A method for the production of cadmium pigments with a reduced content of acid-soluble cadmium

摘要

In the prepn. of Cd pigments having a reduced acid-soluble Cd content from thermally produced Cd pigment an acid or alkaline aq. suspension or press-cake of the pigments is admixed with pref. 1-10 wt.% (w.r.t. pigment) of alkyl- or alkenyl-(alkoxy)-silanes having formula X-R'-Si(OR)3 or (X-R')2Si(OR)2 (where R' is -(CH2)n- or -(CH2)n-CH=CH-; n = 1-10 and R is 1-4C alkyl). The alk(en)yl gp. is opt. substd. The silane-treated pigments are washed, filtered, dried, esp. at 120-130 degrees C, and ground. Prods. include Cd red and orange contg. 0.01%- and Cd yellow contg. 0.001% acid-soluble Cd. The pigments are water-proofed. Colour strength is improved when used in organophilic binders. Photo-oxidn. is reduced and light-stability and weatherability re improved. In an example, 100 pts. Cd red pigment having compsn. Cd(S0.7898.Se0.2344) were dispersed in 100ml. 3% H2SO4 and treated with a soln. of 7.5 pts. gamma-mercaptopropyl-trimethoxy-silane in 150 pts. 2:1 water/isopropanol. Acid-soluble Cd content was reduced from 0.14% to 0.017%.