Long-term environmental solutions drive PUR developments.

Chemical, technical and commercial advancements in replacing CFC blowing agents, whose phaseout in the U.S. is scheduled for December 31,1995, will highlight "Polyurethanes World Congress '93" next month in Vancouver, British Columbia. A total of 84 papers will be presented at this year's conference, cosponsored by SPI's Polyurethane Div., SPI Canada's Rigid Polyurethane Foam Div., and the European Isocyanate Producers Association.

The prevailing theme in at least half the papers is implementation and optimization of CFC-replacement technology, with a strong focus on chlorine-free alternatives with zero ozone-depletion potential (ODP). After the crash programs of the last few years, various industry sources peg current conversion of rigid and flexible foams to alternative blowing-agent technologies at greater than 90%. Now, rigid foam formulators are looking beyond HCFCs, which have come to be regarded as interim solutions they still have some level of ODP, though less than CFCs. Topics to be highlighted at the conference include developments in blowing agents, polyols, flame retardants, antioxidants and surfactants, nearly all of which are geared to aid in production of "zero-ODP" foams. Advancements in urethanes for automotive applications, as well as new developments in processing equipment and recycling will also be addressed.

TOWARD ZERO-ODP RIGID FOAMS

Several companies will give papers on their work with various alternatives to CFC-11 in rigid foams. The alternatives include both HCFCs and zero-ODP replacements such as HFCs, nonfluorinated hydrocarbons such as pentane, and the use of water to generate carbon dioxide.

BASF Corp. Urethanes, Wyandotte, Mich., will give a paper on its evaluation of gaseous HFCs 134a and 227. Results indicate that these blowing agents can produce closed-cell rigid foams with good insulation properties comparable to those of HCFC-blown foams. (CIRCLE 79)

A paper from AlliedSignal Corp., Morristown, N.J., reports on urethane and isocyanurate foams blown with liquid HFCs. Overall, performance of liquid HFCs was determined to be comparable to that of HCFC-141b, although HFCs have reduced solubility and miscibility in polyols. (CIRCLE 80)

DuPont Chemicals, Wilmington, Del., will give a paper summarizing data developed to support conversion from CFC-11 to HFC-134a for insulating and noninsulating applications. Included are a comparison of physical properties, results of vapor-pressure and solubility studies with different polyols, and effects of different surfactants on HFC-134a solubility. (CIRCLE 81)

Solvay S.A. of Belgium, will present results on first experimental runs with a new blowing agent, 1,1,2-trifluoroethane (HFC-143), as a potential replacement for HCFC-141b. A low-boiling liquid this compound is readily soluble in polyols. Except for flammability, says Solvay, all the relevant physico-chemical and environmental characteristics favor HFC-143 over other HFCs. (CIRCLE 82)

Miles Inc., Pittsburgh, and German parent company Bayer AG will have a paper on their work with hexafluorobutane (HFC-356) in appliance foams. Foams blown with HFC-356 meet the technical requirements of the European appliance industry. Miles will report on its current efforts to develop next-generation insulation for North American appliances using HFC-356. Early results indicate HFC-356 holds promise in producing suitable foam density and thermal conductivity. K-factor was only 4% higher than the CFC-11 foam, and 2% above HCFC-141b foam. (CIRCLE 83)

A paper from Dow Europe, Horgen, Switzerland (U.S. offices in Midland, Mich.), reports on evaluations of several potential replacements for CFC-11 in appliance foams. The focus is on formulations based on HFC-134a and cyclopentane, which reportedly offer processing and foam characteristics comparable to 50% CFC-11 systems. (CIRCLE 84)

Italy's EniChem (offices in N.Y.C.) will report on results obtained with improved HFC-134a blown refrigeration foams and its plans to extend the use of this blowing agent to continuous-panel production. (CIRCLE 85)

WORK WITH HYDROCARBONS

Despite their inherent flammability, hydrocarbons such as pentane are gaining interest. Germany's BASF AG has a paper that explores use of cyclopentane in refrigerator foams. Flammability aside, cyclopentane held advantages over HFC-134a in terms of thermal conductivity, foam density, price, and processability. (CIRCLE 86)

Use of hydrocarbons is also being investigated in North America by BASF Corp. for laminate board production. BASF will report on its work to produce Class-I rated isocyanurate foams blown with pentane. Use of a brominated "inerting" co-blower significantly improved the foams, flame resistance. (CIRCLE 87)

Development of pentane-blown PUR and polyisocyanurate (PIR) rigid foams for building insulation is the topic to be discussed by Sumitomo Bayer Urethane of Japan. The company found that highly flame-retardant, pentaneblown PUR and PIR foams had physical properties matching those of CFC-11 blown foams. Small-scale fire tests gave no indication of a higher risk factor than with CFC-11 blown foams. Tests after aging for over three years show pentane remains in the cell gas as long as CFC-11. (CIRCLE 88)

Meanwhile, German processor Liebherr Hausgerate GmbH will report on pentane-blown refrigerator foam that performs as effectively as CFC-11 blown foams. The company determined that pentane can be safely blended into polyols as a premix if the machinery is properly modified. Handling of the premix proved to be much less hazardous than originally expected.

ZERO-ODP INTEGRAL-SKIN FOAMS

BASF Corp. will present results obtained with pentane, HFC-134a, and water in integral-skin applications. According to BASF, pentane produces a well-defined skin with good,physical properties, but flammability is a concern. HFC-134a produces foam with good physical properties and a well-defined skin; however, it is an expensive option and special means of addition must be used because of its low boiling point. Water blowing does not produce a well-defined skin, but with alterations to the isocyanate it can produce foam with satisfactory physical properties, BASF found. (CIRCLE 89)

New rigid composite integral-skin foam produced without CFCs or HFCs is the topic of a paper from EniChem. The skin is produced by a rotational molding technology and the core by a conventional water-blown low-density foam. Rear spoilers for cars were made this way with reportedly excellent appearance. Weight reductions of 27 50% were achieved and scratch resistance was greatly improved, compared with conventional metal-reinforced, integralskin foams. (CIRCLE 90)

IMPROVED WATER-BLOWN RIGIDS

Another approach to zero ODP is the use of water to generate carbon dioxide by reaction with isocyanate. Problems associated with earlier water-blown rigid foams have included higher thermal conductivity, higher foaming pressure, lower dimensional stability, and poor adhesion because of surface friability. Progress in overcoming these limitations will be reported by ICI Polyurethanes, Deptford, N.J., which developed second-generation [CO.sub.2]-blown systems for rigid pour-in-place applications. (CIRCLE 91)

A proprietary family of additives that act as cell openers in completely water-blown rigid foams will be introduced by BASF Corp. Dimensionally stable, water-blown, free-rise rigid foams were prepared with densities as low as 0.90 pcf; little or no volume change (less than 5%) was seen even after 4-6 weeks at 158 F and 100% R.H. (CIRCLE 92)

Data on new types of polyols that give lower permeability in [CO.sub.2]-blown, closed-cell rigid foams is the focus of a paper from Dow Plastics. Foams made from these low-permeability polyols retain the [CO.sub.2] in the foam cells for longer periods than do foams made with conventional polyether polyols, resulting in better retention of insulating properties. (CIRCLE 93)

Miles will report on a novel polyol that was combined with a unique catalyst and surfactant package to produce a [CO.sub.2]-blown PUR foam for insulating water heaters. The resulting product has excellent dimensional stability at a variety of aging, temperature and humidity conditions, along with a more uniform and finer cell structure. (CIRCLE 94)

Eastman Chemical Co., Kingsport, Tenn., will present details on a way to reduce polyol viscosity when using blowing agents such as [CO.sub.2] and HCFC-141b, which increase the viscosity of a resin. The method involves substituting hydroxyl groups with acetoacetate groups, which leads to a reduction in hydrogen bonding. This results in the polyol having lower viscosity but the same functionality as the original polyol. Results have shown up to 95% viscosity reduction can be achieved. (CIRCLE 95)

NEW POLYOLS FOR FLEXIBLES

Advancements in polyol technology to accommodate CFC replacement and new foaming equipment technologies are a dominant theme of the papers on flexible foams. Arco Chemical Co., Newtown Square, Pa., will present a new flame-retardant polyol, Arcol DP 100-9204. This experimental high performance polyol for combustion modified high-resilience (CMHR) foams has been shown to minimize or overcome several of the negative aspects of solid flame-retardant additives such as melamine. Foams made with this polyol do not require any melamine to pass the British flammability test (BS 5852 Part 2, Source 5), and the need for melamine to pass the California TB 133 standard with a wide range of fabrics can be reduced or completely eliminated without the use of interliners. (CIRCLE 96)

Arco will also introduce a novel high-load polymer polyol for carpet underlay. The new polyol is said to overcome a key deficiency that has plagued flexible PURfoams of high hardness--namely, fatigue losses that limited their use in carpet pads. Arco says its new polyol allows formulation adjustments that produce the same densities and hardnesses as traditional foams but at significantly reduced TDI indexes (100-110 instead of commonly used 115-120 values). (CIRCLE 97)

A paper from EniChem shows that flame-retardant HR foams with good physical properties can be produced at low densities and without use of phospho-halogenated additives. Formulations based on developmental polyether polyol MW-6000, which contains a low level of a new fine-particle melamine, in combination with a modified TDI (Tedimont 173) produced foams that met stringent flammability tests and retained all mechanical and processing characteristics. (CIRCLE 98)

A paper on new TDI- and MDI- based technologies for producing HR slabstock will be given by Dow Europe. The focus is on a new generation of high-performance polyols and copolymer polyols that can significantly broaden the quality and grade versatility of current HR slabstock technologies. Included are softback-restgrades using [CO.sub.2] as the sole blowing agent. (CIRCLE 99)

Dow Plastics will present data on pilot-scale evaluations of new polyols and polymer modifiers that yield foams with good integrity at indexes as low as 80 and water levels as high as 6.5 php. They also increase the range of foam grades that can be made with water as the sole blowing agent. (CIRCLE 100)

OTHER ADVANCES IN FLEXIBLES

A novel approach to producing low-density, CFC-free flexible foams is described in a paper from EniChem. It involves use of a new chemical intermediate, described as a nontoxic, nonhalogenated organic compound specially designed to obtain foams with excellent physical properties. In hot molding it's said to provide further density reduction without modification of water level, while retaining physical and mechanical performance of TDI-based molded foams. (CIRCLE 101)

Uniroyal Chemical Co., Inc., Middlebury, Conn. will report on a new, less volatile liquid hindered-phenolic antioxidant that provides performance equivalent to BHT in polyether flexible foams. When used at the same levels as BHT, it reportedly provides equivalent scorch performance. Advantages in physical characteristics and properties of the finished foam are also reported. (CIRCLE 102)

Use of forced cooling as a method for eliminating blowing agents from flexible slabstock foam is the topic of a paper from Dow Plastics. The process is said to overcome many of the common problems related to discoloration and physical-property loss in traditional low-density water-blown foams. Fundamental parameters of this process are discussed, including foam degradation vs. time, color formation vs. time, and selection of amine catalyst, polymer modifier, and polyol. Dow's paper identifies two polyols--XUS-15203.02 and Experimental Polyol A--that have shown better properties than standard polyols in a forced-cooling system. (CIRCLE 103)

A paper by General Foam, div. of PMC, Inc., West Hazelton, Pa, discusses a "Rapid Cure" process for cooling high-water flexible foams made without auxiliary blowing agents. The process has been adapted to the company's existing Maxfoam equipment and has been in fullscale continuous use for more than a year.

NEW SURFACTANTS

German supplier Th. Goldschmidt AG (offices in Hopewell, Va.) will report on new silicone surfactants for rigid insulation foams blown with either HFC-134a or cyclopentane. Special attention was paid to the emulsification properties of the surfactants and preventing loss of nucleation potency or stabilization of the foam during expansion. In systems blown with HFC-134a, new Tegostab B 8465 surfactant gave the best overall processing and foam properties. In cyclopentane-blown foams, new Tegostab B 8455 is the best stabilizer when emulsification of the blowing agent is required. (CIRCLE 104)

Air Products & Chemicals, Inc., Allentown, Pa., will discuss a new surfactant that improves solubilization and compatibilization of pentane in water co-blown rigid foams for appliances. Experimental silicone surfactant XFH25-73 showed excellent performance while maintaining pentane levels in the foam during foaming and aging. In flammability tests, XF-H25-73 demonstrated superior performance in formulations where the pentane was soluble within the polyol preblend. (Soluble formulations consistently yielded better flammability results than formulations where the pentane was only partially soluble and was emulsified into the preblend.) (CIRCLE 105)

A new silicone surfactant for HR slabstock will be featured by Union Carbide Chemicals & Plastics Europe (U.S. office in Danbury, Conn.). Silicone Surfactant L-2100 was developed to meet recent European foam flammability regulations that require melamine and various flame retardants, plus high surfactant performance. Benefits include broad processing latitude, lower compression set, enhanced stability and resiliency. (CIRCLE 106)

AUTOMOTIVE DEVELOPMENTS

A paper from Miles Inc. says cost-effectiveness of RRIM auto fascias can be improved with a new Bayflex RIM polyurethane elastomer, density-reduction technology, and mineral fillers such as Wollastonite, which offer reinforcing characteristics similar to glass fiber. (CIRCLE 107)

Texaco Chemical Co., Austin, Tex.. will report on polyurea foams made with certain high-molecular-weight, amine-terminated polyethers. These foams were molded with high-pressure impingement mixing in a manner similar to RIM. Certain property and processing advantages are said to make these foams excellent candidates for automotive uses. For example, fast-gelling foam systems can be obtained, eliminating need for a gelation catalyst. Also, polyurea foam is more hydrophobic than typical polyurethane foams and less sensitive to the effects of water on the foam. (CIRCLE 108)

A range of new energy-absorbing systems for interior applications including rigid, semirigid, and viscoelastic foams, is introduced in a paper from ICI Polyurethanes. All are CFC-free, waterblown and low-density. The rigid foam is a good candidate for knee-impact protection, while semirigid and viscoelastic foams are suited to sideimpact and head-impact protection. (CIRCLE 109)

Miles will report on new technology for producing energy-absorbing polyurethanes for automotive components, vibration-damping elements, and shoe insoles. Without under-indexing or use of plasticizers, this technology allows formulating for good physical properties over a wide hardness range and outstanding energy absorption over a broad range of temperatures and frequencies. (CIRCLE 110)

Technological advances in cast PUR foam for automotive acoustical applications, presented by ICI Polyurethanes, reportedly make the economics of this technology increasingly competitive with traditional sound-deadening media (i.e., slabstock foam in dash insulators and shoddy pad in carpet). Advantages include density reduction from 5.0 pcf to 4.0 pcf without the use of CFCs, and demold time reduction from 5.0 min to 2.0-2.5 min. (CIRCLE 111)

ICI Polyurethanes also has a paper on advances in formulating rapid-reactivity (creamfoam) PUR for pour-in-fabric auto-interior soft trim. Advantages include density reductions without the use of CFCs (from 3.0 to 2.2 pcf); demold times as low as 30-40 sec; and ability to produce a wide range of firmness. (CIRCLE 112)

RECYCLlNG ADVANCES

Developments in recycling RIM urethane polymers and composites into primary and secondary uses are the focus of a paper from Dow Plastics. In Europe, RIM parts containing RIM regrind powder have been made with automotive Class-A surfaces, and other parts have been compression molded from RIM granulate, Dow reports. The company anticipates imminent commercial use of RIM regrind in North American OEM fascias. Dow's presentation will highlight refinements in the technology, alternative approaches, and approximate costs to configure RIM machines for three-stream regrind processing. (CIRCLE 113)

The Department of Chemical Engineering at Illinois Institute of Technology, Chicago, will report on an energy-saving, continuous method of solid-state shear extrusion (SSSE) for pulverizing flexible and rigid polyurethane foam wastes. The technology uses standard extrusion equipment from the extruder in a broad range of particle sizes (20-200 microns), shapes (aspect ratios of 1:2 to 1:10), densities (1 pcf up to solid) and rigidities (highly resilient to rigid). The resulting powders can be used as fillers in polystyrene and PVC.

NEW PROCESSING EQUIPMENT

Miles Inc.'s Hennecke Machinery Div. will report on its new, patented Deltamat device, now being introduced into North America, for metering lowboiling-point blowing agents HCFC-22 and 141b. A brand-new adaptation of Deltamat, called Pentamat, reportedly allows safe handling of cyclopentane. Both devices, induced-flow metering prevents leakage, reduces lubrication requirements, and allows use of corrosive or flammable blowing agents. (CIRCLE 114)

Martin Marietta Manned Space Systems, New Orleans, will present new developments in spray guns for rigid foam in critical applications such as insulating external tanks on the Space Shuttle. The most promising of several new spray-gun concepts tested was a rotary-valve gun that the company says is likely to be transferable to other applications where critical process control and reliability are required. (CIRCLE 115)

Klockner Ferromatik Desma, Erlanger, Ky., will introduce a new Desma self-cleaning mix head for low-pressure, mechanical-mixing equipment. This option eliminates the need to flush the head but retains advantages of mechanical mixing in the production of smaller parts and in mixing difficult systems. For cleaning, the mixing screw moves forward along the axis of rotation to decrease the distance between the screw and the tapered wall of the mixing chamber Centrifugal force and shear act to extrude residue from the mixing chamber. (CIRCLE 116)