Substrate Follows the Sticky Roll and Is Back-wound Into the Machine During Roll Coater Operation

The melt excessively adheres to a certain roll surface and cannot be smoothly peeled off and transferred to the next roll, manifested as the material film winding around the roll instead of transferring through normally. When roll sticking occurs, production is forced to stop, and the machine must be shut down to clean the wrapped material; in severe cases, material accumulates and burns on the roll surface. Roll sticking is one of the most destructive failures in calendering production; it not only causes downtime losses but may also damage the roll surface finish.

1. Process parameter factors: the coating fluid has very high adhesion, and the substrate's own weight and tension are insufficient to overcome it. 2. Curing process factors: Curing temperature and time determine the completion degree of the coating crosslinking reaction—insufficient temperature or insufficient time leads to incomplete curing (tacky, low hardness, poor solvent resistance), excessive temperature or excessive time leads to over-curing (embrittlement, yellowing, cracking); the curing window of the coating fluid system must be precisely matched.

1. Process parameter optimization and adjustment: Set a mechanical stripping bar or compressed air peeling knife on the peeling side of the coating roll. 2. Systematic troubleshooting method: Troubleshooting of coating problems follows the order of "substrate → coating fluid → coating head → curing → environment". First check the substrate surface tension (corona treatment effect) and cleanliness, then verify the coating fluid viscosity, solid content, and degassing status, then check the coating head gap and cleanliness, further verify the curing temperature and time, and finally evaluate the influence of ambient temperature, humidity, and cleanliness. 3. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points. Establish a regular equipment maintenance system and implement life management for key tooling such as dies/spinnerets/calender rolls/coating heads.

The essence of roll sticking is that the adhesion between the melt and the roll surface exceeds the separation force required for normal peeling. The solution approach is "cooling + angle adjustment + additives": lower the temperature of the roll to reduce adhesion, adjust the peeling angle to increase the directional component of the separation force, and appropriately increase lubricant in the formulation to reduce interfacial adhesion.