How to solve the problem of film bubbles with a three-layer co extrusion blown film machine?

During the production process of three-layer co extrusion blown film machine, film bubbles are a common problem, which not only affects the appearance quality of the film, but also may reduce its physical properties. Therefore, solving the problem of film bubbles is crucial for improving product quality and production efficiency.

1、 The cause of thin film bubbles

Raw material issues

Raw materials are an important factor affecting the quality of thin films. If the raw materials contain moisture, impurities, or volatile substances, these substances will form gases during the high-temperature melting process, leading to the formation of bubbles inside the film. In addition, poor compatibility of different resins may also lead to the generation of bubbles.

equipment problem

The equipment status of the three-layer co extrusion blown film machine directly affects the quality of the film. If the screw design of the extruder is unreasonable, the temperature control is not precise, or the die flow channel design is improper, it may lead to uneven flow of the melt, resulting in bubbles.

Improper setting of process parameters

Unreasonable settings of process parameters such as extrusion temperature, inflation ratio, and traction speed can lead to poor melt flowability or uneven cooling, resulting in the formation of bubbles. For example, excessively high temperatures may lead to resin degradation and gas production, while excessively low temperatures may result in insufficient melt fluidity.

environmental factor

The humidity, temperature, and other conditions in the production environment can also affect the quality of the film. If the environmental humidity is too high, the raw materials are prone to moisture absorption and produce bubbles during the melting process.

2、 Methods to solve thin film bubbles

Optimize raw material selection and processing

Raw material selection: Choose resin raw materials with stable quality and low impurities to ensure that their moisture content and volatile matter content meet the requirements.

Drying of raw materials: Before feeding, the raw materials should be thoroughly dried, especially for resins with strong moisture absorption properties (such as PA, PET, etc.), which usually need to be dried at 80 ℃ -120 ℃ for 4-6 hours.

Compatibility adjustment: For three-layer co extruded films, it is necessary to ensure good compatibility of each resin layer, and if necessary, add compatibilizers to improve interfacial bonding.

Equipment maintenance and improvement

Screw and barrel inspection: Regularly inspect the wear of the screw and barrel to ensure that their surfaces are smooth and undamaged, and to avoid the formation of bubbles due to local melt retention.

Optimization of die flow channel: The design of die flow channel should ensure uniform flow of molten material, avoiding dead corners and stagnant areas. The melt distribution can be improved by adjusting the die gap and channel shape.

Temperature control: Ensure precise temperature control of each section of the extruder to avoid local overheating or overcooling. Multi point thermometers can be used to monitor temperature changes in real-time.

Adjust process parameters

Extrusion temperature: Set the extrusion temperature reasonably based on the melting characteristics of the resin. Excessive temperature can lead to resin degradation, while low temperature may result in insufficient melt flowability.

Inflation ratio and traction speed: The settings of inflation ratio and traction speed should match the melt strength of the resin. Excessive inflation ratio may lead to excessive stretching of the film, resulting in the formation of bubbles; Low traction speed may lead to uneven cooling.

Cooling system: Optimize the design and airflow distribution of the cooling air ring to ensure uniform cooling of the film and avoid the generation of bubbles due to uneven cooling.

environmental control

Humidity control: Install dehumidification equipment in the production workshop to control the environmental humidity within a reasonable range (usually below 60%) and avoid moisture absorption of raw materials.

Temperature control: Maintain stable workshop temperature to avoid affecting melt flowability and cooling effect due to temperature fluctuations.

Online detection and feedback

Online detection: Install online detection equipment (such as bubble detectors) to monitor the quality of the film in real time, detect and handle bubble problems in a timely manner.

Data analysis: Through data analysis, identify the patterns of bubble generation and optimize production processes and equipment parameters.

3、 Case analysis

A certain three-layer co extrusion blown film machine frequently encountered bubble problems during the production of PA/PE/PA structured films. After analysis, the following reasons were found:

PA resin has severe moisture absorption and has not been fully dried;

The extruder temperature is set too high, causing degradation of PA resin;

Excessive inflation ratio and stretching of the film.

The following measures have been taken to address these issues:

Dry PA resin at 120 ℃ for 6 hours;

Reduce the temperature of the extruder to avoid degradation of PA resin;

Adjust the inflation ratio to a reasonable range.

After the above improvements, the problem of film bubbles has been significantly improved, and the product quality has been greatly improved.

The solution to the problem of film bubbles in the three-layer co extrusion blown film machine needs to start from multiple aspects such as raw materials, equipment, process, and environment. By optimizing raw material processing, improving equipment design, adjusting process parameters, and controlling the production environment, it is possible to effectively reduce or eliminate film bubbles, improve product quality and production efficiency. Meanwhile, establishing a comprehensive online detection and data analysis system can help identify and solve problems in a timely manner, achieving stable and efficient production.