| 摘要 |
A process for preparing a thermoelast having segments A and at least one segment B, with the A segments being crystalline at temperatures of less than approx. 60 degree C and the segment B being amorphous at temperatures of greater than approx. -20 degree C, which segments A are polyethers which are derived from monomers of oxetane and derivatives thereof and/or tetrahydrofuran and derivatives thereof, which process comprises: starting with monofunctional, hydroxylterminated segments A which are crystalline at temperatures of less than approx. 60 degree C and separately starting with bi-, tri- or tetrafunctional, hydroxyl-terminated segments B which are amorphous at temperatures of more than approx. 20 degree C, end-blocking the segments A by separately reacting the segments A with a bifunctional diisocyanate, in which one isocyanate group is at least approx. five times as reactive with the terminal hydroxyl group in the segment A as is the other isocyanate group, as a result of which the more reactive isocyanate group tends to react with the terminal hydroxyl group in the segments A, leaving the less reactive isocyanate group free and unreacted, and adding bi-, trior tetrafunctional segments B to the end-blocked segments A in approximately the stoichiometric proportions in which they are intended to be included in the thermoelast, such that the free and unreacted isocyanate group on the endblocked segment A reacts with a functional group in the segment B with the formation of the thermoelasts ABA or AnB. |
