When selecting a defoamer for high-viscosity ink systems, it is necessary to consider the system characteristics
(high viscosity, high solid content, multi-component), the performance of the defoamer, and its impact on the final
quality of the ink. The following are key selection points and recommended directions:
I. Core Challenges of High-Viscosity Ink Systems
Poor fluidity: The ink has high viscosity (usually >1000 cP), making it difficult for bubbles to escape naturally, requiring
a defoamer that can quickly penetrate and act stably.
Complex composition: Contains resins, pigments, fillers, solvents, etc., which can easily adsorb the defoamer, leading to
its inactivation; some systems contain polar groups (such as epoxy, polyurethane) or high-boiling point solvents, requiring
high compatibility with the defoamer.
Shear environment: Grinding and stirring are required during production, so the defoamer needs to be shear-resistant
to avoid decomposition or deactivation.
II. Defoamer Type Selection and Compatibility Analysis
1. Polyether-modified polysiloxane defoamers (preferred) Core advantages:
Strong defoaming ability: The polysiloxane chain segment reduces surface tension and quickly breaks down bubbles;
High compatibility: The polyether chain segment (such as EO/PO block) improves compatibility with polar resins and pigments,
reducing defects such as craters and fisheyes;
Shear resistance: The molecular structure is stable and can withstand shear forces such as grinding and stirring, remaining effective
for a long time.
Applicable scenarios:
Various high-viscosity inks (such as epoxy, acrylic, and polyurethane inks);
Systems containing pigments and fillers (such as color pastes and filled inks).
Typical products:
RK-3067, RK-3041 (Dongguan Ruikun Materials Technology Co., Ltd., polyether-modified polysiloxane, low crater risk);
RK-8405, RK-8409 (Dongguan Ruikun Materials Technology Co., Ltd., strong compatibility, suitable for high-viscosity systems);
RK-3008, RK-3009 (high-efficiency foam suppression, low dosage).
2. Polyether Defoamers (Non-silicone type, second choice) Core Advantages:
Low surface tension: Defoaming through a penetration-spreading mechanism, friendly to non-polar systems;
No cratering risk: Excellent compatibility with resins and pigments, especially suitable for systems sensitive to organosilicones
(such as UV-curing inks);
Environmental friendliness: Silicone-free, meets environmental requirements such as food contact standards.
Limitations:
Defoaming speed is slightly lower than organosilicone types, and the foam suppression time is shorter in high-viscosity systems;
May have insufficient dispersibility in strongly polar systems (such as epoxy inks containing amine curing agents).
Applicable Scenarios:
High-viscosity, low-polarity inks (such as solvent-based and UV-curing inks);
Scenarios where silicone contamination must be avoided (such as food packaging inks).
Typical Products:
RK-3062E (polyether block copolymer, electrolyte resistant);
RK-3062H (low-foaming, suitable for water-based/solvent-based systems).
3. Organosilicone Defoamers (Use with caution) Core Advantages:
Extremely fast defoaming speed: Low surface tension (e.g., dimethyl silicone oil, 20 mN/m), strong inhibitory effect on small
bubbles (micron-sized).
Limitations:
Poor compatibility: Pure organosilicone easily precipitates in high-viscosity polar systems (such as epoxy and polyurethane),
leading to cratering, fisheyes, and reduced gloss;
Weathering risk: May migrate under long-term high temperature or UV irradiation, affecting adhesion.
Applicable Scenarios:
Low-viscosity, non-polar systems (such as solvent-based inks, ink diluents);
Scenarios requiring extremely high defoaming speed and where slight cratering risk is acceptable (requires strict control of addition
amount <0.1%).
4. Mineral Oil/Fatty Amide Types (Not recommended)
Mineral oil types: Poor dispersibility, easily form oil spots at high viscosity, contaminating the ink surface;
Fatty amide types: Low defoaming efficiency, easily agglomerate in high-viscosity systems, only suitable for low-viscosity, simple systems.
III. Key Performance Indicators and Verification Methods
Dispersibility:
The defoamer should be easily dispersible in high-viscosity inks (particle size <5 μm after grinding, observable under a microscope),
avoiding insufficient defoamer in some areas or agglomeration due to uneven dispersion.
Compatibility:
Test method: Mix the defoamer with the ink and let it stand for 24 hours. Observe for stratification, oil separation, or pinholes (e.g.,
no oil spots or pinholes after 3 days).
Defoaming Performance:
Simulate the production process: Place the ink in a container with a stirrer and stir continuously for 30 minutes. Record the amount of
foam generated and the time it takes for the foam to disappear (for high-viscosity systems, continuous defoaming should last for >1 hour).
Impact on Ink Performance:
Test viscosity changes (viscosity fluctuation should be <10% when the addition amount is <0.5%), adhesion (cross-hatch test), gloss
(60° angle), water resistance, etc., to prevent the defoamer from affecting the ink's film-forming properties.
IV. Practical Application Suggestions
Prioritize polyether-modified polysiloxane types: These balance defoaming efficiency and compatibility, suitable for most high-viscosity
inks (such as color pastes and filled inks).
Control the addition amount: Usually 0.1% to 0.5% of the total ink weight. Excessive amounts may lead to thickening or affect gloss.
Pre-dispersion treatment: If the defoamer is a solid (e.g., granular type), it needs to be dispersed with a small amount of ink or solvent
before adding to avoid agglomeration.
Technical collaboration with suppliers: Provide the ink formulation (resin, pigment, solvent) and request the supplier to recommend a
suitable model (e.g., solutions provided by engineers from Dongguan Ruikun Materials Technology Co., Ltd.).
In summary, the selection of defoamers for high-viscosity ink systems should prioritize "compatibility first, while considering efficiency."
Polyether-modified polysiloxanes are the optimal choice, followed by polyethers; avoid pure silicone types and use mineral oil types with
caution. Experimental verification of dispersibility, compatibility, and the impact on ink performance can ensure a balance between
defoaming effect and final quality.
