Coatings are usually based on resin, oil or emulsion, add some additives in it and use organic solvents or water to prepare viscous liquid. Additives in the paint can improve the appearance and performance of the coating, such as, color brightness, light transmittance, mildew resistance, uniform dispersion, adhesion, etc… Sodium hexametaphosphate as a dispersing agent is an important paint additive.
Sodium hexametaphosphate 68% is a kind of polyphosphate with indeterminate composition. Its anion has a high molecular weight. Generally, it contains 30-90 genes and forms a long chain. Due to its property, it will become viscous after absorbing water.
Due to the addition of water glass and other alkaline substances in the paint, its PH value is 10-10.5, that is, the concentration of OH- ions in the paint is large, which can help the further decomposition of H3PO4 and also promote the conversion of shmp to orthophosphate. Moreover, the phosphate at this time will undergo condensation of multiple functional groups, especially the molecular groups of sodium hexametaphosphate will undergo condensation at high temperatures, and the molecular groups after condensation will combine with the three-dimensional network bentonite molecular groups in the paint. Thus, shmp chemical can effectively play the role of bonding.
As the content of sodium hexametaphosphate increases, the effect on brushability becomes more obvious. When the amount of shmp chemical is 2%, the paint is thinner with good fluidity. However, after the paint is painted, there are obvious flow marks, and the effect is poor. When the content of sodium hexametaphosphate in the paint rises to about 6%, the paint will become viscous. After brushing, the paint will automatically level without leaving a trace for a period time. The dripping property of the paint with the content of sodium hexametaphosphate is very low, and the painted paint can maintain its inherent shape under the action of gravity. Of course, the content of shmp chemical used in paint and coatings depends on the specific paint type.