POLYURETHANES BASED ON ACTIVATEDLACTAM CROSS LINKERS

1350526 Thermoplastic polyaddition products BAYER AG 7 April 1972 [10 April 1971] 16146/72 Heading C3R [Also in Division B2] Linear thermoplastic polyaddition products which are soluble in organic solvents are prepared by reacting (1) a diisocyanate, (2) a dihydroxy compound of M.W. 400 to 8000 and (3) a chain lengthening agent having a M.W. below 400 and being water and/or a diol and/or a diamine and/or a hydrazine or substituted hydrazine, the chain lengthening agent being used in admixture with a lactam of the general formula wherein X represents a CH group, in which case R is hydrogen and m is 0 or an integer from 1 to 9 or X represents a nitrogen atom, in which case R is an aliphatic, araliphatic or pyridine radical and m has a value of 3, the chain lengthening agent and the lactam being employed in a molar ratio of 0À1 to 10 : 1. The diisocyanates (1) and the hydroxyl compounds (2) are those conventionally employed in the art. Numerous chain lengthening agents are listed. Preferred lactams are butyrolactam, valerolactam, 1-N- methyl - hexahydro - 1,4 - diazepinone - (3) and especially #-caprolactam. The reaction is preferably carried out by a prepolymer technique in the presence of solvents or in the melt. In a typical example a prepolymer is formed from hexamethylene diisocyanate and a polyester derived from adipic acid and ethylene glycol and the prepolymer is then reacted in acetone with an addition compound of 1 mol of #-caprolactam and 1À2 mols of water to form a polyurethane-polyurea.