Study On Factors Affecting Rheological Properties Of High Solid Content Coatings

As the fine coated paper industry into low-margin era, in order to step out of the currentpredicament, many papermaking enterprises are seeking response strategy. Improving theproduct quality and reducing the production cost have been the most urgent and the most directdemands. It is attached great importance of various paper mill to the paper coating, whichdirectly affects the quality of coated paper and the performance of coating machine. In order todevelop a suitable coating to meet the requirements of high-speed online knife coater, papercoatings are moving towards high solid content and low clay volume trends, the rheologicalproperties of the coating is particularly important, not only affect the normal operation of thecoating machine, but also related to the quality of fine coated paper.In this paper, taking coating which in the actual production process as research object,studied the dispersion of Kaolin dispersion with high solid content by using Minitab softwareTaguchi experimental design method to determine the optimum dispersion conditions; studiedthe effected coating rheological properties of pigment, solid content, dispersing agent, latex andrheology modifier, analyzed the carboxymethyl cellulose (CMC) and sodium carboxymethylstarch (CMS-Na) of the coating and coated paper performances; the actual production of theplant, for example, analyzed the situation changes in the rheological properties of coatingduring the cycle of the blade coating, adhesive migration and impacted on the performance ofcoated paper.The test found that the suitable high-solid clay dispersion conditions, solid content of74%,speed of2500rpm, the dispersion time of15min, the amount of dispersant is0.05%, NaOH inthe amount of0.01%. Among them, the amount of dispersant is the main factor affecting theKaolin dispersion. In actual dispersion process plant operation, the target solid content of claydispersion from the current71%to74%, which also improved coating solid provide thepossibility; the rheological properties of the coating are closely related to its composition, thelow shear viscosity is determined by the surface chemistry, and the high shear viscosity isdetermined by the character of fluid dynamics, the two have fundamentally different. Pigmentparticles, latex, dispersing agents and rheology modifiers are very important factors affectcoating rheology; CMS-Na water retention properties superior to CMC; CMC and CMS-Na caneffect coated paper on whiteness, gloss, ink absorbency and surface strength, but not allcompletely the properties associated with the amount of linear; In the actual high-speed bladecoating process, with the passage of the cycle time, the coating rheological properties wouldproduce a certain effects, the ultra-high shear viscosity and the low shear viscosity will increase,water retention properties of coating will also certain rise. In addition, the solid content of thecoating and adhesive content would have changed, the solid content rising but adhesive leveldeclining, coating adhesive migration phenomenon prominent.Therefore, in the course of modern high-speed blade coating operation, the rheologicalproperties of the coating affects the entire coated paper production operations, the plant focuson the important research direction of coating rheology to ensure the stability of productionquality and operation. According to the actual production needs, we can appropriately change coating formulations, it is desirable to achieve the production conditions.