Synthesis And Application Of Cationic Styrene-based Polymeric Surface Sizing Agent

With the increasing development of printing technology, the high printability of paper is required, for instance, the higher strength of paper sheet is needed as response to the growing speed of printing machine, and the excellent printing opacity of paper is demanded as a result of the development of lower-basic weight paper. All these requirements have tremendously impulse the research and development in paper surface sizing with some special surface sizing agents. Synthesized surface sizing agents attracted more and more attention in papermaking industry, which is related to the structural adjustment of raw material, the diversity of printing process, more rapid printing, and the tendency of higher quality paper products. Surface coating directly acts on the surface of paper sheet, thus, it can overcome a series of operating problems, such as the pollution of machine system, frothing and lower sizing degree under high temperature.In this study, emulsifier-free copolymerization of styrene with cationic monomers was employed to prepare styrene-based cationic surface sizing agents of paper, cationic copolymer-styrene-butyl acrylate, and the structural and physical properties of the resulting polymers were characterized and the application ability of the resulting emulsion was also compared with the market cationic starch.In the preparation process, the cationic copolymer-styrene-butyl acrylate, surface sizing agent, was prepared through two steps. First, emulsifier-free copolymerization was used to prepare cationic polymer-styrene, and optimize the reaction conditions, such as reaction time, initiator dosage, the cationic monomer and its dosage. In the second step, the soft monomer butyl acrylate was added to the polymer-styrene emulsion made in the optimized conditions and ternary polymerization product was formed. The cationic copolymer-styrene-butyl acrylate with suitable glass transition temperature (Tg) was also obtained in this study by adjusting the amount of butyl acrylate.In the second part, the resulting emulsion was characterized by a series of methods, and the results were described as follow.1. From FT-IR spectra, the absorptive peak 3000cm-1~3020cm-1 disappears, which shows that the alkylene double-bond of the monomer has not exist as a result of the occurrence of copolymerization reaction in the reaction system.2. Dispersion of dynastic light was adopted to determine the particle size distribution and the surface charge of two kinds of cationic copolymer-styrene-butyl acrylate. The particle sizes of SBV emulsion are between 90nm and 105nm, while the particle sizes of SBD are between 80nm and 102nm. According to the results of charge density, the higher the charge density is, the lower the sizing degree of the emulsion is. The high charge density implies the high content of cationic monomer and the low content of styrene in the surface sizing agent, so the hydrophobicity of the polymer reduces and then the sizing efficiency reduces correspondingly. 3. Differential scanning calorimeter (DSC) was used to characterize the Tg of the surface sizing agent, SBV and SBD. It is proved that the addition of butyl acrylate can decrease the Tg of copolymer to fulfill the requirement of paper-shaping.4. Characterized by SEM, the emulsion particles distribute uniformly on the fiber surface after sizing. The morphology of emulsion particles remains in the form of square and the size is uniform, which is better for the emulsion to cover on the paper surface and size efficiently. It is demonstrated that the retention of the resulting emulsion on the paper surface has achieved. Due to the positive charge of the resulting surface sizing agent, the retention of cationic copolymer-styrene-butyl acrylate, SBV and SBD on the paper surface can smoothly attain under the action of electrostatic interaction.5. Compared with the blank specimen, the paper treated with SBV and SBD obtain fine properties. The sizing degree, printing surface strength, ink absorptiveness, dry strength and wet strength all obviously improve. In the properties of galling speed, ink absorptiveness and wet strength, the paper treated with SBV and SBD are superior to the one treated with the market cationic starch, but in the dry strength, they represent the equal performance.