to be 30-35% lower than that of cadmium but the opacity and dispersion
characteristics are comparable. All are characterized by excellent heat stability
(up to 2 50°C), as well as having high resistance to weathering and UV light.
Ciba has developed a range of yellow pigments based on bismuth vanadate
(BVA) some of which resist up to 30()°C. This type of pigment is known for its
liveliness and freshness of tint, but heat stability is at present insufficient relative
to the cadmium yellows. BVA yellow pigments are mainly used in semicrystalline
polyolefins (such as HDPE) since they do not show any phenomenon
of warping. Another possible alternative to cadmium yellows, lead chromates,
and diarylid yellows is yellow chromophtal HRP - a brilliant all-round pigment
with very good heat and light stability, which can be used in PVC, polyolefins,
styrenics, and polypropylene fibres.
Clariant has added more than 50 colours to its cadmium-free Universal range,
making a total of 180 colours. Special effects have been extended to include
wood, pearlescence, and edge-glow effects. Colloids has also added 15 stock film
grade colour masterbatches to its existing 35 colours to meet the restriction on
heavy metals in the EC Directive on Waste Packaging, 94/62/EC, Article 11.