Comprehensive Selection Guide for Nano Metal Oxide Dispersants
Covering three major fields: oil-based solvent systems, water-based digital inkjet, and weak solvent digital inkjet; Suitable powders: nano titanium dioxide, transparent iron oxide, nano zinc oxide, nano aluminum oxide, nano silicon dioxide, bismuth vanadate, cobalt oxide and other oxides.
Key basic characteristics (selection criteria)
1. The surface of the particles is rich in hydroxyl groups (- OH), while carboxyl and phosphonic acid groups have the strongest anchoring force;
2. With a huge specific surface area and extremely high surface energy, small molecule dispersants rely solely on charge repulsion, which can easily cause flocculation and precipitation. Therefore, polymer hyperdispersants must provide thick layer steric hindrance;
3. The specific gravity is much higher than that of the medium, which easily causes gravity induced hard precipitation, integrating wetting, dispersion, and long-lasting anti settling;
4. Nano silicon/alumina has a high oil absorption capacity, and the amount of dispersant used is increased by 50% to 100% compared to conventional micro titanium white.
I、 Solvent based (oil-based) ink/coating system
Solvent: xylene, ester, ketone, alcohol ether; Compatible resins: solvents acrylic acid, alkyd acid, epoxy PU、 Amino baking paint, oily UV.
1. Common types of dispersants, matching powders, and grades
(1) Polyamide super dispersant (inorganic+organic pigment compound)
-Model: RK-4028, RK-4029, RK-4042, RK-4064
-Application: Co grinding of oxides and organic color powders to prevent floating and discoloration, as well as to prevent flocculation and aggregation
-Disadvantage: The light colored pure white titanium dioxide system is prone to yellowing and is not recommended as the first choice
(2) Water oil universal non-ionic polymer (low yellowing transparent system)
-Model: RK-4057, RK-4039ACB, RK-4061C0
-Adaptation: Transparent iron oxide, matte UV varnish, electrically neutral, resistant to hydrolysis, does not damage the coating weather resistance
(3) Phosphate ester dispersant (specially designed for corrosion-resistant/high salt environments)
-Model: RK-4011, RK-4012, RK-4013A, RK-4013C
-Applicable: Nano zinc oxide, alumina anti-corrosion paint, ceramic oil slurry
-Features: High temperature and heat resistance, no detachment, no damage to powder rust prevention, UV shielding function; Compound of conventional acrylic dispersant
(4) Acrylic block polymer (mainstream preferred in the industry)
Anchor: polycarboxyl group; Solvation of long hydrophobic carbon chains, dual stability of electrostatic and steric hindrance
-Representative models: RK-4035AC, RK-4059, RK-4057 (universal for water and oil), RK-4039AC nano specific
-Applicable: Nano titanium dioxide, transparent iron oxide, nano zinc oxide, aluminum oxide, matte silica
-Advantages: Strong viscosity reduction, high gloss, no hard precipitation after 30 days of hot storage at 50 ℃, and resistance to cold and hot cycles
-Addition amount: powder 2.5% to 5%; Nano SiO ₂ selects 4% to 6% top grid
2. Oil based system is precisely matched according to powder
1. Nano rutile/anatase TiO ₂ (white paint, high coverage): RK-4061C0, added 2.4%~3.6%;
2. Transparent nano iron oxide (red, yellow, black wood paint): RK-4039ACB, added with 3.4%~5%;
3. Nano ZnO/Al ₂ O3 (antibacterial and anti-corrosion): a combination of phosphate ester and acrylic acid;
4. Nano silica/gas phase (extinction and abrasion resistance): acrylic block dispersion, high dosage of 4% to 6%.
3. Oil taboo
1. Prohibit sodium hexametaphosphate and low molecular weight polyacrylate, which are difficult to dissolve in organic solvents;
2. Fatty acid soaps and small molecule surfactants have weak steric hindrance and return to coarse precipitation within seven days;
3. Nano metal powders (aluminum, zinc) cannot be used alone with polycarboxylates, as they are prone to rusting and bubbling.
II、 Digital inkjet system (divided into two categories: water-based inkjet and weak solvent inkjet)
（1） Water based digital inkjet (textile, ceramic, decorative white ink, coating inkjet, containing 30%+ethylene glycol/propylene glycol co solvent)
Special hard requirements for inkjet printing
Micro bubble zero APEO, anti high alcohol non desorption, D50<100nm after dispersion, persistent circulation without blockage, and stable viscosity.
1. Types and selection of dispersants
① Comb type anionic polycarboxylate (preferred for single component nano oxide white ink)
Model: RK-4010,RK-4017G, domestic 9800 inkjet dispersant
-Principle: Multi carboxyl anchored hydroxyl group, polyether hydrophilic side chain resistant to diols, no hard block precipitation after three months of thermal storage
-Adaptation: Nano TiO ₂ white ink, nano SiO ₂ matte coating ink
-Addition amount: Powder 3%~4.6%
② Amphoteric polyurethane dispersant (high-end compound/cationic ink specific)
Model: RK-4039AB, RK-4044
-Features: Compatible with both nano oxides and organic pigments, with the best alcohol resistance performance; Exclusive matching cationic lotion inkjet
-Applicable: Transparent iron oxide color ink, multi pigment compound ink, ceramic inkjet, nano functional oxide ink
-Addition amount: 3.5%~6%
③ Phosphate ester wetting and dispersing agent (only for auxiliary compounding, cannot be the main dispersant)
RK-4013C, RK-4039AA0 combined with main dispersant to eliminate powder entrapment and reduce the risk of bubble breakage
2. Application strategy of water-based inkjet
1. Pure nano titanium dioxide white ink: comb shaped polycarboxylate (with the highest cost-effectiveness)
2. Nano silica matte inkjet: a combination of polycarboxylate acid and low foaming non-ionic wetting agent
3. Transparent iron oxide colored inorganic ink: amphoteric polyurethane dispersant, anti alcoholysis aggregation plug
4. Cationic system inkjet: can only use amphoteric polyurethane dispersants, ordinary anionic polycarboxylates can directly flocculate and stratify
3. PH control of water-based inkjet printing
The steady-state pH of the system is 8.0 to 9.5, avoiding the isoelectric point of oxides at 5 to 7; Nano silicon should avoid pH exceeding 10 to prevent silicon powder from hydrolyzing and thickening.
（2） Weak solvent digital inkjet (outdoor advertising, PVC, leather printing, solvents: esters, ketones, alcohol ethers, resin weakly soluble acrylic acid)
System characteristics
The solvent solubility is poor, and the dispersant must be fully soluble in ester ketone solvents. Narrow particle size spectrum and circulation anti clogging nozzles need to be controlled.
Specialized dispersant (structured acrylic copolymer)
Model: RK-4035AB, RK-4036B
1. Structure: Long hydrophobic solvation chain, multi-point carboxyl anchored nano oxide;
2. Performance: low viscosity, long-term cycling without settling, nozzle not easily crystallized and blocked;
3. Addition amount: Nano oxide accounts for 4 to 7% (unconventional oil-based paint);
4. Applicable powders: nano titanium dioxide, transparent iron oxide, nano silicon powder, bismuth vanadate pigment;
5. Taboo: Water based polycarboxylate dispersant, insoluble in weak solvents, directly flocculates in layers.
III、Universal supporting process (oil/inkjet universal)
1. Dispersant addition gradient test (required for nano powder)
Gradient setting: 2.5%/3.5%/4.5%/6% (by powder mass)
-Insufficient addition: Insufficient coverage, bimodal particle size, rapid flocculation and precipitation;
-Excessive addition: Free dispersants cause shrinkage of the paint film, inkjet foaming and breakage, and deterioration of water and weather resistance.
2. Stability verification standards
1. Laser particle size: Particle size distribution: D90 is less than 120 nanometers, showing a single peak (without secondary hard agglomeration);
2. Seal at 50 ℃ for half a month, shake well and disperse the sediment at the bottom without any hard lumps;
3. Inkjet testing: Two days of continuous operation without ink interruption or nozzle blockage.
IV、 Quick Selection Guide for Multi emotional Scenarios
Oil solvent coating system
Nano oxide selected acrylic block, fully compatible with epoxy PU alkyd;
Rust resistant zinc oxide aluminum phosphate mixed, mixed color powder selected from polyamide;
Abandon small molecule dispersants and eliminate sedimentation and agglomeration through steric hindrance.
Water based digital inkjet system
Pure white titanium comb shaped polycarboxylate, mixed with colored polyurethane;
Alcohol soluble environment, anti precipitation and anti foaming, cationic inkjet special amphoteric polyurethane;
Maintain a constant pH of 8 to 9.5 and store for a long time with the nozzle connected.
Weak solvent outdoor inkjet system
Customized acrylic acid special supply, completely repelling water-based dispersants;
The ratio is super conventional oily, with fine particles ensuring smooth ink output.
