Fireproof glazing

Fire-resistant glazing comprising at least one intumescent layer of hydrated alkali silicate, the thickness of which is not less than 2 mm, which contains water and possibly hydroxylated compounds (H) that are partly substituted for this, said compounds being either glycerine or ethylene glycol, wherein the alkali silicate is a mixed silicate constituent of sodium and potassium complying with one of the following combinations of conditions between the Na2O/M2O molar ratio, the content by weight of water and hydroxylated compounds (W+H) and the RM SiO2/M2O molar ratio (M being the sum of Na and K):

• Na2O/M2O of 67% to 100% and W+H of 40% to 45% RM>3.5 or W+H of 35% to 40% RM>2.75 or W+H of 25% to 35% RM>2.25
• Na2O/M2O of 34% to 66% and W+H of 40% to 45% RM>4.25 or W+H of 35% to 40% RM>4.0 or W+H of 30% to 35% RM>3.75 or W+H of 25% to 30% RM>3.5
• Na2O/M2O of 0% to 33% and W+H of 40% to 45% RM>4.75 or W+H of 35% to 40% RM>4.5 or W+H of 30% to 35% RM>4.25 or W+H of 25% to 30% RM>4.0.

Glazing according to one of the preceding claims, in which the content of glycerine or ethylene glycol of the intumescent layer is in the range of between 2% and 15% by weight.

Glazing according to one of the preceding claims, in which at least 20% of the silica present in the intumescent layer comes from colloidal silica used during the preparation of the composition that leads to the intumescent layer.

Glazing according to one of the preceding claims, in which the intumescent layer is formed from sodium and/or potassium silicate and in addition thereto lithium is present to 10 atom. % at most of all the alkali metals.

Glazing according to one of the preceding claims, in which the SiO2/M2O molar ratio amounts to 3 to 6.

Glazing according to one of the preceding claims, in which the intumescent layer also contains additives in proportions by weight that do not exceed 6% of the entire intumescent layer.

Process for the production of fire-resistant glazing according to one of the preceding claims, in which to produce the intumescent layer, a starting solution is prepared, in which the initial content of water and glycerine and ethylene glycol is at least equal to 50% by weight of this solution, wherein the solution used to form the intumescent layer is brought to the final values by drying after it has been applied to a support or by dehydration preferably in vacuum conducted on the solution itself.

Process according to claim 16?, in which the starting solution is formed at least partially from industrial alkali silicate, wherein the complement results from the reaction of a suspension of colloidal silica and alkali hydroxide.