| Recent years, the quality of paper and cardboard cannot meet requirements due to the rapid development of papermaking industry and a lack of high-grade paper fiber in China. Adding sizing agent is the effective method to solve the problem. The synthetic surface sizing agent has good properties of film forming and excellent water resistance. And its molecular structure is designability. In addition, it can greatly improve the surface strength and printing adaptability of paper.Emulsion polymerization is one of the methods to prepare surface sizing agent. Anionic styrene-acrylic surface sizing agent with 40% solid contents was prepared by pre-emulsification and semi-continuous technology. It comprised of styrene (St), butyl acrylate (BA), acrylic acid (AA), buffer (Sodium bicarbonate), OP-10 and sodium dodecyl sulfate (SDS). Effects of various components on conversion rate, gel rate and sizing degree were studied. The optimum reaction condition was described as below:m (St+BA)= 18.05 g, n (St:BA)= 1, m (water) =25g, w (AA)= 4%, w (initiator)= 0.45%, w (emulsifier)=1.44%, m (NaHCO3)= 0.05 g. In this condition, the conversion rate, gel rate and sizing degree reached 95.38%,0.38%,2 min respectively. It was analyzed by infrared spectrometer, scanning electron microscope and automatic surface interfacial tension instrument. The infared spectrometer (IR) indicates the structure of monomers was existed in the resin. The SEM demonstrates that the product formed a continuous film at the corrugated paper surface, leading to the surface much smoother. The initial contact Angle which is between corrugated paper and water reached 87.6°, and the contact Angle maintained between 72°and 73°in two minutes. This result shows that the corrugated paper has certain water resistance after surface sizing. Adding N-hydroxymethyl acrylamide as crosslinking agent, when m (crosslinking agent:functional monomer)= 1/3, the conversion rate, sizing degree and initial Contact Angle reached 91.31%,3.67 min and 93.4°, respectively. And the Contact Angle maintained between 73°and 74°in three minutes. Compared with original paper, water resistance of the sizing paper is greatly increased.Taking methacryloxyethyl trimethylammonium chloride (DMC) as reative emulsifier through seeded emulsion polymerization, synthesized the styrene-acrylic latex with 30% solid contents. Studied the effects of emulsion systems, various components, reaction temperature, charging way, pH and amplification experiment on conversion rate, particle size and sizing degree. The optimum reaction condition was demonstrated as below:OP-10-DMC-n-butyl alcohol as emulsion system, V(OP-10)=1ml, w(DMC)=10%, V(n-butyl alcohol)=8ml, m (St+BA)= 36.086 g, n (St/BA)= 1, m (water)=80g, w (AA)=5%, m (initiator)=0.2g,w(initial monomer)=30%(total dosage of monomer), w(initial initiator)= 50%(total dose), T=83-84℃. In this condition, The conversion rate and sizing degree reached 96.65%,130s, respectively. Inspected pH 2-12, when the pH reached 2 and 8, the sizing degree was 130s,141s, respectively. The conversion rate of amplification experiment reached 99.87%. The sizing agent was analyzed by infrared spectrometer, scanning electron microscope, laser nano particle size analyzer and automatic surface interfacial tension instrument. The IR shows that the structure of monomers was existed in the polymer. The SEM demonstrates that the surface of the sizing corrugated paper became much smoother. The laser nano particle size analyzer shows that the mean particle size was 169.9nm and PDI reached 0.023. The Zeta potential of the emulsion reached +36mV. This result shows that this product was stability and can be used in extensive pH range. The initial contact Angle which is between corrugated paper and water reached 97.89°, and the contact Angle maintained between 95°and 94°in two minutes.Above all, styrene-acrylic latex sizing agent synthetized in this article can improve the surface properties of the corrugated paper. |
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