| 摘要 |
The invention relates to a zeolite A with a high cation exchange capacity, with controlled particle size and controlled whiteness, characterised in that it contains at least one neutral or basic colouring additive, which is soluble or which can be dispersed in acidic medium, capable of modifying its coloration throughout the entire wavelength range of the visible spectrum, for the purpose of improving, in a lasting way, its whiteness properties during its subsequent applications. The colouring additive is an organic or inorganic pigment added in the proportion by weight of at least 5 ppm and preferably of 10 to 50 ppm to the zeolite A during its preparation. The predetermined amount of colouring additive (A1 or A2), chosen in particular from the group of phthalocyanines or of aromatic azo derivatives, is preferably introduced during the crystallisation stage (2) of the zeolite A or during the filtration/washing stage (3) of this zeolite, in so far as the colouring additive is not sufficiently stable in concentrated sodium hydroxide medium. The zeolite A thus obtained is particularly suitable for taking part in the composition of washing powders. <IMAGE> |
