(19)

(11)

EP 0 681 556 A1

(12)

(43) Date of publication: 15.11.1995 Bulletin 1995/46 (21) Application number: 93903570.0 (22) Date of filing: 28.01.1993

(51) International Patent Classification (IPC):  C01B 7/ 07( . ) (86) International application number: PCT/US1993/000455 (87) International publication number: WO 1994/016988 (04.08.1994 Gazette 1994/18)

(84) Designated Contracting States: DE ES FR GB IT NL (71) Applicant: E.I. DU PONT DE NEMOURS AND COMPANY Wilmington Delaware 19898 (US)	(72) Inventors: CORBIN, David, R. West Chester, PA 19382 (US) MAHLER, Barry, Asher Glen Mills, PA 19342 (US) (74) Representative: Woodcraft, David Charles, et al  BROOKES & MARTIN High Holborn House 52/54 High Holborn London, WC1V 6SE London, WC1V 6SE (GB)