Complete Technical Guide to Carbon Black Dispersant Selection

Complete Technical Guide to Carbon Black Dispersant Selection

Challenges of carbon black: large specific surface area and significant range of structural heights; based on surface polarity, it can be divided into two main categories: acidic carbon black with more oxygen-containing groups and neutral carbon black produced by furnace process; it is extremely prone to agglomeration; the anchoring ability of the dispersant is the highest priority selection factor, and dispersants for different systems such as water-based, solvent-based, and UV-based systems are almost not universally applicable.

I. Core Performance Judgment Reference Criteria in the Selection Process

1. Carbon Black's Intrinsic Parameters: Higher specific surface area and higher structural grade require a higher amount of dispersant. The dispersant dosage order is: channel black > high-structure furnace black > low-structure furnace black.

2. Carbon Black Surface Compatibility Characteristics: Acidic carbon black is more easily and firmly adsorbed by basic anchoring groups; neutral or inert carbon black requires multi-anchoring block superdispersants for effective dispersion.

3. The core molecular structures of dispersants used in water-based, solvent-based, and UV-curing systems, classified by media properties, are completely different.

4. The dispersion performance requirements for ordinary coatings, water-based inks, digital inkjet inks, and conductive carbon black pastes differ significantly.

II. Selection by System

1. Water-based application systems cover four major categories: water-based coatings, water-based inks, water-based pigments, and water-based inkjet printing.

Based on performance requirements, they are divided into two application levels: general water-based coatings and inks, and digital inkjet printing. Conventional coating dispersants are not suitable for direct use in inkjet systems.

1) General Water-based Coatings and Inks

- High-quality general-purpose water-based polyurethane block dispersants are the preferred primary choice; styrene-maleic anhydride ammonium salt dispersants are the secondary option.

- Reference models: RK-4017E, RK-4010.

- Dispersant addition amount is based on carbon black quality: 50%-80% for high-pigment carbon black; 35%-60% for ordinary furnace black.

- Caution is needed when selecting ordinary polyacrylate ammonium dispersants, as their anchoring ability for high-pigment carbon black is relatively weak, and the dispersed system is prone to coarsening, resulting in a higher overall viscosity.

2) Water-based digital inkjet pigment inks

must employ a comb-like or amphoteric block molecular structure, possessing stable performance resistant to polyol-based humectants;

- Initial formulation: styrene-maleic anhydride copolymer ammonium salt, amphoteric polyurethane dispersant; refer to RK-4010 and RK-4044.

- Dispersant addition range set at 45%-70%; the system must be ground to a particle size D90 less than 200nm.

Water-based systems should avoid small-molecule anionic dispersants: they have insufficient adsorption on pigment particle surfaces, easily desorbing and causing flocculation and coarsening of the entire system.

2. Solvent-based systems cover three application scenarios: solvent-based coatings, solvent-based printing inks, and plastic-based inks.

- The preferred solution for solvent-based carbon black dispersion is a high-molecular-weight polyurethane superdispersant with a polyester-polyamide block structure.

- Reference grades: RK-4016A, RK-4016C, RK-4029HA.

- Addition amount: 55%-85% for high-pigment carbon black; 35%-60% for ordinary carbon black.

Note: High-acid-value phosphate esters are only suitable for some low-structure carbon blacks; for most high-pigment carbon blacks, their anchoring effect is significantly insufficient.

3. UV-curing systems include three core categories: UV-curable inks, UV inkjet printing inks, and UV-curable coatings.

In UV-curing systems, the dispersant component must not contain any residual free primary amines; otherwise, it will cause yellowing of the system and significantly negatively impact the photocuring reaction kinetics.

- The system should preferably use polyester-type block dispersants that do not contain free primary amines.

- Reference models: RK-4029, RK-4039AC.

- Dosage: 50-80% of carbon black mass.

4. Conductive Carbon Black-Carbon Nanotube Composite Conductive Slurry

Conductive carbon black has an extremely high specific surface area, making it significantly more difficult to disperse than ordinary pigment carbon black. Steric hindrance polymeric dispersants should be prioritized, while strictly controlling the introduction of ionic impurities.

- Amphoteric polyurethane resins are suitable for aqueous systems.

- Polyurethane-based superdispersants are suitable for solvent systems.

Note: Excessive dispersant addition will block the conductive pathway; the ideal range must be determined experimentally by plotting a dosage-performance curve.

III. Quick Selection Comparison Table

IV. Key Pitfalls to Avoid in Practical Application

1. The correct order of adding materials is: first, completely dissolve the dispersant in the dispersion medium, then add the carbon black for grinding. Do not add dispersant later in the grinding process.

2. Core indicators for judging the quality of dispersion include: pigment viscosity, blackness, blue phase performance, and system stability under room temperature and heat storage conditions.

3. Higher dosage does not necessarily mean better results: Excessive use will lead to deterioration of the paint film's water and solvent resistance, and will also significantly increase the overall resistance of the conductive paste.

4. Different batches of carbon black have different surface treatment processes. Even with the same dispersant, the final dispersion effect will vary significantly. Therefore, gradient dosage tests must be conducted to determine the appropriate solution.