PROCESS FOR OBTAINING A GEOPOLYMERIC ALUMINO SILICATE AND PRODUCTS THUS OBTAINED

摘要

The geopolymeric alumino silicates have been grouped in three families depending on the atomic ratio Si/Al which may be 1, 2 or 3. With the most commonly used simplified notation, a distinction is made between poly(sialate) Mn(-Si-O-Al-O-)n or (M)-PS; poly(sialate-siloxo) Mn(-Si-O-Al-O-Si-O-)n or (M)-PSS; and poly(sialate-disiloxo) Mn(-Si-O-Al-O-Si-O-Si-O-)n or (M)-PSDS. The object of the invention is to describe a process for obtaining a geopolymer of the alkaline poly(sialate-disiloxo) family (M)-PSDS with the ratio Si/Al=3. It consists in reacting a geopolymeric resin obtained from a reactional mixture containing: a) an aqueous solution of alkaline silicate with a molar ratio SiO2:MnO between or equal to SiO2:M2O 4.0:1 and 6.5:1 the concentration of which is over 60 % wt and where the initial viscosity at 20 °C is 200 centipoises, then increases not to exceed 500 centipoises before 5 hours at 20 °C; b) an alumino silicate oxide (Si2O5,Al2O2) in which the Al cation is in coordination (IV-V) as determined by the MAS-NMR spectrum for 27Al, said oxide being in such a quantity that the molar ratio Al¿2?O3:SiO2 is between or equal to 1:5.5 and 1:6.5, and then letting said geopolymeric resin cure. As against the prior art, the fact that there is no need to add fillers to prevent the geopolymeric matrix from cracking makes it possible to keep a very low viscosity in the geopolymeric resin and develop its film-forming property, which is a distinct advantage when fibres or other granular materials are to be impregnated.