The pH value is an important process parameter to be controlled in the production process of latex paint. In order to investigate the effect of p H value on the viscosity of latex paint, AMP-95 was used as a pH value regulator to test the viscosity of latex paint prepared with different kinds of thickeners at different p H values. The viscosity of latex paint is tested according to the Stormer viscometer method stipulated in the national standard GB/T 9269-2009, and the results are shown in Figure 3-20.
It can be seen from Figure 3-20 that the viscosity of latex paints formulated with montmorillonite powder, HEC, HPMC, MC, and HEUR changes slightly with the increase of pH value, and basically remains unchanged. The viscosity of latex paints formulated with ASE and HASE The viscosity of latex paint increases gradually with the increase of pH value, and then tends to be flat. This is because both the inorganic thickener montmorillonite powder and the cellulose thickener achieve thickening through water absorption and molecular entanglement, and have a large tolerance for changes in the pH value, so the viscosity hardly changes with the increase of the pH value. Change. HEUR forms a relatively stable three-dimensional network structure in the system, and its performance is basically not affected by the pH value. It can be used in a wide range of pH, and the change with the pH value is small, so the viscosity change is also small. Alkali-swellable thickeners are anionic thickeners, which undergo neutralization reactions in alkaline systems, dissociate carboxyl groups, and become swollen, thereby increasing the viscosity of the system. However, as the alkalinity increases, the viscosity of latex paint increases slightly. When the pH value is greater than 10, the alkali-swellable thickener dissolves in water and loses its thickening effect. Therefore, in the alkali-swellable thickener system, it is necessary to control the pH range of latex paint.
