New Type of Bisphenol

About

Background BPA-based epoxies have been and remain the most important coating for lining metal food and beverage cans.  Coatings based on these epoxies display excellent adhesion to metals and corrosion resistance, cause no changes in flavor, enable long shelf lives, are tough and flexible allowing ease of manufacturing, are cost effective, and are compatible with a large variety of food substances.  As a result, BPA-based epoxies are the most important coating by far for the 100 billion food and beverage cans produced in the US each year. In 2011, the global epoxy resin output approximated 2.24 million tons (80%-95% of which were BPA-based materials) and was mainly distributed in Asia, Western Europe and the United States, where their output made up over 90% of the global total. However, consumer preference for canned foods with BPA epoxy coatings has been waning for a decade because of reports that BPA may have adverse effects on health.  BPA and related phenolic compounds have structural similarities to estrogen that are known to create endocrine disrupting potential.  Potential health hazards of endocrine disrupters include various cancers, brain and behavioral changes in fetuses or infants, and female reproductive issues. As a result BPA has been replaced by substitutes for some food contact purposes where suitable substitutes are available.  For instance, polycarbonate-based molded thermoplastic food storage containers, water bottles, blender housings, baby bottles and the like are no longer made from BPA-based polycarbonate because suitable substitutes such as Eastman Chemical’s Tritan are available. Technology UMass Lowell Professor Dan Schmidt has invented a new type of BPA-free epoxy which retains the favorable properties similar to those of bisphenol-based epoxies without need of any phenolic moieties whatsoever.  The new epoxy resin replaces the BPA monomer with CBDO (2,2,4,4-tetramethyl-1,3-cyclobutanedio After hardening with triethylenetetraamine (TETA), a common amine hardener, the low molecular weight CBDO epoxy resin (n < 1) was compared with an equivalent low molecular weight BPA epoxy resin and found to have similar values of glass transition temperature (Tg), Shore D hardness and lap shear adhesion strength to mild steel. The thermal stability of the cured network was measured by thermogravimetric analysis (TGA) and shown to be similar to BPA epoxy. CBDO epoxy is hydrophobic and has very low solubility in water, similar to BPA-epoxy. One difference was the viscosities of the low MW epoxies. The viscosity of CBDO epoxy was much lower than the viscosity of the BPA epoxy. This implies that the higher molecular weight CBDO epoxies (n = 5-10) needed for can coating applications may display lower viscosities vs. their BPA-based counterparts at any given solids content and require less solvent to achieve the same application viscosities used in the can coating industry. Reduced solvent usage could reduce manufacturing costs, associated hazards to workers, the need for engineering controls, cure times, etc. About the Inventor Dr. Daniel Schmidt, Associate Professor in Plastics Engineering, has expertise in polymer cross‐linking and network formation (including sol‐gel techniques), preparation and structure‐processing‐properties relations in polymeric materials and nanocomposites, polymer-derived ceramics and materials analysis, and a strong interest in realizing sustainable solutions wherever possible.