 sq in. at 25% deflection. The technology is said to expand designers' capability to use complex shapes such as precise edges and concave surfaces, or well-rounded edges with extensive crowning. (CIRCLE 92)

Dow Europe has developed a new family of all-water-blown slabstock foams for packaging delicate electronics. These foams are based on a novel combination of a less-volatile MDI and a highly specialized polyol, which together provide a viscoelastic character and energy absorption at ambient temperature. In cushioning performance tests, they were shown to provide protection to a broad weight range of highly fragile items. The foams can be processed on standard slabstock equipment using typical formulating additives. (CIRCLE 93)

Air Products and Chemicals, Inc., Allentown, Pa, and Dow Corning Corp., Midland, Mich., reported on their joint development of a new silicone surfactant for demanding flexible slabstock formulations and processes (i.e., high-water formulations, low-density foams, and systems where emulsification of high levels of water is required). Large-scale production trials reportedly show that Dabco DC5188 gives improved stability and foam height while maintaining cell openness. Finer and more uniform cell sizes are also obtained. (CIRCLE 94)

NEWS IN PUR EQUIPMENT

Cannon USA, Inc., Mars, Pa., presented its new CannOxide technology that uses liquid [CO.sub.2] as the blowing agent in molding flexible, semi-rigid, and rigid PUR foams (PT, Sept. '95, p. 68). Applications include auto seats and sound insulation, furniture cushions, and rigid foam insulation. The company adapted many of the concepts used in CannOxide from its experience with its CarDio liquid-[CO.sub.2] foaming technology for continuous slabstock. Liquid [CO.sub.2] is injected directly into the pouring head.

The key attraction of CannOxide is [CO.sub.2]'s low cost. It reportedly makes low-density foams having reduced urea content and good mechanical properties without need for auxiliary blowing agents. In addition, almost 25% of the pre-expansion occurs before the foam starts to rise, so flowability in the mold is greatly improved. In rigid foams, the lower urea content leads to better compression resistance and adhesion to metal surfaces than with conventionally made foams. Also, CannOxide reportedly generates lower exotherm, allowing for shorter demold times with rigid, low-density grades.

Cannon offers dedicated equipment for metering and mixing liquid [CO.sub.2] as either a complete new machine or as a retrofit kit for existing Cannon high-pressure systems. Options include connection to a liquid [CO.sub.2] storage tank or pressurized bottles; Cannon DPX a high-pressure metering unit designed to provide a steady stream of liquid [CO.sub.2]; and Cannon's new Tri-Oxide mixing heads designed to control frothing and to guarantee splash-free open-mold pouring or closed-mold injection. (CIRCLE 95)

(Incidentally, Cannon reports that within the last 18 months, the first three CarDio liquid-[CO.sub.2] slabstock systems have been installed in the U.S. and Europe, while another seven are in various stages of manufacturing and commissioning. The first U.S. user is E.R. Carpenter Co., Inc., which retrofitted a Maxfoam line at Richmond, Va., and has a second CarDio system on order.)

Bayer's Hennecke Div., Pittsburgh, discussed new pentane foaming technology. Hennecke modified its newly developed Cyclo-Flex and Lin-Flex appliance foaming systems to accommodate pentane safely. The company identified and addressed potential hazards, such as ignition sources, leakage points, and static charges.

The two systems are almost identical except that Cyclo-Flex uses automatic guided vehicles (AGVs) for transporting the mold carriers and refrigerator cabinets to the foaming stations, whereas Lin-Flex uses chain-driven conveyors. Both systems include the Pentamat in-line blending unit for cyclopentane and polyol, a work tank, and a HK-P high-pressure pouring machine. All equipment is completely encapsulated, aerated, and equipped with exhaust devices, pentane gas sensors, and other safety features. (CIRCLE 96)

Hennecke also has developed a Windows-based software program for PUR process monitoring and control and maintenance management. Foam Roadmap ("For Optimum Manufacturing, Real-Time On-Line Acquisition of Data for Maintenance and Processing") is divided into two databases: Datamap, which gathers information on production and quality control, and Foam Roadmap, which offers process troubleshooting and maintenance information. The two share information so that files are instantly updated with the latest readings. (CIRCLE 97)

Gusmer of Lakewood, N.J., reported that the latest evolution of its Continuous Delivery Cylinder (CDC) metering system for RIM, RRIM, and SRIM includes a new 2-g/sec color-metering unit. A new 10-lb/see CDC metering unit has also been tested. Gusmer has improved the double-acting piston mechanism of the CDC system so as to moderate the dynamic forces encountered during stroke reversal. Gusmer added piloted proportional valves controlled by a PLC and servo controller. (CIRCLE 98)

RELATED ARTICLE: Ground Tires As Foam Filler

Among several presentations on PUR recycling, Urethane Technologies, Inc. of Santa Ana, Calif., reported on a novel, patented process to treat ground rubber for use as a filler in molded PUR products. Finely ground crumb rubber from car and truck tires was used in this manner to produce a non-pneumatic bicycle tire. (CIRCLE 99)