CROSSLINKING COTTON CELLULOSE USING THE COMBINATION OF MALEIC ACID AND SODIUM HYPOPHOSPHITE

Durable press finishing agents used to produce wrinkle-resistant cotton garments are crosslinking agents for cotton cellulose. Polycarboxylic acids have been the promising durable press finishing agents to replace the formaldehyde-based compounds when sodium hypophosphite was used as the catalyst. In our previous research, we found that a polycarboxylic acid esterifies cotton cellulose by first forming a 5 membered cyclic anhydride as a reactive intermediate. Maleic acid (MA) is a bifunctional carboxylic acid, therefore is not able to form the second cyclic anhydride intermediate once it forms the first ester linkage with cotton. However, we discovered that MA did impart wrinkle resistance to cotton fabrics when NaH2PO2 was present, thus indicating MA was able crosslink cotton. In this research, we studied how MA forms crosslinkage among cellulose molecules on cotton. Sodium hypophosphite functions as the catalyst for the esterification of cellulose by MA, and the esterification takes place at relatively low temperatures (>= 130 degrees C). Esterification of MA forms single esterlinkage with cellulose and does not crosslink cotton cellulose. As the temperature increases to >= 160 degrees C, NaH2PO2 reacts with MA probably due to the addition of MA by the >C=C< of MA. The bounding of hypophosphite to two MA molecules already esterified with cellulose forms a crosslinkage between two cellulose molecules, thus imparting wrinkle resistance to cotton. The crosslinking mechanism of MA on cotton is supported by all the data presented in this paper.