The invention relates to a composition forming an insulating layer, which composition contains a binder, which is based on a compound having electron-deficient carbon multiple bonds and a carbanion-forming compound. By means of the composition according to the invention, the expansion rate of which is relatively high, coatings having the layer thickness required for the particular fire resistance time can be applied easily and quickly, wherein the layer thickness can be reduced to a minimum and nevertheless a great insulating effect can be achieved. The composition according to the invention is suitable especially for fire protection, in particular as a coating of steel components, such as supports, beams and truss members, for increasing the fire resistance time.

Provided by the present invention is a PVA having highly harmonized adequate water solubility, thickening property and coating film strength, and having superior storage stability in terms of the viscosity in an aqueous solution. A vinyl alcohol polymer having a ratio (Mw (A)/Mn (A)) of the weight average molecular weight (Mw (A)) to the number average molecular weight (Mn (A)) of 3 or greater and 8 or less, and being capable of giving a vinyl alcohol polymer having a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of 2 or greater and less than 3 when treated at 40 C. for 1 hour in a sodium hydroxide solution.

Provided by the present invention is a PVA having highly harmonized adequate water solubility, thickening property and coating film strength, and having superior storage stability in terms of the viscosity in an aqueous solution. A vinyl alcohol polymer having a ratio (Mw (A)/Mn (A)) of the weight average molecular weight (Mw (A)) to the number average molecular weight (Mn (A)) of 3 or greater and 8 or less, and being capable of giving a vinyl alcohol polymer having a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of 2 or greater and less than 3 when treated at 40 C. for 1 hour in a sodium hydroxide solution.