| 摘要 |
The invention relates to a process for preparation of rigid polyurethane foams having low thermal conductivity by reacting … … a) organic and/or modified organic polyisocyanates with … b) at least one relatively high molecular weight compound having at least two reactive hydrogen atoms and optionally … c) low molecular weight chain extenders and/or crosslinking agents in the presence of … d) cyclopentane (d1) or mixtures (d2) which contain: … … d2i) cyclopentane and/or cyclohexane and … d2ii) at least one compound which is homogeneously miscible with cyclopentane and/or cyclohexane and preferably has a boiling point below 35 DEG C, selected from the group consisting of the alkanes, cycloalkanes having not more than 4 carbon atoms, dialkyl ethers, cycloalkylene ethers and fluoroalkanes,… optionally in conjunction with water, as blowing agents (d), … … e) catalysts and optionally … f) auxiliaries and/or additives. … …<??>The rigid polyurethane foams are used in the refrigerator industry and as insulating material in heating and composite elements. |
