| Fast-growing wood high content lignin pulp(referred to as high yield pulp,HYP)have the advantage of keeping a large amount of lignin,high pulp yield,low pollution,wide source of raw materials and so on in the pulping process,and has a broad application prospect.However,due to its high lignin content of HYP,bleached pulp is prone to photogenic yellowing,which greatly limits its application in high quality paper varieties at present.Therefore,how to improve the whiteness of paper and restrain the yellowing of paper is one of the research hotspots in the paper industry.Styrene-type fluorescent brighteners have advantages of high fluorescence intensity,good whitening effect,etc.,and can be used as a yellowing inhibitor for high yield pulp,which has been unanimously recognized and widely used in the paper industry.However,the shortcomings of the styrene-type fluorescent brighteners like poor water solubility,weak bond with paper,large consumption,easy to photo cis-trans isomerism etc.,largely limit their application scope and economic benefits.Therefore,the design and synthesis of a paper surface sizing agent with various functions and excellent performance with whitening,enhancement and water resistance is one of the research focuses in the field of paper industry.In this thesis,three kinds ofpaper surface sizing agent with excellent fluorescence whitening properties were prepared by starch grafting copolymerization on the basis of three kinds of fluorescent monomers synthesized by three-step nucleophilic substitution method,finally the optical and physical properties of the paper after surface sizing were investigated.The specific research contents are as follows:In the first part of this thesis,DSD acid,tripolyhydrogen chloride,diethanolamine and N-hydroxymethyl acrylamide were used as raw material to synthesized a good water-soluble fluorescent monomer(FBs),and then starch graft copolymerization with FBs,acrylamide and styrene were carried out to prepare a starch graft copolymer fluorescent emulsion with hydrophobic properties(ST-st-FBS).The structures and optical properties of the target products were characterized by IR,1HNMR,UV and fluorescence spectra.The inhibition effect of fluorescent emulsion on paper yellowing was detected by 48 h UV accelerated aging experiment.The results show that the initial whiteness of the coated paper is 11.33%higher than that of the blank paper.After 48 h UV aging test,the PC value of the coated paper is 0.96 lower than that of the blank paper Through the paper physical properties test found that after sizing,the water resistance of the paper increased by 16.1%,tensile strength and tear strength increased by 16.9%,15.8%,respectively.In the second part,a fluorescent monomer(UV/FBs)with good UV absorption performance was prepared by introducing 2,4-dihydroxybenzophenone.Then,the fluorescent monomer,cationic quaternary ammonium salt and styrene were graft copolymerized with starch to prepare two kinds of cationic modified starch graft copolymerization fluorescent emulsion(ST-DMDAAC-UV/FBs,ST-DMC-UV/FBs).The test results show that the whiteness of the two kinds of sizing paper is 15.52%and 15.28%higher than that of the blank paper respectively.In addition,after 48 h ultraviolet aging test,the yellow return value of the two kinds of sizing paper are 1.88 and 1.75 lower than that of the blank paper,respectively.It is found that the tensile strength of the two kinds of adhesive sheets increased by 43.1%and 39.7%respectively,and the tearing strength increased by 21.2%and 16.5%respectively.This indicates that the introduction of cationic quaternary ammonium salt could effectively solve the problems of poor light stability and weak paper binding force of the styrene-type fluorescent brightener.In the third part,to further improve the UV aging resistance of the emulsion and the photocis trans isomerism of the styrene-type fluorescent brightener,nanoparticles with ultraviolet shielding effect were introduced in this part of the emulsion.Firstly,a double-bonded nano particle(K-SiO2)was prepared by KH-570 and nano-SiO2.Then,K-SiO2,fluorescent monomer and acrylamide were grafted and copolymerized with starch to obtained a novel organic-inorganic composite fluorescent emulsion(ST-SiO2-AS/FBs).The experimental results showthat there is basically no photocis-trans isomerism in ST-SiO2-AS/FBs.After sizing,the tensile strength and tear strength of the paper increased by 63.2%and 26.4%respectively.The initial whiteness of the coated paper is 21.34%higher than that of the blank paper.After 48 h UV aging test,the PC value of ST-SiO2-AS/FBs coated paper is 1.33 lower than that of the blank paper.The above results indicate that nano particles can improve the optical and physical properties of paper.Based on the above results,ST-SiO2-AS/FBs has the best comprehensive effect on improving the whiteness of paper,inhibiting the yellowing of paper and enhancing the physical properties of paper,and it has certain theoretical significance and practical value for the research on improving the poor optical stability and poor binding ability of the styrene-type fluorescent whitening agent,has a good application prospect. |
PDF Full Text Request