Effects Of Rheological Agents On Rheological Behaviors Of Coating Colour With High Solid Contents And Surface Performance Of Coated White Paper

Recently, with the rapid development of economy, the high quality requirements to coated white paper and paperboard are increased dramatically in package decorating field. Manufactures wish to seek suitable chemicals with better quality to prepare coating colour so that they can meet customers'desiration and also obtain market and economic profits, just after they had completed the adjustments of coating process. So, the key point is how to adjust the coating formulation wih high concentration and low viscosity. That's to say, concentration surpass 60% and has perfect shear-shinning characteristic. The function of rheological agnets in the process of coating colour formulations is improving rheological characteristics,which is one of the important factors work on the quality of coated paper.In this research, some normal used agents including CMC,PVA,Starch and L255 are discussed comprehensively. The coating colors were prepared by adding different rheological angents and changed their dosage separately, coating layer physical properties, surface layer structure characterization and rheological performance were investigated. The effects of rhological agents on rheological properties of paper coating colors were studied with an attempt to offer technological and theoretical support for this field of research.The relationship between viscosity and shear rate was researched by AR550 rheometer, which also could help denifite the linear viscoelasticity zone of coating colours. The results showed that the coating colour has markedly shear-thinning performance in low-medium shear condition ,also Cross equation could be used to fit the curves.Which need to be noticed was that L255 had more intense effects than CMC, just added into typical formula, while H-B model is appropriate for overfitting the relationship between high-shear viscosity and shear rate, but unlike with low shear curves, beyond a certain shear rate, all coating formulations contained with these four style rheological agents, there is shear-thickening. Especailly Starch and PVA have negative effects on the coating operation. L255 can make coating web have similar viscoelastic properties, while starch has the lowest modulus in spite of its highest doasage. The storage modulus is increased firstly then tend to gently with increasing frequency,which is contrast to shear loss modulus.There are no phase angles exceed 15°,which indicate that the elastic character of the color is more pronounced than the viscous character.According to related national standards ,combined the surface layer characteristics by SEM and AFM with coating layer performance analysis,we can see the stacking among compositions clearly in high magnification, pigments interlaced with each other and voids exist. For CMC and L255, they can provide better smoothness and gloss, while Starch and PVA can obtain preferable IGT and ink absorbancy.