| 摘要 |
<p>A method for the preparation of a composition for use in paper making or pigment coating compositions containing also an optical brightening agent (OBA) includes the steps of (a) preparing an aqueous suspension of a clay mineral comprising a kaolin particulate material; and (b) treating the clay mineral by addition of a treatment agent which reduces the harmful effect of metal ions present in the clay mineral on the activity of the OBA, the treatment agent being substantially free of multivalent cations and comprising (i) a complexing agent or (ii) formamidine sulfinic acid (FAS).</p> |
