Sizing Efficiency Improvement Of Cationic Rosin Size

In this paper, the application and sizing efficiency of cationic rosin sizes were investigated. The influences of the dosages of surfactants including dodecyl dimethyl benzyl ammonium chloride, hexadecyl trimethyl ammonium bromide, sorbitan oleate and nonyl phenol ethoxylate on the character of weakly charged cationic acrylate copolymer emulsifier and consequently on the performance of dispersed rosin size emulsified by the acrylate copolymer emulsifier were investigated by means of orthogonal experiment. A weakly charged cationic acrylate copolymer emulsifier prepared by the optimized formula of surfactants shows good emulsifying and stabilizing effects on melted rosin materials. A weakly charged anionic dispersed rosin size prepared by the weakly charged cationic acrylate copolymer emulsifier displays a high sizing efficiency.Then the function of glycerin rosin ester in stabilization and sizing development of cationic rosin size were investigated by using conventional sizing measurement, ESEM and XPS.The results show that glycerin rosin ester can significantly reduce the surface carboxyl groups of cationic rosin size, which prevents the aggregation of rosin particles and improves the stability of cationic rosin size. The improvement of the stability of cationic rosin size may enhance its sizing efficiency. However, the reduction of carboxyl groups by glycerin rosin ester lowers the sizing performance of cationic rosin size.At the same time, the interaction of alum and cationic dispersed rosin size under various conditions and its effect on the rosin sizing development were investigated. The results show that the existence of alum significantly increases the softening and melting points of the cationic dispersed rosin size and improves its distribution while does not prevent the melting and spreading of rosin size on paper surface. Alum also improves the hydrophobicity of rosin size film and promotes the formation of well constructed rosin film during drying. It is the addition level (not the ratio between the alum and rosin size) that is more important to the sizing development of cationic dispersed rosin size.To further improve the sizing efficiency of the cationic rosin size, cationic dispersed rosin sized paper was treated with polar and non-polar organic solvent. We found that the sizing performance of the cationic dispersed rosin size can be further improved dramatically by benzene treatment. Air-dried papers show greater sizing improvement than that of oven-dried paper. While the non-polar solvent such as water, ethanol soaking treatments lower the sizing performance of the rosin size.Finally, the surface sizing efficiency of cationic rosin size/alum was investigated based the trend that more and more internal sizing was replaced by surface sizing for paperboard. The results show that, the pH value and the addition of alum can dramatically affect the function of cationic dispersed rosin size. The addition of suitable amount of cationic starch can increase the rosin sizing efficiency. However, the ratio of alum and cationic rosin size is more important, and also, when the cationic dispersed rosin size is mixed with the cationic starch at 65oC, better sizing efficiency can be obtained. With the proper addition of PVA and PAE, the sizing efficiency of cationic rosin size can be improved too. However, the oxidized starch shows poor synergistic surface sizing effect with cationic dispersed rosin size.