The Development Of Additives For Coated Printing Paper And Study On Compatibility Of Coating Color

The coated paper shows more and more important position in papermaking industry in the world. The development of coated paper market, printing and packaging industry increases the demand for coating chemicals and coating pigment. Coating chemicals used as important composition in production of coated paper reveal its more and more important status too. Then it would be necessary to develop more and more coating chemicals.The low-molecular weight polyacrylate sodium is applied widely as organic dispersant. When the molecular weight is between 500 and 5000, the effect of dispersion is the best for the dispersion of coating pigments. Syntheses of polyacrylate sodium is done by free radical polymerization with water as solvent and (NH4)2S2O8-NaHSO3 as redox initiator at certain temperature. The effects of various factors on the molecular weight of polymer such as the reaction temperature and time, the ratio of oxidant to reductant, the ratio of oxidant to monomer and the concentration of monomer were studied too in the first section of this paper. In addition, the optimum technology for preparing polyacrylate sodium and the sequence of factors effecting on the polymerization by means of orthogonal experimental design was discussed. The results show that the optimum condition for the synthesis of the polyacrylate sodium are temperature 50 C, time 4h, the ratio of oxidant to monomer 1.2%, the ratio of oxidant to reductant 1:4 and the concentration of monomer 30ml/100ml. The sequence of factors effecting on the polymerization is as follows: temperature > the ratio of oxidant to reductant > reaction time>the ratio of oxidant to monomer>the concentration of monomer. A comparative research on the dispersion effects with the dispersant developed in our lab and the commercial dispersant was examined. The results show that the dispersant developed in our lab can reduce the viscosity of coating color and increase the stability of dispersion system when it was used in coating color as a dispersant, and it also can improve the gloss and roughness of the coated paper.The preparation of the wax emulsions with paraffin, beeswax, mineral wax and mixed emulgent was described in the second section. The results show that the amount of emulsifying agent, the emulsification time, emulsification temperature and the agitation speed show great effects on the stability and dispersing ability of emulsion. When wax is emulsionized at 80 C for 90 minutes and stirring 900r/min, mixed emulgent dosage 13%, the product is stable. The wax emulsion is suitable for using as a kind of lubricant. This section also studied the influence of waxemulsion on the coating performance. The results show that the wax emulsion can decrease the viscosity of coating color when it was used as lubricant in coating color and it also have excellent compatibleness with other components of coating color. Further more, when the wax was used in coating color, it shows the effect of defoam. The results of coating also show that the wax emulsion lubricant improves the gloss and decreases the roughness of coated paper. For consideration of both foam and the performance of coating and coated paper, a dosage of about 1.0% lubricant in coating color is good enough to develop its function.The choice of coating formula not only controls the ultimate performance of coated paper, but also decides the runnability of coating color on the coating machine. The third section of this paper described the parameters that should be discussed in details in the coating formula. The parameters include the choice of pigment, pigment proportion, the choice of dispersant and lubricant, the optimization of adhesive (including mono-component adhesive and poly-component adhesive). In addition, the section also described the influence of these parameters on optical properties and printability of coated paper. A good coating formula with low cost and good paper properties was recommended, which is clay 70 parts by weight, calcium carbonate 30 parts by weight, latex 13 parts by weight, starch 3 par...