Pigments | colour & masterbatch
no halogen, and then treating it with chlorine to change the blue to green. The low-halogen route to making the equivalent of Pigment Green 7 is to start with the same blue, and mix it with a halogen-free yellow. It is impossible, given the state of today’s technology, to produce an LHC equivalent of Pigment Green 7 that is exactly the same colour as the original, and which has exactly the same properties; companies specifying colours need to accept that this is the case, and that compromise may just have to be
involved in reaching targets. But in the vast majority of applications the difference is acceptable. The differ- ence is also ameliorated by the fact that Pigment Green 7 is frequently used
in combination with other LHC pigments. Is there a down side to the use of LHC pigments?
Not really. As noted, they perform as well as traditional chlorinated pigments, and they are priced in the same range. Just as with halogenated pigments, there are low-end, mid-range and high-end LHC pigments, with prices matching performance. Today, just about every colour shade is available in an LHC version.
Moving away from lead chromate Another bête noire of the pigments industry is lead chromate, the traditional source of bright yellows as well as oranges and reds. In Europe, REACH regula- tions have set 1 May 2015 as the sunset date for production and use of pigments containing this toxic chemical. It is possible, but unlikely, that lead chromate will be registered for use in exceptional circumstances. The dangers of lead chromate have been known for a
long time, and its use has been falling for many years. It is considered a carcinogen, and can cause negative health effects if swallowed or inhaled. Where it has not been possible (or at least desirable) to use an alternative, users have moved away from the pigment in powder form to an
encapsulated dust-free version. PVC compounders, with their stronger traditions in handling powders, have held out for the longest. But even here, as lead-based stabilisation systems have given way to lead-free ones, the possibility of producing totally lead-free compounds has taken on increased importance. In Europe, it has become increasingly diffi cult to
obtain lead chromate locally in any form, as key suppliers have shut down production. In North America too, the phase-out has been going on for around a decade, even though there is nothing on the statute books to demand this happens. It has to be said, however, that in regions such as Asia and South America, the use of lead chromate has not been the subject of such concern as it has in Europe. But in any case, international regulations, such as the
European Union’s EN 71 governing toy safety, and the Council of Europe’s Resolution AP (89) 1 governing the use of colorants in plastics for food contact applications, place restrictions on the use of heavy metals. As with LHC pigments, there are low-end, mid-
The EU’s EN 71 place restric- tions on the use of heavy metals in toys
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