| abstract |
The present invention relates to a process for the production of rigid polyurethane foams having a content of aromatic radicals of at least 32% by weight which are incorporated into formative components (a), (b) and/or (c) and reduce the thermal conductivity of the polyurethane matrix, by reacting a) modified or unmodified organic, preferably aromatic polyisocyanates with b) at least one relatively high-molecular-weight compound containing at least two reactive hydrogen atoms and preferably containing arylene units, and, if desired, c) low-molecular-weight chain extenders and/or crosslinking agents, in the presence of d) blowing agents, preferably cyclopentane and/or cyclohexane, in combination with water, e) catalysts, and, if desired, f) additives. The rigid polyurethane foams are preferably used as insulating materials in the refrigeration equipment industry and as insulating materials in heating and composite elements. |