| Due to the high utilization rate of recycled pulp, it is often necessary to apply surface sizing agent on paper to meet the requirements in surface strength and water resistance of paper. Acrylic latex is not only easy to get its raw materials, but also very good at film forming, which is often used as surface sizing agent. But the traditional cationic styrene-acrylic latex is difficult to form a piece of dense film on paper, for the lack of crosslinking point with fibers. In this paper, the cationic styrene-acrylic latex was prepared by using the semi-continuous seed emulsion polymerization. And the preparing principles of the cationic styrene-acrylic latex were studied. Subsequently, the cationic styrene-acrylic latex was modified with silicone-containing monomer and silica gel, and the application of the modified latex was studied by using as surface sizing agent. The whole thesis included six chapters, which contained:Chapter 1:Review. The research background was introduced, the research progress of acrylic latex in modifying technology was summarized, and the application of modified acrylic latex as sizing agent was analyzed. The mechanism and the method of surface sizing, the category of surface sizing agents were introduced. Subsequently, the research objects and content of the project were put forward.Chapter 2:A general report on the research of preparing and characterizing the cationic silicone-acrylic latexes. Series of stable cationic silicone-acrylic latexes were prepared by using the semi-continuous emulsion polymerization of styrene (St) and butyl acrylate (BA) in the presence of acrylamide (AM), (2-(methacryloyloxy) ethyl) trimethyl ammonium chloride (DMC) and vinyltriisopropoxysilane (A-173). And the structure and properties of the latexes were characterized by infrared spectroscopy (IR), dynamic light scattering (DLS), transmission electron microscope (TEM), a rotational viscometer and differential scanning calorimetry (DSC). The effects of the ratio of soft and hard monomer, the amount of hydrophilic monomer and the amount of silicone-containing monomer on the properties of the latexes were studied in detail. The more excellent synthetic process of the cationic silicone-acrylic latex was obtained.Chapter 3:The research on the application of the cationic silicone-acrylic latexes using as surface sizing agents. The water-resistance, the ring crush index, the tensile strength, the contact angle and the surface morphology of the sized paper were characterized, and the effects of the silicone-containing monomer amount on the sizing performance of the surface sizing agents containing a little cationic silicone-acrylic latexes were examined. The Cobb value decreased by 40%, the contact angle increased from 44.5° to 93°, the ring crush index increased by 20% and the tensile strength improved to some extent when the starch gel containing a little cationic silicone-acrylic latex, which was produced with the addition of 4% A-173.Chapter 4:A general report on the research of preparing and characterizing the cationic silica/styrene-acrylic hybrid latexes. Series of cationic silica/styrene-acrylic hybrid latexes were prepared by using the semi-continuous seed emulsion polymerization of styrene and butyl acrylate in the presence of acrylamide, (2-(methacryloyloxy) ethyl) trimethyl ammonium chloride and acid silica sol. The effects of the adding way of silica sol, the amount of initiator, the pH of the pre-emulsion and the amount of silica sol on the properties of the latexes were studied in detail. And the properties of cationic silica/styrene-acrylic hybrid latexes were examined by dynamic light scattering, transmission electron microscope and thermal gravimetric analyzer (TGA). Besides, the more excellent synthetic process of cationic silica/styrene-acrylic hybrid latexes was obtained.Chapter 5:The research on the application of the cationic silica/styrene-acrylic hybrid latexes as surface sizing agents. Through the characterization of the water-resistance, the ring crush index and the surface morphology of the paper sized by the cationic silica/styrene-acrylic hybrid latexes, the effects of the modification with silica sol on the sizing performance were examined. In comparison with the sizing performance of the paper sized by pure acrylic emulsion, the Cobb value of the paper sized by the sizing agent produced with the addition of 2%silica sol decreased to 29% and the contact angel decreased to some extent. And the ring crush index increased 40% with respect to the original paper. The Cobb value of the paper sized by the cationic silica/styrene-acrylic hybrid latexes with 8% silica sol was not as small as the Cobb value of the latex with 2% silica sol. However, the contact angel increased from 64° to 120°, with respect to the paper sized by pure acrylic latex.Chapter 6:Conclusions. The conclusions were drawn, the highlight of innovation was put forward, and the further research was proposed. |
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