Coated magnetic metal or alloy pigment useful in recording material - has ortho-silicate ester coating to prevent corrosion in humid aid

摘要

Magnetic metal and alloy pigments are coated with 0.2-30 (1-20 esp. 2-15) wt.% orthosilicate ester(s) (I) and/or its hydrolysates and/or condensates. (I) pref. has the formula (RO)nSi(OR')(4-n) (in which R is a 1-20C (cyclo)alkyl or alkenyl gp., which can be branched and/or have one or more 0 bridges in the chain, or an ar(alk)yl gp. R' is an opt. branched 1-4C alkyl gp. n= 0-4, pref. 1-3). Pref. the coating also contains corrosion inhibitor(s) (II), pref. 0.01-5 (0.1-4, esp. 0.5-3) wt.% cpd(s). of the benzotriazole, benzothiazole, benzimidazole, guanidine, amidine and/or metal carboxylate type. The pigments are specified for use in the prodn. of magnetic recording media. The coating provides protection against attack by atmos. O2 and humidity. The coated particles have very good dispersibility and there are no compatibility problems with conventional binders.