| 摘要 |
The alumosilicates of the formula M2O.Al2O3.2.0 to 3.8 SiO2.XH2O, where M and X have the meanings specified in Claim 1, have an oil absorption of at least 75 ml/100 g, a BET area of at least 50 m<2>/g, a settling volume of more than 160.0 kg/m<3>, a void volume as determined by penetration with mercury of more than 2.0 ml/g, a base exchange capacity of at least 200 mg CaCO3/g and an initial water softening rate of 38.6 mg per litre per minute. Their primary particles are spherical and have a size of from 400 to 500 ANGSTROM . In order to prepare the alumosilicates (a) an at most 4-molar aqueous solution of an alkali metal silicate with an SiO2/M2O molar ratio of from 2.2 to 2.8 is prepared, (b) this solution is stirred vigorously in order to expose it to high shearing stress and turbulence, the solution reaching a linear velocity of from 91 to 122 m/min in the process, and at from 15 to 70 DEG C an at most 2-molar solution of an alkali metal aluminate having an M2O/Al2O3 molar ratio of from 1.2 to 2.8 is introduced slowly, (c) the reaction mixture thus formed is stirred further at a precipitation pH of at least 10.5 and (d) the precipitated finely disperse amorphous alkali metal alumosilicate is isolated. The alumosilicates are water softeners which can be used in detergents and cleaning agents. |
