Preparation and application of soap-free emulsion in surface sizing of base paper

A core-shell structural copolymer latex (PSS) based on styrene, acrylate, (methyl) acrylic acid, sodium alkyl vinyl sulfonate and maleic anhydride was prepared by soap-free emulsion polymerization. The predesigned copolymer structure and morphology of PSS was identified respectively by IR, DSC and TEM. PSS with oxidized starch or not was applied as surface sizing agent to modify the properties of base paper both in our lab and in paper mill. Various properties of base paper including Cobb value, surface and internal bond strength and gloss were improved with the increase of coating weight of PSS. The proper addition ratio of oxidized starch to PSS was also identified at 9 : 1 by weight in our lab. On this condition, compared to the full application of oxidized starch, decreases by 28.6% and 40.8% were individually obtained in the 60s Cobb value of the face and back side of the coated art base paper, meanwhile, wax pick, tensile index, tear index, folding endurance and brightness were respectively increased by 14.2%, 7.4%, 5.1%, 16.7% and 0.7% ISO on the basis of adding the dosages of CaCO3 and CS. Consequently, benefit analysis of this application in paper mill was discussed in this article.