Lead free Dryer Having Two Parts

1. Replacement of Lead Octoate Driers:

• Replacement of lead driers by lower toxicity materials began in the 1970?s and a number of alternatives have been proposed over the years. The most effective replacements have been found to be based on strontium and zirconium. Both are successfully used in paint formulations although strontium driers are now considered to have better all-round performance and are less toxic than zirconium driers.
• Zirconium driers are supplied as octoates of different metal concentrations up to 24% metal.
• Strontium driers are supplied as octoates at different metal contents up to 10% metal.
• It should be noted that although zirconium compounds are considered to be less toxic than lead, they have nonetheless been found to be more toxic than strontium compounds.
• Note: Any substitutions of lead drier by zirconium or strontium driers should be carried out based on the levels of lead drier currently used in the formulation and subsequent testing carried out to ensure that the levels are correct.

2. Replacement of Lead Drier by Zirconium:

• Situations may arise where strontium driers are not readily available and there may be a need to replace lead by zirconium driers.
• Compared to lead driers, zirconium driers are considered to be Less toxic than lead. Zirconium was the first identified alternative to lead.
• Recommended levels of substitution are 3 parts zirconium metal to replace 4 parts of lead metal.
• Zirconium driers do not prevent “Loss of Dry” and additional calcium drier or a cobalt "feeder drier" may be needed to maintain drying times after storage.
• The starting point recommendation for replacement of lead by zirconium is as follows:
• 3 parts by weight of zirconium metal replace 4 parts by weight of lead metal in the formulation.
• So, if a paint formulation contains 0.40% w/w lead, based on resin solids, then the replacement zirconium should be added at 0.30% w/w based on resin solids.
• Zirconium driers are supplied in a range of metal contents. In terms of calculating the amount of zirconium drier to add, there are two possible scenarios either zirconium and lead concentrations in the driers are the same or they are different.