This was a difficult problem to overcome. Within Gemini Dispersions we have not been able to find a single answer; rather we have had to take a product by product approach. This has had economic repercussions too, as most of the replacements are far more expensive. We have yet to find a company offering to pay more for NPE free dispersions!
Humectant
The humectant is required to stop the dispersion drying out. If it dries out on the side of the containers, crumbs break off and fall into the paint - causing streaking. For most applications, monoethylene glycol (MEG) was replaced several years ago. Its physiological properties are inferior to propylene glycol. However, propylene glycol is not acceptable in low VOC (volatile organic compound) paints.
A number of different approaches have been taken to find alternatives, some very novel. However, here at Gemini we believed that the use of carefully formulated polyglycols offered the best solution, and we note that most companies are now following this approach. Two difficulties encountered when replacing MEG or MPG have been the inferior wetting properties of substitutes and therefore a less efficient dispersion process and the fact that MEG or MPG also acted as biocides.
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