However, there is some concern about copper ferrocyanide pigments, and their usage has declined. There is some very interesting work going on to produce new complexes with better environmental profiles, and Gemini are very much involved in this work. The other problems associated with organic pigments are levels of impurities. The German consumer goods ordinance originally restricted the use of many azo ‘colorants’ that were manufactured from various amines. The law was later amended to include a test method for the presence of these amines and almost all pigments met these exacting requirements. The EU has now brought in its own legislation, but it only applies to dyes.
Surfactants
The purpose of the surfactant is to wet out the surface of the pigment, allow the shear processes to divide the pigment agglomerates efficiently and finally to hold the fine particles apart so they do not come back together again (flocculation). The nonyl phenol ethoxylate (NPE) surfactants were effective and cheap. Unfortunately, they are suspected of being endocrine disrupters, i.e. gender benders.
Although the coatings industry uses only relatively small amounts of these products, the industry took a responsible view and offered to cease using them. While in the vast majority of cases they could be replaced without too many problems, there were problems in some of the cheaper binder systems that had poor wetting characteristics, and also in paints that contained high proportions of extenders or with pigment that have a small particle size (carbon black, dioxazine violet, phthalo blue and green). | |
