Compared with open-mixer mixing, internal mixer mixing has the advantages of short mixing time, high efficiency, high level of mechanization and automation, good rubber quality, low labor intensity, safe operation, small dust loss, and good environmental sanitation conditions. However, it is difficult to dissipate heat in the mixing chamber of the Internal Mixer, and the mixing temperature is high and difficult to control, which limits the temperature-sensitive rubber compound and is not suitable for the mixing of light-colored compounds and compounds that change frequently. In addition, the internal mixer needs to be equipped with the corresponding lower plate installation. 1. The amount of glue A reasonable amount of glue should be able to ensure that the rubber material is subjected to maximum friction and shearing in the mixing chamber, so that the compounding agent is evenly dispersed. The amount of glue loaded depends on the characteristics of the equipment and the characteristics of the rubber material. Generally, the calculation is carried out according to the total volume of the mixing chamber and the filling factor, and the filling factor is 0.55~0.75. If the equipment has been used for a long time, due to the wear and tear of the mixing chamber, the filling factor can take a large value, and the amount of glue can be increased. If the pressure of the top bolt is large, or the plasticity of the rubber material is large, the amount of glue can also be increased accordingly. 2. Top bolt pressure Increasing the top bolt pressure can not only increase the glue loading capacity, but also enable faster and more effective mutual contact and extrusion between the rubber compound and the equipment and between various parts inside the compound, and accelerate the mixing process of the compounding agent into the rubber. Shorten the mixing time, improve the production efficiency, reduce the sliding of the material on the contact surface of the equipment, increase the shear stress of the compound, improve the dispersion level of the compounding agent, and improve the quality of the compound. Therefore, at present, measures to increase the diameter of the top bolt air duct or increase the air pressure are often taken to improve the mixing efficiency of the internal mixer and the quality of the mixed rubber. 3. Rotor speed and rotor structure During the mixing process, the shear speed of the rubber compound is proportional to the rotor speed. Improving the shear speed of the rubber compound can shorten the mixing time, which is the main measure to improve the efficiency of the mixer. At present, the speed of the internal mixer has been improved from the original 20r/min to 40r/min, 60r/min, and the highest is 80r/min, so that the dark mixing cycle has been shortened from 12 to 15 minutes to the shortest of 1 to 1.5 minutes. In recent years, in order to meet the requirements of the mixing process, multi-speed or variable-speed internal mixers have been used for mixing, and the speed can be changed at any time according to the characteristics of the rubber and the process requirements to obtain the best mixing effect. The structure and shape of the rotor of the internal mixer has a serious impact on the mixing process. The elliptical rotor of the internal mixer has increased from two to four, which can play a more effective shearing and stirring effect. It can improve the production efficiency by 25~30% and reduce the energy consumption. In recent years, in addition to elliptical, there are also triangular, cylindrical and other rotor shape mixers have been used in production. 4. Mixing temperature During the mixing process of the internal mixer, the heat generation is large and the heat dissipation is difficult. Therefore, the rubber compound heats up quickly and the temperature is high. Generally, the mixing temperature is around 100~130 degrees, and there are also high-temperature kunming at 170~190 degrees. This process has been used in the compounding of synthetic rubber. The temperature of degumming during slow mixing is generally controlled at 125~ 135 degrees, and the temperature of degumming during fast mixing is over 160 degrees. Excessive mixing and temperature transition will reduce the mechanical shearing effect on the rubber, make the mixing uneven, and aggravate the thermal oxidative cracking of the rubber molecules, which will reduce the physical and mechanical properties of the rubber. There is too much chemical separation between carbon blacks to generate too much gel, which reduces the plasticity of the rubber compound, and the surface of the rubber compound is rough, making it difficult to Calender and extrude. 5. Dosing sequence Plastic rubber and master batch should be added first to make them form a whole, and then other compounding agents should be added in turn. Solid softeners and small medicines are added before fillers such as carbon black are added to ensure sufficient mixing time. The liquid softener must be added after the carbon black is added, so as to avoid the formation of agglomeration of the carbon black, which is difficult to disperse; the super accelerator and sulfur are added after the cooling of the unloader, or in the internal mixer during the second-stage mixing. The degumming temperature should be controlled below 100 degrees. 6. Mixing time The mixing time depends on various factors such as the performance characteristics of the internal mixer, the amount of rubber loaded and the formula of the rubber compound. Mixing and increasing the time can improve the dispersion of the compounding agent, but if the time is too long, it is easy to form over-smelting, which will also affect the vulcanization characteristics of the rubber compound. At present, the mixing time of XM-250/20 internal mixer is 10~12min.
The above is about rubber machinery. If you want to know more about our company's dynamics or products, you can consult us. We also sell Dispersion Kneader, Rubber Internal Mixer, Rubber Open Mill, Two Roll Mill, Plastic Granulator and Extrusion Pelletizer.
