Highly Water‐Soluble Alpha‐Hydroxyalkylphenone Based Photoinitiator for Low‐Migration Applications

Abstract

In this study, the bifunctional hydroxyketone based photoinitiator (PI) 1,1′‐{[(2,3‐dihydroxybutane‐1,4‐diyl)bis(oxy)]bis(4,1‐phenylene)}bis(2‐hydroxy‐2‐methylpropan‐1‐one) (Di‐PI) is synthesized with the aim to facilitate a highly photoactive water‐soluble PI which offers high migration stability. Di‐PI provides a five times higher water‐solubility than the state of the art water soluble PI 2‐hydroxy‐1‐[3‐(hydroxymethyl)phenyl]‐2‐methyl‐1‐propanone (I2959). Photo differential scanning calorimetry (Photo‐DSC) measurements reveal that the curing speed and conversion of N ‐acroylmorpholine (NAM) in aqueous solution containing 0.5 mol% of Di‐PI are only slightly lower than formulations containing the reference PI I2959 in a concentration of 1 mol%. Most importantly, Di‐PI offers almost identical activity in dipropylene glycol diacrylate (DPDA) as I2959, although its migration from cured DPDA is significantly reduced by a factor of 7.6 compared to I2959. image