Research On The Process And Mechanism Of Paper Surface Sizing

As China’s economic recovery, the paper industry has been rapid development. Corrugated paper and paperboard as packing container are widely used in all walks of life. With the rapid development of the packaging industry, the corrugated paper was required to be more attractive, more convenient and better quality. Therefore, higher strength, lower weight and lower cost is the direction of corrugated paper manufacturing industry in the future. Surface sizing is one of the effective methods to improve the paper properties. This method can improve the various properties of paper, such as flatness, printing performance, folding, durability, abrasion resistance and so on. Quality of surface sizing agent and paper sizing process directly affect the application performance of corrugated paper, at the same time, they also decide whether corrugated paper can give full play to its own advantages. Therefore, the important problems which should be researched urgently are the preparation of high quality surface sizing agent and improvement of sizing parameters. The thesis summarizes the whole work about paper surface sizing and studies the gelatinization process of starch in papermaking process. Synthetic polymers and natural polymer were chosen as paper surface sizing agent. The compressive strength and water resistance of the paper were studied by series of tests, and the optimum formulation and process parameters were presented. Moreover, surface sizing agent has been applied in actual production. Furthermore, the mechanism of polymer surface sizing agent was also studied. This work provides a theoretical basis and technical support for the development new products, provides guidance and theoretical basis for the production of the paper. The main conclusions are as follows:(1) Starch hydrolysis products were in accordance with the characteristics of pseudoplastic fluid with shear thinning. At the same sheer rate and the temperature conditions, the apparent viscosity reduced gradually following by extension of hold time or increasing the contents of enzyme, but the apparent viscosity increased with the contents of starch or contents of cross-linking. The apparent viscosity increased with reducing of the temperature of the starch pastes under the identical sheer rate. Reducing viscosity and increasing the amount of coating can beneficial to improve the compressive strength.(2) The emulsion particle of starch/styrene-acrylic composites emulsion showed regular spherical. The average particle size was about100nm. Emulsifier affected the value of Zeta potential of polymer emulsion. When cationic starch is used as emulsifier, the value of Zeta potential is positive; when anionic starch is used as emulsifier, the value of Zeta potential is negative. When the monomer ratio was6:4and the contents of enzyme and starch was0.0338g and37.5g, the water resistance and compressive strength of paper has been improved a lot.(3) The distribution of electric charge on the surface of paper is changed by aluminum sulfate, the electrical of paper fiber suspension transitions from medium anionic to weak cationic. When the contents of aluminum sulfate was less, cationic surface sizing agent was adsorbed on the surface of paper by coordination and electrostatic interactions, but anionic surface sizing agent was adsorbed on the surface of paper mainly by coordination. At the same experimental conditions, the surface sizing performance of cationic polymer emulsion was better than anionic polymer emulsion. When added excessive amounts of aluminum sulfate, both surface sizing agent was adsorbed on the surface of paper mainly by coordination. there was no obvious change about Cobb value. The charge of polymer emulsion had no influence on compressive strength(4) There were a lot of microporous on the surface of corrugated paper. Emulsion particles could penetrate into the inside of the paper, so that water resistance of the paper would be improved a lot. The size of emulsion particles had less influence on the compressive strength of paper. The Cobb value decreased with the increased of contents of polymer emulsion, however, the water resistance of paper was no longer continue to enhance when the contents of polymer emulsion exceeded.