| abstract |
Process for making a thermoplastic polyurethane by reacting a mixture comprising at least one polyisocyanate, at least one polyol and fumed silica, wherein (a) in a first reaction step the polyol is reacted in the presence of fumed silica with the polyisocyanate the index factor being 0.95 to 1.00 with a conversion of 95% or more, (b) in a second reaction step additional polyisocyanate is added to the reaction mixture, in an amount that the overall index factor of first and second reaction step is > 1.00 to 1.05, the index factor being defined as isocyanate function quantity / polyol function quantity. |