Patent · US Expired

Magnetic iron oxide pigments and a process for their preparation

US4933014A · kind A · utility

4Cited by

7References

6Claims

0Family size

Assignee

BAYER HEALTHCARE LLC · DE

Inventors

Hendrik Kathrein · McMurray, US
Peter Kiemle · Uerdingen, DE
Fritz Rodi · Moers, DE
Aloys Eiling · Bochum, DE

Key dates

Filing date	Aug 31, 1987
Grant date	Jun 12, 1990
Priority date	—
Expiry date	Aug 31, 2007

Classification

Technology area (CPC Y)Emerging Cross-Sectional Technologies
CPC primaryY10T428/2991
WIPO fieldAudio-visual technology
WIPO sectorElectrical engineering

Abstract

Magnetic iron oxide pigments useful in magnetic signal recordings having a dependence of coercivity on temperature in the temperature range of from 76K to 298K of less than 0.13 kA/mK and having a coercivity on powder compressed to 0.9 g/cm.sup.3 of greater than 51 kA/m are prepared by coating a magnetic iron oxide core material having the composition FeO.sub.x where x is a number from 1.33 to 1.5 in a first step with a compound containing divalent and trivalent iron having a ratio of Fe(III): Fe(II) from 0.01 to less than 2, and then in a second step coating the pre-coated core with a second coating of a cobalt compound.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.