Reducing Hot Melt Char Using Tank Setback Mode

The increasing demand for consumer goods has brand owners focused on efficiency. It is critical to minimize downtime, keep the production lines running, and meet quality standards. Food and beverage manufacturers rely on hot melt packaging adhesives to assure a strong seal in their consumer products. To reduce unplanned downtime on the packaging line, it is important to avoid hot melt adhesive degradation by limiting its exposure to elevated temperatures for extended periods of time when the equipment is not running. Degradation of hot melt packaging adhesive can negatively impact:

• Appearance
• Processability
• Performance

Managing these three criteria allows manufacturers to keep production moving. Setback mode, a common feature of hot melt tanks, is a system feature to reduce hot melt adhesive tank temperature and minimize degradation. Also called standby mode, setback is typically a single button to lower the temperature of the hot melt system up to 38oC (100oF) and return the system to the original temperatures after pressing the button again. Prolonged exposure to heat can break down the adhesive formulation, accelerate gelling and lead to char formation.

It is important to understand the properties of hot melt packaging adhesives, including softening point and the viscosity curve, to optimize the processing. The key is following consistent procedures recommended by the equipment manufacturers along with a thorough understanding of a hot melt packaging adhesive like TECHNOMELT. Implementing a consistent setback plan makes it easier and less costly to prevent char and assure burnt hot melt adhesive does not infiltrate the production line.

Implementing setback into daily maintenance improves uptime of a manufacturing line.  One of the common concerns of using setback mode is increasing downtime resulting from the estimated time to get the hot melt line running again – the contrast between downtime versus melt time. Hot melt adhesive systems warm to operating temperature relatively quickly, often in less than 30 minutes depending on tank size, equipment age and hot melt packaging adhesive product. Scheduling or even automating setback and re-warming into the process involves timing it 30 minutes prior to starting the product line back up.  This assures the adhesive reaches optimal operating temperature when production resumes.

Heat, time and oxidation affect the polymer chains of hot melt adhesive, which can change its appearance to a darker color. This does not necessarily indicate char formation or a change in performance. If the adhesive is overheated too long, it can start to gel and stick to the crevices of the melt tank and walls of hoses forming anchors. These anchored pieces of adhesive are overexposed to heat, and form burnt adhesive or char. The blackened char causes issues with the dispensing and sealing of consumer packaging.

Burnt adhesive can clog filters and nozzles resulting in downtime. Setback allows manufacturers to effectively reduce system clogging. Operators need to watch for extreme changes in color (dark brown or black) and uneven adhesive bead patterns, which can indicate nozzle or filter issues.  These blockages can prevent even flow throughout the system.  Replacing equipment components on a hot melt packaging adhesive line costs both time and money.  Nozzle and filter blockages can impact packaging and potentially cause pop opens.  Replacing equipment parts forces the line to stop for upwards of 15 minutes and can cost upwards of $60 per filter and nozzle.  If the tank reaches extremely poor conditions, the cost could be higher as the tank filter will also need replacement.

Hot melt packaging adhesives have different operating parameters.  Some hot melt adhesives are more susceptible to breakdown than others, and it is critical to understand the optimal operating conditions to avoid performance issues. Following the suggested operating temperature is important to achieve the best performance.

Keeping the temperature at the low end of the recommended application range, is important to maintain performance. Excessive heat impacts the adhesive formulation, accelerates gelling and leads to char formation. Increasing the operating temperature lowers adhesive viscosity and results in filter clogging.  Blocked filters impact the system with:

• Adhesive applicators obstructions
• Marks and streaks on substrates
• Poor packaging adhesive bond

Establishing setback guidelines are easy.  Setback mode lowers hot melt tank temperatures – to as low as 38oC (100oF) while not in use – maintaining adhesive performance and reducing degradation. Many production lines can incorporate automated setback mode to help streamline the operation. Henkel engineers recommend some best practices to achieve optimal adhesive performance. Henkel recommends implementing setback mode if a production line is out-of-services for more than 4 hours.  If a production line is down for more than 24-hours, the hot melt system should be completely powered down.

Food and beverage manufacturers rely on the effectiveness of hot melt packaging adhesives to assure a strong seal or bond. Brand owners need to understand the optimum adhesive performance to produce a secure bond. To gain a better understanding of hot melt adhesives, register for our digital training platform and learn best practices for setback mode to increase the life of your adhesive.