Novel Multi-Phase Acrylics for High Performance Coatings

By Ivan Tyre, Terri Carson

For the past few decades, coatings chemists have been responsible for developing high performance coatings while complying with tightening environmental restrictions, particularly the reduction of volatile organic compound (VOC) content. With the initial restrictions in the early 1990s, a chemist could potentially pull out “extra” solvents such as propylene glycol which enhanced freeze/thaw, flow and leveling, and open time, and reduced the levels of coalescing aids used to lower the minimum film formation temperature (MFFT) of the coatings based on very hard polymers with glass transition temperatures (T_g) in the 40–60ºC range.

As restrictions became even tighter, a strategy employed (and, in some cases, a very effective one) was the blending of soft and hard single phase resins. Care had to be taken with this approach, as film formation with two distinct polymer particles of varied size and MFFT did not always impart desired properties. Clear, haze-free films were not guaranteed¹ and block resistance properties were subject to the ratio and size of the hard polymer to soft particle.² With the advent of computer-controlled reaction vessels, the production of multi-phase particles that have both a soft segment for film formation at lower VOC, along with improved elasticity, and a harder portion for property enhancements such as block and dirt pickup resistance, is possible.

This article does not intend to describe the fine details of manufacturing these resins, but presents a simplified schematic view along with a description of possible morphologies.