Internal mixer

When mixing in an internal mixer with top bolt pressure, the rubber material must be subjected to a certain pressure from the top bolt. It is generally believed that the pressure on the top bolt should be appropriate. When the rotor speed is constant, further increasing the pressure has little effect. When the mixing capacity is insufficient, the upper ejector pressure cannot fully exert its effect. Increasing the upper ejector pressure can reduce the unfilled space in the closed chamber and increase its filling degree by approx. As the capacity and rotational speed increase, the pressure on the top bolt must be increased. Increasing the pressure of the upper ejector will accelerate the heat generation of the rubber during the mixing process and increase the power consumption during mixing. , Rotor structure and type The geometry and size of the rotor working surface determine to a large extent the production capacity and mixing quality of the internal mixer. There are two basic configurations of internal mixer rotors: shear rotors and meshing rotors. Generally speaking, shear-type rotor internal mixers have higher production efficiency and can quickly feed, mix and discharge glue quickly. The meshing rotor internal mixer has the characteristics of high dispersion efficiency and low heat generation rate, and is suitable for manufacturing hard rubber materials and one-stage mixing. The dispersion and homogenization effect of the meshing rotor internal mixer is better than that of the shearing rotor internal mixer, and the mixing time can be shortened~. , Speed: Increasing the speed of the internal mixer rotor is one of the most effective measures to strengthen the mixing process. When the rotation speed is doubled, the mixing cycle will be shortened by approximately ~. Increasing the rotation speed will accelerate heat generation, resulting in a reduction in the viscosity of the rubber compound and a reduction in the mechanical shearing effect, which is not conducive to dispersion.
, Mixing temperature High mixing temperature is beneficial to the plastic flow and deformation of raw rubber and rubber compounds, and is beneficial to the wetting and mixing of the surface of the solid compound particle particles by the rubber, but it also reduces the viscosity of the rubber compounds. It is not conducive to the crushing, dispersion and mixing of compound particles. Excessively high mixing temperature will also accelerate the thermal oxygen aging of the rubber, causing the physical and mechanical properties of the vulcanized rubber to decline. That is, over-refining will also cause the rubber material to scorch, so effective measures must be taken during the mixing process of the internal mixer. Cooling measures should be taken but the temperature should not be too low, otherwise the rubber material will be crushed and dispersed.
. Mixing time. Under the same conditions, the mixing time required to mix rubber materials with an internal mixer is much shorter than that with an open mixer. When the mixing quality is required to be constant, the required mixing time shortens as the internal mixer speed and upper ejector pressure increase. Improper feeding sequence and unreasonable mixing operation will prolong the mixing time. Extending the mixing time can improve the dispersion of the compound in the rubber compound, but it will also reduce production efficiency. If the mixing time is too long, it will easily cause the rubber compound to be over-refined, which will damage the physical and mechanical properties of the vulcanized rubber. It will also cause the thermal history of the rubber compound to increase and scorch will easily occur. Therefore, the mixing time of the rubber compound should be shortened as much as possible. .
Liter mixer
Control of outer diameter
As mentioned above, in order to ensure the size of the outer diameter of the finished cable, in addition to controlling the dimensional tolerance of the wire core (cable core), during extrusion Temperature, screw speed, traction device linear speed and other aspects should be controlled and guaranteed, while the measurement control of the outer diameter comprehensively reflects the accuracy and level of the above control. In the extrusion unit equipment, especially the high-speed extrusion production line, an online outer diameter detector should be equipped to detect the outer diameter of the cable at any time, and feedback the out-of-tolerance signal to adjust the traction or screw speed to correct the outer diameter. Tension control for out-of-tolerance winding requirements In order to ensure winding at different line speeds and constant tension requirements from empty reel to full reel operation, it is hoped that the wire take-up and arrangement device has a storage tension adjustment mechanism, or the constant line speed is considered electrically The electrical automation control of the entire machine such as the winding system and the constant tension system, etc. This is the process control requirement that should be met to realize a high-speed extrusion production line. It is mainly the start-up temperature interlocking working pressure protection and the interlocking extrusion and traction transmission of the two major components. Proportional synchronous control of take-up and traction, synchronous control of outer diameter, online detection and feedback control, single machine and complete machine tracking control of components according to various needs. Section 2 Plastic Extruder Screw The screw is one of the key components of the extrusion system of the extruder host. It not only plays the role of transporting plastic, but also plays an extremely important role in the ease of extrusion, plasticization and molding of plastic. function, so the reasonable selection of screw structure and parameters is an important link in obtaining ideal product quality and output.
Main parameters
Rotor speed and speed ratio, rotor edge ratio, production capacity and filling coefficient of the gap in the inner wall of the mixing chamber, unit pressure power of the ejector to the rubber material.
How to operate the internal mixer
Calculate the amount of primary rubber mixing and the actual formula according to the capacity of the internal mixer mixing chamber and the appropriate filling factor. According to the actual formula, accurately weigh the amounts of various raw materials in the formula. , place raw rubber, small materials (,, accelerators, antioxidants, solid softeners, etc.), reinforcing agents or fillers, liquid softeners, and sulfur respectively, arrange them in order on the storage rack, and open the internal mixer Use the power switch and heating switch to preheat the internal mixer. At the same time, check whether the air pressure, water pressure, and voltage meet the process requirements. Check whether the temperature measurement system, timing device, and power system indication and record are normal. After the internal mixer is preheated, , stabilize for a period of time, prepare to mix the rubber, lift the upper ejector bolt, put the raw rubber cut into small pieces into the internal mixer from the feeding port, lower the upper ejector bolt, mix the rubber, lift the upper ejector bolt, add small materials, and drop the upper ejector bolt. Knead the ejector pin, lift the ejector pin, add carbon black or filler, lower the upper ejector pin to mix, lift the upper ejector pin, add liquid softener, lower the upper ejector pin to mix, drain, and measure the rubber material with a thermocouple thermometer. The temperature of the mixing chamber, record the initial temperature of the mixing chamber, the temperature of the mixing chamber and the debinding temperature at the end of mixing, the maximum power, the rotation speed of the rotor, adjust the roller distance of the open mixer to turn on the power switch, run the open mixer, and turn on the Circulating water valve, and then throw the rubber material discharged from the internal mixer to the upper roller of the open mixer. When the temperature of the rubber material drops below ℃, add sulfur and cut the left and right knives twice each. When the sulfur is completely eaten, the rubber material The surface is relatively smooth and the rubber material is cut off. 1. Adjust the roller distance of the open mill to the point where the rubber material is thinly passed, make a triangular bag, and pass the rubber material all over. Adjust the roller distance to the right, put the rubber material into the roll, wait until the surface is smooth and without bubbles, remove the piece, and weigh the rubber material. The total mass is placed on a flat, clean metal surface and cooled to room temperature. A label is attached to indicate the rubber formula number and mixing date, and it is parked for later use. The mixing process test report for each batch of the internal mixer should record the temperature at the start of mixing, mixing time, rotor speed, top bolt pressure, glue discharge temperature, power consumption, the difference between the quality of the mixed rubber and the total mass of the raw materials, and Mixer type. Note that when starting the mixing experiment, you can first mix a compound with the same formula as the test compound to adjust the working status of the internal mixer, and then formally mix the same batch of compound, the control conditions of the internal mixer and the mixing The time should remain the same.