Flexible packaging polyurethane laminating adhesives are the core materials for film lamination. The coating method directly determines the bonding uniformity, appearance quality and performance of the composite products. The mainstream coating methods in the industry include mesh roller coating, scraper coating and differential kiss coating, which are suitable for different production processes and product requirements.
The screen roller coating method is the most commonly used technique in the production of flexible packaging, suitable for both solvent-based and solvent-free polyurethane laminating adhesives. This method relies on the quantitative mesh holes on the surface of the screen roller to transfer the adhesive liquid, allowing for precise control of the coating amount. The coating uniformity is excellent, and it is compatible with conventional films such as BOPP and PET for high-speed continuous production. It has high stability and is widely used in common food packaging lamination scenarios.
The scraper coating method is simple in structure and easy to operate, and is suitable for high-viscosity polyurethane adhesives and thick coating layers. It achieves coating by scraping off the excess adhesive with the scraper. It has low cost, wide adaptability, but has limited coating accuracy and is prone to form point-like bonding. It is mostly used for conventional packaging products with lower requirements for flatness.
The differential coating method is an optimized and upgraded coating process. It achieves surface coating through differential rolling contact, effectively expanding the bonding area and enhancing the bonding strength. It can avoid defects such as white spots in aluminum-coated film laminations. It is suitable for high-quality production scenarios such as high-end steaming packaging and aluminum-coated film laminations, and is the preferred process for refined composite production.
