Claims
- 1. Substantially spherical magnetite particles suitable for use as magnetic toners, having an apparent density of from 0.40 to 1.00 g/cm.sup.3, an oil absorption value of 15 to 21 ml/100 g, a tinting strength (L value) of 33.0 to 37.1, and being thermally stable with respect to the magnetic properties and discoloration of the particles when exposed to temperatures at which the particles lose their magnetic properties and discolor during the production and development of the magnetic toners, and containing from 0.1 to 5.0 atomic % of Si to Fe, said Si being contained in the particles.
- 2. A process for producing substantially spherical magnetite particles suitable for use as magnetic toners, having an apparent density of from 0.40 to 1.00 g/cm.sup.3, an oil absorption value of 15 to 21 ml/100 g, a tinting strength (L value) of 33.0 to 37.1, and being thermally stable with respect to the magnetic properties and discoloration of the particles when exposed to temperatures at which the particles lose their magnetic properties and discolor during the production and development of the magnetic toners and containing from 0.1 to 5.0 atomic % of Si to Fe, said Si being contained in the particle, comprising the steps of:
- (a) oxidizing Fe(OH).sub.2 in an aqueous suspension at a temperature from 70.degree. to 100.degree. C. by blowing an oxygen-containing gas into an aqueous suspension containing colloidal Fe(OH).sub.2 obtained by reacting an aqueous solution of a ferrous salt with an alkali hydroxide of from 0.80 to 0.99 equivalent to Fe.sup.2+ in an aqueous solution of the ferrous salt, wherein a water-soluble silicate is added into the alkali hydroxide or into the aqueous suspension containing colloidal Fe(OH).sub.2 before blowing the oxygen-containing gas thereto in an amount from 0.1 to 5.0 atomic % (calculated as SiO.sub.2 to Fe of the ferrous salt), thereby forming particles of substantially spherical magnetite,
- (b) adding an alkali hydroxide of more than 1.00 equivalent to residual Fe.sup.2+ in an aqueous suspension after the oxidation reaction to the aqueous suspension, and
- (c) subjecting the resultant aqueous suspension to oxidation treatment by blowing an oxygen-containing gas at a temperature from 70.degree. to 100.degree. C.
Priority Claims (1)
Number |
Date |
Country |
Kind |
59-279558 |
Dec 1984 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 07/045,809, filed Apr. 29, 1987, now abandoned, which is a continuation of application Ser. No. 06,714,676, filed Mar. 21, 1985, now abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
802928 |
Fireman |
Oct 1905 |
|
Foreign Referenced Citations (4)
Number |
Date |
Country |
668 |
Jan 1969 |
JPX |
35900 |
Apr 1974 |
JPX |
44298 |
Apr 1976 |
JPX |
2226 |
Jan 1983 |
JPX |
Non-Patent Literature Citations (3)
Entry |
Hunter, "A Multipurpose Photoelectric Reflectometer". J. Opt. Soc. Am., vol. 30, pp. 536-559 (1940). |
Foner, "Versatile and Sensitive Vibrating-Sample Magnetometer", The Review of Scientific Instruments, vol. 30, No. 7, pp. 548-557 (1959). |
Journal of the Japan Society of Powder and Powder Metallurgy--Autumn 1971 Meeting. Translated Summary of Lecture. |
Continuations (2)
|
Number |
Date |
Country |
Parent |
45809 |
Apr 1987 |
|
Parent |
714676 |
Mar 1985 |
|