| Polyethyleneimine(PEI)is a strong cationic polymer,and its different relative molecular masses have significant effects in different fields.This work uses low,medium and high molecular weight polyethylene imines to solve two problems:In the alumina production industry,the scarring of sodium-silicon slag that is difficult to clean inside the pipeline leads to high energy consumption and high production costs.How to efficiently and simply prevent or treat the scarring in the pipeline has become an urgent problem in the alumina industry;With the continuous development and diversification of specialty papers,the market has increasingly higher requirements for paper.At present,most of the paper enhancers used in large quantities in the market have the disadvantages of releasing formaldehyde and containing organochlorohydrins that are not conducive to the human body and the environment.The wet strength agent with superior synthesis effect and green environmental protection has become the current research focus of paper additives.The main research contents of this topic are as follows:1.Silicon hydrophobic modified polyamine as a scale inhibitor was synthesized by grafting reaction from low molecular weight polyethylenimine(PEI)with y-glycidyloxypropyltrimethoxysilane(KH560)and 1-chlorooctane.The structure and properties of the modified polyamine scale inhibitor were analyzed by FTIR.The results showed that the thermal stability,viscosity,surface tension and solution particle size of the product were improved after modification.The modified polyamine scale inhibitor was used to disperse sodium aluminosilicate particles,the particles before and after treatment were characterized by FTIR,and the dispersion performance of polyamine scale inhibitor was evaluated and its dispersion mechanism was preliminarily discussed by testing the stability and particle settling of the suspended dispersion solution.Under the conditions of m(PEI,Mw=10000):m(KH560):m(1-chlorooctane)?10:2:0.5,reaction time 6 h,and reaction temperature 75?,the synthesized scale inhibitor displayed the best dispersion performance.When the mass concentration of scarring particles was 30 g/L,the particle setting velocity of suspension reached the lowest value of 0.047 cm/d,the decrease degree of particle setting velocity was 94.8%,and the dispersion performance significantly improved.The modified polyethylenimine has a highly effective scale inhibition effect in industrial production of alumina.It can further replace the traditional strong acid scale inhibitor by optimizing the conditions in the factory,so as to reduce the corrosion degree of the pipeline and reduce the energy consumption.2.Epoxy chloropropane(ECH)is used to epoxy crosslinking modification of medium and high molecular weight polyethyleneimine,while improving the cationicity of PEI,to prepare epoxy crosslinking type PEI paper wet strength agent,and then after sizing in papermaking.The addition of the modified PEI wet strength agent can cause electrostatic bonding and cross-linking reaction with the paper fibers,enhancing the bonding force between the fibers and reducing the gaps between the fibers,and synergistically improve the wet strength of paper.The structure and properties of modified PEI-ECH wet strength agent were analyzed by FTIR,TG,particle size analysis,zeta potential and viscosity.The results showed that the epoxy group was successfully grafted onto the long chain of PEI,and the thermal stability,viscosity and zeta potential of the modified polymer were improved.By testing the paper's tensile strength,ring compressive strength,tear strength,bending times,water absorption,pulp zeta potential,X-ray photoelectron spectrum to explore the best modification ratio of different molecular weight PEI,and the influence of paper properties.The results showed that the optimal conditions of epoxy modification were as follows:m(PEI,MW=75W):m(epichlorohydrin)=10:2,reaction temperature of 30?,reaction time of 4 h,m(PEI,MW=6W):m(epichlorohydrin)=8:4,reaction temperature of 60?,reaction time of 2 h.The solid content of the two molecular weight wet strength agents were 12%.Compared with the base paper,the paper enhanced by PEI-ECH has better physical properties.The wet tensile strength index increased from 3.58 N·m·g-1 to 17.68 N·m·g-1,an increase of 394%.The tensile strength index increased from 31.25 N·m·g-1 to 70.60 N·m·g-1,an increase of 126%;The ring compressive strength index of the paper increased from 6.25 N·m·g-1 to 17.52 N·m·g-1,an increase of 180%;The tearing index of the paper increased from 9.76 mN·m2·g-1 to 17.60 mN·m2·g-1,an increase of 80%;The number of folding resistance of the paper has been increased from 500 to 2848,an increase of 467%,and the wet strength performance and various physical properties of the paper have been significantly improved.Compared with the polyamide polyamine epichlorohydrin(PAE)which has the best wetting strength,the wetting strength of PEI-ECH wet strength agent reaches 90%of the performance of the existing mature PAE,and the strength of other kinds of paper has been improved.The microstructure of paper fibers was observed and analyzed by scanning electron microscope(SEM),and the paper enhancement mechanism was proposed by combining the zeta potential of pulp,paper infrared spectroscopy and paper X-ray photoelectron spectroscopy.The results show that:PEI-ECH adheres to the surface of the fiber and enters the fiber to react.The amine group on the long chain of PEI and the hydroxyl group undergo hydrogen bonding,and the epoxy group at the end of the PEI-ECH chain forms an ether bond structure with the hydroxyl group.Under the synergistic effect,the bonding strength between the paper fibers is enhanced,the gaps between the fibers are filled,and a cross-linked network with water resistance is formed,and the paper performance is superior. |
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