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The environmental temperature and humidity, as well as the process temperature and humidity, have a decisive impact on the quality of laminated recyclable packaging products. Therefore, how to eliminate these unstable factors is explained below.
For the temperature and humidity of the processing environment, as long as it is not within the optimal temperature and humidity range, it will affect the stability of the laminating process to some extent.
The first consideration for workshop cooling is air conditioning. Due to energy consumption reasons, many workshops use high-power fans to cool down. Fan cooling not only makes workshop personnel feel comfortable, but also reduces the surface temperature of objects. As the air accelerates the flow, it evaporates liquid substances, absorbs heat, and lowers the temperature. Therefore, it is necessary to consider the additional rapid evaporation of solvents caused by the acceleration of air flow by the fan, as well as the adverse effects of solvent evaporation on the entire workshop environment. The fan drives the air flow, stirring up dust and debris in the workshop. The film accelerates the adsorption of these things, so it is important to pay attention to cleanliness and hygiene to avoid foreign objects from contaminating the laminating film.
When the workshop is relatively well sealed, priority should be given to using dehumidification equipment or utilizing the dehumidification function of air conditioning to reduce workshop humidity and minimize the impact of moisture on adhesive properties. If the above conditions are not met, according to the specific humidity value in the workshop, the proportion of curing agent should be increased when preparing the adhesive, generally considering an increase of 3% to 5% on the original basis; The EVOH, PVOH and other thin films used in composite are very sensitive to humidity. High humidity can change the shape and properties of the film. If the humidity in the space environment is too high, such as exceeding 95%, the controllability of humidity is seriously insufficient. At this time, it is considered to stop producing products containing these material structures.
In workshops without heating or air conditioning, the low temperature in winter does seriously affect the stability of composite film quality. Firstly, the material itself has a low temperature, such as glue and film. Under low temperature conditions, the viscosity of the glue increases, the flowability and lamination performance deteriorate. This not only affects the appearance of the laminating film, but also affects its physical properties, such as laminating strength, heat sealing strength, and may also affect solvent residue. Therefore, under low temperature conditions, the first step is to increase the temperature of the material. For example, the film and adhesive solvent can be preheated in the curing chamber for a certain period of time. When starting up, heat the adhesive water tank, use a viscosity controller with heating function, turn on the preheating roller, and increase the temperature of the oven and laminating heating roller. If the indoor temperature in winter has dropped below zero degrees and the fluidity of the glue is severely affected, and the heating conditions are limited, production should also be stopped.
Especially when the relative humidity is below 25%, the top priority is to eliminate static electricity hazards and avoid fire risks. In addition to improving the facilities for eliminating static electricity on the machine, such as effective grounding, installing static eliminators, ensuring the complete installation of static electricity ropes, static electricity belts, and static electricity brushes, equipping personnel with static electricity elimination piles, operators wearing anti-static clothing and shoes, using explosion-proof tools, etc., and cooperating with ground watering to increase local humidity. Industrial humidifiers can also be used to ensure the increase and stability of workshop humidity, which is beneficial for safe production.
The temperature and humidity of the process will affect each other, whether it is steam heating or electric heating. The temperature and humidity conditions of the workshop environment will change the small environmental temperature and humidity inside the machine oven, which will affect the efficiency and effectiveness of drying. Therefore, the machine process temperature should be set according to the environmental temperature and humidity. The machine temperature setting should be based on the adhesive properties, coating amount, and environmental temperature and humidity
If the drying machine is a four section oven, the oven temperature is generally between 55-60 ℃; 65-70℃； 75-80℃； 85-90 ℃, set the temperature of the laminating roller to 55-70 ℃, and select the appropriate temperature conditions within the above range. The temperature conditions of the oven and the combination of air supply and exhaust are used to ensure that the solvent evaporates fully after coating, so that the residual solvent in the composite film meets the standard; The additional function of increasing the oven temperature is to maintain a certain degree of activation of the glue and ensure the adhesion strength of the film. The temperature of the laminating roller is favorable for the adhesive to be pressed and compacted, ensuring a smooth and white appearance of the composite without bubbles or white spots, while also improving the adhesion strength of the film.
Due to the influence of seasons and regions, significant changes in environmental temperature and humidity are objectively present. In addition to increasing hardware facilities to intervene, improvements can be made to the glue formula. For example, some manufacturers choose winter and summer formulas based on different seasons, and also develop formulas for southern and northern markets based on different regions. These are all solutions to the adverse effects of different temperature and humidity conditions on product quality at the glue level.
Since the impact of temperature and humidity is so significant, monitoring the temperature and humidity in the workshop is very important. Calibrated temperature and humidity meters should be placed around the workshop machines, and the temperature control and display instruments of the machines should be regularly calibrated to ensure accuracy. According to the monitoring data, if intervention is possible, it is necessary to adjust the temperature and humidity in a timely manner.
Longdapac as the leading recyclable packaging manufacturer in China. We are experienced in film lamination under different temperature and huminity. We will provide the best quality packaging to our customers.