On the factors affecting the mixing effect of internal mixer

1. Rotor: the type and number of edges of the rotor. There are many edges and the shear speed is fast, but the heat rise is high, which shortens the mixing time and affects the mixing quality. Affected by the rotor type, the shear dispersion area is between the rotor edge and the internal mixing chamber, with a large and wide force range, large shear force, high efficiency and good mixing quality. Meshing type is that the dispersion zone is between two rotors, with small shear force, low heat generation, long mixing time and good dispersion effect.
2. Upper top bolt pressure: the upper top bolt is used to keep the rubber in the mixing working area of the internal mixing chamber. Insufficient pressure will cause the rubber to slide on the internal mixing chamber wall and the rotor surface. Appropriate pressure can reduce the gap in the material and increase the contact force. The pressure will increase the temperature of the rubber, increase the mixing power, and the filling capacity is insufficient. The upper top bolt pressure cannot play a full role, and the components in the rubber are easy to be dispersed unevenly.
3. Temperature: each kind of rubber has its best mixing temperature range. The type and amount of raw rubber, reinforcing agent and softener determine the mixing temperature rise. At the same temperature, the longer the mixing time, the better the dispersion.
4. Filling amount: it depends on the effective volume of the internal mixer itself, the type of raw rubber in the formula, and the amount of reinforcing filler and plasticizer. If the plasticity of raw rubber is greater, the loading amount should be larger, and the filling coefficient (weight) is between 0.65 and 0.75. The loading amount is insufficient for mixing, and the necessary shear force cannot be obtained.
5. Feeding sequence: different sequences have different effects. I basically choose in the automatic system mixing (using multi-stage mixing, according to the requirements of rubber). The general sequence is raw rubber -- lifting lump -- adding filler / compounding agent -- pressing lump -- lifting lump -- adding softener pressure -- lifting lump -- pressing lump -- lifting lump discharge.
6. Rotating speed: the rotating speed is directly proportional to the shear rate. If the shear rate is high, the uniform mixing will speed up. Increasing the rotating speed will increase the rubber temperature, resulting in the decrease of the viscosity and shear stress of the rubber.
7. Time: the mixing time is related to the amount of filling and the temperature rise of the formula. The mixing temperature of various rubber compounds will affect the time, and the internal mixer speed and the upper top bolt pressure will also affect the mixing time. Therefore, in the mixing process, try to shorten the auxiliary time and feeding time.
8. Cooling water: the temperature of cooling water is generally set at 15 ℃. Low viscosity rubber is not easy to be cooled by hot water and is easy to stick to the rotor. High viscosity rubber is cooled by hot water. Increasing the temperature of cooling water can shorten the mixing time, reduce energy consumption and improve production efficiency.