Acid vs. weak base catalysis in durable press finishing with BTCA or citric acid

Direct comparison of hypophosphorous acid and sodium hypophosphite as curing catalysts has been made in formaldehyde-free durable press (DP) finishing of trouser weight cotton fabric with 1,2,3,4-butanetetracarboxylic acid (BTCA) or citric acid. Use of the acid catalyst caused excessive fabric breaking and tearing strength losses, and was consistently less effective than the sodium salt in imparting wrinkle resistance and smooth drying properties. Hypophosphorous acid as catalyst also increased the fabric bending moment and stiffness with epoxysilicone present as softener. However, adding of moderate amounts of triethylamine made hypophosphorous acid nearly equivalent to sodium hypophosphite in catalytic effects. In an equilibrium mixture of sodium hypophosphite and polycarboxylic acid, both acid and base catalysis may occur to accelerate production of anhydrides as intermediates and speed cellulose crosslinking.