| On the background of rapidly developing paper-making industry and higher quality requirement in paper and paperboard, more and more attention has been paid on the surface sizing owing to its satisfactory application performances. Surface sizing provides the products with high paper strength, good printability, excellent shape stability, good water and oil-resistant ability. And styrene-butyl acrylate emulsion (hereafter referred to as SAE) surface sizing agent plays an important role in the paper-making industry for its simple preparation process, convenient application method and good sizing effects.This essay dealed with two different methods to prepare SAE and the reaction conditions were optimized through the single-factor experiments. Low degree of substitution cationic starch (CS-8) was used as a dispersing agent and grafted with styrene and butyl acrylate to synthesize SAE in the first method. And the property of the starch based SAE was further improved by charging functional monomers such as hydrophobic monomer, cationic monomer and crosslinking monomer. The optimized conditions are pointed as followed. The weight ratio of CS-8to monomers was1:2, the viscosity of the pretreatment starch was between18and25mPa-s, the dosage of FeSO4was2%o of the mixture monomers while the H2O2(30%effective content) was10%, the weight ratio of styrene to butyl acrylate was1.5:1. In addition, dimethylaminoethyl methacrylate (DM) was choosed as the cationic monomer, rosin as the hydrophobic monomer, glyoxal as the crosslinking monomer and alpha-methyl styrene dimer as the chain transfer agent. The stirring speed was set at180rpm and the reaction temperature was fixed at90℃.A cationic polymer was synthesized to carry out styrene-butyl acrylate emulsion polymerization in the second method, and the method was divided into two steps. First of all, the polymer was copolymerized by styrene, acrylonitrile and dimethylaminoethyl methacrylate and then neutralized by acetic acid to generate ammonium salt compound. And the compound can serve as a good dispersing agent in palace of CS-8. The optimized weight ratio of styrene, acrylonitrile, dimethylaminoethyl methacrylate and acetic acid in copolymer preparation was8:4:3:6. The dispersing property of cationic polymer can be improved by adding PEG and chain transfer agent, which would make a great contribution to the emulsion polymerization. In the last, Al2(SO4)3was choosed to improve the sizing performance of SAE and BTHP-NaHSO3was applied to remove the residual monomers.The performances of the two different SAE were compared in surface sizing application of corrugating medium. And the emulsions were charactered in FT-IR, thermal analysis and then further characterized in particle charge, diameter and zeta potential. The particle diameter of starch based SAE was77.8nm. The particle charge of the emulsion was0.081mmol/g and the zeta potential was15.27mV. The Cobb60of one side sized paper was21.0g/m2, the breaking length in machine direction was3.41km and the ring crush index in cross direction was5.37N-m/g. The particle size of polymer based SAE was99.4nm. The particle charge of the emulsion was0.643mmol/g and the zeta potential was32.63mV. The Cobb60of one side sized paper was18.6g/m2, the breaking length in machine direction was3.32km and the ring crush index in cross direction was5.52N-m/g. The properties of these two different surface sizing agents were comparable to the commercial products such as BK styrene butyl-acrylate emulsion surface sizing agents. |
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