Sulfonium Borate Photoinitiators for high performance and low discoloration in Hot Lithography of Epoxy Resins

Abstract

A novel high-temperature 3D printing process called Hot Lithography has enabled the printing of many previously unavailable monomer systems, like the epoxy monomer BADGE. Photoacid generators like sulfonium hexafluorophosphates and perfluorinated tetraphenylborates are well established as initiators for this process. The newly developed sulfonium borate initiator SBCN demonstrates a lower molecular weight and a more cost-effective, scalable synthesis compared to the state of the art. When combined with the epoxy monomer BADGE, which is commonly used in industry, SBCN surpasses commercial initiators across a wide temperature range. Formulations containing SBCN are storage stable even at elevated temperatures and can be sensitized by anthracene derivatives. Hot lithography at 90 °C using the SBCN-BADGE system yields printed parts with excellent layer quality and minimal discoloration compared to state-of-the-art sulfonium initiators.