Lamination Process of Packaging Bags: Upholding Quality with Ingenuity, Forging Excellent Packaging Solutions

In the production chain of the packaging industry, the lamination process is a core link for our enterprise to improve the quality and functionality of packaging bags. By bonding substrates with different properties, such as plastic films, aluminum foils, and papers, the composite packaging bags we produce can possess multiple advantages including barrier properties, puncture resistance, and printability, which are widely used in food, pharmaceutical, chemical and many other fields. We have always been committed to controlling every link to ensure product quality and enhance market competitiveness.​

Substrates are the foundation of the lamination process, and their quality directly affects the lamination effect. We attach great importance to the selection and treatment of substrates to ensure lamination quality from the source.​

In terms of substrate selection, we fully consider factors such as polarity, thickness ratio and surface condition of substrates to ensure that the selected substrates have good compatibility. To achieve this goal, we have established a strict inspection mechanism for incoming substrates. We use dyne pens to test the surface tension of films, which is usually required to reach 38-42 dynes/cm to ensure the effect of corona treatment and guarantee good adhesion between substrates. We screen substrate combinations with good compatibility through thermal shrinkage testing. For example, the combination of PET and CPP is suitable for high-temperature environments due to their similar shrinkage rates, which effectively avoids problems caused by excessive differences in substrate shrinkage rates. In the substrate storage link, we have set up dust-proof and dehumidifying devices to prevent secondary pollution of substrates and ensure the cleanliness of substrate surfaces.​

Adhesives play a "bridge" role in the lamination process, and their performance and usage methods are crucial to the lamination strength. We ensure that adhesives can fully exert their effects through standardized operations and management.​

In the glue preparation process, we adopt an automatic proportioning system to control the mixing ratio of glue, and strictly follow the standard ratio of main agent to curing agent of two-component polyurethane glue (common ratios are 10:1 or 5:1) for preparation, ensuring that the glue can be fully cured and avoiding the impact on lamination effect due to proportioning issues. Meanwhile, we are equipped with online moisture detectors to monitor the quality of diluents, ensuring that the moisture content in diluents does not exceed 0.1% to prevent bubbles generated by the reaction between excessive moisture and isocyanate curing agents.​

In the glue coating process, we pay attention to the control of technical parameters. We regularly calibrate the coating equipment to ensure that the coating amount error is controlled within ±0.2g/m², which not only avoids insufficient bonding force caused by insufficient coating amount, but also prevents excessive coating amount from increasing costs and prolonging drying time. Moreover, after the end of daily production, we clean the coating rollers with special solvents to avoid uneven coating caused by residual curing of the glue layer.​

The operating status of lamination equipment directly affects process stability. We ensure the stability and reliability of the process by precisely controlling the operating parameters of the equipment.​

In terms of temperature control, taking dry lamination as an example, we strictly set the three-stage temperature of the drying channel according to the standard (usually 60℃, 80℃, 100℃), and check the temperature control accuracy of the heating system daily to ensure that the error is ≤±2℃, avoiding excessive solvent residue (the standard requires ≤5mg/m²) caused by improper temperature setting. In terms of pressure control, we calibrate pressure sensors weekly to ensure uniform pressure between the composite steel roller and rubber roller, preventing local poor fitting.​

In terms of speed matching, we have introduced a PLC automatic control system to monitor the unwinding speed and coating speed in real time, ensuring that the difference between them does not exceed 5% to avoid tensile deformation of the substrate. For thin substrates, such as PET films with a thickness of ＜12μm, the system can also precisely control the tension to ensure that the elongation rate does not exceed 1%.​

In terms of equipment maintenance, we have established a three-level maintenance system: daily inspection of the heating system, weekly calibration of pressure sensors, and monthly lubrication and gap adjustment of the transmission system, ensuring that the equipment is always in good operating condition.​

Environmental conditions and post-processing links have an important impact on the lamination effect, and we strictly control them to ensure product quality.​

In environmental control, we pay attention to changes in workshop temperature and humidity, and are equipped with dehumidification equipment to control the relative humidity between 50% and 60%, avoiding the decrease in glue viscosity caused by moisture absorption when humidity exceeds 65%. Meanwhile, the clean workshop adopts the 10,000-class purification standard and is equipped with an air filtration system to control the dust concentration at ≤0.5mg/m³, preventing dust from adhering to the substrate surface to form impurity points.​

Curing treatment is a key link to ensure lamination strength, and we operate strictly in accordance with requirements. Taking polyurethane glue as an example, we ensure that it is cured in a 40℃ environment for more than 24 hours to ensure complete curing of the glue. At the same time, we pay attention to the temperature uniformity of the curing room, controlling the temperature difference in different areas to not exceed 3℃, avoiding quality differences in the same batch of products.​

In the finished product inspection link, we have established a full-item inspection system. We use a tensile testing machine to test the peel strength, ensuring that food packaging meets the requirement of ≥3N/15mm; detect solvent residues through a gas chromatograph; and conduct tightness tests using the negative pressure method. For pharmaceutical-grade packaging, we also add microbial limit testing to ensure compliance with GMP standards and prevent unqualified products from entering the market.​

For our enterprise, the quality control of composite packaging bags is a systematic project, and we strictly control from multiple dimensions such as materials, equipment, processes, and environment. With the improvement of consumers' requirements for packaging safety and increasingly strict environmental protection regulations, we will continue to carry out technological upgrading, such as adopting solvent-free lamination processes, promoting intelligent transformation, introducing AI visual inspection systems, and strengthening standardized management to continuously improve product quality and achieve sustainable development in the fierce market competition.