1、 Process principle
Dry modification achieves surface functionalization of white carbon black through mechanical force or gas-phase reaction under anhydrous or low solvent conditions. Its core mechanism includes:
Mechanical activation: The shear force generated by high-speed mixing opens up white carbon black aggregates, exposing surface hydroxyl groups (- OH) and providing active sites for chemical grafting.
Chemical grafting: The alkoxy group of silane coupling agents (such as Si69) reacts with - OH to form siloxane bonds (Si-O-Si), achieving hydrophobic modification.
Modification objective:
Hydrophobication: Contact angle>110 °, improves water resistance.
Reduce DBP oil absorption value: ≤ 200 mL/100g, improve dispersibility.
Enhanced compatibility: The interface bonding energy is increased by 45%, improving the bonding strength with polymers.
Key control points:
Temperature: 110 ℃ is the critical value, too high can cause the modifier to decompose, and too low can result in incomplete reaction.
Shear rate: ≥ 3500 rpm is the threshold for aggregate depolymerization to ensure uniform modification.
Time: 1.5-2.5 hours, reaction conversion rate>90%.
2、 Equipment selection
High speed mixer:
Applicable scenarios: Small batch production or laboratory research.
Advantages: Flexible operation, suitable for various modifiers.
Limitations: Limited production capacity makes it difficult to achieve continuous production.
Fluidized bed reactor:
Applicable scenario: Large scale industrial production.
Advantages: Adequate gas-solid contact, high reaction efficiency, and the ability to achieve continuous operation.
Key parameters:
Airflow velocity: 0.5-1.5 m/s, ensuring particle fluidization state.
Temperature control: ± 2 ℃ accuracy to avoid local overheating.
Ball mill:
Applicable scenario: Modification of ultrafine grained white carbon black.
Advantage: Surface exfoliation and morphology control are achieved through high-energy collisions.
Limitations: High energy consumption, equipment wear and tear requires regular maintenance.
3、 Selection of modifier
Silane coupling agent:
Representative product: Si69 (bis - [γ - (triethoxysilyl) propyl] tetrasulfide).
Mechanism of action: Alkoxy hydrolysis generates silanol, which reacts with the surface of white carbon black - OH to form covalent bonds.
Dosage: 3-5 wt% (based on the quality of white carbon black).
Silicone oil:
Representative product: Dimethyl silicone oil.
Mechanism of action: By physical adsorption or chemical bonding, surface energy is reduced and hydrophobicity is enhanced.
Applicable scenarios: scenarios that require rapid modification, but have poor long-term stability.
Acrylic polymer:
Representative product: Polyacrylate ester.
Mechanism of action: A polymer layer is formed on the surface of white carbon black through free radical polymerization, enhancing compatibility with the organic matrix.
Advantages: Can design functional groups and expand application fields.
4、 Process characteristics and advantages
High purity products:
Silicon dioxide purity can reach over 99%, suitable for high-end fields such as electronic packaging.
Ultra fine particle size:
The particle size of the product is usually in the range of 10-20 nanometers, with a high specific surface area (150-300 m ²/g), which enhances the reinforcement effect.
Low energy consumption:
Compared to wet processes, it does not require a large amount of water and solvents, reducing drying and post-treatment energy consumption.
Simple process:
There are fewer post-processing steps, making it easy to integrate with gas-phase white carbon black production lines and achieve large-scale production.
Performance advantages:
Reinforcement performance: In silicone rubber, the tensile strength is increased by 30-50%.
Dielectric properties: Stable dielectric constant (3.5-4.0), suitable for high-frequency electronic materials.
Water resistance: The water absorption rate is reduced to below 0.5%, extending the service life of the material.
5、 Application Fields
Rubber industry:
Silicone rubber reinforcement: enhances tensile strength (10-15 MPa) and tear strength (30-50 kN/m).
Tire application: Reduce rolling resistance by 20-30% and improve wet skid resistance.
Paint industry:
Thickener: Adjust the viscosity of the coating (50-150 KU) to improve leveling.
Extinguishing agent: Control glossiness (10-60%), enhance coating texture.
Plastic industry:
Reinforced filler: In PP, the bending modulus is increased by 50-80%, and the hot deformation temperature is increased by 20-30 ℃.
Transparent modification: maintains a light transmittance of>90%, suitable for optical grade materials.
Functional ceramics:
Mechanical properties: fracture toughness improved by 30-50%, and thermal shock resistance enhanced.
Thermal stability: The thermal conductivity is reduced to 0.5-1.0 W/(m · K), suitable for insulation materials.
Electronic packaging:
Organic silicone epoxy resin: Improved sealing performance, reduced water absorption rate to below 0.1%.
Thermal conductive filler: The thermal conductivity is increased to 1.0-2.0 W/(m · K) to meet the heat dissipation requirements.
6、 Technological development trends
Process optimization:
Develop low-temperature modification technology (<100 ℃) to reduce energy consumption.
Real time monitoring and automatic adjustment of temperature and airflow velocity inside the reactor.
Product modification:
Introducing multifunctional modifiers (such as fluorosilane) to endow white carbon black with self-cleaning and anti fouling properties.
Develop gradient modification technology to achieve a core-shell structure with hydrophobic surface and hydrophilic interior.
Environmental improvement:
Adopting a closed-loop system to recycle unreacted modifiers and reduce VOC emissions.
Develop water-based modifiers to replace organic solvents and reduce environmental pollution.
Large scale production:
Construct a 10000 ton production line to reduce unit costs (<5000 yuan/ton).
Develop modular equipment to adapt to different production capacity requirements.