Stabilising magnetic chromium dioxide pigments - by suspending in aqueous medium, treating with hydrolysable organic silane, and drying

摘要

Stabilisation of magnetic dioxide pigments for prepn. of magnetic registering matls. is effected by (a) suspending the pigment in an aqs. and/or alcoholic medium (b) treating the suspended pigment with a silane of formula RnSi(OR')4-n (where R is a 1-18C org. gp; R' is a 1-8C aliphatic org. gp.; and n is 1-3), or with a hydrolysis prod. of this silane, so that least partly hydrolysed silane is situated on the surface of the pigment, after the latter has been separated from the medium, and (c) drying the separated pigment at 50-200 degrees C. Retain their good magnetic properties, even under unfavourable climatic, e.g. hot and humid conditions. The pigments are also easily dispersed and worked.