| 摘要 |
The present invention is directed to substantially linear polyurethanes obtained from 1 mol of relatively high molecular weight macrodiols such as polyesters, polyethers and polycarbonates having a molecular weight of 400 to 5000, preferably about 500 to 3000, about 1.5 to 16.5 mols of aromatic diisocyanates, optionally about 0.01 to 1 mol of chain breaking agents in the form of compounds which are monofunctional in their reaction with isocyanates, and about 0.5 to 15 mols of low molecular weight, difunctional chain lengthening agents, characterized in that at least 10 mol-% of the chain lengthening agents is 2,2,4-trimethylpentanediol-(1,3) and the remaining chain lengthening agents, having molecular weights of 62 to 399 (preferably 62 to 250), are preferably diols. The present invention also relates to a process for the preparation of these polyurethanes and to their use for the production of coatings on flexible or non-flexible substrates, wherein the coatings are optionally filled, preferably with magnetizable pigments, and are optionally cross-linked.
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