2-Oxepanone, polymer with 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, .alpha.-hydro-.omega.-hydroxypoly(oxy-1,2-ethanediyl) and 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane, 2-hydroxyethyl acrylate-blocked