(19) | |
| (11) | EP 0 312 032 A3 |
(12) | EUROPEAN PATENT APPLICATION |
(88) | Date of publication A3: | | 23.08.1989 Bulletin 1989/34 |
(43) | Date of publication A2: | | 19.04.1989 Bulletin 1989/16 |
(22) | Date of filing: 12.10.1988 |
| (51) | International Patent Classification (IPC)4: C01B 31/30 |
|
(84) | Designated Contracting States: | | DE FR GB |
(30) | Priority: | 13.10.1987 JP 258986/87
|
(71) | Applicant: DAIKIN INDUSTRIES, LIMITED | | Osaka-shi, Osaka-fu (JP) |
| (72) | Inventors: | | - Kitamura, Ikuo
Kyoto-shi
Kyoto-fu (JP) - Shibuya, Yoshiyuki
Osaka-shi
Osaka-fu (JP) - Shibanuma, Takashi
Kadoma-shi
Osaka-fu (JP) - Daimon, Shigeo
Osaka-shi
Osaka-fu (JP)
|
(74) | Representative: Barz, Peter, Dr. et al | | Patentanwälte Dr. V. Schmied-Kowarzik
Dipl.-Ing. G. Dannenberg
Dr. P. Weinhold Dr. D. Gudel
Dipl.-Ing. S. Schubert Dr. P. Barz
Siegfriedstrasse 8 80803 München 80803 München (DE) |
|
| |
(54) | Iron carbide fine particles and process for preparing the same |
(57) Iron carbide fine particles consisting essentially of iron carbide, which are characterized in that, in the step of the variation of the weight under the condition of combustion, the increase of the weight in the equilibrium after arrival at the maximum weight is 22% or less, on the basis of the weight before combustion. In which (a) after fine particles of iron oxyhydroxide or iron oxide have been or have not been contacted with a reducing gas containing no carbon atom, (b) the particles are contacted with a carburizing gas or a mixture of a carburizing gas and a reducing gas containing no carbon atom at a temperature of from 250 to 395°C to prepare iron carbide fine particles, and (c) the resulting iron carbide fine particles are contacted with a carburizing gas at a temperature higher than the said temperature by 5 to 20°C for 0.5 to 5 hours.