Loading patent…
AssigneeTitan Kogyo Kabushiki Kaisha
InventorsHideaki Tokunaga, Koji Nakata, Seiji Shinohara, Noriyuki Itofuji, Kouji Kurosaki, Nobuyuki Hashimoto
Estimating the term…
In a process for producing hydrated iron oxide which comprises the steps of adding an aqueous alkali solution to an aqueous solution of a ferrous salt in an amount no more than a neutralizing equivalent amount with respect to said ferrous salt, oxidizing the resulting ferrous hydroxide containing suspension to produce the seed crystals of hydrated iron oxide and subsequently supplying an additional amount of alkali and oxidizing the hydrated iron oxide to grow, sulfurous acid or a sulfite is added to either the aqueous ferrous salt solution or the aqueous alkali solution or the suspension containing ferrous hydroxide before the oxidation of ferrous hydroxide starts. The resulting hydrated iron oxide may be used as a raw material to produce berthollide, maghemite or a cobalt-doped ferromagnetic iron oxide.
A process for producing hydrated iron oxide comprising the first step of adding an aqueous alkali solution to an aqueous solution of a ferrous salt in an amount no more than a neutralizing equivalent amount with respect to said ferrous salt to form a suspension containing ferrous hydroxide, the second step of oxidizing said suspension to form a suspension containing the seed crystals of hydrated iron oxide and the third step of supplying an additional amount of an alkali to said suspension containing hydrated iron oxide and oxidizing said suspension to have the hydrated iron oxide grow, characterized in that sulfurous acid or a sulfite is added in said first step in an amount of 0.1-10 mol % of the ferrous salt which will be neutralized to precipitate during the reaction of forming the seed crystals.
Dependencies are inferred from the claim text.