Synthesis And Properties Of Yellowing Inhibitor Based On Naphthalimide In High Yield Pulp

Due to the rapid decline of forest-covering area,paper industry are challenged with the problems of raw material shortage,environmental pollution and high production cost,etc,and expanding the use of high yield pulp is of great significance for alleviating the shortage of wood resources,reducing production cost,reducing pollution and protecting ecological environment.While high yield pulp contains a large number of lignin and hemicellulose,and is prone to yellowing in the external environment such as light,heat,water,metal ions,and so on,which limits the use of high yield pulp.At present,there are many methods to inhibit the yellowing of high yield pulp.Among them,yellowing inhibitor is widely used in paper industry due to its strong operability and obvious effect.However,traditional yellowing inhibitor with small molecule have some disadvantages,such as poor water solubility,high toxicity,poor adhesion with paper fiber and single function,which limit their application in paper industry.If their solubility is improved,synergistic effect between auxiliaries is brought into play,or nano-silica spheres with UV absorption function are introduced,the yellowing of high yield pulp can be weakened or inhibited from different aspects,and the stability and toxicity can be improved at the same time.Based on the above design ideas,a series of new naphthylimide yellowing inhibitor were synthesized in this thesis.In this thesis,four yellowing inhibitors,namely cationic naphthalimide yellowinginhibitor,water-solublepolymericyellowinginhibitor,multi-functional water-soluble polymeric yellowing inhibitor and fluorescent polymeric yellowing inhibitor supported with nano-SiO₂,were synthesized based on the perspective of water solubility.Firstly,naphthalimide fluorescent brightener with small molecule?N-FBA?was synthesized from4-bromo-1,8-naphthalene anhydride reacted with ethanolamine and sodium alcohol,followed by cationization to prepare cationic naphthalimide fluorescent brightener?CN-FBA?.Secondly,two kinds of water-soluble polymeric yellowing inhibitors were synthesized:the naphthylimide fluorescent monomer NFM was synthesized from naphthylimide fluorescent brightener?N-FBA?and acryloyl chloride,and then reacted with acrylamide?AM?and methyl acryloyl oxy ethyl trimethyl ammonium chloride?DMC?to obtain water-soluble fluorescent brightener?CPNA?;subsequently the multifunctional water-soluble fluorescent brightener?MCPNA?was prepared after introduced the UV absorbing monomer UVAM.Finally,fluorescent polymeric yellowing inhibitor supported with nano-SiO₂?SiO₂-CPNA?was prepared from nano-SiO₂,fluorescent monomerNFM,AMandDMCusing?-?methylacryloyloxy?propyltrimethoxysilane?KH570?as coupling agent.The structures of the products were characterized by nuclear magnetic resonance spectrum,Fourier transform infrared spectroscopy,gel permeation chromatography,and X-ray photoelectron spectroscopy;the thermal stability of the product was tested by thermogravimetric analysis;the morphology of product and coated paper was detected with scanning electron microscope and transmission electron microscope.The cationization degree of solution was detected by Zeta potentiometer;water solubility was analyzed by observing the solubility of solution.The optical properties of products were tested by UV-visible spectrum and fluorescence spectrum.Finally,the UV aging test was carried out on coated paper in the UV aging oven for 36 h to verify the anti-yellowing property of products.The results showed that the cationic naphthalimide fluorescent brightener have good water solubility,and the initial whiteness is increased by 0.16 ISO%compared with blank paper.After UV aging for 36 h,the whiteness is 56.60 ISO%,and the yellowing value is 11.5.Compared with blank paper,the yellowing value decrease by 2.45,and the yellowing inhibition effect is achieved.Polymeric yellowing inhibitor and multi-functional polymeric yellowing inhibitor have good water-soluble,film-forming and anti-UV aging performance.The whiteness of the coated paper is higher than that of the blank paper by 2.64 ISO%and 3.74 ISO%,respectively.After UV aging for 36 h,the whiteness of the coated paper is 61.54 ISO%and62.68 ISO%respectively,which is lower than the original value by 14.78 ISO%and 14.74 ISO%.The fluorescent polymeric yellowing inhibitor supported with nano-SiO₂ can not only play a synergistic role between different groups,but also show significantly improved stability,and strong anti-UV aging effect.After UV aging for 36 h,the whiteness of coated paper is 63.58 ISO%,which is lower than the initial value by 13.92 ISO%.