Technical Guidelines for Selecting Oil-Repellent Agents for Coating and Ink Systems

Technical Guidelines for Selecting Oil-Repellent Agents for Coating and Ink Systems

Definition: The primary function of anti-oil agents is to prevent defects such as craters, pinholes, and fish-eyes caused by oil contamination on the substrate, or by the migration of mold release agents and plasticizers; some grades also provide substrate wetting capabilities. It is important to distinguish that anti-oil agents are not synonymous with leveling agents; most anti-oil agents fall into the category of specialized wetting and leveling additives.

I. Selection Based on the Application System

1. Solvent-based application systems (including solvent-based coatings, solvent-based gravure inks, etc.)

Application Challenges: Plastic substrates often retain residues such as plasticizers, mold release agents, and processing oils. Combined with the rapid evaporation characteristics of solvents, the presence of such oily contaminants easily leads to "fish-eye" defects.

(1) Low-molecular-weight polyacrylate-based, silicone-free anti-oil/leveling additives

✅ Advantages: Broad system compatibility; excellent resistance to oil contamination; does not interfere with lamination processes or inter-layer adhesion; no risk of silicone contamination. An ideal choice for solvent-based inks.

⚠️ Limitations: Effectiveness is significantly reduced on substrates with heavy residues of silicone-based mold release agents.

(2) Low-molecular-weight silicone-modified polysiloxane functional additives

(3) ✅ Advantages: Excellent targeted action against silicone-based mold release agents; highly effective at suppressing fish-eyes and craters in the coating.

⚠️ Limitations: Carries a risk of migration; exercise caution when using in solvent-based gravure ink applications that involve subsequent lamination.

Recommended dosage range: 0.03% – 0.2%

2. Epoxy resin systems (covering both epoxy coatings and epoxy inks)

Epoxy resin systems possess high polarity and are highly sensitive to residual oil on the substrate surface.

Selection priority: Prioritize non-silicone acrylic anti-oil wetting agents (e.g., HR-8014XD). Exercise caution with silicone-based anti-oil additives; excessive dosage can compromise inter-coat adhesion.

3. UV-curable ink and coating systems

Application challenges: When dealing with plastic substrates containing mold release agents, systems often exhibit rapid curing rates and narrow leveling windows; selected additives must not inhibit polymerization.

Recommended choices: Low-silicone modified siloxanes and acrylic anti-oil wetting agents (e.g., HR-8068) specifically designed for UV systems.

⚠️ Selection precautions: Avoid standard solvent-based anti-oil agents and additives containing free polysiloxanes, as these can cause issues such as polymerization inhibition, surface tackiness, and poor overprinting.

Recommended dosage range: 0.05% – 0.3%

4. Water-based systems encompass applications such as water-based coatings and inks.

Application Challenges: Oil contaminants and silicone-based mold release agents adhering to plastic, die-cast aluminum, and sheet metal substrates easily cause surface defects like "fish-eyes" (craters). Furthermore, the inherently high surface tension of water-based systems makes it technically difficult to achieve effective resistance against oil contamination.

(1) Non-silicone specialty acrylic and acetylenic diol composite anti-oil wetting agent (HR-8030K)

✅ Advantages: Completely silicone-free; does not interfere with recoating, overprinting, or lamination processes, thereby eliminating the risk of silicone-related contamination in subsequent steps.

⚠️ Limitations: Resistance to silicone-based mold release agents is weaker than that of silicone-based anti-oil agents; effectiveness on heavily oil-contaminated substrates is somewhat limited.

✅ Suitable Applications: Water-based flexographic inks, multi-layer coating processes, and ink systems requiring lamination.

Recommended dosage range: 0.05%–0.3%; it is advised to determine the optimal dosage through incremental testing.

(2) Low-silicone polyether-modified silicone anti-oil agents (HR-8060, HR-8062)

✅ Advantages: Excellent ability to lower surface tension; provides outstanding resistance to craters and oil contamination while ensuring superior substrate wetting.

⚠️ Limitations: Excessive dosage can lead to foam stabilization issues and reduced recoatability; carries a risk of silicone migration. Caution should be exercised when selecting high-silicone variants for lamination applications.

✅ Suitable Applications: Water-based industrial paints and screen printing ink systems; suitable for metal substrates and various surfaces with heavy oil contamination.

II. Comparison of the Two Major Types

III. Mandatory Verification Tests During the Selection Phase

1.  Foam performance assessment: Most silicone-based oil-resistance additives possess foam-stabilizing properties; therefore, compatibility testing with the corresponding defoamer is required.

2.  Surface side-effect assessment: Observe the coating for defects such as haze or mottling; for ink systems, particular emphasis must be placed on verifying adhesion to composite films and suitability for overprinting.

3.  Oil-resistance verification: Apply a small, measured amount of engine oil or silicone oil to the substrate surface, then apply the coating or ink under test; observe the surface for defects such as fish-eyes or craters.

4.  Storage stability verification: Conduct storage tests under both high-temperature and low-temperature conditions to observe whether the sample exhibits precipitation or phase separation.

5.  Interlayer performance verification: Focus on recoat adhesion and composite film peel strength, with the latter serving as a critical control parameter for ink systems.

IV. Key Risk Mitigation Points During Selection

1. Compatibility Considerations:When silicone-based anti-oil agents and silicone-based leveling agents are used in combination, the cumulative silicon content in the system increases, significantly raising the likelihood of defects caused by silicon migration.

2. Anti-oil Wetting Agents Cannot Replace Substrate Degreasing:These additives serve only as a safeguard against surface defects; proper substrate pretreatment remains the priority during production. Relying solely on anti-oil additives is insufficient to effectively resolve cases of heavy oil contamination.

3. Distinguish Between Types of Surface Oil Contamination:Non-silicone additives suffice for common mineral oil contamination; however, silicone-based anti-oil wetting agents must be used to address residues from silicone-based mold release agents.

4.Higher Dosage Does Not Equate to Better Performance:Exceeding the critical dosage threshold leads to the formation of an isolation layer on the coating surface, directly impairing adhesion. It is recommended to conduct verification tests using dosage increments of 0.05%, 0.1%, and 0.2%.

V. Key Guidelines for Rapid Selection

- For substrates with silicone-based mold release agent residues that require only a single coating layer and no subsequent lamination, a low-silicone type silicone anti-oil agent may be selected.

- For ink systems with specific requirements regarding lamination and overprinting performance, prioritize the use of non-silicone acrylic anti-oil additives.

- UV-curing systems require dedicated UV-grade anti-oil additives; standard solvent-based anti-oil agents should not be used directly.

- Water-based inkjet systems should avoid the use of silicone-based anti-oil agents whenever possible, as they pose a risk of causing printhead clogging.