Eliminate the adverse effects of temperature & humidity on the quality of dry lamination products
For the temperature and humidity of the processing environment, as long as it is not in the best condition range, it will affect the stability of the dry laminating process.
Under high temperature condition, workshop cooling with air condition is the first choice,but due to the energy emission, most workshops use high power fans for cooling. Cooling with fans not only make people feel comfortable, but also reduce the object’s surface temperature. That’s because the accelerated air flow will facilitate the liquid volatilization, absorbing heat and lowering temperature. However, it must be considered that fan will accelerate air flow and bring extra solvent volatilizaiton, resulting in bad effect on the workshop environment. In addictions, air flow will also cause dust and bits, so we need to avoid contamination of laminated film by foreign bodies.
Under high humidity condition, dehumidifier is the first choice for workshops with better tightness, or use dehumidifier function of the air condition to lower the workshop humidity and reduce the water impact on glue performance. In the absence of the above conditions, it can be considered to increase the proportion (generally 3%~5%) of curing agent when gluing in accordance with the specific humidity value of the workshop. When laminating with the water-sensitive materials, like nylon, EVOH and PVDC, high humidity will change the shape and performance of the films. If the room humidity is too high and exceeds 95%, we have to stop producing related products.
Under low temperature condition, the low temperature in winter seriously affects the quality stability of the laminated film in the workshop without heating or air condition. Firstly, the film and glue are both cold, the viscosity of glue becomes larger, and the fluidity and coating performance become worse at low temperature, resulting in bad appearance of the film and even bad impact on laminating and sealing strength. Therefore, it is requested to increase the materials temperature, for example, reheat the film and glue for a while inside the aging room, heat the glue tank when opening the machine, turn on the preheating roll, and increase the temperature of the drying box and laminated heat roll. If the room temperature is below 0℃ and with limited warming conditions in winter, it can be considered to stop production.
Under low humidity condition, especially if the relative humidity is below 25%, eliminating electrostatic hazards and avoiding fire risks are the top priority. It is required to improve the equipment to eliminate static electricity on the machine, including effectively grounded circuit and Installing a static eliminator, and ensure the complete installation of electrostatic rope, electrostatic belt and electrostatic brush. Equipped with human static elimination pile, operators shall wear anti-static clothing and shoes, and use explosion-proof tools. Moreover, Sprinkling water on the ground and using industrial humidifier can improve and maintain the workshop humidity, which is conducive to safe production.
Processing temperature and humidity will affect each other. No matter steam heating or electric heating, the temperature and humidity conditions of the workshops will change those conditions inside the drying box of machine, affecting the drying efficiency and performance. So the processing parameter setting must be in accordance with glue performance, coating volume and ambient temperature and humidity.
Due to the effect of season and region, large changes in ambient temperature and humidity objectively exist. Beside increasing related hardware equipment, improving the glue formulation can be also helpful to solve this issue, such as summer and winter formulation, southern and northern formulation. Due to the great influence of temperature and humidity, controlling these two indicators becomes very important. The calibrated hygrometer should be placed around the machine in the workshop, and the machine temperature controller and display instrument should also be calibrated regularly to ensure accuracy. According to the monitoring data, timely adjustment of temperature and humidity should be carried out.
