Improvement of Twin Screw Extruder from the aspect of cooler and side feeding

Twin-screw extruders are commonly used in plastic production processing. In the actual production process, twin-screw extruders use their own advantage performance to improve the utilization rate of material resources and reduce the residual amount of materials inside the extruder. With the production and processing scale expanding, the modified plastic production and processing industry has put higher-level requirements on the process performance of twin-screw extruders.

Improvements to the cooling box and side feeding device of the twin-screw extruder can effectively improve the production efficiency of the machine.

Cooling box transformation

By adding a cooling box to the twin-screw extruder, the production process of the twin-screw extruder can be improved and optimized. 

In the past, most of twin-screw extruders were adopted with air-cooled cooling. The principle of air-cooled cooling is to form a ring-shaped air groove on the contact surface between the surface of the cylinder and the heater. When the actual temperature of the cylinder is higher than the heating temperature set by heating, the fan connected to the air groove starts work, and the fan will blows the external air through the air slots to take away the heat, so as to achieve cooling. The disadvantage of air cooling is that the lag time of temperature control is too long, and the cooling effect is not good,at the same time, due to the large dust in the production environment of the twin-screw extruders, air cooling will increase the hazards of dust.

Now we improve the barrel flow channel with water-cooled cooling. Its advantages are rapid temperature control response, high precision and good cooling effect. At the same time, the high-temperature water in the water tank can be recovered and reused for secondary energy. The application of water cooling improves the stability of extrusion of plastic products. Reduces the risk of overheating of the melt affecting its properties.

Improvement of side feeding device of twin-screw extruder

In the traditional side feeding device, an exhaust port is set upstream to transport materials into the extruder under the support of the screw rotation force. The material continues to advance along the screw, is heated and melted, and is mixed under the action of the kneading component. However, when the amount of material increases, one side of the feeding port is filled with material, and there is some space left on the other side, causing serious air entrapment during the entire filling process, which seriously affects the filling amount.

1. Reduce the air entrapment during filling

An exhaust port is set upstream of the side feeding port. The original screw is replaced with a lead screw, and the side feeding hopper is divided into two parts. The front part is used for exhaust and the rear part is used for feeding. During the filling conveying process, the lead screw supports the material to compact it, and smoothly discharges the entrapped air through the front part of the hopper and the upstream exhaust port of the side feeding port.

2. Reserve free space on one side of the feeding port

By increasing the free space on one side of the feeding port to meet the actual filling volume requirements, a large lead screw component is designed based on the existing screw, an asymmetric screw component is set upstream of the screw side feeding port, a reverse conveying component is designed on one side of the screw side feeding port, and a reverse groove component is designed on the other side. When the extruder transports materials, the materials enter the main feeding port and enter the extruder, continue to advance along the screw, and melt. When the material reaches the asymmetric component, the state of the distribution changes significantly under the action of the asymmetric component. One side of the feeding port reversely conveys the material while the other side synchronously reversely conveys it. During the reverse conveying process, one side of the feeding port forms a cavity under the action of the reverse conveying component, greatly improving the filling capacity of the side feeding device.

3. Double side feeding system

For some high filling material formulation systems

We have developed two side feeding systems for the following applications:

• High proportion addition for high filling materials. When one or two materials in the formulation process require a higher filling ratio and the main feed has reached the highest conveying capacity, we use split side feeding to reduce the pressure of the main feed. At the same time, the dispersion ability of the main screw is also reduced. achieve the best dispersion effect.
• According to different process requirements: some reactive additives are reacted in the later barrels. If added too early. Additives participate in the reaction and affect the performance of the finished product, especially suitable for reactive extrusion occasions.
• Some materials have low melting temperatures. Mixed with materials with higher melting temperature, in order to avoid overheating decomposition and carbonization of low temperature feed, lateral feed is added at the back end. Low temperature can be set in the side feed adding area.