Preparation And Properties Of Styrene-Acrylic Emulsion With Core-shell Structure For Waterborne Glazing Oil

In the application of waterborne glazing oil, styrene-acrylic latex has animportant position with good adhesion, excellent resistance to contamination, weather,alkali and high capability price ratio. At present, the styrene-acrylic latex was usuallysynthesized by traditional emulsion polymerization which used many emulsifyingagent in preparation. The residual emulsifier can affect the compactness, waterresistance and glossiness of the film, and also could cause environmental pollution.In this paper, combined with soap-free emulsion polymerization and core-shellemulsion polymerization, a new styrene-acrylic latex with core-shell structure hasbeen prepared by self-emulsifying technology. Not only the emulsifier problem can beovercame, the latex particle size can be controlled by the controlling of the amount ofhydrophilic monomer. What’s more, the minimum film forming temperature of thelatex can be significantly reduced because of the core-shell structure.With main raw materials such as styrene (St), methyl methacrylate (MMA), butylacrylate (BA) and acrylic acid (AA), the polyacrylate chain containing carboxyl hasbeen prepared by solvent polymerization first. Then it was dispersed in water withcore monomer St together after carboxyl groups being neutralized. Thus apolyacrylate-styrene dispersion (PA-S) has been obtained by self-emulsifying. Andthe next was the emulsion polymerization. Then hydrophobic polystyrene chainsformed the core of the particle, polyacrylic (ester) containing hydrophilic groupsformed the shell.The influence of preparation process on the latex and the film has been studied.Three kinds of process have been discussed: multistage solvent polymerization andphase transfer process (in the same reactor and in different reactor), solventpolymerization combined with emulsion polymerization process. The result showsthat the last method was better.In the solvent polymerization for PA-S dispersion, the effect such as the type anddosage of initiator, solvent polymerization temperature, holding time, stirringintensity, dispersion process, the way of monomer addition, the AA monomers, theneutralization degree on the performance of dispersion, emulsion and film have beendiscussed.In the emulsion polymerization for styrene-acrylic latex, the effect of the type and content of initiator, the content of core monomer on the performance of emulsionand the film have been discussed, especially the influence of core monomer on theminimum film forming temperature of the emulsion.The polymer and the particle structures have been characterized by multipledevices such as FTIR and TEM. FTIR shows that all the monomers have participatedin the reaction and a styrene-acrylic copolymer has been produced; Transmissionelectron microscopy (TEM) shows that the dispersion of the particle is quite uniformand an obvious core-shell structure has been observed. The waterborne glazing oilfrom this styrene-acrylic latex for paper printing is of good filming properties, highgloss, and good rub resistance.