Tailored oxidation of hydroxypropyl cellulose under mild conditions for the generation of wet strength agents for paper.

Secondary hydroxyl groups of hydroxypropyl cellulose (HPC) are transformed into reactive carbonyl groups selectively via TEMPO-mediated oxidation in the presence of sodium hypochlorite. By using this oxidation protocol, we introduced carbonyl functions in HPC under mild conditions, with a controlled degree of oxidation (DOx) up to 2.5 and a low degradation of the polysaccharide. The effect of the concentration of sodium hypochlorite on the resulting oxidized alcohol groups has been investigated in detail. Oxidized HPC crosslinks spontaneous at room temperature and mild pH-values with a variety of amines to form water stable hydrogels. If applied on lab-made paper sheet, thermally cross-linking this polymer with amines significantly increased the wet tensile strength. The utilization of such wet strength agents could lead to new approaches in terms of recyclability and biodegradability of wet strength agents interesting for a large number of different paper grades.