The reason for the thickening and swelling of PU color paste storage stability is mainly due to the poor matching or compatibility between the polarity of the particle surface of the pigment and the dispersion medium
If the pigment is treated with lipophilic rosin resin, especially when the dosage is high, the polarity of the particle surface will be reduced, and it will be easier to separate from the dispersion medium when it is used for PU color paste coloring, and it will show swelling phenomenon. That is, the pigment particles are aggregated with each other, and the colorant is precipitated and precipitated from the dispersion medium.
2. Adjust the molecular weight of the dispersant
Add additives during the preparation of PU color paste to improve the stability of the dispersion. When selecting additives, attention should be paid to the molecular weight of the additives. Additives with higher molecular weight, especially additives with longer fatty chains and branched chains According to its steric barrier principle, it helps to prevent the aggregation of pigment particles, thereby improving the phenomenon of thickening or swelling.
3. Surface treatment of pigments
It can improve dispersion stability in aqueous media, or coat pigments with hydrophilic acrylic monomers to greatly reduce thickening and swelling.
In addition, when the water quality or the PH value of the pigment is acidic, it is easy to grow bacteria and cause coagulation, thickening and precipitation, and in severe cases, caking and swelling.
