Reduced and Zero CFC-11 Rigid Foams for the Appliance Industry

The development of rigid polyurethane (PUR) foams as the best thermal insulation materials has been based on trichlorofluoromethane (CFC-11) as the essential blowing agent, and because of the closed cell nature it remains encapsulated in the cells contributing to the excellent insulation performance during the working life of the foam. However, it is now known that future usage of CFC-11 will be strictly limited as a consequence of international regulations based on environmental concerns. New hydrofluoroalkanes (HFAs) are under development, with HFA-123 and HFA-141b emerging as front runners to replace CFC-11. However, the future of neither of these alternatives is certain, even given the most optimistic progress before 1993. In the meantime the use of CFC-11 as a blowing agent is being progressively reduced as a result of cooperation between regulatory authorities and industry. Consequently our R&D attack on the problem has been divided into three distinct categories. These should be capable of allowing us to provide performance products from now until well into the next century. These are: i) The development of optimised systems in which up to 50% of the conventional CFC-11 blowing agent can be replaced with an equivalent molar amount of carbon dioxide generated by the water/isocyanate reaction. ii) The short term development of totally CFC-11 free optimised systems by using the best currently available blowing agents that have substantially reduced ozone depleting potentials and are safe to handle by the industry. iii) The development of optimised systems based on HFA 123 and HFA 141b.