Study On The Reinforcement And Protection Of Paper With Chitosan Modified By Epoxicocyclohexane

Paper has a high value of culture,history and scientific research as the cultural carrier of historical inheritance.However,with the passage of time and the change of environment,many paper files are aging and damaged.Therefore,it is of great significance to carry out the protection of paper archives.Chitosan,a natural material,has a good compatibility with paper fibers,but its strengthening properties such as aging,flexibility and adhesion are not good.Epoxy cyclohexane is a small molecular monomer,which has the characteristics of six-membered-ring rigid structures and ternary epoxy base with high activity,therefore,the modified materials of natural polymers can be prepared by combining them organically.The advantages of natural polymers and synthetic materials can be comprehensively utilized,and the good mechanical and chemical properties of small molecular monomers can also be possessed.In this paper,Chitosan was modified by epoxy cyclohexane and methyl methacrylate respectively,and the paper properties were measured.The main research contents and conclusions are as follows.CS-CHO,a modified chitosan derivative,was synthesized with chitosan?CS?as raw material,epoxy cyclohexane?CHO?as oligomer functional monomer,dibutyltin dilaurate?DBTL?as catalyst and dilute acetic acid as reaction solvent.The optimum conditions of synthesis of CS-CHO were found by single factor and orthogonal experiments,and the structure of CS-CHO was characterized by FTIR,XRD and DSC-TGA.The synthetic CS-CHO glue solution was applied to the paper reinforcement.Through the influence of different mass concentration of the glue solution on the paper tensile strength,folding resistance,tearing,whiteness and glossiness,the suitable conditions of CS-CHO for paper reinforcement were found.In addition,the effects of CS-CHO on the heat aging resistance,acid-base resistance and ink of paper were investigated.The results showed that epoxy cyclohexane was successfully connected to C₂-NH₂ of chitosan by N-alkylation.The preparation conditions of CS-CHO were:m?CS?:m?CHO?=1:5.5;reaction temperature 65?;reaction time,7 h and catalyst dosage,0.06 g.When 10%CS-CHO solution was applied to paper,not only the mechanical properties were greatly improved,but also the glossiness and whiteness changed slightly,which conformed to the principle of"repair as old".The aging experiment showed that CS-CHO could obviously improve the mechanical properties and anti-aging properties of paper.The acid-base resistance experiment showed that CS-CHO could penetrate into the paper fiber and form a protective film on the surface of the paper fiber,which could effectively decrease the corrosion of H⁺and OH^-ions on the fiber.According to the ink experiment,CS-CHO glue had no effect on the ink,the paper pattern was clear and the ink did not be diffused.CS-CHO-g-PMMA emulsion for paper protection was synthesized by one-pot synthesized method of free radical grafting polymerization using CS-CHO gel as substrate,methacrylate?MMA?as oligomer functional monomer,potassium persulfate?KPS?as initiator and hydrogen phosphate two sodium?DSP?as buffer reagent.The synthesis conditions were optimized by single factor experiment,and the effects of monomer amount,initiator amount,reaction temperature and polymerization time on grafting parameters and water absorption were investigated.The synthetic CS-CHO-g-PMMA solution was applied to the paper reinforcement,and the suitable applied conditions of CS-CHO-g-PMMA were determined by the effects of different concentrations of glue on paper tensile strength,folding resistance,tearing,whiteness,glossiness,etc.At the same time,the effects of CS-CHO-g-PMMA on the heat aging resistance,reversibility,acid-base resistance and ink of paper were also investigated.In order to improve the mechanical strength of paper and keep the original gloss of paper,CS-CHO-g-PMMA emulsion and phosphate ester starch?HPDSP?were blended to determine the optimum ratio.The results showed that the polymerization conditions of CS-CHO-g-PMMA were as follows:monomer 3 g;the reaction temperature 80?;the amount of initiator,7.5 m L and the reaction time,3 h.The CS-CHO-g-PMMA emulsion synthesized under this condition had good properties,with good free radical graft polymerization effect and good water resistance.Acid-base resistance experiment showed that CS-CHO-g-PMMA emulsion could effectively resist external acid and alkali corrosion and protect paper.The thermal aging test showed that the rate of aging degradation was obviously slowed down when the paper was coated with CS-CHO-g-PMMA emulsion.The reversibility experiment showed that CS-CHO-g-PMMA had certain reversibility.The ink experiment showed that the color and luster of the coated paper would not change,nor did the ink spread,and the paper kept its original appearance.The best combination ratio between CS-CHO-g-PMMA emulsion and gelatinized HPDSP solution was:m?CS-CHO-g-PMMA?:m?HPDSP?=5:2.Under this compound ratio,the performance indexes of the paper met the requirements,conforming to the"repair as old,keep the original"and other requirements.