US4267207A — Process for producing cobalt-containing ferromagn…

Claim 1

Independent Claim 223 words

A process for producing a cobalt-containing ferromagnetic iron oxide powder suitable for magnetic recording which comprises (a) mixing cobalt ion, ferrous ion and an alkali with an aqueous dispersion of acicular ferromagnetic iron oxide nuclei under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation at a temperature of about 50° C. or less; (b) heating the dispersion to a temperature of at least about 60° C. but below the boiling point of the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation to cause a reaction; (c) treating the dispersion at a temperature of at least about 60° C. but below the boiling point of the dispersion under the following conditions: (1) initially treating the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation for about 5 minutes or more; (2) subsequentially treating the dispersion under oxidizing conditions for about 5 minutes or more prior to the termination of the reaction; and (3) a total treating time under non-oxidizing conditions and oxidizing conditions of at least about 30 minutes, said non-oxidizing conditions which completely prevent oxidation being maintained by bubbling nitrogen or an inert gas through said dispersion and said non-oxidizing conditions being maintained continuously from said mixing of said (a) through said initial treating of step (c) (1).

Claim 2

Dependent Claim 223 words

A process for producing a cobalt-containing ferromagnetic iron oxide powder suitable for magnetic recording which comprises (a) mixing cobalt ion, ferrous ion and an alkali with an aqueous dispersion of acicular ferromagnetic iron oxide nuclei under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation at a temperature of about 50° C. or less; (b) heating the dispersion to a temperature of at least about 60° C. but below the boiling point of the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation to cause a reaction; (c) treating the dispersion at a temperature of at least about 60° C. but below the boiling point of the dispersion under the following conditions: (1) initially treating the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation for about 5 minutes or more; (2) subsequentially treating the dispersion under oxidizing conditions for about 5 minutes or more prior to the termination of the reaction; and (3) a total treating time under non-oxidizing conditions and oxidizing conditions of at least about 30 minutes, said non-oxidizing conditions which completely prevent oxidation being maintained by bubbling nitrogen or an inert gas through said dispersion and said non-oxidizing conditions being maintained continuously from said mixing of said (a) through said initial treating of step (c) (1).

Claim 3

Dependent Claim 31 words

The process of claim 1, wherein after the termination of the reaction, the process includes washing the cobalt-containing ferromagnetic iron oxide powder, and then drying the cobalt-containing ferromagnetic iron oxide powder.

Claim 4

Dependent Claim 23 words

The process of claim 2, wherein the washing is carried out until the pH of the washing liquid is about 9.5 or less.

Claim 5

Dependent Claim 21 words

The process of claim 2, wherein the drying is carried out at a temperature of about 40° to about 200° C.

Claim 6

Dependent Claim 33 words

The process of claim 1, wherein the ferromagnetic iron oxide nuclei have an acicular ratio of about 2:1 to about 20:1, and an average particle length of about 0.3 to about 1.5 μm.

Claim 7

Dependent Claim 41 words

The process of claim 1 or 5, wherein the ferromagnetic iron oxide is maghemite, magnetite, a Berthollide iron oxide of the formula FeO x where 1.33<x<1.50, a metallic iron powder at least whose surface is oxidized, or an iron-containing alloy powder.

Claim 8

Dependent Claim 19 words

The process of claim 1, wherein the oxidizing conditions are provided by bubbling an oxygen-containing gas into the dispersion.

Claim 9

Dependent Claim 19 words

The process of claim 1, wherein the oxidizing conditions are provided by adding an oxidizing agent to the dispersion.

Claim 10

Dependent Claim 24 words

The process of claim 9, wherein the amount of the oxidizing agent is about 0.005 to about 0.4 equivalent per equivalent of ferrous ion.

Claim 11

Dependent Claim 15 words

The process of claim 8, wherein the oxidizing agent is nitrate ion or nitrite ion.

Claim 12

Dependent Claim 47 words

The process of claim 10, wherein the source of the nitrate ion is nitric acid, ammonium nitrate, an alkali metal nitrate or an alkaline earth metal nitrate, and the source of the nitrite ion is ammonium nitrate, an alkali metal nitrite or an alkaline earth metal nitrite.

Claim 13

Dependent Claim 28 words

The process of claim 1, wherein the amount of cobalt is at least 1 atomic % based on the entire amount of iron in the ferromagnetic iron oxide.

Claim 14

Dependent Claim 23 words

The process of claim 1, wherein the amount of the ferrous ion is at least equivalent to the amount of the cobalt ion.

Claim 15

Dependent Claim 22 words

The process of claim 1, wherein the source of the cobalt ion is cobalt sulfate, cobalt chloride, cobalt nitrate or cobalt hydroxide.

Claim 16

Dependent Claim 22 words

The process of claim 1, wherein the source of the ferrous ion is ferrous sulfate, ferrous chloride, ferrous nitrate or ferrous hydroxide.

Claim 17

Dependent Claim 38 words

The process of claim 1, wherein the amount of the alkali is such that after neutralization of the cobalt ion and the ferrous ion, the OH - concentration of the reaction mixture is at least about 0.5 N.

Claim 18

Dependent Claim 18 words

The process of claim 1, wherein the alkali is an alkali metal hydroxide or an alkali metal carbonate.

Claim 19

Dependent Claim 228 words

A process for producing a cobalt-containing ferromagnetic iron oxide powder suitable for magnetic recording which consists essentially of the sequential steps of (a) mixing cobalt ion, ferrous ion and alkali with an aqueous dispersion of acicular ferromagnetic iron oxide nuclei under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation at a temperature of about 50° C. or less; (b) heating the dispersion to a temperature of at least about 60° C. but below the boiling point of the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation to cause a reaction; and (c) treating the dispersion at a temperature of at least about 60° C. but below the boiling point of the dispersion under the following conditions: (1) initially treating the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation for about 5 minutes or more: (2) subsequentially treating the dispersion under oxidizing conditions for about 5 minutes or more prior to the termination of the reaction; and (3) a total treating time under non-oxidizing conditions and oxidizing conditions of at least about 30 minutes, said non-oxidizing conditions which completely prevent oxidation being maintained by bubbling nitrogen or inert gas through said dispersion and said non-oxidizing conditions being maintained continuously from said mixing of said (a) through said initial treating of step (c) (1).

Claim 20

Dependent Claim 228 words

A process for producing a cobalt-containing ferromagnetic iron oxide powder suitable for magnetic recording which consists essentially of the sequential steps of (a) mixing cobalt ion, ferrous ion and alkali with an aqueous dispersion of acicular ferromagnetic iron oxide nuclei under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation at a temperature of about 50° C. or less; (b) heating the dispersion to a temperature of at least about 60° C. but below the boiling point of the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation to cause a reaction; and (c) treating the dispersion at a temperature of at least about 60° C. but below the boiling point of the dispersion under the following conditions: (1) initially treating the dispersion under non-oxidizing conditions of nitrogen gas or inert gas which completely prevent oxidation for about 5 minutes or more: (2) subsequentially treating the dispersion under oxidizing conditions for about 5 minutes or more prior to the termination of the reaction; and (3) a total treating time under non-oxidizing conditions and oxidizing conditions of at least about 30 minutes, said non-oxidizing conditions which completely prevent oxidation being maintained by bubbling nitrogen or inert gas through said dispersion and said non-oxidizing conditions being maintained continuously from said mixing of said (a) through said initial treating of step (c) (1).

Claim 21

Dependent Claim 25 words

The process of claim 1 wherein the non-oxidizing conditions in Steps (a), (b) and (c) (1) are maintained by bubbling nitrogen gas through the dispersion.

Claim 22

Dependent Claim 25 words

The process of claim 18 wherein the non-oxidizing conditions in Steps (a), (b) and (c) (1) are maintained by bubbling nitrogen gas through the dispersion.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1984-05-11	1984-11-10	1985-05-12	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1988-05-11	1988-11-10	1989-05-12	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1992-05-11	1992-11-10	1993-05-12	$7700.00	Window Closed / Lapsed

Process for producing cobalt-containing ferromagnetic iron oxide powder

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