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(11)

EP 0 433 387 A1

(12)

(43) Date of publication: 26.06.1991 Bulletin 1991/26 (21) Application number: 89910890.0 (22) Date of filing: 12.09.1989

(51) International Patent Classification (IPC):  B01D 39/ 14( . ) B03C 5/ 00( . ) B01D 35/ 06( . ) (86) International application number: PCT/GB1989/001071 (87) International publication number: WO 1990/002595 (22.03.1990 Gazette 1990/07)

(84) Designated Contracting States: CH DE FR GB LI SE (30) Priority: 12.09.1988 GB 19880021270 12.09.1988 GB 19880021271 (71) Applicant: NATIONAL RESEARCH DEVELOPMENT CORPORATION London SE1 6BU (GB)	(72) Inventors: JUDD, Simon, Jon Dorset DT3 6ED (GB) SOLT, George, Stefan Buckinghamshire MK46 5JH (GB) (74) Representative: Chandler, Derek Richard  Patents Department British Technology Group Ltd 101 Newington Causeway London SE1 6BU London SE1 6BU (GB)