The packaging industry is an industry with large consumption in China, especially for plastic film products. What are the tips of film blowing technology? Please see the following detailed analysis:
Tips of blown film technology: blown film is actually a kind of film between biaxial oriented film and cast film. Biaxially oriented films can also be produced by blowing method. As long as the temperature is appropriate and the ratio of blowing ratio and drawing ratio is appropriate, the orientation degree in both directions can be approximately the same. When the blown film is produced, if the pulling speed is too fast and the difference with the blowing ratio is too large, the difference between the longitudinal orientation and the transverse orientation may be too large. As a result, the transverse strength is low and it is easy to break, as in the process of unidirectional stretching to produce the film cracked fiber. The prevention method is to reduce the traction speed appropriately to match with the expansion ratio; Increase the air volume of the air ring to rapidly cool the blown film and avoid being stretched and oriented under high elastic state at high temperature. The following is an example of 80 film blowing machine: (different models, different specifications)
The first part of the feed heating zone is divided into 5 zones: the rod (diameter 6cm), the shell 8, 7cm, and the 11kw motor (main engine) drive. It is divided into one, two and three heating zones from the feed inlet. The next turn is upward, belonging to four heating zones. The parts are called three-way, 1-way three-way zone, 2-way network exchange outlet, and 3-way five-way zone. The fifth heating zone, that is, the discharge zone, is called the film head, which is the most critical part of the machine. The accessory is a blower.
The second part is the traction area, with a total height of about 3 to 5 meters, and the accessories are air pumps.
The third part is the winding area.
Main materials: low-pressure polyethylene (hPPE) and high-pressure polyethylene (LLDPE) are mixed materials. The low-pressure materials mainly account for about 80%. The more high-pressure materials are added, the better the tension. The disadvantage is that there is no stiffness. Too much will cause the blown film to swing back and forth, and the blown film will not be folded neatly, or even cannot be blown at last.
Start the film blowing process:
First, it is preheated in zone 1, zone 2 and zone 3. The temperature in zone 1 is lower, generally about 170 ° C, and that in other zones is about 200 ° C. if the temperature is high, the material cannot be sent from the rod, or even burnt and discolored.
The next four zones are the three-way zone. A 60 mesh-160 filter screen is placed in the tee to prevent impurities from entering the five zones. The larger the number of screens, the finer the screen, and the thinner the film, including the transparency of the film, the hand sensitivity and smoothness, the tension, etc. but too much and too fine will prevent the material from passing through, and too many will not be blown out. Generally, 3-5 pieces are suitable, and the thickness is determined according to the requirements.
When the material reaches zone 5, the discharge port becomes a circular sticky shape with a diameter of 7cm through the film head. The temperature of the material is basically stable. The suitability of the whole heating process should be controlled according to the situation of the discharge port. If the material is too high, the film will not be stable, and it will be burnt and discolored. If the material is too low, the film cannot be pulled up. The film thickness of the film mouth is not uniform and must be adjusted by the wire of the film head.
