Ultrasound for Dispersing and Grinding: Paint & Pigments

Power ultrasound is well known for its intense and precisely controllable milling and dispersing effects. This makes ultrasonic homogenizers ideal for the production of pigment paste and paint formulations. Industrial ultrasonicators provide a highly uniform particle size distribution in the micron- and nano-range. Process large volume streams of high viscosities with Hielscher sonicators to achieve homogeneous wetting, dispersing, deagglomeration and milling!

Paint Manufacturing with Ultrasound

Improve your Paints, Colors and Coatings with Sonication:

  • Formulation: Whether high viscosities, high particle loads, aqueous- or solvent-based – with Hielscher industrial inline ultrasonicators you can process any formulation.
  • Micron- and Nano-Size: The high shear forces generated by acoustic cavitation reduce particles to minute particle diameters and provide an uniform dispersion. Adjusting ultrasonication parameters to your particle and formulation requirements allow for a reliable production of nano-sized pigments.
  • Optical Properties: To obtain the correct optical properties, pigment particle size have to be controlled. Usually, opacity correlates with particle size: the finer the particle size, the more opacity. For example, TiO2 is specifically processed to a particle size of 0.20 to 0.3 micron, which is approximately the equivalent to one-half the wavelength of light. Ultrasonication reduces the TiO2 pigments to their optimum size, so that ultimate hiding is obtained.
  • High-Performance Particles: Smaller particle sizes result in greater colour saturation, colour consistency and stability. The intense, yet precisely controllable ultrasound forces allow for producing modified and functionalized nano-particles, such as coated particles, SWNTs, MWCNTs and core-shell particles. Such particles show unique characteristics and elevate paint or coating formulations to a new level of quality and functionality (e.g. UV resistance, scratch resistance, strength, adhesiveness, high heat resistance, infrared and solar reflectivity).
  • Modified Particles: Surface modified pigments have very low viscosity at high pigment loadings (2.5cP at 10% solids), superior suspension stability and high purity. Ultrasonically assisted particle functionalization makes it simple to synthesize high-performance pigments with special characteristics.

 

The video is demonstrating ultrasonic dispersion of red color using the UP400St with a S24d 22mm probe.

Ultrasonic Red Color Dispersion using the UP400St

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Pigment pastes are milled and dispersed using ultrasound cavitation and high-shear forces

Ultrasonic processing is a powerful method for milling and dispersing pigment pastes.

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Use ultrasonics for the production of

  • final formulations
  • master batches of pigment paste
  • refining particles after conventional milling

 

Pigment pastes are milled and dispersed using ultrasound cavitation and high-shear forces show a significant size reduction and uniform distribution.

Pigment pastes are milled and dispersed using ultrasound cavitation and high-shear forces show a significant size reduction and uniform distribution. The plot above shows the increasing size reduction at increasing ultrasonic energy.

 

For the production of paint, the components such as pigments, binders/ film formers, diluents/ solvents, resins, fillers and additives have to mixed together into a homogeneous formulation. Pigments are the determining component that gives paint its color. The most important white pigment is TiO2, which needs to be milled to an optimum particle size between 0.2 and 0.3 microns in diameter to show the desired grade of whiteness, brightness, opacity and a very high refractive index. The ultrasonic shear forces provide a very effective and energy-effective deagglomeration and dispersion of TiO2 particles (see image below).

Ultrasonication using the UIP1000hdT results in a fine dispersion of TiO2 nanoparticles (Aeroxide P25)

TEM of ultrasonically dispersed TiO2 nanoparticle suspension with different solid concentrations. Sonication was performed using the ultrasonicator UIP1000hdT
Left: ultrasonic energy input 1.8 × 105 J/L – Right: ultrasonic energy input 5.4 × 105 J/L
(Study and images: ©Fasaki et al., 2012)

 
Ultrasonic milling and dispersing enhance the paint quality by improving its color strength, density, fineness of grinding, dispersion and rheology.

Ultrasonic Dispersing & Grinding Conditions

The quality of paints and coatings relies on the homogenous dispersion of the pigments. Hielscher Ultrasonics supplies effective milling and grinding equipment for paint dispersion, especially for for formulations with high pigment loads. The mechanism of ultrasonic dispersers for milling, grinding, deagglomeration and dispersion applications is mainly based on the shear principle generated by ultrasonic cavitation. The cavitational shear forces necessary for the dissociation of the particles are produced by high pressure differences, local hot spots and liquid jets, which results in the particle break-up by inter-particle collision.
Industrial ultrasonic dispersers such as the UIP16000hdT with 16,000 watts per ultrasonic probe have the capacity to process high volume streams of paints and coatings.


Power ultrasonics for milling, grinding and dispersing of pigments, paint and colors. (Click to enlarge!)

Ultrasonic Processing: 7x UIP1000hdT

Ultrasonically dispersed chalk paint on the grindometer shows complete deagglomeration and homogeneous particle distribution

Sonicated chalk paint on the grindometer demonstrates the perfectly uniform deagglomeration and particle size distribution of the pigments

 

In this video we show you a 2 kilowatt ultrasonic system for inline operation in a purgeable cabinet. Hielscher supplies ultrasonic equipment to almost all industries, such as the chemical industry, pharmaceutical, cosmetics, petrochemical processes as well as for solvent based extraction processes. This purgeable stainless steel cabinet is designed for operation in hazardous areas. For this purpose, the sealed cabinet can be purged by the customer with nitrogen or fresh air to prevent flammable gases or vapors from entering the cabinet.

2x 1000 Watts Ultrasonicators in Purgeable Cabinet for Installation in Hazardous Areas

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Dispersion of Nanoparticles

Ultrasonic grinding and dispersing is often the only method to process nano-particles efficiently in order to obtain sinlge-dispersed primary particles. A small primary particle size results in a large surface area and correlates with the expression of unique particle characteristics and functionalities. At the same time, a smaller particle size is associated with a high surface energy for more severe aggregation and reactivity, so that the intense ultrasonic dispersing forces are required to disperse the nano particles homogeneously into the formulation.
Furthermore, an ultrasonic surface treatment can modify the nano particles which leads to improved dispersibility, dispersion stability, hydrophobicity and other features.
Researchers have recommended the ultrasonic dispersion method for nano particles as preferred solution, “because the material dispersed by the ultrasonic method is much purer than that produced by bead milling.” [Kim et al. 2010].

Ultrasonic Dispersion of UV Black Ink: Ultrasound results in a homogeneous fine dispersion (Click to enlarge!)

UV-Black Pigments: Before and After Ultrasonication

The ultrasonic dispersion technique has many advantages in comparison with traditional milling technologies such as three-roll, ball or media mills. (Click to enlarge!)

The ultrasonic dispersion technique has many advantages in comparison with traditional milling technologies such as three-roll, ball or media mills.

Read more about ultrasonic homogenisation and dispersing of pigments and colorants for masterbatches and paint formulations!

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Please use the form below to request additional information about ultrasonic homogenizers, dispersing applications and prices. We will be glad to discuss your pigment-related process with you and to offer you an ultrasonic disperser meeting your requirements!









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Caution: Video "duration" is missing

The Hielscher SonoStation makes the sonication of mid-size batches using a flow cell reactor easy.
The compact SonoStation combines a 38 liter agitated tank with an adjustable progressive cavity pump that can feed up 3 liters per minute into one or two ultrasonic flow cell reactors.

Ultrasonic Mixing Station - SonoStation with 2 x 2000 Watts Homogenizers

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Literature / References

Facts Worth Knowing

Ultrasonic tissue homogenizers are often referred to as probe sonicator/ sonificator, sonic lyser, ultrasound disruptor, ultrasonic grinder, sono-ruptor, sonifier, sonic dismembrator, cell disrupter, ultrasonic disperser, emulsifier or dissolver. The different terms result from the various applications that can be fulfilled by sonication.

Ultrasonicator UP200St (200W) dispersing carbon black in water using 1%wt Tween80 as surfactant.

Ultrasonic Dispersion of Carbon Black using the ultrasonicator UP200St

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High performance ultrasonics! The Hielscher product range covers the full spectrum from the compact lab ultrasonicator over bench-top units to full-industrial ultrasonic systems.

Hielscher Ultrasonics manufactures high-performance ultrasonic homogenizers from lab to industrial size.


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