(1)The Amount of Glue
A reasonable amount of glue should be able to ensure that the rubber is subjected to the maximum friction and shearing action in the mixing chamber, so that the compounding agent is evenly dispersed. The amount of glue applied depends on the characteristics of the equipment and the rubber. Generally calculated according to the total volume and filling factor of the mixing chamber, the filling factor is 0.55 to 0.75. If the equipment is used for a long time, the filling factor can take a large value due to wear in the mixing chamber, and the amount of glue can be increased. If the pressure of the top plug is large, or the rubber can be large plasticity, the amount of glue can be increased accordingly.
(2) Pressure of the Ram
Increasing the pressure of the ram can not only increase the loading capacity, but also make the rubber material,the equipment and the internal parts of the rubber material contact and squeeze each other more quickly and effectively, thereby accelerating the mixing process of the compounding agent into the rubber process, shortening the mixing time, improving the production efficiency, and at the same time reduce the sliding of the material on the contact surface of the equipment, increase the shear stress of the rubber compound, improve the dispersion degree of the compounding agent, and enhance the quality of the rubber compound. Therefore, at present, measures to increase the diameter of the wind pipe of ram or increase the wind pressure are adopted to improve the mixing efficiency of the mixer and the quality of the rubber compound.
(3)Rotor speed and rotor structure shape
During the mixing process, the shear rate of the compound is proportional to the rotor speed. Increasing the shear rate of the compound can shorten the mixing time,which is the main measure to improve the efficiency of Dispersion Kneader. At present, the speed of dispersion kneader has been increased from the original 20 r / min to 40 r / min, 60r / min, up to 80 r / min, so that the refining cycle from 12 ~ 15 min to the shortest l ~ l.5 Min. In recent years, in order to meet the requirements of the mixing process, it has been mixed with a multi-speed or variable-speed mixer. The speed can be changed at any time according to the characteristics of the rubber compound and the process requirements to achieve the best mixing effect. The structural shape of the mixer rotor has a major impact on the mixing process. The ribs of the elliptical rotor of the dispersion kneader are increased from the original two to four, which can play a better effective shearing and stirring action. It also can increase production efficiency by 25 to 30% and reduce energy consumption.
(4)Mixing temperature
During the mixing process of the mixer, the heat generation is large and the heat dissipation is difficult. Therefore, the rubber material heats up quickly and the temperature is high. Generally, the refining temperature is between 100°C and 130°C, and 170 to 190°C is used for high temperature mixing. This process has been used in synthetic rubber mixing. The temperature of the rubber in slow mixing is generally controlled at 125~135°C, and the temperature of the glue is over 160°C during rapid mixing. Mixing and too high temperature will reduce the mechanical shearing of the rubber compound, make the mixing uneven,which will increase the thermal oxidative cracking of rubber molecules, reducing the physical and mechanical properties of the rubber compound, and promoting the rubber and carbon. Excessive chemical bonding between black produces excessive gelation, which causes the plasticity of the rubber to decrease, and the surface of the rubber compound is rough,making the calendering and extrusion processing difficult.
(5)Order of Adding Material
Mastic rubber and masterbatch should be added first, so that they are formed into a whole, and then other compounding agents are added in order. Solid softeners and small drugs are added before adding fillers such as carbon black to ensure sufficient mixing time. The liquid softener must be added after the addition of carbon black, so as not to cause the carbon black to agglomerate and difference to dispersion; the super accelerator and sulfur are added after the temperature of the lower machine is cooled, or during the second stage in process of the internal mixer, but the discharge temperature should be controlled below 100°C.
(6)Mixing Time
The mixing time depends on factors such as the performance characteristics of the Internal Mixer, the amount of glue loaded, and the formulation of the compound. The mixing time increases, which can improve the dispersion of the compounding agent. But if the time is too long,it may cause the refining overly, and affected the vulcanization characteristics of the rubber compound.
