| With the rapid development of papermaking and related industries, surface sizing plays an important role in the paper modification. Surface sizing can improve the mechanical strength, printability, water resistance and oil resistance of paper. As one of the most commonly used surface sizing agents, styrene-acrylic emulsion (referred to as SAE) has been more and more popular favored by its simple preparation process and excellent performance.In this thesis, three kinds of SAE were prepared according to market application. The first one was the starch based SAE. In order to solve the problems of precipitate and pungent odor existed in the starch based SAE, this thesis studied the effect of polymerization temperature, stirring speed, CS-8 and rosin content on the emulsion properties, water resistance and mechanical strength on the paper. According to the result,the precipitate and pungent odor were solved by the optimized conditions. The optimum conditions were listed as follows: the ratio of hard and soft monomer was 1:1, stirring speed was set at 180rpm, FeSO4 accounted for 3‰ of total monomer mass, H2O2 accounted for 8% of total monomer mass, polymerization temperature was 90 ℃, CS-8 accounted for 40%of total monomer mass, rosin accounted for 4% of total monomer mass, aluminum sulfate accounted for 5% of dry starch mass. EHMA accounted for 2% of total monomer mass.The second one was compound silicon modified styrene-acrylic emulsion (referred to silicone-SAE). The performance of silicone-SAE was optimized by comparing the hydrolysis and condensation reaction condition of three commonly used vinyl silicone.Then γ-Methacryloxypropyltrimethoxy silicone (A-174) was used as the grafting bridge between SAE polymerization monomer and eight methyl tetra silicone (D4). Successively,silicone-SAE was synthesized by continuous emulsion polymerization. The effect of the ratio of A-174 and D4 was also studied. The optimum conditions were listed as follows. The polymerization temperature was 90℃, pH was more suitable for 7, the best mass ratio of A-174 and D4 was 1:3. The third one was a polymer based SAE. Styrene and acrylonitrile were used as monomer of polymer emulsifier, azobisisobutyronitrile were chosen as initiator. Afterward, the effect of the styrene and acrylonitrile dosage on polymer based SAE was optimized. The optimum conditions were as follows: styrene accounted for 40%of mixed monomer one, acrylonitrile accounted for 10% of mixed monomer one.In this thesis, the performances of the previously mentioned three different SAE were compared in surface sizing application. The solid content, particle size, the particle charge density (PCD), zeta potential of emulsion and the Cobb12o, mechanical strength of sized paper were tested. The results showed as follows,the solid content of starch based SAE was 33.08%, the particle size was 85.8nm, PCD was 0.083mmol/g, the zeta potential was 23.60mV, the Cobb120 decreased 41.0% by compared with base paper, the ring crush index in cross direction increased by 3.4% and the breaking length in machine direction increased by 7.1%. The solid content of silicone-SAE was 27.35% , the particle size was 107.2nm, the PCD was 0.674mmol/g, the zeta potential was 27.42 mV, the conversion rate was 96.1%,the gel rate was about 0.3%, the Cobb120 decreased by 53.4% compared with base paper, the ring crush index in cross direction increased by 5.5% and the breaking length in machine direction increased by 12.4%. The solid content of polymer based SAE was 28.76%, the particle size was 99.4 nm, the PCD was 0.603mmol/g, the zeta potential was 32.63 mV, the Cobb120 decreased by compared 55.8% with base paper, the ring crush index in cross direction increased by 5.8% and the breaking length in machine direction increased by 15.0%. three kinds of SAE were analyzed by infrared (IR), thermogravimetric (TG) and scanning electron microscope (SEM) analysis. Finally, the performances of three kinds of self-made SAE were excellent. Among them, the polymer based SAE was the one with the best quality, followed by silicone-SAE. |
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