Technical Innovation for BOPP Film Flexo Printing

Flexographic printing on BOPP film for diaper packaging faces three persistent challenges: low surface energy adhesion, strict baby-safety requirements, and process stability at high printing speeds.

Leveraging years of expertise in water-based ink development, Starcolor has engineered a dedicated ink system for diaper packaging. Through resin modification, surface tension control, and low-migration design, this solution delivers strong adhesion, high safety, and reliable performance for BOPP flexo printing.

Enhanced Adhesion on Low Surface Energy BOPP Film

Untreated BOPP film typically exhibits a surface tension of only 28–30 mN/m, making ink adhesion difficult. Instead of relying on heavy corona treatment or primers, Starcolor improves ink–film bonding at the formulation level.

• Modified acrylic resin system with polar functional groups
• Silane-assisted molecular bonding for stronger ink anchorage
• Reliable adhesion on lightly corona-treated BOPP (≥38 mN/m)

Cross-hatch adhesion consistently reaches ≥4B, exceeding common industry benchmarks for flexible packaging.

Baby-Safe, Low Migration Ink Design

Diaper packaging inks must meet exceptionally high safety standards. Starcolor applies a multi-layer safety strategy to minimize migration and contamination risks.

• Total heavy metals (Pb, Cd, Hg): ≤0.05 mg/kg
• Ink migration: ≤0.01 mg/kg
• VOC content: approximately 8 g/L
• Solvent residue: ≤0.03 mg/dm²

The ink is odor-free and suitable for premium diaper brands and export-oriented packaging.

Stable Performance in High-Speed Flexo Printing

Diaper packaging production typically runs at 150–180 m/min, requiring excellent rheological control and fast drying behavior.

• Surface dry time: ≤2 seconds
• Complete drying time: ≤12 seconds
• Stable viscosity across 20–40°C operating conditions
• Color deviation (ΔE): ≤0.8 for brand spot colors

These properties ensure smooth ink transfer, clean dots, and consistent color throughout long production runs.

Durability for the Full Packaging Lifecycle

Diaper packaging must withstand folding, transport, and storage across different climates. Starcolor ink is designed for durability.

• Sutherland rub resistance: 500 dry rubs, 200 wet rubs
• No cracking or tackiness from –20°C to 40°C
• Stable adhesion after long-term storage and transport

Practical Value for Diaper Manufacturers

After switching to Starcolor water-based ink, a major diaper brand achieved measurable improvements:

• Ink-related quality complaints reduced to near zero
• Waste rate lowered from ~5% to below 0.5%
• Production efficiency improved at 180 m/min
• Annual operational savings exceeding USD 250,000

The improved compliance also supported expansion into Southeast Asian, European, and North American markets.

Conclusion

Successful flexo printing on BOPP film requires more than standard water-based ink. Starcolor delivers a technically advanced solution that combines strong adhesion, baby-safe compliance, and stable high-speed performance—helping diaper brands achieve quality consistency, regulatory confidence, and long-term cost efficiency.