(19)

(11)

EP 0 461 173 A1

(12)

(43) Date of publication: 18.12.1991 Bulletin 1991/51 (21) Application number: 90904397.0 (22) Date of filing: 26.02.1990

(51) International Patent Classification (IPC):  A01C 1/ 06( . ) B02B 1/ 06( . ) (86) International application number: PCT/GB1990/000300 (87) International publication number: WO 1990/009733 (07.09.1990 Gazette 1990/21)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL SE (30) Priority: 28.02.1989 GB 19890004542 (71) Applicant: DOW CHEMICAL COMPANY LIMITED Staines, Middlesex TW18 4SX (GB)	(72) Inventors: MASON, Peter, Robin Huntingdon Cambridgeshire PE17 5JX (GB) CLARKE, Brian Bedfordshire MK45 2PS (GB) (74) Representative: Raynor, John, et al  W.H. Beck, Greener & Co 7 Stone Buildings Lincoln's Inn London WC2A 3SZ London WC2A 3SZ (GB)