Research On The Modification Of Chitosan And Its Application In Dialysis Paper

As the main material for sterilization packaging of medical devices,the demand for medical dialysis paper is increasing.Currently,polymer additives such as cationic polyacrylamide resin（CPAM）and polyamide epichlorohydrin resin（PAE）need to be added to the production process of dialysis paper to improve the physical strength,but PAE hydrolysis will produce chlorine-containing organic compounds and cause harm to the human body and the environment.As a green and environmentally friendly material,chitosan does not contain chlorides harmful to the human body,and has advantages such as biodegradability and biocompatibility compared with CPAM,and its hydroxyl and amino groups combine with the fiber to form ionic and hydrogen bonds,which can improve the dry and wet strength of the paper.it has the natural advantage of becoming a chlorine-free reinforcer.However,chitosan is insoluble in water,alkali and general organic solvents,only soluble in dilute acids,which limits its application,so it is necessary to modify chitosan to improve its water solubility,making it suitable for high-performance medical dialysis paper.In this study,water-soluble maleic anhydride acylated chitosan and carboxymethyl chitosan were efficiently prepared by modifying chitosan through acylation and carboxymethyl reactions,aimed to increase the active groups in the molecular structure of chitosan.Then,high-performance medical dialysis paper was prepared by filling in the pulp and surface sizing.The enhancement effects of modified chitosan on the physical strength,air permeability and antibacterial properties of the dialysis paper were studied.The main contents of the research are as follows:Firstly,the modification and properties of chitosan were studied.Water soluble maleic anhydride acylated chitosan（MAAC）was prepared using maleic anhydride（MA）as a modifier and TEMPO as an oxidant.The effects of preparation conditions on the degree of substitution and solubility of MAAC were studied.The results showed that when the mass ratio of m（CS）:m（MA）:m（TEMPO）was 1:1:0.08 and the reaction time was 4 h,the MAAC had the higher degree of substitution better solubility than others,and the MAAC had a light transmittance higher than 80%in medium and alkaline solutions.Carboxymethyl chitosan（CMCS）with three different substitution positions were successfully prepared using chloroacetic acid as a modifier under alkaline conditions,and the degree of substitution and solubility of CMCS were analyzed.The results showed that N,O-CMCS had the highest degree of substitution and the best solubility,and the solubility of O-CMCS was not affected by p H value,with light transmittance greater than 90%.N-CMCS and N,O-CMCS could only be dissolved in medium and alkaline solutions.Secondly,the effects of the modified chitosan on paper properties were studied.MAAC and CMCS were added to the pulp to prepare dialysis paper,and the effects of the amount of modified chitosan on the physical strength,air permeability,and antibacterial properties of the paper were studied.The results showed that when the amount of MAAC was 2.0%,the comprehensive properties of the paper were better,and the dry and wet tensile,tear,and burst indexes of the dialysis paper were 10.0%,96.6%,30.2%,and 42.9%higher than those of the untreated paper,respectively.The air permeability of the paper reached 8.98μm·（Pa·s）^-1,and the antibacterial rate for Escherichia E.coli reached 91.6%.The three types of CMCS all can improve the dry and wet tensile strength and bursting strength of paper.When the amount of O-CMCS was 2.5%,the comprehensive performance of the paper was the best,and the dry,wet tensile and bursting indexes of the paper increased by 18.8%,113%,and 91.0%,respectively.The air permeability reaches 7.98μm·（Pa·s）^-1,the paper has good antibacterial properties and the antibacterial rate for Escherichia E.coli reached 86.7%.Thirdly,modified chitosan was used as surface agent and its effects on paper properties were studied.MAAC and O-CMCS were mixed with PVA for surface sizing of paper,the results showed that when MAAC/PVA was used as sizing agent and the sizing was 6.5 g/m²,the dry,wet tensile and burst strengths of paper increased by41.4%,53.6%,and 107%,respectively,compared to pure PVA,while the air permeability decreased by 88.2%;when O-CMCS/PVA was used as sizing agent and the sizing was 6.5 g/m²,the dry,wet tensile and burst strengths of paper increased by46.5%,82.2%,and 107%,respectively,while air permeability decreased by 92.4%.The antibacterial experiment results showed that the antibacterial rates of MAAC/PVA and O-CMCS/PVA papers reached 94.8%and 92.9%,respectively;However,the surface sizing greatly reduces the air permeability of the paper.SEM analysis showed that the paper surface gradually formed a film and the porosity reduced with the increase of the sizing,which explained the reason for the drastic decrease in air permeability.In a word,maleic anhydride acylation modification and carboxymethyl modification of chitosan improve the solubility of chitosan in water.Addition of MAAC and O-CMCS to the pulp and surface sizing can improve the physical strength and antibacterial properties of dialysis paper.Modified chitosan can be used as a reinforcing agent and antibacterial agent in the production of medical dialysis paper.