Composite sheet extrusion process

(1) Sheet extrusion process. In-line composite sheet extrusion is carried out at Jiangsu Integrated Decoration Materials Co., Ltd. The three-layer co-extrusion composite sheet production line of Italian Unin company is adopted. The diameter of the main screw is 120mm, and the diameters of the two lateral screws are 70m and 45mm respectively. The die lip of the T-shaped head is controlled by a microcomputer with an accuracy of 0.1m. The extrusion temperature is controlled by 24 points, of which the temperature control of the main screw barrel is 16 sections, and the T-shaped head is 8 sections. The feed end starts at 190°C, the temperature in the middle zone is 22°C, the inlet end of the T-shaped die is 205°C, and the die lip outlet end is 195°C. The die lip gap is 2.3mm, and the distance between the die lip and the pressure roller is 20cm. After coming out of the die lip, the plate enters the lower roller directly, and enters the carriage line from the upper roller through the middle roller. The temperature of the three rolls is 90°C for the lower roll, 80°C for the middle roll, and 80°C for the upper roll.

70°C. PU-non-woven fabric sheet is pre-placed on the lower part of the first pressure roller near the die lip side. After the extrusion process of the substrate is stable, the distance between the three rollers is properly adjusted, and at the same time, the sheet is fed into the first pressure roller from the lower side of the extruded product, and a qualified composite sheet is obtained.

(2) The main factors affecting the quality of composite panels.

① extrudate melt temperature. The temperature difference between the extrudate entering the cold press roll from the molten state is large, and flow orientation and internal stress are likely to occur. Especially when the size of the die lip does not match the gap between the three rolls, the plate will have a large flow orientation resulting in anisotropy. Therefore, it is very important to control the melt temperature of the extrudate. In principle, if the composite sheet can be extruded, the melt temperature of the extrudate should be reduced as much as possible. For PP and its heterogeneous blend system, it is better to control the melt temperature at 190°C to 195°C.

② Control of the gap and temperature of the three rolls. Take the equipment where the extrudate enters from the lower roll and exits from the upper roll as an example. The gap between the lower roll and the middle roll of the extrudate is mainly used to control the balance of the extrusion volume, and the gap between the middle roll and the upper roll is mainly used to control the size of the sheet, and it can also have the functions of glazing and printing patterns according to requirements. Usually, the gap between the middle and upper rolls is smaller than that of the lower and middle rolls, which is due to the cooling shrinkage of the polymer material, as well as the functional requirements of glazing and printing patterns. The temperature control between the three rolls is very important. The temperature of the three rolls decreases sequentially. However, it should be noted that if the roll temperature is too low, a large internal stress will be generated, which will cause the plate to be bowed, which will affect the subsequent processing and application of the plate.