Chitosan is obtained by alkaline hydrolysis of the naturally occurring polysaccharide chitin (Figure 2).

 

Experimental

Anionic cellulose was produced with various carboxymethyl content (up to 125 mmol per 100 g fabric) by a method similar to those previously reported [1, 2, 5, 6, 7, 8]. Bleached cellulosic fabric was impregnated with 20% aqueous NaOH for 10 minutes at room temperature, followed by padding to a wet pickup of 100%. Samples were dried at 60oC. These alkali-treated samples were then steeped for 5 minutes at room temperature in aqueous solutions of chloroacetic acid that had been neutralized with sodium carbonate at various concentrations (0 to 3.0 M). These samples were then squeezed to 100% wet pickup, sealed in plastic bags and heated at 70oC for 1 hour. The samples were then washed and dried at room temperature. Blanks were included. This produced 7 different levels of carboxymethylation, i.e. 6.15, 30.2, 60.7, 87.1, 97.3, 114.5, and 123.7 mmols of carboxymethyl groups per 100 grams of fabric, as determined by titration.

 

Cationic chitosan was produced by the reaction of 85% N-deacetylated chitin with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride using a method that differed somewhat from the method previously reported by Kim et al. [3]. 161 grams of 85% N-deacetylated chitin was slurried in 1156 grams of 69% w/w solution of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride. NaOH (50% w/w) was added dropwise to maintain pH of 10 to 11. The slurry was stirred overnight; then the temperature was raised to 95oC for 4 hours, cooled to room temperature and adjusted to pH 7 with acetic acid. The resulting reaction product was soluble in the reaction mixture. When recovered by drying, the resulting product was easily re-dissolved in room-temperature water at pH 7.

To accomplish the ionic crosslinking, cationized chitosan was applied to the anionic cellulosic fabrics by padding through solutions of cationized chitosan in water at 100% wet pickup, then drying at 105oC. Various concentrations of cationic chitosan were used in the padding bath, i.e. 0, 0.5, 2, 4, and 6% solution concentration.

Materials

The materials used are presented in Table I.

 

All chemicals were used as received.