Isocyanic acid, polymethylenepolyphenylene ester, polymer with .alpha.-hydro-.omega.-hydroxypolyoxy(methyl-1,2-ethanediyl) ether with 2-ethyl-2-(hydroxymethyl)-1,3-propanediol (3:1) and methyloxirane polymer with oxirane ether with 2-ethyl-2-(hydroxymethy