WATER SOLUBLE AROMATIC ACIDS AS FORMALDEHYDE-FREE CROSSLINKING AGENTS FOR WATERBORNE EPOXY RESINS

摘要

Formaldehyde-free and zero VOC crosslinking agents for waterborne epoxy resins have been developed based on aromatic acid technology. These aromatic acids are derived from the reaction of Amoco trimellitic anhydride (TMA) with ethylene glycol (EG) over a TMA:EG mole ratio of from 2:1 to 2:1.4. The resins produced at these mole ratios form association complexes in water which make them several hundred times more soluble than expected. Similar resins, as well as some purified aromatic anhydrides, have been used as epoxy crosslinking agents in both solvent borne and powder coating systems, and this discovery extends the utility of this chemistry to waterborne systems. Coatings prepared by curing an epoxy dispersion with these water soluble aromatic polycarboxylic acids exhibit excellent mechanical properties, exceptional thermal stability, and good solvent resistance. Under pasteurization conditions the coatings retained excellent mechanical properties, making them good candidates for formaldehyde-free epoxy crosslinkers for coating the interior of beer and beverage cans. By providing better film properties at lower usage levels, these resins offer an attractive alternative to conventional crosslinking agents. The polycarboxylic acid resins are compliant with Title 21 Code of Federal Regulations, part 175.300 for food contact surfaces, are listed in the TSCA and EINECS inventories, and are biodegradable.