| abstract |
The invention relates to a process for preparing clear aqueous solutions of silicates, remaining stable at 20°C on storage for at least 6 months, containing 20% to 40% by weight SiO 2 , 10% to 20% by weight M 2 O, where M is a cation from the group consisting of Li + , Na + , K + and NY4 + and Y is an alkyl or alkenyl radical having 1 to 6 C atoms, 0.5% to 6% by weight Al 2 O 3 and 100% by weight water, by introducing an aqueous solution of a silicate of the general formula M 2 O x nSiO 2 , in which M is a cation from the group consisting of Li + , Na + , K + and NY4 + , and where Y is an alkyl or alkenyl radical having 1 to 6 C atoms, and n is a number in the range from 1 to 5, and metering in an aluminium compound in such a way that the viscosity of the reaction mixture remains below 10 000 mPas, and the reaction being carried out in a temperature range from 20 to 140°C, with the proviso that, following the metered addition of the total amount of the aluminium compound, the reaction mixture is cooled to room temperature as soon as the reaction mixture is clear. |