The Preparation Of Cationic Cyclodextrin And Its Application

In recent years,it has attracted significant interest of research to construct artificial enzymes,molecule recognition sensors and other functional models utilizing the cone-shaped cyclodextrins(CDs,including a,β,γCD etc),which processes a hydrophobic cavity and a hydrophilic outside.As a multi-functional molecule,β-CD is proved to be a useful auxiliary in agriculture,industry and pharmacy.However,the inherent defects of naturalβ-CD restrict its practical applications.For instance,the lack of chromospheres or auxochromes poses UV-inertness onβ-CD,which limits the application of UV and Fluorescence analysis to its supramolecular activities(Host-Guest interaction).Moreover,poor water-solubility and deficiency of active functional groups restrict its bioavailability and molecular recognition ability.Due to the above mentioned defects ofβ-CD,the focus of our research was directed to the chemical-selective modification ofβ-CD,aiming to produce novel enzyme-like functional molecules with enhanced properties.Starch is made of glucose unit,whileβ-CD has seven glucose units.The cationic starch is one of the most important derivations of starches.It is widely used as reinforcing agent,surface sized filler,retention and drainage aids in paper industry all over the world. It was inspired by the cationic starch that we are going to quest the synthesis of cationic cyclodextrins and research its repercussion used as the retention and drainage aids,finally discuss the mechanism of action about the cationic cyclodextrins in the wet end chemistry theory.The content of the paper is showed as follows:1.Synthesis of cationicβ-CDCationic-CD was synthesized by half-dry process in our work.We studied the effects of some factors,such as the dosage of etherifying agent,the dosage of alkali,water content of the system,reaction temperature and reaction time.In order to obtain the optimum process conditions,we optimize further condition by RSD.Under the optimum process conditions,the cationic cyclodextrin with DS at about 1.1904 can be prepared by half-dry process.The cationic cyclodextrins were characterized by Fourier transform infrared spectroscopy (FTIR) and its charge density was determined by colloid titration.All the results showed that the preparation of cationic cyclodextrin was successful.2.The discussion of the mechanism of action about the cationic cyclodextrins in the wet end chemistry theory:The advanced technology of colloid titration with PCD,combined with the analysis of Zeta potential,was applied to measure the charge and Zeta potential of furnish systems.The reaction mechanisms of cationic cyclodextrin used as retention and drainage aids were explained theoretically.3.Application of cationic-CD(1) Cationic-modified cyclodextrin was used as cationic component in the conjunction with anionic polyacrylamide-based copolymer as dual-component flocculation/inclusion systems.Flocculation efficiency and influencing factors of the cationic cyclodextrin and anionic polymer systems on the fine clay particles were studied in this work.As dual-component flocculation systems,cationic-modified cyclodextrin induced very effective clay flocculation.(2) In order to invest the application of the cationic-modified cyclodextrin and anionic polyacrylamide-based copolymer as dual-component flocculation/ inclusion systems in the wet-end of papermaking.We discuss the cationic-modified cyclodextrin and anionic polyacrylamide-based copolymer as dual-component flocculation/inclusion systems were used as retention and drainage aids for waste paper pulp and bleached hardwood pulp.The experiments show that the filler retention improves about three times while the DS of cationic eyclodextrin is 1.041 and the dosage is 0.3%,the DS of anionic polyacrylamide-based copolymer is 5% and the dosage is 0.02%for deinked pulp.As the dosage increasing,they have little effect on the drainage but remarkable effects on the strength of papers.When the dual-component flocculation/inclusion systems were used in bleached hardwood pulp and the dosage cationic-modified eyelodextrin was above 0.3%,the filler retention would be increased while breaking length fell remarkably.