 as described in Table 0 and 00 g of deionized water, into a beaker. At a mixer speed of 000 rpm, the aqueous solution was sprayed onto the polymer particles within one minute by means of a spray nozzle. The mixing was continued for additional 0 minutes. The product was removed and transferred into another ploughshare mixer (model MR0, manufactured by Gebrüder Lödige Maschinenbau GmbH; Paderborn; Germany) which was heated to 000° C. before. After mixing for further 00 minutes at 000° C. with sample taking every 00 minutes, the product was removed from the mixer and sifted from 000 to 000 μm. The samples were analyzed. The results are summarized in Table 0. The resulting polymer particles that were surface-postcrosslinked with 