Preparation of carbonxymethyl chitosan and its effects on medical dialysis paper

In order to improve the water solubility of chitosan (CS) and extend its application in the field of papermaking, CS was used as the main raw material and chloroacetic acid was used as the etherification agent to prepare carboxymethyl chitosan (CMCS) under alkaline conditions. CMCS with different substitution sites were obtained by controlling the reaction temperature, time and pH value. Then, the structures of CMCS were analyzed by using infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (¹H-NMR), and their degree of substitution and water solubility were measured. Finally, the prepared CMCS was used as additives to prepare dialysis paper, and the effects of CMCS dosage on the physical strength, permeability and antibacterial performance of dialysis paper were investigated. The results showed that the addition of CMCS with different substitution sites all improved the physical strength of dialysis paper, however, compared with the amino substituted CMCS (N-CMCS) and the amino and hydroxyl substituted CMCS (N,O-CMCS), the addition of the hydroxyl substituted CMCS (O-CMCS) had the most significant effects. When 2.5% O-CMCS was added to the papermaking pulp, the dry tensile, wet tensile and burst index of the paper were 61.6 N·m·g⁻¹, 8.61 N·m·g⁻¹ and 6.19 kPa·m²·g⁻¹, which increased by 18.8%, 113%, and 91.0%, respectively. The air permeability of paper reached 7.98 μm·(Pa·s) ⁻¹, meeting the requirements of air permeability of the dialysis paper. In addition, the paper containing O-CMCS, N-CMCS and N, O-CMCS all showed good antibacterial activity, and had antibacterial rates of 86.7%, 83.8%, and 83.6% against Escherichia coli, respectively.