For coatings manufacturers, laboratory mixing is an exact science. A wide variety of coatings rely on precise mixing where specific formulations, molecular structures or product characteristics are critical. Many coatings require precise formulations for optimal performance. The chemical formulation of paints and coatings also requires careful blending of pigments, binders, solvents and additives.

“The products developed in labs touch nearly every part of our lives. So, when mixing coatings, the results must be accurate, reliable and perhaps most importantly, repeatable. Consequently, utilizing the proper instruments is essential,” says John Bogart, managing director of Kett US, a manufacturer of a full range of laboratory mixing as well as moisture and organic composition measurement equipment.

The challenge is that any mixer that isn’t well suited to a lab’s requirements can be very disruptive. For example, the mixer may lack sufficient speed, leading to incomplete mixing or poor homogeneity. A mixer may also insufficiently combine materials with multiple viscosities, resulting in “ring layers” where the various viscosities settle at different depths in a poorly mixed product. These kinds of issues are problematic when mixtures or products are in laboratory development and accuracy is critical for the results to be reproducible on a larger scale.

According to Bogart, the key for coatings manufacturers is not only finding lab mixers that can perform as desired but also selecting those that can reliably do so while withstanding the toughest viscosities over time. As an industry expert, Bogart shares what coatings manufacturers need to know about selecting the most effective lab mixers for their specific applications.

Choosing the Best Mixer for Your Lab

For coatings manufacturers, the most important step to take in choosing the right mixer is determining the performance specifications that need to be met. For most labs, the prime factors to consider are speed, related torque, safety, viscosity and versatility, according to Bogart.

Mixing Speed and Related Torque

The optimal mixing speed depends on the chemical properties, desired reaction outcome and the specific equipment used. Mixing speeds that are too high or too low can both negatively impact the quality, safety and efficiency of the mixing process. Therefore, choosing a mixer capable of reliably providing the right mixing speed is essential for achieving uniformity, controlling reactions and ensuring the desired product characteristics.

In fluid mixing, torque plays a key role in how effectively a mixture is blended. When mixing, torque is the force that the motor applies to turn blades or impellers, which create the necessary shear and turbulence to mix the components. Adequate torque ensures that the entire fluid or material is mixed uniformly. Without enough torque, areas of the mixture may remain unmixed or may not achieve the desired properties.

Consequently, coatings manufacturers should select a mixer that satisfies their performance requirements in terms of mixing speed and related torque. To meet this need, Kett, for example, manufactures three categories of mixers that fulfill the performance specifications of coatings manufacturers.

An entry-level model with an rpm rate between 0 and 300 rotations per minute provides a related torque of 9.0 kgf·cm and is capable of withstanding high viscosities. A mid-level model can reach up to 600 rpm with related torque of 10.0 kgf·cm, which is ideal for medium-to-high viscosities. A high-performance model can reach up to 1,000 rpm with related torque of 3.0 kgf·cm, covering a low to medium viscosity range.

A basic model will typically provide forward/reverse rotation for efficient mixing. A mid-tier model will have a higher-powered motor in the range of 70 W with automatic forward/reverse rotation for improved mixing performance. A higher-end model will provide a more robust motor, such as 120 W, for high-viscosity liquids and enhanced torque, expanding its application range, according to Bogart.

Safety

Some lab mixers have inherent defects that can present problems when mixing coatings. For example, lesser mixers can have motor issues that spark during operation. Since coatings are often comprised of volatile substances, this can lead to a fire.

Brushless motors can help to eliminate the fire risk. “Brushless motors have been specially engineered to prevent sparking, nearly eliminating the risk of fire, and are entirely encased to prevent particles from creeping in and damaging the inner workings of the motor,” says Bogart.

He adds that dual safety systems, with thermal motor protection and a current limiter, can also help to protect the mixer from overheating.

Maintaining Mixing Speed

Laboratory and factory mixing can be challenging, particularly when coatings manufacture involves materials with varying viscosities. Multiple viscosities can lead to “ring layers” in a mixture, where the varying viscosities settle at different heights within the mixture, resulting in poorly mixed, inadequate materials or products.

To resolve this issue, Kett developed its Z+ model of mixers, which provide high torque regardless of the thickness or viscosity of the mixture.

“Even as mixtures change in viscosity as they are combined and materials react with one another, the speed remains constant,” says Bogart.

To expedite the mixing process and eliminate unmixed “ring regions” toward the top or bottom of a blend with varying viscosities, the OEM offers models that raise and lower when mixing. This reciprocating motion ensures that the entire batch of each coating material is entirely and evenly mixed.

Mixing Versatility

In the course of development over time, coatings manufacturers will often need to mix a wide range of formulations and sample sizes in special conditions. Consequently, it can be advantageous to have a host of options and tools available that can increase the safety, flexibility, efficiency and accuracy of mixer use.

In this vein, keyless chucks can help to streamline the change of mixing shafts with safe, secure attachment to the mixer without a key. Free-Joint™ swivel mounts enable changing shafts and adjusting the mixing height without moving the motor, according to Bogart.

Programmable settings, digital controls, LED digital displays, 0.5-second sampling frequencies and change of rotational direction with the touch of a button can improve mixer accuracy and efficiency as well, he suggests.

To further enhance safety, utilizing a remote control mixer model equipped for fume hood use, with external output for rotation speed and torque control can be helpful. A model with a remote-controlled agitator can be ideal for demanding agitation tasks and external control capabilities. Using a model that provides analog voltage outputs for rotation speed and torque, allowing viscosity monitoring with a recording meter during agitation can help to improve quality control, adds Bogart.

With all the options available, working with an expert OEM that provides a comprehensive range of mixers and accessories along with engineering assistance and technical expertise can help coatings manufacturers select the equipment most suitable for their lab. Utilizing the most accurate, reliable, repeatable and versatile equipment, in turn, will not only streamline product development but also promote quality and successful production scale-up down the line.

For more info, contact Kett: call 800-438-5388; email support@kett.com; or visit www.kett.com.

*Images courtesy of Kett.