| 摘要 |
A process for producing rigid polyurethane foams with reduced density by reacting a) organic and/or modified organic polyisocyanates with b) at least one higher-molecular-weight compound having at least two reactive hydrogen atoms and, if desired, c) low-molecular-weight chain extenders and/or crosslinkers in the presence of d) blowing agents, e) catalysts and, if desired, f) other auxiliaries and/or additives, is described, which comprises using, as blowing agent (d), a mixture of cyclopentane with at least one compound which is homogeneously miscible with cyclopentane selected from the class consisting of the alkanes and/or alkenes having 3 or 4 carbon atoms in the molecule and with the carbon dioxide produced from water and isocyanate, and using, as higher-molecular-weight compound (b) having at least two reactive hydrogen atoms, polyethers which contain aromatics and nitrogen. The use of the rigid foams produced in this way as insulating material is also described.
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