Synthesis And Properties Of Novel Yellowing Inhibitor Based On Stilbene Fluorescent Brighteners

Lignin in the high yield pulp can produce quinone-type groups under the irradiation of ultraviolet light,thus affecting the whiteness of the high yield pulp.In response to this phenomenon,it is necessary to develop yellowing inhibitors that are suitable to use in high yield pulp.However,there are still many drawbacks of the fluorescent brighteners used to suppress the yellowing of the high yield pulp,such as poor water solubility,poor adhesion with fiber,poor light stability,etc.If amino siloxane with high steric hindrance or nano-Si O₂ with UV absorption ability is introduced into the fluorescent molecule,these disadvantages can be effectively improved.From these design ideas,a series of stilbene-based yellowing inhibitors were synthesized in this thesis to inhibit the yellowing of the high yield pulp.In the first part,with cyanuric chloride as a crosslinking monomer,4,4'-diamino stilbene-2,2'-disulfonic acid?DSD acid?as raw materials,3-aminopropyltrimethoxysilane?KH540?,aminocompounds?p-aminobenzenesulfonic acid,ethanolamine and taurine?and stilbene-based fluorescent brightener were introduced into the same molecule by nucleophilic substitution method.Then they were treated with hot sodium hydroxide solution,three kinds of stilbene yellowing inhibitors containing siloxane?KH540-FBs1,KH540-FBs2 and KH540-FBs3?were synthesized.In the second part,using the above KH540-FBs1,KH540-FBs2 and KH540-FBs3 as starting materials,three kinds of fluorescent nanoparticle yellowing inhibitors?SiO₂/KH540-FBs1,SiO₂/KH540-FBs2 and Si O₂/KH540-FBs3?were successfully prepared by the Stober method.In the third part,with cyanuric chloride as a crosslinking monomer,4,4'-diamino stilbene-2,2'-disulfonic acid?DSD acid?as raw materials,amino compounds?p-aminobenzenesulfonic acid and morpholine respectively?,polymers and stilbene-based fluorescent brightener were introduced into the same molecule by nucleophilic substitution method,four stilbene fluorescent polymers were synthesized?PEG-FBs1,PEG-FBs2,COS-FBs1 and COS-FBs2?.Then,based on this,four kinds of fluorescent nanoparticle polymer yellowing inhibitors?SiO₂/PEG-FBs1,SiO₂/PEG-FBs2,SiO₂/COS-FBs1and SiO₂/COS-FBs2?were synthesized by the modified Stober method.The structures of the products were characterized by infrared spectroscopy,nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy.The morphology and particle size of the products were observed by transmission electron microscopy,field emission scanning electron microscopy and nano-particle size analyzer.The thermal stabilities of the products were investigated by thermal gravimetric analyzer.The optical properties of the products were investigated by UV-Vis and fluorescence spectroscopy.Finally,the accelerated aging test by UV light proved that the target product can inhibit the yellowing of the paper.The results showed that stilbene yellowing inhibitors containing siloxane have better water solubility,better paper whitening and yellowing inhibiting effect.The initial whiteness of paper treated increased 17.67ISO%,16.98 ISO%and 12.63 ISO%than that of the blank,and the values of yellowing returned decreased 6.96,6.65 and 7.53 after UV aging for 38 h than that of the blank.The three kinds of fluorescent nanoparticle yellowing inhibitors have better whitening and yellowing inhibition effect on paper,of which yellowing inhibition effect is more obvious.After UV aging for 38 h,the yellowing values of the paper treated were respectively 2.60,2.26 and 4.51,which were lower by 1.04?1.51 and 0.71 than that of fluorescent brightener modified with the non-nano SiO₂.Four kinds of fluorescent nanoparticle polymer yellowing inhibitors are more prominent on paper yellowing inhibition effect.After UV aging for 38 h,the yellowing values of paper treated decreased to 2.03,2.05,1.62 and 2.12 respectively,which were lower by 1.25,1.37,1.77and 1.19 than that of fluorescent polymer modified the non-nano SiO₂.