Before starting the cleaning process, verify that the adhesives are compatible with each other and with the recommended flushing agents and cleaners. In closed application systems, it is crucial that both the PUR hot melt adhesive and the flushing agent are evenly melted to avoid blockages in hoses or nozzles.

For extended machine downtimes, such as weekends, holidays, or scheduled maintenance, it is especially important to clean systems that previously processed PUR adhesives. IWG provides a range of flushing agents and cleaners specifically designed to facilitate safe and effective maintenance.

Melter (Pre-Melter) and Hoses

Flushing agents primarily serve to remove residual adhesive from hoses and the application unit. Due to fluid flow characteristics, the velocity of the flushing agent is lower along the hose walls than in the center. To ensure complete cleaning, a sufficient volume of flushing agent must be used.

Viscosity also plays a critical role. If the flushing agent is too thin, it may only displace adhesive in the center of the hose, leaving residue along the walls. Consult the Technical Data Sheets of both the adhesive and flushing agent to ensure proper viscosity for effective cleaning.

To clean the system, empty the unit and flush it with a suitable agent (e.g., IWG 930.74/.94) until all PUR adhesive is expelled. Residual flushing agent should remain in all adhesive-contacting parts. As the agent cools, it shrinks, enhancing the cleaning effect.

Melting Tank (Glue Pot)

At processing temperature, drain as much PUR adhesive as possible from the melting tank. Remove residual adhesive from the walls carefully to avoid damaging the tank coating.

Fill the tank with a compatible flushing agent according to the adhesive type. Spread the granulate evenly using a wooden or silicone spatula before melting to improve cleaning efficiency. Allow the agent to melt and circulate between the melting tank and the application roller for at least 30 minutes at the previous processing temperature. During this period, rotate the application roller to prevent adhesive buildup.

After soaking, empty the tank or leave the flushing agent in place for extended downtimes. When restarting the system, clean the application roller with a soft brass brush and pressurized air, ensuring that anti-stick coatings on both the roller and melting tank remain intact. Follow all equipment manufacturer guidelines during mechanical cleaning.

Finally, purge the system with a small amount of the new adhesive at processing temperature to remove any remaining flushing agent. Using a wooden spatula to spread the adhesive ensures complete coverage of the reservoir. Colored flushing agents help identify areas contaminated with old adhesive.

Key Notes

• Always check compatibility of adhesives and flushing agents.

• Use adequate volumes of flushing agent for complete hose and tank cleaning.

• Follow proper soaking and circulation procedures for optimal results.

• Protect machine coatings during mechanical cleaning.

• Purge the system with new adhesive to ensure contamination-free bonding.