Thermoplastic Elastomer Granulation

We are already familiar with TPE materials as compound ingredients, which mainly include SEBS/SBS, plastics, filler oil, fillers and other additives. Related materials such as SEBS are thermoplastic and have excellent processing properties, among which there is an important processing process - "granulation".

Basic process of granulation

Before processing and granulating, a complete set of granulation equipment is required, which is the TPE/TPR granulation production line. The basic components include mixing equipment, plasticizing equipment, cooling equipment, granulating equipment, and batch mixing equipment.

TPE/TPR materials use different pelletizing methods to correspond to different plasticizing and granulating production lines.

At present, there are mainly two types: cold cutting and hot cutting.

1.Cold cutting method

Twin screw extrusion and cold cutting is the most common granulation method for thermoplastic TPE, and the equipment and process are relatively simple. The material is plasticized by the extruder and extruded into round bars. After the round bars are air-cooled or water-cooled, they are cut into cylindrical particles through a pelletizer.

2.Hot cutting method

1) Air cooling hot face cutting. Place the rotating cutter tightly against the machine head template to cut the extruded hot round bar material into pellets. In order to prevent the particles from adhering, the pellets are cooled by blowing cold air in the pelletizing hood.

2) Underwater pelletizing. A new technology for TPE granulation. The machine head and cutter work in circulating warm water.

Common TPE/TPR pelletizing production lines include "strand pelletizing", "underwater pelletizing" and "water ring pelletizing".

Particles are generally cylindrical, and the strand cold granulating equipment consists of a granulating diehead, a cooling water tank, a strand pelletizer, an air blower, etc.

The particles are spherical or elliptical in shape. They start to be pelletized when they are extruded and swell. It is mainly composed of an underwater pelletizer head, a warm water circulation system, a separation system, a screening device, etc.

The particles are elliptical in shape. It consist of a water ring pelletizer head, a warm water circulation system, a separation system, a screening system and other parts, which are similar to the previous underwater pelletizing.

The batch mixing equipment is essentially a mixer, the purpose of which is to recycle and mix the products that have been granulated, and improve the factory uniformity and stability of the product particles.

Nanjing Haisi Extrusion Equipment Co., Ltd. can customize twin screw extruder and auxiliary equipment according to your requirement.

If granulation enterprises want to obtain qualified products, in addition to formulas and equipment, processing technology is also a key influencing factor. Suitable processes can promote the performance of particles, and conversely, reduce the performance of various aspects of the material.

 

1. Temperature

Temperature has a significant impact on TPE extrusion performance: it can reduce melt viscosity, improve melt fluidity, reduce extruder power consumption, and appropriately increase screw speed without affecting the plasticization effect of material mixing, which is conducive to improving the strength, brightness and transparency of the final product. However, if the melt temperature is too high, the extruded billet will easily produce its own weight sag phenomenon, resulting in uneven longitudinal wall thickness of the billet.

Extruder temperature setting: Under the premise that the smooth and uniform billet can be extruded without overloading the transmission system, in order to ensure that the billet has a high melt strength, a lower heating temperature should be used as much as possible.

 

2. Melt pressure

The melt pressure of the machine head should be uniform. Appropriately increasing the melt pressure in the extruder can make the material mixed uniformly and make the performance of the parison and the final product stable. To control the melt extrusion pressure, a melt pressure measuring instrument can be installed in the discharge section of the extruder.

 

3. Melt conveying speed

If the melt conveying speed is large, the extruder extrudes a large amount, and the melt conveying speed is improved, which can improve the phenomenon of self-weight sag of the parison and increase the wall thickness of the parison.

 

4. Other details process control

From the above granulation methods, we can know that there are three main TPE/TPR pelletizing methods, in addition to the above control of extruder temperature, screw speed, melt pressure, different cutting methods have corresponding control links. It is also necessary to control the cooling water temperature, circulating cooling system, traction speed, pelletizing speed, etc., in order to comprehensively produce qualified products.