One-stop application solution for ink aluminum silver paste
The selection, formulation design, dispersion process, and printing application of aluminum silver paste in various ink systems ensure that the metallic effect, printability, and finished product quality of ink products meet the expected standards. This SOP is applicable to the application of aluminum silver paste in solvent-based, water-based, and UV ink systems, covering mainstream printing processes such as gravure printing, offset printing, and screen printing.
Floating aluminum silver paste: Aluminum silver paste with its surface treated with low surface tension, which floats on the surface of the ink during drying to form a high-gloss mirror effect.
Non-floating aluminum silver paste: Aluminum silver paste with its surface modified by lipophilic or hydrophilic treatment, which is uniformly dispersed in the entire ink film layer, combining metallic texture with good weather resistance.
· Aspect ratio: The ratio of the average diameter to the thickness of aluminum flake particles, which is a key parameter affecting metallic luster and hiding power.
· Dispersant: A surfactant used to improve the dispersion stability of aluminum silver paste in the ink system and prevent particle agglomeration.
Raw materials
· Aluminum silver paste: Select floating, non-floating, electroplating imitation, fine silver, or flash silver types according to requirements.
· Resin: Solvent-based (such as acrylic, vinyl chloride-vinyl acetate, polyurethane); water-based (such as acrylic emulsion, polyurethane dispersion).
· Solvent/water: Solvent-based (alcohols, ethers, esters); water-based (deionized water).
· Additives: Dispersants, wetting agents, leveling agents, anti-settling agents, pH regulators, defoamers.
Equipment
· Stirring equipment: Low-speed mixer (≤1000rpm), high-speed disperser (for pre-dispersion).
· Testing equipment: Viscometer, fineness gauge, gloss meter, adhesion tester (cross-cut knife), pencil hardness tester.
· Printing equipment: Gravure printing press, offset printing press, screen printing press, flexographic printing press.
Operation steps
1. Selection of aluminum silver paste
1. Select according to the printing effect requirements:
o High-gloss mirror effect: Select floating aluminum silver paste with a particle size of 10 - 15μm.
o Uniform metallic texture and weather resistance: Select non-floating aluminum silver paste with a particle size of 10 - 30μm.
o Fine printing and delicate luster: Select fine silver paste with a particle size of ≤10μm.
o High flashing effect: Select flash silver paste with a particle size of 20 - 30μm.
2. Select according to the ink system:
o Solvent-based ink: Compatible with floating or non-floating aluminum silver paste.
o Water-based ink: Must select water-based non-floating aluminum silver paste modified by hydrophilic treatment.
o UV ink: Select non-floating aluminum silver paste with good compatibility with the UV resin system.
2. Formulation design
1. Determine the addition amount of aluminum silver paste:
o Pure silver ink: 6 - 10%
o Metallic flash ink: 5 - 13%
o Anti-corrosion/packaging ink: 10 - 30%
2. Selection of resin system:
o Give priority to resins with low acid value and low amine value to avoid reaction with the fatty acid on the aluminum surface.
3. Design of solvent/water system:
o Solvent-based: Compound alcohol, ether, and ester solvents, and control the volatilization gradient (fast-drying: slow-drying = 6:4).
o Water-based: Use deionized water as the main component, and add ethylene glycol monobutyl ether (≥70%) to adjust volatilization and wettability.
4. Addition of additives:
o Dispersant: Add 0.5 - 2% of the amount of aluminum silver paste (such as BYK - 190, TEGO Dispers 750W).
o Anti-settling agent: Fumed SiO₂, with an addition amount of 0.5 - 1%.
o Water-based system: Adjust the pH to 8 - 9, and add a corrosion inhibitor to prevent hydrogen evolution.
3. Dispersion process
1. Pre-dispersion:
o Mix aluminum silver paste with solvent/water at a ratio of 1:1 - 1:2, and stir at a low speed (300 - 500rpm) for 10 - 20 minutes until there are no obvious particles.
2. Main dispersion:
o Slowly add the pre-dispersed aluminum silver paste to the resin system, and continue to stir at a low speed (500 - 800rpm) for 30 - 60 minutes.
o Avoid high-shear stirring to prevent damage to the aluminum flake structure.
3. Paint adjustment and filtration:
o Add the remaining solvent/water to adjust the viscosity to the target range (such as 20 - 30s for gravure ink, Ford cup No. 4).
o Filter with a 100 - 200 mesh screen to remove impurities and agglomerated particles.
Printing application
1. Gravure printing:
o Ink viscosity: 20 - 30s (Ford cup No. 4).
o Printing speed: Adjust according to the equipment and substrate to ensure sufficient drying.
o Drying temperature: Dry in stages, with an inlet temperature of 60 - 70°C and an outlet temperature of 80 - 90°C.
2. Screen printing:
o Screen mesh number: Select according to the particle size of aluminum silver paste (N = 4.5√d, where d is the particle size in μm).
o Scraper angle: 70 - 75°.
o Curing conditions: Pre-bake at 70°C for 5 minutes, and cure at 120°C for 15 minutes.
3. Flexographic printing (water-based):
o Ink viscosity: 20 - 30s (Ford cup No. 4).
o Printing speed: 100 - 150m/min.
o Drying temperature: 60 - 70°C to ensure complete drying of the water-based system.
Quality control and inspection
1. Appearance: The ink should be uniform, without lumps or particles.
2. Fineness: Detect with a fineness gauge, ≤20μm.
3. Viscosity: Meet the target range (such as 20 - 30s for gravure printing).
4. Metallic luster: Detect with a gloss meter, and the gloss value should meet the standard.
5. Adhesion: Test with a cross-cut knife, and reach grade 5B.
6. Resistance: Test water resistance, oil resistance, cooking resistance, weather resistance, etc. according to application requirements.
Common Problems and Solutions
Problem/Observation | Possible Cause | Solution |
Dull metallic luster | Disordered aluminum flake alignment, poor dispersion, uneven particle size | Optimize solvent evaporation gradient; increase dispersant dosage; replace with aluminum paste having higher aspect ratio |
Printing dusting/poor adhesion | Insufficient resin adhesion, poor compatibility | Replace with resin having stronger adhesion; adjust solvent system to improve wettability |
Hydrogen evolution, blackening in water-based systems | Reaction of aluminum with water, failed passivation layer | Use specialized water-based passivated aluminum paste; adjust pH to 8-9; add corrosion inhibitor |
Plate clogging, poor leveling | Particle size too coarse, improper viscosity, too fast solvent evaporation | Replace with finer particle size aluminum paste; adjust ink viscosity; add leveling agent; blend with slow solvent |
Poor weather resistance, oxidation blackening | Insufficient aluminum flake protection, weak resin weather resistance | Choose weather-resistant non-leafing aluminum silver paste; add antioxidants; apply transparent overcoat varnish |
Precautions
1. Safety protection: Wear a dust mask and gloves during operation to avoid inhaling aluminum silver paste dust.
2. Storage conditions: Aluminum silver paste should be stored in a sealed container in a cool and dry place, away from direct sunlight and high-temperature environments.
3. Environmental protection requirements: Give priority to water-based aluminum silver paste to reduce VOC emissions and comply with environmental protection regulations.
4. Process records: Record in detail the raw materials, formulations, process parameters, and inspection results of each batch for traceability.
Do you provide free samples?
Yes, we do provide free samples for testing, typically 100g–500g per sample. The sample itself is free, but the shipping cost will need to be covered by your side.
Please let us know the specific type you need (leafing, non-leafing, water-based, fine silver, etc.) and the target application (e.g., gravure ink, screen printing ink). We will prepare the most suitable sample for you.
Contact person：Molly
Whatsapp：+86 131 7601 9165