| 摘要 |
The invention relates to hollow blocks containing at least one chamber in which a rigid polyurethane foam which has a density in the range 30-70 g/l and is produced by reacting at least one polyisocyanate a) with at least one compound b) having at least two hydrogen atoms which are reacted towards isocyanate groups in the presence of at least one catalyst d) using at least one blowing agent c) containing at least one blowing agent ci) which develops its blowing action only during the reaction of a) with b) and a blowing agent cii) which has a boiling point below the temperature at which the components a) and b) are mixed is present, where the pressure buildup during the foaming reaction of the polyurethane remains less than 20 kPa, and also the corresponding process for producing the hollow blocks. |
