Processing of Digital Printing Inks with Colloid Mills

Digital printing inks impose stringent demands on process technology: pigments must be dispersed into the sub-micron range without residual agglomerates blocking the printheads; viscosity must remain controllable from low-viscosity inkjet systems up to highly viscous UV pastes; and neither air bubbles nor temperature spikes may arise, because both adversely affect colour stability and tone. PUC colloid mills are engineered precisely for these challenges.

Precise particle-size control in a single cycle

Within the rotor–stator system the product is guided through a continuously adjustable annular gap. Cutting, impact, friction and shear forces act simultaneously, breaking down pigment clusters into the fine range—one event is often enough to reach the target particle size. Cycle times are reduced and over-milling is prevented.

Wide viscosity window – from inkjet inks to effect pastes

All three PUC series process formulations from <100 cP to 80,000 cP. Throughput can be scaled via machine size, gap setting, and—if required—an integrated recirculation module.

Process reliability and hygiene

• Choice of single- or double-acting mechanical seals or PTFE lip seals in one cartridge simplifies changeover between water- and solvent-based formulations
• ATEX-compliant, pharmaceutical, or sterilisable versions plus heat/cool jackets ensure safe handling of both solvent-borne and temperature-sensitive LED-curable inks
• A closed inline layout prevents oxygen and foreign particle ingress, while an optional cooling mantle keeps pigment chemistry stable

Complete drainability and easy cleaning

PUC mills are designed for discharge free of dead space—vertically mounted chambers empty automatically, horizontal versions have low-point outlets. Only a few grams of residue remain, speeding colour changes and minimising waste. All saturated parts are mirror polished and CIP/SIP-capable; rotor–stator sets can be removed, rinsed, or exchanged in minutes.

Scalable from laboratory to high-volume production

Ink development on the PUC 60 lab model starts with identical shear geometry. After scale-up, Series O and E deliver up to 34 m³/h, while EL mills reach 80 m³/h—allowing full formulation series to be transferred reproducibly to production without specification changes.

Ease of operation and maintenance

Frequency inverters, quick-change rotor–stator sets, and lifetime-lubricated precision bearings cut set up and downtimes—vital when frequent colour changes are required.

Decades of cross-industry experience

Since 1926, Probst & Class have supplied colloid mills to virtually every branch of the processing industry—from chemicals, paints and coatings to food, cosmetics, pharmaceuticals and petrochemicals. This wealth of know-how informs every design detail, making PUC mills dependable components in both new and existing production lines.

Investment security and low total cost of ownership

PUC has supplied spare and wear parts for decades, irrespective of a machine’s year of manufacture. Reliable parts availability, robust stainless-steel construction, and energy-efficient drives keep TCO low and shrink the ecological footprint of your business.

Advantages of digital ink processing

• Consistent colour density and brilliance through narrow particle-size distribution
• Fewer nozzle outages thanks to the absence of coarse particles
• Shorter dispersion times—less energy used per kilogram of ink
• Minimal losses during colour changes due to almost complete drainage
• Fast cleaning = higher line availability in multi-product plants
• Long-term parts availability secures investment and keeps TCO low
• Simple scale-up: identical milling principles from the laboratory to the 80 m³/h production line

With a colloid mill from Probst & Class you invest in more than a machine—you acquire a process-secure, sustainable plant component for the manufacture of stable, high-resolution digital printing inks, from photo-realistic inkjet inks through to highly opaque textile pastes.