Why Food Packaging Imposes the Highest Flexo Standards
Flexible food packaging represents the largest single market for CI flexo printing worldwide. Every ink component and process chemical that may contact food must be evaluated for chemical migration risk. Non-compliance is a public health issue with legal, financial, and reputational consequences.
Key Regulatory Frameworks
EU Regulation (EC) No 10/2011
Governs plastic materials intended to contact food. Key provisions:
- Specific migration limits (SML) for hundreds of substances in inks, adhesives, and coatings
- Overall migration limit (OML) of 10 mg/dm²
- Declarations of compliance required from ink suppliers and converters
US FDA 21 CFR
Indirect food additives (including printing inks) must be listed as safe or receive food contact notification approval. Key sections: 21 CFR 175.300, 21 CFR 176.170.
Ink Migration: The Core Technical Challenge
Three migration pathways exist in flexo-printed food packaging:
- Set-off migration: Ink transfers from printed surface to food-contact surface on wound rolls — the highest-risk pathway.
- Permeation migration: Substances diffuse through the substrate from printed to food-contact side.
- Gas-phase migration: Volatile substances evaporate and condense on food or food-contact surfaces.
Primary mitigations: compliant low-migration ink systems, complete drying during printing, and adequate functional barrier layers.
Low-Migration Ink Systems for Food Packaging
- Water-Based LM Inks: Large-molecule binders with low volatility. Absence of organic solvents eliminates solvent migration risk. Preferred for food packaging.
- UV-Cured LM Inks: Cure by photopolymerization — no evaporation. Low-migration formulations use photo-initiators with large molecular size. Full cure is essential.
- EB-Cured Inks: No photoinitiators required. Extremely low residual volatile levels for the most stringent applications.
Solvent Residual Limits
Most food brand owners specify maximum solvent residuals in finished printed substrate:
- Total solvent residuals: <5 mg/m² (some brands specify <3 mg/m²)
- Ethyl acetate: often limited separately due to odor sensitivity
Practical Compliance Steps
- Obtain Declarations of Compliance from all ink, varnish, and adhesive suppliers
- Validate drying system for residual solvent levels at target production speeds
- Test for set-off migration on wound rolls using appropriate food simulants
- Maintain batch records for all inks and substrates used in food packaging production
- Conduct periodic migration testing using accredited laboratory methods
LISHG CI flexo presses designed for food packaging include validated drying zone specifications and are compatible with low-migration water-based and UV ink systems.
