Raw material dryer​

日期:2022/8/5 8:55:02 / 阅读: / 来源:本站

Raw material dryer
    The main function of raw material dryer is to remove moisture in raw materials. There are many types of facilities for drying raw materials. Dryer is a bucket dryer specially used for extruder production.
3.3 raw material mixing and granulation equipment
    Plastic products are extruded by extruder, and the mixing and granulation process of raw materials is an essential work before extrusion of plasticized raw materials in molten state (when twin-screw extruder or single screw extruder with special structure is used for production, there is generally no raw material granulation process). The quality of this process has a great impact on the quality of plasticized raw materials and molded products of the extruder. The production equipment required in this process includes: mixer for color paste mixing; Some auxiliary raw materials (including color paste, stabilizer, etc.) need grinding machines for refining and grinding; A mixer that mixes all kinds of raw materials used for molding plastic products so that they can be mixed evenly; A cold mixer for cooling the evenly mixed powder and a granulator for pre plasticizing and mixing the mixture.
3.3.1 grinder
    Grinding machine is a kind of equipment used to refine pigments or other additives. Its structure is shown in Figure 3-26. The grinder is mainly driven by three rollers, gear reducer and V-belt. It is composed of copper baffle, roll distance adjusting device, scraping knife and other parts.The working method of the three roll grinder is as follows. The three high-speed rotating rollers are driven by electric motors and driven by V-belts, gear reduction boxes and a set of transmission gears. When the slurry to be ground passes between the three rollers, manually adjust the roller surface gap of the three rollers. According to the running order of the slurry, the gap between the working surfaces of the three rollers changes from large to small, and when the material passes between the roller surfaces of the grinder, the material particles with larger diameter are crushed and refined, so as to achieve the purpose of material particle refinement. For the color paste to be added to the plastic products, after grinding and refining by the grinder, the diffusion of the pigment can be improved and mixed evenly with the plastic resin in the raw materials. The three rollers in the grinder are the main parts of the grinder equipment. The processing accuracy of the rollers and the roughness of the working surface have a direct impact on the quality of the ground and refined materials. The roller is cast by cold cast iron or cast steel, and the roughness of the roller after finishing is r. Should not be greater than 0.20 μ m. The hardness of the working face should also be high. The working speeds of the three rollers are different, and the speed ratio is 1:2.5:6; The middle roller is fixed, and the front and rear rollers can be manually adjusted to move forward and backward to change the distance between the working surfaces of the three rollers.
3.3.2 mixer
   The plastic resin and auxiliary materials mixed together after being measured according to the formula requirements of plastic product molding materials should be evenly dispersed and mixed with the help of mechanical mixing. This kind of equipment that can mix raw materials evenly is called mixer, also known as kneader.Common structures of raw material mixer include Z-shaped mixer as shown in Figure 3-27 and high-speed mixer as shown in Figure 3-28. The difference between the structures of these two mixers is the shape of the mixing paddle. Their structures are shown in Figure 3-29. The working speed of the impeller of the Z-shaped mixer is 20~40r/min and 10~20r/min, while the highest working speed of the impeller of the high-speed mixer can reach 1100r / min.The working principle of the high-speed mixer is as follows. First, steam is introduced into the outer wall cavity of the mixing chamber (also heated by resistance), and then the raw materials are added into the mixing chamber after heating; When the impeller in the mixing chamber rotates at high speed, the raw materials near the impeller rotate with the impeller due to the action of blade friction and blade end thrust; Under the action of high-speed rotating centrifugal force, these materials are thrown to the wall of the mixing chamber and become raw materials that hit the wall continuously. Under the thrust of the later materials, when they rise to a certain height along the inner wall, the gravity of the raw materials themselves makes them fall back to the center of the original mixing chamber, and then they are thrown out by the rotating blades to repeat the original movement; Because there is also a baffle in the mixing chamber, it can destroy the regular movement mode of raw material swirl and disturb the movement direction of the material; The mixing movement of these streams causes friction, collision and pushing between raw materials, and these cross action changes cause a certain amount of friction heat between raw materials; In addition, there is heat supply outside the mixing chamber, which increases the temperature of the mixture. The comprehensive effect of this condition makes all kinds of raw materials in the mixing chamber be evenly mixed.
3.3.3 mixing powder granulation equipment
    The evenly mixed powder (usually PVC resin) can be put into the next production process after being cooled by the cooling mixer. If the single screw extruder is used to extrude the molded products, the powder must first go through the extrusion granulation process and be put into production with the processed uniform pellets; If the products are extruded by twin-screw extruder, the powder with uniform mixing and temperature lower than 45 ℃ can be directly put into the products formed by twin-screw extruder (or the products can be produced by single screw extruder for powder).
3.3.4 raw material feeding machine
    Raw material feeding machine refers to the equipment that produces for the extruder and supplies materials to the extruder hopper. The raw material feeding machine has spring feeding device and vacuum feeding device. If the material is used for the production of multiple extruders, the compressed air pipe conveying centralized feeding method should be used to feed the hopper on each extruder respectively. For those small plastic products factories with only a few extruders, manual feeding method is generally used to feed the extruder hopper.
3.3.4.1 vacuum feeding device
     The structure of vacuum feeding device is shown in Figure 3-30. It is composed of fan, suction pipe, storage bin, suction pipe, filter screen, electric control box and other parts. The working method of the vacuum feeding device is: when the feeding fan is started, the suction pipe 4 and the filter screen 3 make the middle storage bin become negative pressure; At the same time, the suction pipe 8 connected with the intermediate storage bin and the raw material box sucks the raw material in the raw material box into the intermediate storage bin. When a certain amount is inhaled, the feeding relay acts, the fan stops working, and the suction stops; Then, the discharge valve is opened to feed into the extruder hopper.

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