Industry News

Driven by the green packaging trend, water-based inks, owing to their environmental advantages, are becoming a new favorite for flexible packaging products such as baby diaper packaging film, chocolate bar seal film packaging bags, and toilet paper plastic packaging bags. However, adhesion issues between ink and packaging film remain a key obstacle to their widespread adoption. To overcome this challenge, flexo printing machine manufacturers have focused on six core areas: film surface treatment, ink formulation optimization, printing process control, environmental and storage management (temperature and humidity), adhesives, and post-print testing. These efforts have led to effective approaches to improve the adhesion stability of water-based inks, ensuring that they meet stringent food safety standards while maintaining mechanical performance. This approach is driving strong momentum in the green transformation of flexible packaging products such as honey sachet film bags, biscuit candy sugar snack film bags, and nut snack chip pouches.

Flexographic Press for Candy Wrapping Film

Film Surface Treatment

Corona treatment ensures that the film's surface tension meets the specified standards. For example, for BOPP and PE, the standard is 38 dynes or greater. Corona treatment increases surface active groups, such as hydroxyl and carboxyl groups, through oxidation, improving ink wettability, meeting the production requirements of products such as wet wipes packaging wrappers and fried noodles food packaging films. Corona-treated films should be used within 72 hours to avoid prolonged storage, which can lead to surface tension loss. If stored beyond the specified time, re-corona treatment is required.

Flexographic Machine for Tea Milk Powder Packaging

Ink Formulation Optimization

Use high-adhesion binders such as acrylic polyurethane and copolymer resins to enhance the chemical bond between the ink and the film. Solvent Adjustment: Adding ethanol or isopropyl alcohol can adjust the drying speed and improve leveling. Also, maintain a 1:1 to 4:1 alcohol-to-ethanol ratio to avoid excessive dilution that could lead to insufficient resin content. Excessively high or low pH values can affect the drying and adhesion of water-based inks, compromising the flexographic printing quality of products such as adult breathable PE film diaper and sterilized alcohol pad packaging film.

Flexographic Printing Machine for Facial Boby Soap Wrapper Packaging Film

Printing Process Control

Drying conditions utilize a combination of infrared and heated air drying, with the hot air temperature set between 56 and 75°C to prevent the ink layer from completely drying, which can cause sticking on products such as syringe packaging film and sanitary pad outer wrap film. For sensitive materials such as PE and PVC, the initial temperature can be set to 45°C, then increased after accurate color registration. The printing speed should be adjusted based on drying capacity to ensure thorough drying of the ink layer. Avoid excessively fast drying (resulting in incomplete drying) or excessively slow drying (resulting in plate jams). Squeegee parameters can be optimized, with the angle adjusted to 50 to 60 degrees. Additionally, ceramic squeegees can be used to enhance scraping performance.

Flexo Printing Machinery for PE Film Baby Diaper Breathable Pants

Environmental and Storage Management

Maintain a humidity of 60% to 70% in the workshop to prevent moisture absorption by the film and emulsification of the ink. Dehumidification should be increased during hot weather. In cold environments, preheat the film and ink to a suitable temperature. Water-based inks suitable for printing products such as potato chip packaging film and pita chip popcorn packaging film should be sealed and stored at 15-25°C to avoid moisture and high temperatures that may affect performance. Stir the ink before use to restore uniformity.

Flexo Press for Meat Snack Packaging Film

Lamination Process and Glue Matching

Choose an adhesive compatible with water-based inks, such as polyurethane adhesive, to avoid residual solvents that could affect adhesion. Use a high-solids glue to reduce solvent usage. Lamination and aging: After printing, laminate the paint-based materials as soon as possible to minimize ink exposure time and prevent moisture absorption or additive precipitation, which can lead to decreased adhesion.

Flexographic Printer for Jelly Cup Sealing Packaging Film

Quality Verification and Improved Adhesion Testing

A tape peeling method is used, and ink residue of 95% or greater is considered acceptable. A friction test is also used to verify the improved results. For materials such as BOPP, PET, and PE, a full range of water-based inks and solvent-based adhesives are used. Composite strengths of 1.2-4.3 N/15 mm are achieved. A hot air pressure of 55 N/15 mm demonstrates process feasibility.

Flexo Printer for Soft Plastic Packing Juice Foil Film

Corona treatment improves film polarity. By optimizing ink values and solvent systems and strictly controlling printing drying conditions and environmental parameters, water-based inks achieve stable adhesion in flexible food packaging, such as bubble tea cup sealing roll film and popsicle packaging film, meeting food safety and mechanical performance requirements. Careful coordination of all steps is crucial to avoid any single factor's shortcomings impacting the overall effect.