BYK-929 is a modified polyethylene micronized wax for improving matting and surface protection in aqueous and solvent-based systems.
1, Chemical composition: modified polyethylene micronized wax
2, Density: 1.06 g/ml
3, Melting point: 115 °C
4, Particle size distribution (laser diffraction, volume distribution).
D50: 8 µm
D90: 15 µm
5, Supply form: micronized material
The colloidal modifier participates in the dispersion of inorganic pigments and fillers, is adsorbed on the surface, and forms a network structure with the associative thickener through secondary bonds. Table 28-5 is the pigment water dispersion formula. They use colloidal modifiers and associative increasers, colloidal modifiers and cellulose thickeners. Figure 28-9 is a scanning electron microscope photo of the two pigment wax water dispersions at 5000 times magnification. It can be seen that the hydrophobic modification makes the polymer particles, pigments, and filler particles in the coating obtain an ideal and uniform distribution, avoiding the occurrence of cellulose ethers. The volume of hydrated thickeners, such as alkali swelling agents, restricts flocculation and locally aggregates into an island-like distribution, thereby improving the compactness of the coating film and the resistance to rainwater permeability, as shown in Figure 28-10. The test coatings are shown in Table 28-6. After storing the two coatings for 5 days, prepare a coating film of the same thickness and use a 30cm² permeation cup to test the permeability of the coating film. It can be seen that the theory and practice of colloidal modification/association make it a reality to prepare high-solids, low-viscosity, high-resistance, high-decorative, and good-workability latex paints.
The degree of slurry modification in the formulation must be controlled from the following points:
①In order to avoid the gelation caused by adding the film-forming aid after adding the emulsion, the film-forming aid is usually added after the beating is completed. It is used for preparing slurry of hydrophobic formulation. The dosage of colloid modifier is higher. At this time, the slurry is more hydrophobic. In the case of higher solid content of the slurry, the addition of dodecyl alcohol, a film forming aid Cause gelation. The degree of hydrophobic modification of the slurry must be controlled, and if necessary, an appropriate wetting agent must be selected for shielding.
In the more hydrophilic system of acetone type, even for medium and low PVC, the ability of associative thickener to control low shear viscosity is generally poor. Extensive use of hydrated thickeners will reduce the wet rub resistance and leveling properties of the coating film. At this time, simply focusing on the choice of thickeners can no longer be effective. Trying to hydrophobically modify the inorganic slurry can greatly improve the association effect, thereby changing the can-opening effect of the coating.
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