1. What Benefits Can Modification Processes Bring to Ground Calcium Carbonate (GCC) Manufacturers?
First and foremost, calcium carbonate surface coating modification enhances the performance of GCC powder. When modified with stearic acid, GCC particles are less likely to agglomerate, ensuring better dispersion in the matrix. Additionally, the modification process reduces the gaps between particles, significantly lowering the oil absorption value. This in turn decreases the required amount of organic polymers or resins and reduces cost.
Most importantly, the modification process greatly increases the added value of GCC products. The market price of regular GCC powder ranges from 200 to 600 CNY per ton, but due to severe overcapacity, competition is intense. In contrast, coated and modified GCC powder typically sells for 800 to 1,200 CNY per ton, with some high-quality modified powders reaching 1,800 to 2,200 CNY per ton.
Thus, the modification process is a powerful tool that helps GCC manufacturers break free from the fiercely competitive “red ocean” market and tap into the more profitable “blue ocean” opportunities.
2. What Are the Mainstream Modification Processes for Ground Calcium Carbonate (GCC)?
1) High-Speed Mixer Modification
After decades of development and iteration, high-speed mixer modification has become one of the most mature and stable modification processes.
The process involves first drying the GCC powder to reduce its moisture content below 1%. Simultaneously, stearic acid is heated until liquefied. The high-speed mixer’s rapidly rotating blades create turbulent flow, effectively dispersing the GCC powder and ensuring thorough mixing with stearic acid, completing the surface coating. This method is simple to operate, requires low-cost equipment, and produces consistently high-quality modified GCC powder.
The most advanced high-speed mixer processes can achieve a modification rate of over 95%, with stearic acid dosage below 2%. Since stearic acid costs approximately 11,000 CNY per ton, reducing its dosage by just 1% in large-scale production can save thousands of yuan in daily costs. However, the capacity of high-speed mixer modification is limited, making it suitable for small-batch modifications in laboratories or pilot production.
2) Pin Mill Modification
Pin mill modification is currently the most effective process, achieving a modification rate as high as 99%.
Similar to the high-speed mixer method, the GCC powder is dried, and stearic acid is heated until liquefied. In this process, two pin discs rotate at high speeds in opposite directions, dispersing the GCC powder while ensuring stearic acid coating occurs within the chamber.
This method is highly complex, often requiring weeks of parameter adjustments. It is best suited for large-scale, continuous GCC modification. The stearic acid dosage is below 1%, further lowering the per-unit modification cost. However, pin mills are expensive, require skilled personnel for operation and manutenção, and are only suitable for large-scale enterprises with strong technical capabilities.
3) Three-Rotor Modification Machine
The three-rotor modification process is widely used in China. The machine consists of three rotors arranged in a “品”-shaped structure, forming the activation chamber. It operates in a continuous mode and can be used independently or connected to grinding equipment.
The process relies on three rotors spinning at high speeds, generating chamber temperatures of 120–140°C. This creates turbulence within the chamber, ensuring effective dispersion and coating of the GCC powder with stearic acid. The entire modification process occurs within the chamber.
The modification rate for this process exceeds 95%, with a stearic acid dosage of around 4%. The cost of a three-rotor modification machine is lower than a pin mill but higher than a high-speed mixer. While it requires professional maintenance, its complexity is lower than that of pin mills, making it a popular choice for mid-sized manufacturers.
3. How to Evaluate Modification Results?
A general and intuitive method for assessing GCC powder modification is as follows:
1) Principle
This method evaluates the surface coating degree based on the hydrophobic characteristics of modified calcium carbonate.
2) Testing Equipment
100 mL graduated cylinder with stopper
3）Analysis Steps
- Pour 20 mL of distilled water into the 100 mL graduated cylinder.
- Accurately weigh 5 g (±0.01 g) of the sample and place it into the cylinder.
- Add water to reach the 80 mL mark, seal the cylinder, and shake it up and down for 30 seconds (240 shakes per minute).
- Let the mixture stand for 30 minutes and record the data.
4) Test Process Images
After settling, the activation degree can be visually assessed through images of the sample.
