Fine Grinding Mill for pigment powders is a key process for improving pigment dispersion, tinting strength, and stability. Particle size is one of the important indicators of pigments. Generally, it is required that the pigment particles have a stable physical form, uniform particle size, and good dispersibility without agglomeration or precipitation.
Efficient ultrafine grinding technology reduces particle sizes to the micron or even submicron level. This greatly enhances performance in coatings, inks, plastics, and other applications. It meets the demands for high-quality, refined products.

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Iron oxide pigment is known for its excellent dispersibility, lightfastness, and weather resistance. It mainly includes four types: red, yellow, black, and brown iron oxide pigments, all based on iron oxides. Among them, red iron oxide is the most widely used.

Precipitated (wet-process) iron oxide pigments are very fine in nature. However, during filter pressing and drying, van der Waals forces, hydrogen bonding, and electrostatic charges cause micro-aggregates to form large agglomerates. These cannot be directly used in high-end coatings for coloration and must undergo fine grinding mill. Currently, common ultrafine grinding equipment includes jet mills, air classifier mills, ball mills, vibratory mills,and ring roller mills etc.

jet milling

Jet mill is one of the most important ultra-fine grinding equipment, and the product fineness can generally reach 1-45μm.

Using high-pressure air, inert gas, or superheated steam, rapid expansion and cooling generate a high-speed flow field. This drives material particles to collide, rub, and shear against each other within the jet stream, achieving particle size reduction.

The product features fine particle size, narrow size distribution, smooth surface, regular shape, high purity, high activity, good dispersibility, and low temperature rise during grinding.
Disadvantages: high equipment manufacturing cost, large initial investment, high energy consumption, and high powder processing cost.

Alr classifier mill

The air classifier mill is widely used in the non-metallic mineral industry for fine grinding.
It typically achieves a product fineness of d97 = 10 μm (approx. 1250 mesh). When combined with a high-performance precision classifier, it can produce ultrafine powders with d97 = 5–7 μm.

The material is uniformly sent into the grinding chamber by the feeding system. It is strongly impacted by the high-speed rotating grinding disc. At the same time, it is subjected to centrifugal force. The material collides with the crushing ring gear. It experiences various comprehensive forces, such as shearing, friction, and collision.The material is ground, and the crushed material moves to the classification area with the airflow. The coarse and fine materials are separated through the classification wheel adjusted by the frequency conversion. 

ball mill

A ball mill is a type of ultrafine grinding equipment consisting of a stationary chamber filled with grinding media and a rotating agitator. It can achieve product fineness below 1 μm. The agitator stirs the grinding media to generate irregular motion, applying impact, shear, and friction forces to break down the material.

ring roller mill

Ring roller mills and roller presses use layer-by-layer compression grinding technology for ultrafine size reduction. Under high pressure, stress concentration causes cracks to form and propagate, creating microcracks and surface fractures that ultimately break the material.

grindhing of special pigments

Iron Oxide Pigments：
During filter pressing and drying of iron oxide pigments, micro-aggregates tend to form larger agglomerates due to van der Waals forces, hydrogen bonding, and electrostatic interactions. These agglomerates cannot be dispersed by ordinary mechanical means.
Using a fluidized bed or disc-type jet mill to process iron oxide pigments can achieve the following Hegman fineness:
Iron oxide red: 5.5–7.0 (darker color indicates finer particle size),
Iron oxide yellow: 7.5,
Iron oxide black: 7.0.

After ultrafine grinding, iron oxide pigments are deagglomerated from large to small aggregates. In paint production, only a short period of high-speed stirring is needed to reach the required fineness, reducing processing costs. Moreover, the small pigment aggregates are less likely to re-agglomerate, ensuring stable coating quality.

Black Heat-Resistant Manganese Ferrite Pigment：

After surface coating, surface modification, drying, and grinding, the fine particles of manganese ferrite pigment re-agglomerate. The re-agglomeration results in coarse particles to varying degrees. This hinders the effective use of its pigment properties.
By using fluidized bed or disc-type jet mills for deep processing and grinding, the Hegman fineness of manganese ferrite pigment reaches approximately 7–7.5. With excellent dispersibility, the pigment can fully exhibit its optical and pigment properties.

Brown Ceramic Pigment：

Using a flat-type jet mill to ultrafine grind brown ceramic pigments, at an air pressure of 7.5×10^5 Pa and a feeding rate of 100 kg/h, the product achieves a d50 of 4.55 μm, with a maximum particle size of 9.64 μm.

conclusion

In conclusion, Fine Grinding Mills play a crucial role in the production of pigment powders by achieving precise particle size control and enhancing dispersion properties. By utilizing advanced milling technologies, manufacturers can optimize pigment performance, ensuring high-quality products with improved color strength, stability, and consistency across various applications.

epic powder

Epic Powder, 20+ years of work experience in the ultrafine powder industry. Actively promote the future development of ultra-fine powder, focusing on crushing,grinding,classifying and modification process of ultra-fine powder.  Contact us for a free consultation and customized solutions! Our expert team is dedicated to providing high-quality products and services to maximize the value of your powder processing. Epic Powder—Your Trusted Powder Processing Expert !