Stilbene-based optical brightening agents (OBAs) are used widely in the manufacture of coated and uncoated white paper and board with with around 125,000 tons being produced in countries such as China, Europe, India, Taiwan, and Indonesia.
Chemically, this type of OBAs is based on a diamino-stilbene structure (abbreviated to DAST or DASDA) which derives from toluene through various intermediates. DAST has recently been in short supply as key production units were closed for environmental reasons in China, where the largest production capacity is situated. It is estimated that the current DAST capacity is around 70,000 tons/year.
For paper optical brighteners and the stilbene brighteners used in detergents, the diamino-stilbene is then reacted with cyanuric chloride [CYCL] followed by one of the following: aniline, sulphanilic acid [SANS] or aniline disulphonic acid [ALDS], depending which OBA is required. A schematic of the route to producing OBAs is shown below. OBA Key Materials – website[embeddoc url=”http://www.canda-international.com/wp-content/uploads/2015/05/OBA-Key-Materials-website.pdf” viewer=”google”]