Factors Affecting The Mixing Process of Kneader Machine

Process parameters that affect mixing in the kneader:

1: Filling coefficient and feeding materials

Add materials appropriately according to the volume of the internal mixer. Do not add too much or too little. Too much or too little will affect the dispersion of the materials and the mixing effect.

2: Mixing procedure and feeding sequence

Generally, the activator should be added after the ethylene-propylene rubber is added and before the carbon black is added; or at the same time as the carbon black;

The operating oil should be added immediately after fillers such as carbon black are added. Adding it too late may cause the surface of the rubber compound to slip and become difficult to disperse, thus prolonging the mixing time;

The vulcanizing agent and accelerator should be added after the other ingredients are dispersed, but the temperature should be controlled below 100 degrees to avoid scorching during the mixing process.

3: Mixing temperature

When materials are mixed in an internal mixer, a large amount of heat will be generated due to friction and shear.

Often when the rotor speed is increased and the ejector pressure on the internal mixer is increased, the temperature will rise due to increased rubber shear force and friction.

During the mixing process of the kneader machine, the glue temperature continues to rise, and mixing usually ends when the specified upper limit temperature is reached.

When the mixing temperature is low, the viscosity of the rubber is high, the wettability and dispersibility of the compounding agent are poor, the equipment load is large, but the shear force is also large, which is beneficial to the mixing of low hardness rubber.

When the temperature is too high, the rubber becomes soft, which is beneficial to the mixing of powder and raw rubber, but the reduced shearing effect is not conducive to the dispersion of powdery groups, and makes the unloading operation difficult after discharging.

The setting of the mixing temperature for different formulas of rubber materials usually depends on the characteristics of the raw rubber or rubber materials, as well as the characteristics of the formula.

Like the debinding temperature, the starting temperature of the ethylene-propylene rubber mixed in the internal mixer is also important for accelerating the start-up and mixing and dispersion.

The dispersion effect of mixing starting at 70 degrees is better than that at 50 degrees.

High-fill mixing requires higher mixing temperatures, especially in large internal mixers. Preheating the oil before adding it is also beneficial to diffusion and dispersion.

4: Mixing time

Although extending the mixing time during operation can improve the dispersion of the ingredients, too long a time can easily cause the rubber material to be over-mixed or the temperature to be too high and cause scorch.

5: Rotor speed

The lower rotor speed is suitable for mixing heat-sensitive rubber materials, or when serious problems occur during the mixing and dispersion processes and the mixing time is extended.

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