Homogenous Synthesis Of Amphoteric Cellulose In One Pot Using NaOH/Urea Aqueous Solution As Solvent

As a special cellulose derivative, amphoteric cellulose (AC) is promising in a number ofapplications such as colloid stability agents, wetting agents, lubricants, adsorbents and paper drystrength additives for paper due to its unique solution property and rheological properties since itpossesses both cationic groups and anionic groups in one molecule. Amphoteric cellulose isusually synthesized by two steps and therefore it needs separation, purification between steps. Afacile procedure to synthesize amphoteric cellulose in one pot in the homogenous condition wasdeveloped in this investigation. The strong basic condition of cellulose solvent-NaOH/Ureasystem was taken advantage for etherifications which introduce both cationic and anionic groupsonto the backbone of cellulose molecule. In this work, microcrystalline cellulose (MCC) wasused as raw material and initially dissolved in7wt%NaOH/12wt%urea aqueous solution atcold temperature. Cationic and anionic agents of3-chloro-2-hydroxypropyltrimethylammoniumchloride and3-chloro-2-hydroxypropanesulfonic acid sodium salt were sequentially orsimultaneously added into the system to react with cellulose at basic condition. By varying thereaction temperature between25°C and90°C, the molar ratio of1and12mol cationic andanionic reagents per mol anhydroglucose unit, the reaction time and the addition orders of thetwo reagents, amphoteric cellulose with degree of total substitution (DS) values in the range of0.047and0.76was obtained. Amphoteric cellulose samples were characterized with FT-IR,elemental analysis, NMR, and viscosity measurements. The results indicate that the total DS isincreased with the increase of the molar ratio and the reaction time; however, the total DSdecreased when the molar ratio is12. The maximum DS was obtained at the molar ratio of1:9.The total DS is also increased with the increased of the temperature; however, the total DS isdecreased when the temperature is increased to90°C. Adding the cationic agents first and thenadding the anionic agents as follows is the best adding orders comparing with the other twoadding methods. While we used the amphoteric cellulose as paper strength agent, we found thatthe effect of enhancement is better when the total DS of the amphoteric cellulose is higher. Whenthe total DS reached to0.69, the tensile index, burst index and tear index of the sheet areincreased about21%,19.2%,22.8%, respectively. And the application experiment showed thatamphoteric cellulose improved paper strengths to significant extents when the dosage was about0.5%.