| In recent years, China’s papermaking industry is facing excessive capacity, intensive competition, and declining profit. At the same time, constantly improving environmental protection requirements make the pressure of energy conservation, emission reduction and green production keep rising. To increase profit, papermaking companies are keen to produce high-quality products with cheaper raw materials. By the application of dry strength agent, reducing fiber dosage or using low-end raw materials to replace high quality fibers without prejudice to paper strength—to reduce the cost—is possible. But as the closure degree of white water circulation system increases, the application environment of dry strength agent becomes more complex, with more interference factors. Competition of current domestic dry strength agent market is intensive, with numerous domestic or foreign manufacturers, whose products are very uneven in quality. Several Japanese products are occupying the high-end market, with a considerable gap between them and domestic ones. Therefore, the development of a highly efficient and strongly adaptive dry strength agent product with independent intellectual property is in needed.The product—the cross-linked amphoteric polyacrylamide (AmPAM) dry strength agent— was synthesized by the technique of free radical copolymerization in water solution, with acrylamide (AM) as the main monomer,2-methacryloxyethyl trimethyl ammonium chloride (DMC) as the cationic monomer, acrylic acid (AA) as the anionic monomer, and N-methylol acrylamide (NMA) as the crosslinking agent, sodium formate (SF) as the chain transfer agent, ethylenediamine tetraacetic acid disodium salt (EDTA-2Na) as the chelating agent, ammonium persulfate as the initiator, and sodium bisulfite as termination agent. Based on previous research, this product had already completed its laboratory optimization, and established the optimum synthetic process and conditions. Its preliminary exploration of industrialization had also been carried on. The product’s application is of superior performance and stable quality. And its enhancing effect is at the advanced level of this industry, also having favorable salt resistance and shear resistance properties.In this paper,the expansion of the dry strength agent’s production scale was realized through the optimization of process temperature control. And some simple industrialized production designs (including equipment specification, production process and process control) of this product was accomplished. Then, a series of process improvements were proceeded, to simplify the operation and reduce production cost. In addition, the main factors concerning polymer’s two important features (molecular structure&charge density) and their influence on synthesis and polymer application were studied. Finally, the basic performance indexes and rheological properties of the product were tested, and product’s application effect was evaluated.Established by experiments, the process conditions fitting for current production environment are as follows:the reaction concentration is 20wt.%, the initiation temperature is 78℃, the holding temperature is 80℃,22% of monomer is used for adding into reactor(during production process), the dosage of crosslinking agent is 0.7wt.%o, there is no N2 treatment before reaction, and tap water instead of deionized water used as reaction solvent is possible. The product obtains positive charge density of 0.7-0.8mmol/g, and its apparent viscosity is about 10000-25000mPa·s. The industrialized mass production(max scale:10 t/kettle) was achieved, with gentle reaction exotherm, easy operation, and optimal product quality equal to laboratory optimum sample, as well as good controllability. The application effect of cross-linked AmPAM dry strength agent produced under optimized conditions was proved, both in lab and paper factory conditions, to be excellent in enhancing paper strength and applicability of wet end environment. |
PDF Full Text Request