Use dispersants skillfully to make water-based gold powder "obedient" to disperse
When using water-based gold powder dispersants, it is necessary to combine its characteristics with the gold powder
application scenarios, and optimize from the aspects of dispersant selection, dosage control, dispersion process, storage
and use environment to achieve stable dispersion and performance of gold powder in water-based systems. The following
are specific usage methods and precautions:
1. Dispersant selection
Matching gold powder characteristics: Select special dispersants according to the particle size, shape, and surface
properties of gold powder. For example, for nano-scale gold powder, it is necessary to select dispersants with strong
steric hindrance effects or electrostatic stabilization.
Compatibility verification: Ensure that the dispersant is compatible with water-based resins, solvents and other additives
(such as leveling agents, defoamers) to avoid flocculation or stratification.
Dispersion efficiency evaluation: Preferentially select dispersants that can reduce the surface tension of gold powder
and improve wettability, such as polymer dispersants containing carboxylic acid groups and phosphate groups.
2. Dispersion process
Pre-dispersion: Mix the gold powder and dispersant in proportion (usually 1%-5% of the weight of the gold powder), add
a small amount of water (or solvent) and stir until it is a uniform paste, avoiding the direct addition of a large amount of
liquid to cause agglomeration.
High-speed dispersion: Use a sand mill, ball mill or high-speed mixer to disperse for 30-60 minutes at a speed of 1000-3000
rpm to ensure that the gold powder particles are fully dispersed.
Post-treatment: After dispersion, large particle impurities can be removed by filtration or centrifugation to further optimize
the dispersion effect.
3. Dosage control
Recommended dosage: According to the instructions of the dispersant, it is usually 1%-5% of the weight of the gold powder.
Excessive dosage may cause the system viscosity to be too high, affecting the construction performance.
Dynamic adjustment: Determine the optimal dosage through experiments, and observe the stability, glossiness and rheological
properties of the dispersion.
4. Storage and use environment
Storage conditions: The dispersed gold powder slurry needs to be stored in a sealed environment at 5-35℃, avoiding direct sunlight
and high temperature to prevent gold powder oxidation or dispersant failure.
Construction environment: During construction, the ambient humidity should be lower than 80% and the temperature should be between
10-35℃ to ensure the dispersion stability of the gold powder.
5. Precautions
Avoid metal ion contamination: The tools and containers used in the dispersion process must be non-metallic materials to prevent metal
ions such as iron and copper from catalyzing the oxidation of gold powder.
pH value control: Some dispersants are sensitive to pH, and the system pH needs to be controlled between 7-9 to ensure the dispersion effect.
Stability test: After dispersion, centrifugal stability test (3000 rpm, 30 minutes) and thermal stability test (50℃, 7 days) are required to ensure
no precipitation or stratification.
6. Common problems and solutions
Flocculation problem: If flocculation occurs, try to increase the amount of dispersant or adjust the pH value, and add a small amount of
anti-settling agent if necessary.
Insufficient gloss: It may be that the dispersion is insufficient or the gold powder particle size is too large. It is necessary to optimize the
dispersion process or replace the gold powder with a finer particle size.
Discoloration problem: Oxidation of gold powder may cause discoloration, and antioxidants need to be added or inert gas protection is used.
7. Recommended products and process parameters
Dispersant types: polycarboxylate, phosphate, polymer block copolymer dispersants.
Process parameters: dispersion temperature 20-30℃, dispersion time 30-60 minutes, stirring speed 1500-2500 rpm.
The above method can effectively achieve stable dispersion of water-based gold powder and improve the gloss, weather resistance and
mechanical properties of the coating.
