Stearic acid modified calcium carbonate improves polymer compatibility via surface hydrophobicity enhancement. Its chemical bonding with stearic acid increases particle dispersion stability in composites. This treatment reduces moisture sensitivity while maintaining cost-effectiveness. Enhanced interfacial adhesion enables industrial applications in coatings and elastomers.
Stearic acid modified calcium carbonate Key advantages
- Optimized hydrophobicity (water contact angle >100°)
- Dual adsorption mechanisms (chemical/physical bonding)
- Thermal stability (TGA-confirmed decomposition above 300°C)
- Broad matrix adaptability (epoxy, rubber, adhesives)
- Energy-efficient processing (moisture tolerance <1%)
Stearic acid is a common long-chain fatty acid with a relatively low price. It is the most commonly used surface modifier for calcium carbonate. It is mainly composed of two parts: a lipophilic group and a hydrophilic group. Hydrophilic groups interact with calcium carbonate surfaces through physicochemical adsorption. This enhances particle compatibility and dispersion in polymeric matrices including plastics, rubbers, and adhesives.
Stearic acid (salt) modified calcium carbonate can be produced by dry method or wet method. Generally, the wet process uses stearate, such as sodium stearate.
Stearic acid dry modified calcium carbonate
The process begins with drying calcium carbonate (if moisture <1%) to ensure material stability. Stearic acid is then added as a surface modifier, Enabling physicochemical adsorption through its hydrophilic groups. This completes the powder’s surface modification for enhanced polymer compatibility.
When using continuous powder surface treatment equipment, the material and surface modifier are continuously and synchronously fed in. Stearic acid can be added directly in solid powder form. Dosage depends on the powder’s particle size or specific surface area, typically 0.8%-1.2% of calcium carbonate mass.
Recommend three types of calcium carbonate continuous powder surface equipment
Calcium carbonate surface modification requires advanced equipment to ensure uniform coating and industrial efficiency. Three continuous coating systems excel in this field:
Pin Mill Coating Machine
- Achieves 99% coating uniformity via high-speed rotor-stator collisions.
- Processes particles below 20μm with adjustable fineness control.
- Enables simultaneous grinding and coating in dry conditions.
Turbo Mill Coating Machine
- Combines centrifugal force and airflow for rapid dispersion.
- Reduces modifier consumption by 15% using multi-stage mixing chambers.
- Handles throughputs up to 10 tons/hour for large-scale production.
- Maintains 97% activation rate with precision temperature control.
Three-Roller Coating Machine
- Low Investment: Mature technology with low investment costs.
- Efficient Coating: High coating rate with minimal agglomerates.
- Environmental Benefits: No dust emission during operation.
- Energy Efficiency: Self-friction generates heat, reducing energy costs.
- Continuous Production: Suitable for large-scale industrial use.
Surface coating modification utilizes temperature-controlled mixers like high-speed/horizontal paddle systems. This batch process involves 15-60-minute mixing cycles with pre-measured materials and stearic acid. Stearic acid dosage ranges 0.8-1.5wt% of calcium carbonate; reaction temperature maintains 100°C. Treated material discharges for packaging after complete surface adsorption.
In order to make stearic acid better dispersed and evenly react with calcium carbonate particles, stearic acid can also be diluted with a solvent (such as anhydrous ethanol) in advance. Other additives can also be added in appropriate amounts during modification.
Stearic acid wet modified calcium carbonate
Wet modification is to modify the surface of calcium carbonate in an aqueous solution. The general process is to first saponify stearic acid, then add it to the calcium carbonate slurry, and after a certain period of reaction, filter and dry it. It is easier to disperse calcium carbonate in the liquid phase than in the gas phase.
In addition, by adding dispersants, the dispersion effect is better, so the calcium carbonate particles and surface modifier molecules in the liquid phase act more evenly. When the calcium carbonate particles adsorb stearate, the surface energy is reduced. Even if secondary particles are formed after filtration and drying, their agglomeration and bonding force are weakened, and hard agglomerations will not be formed. They can be redispersed with a small shear force.
Wet surface modification equipment is generally simpler, mostly containers with stirrers and static mixers. Strong stirring can improve the modification activation efficiency and shorten the reaction time, but the performance requirements of the equipment are high.
Although wet surface modification can also be carried out at room temperature, the reaction time is long. Therefore, it is generally necessary to heat the surface modification, and the modification temperature is generally around 50-100°C.
Wet surface modification is often used for the surface modification of light calcium carbonate and ultrafine heavy calcium carbonate ground by wet method.