MANUFACTURE OF GAMMA-IRON(III)OXIDE

摘要

1506756 Acidular gamma-iron(III)oxide BASF AG 13 June 1975 [14 June 1974] 25337/75 Heading C1A Acidularγ-Fe 2 O 3 of high coercive force is manufactured by treating an acidular non-magneticα-Fe 2 O 3 or goethite pigment with a liquid medium containing therein an organic compound having a betaine structure, drying the so-treated pigment to form acidular particles coated with the organic compound, heating the dried pigment to a temperature of from 250 to 700‹C. in an inert or reducing atmosphere and oxidizing the so-formed magnetite in an oxidizing atmosphere at a temperature of from 150 to 500‹C. Organic compounds of the general formula: in which R1 and R2 are each independently hydrogen or a C 1 to C 24 alkyl or C 2 to C 24 alkenyl group; R3 is hydrogen or a C 1 to C 24 alkyl or C 2 to C 24 alkenyl group optionally substituted with an anionic group of the formula (RX)-; (RX)- is an aliphatic or aromatic carboxylic acid radical containing not more than 18 carbon atoms, a sulphonic acid radical or a phosphoric acid ester radical; and when more than one (RX)- radical is present they need not be identical. Specified organic compounds are N-oleyl-methylamino acetic acid; N,N-dimethyl-tridecylpropiobetaine and the calcium salt of the betaine of N,N-dimethyl-N- 3-sulphobenzyl-aniline-3-sulphonic acid. Alternatively phosphoric acid aminoalkyl esters (e.g. R 2 HN+-CH 2 -CH 2 OPO 3 H-) or soybean lecithin may be used. Cobalt modifiedγ-Fe 2 O 3 can be obtained by using cobalt modifiedα-Fe 2 O 3 or goethite as starting material.