A synthesis method of benzoxazole based optical brighteners

Abstract

The present invention is a synthesis method for benzoxazole based optical brighteners characterized by comprising the steps of; placing in a reactor vessel at least one acid selected from thiophene-2,5-dicarboxylic acid or stilbene-4,4′-dicarboxylic acid, at least one catalyst and at least one compound selected from liquid paraffin and/or xylene; obtaining a mixture by adding 2-amino-4-tert-butylphenol in the reactor vessel if the said at least one acid is selected as thiophene-2,5-dicarboxylic acid or adding 2-aminophenol in the reactor vessel if the said at least one acid is selected as stilbene-4,4′-dicarboxylic acid; mixing the obtained mixture for a first time period under nitrogen atmosphere to carry out the synthesis reaction of benzoxazole based optical brighteners; during mixing the obtained mixture, increasing the temperature of the said mixture gradually to a first temperature; after mixing obtained mixture for the first time period, filtering the mixture; after filtering the mixture, obtaining a first benzoxazole based optical brightener or a second benzoxazole based optical brightener.

Dependencies are inferred from the claim text.