Compared with mixing mill, the mixer mixing has short mixing time, high efficiency, high degree of mechanization automation, good rubber compound quality, low labor intensity, safe operation, small loss of drug flying, good environmental sanitation, etc. Advantages, but the mixing chamber of the mixer is difficult to dissipate heat, the mixing temperature is high and difficult to control, so that the temperature-sensitive rubber is limited, and it is not suitable for the mixing of the light-colored rubber compound and the variety change. In addition, the mixer mixing needs to be equipped with the corresponding lower piece device.

(1) Packing amount
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 characteristics of the rubber. Generally calculated according to the total volume and filling factor of the mixing chamber, the filling factor is taken as 0. 55 to 0. 75. If the equipment is used for a long time, due to wear in 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 plug is large, or the rubber can be plastic, the amount of glue can be increased accordingly.

(2) Top plug pressure
Increasing the pressure of the top plug can not only increase the loading capacity, but also make the glue and the equipment and the various parts inside the rubber material contact and squeeze each other more quickly and effectively, thereby accelerating the mixing process of the compound into the rubber process, thereby Shorten the mixing time, improve 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 improve the quality of the rubber compound. Therefore, at present, measures to increase the diameter of the upper top wind pipe 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 and is the main measure to improve the efficiency of the mixer. At present, the rotational speed of the internal mixer has been increased from 20 r / min to 40 r / min, 60 r / min, up to 80 r / min, so that the refining cycle is shortened from 12 to 15 min to a minimum of 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, and the speed can be changed at any time according to the characteristics of the rubber compound and the process 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 internal mixer are increased from the original two to four, which can play a more effective shearing and stirring action. It can increase production efficiency by 25 to 30% and reduce energy consumption. In recent years, in addition to the elliptical shape, there are also rotor-shaped internal mixers of a triangular shape, a cylindrical shape, and the like.

(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 and 130 'C, and 170 to 1 90 'C high temperature is used. This process has been used in synthetic rubber mixing. The temperature of the debinding is generally controlled during slow mixing. At 125 ~ 135 'C, the temperature of the glue is 160 during rapid mixing. C or more. If the temperature is too high, the mechanical shearing of the rubber compound will be reduced, the mixing will be uneven, and the thermal oxidative cracking of the rubber molecules will be aggravated, and the physical and mechanical properties of the rubber compound will be lowered, and at the same time, the rubber and the rubber will be promoted. Excessive chemical bonding between the carbon blacks produces excessive gelation, which causes the plasticity of the rubber to decrease, and the surface of the rubber compound is rough, which makes the calendering and extrusion processing difficult.

(5) Dosing sequence
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 cause dispersion; the super accelerator and sulfur are added after the lowering machine is cooled down, or the second stage is mixed in 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 installed, and the formulation of the compound. Mixed: post, time growth, can improve the dispersion of the compounding agent, but too long time is likely to cause over-refining, and will also affect the vulcanization characteristics of the compound. At present, the mixing time of the XM-2 5 0 / 20 type internal mixer is 10 to 12 minutes.