(19)

(11)

EP 0 646 162 A1

(12)

(43) Date of publication: 05.04.1995 Bulletin 1995/14 (21) Application number: 94912793.0 (22) Date of filing: 17.03.1994

(51) International Patent Classification (IPC):  C11B 3/ 00( . ) C11B 3/ 10( . ) (86) International application number: PCT/US1994/002848 (87) International publication number: WO 1994/021765 (29.09.1994 Gazette 1994/22)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IE IT LI LU MC NL PT SE (30) Priority: 18.03.1993 US 19930032967 (71) Applicant: PQ Corporation Valley Forge, PA 19482 (US)	(72) Inventors: CANESSA, Carlos E. Norristown, PA 19401 (US) SEYBOLD, Jed C. Exton, PA 19341 (US) (74) Representative: Weisert, Annekäte, Dipl.-Ing. Dr.-Ing., et al  Patentanwälte Kraus Weisert & Partner Thomas-Wimmer-Ring 15 D-80539 München D-80539 München (DE)