Extrusion granulation technology (b)
Raw material weighing
Input kneading machine or mixer mixing, mastication of raw materials, the first volume should be equipment capacity
Product and feed coefficient estimated feed, and then calculated according to the formula of each feedstock feed.
For example, 200 L of high-speed kneader, PVC pot per dose of about 80-90 kg,
Weighing must be accurate, the instrument should be calibrated regularly zero, automatic metering device must
Regular inspection and correction. If necessary, repeat the name.
In the weighing process, we must ensure that within the specified relative error, the general requirements of the phase
The error is within 2%, for which, can be used proportioning device and fully automatic metering mixed device
Set to carry out weighing, conveyor belt can also be used to automatically weigh the material.
Weighing resin commonly used ingredients automatically, to achieve process control, the set value can be arbitrary
Change, precision to meet industrial production requirements. Measurement of liquid components in addition to the use of automatic weighing
In addition, you can also use metering pumps, liquid meters and other volumetric measurement. The disadvantage of volumetric measurement is accurate
Indeed by the temperature greater impact.
High-speed mixing technology
1. Hot mix
High-speed mixer to warm up before boot, the pot temperature is 60-80 ℃, the temperature is not
Can be too high The order of addition has some effect on the quality of the mix, especially for semi-hard
PVC plastic soft and hard degree of great influence. In general, resin and stabilizer first added,
Start low-speed mixing, then add plasticizer, stirring for about 5 min before adding filler, the most
After adding pigment or paste.
From high-speed hot mix out of the material, the temperature is often over 100 ℃, if released from storage
Discoloration in the barrel requires immediate cooling, caking or even degradation. So on the extrusion
Granulation process, the mixture material temperature dropped to below 50 ℃ to storage.
PVC plastic mixing process
The quality of the mixture is mainly manifested in these points: ① was loose group-like weft '
② better flexibility; ③ uniform color.
High-speed mixer operating characteristics are as follows.
Mixing quality and stirring paddle shape, speed, material temperature, mixing room material
The filling rate, the type of additives and methods of adding people and other factors.
The rotational speed of the paddle determines the amount of energy delivered to the material, which is within the mixing chamber
Exercise and temperature have a direct impact. The speed is generally taken 10 a 35 r / min, stirring paddle
The outer edge of the line speed control in 20 50 m / s.
Filling rate is also a factor affecting the quality of the mix. Filling rate is small, mixed materials
The flow of space is large, is conducive to mixing, but the impact of production. Under normal circumstances, the fill rate in
0.5 a 0.7; for high stirring paddle, filling rate of 0.9.
High-speed mixer power is generally 150-300 W / kg; when the plasticizer content is higher
When, it is preferable 600 W / kg above.