Preparation And Properties Of Naphthalimide Fluorescent Polymers

Due to the sharp decline of forest coverage,the papermaking industry began to vigorously promote the application of high yield pulp(HYP).However,there is some lignin in HYP,which is easy to turn yellow in the light,heat and radiation environment,which limits the application of HYP.At this point,the fluorescent brighteners play a crucial role.The naphthalimide has a good light fastness and is a compound with high fluorescence quantum yield.It is valuable to be a fluorescent brightener.Naphthalimide absorbs energy in the ultraviolet region and emits blue light in the visible region,which inhibits the yellowing of the paper in two ways,that were absorbing ultraviolet and compensating light.However,there are many problems in the application of naphthalimide molecules,such as poor solubility,poor heat resistance and independent film formation.In response to these problems,we try to turn the naphthalimide brighteners into the direction of aqueous additives through polymerization method,from the perspective of molecular design.The specific experiments are described as follow.In this thesis,from the view of water solubility,we first tried to draw sulfamate-based molecules(sulfanilic acid,taurine)and siloxane(KH-540,KH-570)into naphthalimides,which was copolymerized with acrylamide,and 4kinds of paper fluorescent brighteners(SA-PFBs,Tau-PFBs,540-PFBs,570-PFBs)were obtained.Then,from the view of aqueous emulsion,the naphthalimide monomer and styrene were copolymerized by emulsion polymerization,and a PS-PFBs fluorescent emulsion was obtained.Afterwards,a hydrophilic monomer acrylamide was added to the system to obtain a PS-PAM-PFBs fluorescent emulsion after copolymerization of the three.Structures of six products were characterized by FT-IR and gel permeation chromatography GPC.The optical properties of 6 kinds of products were tested by UV-vis and fluorescence spectra.The inhibition effect of 6 kinds of products was measured by aging accelerated test.The mechanical properties of SA-PFBs,Tau-PFBs,540-PFBs,and 570-PFBs were measured by tensile strength test.The thermal stability of SA-PFBs,Tau-PFBs,540-PFBs and 570-PFBs was determined by thermogravimetric analyzer.And the effect of PS-PFBs on the hydrophobicity of paper was determined by measuring the contact angle.The effect of polymers on the surface morphology of paper was observed by scanning electron microscope(SEM);the morphology of the emulsion was observed by transmission electron microscope(TEM).The results showed that,firstly,the water solubility of SA-PFBs,Tau-PFBs,540-PFBs,and 570-PFBs was increased,with some yellowing inhibition.At the same time,paper-enhancing effects were obtained,especially540-PFBs and 570-PFBs.After aging 36 h,the whiteness of SA-PFBs and Tau-PFBs decreased by 4.26 ISO%and 6.54 ISO%,respectively,compared with blank paper.After coating the paper,the initial whiteness of 540-PFBs and570-PFBs was 4.42 ISO%and 2.88 ISO%higher than that of blank paper,respectively.After 48 hours of aging,the whiteness of 540-PFBs and 570-PFBs decreased by 5.90 ISO%and 4.93 ISO%,respectively,compared to blank paper.The SEM images showed that the surface cracks of the coated paper disappeared and became smoother.Secondly,the particle size distribution of the polymer emulsions was uniform,and the electrostatic adsorption was produced on the paper,so that the micelle particles were evenly distributed on the surface of the paper.After the PS-PFBs was coated on the paper,the contact angle of the treated paper was 20~°larger than that of the blank paper.And the initial whiteness increased by 15.99 ISO%,after aging 48 h,the whiteness of PS-PFBs-coated paper was 8.79 ISO%and 8.08 ISO%lower than that of blank paper and paper coated with small-molecule optical brightener,respectively.The fluorescence quantum yield of PS-PAM-PFBs is 78.57%.After PS-PAM-PFBs were coated on the paper,the initial whiteness was increased by 8.19 ISO%,aging 48 hours,the whiteness of the paper,which was coated with PS-PAM-PFBs,was reduced by 3.68 and 3.16 ISO%,respectively,when compared with the blank paper and the paper coated with the micromolecule.It showed that the PS-PAM-PFBs emulsion has good combination with paper,and has whitening and yellowing inhibition effects.