A study on the synthesis of urethane oligomers

A method of preparation of isocyanate- or hydroxy-terminated urethane oligomers of narrow molecular weight distribution was developed and the products used for preparation of polyurethane elastomers. The method consists of the controlled step-wise reaction of 2,4- and 2,6-toluene diisocyanate (TDI) with butan-1,4-diol (BD) (in the first step) or with polyoxyethylene glycols of molecular weight varying from 200 to 1000 (following steps). All reactions were carried out in bulk. The clue was that the isocyanate- or hydroxy-terminated oligourethanes obtained in a previous step were used as the substrates in the next preparation step where they reacted with an excess of appropriate glycol or TDI, respectively. The unreacted monomer excess was removed by extraction. The products of subsequent steps characterized by spectral analysis IR and NMR and their molecular weight were determined by matrix-assisted laser desorption ionization–time of flight and electrospray ionization mass spectroscopy and gel-permeation chromatography. The oligomers were cross-linked with trifunctional low-molecular chain extenders yielding polyurethane elastomers.