Jen Lepore, Mar 13, 2024 8:02:13 AM
In the paint production process, achieving consistency, uniformity, and optimal performance poses critical challenges for manufacturers of paints and coatings. Milling and dispersion processes are vital to achieving these goals.
The dispersion process in paints, inks, and coatings can be incredibly complex. Each component adds its own variables to the mix, and their potential interaction demands scientific know-how.
Particle sizes can affect attributes ranging from color, level of gloss, and hiding power of paint methods to the coefficient of friction in industrial coatings. Tight control over milling and dispersion processes is an absolute must for consistent quality.
Grinding and blending processes need to address characteristics that range from abrasiveness to viscosity to temperature sensitivity and more.
In addition to achieving target particle sizes, grinding is indispensable for blending and dispersion. This is true whether the product is a liquid dispersion (such as solvent- or water-based paint) or a powdered solid (as in heat-cured coatings used in metal finishing).
The path to optimal particle sizes, homogenous dispersions, and high-performance paints, inks, and coatings can involve multiple technologies and a wide range of variable adjustments. Particle surface treatments like coating and encapsulation can be game-changers, but it takes an expert team to help make them work for your formulation.
When considering a toll processing partner for grinding and blending in the paint production process, focus on these critical factors:
- Particle size determines many critical characteristics of inks, pigments, paints, and coatings.
- Homogenous dispersions can be challenging to achieve.
- Demonstrated mastery in processes including surface treatments is a must for your toll manufacturer to reliably achieve your product goals.
Read on to learn more about the particle size reduction, uniform blending, surface treatments, and milling methods your toll processor may use to ensure consistent pigments, inks, paints, and coating formulations.
1. PARTICLE SIZE IMPACT IN PAINT PRODUCTION: CRITICAL CHARACTERISTICS
Most ink, paint and coating formulations are composed of ingredients that may include pigments, fillers, resins, solvents, catalysts, and/or additives. Particle sizes and distributions in the formulation can affect the final product’s functionality, durability, and appearance.
Particle size can affect many characteristics of paint, primer, lacquer, or other liquid-applied coating, including:
- Hue/tint strength
- Hiding power
- Color uniformity
- Gloss vs. flatting
- Viscosity
- Stability or settling
- Strength on aging
- Water resistance
In industrial coatings, the use of waxes, polyethylenes, and polymers achieve smoothness, scuff resistance, and reduced metal marking. These additives rise to the surface as the finish cures, so particle size is vital. Larger particles can cause problems during heat curing. Very tiny particles agglomerate easily and can also result in an unintended flat finish.
Particle size can affect a coating’s behavior during application and curing, including:
- Movement in a fluidized bed chamber
- Electrostatic charging
- Spray trajectories
- Layer build-up
- Adhesion
Just as in a paint formulation, particle size can also affect coating properties including color, matting, texture, and weather-resistance or durability.
Dispersing solid pigments in inks requires advanced technical know-how to prevent unstable formulations that can lead to settling — which can cause serious performance problems that can even damage printing equipment.
As with paints and powder coatings, printing inks are often formulated to perform on a specific set of equipment and substrate. A deep technical understanding of all the specifics can help you ensure proper flow, adhesion, curing, and final print quality.
2. OVERCOMING CHALLENGES: ACHIEVING HOMOGENEOUS DISPERSIONS
When blending paint ingredients, particle size can make it easier or harder to disperse pigments in solvent. The smaller the particle size, the more surface area, and the more pigment particles will tend to agglomerate - so it's not enough to know your tolling partner has the right particle dispersion equipment.
Expertise in the process is crucial for selecting suitable additives and agents for wetting, dispersing, and stabilizing, alongside the appropriate technology. Milling and blending technologies not only help ensure homogenous dispersion throughout the batch of liquid slurry; they also help create a more stable mixture that resists settling and sedimentation.
Wet and dry dispersion processes in paints, inks, and coatings can also call for specialty in-process dispersion additives or particle surface treatments to achieve precise characteristics such as surface tension or other particle behavior.
Powder coatings may undergo a series of prescribed milling and grinding to ensure uniform dispersion and consistent quality. First, ingredients may be individually milled to their various required particle sizes. Next, they may be melted and blended using an extrusion method such as a twin screw extruder. The resulting blended product requires another milling step before it can be used.
3. OPTIMIZING HIDING POWER: UTILIZING MULTIPLE MILLING METHODS AND PROCESS
In the cases of paints, inks, pigments, and powder coatings, depending on the raw material and desired particle size, mechanical milling, wet media milling, or jet milling be required at various steps in the process. Specialty dispersion blenders can be equipped to address issues such as temperature sensitivity, high viscosity, pigment reagglomeration, and more.
After powder coating ingredients are milled and blended, often in a twin screw extruder, they need to be milled to a fine powder or micronized. Sometimes, several mill types are used in succession — such as a roller mill followed by a hammer mill or a jet mill and classifier — to achieve the necessary final particle size (typically 15 to 60 microns) and shape.
To enhance the hiding power of paint, method and process adjustments and specialty services such as cryo-milling or particle surface conditioning may be required. This involves applying special coatings and treatments to create a thin film at the particle level on pigment surfaces, ensuring specific product qualities are achieved.
SELECTING THE IDEAL TOLL PROCESSOR FOR PIGMENTS, PAINTS, INKS, AND COATINGS
The paint production process can use an array of milling, blending, and dispersion equipment. Coupled with various process steps, technologies, and fine adjustments, there are nearly infinite combinations of capabilities a skilled toll processor can achieve. That’s why it’s so important to choose a toll processing partner that brings more than just advanced equipment to the job.
Having the capacity to meet your toll milling, blending, and dispersion challenges demands a scientific approach to problem-solving, years of experience, and the technical expertise of a trusted team. Material scientists, engineers, and equipment operators with years of experience in pigments, inks, paints, and coatings will approach your project with a deep understanding of your challenges and goals, and a solid foundation in processing formulations like yours.
For detailed insights into milling technologies and their applications within the paint production process, explore our comprehensive Milling Methods Comparison Guide. Just click below to download. And if you have questions or want to reach out, it’s easy to contact CPS.
