Discussion on how to solve the problem of packaging bag glue not drying and wrinkling (solventless laminating machine)

In solvent-free composite production, non-drying and wrinkling of adhesive in packaging bags are common and challenging issues that affect product quality. Through practical observation and analysis, these problems arise from multiple factors and require systematic solutions from the perspectives of process, equipment, and environment. The following discussion is based on actual production conditions.

I. Analysis of Causes for Non-Drying and Wrinkling of Adhesive

(1) Unstable Adhesive Ratio and Supply

Solvent-free adhesive consists of components A and B mixed in a specific ratio. During production, unstable adhesive supply, uneven coating, or inconsistent mixing can disrupt the ratio. For example, fluctuations in the supply process—where the output of components A and B varies unpredictably—can alter the initial tack and curing properties of the mixed adhesive. This leads to incomplete curing after lamination, resulting in non-drying. Additionally, changes in adhesive consumption during production and parameter fluctuations can further disturb the ratio, weakening peel strength and, in severe cases, directly causing non-drying.

(2) Blockages in Mixing and Delivery Systems

Residues and impurities can accumulate in mixing pipelines, adhesive tanks, mixing heads, static mixers, and filters, causing blockages. These blockages disrupt adhesive flow stability, leading to insufficient mixing and uneven coating. For instance, a clogged static mixer prevents effective blending of components A and B, causing localized non-drying due to incomplete reactions and subsequent wrinkling.

(3) Impact of Environmental Temperature and Humidity

Workshop temperature and humidity significantly affect adhesive curing. High humidity causes nylon to absorb moisture, depleting the curing agent and resulting in incomplete curing and frequent non-drying issues. Low or uneven temperatures—such as variations between the core, sides, and bottom of composite film rolls—create localized heat deficiencies, slowing or preventing curing. Uneven heating of packaging bags can also cause wrinkling.

(4) Inadequate Curing Conditions and Operational Standards

Insufficient curing temperature and time are critical factors. Solvent-free adhesives typically require specific curing temperatures; if temperatures are too low, molecular cross-linking reactions cannot proceed fully. Short curing times—such as failing to meet standards for retort pouches (minimum 48 hours) or aluminum foil retort pouches (minimum 72 hours)—leave the adhesive incompletely cured internally, leading to non-drying. Additionally, irregular worker practices, such as arbitrary adhesive changes or poor mixing ratio control, can exacerbate the problem.

II. Targeted Solutions

(1) Stabilizing Adhesive Supply and Ratio

Select high-quality solvent-free adhesives and avoid frequent changes to prevent performance fluctuations. Optimize mixing equipment to ensure stable adhesive supply and precise mixing. Advanced control systems can monitor and dynamically adjust the flow and ratio of components A and B in real time, ensuring uniform mixing. During production, closely track adhesive consumption and parameter changes, making fine adjustments to maintain ratio stability and minimize non-drying risks.

(2) Optimizing Mixing and Delivery Systems

Regularly clean key components such as mixing pipelines, adhesive tanks, and mixing heads, following a defined schedule and using specialized cleaning agents to remove residues and prevent blockages. Replace wear-prone parts like static mixers promptly to maintain mixing efficiency and ensure thorough blending before coating, improving curing quality.

(3) Precise Control of Environmental Conditions

Install temperature and humidity monitoring and regulation equipment to track workshop conditions in real time. Use dehumidifiers to maintain humidity within an optimal range (typically 40%–60%) during high-humidity periods. In low-temperature conditions, employ heating systems (e.g., workshop heaters, equipment preheating) and temperature distribution tools (e.g., circulating fans) to ensure uniform temperatures across the workshop and composite equipment, creating an ideal curing environment.

(4) Standardizing Curing Operations and Procedures

Strictly adhere to curing process standards, setting precise temperature and duration based on packaging bag type (e.g., standard composite bags, retort pouches). Utilize smart temperature control and timing devices to ensure stable curing conditions. Enhance worker training to standardize procedures, including approval and execution requirements for adhesive changes and mixing ratio adjustments, reducing human errors.

(5) Optimizing Special Areas (e.g., Sealed Edges)

For prone areas like sealed edges, improve adhesive mixing and coating methods. Auxiliary devices (e.g., small mixing chambers, buffers) can be added to mixing heads to ensure thorough blending and pressure stabilization before adhesive reaches sealed edges, preventing ratio imbalances caused by head movement or residual pressure. Mixer pipe designs can also be optimized to adjust swing ranges and stopping positions, ensuring uniform mixing and coating in sealed edge areas for better curing.

III. Summary and Continuous Improvement

Resolving non-drying and wrinkling issues in packaging bags requires a holistic approach addressing process, equipment, environment, and operations, with targeted measures based on root causes. In practice, continuously monitor the effectiveness of implemented solutions, regularly collect product quality data, and analyze recurrence or improvement levels. Encourage worker feedback on production anomalies, and through experience sharing and technical discussions, refine solutions to establish standardized production processes. This ensures long-term composite quality and enhances market competitiveness.