Key points of extrusion compounding process
DATE：2021/10/7 8:29:12 / READ： / SOURCE：This station
Key points of extrusion compounding process
1. Extrusion temperature of extruder
Different plastic resins should use different extrusion temperatures, and the heating temperature directly relates to the quality of the coating material, especially the die temperature. Too low temperature will cause poor plasticization, reduce product transparency and surface gloss; even appear fish-eye bubbles, shark skin and other inferior products; poor composite fastness. If the temperature is too high, the plastic will be easily decomposed, the product will be brittle and hard, the shrinkage of the extruded film will increase, and the heat-sealability will deteriorate.
2. The melt flow rate and density of the resin
Melt flow rate is an indicator of resin fluidity. The melt flow rate is the mass (g) of the resin melt through a standard capillary for 10 minutes under a certain temperature and pressure. The unit of the melt flow rate is g/10min. The higher the melt flow rate of the resin, the better the fluidity. , The lower the viscosity of the molten film, the greater the adhesion. In addition, the resin has low density, high branch chain content, easy surface activation, and poor adhesion.
3. Air gap
The middle air gap refers to the distance from the die lip to the contact line between the two composite rollers. Large air gap thermal film heat loss is large, and the temperature of the contact point with the substrate is low, the coating fastness is poor, and the air gap distance is generally controlled between 50-150m. In addition, the air gap distance is large.
4. Cooling steel roll temperature
The surface temperature of the cooling steel roll is low, the cooling is accelerated, and the transparency of the coating layer is increased, but the composite strength is reduced; the surface temperature of the cooling steel roll is high, the cooling is slow, and the opening is worse. Generally, the surface temperature of the cooling steel roll should not exceed 60°C, and it is best to control it at about 30°C. In addition, the hot melt film blank is best to contact the substrate first, which will help improve the composite strength
5. Double-sided printing substrate
One-time composite treatment of double-sided printing substrate. When the substrate is a double-sided gravure printing pattern, it is necessary to make a one-time composite product. It is necessary to install electric eye tracking devices on the left and right sides of the composite device to control the surface tension of the unwinding substrate to adjust the left and right substrates to synchronize the composite. In addition, the following simple methods can also be used
(1) Adjust the extrusion temperature of the die heads on both sides to make the flow rate of the extruded hot melt film blank.
(2) Stick adhesive paper on the flat and aligned color printing film on both sides, and paste it on the base material that passes into the middle of the dual die.
(3) A handwheel with a diameter of about 350m is installed at one end of the film roll mandrel of the color film unwinding device facing upward.
(4) Install an incandescent bulb or fluorescent tube outside the guide roller, and reverse the color film rule label compounded below.
(5) An operator holds the upper and lower rule markings, and uses the handwheel on the unwinding mandrel to adjust the surface tension of the upper substrate to achieve pattern alignment on both sides. In the above operation, there will be errors in the double-sided printing pattern, which can be used for products with large length and good transparency.
Author：admin