GEOPOLYMERIC FLUORO-ALUMINO-SILICATE BINDER AND PROCESS FOR OBTAINING IT.

摘要

PCT No. PCT/FR91/00176 Sec. 371 Date Sep. 2, 1992 Sec. 102(e) Date Sep. 2, 1992 PCT Filed Mar. 5, 1991 PCT Pub. No. WO91/13840 PCT Pub. Date Sep. 19, 1991.A geopolymeric fluoro-alumino-silicate binder is provided which makes it possible to manufacture items with excellent mechanical and heat resistance at temperatures between 250 DEG C. and 650 DEG C. with a variable coefficient of thermal expansion 5.10-6/ DEG C.< DELTA lambda <35.10-6/ DEG C. After curing, the geopolymeric compound thus obtained is a solid solution comprising: a) a geopolymer of the fluoro-alkaline poly(sialate-disiloxo) type (M,F)-PSDS of formula b) an alkaline-alumino-fluoride M3A1F6 such as elpasolite K2NaAlF6; c) a silicious phase SiO2 of the Opal CT type, hydrous SiO2; where "M" represents the cations Na and/or K, and "n" the degree of polymerisation. The process for obtaining fluoro-alumino-silicate geopolymer binders consists of reacting a geopolymeric resin obtained from a reactional mixture containing: a) an aqueous solution of alkaline silicate with a molar ratio M2O:SiO2 comprised between or equal to M2O:SiO2 1:4.0 and 1:6.5 the concentration of which is over 60% wt and where the initial viscosity at 20 DEG C. is 200 centipoises, then increases but does not exceed 500 centipoises before 5 hours at 20 DEG 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, c) sodium fluosilicate Na2SiF6. The mixture of the constituents a)+b)+c) has a water content lower than 30% wt and leads to a geopolymeric resin whose starting viscosity is in the 350-500 centipoises, with oxide molar ratios comprised between or equal to Al2O3:M2O1:1.0 and 1:20 Al2O3:SiO21:5.5 and 1:75, M2O:H2O1:5.0 and 1:12.0 Al2O3:F-1:0.5 and 1:50 and then allowing the geopolymeric resin to cure.