In the flexographic printing of flexible packaging, solvent-based inks remain the mainstream choice in the industry due to their strong print adaptability and stable color performance. Despite years of development in environmentally friendly water-based inks, practical applications in composite film printing still face technical challenges such as adhesion and drying performance.
Amid increasingly stringent environmental and food safety requirements, effectively controlling solvent residue has become a critical issue that flexible packaging enterprises must address. Based on long-term production experience, Haide Packaging has developed a comprehensive solvent residue control system covering the entire process from pre-press to printing and testing, which we share here with the industry.
I. The Dual Goals of Solvent Residue Control: Environmental Compliance and Food Safety
When using solvent-based inks for printing, enterprises must balance two core requirements:
Solvent Emission Control: Must comply with national VOCs management and "dual-carbon" policies.
Solvent Residue Control: Directly relates to the hygiene and safety of packaged contents.
These two aspects are closely interconnected. The industry widely adopts "airflow reduction and concentration increase" processes to improve VOCs treatment efficiency and reduce energy consumption. However, this also leads to higher solvent concentrations within the printing system, increasing residue risks.Haide Packaging believes that scientific process design and management are essential to achieve a balance between environmental compliance and product quality.
II. Standards Interpretation and Control Targets
Current national standards provide clear guidance for solvent residue control:
VOCs Emissions: Compliance with GB 37822-2019, requiring non-methane hydrocarbon emission concentrations not exceeding 40 mg/m³.
Solvent Residues: According to GB/T 10004-2008, total residue must be ≤5.0 mg/m², with benzene-based solvents undetectable.
To ensure final products meet standards, Haide Packaging recommends that enterprises set an internal control target for solvent residue during the printing process at ≤2 mg/m², allowing a safety margin for subsequent processes such as lamination.
III. Key Aspects of Systematic Control
1. Pre-Press Design Optimization – Prevention Over Correction
The pre-press stage is the first line of defense in solvent residue control:
Optimize layout design to reduce large-area multi-color overprinting, using spot colors as alternatives.
Use special inks such as metallic or pearlescent inks cautiously, with full-process evaluation when necessary.
Set appropriate anilox cell parameters to avoid excessive ink layers affecting drying.
Prioritize high-solid, low-viscosity inks to reduce solvent usage from the source.
Develop printing process plans based on equipment drying capabilities for proactive risk management.
2. Scientific Selection of Inks and Solvents
Ink composition directly affects solvent evaporation:
Resin Selection: The resin's solvent release properties are crucial. Choose resin systems with good solvent release to avoid high residue due to strong affinity.
Pigment Characteristics: Finer pigment particles make solvent evaporation more difficult. Pay special attention to the drying performance of black and magenta inks.
Solvent Formulation: Scientifically balance fast- and slow-drying components in mixed solvents to avoid excessive residue from high-boiling-point solvents.
3. Refined Management of the Printing Process
Drying System Adjustment: Adjust air temperature and volume in real time based on printing speed and ink layer thickness to ensure thorough solvent evaporation.
Solvent Purity Monitoring: Strictly control solvent water content to avoid delayed drying.
Stable Viscosity Control: Maintain consistent ink viscosity for uniform and controllable solvent release.
IV. Haide Packaging's Integrated Management Approach
Solvent residue control is a systematic project requiring the integration of technology, process, and management. Haide Packaging provides comprehensive support to clients through the following methods:
Process Diagnosis and Optimization: Systematically evaluate existing printing processes to identify residue risk points.
Material Coordination and Adaptation: Recommend suitable ink and solvent combinations based on product structure.
Standardization of Drying Parameters: Establish drying process databases for different product categories.
Testing and Feedback Loop: Equip with professional testing devices for real-time monitoring and traceability of process residues.
We believe that only by integrating solvent residue control throughout the entire process-from pre-press planning and material selection to process monitoring and finished product testing-can we truly achieve "excellent printing, safe packaging," providing end consumers with reliable and secure products.