ABSTRACT
The HCFC-141b - the dominating blowing agent for rigid polyurethane foam in the United States for a number of years now - will be phased out on January 1st, 2003. New formulations and systems with alternative blowing agents for the variety of insulation foams have to be developed and approved by manufacturers and the necessary adjustments in the production have to be made under a pretty tight schedule. As it is imperative to use the most efficient insulation material to match the requirements of the Department of Energy, HFC-245fa has become an accepted option for the appliance industry in the US, meeting many of the additional requirements, also.
Initial screenings with HFC-245fa, including silicone surfactants, were done to have foam products for basic tests needed to prove the principle suitability of HFC-245fa as a blowing agent. With the change ahead it is urgent now to get back for final optimization of the chemistry and the processing.
Each blowing agent has its very specific properties, some effecting the final foam properties such as vapor thermal conductivity, others being most relevant for processing, such as solubility in the raw materials and the boiling point. All these characteristics have to be addressed in formulating a new system around a blowing agent. Therefore further system modifications are anticipated which will influence the choice of the silicone surfactant.
This paper reports on work being done at Goldschmidt to identify the most important requirements on silicone surfactants in HFC-245fa blown appliance formulations. Information will be provided on questions like: Do we need emulsification of HFC-245fa in the raw materials or in the polymer being formed? How are the typical froth defects minimized? Can we focus on superior nucleation to achieve the finest cell structure and lowest k-factors?
The results of this work will enable us to quickly develop surfactants for the new HFC-245fa blown appliance formulations from the different system suppliers and appliance manufacturers.
