Chemical modification of cotton-based natural materials: Products from carboxymethylation

The processing of cotton generates a number of byproducts, two of which are cotton burr and cottonseed hull. A proximate analysis indicates that they contain about 30–32% cellulose, 17–19% lignin and lesser amounts of protein and oil. They differ in level of hemicellulose with burr containing ∼6% and hull containing ∼20%. Both materials can swell in aqueous NaOH–isopropanol solutions in which state they become susceptible to reaction with monochloroacetic acid. The products of this reaction consist of a water-soluble fraction (observed weight yields ranging from 28% to 55%) and a water-insoluble residue. The water-soluble fractions produce clear films that dissolve slowly in water with viscosities that are somewhat lower than for carboxymethyl products generated from purified cellulose. The products were characterized by NMR and IR and were found to consist mostly of carboxymethyl derivatives of cellulose and hemicellulose.