Process for obtaining a geopolymeric alumino-silicate and products thus obtained

Abstract

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 M.sub.n --(Si--O--Al--O) .sub.n-- or (M)--PS, (sialate) poly M.sub.n --(Si--O--Al--O--Si--O) .sub.n-- or (M)--PSS, (sialate- siloxo) poly M.sub.n --(Si--O--Al--O--Si--O--Si--O) .sub.n-- or (sialate- (M)--PSDS disiloxo). ______________________________________ A process for obtaining a geopolymer of the alkaline poly(sialate-disiloxo) family (M)-PSDS with the ratio Si/Al=3 involves producing geopolymeric resin obtained from a reactional mixture containing: a) an aqueous solution of alkaline silicate with a molar ratio SiO.sub.2 :M.sub.2 O comprised between or equal to SiO.sub.2 :M.sub.2 O 4.0:1 and 6.6:1 the concentration of which is over 60% wt and where the initial viscosity at 20.degree. C. is 200 centipoises, then increases but does not exceed 500 centipoises before 5 hours at 20.degree. C.; b) an alumino-silicate oxide (Si.sub.2 O.sub.5,Al.sub.2 O.sub.2) in which the Al cation is in coordination (IV-V), as determined by the MAS-NMR spectrum for .sup.27 Al, the said oxide being in such a quantity that the molar ratio Al.sub.2 O.sub.3 :SiO.sub.2 is comprised between or equal to Al.sub.2 O.sub.3 :SiO.sub.2 1:5.5 and 1:6.5, and then allowing the geopolymeric resin to 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 fibers or other granular materials are to be impregnated.

Dependencies are inferred from the claim text.