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Hard PVC formulations have many components and the dosing sequence should be strictly observed. The selected dosing sequence should be conducive to the role of additives, to avoid adverse synergistic effects of additives, but also to improve the mixing and dispersion speed. So, how should you add various additives when using an automatic compounding system?
The following is a list of content
The main points of adding various additives during high-speed mixing
Suggested charging sequence (take lead salt stabilizer series formulation as an example)
Simplified dosing sequence (lead salt stabilizer series formulation, manual dosing in mixer below 200L)
Stabilizers should be added to the hot mixer after the resin is added or at the same time with the resin, in order to play a stabilizing role in the warming up with the resin early and evenly mixed.
Soap stabilizer and internal lubricant should be added afterward in order to melt and fully penetrate into the resin.
Wax external lubricant should be added last when the material temperature is close to the material temperature, such as in 85-100 ℃ to avoid wax interference with the dispersion of other additives, to avoid reducing the coefficient of friction on the surface of the resin particles since the speed of friction heat generation is reduced, extending the mixing time.
The filler has an absorption effect on the additives, and the general amount is larger, it should be added before or together with the external lubricant. In order to make the additives first in the resin to be dispersed, reduce the absorption of the filler on the additives. Also can reduce the wear and tear of the hot mixer.
A processing modifier should be added before the waxes are added and after the stabilizers are added. The impact modifier can be added to the hot mixer with the resin, especially for modifiers with a tendency to thermal decomposition, such as CPE. processing modifier ACR is a fine powder, mixing dust is also easy to run off with the exhaust, so generally choose to add in the later stages of high mixing, higher material temperatures, viscosity, to minimize losses.
Liquid additives should be added slowly in the mixing process.
In short, the auxiliaries should be added to the order to play as much as possible the efficacy of the auxiliaries, to avoid the elimination of additives between each other, to improve the complementary effect of the auxiliaries is appropriate.
Add PVC resin to the mixing pot at low speed.
At 60℃, add stabilizer and soap to the resin at high speed.
At about 80℃, add process modifier, internal lubricant, pigment, and impact modifier to the material at high speed.
At about 90℃, fillers are added at high speed.
At 100°C, external lubricants such as waxes are added at high speed.
At 125°C, the material is discharged into the rotating cold mixer at a low speed.
At 45℃ or below, the material is discharged from the cold mixer.
Sieving, metering, bagging, and storage for use.
Add PVC resin and heat-stabilized, impact modifier to the mixing pot before starting the motor and cover it with a lid.
Start the motor at low speed and enter high speed mixing after normal.
At about 80℃, add processing modifier, internal lubricant, pigment, and filler to the material at high speed.
At about 100℃, add external lubricant (such as wax) at high speed.
At 125°C, the material is discharged into the rotating cold mixer at a low speed.
At lowering below 45°C, the cold mixer discharges the material.
Sieving, measuring, bagging, and storage for use.
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