The Internal Mixer Improves The Mixing Effect And Shortens The Mixing Time

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, rubber discharge temperature, power consumption, the difference between the quality of the mixed rubber and the total quality of the raw materials And the type of internal mixer.

Note: When starting the mixing experiment, you can first mix a compound with the same formula as the test compound to adjust the working state of the internal mixer, and then formally mix; for the same batch of mixed rubber, the control conditions of the internal mixer The mixing time should remain the same.

In internal mixer mixing, the order of adding raw rubber, carbon black and liquid softener and the mixing time are particularly important. Generally, the raw rubber is added first, followed by the addition of carbon black, until the carbon black is basically in the rubber compound. Add liquid softener after dispersion, which is conducive to mixing, improving mixing effect and shortening mixing time. If the liquid softener is added too early or too late, it is not good for the mixing, and it is easy to cause uneven dispersion, prolong the mixing time, and increase the energy consumption. The addition time of the liquid softener can be determined by the partition coefficient K. Sulfur and overspeed accelerator are usually added in the late stage of mixing or discharged to the tablet press to reduce the risk of scorching. Small medicines (solid softeners, activators, accelerators, anti-aging agents, anti-scorching agents, etc.) are usually added after raw rubber and before carbon black.

When mixing in an internal mixer, the rubber material must be subjected to a certain pressure from the top bolt. It is generally believed that the pressure of the top bolt should be 0.6-0.8MPa. When the rotor speed is constant, the effect of further increasing the pressure is not great. When the mixing capacity is insufficient, the pressure of the top plug cannot be fully exerted. Increasing the pressure of the top bolt can reduce the unfilled space in the enclosed room and increase the filling degree by about 10%. As the capacity and speed increase, the pressure of the top bolt must be increased.