DEVELOPMENT OF MICROCELLULAR OPEN CELL RIGID POLYURETHANE FOAMS

With the increasing concern over the threat of ozone depletion and global warming, the rigid polyurethane foam insulation industry is facing a major challenge of selecting alternatives for chlorofluorocarbons (CFCs). Under the present situation, however, the effective means of solving this problem haven't been taken yet. Moreover, with more concern with the saving of energy worldwide, there is hope of insulators with higher performance. This paper reports on a micro cellular open cell polyurethane foam, which is very effective as a core material for evacuated insulators. In addition, thermal insulation panels with high performance are developed by utilizing the open cell foam as a core material. The evacuated insulators, so-called ''vacuum insulation panels,'' have an insulation effectiveness four times better than those of the conventional rigid polyurethane and polyisocyanurate foams (thermal conductivity is 0.005 W/mK) and are also very lightweight compared to those made of inorganic substances such as silica powder. The vacuum insulation panels were manufactured by packing the core material and absorbents in a film-like laminated plastic container, which is suitable for holding a vacuum, followed by sealing in the industrial vacuum level (0.01 approximately 0.1 mm Hg). We have developed the micro cellular (100 approximately 200 mum) and 100% open cell foam by selecting polyol compositions, modified polyisocyanates, surfactants and cell opening additives. The micro cellular open cell foam has excellent physical properties such as heat resistance, compressive strength and low shrinkage as well as non-scorch at the stage of slabstock foaming. These properties will be very important for manufacturing the vacuum insulation panels. The open cell foams were blown by using the most conventional and alternative blowing agents in rigid foam systems. In the near future, we hope that this open cell foam technology will contribute to the development of environmentally friendly and high performance products in the insulation industry.