Journal of Cellular Plastics

This paper reports the way different combinations of organic acids and tertiary amines work as catalysts in various polyurethane systems. The term "delayed action" is defined with examples of model reactions and commercially available polyurethane formulations. The effects on the reaction parameters in several foam systems and one elastomeric formulation will be presented. From amongst the broad range of amine catalysts we chose the following for our study:

* 33.3% solution of triethylene diamine in dipropylene glycol THANCAT TD 33 A

##

* methylazanorbornane as pure substance THANCAT AN 10 or a 33.3% solution in dipropylene glycol

##

This paper describes the preparation, processing, properties and applications of open cell rigid isocyanurate foams. A mechanism for the formation of open cell rigid foams is discussed. The open cell foams were blown by using a blend of methylene chloride and n-pentane at specific ratios between 95/5 and 50/50 by weight. The resulting foams had open cell contents of about 50-95%, depending upon the reaction conditions employed at densities of 30-50 kg/M³. When pour-in-place foams were further exposed to vacuum after foaming, the resulting foams had an increased open cell content. This open cell foam technology suggests a variety of potential applications, not only for household refrigerators and deep freezers, but also for cryogenic liquid tank insulation, e.g., liquid hydrogen, liquid oxygen, liquid nitrogen, and liquefied natural gas.

In response to the environmental dangers posed by CFC-11 use, rigid polyisocyanurate foam insulation manufacturers are currently making the transition to HCFC-141b. This change has forced manufacturers to requalify their commercial roofing products on the Factory Mutual Calorimeter. Factory Mutual certification is demanded by the marketplace, but the cost of attainment is high. With HCFC-141b technology being perfected, and its eventual replacement looming on the horizon, it is evident a great deal of Calorimeter testing will be required in the near future.

There are a number of small scale tests in existence to measure fire resistance, but their effectiveness as predictors of Calorimeter performance has not been fully assessed. Trimer conversion is a crucial aspect of the fire resistance of polyisocyanurate foam, but a convenient and inexpensive measurement has not been documented. This paper introduces such a novel trimer conversion test, the PIR/PUR ratio.

A high degree of correlation exists between Calorimeter results and the PIR/PUR ratio. Strong correlations also exist between the Calorimeter and certain other small scale tests. However, relying on only one test to predict calorimeter performance is insufficient. Consideration must be given to all relevant tests. Forming a composite index from the individually relevant test results, using weighted factor techniques, provides the best indication of Calorimeter performance.

The information in this paper should enable polyisocyanurate insulation manufacturers to make better predictions of Calorimeter performance, avoiding costly failures.

As we move toward final phaseout of chlorofluorocarbon blowing agents, new compounds and technologies are emerging to produce the polyurethane foams essential to so many products. In considering zero-ozone-depleting compounds that are currently available, the potential hydrofluorocarbon (HFC) candidates are gases at ambient conditions. Development programs are under way to understand feasibility and demonstrate use of one candidate, HFC-134a, to replace CFC-11.

This paper summarizes basic data developed to support commercial process conversion from CFC-11 to HFC-134a. Topics include a comparison of physical properties, results of vapor pressure and solubility studies with different polyols, effects of different surfactants on HFC-134a solubility, confirmation of product stability in foaming applications, B-side system viscosity effects, and materials-of-construction compatibility data.

With respect to processing, the paper summarizes experience developed in modifying equipment to handle higher B-side mixing and storage pressures and discusses effects of process settings on foam quality.

Finally, the paper summarizes results of commercializing 134a/polyurethane foam systems for both insulating and non-insulating applications.

The replacement of blowing agent from CFC-11 to HCFCs is proceeding in rigid polyurethane foam applications in order to meet the revised Montreal Protocol. The foams using HCFCs, however, have about 5 to 10% higher thermal conductivity than that using CFC, owing to the high thermal conductivity of HCFCs. Though improved HCFC blown foams have realized similar thermal conductivity to conventional CFC-11 blown foams, these foams have about 15 to 20% higher densities. This performance level can not be accepted as an insulation foam for refrigeration appliances.

Kao Corporation has developed new catalyst systems, which is Kaolizer KLP-200 series. The use of our new catalysts for HCFC-141b blown foams can realize low thermal conductivity, derived from formation of finer cell structure by acceleration of initial gelling reaction, and has performance to improve flowability in the foaming process at the same time. These characteristics give about 10 to 15% lower density foams than that using conventional catalysts in comparison with similar thermal conductivity. In addition, the formulation using Kaolizer KLP-200K can reduce the level of HCFC-141b compared with that using conventional catalysts to obtain the expected thermal conductivity of the foams, provided these foams have the same density.

This paper describes the effect of Kaolizer KLP-200K for HCFC-141b blown rigid foam. The system using Kaolizer KLP-200K results in lower density foam and reduced HCFC-141b compared to that using conventional catalysts. Moreover, Kaolizer KLP-200 is effective for cyclopentane blown rigid foam.

The industry is continuously being challenged by regulatory agencies to find alternatives to CFCs (chlorofluoro-carbons) for use in all applications. Two solutions investigated were to replace CFCs with HCFCs (hydrochloro-fluorocar-bons or PFAs (perfluoroalkanes). However, the contribution of HCFCs to the depletion of the ozone layer has been determined to be too high for them to be viewed as anything but an intermediate solution. PFAs have been getting attention for their high halogen global warming potential (HGWP) due to their long atmospheric lifetime and, thus, seem unlikely even as additives. At this time, it appears that both HCFCs and PFAs have a finite usage period in our industry.

In our search for alternatives, we have discovered that HFAs (hydrofluoroal-kanes or partially fluorinated alkanes) make fine, closed cell foams. As a result of this, HFA-blown rigid foams at 2.0 pcf density or lower have low initial k-factors (0.13 Btu in./hr ft²⁰F). Aged k-factors are excellent because of the relatively slow cell gas diffusion of HFAs. These insulation values are similar to or better than those of foams made with HCFCs and PFAs! The advantage to this technology is that HFAs have zero-ozone depletion potential (ODP) and relatively low HGWP, making HFAs viable long-term alternatives.

Processing of the alternatives evaluated is similar to HCFC-22 technology, because the HFAs used in this investigation are gases at room temperature and pressure. The HFAs examined in this study were HFA-32, 134a, 125, and 227. These HFAs all show the same characteristics of low solubility, low blowing efficiency, and higher working vapor pressures; therefore, emulsion technology was used (as with PFAs). Good quality foams were produced without utilizing special compatibilizers.