Prevent Pigment Particles from Settling and Aggregating in Ink

The use of ultrasonic dispersion equipment is a highly effective high-tech physical method to prevent pigment particles from settling and aggregating in ink.

Below, I will explain in detail its principles, advantages, application methods, and precautions.

The principle of ultrasonic anti settling: why is it effective?

The fundamental reason for pigment settling is the van der Waals force between particles, which causes them to attract each other and form agglomerates. These aggregates will gradually settle to the bottom under the action of gravity. Ultrasonic dispersion breaks this state through the following mechanism:

1. Cavitation effect – core mechanism

• Ultrasonic generators (transducers) convert high-frequency electrical signals (typically 20kHz-40kHz) into mechanical vibrations.
• This vibration is transmitted into the ink through a probe (amplitude lever), generating alternating high and low pressure cycles.
• In low-pressure circulation, tiny vacuum bubbles (cavitation bubbles) are generated in the liquid.
• In the following high-pressure cycle, these cavitation bubbles will collapse and implode at extremely high speeds, instantly generating extremely strong shock waves and local high temperatures (about 5000K) and high pressures (about 1000 atmospheres).
• These shock waves are like countless’ micro bombs’, impacting pigment aggregates with extremely high energy, breaking them into primitive, small primary particles.

2. Turbulence and shear forces

• Ultrasonic waves propagate in liquids and generate strong acoustic and microjet flows, creating intense turbulence.
• This fluid mechanics effect further generates shear forces on particles, assists in separating already loose aggregates, and promotes uniform distribution of particles in the liquid.

3. Particle surface activation

• The high energy generated by cavitation can temporarily alter the surface properties of pigment particles, making them more easily wetted by resins and solvents, thereby better combining with dispersants to form stable steric hindrance or electrostatically stable structures.

Summary: Ultrasonic dispersion, through the physical “violent” means of “cavitation”, fundamentally disintegrates the aggregates that cause sedimentation and makes it difficult for them to reunite again.

Advantages of Ultrasonic Dispersion

• High efficiency: Short processing time, good dispersion effect, can reach or even exceed the original particle size of the pigment.
• Stable effect: The particle size distribution of the processed slurry is narrower, the stability is significantly improved, and it is less prone to settling and clumping.
• Wide applicability: Effective for various pigments (organic, inorganic), carbon nanotubes, graphene and other difficult materials.
• Process controllability: Parameters such as power, time, and temperature can be precisely controlled to ensure batch consistency.
• Pollution free: a purely physical process that generally does not introduce new chemical substances.

How to apply ultrasonic dispersion in ink production?

There are usually two ways of application:

1. Batch processing (intermittent)
This is the most common method, suitable for laboratory research and small-scale production.

• Process: Pour the pre mixed ink (pigment+resin+solvent+additive) into a beaker or container, immerse the ultrasonic probe below the liquid level, and turn on the equipment for timed processing.
• Advantages: Flexible and easy to optimize process parameters.

2. Online processing (continuous)
Suitable for large-scale industrial production.

• Process: Install an ultrasonic flow chamber (reactor) in the production line pipeline. The pre mixed ink is pumped and undergoes ultrasonic treatment as it flows through the chamber.
• Advantages: High degree of automation, high production efficiency, and easy integration into existing production lines.

Conclusion

Ultrasonic dispersion equipment is a powerful tool for preventing ink pigment settling. It can effectively depolymerize pigment aggregates through intense cavitation, achieving uniform dispersion at the nanometer or micrometer level.

The key to success lies in treating ultrasound as a part of the entire dispersion stabilization system and combining it with appropriate dispersants, resin systems, and rheological agents. By finely optimizing parameters such as power, time, and temperature, you can significantly improve the quality, stability, and production efficiency of ink.

It is recommended to conduct sufficient parameter optimization experiments in the laboratory before investing in large-scale production.

About Chemisonic

Chemisonic specializes in ultrasonic liquid processing technology. For decades, we have dedicated to designing, developing, and manufacturing ultrasonic liquid processors independently, from laboratory application to industrial level. Cutting-edge ultrasonic technology, high quality device and easy-to-use operating system are the fundamentals for our company to achieve continued business growth.