Lothar Zipfel

HFC-365mfc and HFC-245fa progress in application of new HFC blowing agents

For a few years now we have regularly reported our progress in the evaluation of possible 3rd generation blowing agents, and we have come to the conclusion that HFC-245fa and HFC-365mfc are the two leading candidates. Previous work included lab scale evaluation of foam samples, measurements of the main relevant physico-chemical characteristics, as well as a thorough evaluation of the chemical stability of HFC-365mfc and HFC-245fa in rigid polyurethane foams [1]. With larger quantities now available from our micropilot plant in Hannover, Germany, we have been able to enlarge our knowledge of HFC-365mfc to allow a sound comparison with the data already available for HFC-245fa. In particular, physico-chemical characteristics have been refined and new ones have been measured; the evaluation of the chronic toxicity of HFC-365mfc is ongoing with first data reported here. Most importantly, additional lab scale tests and large scale trials on industrial lines have been performed to allow an in-depth study of performances in rigid polyurethane foams. This paper completes our previous reports to offer the unique comprehensive comparison of HFC-365mfc and HFC-245fa.

The Next Generation Blowing Agents: From One Single Product to a Product Range

In the context of the HCFC-141b phase out, the two candidates HFC-365mfc and HFC-245fa have been selected over the last few years, as reported in previous papers. Since our last presentation, a lot of work has been performed to increase our knowledge of these new products and to study their behavior in various applications. Although HFC-365mfc and HFC-245fa are promising candidates, a single HFC blowing agent cannot match all the outstanding characteristics of traditional fluorocarbon blowing agents: right boiling point, non flammability, cost effectiveness..., to name but a few. It is very unlikely that a single blowing agent will cover all the future needs of the polyurethane industry. Such a trend is already seen today with at least seven physical blowing agents finding commercial applications in the different sectors of the industry (HCFC-141b, HCFC-22/HCFC-142b, HFC-134a, cyclopentane, pentane or isopentane). The main reason why HFC blowing agents will be used in the future is their ability to give foams with optimized thermal conductivity. However, because of possible condensation phenomena at low temperature for relatively high boiling blowing agents, the rating of different blowing agents is a function of temperature. We have now measured foam thermal conductivity over the temperature range between -20°C and +45°C for several blowing agents, including HFC-245fa, HFC-365mfc, pentane isomers and blends thereof. Included in this study are the newly discovered low boiling azeotropes of HFC-365mfc with all three pentane isomers. In this paper, we will especially show that the evolution of thermal conductivity with temperature can be a very good selection criteria to find the most appropriate blend for a specific application.

HFC-365mfc Blends: Status and Development as Blowing Agent for High Performance Insulation Foams

The recent developments confirm that HFC-365mfc is a very attractive blowing agent option, especially if we consider the various blends which have been developed to meet customers needs, for example non-flammability in a blend withHFC-134a or k-value improvement for hydrocarbon blown foams. The non-flammable blend HFC-365mfc/134a is an option for the construction market, notably for systems, for spray and for pour-in-place foams and is a direct replacement for HCFC-141b; as this blend is a mixture, there is an important difference compared to HCFC-141b. The special behavior during storage and handling will be explained, including details regarding its safety status.We will report our experience for a safe application and about new results in foams. For cost-drive markets, where explosively flammable options are acceptable, blends of HFC-365mfc with hydrocarbons are an attractive way to improve the k-value of foams. This paper will report the outstanding versatility of HFC-365mfc to provide the construction foam industry with a solution for all markets. The full commercialization of HFC-365mfc is scheduled for the end of the year 2002.

HFC-365mfc: A Versatile Blowing Agent for Rigid Polyurethane Foams

HFC-365mfc and HFC-245fa are now well documented as promising blowing agents, and their production will come on stream in a few years. However, none has the same ideal boiling point as CFC-11 or HCFC-141b. Blends may offer the best compromise to customize the different end-use requirements. Two different directions for further developments have emerged from our work: Two binary, non-azeotropic blends of HFC-365mfc with HFC-245fa or HFC-134a open the door to non-flammable blowing agents with a convenient boiling point in the range of 20 to 25°C (depending on actual composition) and a very good gas phase thermal conductivity. These new blowing agents could be safely used in the same manner as CFC-11 or HCFC-141b, but would be the most expensive option in the series of blowing agents currently under examination. It would fit the needs of foamers looking especially for non flammability (ease of handling, low investments) and optimized foam thermal conductivity. Three low boiling, binary azeotropes have been found with HFC-365mfc and the three pentane isomers (n-, iso-, and cyclo-pentane). Although these azeotropes are flammable, they open the door to more cost effective formulations with improved properties over formulations blown with straight pentane. It is anticipated that each mixed blowing agent now under investigation will find applications in specific end-uses. HFC-365mfc appears to be a key building block to design a full range of blowing agents which offers a wide flexibility to system houses and polyurethane foamers, both in the direction of non flammable or flammable blowing agents. Semi industrial trials with the blends and industrial trials with straight HFC-365mfc are reported as a practice related example of the suitability of these blowing agents.

Analysis of the Evolution of PIR Foams in the Context of the Phase Out of HCFCs

PIR foams are known for their outstanding fire properties and for their good insulation performances. The fire behavior can be attributed to the aromatic structure of the isocyanurate ring and to the nonflammability of the blowing agent that is used nowadays. For environmental reasons, HCFC-141b will have to be phased out as of 01.01.2003 for the production of PIR laminates boards, in Europe and in the United States. This evolution represents a challenge for the producers as they need to find a high performance alternative in a relatively short period of time. As a major requirement, this alternative will have to maintain the properties of the PIR foams, notably the fire behavior and the k-value at a high quality level. Several blowing agent alternatives have been presented, and some of them have already been implemented in production plants. Among them, pentane is seen as a candidate for economical reasons, but because of its high flammability, its use shows some limitations. The nonflammable alternative HFC-365mfc/HFC-227ea has proven to be an interesting alternative to obtain a good insulation value and good fire properties. Besides, the existence of azeotropic blends between HFC-365mfc and the pentane isomers increases the degree of freedom of the system and makes the optimization process easier. When using the right combination of blowing agent, it is possible to reach an interesting compromise between the insulation characteristics, the fire performance and the cost of the system. An analysis of properties of PIR foams produced with the several alternatives will be presented in this paper.

Optimization of formulations based on HFC-365mfc and blends thereof

As already mentioned in our last SPI publications, HFC-365mfc has to be considered as a key building block for a new generation of blowing agents. Interesting blends have been identified in order to answer the demand of the various segments of the rigid foam market. New PU formulations based on HFC-365mfc and blends have now been developed for the laboratory scale. Whilst the use of HCFC-141b was found to be easy thanks to its good solubility characteristics in standard polyols, the use of HFCs, notably HFC-365mfc is more difficult. Indeed, because of their low polarity, the solubility of HFCs in most standard polyols is limited. This is advantageous for dimensional stability but means that the systems that are being used now will need to be adapted in order to obtain a homogeneous polyol blend. In this paper, we report on ways to increase the compatibility of HFC-365mfc and blends thereof with polyol systems. The evaluation of foams obtained from these new systems has also been performed in order to allow the selection of the most appropriate combination for a given application. Foaming trials using the non flammable blend HFC-365mfc/HFC-134a will be presented, especially for spray foam, and one trial using the azeotrope HFC-365mfc/n-pentane for PIR laminates. The main properties being reported are notably the resulting pressure above system premixes, the dimensional stability and the foam thermal conductivity. SOLVAY have taken the decision to start a pilot plant for HFC-365 mfc in September 1999, and commercial production is planned to come on stream in the year 2002.

1,1,2-Trifluoroethane (HFC-143):Zero-ODP Blowing Agent for Rigid Polyurethane Foams Using Conventional Dispensing Equipment

For the time being, it is indisputable that the prime blowing agent for rigid polyurethane foams is HCFC-141b. Nevertheless, this transitional substance is already subject to growing political pressure which will lead to restriction of its use early in the 21st century. Additional efforts are needed to identify zero-ODP blowing agents. Solvay has undertaken a thorough screening of 1,1,2-trifluoroethane (HFC-143), a compound which probably represents the best compromise among zero-ODP fluorocarbons for blowing rigid PUR foams. In this contribution we present evidence for the environmental acceptability of HFC-143, and we discuss its suitability as a PUR blowing agent; in both cases advantages over other possible alternatives are stressed. Results more specifically pertinent to rigid polyurethane foam blowing indicate that under given conditions and for a given formulation, HFC-143 can be processed much more easily than HFC-134a. In this regard, whilst HFC-134a requires a completely new technology, HFC-143 can be considered to be a practically drop-in substitute for HCFC-22/HCFC-142b blends.