| 摘要 |
1,201,962. Linear polyurethanes. GLANZSTOFF A.G. 24 Nov., 1967 [2 Dec., 1966], No. 53516/67. Heading C3R. Linear polyurethanes having a particular viscosity are prepared by forming a pre-adduct having terminal NCO groups by reacting a polymeric diol with a diisocyanate which contains at least one aromatic radical and further reacting the pre-adduct in the presence of a solvent after or during its formation with a mixture of chain extenders comprising 0À15 to 0À85 mol. of one or more diamines and/or hydrazine and/or hydrazine derivatives and 0À1 to 0À8 mol. of a dialkanolamine per mol. of pre-adduct, the sum of the mols. of the chain extenders being smaller than the number of mols, of pre-adduct, and stopping the reaction by adding a monoalcohol when the required viscosity is reached. The pre-adduct is prepared from conventional polymeric diols, e.g. polyethers and polyesters and aromatic diisocyanates and is added to an inert organic solvent, the chain extenders and the monoalcohol being added to the mixture so formed suitably dissolved in the same solvent. Exemplified chain extenders are 1,3-diaminopropane, ethylene diamine, an isomeric mixture of 2,2,4- and 2,4,4-trimethyl-hexamethylene diamine, 1 - amino - 3 - aminomethyl - 3,5.5- trimethyl - cyclohexane, diethanolamine and diisopropanolamine. The monoalcohol may be methanol or ethanol. The pre-adduot may be prepared in the presence of a low M.W. diol. Suitable solvents are toluene and dimethyl - formamide. |
