In the ground mill base, the depolymerization process of the pigment particles can not only fully make the liquid paint wet the surface of the pigment (filler) particles, improve the stability of the mill base, but also improve the pigment's tinting strength, The hiding power will be improved accordingly, and the gloss and other properties of the paint film will also be improved. Therefore, the selection of effective grinding and dispersing equipment can greatly improve the degree of dispersion of pigments in the paint, so that while improving the stability of the paint slurry, it can reduce the amount of pigments used and improve the quality of paints and coatings. The improvement of the degree of pigment dispersion is accompanied by the improvement of pigment coloring power and hiding power, so that some expensive pigments in the paint formula can be replaced by cheap fillers, reducing costs and improving economic benefits. Because in general, the savings achieved by reducing the amount of expensive pigments clearly exceed the consumption associated with a higher degree of dispersion, the intensification of the dispersion process in the production of paints, as well as the selection and application of effective grinding and dispersion equipment, and the use of pigments The improvement of dispersion requirements is a matter of great concern to paint workers. When we understand the principle of dispersion, choose dispersion equipment and evaluate the dispersion effect, we should clarify the following concepts:
①In the grinding and dispersing equipment currently used to disperse pigment (filler) material particles in liquid paint, the deagglomeration of aggregates and agglomerates is due to the fact that the ground mill base passes through different forms of mill base passages (such as three rollers) The gap between the rollers of the machine, the double ring action area between the two dispersion discs of the sand mill), the contact stress generated during the movement plays a role in depolymerization, rather than relying on the working parts of the equipment to face the color (filling ) the direct action of material aggregates or agglomerates;
②The selection of grinding and dispersing equipment not only considers the dispersion time, but also considers the influence of factors such as the ability of the paint slurry to reach a suitable stable state, and the ability of the pigment to exert suitable performance;
③ The evaluation of the dispersion effect is to obtain suitable pigment performance and paint film performance as the main goal, and the fineness value of the scraper Fineness Meter cannot be used as the goal.
As mentioned earlier, the depolymerization process of the pigment is the process of restoring the secondary particles of the pigment to or close to its primary particles. This degree of transformation from large particle size pigment groups to small pigment particles is the most important in color paints. In the production, it is expressed by the "fineness" index of the paint liquid (or ground varnish). The physical meaning of fineness refers to the maximum size of the pigment particle size allowed in the paint. It is usually measured with a scraper Fineness Meter, expressed in μm. For example, if the fineness value of a color paint product is required to be less than 20 μm, it means that the maximum particle size of the pigment in this color paint product should be less than (or equal to) 20 μm, and the smaller the required value, the higher the fineness index.
Other methods for evaluating the degree of depolymerization include electron microscopy, galvanometer method, and pigment tinting strength comparison method. Although these three methods are more accurate than the Fineness Meter method, they are usually limited to use in scientific research due to time-consuming or high instrument prices.
