Linear polyurethane hot melt adhesives - prepd. from linear polyester, aliphatic diol chain extender and aromatic diisocyanate

Prepn. of linear, non-crosslinked polyurethane hot melt adhesive softening at 60-115 degrees C, melting at 90-190 degrees C, and having melt flow index 1-15 at 15-120 degrees C or 10-30 at 30-190 degrees C. Process comprises continuously charging a flow-through reactor, which can be heated and cooled with (a) 1 mole linear polyester having mol. wt. 1000-3000 (pref. 2000) and OH-index 42-112 (56), of (i) >=1 aliphatic 6-10C dicarboxylic acids and >=1 aliphatic 2-6C diols, of (ii) lactones of epsilon-hydroxy-carboxylic acids, esp. caprolactone (b) 0.7-2 (0.8-1.5) mol. of aliphatic 2-6C diols as chain-extenders; (c) 0-0.4 (0.04-0.08) mol (w.r.t. sum of components A + B) chain growth regulators consisting of (iii) unbranched satd., aliphatic, monohydric 8-18C alcohols and/or (iv) N-bi-substd. aliphatic aminoalcohols, where alkyl part of aminoalcohol contains 2-4C, in which N-atom is substd. by a benzenesulpho- or toluenesulpho gp. and by an aliphatic 1-4C gp.; and (d) a mol. no. equal to mol. sum of A + B + C (pref. 1.84-2.575 mol) of >=1 aromatic diisocyanates mixed with 0-50 mol % aliphatic diisocyanates. The polyaddition prod. obtd. is continuously discharged from reactor. The polyurethanes are used for hot-sealing substrates under heat and press., esp. for joining non-textile substrates over whole surface or at specific points, e.g. for metal, ceramic and/or glass. Excellent, permanent bonding is achieved. Polyurethanes are stable in molten condition. Softening and melting points are such as to allow use on textiles, furs and leather and to resist dry-cleaning.