Synthesis And Application Of Self-emulsifying Styrene-acrylic Emulsion As Surface Sizing Agent

With the rapid development of packaging and printing industry, the market have increasingly high requirement to the paper strength, surface properties and printability. As we all known, improving the performance of paper can depend on adding chemicals or surface sizing on paper. In high speed paper machine using white water recycling is important, but adding wet-end chemicals can lead to accumulation of anionic trash and the negative impact on paper machine wet end, Therefore, the research and development of new surface sizing agent and sizing on paper to improve the properties are increasing, and the development of synthetic surface size is the main research direction. Compared with SMA and SAA, SAE for its excellent film-forming property and water resistance has been becoming the current largest and fastest growing surface sizing agent. SAE obtained by self-emulsifying emulsion polymerization shows high monodispersity and clear surface overcoming the disadvantages of traditional emulsion with emulsifier residue.Self-emulsifying SAE with high solid content, good stability and excellent applying properties was synthesized from St and BA by soap-free emulsion polymerization while AA was functional monomer and the mixture of persulfate and Fenton reagent was the initiation system. FT-IR, DSC, TGA, SEM, PCD and laser particle sizer were used to characterize polymerization product.Effects of the amount of AA, initiator and the monomer mole ratio of St and BA, reaction time, temperature and concentration on properties of emulsion were studied, The results show that, when the amount (relative to the total amount of monomer) of AA, APS and Fenton agent are 7%,2%,0.15%-0.2%, respectively, the monomer mole ratioes of St and BA are 1.5:1,1:1 and 1:2, reaction temperature is 80℃, reaction time is 5-6h and reaction concentration is 25%-30%, the properties of self-emulsifying SAE, such as stability, particle size and charge density, are better.Decorating base paper treated with self-made SAE has good surface strength and tensile strength, at the meanwhile, the absorbability of paper has met the requirements of the national standard. The optimized process of surface treating decorating base paper is as follows:sizing base liquid is starch, the amount of APS is 2%, the viscosity of starch is 70mPa.s, the ratio of starch and SAE is 20:1, the dosage of sizing is 2g/m2.Considered of the absorbability of decorating base paper, optimized polymerization process of SAE used to surface treating decorating base paper is that, the amount (relative to the total amount of monomer) of AA, APS and Fenton agent are 7%,2%,0.2%, respectively, the monomer mole ratio of St and BA is 1:1, reaction temperature is 80℃, reaction time is 5h and reaction concentration is 30%. SAE obtained under above conditions can significantly improve the surface strength and printability of decorating base paper, while the paper treated by SAE made by traditional process can not satisfy the absorbability of the national standard.SAE made by the optimized polymerization process was applied in the surface size of fine paper. The results show that, the surface and physical strength, printability of treated fine paper are best, when the ratio of St and BA is 1:1. Compared to untreated paper, the surface strength, tensile strength and color density of paper treated by SAE increase in 171.3%,34.9%,6.36%, respectively, the slope of tone curve is the biggest, the color of print is rich, and the repeatability of tone is excellent.