Water and moisture sorptive properties of some cellulosic graft copolymers.

Cellulosic water-absorbents of fibrous shape or sheet form, instead of the conventional powder form, were prepared by graft copolymerization of acrylic monomers using a ceric ion initiator onto some kinds of cellulosics and post-hydrolysis. Two kinds of bleached kraft pulps from softwood (NBKP) were used for the preparation of the fibrous absorbents, and a slightly cyanoethylated NBKP (CE•NBKP), which is water-soluble, were altered to the powdered absorbents. With an increase in the degree of grafting, the water retention values (WRVs) of the grafted pulps increased rapidly and reached a respective maximum at about 200% grafting. The grafted NBKP and the grafted CE•NBKP could absorb water up to 2500g/g and 3000g/g of the grafted pulp, respectively. The saline retention values (SRVs) determined from absorbency for 0.9% sodium chloride solution were lowered to 1/20 of these WRVs. The sheet shape absorbents from a cellulose film (FILM) and a nonwoven fabric (NWF) could absorb about 150-250g water per graft copolymer at high grafting, and the grafted NWF kept their sheet shapes after swelling. The grafted NWF had high hygroscopicity and indicated the reversible sorption-desorption behavior with hysteresis.