Study On The Stability And Stabilization Mechanism Of AKD Emulsion With High Charge Density

Alkyl ketene dimer(AKD) has been widely used in papermaking sizing and water resistance modification of biomass materials, but the AKD emulsion still has some problems such as easy to hydrolysis or poor stability. It is a big problem for the researchers that the stability of AKD emulsion is not effectively solved. This paper starts with the study of the mechanism of AKD sizing, then develop a new type of high charge density cationic polymer emulsifier, fundamentally solve the problem of poor stability, and the lag of the AKD emulsion emulsion, and to investigate the mechanism and the mechanism of its stability.Firstly, we synthesized polyamine emulsifier with high cationic charge density and then investigate the effects of the reaction temperature, reaction time, monomer ratio, initiator dosage and p H on the viscosity-average molecular weight and charge density. Then the high charge density of the experimental system was used to the emulsion of AKD, and we discussed the effects of emulsifier synthesis conditions on the stability of emulsion and water resistance of paper. we got the results that the best reaction temperature was 80 ℃, the reaction time was 3 hours, the best ratio of dimethyl diallyl ammonium monomers and diallylamine was 100:4, the dosage of initiator-ammonium persulfate was 0.1%, p H was five. Under this condition, the synthesis of polyamine type emulsifier and AKD binding strength is high, the dispersion of emulsion is improved, the emulsion particle size is reduced to a largeextent, and the Zeta potential of the emulsion is improved. At the same time, the effects of two different stabilizers, sodium carboxymethyl cellulose and sodium carboxymethyl cellulose, on the high charge density AKD emulsion were discussed.The addition of stabilizer changed the viscosity of emulsion dispersed phase. The particle collision rate slows down, so that the emulsion stability is enhanced, and with the increase of the time, the emulsion is more stable than the stabilizer, there is no obvious instability of the phenomenon of flocculation and flocculation.Then, the HLB value of emulsifier BS-1 is used as the theoretical basis,compounded with PDMDAAC and get compound emulsifier applied to AKD emulsion,The effects of solid content, emulsifying temperature, emulsifying time and AKD pre melting on the emulsion stability and sizing effect were discussed. Experimental results show that can achieve better emulsifying effect when the solid content is 12%,the temperature of 80 ℃, emulsifying time is 10 minutes, PDMDAAC and emulsifier BS-1 mixing ratio of 20:1, AKD emulsion stability better. Under the premise of reducing the cost and increasing the efficiency of sizing, the poor emulsion stability,easy to be hydrolyzed, and the sizing lag is also solved.Finally, the stabilization mechanism of AKD emulsion was studied, the hydrolysis conditions of AKD under different conditions were discussed respectively. The effects of different temperature, p H value, aluminum sulfate and light calcium carbonate(PCC)on the hydrolysis rate of AKD were studied, which provided the basis for the preparation and storage of AKD emulsion.It showed that hydrolysis temperature, time and p H increased would exacerbate the AKD, under alkaline conditions, aluminum sulfate will be added the stability of influencing AKD. PCC also has obvious promoting effect on the hydrolysis of AKD.