Study On The Synthesis And Application Of Guanidine Antimicrobial-wet Strength Agent For Papermaking

Antimicrobial agents refer to some chemicals which can inhibit the growth and reproduction of germ or kill germ when even added with a small dosage. Wet strength agent is a kind of chemicals for paper making. Even if paper is soaked by water, the wet strength of paper can still maintain more than 15% of dry strength after wet strength agent is added into paper. In this thesis, antimicrobial-wet strength agent was synthesized by two steps. Firstly, prepolymer was obtained by condensation from guanidine salt, adipic acid, hexamethylene diamine and diethylenetriamine, then the prepolymer was further reacted with epichlorohydrin to prepare antimicrobial-wet strength agent.In the antimicrobial-wet strength agent, guanidine group has antimicrobial function so its content has great effect on antimicrobial activity of resulting product. It was found that guanidine group showed higher antimicrobial activity when it was connected directly to a straight and stiff molecular. Hexamethylene diamine possesses this structure and was proved to be easy to react with guanidine, therefore the content of hexamethylene diamine in synthesis reaction is a key factor. The azetidinium ring (AZR) bearing positive charge which was formed by the reaction of imido in diethylenetriamine and epichlorohydrin made contribution to wet strength of paper, so the content of diethylenetriamine and epichlorohydrin is important to the wet strength function of polymer. In order to make the polymer have antimicrobial and wet strength function together, the ratio of guanidine salt, adipic acid, hexamethylene diamine and diethylenetriamine must be coordinated suitably and the content of epichlorohydrin in the second step must be fixed rightly. Apart from ratio of monomer, reaction time, temperature and adding sequence of monomer also affect the wet strength and antimicrobial activity of polymer.Structure of the polymer was characterized by FTIR and NMR. Molecular weight (MW) of polymer was measured by GPC. Antimicrobial function of polymer was determined by minimum inhibitory concentration (MIC) and shaking-flask methods, and Escherichia coli was used in the test. The results revealed that the MIC of the polymer was 31ppm and around 75% E. coli were killed based on the shaking-flask method. After contacting with polymer, the cell of E. coli was observed through AFM and ESEM. Against normal cell of E. coli, the treated cell of E. coli was damaged by polymer. The antimicrobial mechanism of polymer was that polymer bearing cationic charge was attracted on the cell membrane of E. coli bearing anionic charge and destroyed the membrane to lead to outflow of intracellular components. The wet strength of handsheet was increased more than 5 times and the wet to dry strength ratio was 17% when the amount of polymer was 1 % (wt on o. d. fibers). Through the method of potentiometric titration, the factors which affected the absorption amount of polymer to fiber were researched.