Abstract: A method for making a bloom-free thermoplastic polyurethane is disclosed. The method entails blending a chain terminator such as monofunctional alkylene alcohol having at least 14 carbon atoms, mono-isocyanate and mono-amine, in a thermoplastic polyurethane that would, but for the blending of the chain terminator of the invention, feature a blooming defect. The polyurethane suitable for the use in the inventive process is the product of a reaction wherein reactants comprise (i) at least one hydroxy functional polyol such as polyester polyol, polyether polyol and polycarbonate polyol, having a number average molecular weight of 500 to 5000 and a hydroxyl functionality of at least 2, (ii) a chain extending compound, and (iii) an organic diisocyanate. The ratio NCO/H characterizing the relative amounts of named reactants is 0.95 to 1.05. The addition of the chain terminator renders the product bloom-free.

Abstract: Blooming in certain thermoplastic polyurethane products is substantially or completely eliminated by including a chain terminator. More specifically, at least one hydroxy functional polyester polyol having a molecular weight of at least 500 and a hydroxyl functionality of at least 2, a chain extender and an organic diisocyanate are combined with a chain terminator. The chain terminator which is preferably a monofunctional compound that is reactive with an isocyanate. These reactants are used in amounts such that the of NCO/H index of the formulation is at or near 100.