A Mandatory Course in Packaging Printing: Compatibility Knowledge Between Offset Printing Ink And BOPP Lamination Film

Laminating is a critical post-printing process in packaging production, directly impacting the competitiveness of finished packaging products. BOPP (Biaxially Oriented Polypropylene) lamination film, boasting high transparency, moderate cost and excellent weather resistance, has become the mainstream laminating material for industries such as food and pharmaceuticals. Offset printing is the most widely used printing method, and the compatibility between its ink and BOPP lamination film is the core of laminating quality. Incompatibility will lead to defects like warping, bubbles and delamination, increasing material waste and reducing product qualification rates. This article breaks down key compatibility knowledge from four dimensions: basic understanding, core compatibility points, fault troubleshooting, and compliance control, helping enterprises improve packaging quality.

• Core Properties of BOPP Lamination Film

BOPP lamination film uses biaxially oriented polypropylene as the base material, with a hot-melt adhesive or water-based adhesive coated on its surface. Classified by gloss, it includes high-gloss, matte and flat types, suitable for diverse packaging scenarios. The key indicators for its compatibility with ink are adhesive layer type, melting point, adhesion and transparency. Among them, the hot-melt adhesive type has a melting point of 80-120°C, featuring strong viscosity when heated and suitable for conventional packaging. The water-based adhesive type requires no high temperature, making it ideal for temperature-sensitive printed products. Uneven adhesive layers easily cause bubbles, while overly thin base material may lead to film breakage. Currently, it is widely applied to paper-based packaging such as corrugated cartons and color boxes, providing both protection and aesthetic appeal.

• Core Properties of Packaging-Grade Offset Printing Ink

Packaging-grade offset printing ink consists of pigments, resins, solvents and additives. Classified by drying mechanism, it includes oxidation-drying, UV-curable and infrared-drying types. The oxidation-drying type, with low cost and good printability, is the most commonly used and cures through the reaction between resin and oxygen. Key compatibility indicators with lamination film include drying speed, adhesion and surface tension-failure to meet any indicator will result in incompatibility. Food and pharmaceutical packaging requires low-migration ink to prevent harmful component migration, imposing stricter compatibility requirements.

• Drying Degree Compatibility: The Core of Ink-Lamination Film Compatibility

The drying level of offset printing ink directly determines the laminating effect. Insufficient drying causes delamination and ink transfer, while excessive drying easily leads to warping. In practical operation, the finger-touch test and drying time can be used for judgment: surface dryness is achieved when no stickiness or ink transfer occurs upon light finger contact. Oxidation-drying ink takes 2-4 hours to dry thoroughly at room temperature and normal humidity. Drying time should be extended in high-humidity or low-temperature environments; ventilation or heating can accelerate drying, and ink usage should be controlled to avoid overly thick ink layers that prolong drying.

• Type Compatibility: Precise Matching of Ink Type and Lamination Film Adhesive Layer

Ink and the adhesive layer of lamination film must be precisely matched to avoid laminating failure. Oxidation-drying ink paired with hot-melt adhesive lamination film is the optimal combination-the hot-melt adhesive melts at high temperatures and bonds strongly with ink resin, offering excellent compatibility and cost-effectiveness. UV-curable ink is suitable for pairing with water-based adhesive lamination film, as the water-based adhesive layer has good permeability and prevents bubbles and warping. Avoid incompatible combinations such as UV ink with hot-melt adhesive film or oxidation-drying ink with water-based adhesive film, which cause delamination and ink discoloration.

• Process Parameter Compatibility: Coordinated Control of Temperature, Pressure and Speed

Laminating temperature, pressure and speed must be coordinated. For hot-melt adhesive lamination film, the temperature is controlled at 100-130°C, and for water-based adhesive film at 80-100°C. Excessively high temperature causes ink discoloration and film shrinkage, while low temperature results in poor adhesion. Pressure is set at 0.3-0.5 MPa-excessive pressure leads to ink transfer and film breakage, while insufficient pressure causes warping. The speed is maintained at 10-15 m/min; fast speed results in incomplete bonding, while slow speed reduces production efficiency. Adjust parameters based on actual conditions.

• Surface Tension Compatibility: Matching Between Ink and Film Surface Tension

The compatibility principle is that the surface tension of BOPP lamination film is slightly higher than that of ink, with a difference of 2-5 dyn/cm. The surface tension of the lamination film must reach 38-42 dyn/cm; corona treatment can enhance insufficient surface tension, but excessive treatment damages the film. If ink surface tension is too high, add surfactants for adjustment, and control ink viscosity to avoid affecting compatibility.

Improper compatibility often causes various faults in production, with specific solutions as follows:

• Fault 1: Laminating Warping and Delamination

Core causes: Insufficiently dried ink, mismatched material types, inadequate temperature and pressure.

Solutions: Extend drying time, replace compatible ink/lamination film, adjust temperature and pressure parameters.

• Fault 2: Laminating Bubbles

Core causes: Impurities on the ink surface, uneven adhesive layer, excessively high temperature.

Solutions: Clean the surface of printed products, replace lamination film with a uniform adhesive layer, lower the temperature appropriately.

• Fault 3: Ink Transfer

Core causes: Insufficiently dried ink, excessive pressure, poor ink adhesion.

Solutions: Extend drying time, reduce pressure, select high-adhesion ink.

• Fault 4: Surface Haze and Opacity

Core causes: Incomplete melting of the adhesive layer, reaction between ink and adhesive layer, poor transparency of lamination film.

Solutions: Raise temperature to fully melt the adhesive layer, replace compatible products, select high-transparency lamination film.

Food and pharmaceutical packaging requires low-migration ink and food-grade lamination film, complying with standards such as GB 9685 and GB 7718. Exported packaging must meet requirements like the EU REACH Regulation and U.S. FDA standards. After laminating, conduct tests on adhesion, rub resistance and temperature resistance to ensure compliance. Store ink and lamination film separately: ink in a ventilated environment at 15-25°C with 50%-60% humidity, and lamination film away from moisture, high temperature and extrusion deformation.

Compatibility between offset printing ink and BOPP lamination film hinges on four key dimensions: drying degree, material type, process parameters and surface tension. Precise control of these aspects avoids faults and reduces material waste. As the packaging industry advances toward green development and high quality, new eco-friendly products emerge continuously, requiring practitioners to keep learning compatibility techniques. This series will continue to share compatibility experience for diverse scenarios, helping enterprises enhance competitiveness and promote high-quality industry development.